Ceramic Matrix Composites Taking Flight at GE Aviation Featuring

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ACerS Anniversary Ad 2.indd 1 2/13/19 3:44 PM contents April 2019 • Vol. 98 No.3 feature articles

Ceramic matrix composites taking flight at 30 GE aviation The holy grail for jet engines is efficiency, and the improved high-temperature capability of CMC systems is giving General Electric a great advantage. department News & Trends ...... 4 by Jim Steibel Spotlight...... 10 Ceramics in Energy...... 19 cover story Research Briefs...... 21 Nonoxide polymer-derived CMCs for 34 “super” turbines The melting point of single-crystal blades limits further columns advancement in operating temperature of gas turbines with metallic materials. Ceramics, which have much higher melt- All about aircraft ...... 29 ing points, hold the promise for future “super” turbines. Infographic by Lisa McDonald by Zhongkan Ren and Gurpreet Singh Deciphering the Discipline . . . . . 64 Ultra-high temperature oxidation of high entropy UHTCs Taking off: Advanced materials contribute by Lavina Backman 40 to the evolution of electrified aircraft Commercial electrified aircraft are expected to take off within the next decade—and advanced materials are playing an increasingly critical role in solving key technical challenges that will push the boundaries even higher. meetings 25th International Congress on by Ajay Misra Glass (ICG 2019) ...... 56 GFMAT-2/Bio-4 ...... 58 Environmental barrier coatings enhance 3rd Annual Energy Harvesting 46 performance of SiC/SiC ceramic matrix Society Meeting (EHS 2019) . . . 59 composites Environmental barrier coatings protect the structural integrity and mechanical strength of ceramic matrix composites, allowing these revolutionary materials to boost gas turbine engine efficiency. resources Calendar...... 60 by Kang N. Lee and Mark van Roode Classified Advertising...... 61 Display Ad Index...... 63 Ceramics Expo 2019 54 I-X Center in Cleveland—April 29 - May 1 Channeling ceramic enterprise and expertise

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 1 AMERICAN CERAMIC SOCIETY bulletin online Editorial and Production www.ceramics.org Eileen De Guire, Editor ph: 614-794-5828 fx: 614-794-5815 [email protected] April 2019 • Vol. 98 No.3 Lisa McDonald, Science Writer Michelle Martin, Production Editor Tess Speakman, Senior Graphic Designer Editorial Advisory Board Darryl Butt, University of Utah http://bit.ly/acerstwitter http://bit.ly/acerslink http://bit.ly/acersgplus http://bit.ly/acersfb http://bit.ly/acersrss Michael Cinibulk, Air Force Research Laboratory Fei Chen, Wuhan University of Technology, China Thomas Fischer, University of Cologne, Germany Kang Lee, Chair NASA Glenn Research Center As seen on Ceramic Tech Today... Chunlei Wan, Tsinghua University, China Eileen De Guire, Staff Liaison, The American Ceramic Society Optical fibers shake up earthquake Customer Service/Circulation monitoring systems ph: 866-721-3322 fx: 240-396-5637 [email protected] A team of Lawrence Berkeley National Laboratory researchers showed “dark fibers,” unused fiber-optic Advertising Sales cables that crisscross the United States underground, National Sales could be coopted to serve as sensors in earthquake Mona Thiel, National Sales Director monitoring systems. [email protected] ph: 614-794-5834 fx: 614-794-5822 Europe Richard Rozelaar Credit: Jonathan Ajo-Franklin, Berkeley Lab [email protected] ph: 44-(0)-20-7834-7676 fx: 44-(0)-20-7973-0076 Executive Staff Read more at www.ceramics.org/earthquakes Mark Mecklenborg, Executive Director and Publisher [email protected] Eileen De Guire, Director of Technical Publications and Communications Also see our ACerS journals... [email protected] Composite reinforcement: Recent development of continuous Marcus Fish, Development Director glass fibers Ceramic and Glass Industry Foundation By H . Li, T . Charpentier, J . Du, and S . Vennam [email protected] Michael Johnson, Director of Finance and Operations International Journal of Applied Glass Science [email protected] Sue LaBute, Human Resources Manager & Exec . Assistant High-performance infrared emissivity of micro-arc oxidation [email protected] coatings formed on titanium alloy for aerospace applications Andrea Ross, Director of Meetings and Marketing By H . Tang, W . Tao, H . Wang, et al . [email protected] International Journal of Applied Ceramic Technology Kevin Thompson, Director of Membership [email protected] Mechanical behavior of SiC joints brazed using an active Officers Ag–Cu–In–Ti braze at elevated temperatures Sylvia Johnson, President By F . Moszner, G . Mata-Osoro, M . Chiodi, et al . Tatsuki Ohji, President-Elect Michael Alexander, Past President International Journal of Applied Ceramic Technology Stephen Houseman, Treasurer Mark Mecklenborg, Secretary Scalable measurements of tow architecture variability in braided ceramic composite tubes Board of Directors Mario Affatigato, Director 2018–2021 By F . M . Heim, B . P . Croom, C . Bumgardner, and X . Li Kevin Fox, Director 2017–2020 Journal of the American Ceramic Society Dana Goski, Director 2016–2019 John Kieffer, Director 2018–2021 Lynnette Madsen, Director 2016–2019 Sanjay Mathur, Director 2017–2020 Martha Mecartney, Director 2017–2020 Gregory Rohrer, Director 2015–2019 Jingyang Wang, Director 2018–2021 Read more at www.ceramics.org/journals Stephen Freiman, Parliamentarian

American Ceramic Society Bulletin covers news and activities of the Society and its members, includes items of interest to the ceramics community, and provides the most current information concerning all aspects of ceramic technology, including R&D, manufacturing, engineering, and marketing . The American Ceramic Society is not responsible for the accuracy of information in the editorial, articles, and advertising sections of this publication . Readers should independently evaluate the accuracy of any statement in the editorial, articles, and advertising sections of this publication . American Ceramic Society Bulletin (ISSN No . 0002-7812) . ©2019 . Printed in the United States of America . ACerS Bulletin is published monthly, except for February, July, and November, as a “dual-media” magazine in print and electronic formats (www ceramics. org). . Editorial and Subscription Offices: 550 Polaris Parkway, Suite 510, Westerville, OH 43082-7045 . Subscription included with The American Ceramic Society membership . Nonmember print subscription rates, including online access: United States and Canada, 1 year $135; international, 1 year $150 *. Rates include shipping charges . International Remail Service is standard outside of the United States and Canada . *International nonmembers also may elect to receive an electronic-only, email delivery subscription for $100 . Single issues, January–October/November: member $6 per issue; nonmember $15 per issue . December issue (ceramicSOURCE): member $20, nonmember $40 . Postage/handling for single issues: United States and Canada, $3 per item; United States and Canada Expedited (UPS 2nd day air), $8 per item; International Standard, $6 per item . POSTMASTER: Please send address changes to American Ceramic Society Bulletin, 550 Polaris Parkway, Suite 510, Westerville, OH 43082-7045 . Periodical postage paid at Westerville, Ohio, and additional mailing offices . Allow six weeks for address changes . ACSBA7, Vol . 98, No . 3, pp 1– 64 . All feature articles are covered in Current Contents .

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From rooftop to reservoir— Benefits of floatovoltaics The California Building Standards Commission recently upheld a decision to require solar panels on all new homes up to three stories high, effective Jan 1., 2020. In the long term, homeowners are expected to benefit, but the requirement could greatly increase upfront costs. The idea of increasing investment in Credit: Dennis Schroeder, NREL A floating photovoltaic system being installed in Walden, Colo. A new National Renewable solar panels is gaining traction, but plac- Energy Laboratory study outlines benefits of these systems over land-based solar panels. ing the burden of uptake on homeowners—or even placing solar panels on land According to scientists at the National than on land. The concept was first dem- at all—may face severe opposition from Renewable Energy Laboratory (NREL), onstrated more than 10 years ago when a citizens concerned about panels taking it might be time to consider moving large-scale floatovoltaic system was installed up valuable agriculture land, contaminat- from rooftops and instead installing at a California winery, and now there are ing the environment, or even damaging on reservoirs. more than 100 floatovoltaic sites around community aesthetics. “Floatovoltaics,” or floating photovol- the world. Where else could solar panels be taic (PV) panels, are traditional PV panels Recently, NREL researchers released installed if not on houses nor land? installed on manmade reservoirs rather a study detailing potential benefits of

4 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Let’s explore new possibilities. By creating specialty glass that stands out with unmatched properties, we enable engineers and designers to think in new dimensions. What’s your next milestone?

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floatovoltaic systems, which include lower installation costs than land-based solar Corporate Partner news panels and preventing harmful algae Lithoz becomes member blooms. However, floatovoltaic systems of ADAPT Consortium also face unknowns, such as effects on The Alliance for the local wildlife and long-term performance. Development of Additive “This gap in our understanding is Processing Technologies important to reconcile as floatovoltaics (ADAPT), an industry- have enormous technical potential,” says academia consortium at Rebecca Hernandez, an assistant profes- Colorado School of Mines sor of earth system science and ecology that advances data informat- at the University of California, Davis, ics and advanced characteriza- who was not involved in the study, in an tion technologies to optimize Shawn Allan, vice president of Lithoz NBC news article. for additive manufacturing, America (left), shows the CeraFab When it comes to enormous poten- welcomed new member tial, NREL researchers agree—they calcu- Lithoz, a world leader in 7500 printer installed at the Colorado lated that if floatovoltaics are installed development and production School of Mines to graduate student on just one-fourth of manmade reser- of ceramic materials and addi- Sarah Sortedahl and ADAPT industry voirs in the United States, these panels tive manufacturing systems. director Craig Brice. could generate about 10 percent of U.S. “The Lithoz membership Credit: Colorado School of Mines energy needs. (Solar panels currently in ADAPT formally marks our commitment to expand ADAPT’s research mission generate a little over 1 percent.) to all solid materials, beyond the alloys focus we had in our first few years,” says Visit https://www.nrel.gov/news/ ADAPT executive director Aaron Stebner. n press/ to learn more. n

6 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 , C

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Business news

PLANTS, CENTERS, AND FACILITIES PLG Glass acquires 50,000 sq. ft. Peterlee plant India’s Lohia Group acquires Israeli composite specialist PLG Glass, part of United Glass Group Ltd., bought its 50,000 sq. Indian manufacturing group Lohia acquired Israeli company Light ft. facility in Mill Hill, Peterlee with help of a £1.3m (US$1.68m) & Strong Limited, a producer of composites for aerospace and loan from Lloyds Bank. Since acquisition, PLG Glass created four military applications. Light & Strong Limited specializes in carbon new jobs and expects to generate revenues of £4m (US$5.17m) fiber and glass fiber composite component production. by 2020. https://bdaily.co.uk/articles/2019. https://www.janes.com/industry.

Hoya building next-gen HDD glass substrate production facility LifeSaver, National Graphene Institute exclusive research Japanese optical glass maker Hoya Corp. started construction of partnership its new production facility for hard drive platter glass substrates. LifeSaver, a UK-based manufacturer of portable and reusable These substrates could be used to make conventional 2.5-inch water filtration systems, and the National Graphene Institute HDD platters as well as next-generation platters for hard drives at The University of Manchester will conduct an 18-month that use energy-assisted magnetic recording technologies. research project to develop graphene technology for enhanced https://www.anandtech.com/. water filtration. https://www.snewsnet.com/press-release.

Energy Department opening battery recycling center MARKET TRENDS United States Department of Energy will open a battery recycling New report: Refractories market worth $26.3 billion by 2023 center at Argonne National Laboratory, aiming to reclaim and A new Refractories Market research report projects the recycle critical materials from lithium-based battery technology. refractories market will reach US$26.3 billion by 2023, at a CAGR https://www.energy.gov/news-blog. of 2.5 percent between 2018 and 2023. Unshaped refractories are projected to be largest segment of market, and growing Alteo opening a new affiliate in India demand from glass/ceramic industries are expected to drive To support alumina market growth in India, Alteo is opening a market for acidic and neutral refractories. new office, Alteo India Aluminas Private Ltd., in Mumbai. This https://www.whatech.com/market-research/industrial. new office will offer technical support, supply reliability, and a large product range to regional customers. Study finds 60 percent of advanced ceramics sales https://www.ceramicindustry.com/. concentrated in power and metallurgy According to a recent Fact.MR study, advanced ceramics ACQUISITIONS AND COLLABORATIONS sales surpassed 40,500 million tons in 2018, with demand Army lab and Lockheed Martin announce partnership in electronics and power and industrial and metallurgical The United States Army Research Laboratory and Lockheed applications collectively accounting for approximately 60 percent Martin Corporation entered into a five-year cooperative of overall sales in 2018. https://globenewswire.com/NewsRoom. agreement to develop rapid prototyping methods using bioproduction and self-assembly to create building blocks of Calcium aluminate cement demand to reach 1M tons on novel materials for defense optical technology and protective growing refractories industry coatings. https://www.army.mil/news. Global demand for calcium aluminate cement is forecast to reach one million tons between 2021 and 2022, according to Optoscribe, Sumitomo Electric announce cooperation CW Research’s Global Calcium Aluminate Cement Market Report Optoscribe, a supplier of 3D glass-based integrated photonics and Forecast. The upward trend will be underpinned by the components, and Sumitomo Electric Industries, an optical refractories industry, the biggest consumer of calcium aluminate fiber cable and component manufacturing technology cement. https://www.openpr.com/news/archive.html. n supplier, announced formation of a strategic cooperation to provide multicore fiber components for datacom and telecom applications. https://www.businesswire.com.

8 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Alumina Sapphire Quartz Credit: Kyocera Kyocera’s Junichi Jinno (left), general manager of corporate legal and intellectual property group, receives trophy from Daniel Videtto, president of Clarivate Analytics IP & Standards. High Purity Metallization Laser Kyocera named among Derwent Top 100 Global Powders Machining Innovators by Clarivate Analytics Kyocera Corporation was recognized as one of the Derwent Http://www.advaluetech.com Top 100 Global Innovators 2018–19 by Clarivate Analytics, a Philadelphia-based global information solutions provider Your Valuable Partner in Material Science focusing on intellectual property and the sciences. Kyocera’s patent success rate (more than 18,000) and global reach were Tel: 1-520-514-1100, Fax: 1-520-747-4024 identified as outstanding, marking the fifth consecutive for Email: [email protected] Kyocera to receive this recognition. The award was presented 3158 S. Chrysler Ave., Tucson, AZ 85713, U.S.A at Kyocera headquarters in Kyoto, Japan. n

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 9 acers spotlight

SOCIETY, DIVISION, SECTION, AND CHAPTER NEWS

ACerS signs MOU with partners to explore two-year ceramic technology degree Opportunities in the field of ceramic engineering technology have taken a significant step forward with the signing of a memorandum of understanding between Central Ohio Technical College (COTC), the Edward Orton Jr. Ceramic Foundation, and The American Ceramic Credit: COTC Society. Through the February 19th From left to right: ACerS executive director Mark Mecklenborg, COTC president John M. MOU signing, the entities have agreed Berry, Ph.D., and Edward Orton Jr. Ceramic Foundation general manager Mark Lawson to work together to launch at COTC the signed the MOU at COTC’s Newark campus on Tuesday, Feb. 19. only two-year ceramic engineering tech- tor. “We welcome the opportunity to the creation of a Ceramic Learning Lab at nology degree program in the nation. continue to meet the evolving needs of the COTC Newark campus, will provide “The American Ceramic Society was industry and to introduce a new genera- students an economical path to a techni- founded to serve the needs of the ceram- tion workforce to the rewards of working cal career as well as provide skilled work- ic manufacturing industry,” said Mark with these unique materials.” ers for the ceramic and materials process- Mecklenborg, ACerS executive direc- The proposed program, which includes ing and product industries. n Specialty GLASS Inc. solving the science of glass™ since 1977 Leading Manufacturer of Glass Materials with Innovative Production Techniques • Standard, Custom, Proprietary Glass and Glass- Ceramic Compostions Melted • Available in Frit, Powder (wet/dry milling), Rod or Will Develop a Process to Custom Form • Research & Development • Electric & Glass Melting up to 1650°C • Fused Silica Crucibles and Refractory Lined Tanks • Pounds to Tons www.sgiglass.com TOLL FREE: 1-800-332-5779

10 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 SOCIETY, DIVISION, SECTION, AND CHAPTER NEWS

Serbian Chapter of ACerS neer, materials design consultant, and consulting company to assist clients in expert in global marketing of nuclear the nuclear, automotive, armor, oil and storage materials. Long established gas, and chemical process industries. Engineered Materials Insights in 2009 We extend our deep appreciation to as an advanced ceramics and composites Long for his service to our Society! n Credit: Serbian Chapter Second meeting of the Serbian Chapter. The ACerS board approved the Serbian Chapter of ACerS, sponsored by the Serbian Ceramics Society (SCS), at the end of 2018. The SCS organizes the Advanced Ceramics and Applications VIII: New Frontiers in Multifunctional Material Science and Processing conference, which will be Sept. 23–25, 2019 at the Serbian Academy of Sciences and Arts, Knez Mihailova 35, Belgrade, Serbia. The annual ACA confer- ences bring together leading scientists, engineers, professors, Ph.D. students, experts, and manufacturers of advanced ceramics, glasses, and refractories to exchange information on their key achievements and research projects. To learn more about the SCS and ACA conference, please visit: http://www.ser- bianceramicsociety.rs/index.htm. n

Volunteer Spotlight ACerS is pleased to announce the second recipient of our new Volunteer Spotlight program through which we recognize a member who Long demonstrates outstanding service to The American Ceramic Society through volunteerism. William Long is an active Emeritus member of ACerS. He was instrumental in the successful launch of the Colorado Section of ACerS and belongs to the Engineering Ceramics Division. He is an advanced ceramics and composites engi-

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 11 acers spotlight

Society, Division, Section, and Chapter news (cont.)

President Johnson visits the Show-Me state Names in the news Trolier-McKinstry elected to National Academy of Engineering Susan Trolier-McKinstry, ACerS Fellow and profes- Trolier-McKinstry sor of ceramic science and engineering at The Pennsylvania State University, was named a member of the National Academy of Engineering.

Credit: Academy membership honors those who have made outstanding contributions to “engineering research, practice, or educa- Sylvia Johnson, ACerS president, visited The Missouri University of Science and tion,” and to “the pioneering of new and Technology in Rolla, Mo., on February 14. Johnson toured the university, gave developing fields of technology, mak- a talk, “Brief history of thermal protection systems,” and held a discussion about ing major advancements in traditional ACerS. The following day she visited Mo-Sci, an area glass manufacturer and fields of engineering, or developing/ ACerS Diamond Corporate Partner. n implementing innovative approaches to engineering education.” n 1800oC In Air - 100% ZIRCAR Ceramics 100% of the Insulation. 100% of the Engineering. 100% of the Fabrication. When OEM Furnace Builders and End Users have uniquely challenging thermal process furnace chamber requirements, ZIRCAR Ceramics’ proven line of high temperature thermal insulation, extensive custom fabrication facilities and nearly 40 years experience can be the best solution. Contact us now. 100% Satisfaction.

