Bibliografie tematiche / Bulk magnets

Letteratura scientifica selezionata sul tema "Bulk magnets"

Autore: Grafiati

Pubblicato: 8 giugno 2024

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Articoli di riviste sul tema "Bulk magnets":

Saito, Tetsuji, Masahiro Tanaka e Daisuke Nishio-Hamane. "Production of Mn-Ga Magnets". Materials 17, n. 4 (14 febbraio 2024): 882. http://dx.doi.org/10.3390/ma17040882.

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Mn-based magnets are known to be a candidate for use as rare-earth-free magnets. In this study, Mn-Ga bulk magnets were successfully produced by hot pressing using the spark plasma sintering method on Mn-Ga powder prepared from rapidly solidified Mn-Ga melt-spun ribbons. When consolidated at 773 K and 873 K, the Mn-Ga bulk magnets had fine grains and exhibited high coercivity values. The origin of the high coercivity of the Mn-Ga bulk magnets was the existence of the D022 phase. The Mn-Ga bulk magnet consolidated at 873 K exhibited the highest coercivity of 6.40 kOe.

Saito, Tetsuji, e Daisuke Nishio-Hamane. "Production of Nd-Fe-B bulk nanocomposite magnets by hot deformation". AIP Advances 13, n. 2 (1 febbraio 2023): 025040. http://dx.doi.org/10.1063/9.0000381.

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In this study, the effects of Nd70Cu30 alloy powder addition on the microstructures and magnetic properties of Nd4Fe77.5B18.5 hot-deformed magnets were investigated. The Nd4Fe77.5B18.5 hot-deformed magnets consisted of the α-Fe, Fe3B, and Nd2Fe14B phases and were found to be nanocomposite. The coercivity of the Nd4Fe77.5B18.5 bulk nanocomposite magnets increased with Nd70Cu30 alloy powder addition. It was found that the Nd70Cu30 alloy reacted with the α-Fe and Fe3B phases in the Nd4Fe77.5B18.5 bulk nanocomposite magnets and formed the Nd2Fe14B phase. The Nd-Fe-B bulk nanocomposite magnet with 30% Nd70Cu30 alloy exhibited a high remanence of 9.72 kG and a high coercivity of 2.65 kOe.

Ma, Jun. "The Effect of the Horizontal Distance between the Permanent Magnets on the Levitation Force in Hybrid Magnetic Levitation System". Advanced Materials Research 750-752 (agosto 2013): 987–90. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.987.

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It has been investigated that the interaction force in hybrid magnetic levitation systems with a GdBCO bulk superconductor and a permanent magnet system and two permanent magnets (PM2) and two cubic permanent magnets (PM3) system in their coaxial configuration at liquid nitrogen temperature. A single-domain GdBCO sample is of 20mm and 10mm in thickness, the permanent magnet PM1 is of rectangular parallelepiped shape, the permanent magnets PM2 and PM3 are of cubic shape; the system placed on the middle of system and their coaxial configuration; It is found that the maximum levitation force decreases from 46.3N to 16.3N while the horizontal distance (Dpp) between the rectangle permanent magnet and two cubic permanent magnets (PM2) is increased from 0mm to 24mm and the horizontal distance (Dsp) between a GdBCO bulk superconductor and two cubic permanent magnets (PM3) is 0mm, The results indicate that the higher levitation force can be obtained by introducing PM-PM levitation system based on scientific and reasonable design of the hybrid magnetic levitation system, which is helpful for designing and constructing superconducting magnetic levitation systems.

Yue, Ming, Meng Tian, Wei Qiang Liu e Jiu Xing Zhang. "Spark Plasma Sintering Nd₂Fe₁₄B/α-Fe Bulk Exchange-Spring Magnets". Materials Science Forum 475-479 (gennaio 2005): 2161–64. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.2161.

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The Nd2Fe14B/α-Fe bulk exchange-spring magnets have been prepared by spark plasma sintering melt spun Nd9.8Dy0. 4Fe78.4Co5.6B5.8 flakes under different temperatures and pressures. It was found that higher sintering temperature improved the densification of the magnets, while deteriorated their magnetic properties simultaneously. An increased compressive pressure can restrain the grain growth remarkably and then leads to better magnetic properties and higher density for the magnet at same sintering temperature. XRD analysis showed that with the increase of sintering pressure, some peaks indicating c-axis texture such as (006) and (105) became dominant. As a result, the bulk magnet exhibited higher remanence and maximum energy product than starting powders.

Ma, Jun. "The Effect of the Distance between the Permanent Magnets on the Levitation Force in Hybrid Magnetic Levitation System". Advanced Materials Research 721 (luglio 2013): 278–81. http://dx.doi.org/10.4028/www.scientific.net/amr.721.278.

