Academic literature on the topic 'Ferrofluids'
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Journal articles on the topic "Ferrofluids"
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Hodenius, Michael A. J., Thoralf Niendorf, Gabriele A. Krombach, Walter Richtering, Thomas Eckert, Heiko Lueken, Manfred Speldrich, et al. "Synthesis, Physicochemical Characterization and MR Relaxometry of Aqueous Ferrofluids." Journal of Nanoscience and Nanotechnology 8, no. 5 (May 1, 2008): 2399–409. http://dx.doi.org/10.1166/jnn.2008.18276.
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The synthesis and characterization of ferrofluid based MR contrast agents, which offer R2* versatility beyond that of ferucarbotran, is described. Ferrofluids were formed after stabilizing magnetite cores with dodecanoic acid (a), oleic acid (b), dodecylamine (c), citric acid (d) or tartaric acid (e). Core sizes were deduced from TEM micrographs. Magnetic properties were determined by SQUID magnetometry. Hydrodynamic particle diameters were determined by dynamic light scattering measurements. Zeta potentials were measured by combining laser Doppler velocimetry and phase analysis light scattering. Iron contents were evaluated colorimetrically. MR relaxometry including R1 and R2* was conducted in vitro using homogeneous ferrofluid samples. The average core diameters of ferrofluids a, b and c equaled 9.4±2.8 nm and approximately 2 nm for ferrofluids d and e. Magnetization measurements at 300 K revealed superparamagnetic behaviour for the dried 9 nm diameter cores and paramagnetic-like behaviour for the dried cores of ferrofluids d and e. Iron contents were between 32–75 mg Fe/mL, reflecting the ferrofluids' high particle concentrations. Hydrodynamic particle diameters equaled 100–120 nm (a, b and c). For the ferrofluids a, b, d and e coated with anions, strong negative zeta potential values between −27.5 mV and −54.0 mV were determined and a positive zeta potential value of +33.5 mV was found for ferrofluid c, covered with cationic dodecylammonium ions. MR relaxometry yielded R1-values of 1.9±0.3 (a), 4.0±0.8 (b), 5.2±1.0 (c), 0.124±0.002 (d) and 0.092±0.005 s−1 mM−1 (e), and R2*-values of 856±24 (a), 729±16 (b), 922±29 (c), 1.7±0.05 (d) and 0.49±0.05 s−1 mM−1 (e). Thus, the synthesized ferrofluids reveal a broad spectrum of R2* relaxivities. As a result, the various MR contrast agents have a great potential to be used in studies dealing with malignant tissue targeting or molecular imaging.
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Zhang, Jian Hui, and Hai Bo Sun. "Synthesis and Properties of Fe3O4 Ferrofluids with Narrow Particle Size Distribution." Materials Science Forum 694 (July 2011): 575–79. http://dx.doi.org/10.4028/www.scientific.net/msf.694.575.
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Fe3O4 ferrofluids with uniform magnetic particles were prepared via improved chemical coprecipation technique. A narrow distribution of 8.6-10.8 nm particle sizes was obtained from the magnetization curve using the free-form-model based on Bayesian inference theory. The mean particle diameter about 9.8 nm is consistent with the XRD and SEM results. The hydrodynamic properties of ferrofluids were investigated with different applied magnetic field and shear rate. The experimental results show that diluted ferrofluid and concentrated ferrofluid are Newtonian-fluid and Bingham-plastic fluid, respectively.
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Frycz, Marcin. "Effect of Temperature and Deformation Rate on the Dynamic Viscosity of Ferrofluid." Solid State Phenomena 199 (March 2013): 137–42. http://dx.doi.org/10.4028/www.scientific.net/ssp.199.137.
