Silicon carbide (SiC), also known as carborundum or SiC,. is one of the lightest, hardest, and strongest technical ceramic materials. It has exceptional thermal conductivity, resistance to acids, and low thermal expansion.
Since the late 19th century, silicon carbide ceramics have been an important material for sandpapers, grinding wheels, and cutting tools. More recently, it has found application in refractory linings and heating elements for industrial furnaces, in wear-resistant parts for pumps and rocket engines, and in semiconducting substrates for light-emitting diodes.
There are 250 crystalline forms of silicon carbide. The polymorphic feature of SiC is a large class of similar crystal structures called polymorphs. They are variants of the same compound, the same in two dimensions but different in three dimensions. Therefore, they can be viewed as layers stacked in a specific order.
Alpha silicon carbide (α-SiC) is the most common polymorph. It is formed at temperatures above 1700°C and has a hexagonal crystal structure (similar to wurtzite). The beta modification (β-SiC), with a zinc blende crystal structure, is formed at temperatures below 1700 °C.
|Melting Point||2,730° C (4,946° F) (decomposes)|
|Density||3.0 to 3.2 g/cm3|
|Electrical Resistivity||1 to 4 10x Ω-m|
|Poisson’s Ratio||0.15 to 0.21|
|Specific Heat||670 to 1180 J/kg-K|
Until the invention of boron carbide in 1929, silicon carbide was the hardest synthetic material known. It has a Mohs hardness rating of 9, approaching that of a diamond. In addition, SiC crystal has fracture characteristics that make them extremely useful in grinding wheels and in abrasive paper and cloth products.
Its high thermal conductivity, together with its high-temperature strength, low thermal expansion, and resistance to chemical reaction and thermal shock, makes silicon carbide valuable in the manufacture of high-temperature bricks and other refractories.
SiC ceramic is also classed as a semiconductor, having an electrical conductivity between that of metals and insulating materials. This property, in combination with its thermal properties, makes SiC a promising substitute for traditional semiconductors such as silicon in high-temperature applications.
Advanced Ceramic Materials (ACM) is a leading supplier of silicon carbide ceramic products of the highest quality for a wide range of applications. We are happy to provide advice on materials, design, and application. Feel free to contact us for any questions about SiC or other ceramic materials that are not listed on the website.