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  • Author or Editor: H. El-Boohy x
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Abstract  

Preparation of membranes of poly-(tetrafluoroethylene-perfluorovinylether (TFA) and poly-tetrafluoroethylene-polyethylene (ET) films grafted with 4-vinylpyridine using γ-rays has been carried out. The appropriate reaction conditions were selected. Furthermore, quaternization of the pyridine of the grafted chains was conducted. The effect of monomer concentration on the rate of grafting was also investigated. The order of the grafting rate gram per hour depending on monomer concentration was found to be 0.94 and 1.0 for TFA and ET films, respectively. Some selected properties of the grafted films such as swelling behavior, dimensional stability, mechanical and electrical properties were investigated. The grafted film of TFA and ET showed a marked decrease in elongation with a significant increase in the tensile strength.

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Abstract  

NiO-doped Co3O4 samples precalcined at 500 °C were subjected to various doses of -rays within the range 0.2-1.6 MGy. The particle size and BET-surface areas of different samples were determined using XRD and nitrogen adsorption at -196 °C. The catalytic reactions studied were conversion of ethanol and isopropanol at 250-400 °C using a micropulse technique and H2O2 decomposition in aqueous solution at 30-50 °C. The results revealed that the -irradiation brought a significant decrease in the particle size of Co3O4 phase with subsequent increase in the SBET surface areas. The treatment brought also a progressive decrease in the total conversion of both alcohol (dehydration and dehydrogenation) falling to a minimum value (about 20% of its initial activity) at a dose of 0.8 MGy. The catalysts retain their initial activity upon exposure to a dose of 1.6 MGy. On the other hand, the catalytic activity in H2O2 decomposition of the investigated system decreased progressively by increasing the dose of -rays and the catalysts lost more than 90% of their initial activity upon exposure to a dose of 1.6 MGy.

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Abstract  

Manganese oxide samples obtained from thermal decomposition of manganese carbonate at 400 and 600 °C were subjected to different doses of g-irradiation within the range 0.2 to 1.6 MGy. The surface and catalytic properties of the above samples were studied using nitrogen adsorption isotherms measured at -196 °C and catalytic conversion of ethanol and isopropanol at 300-400 °C using micropulse technique. The results obtained revealed that manganese oxides obtained at 400 °C consisted of a mixture of Mn2O3 and MnO2 while the samples calcined at 600 °C composed entirely of Mn2O3. Gamma-irradiation resulted in a decrease in the particle size of manganese oxide phases with subsequent increase in their specific surface areas. Gamma-irradiation with 0.2 and 0.8 MGy effected a measurable progressive decrease in the catalytic activity in dehydration and dehydrogenation of both alcohols. However, the treated catalyst retained their initial activity upon exposure to a dose of 1.6 MGy. Also, g-irradiation increased the selectivities of the investigated solids towards dehydrogenation of both alcohols. The catalyst samples precalcined at 600 °C exhibited higher catalytic activities than those precalcined at 400 °C.

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Abstract  

The effect of γ-irradiation on surface and catalytic properties of CuO/Al2O3, NiO/Al2O3 and Fe2O3/Al2O3 was investigated. The techniques employed were XRD, nitrogen adsorption at −196 °C and catalytic conversion of ethanol and isopropanol at 250–400 °C using micropulse technique. The results showed that the supported solids being calcined at 400 °C consisted of well crystallized CuO, NiO, Fe2O3 and AlOOH phases. The AlOOH crystallized into a poorly crystalline γ-Al2O3 upon heating at 600 °C. All phases present in different solids calcined at 400 and 600 °C showed that these solids are of nanocrystalline nature measuring an average crystallite size between 6 and 85 nm. The crystallite size of crystalline phases present was found to be much affected by the dose of γ-rays and the nature of the metal oxide. This treatment resulted in a progressive increase in the specific surface area reaching to a maximum limit at a dose of 0.8 MGy. The dose of 1.6 MGy exerted a measurable decrease in the S BET. A radiation dose of 0.2 to 0.8 MGy brought about a progressive significant decrease in the catalytic activity of all the catalytic systems investigated. All the catalytic systems retained their high activity upon exposure to a dose of 1.6 MGy. The rise in precalcination temperature of the systems investigated from 400 to 600 °C brought about a measurable increase in their catalytic activity in the conversion of alcohols.

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