Electrodeposition of Ni-Fe/BN Nano-Composite Coatings from a Non-aqueous Bath and Their Characterization

摘要

Ni-Fe alloy matrix nano-composite coatings containing uniformly dispersed 24 wt% BN (boronnitride) particles (micron-sized) were electrolytically codeposited under direct current condition from anon-aqueous sulfamate-ferrous sulphate-dimethylformamide bath. Effect of various deposition++ parameters like Fe ion concentration, current density, temperature, stirring rate, etc. on thecomposition and properties of the electrodeposits was studied and optimum condition for maximumincorporation of BN particles was determined. The composite coatings thus obtained werecharacterized by XRD, SEM, EDAX, DSC and spectrophotometric analyses. The iron content in thealloy deposits varied between 7-25 wt%. The deposition of alloy matrix showed anomalous behaviourand was found under charge transfer and diffusion control. The calculated crystallite size of thecomposite deposits was found between 4-13 nm while the calculated strain in the composite coatingsranged 0.017-0.02. All the composite coatings showed fcc structure with preferred orientation in crystallographic direction. The lattice parameter of the composite coatings was found to beslightly larger than that of pure nickel. Hardness of as deposited and heat treated nano-compositecoatings was found to be significantly higher than that of the parent Ni-Fe alloy. A correlation betweencrystallite size and strain with hardness has been worked out. The hydrogen content analysis of thecomposites showed almost minimal hydrogen inclusion (~ 1-2 ppm) in the deposits.