Different materials transport mechanisms led to distinctly different morphological evolution during the sintering of ceramic particles. These behaviours were analyzed using meso-scale, finite-element models based on rigorous formulations of coupled equations for continuum transport and interfacial phenomena. While such two-particle models were simplistic with respect to a real powder compact, they nevertheless provided important mechanistic understanding of the sintering behaviour of different systems. Calculations clearly showed how viscous flow mechanisms for glassy particles produce simultaneous shrinkage and neck growth due to the global nature of materials transport. In contrast, results for crystalline systems without grain boundaries showed that the more localized nature of diffusive transport led to neck growth with very little densification until late stages of sintering. Surprisingly, surface vacancy diffusion led to system elongation before densification occurred.

Transport Mechanisms and Densification during Sintering - I. Viscous Flow versus Vacancy Diffusion. H.Djohari, J.I.Martínez-Herrera, J.J.Derby: Chemical Engineering Science, 2009 , 64[17], 3799-809