Doctoral Dissertations
Keywords and Phrases
Borides; Carbides; Densification; High-Entropy
Abstract
"This work focuses on the processing and densification of multiphase, high-entropy ceramics to promote their use in friction stir welding technologies. Several high-entropy systems including high-entropy borides, carbides, and their composites were produced. Boro/carbothermal and carbothermal synthesis were used to produce high-entropy powders from oxide powder mixtures. Composites of high-entropy borides and high-entropy carbides were produced using a sequential approach to produce both phases. The carbide was first produced using carbothermal reduction, then ZrH2 and B4C were added to the carbide powder to produce the high-entropy boride phase. The resulting powder was densified by spark plasma sintering and pressureless sintering, although higher relative densities and smaller grain sizes were obtained for the spark plasma sintered ceramics. Thermodynamic calculations were used to understand the segregation of metals to certain high-entropy phases. To investigate the densification behavior of high-entropy borides and carbides during densification, the intermediate stage densification kinetics were examined for the boride and carbide of the Hf-Nb-Ta-Ti-Zr system. Tests in the temperature range of 1700°C to 1850°C indicated that the high-entropy carbide densified by lattice diffusion and the high-entropy boride densified by grain boundary diffusion. Densification of both systems was limited by the diffusion of Nb into the high-entropy phase. Boride-SiC-B4C ceramics were produced with a high-entropy boride phase to determine the high-entropy phase affected the resulting hardness and microstructure"-- Abstract, p. iv
Advisor(s)
Fahrenholtz, William
Committee Member(s)
Hilmas, Greg
Watts, Jeremy Lee, 1980-
Graham, Joseph T.
O'Malley, Ronald J.
Department(s)
Materials Science and Engineering
Degree Name
Ph. D. in Ceramic Engineering
Publisher
Missouri University of Science and Technology
Publication Date
Spring 2025
Pagination
xiii, 128 pages
Note about bibliography
Includes_bibliographical_references_(pages 39, 50, 74, 94, 111 and 120-127 )
Rights
©2024 Steven Smith , All Rights Reserved
Document Type
Dissertation - Open Access
File Type
text
Language
English
Thesis Number
T 12473
Recommended Citation
Smith, Steven, "Processing And Densification Of Multi-Phase High-Entropy Ceramics" (2025). Doctoral Dissertations. 3365.
https://scholarsmine.mst.edu/doctoral_dissertations/3365
