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Sotelo, Diana C., Nancy Ornelas-Soto et Johann F. Osma. « Novel Magnetic Polymeric Filters with Laccase-Based Nanoparticles for Improving Congo Red Decolorization in Bioreactors ». Polymers 14, no 12 (8 juin 2022) : 2328. http://dx.doi.org/10.3390/polym14122328.
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In this work, five different magnetic biofilters, containing magnetic nanoparticles (142 nm), immobilized laccase on nanoparticles (190 nm) and permanent magnetic elements, such as neodymium magnets and metallic meshes, were designed, manufactured and tested. The five types of filters were compared by measuring the decolorization of Congo Red dye inside bioreactors, the half-life of the filters and the amount of magnetic nanoparticle and enzyme lost during multiple cycles of operation. Filters containing laccase immobilized on magnetite (Laccase-magnetite), permanent magnets and metallic mesh presented the highest Congo Red decolorization (27%) and the largest half-life among all types of filters (seven cycles). The overall dye decolorization efficiencies were 5%, 13%, 17%, 23%, and 27% for the paper filter, paper filter with magnetite, paper filter with Laccase-magnetite, paper filter with Laccase-magnetite with magnets and paper filter with Laccase-magnetite with magnets and metallic mesh, respectively. Although the highest losses of magnetite occurred when using the filters containing magnets (57 mg), the use of permanent magnetic elements in the filters increased the half-life of the filter three-fold compared to the filters without enzymatic properties and two-fold compared to the filters with Laccase-magnetite. Results indicate that the novel use of permanent magnetic elements improved the nanoparticle retention in the filters and promoted the mass transfer between the dye and the biocatalyst to enhance wastewater treatment.
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Bagabas, Abdulaziz A., Khalil A. Ziq, Ahmad F. Salem et Emad S. Addurihem. « Magnetic Properties of Some Hydrated Transition Metal Oxide and Hydroxide Nanoparticles Synthesized in Different Media ». Advanced Materials Research 123-125 (août 2010) : 727–30. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.727.
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Nanoscale particle size of metal oxides and hydroxides showed enhanced various physical properties and performance. We established a simple, cost-effective, room-temperature (RT) precipitation method for the preparation of the magnetic, first-raw transition metal (TM) hydrated oxide and hydroxide nanoparticles. This method is based on the use of the TM nitrate, as the metal source, and cyclohexylamine (CHA), as a precipitating agent, either in the water (H2O) or ethanol (EtOH) medium. We found that the precipitation medium and the identity of precipitated TM strongly affect the morphology, particle size, and magnetism of the product. The morphology varies from spherical, to rectangular, to rod shape; while the size varies in the range of 5-30 nm. All samples showed paramagnetic behavior with Curie temperatures span over a wide range (20-150K). Huge hysteresis looses has been observed for manganese (Mn) sample, prepared in H2O. The coercively (Hc) at 4.2K for this sample is about 1.5T, which is comparable to the strongest permanent magnets (Nd-based magnets) available at room temperature. The energy product (Hc*MR) is about 4.5*105 (emu/g)Oe.
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Panina, Larissa V., Anastasiya Gurevich, Anna Beklemisheva, Alexander Omelyanchik, Kateryna Levada et Valeria Rodionova. « Spatial Manipulation of Particles and Cells at Micro- and Nanoscale via Magnetic Forces ». Cells 11, no 6 (10 mars 2022) : 950. http://dx.doi.org/10.3390/cells11060950.
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The importance of magnetic micro- and nanoparticles for applications in biomedical technology is widely recognised. Many of these applications, including tissue engineering, cell sorting, biosensors, drug delivery, and lab-on-chip devices, require remote manipulation of magnetic objects. High-gradient magnetic fields generated by micromagnets in the range of 103–105 T/m are sufficient for magnetic forces to overcome other forces caused by viscosity, gravity, and thermal fluctuations. In this paper, various magnetic systems capable of generating magnetic fields with required spatial gradients are analysed. Starting from simple systems of individual magnets and methods of field computation, more advanced magnetic microarrays obtained by lithography patterning of permanent magnets are introduced. More flexible field configurations can be formed with the use of soft magnetic materials magnetised by an external field, which allows control over both temporal and spatial field distributions. As an example, soft magnetic microwires are considered. A very attractive method of field generation is utilising tuneable domain configurations. In this review, we discuss the force requirements and constraints for different areas of application, emphasising the current challenges and how to overcome them.
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Imarah, Ali O., Fausto M. W. G. Silva, László Tuba, Ágnes Malta-Lakó, József Szemes, Evelin Sánta-Bell et László Poppe. « A Convenient U-Shape Microreactor for Continuous Flow Biocatalysis with Enzyme-Coated Magnetic Nanoparticles-Lipase-Catalyzed Enantiomer Selective Acylation of 4-(Morpholin-4-yl)butan-2-ol ». Catalysts 12, no 9 (17 septembre 2022) : 1065. http://dx.doi.org/10.3390/catal12091065.
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This study implements a convenient microreactor for biocatalysis with enzymes immobilized on magnetic nanoparticles (MNPs). The enzyme immobilized onto MNPs by adsorption or by covalent bonds was lipase B from Candida antarctica (CaLB). The MNPs for adsorption were obtained by covering the magnetite core with a silica shell and later with hexadecyltrimethoxysilane, while for covalent immobilization, the silica-covered MNPs were functionalized by a layer forming from mixtures of hexadecyl- and 3-(2-aminoethylamino)propyldimethoxymethylsilanes in 16:1 molar ratio, which was further activated with neopentyl glycol diglycidyl ether (NGDE). The resulting CaLB-MNPs were tested in a convenient continuous flow system, created by 3D printing to hold six adjustable permanent magnets beneath a polytetrafluoroethylene tube (PTFE) to anchor the MNP biocatalyst inside the tube reactor. The anchored CaLB-MNPs formed reaction chambers in the tube for passing the fluid through and above the MNP biocatalysts, thus increasing the mixing during the fluid flow and resulting in enhanced activity of CaLB on MNPs. The enantiomer selective acylation of 4-(morpholin-4-yl)butan-2-ol (±)-1, being the chiral alcohol constituent of the mucolytic drug Fedrilate, was carried out by CaLB-MNPs in the U-shape reactor. The CaLB-MNPs in the U-shape reactor were compared in batch reactions to the lyophilized CaLB and to the CaLB-MNPs using the same reaction composition, and the same amounts of CaLB showed similar or higher activity in flow mode and superior activity as compared to the lyophilized powder form. The U-shape permanent magnet design represents a general and easy-to-access implementation of MNP-based flow microreactors, being useful for many biotransformations and reducing costly and time-consuming downstream processes.
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Frolova, Liliya A. « Investigation of Magnetic and Photocatalytic Properties of CoFe2O4 Doped La3+, Nd3+, I3+ ». ECS Meeting Abstracts MA2022-01, no 30 (7 juillet 2022) : 2496. http://dx.doi.org/10.1149/ma2022-01302496mtgabs.
