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Correlation between structural and optical properties of SiO2/TiO2multibilayers processed by sol-gel technique and applied toBragg reflectors

H.Sedrati, R.Bensaha, M.Brahimi, H.DEHDOUH, H.Bensouyad, F.Abbas, B.Toubal  (2013)

SiO2 and TiO2 thin layers processed by sol-gel technique have been deposited,alternatively, on glass substrates and Si (111) wafer. Dip-coatedmultibilayerswere characterized by different experimental techniques:XRD,SEM, FTIRandUV-VIS-NIR. The obtainedX-ray diffraction patterns analysishave shown that our films crystallize in anatase and rutile phases whateveris the number of bilayers and the corresponding grain sizes increasefrom 5.48 nmto 16.11 nm. The SEMmicrograph shows that our layers arehomogeneous without any visual cracks. The FTIR spectra have shownthat the vibration of Si-O-Ti bonds becomes intense by the increase in thenumber of bilayers. This increase, on the on hand, decreases the transmissioncoefficient from 4.58% to 0.55% and increases the width of the stopband shown in UV-VIS-NIR spectra. On the other hand, the band-gap decreasesfrom3.73 eV to 3.59 eV. In addition, a pseudo band-gap is locatedbetween 300 nmand 400 increasing from1.76 eVto 2.29 eV.? 2013 Trade Science Inc. - INDIA Voir les détails

Mots clés : Sol-gel;, Anatase;, Rutile;, Stop band;, Si-O-Ti;, Band-gap.

Simulation du L’implantation ionique du phosphore dans la matrice de ZnO

Article de conférence

Le matériau ZnO montre de manière quasi-naturelle un dopage de type n [1]. Son dopage de type p représente une importante problématique récurrente depuis plus d'une quinzaine d'années. Dans ce travail nous avons fait une simulation numérique du dopage de ZnO en type p. Pour cela, nous avons utilisé le code dénommée TRIM (Transport and Range of Ions in Matter) et SRIM (Stopping and range of Ions in Matter) développé par Ziegler et al [2].C’est une simulation faite pour caractériser l'interaction des ions avec des cibles échantillons en gaz ou en solides. Les résultats numériques visent à étudier l'interaction d'un faisceau d'ions avec la surface semi-conductrice du ZnO. Dans notre étude le bombardement des ions du phosphore P tombe sur la cible ZnO selon une incidence normale au plan de la surface du matériau avec la possibilité de former des postes vacants sur la zone irradiée le composé de type II-VI ZnO Voir les détails

Mots clés : ZnO, SRIM, TRIM


M. T. AbedGhars; M. Ghers; S. Bouhouche; B. Bezzina  (2017)
Article de conférence

Abstract.This work has a double objective. On the one hand, the valorization of natural raw materials, in particular, the oolithic iron ores which do not find their use in iron and steel because of their high phosphorus content and on the other hand the recycling of steel by-products.. The ultimate goal is to synthesize an anti-corrosion paint.In this first part, we will study the characterization of these two components by their chemical analysis, their grinding (fineness) and their thermal analysis (TGA, DSC).Chemical analysis showed that the pigment contains 53.18% of total iron and gangue dominated by silica. Calamine in turn contains 73.83% of iron in the form of iron oxides (FeO, Fe3O4 and Fe2O3).Iron pigment is composed mainly of hematite with a little of goethite.Grinding tests showed that the scale is much more suitable for grinding than pigment. The granulometric analysis measured by a laser granulometer (Hydro 2000MU) gave us a volume distribution of the particles with a size between 0.7 and 32 microns for scale and between 0.6 and 40 microns for the pigment and Their specific areas are 1.6 and 1.5 m2 / g..Thermogravimetric analysis (TGA) and the thermal variation of flow (DSC) showed that the iron pigment loses weight with phase dissolution by consuming energy when the temperature increases. Scale gains weight by the formation of new phase with heat.Exploration picture by scanning electron microscope of red iron pigment shows a grain aggregate formed rounded over at least iron oxide and gangue. The analysis by EDS shows a predominance of iron with a relatively large matrix containing the four predominant oxides in the case of iron ore deposits. Chemical elements forming these four oxides are silicon, calcium, aluminum and magnesium.The observation scale milled for 5 min SEM showed a homogeneous structure composed of sizes of iron oxide grains and shapes ranging from 1 µm to 10 µm. Voir les détails

Mots clés : Pigment iron, scale (calamine), iron oxides, grinding, Simultaneous thermal analysis.

