•Tm substituted Co ferrite were fabricated by sonochemical method.•IT exhibited a superparamagnetic nature at RT for × = 0.00 and 0.02 samples and ferromagnetic nature in the other products.•Tm ...substitution affects considerably the magnetizations data.
Co-Tm nano-spinel ferrite with chemical formula CoTmxFe2−xO4 (0.0 ≤ x ≤ 0.08) NPs were prepared via sonochemical approach. X-ray powder diffraction patterns, microscopic images (SEM and TEM) and infrared spectra proved the formation of Co spinel ferrite. The effect of Tm3+ substituted on spinal structure was evaluated by lattice parameters, tetrahedral and octahedral bond length and cationic distribution. The band gap energy (Eg) of samples were estimated by performing UV–Vis percent diffuse reflectance (% DR) and applying the Kubelka-Munk theory. Eg values are in an interval between 1.33 eV and 1.64 eV. The analyses of magnetization were performed at room (300 K; RT) and low (10 K) temperatures. Different magnetic parameters including coercivity Hc, saturation magnetization Ms, remanence Mr, squareness ratio (SQR = Mr/Ms) and magnetic moment nB were deduced and discussed. The results showed superparamagnetic (SPM) nature at RT for x = 0.00 and 0.02 samples. However, the other products exhibit ferromagnetic (FM) nature. At 10 K, all synthesized NPs display FM behavior. An amazing increase in the magnitudes of Ms, Mr and Hc was observed at 10 K in comparison to RT, which is principally due to the reduced thermal fluctuations of magnetic moments at lower temperatures. The Tm3+ substitution affects considerably the magnetizations data. An enhancement in the Ms, Mr, and nB was detected on increasing the Tm3+ concentration. The SQR values at RT are found to be smaller than 0.5 postulating a single domain nature with uniaxial anisotropy for all produced ferrites. However, SQRs are in the range 0.66–0.76 at 10 K, suggesting the multi magnetic domain at low temperature, except the x = 0.02 product where the SQR = 0.47 indicating the single magnetic domain. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties.
•Tb3+ substituted NiCuZn nano-ferrites were synthesized via ultrasonic approach.•Band gap (Eg) values are in a narrow range of 1.87–1.98 eV.•Mössbauer spectroscopy showed that Tb3+ ions prefer to ...occupy Oh site.•Tb substituted NiCuZn nano-ferrites revealed superparamagnetic trait T = 300 K.•Tb substituted NiCuZn nano-ferrites display soft ferromagnetic behavior at T = 10 K.
The Fe3+ ions were replace with Tb3+ ions as highly paramagnetic rare earth element within the structure of Ni0.4Cu0.2Zn0.4Fe2O4 nano-spinel ferrites (NSFs). The structural, magnetic, spectroscopic and optic properties have been studied in details. All products have been synthesized via ultrasonic approach via Qsonica ultrasonic homogenizer, frequency: 20 kHz and power: 70 W for 60 min. No annealing or calcination process was applied for any product. The microstructural analysis of products has been done via X-ray powder diffractometry (XRD) which presented the cubic spinel structure with nanosized distribution of all. The cubic morphology of all products were confirmed by both HR-TEM and FE-SEM. Optical band gap (Eg) values were assessed by applying %DR (percent diffuse reflectance) analysis and Kubelka-Munk theory. The Tauc schemes showed that Eg values are in a narrow range (1.87–1.98 eV). The quadrupole splitting, line width, hyperfine magnetic field, isomer shift values and cation distribution have been determined from 57Fe Mossbauer analysis. The magnetic properties of various nanoparticles have been obtained from VSM (vibration sample magnetometer) measurements at 10 and 300 K (RT). The magnetic results revealed superparamagnetic and soft ferromagnetic traits at 10 and 300 K, respectively. Ms (saturation magnetization) and Mr (remanence) initially increase with increasing Tb3+ substituting level up to x = 0.06 then diminish for further x values. Hc (coercivity) shows an opposite variation tendency of Ms and Mr. The observed magnetic traits are deeply discussed in relation with the structure, morphology, magnetic moments and cation distributions.
We report in this investigation the preparation as well as characterization of bulk YBa2Cu3O7-δ superconductor produced by solid state reaction route and added by various amount (x) of CNTs (x = 0.0, ...0.1 and 1.0 wt%). The analysis of X-ray diffraction (XRD) indicated the achievement of orthorhombic structure of YBCO phase for various sintered samples. No relevant variations in the lattice parameters is observed with CNTs inclusion. The analysis of microstructure revealed a dispersion of CNTs into YBCO and presence of lattice defects for CNTs added samples. We evaluated the impacts of CNTs on inter-granular traits of YBCO using AC susceptibility measurements. Various superconducting parameter including critical temperature (Tc), inter-granular critical current density (Jc inter), grain volume fraction (fg), grains susceptibility (χg) and matrix susceptibility (χm) were estimated and deeply discussed. The obtained results confirm that the CNTs addition has a beneficial role on the inter-granular properties of YBCO system. Also, the critical current density Jcm was determined and its value has been shown to be greatly enhanced with the addition of CNTs in the existence of the applied magnetic field.
