Subtle interactions in silica-alumina mixtures

Object of the study in this paper was the mechanical mixtures of amorphous silica and α-Al₂O₃ with different precursors (gibbsite, boehmite, and γ-Al₂O₃). The results obtained revealed that measurable interactions exist in different binary systems without previous thermal treatment. These interactions could be explained by the existence of attractive and repulsive forces which appear between the OH⁻ groups present on the surfaces of alumina and silica constituents. In thermally treated samples, the interactions are not driven by intermolecular forces but rather by polymorphic transformations of alumina and silica, which are followed by sintering.