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Cobalt ferrites are widely used for permanent magnets, magnetic fluids, microwave devices, high density information storage and environmental technologies. The properties of nanosized magnetic materials strongly depend on the shape, size, and phase composition of the particles. The great interest of researchers in nanosized materials in recent years is associated with the possibility of changing the properties of magnetic materials by controlling the particle size and distribution of cations over sublattices in ferrite [1]. Nanoparticles of doped cobalt ferrite showed improved physicochemical characteristics compared to individual components due to the synergistic effect of the mutual presence of cations. Currently, various technologies for producing ferrites are used. However, to obtain a single-phase product, calcination of the precursors at a temperature of 1300-1500 0C is required, which causes agglomeration and sintering of the product. The use of modern methods of electrochemical synthesis is the basis for obtaining ferrites from transition materials with a given set of properties. A characteristic recent trend is the development of new technologies and compositions for the production of precisely nanodispersed ferrites [2]. The purpose of this work is to study the possibility of using contact low-temperature nonequilibrium plasma for the synthesis of cobalt ferrites doped with La3+, Nd3+, I3+ cations, to establish a relationship between the cationic composition of ferrites and its phase composition, magnetic and structural characteristics. Ferrites were synthesized in the form of nanoparticles using contact nonequilibrium low temperature plasma in an electrochemical reactor. The crystalline microstructure of the samples was revealed by X-ray diffraction and X-ray phase methods. The magnetic characteristics were determined from hysteresis loops. The EPR spectra were obtained on a Radiopan SE/X-2543 radiospectrometer. To characterize the EPR signals, the intensity and width of the signal, and the resonant frequency were used. The visualization of the dependences of the technological characteristics of La3+-Nd3+-I3+ ferrites on the cationic composition was carried out by the simplex method using the STATISTICA 12 program. It has been established that the nature of the rare-earth metal cation in cobalt ferrite directly determines the magnetic and photocatalytic properties of spinel ferrites. The effect of the mutual influence of the content of cations on the saturation magnetization and coercive force is determined. The most influencing factor is the content of neodymium cations. Low values of the coercive force for Mn-Zn and Co-Zn ferrites and high values for the entire range of Co-Mn ferrites are established. An increase in the content of cobalt cations leads to an increase in the saturation magnetization value of Co-Mn ferrites. The EPR spectra show that the values of the resonance field and linewidth in the EPR spectrum correlate with the value of magnetic saturation. Simultaneous substitution of Nd3+ and La3+ in CoFe2O4 nanoparticles affected the structure, magnetic and photocatalytic properties. Structural parameters were investigated and calculated using X-ray diffraction studies. The magnetization analyzes were carried out at room temperature. Various magnetic parameters have been obtained and discussed, including remanence (Mr), coercive force (Hc), saturation magnetization (Ms), squareness ratio (SQR=Mr/Ms) and magnetic moment (nB). An increase in Mr, Ms, Hc and nB was found at lower concentrations of Nd3+ and La3+. An increase in the content of Nd3+ cations leads to a significant increase in the coercive force. The analysis of photocatalytic activity in the reaction of isolation of furacilin showed the best results (destruction rate 98%, time 40 minutes) for the ternary composition. References Caldeira, Luis Eduardo, et al. "Correlation of synthesis parameters to the structural and magnetic properties of spinel cobalt ferrites (CoFe2O4)–an experimental and statistical study." Journal of Magnetism and Magnetic Materials550 (2022): 169128. Lu, Yuzheng, et al. "Effect of Gd and Co contents on the microstructural, magneto-optical and electrical characteristics of cobalt ferrite (CoFe2O4) nanoparticles." Ceramics International2 (2022): 2782-2792.
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Liu, Yuan, Jie Lai et Yun Liu. « Preparation, Characterization, and Microwave Absorption Properties of Cobalt-Doped SrFe12O19 Nanoparticles ». Journal of Nanoelectronics and Optoelectronics 16, no 6 (1 juin 2021) : 998–1004. http://dx.doi.org/10.1166/jno.2021.3042.
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Ferrite is the major absorbing components of conventional radar absorbing materials (RAM). However, conventional RAM made of the single-absorbing components cannot meet the comprehensive requirements of “thin, wide, light, and strong.” To overcome this limitation, a composite compound of cobalt-doped SrFe12O19 nanoparticles is currently exploited to improve absorbing ability. SrFe12−xCoxO19 (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25) composite ferrites were prepared using the sol-gel method. Results show that the powders obtained are pure lead-magnetite ferrite, and the properties of the samples are improved evidently after Co substitution. At room temperature, the samples substituted using Co exhibit typical permanent magnetism. When x = 0.2, the maximum saturation magnetization and coercivity of the powders are 55.8 A·2/kg and 302.4 kA/m, respectively. The real complex permittivity part of SrFe12−xCoxO19 first increases and then decreases with the increase in x and has a maximum value of x = 0.2. The complex imaginary permittivity part fluctuates with the increase in x; it first decreases, then increases, and finally decreases. With the increase in x, the complex permeability real part of the sample does not change much between 2 GHz to 16 GHz but first increases and then decreases in the range of 16-18 GHz. The imaginary part of the complex permeability first increases and then decreases, reaching its maximum at x = 0.2. The attenuation constants and absorbing properties of the samples before and after substitution were analyzed. The matching thickness of strontium ferrite (SrFe12O19) is 5.2 mm, the matching thickness of SrFe11,8Co0.2O19 (x = 0.2) is reduced to 2.4 mm, the minimum reflectivity is −24.7 dB (13.8 GHz), and the microwave absorption bandwidth lower than −10 dB is 4.7 GHz (11.6-16.3 GHz). These results indicate that an appropriate amount of Co substitution could greatly improve the absorbing performance of SrFe12O19. This study provides a simple method for the preparation of Co doped strontium ferrite. The microwave absorbing properties of the composite powders are excellent and have potential engineering application value.
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Takeda, Shin-Ichi, Bungo Terazono, Fumihito Mishima, Hironori Nakagami, Shigehiro Nishijima et Yasufumi Kaneda. « Novel Drug Delivery System by Surface Modified Magnetic Nanoparticles ». Journal of Nanoscience and Nanotechnology 6, no 9 (1 septembre 2006) : 3269–76. http://dx.doi.org/10.1166/jnn.2006.483.
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In the recent progress of gene and cell therapy, novel drug delivery system (DDS) has been required for efficient delivery of small molecules/drugs and also the safety for clinical usage. We have already developed the unique transfection technique by preparing magnetic vector and using permanent magnet. This technique can improve the transfection efficiency. In this study, we directly associated plasmid DNA with magnetic nanoparticles, which can potentially enhance their transfection efficiency by magnetic force. Magnetic nanoparticle, such as magnetite, its average size of 18.7 nm, can be navigated by magnetic force and is basically consisted with oxidized Fe that is commonly used as the supplement drug for anemia. The magnetite particles coated with protamine sulfate, which gives a cationic surface charge onto the magnetite particle, significantly enhanced the transfection efficiency in vitro cell culture system. The magnetite particles coated with protamine sulfate also easily associated with cell surface, leading to high magnetic seeding percentage. From these results, it was found that the size and surface chemistry of magnetic particles would be tailored to meet specific demands on physical and biological characteristics accordingly. Overall, magnetic nanoparticles with different surface modification enhance the association with plasmid DNA and cell surface as well as HVJ-E, which potentially help to improve the drug delivery system.
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Kaphle, Kishor, Gyanendra Karki et Amrit Panthi. « Alternative Approach for the Calculation of Magnetic Field due to Magnet for Magnetic Field Visualization and Evaluation ». Journal of the Institute of Engineering 15, no 1 (16 février 2020) : 150–60. http://dx.doi.org/10.3126/jie.v15i1.27724.
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The magnetic field of different geometry of the permanent magnet is analytically calculated by using basic principles of the magnetism in very easier approach. Concept of origin shifting and geometrical shape transformation are used to formulate the formula for cuboidal, cubical and cylindrical permanent magnets. This concept can be used for the analysis of magnetic field distribution in space around for permanent magnet as well as electromagnet in a very easier approach. Handy and simplified software is made to calculate the magnetic field due to permanent magnet and electromagnet at any desired position on space. Magnetic field visualization is also done in both magnitude and direction by using MATLAB.
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Forringer, Edward Russell. « Measuring and Modeling the Force between Permanent Magnets ». Physics Teacher 60, no 7 (octobre 2022) : 546–48. http://dx.doi.org/10.1119/5.0058797.
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In a 1993 book review, E. Pearlstein asks, “Why don’t textbook authors begin their discussion of magnetism by talking about magnets? That’s what students have experience with.” A similar question can be asked, “Why don’t professors have students measure the force between permanent magnets in introductory physics labs?” The answer to both questions may be the same. There is no simple equation describing the force between two permanent magnets. Yet, this familiar magnetic phenomenon deserves investigation. This article presents a novel apparatus using 3D-printed parts for measuring the force between two small cylindrical neodymium permanent magnets as a function of their separation. Data collected using this apparatus is compared to two models, namely an ideal dipole–dipole interaction, and the force between parallel coaxial loops of current.
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Haneda, K. « Recent advances in the magnetism of fine particles ». Canadian Journal of Physics 65, no 10 (1 octobre 1987) : 1233–44. http://dx.doi.org/10.1139/p87-198.
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Recent advances in fine-particle magnetism are reviewed from an experimental point of view, especially with reference to surface magnetism and also to magnetism in low dimensions. Emphasis is placed on intrinsic properties as compared with the behavior of bulk ferromagnets. The spontaneous magnetization is discussed in connection with magnetic-surface reconstruction. Other intrinsic parameters such as magnetic hyperfine fields and magnetic anisotropy of fine particles are also discussed. Emphasis is placed on information provided by Mössbauer spectroscopy.Recent development in applications based on fine-particle magnetism are presented, including the following topics: magnetic fluids, particulate magnetic-recording media, permanent magnets, and catalysts. Finally, some future research prospects are reviewed.
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Bernad, Sandor I., et Elena Bernad. « Magnetic Forces by Permanent Magnets to Manipulate Magnetoresponsive Particles in Drug-Targeting Applications ». Micromachines 13, no 11 (25 octobre 2022) : 1818. http://dx.doi.org/10.3390/mi13111818.
