A. Guittoum - Academia.edu (original) (raw)

Papers by A. Guittoum

Nous avons elabore des poudres nanostructurees Fe80Ni20 a l’aide du vario-broyeur planetaire pulv... more Nous avons elabore des poudres nanostructurees Fe80Ni20 a l’aide du vario-broyeur planetaire pulverisette « P4 », pour des temps de broyage allant de 3 a 25 h. L’etude des proprietes structurales (formation de la solution solide, taille des grains et parametre de maille) a ete faite a l’aide de diffraction des Rayons X (DRX). Nous avons montre que la solution solide Fe(Ni) commence a se former a partir de 6 h de broyage et est completement formee a 10 h de broyage. La taille des grains diminue lorsque le temps de broyage augmente et atteint une valeur minimale de 11 nm apres 25 h de broyage. Le parametre de maille augmente lorsque le temps de broyage augmente pour atteindre une valeur inferieure a celle de l’alliage Fe80Ni20 massif. L’ensemble des resultats sera correle et discute

Surface Review and Letters

Ni thin films have been electrodeposited on [Formula: see text]-Si (100) substrates for different... more Ni thin films have been electrodeposited on [Formula: see text]-Si (100) substrates for different deposition times at a fixed potential of 2[Formula: see text]V. The as-elaborated films have been characterized by Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). From RBS spectra, we have extracted the Ni film thicknesses, [Formula: see text], which ranges from 105 nm to 710 nm. The analysis of XRD spectra shows the existence of a strong [Formula: see text]111[Formula: see text] texture for all film thicknesses. The strain values [Formula: see text] are negative for all Ni films indicating that they are under compressive stresses. The grains size, [Formula: see text], increases to reach a maximum for [Formula: see text][Formula: see text]nm then decreases again with increasing [Formula: see text][Formula: see text](nm). From AFM images, we have shown that the films become progressively smoothe...

Journal of Electronic Materials

A two-step process was used to prepare a nickel-polyaniline nanocomposite (Ni (NPs)-PANI). The fi... more A two-step process was used to prepare a nickel-polyaniline nanocomposite (Ni (NPs)-PANI). The first step consisted of the electrodeposition of polyaniline (PANI) in the form of thin films on fluorine-doped tin oxide (FTO) substrates from a solution of aniline, lithium perchlorate, and sulfuric acid at a pH of 0.5. In the next step, the obtained Ni (NPs) were deposed in this polyaniline films. The structural, morphological, and electrocatalytic properties of the prepared nanocomposites were then investigated. X-ray diffraction (XRD) confirmed the cubic structure of the nanocomposites, and Fourier-transform infrared spectroscopy (FTIR) indicated the existence of nickel and polyaniline in the prepared nanocomposites. Morphological analysis carried out through SEM revealed that the nanocomposites exhibit uniform dispersion of nickel nanoparticles into the polyaniline matrix. Amperometry and cyclic voltammetry were employed to investigate the electrocatalytic glucose oxidation behavior of the nanocomposite electrode in the alkaline medium. The prepared nickel-polyaniline nanocomposite electrode exhibited high sensitivity (278.8 µA mM−1 cm−2) in a range from 0.02 to 1 mM at a sufficiently fast response time of 3 s and a low glucose detection limit of 1 µM (S/N = 3). A cost-effective and straightforward synthesis procedure to prepare Ni (NPs)-PANI nanocomposite would make this material an efficient glucose sensor with appropriate stability, higher reproducibility, and excellent sensitivity.

Materials Letters

Abstract We have investigated the effect of the Nickel concentration on the crystal structure and... more Abstract We have investigated the effect of the Nickel concentration on the crystal structure and microstructure, as well as on the hyperfine and magnetic properties of nanostructured (Fe0.7Al0.3)100-xNix powders (x = 0, 5, 10 and 15 at.%) fabricated by mechanical alloying. After 72 h of milling, all the Fe(Al, Ni) samples are single-phase disordered solid solutions with body centred cubic crystal structure. A progressive reduction of the lattice parameter value from 2.9084 A for the Ni-free FeAl binary alloy down to 2.8897 A for the x = 15 ternary compound is observed. The mean grain size of the nanocrystals also diminishes down to c.a. 20 nm as the Ni concentration is increased, whereas the mechanically-induced microstrain remains almost constant at around 0.5%. The magnetic measurements show a ferromagnetic character of all the samples at room temperature with a slight decrease of both saturation magnetization and coercivity as the Ni concentration rises. The fit of Mossbauer spectra collected at room temperature gives an almost constant value (around 26 T) for the mean hyperfine magnetic field, (T). Hence, the addition of Ni to Fe (Ni,Al) solid solution has not a clear influence on the value of , although the hyperfine field distributions suggest somewhat different local environments of Fe atoms.

