Physique
Magnetic and eddy current testing of iron/silicon oxide-based nanocomposites
Le nano-composite de fer-oxyde de silicium présente d'excellentes propriétés par rapport aux matériaux conventionnels de même concentration en raison de l'impact de la taille cristalline. Ce travail vise à étudier les changements de comportement électromagnétique et magnétique du nano-composite fer-silicium au cours du processus d'élaboration. L'approche adoptée dans cette étude consiste à utiliser des techniques de contrôle non destructif (CND) par les méthodes magnétiques pour suivre l'évolution de sa structure, des contraintes résiduelles, des défauts, des changements magnétiques et du comportement électromagnétique lors du processus d'élaboration. De plus, il vise à établir une relation entre les techniques structurales et les techniques de CND Voir les détails
Mots clés : Le nano-composite de fer-oxyde de silicium, cnd
Integration of reconfigurable fault-tolerant three-level inverter in photovoltaic power system
A lot of previous studies have shown a great interest in connecting photovoltaic (PV) arrays to electric power grids. A Maximum Power Point Tracker (MPPT) controlled 100 kW PV array to boost its power that feeds the grid with the help of a three-level inverter. This paper investigated the effects of open-circuit faults of three-level inverter IGBT switches on the performance of the PV array system. This paper proposes a new diagnostic method called the Double Threshold-Trigonometric Coordinates (DT-TC) that relies on the double threshold technique and the trigonometric coordinates, respectively, for early detection and the precise location of open-circuit faults. To the best knowledge of the authors, two simultaneous open-circuit faults were not considered in the previous studies. The obtained simulation results prove the great success of the proposed diagnosis method even under noticeable changes in irradiation, temperature, and the number of PV array connected in series and in parallel. In this study, the reconfigurable fault-tolerant inverter was included to ensure the perfect continuity of the PV array system and its recovery in an extremely very short time up to 7 ms. Voir les détails
Mots clés : diagnosis, DT-TC, fault-tolerant, IGBT, Multi-level Inverter, Open-circuit faults, PV array, reconfigurable
Effect of CaF2 addition on the densification behavior and mechanical properties of resistant anorthite and its bioactivity
In the current study, anorthite ceramic (CaO, Al2O3, 2SiO2) was synthesized by a simple solid-state reaction method, using local Algerian raw materials. The effect of sintering temperature at 800, 850, 900, 950, 1000, and 1100 °C for 1h under atmosphere, and 0.5, 1.5, and 3 wt % calcium fluoride (CaF2) addition on the densification and mechanical properties of anorthite were studied. The correlation between these properties and the bioactivity of samples was investigated. The results showed that samples with 1.5 wt.% CaF2 sintered at 900 °C has the highest bulk density (2.7 g.cm-3), lowest apparent porosity (3%), outstanding micro-hardness (8.7 GPa), and high flexural strength (222 MPa) of anorthite. The in vitro bioactivity test was assessed by determining the changes in surface composition and morphology after immersion in a simulated body fluid (SBF) for 8 h to 21 days. The results of the bioactivity test determined the formation of hydroxyapatite (Ca5(PO4)3OH) on the sample surface after 3 days, suggesting it is a bioactive ceramic. Voir les détails
Mots clés : anorthite, CaF2 addition amount, bioactive properties Mechanical, sintering temperature
Theoretical study of structural and optical properties of ZnO in wurtzite phase
Our calculations are done with the help of density functional theory (DFT). Actually, we could find the structural and optical properties of the wurtzite-type ZnO compound. The pseudo-potential linearised augmented plane wave (PP-LAPW) method is applied to solve the Kuhn-Sham equations. The results are obtained using Both Generalized Gradient Approximation according to the scheme described by Perdew-Burke-Ernzerhof(GGA-PBE) and Local Density Approximation according to the scheme described by Ceperly-Alder (LDA-CA) approximations as two types of exchange-correlation. The convergence of energy and charge has been checked. This is in order to study the properties of the ground state. It was found that the primary cell constants calculated in the equilibrium state are very close to the previous theoretical works. The general results of optical properties including the imaginary part of the dielectric constant, reflectivity, absorption coefficient, refractive index, optical conductivity, and extinction coefficient of wurtzite-phase ZnO under the imposed conditions are discussed and compared with previous works. Our results show new and important optical properties. Besides, we predicted the behavior of transparent conductive oxides in the direction of light. Voir les détails
Mots clés : ZnO, Structural properties, reflectivity, absorption, Refractive index, Optical conductivity
Investigation of Structural, Morphological, and Photoluminescence Properties of Zn1_xMgxS Nanoparticles Prepared by Solvothermal Method: Insight from Experimental and DFT Study
Various concentrations of Mg2+ substitutional doped ZnS nanoparticles (Zn1-xMgxS,x = 0, 0.02, 0.07, and 0.1) were prepared by adopting the solvothermal method, using ethanol as the solvent at 135°C. The obtained micro/nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and room temperature photoluminescence (PL) spectroscopy. XRD revealed the conservation of the host ZnS crystal phase after the substitution of Zn2+ by Mg2+ but was accompanied by a weak decrease of the lattice parameter. SEM analysis showed the formation of aggregated particles that were evenly distributed. PL spectra exhibited a near-band-edge (NBE) emission centered at 430 nm, and another band at 585 nm, related to sulfur defects; moreover, no shift occurred when x increased. To explain this finding, computational density functional theory (DFT) calculations were performed, revealing constant gap energy after substitution was maintained at the point G, whereas the density of stats of both CV and BV were reinforced near the band gap Voir les détails
Mots clés : solvothermal preparation, Zn1-xMgxS substitution doped, structural study, Photoluminescence (LP), DFT calculations
Elaboration par électrodéposition et caractérisation des couches minces de Ni/Si: Effet du potentiel de dépôt
Ni thin films deposited onto on n-Si (111) substrates using pulsed electrodeposition (PED) method show an influence of the applied potential and the Ni thickness on the structural, surface morphology, electrical and magnetic properties. Significant linearly increase in Ni thickness t (t ranges from 50 to 390 nm) has been observed with increasing applied potential (from -1.6 to -2.6 V). All samples show the polycrystalline films prefers growth with the <111> texture. The strain ε (%) is negative for all samples and their variation as a function of the applied potential has a critical value corresponding to a critical potential (VCr = -2.2 V); the stress increases up to VCr, then stress is relieved. The grain size increases monotonically with increasing Ni thickness and applied potential. Voir les détails
Mots clés : Ni thin films, electrodeposition, Structural properties, microstructure.
