Browsing by Author "P.K. Tikoo"

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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.
Corrosion of Plated Nickel in Formamide-Water Mixtures
(1981) Lai Bahadur; V.B. Singh; P.K. Tikoo
Corrosion behavior of plated nickel in formamide-water mixtures has been studied at 25 °C galvanostatically covering the whole range of solvent composition. It has been observed that solvent composition has a pronounced effect on the corrosion behavior of nickel and it has been found that nickel is anodically active in water-rich solvent composition region while it becomes passive in formamide-rich region. © 1981, The Electrochemical Society, Inc. All rights reserved.
EFFECT OF BORIC ACID, Cl** minus AND K** plus ON THE PHYSICAL PROPERTIES OF NICKEL ELECTRODEPOSITED FROM DMF/WATER MIXTURE BATH.
(1985) S. Sultan; P.K. Tikoo
Addition of boric acid, nickel chloride and potassium acetate to a nickel acetate-5 mol percent DMF/water bath produced softer deposits with a reduced number of cracks. Micrographs of electrodeposits obtained from the nickel acetate bath without addition had multiple cracks near side edges, microhardness of these deposits being greatest. Addition seems to help relieve the internal stress, reducing the number of cracks.
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.
EFFECT OF NH4 + AND Co + + IONS ON THE HARDENING OF ELECTRODEPOSITED NICKEL FROM NICKEL ACETATE IN AMIDE SOLVENTS.
(1987) H.K. Srivastav; P.K. Tikoo
[No abstract available]
Electrodeposition of nickel from formamide
(1984) S. Sultan; P.K. Tikoo
The electrodeposition of nickel from nickel acetate in formamide was carried out. The effect of the electrolyte concentration, the current density and additions of boric acid, ammonium acetate, ammonium sulphate and KCl on the variation in the cathode current efficiency was examined. Boric acid in low concentration (less than 0.1 M) was found to enhance the cathode current efficiency and was also effective in improving the quality of the deposits. Ammonium acetate, ammonium sulphate and boric acid improved the quality of the deposits and the cathode current efficiency. The optimum concentration for obtaining good deposits from nickel acetate in formamide was found to be 0.2 M. Nickel sulphate hexahydrate was also tried as an electrolyte in formamide for obtaining nickel deposits. The solubility of the nickel sulphate was comparatively greater than that of the acetate. This may be due to the similar nature (polar) of the solute and solvent. Nickel sulphate gave deposits at a concentration of 0.3 M without additives and seems to be a better electrolyte for obtaining nickel deposits from formamide. © 1984.
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.
Electrodeposition of nickel-cobalt-molybdenum alloy
(1978) V.B. Singh; P.K. Tikoo
Bright uniform crack-free deposits of ternary nickel-cobalt-molybdenum alloys containing 54-92% Ni, 7-44% Co, 0.6-4.7% Mo have been obtained from an acetate bath. From the experiments, optimum conditions are 0.2545 M nickel acetate, 0.0282 M cobalt acetate, 0.0010 M sodium molybdate, current density 2 A dm-2, pH 5, temperature 25 °C. The cobalt and molybdenum contents decreased with increase in current density, pH and temperature. X-ray studies showed the formation of an alloy with f.c.c. structure. © 1978.
Electrodeposition of ternary nickel-cobalt-cadmium alloys from acetate bath
(1978) V.B. Singh; P.K. Tikoo
[No abstract available]
Electrodeposition of ternary nickel-iron-cobalt alloys from acetate bath
(1977) V.B. Singh; P.K. Tikoo
Ternary nickel-iron-cobalt alloys of wide range composition have been deposited from acetate baths under a variety of conditions and the optimum conditions established are: nickel acetate 0.2828 M, ferrous sulphate 0.0359 M, cobalt acetate 0.2828 M, boric acid 0.1617 M, ascorbic acid 0.0056 M, pH 5.0, cd 1.5 A/dm2 and temperature 30°. The bath gave bright, smooth and adherent deposits. Iron and cobalt contents decreased with an increase in cd and pH, X-ray studies of the deposits revealed fcc structure within the composition range studied (43.6-54.0% Ni). The results indicate that acetate bath can be successfully employed for plating purposes. © 1977.
