Rocky MOUNTAIN REGIONAL VIRTUAL MEETING 2020 PROGRAM
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Superhard and Superconducting B6C
Superhard and Superconducting B6C Kang Xia a, Mengdong Ma b, Cong Liu a, Hao Gao a, Qun Chen a, Julong He b, Jian Sun a,*, Hui-Tian Wang a, Yongjun Tian b, and Dingyu Xing a a National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093, China b State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China ABSTRACT Crystal structure searching and ab initio calculations have been used here to explore low-energy structures of boron carbides under high pressure. Under pressures of 85–110 GPa, a metastable B6C with R3 m symmetry is found to be energetically more stable than the mixture of previous B4C and elemental boron. This B6C is a rhombohedral structure and contains mooncake-like B24 clusters with stuffing of C2 pairs. The mechanical and dynamical stabilities of this structure at ambient pressure are confirmed by its elastic constants and phonon dispersions. The bulk modulus and shear modulus of this newly predicted B6C at ambient pressure reach high values of 291 GPa and 272 GPa, respectively. The Vickers hardness is calculated to be around 48 GPa, and its melting temperature at ambient pressure is estimated to be around 2500 K, indicating that this metastable B6C is a potential superhard material with very good thermal stability. Interestingly, this superhard B6C structure is also found to be superconducting and its superconducting critical temperature (Tc) is evaluated to be around 12.5 K at ambient pressure by electron-phonon coupling. * Corresponding author. E-mail address: [email protected] 1. -
Edward M. Eyring
The Chemistry Department 1946-2000 Written by: Edward M. Eyring Assisted by: April K. Heiselt & Kelly Erickson Henry Eyring and the Birth of a Graduate Program In January 1946, Dr. A. Ray Olpin, a physicist, took command of the University of Utah. He recruited a number of senior people to his administration who also became faculty members in various academic departments. Two of these administrators were chemists: Henry Eyring, a professor at Princeton University, and Carl J. Christensen, a research scientist at Bell Laboratories. In the year 2000, the Chemistry Department attempts to hire a distinguished senior faculty member by inviting him or her to teach a short course for several weeks as a visiting professor. The distinguished visitor gets the opportunity to become acquainted with the department and some of the aspects of Utah (skiing, national parks, geodes, etc.) and the faculty discover whether the visitor is someone they can live with. The hiring of Henry Eyring did not fit this mold because he was sought first and foremost to beef up the graduate program for the entire University rather than just to be a faculty member in the Chemistry Department. Had the Chemistry Department refused to accept Henry Eyring as a full professor, he probably would have been accepted by the Metallurgy Department, where he had a courtesy faculty appointment for many years. Sometime in early 1946, President Olpin visited Princeton, NJ, and offered Henry a position as the Dean of the Graduate School at the University of Utah. Henry was in his scientific heyday having published two influential textbooks (Samuel Glasstone, Keith J. -
Tribute to Josef Michl
Editorial Editorial TributeTribute to JosefJosef Michl Michl IgorIgor Alabugin Alabugin 1,1,** andand Petr Petr Klán Klá n2,*2, * 1 1 Department of of Chemistry Chemistry and and Biochemistry, Biochemistry, Florida Florida State University,State University, Tallahassee, Tallahassee, Fl 32306, Fl USA 32306, USA 2 2 Department of of Chemistry Chemistry and and RECETOX, RECETOX, Faculty Faculty of Science, of Science, Masaryk Masa University,ryk University, Kamenice Kamenice 5, 5, 625 00 Brno,Brno, Czech Czech Republic Republic * Correspondence: [email protected] (I.A.); [email protected] (P.K.) * Correspondence: [email protected] (I.A.); [email protected] (P.K.) It is our great pleasure to introduce the Festschrift