In UCS, pressure is maintained duri

In UCS, pressure is maintained during Stage II. The pressure application during drying causes some basic differences in the final microstructure with respect to pressureless drying: (i) the grain boundary interphase film thickness is reduced because the external pressure pushes the particles closer, (ii) the precipitation process is driven only by the solvent evaporation (which induces supersaturation) or pressure differences in different loci (i.e. neck centre and neck borders), and (iii) particles modify their shape because of anisotropic mass transport and sintering induced by the external pressure. The modification of the particle shape causes the formation of polygonal grains and flat/thin boundaries as reported in Figure 9 for the case of cold sintered ZnO (micrographs taken from [6]) and α-quartz (micrographs taken from [17]). The final grain shape and microstructure differ significantly from thoseobtained by ICC (Figure 8).