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Role of alkaline nitrites in the corrosion performance of steel in composite cements
No full textThe influence of alkaline nitrites on the inhibition
of corrosion of steel in binary and ternary cement
environments was tested. pH measurements carried out for
binary and ternary cement extracts showed that the alkalinity
of the cement was not affected by making use of
binary and ternary cements. Gravimetric measurements
showed that the decrease in the corrosion rate of steel in
different systems follows the order: Ternary [ (OPC +
PSC) [ (OPC + PPC) [ (PPC + PSC). Potential–time
studies indicated that the ability to maintain the passivity of
steel in different systems also follows the order as above.
Potentiodynamic polarisation studies for steel in binary and
ternary cement environments showed the favourable
influence of the presence of higher amounts of chlorides.
Nitrites of sodium, potassium and calcium act as anodic
inhibitors and they compete with chloride ions for the
ferrous ions at the steel to form a film of ferric oxide. An
efficiency as high as 91% is obtained for the ternary system
containing 1% chloride and 0.5% nitrite. The degree of
surface coverage showed a maximum value for the ternary
system ([0.9) even in the presence of a higher amount of
chloride thereby indicating the better performance of the
system
Hydrogel membrane electrolyte for electrochemical capacitors
No full textPolymer electrolytes are known to possess excellent physicochemical properties that are very
useful for electrochemical energy systems. The mobility in polymer electrolytes is understood to be
mainly due to the segmental motion of polymer chains and the ion transport is generally restricted to the
amorphous phase of the polymer. Gel polymer electrolytes (GPE) that are formed using plastizicers and
polymers along with ionic salts are known to exhibit liquid-like ionic conductivity while maintaining the
dimensional stability of a solid matrix. In the present study, the preparation and characterization of
poly(vinyl alcohol)-based hydrogel membranes (PHMEs) as electrolytes for electrochemical capacitors
have been reported. Varying HClO4 dopant concentration leads to different characteristics of the capacitors.
The EC comprising PHME doped with 2 M HClO4 and black pearl carbon (BPC) electrodes has
been found to exhibit a maximum specific capacitance value of 97 F g–1, a phase angle value of 78°, and
a maximum charge–discharge coulombic efficiency of 88%
Nanocrystalline zinc–nickel alloy deposition using pulse electrodeposition (PED) technique
No full textZinc–nickel alloy was electrodeposited on stainless steel using pulse current deposition (PED)
from a chloride–sulphate bath. Duty cycles were varied between 10 and 80% and frequency was
changed from 10 to 100 Hz. The deposit characteristics were analysed using SEM, XRD and AFM
and the results are presented in this paper. The corrosion resistance of zinc–nickel alloy
deposited from direct current deposition (DCD) has been compared with that of the deposit
obtained by pulse current using the electrochemical impedance spectroscopy method
Effect of manganese addition on anode characteristics of electrolytic magnesium
No full textPurpose – The purpose of this paper is to investigate the influence of manganese addition on sacrificial anode characteristics of electrolytic
magnesium.
Design/methodology/approach – Different contents of manganese were added to magnesium. Anode characteristics were evaluated and correlated
to added manganese.
Findings – The performance of an anode depends strongly on the manganese content. An optimum value for the manganese to be added was
identified. The impurity levels to obtain efficiencies above 50 per cent also are reported.
Originality/value – This paper highlights the properties of magnesium-manganese binary alloys for use as sacrificial anodes in cathodic
protection
Pulse electrodeposited zinc selenide films and their characteristics
No full textZinc selenide (ZnSe) thin films were pulse deposited for the first time using polycyclic
acid. The films exhibited hexagonal structure. The band gap of the films varied in the
range of 2.7 – 3.1 eV as the concentration of silico-tungstic acid increased. Atomic force
microscopy indicated grain size decreased from 60 – 15 nm after addition of silicotungstic
acid. Laser Raman spectrum exhibited LO phonons corresponding to ZnSe. The
photoluminescence spectrum peaks at 675 nm. As the concentration of silico-tungstic acid
increases, the PL emission peak shifts to shorter wavelenghths
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
Pulse plated cadmium telluride films and their characteristics
No full textCadmium telluride thin films were deposited on
conducting glass and titanium substrates by the pulse plating
technique at different duty cycles in the range 10–50%. The
films were characterised by X-ray diffraction and were found
to possess single phase cubic structure. Optical studies
indicated a direct band gap of 1.45 eV. Surface morphology
of the films indicated that the crystallite size increases with
increase of duty cycle. X-ray photoelectron spectroscopy
studies confirmed the formation of CdTe. Electron-dispersive
X-ray studies were made to estimate the composition. Crossplane
resistivity measurements indicated that the resistivity
decreases with increase of duty cycle
Influence of Additives and the Effect of Aging in Modifying Surface Topography of Electrodeposited Copper
No full textThe influence of most common additives used for copper electrodeposition on the physical, microstructure as well as the morphological
character of the deposit has been studied. The effect of room-temperature aging on the microstructure of the copper
deposit is also discussed in the present work. The X-ray diffraction pattern of the copper deposit has a prominent (111) orientation
in addition to (200), (220), and (311) planes typical of copper deposits; the intensity of the planes during aging has a prominent
�200� plane; and the ratio of I111 to I200 changes significantly. The scanning electron microscopy analysis showed that the deposit
normally appears to have round or globular features and that there is a change in grain size with respect to a particular additive.
From the atomic force microscopy analysis, we can confirm that the average grain size and the roughness of the copper deposits
strongly depend on the deposition rate and the type of additive in the bath. There is a change in the grain size and the morphology
of the copper deposit due to room-temperature aging. The roughness of the surface increases, and an abrupt shift in the hardness
of the coating occurs during agin
An improved ph transmitter device for on-line high current applications
No full textA pH tr ansmitter for on-line high current applications, that has a current output of 4 to 20mA, comprising of a pH sensor, electronic hardware circuits to process the sensor output, to compensate for pH variation with temperature, to calibrate the transmitter using buffers, and to provide current output corresponding to 0 to 14 pH, has been developed that has application to monitor and transport the pH signal over a large distance in chemical and electrochemical processes that involve high currents in industrial environmen
Electrochemical Behavior of LiM0.25Ni0.25Mn1.5O4 as 5 V Cathode Materials for Lithium Rechargeable Batteries
No full textGlycine-assisted sol-gel–synthesized multiple-doped spinels, LiM0.25Ni0.25Mn1.5O4 M = Cr, Fe, and Co have been studied as 5 V
cathode materials. The sol-gel technique provides homogeneity, high purity, lower processing temperature, controlled particle size,
and morphology. The synthesized samples were subjected to physical characterization studies, viz., thermogravimetric and differential
thermal analysis, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical
charge–discharge studies. Galvanostatic charge–discharge studies of the samples reveal that LiFe0.25Ni0.25Mn1.5O4 using glycine as
a chelating agent delivers a stable capacity of 120 mAh g−1 even after 20 cycles when cycled between 3 and 5 V