Silicon nitride ceramics, as an advanced ceramic material with excellent performance, have broad application prospects in many fields. Reaction sintering method is one of the commonly used methods for preparing silicon nitride ceramics.
Firstly, the molding process is crucial. Suitable silicon powder is usually selected as the raw material and pressed into green bodies with specific shapes using conventional methods such as dry pressing and isostatic pressing. During the dry pressing process, the silicon powder needs to be placed in a specially designed mold and molded under a certain pressure. This method is suitable for producing blanks with regular shapes and relatively small sizes; Isostatic pressure forming is the process of loading silicon powder into an elastic mold and placing it into a high-pressure container. By uniformly applying pressure through a liquid medium, it can effectively avoid the problem of uneven density of the billet and can be used to manufacture more complex shaped billets.
Then enter the pre nitriding stage. Place the formed green body into a nitriding furnace and conduct the reaction in a nitrogen environment at approximately 1200 ℃. At this point, silicon powder will undergo a chemical reaction with nitrogen gas, partially converting into silicon nitride. As a result, the green body will have a certain strength and be able to maintain its own shape, laying the foundation for subsequent processes.
Finally, there is the secondary nitriding process. It is necessary to raise the temperature to 1350 ℃ -1450 ℃, which is higher than the melting point of silicon. In such a high temperature environment, the remaining silicon powder will continue to react fully with nitrogen gas until it is completely converted into silicon nitride.
The advantages of reaction sintering method are very obvious, and it is particularly suitable for manufacturing silicon nitride ceramic parts with complex shapes and high dimensional accuracy requirements. Moreover, due to the relatively low equipment investment and complex operating conditions required for the entire process, the cost is also relatively low. However, this method also has some shortcomings, such as longer nitriding time, which can affect production efficiency, and the density and strength of the final product may be slightly lower compared to silicon nitride ceramics prepared by other sintering methods. However, in some application scenarios where density and strength requirements are not extremely strict, reaction sintering still plays an irreplaceable role, such as producing industrial components with special shapes.

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