Kaj je silicijev karbid?

Silicon carbide is one of the hardest materials known, boasting a Mohs hardness greater than diamond. Furthermore, its mechanical properties include excellent tensile strength and Young’s modulus values.

Electrical properties of graphene include high saturation electron mobility and voltage breakdown resistance, making it suitable for high performance electronics such as inverters.

Chemical Composition

Silicon carbide (SiC) is an alloy composed of carbon and silicon with covalent bonding structures. SiC can be produced through reacting a mixture of carbon and silica in electric resistance furnaces at temperatures ranging between 1700-2500 degC; this produces a solid cylindrical ingot composed of graphite, alpha SiC, beta SiC metallurgical grade material, as well as any unreacted material on its outside surfaces.

SiC is a yellow to green to bluish-black crystalline form with a density of 3.21 g cm-3 and sublimes at 2700 degC; it can also dissolve in liquid alkalis and iron soluble solutions.

SiC is a polycrystalline material with variable internal microstructure depending on its polycrystalline type and method of formation, with wide-ranging properties. One key difference between the a-SiC and b-SiC polymorphs lies in their respective crystal systems: hexagonal wurtzite for a-SiC and rhombohedral tungsten carbide (WC) respectively – although the latter has lower melting point of 1875 degC than its counterpart making it the more popular choice among these polymorphs.

Fizikalne lastnosti

Crystalline SiC consists of silicon and carbon atoms arranged in a three-dimensional lattice structure that forms covalent bonds between layers, giving this material high melting points and resistance to internal oxidation while contributing to its hardness.

Electrical properties of crystalline SiC depend on its polytype (Cubic, Hexagonal or Rhombic). Each polytype exhibits distinctive semiconductor electronic properties due to the different arrangements of Si and carbon atoms within its crystal lattice.

In an typical production process, pure SiC is sublimed at high temperature in an argon gas atmosphere and then crystallized onto seed crystals using Lely’s process, creating single crystals which are processed further for power electronics applications using well-established process stages.

Mehanske lastnosti

Silicon carbide’s hard, wear-resistant properties make it an excellent abrasive material in modern lapidary. Furthermore, silicon carbide has also been utilized as refractory lining material in industrial furnaces as well as used to construct grinding wheels and cutting tools.

SiC has mechanical properties which vary significantly based on its forming and firing processes, grain size, purity, stoichiometry and pore structure within its densified body. Temperature has an enormous influence over these characteristics which may even differ greatly between sources.

Young’s modulus for dense SiC is approximately 400-450 GNm-2 at 20degC and 360-400 GNm-2 at 1500degC; its shear strength accounts for half this value; bend strength can be difficult to measure for such materials; values reported in literature range between 500-660 MNm-2 at 20degC and about 5000-6000 MNm-2 at 1500degC; creep resistance is excellent, while tensional stress levels must remain within reasonable levels to prevent cracking and fracture from arising.

Električne lastnosti

Silicon carbide has the ability to withstand high temperatures and chemical reactions, providing protection from degradation in harsh environments. Unfortunately, however, this brittle and hard material reaches room temperature tensile strengths of around 4GPa (Engineering Property Data’ 1979).

SiC is known for its superior electrical conductivity and low resistance; this makes it suitable for power and RF electronics applications, with low resistivity and high saturation electron mobility that can be leveraged to great effect. Furthermore, SiC’s durability extends into radiation resistance and thermal shock resistance as well as being long lasting.

Manufacturers use various processes to produce cubic SiC. One method involves reaction-bonded SiC, produced by mixing powdered carbon with plasticizer and firing it; subsequent infusing can then add gaseous silicon or molten carbon into it to form more SiC. Another approach uses chemical vapor deposition whereby gases enter a vacuum chamber before depositing onto substrates for growth; this technology has proven popular within the semiconductor industry.