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Corrosion performance of steel in composite concrete system admixed with chloride and various alkaline nitrites
No full textComposite concrete systems consist of both binary and ternary cements were designed. The
corrosion performance of steel in composite concrete systems admixed with sodium chloride
(3%NaCl) and different alkaline nitrites (0?5%NO2 2 ), namely sodium nitrite (NaNO2), potassium
nitrite (KNO2) and calcium nitrite [Ca(NO2)2] were studied by conducting various electrochemical
and non-electrochemical techniques. Open circuit potential and weight loss measurements were
carried out for 180 days of exposure. The permeability characteristics of the composite concrete
systems were studied using impressed voltage technique and rapid chloride permeability test.
Linear polarisation studies showed better corrosion resistance properties of steel in binary and
ternary cement concrete even in the presence of 3% sodium chloride. Chloride diffusion studies
revealed that the diffusion coefficient was found to be much less for (OPCzPSC) and ternary
systems. Nitrites of sodium, potassium and calcium act as anodic inhibitors and they compete
with chloride ions for the ferrous ions at the steel surface to form a film of ferric oxide. Ternary
systems and (OPCzPSC) performed better even in the presence of a higher amount of
aggressive chloride ions. The reduction in the corrosion rate of steel in composite concrete
systems follows the order: (OPCzPPCzPSC).(OPCzPSC).(OPCzPPC).(PPCzPSC)
Polyaniline–polyelectrolyte–gold(0) ternary nanocomposites: Synthesis and electrochemical properties
No full textTernary composites based on polyaniline (PAni), a polyelectrolyte-namely poly(diallyldimethylammoniumchloride)
(PDDMAC) and gold (Au(0)) nanoparticles have been formulated and synthesized where
the high concentration of PDDMAC acted as medium of reaction. The nanocomposites are characterized
by FT-IR, UV–vis, XRD, XPS, SEM, AFM and TEM techniques. XRD showed the presence of all
three viz., polyaniline, PDDMAC and Au(0) components in the ternary system. The composites exhibited
higher conductivities in the range 26×10−6 to 217×10−6 S/cm compared with the binary composite of
PAni–PDDMAC. The ternary compositeswere adsorbed on a GC electrode and used for sensing dopamine.
The composites are useful in sensing as low as 0.05mM concentration of dopamine at lower potential
values compared to some binary PAni–Au nanocomposites
Co-assembly of aNafion–Mesoporous ZirconiumPhosphate Composite Membrane for PEM Fuel Cells
No full textSynthesis of mesoporous zirconium phosphate (MZP) by coassembly
of a tri-block copolymer, namely pluronic-F127, as
a structure-directing agent, and a mixture of zirconium butoxide
and phosphorous trichloride as inorganic precursors
is reported. MZP with a specific surface area of 84 m2 g–1,
average pore diameter of about 17 nm and pore volume of
0.35 cm3 g–1 has been prepared, and characterised by X-ray
diffraction (XRD) and transmission electron microscopy.
Nafion–MZP composite membrane is obtained by employing
MZP as a surface-functionalised solid-super-acid-proton-
conducting medium as well as an inorganic filler with
high affinity to absorb water and fast proton-transport
across the electrolyte membrane even under low relative
humidity (RH) conditions. The composite membranes have
been evaluated in H2/O2 polymer electrolyte fuel cells
(PEFCs) at varying RH values between 18 and 100%; a peak
power density of 355 mW cm–2 at a load current density of
1,100 mA cm–2 is achieved with the PEFC employing
Nafion–MZP composite membrane while operating at optimum
temperature (70 °C) under 18% RH and ambient pressure.
