The properties of Si3N4 materials:
Si3N4 material, which is 60.06% Si and 39.94% N makes up the molecular structure of silicon nitride. Si and N bond by a strong covalent link (the strength of the ionic bond is 30%). Si3N4 also has high hardness (Mohs Hardness 9, high melting point, and stable structure.
Silicon dioxide does not have a melting point and can be sublimated at 1900C under normal pressure with a heat specific to 711.8J/kg*degC. A phase’s microhardness is 1016GPa while the phase of b has 24.532.65GPa. The strong covalent bonds compound prevent liquid phase formation below 1900°C. It is essential that the silicon nitride materials be sintered by using oxide additives. Most oxide materials which promote sintering are Y2O3, A2O3, and so on. The reaction principle involves using the SiO2 dioxide film that forms on top of silicon nitride particle and adding the oxide to make a liquid phase. This will penetrate the crystal. This is to guarantee the maximum diffusion of the material’s migration.
A thermodynamically stable material, Si3N4 is available. The temperature range for silicon nitride ceramics is 1400 to 1400 degrees Celsius in an oxidizing atmosphere and 1850 to 1850 degrees Celsius in a neutral atmosphere or reducing environment.
Refractory materials can use silicon nitride substances
High-temperature structures made of silicon nitride are often considered promising because they have excellent properties at high temperatures, including high heat strength and wear resistance. Si3N4 ceramics can only be made due to their strong covalent bond, low diffusion coefficient and high temperature requirements. Otherwise, it would be difficult to produce silicon nitride materials of high quality. This high production cost, along with the limitations of equipment are unacceptable for the metalurgical industry. The research into refractories was not done in depth and began too late. While there are many theories that can be drawn from ceramics, the majority of them do not have much novelty. In the past, silicon Nitride was only used as a bonding agent in refractory materials. The combination of aggregates, such as corundum and silicon carbide with fine powder was used to produce a variety of products that are difficult to sinter.
Part of the fine powder is the ceramic shed, which is silicon carbide aggregate. It utilizes silicon nitride, which can be used to make silicon nitride. The material is then combined with silicon carbide, resulting in a silicon nano-bonded silicon caride material. It has a better high-temperature performance than clay-bonded Silicon Caride shed. This eliminates problems like swelling and damage from silicon carbide oxidation. Baosteel’s second phase project uses Si3N4 and cast steel as the refractory material binding phases.
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