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Preparation and characterization of LaAI03
No full textLanthanum aluminate has been prepared by combustion synthesis proc S' using nitrate salts of lanthanum and aluminium as cation precursors and urea as the fuel. The powder density and the compacted pellet density have been determined. Sintering proc' s reduces the porosity of the pellets by the agglomeration proc~ s. ThL' conductivity of LaAIO, increases with sintering temperature and the value is found to be 1.75 Scm-1 at 1000" . he diekclJic constant and loss tangent values are found to decrease with the applied frequency. This may be du' to the change in orientation and ionic effects rcsulted frum the inertia of ions and molecular levels. The XRD studies reveal that the material is as igned to be a pselldocubic structure. The FTIR spectra show the higher frequency and lower frequency bands arc assigned to AI01> octahedra in LaAIO,. S M micrographs divulge the presence of platelet aggregates into globular mass with larger surface area. The electrochemical polarization was performed for a synthesized and sintered LaAI01 materials in 0.5-2.0 M KOR In general the corrosion kinetic parameters elucidate the fact that the green samples are found to be prone to corrosion than the sintered material
Phthalic acid assisted nano-sized spinel LiMn2O4 and LiCrxMn2xO4 (x = 0.00–0.40) via sol–gel synthesis and its electrochemical behaviour for use in Li-ion-batteries
No full textNano-sized particles of spinel LiMn2O4 and LiCrxMn2xO4 (x = Cr; 0.00–0.40) have been synthesized using phthalic acid as chelating agent for the first time by sol–gel method. When compared to solid-state synthesis method, the sol–gel route reduces heating time of synthesize and to obtain particles of uniform surface morphology. The synthesized samples were characterized through thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM images of the parent compounds show nanospherical grains of LiMn2O4 when compared to chromium-doped ones. XRD patterns of LiMn2O4 ascertain amorphous nature and for high calcined LiCrxMn2�xO4 single phase highly crystalline patterns were obtained. TEM images of the parent and chromium-doped spinel particles depict individual grain morphology with well-separated grain boundaries. LiCr0.10Mn1.90O4 excels in discharge and cycling behaviour and offer higher
columbic efficiency, when compared to un-doped LiMn2O4. Cyclic voltammograms of LiMn2O4 and LiCrxMn2�xO4 exhibit
oxidation and reduction peaks corresponding to Mn3+/Mn4+ and Cr3+/Cr4+
Efficient green luminescence in Tb3+-activated borates, A6MM0(BO3)6
No full textPhotoluminescence of several new green-emitting Tb3+-activated borates of the type Sr6MM0(BO3)6
[A = Sr; M = Gd, Y; M0 = Al, Ga, In, Sc, Y] and LaSr5MM0(BO3)6 [A = Sr, La; M = Y; M0 = Mg] with Tb3+ at
the M or M0 site has been studied and the results are presented here. All these borates are synthesized
by the solid state reactions under reducing atmospheres and are characterized by powder XRD, density,
TG/DT, particle size analysis and photoluminescence techniques. These borates are synthesizable at temperatures
below 1000 �C as evidenced by thermal studies and are found to have narrow range of particle
sizes (5–15 lm). The photoluminescence excitation spectra of these borates show a broad band at
�257 nm due to 4f–5d transition of Tb3+ ion, which also depends on Tb3+ concentration. Under excitation
with 254 nm, all these borates display high intense green emission at 542 nm due to 5D4–7F5 transition of
Tb3+ ion. The influence of ions doped at the M0-site on the luminescence of Tb3+ is also studied. The luminescence
properties of all these borates have been compared with each other and with the standard phosphor,
LaCePO4:Tb3+. The results show that these borate phosphors have several advantages over the
standard green phosphors. Thus, the group of Tb3+-activated hexaborate phosphors is an efficient alternative
to the existing commercial green phosphors for use in tri-color low pressure mercury vapor lamps
Development of coating for temperature sensing
No full textFluorescence from a phosphor coating will indicate the temperature of the substrate to which it is attached, assuming thermal equilibrium is
achieved. Synthesis of a phosphor pigment with europium as a doping element in RE2O3 (RE =Y) has been made. The synthesis is carried out by
direct combustion method. The prepared Y2O3:Eu phosphor pigment was characterized by XRD, SEM and TEM. Using the synthesized phosphor
pigment the paint has been formulated in silicone resin. The fluorescence was measured using fluorescence spectrometer and results are presented
in this pape
Bright zinc–nickel alloy deposition from alkaline non-cyanide bath
