Surface tension, compression/compaction

During pressure sintering, interiDarticle compressive stress, approximated by the externally applied stress and nonnalized by the relative density of the compact p, supplements the surface tension driving force for pore shrinkage ... 

The results presumably were distorted by the unavoidable heating of the microcrystals occurring in the electron beam and other side effects. However, if the A a detected in the (111) reflexions is real, then the surface stress or rather surface tension 7S causing the compression of the lattice can be calculated. If R i and R2 in Eq. (37) are supposed to be identical and equal to 0.5 D, see above, then Pc= 4 ys/D. Let k be the compressibility of the micro-crystal, i.e., -dV/V.dp. Then the relative compaction under the pressure, that is -dV/V, is 4 ysk/D. The ratio dV/V may be approximated as 3 A aja. Hence... 

Under these conditions, a compressive pressure is exerted between the two particles due to the capillary pressure and the surface tension of the liquid. (See Section 14.2.) Because of this compressive pressure at the contact area, the chemical potential of atoms at the contact area is higher than elsewhere (i.e. at the surface of the neck region). Therefore, the solid at the contact area dissolves and the dissolved material is transported to the surface of the neck. As a result of this material transport, the contact area increases and the grain shape is accommodated (contact flattening). At the same time, the pore shrinks continuously and the compact is densified. Kingery considered the pressure... 

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