Assistance Of Magnetic Field Research Articles

Synthesis of Chitosan-Coated Co0.5Zn0.5Fe2O4 Nanoparticles for Contrast Enhancement in Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is an imaging technique that is widely used for the identification of internal organs, and for the medical diagnosis of tumors and cancer in the body. In general, gadolinium is used as a contrast agent to enhance image contrasting in MRI. In this study, chitosan-coated Co0.5Zn0.5Fe2O4 nanoparticles were synthesized using a co-precipitation method with a calcination temperature of 500 °C. The nanoparticles were then coated with chitosan and treated under an external magnetic field of 400 mT. X-ray diffractometer results showed that the chitosan-coated Co0.5Zn0.5Fe2O4 nanoparticles had a pure phase of Co0.5Zn0.5Fe2O4 at the (3 1 1) plane, with an average particle size of 26 nm. The presence of chitosan on the Co0.5Zn0.5Fe2O4 nanoparticles was confirmed by Fourier transform infrared spectroscopy, which showed the primary amine and secondary amine functional groups of chitosan. Here, coating the nanoparticle with chitosan not only prevented nanoparticle agglomeration, but also improved the particle surface charge and reduced the particle toxicity for in vivo testing. Vibrating sample magnetometer results showed that the maximum magnetization value of the magnetic field-assisted process was increased to 8.85 emu/g. Finally, chitosan-coated Co0.5Zn0.5Fe2O4 nanoparticles with 400 mT of magnetic field assistance increased the average brightness in MRI of mouse liver by 21% compared to using gadolinium.

Flexible Pressure Sensor with an Excellent Linear Response in a Broad Detection Range for Human Motion Monitoring.

Pressure sensing is highly demanding in wearable devices, robotics, and artificial intelligence, whereas it is still a big challenge to develop a pressure sensor with an excellent linear response in a broad detection range. Herein, a flexible and porous carbon nanotube (CNT)/carbon black (CB)/carbonyl iron powder (CIP)/silicone composite is proposed by a simple strategy of mixing, curing, and washing. Due to the porous structure induced by the sacrifice of sugar particles, an excellent linear response (R2 = 0.999) is achieved for the composite sensor by manipulating the contributions of contact resistance and tunnel resistance to the sensing performance via the alternation of CB and CNT contents. Moreover, the porous structure donates the composite sensor a low compressive modulus at a low pressure level, while the CIPs introduced lead to a high compressive modulus at a high pressure level with the assistance of an external magnetic field. As a result, the sensor produced has a wide linear response range of 80 Pa to 220 kPa, much wider than most of the linear response pressure sensors reported previously. The wide detection range is demonstrated by cyclic pressure tests in the frequency range of 0.1-5 Hz, durability tests, and monitoring human or robot motions including breathing, walking, lifting, and boxing, etc. Taking the advantages of low cost, high sensitivity, and excellent linear response in a wide pressure range, the current composite sensor is promising for precise monitoring of human motions and delicate controlling of robots.

Interaction of a tubular charged-particle beam with eigenwaves of a plasma solid-state cylinder located in strong longitudinal magnetic field

An electrodynamic system in which a magnetized tubular electron beam blows around a cylindrical solid-state plasma waveguide located coaxially in a longitudinal magnetic field is theoretically studied. It has been established, when quasi-stationary conditions are satisfied, hybrid bulk-surface or surface electromagnetic waves of helicon origin are excited in the waveguide. The waveguide eigenwaves are excited by the space-charge field of beam with matching of the longitudinal spectral components of electric field. It is noted that helicons and waves of their nature are formed in a conducting plasma medium in the assistance of an external magnetic field. It is shown the instability of coupled waves of the electrodynamic system is due to the Vavilov–Cherenkov effect.

Novel neurolisteriosis therapy using SPION as a drivable nanocarrier in gallic acid delivery to CNS.

