Hydrothermal Preparation Of Alumina Ceramic Powders

With the increasing demand of market for ultra-fine, high-purity alumina powder, to study the preparation methods of alumina powder have become one of the focus and the key object is to find a method to control the particle size , have clean surface, have not aggregation and can be synthesized easily high quantity Al₂O₃ powder. Because hydrothermal method can be operated with low temperature thermo-press, crystallizing in liquid medium, micrograph controllable and no pollution, preparing α-Al₂O₃ powders through hydrothermal method is founded in time.α-Al₂O₃ powders were prepared by using Al(NO₃)₃ · 9H₂O and urea as the main raw material in this paper. The paper consists of three parts. Firstly, the method to prepare Al(OH)₃ which would act as the precursor was optimized. And the scheme was modified according to the result of XRD and SEM in order to provide the best precursor for preparing α-Al₂O₃ powders. Secondly, A100H ultrafine powders were prepared with hydrothermal method. According to the result of XRD and SEM about A100H powders, different scheme were used in order to make the size controllable and non-aggregation A100H ultrafine powders. Thirdly, α-Al₂O₃ powders were prepared also with the hydrothermal method. Based of the results of first two parts of experiments, the effect of different conditions to preparing α-Al₂O₃ powders were studied.The study about preparing Al(OH)₃ indicates, when the concentration of Al (NO₃)₃ solution, the velocity of urea drop flow and the pH value of reactive system was controlled at about 0.2mol/L, 25ml/min and 9 respectively, well dispersive and steady Al (OH) 3 solution can be obtained.The study about preparing AlOOH powders indicates: first, when precursor was hydrothermal treated for 8h at 260°C without seeds, ultrafine A100H powders could be obtained with good dispersancy, ellipse film-like shape and narrow size distribution. Second, when precursor was hydrothermal treated at higher temperature(360℃)without seeds, the obtained AlOOH powders was square sheet-like shape...