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Nombre total de résultats : 1847
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Nitriding effect on structural stability and magnetic properties of FeAl alloys:DFT study

Ismahane Berrached, Lyacine RABAHI, Malika Gallouze, Abdelhafid Kellou  (2019)
Publication

Using the DFT calculations, the phase stability, structural deformation and magnetic momentof Fe-riche FeAl alloys in presence of different percents of nitrogen were calculated. Theformation enthalpy of these Fe-Al alloys indicates that N preferred the octahedral site than thesubstitution one. Significant changes occur in this energy, affected by N and Fe contentcausing local distortions. From 25 at.% N, the phenomenon of saturation appeared and thesubstitution takes place. The addition of 6 at.% N stabilizes Fe 9 Al 7 and Fe 10 Al 6 . The presenceof N atom leading to decrease the total magnetic moment of FeAl nitride when the magneticorder is antiferromagnetic between N and Fe atom. This magnetic moment increased by theferromagnetic coupling between Fe and N, thus increasing the Fe local magnetic moment andthe magneto-volume effect. Voir les détails

Mots clés : Nitriding, Magnetic Properties, Structural Stability., FeAl Alloys, DFT

Comparative investigation of the Ni and the Fe effect on the structure andmechanical response of a WC-W-Ni hardmetal obtained by infiltration

H. Bouchafaa, D. Miroud, S. MATO, Z. Boutaghou, B. Cheniti, F.J. PÉREZ, G. ALCALÁ  (2019)
Publication

In the present work, and in order to enhance the efficiency of drilling tools for the oil and gas industry, theinfluence and performance of Ni and Fe during spontaneous infiltration on a WC-W-Ni composite materialmechanical behaviour was addressed. Solid-state activity of Fe and Ni during infiltration exhibits partial dissolution in the metallic binder. The chemical affinity between Fe and Ni, provided by the Fe powder and thebinder respectively, derived on the formation of the (Fe, Ni) solid solution and FeNi3 intermetallic precipitates inthe particle/matrix diffusion region, with a hardness (12 GPa) close to that of WC and high elastic modulus (230 GPa). Furthermore, the diffusion of Fe to the matrix leads to the formation of sub-micrometer precipitatesof α-Fe with some (Ni, Mn) in solid solution and of Ni3Sn with a small amount of Cu dissolved, driving to anincrease of about 30% in its elastic modulus, and without appreciable effect in the hardness observed. Voir les détails

Mots clés : Metal matrix composites, Liquid-solid reactions, Precipitation, powder metallurgy, diffusion, mechanical properties

TiO2 doped with nickel thin films Properties

H. Dehdouh, M-C. BENACHOUR, R. Bensaha, M. Zergoug  (2018)
Article de conférence

Thin films of un-doped and Ni-doped TiO2 were synthesized by the sol–gel dip-coating technique and deposited on glass substrates, for different annealing temperatures (from 400 °C to 500 °C). The X-rays diffraction and Raman show the formation of anatase phase, we also notice that doping with Ni influence the intensity of anatase peaks and decreases of grain sizes (from 24.3 to 15.23 nm). The nanostructure Ni-doped TiO2 thin films was observed AFM, which shows that the elaborated films are smooth and dense with Rms values of about 3 nm. The calculate values of refractive index of thin films increases from 2.22 to 2.38, and reduction in transmittance and band gap with the increase in the nickel concentration. Vibrating sample magnetometer results of un-doped TiO2 thin films reveal a ferromagnetic behavior at room temperature with Ms = 0.67 10-4 emu and low content of nickel doping leads to an enhancement of the saturated magnetic moment Ms =1.11 10-3 emu. Voir les détails

Mots clés : Ni-doped TiO2, sol-gel, Thin films, TiO2 properties

Structural modification, photoluminescence, andmagnetic property enhancement with Er3+ doping,of sol–gel TiO2 thin films

