G. Paruthimal Kalaignan

Studies with porous zinc electrodes with additives for secondary alkaline batteries

Abstract The effect of the presence of additives like ZnO, V2O5, PbO and (NH4)2CS in solution phase on the performance of solid zinc electrode has already been reported. Small additions of HgO, Sb2O3, TiO2 and Pb3O4 to the pasted zinc electrodes have been evaluated using Cyclic Voltammetry, Potentiodynamic Polarization (with temperature effect), A.C. Impedance measurements, Solution Analysis, and Porosity measurements. Though the additives HgO and Sb2O3 are known for their high hydrogen overpotential, HgO additive has the beneficial effect of imparting minimum standby corrosion, enhanced ageing behaviour and minimum shape change. As regards the additive TiO2, its behaviour is superior to that of HgO as far as the ageing and high temperature performance are concerned. For Pb3O4, the corrosion behaviour as well as ageing are fairly good. However, this additive imparts a disadvantage of lead getting deposited on the counter electrode which would become a setback from the battery point of view. Details of the study are discussed in this paper.

Effect of additives on zinc electrodes in alkaline battery systems

Zinc secondary systems have high energy density, power density, rugged physical structure, and good low-temperature performance. Zinc secondary systems are mainly used in electric vehicles, as well as in military and commercial aircraft. The main problems of zinc-based secondary systems are shape change, dendritic growth and high solubility of the oxidation products of zinc in the electrolyte. The present study deals with the effect of additives added to the alkaline solution for the improvement of the zinc electrode. The effect of the addition agents is examined by potentiodynamic polarization and triangular potential sweep voltammetric techniques. A discussion is given of the effect of various percentages of vanadium pentoxide, zinc oxide, lead oxide and thiourea on the reversibility of the redox couple. Potentiodynamic polarization experiments have been carried out over a wide range of temperatures, i.e., from 30 to 60 °C. A suitable electrolyte composition for the zinc-alkaline system is suggested.

Characterization of Chemical Grafting of Polyaniline onto Wool Fiber

Abstract Polyaniline grafted wool fiber was prepared by a chemical polymerization method using potassium peroxydisulfate (PDS) as a lone initiator under optimized conditions. The simultaneous homopolymer formed, as well as physisorbed polyaniline (PANI) onto wool fiber, were removed by a systematic procedure. The isolation procedure was quantified through UV-visible spectroscopy. The isolated grafted PANI-wool fiber was tested by conductivity measurements cyclic voltammetrv. and IR spectroscopy to provide further evidence for chemical grafting.

CHEMICAL GRAFTING OF ANILINE AND O-TOLUIDINE ONTO POLY (ETHYLENE TEREPHTHALATE FIBER)

Graft copolymerization of poly(aniline) and poly(o-toluidine) onto poly(ethylene terephthalate) fiber was conducted by using peroxydisulfate as a lone initiator under nitrogen atmosphere at various experimental conditions in aqueous hydrochloric acid medium. The grafting of poly(aniline) and poly(o-toluidine) onto poly(ethylene terephthalate) fiber was verified by recording cyclic voltammetry of the grafted fiber, conductivity measurements, and thermal analysis. Graft parameters-such as % grafting, % efficiency, and the rate of grafting-were followed. Grafting was always accompanied by homopolymerization. The rate of homopolymerization was also followed in all experimental conditions.

Pulse electrodeposition and corrosion properties of Ni–Si3N4 nanocomposite coatings

The development of modern technology requires metallic materials with better surface properties. In the present investigation; Si3N4-reinforced nickel nanocomposite coatings were deposited on a mild steel substrate using pulse current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of Ni and Ni–Si3N4 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of Si3N4 particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon nitride particles were obtained and the crystal grains on the surface of Ni–Si3N4 composite coating are compact. The crystallite structure was face centred cubic (fcc) for electrodeposited nickel and Ni–Si3N4 nanocomposite coatings. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si3N4 particle content. The corrosion potential (Ecorr) in the case of Ni–Si3N4 nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating.