of Chemistry to honor professor JosefIt Michl is our (Figure great pleasure 1) on the to o introduceccasion of the hisFestschrift 80th birthdayof Chemistry and toto recognize honor professor his exceptional Josefcontributions Michl (Figure to 1the) on fields the occasion of organic of his photoc 80th birthdayhemistry, and quantum to recognize chemis his exceptionaltry, biradicals and contributionsbiradicaloids, to electronic the fields of and organic vibrational photochemistry, spectroscopy, quantum magnetic chemistry, circular biradicals dichroism, and sili- biradicaloids,con and boron electronic chemistry, and vibrational supramolecular spectroscopy, chem magneticistry, singlet circular fission, dichroism, and molecular silicon ma- andchines. boron chemistry, supramolecular chemistry, singlet fission, and molecular machines. -
Materials Science
Plutonium Futures—The Science Materials Science Materials Science 91 Poster Session 92 P u F u t u r e s — T h e S c i e n c e XANES and EXAFS Studies of Plutonium(III, VI) Sorbed on Thorium Oxide The study of plutonium sorption mechanisms on mineral surfaces seems very R. Drot, interesting considering radwaste management and, in particular, for underground E. Ordonez-Regil, disposal after advanced reprocessing. Indeed, radionuclides retention processes E. Simoni on engineered or geological barriers could enhance retardation. Thus, it appears Institut de Physique important to understand such phenomena at both the macroscopic and molecular Nucléaire, Université Paris Sud, Groupe de levels.1,2 In this context, as plutonium is a very radiotoxic element, it is necessary Radiochimie, to model its behavior in the geosphere and its interaction with natural minerals. 91406 Orsay Cedex, Such an investigation is complicated by the existence of several oxidation states France for plutonium. Then, sorption mechanisms could be different considering Pu(III), Ch. Den Auwer, (IV), or (VI). This work deals with the influence of the oxidation state of pluto- Ph. Moisy nium on the structure of the sorbed complex. X-ray absorption spectroscopy has CEA Marcoule, DCC/ been chosen to perform this study. We have considered thorium oxide as a reten- DRRV/SEMP, Valrhô, tion matrix because, on one hand, it is a sparingly soluble material; thus, dissolu- 30207 Bagnols-sur- tion processes of the solid can be neglected during sorption experiments. On the Cèze, France other hand, only one type of sorption site is expected, which allows us to simplify the study. -
LIST of PUBLICATIONS of JOSEF MICHL B: Book P: Patent C
LIST OF PUBLICATIONS OF JOSEF MICHL B: Book P: Patent C: Communication R: Review or Chapter in a Book P 1. Kopecký, J.; Michl, J. "Zpùsob výroby pyrrolo(2,3-d)-pyrimidinù", Czechoslovak patent no. 97821, August 11, 1959. C 2. Zuman, P.; Michl, J. "Role of Keto-Enol Tautomerism in the Polarographical Reduction of Some Carbonyl Compounds", Nature 1961, 192, 655. C 3. Horák, V.; Michl, J.; Zuman, P. "A Contribution to the Studies of Elimination Reactions of Mannich Bases, Using Polarographic Method", Tetrahedron Lett. 1961, 744. C 4. Zahradník, R.; Michl, J.; Koutecký, J. "Fluoranthene-like Hydrocarbons: MO-LCAO Study of Electronic Spectra, Charge-Transfer Spectra and Polarographic Reduction", J. Chem. Soc. 1963, 4998. 5. Koutecký, J.; Hochman, P.; Michl, J. "Calculation of Electronic Spectra of Non-Alternant Conjugated Hydrocarbons by the Semiempirical Method of Limited Configuration Interaction", J. Chem. Phys. 1964, 40, 2439. 6. Zahradník, R.; Michl, J.; Koutecký, J. "Tables of Quantum Chemical Data. II. Energy Characteristics of Some Non-Alternant Hydrocarbons", Collect. Czech. Chem. Commun. 1964, 29, 1932. 7. Zahradník, R.; Michl, J.; Koutecký, J. "Tables of Quantum Chemical Data. III. Molecular Orbitals of Some Fluoranthene-like Hydrocarbons, Cyclopentadienyl, and Some of its Benzo and Naphtho Derivatives", Collect. Czech. Chem. Commun. 1964, 29, 3184. 8. Zahradník, R.; Michl, J. "Electronic Structure of Non-Alternant Hydrocarbons, Their Analogues and Derivatives. Introductory Remarks", Collect. Czech. Chem. Commun. 1965, 30, 515. 9. Zahradník, R.; Michl, J. "Electronic Structure of Non-Alternant Hydrocarbons, Their Analogues and Derivatives. I. A Theoretical Treatment of Reid's Hydrocarbons", Collect. Czech. Chem. Commun. -
