boron carbide, a black powder, is the hardest of the conventional abrasives, its mohs hardness is 9.36, melting point 24500c,density 2.51g/cm3. it has following unique features: neutron absorbing,of semi-conductivity, low thermal conductivity,high grinding efficiency and no reaction with either acids or alkali etc. boron carbide is widely used to grind and polish hard metal alloy, super-hard metal, high carbide steel, jewel, hard ceramic and other hard materials, to manufacture wear-resisting parts, metal cutting tools, nozzles and neutron-absorbing rods, used as metal additive for compound materials for military planes and as raw materials for matal boride, metal ceramic, boron steel, boron alloy and for special welding and refractory materials