Magnetic properties of metal layer deposited by reduction of polymer containing metal ions

Magnetic properties of metal layer deposited by reduction of polymer containing metal ions were investigated. Varying the ratio of the cobalt ion to the nickel ion in the polymer, the coercivity, the maximum flux density and the remanent flux density of the deposited metal layer were changed from 100 to 600 Oe, from 1 000 to 12 600 G and from 500 to 7 600 G, respectively. The X-ray diffraction pattern of the metal layer with excellent magnetic properties gives distinct peaks corresponding to the (101) and (100) planes of the crystal of α-Co. This suggests that such a deposited metal layer has the structure of highly crystalline metal layer.     

Monitoring the dielectric properties of Mn-ferrite nanoparticles by controlling crystallite size and applying static magnetic field

Mn-ferrite (MnFe₂O₄) nanoparticles were synthesized by a co-precipitation method. Temperature annealing and ball milling were used to change the crystallite size. X-Ray diffractograms (XRD) con?rmed the single phase spinel structure for all samples and calculations showed that the crystallite size is in the range of 8–33 nm. Transmission electron microscope (TEM) images reveals 17–43 nm particle sizes. The frequency and crystallite size dependence of resistivity ρ_ac, dielectric constant ε' and dielectric loss ε'' of all samples were studied without magnetic field and under a dc magnetic field that ranges from 0.1 T to 0.5 T in both the parallel and perpendicular directions to the applied electric field. For all samples, ρ_ac, ε' and ε'' were found to decrease with increasing the applied electric field frequency. ρ_ac decreases while ε' and ε'' increase with increasing the crystallite size. On the other hand, they have the reverse trend with applied magnetic field. All factors that affect these parameters were discussed to explain their behavior. Interestingly, it was found that the resistivity depends linearly on the applied magnetic field. This enables these samples to be used as magnetic sensors. Finally, the sensor sensitivity was controlled by changing the crystallite size of the samples. This work establishes valid ideas for promising applications in the field of magnetic sensors.     

Fabrication of DLC thin films with improved diamond-like carbon character by the application of external magnetic field

Diamond-like carbon (DLC) thin films were grown on Si-(100) substrates by a magnetically-assisted pulsed laser deposition (PLD) technique. The role of magnetic field on the structural, morphological, mechanical properties and deposition rate of DLC thin films has been studied. The obtained films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) and nanoindentation techniques. It was found that the diamond-like character, thickness and deposition rate of the DLC films increase in the presence of magnetic field. The films deposited under magnetic field exhibit a denser microstructure and smoother surface with lower surface roughness. Meanwhile, the mechanical properties of the magnetically processed DLC thin films experience an improvement, relative to the conventionally processed ones. It seems that the DLC films deposited under magnetic field can be better candidate for hard and wear resistance coating applications.     

The effect of magnetic field on the oxygen reduction reaction and its application in polymer electrolyte fuel cells

The effect of magnetic field gradients on the electrochemical oxygen reduction was studied with relevance to the cathode gas reactions in polymer electrolyte fuel cells. When a permanent magnet was set behind a cathode, i.e. platinum foil or Pt-dispersed carbon paper for both electrochemical and rotating electrode experiments and oxygen was supplied to the uphill direction of the magnetic field, electrochemical flux was enhanced and the current increased with increasing the absolute value of magnetic field. This magnetic effect can be explained by the magnetic attractive force toward O₂ gas. When magnet particles were included in the catalyst layer of the cathode and the cathode was magnetized, the current of oxygen reduction was higher than that of nonmagnetized cathode. A new design of the cathode catalyst layer incorporating the magnet particles was tested, demonstrating a new method to improve the fuel cell performance.     

Magnetic liposomes for colorectal cancer cells therapy by high-frequency magnetic field treatment

In this study, we developed the cancer treatment through the combination of chemotherapy and thermotherapy using doxorubicin-loaded magnetic liposomes. The citric acid-coated magnetic nanoparticles (CAMNP, ca. 10 nm) and doxorubicin were encapsulated into the liposome (HSPC/DSPE/cholesterol = 12.5:1:8.25) by rotary evaporation and ultrasonication process. The resultant magnetic liposomes (ca. 90 to 130 nm) were subject to characterization including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), zeta potential, Fourier transform infrared (FTIR) spectrophotometer, and fluorescence microscope. In vitro cytotoxicity of the drug carrier platform was investigated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L-929 cells, as the mammalian cell model. In vitro cytotoxicity and hyperthermia (inductive heating) studies were evaluated against colorectal cancer (CT-26 cells) with high-frequency magnetic field (HFMF) exposure. MTT assay revealed that these drug carriers exhibited no cytotoxicity against L-929 cells, suggesting excellent biocompatibility. When the magnetic liposomes with 1 μM doxorubicin was used to treat CT-26 cells in combination with HFMF exposure, approximately 56% cells were killed and found to be more effective than either hyperthermia or chemotherapy treatment individually. Therefore, these results show that the synergistic effects between chemotherapy (drug-controlled release) and hyperthermia increase the capability to kill cancer cells.     

