Browsing by Author "H.K. Srivastava"

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Bright and hard electrodeposits of nickel from nickel acetate-formamide bath
(1988) H.K. Srivastava; P.K. Tikoo
The electrodeposition of nickel from nickel acetate dissolved in pure formamide was carried out and the effect of pH, current density, temperature, and boric acid concentration was studied. The temperature range of 40-50° C wasfound to be the best operating parameter at which usually bright and hard deposits having high cathode current efficiencies were obtained. A concentration of 0·1M boric acid in conjunction with 0’2M ammonium acetate resulted in deposits having exceptionally high levels of hardness. Variation of pH by hydrochloric acid led to bright, fine grained hard deposits, while changing pH by acetic acid possessing bulkier acetate ions resulted in soft and thin electrodeposits. Scanning electron microscopy revealed refinement in grain size with increasing temperature. A definite change in microstructure occurred when nickel electroplates were annealed to 400-600°C for 1h and cooled slowly under atmospheric pressure. © 1988 The Institute of Metals.
EFFECT OF DIELECTRIC CONSTANT AND BASICITY ON THE ELECTRODEPOSITION OF NICKEL FROM AMIDE SOLVENTS.
(1986) H.K. Srivastava; P.K. Tikoo
This work studies the physical characteristics of nickel electrodeposited from NiCl//2. 6H//2O dissolved in pure formamide, N-methylformamide and N,N-dimethylformamide separately. Experimental results show that N,N-dimethylformamide is a most suitable solvent as compared to N-methylformamide or formamide for deposition of nickel using nickel chloride electrolyte. Boric acid (0. 2M) enhances the hardness more in case of N less than N-dimethylformamide.
Electrodeposition of Nickel from N,N-dimethylformamide
(1987) H.K. Srivastava; P.K. Tikoo
The electrodeposition of nickel from nickel chloride dissolved in pure N,N-dimethylformamide (DMF) was carried out. The presence of a little hydrochloric acid (specific gravity, 1.18) was essential for electrolysis to occur. Cathode current efficiencies as high as 95%-100% were recorded. A bright deposit with a cathode current efficiency of 97.2% was obtained under operating conditions of pH 4.7, temperature 40 °C and current density 0.5 A dm-2. An NiCl2·6H2O-DMF electrolyte resulted in minimum evolution of hydrogen gas during electrodeposition. X-ray analysis confirmed the deposition of nickel in its purest form with an f.c.c. lattice. A small concentration of Co2+ played a vital role in enhancing the cathode current efficiency as well as significantly improving the hardness. Scanning electron micrographs revealed a fine-grained structure void of cracks when the coating was deposited in the presence of an optimum concentration of cobalt chloride. © 1987.
HARDNESS AND STRUCTURE OF NICKEL ELECTRODEPOSITED FROM ITS CHLORIDE AND ACETATE SALTS DISSOLVED IN PURE DIMETHYSULFOXIDE.
(1987) H.K. Srivastava; P.K. Tikoo
Earlier studies on the electrodeposition of nickel from nickel chloride or nickel borofluoride dissolved in pure dimethylsulfoxide did not lead to satisfactory results. However, nickel acetate/DMSO bath resulted in deposition but conductivity of the bath was too low. Addition of ammonium acetate improved the conductivity of the bath and quality of the deposit. As an extension of this work, deposition was studied with nickel chloride solutions in presence of varying concentration of ammonium acetate.