Coercivity Values Research Articles

Urban and suburban's airborne magnetic particles accumulated on Tillandsia capillaris

Air particle pollution is a current issue that can cause adverse problems to human health and the urban environment. A fraction of these emitted particles is magnetite and iron-rich materials, which may be accumulated by biological indicators and effectively characterized by environmental magnetism methods. Thus, we studied this emitted particle fraction using the epiphytic species Tillandsia capillaris growing in northwestern Argentina's urban, suburban, and rural areas. The accumulated airborne magnetic particles' properties revealed valuable information regarding potentially toxic elements, magnetic mineralogy, sizes, morphology, and concentration. Magnetite was detected in samples from all studied areas, and its remanent coercivity values (Hcr = 32.1–42.6 mT) in (sub)urban sites are similar to other reported cities in Latin America. The concentration of these airborne magnetic particles AMP varied between urban sites (mean and (s.d.) values of in situ magnetic susceptibility κis = 16.2 (9.4) × 10−6 SI, and specific magnetic susceptibility χ = 61.9 (31.4) × 10−8 m3 kg−1) and suburban sites (κis = 13.9 (9.9) × 10−6 SI, and χ = 43.9 (32.2) × 10−8 m3 kg−1), and it was distinctively higher than in clean sites. The spatial distribution of AMP was analyzed using a geostatistical model for the concentration-dependent magnetic parameter κis, which showed zones with high magnetic particle accumulation associated with vehicular traffic in the city and industrial emission in a suburban site. Among concentration-dependent magnetic parameters, the κis is recommended for magnetic biomonitoring because Tillandsia species' individuals are not processed for laboratory measurements, preserving them and allowing us the possibility of measurements over time.

Structural, ferromagnetic, ferroelectric, and bio-medical behaviour of yttrium doped strontium hexaferrite (SrFe12-xYxO19) nano materials, assisted with sol-gel cost effective technique

Rare earth Yttrium (Y3+) substituted strontium hexaferrite (SrFe12-xYxO19) with X = (0.25–1.0), is synthesized using an economical and chemical-based sol–gel technique. The reflected planes in the XRD patterns justify that samples possessed hexagonal symmetry (P63/mmc space group). Crystallite size and strain calculations for SrFe12-xYxO19 samples were performed with a W-H plot. Lattice constants change minutely but regularly with Y3+ composition. The morphological structure of the sample SrFe12O19, SrFe11.50Y0.50O19, and SrFe11Y1O19 have been visualized from SEM micrographs, which reveal hexagonal crystal symmetry, possessing agglomeration with an average particle size of 49.84 nm, 73 nm, and 39.66 nm respectively. TEM, HRTEM, and SAED have been performed for confirming the lattice fringe distance, the grain size of nanoparticles (NPs), and diffraction planes. Grain size is 44.15 nm and 37.27 nm for X = 0.00 and X = 1.0 composition of Y3+. Raman spectral pattern exhibited that all the peak of the synthesized sample is indexed to Raman vibration modes and strontium hexaferrite (SHF) structure. FTIR analysis supports the stretching of metal-oxygen bonding and helps to find the force constant, bond length, and functional group of samples. The highest luminescent peak is observed at 481 nm, using the PL spectrum. Using UV-Visible spectroscopy direct band gap (Eg) of the synthesized sample was evaluated and is found to decrease from 2.3 eV-1.93 eV with Y3+ concentration. With an increase in the composition of non-magnetic ions of Y3+, Ms and Mr parameters decrease systematically. In contrast, the coercivity value increases drastically from 5983–6595 Oe and is one of the novel works of this report. The occupancy of Y3+ ions in SrFe12-xYxO19 lattice obstructs electrical leakage to generate remnant polarization (Pr) and coercive polarization (Pc) of values 25.45 μC cm−2 and 2.91 kV cm−1 respectively. Moreover, cytotoxicity assay reveals that at lower concentrations up to 250 μg ml−1, the synthesized material SrFe12-xYxO19 for X = 0.00 and X = 1.0 promotes the growth of cell and hence represents non-toxic and biocompatible behavior with cell. Hence anticipation can be made that it may be used for biological and biomedical applications such as bone replacement, magnetic drug delivery, and coating on metal implants. Thus, improved physical properties of Y3+ doped SHF nanomaterials pave the way for promising optical, magnetic, electrical, biological, and biomedical applications.

