Initial sintering stage of nanostructured metal powder networks studied by dc-conductivity measurements

In powder metallurgy sintering is one of the most fundamental phenomena. Technical sintering is usually realized in a temperature region above 2/3 Tm. Under special conditions the initial stage of sintering can be observed at much lower temperatures. These conditions are: high specific surface area corresponding to a small particle size. This leads to a high specific surface energy as a driving force for sintering. Clean, i.e. oxid-free powder surfaces. Coverage with gaseous impurities would suppress the self diffusion during sintering. This condition are fulfilled for metall powders produced by the inert gas condensation technique using a ultra high vacuum device. The aim of this paper is to figure out the temperature range where sintering actually starts in ultrafine powders. For this purpose in in-situ dc-conductivity measurements have been performed.