| Summary: | In this paper, by using the hot-pressed sintered technology, pure Si3N4 ceramics and Si3N4 composite ceramics containing different volume fraction(hBN) are prepared with the sintered catalyst of Al2O3 and Y2O3(total 10vol%) by HIGH MULTI 5000 multi-functional high temperature sintering furnace. And the phase compositions, microstructure and mechanical properties of specimen were studied. The results show that, based on the hot pressing sintering process, the α-Si3N4 is all changed into β-Si3N4. Addition of hBN into Si3N4 inhibits the growth of the crystal grain and makes the ceramic materials generate hBN segregation zone in internal materials, which causes the addition of hBN that cannot improve the physical mechanical properties effectively just because the serious stress concentrates and fatigue break down. In addition, compared with other sintering process, the physical and mechanical properties of Si3N4 prepared by hot-pressing sintering are better than other methods. Improvement of sintering temperature and time can refine the crystal grain and be a helpful densification. The changed β-Si3N4 grain completely forms an intertwined structure and increases the physical and mechanical properties of Si3N4. Meanwhile, Y2O3 and Al2O3 additives are melted and filled into Si3N4 particles at the high temperature, leading to a significant drop of the porosity and the increase of density.
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