氮化铝（AlN）是一种应用前景广阔的功能性陶瓷材料，其高热导率、低介电损耗、优良的电绝缘性、机械强度以及与硅片相匹配的热膨胀系数使其相比于其他材料在未来向高集成化发展的电子器件封装领域具有巨大的应用优势。氧化铝碳热还原法是大规模制备高纯度、粒度均匀的氮化铝粉末的主要方法，但是我国采用氧化铝碳热还原工艺生产的氮化铝粉体目前在颗粒粒径分布和杂质含量方面与发达国家存在较大差距，且碳热还原反应机理尚不清晰，急需对工艺和机理进行进一步探究。本论文将碳热还原法分为高温氮化步骤和脱碳步骤分别研究，系统研究了铝源、碳源种类，铝源的孔容，Al/C比，混合方式，氮化时间和温度，焙烧曲线，氮气流速，脱碳时间和温度等对产品纯度、微观形貌的影响规律，最终制备得到高性能的氮化铝粉末。通过对前驱体和产品的微观形貌表征分析，本文推测得出氮化反应机理为固相反应机理，即氧化铝在固体碳的还原作用下生成铝蒸汽和铝的低价氧化物蒸汽，这些中间气态产物再和氮气反应生成氮化铝。在不同氮化时间和温度下对筛选出的前驱体进行反应得到的转化率数据，通过动力学模拟可以得出该反应为内扩散控制，表观活化能为516kJ/mol，明显小于使用普通的α-Al2O3和炭黑为前驱体时的活化能757.4kJ/mol，进一步证明该前驱体具有更高的反应活性。本文创新性地采用微反制备的孔容为0.7ml/g左右的拟薄水铝石为铝源，与高纯炭黑球磨混合后在1200℃下保温1h再在1500℃保温3h，得到的AlN-C混合物在650℃下进行3h脱碳处理，最终得到晶型完整的AlN颗粒，产品粒径分布均匀，平均粒径约为150nm，其O元素含量为0.55%，C元素含量为0.06%。该工艺条件能够稳定制备平均粒径小和O杂质含量低的氮化铝粉体，且不增加碳热还原制备法的难度，证明采用该法降低了碳热还原工艺的生产要求且提高了产品的品质。
Aluminum nitride (AlN) is a kind of functional ceramic material with broad application prospect. Its high thermal conductivity, low dielectric loss, excellent electrical insulation, mechanical strength and thermal expansion coefficient matching with silicon make it have great application advantages compared with other materials in the field of electronic device packaging which is developing towards high integration in the future. Alumina carbothermal reduction is the main method to prepare AlN powder with high purity and uniform particle size. However, the particle size distribution and impurity of AlN powder produced by alumina carbothermal reduction process in China are not good as those in developed countries. And the mechanism of carbothermal reduction reaction is still controversial. So, the exploration to the process optimization and mechanism is quite necessary.In this paper, carbothermal reduction process was divided into high-temperature nitriding step and decarburization step respectively. The system research was carried out on the influence law of aluminum source, carbon source, aluminum source pore volume, Al/C ratio, mixing method, nitriding time and temperature, roasting curve, nitrogen gas flow rate, decarbonization time and temperature on the purity and microstructure of the product.Through the analysis of the microstructure of the precursor and the product, it is speculated that the nitriding reaction mechanism is the solid phase reaction mechanism, that is, aluminum vapor and aluminum oxide vapor are generated by the reduction action between alumina and solid carbon, and these intermediate gaseous products then react with nitrogen to generate AlN. Under different nitriding time and temperature, the conversion data of the reaction can be concluded that the reaction is diffusion controlled through dynamics simulation. The apparent activation energy was 516 kJ/mol, much smaller than the activation energy of 757.4 kJ/mol which used normal α-Al2O3 and carbon black as the precursor, proving that the precursor in this paper had higher reactivity.By using the pseudo-boehmite with pore volume 0.7ml/g as aluminum source, high purity nano carbon black as the carbon source, ball-milling for 10 min, the mixing precursor was treated under 1200 ℃ for 1 h and 1500 ℃ for 3 h, keeping the nitrogen flow rate at 1 l/min. The product was decarburized under 650 ℃ for 3h to get the resulting AlN particles with complete crystal forms, and the carbon mass content is 0.06%, approximating the market product parameters. The product has a uniform particle size with an average particle size of about 150nm, and the mass content of oxygen is 0.55%. The average particle size and impurity content of O are far lower than those of market products. It is proved that the adoption of this precursor and process conditions is conducive to the production of AlN powder with better performance.