Heider DEHDOUH, Rabah Bensaha, Mourad ZERGOUG  (2017)
Publication

Nanocrystalline undoped and Er3+ doped TiO2 thin films were prepared by sol–gel dip-coatingtechnique onto glass substrates. Post-deposited films were annealed at 450 °C for 1 h. Differentialscanning calorimetric analysis showed that undoped film crystallization occurred at 339 °C, whileit appears at lower temperature for Er:TiO2. X-ray diffraction and Raman spectroscopy resultsindicate that the films crystallize only into anatase phase, and the crystallite size decreases from24.3 to 21.16 nm with increasing Er3+ doping ratio. The photoluminescence (PL) spectra arecomposed of two broad peaks at 520–570 nm and 640–680 nm assigned to (2H11/2, 4S3/2)–4I15/2 and4F9/24I15/2 transitions of Er3+ ions, respectively. PL emission intensities increase gradually raisingthe erbium doping ratio. Vibrating sample magnetometer results of undoped TiO2 thin films reveala ferromagnetic behavior at room temperature and erbium doping leads to an enhancement of thesaturated magnetic moment (Ms). Voir les détails

Mots clés : TiO2 doped Er3+, Sol–gel, Photoluminescence, Magnetic Properties

Elaboration and characterization of ITO electrode modi?ed bytransition metal dispersed into polyaniline thin ?lms

Oua?a Belgherbi, Dalila Chouder, M.A. Saeed  (2018)
Publication

This work presents the characteristics of composite materials thin ?lms of polyaniline (PAni) andnickel (Ni) particles deposited onto indium tin oxide (ITO) substrate. The electropolymerizationof aniline was performed in acidic medium by potentiodynamic methods. The nickel particleswere electrochemically deposited on the surface of PAni/ITO by reducing metal ions (Ni) usinga potentiostatic method from a separate solution. The e?ect of applied potential as well as immersingtime of complexation on the amount of nickel dispersed was investigated. Di?erentcharacterization techniques were employed to study the electrochemical behavior and surfacecharacteristics of the Ni-PAni/ITO thin ?lms such as Electrochemical Impedance Spectroscopy(EIS), Cyclic Voltammetry, Fourier Transform Infrared Spectroscopy (FTIR), UV–visSpectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).The morphology of the obtained composites shows a uniform dispersion of nickel particlesonto the polyaniline matrix and reveals that the immersing times of complexation has a signi?cante?ect on the amount of incorporated particles. The impedance spectroscopy study revealsthat the conductivity of the composite ?lm increases with the amount of nickel incorporated.UV–vis and FTIR results con?rm the presence of PAni and Ni particles on theelectrode surface. Voir les détails

Mots clés : polyaniline, Electro-polymerization, Nickel particles, Chronoamperometry, Materials composites

Design of Sobel Filter in VHDL

Mazouz Nezhate, Bouhouche Salah, Ziad Mostepha, DRAI Redouane  (2018)
Article de conférence

In order to automate the quality control process of pipe’s welding joint, we present in this paper a new design of an embedded computer vision system, which is based on a camera, controlled by an FPGA platform (Zynq-7000) for acquisition and image processing on the same FPGA circuit. A VHDL implementation of Sobel Edge Detection Algorithm is proposed. The obtained results were validated with those obtained by MATLAB.This will allow us to develop other tools more powerful and more robust. Voir les détails

