The role of near-surface on the reactivity of metal oxide powders in solid-solid reactions - applications of emanation thermal analysis

The role of near-surface on the reactivity of metal oxide powders in solid-solid reactions increases with a decrease in particle size. Emanation thermal analysis (ETA) using a surface impregnation method with 226Ra parent isotope was applied to the investigation of the thermal characterization of the near-surface of various inorganic powders with different preparation histories. Further, in order to consider the surface reactivity of these materials, the thermal behaviour of the labelled species in solid-solid mixed systems were were followed by means of the ETA under the working state at high temperatures. The ETA results for single powders, Al2O3 and Fe2O3, and mixed systems, Fe2O3-ZnO, BaCO3-TiO2 and Fe2O3-Al2O3, were represented as typical examples. ETA provided useful informations on the surface characterization of oxide powders, and on the phase-boundary processes taking place in the initial reaction step for the mixed systems. (author) 25 refs., 11 figs., 1 tab