In incude synthesis and investigations of novel multifunctional strong materials - transition metal (TM=Fe, Cr, Mn, Mo, W, Ti) borides
Final Report Abstract
The project aimed at the synthesis and characterisation of advanced multifunctional strong materials, in particular, transition metals borides and novel high-pressure phases of elemental boron. It has been realized in a few steps, which included (1) Technological development of the scientific instrumentation: designing, purchasing and installation of the large volume press with a specially designed large-volume pressure chamber for materials synthesis, (2) Synthesis and investigations of transition metals borides in the Fe-B, Mn-B, and Co-B systems, and (3) Synthesis and investigations of single crystals of perspective boron compounds and novel high-pressure phases of elemental boron. All initial project’s objectives have been achieved. The highlights of the major results are summarized below. In the course of the project we designed, installed and brought to operation a new scientific instrument for high-pressure and high-temperature materials synthesis. Using this instrument, we developed reproducible and verifiable methods of high-pressure high-temperature synthesis of single crystals of boron allotropes, boron carbide, and transition metals carbides and borides. All of these solids belong to the class of hard and superhard materials. Availability of high-quality single crystals allowed for the first time experimental electron density studies of boron allotropes and a stoichiometric boron carbide. Uncovering unprecedented bonding features contributes to the fundamental chemistry and materials science of boron compounds. High-pressure synthesis of unique transition metal borides led to a discovery from scratch of the first superhard iron tetraboride superconductor and elucidating the structure, magnetic and mechanical properties of a number of novel borides. The present work resulted in the HPHT synthesis of the first previously unknown nonicosahedral boron allotrope ζ-B. This finding confirmed earlier theoretical predictions, which stayed unproven for decades because of experimental challenges which couldn’t be overcome until recently. Structural stability of α-B and β-B in the Mbar pressure range and boron carbide B13C2 up to 68 GPa was experimentally proven. Accurate measurements of the unit cell and B12 icosahedra volumes of the stoichiometric boron carbide B13C2 as a function of pressure led to the conclusion that they undergo a similar reduction upon compression that is typical for covalently bonded solids. Neither ‘molecularlike’ nor ‘inversed molecular-like’ solid behavior upon compression was detected that has closed a longstanding scientific dispute. A comparison of the compressional behavior of B13C2 with that of α–B and γ–B allotropes and B4C showed that it is determined by the types of bonding involved in the course of compression.
Publications
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Discovery of a superhard iron tetraboride superconductor, Phys. Rev. Lett. 111, 157002 (2013)
H. Gou, N. Dubrovinskaia, E. Bykova, A. A. Tsirlin, D. Kasinathan, W. Schnelle, A. Richter, M. Merlini, M. Hanfland, A. M. Abakumov, D. Batuk, G. Van Tendeloo, Y. Nakajima, A. N. Kolmogorov, L. Dubrovinsky
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Novel nonmagnetic hard boride Co5B16 synthesized under high pressure. J. Alloys Comp. 608, 69– 72 (2014)
E. Bykova, A.A. Tsirlin, H. Gou, L. Dubrovinsky, N. Dubrovinskaia
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Crystal structures and compressibility of novel iron borides Fe2B7 and FexB50 synthesized at high pressure and high temperature. J. of Solid State Chemistry 230, 102–109 (2015)
E. Bykova, H. Gou, M. Bykov, M. Hanfland, L. Dubrovinsky, N. Dubrovinskaia
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Disorder and defects are not intrinsic to boron carbide. Scientific Reports 6, 19330
S. Mondal, E. Bykova, S. Dey, Sk I. Ali, Natalia Dubrovinskaia, L. Dubrovinsky, G. Parakhonskiy, S. van Smaalen
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First non-icosahedral boron allotrope synthesized at high pressure and high temperature. Phys. Rev. B 95, 180102- 1-6 (R) (2017)
I. Chuvashova, E. Bykova, M. Bykov, V. Prakapenka, K. Glazyrin, M. Mezouar, L. Dubrovinsky, N. Dubrovinskaia
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Structural stability and mechanism of compression of stoichiometric B13C2 up to 68 GPa. Scientific Reports 7, 8969 (2017)
I. Chuvashova, E. Bykova, M. Bykov, V. Svitlyk, L. Dubrovinsky, N. Dubrovinskaia
