LINEAR RATE LAW FOR THE DECAY OF THE EXCESS SURFACE-AREA OF A COALESCING SOLID PARTICLE

A linear rate law has been derived for the final stages of decay of th e excess surface area of a spheroidal solid particle approaching a sph erical shape. Solid-state diffusion within the particle, driven by str ess gradients resulting from nonsphericity, is assumed to be the contr olling mechanism. The derivation is based on a solution to Laplace's e quation for the chemical potential inside the solid particle, which sa tisfies the boundary condition for the chemical potential on the parti cle surface. The characteristic frequency for the decay is 16v(m)(2)L sigma/R(3) where v(m) is the molecular volume, sigma the surface tensi on, and R the radius of the sphere. The phenomenological coefficient L appears in the diffusional flux, driven by the chemical-potential gra dient.