ROLE OF WETTING IN SINTERING AND REDISPERSION OF SUPPORTED METAL CRYSTALLITES

Sintering and redispersion of crystallites on a substrate are examined in terms of the thermodynamics of wetting, on the basis of the free energy of formation σ(h) of a thin film of thickness h on a substrate. Conditions are identified under which sintering by migration of crystallites or by Ostwald ripening occurs. One concludes, among others, that a necessary condition for sintering to take place via Ostwald ripening is the change of the sign of σ(h) from positive to negative values when h decreases and becomes sufficiently small. If σ(h) is positive for any value of h, then migration and coalescence is the only mechanism of sintering. © 1979.