Electrolytic Synthesis of Nickel Based Alloys and Their Characterization

Abstract

This thesis titled, Electrolytic synthesis of nickel based alloys and their characterization details a comprehensive approach for improving the corrosion resistance and electrocatalytic activity of Ni–M (where M = Sn and Mo) alloys through an inexpensive, yet advanced electrodeposition method. The coating properties have been improved by regulating the mass transfer process at cathode film, parallel to the process of deposition. The modulation in the mass transfer was affected by pulsing the current density (c.d.), magnetic field intensity (B) and ultrasonic power density (p.d.). The thesis comprises the optimization of two new binary alkaline baths, namely Sn–Ni and Ni–Mo using direct current (DC) for highest performance of corrosion resistance and electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The corrosion behaviors were evaluated in 5% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. Experimental results revealed that corrosion resistance of multilayer Sn–Ni alloy coatings developed by pulsing ultrasound p.d. is many folds better than its monolayer counterpart. The kinetic parameters for HER and OER were determined by cyclic voltammetry (CV) and chronopotentiometry (CP) methods in 1.0 M KOH medium. The electrocatalytic activity of magneto-electrodeposited Ni–Mo alloy coatings were improved, due to changed limiting c.d. (iL) of more readily deposit-able metal, explained by the hydrodynamic effect. Effect of addition of reduced graphene oxide (rGO) into the alloy matrix and the anodic dissolution of the as-deposited coating as a tool to enhance the electrocatalytic activity of Ni–M alloys has also been examined. The changed property of alloy coatings was found to bear a close relationship with their composition, phase structure, surface morphology and roughness, confirmed by EDX, XRD, SEM and AFM analyses, respectively. The experimental data are compared, and results are discussed with Tables and Figures, a note for future work is mentioned at the end.