Philosophical Magazine Letters

ABSTRACT Cold-worked Zircaloy-4, used for the fuel grid of research reactors, was irradiated with... more ABSTRACT Cold-worked Zircaloy-4, used for the fuel grid of research reactors, was irradiated with 20 MeV Cu ions at different doses varying from 0.007 to 0.15 displacements per atom (dpa) at room temperature. The microstructure evolution was investigated by grazing X-ray diffraction and positron annihilation spectroscopy techniques (PAS). The mechanical properties were studied using nanoindentation. The microstrain, S parameter and nanohardness present similar behaviour. They all increase rapidly during the beginning of irradiation (first stage) and reach saturation value at 0.15 dpa. The experimental results reveal radiation-induced lattice distortion along the (110) direction indicating an anisotropic displacement energy.

Journal of Nano Research

Nanostructured (Fe0.6Al0.4)100-xSix powders with x= 0, 5, 10, 15 and 20 at.% were elaborated by m... more Nanostructured (Fe0.6Al0.4)100-xSix powders with x= 0, 5, 10, 15 and 20 at.% were elaborated by means of mechanical alloying for a fixed milling time of 72 h. We have investigated the effect of silicon addition on the microstructure and magnetic properties of these ternary alloys. X-ray diffraction experiments reveal that these powders are single-phase disordered solid solutions with body centered cubic crystal structure. The lattice parameter diminishesalmost linearly as the Si content increases. The mean crystallite size,, is around three times smaller for the samples with higher amount of Si (≈ 10 nm) compared with that of the binary alloy (27 nm). Moreover, the volume fraction of grain boundaries (fgb) seems to be higher with increasing the Si content, as well as both dislocation density (ρ) and lattice microstrain (),that follow alinear trend. The SEM images show that the Si helps in refining the shape and size of the powder particles, leading to a nearly homogeneous small part...

SPIN

The Magneto-Optic Kerr Effect (MOKE) technique has been used to investigate the magnetic properti... more The Magneto-Optic Kerr Effect (MOKE) technique has been used to investigate the magnetic properties of Ni thin films, with thickness [Formula: see text] ranging from 9 to 163[Formula: see text]nm, evaporated onto several substrates (glass, Si (111), mica and Cu) with and without an evaporated Cu underlayer. The MOKE observations were correlated with the surface morphology inferred from Scanning Electron Microscope images and with the structural properties (grain size and strain). Some interesting behaviors of the coercive field (with values in the 2 to 151 Oe range), the squareness (between 0.1 and 0.91) and the saturation field (25–320 Oe) are observed as a function of [Formula: see text], the substrate and the Cu underlayer. A thickness-dependent stress-induced anisotropy is found in these films. The differences between the present MOKE results and the ones obtained from the Vibrating Sample magnetometer (VSM) are highlighted. The former describe the surface magnetism of these sys...

Journal of Superconductivity and Novel Magnetism

We report on the synthesis of Co30Ni70 nanoparticles using hydrothermal method at low temperature... more We report on the synthesis of Co30Ni70 nanoparticles using hydrothermal method at low temperatures and short times (100 °C, 2 h) without any surfactant or external magnetic field. The effect of NaOH concentration on the crystal structure, microstructure, and magnetic properties of CoNi samples has been investigated by x-ray diffraction (XRD), scanning (SEM) and high-resolution transmission (HRTEM) electron microscopy, and vibrating sample magnetometry (VSM). From the Rietveld refinement of x-ray powder diffraction patterns, we have evidenced the coexistence of two phases with face-centered cubic (FCC) and hexagonal (HCP) crystal structures, being 12 nm and 3 nm, respectively, the values for the mean grain size of both phases. SEM images show that the basic microstructure is composed of quasi-spheres and a chain-like morphology appears with increasing the amount of NaOH. HRTEM images evidence the formation of such chains, and confirm the coexistence of FCC and HCP phases. The magnetic hysteresis loops show a clear dependence of the coercivity on the particle morphology indicating the role played by the magnetic shape anisotropy.