Neurolisteriosis is an infectious disease of the central nervous system (CNS) with a high mortality rate caused by Listeria monocytogenes. The CNS disorders suffer from inadequacy of drugs accessibility. An experimental in vivo model of neurolisteriosis was developed by oral administration of the bacteria in Wistar rats. It's speculated the capability of magnetite nanoparticles (MNPs) in ferrying gallic acid (GA), as a natural antimicrobial agent, through the blood-brain barrier (BBB) with the assistance of an external magnetic field (EMF). The capability of the formulated nanodrug in traversing through the BBB was approved by detecting blue spots in the Perls' Prussian staining of the brain tissue sections and by an increased iron content of the brain determined by the inductively coupled plasma spectroscopy. The GA release pattern and the nanodrug toxicity assay were promising. Anti-listeriosis effect of the formulated nanodrug was evaluated by molecular quantification of the relative abundance of survived bacteria in brain tissue samples. Besides, the relative expression of the listeriolysin O-encoding hly gene, the prominent virulence factor of L. monocytogenes, was determined using the rplD gene as a reference gene. The nanodrug-received rats showed a significantly less viable bacteria (13.2 ± 7.6%) and a 4.4-fold reduction in the relative expression of the hly gene in comparison to the sham group. Magnetite nanoparticles (MNPs) were synthesized by co-precipitation method, functionalized with GA, and finally coated with Tween 80. The physicochemical properties of the bare and surface modified materials were investigated using different techniques including X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopies, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), dynamic light scattering (DLS) and Zeta Potential analyses, and vibrating sample magnetometry. In conclusion, MNPs displayed a considerable potential for drug delivery intentions to various target sites such as the CNS. Gallic acid exhibited a binary anti-listerial effect, the destruction of L. monocytogenes bacteria in addition to reducing the expression of the hly gene, which in turn causes reduced survivability of the bacteria in the CNS.

Analysis of spin-orbit torque magnetic tunnel junction model without external magnetic field assistance based on antiferromagnetism

The effect of spin-orbit torque (SOT) provides a new method of implementing ultra-low power spintronic devices. The in-plane exchange bias (EB) field in antiferromagnetic material can effectively assist SOT magnetization switching. Meanwhile, the utilization of voltage-controlled magnetic anisotropy (VCMA) can effectively reduce the switching barrier. Taking advantage of the EB and VCMA effect, it is possible to realize SOT magnetic tunnel junctions without external field assistance. In this work, a spin-orbit torque magnetic tunnel junction model composed of antiferromagnetic/ferromagnetism/oxides without external magnetic field is developed by solving the modified Landau-Lifshitz-Gilbert (LLG) modular equation, and its magnetization dynamics is analyzed and studied. The effective fields in the model include the demagnetization field, thermal noise field, perpendicular magnetic anisotropy field with VCMA effect, and exchange bias field. Taking IrMn/CoFeB/MgO material system for example, the factors affecting the precession of magnetization are investigated, such as the effect of the exchange bias field, the VCMA effect and the mechanism of SOT field-like torque. Considering the practical applications, the effect of the deviation of the fabrication process of magnetic tunnel junctions is also analyzed. The simulation results demonstrate that the combined effect of <inline-formula><tex-math id="M5">\begin{document}$ {{\boldsymbol{H}}_{{\text{EB}}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M5.png"/></alternatives></inline-formula> with VCMA effect can greatly reduce the critical <i>I</i><sub>SOT</sub>, thus assisting and realizing the complete field-free magnetization reversal; the SOT field-like torque plays a dominant role in realizing the magnetization reversal, and by adjusting the ratio of the SOT field-like torque to the damping-like torque, field free switching can be realized in the device at the ps grade ; and the MTJ can realize effective switching when the deviation of oxide thickness <inline-formula><tex-math id="M6">\begin{document}$ {\gamma _{{\text{tf}}}} \leqslant 10{\text{%}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M6.png"/></alternatives></inline-formula> or the deviation of free layer thickness <inline-formula><tex-math id="M7">\begin{document}$ {\gamma _{{\text{tox}}}} \leqslant 13{\text{%}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M7.png"/></alternatives></inline-formula>. Spin-orbit torque devices based on the antiferromagnetic without external magnetic field will provide highly promising solutions for a new-generation ultra-low power, ultra-high speed, and ultra-high integration devices and circuits.

