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Investigations on the Structural, Morphological, Electrical, and Magnetic Properties of CuFe2O4-NiO Nanocomposites
No full textCuFe2O4-xNiO (x ) 1, 5, 10, and 20 wt %) nanocomposites have been successfully prepared by a
simple combustion method using urea-nitrate precursors. The samples were sintered at different
temperatures, namely 600, 800, 1000, and 1100 °C, for 5 h to enhance the compound formation and
phase purity, studied by means of XRD patterns. Then the 1100 °C sintered sample was further
characterized for its structural (EXAFS, XANES, FT-IR, UV–vis), morphological (SEM, TEM, HRTEM,
SAED), electrical (ac conductivity, dielectric constant, dielectric loss tangent), and magnetic (Mössbauer)
properties. The EXAFS and XANES studies reveal the formation of NiFe2O4 and CuO, in addition to the
existence of CuFe2O4 and NiO phases. A partial substitution of metal cations by nickel ions could also
be evidenced. The stretching and bending vibration of the tetrahedral and octahedral complexes have
been established from FT-IR spectra. The UV–vis spectra elucidate that the prepared materials are
semiconductors and also show the quantum size confinement effect. The well-defined grain and grain
boundary structure was identified from the SEM studies. The nanosize of the synthesized materials has
been identified by TEM investigations. The HRTEM and SAED images reveal the crystallinity and
polycrystalline behavior of the as-synthesized materials. The electrical studies show the normal
ferrimagnetic behavior of the materials. The inverse spinel nature of the materials has been enumerated
from Mössbauer spectra, which also illustrates the phase transition behavior
A complex parameter boundary element method for modeling AC impedances of electrochemical systems by analytic continuation— Application to a slit geometry
No full textA complex parameter boundary element method is advanced to compute the AC impedances of electrochemical systems by solving the
Laplace equation with complex boundary conditions. This method, which is based on analytic continuation from the corresponding
secondary current distribution, is applied to a slit geometry, besides two illustrative cases: plane-parallel electrodes and concentric
cylinder electrodes. The AC impedance responses for the slit geometry are computed for several electrode and slit dimensions for (1)
purely capacitive working electrode and (2) a working electrode represented by a Voigt element. Interesting effects of the electrode and
the slit dimensions on the AC response are noted. Applications of this method in viscoelastic systems, rheology and electronic/electrical
devices are discussed. User-friendly implementations of the method in the BEASY group of softwares are also suggested
Molecular interactions of polyvinylpyrrolidone and cellulose acetate butyrate solutions in dimethylformamide
No full textThe ultrasonic velocity, density, and ViScosIties of polyvinylpYITolidone (PVP) and cellulose acetate butyrate (CAB) solutions in dimethyllonnamide (DMF) have been measured in the temperature range, 303K-323 K. Using these data, free energy of mixing, solvation number and different polymer-solvent interaction parameters for the solution systems have been calculated to know the presence of molecular interactions in the system. The trends in the variation of the solution property parameters indicate the existence of positive molecular interactions between tile polymer and the solvent in solutions. The results also show the presence of higher degree of interaction between I'VP and DMF in solution compared to CAB and DMF
Study of CuFe2O4–SnO2 nanocomposites by Mössbauer spectroscopy with high velocity resolution
No full textHigh velocity resolution Mössbauer spectroscopy was used to study of
(CuFe2O4)1−x(SnO2)x nanocomposites (x = 0, 1, 5, 10, 20 wt.%). Mössbauer spectra
were measured at room temperature with registration in 4,096 channels and further
presentation in 1,024 channels. Mössbauer spectra of CuFe2O4 and (CuFe2O4)0.99 +
(SnO2)0.01 were better fitted using three sextets while spectra of (CuFe2O4)0.95 +
(SnO2)0.05 and (CuFe2O4)0.80 + (SnO2)0.20 were better fitted using four sextets
and one doublet. In contrast, spectrum of (CuFe2O4)0.80 + (SnO2)0.20 was better
fitted using five sextets and one doublet. Mössbauer hyperfine parameters were
related to octahedral and tetrahedral sites in copper ferrites. The presence of two
different tetrahedral sites in studied ferrites and two different octahedral sites in
(CuFe2O4)0.80 + (SnO2)0.20 was supposed
Studies on the Fluidized Bed Electrode
No full textThe present investigation attempts to study the hydrodynamic characteristics
of the fluidized bed electrode. A core-annular flow model with a transfer of particles
between core-annular layers has been proposed to describe the flow behavior