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This paper presents the results of studies which characterize the dynamic viscosity changes of ferrofluid in terms of changes of selected physical conditions of its work. Knowledge of the variation of the ferrofluids density, lubricity, and especially viscosity depending on the concentration of Fe3O4 magnetic particles, temperature, deformation speed and impact direction, type and value of magnetic induction, it is necessary to analyze the changes of operating conditions of the slide journal bearing ferrofluids lubricated. This theme is the broader context of the authors interests and his research. In this article has been briefly characterized the viscous properties of the tested ferrofluid. There also has been shown an analysis of the impact of changes in temperature and velocity of deformation on the change of ferrofluids dynamic viscosity. The paper has been summarized the observations and conclusions reached on the basis of analysis results.
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Ganachari, Sharanabasava V., Veerabhadragouda B. Patil, Nagaraj R. Banapurmath, Manzoore Elahi M. Soudagar, Kiran Shahapurkar, Ashraf Elfasakhany, Mishal Alsehli, et al. "The Investigation of Mixed Ferrofluids Containing Iron Oxide nanoparticles and Microspheres." Advances in Materials Science and Engineering 2021 (December 9, 2021): 1–11. http://dx.doi.org/10.1155/2021/7616666.
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The aim of the present work is the synthesis and characterization of iron oxide (Fe3O4) nanoparticles. These nanoparticles are coated with oleic acid and polyvinyl butyral and mixed with microspheres and further developed ferrofluids with silicon oil. Studies of the performance of the nanoparticles in these ferrofluids with and without coating agents were carried out. The nanoparticles were synthesized using the chemical co-precipitation technique and coated with oleic acid and polyvinyl butyral, and it further mixed with microsphere ferrofluids and developed using silicon oil. The prepared Fe3O4 nanoparticles and their coated forms of oleic acid and polyvinyl butyral were mixed with microspheres; furthermore, ferrofluids were developed with silicon oil. All forms of these ferrofluids are characterized for morphology and phase purity (SEM, XRD, and FTIR). The iron oxide (Fe3O4) nanoparticles have shown different magnetic properties, differentiating macroscopic iron oxide in suspended particles. The ratio of surface to volume increases along with the decrease in atomic size, essential for assessing the surface morphological properties. The magneto-rheological (MR) fluids were determined, and shear stress of Expancel microsphere mixed iron oxide nanoparticle with and without them was found almost equal. However, the ferrofluid with PVB coated nanoparticles and microspheres emerged as a stable rheological ferrofluid, sustaining high shear stress and low viscosity with increasing shear rate. Also, shear rates up to 650 s−1 have been observed, showing very high shear stress withstanding capacity. The stability and performance of the magnetic colloidal ferrofluids depend on the thermal contribution and the balance between attractive/repulsive interactions.
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Li, Wangxu, Zhenggui Li, Wei Han, Yibin Li, Shengnan Yan, Qin Zhao, and Fang Chen. "Measured viscosity characteristics of Fe3O4 ferrofluid in magnetic and thermal fields." Physics of Fluids 35, no. 1 (January 2023): 012002. http://dx.doi.org/10.1063/5.0131551.
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The rheological mechanisms governing the viscosity characteristics of nano-ferrofluids are very complicated; there is no universal theoretical treatment that explains the dependence of the ferrofluid viscosity on the flow, magnetic, and temperature fields. Thus, determining the viscosity characteristics of ferrofluids in various physical fields is of great theoretical and practical significance. This study explores experimentally the relationship between the ferrofluid viscosity and temperature, magnetic-field strength, and magnetic-field inclination. A special experimental bench on which the magnetic field and temperature can be precisely controlled is designed and constructed. It is found that the ferrofluid viscosity is negatively correlated with temperature. Increasing the percentage of the magnetic particles in the ferrofluid increases the viscosity at any given temperature. Ferrofluids are shown to exhibit the magnetic–viscosity phenomenon: under the action of a magnetic field, the viscosity increases until a magnetic viscosity saturation value is reached. Increasing the magnetic field inclination can aggravate the magnetic–viscosity phenomenon but does not change the saturation value. Contrary to the naïve Hall theory but in agreement with earlier phenomenological studies, the magneto-viscous effect is greater with horizontal than with vertical magnetic fields. Simultaneous exposure to temperature and magnetic fields is investigated; the two fields appear to act independently on the viscosity. The magnetic viscosity saturation value is not affected by temperatures in the range of 30–60 °C.