Structure and properties of ta-C films prepared by vacuum cathodic arc with an unbalanced external electromagnetic field

ta-C thin films were deposited by vacuum cathodic arc technology with an unbalanced external electromagnetic field. The intensity of the magnetic field was adjusted by changing coil current and its effect on structure and properties of ta-C films was studied. FEM simulation results showed that as coil currents increased, the transverse, normal magnetic field and the magnetic intensity from arc cathode to substrates holder gradually increased. The UBM system increases the magnetic field intensity of the entire vacuum chamber by mainly improving the normal magnetic flux density near the arc cathode. The surface morphology, microstructure, tribo-mechanical properties of ta-C films were analyzed by SEM, Raman spectrometer, XPS, 3D surface profiler, Nano-indentation and ball-on-disk tribometer. Results showed that as the coil current increased, the average target voltage increased from 21.14 V to 25.97 V and target power rose from 845 W to 1043 W. Changes of magnetic field affected the plasma in vacuum chamber and the number of ions reaching the substrates, which had significant influences on film structure and properties. With a proper magnetic field (at coil current of 4A), ta-C films perform the highest hardness of 58.8 GPa, and the highest sp³ content of about 71% with the lowest ratio of I_D/I_G (0.38). During the wear process, the transfer layer was formed by oxidation and graphitization of contact surfaces. High hardness provided good support for transfer film, which leads to a low wear rate.     

Magnetic field facilitated electrocatalytic degradation of tetracycline in wastewater by magnetic porous carbonized phthalonitrile resin

Herein, the magnetic field facilitated electrocatalytic degradation of tetracycline is reported for the first time. A magnetic porous carbonized phthalonitrile resin electrocatalyst has been prepared through directly annealing phthalonitrile monomer, polyaniline coated barium ferrite and potassium hydroxide. The tetracycline degradation percentage (DP%) by such electrocatalyst is significantly increased up to 37.42% under magnetic field with the optimal pH value of 5.0 and bias voltage of 1.0 V (vs. SCE). The mechanism of this phenomenon is explained by the spin-selective electron removal process in the reaction between metal-oxygen species and tetracycline on the electrocatalyst. The comparison of degradation pathways for tetracycline with and without magnetic field confirms the improvement of tetracycline DP%. This work opens a new direction for the application of an external magnetic field in the electrocatalytic degradation of antibiotics in wastewater.     

磁场强度对水煤浆性能的影响

在弱电磁场下考察了北宿煤和淮南洗精煤的成浆性能 ;经弱电磁场处理后的煤和水 ,对水煤浆性能有一定改善。提高磁场强度 ,并使磁场短时间作用于水煤浆 ,会使水煤浆粘度升高 ,流动性变好 ,析水率降低 ,稳定性得到改善     

Iron filled carbon nanotubes grown on substrates with thin metal layers and their magnetic properties

The thermal decomposition of ferrocene combined with a catalyst-assisted structuring of a Si-substrate surface is a favourable way to produce Fe-filled carbon nanotubes in good quality and in high yields. In this work we have studied the growth of such aligned filled nanotubes on iron and cobalt pre-coated Si-substrates and their dependence on the deposition time. The nanotube diameter depends on the used catalyst metal on the substrate surface. Magnetization measurements were carried out perpendicular (along tube axis) and parallel to the substrate and show excellent coercivities, a strong uniaxial anisotropy (ratios of H_c,per/H_c,par up to 6) and high saturation magnetization moments per substrate square. The magnetic behavior has been also interpreted as a function of deposition time and of the catalyst metal on the substrate. These investigations were complemented by X-ray diffraction, which revealed a majority fraction of α-Fe and a small amount of Fe₃C.     

