Masters Theses

Abstract

"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.

Advisor(s)

Fahrenholtz, William
Hilmas, Greg

Committee Member(s)

Huebner, Wayne

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Materials Science and Engineering

Sponsor(s)

United States. Air Force. Office of Scientific Research

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2014

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

Pagination

xi, 113 pages

Note about bibliography

Includes bibliographical references (pages 104-112).

Rights

© 2014 Devon Lee McClane, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Ceramics -- Thermal properties
Zirconium -- Thermal properties
Borides -- Thermal properties
Transition metals

Thesis Number

T 10463

Electronic OCLC #

882486393

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