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  • Author or Editor: V. Rao x
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Abstract  

Catalysis of mixed oxide LaMnO3 was studied for the decomposition of hydrogen peroxide (H2O2). The catalyst was -irradiated in open petri dishes, vacuum, dry oxygen and moist oxygen. LaMnO3 irradiated in moist oxygen showed highest catalytic activity. X-ray photoelectron spectroscopic (XPS) studies were carried out to investigate the surface modifications occurred during -irradiaiton of LaMnO3. No significant change in the surface was noticed in LaMnO3 irradiated in vacuum and dry oxygen. However, LaMnO3 irradiated in moist oxygen and in open petri dishes showed the reduction of transition metal (MN3+ to Mn2+) which in turn leads to the formation of chemisorbed superoxide ions (O 2 ) and surface carbonate species (CO 3 2– ). The latter processes decreases the electrical conductivity by trapping the charge carriers. The hydrated electron generated by the radiolysis of moisture reduces the transition metal. A qualitative molecular orbital model has been proposed for the chemisorption of O 2 on the reduced transition metal centers (Mn2+).

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Abstract  

A method has been proposed for the determination of hydrogen sulphide and sulphur dioxide in a mixture. The method is based upon the quantitative oxidation of sulphide and sulphite with an excess of radiochloramine-T in alkaline medium /0.1N NaOH/. The released chloride activity is proportional to the total amount of sulphide and sulphite present. Addition of 1% CdSO4 solution to the mixture of sulphide and sulphite precipitates sulphide, and sulphite in the filtrate determined by the reagent. From the difference in activities, the amount of sulphide can be calculated. This method can be employed for the determination of hydrogen sulphide and sulphur dioxide in air samples.

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Abstract  

Electronspin resonance (ESR) studies of -irradiated LaNiO3 revealed the formation of chemisorbed superoxide ion (O 2 ) and F centers (electrons trapped in anion vacancies). X-ray photoelectron spectroscopy (XPS) showed that the -irradiation of LaNiO3 in the presence of moisture leads to the reduction of the transition metal (Ni3+ to Ni2+) which in turn facilitates the formation of O 2 and surface carbonate species (CO 3 2– ). A qualitative molecular orbital model has been proposed for the chemisorption of O 2 on the reduced transition metal centers (Ni2+). The hydrated electron generated by the radiolysis of moisture reduces the transition metal. Gamma-irradiated LaNiO3 shows enhanced catalytic activity for the decomposition of hydrogen peroxide (H2O2) and the increase in catalytic activity is attributed to the reduced metal content. The formation of chemisorbed oxygen decreases the electrical conductivity by trapping the charge carriers.

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Abstract  

Solvent extraction of65zinc,60cobalt and152+154europium from aqueous buffers into benzene containing 4-thiobenzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (SBMPP) has been investigated in detail (μ=0.1, T=26±1°C). The species extracted and the values of log Kex, where Kex refers to the extraction equilibrium, are ZnL2 (−2.68) CoL2(−3.08) and EuL3(−7.08), where L is the anion of the ligand. The sulfur analog appears to be more effective than the parent ligand 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one in the extraction of zinc(II) and cobalt(II), whereas the reverse is true with europium(III).

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Abstract  

Phase transformation studies carried out on Mn−Al−C permanent magnet alloy employing DSC and electrical resistivity measurements, are reported and discussed. The transformation of the hexagonal Mn−Al phase (disordered and non-magnetic) to the ferromagnetic fct phase proceeds via the formation, in at least two stages, of the ordered orthorhombic phase. The activation energy for the formation of the fct phase is ≈34.65 kcal/mol. Microstructural changes occurring at various stages of the transformation are also studied.

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Abstract  

The thermal behavior of chitosan (CS)/natural rubber latex (NRL) blends has been studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). Decomposition behavior of CS changes with the addition of NRL. The effect of blend composition on the amount of residue remaining at various temperatures has been studied. Activation energies of degradation have been calculated using Horowitz-Metzger equation. From the activation energy values, it is found that among the series of the blend compositions, CS15NRL85 exhibits better thermal stability. DSC studies reveals that the CS/NRL blends are thermodynamically incompatible. This is evident from the presence of two glass transitions, corresponding to CS and NRL phases in the blend.

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