On operating the PEFC employing Nafion–MZP membrane
electrolyte with hydrogen and air feeds at ambient
pressure and a RH value of 18%, a peak power density of
285 mW cm–2 at the optimum temperature (60 °C) is
achieved. In contrast, operating under identical conditions, a
peak power density of only ∼170 mW cm–2 is achieved with
the PEFC employing Nafion-1135 membrane electrolyte
Simulated XRD profiles of carbon nanotubes (CNTs): An efficient algorithm and a recurrence relation for characterising CNTs
No full textWe develop an efficient algorithm and a novel recurrence relation for computing the Debye function of carbon nanotubes. This allows the computation of the XRD pronle of CNTs for arbitrary lengths in times which scales linearly with the tube length. Using the recurrence relation, we further show that the XRD peak intensities are proportional to the tube length. The slopes and intercepts ofthe peak intensity versus tube length plots are characteristic of the CNT type. This work will help to create a database for CNTs akin to the ICDD data for 3-D crystals. Methods are also sketched to deduce tube properties from the XRD data
Electrochemical investigations and characterization of a metal hydride alloy (MmNi3.6Al0.4Co0.7Mn0.3) for nickel metal hydride batteries
No full textThe use of new hydrogen absorbing alloys as negative electrodes in rechargeable batteries has allowed the consideration of nickel/metal hydride
(Ni/MH) batteries to replace the conventional nickel cadmium alkaline or lead acid batteries. In this study the performance of trisubstituted hydrogen
storage alloy (MmNi3.6Al0.4Co0.7Mn0.3) electrodes used as anodes in Ni/MH secondary batteries were evaluated. MH electrodes were prepared and
the electrochemical utilization of the active material was investigated. Cyclic voltammetric technique was used to analyze the beneficial effect of
the alloy by various substitutions. The electrochemical impedance spectroscopic measurements of the Ni/MH battery were made at various states
of depth of discharge. The effect of temperature on specific capacity is studied and specific capacity as a function of discharge current density was
also studied and the results were analyzed. The alloy metal hydride electrode was subjected to charge/discharge cycle for more than 200 cycles.
The discharge capacities of the alloy remains at 250 mAh/g with a nominal fading in capacity (to the extent of ∼20 mAh/g) on prolonged cycling
Redox mediated electrochemical method for vat dyeing in ferric-oxalate-gluconate system: process optimization studies
No full textPreliminary efforts were made to identify
alternative ligands for relatively greener and cheaper than
triethanolamine (TEA), leading to a new ferric-oxalategluconate
mixed ligand system as a potential alternative.
Cyclic voltammetry was employed to study the mechanism
involved. A low concentration of electrogenerated FeII-
oxalate is transformed into FeII-gluconate, which is the
reducing agent in the overall process. The influences of
electrolyte medium, electrode material, nature of dye, dye
concentration, material to liquor ratio (MLR), and other
related parameters were studied to arrive at optimum
experimental condition. Copper cathode and stainless steel
anode were the material of choice. The optimum cathode
current density was found to be 2.30 mA cm-2. Under
optimum condition, both cotton fabric and yarn could be
efficiently dyed using this electrochemical process. The
electrolyte could also be recycled. Color intensity for different
dyed materials was evaluated using K/S values
according to the Kubelka–Munk equation
Pulsed electrodeposition of microcrystalline chromium from trivalent Cr-DMF bath
No full textPulsed electrodeposition (PED) with square
wave has successfully been applied to deposit microcrystalline
chromium from Cr-dimethylformamide (DMF) bath.
