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bulletin cover story Laser-driven chemical vapor deposition for high-performance and powders

By Shay Harrison and Mark Schaefer

Laser-driven chemical vapor deposition is a remarkably innovative technology that significantly improves the quality of high-performance fibers and powders and broadens the input laser into hundreds of parallel beams, allowing for simultane- ous fabrication of many fibers. This patented opto-mechanical design catalog of compositions available to the materials community. unlocked the potential for the LCVD technology to positively impact a range of material-focused markets, including , jet engines, power , hypersonics, windows, nuclear clad- ding, armor material, and lightweighting of matrix composites for the aircraft and aerospace industry. he company Free Form TFibers (FFF), located in What is LCVD? The fundamental basis of LCVD entails a laser directed at a substrate Saratoga Springs, New York, has spent located in a reaction chamber that also contains a planned mixture of 15 years perfecting the process of precursor gases. The focused laser beam induces a heterogeneous chemi- cal reaction amongst the precursors, leading to a solid deposit forming growth using laser-driven chemical on the substrate. As solid material deposits, the laser or the substrate vapor deposition (LCVD), with par- can be pulled away to continuously form the fiber format. Similarly, ticular expertise and understanding in solid can be formed on the fiber surface using the same LCVD concept in subsequent stages, creating layers of uniform thickness. In fabricating fibers. this manner, LCVD can be viewed as the only gas-to-solid additive man- The integral development at FFF in transitioning ufacturing-based approach to high-value material fabrication. LCVD from a laboratory-scale technique to a scalable LCVD technology is part of a family of chemical vapor deposition manufacturing process was the parallelization of the (CVD) based processes that differ primarily in the energy delivery

38 Celebrating 100 years www..org | American Ceramic Society Bulletin, Vol. 100, No. 7 approach used to drive the gas reaction. The most well-known example is hot wall CVD, employed in micro- electronics chip fabrication, in which the entire volume of a large chamber is SiC uniformly heated to drive deposition of Filament precisely controlled layers on a substrate positioned in the chamber. Similarly, a Laser--Printed Induced Laser number of related techniques use various Plasma energy sources, such as microwaves, heat Filament Array Laser Array lamps, ultraviolet radiation, and plasma Beam enhancement of the hot wall approach, 1 mm to achieve different deposition aims. Most of these microelectronics-focused x15 Mag. 100100 µmµm methods yield deposition rates that range from tens to several hundreds of microns thickness per hour.1,2 PATENTS:PATENTS: In contrast to these techniques, x5 Mag. JPJP Pat.Pat. 63533686353368 EPEP 22 804804 969969 B1B1 LCVD uses a focused laser beam with 250 µm 250 µm CNCN Pat.Pat. ZLZL 20132013 88 0015183.80015183.8 a spot size on the order of 20 microns