•YBa2Cu3O7-δ/(CNTs)x with 0.0 ≤ x ≤ 1.0 wt% were produced by solid-state reaction process.•Microstructural analysis revealed a dispersion of CNTs into YBCO.•Presence of lattice defects for CNTs added samples.•Highest critical current density was achieved with CNTs addition into YBCO superconductor.•CNTs addition has a beneficial role on the inter-granular properties of YBCO system.
•Single-phase Ni0.3Cu0.3Zn0.4TmxFe2−xO4 (0.0 ≤ x ≤ 0.10) nanospinel ferrites were synthesized via sonochemcial approach.•The optical band gap energy Eg increased with the increase in Tm3+ ...content.•Magnetic properties revealed superparamagnetic property at room temperature and soft ferromagnetic nature at 10 K.•Tm3+ substitutions significantly affect the magnetizations data of NiCuZn nanoferrite.•A decreasing trend in the Ms, Hc, Mr, and nB values was detected with Tm3+ substitution.
In this study, Tm3+ ion substituted NiCuZn nanospinel ferrites, Ni0.3Cu0.3Zn0.4TmxFe2−xO4 (0.0 ≤ x ≤ 0.10), have been synthesized sonochemically. The structural, spectroscopic, morphological, optic and magnetic investigation of the samples were done by X-ray powder diffractometry (XRD), Fourier transform infrared spectrophotometry (FT-IR), UV–Vis diffused reflectance (%DR) spectrophotometry, transmission and scanning electron microscopies (TEM and SEM) along with EDX, Vibrating sample magnetometry (VSM), respectively. The purity of prepared products were confirmed via XRD, FT-IR, EDX and elemental mapping analyses. The analyses of magnetization versus M(H) (applied magnetic field) were performed at 300 and 10 K. The following magnetic parameters like Ms (saturation magnetization), SQR = Mr/Ms (squareness ratio), nB(magnetic moment), Hc (coercivity) and Mr (remanence) have been discussed. M(H) loops revealed superparamagnetic property at RT and soft ferromagnetic nature at 10 K. It is showed that the Tm3+ substitutions significantly affect the magnetizations data. A decreasing trend in the Ms, Hc, Mr, and nB values was detected with Tm3+ substitution.
•Nanosized M-type SrFe12−xVxO19 (0.00 ≤ x ≤ 0.1) hexaferrites have been synthesized via sol-gel auto-combustion method.•Lattice constant ‘c’ found to be increased with vanadium substitution.•The ...Vanadium substitutions weaken the magnetic properties of SrM hexaferrites.•The V3+ ions have the preference to occupy the 2a and 2b sites.
In the present study, the preparation of nanocrystalline strontium vanadium nanohexaferrites was undertaken using a sol-gel auto-combustion method. The structural and morphological properties were characterized using X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) analysis, and scanning electron microscopy (SEM). The XRD analysis showed that the crystallite sizes (t) of the products vary between 55 and 60 nm, while the SEM analysis confirmed the hexagonal platelet structure of the products. The magnetic hysteresis loops indicated that the synthesized nanohexaferrites exhibit ferrimagnetic-like (FM) behavior. The deduced saturation (MS) and the remnant (Mr) magnetizations, the coercive (HC) and magneto-crystalline anisotropy (Ha) fields diminished as the V3+ content increased. The Ha values are very high, pointing to the hard FM characteristics of the synthesized nanohexaferrites. Except for x = 0.0, the squareness ratios, Mr/MS, are below 0.50, suggesting the presence of multi-domain nano-sized particles for SrFe12−xVxO19 (0.00 ≤ x ≤ 0.1) nanohexaferrites.
•(1-x)BaTiO3/xSr0.92Ca0.04Mg0.04Fe12O19 composites were prepared.•The grains size of BTO phase decreased with increasing SrCaMg hexaferrite content.•The band gap energy (Eg) reduced with the increase ...in x ratio.•Ms, Mr and Hc increased with increasing x ratio.•Dielectric properties depend largely on x content and microstructure of composite.
