Production, processing and application of black silicon carbide
Black silicon carbide (SIC) is made from quartz sand, petroleum coke (or coal char) and sawdust by high temperature smelting in resistance furnace. Black silicon carbide contains about 98.5% SiC, and its toughness is higher than that of green silicon carbide. Most of them are used for processing materials with low tensile strength, such as glass, ceramics, stone, refractory, cast iron and non-ferrous metals. Due to its stable chemical properties, high thermal conductivity, small thermal expansion coefficient and good wear resistance, black silicon carbide has many other uses besides abrasives. For example, coating silicon carbide powder on the inner wall of turbine impeller or cylinder block by special process can improve its wear resistance and prolong its service life by 1-2 times; the high-grade refractory material made of black silicon carbide has the advantages of heat resistance, shock resistance, small volume, high resistance to heat and shock Light weight and high strength, good energy saving effect. Low grade silicon carbide (containing about 85% SiC) is an excellent deoxidizer. It can accelerate the speed of steelmaking, control the chemical composition and improve the quality of steel. In addition, silicon carbide is also widely used in the production of electric heating elements.
Black silicon carbide has high hardness and excellent thermal conductivity. Based on these characteristics, SiC abrasives are also ideal products for advanced sandblasting, grinding and polishing industries.
Raw materials and processing methods for black silicon carbide and green silicon carbide production:
Black silicon carbide is made of quartz sand, petroleum coke and high-quality silica as the main raw materials by high-temperature smelting in resistance furnace. Its hardness is between corundum and diamond, and its mechanical strength is higher than that of corundum.
Green silicon carbide is made from petroleum coke and high-quality silica as main raw materials and salt as additive by high-temperature smelting in resistance furnace. Its hardness is between corundum and diamond, and its mechanical strength is higher than that of corundum.
There are two kinds of silicon carbide abrasives in common use. One is green silicon carbide, which contains more than 97% SiC. It is mainly used for grinding hard tools containing gold. The other material containing more than 95% silicon carbide and silicon carbide is mainly used for grinding.
The molecular formula of SiC is SiC. Its hardness is between corundum and diamond, and its mechanical strength is higher than that of corundum. It can be used as abrasives and other industrial materials. Silicon carbide for industrial use was successfully developed in 1891, which is the earliest artificial abrasive. Although a small amount of silicon carbide exists in meteorites and crust, no ore source has been found for mining. Pure silicon carbide is a colorless and transparent crystal. Industrial silicon carbide is light yellow, green, blue and even black due to the different types and contents of impurities. The transparency of industrial silicon carbide varies with its purity. The crystal structure of silicon carbide is divided into hexagonal or rhombohedral α - SiC and cubic β - SiC (called cubic silicon carbide). More than 70 kinds of α - SiC have been found due to the different stacking sequence of carbon and silicon atoms in its crystal structure. β - SiC transforms into α - SiC above 2100 ℃.