Evaluation and control of the characteristics and morphology of functional fine particles preparing by spray pyrolysis method.

采用喷雾热解法制备了用于荧光粉或晶体材料的硫化锌、硫化镉等金属硫化物微粒，以及用作太阳电池材料的CuS微粒。在此过程中，研究了1)液滴大小、2)起始溶液初始浓度、3)液滴或颗粒的加热速度和停留时间对金属硫化物颗粒的特性和形貌的影响。将液滴引入管式加热炉，制备的颗粒可在加热炉出口收集。从X射线衍射和扫描电子显微镜照片分析可知，通过改变前驱体的组成比例，可以在较宽的温度范围内得到单一相的CuS、ZnS和CDS粒子。目前，由于数学上的复杂性和获取数据或性质的困难，所提出的模型或理论研究非常有限。1)在液滴蒸发过程中，通过数值求解扩散方程，得到液滴内的溶质浓度分布和炉膛内的蒸汽分布。2)在确定了液滴中溶质成核的起始时间后，我们可以计算形成的溶质沉淀分布，从而可以预测颗粒的形态。将该模型应用于氧化锆微粒子的制备。选择该体系是因为前驱体的性质比较清楚。数值模拟结果能较好地描述实验结果。

Using spray pyrolysis method, the preparation of fine metal sulfide particles such as ZnS and CdS used as phosphor or crystalline materials, and CuS used as solar cell materials, were investigated experimental and numerically. During the process, the effects of 1) droplet size, 2) initial concentraiton of starting solution, 3) heating rate and residence time of droplets or particles, on the characteristics and morphology of metal sulfide particles were investigated.The starting solutions were sprayd to micron scale droplets by an ultrasonic nebulizer and an electrospray atomizer. The droplets were introduced into a tubular furnace and the prepared particles could be collected at the outlet of the furnace. From the analysis of X-ray diffraction and SEM photographs, single phase of CuS,ZnS and CdS particles could be obtained at wide range temperatures by changing the composition ratio of the precursors.By the way, the study of spray pyrolysis is not well understood. At present, the models or theoretical studies proposed were very limited due to the mathematical complication and the difficulty to obtain the data or properties. We developed a simulation software to evaluate the preparation of fine particles during spray pyrolysis using the following steps : 1) during the droplet evaporation, the solute concentration profiles in the droplet and the vapor distribution inside the furnace could be obtained by solving numerically the related diffusion equations. 2) After determining the onset of solute nucleation in droplet, we could calculate the solute precipiration profiles formed and as the result, the particle norphology could be predicted. The model was applied to the preparation of zirconia fine particles. This system was chosen because the properties of the precursor are relatively well knwon. The numerical simulation could describe the results obtained by experiments.