IR@CECRI
Not a member yet
2644 research outputs found
Sort by
Growth aspects of barium oxalate monohydrate single crystals in gel medium
No full textSingle crystals of barium oxalate monohydrate (BaC2O4.H2O, BOM) were grown in pure form by controlled
diffusion of Ba2+ using the gel technique at different temperatures. Starting from aqueous Ba2+ chloride
(BaCl2) and acetic acid (C2H2O4) in gel, this method offers a low-cost and an easiest alternative to other
preparation methods for the production of barium oxalate bulky single crystals. The optimal conditions for the
growth of BOM crystals in silica gel were found by investigating different growth parameters such as gel pH,
gel aging and crystallization temperature. Irrespective of all such crystallization environments, growth rate of
the crystals were initially less and then exhibited supersaturation effect leading to non-linearity. Gel aging and
temperature has profound effect on nucleation density that resulted less number of crystals of maximum size
in the gel matrix. Perfect single crystals were grown on gels of higher pH. The macropore morphology and
porosity was controlled by changing age of the gel. It has been found that temperature has a fabulous effect in
controlling the nucleation density by altering the supersaturation conditions for the formation of critical
nuclei. The entire growth kinetics informed that the grown crystals were derived by the one dimensional
diffusion controlled process
Structural and electrochemical investigation of Li2MgSnO4 anode for lithium batteries
No full textHexagonal Li2MgSnO4 compound was synthesized at 800 C using Urea Assisted Combustion (UAC)
method and the same has been exploited as an anode material for lithium battery applications. Structural
investigations through X-ray diffraction, Fourier Transform Infra Red spectroscopy and 7Li NMR (Nuclear
Magnetic Resonance spectroscopy) studies demonstrated the existence of hexagonal crystallite structure
with a = 6.10 and c = 9.75. An average crystallite size of 400 nm has been calculated from PXRD pattern,
which was further evidenced by SEM images. An initial discharge capacity of �794 mA h/g has been
delivered by Li2MgSnO4 anode with an excellent capacity retention (85%) and an enhanced coulombic
efficiency (97–99%). Further, the Li2MgSnO4 anode material has exhibited a steady state reversible capacity
of �590 mA h/g even after 30 cycles, thus qualifying the same for use in futuristic lithium battery
applications
Improved anode performance of thermally treated SiO/C composite with an organic solution mixture
No full textmade in the form of a slurry using a simple solution mixture consisting of propylene carbonate (PC) and acetone (AC) and then heat
treated. Cycle life study of the pristine composite and heat treated organic slurry composite showed the charge capacity values as 318
and 500 mAh g�1, respectively at 100th cycle. Analysis of change of delithiation capacity with cycling and delithiation current between
0.3 and 0.6 V from cyclic voltammogram (CV) along with scanning electron microscope (SEM) and X-ray diffraction (XRD) of the electrodes/
composites leads to conclude thermal processing of the organic slurry treated pristine composite converts dispersed active materials
of the pristine composite into a compact structure trapped/wrapped with carbon particles (Cx, x varies from 1 to 3) providing
apparently a resistor like behaviour and makes the anode deliver a stable reversible capacity with cycling
Platinum–tin bimetallic nanoparticles for methanol tolerant oxygen-reduction activity
No full textCarbon-supported Pt–Sn/C bimetallic nanoparticle electrocatalystswere prepared by the simple reduction
of the metal precursors using ethylene glycol. The catalysts heat-treated under argon atmosphere to
improve alloying of platinum with tin. As-prepared Pt–Sn bimetallic nanoparticles exhibit a single-phase
fcc structure of Pt and heat-treatment leading to fcc Pt75Sn25 phase and hexagonal alloy structure of
the Pt50Sn50 phase. Transmission electron microscopy image of the as-prepared Pt–Sn/C catalyst reveals
a mean particle diameter of ca. 5.8nm with a relatively narrow size distribution and the particle size
increased to ca. 20nm when heat-treated at 500 ◦C due to agglomeration. The electrocatalytic activity
of oxygen reduction assessed using rotating ring disk electrode technique (hydrodynamic voltammetry)
indicated the order of electrocatalytic activity to be: Pt–Sn/C (as-prepared) > Pt–Sn/C (250 ◦C) > Pt–Sn/C
(500 ◦C) > Pt–Sn/C (600 ◦C) > Pt–Sn/C (800 ◦C). Kinetic analysis reveals that the oxygen reduction reaction
on Pt–Sn/C catalysts follows a four-electron process leading to water. Moreover, the Pt–Sn/C catalyst
exhibited much higher methanol tolerance during the oxygen reduction reaction than the Pt/C catalyst,
assessing that the present Pt–Sn/Cbimetallic catalystmay function as amethanol-tolerant cathode catalyst
in a direct methanol fuel cell
Pulse and pulse reverse plating—Conceptual,advantages and applications
No full textA review on pulse and pulse reverse techniques for electrodeposition have been attempted. Pulse electrodeposition (PED) of some metals and
alloys are reported. The effects of mass, transport, electrical double layer pulse parameters and current distribution on surface roughness and
morphology are presented. Applications, advantages and disadvantages of PC and PRC techniques are discussed along with theoretical aspects