Melting and Decomposition of Orthorhombic B6si Under High Pressure
Melting and decomposition of orthorhombic B6Si under high pressure Vladimir L. Solozhenko,1,* Vladimir A. Mukhanov 1 and Vadim V. Brazhkin 2 1 LSPM–CNRS, Université Paris Nord, 93430 Villetaneuse, France 2 Institute for High Pressure Physics, Russian Academy of Sciences, 108840 Troitsk, Russia Abstract Melting of oorthorhombicrthorhombic boron silicide B6Si has been studied at pressures up to 8 GPa using in situ electrical resistivity measurements and quenching. It has been found that in the 2.6–7.7 GPa range B6Si melts congruently, and the melting curve exhibits negative slope of -31(2) K/GPa that points to a higher density of the melt as compared to the solid phase. At very high temperatures B6Si melt appears to be unstable and undergoes disproportionation into silicon and boron-rich silicides BnSi (n 12). The onset temperature of disproportionation strongly depends on pressure, and the corresponding low-temperature boundary exhibits negative slope of -92(3) K/GPa which is indicative of significant volume decrease in the course of B6Si melt decomposition. Keywords: boron silicide, melting, decomposition, high pressure, high temperature. 1. Introduction The boron–silicon system – despite of rather long research history – remains not fully understood even at ambient pressure [1]. There are three main groups of B–Si binary compounds usually referred to as "B3Si" (with the stoichiometry ranging from B2.8Si to B4.8Si); B6Si; and boron-rich silicides i.e. BnSi (12 n 50) (for details see [2] and references therein). Boron silicides attract considerable attention due to superior thermal stability, excellent chemical resistance, promising mechanical and electronic properties that offers potential for their use as advanced engineering and smart functional materials. -
Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting
catalysts Review Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting Anand P. Tiwari 1,†, Travis G. Novak 1,†, Xiuming Bu 2, Johnny C. Ho 2,* and Seokwoo Jeon 1,* 1 Department of Materials Science and Engineering, KAIST Institute for the Nanocentury, Advanced Battery Center, KAIST, Daejeon 305-701, Korea; [email protected] (A.P.T.); [email protected] (T.G.N.) 2 Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong; [email protected] * Correspondence: [email protected] (J.C.H.); [email protected] (S.J.); Tel.: +82-42-350-3342 (S.J.) † These authors contributed equally. Received: 30 October 2018; Accepted: 13 November 2018; Published: 16 November 2018 Abstract: Water splitting plays an important role in the electrochemical and photoelectrochemical conversion of energy devices. Electrochemical water splitting by the hydrogen evolution reaction (HER) is a straightforward route to producing hydrogen (H2), which requires an efficient electrocatalyst to minimize energy consumption. Recent advances have created a rapid rise in new electrocatalysts, particularly those based on non-precious metals. In this review, we present a comprehensive overview of the recent developments of ternary and quaternary 6d-group transition metal chalcogenides (TMCs) based electrocatalysts for water splitting, especially for HER. Detailed discussion is organized from binary to quaternary TMCs including, surface engineering, heterostructures, chalcogen substitutions and hierarchically structural design in TMCs. Moreover, emphasis is placed on future research scope and important challenges facing these electrocatalysts for further development in their performance towards water splitting. -
New Synthesis Route for Complex Borides
