Doctoral Dissertations

Keywords and Phrases

composite; nanocomposite; reaction processing

Abstract

"Research presented herein details the synthesis and characterization of nanocomposite ceramics featuring novel heterogeneous microstructures of potential interest in a variety of electrical and structural applications. Specifically, W-TiCy composite ceramics featuring tungsten nanoprecipitates located primarily within TiCy grains have been produced via sintering of intragranular nanocomposite powders produced via reaction processing-based techniques. This dissertation details the thermodynamic basis and applied kinetics of a processing scheme for fabricating nanocomposite ceramics whose morphological heterogeneity reflects that originally developed in the powder state. The first study in this series overviews the motivation for applying metallothermic displacement reactions, conducted through gaseous intermediates, to solid solution systems and serves as proof of concept for the demonstrated reaction process. Application of the studied reaction process to commercial (Ti0.77W0.23)C powder resulted in the formation of a 27 wt. % W-TiCy composite powder that exhibited significant grain-to-grain microstructural variation caused by polycrystallinity and internal compositional variation in the precursor powder. The second study details the use of a liquid aluminum flux method to improve precursor quality by enabling synthesis of (Ti1-xWx)C powders with enhanced homogeneity and Mono crystallinity. The final report details the application of the previously reported gas-solid reaction process to flux-synthesized powders, to produce intragranular nanocomposite powders with up to 28 wt. % W. Subsequent spark plasma sintering resulted in the retention of the fine nanostructures produced in the powder state, as established by SEM and XRD characterization. The two scientific contributions of the present research are 1) the development of a novel processing scheme for producing bulk nanostructured composite ceramics, which has potentially broad applicability in the field of ceramics, and 2) the development of a method for controlling dispersant location in nanocomposite ceramics, specifically in a system with a non-oxide chemistry"--Abstract, p. iv

Advisor(s)

Lipke, David W.

Committee Member(s)

Moats, Michael S.
Schwartz, Robert W.
Watts, Jeremy Lee, 1980-
Wu, Chenglin

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Ceramic Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2023

Pagination

xiv, 141 pages

Note about bibliography

Includes_bibliographical_references_(pages 133-140)

Rights

© 2023 Ryan Daniel Dempsey, All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12243

Electronic OCLC #

1426051589

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