Ultrathin coating of fluidized particles by means of aerosol

通过气溶胶对流化颗粒进行超薄涂层

• 批准号: 452247553
• 负责人: Professor Dr.-Ing. Evangelos Tsotsas
• 金额: --
• 依托单位: Lehrstuhl für Thermische Verfahrenstechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/452247553?language=en
• 关键词: Ultrathin; coating; fluidized; particles; means

Coated particles for various applications are usually produced by spraying solid-containing liquid on mechanically agitated or fluidized cores. Every spray droplet which is deposited on the surface of a core particle leaves behind a solid remnant after evaporation of the solvent or suspension liquid (preferably water). Each such deposit is a building block (BB) of the coating layer. However, spray droplets are quite large (typically 40 µm with two-fluid nozzles) in present technology, so that BBs are also large, resulting in coarse and thick coating. Radically thinner and finer resolved coating layers (down to the nanoscale) could be produced on fluidized particles by using aerosol (with droplet diameters around 1 µm or less) instead of common spray. Feasibility of the respective aerosol fluidized bed (AFB) coating process has recently been shown by a proof-of-principle experiment. On this basis, the present project aims at a thorough scientific investigation of the novel AFB process. This includes batch coating experiments with variation of operating parameters, materials, as well as aerosol generation and entrance conditions. The quality of coated particles is characterized thoroughly by scanning electron microscopy and various image analysis techniques in regard of intra-particle coating thickness distribution, inter-particle coating thickness distribution, average porosity, porosity distribution, and pore size distribution. Supported by such unique data, a stochastic (Monte Carlo) model is developed and parameterized to accurately simulate the buildup of coating layers on single particles and in the population of particles; Moreover, in the surface coverage period (possibly with island growth) and later on (in the coating layer growth period). Finally, measurements are conducted and a model is developed to predict solids yield of the process, which is equivalent to the efficiency of the fluidized bed in filtering aerosol droplets out of the gas flow.

用于各种应用的包覆颗粒通常通过在机械搅拌或流化的芯上喷涂含固体的液体来生产。沉积在核颗粒表面上的每个喷雾液滴在溶剂或悬浮液（优选水）蒸发后留下固体残余物。每个这样的存款是涂层的结构单元（BB）。然而，在目前的技术中，喷雾液滴相当大（对于双流体喷嘴，通常为40 μm），使得BB也很大，导致粗糙且厚的涂层。通过使用气溶胶（液滴直径约为1 µm或更小）代替普通喷雾，可以在流化颗粒上产生更薄、更精细的涂层（低至纳米级）。各自的气溶胶流化床（AFB）涂层工艺的可行性最近已被证明的原理实验。在此基础上，本项目旨在对新型AFB工艺进行全面的科学研究。这包括操作参数、材料以及气溶胶生成和入口条件变化的批量涂覆实验。包覆颗粒的质量通过扫描电子显微镜和各种图像分析技术在颗粒内包覆厚度分布、颗粒间包覆厚度分布、平均孔隙率、孔隙率分布和孔径分布方面彻底表征。在这种独特数据的支持下，开发了一种随机（Monte Carlo）模型并将其参数化，以准确模拟单个颗粒上和颗粒群中涂层的累积;此外，在表面覆盖期（可能有岛生长）和以后（在涂层生长期）。最后，进行测量，并开发一个模型来预测固体产量的过程中，这是相当于过滤气溶胶液滴的气流中的流化床的效率。