Physique

Nombre total de résultats : 265
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Élaboration par fusion haute fréquence et caractérisation des alliagesAl-Co-Ti.

Nacira SASSANE (2018)
Thèse de doctorat

L’objet de ce travail de thèse est d’étudier l’effet de l’addition du cobalt à l’aluminium pur,pour une teneur en titane constante, sur le comportement microstructural, mécanique,thermique et électrochimique. Ce système d’alliage Al-Co-Ti a été élaboré sous inductionélectromagnétique à haute fréquence et sa caractérisation présente des phases intermétalliquescomplexes telles que Al13Co4, Al9Co2 et Al5Co2. L’addition du cobalt à l’aluminium faitégalement apparaitre une structure quasi cristalline pour les alliages contenant 20%Co et25%Co. Par ailleurs, l’analyse électrochimique montre l’importance de la composition à15%Co par rapport aux autres alliages du point de vue de la tenue à la corrosion. Voir les détails

Mots clés : alliage Al-Co-Ti, élaboration, induction magnétique, microstructure, DRX, dureté, corrosion.

Characterization and valorization of steel co-products

L. Tairi, B. Maalem, A. Boudiaf, D. BERDJANE, N. Ziani, H. Meradji, S. Ghemid (2018)
Article de conférence

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

One-dimensional Parametric Study of Damage Detection in a Solid Material using a Nonlinear Wave Modulation Spectroscopy (NWMS) Technique.

N. HOUHAT, T. Boutkedjirt, V. Tournat (2016)
Article de journal

Nonlinear Wave Modulation Spectroscopy (NWMS) is one of the most powerful techniques used to detect damage in materials. It consists in simultaneously applying two continuous waves with different frequencies, the one high, f2, and the other low, f1. When the material is damaged, the frequency spectrum exhibits harmonics and sidebands which are located at (f2 + f1) and (f2 - f1). This paper presents a parametric simulation study of the nonlinear propagation of elastic waves in solid media, which can be represented by a one dimensional mass-spring system. The system of motion equations is resolved by a fourth order Runge-Kutta iterative method. A quadratic nonlinearity can be introduced locally in the system at any spring. The objective of the paper is to highlight the ability of the nonlinear acoustic methods, especially the NWMS (Nonlinear Wave Modulation Spectroscopy), to detect damages in solid material. The study of the evolution of the sidebands amplitude, according to the low frequency of the wave (pump wave), f1, in cracked and intact material will be presented. It is shown that this amplitude reaches a maximum when the pump frequency corresponds to a resonance frequency of the system. In addition, the study shows the strong dependency of the resulting frequency spectrum of the received signal upon the nonlinearity magnitude as well as the rigidity of the simulating crack spring.Voir les détails

Mots clés : Nonlinear Modulation Spectroscopy, Damage detection, nonlinear wave propagation simulation

ELABORATION ET CARACTERISATION DES COUCHESMINCES SUR LES ACIERS PAR LES METHODES NONDESTRUCTIVES

Aicha ZIOUCHE (2018)
Thèse de doctorat

Le but de cette étude est l’évaluation et la caractérisation par les méthodes non destructives, les courantsde Foucault et les courants de Foucault pulsés, l’effet des traitements thermiques sur des aciersfaiblement alliés et des aciers inoxydables duplex ainsi que sur des couches minces élaborés parélectrodéposition.Des caractérisations structurales par microscope électronique à transmission (MET), des caractérisationsmécaniques (dureté, résilience,…) et électrochimiques ont été effectuées sur les aciers traités.Les couches minces protectrices contre la corrosion sont élaborées à partir d'un bain de nickel et del'alumine avec une variation de la quantité d'alumine de 5-20g / l. La morphologie de la surface et lamicrostructure des revêtements Ni-Al2O3 ont été déterminées au moyen de la microscopie électroniqueà balayage (MEB) et de la diffraction des rayons X (XRD). Les résultats obtenus de la mesure de ladureté par nano-indentation, la mesure de l'épaisseur et les essais électrochimiques ont abouti à uneaugmentation de la résistance à la corrosion lorsque la quantité d'alumine augmente. Il a été trouvé unebonne corrélation entre les résultats obtenus à partir des essais non destructifs et les méthodestraditionnelles. Voir les détails

Mots clés : corrosion, revêtement, traitement thermique, contrôle non destructif, couches minces.

SIMULATION STUDY OF SUPER-RESOLUTION IN HYDROPHONE MEASUREMENTS OF PULSED ULTRASONIC FIELDS

Wahiba Djerir, Tarek Boutkedjirt (2018)
Article de journal

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.

