2. Wen Tai Science and Technology: In 2020, the operating income was 565,438+0.765,438+0 billion, with a year-on-year increase of 24.36%. The company will increase investment in the third-generation semiconductor field and vigorously develop gallium nitride and silicon carbide technologies.
Three. *ST King Kong: In 2020, it will realize an operating income of 478 million, a year-on-year increase of -49.93%. The company's products can be used in semiconductor silicon wafers and other fields.
Four. Taiji shares: In 2020, the operating income was 388 million, a year-on-year increase of 46.54%. Hubei enterprises (may be given priority investment by the second phase of the big fund); An important enterprise in the power semiconductor market segment, tracking and developing the third generation wide band gap semiconductor materials and device technologies represented by SiC (silicon carbide) and GaN (gallium nitride).
Silicon carbide is an inorganic substance with the chemical formula of SiC, which is made of quartz sand, petroleum coke (or coal coke), sawdust (salt is needed in the production of green silicon carbide) and other raw materials by high-temperature melting in a resistance furnace. Silicon carbide also exists in nature as a rare mineral-molybdenite. Among the non-oxide high-tech refractory materials such as carbon, nitrogen and boron, silicon carbide is the most widely used and economical one, which can be called diamond sand or refractory sand. Silicon carbide produced in China is divided into black silicon carbide and green silicon carbide, both of which are hexagonal crystals with specific gravity of 3.20 ~ 3.25 and microhardness of 2,840 ~ 3,320 kg/mm2.
Material type:
There are two commonly used basic varieties of silicon carbide, black silicon carbide and green silicon carbide, both of which belong to α-SiC. ① Black silicon carbide contains about 95% SiC, and its toughness is higher than green silicon carbide. It is mostly used to process materials with low tensile strength, such as glass, ceramics, stone, refractories, cast iron, nonferrous metals, etc. ② Green silicon carbide contains more than 97% SiC and has good self-sharpening. It is mostly used for machining cemented carbide, titanium alloy, optical glass, honing cylinder liners and grinding high-speed steel tools. In addition, there is cubic silicon carbide, which is a yellow-green crystal prepared by a special process. The abrasive tool used for manufacturing is suitable for ultra-precision machining of bearings, and the surface roughness can be machined to Ra32 ~ 0. 16 micron to Ra0.04~0.02 micron at one time.
Physical and chemical properties:
Material characteristics:
Silicon carbide has many other uses besides abrasives because of its stable chemical properties, high thermal conductivity, small thermal expansion coefficient and good wear resistance. If silicon carbide powder is coated on the inner wall of turbine impeller or cylinder by special process, its wear resistance can be improved and its service life can be extended by 1 ~ 2 times. Advanced refractories made of it have the advantages of thermal shock resistance, small volume, light weight, high strength and good energy saving effect. Low-grade silicon carbide (containing about 85% SiC) is an excellent deoxidizer, which can speed up steelmaking, control chemical composition and improve steel quality. In addition, silicon carbide is also widely used to manufacture silicon carbide rods for electric heating elements.
The hardness of silicon carbide is very high, and the Mohs hardness is 9.5, which is second only to the hardest diamond in the world (10). It is a semiconductor with excellent thermal conductivity and can resist oxidation at high temperature.