Silicon Carbide (aka Carborundum or Moissanite)
Silicon carbide was first synthesized by accident in the late nineteenth century while trying to replicate real diamond – an occupation that was fairly common around that time and which led to a number of new carbides and nitrides – materials that offer the hardest alternatives to diamond – being discovered, It appears to have been discovered simultaneously by American inventor Edward G. Acheson and chemist Henri Moissan. A blend of sand (silica) and carbon, silicon carbide, like diamond, is distinguishable by its incredibly hard-wearing properties. It maintains its shape at temperatures over 1000°C (1832°F) and has very high resistance to thermal shock, a property that allows it to go quickly from one extreme temperature to another without damage.
Although it’s not a particularly new material it has been used in powdered form to create a brutally coarse, hard, dark green/grey stone-like material used as an abrasive for more than 100 years. It is used for its hardness in abrasive machining processes such as grinding and honing. As an offshoot of Moissan’s discovery, Moissanite – another form of silicon carbide – was discovered and marketed as a gemstone with a hardness that approaches that of diamond but with greater clarity, contributing yet another story to the increasingly varied world of ceramic materials.
Image: Silicon carbide grinding stone
•Very high resistance to wear
•High resistance to thermal shock
•Excellent hardness
•Excellent compression strength
•Low thermal expansion
•High thermal conductivity
•High chemical inertness
Sources
Available through specialist global suppliers.
Cost
Price varies widely as there are many grades of silicon carbide, but it is generally a cost effective option.
Sustainability issues
Silicon carbide is considered a hazardous substance in its crystalline state, and can cause irritation to eyes, skin and lungs as well as damaging the environment.
Production
Silicon carbide can be processed using a number of diverse techniques. These include using the powdered form for dry pressing (which is suited to batch production), sintering, ceramic injection moulding, isostatic pressing, extrusion and slip casting (for producing thin-walled hollow shapes). It can also be machined and ground with diamond wheels. Silicon carbide fibres are also used as reinforcement for plastics to increase strength, stiffness and wear resistance.
Typical applications
A main area of application is grinding media in environments where there are extreme changes of temperature and high wear and tear. These applications are based in heavy industry in objects such as seals and bearings, and turbine components. As well as Moissanite’s use in jewellery, another main consumer application is car brake pads; the Porsche Carrera is one car that exploits its qualities, creating a compelling high-tech story. Silicon carbide fibres can also be added to plastic mouldings to increase hardness of parts.
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–Versatile processing –Extremely hard and strong –High thermal conductivity |
–Only available through specialist suppliers |