Publications Internationales
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Item Structure, Microsctructure and Magnetic Properties of Ternary (Fe0.6Al0.4)100-xSix Nanostructured Powders: Effect of Si Addition(2019) Boukherroub, N.; Hemmous, M.; Guittoum, A.; Martínez-Blanco, D.; Souami, N.; Gorria, P.; Blanco, J.A.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 (<ε>),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 particles.The addition of Si strongly affects the value of the saturation magnetization, Ms, that falls nearly an order of magnitude for the sample with 20 at.% Si, while the coercivity remains almost unchanged. The Mössbauer spectra show the presence of a sextet (ferromagnetic phase) and a singlet or a doublet (non ferromagnetic phase), except for the sample corresponding to x = 10, where only one singlet is observed in the spectrum.Item Hydrothermal synthesis of co nanoparticles : structure, morphology and magnetic properties(World Scientific, 2021) Bouelkreb, I.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Blanco, J. A.; Boukherroub, N.We have investigated the crystal structure, the microstructural and morphological characteristics, as well as the magnetic properties of Co nanoparticles (NPs) synthesized by a hydrothermal method. A series of samples has been elaborated for different concentrations of sodium hydroxide. The analysis of X-ray diffraction patterns, using two different wavelengths, has evidenced the coexistence of both α-Co and β-Co phases in the samples. The lattice parameter for both phases is in good agreement with those values expected for their bulk Co counterparts; the grain sizes of NPs were found to be dependent on the NaOH concentration. The scanning electron microscope micrographs show that Co NPs are agglomerated forming micrometer-sized entities whose shape evolves, indicating that the synthesis process affects the morphology of the powdered samples. Magnetic measurements indicate that the coercivity is slightly larger, HC>200 Oe, for Co NPs with dendritic-like shape, probably due to an increase in the magnetocrystalline anisotropyItem The role of siliconon the micro structure and magnetic behaviour of nanostructured (Fe0.7Co0.3)100_xSix powders(Elsevier, 2017) Hocine, M.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Rahal, B.; Blanco, J.A.; Sunol, J.J.; Laggoun, A.Item The role of silicon on the microstructure and magnetic behaviour of nanostructured (Fe0.7Co0.3)100_xSix powders(Elsevier, 2017) Hocine, M.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Rahal, B.; Blanco, J.A.; Sunol, J.J.; Laggoun, A.Single-phase(Fe0.7Co0.3)100 xSix nanostructured powders(x¼0,5, 10,15and20)havebeenelaboratedby mechanical alloyinginordertoinvestigatetheeffectofsilicononthemicrostructureandmagnetic properties ofthesealloys.AdisorderedFe(Co,Si)solidsolutionwithbodycentredcubic(bcc)crystal structure isformedafter72hofmillingforallthecompositions.TheadditionofSigivesrisetoapro- gressivedecreaseofthelatticeparameter,fromabout2.865ÅforthebinaryFe70Co30 compound downto 2.841Åforthepowderwith x¼20. ThesamplewiththeuppermostSicontentexhibitsthelowestvalue for themeangrainsize(E10nm)aswellasthelargestmicrostrain(above1.1%).Allthesamplesare ferromagnetic atroomtemperature,althoughthesaturationmagnetizationvaluereducesalmostlinearly by addingSitothecomposition.Asimilartrendisobservedforthehyperfine magnetic field obtained from theanalysisoftheroomtemperatureMössbauerspectra.Thehyperfine field distributionsshowa broad double-peakshapefor x40, whichcanbeascribedtomultiplelocalenvironmentsfortheFe atoms insideadisorderedsolidsolutionItem Microstructure and magnetic properties of nanostructured (Fe0.8Al0.2)100-xSix alloy produced by mechanical alloying(Elsevier, 2015) Boukherroub, Nadia; Guittoum, A.; Laggoun, A.; Hemmous, M.; Martínez-Blanco, D.; Blanco, J.A.; Souami, N.; Gorria, P.; Bourzami, A.; Lenoble, O.Item Mixing of Au in Si induced by secondary and high-order recoil implantation(Radiation Effects and Defects in Solids, 2005) Khalfaoui, R.; Benazzouz, C.; Guittoum, A.; Tobbeche, S.The mixing of Au in Si induced by secondary and high-order recoil implantation was investigated using 350 keV Ar + and 350 keV Kr + ions to fluences from 1?×?10 16 to 3?×?10 16 ions/cm 2 at room temperature. The thickness of the Au layer evaporated on Si substrate was ~2400 .The ranges of the Ar and Kr ions were chosen to be lower than the thickness of the Au layer in order to avoid the ballistic mixing produced by the primary knock-on atoms. Rutherford backscattering spectrometry (RBS) experiments were carried out to study the effects induced by Ar and Kr irradiation at the interface of Au-Si system. We observed that in the case of the irradiation with Ar + ions, a broadening of the Au-Si interface occurred only at the fluence of 3?×?10 16 Ar + /cm 2 and it is attributed to the surface roughening induced by ion bombardment. In contrast, the RBS analysis of a sample irradiated with 2?×?10 16 Kr + /cm 2 clearly showed, in addition to the broadening effect, the formation of a mixed zone of Au and Si atoms at the interface. The mixing of Au in Si atoms can be explained by the secondary and high-order recoil implantation followed by subsequent collision cascadesItem Irradiation-induced gold silicide formation and stoichiometry effects in ion beam-mixed layer(Vacuum, 2006) Khalfaoui, R.; Benazzouz, C.; Guittoum, A.; Tabet, N.; Tobbeche, S.The irradiation-induced silicide formation in ion beam-mixed layer of Au/Si(1 0 0) system was investigated by using 200 keV Kr+ and 350 keV Xe+ ions to fluences ranging from 8×1014 to 1×1016 ions/cm2 at room temperature. The thickness of Au layer evaporated on Si substrate was ∼500 Å. Rutherford backscattering spectrometry (RBS) experiments were carried out to study the irradiation effects on the mixed layers. We observed that at the fluence of 1×1016 Kr+/cm2 and starting from the fluence of 8×1014 Xe+/cm2, a total mixing of the deposited Au layer with Si was obtained. RBS data corresponding to the fluences of 1×1016 Kr+/cm2 and 8×1014 Xe+/cm2 clearly showed mixed layers with homogenous concentrations of Au and Si atoms which can be attributed to gold silicides. The samples irradiated to fluences of 1×1016 Kr+/cm2 and 1×1016 Xe+/cm2 were also analyzed by X-ray photoelectron spectroscopy (XPS). The observed chemical shift of Au 4f and Si 2p lines confirmed the formation of gold silicides at the surface of the mixed layers. Au2Si phase is obtained with Kr+ irradiation whereas the formed phase with Xe+ ions is more enriched in Si atoms. © 2006 Elsevier Ltd. All rights reservedItem A comparative structural and magnetic study of Fe100-xPdx(x=15, 20 and 36) thin films deposited on Si (100) and glass substrates(Elsevier, 2015) Bahamida, Saida; Fnidiki, A.; Laggoun, A.; Guittoum, A.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. & 2015