Effect of Sintering Temperature on SIC/B4C Multiphase Ceramics

In the material design, the ratio of Al2O3/Er2O3 is close to 80:20, and domestic micron-level SIC powder is used, and the powder particle diameter is D50=1.5um. The Al2O3/Er2O3 powder is selected as the sintering aid, with a purity greater than 99.5%, and a mass fraction of the additive of 10%, in which the ratio of Al2O3/Er2O3 substance is 5:3. The mass fraction of B4C added is 10%. The sintering aid and siC powder are wet mixed, dried and sieved for use. The hot-pressing sintering method is used to prepare a round cake-like block material with a thickness of 10mm and a diameter of 40mm. The process parameters are sintering for 1 hour, Ar is used as a protective gas and the sintering pressure is 0.04 ~ 0.06 MPa, and the sintering temperature is set to 1800C, 1835C, 1875C, 1900C and 1935C. XRD patterns of SiC/B, C composite ceramic components at different sintering temperatures . Among these five materials, the main crystalline phases of B4C/SiC composite ceramic materials are SiC, B4C Er2O3 and Er:Al5O12 phases, but no traces of Al and O3 phases are detected. part

During the sintering process, a gas phase is formed and volatilized, and part of Al2O3 participates in the reaction to form Er3Al5O12 phase. There is no Er3Al5O12 phase in the raw materials, which means that during the sintering process, Al, O3 and Er3Al5O12 react to form Er, Al, and O. Mutually. With the increase of the sintering temperature, the B4C diffraction peak weakens and the B4C phase decreases. The reason is that part of the B4C participates in the reaction to form a eutectic phase, which is distributed at the ceramic particle boundary. Al2O3/Er2O3, the additive system can promote B, CsSC composite ceramics Densification.

The microstructure of SIC/B4C composite ceramics at different sintering temperatures. When the sintering temperature changes in the range of 1800C-1900C, the size of the SiC particles does not change significantly, indicating that the densification of SIC/B4C composite ceramics can be achieved by controlling the content of the additive and the manufacturing process, and the sintering time is short and the sintering In the case of low additives, the sintering temperature has little effect on the microstructure of SIC/B4C composite ceramics.

Secondly, the relationship between the sintering temperature and the relative density of siC ceramics. As the sintering temperature increases, its relative density shows a trend of first increasing and then decreasing. When the temperature is lower than 1800, the relative density of Sic ceramics is lower. When the temperature reaches 1900C, the relative density of SiC ceramics is the largest. During the sintering process, ALO, Er, O3 and B, C form a low melting point phase Al-Er-B-C-0 which will promote the sintering process. Especially when the sintering temperature reaches 1900C, the grain boundary phase Al-Er-B-C-0 can fully wet the SiC ceramic particles and promote the densification of the material. When the sintering temperature is lower than 1800C, the relative density is lower than 88%; when the sintering temperature reaches 1900C, the volume shrinkage rate is only 96%. Judging from this, in the Al2O3/ErO3 system of SiC/B, C multiphase ceramics, when the mass fraction of the auxiliary agent remains constant (less than 10%), when the sintering temperature is changed within a certain range, the SiC/B, The degree of densification of C-composite ceramics has a greater impact.

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