Magnetocaloric Effect in CoFe-Electroplated Ni50Mn33In16Cr1 Alloy

A high-saturation magnetization CoFe layer was electroplated onto Ni50Mn33In16Cr1 alloy using a magnetic field assistance electroplating bath. This CoFe-coated alloy can function as an active magnetic regenerator owing to its magnetocaloric effect. The CoFe coating layer did not affect the entropy change calculated from the isothermal magnetization of the alloy, but it significantly affected the temperature variation of the alloy by changing the externally applied magnetic field. The temperature change of the CoFe-coated alloy increases with increasing CoFe coating times. By comparing with the as-sintered alloy, a maximum increase of 150% in temperature change can be observed in the alloy coated with CoFe for 2 h.

Experimental investigations into ultrasonic assisted magnetic abrasive flow machining process

ABSTRACT In the present study, an advanced variant of abrasive flow machining (AFM) is developed. Ultrasonic assistance and magnetic field assistance with rotating effect have been designed, fabricated, and simultaneously used to develop ultrasonic-assisted magnetic abrasive flow machining (UAMAFM) process. The ultrasonic horn and electromagnets were designed based on the simu modified by adding iron particles to make abrasive media respond effectively under the applied magnetic field. The effects of the external assistances, machine, and media-based parameters were explored on the amount of material removed (MR) and percentage improvement in the surface roughness (% ΔRa) for pure titanium (Grade II). The influence of input parameters was investigated using analysis of variance (ANOVA) by analyzing the process responses. Quadratic regression models showing the effect of input parameters and their interaction were developed for each response. The influence of individual parameters on process outcomes and response surface plots for significant interactions have also been discussed. The maximum MR of 26.62 mg and ΔRa of 54.42% were achieved at the optimized setting of process parameters. The predicted values of MR and % ΔRa from developed statistical models agreed with the experimental results.

Experimental investigation on the effects of magnetic field assistance on the quality of surface finish for sustainable manufacturing of ultra-precision single-point diamond turning of titanium alloys

Single-point diamond turning (SPDT) is the state-of-the-art technology for ultra-precision manufacturing of optical products with optical surface roughness down to 1 nm. The SPDT technology has an important role in advanced manufacturing of critical components in different fields of industry. In a SPDT process, different cutting mechanisms affect the optical surface generation and reduce the quality of the turned product. Different efforts have been undertaken to improve the machining conditions as well as optical surface generation mechanisms. Recently, the application of magnetic field assistance in non-conventional SPDT platforms has shown promising results in terms of improving the cutting stability as well as the quality of surface finish. The application of magnetic field assistance becomes more important in SPDT of hard-to-cut materials including titanium alloy. In this study, magnetic field assistance is used in SPDT of Ti-6Al-4V alloy. The machining results show that using this technique could significantly improve the machining conditions and the quality of optical surface generation. The magnetic field assisted SPDT with air coolant could successfully improve the quality of surface finish by 62.5% when compared to non-magnetic purely mechanical SPDT process in dry cutting conditions. Magnetic field assistance is a passive machining technique, environmentally friendly, and it can promote green manufacturing and clean production in ultra-precision SPDT applications.

Promoting the densification and grain refinement with assistance of static magnetic field in laser powder bed fusion

Owing to its high accuracy and good design flexibility, the application of laser powder bed fusion (LPBF) to metallic parts has been rapidly increasing. However, the parts fabricated using LPBF exhibit high porosity and rough texture, which severely hinders the development of this technology. In this study, typical Al-based (AlSi10Mg) and Ni-based (Inconel 718) alloys were fabricated under a wide range of parameter spaces using static magnetic field (SMF) of up to 0.2 T. The experimental results showed that the fabricated parts had a higher density with SMF than the samples fabricated without SMF. A comparison of the samples fabricated with and without SMF revealed that the SMF refined the grain size and improved the mechanical properties. Furthermore, physics-based models, including the Seebeck effect, heat transfer, and fluid flow, in melt pools dynamics were used to simulate the thermos-electric-magnetic (TEM) forces and flow patterns during LPBF. The results of the simulation suggest that at the melt pool scale, the depression zone depth increases with increasing SMF intensity, and the correspondingly increased laser absorptivity is the main reason for the decrease in the lack-of-fusion defects. In addition to the flow pattern change at the melt pool scale, the TEM force acting on the cellular dendrite also plays an important role in grain refinement, reaching 105 N/m3 under a SMF of 0.1 T. Furthermore, the results of the tensile tests showed an increase in the ultimate tensile strength and elongation of the printed samples under the applied SMF. The present study can guide the porosity control and the widening of the processing window in LPBF.

