Silicon Carbide, also known as carborundum, is a silicon-carbon compound. This chemical compound is a constituent of the mineral moissanite. The naturally occurring form of Silicon Carbide is named after Dr Ferdinand Henri Moissan, a French pharmacist. Moissanite is typically found in minute amounts in meteorites, kimberlite, and corundum. This is how most commercial Silicon Carbide is made. Although naturally occurring Silicon Carbide is difficult to find on Earth, it is abundant in space.
Variations of Silicon Carbide
Silicon Carbide products are manufactured in four forms for use in commercial engineering applications. These include
Sintered Silicon Carbide (SSiC)
Reaction Bonded Silicon Carbide (RBSiC or SiSiC)
Nitride bonded Silicon Carbide (NSiC)
Recrystallized Silicon Carbide (RSiC)
Other variations of the bond include SIALON bonded Silicon Carbide. There is also CVD Silicon Carbide (CVD-SiC), which is an extremely pure form of the compound produced by chemical vapor deposition.
In order to sinter Silicon Carbide, it is necessary to add sintering aids which help to form a liquid phase at the sintering temperature, allowing the Silicon Carbide grains to bond together.
Key properties of Silicon Carbide
High thermal conductivity and low coefficient of thermal expansion. This combination of properties provides exceptional thermal shock resistance, making Silicon Carbide ceramics useful in a wide range of industries. It is also a semiconductor and its electrical properties make it suitable for a wide range of applications. It is also known for its extreme hardness and corrosion resistance.
Applications of Silicon Carbide
Silicon Carbide can be used in a wide range of industries.
Its physical hardness makes it suitable for abrasive machining processes such as grinding, honing, sandblasting, and waterjet cutting.
Silicon Carbide's ability to withstand extremely high temperatures without cracking or deforming is used in the manufacture of ceramic brake discs for sports cars. It is also used as an armor material in bulletproof vests and as a sealing ring material for pump shaft seals, where it often runs at high speeds in contact with a Silicon Carbide seal. Silicon Carbide's high thermal conductivity, which is able to dissipate the frictional heat generated by a rubbing interface, is a significant advantage in these applications.
Due to the high surface hardness of the material, it is used in many engineering applications where high levels of resistance to sliding, erosive and corrosive wear are required. Typically, this applies to components used in pumps or valves in oilfield applications, where conventional metal components would exhibit excessive wear rates leading to rapid failure.
The compound's exceptional electrical properties as a semiconductor make it ideal for manufacturing ultrafast and high-voltage light-emitting diodes, MOSFETs, and thyristors for high-power switching.
Its low coefficient of thermal expansion, hardness, stiffness, and thermal conductivity make it ideal for astronomical telescope mirrors. Thin filament pyrometry is an optical technique that uses Silicon Carbide filaments to measure the temperature of gases.
It is also used in heating elements that must withstand extremely high temperatures. It is also used to provide structural support in high-temperature gas-cooled nuclear reactors.