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t has been investigated that the interaction force in hybrid magnetic levitation systems with two GdBCO bulk superconductors and two permanent magnets system and a cubic permanent magnet (PM2) and a cubic permanent magnet (PM3) system in their coaxial configuration at liquid nitrogen temperature. The two single-domain GdBCO samples are of φ20mm and 10mm in thickness, the permanent magnet PM1 is of rectangular parallelepiped shape, the permanent magnets PM2 and PM3 are of cubic shape; the system placed on the middle of system and their coaxial configuration; It is found that the maximum levitation force decreases from 40.6N to 17.8N while the distance (Dpp) between the permanent magnets is increased from 0mm to 24mm and the distance (Dsp) between the two GdBCO bulk superconductors and a cubic permanent magnet PM3 is 0mm, The results indicate that the higher levitation force can be obtained by introducing PM-PM levitation system based on scientific and reasonable design of the hybrid magnetic levitation system, which is helpful for designing and constructing superconducting magnetic levitation systems.

Liao, Hengpei, Weijia Yuan, Zhiwei Zhang e Min Zhang. "Magnetization mechanism of a hybrid high temperature superconducting trapped field magnet". Journal of Applied Physics 133, n. 2 (14 gennaio 2023): 023902. http://dx.doi.org/10.1063/5.0133219.

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This paper studies the magnetization mechanism of a hybrid high temperature superconducting (HTS) trapped field magnet. To address the size limitation of traditional HTS bulk materials, hybridization between HTS-stacked ring magnets and HTS bulks is proposed here. A jointless HTS-stacked ring magnet is used to increase the trapped field area for HTS bulks. A hybrid HTS magnet with 90 mm in length and 60 mm in width was tested to provide a trapped field of 7.35 T in a field cooling magnetization. The paper focuses mainly on understanding the novel magnetization mechanism of this hybrid HTS trapped field magnet. A numerical model based on homogenized H formulation was used to compare with experimental results, and a good match was found. Our experimental and numerical study of the electromagnetic interaction between the HTS-stacked ring magnet and the HTS bulks reveals that there are two magnetization stages, and the magnetization speed differs in these two stages by a sing criterion: whether the HTS-stacked ring magnet is fully penetrated or not. This study confirms that hybridization helps to build large HTS trapped field magnets.

Vuong, Nguyen Van. "MnBi Magnetic Material: A Critical Review". Communications in Physics 29, n. 4 (16 dicembre 2019): 441. http://dx.doi.org/10.15625/0868-3166/29/4/14326.

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Manganese Bismuth (MnBi) - the ferromagnetic material attracting a great interest of the world magnetic society last years. The absence of rare-earth elements in compositions, the sizable magnetocrystalline anisotropy, the room-temperature moderate but high-temperature reasonable magnetization plus the positive temperature coefficient of coercivity and the moderate Curie temperature make MnBi bulk magnets very potential for high-temperature magnet application. This bright future is a little gray because the research results in the past were not as expected. The paper summarizes the results concerning the MnBi alloys, powders and bulk magnets investigated during past 67 years. The look on the difficulties inhibiting the development of this material is given and the proposals that might allow overcoming the difficulties and push again the efforts of research towards the goal of 12 MGOe for the energy product (BH)max of MnBi bulk magnets are discussed.

Saito, Tetsuji. "Production of Sm2Fe17N3 Bulk Magnets". Inorganics 12, n. 4 (23 marzo 2024): 95. http://dx.doi.org/10.3390/inorganics12040095.

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Sm2Fe17N3 powder exhibits excellent magnetic properties but is unstable and decomposes into α-Fe and SmN phases at high temperatures. Therefore, the key to producing Sm2Fe17N3 bulk magnets is to reduce the deterioration of Sm2Fe17N3 powder during sintering. Herein, Sm2Fe17N3 bulk magnets were made using the spark plasma sintering (SPS) method with the addition of zinc stearate powder and zinc powder. Adding small amounts of zinc stearate powder and zinc powder improved the magnetic anisotropy and the coercivity of the magnets, respectively. The magnets produced by the SPS method using zinc stearate powder and zinc powder exhibited enhanced magnetic properties almost comparable to those of Sm2Fe17N3 powder.

Oka, Tetsuo, Tomoki Muraya, Nobutaka Kawasaki, Satoshi Fukui, Jun Ogawa, Takao Sato e Toshihisa Terasawa. "Magnetizing of permanent magnets using HTS bulk magnets". Cryogenics 52, n. 1 (gennaio 2012): 27–31. http://dx.doi.org/10.1016/j.cryogenics.2011.10.005.

