Papers by Author: Ya Wei Zhai

Abstract: α-Si₃N₄ possesses excellent sintering activity, which is used to prepare high performance Si₃N₄-based ceramics and composite refractory. Si₃N₄ powder is always synthesized by nitriding silicon in controlled-atmosphere furnace whose furnace volume is very small(effective volume: 1840×1420×1660mm), the extreme reaction heat is difficult to diffuse, which leads to high reaction temperature and conversion of α-Si₃N₄ to β-Si₃N₄, thus α-Si₃N₄ is difficult to be obtained in controlled-atmosphere furnace. While flame-isolation nitridation shuttle kiln has much larger furnace volume to conduct reaction heat (effective volume: 11500×4190×1684mm), so it owns homogeneous temperature field and stable low-temperature environment which benefits the preparation of α-Si₃N₄. Thermodynamic analysis of Si-N system is shown that Si₃N₄ can be formed by two formats: direct nitridation of Si(s) and indirect nitridation of SiO(g); to ensure completely nitridation, the particle size of silicon powder should be less than 88μm. With reclaimed powder from polysilicon cutting slurry as starting materials, both reactive α-Si₃N₄ and SiC mixed powder were successfully prepared in flame-isolation nitridation shuttle kiln. Because of the gas-gas reaction between SiO(g) and N₂(g), α-Si₃N₄ is fiber-like and in favor of processing high quality Si₃N₄-based materials.

Abstract: Si-Si₃N₄-SiC composites was prepared by firing at 1450°C for 8hrs in air atmosphere with SiC, Si₃N₄, Si as principal raw materials. Si-Si₃N₄-SiC composites has good performance and its services life is 5~7 times than that of oxides sagger. This paper also studies the material attack mechanism and observes the microstructure of Si-Si₃N₄-SiC composites which has been used 15 cycles.

Abstract: The Si-Fe (≤0.043 mm) fine powder was added to the Al₂O₃-ZrO₂-C slide gate, and the influences of adding different Si-Fe contents (2wt%, 4wt%, 6wt%, 8wt%) are studied. Two different firing ways of nitridation and carbonazation atmosphere were used. The experimental results indicated that the addition of Si-Fe improve the physical and chemical properties of the slide gate, the performance is the best when the addition of Si-Fe is 6wt% and the properties of slide gate sintering in N₂-flowing atmosphere is better than that in CO-flowing atmosphere. Si-Fe will react with nitrogen and generate Si₃N₄ in the N₂-flowing atmosphere, while it will react with C or CO to produce SiC in CO atmosphere.