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Influence of rare earth content on electrode kinetics in Misch metal-based AB5 MH alloys – Cyclic voltammetric investigations
No full textThe influence of lanthanum/cerium ratio (0.42–14.14) in Misch metal (Mm)-based AB5-type
hydrogen storage alloys has been investigated. The samples were subjected to X-ray
florescence (XRF) and cyclic voltammetry (CV) studies. The metal hydride electrodes were
assembled, and their discharge capacity was determined. These alloys delivered discharge
capacity between 118 and 266 mAh/g. CV investigations threw light on charge-transfer
reactions at the electrode/electrolyte interface and hydrogen surface coverage capacity.
The CV parameters in general indicate that the battery activity increases with lanthanum/
cerium ratio. At low lanthanum/cerium values, the discharge reactions proceed at potentials
that are more negative. Furthermore, electrochemical reversibility of the hydrogen
absorption–desorption on the alloy surface is enhanced at optimum lanthanum/cerium
ratio as revealed by decreasing values of peak separation. The slopes of graphical plots of
Ipeak (anodic) vs. n1/2 for the fully charged samples reverse direction at very high
lanthanum/cerium values. The results suggest that the discharge plateau is optimum at
lanthanum/cerium ratio around 12
Synthesis and characterization of ZnCo2O4 nanomaterial for symmetric supercapacitor applications
No full textZnCo2O4 nanomaterial was prepared by coprecipitation
method and characterized by X-ray diffraction
(XRD), scanning electron microscope (SEM), transmission
electron microscopy (TEM), cyclic voltammetry (CV), and
galvanostatic charge–discharge tests at various current
densities. It is shown that the crystal structure and surface
morphology play an important role in the enhancement of
the specific capacitance. The TEM results clearly indicate
that the prepared material shows aggregated particles. The
particle size powder was about 50 nm, and SEM pictures
indicate a porous morphology. The electrochemical behavior
of ZnCo2
O4 was characterized by mixing equal
proportion of carbon nanofoam (CNF). From CV, it is
concluded that the combination of redox and pseudocapacitance
increases the specific capacitance up to
77 F g−1 at 5 mV s−1 scan rate. The ZnCo2O4-based
supercapacitor cell has good cyclic stability and high
coulombic efficiency
Effect of mixed cations in synergizing the performance characteristics of PVA-based polymer electrolytes for novel category Zn/AgO polymer batteries—a preliminary study
No full textThin films of polymer electrolytes comprising of
PVA and KOH (A) with and without the addition of zinc
salts, viz., zinc acetate (B) and zinc triflate (C) as mixed
cations were prepared via. solution casting method. The
thermal stability and ionic conductivity of PVA–KOH solid
polymer electrolyte (A) were improved by the partial
substitution of KOH with zinc salts. Among the two salts,
zinc triflate was found to improve both the physical as well
as electrochemical properties of the PVA–KOH films more
significantly than zinc acetate. An attempt to optimize the
ratio of various components of polymer electrolytes, viz.,
polymer: KOH: zinc salt was also made, based on the
dimensional stability and ionic conductivity values. Finally,
the select category polymer film containing PVA–KOH–
zinc triflate (C) in an optimum ratio of 40:35:25 was
deployed in coin cell fabrication and subjected to charge–
discharge studies with a view to demonstrate the possible
electrochemical reversibility characteristics. Based on the
encouraging results obtained from the cycling study, C type
films [PVA–KOH–zinc triflate] qualify themselves as
potential polymer electrolytes for use in rechargeable Zn/
AgO polymer batteries
Miscibility of Polymethylmethacrylate and Polyethyleneglycol Blends in Tetrahydrofuran
No full textThe miscibility of polymethylmethacrylate
(PMMA) and polyethyleneglycol (PEG) blends in tetrahydrofuran
(THF) has been investigated by viscosity, density,
refractive index, and ultrasonic velocity studies. Various
interaction parameters such as polymer–solvent and blend–
solvent interaction parameters and heat of mixing have
been calculated using the viscosity, density, and ultrasonic
velocity data. The results indicated the existence of positive
interactions in the blend polymer solutions and that they
are miscible in THF in the entire composition range. The
study also revealed that variation in the temperature does
not affect the miscibility of PMMA and PEG blends in THF
significantly. The presence of hydrogen bonding in the
blends in the solid state has also been indicated by FTIR
studie
Waste Minimization in Electroplating Industries: A Review
No full textWastewater, spent solvent, spent process solutions, and sludge are the major waste
streams generated in large volumes daily in electroplating industries. These waste
streams can be significantly minimized through process modification and operational
improvement.Waste minimization methods have been implemented in some of the electroplating
industries. Suggestions such as practicing source reduction approaches, reduction
in drag out and waste, process modification and environmental benefits, have
also been adopted. In this endeavor, extensive knowledge covering various disciplines
