Homogeneous Ni-P/Al 2O 3 nanocomposite coatings from stable dispersions in electroless nickel baths

Abstract

The dispersion stability of aluminum oxide colloidal particles stabilized with comb-polyelectrolytes in an electroless nickel (EN) solution was studied under plating conditions (80–90 °C). The nanodispersions which were stable at room temperature for several weeks flocculate rapidly as the temperature approached ∼65 °C. Hydrotropes such as propylene glycol and urea are found to induce stability under plating conditions. A dependency of the critical flocculation temperature (CFT) on additives, comb-polyelectrolyte polyether side chain, and particle morphology is found. The codeposition of stabilized and nonstabilized nanoparticle dispersions resulted in very different particle density and distribution in the composite coatings. Highly homogeneous Ni-P/alumina nanocomposite coatings plated from stabilized baths with up to 50 vol% particle incorporation have been demonstrated.