www.nature.com/scientificreports OPEN New Synthesis Route for Complex Borides; Rapid Synthesis of Thermoelectric Yttrium Aluminoboride via Liquid-Phase Assisted Reactive Spark Plasma Sintering Hyoung-Won Son1,2, David Berthebaud3, Kunio Yubuta4, Akira Yoshikawa4, Toetsu Shishido4, Keiko Suzuta5 & Takao Mori1,2 ✉ YxAlyB14 ceramics are of high interest as high temperature thermoelectric materials with excellent p, n control. In this study, direct synthesis of dense polycrystalline YxAlyB14 (x ~0.64, 0.52 ≤ y ≤ 0.67) ceramics was successfully carried out by spark plasma sintering using commercially available precursors. YB4, AlB2 and B powders were reactively sintered with an additive AlF3 at 1773 K for 5–60 min in reduced Ar atmosphere. The sinterability was remarkably enhanced by liquid phase sintering comparing to conventional synthesis techniques. Phase composition analysis by X-ray difraction showed that main peaks belong to YxAlyB14 with the MgAlB14 structure type and no peaks of AlF3 were detected. The thermoelectric behavior was changed from p-type to n-type with increasing Al occupancy. Power factor and ZT values measured in this study were found to be in the same range as the best values previously reported. This original synthesis process is found to be less precursor-consuming as compared to previous synthesis processes, and strikingly, less time-consuming, as the synthesis time, is shortened from 8 h to 5 min for p-type and to 1 h for n-type. The total process time is shortened from ≥3 days to ~4–5 h. This discovery opens the door for more accessible synthesis of complex borides. Termoelectric materials utilize the solid state Seebeck efect and thereby can directly convert heat to electricity. -
Single-Crystal Calcium Hexaboride Nanowires: Synthesis And
NANO LETTERS 2004 Single-Crystal Calcium Hexaboride Vol. 4, No. 10 Nanowires: Synthesis and 2051-2055 Characterization Terry T. Xu,† Jian-Guo Zheng,‡ Alan W. Nicholls,§ Sasha Stankovich,† Richard D. Piner,† and Rodney S. Ruoff*,† Department of Mechanical Engineering, Northwestern UniVersity, EVanston, Illinois 60208, NUANCE Center, Northwestern UniVersity, EVanston, Illinois 60208, and Research Resource Center, UniVersity of Illinois at Chicago, Chicago, Illinois 60612 Received August 17, 2004 ABSTRACT Catalyst-assisted growth of single-crystal calcium hexaboride (CaB6) nanowires was achieved by pyrolysis of diborane (B2H6) over calcium oxide (CaO) powders at 860−900 °C and ∼155 mTorr in a quartz tube furnace. TEM electron diffraction and Raman spectroscopy indicate that the nanowires are single-crystal CaB6 and have a preferred [001] growth direction. Analysis of TEM/EDX/EELS data proves the nanowires consist of CaB6 cores and thin (1−2 nm) amorphous oxide shell material. The CaB6 nanowires have diameters of ∼15−40 nm, and lengths of ∼1−10 µm. -2 22 Calcium hexaboride (CaB6), one of the divalent alkaline- (CaCO3) and boron carbide (B4C) at 1400 °C and 10 Pa, earth cubic hexaborides, has low density (2.45 g/cm3), high by reduction of calcium oxide (CaO) with B at 1200-1800 3 melting point (2235 °C), high hardness (Knoop: 2600 kg/ °C in vacuum, and by reaction of calcium chloride (CaCl2) 2 mm ), high Young’s modulus (379 GPa), and high chemical with sodium borohydride (NaBH4)at500°C in an autoclave 1,2 23 stability. CaB6 has found application as a high-temperature for8h. The finest crystalline CaB6 powders synthesized material, is used for surface protection, and as a wear resistant so far have an average size of 180 nm.23 1,2 material. -
1-Coordination of Beryllium Atoms in the Graphite Analogue
Angewandte Chemie DOI: 10.1002/anie.200705023 Beryllium Boride Carbide The h6,h1-Coordination of Beryllium Atoms in the Graphite Analogue BeB2C2** Kathrin Hofmann, Xavier Rocquefelte, Jean-François Halet, Carsten Bähtz, and Barbara Albert* Dedicated to Dr. Joseph Bauer on the occasion of his 65th birthday The coordination of beryllium ions in homoleptic beryllocene, We were recently able to show that it is possible to [Be(C5H5)2], has for decades been the subject of debate and distinguish between several possible structural models for theoretical as well as experimental investigations. It was not MB2C2 compounds (M = Ca, La) by comparing the exper- [1] until quite recently that Schurko and co-workers were able imental fine-edge structures of the BK ionization edges with [8] to show beyond doubt that Be is present in [Be(C5H5)2] in the those obtained by DFT calculations. This result was later h5,h1-coordination mode, which is consistent with the octet confirmed by independent DFT calculations.