Academic literature on the topic 'Magnetic nanoparticles, permanent magnets, magnetism'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Magnetic nanoparticles, permanent magnets, magnetism.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Magnetic nanoparticles, permanent magnets, magnetism"
1
Sotelo, Diana C., Nancy Ornelas-Soto, and Johann F. Osma. "Novel Magnetic Polymeric Filters with Laccase-Based Nanoparticles for Improving Congo Red Decolorization in Bioreactors." Polymers 14, no. 12 (June 8, 2022): 2328. http://dx.doi.org/10.3390/polym14122328.
Full textAbstract:
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.
2
Bagabas, Abdulaziz A., Khalil A. Ziq, Ahmad F. Salem, and Emad S. Addurihem. "Magnetic Properties of Some Hydrated Transition Metal Oxide and Hydroxide Nanoparticles Synthesized in Different Media." Advanced Materials Research 123-125 (August 2010): 727–30. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.727.
Full textAbstract:
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.
3
Panina, Larissa V., Anastasiya Gurevich, Anna Beklemisheva, Alexander Omelyanchik, Kateryna Levada, and Valeria Rodionova. "Spatial Manipulation of Particles and Cells at Micro- and Nanoscale via Magnetic Forces." Cells 11, no. 6 (March 10, 2022): 950. http://dx.doi.org/10.3390/cells11060950.
Full textAbstract:
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.
4
Imarah, Ali O., Fausto M. W. G. Silva, László Tuba, Ágnes Malta-Lakó, József Szemes, Evelin Sánta-Bell, and 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 (September 17, 2022): 1065. http://dx.doi.org/10.3390/catal12091065.
Full textAbstract:
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.
5
Frolova, Liliya A. "Investigation of Magnetic and Photocatalytic Properties of CoFe2O4 Doped La3+, Nd3+, I3+." ECS Meeting Abstracts MA2022-01, no. 30 (July 7, 2022): 2496. http://dx.doi.org/10.1149/ma2022-01302496mtgabs.
Full textAbstract:
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.
6
Liu, Yuan, Jie Lai, and Yun Liu. "Preparation, Characterization, and Microwave Absorption Properties of Cobalt-Doped SrFe12O19 Nanoparticles." Journal of Nanoelectronics and Optoelectronics 16, no. 6 (June 1, 2021): 998–1004. http://dx.doi.org/10.1166/jno.2021.3042.
Full textAbstract:
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.
7
Takeda, Shin-Ichi, Bungo Terazono, Fumihito Mishima, Hironori Nakagami, Shigehiro Nishijima, and Yasufumi Kaneda. "Novel Drug Delivery System by Surface Modified Magnetic Nanoparticles." Journal of Nanoscience and Nanotechnology 6, no. 9 (September 1, 2006): 3269–76. http://dx.doi.org/10.1166/jnn.2006.483.
Full textAbstract:
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.
8
Kaphle, Kishor, Gyanendra Karki, and 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 (February 16, 2020): 150–60. http://dx.doi.org/10.3126/jie.v15i1.27724.
Full textAbstract:
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.
9
Forringer, Edward Russell. "Measuring and Modeling the Force between Permanent Magnets." Physics Teacher 60, no. 7 (October 2022): 546–48. http://dx.doi.org/10.1119/5.0058797.
Full textAbstract:
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.
10
Haneda, K. "Recent advances in the magnetism of fine particles." Canadian Journal of Physics 65, no. 10 (October 1, 1987): 1233–44. http://dx.doi.org/10.1139/p87-198.
Full textAbstract:
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.
Dissertations / Theses on the topic "Magnetic nanoparticles, permanent magnets, magnetism"
1
Matsumoto, Kenshi. "Crystal Structural Control of Nanomaterials toward High-Performance Permanent Magnets." Kyoto University, 2019. http://hdl.handle.net/2433/245309.
Full text
2
Anagnostopoulou, Evangelia. "A new route for rare-earth free permanent magnets : synthesis, structural and magnetic characterizations of dense assemblies of anisotropic nanoparticles." Thesis, Toulouse, INSA, 2016. http://www.theses.fr/2016ISAT0045/document.
Full textAbstract:
Cette thèse a eu pour objectif la préparation d’aimants nanostructurés sains terres rares à base d’un assemblage dense de nanobâtonnets de cobalt (Co NBs). Nous avons démontré la faisabilité d’un changement d’échelle du procédé polyol, avec des conditions d’agitation contrôlées, pour obtenir 5 g de NBs monodisperse. La modification de l’agent nucléant nous a permis de contrôler la taille et la forme des NBs conduisant à des valeurs élevées de champ coercitif. La réalisation d’aimants macroscopiques denses et robustes a été possible via la dispersion des bâtonnets dans du chloroforme et son évaporation sous champ magnétique à température ambiante. La valeur de (BH)max résultante a atteint dans le meilleur des cas une valeur de 165 kJ·m-3. Des résultats préliminaires sur la compaction d’assemblées de NBs montre que la fraction volumique magnétique peut être augmenté significativement (jusqu’à 30%). Cette étude prouve que l’approche « bottom-up» est très prometteuse pour obtenir des nouveaux matériaux magnétiques durs qui peuvent compléter le panorama des aimants permanents et combler le fossé entre les ferrites et les aimants NdFeBThe objective of this thesis is the preparation of nanostructured rare earth free permanent magnets based on dense assemblies of Co nanorods. We demonstrate the up-scaling of the polyol process for the synthesis of 5 g of monodispersed cylindrical Co NR with controlled cylindrical-like shape. Modification of the nucleating agent allows optimizing further the nanorods’ shape, leading to the highest coercivity values measured. Dense and robust macroscopic magnets were obtained via the rods’ alignment under a magnetic field presenting an ideal hysteresis loop. Additional structural and magnetic characterization was accomplished via small angle neutron scattering. A quantitative assessment of the (BH)max values showed a maximum of 165 kJ·m-3. Preliminary compaction experiments resulted in the fabrication of bulk magnets with increased magnetic volume fraction (up to 30%). We prove that the bottom-up approach is very promising to get new hard magnetic materials that can compete in the permanent magnet panorama and fill the gap between the ferrites and the NdFeB magnets
3
Pousthomis, Marc. "De la synthèse chimique de nanoparticules aux matériaux magnétiques nano-structurés : une approche pour des aimants permanents sans terre rare." Thesis, Toulouse, INSA, 2016. http://www.theses.fr/2016ISAT0012/document.
