Molecular dynamics study of silica-alumina interfaces

Computer simulations of silica-alumina interface formation by a sol-gel process were performed using the molecular dynamics method. The polymerization reaction of silicic acid molecules was simulated for 1 ns (10 000 000 time steps). A complete transformation from liquid silicic acid to dense silica was observed due to removal of water from the sample. The reaction kinetics was characterized using the degree of polymerization of polysiloxane chains and relative concentrations of silicon Q species. Hydroxyl groups originally present on the alumina surface played a crucial role in formation of an ordered atomic structure in the interface region.