Boron carbide (B4C) is a boron–carbon ceramic and covalent substance with an extraordinarily hard chemical formula. It is one of the most rigid ceramic materials known, coming in second only to diamond and cubic boron nitride. It has become the material of choice for body armor systems due to its low density (2520 kg/m3). It is the most difficult substance to make in tonnage numbers. Boron carbide was discovered in the mid-nineteenth century as a byproduct of the manufacturing of metal borides, but it has only been investigated in depth since 1930. Boron carbide powder is primarily manufactured by combining carbon with B2O3 in an electric arc furnace, through carbothermal reduction, or through gas-phase processes. B4C ceramic powders for commercial usage are typically processed and filtered to remove metallic contaminants.
Like other non-oxide materials, Boron carbide ceramic is challenging to sinter to total density, requiring hot pressing or sinter HIP to obtain more than 95 percent of theoretical density. Even with these approaches, tiny amounts of dopants such as fine carbon or silicon carbide are frequently required to achieve sintering at reasonable temperatures (e.g., 1900 – 2200°C). B4C can also be produced as a coating on a suitable substrate utilizing vapor phase reaction procedures, such as the reaction of boron halides or di-borane with methane or another chemical carbon source.

History of Boron Carbide
Boron carbide was discovered in the 19th century as a byproduct of metal boride processes, but its chemical formula was unknown. Until the 1930s, the chemical composition was determined to be B4C ceramic. Whether the material had this exact 4:1 stoichiometry remained unresolved, as, in practice, the material is always slightly carbon-deficient about this formula, and X-ray crystallography reveals that its structure is highly complex, with a mixture of C-B-C chains and B12 icosahedra. These characteristics are argued against a relatively simple, accurate B4C empirical formula. Because of the B12 structural unit, the chemical formula of “ideal” boron carbide is commonly represented as B12C3, and the carbon shortage of boron carbide ceramics is defined in terms of a combination of the B12C3 and B12CBC units.

Applications
Boron carbide powder is utilized as an abrasive in polishing and lapping applications and a loose abrasive in cutting applications such as water jet cutting due to its high hardness. It is also helpful for diamond tool dressing.

Because of its great hardness, boron carbide ceramics has exceptional wear and abrasion resistance, and it is used in nozzles for slurry pumping, grit blasting, and water jet cutters.
Its ability to absorb neutrons without producing long-lived radionuclides makes it appealing as a neutron absorber in nuclear power reactors. Boron carbide is also used in nuclear applications such as shielding, control rods, and shut down pellets.
Boron carbide ceramic is also used in ballistic armor (particularly body or personal armor), where the combination of high hardness, high elastic modulus, and low density gives the material an extraordinarily high specific stopping power to repel high-velocity projectiles.
Ceramic tooling dies, precise toll components, evaporating boats for material testing, and mortars and pestles are other applications.