Characteristics of Aluminum Nitride Powders Synthesized by Carbcthermal Reduction-Nitridation of Alumina with CaF_2 Addition

摘要

Effect of characteristics of raw Al_2O_3 powder on the synthesis of AlN by the carbothermal reduction-nitridation method was investigated. Four types of Al_2O_3 powders characterised by synthesising method and particle size were selected. An Al_2O_3/C molar ratio of 0.29 was fixed, and the amount of CaF_2 was varied from 3 to 30wt%. The reduction-nitridation was conducted at 1350 to 1450℃ in N_2 flow The nitridation fate tended to increase with decreasing particle size of raw Al_2O_3 and was found to depend on the Al_2O_3 synthesising method. It was confirmed that, even though different particle sizes of Al_2O_3 powders were used, AlN powders synthesised under the same conditions exhibited almost the same particle size, round shape, and narrow size distribution. From XRD analysis, CaO·6Al_2O_3 and CaO·2Al_2O_3 were identified as intermediate compounds. The above phenomena suggest that the formation of A1N particle resulted from the nitridation of the intermediate compounds bough the liquid phase of the system CaF_2-CaO·Al_2O_3-CaO·Al_2O_3.