Correlating the solubility of supercritical gases in high‐molecular weight substances using a density‐dependent equation

Chrastil (1982) established that the solubility of a substance in a supercritical fluid can be correlated with the density of the pure supercritical gas. Recently, the solubility of supercritical fluids in different organic liquids was successfully correlated as a function solely of the supercritical fluid density, since we demonstrated that the supercritical fluid density also defines the solubility of the gas in the liquid phase. In this work, the solubility of supercritical carbon dioxide in high‐molecular weight substances, such as high‐molecular weight paraffins, alcohols, fatty acids, fatty acid methyl and ethyl esters, has been correlated and constants provided. More than 20 binary systems comprising around 1000 solubility data points were correlated, obtaining regression coefficients greater than 0.96 and confirming the goodness of the density‐dependent equation previously reported. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Preparation of poly(vinylidene fluoride)/phosphotungstic acid composite nanofiber membranes by electrospinning for proton conductivity

A composite nanofiber containing poly(vinylidene fluoride) (PVDF) and phosphotungstic acid (PWA) is prepared by electrospinning of their mixtures. The nanofibers are characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction spectroscopy (XRD). The spun nanofibers are in the β phase of PVDF and are bead-free in structure. Membranes prepared from the nanofibers can be used as a proton conductivity membrane for fuel cell applications.     

Thermal stability of polyfuran/pechlorate doped films

Thermogravimetry, Fourier transform infrarred spectroscopy and scanning electron microscopy were performed on polyfuran films to assess thermal stability. The influence of temperature on the structure and morphology of doped polyfuran conducting films was discussed. Thermal degradation began around 95°C, although aromaticity, structure and ordered nodular morphology in the growth face and the honeycomb appearance in the cross-section were partially conserved until about 210°C. Received: 9 June 1999/Accepted: 26 July 1999     

Characterization of the insulation and leakage currents of PV generators: Relevance for human safety

Protection against electric shock in photovoltaic generators (PVGs) with active protective measures requires an in-depth knowledge of the electrical behaviour of PVG insulation and PVG response under operating conditions with insulation faults. On the one hand, this knowledge can be obtained with an equivalent circuit model that characterises this insulation. The model presented can be used to: (i) evaluate PVG insulation resistance and leakage current; (ii) analyse potential hazards for the general public; (iii) design the best means of protection. On the other hand, this article also describes the insulation of a functioning PVG, and its reaction to meteorological variables (MVs) in laboratory and field conditions. Test results highlight those MVs that have a greater influence on PVG insulation as well as the relation between weather and insulation. This type of characterization is crucial when it comes to testing the operating capacity of the protective devices used in active protective measures against electric shock under different meteorological conditions.     

High dosage thermoluminescence diamond dosimeters

Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of ⁹⁰Sr beta particles. The diamond thin films have been synthesized from commercial Tequila as a precursor using Pulsed Liquid Injection by the Chemical Vapor Deposition (PLICVD) technique reported recently. Thermoluminescence (TL) phenomena at these doses exhibit peak curve shift to higher temperatures (from 370 to 440 K) in the glow curve and the integrated TL curve show a linear behavior. Therefore, it has been considered that diamond thin films could be used as high doses dosimeters.     

SBE type cobalt-aluminophosphates (Co/Al ~ 1): synthesis aging effect,detemplation mechanism from coupled TGA/FTIR analyses,and structural stability after detemplation

Cobalt-rich SBE-type aluminophosphate (AlPO) microporous solids were prepared by employing different aging periods during the hydrothermal synthesis. According to XRD, SEM, and porosimetry tests, aging for 168 h results in a material with good long-range framework and textural features. The latter were analyzed after careful removal of the structure-directing agent (SDA) or detemplation, which produced a micropore surface area of ca. 600 m²/g, the highest ever reported for an AlPO having a multi-dimensional pore system and the highest cobalt-to-aluminum framework ratio. Coupled TGA/FTIR was employed in an attempt to elucidate the SDA decomposition mechanism in both inert and oxidative environments. Careful analysis confirmed that the latter case results in encapsulation of some of the detemplation species due to structural collapsing. Finally, the structural stability of detemplated material was evaluated in the presence of humidity and ambient air. The results indicate that the framework cobalt appear to readily oxidize upon adsorption of di-oxygen at ambient conditions, leading to an irreversible collapsing of the structure. However, the detemplated microporous solid appears to be stable in the presence of moist inert atmospheres.     

Metastability of heavy lanthanides in the ZnO wurtzite structure

The introduction and stability of the heavy lanthanide Er, into ZnO was studied by HRTEM, XRD and thermal treatments. The applied synthesis route allows introducing the Er atoms in the lattice in a metastable state. The stability depends on the Er concentration. ZnO with Er concentrations of less than 2% are stable up to 800 °C, while higher concentrations result in a phase segregation at T > 700 °C. Unit cell parameters obtained from the Rietveld refinement of XRD patterns provide a conclusive evidence of the incorporation of the Er ions in the host ZnO matrix.