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Vuong, Nguyen Van. "HIGHLY ANISOTROPIC MnBi MAGNETS". Vietnam Journal of Science and Technology 54, n. 1A (16 marzo 2018): 58. http://dx.doi.org/10.15625/2525-2518/54/1a/11806.

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The rare-earth-free MnBi magnetic material is promising for high-temperature (150 200 oC) application of permanent magnets because of its large magnetocrystalline energy and especially the positive thermal coefficient of coercivity (dHc/dT > 0). Because of the moderate value of the spontaneous magnetization Ms 74 emu/g, the anisotropy of MnBi bulk magnets should be investigated to enhance the remanence Mr. With large ratio Mr/Ms and appropriate microstructure, the squareness of MnBi magnets should have high value leading the remanent coercivity bHc close to the intrinsic coercivity iHc, thus enhancing the energy product (BH)max. The paper presents an approach to loading and compacting of MnBi powders in the 18 kOe magnetic field oriented perpendicular to the pressing direction where MnBi grains can be freely rotated and oriented parallel to the field direction. Based on the energy minimization of the assembly of magnetized grains, the compacting pressure was chosen to optimize two parameters, the mass density and the coercivity iHc of magnets. The prepared MnBi bulk magnet had 8.4 g/cm3, Mr/Ms 0.92, 0.89 and (BH)max reached 8.4 MGOe.

Più fonti

Tesi sul tema "Bulk magnets":

Lwin, Mark. "The dynamic compaction of the metastable hard magnet powder Sm!b2!sFe!b17!sNx to form bulk magnets". Thesis, Queensland University of Technology, 1994.

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Unge, Mikael. "Molecular Electronics : A Theoretical Study of Electronic Structure of Bulk and Interfaces". Doctoral thesis, Linköpings universitet, Beräkningsfysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6938.

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This thesis deals with theoretical studies of the electronic structure of molecules used in the context of molecular electronics. Both studies with model Hamiltonians and first principle calculations have been performed. The materials studied include molecular crystals of pentacene and DNA, which are used as active material in field-effect transistors and as tentative molecular wires, respectively. The molecular magnet compound TCNE and surface modification by means of chemisorption of TDAE on gold are also studied. Molecular crystals of pentacene are reported to have the highest field-effect mobility values for organic thin film field-effect transistors. The conduction process in field-effect transistors applications occurs in a single layer of the molecular crystal. Hence, in studies of transport properties molecular crystals of pentacene can be considered as a two dimensional system. An open question of these system is if the charge transport is bandlike or if as a result of disorder is a hopping process. We address this question in two of the included papers, paper I and paper II. The conducting properties of DNA are of interest for a broad scientific community. Biologist for understanding of oxidatively damaged DNA and physicist and the electronics community for use as a molecular wire. Some reports on the subject classifies DNA as a conductor while other report insulating behavior. The outcome of the investigations are heavily dependent on the type of DNA being studied, clearly there is a big difference between the natural and more or less random sequence in, e.g., λ-DNA and the highly ordered syntethic poly(G)-poly(C) DNA. It has been suggested that long-range correlation would yield delocalized states, i.e., bandlike transport, in natural DNA, especially in the human chromosome 22. In paper III we show that this is not the case. In general our results show that DNA containing an approximately equal amount of the four basis is an insulator in a static picture. An emerging research field is spintronics. In spintronic devices the spin of the charge carrier is as important as the charge. One can envision a device where spin alone is the carrier of information. In realizing spintronic devices, materials that are both magnetic and semiconducting are needed. Systems that exhibit both these properties are organic-based magnets. In paper IV the electronic structure of the molecular magnet compound TCNE is studied, both experimentally and theoretically. The injection of carriers from metal contacts to organic semiconductors is central to the performance of organic based devices. The interface between the metal contact and the organic material has been pointed out to be one of the device parameters that most significantly influences the device performance. This relates to the process of injection of charge carriers in to the organic material. In some contact and organic material combinations the energy barrier for charge injection can be very high. The barrier can be reduced by modify the interface dipole, this is achieved by a monolayer of adsorbed molecules at the interface. The molecule TDAE chemisorbed on gold is studied in paper V.

Kapek, Jakub. "Modélisations 2D et 3D, conception et réalisation d’un inducteur pour aimanter un ensemble de pastilles supraconductrices". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0113.

