The best sintering method for silicon carbide industrial ceramics - pressureless sintering

The different sintering methods of silicon carbide ceramics can lead to some differences in their properties. Therefore, our ceramic factory will introduce in detail several different sintering methods of silicon carbide industrial ceramics and their performance comparisons. Firstly, let's introduce pressureless sintering.

Pressure free sintering of silicon carbide industrial ceramics:

Pressure free sintering:

In 1974, GE Corporation of the United States passed the β A small amount of B and C were added to SiC fine powder simultaneously, and high-density SiC ceramics were successfully obtained using a pressureless sintering process at 2020 ℃. At present, this process has become the main method for preparing SiC industrial ceramics.

Researchers from GE in the United States believe that a ratio of grain boundary energy to surface energy less than 1.732 is a thermodynamic condition for densification. When B and C are added simultaneously, B solidly dissolves into SiC, reducing the grain boundary energy. C reduces SiO2 on the surface of SiC particles and improves surface energy. Therefore, the addition of B and C creates thermodynamic favorable conditions for densification of SiC. However, Japanese researchers believe that there are no thermodynamic limitations to the density of SiC.

Some scholars believe that the densification mechanism of SiC may be liquid-phase sintering. They suggest that the addition of B and C simultaneously β- In the SiC sintered body, there is a liquid phase rich in B present at the grain boundaries. There is currently no consensus on the mechanism of pressureless sintering. Dense sintering of SiC can also be achieved by using a-SiC as raw material and adding B and C.

Research has shown that using B and C alone as additives does not help SiC ceramics to be fully dense. Only when B and C are added simultaneously can the high-density of SC ceramics be achieved. For the dense sintering of SiC, the specific surface area of SiC powder should be above 10m2/g, and the oxygen content should be as low as possible. The addition amount of B is about 0.5%, and the addition amount of C depends on the oxygen content in the SiC raw material. Usually, the addition of C

The dosage is directly proportional to the oxygen content in SiC powder. Recently, researchers have added A 시 203 and Y2O3 to submicron SiC powder to achieve dense sintering of SiC at temperatures ranging from 1850C to 2000 ℃. Due to the low sintering temperature and significantly refined microstructure, its strength and toughness are greatly improved.

In summary, the performance of SiC industrial ceramic ceramics varies depending on the sintering method. Generally speaking, the comprehensive performance of pressureless sintered SiC ceramics is superior to that of reaction sintered SiC ceramics, but inferior to that of hot pressed and hot isostatic pressing sintered SIC ceramics. SIC ceramics can be customized and processed into various industrial ceramic parts through a series of ceramic processing and sintering.

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