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Abstract  

The thermal decompositions of cobalt(II), nickel(II) and copper(II) complexes of4-(3'-sulfonylazido-6'-methoxyphenylazo)-1-phenyl-3-methyl-2-pyrazolin-5-one H(D1–SO2N3) and 4-(4'-sulfonylazido phenylazo)-3-phenyl-3-methyl-2-pyrazolin-5-one H(D2–SO2N3) were studied by thermogravimetry. The decomposition in all cases takes place along two stages. The first stage is due to the elimination of water and nitrogen molecules with the formation of tetracoordinate complexes containing nitrene reactive species[M(DSO2N:)2]. The second stage represents the decomposition of the material to the metal oxide. The kinetics of the decomposition were examined by using Coats–Redfern, the decomposition in all complexes was found to be first order for the first and second stages. The activation energies and other activation parameters ( H * and S * and G *) were computed and related to the bonding and stereochemistry of the complexes.

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Abstract  

The stability constants of UO 2 2+ -squarate complexes are measured at ionic strengths of 0.05M, 0.06M, 0.075M, 0.09M, 0.1M (squaric acid-perchloric acid) using a solvent extraction method at a pH of 1.1 and a temperature of 25 °C. The extractant used is dinonylnaphthalenesulfonic acid in n-heptane. The aqueous phase was made of a mixture of squaric and perchloric acid and233U radio tracer. The stability constants of squarate complexes of UO 2 2+ is seen to decrease linearly with the square root of the ionic strength.

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Abstract  

Extraction of Eu3+ from 0.1M aqueous perchlorate medium by thenoyltrifluoroacetone (HTTA) and by mixtures of HTTA and tributylphosphate (TBP), HTTA and triphenylphosphine oxide (TPPO), HTTA and trioctylphosphine oxide (TOPO) and HTTA and triphenylarsine oxide (TPAsO) has been studied at various temperatures allowing for the elucidation of the mechanism of extraction in each case and a comparison between the various bases.

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Abstract  

The radiochemical separation of 88Y from proton irradiated natSrCO3 and alpha-particle irradiated natRbCl, of 86Y from proton irradiated 86SrCO3, and of 87Y from alpha-particle irradiated natRbCl were studied at no-carrier-added levels by two techniques, namely, ion-exchange chromatography using Dowex 50W-X8 and Dowex 21K resins, and solvent extraction using HDEHP. Out of all those methods, the ion-exchange chromatography using Dowex 50W-X8 (cation-exchanger) was found to be the best: the separation yield was high, the chemical impurity in the separated radioyttrium (inactive Sr or Rb) was low (0.5 μg) and the final product was obtained in the form of citrate. The optimized separation method using Dowex 50W-X8 was applied in practical production of 86Y and 88Y via proton irradiations of 86SrCO3 and natSrCO3, respectively, at 16 MeV as well as of 87Y and 88Y via α-particle irradiation of natRbCl at 26 MeV. The tangible experimental yields of 86Y and 87Y amounted to 150 and 5.7 MBq/μA·h, respectively. The yields of 88Y obtained were 0.06 MBq/μA·h and 1 MBq/μA·h for alpha-particle and proton irradiations, respectively. Each yield value corresponds to more than 70% of the respective theoretical value.

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Abstract  

The adsorption behaviors of no-carrier-added radioiodine and a bulk of tellurium on the anion-exchange resin in different media, namely, hydrochloric acid and sodium hydroxide solution were studied. The effect of shaking time on the uptake percentage of the no-carrier-added radioiodine was carried out using the batch technique in both 7 M HCl and 8 M NaOH. In column experiments for the separation of radioiodine from Te-bulk, different liquid phases such as, 2 M NaOH, 70 % methanol, a mixture of ethyl acetate to ethanol (1:1 v/v) and 5 mM tetra-butyl ammonium bromide in ethyl acetate without and with few drops of 0.01 M sodium metabisulfite were employed as eluants. Not only this, the bed depth of the resin was also taken into consideration. Different weights of Amberlyst A-27 correspond to different bed depths (3, 4, 5, 6 cm) were employed. Under the optimum conditions the overall radiochemical yield for the separated radioiodine was 90 % and recovery of Te-bulk was 98 %.

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Abstract  

The radiochemical separation of no-carrier-added cerium from proton irradiated lanthanum was studied by solvent extraction using DEE, TBP and TPPO, the latter reagent being employed for the first time for separation of radiocerium from bulk of lanthanum. Distribution coefficients of cerium and lanthanum were investigated as a function of equilibrium time and concentration of HNO3. A mixture of 0.05M K2Cr2O7 and 0.1M H2SO4 was used as an oxidizing agent to improve the separation efficiency of cerium. A comparative study of the three extractants released that DEE is the best for separation of cerium from bulk of lanthanum oxide. The target was prepared by pressing. The production of 139Ce of high radionuclidic purity and chemical purity via irradiation of lanthanum oxide target at MGC-20 cyclotron with protons of energy 14.5 MeV is described. The experimental yield was found to be 153 kBq/μA·h.

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Abstract  

Thermal analysis, DTA, TG, TMA and DSC were performed on LiKSO4 in the temperature range 300 to 800 K, using a Heraeus TA 500 thermal analyser. The thermal expansion coefficients measured along the three fundamental crystallogrpahic axes, together with the specific heatC p, show anomalous behaviour around the phase transition temperature of these crystals atT c=705 K. Anisotropy in the thermal expansion coefficient as well as endothermic peaks aroundT c were also observed, while no loss of weight was detected. The temperature-dependence of the thermal conductivity of LiKSO4 crystals has been estimated, using the temperature-variation of the thermal diffusivity.

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Abstract  

The adsorption behaviour of La/Ce system on Dowex 50W-X8 in different media, namely, nitric acid, acetate buffer and citrate buffer was studied as a function of the concentration of nitric acid and buffer pH. In addition, in cation-exchange column chromatography experiments, three different eluants, namely, citrate buffer of pH 5.5, 0.1 M EDTA and 0.2 M α-HIBA, were employed for separation of Ce(III) from La(III). The optimum conditions for improvement of radiochemical separation of no-carrier-added 139Ce from proton irradiated lanthanum were applied using the most suitable chelating agent 0.2 M α-HIBA. The purification of 139Ce from macro amount of La(III) was done using two columns in a sequence. The target was prepared by pressing. The production of high radionuclidic and chemical purity 139Ce via irradiation of lanthanum oxide target at MGC-20 cyclotron of proton energy 14.5 MeV was described. The experimental yield was found to be 200 kBq/μA h.

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Thermomechanical analysis, TMA, was used to evaluate the linear thermal expansion coefficient,α, of four different types of dental amalgams: Conventional lathe-cut alloy, conventional spheralloy, high copper dispersalloy and high copper ternary alloy. Dynamic thermal expansion studies showed an interesting contraction behaviour around 85 °C for conventional amalgams and 105 °C for high copper amalgams which coincided with the endotherms produced by differential scanning calorimetry, DSC, and was attributed to the existence of theγ 2 andγ 1 phases, respectively. Pure single phases were prepared and characterized by DSC at 210 °C forγ 2 and 120 °C forγ 1. When theγ 2 was enriched with mercury, the decomposition endotherm showed gradual shift to lower temperatures and reached 85 °C. The value of the linear coefficient of thermal expansion ranged between 15 and 35 ppm/°C for all the investigated brands.

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Journal of Thermal Analysis and Calorimetry
Authors: M. El-Hadary, A. Kamar, A. El-Kady, S. Kandil, M. El-Gamal, and S. Morsi
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