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Preparation of nanoparticles of oxides by the citrate–nitrate process

Effect of metal ions on the thermal decomposition characteristics

Journal of Thermal Analysis and Calorimetry
Authors: S. Banerjee, A. Kumar and P. Sujatha Devi

Abstract

This paper reports preparation of nanoparticles of oxides by the citrate–nitrate process and the effect of metal ions on the thermal decomposition characteristics of the corresponding citrate–nitrate gel precursors. In order to understand the effect of metal ions on the thermal decomposition characteristics of the precursors, we have prepared a series of single component oxides such as MO, where M = Zn, MO2, where M = Sn, Ce, Zr, and M2O3 where M = Al, Fe, Bi. In all the cases the citrate to nitrate ratio was fixed at 0.3. In order to ascertain the decomposition characteristics of the gel samples, TG/DTA studies were performed on the dried gel samples. After complete physico-chemical characterization of the precursors and the calcined products, it could be concluded that the nature of decomposition of the precursors depends largely on the nature of the metal ions. Finally, the advantages of the citrate–nitrate process such as its high degree of reproducibility, its potential for large-scale production of nano-crystalline ceramic oxide powders and its lower cost could be established based on a series of experiments and examples.

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A precise, sensitive and rapid analytical technique has been developed for the simultaneous determination of Zr and Hf in natural silicate matrices. The technique is based on radiochemical neutron activation analysis and employs a rapid fusion dissolution of the sample and simultaneous precipitation of the Zr−Hf pair with p-hydroxybenzene arsonic acid in an acidic medium. The indicator radionuclides,95Zr and181Hf, are counted with a pair of high resolution Ge(Li) detectors and the95Zr activity is corrected for the contribution from U fission. The chemical yields of the radiochemical separation are based on Hf carrier, which quantitatively carries both Zr and Hf. The yield is determined by reactivation of the processed samples and standards with a252Cf isotopic neutron source and by counting the 18.6 sec half-life179mHf. The sensitivity, precision and accuracy of the procedure are demonstrated by replicate analyses of several standard rocks, meteorites and lunar samples which exhibit a wide range of Zr and Hf abundances.

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Thermal decomposition of mono pyridine N-oxide complexe; of cobalt(II), nickel(II) and copper(II) propionates and mono quinoline N-oxide complex of copper(II) ben zoate has been studied by TG and DTA techniques. These dimeric complexes are stable upto 350–380 K and decompose in two stages: (i) successive elimination of the two ligand molecules (mostly endothermic); and (ii) decomposition of the resulting anhydrous metal(II) carboxylates by an exothermic multistep process in air.

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Abstract  

Flash point of a chemical characterizes its operating safety envelope. Tri-isoamyl phosphate (TiAP) is being proposed as an alternate to conventional nuclear solvent tri-n-butyl phosphate but flash point of TiAP containing organic solutions are not available in literature. Flash points of C8–C16 n-alkanes and 36% TiAP/C8–C16 n-alkane solutions were experimentally measured and correlated by means of empirical correlations. This paper is probably the first reported work in the literature on flash points of TiAP containing solutions.

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Abstract  

To achieve end user’s specified PuO2, controlling and monitoring of Pu in its fourth valency state is essential prior to the conversion of Pu-nitrate to its oxide through oxalate precipitation process. Conventional radiometric procedure for the analysis of Pu oxidation state in Pu-nitrate solution containing trace level of Pu(III) has limitation due to oxidation of Pu(III) during the sample preparation with respect to acidity. A simple direct spectrophotometry using an optic fiber spectrophotometer was attempted for the estimation of trace level of Pu(III), after separating the bulk amount of Pu(IV) by maintaining the sample acidity. By using a synergistic mixture of 30 % TBP and 1 M theonyl trifluoro acetone in benzene, the Pu(IV) could be removed to a level which doesn’t interfere in the Pu(III) absorption.

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Abstract  

During nuclear fuel reprocessing, monitoring of U and Pu concentration in every stage is very essential for process control purpose. A simple and fast spectrophotometric method for a simultaneous estimation of U and Pu in Plutonium Uranium Recovery by Extraction (PUREX) process’s tail end stream like Pu product where Pu concentration is much richer than that of U is described here. The method involves reduction of the bulk amount of Pu to Pu(III) using ascorbic acid in 1 M HNO3. Visible absorption peaks were measured at 416 nm for U and at 600 nm for Pu using a fiber optic probe of path length 40 mm. The methodology enables quantification of U and Pu concentration in the Pu product samples with a precision of 2.8 and 2.1%, respectively.

