Characterization and electrical analysis of carbon-based solid lubricant coatings

Abstract

• Electrophoretic deposition of different carbon nanoparticles on copper substrate. • Nanoparticle coatings protect substrate, reduce wear, and lubricate contacts. • Hierarchy in electrical contact resistance values established among nanoparticles. • Carbon nanotubes and nanohorns show promising results as electrical contact coating. The use of electrical devices has skyrocketed over the past decades, increasing the demand for electrical connectors worldwide. Therefore, it is of utmost importance to produce more reliable, energy and material efficient, and durable electrical contact material systems; particularly in low-redundancy systems, such as in passenger vehicles. This work analyzes the potential use of carbon nanoparticle coatings applied via electrophoretic deposition over copper substrates to reduce wear, require lower insertion forces, and to protect the connectors from atmospheric conditions, while reducing the gain on the overall resistance of the system. Four carbon nanoparticles were considered due to their well-known solid-lubricating capabilities, namely: graphite flakes, graphene oxide, carbon nanotubes, and carbon nanohorns. Through a comprehensive characterization of the coatings, aspects like coating topography, compactness, thickness, elasticity, and electrical contact resistance were analyzed. Carbon nanotubes and nanohorns proved to have the highest potential. In addition to their previously documented outstanding solid-lubricity and environmental protection - after chemical modification of the coatings’ surfaces - these nanoparticles showed low resistance values for loads above 4 N, i.e., below 400 mΩ. Moreover, the coatings produced were thin and homogeneous, with adequate mechanical stability, and elastic behavior.