Search Results (77)

In this study, a Zn-Mn ferrite soft magnetic material (Mn_0.6Zn_0.4Fe₂O₄) was successfully prepared from a spent Zn-Mn battery using a novel multi-step process involving bioleaching, co-precipitation, and boiling reflux. The green Zn–Mn ferrite exhibited optimal magnetic properties, with Ms, Mr, and Hc values of 68.9 emu/g, 4.7 emu/g, and 53.6 Oe, respectively. The adsorption kinetics and isotherms of Cd (II), As (III), and Pb (II) in wastewater on Mn_0.6Zn_0.4Fe₂O₄ were subsequently investigated. The sorption dosages of Cd (II), As (III), and Pb (II) were 22.9 mg/g, 8.7 mg/g, and 33.9 mg/g, respectively. The pseudo-second-order kinetic model provided a fitting correlation with the experimental data. The adsorption process exhibited a good correlation with the Langmuir model, with R² = 0.997, and the q_m and b values were 33.44 mg/g and 2.43 L/mg, respectively. The sorption rates followed the sequence Pb (II) > Cd (II) > As (III). On increasing the temperature, the saturated adsorption capacity of the Cd (II), As (III), and Pb (II) increased, thus indicating that the adsorption reaction was endothermic, with the corresponding activation energy (Ea) values determined to be 9.5 KJ/mol, 32.2 KJ/mol, and 1.4 KJ/mol, respectively. Full article

Liquid metal embrittlement (LME) in Zn-coated advanced high-strength steels (AHSSs) is an increasing concern, particularly in automotive assembly, where it can cause early failure and reduce ductility during resistance spot welding (RSW). This study explores the impact of adding 0.2 wt% Mo on the LME susceptibility of 0.2C-2Mn-1.5Si AHSS through hot tensile testing, RSW, and advanced microstructural analyses, including atom probe tomography (APT) and transmission electron microscopy (TEM). The results suggest that Mo enhances resistance to LME, as evidenced by the increased tensile stroke from 2 mm in the case of the 0 Mo alloy and to 2.75 mm in the case of the 0.2 Mo sample. Also, the average crack length in the shoulder of the welded samples decreased from 109 ± 7 μm to 28 ± 3 μm by adding 0.2 wt% Mo to the base alloy. APT analysis revealed that, in the presence of Mo, there is increased boron (B) segregation at austenite grain boundaries, improving cohesion, while TEM suggested more diffusion of Zn into the substrate, facilitating the formation of Zn-ferrite. These findings highlight Mo’s potential to reduce LME susceptibility of AHSS for automotive applications. Full article

Large-scale superconductor applications necessitate a superconducting matrix with pinning sites (PSs) that immobilize vortices at elevated temperatures and magnetic fields. While previous works focused on the single addition of nanoparticles, the simultaneous inclusion of different nanoparticles into a superconducting matrix can be an effective way to achieve an improved flux pinning capacity. The purpose of this study is to explore the influence of mixed-nanoparticle pinning, with the co-addition of non-magnetic (BaTiO₃; BT) and various types of magnetic spinel ferrite (MFe₂O₄, abbreviated as MFO, where M = Mn, Co, Cu, Zn, and Ni) nanoparticles, on the superconductivity and flux pinning performances of the high-temperature superconductor YBa₂Cu₃O_y (YBCO). An analysis of X-Ray diffraction (XRD) data of BT–MFe₂O₄-co-added YBCO samples showed the formation of an orthorhombic structure with Pmmm symmetry. According to electrical resistivity measurements, the emergence of the superconducting state below $T_c^{offset}$ (zero-resistivity temperature) was proven for all samples. The highest $T_c^{offset}$ value was recorded for the Y-BT-MnFO sample, while the minimum value was obtained for the Y-BT-ZnFO sample. Direct current (DC) magnetization results showed good magnetic flux pinning performance for all the co-added samples compared to the pristine sample but with some discrepancies. At 77 K, the values of the self-critical current density (self-$J_{cm}$) and maximum pinning force ($F_{pmax}$) for the Y-BT-MnFO sample were found to be eight times higher and seventeen times greater than those for the pristine sample, respectively. The results acquired suggested that mixing the BT phase with an appropriate type of spinel ferrite nanoparticles can be a practical solution to the problem of degradation of the critical current density of the YBCO material. Full article

