Résumé: Nanocrystalline Fe55Co30Ni15 powder alloy was synthesized by mechanical alloying in a planetary ball mill Fritsch P7, under an argon atmosphere. Structural, microstructural, and magnetic properties were assessed using X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). The structural refinement reveals the coexistence of BCC (a=2.861910-4 Å, = 11 nm, 96%) and FCC (a=3.585510-4 Å, = 20 nm, 4%) solid solutions after 24 h of milling. The BCC and FCC solid solutions display a high density of dislocations (~1016 m-2). The obtained powder alloy exhibits a soft magnetic behavior with a saturation magnetization of 206.5 emu/g and a coercivity of 32.63 Oe. According to the Mr/Ms ratio, the produced powders are multidomain. Theoretical analysis confirmed the accurate selection of fundamental computational simulation structure and lattice parameters at room temperature.

Résumé: Nanocrystalline (CoMn)50Ni50 powders were prepared by the mechanical alloying process in a high-energy planetary ball mill under an argon atmosphere. Morphology, structure, microstructure, and magnetic properties were investigated using scanning electron microscopy, X-ray difraction, and magnetometry. The (CoMn)50Ni50 powders exhibit a highly disordered solid solution with a lattice parameter of a =0.3542(4) nm, and undergo a ferromagnetic to paramagnetic transition at a Curie temperature of about 700 K. Diferent magnetic parameters were extracted from the approach to magnetic saturation. The electronic structure of the ferromagnetic powders was performed by the self-consistent ab initio calculations based on the Korringa–Kohn–Rostocker (KKR) method combined with the Coherent Potential Approximation (CPA). The total DOS is mainly due to the 3d-like states of the constituent elements Co, Mn, and Ni. The powders were tested in the discoloration reaction of Methylene Blue under diferent operation conditions via a heterogeneous Fenton-like process.

Résumé: Nickel ferrite NiFe2O4 (NFO), cobalt ferrite CoFe2O4 (CFO), and nickel-cobalt ferrite Ni0.5Co0.5Fe2O4 (NCFO) were produced by a green synthesis method utilizing olive leaf extract (OLE) as a fuel. Crystal structure, microstructure, and magnetic properties were studied using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. The NFO, CFO, and NCFO ferrites display a single cubic spinel structure belonging to the Fd-3m space group with crystallite sizes ranging from 123 to 170 nm. The lattice parameter (a) increases from 8.349910-4Å for NFO to 8.367310-4 Å and 8.387210-4 Å for Co-containing NCFO and CFO ferrites, respectively. The estimation of the cation distribution from the Rietveld refinement reveals that the CFO shows a higher inversion degree of 0.67 compared to that of NFO and NCFO ferrites ( = 0.46). The CFO, NFO, and NCFO samples exhibit mixed ferrite structures. Fourier-Transform Infrared spectroscopy measurements confirm the formation of the spinel structures. The saturation magnetization, coercivity, remanence, and constant anisotropy K1 of the cobalt-containing CFO and NCFO ferrites are higher than those of NFO.

Résumé: The effect of Co-doping on the structure, microstructure, martensitic phase transformation kinetics, and magnetic properties of the melt-spun (Ni50Mn40In10)1−xCox (x = 1, 2, and 3) Heusler ribbons, named hereafter Co1 (x = 1), Co2 (x = 2), and Co3 (x = 3), was assessed using X-ray diffraction, scanning electron microscope, energy-dispersive spectroscopy, X-ray fluorescence, differential scanning calorimetry, and vibrating sample magnetometer. The XRD results reveal the formation of a 14M martensite structure alongside the face-centered-cubic (fcc) γ phase. The crystallite size ranges between 50 and 98 nm for the 14M martensite and from 9 to 16 nm for the γ phase. The mass fraction of the γ phase lies between 36.4 and 44.2%. Co-doping affects the lattice parameters and the characteristic temperatures (martensite start, martensite finish, austenite start, and austenite finish). The calculated activation energy values for the non-isothermal martensitic transformation kinetics are 257 kJ mol−1 and 135.6 kJ mol−1 for the Co1 and Co2, respectively. The produced ribbons show a paramagnetic behavior. The variation in the coercivity can be related to the crystallite size and mass fraction of the γ phase. The produced ribbons exhibit an exchange bias at room temperature that decreases with increasing the Co content.

Résumé: High entropy FeCoCrNiMn (C1) and FeCoCrNiMn10Al10 (C2) alloys (HEAs) were mechanically alloyed for 24 h and heated to 900°C (C1_900°C and C2_900°C). The powders were also compacted into pellets (C1_pellet and C2_pellet) and sintered at 500°C for 1 h. Crystal structure, micro-structure, magnetic, and mechanical properties were investigated by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry, and microindentation. During the milling process, a mixture of body-centered-cubic (BCC) and face-centered-cubic (FCC) phases with a crystallite size in the range of 9-13 nm was formed in the C1 HEA alloy. The dual FCC+BCC solid solutions remain for the C1_pellet and transform to a single FCC for the C1_900C powders. Al addition stabilizes the BCC structure in the FeCoCrNiMn10Al10 HEA alloy as revealed by the structural refinement. The structure exhibits a mixture of BCC+FCC solid so-lutions for the C2 powders, and BCC+FCC+CrCo sigma phase for the C2_pellet and C2_900°C powders. The crystallite sizes are in the range of 6-93 nm for all the samples. The saturation magnetization (Ms), coercivity (Hc), and squareness ratio (Mr/Ms) are estimated to be 24.2 emu/g, 153.62 Oe, and 0.165, respectively, for C1 and 28.45 emu/g, 188.48 Oe, and 0.172 for C2. The C1_900C and C2_900°C powders exhibit, respectively, paramagnetic and soft magnetic behaviors and an exchange bias at room temperature. The C1_pellet and C2_pellet HEAs show high hardness values of 584.85 Hv and 522.52 Hv, respectively.

