Types and characteristics of silicon nitride ceramics
Silicon nitride ceramics is an inorganic material that does not shrink during sintering. It uses silicon powder as a raw material and is first formed into the desired shape by conventional molding methods. It is pre-nitrided in nitrogen at a high temperature of 1200 degrees, and a part of it reacts with nitrogen to form Silicon nitride, at this point the entire green body already has a specified strength. Then, the second nitriding is carried out in a 1350~1450 high temperature furnace to make it react with silicon nitride. Then, let's learn about the types and characteristics of silicon nitride ceramics together!
Silicon nitride with a theoretical density of 99% can be obtained by hot-pressing sintering. Silicon nitride has high strength, especially hot-pressed nitride is one of the hardest substances in the world. At extremely high temperature, the strength can be maintained at a temperature of 1200 without decreasing, even if it is heated, it will not melt in sequence, and it will decompose to 1900. It has amazing drug resistance, and can withstand most inorganic acids and less than 30% per month. Alkali solution can also withstand the corrosion of various organic acids; it is also a high-performance electrical insulating material.
Silicon nitride ceramics can be made into combustion chambers of gas turbines, initial sealing rings, pipelines and valves of electromagnetic pumps for conveying molten aluminum, permanent molds, and molten steel separation rings. The small friction coefficient of silicon nitride is especially suitable for use as a high-temperature bearing. Its operating temperature is 1200, which is 2.5 times higher than that of ordinary alloy bearings, and its operating speed is 10 times that of bearings. Using the excellent electrical insulation and rapid cooling and heat resistance of silicon nitride ceramics, the liter can be used as a glow plug. Using it for car ignition can greatly shorten the starting time of the engine and start the car quickly in cold weather. On the other hand, due to the brittleness of the material itself, the application range of silicon nitride ceramics is limited, and improving the toughness of the material has become an important direction of current research. Now, the improvement of material toughness is mainly due to particle dispersion, whiskers, etc.
In short, as a new type of basic material, silicon nitride ceramic material has excellent properties that traditional metal materials do not have. It can replace metal materials in demanding working environments and adapt to the high temperature, high pressure, and corrosion required by modern technology. The environment with high temperature and strong oxidation has a relatively wide application prospect. However, due to the brittleness of the material itself and some problems in the preparation process, the application and development of the material have been hindered. Future research will focus on solving the problem of the material itself and the preparation process. The problems that arise will promote the application of silicon nitride ceramic materials in various fields of actual social life, and play a role in promoting social development and people's lives.
Silicon nitride ceramics also have good microwave transmission properties, dielectric properties and high edge strength, and are used as radomes for missiles and aircraft. For Si3N4 and Sialon sintered bodies, we now provide a superplastic forming process that does not form a composite material but maintains a single state, and provides sintered bodies formed according to the recorded process, silicon nitride and sintered bodies, the relative density is more than 95%, and the linear density is relatively The length of 50 pm on the two-dimensional cross-section of the sintered body is in the range of 120~250; it is formed by stretching or compressing at a temperature of 1300~1700 to make it plastically deformed at a strain rate of less than 10-1/second. Forming The finished teosinte has excellent mechanical properties at room temperature.
The above are the types and characteristics of silicon nitride ceramics . If you need to know more, please feel free to contact us!