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12 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Batch Hot Press Continuous Society, Division, Section, and Chapter news (cont.) All types of High Temperature Ceramics Laurencin awarded 2019 AAAS Philip Processing Vacuum Furnaces Hauge Abelson Prize PRODUCTION AND LABORATORY Cato T. Laurencin, founding director of the All non-oxides: Institute for Regenerative Engineering and SiC, AIN, BN, the Sackler Center for Biomedical, Biological, Ti82, 84( & Si3N4 Physical, and Engineering Sciences at the Laurencin University of Connecticut, was awarded the Hot Presses from 0.5 to 2019 American Association for the Advancement of Science 1500 tons Philip Hauge Abelson Prize. An eminent biomedical engineer and orthopedic surgeon, the prize honors his global leadership CVI has built over 6,500 furnaces since 1954 in biomedical technology innovation, public service in shaping United States technology policy, and invaluable mentorship to a • Max Possible Temperature: 3,500°c (6,332°F) generation of minority scientists. n • Hot Zones: 10 cc to 28 cu meters (o_6 cu in to 990 cu ft) • Debind, Sinter, Anneal, Hot Press, Diffusion Bond, CVD, Boccaccini elected to the National CVl,MIM Academy of Science and Engineering of • CVI testing in our lab to 2,8oo°C (5,072°F) Germany • Worldwide Field Service, rebuilds and parts for all makes Aldo R. Boccaccini, professor and head of the Institute of Biomaterials, University of Erlangen- 55 Northeastern CentorrBlvd., Nash Vacuumua NH 03062 Industries USA • Toll free: 800-962-8631 Nuremberg, Germany, has been elected ordinary Ph: 603-595-7233 • Fax: 603-595-9220 • E-mail: [email protected] Boccaccini member of the National Academy of Science and Engineering of Germany. Election to the Academy is based Details at www.centorr.com on scientific achievements and reputation. n

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 13 acers spotlight

AWARDS AND DEADLINES

Nominations open for three Nominations close May 15 for Society, Division, Section, engineering awards GOMD and Electronics Division and Chapter news (cont.) The Engineering Ceramics Division awards invites nominations for the 2020 James Nominations close May 15 for three I. Mueller, Bridge Building, and Global Brinkman new mate- awards concerning glass and electronics. Young Investigator awards. The dead- Glass & Optical Materials Division: rials science/engi- line for submitting nominations for all neering department Alfred R. Cooper Scholars Award recog- three awards is July 1, 2019. nizes undergraduate students who have chair at Clemson The Mueller Award demonstrated excellence in research, University The Mueller Award recognizes long- engineering, and/or study in glass sci- Brinkman Effective March 1, Kyle term service to ECD and work in ence or technology. Brinkman is the new the area of engineering ceramics that Electronics Division: Edward C. chair of the Materials Science and has resulted in significant industrial, Henry Award recognizes an outstand- Engineering Department at Clemson national, or academic impact. Award ing paper reporting original work in the University. An early goal is to establish selection can be based on either crite- Journal of the American Ceramic Society or a council to help advise the university ria. The award consists of a memorial the ACerS Bulletin during the previous on investment in advanced materials, plaque, certificate, and an honorarium calendar year on a subject related to elec- one of six innovation clusters identified of $1,000. For information, contact tronic ceramics. as strategic research priorities in the Manabu Fukushima at manabu-fuku- Electronics Division: Lewis C. ClemsonForward plan. [email protected]. Hoffman Scholarship recognizes academic Brinkman replaces Rajendra Bordia, interest and excellence among under- who will remain on the Clemson fac- The Bridge Building Award graduate students in the area of materials ulty and focus on teaching, research, The Bridge Building Award recognizes science and engineering. and scholarship. n contributions to the field of engineer- Award criteria and nomination ing ceramics, including expansion of forms can be found at ceramics.org/ the knowledge base and commercial One and done—pay your dues members/awards. Contact Erica use thereof, and contributions to the Zimmerman at ezimmerman@ceramics. once with an ACerS Lifetime visibility of the field and international org for information. n Membership advocacy. Award selection can be based on either criteria. The award A case for continuous member- ACerS Lifetime Membership allows consists of a glass piece, certificate, members to avoid future dues increases, and an honorarium of $1,000. For ship . . . continued maintain awards eligibility, and the need information, contact Surojit Gupta at The March issue of the Bulletin to renew each year. The cost to become [email protected]. explained how a gap in membership can a Lifetime Member is a one-time pay- make you ineligible to become an ACerS ment of $2,000. Join the growing list of The Global Young Investigator Fellow. The same is true for Emeritus Lifetime Members while securing ACerS Award membership eligibility. member benefits for your entire lifetime. The Global Young Investigator Award If you are over 65 years old, and have To learn more about Lifetime recognizes an outstanding scientist con- been a member for 35 or more years, Membership, contact Kevin Thompson ducting research in academia, industry, you qualify for Emeritus membership. at (614) 794-5894 or kthompson@ or a government-funded laboratory. As an Emeritus member you no lon- ceramics.org. n Candidates must be ACerS mem- ger pay annual membership dues, and bers and 35 years of age or younger. you pay discounted registration fees to Selection of the awardee will be based attend meetings. on the nomination and accompanying But, you must maintain 35 continu- evidence of scientific contributions and In memoriam ous years of membership to be eligible. visibility of the field, and advocacy of So, keep your membership current. You Thomas F. Root the global young investigator and pro- can easily renew online each year for one Alexander Marker fessional scientific forum. The award or multiple years. For more information consists of $1,000, a glass piece, and Some detailed obituaries can also be found at about Emeritus, Fellow, or other awards www.ceramics.org/in-memoriam. certificate. For information, contact eligibility, visit www.ceramics.org/ Valerie Wiesner at valerie.l.wiesner@ members/awards. n nasa.gov. n

14 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 24/7 CUSTOMER SUPPORT ON-SITE SERVICE MEMBER SPOTLIGHT Engineered Solutions ACerS member helps students find career success FOR POWDER COMPACTION Claire Xiong knows firsthand the importance of being part of a scientific community. She was born into a scientific family—her father was an electrical engineer and her mother was an analytical CNC HYDRAULIC AND ELECTRIC PRESSES chemist. When you are surrounded by science your entire child- Easy to Setup and Flexible for hood, there is a chance you may follow a similar career path. Simple to Complex Parts And that is just what Xiong did. Xiong earned a B.E. in applied chemistry and a master’s degree in inorganic chemistry from East China University of Science and Technology (Shanghai). She earned her Ph.D. in electrochemistry from the University of Pittsburgh (Pa.), studying one-dimensional nanostructured electrodes using scanning elec- HIGH SPEED PTX PRESSES Repeatable. Reliable. Precise. trochemical microscopy. As associate professor at Micron School of Materials Science and Engineering at Boise State University, COLD ISOSTATIC PRESSES Xiong’s research focus lies Featuring Dry Bag Pressing in the synthesis, characterization, and development of advanced functional 814.371.3015 nanomaterials for sustain- Credit: Claire Xiong [email protected] able energy systems. Claire Xiong www.gasbarre.com POWDER COMPACTION SOLUTIONS 1896 That was then Professor Edward Orton Jr. began manufacturing pyrometric cones at Ohio State University in 1896. This was the start of this is now. the Standard Pyrometric Cone 2019 Company. In 1932 the company STILL THE STANDARD transformed into The Edward Today Orton continues to manufacture pyrometric cones, and Orton Jr. Foundation. new TempChek shrinkage products. We build thermal analysis instruments and offer comprehensive thermal testing service of refractories, glasses, ceramics and other materials. Funds from operations support industry, education, art and research.

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 15 acers spotlight

Member spotlight (cont.)

She joined The American Ceramic Society around the same Xiong also participated as a panelist on an NSF-sponsored time she started her job at Boise State. career workshop. She explains, “It was valuable for students “At that time, I was still new [at Boise State], and was trying and faculty who are beginning their careers. They really liked to figure out where to find a ‘home’ in a professional society,” the advice they got from the panelists.” she explains. “I had been a member of electrochemical, electro- Because of the advantages she gained from new relation- analytical chemistry societies, and Material Research Society.” ships and thought-leadership opportunities, Xiong encourages One of her colleagues, ACerS Fellow Darryl Butt, indirectly her students to get involved in the Society. introduced her to ACerS during a leadership summit. “He “It’s important for meeting organizers to provide opportuni- introduced me to program managers at the National Science ties for ACerS members and students to become involved,” Foundation (NSF) and the Department of Energy,” she says. she says. “We try to arrange activities at each [EMA] meeting “He wanted me to meet Lynnette Madsen, who encouraged for students and those early in their careers to get perspectives me to attend a principle investigator meeting. Everyone was so from seasoned scholars.” welcoming, especially to the newcomers. That’s how I ended Xiong talked about one of her students that she brought to up joining ACerS.” an EMA meeting. “She spent time networking at the meeting Xiong is currently secretary of ACerS Electronics Division, and found a postdoc job,” Xiong says proudly. “These meet- which coorganizes the Electronic Materials and Applications ings are really good exposure for students.” n meeting (EMA) every year with the Basic Science Division. Xiong has gotten to know more ACerS members by regularly attending meetings and presenting research. STUDENTS AND OUTREACH “I gave a talk at MS&T [in 2018],” she says, “and discovered that people are really very supportive and friendly. You ICG 2019 housing options can generate more ideas, feedback, and comments about the Are you attending ICG 2019 in Boston this year? If so, visit research you’ve presented.” ICG 2019 Facebook event page to meet other attendees prior to the event, work out possible roommates, set up dinners with others, and utilize the page for overall networking. Search “@acersgrads” to find the GGRN Facebook page and locate the ICG event under the events tab. n Show your expertise in ACerS Next Top Demo Show off your demonstration skills! Get a group of fellow students together and submit a video of a ceramic or glass outreach demonstration. ACerS Next Top Demo is a virtual competition organized by ACerS President’s Council of Student Advisors to educate the public while advertising the community outreach that you and your university or group already perform. Visit www.ceramics.org/pcsa to view the PCSA programs and find out how to compete, and send your video submissions for the Next Top Demo competition. Deadline is April 15, 2019. n ACerS GGRN membership for graduate-level ceramic and glass students Build an international network of peers and contacts within the ceramic and glass community with ACerS Global Graduate Researcher Network! ACerS GGRN addresses the professional and career development needs of graduate-level research students. GGRN members receive all ACerS individual member benefits plus special events at meetings, and free webinars on targeted topics relevant to the interest of the graduate student community. ACerS GGRN is only $30 per year. If you are a current graduate student focusing in ceramics or glass, visit www.ceramics.org/ ggrn to learn what GGRN can do for you and to join directly. n

16 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Student and outreach (cont.) Apply for 2019–20 ACerS PCSA The President’s Council of Student Advisors is the student-led committee of the Society composed of ceramic- and glass- focused students. The PCSA seeks dedicated and moti- vated undergraduate and graduate students to help advance ACerS into the future. Interested students should visit www. ceramics.org/applypcsa to apply. Application deadline is April 15, 2019. n

ACerS offers early career memberships ACerS offers a one year Associate membership at no charge for recent graduates who have completed their terminal degree. To receive the benefits of membership in the world’s premier membership organization for ceramics and glass professionals, visit www.ceramics.org/associate. Also, consider joining ACerS Young Professionals Network. ACerS YPN is for members who have completed their degree and are 25 to 40 years old. YPN gives young ceramic and glass scientists access to invaluable connections and opportunities. Visit www.ceramics.org/ypn for more information, or contact Yolanda Natividad at [email protected]. n

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 17 acers spotlight

Student travel assistance available for summer school in Italy Credit: Politecnico di Torino The 2019 Summer School, “High and Ultra-High Temperature Ceramics,” will take place June 14 and 15, at Politecnico di Torino in Torino, Italy, prior to the 16th Conference of the European Ceramic Society (ECerS). The aim of this school is to create a forum that brings together students, professors, and industrialists from the high and ultra- high temperature ceramics field to develop links and a common language for better research and technological innovations, to define key challenges, and discuss questions to move toward effective solutions. The Ceramic and Glass Industry Foundation is offering up to $1,000 in travel support to selected undergraduate, graduate, and Ph.D. students from non-European based universities. To be eligible for consideration, applicants must be members of The American Ceramic Society, Material Advantage, Keramos, or the ACerS Global Graduate Researcher Network. Students wishing to apply for ACerS financial assistance are strongly encouraged to first secure support from their home institutions for the experience. To determine ACerS support eligibility, students must submit: 1. A completed application (http://bit.ly/studenttravelapp) 2. A brief letter of recommendation from a faculty member 3. A single-page letter of interest explaining · The relevance of this summer school to their field of study and career ambitions · Other sources of financial support with amounts The required application and supporting documents can be emailed to Belinda Raines, outreach manager, at braines@ ceramics.org by March 30, 2019. Visit https://bit.ly/cgiftorino for additional information. Summer school attendees are encouraged to also attend ECerS XVI Conference, which will be held in Torino, Italy, on June 16–20, 2019. n

18 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 ceramics in energy

Improved nanocatalyst stability boosts artificial photosynthesis efficiency Though hydrogen and other alternative fuels like methanol are promoted as ways to bypass traditional fossil fuels, the main method for extracting these elements from compounds requires burning fossil fuels like natural gas and coal—meaning that creating alternative fuels produces carbon dioxide, the exact thing alternative fuels try to avoid producing. New research on YOUR PARTNER FOR ADVANCED artificial photosynthesis by scientists at the University of São CERAMICS Paulo, the University of California, Davis, and the Brazilian Nanotechnology National Laboratory, though, could help make OFFERING A WIDE RANGE OF TECHNOLOGIES, E.G. alternative fuels a truly green alternative. ADDITIVE MANUFACTURING, CIM, AXIAL PRESSING Artificial photosynthesis produces hydrogen, methanol, and AND FUNCTIONAL COATINGS other organic molecules by using solar energy to break apart • UNEXPECTED DESIGN OPPORTUNITIES WITH water and CO2. However, artificial photosynthesis is currently CERAMICS most successful at just producing hydrogen because that only • OUR CORE COMPETENCIES IN MATERIAL, MANU- requires breaking down water. To create organic molecules FACTURING AND FUNCTIONALIZATION AS BASIS like methanol, an additional step of CO2 photoelectrocatalytic FOR SMART CERAMICS reduction is required, which is a harder process to achieve. Additionally, the material commonly used to capture and VISIT US: catalyze water and CO2 from the atmosphere—titanium dioxide CLEVELAND OHIO nanoparticles—readily adsorbs water to its surface, but does not 30TH APRIL – 1ST MAY · BOOTH 459 so readily adsorb CO . 2 NUREMBERG, GERMANY In their study, the researchers looked to improve the pho- 25TH JUNE – 27TH JUNE · BOOTH 5-326 toelectrocatalytic reduction process both indirectly (increased

CO2 adsorption capability) and directly (interface segregation) by doping TiO2 nanoparticles with barium oxide. Barium oxide was chosen as a possible dopant due to its CO2 adsorption capabilities and its susceptibility to surface segregation. www.cerix-ceramics.de “The interface segregation knowledge is one of the keys for designing the surface of any nanocatalyst,” says Andre Silva, a postdoctoral researcher at the University of São Paulo. That

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 19 ceramics in energy

Advanced Ceramic is because segregation of ions is intrinsically connected to the thermodynamic stability of nanoparticles by the surface Powders energy term. If a nanocatalyst is doped with the right ions, thermodynamic stability of the material will increase and surface energy will decrease, leading to “smaller crystallite sizes Sinter-Pur® products include and higher specific surface area, which lead to more active sites for the reaction [to take] place,” explains Silva. Alpha Silicon Carbide, Beta Silicon After doping with barium oxide and using a lixiviation Carbide and Boron Carbide method to quantify the barium ion content located at the Our sinterable non-oxide powders, surface and grain boundary interfaces, the researchers com- are available in microgrit and sub- bined this knowledge with direct calorimetric measurements micron sizes. of surface energies and microstructural studies to reach a conclusion: surface segregation of barium ions improves nanocatalyst stability. “This paper is a very good reference for understanding how to design nanoparticle surfaces to increase nanostability through surface segregation,” Silva says. He adds that the study is part of a larger research pro-

gram looking to decrease CO2 concentration using artificial

photosynthesis: CO2 abatement programme—Project 31. The www.SuperiorGraphite.com project is run by the Research Centre for Gas Innovation, a center supported by the São Paulo Research Foundation and Shell that studies the sustainable use of natural gas, biogas, and hydrogen, and management, transport, storage, and use of CO . DU-CO CERAMICS COMPANY manufactures 2 “The next step of the research is to perform the artificial a variety of custom technical ceramics by using photosynthesis tests using a reactor that is being built in dry press and extrusion methods with secondary our group,” Silva says. “In the future, we believe that it will be possible to have portable systems, as panels with active machining available. Materials; Steatite, nanoparticles that could be placed in many places, like houses or offices, to transform the CO from the atmosphere in use- Alumina (standard and high purity), 2 ful organic composites.” MgO (standard and high purity), The paper, published in Journal of Physical Chemistry C, is “TiO surface engineering to improve nanostability: The role Forsterite, 2 of interface segregation” (DOI: 10.1021/acs.jpcc.8b12160). n Cordierite and Mullite.

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Please contact us Credit: Hiram Cook, YouTube Researchers found that doping titanium dioxide nanopar- ph: (724) 352-1511 ticles with barium oxide improves artificial photosynthesis email: [email protected] efficiency, which could allow for truly green production of web: www.du-co.com alternative fuels such as methanol.

20 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 CMC laboratories research briefs Innovative Materials Solutions Discover More...... Ferroelectric crystals could revolutionize The Industry Leader in Advanced Ceramic optical data transmission Material Testing Services Researchers from Lehigh University and Lebanon Valley College collaborated with Oak Ridge National Laboratory and Common Materials Analyzed Corning Inc. to fabricate single-crystal waveguides in optical - Advanced Ceramics (AlN, Alumina, LTCC, etc) - Ceramic Composites fibers. They showed that despite being constrained inside glass, - Sapphire and Diamond these crystals retained their ferroelectric properties. - Layered Structures Instead of creating single crystals using the common liquid- - Metals and MMCs solid transformation method, the researchers used a solid-solid - Plastics and Polymers transformation technique called single-crystal-architecture-in-glass - Glasses and Dielectrics (SCAG), which involves heating a glassy material with a laser to just its crystallization temperature to form the single crystals. Testing and Analysis Services In an email, Himanshu Jain, ACerS Fellow and professor - Advanced Metallographic SEM/EDS Analysis of materials science and engineering at Lehigh University, - Rootcause Failure Analysis explains the researchers were unsure if the single crystals would - Flexural Strenght per ASTM C1161 exhibit ferroelectric properties. “At the outset it was unclear - High Temp DC Resistivity per ASTM D257 to us if such a crystal when grown and physically constrained - Grain Size per ASTM E112 inside the glass would be able to retain its ferroelectric behav- - Micro-Hardness per ASTM E384 - Thinﬁlm, thickﬁlm, and plating application ior and corresponding active properties,” Jain says. The researchers performed electron backscatter diffraction and piezoresponse force microscope (PFM) measurements on lithium niobosilicate glass to generate theoretical and experimental piezoresponse maps, respectively, for comparison. They www.CMClaborCMCatories.com found that, except for a specific region near the grain bound- CMC laboratories Innovative Materials Solutions FURNACE CO,INC Laser Flash Thermal Conductivity Analysis per ASTM E1461

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 21 research briefs

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• Ceramics • Batteries Credit: Groman123, Flickr (CC BY-SA 2.0) An academic and industry collaboration showed that single-crystal waveguides grown in glass retain their ferroelectric properties, a For more information, please contact us at finding that could revolutionize optical data transmission. 2194624141 ext. 244 or [email protected] ary, both maps agreed with each other and showed what the 5103 Evans Avenue Valparaiso, IN 46383 researchers were hoping for—a ferroelectric domain structure. www.pptechnology.com “The PFM maps indicate the as-grown crystals possess a nonuniform ferroelectric domain structure consisting of oppositely oriented domains on the micro- and nano-scale,” the researchers say in the paper. Though this discovery was promising, Jain explains most photonic applications “would like to have uniform domain structure so that desired properties can be realized in a predict- High Quality Manganese for the able manner.” So, the researchers then tried uniformly orient- ing the ferroelectric domain structure using the PFM cantilever Brick, Paver & Roof Tile Industry tip to perform a two-step poling process. The experiment did

not work at room temperature (as it does for bulk LiNbO3 single crystal), but it succeeded when the sample temperature was elevated to 100°C. After 24 hours, the modified regions remained stable and unaltered. Jain explains that the team has an extensive, ongoing program “to perfect the quality of single crystal architecture fabricated

Research News NIOKEM Advances in stretchable rubbery semiconductors, rubbery integrated electronics Mn304 University of Houston researchers created a stretchable, high- performance semiconductor device with fully integrated electronics and logic circuits. Previous stretchable semiconductors were hampered by low carrier mobility, along with complex fabrication requirements. For this work, the researchers discovered that adding minute amounts of metallic carbon nanotubes to polydimethylsiloxane composite, a We can supply your manganese needs, rubbery semiconductor, led to improved carrier mobility by providing a Mn0 “highway” to speed up carrier transport. Their low-cost semiconductor and we offer the best customer service! material retained its high charge carrier mobility, even when subjected to 50 percent stretching. The team’s work could lead to development Call Stephen Cox for current pricing of practical new technologies including wearable electronics. For more n 828-774-8745 information, visit http://www.uh.edu/news-events/archive.php.