Résumé: The crystallization process, microstructure, thermal stability, and magnetic properties of Fe86Cr6P6C2 amorphous ribbons were studied by X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, differential scanning calorimetry, and vibration sample magnetometery. The crystallization process occurs in three stages where nanocrystalline -Fe solid solution, Fe3P phosphide, -Fe3C and -Fe3C carbides are formed. The crystallite size increases with increasing annealing temperature and remains at the nanometer scale (2088 nm). The microstructure of the annealed ribbons consists of lamella, fine platelets, alternate planes of ferrite and cementite, and grains with different shapes and sizes. The activation energies (499, 386, and 369 kJ/mol) are determined by Kissinger method. The melt-spun ribbons exhibit a low coercivity of 16.598 Oe and a high saturation magnetization of 0.635 emu compared to the annealed ones. The saturation magnetization decreases to a minimum value for the annealed ribbons at 758 K and then increases with increasing the annealing temperature. The Curie temperature increases from 447.4 K for the melt-spun ribbons to 638 K for the fully crystallized ribbons due to the development of the α-Fe phase.

Résumé: Structure, hyperfine, thermal stability, and magnetic properties of the mechanically alloyed Fe47.5Co50Ni2.5 (Fe47.5) and Fe50Co47.5Ni2.5 (Fe50) powders were investigated by using X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, differential scanning calorimetry, and vibrating sample magnetometer, respectively. The XRD results show the existence of bcc Fe type, bcc FeCo, and hcp Co-type structures. 57Fe Mössbauer spectrometry confirms the formation of Fe and Co-rich environments. The average hyperfine magnetic field and the saturation magnetization exhibit different behaviors up to 24 h but a similar trend after 48 h of milling for both samples. The variation of the coercivity is different up to 12 h of milling but identical after 24 h of milling for both samples. The addition of 2.5wt.%Ni lowers the disordered-to-ordered (T’) and  (T) phase transformation temperatures. The structure of ball-milled and heat-treated samples consists of bcc Fe type (a=0.28640.2874 nm) and FeCo (a=0.2853-0.2858 nm) phases with crystallite sizes of approximately 39-54 nm. The saturation magnetization increases to about 201-220 emu/g and the coercivity decreases to approximately 35-57 Oe after thermal annealing. According to the squareness Mr/Ms ratio, the as-milled and heat-treated powders are multidomain.

Résumé: The structure, morphological, thermal, and magnetic properties of the mechanically-alloyed Fe90Al8C2 (wt.%) powders were investigated by using X-ray diffraction (XRD), scanning electron microscopy, differential scanning calorimetry, and vibrating sample magnetometry, respectively. The XRD analysis reveals a mixture of three disordered solid solutions (Fe1-SS, Fe2-SS, and Fe3-SS) with different lattice parameters and crystallite sizes. The saturation magnetization swings between 128 and 133 emu/g, and the coercivity is between 90 and 62 Oe. After heating to 1100 °C, the XRD results show the formation of nanocrystalline (Fe, Al)3C-type carbide and two Fe-type solid solutions. The heated samples exhibit enhanced magnetic properties with enhanced saturation magnetization (Ms= 132.97-179.76 emu/g) and reduced coercivity (Hc=46.59-53.63 Oe). The composite Fe-Al-C structure can be considered a potential candidate for soft magnetic applications.

Résumé: This study uses mechanical alloying to prepare nanostructured Co27Mn13Ni60 (wt.%) powders. 24 h of milling leads to the formation of a single fcc-solid solution that undergoes ferromagneticparamagnetic transition at a Curie temperature of about 790 K. Powders were tested for Fenton catalysis,nand their performance was investigated for methylene blue discoloration.

Résumé: Heusler alloy with atomic composition Ni51.82Mn32.37In15.81 was prepared by melt spinning from arc melted ingots. X−ray diffraction, scanning electron microscopy, and magnetic measurements were used to study the structural, microstructural and magnetic properties. The crystal structure consists of a mixture of B2 austenite (~50%) and 14M martensite (~50%). The alloy undergoes a second order magnetic transition at a Curie temperature of T_c^A=194.2 K. The hysteresis loop reveals the occurrence of exchange bias phenomenon at room temperature. The critical exponents β, γ and δ were estimated using modified Arrott plots, Kouvel-Fisher curves and critical isothermal analysis. The respective values are β=0.500±0.015, γ=1.282±0.055 and δ=3.003±0.002. The critical behaviour in ribbons is governed by the mean field model with a dominated long-range order of ferromagnetic interactions. The maximum entropy change, ∆S_M^max, for an applied magnetic field of 5 T reaches an absolute value of 0.92 J/kg.K. The experimental results of entropy changes are in good agreement with the calculated ones using Landau theory.

