Physique

Nombre total de résultats : 263
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L'effet de l'incorporation de Zn sur les propriétés physiques des couchesminces CdS pour cellules solaires de type (Cd, Zn) S/Cu2SnZnS4

ZELLAGUI Rahima (2021)
Thèse de doctorat

Le but de ce travail est la réalisation des couches minces CdS par la technique Bain chimiquepour l’application photovoltaïque (cellule solaire). En effet, le cadmium est un élémenthautement cancérigène qui bien que présent en très faible quantité en tant que couche tamponet pouvant être recyclé en fin de vie des panneaux, Enfin, au niveau industriel, la synthèse dece composé s’effectue par CBD et entraine une rupture du vide sur la chaine de production,ainsi que des coûts occasionnés par le stockage de réactifs dangereux (cadmium, thiourée,ammoniaque) et le traitement des déchets toxiques pour cela on fait l'étude de l'effet del'incorporation de Zn sur les propriétés physiques des couche minces CdS pour cellules solairede type (Cd, Zn) S/ Cu(Sn, Zn)S2.Des couches minces de CdxZn1-xS ont été déposées sur des substrats en verre par uneméthode chimique simple et économique, c'est-à-dire le dépôt chimique en bain (CBD), pourleurs applications potentielles dans le photovoltaïque. Les propriétés structurales,morphologiques, chimiques et optiques des couches minces déposéesont été étudiées pardiffraction des rayons X, microscopie électronique à balayage, UV-VIS et spectrométrieRaman. Les propriétés structurelles ont révélé que les couches minces déposées présentent à lafois des structures cristallines hexagonale et cubique. Les films minces CdxZn1-xS avec unegranulométrie comprise entre 6 et 25 nm et présentent une transmittance de 50 à 80% dans larégion visible. L'énergie de bande interdite optique de la couche mince déposée se situaiententre 2,6 et 3,6 eV, illustrant leur viabilité potentielle pour dispositifs optoélectroniques etphotovoltaïques. Voir les détails

Mots clés : couche mince, Bain Chimique(CBD), CdZnS, morphologie, propriétés Optique

First principal investigation of structural, morphological, optoelectronic and magnetic characteristics of sprayed Zn: Fe2O3 thin films

Rihab BenAyed, MejdaAjili, Jorge M.Garcia, AichaZiouche, Jose Luis CostaKramer, Najoua KamounTurki  (2020)
Publication

Undoped and Zn-doped Fe2O3 thin films were grown through spray pyrolysis. Zinc doping effect on the physical properties was investigated in detail. X-ray diffraction analysis confirms that all the Fe2O3 thin films showed a rhombohedral structure. The surface morphological study shows an interesting dendrite structure. The estimated band gaps energies were increased from 2.13 to 2.21 eV for indirect transition and from 1.80 to 1.85 eV for direct transition as function of doping ratio which was increased from 2 to 8 at. % Zn. The resistivity value (ρ) of un-doped Fe2O3 thin film is 6.06 × 104 Ω. cm and as adding Zn ions, ρ consequently decreased to 52 Ω. cm for 6 at. % Zn-doped Fe2O3 thin films. Vibrating sample magnetometer (VSM) measurements showed an increase of the saturation magnetization with the Zn2+ insertion. Further, a ferromagnetic behavior was observed. Voir les détails

Mots clés : Ferromagnetic, semiconductor, Fe2O3, Zinc doping, Low resistivity

Unraveling the effect of Bi2S3 on the optical, electrical and magnetic properties of γ-MnS-based composite thin films