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This study presents preliminary computational and experimental findings on two alternative permanent magnet configurations helpful for magnetic drug administration in vivo. A numerical simulation and a direct experimental measurement of the magnetic induction on the magnet system’s surface were used to map the magnetic field. In addition, the ferrite-type (grade Y35) and permanent neodymium magnets (grade N52) to produce powerful magnetic forces were also examined analytically and quantitatively. Ansys-Maxwell software and Finite Element Method Magnetism (FEMM) version 4.2 were used for all numerical computations in the current investigation. For both magnets, the generated magnetic fields were comparatively studied for targeting Fe particles having a diameter of 6 μm. The following findings were drawn from the present investigation: (i) the particle deposition on the vessel wall is greatly influenced by the intensity of the magnetic field, the magnet type, the magnet size, and the magnetic characteristics of the micro-sized magnetic particles (MSMPs); (ii) ferrite-type magnets might be employed to deliver magnetoresponsive particles to a target location, even if they are less powerful than neodymium magnets; and (iii) the results from the Computational Fluid Dynamics( CFD) models agree well with the measured magnetic field induction, magnetic field strength, and their fluctuation with the distance from the magnet surface.
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Ma, Shilun, Xueyi Zhang et Wenjin Hu. « Design Optimization of Interior Double-Radial Synthetic Magnetic Field Permanent Magnet Generator for Electric Vehicle ». MATEC Web of Conferences 202 (2018) : 02001. http://dx.doi.org/10.1051/matecconf/201820202001.
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The Interior double-radial permanent magnent generator (IDRPMG) which composed by two groups of rectangular permanent magnets to provide parallel magnetic circuits of the rator and the sator core with less eddy current loss, low hormonic content and low cogging torque of the stator with fractional slot winding is developed. It has the advantages of remarkable magnetism gathering effect, strong magnetic field intensity and high space utilization. Combining Taguchi method and finite element method, the relevant parameters of the permanent magnet size and the angle between the first and second rectangle permanent magnets in rotor are optimized to get better the distortion rate of output voltage waveform, lower cogging torque and higer peak value of airgap flux density. Then finite element simulation is taken for the best optimization scheme through comparative analysis of the machine by before and after optimization. It showed that each performance index is improved after optimization. Finally, the prototype is manufactured, according to the optimization parameters and some experiments are conducted, which results verify the analys is preview well.
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Murakami, Y., T. Tanigaki, T. T. Sasaki, Y. Takeno, H. S. Park, T. Matsuda, T. Ohkubo, K. Hono et D. Shindo. « Magnetism of ultrathin intergranular boundary regions in Nd–Fe–B permanent magnets ». Acta Materialia 71 (juin 2014) : 370–79. http://dx.doi.org/10.1016/j.actamat.2014.03.013.
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Liu, Zhong Wu. « New Developments in NdFeB-Based Permanent Magnets ». Key Engineering Materials 510-511 (mai 2012) : 1–8. http://dx.doi.org/10.4028/www.scientific.net/kem.510-511.1.
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NdFeB based alloys have been used as permanent magnets for almost thirty years. The recent researches aim at optimizing the composition, microstructure and properties, reducing cost, and developing new processes. The demand for sintered magnet is increasing. Efforts are directed towards improving properties by controlling grain boundary diffusion, minimizing the rare earth (RE) content and also improving production yield. As for bonded magnets, to enhance remanence and energy product, nanocrystalline powders are employed. High thermal stability has been realized by mixing NdFeB with hard ferrite powders. For nanocrystalline and nanocomposite NdFeB based alloys, both compositional modification and microstructural optimization have been carried out. New approaches have also been proposed to prepare NdFeB magnets with idea structure. Surfactant assisted ball milling is a good top-down method to obtain nanosized hard magnetic particles and anisotropic nanoflakes. Synthesis of NdFeB nanoparticles and NdFeB/Fe (Co) nanocomposite powders by bottom-up techniques, such as chemical reduction process and co-precipitation, has been successful very recently. To assemble nanocrystalline NdFeB powders or nanoparticles into bulk magnets, various novel consolidation processes including spark plasma sintering and high velocity press have been employed. Hot deformation can be selected as the process to achieve anisotropy in nanocrystalline magnets.
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Ciobanu, Robert, Maurizio Repetto, Octavian Dontu, Fabio Freschi et Tudor Prisecaru. « Device Used for Magnetic Treatment of Fuel Fluids before Burner ». Applied Mechanics and Materials 186 (juin 2012) : 214–18. http://dx.doi.org/10.4028/www.scientific.net/amm.186.214.
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Worldwide magnetism was considered a "stepchild" of electromagnetism, but lately this has changed, and scientists give it great importance today, making a series of studies in which it is the main "actor". Regarding the magnetostatic field, the appearance of magnets with high performance, has led the development of permanent magnet structures with different technical applications, which successfully replace electromagnets. In this paper our main objective was to design and test a device used for magnetic treatment of fuel fluid which flow through pipes before burner to improve combustion dynamics and decrease the released fumes.
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Blümler, Peter. « Magnetic Guiding with Permanent Magnets : Concept, Realization and Applications to Nanoparticles and Cells ». Cells 10, no 10 (9 octobre 2021) : 2708. http://dx.doi.org/10.3390/cells10102708.
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The idea of remote magnetic guiding is developed from the underlying physics of a concept that allows for bijective force generation over the inner volume of magnet systems. This concept can equally be implemented by electro- or permanent magnets. Here, permanent magnets are in the focus because they offer many advantages. The equations of magnetic fields and forces as well as velocities are derived in detail and physical limits are discussed. The special hydrodynamics of nanoparticle dispersions under these circumstances is reviewed and related to technical constraints. The possibility of 3D guiding and magnetic imaging techniques are discussed. Finally, the first results in guiding macroscopic objects, superparamagnetic nanoparticles, and cells with incorporated nanoparticles are presented. The constructed magnet systems allow for orientation, movement, and acceleration of magnetic objects and, in principle, can be scaled up to human size.
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Qi, Li Qiang, et Yong Tao Yuan. « Designing on Magnetic Seal Ash-Unloader without Abrasion ». Advanced Materials Research 148-149 (octobre 2010) : 758–62. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.758.
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The rigid seals currently being used for the ash unloading device with the impeller under the hopper of the electrostatic precipitator are easy targets of wear and tear. In addition, the airproof capability of these seals is not perfect. In this light, an advanced powder magnetic seal design which installs permanent magnets at the top of the vane and utilizes the magnetism of Fe3O4 in fly ash to seal the space between two vanes is discussed in this paper. In the self-designed device, three categories of permanent magnet parameters and four kinds of powders with respective with respective magnetic powder mass fractions of 7%, 9%, 12%, and 15% were chosen. The airproof capability was also measured. The results show that this device has excellent airproof capability, can withstand wear and tear, and has a low replacement frequency.
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Crisan, Alina Daniela, Aurel Leca, Cristina Bartha, Ioan Dan et Ovidiu Crisan. « Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets ». Nanomaterials 11, no 4 (31 mars 2021) : 896. http://dx.doi.org/10.3390/nano11040896.
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Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic parameters and to illustrate the viability of these alloys as the next generation of rare earth (RE)-free magnets. By differential scanning calorimetry (DSC), activation energies and temperatures of onset of the ε-τ phase transformation were obtained. Structural analysis was performed using X-ray diffraction (XRD) and the resulting XRD patterns were quantitatively assessed using full profile Rietveld-type analysis. Appropriate annealing was performed in order to enable the ε-τ phase transformation. While hcp ε-phase was found to be predominant in the as-cast samples, after appropriate annealing, the tetragonal τ-phase, the one that furnishes the relevant magnetic response, was found to be predominant with an abundance of about 90%. The data suggested a mechanism of hcp ε-phase decomposition controlled by the segregation towards the interfacial regions, having the rate of transformation governed by antiphase boundary diffusion processes. Magnetic measurements of annealed sample Mn53Al45C2, consisting of predominant tetragonal τ-phase, showed high values of magnetization and increased coercivity, consistent with an energy product of about 10 MGOe, similar with previously reported magnetization measurements, providing further insight into the realization of future class of RE-free low-cost permanent magnets.
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Cao, Quanliang, Xiaotao Han et Liang Li. « Numerical analysis of magnetic nanoparticle transport in microfluidic systems under the influence of permanent magnets ». Journal of Physics D : Applied Physics 45, no 46 (23 octobre 2012) : 465001. http://dx.doi.org/10.1088/0022-3727/45/46/465001.
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Zhu, L. J., et J. H. Zhao. « Electrical Transport of Perpendicularly Magnetized L10-MnGa and MnAl Films ». SPIN 07, no 03 (septembre 2017) : 1730001. http://dx.doi.org/10.1142/s2010324717300018.