Molten pool behavior and solidification characterization in steady magnetic field assisted laser-MIG hybrid welding of aluminum alloy

Microstructure evolution is highly correlated with the melt flow characterization in welding. In this study, a 3D heat flow model with consideration of magnetic field was constructed to describe the temperature field, the flow and keyhole behaviors in the molten pool during the laser-MIG hybrid welding. The role of magnetic flux density in the molten pool dynamics and microstructure evolution was explored. A moving hybrid heat source model including Gaussian surface heat source model and Gaussian rotary body heat source model as well as double ellipsoidal heat source model was carried out to elucidate the laser and MIG arc energy distribution. Decent agreement is realized between the measured weld geometry and predicted weld pool dimension. Numerical results indicate that an expanded molten pool is clearly observed under magnetic field. As the magnetic flux density increases, the downward flow velocity of the molten pool is enhanced. Moreover, visible difference of oscillation growth period for keyhole depth is produced and this leads to a variation in the time it takes for the molten pool to stabilize. Significant grain refinement appearing in both arc-affected zone at the weld upper part and laser-affected zone at the weld lower part is documented although the refinement degree varies at different zones. This is attributed to the formation of many initial nuclei or crystallites, originated from the enhanced flow of the molten pool with the assistance of magnetic field. This study provides a perspective in understanding the physical phenomena involved in magnetic field assisted laser-MIG hybrid welding and lays the foundation for weld microstructure optimization.

Tribological properties of the FeNi alloys electrodeposited with and without external magnetic field assistance

The hereby work presents the tribological properties of the iron-nickel alloys and their dependence on the microstructure and thickness of the probes as well as the presence of an external magnetic field during the synthesis. Coatings were electroplated on the brass and copper metallic substrates using galvanostatic deposition in the same electrochemical bath condition (Fe and Ni sulfates) and the electric current density. The surface morphology of the films was observed by Scanning Electron Microscopy. The average composition of all FeNi coatings was measured using Energy Dispersive X-ray Spectroscopy. Tribo-mechanical properties such as microhardness, roughness, and friction coefficient were determined in the obtained structures. The morphology and tribologial properties of the FeNi coatings clearly depend on both the substrate (Cu, CuZn) itself and the presence of an external magnetic field (EMF) applied during the deposition process.

Advances in magnetic field-assisted electrolyte's physicochemical properties and electrokinetic parameters: A case study on the response ability of chloramphenicol on Fe3O4@carbon spheres-based electrochemical nanosensor

Despite the utilization of external magnetic field (MF) in promoting the intrinsic unique features of magnetic nanomaterials in many different applications has been reported, however the origin of MF-dependent electrochemical behaviors as well as the electrochemical response of analytes at the electrode in sensor applications is still not clear. In this report, the influence of MF on the electrolyte's physicochemical properties (polarization, mass transport, charge/electron transfer) and electrode's properties (conductivity, morphology, surface area, interaction, adsorption capability, electrocatalytic ability) was thoroughly investigated. Herein, the working electrode surface was modified with carbon spheres (CSs), magnetic nanoparticles (Fe3O4NPs), and their nanocomposites (Fe3O4@CSs), respectively. Then, they were directly used to enhance the electrochemical characteristics and response-ability of chloramphenicol (CAP). More interestingly, a series of various kinetic parameters related to the diffusion-controlled process of K3[Fe(CN)6]/K4[Fe(CN)6)] and the adsorption-controlled process of CAP were calculated at the bare electrode and the modified electrodes with and without the presence of MF. These parameters not only exhibit the crucial role of the modification of electrode surface with the proposed materials but also show positive impacts of the presence of external MF. Besides, the mechanism and hypothesis for the enhancements were proposed and discussed in detail, further demonstrating the development potential of using Fe3O4@CS nanocomposites with MF assistant for advanced energy, environmental, and sensor related-applications.