Full textAbstract:
La fabrication d’aimants permanents nano-structurés est l’une des solutions envisagées pour remplacer les aimants actuels à base de terres rares, pour lesquelles se posent des problèmes géopolitiques et environnementaux. Dans le but d’élaborer de tels matériaux, nous avons suivi une approche bottom-up utilisant des méthodes chimiques.Nos travaux ont visé dans un premier temps à synthétiser des nanoparticules (NPs) magnétiques dures qui peuvent servir de briques élémentaires dans la fabrication d’aimants nano-structurés. Notre étude systématique sur des nanobâtonnets de cobalt (NBs Co) synthétisés par voie polyol, a montré que leur champ coercitif augmente de 3 à 7 kOe avec la diminution du diamètre et l’augmentation du rapport d’aspect structural. Des simulations micro-magnétiques ont montré qu’un mécanisme de retournement d’aimantation par nucléation-propagation de parois rendait compte des résultats expérimentaux. Des NPs bi-métalliques FePt et tri-métalliques FePtX (X = Ag, Cu, Sn, Sb) de structure CFC ont été obtenues par l’adaptation d’une synthèse organométallique ou par la réduction d’acétylacétonates métalliques. Les recuits à haute température (650°C pour FePt, 400°C pour FePtX) ont conduit à la transition de phase FePt CFC L10 et à des champs coercitifs élevés (>12 kOe). La maîtrise d’un procédé multi-étapes, impliquant la protection des NPs FePt CFC par une coquille MgO et un recuit à 850°C, a permis d’obtenir des NPs FePt L10 de taille moyenne 10 nm présentant des champs coercitifs jusqu’à 27 kOe.La seconde partie de nos travaux a porté sur l’assemblage de NPs présentant des anisotropies différentes. Deux systèmes ont été étudiés : FePt CFC+FeCo CC, FePt L10+NBs Co HCP. Dans les deux cas, le contact entre les deux types de NPs a été favorisé par l’utilisation d’un ligand bi-fonctionnel suivi d’un traitement thermique. Dans le système FePt+FeCo, le recuit à haute température (650°C), nécessaire pour obtenir la phase FePt L10, a entraîné l’inter-diffusion des phases et la quasi-disparition de la phase FeCo CC. Dans le second système FePt+Co, un comportement de spring magnet a clairement été identifié, les deux phases étant efficacement couplées. L’inter-diffusion des phases a été limitée par la température modérée du recuit (400°C). Un champ coercitif de 10 kOe a été mesuré pour une teneur en Pt de seulement 25%at., malgré la perte de la forme anisotrope des NBs CoThe production of nano-structured permanent magnets is a promising alternative to rare earth magnets, which induced geopolitical and environmental issues. In order to elaborate such materials, we followed a bottom-up approach based on chemical methods. A first objective consisted in synthesizing hard magnetic nanoparticles (NPs) as building blocks for nano-structured magnets. The properties of cobalt nanorods (Co NRs) synthesized by the polyol process have been systematically studied. Coercive fields could be raised from 3 to 7 kOe by decreasing the diameter and improving the structural aspect ratio. Micro-magnetic simulations showed that a magnetization reversal following a nucleation and domain-wall propagation process could explain the experimental results. Bi-metallic FePt and tri-metallic FePtX (X = Ag, Cu, Sn, Sb) exhibiting the FCC structure were synthesized following two routes based on the reduction of an organometallic Fe precursor or of metallic acetylacetonates. Annealing at high temperatures (650°C for FePt, 400°C for FePtX) allowed the phase transition FCC L10 to occur, leading to high coercive fields (>12 kOe). A multi-steps process, involving the protection of FePt NPs with an MgO shell and an annealing at 850°C, was optimized to produce L10 FePt NPs with a mean size of 10 nm and a coercivity up to 27 kOe. In the second part of our study, we worked on assemblies of NPs with different magnetic anisotropies. Two systems were studied : FCC FePt+BCC FeCo, L10 FePt+HCP Co NRs. In both cases, the contact between the two types of NPs was favored by the presence of a bi-functional ligand followed by an annealing step. Concerning the FePt+FeCo system, the high temperature annealing (650°C), required to get the L10 FePt phase, led to the inter-diffusion of the phases and to the dissolution of the BCC FeCo phase. For the FePt+Co system, a spring magnet behavior has been clearly evidenced, the two phases being efficiently coupled The inter-diffusion of the phases was limited thanks to the fairly low annealing temperature (400°C). A coercive field of 10 kOe was measured for a Pt content as low as 25%at., eventhough the Co NRs anisotropic morphology was lost
4
Fersi, Riadh. "Intermétalliques magnétiques praséodyme-cobaltnanostructurés : étude multiéchelle et optimisation." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1127.
Full textAbstract:
Ce travail s'inscrit dans le cadre général de l'étude structurale et magnétique de nanomatériaux magnétiques à base de terres rares (R) et de métaux de transition (T) dont le domaine d'application concerne les aimants permanents ou l'enregistrement magnétique à haute densité. Dans la recherche de nouvelles phases aux caractéristiques magnétiques performantes, nous nous sommes intéressés à l'alliage Pr2Co7 . Ce composé a des propriétés magnétiques dures intéressantes : température de Curie élevée et une anisotropie magnéto-cristalline uniaxiale importante. Du point de vue magnétique, les interactions d'échange Co-Co sont les plus fortes, suivies par les interactions R-Co, tandis que les interactions R-R sont très faibles. La dominance des interactions Co-Co induit des températures de Curie assez élevée dans les composés Pr2Co7 . L'anisotropie magnétocristalline résulte de la combinaison de deux anisotropies uniaxiales des réseaux de praséodyme et de cobalt. Afin de renforcer ces interactions, il s'avère nécessaire de substituer partiellement le cobalt dans les composés Pr2Co7 par un élément approprié tel que le fer qui a un rayon légèrement plus gros que celui du cobalt ou par insertion d'un élément léger tel qu’hydrogène ou le carbone qui peuvent augmenter les distances interatomiques et renforcer le moment magnétique. De plus, parallèlement à des propriétés magnétiques intrinsèques performantes, il est nécessaire d'optimiser les propriétés magnétiques extrinsèques de l'alliage par la recherche d'un état nonocristallin convenable correspondant aux applications potentielles. Les propriétés extrinsèques des composés Pr2Co7 n'ont été que très peu étudiées. Plusieurs méthodes ont été utilisées pour l'élaboration des nanomatériaux. Dans notre étude, nous avons mis en œuvre la technique de broyage à haute énergie suivie d'une recristallisation contrôlée, méthode de synthèse qui jusque-là n'avait pas encore été utilisée pour synthétiser ce type de composé. À cette échelle, la taille des grains devient de l'ordre de grandeur de la longueur d'échange. Cette méthode qui constitue un processus de synthèse hors équilibre, permet l'obtention de poudres nanostructurées métastables à partir d'un mélange de poudres élémentaires. Cette technique est particulièrement efficace dans le cas des alliages à base de terre rares (Pr, Sm...) qui sont extrêmement volatil. En effet, elle permet d'éviter l'état liquide puisque la réaction a lieu en dessous de la température de fusion et conduit à des quantités importantes reproductibles et homogènes d'alliages. Nous avons utilisé différentes méthodes de caractérisation à savoir : la diffraction de rayon X (DRX), la microscopie électronique à transmission (MET) couplée avec l'analyse EDX,la Magnéto/susceptométre Manics DSM-8This work falls within the general framework of the structural and magnetic nanomaterials based magnetic rare earth (R) and transition metal (T) whose domain of application concerns the permanent magnets or magnetic recording high density. In search of new magnetic phases in performance characteristics, we were interested in the alloy Pr2Co7. This compound has interesting hard magnetic properties: high Curie temperature and uniaxial magnetocrystalline anisotropy important. From the perspective of magnetic exchange interactions Co-Co are the strongest, followed by R-Co interaction, while the RR interactions are very weak. The dominance of Co-Co interactions induces relatively high Curie temperatures in compounds Pr2Co7.The magnetocrystalline anisotropy results from the combination of two networks uniaxial anisotropy praseodymium and cobalt. To strengthen these interactions, it is necessary to partially substitute cobalt in compounds Pr2Co7 by an appropriate element such as iron which has a radius slightly larger than that of cobalt or by insertion of a light element the hydrogen and carbon that can increase the interatomic distances and enhance the magnetic moment. Moreover, along with intrinsic magnetic properties improves, it is necessary to optimize the extrinsic magnetic properties of the alloy by the search for a suitable nanocrystalline state corresponding to the potential applications. The extrinsic properties of compounds Pr2Co7 have been little studied.Several methods were used for the development of nanomaterials. In our study, we have W arranty the technique of high energy milling followed by recrystallization controlled synthesis method which until then had not yet been used to synthesize this type of compound. At this scale, the grain size becomes of the order of magnitude of the exchange length. This method which is a non-equilibrium synthesis process, allows the production of nanostructured powders metastable from a mixture of elemental powders. This technique is particularly effective in the case of alloys based on rare earth (Pr, Sm ...) that are extremely volatile. Indeed, it avoids the liquid state since the reaction takes place below the melting temperature and led to reproducible and large quantities of homogeneous alloys. We used different characterization methods, namely: the X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with EDX analysis, the magneto / susceptometer Manics DSM-8
5
Patel, Anup. "Pulsed field magnetization of composite superconducting bulks for magnetic bearing applications." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/256579.