Green synthesis of reduced graphene oxide anchored Fe3O4‐Pd hetero‐nanostructure: An efficient, magnetically separable and reusable catalyst for Beckmann rearrangement of aldoximes to amides

The multifaceted Fe3O4‐Pd@rGO nanocomposite (NC) has been synthesized successfully by a biogenic method using Ocimum tenuiflorum leaf extract. The preparation of graphene oxide (GO) was done by the well‐known modified Hummer method. The as‐synthesized Fe3O4‐Pd@rGO NC was extensively characterized by various analytical techniques, namely, Fourier transform infrared (FTIR), X‐ray diffraction (XRD), field emission scanning electron microscopy‐energy‐dispersive X‐ray spectroscopy (FESEM‐EDX), high‐resolution transmission electron microscopy (HRTEM), inductively coupled plasma‐atomic emission spectrometry (ICP‐AES), X‐ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM) and Brunauer–Emmett–Teller (BET) surface area analysis. The absence of peak corresponding to υ(CO) at 1732 cm−1 in the FTIR spectrum of Fe3O4‐Pd@rGO enumerates the reduction of GO to reduced graphene oxide (rGO) during Fe3O4‐Pd nanoparticle (NP) synthesis with O. tenuiflorum leaf extract. The XRD pattern reveals the existence of rGO, cubic‐phased spinel‐structured Fe3O4 along with the formation of metallic Pd NP without any impurities. The FESEM image designates the spherical and flake‐like morphology of the NC. The crystallite size of the NC was calculated employing the Debye–Scherrer equation and was found to be 3.45 nm corresponding to the (220) plane. The average particle size of Fe3O4‐Pd NPs as estimated from the particle size distribution curve was ascertained as 3.03 nm. The utmost saturation magnetization value of the NC as evaluated by VSM study has appeared at 0.6219 emu g−1 having coercivity value of 335.1 Oe and remanent magnetization value of 0.0767 emu g−1, suggesting the existence of a ferromagnetic material in the synthesized NC. It was a stable and highly efficient catalyst for Beckmann rearrangement of aldoximes using in an environment‐friendly medium. It afforded up to 99% isolated yield of the preferred products under acid‐free condition, avoiding the use of any harsh chemicals that will be beneficial for future industrial applications. Finally, the magnetic component of the NC allowed for easy recovery of the catalyst, thereby eliminating the chance of leaching of metal atoms, and was reusable till six successive cycles without apparent loss of its catalytic performance.

Modifications in structure dependent magnetic parameters of Nd-doped Ba–Ca hexaferrites synthesized by sol gel using lemon extract as a fuel