This work presents the development of a magnetic levitation system with a ferrite core, designed for electromagnetic energy harvesting from mechanical vibrations. The system consists of a fixed enamel-coated copper coil and five neodymium-iron-boron permanent magnets housed within a PVC spool. To enhance magnetic flux concentration, a manganese-zinc ferrite (Mn-Zn) ring was employed within the spool. Experimental tests were conducted at frequencies up to 20 Hz, demonstrating the device’s potential for harvesting energy from small vibrations, such as those generated by human biomechanical movements, achieving operating voltages up to 3 V. Additionally, the architecture is scalable for larger systems and allows for the integration of multiple transducers without magnetic field interference, independent of the frequency or excitation phase of each transducer. Full article

Spinel ferrites demonstrate extensive applications in different areas, like electrodes for electrochemical devices, gas sensors, catalysts, and magnetic adsorbents for environmentally important processes. However, defects in the real spinel structure can change the many physical and chemical properties of spinel ferrites. Although the number of defects in a crystal spinel lattice is small, their influence on the vast majority of physical properties could be really decisive. This review provides an overview of the structural characteristics of spinel compounds (e.g., CoFe₂O₄, NiFe₂O₄, ZnFe₂O₄, Fe₃O₄, γ–Fe₂O₃, Co₃O₄, Mn₃O₄, NiCo₂O₄, ZnCo₂O₄, Co₂MnO₄, etc.) and examines the influence of defects on their properties. Attention was paid to the classification (0D, 1D, 2D, and 3D defects), nomenclature, and the formation of point and surface defects in ferrites. An in-depth description of the defects responsible for the physicochemical properties and the methodologies employed for their determination are presented. DFT as the most common simulation approach is described in relation to modeling the point defects in spinel compounds. The significant influence of defect distribution on the magnetic interactions between cations, enhancing magnetic properties, is highlighted. The main defect-engineering strategies (direct synthesis and post-treatment) are described. An antistructural notation of active centers in spinel cobalt ferrite is presented. It is shown that the introduction of cations with different charges (e.g., Cu(I), Mn(II), Ce(III), or Ce(IV)) into the cobalt ferrite spinel matrix results in the formation of various point defects. The ability to predict the type of defects and their impact on material properties is the basis of defect engineering, which is currently an extremely promising direction in modern materials science. Full article

MnZn ferrite powders were prepared based on the novel nano in situ composite method and through chemical sol-spray drying–calcination technology. The precursor powders were calcined at 1060 °C at different calcination times (1–9 h) to research the influences of the calcination time on MnZn ferrite powders. The research results revealed that all samples had similar morphologies composed of fine particles. The pure MnZn ferrite spinel phase can only be obtained when the calcination time does not exceed 3 h. Otherwise, some α-Fe₂O₃ or γ-Fe₂O₃ impurities will appear. The particle size descended with an increasing calcination time and then ascended. After 3 h of preservation, the smallest particle size was obtained, and it exhibited a unimodal distribution. The saturation magnetization (M_s) increased at first and decreased later with an increasing calcination time, and the optimal value (53.4 emu/g) was reached after holding for 3 h. In view of this work, the optimal calcination time is 3 h. Full article

Core–shell inorganic/organic composites have often been applied as fillers in electromagnetic interference shielding. Those composed of conducting polymers and ferrites are of particular interests with respect to their electrical and magnetic properties. Pyrrole was oxidized in aqueous medium in the presence of manganese-zinc ferrite microparticles with ammonium peroxydisulfate or iron(III) chloride to yield polypyrrole-coated, core–shell microstructures. The effect of methyl orange dye on the conversion of globular polypyrrole to nanotubes has been demonstrated by electron microscopy when iron(III) chloride was used as an oxidant. The formation of polypyrrole was proved by FTIR spectroscopy. The completeness of ferrite coating was confirmed by Raman spectroscopy. The resistivity of composite powders was determined by four-point van der Pauw method as a function of pressure applied up to 10 MPa. The conductivity of composite powders was determined by a polypyrrole matrix and only moderately decreased with increasing content of ferrite. The highest conductivity of composites, 13–25 S cm⁻¹, was achieved after the deposition of polypyrrole nanotubes. Magnetic properties of composites have not been affected by the polypyrrole moiety, and the magnetization of composites was proportional to the ferrite content. Full article