In the present work, we investigated the correlation between structure, microstructure, optical, electrical, dielectric and magnetic properties in composites based on ferrimagnetic Sr0.92Ca0.04Mg0.04Fe12O19 (noted SrCaMg) and ferroelectric BaTiO3 (noted BTO) phases in different ratio. Series of (1-x)BaTiO3/xSr0.92Ca0.04Mg0.04Fe12O19 mixtures (with x = 0.00, 0.25, 0.50, 0.75 and 1.00) were synthesized. The constituents were selected by taking into consideration the perspective ferroelectric and ferrimagnetic characteristics of BaTiO3 and Sr0.92Ca0.04Mg0.04Fe12O19, respectively. X-ray diffraction (XRD) investigations showed the co-existence of tetragonal BaTiO3 (noted BTO hereafter) and Sr0.92Ca0.04Mg0.04Fe12O19 hexagonal ferrite (noted SrCaMg HF) phases in the produced composites. The phase content of ferrimagnetic SrCaMg HF phase is increasing with increasing x content. The lattice parameter ‘a’ for both BTO and SrCaMg HF phases is almost constant with increasing the x content. However, the lattice parameter ‘c’ is decreasing for BTO phase and increasing for SrCaMg HF phase. The crystallites size (DXRD) is decreasing for BTO phase and increasing in SrCaMg HF phase as the x content increases. The homogeneous distribution of different phases was confirmed via scanning and transmission electron microscopies analyses and the corresponding selected area electron diffraction (SAED) patterns. On increasing the content of SrCaMg hexaferrite phase, the grains size of BTO phase is decreasing. The band gap energy (Eg) values were determined from the analysis of UV–vis diffuse reflectance spectra. BTO nanoparticles (x = 0.00) displays Eg value equal to 3.27 eV. It is found that Eg value is reduced with increasing the concentration of SrCaMg hexaferrite phase reaching values of 3.21, 3.08, 2.91 and 1.23 eV for x = 0.25, 0.50, 0.75 and 1.00, respectively. The saturation magnetization (Ms) and remanence (Mr) were increased with increasing the concentration of SrCaMg HF in the composite. Ms and Mr values are increased from about 0.09 and 0.02 emu/g for x = 0.00 to around 68.8 and 44.7 emu/g for x = 1.00. Compared to x = 0.00 sample, the coercivity (Hc) was increased sharply from 400.5 to 3295 Oe for x = 0.25 and then slightly diminishes with further increasing x. It was noticed that the dielectric properties of various composites depend largely on the x content that alters the microstructure of composite. This was discussed with respect to the microstructure and temperature effect.
Ce3+ ion substituted Sr-hexaferrite magnetic nanoparticles (MNPs), SrCexFe12-xO19 (0.0 ≤ x ≤ 0.5) MNPs, were fabricated by citrate sol-gel combustion approach. All products have been characterized ...using X-ray diffraction (XRD), Photoluminescence, scanning electron microscopy (SEM), elemental mapping (EDS), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) at 300 and 10 K. The XRD pattern presents effective substitution of Ce3+ on the sites of strontium hexaferrite lattice. With Ce3+ doping, the lattice parameters a is almost unchanged, whereas c is a little increases with increasing the dopant contents. The hysteresis loops M-H showed the ferromagnetic nature of all elaborated. The saturation magnetization (Ms) and the remnant magnetization (Mr) are reduced with increasing Ce amount. All the elaborated products presented typically squarness ratio (Mr/Ms) around 0.5, indicating the existence of non-interacting single domain MNPs with a uniaxial anisotropy. The anisotropy fields (Ha) are found to be very large proving that all products are magnetically hard. With increasing the Ce content, Ha increases which indicate the strengthening of magnetic properties. Consequently, the values of coercive field (Hc) are enhanced, leading these products to be utilized in many uses, such as recording media and permanent magnets. ZFC and FC magnetizations curves indicated shifts of the blocking temperature (TB) to lower temperatures with increasing Ce content. This is accredited to the reducing of particle size with Ce-substitution.
