The different stages of solid phase sintering
Sintering: physico-chemical aspects - Part 1: Solid phase sintering

Consider a mole of copper (63.5 g), made up of 1 µm cubic grains, and the same mole of copper made up of a single grain (figure 7). These two systems differ in the areas of their solid-gas interfaces. The single grain has a lower specific surface area (surface area per unit mass) than the dispersed system. This decrease in surface area d A_sg corresponds to a decrease in energy of the form γ_sg d A_sg. The proportionality coefficient γ_sg is called surface tension (or surface energy); it is positive and therefore measures the amount of work required to increase the material's area by one unit [6]....