Boron+Carbide

Chemical Formula: B4C Boron Carbide is an extremely hard ceramic. It is a material that is used for tank armor, bulletproof vests and other industrial applications. It is one of the hardest materials known to man, just behind cubic boron nitride and diamond. Pictured above is a solid piece of boron carbide but it can be found as a dark gray or black powder. It is odorless as well as insoluble in water. Boron carbide powder is mainly produced by reacting carbon with B2O3 in an electric arc furnace through carbothermal reduction or by gas phase reactions. Boron carbide is known as a robust material having high hardness, high cross section for absorption of neutrons (i.e. good shielding properties against neutrons), stability to ionizing radiation and most chemicals. Its Vickers hardness (38 GPa) and fracture toughness (3.5 MPa·m1/2) approach the corresponding values for diamond (115 GPa and 5.3 MPa·m1/2).

Boron carbide was discovered in the 19th century as a by-product of reactions involving metal borides, however, its chemical formula was unknown. It was not until the 1930s that the chemical composition was estimated as B4C. There remained, however, controversy as to whether or not the material had this exact 4:1 stoichiometry, as in practice the material is always slightly carbon-deficient with regard to this formula, and X-ray crystallography shows that its structure is highly complex, with a mixture of C-B-C chains and B12 icosahedra. These features argued against a very simple exact B4C empirical formula. Because of the B12 structural unit, the chemical formula of "ideal" boron carbide is often written not as B4C, but as B12C3, and the carbon deficiency of boron carbide described in terms of a combination of the B12C3 and B12C2 units. The ability of boron carbide to absorb neutrons without forming long lived radionuclides makes it attractive as an absorbent for neutron radiation arising in nuclear power plants. Nuclear applications of boron carbide include shielding, control rod and shut down pellets. Within control rods, boron carbide is often powdered, to increase its surface area.
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 * ~ Properties ||
 * Molecular formula || B4C ||
 * Molar mass || 55.255 g/mol ||
 * Appearance || dark gray or black powder, odorless ||
 * Density || 2.52 g/cm3, solid. ||
 * Melting point || 2763 °C, 3036 K, 5005 °F ||
 * Boiling point || 3500 °C, 3773 K, 6332 °F ||
 * Solubility in water || insoluble ||
 * Acidity (p//K//a) || 6–7 (20 °C) ||