Characterization of spontaneously deposited ceria on copper and its nucleation

A novel dip-coating process for depositing cerium oxide on aluminum has been previously developed at the University of Missouri-Rolla. The original intent of developing the novel coating process was to produce chromate-free conversion coatings for corrosion protection of aluminum. Subsequently, the new coating technique was expanded to include substrates other than aluminum, such as nickel and copper. This report focuses on characterizing cerium oxide coatings deposited on copper using a spontaneous dip coating technique. Specifically, it focuses on possible routes to the coating’s nucleation and characterization of the coating and the coating/substrate interface. Extensive transmission electron microscopy studies have been performed on the coatings as well as x-ray photoelectron spectroscopy. The transmission electron microscopy studies were done to obtain average particle sizes and distributions, coating thicknesses, lattice d-spacings, and interface information. The x-ray photoelectron spectroscopy was done to obtain oxidation state information at the coating/substrate interface. It was found that the average particle size and the pH with which they were associated did not correspond to the pH observed at the coating/substrate interface in aqueous precipitation experiments. It was also found from diffraction measurements that the coatings are most closely matched with CeO2 and that the interface between the coatings and their substrates is abrupt, with no mixed oxide layer separating the coating from the substrate as was seen in the case of coatings on aluminum --Abstract, page iii