Résumé: A disordered ε-FeSi crystalline structure was produced by selective laser melting in Fe92.4Si3.1B4.5 powder alloys fabricated with different laser powers at a laser scanning speed of 0.4 m/s. The phase formation, microstructure, roughness, microhardness, and hyperfine and magnetic properties were studied using X-ray diffraction, scanning electron microscopy, atomic force microscopy, a profilometer, a microdurometer, transmission 57Fe Mössbauer spectrometry and vibrating sample magnetometry. The aim of this work was therefore to study the effect of laser power on the phase formation, microstructure, morphology, and mechanical, hyperfine and magnetic properties. The XRD patterns revealed the coexistence of a bcc α-Fe0.95Si0.05, a tetragonal Fe2B boride phase and a disordered ε-FeSi type structure. The existence of the disorder was confirmed by the presence of different FeSi environments observed in the Mössbauer spectra. The Fe2B boride contained about 51–54% of Fe atoms. The porosity and roughness decreased whereas laser power increased. The sample produced with a laser power of 90 W had a smooth and dense surface, high microhardness (~1843 Hv) and soft magnetic properties (saturation magnetization Ms = 200 emu/g and coercivity Hc = 79 Oe).

Résumé: Nanocrystalline (Co2Mn)100-xNix (x=0, 20, 40, and 60 wt.%) alloy powders were prepared by mechanical alloying in a high-energy planetary ball mill. Morphology, structure, and microstructure have been analysed using scanning electron microscopy and X-ray diffractometry. Magnetic properties have been investigated employing magnetization measurement in range under an applied magnetic field up to 1 T. The Ni addition to Co2Mn powders led to the formation of a highly disordered face-centred-cubic solid solution (FCC-SS) with a soft magnetic character. The lattice parameter and the crystallite size are increased with Ni addition; while the microstrains’ variation is reduced. Electronic structure calculations have been performed in the framework of the self-consistent ab initio calculations, based on Korringa-Kohn-Rostocker (KKR) method combined with the Coherent Potential Approximation (CPA). The powders were tested in the oxidation of methylene blue via a heterogeneous Fenton-like process in which H2O2/•OH were produced in situ. Up to 97.13% of oxidation was achieved after 70 min with 30 mg of powders at 50 °C.

Résumé: Strombidae strombus seashells have been used as calcium precursors to prepare nanocrystalline hydroxyapatite (HAp) via a wet chemical route. The as-prepared HAp powder has been investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and complex impedance spectroscopy to examine the morphology, elemental composition, crystal structure, functional groups, and electric properties. The synthesized HAp exhibits a single and nanocrystalline (23 nm crystallite size) hexagonal structure with lattice parameters a = 9.3819 ± 10–4 Å and c = 6.8927 ± 10–4 Å. FT-IR and Raman spectroscopy results confirm the presence of P−O, O− H, and C−O bonds. The AC conductivity is frequency and temperature-dependent. The activation energy values are in the range of 0.238−0.319 eV, and the conduction mechanism proceeds by proton hopping. The Nyquist plots are modeled by an equivalent circuit composed of (Rg//CPEg) + (Rgb//L//CPEgb) elements.

Résumé: Nanocrystalline nickel-deficient ferrites have been prepared by a facile co-precipitation method using different Fe/Ni ratios. The obtained powders were studied by X-ray diffraction (XRD), scanning electron microscopy equipped with energy-dispersive X-ray spectrometry, Raman spectrometry, and vibrating sample magnetometer. The XRD results reveal the formation of a nonstoichiometric NiFe2O4-type spinel structure with a lattice parameter in the range of 8.353–8.364 Å and an average crystallite size that varies between 51 and 64 nm. The Rietveld refinement shows that the Fe/Ni ratio increases with the increase in Fe content and the obtained structures are nickel-deficient ferrites. Five characteristic vibration modes of the spinel structures have been observed in the Raman spectra. The saturation magnetization values are in the range of 40.14–69.29 emu/g and the coercivity lies between 185 and 200 Oe. According to the Mr/Ms squareness ratio values (0.239–0.265), the spinel ferrites fall into the pseudo-single domain.

Résumé: First-principles calculations were performed on the cubic rocksalt Cd0.75TM0.25O (TM= Mn, Fe, Co, and Ni) compounds to investigate the effect of 3d transition metals (TM) substitution on the structure, magnetic, electronic, and elastic characteristics by utilizing the full-potential linearized augmented plane wave (FP-LAPW) route. The calculations were performed in the framework of the density functional theory (DFT) within Generalized Gradient Approximation and the modified Becke-Johnson (TB-mBJ) potential approximation. The ground-state properties were determined in the rocksalt NaCltype B1 structure. The band structure calculations reveal that CdO and Cd0.75TM0.25O compounds have an indirect bandgap (ΓR) in the range of 1.412.64 eV. The magnetic moment of the Cd0.75TM0.25O compounds decreases from 5B to 4B to 3B to 2B for Mn, Fe, Co, and Ni substitution, respectively. The exchange constants N0α and N0β have been estimated using the splitting energy depending on the direction of spins. The studied compounds exhibit mechanical stability. The Cd0.75Ni0.25O is nearly isotropic and shows higher values of the elastic properties.