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Zuhroh, Sayyidati, Ahmad Taufiq, Arif Hidayat, and Nasikhudin. "Exploration of the Antifungal Activity of Zn<sub>0.2</sub>Fe<sub>2.8</sub>O<sub>4</sub>/ Ag Ferrofluids with Double Surfactants and Sunflower Seed Oil as Dispersion Medium." Key Engineering Materials 940 (January 30, 2023): 65–71. http://dx.doi.org/10.4028/p-bmrq2p.
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Candidiasis is an infection caused by the fungus C. albicans. Ferrofluid Zn0.2Fe2.8O4/Ag is the best candidate to overcome the problem of infection caused by this fungus. In addition to the safe ingredients used, its ability to create ROS and maintain stability has the potential to be an excellent antifungal agent. The purpose of this study was to create a new ferrofluid with double surfactants for the antifungal C. albicans. Zn0.2Fe2.8O4/Ag ferrofluids were synthesized using a bottom-up method, starting from the synthesis of Zn0.2Fe2.8O4 nanoparticles, Zn0.2Fe2.8O4/Ag nanocomposites, to the synthesis of Zn0.2Fe2.8O4/Ag ferrofluids. Zn0.2Fe2.8O4/Ag powder was characterized using XRD and SEM to determine the particle structure and morphology. Meanwhile, Zn0.2Fe2.8O4/Ag ferrofluids were characterized using FTIR and antifungal activity tests to determine the functional group and zone of inhibition against the growth of the fungus C. albicans. The results of the characterization analysis showed that Zn0.2Fe2.8O4/Ag nanoparticles had good crystallinity, with a crystallite size of Zn0.2Fe2.8O4/Ag of 11.32 nm and an Ag crystallite size of 7.00 nm. SEM characterization showed that Zn0.2Fe2.8O4/Ag nanoparticles had agglomeration with the average particle size distribution of 443 nm. The functional groups detected by FTIR confirmed the success of the ferrofluid synthesis Zn0.2Fe2.8O4/Ag where spinel functional groups, olefin groups, and functional groups S=O were formed. The results of the antifungal activity test showed that Zn0.2Fe2.8O4/Ag ferrofluids were relatively active as an antifungal agent, with a diameter of the C. albicans growth inhibition zone of 9.63 mm.
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Saputro, Rosy Eko, Ahmad Taufiq, Sunaryono, Nurul Hidayat, and Arif Hidayat. "Effects of DMSO Content on the Optical Properties, Liquid Stability, and Antimicrobial Activity of Fe3O4/OA/DMSO Ferrofluids." Nano 15, no. 05 (May 2020): 2050067. http://dx.doi.org/10.1142/s1793292020500678.
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Fe3O4 nanoparticles were synthesized through a sonochemical method and were subsequently investigated by X-ray diffraction (XRD), which showed that the phase obtained was Fe3O4 with the most intense peak at 2[Formula: see text] of 35.5∘. The particle size of the Fe3O4 nanoparticles was 11.4[Formula: see text]nm. The dried ferrofluids containing Fe3O4 as a filler, oleic acid (OA) and dimethyl sulfoxide (DMSO) as surfactants tended to be amorphous. Scanning electron microscopy (SEM) observation of the Fe3O4 nanoparticles revealed agglomeration, and the dried ferrofluids morphology showed excellent dispersion. The constituent elements of both the Fe3O4 nanoparticles and the Fe3O4/OA/DMSO ferrofluids were identified through energy-dispersive X-ray spectroscopy to be Fe, O and C. Fourier transform infrared (FTIR) investigation revealed functional groups of the Fe3O4/OA/DMSO ferrofluids constituent Fe3O4 as the filler, OA and DMSO as surfactants, and olive oil as a dispersant. The absorbance of the samples was characterized by UV–Vis spectrophotometry, and the results were used to calculate the energy gap of the Fe3O4/OA/DMSO ferrofluids ranged from 2.20[Formula: see text]eV to 2.45[Formula: see text]eV. Through the absorbance measurements, the optical properties of Fe3O4/OA/DMSO ferrofluids were evaluated on the basis of their refractive indices, which ranged from 2.86 to 3.02. The stability of the Fe3O4/OA/DMSO ferrofluids was characterized by transmittance data collected for 12[Formula: see text]h, and excellent stability was obtained, as indicated by a relatively stable transmittance. Last, the antimicrobial activity of the Fe3O4/OA/DMSO ferrofluids was assessed through the diffusion method; the results showed that increasing DMSO volume resulted in greater ferrofluid antimicrobial activity.
