水热处理对片组装花型硫酸铝水解产物微观形貌的影响

摘要

以水合硫酸铝为原料、尿素为沉淀剂、乙醇水混合液为溶剂,采用水热处理方法制备了块状碱式硫酸铝及花形薄水铝石,利用XRD和SEM等表征手段,探讨了水热温度和水热时间对产物微观形貌的影响,并对其晶体结构和形貌变化的形成机制进行了初步分析.结果表明:水热温度较低或水热处理时间较短时,尿素分解量小,溶液pH值低,且大量乙醇及SO42-的存在阻止了Al3+和OH-的过快成核,有利于形成块状(H3O)Al3(SO4)2(OH)6;随水热温度的提高或水热处理时间的延长,尿素分解量增大,溶液pH值增大,块状碱式硫酸铝在OH-侵蚀作用下发生原位分化,形成片状薄水铝石,最后形成以片组装的花形薄水铝石.煅烧后,氧化铝粉体的微观形貌继承了其前驱体氢氧化铝粉体的微观形貌.%The block aluminum hydroxide sulfate and flower-like boehmite were synthesized using Al2(SO4)3l8H2O as precursor, urea as precipitator, and mixture solution of ethanol and water (volume ratio is 2:1) as solvent by a hydrothermal treatment method. The effects of hydrothermal temperature and time on the morphology were studied by XRD and SEM. The mechanisms of the crystal structure and morphology changes were also analyzed. The results show that block aluminum hydroxide sulfate can be obtained at lower hydrothermal temperature or shorter hydrothermal time since the amount of urea decomposition is little, the solution pH value becomes low, and a large amount of ethanol and SO42' stop the rapid nucleation of Al3+ and OH" under the condition of lower hydrothermal temperature or shorter hydrothermal time. As the hydrothermal temperature increases or hydrothermal time prolongs, the block aluminum hydroxide sulfate begins to in situ differentiate by OH erosion because of the increased decomposition amount of urea and higher pH value. At the end, the flower-like boehmite assembled by flakes forms. After the calcination, the morphology of alumina powder inherits that of its precursor of powder aluminum hydroxide.