Preparation of M metal/alumina-pillared mica composites (M = Cu, Ni) by in situ reduction of interlayer M ions of alumina-pillared fluorine micas

Alumina-pillared fluorine micas form micropores in the interlayer region and exhibit cation exchangeability. Reduction of 3d transition metal cations (Cu²⁺ and Ni²⁺) in the interlayer regions of the cation exchanged alumina-pillared micas was attempted using ethylene glycol or diethylene glycol. The Cu²⁺-exchanged pillared mica led to the formation of a pillared mica composite containing interlayer zero-valence Cu⁰ metal clusters along with Cu⁰ metal fine particles on external surfaces of pillared mica flakes when refluxed in either ethylene glycol or diethylene glycol. Ni²⁺ cations in the interlayer region were also found to be reducible by refluxing in diethylene glycol. The zero-valence metal contained in the refluxed products occurs in three forms: M⁰ clusters in the interlayer region, elongated fine particles sandwiched between silicate layers, and submicron spherical particles on external surfaces of mica crystals. The zero-valence metal/alumina-pillared mica composites thus obtained largely retained the micropore properties of the alumina-pillared micas.     

Enhanced spontaneous emission in hydrogen-plasma-passivatedAlGaAs/GaAs vertical-cavity surface-emitting laser structures grown onSi substrate

The effect of hydrogen (H) plasma passivation on a vertical-cavity surface-emitting laser (VCSEL) structure consisting of an active layer of Al_0.3Ga_0.7As/GaAs multi-quantum-well (MQW) grown on an Si substrate is investigated by photoluminescence (PL) measurement. Significant spontaneous emission enhancement is observed at the cavity mode for the H-plasma-passivated sample. This is attributed to the increased MQW PL emission resulting from the incorporation of hydrogen atoms which passivated the electrical activity of the defects-related nonradiative deep centres and increased the minority carrier lifetime     

Effect of time and temperature on nonlinear constitutive equation in polypropylene

In order to investigate viscoelastic-plastic properties and discuss a constitutive equation at finite strains in polymer solids, uniaxial compression tests were executed at different temperatures using polypropylen (PP) rods under conditions of constant strain rate, abrupt change of strain rate, stress relaxation, creep loadings and their combination. Several viscoelastic-plastic properties which must be taken into account in the constitutive equation of PP are pointed out, and the experimental data are compared with the numerical results based on the concept of an over stress model. It is found that the model describes the stress-strain behaviours of PP well in the case where the current strain is not below the previous one.     

Epitaxial lift-off process for GaAs solar cell on Si substrate

This research has established the process to transplant GaAs solar cells from GaAs substrate to Si substrate without degrading the conversion efficiency. The conversion efficiency of GaAs solar cell bonded to Si substrate using epitaxial lift-off process is almost the same as that grown on GaAs substrate and is superior to that grown on Si substrate by heteroepitaxy.     

Properties of an n-C:P/p-Si carbon-based photovoltaic cell grown by radio frequency plasma-enhanced chemical vapor deposition at room temperature

The phosphorus-doped amorphous carbon (n-C:P) films were grown by radiofrequency (RF) power-assisted plasma-enhanced chemical vapor deposition (PECVD) at room temperature using a solid phosphorus target. The influence of phosphorus doping on the material properties of n-C:P based on the results of simultaneous characterization are reported. Moreover, solar cell properties such as series resistance, short-circuit current density, open-circuit current voltage, fill factor and conversion efficiency along with the spectral response are reported for the fabricated carbon-based n-C:P/p-Si heterojunction solar cells by standard measurement technique. The cells’ performances have been given in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination condition (100 mW/cm², 25 °C). The maximum open-circuit voltage (V_oc) and short-circuit current density (J_sc) for the cells are observed to be approximately 236 V and 7.34 mA/cm², respectively, for the n-C:P/p-Si cell grown at a lower RF power of 100 W. The highest energy conversion efficiency (η) and fill factor (FF) were found to be approximately 0.84% and 49%, respectively. We have observed that the rectifying nature of the heterojunction structures is due to the nature of n-C:P films.     

Low substrate temperature synthesis of carbon nanowalls by ultrasonic spray pyrolysis

In this paper, we report the synthesis of two-dimensional wall like carbon nanostructures (i.e. carbon nanowalls) by ultrasonic spray pyrolysis of ethanol and fullerene mixture. At higher temperature carbon nanofibers were formed on the substrate placed at the center of the reactor tube, whereas carbon nanowalls were observed on the substrate placed downstream of the tube below 100 °C. Spaces between the nanowalls changed with distance of the substrates from the furnace. Qualitative analysis of materials was performed using scanning electron microscopy, transmission electron microscopy and Raman spectroscopy.     

Comparison of Performances of Turbines for Wave Energy Conversion

The Wells turbine for a wave power generator is a self-rectifying air turbine that is available for an energy conversion in an oscillating water-air column without any rectifying valve. The objective of this paper is to compare the performances of the Wells turbines in which the profile of blade are NACA0020, NACA0015, CA9 and HSIM15-262123-1576 in the small-scale model testing. The running characteristics in the steady flow, the start and running characteristics in the sinusoidal flow and the hysteretic characteristics in the sinusoidal flow were investigated for four kinds of turbine. As a conclusion, the turbine in which the profile of blade is NACA0020 has the best performances among 4 turbines for the running and starting characteristics in the small-scale model testing.