Size effects in oxide mechanochemistry

A new size effect has been experimentally found: the mechanochemical synthesis of previously mechanically activated powder mixtures of MgO-Al2O3 oxides with a block size of about 80 nm leads to the formation of MgAl2O4 spinel at room temperature. A model is proposed according to which the mechanism of mechanochemical solid-phase synthesis changes from dislocation transgranular embrittlement to grainboundary sliding, which is accompanied by the generation of dynamic vacancies and low-temperature phase formation via the diffusion-induced migration of grain boundaries.