Eletrodeposição pulsada e caracterização de revestimentos de cobre/nanotubos de carbono em ligas de alumínio 3003 e 1350

Abstract

The demand for more efficient and sustainable electrical systems has driven research toward innovative materials that enhance the properties of electrical conductors. Aluminum (Al) and its alloys are widely used in power transmission and distribution due to their low density and good electrical conductivity. The pursuit of improved electrical properties has led to the development of coatings that increase conductivity without compromising the lightweight nature of the material. This study presents an investigation into the anodization of Al substrates as a preparation step for nanostructured coatings, combined with pulsed current electrodeposition of a copper (Cu) and multi-walled carbon nanotube (MWCNT)-based nanocomposite, focusing on the correlation between electrical properties and microstructure. Experiments were conducted on Al 3003 alloy sheets, and on wires and cables made from Al 1350 alloy. Optimized anodization parameters were established using 100% H₂SO₄, direct current of 3 A, and 10 V applied for 2 hours. For the pulsed current electrodeposition, a concentration of 1 mg/mL of MWCNTs, an 80% duty cycle, 2 A, and 10 V were applied for 1 hour. Field Emission Gun Scanning Electron Microscopy (FEG-SEM) micrographs confirmed the formation of a uniform and porous aluminum oxide (Al₂O₃) layer, essential for coating adhesion, and revealed the homogeneous and effective distribution of the nanocomposite over the anodized surface. Energy Dispersive Spectroscopy (EDS) verified the presence of Cu and carbon (C) elements distributed throughout the coating layer. Raman spectroscopy identified characteristic vibrational modes of MWCNTs: D, G, and G′ bands, showing variations in intensity and bandwidth due to structural modifications induced by electrodeposition. X-ray Diffraction (XRD) analysis revealed the crystalline phases present in the coating and structural changes resulting from the surface treatment, confirming the integration of the nanocomposite into the metallic substrate. Electrical conductivity tests using the four-point Kelvin probe method, before and after coating, demonstrated a significant increase in electrical conductivity (σ), indicating improved charge transport efficiency due to the synergy between Cu and MWCNTs. Among the results, a ∼ 52.33% increase in surface electrical conductivity (σₛ) of the Al sheets and an increase in IACS from 67.76% to ∼ 73.5% in the coated wires stood out. Similarly, the average resistance of the coated cable decreased from 4.88×10⁻⁴ Ω to 1.934×10⁻⁴ Ω, a reduction of ∼ 60.37% compared to the uncoated cable. Statistical analyses supported these findings and confirmed their significance. Joule heat dissipation and ampacity calculations confirmed the superior performance of the coated material and its potential for application in power transmission and distribution systems. Therefore, the Cu-MWCNT nanocomposite coating obtained via pulsed current electrodeposition on anodized surfaces represents a promising approach for improving the electrical properties of Al-based conductors.