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  • Author or Editor: A. Rao x
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Abstract  

The equilibrium extraction behavior of Sm(III), Eu(III) and Dy(III) from aqueous NaClO4 solutions in the pH range of 4–9 at 0.1 M ionic strength into organic solutions of 1-nitroso-2-naphthol (HA) and 1,10-phenanthroline (Phen) has been studied. The equilibrium concentrations of Eu were assayed through the 344 keV photopeak of the152Eu radiotracer used. The concentrations of Sm and Dy were measured by irradiating one mL portions of the organic extract and analyzing the 104 and 108 keV photopeaks of the short-lived neutron activation products,155Sm and165mDy, respectively. Quantitative extraction of Eu with 5×10–2 M HA alone was obtained in the pH range of 6.7–7.8 with n-butanol, 7.4–8.5 with chloroform, 8.0–8.7 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.1–8.0 with methyl isobutyl ketone (MIBK). But, Eu was extracted only to a maximum of 78% and 83% in the pH range of 8.3–8.9 and 7.4–8.1 with carbon tetrachloride and xylene, respectively. The extraction of Sm and Dy were found quantitative in the pH range of 6.3–7.0 and 6.6–7.1, respectively, with 5×10–2 M HA alone in MIBK solutions. The synergistic extraction of Eu was quantitative in the pH range of 6.6–9.8 with chloroform, 7.8–8.9 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.0–9.6 with MIBK when 1×10–2 M each of HA and Phen were employed. Sm and Dy were quantitatively extracted into MIBK solutions containing 5×10–2 M each of HA and Phen in the pH range 6.0–7.5 and 6.1–7.5, respectively. The distribution ratios of these lanthanides (Ln) were determined as a function of pH, and HA and Phen concentrations. The analysis of the data suggests that these Ln are extracted as LnA3 chelates when HA alone is used. In the presence of HA and Phen, both LnA3(Phen) and LnA3(Phen)2 adducts are formed only in the MIBK system while LnA3(Phen) complexes are the predominant ones in all other solvent systems studied. The extraction constants and the adduct formation constants of these complexes have been calculated.

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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  

A method has been developed for the simultaneous preconcentration of Cd(II), Co(II), Cu(II), Hg(II), Mn(II), Th(IV), U(VI), V(IV) and Zn(II) from 500–1000 ml of water samples by coprecipitation using a combination of 1-(2-thiazolylazo)-2-naphthol, ammonium pyrrolidinedithiocarbamate and ammonium salt of N-nitroso-phenylhydroxylamine. The elemental contents have been measured by neutron activation analysis using different schemes of irradiation, decay and counting periods. Quantitative recoveries of all the above elements have been achieved between pH 6.0 and 7.2. For most of the elements, the enrichment factors are of the order of 104. The precision, expressed in terms of relative standard deviation, and accuracy of measurements are within ±5–10%. The detection limits are in the ppb range. The method has been applied to sea and drinking water samples and biological materials.

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Abstract  

The complex formation of Eu(III) by bicarbonate/carbonate ions has been studied at 0.1 M ionic strength and 25°C using synergistic solvent extraction system of 1-nitroso-2-naphthol and 1,10-phenanthroline in chloroform. Concentrations of bicarbonate (5·10–3 to 1·10–1 M) and carbonate (5·10–4 to 1·10–2 M) ions in the aqueous phase have been varied in the pH range of 8.0 to 9.1 to simulate ground and natural water compositions. Under these conditions, the following species have been identified: Eu(HCO3)2+, Eu(HCO3)2 +, Eu(CO3)+ and Eu(CO3)2 . Their conditional formation constants (log ) have been calculated as 4.77, 6.74, 6.92 and 10.42, respectively. These values suggest that the carbonate complexes of Eu(III) are highly stable.

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Abstract  

The extraction behavior of Sm(III), Eu(III) and Dy(III) with 1-nitroso-2-naphthol (HA) and trioctylphosphine oxide (TOPO) in methyl isobutyl ketone (MIBK) from aqueous NaClO4 solutions in the pH range 4–9 at 0.1M ionic strength has been studied. The equilibrium concentrations of Sm and Dy were measured using their short-lived neutron activation products,155Sm and165mDy, respectively. In the case of Eu, the concentrations were assayed through the152,154Eu radiotracer. The distribution ratios of these elements were determined as a function of pH, 1-nitroso-2-naphthol and TOPO concentrations. The extractions of Sm, Eu and Dy were found to be quantitative with MIBK solutions in the pH range 5.9–7.5, 5.6–7.5 and 5.8–7.5, respectively. Quantitative extraction of Eu was also obtained between pH 5.8 and 8.8 with chloroform solutions. The results show that these lanthanides (Ln) are extracted as LnA3 chelates with 1-nitroso-2-naphthol alone, and in the presence of TOPO as LnA3(TOPO) and LnA3(TOPO)2 adducts. The extraction constants and the adduct formation constants of these complexes have been calculated.

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Abstract  

Reactions of recoil80, 80mBr with CH2ClBr and CCl3Br have been investigated. Relative reactivities of recoil bromine atoms in binary mixtures of CH2ClBr and CCl3Br with c–C6H12, CH3OH and C6H5N/CH3/2 have been determined using the model developed by Kontis and Urch.

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Abstract  

The crystallization kinetics of amorphous Cu50Ti50 has been studied using differential scanning calorimetry (DSC) under non-isothermal conditions. The curves at different linear heating rates (2, 4, 8 and 16 K min-1) show sharp crystallization peaks. The crystallization peak shifts to higher temperatures with increasing heating rate. The Kissinger's method of analysis of the shift in the transformation peak is applied to evaluate the activation energy (E c). The KJMA formalism, which is basically developed for isothermal experiments, is also used to obtain E c and the Avrami parameter (n). The DSC data have been analysed in terms of kinetic parameters, viz. activation energy (E c), Avrami exponent (n) and frequency factor K 0 using three different theoretical models. It is observed that the activation energy values derived from KJMA approach and modified Kissinger equation agree fairly well with each other. The activation energy values obtained from normal Kissinger method, and Gao and Wang expression underestimate the activation energy.

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Abstract  

Recycling of aluminum scrap has gained interest owing to its economic and ecological benefits. Unfortunately, during the collection of scrap from a mixer of junk from various sectors it is difficult to ensure that the recycled alloy has the same chemical composition as that of already existing commercial alloys. Consequently, some of the alloying elements become trace/tramp elements in the recycled alloy. Therefore, in order to obtain high performance recycled alloys, controlling the impurity levels of the aluminum melt is of vital importance. Normally, computer aided cooling curve analysis (CA-CCA) is used to find the relationship between cooling curve parameters, melt treatments, alloy composition, and properties. In the present study, the first differential thermal analysis (DTA) approach has been used to detect and quantify impurity elements in scrap-like liquid aluminum alloys.

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