The Nd doped Ba–Ca ferrites, Ba0.5Ca0.5NdXFe12-XO19 (x = 0 to 0.2, Δx = 0.05) are synthetically prepared by sol gel auto-ignition method using lemon extract as the fuel. Differential thermal analysis of the thermogravimetric spectrum clearly exhibits the thermal decomposition till 1050 °C. The powder X-ray diffraction (XRD) patterns of the hexaferrites sintered at 1050 °C reveals the single-phase M-type hexaferrites possessing nano dimensions. The lattice parameters, unit cell volumes, densities, and porosities of the hexaferrites were computed from the XRD patterns. The morphology of the synthesized hexaferrites is analyzed from the digital images of the powder samples obtained by utilizing Field Emission Scanning Electron Microscope (FESEM). The relative abundance of the elements within the hexaferrites was studied by means of Energy Dispersive X-Ray Analysis (EDAX). The oxidation states and valence of the metal elements within the hexaferrites are confirmed by means of the X-ray photoelectron spectroscopy (XPS). Magnetic parameters such as coercivity, saturation magnetization, and remanence are measured by using Vibrating-Sample Magnetometer (VSM). The Mössbauer spectra of the hexaferrites are obtained to analyze the hyperfine interactions by measuring the parameters such as hyperfine field, isomer shift, quadrupole splitting, relative area, and outer line width. The varying Nd doping concentrations have modulated the magnetic parameters of Ba–Ca hexaferrites showing the control of Nd doping on magnetic behavior of the hexaferrite. The moderate saturation magnetization and high coercivity values suggest the possible use of the hexaferrites as the permanent magnets.

Strategy and mechanism for substantially enhanced coercivity in multi-main-phase Nd-La-Ce-Fe-B sintered magnets

Improving the coercivity of high La/Ce content multi-main-phase (MMP) sintered magnets is crucial for promoting the use of La/Ce elements in permanent magnets. In this work, we used a novel strategy to accurately manipulate the chemical heterogeneity and grain boundary (GB) structures of MMP Nd-La-Ce-Fe-B sintered magnets, namely, by adjusting the composition of the LaCe-free alloys. We obtained an ultrahigh coercivity value of 13.75 kOe for the MMP-LaCe35 (LaCe accounted for 35 wt.% of total rare earth) magnet. This was attributed to the effect of Al-Cu-Ga element addition in LaCe-free alloys toward enhancing chemical heterogeneity (thicker Nd-rich shells) and optimizing the GB structures (continuous lamellar GBs). The former had a higher anisotropy field (HA) value, which enhanced the nucleation field, while the latter had a lower Fe concentration, which improved the magnetic isolation effect. Based on the above mechanisms, a coercivity of 12.09 kOe was attained for the MMP-LaCe40 magnet produced utilizing an alloy with the same composition. In addition, reducing the Nd content while maintaining the addition of Al-Cu-Ga elements in the LaCe-free alloy proved that adding Al-Cu-Ga elements improved the GB phase wettability of the MMP magnets, thereby forming continuous lamellar GBs to enhance coercivity. Our findings revealed that the enhanced chemical heterogeneity also effectively improved the coercivity temperature stability of the MMP magnets. This study provided an effective and feasible strategy for microstructure manipulation to prepare ultrahigh coercivity MMP-sintered magnets with higher LaCe content, which is crucial for promoting the comprehensive utilization of rare earth resources.

Enhanced photodegradation of CuCo2O4 nanoflower for the dye degradation of Rhodamine B and Methyl Violet

The investigation examined into the effect of different hydrothermal reaction temperatures and durations on the formation of nanoflower-shaped CuCo2O4 nanostructures (CCO NPs). The structural, morphological, functional, optical, and magnetic properties of the synthesized CCO NPs were thoroughly examined. The optimal calcination temperature was determined using Thermogravimetric and Differential Thermal Analysis (TG/DTA), which identified 400 °C as the ideal temperature. Following X-ray Diffraction (XRD) analysis, pure CuCo2O4 samples were formed, with calculated average crystallite sizes of 27 nm for CCO-A, 48 nm for CCO-B, 30 nm for CCO-C, and 31 nm for CCO-D samples. Fourier Transform Infrared (FTIR) analysis provided additional confirmation of pure CuCo2O4 formation, with characteristic bands in the 665–662 cm-1 and 583–567 cm-1 ranges indicating the presence of CuO and CoO bonds. SEM, High-Resolution SEM (HRSEM) and High-Resolution Transmission Electron Microscopy (HRTEM) all supported the observation of a distinct flower-like structural morphology. The optical properties of an optimized sample were revealed by UV–Visible Diffuse Reflectance Spectroscopy (UV-DRS) analysis, which revealed a band gap of 3.3 eV. According to Vibrating Sample Magnetometer (VSM) results, the magnetic behavior of CCO-D nanostructures at room temperature exhibited paramagnetic characteristics. The saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) values were determined to be 0.26218 emu/g, 2.7214 × 10–3 emu/g and 29.787 Oe, respectively. To evaluate photocatalytic performance, the CCO-D photocatalyst was used to degrade Methyl Violet and Rhodamine B dyes. CCO-D degraded MV dye with greater efficiency (93%) than RhB (85%) when exposed to sunlight. These findings highlight CCO-D's potential as a photocatalyst for the degradation of organic dyes.