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SCHUMACHER, KRISTOPHER R., JAMES J. RILEY, and BRUCE A. FINLAYSON. "Homogeneous turbulence in ferrofluids with a steady magnetic field." Journal of Fluid Mechanics 599 (March 6, 2008): 1–28. http://dx.doi.org/10.1017/s0022112007009640.
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The general equations necessary for a basic theoretical interpretation of the physics of turbulence in ferrofluids are presented. The equations are examined and show multiple novel turbulence aspects that arise in ferrofluids. For example, two new modes of turbulent kinetic energy and turbulent kinetic energy dissipation rate occur, and unique modes of energy conversion (rotational to/from translational kinetic energy and magnetic energy to/from turbulent kinetic energy) are exhibited in turbulent ferrofluid flows. Furthermore, it is shown that potential models for turbulence in ferrofluids are complicated by additional closure requirements from the five additional nonlinear terms in the governing equations. The equations are applied to turbulence of a ferrofluid in the presence of a steady magnetic field (as well as the case of no magnetic field) in order to identify the importance of the new terms. Results are presented for the enhanced anisotropy in the presence of a magnetic field, and results show how turbulence properties (both classical ones and new ones) vary with the strength of the magnetic field. Three different equations for the magnetization are examined and lead to different results at large magnitudes of the applied magnetic field.
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Rosenthal, Adam D., Carlos Rinaldi, Thomas Franklin, and Markus Zahn. "Torque Measurements in Spin-Up Flow of Ferrofluids." Journal of Fluids Engineering 126, no. 2 (March 1, 2004): 198–205. http://dx.doi.org/10.1115/1.1669030.
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Measurements of magnetic-field-induced torque in applied uniform rotating magnetic fields are presented and compared to theoretical analyses for water- and oil-based ferrofluids. These experiments measure the viscous torque on the inner wall of a stationary hollow polycarbonate spindle that is completely filled with ferrofluid and attached to a viscometer functioning as a torque meter. The spindle remains stationary and is centered inside a three-phase AC 2-pole motor stator winding, creating uniform time-varying rotating magnetic fields. The viscous torque is measured as a function of magnetic field amplitude, frequency, and direction of rotation. These measurements demonstrate that ferrofluid flow and torque are present even in the absence of free surfaces and agree with a recently derived analysis of the torque during spin-up flow of ferrofluids.
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Lavrova, Olga, Viktor Polevikov, and Sergei Polevikov. "NUMERICAL MODELLING OF MAGNETIC SHIELDING BY A CYLINDRICAL FERROFLUID LAYER." Mathematical Modelling and Analysis 24, no. 2 (February 5, 2019): 155–70. http://dx.doi.org/10.3846/mma.2019.011.
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A coupled method of finite differences and boundary elements is applied to solve a nonlinear transmission problem of magnetostatics. The problem describes an interaction of a uniform magnetic field with a cylindrical ferrofluid layer. Ferrofluid magnetisations, based on expansions over the Langevin law, are considered to model ferrofluids with a different concentration of ferroparticles. The shielding effectiveness factor of the cylindrical thick-walled ferrofluid layer is calculated depending on intensities of the uniform magnetic field and on thickness of the ferrofluid layer.
Dissertations / Theses on the topic "Ferrofluids"
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Hejazian, Majid. "Magnetofluidics for Enhancement of Heat and Mass Transfer in Microscale." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/366857.
