Search Results (294)

This research investigates the formation of an amorphous phase in a non-equiatomic aluminum-based alloy, Al₈₂Fe₁₂Cu₂Nb₂Co₂, synthesized via mechanical alloying. By utilizing minor additions of Nb, Co, and Cu, structural stability and “chemical complexity” effects are achieved in a matrix dominated by a single element (82% Al). Thermodynamic analysis reveals that a moderately negative mixing enthalpy (ΔH_mix = −6.89 kJ/mol) and elevated configurational entropy (ΔS_mix = 5.420 J/mol·K) are the primary thermodynamic drivers of amorphization, supplemented by a transitional-regime atomic size mismatch (δ = 4.82%). The evolution of the structure, morphology, and magnetic properties of mechanically alloyed amorphous Al₈₂Fe₁₂Cu₂Nb₂Co₂ as a function of milling time was systematically investigated using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and a vibrating sample magnetometer. Full article

The preparation of new magnetic materials is important because of their potential application in various electronic components. In the present work, the synthesis of glass-crystalline materials in the system Na₂O-MnO-SiO₂-Fe₂O₃ prepared by applying melt-quenching is reported. The phase composition as studied by X-ray diffraction and Raman spectroscopy reveals the precipitation of monophase Mn_xFe_3−xO₄ based solid solutions. The microstructure is studied by scanning electron and optical microscopy and shows bulk crystallization and the presence of polygon-shaped as well as of dendritic crystals, depending on the iron oxide concentration and used raw materials. Mössbauer spectra show that in the amorphous matrix the Fe ions are mainly present as Fe³⁺ in tetrahedral coordination and as Fe³⁺ in a solid solution with the composition Mn_xFe_3−xO₄. The simultaneous presence of MnFe₂O₄ (jacobsite) and a Mn-containing solid solution based on Fe₃O₄ (magnetite) is suggested. The room temperature magnetic properties were studied by vibrating sample magnetometer and reveal ferrimagnetic properties for all investigated glass-crystalline materials. Full article

LaFeO₃ nanofibers and Ag-doped LaFeO₃ nanofibers were fabricated via an approach combining electrospinning with calcination. Their crystal structures, micro-morphologies, and chemical compositions were determined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. In addition, the conduction mechanisms and magnetic properties of the two samples were investigated using a semiconductor analyzer and a vibrating sample magnetometer. Rietveld refined X-ray diffraction analyses confirmed the orthorhombic structure. The two samples showed a nanofibrous structure. For Ag-doped LaFeO₃, the conduction was dominated by the ohmic conduction mechanism in a low-resistance state, while it was governed by space-charge-limited current conduction in a high-resistance state. It also showed a high on/off ratio of 3.6 × 10³. The coercivity and remanence values of Ag-doped LaFeO₃ were 200 Oe and 0.000404 emu g⁻¹. This, thus, indicates the considerable application potential of Ag-doped LaFeO₃ for resistive random-access memory devices and magnetoresistive random-access memory devices. Full article

The coal-based direct reduction followed by magnetic separation (CDRMS) is an efficient iron extraction and dephosphorization process, which requires adding additives to improve the phosphorus removal rate. Compared with other additives, sodium carbonate has the advantages of good iron index, high phosphorus removal rate and less environmental pollution. Its role in phosphorus-rich oolitic iron ore (PROIO) where phosphorus exists in the form of apatite has been proved. However, the influence on the phosphorus transformation process in the lattice of iron minerals is not clear. In this paper, the effect of sodium carbonate on phosphorus removal in iron minerals and iron recovery during CDRMS was studied. Compared with not adding chemicals, the addition of sodium carbonate significantly reduced the phosphorus content of direct reduced iron (DRI) from 0.69% to 0.09%. The iron grade increased from 93.28% to 95.08%, and the iron recovery rate rose from 90.61% to 96.48%. The mechanism of sodium carbonate was revealed by using a synchronous thermal analyzer (TG–DSC), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), scanning electron microscope and energy dispersive spectrometer (SEM–EDS), and vibrating sample magnetometer (VSM). The results show that sodium carbonate reacted with silicon and aluminum components to form nepheline, and the lattice substitution of phosphorus in iron minerals and silicon in nepheline prevents the reduction of phosphorus. In addition, sodium carbonate promotes the reduction of iron minerals, resulting in an increase in the magnetic properties of the reduction products. Full article

