Silicon carbide is used for various applications due to its excellent high temperature and corrosion resistance properties. This material can be made into various products like abrasives, coated abrasives, grinding wheels, lapping tools, lapping foil insulation and even metallurgical and refractories applications.
Silicon carbide is most often produced using the Acheson process. This involves heating a mixture of silica sand and carbon in coke at high temperatures until chemical reactions occur that produce pure silicon carbide crystals.
Acheson Process
The Acheson process is widely used commercially to produce silicon carbide. This high-energy process involves mixing silica with petroleum coke and heating it at high temperature before discharging into an electric furnace for processing. A mass transfer model was created to help better understand this complex procedure, and results showed that silicon carbide formation was predominantly controlled by solid-gas reactions rather than liquid phase reactions as previously believed.
As in a normal Acheson furnace operation, the mixture is packed into a furnace along with a carbon or graphite resistor 14 made up of coke and fire sand reclaimed from previous runs as an Acheson resistor 14. Electrical power is applied to this resistor in order to create high voltage within the reaction mass, while temperatures are monitored throughout and near graphite slabs placed along the sides of the furnace.
Silicon carbide (SiC), an energy intensive and highly energy intensive process, has recently been revolutionized through two processes based on it: Acheson and Lely processes. While Acheson produces coarse-grained SiC crystals through sublimation, Lely synthesizes more fine crystalline material.
Lely Process
The Lely process is an alternative method used in silicon carbide manufacturing that utilizes a chemical blend encased within an enclosed vacuum environment to combine before depositing onto a substrate. This procedure takes an enormous amount of energy, equipment and expertise – not to mention time – and is only possible with great precision.
Manufacturers use the modified Lely process to produce large single crystals of SiC for electronic fabrication, using it as raw material for hardened surface mount devices (HMD). Such materials must be hard, durable, and electrically conductive – qualities SiC is capable of fulfilling thanks to its crystalline structure. Furthermore, SiC also boasts unique properties not found elsewhere such as its unparalleled hardness and chemical resistance against alkalies and acids.
One common modification to the Lely method employs a graphite crucible equipped with induction coils for heating. Once heated, this vessel is lined with thin layer of silicon carbide to prevent impurities from escaping the sublimation space and crystals can then be used to form ingots that can then be accurately sorted and further processed for different applications.
Example 1 describes a process where ingots are subjected to nitrogen-containing gas flows in order to produce products with high n-conductivity, making possible components which perform under extreme conditions, such as those required in jet engines and rocket nozzles.
Reaction Bonding
Reaction bonding is one of the oldest methods for creating silicon carbide ceramics. This technique involves mixing coarse silicon carbide, clay, plasticizers, and other materials together into a formable paste which can then be heated to fuse its materials together before being hardened into solid form with cooling. Reaction bonding was one of the earliest means of producing silicon carbide.
This process facilitates the production of reaction-bonded silica, which boasts superior wear resistance and higher fracture toughness than other forms of silicon carbide. Furthermore, its thermal conductivity and low thermal expansion properties make it suitable for use in electrical components like power transistors and diodes.
Scientists have developed a new processing method to enhance the performance of reaction-bonded silica, by bonding it at lower temperatures. This decreases the amount of free silicon present that could erode and wear away at its materials and increase wear rates.
Reaction-bonded silicon carbide (RBSC) has many applications because of its resistance to heat, wear and corrosion. It is widely used in kiln furniture thanks to its excellent thermal shock resistance; furthermore it can be turned into ceramic components for high temperature applications like seals or vanes; furthermore its high melting point makes it ideal for fusion experiments using crucibles.
Ceramics
Solid-phase sintered silicon carbide ceramic is one of the hardest and most durable of fine ceramics, maintaining its strength up to 1400degC without losing strength or expanding or contracting significantly – ideal for heat resistant applications like burner nozzles, jet and flame tubes used in chemical processing equipment, as well as general industrial machine components. Additionally, its resistance to corrosion, abrasion and corrosion makes it highly corrosion resistant with low expansion and semiconductivity properties which makes it suitable for refractory uses like burner nozzles jet tubes used in chemical processing equipment along with general industrial machine components used throughout machinery.
SiC is widely known for its high hardness and chemical stability, making it an excellent raw material for manufacturing abrasives. SiC serves as the base material for coated and free grinding abrasives used on glass, ceramics, stone, cast iron, non-ferrous metals as well as non-ferrous metals like aluminium. Refractories also use SiC, including shed boards used in firing ceramic products kilns; silica-coated kiln linings; and crucibles used with aluminium electrolytic cells.
Reaction bonding is another method for producing silicon carbide ceramics used in industries like abrasives, metallurgy and refractories. A mixture of coarse sand, silicon powder and plasticizers are heated in an electrical resistance-type furnace until carbon from coke reacts with silica to form silicon carbide and carbon monoxide gas – this allows for shaping into desired shapes or pressing into powder for further use.
As it offers high density and compressive strength, polycarbonate ballistic protection offers greater ballistic resistance for its weight than steel or aluminium solutions.
Swedish 
English