No full textZinc–nickel alloy deposition with polyvinyl alcohol and piperonal as bath additives has been
investigated. The effects of additive concentration, triethanolamine concentration and other
parametric variables on the deposit and solution properties have been studied. Polarisation
studies were carried out under different conditions to understand the effect of triethanolamine and
the brighteners on the co-deposition. Results indicated that the additives lead to bright alloy
deposition containing ,10% nickel. The deposit produced at the optimum conditions with the
additives has a nanograined structure with a c phase
A process for manufacturing activated fly ash with improved mechanical and corrosion-resistance properties
No full textIn the present invention there is provided a process for manufacturing activated fly ash from pond ash / bottom ash by physical, thermal and chemical activation, resulting in activated fly ash with improved mechanical and corrosion resistance properties. The novel process of the present invention involves physical activation, thermal activation and chemical activation of as-received un-activated pond fly ash / bottom fly ash. The performance characteristics were tested by aggressive macro cell corrosion technique. The activated fly ash system showed lowest corrosion rate, highest durability factor and lowest macro cell current under accelerated macro cell corrosion conditions. The process of the present invention particularly provides activated fly ash which is useful for making blended cement concrete with improved mechanical and corrosion resistance properties for structural applications
Electrochemical studies on cathode blends of LiMn2O4 and Li[Li1/15Ni1/5Co2/5Mn1/3O2]
No full textComposite cathodes were prepared by blending LiMn2O4 spinel and Li[Li1/15Ni1/5Co2/5Mn1/3O2] layer by
simple mixing/ball milling followed by calcination at 800 ◦C. The prepared blend materials were subjected
to XRD and charge–discharge studies. The cycling results revealed that the discharge capacity
and cycleability of LiMn2O4 can be considerably increased upon blending the material with layered
Li[Li1/15Ni1/5Co2/5Mn1/3O2]
Influence of metal cations on the inhibitive effect of polyaniline for iron in 0.5 M H2SO4
No full textPolyaniline and metal cations such as Zn2+ and Mn2+ ions have been found to inhibit corrosion of iron in sulphuric acid moderately. It has been reported that the metal cations are found to interact directly with polyaniline via protonation of imine nitrogen atom of quinoid groups of polyaniline and induce chemical and confirmational changes to polymer. Hence a study has been made on the inhibition of iron in 0.5 M H2So4 by polyaniline in the presence of Zn2+ and Mn2+ ions (1 * 10pow-3 M) by electrochemical impedance spectroscopy, linear polarization and tafel polarization methods. The inhibition efficiencies of polyaniline are found to be 40% for 10 ppm and 72% for 100 ppm. But in the presence of metal cations, the inhibition efficiencies of polyaniline are found to be increased to 80% for 10 ppm and more than 90% for 100 ppm. Higher inhibition efficiency of polyaniline in the presence of metal cation is attributed to the increased electron rich benzenoid groups absorb more effectively on iron surface and there by reduces the corrosion rate markedl
Effect of oxygenation on the structural and dielectric properties of Sr1−xCaxTiO3 with 0.20ÏxÏ0.40
No full textEffects of oxygenation on the structural and dielectric properties of Sr1−xCaxTiO3 �0.20�x�0.40�
ceramics, prepared through solid-state reaction, have been studied employing x-ray diffraction,
transmission electron microscopy, and temperature dependent dielectric permittivity measurements.
It has been found that oxygenation has drastic effects on the ceramics’ dielectric properties, but their
crystal structure remains least affected. The effect of oxygenation on the sharpening of the first order
antiferroelectric phase transition has been studied
A Novel Approach to Updating the Corrosiveness Maps of India
No full textAtmospheric corrosion behavior ofengineering materials, viz,. carbon steel. zinc. galvanized steel. and aluminium. has been studied over a period ofone year at 41 exposure sites in India using weight-loss methods. Deposition rates ofsalinity. suljUr dioxide. and climatic variables were determined. Using these data, Indian maps ofatmospheric corrosion for carbon steel. zinc. galvanized steel. and aluminum were constructed using pie charts to report results. where the diameter of the pie represents
the corrosion rate ofthe material in each area and the sizeofthepieporiions represent theeffect ofeachvariable in the atmospheric corrosion process