Silicon Carbide Formula - Silicon Carbide Uses, Properties, Structure and Formula

Silicon carbide, also known as carborundum, is a unique compound of carbon and silicon and is one of the hardest available materials.

Formula and structure: The chemical formula of silicon carbide is SiC. Its molecular formula is CSi and its molar mass is 40.10 g/mol. It is a simple compound with the carbon atom attached to silicon through a triple bond, leaving both atoms with a positive and negative charge. However, the bonding between them has a predominantly covalent character, rather than ionic. Solid silicon carbide exists in many different crystalline forms, with the hexagonal crystal structure being the most commonly found one.

Occurrence: Silicon carbide occurs naturally as the rare mineral moissanite.

Preparation: Silicon carbide is prepared industrially by the Acheson method, in which pure silica sand (SiO₂) and finely ground coke (carbon) are mixed together and heated to very high temperatures in an electric furnace.

SiO₂ + 3 C → SiC + 2 CO

Physical properties: Pure SiC is obtained as colorless crystals, with a density of 3.21 g/mL and an extremely high melting point of 2,730 °C. It is more commonly found as a bluish-black, iridescent crystalline solid, due to small amounts of iron or other impurities from the industrial production.

Chemical properties: Silicon carbide is a very stable and chemically inert compound. It is an extremely hard material, with a Mohs hardness rating of 9, close to that of diamond. It is also characterized by its high thermal conductivity, high-temperature strength, low thermal expansion, resistance to chemical reaction, and ability to function as a semiconductor.

Uses: As a very hard substance, silicon carbide is widely used as an abrasive. It is used to make various materials such as sandpapers, grinding wheels, cutting tools, hard ceramics, automobile parts, refractory linings, high temperature bricks, heating elements, wear-resistant parts for pumps and rocket engines, and even jewelry. It is also an important material in the electronics industry and used for making light-emitting diodes (LEDs) and semiconductor devices.

Health effects/safety hazards: Silicon carbide dust and fibers produced during its processing are the main hazards of this material. The SiC dust can irritate the eyes, skin, and upper respiratory system and lead to lung fibrosis and lung cancer.