Preparation of Silicon Carbide Industrial Ceramic Powder

Silicon carbide ceramic is the most widely used metal-free ceramic in industrial ceramics, and it is an ultra-high temperature resistant ceramic. Its structural performance is very high, and the microstructure of silicon carbide material is required to be refined, so the preparation of silicon carbide ceramic powder becomes the key link of high-performance silicon carbide ceramics.

Silicon carbide, with the chemical formula of SiC, is a covalent bond material. C and Si belong to the same family, and both have tetravalent chemical bonds. At the same time, Si also has metallic properties. The substance composed of the two elements has the characteristics of network and body shape in structure and high strength in nature, so the properties of silicon carbide material are good high-temperature strength, wear resistance, corrosion resistance, high thermal conductivity and high insulation.

The preparation methods of silicon carbide powder include traditional solid-state reaction method, the latest sol-gel method, laser method and plasma method. In this paper, the commonly used methods are classified as follows according to gas, solid and liquid.

Solid phase method

1.1. carbothermal reduction method

The method was invented by Acheson. The specific method is as follows: in an Acheson electric furnace, silicon dioxide in quartz sand is reduced by carbon to produce silicon carbide. The silicon carbide particles obtained by this method are coarse and consume a lot of electricity. The reaction equation is as follows:

SiO2+3C=SiC+2CO

Subsequently, Acheson method was improved in many countries, such as Pan Shunlong et al. [1]. Carbon black and water glass solution were used as raw materials, and hydrogen was used as protective gas, and the reaction was carried out in a high-temperature graphite furnace at 1550℃ for 5 hours to obtain silicon carbide powder.

Carbon-silicon direct reaction method

1.2.1. Self-propagating high temperature synthesis (SHS)

The external heat source ignites the reactant blank, and the synthesis process is maintained by using the chemical reaction heat released by the material during the synthesis process.

SiO2+C+2Mg-SiC+2MgO

The powder obtained by this method has high purity and small particle size, but it needs pickling and other processes to remove Mg.

1.2.2. Mechanical alloying method

Yang Xiaoyun et al. [2] made carbon powder and silicon powder into mixed powder according to the molar ratio of 1:1, and the grinding ball and powder were packaged in an argon tank according to the mass ratio of 40:1, and mechanically ball-milled on a ball mill, and after 25 hours, silicon carbide powder with an average grain size of about 6nm was obtained.

liquid phase method

2.1 Sol-gel method

In this method, liquid chemical reagent is used to prepare an alkoxide precursor of Si, which is dissolved in a solvent at low temperature to form a uniform solution; appropriate coagulant is added to make the alkoxide undergo hydrolysis and polymerization to generate a uniform and stable sol system; after standing or drying for a long time, it is concentrated into a mixture or polymer of Si and C at the molecular level, and then it is continuously heated to form a two-phase mixture of SiO2 _ 2 and C with uniform components and fine particle size, and finally SiC fine powder is prepared by carbon reduction reaction at 1460~1600℃.

2.2. Polymer decomposition method

Chinag et al [3] used polymer pyrolysis method to form glassy carbon and immersed it in liquid silicon to prepare silicon carbide ceramic materials. The mixture of triethylene glycol, dihydroxy ethyl ether and furfuryl alcohol resin was used for polymerization and furfuryl alcohol phase separation under the catalysis of organic acid, and then pyrolyzed to form microporous carbon. Finally, liquid silicon was sintered and free silicon was removed. So as to obtain silicon carbide powder.

Gas phase method

3.1. Gas phase reaction precipitation method

Yang Xiuchun et al. studied the SiH4-C2H4-H2 system at 1423~1673K, and obtained silicon carbide with an average particle size of 11nm.

3.2. Plasma method

Yu Wei et al. prepared silicon carbide by plasma chemical vapor deposition.

3.3. Laser induced gas phase method

Zhan Ketao et al. [6] used SiH4 and C2H4 as raw materials, and the average particle size was 20nm.

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