Sintering of Ultrafine Metal Powders. II. Neck Growth Stage of Au, Ag, Al and Cu

Abstract

The neck growth stage in the sintering of ultrafine powders of Au, Ag, Al and Cu has been studied by electrical resistance measurement and electron microscopy. A formula for the electrical resistance at the necks of ultrafine metal powders is proposed. The decrease in the resistance of powders isothermally annealed at room temperature without compacting is explained as the neck growth among powders due to surface diffusion. The activation energy for the surface diffusion of Au is found to be 0.88±0.02 eV from resistance measurements. Obstruction of the neck growth is clearly detected in an atmosphere of O 2 in all the materials examined, whereas obstruction by N 2 , Ar and aqueous vapour is found to be negligible compared with that of O 2 .