Surface effects on the sintering behavior of nano metric metallic particles

Nano metric Cu and Fe powders (NP) were sintered in H2 after uniaxial cold pressing. The sintering behavior of samples was studied using dilatometric and calorimetric techniques. The sintering temperature Td and the self-diffusion activation energy Qa obtained in H2 for Fe were 350 Centigrade and 60 kJ/mole respectively, and those obtained in H2 for Cu were of 220 Centigrade and 43 kJ/mole. According to the present results, the activation energies obtained from both NP in H2 could be associated to those for self-diffusion in the liquid state (Fe 65 kJ/mole and Cu 41 kJ/mole). Assuming Td related to the surface melting temperature, the size dependence of surface melting of nano metric metallic particles is proposed on the basis of a simple Debye model together with the Lindemann law, by phenomenologically taking into account a surface phonon softening process. (Author)