Papers by Author: Jun Bo

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: The reaction between SiC and AlF₃ has been investigated in CO atmosphere at high temperature. Experimental results are shown that the reaction intensity between SiC and AlF₃ is accelerated with the rise of temperature. At the temperature of 950 (aluminum electrolytic operation temperature is 935±15), the reaction intensity of SiC and AlF₃ is not high and the major reaction products are SiF₄ gas and Al₄C₃; Al₄C₃ occur severe hydration at room temperature which leads to the pulverization of specimens. The unexpected cells stop should try to be avoided or reduced during the usage of Si₃N₄-bonded SiC sidewall brick in aluminum electrolysis cells because of Al₄C₃ existents possibly.