The role of Al and Mg in the hydrogen storage of electrospun ZnO nanofibers

Pure and doped ZnO nanofibers with Al and Mg were successfully synthesized via an electrospinning method using a sol–gel containing Polyvinylpyrrolidone as a spinning aid and a zinc nitrate precursor. Calcination of the doped and undoped electrospun nanofibers was conducted at 500 °C in air, and the resultant structures were analyzed by X-ray diffraction (XRD) and Raman spectroscopy. The diameter of the doped nanofibers decreased with increasing viscosity and conductivity, as measured by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive spectroscopy (EDS) showed that Mg and Al are present in ZnO nanofibers. The pressure composition isotherm (PCI) demonstrated that the capacity of hydrogen storage in pure zinc oxide nanofibers is a factor of two greater than that of zinc oxide nanoparticles. However, Al-doped ZnO nanofibers have the highest capacity of hydrogen storage (2.81 wt%) at room temperature.     

Tuning the conditions for the deposition of nanocrystalline diamond by hot filament chemical vapour deposition

Although large focus has been placed into the deposition of nanocrystalline and ultra-nanocrystalline diamond films, most of this research uses microwave plasma assisted CVD systems. However, the growth conditions used in microwave systems cannot be directly used in hot-filament CVD systems. This paper, aims to enlarge the knowledge of the diamond film depositing process. H2/CH4/Ar gas mixtures have been used to deposit micro, nano and ultra-nanocrystalline diamond films by hot-filament CVD systems. Additionally, the distance between the filaments array and the substrate was varied, in order to observe its effect and consequently the effect of a lower substrate temperature in the nucleation density and deposition. All the samples were characterized for microstructure and quality, using scanning electron microscopy and Raman spectroscopy.     

Pore structure and effective diffusion coefficient of catalyzed electrodes in polymer electrolyte membrane fuel cells

For polymer electrolyte membrane (PEM) fuel cells, the pore structure and small effective diffusion coefficient (EDC) of the catalyst layers have significant impact on the cell performance. In this study, both the pore structure and EDC of the catalyst layers are investigated experimentally; the pore structure of the catalyst layer is characterized by the method of standard porosimetry, and the EDC is measured by a modified Loschmidt cell for oxygen-nitrogen mixture through the catalyzed electrodes. It is found that Pt loading has a direct impact on the pore structure and consequently the EDC of the catalyzed electrodes. As the Pt loading is increased, the porosity and mean pore size of the catalyzed electrode decrease, and the EDC decreases accordingly, however, it is increased by 15–25% by increasing the temperature from 25 °C to 75 °C. The EDC of the catalyst layer is about 4.6 × 10^?7 m² s^?1 at 75 °C, compared with 25.0 × 10^?7 m² s^?1 for the uncatalyzed electrode at the same temperature.     

Textile with immobilised nano titanium dioxide for repeated discoloration of CI Reactive Black 5 under UV‐A

A commercially available catalyst with high photocatalytic activity (Degussa p‐25) was immobilised on a comparatively inexpensive substrate that included cotton/polyester knitted fabric by citric acid under sonication. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy analysis revealed the presence of nano titanium dioxide on the surface of the fabric. Discoloration of CI Reactive Black 5 in aqueous solution was successfully carried out by adding a piece of nano titanium dioxide‐treated fabric into the dye solution under UV‐A irradiation. The ultraviolet–visible spectra indicated complete discoloration of CI Reactive Black 5 dye solutions. CI Reactive Black 5 solution, along with electrolytes including sodium sulphate and calcium carbonate, was also successfully discoloured with lower efficiency. Further, the photocatalytic properties of the nano titanium dioxide‐immobilised fabric did not change after dye solution discoloration and it was used several times for discoloration of the same solutions. The proposed system can be developed on a large scale.     

Thermal stability,aging properties,and flame resistance of NR‐based nanocomposite

Polymer/clay nanocomposites have some unique properties due to combination of flame resistance and improved mechanical and thermal stability properties which are important to enhance the material quality and performance. The objective of this work was to investigate the effect of organically modified montmorillonite (org‐MMT) on the thermal and flame retardant as well as hardness and mechanical properties of the nanocomposites based on the natural rubber (NR). It was shown that by the addition of 3 wt % of org‐MMT to NR, its aging hardness rise was decreased more than 55% and the ignition time was delayed about 150%. The reduction in heat release rate peak value was equal to 54% compared to the pristine NR. Addition of org‐MMT improved the thermal stability of the NR. Furthermore, nanocomposites which were calendared before curing showed much more thermal stability and fire resistance than those which contained similar amount of organoclay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dynamic Modeling and a Parametric Study of an Indirect Solar Cabinet Dryer

A dynamic mathematical model for drying of agricultural products in an indirect cabinet solar dryer is presented. This model describes the heat and mass transfer in the drying chamber and also considers the heat transfer and temperature distribution in a solar collector under transient conditions. For this purpose, using conservation laws of heat and mass transfer and considering the physical phenomena occurring in a solar dryer, the governing equations are derived and solved numerically. The model solution provides an effective tool to study the variation of temperature and humidity of the drying air, drying material temperature, and its moisture content on each tray. The predicted results are compared with available experimental data. It is shown that the model can predict the performance of the cabinet solar dryer in unsteady-state operating conditions well. Furthermore, the effect of some operating parameters on the performance and efficiency of dryer is investigated and compared with selected published data.     

Investigating the effects of chemical composition of motor oils on their viscosity indices using gas chromatography and chemometrics techniques

Abstract

In this study, we focused on combination of gas chromatography and chemometrics techniques for relating the viscosity indices (VI) of motor oils to their chemical compositions. Partial least square (PLS) algorithm was used for relating the retention times of the collected chromatograms to VI of motor oils. The constructed model showed acceptable statistical values which indicate the robustness of the developed PLS model. GC-MS analysis was used for identification of the important chemicals affecting the values of VIs. Nonane, Pentafluoropropionic acid, Phthalic acid, nonylphenol and Tetracosane were suggested to have positive impacts on the values of VIs of motor oils.     

Retraction Note: Prediction of aggregate modified index (AMI) using geomechanical properties of limestones

Bulletin of Engineering Geology and the Environment -     

Loofa immobilized Bacillus sp. DSM 2523 as a whole cell biocatalyst for production of cyclodextrin glucanotransferase in an airlift reactor with a net draft tube

Cyclodextrin glucanotransferase (CGTase) production was studied using loofa-immobilized Bacillus sp. DSM 2523 and starch substrate. The bacterial cells from 2- and 4-day old cultures were used in the flask studies. Loofa and chitosan were added for cell immobilization and cell flocculation, respectively, and different treatments were considered according to the timing of their addition. The cell responses were evaluated for their degree of cell immobilization and level of CGTase activity. With the use of the selected treatment, testing was carried out in an airlift reactor with a net draft tube having specific geometric properties. The cell capacity for reusability also was examined. The production of CGTase was higher in the second cycle in the reactor operated at 0.25 vvm where the enzyme activity reaching 0.20?U/ml within 2?h. In the flask experiments, CGTase activity reached 0.23?U/ml after 19?h in the second cycle.