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Li3MxV22x(PO4)3/C (M=Fe, Co) composite cathodes with extended solubility limit and improved electrochemical behavior
No full textA first attempt has been made to prepare Li3MxV22x(PO4)3/C (M=Fe, Co) composite solutions by
adopting a novel oxalic dihyrazide assisted combustion (ODHAC) method. The pillaring effect of Fe
in Li3FexV22x(PO4)3/C and the possible electrochemical activity of the Co3+/4+ redox couple of
Li3CoxV22x(PO4)3/C at a 4.8 V limit increases the structural and cycling stability of the native
Li3V2(PO4)3/C cathode respectively, thereby ultimately improving the electrochemical behaviour of
Li3MxV22x(PO4)3/C solid solutions. An extended solubility limit of x = 0.10 for Fe dopant has been
achieved for the first time through the present study against the reported value of x = 0.05 in
Li3FexV22x(PO4)3/C compounds. The study demonstrates the suitability of the ODHAC synthesis
approach in preparing a wide variety of phase pure Li3MxV22x(PO4)3/C cathodes. Further, the
superiority of Li3Co0.10V1.90(PO4)3/C in exhibiting the highest capacity (178 mAh g21) and negligible
fade (4%) and the demonstrated cyclability under the influence of 10 C rate has been understood as a
function of the synergistic effect of the ODHAC synthesis method and the optimum concentration of
Co dopant chosen for the stud
Electrochemical Removal of Boron from Water: Adsorption and Thermodynamic Studies
No full textThe present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and
stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such
as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2%
was achieved at a current density of 0.2 A dm−2 at pH of 7.0. First-, second-order rate equations, Elovich and Intraparticle models were applied to
study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)3 were determined and correlated with isotherm equations such as Langmuir,
Freundlich and D-R models. Thermodynamic parameters, such as standard Gibb’s free energy (G◦), standard enthalpy (H◦) and standard entropy
(S◦), were also evaluated by Van’t Hoff equation. The adsorption process follows second-order kinetics. The adsorption of boron preferably fits
with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)3 was found to
be spontaneous and endothermi
Synthesis and characterization of epoxy–silicone–polythiophene interpenetrating polymer network for corrosion protection of steel
No full textPolymer alloys, particularly interpenetrating polymer networks (IPNs) exhibit excellent coating properties.
Often combination of polymers result in IPNs with controlled morphologies and synergistic behavior.
In this study, corrosion-resistant IPNs were prepared from immiscible resins (epoxy, silicone and thiophene)
using a cross-linking agent and a catalyst. GPC, FTIR, NMR, TG, DTA and SEM studies used to fix
the best performing IPN. Surface morphology studies using SEM confirm the incorporation of silicone
and polythiophene in to the epoxy polymer to form homogeneously micro structured IPN. The heatresistance
of the IPN was determined as per ASTM 2485. The improved corrosion resistance of the IPN
was evaluated by AC impedance measurement
Effect of reaction time on the synthesis and electrochemical properties of Mn3O4 nanoparticles by microwave assisted reflux method
No full textSpherical Mn3O4 nanoparticles were synthesized by microwave assisted reflux method at different reaction
times (1, 5, 10, 15, and 20 min). The single phase formation of Mn3O4 nanoparticles was identified
through XRD analysis. The FT-IR and Raman spectra revealed the presence of functional groups of Mn3O4
and further support the XRD results. The spherical morphology of Mn3O4 was identified via SEM analysis.
The cyclic voltammetry analysis implies that 15 min synthesized Mn3O4 (MN-15) shows the higher
specific capacitance of 135 F g−1 among all the prepared Mn3O4 electrodes. The EIS spectra of MN-15 substantiate
the less charge-transfer resistance (Rct) of 0.553 �, when compared with the other samples. The
discharge capacitance of MN-15 was 103 F g−1 at 0.5 mA cm−2 in 1 M NaNO3 solution. The cycling stability
curve over 100 cycles implies that the discharge capacitance is increased from 47 to 68 F g−1 at 5 mA cm−2.