Enhanced superconducting properties of YBa2Cu3O7−δ thin film with magnetic nanolayer additions

Vertically aligned nanocomposite (VAN) (La_0.7Sr_0.3MnO₃)_0.5(CeO₂)_0.5 and pure La_0.7Sr_0.3MnO₃ layers were incorporated into YBa₂Cu₃O_7−δ (YBCO) thin films as bilayer stacks for magnetic flux pinning enhancement. The films show high epitaxial quality, suggested by XRD and TEM study. The critical temperature T_c of the bilayers is about 90 K, which is close to that of pure YBCO films, while both the self-field J_c^sf and in-field critical current density J_c^in-field are largely enhanced. Among all samples, the film with VAN cap layer shows the highest J_c values in all field ranges. This study demonstrates an effective way towards the tunable pinning effect for YBCO coated conductors by both defect and magnetic pinning.     

Improving the electrical and electromagnetic shielding properties of conductive silicon rubber filled with Ni-coated carbon fibre by magnetic field

In this work, the effects of magnetic field induction on electrical and electromagnetic shielding properties of conductive silicon rubbers (CSRs) filled with Ni-coated carbon fibres (Ni/CFs) have been investigated. When the magnetic field intensity is above the threshold value of 0.10?T during the vulcanisation, it is beneficial to their electrical property that the volume resistivity decreases from 48.7?Ω·cm to 1.57?Ω·cm, owing to the orientation alignment of Ni/CFs in CSRs filled with Ni/CFs (40?phr). Moreover, with the aids of magnetic field induction, the prepared CSRs with lower amount of Ni-CF filler can receive better electromagnetic shielding of 65?dB in 500?MHz–3?GHz, which reduce cost effectively. This vulcanisation process shows promises for various applications in power transmission and transformation industries.     

Deposition of REBCO with different rare earth elements on CeO2 buffered technical substrates by fluorine-free metal organic decomposition route

Pristine REBa₂Cu₃O_7?δ (REBCO, RE with Yb, Y, Dy, Gd, Eu and Sm) superconducting films are deposited on CeO₂ buffered technical substrates by fluorine-free metal organic decomposition (FF-MOD) method. The structure and superconductivity are comprehensively characterized and studied. Under the optimal conditions, all the films form good crystallinity and strong biaxial texture examined by XRD. A smooth and dense morphology is observed in the YBCO, GdBCO, EuBCO and SmBCO films. For all the films, T_c^onset values are lower than that in the corresponding bulk materials, implying a certain degree of microstructure defects (e.g., RE-Ba substitution, and/or oxygen vacancies). Among all the compositions, the GdBCO film shows a high T_c^onset value (>90 K), while the high J_c values are achieved at 77 K in broad field regime, also being with the largest maximum pinning force of 2.3 GN m^?3. On the other hand, a high J_c value (at 77 K self-field) is obtained in the YBCO film, however, the rapid J_c decay with increase of the magnetic fields is found. These results reveal that defects in the YBCO film could only serve as weak pinning centers at least at 77 K. According to Dew-Hughes fitting models, we found that the primary pinning mechanism in all the REBCO films attributes to typical 2D non-superconducting phase i.e., Normal surface pinning. This work for the first time systemically demonstrates feasibility of deposition REBCO with various rare earth elements on technical substrates through the FF-MOD route, and provides a guideline for further growth of nano-composited and mixed rare earth REBCO films.     

Texturing of 3Y-TZP zirconia by electrophoretic deposition in a high magnetic field of 17.4 T

Ceramics can be textured during colloidal processing by aligning the suspended particles in a strong magnetic field and retaining this alignment in the green body. Attempts to align tetragonal zirconia particles however were not successful, not even in 12 T magnetic fields. In the current work, monoclinic zirconia was successfully aligned with its (1 0 0) plane perpendicular to the magnetic field direction by electrophoretic deposition (EPD) in a 17.4 T field. Moreover, textured tetragonal zirconia was developed by reactive sintering of undoped pure monoclinic zirconia and co-precipitated 8 mol% yttria-stabilized zirconia. The sintered tetragonal zirconia inherited the alignment of the monoclinic zirconia particle precursor and aligned with its (0 0 1) plane perpendicular to the magnetic field direction. The toughness of the (0 0 1)-oriented 3Y-TZP along the [0 0 1] direction of the textured zirconia was 65% higher than normal to it and 48% higher than the randomly oriented material.     

On the action of magnetic gradient forces in micro-structured copper deposition

In order to shed more light on the role of magnetic gradient forces and Lorentz forces on the deposition pattern found recently at copper electrodes, experiments and numerical simulations have been performed in a simple geometry that consists of a single small cylindrical permanent magnet which is placed behind the cathode. The cylinder axis coincides with the magnetization direction and points normal to the electrode surface. The electrode is oriented vertically which allows a separate discussion of the influence of both forces.Experiments and numerical simulations are found to give very good qualitative agreement with respect to the deposition pattern. Our analysis clearly shows that the major influence is due to the action of the magnetic gradient force. Numerical simulations prove that the separate action of the Lorentz force does not reproduce the deposition structure. A detailed analytical discussion of the motion forced by the different magnetic forces in superposition with natural convection is given.     