Preparation and Characterization of Fe2O3 from Iron Sand of the Coastal Sea of Cidaun Beach-South Cianjur (Indonesia) using the Co-precipitation Method

The synthesis and characterization of Fe2O3 from Iron Sand of the coastal sea of Cidaun Beach - South Cianjur using the coprecipitation method has been carried out. The purpose of this research was to identify the crystal structure, magnetic mineral content, and magnetic properties of iron sands. The characterizations used in this research are X-Ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) and Vibrating Sample Magnetometer (VSM). Based on the XRD results, it shows that the iron sand sample produces multi-phases, namely hematite (????-Fe2O3), maghemite (????-Fe2O3) and ilmenite (FeTiO3). SEM-EDX results indicate that the iron sand samples have an average particle size of 12.396 ????m. VSM results indicate that the iron sand sample is soft magnetic (ferrimagnetic) with saturation, remanence and coercivity values of 47 emu/g, 1.53 emu/g and 102.97 Oe, respectively.

Cobalt Boride (Co2B) Particle Synthesis by One-step Carbothermic Reduction

In this study, crystalline Co2B powder production was carried out by a one-step carbothermal reduction method starting from cheap, easily accessible oxide-based materials. Firstly, to determine the carbothermic CoxB formation conditions, the decomposition temperatures of the raw materials were analysed by TG/DTA, and the temperature-varying Gibbs free energies of the expected reactions were calculated. Then, Co2B production was carried out at constant CoO/B2O3/C (3.22/1.5/1.3) weight ratios at temperature (1273-1473 K) and time (30-270 min). scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) were used to characterize the particles. XRD results showed that reaction temperature and time are the primary control on CoxB formation. Single-phase crystalline Co2B particles with crystallite sizes of 88 nm were successfully produced at 1473 K and 150 min. The permanent magnetization, saturation magnetization, and coercivity values of Co2B particles were defined as 16.58 Oe, 35.361 emu/g, 0.501 emu/g, respectively

Unveiling the origin of the large coercivity in (Nd, Dy)-Fe-B sintered magnets

Nd-Fe-B-based permanent magnets are widely used for energy conversion applications. However, their usage at elevated temperatures is difficult due to the relatively low coercivity (Hc) with respect to the anisotropy field (HA) of the Nd2Fe14B compound, which is typically 0.2HA. In this work, we found that the coercivity of an (Nd0.8Dy0.2)-Fe-B sintered magnet could reach 0.4HA, which was twice as high as the Hc/HA of its Dy-free counterpart. Detailed microstructural characterizations, density functional theory and micromagnetic simulations showed that the large value of coercivity, Hc = 0.4HA, originated not only from the enhanced HA of the main phase (intrinsic factor) but also from the reduced magnetization of the thin intergranular phase (extrinsic factor). The latter was attributed to the dissolution of 4 at.% Dy in the intergranular phase that anti-ferromagnetically coupled with Fe. The reduction in the magnetization of the intergranular phase resulted in a change in the angular dependence of coercivity from the Kondorsky type for the Dy-free magnet to the Stoner–Wohlfarth-like shape for the Dy-containing magnet, indicating that the typical pinning-controlled coercivity mechanism began to show nucleation features as the magnetization of the intergranular phase was reduced by Dy substitution.

