Silicon carbide is the only chemical compound of carbon and silicon. SiC is a widely used ceramic material with many high-performance applications, including abrasives, refractories and electronic components.
In its crystalline form, SiC crystallizes in a tightly packed, covalently linked structure of two main coordination tetrahedra: four carbon and four silicon atoms link to a central Si and C atom. The tetrahedra form a single crystal that is highly resistant to oxidation and chemical attack.
For structural use, silicon carbide can be produced in a variety of forms and with various chemical aids. Nitride-bonded silicon carbide is a popular option and is made by dispersing fine silicon powder in a compact of larger silicon carbide particles and sintering in a nitrogen furnace; this produces a predominantly silicon carbide structure with a large percentage of its porosity filled with silicon nitride.
Sintered silicon carbide is also a good choice for heating elements. Unlike metallic heating elements, which are often water-cooled, these heat sources can operate at very high temperatures with little maintenance. In addition, they can have a high efficiency and produce a low wattage output per pound of energy.
The first references to silicon carbide heating elements were in the early 20th century, and production began at Acheson’s Carborundum Company in the U.S. and EKL in Berlin, Germany. These heaters featured water-cooled terminals that brought the electric current to the hot zone of the element and were held in place by weights or springs. Later, separate low resistance silicon carbide “cold ends” were used, usually of a larger diameter than the hot zone, to increase operating temperature and efficiency.