Mathematical Modeling of Material Removal and Surface Roughness in Ultrasonic-Assisted Magnetic Abrasive Flow Machining Process

Abstract Ultrasonic-assisted magnetic abrasive flow machining (UAMAFM) process shows enhanced finishing performance compared to conventional abrasive flow machining (AFM). In this present research paper, mathematical models for M˙R and Ra have been developed for the UAMAFM process by considering both steady-state and transient phenomena. The external ultrasonic and magnetic field assistance enhanced the velocity and length of contact of active abrasives, calculated from the kinematic analysis. The resultant finishing forces have also been evaluated by considering these external aids. The steady-state material removal per finishing cycle remains constant and depends on the velocity of motion, length of contact, resulting forces, number of active abrasives, and work material hardness. The transient material removal per finishing cycle was calculated in terms of the volume of irregularities present over the work surface, i.e., initial surface roughness. The mathematical model for surface roughness was developed in terms amount of material removed (MR), and initial (Ra0) and critical surface roughness (Racr). The predicted values of material removed and surface roughness from developed mathematical models agreed with experimental results with a deviation of 7.80% and 2.44%, respectively.

Experimental investigation for ultra-precision cutting of nickel based superalloy with the assistance of magnetic field

Experimental investigation for ultra-precision cutting of nickel based superalloy with the assistance of magnetic field

Microstructure of WTaNbMo refractory high entropy alloy coating fabricated by dynamic magnetic field assisted laser cladding process

WTaNbMo refractory high entropy alloy (RHEA) coatings were prepared by laser cladding assisted with reciprocating dynamic magnetic field on Inconel 718 substrates. The effects of dynamic magnetic field on the microstructure, defects and residual stress were discussed. The results show that the reciprocating magnetic field improves the microstructure homogeneity of the laser cladded WTaNbMo coating. The coatings are composed of WTaNbMo solid solution (BCC) and γ-(Ni, M). With reciprocating magnetic field assistance, the flow in the molten pool is accelerated, porosity is reduced. The residual stress inside the coating is depressed, thereby cracks in the coating are inhibited. The flow behavior in the molten pools was also discussed.

Improving spreadability of molten metal in MIG welding-brazing of aluminum to steel by external magnetic field

A modified metal inert gas (MIG) welding-brazing process of aluminum and steel with the assistance of external magnetic field (EMF) was proposed in this study. An alternative EMF along the welding direction was used to promote the arc and the droplet to swing along the weld width direction by producing an alternative electromagnetic force perpendicular to the welding direction. The effect of the excitation current level and frequency on weld bead appearance, spreadability of molten metal and the welding process stability was investigated by experimental observation. As the excitation current level increased, the width of the weld seam was increased and the spreadability of the molten metal was enhanced. When it was beyond a critical level, the arc stability was disrupted. Excessive excitation current caused the excessive inclination of the arc especially in base current stage, which was extremely easy to result in arc extinguishing. When the frequency of the excitation current changed from 2 Hz to 15 Hz, the weld width was decreased. If the excitation current exceeded 15 Hz, the weld width kept constant. The wetting angle of the aluminum metal was decreased as the optimized EMF was applied. Besides, the tensile strength of the joint was enhanced due to the enhancement of spreading of molten metal under the action of EMF.

Effect of SiO2in situ cross-linked CS/PVA on SrFe12O19 scaffolds prepared by 3D gel printing for targeting