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Aujourd’hui, les supraconducteurs trouvent de nombreuses applications, par exemple dans les câbles, les moteurs, les alternateurs ou la génération de champ magnétiques intenses. Les supraconducteurs sont disponibles sous forme de rubans, de fils ou de matériaux massifs. Le processus d'aimantation des supraconducteurs permet d'obtenir des supraconducteurs massifs avec un champ magnétique piégé de bien plus grande valeur que les aimants classiques à base de fer. Une aimantation correcte est la clé d'un champ magnétique piège très fort. Les travaux développés dans cette thèse concernent la modélisation en 2D et 3D, la conception et la réalisation d’un inducteur pour aimanter un ensemble de pastilles supraconductrices. D'une manière générale, il existe trois techniques d'aimantation des supraconducteurs : Zero Field Cooling (ZFC), Field Cooling (FC) et Pulsed Field Magnetization (PFM). Nous nous concentrons sur la PFM car c’est une solution plus compacte et moins onéreuse comparée aux autres techniques. Le procédé d’aimantation évoqué et tous les phénomènes qui en découlent ont été résolus en se basant sur la méthode des éléments finis (MEF) et à l’aide de différentes formulations. Dans ce travail, nous avons étudié et comparé en 2D et 3D la formulation en A, la formulation en H ainsi qu’une une formulation A – H en couplant les différentes variables sur les frontières des matériaux. La comparaison effectuée a montré les avantages de la formulation A – H dans la modélisation des problèmes liés aux supraconducteurs. En effet, dans certains cas, nous avons montré que l'utilisation de la formulation A – H permet de réduire le temps de simulation. Le modèle développé à partir de cette formulation constitue donc un outil intéressant pour de futurs travaux de dimensionnement et le développement d’applications des supraconducteurs au GREEN. Nous avons également dimensionné et étudié numériquement un modèle complet d’inducteur permettant d’aimanter un ou plusieurs supraconducteurs simultanément. Nous étudions deux configurations : le prototype I pour aimanter un seul supraconducteur (problème 2D) et le prototype II pour aimanter trois supraconducteurs (problème 3D). Ces deux configurations sont résolues en considérant les phénomènes électromagnétiques et thermiques ainsi que le couplage avec les équations du circuit alimentant l’inducteur. Les simulations ont montré que l’élévation de température dans le supraconducteur d’une dizaine de Kelvin générée lors de l’aimantation par PFM affectait le champ magnétique piégé. Il a été observé que la présence d’une ou plusieurs pastilles supraconductrices n’influençait pas l'impulsion de courant dans l’inducteur. Le champ piégé maximal obtenu numériquement pour le prototype I était de 706 mT et de 736 mT pour le prototype II. Les résultats obtenus ont ensuite été comparés aux résultats de la simulation. Cependant, certains supraconducteurs présentaient une forte inhomogénéité de leurs propriétés ce qui a eu pour conséquence de réduire le champ magnétique piégé observé expérimentalement. Des hypothèses ont été faites pour tenter de reproduire numériquement ces inhomogénéités et leurs effets. Néanmoins, ce calcul numérique ne peut se faire que par une modélisation 3D sans utilisation possible de symétries, et conduit à un de temps de calcul pouvant aller jusqu’à plusieurs jours. L'expérimentation avec des prototypes a permis d'obtenir un champ magnétique piégé maximal de 686 mT lors de l’aimantation d’une pastille, tandis qu’il était de 606 mT lorsque plusieurs pastilles ont été aimantées simultanément. Un abaissement de la température par l’utilisation d’un autre fluide cryogénique comme l’hydrogène liquide ou d’un autre système de refroidissement permettrait d’augmenter cette valeur de champ magnétique piégé à des valeurs beaucoup plus intéressantes pour les applications visées en génie électrique
Today, superconductors are used in many applications, for example in cables, motors, alternators or for the generation of strong magnetic fields. Superconductors are available as tapes, wires or bulk materials. The process of magnetising superconductors results in bulk superconductors with a much higher trapped magnetic field than conventional permanent magnets. Proper magnetisation is the key to a very strong trapped magnetic field. The work developed in this thesis concerns the 2D and 3D modelling, design and realisation of an inductor to magnetise a set of superconducting pellets. Generally speaking, there are three techniques for magnetising superconductors: Zero Field Cooling (ZFC), Field Cooling (FC) and Pulsed Field Magnetization (PFM). We focus on PFM because it is a more compact and less expensive solution compared to the other techniques. The mentioned magnetisation process and all the phenomena involved have been solved based on the Finite Element Method (FEM) and using different formulations. In this work, we studied and compared in 2D and 3D the A-formulation, the H-formulation and an A-H formulation by coupling the different variables on the material boundaries. The comparison showed the advantages of the A-H formulation in modelling superconducting problems. Indeed, in some cases, we have shown that the use of the A-H formulation allows to reduce the simulation time. The model developed from this formulation is therefore an interesting tool for future dimensioning work and the development of superconductor applications at GREEN laboratory. We have also dimensioned and numerically studied a complete inductor model allowing one or more superconductors to be magnetised simultaneously. We study two configurations: prototype I for magnetising a single superconductor (2D problem) and prototype II for magnetising three superconductors (3D problem). Both configurations are solved by considering the electromagnetic and thermal phenomena as well as the coupling with the circuit equations feeding the inductor. The simulations showed that the temperature rise in the superconductor of about 10 Kelvin generated during the PFM magnetisation affected the trapped magnetic field. It was observed that the presence of one or more superconducting bulks did not affect the current pulse in the inductor. The maximum trapped field obtained numerically for prototype I was 706 mT and 736 mT for prototype II. The results obtained were then compared with the simulation results. However, some of the superconductors exhibited strong inhomogeneity in their properties, which resulted in a reduction in the experimentally observed trapped magnetic field. Hypotheses were made to try to reproduce numerically these inhomogeneities and their effects. However, this numerical calculation can only be done by 3D modelling without the possibility of using symmetries, and leads to a calculation time of up to several days. Experimentation with prototypes resulted in a maximum trapped magnetic field of 686 mT when one pellet was magnetised, while it was 606 mT when several pellets were magnetised simultaneously. Lowering the temperature by using another cryogenic fluid such as liquid hydrogen or another cooling system would increase this trapped magnetic field value to much higher values for the targeted electrical engineering applications

