Mustapha Haddad

Electronic and ionic conductivity of glasses inside the Li2O–MoO3–P2O5 system

Abstract A wide range of coloured electronic or mixed electronic–ionic glasses has been shown in the alkali oxide poor-region of the Li 2 O–MoO 3 –P 2 O 5 system, next to the colourless ionic glasses located in the alkali oxide rich-region. These coloured glasses have been studied by electron paramagnetic resonance (EPR) spectroscopy. The Mo 5+ and Mo 6+ cation percentages have been evaluated for several series of glasses corresponding to either a fixed Li 2 O rate or a constant Mo/P ratio. The electronic and the ionic contributions to the total conductivity of these glasses have been determined. The existence of a polaronic hopping conduction mechanism between Mo 5+ and Mo 6+ cations is suggested in the purely electronic conductor glasses. An ion–polaron soft coupling is proposed in the ionic–electronic conductor glasses.

Electrical properties of glasses in the Na2O–MoO3–P2O5 system

Abstract A range of coloured electronic or mixed ionic–electronic glasses has been evidenced in the Na 2 O–MoO 3 –P 2 O 5 system. The properties of these glasses have been studied along different composition lines corresponding either to a fixed Na 2 O content or a constant Mo/P ratio. An EPR spectroscopy investigation of these glasses has allowed to determine the Mo 5+ ion percentages in these materials. The electrical properties of these glasses have been studied by impedance spectroscopy, and the electronic and ionic contributions have been evaluated. The properties of these sodium glasses have been compared with those of lithium glasses with the same compositions.

EPR and Magnetic Susceptibility of Na2O–CuO–P2O5 Glasses

Abstract (50−x/2)Na2O–xCuO–(50−x/2)P2O5 glasses (x=1, 5, 15, or 30 mol%) have been prepared and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The shape of the Cu2+ EPR spectrum depends on the Cu content, and the corresponding computer simulations suggest that the Cu2+ ions occupy two different sites in these glasses: one of them is preponderant at low Cu content and the other is preponderant at high content, in which the Cu2+–Cu2+ interactions are more important. From EPR parameters, it was found that for the site at low content, the covalency of copper ion bonding with the surrounding ligands is appreciable. The magnetic susceptibility data appear to follow the Curie–Weiss law (χ=C/(T−θp)) with negative paramagnetic Curie temperature θp indicating antiferromagnetic interactions between Cu2+ ions that are more significant in the samples with high Cu content, in agreement with EPR results.

Photophysics of Genistein isoflavone: Solvent and concentration effects studied by UV–visible spectroscopy and theoretical simulation

Genistein isoflavone is shown to exist in two different conformations which are the 90 degrees completely twisted geometry and the 50 degrees less twisted one. Specific interactions with the solvent cage as well as self-association processes seem shifting the isoflavone from the perpendicular conformation towards the less twisted one. The theoretical simulation, using analytical atom-atom pair potential, predicts a self-dimer in a slipped non-sandwich, face to river, perpendicular structure. From the UV-visible photophysics investigations it is revealed that monomeric species cannot exist alone even at very low solute concentration (approximately 10(-6) M), the self-association process occurs already in this concentration range.

PIXE ANALYSIS OF MOROCCAN ARCHITECTURAL GLAZED CERAMICS OF 14TH-18TH CENTURIES

The PIXE analysis of glazes and ceramic bodies of a set of architectural glazed ceramics (mostly the zellige mosaics), sampled from seven Moroccan monuments from the 14th to the 18th century AD, has been performed. We have identified high lead glazes, opacified with tin-oxide, laid over a calciferous body to produce hard tiles easy to chisel as required by the zellige technique. The analysis has revealed significant differences between the monuments examined: in particular in the formulation of the base glass and in the use of stains to produce coloured glazes. We observed the peculiarity of materials used in Marrakech and we could distinguish, both in terms of glazes and ceramic bodies, the two almost contemporary Madersas dedicated to the sultan Bou Inan, one in Meknes the other in Fez. The PIXE measurements integrate a broad range of spectrometric investigations performed in the past few years.

Zelliges from Dar‐El Beïda Palace in Meknes (Morocco): Optical Absorption and Raman Spectrometry

Abstract Samples of zelliges, from the Dar‐El Beïda Palace built in Meknes (Morocco) in the 18th century, were studied by optical absorption and Raman spectroscopies. The results obtained by the two techniques were in agreement and show that the glazes of the zelliges are lead oxide–rich in composition. Other phases were also detected, mainly the SnO2 cassiterite opacifier for the white glaze, and heamatite (α‐Fe2O3) in association with magnetite Fe3O4 and manganese oxide (MnO2) for the brown glaze. For the blue and green glazes, the elements responsible for the coloring are cobalt (Co2+) and copper (Cu2+), respectively.

On-site XRF characterization of archaeological materials in CERA center of Rissani (Morocco)

Different glazed ceramics and glass artifacts, coming from the excavations of the Sijilmassa site and exhibited in CERA (center for Alaouite studies and research) in Rissani (Morocco), were analysed by portable X-ray fluorescence spectrometry. All glazed ceramics are lead glaze and their ceramic bodies are calcareous clay. Glass objects are different nature: lead-glass, lead-lime-alkaline and potassium-lime glass. Classical elements were used to colour glaze and glass: tin for white, cobalt ore for blue, copper for green, manganese and iron for black and iron for yellow.