How is Silicon Carbide Made?

Silicon carbide (SiC) is a hard, chemically inert material widely used as both an abrasive and ceramic component in high endurance products. Available in various grain sizes and binder formats with differing purity levels and densities, SiC can be found everywhere from industrial applications to consumer goods manufacturing facilities.

SiC was first mass produced commercially by Edward Goodrich Acheson in 1891 through his Acheson process after discovering what appeared to be moissanite-like black crystals while heating an electrically heated solution of clay and powdered coke.

The chemical process

Silicon Carbide (SiC) is an extremely hard material with unique ceramic and semiconductor properties, which makes it a fantastic option for high-temperature and wear resistant applications. Due to its wide band gap semiconductor properties, SiC can operate at much higher temperatures than conventional semiconductors while boasting outstanding abrasion resistance, ceramic strength and electrical properties – qualities which have contributed significantly to power electronics revolution currently taking place.

SiC can occur naturally as the mineral moissanite in very limited quantities; however, its main use in industry is synthetic production. One method commonly employed to do so is known as the Acheson process, first discovered accidentally by Edward Goodrich Acheson while trying to create diamonds in 1891. By mixing silica powdered coke into an electric furnace and passing an electrical current through it Acheson was able to create hard blue crystals which he called “carborundum.”

This process is now widely employed to produce SiC, with several plants worldwide using Acheson’s design for producing it. The procedure starts by mixing together large amounts of silica sand and carbon powdered coke before heating in an electric furnace fitted with a graphite rod as a heat sink to avoid silicon carbide formation from carbon monoxide gas.

Once cooled, the mixture will have solidified into a cylindrical ingot with layers of a-SiC, b-SiC, and unreacted material on its outside. B-SiC features coarse crystal structures while A-SiC boasts very fine ones; then these green or black SiC ingots can be processed further depending on their intended application – sometimes crushed, milled and chemically treated to achieve quality for each application.

To create the final product, a-SiC is ground into a powder form before being mixed with non-oxide sintering aids like organosilicon to form a paste. Once formed, this paste can then be compacted and shaped either through extrusion or cold isostatic pressing to produce sintered material which then undergoes various inspections, tests and quality control checks to ensure it fulfills its specific application needs.

The physical process

Silicon carbide is created through heating silica sand with carbon from coal or low ash petroleum coke (commonly referred to as pitch coke). This material can be found naturally as moissanite in minute amounts; however, most commercial production involves synthetic methods and has its bandgap wider than metal for improved electrical applications.

This process, known as the Lely method, utilizes a granite crucible heated to high temperatures of 2700 degrees Celsius in order to sublimate silicon and carbon into silicon carbide crystals – pure silicon carbide crystals are colorless; industrial products sometimes contain iron impurities. Once heated up to these temperatures, crystals then deposit on graphite at lower temperatures, eventually becoming industrial grade (a-SiC) or metallurgical (b-SiC) products.

Materials made of silicon carbide have numerous applications in various fields, from abrasives and cutting tools to semiconductor electronics and wear parts production. Their hardness (9 on the Mohs scale) makes them particularly sought-after by metallurgy and refractories industries, due to its anticorrosive qualities as well as being used to withstand corrosion and abrasion resistance – ideal properties that make this tough material great for wear part production. Silicon carbide also boasts excellent electrical insulating qualities, making it suitable for electronics use thanks to its ability to withstand very high voltages – perfect for manufacturing wear parts production!

Silicon carbide exists as two polymorphs: a-SiC and b-SiC, each having their own crystal structures. A-SiC is the more prevalent of the two and exhibits a hexagonal crystal structure similar to Wurtzite while b-SiC typically features zinc blende structures; neither form of silicon carbide is as popular.

a-SiC is generally the preferred industrial form of silicon carbide and should be its first choice for high temperature applications. Although more costly, its superior hardness and thermal conductivity make it especially well suited to these uses. Furthermore, doping can further harden it and enhance abrasion resistance; such doping options could include nitrogen, phosphorus or beryllium additions.

Chemical composition makes a-SiC ideal for use as a ceramic, an inorganic material. Ceramic is often confused with silicon carbide due to their similar physical properties; however, mechanical engineers typically refer to impure a-SiC crystallites bonded together by various biners under high pressure and temperature as ceramic, while electrical engineers use the term to refer to pure wafers of this material.

The mechanical process

Silicon carbide is an extremely hard material, second only to diamond. Found naturally in moissanite and mass produced since 1893 as an abrasive, grains of this material can also be joined together via sintering to produce very hard ceramic materials which have found use in applications like car brakes and bulletproof vests as well as transparent ceramic forms known as briquettes for use with light emitting diodes (LEDs).

Silicon carbide for use in metalworking and refractories is typically manufactured using an electrical resistance furnace equipped with carbon conductor walls. A current is then passed through this conductor to initiate chemical reaction between carbon from coke and silica in sand resulting in pure cubic silicon carbide powder that has light yellow hue.

Silicon carbide production follows this general method, though there may be variations. Some manufacturers use refractory clay that is combined with powder before heating to prevent neck growth; other processes produce denser forms by infiltrating a fired body with gaseous or liquid silicon.

Silicon carbide’s extreme hardness and resistance to wear, high temperatures and thermal shock make it an invaluable material. Silicon carbide plays a significant role in steel production because it increases furnace efficiency by producing purer iron. Furthermore, silicon carbide serves as an outstanding refractory material because of its resistance to both heat and thermal shock.

Silicon carbide’s strength, hardness and refractoriness makes it an indispensable material for grinding wheels used to machine steel, aluminum oxides and ceramics. Furthermore, its ability to withstand high voltage demands makes it a prime candidate for electric motors and generators in electrical vehicles; additionally it’s ideal for high-speed alternators in electric cars as its use helps extend driving distance while simultaneously decreasing size and weight of energy storage systems.

The electrical process

Silicon carbide is one of the hardest materials known to man, yet its other useful properties include chemical and thermal resistance as well as high strength and durability. Semiconducing properties make the material particularly appealing as they enable its use in electronic devices that amplify, switch or convert signals within an electrical circuit. Furthermore, silicon carbide operates at higher temperatures and frequencies than traditional silicon semiconductors making it a superior choice for power electronic applications.

Silicon Carbide was artificially synthesized for the first time by chemist Edward Goodrich Acheson in 1891 while attempting to make diamonds by passing an electric current through clay. Instead, Acheson discovered hard black crystals resembling silicon dioxide which were commercialized as industrial abrasives under its original name, carborundum.

Manufacturers utilize a controlled high-temperature process to produce single-crystal silicon carbide using base materials with highly pure silicon and carbon, typically done through powdered source material as the raw material for crystal growth in an environment free from air or dust pollution.

Base materials are combined in a furnace and subjected to intense heat and pressure in order to produce one single, large-diameter seed crystal. This seed crystal is essential as its characteristics will determine what ultimately becomes silicon carbide; hence its quality must be unimpeachable. Furthermore, source material concentration must be adjusted precisely so as to produce silicon carbide in accordance with desired stoichiometry: three carbon atoms for every two silicon atoms produced in silicon carbide production.

After cooling, the ingot is carefully crushed and classified, sometimes milled again, before chemically treating to achieve specific characteristics for specific uses. The resultant material is a tough ceramic with outstanding hardness of 9 on Mohs scale that is highly corrosion resistant as well as chemically inert to most alkalies and acids – and highly stable under high temperature conditions.

Once cut into wafers, these ingots are sliced up and shaped using various techniques into products suitable for specific applications. After shaping is complete, sintered silicon carbide must pass dimensional tests and inspections to ensure it complies with quality standards before being released for use.