1. The reaction sintering method is to mold silicon powder or a mixture of silicon powder and silicon nitride powder according to the general ceramic product production method. Then in the nitriding furnace, pre-nitriding is performed at 1150~1200℃. After obtaining a certain strength, it can be machined on the machine tool, and then further nitrided at 1350~1450℃ for 18~36h until all becomes silicon nitride. . The products produced in this way are precise in size and stable in volume.
2. The hot pressing sintering rule is to heat-form and sinter silicon nitride powder with a small amount of additives (such as MgO, Al2O3, MgF2, AlF3 or Fe2O3, etc.) at a pressure of more than 19.6MPa and 1600~1700℃. Generally, products made by hot pressing sintering have higher density and better performance than products made by reaction sintering. The properties of silicon nitride ceramics produced by these two methods are listed in Appendix Table 1.
3. Spark plasma sintering is another method that can prepare purer bulk materials. The compacted powder is subjected to current pulses in a very short time (a few seconds). In this method, it can be used at 1500-1700°C. At the temperature, a compact and dense silicon nitride block is obtained.
