Strong boride hierarchical composites for ultra-high temperature applications

A simple method to obtain highly refractory boride-based ceramic nano-composites is presented. Fundamental requirement for the development of a hierarchical boride composite is the formation of a solid solution around the native MB2 boride grain during the densification step. This can be obtained upon addition of soluble transition metal compounds. In the present case, introduction of WC enabled to form (M,W)B2 shells around the original MB2 cores. Subsequent annealing treatment at high temperature further developed a nano-texturing in the shell, which constituted a nano-composite where metallic W nano-particles were embedded within MB2 grains and displayed unprecedented refractoriness. Here we show the microstructural evolution from the as-sintered to the annealed state of different diboride composite and show how these microstructural change impact on the ultra-high temperature strength. The unique microstructural findings reported open vast opportunities for nano-composite ceramic development, manufacturing and applications.