Thermal stability and grain growth of nanocrystalline metal silver

Abstract

The nanocrystalline metal silver (n-Ag) with average grain size of 10 nm was synthesized by using an inert gas evaporation and in situ compacting technique. The thermal stability of grain size and grain growth caused by isothermally annealing heat treatment, as well as the thermal behavior during grain growth, have been studied. The results indicated that the thermal stability temperature of grain size is about 200°C. The grain growth depends upon the annealing temperature and exhibits three different stages, i.e., slow, fast, and rapid growth stages, corresponding to the temperature ranges from 200°C to 300°C, from 300°C to 400°C and above 400°C, respectively. An exothermal peak and an endothermal peak occur on the differential scanning calorimetriy (DSC) curve of n-Ag. The exothermal peak and the endothermal peak appear in the temperature range from 200°C to 400°C, and from 400°C to 660°C, respectively. The enthalpies calculated from the above two peaks depend on the compacting pressure. Further analyses indicated that the grain growth of n-Ag is related to the release of the surface energy of grains and the interfacial energy, as well as the strain energy stored in the bulk samples induced by compacting process.