Influence of Nanoeffects on the Oxidation of Cr-C/Ag Thin Films Containing Silver Nanoparticles

Well-controlled functionalization of carbide-based nanocomposite films with noble-metal surface nanoparticles of different sizes may lead to new materials with novel multifunctional properties. In this work, magnetron sputtering was used to deposit nanocomposite films comprising amorphous chromium carbide (a-CrCx), amorphous carbon (a-C), and a minority of silver in the form of embedded nanoclusters. Up to 510(10) surface nanoparticles per cm(2) with different size distributions were also found to be formed, owing to the diffusion of silver from the bulk of the film. The influences of these conductive nanoparticles on the electrochemical behavior of the films were investigated in dilute sulfuric acid. Although silver is a noble metal, the oxidation potential of the nanoparticles was about 0.4V more negative than the Ag+/Ag standard potential, meaning that the nanoparticles were oxidized in the Cr passive potential region. While this effect can mainly be explained by a low concentration of Ag+ in the electrolyte, the sizes of the nanoparticles and interactions with the matrix were also found to be important. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to analyze the surface chemistries. As Ag can be replaced by other noble metals, the concept is of general interest for further studies.