Effect of nitrogen and carbon dioxide as fuel impurities on PEM fuel cell performances

Polymer electrolyte membrane (PEM) fuel cells are considered to have the highest power density of all the fuel cells. They operate on hydrogen fuel, which is generally produced by reforming of hydrocarbons, and may contain large amounts of impurities such as carbon dioxide, nitrogen, and trace amounts of carbon monoxide. We studied the effect of dilution of hydrogen gas with carbon dioxide on PEM fuel cells by polarization studies. The polarization curves were different when hydrogen gas was diluted with same quantities of carbon dioxide and with nitrogen. It may be due to carbon monoxide formation by reverse shift reaction and poisoning of anode platinum catalyst. Use of Pt–Ru alloy catalyst was found to suppress the poisoning. The effects of hydrogen gas composition, temperature, current density, and anode catalyst on fuel cell performances were examined in this study.

Electrochemical behaviour of addition agents impregnated in cadmium hydroxide electrodes for alkaline batteries

Abstract The development of electrode additives for the cadmium electrode of the nickel/cadmium battery is aimed mainly at increasing the discharge capacity and minimizing self-discharge. The dissolution and passivation of porous cadmium electrodes containing hydroxide and the relative stability of oxides are of importance in understanding the reversible behaviour of the cadmium electrode. Under standard conditions, the equilibrium potential of Cd(OH)2/Cd lies above the hydrogen-evolution reaction when the cell is not in use, and the active material of the cadmium electrode undergoes self-reductive dissolution (i.e., loss of active material) accompanied by oxygen evolution. The triangular potential sweep voltammetric technique is used to determine the reversibility of the cadmium electrode in alkaline solution. The role of additives such as Ni(NO3)2 (0.25–0.1 M) and FeSO4 (0.1–0.4 M), TiO2 (0.01–0.03 M) and Na2S (0.01–0.03 M) in Cd(NO3)2 on the reversibility of the electrode are discussed. The effect of discharge rate on the cyclic efficiency is also investigated. Self-discharge currents are determined by potentiostatic polarization method.

Studies on the electrodeposition and characterization of PTFE polymer inclusion in Ni–W–BN nanocomposite coatings for industrial applications

A Ni–W–BN–PTFE nanocomposite coating with excellent corrosion and friction resistance alongside hardness and a smooth surface was developed. This was achieved by introducing polytetrafluoroethylene (PTFE) polymer to an optimized Ni–W–BN nanocomposite coating deposited on a mild steel substrate by direct current (DC) and pulse current (PC) methods. The deposition was characterized using field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDAX) and X-ray diffractometry (XRD). The microhardness and friction resistance of the coatings were measured by using a Vicker’s microhardness tester and a TR-101-M4 scratch tester. The contact angle (CA) of a water droplet on the surface of the nanocomposite coating was measured by optical contact goniometry (OCA 35). The corrosion behaviour was measured using Tafel polarization and impedance methods in 3.5% NaCl solution. It was observed that the co-deposition of PTFE solid lubricant particles on the Ni–W–BN nanocomposite coating resulted in a comparatively smooth surface, higher microhardness, a lower friction coefficient, excellent water repellency and enhanced corrosion resistance. The PC method showed enhanced performance over the DC coating due to uniform and smaller grain deposits.

Enhanced corrosion resistance of Ni-W alloy with inclusion of TiN nanoparticles by electrodeposition method

Abstract Electrodeposition of Ni–W–TiN nanocomposite on mild steel substrate from an ammoniacal citrate bath containing dispersed titanium nitride has been demonstrated. The structure, surface morphology, composition and corrosion resistance properties of the nanocomposite deposits have been characterised by using various techniques. X-ray diffraction analysis (XRD) of the electrodeposited Ni–W–TiN nanocomposite shows that it is fcc crystalline. Scanning electron micrography (SEM) reveals smaller grains and uniform distribution of the titanium nitride in the alloy matrix. The microhardness of the nanocomposite coatings is higher than that of the alloy. The corrosion resistance of the electrodeposited nanocomposite evaluated by electrochemical impedance and Tafel polarization studies showed that the Ni–W–TiN nanocomposite is more corrosion resistant than the Ni–W alloy deposit. The finer grain and uniform distribution of the titanium nitride in alloy matrix favour the enhanced microhardness and corrosion resistance of the nanocomposite.

Performance characteristics of electrochemically impregnated nickel oxide electrodes for alkaline batteries

Abstract Nickel oxide electrodes are widely used as cathodes in alkaline batteries. The introduction of electroactive material can take place by chemical and electrochemical methods. The effects of various additives to nickel nitrate solutions, used to impregnate sintered nickel electrodes electrochemically, have been studied at different current densities. The variation in active material composition was determined using atomic absorption and infrared spectroscopy. Ideal conditions for the preparation of nickel oxide electrodes have been identified.