Physique
Characterization and valorization of steel co-products
The iron industries generate large quantities of slags and mill scale at different scales. We have focused on the physicochemical characterization of slag and battitures from the El Hadjar sideal complex. To evaluate the quality of these co-products, we first used particle size analysis by the laser method followed by density measurements. Finally a microstructural analysis by X-ray diffraction has been completed. Voir les détails
Mots clés : slag, Battitures, valorization, characterization
Theoretical design and performance of InxGa1-xN single junction solar cell
The insertion of optimized Window and a back surface field (BSF) layers on an InxGa1-xN p-n basic single junction (BSJ) solar cell is the chief reason behind the reduction of front and back recombination. In this context, this work is focused on the selection of the suitable parameters including the indium (In) content, thickness and doping concentration for the InxGa1-xN inserted layers, that gives the best photovoltaic performances. At this aim, numerical simulations were performed using the computational numerical modeling TCAD Silvaco-Atlas to design, optimize the InxGa1-xN BSJ and extract the above Window and BSF parameters that enhance the BSJ performances. A short circuit current density ?(J?_sc) of 26.15 mA⁄?cm?^2 , an open circuit voltage ?(V?_oc) value of 0.904 V and a fill factor (FF) value of 79.67 % are obtained under AM1.5G illumination, exhibiting a maximum conversion efficiency (η) of 19.62 %. Other parameters like the external quantum efficiency (EQE), electric field developed, the current density-voltage (J-V) and the power density-voltage (P-V) characteristics are also calculated and plotted for the designed solar cell. Voir les détails
Mots clés : InGaN, solar cell, BSF layer, Window layer, simulation, Silvaco
Numerical simulation study of a high efficient AlGaN-based ultraviolet photodetector
In this paper, a two-dimensional (2D) numerical simulation study of a p+-n-n+ AlGaN-based ultraviolet (UV) photodetector, which is designed to achieve true solar blindness with a cutoff wavelength of 0.31 µm, is presented. The device performance is evaluated by investigating both the current density-voltage characteristics and the spectral response (SR). The proposed structure is optimized in terms of the fundamental geometrical and doping parameters. During the simulations, it was found that the detector is sensitive to the UV rays in the 0.155-0.37 µm wavelength range and the spectral response can reach 0.156 AW-1 under a light intensity of 1 Wcm-2 at zero-bias voltage and room temperature. This SR peak value increases further under reverse bias conditions. The temperature effect on the detector SR and the impact of an explicit trap concentration located into the p+ and n-region are also investigated. The spectral response decreases for a temperature exceeding 420 K. At the same time, the SR reference values begin to be affected only for acceptor and donor trap densities that are much higher than the local (total) doping concentration. Voir les détails
Mots clés : AlGaN, Numerical simulation, Photodetector, Spectral response, Trap Density
SIMULATION STUDY OF SUPER-RESOLUTION IN HYDROPHONE MEASUREMENTS OF PULSED ULTRASONIC FIELDS
In order to carry out reliable measurements of pulsed ultrasonic fields, the use of a piezoelectric hydrophone as receiver is recommended. However, due the finite size of the receiver aperture the measured acoustic pressure is affected by spatial averaging on the surface active face. The aim of this work is to deconvolve the spatial effects of the receiver hydrophone in order to reconstruct the pulsed ultrasonic field with a better spatial resolution. Hereby, the linear pulsed pressure field radiated in water by wideband planar transducers of 19 mm diameter, with central frequencies fc=2.25 MHz and fc=15 MHz are considered. The receivers are PVDF membrane hydrophones of 25 µm - thickness with rectangular and circular apertures. The results of this study show the strong dependency of the reconstruction quality upon the signal-to-noise ratio (SNR). Generally, the quality of the reconstruction decreases with decreasing SNR. Good reconstruction quality has been obtained with correlation coefficient larger than 0.9936 when the “acquired” signals are not too much noisy (SNR=60dB). In this case, improvement of the spatial resolution by a factor of 5 and 9 respectively could be reached. The reconstruction quality depends also upon the hydrophone dimensions, the axial distance to the source, the central frequency and the spectral frequency bandwidth of the pressure pulse. Voir les détails
Mots clés : Super-resolution, spatial inverse filter, spatial Wiener filter, PVDF hydrophone, pulsed ultrasonic field, ultrasonic field reconstruction.
