Self-assembled monolayers of alcanethiols on nickel surfaces for low level electrical contact applications

Nickel can be used as final coating for separable electrical contacts in various types of applications: batteries, automotive connectors, etc. The possible growth of a poorly conducting layer on the metal due to environmental conditions has limited up to now the use of such coatings to common applications. However durable quality performances can be expected with a proper protective material avoiding corrosion. The new approach we have been working on, is to find compounds that bind to nickel and form well-defined layers. We report here the first results describing the behaviour of self-assembled monolayers of thiol molecules deposited on bare nickel substrates. We briefly describe the deposition method, the type of molecules and of substrates used and summarize the main physicochemical characterisations available. The electrical and tribological properties of the monolayers formed on nickel slabs are investigated in a ball/plane configuration simulating a real contact element. The influence of an electrochemical pretreatment of the nickel surface prior to the layer assembly is shown. Excellent tribological behaviours can already be obtained with corresponding values of the contact resistance varying between 1 /spl Omega/ and 10 m/spl Omega/. The results show that building organised monolayers acting as protective coatings is of high interest for electrical contacts.