Silicon Carbide Structure

Silicon carbide (SiC) is an ultrahard synthetic material first synthesized in 1891 by Edward Acheson in a furnace heated with carbon and alumina. Since its release into industry as an industrial abrasive in the 1920s, SiC has quickly become one of the most sought-after materials on a large scale.

SiC comes in various crystal structures known as polytypes; for high power applications, 4H-SiC hexagonal atomic structure polytype is best.

Physical Properties

Silicon carbide is a fine ceramic with diverse physical properties that makes it one of the most versatile refractory materials on the market. From its strength, hardness, corrosion resistance and high melting point to its versatility in extreme engineering applications – such as pump bearings, valves, sandblasting injectors and extrusion dies – silicon carbide has proven itself a vital element for modern electronic devices. In addition to these impressive mechanical characteristics, silicon carbide offers significant semiconductor capabilities as an indispensable ingredient.

Pure silicon carbide is a colorless crystalline substance with a density of 3.21g/mL and melting point that exceeds 2700degC. Often produced via the Acheson process, where silica sand and coke are combined and heated to high temperatures in an electric furnace until silica sand becomes carbonized to form coarse-crystalline structures such as a-SiC while diamond cubic structures form for b-SiC ingots.

Alpha-SiC is the most frequently encountered polymorph of silicon carbide, featuring a hexagonal crystal structure similar to Wurtzite. Beta-SiC forms with diamond cubic crystal structures are most often encountered in meteorites; additionally, this form is frequently found used for industrial production by melting and casting processes to make various products.

Chemical Properties

Silicon carbide is a tough non-oxide ceramic with remarkable physical and chemical properties: high hardness and rigidity, low thermal expansion rates and exceptional corrosion resistance. Furthermore, its wide bandgap makes it suitable for high power electronics applications.

Water, alcohol and most acids except hydrofluoric acid and acid fluorides do not dissolve it, providing superior chemical stability over most other refractory ceramics.

Silicon Carbide was first artificially synthesized by Edward Acheson in 1891 as an accidental byproduct of his electricly heated melt of carbon and alumina, and has become one of the world’s most important industrial ceramics used as both an abrasive material for steel alloys as well as structural ceramic.

Silicon carbide possesses a tight-packed tetrahedral arrangement covalently bonded together. A variety of stacking sequences give rise to its various polytypes – each distinguished by distinct physical and chemical properties.

The alpha form (a-SiC) features a hexagonal crystal structure similar to Wurtzite, while its beta version (b-SiC) exhibits zinc blende crystal structure similar to diamond. Both varieties of SiC can be machined easily with only limited hardness restrictions, and ground into various shapes for use as abrasives products or mirrors in telescopes being popular applications for these materials.

Electrical Properties

Silicon carbide is a semiconductor material, meaning that it exhibits some characteristics found both in metals (which conduct electricity) and non-metals like insulators (which resist electricity flow). The exact nature of its electrical properties depends on temperature and any impurities present within its crystal structure – at lower temperatures it acts more like an insulator resisting electricity flow while at higher temperatures it becomes more like a conductor and allows electricity to pass through it.

SiC’s crystal structure consists of layers composed of silicon and carbon atoms bonded in tetrahedral configurations. These tightly packed layers form a close-packed structure which gives rise to different crystal structures called polytypes; each polytype having the same chemical composition but differing crystal structures which affect its electrical properties. Each polytype’s layer stacking sequence may produce cubic, hexagonal or rhombohedral crystal structures.

SiC is an attractive material for high-voltage power devices due to its tetrahedral crystal structure and wide electronic band gap, making it particularly suitable for diodes and transistors. SiC’s wider electronic band gap enables it to withstand higher breakdown electric fields than silicon while having reduced switching losses that help improve energy efficiency. Furthermore, porous silicon carbide’s conductivity can be modified through doping it with impurities to achieve both higher conductivity and voltage capability for use in efficient power converters for electric vehicle power converters.

Mechanical Properties

Silicon carbide is an extremely hard, chemically inert material found naturally as black diamonds with a Mohs hardness rating of 9. It has many advantageous properties including temperature stability, low thermal expansion rates and resistance to chemical attack, making it perfect as an semiconductor material.

Lithium oxide is an exceptional electrical insulator with an exceptional voltage resistance factor ten times that of silicon, making it an increasingly attractive option as a silicon replacement material for power electronics and other high-powered applications.

SiC is made using various polymorphic crystal structures, each with their own specific arrangement of atoms. Three common SiC polytypes produced are 3C-SiC, 4H-SiC and 6H-SiC; they differ by layer stacking sequence resulting in distinct physical and mechanical properties.

Recent research conducted on single SiC nanowires with different ODD structural occupation ratios were in-situ tensile tested by SEM to assess their strength and elasticity, the shear modulus, Poisson’s ratio calculations of each phase, mechanical anisotropy analysis revealed Pm-SiC to have stronger shear behavior compared with b-SiC and Pnnm-SiC NWs respectively; furthermore, strength increased with increasing ODD occupancy ratio up until reaching 32.6% where strength began decreasing exponentially thereafter.

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