22 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 in glass, and also provide new controls on the characteristics of Manufacturing solutions such crystals, such as their orientation.” Additionally, Jain says the partnership with Corning ensures the work will progress toward a realistic application in a reasonable time. “We discuss the results every 2–3 weeks, and our partners at Corning provide feedback regularly and also facilitate testing of the structures fabricated at Lehigh at their facility,” Jain adds. The paper, published in MRS Communications, is “Ferroelec- tric domain engineering of lithium niobite single crystal con- fined in glass” (DOI: 10.1557/mrc.2018.234). n

Ripplocations describe deformation of layered Visit CARBO at Ceramics Expo Booth 369 solids Instead of basal dislocations, researchers from Drexel Bring your products to market University and Colorado School of Mines suggest layered crys- faster while minimizing long- talline solids deform via nucleation and propagation of ripplocations, a phenomenon they showed for the first time on the term investment. macroscale in new research. Ripplocations are a “micromechanism by which layered Our state-of-the-art facilities and equipment solids deform,” explains Michel Barsoum, ACerS Fellow and oﬀ er maximum manufacturing ﬂ exibility: professor of materials science and engineering at Drexel Uni- versity, in an email. The term “ripplocations” was coined by Wet and dry blending and mixingCarbo

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 23 research briefs Credit: Michel Barsoum, Drexel University Drexel University and Colorado School of Mines researchers demonstrated ripplocation deformation in macroscale objects, such as this deck of cards. They say a ripplocation framework can explain deformations in most layered solids. Akihito Kushima and coauthors in a 2015 paper, in which they used the term to describe near-surface deformations in 2D van der Waals solids. Barsoum and his group were curious if this 2D phenomenon would apply to materials in bulk, so they applied a ripplocation framework to deformations occurring in graphite and MAX phase materials, reported in three separate papers from 2016, 2017, and 2018. They found ripplocations could describe bulk materials as well, and decided to take their research to the next level by presenting direct macroscopic evidence for ripplocation existence. “[This study] is the first time we can actually see ripplocations and [ripplocation boundaries] in action,” Barsoum says. They looked for ripplocations in three macroscale objects—a deck of plastic cards, thin steel, and aluminum sheets—and compared this deformation behavior to simulated models of ripplocations in graphite. The researchers indented each stack of materials and found that once the indenter pressed the stacks to a critical indentation depth, a very rapid nucleation of multiple—and oppositely- signed—ripplocations occurred. Once the indenter was retracted,

Research News

Understanding high efficiency of deep ultraviolet LEDs A team of Japanese researchers found deep ultraviolet light-emitting diodes (LEDs) made from aluminium gallium nitride efficiently transfer electrical energy to optical energy due to the growth of one of its bottom layers in a step-like fashion. They fabricated an AlGaN-based LED by growing a layer of aluminium nitride on top of a sapphire substrate, and then they grew a cladding layer of AlGaN with silicon impurities on top of the aluminium nitride layer followed by three AlGaN ‘quantum wells’ grown on top of this. Microscopic investigations revealed that terraced steps form between the bottom aluminium nitride and AlGaN layers and affect the shapes of the quantum well layers above them. This finding can lead to development of even more efficient LEDs. For more information, visit https://www.tohoku.ac.jp/en/press/.n

24 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 all layers spontaneously recovered to pre-pressed states. “This first investigation showed that ripplocations exist and Custom Designed are more or less fully reversible and that they dissipate energy Vacuum Furnaces for: in a manner that we have observed in layered solids at the • CVD SiC Etch & RTP rings atomic scale for more than a decade now,” Barsoum says in a • CVD/CVI systems for CMC components Drexel University press release. “But demonstrating the same • Sintering, Debind, Annealing behavior in layered materials that we can see directly is an important step toward proving that the behavior happens in materials of all sizes.” In an email, Barsoum says this paper just “scratched the Unsurpassed thermal and deposition uniformity surface” of what can be studied about ripplocations, so it is Each system custom designed to too early to tell if all layered solids behave this way. “I leave suit your specific requirements the door open. I think that there [are] layered solids that are Laboratory to Production brittle, for example, and thus do not deform by the movement Exceptional automated control of ripplocations,” Barsoum explains. “The evidence so far on systems providing improved product quality, consistency some of the newly discovered MAB phases appear that they and monitoring microcrack rather than ripple.” Worldwide commissioning, In the future, Barsoum says there are a variety of other stud- training and service ies they can perform to build on this research. “There are a lot of variables that we need to test, like thickness of individual layers, friction between them, etc.” 100 Billerica Ave, www.tevtechllc.com Billerica, MA 01862 The paper, published in Physical Review Materials, is “Ripplo- Tel. (978) 667-4557 Fax. (978) 667-4554 cations: A universal deformation mechanism in layered solids” [email protected] (DOI: 10.1103/PhysRevMaterials.3.013602). n

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 25 research briefs

Heal cracks in ceramic composites at room temperature Osaka University researchers showed anodic oxidation can heal cracks in ceramic composites, thus bypassing the need to rely on high-temperature heat treatments. Scientists commonly rely on high-temperature heat treatments to heal cracks in ceramic composites, but at these high temperatures (generally above 1,000°C), unexpected and/or Nutec unwelcome reactions can take place in addition to desired oxidation. In contrast, anodic oxidation, unlike high-temperature heat treatment, relies on an electrochemical method to initiate oxidation and thus can take place at room temperature. Con- ductive metals have been repaired at room temperature using this method, but, according to the Osaka researchers, the technique has not been applied to ceramics until now. To achieve anodization of their ceramic, the researchers explain in the paper that they needed to overcome two challenges. First, they needed to transform the ceramic material from insulating to conductive, which could be achieved by embed- ding metal particles into the ceramic matrix. Second, they then needed to convert these embedded metal particles into oxides. In previous studies, the Osaka researchers dispersed fine metallic micrometric titanium particles into an aluminum

oxide ceramic matrix, creating electrically conductive Al2O3/Ti composites. Based on these results, they hypothesized the titanium particles could be anodized to form titanium oxides.

They cracked their Al2O3/Ti composite using an FV–310e Vickers hardness tester and then performed the crack-healing

anodization at room temperature in 1 mol/L H3PO4 electrolyte solution using platinum as the cathode and the composites as anodes. The anode and cathode were set 15 mm apart, and anodization took place under three different conditions: two conditions (A1 and A2) used a three-step process, while the last condition (A3) used a one-step process. One of their most crucial discoveries was that while samples with higher electrical conductivity (containing more titanium Research News Researchers develop a novel chip-based device for quantum communication Researchers at the National Institute of Standards and Technology developed a way to solve a problem in quantum communication. In quantum communication systems, the optical components that store and process quantum information typically require visible- light photons to operate. However, only near-infrared photons can XIETA transport that information over kilometers of optical fibers. The NIST • High density alumina balls - Lining bricks team created quantum-correlated pairs made up of one visible and Nanobeads AZ.- Specialty pure aluminas one near-infrared photon using chip-based optical components that XIETA·INTERNATIONAL S.L. can be mass-produced. To create the entangled pairs, the team constructed a specially tailored optical “whispering gallery”—a www.xleta.com nano-sized silicon nitride resonator that steers light around a tiny Travessera de Gracia 62 08006 Barcelona - Spain - Tel +34 934 147 227 Fax+34 934142 837 - e-mail: [email protected] racetrack. For more information, visit https://www.nist.gov/news- events/news/2019/. n

26 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 ROBOCASTING Journal of the American Ceramic Society , Wiley Credit: Schemes of the crack-healing mechanism induced by anodization in ceramic-based composites. Osaka University researchers found TM anodic oxidation allowed them to self-heal ceramic-based com- PRINTED FILTERS posites at room temperature. particles) were more effective for anodization, samples with - D Printed lower electrical conductivity and fewer titanium particles dis- Ceramics played better crack-healing ability. The researchers attributed - Molten Metal this finding to differences in fracture toughness. Filters The sample with lower conductivity and fewer titanium particles had a higher fracture toughness value, leading to shorter - Made in crack length during crack propagation. In contrast, the sample the USA with higher conductivity and more titanium particles had a lower fracture toughness value, leading to longer crack length during crack propagation. “Based on the obtained results, when comparing the fracture toughness and the conductivity, the for- mer had a stronger influence in the crack-healing ability for the same indentation load,” the researchers explain in the paper. When looking at individual samples, the researchers found size of the crack open distance (COD) determined what current density was needed to heal the crack. For example, in samples containing 20 vol% titanium, when current density was 3 A/dm2 and COD was greater than 0.5 μm, part of the crack remained unconnected. However, when COD was less than 0.3 μm, the expanded oxides sealed the crack. “For different crack sizes, the optimal anodization conditions must be experimentally determined,” the researchers say.

Though their study focused on Al2O3/Ti composites, the researchers say this technique is not limited to that composite system. “The results of our study can also be applied to ceramic- based composite systems other than Al2O3/Ti composites as a new crack-healing method for ceramics and a technique for ensuring the reliability of the ceramics themselves,” senior author Tohru Sekino, ACerS member and professor of engineering at Osaka University, says in an Osaka University press release.

Additionally, the researchers emphasize that their Al2O3/Ti composites could be of great importance for unexplored potential applications. “With the combination of the high strength of the Al2O3 ceramic and the high fracture toughness and better biocompatibility of the [titanium] metal, the resultant

Al2O3/Ti composites are expected to be useful as structural components in engineering applications and as biomaterials Trust me, you need with novel functions, such as room–temperature crack healing,” the researchers add in the paper. The open-access paper, published in Journal of the American zirconia Ceramic Society, is “Electrochemically assisted room-temperature ZYF felt crack healing of ceramic-based composites” (DOI: 10.1111/ n jace.16264). www. zirconia.com

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 29 bulletin cover story Ceramic matrix composites taking flight at GE Aviation Credit: GE Aviation

dvanced materials have played Aa key role in improving turbine engine performance ever since the advent of By Jim Steibel the first turbojets in the 1940s.1 Nickel-based superalloys are the primary high-temperature structural material used within turbines, and The holy grail for jet engines is efficiency, and the improved the advancements in metals technology are high-temperature capability of CMC systems is giving General well-documented by Schafrik and Sprague.2 Electric a great advantage. Gas turbine aero engines employ the Brayton cycle in their operation. A critical parameter for high thermal efficiency is a high overall pressure ratio, which in turn drives high turbine flowpath temperatures. Turbine inlet flowpath temperatures are generally higher than the thermal limits of the component materials. Therefore, air from the compressor cools the components by a combination of internal and external flowpath cooling. However, minimizing the required cooling flow increases the overall efficiency of the cycle. Hence the need for developing and maturing advanced material technologies with improved high-temperature capability, such as ceramic matrix composites (CMCs). Overall, the introduction of CMCs enables a fuel burn reduction up to two percent—few other technologies in today’s pipeline have this much capability for fuel burn reduction. Additionally, the material density of CMCs is one-third that of today’s nickel- based alloys, enabling over 50 percent reduction in the turbine component weight. General Electric’s CMC development and maturation activities have been on-going for more than 30 years, and the business has invested more than $1.5 billion in the last decade on the technology. Early development and investment was supported by the United States Department of Energy, Department of Defense, and NASA.

30 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Capsule summary HOTTER, LIGHTER ENGINES CMCS HAVE THE RIGHT STUFF BLUE SKIES AHEAD To burn less fuel, aircraft engines must operate GE has invested more than $1.5 billion to devel- Through joint ventures and development of a at higher temperatures and contribute less op SiC/SiC ceramic matrix composite materials, vertically integrated supply chain, GE Aviation weight than nickel-base superalloys. Ceramic components, and manufacturing processes. has launched high-rate CMC production. matrix composites of SiC/SiC can take the heat and cut component weight by half.

GE Aviation has invested significantly in development of CMC material and process technologies, as well as manufacturing scale-up and supply chain. This investment has enabled commercial introduction of CMC high-pressure turbine shrouds in the LEAP engine (see Figure 1a). Certified by the Federal Aviation Authority and European Aviation Safety Agency (EASA) in May of 2016, the CMC shrouds have already surpassed four million hours of flight time in commercial LEAP engines flying on Airbus, Boeing, and COMAC aircraft. GE Aviation currently is developing the largest aircraft engine in the world— the GE9X—which has five CMC parts 1a throughout the engine hot section Credit: GE Aviation (Figure 1b). These parts include one Figure 1a. CMC high-pressure combustor inner liner and one outer turbine shrouds. liner, as well as HPT Stage 1 shrouds and nozzles, plus HPT Stage 2 nozzles. The GE9X enters service on the Boeing Figure 1b. Schematic drawing 777X in 2020. CMCs also are being shows use of CMC components incorporated into the architectures of in jet engine. advanced military engines to enable 1b increased thrust and reduced specific Credit: GE Aviation fuel consumption in future platforms. coating steps to apply thin coatings on each filament in the tow bundle using Material system capabilities chemical vapor deposition (CVD) pro- GE has developed a prepreg/melt infil- cesses. As shown in Figure 3, the coated tration (MI) process that has unique capa- fiber is then drum-wound to create a uni- bilities for fabrication of SiC/SiC CMC directional tape material. turbine engine components with small, The tape is subsequently cut into complex features. The molten silicon infil- shapes and stacked in tooling to create tration process produces a highly dense the finished part geometry after consoli- matrix, and the prepreg process enables a dation in an autoclave (Figure 4). Two relatively uniform distribution of individu- high-temperature furnace operations ally coated fiber filaments. This unique follow. First is a pyrolysis step to remove microstructure (shown in Figure 2) leads to any remaining organics, and the second superior mechanical properties, including step involves molten silicon infiltration the material durability required for turbine to convert residual carbon to silicon car- engine components. bide. The densified composite preform The SiC/SiC material system consists is then ready for machining to finalize of a 500-filament stoichiometric SiC fiber the geometry, and inspection to ensure tow (Hi-Nicalon Type S) produced by conformance of the dimensions and NGS, a joint venture between Nippon material requirements. X-ray computed Credit: GE Aviation Figure 2. Microstructure of GE’s SiC/ Carbon (Tokyo, Japan), GE Aviation tomography (CT), ultrasound (UT) and SiC CMC material fabricated with a pre- (Evendale, Ohio) and Safran (Paris, infrared thermography (IR) are the lead- preg/melt infiltration process. France). The SiC fiber undergoes two ing modalities when it comes to SiC-SiC

American Ceramic Society Bulletin, Vol. 98, No.3 | www.ceramics.org 31 Ceramic matrix composites taking flight at GE Aviation Credit: GE Aviation Figure 3. Prepreg/melt infiltration process flowchart for fabricating SiC/SiC CMC components. The final step after component fabrication is to apply an environmental barrier coating. CMC inspection. Application of an envi- Building the blueprint to CMC • A low-rate production facility in ronmental barrier coating (EBC) is the industrialization Newark, Del., for both CMC raw materi- final step to protect the CMC material GE Aviation is taking CMCs from al and components to demonstrate con- from high-temperature water vapor. The the laboratory to full-rate production by cept production readiness and employ manufacturing process, scaled-up to full establishing the first vertically integrated lean manufacturing practices. production rates at GE Aviation, takes CMC supply chain in the U.S. By the • A full-rate production facility in less than 30 days to convert SiC fiber to end of 2020, GE estimates it will have Huntsville, Ala., for raw material. The a finished part of any geometry. about 750 employees producing up to facility will begin producing SiC fiber and Table 1 summarizes the primary ther- 20 tons of CMC prepreg, 10 tons of SiC unidirectional tape in 2019 (Figure 5). mal and static mechanical properties fiber, and over 50,000 CMC turbine • A full-rate production facility in considered for turbine component appli- engine components per year. Asheville, N.C., producing CMC parts cations. The MI SiC/SiC properties rep- The business created an industrializa- for jet engines (Figure 6). resent a range of average values for tem- tion strategy for CMCs that aligns the In addition to the NGS joint ven- peratures between 1,500˚F and 2,400˚F. appropriate equipment, facilities, and ture, GE Aviation's supply chain also In general, the mechanical properties resources for each stage of technology includes Advanced Ceramic Coatings (a are relatively high, with the compressive maturity. The basic or fundamental joint venture between GE Aviation and strength about four times greater than research occurs at GE's Global Research Turbocoating Corp. in Hickory, N.C.), the tensile strength, achieving values Center (GRC) in Niskayuna, N.Y., which manufactures EBC’s at GE’s new that exceed 1,000 MPa. The in-plane where pioneering work in CMCs was facility in Duncan, S.C. mechanical properties have been char- performed in the 1980s, and continues GE expects CMC part production acterized extensively to understand the with recent technical innovations. to grow ten-fold over the next decade. cyclic durability as statistically-derived Beyond GRC, GE’s CMC supply GE Aviation’s fast and flexible vertical design allowables have been established chain includes four unique facilities: supply chain will allow the capability of for over 100 different material curves. • A CMC fastworks laboratory at manufacturing from fiber to finished Also, the high interlaminar strengths the Evendale, Ohio, headquarters to CMC engine part for a wide range of (exceeding 100 MPa) observed in GE’s quickly evaluate the viability of CMC component types. This versatility is MI CMC are a key to its use in more design changes and manufacturing pro- enabled by understanding and modeling complex turbine airfoils. cess improvements. of each major process step, as well as establishing specifications and control plans for key characteristics. GE’s progressive expansion of CMC production capability for additional engine components includes HPT nozzles, shrouds, and combustor liners for the GE9x engine. The current manufacturing readiness capability for the 9x components is at MRL 8 (pilot production demonstrated and ready for low-rate production). Plans are to achieve full-rate production this year. GE Aviation has matured the prepreg/ MI manufacturing process to MRL 10 (full-rate production) for HPT turbine Credit: GE Aviation Figure 4. Ply shapes being removed from a tape immediately after ply cutting opera- shrouds. This year alone, GE expects tion has been completed. Asheville, N.C. to ship more than 1,800 CFM* LEAP engines. GE Aviation Asheville, which *CFM is the 50/50 joint company of GE and Safran Aircraft Engines of France

32 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Credit: GE Aviation Credit: GE Aviation Figure 5. Unidirectional tape manufactur- Figure 6. A full-rate production facility in Asheville, N.C. ing. Huntsville, Ala. shipped around 23,000 LEAP HPT Stage 1 shrouds in 2018, About the authors plans to ship another 36,000 shrouds this year. Jim Steibel is a consulting engineer for the CMC team Asheville’s CMC site has doubled its employee base every at GE Aviation in Evendale, Ohio. Contact Steibel at jim. year since opening in 2014, growing to more than 300 employ- [email protected]. ees currently. The team converts the SiC fiber-reinforced tape to a manufactured part using the component fabrication steps References outlined in Figure 3. The incoming unidirectional tape currently 1Felice, M. (2013, May). Materials through the ages: Materials for aeroplane comes from the Newark, Del., plant. engines. Materials World. Retrieved from https://www.iom3.org/materials- GE is investing more than $200 million in its two-plant world-magazine/feature/2013/may/09/materials-through-ages-materials-aeroplane-engines Huntsville site, with $21.9 million in supporting funding from 2Schafrik, R. & Sprague, R. (2008). Superalloy Technology—A Perspective on the U.S. Air Force Research Laboratory under the Defense Critical Innovations for Turbine Engines. Key Engineering Materials, 380, pp. Production Act Title III Program. Construction of the two 113–134. DOI: 10.4028/www.scientific.net/KEM.380.113 n plants began in mid-2016 and finished recently. GE Aviation Huntsville, 130 employees strong and growing, is currently commissioning equipment in anticipation of production start-up in 2019. The Alabama facility will dramatically increase U.S. capability to produce SiC ceramic fiber for high-temperature applications. The fibers will also be converted into tape in the adjacent ceramic processing factory prior to shipment to Asheville. GE Aviation adopted Big Data principles and collects thousands of data points to link each of these CMC facilities at every stage of the manufacturing process. The scope of digitization also includes tracking product performance in customer applications. The CMC team has a real-time view through automation tools to enable maximizing product management throughout its lifecycle. These automation tools have driven productivity, cost, part delivery, and evolution of science understanding, resulting in increased part yields essential as GE Aviation and CFM anticipate near-record levels of engine demand.

