Catalytic oxidation of naphthalene using a Pt/Al2O3 catalyst

Polycylic aromatic hydrocarbons (PAHs) are listed as carcinogenic and mutagenic priority pollutants, belonging to the environmental endocrine disrupters. Most PAHs in the environment stem from the atmospheric deposition and diesel emission. Consequently, the elimination of PAHs in the off-gases is one of the priority and emerging challenges. Catalytic oxidation has been widely used in the destruction of organic compounds due to its high efficiency (or conversion of reactants), its economic benefits and good applicability.

This study investigates the application of the catalytic oxidation using Pt/γ-Al₂O₃ catalysts to decompose PAHs and taking naphthalene (the simplest and least toxic PAH) as a target compound. It studies the relationships between conversion, operating parameters and relevant factors such as treatment temperatures, catalyst sizes and space velocities. Also, a related reaction kinetic expression is proposed to provide a simplified expression of the relevant kinetic parameters.

The results indicate that the Pt/γ-Al₂O₃ catalyst used accelerates the reaction rate of the decomposition of naphthalene and decreases the reaction temperature. A high conversion (over 95%) can be achieved at a moderate reaction temperature of 480 K and space velocity below 35,000 h⁻¹. Non-catalytic (thermal) oxidation achieves the same conversion at a temperature beyond 1000 K. The results also indicate that Rideal–Eley mechanism and Arrhenius equation can be reasonably applied to describe the data by using the pseudo-first-order reaction kinetic equation with activation energy of 149.97 kJ/mol and frequency factor equal to 3.26 × 10¹⁷ s⁻¹.     

Study of the electroluminescent properties of crystalline silicon wafers in devices based on junctions of indium-doped zinc oxide and porous silicon

In this study we obtained electroluminescent devices (ELD) based on junctions of indium doped zinc oxide (ZnO:In) and porous silicon layers (PSL). The PSL were obtained by electrochemical etching with different types and resistivities of silicon wafers. In the visible part of the electromagnetic spectrum, the porous silicon (PS) exhibits photoluminescence (PL) that is centered around 680 nm. Once the devices were obtained, they were optically and electrically characterized. The PSL were coated with ZnO:In film, which was gotten by the ultrasonic spray pyrolysis technique (USP). When the devices were electrically polarized they showed optical response in the regions corresponding to the visible and infrared band of the electromagnetic spectrum. The observed electroluminescence (EL) in the visible region goes from 400 to 750 nm and the corresponding emission of the infrared part is around 750–1150 nm. The devices presented luminescent spots on the surface which were visible to the naked eye. The analysis of the results shows that the emission source in the visible part is attributed to the filaments present in the PS, and also to the ZnO:In films and the emission in the infrared part is associated to the silicon substrate. The electrical characterization was carried out by current–voltage curves (I–V) that show in the devices a rectifying behavior.     

Band gap engineering by substitution of S by Se in nanostructured CdS1−xSex thin films grown by soft chemical route for photosensor application

Ternary alloys of CdS_1−xSe_x (x=0, x=0.2, x=0.4, x=0.6, x=0.8, x=1) thin films were prepared on to glass substrates by a simple and economical soft chemical route (chemical bath deposition) at 50° to 80 °C in air. The as-grown films were characterized by optical and electrical measurement systems, X-ray diffraction (XRD), Energy dispersive X-ray analysis (EDAX) and SEM (scanning electron microscopy). The optical study reveals shift in the absorption edge towards the higher wavelengths, i.e. the band gap decreases as a function of ‘x’ (quantity of selenium in the bath). I–V measurement of CdS (resulted when x=0), CdS_1−xSe_x (x=0.2, x=0.4, x=0.6, x=0.8) and CdSe (resulted when x=1) thin films under dark and illumination conditions (60 W) were measured. Increase in photoconductivity is observed, suggesting its applicability in photosensor devices. Electrical resistivity shows semiconducting behavior and activation energy decreases. The XRD patterns reveals that deposited thin films have hexagonal mixed structure. EDAX confirmed the compositional parameters. SEM images showed uniform deposition of the material over the entire glass substrate.     

Reduction of excessive energy in the four-noded membrane quadrilateral element. Part I: Linear theory-compressible materials

The objective of the paper is to set forth, in a consistent manner, reasons for the appearance of excessive energy in the four-noded membrane quadrilateral element and to propose a formulation leading to simple and reliable elements that are less sensitive to distortions of the geometrical shape. By presenting the differential geometry, emphasis is placed upon those geometrical attributes which are inherently related to the quadrilateral. A modified version of the functional of Hu-Washizu is employed for the discretization. Appropriate approximations for the displacements/rotations are chosen and the physical meaning of the various parameters is identified. A systematic procedure is followed for the approximation of stress and strain. The convergence of the formulation is investigated by examining the inf–sup condition and applying the patch test. Also, results of numerical examples and comparisons with other elemental formulations are presented.     

