Research On The Kinetics Of In-situ Formation Of Sialon In The Al₂O₃-Si-Al System

This paper researches the machanism for nitridation of the in-situ formation in the Al2O3-Si-Al system and the process of the reaction by using continous weighing. The author has analysed the thermodynamics of Al2O3-Si-Al system, the microstructure and the function of reactional products.The research shows the reational feasibility is determined by thermodynamic analysis, Based on the reaction,the a dynamic model is set up. First, the gas diffuses onto the surface of metal particles through pores of the sample. Second, the gas reacts with the metal particles. Third, the gas diffuses through the layer of the products and reacts with Si and Al. from which we know that total reaction rate of nitridation is determined by the chemical reaction at low temperature between 900-1150℃, the activation energies is E = 58.5KJ.mol-1, while at high termperature stage between 1200-1450℃, it determined by the diffusion, E = 27.26KJ.mol-1. The result is in accordance with the dynamic model.The experiment results show that the nitrigon reaction is connected with the molding pressure, Si/Al of the sample and nitridation temperature. The ratio of nitridation will decrease with the rising pressure. The smaller the ratio of Si/Al is, the higher the ratio of nitridation is. The sample of B5, which have the reational rate of Si/Al(1:2), enhances the contacts between the ceramic particles and therefore guarantees the good crushing strength of sample B5. As for the sample obtained in low temperature, the hydration will take place on its surface with the increasing ratio of nitridation.