Dynamics of wetting in reactive metal ceramic systems

Dynamics of wetting of metallic drops on smooth ceramic surfaces are discussed for the case of liquid-solid couples leading to the formation of a continuous layer of a reaction product at the interface, by reaction between a component of the liquid and the solid substrate. This paper is focused mainly on the following two questions: (i) the driving force of reactive wetting, i.e. the origin of this force and the crucial question of the final contact angle in a reactive system and (ii) the different processes which can be rate-limiting, namely the viscous flow, the diffusion within the drop and chemical kinetics at the triple line. From experimental results on model systems published in the last three years, clear answers to point (i) were given. Current experimental and theoretical results on spreading kinetics are the starting point For a fundamental approach to these complex kinetic phenomena. (C) 1998 Acta Metallurgica Inc.