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Ferromagnetic films of [Formula: see text]-ordered MnGa and MnAl that exhibit giant perpendicular magnetic anisotropy and great controllability in the magnetism and structural disorders show promising applications not only in magnetic recording, permanent magnets and spintronics, but also in controllable studies of disorder-relevant electrical transport phenomena. In this paper, we review the intriguing experimental observations of the orbital two-channel Kondo effect and anomalous Hall effect in [Formula: see text]-ordered MnGa and MnAl thin films with perpendicular magnetic anisotropy. We also give a perspective with regards to the future technological and fundamental applications of these perpendicularly magnetized Mn-based binary alloy films.
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Martin, Leisha M. A., Jian Sheng, Paul V. Zimba, Lin Zhu, Oluniyi O. Fadare, Carol Haley, Meichen Wang, Timothy D. Phillips, Jeremy Conkle et Wei Xu. « Testing an Iron Oxide Nanoparticle-Based Method for Magnetic Separation of Nanoplastics and Microplastics from Water ». Nanomaterials 12, no 14 (9 juillet 2022) : 2348. http://dx.doi.org/10.3390/nano12142348.
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Nanoplastic pollution is increasing worldwide and poses a threat to humans, animals, and ecological systems. High-throughput, reliable methods for the isolation and separation of NMPs from drinking water, wastewater, or environmental bodies of water are of interest. We investigated iron oxide nanoparticles (IONPs) with hydrophobic coatings to magnetize plastic particulate waste for removal. We produced and tested IONPs synthesized using air-free conditions and in atmospheric air, coated with several polydimethylsiloxane (PDMS)-based hydrophobic coatings. Particles were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), superconducting quantum interference device (SQUID) magnetometry, dynamic light scattering (DLS), X-ray diffraction (XRD) and zeta potential. The IONPs synthesized in air contained a higher percentage of the magnetic spinel phase and stronger magnetization. Binding and recovery of NMPs from both salt and freshwater samples was demonstrated. Specifically, we were able to remove 100% of particles in a range of sizes, from 2–5 mm, and nearly 90% of nanoplastic particles with a size range from 100 nm to 1000 nm using a simple 2-inch permanent NdFeB magnet. Magnetization of NMPs using IONPs is a viable method for separation from water samples for quantification, characterization, and purification and remediation of water.
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Thalmayer, Angelika, Samuel Zeising, Georg Fischer et Jens Kirchner. « Investigation of Particle Steering for Different Cylindrical Permanent Magnets in Magnetic Drug Targeting ». Engineering Proceedings 2, no 1 (14 novembre 2020) : 24. http://dx.doi.org/10.3390/ecsa-7-08269.
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Magnetic Drug Targeting is a promising cancer treatment that offers the possibility of increasing therapeutic efficiency while reducing the patient’s side-effects. Thereby, the cancer-drug is bounded to magnetic nanoparticles, which are injected into a vessel and guided through the cardiovascular system into the tumor by an external magnetic field. However, a successful navigation depends on several multiphysical parameters including the properties of the nanoparticles, the flow characteristics of blood, and the gradient of the applied magnetic field. To investigate their impact, the propagation of particle packets within a 45∘ bifurcation vessel was modeled in COMSOL Multiphysics®. Therefore, magnets with varying radius-to-length ratios and magnetizations (radial and axial) were placed right before the bifurcation. Furthermore, different fluid velocities in addition to the influence of the gravitational force were evaluated. Overall, a strong dependency of the particle steering on the fluid velocity and the magnet’s radius-to-length ratio was observed. Moreover, a radial magnetization has a greater impact on the particle propagation, while the gravitation can be neglected for higher velocities. However, when a single permanent magnet is used, the results depict that it is a fine line between deflecting or trapping a particle at the vessel wall.
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Imarah, Ali Obaid, Pál Csuka, Naran Bataa, Balázs Decsi, Evelin Sánta-Bell, Zsófia Molnár, Diána Balogh-Weiser et László Poppe. « Magnetically Agitated Nanoparticle-Based Batch Reactors for Biocatalysis with Immobilized Aspartate Ammonia-Lyase ». Catalysts 11, no 4 (9 avril 2021) : 483. http://dx.doi.org/10.3390/catal11040483.
Texte intégralRésumé :
In this study, we investigated the influence of different modes of magnetic mixing on effective enzyme activity of aspartate ammonia-lyase from Pseudomonas fluorescens immobilized onto epoxy-functionalized magnetic nanoparticles by covalent binding (AAL-MNP). The effective specific enzyme activity of AAL-MNPs in traditional shake vial method was compared to the specific activity of the MNP-based biocatalyst in two devices designed for magnetic agitation. The first device agitated the AAL-MNPs by moving two permanent magnets at two opposite sides of a vial in x-axis direction (being perpendicular to the y-axis of the vial); the second device unsettled the MNP biocatalyst by rotating the two permanent magnets around the y-axis of the vial. In a traditional shake vial, the substrate and biocatalyst move in the same direction with the same pattern. In magnetic agitation modes, the MNPs responded differently to the external magnetic field of two permanent magnets. In the axial agitation mode, MNPs formed a moving cloud inside the vial, whereas in the rotating agitation mode, they formed a ring. Especially, the rotating agitation of the MNPs generated small fluid flow inside the vial enabling the mixing of the reaction mixture, leading to enhanced effective activity of AAL-MNPs compared to shake vial agitation.
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Wen, Xiaogang, Lin Gu et Alexander M. Bittner. « Simple Electroless Synthesis of Cobalt Nanoparticle Chains, Oriented by Externally Applied Magnetic Fields ». Zeitschrift für Physikalische Chemie 232, no 9-11 (28 août 2018) : 1631–46. http://dx.doi.org/10.1515/zpch-2018-1135.
Texte intégralRésumé :
Abstract The electroless (chemical) deposition of cobalt on palladium-sensitized oxidized silicon wafers produces nanowires and chains made up by nanoparticles. We demonstrate that the application of moderate magnetic fields, provided by permanent magnets, during the growth produces highly oriented cobalt nanowires and nanoparticle chains. By adjusting the magnetic field direction in plane, parallel and crossed cobalt chain patterns are readily accessible. Perpendicular orientation of the field results in rod-like, standing-up chains of nanoparticles. We explain the observed structures with magnetostatic arguments.
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Antonov, Yuri F. « Calculation, design and manufacture of heteropolar magnetic levitation and linear drive systems of maglev transport ». Transportation Systems and Technology 7, no 2 (1 juillet 2021) : 119–29. http://dx.doi.org/10.17816/transsyst202172119-129.
Texte intégralRésumé :
Background: The methods of calculation and elements of the technology for creating heteropolar magnetic systems of levitation, lateral stabilization and a rotor-runner of a traction linear synchronous motor for the development of the transport technology "Russian Maglev" in order to achieve an increased levitation gap of 0.2 m, reduce the threshold speed of the exit vehicle in levitation mode up to 10 km/h.
Aim: to develop methods for calculating and designing heteropolar poles from elementary permanent magnets, coils of the same type based on composite low-temperature superconductors and high-temperature tape superconductors of the second generation and a step-by-step technology for their production.
Tasks:
Creation of an on-board magnetic system of levitation and lateral stabilization, allowing to provide a levitation gap of 0.2 m, a threshold value of vehicle speed of 10 km/h when transition to levitation mode, to reduce stray magnetic fields to the level of the natural field of terrestrial magnetism of 50 T;
Creation of a rotor-runner of a linear synchronous motor with an ironless stator with a power of 10 MW.
Methods: outlines the main calculation methodologies: "analysis" and "synthesis". The "analysis" methodology is adopted in solving the "direct" calculation problem, when the configuration of the magnetic system is set and the magnetic field in the working area is calculated, and, if necessary, the stray magnetic fields. This methodology can be effectively applied if there is experience in creating magnetic systems. Otherwise, the "synthesis" methodology is applied, which is used in solving the "inverse" calculation problem, in which the picture of the distribution of the magnetic field in the working zone is set and the configuration of the magnetic system is found (synthesized).
Results of the study performed:
The parameters and characteristics of high-energy permanent magnets made of rare-earth metals, low-temperature and high-temperature superconducting winding materials have been analyzed, the choice of permanent magnets and superconducting winding material has been made;
Calculations of the magnetic system of permanent magnets in the "Halbach assembly" and in the traditional assembly in a toothed ferromagnetic core have been carried out;
Calculations of a track coil with a rectangular cross-section of the winding are performed;
Methods for calculating and optimizing superconducting magnetic systems from a set of similar track modules have been developed;
Conclusions: The results of the performed fundamental research will allow starting the calculation, design and construction of conveyor-main passenger and freight lines of maglev transport, as well as urban public transport.
