Sol-enhanced nanostructured metal-oxide composite coatings: structures, properties and mechanisms

Abstract

In the present research, a novel sol-enhanced electro- or electroless deposition processs has been developed to prepare composite coatings reinforced by highly dispersive nano-particles. A transparent TiO₂ sol was added into the traditional electro-/electrless plating Ni electrolyte. The TiO₂ nano-particles in situ formed, and then co-deposited with Ni atoms to form highly dispersive TiO₂ nano-particles reinforced Ni-based composite coatings. Two electrochemical deposition systems, i.e. electro- and electroless plating, were used in this thesis to synthesize sol-enhanced electroless plated Ni-P-TiO₂ and electroplated Ni-TiO₂ composite coatings. The objective of the research in the thesis was to understand the formation mechanism and electrochemical behaviours of the sol-enhanced composite coatings; to investigate the effect of highly dispersive nano-particles on the mechanical/physical properties and corrosion resistance of composite coatings. The research was started with an investigation of the processing of sol-enhanced electroless plated Ni-P-TiO₂ composite coatings. Then systematic investigations were conducted on sol-enhanced electroplated Ni-TiO₂ composite coatings based on three aspects: the effect of the sol concentration, the electrochemical process, and the thermal stability & tensile properties.