Erbium substituted baddeleyites (ErxZr(1-x)O2): Structural, ferroelectric, magnetic and electrochemical analysis for supercapacitors electrodes using walnut shells charcoal

The fabrication of ErxZr(1-x)O2 (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) is carried out with solid-state method at 1200 °C temperature for 4-hrs to get the desired monoclinic structure. The structural, ferroelectric magnetic and electrochemical properties are investigated with X-ray diffractometer, ferroelectric, magnetic, cyclic voltametric, charging/discharging and electrochemical impedance respectively. The XRD and refinement parameters shows the formation of monoclinic symmetry. The low value of R-factors ensures the structural stability. The vista and diamond software are used to determine the different physical properties. The characteristic band at 665 and 721 cm−1 confirms the monoclinic identity of ZrO2 with ATR-FTIR. The SEM graphs show that the average particle size is present in 127-122 nm range. The decreased particle size is associated with the enhanced Csp due to the incease of surface-to-volume ratio. The ferroelectric analysis revealed the centrosymmetric alignment of tetrahedron sites having the 4-faces, 6 edges and 4-vertices. The magnetic analysis exposed the soft-diamagnetic feature. The high value of coercivity (Hc < Mr/2) gives the direction towards energy storage application. The CV graphs gives the good 389.8 F/g Csp which correlated with the GCD and EIS data. The highest 396.1 F/g Csp is measured using the charge/discharge curve and 309.75 F/g is calculated using the frequency-dependent EIS spectra. These high aggregates of specific capacitance values make them eligible for supercapacitors application.

Influence of heat treatment conditions on crystallization and magnetic property of FeZrB amorphous alloys

Fe84Zr7B9 amorphous alloy prepared by a single-roller rapid quenching method was annealed under different heat treatment conditions (different annealing temperatures, heating rates, and vacuum pressure in the cooling process). The different heat treatment conditions result in different crystallization process. The different vacuum pressures used during cooling resulted indifferent distributions of Fe, Zr, and B in the crystallization phase, thus affording completely different crystalline phases. After low-temperature heat treatment, the saturation magnetization of the alloys treated with continuous vacuum is higher than that of the alloys treated without continuous vacuum, and the coercivity values of the alloys treated with and without continuous vacuum were similar. After high-temperature heat treatment, the saturation magnetization and the coercivity values of the alloys treated without continuous vacuum are higher than those of the alloy treated with continuous vacuum.

Comparison the effect of co-precipitation and sol-gel techniques on the structural and magnetic attributes of ZnO and Zn(1-x)Fe0.05CoxO nanoparticles for attaining room temperature ferromagnetism (RTFM)

In current study, ZnO and Fe/Co co-doped ZnO (Zn1-x Fe0.05 Cox O where x = 0, 0.005) nanoparticles were prepared by using two different methodologies: sol gel method and coprecipitation method. The structural properties were determined by X-Ray diffraction technique which verifies the hexagonal wurtzite structure of prepared nanoparticles. Crystallite size varies from 18.68-37.43 nm for the samples synthesized by co-precipitation method and it varies from 19.97-38.45 nm for sol-gel method. Fourier transform infrared transmittance spectra were used to investigate the type of functional groups present in all the prepared nanoparticles. The UV-Visible absorption spectroscopy was employed to investigate the optical properties of ZnO and doping of Fe/Co in ZnO semiconducting host. The energy band gap varies from 3.03 - 3.68 eV for the samples synthesized by coprecipitation method and for sol-gel method, it ranges from 3.13 - 3.86 eV, by increasing dopant concentration. Vibrating sample magnetometer was used to inquire the magnetic behavior of synthesized nanoparticles which shows the weak ferromagnetic behavior of the doped nanoparticles prepared by both the techniques. Samples prepared by co-precipitation method showed higher values of saturation magnetization and coercivity as compared to the samples prepared by the sol-gel method. In comparison of two synthesis techniques, a slight change was observed in the particle size, energy band gap and magnetization values. The improved optical and magnetic behavior favors the co-precipitation method rather than sol gel method for obtaining room temperature ferromagnetism for practical applications in spintronics field.

