a1 Department of Materials Science, Tampere University of Technology, FIN-33101 Tampere, Finland
In this work, the oxide structures of three polycrystalline copper grades, unalloyed oxygen-free (OF) copper and alloyed CuAg and deoxidized high-phosphor (DHP) copper, were studied using cross-sectional analytical transmission electron microscopy (AEM) samples. The oxidation treatments were carried out in air at 200 and 350 °C for different exposure times. The detailed oxide layer structures were characterized by AEM. At 200 °C, a nano-sized Cu2O layer formed on the all copper grades. At 350 °C, a nano-sized Cu2O layer formed first on the all copper grades. After longer exposure time at 350 °C, a crystalline CuO layer grew on the Cu2O layer of the unalloyed OF-copper. In the case of the alloyed CuAg- and DHP-copper, a crystalline and columnar shaped layer, consisting of Cu2O and CuO grains, formed on the nanocrystalline Cu2O layer. At 350 °C, the unalloyed copper oxidized notably slower than the alloyed coppers, and its oxide structures were different than those of the alloyed coppers.
(Received August 24 2007)
(Accepted January 30 2008)