Table 1: Primary thermal and static mechanical properties required of melt- infiltrated CMCs in turbine component applications. Property Unit Values Thermal conductivity W/m-K 15–25 Coefficient of thermal expansion Ppm/K 4–5 Tensile strength MPa 250–325 Bending strength MPa 400–550 Compressive strength MPa 1,000–1,300 Strain-to-failure % 0.2–0.7 Young’s modulus GPa 200–275 Interlaminar strength MPa 80–110

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 33 Nonoxide polymer-derived CMCs for “super” turbines

uperalloy turbine blades for gas turbines Smay have been the most significant energy and transportation technology development in the last century. It empowered our military prowess, made it possible for civilian aircraft to fly halfway around the world, and now single-crystal blades are employed in gas turbines for energy conversion because of their superior creep resistance over traditional polycrystal alloys. The single-crystal technology evolved over 50 years, through an intimate coupling between materials science, mechanical engineering, and manufacturing research. These single-crystal blades, coated with low thermal conductivity ceramics, now perform close to their melting points for thousands of hours (Figure 1). However, the melting point limits further advancement in the operating temperature of gas turbines with metallic materials. Ceramics, which have much higher melting points than metals, hold the promise for “super” turbines in the future (Figure 2). But while ceramics By Zhongkan Ren and Gurpreet Singh have high strength at high temperatures, ceramics also suffer from thermal shock. Structural ceramics are of two kinds: oxides, like aluminum oxide (think sapphire), and nonoxides, mainly silicon carbide (SiC). Oxides generally have a high coefficient of expansion that renders them prone to thermal shock, but they also have better oxidation resistance than SiC in extreme environments (Figure 1b). The current ceramics technology is therefore based upon structures made from SiC with environmental bar- The melting point of single-crystal blades limits rier coatings made from oxides. further advancement in operating temperature of Work from the 1980s to 1990s on ceramics for high-temperature struc- gas turbines with metallic materials. Ceramics, tures demonstrated that fibrous composites would be able to avoid brittle behavior because cracks that inevitably form in the matrix are unable to which have much higher melting points, hold the grow into the fibers if the interface is sufficiently weak. And if this condi- promise for future “super” turbines. tion is met then any single-fiber fractures in fiber-bundles would also be rendered harmless by displacement between the broken ends—the ends being accommodated by neighboring fibers through interfacial sliding.

Critical components to a CMC There are three critical components to a ceramic matrix composite (Figure 3): reinforcement, interface coating, and ceramic matrix.4 Reinforcement provides strength and structural foundation or shape for the composite, gen-

34 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Capsule summary

METALS MEET THEIR LIMIT CERAMIC POSSIBILITIES MULTIPLE WAYS FORWARD Single-crystal technology empowered our Ceramics, which have much higher melting New preceramic polymers, reinforcement fiber military prowess, increased civilian aircraft points than metals, hold the promise for “su- materials, failure prediction methods, and flight distance, and served in gas turbines for per” turbines. Three critical components— additive manufacturing methods all offer ways energy conversion. However, this technology has reinforcement, interface coating, and ceramic to increase performance of nonoxide polymer- reached its limit—the melting point limits further matrix—play a role in ceramic matrix derived ceramic matrix composites in the future. advancement in operating temperature. composite performance.

erally in the form of a complex 3D woven structure designed to closely match the

final shape of the component. Interface ) –1 )

coating is a thin coating on the fiber that –3 provides a low-strength interface between hard ceramic matrix and high-strength fiber. Ceramic matrix provides the load (MPa (Mg m (MPa

transfer between fibers and the majority MRS Bulletin (left); Nature Materials (right) Temperature (°C) Temperature Credit:

of chemo-thermophysical properties of Specific fast-rupture strength the composite—in some cases, the whole CMC is coated with an environmental Year Temperature (°C) barrier coating to further improve perfor- Figure 1. (a) Firing temperature trend and material capability over time [Adapted from mance under harsh conditions. MRS Bulletin1]. (b) A comparison of high temperature mechanical property of SiC/SiC Reinforcement in a CMC is added ceramic matrix composites (CMCs) with oxide CMCs and aeroengine materials like the mainly to improve toughness. It is typi- nickel-based super-alloy Inconel [Reproduced with permission from Nature Materials2]. cally in the form of either a carbon/ The current genesis of multi-component silicon-based polymer-derived ceramic (PDC)- graphite fiber or an oxide or nonoxide CMC technology will continue to evolve over the next decade. ceramic fiber that can withstand high- alumina show better oxidation resis- exist—chemical vapor deposition (CVD), application temperatures. Carbon fibers tance than nonoxide fibers, oxide-based extrusion/sintering of powder slurries, are generally the least expensive while fibers’ strength retention and creep and the polymer precursor route. nonoxide fibers are the most expensive. resistance at high temperatures is com- CVD is the oldest method for pro- Although oxide-based fibers such as promised due to grain growth at elevat- duction of SiC fibers. In this method, ed temperatures. In some SiC generally is deposited on a heated cases, creep rates for oxide amorphous carbon or tungsten wire fiber can be two orders of (“core”) resulting in a high-strength magnitude greater than fiber.5,8,9 Such fibers are monofilaments those of nonoxide fibers. with minimum diameter in the range of Because of light weight, 75 to 100 microns, which limits their good oxidation resistance, minimum bend radius and renders them good thermal shock resis- unsuitable for weaving into textile or tance, and relatively high making complex-shaped ceramic parts. modulus and strength Such high-strength fibers, however, values, only silicon-based could be used as reinforcement in a nonoxide ceramic fibers metal matrix composite. (tending toward SiC com- The extrusion/sintering to make SiC position) are preferred for fiber involves spinning SiC powder in a ultra-high temperature aero- polymeric binder followed by sintering. space applications. Oxide These fibers are generally thicker than CMCs are perhaps more 30 microns, have surface defects, and suitable for relatively less never fully densify due to difficulty in sin- demanding applications.4-7 tering a nonoxide ceramic.5,9

Credit: General Electric Because high-temperature CMCs Figure 2. Schematic (cross-section) of a GE gas turbine Manufacturing nonox- would require high-strength flexible engine. Polymer matrix composites (PMCs) are preferred ceramic fibers (diameters less than for low temperature applications while polymer-derived ide ceramic fibers ceramics (PDCs) are attractive materials for the engine Three different 20 microns), research on alternate routes hot section, for example, turbine blade and shroud. approaches to manufactur- to obtain continuous and flexible fibers Background turbine engine image courtesy General ing nonoxide ceramic fibers had been ongoing when a discovery by Electric.3 Labels by Zhongkan Ren.

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 35 Nonoxide polymer-derived CMCs for “super” turbines

3. Curing (thermally, chemically, or radiation) of green fiber to cross-link molecular chains into duroplastic-like state, rendering it infusible during pyrolysis; and 4. Pyrolysis of green fiber under argon at high temperature to obtain ceramic fiber. The first generation SiC fibers based on Yajima et al.10 were spun in inert environments but required curing in air to make them infusible during pyrolysis at high temperatures. As a result, such Credit: Zhongkan Ren fibers had oxygen in the ceramic upon Figure 3. Polymer versus ceramic matrix composites. Unlike PMCs, fiber-reinforced pyrolysis and the fibers were amorphous, CMCs require weak interphases to deflect cracks in the matrix around the fibers, non-stoichiometric Si-O-C instead of thereby avoiding catastrophic failure during service. Figure created by Zhongkan Ren, crystalline SiC. The relatively poor adapted from Campbell.4 thermal and mechanical properties of Yajima et al.10 in late 1970s showed how ceramic-fiber ceramic-matrix technology the fiber were attributed to high oxygen high-temperature ceramic fibers could that heralds the next-generation turbine content of these fibers. The second be made from certain organometallic engines,6 as discussed below. generation SiC fibers focused on reduc- oligomers or silicon-based polymers The production of these fibers ing oxygen content by curing the green using a combination of polymer and involves steps (Figure 4) that are some- fibers under gamma or electron irradia- ceramic processing methods. This what similar to those used for manufac- tion in inert environment. As a result, process was later developed into a com- turing carbon fibers from polyacryloni- these fibers had larger SiC grains along mercial technology in Japan. These fine trile (PAN):5,9–12 with the graphene-like carbon.5 fibers show good mechanical proper- 1. Synthesis of preceramic polymer The third-generation fibers were ties, thermal properties, and oxidation with desired rheological properties for manufactured at even higher pyrolysis resistance, and can be woven in textile spinning processes; temperatures with addition of trace to make complex-shaped ceramic parts. 2. Melt or dry spinning of precursor amounts of aluminum, titanium, or These SiC fibers are the backbone of the into green fibers; boron to sintering of SiC. Such fibers CMC MATRIX manufacturing techniques Infiltration is the most common technique for creating aerospace Melt infiltration: Molten silicon at approximately 1,500°C is grade SiC/SiC ceramic matrix. Fiber preforms can be infiltrated introduced into a carbon or SiC fiber preform (or into a preform with matrix material in gaseous (CVD) or liquid (melt infiltration and containing carbon particles), and SiC is formed at the interface as polymer infiltration) form.6 The fiber preform preparation requires molten silicon reacts with carbon. The process is expensive due to a rather complex approach—the preform is generally a 3D replica high temperatures required for melting. In addition, the byproducts of the final component (e.g., combustion liner or vane) designed may react with furnace elements, causing damage or significant computationally based on function of the component, expected downtime.9 Excess or unreacted silicon could be present in the mechanical and thermal loadings at the site, and topology/materials final part, which significantly degrades mechanical properties at properties of the fiber, matrix, and interface coating.2 high temperatures. CVD or CVI: CVD processing involves introduction of vapors of Polymer infiltration and pyrolysis: This technique is similar to silicon-based metal organic compounds (generally methyltricholo- those employed for fabrication of polymer matrix composites. The rosilane) along with a carrier gas, such as hydrogen, into a cham- fiber preform is infused with liquid preceramic polymer that trans- ber containing heated fiber preform substrate. The silicon-based forms into ceramic matrix upon pyrolysis (PDC route). Because of precursor decomposes at a high temperature to yield high purity its simplicity, relatively lower processing temperatures, and ability SiC, which fills the preform to form the continuous matrix phase. to produce complex CMCs, this technique is relatively cost effec- This process is slow due to lower ceramic yields and deposition tive. Preceramic polymers with high ceramic yield and improved rates. Large amounts of highly corrosive vapors are produced stability against moisture and air (long shelf life) are preferred; during the deposition process, which increases the capital equip- carbosilane-based preceramic polymers that yield stoichiometric ment cost and downtime. Large-size, thick CMC parts are prone SiC composition are most desired. n to nonuniform coating and density gradients.9

36 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 of CMC-turbine blades is rumored. GE Aviation expects that increased jet engine production will increase demand for SiC fibers and tapes as much as tenfold over the next decade.15 The high cost of these fibers is a major barrier to future growth.

Engineering new compounds Over the last 25 years, fundamental research in Si-C-O-N compounds yielded

Credit: Gurpreet Singh new results that show how their nano- Figure 4. Schematic showing various steps involved in PDC fiber processing. structure relates to mechanical properties and thereby provides the insights needed to engineer new compounds for turbine engine applications (Figure 5): •Stability of the amorphous structure: While the binary Si-C crystallizes at 1,200°C, the ternary and quaternary compounds are intrinsically amorphous, with a negative enthalpy of formation relative to the crystalline state. •The nanodomain network of graphene: The Si-C-O-N materials contain a network of graphene or sp2 carbon with a domain size of 1–5 nanometers. The Journal of the American Ceramic Society domain boundaries consist of mixed Credit: bonds of Si-C- (N,O) while the tetrahe- Figure 5. Amorphous nanodomain structure is the hallmark of PDC materials—such dral of Si-(O,N) occupy the space within microstructure has been shown to improve chemo-thermo-mechanical properties at high the domains. temperatures.16 •Zero creep behavior: The carbon net- are essentially polycrystalline SiC with trol of oxygen content—costly autoclave work imparts unusual mechanical prop- small amounts of sp2 carbon phase at techniques are needed for synthesis of erties such as zero creep in the steady grain boundaries. Higher sintering tem- the preceramic polymer while additional state at temperatures up to 1,500°C, perature generally leads to larger SiC pyrolysis steps are required to drive out while the interlaced Si-O-N protects the grain size, elastic modulus, strength, and oxygen from the ceramic fiber. carbon from oxidation. creep resistance over a wide temperature The General Electric Company Polycarbosilane-derived nanocrystal- range. Such fibers, however, are exorbi- recently introduced CMC components line SiC fibers contain grain boundaries. tantly expensive, costing over €18,000/ into its LEAP engines. This innovation Although such fibers are known for their kg.5 The high cost of manufacturing SiC is expected to generate tens of billions in ultra-high-temperature stability, presence fibers is apparently related to the con- new revenue for GE. The development of grain boundaries and some low melt- Developing negligible creep resistance and international student exchange opportunities The challenge is to develop ceramic fibers constituted from silicon, boron, carbon, nitrogen, or oxygen that exhibit negligible creep resistance at temperatures up to 1,600°C in oxidizing environments, with a target production cost of approximately $1,000/kg (Figure 4). To address this technical challenge and create international student exchange opportunities in PDC science, the National Science Founda- tion awarded a five-year $4.7 million Partnerships for International Research and Education (PIRE) grant to Gurpreet Singh and co-investi- 50.0µm gators (Alexandra Navrotsky, University of California, Davis; Himanshu Credit:: Gurpreet Singh PDC SiCNO fibers being investigated in Singh’s lab. (a): digital Jain, Lehigh University; Rishi Raj and David Marshall, University of camera picture and (b): SEM image. Foot-long fibers of prece- Colorado Boulder; Elsa Olivetti, Massachusetts Institute of Technology; ramic polymer could be drawn by hand using a glass rod. The and Peter Kroll, University of Texas at Arlington). So far, Singh et al. challenge, however, is to maintain structural integrity of the have demonstrated the feasibilty of drawing such low-cost fibers. n fiber during the pyrolysis process.

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 37 Nonoxide polymer-derived CMCs for “super” turbines

improve chemical and thermal Future directions for nonoxide stability.9,12,17,18 The SiCNO CMC materials and manufacturing ceramics are amorphous and processes contain significant amounts 1. New preceramic polymers based on of oxygen, which is rendered ternary and quaternary systems for CMC harmless by its nanodomain matrices: Liquid-phase high-purity, structure of graphene. The low-cost, high-yield polymers that are synergy between the carbon nontoxic and noncorrosive are being network and the Si-O-C matrix researched at both university and indus- within which it is embedded try levels. Preceramic polymers that can imparts thermodynamic stabil- produce amorphous ceramics with Si-X- ity to the amorphous structure, C-N/O, where X is boron, hafnium, or creep resistance, and, most zirconium, composition are of particu- importantly, the opportunity lar interest due to improved thermal to manufacture fibers at low stability and corrosion resistant of the cost (polysiloxanes and polysi- resulting ceramic. Likewise, preceramic lazanes are significantly more polymers that are photocurable (for abundant and cheaper than example, via chemical interfacing with polycarbosilanes—Table 1). photo polymers) at room temperature

Credit: Rishi Raj Ceramic fibers also gen- are being studied. Polymers that contain erally require an interface- simpler side (hydrocarbon) groups with Figure 6. High-temperature ceramic fibers are the compliant coating (100 nano- high ceramic yield at increased heating bridge between basic research on synthesis of pre- meters to 1 micron thick) and rates are desired in order to minimize ceramic polymers with desired properties and CMC a SiC overcoating to provide release of volatile components during processing based on real time failure predictions. a weak fiber/matrix bond in pyrolysis stages and lower processing ing phases/impurities at grain boundaries order to realize high toughness costs, respectively—larger hydrocarbons, may make them susceptible to deforma- in CMCs and to protect the fiber from which diffuse out during pyrolysis, could tion and creep at temperatures as low harsh oxidation environments, respec- lead to increased porosity in the matrix. as 900°C. For example, the SiC grains tively.19,20 The coating, generally com- This task is not trivial considering that may slide relative to one another due to posed of pyrocarbon or hexagonal boron thermal stability and rheological proper- softening at grain boundaries, leading to nitride (or a combination of both) has ties of preceramic polymer are tied to creep cracks and the eventual deformation low shear strength and is applied directly the composition and molecular weight of fiber.8 In addition, the role of small to the fibers via CVD techniques.4,7 CVD of the side groups. amounts of oxygen in commercial SiC of interface boron nitride and overcoat 2. New reinforcement fiber materials: As fibers is poorly understood. In contrast, SiC is expensive, time consuming, and stated earlier, oxygen-containing amor- multi-component amorphous fibers such requires use of hazardous chemicals; as phous PDC fibers based on ternary and as SiCN, SiOC, and SiBNC could be a result, the costs associated with such quaternary systems composed of com- produced by suitable selection of prece- coatings could be 10 to 50 times on a binations of elements that form strong ramic polymer (Table 1). Such ternary square-meter basis than a fabric of carbon covalent bonds (such as silicon, carbon, and quaternary systems are shown to or graphitic fiber.9 nitrogen, boron, oxygen) and show resis-

Table 1. Cost, availability, and properties of bulk PDC ceramics.