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DING, XIA, JINGJIE LI, MUSEN LI, SHENGSONG GE, XIUCHUN WANG, KAIHONG DING, SHENGLI CUI et YONGCONG SUN. « CORROSION PROTECTION OF ND–FE–B MAGNETS VIA PHOPHATIZATION, SILANIZATION AND ELECTROSTATIC SPRAYING WITH ORGANIC RESIN COMPOSITE COATINGS ». Surface Review and Letters 21, no 06 (décembre 2014) : 1450077. http://dx.doi.org/10.1142/s0218625x14500772.
Texte intégralRésumé :
Nd – Fe – B permanent magnets possess excellent properties. However, they are highly sensitive to the attack of corrosive environment. The aim of this work is to improve the corrosion resistance of the magnets by phosphatization, silanization, and electrostatic spraying with organic resin composite coatings. Field emission scanning electron microscope (FE-SEM) and energy dispersive spectrometer (EDS) tests showed that uniform phosphate conversion coatings and spray layers were formed on the surface of the Nd – Fe – B magnets. Neutral salt spray tests exhibited that, after treated by either phosphating, silanization or electrostatic spraying, the protectiveness of Nd – Fe – B alloys was apparently increased. And corrosion performance of magnets treated with silane only was slightly inferior to those of phosphatized ones. However, significant improvement in corrosion protection was achieved after two-step treatments, i.e. by top-coating spray layer with phosphate or silane films underneath. Grid test indicated that the phosphate and silane coating were strongly attached to the substrate while silane film was slightly weaker than the phosphate-treated ones. Magnetic property analysis revealed phosphatization, silanization, and electrostatic spraying caused decrease in magnetism, but silanization had the relatively smaller effect.
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Pourshahidi, Ali Mohammad, Stefan Achtsnicht, Andreas Offenhäusser et Hans-Joachim Krause. « Frequency Mixing Magnetic Detection Setup Employing Permanent Ring Magnets as a Static Offset Field Source ». Sensors 22, no 22 (14 novembre 2022) : 8776. http://dx.doi.org/10.3390/s22228776.
Texte intégralRésumé :
Frequency mixing magnetic detection (FMMD) has been explored for its applications in fields of magnetic biosensing, multiplex detection of magnetic nanoparticles (MNP) and the determination of core size distribution of MNP samples. Such applications rely on the application of a static offset magnetic field, which is generated traditionally with an electromagnet. Such a setup requires a current source, as well as passive or active cooling strategies, which directly sets a limitation based on the portability aspect that is desired for point of care (POC) monitoring applications. In this work, a measurement head is introduced that involves the utilization of two ring-shaped permanent magnets to generate a static offset magnetic field. A steel cylinder in the ring bores homogenizes the field. By variation of the distance between the ring magnets and of the thickness of the steel cylinder, the magnitude of the magnetic field at the sample position can be adjusted. Furthermore, the measurement setup is compared to the electromagnet offset module based on measured signals and temperature behavior.
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Akbar, S., Z. Ahmad, M. S. Awan, M. N. Sarwar et M. Farooque. « Single Step Heat Treatment Cycle for Development of Isotropic Fe-Cr-Co Magnets ». Key Engineering Materials 510-511 (mai 2012) : 315–20. http://dx.doi.org/10.4028/www.scientific.net/kem.510-511.315.
Texte intégralRésumé :
This study is focused on the development of isotropic Fe-Cr-Co based permanent magnets. Two compositions Fe-25Co-30Cr-3.5Mo-0.8Ti-0.8 and Fe-24 Co-32Cr-0.5Si-0.8V-0.8Ti were tried to optimize by adjusting heat treatment cycle. A modified single step heat treatment cycle was established which made processing easy and quick. Alloys were prepared in tri-arc melting furnace under inert atmosphere of Argon. Samples were solution treated at 1250 °C for 5 hours followed by water quenching. Then a spinodal decomposition heat treatment cycle in the temperature range 620 645 °C was applied in order to produce magnetism in this material. Samples were characterized for metallographic, chemical, structural and magnetic properties using Optical microscope, Scanning electron microscope equipped with Energy dispersive spectrometer, X-ray diffractometer and DC magnetometer. This study reveals that magnetic properties are sensitive to the spinodal decomposition temperature. Only + 5 °C change in temperature from optimum temperature can cause remarkable attenuation in magnetic properties. Magnetic properties of the alloys were achieved by controlling the spinodal decomposition temperature and subsequent cooling rate. The best magnetic properties in Mo and V containing alloys were obtained as 880 Oe (Hc), 7960 G (Br), 2.3 MGOe (BHmax) and 700 Oe (Hc), 7750 G (Br), 1.8 MGOe (BHmax), respectively.
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Akbar, Ahmad Radikal, et Mokhtar Awang. « Performance Prediction of Inertial Auto-Reinforce Magnetic Flywheel Energy Storage Device Using Finite Element Magnetic Modeling ». Applied Mechanics and Materials 663 (octobre 2014) : 169–74. http://dx.doi.org/10.4028/www.scientific.net/amm.663.169.
Texte intégralRésumé :
A new feature for flywheel energy storage device is proposed considering the deficiencies in former technology. This feature is introduced as auto-reinforce performance which means giving-back the kinetic energy for flywheel after speed-down occurred (as result of sudden loading). Auto-reinforce performance is an ability to recover the kinetic rotational energy which significantly keeps longer the stored energy of a flywheel device. This novel concept of flywheel is engineered by installing a number of Permanent Magnets (PM) in certain mounting. Hence, the magnetism configuration such magnetic strength, magnetic energy density, pole direction, geometry, and dimension are influential parameters to the mechanical performance. By practicing Finite Element Magnetic Modeling (FEMM), it is possible to predict some designed mechanical parameters such magnetic force and magnetic torque. Finally by evaluating these mechanical parameters, the key performance of this device such as percentage of energy reinforcement and percentage of discharge elongation can be predicted. The main ideas of this paper are: 1) presenting the development stages especially in design prediction using Finite Element Analysis (FEA) software; and 2) discovering the correlation of designed magnetic properties and mechanical parameters for prototyping references.
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Garzón, Daniela, Luz Helena Camargo et Diego Julián Rodríguez. « Collisions model between magnetic nanoparticles and the arterial wall ». Journal of Physics : Conference Series 2090, no 1 (1 novembre 2021) : 012051. http://dx.doi.org/10.1088/1742-6596/2090/1/012051.
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Abstract At present, there are different treatments against cancer, however, some of them, such as chemotherapy, are very invasive for the human body, since they affect healthy tissues. Magnetic targeting of drugs by means of magnetic nanoparticles is one of the alternative techniques that has emerged in the last decade, it is based on the targeting of drug delivery to the tumor without affecting healthy tissues, via of injected nanoparticles with diamagnetic properties directly into the bloodstream, driven by external magnetic fields produced by permanent magnets. This technique in literature is often come upon as MTD for its acronym in English. In this work, a numerical model was developed in order to quantify the loss of nanoparticles in the process of interaction with the walls of the bloodstream. For this model, the Kinetic technique was used, quantifying the probability of adsorption and absorption taking into account the following parameters: diameter of the nanoparticle (200 nm), density of the nanoparticle (6450 kg · m -3), diameter of the cell endothelial (0.1 μm - 1 μm), transcellular pores of the fenestrated endothelium (70 nm) and modulus of elasticity of the endothelium (4.1 ± 1.7 kPa).
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Maglio, Melania, Maria Sartori, Alessandro Gambardella, Tatiana Shelyakova, Valentin Alek Dediu, Matteo Santin, Yolanda Piñeiro et al. « Bone Regeneration Guided by a Magnetized Scaffold in an Ovine Defect Model ». International Journal of Molecular Sciences 24, no 1 (1 janvier 2023) : 747. http://dx.doi.org/10.3390/ijms24010747.
Texte intégralRésumé :
The reconstruction of large segmental defects still represents a critical issue in the orthopedic field. The use of functionalized scaffolds able to create a magnetic environment is a fascinating option to guide the onset of regenerative processes. In the present study, a porous hydroxyapatite scaffold, incorporating superparamagnetic Fe3O4 nanoparticles (MNPs), was implanted in a critical bone defect realized in sheep metatarsus. Superparamagnetic nanoparticles functionalized with hyperbranched poly(epsilon-Lysine) peptides and physically complexed with vascular endothelial growth factor (VEGF) where injected in situ to penetrate the magnetic scaffold. The scaffold was fixed with cylindrical permanent NdFeB magnets implanted proximally, and the magnetic forces generated by the magnets enabled the capture of the injected nanoparticles forming a VEGF gradient in its porosity. After 16 weeks, histomorphometric measurements were performed to quantify bone growth and bone-to-implant contact, while the mechanical properties of regenerated bone via an atomic force microscopy (AFM) analysis were investigated. The results showed increased bone regeneration at the magnetized interface; this regeneration was higher in the VEGF-MNP-treated group, while the nanomechanical behavior of the tissue was similar to the pattern of the magnetic field distribution. This new approach provides insights into the ability of magnetic technologies to stimulate bone formation, improving bone/scaffold interaction.
