Sciences des matériaux
Structural and morphological characterization of thin films based on zinc oxide
Zinc oxide (ZnO) is a semiconductor wide direct gap (3.37 eV), which has many interesting properties (chemical, piezoelectric, optical, catalytic ...) .A wide range of applications makes it one of the most studied materials in the last decade, especially in nanostructured form. In this work, we study the electrochemical synthesis of thin films by anodizing a wafer of zinc in aqueous solution. It was found that the morphology and the structure of final deposits are sensitive to conditions preparation (temperature; concentration and pH of the solution). The structure and morphology are studied by means techniques of X-ray diffractometry (XRD and scanning electron microscopy (SEM) Voir les détails
Mots clés : Zinc oxidation, thin layer, Anodic polarization, Zinc oxide
Study of Nickel oxide thin films deposited by spray pyrolysis, solar cells applications
Nickel oxide (NiO) thin films were deposited on glass substrates by chemical spray pyrolysis technique. A high quality crystal was obtained after annealing at 500 K. The structural properties of the films have been studied by the X-ray diffraction (XRD). It has been shown that thin films in the NiO crystallized structure is attained after the deposition. Whatever the precursor molarity, the grain size is about 28-62 nm. The crystallites are preferentially oriented in the directions (111) at 0.2M and (200) at 0.3M. Voir les détails
Mots clés : thin film, NiO, spray pyrolyse, Structural properties, solar cells, X-ray diffraction
Elaboration and characterization of Ti-Al and TiAl-N thins film sprepared by PVD
Depuis une vingtaine dannées, de nombreux travaux traitent de lélaboration de couches minces par différents procédés de dépôt en vue de fonctionnaliser les surfaces des matériaux et de leur procurer des propriétés superficielles particulières. Ce travail porte sur linfluence de quelques paramètres de dépôt surcertaine propriétés des films de Cr, Ti-Al, Cr-N et Mo-Cr-N élaborés par PVD sur des substrats en silicium. L'influence de l'épaisseur des films sur les contraintes résiduelles et sur la résistivité a été étudiée. La détermination des contraintes a été faite en utilisant soit un profilmètre soit un dispositif des « Anneaux de Newton ». Et la détermination de la résistivité a été réalisée à l'aide d'un montage « Quatre pointes ». Un pic de contrainte a été mis enévidence dans tous les films élaborés. Il localisé à 200nm, environ. L'effet de l'épaisseur des films sur la résistivité des films de chrome a été montré. Il existe une corrélation entre la variation de la contrainte, de la résistivité et le phénomène de croissance des couches minces. On n'a noté, aussi, l'effet de l'azote sur l'épaisseur des films et la largeur des colonnes constituant la couche mince de Mo-Cr-N. Voir les détails
Mots clés : PVD, revêtements durs, contraintes résiduelles, résistivité.
Effet de Silicium sur les propriétés de Ti déposé par évaporation thermique sous vide
In this work, structural, morphological, and mechanical properties of Ti-Si thin films grown by Vacuum Thermal Evaporation were investigated. A series of Ti-Sicoatings have been deposited by vacuum thermal evaporation technique, on Z200 steel and Si (100) substrates.180 mg of titanium powder and,4at.%, 7at.%, 11at.%, 17 at.%of Silicon grains were used as deposition source. X-ray diffraction, Scanning Electronic Microscopy were employed for structural and morphological study of the films, nano-indentation hardness testing test was used to evaluate the mechanical properties, the corrosion behaviors of the coatings were studied in aerated 3.5 wt. % NaCl aqueous solutions by interpretation of the electrochemical anodic polarization curves.The X-Ray Diffraction patterns reveal that all films are polycrystalline and matched those of -Ti , Ti5Si3, Ti-Si, and Ti4Si, the hardness and the Youngs Modulus increase firstly to achieve a maximum value 33 GPa, and 795 GPa then decrease smoothly with a further addition of Si to a weak value Voir les détails
Mots clés : Ti-Si, Vacuum Thermal Evaporation
Flare Test, an application on the welded steel tubes, study with simulation
In this study, we try to describe the flare test that we have apply on tubes that have been welded by high frequency induction HF, and its experimental procedure. The test is carried out in ENTTPP (National company of pipe mill and processing of flat products) on pipes has been made from steel of type S235JR.All the work steps focus on the welded joints and its mechanical properties where the flare test one of the destructive testing (CD) series can ensure the efficiency of the welding. Voir les détails
Mots clés : Induction welding, steel, drafts tube, tube finished, high frequency induction, S235JR, attraction, flare, destructive testing, Castem 2001.
Magneto-electrique and magnetic studies of the Sr-doped Samarium manganite synthsesed by citrate gel method.
