"This research focuses on the thermal properties of zirconium diboride (ZrB₂) based ceramics. The overall goal was to improve the understanding of how different transition metal (TM) additives influence thermal transport in ZrB₂. To achieve this, ZrB₂ with 0.5 wt% carbon, and 3 mol% of individual transition metal borides, was densified by hot-press sintering. The transition metals that were investigated were: Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, and Re. The room temperature thermal diffusivities of the compositions ranged from 0.331 cm²/s for nominally pure ZrB₂ to 0.105 cm²/s for (Zr,Cr)B₂ and converged around 0.155cm²/s at higher temperatures for all compositions. Thermal conductivities were calculated from the diffusivities, using temperature-dependent values for density and heat capacity. The electron contribution to thermal conductivity was calculated from measured electrical resistivity according to the Wiedemann-Franz law. The phonon contribution to thermal conductivity was calculated by subtracting the electron contribution from the total thermal conductivity. Rietveld refinement of x-ray diffraction data was used to determine the lattice parameters of the compositions. The decrease in thermal conductivity for individual additives correlated directly to the metallic radius of the additive. Additional strain appeared to exist for additives when the stable TM boride for that metal had different crystal symmetries than ZrB₂. This research provided insight into how additives and impurities affect thermal transport in ZrB₂. The research potentially offers a basis for future modeling of thermal conductivity in ultra-high temperature ceramics based on the correlation between metallic radius and the decrease in thermal conductivity."--Abstract, page iv.
Materials Science and Engineering
M.S. in Materials Science and Engineering
United States. Air Force. Office of Scientific Research
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Thermal Properties of (Zr,TM)B₂ Solid Solutions with TM = Hf, Nb, W, Ti, and Y
- Thermal Properties of (Zr,TM)B₂ Solid Solutions with TM = Ta, Mo, Re, V, and Cr
xi, 113 pages
© 2014 Devon Lee McClane, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Ceramics -- Thermal properties
Zirconium -- Thermal properties
Borides -- Thermal properties
Electronic OCLC #
McClane, Devon Lee, "Thermal properties of zirconium diboride - transition metal boride solid solutions" (2014). Masters Theses. 7265.