Advantage
Higher density and strength: Hot pressing sintering method is a process of simultaneously forming and sintering silicon nitride powder in a mold under high temperature (above 1600 ℃) and high pressure (above 1916 MPa) conditions. This extreme condition can promote the close packing and sufficient bonding between powder particles, resulting in a high density and fewer internal pores of the prepared silicon nitride ceramics, and correspondingly, their strength is also better. For example, in some high-end machining tool application scenarios that require strict mechanical properties of materials, silicon nitride ceramic tools prepared by hot pressing sintering method can better withstand cutting forces, maintain the sharpness and stability of the blade, while products prepared by reaction sintering method have slightly lower strength due to their relatively lower density, making it difficult to meet such high-strength usage requirements.
More uniform product performance: During hot pressing sintering, high temperature and high pressure are applied to the entire body, allowing the powder particles in various parts of the body to complete the sintering process more evenly. The final silicon nitride ceramic product obtained has a more uniform and consistent microstructure and performance. On the other hand, the nitriding process of the reaction sintering method is gradual, and there may be differences in the performance of different parts of the product due to factors such as uneven reaction.
The production cycle is relatively short: the reaction sintering method requires a long nitriding process, first pre nitriding and then secondary nitriding, which takes a long time for the entire process. The hot pressing sintering method can quickly densify the green body under high temperature and high pressure, completing sintering and forming. Relatively speaking, it can prepare finished products in a shorter time, which helps to improve production efficiency, especially suitable for situations with certain batch production needs and production cycle requirements.

Disadvantage
High manufacturing costs: Hot pressing sintering method requires extremely high equipment requirements, requiring specialized sintering equipment that can withstand high temperature and high pressure, and the purchase cost, maintenance cost, and operating cost of such equipment are quite high. The equipment for reaction sintering method is relatively simple and does not require such complex and expensive high-temperature and high-pressure equipment. From the perspective of equipment investment, the cost advantage of reaction sintering method is obvious.
Limited dimensional accuracy: Hot pressing sintering is carried out in a mold, and the size and shape of the mold limit the size and shape of the product, making it difficult to manufacture silicon nitride ceramic parts with complex shapes and large sizes. The reaction sintering method is more suitable for manufacturing components with complex shapes and high dimensional accuracy requirements, as it can first form a green body and then perform nitriding treatment, making it easier to shape complex shapes during the green body production stage.
Difficult to achieve large-scale production: Due to the special nature of hot press sintering equipment, the number of products sintered each time is limited, and the operations of loading and unloading are relatively cumbersome, making it difficult to carry out large-scale continuous production as conveniently as reaction sintering method, which is not conducive to achieving large-scale industrial production. When dealing with large-scale market demand, production capacity may become a bottleneck.

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High termperature curing polysilazane, pls check IOTA 9108, IOTA 9118.