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K. Benyelloul Y. Bouhadda M. Bououdina H.I. Faraoun H. Aourag L. Seddik 《International Journal of Hydrogen Energy》2014
In this paper, the density functional theory (DFT) within the generalized gradient approximation (GGA) was used. The single crystal elastic constants for the intermetallic FeTi and its hydrides FeTiH and FeTiH2 are successfully obtained from the stress–strain relationship calculations and the strain energy-strain curves calculations, respectively. The shear modulus, Young's modulus, Poisson's ratio and shear anisotropic factors are also calculated. The bulk moduli derived from the elastic constants calculations of the cubic FeTi, orthorhombic P2221 FeTiH and Cmmm FeTiH2 are calculated. For cubic FeTi compound, the bulk modulus is in a good agreement with both theoretical results and experimental data available in the literature. More importantly, it is found that, the insertion of hydrogen into the FeTi crystal structure causes an increase in the bulk modulus. From the analysis of shear-to-bulk modulus ratio, it is found that FeTi compound and its hydrides are ductile and that this ductibility, changes with changing the concentration of hydrogen. 相似文献
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Boukeffa Saida Tebib Wassila Redouani Locif Bououdina Mohamed 《Journal of Superconductivity and Novel Magnetism》2022,35(1):125-132
Journal of Superconductivity and Novel Magnetism - This study aims to investigate the dependence of phase composition, structural/microstructural parameters, and the magnetic properties as function... 相似文献
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Cadmium oxide powder codoped with Cu and Co ions (Cd0.94Cu0.01Co0.05O) was synthesised by thermal co-decomposition of a mixture of cadmium acetate dihydrate, bis(acetylacetonato)copper(II) and bis(acetylacetonato)cobalt(II) complexes. The purpose of the present investigation is to study the effect of H2-annealing conditions on the evolution of structure, optical and magnetic properties by varying temperature (300, 350 and 400 °C) and duration time (30 and 60 min). X-ray fluorescence (XRF) and X-ray diffraction (XRD) methods confirm the purity and the formation of single nanocrystalline phase of the as-prepared powder; thus, both Cu and Co ions were incorporated into CdO lattice, forming solid solutions. Magnetic measurements reveal that the as-prepared solid solution (SS) gained paramagnetic (PM) properties, although pure CdO itself is considered as diamagnetic (DM). The measured effective magnetic moment of doped Co2+ was 3.55 μ B. Interestingly, it was found that the hydrogenation process could transform the properties of the SS into room-temperature ferromagnetic (RT-FM) only. For example, the coercivity (H c), remanence (M r) and saturation magnetisation (M s) were 279 Oe, 0.187 emu/g and 1.739 emu/g, respectively for SS annealed in H2 gas at 350 °C for 30 min. Thus, the possibility of producing CdO with RT-FM was proved, where the magnetic characteristics were tailored by doping and post treatment under H2 gas, thereby a new potential candidate to be used as a dilute magnetic semiconductor (DMS). However, the real effect of H2 annealing on such drastic transformation in the magnetic behaviour needs some in-depth theoretical research work. 相似文献
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A.M. Al-Saie M. Bououdina A. Jaffar S. Arekat John M. Melnyczuk Ynhi T. Thai Christopher S. Brazel 《Journal of Alloys and Compounds》2011
Single and nanosized spinel CoFe2O4 phase has been prepared successfully by a simple combination of mechanical milling from a mixture of Fe2O3 and Co3O4 powder precursors followed by a subsequent annealing. X-ray diffraction analysis reveals that the estimated crystallite size of CoFe2O4 increases with increasing temperature but remains at the nanoscale, i.e. 85 nm at 900 °C. Moreover, magnetic measurements show that a great enhancement in the saturation magnetization was achieved whereas a large hysteresis loop was observed (i.e.72 emu/g at 900 °C). Evaluation and applicability of CoFe2O4 nanoparticles under high frequency AC magnetic field for heating in biomedical applications were examined. It was found that under fixed amplitude (516 Oe) and frequency (229 kHz), the prepared nanoparticles generate significant heat: after 5 s the temperature was around 97 °C for the as-milled powder and reached almost 178 °C for the powder annealed at 900 °C. 相似文献
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S. Azzaza M. El-Hilo S. Narayanan J. Judith Vijaya N. Mamouni A. Benyoussef A. El Kenz M. Bououdina 《Materials Chemistry and Physics》2014
