Magnesium aluminate precursor sol were prepared using aluminium chloride hexahydrate as alumina source,magnesium chloride hexahydrate as magnesia source,and ammonia as a precipitating agent.The solid content,pH value and density of the sol were determined.The gel powder was analyzed by thermal analysis,infrared spectrum analysis,XRD and TEM.The results showed that the colloidal particle of precursor sol was a hybrid mixture of Mg2Al(OH)7 and Al(OH)3.The solid content of as prepared sol was 5.8%and the density 1.21 g/cm3.When the dry gel powder is heated,Mg2Al(OH)7 and Al(OH)3 decompose,and MG-Al spinel crystals begin to form at 500℃,and the particle size of Mg-Al spinel is smaller at 700℃,about 15 nm.As further increasing the heat treatment temperature,the lattice of magnesium aluminate spinel tends to be perfect and the average grain size increases.
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