USUS 10,047,01510,047,015 B2B2,, 9,938,3939,938,393 B2,B2, 9,896,3859,896,385 B2,B2, 10,876,22710,876,227 B2B2 Credit: Free Form Fibers to deliver the energy required for gas Figure 1. Schematic of the laser-driven chemical vapor deposition process. decomposition. The resulting tempera- ture gradient is on the order of 105 K/m, are essentially impossible using the and developed into commercial SiC fiber whereas CVD is essentially isothermic.3 polymer-based route. Similarly, preci- products by Nippon and Ube. This temperature gradient drives fiber sion control of the fiber diameter offers The use of polymer-based polycarbosi- deposition rates that can range from 30 a flexibility of production not available lanes as a precursor unlocked the prom- to 300 microns per second, with rates in in spinneret-based production. ise of a high-temperature nonoxide com- the millimeter/second range for some As stated previously, a significant posite material system, leading to various material systems such as carbon. technical advance made by FFF in scaling SiC fiber reinforcement products; howev- Because of the CVD “DNA” that is LCVD is the parallelization of the input er, there are material limitations inherent central to LCVD, the range of materials laser beam (Figure 1), which allows for in batch chemical mixing and forming that can be fabricated in fiber format multiple fibers to be grown simultane- and the subsequent thermal processing is broad, based on 70+ years of precur- ously. Fibers are self-seeded. The pull rate of green fibers. A broad array of advanta- sor development for the of the substrate matches the deposition geous features and properties arise from industry, which required delivery of spe- rate of material onto the formed fiber. LCVD-based fabrication of fibers. cific chemical elements to the functional Because material builds from the bottom The most fundamental characteristic, layers needed for chip operation. This up, LCVD is analogous to additive man- particularly evident in SiC fibers, is delivery method provides an essential ufacturing (AM), but the main difference the presence of a gradient microstruc- difference from polymer precursor-based is the capability of LCVD to produce ture across the fiber radius. The center approaches to fiber fabrication, which solid material directly from the gas phase. reveals elongated grains in the direction are limited to polymer chemistries that Also similar to AM, through its efforts of the fiber axis, on the order of 50 nm can be developed to successfully yield to recycle the gas precursors and access long and 10 nm wide. At the mid-radial the targeted final composition. maximum utilization of these raw mate- point, the grains are nominally 5 nm LCVD fiber composition is tailored rial feedstocks, FFF aims to achieve a and equiaxed, transitioning to amor- through the selection of gas precursors waste-less process with any produced by- phous at the fiber edge. This feature and only those desired elements are product gases capable of being employed stands in contrast to the homogeneous, incorporated. Polymer-derived fibers in other applications, such as redirecting invariant microstructure found in the contain unreacted or partially reacted extra generated from the pro- polymer precursor-based SiC fibers. contaminant species, in addition to duction of products for The impact of this inhomogeneous the possible inclusion of metal catalysts use in the H2-based transportation sector. distribution is hypothesized to drive the in some fiber products to drive the tensile and behavior found in the polymer conversion process, that nega- Advantages of LCVD LP30-SC material. For other materials, tively impact the ultimate temperature LCVD technology stands in signifi- understanding and control of the LCVD capability. Precision control of the cant contrast to the chemical conversion process parameters can yield variations fiber composition also allows LCVD processing that was patented in the late in the fabricated microstructure. For to produce complex chemistries that 1970s, known as the Yajima method,4,5 example, fiber has been produced

American Ceramic Society Bulletin, Vol. 100, No. 7 | www.ceramics.org Celebrating 100 years 39 Laser-driven chemical vapor deposition for high-performance fibers and powders

1 mm Credit: Free Form Fibers Figure 2. “Sausage-link” variable diameter LP30-SC fibers.

71:29 composition. The 77:23 The physical characteristics of fibers fiber chemistry, while limited to produced by LCVD also highlight the temperatures below the silicon unique capabilities of the technology. melting temperature of 1,412°C, Electron microscopy at multiple labora- revealed a very high single fiber tories showed a very high cross-sectional tensile strength at room temper- with no evident. This 80 micron diameter fiber ature, on the order of 7–8 GPa. structure obviously drives mechanical 2 1/2" diameter coil This flexibility opens up design performance by limiting the number of considerations for composites in internal crack initiation sites. Precision tailoring the fiber composition control of the laser leads to a range of to the desired property perfor- functional modifications that can be mance by component function embedded into the fiber geometry. The and location. filament diameter can be varied during Related to the fiber composi- growth. Figure 2 illustrates a SiC fiber

