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Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | Hosni F.,Center National des science et Technology Nucleaires | Mejri A.,Center National des science et Technology Nucleaires | And 3 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2014

Samples of a commercial silicate glass have been subjected to ion exchange at 320 C in a molten mixture of AgNO3 and NaNO3 with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1-250 kGy and heating at the temperature of 550 C for different time periods ranging from 10 to 582 min. The spectral absorption in UV-Vis range of the Ag-Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy. © 2014 Elsevier B.V. All rights reserved. Source

Hosni F.,Center National des science et Technology Nucleaires | Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | Mejri A.,Center National des science et Technology Nucleaires | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2012

The present paper reports the results of the study on the effect of the fractionation dose on the response of Red-Perspex dosimeter. Several experiments were carried out by combining the two factors: number of fractionation and storage time between fractions. Dosimeters were irradiated by gamma-rays to total doses of 10 and 40 kGy. These doses were delivered as single fraction, as well as in five fractions separated by different intervals of time: 1, 24 h and stored at 10 or 40 °C between successive irradiation. Three batches of Red-Perspex dosimeters (KS, GB, and EB) were used in this study. The relative specific response of dosimeters indicates a marked dependence of the number of fractionation and storage time. It was found that response variations due to dose fractionation can reach 18% in particular at high storage time and high temperatures. The dose fractionation effect has been found to be dependent of the batches. The obtained results allowed us to determine the necessary corrections for estimating doses with high accuracy. Source

Abdel Wahed M.S.M.,Lappeenranta University of Technology | Abdel Wahed M.S.M.,Beni Suef University | Mohamed E.A.,Beni Suef University | El-Sayed M.I.,Beni Suef University | And 2 more authors.
Journal of African Earth Sciences | Year: 2014

Lake Qarun is an inland closed saline lake. It lies within the Fayoum Depression in the Western Desert of Egypt. Evaporation modeling has been carried out using PHREEQC to simulate the geochemical evolution of surface drainage waters inflow towards lake water. In the case of Lake Qarun, it is the first attempt to carry out such kind of modeling. Performance of this model helped to address the different sources of dissolved major ions to Lake Qarun and to identify the mechanisms control the lake's water chemistry. The model demonstrated that evaporation-crystallization process is the main mechanism controlling the evolution of lake water chemistry where major ions Na+, Mg2+, Cl- and SO4 2- have been built up in the lake by evaporation while Ca2+ and HCO3 - are depleted by calcite precipitation. Moreover, the simulated model reproduced the real data observed in Lake Qarun except in the case of SO4 2- which is in real more enriched in the lake than the model output. The additional source of SO4 2- is reported to be from groundwater. The models result agreed well with the modified evolutionary Hardie and Eugster's scheme (1970) in which the final major composition of Lake Qarun water is Na-Mg-SO4-Cl type. In future, the monitoring of Lake Qarun chemistry with detection of any other sources of elements and/or local reactions inside the lake can be detected by performing the simulated evaporation model reported by the present study. © 2014 Elsevier Ltd. Source

Hamzaoui H.,Center National Of Recherche En Science Des Materiaux
EPJ Applied Physics | Year: 2010

The present paper reports the study of a porous silicon based microcavity for a potential chemical sensing application using tris-(8-hydroxyquinoline) aluminum (Alq3) molecules. Porous silicon based planar microcavity was first designed and fabricated using the electrochemical etching technique. Photoluminescence emission of a single porous silicon layer after immersion in an Alq3 solution was first carried out in order to verify that the Alq3 molecules were bound to the porous surface. A wide green band centered at 519 nm, typical of a nano-structured Alq3 film, was observed. Reflectivity measurements of the porous silicon microcavity were then performed for different aluminum concentrations of the Alq3 solution. The microcavity device showed a good sensibility for the Alq3 molecules and an important shift of the microcavity photonic resonance was observed. This device might be considered for a potential aluminiun sensing application. © 2010 EDP Sciences. Source

Hellali T.,University of Tunis | Hafidh A.,University of Tunis | Touati F.,Institute National Of Recherche Et Danalyse Physico Chimique Inrap | Hamzaoui A.H.,Center National Of Recherche En Science Des Materiaux
Phosphorus, Sulfur and Silicon and the Related Elements | Year: 2016

New hybrid organic–inorganic baterials have been obtained by the reaction of tetraethylorthosilicate (TEOS) with bi-functional heterocyclic molecules in ethanol using HCl as a catalyst at room temperature. This reaction has led to the formation of colored and transparent gels. The characterization of xerogels has been carried by infrared, 29Si and 13C CP MAS-NMR, DTA–TGA, scanning electron microscopy, Brunauer–Emmet–Teller method (BET), and DRX. The obtained results show that organic molecules react with TEOS leading to gels, in which Si–N, Si–O, and Si–S bridges are formed. According to N2-physisorption results, isotherms seem to have a similar sit, and classified as type IV according to the International Union of Pure and Applied Chemistry, synthesized X1, X2, and X4 are mesoporous solids but X3 is microporous. The BET surface area of these materials is important. It varied from 47 to 302 m2g−1. The optic and magnetic properties of hybrids are also studied by Ultraviolet–visible spectroscopy and résonance para-électronique. The obtained results show that all materials are semiconductors, and X2, X3, and X4 are paramagnetic but X1 is diamagnetic. © 2016 Taylor & Francis Group, LLC Source

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