The Scaled-Up Synthesis of Nanostructured Ultra-High-Temperature Ceramics and Resistance Sintering of Tantalum Carbide Nanopowders and Composites
dc.contributor.advisor | Graeve, Olivia | |
dc.contributor.author | Kelly, James | |
dc.date.accessioned | 2017-02-07T15:22:55Z | |
dc.date.available | 2017-02-07T15:22:55Z | |
dc.date.issued | 2013-02 | |
dc.description | Advisory committee members: Linda Jones, William Carty, Geoffrey Bowers. Dissertation completed in partial fulfillment of the requirements for the degree of PHD in Ceramics at the Inamori School of Engineering, New York State College of Ceramics at Alfred University | en_US |
dc.description.abstract | Ultra-high temperature ceramics (UHTCs) are a unique class of materials with the potential to withstand harsh environments due to covalent bonding, which gives these materials high melting temperatures, although decomposition temperatures should also be considered. For example, the melting temperature of TaC is near 4000 K, but may vaporize at lower temperratures. The high melting temperatures also make them difficult to process without high pressures and temperatures and to achieve dense ceramics with a nanostructure. Such materials however are appealing for aerospace technologies. The ability to generate high density compacts and maintain a nanostructure could allow for unprecedented control and improvement to the mechanical properties. The goal of this work is to develop processes for the synthesis and consolidation of nanostructured UHTCs. A self-propagating solvothermal synthesis technique for making UHTC nanopowders is presented. The technique is fast, scalable, and requires minimal external energy input. Synthesis of transition metal boride, carbide, and nitride powders is demonstrated. TaC is synthesized using a range of synthesis conditions and characterized to determine the fundamental mechanisms controlling the nanopowder characteristics. Discussion on purification of the powders is also presented. The sintering of TaC nanopowders produced by the solvothermal synthesis method is performed by resistance sintering. The effects of temperature, heating rate, and dwell time on densification and grain growth is presented. Adequate powder processing, carbon content, volatilization, and additives are found to be critical factors affecting the densification, microstructure, and grain growth. The optimal range of carbon addition for minimizing oxygen content is determined. WC and ZrC are evaluated as additives for reducing grain growth of TaC. Secondary phases and/or solid solutions are capable of suppressing grain growth. A unified approach to solid solution chemistries to control the densification, microstructure, and properties of UHTCs in general is presented. This work has important consequences on advancing the properties of UHTCs. | en_US |
dc.format.extent | 231 pages | en_US |
dc.identifier.uri | http://hdl.handle.net/10829/7349 | |
dc.language.iso | en_US | en_US |
dc.publisher | New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering. | en_US |
dc.relation.ispartof | Scholes Library | en_US |
dc.rights.uri | https://libraries.alfred.edu/AURA/termsofuse | en_US |
dc.title | The Scaled-Up Synthesis of Nanostructured Ultra-High-Temperature Ceramics and Resistance Sintering of Tantalum Carbide Nanopowders and Composites | en_US |
dc.type | Thesis | en_US |
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