Full textAbstract:
Permanent magnets are essential components for many devices such as motors, which currently account for 45 % of global electricity consumption, generators and also superconducting magnetic bearings used for applications such as flywheel energy storage. But even the most powerful rare-earth magnets are limited to a remanent field of 1.4 T, whereas superconducting materials such as YBCO in their bulk form have the extraordinary ability to trap magnetic fields an order of magnitude higher, whilst being very compact. This gives them the potential to increase efficiency and allow significant volume and weight reductions for rotating machines despite the need for cooling. A new design of superconducting magnetic bearing has been developed which uses magnetized bulks as the field source, eliminating permanent magnets. Finite element modelling shows that the bulk – bulk design can achieve much higher force densities than existing permanent magnet – bulk designs, giving it potential to be used as a compact magnetic bearing. A system was created to magnetize bulks using a pulsed magnetic field down to 10 K and then measure levitation force. In proving the concept of the proposed design, the highest levitation forces ever reported between two superconducting bulks were measured, including a levitation force of 500 N between a 1.7 T magnetized YBCO bulk and a coaxial $MgB_{2}$ bulk tube. The biggest factor limiting the use of magnetized bulks in applications is magnetizing them in the first place. Using a pulsed magnetic field is most practical but generates excessive heat dissipation leading to a loss of flux in conventional bulk superconductors, which are 100% superconductor. Although multi-pulse techniques help maximise the trapped field, the poor thermal properties of bulk (RE)BCO are a limiting factor. New composite superconducting structures are reported which can overcome these problems by using high thermal conductivity materials, the motivation for which came from finite element modelling of the critical state coupled with heat transfer. In particular, composite structures created by cutting and stacking 12 mm wide (RE)BCO superconducting tape are shown experimentally to have exceptional field trapping ability due to superior thermal and mechanical properties compared to existing bulks. Up to 2 T was trapped in a stack of commercially available tape produced by SuperPower Inc. in the first reported pulsed magnetization of such a stack. Over 7 T was trapped between two stacks using field cooling at 4.2 K, the highest field yet trapped in such a sample.
6
Cedervall, Johan. "Magnetic Materials for Cool Applications : Relations between Structure and Magnetism in Rare Earth Free Alloys." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331762.
Full textAbstract:
New and more efficient magnetic materials for energy applications are a big necessity for sustainable future. Whether the application is energy conversion or refrigeration, materials based on sustainable elements should be used, which discards all rare earth elements. For energy conversion, permanent magnets with high magnetisation and working temperature are needed whereas for refrigeration, the entropy difference between the non-magnetised and magnetised states should be large. For this reason, magnetic materials have been synthesised with high temperature methods and structurally and magnetically characterised with the aim of making a material with potential for large scale applications. To really determine the cause of the physical properties the connections between structure (crystalline and magnetic) and, mainly, the magnetic properties have been studied thoroughly. The materials that have been studied have all been iron based and exhibit properties with potential for the applications in mind. The first system, for permanent magnet applications, was Fe5SiB2. It was found to be unsuitable for a permanent magnet, however, an interesting magnetic behaviour was studied at low temperatures. The magnetic behaviour arose from a change in the magnetic structure which was solved by using neutron diffraction. Substitutions with phosphorus (Fe5Si1-xPxB2) and cobalt (Fe1-xCox)5PB2 were then performed to improve the permanent magnet potential. While the permanent magnetic potential was not improved with cobalt substitutions the magnetic transition temperature could be greatly controlled, a real benefit for magnetic refrigeration. For this purpose AlFe2B2 was also studied, and there it was found, conclusively, that the material undergoes a second order transition, making it unsuitable for magnetic cooling. However, the magnetic structure was solved with two different methods and was found to be ferromagnetic with all magnetic moments aligned along the crystallographic a-direction. Lastly, the origin of magnetic cooling was studied in Fe2P, and can be linked to the interactions between the magnetic and atomic vibrations.
7
Lendínez, Escudero Sergi. "Magnetization dynamics at the nanoscale in nanoparticles and thin films: single-molecule magnets, magnetic vortices, and magnetic droplet solutions." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/395194.
Full textAbstract:
Research in magnetic materials leads to new devices and technologies. As the technology progresses, the devices become smaller and this miniaturization allows more storage capacity and lower costs in the production of new technologies. As new and smaller materials are fabricated, new phenomena appear and thus new physics is needed to describe them. Nanomaterials meet characteristics of both the microscopic quantum world and the macroscopic classic world. This intermediate length scale is known as mesoscale. Nanomaterials can be obtained in a variety of forms, being nanoparticles and magnetic ultra-thin films some of the most used. These magnetic systems are very different in their composition: nanoparticles are grown with chemical reactions, and thin films are grown on a substrate by nanofabrication techniques such as sputtering or electron-beam evaporation. The magnetization might not be uniform in a magnetic thin film or in a large magnetic nanoparticle leading to the formation of magnetic domains. Magnetic domains are static structures that appear due to competition of the different magnetic energies and can be used to store and transport information.
In all these systems, the magnetization dynamics gives rise to new behavior not visible in static measurements: quantum steps of the magnetization in molecular magnets; characteristic resonant frequencies that can be used to control the magnetic state of vortices; and formation of magnetic droplet solitons in thin films with perpendicular magnetic anisotropy.
