Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 8 of 8 for “"Diborides"”.
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Chemical Vapor Deposition of Transition Metal Diborides From Borohydride Precursors
Both HfB2 and CrB2 depositions were highly conformal. For example, a 65 nm wide trench with a 19:1 depth-width aspect ratio was coated uniformly with HfB2. The coverage improved further when an additional flux of a growth suppressor was added during deposition. Super-conformal CrB2 films were …
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Rhenium, osmium and iridium diborides by mechanochemistry: Synthesis, structure, thermal stability and mechanical properties
… properties. In particular, transition metal diborides are of special interest. In the recent years, borides of rhenium (Re), osmium (Os) and iridium (Ir) have been studied as for their ultra-hardness and superior stiffness. In this dissertation, a mechanochemical method is introduced to …
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Reaction processing for the development of ultra-high temperature ceramics
… candidates for these extreme conditions. These diborides have melting temperatures that exceed 3000⁰C, the potential for strength retention at elevated temperatures, and moderate oxidation resistance when compared to high temperature carbides. However, diborides have often been reported to …
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Solution-based synthesis and processing of nanocrystalline ZrB₂-based composites
Zirconium- and tantalum-based diborides, and diboride/carbide composites are of interest for ultra-high temperature applications requiring improved thermomechanical and thermochemical stability. This thesis focuses on the synthesis, processing and sintering of nanocrystalline powders with Zr- and …
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The influence of microstructure on the mechanical properties of some refractory compounds
… microstructure of transition metal carbides and diborides. The local atomic structure of amorphous titanium diboride thin films, prepared by electron beam vaporization of the crystalline compound onto liquid nitrogen-cooled substrates, is examined using extended x-ray absorption fine structure …
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Processes and Materials for Space Exploration and Colonization
… work, new materials based on transition metal diborides are being synthesized, sintered and characterized according to innovative technologies, and their performance are being assessed in terms of mechanical properties and oxidation resistance. Research is focused on multicomponent transition …
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Densification, microstructure, and mechanical properties of zirconium diboride based ultra-high temperature ceramics
"The first part of this dissertation was aimed at studying the densification of ZrB₂ ceramics by pressureless sintering techniques. Various processes have been applied to coat ZrB₂ powders with polymer precursors, which were used to produce C after charring. After sintering at 1900⁰C, relative …
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Synthesis and characterization of ceramics in the Ti-B-N-C system
… the relative stability of the single phase mixed diborides with respect to pure diboride phase. The central aim of this part is to establish the mechanism of the synthesis reaction leading to the formation of uniform size of titanium diboride crystals. Titanium boride (TiB2) powder was produced in …