Effective CuSO4 Concentration on Phase Formation and Optical Characteristics of Electrodeposited Ni-Cu Alloy

Abstract

Ni-Cu alloys play a critical role in various industrial applications due to their exceptional characteristics. Despite extensive study of these alloys for their mechanical and corrosion characteristics, their optical properties have received limited attention. In this research, the electrodeposition of Ni-Cu alloy coatings was conducted using copper sulfate concentrations ranging from 1.25 to 10 g/L, leading to successful film formation with various phases. XRD examination associated with the Rietveld calculation exhibited modified phase fraction, crystallite size, micro-strain, and lattice constant. Scanning Electron Microscopy (SEM) analysis revealed a different thickness and a dendritic microstructure. As an increase in CuSO4, there was observed an increase in the values of the absorption edge (showing 1.61 - 1.90 eV), texture coefficient (0.46 - 0.82), and film thickness (0.63 - 1.74 µm). These various morphologies enhanced the material’s properties. In more added CuSO4 samples, the coatings significantly reveal a modification in the crystal, film growth, and optical properties. The advancements in visible light absorption suggest an enhanced coating for optical technology applications. HIGHLIGHTS The texture coefficient (TC) values of the (111) plane of Cu81Ni0.19 phase were found to increase with higher CuSO4 concentrations. Specifically, the TC values for 1.25Cu-Ni, 2.5Cu-Ni, 5.0Cu-Ni, 7.5Cu-Ni, and 10Cu-Ni were 0.46, 0.48, 0.77, 0.77, and 0.82, respectively. These values, all below 1, indicate low crystallinity but show a trend of increasing crystallinity with higher CuSO4 concentrations. The film thickness also increased with higher CuSO4 The thicknesses were 0.63 µm for 1.25Cu-Ni, 0.65 µm for 2.5Cu-Ni, 1.36 µm for 5.0Cu-Ni, 1.54 µm for 7.5Cu-Ni, and 1.74 µm for 10Cu-Ni. The grain morphology of the coatings evolved from small, elongated platelets in lower CuSO4 concentrations to larger, more dendritic structures at higher concentrations. This change in morphology is attributed to the increased CuSO4 concentration, which affects the crystal growth mechanisms during electroplating. GRAPHICAL ABSTRACT