On the Thermodynamics of Adsorption at Interfaces as it Influences Decohesion

Earlier computations on the work of separation of boundaries with adsorbed solute atmospheres are reconsidered in terms of reversible work cycles. Special attention is given to two limiting cases. These are the separation of a material interface under fully equilibrated conditions, for which the chemical potential of the adsorbed solute remains constant, and separation under constrained conditions for which the surface excess solute concentration remains consta.nt (i.e., the same on the two newly created free surfaces as present initially on the unstressed mterface). The results are consistent with the limiting cases treated before and include the extension to more general cases of solute interactions, including multicomponent systems. The work terms are conveniently represented on diagrams of chemical potential vs surface excess solute concentration. A general separation process is then represented as a path in this diagram which begins on the adsorption isotherm for the unstressed interface and end~ on the adsorption isotherm for the pair of newly created surfaces.