Effects of Preparation Conditions on Alkali-Activation Reactivity of Chemosynthetic Al2O3-2SiO2 Powders

Pure Al2O3-2SiO2 powders with alkali-activation reactivity were prepared by a sol-gel method. The effects of preparation conditions on alkali-activation reactivity were studied and the optimum preparation conditions were obtained. The results show that calcination temperature is a key factor affecting the alkali-activation reactivity of the powders, while other preparation conditions such as synthetic temperature, the molar ratio of solvents to starting materials and drying time have fewer effects on alkali-activation reactivity than calcination temperature. The structure of the powders was investigated by 27Al magic-angle spinning nuclear magnetic resonance spectra. The data show that the Al2O3-2SiO2 powders with the high alkali-activation reactivity are of high content of 5-coordinated Al and the peaks attributed to 5-coordinated Al are strengthened with the rise of calcination temperature of the powders.