Mots clés : Quality control, pipe welds, FPGA, Sobel, VHDL

Etude du composrtement à l'endommagement des materoaux composites stratifiés

HALIMI Rafik (2018)
Thèse de doctorat

Dans ce travail, plusieurs composites stratifiés à matrice époxyde ont fait l’objet d’une étude expérimentale dans le but de déterminer l’influence de certains paramètres tels que, le type de renforts, la séquence d’empilement et l’hybridation sur le comportement mécanique et dynamique amortissant. Une étude détaillée est d’abord menée pour déterminer les propriétés mécaniques des différents composites stratifiés, en traction statique et en flexion 3-points. Les résultats obtenus ont été analysés et comparés à ceux trouvés par la méthode ultrasonore. Des observations microscopiques au microscope optique et au microscope électronique à balayage (MEB) des faciès de rupture des différentes éprouvettes ont été présentées et les modes d’endommagement ont été analysés.           Ensuite, une analyse du comportement dynamique, en utilisant la méthode d’analyse dynamique mécanique (DMA) et la méthode d’analyse modale expérimentale (EMA), est mise en place pour identifier les propriétés viscoélastique et dissipatives des différents matériaux.          Enfin, l’utilisation de la méthode d’analyse modale et la méthode ultrasonore (propagation des ondes de Lamb) pour la détection de la présence d’endommagement a permis d'éclairer le lecteur sur la sensibilité de ces deux méthodes d’analyse, et de mettre en évidence l’évolution des propriétés mécaniques de la structure composite en fonction du niveau de dégradation. Voir les détails

Mots clés : Composites stratifiés, Comportement viscoélastique, Interface, vibrations, Analyse modale, amortissement, Cohésion, endommagement

Analyse par spectroscopie Infrarouge à transformée de Fourier et diffraction des rayons X d’un matériau composite.

N. Sassane, L. Alimi, T. Guettaf Temam, M. HASSANI, S.Boukhezar  (2019)
Article de conférence

Les composites à matrice polymère sont utilisés en général comme des biomatériaux à cause de leurs constituants. Le matériau analysé est un composite à matrice en polymère renforcé par une fibre de verre utilisé comme prothèse orthopédique d’un tibia. Les résultats obtenus de diffraction des rayons X et spectroscopie Infrarouge à transformée de Fourier(FTIR) montrent la présence de la silice SiO2 et de l’alumine Al2O3 se sont parmi les constituants de la fibre de verre ainsi que la présence des molécules organiques se sont parmi les constituants de la résine polyester. Voir les détails

Mots clés : composite, Prothèse orthopédiques, DRX, FTIR.

Effet de la cinétique de précipitation sur la résistance à la corrosion de l’acier inoxydable duplex 2205 et de l’alliage d’aluminium 2000

DJAMA Mustapha (2018)
Thèse de doctorat

This thesis is subdivided into two main parts. First, the influence of the microstructure of the AA2214-T6 aluminum alloy on the morphologies and electrochemical properties of anodic alumina oxide films was investigated. (AAO) formed,  and then to see if the heat treatment T4 brought to the AA2214 alloy brought improvements in term of the morphologies of (AAO) and in term of resistance to the corrosion of the anodic alumina oxide films .Secondly, we orientate this work to correlate the pitting potential (Epit) evolution with the kinetics of σ phase precipitation in the 2205 duplex stainless steel aged at 850°C after solution treatment at 1150°C. The potentiodynamic polarization curves indicate a reduction of the pitting corrosion resistance with the aging time, which is revealed by a decrease in the Epit values from 0.65 to 0.40 VSCE. Thus, Epit values are used to determine the kinetics parameters of the σ phase precipitation. The experimental transformed fraction agrees well with the one calculated by using the modified Kolmogorov–Johnson–Mehl–Avrami equation with an impingement parameter c = 0.6. Voir les détails

Mots clés : Kinetics, KJMA, Pitting corrosion, Potentiodynamic polarization, sigma phase precipitation, Aluminum alloy, (AAO) anodic alumina oxide, porous structure, T4, EIS

Electric Field Distribution in point-insulating barrier-Plane System using experimental and Theoretical method

S.Benharat, S.Bouazabia, S.BELGACEM  (2019)
Article de conférence

The present paper deals with the influence of insulating barriers on the breakdown and the electric field distribution in the Point –insulating barrier- plane air gap system. An experimental investigation on the influence of different parameters such as gap distance between electrodes and barrier dimensions, under AC voltage, have been studied. The results show that the width and thickness of the insulating barrier effect the electric field variation which increases with increasing applied voltage. The experimental results are compared with a numerical model. Voir les détails

Mots clés : Electric field, Finite Element Method, breakdown voltage, insulating barrier, point- plane system