Doctoral Dissertations

Author

Yue Zhou

Keywords and Phrases

First-Principle Calculations; Phase Formation; Powder Synthesis; Thermal Conductivity; Zirconium Carbide

Abstract

“This research focused on the synthesis and phase formation of zirconium carbide with different carbon contents, and lattice thermal conductivity of zirconium carbide with different carbon vacancy, hafnium, and oxygen contents.

Nominally pure phase ZrCx was synthesized by solid-state reaction of zirconium hydride (ZrHs) and carbon black at a temperature as low as 1300°C. The powder synthesized at 1300C was carbon deficient ZrCx . Carbon stoichiometry of the as- synthesized powders increased as the synthesis temperature increased. As the synthesis temperature increase, the oxygen content of ZrCx decreased due to the increasing C site occupancy. Low stoichiometry ZrC0.6 powders were synthesized at 1300C and 2000C, and the formed phases were investigated. Carbon vacancy ordered phases were detected by neutron diffraction and selected area electron diffraction.

Lattice thermal conductivities of ZrCx with different carbon contents (x = 1.0, 0.75, 0.5) and different hafnium contents (3.125 at% and 6.25 at% were studied theoretically. A combination of first-principles calculations and the Debye-Callaway model was employed to predict the lattice thermal conductivities. Lattice thermal conductivities of all the compositions decreased as temperature increased. Increasing carbon vacancy content reduced the lattice thermal conductivity while increasing the grain size increased the lattice thermal conductivity. Lattice thermal conductivities of ZrCx also decreased as the content of Hf increased. Carbon vacancies and Hf impurities decreased the phonon transport, thus the lattice thermal conductivity decreased”--Abstract, page iv.

Advisor(s)

Fahrenholtz, William

Committee Member(s)

Hilmas, Greg
Watts, Jeremy Lee, 1980-
Huebner, Wayne
Graham, Joseph T.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Comments

This research was supported by the Ceramics program of the U.S. National Science Foundation as part of project DMR 1742086.

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2021

Journal article titles appearing in thesis/dissertation

  • Synthesis of ZrCₓ with Controlled Carbon Stoichiometry by Low Temperature Solid State Reaction
  • Carbon Vacancy Ordering in Zirconium Carbide Powder
  • From Thermal Conductive to Thermal Insulating: Effect of Carbon Vacancy Content on Lattice Thermal Conductivity of ZrCₓ
  • Electronic Structure and Thermal Conductivity of Zirconium Carbide with Hafnium Additions

Pagination

xiv, 129 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2021 Yue Zhou, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11933

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