Structural, optical and room temperature magnetic properties of Mn-doped MgO nanoparticles with Mn fractions (5–50 at.%), were investigated. The as-prepared pure MgO, with grain size of about 15 nm, exhibits two magnetization components, one is diamagnetic and another is superparamagnetic. After removing the diamagnetic contribution, the magnetization curve exhibits superparamagnetic behavior which may be attributed to vacancy defects. As the Mn content increases, the lattice parameter decreases, the ferromagnetism appears and the emission bands were considerably blue shifted. First principle electronic structure calculations reveal the decrease of both the gap and the Curie temperature with increasing Mn concentration. The obtained results suggest that both Mn doping and oxygen vacancies play an important role in the development of room temperature ferromagnetism. 相似文献
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N.Mohamed Basith J.Judith Vijaya L.John Kennedy M.Bououdina S.Jenefar V.Kaviyarasan 《材料科学技术学报》2014,30(11):1108-1117
Un-doped and Co-doped ZnO nanoparticles (NPs) with different weight ratios (0.5, 1.0, 1.5, and 2.0 wt% of Co) were synthesized by a facile and rapid microwave-assisted combustion method using urea as a fuel. The prepared NPs were characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated that Co-doped ZnO had a single pure phase with wurtzite structure suggesting that Co^2+ ions would occupy Zn^2+ ionic sites within the ZnO crystal lattice. Interestingly, the morphology was found to convert substantially from grains to nanoparticles with close-packed periodic array of hexagonal-like shape and then into randomly distributed spherical NPs with the variation of Co-content. The optical band gap estimated using DRS was found to be red-shifted from 3.22 eV for the un-doped ZnO NPs then decrease up to 2.88 eV with increasing Co-content. PL spectra showed a strong green emission band thus confirming the formation of pure single ZnO phase. Magnetic studies showed that Co-doped ZnO NPs exhibited room temperature ferromagnetism (RTFM) and that the saturation magnetization attained a maximum value of 2.203 × 10^-3 emu/g for the highest Co-content. The antibacterial studies performed against a set of bacterial strains showed that the 2.0 wt% Co-doped ZnO NPs possessed a greater antibacterial effect. 相似文献
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Z. Todorova N. Dishovsky R. Dimitrov Farid El‐Tantawy N. Abdel Aal A. Al‐Hajry M. Bououdina 《Polymer Composites》2008,29(1):109-118
A novel electrically conductive composite for NTC thermistor and piezoresistive sensor was successfully fabricated by homogeneously dispersing conductive SiC and B4C in an insulating natural rubber (NR) matrix. The morphology of the composites was investigated by means of scanning electron microscopy, cross linking density (n), volume fraction of rubber (Vr), and interparticle distance among conductive phases (rp). The influence of the filler concentrations on the mechanical properties such as modulus of elasticity (E); hardness shore A (H), and elongation at break (EB) were studied in details. The dependences of volume resistivity of NR based composites filled with B4C and SiC as a function of fillers concentration was investigated. Temperature dependencies of volume resistivity were also measured to examine the possible application of the composites to polymer linear negative temperature (NTC) thermistors. Furthermore, the temperature dependencies of dielectric constant of the composites were studied. For practical application, the thermal stability of the composites was examined by means of resistivity temperature and pressure hysteresis cycle. In parallel, the conduction mechanism of conductivity of the composites was interpreted in terms of the computed the activation and hopping energy. The applicability of the composites to piezoresistive sensor was examined too. The good mechanical properties and thermal stability of NR composites behavior can be utilized for fabricating various electronic devices as NTC thermistors and piezoresistive sensor (i.e. transducers in pressure sensors). POLYM. COMPOS., 29:109–118, 2008. © 2007 Society of Plastics Engineers 相似文献
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The TiCr2−xVx compounds with 0.0≤x≤1.2 series have been synthesised and characterised by X-ray powder diffraction. X-Ray qualitative and quantitative phase analysis has been carried out on the as-cast alloys using the Rietveld method. The refinements of the structure shows that the materials crystallise either in the hexagonal or in the cubic Laves phase type for low V contents. For x>0.6, the system is found of b.c.c.-type structure only. The pressure–composition–temperature (P–C–T) isotherms measured at 298 K show that the as-cast alloys absorb large amounts of hydrogen, from 4 to 5.2 H/f.u. The P–C–T diagrams reveal also the presence of a relatively flat plateau, and a large hysterisis effect, and correspondingly the hydride cannot be completely dehydrogenated. 相似文献