Al-O-Si bond formation in boehmite-fumed silica mixtures during mechanochemical activation

Al-O-Si bond formation in boehmite-fumed silica mixtures during mechanochemical activation was investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), magic angle spinning nuclear magnetic resonance (MAS-NMR) and X-ray photoelectron spectroscopy (XPS). The intrinsic structure deformation of the boehmite was examined with XRD. Formation of new Al-O-Si bonds was illustrated by the incorporation of Al³⁺ in Si-O-Si linkages, the change in the Al coordination number of boehmite, and the appearance of new resonance in the ²⁹Si NMR spectrum of the ground mixture. The presence of Al-O units in silica frameworks was verified by the increase of Al 2p binding energy and the decrease of Si 2p binding energy.