Silicon carbide (SiC) ceramics are widely revered for their superior properties, including strength at high temperatures, resistance to oxidation, chemical stability and thermal conductivity. As a result, SiC ceramics find applications both as refractories and in abrasive applications.
Hard armour ballistic protection using silica carbide also exists, and is produced by sintering fine SiC particles together.
Hardness
Silicon carbide, commonly referred to as SiC, is a synthetically produced crystalline compound of silicon and carbon that boasts a Mohs hardness rating of 13. This makes SiC one of the hardest materials known to man – rivaled only by diamond and cubic boron nitride in terms of hardness. SiC’s incredible hardness enables it to withstand wear-and-tear abrasion well, making it suitable for use in harsh environments with high mechanical stress levels and for mechanically stressed applications.
SiC ceramics boast exceptional impact resistance thanks to their high strength. Indeed, SiC is widely used as ballistic armour material; simulation and experimental tests indicate it can withstand 7.62mm AP bullets fired at up to 850 m/s without deforming.
Silicon carbide ceramics stand out from other industrial ceramics by their lower density. Relative to other industrial ceramics, silicon carbide boasts lighter characteristics without compromising strength of final products. Furthermore, this lower density contributes to chemical resistance making silicon carbide an excellent option for use in harsh environments.
Solid-phase sintered silicon carbide exhibits superior chemical and thermal stability when exposed to temperatures up to 1400 degC, as well as robust mechanical properties, making it an indispensable material in many modern technological and industrial applications.
Corrosion Resistance
SiC ceramics are extremely corrosion-resistant materials and can be utilized in numerous applications. Their materials can withstand most acids, alkalis, and molten salts at elevated temperatures while having low coefficients of thermal expansion and being capable of withstanding high mechanical loads – making them the ideal choice for chemical processing equipment such as spray nozzles, shot blast nozzles and cyclone components.
Silicon carbide is one of the lightest, hardest and strongest advanced ceramic materials on the market today. Additionally, it makes an excellent abrasive material and can be found in cutting tools or used for machining applications; additionally it can be cast and melted for industrial uses.
Moissanite occurs naturally only in very limited quantities and is more commonly known by its moniker of “moussanite”, however large scale production is possible by heating a mixture of silica sand (silicon dioxide) and petroleum coke (carbon). Edward Goodrich Acheson invented this process back in 1891 when trying to fuse diamonds. His method became known as the Acheson furnace and continues today.
Aluminum Nitride (AlN), another ceramic material widely used, offers many advantages, including superior thermal conductivity and electrical insulation properties. Unfortunately, its high sintering temperatures and complex preparation methods make its widespread usage impractical.
Thermal Expansion Coefficient
Silicon carbide can tolerate very high temperatures while having a low thermal expansion coefficient, making it suitable for applications where constant stress is applied to it, such as abrasive wear or frictional shock. Furthermore, this material boasts superior fatigue resistance that allows large strains without cracking under strain.
Refractory ceramic is also one of the lightest options, making it well suited to construction materials that must perform under tough environments like chemical plants, mills and expanders. Refractory ceramic has proven itself adept at resisting corrosion, abrasion and erosion as well as frictional wear wear over its lifetime.
Silicon carbide for use in abrasives, metallurgical and refractories industries is produced using Acheson’s process. This involves mixing silica sand with coke and carbon in an electrical resistance furnace before passing an electric current through it with the help of a carbon conductor; this causes chemical reactions which produce SiC and carbon monoxide gas as by-products.
This granular material typically appears as hexagonal crystals with structures similar to Wurtzite. This variety can also be found as polytypes and stacking arrangements, such as cubic b-SiC variations featuring zincblende crystal structures (similar to diamond). Each type has unique properties; our ceramic material property cards provide comparison graphs comparing dilatometric expansion coefficient for all different b-SiC types with other non-oxide engineering ceramics in our database.
Electrical Conductivity
Silicon carbide is a semiconducting material with an Ohm*cm3 resistance range between 105 – 107, which can be further increased by adding electrically conducting second phases such as aluminium or boron to its crystal structure. Silicon carbide appears black or green when pure and has an exceptionally high specific density, making it denser than common ceramic materials yet less dense than many metals.
Silicon carbide’s chemical inertness and mechanical strength make it an ideal material for harsh environments where traditional ceramics would succumb to corrosion or deformation, such as cutting tools. Silicon carbide is often employed in cutting tools for use with abrasive cutting materials as well as mechanical seal parts, pump components and forging processes used throughout engineering sectors; additionally it has thermally conducting capabilities used by forging operations and thermally conducting applications used across engineering. Furthermore its ability to withstand temperatures up to 500oF allows it to be employed in critical petrochemical applications such as turbine blades or burner nozzles in these industries.
Silicon carbide occurs naturally only in very limited quantities as moissanite gemstones and meteorites; most silicon carbide used as an abrasive is manufactured in factories. One of the hardest substances on Earth, cutting silicon carbide requires diamond-tipped blades with Mohs hardness of 9 and can be manufactured into extremely precise dimensions. Due to its chemical inertness and resistance against most chemicals it remains stable even in harsh environments.