Boron carbide

Carbide of boron B4c - black bright crystals, is decomposed above 2450c on the hardness it the third, inferior only to diamond and nitride of boron. Abrasive and grinding material; neutron absorber in the nuclear reactors.It adapts in atomic power engineering as the material of the rods, which regulate the flow of nuclear reactions. It is used as the component part of the mixtures for the diffusion boronizing of steels and refractory metals. From carbide of boron are made the sand-blowing nozzles, the nozzles for dispersing of pulps and fertilizers, it possesses high chemical stability in different aggressive media. According to the hardness and the abrasive ability it exceeds electrocorundum and carbide of silicon. It is produced, beginning from the fraction of the size of 20 mm and concluding by micropowder with the size of particles 1 μ, density 2.52 g/cm3, the melting point of 2360 c. It is steady in air up to 1000 o, does not react with the acids, but it is decomposed by alkalis.