Description of the solid method of BaTiO3 ceramics elaborations

Guessoum Mounia, Boukazouha Faiza, Sedda Kamel (2018)
Article de conférence

Abstract— There are two major methods of the barium titanate ceramic BaTiO3 elaboration, the solid and the liquid methods (Hydrothermal, sol-gel processing, and Coprecipitation) [1, 2, 3].In this work, we present a theoretical study to describe the solid method of BaTiO3 elaboration, it is the most method used in the industry, because it is very economical, inexpensive and easier to implement.Voir les détails

Mots clés : component formatting; style; styling; insert

Synthesis, characterization and structural study of perovskite ceramics for piezoelectric applications

K. Sedda, R. Djafar, K. Boumchedda, F. Boukazouha, M. Guessoum, A. Badidi Bouda (2018)
Article de conférence

In this work we have prepared lead-free ceramics BaTiO3, CaTiO3 and Ba0.85Ca0.15Ti0.9Zr0.1O3 successfully from different raw materials barium carbonate (BaCO3) calcium carbonate (CaCO3) dioxide of titanium (TiO2) and zirconium dioxide (ZrO2) by the conventional solid state reaction technique at different sintering temperatures. These materials are mixed for 6 hours and sintered at temperatures of 1200 °C to 1300 °C for 2 hours. The sintering temperature has been varied to study its effects on microstructure and structural properties. Structural parameters were analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM). Differential thermal analysis coupled with thermogravimetric analysis (ATG-ATD) was performed mainly to follow the process of precursor decomposition and formation of the perovskite phase. The XRD analysis results clearly show the synthesis of the perovskite phase as well as highlighting the formation of the Ba2TiO4 phase in addition to the BaTiO3 phase. The diffractogram obtained shows that the BCTZ symmetry is both Cubic with a space group Pm-3m and orthorhombic with a space group R3m. The calculated phase rates are: 10% and 90% respectively.Voir les détails

Mots clés : Lead free ceramics, synthesis, microstructure, Perovskite

Modeling and simulation of In0.15 Ga0.85 N/GaN strainquantum well structure for solar cells application

S. Dehimi, S. Kahla, A. Kellai, L.Kaba, N.Hammouda, A.Boutaghane (2018)
Article de conférence

Quantum well solar cells based on III-V nitridesemiconductor materials are a great technological interest bymeans to their physical and optical properties. In this study theeffect of quantum well number on the characteristics (J-V), (P-V)and efficiency for the structure GaN/In 0.15 Ga0.85 N/ GaN wasstudied. our result showed that, the increase in the number ofwells is accompanied by the increase of the light current densityand the efficiency, for example with 50 wells we found Jight = 14(mA /cm2) and a efficiency 28%.Voir les détails

Mots clés : Quantum well, solar cell, GaN, InGaN

Structural study of Al-doped ZnO thin films produced by the sol-geltechnique

Fayssal BOUFELGHA, N. Brihi, A. BOUAINE, R. Zellagui, N. OUAFAK, et A. BOUGUELLOTE (2018)
Article de conférence

In this work we studied the effect of aluminum doping concentration on the structural properties of zinc oxidethin films, we deposited samples of ZnO and aluminum doped ZnO with a doping rate of 1, 2, 3, 4 and 5%,on glass substrates by the spin coating technique. The structural characterization of the samples is done by theXRD and SEM techniques, the XRD spectra show that the layers are polycrystalline with a hexagonalwürtzite structure, and a preferred orientation in the plane (002), and for the doping 5% the structure is almostmonocrystaline (002). SEM images are used to confirm grain sizes and surface conditions. Opticalcharacterization is done by UV-visible spectroscopy, gives a good visible transmittance up to 80% andexceeds 90% for 2% doping, and the gap varies with the doping variation with a small gap for the samedoping (2%)Voir les détails

Mots clés : Thin films, spin coater, ZnO / Al, XRD, SEM, UV-visible

Electrical Circuit Constants Determination andVoltage Gain Measurement of Unloaded RosenType Piezoelectric Transformer Operating inFirst Mode

F. Boukazouha1, H. Barkat2, A. Herbadji2, A. Rouabha2. M. Guessoum1 and K. Sedda1 (2018)
Article de conférence

Abstract- In this paper a voltage gain of 155 for anunloaded Rosen type piezoelectric transformer operatingat the first mode was successfully measured with aprecision of 5%. For this purpose, it was necessary toensure a good impedance matching along the measuringcircuit. Also, using the admittance circles obtained fromthe measured admittances, the PT equivalent circuitconstants were determined experimentally and foundmatching the calculated ones (model 1D). Precisions lessthan 10% have been reported.Voir les détails

Mots clés : Index Terms- Acoustic wave, Equivalent circuit, High voltage, Measurements, Piezoelectric transformer, Voltage gain.