Properties and Applications of Silicon Nitride Bonded Silicon Bricks

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 and slag corrosion resistance, and good thermal shock stability. Excellent performance, anti-oxidation performance is also good.

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 Bonded Silicon Carbide Products

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

(1) Iron-making blast furnace and non-ferrous metal smelting

Silicon nitride combined with silicon carbide refractory is a widely used material in the iron and steel metallurgy industry. Because of its good thermal shock stability, slag resistance and oxidation resistance, it can be used in the lower part of the blast furnace shaft, such as the furnace waist. These materials are used, and the effect is relatively good. Silicon nitride combined with silicon carbide products have good resistance to alkali metal vapor corrosion.

Wetting and low wettability to slag increases its resistance to erosion and slag penetration. In the non-ferrous metal smelting industry, the non-wetting properties of silicon nitride combined with silicon carbide products to aluminum, copper, magnesium and other metal melts have gradually been used 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 electrolysis of aluminum, the side wall will be in direct contact with molten alumina and electrolyte, and at the same time, a large amount of heat will be released during the process, which requires the side wall material to have the following properties: 1) High thermal conductivity, which is beneficial to the side wall The formation of the protective furnace side of the wall material: 2) It does not react with aluminum, sodium and molten cryolite electrolyte; 3) The apparent porosity is low, preventing the erosion and penetration of molten electrolyte and molten aluminum from causing damage to the material; 4) Resistant Good oxidation properties. Carbonaceous materials and silicon nitride combined with silicon carbide materials can basically meet the above performance requirements. In the traditional electrolytic aluminum industry, they are mostly used as sidewall materials of aluminum electrolytic cells. Carbonaceous materials do not wet the metal melt, and at the same time, their thermal conductivity is also high and the cost is low. At the beginning, carbonaceous materials have always been the preferred materials for the side walls of aluminum electrolysis cells. However, carbonaceous materials have the biggest disadvantage. It is easily oxidized at higher temperatures, causing the material to become loose and the molten electrolyte to penetrate more easily into the material. The oxidation resistance of silicon nitride combined silicon carbide bricks is obviously better than that of carbonaceous materials, and its performance meets the requirements of aluminum electrolytic cell sidewall materials to a large extent. Therefore, it has gradually replaced carbonaceous materials and has become the electrolytic aluminum industry. Main opening for mid-side wall material.

(3) Fine ceramics field

Si3N4/SiC composite ceramics have been the research hotspot in the field of fine ceramics in the past 20 to 30 years, and the corresponding theories are quite mature, and there are many research results. Compared with Si3N4 ceramics, Si3N4/SiC composite ceramics have better high temperature performance, because Si3N4 will undergo grain boundary slip at high temperature, which will deteriorate its performance. Therefore, most of the current methods are to introduce SiC particles or whiskers into Si3N4-based ceramics. Through a special sintering method, the SiC particles/whisker toughening phase can quickly enter the Si3N4 grain boundary, and through its anchoring effect, the sample can be improved in Creep resistance at high temperature, thereby improving the overall high temperature performance of the sample. On this basis, Si3N4/SiC composites have been widely used. Due to their advantages of good high temperature strength, low thermal diffusivity, and good thermal shock resistance, Si3N4/SiC composites have become the most popular in high temperature or ultra-high temperature fields. Promising high temperature composite ceramics.