has been studied, which makes problem solving extremely easy. Moreover, available
process data pertaining to waste minimization (WM) is usually imprecise, incomplete,
and uncertain due to the lack of sensors, the difficulty of measurement, and process
variations. In this article waste minimization techniques and its advantages on
the improvement of working atmosphere and reduction in operating cost have been
discussed
Electrochemical recovery of silver from waste aqueous Ag(I)/Ag(II) redox mediator solution used in mediated electro oxidation process
No full textThe paper presents a process for the electrochemical recovery of silver(Ag) by electro deposition on the
electrode surface from the waste solutions of Ag(I)/Ag(II) redox system in nitric acid medium used for the mediated
electrochemical process. Electrochemical recovery was carried out in an undivided cell with DSA-O2 electrodes at room
temperature condition. At an optimized current density of 12 A/dm2, 99% of Ag recovery efficiency was achieved with
high yield and low energy consumption. Experimental runs were made in order to observe the performance of the Ag
recovery process. The operating conditions like current density, temperature and Ag(I) concentration of the electrolyte,
the acid concentrations, agitation rate and inter-electrode distance were optimized
Electrochemical characterization of supercapacitors based on carbons derived from coffee shells
No full textCarbons derived by pyrolysis of coffee shells treated with ZnCl2 were used as electrode materials in
symmetric electrochemical supercapacitors. Scanning electron microscopy showed that the carbon from
the porogen-free shells showa flake-like structure, while those fromthe ZnCl2-treated coffee shells have a
loose, disjointed structure with no definite shape. X-ray diffraction studies indicated the presence of small
domains of coherent and parallel stacking of the graphene sheets. The average surface area of the carbon
was 842m2 g−1, with an average micropore area of 400m2 g−1. Cyclic voltammetric studies suggested a
specific capacitance of about 150 F g−1. Self-discharge studies on the devices showed a large retention
time
Electric field induced enhancement in the interfacial charge transfer kinetics of a solid polymer electrolyte
No full textA novel electrostaticmethod for preparing modified solid polymer electrolytes (SPEs) is reported. Application
of an electric field on an evaporating mixture of KYNAR, ethylene carbonate (EC), propylene carbonate
(PC) and LiPF6 dissolved in tetra hydro furan (THF) resulted in a solid polymer electrolyte whose charge
transfer resistance was at least an order of magnitude lower than that formed without the application of
an electric field. We believe that the observed enhancement is probably due to an electric field induced
orientation of dipoles in the polymer chai
Anthraquinone catalysis in the glucose-driven reduction of indigo to leuco-indigo
No full textAnthraquinone immobilised onto the surface of indigo microcrystals enhances the reductive
dissolution of indigo to leuco-indigo. Indigo reduction is driven by glucose in aqueous NaOH and a
vibrating gold disc electrode is employed to monitor the increasing leuco-indigo concentration with
time. Anthraquinone introduces a strong catalytic effect which is explained by invoking a molecular
‘‘wedge effect’’ during co-intercalation of Na+ and anthraquinone into the layered indigo crystal
structure. The glucose-driven indigo reduction, which is ineffective in 0.1 M NaOH at 65 1C,
becomes facile and goes to completion in the presence of anthraquinone catalyst. Electron
microscopy of indigo crystals before and after reductive dissolution confirms a delamination
mechanism initiated at the edges of the plate-like indigo crystals. Catalysis occurs when the
anthraquinone–indigo mixture reaches a molar ratio of 1 : 400 (at 65 1C; corresponding to 3 mM
anthraquinone) with excess of anthraquinone having virtually no effect. A strong temperature effect
(with a composite EA E 120 kJ mol�1) is observed for the reductive dissolution in the presence of
anthraquinone. The molar ratio and temperature effects are both consistent with the heterogeneous
nature of the anthraquinone catalysis in the aqueous reaction mixture
Corrosion protective performance studies of coating systems in soda ash chemical industry
No full textOrganic coatings are widely used to protect steel structures. The performance of the coating system
depends upon the atmospheric conditions prevailing in the chemical industry. Before selecting a protective
system, the corrosivity of the atmosphere has to be determined. A study has been made for selecting
a good protective system for a soda ash chemical industry where chemicals such as soda ash, sodium
chloride and hydrochloric acid are produced by using sea water as a raw material. Under these conditions,
after collecting the corrosivity rate at various places of industrial areas, coated steel panels with
various paint combinations were exposed in different sites for a period of 2 years. The performance of the
coatings was monitored by EIS studies besides visual inspection. The corrosion protection performance
of the various coating systems of zinc rich primer with different types of under coats and top coats has
been studied and the results are reported