Towards improved electroplating of metal-particle composite coatings
Frank C. Walsh, Clive Larson
Abstract
The electrodeposition of composite coatings containing included particles in a metal matrix dates back, at least, to the 1920s. The process involves both electroplating of metal and electrophoretic coating of particles but can often be carried out in modified electroplating tanks. It is not always appreciated that a stable suspension of particles of suitable surface charge in the bath, the electrode geometry and electrolyte flow conditions are critical and integrated aspects of the overall process. Particles having different shape, size distribution and wettability can be involved. The resulting composite deposit can be tailored to have important mechanical, chemical, physical and electronic properties, leading to increasingly diverse applications in tribology, aerospace, corrosion resistance and speciality electronics. Modern uses include coatings for industrial electrochemical technology, supercapacitors, fuel cells and batteries. Interactions among bath composition, operational conditions and deposit properties are reviewed. Advances and limitations in models describing composite electrodeposition are summarised. Challenges to continued advances in this field, from a fundamental and technological viewpoint, necessitate further R & D effort.