Credit: Free Form Fibers tion, the LCVD process yields produced with periodic discontinuous Figure 3. LP30-SC fiber coil. materials without contamination diameter changes. Similarly, the fila- in both amorphous and nanocrystalline of undesired chemical species. ment axis needs not be straight. Lateral states by using different precursor gases. For instance, a LCVD fiber motions of the laser can be tracked Another critical capability of the has only silicon and nitrogen present. (within limits) via fiber growth to create LCVD technology, harnessed through This advantage is crucially important in a curvilinear filament. This feature is years of developed expertise, is the precise reference to , which drives deleteri- illustrated by the coil shown in Figure 3. control of the final of the ous oxidation behavior at high tempera- produced fibers, which reveals itself in tures in a range of ceramic materials. In LCVD products and performance several ways. Focusing on the SiC chem- particular, oxygen contamination impacts FFF has embraced LCVD technology istry, a nominally stoichiometric fiber will the temperature capability range for SiC to deliver state-of-the-art high-perfor- have a composition of 70 weight percent fibers. NGS, the U.S. manufacturer of Hi mance materials in either fiber or pow- silicon and 30 weight percent carbon Nicalon-Type S, presently reports the level der format to the high-tech marketplace, 6 (referred to as 70:30). FFF has produced of residual oxygen at 0.8 wt.%. This oxy- where these products can fill unique fibers in the range from 70:30 to 77:23, gen content remains even after electron gaps critical to furthering material per- a high silicon content fiber, through the beam processing and subsequent thermal formance in a range of applications. finely calibrated introduction and control cycling of the green fibers for chemical An important focus area has been of the constituent gas precursors. A 71:29 conversion of the polymer. silicon carbide (SiC) fibers for the rein- fiber has proven to be the most appropri- Conversely, as-produced LP30-SC fibers forcement phase in SiC-based ceramic ate for 1,500°C applications, through and stoichiometric powder materials have matrix composites (CMCs), in par- high-temperature exposure and creep undergone several evaluation techniques, ticular optimizing the LCVD process testing. Also, the fiber is adaptable to including Auger electron spectroscopy to create a scalable path to fabricating handling and composite fabrication pro- (AES), electron energy loss spectroscopy 1,500°C-capable SiC fibers. The need cessing, demonstrated by its 1/16” bend (EELS), and Leco oxygen analysis. Neither for this demanding thermal capacity is radius. Based on microscopy evaluation of the AES nor EELS revealed detectable driven by the long-desired operational the 71:29 material, the excess silicon pres- oxygen in the cross section of many fiber parameters of turbo machinery in the ent appears to be distributed in the grain samples while the Leco measurements on aviation propulsion field. boundaries throughout the microstruc- powder showed approximately 0.1 wt.%, Crucially, the SiC fiber product ture, as opposed to being concentrated at which is consistent with surface absorp- LP30-SC is an overwhelmingly beta-phase the outer edge of the fiber diameter. tion upon exposure to air. This minimal material, a necessity for high performance The data presented in this article level of oxygen content is an important in thermomechanical applications. LP30- for the FFF LCVD silicon carbide fiber characteristic of the LCVD SiC being a SC underwent several evaluations to material, named LP30-SC, is from the functional 1,500°C material. determine its suitability for the 1,500°C

40 Celebrating 100 years www.ceramics.org | American Ceramic Society Bulletin, Vol. 100, No. 7 A

30 microns B I

