The content of silicon in the earth's crust is second only to oxygen, accounting for 26.3% of the total mass of the earth's crust. It is an element with semiconducting properties. Silicon is quite active, and there is no free silicon in nature. Silicon is mainly present in the form of a silicate mineral or silica combined with oxygen. Similar to carbon, silicon can also form covalent compounds with high melting point and high hardness with certain non-metallic elements, of which silicon carbide and silicon nitride are typical representatives.
Silicon carbide, commonly known as silicon carbide, is usually made by mixing electricity with silica and coke. The silicon carbide component is SiC, which exhibits colors such as green, black, and yellow due to impurities. According to the color, the industry is divided into green silicon carbide and black silicon carbide. The SiC content is ≥99% and 98.5%, respectively. Silicon carbide is a covalent bond compound with strong interatomic bonding, high melting point and high hardness. High strength and low expansion, high thermal conductivity, high electrical conductivity, strong chemical stability, and therefore a good refractory raw material. However, in an oxidizing atmosphere, silicon carbide is easily oxidized, and only when a protective film of SiO2 is formed can the oxidation be slowed down.
The molecular formula of silicon nitride is Si3N4, and the crystal form has both α-form and β-form, both of which are hexagonal. Silicon nitride is gray, with a Si3N4 content of 98.5% and free silicon of 1.5%. Its melting point is 1900 ° C (sublimation decomposition), high strength, low thermal expansion, toughness, strong corrosion resistance. Silicon nitride is obtained by nitriding silicon powder with nitrogen and sintering it. Mainly used in advanced refractory materials.
Through the introduction of the above information, we can not only clearly understand the difference between silicon nitride and silicon carbide through analysis and summary, but also deepen your understanding of silicon carbide and silicon nitride.
