Liste des documents
ELECTRODEPOSTION OF ZnO NANOWIRES FOR ENERGY HARVESTING
Zinc oxide is a transparent n-type semiconductor with a direct bandgap ranging between 3.3 and 3.5 eV. Polycrystalline ZnO has found numerous interesting applications such as piezoelectric transducers varistors , phosphors, transparent conducting films, transparent windows or nanostructured electrode for solar cells. ZnO nanostructures such as nanowires (NWs) and nanorods (NRs) showed attractive characteristics for certain applications ZnO, is among the most interesting materials in terms of piezoelectric properties that are relatively large compared to other non-ceramic piezoelectric materials . It also has the advantage of being easily burn which is of great interest for microtechnolog.To get, the ZnO thin films and nanowire must present a good cristallinity with preferential orientation (002) direction. Also, films electrodeposited must have good morphological properties, and NW must show good alignment and have direction of growth perpendicular to the substrate. This work is related to the fabrication of ZnO nanowires and nanrcords at room temperature also we showed the influence of the concentration of ZnCl2 on the morphological and structural properties of the deposits made by electrochemical route (NW and thin films). We made these deposits in an aqueous solution at room temperature and without buffer layer. Voir les détails
Mots clés : ZnO, nanowires, thin film, electrodeposition.
Electrochemical synthesis of ZnO thin film and nanowire for piezoelectric applications
ZnO thin films and ZnO nanowire (NW) having piezoelectric qualities can be used in respectively SAW devices (Surface Acoustic Wave) and nanogenerators. In this work, we are interested in optimizing experimental conditions of ZnO electrodeposition to obtain thin films and nanowire with good piezoelectric performances. To achieve this goal, the ZnO thin films and nanowire must firstly present a good cristallinity with preferential orientation along (002) direction. Also, films electrodeposited must have good morphological properties (not porous and with insignificant surface rugosity), and NW must show good alignment and have direction of growth perpendicular to the substrate. The electrodeposition of ZnO was performed in a classical three electrodes electrochemical cell, under potentiostatic mode and at room temperature. The substrate was a molybdenum foil of 0.1 mm thick and with 99.95% purity. The electrolytic bath was initially composed of 5mM ZnCl2, 5mM H2O2 and 100 mM KCl (supporting electrolyte), pH value being about 6.8. The initial conditions which give a well aligned of ZnO-NW (see fig. 1) were progressively modified in order to obtain a ZnO thin film. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Electrochemical impedance spectroscopy (EIS), to obtain information about microstructure, morphology, composition and electronic properties of the films and nanostructures electrodeposited. Voir les détails
Mots clés : ZnO, nanowires, thin film, electrodeposition, piezoelectric.
Eddy current characterization of nanomaterials
NDT Magnetic measurements as impedance in Eddy currents, remanence and corecitif in hysteresis loop are used to study the different stages of mechanical alloying in the Fe-Co system. In this paper, we want to change the electromagnetic properties of Fe-Co, by developing their metallurgical parameters such as grain size. For this we are used a planetary ball mill, we are milled the Fe-Co alloy for different milling times until to obtain nanostructure, the lamellar structure with some small particles embedded in them was observed during the first stage of mechanical alloying. The characterization by X-ray diffraction shows after 10 h of milling the formation of a disordered solid solution having a body-centered cubic (bcc) structure. After 40h of milling, morphological studies indicated that the average crystallites size is around 15 nm. Voir les détails
Mots clés : nanostructure materials powder metallurgy, NDT, Eddy Current, Magnetic measurement.
Analysis and optimization of a coplanar isolator for microwave systems
The miniaturization of circuits and the increasing frequency are two important issues of future communication systems and non-destructive testing equipment. This requires a high degree of integration and higher performance at reduced cost. The objective of this work is the study of a coplanar isolator for telecom applications. This isolator is constructed with a coplanar line charged by a ferrimagnetic material. We have started with an analytical study of a coplanar isolator, this allowed us to highlight the essential parameters influencing on the performances of our isolator, which are the longitudinal component of the magnetic field and the imaginary part of the non diagonal terms of permeability tensor. This confirms the importance of ferrite in the operation of our component. Then, we have contributed to the development of a resonance coplanar isolator using the simulator HFSS (High Frequency Structure Simulator) which concurrential comparatively to other works advantageous. The simulation results are very encouraging because we get insertion losses less than 2 dB and isolation more than 28 dB. Voir les détails
Mots clés : Magnetic material, Microwave, non reciprocal passive component, Coplanar isolator, Ferrite
Rechargement par soudage en acier inoxydable sur une fonte grise
