Silicon Carbide

Chemical formula: SiC

Melting point: 2730 °C

Density: 3.21 g/cm3

Silicon carbide has been known since the late 19th century, but its industrial development began in the early 20th century when Edward Acheson perfected an economical synthesis method that allowed for its large-scale production. Its ingredients are abundant and inexpensive: silicon dioxide (SiO₂), found in sands and quartz, and carbon, typically obtained from coke. When heated together at temperatures above 2,000 °C, silicon dioxide reacts with carbon, releasing carbon monoxide (CO) and forming SiC crystals. This process, despite its apparent simplicity, requires technical control to achieve high qualities. 

SiC can exhibit varied colors depending on its purity. Although theoretically it should be transparent, small metallic impurities—especially iron—often tint it black or dark green. This ease of contamination has limited its use as a synthetic gem to imitate diamonds, although gem-quality silicon carbide is known as moissanite when natural and carborundum when artificial. Its extreme hardness makes it an exceptional abrasive material, while its toughness, superior to that of other ceramics, allows for its use without the need for metallic binders.

Silicon carbide maintains its structural integrity and rigidity up to temperatures near 900 °C without losing mechanical properties, unlike most ceramics, which begin to oxidize above 150 °C to 200 °C. It is chemically inert to most reagents, possesses high resistance to corrosion and oxidation by friction (crepitation), and acts as a semiconductor with highly valuable electronic properties for power devices.

Thanks to its hardness, silicon carbide is massively used as an abrasive in cutting discs, sandpaper, and wear tools. In the defense sector, its plates are employed in bulletproof vests and lightweight armor due to the combination of hardness and low weight. In precision engineering, it is used in bearings, bushings, and turbine components for its wear resistance, ability to withstand extreme mechanical loads, and dimensional stability.

In the automotive industry, SiC is the key material in high-performance “ceramic” brake discs, including those used in luxury cars and Formula One. Its resistance to abrasion, impact, and thermal corrosion ensures durability and safety at high speeds and extreme temperatures. Furthermore, its semiconductor nature makes it ideal for manufacturing high-power and high-temperature electronic devices, such as transistors and diodes for power inverters, electric automotive systems, and aerospace equipment.

Silicon carbide is, without a doubt, the most important and versatile non-metallic carbide. Its cost-effectiveness remains excellent, with applications ranging from traditional abrasive industries to cutting-edge microelectronics and advanced defense systems. Despite attempts to use it as a diamond substitute in jewelry, cubic zirconia has displaced carborundum due to its ease of manufacturing and greater brilliance, although SiC remains valued in gemology for its hardness and light dispersion.