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In recent years, antimony sulfide (Sb2S3) has been investigated as a photovoltaic absorber material due to its suitable absorber coefficient, direct band gap, extinction coefficient, earth-abundant, and environmentally friendly constituents. Therefore, this work proposes Sb2S3 film preparation by an effective two-step process using a new graphite box design and sulfur distribution, which has a high repeatability level and can be scalable. First, an Sb thin film was deposited using the RF-Sputtering technique, and after that, the samples were annealed with elemental sulfur into a graphite box, varying the sulfurization time from 20 to 50 min. The structural, optical, morphological, and chemical characteristics of the resulting thin films were analyzed. Results reveal the method's effectivity and the best properties were obtained for the sample sulfurized during 40 min. This Sb2S3 thin film presents an orthorhombic crystalline structure, elongated grains, a band gap of 1.69 eV, a crystallite size of 15.25 Å, and a nearly stoichiometric composition. In addition, the formation of a p-n junction was achieved by depositing silver back contact on the Glass/FTO/CdS/Sb2S3 structure. Therefore, the graphite box design has been demonstrated to be functional to obtain Sb2S3 by a two-step process. [ABSTRACT FROM AUTHOR]

The development and testing of protective coatings against corrosion for magnesium is reported. The coatings were based on the MgOx-TiOx composite and for their fabrication the reactive RF-sputtering technique in the co-deposition mode was employed. MgOx-TiOx coatings with chemical composition ranging from pure Mg oxides to pure Ti oxides, including its mixture, were obtained through the variation of the rate of the sputtering powers applied to the Mg and Ti targets. Characterization (XRD and XPS) showed changes in the crystalline structure according to the rate of the sputtering powers and confirmed the presence of MgO2, MgO, Ti2O3 and TiO2 in different proportions. Electrochemical polarization measurements (Tafel) made by employing the Hank's solution showed that both Vcorr and Icorr depend on the chemical composition of the coatings, having better corrosion resistance when the content of Ti oxides is higher. Results showed that corrosion resistance of Mg could be modulated by changing the chemical composition of the MgOx-TiOx coatings. [ABSTRACT FROM AUTHOR]

This article presents the results of the synthesis and morphological characterization of carbon nanostructures obtained from the decomposition of residual solid from waste tires (RSWT) in quartz tubes under reduced pressure (1.33 Pa) at 900°C for 15 min. The synthesis led to the formation of two phases, a fragmented solid black powder composed of multi-walled carbon nanotubes (MWCNTs), onion-type fullerenes, and spheres, and a very bright metallic dark film. Analysis by microscopy (SEM and TEM) showed that the MWCNTs had an average diameter of approximately 25 nm and a length greater than 100 nm while the diameter of the onion-type fullerenes was found to be 8 nm. The nanospheres showed different diameters ranging from 500 nm to 1.5 μm, and some had a metallic core surrounded by layers of carbon. The infrared spectra of the nanotubes exhibited absorption bands at 1558 and 1458 cm−1, corresponding to CC and CC bonds, and signals at 3438 and 1080 cm−1 related to the OH and CO groups from oxidized graphite as it was identified in the dark film. The Raman spectra of the carbon nanostructures present D and G-bands at 1331 and 1597 cm−1, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

A novel, green route for pre-exfoliation of graphite based on a biodegradable polymer and high-power ultrasound is presented. Candelilla wax (CW), derived from the leaves of the candelilla plant, has been used for the first time as a natural non aqueous medium to induce the pre-exfoliation of expanded graphite (EG) under ultrasonic irradiation in an economical way. The proposed method uses also D-limonene as a natural organic solvent for reducing viscosity and increasing the affinity between the polar groups of EG and candelilla wax, thus improving the intercalation/exfoliation of EG. The quality of dispersion of the nanofiller in the natural wax matrix has been evaluated using multiple techniques. The addition of EG to wax and use of ultrasonic treatment leads to a reduced crystallinity, probably due to restrictions of the molecular movements, improved thermal stability of wax, and to an increased shear thinning exponent, which are all indicative of a high degree of EG dispersion. The ultrasonic dynamic mechanical results suggest a reduction in the cluster size and a better filler dispersion in the wax matrix promoted by polar or chemical reactions between the CW fractions and the graphite stacks, which was observed by XPS analysis. The results were compared to those obtained with paraffin, a synthetic wax, and confirmed the dispersion improvement obtained by using natural wax as a pre-exfoliating medium. [ABSTRACT FROM AUTHOR]