Effect of the etching time on the morphological, optical and electronic properties of silicon nanowires

ABSTRACT: Owing to their interesting electronic, mechanical, optical and transport properties, silicon nanowires (SiNWs) have attracted much attention, giving opportunities to several potential applications in nanoscale electronic, optoelectronic devices and silicon solar cells. For photovoltaic (PV) application, a superficial film of SiNWs could be used as an efficient antireflection coating (ARC). In this work, we investigate the morphological, optical and electronic properties of SiNWs fabricated at different etching time. Characterizations of the formed SiNWs films were performed using a Scanning Electron Microscope (SEM), UV-Vis-NIR spectrophotometer and Light-Beam-Induced-Current (LBIC) technique. The later technique was used to determine the effective diffusion length in SiNWs films. From LBIC investigations, we deduce that the homogeneity of the SiNWs film play a key role on the electronic properties.     

Characterization of the Tunisian phosphogypsum and its valorization in clay bricks

This study concerns the analysis of the incorporation of phosphogypsum (PG) into the fired clay bricks. In Tunisia, for several years, a set of phosphoric acid production factories have produced PG in large quantities (approximately 10 million tons per year). Currently, in Sfax (Center-East of Tunisia), the PG is stored into piles in the vicinity of the factory, by dry or wet process. The storage of PG, even though presenting a low radioactivity, causes pollution to the watertable and to the soil (due to the infiltration of acid and heavy metals). After characterization, the Tunisian PG, which plays the part of a grease-remover, was introduced into the clay bricks with different mass percentages of 0%, 5%, 15%, 25%, 30% and 40%. The study involved physical, chemical, mechanical and environmental tests on the obtained bricks.The obtained results showed that with 30% of PG incorporation, the bricks successfully satisfied the standard requirements. The increase of the percentage of PG resulted in a decrease in the mechanical strengths of these mini-bricks, but it is still higher than the standards limits. The 25% ratio of substitution appeared to be the most effective considering the performed tests.     

Hematological toxicity associated with tissue extract from poisonous fish Lagocephalus lagocephalus--influence on erythrocyte function in Wistar rats

The puffer fish Lagocephalus lagocephalus represents serious public health problems in the world. The relative toxicity of each organ (liver and flesh) was determined by the relation dose-death time "mouse bioassay." The average liver toxicity of the puffer fish was the highest when compared with flesh giving 14.32 and 10.88 MU/g, respectively. A mouse unit is the amount of toxin (extract of fish organ) that kills a 20 g male mouse in 30 min after intraperitoneal injection. One mouse unit is equivalent to 0.22 microg of TTX. For the rat bioassay tests, Wistar rats were daily i.p. injected, for 10 d, with extracts of liver (LT) or flesh (FT) (muscles + skin) of L. lagocephalus. Control rats received injection of NaCl (0.9%). During the experiment, a significant reduction in red blood cell number (RBC), hemoglobin (HGB) concentration, and hematocrit (HCT) was observed essentially after 10 d of treatment in the FT and LT-exposed groups. Consequently, treatment led to severe anemia and hemolytic action as indicated by a significant reduction in the total number of erythrocytes. In fact, our study revealed a significant increase in erythrocyte lipid peroxidation (LPO) in FT and LT groups compared with controls after experimental exposure. The flesh and liver tissue extracts also altered antioxidative enzymes activities: catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Histopathological alterations in the spleen occurred exclusively at the end of treatment. We marked also an increase in reticulo-endothelial cells, which led to remove damaged erythrocytes.     

Synthesis and structural characterization of a new yttrium phosphate:Na2.5Y0.5Mg7(PO4)6 with fillowite-type structure

A new phosphate, Na2.5Y0.5Mg7(PO4)6 was synthesized as single crystals by the flux method and as a powdered sample by the Pechini technique, and investigated by single crystal X-ray diffraction, charge distribution (CD) and 31P NMR spectroscopy. This compound crystallized in the rhombohedral space group R 3 and its equivalent hexagonal cell had the following parameters: a=1.4976(6) nm, c= 4.2599(7) nm, Z=18. The structure consisted of MgO5, MgO6, YO6, (Na,Y)O8 and NaOx (x=6, 7 and 9) polyhedra which were li...     

Studies on the recovery of aflatoxin B1 injection into frozen beef at different intervals of storage

Summary Beef stored at –18° C for 20, 25, 32, 153, and 183 days showed a diminution in the recovery of injected aflatoxin B₁. An unusual passing of aflatoxin in ether and hexane fractions of silica gel column was noted. Ether fraction contained aflatoxin B₁-like substance from stored beef samples. Probable occlusion of aflatoxin B₁ to meat constituents due to physico-chemical changes associated with muscle during storage was discussed.

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Studien über die Wiederfindungsrate von in gefrorenem Rindfleisch injizierten Aflatoxin B₁ bei verschiedenen Lagerungszeiten

Zusammenfassung Bei –18° C zeigte sich bei 20, 25, 32, 153 und 183 Tagen gelagertem Rindfleisch eine Reduzierung in der Wiederfindungsrate von injiziertem Aflatoxin B₁. Ein ungewöhnlicher Übergang des Aflatoxins in Äther- und Hexanverbindungen einer Silicium-Gel-Säule wurde festgestellt. Ätherfraktionen enthielten Aflatoxin B₁-ähnliche Substanzen aus den gelagerten Rindfleischproben. Es wird eine wahrscheinliche Komplexverbindung des Aflatoxin B₁ zu den Fleischbestandteilen diskutiert, die auf physikalisch-chemische Änderungen des Muskels während der Lagerung zurückgeführt werden.

     

Effect of Silicon Supply Methods on Durum Wheat (Triticum durum Desf.) Response to Drought Stress

Silicon - Drought is a limiting factor of durum wheat production. Silicon (Si) is known by its positives effects on plant growth and development under these conditions. Thus, the current study was...     

Synthesis and properties of hybrid alkyd–acrylic dispersions and their use in VOC-free waterborne coatings

Hybrid waterborne alkyd–acrylic dispersions with solid content of 40%, free from any surfactant and exempt of any organic solvent, were successfully synthesized by a melt co-condensation reaction between an acrylic prepolymer bearing carboxylic groups and a long-oil alkyd resin. Spontaneous emulsification of the ensuing hybrid resin was achieved by the addition of an aqueous ammonia solution that neutralized the carboxylic functions. The key role of the carboxylic groups on the stabilization process and on the storage stability of the dispersion was assessed and it was shown that the insertion of anhydride moieties within the acrylic prepolymer ensured the efficient coupling between the acrylic and the alkyd resin and prevented the phase separation. These dispersions are easy to implement and might be used to prepare high quality zero VOC coatings in terms of drying time, stability and gloss. The most stable dispersion was also used in the formulation of air-drying waterborne lacquers and their coating properties were evaluated.