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Abstract: The sintering stress is originally defined for equilibrium states, where the mechanical stress just balances the internal surface tension forces so that the porous material does not shrink. The sintering stress for a given porous structure in equilibrium was calculated by three methods theoretically; the energy difference method, the curvature method, and the force balance method. The sintering stresses by three different methods were exactly the same for idealized porous materials in equilibrium, in which the pore surface had a constant curvature at any point. The grain boundary energy contributed to the sintering stress, and it affected the thermal stability of the porous structure. [Copyright &y& Elsevier]

Three-dimensional grain growth was analysed using the Surface Evolver program that simulates grain-boundary motion by curvature. When the grainboundary network reached a statistically self-similar steady state structure in the norm al grain growth period, the mean life span until the disappearance of grains could be predicted from the distribution function of the norm alized grain size and the distribution function of the num ber of faces in normal grain growth period. [ABSTRACT FROM AUTHOR]

Abstract: The shrinkage of a closed pore in the sintering of a particle cluster was analyzed. The shrinkage rate was proportional to the sintering stress, and inversely proportional to the macroscopic viscosity. The sintering stress was determined as a function of the pore volume, the dihedral angle, and the pore coordination number. The macroscopic viscosity was expressed as a function of pore volume in sintering by viscous flow, lattice diffusion, interface-controlled lattice diffusion, or grain boundary diffusion. The pore shrinkage was simulated using the Surface Evolver program in three dimensions. As the large pore shrank, the pore coordination number decreased gradually. This topological transformation of the pore increased the sintering stress and promoted densification. [Copyright &y& Elsevier]

Abstract: Coarsening during sintering results from surface motion, while grain growth results from grain boundary motion. The sintering of two spherical particles of different sizes, and subsequent coarsening and grain growth, were studied until the smaller particle disappeared. When the grain boundary mobility Mgb was comparable to the surface mobility Ms, the curved grain boundary migrated out of the smaller particle in a shorter time with increasing ratio of grain boundary energy γgb to surface energy γs. As long as the grain boundary was anchored to the surface triple junction, the grain boundary was approximated to be flat at the limit of Mgb≫Ms. The motion of flat grain boundary was affected by γgb/γs in a different way to that of the curved grain boundary. [Copyright &y& Elsevier]

Abstract: A method to analyze the mechanics of sintering of a single grain boundary was developed by using specimens fabricated by focused ion beam micro-machining. The translational motion and rotation of particles in sintering are influenced by the grain boundary diffusion coefficient and grain boundary energy; both are dependent on crystallographic orientation. Three-dimensional computer simulation was used to analyze the shrinkage and rotation as a response to sintering force and torque, respectively. The model experiments on gold were compared with the simulation results to determine the depth of the cusps on the plot of grain boundary energy vs. misorientation angle, the grain boundary diffusion coefficients, and the surface diffusion coefficient. [Copyright &y& Elsevier]