Boron carbide.

Boron carbide - B4C - black crystals. Boron-carbon compound. Decomposition temperature >2450 °C; density 2.52 g/cm3; thermal conductivity 121 W/(mK) at 300 °K; microhardness 49.1 GPa; elastic module 450 GPa; p-type semiconductor. Boron carbide is one of the most stable substances. The air does not oxidize to 600 °C. It does not dissolve in water, concentrated acids, decomposes in boiling solutions of alkalis. Up to 1250 °C does not interact with nitrogen, phosphorus and sulfur. Reacts with chlorine at 1000 °C to form boron trichloride and carbon.

Boron carbide is used for the manufacture of abrasive and grinding materials, chemical dishes, in electronics and the nuclear industry. Products made of boron carbide are obtained by hot pressing.