The influence of the duty cycle, on-time, off-time, frequency,
and pulse peak current on thickness, current efficiency, and
hardness were investigated. Based on the analysis of
the microstructure, the corrosion behavior of both directcurrent
deposited (DCD) and pulse-current deposited (PED)
chromiumin 3.5% NaCl solution was studied using potentiodynamic
polarization and electrochemical impedance spectroscopy
(EIS). The results indicated that both pulsed
electrodeposits and direct-current deposits have high charge
transfer resistance Rct and very low Icorr compared with mildsteel
substrate
An Eco-friendly Synthesis of A Terpolymer Resin: Characterization and Chelation Ion-exchange Property
No full textAnthranilic acid-thiourea-formaldehyde terpolymer resin was synthesized by an
eco-friendly technique using dimethylformamide as a reaction medium. The
resin was characterized by FTIR, 1H NMR, 13C NMR, thermal analysis and
viscosity-average molecular weight. The physicochemical parameters have been
evaluated for the terpolymer resin. The kinetic parameters such as energy of activation
and the order of the reaction have also been evaluated on the basis of the thermogravimetric
data using Freeman-Caroll method. The surface morphology of the terpolymer
resin was examined by scanning electron microscopy and the transition state between
crystalline and amorphous nature was established. The colour of the terpolymer resin
was confirmed by optical microscopy. The electrical property of the terpolymer resin
showed an appreciable change in its conductivity at various concentrations and
temperatures. One of the important applications of these types of polymers is their
capability to act as chelating ion-exchangers. The chelation ion-exchange property of
the terpolymer showed a powerful adsorption towards specific metal ions like Zn2+,
Mn2+, Cu2+, Ba2+, and Mg2+. A batch equilibration method was adopted to study the
selectivity of the metal ion uptake involving the measurement of the distribution of the
given metal ion between the polymer sample and a solution containing the metal ion
over a wide range of concentrations and pHs of different electrolytes
Nitrate removal by electro-bioremediation technology in Korean soil
No full textThe nitrate concentration of surface has become a serious concern in agricultural industry through out
the world. In the present study, nitrate was removed in the soil by employing electro-bioremediation, a
hybrid technology of bioremediation and electrokinetics. The abundance of Bacillus spp. as nitrate reducing
bacteria were isolated and identified from the soil sample collected from a greenhouse at Jinju City
of Gyengsangnamdo, South Korea. The nitrate reducing bacterial species were identified by 16 s RNA
sequencing technique. The efficiency of bacterial isolates on nitrate removal in broth was tested. The
experimentwas conducted in an electrokinetic (EK) cell by applying 20Vacross the electrodes. The nitrate
reducing bacteria (Bacillus spp.) were inoculated in the soil for nitrate removal process by the addition of
necessary nutrient. The influence of nitrate reducers on electrokinetic process was also studied. The concentration
of nitrate at anodic area of soilwas higher when compared to cathode in electrokinetic system,
while adding bacteria in EK (EK + bio) system, the nitrate concentrationwas almost nil in all the area of soil.
The bacteria supplies electron from organic degradation (humic substances) and enhances NO3− reduction
(denitrification). Experimental results showed that the electro-bio kinetic process viz. electroosmosis
and physiological activity of bacteria reduced nitrate in soil environment effectively. Involvement of Bacillus
spp. on nitrificationwas controlled by electrokinetics at cathode area by reduction of ammonium ions
to nitrogen gas. The excellence of the combined electro-bio kinetics technology on nitrate removal is
discussed
Amorphous to crystalline transition and optoelectronic properties of nanocrystalline indium tin oxide (ITO) films sputtered with high rf power at room temperature
No full textITO thin films were deposited on quartz substrates by the rf sputtering technique using various rf power
keeping the substrates at room temperature. The influence of rf power on the structural, electrical, optical
and morphological properties was studied by varying the rf power in the range 50–350 W. X-ray diffraction
results show an amorphous – crystalline transition with nano grains. At a power of 250 W, the ITO
film showed preferential orientation along (4 0 0) peak. It is observed from the optical transmission studies
that the optical band gap increased from 3.57 to 3.69 eV when the rf power was increased from 50 to
250 W. The resistivity value is minimum and grain size is maximum for the ITO film deposited at 250 W.
The X-ray photoelectron spectroscopy (XPS), Energy dispersive X-ray (EDX) and Atomic force microscopy
AFM results confirm that the ITO films are stoichiometric and the surface contained nano-sized grains
distributed uniformly all over the surface. It can be concluded that the ITO film deposited at room temperature
with 250Wrf power, can provide the required optical and electrical properties useful for developing
optoelectronic devices at lower temperatures