Tunable magnetic properties and magnetic domain structure of nanocomposite permanent materials via Ti addition into Nd-Fe-Co-B alloys

In this work, the effect of tunable Ti content on the microstructure, magnetic domain structure, and magnetic properties of as-spun and annealed Nd9.5Fe79-xCo5TixB6.5(x = 0,1,2,3,4) alloys at the quench speed of 18 m/s were investigated. For the as-spun alloy, augmenting the Ti content enhanced the initial crystallization temperature and the stability of the amorphous phase. Simultaneously, the incorporation of Ti led to augmentation in the quantity of nanocrystals within the amorphous matrix, thereby facilitating the formation of vortex-like magnetic domains with large size but reduced the saturation magnetization Ms. For the annealed alloy, the incorporation of Ti inhibited the precipitation of α-Fe phase, refined the grain, enhanced the exchange coupling between the soft and hard magnetic phase and facilitated the formation of smaller, more uniform vortex-like magnetic domains, These alterations were beneficial to improve the comprehensive magnetic properties. Furthermore, the addition of tunable Ti resulted in a remarkable impact on coercivity enhancement. The coercivity value exhibited a significant increase of 54.30%, surging from 374.24 kA/m to 577.51 kA/m. Upon a thorough analysis of the magnetic domains and coercive force mechanisms, it was ascertained that the introduction of Ti substantially augmented the creation of vortex-like domains. These domains effectively impede domain motion, consequently elevating the material's coercivity.

Molybdenum substituted M‐type hexagonal barium ferrite for high microwave absorption performance

AbstractWith the advancement of electrical and electronic devices, overcoming electromagnetic pollution turns into an urgent problem. In this work, high‐valence molybdenum (Mo6+) was doped into M‐type hexagonal barium ferrite (BaFe12‐xMoxO19) to improve its electromagnetic performance. The relationship between the Mo6+ doping concentration and the crystallographic structure, morphology and electromagnetic properties was studied in detail. Structural characterizations authenticate that the Mo6+ ions prefer the 2b site, increasing the lattice values and grain size, and boosting more Fe3+ conversion into Fe2+. The magnetic hysteresis loops demonstrate a reduction of saturation magnetization and coercivity values with the increase of Mo6+ concentration. While the microwave absorption properties were obviously improved by the doping Mo6+, and obtained the highest RLmin value of ‐56.12 dB@16.1 GHz and effective absorption bandwidth of 4.2 GHz at x = 0.1, displaying a potential role in absorbing material.

Influence of Nb and Mo Substitution on the Structure and Magnetic Properties of a Rapidly Quenched Fe79.4Co5Cu0.6B15 Alloy.