and mechanism
Dye Destruction and Simultaneous Generation of Sodium Hydroxide Using a Divided Electrochemical Reactor
No full textTextile dye bath effluent contains high concentrations of organic dye, sodium chloride, and other chemicals
which inhibit the activity of microorganisms during biological oxidation. Hence high concentrations of
organic dye and total dissolved solids have to be removed considerably before biological treatment. In
this paper, degradation of dye effluent and simultaneous generation of caustic soda in an electrochemical
membrane cell was investigated. Experiments were carried out at different current densities and different
flow rates using Ti/RuO2/IrO2 as anode and stainless steel as cathode. In the present study of dye effluent
treatment the results showed that the electrochemical process could effectively remove COD and color
by anodic oxidation (92.16% and 100%) and concentrate caustic soda from 40 to 210.28 g L-1
Linear sweep voltametry studies on oxygen reduction of some oxides in alkaline electrolytes
No full textThe study uses linear sweep voltametry (LSV) to observe the efficiency of oxygen reduction
on some oxides and their mixtures in 6 M KOH at 25 �C. The investigated materials are
Ag2O, MnO2, Sm2O3, Dy2O3 and NdO2. The electrocatalytic oxygen reduction reactions (ORR)
on Teflon-bonded, oxide þ graphite electrodes are studied. The oxygen reduction potentials
for electrodes containing these materials as catalyst are seen as �60.67, �270.31, �111,
�159.58 and �130.24 mV, respectively. Mixture combinations of these oxides give a higher
ORR peak current thereby showing evidence of synergetic effect. Air–MH cells using some
of the above investigated oxides as catalyst for air electrode are constructed and studied.
Best performance is obtained with silver oxide. The LSV findings are in accordance with
air–MH cell charge/discharge experiments and for best performance prefer shift of the ORR
onset potential to more positive positions
Preparation and evaluation of ionomeric membranes based on sulfonated-poly (styrene_isobutylene_styrene) membranes for proton exchange membrane fuel cells (PEMFC)
No full textSulfonated polystyrene-block-poly-(ethylene-ranbutylene)-
block-polystyrene membranes with different sulfonated
levels have been prepared and evaluated as proton
exchange membrane for polymer electrolyte membrane fuel
cell. The polymer was sulfonated by chlorosulfonic acid.
Homogeneous membranes were prepared by solvent casting
method. Ion exchange capacity, degree of sulfonation,
absorption, and solubility of the membranes were studied.
The membranes were characterized by Fourier transform
infrared, thermogravimetric analyzer, differential scanning
calorimetry, and impedance spectroscopy
PVA-PSSA Membrane with Interpenetrating Networks and its Methanol Crossover Mitigating Effect in DMFCs
No full textA membrane with interpenetrating networks between polyvinyl alcohol PVA and polystyrene sulfonic acid PSSA coupled
with a high proton conductivity is realized and evaluated as a proton exchange membrane electrolyte for a direct methanol fuel cell
DMFC. Its reduced methanol permeability and improved performance in DMFCs suggest the new blend as an alternative
membrane to Nafion membranes. The membrane has been characterized by powder X-ray diffraction, scanning electron microscopy,
time-modulated differential scanning calorimetry, and thermogravimetric analysis in conjunction with its mechanical
strength. The maximum proton conductivity of 3.3 10−2 S/cm for the PVA–PSSA blend membrane is observed at 373 K. From
nuclear magnetic resonance imaging and volume localized spectroscopy experiments, the PVA–PSSA membrane has been found
to exhibit a promising methanol impermeability, in DMFCs. On evaluating its utility in a DMFC, it has been found that a peak
power density of 90 mW/cm2 at a load current density of 320 mA/cm2 is achieved with the PVA–PSSA membrane compared to
a peak power density of 75 mW/cm2 at a load current density of 250 mA/cm2 achievable for a DMFC employing Nafion
membrane electrolyte while operating under identical conditions; this is attributed primarily to the methanol crossover mitigating
property of the PVA–PSSA membrane
The effect of substituents and operating conditions on the electrochemical fluorination of alkyl phenylacetates in Et3N4HF medium
No full textSelective electrochemical fluorination of alkyl phenylacetates (Ph–CH2–COOR, where R is methyl, ethyl, n-propyl, n-butyl, i-propyl and secbutyl)
under galvanostatic conditions were reported in Et3N4HF medium. Preparative electrolysis experiments were carried out both in preelectrolysed
dry Et3N4HF and the same electrolyte medium without pre-electrolysis. Very little hydrolysed fluorinated products were obtained in
pre-electrolysed medium where as significant quantities of hydrolysed products leading to fluorinated phenylacetic acid were obtained from
Et3N4HF without pre-electrolysis. Under optimum experimental conditions up to 87% selectivity of monofluoro ester could be achieved. Difluoro
alkyl phenylacetate, monofluoro and difluoro phenylacetic acids were the other predominant side products obtained. The hydrolysis appears to be
initiated by tautomeric transformation of proton after the initial electro oxidative formation of the cation radical. 19F as well as 1H NMR
spectroscopy have been employed to identify the minor constituents formed during the electro oxidative process