The Effect of Nanosizing on the Oxidation of Partially Oxidized Copper Nanoparticles.

Copper nanoparticles are of great interest in various applications, such as catalysis, cooling fluids, conductive inks or for their antibacterial activity. In this paper, the thermal behavior of copper nanoparticles was studied using thermogravimetry, differential thermal analysis and differential scanning calorimetry. Original Cu samples as well as the products of oxidation were analysed by X-ray diffraction, scanning/transmission electron microscopy and energy dispersive spectroscopy. A step-by-step oxidation mechanism during the oxidation of Cu nano-powders was observed. The Cu-nano oxidation starts slightly above 150 °C when bulk copper does not yet react. The dominant oxidation product in the first step is CuO while CuO was identified as the final state of oxidation. Our results confirm an easier oxidation process of Cu-nano than Cu-micro particles, which must be attributed to kinetic not thermodynamic aspects of oxidation reactions.