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Landa, Alexander, Per Söderlind, Emily E. Moore et Aurélien Perron. « Thermodynamics and Magnetism of SmFe12 Compound Doped with Co and Ni : An Ab Initio Study ». Applied Sciences 12, no 10 (11 mai 2022) : 4860. http://dx.doi.org/10.3390/app12104860.
Texte intégralRésumé :
Ni-doped Sm(Fe1−xCox)12 alloys are investigated for their magnetic properties. The Sm(Fe,Co)11M1 compound (M acts as a stabilizer) with the smallest (7.7 at.%) rare-earth-metal content has been recognized as a possible contender for highly efficient permanent magnets thanks to its significant anisotropy field and Curie temperature. The early transition metals (Ti-Mn) as well as Al, Si, and Ga stabilize the SmFe12 compound but significantly decrease its saturation magnetization. To keep the saturation magnetization in the range of 1.4–1.6 T, we suggest replacing a certain amount of Fe and Co in the Sm(Fe1−xCox)12 alloys with Ni. Ni plays the role of a thermodynamic stabilizer, and contrary to the above-listed elements, has the spin moment aligned parallel to the spin moment of the SmFe12 compound, thereby boosting its saturation magnetization without affecting the anisotropy field or Curie temperature.
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Silva, Fausto M. W. G., Ali O. Imarah, Orsolya Takács, László Tuba et László Poppe. « Scalability of U-Shape Magnetic Nanoparticles-Based Microreactor–Lipase-Catalyzed Preparative Scale Kinetic Resolutions of Drug-like Fragments ». Catalysts 13, no 2 (10 février 2023) : 384. http://dx.doi.org/10.3390/catal13020384.
Texte intégralRésumé :
The production of active pharmaceutical ingredients (APIs) and fine chemicals is accelerating due to the advent of novel microreactors and new materials for immobilizing customized biocatalysts that permit long-term use in continuous-flow reactors. This work studied the scalability of a tunable U-shape magnetic nanoparticles (MNPs)-based microreactor. The reactor consisted of a polytetrafluoroethylene tube (PTFE) of various inner diameters (ID = 0.75 mm, 1.50 mm, or 2.15 mm) and six movable permanent magnets positioned under the tube to create reaction chambers allowing the fluid reaction mixture to flow through and above the enzyme-loaded MNPs anchored by permanent magnets. The microreactors with various tube sizes and MNP capacities were tested with the preparative scale kinetic resolution of the drug-like alcohols 4-(3,4-dihydroisoquinolin-2(1H)-yl)butan-2-ol (±)-1a and 4-(3,4-dihydroquinolin-1(2H)-yl)butan-2-ol (±)-1b, utilizing Lipase B from Candida antarctica immobilized covalently onto MNPs, leading to highly enantioenriched products [(R)-2a,b and (S)-1a,b]. The results in the U-shape MNP flow reactor were compared with reactions in the batch mode with CaLB-MNPs using similar conditions. Of the three different systems, the one with ID = 1.50 mm showed the best balance between the maximum loading capacity of biocatalysts in the reactor and the most effective cross-section area. The results showed that this U-shaped tubular microreactor might be a simple and flexible instrument for many processes in biocatalysis, providing an easy-to-set-up alternative to existing techniques.
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Huang, Lanqing, Jingeng Mai, Qihui Zhu, Zhen Guo, Siying Qin, Peilin Yang, Xuanxuan Li et al. « Reversible rearrangement of magnetic nanoparticles in solution studied using time-resolved SAXS method ». Journal of Synchrotron Radiation 26, no 4 (11 juin 2019) : 1294–301. http://dx.doi.org/10.1107/s1600577519004909.
Texte intégralRésumé :
Superparamagnetic nanoparticles have broad applications in biology and medicines. Quantitative measurements of magnetic beads in solution are essential in gaining comprehensive understanding of their dynamics and developing applications. Here, using synchrotron X-ray sources combined with well controlled magnetic fields, the results from small-angle X-ray scattering (SAXS) experiments on superparamagnetic particles in solution under the influence of external magnetic fields are reported. The particles mostly remain in monodispersed states and the linear aggregates tend to be aligned with the external magnetic field. After removing the magnetic fields, the superparamagnetic nanoparticles quickly recover to their original states indicating high reversibility of the rearrangement under the control of a magnetic field. The external magnetic field instrument composed of paired permanent magnets is integrated into the SAXS beamline at the Shanghai Synchrotron Radiation Facility providing a platform for studying time-resolved dynamics induced by magnetic fields.
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Harris, V. G., Y. Chen, A. Yang, S. Yoon, Z. Chen, A. L. Geiler, J. Gao et al. « High coercivity cobalt carbide nanoparticles processed via polyol reaction : a new permanent magnet material ». Journal of Physics D : Applied Physics 43, no 16 (8 avril 2010) : 165003. http://dx.doi.org/10.1088/0022-3727/43/16/165003.
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Hong, Sung-Jei, Ajin Jo, Sang Hyeok Hong, Byeong Jun Kim, Young Sung Kim, Suwon Yang et Jae-Yong Lee. « Effect of Polyvinylpolypyrrolidone Surfactant on Characteristics of Iron-Oxide Nanoparticles Synthesized by Using Recycled Waste Permanent Magnets ». Micromachines 13, no 11 (19 novembre 2022) : 2020. http://dx.doi.org/10.3390/mi13112020.
Texte intégralRésumé :
In this study, iron oxide nanoparticles (FeOx NPs) were synthesized by using Fe solution recycled from NdFeB permanent magnet scrap. Furthermore, the effect of polyvinylpolypyrrolidone (PVP) as a surfactant on the characteristics of the FeOx NPs was investigated. Firstly, Fe solution was prepared by using 10% H2SO4 solution and Na2SO4 salt. In addition, three reducing agent solutions were prepared by dissolving PVP in 0.5 M NH4OH solution in distilled (D.I.) water with concentrations of 0 wt%, 1 wt%, and 2 wt%, respectively. Each reducing agent solution was added dropwise into the Fe solution to precipitate three precursors of FeOx NPs, and they were heat-treated at 400 °C to prepare three FeOx NPs samples, P0, P1, and P2. In X-ray diffractometer (XRD) analysis, diffraction peaks of P0 sample are consistent with the Fe3O4 with (311) preferred orientation. The XRD peak shifted from Fe3O4 to Fe2O3 structure as PVP concentration increased, and the crystal structure of P2 sample was transformed to Fe2O3 with (104) preferred orientation. Brunauer, Emmett, and Teller (BET) specific surface area increased in proportional to PVP concentration. HRTEM observation also supported the tendency; the particle size of the P0 sample was less than 40 nm, and particle size decreased as PVP concentration increased, leading to the particle size of the P2 sample being less than 20 nm in width. In addition, particle morphology started to be transformed from particle to rod shape as PVP concentration increased and, in the P2 sample, all the morphology of particles was transformed to a rod shape. Magnetic properties analysis revealed that the P0 sample exhibited the highest value of magnetic moment, 65.6 emu/g, and the magnetic moment was lowered in the P1 sample, and the P2 sample exhibited the lowest value of magnetic moment, 2.4 emu/g.
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Dairy, Abdul Raouf Al, Lina A. Al-Hmoud et Heba A. Khatatbeh. « Magnetic and Structural Properties of Barium Hexaferrite Nanoparticles Doped with Titanium ». Symmetry 11, no 6 (28 mai 2019) : 732. http://dx.doi.org/10.3390/sym11060732.
Texte intégralRésumé :
Samples of Barium Hexaferrite doped with Titanium BaFe12−xTixO19 with (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized by the sol–gel auto-combustion technique. The powdered samples were divided into two parts, one sintered at 850 °C and another sintered 1000 °C for 1 h and samples were characterized by different experimental techniques. The XRD patterns confirmed the presence of M-type hexaferrite phase. The sizes of the crystallites were calculated by the Scherer equation, and the sizes were in the range of 27–42 nm. Using the hysteresis loops, the saturation magnetization Ms, remanence (Mr), the relative ratio (Mr/Ms), and the coercivity (Hc) were calculated. The study showed that the saturation magnetization (Ms) and remanence (Mr) decreased with increasing titanium concentration and were in the range from 44.65–17.17 emu/g and 23.1–7.7 emu/g, respectively. The coercivity (Hc) ranged between 0.583 and 4.51 (kOe). The magnetic properties of these Barium Hexaferrite doped with Titanium indicated that they could be used in the recording equipment and permanent magnets.
