Boride Hierarchical Composites with Excellent Strength up to 2100°C

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 Ta- or W-compounds enabled to form (M,Ta/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 carbide or metallic 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 composites 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.