共沸蒸馏法制备AMH纳米材料及其机理研究

Studies on Preparation and Mechanism of Nanometer Sized Aluminum Magnesium Hydroxide Material by Azeotropic Distillation Method

利用苯，正丁醇和丙酸有机溶剂能与水形成共沸物的特性，采用共沸蒸馏法制备氢氧化铝镁（ＡＭＨ）固体材料，即分别将有机溶剂与溶胶共沸蒸馏，脱除溶胶中的水份，再真空干燥，研究了制备机理和对产品性能的影响。发现苯和正丁醇可有效地阻止干燥过程中硬团聚问题，制成了粒径为３０～５０ｎｍ的纳米粉体材料，其机理是靠降低粒子间毛细管力来减少聚集作用的，产品的晶态、热失重和等电点等性能与直接干燥法产品的相同。丙酸与胶粒表面羟基虽能发生反应，但没能制成纳米粉体，可能发生了脱附－聚集作用，产品的晶态、热失重和等电点等性能也有很大变化。

Aluminum magnesium hydroxide (AMH) hydrous sol was dehydrated by heterogeneous azeotropic distillation process of the systems consisting of the sol and benzene, n-butanol and propanoic acid, respectivily, according to the properties that those organisms with water may form azeotropes, and then vacuumly desiccated to obtain AMH solid materials. The preparation mechanism and properties of AMH solid materials were investigated. It was found that benzene and n-butanol may effectively prevent the hard agglomeration in the drying process to produce nanometer sized powder in diameter of 30～50nm, and the mechanism may be attributed to the decrease of capillary force amonge the particles during drying process because of the substitution of the organisms for water which didn't affect the properties of crystal structure, thermogravimetric analysis and iso-electric point etc. However, the nanometer sized AMH powder can't be prepared with propanoic acid although propanoic acid may chemically react with surface hydroxys of AMH particles which may apparently affect the properties of the product.