Résumé: Structural, microstructural, and magnetic properties of Heusler Ni50Mn50-xInx (x = 5 and 10) rib-bons have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and vibrating sample magnetometry (VSM). The as quenched Ni50Mn45In5 ribbons exhibit a mixture of monoclinic 14M (a = 4.329(3) Å, b = 5.530(3) Å, c = 28.916(3) Å), and tetragonal L10 (a = b = 3.533(3) Å, and c = 7.522(3) Å) martensite structures, while Ni50Mn40In10 ribbons display a single monoclinic 14M phase (a = 4.262(3) Å, b = 5.692(3) Å, and c = 29.276(3) Å). After three heat-ing/cooling cycles, in the temperature range of 303–873 K, the Rietveld refinement of the XRD patterns reveal the presence of a single 14M martensite for Ni50Mn45In5 ribbons, and a mixture of cubic L21 (31%) and 14M (69%) phases for Ni50Mn40In10 ribbons. The characteristic temperatures of the martensitic transition (Astart, Afinish, Mstart, and Mfinish), the thermal hysteresis temperature width and the equilibrium temperature decrease with increasing indium content and heating cy-cles. The samples show a paramagnetic like behaviour in the as quenched state, and a ferromag-netic like behaviour after the third heating/cooling cycle.

Résumé: Nanocrystalline and thermally stable hydroxyapatite (HA) powder with nominal composition of Ca10(PO4)6(OH)2 was prepared by wet chemical route from calcium hydroxide Ca(OH)6 and mono ammonium phosphate NH4H2PO4 as calcium and phosphate sources, respectively. The effect of calcination temperature on the structure, microstructure, molecular bonding, thermal behavior and morphology was investigated by X-ray diffraction patterns (XRD), Fourier Transform Infra-Red (FT-IR), Raman spectroscopy, thermogravimetry (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) analysis. The XRD patterns of the as-prepared and calcined powders exhibit a single phase of hydroxyapatite. The crystallite size of as-prepared and calcined HA is in the range of 44−182 nm. FT-IR and Raman spectroscopy results are in good agreement with XRD ones. The EDS analysis reveals the presence of all elements. The thermal stability of the synthesized powders is evidenced by TGA/DTA scans which show a weight loss smaller than 2%.

Résumé: A detailed investigation of structure, critical behaviour and magnetocaloric properties of Ni50Mn30Sn20 (Sn20) and Ni50Mn30In20 (In20) alloys has been investigated by means of X-rays diffraction and magnetic measurements. Ni50Mn30Sn20 alloy shows a cubic austenite 〖L2〗_1 structure, and undergoes a second order magnetic transition at a Curie temperature of T_(c,1)^A (Sn20)=333 K. However, the Ni50Mn30In20 alloy exhibits a mixture of cubic 〖L2〗_1 and B2 austenite structures having Curie temperatures of T_(c,2)^A (In20)=285 K and T_c^* (In20)=330 K, respectively. The modified Arrott plots, Kouvel-Fisher curves and critical isotherm analysis have been used to estimate the critical exponents (, , and ) around the Curie temperature. For Sn20 alloy, the reliable exponents are consistent with the mean field model, revealing long-range ferromagnetic interactions. Nevertheless, the critical exponents of In20 alloy around 330 K cannot be arranged into any of the universality classes of well-known classical standard models. The maximum entropy change under 5 T of Sn20 (∆S_M^max=2.43 J/kg.K) is slightly higher than that of In20 (∆S_M^max=2.05 J/kg.K). The experimental results of entropy changes are in good agreement with those calculated using Landau theory. Keywords: NiMn-based alloys; Magnetic transition; Critical behavior; Magnetocaloric effect; Landau theory.

Résumé: Hyperfine, thermal and magnetocaloric properties of the mechanically alloyed Fe72Nb8B20 powders have been examined by Mössbauer spectrometry, differential scanning calorimetry (DSC), and magnetic measurements. The Mössbauer spectrometry results show the existence of nanostructured Fe(B) and Fe(Nb) solid solutions, Fe2B boride and amorphous phase. The endothermic and exothermic peaks that are observed in the DSC curves might be correlated to the magnetic transition and the crystallization of the amorphous phase, respectively. The critical exponents values around the magnetic transition of the amorphous phase (TC= 480 K), are deduced from the modified Arrott plots, Kouvel-Fisher curves and critical isotherm examination. The calculated values (β = 0.457 ± 0.012, γ = 0.863 ± 0.136 and δ = 3.090 ± 0.004) suggest that the Fe72Nb8B20 alloy belongs to the mean field model with long-range ferromagnetic interactions. The maximum entropy change and the refrigerant capacity values are 1.45 J/kg·K and 239 J/kg, respectively, under a magnetic field of 5 T. Keywords: ball milling; Fe-Nb-B system; magnetocaloric properties; thermal analysis; Mössbauer spectroscopy; critical behavior.

