Doctoral Dissertations

Keywords and Phrases

Zirconium diboride

Abstract

"The research presented in this dissertation focuses on the processing and thermomechanical properties of ZrB₂ based ceramics. The overall goal was to improve the understanding of thermal and mechanical properties based on processing conditions and additives to ZrB₂. To achieve this, the relationships between the thermal and mechanical properties were analyzed for ZrB₂ ceramics that were densified by different methods, varying amounts of carbon, B₄C, or TiB₂ additions. Four main areas were investigated in this dissertation. The first showed that decreased processing times, regardless of densification method, improved mechanical strength to >500 MPa. This study also revealed that lower oxygen impurity contents led to less grain coarsening. The second study showed that higher heating rates narrowed the grain size distribution, which resulted in strengths above 600 MPa. However, the decreased processing times led to retention of ZrO₂, which decreased the thermal conductivity. The third study revealed that carbon additions interacted with ZrO₂ and WC impurities introduced during powder processing to form (Zr,W)C, which led to higher thermal conductivity than ZrB₂ with no carbon added. The last area examined the effect of solid solution additions on the electron and phonon contributions to thermal conductivity. The formation of solid solutions decreased thermal conductivity to <60 W/mʺK compared to 93 W/mʺK for nominally pure ZrB₂ at 25⁰C. Taken as a whole, this research adds insight into the fundamental aspects of microstructure and composition that control the thermal and mechanical properties of ZrB₂. These changes impact thermal and mechanical properties, which control the performance of ZrB₂ based ceramics"--Abstract, page iv.

Advisor(s)

Hilmas, Greg
Fahrenholtz, William

Committee Member(s)

Smith, Jeffrey D.
Miller, F. Scott, 1956-
Switzer, Jay A., 1950-

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2012

Journal article titles appearing in thesis/dissertation

  • Effect of starting particle size and oxygen content on densification of ZrB₂
  • Elevated temperature thermal properties of ZrB₂ with carbon additions
  • Heating rate effects on the thermal and mechanical properties of ZrB₂
  • Thermal properties of ZrB₂-TiB₂ solid solutions

Pagination

xiii, 215 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2012 Matthew J. Thompson, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Borides -- Thermal properties
Ceramics -- Thermal properties
Zirconium -- Thermal properties

Thesis Number

T 10015

Print OCLC #

815749508

Electronic OCLC #

786191611

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