Carbothermal Reduction Synthesis and Structural Evolution of Nanocrystalline Ultra High Temperature Carbides
Abstract
Zirconium carbide (ZrC) and hafnium carbide (HfC) powders were produced by the carbothermal reduction reaction of carbon and the corresponding metal oxide (ZrO2 and HfO2, respectively). Solution-based processing was used to achieve a fine-scale (i.e., nanometer-level) mixing of the reactants. The reactions were substantially completed at relatively low temperatures (<1500 C) and the resulting products had small average crystallite sizes (^5O-l3O nm). Dry-pressed compacts prepared using ZrC-based powders with ^100 nm crystallite size could be pressurelessly sintered to ^99% relative density and zero open porosity at l950C. Silicon carbide (SiC) powders with crystallite size <25 nm were prepared at low temperature (^l3OOC) by carbothermal reduction reactions in silica/carbon mixtures. Solution-based processing was again used to achieve fine-scale mixing of the reactants. Mechanistic studies indicated that the SiC formed in accordance with the "shrinking core" reaction model in which the rate was controlled by the reaction of silicon monoxide vapor at carbon surfaces.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2004
- Accession Number
- ADA430219
Entities
People
- Michael D. Sacks
Organizations
- Georgia Tech Research Corporation