Characterization of β-In2−xAlxS3 thin films prepared by chemical spray pyrolysis technique

Indium sulfide (In₂S₃) is a good window or buffer layer for photovoltaic application. In this work, β-In_2?xAl_xS₃ thin films with different thicknesses (400, 442, 646 and 714 nm) are successfully synthesized on heated glass substrates using a chemical spray pyrolysis technique. The thin film thickness effect on the structural, optical and photoluminescence (PL) properties of β-In_2?xAl_xS₃ material is studied. The X-ray diffraction patterns suggest the formation of β-In₂S₃ cubic phase preferentially oriented towards (400) direction. The level of the residual dislocation seems to be reduced to 3.12 × 10⁹ lines mm^?2 for the optimum thickness (646 nm) for which the β-In_2?xAl_xS₃ film crystallinity is the best one. In order to enhance the electrical properties, β-In_2?xAl_xS₃ layers are annealed in air at 400 °C for different annealing times (15, 30 and 45 min). The minimum resistivity, maximum Hall mobility and carrier concentration are found for β-In_2?xAl_xS₃ films annealed for 30 min. All samples have high transmittance of about 75 % but the wide band gap (E_g = 3.32 eV) is obtained for this optimum thickness. This result indicates good optical quality of β-In_2?xAl_xS₃ layers. Defects-related PL properties are also discussed.     

X-Ray Diffraction and Mössbauer Studies of Nanostructured Ni40Fe60 Powder: Structure Defects and Hyperfine Structure

Journal of Superconductivity and Novel Magnetism - A nanostructured nickel–iron alloy having the Ni40Fe60 composition was prepared through the mechanical alloying of the elemental powders in...     

Characterization of nanocrystalline Al-based alloy produced by mechanical milling followed by cold-pressing consolidation

In the present study high energy mechanical milling followed by high-pressing consolidation has been used to obtain bulk nanocrystalline aluminum based alloy. Fully dense disks with homogenous microstructure were obtained. X-ray analysis indicates that high strain imposed by mechanical milling and severe plastic deformation (SPD) processing causes microstructure showing a mixture of a significant lower value of the crystallite size (around 60 nm) and the creation of a large number of linear defects which induces microstrains (around 0.7%). In addition, the elevated value of hardness which was obtained for the consolidated disks and the favorable comparison with the value measured for the same as-received alloy confirm the potential of the SPD technique when it is collected with high energy mechanical milling for producing higher performance materials. On the basis of calorimetric measurements, as a function of consolidation stresses, we can say that the thermal behaviour was characterized by a significant heat release and grain growth during the heating cycle. Moreover, the noticed broad endothermic peak can be attributed to some precipitants containing magnesium.     

Isolation and characterization of a mesophilic heavy-metals-tolerant sulfate-reducing bacterium Desulfomicrobium sp. from an enrichment culture using phosphogypsum as a sulfate source

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1-20g/L phosphogypsum to sulfide with reduction of sulfate contained in 2g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125ppm Zn and 100ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC(50) values, was Cu, Te>Cd>Fe, Co, Mn>F, Se>Ni, Al, Li>Zn.     

Effect of insoluble materials on the volumetric behavior of rock salt

This paper focuses on the presence of nodules of insoluble materials within salt specimens,and their effect on the volumetric strain measurements and the dilatancy phenomenon.We analyzed experimental results of over 120 conventional triaxial compression tests,and found that in 20%of the cases,the volumetric strain measurements were atypical.We also noted that the natural variability of the specimens can lead to a non-negligible data scattering in the volumetric strain measurements when different specimens are subjected to the same test.This is expected given the small magnitude of those strains,but it occasionally implies that the corresponding specimens are not representative of the volumetric behavior of the studied rock.In order to understand these results,we numerically investigated salt specimens modeled as halite matrices with inclusions of impurities.Simulations of triaxial compression tests on these structures proved that such heterogeneities can induce dilatancy,and their presence can lead to the appearance of tensile zones which is physically translated into a micro-cracking activity.The modeling approach is validated as the patterns displayed in the numerical results are identical to that in the laboratory.It was then employed to explain the observed irregularities in experimental results.We studied the natural variability effect as well and proposed a methodology to overcome the issue of specimen representativity from both deviatoric and volumetric perspectives.     

Catalytic wet air oxidation of olive oil mill effluents: 4. Treatment and detoxification of real effluents

Olive oil mill wastewater (OMW) generated by the olive oil extraction industry constitutes a major pollutant, posing severe environmental threats. It contains a high organic load and phytotoxic and antibacterial phenolic compounds which resist biological degradation. Platinum and ruthenium supported titania or zirconia were studied in the catalytic wet air oxidation (CWAO) of OMWs in a batch reactor and in a continuous trickle-bed reactor. CWAO experiments at 190 °C and 70 bar total air pressure confirmed the effective elimination of the TOC (total organic carbon) and of the phenolic content of actual diluted OMW. Simultaneously, toxicity towards Vibrio fischeri was reduced and a decrease in phytotoxicity occurred. The ruthenium catalysts were found stable over a long period of operation in a trickle-bed reactor.The biodegradability of the oxidized waste has been enhanced and this study also examined the feasibility of coupling CWAO and an anaerobic digestion treatment. The pretreatment of the OMW in the presence of a ruthenium catalyst reduced considerably the total phenolic contents of the wastewater, and produced an effluent suitable to be treated by anaerobic treatment with increased biomethane production compared to the untreated effluent.     

Screening of Fe–BEA catalysts for wet hydrogen peroxide oxidation of crude olive mill wastewater under mild conditions

A series of Fe–BEA catalysts, differing in the amount of iron have been characterized by XRD, BET surface area, UV–vis spectroscopy and chemical analysis. The zeolite samples have been tested as heterogeneous catalysts for the wet hydrogen peroxide oxidation of crude olive mill wastewaters (OMW) under very mild conditions (at 28 °C and atmospheric pressure). All experiments were performed on a laboratory scale set-up.BSE-1/3 catalyst with a moderate Fe content (Fe/Al = 1.19) showed the best results in terms of catalytic activity and loss of active species into the aqueous solutions. The stability of Fe species has been shown to be strongly dependent on the Fe environment into the zeolite framework.Over the selected catalyst, application of catalytic procedure on diluted OMW solution permitted high removal efficiencies of pollutants. The process produces a removal capacity of 28% of total organic carbon (TOC), 40% of total phenols, 30% of chemical oxygen demand (COD) and 59% of colour, just after 12 h. 5-Day biochemical oxygen demand (BOD₅), and toxicity towards the bioluminescent bacteria Vibrio fischeri were selected to follow the performance of this process in terms of reducing the ecotoxicity of OMW. Results showed an increase in the biodegradability of the treated sample and a decrease of the microtoxicity from 100% to 70% load towards V. fischeri.Occurrence of small catalyst deactivation by carbonaeous during the oxidation reaction was observed through scanning electron microscopy (SEM) and elemental analysis.