Mechanical Activation Assisted Self-Propagating High-Temperature Synthesis of HfB2-HfC Composites

The structure as well as the phase and granulometric compositions of the submicron-sized heterophase HfB2-34 at % HfC powders fabricated by mechanical activation assisted self-propagating high-temperature synthesis from (Hf + B + C) mixtures were studied. It was demonstrated that HfB2-HfC powders can be produced from (Hf + B + C) mixtures by mechanochemical synthesis in a planetary ball mill (centrifugal factor, 60 g) during more than 15 min. The SHS product with composition HfB2-34 at % HfC consisted of a combination of highly porous agglomerates sized 5-100 & mu;m, which can be easily broken into composite HfB2-HfC particles sized 1-10 & mu;m. Important that each composite particle of powder have a heterophase structure which consists of HfB2 grains sized 0.5-2.0 & mu;m and equiaxial HfC grains sized 0.3-1 & mu;m. Impurity oxygen content in the SHS products did not exceed 0.29 wt %. Milling of the SHS product allowed to obtain the HfB2-34 at % HfC powder characterized by the average particle size of 4 & mu;m with heterophase submicron-sized microstructure and oxygen content of 0.72 wt %.