The kinetic study of the synthesis of magnesium aluminate spinel from mechanochemically treated mixtures of oxide-hydroxide

Abstract

The kinetics of solid-state reaction of magnesium aluminate (MA) spinel formation from the mechanically activated mixtures of both Mg and Al oxides and hydroxides was studied in situ by high-temperature X-ray diffraction at elevated temperatures. The degree of conversion α of the MA spinel formation was determined by the Rietveld method. The dependence of the conversion degree of the MA spinel formation on the time of isothermal heating of the particular mixtures was studied. Time dependence α(t) of the crystalline MgAl2O4 formation at the temperature T was analysed by the equation corresponding to the first order kinetics α(t) = P1 · [1 − P2 · exp(−k · t)], where P1, P2, and k are the parameters. The rate constants k and the activation energies of the crystalline MgAl2O4formation for the selected mixtures were calculated by the fitting the kinetic data. Comparison of acquired data shows that the most beneficial results for MA spinel synthesis were obtained from the mechanically activated hydroxide mixture Mg(OH)2 + Al(OH)3.