Two samples of Zn_xMn_1−xFe₂O₄ (x = 0, sample A; and x = 0.4, sample B) were synthesized by the hydrothermal method. From complex impedance measurements in the range 100 Hz–2 MHz and for temperatures T between 30 and 130 °C, the barrier energy between localized states ΔE_relax was determined for the first time in these samples. For sample B, a single value of ΔE_relax was highlighted (0.221 eV), whilst, for sample A, two values were obtained (0.012 eV and 0.283 eV, below 85 °C and above 85 °C, respectively), associated with two zones of different conductivities. Using the Mott’s VRH model and the CBH model, we determined for the first time both the bandgap energy barrier (W_m) and the hopping (crossover) frequency (ω_h), at various temperatures. The results show that, for sample A, W_m has a maximum equal to 0.72 eV at a temperature between 70 and 80 °C, whilst, for sample B, W_m has a minimum equal to 0.28 eV at a temperature of 60 °C, the results being in good agreement with the temperature dependence of the static conductivity σ_DC(T) of the samples. By evaluating σ_DC and eliminating the conduction losses, we identified, using a novel approach, a dielectric relaxation phenomenon in the samples, characterized by the activation energy E_A,rel. At various temperatures, we determined E_A,rel, which ranged from 0.195 eV to 0.77 eV. These results are important, as understanding these electrical properties is crucial to various applications, especially in technologies where temperature variation is significant. Full article

Bismuth ferrite BiFeO₃ (BFO)-based ferroelectrics have great potential as inorganic perovskite-like oxides for future solar cells applications due to their unique physical properties. In this work, La and Mn co-doped BFO thin films with compositions Bi_0.9La_0.1(Fe_1−xMn_x)O₃ (x = 0, 0.05, 0.1, 0.15) (denoted as BLF, BLFM5, BLFM10, BLFM15, respectively) were prepared via a sol–gel technique on indium tin oxide (ITO) glass. All the films are monophasic, showing good crystallinity. The optical bandgap E_g was found to decrease monotonously with an increase in the Mn doping amount. Compared with other compositions, the BLFM5 sample exhibits a better crystallinity and less oxygen vacancies as indicated by XRD and XPS measurements, thereby achieving a better J–V performance. Based on BLFM5 as the light absorbing layer, the ITO/ZnO/BLFM5/Pt and ITO/ZnO/BLFM5/NiO/Pt heterostructure devices were designed and characterized. It was found that the introduction of the ZnO layer increases both the open circuit voltage (V_oc) and the short circuit current density (J_sc) with V_oc = 90.2 mV and J_sc = 6.90 μA/cm² for the Pt/ BLFM5/ZnO/ITO device. However, the insertion of the NiO layer reduces both V_oc and J_sc, which is attributed to the weakened built-in electric field at the NiO/BLFM5 interface. Full article

The PEG-coated ferrite nanoparticles Co_0.2Mn_0.6Zn_0.2Fe₂O₄ (X1), Co_0.4Mn_0.4Zn_0.2Fe₂O₄ (X2), and Co_0.6Mn_0.2Zn_0.2Fe₂O₄ (X3) were synthesized by the coprecipitation method. The nanoparticles were characterized by XRD, Raman, VSM, XPS, and TEM. The magnetic hyperthermia efficiency (MH) was determined for PEG-coated nanoparticles using an alternating magnetic field (AMF). X2 nanoparticles displayed the highest saturation magnetization and specific absorption rate (SAR) value of 245.2 W/g for 2 mg/mL in a water medium. Based on these properties, X2 nanoparticles were further evaluated for antiproliferative activity against HCT116 cells at an AMF of 495.25 kHz frequency and 350 G strength, using MTT, colony formation, wound healing assays, and flow cytometry analysis for determining the cell viability, clonogenic property, cell migration ability, and cell death of HCT116 cells upon AMF treatment in HCT116 cells, respectively. We observed a significant inhibition of cell viability (2% for untreated control vs. 50% for AMF), colony-forming ability (530 cells/colony for untreated control vs. 220 cells/colony for AMF), abrogation of cell migration (100% wound closure for untreated control vs. 5% wound closure for AMF), and induction of apoptosis-mediated cell death (7.5% for untreated control vs. 24.7% for AMF) of HCT116 cells with respect to untreated control cells after AMF treatment. Collectively, these results demonstrated that the PEG-coated (CoMnZn-Fe₂O₄) mixed ferrite nanoparticles upon treatment with AMF induced a significant antiproliferative effect on HCT116 cells compared with the untreated cells, indicating the promising antiproliferative potential of the Co_0.4Mn_0.4Zn_0.2Fe₂O₄ nanoparticles for targeting colorectal cancer cells. Additionally, these results provide appealing evidence that ferrite-based nanoparticles using MH could act as potential anticancer agents and need further evaluation in preclinical models in future studies against colorectal and other cancers. Full article