This capacitance enhancement during cycling is due to the influence of phase or morphological variation
of Mn3O4 electrode
Studies Relating to Cathodic Reduction of Hypochlorite in Neutral Chloride Solutions – Used in Chlorate Processes
No full textThe inhibition effect of the chromium hydroxide film for the reduction of hypochlorite has so far been studied on gold,
platinum and iron electrodes in sodium hydroxide and sodium chlorate solution. But there is no reports were available in the
case of alkaline earth metal chlorates. In order to more clearly distinguish, the effects of the film, the addition of chromate
and its effect on the cathodic reduction of hypochlorite in sodium and alkaline earth metal chlorates solutions, the studies
were carried out in platinum electrode. It was found that the addition of chromate to the sodium chlorate solution suppresses
the hypochlorite reduction by forming a thin layer of chromium hydroxide on the electrode surface. In the case of
magnesium, strontium and barium chlorate solutions the hypochlorite reduction was suppressed even without the addition of
chromate in the electrolyte due to the formation of corresponding metal hydroxides on the electrode surfac
Influence of nitrogen flow rates on materials properties of CrNx films grown by reactive magnetron sputtering
No full textChromium nitride (CrN) hard thin films were deposited on different substrates by reactive direct current
(d.c.) magnetron sputtering with different nitrogen flow rates. The X-ray diffraction patterns showed mixed Cr2N
and CrN phases. The variations in structural parameters are discussed. The grain size increased with increasing
nitrogen flow rates. Scanning electron microscopy image showed columnar and dense microstructure with varying
nitrogen flow rates. An elemental analysis of the samples was realized by means of energy dispersive spectroscopy.
The electrical studies indicated the semiconducting behaviour of the films at the nitrogen flow rate of 15 scc
Cobalt Recovery from Waste Catalysts (Petroleum Refining Industry from Gujarat)
No full textA hydrometallurgical process has been developed for cobalt recovery from a waste catalyst (petroleum refining Indus- try). This waste catalyst containing about 2.18 weight % of Co, is highly contaminated by Mg, Al, Si, Ca, Fe, Ni, Cu, Zn, Mo. The major steps are: 1) The spent catalyst is roasted with flux material in an electrical furnace at very high temperature (700°C) for a specific duration; 2) The roasted sample is leached with sulphuric acid to bring the metal con- tents into solution form; 3) For separating cobalt values from the leach solution, the solution pH is raised by NaOH ad- dition, where all cobalt content is precipitated at a pH of about 12; 4) This cobalt hydroxide precipitate is filtered and dissolved in minimum amount of sulphuric acid to get cobalt sulphate solution which is used as the electrolyte for the electrolytic recovery of cobalt. For optimizing various parameters like 1) H2SO4 concentration; 2) Duration; 3) Cobalt concentration; 4) Current density; 5) Temperature; 6) Stirring etc. The particle surface morphology and deposited lay- ers have been characterized by scanning electron microscopy (SEM). A compact metallic deposit containing 70% cobalt was obtaine
Effect of sulphonic acids on electrodeposition of nickel and its structural and corrosion behaviour
No full textThe influence of methane sulphonic acid, naphthalene sulphonic acid and phenol sulphonic acid
on the electrodeposition of nickel from a citrate buffered nickel bath was investigated. Solution
characteristics such as cathode efficiency and throwing power have been assessed, and
corrosion resistance of the coatings was measured by electrochemical impedance spectroscopy
method. The X-ray diffraction pattern obtained for electrodeposited nickel showed a polycrystalline
fcc structure. A uniform and pinhole free surface was observed under SEM analysi
Nitrate reduction in water: Influence of the addition of a second metal on the performances of the Pd/CeO2 catalyst
No full textAn attempt is made to improve the catalytic nitrate reduction on Pd/CeO2 catalysts by the addition of a
second metal. The influence of the second metal such as Sn, In and Ag on the Pd/CeO2 for nitrate reduction is explored. The second metal is introduced over monometallic Pd/CeO2 by a redox reaction. Pd/CeO2 is more active than the bimetallic catalysts under pure hydrogen flow. Whereas in presence of CO2 the monometallic Pd/CeO2 is inactive for nitrate reduction, bimetallic catalysts are found to be more active
than under pure hydrogen flow and also than the monometallic catalyst with a low selectivity towards ammonium ions, undesired product of the reaction. The Pd–Sn/CeO2 catalyst is comparatively the most suited for nitrate reductio
Role of pH in the synthesis of 3-aminopropyl trimethoxysilane stabilized colloidal gold/silver and their alloy sols and their application to catalysis
No full textA general method for the synthesis of nano-alloy dispersions of noble metals like Au and Ag in organically
modified aminosilicate sol is presented with an emphasis on the influence of pH on the sol stability. The alloys of Au–Ag were synthesized by co-reduction of solutions of gold and silver salts using borohydride as the reducing agent at a suitable pH in the medium containing 3-aminopropyltrimethoxysilane (APS) stabilizer. Organosilanes with amine functional group have multiple roles in the formation of stable sols such as the formation of siloxane network structures by hydrolysis and condensation and the interaction of amino group with metal ions in solution electrostatically.Monometal and alloy sols were characterized by transmission electron microscopy (TEM), ultraviolet–visible (UV–vis) spectroscopy. The stable alloy
sols were found to catalyze the chemical reduction of 4-nitrophenol to 4-aminophenol and the catalytic rate constants were evaluated from UV–vis spectroscop