Preceramic Density Modulus Fracture Fracture polymer* Cost Availability PDC* (g/cm3) (GPa) strength toughness CTE Oxidation Decomposition (MPa) (MPa·√m) (106/K) temp. (˚C) temp. (˚C)

Polysilazane Low- Commercially available medium (medium availability) SiCN 2.3 80 to 155 <1,200 <3.5 3 ~1,300 ~1,600 Polycarbosilane High Commercially available (limited availability) SiC 3.1 405 418 4 to 8 3.8 ~1,200 — Polysiloxane Low Commercially available (large availability) SiOC 2.3 <113 < 900 <1.8 3.2 — —

Polyborosilazane Very high Laboratory synthesis (very limited availability) SiBCN 2.3 — — — — ~1,600 ~2,300 *Physical state of preceramic polymer and engineering properties of the pyrolyzed ceramic are strongly influenced by the molecular structure and composition of preceramic polymer and processing conditions used. Data from Journal of the American Ceramic Society and American Ceramic Society Bulletin.12–14

38 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 tance to crystallization and high tempera- properties in an economical manner. 10Yajima, S., Hayashi, J., Omori, M., & Okamura, ture creep should be the focus of future Very limited data has been reported in K. (1976). Development of a silicon carbide fibre with high tensile strength. Nature, 261(5562), pp. research. Such ceramics could be pre- literature on such composites—some new 683–685. pared from preceramic polymers based reports from the Air Force Research 11Gottardo, L., Bernarnd, S., Gervais, C., on polysiloxanes and polysilzanes, which Laboratory, HR Lab, and university Inzenhofer, K., Motz, G., Weinmann, M., Balan, are relatively cheaper and easy to mass researchers in Italy and the United C., & Miele, P. (2012). Chemistry, structure and produce compared with carbosilanes. As States have started to emerge.13 processability of boron-modified polysilazanes as tailored precursors of ceramic fibers. Journal of for fiber processing, preceramic polymers Materials Chemistry, 22(16), pp. 7739–7750. that can be melt-spun or electro-spun Acknowledgement 12Colombo, P., Mera, G., Riedel, R., & Soraru, are preferred over traditional dry spin- Financial support from National G.D. (2010). Polymer-derived ceramics: 40 years ning techniques, to keep costs lower due Science Foundation Grant #1743701 of research and innovation in advanced ceramics. to reduced number of processing steps. is gratefully acknowledged. Authors Journal of the American Ceramic Society 93(7), pp. Likewise, polymers that allow rapid in- thank Professor Rishi Raj (University 1805–1837. line curing (cross-linking) and pyrolysis of Colorado) for help in preparation of 13Colombo, P., Schmidt, J., Franchin, G., Zocca, A., & Günster, J. (2017). Additive manufacturing with high ceramic yields (greater than 85 this manuscript. Singh thanks Dr. David techniques for fabricating complex ceramic compo- percent) are expected to be significantly Marshall for his comments. nents from preceramic polymers. American Ceramic cheaper and hold low porosity and sur- Society Bulletin, 96(3), pp. 16–24. face defects. About the authors 14Liew, L., Zhang, W., An, L., Shah, S., Luo, R., 3. CMC failure prediction: Experimental Zhongkan Ren is a doctoral student and Liu, Y., Cross, T., Dunn, M.L., Bright, V., Daily, approaches to understanding ultra-high Gurpreet Singh is an associate professor J.W., & Raj, R. (2001). Ceramic MEMS: New Materials, Innovative Processing and Future temperature thermo-chemo-mechanical of mechanical and nuclear engineering in Applications. American Ceramic Society Bulletin, behavior of a CMC material could be the Mechanical and Nuclear Engineering 80(5), pp. 25–31. cost prohibiting. To ensure rapid com- Department at Kansas State University. 15https://ceramics.org/ceramic-tech-today/ge- mercialization of CMCs would require Contact Singh at [email protected]. aviation-invests-additional-105m-to-manufacture- guidance regarding material development ceramic-matrix-composites-for-jet-engines. Accessed and design of fiber preform (Figure 6).21 References March 12, 2019. 16Saha, A., Raj, R., & Williamson, D.L. (2006). A This could be achieved to some extent by 1Clarke, D.R., Oechsner, M., & Padture, N.P. model for the nanodomains in polymer-derived (2012). Thermal-barrier coatings for more efficient developing and employing analytical fiber SiCO. Journal of the American Ceramic Society, 89(7), gas-turbine engines. MRS Bulletin, 37(10), pp. and CMC material models for time-tem- pp. 2188–2195. 891–898. perature deformation and rupture behav- 17Riedel, R., Ruswisch, L.M., An, L., & Raj, R. 2Padture, N.P. (2016). Advanced structural ceramics ior. These models may involve computing (1998). Amorphous silicoboron carbonitride in aerospace propulsion. Nature Materials, 15(8): ceramic with very high viscosity at temperatures responses under conditions that induce pp. 804–809. above 1500 C. Journal of the American Ceramic severe thermomechanical gradients and 3General Electric. “Gas turbine engine.” GE Society, 81(12), pp. 3341–3344. be able to capture progressive failure of Newsroom, Accessed 22 Feb. 2019. Retrieved from 18Bhandavat, R. & Singh, G. “Boron-modified 22 https://www.genewsroom.com/sites/default/files/ CMCs —CMC material models that silazanes for synthesis of SiBNC ceramics.” United media/201409/86b712a08e9398f75bb40f0a557f accommodate effects of high strain rate States Patent No. 9,453,111, issued on Sept. 27, bb75.png and fatigue would be needed for design 2016. 4Campbell, F.C. (2010). Structural composite materi- of high-speed rotating components inside 19Luthra, K.L. (1997). Oxidation resistant fiber als. Materials Park, Ohio; ASM International. turbine engines. coatings for non-oxide ceramic composites. 5Flores, O., Bordia, R.K., Nestler, D., Krenkel, Journal of the American Ceramic Society, 80(12), pp. 4. Additive manufacturing of PDC W., & Motz, G. (2014). Ceramic fibers based on 3253–3257. CMCs: Like PMCs, a variety of additive SiC and SiCN systems: Current research, develop- 20Morscher, G.N. (1999). Stable Boron Nitride ment, and commercial status. Advanced Engineering manufacturing or 3D printing technolo- Interphases for Ceramic Matrix Composites. Materials, 16(6), pp. 621–636. gies could potentially be employed to Retrieved from https://ntrs.nasa.gov/archive/ manufacture CMCs from silicon-based 6Zok, F.W. (2016). Ceramic-matrix composites nasa/casi.ntrs.nasa.gov/20050179368.pdf. Accessed preceramic polymers. Opportunities exist enable revolutionary gains in turbine engine effi- March 12, 2019. ciency. American Ceramic Society Bulletin, 95(5), pp. 21Cox, B.N., Bale, H.A., Begley, M., Blacklock, in use of preceramic polymers to pro- 22–28. M., Do, B.C., Fast, T., Naderi, M., Novak, M., duce ceramic components in a range of 7Naslain, R. (2004). Design, preparation and proper- Rajan, V.P., Rinaldi, R.G., & Ritchie, R.O. (2014). compositions using either conventional ties of non-oxide CMCs for application in engines Stochastic virtual tests for high-temperature ceram- stereolithography printing (via chemi- and nuclear reactors: an overview. Composites Science ic matrix composites. Annual Review of Materials cal interfacing with photopolymers) or and Technology, 64(2), pp. 155–170. Research, 44, pp. 479–529. direct extrusion-based fused deposition 8National Research Council (1998). Ceramic Fibers 22Enakoutsa, K., Hammi, Y., Crawford, J.E., modeling of composite slurries followed and Coatings: Advanced Materials for the Twenty-First Abraham, J., & Magallanes, J. (2016). Modeling Century (Vol. 494). Washington, DC: The National 13 the thermo-mechanical behavior of a woven ceram- by pyrolysis at high temperatures. The Academies Press. ic matrix composite at high temperatures. arXiv challenge lies in the ability to produce 9Colombo, P., Soraru, G.D., Riedel, R., & Kleebe, preprint arXiv:1609.08191. n uniform, large-area, defect-free compo- A. (2009). Polymer derived ceramics: theory and applica- nents with desired thermomechanical tions. Lancaster, PA: DEStech Publications.

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 39 Taking off: orldwide, there is significant inter- West to develop electrified propul- Advanced materials sion systems for aircraft across a wide range of market segments. This is mainly driven by contribute to the higher efficiency of electrical components, reduced emissions, lower operating costs, and evolution of additional flexibility in aircraft design and architecture. The segment that has received the electrified aircraft most attention over the past 2–3 years is the urban air mobility market, which would use small electrified aircraft with 2–4 passengers By Ajay Misra for urban air taxis. Uber has been one of the drivers for this market segment and Commercial electrified aircraft are expected to take off is planning commercial introduction of electrified aircraft for within the next decade—and advanced materials are the urban air mobility market starting in 2022.1 Many compa- playing an increasingly critical role in solving key techni- nies—including Airbus, Boeing–Aurora Flight Sciences, Bell, and Embraer—are developing electrified aircraft concepts to meet the cal challenges that will push the boundaries even higher. needs of the urban air mobility market.2 Zunum and Eviation are also developing electrified concepts for ~10-passenger commuter Capsule summary EMERGING MARKET TECHNOLOGY CHALLENGES MATERIALS SOLUTIONS Driven by higher efficiency and design flex- Technology advances in major components of Advanced materials will be the enabling ibility as well as lower emissions and operating the electrical propulsion system will be required technology to afford higher power densities costs, electrified propulsion systems for aircraft for evolution of electrified aircraft from small and energy densities for electrified aircraft, are gaining momentum. Electrified aircraft are urban air mobility aircraft to regional and large including high-electrical conductivity materials, expected to continue an upward trajectory, aircraft. Key technical challenges will be to superconducting materials, magnetic materi- although technology readiness and economic improve the power density and efficiency of als, insulation materials, and thermal interface viability will dictate the timing of this expansion. electric motors and power conversion system, materials. Ceramic materials offer unique op- increase specific energy of batteries, and portunities to meet the needs of this expanding decrease weight of power transmission and class of aircraft. thermal management systems.

40 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Credit: NASA

Figure 1. Types of electrified propulsion systems for aircraft. aircraft for point-to-point travel.3 This increased lift is necessary to maintain demand, and economic viability. While will meet the vision of thin-haul avia- stable flight at lower airspeeds, the X-57 it is difficult to predict the evolution of tion, which refers to a growing market will use the DEP concept, which consists electrified propulsion for commercial that encompasses a large distribution of 12 small electric motors spread out aviation, a notional roadmap (Figure of short routes, each with limited and across the leading edge of the wings. The 3) can be envisioned based on the pace sporadic demand, but collectively with distributed motors force air directly over of current research, development, and enormous aggregate volume. the wing surfaces with the benefit of demonstration activities throughout the Electrified propulsion for aircraft falls increased air flow over the wing at lower world. The electrified propulsion market into three categories: all-electric, hybrid- speeds, increasing its lift. The increased for the aviation sector will potentially electric, and turboelectric (Figure 1). In lift allows it to operate on shorter run- evolve with the introduction of urban an all-electric concept, an energy stor- ways. Such a wing could be only a third air mobility and 10-passenger thin-haul age device or energy conversion system of the width of the wing it replaces, sav- aircraft in 2022–25, 40–50-passenger (e.g., fuel cell) powers an electric motor ing weight and fuel costs. regional aircraft in 2030, and single-aisle, that drives the fan for propulsion. In a The timing for introduction of elec- greater than 100-passenger aircraft in hybrid-electric concept, both an energy trified propulsion for various market 2035 or beyond. The pace of introduc- storage device and gas turbine engine (or segments would be a strong function tion for electrified aircraft propulsion internal combustion engine) are used for of technology readiness level, market in different market segments will be propulsion. In a turboelectric concept, the gas turbine engine runs a generator to produce electricity, which then drives the motor and fan. Electrified propulsion can enable the concept of distributed electric propulsion (DEP) in which the propulsors can be placed, sized, and operated with greater flexibility to leverage the synergis- tic benefits of aero-propulsive coupling and provide improved performance over more traditional designs. An example of the DEP system is shown in Figure 2, which is a NASA experimental plane known as X-57, designed to demonstrate the performance benefits of DEP. The concept for the X-57 employs two large electric motors, one on either wing tip, Figure 2. A NASA X-57 experimental aircraft, an example for the main propulsion of the plane. of a distributed electric propulsion architecture.

During takeoff and landing when Credit: NASA

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 41 Taking off: Advanced materials contribute to the evolution of electrified aircraft Credit: NASA

Year commercial of introduction

Figure 3. Notional progression of electrified aircraft market segment. a strong function of many technology The power levels from urban air mobility efficiency (Figure 5), which is finding advances described later. aircraft are typically several hundreds of application in small electrified aircraft for kilowatts (less than 1 MW), whereas sev- the urban air mobility market segment.4,5 Technology needs for electrical eral megawatts of power are required for For regional and large, single-aisle components regional and large, single-aisle aircraft. aircraft using MWs of power, a power Major electrical components of the The key technical challenges for density on the order of 15 kW/kg will electrical propulsion system for aircraft electric motors are power density and be desirable. Power densities above include the motor/generator, power efficiency. The power density needs to 20 kW/kg will be required for large conversion system or power electron- increase by a factor of three to five for commercial aircraft. ics, power transmission system, and large commercial transport. Figure 4 Power densities on the order of energy storage system (e.g., batteries). shows a notional roadmap for increasing 15 kW/kg may be achieved with conven- Technology advances in each of these power density of electric motors. tional (or noncryogenic) motors using components will be required for evolu- The power density of state-of-the-art copper coils, whereas power densities tion of the electrified aircraft market electric motors for electric vehicles is on more than 20 kW/kg will require super- segment from small urban air mobility the order of 2 kW/kg. Recently, Siemens conducting motors that use superconduct- aircraft to regional and large aircraft. developed a 200-kW electric motor with ing materials at cryogenic temperatures. power density of 5 kW/kg at 95 percent The efficiency of electric motors needs to increase from the state-of-the-art of about 95 percent to greater than 98 percent to mitigate thermal management challenges. Power conversion systems (also referred to as power electronics) are critical components of the electric propulsion system. A power electronic converter consists of many elements, including a power semiconductor, induc- tor, capacitor, switches, and thermal management system. The power density for a state-of-the-art power converter for aerospace applica-

Credit: NASA tions is on the order of 5–10 kW/kg with 95 percent efficiency. However, the Figure 4: Roadmap for increasing power density of electric motors for electrified aircraft. power density needs to increase by a fac-

42 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 tor of three to five for large aircraft using megawatts of power. NASA’s current research and development efforts focus on achieving power density of 15 kW/kg and efficiency of 99 percent. A long-term goal of 50 kW/kg with 99 percent efficiency can potentially be realized with innovative topologies, emerging power semiconductor and passive component technologies, and innovative thermal design. Transmitting megawatt levels of power in electrified aircraft is a major challenge. Typically, copper power transmission cables transmit non-propulsive power in current aircraft. Transmission of megawatt-level power for electrified propulsion systems would require large-diameter copper cables, which would add significant weight to the aircraft. Large electrified aircraft with 20–30 MW power systems will require transmission voltages on the order of several thousand volts and variable frequency of 400–4000 Hz, along with the capability to operate at high altitudes. With the use of very high voltages, preventing partial discharge at high altitudes will require a prohibitively large insulation thickness. Batteries are enabling components for electrified propulsion systems. The key parameter is specific energy (Wh/kg) for electrified propulsion applications. The specific energy of the state-of- the-art Li-ion battery used in electric vehicles is on the order of 250–270 Wh/kg at the cell level and ~150–170 Wh/kg at the pack level.

The state-of-the-art Li-ion battery can enable initial introduc- Credit: Siemens tion of small electrified aircraft for urban air mobility with lim- Figure 5: Siemens high power density, 200 kW motor ited range. The battery can also enable 10-passenger, thin-haul aircraft with limited range. Expansion of the electrified aircraft Role of advanced materials market beyond the initial introduction with limited range Expansion of electrified aircraft will require significant requires a significant increase in specific energy of batteries. increases in power density and energy density of electrical The following are examples of potential missions enabled by components. Design advances along with advanced materials higher specific energy batteries. Specific energy corresponds to will help achieve the very aggressive goals for electrified aircraft pack level. The range should be considered as notional. propulsion systems. • State-of-the-art (150–170 Wh/kg): Urban air taxi, 4-pas- High-power density electric motor senger, all-electric, ~25–30-mile range; thin-haul commuter, Major components of permanent magnet motors include 10-passenger, hybrid electric, 300–600-mile range. permanent magnets, conductor coils, and laminated stator • 300 Wh/kg: Urban air taxi, 4-passenger, all-electric, cores. For permanent magnets, Fe-Nd-B is the current material. 50–60-mile range. However, permanent magnets with higher magnetic strength

• 400 Wh/kg: Urban air taxi, 4-passenger, all-electric, or higher values of the parameter (BH)max, which is an indirect ~100-mile range; multiple vertical takeoff and landing aircraft measure of energy density, are desired. missions, 4–5-passenger, hybrid electric; thin-haul commuter Novel approaches to increase (BH)max include development aircraft, 10–20-passenger, >600-mile range. of nanocomposite magnets using a combination of hard and • 500 Wh/kg: regional, ~50–70-passenger, hybrid electric, soft magnets, the feasibility of which has been demonstrated 300–500-mile range. in thin films.6 There is also a need to increase the temperature

• 600 Wh/kg: large transport, narrow body, 180-passenger, capability of permanent magnets without sacrificing (BH)max. hybrid electric, 500–600-mile range. The conductor coil typically consists of a copper coil that Another major challenge is thermal management. For a carries current and generates magnetic fields. Higher power 5–10-MW system that corresponds to electrified propulsion for density can be achieved by increasing current density, which regional and large aircraft, hundreds of kilowatts of heat would leads to a higher level of joule heating. Higher current den- be generated due to efficiency losses in various components. sity and lower heating can be achieved by decreasing the elec- Thermal management challenges include: (1) integration of trical resistance (or increasing electrical conductivity) of the heat rejection from multiple sources, (2) low-grade heat at conductor coil. temperatures on the order of 200°C, and (3) increasing use of Carbon nanotubes (CNTs) could potentially have higher composites in aircraft that lower heat rejection capability of electrical conductivity than copper if metallic CNT can be the system. separated from semiconductor CNT during fabrication or

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 43 Taking off: Advanced materials contribute to the evolution of electrified aircraft through post-treatment. Development of a material with a sive components. For inductors to operate at high switching higher electrical conductivity than copper will be game-chang- frequencies, magnetic materials capable of operating at high ing for electric motors. frequencies with low losses are required. Current research Temperature rise associated with high current density in cop- focuses on developing amorphous nanocomposite magnets. per conductor coils can increase resistivity of copper coils, which Capacitors with capability for higher frequency operation are decreases efficiency and power density. Heat generated in copper also required. coils is transmitted through the insulation material surrounding The SiC-based power electronics system offers high-temper- the coil to the heat sink. Advanced insulation materials with ature operation capability, which can eliminate or simplify the higher thermal conductivity will help maintain the copper coil thermal management system with the benefit of an increase in temperature at the desired level at high current densities. power density. Higher-temperature power electronic devices The insulation material must have high thermal conductiv- will also enable better integration with aircraft components at ity, low electrical conductivity, and high breakdown strength to higher temperatures. operate at high voltages. Thermal conductivity of state-of-the- Although the theoretical limit for the operation of SiC power art polymer insulating materials used in electric motors is on devices can be as high as 700–1,000°C, the full potential of the the order of 0.1 W/m•K, which needs to increase by a factor temperature capability of SiC-based power electronics devices has greater than 10. Adding ceramic fillers to polymers is an active not been realized. The practical temperature capability of SiC area of research to increase the thermal conductivity of motor power electronics devices is significantly lower than the theoreti- insulation materials.7 cal limit.10 Some of the barriers to achieving higher temperature The power density of motors can be increased by increas- capability in SiC-based power electronic systems include higher ing the operating frequency, which translates to higher speeds. temperature capability for passive components (capacitors and Laminated magnetic steel that is currently used as a stator core inductors) and high-temperature packaging technology.11 material in motors loses power at high frequencies as it heats High-voltage power transmission cables up. Magnetic steel with higher silicon content is one approach There are some unique challenges related to durability of to reduce core losses at high frequency. Amorphous materials, high-voltage cable insulation materials for aircraft, including particularly metallic amorphous nanocomposite magnets, are corona discharge at high altitudes, increased electrical and gaining considerable attention for use in stator cores for high- thermal stress resulting from high-voltage and high-frequency frequency operation, which has the potential to significantly operation, and thermal cycling-induced degradation. 8 increase power density of motors. One approach to overcome the high-voltage challenges is to Achieving power densities beyond 20 kW/kg will require develop multilayer and multifunctional insulation materials superconducting motors operating at cryogenic temperatures. based on polymers and ceramics, in which each layer has a dif- Superconducting materials of interest for such motors include ferent function (e.g., one layer with dielectric properties and yttrium barium copper oxide (YBCO) and magnesium dibo- another to mitigate the effect of corona discharge). ride (MgB ). While YBCO is superconducting at 93 K, requir- 2 High-specific energy batteries ing liquid nitrogen cooling, MgB2 is superconducting at 39 K, requiring liquid hydrogen for cooling. There is considerable The high specific energies required for electrified aircraft will require use of lithium metal as an anode instead of the interest in MgB2 because it is easier to fabricate the material into wires, filaments, and other shapes. graphite used in state-of-the-art Li-ion batteries. While lithium In addition, additive manufacturing of electric motor com- metal-based batteries offer the promise of high specific energy, ponents, which is in its infancy, offers significant potential to cyclic life and durability need to be improved. increase power density of electric motors. Additive manufactur- Advanced ceramic materials (e.g., materials with optimized ing of multimaterial systems can enable higher fill factors for defect chemistry and conductivity) and manufacturing pro- copper coils by simultaneously printing copper and ceramic cesses (e.g., processes to create engineered, 3D microstruc- insulator materials.9 This also provides greater flexibility for tures that can accommodate large volume expansion associ- insulation materials, particularly ceramic insulation materials. ated with use of lithium metal anodes) will be critical to develop lithium metal batteries. High-power density power electronics (or power converters) Lithium metal-based all solid-state batteries (ASSBs) are Compared to state-of-the-art power electronics using sili- attractive for electrified aircraft applications. For an ASSB, con semiconductors, high-power density power electronics specific energy of the battery pack can be 90 percent of the converters will be based on wide-bandgap materials, such cell specific energy, compared to 60–70 percent for liquid as silicon carbide. SiC offers several advantages compared electrolyte-based batteries. Further, unlike batteries with liquid to silicon, including higher efficiency, higher switching fre- electrolytes, ASSBs are not prone to fire. Advanced ceramic quency, high voltage capability, and higher maximum oper- materials and manufacturing processes are critical to realize ating temperatures. high-specific energy ASSBs for electrified aircraft. Passive components, such as inductors and capacitors, make significant contributions toward weight and volume of the Thermal management power conversion system. High switching frequencies enabled While there is a great need for advanced design and inte- by SiC semiconductors can significantly reduce the size of pas- gration concepts to address thermal management challenges,

