Physique
RF magnetron sputtering deposition of NiO/Ni bilayer and approach of the Magnetic behavior using the Preisach model
Bilayer of nickel and nickel oxide were deposited on glass substrates using RF magnetron sputtering technique. The magnetic properties of the prepared thin films were carried out at room temperature in both parallel and perpendicular magnetic field to the sample. The Preisach model was applied to provide a mathematical model of the magnetic hysteresis loop in the case of parallel geometry, along the easy axis of the bi-layer NiO / Ni. Good agreement was obtained between the theoretical and experimental results. Voir les détails
Mots clés : Ni/NiO bilayer;, Magnetic properties;, Preisach Model
Microstructural Study of Thin Films CuFe Obtained by Thermal Evaporation of Nanostructured Milled Powder
Commercial copper and iron powders were used as starting materials. These powders were mechanically alloyed to obtain Cu(100-x) Fex supersaturated mixture. The milling duration was chosen in such a way as to obtain a nanostructured mixture and to form a supersaturated solid solution of CuFe; the powder mixture was used to deposit CuFe on a glass substrate. The elaboration of our films has been carried out using thermal evaporation process (physical vapor deposition) under 1 × 10-6 mbar vacuum from an electrically heated tungsten boat, using the supersaturated solid solution Cu(100-x) Fex powder obtained by mechanical alloying. The films deposition has been done on glass substrates. In this study, we present the composition effect on the structural and magnetic proprieties of Cu(100-x) Fex powder and thin films. The chemical composition, structural and magnetic proprieties of milled powders and thin films were examined by SEM, TEM, XRD, XRF and VSM. Voir les détails
Mots clés : CuFe Solid Solution, DRX, MET, microstructure, thin film, VSM
Structure and Magnetic Properties of Ternary Nanosized FeAlSn and CuFeCo Powders Synthesized by Mechanical Milling
Ternary Fe72Al26Sn2 and Cu70Fe18Co12 alloys were obtained by mechanical alloying of pure Fe, Al, Sn, Cu and Co powders using a high energy ball mill. X-ray diffraction and electron microscopy supported by magnetic measurements have been applied to follow changes in the microstructure, phase composition and magnetic properties in dependence on milling time. With the increase of milling time all Al and Sn atoms dissolved in the bcc Fe and the final product of the MA process was the nanocrystalline Fe (Al, Sn) solid solution in a metastable state with a large amount of defects and mean crystallite size of 5 nm. However, the obtained crystallite size value is about 10 nm for the ball milled Cu70Fe18Co12 powders. The electron microscope observations show the morphology of powder particles. Magnetic properties of the nanocrystalline mechanically alloyed FeAlSn and CuFeCo were also investigated and were related to the microstructural changes. Voir les détails
Mots clés : CuFe Solid Solution, DRX, FeAl, Mechanical Alloying, SEM, VSM
Prediction of thermal and mass loss behavior of mineral mixture using inferential stochastic modeling and thermal analysis measurement data
Abstract:Characterization methods of material are widely used in different steps of quality control in material sciences and engineering. Such methods are relatively complex according to the considered case. This paper is concerned by a characterization method for mineral material analysis using thermal analysis i.e. Differential Scanning Calorimetric. The thermal analysis is a physical method based on the heating; the sample is heated using a ramped set point of the input temperature, according to its properties, the sample gives a thermal response qualified by endothermic and exothermic reactions: Such responses are fundamental for phase’s identification.In mineral industry, different material mixture is used in different stage of manufacturing process; the thermal behavior prediction of mixture between two or more materials is very interesting. The thermal mixture behavior is predicted in basis of individual thermal behavior of each input element and the mixture ratio.A mathematical modeling based on artificial neural network is designed to have a soft sensor for predicting the thermal and mass behavior of the mixture, validation using measurement and prediction uncertainties is also considered.Using such approach, the prediction of the mineral mixture characteristics is given by an implementation of the obtained model using the individual behavior and the mixture proportion of the inputs elements. Voir les détails
Mots clés : • Modeling and identification; • Artificial neural network (ANN); • Monte Carlo Simulation (MTCS); • Thermal analysis; • Material/mineral mixture; • Uncertainty of measurement
Modelling of thermodynamics of adsorption on sensor array films : application to the generalized multicomponent adsorption model of Langmuir
In the present study, by using of Gibbs Duhem formalism and simple mathematics, new models, which describe the response of the elements of a sensor array , have been developed .In addition , the thermodynamic ehavior of the interfaces sensor array fims gas mixture has been treated . Finally, the derived models were used for the generalized model of adsorption of Langmuir. Voir les détails
Mots clés : adsorption of Langmuir, Gibbs Duhem equations, intrinsic conducting polymers, modeling, sensor array
Effect Of Thickness On The Structural, Microstructural, Electrical And Magnetic Properties Of Ni Films Elaborated By Pulsed Electrodeposition On Si Substrate
We have studied the effect of thickness on the structural, microstructural, electrical and magnetic properties of Ni films electrodeposited onto nn-Si (100) substrates. A series of Ni films have been prepared for different potentials ranging from −−1.6V to −−2.6V. Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), four point probe technique, atomic force microscopy (AFM) and vibrating sample magnetometry (VSM) have been used to investigate the physical properties of elaborated Ni thin films. From the analysis of RBS spectra, we have extracted the films thickness tt (tt ranges from 83nm to 422nm). We found that the Ni thickness, tt (nm), linearly increases with the applied potential. The Ni thin films are polycrystalline and grow with the ?111??111? texture. The lattice parameter aa (Å) monotonously decreases with increasing thickness. However, a positive strain was noted indicating that all the samples are subjected to a tensile stress. The mean grain sizes DD (nm) and the strain εhklεhkl decrease with increasing thickness. The electrical resistivity ρρ (μΩ.μΩ.cm) increases with tt for tt less than 328nm. The diffusion at the grain boundaries may be the important factor in the electrical resistivity. From AFM images, we have shown that the Ni surface roughness decreases with increasing thickness. The coercive field HCHC, the squareness factor SS, the saturation field HSHS and the effective anisotropy constant K1effK1eff are investigated as a function of Ni thickness and grain sizes. The correlation between the magnetic and the structural properties is discussed Voir les détails
Mots clés : Ni thin films; pulsed electrodeposition; structural properties; microstructure; magnetization curves; magnetic anisotropy.