The design of magnetic composite scaffolds with superior properties has the potential to construct a targeted delivery platform with hyperthermia. In this study, strontium hexaferrite (SrFe12O19, SrM) magnetic nanoparticles (MNPs) were obtained by the chemical precipitation method. Non-toxic cross-linked biogels were prepared for adhesive ceramic scaffolds, and chitosan/polyvinylalcohol (CS/PVA)-bonded SrM magnetic nanoscaffolds were successfully prepared by 3D gel printing (3DGP) method. The effects of PVA physical cross-linking and in situ formed SiO2 on the properties of CS-bonded scaffolds were evaluated, and the compressive strengths were increased from 6.13 ± 2.45 MPa to 8.80 ± 2.02 MPa and 17.18 ± 2.15 MPa, respectively. The results showed that the saturation magnetization of SiO2/CS/PVA/SrM composite scaffolds was 59.96 emu/g. In vitro immersion experiments showed that the degradation rates of SiO2/CS/PVA/SrM scaffolds were 4.90% after 28 days, and the in situ SiO2 improved the deposition of calcium salts on the scaffolds. The experiments showed that the SrM magnetic scaffolds could not only concentrate magnetic fields to improve the efficiency of targeting deposition but also achieve a weak targeting process without external magnetic field assistance. In vitro cell proliferation test showed that MC3T3-E1 cells had good adhesion and proliferation on the surface of SiO2/CS/PVA/SrM scaffolds, which indicated that the scaffolds may be used for bone repairing.

Microstructure and Crystallization Evolution of Directionally Solidified Al–Cu–Si Alloys With the Assistance of a Static Magnetic Field

Microstructure and Crystallization Evolution of Directionally Solidified Al–Cu–Si Alloys With the Assistance of a Static Magnetic Field

Significantly enhancing fracture toughness of epoxy composite with promising γ-FeOOH@Fe2O3 hybrid nanoparticles by magnetic field assistance

The toughening of epoxy resin (EP) and the interlaminar toughening of carbon fiber reinforced composite (CF/EP) laminates have been widely concerned. In this work, the needle-like γ-FeOOH nanoparticles were prepared by liquid phase deposition-air oxidation method, and then were calcined under different conditions to obtain γ-FeOOH and γ-Fe2O3 hybrid nanoparticles (γ[email protected]2O3). Effect of calcination condition of γ[email protected]2O3 and magnetic field assistance on fracture toughness (KIC) of EP was systematically investigated. Then the selected γ[email protected]2O3 with the best toughening effect were used to improve the mode I interlaminar fracture toughness (GIC) of CF/EP laminate. The resulting γ[email protected]2O3 have a length of around 1 ​μm, a diameter of around 100 ​nm and the Ms of 8.99–45.96 emu/g. After calcinated at 250 ​°C for 1 ​h, the γ[email protected]2O3 containing 24 ​wt% FeOOH and 76 ​wt% Fe2O3 achieved the best toughening effect. Under a magnetic field of 0.09 ​T, the KIC of the γ[email protected]2O3/EP composite (2.45 ​MPa ​m1/2) is 81.7% and 66.7% higher than that of neat epoxy and the composite without magnetic field induction, respectively. Furthermore, the GIC of the γ[email protected]2O3/CF/EP composite (0.914 ​kJ/m2) is also significantly increased by 88.8% and 51.8% compared to that of CF/EP and the corresponding composite without magnetic field induction, respectively.

FeNi alloy films prepared by directional magnetic field assistance and their degradation and adsorption on azo dyes

Synthetic dyes in the aquatic environment caused various ecological and health problems that are detrimental to sustainable development. To solve these problems, we designed a dense Fe3Ni2 phase alloy film (FeNi-M) on copper substrate by the directional magnetic field-assisted wet chemical film formation method. The degradation and adsorption of Congo red (CR) in water were achieved by using the surface activity of the film. The degradation rate of FeNi-M alloy film reached 99.5% at 48 h and the kobs is 0.10982 h−1, which is 2.1 and 7.5 times of FeNi alloy film (0.05147 h−1) and Ni film （0.01465 h−1）, respectively. The degradation processes of all three films were in accordance with the pseudo-first-order kinetic model. In addition, FeNi-M alloy films have excellent cycling performance with more than 90% removal rate after 5 cycles. We also discussed the possible degradation mechanism and pathway of CR. We speculated that the main part of alloy responsible for providing electrons were iron atoms and very few electrons were produced by nickel. However, nickel was beneficial to increase the activity of iron atoms and played a catalytic role, thereby greatly enhancing the efficiency of iron atoms on the reaction.