44 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 advanced materials and manufacturing processes will play an 6Coey, J.M.D. (2011). Hard Magnetic Materials: A Perspective, important role in the design of thermal management systems. IEEE Transactions on Magnetics, 47, pp. 4671–4681; https://doi. This will require advanced thermal interface materials with org/10.1109/TMAG.2011.2166975 high thermal conductivity. 7Woodworth, A.A., Jansen, R., Duffy, K., Naghipour, P., & Shin, There has been considerable interest in the use of graphene E. (9–11 July 2018). Creating a Multifunctional Composite Sltator Slot as a thermal interface material because of its very high thermal Material System to Enable High Power Density Electrical Machines for conductivity. For thermal management approaches using phase Electrified Aircraft Applications. Presented at AIAA Propulsion and Energy Forum, Cincinnati, Ohio. Retrieved Feb. 25, 2019 from change materials, lightweight, high-heat of fusion materials https://www.researchgate.net/publication/326263549 with desired melting points will be required. 8 There is significant opportunity for additive manufactur- Byerly, K., Ohodnicki, P.R., Moon, S.R., Leary, A.M., Keylin, V., … Bhattacharya, S. (2018). Metal Amorphous Nanocomposite ing to enable innovative heat exchanger designs (e.g., micro- (MANC) Alloy Cores with Spatially Tuned Permeability for Advanced channels) that are not possible via conventional manufac- Power Magnetics Applications, JOM, 70, pp. 879–891; https://doi. turing processes. org/10.1007/s11837-018-2857-5 9Flaherty, N. (7 May 2018). First 3D printed motor leads to startup. Summary Retrieved Feb. 25, 2019 from https://www.eenewspower.com/news/ The market penetration of electrified aircraft is expected first-3d-printed-motor-leads-startup to grow over time—but the timing of introduction of various 10Seal, S. & Mantooth, H.A. (2017). High Performance Silicon classes of electrified aircraft will be a function of technology Carbide Power Packaging – Past Trends, Present Practices, and Future readiness and economic viability. Direction, Energies, 10(3), 341; https://doi.org/10.3390/en10030341 Advanced materials will enable the higher power densities 11Buttay, C., Planson, D., Allard, B., Bergogne, D., Bevilacque, P., and energy densities that are required for electric propulsion … Raynaud, C. (2011). State-of-the-art High Temperature Power components. Critical materials include high-electrical conduc- Electronics, Materials Science and Engineering B, 176(4), pp. 283–288; tivity materials, superconducting materials, magnetic materials, https://doi.org/10.1016/j.mseb.2010.10.003 ■ electrically insulating materials with high thermal conductivity, high-voltage insulation materials, high-temperature capacitors, battery materials, and thermal interface materials. Ceramic materials will meet these needs through applications in high-power density superconducting motors, high- temperature capacitors, ASSBs, and as part of the thermal insulation system.

About the author Ajay Misra is deputy director of research and engineering at NASA Glenn Research Center (Cleveland, Ohio). Contact Misra at [email protected].

References 1Uber (6 June 2018). Uber Elevate, eVTOL Vehicle Requirements and Missions [PDF file]. Retrieved Feb. 25, 2019 from https:// s3.amazonaws.com/uber-static/elevate/Summary+Mission+and+Requ irements.pdf 2Warwick, G. (11 Aug. 2017), "Inside the e-VTOL Explosion," Aviation Week and Space Technology. Retrieved Feb. 25, 2019 from https://aviationweek.com/program-management-corner/inside-evtol- explosion#slide-9-field_images-1669451 3Morris, C. (11 Sept. 2017). Flying electric: Both startups and industry giants push ahead with electric airplanes. Retrieved Feb. 25, 2019 from https://chargedevs.com/features/flying-electric-both-startups- and-industry-giants-push-ahead-with-electric-airplanes/ 4Siemens AG. (1 June 2018). Electric flight. Retrieved Feb. 25, 2019 from https://www.siemens.com/press/en/feature/2015/ corporate/2015-03-electromotor.php?content%5b%5d=Corp 5Kane, M. (24 Aug. 2016). Siemens demonstrates electric motor for aircrafts—260 kW, weighing 50 kg. Retrieved Feb. 25, 2019 from https://insideevs.com/siemens-demonstrates-electric-motor-for-aircrafts-260-kw-continuous-output-at-50-kg-weight/

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 45 he continued global increase in air Ttravel requires commercial vehicles to become increasingly more efficient. To minimize fuel consumption and emissions, engines must operate at higher temperatures and higher efficiencies. Therefore, gas turbine hot section materials—specifically materials with lower density and higher temperature capability—are a critical technology. Silicon carbide ceramic matrix composites (CMCs) are a game- changer for gas turbine hot section materials technology because of their excellent high-temperature mechanical properties, oxidation resistance, and light weight. Extensive development of SiC/SiC CMCs has led to fabrication of gas turbine hot section components, such as CMC shrouds, combustor liners, vanes, and blades. SiC/SiC CMCs consist of three major constituents: SiC fiber reinforcement, fiber coating to allow graceful failure, and SiC matrix. CMCs refer to SiC/SiC CMCs throughout the text. Environmental Dense slow-growing silica scale is responsible for the excellent oxidation resistance of CMCs. Volatilization of SiO2 scale by water vapor generated during combustion reactions and the resulting rapid surface recession is the Achilles heel of CMCs because it erodes barrier coatings structural integrity and mechanical strength. Therefore, external barrier coatings, known as environmental barrier coatings (EBCs), have been developed to protect CMCs from surface recession.1,2 enhance perfor- In the late 1990s, the NASA High Speed Civil Transport program developed the first generation of EBCs, represented by a three-layer silicon/mullite/barium-strontium-aluminosilicate (BSAS) coating. Then in the early 2000s, the NASA Ultra-Efficient mance of SiC/SiC Engine Technology program developed the second generation of EBCs based on rare-earth silicates. Extensive laboratory, rig, and engine tests then commercialized these EBCs for CMC components. Extensive detail on first- and second-generation EBCs can be ceramic matrix 1,2 found in published review papers. More than two decades of intense efforts led to the first EBC- coated CMC component—a high-pressure turbine CMC shroud—to composites enter service in LEAP engines in the Airbus A320neo in 2016 and Boeing 737max in 2017 by CFM International (Cincinnati, Ohio), a joint venture between GE Aviation (Evendale, Ohio) and Safran Aircraft (Courcouronnes, France). Today, development of new EBCs with enhanced performance for next-generation gas turbines contin- By Kang N. Lee and Mark van Roode ues at national laboratories, industry, and academia.

Environmental barrier coatings protect the structural integrity Surface recession of CMCs SiC has excellent oxidation resistance due to the formation of and mechanical strength of ceramic matrix composites, a dense, slow-growing surface scale of SiO2, which protects CMCs allowing these revolutionary materials to boost gas turbine against oxidation.3 In combustion environments, however, the pro- engine efficiency. tective SiO2 scale reacts with water vapor, a combustion reaction 4 product, to form volatile products such as Si(OH)4.

SiO2(s) + 2H2O(g) = Si(OH)4(g) (1)

46 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Capsule summary IT’S GETTING HOT IN HERE PROTECTION FROM RECESSION TAKING OFF Gas turbine hot section materials with lower Significant work over the past few decades has Several environmental barrier coating chal- density and higher temperature capability are a helped environmental barrier coatings better lenges remain for the continued success of critical technology to improve engine efficiency. protect the structural integrity and mechanical ceramic matrix composites in next-generation Ceramic matrix composites, protected from strength of ceramic matrix composites. However, gas turbines. However, continued efforts to surface recession by environmental barrier next-generation gas turbines operating at higher improve the materials’ life and temperature coatings, rise to this materials challenge. temperatures and pressures will require ad- capability will lead to the next breakthrough in ditional efforts to mitigate surface recession. engine efficiency.

Due to these two competing reac- nitride) to mitigate contact stress damage line mullite coating with dramatically tions—silica growth and silica volatiliza- and degradation from molten salt cor- improved thermal cycling durability. tion—over time the CMC surface recedes, rosion. Mullite (3Al O ∙2SiO ) was one 2 3 2 First-generation EBCs the component thins, and its mechanical of the most promising candidate coating In the mid-1990s, the NASA High properties degrade. materials because it has a coefficient of Speed Civil Transport program’s discov- NASA Glenn Research Center (GRC) thermal expansion (CTE) close to that of ery of SiO2 recession in water vapor trig- has generated a large amount of SiC SiC and excellent chemical compatibility gered formation of a joint NASA–GE– volatility data in a high-pressure burner with SiC. Pratt & Whitney team to develop new rig. Equations 2 and 3 summarize the In the mid-1980s, Solar Turbines coatings to protect CMCs from water results for rich and lean burn combus- Inc. evaluated various refractory oxides, vapor. This new class of coatings became 5 tion conditions, respectively. including mullite, zircon, alumina, yttria, known as EBCs. 1 Volatility (rich) = 82.5 exp[-159(kJ/ yttria-stabilized zirconia, and hafnia. Mullite is not a viable EBC because it mol)/RT]P1.74v0.69 (2) While these coatings provide a measure recesses fairly quickly due to its relatively of protection against molten salt corro- high SiO activity ( 0.3–0.4).1 Improved 2 ~ Volatility (lean) = 2.04 exp[-108(kJ/ sion, they showed deterioration from mullite, however, became the basis for 1.50 0.50 mol)/RT]P v (3) cracking and debonding. Mullite per- early EBCs. formed best among the evaluated oxides. Volatility is in mg/cm2∙h, T is gas An extensive search identified BSAS A major breakthrough occurred in temperature in Kelvin, P is total pres- (1-xBaO∙xSrO∙Al O ∙2SiO , 0 ≤ x ≤ 1) as the early 1990s, when scientists at NASA 2 3 2 sure in atm, v is gas velocity in m/s, and a promising candidate material.8 It has GRC identified that crystallization of R is the gas constant, 8.314 J/mol∙K. an excellent CTE match with SiC, low amorphous mullite and the accompany- The SiC recession rate (µm/h) can be SiO activity ( 0.1), and a low modulus. ing shrinkage under thermal cycling in 2 ~ obtained by multiplying the volatility in BSAS, however, forms a detrimental conventionally plasma-sprayed mullite equations 2 and 3 by a factor of 3.1. The glassy reaction zone in contact with the were the root cause for poor durabil- projected recession at 5,000 h as a func- CMC due to a eutectic reaction with ity of previous plasma-sprayed mullite tion of gas velocity in a lean burn com- SiO scale. coatings.7 NASA GRC subsequently 2 bustion environment at P = 10 atm and The improved mullite coating was developed a modified plasma spray pro- T = 1,200°C–1,400°C using Equation 3 used as an intermediate coat to elimi- cess that enabled deposition of a crystal- is shown in Figure 1. Several millimeters of CMC recession will rapidly consume CMC components. In 1997, Solar Turbines Inc. (San Diego, Calif.) field-tested a set of CMC combustor liners at an industrial site.6 A CMC liner (~3-mm-thick) tested for 5,000 h lost as much as 80 percent of its thickness at about 1,260°C. Recession rates will be even higher in next-generation gas turbines operating at higher temperatures and pressures. CMCs, therefore, are not viable in gas turbine hot sections without efforts to mitigate recession.

Development of EBCs Credit: Lee; NASA Initial work focused on coating sili- Figure 1. Projected recession at 5,000 h as a function of gas velocity in a lean burn combustion environment at P = 10 atm and T = 1,200°C–1,400°C using Equation 3. con-based monolithics (SiC and silicon

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 47 Environmental barrier coatings enhance performance of SiC/SiC ceramic matrix composites Credit: Lee; JACerS Figure 2. Cross-section of Si/mullite+20 wt% BSAS/BSAS-coated

CMC after 100 one-hour cycles at T = 1,300°C, P(H2O) = 0.9 atm, 8 Ptotal = 1 atm, and v = 10 cm/s. nate chemical incompatibility. Adding approximately 20 wt% BSAS to the mullite intermediate coat significantly improved thermal cycling durability. Another key improvement was the identification of silicon as a bond coat. This first-generation EBC can be represented as silicon/ mullite+BSAS/BSAS. Figure 2 shows a micrograph of this first- generation EBC after a 100 one-hour cycle tests at 1,300°C Credit: Lee; JECerS

(2,372°F), P(H2O) = 0.9 atm, Ptotal = 1 atm, and v = 10 cm/s. These EBCs were deposited using air plasma spraying. Figure 3. Volatility of BSAS and RE silicates at T = 1,500°C, P(H O) = 0.5 atm, and P = 1 atm.9 Second-generation EBCs 2 total NASA initiated research in 1999 under the Ultra-Efficient Engine Technology program to develop EBCs with higher temperature capability than first-generation EBCs. Its goals for EBC–CMC interface and EBC surface temperatures were 1,316°C (2,400°F) and 1,482°C (2,700°F), respectively. Research identified classes of rare-earth silicates with the general formula RE2SiO5 (monosilicates) and RE2Si2O7 (disilicates) as promising candidates,9 with RE elements such as yttrium, ytterbium, scandium, or lutetium. Key attributes include low SiO2 volatility in water vapor, high melting points, and close CTE match with CMCs. Figure 3 shows the experimentally measured volatility of BSAS, RE disilicates, and RE monosilicates at T = 1,500°C, P(H O) = 0.5 atm, and P = 1 atm. RE monosilicates are sig- Credit: Lee; JECerS 2 total Figure 4. Cross-section of silicon/mullite/Yb SiO -coated CMC nificantly less volatile than RE disilicates and BSAS, while the 2 5 after 1,000 one-hour cycles at T = 1,380°C, P(H2O) = 0.9 atm, volatility of RE disilicates is similar to that of BSAS. P = 1 atm, and v = 10 cm/s.9 Figure 4 shows a cross-section of a three-layer silicon/ total Environmental durability of EBCs mullite/Yb2SiO5-coated CMC after a 1,000 one-hour cycle test at T = 1,380°C (2,516°F), P(H O) = 0.9 atm, P = 2 total Recession 1 atm, and v = 10 cm/s. The EBC maintained excellent Silicate EBC volatility scales with the SiO activity of silicates. adherence and crack resistance. 2 The SiO2 activity of monosilicates is about two orders of mag- A second-generation EBC-coated CMC vane was tested in 10 nitude lower than the SiO2 activity of disilicates. This explains a NASA high pressure burner rig (~1,260°C–1,316°C, 102 the superior stability of RE monosilicates compared to RE disili- total cycles with 2-min cycles, 5 total test hours, P = 6 atm, total cates (Figure 3). RE silicates volatilize in water vapor according v = 24m/s) next to two superalloy vanes for comparison. The to the following reactions. EBC remained intact, while the superalloy vanes and holder RE Si O + 2H O (g) à RE SiO + Si(OH) (g) (4) suffered significant damage (Figure 5). 2 2 7 2 2 5 4

RE2SiO5 + 2H2O (g) à RE2O3 + Si(OH)4 (g) (5)

48 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Credit: Lee; NASA Figure 5. Second generation EBC-coated CMC vane compared to a superalloy vane after completing a NASA high-pressure burner rig test ( 1,260°C–1,316°C, 102 total cycles with 2-min Credit: Corman; U.S. Department of Energy ~ Figure 6. EBC-coated GE CMC shroud and sections.23 cycles, 5 total test hours, Ptotal = 6 atm, v = 24m/s). RE disilicate and RE monosilicate coatings have similar bond coat/ceramic Gas turbine original equipment transform to RE monosilicate and RE coat architecture. Sources for strain manufacturers have generated valuable oxide, respectively. Recession studies of energy in EBCs include growth stress data since the late 1990s on the per- RE disilicates in high-velocity–high-steam due to approximately 2.2-fold volume formance of EBCs in their equipment. rig tests confirm the formation of a RE expansion during oxidation of silicon to Published assessments are available 11,12 monosilicate surface layer. Among SiO2 TGO, thermal stresses due to CTE from field testing conducted under current silicate topcoats, RE monosili- mismatch between SiO2 TGO (10.3 x government-funded programs led by –6 –6 cates are the most recession-resistant. 10 /°C) and CMC (~4–5 x 10 /°C), Solar Turbines Inc. during 1997–2007 However, RE monosilicates have higher and stresses due to β to α cristobalite and from rig and field testing of a gov-

CTEs than CMCs and therefore are SiO2 TGO phase transformation at ernment-funded program led by General prone to crack in thermal cycling. about 200°C, which is accompanied by Electric Co. during 2000–2010. RE oxides and thermal barrier coat- about 5 percent volume reduction.14 Previous reports detail the Solar ings such as zirconia and hafnia are 6,19–21 Calcium-magnesium-aluminosilicate Turbines work. These tests involved very stable in water vapor, making them (CMAS) more than 88,974 h of engine field promising candidates as recession barri- Degradation by CMAS is a glass ceil- testing with CMC combustor liners on ers. These materials, however, have over ing to the upper use temperature of Centaur 50S industrial gas turbines at 2-fold higher CTE than CMCs, so ther- current TBCs, with the same challenge three customer sites. A total of 83,010 h mal stresses must be mitigated before to EBCs. CMAS deposits form when of these engine tests were conducted they can function as recession barriers. air-breathing turbine engines ingest par- with EBC-coated CMC components. Oxidation ticulates such as sand, volcanic ash, and Two government contractor reports 22,23 Water vapor is the primary oxidant for other siliceous debris. Ingested particu- detail the GE work. These tests were silicon or SiC in H O + O environments lates can cause several issues. shorter and included 6,903 h of engine 2 2 tests of EBC-coated CMC first-stage inner because the permeability of H2O in SiO2 At temperatures above about 1,230°C scale is about 10-times higher than that of (2,246°F), CMAS melts and adheres shrouds on two GE 7FA utility engines. oxygen.13 In first- and second-generation to hot section components, resulting GE EBC-coated CMC shroud test

EBCs, H2O permeates through the ceram- in undesirable chemical reactions with The GE engine shroud tests were ic coat and reacts with the silicon bond EBCs. Additionally, molten CMAS accompanied by rig testing, which coat, forming a layer of SiO2 scale known can infiltrate porous EBCs, leading to explored ways to elucidate degradation as thermally grown oxide (TGO) at the undesired stresses. Both chemical and mechanisms and improve component silicon–ceramic coat interface. mechanical interactions are detrimental design. The temperature on the shroud Identified in laboratory tests and con- to EBCs, ultimately leading to crack- surface was about 1,200°C (2,192°F). firmed in rig and engine tests, spallation ing and spallation. Current research The first engine test was for a total of due to TGO growth is one of the most shows that first- and second-generation 5,366 h with 14 start–stop cycles. frequently observed EBC failure modes. EBCs do not afford adequate protection Shrouds were fabricated from GE’s Laboratory steam oxidation tests show against CMAS attack under simulated proprietary HiPerComp melt-infiltrated that EBCs fail at or near the TGO when aircraft engine conditions.15–18 CMC with two fabrication routes, pre- it reaches a critical thickness.14 TBCs preg and slurry-cast. Slurry-cast CMC based on zirconia also typically fail at or EBC field testing was also supplied by BF Goodrich near the TGO, which is attributed to the Laboratory and rig testing can rapidly (Charlotte, N.C.). A total of nine CMC strain energy resulting from CTE mis- evaluate candidate EBC compositions shrouds—six prepreg and three slurry-cast match between the TGO and substrate. and performance. Field testing comple- CMCs—replaced nine out of 96 metallic The strain energy-induced TBC fail- ments and expands these results with shrouds in this “rainbow” field test. ure mechanism is likely applicable to data collected over longer durations and The EBC was mostly first-generation EBC failure as well, considering the two under typical service conditions. three-layer silicon/mullite+BSAS/BSAS.