Mechanism for phosphorus deactivation in silicon-based Schottkydiodes submitted to MW-ECR hydrogen plasma
Current work reveals the deactivation mechanism of phosphorus in silicon-based Schottky diodes. Microwave plasma power(P) was fixed at 650 W to observe the variation in different operational parameters of diodes such as initial phosphorusconcentration, flux and hydrogenation temperature (TMWH) and process time (t). The analysis of variation in concentrationof phosphorus by hydrogenation has been carried out by capacitance–voltage (C–V) measurements to monitor the dopingactivation/deactivation. The results clearly show that the atomic species H+H is dominant in the reactors MW-ECR plasma.Therefore, the rates and depth of neutralization were obtained in the low phosphorus-doped silicon sample. The H becomesH0 and prefers an interaction with another H0 instead of gaining an electron to become a negative ion. The hydrogenationtemperature study indicates that the deactivation rate of phosphorus is achieved in a complex manner. Indeed, as the hydrogenationtemperatureincreases,deactivationof phosphorus also increasestill saturationat 250 °C.Athigher temperature,lowor evenno phosphorus–hydrogen complexexistsdue totheirthermaldissociation. The same behaviorwasconfirmedbylonghydrogenation. Voir les détails
Mots clés : MW-ECR plasma, Hydrogenation, phosphorus deactivation, C–V measurement
Friction stir welding process improvement through coupling an optimizationprocedure and three-dimensional transient heat transfer numerical analysis
The present study deals with the improvement of the Friction Stir Welding process, through the prediction of theoptimal operating conditions, necessary for welding typical Aluminum-Lithium alloy material AA2195-T8. Anoptimization strategy coupled with 3D transient heat transfer computation were used to improve the FSWprocess parameters such as welding velocity, tool rotation velocity, tool diameter and applied force. The optimizationprocedure is based on three criteria: the control of the maximum temperature during FSW; the minimizationof the Heat Affected Zone (HAZ) length and finally the reduction of the total welding energy. Theobtained optimal parameters have given an ideal welding temperature in the workpiece, thereby ensuring goodwelding quality, gain in energy consumption and decrease both the welding time and the HAZ length. Voir les détails
Mots clés : Friction Stir Welding (FSW), Heat transfer, finite volume method, SQP algorithm optimization method
Etude structurale et microstructurale d’alliage nanométrique.
Des poudres nanométriques de ZnO dopées au fer ont été obtenues par broyage mécanique pour étudier leurs propriétés structurales et microstructurales en utilisant la diffraction des rayons X (XRD), microscope électronique à balayage (SEM) et le magnétométre à échantillon vibrant (VSM). La poudre pure de ZnO au départ a une structure cristalline hexagonale de groupe d’éspace p63mc ,mais après l’introduction de 1%Fe dans le ZnO, la phase hexagonale de ZnO reste sans changement, tandis que les paramètres microcristaux subissent des variations dues à l’introduction des atomes de fer dans la matrice hexagonale de ZnO pour remplacer ceux de l’oxygène, La taille des cristallites et les microcontraintes s’avèrent fonction du temps de broyage Voir les détails
Mots clés : microstructure, ZnO, Broyage Mecanique, XRD, SEM, VSM
Etude des propriétés structurales et magnétiques des couches minces de nickel élaborées par électrodéposition sur des substrats semiconducteurs
Nous avons étudié l’effet du potentiel de dépôt [-2.6 à -1.6 V], de l’épaisseur [50 à 422 nm] et de l’orientation cristallographique du substrat [n-Si (100) et n-Si (111)] sur les propriétés structurales, microstructurales, électriques et magnétiques des couches minces de Ni élaborées par électrodéposition à partir d'une solution aqueuse de sulfatede Ni. Une variation linéaire entre l’épaisseur, Voir les détails
Mots clés : Ni films ; Electrodéposition; Propriétés structurelles; Microstructure; cycles d'hystérésis;
First-principales study of the structural, vibrationa, phonon and thermodynamic properties of the complex K2PtCl6 structure hydrides Ca2OsH6
We have presented a full first-principles study of the structural, phonon and vibrational properties for Ca2OsH6 com-pound at the GGA-PBE level. The calculations are performed using the plane-wave pseudopotential method, density functional perturbation theory and the quasiharmonic approximation implemented in the CASTEP code. In particular, our theoretical lattice parameters obtained using the GGA-PBE to include the exchange-correlation functional are in good agreement with experiment. To our knowledge, there no experimental data or theoretical calculation for the study of frequency modes of NaCl structure of the studied hydrides for comparison. Voir les détails
Mots clés : Hydrides, structural, phonon and vibrational properties, ab initio
FIRST-PRINCIPALES STUDY OF THE STRUCTURAL, VIBRATIONA, PHONON AND THERMODYNAMIC PROPERTIES OF THE COMPLEX K2PtCl6STRUCTURE HYDRIDES Ca2OsH6.
We have presented a full first-principles study of the structural, phonon and vibrational properties for Ca2OsH6 com-pound at the GGA-PBE level. The calculations are performed using the plane-wave pseudopotential method, density functional perturbation theory and the quasiharmonic approximation implemented in the CASTEP code. In particular, our theoretical lattice parameters obtained using the GGA-PBE to include the exchange-correlation functional are in good agreement with experiment. To our knowledge, there no experimental data or theoretical calculation for the study of frequency modes of NaCl structure of the studied hydrides for comparison. Voir les détails
Mots clés : ab initio, Hydrides, structural, phonon and vibrational properties.