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Optimal time-varying potential profile for electro-hydro-dimerization reactions
No full textOptimal time-varying potential profile for batch electrochemical reactor is evaluated for a major industrial
electro-organic synthesis, the electro-hydro-dimerization of acrylonitrile to adiponitrile. The control
vector iteration technique is used for computing the optimal profiles. As the technique is continuous on
both state and adjoint variables, it can give more accurate profile with no need for any polynomial
approximation. A heterogeneous model of the reactor is uniquely used for the formulation of dynamic
optimization problem statements by expressing the differential constraints in terms of concentration
variations in bulk as well as at the electrode surface. In addition to taking an account of surface concentration
variations, the separation of total current as faradic and non-faradic currents is also considered as
an additional equality constraint. A path constraint on the electrode potential is imposed for safe reactor
function and economical operation. The results of optimum time-varying potential profile are compared
with those of applying a steady potential
Properties of Zinc alloy electrodeposits produced from acid and alkaline electrolytes
No full textZinc–cobalt (Zn–Co) and zinc–nickel (Zn–Ni)
alloy electrodeposits each prepared from acid and alkaline
formulations were compared for their properties. Compared to
alkaline baths, acid baths offer higher metal percent of the
alloying element and higher current efficiency. In alkaline
baths, the variation of metal percent in deposit with current
density is less significant, but that of current efficiency with
current density is more. Electrolyte pH does not change
significantly in alkaline solutions compared to acid solutions.
X-ray diffraction evaluation of Zn–Co deposits from both
electrolytes indicated their presence in the η-phase, while Zn–
Ni shows pure γ-phase for deposits obtained from alkaline
solutions and the existence of γ-phase with traces of η-phase
of zinc for deposits obtained from the acid electrolytes.
Scanning electron microscope examination shows finer grain
structure for deposits obtained from alkaline solutions, and
atomic force microscope studies confirm their nanostructure
with reduced surface roughness. Deposits obtained from the
alkaline baths exhibited higher corrosion resistance probably
due to their nanostructure
Ultrasonic study on binary mixture containing dimethylformamide and methanol over the entire miscibility range (0<x<1) at temperatures 303–323K
No full textThe experimental density and speed of ultrasound measurements in connection with literature data have
been measured for pure N,N-dimethylformamide (DMF), methanol and their binary mixtures over the
whole miscibility range at different temperatures 303, 308, 313, 318 and 323 K. These parameters were
used to determine the adiabatic compressibility, intermolecular free length, molar compressibility, molar
sound velocity, acoustic impedance, relaxation strength and their excess values. The variation of these
parameters with composition of mixture indicates the nature and extent of interaction between unlike
molecules. The non-ideal behavior of the systemstudiedwas explained on the basis of the dipole-induced
dipole interactions and hydrogen bonding. The complex formation through intermolecular hydrogen
bonding was confirmed from the recorded FTIR spectra. Available thermal energy breaks the bonds
between the associated molecules into their respective monomers on increasing the temperature
Electroless nickel deposition from methane sulfonate bath
No full textElectroless plating is a controlled autocatalytic chemical reduction process for depositing metals. The
process involves a continuous build up of a nickel coating on a substrate by immersion of the substrate in
a suitable nickel plating under appropriate conditions. In this paper the authors have studied the effect of
pH and temperature on the rate of deposition and phosphorous content from nickel methane sulfonate
bath. Effect of phosphorous content on hardness, wear resistance and corrosion resistance were also
studied. SEM and XRD measurements show nodular and amorphous character of the deposits. As the
bath is free from sulfate ions the bath can be operated for more number of turn overs and orthophosphite
formed during the process can be removed easily
Electrochemical Studies on the Performance of SS316L Electrode in Electrokinetics
No full textOrganic and trace metal pollutants are removed by employing various electrodes in an electrokinetic (EK)
process. Stainless steel was used either as an anode or a cathode by various investigators in electroremediation
systems. In the present study, the role of SS316L as an anode and cathode in EK system was studied by
the measurements of pH, conductivity of electrolyte, and potential of the anode and cathode at different current
densities. The weight loss of the anode and cathode and the leaching of chromium, iron, and nickel at different
current densities were measured and discussed with an electroosmosis process. The electrochemical behavior
of SS316L electrode in neutral, acidic and alkaline pH in soil environment was studied by an electrochemical
technique viz. polarization study. Surface analysis of SS316L after EK was done by XPS and SEM. The
higher conductivity was noticed at anolyte when compared to catholyte. The weight loss of the anode was
in the following order 0.615 > 0.307 > 0.123 mA/cm2 and the cathode corrosion rate was vice versa. Peroxide
production was also noticed at the anolyte, which may encourage the degradation of the total organic content
(TOC) in the soil. The OCP (open circuit potential) of SS316L was about +75 mV vs SCE in the soil extract;
while adding acetic acid, the potential shifted to the positive side, to about +380 mV vs SCE. The breakdown
potential and the range of passivation potential were higher in acetic acid added system when compared
to other systems. Pitting was observed on both the anode and cathode within 48 h during the EK process.