I15 microns Credit: Free Form Fibers Figure 4. A) LP30-SC (FFF) SiC fiber before (left) and after (right) flame test exposure. B) HNS SiC fiber before (left) and after (right) flame test exposure. environment. First, a new single fiber tensile testing protocol was released by oxidation of the SiC). This work was done in col- designed in-house to address misalignment issues when testing laboration with Exothermics, Inc. and performed at its facility using paper tabs for attachment to the grips of a mechanical test in Amherst, N.H., in two separate studies. rig.7,8 In using Spectra fishing line and polyacrylate adhesive to • Study one: A glass-ceramic matrix composite produced secure the fiber sample, this evaluation approach revealed ten- with a barium strontium aluminosilicate (BSAS) matrix using sile strengths in the 3 to 6 GPa range. Using the same sample hot pressing at a 1,550°C hold temperature for 30 minutes in attachment procedure, researchers at FFF also devised a single an atmosphere with 10.3 MPa applied load. fiber creep testing method to understand the fundamental high- • Study two: A SiC-zirconium diboride (ZrB2) matrix com- temperature performance behavior of SiC fibers, including com- posite formed by reaction of constituent powders during hot mercial products like Hi-Nicalon Type S (HNS) as well as the pressing at 1,900°C hold temperature for 60 minutes in an LP30-SC.9 The data from this creep rig revealed several interest- argon atmosphere with 30 MPa applied pressure. ing results. Cross-sectional microscopy images from each composite • HNS samples fractured in a brittle manner in testing in coupon fabricated are shown in Figures 5 and 6. Both cases an argon gas environment (with oxygen levels measured at demonstrate that the LP30-SC fiber can successfully endure ~ 0.15% using a residual gas analyzer) with 700 MPa stress the high-temperature processing steps required for compos- applied at 1,500°C, over an approximate range of 75 to 150 ite fabrication. hours exposure time. In an interesting development, subsequent flexural mode • LP30-SC samples survived comparable testing conditions of the BSAS composite sample showed evidence of for 175 hours without failure. fiber pullout and corresponding residual rabbit holes, even • In cyclic testing, LP30-SC fiber went through without the application of an interphase to enable eleven 24-hour exposure cycles after an initial 100-hour cycle fracture toughened behavior. This response is believed to (for a cumulative total of 364 hours at elevated temperature) have arisen because of the relative mismatch of elastic moduli at 1,500°C and 550 MPa applied stress in an open air environ- between the BSAS glass-ceramic matrix (~80 GPa) and the SiC ment, producing a residual creep strain of 0.96%. fiber (~400 GPa). Extreme environment testing on LP30-SC and other SiC The LCVD technology is capable of producing fibers in fiber products (HNS and Sylramic) was conducted using an user-determined lengths, whether on the order of several mil- oxy-acetylene torch. The experimental setup involved tautly limeters or in long, continuous parallel arrays. FFF demonstrat- securing a number of fiber samples across a metal frame, then ed continuous fiber out to 32-foot strands, with typical 50-fiber exposing these samples to the flame tip of the torch while array production at 2 feet. These parallel arrays are appropriate video recording the setup to document the precise time of for two-dimensional CMC tape preforms. fiber failure and thus time span of exposure. Figures 4A and Efforts to grow short fibers are directed to developing a non- 4B show the comparative behavior of the LP30-SC and HNS woven fiber architecture for the CMC reinforcement phase, as through a series of these environmental exposure tests. these fibers would be processed into a veil (analogous to wood Proof-of-concept evaluations demonstrated that the LP30- pulp in paper production) then sectioned into the desired SC fiber could survive high-temperature composite fabrication layer layup shape and size to produce the component design. processing steps without degradation. The aim of this effort Nonwoven architecture is a promising reinforcement design was to determine whether the SiC fiber (employed without an because of the resulting interlayer locking of adjacent veil interphase coating) showed evidence of chemical interaction layers, enhancing the interlaminar shear strength and reduc- with the matrix or reactive breakdown, such as a stream of gas ing the risk of or other deleterious interlayer bubbles emanating from the fiber into the matrix (CO/CO2 boundaries and inhomogeneities. In addition, the simplicity of