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Lottini, E., A. López-Ortega, G. Bertoni, S. Turner, M. Meledina, G. Van Tendeloo, C. de Julián Fernández et C. Sangregorio. « Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy : A Strategy toward Rare-Earth-Free Permanent Magnets ». Chemistry of Materials 28, no 12 (6 juin 2016) : 4214–22. http://dx.doi.org/10.1021/acs.chemmater.6b00623.
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Todkar, G. B., R. A. Kunale, R. N. Kamble, Khalid M. Batoo, M. F. Ijaz, A. Imran, M. Hadi, E. H. Raslan, Sagar E. Shirsath et R. H. Kadam. « Ce–Dy substituted barium hexaferrite nanoparticles with large coercivity for permanent magnet and microwave absorber application ». Journal of Physics D : Applied Physics 54, no 29 (13 mai 2021) : 294001. http://dx.doi.org/10.1088/1361-6463/abf864.
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Gopinadhan, Manesh, Youngwoo Choo, Kohsuke Kawabata, Gilad Kaufman, Xunda Feng, Xiaojun Di, Yekaterina Rokhlenko et al. « Controlling orientational order in block copolymers using low-intensity magnetic fields ». Proceedings of the National Academy of Sciences 114, no 45 (23 octobre 2017) : E9437—E9444. http://dx.doi.org/10.1073/pnas.1712631114.
Texte intégralRésumé :
The interaction of fields with condensed matter during phase transitions produces a rich variety of physical phenomena. Self-assembly of liquid crystalline block copolymers (LC BCPs) in the presence of a magnetic field, for example, can result in highly oriented microstructures due to the LC BCP’s anisotropic magnetic susceptibility. We show that such oriented mesophases can be produced using low-intensity fields (<0.5 T) that are accessible using permanent magnets, in contrast to the high fields (>4 T) and superconducting magnets required to date. Low-intensity field alignment is enabled by the addition of labile mesogens that coassemble with the system’s nematic and smectic A mesophases. The alignment saturation field strength and alignment kinetics have pronounced dependences on the free mesogen concentration. Highly aligned states with orientation distribution coefficients close to unity were obtained at fields as small as 0.2 T. This remarkable field response originates in an enhancement of alignment kinetics due to a reduction in viscosity, and increased magnetostatic energy due to increases in grain size, in the presence of labile mesogens. These developments provide routes for controlling structural order in BCPs, including the possibility of producing nontrivial textures and patterns of alignment by locally screening fields using magnetic nanoparticles.
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Li, Xingfu, et Toshio Fukuda. « Magnetically Guided Micromanipulation of Magnetic Microrobots for Accurate Creation of Artistic Patterns in Liquid Environment ». Micromachines 11, no 7 (18 juillet 2020) : 697. http://dx.doi.org/10.3390/mi11070697.
Texte intégralRésumé :
In this paper, a magnetically guided micromanipulation method is proposed to accurately create artistic patterns with magnetic microrobots in a liquid environment for tissue engineering. A magnetically guided device is developed depend on symmetrical combination of square permanent magnets and array layout of soft magnetic wires, which changed the space distribution of magnetic field of conventional permanent magnet and generated powerful magnetic flux density and high magnetic field gradient. Furthermore, the morphological structure of the magnetic microrobot is flexibly adjusted via precise control of the volumetric flow rates inside the microfluidic device and the magnetic nanoparticles are taken along to enable its controllability by rapid magnetic response. And then, the spatial posture of the magnetic microrobot is contactless controlled by the magnetically guided manipulator and it is released under the influence of surface tension and gravity. Subsequently, the artistic fashions of the magnetic microrobots are precisely distributed via the dot-matrix magnetic flux density of the magnetically guided device. Finally, the experimental results herein demonstrate the accuracy and diversity of the pattern structures in the water and the developed method will be providing a new way for personalized functional scaffold construction.
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Li, Jing, Xin Zhang, Cong Wang, Jingjiang Qiu, Yudong Zhang, Xiang Zhang et Zonhan Wei. « Study of magnetic microspheres screening in microfluidic chip based on co-simulation method ». AIP Advances 13, no 2 (1 février 2023) : 025136. http://dx.doi.org/10.1063/5.0135616.
Texte intégralRésumé :
Magnetic microspheres have been widely applied in DNA determination, bacterial analysis, and information coding. Magnetic microspheres screening is important, as the sizes of the obtained microspheres vary with different manufacturing methods, causing considerable impact on subsequent applications. In this paper, a co-simulation method based on MATLAB and COMSOL was presented to design the magnetic microfluidic chip, which was utilized to separate the magnetic micro-spheres of different sizes efficiently. In order to complete the separation and screening of magnetic microspheres in the microchannel, a movable permanent magnet device was adopted to adjust the magnetic interactions in the separation area, allowing the microspheres to deviate from different distances. A batch analysis of chip model was performed with this method, and an optimal design that showed high efficiency in separating microspheres of different sizes and magnetic properties was also revealed. Moreover, detailed analysis focused on the influence of flow rate, magnetism and arrangement of magnets on the separation effect of the chip. The presented simulation method will not only shorten the chip design time but also have a better understanding of the factors that can affect the separation of particles. This study has shown its potential in the computer-aided design of microfluidic chips for magnetic microspheres screening.
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Ghosh, Suvojit, et Ishwar K. Puri. « Changing the magnetic properties of microstructure by directing the self-assembly of superparamagnetic nanoparticles ». Faraday Discussions 181 (2015) : 423–35. http://dx.doi.org/10.1039/c4fd00245h.
Texte intégralRésumé :
Magnetic nanoparticles (MNPs) in a liquid dispersion can be organized through controlled self-assembly by applying an external magnetic field that regulates inter-particle interactions. Thus, micro- and nanostructures of desired morphology and superlattice geometry that show emergent magnetic properties can be fabricated. We describe how superferromagnetism, which is a specific type of emergence, can be produced. Here, superparamagnetic nanoparticles that show no individual residual magnetization are organized into structures with substantial residual magnetization that behave as miniature permanent magnets. We investigate the emergence of superferromagnetism in an idealized system consisting of two MNPs, by considering the influence that interparticle magnetostatic interactions have on the dynamics of the magnetic moments. We use this model to illustrate the design principles for self-assembly in terms of the choice of material and MNP particle size. We simulate the dynamics of the interacting magnetic moments by applying the stochastic Landau–Lifshitz–Gilbert equation to verify our principles. The findings enable a method to pattern material magnetization with submicron resolution, a useful feature that has potential applications for magnetic recording and microfluidic particle traps. The analysis also yields useful empirical generalizations that could facilitate other theoretical developments.
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Zhang, Xiangyong, Haipeng Liu, Yunli He, Tingrui Peng, Bin Su et Huiyuan Guan. « Analysis of the Influence of Ferromagnetic Material on the Output Characteristics of Halbach Array Energy-Harvesting Structure ». Micromachines 12, no 12 (11 décembre 2021) : 1541. http://dx.doi.org/10.3390/mi12121541.
Texte intégralRésumé :
Due to the particular arrangement of permanent magnets, a Halbach array has an significant effect of magnetism and magnetic self-shielding. It can stretch the magnetic lines on one side of the magnetic field to obtain an ideal sinusoidal unilateral magnetic field. It has a wide application range in the field of energy harvesting. In practical applications, magnetic induction intensity of each point in magnetic field is not only related to the induced current and conductor but also related to the permeability of the medium (also known as a magnetic medium) in the magnetic field. Permeability is the physical quantity that represents the magnetism of the magnetic medium, which indicates the resistance of magnetic flux or the ability of magnetic lines to be connected in the magnetic field after coil flows through current in space or in the core space. When the permeability is much greater than one, it is a ferromagnetic material. Adding a ferromagnetic material in a magnetic field can increase the magnetic induction intensity B. Iron sheet is a good magnetic material, and it is easy to magnetize to generate an additional magnetic field to strengthen the original magnetic field, and it is easy to obtain at low cost. In this paper, in order to explore the influence of ferromagnetic material on the magnetic field and energy harvesting efficiency of the Halbach array energy harvesting structure, iron sheets are installed on the periphery of the Halbach array rotor. Iron sheet has excellent magnetic permeability. Through simulation, angle between iron sheet and Halbach array, radian size of iron sheet itself and distance between iron sheet and Halbach array can all have different effects on the magnetic field of the Halbach array. It shows that adding iron sheets as a magnetic medium could indeed change the magnetic field distribution of the Halbach array and increase energy harvesting efficiency. In this paper, a Halbach array can be used to provide electrical power for passive wireless low-power devices.
