Study On The Sintering And Refinement Process Of High Purity Alumina Using For LED

High purity alumina powder refers to one kind of alumina powder material, of which the purity is over99.99%and the particle size distribution is uniformly. Because of the excellent physical, optical, mechanical and thermal properties, the high purity alumina powder has been widely used in many fields, for example chemical, electronics, machinery, special ceramics, etc., and its role in the industries of lighting and semiconductor becomes more important. High purity alumina powder is the basic material of the LED sapphire substrate. Facing the realities that the global energy shortage, environmental pollution problems becoming more serious and the rapid development of LED industry, reducing the sintering temperature and production cost of high purity alumina powder using for LED has important piratical significance.Currently, the foreign preparation technology of high purity alumina powder is quite mature. The alumina powder produced by French Baikowski, Taimei Chemicals Co., Ltd. and the Japanese Sumitomo Chemical Industry can achieve the excellent properties of high purity, superfine, narrow particle size distribution and none hard agglomeration. This kind of high purity alumina powder is widely used in the production of high quality aluminum products globally. But the production of high-end aluminum products in China mainly depends on imports of raw alumina powder. Since2000, China has begun to attach importance to the research and development of high purity alumina powder, but the technical preparation of high purity ultrafine alumina powder is still relatively backward so far. Dalian Highland Photoelectric Material Co., Ltd. firstly established the hydrolysis of metal alkoxide method for preparing high purity alumina powder. The powder purity is over99.999%, which is beneficial. But the powder size distribution is wide and the powder is easily to reunite, which lead the final application performance is not ideal. Therefore, exploring the preparation technology of high purity ultrafine alumina powder on the basis of ensuring the purity becomes the goal of many domestic enterprises.Traditional ball-milling techniques for grinding high purity alumina powder are inefficient, what is worse, will decrease the alumina purity. In order to prepare high purity ultrafine alumina powder, we adopted the advanced dry consecutive ultrafine crushing technology to grind the high purity alumina powder from Dalian Highland Photoelectric Material Co., Ltd., discussed the effects of blender speed, grinding balls adding amount, grinding aid adding amount on the grinding effect and powder property. We adopted SEM, BET, particle size analysis, purity analysis to represent the raw and ground powders. The results indicated that setting the right blender speed, grinding balls adding amount, grinding aid adding amount can obtain ground high purity alumina powder, of which the medium particle size is about130nm. What is more, the ground powder owns narrow particle size distribution and good dispersion.In this paper, we sintered the raw and ground powders under normal pressure, discussed the effects of sintering temperature, temperature holding time and molding condition on the sintered bulk density and then determined the optimal sintering process. In addition, we also analyzed the high temperature sintering properties of the raw and ground high purity alumina powders as expand research. The results indicated that using the ground powder, adapting the cooling isostatic pressing technology and extending holding time can decrease the sintering temperature. The raw and ground powders were sintered at1500℃,1600℃,1700℃. When sintered at the same temperature, the density and mechanical properties of sintered bulk increased with the declining of powder particle size.The aim of researching the powder grinding and sintering technology is to lower the sintering temperature and then meet the energy saving and emission reduction goals. We calculated the actual power and electric consume using Kanthal Volume-Temperature regression curve, and then determined the feasible and practical sintering process. The results indicated that generalizing the optimal sintering technology to factory production can save energy and obtain considerable economic benefits.