Abstract
The thermal decomposition behaviours of the hydrates of aluminium chloride, nitrate and sulphate, and of ammonium alum, the formate and acetate of basic aluminium and the lactate, citrate and tartrate of aluminium and the thermal transformation of the formed anhydrous aluminas to α-alumina have been investigated by thermogravimetry, differential thermal analysis, X-ray diffraction and infrared spectrophotometry. From the results, it is suggested that the aluminum salts are thermally decomposed as follows:
AlCl3·6H2O→amorphous alumina→γ-alumina→θ-alumina→α-alumina
Al(NO3)3·9H2O→amorphous alumina→γ-alumina→θ-alumina→α-alumina
Al2(SO4)3·18H2O→Al2(SO4)3·6H2O→Al2(SO4)3→amorphous→alumina→γ-alumina→δ-alumina→θ-alumina→α-alumina
NH4Al(SO4)2·12H2O→NH4Al(SO4)2·2H2O→NH4Al(SO4)2→Al2(SO4)3→amorphous alumina→γ-alumina→δ-alumina→θ-alumina→α-alumina
Al(OH)(HCOO)2→Al2O(HCOO)4→AlO(HCOO)→amorphous alumina→γ-alumina→δ-alumina→θ-alumina→α-alumina
Al(OH)(CH3COO)2→Al2O3·xCO2·yH2O→amorphous alumina→γ-alumina→δ-alumina→θ-alumina→α-alumina
Al[CH3CH(OH)COO]3 Al[CH2C(OH)CH2(COO)3] Al2{[CH(OH)COO]2}3} →amorphous alumina→γ-alumina→δ-alumina→θ-alumina→α-alumina