STUDY OF CIGS PSEUDO-HOMOJUNCTION THIN FILM SOLAR CELL USING SCAPS-1D
) have been used as indicators to evaluate the device performances. Simulation outcomes have proved that for a best performance for CIGS P-HTFSC device, the optimal thickness for CIGS and ODC layers should be small than 2 µm and few nm, respectively, while the optimal defect concentration within the layer should be 10hThe present modelling study reports the performance of defected CIGS pseudo-homojunction thin film solar cell (P-HTFSC) and determines its optimum parameters for high performance using the Scaps-1D software under the AM1.5 illumination and the operating temperature of 300 K. To focus the discussion on the optimal parameters (thickness, doping concentrations, deep/interface defect concentrations and bandgap) for the ZnO, CdS, ODC and CIGS thin film layers, cross sectional (1D) simulations have been performed on the ZnO/CdS/ODC/CIGS P-HTFSC device for obtaining its optimal structure that confers high light-into-electricity conversion efficiency. The four light J-V characteristics (short-circuit current: JSC, open-circuit voltage: VOC, fill factor: FF and conversion efficiency:13 cm-3 and between 1013 cm-3-1018 cm-3, respectively. Voir les détails
Mots clés : CIGS, J-V characteristics, ODC, Pseudo-homojunction, Scaps-1D
Antibacterial activity of intermetallic NixMgy and NiO–MgO phases in nickel-magnesium oxide nanocomposites
This work focuses on Ni–Mg metallic nanomaterials and NiO–MgO composites, especially on their antibacterial activity against Escherichia coli (E. coli (G-)) and Staphylococcus aureus (S. aureus (G+)) in relation with their size and structure. They are generated by impregnation of nickel formate, followed by either calcination (T = 100–600 °C) or gamma-irradiation at room temperature. In samples prepared by calcination at temperatures T ≤ 300 °C or irradiation, the structural study by XRD and HRTEM reveals the presence of nanoscaled Ni–Mg intermetallic phases: NiMg2, Ni2Mg and NiMg6.33 (2–4 nm diameter) and magnesium hydroxide Mg(OH)2. At T > 300 °C, only the NiO–MgO solid solution is formed. Bare MgO and NiO–MgO nanoparticles exhibit a bacterial activity only against E. coli and S. aureus, respectively. In contrast, the Ni–Mg intermetallic phases of high specific area, that are present in irradiated (T = 20 °C) or calcined (T ≤ 300 °C) samples, exhibit a significant antibacterial activity against both E. coli and S. aureus. Voir les détails
Mots clés : Antibacterial Activity, Gamma radiolysis, intermetallic Compounds, NiO–MgO, Ni–Mg
Caractérisation des écoulements en micro fluide par vélocimétrie à l’échelle micron appliquée aux microsystèmes
Microfluidics has been a field of research in full expansion for ten years, whose vitality is nourished by the diversity of its applications Today, new technologies indeed make it possible to manufacture electromechanical systems of micro and nanometric size, up to 'at significant levels of complexity, and equipped with all kinds of functionalities. These new possibilities have been used in aspectacular way for many applications, such as DNA microarrays, or lab-onchip. In all these systems, the problem of controlling flows in devices whose dimensions or internal patterns vary from a few hundred nanometers to a few tens of micrometers arises, this work will be devoted to an analysis and characterization of the flows applied to microsystems. Voir les détails
Mots clés : microfluidics, DNA microarrays, microsystems
Effect of Cu/Ni Ratio on the Chemical composition, Magnetic behaviour, and Structural properties of a FeCuNi based alloy
The aim of this project is to study and understand the influence of copper and nickel concentration on the magnetic, morphological and structural properties of the Fe70Cu30-xNixalloy. The alloy was elaborated by mixing iron, nickel and copper powders by the mechanicalalloying technique for 10 hours of milling. The elements were characterised by different techniques: X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Vibrating Sample Magnetometer (VSM). The X-ray diffraction study shows that the crystallite size decreases with increasing Ni. When it come to the magnetic properties, the coercivityHc and the saturation moment Ms rise from 83 Oe, 121.5 emu/g to 156 Oe, 140 emu/g respectively. Voir les détails
Mots clés : Fe70Cu30-xNix, Scanning Electron Microscope (SEM), X-ray diffraction