In this paper, a series of iron thin films were prepared using the direct current magnetron sputtering method at different deposition times. By means of characterization techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and vibrating sample magnetometer (VSM), the structure, surface morphology, and magnetic properties of the iron thin films prepared at different deposition times were systematically investigated. The XRD results indicate that all the iron thin films exhibit a polycrystalline body-centered cubic structure, with an obvious preferred orientation in the (110) direction. As the deposition time increases, the average grain size of the iron thin films gradually increases. This is mainly because the post-sputtered atoms can provide the energy required for the formation, movement, and growth of the already deposited grains or clusters. When the deposition time is too long, factors such as elastic effects and size constraints will limit the growth of grains and clusters. Therefore, for the thin films deposited after 120 s, the average grain size gradually stabilizes. When the deposition time is short, the thin films usually grow in the form of island-like accumulation. Grains and clusters of uneven sizes accumulate on the substrate, so the roughness gradually increases. This also implies an increase in the density of defects such as internal stress and vacancies within the thin film. As the deposition time increases, the thin films gradually transform to grow in a layered and flat manner, and the grain size gradually stabilizes and becomes relatively uniform. Therefore, the roughness of the thin film samples decreases and tends to be stable. The magnetic property test results show that all the iron thin films exhibit ferromagnetism. The iron thin film prepared at a deposition time of 120 s has the best comprehensive performance, with a saturation magnetization M_s of 1567 emu/cm³, a coercivity of 92 Oe, and a remanence ratio of 0.86. Full article

The contamination of water bodies by polycyclic aromatic hydrocarbons (PAHs) poses a significant concern for the ecological systems, along with public health. Magnetic adsorption stands out as a green and practical solution for treating polluted water. To make the process more efficient and economical, it is important to create materials that not only absorb contaminants effectively but also allow for easy recovery and reuse. This study proposes a simple yet effective method for coating Fe₃O₄ nanoparticles with hydroxypropyl-β-cyclodextrin polymer (HP-β-CDCP). The physicochemical properties of the synthesized sorbent were characterized using a transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Vibrating Sample Magnetometer (VSM) analysis. The adsorption performance of HP-β-CDCP/Fe₃O₄ nanoparticles was well-described by the pseudo-second-order kinetic model, thermodynamic analysis, and the Freundlich isotherm model, indicating multiple interaction mechanisms with PAHs, such as π–π interactions, hydrogen bonding, and van der Waals forces. Using HP-β-CDCP/Fe₃O₄ nanoparticles as the adsorbent, the purification rates for the fifteen representative PAHs were achieved within the range of 33.9–93.1%, compared to 15.3–64.8% of the unmodified Fe₃O₄ nanoparticles. The adsorption of all studied PAHs onto HP-β-CDCP/Fe₃O₄ nanocomposites was governed by pH, time, and temperature. Equilibrium in the uptake mechanism was obtained within 15 min, with the largest adsorption capacities for PAHs in competitive adsorption mode being 6.46–19.0 mg·g⁻¹ at 20 °C, pH 7.0. This study points to the practical value of incorporating cyclodextrins into tailored polymer frameworks for improving the removal of PAHs from polluted water. Full article

This paper introduces innovative approaches to the design of railway point machines, with particular emphasis on the implementation of multi-component AlNiCoFe alloys, classified as semi-hard magnetic materials. A comprehensive review of existing mechanisms for mechanical force transmission—from the electric motor to the throwing bar—was conducted. The inherent limitations of conventional dry friction clutches, commonly used in current point machine designs, are critically analyzed. Furthermore, the feasibility of employing multi-component AlNiCoFe alloys as functional materials in hysteresis magnetic clutches is examined, with a view toward enhancing the reliability and performance of railway point actuation systems. A review of diagnostic methods for railway point machines was conducted to evaluate the potential application of a novel magnetic torque limiter as a means to eliminate maintenance activities typically required for systems utilizing dry friction clutches. Experimental research was performed on AlNiCoFe alloys employed as the hysteresis layer in the proposed torque limiter. Microstructural and compositional analyses were carried out using scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD) to determine the crystallographic structure, chemical composition, and selected physical properties of the tested materials. The hysteresis loops of the tested materials were measured using a Vibrating Sample Magnetometer (VSM) over a wide temperature range. A prototype magnetic clutch, functioning as a torque limiter in a railway point machine, was developed and presented. The operational characteristics—specifically the throwing force as a function of time—were recorded for a railway point machine equipped with an electromechanical module incorporating the new magnetic torque limiter. The advantages of the proposed solution in terms of force transmission and overall system performance in railway point machine design were analyzed and discussed. Full article