Modelling of a Cd1−xZnxTe/ZnTe Single Quantum Well for Laser Diodes
In this paper, the carrier density, temperature and quantum well width effect have been investigated for the optical gain for a Cd1−xZnxTe/ZnTe Zinc-blend strained quantum well structure. The device emits laser radiations in green–yellow–orange. Our results showed that the optical gain significantly increases with the increasing of the carrier density. It also increases with the decreasing of the Zn concentration, the well width and the temperature. In addition, the optimal threshold current density values were determined for three alloy compositions as 0.7, 0.8 and 0.9. Voir les détails
Mots clés : Quantum wells diode laser gain CdZnTe optoelectronics
Modeling and simulation of ZnxCd1-xTe/ZnTe quantum well structure for laser applications
In this work, we modeled and simulated aZnxCd1-xTe/ZnTe based single quantum well structure. We have taken into account the effect of carrier density, alloy composition, temperature and wells width on the optical gain as well as threshold current density. The use of ZnTe as a barrier leads to the improvement of the carrier confinement such as Qc (83%)/Qv (17%). Then, we have optimized the quantum well structure that allows obtaining a threshold current density Jth = 500 A/cm2. This study allowed us to achieve laser diodes VCSEL quantum well reliable and emitting around 0.740 μm. Voir les détails
Mots clés : Quantum well Semiconductor laser Gain ZnCdTe Optoelectronics
Amorphous SiC/c-ZnO-Based Quasi-Lamb ModeSensor for Liquid Environments
The propagation of the quasi-Lamb modes along a-SiC/ZnO thin composite plates wasmodeled and analysed with the aim to design a sensor able to detect the changes in parametersof a liquid environment, such as added mass and viscosity changes. The modes propagation wasmodeled by numerically solving the system of coupled electro-mechanical ?eld equations in threemedia. The mode shape, the power ?ow, the phase velocity, and the electroacoustic couplingef?ciency (K2) of the modes were calculated, speci?cally addressing the design of enhanced-coupling,microwave frequency sensors for applications in probing the solid/liquid interface. Three modeswere identi?ed that have predominant longitudinal polarization, high phase velocity, and quitegood K2: the fundamental quasi symmetric mode (qS0) and two higher order quasi-longitudinalmodes (qL1 and qL2) with a dominantly longitudinal displacement component in one plate side.The velocity and attenuation of these modes were calculated for different liquid viscosities andadded mass, and the gravimetric and viscosity sensitivities of both the phase velocity and attenuationwere theoretically calculated. The present study highlights the feasibility of the a-SiC/ZnO acousticwaveguides for the development of high-frequency, integrated-circuit compatible electroacousticdevices suitable for working in a liquid environment. Voir les détails
Mots clés : Lamb Modes, Amorphous SiC, Coupling configurations, sensors, viscous liquids
FINITE ELEMENT MODELING OF GROUND MOVEMENT ON THE ROADCW16 SÉRAIDI -CHÉTAIBI (ANNABA, ALGERIA)
Grounds movements are considered a natural hazard, some of which have, over time, significant slow movements.Significance of these dynamic effects involves a risk which generates human and material damage. Policymakers musttake this issue into account in their permanent security organization program. Some landslides exhibit a function of time,significant slow movements. They are assigned to a behavior of clay materials mechanism caused by the variation ofgeotechnical properties. The effects of water seepage in wet periods generally linked to the viscous nature of claymaterials are causes primarily .They can also be related to the variation modeling parameters. The land slip site is locatedat the road CW16 Seraidi -Chétaibi, (Annaba, Algeria) area with an annual rainfall of more than 700mm. Analysis of theslope stability is carried out using several methods of deformation calculation of the natural ground state. In our case weuse a plastic Mohr Coulomb from supported models. The project proposes to examine the different causes using theexample of Cam Clay. The project will examine the different causes using the example of Cam Clay; elasticvisco plasticmodel with time (SSCM: Soft Soil Creep Model) set in a finite element program Plaxis. This technique can show us howdifferent behavioral assumptions can describe the slow movements of a slope. A comparison will be made with the MohrCoulomb (MC). Voir les détails
Mots clés : Mohr Coulomb, slip, numerical modeling, plaxis, cam clay, elasticvisco plastic model