This study investigates the magnetization mechanisms in MnZn ferrites, which are key materials in high-frequency power electronics, to understand their behavior under various sintering conditions. Employing X-ray diffraction and scanning electron microscopy, we analyzed the microstructure and phase purity of ferrites sintered at different temperatures. Our findings confirm consistent spinel structures and highlight significant grain-growth and densification variabilities. Magnetic properties, particularly the saturation magnetization (M_s) and initial permeability (μ_i), were explored, revealing their direct correlation with the sintering process. The decomposition of magnetic spectra into domain-wall-motion and spin-rotation components offered insights into the dominant magnetization mechanisms, with the domain wall movement becoming increasingly significant at higher sintering temperatures. The samples sintered at 1310 °C showcased superior permeability and the least loss in our investigations. This research underscores the impact of sintering conditions on the magnetic behavior of MnZn ferrites, providing valuable guidelines for optimizing their magnetic performance in advanced electronic applications and contributing to the material science field’s understanding of the interplay between sintering, microstructures, and magnetic properties. Full article

This article proposes a simulation model of single-phase common-mode inductors to evaluate the small-signal characteristic of common-mode inductors when the stray capacitance cancellation method is applied. From the estimated stray capacitance of common-mode inductors, the value of the cancellation capacitors is determined and implemented into the model. Thus, the proposed model can simulate the small-signal characteristic of common-mode inductors with the capacitance cancellation method at the design stage. To validate the proposed model, a comparison between measured and simulated attenuation characteristics of fabricated single-phase common-mode inductors is performed. The comparison result clarifies that the high-frequency attenuation improvement of the capacitance cancellation method is limited for manganese–zinc ferrite-based common-mode inductors due to the steep change of the complex permeability. Full article

Spinel ferrites, ZnFe₂O₄, MnFe₂O₄, and ZnMnFe₂O₄, were synthesized using the sol–gel method and thoroughly investigated for their potential as catalytic and magnetic materials. Experiments unveiled that ZnMnFe₂O₄ exhibited excellent catalytic and magnetic properties, whereas the Density Functional Theory (DFT) calculations provided insight into the excellent performance of ZnMnFe₂O₄ compared with ZnFe₂O₄ and MnFe₂O₄. The catalytic efficiencies of the synthesized spinel ferrites were evaluated against a model reaction, i.e., the gas-phase oxidation of octanol to a corresponding aldehyde, utilizing molecular oxygen as an oxidant. The results indicated that the order of catalytic activity was ZnMnFe₂O₄ > MnFe₂O₄ > ZnFe₂O₄. The reaction was found to follow Langmuir Hinshelwood’s mechanism for dissociative adsorption of molecular oxygen. Owing to their superb catalytic and magnetic properties, mixed ferrites can be extended to a variety of organic transformation reactions. Full article

Mixed manganese–zinc ferrite nanoparticles coated with PEG were studied for their potential usefulness in MRI thermometry as temperature-sensitive contrast agents. Particles in the form of an 8.5 nm core coated with a 3.5 nm layer of PEG were fabricated using a newly developed, one-step method. The composition of Mn_0.48Zn_0.46Fe_2.06O₄ was found to have a strong thermal dependence of magnetization in the temperature range between 5 and 50 °C. Nanoparticles suspended in an agar gel mimicking animal tissue and showing non-significant impact on cell viability in the biological test were studied with NMR and MRI over the same temperature range. For the concentration of 0.017 mg/mL of Fe, the spin–spin relaxation time T₂ increased from 3.1 to 8.3 ms, while longitudinal relaxation time T₁ shows a moderate decrease from 149.0 to 125.1 ms. A temperature map of the phantom exposed to the radial temperature gradient obtained by heating it with an 808 nm laser was calculated from T₂ weighted spin-echo differential MR images. Analysis of temperature maps yields thermal/spatial resolution of 3.2 °C at the distance of 2.9 mm. The experimental relaxation rate R₂ data of water protons were compared with those obtained from calculations using a theoretical model incorporating the motion averaging regime. Full article

The results of electron beam processing of Mn-Zn ferrite samples using pulsed and continuous electron beams in the fore-vacuum pressure range (10 Pa) are presented. We find that continuous electron beam processing leads to surface structuring of the ferrite, changes in elemental composition on the surface, and electrical property modification. The degree of ferrite parameter changes exhibits a threshold behavior. For surface processing temperatures below 900 °C, changes are barely noticeable, while for temperatures over 1100 °C the surface resistance decreases by more than an order of magnitude to values of less than 3 kOhm. Electron beam processing with millisecond pulse duration and pulse energy density exceeding 15 J/cm² results in the formation of low zinc content melt islands, while the remaining surface area (outside the islands) elemental content and ferrite properties remain largely unchanged. The thickness of the modified layer depends on the processing mode and can be controlled over the range of 0.1–0.5 mm. Due to its low resistance, the modified layer can be utilized to enhance the RF-absorbing properties of the ferrite, which is important in the design of modern magnetic elements of electronic equipment. Full article