The importance of amorphous and nanocrystalline Fe-based soft magnetic materials is increasing annually. Thus, characterisation of the chemical compositions, alloying additives, and crystal structures is significant for obtaining the appropriate functional properties. The purpose of this work is to present comparative studies on the influence of Nb (1, 2, 3 at.%) and Mo (1, 2, 3 at.%) in Fe substitution on the thermal stability, crystal structure, and magnetic properties of a rapidly quenched Fe79.4Co5Cu0.6B15 alloy. Additional heat treatments in a vacuum (260-640 °C) were performed for all samples based on the crystallisation kinetics. Substantial improvement in thermal stability was achieved with increasing Nb substitution, while this effect was less noticeable for Mo-containing alloys. The heat treatment optimisation process showed that the least lossy states (with a minimum value of coercivity below 10 A/m and high saturation induction up to 1.7 T) were the intermediate state of the relaxed amorphous state and the nanocomposite state of nanocrystals immersed in the amorphous matrix obtained by annealing in the temperature range of 340-360 °C for 20 min. Only for the alloy with the highest thermal stability (Nb = 3%), the α-Fe(Co) nanograin grows, without the co-participation of the hard magnetic Fe3B, in a relatively wide range of annealing temperatures up to 460 °C, where the second local minimum in coercivity and core power losses exists. For the remaining annealed alloys, due to lower thermal stability than the Nb = 3% alloy, the Fe3B phase starts to crystallise at lower annealing temperatures, making an essential contribution to magneto-crystalline anisotropy, thus the substantial increase in coercivity and induction saturation. The air-annealing process tested on the studied alloys for optimal annealing conditions has potential use for this type of material. Additionally, optimally annealed Mo-containing alloys are less lossy materials than Nb-containing alloys in a frequency range up to 400 kHz and magnetic induction up to 0.8 T.

Design, characterization, fabrication, and performance evaluation of ferroelectric dielectric resonator antenna for high-speed wireless communication applications

The research comprehensively analyzes the structural, electrical, and electrodynamic characteristics of Ba0.7Sr0.3TiO3 nanoparticles synthesized using a sol-gel approach. The formation of a tetragonal perovskite phase and the nano-crystalline nature have been confirmed using X-ray diffraction (XRD) analysis. Fourier transform infrared (FTIR) spectroscopy has been employed to identify characteristic absorption bands correlated with the crystal lattice vibrations of Ba0.7Sr0.3TiO3. The sample’s morphology has been examined using scanning electron microscopy (SEM), revealing a relatively dense and homogeneous composition composed of small spherical particles. The electrical properties of Ba0.7Sr0.3TiO3 nanoparticles have also been investigated using a ferroelectric measurement technique. The soft electric hysteresis loop with a small coercive field value makes the sample suitable for photovoltaic applications. Finally, a compact dielectric resonator antenna (DRA) based on Ba0.7Sr0.3TiO3 nanoparticles has been designed and characterized. The designed DRA demonstrates good impedance matching, broadside radiation pattern, and high antenna gain and efficiency at the frequency band of 5.6–6.15 GHz, making it suitable for sub-6 GHz (5 G) applications.

Green conversion of waste PET into magnetic Ni0·4Fe2·6O4/(Fe,Ni)@carbon nanostructure for adsorption and separation of dyes from aqueous media

A nanostructured core-shell composite (Ni0·4Fe2·6O4/(Fe,Ni)@carbon, NFC) comprising magnetic nano-cores encapsulated with graphitic shells (≈80 wt%) is prepared by facile and clean mechanochemical-molten salt processing approach using waste PET; providing a specific surface area of 201.9 m2 g−1, well-developed mesopores, and ferromagnetic behavior characterized by the coercivity value of 149 Oe. NFC is utilized as a high-performance adsorbent for the removal of organic dyes from their aqueous solutions. Moreover, the magnetic performance of NFC enables the facile collection of the exhausted adsorbent out of the purified water. Performances of NFC for the removal of crystal violet dye (CV), methyl orange (MO) and rhodamine B (Rh B) from their aqueous solutions are systematically investigated under different environmental conditions including the adsorbent dosage and dye concentration, as well as the solution pH and temperature, where an impressive CV removal capacity of 201.6–243.8 mg g−1 is recorded for a wide pH range of 2–10. Mechanism and kinetics involved in the adsorption process are investigated by studying the adsorption isotherms and thermodynamics. The dye adsorption of the nanocomposite material is confirmed to follow the pseudo-second-order kinetic model combined with the Langmuir isotherm model, exhibiting an excellent spontaneous and exothermic monolayer adsorption capacity of around 153 mg g−1 (for MO) for the fresh adsorbent and around 89 mg g−1 after three adsorption-regeneration cycles.

