Processing of Ternary High Temperature Ceramic Composites With Enhanced Properties

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The research objective of this award is to gain fundamental understanding of processing-microstructure-property correlations in the fabrication of high-temperature ternary composite ceramics, processed by Spark Plasma Sintering (SPS). The specific aims of the project are to: 1) sinter by SPS zirconium diboride (ZrB2) and hafnium diboride (HfB2) model samples and evaluate their material properties; 2) synthesize zirconium(hafnium)diboride-silicon carbide-zirconium carbide (Zr(Hf)B2-SiC-ZrC) ultra-high temperature ceramics by SPS; 3) examine the effects of heating rate and the application of an electrical field on the sample density and microstructure; and 4) achieve compositional control of these material systems. The resulting composites are expected to display excellent high-temperature structural properties, good electrical and thermal conductivity, chemical inertness against molten metals, and very good thermal shock resistance. If successful, the results of this research will lead to the development of the processing science necessary to manufacture bulk ultra-high temperature ceramics (UHTC) with fine microstructure, improved mechanical properties, high density and higher heat and oxidation resistance than materials presently available. Other important expected advances include understanding the interplay of pulse current, temperature and pressure effects on UHTC sintering and coarsening at different length scales; development of a consistent process design/characterization methodology that is applicable to UHTCs for large and net shape parts; and systematic defect characterization for quality control in the fabrication of ultra-high temperature ceramics. It is also anticipated that the results of this investigation will improve overall confidence in using SPS as an advanced processing technique for manufacturing ultra-high temperature ceramics as thermal protection materials for various applications.