前驱体种类对非水解溶胶-凝胶法合成镁铝尖晶石的影响

运用非水解溶胶-凝胶法(NHSG法)合成了镁铝尖晶石粉体,借助X射线衍射分析和傅里叶变换红外光谱分析研究了铝源及镁源种类对镁铝尖晶石粉体合成造成的影响,利用场发射扫描电镜表征了制备样品的形貌。结果表明:氟化铝和氟化镁的离子键成分过高,以其作为前驱体原料时,无法与对应的镁前驱体或铝前驱体发生异质缩聚反应,因此不能实现镁铝尖晶石的低温合成。醋酸镁为镁源对铝醇盐的形成过程有一定影响,造成样品的低温合成效果不佳。优选出铝源和镁源分别为铝粉和镁粉,铝粉和镁粉分别与乙醇发生反应生成金属醇盐,然后脱醚缩聚形成Mg-O-Al键,因而能在700℃低温合成MgAl2O4纯相。且制得样的粉体分散性好,平均粒径为11nm,粒径分布较窄。

Effects of Precursors on the Synthesis of Magnesia-alumina Spinel Powder via Non-hydrolytic Sol-gel Method

Magnesia-alumina spinel powders were synthesized via non-hydrolytic sol-gel method.Effects of aluminum and magnesium sources on the synthesis of magnesia-alumina spinel were studied by XRD and FT-IR.Moreover,the morphology of the powders was characterized by FE-SEM.Owing to their relatively high ionic bond composition,aluminum fluoride or magnesium fluoride could not react with corresponding magnesium precursor or aluminum precursor.Thus,magnesia-alumina spinel could not be synthesized at 700℃with the fluoride precursors above.Magnesia-alumina spinel could not be synthesized at 700℃either when magnesium acetate is used as magnesium source,due to its negative impact on aluminum ethoxide formation.Eventually,the optimized aluminum and magnesium sources are aluminum powder and magnesium powder,respectively.These metal powders could react with the oxygen donor ethanol to produce corresponding metal ethoxide.Then these metal ethoxides react with each other accompanied by the formation of Mg-O-Al bond through deether polycondensation.The magnesia-alumina spinel forms at700℃without impurity.Notably,the prepared powder is excellently dispersed with an average particle size of 11 nm.