Given that the thickness of the liq

Given that the thickness of the liquid phase(s) trapped between particles is a function of the effective local contact pressure,45 one can assume that in directions other than the one of the applied pressure, two main effects may lead to a thicker polymer layer between two grains and thus limit the mass transport limitation: a) the local stress at grain contacts whose surfaces are not orthogonal to the applied pressure experience significantly less pressure and a commensurately reduced driving force for densification, b) these aforementioned areas of lower stress also act as areas for polymer accumulation for material extruded out from the more highly constrained contact points between ceramic grains, further restricting the densification process (Figure 1d).