HYDRIDING KINETICS OF POWDERS

Kinetic measurements of gas-solid reactions performed on powders, are usually interpreted according to single-particle analysis (SPA) models . The use of SPA functions is not a priori justified, since deviations from that functional dependence may occur in the powder, owing to thr ee factors: (i) particle size distributions, (ii) particle shape varia tions and (iii) time distributions for the beginning of the reaction o n each one of the particles composing the powder. The effects of these factors are quantitatively analysed and their interference in the SPA procedure is estimated. It is concluded that under certain circumstan ces the SPA can yield the correct reaction mechanism and even enables a reasonable estimate of the corresponding intrinsic kinetic parameter s. This analysis is relevant generally to gas-solid kinetics, with par ticular emphasis on hydriding reactions.