With the industrial production and application of a series of advanced high-strength steels containing austenite phases, quantifying austenite content has become vital for optimizing production processes and guaranteeing product quality. Traditional austenite measurement methods typically demand laborious, meticulous sample preparation and complex subsequent data processing, rendering them unsuitable for large-scale industrial standardization. The industry urgently requires a simple, stable technique for determining austenite content in bulk samples of these advanced steels. This article explored an innovative permeameter method to achieve the simple and stable quantitative determination of the austenite content in multiphase steels. This method measures the magnetization data within the near-saturation range, then utilizes the linear Frölich–Kennelly relationship to fit the data and indirectly derive the saturation magnetization, and subsequently determines the austenite content. Using medium manganese steels with varied austenite fractions as experimental materials, we conducted cross-comparisons with conventional methods—using a vibrating sample magnetometer and X-ray diffraction—to rigorously demonstrate the method’s feasibility, accuracy, and reliability. Extensive experimental results confirm that this method is both feasible and sensitive, with the measurement error meeting industrial requirements for quantitative austenite determination. It offers significant advantages in operational simplicity, analysis efficiency, measurement stability, and sensitivity, making it particularly well-suited for the quantification of austenite in medium manganese steels. Full article

The phase transformation of fayalite from copper slag during oxidation roasting was systematically studied in this work with an analysis using X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometer, scanning electronic microscope, and energy dispersive spectrometer. The results show that the oxidation of fayalite occurs at ≥300 °C. Fayalite is first oxidized into amorphous Fe₃O₄ and SiO₂ during oxidation roasting. The former then converts into Fe₂O₃ while the latter converts into cristobalite solid solution with increasing temperature. Meanwhile, the specific saturation magnetization of roasted products increases from 9.43 emu/g at 300 °C to 20.66 emu/g at 700 °C, and then decreases to 7.31 emu/g at 1100 °C. The migration of iron in fayalite is prior to that of silicon during oxidation roasting. Therefore, the thickness of the iron oxide layer on the particle surface steadily increases with roasting temperature, from about 1.0 μm at 800 °C to about 5.0 μm at 1100 °C. This study has guiding significance for the iron grain growth in copper slag during the oxidation-reduction roasting process. Full article

Fe-CNT composites were synthesized via mechanical ball milling, incorporating varying amounts of carbon nanotubes (CNTs) into iron powder at concentrations of 1 wt%, 2 wt%, and 3 wt%. The impact of different CNT contents on the phase structure, microstructure, and magnetic properties of the composites was examined. Raman spectroscopy and X-ray diffraction (XRD) analyses revealed that despite some damage, CNTs retained a predominantly one-dimensional nanostructure post-ball milling. Moreover, an increase in CNT content led to a gradual rise in grain size and lattice strain of the iron powder, attributed to the formation of solid solutions and iron–carbon compounds. Scanning electron microscopy (SEM) observations demonstrated that the majority of CNTs were integrated within the iron matrix particles, with a minority either partially embedded or entirely unembedded on the iron powder surface. With higher CNT concentrations, local CNT agglomeration emerged and intensified. Vibrating sample magnetometer (VSM) measurements indicated that Fe-CNT composites exhibited enhanced saturation magnetization (2.25%) and reduced coercivity (91.74%) compared to pure iron, underscoring the potential of CNTs in enhancing the magnetic properties of iron powder. Full article

Wiegand sensors are essential components in self-powered Internet of Things (IoT) nodes, as they can output pulse voltages without an external power supply. Previous research has established that the attachment of ferrite beads to Wiegand wire terminals substantially enhances the sensor’s pulse voltage output. However, the fundamental mechanism responsible for this enhancement remains unclear at the microscopic magnetic level. This investigation systematically examines how ferrite bead attachments alter magnetization reversal processes, Barkhausen jump characteristics, and the energy output in Wiegand wires. Experimental results reveal that ferrite beads enhance irreversible magnetization, modify interaction distributions, and transform the magnetic structure of Wiegand wires. These modifications collectively result in a 1.5–2.0 times higher pulse voltage amplitude and 30–40% greater output energy, establishing a theoretical framework for Wiegand sensor optimization. The research methodology combines vibrating sample magnetometer (VSM) measurements with first-order reversal curve (FORC) analysis to elucidate the underlying micromagnetic mechanisms. Full article

