The Preparation Of Porous Alumina Ceramics And Monte Carlo Simulation Of Crystals Organization Evolution

Porous Al2O3 ceramic has been extensively applied in aerospace, mechanics, and electronics, owing to its high specific surface area and unique surface physics, as well as the excellent properties of high corrosion resistance and high temperature stability of ceramic itself. Majority of porous Al2O3 ceramic was prepared by solid-phase sintering, and its mechanical properties were affected by variety of grains size and pore distribution during the sintering process. As a result, it is quite significant to study the evolution of microstructure during the sintering process of porous Al2O3 ceramic.The traditional research on material microstructure focuses mainly on theoretical and experimental analysis. With the development of computer technology, computer simulation has become another important way of research. Currently, the most widely used and more mature approach to simulate grain growth is Monte Carlo (MC) method, which, with relatively little calculation and short simulation time, is non-iterative calculation method widely used in simulating ceramics microstructure evolution.Based on the classic Monte Carlo, this paper applied two-dimensional MC model to improve the Monte Carlo method in terms of the probability of grain growth, the solid gas diffusion rate as well as the choice of the number of grain orientation. By doing these, this paper improved the efficiency and accuracy of simulation. At the same time, the fitting calculation was carried out based on grain size of porous ceramics simulated by Monte Carlo. It was found that the grain growth index of porous alumina was 2.95 at 1573K, in accordance with theoretical value of 3, indicating that the results simulated by modified Monte Carlo method were in good agreement with theoretical analysis.Systemical investigation was conducted on the influence of that the sintering temperature, holding time and the granularity and content of graphite on the grain size and pore distribution by experimental study and computational simulation. The results show that the grain size increased and porosity decreased as sintering temperature or holding time increased. The porosity was increased with increasing content of graphite, while had little effect on the grain size. However, the porosity of ceramic had not obviously change, and the grain size gradually increased as the granularity of graphite decreasing. The sintering theory and model for the preliminary, medium and later stages were proposed on the basis of the experimental results. It was found that the grain growth of principle phase happened and the pores size was changed in the biphase system and meanwhile pinning effects of pores confined the grain growth simultaneously. The process of grain growth was verified by the Al2O3 sintering experiment.