A non-linear kinetic law, and its corresponding variational principle, were developed for solid-state diffusion under a large thermodynamic driving force. These were used to model the sintering of spherical particles. It was demonstrated that the classical linear diffusion law significantly underestimated the sintering rate for nanosized particles.

Solid-State Diffusion under a Large Driving Force and the Sintering of Nanosized Particles. J.Pan: Philosophical Magazine Letters, 2004, 84[5], 303-10