Z.Amara, M.Khadraoui, R.Miloua, A.Boukhachem, A.ZIOUCHE  (2020)
Publication

(Bi2S3)x (γ-MnS)1-x composite thin films have been deposited onto glass substrates using spray pyrolysis method. The structural and compositional investigations confirmed the co-existence of Bi2S3 and γ-MnS binary compounds in the thin films. The surface morphology indicated that the increase in Bi2S3 concentration influences both the shape and the size of γ-MnS crystallites. The optical analysis via transmittance and reflectance measurements revealed that the band gap energy Eg decreased from 3.29 eV to 1.5 eV in terms of Bi2S3 content. The electrical parameters such as resistivity ρ, mobility μ, carrier concentrations and Hall coefficient have been obtained by Hall Effect measurements. It is found than incorporation of Bi2S3 enhances the conductivity, and p-type conduction of γ-MnS could be converted to n-type at x = 0.5. The vibrating sample magnetometer measurement has revealed that (Bi2S3)x (γ-MnS)1-x composite thin films have a ferromagnetic behavior at room temperature. Voir les détails

Mots clés : γ-MnS, Bi2S3, Spray pyrolysis, Magnetic Properties

Calcul des corrections d’absorption des Neutrons par La Méthode de Monte Carlo sur des Echantillons de Poudres Cristallines 

Richi Wissem (2012)
Mémoire de magister

We have studied the angular behavior of the absorption coefficient in diffraction experiments of thermal neutrons incident on highly absorbing cylindrical samples. We have thus developed a code based on the Monte Carlo method to carry out the transport of such thermal neutrons and the evaluation of the finite-geometry induced effects, in addition to the study ofthe role played by multiple scattering, the absorption and the shape of the scattering sample as well. Thus, we were able to determine that the angular behavior of the transmission coefficient of the full-cylinder geometry is different from that of an annular-cylinder geometry containing the same number of scattering material. An enhancement of the diffracted intensity by a factor of 10, for small Bragg angles, is observed whenever the annular-cylinder shape is used instead of the full-cylinder one. Our code is further validated by the agreement of its results with those obtained previously par other workers using semi analytic methods. Voir les détails

Mots clés : Absorption coefficient, thermal neutrons, highly absorbing cylindrical samples, Monte Carlo Method

Effect of the c-axis tilting angle in piezoelectric ZnO crystal on the performances of electroacoustic SAW sensors

Farouk LAIDOUDI, Fayçal Medjili, Hassene NEZZARI, Mouloud Mebarki, Fouad Boubenider  (2020)
Article de conférence

This paper aims to study the effect of c-axis tilting angle of piezoelectric ZnO/Si on the performances of electroacoustic SAW sensors, the dispersion curves of phase velocity, the electromechanical coupling factor K² and sensitivity to mass loading of Rayleigh and Sezawa modes are studied for different hZnO/λ and for different c-tilting angles (0, θ, 90°). The effect of the tilting angle θ on the performances of electroacoustic devices, is studied by finite element analysis. Based on the obtained results, SAW device is fabricated onto a ZnO/SiO2/Si multilayered structure. The obtained results show best performances and high sensitivity to gas and will contribute in enhancing the sensitivity and performances of SAW electroacoustic devices. Voir les détails

Mots clés : surface acoustic waves, electroacoustic devices, Finite Element Analysis, Piezoelectric materials, c-tilted ZnO

SnS THIN FILMS DEPOSITION BY SPRAY PYROLYSIS: SOLVENT INFLUENCE

M. MESSAOUDI, M. S. AIDA, N. Attaf, S. SATTA  (2019)
Publication

Tin monosulfide (SnS) films are a new generation of absorber layers for thin ?lm heterojunction solar cell. The goal of the present study is the investigation of the role of the solvent on SnS thin films properties. Films were synthesized by ultrasonic spray pyrolysis technique. The used solution is a mixture of SnCl2.2H2O and thiourea (SC(NH2)2 precursors prepared with two different solvents: methanol and distilled water. X-ray diffraction (XRD) analysis reveals the SnS orthorhombic polycrystalline phase in different films. Using methanol as solvent leads to Sn2S3 secondary phase formation. While, film prepared with distilled water contains SnS2 as secondary phase. Scanning electron microscopy (SEM) observations reveal that films deposited with the methanol are rough with the presence of craters bubbles on the surface due to gas exo-diffusion during film growth. However, the film deposited with distilled water has a smooth, uniform, homogeneous and pinholes free surface. The electrical measurements reveal that films are p-type semiconductors, the dark conductivity increases from 3.07×10-4 (W.cm)-1 in film prepared with methanol to 5.15×10-3 (W.cm)-1 when using distilled water. We inferred that using distilled water leads to films with better quality than methanol as solvent. Voir les détails

