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- Author or Editor: S. Patnaik x
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Abstract
An attempt js made to study the behaviour of recoil128I atoms in neutron irradiated I2O5 at ambient temperature. The initial retention is found to be 44±2%. However, a substantial increase /57±2%/ in the value is observed upon heating the sample at 473 K for 1 h prior to irradiation. A kinetic study of post-recoil thermal annealing of neutron irradiated material is also presented. Effect of pre-heat treatment results in a decrease of rate constants and saturation retention values at respective temperatures while the Eact for the overall process remains almost unaltered.
Abstract
The thermal annealing of the damage caused by /n,
/ reaction has been investigated for anhydrous copper iodate in crystalline phase. Solvent extraction and fractional precipitation methods were employed to distinguish the recoil species containing recoil iodine-128 atoms. The role of reaction intermediates have been discussed.
The effects of admixtures of potassium bromide (2.5% and 5%) on the thermal decomposition of potassium bromate were studied within the temperature range 653–683 K. The fraction decomposed(α) vs. time (t) relations revealed (i) initial gas evolution, (ii) acceleratory and (iii) decay steps. The data were analysed on the basis of the first-order law with two rate constantsk 1 andk 2,k 1 being the rate constant for the initial, slow first-order process (0.02, 0.26), andk 2 being the rate constant for the subsequent faster process, holding within the range 0.21 to 0.98. Upon increase of the concentration of added potassium bromide to 5%, the range for the slow and faster processes became 0.01 to 0.16 and 0.1 to 0.98, respectively. At a given temperature,k 1 increased with increasing bromide concentration, whereask 2 almost identical for pure potassium bromate and its mixtures (2.5% and 5% bromide).
Abstract
The oxidation of solid arsenite by bromate, chlorate and perchlorate ions has been studied at different temperatures and at a constant composition of 1
2. Arsenite is completely oxidized to arsenate. The fraction oxidized /
/ — time /t/ data are reproducible. The rate of oxidation increases with an increase in temperature. Gamma radiation has no significant effect on the temperature independence of the oxidation process of this particular composition, although delayed oxidation appears with irradiated systems. The kinetics of oxidation process follows the conventional first order. The activation energies for the oxidation of As/III/ to As/V/ are 30.5, 44.0 and 67.9 kJ mol–1, respectively, for bromate, chlorate and perchlorate systems, and for irradiated 29.8 and 67.3 kJ mol–1, respectively, for bromate and perchlorate systems.
Abstract
Solid phase oxidation of iodide ion by bromate, chlorate and perchlorate has been investigated at different temperatures. The bromate-iodide oxidation with equimolecular mixture is independent of temperature. The period of half-oxidation is limited to 5 minutes. Gamma-radiation has no significant effect on the temperature independence of the oxidation process of this particular composition, although delayed oxidation appears with irradiated mixtures. With increase of bromate, the iodide is completely oxidized and the rate is dependent on temperature. However, with chlorate and perchlorate, there is no prescription of composition for oxidation with 1
1 mixture. The reaction proceeds with an appreciable oxidation. The rate increases with the temperature and goes to completion. In the case of irradiated mixtures delayed oxidation appears. The kinetics of iodide ion oxidation follows conventional first order.
Abstract
Studies on the thermal decomposition of the acetyl acetonate complexes of transitional metal ions Cu/II/, Cr/III/, Mn/II/, Co/II/, Fe/III/, Vo/II/, Zn/II/, and Cd/II/ have been performed by thermogravimetric method. Taking the initial decomposition temperature as a measure of thermal stability, the relative order of the thermal stability of these complexes shows the following order: Zn/II/<Cd/II/< VO/II/<Fe/III/<Cr/III/<Cu/II/
Co/II/< Mn/II/. The nature of decomposition of Cu/II/ and Cr/III/ complexes is similar, a sigmoid curve exists. In other cases a long linear decomposition follows the sigmoid pattern. The linear decomposition is a function of final decomposition temperature and percentage of decomposition. The kinetics of the decomposition is analyzed according to the Coats-Redfern equation. The results are discussed on the basis of structural and other aspects leading to the decomposition.
Abstract
Copolymers of vinyl acetate and ethylene were prepared by emulsion polymerization using ammonium persulphate and sodium metabisulphite as initiators in presence of cyclohexane. Several copolymer samples were prepared by changing initial pressure of ethylene from 100 to 250 psi. The copolymer composition was determined by 1H-NMR and thermogravimetric analysis in nitrogen atmosphere.
