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Performance and application of silicon nitride bonded silicon carbide brick

wallpapers News 2020-10-15
Silicon nitride combined with silicon carbide refractory material is a high-hardness non-metallic material with good wear resistance, high-temperature strength, high temperature creep resistance, strong slag erosion resistance, and good thermal shock stability. Excellent performance and good oxidation resistance.

Silicon nitride bonded silicon carbide bricks have a lower thermal expansion coefficient and higher thermal conductivity than silicon carbide bricks, so they are not prone to thermal stress when used at high temperatures and have good thermal shock resistance.

Application of silicon nitride combined with silicon carbide products

Silicon nitride combined with silicon carbide materials is widely used in large-scale ironmaking blast furnaces, non-ferrous metal smelting, sidewall materials of aluminum electrolytic cells, ceramic kiln furniture and fine ceramics due to their excellent high-temperature mechanical properties and chemical stability.

(1) Ironmaking blast furnace and non-ferrous metal smelting

Silicon nitride, combined with silicon carbide refractories, is a widely used material in the iron and steel metallurgy industry. Due to its good thermal shock stability, slag resistance and oxidation resistance, it is used in the lower part of the blast furnace body, such as the furnace waist. These materials are used, and the effect is relatively good. Silicon nitride, combined with silicon carbide products, has good resistance to alkali metal vapor corrosion. In ironmaking or steel-making systems, they do not affect molten steel and molten iron.
The wettability and low wettability of the slag improve its corrosion resistance and slag penetration resistance. In the non-ferrous metal smelting industry, silicon nitride's non-wetting properties combined with silicon carbide products to aluminum, copper, magnesium, and other metal melts have gradually been applied in this industry.

(2) Aluminum electrolytic cell

In recent years, silicon nitride bonded silicon carbide bricks have been widely used as sidewall materials for aluminum electrolytic cells. In the process of electrolyzing aluminum, the sidewall will directly contact the molten alumina and electrolyte, and the process will release a large amount of heat, which requires the sidewall material to have the following properties:

1) High thermal conductivity, which is conducive to the formation of protective furnace ledges for sidewall materials;
2) Does not react with aluminum, sodium and molten cryolite electrolyte;
3) The apparent porosity is low to prevent the erosion and penetration of molten electrolyte and molten aluminum from damaging the material;

4) Good oxidation resistance.

Carbonaceous materials and silicon nitride combined with silicon carbide materials can meet these performance requirements. In the traditional aluminum electrolytic industry, they are mostly used as sidewall materials for aluminum electrolytic cells. Carbonaceous materials are non-wetting to molten metal, and at the same time, they have high thermal conductivity and low cost. In the beginning, they have always been the material of choice for the sidewalls of aluminum electrolytic cells. However, carbonaceous materials have one of the most significant shortcomings. When the temperature is higher, it is easy to be oxidized, causing the material to become loose, and the molten electrolyte is more comfortable to penetrate the fabric. The oxidation resistance of silicon nitride bonded silicon carbide bricks is significantly better than that of carbonaceous materials. In terms of performance, they meet the requirements of aluminum electrolytic cell sidewall materials to a large extent. Therefore, they have gradually replaced carbonaceous materials and become the electrolytic aluminum industry—the middle wall material's main flow port.

(3) Fine ceramics field

Si3N4/SiC composite ceramics has been a research hotspot in the field of fine ceramics for the past two to three decades, and the corresponding theories have been quite mature, and there have been many research results. Compared with Si3N4 ceramics, Si3N4/SiC composite ceramics have more excellent high-temperature performance because Si3N4 will have grain boundary slip at high temperatures, which deteriorates its performance. Therefore, most of the current methods are to introduce SiC particles or whiskers into Si3N4-based ceramics. Through a unique sintering method, the SiC particles/whisker toughening phase can quickly enter the Si3N4 grain boundary and the anchoring effect of the creep resistance at high temperature, thereby improving the overall high-temperature performance of the sample. On this basis, Si3N4/SiC composite materials have been widely used. Due to their high-temperature strength, low thermal diffusion coefficient, and good thermal shock resistance, Si3N4/SiC composite materials have become the most popular in high-temperature or ultra-high temperature fields. The promising high-temperature composite structure ceramics.
 
Trunnano is one of the world's largest producers of silicon nitride powder. If you have any questions or needs, please contact Dr. Leo by email: brad@ihpa.net.

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