The application of focused microwave irradiation coupled with freeze drying to investigate the reaction of MgO and Al2O3 slurries in the formation of layered double hydroxides

Abstract

Focused microwave irradiation (MI) and freeze drying (FD) techniques have been used to study the generation of layered double hydroxides prepared from MgO–Al2O3–H2O systems. Reactions were undertaken at temperatures of between 100 and 180 °C in order to study the formation of the 3R1 and 3R2 polytypes, respectively. MI was found to enhance the rate of formation of both polytypes. FD provided an effective means of quenching the reaction, enabling effective ex situ analysis at intermediate stages. The phase selectivity of the reaction was shown to vary with temperature, promoting the formation of an impurity Mg(OH)2 at elevated temperatures.