The Role of Oxide Passivation Layers in Nanocrystalline Metal Powders and Consolidated Materials

摘要: Ultrafine powders of different metals (Al, Ag and Fe) have been prepared by the inert gas evaporation method. In all cases samples passivated pure oxygen air exposure before compaction material into 13 mm discs. Due to passivation with individual grains are covered a layer that contains oxygenated phases. Depending on metal, characteristics oxide leads properties consolidated material. Characterisation has carried out transmission electron microscopy (TEM), X-ray diffraction (XRD) photoelectron spectroscopy (XPS). For aluminium, dense compact prevents from grain growth during heating temperatures above melting point metal. Silver, as noble does not form layer, so total coalescence nanometric silver occurs after in an argon atmosphere. An intermediate situation is observed case Fe where upon heating. Finally, we found stabilization metastable γ-Al 2 O 3 γ-Fe (and/or 4 ) phases layers Al Fe, respectively. The formation these γ-phases attributed character particles.