The ordered tetragonal FeNi L1₀ phase, tetrataenite, is a promising candidate for rare earth-free permanent magnets due to its competitive magnetic properties and the low cost of the constituent elements. In this work, we have investigated the effect of molybdenum and aluminum substitution on the formation of the ordered L1₀ phase. The alloys were prepared with die casting and melt spinning techniques, further processed using cold rolling and cryomilling, and finally annealed below the estimated order–disorder temperature (T_OD). To study the influence of composition and processing of the alloys, structural characterization and microstructural analysis were performed with synchrotron radiation X-ray diffractometry (SR-PXD) and Scanning Transmission Electron Microscopy (STEM), respectively. The presence of tetrataenite in the alloys investigated in this work could not be confirmed. In situ SR-PXD and STEM indicated minimal structural changes in the temperature stability range of the materials. A full-loop hysteresis curve acquired using a vibrating sample magnetometer (VSM) indicated no signs of magnetic hardening of the alloys with the measured coercivity being below 10 Oe, and thus consistent with FeNi without ordering. Full article

This paper presents experimental research on the relationship between the magnetic properties and the viscosity of ferrofluid based on ultra-pure magnetite nanoparticles, with the aim of studying behaviour through a microchannel. The magnetite nanoparticles have been obtained by chemical coprecipitation. Some examination methods, such as X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer, have been used to characterize the magnetite nanoparticles. The variation on the viscosity in the magnetic field of ferrofluids based on superparamagnetic magnetite has parabolic allure and in the absence of the magnetic field has a linear allure. The colloidal stability of the ferrofluids was evaluated using zeta potential measurements. Also, the behaviour of ferrofluids in a microchannel made inside the transparent polydimethylsiloxane (PDMS) matrix was observed under a digital microscope. Full article

Background and Objectives: Dental adhesives augmented with magnetic nanoparticles (MNPs) have been proposed to prevent microleakages. MNPs dispersed in a dental adhesive reduce the thickness of the adhesive layer applied in a magnetic field and enhance the bond strength by favoring the penetration of the adhesive into dentinal tubules. However, the restoration’s color has been found to be affected by the MNPs. This study tests the hypothesis that MNP coating can alleviate the esthetic impact of magnetic dental adhesives. Materials and Methods: We synthesized Fe₃O₄ MNPs with silica coating (MNPs-SiO₂), calcium-based coating (MNPs-Ca), and no coating. Their morphology was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Their chemical composition was assessed by energy-dispersive X-ray spectroscopy (EDX), and magnetic properties were measured using a vibrating sample magnetometer. FTIR spectroscopy was used to evaluate the polymerization of the MNP-laden adhesive. We prepared cavities in molar phantoms divided in four groups (n = 15 each) restored using the same adhesive with different MNP contents: Group 0 (G0)—no MNPs, G1—MNPs-SiO₂, G2—MNPs-Ca, and G3—uncoated MNPs. The restoration’s color was quantified in the CIELAB color space using a dental spectrophotometer. Results: MNPs-SiO₂ were globular, whereas MNPs-Ca had a cubic morphology. The SiO₂ layer was 73.1 nm ± 9.9 nm thick; the Ca(OH)₂ layer was 19.97 nm ± 2.27 nm thick. The saturation magnetization was 18.6 emu/g for MNPs-SiO₂, 1.0 emu/g for MNPs-Ca, and 65.7 emu/g for uncoated MNPs. MNPs had a marginal effect on the adhesive’s photopolymerization. The mean color difference between G0 and G2 was close to the 50:50% acceptability threshold, whereas the other groups were far apart from G0. The mean whiteness index of G2 did not differ significantly from that of G0; G1 deviated marginally from G0, whereas G3 differed significantly from G0. Conclusions: These results suggest that MNP coating can mitigate the influence of MNP-laden dental adhesives on the color of restorations. Full article

In this work magnetic nanoparticles (Fe₃O₄, or ZnFe₂O₄, or SrFe₁₂O₁₉) and BaTiO₃ microparticles were embedded in an epoxy resin for the synthesis of three series of hybrid magnetic polymer nanocomposites. Barium titanate content was kept constant, while magnetic phase content was varied. Fabricated specimens were structurally and morphologically characterized by employing scanning electron microscopy images and X-ray diffraction patterns. Results implied successful synthesis of the hybrid nanocomposites. The magnetic behavior of the pure magnetic nanoparticles and the fabricated nanocomposites was investigated via a Vibrating Sample Magnetometer. The magnetic performance of each type of magnetic phase (i.e., soft and hard) was induced in the nanocomposites, and magnetic performance is strengthened with the increase in magnetic phase content. Initial magnetization curves were used for the determination of mass magnetic susceptibility of all nanocomposites. Magnetic saturation and magnetic remanence have been found to follow a linear relationship with magnetic phase content, giving the opportunity to predict the system’s response in advance. Full article