Résumé: The infuence of Cu doping on structural and magnetic properties of Ni50−xMn36Sn14−yCux,y (x = 0, 1, 2 and y = 1 at.%) ribbons produced by melt spinning has been investigated. The crystalline structures of the alloys were determined by X-ray difraction (XRD) patterns analysis XRD measurements. Cu addition in specifc sites shifts structural transition temperatures. The L21 austenite is found for x = 0, 1 and 2 and modulated martensitic structure for y = 1. Characteristic transformation temperatures were obtained from diferential scanning calorimetry scans. It is found that the addition of Cu for Ni stabilizes the austenite phase (increasing martensitic start temperature from 194 to 228 K), whereas replacing small amounts of Cu for Sn stabilizes the modulated martensite phase (increasing martensitic transformation temperature from 194 to 325 K). The transformation temperatures generally increases as the Cu content increases. Therefore, the magnetostructural transition, analysed by vibrating sample magnetometry, is tuned by appropriate Cu doping in the alloys. Likewise, both martensitic and austenitic states exhibit ferromagnetic behaviour. Keywords Martensitic transformation · Magnetic properties · Phase transitions · Cu additions · Heusler alloys

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Résumé: The effect of the B content on the microstructural, structural, and magnetic properties of partially amorphous Fe92−xNb8Bx (x = 5, 10, 15, and 20) alloys has been investigated by means of scanning electron microscopy, X-ray diffraction, high and low-temperature extraction-type magnetometers. The XRD results reveal the formation of a nanocomposite structure where nanocrystalline bcc α-Fe and Fe2B phases are embedded into an amorphous matrix. The FeB boride is observed for higher boron contents (x = 15 and 20), and the crystallite sizes are in the range of 7–24 nm. As the B content increases, the amorphous phase-relative proportion and coercivity increase, whereas the saturation magnetization decreases. An important magnetic hardening occurs by lowering the temperature from 400 to 5 K for x = 20% B. The variation of the Curie temperature can be attributed to the heterogeneity of the amorphous matrix.

Résumé: Fluorine-doped indium oxide thin films (In2O3: F) have been successfully synthesized by spray pyrolysis technique on glass substrates and irradiated by different doses (1, 5, 10 and 100 kGy) of gamma-radiations using Co60 gamma source. The effect of this high energy on physical properties of In2O3: F has been studied by X-Ray diffraction, Raman spectroscopy, Spectrophotometer, Photoluminescence spectrometer and Hall Effect measurements. In our study γ-radiation induces an enhancement on the physical properties of fluorine doped indium oxide thin films. Especially at 10 kGy, optical transmission and electrical resistivity were improved after irradiation so the transparent conductor character has been improved also. In2O3: F thin film crystallized into the cubic structure with predominant plan orientation (4 0 0) located at 2θ = 35.46°. An increase of transmission values from 77 to 83% is detected after irradiation. The optical band gap increases from 3.01 eV to 3.18 eV. The effect of gamma radiation on optical constants such as refractive index n (λ), extinction coefficient k (λ), lattice dielectric constant εL, high frequency dielectric constant ε∞, plasma frequency ωP have been determined. The Wemple model based on the envelope method were applied to calculate the single oscillator energy E0 and dispersion energy Ed. A decrease of electrical resistivity from 0.43 to 0.14 Ω cm is also detected after irradiation. All these experimental results suggest that In2O3: F thin films can be used as transparent conductive electrode in photovoltaic devices. This study also illustrates that In2O3: F thin film irradiated at 100 kGy can be used as a photocatalytic material with an efficiency to decompose the dye around 84%.

Résumé: This paper deals with synthesis and physical investigation of iron doped Lanthanum oxide thin films (La2O3: Fe). These films are grown on glass substrates at 460 °C by spray pyrolysis with different molar ratios of Fe to La, varying from 0 to 5%. X-ray diffraction analysis shows that undoped La2O3 thin film crystallizes under a mixture of hexagonal and cubic structures. SEM images reveal porous and fuzzy network of nanocrystalline La2O3. AFM images confirm the granular and nanocristalline structure of these films. The principal Raman peak owed to La–O vibration mode at 340 cm−1, confirms the formation of lanthanum oxide La2O3. For iron- doped films, FTIR spectroscopy reveals not only the La–O vibration mode at 457 cm−1 but also a peak at 1394 cm−1 which is related to the ternary LaFeO3. Photoluminescence spectra show that iron doping reduces radiative recombination. Thereby, doped samples can be used for photocatalysis experiment with methylene blue (MB). After 120 min exposure to solar light, a noticeably photodegradation of MB is obtained with 4% Fe doped La2O3. This work shows that Fe doped La2O3 is a promising material for various sensitive applications such as gas detection and bio-sensors.

Résumé: The present work is devoted to the study of the impregnation of both the raw and calcined Algerian diatomite with a mixture of paraffin wax (PW) and liquid paraffin (LP) in order to obtain composite PCMs with a melting temperature below 30 °C and an appropriate latent heat. Structural, microstructural and thermal properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT−IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The raw diatomite contains many phases such as quartz (hexagonal SiO2), tridimite (trigonal SiO2) corundum (α-Al2O3, trigonal), CaSO4 (orthorhombic) and calcite (CaCo3, trigonal). After calcination, the main phases are quartz, tridimite, calcite and CaSO4. The SEM micrographs show that the PCMs are well impregnated into the diatomite pores. The FT−IR results reveal the absence of chemical interaction between paraffin and diatomite. The paraffin/calcined diatomite composite PCMs exhibits a melting temperature of 28.44 °C and a latent heat of about 56.40 J/g. Due to their thermal reliability and thermal energy storage performance after thermal cycling, the prepared composites PCMs are good candidates for thermal energy storage in buildings.