Understanding the dynamics of nanomaterials and the evolution of the magnetization is a key process to develop faster devices and technologies. The early studies of molecular magnets showed quantum effects at the macroscopic scale, which have allowed a better understanding of spin. Magnetic vortices have been proposed for multiple applications, from magnetic storage of information to cancer cell destruction. The recently discovered magnetic droplet soliton is also a very good candidate for technological applications due to the low current and magnetic field needed for its generation, and it is now a system with a growing interest in spintronics.
In this dissertation we show some new dynamic phenomena. In the first part of the thesis we study systems that allow a macroscopic-spin model where spatial variations of magnetization are neglected. We develop a theory that sets the requirements for the observation of the rotational Doppler effect in a ferromagnetic system and we measure quantum effects in randomly oriented nanoparticles of a single-molecule magnet, which might be a good candidate for the observation of the Doppler effect. In the second part of the thesis, we study the magnetization dynamics in macroscopic systems that require a spatial dependence of the magnetic moment. We generate and control the dynamic states of the magnetic domains with oscillating fields, in the case of magnetic vortices, and with electrical currents, in the case of droplet solitons.La investigación en materiales magnéticos ha dado lugar a nuevos dispositivos y tecnologías. A medida que la tecnología progresa, los dispositivos se hacen más pequeños. Esto permite una mayor capacidad de almacenamiento y reducir los costes de producción. A medida que se fabrican materiales más pequeños, surgen nuevos comportamientos. Los nanomateriales reúnen características tanto del mundo cuántico microscópico como del mundo clásico macroscópico. Esta escala de longitud se conoce como mesoescala. Existen variedad de forms de nanomateriales, entre las cuales nanopartículas y capas magnéticas ultrafinas. La composición de estos sistemas es diversa: las nanopartículas se obtienen a partir de reacciones químicas y las capas finas se crecen en un sustrato mediante técnicas de nanofabricación. La magnetización en las capas finas o en nanopartículas magnéticas grandes puede no ser uniforme, lo que lleva a la formación de dominios magnéticos. En todos estos sistemas, la dinámica de la magnetización da lugar a un nuevo comportamiento que no es visible en las mediciones estáticas: fenómenos cuánticas de la magnetización en imanes moleculares; frecuencias de resonancia características que se pueden utilizar para controlar el estado magnético de los vórtices; y la formación de solitones “droplet” magnéticos en capas finas con anisotropía magnética perpendicular. La comprensión de la dinámica de los nanomateriales y la evolución de la magnetización es un proceso clave para el desarrollo de dispositivos y tecnologías más rápidas. Los primeros estudios de imanes moleculares mostraron efectos cuánticos a escala macroscópica, que han permitido una mejor comprensión del espín. Los vórtices magnéticos se han propuesto para múltiples aplicaciones, desde el almacenamiento magnético de la información a la destrucción de células de cáncer. El solitón “droplet” magnético, descubierto recientemente, es también muy buen candidato para aplicaciones tecnológicas debido al bajo campo magnético y baja corriente necesarios para su generación. En esta tesis se muestran algunos nuevos fenómenos dinámicos. En la primera parte de la tesis, estudiamos sistemas que permite un modelo de macroespín, en el que no hay variaciones espaciales de la magnetización. En la segunda parte estudiamos la dinámica en sistemas con dominios magnéticos, lo cual requiere una dependencia espacial de la magnetización.
8
Silva, Tiago Luis da. "Síntese e auto-organização de nanopartículas ferromagnéticas metálicas visando aplicações em gravação magnética de ultra-alta densidade e imãs permanentes de elevado desempenho." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-24082015-094349/.
Full textAbstract:
Nanomateriais de fct-FePt, SmCo e Carbeto de Cobalto têm sido bastante estudados para a aplicação em gravação magnética e imãs de elevado desempenho, devido as suas energias magnetocristalinas e coercividades elevadas. Nanopartículas de FePt unidimensionais foram propostas na tentativa de obter melhora no alinhamento magnético das estruturas auto-organizadas. Neste trabalho, a formação de nanobastão e nanofios de FePt foi estudada através da presença de oleilamina e pequena quantidade de monóxido de carbono liberado pelo pentacarbonilferro(0). Estes dois parâmetros foram estudados a fim de analisar a influência no alongamento das nanopartículas e verificou-se que ambos atuam sinergicamente. Foram obtidos tanto nanofios de FePt ramificados de comprimento de 20-100 nm quanto nanobastões de FePt de 20-60 nm de comprimento, ambos com diâmetro de 2-3 nm. Todas as nanopartículas sintetizadas foram obtidas na fase cúbica de face centrada e o processo de tratamento térmico nas temperaturas de 450 oC e 560 oC levou a conversão para a fase tetragonal de face centrada, com custo da sinterização das nanopartículas. Os nanobastões, entretanto, apresentaram maior estabilidade térmica se comparado com o nanofio ramificado, obtendo propriedade ferromagnética na amostra. Alternativamente, têm sido obtidos satisfatoriamente nanobastões de platina para posterior recobrimento com ferro para a formação da liga FePt após o processo de recozimento. Na síntese de SmCo, foi estudada a formação da liga diretamente por via química através do uso de redutores comumente utilizandos em síntese de nanopartículas, porém foi possível observar apenas uma pequena quantidade da liga Sm2Co17 quando se utiliza o boroidreto de sódio. Isto se deve, principalmente, ao alto potencial de redução de Sm3+ e a sua instabilidade química. Entretanto, foram desenvolvidos métodos promissores para a obtenção de nanopartículas de CoO e SmCoO com tamanho e forma controlada. Além destes sistemas, tem sido obtidas diretamente através de síntese química nanopartículas de carbeto de cobalto com coercividade de até 2,3 kOe e magnetização de 45 emu/g, além de desenvolver um método geral de síntese de carbetos de outros metais.SmCo, fct-FePt and CoC nanomaterials have been studied for application in magnetic recording and permanent magnets due to theirs high coercivity and magnetocrystalline anisotropy. One-dimensional FePt nanoparticles were proposed to improve the magnetic alignment of self-assembled system. In this work, the formation of FePt nanorods and nanowires was studied by using a small amount of carbon monoxide from the precursor pentacarbonyliron(0) and oleylamine. Both parameters of synthesis were studied and was verified that they influence the one-dimensional growth of FePt. In fact, branched FePt nanowires with 20 - 100 nm of length and nanorods with 20 - 60 nm were obtained, both with 2-3 nm of diameters. The FePt nanoparticles were obtained in face centered cubic phase and the transformation to face centered tetragonal phase was carry out in the temperatures of 450 oC and 560 oC, which led the formation of sintered nanoparticles. FePt nanorods have better thermal stability than nanowires according the results obtained. The platinum nanorods covered with iron oxide also were obtained to formation of FePt by thermal treatment. In concern of SmCo syntheses, the formation of SmCo phase directly by chemical synthesis was investigated by using some reduction agent, but was obtained a small amount of smco phase only if the sodium borohydrate was used in the synthesis. This could be occurred due to high reducing potential of Sm3+ and its chemical instability. However, some methods were obtained to obtain CoO and SmCoO nanoparticles with size and shape control. Furthermore, cobalt carbide nanoparticles were well obtained with coercivity of 2,3 kOe and magnetization of 45 emu/g, and a new general method to obtain metals carbides was developed.
