Boron carbide (B4C) is an essentially synthetic material. It was discovered in the 19th century as a by-product of reactions involving metal borides. It is produced by reacting boron oxide with carbon in an electric arc furnace.
It is most often used in powder form or as a solid material. Like silicon carbide, it is sintered at a very high temperature (> 2,000°C) in a neutral or reducing atmosphere to prevent oxidation problems.
The two main properties of boron carbide are its very low density (2.5 g/cm3) and a hardness comparable to that of diamond. It is the third hardest material (Mohs > 9.5). In addition to its very high mechanical properties (Young's Modulus, resistance to compression, etc.) it also has very good resistance to corrosion (acid environment) and excellent resistance to heat.
Boron carbide is used for the manufacture of pipes and nozzles for very abrasive materials. It is also used for machining and polishing very hard materials (tungsten carbide, silicon carbide, etc.). Combined with these exceptional mechanical properties, its low density makes it a high-quality material of choice for armour plating. Lastly, it is often used in nuclear applications due to its ability to absorb neutrons.