of conducting particles in the fluidized bed electrode. The effect of individual
parameters on the rate of the particle transfer across the layer and thickness of
the core-annular has been critically examined and the model simulation has been
verified with the data reported in the literature
Influence of Sacrificial Cathodic Protection on the Chloride Profile in Concrete
No full textThe durability of reinforced concrete structures significantly depends on the condition of the steel
embedded in them. Structures exposed to chloride containing environment have reduced durability due
to corrosion of the reinforcement steel. Several diffusion models have been proposed for chloride
penetration. They mainly aim at predicting the initiation of corrosion of the reinforcement. They are
based on diffusion conditions influenced by parameters such as relative humidity, temperature, rains
etc. This work presents the influence of sacrificial cathodic protection on the chloride profile in
concrete. Cathodic protection to the embedded steel in concrete was established by plugging-in a
sacrificial magnesium alloy anode at the center of the slab and providing an electrical link between
them. The current flowing between the magnesium anode and the embedded steel was regularly
measured. The water soluble chloride content at different distances from the anode and at different
times was determined after implementation of cathodic protection. The chloride content decreased at
different distances from the anode, with increase in time. The diffusion of chloride occurred at a more
accelerated rate due to the flow of cathodic protection current
Synthesis of Poly(p-phenylene diamine) and Its Corrosion Inhibition Effect on Iron in 1M HCl
No full textWater-soluble poly(p-phenylene diamine)
was chemically synthesized. Its corrosion inhibition performance
was evaluated for iron corrosion in 1M HCl at
various concentrations, and the results were compared
with that of the monomer. The corrosion inhibition properties
were evaluated by polarization techniques and electrochemical
impedance spectroscopy. The results showed
that poly(p-phenylene diamine) was a more efficient corrosion
inhibitor than the monomer and gave an 85% inhibition
efficiency at a concentration of 50 ppm, whereas the
monomer gave an efficiency of 73% at 5000 ppm
Characteristics of sol–gel dip coated Ceria films
No full textCerium oxide(CeO2) thin films were deposited
by the sol–gel dip coating technique using cerium chloride,
acrylamide and N,N bis methylene acrylamide. The as
deposited films were heat-treated at different temperatures
in air. X-ray diffraction studies indicated the films to be of single phase CeO2. Optical bandgap in the range of 3.53–
3.60 eV was obtained from optical studies. Laser Raman
studies exhibited Raman bands around 457 cm�1
Effect of varying poly(styrene sulfonic acid) content in poly(vinyl alcohol)–poly(styrene sulfonic acid) blend membrane and its ramification in hydrogen–oxygen polymer electrolyte fuel cells
No full textPoly(styrene sulfonic acid) (PSSA) content in poly(vinyl alcohol) (PVA) and PSSA blend membrane is varied
and its effect on proton conductivity is studied at varying relative humidity (RH) values. The maximum
proton conductivity is observed for the PVA–PSSA membrane with about 35 wt. % PSSA at all humidity
values. At 30% RH value, the conductivity of PVA–PSSA blend membrane is 1.20×10−3 S/cm, which
is about two orders of magnitude higher than the conductivity value of 2.27×10−5 S/cm observed for
pristine PVA membrane. Water self-diffusion coefficients and water release kinetics of these materials
have been characterized by nuclear magnetic resonance (NMR) imaging technique, which validate the
use of this membrane in polymer electrolyte fuel cells (PEFCs). A peak power density of 210mW/cm2 at
a load current-density of 500mA/cm2 is achieved for the PEFC with the optimized PVA–PSSA membrane
as electrolyte compared to a peak power density of only 38mW/cm2 observed at a load current-density
of 80mA/cm2 for the PEFC with pristine PVA membrane as electrolyte while operating at 75 ◦C with H2
and O2 feeds to the fuel cell maintained at atmospheric pressure
Polyvinylidene fluoride–hexafluoropropylene (PVdF–HFP)-based composite polymer electrolyte containing LiPF3(CF3CF2)3
No full textThis paper describes the preparation and characterization of lithium fluoroalkylphosphate-containing
composite polymer electrolyte based on a polyvinylidene fluoride–hexafluoropropylene (PVdF–HFP)
matrix. A mixture of ethylene carbonate and diethyl carbonate was used as a plasticizing agent and nanoscopic
Al2O3 as a filler. The membranes were characterized by ac impedance, SEM, DSC, FTIR and fluorescence.
An electrolyte with 2.5 wt% Al2O3 exhibited a conductivity of 9.8 104 S cm1 at ambient
temperature. It was found that filler contents above 2.5 wt% rendered the membranes less conducting