9
Edström, Alexander. "Theoretical and Computational Studies on the Physics of Applied Magnetism : Magnetocrystalline Anisotropy of Transition Metal Magnets and Magnetic Effects in Elastic Electron Scattering." Doctoral thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304666.
Full textAbstract:
In this thesis, two selected topics in magnetism are studied using theoretical modelling and computational methods. The first of these is the magnetocrystalline anisotropy energy (MAE) of transition metal based magnets. In particular, ways of finding 3d transition metal based materials with large MAE are considered. This is motivated by the need for new permanent magnet materials, not containing rare-earth elements, but is also of interest for other technological applications, where the MAE is a key quantity. The mechanisms of the MAE in the relevant materials are reviewed and approaches to increasing this quantity are discussed. Computational methods, largely based on density functional theory (DFT), are applied to guide the search for relevant materials. The computational work suggests that the MAE of Fe1-xCox alloys can be significantly enhanced by introducing a tetragonality with interstitial B or C impurities. This is also experimentally corroborated. Alloying is considered as a method of tuning the electronic structure around the Fermi energy and thus also the MAE, for example in the tetragonal compound (Fe1-xCox)2B. Additionally, it is shown that small amounts (2.5-5 at.%) of various 5d dopants on the Fe/Co-site can enhance the MAE of this material with as much as 70%. The magnetic properties of several technologically interesting, chemically ordered, L10 structured binary compounds, tetragonal Fe5Si1-xPxB2 and Hexagonal Laves phase Fe2Ta1-xWx are also investigated. The second topic studied is that of magnetic effects on the elastic scattering of fast electrons, in the context of transmission electron microscopy (TEM). A multislice solution is implemented for a paraxial version of the Pauli equation. Simulations require the magnetic fields in the sample as input. A realistic description of magnetism in a solid, for this purpose, is derived in a scheme starting from a DFT calculation of the spin density or density matrix. Calculations are performed for electron vortex beams passing through magnetic solids and a magnetic signal, defined as a difference in intensity for opposite orbital angular momentum beams, integrated over a disk in the diffraction plane, is observed. For nanometer sized electron vortex beams carrying orbital angular momentum of a few tens of ħ, a relative magnetic signal of order 10-3 is found. This is considered realistic to be observed in experiments. In addition to electron vortex beams, spin polarised and phase aberrated electron beams are considered and also for these a magnetic signal, albeit weaker than that of the vortex beams, can be obtained.Felaktigt ISBN i den tryckta versionen: 9789155497149
10
Nakouri, Kalthoum. "Synthèse et caractérisation de poudres magnétiques pour aimants nanocomposites." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR098.
Full textAbstract:
La réalisation d’aimants permanents nanocomposites constitués d’un mélange d’une phase magnétique dure, de coercitivité élevée, et d’une phase magnétique douce, d’aimantation élevée, est une des possibilités d’obtenir de nouveaux matériaux pour aimants permanents sans terres rares. Dans ce travail, le choix s’est porté sur la phase Fe65Co35 comme phase douce et sur la phase SrFe12O19 comme phase dure. Des poudres nanométriques ont été synthétisées par voie chimique, en adaptant des procédés existants. Des nanoparticules Fe65Co35 d’une taille d’environ 10 nm ont été synthétisées par la méthode polyol, en présence de RuCl3 comme agent nucléant. La synthèse de nanoparticules SrFe12O19 a été effectuée par une méthode dite «sol-gel modifiée» mise au point dans le cadre de ce travail. Cette méthode, qui consiste en une calcination dans une matrice de NaCl, a permis d’obtenir des nanoparticules monodomaines bien dispersées et possédant des propriétés magnétiques supérieures à celles obtenues par voie sol-gel classique. L’assemblage des phases dure et douce a été effectué par méthode «in-situ», pour laquelle des nanoparticules de SrFe12O19 sont introduites dans le milieu réactionnel lors de la synthèse des nanoparticules de Fe65Co35. Un couplage d’échange magnétique a été obtenu pour les nanocomposites avec des teneurs de 5% et 10% de phase Fe65Co35The synthesis of nanocomposite permanent magnets composed of a mixture of a hard magnetic phase, with high coercivity, and of a soft magnetic phase, with high magnetization, is one of the possible paths to obtain new rare earth free permanent magnets materials. In this work, the Fe65Co35 phase has been chosen as the soft phase and the SrFe12O19 phase has been chosen as the hard phase. Nanometric powders have been chemically synthesized, adapting existing processes. Fe65Co35 nanoparticles about 10 nm in size were synthesized by the polyol method, in the presence of RuCl3 as nucleating agent. The synthesis of SrFe12O19 nanoparticles was carried out by a so-called “modified sol-gel” method developed in this work. This method, which consists of calcination in a NaCl matrix, allows obtaining monodomain nanoparticles that are well dispersed and have magnetic properties superior to those obtained by the conventional sol-gel route. The assembly of hard and soft phases was carried out by a so-called "in-situ" method, for which SrFe12O19 nanoparticles are introduced into the reaction medium during the synthesis of the Fe65Co35 nanoparticles. Magnetic exchange coupling was obtained for nanocomposites with 5% and 10% Fe65Co35 phase contents
Books on the topic "Magnetic nanoparticles, permanent magnets, magnetism"
1
Kübler, Jürgen. Theory of Itinerant Electron Magnetism, 2nd Edition. 2nd ed. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895639.001.0001.
Full textAbstract:
The book, in the broadest sense, is an application of quantum mechanics and statistical mechanics to the field of magnetism. Under certain well-described conditions, an immensely large number of electrons moving in the solid will collectively produce permanent magnetism. Permanent magnets are of fundamental interest, and magnetic materials are of great practical importance as they provide a large field of technological applications. The physical details describing the many-electron problem of magnetism are presented in this book on the basis of the density-functional approximation. The emphasis is on realistic magnets, for which the equations describing properties of the many-electron problem can only be solved by using computers. The great recent and continuing improvements are, to a very large extent, responsible for the progress in this field. Along with an introduction to the density-functional theory, the book describes representative computational methods and detailed formulas for physical properties of magnets, which include among other things the computation of magnetic ordering temperatures, the giant magnetoresistance, magneto-optical effects, weak ferromagnetism, the anomalous Hall and Nernst effects, and novel quasiparticles, such as Weyl fermions and magnetic skyrmions.
2
Furst, Eric M., and Todd M. Squires. Magnetic bead microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0008.