Résumé: Zinc orthotitanate Zn2TiO4 spinel structures have been prepared by solid state reaction in two stages. First, a mixture of ZnO and TiO2 (67% anatase+33%rutile) in a molar ratio of 2:1 was mechanically milled for 6 and 18 h, at room temperature, in a high energy planetary ball mill under argon atmosphere. Next, the ball milled powders were calcined at 900 °C for 2 h, pressed into pellets and then sintered for 4 h at 1100 °C in air. Phase formation, microstructure, surface morphology and optical properties were characterized by X-ray diffraction, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and UV–visible spectrophotometery. The mechanical milling process for 6 h gives rise to the formation of nanocrystalline orthotitanate Zn2TiO4 (15.5%, = 13.2 nm) in addition to unreacted rutile TiO2, anatase TiO2 and ZnO structures. As the milling process progresses up to 18 h, the volume fraction of Zn2TiO4 increases to about 44.5%. The sintered pellets exhibit a composite structure where about a small amount of rutile nanograins are dispersed into the Zn2TiO4 matrix. FT-IR and Raman results confirm the biphasic character of the sintered pellets. The band gap energy is milling time dependent. It varies from 3.22 for pellet 6 h to 3.45 for pellet 18 h.

Résumé: The thermal stability of Fe-8P (wt.%) ball milled powders was investigated by differential scanning calorimetry X-ray diffraction and 57Fe Mössbauer spectrometry. The effect of structural disorder is evidenced in the DSC thermogram by the presence of a large exothermic reaction consists of several overlapping peaks and spread over the temperature range (150-700)°C. The result of the Rietveld refinement of the XRD patterns indicates that during the annealing of the powders up to 210°C, three phases are observed: α-Fe(P), solid solution Fe3P and FeP phosphides. The Mössbauer spectra analyses show that the paramagnetic FeP phosphide phase is the only product after the annealing (∼ 2%). The annealing at 450°C leads to a mixture of α-Fe(P) solid solution, Fe3P nanophase and a small amount of a paramagnetic FexP (1 < x < 2) phosphide phase (∼ 3%) in addition to iron oxides.

Résumé: FeSiB alloys have been fabricated by selective laser melting (SLM) using a laser scan rate of 0.1–1.5 m/s, laser power of 90 W, scan line spacing of 40 μ m, and layer thickness of 50 μ m. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, profilometer, microdurometer, and vibrating sample magnetometer have been used to investigate the structural, microstructural, roughness, microhardness, and magnetic property changes during the laser melting process. The produced samples exhibit a nanocomposite structure consisting of nanocrystalline α-Fe0.95Si0.05 and Fe2B phases embedded into an amorphous ε-FeSi-type matrix. The selective laser-melted samples show high density, low surface roughness, higher microhardness values (1654–2273 Hv), and soft magnetic properties (Ms = 188.6–199 emu/g and Hc = 43.8–73 Oe).

Résumé: This work covers some physical investigations on (Co, Ni) codoped molybdenum oxide thin films deposited on glass substrates at 460 °C by the spray pyrolysis technique. The effects of Co and Ni contents on the structural, morphological, optical and magnetic properties of these films were studied using several physical investigations. First, X-ray diffraction analysis revealed the formation of an orthorhombic structure related to α-MoO3 allotropic phase with (020) and (040) preferred orientations. Also, the scanning electron microscopy (SEM) micrographs showed the enhancement of the surface roughness of MoO3 films by cobalt and nickel concentrations. Second, the optical investigations through reflectance and transmittance measurements indicated a direct transition of all prepared thin films with a remarkable increase of the optical band gap from 3.70 to 3.95 eV with increasing both Co and Ni elements. Finally, the magnetic measurements at room temperature revealed a ferromagnetic behavior of Co and Ni codoped MoO3 films. A ferro-diamagnetic transition phenomenon was occurred for codoped film at Ni 2%and Co 2%.

Résumé: Microstructure, structural and magnetic phase transitions of the melt spun Ni50Mn35Sn15 ribbons have been examined by means of scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and magnetic measurements. The melt spun ribbons exhibit a single phase cubic L21 austenite structure at room temperature with a space group Fm−3m, and lattice parameter a = 5.956 Å. The DSC results reveal the first order reverse and forward martensitic transition (Ms = 147.4 K, Mf = 133.7 K, As = 155 K and Af = 171 K) with a thermal hysteresis of about 21.3 K around the martensitic transition between heating and cooling. The thermomagnetic measurements show that the melt spun ribbons undergo a second order magnetic transition at a Curie temperature TC = 310 K and a first order martensitic transition at TM = 160 K. The critical behavior associated with the magnetic phase transition has been investigated through the isothermal magnetization measurements around TC. The critical exponents have been estimated by several methods such as the modified Arrott plots, Kouvel-Fisher method and critical isothermal analysis. The critical exponents values , and are close to those predicted from the mean field model revealing a dominated long-range order of magnetic interactions. For an applied magnetic field of 5 T, the maximum magnetic entropy change and the relative cooling power (RCP) values around TC are of about 2.105 J/kg.K and 132.5 J/kg, respectively. The melt-spun Ni50Mn35Sn15 alloy is a good candidate for magnetic refrigeration near room temperature.

Résumé: Structural, magnetic and magnetocaloric properties of La0.5□0.1Ca0.4MnO3 manganite prepared by conventional solid state reaction route have been carried out. The X-ray diffraction characterization has revealed that this sample crystallized in the orthorhombic symmetry, with Pnma space group. In order to check if this sample can be good candidate for magnetic refrigeration, relative cooling power was determined depicting that the sample can be useful for magnetic refrigeration at with about 232.20 J/kg under a magnetic field of 5 T. The magnetocaloric data has been well analyzed by using the Landau theory. The theoretical and experimental plots seem nearly similar. Based on these amazing properties, our compound is suggested as an effective candidate for various potential applications such as refrigeration application.

