Effect of ZnO layer thickness upon optoelectrical properties of NiO/ ZnO heterojunction prepared at room temperature

In this work, p-NiO/n-ZnO heterostructures were successfully prepared at room temperature using RF sputtering technique. The influence of ZnO layer thickness on the performance of the heterojunction was investigated. The deposited ZnO layers have a hexagonal Wurtzite structure with preferable growth orientations along (002) and (103) for thinner films. Increasing the thickness results in more crystallographic orientation randomness. The current–voltage measurements of the realized heterojunctions showed a clear rectifying behavior. The measured ideality factor varies from 2.5 to 1.6 according to the thickness of ZnO layer. The series resistance of the device is enlarged with increasing ZnO thickness. The deduced parameters from the I–V characteristics suggest that 200 nm is the optimal thickness of the ZnO layer according to our experimental conditions. We attribute the relatively better performance of this thickness to achieving reasonable compensation between serial resistance and ideality factor. The best heterojunction was tested and successfully used as a UV detector.     

The effects of regeneration-phase CO and/or H2 amount on the performance of a NOX storage/reduction catalyst

The effects of regeneration-phase CO and/or H₂, and their amounts as a function of temperature on the trapping and reduction of NO_X over a model and a commercial NO_X storage/reduction catalyst have been evaluated. Overall, for both catalysts, their NO_X removal performance improved with each incremental increase in H₂ concentration. For the commercial sample, using CO at 200 °C, beyond a small amount added, was found to decrease performance. The addition of H₂ to the CO-containing mixtures resulted in improved performance at 200 °C, but the presence of the CO still resulted in decreased performance in comparison to activity when just H₂ was used. With the model sample, the presence of CO resulted in very poor performance at 200 °C, even with H₂. The data suggest that CO poisons Pt sites, including Pt-catalyzed nitrate decomposition. At 300 °C, H₂, CO, and mixtures of the two were comparable for trapping and reduction of NO_X, although with the model sample H₂ did prove consistently better. With the commercial sample, H₂ and CO were again comparable at 500 °C, but mixtures of the two led to slightly improved performance, while yet again H₂ and H₂-containing mixtures proved better than CO when testing the model sample. NH₃ formation was observed under most test conditions used. At 200 °C, NH₃ formation increased with each increase in H₂, while at 500 °C, the amount of NH₃ formed when using the mixtures was higher than that when using either H₂ or CO. This coincides with the improved performance observed with the mixtures when testing the commercial.     

Correction to: Influence of Incorporation of Gallium Oxide Nanoparticles on the Structural and Optical Properties of Polyvinyl Alcohol Polymer

Journal of Inorganic and Organometallic Polymers and Materials -     

Kinetic analysis and modelling of thermal degradation of perspex (PMMA) and perspex blend plastic waste

The thermal decomposition of pure perspex and a mixture of 50% perspex and 50% poly(ethylene terephthalate; PET) was carried out between 295 and 325°C using a thermogravimetric analyser (TGA) in air and nitrogen (N₂) atmosphere. The weight losses of decomposition products were measured during these experiments. The thermal degradation process is slower in inert atmosphere than air, where oxidation reaction expedites the decomposition process. Kinetic rate constants (k), pre‐exponential factor (A) and activation energy (E) for both pure prespex and a blend of perspex/PET were calculated for both air and N₂ conditions. The thermal degradation process followed a third‐order reaction in air and second‐order in N₂. A second‐order (n = 2) model for the pyrolytic process based on simultaneous reactions was developed using experimental data for pure and blend. The pyrolytic products are gases, liquids, waxes, aromatics and char, which can be ultimately used as raw material and fuel in various applications. It is important to note that the addition of PET to perspex was found to suppress/inhibit the decomposition of perspex compared with pure perspex. Pre‐exponential factor (A) and activation energy (E) values support such an observation. © 2012 Canadian Society for Chemical Engineering     

Physiological and molecular study on the anti-obesity effects of pineapple (Ananas comosus) juice in male Wistar rat

Food Science and Biotechnology - The present study was performed to assess anti-obesity effects of raw pineapple juice in high fat diet (HFD)-induced fatness. Based on food type, rats were divided...     

