The Effects Of Hydrothermal Synthesis On The Properties Of Hydrous Alumina And Alumina

In this dissertation hydrous alumina and alumina with peculiar morphology and different properties have been synthesised by alkoxide-hydrolysis and hydrothermal synthesis methods, IR,XRD,TEM, TG, SEM were used to characterize the samples synthesized,and studied the effects of different synthesis conditionds on the properties of hydrous alumina and alumina systematically.The results indicate that,the hydrous alumina prepared by alkoxide-hydrolysis method is pseudo-boehmite, with the properties of small crystallite size,below 10nm,poor crystallinity, irregular clew-like, consisting of physical and layer structural water;the hydrous alumina prepared by alkoxide-hydrolysis method combined with hydrothermal synthesis and when hydrothermal temperature was up to 140℃is boehmite,with the properties of big crystallite size,between 30～70nm,good crystallinity,rhombic thin plate,good dispersity,almost no physical water,only concluding layer structural water.γ-Al₂O₃ prepared by pseudo-boehmite is irregular clew-like and with poor crystallinity;γ-Al₂O₃ prepared by boehmite is rhombic thin plate and with good crystallinity,which indicate that the morphology ofγ-Al₂O₃ crystallites has memory of that of boehmite crystallites.Hydrous alumina and alumina crystal whiskers have been synthesized by hydrothermal synthesis method used CTAB as template,with the hydrothermal synthesis temperature rose and hydrothermal synthesis time extended,the size of crystal whiskers increases, the length of crystal whiskers hydrous alumina synthesized when the hydrothermal synthesis temperature was 120℃is about 5 um and the diameter is about 250nm,length/diameter is about 20,and the length ofγ-Al₂O₃ crystal whiskers is 1.5～5um,the diameter is 200～300nm,and with porous propertie,andα-Al₂O₃ crystal whiskers are arranged regularly by many small sphere particals.Alkoxide-hydrolysis and hydrothermal synthesis were first combined together in this dissertation,which absorbed the merits of both the methods,improved the properties of hydrous alumina and alumina,which can explore greater application field for hydrous alumina and alumina.