The present study concludes that SS is not a proper electrode material for the EK process
Migrating vs admixed corrosion inhibitors for steel in Portland, Pozzolona and Slag cement concretes under macro cell condition
No full textThe inhibitive performance of migrating and admixed inhibitors for steel embedded in ordinary Portland cement
(OPC), Portland pozzolona cement (PPC), and Portland slag cement (PSC) concretes were evaluated under macro
cell corrosion condition. Macrocell corrosion parameters, such as anode potential, macro cell current, and total
integrated current, were monitored over a one year exposure period. The corrosion rate of steel embedded in
different concretes was assessed by the gravimetric weight loss method. The surface of the specimens was further
examined by UV and FTIR spectroscopy. All the studies revealed that migrating corrosion inhibitor (MCI)
performed better than admixed inhibitor in reducing the corrosion rate of steel embedded in different concretes under
macrocell condition
Synthesis of Conducting Polymer Supported Pd Nanoparticles in Aqueous Medium and Catalytic Activity Towards 4-Nitrophenol Reduction
No full textWe report here the synthesis of palladium (Pd)
nanoparticles incorporated poly-(3,4)ethylenedioxythiophene
(PEDOT) matrix in aqueous medium and its
catalytic performance towards 4-nitrophenol reduction.
This simple one-pot synthesis involving a redox reaction
between 3,4-ethylenedioxythiophene and palladium chloride
(PdCl2) precursor, leads to the formation of Pd
nanoparticles supported on particulate PEDOT. Pd nanoparticles
of size 1–9 nm were found to distribute uniformly
over the PEDOT matrix. Morphology of the Pd–PEDOT
nanocomposite was characterized by field emission-scanning
electron microscopy and transmission electron
microscopy and the crystallographic details obtained using
X-ray diffraction. The chemical nature of the PEDOT
support matrix was analyzed using Fourier transform-infra
red (FT-IR) spectroscopy. The catalytic activity of the
composite was demonstrated using a model reaction, i.e.,
reduction of 4-nitrophenol to 4-aminophenol. The value
of the apparent rate constant, ca. 65.8 9 10-3 s-1 obtained
using UV visible spectroscopy of the reduction of
4-nitrophenol at the Pd–PEDOT nanocomposite is
comparable to those reported for other catalytic systems
Effect of substrate temperature on structural and materials properties of zirconium nitride films on D9 steel substrates
No full textThin zirconium nitride (ZrN) films were prepared by using reactive direct current (DC) magnetron sputtering
onto D9 steel substrates. XRD technique was employed to study the coatings, observing variations of
crystallite size, crystallite texture and lattice constant, as a function of substrate temperature. Chemical states
of the ZrN thin films were determined by X-ray photoelectron microscopy (XPS). AFM picture showed the
presence of spherical shaped grains on the top of homogeneous granular surface. The hardness and elastic
modulus values were measured by nanoindendation and their values are 18.5 and 343 GPa respectively
Organically Soluble Bifunctional Polyaniline–Magnetite Composites for Sensing and Supercapacitor Applications
No full textSoluble conducting polyaniline composites with low-level loadings of Fe3O4 have been synthesized and characterized. The
composites are dispersible in many solvents including water and soluble in polar organic solvents, such as chloroform,
N-methylpyrrolidone, and methanol. The conductivity of the sample increases with increase in Fe3O4 loading and typically is in
the range of 0.042–0.42 S/cm. The composites are bifunctionally useful in detecting dopamine electrochemically in the concentrations
range 1–50 �M and also work as electrode materials for supercapacitor application
Performance evaluation of low cost adsorbents in reduction of COD in sugar industrial effluent
No full textStudies on reduction of chemical oxygen demand (COD) in effluent from sugar industry have been carried
out by employing different absorbents optimizing various parameters, such as initial concentration of
adsorbate, pH, adsorbent dosage and contact time. Experimental studies were carried out in batches
using metakaolin, tamarind nut carbon and dates nut carbon as adsorbents by keeping initial adsorbent
dosage at 1 g l−1, agitation time over a range of 30–240 min, adsorbent dosage at 100–800mg l−1 by
varying the pH range from 4 to 10. Characterization of there adsorbents were done using techniques
such as Fourier transforms infra red spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron
microscope (SEM). The experimental adsorption data fitted well to Langmuir and Freundlich adsorption
isotherms. The isotherms of the adsorbents indicate appreciable adsorption capacity. Higher CODremoval
was observed at neutral pH conditions. Studies reveal that maximum reduction efficiency of COD takes
place using metakaolin as an absorbent at a dosage of 500mgl−1 in a contact time of 180 min at pH 7 and
it could be used as an efficient absorbent for treating sugar industrial effluent