Investigating the Effect of NO Versus NO2 on the Performance of a Model NO X Storage/Reduction Catalyst

The effects of using NO or NO₂ as the NO _X source on the performance of a NO _X storage/reduction catalyst were investigated from 200 to 500 °C. The evaluation included comparison with constant cycling times and trapping the same amount of NO _X during the lean phase. With NO₂ as the NO _X source, better trapping and reduction performance was attained in comparison to NO, at all operating temperatures except 300 °C. This exception, under the conditions tested, was likely due to high NO oxidation activity and rapid trapping of NO₂, although it is expected that extending the trapping time would lead to consistent differences. Several reasons for the observed improvements at 200, 400 and 500 °C with NO₂ relative to NO are discussed. One that can explain the data, for both trapping and release improvement, is treating the monolith as an integral reactor. With NO₂, more NO _X is trapped at the very inlet of the catalyst, whereas with NO, the maximum in trapping during cycling occurs slightly downstream. Thus more of the catalyst can be used for trapping with NO₂ as the NO _X source. The decreased release during catalyst regeneration is similarly explained; with more being released at the very inlet, there is more residence time and therefore contact with downstream Pt sites, but more importantly more interaction between reductant and stored NO _X . NH₃ and N₂O measurements support this conclusion.     

Competitive no,co and hydrocarbon oxidation reactions over a diesel oxidation catalyst

The oxidation of NO, CO and hydrocarbons (HC) individually, in mixtures, and with NO₂ were investigated over a monolith‐supported Pt/Al₂O₃ catalyst under oxidising conditions. Although competitive adsorption and inhibition by other species on oxidation reactions is a relatively well‐known phenomenon, this study represents a more comprehensive examination of such effects between key components in vehicle exhaust gases. NO₂ was completely reduced by CO and C₃H₆, under NO₂ limited conditions, at temperatures as low as 110°C and at temperatures above 140°C with dodecane and m‐xylene. NO₂ was then again observed once the extent of oxidation of the other species by oxygen was significant. Under the conditions tested, NO, CO and HC oxidation was inhibited by NO₂ in the feed gas mixture. HC were also found to inhibit the oxidation of NO and other HC species due to site adsorption competition. For CO, HC did not change the onset of oxidation, but did inhibit the extent after their light off began. At low temperatures, CO was initially found to inhibit NO oxidation, but at higher temperatures, once CO oxidation was significant, CO promoted NO conversion to NO₂. The observed inhibition effects of the different gases on HC oxidation were not additive, indicating one species would cause inhibition, but once its inhibition ended, another species could still then cause inhibition. The combined effect of C₃H₆, NO and NO₂ on CO conversion was found to be additive. This is because CO oxidation started prior C₃H₆. © 2011 Canadian Society for Chemical Engineering     

Influence of Incorporation of Gallium Oxide Nanoparticles on the Structural and Optical Properties of Polyvinyl Alcohol Polymer

In the present work, gallium oxide nanoparticles (nGa₂O₃) are synthesized via the thermal microwave combustion method, while nanocomposites of polyvinyl alcohol (PVA) polymer with various concentrations (0, 1, 2, 3, 4, and 5 wt%) of nGa₂O₃ are prepared by the casting technique. The structural characterization of nGa₂O₃, PVA, and films of PVA-Ga₂O₃ nanocomposites are studied using X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), and Fourier-transform infrared (FTIR) spectroscopy. The HRTEM and XRD examinations showed that the prepared nGa₂O₃ has an average crystallite size of?~?5.6 nm and particle size of?~?0.9 µm. The FTIR analysis reveals the occurrence of some interactions between nGa₂O₃ and the functional groups of the PVA structure. On another side, the refractive index, absorption coefficient, and optical bandgap (E_g) were determined using the Wemple-DiDomenico single oscillator model. It was shown that E_g slightly reduced from 3.61 to 3.55 eV with increasing the Ga₂O₃ content to 3 wt%, while raised again up to 3.58 eV for 5 wt% Ga₂O₃. Other optical characteristics such as the optical density, extinction coefficient, optical susceptibility, thermal emissivity, optical sheet resistance for the PVA?Ga₂O₃ nanocomposites are investigated. The linear and nonlinear optical parameters together with their dependencies on the doping ratio reveals the qualification of PVA?Ga₂O₃ nanocomposites for nonlinear optical applications.