Résumé: (Fe1−xMnx)2P phosphide powders in the composition range 0.15 ≤ x ≤ 0.75 have been mechanically alloyed and their structural, magnetic and thermal changes with composition have been investigated by means of X-ray diffraction, 57Fe Mössbauer spectrometry, magnetization measurements and differential scanning calorimetry. The milling process induces changes in the crystal phase diagram of the (Fe1−xMnx)2P system. The XRD results reveal the coexistence of a bcc Fe(Mn)-type, hexagonal (Fe2P and Mn2P-type), orthorhombic (MnP-type) and tetragonal Fe3P-type structures for all compositions. The room temperature Mössbauer spectra confirm the formation of the Fe(Mn)-type, non-stoichiometric Fe2P-type, FeP-type and Fe3P-type structures. Saturation magnetization exhibits a comparable behavior to that of the average hyperfine magnetic field. The DSC scans show the existence of several endothermic and exothermic peaks in the temperature range (100–700) °C related to different phase transitions. The endothermic peak at about 582–589 °C can be related to the ferromagnetic/paramagnetic transition temperature (Curie temperature, TC) of the Fe(Mn)-type structure.

Résumé: Nanocrystalline Cu50Ni50 alloy powder was prepared by the mechanical alloying process in high-energy planetary ball mill P7 under an argon atmosphere. Structural, microstructural, morphological, and magnetic properties were followed by X-ray diffraction, scanning electron microscopy coupled with EDX analysis, and vibrating sample magnetometry. The mixing of Cu and Ni powders at the atomic level leads to the formation, after 30 h of milling, of two fcc NiCu structures having crystallite sizes of about 15.6 and 65.9 nm and close lattice parameters of about 3.5783 and 3.5794 Å that would correspond to Ni 41.8Cu 58.1 (40.75 %) and Ni 40.6Cu 59.4 (59.25 %) compositions, respectively. Magnetic measurements reveal that the obtained powders are typical soft magnetic materials. According to the Mr/Ms ratio, the grains are either pseudo-single domain or multidomain.

Résumé: The structure, morphology, and magnetic properties of the mechanically alloyed iron manganese phosphides (Fe1−x Mn x )2P with 0.15 ≤ x ≤ 0.75 (Mn/Fe ratio = 0.17, 0.33, 0.66, and 3) have been studied by means of X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, and BS1 and BS2 magnetometry. The powder form (Fe1−x Mn x )2P compounds exhibit multiphase structures that contain Fe(Mn)-type solid solution and Fe2P-type, Mn2P-type, Fe3P-type, and MnP/FeP-type phosphides. The magnetization versus temperature reveals the existence of multiple magnetic phase transitions. The saturation magnetization, coercivity, and squarness M r/M s ratio values are discussed as a function of both the Mn content and the temperature. From the approach to saturation magnetization studies, several fundamental magnetic parameters were extracted. The local magnetic anisotropy constant K 1 was determined.

Résumé: The critical exponents around the ferromagnetic–paramagnetic (PM-FM) phase transition and the magnetocaloric effect in the nanocrystalline (NC) Cu50Ni50 powders have been investigated. The alloy powder exhibits a second order magnetic phase transition. For a field change of 1 and 7 T, increases from 0.30 to 1.54 J/kg.K, respectively, and the relative cooling power values were found to vary between 43.6 and 271.9 J/kg. The critical behavior has been studied in details by using the modified Arrott plots and critical isotherm plots. The obtained critical exponent values , and are close to those predicted from the universal theory of mean-field model. This suggests that the magnetic interactions are long range around the Curie temperature, TC. Low cost magnetocaloric NC CuNi powders are good candidates for magnetic cooling applications.

Résumé: Molybdenum-doped In2O3 thin films with different atomic ratios of = 0 at.%, 1 at.%, 3 at.%, 5 at.%, and 7 at.% have been prepared by spray pyrolysis. X-ray diffraction (XRD) analysis showed that the Mo-doped In2O3 thin films crystallized in cubic structure with (222) preferred orientation. The best crystallinity was obtained for molybdenum concentration of 3 at.%, with an increase in grain size up to 155 nm. MAUD software was applied to the x-ray diffraction patterns to determine the phases, average grain size (d), microstrain () and lattice parameters. The optical transmission was close to 75%. Doped films displayed large bandgap energy on the order of 3.52 eV to 3.56 eV. Optical parameters such as refractive index (n), packing density (p), porosity, oscillator energy (E 0), and dispersive energy (E d) were studied using the envelope method. The electrical resistivity (ρ) decreased from 650.20 × 10−3 Ω cm to 2.03 × 10−3 Ω cm for undoped and In2O3:Mo(3 at.%) thin film, respectively. Heat treatment of In2O3:Mo(3 at.%) thin film under nitrogen atmosphere at 250°C for 2 h led to further decrease in the electrical resistivity to about 5.55 × 10−4 Ω cm. These results prove that annealed In2O3:Mo(3 at.%) thin film can be considered a key material for use in optoelectronic devices as a transparent electrode or an optical window for solar cells.

