The density of boron carbide (B4C) is 2.51 x 103kg/m3.
Boron carbide is an extremely hard, low-density ceramic and covalent material, which ranks third behind diamond and cubic boron nitride. Its high hardness makes it suitable as an abrasive. It is also used to make tools, nozzles and nuclear reactor neutron absorbers.
The density of B4C is a function of the melting point and the thermal expansion coefficient. It is a very good control material for high-temperature reactors because of its high thermal neutron capture cross section and the fact that the reaction rates and irradiation are uniform throughout the absorber.
Phase constitution, morphology and stoichiometry of synthesized powders were investigated by X-ray diffraction and field-emission scanning electron microscopy (FESEM). The effect of heating temperature and starting composition on phase constitution, morphology as well as stoichiometry were also determined.
A series of boron carbide powders were synthesized at 1900 degC from precursor mixtures with different molar ratios of B2O3/C. The stoichiometric B4C powders had an average grain size of 300 nm. The powders exhibited a highly uniform crystalline structure and showed a strong crystal symmetry between the carbon and boron atoms.
During heat treatment, the powders underwent a combination of liquid-solid and gas-solid reactions, resulting in fine-sized and elongated platelet B4C powders. These powders are characterized by a relatively large pore volume and an indentation resistance of 40000 BHN, which is comparable to diamond. In addition, they are wear-resistant and semiconductive.