Full textAbstract:
Magnetism is a convenient force for actively pulling colloidal particles in a material. Many materials of interest in a microrheology experiment have a negligible magnetic susceptibility, and so embedded magnetic particles can be subject to relatively strong forces by fields imposed from outside of the sample. These are usually generated by electromagnets, but can also include the use of permanent magnets, or a combination of both. Such “magnetic tweezers” are used as sensitive force probes, capable of generating forces ranging from femtonewtons to nanonewtons. Magnetic forces and magnetic materials are reviewed and magnetic tweezer designs discussed. Linear and non-linear measurements using magnetic tweezers are presented, including studies yield stress and shear thinning. The operating regime of magnetic tweezer microrheology is presented, which enables microrheology experiments to access stiffer materials.
3
Michels, Andreas. Magnetic Small-Angle Neutron Scattering. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198855170.001.0001.
Full textAbstract:
This book provides the first extensive treatment of magnetic small-angle neutron scattering (SANS). The theoretical background required to compute magnetic SANS cross sections and correlation functions related to long-wavelength magnetization structures is laid out; and these concepts are scrutinized based on the discussion of experimental neutron data. Regarding prior background knowledge, some familiarity with the basic magnetic interactions and phenomena, as well as scattering theory, is desired. The target audience comprises Ph.D. students and researchers working in the field of magnetism and magnetic materials who wish to make efficient use of the magnetic SANS method. Besides revealing the origins of magnetic SANS (Chapter 1), and furnishing the basics of the magnetic SANS technique (Chapter 2), much of the book is devoted to a comprehensive treatment of the continuum theory of micromagnetics (Chapter 3), as it is relevant for the study of the elastic magnetic SANS cross section. Analytical expressions for the magnetization Fourier components allow one to highlight the essential features of magnetic SANS and to analyze experimental data both in reciprocal (Chapter 4) and real space (Chapter 6). Chapter 5 provides an overview of the magnetic SANS of nanoparticles and so-called complex systems (e.g., ferrofluids, magnetic steels, spin glasses, and amorphous magnets). It is this subfield where major progress is expected to be made in the coming years, mainly via the increased use of numerical micromagnetic simulations (Chapter 7), which is a very promising approach for the understanding of the magnetic SANS from systems exhibiting nanoscale spin inhomogeneity.
Book chapters on the topic "Magnetic nanoparticles, permanent magnets, magnetism"
1
Buschow, K. H. J., and F. R. de Boer. "Permanent Magnets." In Physics of Magnetism and Magnetic Materials, 105–29. Boston, MA: Springer US, 2003. http://dx.doi.org/10.1007/0-306-48408-0_12.
Full text
2
de Moraes, Isabelle, and Nora M. Dempsey. "Nanocomposites for Permanent Magnets." In New Trends in Nanoparticle Magnetism, 403–33. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-60473-8_17.
Full text
3
McGrath, Andrew J., and Karthik Ramasamy. "Nanoparticles and nanocomposites for new permanent magnets." In Nanoscience, 60–90. Cambridge: Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/9781788017053-00060.
Full text
4
Laptoiu, Dan Constantin, Iulian Antoniac, and Aurora Antoniac. "Testing the Effect of Permanent Magnets on Magnetic Nanoparticles Ferrofluid – Targeted Delivery Inside Knee Articulation." In DAAAM Proceedings, 0937–38. DAAAM International Vienna, 2011. http://dx.doi.org/10.2507/22nd.daaam.proceedings.457.
Full text
5
Nascimento Correa, Tarcisio, Igor Nunes Taveira, Rogerio Presciliano de Souza Filho, and Fernanda de Avila Abreu. "Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools." In Biomineralization [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94465.
Full textAbstract:
Biomineralization in the microbial realm usually gives origin to finely structured inorganic nanomaterials. Perhaps, one of the most elegant bioinorganic processes found in nature is the iron biomineralization into magnetosomes, which is performed by magnetotactic bacteria. A magnetosome gene cluster within the bacterial genome precisely regulates the mineral synthesis. The spread and evolution of this ability among bacteria are thought to be a 2,7-billion-year process mediated by horizontal gene transfers. The produced magnetite or greigite nanocrystals coated by a biological membrane have a narrow diameter dispersibility, a highly precise morphology, and a permanent magnetic dipole due to the molecular level control. Approaches inspired by this bacterial biomineralization mechanism can imitate some of the biogenic nanomagnets characteristics in the chemical synthesis of iron oxide nanoparticles. Thus, this chapter will give a concise overview of magnetosome synthesis’s main steps, some hypotheses about the evolution of magnetosomes’ biomineralization, and approaches used to mimic this biological phenomenon in vitro.
6
Kennel, Charles F. "Introduction." In Convection and Substorms. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195085297.003.0004.
Full textAbstract:
In the year 1600, the the man about to become physician to Queen Elizabeth I of England published a long treatise summarizing his two decades of experimentation on magnetism. After disposing of such issues as whether garlic causes magnets to “lose their virtue” William Gilbert recounted his observations upon moving a compass over the surface of a permanent magnet that had been specially fashioned in the form of a sphere (Gilbert, 1893, 1958). The similarity between the compass readings on the surface of his magnet and those recorded in mariners’ charts led Gilbert to conclude that his magnet was a terrella, a little earth, and that our big earth is (among other things) a giant magnet. Gilbert’s little earth organized the pattern of compass readings not only on its surface but also in the space surrounding it. From this, he boldly asserted that the big earth’s magnetic influence continues far into empty space, where no mariner of his day could ever go. The profundity of this remark was not lost on Gilbert’s younger contemporary, Johannes Kepler, who found in it an explanation of the earth’s annual motion around the sun. Kepler reasoned more or less as follows (in modern language): Since the earth and the sun are both celestial bodies, they both should rotate, and they both should have magnetic fields surrounding them in space. Their two rotating fields interact somehow, somewhere, in the space between them, communicating the sun’s rotational motion to the earth and pushing the earth around its orbit. In this curious way, Kepler might have been the first to perceive that the sun acts upon terrestrial magnetism. He was not the last. In 1580, Kepler’s teacher, Michael Maestlin, had recorded an observation of a distinct region of oscillating luminosity in the northern sky, an aurora. The aurora had been a topic of scientific interest since Graeco-Roman antiquity [of particular importance was Aristotle’s (384-322 B.C.) discussion of it in his Meteorology], but it had become an object of superstition in the European Middle Ages, and scientific interest in it only began to re-emerge in the second half of the 16th century (Link, 1957).
Conference papers on the topic "Magnetic nanoparticles, permanent magnets, magnetism"
1
Suo, Jin, Sheng Tong, Michael McDaniel, Habib Samady, Robert W. Taylor, Gang Bao, and Don Giddens. "Numerical Simulation of Magnetic Nanoparticles Targeted at an Atherosclerotic Lesion in the Left Coronary Artery of Patient." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80029.