Lewin, Richard Peter. "Superconductors and high magnetic fields". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:09992030-625d-4e6c-8152-6a61bb2cdb07.

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This thesis describes a portfolio of work aimed at the high field applications of superconductors and can be split into four main topics: The thermal stability of technical superconductors. This section investigates the effects of thermal perturbations on technical superconducting wire used in MRI scanner construction. The ultimate aim of this section is to predict how the architecture of the wire may affect its thermal stability. To this end a detailed finite element analysis model was constructed, verified by detailed experimental data, which could then be used to quickly and easily vary the wire’s parameters. Design of a high field pulsed electromagnetic coil for flux trapping in superconductors. This section details the design, construction and testing of a novel pulsed high field magnet. The design uses finite element analysis to predict the electromagnetic, thermal and structural properties of the coil. Explosive testing of high tensile fibres used in the construction of the high field coil. This section describes the refinement and use of a novel method for testing the mechanical properties of high tensile fibres in cylindrical geometries by using highly pressurized copper vessels. Pulsed field magnetization of bulk high temperature superconductors. This section discusses the process of magnetizing bulks of high temperature superconductors by using pulsed magnetic fields. It investigates how the trapped field varies with the magnitude and rise-time of the magnetizing field, sample temperature and time after magnetization.

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.

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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.

Jensen, Morten R. F. "Far infrared magneto-spectroscopy of bulk and surface magnetic excitations in FeFâ†2". Thesis, University of Essex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361040.

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De, Silvestri Federica. "Investigation of the magnetic levitation between HTS bulks and permanent magnets". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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Lo scopo di questa ricerca è lo studio della levitazione magnetica risultante dall'interazione fra bulk di superconduttori ad alta temperatura critica e magneti permanenti. E' stato realizzato un modello numerico 2D in Comsol che simula l'interazione fra i due componenti, per studiare la forza di levitazione ottenuta. Il modello è stato successivamente validato con i risultati sperimentali ottenuti nei laboratori del dipartimento di Ingegneria dell'Energia Elettrica dell'Università di Bologna, ottenendo un buon riscontro sia per quanto riguarda i valori della forza sia per quanto riguarda le distribuzioni di campo e di corrente.

Masood, Ansar. "Functional Metallic Glasses". Doctoral thesis, KTH, Teknisk materialfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101901.

