Synthesis of α-Al2O3 platelets and kinetics study for thermal decomposition of its precursor in molten salt

The precursor, ammonium aluminum carbonate hydroxide (AACH) was synthesized via solid-state reaction at 60 °C. The experimental results show that the AACH is orthorhombic NH4Al(OH)2CO3, and the calcined powder products are hexagonal platelets of α-Al2O3 which can be obtained from calcining AACH in molten salt at 1000 °C. The linear and nonlinear methods were used to calculate the activation energies of the thermal process of AACH. The calculated results indicated the decomposition process involved two stages which were single-step kinetic processes. The most probable reaction mechanisms of the two stages were estimated by two comparative methods. The values of pre-exponential factor A of the two stages were obtained on the basis of Eα and the reaction mechanisms.