Full textAbstract:
A numerical investigation simulating feasibility of magnetic drug targeting (MDT) at an atherosclerotic lesion of the left coronary artery of a patient using iron nano-particles coated with a therapeutic agent is reported. Progression of a plaque in the left coronary artery over a six month period was previously determined by intravascular ultrasound (IVUS). The site where the progression is active is located on the leeward side of the plaque. The proximal segment of the left coronary artery including the lesion was reconstructed by our 3D IVUS technique, and a Doppler measurement provided velocity waveforms in the lumen. These data are used to simulate blood flow employing computational fluid dynamics (CFD). Wall shear stress (WSS) and flow pathlines show that few nanoparticles would reach the active lesion region of the plaque. Therefore, MDT is considered as a possible effective therapy. Numerical investigations are performed to examine the feasibility for treatment by modeling hypothetical magnet fields, iron nano-particles, and coronary artery flow conditions. The magnetic field in the lesion segment produced by a permanent magnet located outside the lumen is calculated. The motion of the nano-particles in the segment is a combined result of the velocities produced by hemodynamic and magnetic forces. Various particles and magnets are investigated in the simulations. Two kinds of results are presented: the distribution of the magnetic force produced by the magnets, and the quantity of captured particles at the lesion during various time intervals (number of heart beats).
2
Russo, Alessandro, Silvia Panseri, Tatiana Shelyakova, Monica Sandri, Chiara Dionigi, Alessandro Ortolani, Steve Meikle, et al. "Critical Long Bone Defect Treated by Magnetic Scaffolds and Fixed by Permanent Magnets." In ASME 2013 2nd Global Congress on NanoEngineering for Medicine and Biology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/nemb2013-93193.
Full textAbstract:
Diaphyseal bone defect represents a significant problem for orthopaedic surgeons and patients. In order to improve and fasten bone regenerating process we implanted HA biodegradable magnetized scaffolds in a large animal model critical bone defect. A critical long bone defect was created in 6 sheep metatarsus diaphysis; then we implanted a novel porous ceramic composite scaffold (20.0 mm in length; 6.00 mm inner diameter and 17.00 mm outer diameter), made of Hydroxyapatite that incorporates magnetite (HA/Mgn 90/10), proximally fixated by two small cylindrical permanent parylene coated NdFeB magnets (one 6.00 mm diameter magnetic rod firmly incorporated into the scaffold and one 8.00 mm diameter magnetic rods fitted into proximal medullary canal, both 10.00 mm long); to give stability to the complex bone-scaffold-bone, screws and plate was used as a bridge. Scaffolds biocompatibility was previously assessed in vitro using human osteoblast-like cells. Magnetic forces through scaffold were calculated by finite element software (COMSOL Multiphysics, AC/DC Model). One week after surgery, magnetic nanoparticles functionalized with vascular endothelial growth factor (VEGF) were injected at the mid portion of the scaffold using a cutaneous marker positioned during surgery as reference point. After sixteen weeks, sheep were sacrificed to analyze metatarsi. Macroscopical, radiological and microCT examinations were performed. Macroscopical examination shows bone tissue formation inside scaffold pores and with complete coverage of scaffolds, in particular at magnetized bone-scaffold interface. X-rays show a good integration of the scaffold with a good healing process of critical bone defect, and without scaffolds mobilization. These datas were confirmed by the microCT that shown new formation of bone inside the scaffolds, in particular at magnetized bone-scaffold interface. These preliminary results lead our research to exploiting magnetic forces to stimulate bone formation, as attested in both in vitro and in vivo models and to improve fixation at bone scaffold interface, as calculated by finite element software, and moreover to guide targeted drug delivery without functionalized magnetic nanoparticles dissemination in all body. Histological analysis will be performed to confirm and quantify bone tissue regeneration at both interfaces.
3
Masud, Md Abdulla Al, Noel D’Souza, Paris von Lockette, and Zoubeida Ounaies. "On the Dielectrophoretic and Magnetic Alignment of Magnetoactive Barium Hexaferrite-PDMS Nanocomposites." In ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3988.
Full textAbstract:
In this study, we demonstrate the electric and magnetic manipulation of nanoscale M-type Barium Hexaferrite (nBF) in polydimethylsiloxane (PDMS) to engineer a multifunctional nanocomposite with improved dielectric and magnetic properties. First, we synthesized the single crystal nBF via the hydrothermal synthesis route. The hydrothermal temperature, duration, and surfactant conditions were optimized to improve the magnetic properties of the nBFs, with further improvement achieved by post-annealing. The annealed nBFs were aligned dielectrophoretically (DEP) in the polymer matrices by applying an AC electric field. Under the influence of this electric field, nBFs were observed to rotate, align and form chains within the polymer matrix. Optical microscopy (OM) imaging was used to determine the electrical alignment conditions (duration, magnitude, and frequency) and these parameters were used to fabricate the composites. A Teflon setup with Indium Tin Oxide (ITO) coated Polyethylene Terephthalate (PET) was used, where the ITO coatings act as electrodes for the electric field-manipulation. To simultaneously apply the magnetic field, this Teflon setup is placed between two permanent magnets capable of generating a 0.6 T external magnetic field. Along with electric and magnetic fields, concurrent heating was applied to cure the PDMS and freeze the microstructure formed due to electric and magnetic fields. Upon completion of the curing step, parallel chain formation is observed under OM. The X-Ray Diffraction (XRD) results also confirm that the particles are magnetically oriented in the direction of the magnetic field within the chain. Vibrating Sample Magnetometry (VSM) measurements and dielectric spectroscopy are used to characterize the extent of anisotropy and improvement in dielectric and magnetic properties compared to random composites. We find that simultaneous electric and magnetic field alignment improves the dielectric properties by 12% compared to just magnetic alignment. We also observe 19% improved squareness ratio when both fields are applied. The possibility of simultaneous electrical and magnetic alignment of magnetic nanoparticles will open up new doors to manipulate and design particle-modified polymers for various applications.
4
Zhao, Nannan, Dianli Zhao, and Hongbin Ma. "Experimental Investigation of Magnetic Field Effect on the Magnetic Nanofluid Oscillating Heat Pipe." In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58170.
Full textAbstract:
The magnetic field effect on the oscillating motion and heat transfer in an oscillating heat pipe (OHP) containing magnetic nanofluid was investigated experimentally. The nanofluid consists of distilled water and Dysprosium (III) oxide nanoparticles with sizes less than 100 nm. A magnetic field was applied to the evaporating section of the OHP by using the permanent magnet. The heat pipes charged with magnetic nanofluids at mass ratios of 0.1%, 0.05%, and 0.01%, respectively, were tested. In addition, the effects of orientation and input power ranging from 50 W to 250 W on the heat transport capability of the heat pipe were investigated. The experimental results demonstrate that the magnetic field can affect the oscillating motions and enhance the heat transfer performance of the magnetic nanofluid OHP. The magnetic nanoparticles in a magnetic field can reduce the startup power of oscillating motion and enhance the heat transfer performance in a low input power.
5
Singh, Manpreet, Qimei Gu, Ronghui Ma, and Liang Zhu. "Temperature Distribution and Thermal Dosage Affected by Nanoparticle Distribution in Tumours During Magnetic Nanoparticle Hyperthermia." In ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/mnhmt2019-4233.