Electrodeposition of ternary nickel-iron-molybdenum alloys from an acetate bath
(Kluwer Academic Publishers, 1978) V.B. Singh; P.K. Tikoo
Ternary nickel-iron-molybdenum alloys containing 0.5-8.5% molybdenum, 18-48% iron and balance nickel were electrodeposited from an acetate bath under a variety of conditions. Satisfactory deposits were obtained from the bath containing 0.3394 M nickel acetate, 0.02878 M ferrous sulphate, 0.0015 M sodium molybdate at current density 2.0 A dm-2, pH 5.0 and temperature 20°C without agitation for plating times up to 30min. The alloy deposits were examined for their crystal structure by X-ray diffraction and microstructure by metallography. © 1978 Chapman and Hall Ltd.
Hardness and structure of nickel electrodeposited from a nickel acetate-N,N-dimethylformamide-water bath
(1984) S. Sultan; P.K. Tikoo
The electrodeposition of nickel from nickel acetate in a 5mol.%N,N- dimethylformamide-water mixture was carried out. The microhardness and microstructure of the surface of the deposit were studied. The smooth and hard deposits obtained in this bath are the result of the buffering action of the acetate electrolyte. The increase in hardness with increasing pH is explained on the basis of production of basic colloidal hydroxides in the catholyte. Microcracks were observed near the edges as a result of the high internal stress produced by the enhanced current density. The hardness alongside and in between the cracks was quite high compared with the hardness elsewhere. © 1984.
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.
Hardness and structure of nickel electrodeposited from its sulphate and acetate salts in a 5mol.%N-methylformamide-water mixture
(1984) S. Sultan; P.K. Tikoo
The electrodeposition of nickel from its sulphate and acetate salts in a 5mol.%N-methylformamide-water mixture was carried out. The deposits obtained from the sulphate bath were milky in appearance and hard with a nodular structure, whereas those from the acetate bath were extremely bright but cracked and soft. The cracked and brittle structure of the deposits obtained from the acetate bath is attributed to the adsorption and/or codeposition of hydrogen and its subsequent diffusion outwards. The comparatively low ionization in the acetate bath may be due to complex formation with cosolvent molecules (N-methylformamide), which gives rise to a fine-grained bright deposit. © 1984.
Influence of tube walls on Joshi effect in iodine vapour
(1964) P.K. Tikoo
[No abstract available]
Influence of tube walls on the starting potentials in iodine vapour
(1963) P.K. Tikoo
[No abstract available]
IR spectral evidence for polymeric 7-coordinated U(IV)
(1980) I.S. Ahuja; P.K. Tikoo; Raghuvir Singh
[No abstract available]
NICKEL ELECTRODEPOSITION IN MIXTURES OF DIMETHYLFORMAMIDE AND WATER.
(1984) P.K. Tikoo; V.B. Singh; Salman Sultan
Mixing dimethylformamide with nickel acetate or nickel sulfate solution buffered with boric acid reduced cathode efficiency and increased the hardness of the nickel deposits obtained at 1. 5 A/dm**2. The increase in hardness was greater for deposits from the acetate bath, which had a higher pH. These deposits probably contained a greater proportion of colloidal hydroxides or basic salts, accounting for their greater hardness.
PHYSICAL PROPERTIES OF NICKEL ELECTRODEPOSITED FROM ITS SULFATE SALT IN A 5 MOL PERCENT DIMETHYLFORMAMIDE-WATER MIXTURE.
(1985) P.K. Tikoo; Salman Sultan
The effects of current density, temperature, pH and nickel concentration on the cathode current efficiency and microhardness of nickel electrodeposited in a mixture of water and 5 mol percent N,N-dimethylformamide are attributed to the formation of colloidal hydroxide in the catholyte layer. The role of excess hydrogen gas evolution at low pH values and the favorable effect of surface smoothing at high pH values (due to colloidal hydroxides) explain the typical microstructures obtained at these pH values.
Role of N-methylformamide in Producing Bright and Hard Nickel Deposits
(1989) M.M. Rahman; P.K. Tikoo
Nickel was electrodeposited from nickelsulfamate dissolved in N-methylformamide (HCONHCH3)-water mixtures of varying compositions. The deposit obtained from mixed solvents was found to be better with respect to quality, efficiency and hardness and with lesser defects in surface structure, compared to conventional nickel deposits. These are attributed to the structural changes in the solvent mixtures. Bright, smooth and hard deposits were obtained from 5 mol% NMF-water mixture and hence the influence of current density, temperature and addition of boric acid on cathode current efficiency, microhardness and microstructure was investigated in this system. Presence of boric acid increases the rate of nickel deposition, inhibits the outgrowth of crystals, thus enhancing the grain refinement which is attributed to its catalytic influence. © 1989, The Japan Institute of Metals. All rights reserved.