American Ceramic Society Bulletin, Vol. 100, No. 7 | www.ceramics.org Celebrating 100 years 41 Laser-driven chemical vapor deposition for high-performance fibers and powders Credit: Free Form Fibers Credit: Free Form Fibers

Figure 5. Cross-section micrograph of BSAS matrix glass-CMC Figure 6. Cross-section micrograph of ZrB2-SiC matrix CMC with with LP30-SC SiC fibers. LP30-SC fibers. manufacturing nonwovens, the lack of damage imparted to the boron compared to carbon can lead to greater than 2X reduc- constituent fibers compared to processes that work with woven tions in overall structural weight. or crushed fiber tows, and efficient matrix introduction pro- A final example of demonstrated fiber material production cessing due to the accessible porosity are important advantages is boron carbide, which revealed an elastic modulus greater for this architecture, all of which contribute to the economic than 600 GPa during evaluation. Protective armor, whether case for short fiber-based veils as a path to make SiC-SiC com- personal or vehicle, is the obvious application for such a boron posites cost competitive. carbide fiber-reinforced system. FFF is partnering with Southeast Nonwovens (Clover, S.C.) An important feature of LCVD technology is the ability to form veil products from the LP30-SC short fibers (Figure 7). to overcoat fibers with the same laser-based processing. CMC These veils are employed in the fabrication of CMC compo- material systems generally require an interphase coating on the nents for property evaluation and thin-wall, composite-based fiber to separate the fiber from the matrix and achieve frac- fuel rod cladding samples for in-pile irradiation exposure and ture toughened mechanical behavior that improves on that of subsequent study. monolithic ceramics. The coating must have a layered structure to promote crack energy dissipation along the length of the Beyond SiC: LCVD of other materials fiber, as opposed to the crack propagating through the fiber.

