Research on the preparation and current-carrying friction properties of carbon nanotube/copper composite fibers

Brush–slip ring systems are essential for reliable power and signal transmission in spacecraft, while increasing power density and current-carrying requirements have intensified wear and degradation of conventional metallic brushes. In this work, carbon nanotube (CNT)-reinforced copper composite fibers were developed by integrating the lightweight, flexible, and high-current-carrying capability of CNT frameworks with the excellent electrical conductivity of Cu. CNT fibers (CNTF) were fabricated by twisting CNT film ribbons, followed by Cu electrodeposition to obtain CNTF/Cu composite fibers. The current-carrying tribological behavior and wear mechanisms were systematically investigated. At a twist level of 20 r·cm⁻¹, the CNTF/Cu fibers exhibited an average diameter of 300 μm, a density of 3.32 g cm⁻³, an electrical conductivity of 3 × 10⁶ S m⁻¹, and a current-carrying capacity of 2.1 × 10⁴ A cm⁻². Under a normal load of 0.1 N, the wear rate increased with increasing current density due to enhanced Joule heating. Higher sliding speeds intensified frictional heating, leading to increased friction coefficient and surface damage. Even under a high current density of 4244 A cm⁻², the CNTF/Cu fibers maintained a friction coefficient of 0.248 and a low wear rate of 5.36 × 10⁻⁷ g N⁻¹ m⁻¹. Furthermore, a 50 km long-term sliding test demonstrated excellent wear resistance with a wear rate of 4.23 × 10⁻⁸ g·N^{− 1} m⁻¹. The wear mechanism involved the synergistic effects of abrasive, adhesive, oxidative, and electrical wear. These findings demonstrate that CNTF/Cu composite fibers provide a promising approach for lightweight, high-power-density, and long-life electrical contact materials.