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Formation and reactivity of some metal borides and carbidesChaudry, Asghar Ali January 1973 (has links)
Most recent developments in the production, properties and applications of borides and carbides are reviewed. The reactivity and sintering of finely-divided boron carbide with metal additives has been investigated. The additives (Fe, T i , Zr, V, Nb, Ta, Mo, W and Al) generally promote sintering of the boron carbide. Their effectiveness is reduced occasionally when there is some surface activation caused by the metals reacting vjith the boron carbide to form metal borides and carbides of different, crystal lattice type and molecular volume. The more metallic character of the bonding in the metal borides and carbides enhances surface and crystal lattice diffusion at the grain boundaries of the more covalent boron carbide. Iron is much more effective than the other metal addives tested in promoting sintering of the boron carbide at 1800 degree C since it forms the lowest-melting borides. It also enhances sintering during hot pressing of boron carbide at this temperature.
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Electronic transitions of transition metal monoboridesNg, Yuk-wai, 吳育煒 January 2014 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
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An investigation of the borides and the silicides ...Watts, Oliver P. January 1906 (has links)
Thesis (Ph. D.)--University of Wisconsin. / Bibliography: p. 314-318.
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High temperature studies of crystalline boric oxide and of hafnium borideBarnes, Dennis William, January 1961 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1961. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 24).
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Kinetics of TiB formationWalther, George Charles, January 1976 (has links)
Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 235-244).
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Electronic transitions of transition metal monoboride and monoxidesWang, Na, 王娜 January 2014 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
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Theoretical and Experimental Studies on the Formation of Metal BoridesRajan, Lisa 01 May 2011 (has links)
AN ABSTRACT OF THE THESIS OF Lisa Rajan, for the Master of Science degree in Mechanical Engineering, presented on April 1, 2011, at Southern Illinois University Carbondale. TITLE: THEORETICAL AND EXPERIMENTAL STUDIES ON THE FORMATION OF METAL BORIDES MAJOR PROFESSOR: Dr. Rasit Koc Formation studies were done on six metal borides, TiB2, ZrB2, HfB2, AlB2, CaB6, and LaB6. The goal of this research is to research materials used for coatings on bipolar plates used in polymer electrolyte, PE, fuel cells. Theoretical calculations were done with formation equations from these six materials. Software used was HSC Chemistry version 5.0. Each equation was fully entered, and the range of formation temperature was narrowed till a value was obtained. Experimental work was done on TiB2 using thermogravimetric analysis and x-ray diffraction. Studies were done on carbon coated TiO2 precursors mixed with B4C and mixed carbon and TiO2 precursors mixed with B4C. The studies show that TiB2 is a very excellent material and easy to make. ZrB2, HfB2 and CaB6 are also easily processed and available for use in the market. AlB2 needs more research so that effective conclusions can be made about its formation temperature and suitable methods of production. Although made by methods uncommon to those studied in this work, LaB6 is already in commercial production and used in electron microscopes. Examination of previous experimental studies shows that the reduction reaction methods and formation of powders in an autoclave are the most consistent methods of metal boride formation. Calculations in the HSC 5.0 software confirmed that. When reactions for these methods were done, they consistently produced precise formation temperatures. Several variations of the combined reduction reaction were found in the literature, and all produced the same theoretical formation temperature. Molar amounts did not affect this temperature. Each method produced submicron particle powders. Thermodynamic data was useful in determining the certainty of each reaction being done experimentally. Most reactions were thermodynamically possible with a few exceptions. Change in enthalpy, ∆H, change in entropy, ∆S, change in Gibb's free energy, ∆G, and the formation constant K were all factors that were calculated and used to describe metal boride formation. The experimental studies showed that coated precursors have a lower temperature at which the reaction begins. The process is more gradual for coated precursors, although both coated and mixed precursors reach a pure TiB2 phase by 1400°C. The mixed precursor had a higher phase of purity than the coated precursor at 1400°C.
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Grain refinement in aluminium containing magnesium alloysJoshi, Utsavi Mukeshbhai January 2016 (has links)
The novel grain refiners developed in this research could be broadly classified into borides and carbides. The motive behind choosing MgB2, AlB2 and their master alloys Mg-MgB2 and Mg-AlB2 as the grain refiners was driven by the crystallographic matching of the hexagonal borides with the magnesium crystal structure. Apart from this lightweight borides, denser borides such as CrB and WB have also shown excellent grain refinement in AZ91, AM50 and AZ31 alloys. It is suggested that the grain refinement effect in the magnesium alloys could be improved through a combined addition of bismuth along with the boride. The carbon based grain refiners were also explored as they are well-established for the grain refinement of aluminium containing magnesium alloys. The new carbon based grain refiners identified through this research are B4C, Mg-B4C, Mg-3Ti-1C. Magnesium matrix was chosen for the development of each of these master alloys to eliminate any impurity contamination during the grain refiner addition to the magnesium melt. The pressureless melt infiltration techniques was involved in the development of Mg-MgB2, Mg-AlB2 and Mg-B4C while, the ‘halide salt route’ was adopted for producing Mg-3Ti-1C master alloys. The application of ultrasonic cavitation for the development of a new Al-1.5B-2C master alloy was shown to be effective for a homogenous distribution of the intermetallic phases in the form of Al3BC. The potential heterogeneous nucleating sites proposed in the commercial aluminium containing magnesium alloys are MgB2 for Mg-MgB2 master alloy; Mg1-xAlxB2 (0.10 < x < 0.18) for AlB2 grain refiner; MgB2C2 for B4C grain refiner; CrB and WB for their individual powder additions respectively; Ti2AlC for Mg-3Ti-1C master alloy; Al3BC and Al4C3 for the Al-1.5B-2C master alloy.
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A study on magnetic anisotropy induced in the HDDR processFujita, Akira January 1999 (has links)
No description available.
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Structural and electrical characterisation of Si:B/Siâ†1â†-â†xGeâ†x/Si(001) heterostructuresMcGregor, Barry Michael January 1997 (has links)
No description available.
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