Les impératifs techniques et économiques des industriels de tous les secteurs imposent la réduction des coûts et l’amélioration des performances, pour faire face à ces exigences de nombreux différents traitements de surface ont été mis au point et sont aujourd’hui utilisés industriellement. Parmi ces traitements de surface, ont effectué le rechargement par soudage avec l’électrode enrobée comme procédé, sur un substrat de fonte grise dont les propriétés mécaniques fait l’objet de ce travail. La matière à déposer est sous forme d’une électrode en Inox après un beurrage à base de nickel Ni. Un arc électrique permet de fusionné l’électrode par l’effet de court-circuit ainsi déposée sur la surface à revêtir. Le substrat possède une composition chimique de 3,5% de carbone et 2,4% de silicium, dont la fonte grise a été obtenue par refroidissement dans un moule en sable. Le but de cette étude étant de connaître l'adhésion de la couche de rechargement à base d’acier Inoxydable " 304L " austénitique et son effet sur le comportement mécanique de la fonte grise par métallographie, effort de traction et par une filiation de micro dureté. Voir les détails
Mots clés : rechargement, soudage, fonte grise, métallographie
Real Time Implementation of Shunt ActivePower Filter (SAPF) for Harmonic suppressionand Power Quality Improvement
In this paper, A Shunt Active Power Filter (SAPF) is implemented using a dSPACE DS1104 processorto compensate harmonics and reactive power produced by nonlinear load. The reference source currentis computed based on the measurement of harmonics in the supply voltage and load current.A hysteresis based current controller has been implemented in a DSP processor for injecting thecompensating current into the power system, so that SAPF allows suppression of the harmonics andreactive power component of load current, resulting in a supply current that is purely sinusoidal.Simulation and experimental results of the proposed SAPF to meet the IEEE-519 standards arepresented. Voir les détails
Mots clés : Harmonics, Power quality, Active power filter, Hysteresis comparator, Real-time control
Champs Thermiques Sous L’effet de la RéactionChimique du Reformage Interne Direct d’une PileSOFC
Cette étude présente les champs thermiques d’une pileà combustible standard (Ni-YSZ//YSZ//LSM) type SOFC à anodesupportée. Cette étude est faite dans le plan perpendiculaire àl’écoulement des gaz. La PàC est alimentée par l’air et lecarburant; CH4, H2, CO2, CO et H2O d’où la naissance duphénomène du reformage interne direct (RID-SOFC). Elle estbasée sur les réactions chimiques de reformage; la réaction devaporeformage et la réaction du gaz à l’eau. Le but principal dece travail est la visualisation des champs thermiques sous l’effetdes réactions chimiques globales et la confirmation ducomportement thermique de cette réaction chimique. Les champsthermiques sont obtenus par un programme informatique(FORTRAN). Voir les détails
Mots clés : Pile à combustible SOFC, Reformage interne directe, Réaction chimique globale, Carburant, Anode supportée, Champsthermiques.
Etude comparative entre trois techniques de filtrage actif parallèle sélectif
Dans le présent travail, nous présentons une étude comparativeentre trois techniques de filtrage actif parallèle sélectif desharmoniques, afin d’améliorer, le facteur de puissance du réseauélectrique FP. Ces trois techniques sont la théorie des puissancesinstantanées (P-Q), le référentiel synchrone de Park (d-q) etl’approche des filtres multi variables (FMV). Le principe de chaquetechnique est d’extraire les harmoniques de références du courant decharge, sélectivement ou simultanément. Généralement lesharmoniques en questions sont de basses fréquences et d’ordre 5 et7. L’objectif est que le courant du réseau ne contient pas lesharmoniques désirés à filtrés. Les formes d’ondes et les valeurs desTHD du courant de réseau avant et après le filtrage actif parallèlesélectif des harmoniques 5 et 7 issues des résultats de simulationsnumériques sous l’environnement Matlab/Simulink mettent enévidence l’efficacité et la meilleure des trois techniques élaborées. Voir les détails
Mots clés : PF, FAP, harmonique, P-Q, d-q, FMV, MLI, THD
Wind Power Relationships Homer Methodology Calculation
This paper simplifies the evaluating designs task ofpower systems for a variety of applications. When we design a power system, we should make many decisions about the configuration of the system, a task that Homer takes in hand.HOMER simulates the operation of a system by making energy balance calculations for each of the 8,760 hours a year.In this work, stages of wind energy conversion system are given through a mathematical formulation, knowing that wind power is probably the most promising sustainable energy resource. The wind is a clean and inexhaustible resource available all over the world. Voir les détails
Mots clés : wind layer, wind turbine output power, mathematical formulation, calculation, Homer.
Technico-Economical Sizing of Stand Alone Hybrid System for Rural Electrification in an Algerian Territory—a Case Study
The Tindouf region in Algeria enjoys an average windspeed of 4.3 m/s at 10 m elevation and an average daily solar radiation of 5.9 kWh/m2/d. Within this perspective, a remote rural village in Tindouf region within ten homes can readily be expected to have more than enough potential for its load demand to be supplied with a stand-alone hybrid renewable energy system. For this purpose, a wind-pv-diesel hybrid power system has been designed. The study found a wind-pv-diesel hybrid power system with 74% renewable energy penetration (26% wind and 48% solar PV) to be the feasible system with cost of energy of 0.433 US$/kWh. The proposed system was comprised of one wind turbine of 3 kW, 3.5kW of PV panels, and one diesel generating set of 5.5 kW rated power. The system was able to meet the energy requirements (AC primary load of 9.49 MWh/y)of the village with 289 kWh/y energy in excess. The annual contributions of wind, solar pv and the diesel generating set were 3 234, 5 958, and 3 274 kWh, respectively. The proposed hybrid power system resulted in avoiding addition of 16.26 t/y of CO2 gas in to the local atmosphere of the village and conservation of 6176.15 liters of fossil fuel annually. Voir les détails
Mots clés : Wind-pv-diesel hybrid system, Homer, optimum system sizing, Net Present Cost, Algeria