[9] The fine-edge rule for Be. We have now found an analogous disposition for structure of the BK edge in borides and boride carbides is Be in a solid-state compound, namely BeB2C2, in which six- highly variable with respect to weak structural and electronic membered rings of boron/carbon (B/C) layers coordinate to influences.[10] beryllium atoms in a h6,h1 fashion. The work described herein derives an otherwise inacces- 3 BeB2C2 is the first boride carbide with slipped 6 B/C sible, coherent structural model for BeB2C2 by calculating the layers as in graphite. -
Facile Synthesis of Nanostructured Metal Borides and Composites for Applications in Sustainable Energy
Scholars' Mine Masters Theses Student Theses and Dissertations Spring 2018 Facile synthesis of nanostructured metal borides and composites for applications in sustainable energy Maalavan Arivu Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Materials Science and Engineering Commons Department: Recommended Citation Arivu, Maalavan, "Facile synthesis of nanostructured metal borides and composites for applications in sustainable energy" (2018). Masters Theses. 7753. https://scholarsmine.mst.edu/masters_theses/7753 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. i FACILE SYNTHESIS OF NANOSTRUCTURED METAL BORIDES AND COMPOSITES FOR APPLICATIONS IN SUSTAINABLE ENERGY by MAALAVAN ARIVU A THESIS Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE IN MATERIALS SCIENCE AND ENGINEERING 2018 Approved by Dr. Manashi Nath, Advisor Dr. William G. Fahrenholtz Dr. Fatih Dogan ii 2018 Maalavan Arivu All Rights Reserved iii PUBLICATION THESIS OPTION This thesis has been prepared in the form of journal article formatted to the specifications prescribed by Missouri University of Science and Technology. The paper, pages 33 to 47 has been published in Electrochemistry Communications, a journal of Elsevier. iv ABSTRACT Electrocatalytic water splitting is a promising solution for sustainable energy generation since one of the half reactions lead to the formation of H2 which is a clean fuel. -
Obituary: Rudolf Zahradník Rudolf Zahradník Was Born in 1928 to A
Obituary: Rudolf Zahradník Rudolf Zahradník was born in 1928 to a Czech family in Slovakia. On the eve of the second world war, the family moved to Prague. It was during participation in the Prague uprising in May of 1945 that he met the love of his life, the slightly younger Milena. They were married in 1954 and lived in Prague until the fall of 2020, when they passed away within a week of each other, leaving a daughter and a grandson. Rudolf completed his undergraduate education at the Institute of Chemical Technology in Prague in 1952. This was a time of massive political oppression and he was prevented from entering the graduate program in chemistry. He was fortunate in that an enlightened and courageous director of a Research Institute for Work Hygiene and Occupational Diseases, Prof. J. Teisinger, offered him a refuge. There, Rudolf was in essence his own Ph.D. research supervisor and completed his dissertation in 1956. His work laid the foundations of the QSAR (Quantitative Structure-Activity Relationships) method for computer-aided drug design, simultaneously with and independently of C. Hansch at Pomona College in California. The procedure turned out to be very useful and became very popular throughout the world. However, Rudolf soon found the purely empirical nature of QSAR unsatisfactory, and turned his attention to quantum chemistry, which offers truly fundamental insight into chemical processes. He was able to secure a position in one of the institutes of the Academy of Sciences, directed by a leading Czech physical chemist at the time, Prof. R.