Comparison of phenol formaldehyde with polyvinyl chloride resin as binder bonded NdFeB magnet for axial flux generator

Bonded permanent magnets are made by mixing a magnetic powder material Neodymium Iron Boron (NdFeB) commercial MQP type 16-7 with a polymer material powders phenol formaldehyde (Bakelite) and polyvinyl chloride (PVC) resin. Comparison between the composition of NdFeB powder and the polymer powders were varied at 80:20, 90:10, and 95:5 wt%, respectively. This mixture is then pressed with a hot press system and then carried out magnetic alignment axial flux using a magnetizer machine, Magnet Phisyk-Germany, with an impulse system. Magnetic properties were characterized by permagraph Magnet Phisyk-Germany. The best value obtained for the composition of 95: 5% NdFeB-pvc resin powder to the value of remanence magnet (Br) = 0.604 Tesla (T), the value of coercivity (Hc) = 480 kA/m and maximum energy product (BH)max = 50.05 kJ/m3. Fabrication is done by the size of the magnetic 50 mm diameter, 8 mm thick and was applied to the axial flux generator. The output voltage of the generator has been tested with variations of 50 to 300 rotations per minute (rpm) using a Hantek 6022BE oscilloscope, and the measurement results obtained values of 1.9 to 12.2 Volts.

Investigation of the Structural, Dielectric, Magnetic, and Magnetoelectric Properties of Nd-Substituted Sr3Co2Fe24O41 Z-Hexaferrite

The Neodymium (Nd) substituted Sr-based Z-Hexaferrites having composition Sr3-xNdxCo2Fe24O41 (x = 0, 0.15, 0.30 and 0.45) corresponding to pristine, 5, 10 and 15% substitution were prepared using solid-state reaction method in pre-optimized rare Earth metal solubility range (x ≤ 0.45) and labeled as SCFO, SNCFO5, SNCFO10 and SNCFO15, respectively. X-ray diffractometer and Scanning Electron Microscopy (SEM) were utilized to investigate the prepared samples’ structure and grain morphology. The X-ray diffraction (XRD) patterns confirmed Z-hexaferrite formation with adequate phase purity. Dielectric measurements exhibited a relaxation-type, frequency-dependent, and thermally activated dielectric response across all prepared samples. In Nd substituted SCFO, the obtained value of coercivity (Hc) ranges from 52.2–68.45 oersted, confirming a soft magnetic behavior. Magnetoelectric coupling coefficient(α) recorded at room temperature has a maximum value of 0.2133 mV cm−1Oe−1 for the pristine sample and this value of α varies with Nd substitution for all prepared samples.

Nanocomposites Based on Pyrolyzed Polyacrylonitrile Doped with FeCoCr/C Transition Metal Alloy Nanoparticles: Synthesis, Structure, and Electromagnetic Properties.

In the last decade, the development of new materials that absorb electromagnetic radiation (EMR) has received research interest as they can significantly enhance the performance of electronic devices and prevent adverse effects caused by electromagnetic pollution. Electromagnetic radiation absorbers with a low weight and small thickness of the absorber layer, good absorption capacity, and a wide frequency response bandwidth are highly demanded. Here, for the first time, the properties of polymer nanocomposites FeCoCr/C synthesized by doping FeCoCr alloy nanoparticles into a polymer matrix of pyrolyzed polyacrylonitrile are investigated. An analysis of the magnetic properties of FeCoCr/C nanocomposites showed that increasing the synthesis temperature increased the specific magnetization and coercive force values of the FeCoCr/C nanocomposites. The dependence between the ratio of metals in the precursor of pyrolyzed polyacrylonitrile and the electromagnetic and wave-absorbing properties of FeCoCr/C nanocomposites is considered, and the results of complex dielectric and magnetic permeability measurements are analyzed. It is found that the most promising of all the studied materials are those obtained at T = 700 °C with the ratio of metals Fe:Co:Cr = 35:35:30.