Journal of Magnetism and Magnetic Materials

Abstract In the present work, nanocrystalline (Fe70Al30)100−xSix (x = 0, 5, 10, 15 and 20 at.%) p... more Abstract In the present work, nanocrystalline (Fe70Al30)100−xSix (x = 0, 5, 10, 15 and 20 at.%) powders were prepared by mechanical alloying for a fixed milling time of 72 h. The powder samples were characterized in terms of structural evolution, morphological changes and magnetic behavior. The X-ray diffraction measurements reveal that all the samples are of (bcc) single phase with an average crystallite size less than 22 nm. Besides, the lattice parameter decreases with Si content (x) up to the solubility limit of Si atoms into the α-Fe lattice where it remains independent of the composition. The magnetic data obtained by Vibrating Sample Magnetometer showed that the saturation magnetization decreases monotonously with Si content increasing x, whereas coercivity which not only depends on composition but also on structure of the sample decreases to a minimum of 20.3 Oe at x = 10 at.% and increases abruptly at the higher x value (x = 20 at.%). Mossbauer spectroscopy analyses indicated that the sample with x = 5 at.% exhibits a fully ferromagnetic behavior and that beyond this concentration, the content of the ferromagnetic phase gradually decreases due to the non magnetic nature of Si.

SPIN

We have studied the effect of the silicon concentration on the structural and hyperfine propertie... more We have studied the effect of the silicon concentration on the structural and hyperfine properties of nanostructured Fe[Formula: see text]Six powders ([Formula: see text], 20, 25 and 30[Formula: see text]at.%) prepared by mechanical alloying. The X-ray diffraction (XRD) studies indicated that after 72[Formula: see text]h of milling, the solid solution bcc-[Formula: see text]-Fe(Si) is formed. The grain sizes, [Formula: see text]D[Formula: see text] (nm), decreases with increasing Si concentration and reaches a minimum value of 11[Formula: see text]nm. We have found that the lattice parameter decreases with increasing Si concentration. The changes in values are attributed to the substitutional dissolution of Si in Fe matrix. From the adjustment of Mössbauer spectra, we have shown that the mean hyperfine magnetic field, [Formula: see text]H[Formula: see text] (T), decreases with increasing Si concentration. The substitutional dependence of [Formula: see text]H[Formula: see text] (T) c...

2015 IEEE International Conference on Plasma Sciences (ICOPS), 2015

Permalloy (Py) thin films were evaporated from nanocrystalline soft Ni75Fe25 powder onto glass an... more Permalloy (Py) thin films were evaporated from nanocrystalline soft Ni75Fe25 powder onto glass and Al2O3 substrates. The thicknesses of these films range from 16 nm to 250 nm. The as deposited films were characterized by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). From the GIXRD spectra, we have shown that the films are amorphous for the thinner films. However, for the thicker films, a polycrystalline FCC structure is present. For the intermediate thicknesses, the nature of substrate determines the texture of the films. The SEM micrographs indicate that the nature of substrate influences on the morphology and grains size of Py films. From AFM observations, the nanocrystalline nature of the grains is evidenced. Hysteresis loops reveals the ferromagnetic character of Py films. We have shown that the values of coercive field, Hc, generally, decrease with increasing thickness. Moreover, the Hc values are higher for films deposited onto a Al2O3 substrate than those on the glass substrate. The nature of substrate and thickness seems to influence the magnetic properties of Py films. A correlation between these physical properties will be established and discussed.

