Journal of Interface, Thin Film and Low Dimension Systems
Volume:3 Issue: 2, Winter-Spring 2020

Nowadays, exploitation and production of maximum energy from the solar spectrum is a major concern. In the present paper, a numerical study of a new hybrid system consisting of a parabolic trough concentrator coupled with a cylindrical thermoelectric generator is performed using the Gauss-Seidel iterative method. A realistic climatic condition is used regarding direct sunlight and ambient temperature. The effects of thermoelectric generator thickness together with hot and cold flow on the electrical and thermal performance are analyzed and discussed. In order to validate the results of the numerical model, a new validation method has been used. The obtained results show a good agreement with the exact results. Furthermore, for a cold mass flow rate of 0.25 kg/s, the maximum thermal efficiency is attained at 60.646%, along with an electrical efficiency of 9.72% corresponding to 273.15 W in addition to power output.

Since it can be obtained from renewable sources and has a high heat value, hydrogen is a promising energy source. Chemical hydrides, such as sodium borohydride (NaBH4), are used as hydrogen resources. This is due to their relatively high hydrogen content together with their recyclability. In this study, Ni-B catalysts with Ti addition were prepared for the hydrolysis reaction of NaBH4. In the preparation of Ni-Ti-B catalysts, the chemical reduction technique was used. NiCl2 salt was used as the Ni source, where TiCl3 salt was preferred as the Ti source as the variations of the catalyst activities were determined. With the evaluation of the results, subsequent studies were carried out with the most effective Ti metal salt concentration. The effect of catalysts in different Ti/(Ni+Ti) molar ratios was examined according to the temperature, catalyst loading amount, NaBH4, and NaOH concentrations. The microstructure and elemental analysis of each catalyst were explained by SEM-EDS. After determining the highest performance Ti/(Ni+Ti) molar ratio, the calcination process was performed at different temperatures. For Ni-B catalysts, 5 wt.% NaOH and 5 wt.% NaBH4 were determined as the optimum fuel composition. Moreover, the Ti doped catalysts demonstrated longer durability and hydrogen production rate for hydrolysis of NaBH4.

The current paper investigates the optical absorption spectrum of Al_0.3 Ga_0.7 N/GaN multi-quantum well (MQW) under hydrostatic pressure. To obtain the parameters of Al_0.3 Ga_0.7 N/GaN MQW, such as electron and hole density, bandgap, interband transition energy, electron-hole wave functions, effective mass and dielectric constant, and the hydrostatic pressure effects are taken into account. Finite difference techniques have been used to acquire energy eigenvalues and their corresponding eigenfunctions of  Al_0.3 Ga_0.7 N/GaN  MQW and the hole eigenstates are calculated via a 6 × 6 k.pmethod under an applied hydrostatic pressure. It was found that the depth of the quantum wells, bandgaps, band offset, the electron, and hole density increases with the hydrostatic pressure. Also, as the pressure increases, the electron and hole wave functions will have less overlap, the amplitude of the absorption coefficient increases, and the binding energy of the excitons decreases. A change in pressure of up to 10 GPa causes the absorption coefficients peaks of light and heavy holes to shift to low wavelengths of up to 32 nm.

The Rashba spin-orbit coupling in nanostructures is an important parameter that can affect their physical properties. Hence, it is demonstrated that the nonlinear optical properties of quantum dot such as second harmonic generation and optical rectification can be controlled by the Rashba spin-orbit coupling. Also, the effect of electric field and confinement potential strength on the nonlinear optical properties is examined. Our numerical study shows that magnitude of the second harmonic generation raises when the Rashba strength increases, while its peak position is not shifted. Moreover, the optical rectification of doped asymmetric quantum dot shifts to higher energies when the electric field enhances.

Temperature above 600°C during the fabrication process is required to form the L10 compound ordering phase in FePt nanoparticles. The L10-FePt nanoparticles are ferromagnetic with high magnetic anisotropy. Practically, another ordering that is required is the orientation of their crystal c axis perpendicular to the plane of the nanolayer. The effects of the presence of Ag in reducing the transition temperature and making FePt nanocrystals in the L10-FePt phase aligned, in this work, have been studied and determined. The results of XRD analysis indicate that in fabrication using the co-sputtering method, firstly, the presence of Ag before annealing gives rise to the decline of the c parameter of the crystal lattice. This result of XRD analysis has been compared with the result of the RKKY exchange interaction model as an experimental confirmation of this model. Secondly, during annealing, with the formation of FePt-Ag nanostructure, the easy axis of FePt nanoparticles in the L10-FePt phase appears parallel to each other. These results, which are the consequence of the presence of Ag, are obtained by studying FE-SEM images, XRD patterns, and magnetic characterization.

In this work, a simple solution synthesis route for CoSe nanostructure thin films using the chemical bath deposition method is presented. The ions concentration role that affects the evolution of the nanostructure thin film configuration and optical band gap in CoSe nanoparticle arrays are investigated. The experimental data showed that the ions concentration can affect the optical band gap, surface topography, and configuration of a thin layer in the same way as they affect the optical band gap and thin film thickness. Derivation ineffective thickness method has been employed for optical band gap determination and index transitions without any presumption about the transition nature. The useful numerical data for characterization of the surface topography extracted from atomic force microscopy data has been examined. The influence of the ions concentration on the 3-D surface morphology of cobalt selenide (CoSe) nanostructure thin films prepared by the chemical bath deposition method has been considered.