W2.5   

BORON CARBIDE ,( the structural formula is B4C ,and the molecular weight is 55.26 ) is a nonmetallic material for high performance structuring ceramics . It also considered as the material for the high performance functioning ceramics , is one of the hardest Man-Made materials (only near upon diamond and cubic boron nitride), its hardness with Mohs hardness 9.36 and microscopic hardness 5400- 6300kgmmz , its density 2.52 gcm3 and melting point at 2450 aC . The material possess properties of endurance hilow temperature, no reaction with either acids or alkalis, it is also possesses the specialty properties of light quality, high hardness , semi-conductivity etc so that it is widely applied as following :Boriding refractory, ion transfuse, lilm layer as well as grinding , polishing , drilling hard metal alloys ,jewels etc. Meanwhile , it is main materials for the wear-resisting parts , precise meter-age element , precise spray nozzle, sealed washer smelting boron steel , boron ally etc . For boron , it possesses the characteristic of absorbing the neutron , so boron carbide is also used as the main boric material for reaction speed adjusting bar in nuclear reactor .