Full textAbstract:
Abstract Recent microCT imaging study has demonstrated that local heating caused a much larger nanoparticle distribution volume in tumors than that in tumors without localized heating, suggesting possible nanoparticle redistribution/migration during heating. In this study, a theoretical simulation is performed to evaluate to what extent the nanoparticle redistribution affects the temperature elevations and thermal dosage required to cause permanent thermal damage to PC3 tumors. Two tumor groups with similar sizes are selected. The control group consists of five PC3 tumors with nanoparticles distribution without heating, while the experimental group consists of another five resected PC3 tumors with nanoparticles distribution obtained after 25 minutes of local heating. Each generated tumor model is attached to a mouse body model by microCT scans. A previously determined relationship between the nanoparticle concentration distribution and the volumetric heat generation rate is implemented in the theoretical simulation of temperature elevations during magnetic nanoparticle hyperthermia. Our simulation results show that the average steady state temperature elevation in the tumors of the control group is higher than that in the experimental group when the nanoparticles are more spreading from the tumor center to tumor periphery (control group: 64.03±3.2°C vs. experimental group: 62.04±3.07°C). Further we assess the thermal dosage needed to cause 100% permanent thermal damage (Arrhenius integral Ω = 4) to the entire tumor, based on the assumption of unchanged nanoparticle distribution during heating. The average heating time based on the experimental setting from our previous studies demonstrates significantly different designs. Specifically, the average heating time for the control group is 24.3 minutes. However, the more spreading of nanoparticles to tumor periphery in the experimental group results in a much longer heating time of 38.1 minutes, 57° longer than that in the control group, to induce permanent thermal damage to the entire tumor. The results from this study suggest that the heating time needed when considering dynamic nanoparticle migration during heating is probably between 24 to 38 minutes. In conclusion, the study demonstrates the importance of including dynamic nanoparticle spreading during heating into theoretical simulation of temperature elevations in tumors to determine accurate thermal dosage needed in magnetic nanoparticle hyperthermia design.
6
Williams, Alicia, Ashok Sinha, Pavlos Vlachos, and Ishwar K. Puri. "Magnetic Targeting of Particle Transport Under Pulsatile Flow." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98124.
Full textAbstract:
Magnetic Drug Targeting (MDT) has been shown to be a promising technique to effectively deliver medicinal drugs via functionalized [1] magnetic particles to target sites during the treatment of cancer and other diseases [2,3,4]. In this paper, we investigate the interaction of steady and pulsatile flows injected with a ferrofluid, which is a colloidal suspension of superparamagnetic nanoparticles in a glass tube under the influence of a magnetic field. Ferrofluids are colloidal suspensions of single domain magnetic nanoparticles that are of the order of 10 nm in diameter. In this experiment, the ferrofluid particles were directed to a particular region of interest within a 10 mm diameter glass vessel by means of an applied localized magnetic field that originated outside of the vessel. The magnetic field was generated using a rare earth sintered permanent magnet which produced the magnetic field gradient required for inducing a body force on the volume of the ferrofluid. The experimental results reveal flows with rich dynamical phenomena. The aggregation of the ferrofluid produces a self-assembled hemispherical structure which dynamically interacts with the host flow. The aggregation generates an occlusion creating a flow field that is similar to that past an obstruction. However, since the structure itself is of a fluidic nature, it is subject to shear forces caused by the host fluid. In addition, the wake of the flow behind the aggregation creates vortices which are critical to study the stability of the ferrofluid aggregate. This paper presents a detailed investigation of the dynamics of the flow using Time-Resolved Digital Particle Image Velocimetry. To the best of the authors’ knowledge, these are the first quantitative, spatiotemporally resolved measurements documenting the interaction of a host fluid with a ferrofluid aggregate under steady or pulsatile flow conditions.
7
Jiajia Sun, Zongqian Shi, Jun Bai, Shenli Jia, and Pengbo Zhang. "Numerical investigation on the magnetic field of cylindrical permanent magnet for magnetic nanoparticles application." In 2015 IEEE 15th International Conference on Nanotechnology (IEEE-NANO). IEEE, 2015. http://dx.doi.org/10.1109/nano.2015.7388799.
Full text
8
Williams, Alicia M., and Pavlos P. Vlachos. "The Dynamics of Accumulating Ferrofluid Aggregates." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55101.
Full textAbstract:
The physics of steady and pulsatile flows laden with superparamagnetic nanoparticles in a square channel accumulating under the influence of a 0.5 Tesla permanent magnet are studied by means of focused shadowgraphs. The accumulation physics of these nanoscale particles is explored as functions of the flow type (steady and unsteady) and accumulation type (injected from the top of channel versus bottom of channel). Ferrofluid is accumulated by the steady injection of a streakline that enters the test section upstream of the magnet, where an aggregate forms. The interfacial phenomena resulting from the interaction of the ferrofluid with the bulk flow is resolved using shadowgraph imaging, where a digital camera captures the side view of the aggregate. Ferrofluid aggregate physics is examined both visually in the raw frames as well as by post-processing to determine the aggregate size evolution in time and couple that bulk information with interfacial behavior using the Proper Orthogonal Decomposition (POD). The shadowgraphs show that the aggregate exhibits different regimes based on bulk flow Reynolds number, which is varied between 100 and 1000, based on the mean flow rate. The aggregate exhibits stable behavior at low Reynolds numbers, where it stretches as it grows and minimal decay of the aggregate occurs. At moderate Reynolds numbers above 400, inertial forces dominate the dynamics, and aggregates do not attain the same size and height as in low Reynolds number cases. Therefore, the interaction of the aggregate with the bulk flow is diminished. The accumulation of ferrofluids is positively impacted by increased magnetic field gradients for some Reynolds numbers, while very high or low magnetic field gradients result in smaller, unstable aggregates. This work is the first to study the accumulation of ferrofluid aggregates over such a large parameter space, which reveals many physics that were previously unexplored in ferrohydrodynamics.
9
Zablotskii, Vitalii, José Martín Pastor, Silvia Larumbe, José Ignacio Pérez-Landazábal, Vicente Recarte, Cristina Gómez-Polo, Urs Häfeli, Wolfgang Schütt, and Maciej Zborowski. "High-Field Gradient Permanent Micromagnets for Targeted Drug Delivery with Magnetic Nanoparticles." In 8TH INTERNATIONAL CONFERENCE ON THE SCIENTIFIC AND CLINICAL APPLICATIONS OF MAGNETIC CARRIERS. AIP, 2010. http://dx.doi.org/10.1063/1.3530005.
Full text
10
Russo, A., S. Panseri, D. Casino, T. Shelyakova, A. Tampieri, N. Bock, V. Goranov, et al. "Innovative Magnetic Nanoparticles Approaches for Bone and Osteochondral Tissue Engineering." In ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13114.
Full textAbstract:
The necessity of new clinical approaches regarding musculoskeletal system regeneration is evident. Nowadays different strategies such as autografts, allografts also used in synergy with cell therapy are already used in clinical treatments for moderate defects, but they face significant limitations due to limited supply, and risk of immune rejection. Currently, the treatments of extended osteochondral and bone defects involve invasive permanent metallic prosthesis, challenging reconstructive procedures and long rehabilitation period. Despite that, the gold standard seems to be far to obtain.