Prediction of thermal and mass loss behavior of mineral mixture using inferential stochastic modeling and thermal analysis measurement data

M.T. AbedGhars, S. Bouhouche, M. Ghers  (2017)

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

Structure and Magnetic Properties of Ternary Nanosized FeAlSn and CuFeCo Powders Synthesized by Mechanical Milling

Z. Hamlati, W. Laslouni, Mohammed AZZAZ, M. Zergoug, D. Martínez-Blanco, J.A. Blanco, P. Gorria  (2017)

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

Physical investigations on perovskite LaMnO3-δ sprayed thin films for spintronic applications

A.Boukhachem. A.Ziouche. M.BenAmor. .O.Kamoun. M.Zergoug, .H.Maghraoui-Meherzi, .A.Yumak, K.Boubaker, M.Amlouk  (2016)

Oxygen deficient LaMnO3 thin films were successfully grown on glass substrate by spray pyrolysis at 460 °C. XRD studies show oxygen vacancies corresponding to the orthorhombic La4Mn4O11 with (040) preferential orientation. Optical properties were investigated through optical band gap and Urbach energy. The dispersion of the refractive index was discussed in terms of both Cauchy and Wemple & Di-domenico models. Raman spectroscopy shows the band positions corresponding to LaMnO3 with a shift related to oxygen deficiency. Electrical properties were quantified using impedance spectroscopy technique within frequency range of 5 Hz–13 MHz at various temperatures. Both the DC conductivity and relaxation frequency were thermally activated with activation energy around 0.9 eV. Also, AC conductivity was investigated through Jonscher law. Finally, magnetic measurements at room temperature using vibrating sample magnetometer (VSM) technique show ferromagnetic behavior of these ternary sprayed thin films. Voir les détails

Mots clés : Thin films, Magnetic Properties, Raman spectroscopy, Impedance spectroscopy, X-ray diffraction, Dielectric properties

Microstructure and Magnetic Properties of NiP Alloys

S. Alleg, A. Boussaha, W. Tebib, M. Zergoug, J. J. Su?ol  (2016)

Ni-P alloys were prepared by electrodeposition on a copper substrate at different plating conditions (applied potential and deposition time). The morphology, composition, microstructure, structure, and magnetic properties of the films were investigated by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, and vibrating sample magnetometry, respectively. The phosphorous content is about 8.6–12.2 at.%. The deposits exhibit either a nanocomposite structure where Ni(P)–1 and Ni(P)–2 solid solutions are embedded into an amorphous matrix, or a mixture of Ni2P phosphide and Ni(P)–1 and Ni(P)–2 solid solutions. The coercivity and magnetization are plating condition dependent. All samples exhibit a soft magnetic character with coercivity lower than 58 Oe. The squareness ratio Mr/Ms values that are in the range 0.019–0.123 correspond to a multidomain (<0.1) for all samples except sample B (−1.15 V, 10 min) which falls into a pseudo-single domain (Mr/Ms = 0.123). Voir les détails

Mots clés : Electrodeposition Ni-P alloys Microstructure Magnetic properties X-ray diffraction

Microstructural Study of Thin Films CuFe Obtained by Thermal Evaporation of Nanostructured Milled Powder

H. Mechri, Ahmed HADDAD, M. Zergoug, Mohammed AZZAZ  (2017)

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

RF magnetron sputtering deposition of NiO/Ni bilayer and approach of the Magnetic behavior using the Preisach model

A. Bendjerad, S. Boukhtache, A. Benhaya, A. Lahmar, M. Zergoug, D. Luneau  (2017)

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

Spatio-temporal aspects of the domain propagation in a spin-crossover lattice with defect

R. Traichea, H. Oubouchoua, M. Zergoug, K. Boukheddaden  (2017)

the collective spatiotemporal dynamics of the metastable high-spin state (HS) upon relaxation towards the low-spin (LS) is investigated using an electro-elastic model which includes the change of the spin states and the lattice volume at the transition. The present work focusses on the case of a lattice in which is embedded a structural defect in the center, represented here by a hole with a fixed size. The simulations are made on a 2D rectangular-shaped and compared to those of an ideal system. To account for the volume change, we set the distances between the sites as spin-dependent which requires the use of Monte Carlo simulations on spin states and atomic positions to solve the present problem. It is found that the presence of the defect affects the dynamics of the spin-crossover transformations which starts stochastically from a corner of the lattice, then propagates in the first stage along the width (shortest distance to the surface), before to proceed via a second longitudinal regime whose velocity slows down significantly at the vicinity of the defect, which plays the role of a pining center. After a while, the interface leaves the defect, and accelerates when it approaches the lattice's border. We have also investigated the spatial dependence of the displacement field, from which we derived the distribution of the divergence and rotational of the displacement field, which directly connects to the trace of the strain tensor and to shear strains respectively. Valuable information on the relaxation process of the elastic field are derived and discussed in direct relation with the presence of the defect. Voir les détails

Mots clés : Spin Crossover, Phase transition;, Interface propagation;, Spatiotemporal effects, elasticity