Strategy development for the coating of open-pore structured, nanoporous materials with low density

涂层对于多孔材料的许多应用是有利的，例如保护包封在多孔结构内的物质免受水分影响或在储存和运输期间实现多孔网络的机械稳定。本项目的目的是开发一种使用有机气凝胶颗粒作为模型材料的低密度开孔结构纳米多孔材料涂层的策略。在该涂覆方法中，气凝胶的敏感孔结构不应被喷雾的液体溶液或熔体的渗透破坏。因此，应研究使用溶液或熔体的加工是否更适合于开孔材料的涂层。在第一步中，研究了具有不同粒度和密度的气凝胶颗粒的生产。使用乳液凝胶化方法和JetCutter装置以升规模生产球形凝胶颗粒，以实现几微米至2 mm的尺寸范围。随后将形成的凝胶颗粒超临界干燥，从而得到高度多孔的气凝胶颗粒。所产生的气凝胶颗粒的涂覆在棱柱形喷动床装置中进行。测试了这些具有不同密度（颗粒孔隙率）和颗粒直径的极轻粘性颗粒的流化行为，并将其归类为Geldart图。对于颗粒的涂覆，应找到最佳工艺条件以实现核-壳结构，同时保持气凝胶颗粒的孔结构。此外，流化和喷雾干燥-壳形成的整个过程链将通过耦合CFD-DEM模拟建模和优化。

A coating is advantageous for many applications of porous materials, for example to protect substances encapsulated within the porous structure from moisture or to achieve mechanical stabilization of the porous network during storage and transport. The aim of this project is to develop a strategy for the coating of open-pore structured, nanoporous materials with low density using organic aerogel particles as model material. In this coating process the sensitive pore structure of the aerogels should not be damaged by penetration of the sprayed liquid solution or melt. Therefore it should be investigated whether processing using the solution or the melt is more suitable for the coating of open-porous materials. In the first step, the production of aerogel particles with different particle sizes and densities is investigated. Spherical gel particles are produced in the liter scale using the emulsion gelation method and the JetCutter apparatus to achieve the size range between a few micrometers and 2 mm. The formed gel particles are subsequently supercritically dried resulting in highly porous aerogel particles. The coating of the produced aerogel particles is performed in a prismatic spouted bed apparatus. The fluidization behavior of these extremely light, cohesive particles with different density (particle porosity) and particle diameter is tested and classified into the Geldart diagram. For the coating of the particles, the optimum process conditions should be found in order to achieve a core-shell structure while preserving the pore structure of the aerogel particles. In addition, the fluidization and the entire process chain of spraying - drying - shell formation will be modeled and optimized by means of coupled CFD-DEM simulations.