Ultra-high temperature ceramics (UHTCs) and refractory carbides with high hardness and oxidation resistance demonstrate significant promise in armor and hypersonic engine applications. However, to date, they have been too brittle and expensive to widely implement on an industrial scale. Our efforts report on new approaches to synthesize and sinter boron carbides, silicon carbides, and zirconium carbides. We incorporate elemental inclusions, heterogeneous carbide phases, and carbon nanomaterials into carbides to improve the strength and shock resistance of the resulting composites. This nanostructuring approach uses commercially viable high-energy ball milling and slurry dispersion methods and yields powders, monoliths, and multilayered composites composed of optimized ceramics. We report on the resulting structures, properties, and performance of these optimized UHTCs. We developed a novel materials fabrication route that synthesizes shaped carbides from compressed powder mixtures of metal precursors and a carbon resin (1,2,4,5-tetrakis(phenylethynyl)benzene, or TPEB). This one-step in situ reactive melt infiltration approach yields dense ceramics with application-specific shapes such as disks and spheres and relies on pressureless tube furnace synthesis at temperatures below 1,500 °C. Our approaches yield exceptionally pure, dense (99% of TMD) ceramics with nanosized grains (&lt; 30 nm). We report on the structure and synthesis and demonstrate processing modifications steps that produce nanostructured composites with tunable electronic and thermal conductivity properties. In an alternative to energy-intensive and commercially inefficient hot pressing, we present a sintering approach that irradiates greenbody ceramics with microwaves to densify metal carbides. This pressureless sintering method rapidly compacts boron carbides, incorporates elemental inclusions, and yields highly dense (over 93% of TMD) structures. This technique requires shorter sintering times (&lt; 30 minutes) and temperatures (&lt; 1,300 °C), which improves the commercial viability of B4C in a broad range of commercial and military applications.

Nanostructured refractory ceramics

254th National Meeting (2017)

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