Mots clés : Tin monosulfide, Spray pyrolysis, Thin films, solar cells

Effet d’un traitement de phosphatation sur l’oxydation à haute température d’alliages de Titane

GUERFI Souad (2007)
Mémoire de magister

Les aluminiures de titane offrent d'intéressante s propriétés en vue de leur application dans l'aéronautique, notamment pour la fa brication de tuyères, d'aubes et de rotors des turbines ou, encore sous forme de revêtements de pièces évolua nt à haute température. Ils sont caractérisés par de bonnes propriétés mécaniques à haute température (module d'élasticité et résistance au fluage élevés jusqu'à 1100°C). De plus, ils ont une densité relativement faible qui varie, selon la composition des alliages, entre 3,7 et 4,7. Cette caractéristique conduit à les considérer comme de bons candidats pour remplacer, à terme, les alliages base nickel dont la densité est comprise entre 7,9 et 8,9. Cependant, ils sont moins résistants à l'oxydation pour de s températures supérieures à 800°C et souffrent d'une fragilité à température ambiante (faible ténacité, ductilité réduite). Cette limite pose un certain nombre de problèmes qui conduisent à la fois à des incertitudes sur la fiabilité du matériau, et à des surcoûts liés aux difficultés plus grandes dans les procédés de fabrication et de contrôle. D'après des études menées en environnements agressifs de ces alliages, cette mauvaise résistance à l’oxydation est due à la formation simultanée de deux oxydes à la surface: le rutile et l'alumine. La compétition entre ces deux oxydes em pêche la formation d'une couche continue et homogène d'alumine en surface, laquelle protègerait efficacement le substrat contre la corrosion. Voir les détails

Mots clés : TA 6V, traitement thermique, oxydation

RELATIONSHIP BETWEEN AE PARAMETERS AND FRACTURE OF COMPOSITE MATERIALS UNDER SOLICITATIONS

FACI Youcef  (2019)
Article de conférence

Abstract: Acoustic emission (AE) techniques have been extensively studied in concrete engineering. There has been much research in relating AE parameters, such as energy, amplitude, count number, rise time to physical properties such as crack area delaminating, pull out, break down. Our work is performed using of carbon fiber reinforced polymer to study the evolution of AE parameters under solicitations. Meanwhile the waveforms created by the failure were monitored by AE sensors attached to the concrete beam.Examination of the waveforms produced by a range of four sensors with different frequency responses reveals that the fracture depth affects the AE parameters detected during failure. Relationship between fracture area and AE parameters was examined. These results can be used to aid the quantification of damage size based on energy release from concrete structures in the field. Voir les détails

Mots clés : acoustic emission, carbon fiber, sollicitation, quantifi

Welded micrographic structure determination using ultrasonic analysis

Faiza Boukazouha, Djili Sonia, HALIMI Rafik  (2006)
Publication

In this paper, the aim of our study is the use of ultrasound to show experimentally the change of the microstructure of a material after a welding operation. Two welded carbon steel plates have been selected to be investigated. Two processes are considered: The flux wire process and manual arc process. Voir les détails

Mots clés : Ultrasonic Analysis, welding, microstructure

Defects Detection in Welds Using Ultrasonic Analysis

Sonia Djili, Faiza Boukazouha, Rafik HALIMI, Ali BADIDI BOUDA  (2006)
Publication

In some austenitic stainless steel welds grains orientation cause deviation and splitting of the ultrasonic beam. It is especially true in the case of multipass welds when the remelting process after each pass causes complex solidification process. With these orientations we define a precise description of the heterogeneous and anisotropic material. Non destructive testing (NDT) is commonly used industrial method to evaluate the integrity ofindividual components. In service induced cracks such as fatigue and stress corrosioncracks can, if they are detected, be sized and monitored in order to postpone repairsor replacements. Voir les détails

Mots clés : Non destructive testing, Ultrasonic Analysis, Weld