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For decades, Metallic Glass, with its isotropic featureless structure while exhibiting outstanding mechanical properties was possible only at a high rate of quenching and with at least one dimension in the submicron regime. This limitation was overcome with the discovery of Bulk Metallic glasses, BMGs, containing three or more elements following the additional two empirical rules of optimum geometric size differences and negative energy of mixing among the constituent elements. Since then thousands of Fe-, Ni-, Al-, Mg-, Ti- based BMGs have been discovered and comprehensively investigated mainly by groups in Japan and USA. Yet the discovery of new combinations of elements for BMGs is alchemy. We do not know with certainty which element when added will make possible a transition from being a ribbon to a bulk rod. In this thesis we report a discovery of castable BMGs rods on substitution of Fe by nickel in an alloy of FeBNb which could otherwise have been only melt-spun into ribbons. For example, we find that substitution of just 6 at.% of Fe raises the glass forming range, GFA, to as much as ∆Tx =40K while the other parameters for GFA like Trg, γ, and δ reach enhanced values 0.57, 0.38, and 1.40 respectively. Furthermore, the electrical conductivity is found to increase by almost a factor of two. Magnetically it becomes softer with coercivity 260mOe which further reduces to much lower values on stress relaxation. Ni does not seem to carry a magnetic moment while it enhances the magnetic transition temperature linearly with Ni concentration. We have investigated the role of Ni in another more stable BMGs based FeBNbY system in which case ∆Tx becomes as large as 94K with comparable enhancement in the other GFA parameters. Due to the exceptional soft magnetic properties, Fe-based bulk metallic glasses are considered potential candidate for their use in energy transferring devices. Thus the effect of Ni substitution on bulk forming ability, magnetic and electrical transport properties have been studied for FeBNb and FeBNbY alloy systems. The role of Ni in these systems is densification of the atomic structure and its consequence. We have exploited the superior mechanical properties of BMGs by fabricating structures that are thin and sustainable. We have therefore investigated studies on the thin films of these materials retaining their excellent mechanical properties. Magnetic properties of FeBNb alloy were investigated in thin films form (~200-400nm) in the temperature range of 5-300K. These Pulsed Laser deposited amorphous films exhibit soft magnetism at room temperature, a characteristic of amorphous metals, while they reveal a shift in hysteresis loop (exchange anisotropy, HEB=18-25Oe), at liquid helium temperature. When thickness of films is reduced to few nanometers (~8-11nm), they exhibit high transparency (>60%) in optical spectrum and show appreciably high saturation Faraday rotation (12o/μm, λ= 611nm). Thin films (~200-400nm) of Ni substituted alloy (FeNiBNb) reveal spontaneous perpendicular magnetization at room temperature. Spin-reorientation transition was observed as a function of film thickness (25-400nm) and temperature (200-300K), and correlated to the order/disorder of ferromagnetic amorphous matrix as a function of temperature. These two phase films exhibits increased value of coercivity, magnetic hardening, below 25K and attributed to the spin glass state of the system. Using the bulk and thin films we have developed prototypes of sensors, current meters and such simple devices although not discussed in this Thesis. Ti-based bulk metallic glasses have been attracting significant attention due to their lower density and high specific strength from structural application point of view. High mechanical strength, lower values of young’s modulus, high yield strength along with excellent chemical behaviors of toxic free (Ni, Al, Be) Ti-based glassy metals make them attractive for biomedical applications. In the present work, toxic free Ti-Zr-Cu-Pd-Sn alloys were studied to optimize their bulk forming ability and we successfully developed glassy rods of at least 14mm diameter by Cu-mold casting. Along with high glass forming ability, as-casted BMGs exhibit excellent plasticity. One of the studied alloy (Ti41.5Zr10Cu35Pd11Sn2.5) exhibits distinct plasticity under uniaxial compression tests (12.63%) with strain hardening before failure which is not commonly seen in monolithic bulk metallic glasses.

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Ahmed, Naseer. "Magneto-optics of MBE grown bulk and low dimensional III-V semiconductors". Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/1084.

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Mitra, Chandrima. "COMPUTATIONAL STUDIES OF GADOLINIUM IN NITRIDES : BULK GDN AND GD-DOPED GAN". Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1238690053.

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Libri sul tema "Bulk magnets":

Prüser, Henning. Scanning Tunneling Spectroscopy of Magnetic Bulk Impurities. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06385-0.

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1947-, Komoroski Richard A., a cura di. High resolution NMR spectroscopy of synthetic polymers in bulk. Deerfield Beach, Fla: VCH Publishers, 1986.

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Stefanita, Carmen-Gabriela. From bulk to nano: The many sides of magnetism. Berlin [u.a.]: Springer, 2010.

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Fedotov, V. D. Structure and dynamics of bulk polymers by NMR-methods. Berlin: Springer-Verlag, 1989.

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Fedotov, V. D. Structures and dynamicsof bulk polymers by NMR-methods. Berlin: Springer-Verlag, 1989.

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G, Rosenbaum Joseph, e Geological Survey (U.S.), a cura di. Sediment magnetic and paleomagnetic data from Buck Lake, Oregon. Denver, CO: U.S. Dept. of the Interior, U.S. Geological Survey, 1994.