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An investigation to standardize the protocol for in vitro application of colchicine for enhancing the doubled haploid production in wheat was done. Two tetraploid (PDW-314 and A-9-30-1); and two hexaploid (DH-40 and C-306) wheat genotypes were used as maternal parents, whereas, the pollen sources involved Zea mays (cv. Bajaura Makka) and Imperata cylindrica. During the rabi seasons of years 2013–14 and 2014–15, wheat × maize and wheat × I. cylindrica hybridization was carried out followed by treatment of their haploids produced as a result of elimination of chromosomes of maize and I. cylindrica respectively, with varied doses of colchicine for different durations The various doses of colchicine were categorized into two groups: lower doses for longer durations (0.01, 0.025, 0.05% each for 5, 7, 9, 11 hrs) and higher doses for shorter durations (0.05, 0.075, 0.10, 0.15, 0.20, 0.25% each for 5, 4, 3, 2 hrs). The response of different concentrations of colchicine applied for varied durations revealed significant differences for various doubled haploidy parameters viz., per cent survived plants, per cent doubled haploid formation and per cent doubled haploid seed formation. In hexaploid and tetraploid wheats, colchicine doses of 0.075% for 4 hrs and 0.15% for 4 hrs, respectively were established as optimum for enhanced doubled haploid production.

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Twenty-four promising drought tolerant genotypes of IRRI and different parts of India were evaluated for genetic variability and drought susceptibility index (DSI) for 12 quality characters and grain yield under irrigated (E1) and drought (E2) conditions. In the present study differences among the genotypes are highly significant for all the characters; between the environments head rice recovery, alkali spreading value, water uptake, kernel length after cooking and yield were significant, while genotype × environment interaction was only significant for hulling, milling, head rice recovery and water uptake. Head rice recovery, alkali spreading value, water uptake and amylose content were observed to be governed by additive gene action under both the environments. Grain yield was positively correlated with kernel width and amylose content under stress environment while, kernel width was positively correlated with hulling and milling and kernel length was correlated with amylose content. The path coefficient analysis revealed that only kernel width in both the environments and amylose content in E2 had positive direct effect on yield. Most of the genotypes expressed low DSI value (<1) for yield and quality characters. However, Swarna and IR 78877-181-B-1-2 were identified as stable genotypes with low DSI value for seed yield and quality characters.

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Genotype by environment interaction distorts genetic analysis, changes relative ranking of genotypes and a major obstruction for varietal release. AMMI model is a quick and relevant tool to judge environmental behaviour and genotypic stability in comparison to ANOVA, multiplicative model and linear regressions. We evaluated 19 barley genotypes grown at 08 diverse locations to identify discriminating environments and ideal genotypes with dynamic stability. In AMMI ANOVA, the locations and genotype by environment interaction exhibited 66% and 14.7% of the total variation. The initial first two principal components showed significant interaction with 36.0 and 28.4% variation, respectively. AMMI1 biplot showed that the environments Bawal, Ludhiana and Durgapura were high yielding with high IPCA1 scores and located far away from the biplot origin. However, in AMMI1and AMMI2 biplots the locations Hisar, Ludhiana, Karnal, Bathinda and Modipuram were found suitable with low IPCA2 scores. Yield stability index (YSI) was highly useful with ASV ranks and the genotypes DWRB150 and BH1013 and checks BH902, DWRUB52 and DWRB101 were selected for high grain yield and wider adaptability across the locations.

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Actinomycetes, especially species of Streptomyces are prolific producers of pharmacologically significant compounds accounting for about 70% of the naturally derived antibiotics that are presently in clinical use. In this study, we used five solvents to extract the secondary metabolites from marine Streptomyces parvulus DOSMB-D105, which was isolated from the mangrove sediments of the South Andaman Islands. Among them, ethyl acetate crude extract showed maximum activity against 11 pathogenic bacteria and six fungi. Presence of bioactive compounds in the ethyl acetate extract was determined using GC-MS and the compounds detected in the ethyl acetate extract were matched with the National Institute of Standards and Technology (NIST) library. Totally eight compounds were identified and the prevalent compounds were 2 steroids, 2 alkaloids, 2 plasticizers, 1 phenolic and 1 alkane. Present study revealed that S. parvulus DOSMB-D105 is a promising species for the isolation of valuable bioactive compounds to combat pathogenic microbes.

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