Abstract
Improving efficient electrocatalysts (ECs) for hydrogen generation through water splitting is of significant interest in tackling the upcoming energy crisis. Sustainable hydrogen generation ...is the primary prerequisite to realizing the future hydrogen economy. This work examines the electrocatalytic activity of hydrothermally prepared vanadium doped MnCo spinel oxide microspheres (MC), MnV
x
Co
2−x
O
4
(V
x
-MnCo MC, where x ≤ 0.4) in the HER (hydrogen evolution reaction) process. Magnetization measurements demonstrated a paramagnetic (at high temperatures) to a ferrimagnetic (at low temperatures) transition below the Curie temperature (Tc) in all the samples. The magnetization is found to intensify with the rising vanadium content of MCs. The optimized catalyst V
x
-MnCo MCs (x = 0.3) outperformed other prepared ECs with a Tafel slope of 84 mV/dec, a low onset potential of 78.9 mV, and a low overpotential of 85.9 mV at a current density of 10 mA/cm
2
, respectively. The significantly improved HER performance of hydrothermally synthesized V
x
-MnCo MCs (x = 0.3) is principally attributable to many exposed active sites, accelerated electron transport at the EC/electrolyte interface, and remarkable electron spectroscopy for chemical analysis (ECSA) value was found ~ 11.4 cm
2
. Moreover, the V
x
-MnCo MCs (x = 0.3) electrode exhibited outstanding electrocatalytic stability after exposure to 1000 cyclic voltametric cycles and 36 h of chronoamperometric testing. Our results suggest a feasible route for developing earth-abundant transition metal oxide-based EC as a superior electrode for future water electrolysis applications.
In the current investigation, we report the impact of TiO2 nanowires (NW) and nanoparticles (NP) addition on flux pinning and superconducting characteristics of YB2Cu3O7-d (Y-123 or YBCO) material. ...Specimens were produced through solid-state reaction (SSR) route. The microstructure of samples showed an almost regular dispersion of nanometer scale entities for NP-added samples and a distribution of nanowires inside the grain boundaries for NW-added samples. The Y-123 phase structure was maintained with the addition of TiO2 nano-entities up to 0.1 wt%. An improvement of superconducting properties was observed for samples added with 0.1 wt% of TiO2 nano-entities compared to non-added one. Among all the prepared samples, a considerable augmentation of critical current densities in the absence and in the existence of applied magnetic fields was obtained for 0.1 wt% TiO2 NP added samples. The possible flux pinning mechanisms and correlation between the shapes of nano-entities, structure and superconducting properties was studied and discussed. An important result of the current study is that there is an increase of effective pinning centers and a complete change of vortex pinning mechanisms; from the fluctuation in the Tc(δTc) to the mean free path of the charge carriers (δℓ) for the 0.1 wt% TiO2 NP added sample compared to the non-added and 0.1 wt% TiO2 NW added samples.
•Impact of TiO2 nano-entities addition on superconducting properties of Y-123.•No phase transition in Y-123 structure with the addition of TiO2 nano-entities.•Transport electrical and magnetic properties are enhanced with TiO2 addition.•Possible flux pinning mechanisms were examined.•A change from δTc to δℓ pinning mechanisms is seen for TiO2 nanoparticles addition.
•Synthesis of new composites via the sol-gel method assisted sintering process.•XRD indicated a tetragonal phase for pure BTO and cubic structures for composites.•SEM images showed a compacted and ...less porous microstructures for the composites.•HVL and MFP results showed enhanced radiation shielding for the composites.•The radiation protection efficiency for composites is almost 100% at 0.122 MeV.
The search for materials that serve as good shields for radiation has become very important in light of the increasing exposure to ionizing radiation in various vital sectors. This research presents the synthesis of composites consisting of ferroelectric BaTiO3 (BTO) phase mixed with magnetic phase via sol-gel process assisted sintering process and the study of their gamma γ ray shielding, structural and morphological features. XRD and FTIR analyses proved the formation of the desired materials. The results of XRD indicated that the BTO phase possesses a tetragonal structure confirming its ferroelectric nature. The tetragonal structure transits to cubic in the composite samples. The morphology was examined by SEM technique and the results showed that the composite ceramics showed a more compacted and less porous morphology compared to pure ceramic. The average grain size and the porosity decreases with increasing the content of the magnetic phase. Experimentally, we measured the linear attenuation coefficient (LAC) at ten distinct energies varying from 0.122 to 1.410 MeV. The pure BTO ceramic (i.e. x = 0.00) has the lowest LAC at any energy, while the addition of the magnetic phase has a notable influence on the LAC and causes an enhancement of the radiation shielding ability of the prepared composites. At 0.122 MeV, the LAC for the pure sample is 5.080 cm−1, while adding magnetic phase by 5, 10, and 20 led to an increase in the LAC to 6.134, 6.893, and 7.476 cm−1 respectively. The maximum attenuation ability for the radiation by the prepared composites occurred at 0.122 MeV, while the ability of the attenuation by these composites is gradually decreased and attained the minimum ability at 1.410 MeV. The radiation protection efficiency (RPE) for the prepared composites is almost 100% at 0.122 MeV. In the range of low energy, the RPE results demonstrated that the prepared composites can stop all the incoming photons, thus these composites can be used effectively in low energy-radiation protection applications.
PDF