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V, Gardner James, e Geological Survey (U.S.), a cura di. P-wave velocity, wet bulk density, magnetic susceptibility, acoustic impedance, and visual core descriptions of sediment recovered during Research Cruise EW9504: Data, techniques, and procedures. [Reston, Va.]: U.S. Dept. of the Interior, U.S. Geological Survey, 1995.

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Capitoli di libri sul tema "Bulk magnets":

Fidler, J. "Review of Bulk Permanent Magnets". In Magnetic Hysteresis in Novel Magnetic Materials, 567–97. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5478-9_63.

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Jin, Z. Q., K. H. Chen, J. Li, G. Kennedy, H. Zeng, S. F. Cheng e Z. L. Wang. "Shock Compaction of Exchange-Coupled Bulk Nanocomposite Magnets". In Powder Materials: Current Research and Industrial Practices III, 91. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118984239.ch11.

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Liu, J. P. "Fabrication of Bulk Nanocomposite Magnets by Nano-Powder Metallurgy". In Powder Materials: Current Research and Industrial Practices III, 179–85. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118984239.ch18.

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Brecharya, G. P., E. A. Vasilyeva e N. F. Janchik. "Gas-atomization Nd-Fe-B Powders for Permanent Magnets". In Materials Development and Processing - Bulk Amorphous Materials, Undercooling and Powder Metallurgy, 287–91. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527607277.ch46.

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Gatteschi, Dante, Luca Pardi, Anne Laure Barra e Achim Müller. "Polyoxovanadates: The Missing Link between Simple Paramagnets and Bulk Magnets?" In Topics in Molecular Organization and Engineering, 219–31. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0920-8_16.

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Kamijo, Hiroki, Kaoru Nemoto e Hiroyuki Fujimoto. "Case Study of High-Tc Superconducting Bulk Magnets for Maglev". In Advances in Superconductivity XII, 812–14. Tokyo: Springer Japan, 2000. http://dx.doi.org/10.1007/978-4-431-66877-0_240.

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Brecharya, G. P., E. A. Vasilyeva, Yu G. Putilov e S. V. Ustinova. "The Structure and Properties of Powder Didymium-Iron-Boron Magnets". In Materials Development and Processing - Bulk Amorphous Materials, Undercooling and Powder Metallurgy, 281–86. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527607277.ch45.

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Jakubovics, J. P. "Bulk magnetic properties and their measurement". In Magnetism and Magnetic Materials, 49–97. 2^a ed. London: CRC Press, 2023. http://dx.doi.org/10.1201/9781003422044-3.

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Yue, Ming, Meng Tian, Wei Qiang Liu e Jiu Xing Zhang. "Spark Plasma Sintering Nd₂Fe₁₄B/α-Fe Bulk Exchange-Spring Magnets". In Materials Science Forum, 2161–64. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-960-1.2161.

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Turner, Scott S. "Measurement of Bulk Magnetic Properties". In Multi Length-Scale Characterisation, 1–61. Chichester, UK: John Wiley & Sons, Ltd, 2013. http://dx.doi.org/10.1002/9781118683972.ch1.

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Atti di convegni sul tema "Bulk magnets":

Gopalan, R., A. A. Kundig, M. Ohnuma e K. Hono. "High coercivity in FePt-based bulk magnets". In INTERMAG Asia 2005: Digest of the IEEE International Magnetics Conference. IEEE, 2005. http://dx.doi.org/10.1109/intmag.2005.1464070.

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Ohsaki, H., M. Tokuda e M. Tsuchiya. "Electromagnetic levitation assisted by bulk superconducting magnets". In IEEE International Magnetics Conference. IEEE, 1999. http://dx.doi.org/10.1109/intmag.1999.837487.

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Lo, W. "Melt processing bulk magnets - what can be achieved". In IEE Colloquium on High Tc Superconducting Materials as `Magnets'. IEE, 1995. http://dx.doi.org/10.1049/ic:19951521.

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Ohsaki, Hiroyuki, Satsuki Okumura e Fumiya Harashima. "Damping Characteristics of Magnetic Levitation using Bulk Superconductors and Permanent Magnets". In 2023 14th International Symposium on Linear Drivers for Industry Applications (LDIA). IEEE, 2023. http://dx.doi.org/10.1109/ldia59564.2023.10297459.

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Ener, Semih, Ulysse Rocabert, Fernando Maccari, Alex Aubert, Guixiang Qin, Andres Martin-Cid, Alberto Bollero e Oliver Gutfleisch. "Magnetic, physical and chemical properties of consolidated Mn-Al-C bulk magnets". In 2023 IEEE International Magnetic Conference - Short Papers (INTERMAG Short Papers). IEEE, 2023. http://dx.doi.org/10.1109/intermagshortpapers58606.2023.10228812.