In This paper we report study the effect of sintering temperature on the magnetotransport properties of Sm1-xSrxMnO (with x=0.3) manganite syntesized by citrate gel method. The Sm30.7Sr0.3MnO has been sintered at 700C (SSM7), 900C (SSM9) and 1300C (SSM13). XRD confirms that phase formation starts at 700C. All the samples are single phasic having orthorhombic unit cell. The lattice parameters decrease on lowering the sintering temperature. The crystallite as well asparticle size also show strong dependence on the sinteringtemperature. All the samples possess insulator-metal (TIM) aswell as paramagnetic-ferromagnetic (TC) transitions. The TCshows a small variation [274K to 256K]. The temperature causes a great increase of resistivity and lowers the temperature of the metal-insulator transition T3. Under applied magnetic field, a significant reduction in the resistivity and a shift of TP to higher temperatures values are observed. In the insulating region(T>T), the resistivity curves are well fitted by the small polaron hoping mechanism while in the metallic region (T
Mots clés : manganite, citrate, magnetotransport, Structure.
Study of the effect of γ-ray irradiation on the optical properties of polyethylene terephthalate polymer
The effect of γ-ray irradiation on optical properties of polyethylene terephthalate (PET) has been studied using UV-Visible spectrophotometry technique. γ-ray irradiations were performed, using 60Co source with mean energy of 1.25 MeV, at Nuclear Research Centre of Algiers, Algeria. The dose rate was about 1.3 kGy/h as measured using the Frick dosimeter. Several PET samples with a thickness of 6 µm were irradiated at room temperature in air atmosphere at dose range 0.05 - 5 MGy. After irradiation, the colour of the PET thin film, which is initially transparent, becomes slightly yellowish at high γ-ray dose. The UV-Visible absorption spectra of pristine and irradiated PET polymer have been obtained by a double beam Cintra 40 spectrophotometer in the range 200 900 nm. The absorption measurements show a large absorption band extended from 310 to 355 nm assigned to the formation of extended systems of conjugate bonds with the creation of carbon clusters.The optical absorbance in this range increases linearly with the ray dose. An empirical relation is established to estimate gamma dose from this correlation. Both direct and indirect energy gaps deduced from the Tauc relation are found to decrease with increasing γ-ray dose indicating the appearance of new electronic transitions. Moreover, it is also observed that the Urbach energy increases with the γ-ray dose. This indicates the disorganization of the PET structure after irradiation. Moreover, the linear behavior of the absorption band versus γ-ray dose observed in the present study suggests the potentiality of using PET polymeras gamma dosimeter. Voir les détails
Mots clés : polyethylene terephthalate, UV-visible, optical properties, γ-ray
Crystallization kinetics phenomena assessment in aglass-ceramic material, by non-destructive spectroscopic methods
Non destructive tests are very useful to follow crystallization kinetics phenomena during the synthesis of aluminosilicate glass-ceramic materials. These composite matrices are dedicated for nuclear waste storage. In this study,we assessed the crystallization kinetics dependence, by many non destructive tests, on the structure of an aluminosilicate glass ceramic ceramized by a nucleation crystallization treatment at 790°C during 2 h, and 900°C, for different periods of time ranging from 6 to 12 h. These tests are X-ray diffraction; scanning electron microscopy and Fourier transform Infra-redspectroscopy. For the whole of materials, Archimedes density is between 2530-2578 kg/m3. Both X-ray diffraction and scanning electronmicroscopy analyses reveal two main crystalline phases for the whole of heating treatments, namely spodumen and leucite. These phases grow regularly with the crystallization time. FTIR analysis shows Si-O-Si vibrations (680 cm-1and 457-467 cm), which shift toward lower values indicating Si-O-Me bonds formation (Me = metal), which are abundant for high ceramization times. The metals incorporated in the materials structure are well binded in the structure, conferring it durable properties. These non-destructive spectroscopic techniques allow following crystallization progress in the materials without altering the materials bulk, and are recommended for such studies. Voir les détails
Mots clés : glass-ceramic, alluminosilicate glass, FTIR, SEM, XRD
Teaching Learning Based Optimization Neural Networks for Waveguide Filter Modeling
Artificial neural networks (ANN) provide fast and accurate models for the modeling, simulation, and optimization of microwave component. In this paper, an efficient optimization method, called teaching learning-based optimization (TLBO) is proposed for training artificial neural networks (ANN). Then, the trained networks are applied to modeling waveguide filter structures .The results obtained using teaching-learning based optimization neural networks (TLBO-NN) algorithms are validated by comparing them with those obtained using particle swarm optimization neural networks (PSO-NN). Voir les détails
Mots clés : neural networks, Teaching Learning Based Optimization, modeling, Waveguide Filter
Eddy-current non-destructive testing system using amagnetic sensor based on GMR
Detecting the cracks is a major challenge in the development of Eddy Current (EC) Non-Destructive Testing (NDT). In fact, the detection sensitivity of EC-NDT depends on the interaction between the crack characteristics and the EC formed in the materials. The induced currents are primarily generated along a single direction in the tested sample. This paper presents a excitation method for generating a ac magnetic field and, consequently, eddy currents. This method significantly improves the detection of cracks of two different kind of material (non magnetic conductive material and ferromagnetic material). The magnetic flux density signature of the defect is studied using a 2D Finite Element Model FEM. Voir les détails
Mots clés : Eddy Current, Non-Destructive testing, Giant Magneto Resistance, Finite Element Method