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Debnath, Bharati, Hemant G. Salunke et Sayan Bhattacharyya. « Spin Disorder and Particle Size Effects in Cobalt Ferrite Nanoparticles with Unidirectional Anisotropy and Permanent Magnet-like Characteristics ». Journal of Physical Chemistry C 124, no 47 (11 novembre 2020) : 25992–6000. http://dx.doi.org/10.1021/acs.jpcc.0c07382.
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Lohmaah, Abdulmumeen, Komkrich Chokprasombat, Supree Pinitsoontorn et Chitnarong Sirisathitkul. « Magnetic Properties and Morphology Copper-Substituted Barium Hexaferrites from Sol-Gel Auto-Combustion Synthesis ». Materials 14, no 19 (7 octobre 2021) : 5873. http://dx.doi.org/10.3390/ma14195873.
Texte intégralRésumé :
The copper (Cu) substitution in barium hexaferrite (BaFe12O19) crystals from the sol-gel auto-combustion synthesis is demonstrated as a cost-effective pathway to achieve alterable magnetic properties. Subsequent heat treatments at 450 °C and 1050 °C result in irregularly shaped nanoparticles characterized as the M-type BaFe12O19 with the secondary phase of hematite (α-Fe2O3). Despite the mixed phase, the substantial coercivity of 2626 Oe and magnetization as high as 74.8 emu/g are obtained in this undoped ferrite. The copper (Cu) doing strongly affects morphology and magnetic properties of BaFe12−xCuxO19 (x = 0.1, 0.3, and 0.5). The majority of particles become microrods for x = 0.1 and microplates in the case of x = 0.3 and 0.5. The coercivity and magnetization tend to reduce as Cu2+ increasingly substitutes Fe3+. From these findings, magnetic properties for various applications in microwave absorbers, recording media, electrodes, and permanent magnets can be tailored by the partial substitution in hexaferrite crystals.
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Zeng, Lin, Xi Chen, Rongrong Zhang, Shi Hu, Hongpeng Zhang, Yi Zhang et Hui Yang. « High-Resolution Separation of Nanoparticles Using a Negative Magnetophoretic Microfluidic System ». Micromachines 13, no 3 (26 février 2022) : 377. http://dx.doi.org/10.3390/mi13030377.
Texte intégralRésumé :
The separation and purification of a sample of interest is essential for subsequent detection and analysis procedures, but there is a lack of effective separation methods with which to purify nano-sized particles from the sample media. In this paper, a microfluidic system based on negative magnetophoresis is presented for the high-resolution separation of nanoparticles. The system includes on-chip magnetic pole arrays and permalloys that symmetrically distribute on both sides of the separation channel and four permanent magnets that provide strong magnetic fields. The microfluidic system can separate 200 nm particles with a high purity from the mixture (1000 nm and 200 nm particles) due to a magnetic field gradient as high as 10,000 T/m being generated inside the separation channel, which can provide a negative magnetophoretic force of up to 10 pN to the 1000 nm particle. The overall recovery rate of the particles reaches 99%, the recovery rate of 200 nm particles is 84.2%, and the purity reaches 98.2%. Compared with the existing negative magnetophoretic separation methods, our system not only exhibits high resolution on particle sizes (800 nm), but also improves the sample processing throughput, which reaches 2.5 μL/min. The microfluidic system is expected to provide a new solution for the high-purity separation of nanoparticles, as well as nanobiological samples.
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Blyakhman, Felix A., Grigory Yu Melnikov, Emilia B. Makarova, Fedor A. Fadeyev, Daiana V. Sedneva-Lugovets, Pavel A. Shabadrov, Stanislav O. Volchkov et al. « Effects of Constant Magnetic Field to the Proliferation Rate of Human Fibroblasts Grown onto Different Substrates : Tissue Culture Polystyrene, Polyacrylamide Hydrogel and Ferrogels γ-Fe2O3 Magnetic Nanoparticles ». Nanomaterials 10, no 9 (28 août 2020) : 1697. http://dx.doi.org/10.3390/nano10091697.
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The static magnetic field was shown to affect the proliferation, adhesion and differentiation of various types of cells, making it a helpful tool for regenerative medicine, though the mechanism of its impact on cells is not completely understood. In this work, we have designed and tested a magnetic system consisting of an equidistant set of the similar commercial permanent magnets (6 × 4 assay) in order to get insight on the potential of its experimental usage in the biological studies with cells culturing in a magnetic field. Human dermal fibroblasts, which are widely applied in regenerative medicine, were used for the comparative study of their proliferation rate on tissue culture polystyrene (TCPS) and on the polyacrylamide ferrogels with 0.00, 0.63 and 1.19 wt % concentrations of γ-Fe2O3 magnetic nanoparticles obtained by the well-established technique of laser target evaporation. We used either the same batch as in previously performed but different biological experiments or the same fabrication conditions for fabrication of the nanoparticles. This adds special value to the understanding of the mechanisms of nanoparticles contributions to the processes occurring in the living systems in their presence. The magnetic field increased human dermal fibroblast cell proliferation rate on TCPS, but, at the same time, it suppressed the growth of fibroblasts on blank gel and on polyacrylamide ferrogels. However, the proliferation rate of cells on ferrogels positively correlated with the concentration of nanoparticles. Such a dependence was observed both for cell proliferation without the application of the magnetic field and under the exposure to the constant magnetic field.
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Gómez Rodríguez, Alvaro Javier, Dagoberto Oyola Lozano, Humberto Bustos Rodríguez, Yebrail Rojas Martínez, German Antonio Pérez Alcázar, Ligia Edith Zamora Alfonso et Juan Sebastian Trujillo Hernandez. « Production and Characterization of Nanostructured Powders of Nd2Fe14B and Fe90Al10 by Mechanical Alloying ». Molecules 27, no 21 (24 octobre 2022) : 7190. http://dx.doi.org/10.3390/molecules27217190.
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The objective of this work is to evaluate the applicability of exchange coupling between nanoparticles of Nd2Fe14B (hard magnetic material) and Fe90Al10 (soft magnetic material), as permanent magnets produced by surfactant-assisted mechanical alloying. The obtained powders were then mixed with 85% of the Nd2Fe14B system and 15% of the Fe90Al10 system and subsequently sintered at 300 °C, 400 °C and 500 °C for one hour. The results obtained by Mössbauer spectrometry (MS) show a ferromagnetic behavior with six magnetic sites represented by sextets (16k1, 16k2, 8j1, 8j2, 4c and 4e), characteristic of the Nd2Fe14B system. X-ray diffraction (XRD) results show a tetragonal and BCC structure for the Nd2Fe14B and FeAl systems, respectively. The results obtained by vibrating sample magnetometry (VSM), for mixtures of the Nd2Fe14B and Fe90Al10 sy stems sintered at 300 °C, 400 °C and 500 °C, allow for the conclusion that the coercive field (Hc) decreases drastically with temperature and the percentage of soft phase at values of Hc = 132 Oe compared to the coercive field values reported for Nd2Fe14B Hc = 6883 Oe, respectively. Images obtained by transmission electron microscopy (TEM), for the Fe90Al10 system, show a tendency for the nanoparticles to agglomerate.
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Parapurath, Shahid, Arjun Ravikumar, Nader Vahdati et Oleg Shiryayev. « Effect of Magnetic Field on the Corrosion of API-5L-X65 Steel Using Electrochemical Methods in a Flow Loop ». Applied Sciences 11, no 19 (8 octobre 2021) : 9329. http://dx.doi.org/10.3390/app11199329.
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Limited studies have been conducted on the effect of a magnetic field on the corrosion behavior of steels. Investigating the effect on pipeline material in the oil and gas industries will be beneficial regarding corrosion prediction and control. In this work, the effect of a magnetic field on the corrosion process of API 5L X65 carbon steel was investigated in a well-developed flow loop using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Using permanent magnets and a well-designed corrosion electrode set-up, the corrosion mechanism of API 5L X65 steel was studied at different magnetic orientations and different flow conditions in a NaCl solution. The surface morphology of the corroded samples was studied using a scanning electron microscope, and the micro-morphologies of the corrosion deposits and the surface elemental composition were analyzed. The results show that the presence of a magnetic field increases the corrosion rate of API 5L X65 carbon steel, and that flow velocities and magnetic orientation have a significant influence on the anodic corrosion current. The results of the polarization curves indicate a negative shift in the Tafel curve, leading to an increase in the corrosion rate with the introduction of a magnetic field in the flow system. The results of the EIS show that the charge transfer rate is decreased when a magnetic field is applied. This work provides important direction in terms of the understanding of the combined effect of magnetism and flow on the corrosion in pipelines used in the oil and gas industries.