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 49 Environmental barrier coatings enhance performance of SiC/SiC ceramic matrix composites Credit: Corman; U.S. Department of Energy

Credit: U.S. Department of Energy Figure 8. Micrographs of the edge of a GE prepreg CMC shroud Figure 7. EBC-coated Solar Turbines CMC liner set.19 showing progression of EBC damage along hot gas path edges in the 5,366h “rainbow” engine test.23 The EBC was deposited by air plasma CMCs were fab- spraying at GE. Figure 6 shows an EBC- ricated by chemical coated CMC shroud and sections. The vapor infiltration or EBC was applied both to the gas path melt infiltration and surface and backside. The part is similar to were supplied by BF shrouds used in engine testing. Goodrich Aerospace The second engine test was for a total and DuPont Lanxide of 1,537 h with 497 start–stop cycles Composites Inc. and was carried out with a full set of 96 The latter eventually CMC shrouds. Only prepreg melt-infil- became GE Ceramic trated CMC shrouds were used because Composites Products Credit: Corman; U.S. Department of Energy Figure 9. Micrographs of the 5,366-h GE “rainbow” test of degradation of slurry-cast CMC LLC after going shrouds. Top shows CMC recession at the EBC spall location on shrouds in the first engine test. through several own- a prepreg shroud. Bottom shows CMC recession under an EBC That first engine test had a significant ership changes. CMC tooling bump pit on a slurry-cast shroud.23 blade tip gap to avoid blade tip rub. This liners were about gap was reduced in the second test to 3–4 mm thick and Degradation of EBCs in field test improve performance by adding a thick usually had a dense CVD SiC seal coat Bond coat oxidation and spallation abradable EBC top layer. In addition to (125–500 µm thick). Pratt & Whitney/ Oxidation of the silicon bond coat was three-layer silicon/mullite+BSAS/BSAS United Technologies Research Center mostly responsible for progressive degrada- EBC, some shrouds also had coatings and its EBC supplier applied the EBCs. tion of EBCs. The strain energy-induced that incorporated RE silicates. The outer Figure 7 shows the EBC-coated CMC EBC failure mechanism due to TGO was abradable EBC was made by spraying liner set. The outer liner was coated with discussed previously. Water vapor perme- additional ridges of BSAS on top of the a silicon/mullite+BSAS/BSAS EBC. ates through the ceramic coat and reacts layered EBC using two spray patterns, a EBCs were approximately 125 µm thick. with the silicon bond coat, forming a layer ridge pattern and cross-hatch pattern. EBCs increased the CMC liner life from of SiO2 TGO. Cracks in the EBC, formed Solar Turbines EBC-coated CMC com- about 5,000 h to 12,000–15,000 h. Melt- either during processing or during service, bustor liner test infiltrated liners performed better than accelerate TGO growth by providing fast The combustor liners in the Solar chemical vapor-infiltrated liners and were pathways for water vapor. Turbines engine tests are concentric cyl- therefore mostly used in the latter phases The first-generation EBC-coated inders connected to cones in the aft posi- of field testing. CMC combustor liner after 15,144 h of tion. In this test, CMC liners with mini- Testing showed that the silicon/ engine testing by Solar Turbines devel- mal backside cooling were used to replace mullite+BSAS/BSAS EBC was superior to oped horizontal cracks along the (mull- silicon/mullite/BSAS EBC. The test was metallic liners. Diameter of the outer liner ite + BSAS)–SiO2 TGO interface and was 76 cm, and diameter of the inner liner halted after 13,937 h and 61 start–stops through the silicon bond coat, followed was 36 cm. Both liners were 20 cm long. because borescope inspection revealed by debonding and spallation of EBC. The highest temperature on the surface of a small hole in the inner liner. Over 10 Figure 8 shows micrographs of the an uncoated CMC combustor liner was years, field testing accumulated more than edge of a GE prepreg CMC shroud, 88,974 h of CMC exposure, including demonstrating progression of EBC about 1,260°C (2,300°F). The P(H2O) in the combustor section was about 1 atm. 83,010 h with EBC-coated CMCs. damage along hot gas path edges in the

50 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 Credit: Lee; NASA Credit: Lee; JACerS

Figure 10. Cross-section of silicon/Yb2Si2O7 and silicon/Yb2Si2O7 Figure 11. Slurry EBC-coated NASA CMC airfoil after 15 total test +4.66 wt% YAG +1.39 wt% mullite EBCs on CMC after hours–150 total cycles at 1,371°C–1,482°C in Pratt & Whitley

1,000 one-hour cycles at T = 1,316°C, P(H2O) = 0.9 atm, combustion rig test (5 total test hours–50 total cycles at 1,371°C 14 Ptotal = 1 atm, and v = 10 cm/s. followed by 5 total test hours–50 total cycles at 1,427°C and 5 total test hours–50 total cycles at 1,482°C, P(H O) 0.82 atm, 2 ~ 5,366 h “rainbow” engine test. Initially, test. While visually P 8.2 atm, v 116 m/s, and delta T across EBC+CMC = total ~ ~ formation of TGO on the silicon bond intact, nondestruc- 200–300°F ). coat led to cracks in the EBC top layers, tive evaluation of One recent study illustrates an as shown in the upper left micrograph. as-fabricated liners suggests possible example of improved EBC oxidation life Ingress of water vapor along these cracks debonding near the edge. by reducing SiO TGO growth rates.14 enhanced oxidation of the bond coat 2 Water vapor recession is another Addition of Al O or oxide compounds, laterally from the crack position, forming 2 3 life-limiting factor, especially over the such as mullite and YAG (Y Al O ), to additional EBC cracks around the cor- 3 5 12 long service lives of gas turbines in com- modify plasma-sprayed second-generation ners. Eventually bond coat oxidation was mercial applications. Severe recession EBC (silicon/Yb Si O ) reduced SiO severe enough to liberate entire pieces of 2 2 7 2 was observed after the 13,937-h Solar TGO thickness by about 80 percent EBC along the corners. Most other spalls Turbines field test, with some areas los- compared to baseline silicon/Yb Si O noted on the hot gas path face progressed 2 2 7 ing most of the BSAS top layer. EBC after 1000 one-hour cycles at from these edge spalls or from other coat- 1,316°C in steam oxidation. ing defects, such as pinholes. Challenges for next-generation Figure 10 compares the EBC Formation of pinholes EBCs cross-section of Si/Yb Si O and Si/ Development of next-generation 2 2 7 Figure 9 shows micrographs of pin- Yb2Si2O7+4.66 wt% YAG+1.39 wt% sized hole defects observed in two GE EBCs focuses on improving EBC life mullite EBCs after 1,000 one-hour cycles shrouds after the 5,366-h “rainbow” test. and temperature capability. Oxidation at T = 1,316°C, P(H O) = 0.9 atm, is a key EBC failure mode in both labo- 2 The CMC surface under the EBC had Ptotal = 1 atm, and v = 10 cm/s. The recessions of about 0.8–0.9 mm, which ratory and engine tests. The upper tem- reduced TGO growth rates translate to is within the 0.5–1.1 mm range predict- perature of current EBCs at the EBC– approximately 20-fold improvement in ed by the NASA volatility model.5 CMC interface is limited by the melting EBC life. The TGO may have become Holes in the EBC were mostly associ- point of silicon (1,414°C/2,577°F). The less permeable to H O because the oxide upper temperature of first-generation 2 ated with tooling bumps on slurry-cast additives modified the SiO2 network shrouds, but prepreg shrouds also had EBCs at the EBC–CMC interface is structure.14 Further studies are underway limited by the BSAS-SiO eutectic tem- a smaller number of small holes in the 2 to understand the oxidation mechanism EBC. There was undercutting of the perature (1,310°C/2,390°F). The upper of modified EBCs. temperature of current silicate EBC EBC coating due to recession of the CMAS resistance CMC. While the EBC is relatively stable topcoats is limited by EBC–environ- CMAS-resistant EBC research focuses in the combustion gas environment, deg- ment interactions, such as H2O reces- on a multilayer coating architecture, radation proceeds rapidly when the EBC sion and CMAS degradation. where a top layer arrests CMAS penetra- is breached. Occurrence of these pin- Oxidation resistance tion at or near the surface and underly- holes was reason to eliminate slurry-cast A logical approach to improve EBC ing layers provide protection from oxida- CMC shrouds in the second engine test. oxidation life is to reduce TGO growth tion. At present, gadolinium zirconate rates. TGO growth rates can be reduced Edge defects and recession (Gd2Zr2O7), which was designed for use Defects may arise in EBCs at the com- by minimizing the permeability of oxi- as a TBC layer, has shown promise to ponent edges. These defects may origi- dants through the coating and/or TGO. arrest CMAS infiltration. nate in the coating deposition process or In TBC-coated superalloys, TBC life has Understanding the effect of CMAS occur during service. Borescope inspec- been significantly improved by reducing composition as well as trace oxides in Al O TGO growth rates on the bond tion revealed edge spalls at the shroud 2 3 volcanic ash or regional sand on crystal- edges (hot gas path, leading edge and coat by adding reactive elements, such lization, viscosity, thermal and mechanical as Y, Zr, and Hf, in the Al O -forming trailing edge flanges) during the 1,537-h 2 3 properties, chemical reactivity with EBCs, test. Edge effects also led to larger spalls bond coat. These additives reduce diffu- etc. is important to develop strategies to sivity of oxygen through Al O TGO. after the Solar Turbines 13,937-h engine 2 3 mitigate CMAS. Advanced EBC technol-

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 51 Environmental barrier coatings enhance performance of SiC/SiC ceramic matrix composites ogies via new compositions, architectures, The next breakthrough 5R.C. Robinson, J.L. Smialek, “SiC recession and modeling are expected to provide the CMCs hold tremendous promise caused by SiO2 scale volatility under combus- tools needed to protect next-generation to provide the materials technology tion conditions: I. Experimental results and CMC components from CMAS. required for the next breakthrough empirical model,” J. Am. Ceram. Soc. 82(7), in gas turbines. EBCs are an enabling 1817–1825 (1999). Temperature capability 6 technology for CMCs in the gas turbine M. van Roode, J.R. Price, J. Kimmel, N. The temperature capability goal Mariela, D. Leroux, A. Fahme, K. Smith, for next-generation CMCs is 1,482°C hot section. Following the first entry into service of the EBC-coated high- “Ceramic matrix composite combustor liners: (2,700°F). This requires a new class of a summary of field evaluations. ASME Paper pressure turbine CMC shroud in 2016, EBC bond coats with 1,482°C tempera- GT2005-68420. ASME TURBO EXPO, ture capability. New bond coats will likely additional high-pressure turbine CMC Power for Land, Sea & Air, Reno/Tahoe, be based on ceramics because no metallic components, such as combustor liners, NV, USA, June 6-9, 2005,” Transactions bond coats are likely viable at 1,482°C. vanes, and blades, are scheduled to enter of the ASME, J. Eng. Gas Turbines & Power 129(1), 21–30 (2007). NASA GRC recently developed an into service in the near future. Several EBC challenges still remain for 7K.N. Lee, R.A. Miller, N.S. Jacobson, “New EBC with an Yb2Si2O7-based bond coat using a slurry process. Slurry EBC-coated continued successful CMC implementa- generation of plasma-sprayed mullite coatings on silicon-carbide,” J. Am. Ceram. Soc. 78(3), CMC coupons demonstrated 500 one- tion in next-generation gas turbines. These 705–710 (1995). hour cycle durability at 1,427°C (2,600°F) challenges include oxidation resistance, 8 in steam oxidation tests, and a slurry CMAS resistance, recession resistance, and K.N. Lee, D.S. Fox, J.I. Eldridge, D. Zhu, R.C. Robinson, N.P. Bansal, et al, “Upper EBC-coated CMC airfoil demonstrated temperature capability. Other challenges temperature limit of environmental barrier 15 h–150 cycle durability at 1,371°C– also should not be overlooked, including thermo-mechanical stability, erosion resis- coatings based on mullite and BSAS,” J. Am. 1,482°C (2,500°F–2,700°F) in a Pratt & Ceram. Soc. 86(8), 1299–1306 (2003). Whitley combustion rig test (5 total test tance, and foreign object damage. 9K.N. Lee, D.S. Fox, N.P. Bansal, “Rare earth hours–50 total cycles at 1,371°C, followed Robust EBC life models and relevant testing capabilities to validate the silicate environmental barrier coatings for by 5 total test hours–50 total cycles at SiC/SiC composites and Si N ceramics,” J. 1,427°C and 5 total test hours–50 total life models must be developed as well. 3 4 Continued collaborations between Eur. Ceram. Soc. 25, 1705–1715 (2005). cycles at 1,482°C, P(H O) 0.82 atm, 10 2 ~ N.S. Jacobson, “Silica activity measurements P 8.2 atm, v 116 m/s, and delta T government laboratories, industry, and total ~ ~ in the Y O –SiO system and applications to across EBC+CMC = 100–150°C). academia are paramount to successfully 2 3 2 address these challenges. modeling of coating volatility,” J. Am. Ceram. Figure 11 shows the post-combustion Soc. 97, 1959–1965 (2014). rig test NASA CMC airfoil (3” x 3”) 11 About the authors M. Fritsch, H. Klemm, “The water vapor sandwiched between two CMC spacers hot gas corrosion behavior of Al O -Y O Kang N. Lee is a senior research materi- 2 3 2 3 (3” x 1”) coated with the same EBC. The materials, Y SiO and Y Al O -coated alu- als engineer in the Environmental Effects 2 5 3 5 12 spacers filled the gap between the airfoil mina in a combustion environment,” The and inner wall of the test section. After a and Coatings Branch of the NASA Glenn 30th Int. Conf. & Exp. On Adv. Ceram. & total of about 50 h–500 cycle exposures Research Center Materials & Structures Composites. Cocoa Beach, Fla; January 2006. Division (Cleveland, Ohio). Mark van at 1,371°C–1,482°C, the CMC spac- 12E.J. Opila, unpublished research, University ers were mostly intact, while the CMC Roode is the Principal at Mark van Roode of Virginia. & Associates (San Diego, California). airfoil had limited spallation along the 13B.E. Deal, A.S. Grove, “General relation- Contact Lee at [email protected]. leading edge, with spallation mostly at ship for the thermal oxidation of silicon,” J. the bond coat–topcoat interface. Appl. Phys. 36(12), 3770–3778 (1965). References 14 These results demonstrate the poten- K.N. Lee, “Yb2Si2O7 environmental barrier tial for oxide-based bond coats to meet 1K.N. Lee, H. Fritze, Y. Ogura, Progress in coatings with reduced bond coat oxidation the higher temperature requirements of Ceramic Gas Turbine Development, Vol. 2. rates via chemical modifications for long next-generation EBCs. The surface tem- Edited by M. van Roode, M. Ferber, D.W. life,” J. Am. Ceram. Soc. 102(3), 1507–1521 Richerson. ASME Press; New York, NY. pp. (2019). perature goal of next-generation EBCs is 641–664 (2003). 1,650°C (3,000°F). Water vapor recession 15K. Grant, S. Kramer, J. Lofvander, C. 2 and CMAS degradation are key chal- K.N. Lee, “Environmental barrier coatings Levi, “CMAS degradation of environmental for CMCs,” In Ceramic Matrix Composites. lenges to achieve this goal. Recession- and barrier coatings,” Surf. Coat. Technol. 202, Edited by N.P. Bansal, J. Lamon. Wiley; New 653–657 (2007). CMAS-resistant compositions capable York, NY. pp. 430–451 (2015). of 1,650°C must be incorporated in the 16K. Grant, S. Kramer, G. Seward, C. Levi, 3N.S. Jacobson, “Corrosion of silicon-based EBC topcoat, which will require a careful “Calcium-magnesium-silicate interaction ceramics in combustion environments,” J. with yttrium monosilicate environmental balancing act among various durabil- Am. Ceram. Soc. 76(1), 3–28 (1993). barrier coatings,” J. Am. Ceram. Soc. 93(10), ity requirements, including recession, 4E.J. Opila, R. Hann, “Paralinear oxidation 3504–3511 (2010). CMAS, and thermal stresses. of CVD SiC in water vapor,” J. Am. Ceram. 17B.J. Harder, J. Ramirez-Rico, J.D. Almer, Soc. 80(1), 197–205 (1997). K.N. Lee, K.T. Faber, “Chemical and

52 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 mechanical consequences of environmental barrier coating exposure to calcium-magnesium-aluminosilicate,” J. Am. Ceram. Soc. 94(S1), S178–S185 (2011). 18F. Stolzenburg, M.T. Johnson, K.N. Lee, N.S. Jacobson, K.T. Faber, “The interaction of calcium-magnesium-aluminum-silicate with ytterbium silicate environmental barrier materials,” Surf. Coat. Technol. 284, 44–50 (2015). 19“Ceramic Stationary Gas Turbine Development. Final Report Phase III. October 1, 1996–September 30, 2001.” U.S. Department of Energy Contract DE-AC02-92CE40960, September 30, 2003. 20J. Kimmel, E. Sun, G.D. Linsey, K. More, P. Tortorelli, J. Price, “The evaluation of CFCC liners after field testing in a gas turbine IV,” ASME paper GT2003-38920, ASME Turbo Expo, Power for Land, Sea & Air; Atlanta, Ga., USA, June 16–19, 2003. 21“Advanced Materials for Mercury 50 Gas Turbine Combustion System. Final Report, Solar Turbines Incorporated.” DOE Contract Number DE-FC26-00CH11049, May 28, 2009. 22G.S. Corman, K.L. Luthra, “Melt Infiltrated Ceramic Composites (HIPERCOMP®) for Gas Turbine Engine Applications. Continuous Fiber Ceramic Composites Program, Phase II Final Report, for the Period May 1994–September 2005.” U.S. Department of Energy Contract DE-FC26-92CE41000, January 2006. 23G.S. Corman, “Melt Infiltrated Ceramic Matrix Composites for Shrouds and Combustor Liners of Advanced Industrial Gas Turbines. Advanced Materials for Advanced Industrial Gas Turbines (AMAIGT) Program Final Report.” U.S. Department of Energy Cooperative Agreement DE-FC26-00CH11047, December 2010. n

Save the date! www.ceramics.org/cements2019

10TH ADVANCES IN CEMENT-BASED MATERIALS June 16 – June 18, 2019 Unierity of inoi at UranaCampaign Campaign L USA

Technical program Additie anfatring Uing Cementitio eoogy and Adane in SCC ateria Smart ateria and Senor Cement Cemitry roeing and ydration Sppementary and Aternatie Cementitio Comptationa ateria Siene ateria Draiity and SerieLife odeing Nanotenoogy in Cementitio ateria ateria Carateriation enie Nondetrtie eting

American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 53 I-X Center, Cleveland, Ohio, USA Exhibits and Conference: April 30-May 1, 2019 Welcome Reception (invite only): April 29, 2019

Participating The materials, manufacturing companies include: & components show

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Register for a FREE pass at www.ceramicsexpousa.com I-X Center, Cleveland, Ohio, USA Exhibits and Conference: April 30-May 1, 2019 Welcome Reception (invite only): April 29, 2019

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th 25 International Congress on Glass (ICG2019) Hosted By ACerS Glass & Optical Materials Division

