Silicon carbide (SiC) is an alloy composed of silicon and carbon. While naturally present as moissanite mineral, SiC has been mass produced since 1893 for use as an abrasive and long-term ceramics used for car brakes, clutches and bulletproof vests.
Workers exposed to manufacturing SiC may develop lung conditions resembling silicosis.
History
Edward Goodrich Acheson of America discovered Silicon Carbide by accident while attempting to create artificial diamonds in 1891. While using an electric current to heat clay (aluminium silicate) with carbon, Acheson noticed some hard crystals from his experiment that resembled corundum which is an aluminium oxide compound; due to this similarity he named his discovery carborundum based on how similar its hard crystals looked like corundum as well as being harder than rubies and sapphires.
Acheson quickly discovered that SiC could be manufactured in large quantities by heating a mixture of silica and coke in an electric furnace, producing a powder that could be crushed and used as an abrasive. SiC is also an important semiconductor material and can be doped with either n-type or p-type conductors such as boron, phosphorus or nitrogen to make different versions.
Carborundum flourished following World War I and the industrial boom of the 1920s. Following this success, they expanded further during the 1950s with the development of Fiberfrax ceramic fiber made of aluminum oxide and silica; this cottonlike material could withstand high temperatures while resisting water corrosion and chemical corrosion, transmitting only minimal heat, finding many uses in automotive, chemical papermaking, and electrical industries.
Carborundum expanded its diversification during the 1980s by opening a plant in Niagara Falls which manufactured electrical resistance elements and manufacturing fiberglass insulation products. They also invested in alumina and zirconium but market saturation resulted in stagnated earnings per share growth for these products; ultimately BP sold Carborundum off to St. Gobain who had long purchased its products from them.
Properties
Silicon carbide is a hard, tough ceramic with excellent mechanical strength even at temperatures as high as 1400degC. As the third hardest material on Earth (after diamond and boron carbide), with a Mohs hardness rating of 13, it offers tremendous wear resistance as well as being chemically inert and corrosion proof.
Carborundum is widely used as an abrasive in applications requiring high endurance such as car brakes and clutches, ceramic coatings, light emitting diodes (LEDs) and transistors, among other electronic devices.
Simulated silica-carbon ceramics are produced through reacting silica with carbon in an electric furnace and come in various forms including granules, powders, blocks and sintered products. Sintering bonds the granules together into large long-term products with excellent wear resistance and abrasion properties.
Granules of this material can be ground into fine powder for use in various grinding, shaping and finishing applications. Furthermore, it serves as the raw material for manufacturing vitreous fiber refractories which have been widely used since 1881 for their superior heat stability, thermal conductivity and electrical current density properties. Studies have revealed however that inhalation may cause fibrotic lung disease which remains an area of research.
Manufacturing
Silicon carbide or carborundum, is an industrial abrasive made up of silica and carbon. Refractory ceramic fibers manufactured artificially have high thermal conductivity and electrical current density for use in electronic devices as well as friction products such as brakes, friction plates and car clutches. Carbon nanotubes boast one of the highest abrasion resistances and are chemically inert against most alkalies, acids and hydrocarbons, making it one of the world’s hardest naturally occurring substances surpassed only by diamond, cubic boron nitride and tungsten carbide. Their color can range from brown to black due to iron impurities; for enhanced properties they may also be doped n-type with nitrogen or phosphorus or doped p-type with beryllium, boron or aluminium for enhanced properties.
Silicon carbide was first produced commercially for industrial use by Pennsylvania inventor Edward G Acheson in 1893 and today ranks among the most important of synthetic abrasives. Acheson’s process, in which fine ground carbon (petroleum coke) and sand are fused together in an electric furnace at high temperatures to form SiC, remains the primary manufacturing method worldwide.
Susteon has developed an innovative low-emissions manufacturing technique for SiC through the Acheson process that significantly lowers emissions such as hydrocarbons and organic vapors during production. The technology utilizes dehydrogenation of petroleum coke prior to using in an Acheson furnace – this significantly increases energy yield while significantly decreasing pollutant gases released into the environment.
Applications
Carborundum abrasives are mass produced on an industrial scale by fusing high-grade silica sand with finely ground carbon (petroleum coke) in electric furnaces, creating hard, tough material with excellent resistance to angular abrasion but less so than structural ceramics. Carborundum requires high temperatures when being machined but distortion should not occur as easily; its strength, wear resistance, and corrosion resistance make it popularly chosen as grinding media in milling and drilling applications.
Silicon carbide grains possess sharp edges which are ideal for cutting and milling metals. Furthermore, this material serves as the basis of long-wearing ceramic plates in bulletproof vests as well as the primary ingredient in refractory materials for blast furnaces, zinc furnace linings, incinerator linings and kiln systems – while its electrical properties also prove invaluable when applied as lightning arresters in electric power distribution networks.
Numerous studies indicate that workers exposed to carborundum abrasives during manufacturing or usage may develop symptoms similar to silicosis. Particulates from carborundum materials, and fine dusts from its particles have been shown to cause lung damage that may exceed that caused by exposure to crystalline silica particles. Granulomas in the lungs have even been documented which can be diagnosed using chest radiograph imaging or confirmed through biopsy or autopsy.
English 
Swedish