T. Vasudevan

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.

Electrochemical Copolymerization of Diphenylamine with Aniline by a Pulse Potentiostatic Method

Electrochemical copolymerization of diphenylamine (DPA) with aniline (ANI) has been carried out in aqueous sulfuric acid medium using a pulse potentiostic method (PPSM). The polymeric films were electrodeposited by employing different tunable parameters like pulse width (Pw), pulse number (Pn) etc., and the films deposited by PPSM were studied by cyclic voltammetry to identify their electrochemical characteristics and growth behavior. A growth equation for copolymer deposition relating the paramet ers of operation and charge associated for film deposition was obtained: Qa (mC/ms) 5 1.05 3 10 27 [DPA][ANI] 21/2 . The surface parameters of these films were evaluated. The copolymer was also characterized through Fourier transform infrared (FTIR) and ultraviolet (UV)-visible spectroscopic analysis. The cyclic voltammograms of the chemically synthesized and electrodeposited copolymer films were obtained.

Development of acrylonitrile copolymers for scale control in cooling water systems

Abstract The formation of calcium sulphate and carbonate scale has been prevented by using acrylonitrile-acrylic acid (AN-AA) and acrylonitrile-methacrylic acid (AN-MAA) copolymers over a temperature range of 50–80°C at different pHs from 7.0 to 8.5. The efficiency of the antiscalants was assessed by various techniques such as a chemical screening test, constant potential electrolysis and impedance measurements. The change in crystal habits by the addition of antiscalant was seen using XRD spectrum and SEM photographs. The effectiveness of polymers on microorganisms and forming gelation with calcium ion and iron-dispersing ability were also studied. The amount of scale deposition increased with increase in temperature and pH. The polymers acted as good antiscalants at low temperature and pH ranges. They also acted as good flocculants under some special conditions. For example, at a higher pH of 8.5 and temperature 80°C with 20 ppm dosage level of the AN-AA polymer, 100% was achieved. Further, they had good iron dispersibility and can gelate with Ca2+ ions.

Polyol-mediated thermolysis process for the synthesis of MgO nanoparticles and nanowires

The main aim of this work is to prepare MgO nanoparticles and nanowires by a novel polyol-mediated thermolysis (PMT) process. The influence of different mole concentration of magnesium acetate, polyvinyl pyrrolidone (PVP; capping agent) and ethylene glycol (EG; solvent as well as reducing agent) on the formation of nanoparticles and nanowires and the effect of calcination on the crystalline size of the samples were also examined. The resultant oxide structure, thermal behaviour, size and shape have been studied using x-ray diffraction (XRD) studies, thermal (TG/DTA) analysis and scanning electron microscopy (SEM)/transmission electron microscopy (TEM) respectively.

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.

Chemical grafting of poly(aniline) and poly(o-toluidine) onto PET fibre — a comparative study

Abstract Oxidative chemical polymerization of aniline and o-toluidine was carried out by using peroxo monosulphate as a lone initiator in an aqueous acidic medium in the presence of PET fibre. The PET fibre was tested for chemical grafting of poly(aniline) (PANI) and poly(o-toluidine) (POT) onto that. The content of PANI (wt%) in the backbone was found to vary while varying the [monomer], [initiator] and amount of fibre during the polymerization of aniline and o-toluidine. Various graft parameters like the rate of grafting (Rg), % grafting and % efficiency were evaluated. The rate of homopolymerization (Rh) was also followed in both cases. The chemical grafting was confirmed using FTIR, UV-Visible and conductivity measurements.

Peroxosalts initiated graft copolymerization of aniline onto wool fibre—a comparative kinetic study

Chemical grafting of aniline (ANI) onto wool fibre was carried out in aqueous acidic medium by using peroxosalts such as peroxodisulphate (PDS) and peroxomonosulphate (PMS) as an initiator for various [Monomer], [Initiator] and (fibre weight). It was observed that both Rh and Rg increased with increase in the concentration of each component. The chemical grafting was confirmed using FTIR spectroscopy, cyclic voltammetry (CV) and conductivity measurements.

In situ UV–visible spectroelectrochemical studies on the copolymerization of diphenylamine with ortho-methoxy aniline

UV-visible spectroelectrochemical studies on copolymerization of diphenylamine (DPA) with ortho-methoxy aniline (OMA) were carried out for different feed ratios of DPA and OMA using indium tin oxide (ITO)-coated glass as working electrode. The UV-visible spectra show clear dependencies on the molar feed composition of DPA or OMA used in electropolymerization. Derivative cyclic voltabsorptogram (DCVA) was deduced at the wavelengths corresponding to the absorption by the intermediate species and used to confirm the intermediates generated during the electropolymerization. The composition of DPA and OMA in the copolymer for the copolymers synthesized with different molar feed ratios of DPA and OMA was determined by UV-visible spectroscopy. Reactivity ratios of DPA and OMA were deduced by using Fineman-Ross and Kelen-Tudos methods and correlated with spectroelectrochemical results.