While SiC is an important area of focus of fiber develop- In SiCfiber-SiCmatrix composites, the two generally agreed upon ment and production at FFF, a range of other materials also interphase materials are boron nitride and carbon. To date, were demonstrated as unique fiber material products. Silicon the application step of the coating layer typically has occurred nitride (Si3N4) fibers were produced in two feet arrays and then on the SiC fiber tow, which leads to incomplete coating cover- included as a reinforcement phase in a boron nitride matrix, age and therefore underperforming toughened mechanical processed to form a composite at Exothermics. Similar to the behavior. With LCVD, each individual fiber, whether in short demonstrations with SiC fiber, the intent was to determine the or long length format, can be fully coated around the entire fiber viability through the aggressive hot-pressing conditions circumference. The thin diameter nature of the LCVD-formed (1,800°C hold temperature for one hour in a nitrogen atmo- fibers allows for essentially instantaneous heat transfer, which sphere with 6.9 MPa applied load). Microscopy revealed that enables homogenous deposition. the Si3N4 successfully survived the fabrication process intact, The key advantage, as with the material agnosticism of the which opens the possibility of composite applications for elec- process, is the simplicity of the processing step required—a tromagnetic windows and radomes. straightforward changeover of the gas precursor environment, Boron fiber also was fabricated at FFF with the aim of pro- from the chemistry required for fiber fabrication to that needed viding a lightweighting replacement for carbon fiber used in for the coating. FFF demonstrated multiple coating materials, structural applications of polymer matrix composites. The cru- including boron nitride, carbon, SiC, and hafnium carbide, cial difference and benefit of the LCVD boron fiber compared as well as multilayer coatings of different materials. The ability to other commercial boron fiber products is that it is core-less, to coat fibers leads to several unique product concepts in the meaning it does not have a dissimilar, heavier material core on nuclear field, such as a fuel-in-fiber multilayer structure with an which the boron material is deposited. A 25-micron diameter active uranium layer akin to TRISO fuel pellets; and embedded fiber contains only boron throughout. In applications where sensors, in which functional layers are added consecutively on a component weight comes at a premium cost, such as aerospace fiber to produce a desired electromagnetic behavior, such and aviation, the higher strength-to-weight ratio of amorphous as is needed for a thermocouple.

42 Celebrating 100 years www.ceramics.org | American Ceramic Society Bulletin, Vol. 100, No. 7 An offshoot of the SiC fiber effort is to of 1,200 beams. A establish the capability to produce high- critical feature and purity, high beta-phase content SiC pow- advantage of these der from the LCVD stoichiometric fiber LCVD production feedstock. The capacity for the LCVD tools is that the technology to yield the kind of clean same equipment can powder with the appropriate beta-phase manufacture any of composition presents a significantly sim- the possible material pler manufacturing path when compared compositions avail- to the multiple processing steps necessary able through the from the traditional Acheson approach extensive catalog of

(or modified reaction driven techniques gas precursors. The Credit: Free Form Fibers using silica and coke-based raw mate- only adjustment to Figure 7. Nonwoven veils produced from LP30-SC short SiC fibers. rial) with subsequent phase conversion be made in making improving on the application perfor- required. The availability of such a high- silicon carbide and then silicon nitride in a mance of established systems. quality powder material will impact the subsequent run, for instance, is to change CMC market, as a matrix filler to reduce the input gas feed to the tool. About the authors residual porosity, and the burgeoning Shay Harrison is the CEO of Free SiC-based high power semiconductor Next-generation technology Form Fibers, formerly senior materials field. FFF is also exploring other technical with LCVD scientist, and has been a member of the areas where the requirements for high- Laser-driven chemical vapor deposi- team since 2012. Mark Schaefer is mate- purity powder are critical and the avail- tion is an innovative, extremely flexible rials scientist at Free Form Fibers since ability is limited, such as materials for the technology that produces materials 2020, having recently completed his microelectronics industry. which will drive significant advance- Ph.D. at Rutgers University. For more In addition to some of the ceramic and ments in high performance fields, in information, please contact Jeff Vervlied, boron materials discussed, other demon- particular in the aerospace composites director of sales and business develop- strated fiber compositions at FFF include and high-power electronics industries. ment, at [email protected]. tungsten carbide and carbon as well as The high-purity products produced by materials of interest in the nuclear fuel the laser-based process and the material References field, such as uranium, uranium carbide, agnostic capability to form nearly limit- 1Zorman, C.A., et al., “Epitaxial growth of and uranium disilicide. This composi- less chemistries, among other important 3C-SiC films on 4 inch diameter (100) silicon tional flexibility is actually even broader advantages, offer a unique opportunity wafers by atmospheric pressure chemical vapor as ‘composite’ fiber chemistries can be to tailor fibers and powders with precise- deposition,” Journal of Applied Physics, vol. 78, pp. formed as bulk mixtures or dopant level ly tuned properties, thereby maximizing 5136–5138, 1995 2 additions to a primary composition.10 As application-specific performance. Otani, M., et al., “Quartz crystal microbalances a demonstration example, FFF fabricated for evaluating gas motion differences between As Free Form Fibers enters the com- dichlorosilane and in ambient SiC fibers with boron additions at dopant mercialization phase, manufacturing hydrogen in a slim vertical cold wall chemical levels and at a 20% constituent precursor materials for system-level evaluations in vapor deposition reactor,” Advances in Chemical gas mixture. This effort, along with similar a range of applications and markets is Engineering and Science, vol. 10, pp. 190–200, 2020 evaluations, was focused on understanding the key next step to bring the capabili- 3Goduguchinta, R., and Pegna, J., “Variational how to enhance high-temperature per- ties of LCVD to bear. For instance, SiC analysis of LCVD rod growth,” Applied Physics A: formance for use in mechanically loaded Materials Science & Processing, vol. A88, no. 1, fiber nonwoven veils for thermome- pp. 191–200, July 2007 applications like blades. Fibers chanical applications of composites, in 4Yajima, S., Hayashi, J., and Omori, M., Chemistry with complex chemistries can be explored particular at use temperatures greater Letters, pp. 931–934, 1975 with LCVD using binary, ternary, and than 1,400°C, are being manufactured 5Yajima, S., Okamura, K., Hayashi, J., and quaternary phase diagrams, among others, and implemented in composite test Omori, M., Journal of the American Ceramic Society, as a foundational scientific basis for dem- articles for benchmarking of mechanical vol. 59, nos. 7–8, pp. 324–327, 1976 onstration of manufacturability. 6 performance. Similarly, Si3N4 materials NGS Advanced Fibers Co.; Toyama, Japan; FFF is entering the commercialization for electromagnetic transparency in high- http://web.archive.org/web/20200217051033/ stage, after extensive research and develop- temperature environments are in evalu- http://ngs-advanced-fibers.com/eng/item/ ment efforts, through scale-up of produc- ation for fiber properties and composite 7Pegna, J. and Goduguchinta, R.K., “Tensile tion capacity by bringing on-line the first component performance. test for high modulus monofilament fiber, full-scale manufacturing tools. One tool, As composites of all matrix types Part 1: Analytical review of the current ASTM Standard,” Special Issue on Mechanical consisting of multiple opto-mechanical find broader use, LCVD will open new, Characterization of Small Scale Specimens for heads each including a laser and reactor previously unavailable fiber reinforced Materials Performance and Characterization, ASTM chamber, can be operated with upwards composite material systems while also (In press)