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Suzuki, Keisuke, Tatsuya Nakasaki, Hidetaka Nakashima, Panart Kajornrunruan, Misaki Onomata, Yushi Kinoshita, Ruizhe Zhang e Edmund Soji Otabe. "Study on Polishing Method Using Double Magnet System by Superconductive Assisted Machining Method". In JSME 2020 Conference on Leading Edge Manufacturing/Materials and Processing. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/lemp2020-8553.

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Abstract (sommario):

Abstract Superconductive Assisted Machining Method (SUAM) has been studied for polishing methods inside the hollow structure such as SUS tube. Levitation tool with Nd permanent magnet in the SUAM system is trapped by magnetic flux pinning effect into the superconductor bulk mounted in the liquid nitrogen box. In this case, initial displacement of the levitation tool can be adjusted until 12mm during cooling process under magnetic field. Movement of the superconductor bulk controls the applied force and rotation speed of the levitation tool. In previous research, we demonstrated that the SUAM could be applied lapping and polishing process on concave and flat shapes of the resin, aluminum and SUS materials. In present study, we develop the double magnet system that Nd permanent magnet fixed under the superconductor to increase holding force of the levitation tools. As results, holding force and levitation amount of the double magnet system increase against the conventional single magnet system. We also evaluate dominant parameters such as the placement of the superconductors and magnet flux density distribution from double permanent magnets on the holding force and levitation amount. In this case, the holding force and floating amount is calculated by JMAG using Finite Element Method to compare with the experimental results.

Yue, M., P. Niu e J. Zhang. "Spark plasma sintering Fe3B/(Pr,Tb)2Fe14B bulk nanocomposite permannet magnets". In INTERMAG 2006 - IEEE International Magnetics Conference. IEEE, 2006. http://dx.doi.org/10.1109/intmag.2006.375809.

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Feng, X., G. Gao, K. Davey, M. Werst, R. Hebner, R. Weinstein, D. Parks e R. Sawh. "Radial flux high temperature superconductor motor using bulk trapped field magnets". In 2009 IEEE International Electric Machines and Drives Conference (IEMDC). IEEE, 2009. http://dx.doi.org/10.1109/iemdc.2009.5075246.

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Chiriac, H., e N. Lupu. "New FeNbB based bulk amorphous and nanocomposite soft magnets for applications". In INTERMAG Asia 2005: Digest of the IEEE International Magnetics Conference. IEEE, 2005. http://dx.doi.org/10.1109/intmag.2005.1463694.

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Nariki, S. "Trapped-field of RE-123 (RE=Gd,Dy) bulk superconducting magnets". In ADVANCES IN CRYOGENIC ENGINEERING: Proceedings of the International Cryogenic Materials Conference - ICMC. AIP, 2002. http://dx.doi.org/10.1063/1.1472603.

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Rapporti di organizzazioni sul tema "Bulk magnets":

Kwun, H. L51694 Investigation of Techniques for Bulk Stress Measurement on Exposed Pipelines-Phases I and II. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), ottobre 1993. http://dx.doi.org/10.55274/r0010318.

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Abstract (sommario):

Differential movement of a buried pipeline resulting from terrain instabilities such as subsidence, fault slippage, frost heave, ice scouring, soil movement, and landslide can create localized areas of high stress in a pipeline. These areas may be susceptible to mechanical failure and therefore may compromise the structural integrity of the line. Nondestructive testing (NDT) methods that can detect high-stress regions and measure the magnitude of the stress in the pipeline are needed to determine if or when remedial action must be taken to prevent stress-related damage. The areas of high stress can compromise the integrity of the pipeline, despite the fact that the highly stressed areas may not be readily detectable. �This report describes two phases of development for a nonintrusive technique to quantify the local, throughwall average axial stress in an exposed pipe. The technique selected for evaluation and development is a low-frequency, electromagnetic technique, called multiparameter magnetic measurement (MPMM). MPMM is a combination of existing magnetic techniques including magnetic hysteresis measurement, nonlinear harmonic analysis, and multiparameter correlation. The work included both a proof-of-principle demonstration of the technique using samples of grade X-42, X-46, and X-52 pipe (Phase I), and further determination of practical applicability of the MPMM technique (Phase II). Phase II focused on evaluating the variability of magnetic response to stress among five samples of grade X-42 pipe.

Grosjean, E., D. S. Edwards, C. J. Boreham, D. DiBugnara e T. Buckler. Magnetic susceptibility and bulk density data from Waukarlycarly 1, Canning Basin, Australia: destructive analysis report 2020-007. Geoscience Australia, 2020. http://dx.doi.org/10.11636/record.2020.019.

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