Go-reinforced composite materials for electrical contact applications

The continuous advancement of modern technology, particularly in electronics, energy systems, and electrical engineering, has increased the need for materials that combine high electrical conductivity, mechanical robustness, and environmental stability. Electrical contact materials play a crucial role in determining the reliability, performance, and lifetime of electromechanical systems, as they must endure severe operating conditions such as high current density, elevated temperature, and corrosive atmospheres. Copper is one of the most commonly used metals in this field owing to its outstanding electrical and thermal conductivity, excellent formability, and relatively low cost compared with noble metals such as silver and gold. However, the inherent softness and chemical reactivity of pure copper significantly limit its long-term functionality. Under conditions of high current flow and temperature, copper tends to oxidize rapidly, which leads to an increase in electrical resistance, surface degradation, and contact failure. This issue has motivated intensive research into copper-based composite coatings that can retain the electrical advantages of copper while improving its mechanical and corrosion performance. In this study, graphene oxide (GO), a two-dimensional carbon nanomaterial derived from the oxidation of graphite, was incorporated into a copper matrix to form Cu–GO composite coatings using an electrochemical (current-assisted) deposition method. GO exhibits a unique combination of large surface area, excellent chemical stability, high mechanical strength, and the presence of oxygen-containing functional groups that promote good dispersibility in aqueous electrolytes and strong interfacial bonding with metallic matrices. By integrating GO within copper coatings, it was anticipated that the mechanical and tribological performance of the copper surface could be significantly improved through mechanisms such as grain refinement, dislocation pinning, and solid lubrication, while the oxygen barrier effect of GO could enhance corrosion resistance. The coatings were fabricated via pulse electroplating under different current densities (0.25, 0.5, and 1 A/cm²) using an electrolyte containing CuSO₄·5H₂O, H₂SO₄, and sodium dodecyl sulfate as a surfactant, with a GO concentration of 0.15 g/L. Prior to deposition, the GO particles were dispersed in the electrolyte by mechanical stirring followed by ultrasonication to minimize agglomeration. Steel substrates (St37) served as cathodes and copper plates as anodes. The coatings were designated as CuGO0 (pure Cu), CuGO1 (GO-reinforced at 0.25 A/cm²), CuGO2 (GO-reinforced at 0.5 A/cm²), and CuGO3 (GO-reinforced at 1 A/cm²). The structural, microstructural, and mechanical features of the coatings were systematically characterized using Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction (XRD). Mechanical and tribological tests were performed via nanoindentation and ball-on-disc wear testing, respectively, while Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion behavior in 3.5 wt% NaCl solution. FESEM analysis revealed that GO incorporation substantially modified the surface morphology and grain structure of the electrodeposited coatings. The pure copper coating exhibited a relatively coarse and nodular surface with irregular grain boundaries, whereas the addition of GO resulted in the formation of finer grains due to the creation of additional heterogeneous nucleation sites on the cathode surface. At an optimum current density of 0.5 A/cm² (CuGO2), the coating displayed a compact, uniform, and defect-free microstructure with the most homogeneous GO distribution. Conversely, increasing the current density to 1 A/cm² (CuGO3) led to local GO agglomerations and irregular grain growth due to excessive deposition rates. XRD patterns confirmed the face-centered cubic (fcc) structure of copper, with dominant reflections from (111), (200), and (220) planes. The incorporation of GO caused a reduction in peak intensity and an increase in the full width at half maximum (FWHM), implying lattice strain and crystallite size refinement. The Williamson–Hall analysis indicated that internal microstrain reached its minimum value at 0.5 A/cm², correlating with the finest crystallite size (~50 nm). These structural changes confirmed that GO effectively restricted excessive crystal growth by hindering dislocation movement and promoting a dense, refined grain structure. Mechanical characterization by nanoindentation demonstrated a remarkable enhancement in hardness and elastic modulus with GO reinforcement. The hardness increased from 1.4 GPa for pure Cu (CuGO0) to 2.53 GPa for CuGO2, while the elastic modulus improved from 212 GPa to 282 GPa. The enhancement was attributed to the synergistic effects of grain refinement and load transfer between the copper matrix and the well-dispersed GO sheets. However, further increasing the current density to 1 A/cm² resulted in a slight reduction in hardness (2.1 GPa) and modulus (256 GPa) due to the appearance of microvoids and structural defects caused by rapid metal ion deposition. Electrochemical analysis revealed that the addition of GO dramatically enhanced corrosion resistance. The EIS spectra exhibited larger capacitive loops and higher charge transfer resistance (Rct) for the GO-containing coatings compared to pure copper, confirming that GO acts as an efficient physical barrier that restricts the diffusion of chloride ions and retards electrochemical reactions. Among the tested samples, CuGO2 demonstrated the best corrosion resistance due to its uniform microstructure and well-dispersed GO network, which effectively reduced electrolyte penetration through the coating. Tribological tests performed under a 2 N load and a sliding speed of 0.1 m/s revealed that GO incorporation substantially reduced both the coefficient of friction (COF) and the wear rate. The COF decreased from 0.51 for CuGO0 to 0.26 for CuGO2, while the wear rate was reduced from 4.1 × 10⁻⁵ mm³/N·m to 2.82 × 10⁻⁵ mm³/N·m. These results were attributed to the formation of a continuous GO-based tribofilm on the surface, which acted as a solid lubricant minimizing adhesive and abrasive wear. Furthermore, the increase in hardness and structural compactness contributed to reduced material removal during sliding. The highest current density (1 A/cm²) again led to slight deterioration due to non-uniform GO distribution and localized surface roughness. The overall results indicated that the synergistic interaction between copper and GO generated coatings with enhanced microstructural integrity, mechanical strength, and corrosion protection without compromising electrical conductivity. The optimum coating, CuGO2, combined the advantages of a refined microstructure, high hardness and modulus, low friction coefficient, and superior electrochemical stability. The study also highlighted the importance of controlling deposition parameters such as current density, duty cycle, and GO dispersion to achieve consistent coating quality. In summary, the incorporation of graphene oxide into electrodeposited copper coatings significantly improved their tribological and electrochemical behavior. GO not only functioned as a strengthening and lubricating phase but also acted as a barrier layer that prevented corrosion initiation and propagation. The findings confirm that GO-reinforced Cu coatings can serve as promising, cost-effective, and environmentally sustainable alternatives to traditional copper coatings in electrical contact applications. Such coatings can extend the service life of components operating in aggressive environments while maintaining excellent electrical performance. The present research provides valuable insight into the design of multifunctional metal–carbon nanocomposite coatings, offering potential applications across a wide range of industries including microelectronics, energy transmission, automotive systems, and defense technologies. By combining superior conductivity, wear resistance, and corrosion protection, the developed Cu–GO coatings represent a significant advancement toward next-generation functional materials for sustainable engineering systems.