American Ceramic Society Bulletin, Vol. 100, No. 7 | www.ceramics.org Celebrating 100 years 43 Laser-driven chemical vapor deposition for high-performance fibers and powders

8Pegna, J. and Harrison, S.; “Tensile test for high 9Harrison, S. et al., “High-temperature per- 10US Patent # 9,896,385B2, “Contiguously modulus monofilament fiber, Part 2: A perturba- formance of next-generation silicon carbide blended nano-scaled multi-phase fibers,” by S. tion-free measurement technique,” Special Issue on fibers for CMCs,” Materials Performance and Harrison, J. Pegna, J.L. Schneiter, K. L. Williams, Mechanical Characterization of Small Scale Specimens Characterization. Published ahead of print, and R. Goduguchinta, granted February 2018 100 for Materials Performance and Characterization, 14 April 2021, https://doi.org/10.1520/ ASTM (In press) MPC20200131.

History of Free Form Fibers Free Form Fibers was established in Compositional and end-use 2006 by Joseph Pegna, Ram Godugu- areas of particular focus chinta, and Kirk Williams. Pegna has • Silicon carbide fiber reinforced been active in additive manufacturing ceramic composites for thermal since the late 1980s, with particular management and thermal- emphasis on LCVD in leading research mechanical performance in programs at the University of California, high-temperature aerospace Kirk Williams, company co-founder and senior manager of R&D, Irvine; Rensselear Polytechnic Institute; propulsion, including combustion connects a fiber optic cable to one of the lasers in preparation for a–c running the system to produce LCVD materials. and the University of Montreal. Godu- liners, shrouds, and blades. Credit: Free Form Fibers guchinta (with Pegna as his advisor) and cLongtin, R., Fauteux, C., Carignan, L.-P., Williams both elucidated fundamental • Silicon nitride fiber reinforced ceramic Therriault, D., and Pegna, J., “Laser-assisted syn- understanding of LCVD concepts in their composites for electromagnetic transmis- thesis of carbon nanofibers: from arrays to thin doctoral theses.d–h sion at high operational temperatures in films and coatings,” Surface & Coatings Technology, hypersonic vehicles, such as apertures vol. 202, no. 12, pp. 2661–2669, 15 March 2008 Initially locating FFF in Plattsburgh, N.Y., and antennas. dWilliams, K.L., Köhler, J., and Boman, M., the three built off a rich history of R&D “Fabrication and mechanical characterization of in academia, in particular at the Georgia • Boron fiber reinforced polymer compos- LCVD-deposited carbon microsprings,” Sensors and Actuators, A: Physical, vol. 130–131, pp. 358- Institute of Technology, University of Illinois ites for replacement of carbon in aero- structure applications, including the large 364, 2006 at Champaign-Urbana, University of Texas e surface area of airframes. (The composite Williams, K.L., et al., “Electrothermal feasibil- at Austin, University of Connecticut, Uppsa- ity of carbon microcoil heaters for cold/hot gas la University in Sweden, the Max-Planck- leverages the advantageous strength-to- microthrusters,” Journal of Micromechanics and Institut für Biophysikalische Chemie in weight ratio of a boron-only fiber, with no Microengineering, vol.16, pp.1154–1161, 2006 Göttingen, Germany, and Johannes-Kepler dissimilar heavy metal core.) fStuke, M., et al., “Direct-writing of three-dimen- Universität, in Linz, Austria.i–n • Ultrahigh-temperature fiber materials sional structures using laser-based processes,” MRS Bulletin, vol. 32, no. 1, pp. 32–39, 2007 as the reinforcement phase for multi- Staying true to the adage that develop- gGoduguchinta, R., and Pegna, J., “Variational ing “hardware is hard,” FFF focused on use composites in extreme temperature analysis of LCVD rod growth,” Applied Physics A: perfecting a range of specialized functions environments (greater than 2,000°C) at Materials Science & Processing, vol. A88, no. 1, necessary for the commercial implemen- leading edges of hypersonic vehicles and pp. 191–200, July 2007 tation of LCVD, such as the beam paral- spacecraft. (These fibers are transition hGoduguchinta, R., and Pegna, J., “Position dependence of growth rate in convection lelization, precision gas feed and control, metal based-chemistries, such as lantha- num, niobium, tantalum, and hafnium, in enhanced laser CVD of carbon rods,” Applied and mechanical system design to ensure Physics A: Materials Science & Processing, vol. A88, fiber stability during growth. FFF’s work carbide, diboride, and nitride formulations.) no. 2, pp. 329–332, August 2007 has in part been supported by several • High-purity silicon carbide powder iBoman, M. and Bauerle, D., “Laser-assisted government funding agencies, includ- for component fabrication in the power chemical vapor deposition of boron,” Journal of ing the Department of the Army, DARPA, the Chinese Chemical Society, vol. 42, no. 2, pp. electronics industry. 405–411, 1995 NASA, the National Science Foundation, References jHarrison, S. and Marcus, H.L., Journal of Advanced New York State Energy Research and a Materials, vol. 32, no. 2, pp. 3–8, 2000 Development Agency, and the Department Maxwell, J.L., Pegna, J., DeAngelis, D.A., and Messia, D.V., “Three-dimensional laser chemical kHarrison, S. and Marcus, H.L., Materials and of Energy. vapor deposition of nickel-iron alloys,” Advanced Design, vol. 20, nos. 2–3, p 147–152, 1999 Today, FFF employs 11 members across a Laser Processing of Materials—Fundamentals and lWallenburger, F., Nordine, P., Boman, M.; Applications. MRS (1996) pp. 601–606. range of business and technical functions, “Inorganic fibers and microstructures grown bMaxwell, J.L., Pegna, J., and Messia, D.V., “Real- directly from the vapor phase,” Composites Science and is finishing its first phase of commer- time volumetric growth rate measurements and and Technology, vol. 51, pp. 193–212 cialization, bringing online scaled produc- feedback control of three-dimensional laser chemi- mMi J., Johnson, R., and Lackey, J., Journal of Applied Physics A: Materials tion tools for high-volume manufacturing cal vapor deposition,” the American Ceramic Society, vol. 89, no. 2, pp. Science and Processing of fiber and powder products. , vol. 67, no. 3, pp. 323–329, 519–526, 2006 Sept. 1998 nMi J., Lackey, J., Journal of Materials Processing Technology, vol. 209, pp. 3818–3829, 2009 100

44 Celebrating 100 years www.ceramics.org | American Ceramic Society Bulletin, Vol. 100, No. 7