碳化硅是如何制造的？

Silicon carbide (SiC) is a hard chemical compound comprised of silicon and carbon, found naturally as moissanite gemstone and produced mass-scale for use in abrasives, metallurgical applications and refractories.

SiC is ideal for fire bricks and other refractory products due to its resistance to high temperature and thermal shock, its semi-conductive nature, and atomic structure which renders it heatproof.

Chemical Reactions

Silicon carbide, more commonly referred to as carborundum or SiC, is a ceramic material with both structural and semiconductor properties. With strength, high temperature resistance and chemical inertness even at elevated temperatures, SiC makes for an excellent material in abrasives, metallurgy and refractories applications; in addition, its semiconductor-like characteristics make it well suited for high power devices operating at temperatures that conventional semiconductors cannot support.

SiC can be produced using various production techniques, each offering distinct advantages for specific applications. For instance, Acheson process offers high strength complex shapes; reaction-bonded silicon carbide (RBSC) process provides high purity; while chemical vapor deposition offers the potential to create ultrapure coatings.

Commercial silicon carbide production typically uses an electric furnace process with low-ash petroleum coke as its carbon source, before being crushed and milled before being sorted and chemically treated to meet specific performance characteristics.

Silicon and carbon react chemically in raw materials to form polytypes or stacking arrangements of elements, with cubic silicon carbide (a-SiC) being one of the more popular polytypes with its Mohs hardness of 9. While raw minerals of this nature may be mined as raw mineral sources, most often it is produced through combination processes: reaction bonding and sintering.

Reaction-bonded is a process where a mixture of ground silica sand and carbon in the form of low ash petroleum coke are combined and built up around an electrical resistive furnace via reaction bonding. An electric current is then passed through a conductor, setting off a chemical reaction and producing a cylindrical ingot of both a-SiC and b-SiC; any unreacted a-SiC remains on its surface of the ingot. Liquid silicon is then added, binding the initially separate crystals together into one continuous structure of cubic SiC crystals that is suitable for most industrial uses; sometimes further processing may occur to produce metallurgical grade material.

Heating

Silicon carbide (SiC) is an inorganic chemical compound composed of carbon and silicon that occurs naturally as the rare mineral moissanite; however, since 1893 it has also been synthetically manufactured as a powder form to be used as an abrasive. Silicon carbide boasts the hardest synthetic material rating between Alumina (aluminum oxide) and Diamond on Mohs’ scale hardness scale and its thermal conductivity, low thermal expansion rates, chemical inertness make it highly suitable for industrial refractory applications such as furnace bricks.

Producing metallurgical grade SiC is usually carried out through the Acheson process, which entails mixing raw materials such as quartz sand (silica sand) with petroleum coke or anthracite coal in an electric arc furnace heated to about 2600degC. As part of this heating process, silicon dioxide (SiO2) is reduced and changed into SiC and other compounds called metallurgical silicates that are later ground up again into black or green silicon carbide, depending on their quality.

Silicon carbide production using this technique yields high yield, producing up to 11.3 tons per furnace charge of black silicon carbide. However, higher purity SiC can be obtained using more expensive methods such as Lely’s process.

Silicone carbide occurs in different polymorphs or forms, each possessing distinctive characteristics and properties. For instance, alpha silicon carbide (a-SiC) has a hexagonal crystal structure similar to wurtzite while beta modified b-SiC contains zinc blende crystal structures similar to diamond.

No matter its polymorph, all forms of silicon carbide share a similar layered structure containing silicon and carbon atoms bonded together into a tetrahedral configuration. SiC is distinguished from boron carbide by having three carbon atoms for every silicon atom in its structure – unlike its diamond-like structure which gives boron carbide its superior mechanical properties and more commercial viability; consequently a-SiC boasted superior mechanical properties, becoming dominant until b-SiC came along and more soluble.

Drying

Silicon carbide is an extremely hard, crystalline material with multiple industrial applications. Most notably it is commonly employed as an abrasive in grinding wheels, cutting tools and sandpaper due to its very high strength and hardness; however, other uses include electrical insulators, refractories and ceramics – its low thermal expansion properties make it the perfect material to be used in high temperature environments – though it’s often coated with aluminum oxide to extend its longevity further still.

Silicon carbide production begins by first heating raw silica and carbon in an electric furnace until their compounds combine to produce silicon dioxide and carbon monoxide gas, followed by drying in an inert atmosphere for several days at temperatures ranging between 1,400-2,700 degrees Celsius – this allows impurities to be effectively removed leaving behind an almost pure silicon carbide ingot.

Skilled workers then sort and classify this ingot into various sizes, shapes, and chemical compositions that meet different applications. Once sorted and classified by skilled workers, it may then be further processed for use in industries like abrasives, metallurgy and refractories as well as becoming dopants for semiconductor production products when added dopants to it.

Dopants added to an ingot can produce multiple polytypes with distinct physical and electrical properties. Boron and aluminum will make silicon into a p-type semiconductor while nitrogen and phosphorus creates an n-type semiconductor.

Producing pure silicon carbide requires an intricate and meticulous process that requires precise attention to every step. Refractories produced with silicon carbide for use in the abrasive, metallurgical and refractory industries often have unique specifications such as grain sizes, binder types, purity level, density level and porosity requirements. Our Washington Mills team will gladly work with customers to understand their individual requirements while exploring all the possibilities with CARBOREX products.

Sintering

Silicon carbide can be difficult to work with and grind, requiring diamond or ultrasonic tools for cutting or grinding operations. Furthermore, its delicate surface requires careful handling in order to avoid flaking or chipping; since its durability allows it to withstand very high temperatures well in furnaces or kilns.

Acheson Process. Silicon carbide can be created using this process by mixing silica sand with carbon powdered coke in order to form a green or black solid that can then be ground to form fine powder and mixed with other ingredients to form plasticizer, enabling silicon dioxide and carbon atoms to bond together and then formed using molds before infiltrating with liquid silicon to produce a reaction bonded material, or sintered material.

Sintered silicon carbide boasts higher purity than reaction bonded, is easier to machine and shape, and has excellent corrosion, wear and thermal shock resistance – being capable of withstanding temperatures of 1600degC without succumbing to oxidation or chemical attack. As a result it is used in a wide range of industrial applications due to these attributes.

Sintering technology is used extensively in advanced electronic applications. For this, large single crystal boules are produced through the sintering process and then cut into wafers for use in semiconductor devices. Sometimes pure materials may be mixed with boron or aluminum to increase hardness and hardenability.

Sintering can create high strength ceramics that are resistant to cracking. Not only is this type of ceramic resistant to high temperatures but it is also highly refractory to chemicals like sulphuric and hydrofluoric acids; hence the name sintered a-SiC. Silicon carbide’s hardness, rigidity, thermal conductivity and hardness also make it desirable as an astronomical telescope mirror material; unlike many other mirror materials it remains stable during temperature shifts without deforming under its own weight allowing it to replace glass in various telescope models from small handheld models to huge space observatories.