The growing electrification of mobility, coupled with the increased demand for consumer electronics and the green energy transition towards renewable alternatives has substantially increased the requirements for electrical contact materials.[1] For supply to meet the demand (e.g., silver and copper) and to minimize the carbon footprint of these materials, it is imperative that sustainability becomes central to contact design and manufacturing; thus ensuring an efficient material use,
prolonged duty life, as well as improving end-of-life management (i.e., material recovery and reinsertion into the economic loop). However, design can only go so far since electrical contact degradation is intrinsic to the applications for which they are intended. Accordingly, product life
extension techniques are required to reduce wear (e.g., in sliding contacts), electrode degradation (e.g., via arc erosion in separable contacts), corrosion, etc. Well-established industrial processes such as material alloying, electrode platings, and protective coatings are commonly used to minimize material deterioration. However, most of these techniques are associated with an undesirable increase in electrical resistance. As a result, there has been an increasing interest and research into the incorporation carbon nanoparticles (CNP) into electrical contact materials, for example as carbon coatings or as a reinforcement phase in composite materials. The attention garnered by carbon is not only due to its inherently high transport properties and lubricating capabilities, but also due to its environmental benefits, as carbon is abundant in nature and can be derived from renewable resources, it is recyclable, and adds less complexity to the system compared to more conventional
alternatives such as thiol and fluor-containing lubricants [2].
The incorporation of carbon nanotubes (CNT) in metallic matrices reduces the overall amount of metal mining, since a certain amount of copper and silver is replaced by carbon (promoting dematerialization – weight reduction – and reducing material diversity by potentially eliminating alloying and coating requirements). Moreover, the addition of carbon produces steady state electrical contact resistance (ECR) during fretting wear while slightly increasing the resistance of the system on account of the addition of the reinforcement phase.[3–9] Likewise, carbon coatings minimize material system complexity, by potentially substituting complex coatings, platings, etc. CNP coatings have been shown to marginally increase the resistance of the system (reliant on the type of nanostructure used).
Nonetheless, CNP coatings demonstrate favorable wear reduction behavior irrespective of atmospheric conditions.[10,11] Furthermore, CNP coatings show promising results as protective coatings from atmospheric conditions due to their hydrophobic nature.[12,13] Moreover, the high elasticity of CNT has highlighted the topographic-independence on the electrical performance of copper-based electrodes.[14]

References
[1] T. Barai, V. Kumar, Connector Market: Global Opportunity Analysis and Industry Forecast 2023-2032,
2023.
[2] M.M. Titirici, R.J. White, N. Brun, V.L. Budarin, D.S. Su, F. Del Monte, J.H. Clark, M.J. MacLachlan, Chem
Soc Rev, 2015, 44, 250–290.
[3] D. García, S. Suárez, K. Aristizábal, F. Mücklich, Adv Eng Mater, 2022, 24, 2100755.
[4] S. Suarez, B. Alderete, R. Puyol, F. Mucklich, IEEE 67th Holm Conference on Electrical Contacts (HLM),
2022, 1–6.