PHASE TRANSFORMATIONS AND MASS TRANSPORT IN MECHANICALLY ACTIVATED LOW-TEMPERATURE FORMS OF ALUMINA

摘要

Polymorphic transformations and mass transport in mechanically activated γ- and χ-Al_2O_3 were studied by x-ray diffraction analysis, diatometry, and BET measurements .Mechanical processing of active alumina was found to reduce the temperature of corundum formation and intensify mass transport ,as evidenced by the observed increase in the effective diffusion coefficient with mechanical-activation time and specific power. As a result of the fast mass transport at relatively low temperatures, the specific surface decreases notably before α-Al_2O_3 begins to form.