Load-dependent electrical contact resistance of carbon nanotube-reinforced metal matrix composites

The reliability of contacting systems is determined, among other factors, by its electrical contact resistance (ECR) development. ECR in closed state must be as low as possible, to avoid energy losses, overheating and to ensure the proper circuit opening afterwards. Furthermore, to improve the electrode's performance, there are key characteristics that should be optimized such as its mechanical and thermal stability. This study analyses the behavior of the ECR as a function of the applied normal load of carbon nanotube (CNT)-reinforced Ni composites with different concentrations. The first test consisted of performing a DC current sweep from 30 µA to 1 A at a constant mechanical load (4 N) and contrast the behavior to a pure metal sample. In all the CNT-containing samples, the contact resistance was below that of the reference sample, achieving a reduction of up to 80%. The second test dealt with the load-dependent behavior of the contact resistance. The normal load was varied from 0.25 to 10 N and the circuit DC current was 100 mA. In this case, the composites showed lower contact resistance for a wide load range, except at the highest load, where the dominant mechanisms may change to a pure metal-metal contact.