Browsing by Author "DJELLAL Nacira"

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    Contribution à l’étude de quelques propriétés physico-chimiques de matériaux nanostructurés à base de Fe-Co-R
    (Ecole Nationale Supérieure des Mines et de la Métallurgie- Annaba, 2022-07-28) DJELLAL Nacira; TAHRAOUI Tarek (Co-Directeur de Thèse)
    Des poudres nanostructurées (Fe65Co35)95 (Pr6O11)5 et (Fe65Co35)95 (R2O3)5 (R= Rien, La, Nd, Sm) ont été préparées par broyage mécanique haute énergie (correspond à une vitesse de rotation, W, égale à 1200 rpm) afin d'étudier l'effet des terres rares sur les propriétés microstructurale magnétiques de Fe65Co35. Des nanomatériaux de type (Fe65Co35)95 (Pr6O11)5 ont également été préparés par broyage mécanique basse énergie (correspond à une vitesse de rotation, W, égale à 250 rpm) afin d’analyser l’effet du temps et de la vitesse de broyage sur le comportement microstructural, structural et magnétique de ces alliages. Le temps minimum pour leur obtention a été établi. L’identification des phases, l’évolution des paramètres à l’échelle atomique (taille moyenne de cristallites, microcontraintes et paramètre de maille), la morphologie des particules de poudres, la magnétisation et la coercivité en fonction de la température ainsi que la stabilité thermique des systèmes élaborés ont été étudiés par diffraction des rayons X, microscopie électronique à balayage, magnétomètrie à échantillon vibrant, spectrométrie Mössbauer et calorimétrie différentielle à balayage. L’affinement Rietveld des diffractogrammes de rayons X et l’analyse des spectres Mössbauer ont montré la dissolution totale de Co, Pr6O11 et R2O3 (R= La, Nd, Sm) dans la structure cristalline cubique centrée de Fe. L'addition de terres rares a donné lieu à une diminution des micro-contraintes, et de la taille des cristallites. Les spectres Mössbauer ont révélé l’augmentation du champ hyperfin moyen en ajoutant des terres rares à la composition initiale Fe65Co35. Les mesures magnétiques ont montré le comportement ferromagnétique de toutes les compositions préparées.
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    Influence of Pr6O11 addition on structural and magnetic properties of mechanically alloyed Fe65Co35 nanoparticles
    (Frattura ed Integrità Strutturale, 2022) DJELLAL Nacira
    This work focuses on the synthesize of nanostructured (Fe65Co35)100-x (Pr6O11)x (x = 0, 5) powders using high energy ball milling. The influence of Pr6O11 on structural, morphological and magnetic properties of Fe65Co35 nanoparticles were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) with a dispersive energy analyzer (EDS), vibratory sample magnetometer (VSM) and differential scanning calorimetry (DSC). Results show that the praseodymium oxide addition increased the decrement rate of the crystallite size with milling time of about 27 % and decreased the increment rate of the internal micro-strain of 50 %. Moreover, because of its high grain fragmentation tendency, Pr6O11 increases the hardness and brittleness of Fe-Co powders. Moreover, it minimized the cold welding between Fe-Co ductile particles leading to a significant decrease in the average particle size (~1µm). The magnetic measurements conducted at room temperature show that the saturation magnetisation (Ms) and the coercivity (Hc) increased with milling time in both compositions. A low Ms and high Hc values were detected in (Fe65Co35)95 (Pr6O11)5 nanoparticles. The results demonstrated a soft ferromagnetic nature in all of the synthesized nanoparticles with Ms in the range 207 – 216 emu/g and Hc is found to be 113 Oe.
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    Tailoring Magnetic Properties of Fe0.65Co0.35 Nanoparticles by Compositing with RE2O3 (RE = La, Nd, and Sm)
    (MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations, 2022-10-18) DJELLAL Nacira
    Fe-Co alloys are the most important soft magnetic materials, which are successfully used for a wide range of applications. In this work, the magnetic properties of lanthanide-substituted (Fe0.65Co0.35)0.95(RE2O3)0.05 (RE = La, Nd, and Sm) nanoparticles, prepared by mechanical alloying, are reported. Our comprehensive studies (X-ray diffraction, Mössbauer spectroscopy, scanning elec tron microscopy with X-ray energy dispersive spectrometry, SQUID magnetometry and differential scanning calorimetry) have revealed different properties, depending on the dopant type. The RE2O3 addition led to a decrease in the crystallite size and to an increase in the internal microstrain. More over, because of the high grain fragmentation tendency of RE2O3, the cold welding between Fe–Co ductile particles was minimized, indicating a significant decrease in the average particle size. The parent Fe0.65Co0.35 alloy is known for its soft ferromagnetism. For the La-substituted sample, the mag netic energy product was significantly lower (0.450 MGOe) than for the parent alloy (0.608 MGOe), and muchhigher for the Sm-substituted compound (0.710 MGOe). The processing route presented here, seems to be cost-effective for the large-scale production of soft magnetic materials.