Synthetic silicon carbide crystal aggregate: iridescent twinned crystals in foreground with untwinned tabular crystals in background. They have a metallic lustre and are razor_sharp.
Most silicon carbide is man_made for use as an abrasive (when it is often known by the trade name carborundum), or more recently as a semiconductor and moissanite gemstones. The simplest manufacturing process is to combine sand and carbon at a high temperature, between 1600°C and 2500°C. Purer product can be made by the more expensive process of chemical vapor deposition. Its high melting point (above 1600°C) makes it useful for bearings and furnace parts. It is also highly inert. There is currently much interest in its use in electronics, where its high thermal conductivity, high electric field breakdown strength and high maximum current density make it more promising than silicon for high_powered devices. In addition, it has strong coupling to microwave radiation and that, together with its high melting point permits practical use in heating and casting metals.
Silicon carbide is used for blue LEDs, ultrafast Schottky diodes and MESFETs. Due to its high thermal conductivity, SiC is also used as substrate for other semiconductor materials.
In the 1980s and 1990s, silicon carbide was studied on several research programs for high temperature gas turbines in the Japan, and Europe. The components were intended to replace nickel superalloy turbine blades or nozzle vanes. However, none of these projects resulted in a production quantity, mainly because of its low impact resistance and its low fracture toughness.
External links
Computer chips get tough (http://www.nature.com/news/2004/040823/full/040823-9.html) (news@nature.com)
NASA Glenn High Temperature Integrated Electronics and Sensors Team (http://www.grc.nasa.gov/WWW/SiC/SiC.html)
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