June 9–14, 2019 | Boston Park Plaza Hotel and Towers | Boston, Massachusetts | USA Make your plans now to attend the International Congress on 100 years Glass (ICG) 2019 in Boston, Mass., June 9–14, 2019 and join the ORGANIZATION CHAIRS: expected 1,000 attendees and more than 900 papers and posters ICG 2019 Congress president representing the best and brightest glass science and technology Richard K. Brow minds in the world. Missouri University of Science & Technology Held every three years since the late 1980s, the International [email protected] Congress on Glass provides valuable networking and collabora- tive efforts. ICG 2019 will include: th • Special recognition of the 100 anniversary of GOMD Brow • A strong and vibrant technical program • Sessions organized by ICG Technical Committees ICG 2019 program chair •Student activities including a poster contest John C. Mauro • The Arun K. Varshneya Festschrift The Pennsylvania State University [email protected] Register now for this important glass science and technology meeting. ACerS Glass & Optical Materials Division is the ICG 2019 host. Mauro

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56 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 SCHEDULE AT A GLANCE

Sunday, June 9, 2019 Wednesday, June 12, 2019 ICG Technical Committee meetings 8 a.m. – 6 p.m. Registration 7:30 a.m. – 12:30 p.m. Registration 3 – 6 p.m. Michael Cable Memorial lecture 8 – 9 a.m. Concurrent sessions 9 a.m. – 12:30 p.m. Monday, June 10, 2019 Technology Fair 8:30 a.m. – 12:30 p.m. Registration 7 a.m. – 5 p.m. Free time 12:30 p.m. to end of ICG opening ceremony, awards presentation, 8 – 11:45 a.m. day and plenary session Technology Fair 9:30 a.m. – 8 p.m. Thursday, June 13, 2019 Lunch and GOMD 100th anniversary celebration 11:45 a.m. – 1:20 p.m. Registration 7:30 a.m. – 5 p.m. Concurrent sessions 1:20 – 5 p.m. Concurrent sessions 8 a.m. – 5 p.m. CTC business meeting 2 – 5 p.m. Lunch on own Noon – 1:20 p.m. Welcome reception, poster session (1 of 2) , and 6 – 8 p.m. Dinner banquet 7 – 9:30 p.m. Technology Fair Friday, June 14, 2019 Tuesday, June 11, 2019 Registration 7:30 a.m. – Noon Registration 7:30 a.m. – 5 p.m. Concurrent sessions 8 a.m. –12:30 p.m Concurrent sessions 8 a.m. – 5 p.m. Lunch on own 12:30 – 2 p.m. Lunch on own Noon – 1:20 p.m. Closing ceremony 2 – 3 p.m. Technology Fair 10 a.m. – 7 p.m. ICG Steering Committee meeting 9 a.m. – Noon ICG Council meeting 1 – 4 p.m. Poster session (2 of 2), technology fair, and 5 – 7 p.m. reception

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 57 nd Global Forum on Advanced Materials 2 and Technologies for Sustainable Development (GFMAT-2) REGISTER th International Conference on Innovations NOW 4 in Biomaterials, Biomanufacturing, and Biotechnologies (Bio-4) July 21–26, 2019 | Marriott Downtown at CF Toronto Eaton Centre Hotel, Toronto, Canada

SOLVING SOCIETY’S CHALLENGES GFMAT-2 Plenary BIO-4 Plenary IN TWO IMPORTANT MEETINGS Speakers Speakers Is sustainability integrated into your research? Claude Delmas, Robert M. Pilliar, CNRS research professor emeritus, Are you working on energy-efficient and eco-friend- director at the Faculty of Dentistry ly technologies? Are you studying biomaterials for Bordeaux Institute of and Institute of health-related applications? Condensed-Matter Biomaterials and Chemistry, University Biomedical Engineer- GFMAT-2/Bio-4 brings together researchers and subject Delmas of Bordeaux 1, France Pilliar ing, University of Toronto, Canada matter experts to address the societal challenges of popula- Title: From Volta to tion growth and the opportunities they present for creating Solar Impulse: A battery journey Title: Porous calcium polyphosphates— sustainable solutions for energy and health care applications. Biodegradable bone substitutes and beyond As the population increases, the goal of sustainability becomes more important as we continue to deplete our natu- Mrityunjay Singh, Serena M. Best, ral resources, produce more waste, and discharge additional chief scientist, Ohio professor, Materials toxic emissions into the environment. If you are interested Aerospace Institute, Science, University of in cutting-edge research that addresses these environmen- USA Cambridge, United tal challenges, you will want to attend GFMAT-2. Title: Fourth Industrial Kingdom Revolution and its Title: Optimizing GFMAT-2’s symposia include topics like green manufactur- Singh impact on sustainable Best bioactive scaffolds: ing technologies, energy storage applications, and advanced societal development Cellular response to calcium phosphate ceramics and composites for energy and environmental composition and architecture applications, to name a few.

If you want to hear about the latest advancements and product developments for the health care industry, includ- HOTEL INFORMATION ing orthopedic, dental, and maxillofacial applications; or Marriott Downtown at CF Toronto Eaton Centre Hotel manufacturing technologies, nanomedicine, sensors, and 525 Bay St. Toronto, Ontario, Canada diagnostic devices, plan to attend Bio-4. 1-416-597-9200 Bio-4’s symposia include advanced materials and devices for brain disorder treatments, material needs for medical Group rate from $229 CAD + taxes devices, and nanotechnology in medicine, for example. (currently 16%) based upon availability. Mark your calendar now and plan to attend The cut off is on or before GFMAT-2/Bio-4. June 18, 2019, or until the block sells out.

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58 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3 3RD ANNUAL ENERGY HARVESTING SOCIETY MEETING (EHS 2019) SUBMIT YOUR ABSTRACTS BY SEPTEMBER 4–6, 2019 APRIL 3! Falls Church, Virginia USA www.ceramics.org/ehs19

Energy harvesting has become the key to the future of wireless sensor and actuator networks for a variety of applications including monitoring of temperature, humidity, light, location of persons in the building, chemical/gas sensors, and structural health monitoring.

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Image Credit: Monofrax resources Calendar of events

April 2019 16–18 10th Advances in Cement- August 2019 8–10 Based Materials – University of Illinois 19–23 Imformed Rendezvous – Les at Urbana-Champaign, Champaign, Ill.; Materials Challenges in Jardins du Marais, Paris, France; www.ceramics.org/cements2019 Alternative & Renewable Energy 2019 http://imformed.com/get-imformed/ (MCARE2019) – Lotte Hotel, Jeju forums/imformed-rendezvous 24–27 ACerS Structural Clay Products Island, Republic of Korea; Division & Southwest Section Meeting www.mcare2019.org 22–26 2019 MRS Spring Meeting & in conjunction with the National Brick September 2019 Exhibit – Phoenix, Ariz.; Research Center Meeting – Omni www.mrs.org/spring2019 Severin Hotel, Indianapolis, Ind.; 4–6 3rd Annual Energy Harvesting www.ceramics.org/scpd2019 30–May 1 5th Ceramics Expo – Society Meeting (EHS19) – Falls I-X Center, Cleveland, Ohio; July 2019 Church Marriott Farview Park, Falls www.ceramicsexpousa.com Church, Va.; 10–11 Ceramics UK colocated with www.ceramics.org/ehs2019 May 2019 The Advanced Materials Show – The 13–15 International Centre, Telford, UK; MagForum 2019, Magnesium www.ceramics-uk.com Dates in RED denote new entry in Minerals & Markets Conference – this issue. Occidental Bilbao, Bilbao, Spain; th 21–26 4 Int’l Conference on Entries in BLUE denote ACerS http://imformed.com/get-imformed/ Innovations in Biomaterials, events. forums/magforum-2019 Biomanufacturing, and Biotechnologies denotes meetings that ACerS (Bio-4), combined with the 2nd Global June 2019 cosponsors, endorses, or other- Forum on Advanced Materials wise cooperates in organizing. 9–14 th and Technologies for Sustainable 25 Int’l Congress on Glass – n Ceram a i ic c r S e o m ✯ ✯ ✯ c A i e

e t

y y

Development (GFMAT-2) – Toronto y

h h

T T T Boston Park Plaza Hotel and Towers, T SEAL denotes Corporate partner  ✯ ✯ ✯  F o u 99 Boston, Mass.; Marriott Downtown Eaton Centre nded 18 www.ceramics.org/icg2019 Hotel, Toronto, Canada; www.ceramics.org/gfmat-2-and-bio-4

www.ceramics.org/brick2019 AC��S STRUCTURAL CLAY PRODUCTS DIVISION & SOUTHWEST SECTION MEETING in conjunction with the National Brick Research Center Meeting

June 24 – 27, 2019 Indianapolis, IN USA If you are involved in the structural clay industry— and that includes manufacturing, sales and mar- SAVE THE keting, consultants, and material or equipment suppliers—then join us June 24–27, 2019, at the DATE! Omni Severin Hotel in downtown Indianapolis, Indiana. This is the third year for combined meetings with ACerS Structural Clay Products, its Southwest Section, and the National Brick Research Center.

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American Ceramic Society Bulletin, Vol. 98, No. 3 | www.ceramics.org 63 deciphering the discipline Lavina Backman A regular column offering the student perspective of the next generation of ceramic and glass Guest columnist scientists, organized by the ACerS Presidents Council of Student Advisors.

Ultra-high tempera- My work in the Opila group at UVA is focused on studying ultra-high temperature oxidation of high ture oxidation behavior of HE-UHTCs and, ultimately, developing a framework entropy UHTCs to aid in design of a HE-UHTC optimized for oxidation resistance at tem- Ultra-high temperature ceramics peratures greater than 1,700°C. (UHTCs), most notably refractory metal An important question regarding carbides, nitrides and borides, hold oxidation of high entropy materials is the key to advanced maneuverability whether all components in solid solu- in hypersonic vehicles. UHTCs exhibit tion will oxidize simultaneously, or melting temperatures exceeding 3,000°C, whether selective oxidation will occur. making them appropriate candidates to When a multicomponent material is withstand extreme temperatures experi- exposed to an oxidizing environment, enced by leading edges of aircraft during it is expected that all species in contact hypersonic flight.1 However, UHTCs’ with the environment will initially oxi- propensity to react rapidly with oxygen dize. As the system progresses toward may limit their sustained application. equilibrium, the resulting oxide prod- Credit: Lavina Backman Figure 1. (a) Thin section of an HE-UHTC State-of-the-art UHTCs address this ucts would then be governed by their dogbone specimen, of composition limitation through addition of silicon relative thermodynamic stability and (HfZrTiTaNb)C, tested in 1 percent O2 at carbide, for example, to boride UHTCs, the rate controlling kinetics. Recent 1,700°C for five minutes. The hot zone is to promote formation of a protective work3 showed there can be large differ- outlined by the white dotted line. (b) Plan silica or silicate layer. Unfortunately, the ences in the relative thermodynamic view image of the multiphase oxide scale, highest melting temperature in the boria- stabilities of the formed oxides, suggest- consisting primarily of Group IV elements, silica system is that of silica, which is just ing the possibility that selective oxida- formed in the hot zone. over 1,700°C. Therefore, relying on for- tion will occur in HE-UHTCs—resulting other collaborators will be tested using this mation of silica is not viable above this in depletion of those components from set-up. The understanding of oxidation temperature; the liquid oxide may shear the underlying material. Given that mechanisms gained through these studies 1 off during hypersonic flight. configurational entropy scales with will be used by collaborators in the MURI A new paradigm in UHTC design number of components in solid solu- to optimize the design of an HE-UHTC for has emerged in recent years, following tion, it is therefore critical to under- oxidation resistance and other properties. in the wake of research on high entropy stand the extent to which selective alloys and entropy-stabilized oxides.2 oxidation and component depletion References Multi-principal component UHTCs or occurs in high entropy materials. 1E. Wuchina, E. Opila, M. Opeka, W. Fahrenholtz, high entropy UHTCs (HE-UHTCs) are One of the biggest challenges of and I. Talmy, The Electrochemical Society Interface, 16 [4], solid solutions of four or more refractory studying UHTCs is engineering an pp. 30–36 (2007). metal carbides and borides stabilized by experimental setup for achieving ultra- 2C.M. Rost, E. Sachet, T. Borman, A. Moballegh, E.C. configurational entropy. This approach high temperatures in a laboratory, with- Dickey, D. Hou, J.L. Jones, S. Curtarolo, et al., Nature Communications, 6 (2015). DOI: 10.1038/ncomms9485 has vastly expanded the UHTC compo- out compromising the sample or the 3 sitional palette, creating new opportuni- equipment. I employ a unique resistive L. Backman and E.J. Opila, Journal of the European Ceramic Society, 39 [5], pp. 1796–1802 (2019). DOI: ties in materials design for improved heating experimental setup in the Opila 10.1016/j.jeurceramsoc.2018.11.004 4 oxidation resistance, mechanical, and lab. Test specimens are heated to ultra- 4K. Shugart and E. Opila, Journal of the American thermal properties. high temperatures (at or above 1,700°C) Ceramic Society, 98 [5], pp. 1673–1683 (2015). DOI: I work as part of a Multidisciplinary through Joule heating in a sealed cham- 10.1111/jace.13519 University Research Initiative (MURI) ber, which enables experiments at vari- Lavina Backman is a Ph.D. candidate at funded by the Office of Naval Research ous, controlled pO2 environments. The that seeks to understand HE-UHTCs temperature-controlled region, or hot the University of Virginia, and a Virginia at the fundamental level. Other col- zone, is a small area in the center of the Space Grant Consortium Graduate laborators include groups at University of the specimen, isolated from the rest Research Fellow. She worked as a manufac- of Virginia (UVA), North Carolina of the experimental set-up and contami- turing engineer before returning to gradu- State University, The Pennsylvania nation risks (Figure 1). ate school to pursue a degree in materials State University, Duke University, and Candidate compositions recommend- science. Outside the lab, she loves cooking, University of California, San Diego. ed by the computational work and by reading science fiction, and travelling. n

64 www.ceramics.org | American Ceramic Society Bulletin, Vol. 98, No. 3

yttrium iron garnet glassy carbon photonics fused quartz beamsplitters piezoceramics europium phosphors additive manufacturing III-IV semiconductors ITO 1 1 2 2 H He 1.00794 4.002602 Hydrogen transparent conductive oxides sol-gel process bioimplants Helium YSZ 3 2 4 2 5 2 6 2 7 2 8 2 9 2 10 2 1 2 3 4 5 6 7 8 Li Be B C N O F Ne 6.941 9.012182 10.811 12.0107 14.0067 15.9994 18.9984032 20.1797 zeolites Lithium Beryllium raman substrates barium uoride Boron Carbon Nitrogen Oxygen FluorinenanoNeon ribbons 11 2 12 2 13 2 14 2 15 2 16 2 17 2 18 2 8 8 8 8 8 8 8 8 1 2 3 4 5 6 7 8 Na Mg Al Si P S Cl Ar 22.98976928 24.305 26.9815386 28.0855 30.973762 32.065 35.453 39.948 anode Sodium Magnesium sapphire windows anti-ballistic ceramicsAluminum Silicon Phosphorus Sulfur Chlorine Argon silicates

19 2 20 2 21 2 22 2 23 2 24 2 25 2 26 2 27 2 28 2 29 2 30 2 31 2 32 2 33 2 34 2 35 2 36 2 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 9 10 11 13 13 14 15 16 18 18 18 18 18 18 18 18 K 1 Ca 2 Sc 2 Ti 2 V 2 Cr 1 Mn 2 Fe 2 Co 2 Ni 2 Cu 1 Zn 2 Ga 3 Ge 4 As 5 Se 6 Br 7 Kr 8 39.0983 40.078 44.955912 47.867 50.9415 51.9961 54.938045 55.845 58.933195 58.6934 63.546 65.38 69.723 72.64 74.9216 78.96 79.904 83.798 oxides Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton cermet 37 2 38 2 39 2 40 2 41 2 42 2 43 2 44 2 45 2 46 2 47 2 48 2 49 2 50 2 51 2 52 2 53 2 54 2 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 8 8 9 10 12 13 13 15 16 18 18 18 18 18 18 18 18 18 Rb 1 Sr 2 Y 2 Zr 2 Nb 1 Mo 1 Tc 2 Ru 1 Rh 1 Pd Ag 1 Cd 2 In 3 Sn 4 Sb 5 Te 6 I 7 Xe 8 85.4678 87.62 88.90585 91.224 92.90638 95.96 (98.0) 101.07 102.9055 106.42 107.8682 112.411 114.818 118.71 121.76 127.6 126.90447 131.293 Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

TiCN 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 h-BN 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 8 8 9 10 11 12 13 14 15 17 18 18 18 18 18 18 18 18 Cs 1 Ba 2 La 2 Hf 2 Ta 2 W 2 Re 2 Os 2 Ir 2 Pt 1 Au 1 Hg 2 Tl 3 Pb 4 Bi 5 Po 6 At 7 Rn 8 132.9054 137.327 138.90547 178.48 180.9488 183.84 186.207 190.23 192.217 195.084 196.966569 200.59 204.3833 207.2 208.9804 (209) (210) (222) Cesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon

87 2 88 2 89 2 104 2 105 2 106 2 107 2 108 2 109 2 110 2 111 2 112 2 113 2 114 2 115 2 116 2 117 2 118 2 ZnS 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 InGaAs 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 18 18 18 32 32 32 32 32 32 32 32 32 32 32 32 32 32 32 8 8 9 10 11 12 13 14 15 17 18 18 Nh 18 18 Mc 18 18 Ts 18 Og 18 Fr 1 Ra 2 Ac 2 Rf 2 Db 2 Sg 2 Bh 2 Hs 2 Mt 2 Ds 1 Rg 1 Cn 2 3 Fl 4 5 Lv 6 7 8 (223) (226) (227) (267) (268) (271) (272) (270) (276) (281) (280) (285) (284) (289) (288) (293) (294) (294) Francium Radium Actinium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Si3N4 epitaxial crystal growth cerium oxide polishing powder rutile 58 2 59 2 60 2 61 2 62 2 63 2 64 2 65 2 66 2 67 2 68 2 69 2 70 2 71 2 8 8 8 8 8 8 8 8 8 8 8 8 8 8 18 18 18 18 18 18 18 18 18 18 18 18 18 18 19 21 22 23 24 25 25 27 28 29 30 31 32 32 9 8 8 8 8 8 9 8 8 8 8 8 8 9 Ce 2 Pr 2 Nd 2 Pm 2 Sm 2 Eu 2 Gd 2 Tb 2 Dy 2 Ho 2 Er 2 Tm 2 Yb 2 Lu 2 140.116 140.90765 144.242 (145) 150.36 151.964 157.25 158.92535 162.5 164.93032 167.259 168.93421 173.054 174.9668 quantum dots Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium spintronics 90 2 91 2 92 2 93 2 94 2 95 2 96 2 97 2 98 2 99 2 100 2 101 2 102 2 103 2 8 8 8 8 8 8 8 8 8 8 8 8 8 8 18 18 18 18 18 18 18 18 18 18 18 18 18 18 32 32 32 32 32 32 32 32 32 32 32 32 32 32 18 20 21 22 24 25 25 27 28 29 30 31 32 32 10 9 9 9 8 8 9 8 8 8 8 8 8 8 Th 2 Pa 2 U 2 Np 2 Pu 2 Am 2 Cm 2 Bk 2 Cf 2 Es 2 Fm 2 Md 2 No 2 Lr 3 SiALON 232.03806 231.03588 238.02891 (237) (244) (243) (247) (247) (251) (252) (257) (258) (259) (262) YBCO Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium GDC transparent ceramics chalcogenides nanodispersions perovskites alumina substrates superconductors fuel cell materials laser crystals sputtering targets TM CVD precursors deposition slugs Now Invent. silicon carbide MBE grade materials beta-barium borate scintillation Ce:YAG solar energy The Next Generation of Material Science Catalogs lithium niobate photovoltaics Over 15,000 certi ed high purity laboratory chemicals, metals, & advanced materials and a magnesia state-of-the-art Research Center. Printable GHS-compliant Safety Data Sheets. Thousands of ber optics new products. And much more. All on a secure multi-language "Mobile Responsive” platform. thin lm MgF2 dialectric coatings ultra high purity materials borosilicate glass metamaterials

American Elements opens a world of possibilities so you can Now Invent! superconductors www.americanelements.com indium tin oxide