Journal of Magnetism and Magnetic Materials, 2015

Abstract Various structural and magnetic characterization techniques have been used to investigat... more Abstract Various structural and magnetic characterization techniques have been used to investigate Fe100−xPdx (x=15, 20 and 36) thin films deposited onto silicon and glass substrates, by thermal evaporation technique. X-ray diffraction analysis shows the presence of supersaturated solid solution with bcc structure for Pd concentrations of 15% and 20%. However, for 36% of Pd, in addition to the supersaturated α-FePd (bcc) phase, another disordered FePd3 phase with fcc structure is present. At 20 at% Pd, the magnetic characterization shows a saturation of the bcc (α-FePd) phase and the appearance of the fcc phase. The correlation between the structure and magnetic properties allows us to compare the two substrates effects on deposited thin films. As results, the measurements indicate that the grain size D, the thin film thickness and the d(110) spacing significantly affect the magnetic coercivity HC. The Fe–Pd alloys deposited on a monocrystalline Si (100) and glass substrate show that the coercivity HC is given by the random anisotropy model.

Radiation Measurements, 2013

ABSTRACT The damaged produced by proton beam slowed down in CR-39 polymer results in highest degr... more ABSTRACT The damaged produced by proton beam slowed down in CR-39 polymer results in highest degree of disorder with change of free volume proprieties. Positron annihilation lifetime spectroscopy (PALS) is nowadays well recognized as powerful tool of microstructure investigations. PALS is used in order to get more information at an atomic scale of modifications induced by irradiation of polymers particularly the variation of free volume in the irradiated region. In this paper, the mean free volume hole radii and average free volume of the micro-voids in CR-39 polymer irradiated with 200 MeV therapy proton beam at different positions in spread out Bragg Peak region (SOBP) at Ithemba proton therapy facility have been determined using PALS. © 2006 Elsevier Ltd. All rights reserved.

The European Physical Journal Applied Physics, 2009

... References 1. R. Naik, C. Kota, JS Payson, GL Dunifer, Phys. Rev. B 48, 1008 (1993) 2. F. D&#... more ... References 1. R. Naik, C. Kota, JS Payson, GL Dunifer, Phys. Rev. B 48, 1008 (1993) 2. F. D'Orazio, G. Gubbiotti, F. Lucari, E. Tassoni, J. Magn. Magn. Mater. 535, 242 (2002) 3. YB Xu, ETM Kernoham, DJ Freeland, M. Tselepi, A. Ercole, JAC Bland, J. Magn. Magn. Mater. ...

Applied Surface Science, 2011

Series of Fe thin films have been prepared by thermal evaporation onto glass and Si(100) substrat... more Series of Fe thin films have been prepared by thermal evaporation onto glass and Si(100) substrates. The Rutherford backscattering (RBS), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and the four point probe techniques have been used to investigate the structural and electrical properties of these Fe thin films as a function of the substrate, the Fe thickness t in the

Journal of Magnetism and Magnetic Materials

Surface Review and Letters

We have studied the effect of thickness on the structural, microstructural, electrical and magnet... more We have studied the effect of thickness on the structural, microstructural, electrical and magnetic properties of Ni films electrodeposited onto [Formula: see text]-Si (100) substrates. A series of Ni films have been prepared for different potentials ranging from [Formula: see text]1.6[Formula: see text]V to [Formula: see text]2.6[Formula: see text]V. 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 [Formula: see text] ([Formula: see text] ranges from 83[Formula: see text]nm to 422[Formula: see text]nm). We found that the Ni thickness, [Formula: see text] (nm), linearly increases with the applied potential. The Ni thin films are polycrystalline and grow with the [Formula: see text] texture. The lattice parameter ...

Materials Chemistry and Physics, 2015

Surface Review and Letters

Journal of Electronic Materials

Materials Letters

Philosophical Magazine Letters

Journal of Nano Research

SPIN

Journal of Superconductivity and Novel Magnetism

Journal of Magnetism and Magnetic Materials

SPIN

2015 IEEE International Conference on Plasma Sciences (ICOPS), 2015

Journal of Magnetism and Magnetic Materials, 2015

Radiation Measurements, 2013

The European Physical Journal Applied Physics, 2009

Applied Surface Science, 2011

Journal of Magnetism and Magnetic Materials

Surface Review and Letters

Materials Chemistry and Physics, 2015