Résumé: The structural, magnetic, and magnetocaloric properties of Er6Fe23−xAlx (x = 0 and 3) intermetallic compounds have been studied systematically. Samples were prepared using the arc furnace by annealing at 1073 K for one week. Rietveld analysis of XRD shows the formation of pure crystalline phase with cubic Fm-3m structure. Refinement results show that the unit cell volume decreases with increasing Al content. The Curie temperature Tc of the prepared samples was found to be strongly dependent on the aluminum content. This reduces magnetization and the ferrimagnetic phase transition temperature (Tc) from 481 K (for x = 0) to 380 K (for x = 3), is due to the substitution of magnetic element (Fe) by non-magnetic atoms (Al). With the increase of the Al content, a decrease in the values of magnetic entropy is observed. The magnitude of the isothermal magnetic entropy (|∆SM|) at the Tc decreases from 1.8 J/kg·K for x = 0 to 0.58 J/kg·K for x = 3 for a field change 14 kOe. Respectively, the relative cooling power (RCP) decreases with increasing Al content reaching 42 Jkg−1 for x = 0 to 28 Jkg−1 for x = 3. Keywords: intermetallic; rare earth; crystal structure; magnetocaloric effect; relative cooling power

Résumé: Metal transition doped oxide thin films or nanocomposites have recently emerged at the forefront of potentials research. With the focus mainly on efficiency, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work covers the synthesis of silver doped lanthanum oxide thin films (La2O3:Ag) which have been prepared by the spray pyrolysis technique on glass substrates at 460 °C. Then, Ag thin films were grown on lanthanum oxide thin films by thermal evaporation. The present work aims to reach the synthesis of La2O3:Ag thin films using both the spray pyrolysis and thermal evaporation techniques. First, X-ray diffraction analysis shows that undoped and Ag doped films crystallize in a mixture of hexagonal and cubic phase with crystallites oriented along (001) direction. Raman spectroscopy shows the bands positions corresponding to hexagonal and cubic phases. On the other hand, an attempt regarding their optical properties has been carried out by means of photoluminescence measurements. Second, from electrical conductivity measurements, the activation energy decreases from 1.42 to 1.09 eV with the increase of annealing time and the charge carriers are following the CBH model as dominant charge transport mechanism. Finally, the annealing time influences the surface wettability property and transforms La2O3 character from hydrophobic (θ > 90°) to hydrophilic (θ < 90°).

Résumé: We have investigated the structural and magnetic properties of [Co/CoxZn1−x]12 superlattices (x≤6.5) grown using electrochemical dual bath. X-ray diffraction shows that CoxZn1−x layers crystallize in a monoclinic phase. We have found that the magnetization of samples is significantly smaller than the expected one. Using ab initio calculations based on the fully relativistic Korringa-Kohn-Rostoker (KKR) method combined with the coherent potential approximation (CPA), we show that the interfacial mixing at the interface between Co/CoxZn1−x can explain the decrease in magnetization. This can be understood in terms of existence of magnetically dead layer rich in Zn at the interface with a corresponding thickness of around 6.5 Å.

Résumé: Nanocrystalline hydroxyapatite (HAp) has been successfully used for biomedical applications during the last decades owing to its chemical similarity with natural apatite, its remarkable biocompatibility, bio-affinity, and bioactivity that can be related to its crystal structure. HAp is the most stable, least soluble of all calcium orthophosphates, and is one of the most promising calcium phosphate biomaterials which can be obtained from chemical reagent, natural sources, animal-like dental enamel, corals, etc. Thermally stable HAp powders have been prepared using wet chemical route and co-precipitation method from various precursors such as naturally abundant seashell waste, calcium hydroxide Ca(OH)6 and mono ammonium phosphate NH4H2PO4 as calcium and phosphate sources, respectively. The crystal structure, morphology, elemental analysis, molecular bonding, and electric properties of the synthesized HAp powders have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and complex impedance spectroscopy. The effect of simulated body fluids immersion on the molecular bending and electric properties is also reported.

Résumé: Nanostructured materials (NMs), typically with crystallite size less than 100 nm, are excellent candidates for both fundamental studies of length-scale-induced new phenomena and novel technological applications based on atomic-level structure control via material design. NMs have been synthesized by various physical, mechanical and chemical methods which include precipitation at ambient/elevated temperatures, electrodeposition, powder metallurgy, et. Nanoscale iron particles have large surface area and high surface reactivity which are very effective for the transformation and detoxification of a wide variety of common environmental contaminants. Interest in iron based-nanophase powders originates from iron’s magnetic properties, thermal stability, its ready availability and low cost as well as its high reactivity, particularly in reducing atmospheres. The physical properties of iron powders are influenced by materials and processing parameters. This review chapter covers the importance of pure iron nanophase powders and the various applications.

Résumé: This paper reviews the obtained results on mechanically alloyed binary, ternary, and quaternary Fe-based materials from pure elemental powders by the structural disintegration of coarser-grained structure through the severe plastic deformation. This later can force atoms into positions where they may not be at equilibrium and leads, therefore, to the formation of nanocrystalline solid solutions, intermetallic compounds, amorphous phases, etc. Microstructural, structural, morphological, thermal stability and magnetic properties changes during the milling process were investigated by X-ray diffraction, scanning electron microscopy, Mössbauer spectrometry, differential scanning calorimetry, and magnetic measurements. Depending on the milling conditions, the kinetics of elemental powders mixing can be described by one or two stages which are characterized by small values of Avrami parameter.