Heat generation properties in AC magnetic field for Y3Fe5O12 powder material synthesized by a reverse coprecipitation method

Ferrimagnetic Y₃Fe₅O₁₂ powder was synthesized by a reverse coprecipitation method in order to study its heat generation property in an AC magnetic field. An orthorhombic YFeO₃ phase having a small particle size (<100 nm) was obtained for the samples calcined at a low temperature. The maximum heat generation ability in an AC magnetic field was obtained for the Y₃Fe₅O₁₂ ferrite powder by calcination at 1100 °C. The heat generation ability was reduced for the samples calcined at a higher temperature. The particle growth with the formation of the cubic single phase might influence the heat generation ability. The heat generation ability and the hysteresis loss value were proportional to the cube of the magnetic field (H³), because the coercivity value of the B–H curve was proportional to the square of the amplitude of the AC magnetic field (H²). The heat generation ability (W g⁻¹) of the Y₃Fe₅O₁₂ sample sintered at 1100 °C can be expressed by the equation 2.2×10⁻⁴∙f∙H³ using the frequency (f/kHz) and the magnetic field (H/kA m⁻¹), which has the highest heat generation ability of the reported magnetic materials. The hysteresis loss value for the B–H curve agreed with the heat generation ability of the samples calcined at 1100 °C and lower temperatures.     

Microstructure and bioactivity in SBF of the hydroxyapatite coatings plasma sprayed with a magnetic field

A 100 mT magnetic field was introduced during the plasma spraying of hydroxyapatite (HA) coating on Ti6Al4V substrate. The influence of the magnetic field on the microstructure, bonding strength, and bioactivity of the coating was investigated. Compared with as-sprayed coating, the coating sprayed under a magnetic field showed fewer porosity and microcracks and a significantly decreased absolute value of the residual stress. The bonding strength of the coating sprayed under a magnetic field was approximately 173.6 % greater than as-sprayed coating. With increasing time in simulated body fluid, the width of microcracks on the surface of both coatings first increased and then decreased. The widths of microcracks on the coating sprayed under a magnetic field were much smaller than as-sprayed coating. During spraying process, the magnetic field would enhance the wetting and flowing ability of the HA molten droplets, prolonging their cooling, which affects the microstructure and bioactivity of the coating.     

Magnetically stabilized fluidization of a mixture of magnetic and non-magnetic particles in a transverse magnetic field

This paper presents an investigation of the hydrodynamic behavior of a gas-solid magnetically stabilized fluidized bed. It consists of a mixture of spherical steel particles with glass balls subjected to a magnetic field, transverse to the gas flow, which is created by two permanent magnets. Pressure drop, bed stability and expansion are studied. A data correlation in good agreement with experimental results was developed. It takes into account the modification of the bed structure in the presence of two types of particles: steel particles forming chains following the field lines and considered as “pseudo-plate” particles and non-aggregated non-magnetic particles.     

Controlled morphology and optical properties of n-type porous silicon: effect of magnetic field and electrode-assisted LEF

Fabrication of photoluminescent n-type porous silicon (nPS), using electrode-assisted lateral electric field accompanied with a perpendicular magnetic field, is reported. The results have been compared with the porous structures fabricated by means of conventional anodization and electrode-assisted lateral electric field without magnetic field. The lateral electric field (LEF) applied across the silicon substrate leads to the formation of structural gradient in terms of density, dimension, and depth of the etched pores. Apart from the pore shape tunability, the simultaneous application of LEF and magnetic field (MF) contributes to a reduction of the dimension of the pores and promotes relatively more defined pore tips as well as a decreased side-branching in the pore walls of the macroporous structure. Additionally, when using magnetic field-assisted etching, within a certain range of LEF, an enhancement of the photoluminescence (PL) response was obtained.     

弱磁场强化零价铁去除废水中重金属离子试验研究

考察了弱磁场对零价铁去除铜冶炼废水中重金属离子的加速作用。结果表明,当稀贵车间废水初始p H为4.0~5.0,微米铁粉投加量为0.1~0.5 g/L时,预磁化和加磁均能加速零价铁对稀贵车间废水重金属离子的去除。在初始p H为4.0,微米铁粉投加量为1.0 g/L的条件下,对水淬车间高砷废水进行处理,结果发现,外加磁场对微米铁去除高砷废水中总砷仍有很强的促进作用。