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Abstract  

Hybrid materials were prepared by γ-irradiation of a mixture of polydimethylsiloxane (PDMS), with tetraethylorthosilicate (TEOS) and zirconium propoxide (PrZr), using a 60Co γ source, without any addition of solvents. Thermogravimetry, differential scanning calorimetry and X-ray diffraction measurements showed that the obtained hybrids are amorphous materials of the nanocomposite type. The results highlighted the different influence of each of the metallic alkoxides on the hybrid structure. The material rupture temperature, associated with the degradation of the organic component, depends mainly on the TEOS content, whereas the inorganic component structural stability depends on the relative PrZr content in the alkoxides mixture.

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Abstract  

The dried blends containing sodium and ammonium salts of lignite humic acids (humates, 0.5–10% w/w) in polyvinyl alcohol (PVA) were exposed to high dosage of γ-irradiation in the range of doses 127–806 kGy. Resulted products were then tested for their stability using thermogravimetrical analysis. As a reference the non-treated blends were used since the pure PVA exposed to γ-irradiation very quickly lost its stability and resulting consistence did not allow the stability tests. Stabilities showed a strong concentration and counterion dependency. While sodium counterion caused mostly destabilization with increasing dose, the ammonium counterion acted in an opposite way. The tests carried out in a moisturizing container revealed the changes in water absorbing capacity of irradiated samples and allowed partial explanation of humate stabilizing effect. Generally, at lower concentration of a humate the increase was observed with an increase in the γ-irradiation dose and vice versa. The results confirmed the antioxidant and stabilizing effect of humic acids added to some synthetic polymers and their applicability in materials exposed to γ-irradiation.

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Abstract  

Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected toγ-irradiation up to a final dose of 20 MGy. The effects of the γ-irradiation were examined by X-ray powder diffraction, laser Raman spectroscopy, differential scanning calorimetry and microelectrophoretic measurements. It was found that γ-irradiation had no influence on the behaviour of zirconium hydroxide during calcination and subsequent cooling. The results of microelectrophoretic measurements showed that γ-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium hydroxide precipitated at pH 2 proved to be the most susceptible to γ-irradiation, while the sameγ-irradiation had very little (if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After γ-irradiation, the electrophoretic mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase in its adsorption capacity. The analogy observed between the pH-dependence of the effects of γ-irradiation on the electrokinetic behaviour of zirconium hydroxide and the influence of ball-milling on the thermal behaviour of zirconium hydroxide [8] suggested that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH.

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Abstract  

Irradiation of α-Al2O3 (Corundum) was carried out in contact with acidic media and with different doses (100-to-2500 kGy) and dose-rates (0.9, 2.6 and 6.1 kGy·h−1) of γ-rays. Simultaneously parallel experiments were carried out using the same procedure, but preheated at 150°C for two days and then irradiated without acidic media. The solid thus obtained was used to determine the effect of γ-irradiation on the sorption capacities of microamounts of fission products from strongly alkaline aqueous solutions of uranium. The results revealed that the effect of γ-irradiation of α-Al2O3 and the acidic media in which it is immersed, is associated with a stable matrix resistant to significant changes in the composition of the surface layer; whilst it seems that the effect of γ-irradiation of preheated α-Al2O3, is connected with changes of surface-OH groups strongly affected by heat treatment and irradiation dose.

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Abstract  

Effects induced by γ -irradiation in the dose range of 0-10 Mrad on Tuffak polycarbonate track detector films have been studied by thermogravimetry (TG). The samples were irradiated with 60Co γ -rays for doses of 3, 5 and 10 Mrad. The TG studies indicate that unirradiated and the γ -irradiated samples degrade in two steps. The kinetics of the two steps of degradation was also evaluated from the TG curves. Irradiation enhances the degradation rate and the effect increases further with increasing radiation dose. The activation energy values calculated for all the steps decrease on irradiation. A linear relationship observed between the decrease in activation energy and the dose received by the sample suggests the possibility of the use of Tuffak polycarbonate detector as γ dosimeter.

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Abstract  

Intermediates stabilized in γ-irradiated mono-and dibenzosubstituted crown ethers are studied by ESR spectroscopy at 77 K. PhO radicals and radicals with H-atom abstraction from polyether ring are the main products at low temperature γ-radiolysis. The nature of radicals produced in radiolysis and the yield of radicals,G R depend on macroring size and on the number of aromatic substiuents. Negative deviation from additive in function ofG R versus ε of substituents is an evidence of efficient transfer of adsorbed energy to the π-system of aromatic group.

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Abstract  

The crystallization kinetics of the γ-irradiated and the unirradiated glass Ag7I4VO4 was studied dynamically by means of DTA, and isothermally via electrical conductivity measurements. The influence of doping with alkali metal ions (Li+, Na+, K+, Rb+ or Cs+) on the crystallization process in the glass was also investigated. The results showed that the rate of crystallization depends on the nature of the added metal ion and on the crystallization growth mechanism. The latter is a two-dimensional process for both the pure and the alkali metal-doped glasses. The effects of irradiation and additive ions on the crystallization process are discussed.

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Abstract  

The behavior of triazines upon -irradiation from a60Co source has been studied. The triazines selected were: atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], ametryne [2-ethylamino-4-(isopropylamino)-6-(methylthio)-s-triazine] and simazine [2-chloro-4,6-bis(ethylamino)-s-triazine]. The irradiation doses varied from 5.0 to 640.0 kGy, with a dose rate of 3 kGy h–1. Following irradiation, the samples were analyzed by gas chromatography with flame ionization (FID) detection. The triazines remained stable after the irradiation process.

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Abstract  

The thermal decomposition of -irradiated cadmium bromate was studied by dynamic thermogravimetry. The reaction order, activation energy, frequency factor and entropy of activation were computed using the Coats-Redfern method and were compared with those of the unirradiated salt. Irradiation enhances the decomposition and the effect increases with irradiation dose. The activation energy decreases on irradiation. The mechanism for the decomposition of unirradiated and irradiated cadmium bromate follows the Avrami model equation, 1-/1-/1/3=kt, and the ratecontrolling process is a phase-boundary reaction assuming spherical symmetry.

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Abstract  

Solvoluminescence /SL/ of -irradiated LiCl crystals have been studied in some organic solvents. The SL emission spectra of LiCl crystals were recorded in N-methyl acetamide, nitrobenzene, cyclohexanol, cyclohexanone and pure water. The total SL intensity of LiCl in various organic solvents was found to vary with the type and nature of the solvent. The results are explained on the basis of the electron-scavenging effect and complexing abilities of the solvents.

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