Low frequency damping properties of a NiMnTi shape memory alloy

The present study investigated the low frequency damping properties of a NiMnTi shape memory alloy (SMA) for the first time. The NiMnTi SMA had a high β?θ′ internal friction peak at approximately 125 °C and a low relaxation peak at approximately − 45 °C in the dynamic mechanical analysis cooling tan δ curve. The relaxation peak possessed an activation energy of 0.64 ± 0.03 eV and its damping capacity gradually decreased with the increase of thermal cycling. The NiMnTi SMA also had a good inherent internal friction with tan δ = 0.009 at approximately 140 °C and is a promising high damping alloy for high temperature applications.     

Influence of chemical composition on the damping characteristics of Cu–Al–Ni shape memory alloys

Cu–XAl–4Ni shape memory alloys (SMAs) are capable of martensitic transformation across a wide temperature range through the precise adjustment of their chemical composition from X = 13.0 to 14.5. In addition, the variations in chemical composition significantly influence the internal friction characteristics of Cu–XAl–4Ni SMAs. Cu–XAl–4Ni SMAs with a higher content of Al exhibit lower internal friction peaks due to decreases in the amount of transformed martensite and the formation of γ₂ phase precipitates. The damping capacity of the inherent and intrinsic internal friction for Cu–13.5Al–4Ni SMA is extremely low due to the fact that the transformed β^′₁(18R)${{\beta }^{\prime }}_1(18\text{R})$ martensite has only an ordered 9R structure with stacking faults. The Cu–14.0Al–4Ni SMA exhibits a relative increase in the inherent and intrinsic damping capacity because the transformed γ^′₁(2H)${{\gamma }^{\prime }}_1(2\text{H})$ martensite exhibits twinning with abundant moveable twin boundaries.     

Development of miniature optical fiber hybrid WDM coupler employing the FBT technology

An innovative technique for fabricating the optical fiber hybrid wavelength-division multiplexing (WDM) coupler is presented. The device is comprised of two components, a wavelength division multiplexer and an optical fiber coupler, in a miniature stainless steel tube. The outstanding features of the ultra-low polarization dependent loss (PDL) under 0.05 dB and the compact size of ∅3.5 × 65 mm for bare-fiber type of package are accomplished by using the pioneering methodology combining the main techniques of twisted and parallel fusion processes in the fused biconical taper (FBT) technology. Besides, its miniaturization is more competitive in both of the applications of optical communication and sensing systems where a compact-sized package is required for extending the flexibility of installation.     

Effect of heating temperature on the sintering characteristics of sewage sludge ash

This study investigated and analyzed the effects of the heating temperature on the properties of the sintered sewage sludge ash. The results indicated that the water absorption rate of the sintered sewage sludge ash samples decreased when the firing temperature was increased from 800 to 900 degrees C. When the heating temperature reached 1000 degrees C, the absorption rate decreased significantly. The bulk density of the sewage sludge ash samples increased by 2.3g/cm3 when the heating temperature was increased from 900 to 1000 degrees C, indicating that the densification was affected by heating. The porosity of the sintered sewage sludge ash samples ranged from 36% to 39% when the heating temperature ranged from 600 to 900 degrees C. The least porosity occurred at 1000 degrees C; the sintered samples were well densified. When the temperature was between 900 and 1000 degrees C, the strength appeared to increase significantly, reaching 2040 kgf/cm2, implying an advance in densification due to sintering. The SEM observations were in general agreement with the trends shown by the density data.     

Degradation of di-n-butyl phthalate using photoreactor packed with TiO2 immobilized on glass beads

This study evaluated the performance of a photoreactor packed with TiO2/glass, TiO2 immobilized on glass beads, initiated by UV irradiation, denoted as UV/TiO2/glass, to decompose di-n-butyl phthalate (DBP) in an aqueous solution. The photodegradation rate of DBP by this UV/TiO2/glass process was found to obey pseudo first-order kinetics represented by the Langmuir-Hinshelwood model. The experimental results of this study show that the influence of pH value of an aqueous solution to reaction rate was negligible at the pH values 4.5-9. The effect of cations on the photodegradation rate of DBP reveals that the larger the charge and size of cations contained, the more the inhibition of reaction rate increased. The UV/TiO2/glass process yielded a 75% degradation efficiency of DBP with initial concentration of 5 mg L(-1) at 80 min reaction time.