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Magnetofluidics is the science and technology that combine magnetism and fluid dynamics to modify transport phenomena for a variety of applications. Magnetofluidics often works with conventional microfluidics to take advantage of the small size, the low cost and the low consumption of sample for chemical and biological studies. Magnetofluidics has been used for actuation and manipulation of fluid flow and suspended particles or cells in microfluidic devices.
The use of bio-compatible ferrofluids as a paramagnetic carrier fluid in the field of microfluidics has attracted great interest recently. Ferrofluid is a colloidal liquid made of ferromagnetic or ferrimagnetic nanoparticles suspended in a carrier fluid. In the presence of a magnetic field, a ferrofluid becomes strongly magnetized. Thus, a small amount of samples containing ferrofluid could be manipulated for applications such as mixing, pumping, sorting of particles and cells, enhancement of heat and mass transfer phenomena and chemical reactions. On the other hand, magnetic force can be induced wirelessly and is suitable for biological studies as it sustains cell viability. Therefore, the combination of magnetofluidics and microfluidics has proven to be a low cost, efficient and versatile technology for a number of applications.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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Daffé, Niéli. "Anisotropies and Magnetic Couplings of Texturable Ferrofluids." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066640/document.
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Les ferrofluides sont des suspensions colloïdales de nanoparticules magnétiques dispersées dans un liquide porteur. La possibilité de moduler les propriétés des ferrofluides in situ en appliquant un champ magnétique externe leur procure un fort potentiel d’étude, à la fois d’un point de vue fondamental ou pour des applications industrielles variées. En particulier, les nanospinels de ferrite ferrimagnétiques MFe2O4 (M = Fe2+, Co2+, Mn2+…) sont largement étudiés pour leurs propriétés électriques et magnétiques. Plus spécifiquement, une forte énergie d’anisotropie de ces matériaux à l’échelle nanométrique est requise pour des applications dans le stockage de l’information ou l’hyperthermie pour lesquels ils sont considérés. Une connaissance fine des mécanismes régissant ces propriétés d’anisotropies magnétiques est ainsi primordiale pour la création de nouveaux objets aux propriétés magnétiques contrôlées à l’échelle nanométrique. L’originalité de notre approche consiste à utiliser une technique fine du magnétisme, le dichroïsme magnétique circulaire des rayons X (XMCD) à l’étude des anisotropies et couplages magnétiques des nanospinels composants les ferrofluides. Au cours de cette thèse, nous nous sommes intéressés à différentes stratégies possibles pour induire une forte énergie d’anisotropie aux nanospinels de ferrite par l’utilisation de cobalt. Des nanoparticules de tailles et compositions variées ont été obtenues par différentes voies de synthèse, et nous démontrons que l’anisotropie magnétique de ces systèmes est fortement gouvernée par la symétrie de site du Co2+ en structure spinel qui peut être directement corrélé au processus de synthèse utilisé. Nous nous sommes aussi intéressés à l’ordre et au couplage magnétique de ferrite spinels structurés en coeur-coquille, dont le cœur et la coquille sont réalisés à partir de matériaux aux propriétés magnétiques intrinsèques différentes. Nous montrons ainsi que pour des nanospinels MnFe2O4@CoFe2O4, la très fine coquille formée de CoFe2O4 impose une forte anisotropie magnétique au cœur doux de MnFe2O4. Enfin, nous nous sommes intéressés à une troisième classe de ferrofluide à base de nanospinels, les ferrofluides binaires, constitué d’un mélange physique de ferrofluides aux propriétés magnétiques intrinsèques différentes. Pour de tels systèmes, il est essentiel de préserver le liquide porteur du ferrofluide pour ne pas dénaturer les interactions entre particules existantes. L’un des objectifs de cette thèse fut donc d’étendre la technique du XMCD à l’étude d’échantillons de ferrofluides in situ, dans leur phase liquide ou gelée. Nous avons débuté la conception d’une cellule liquide compatible avec les rayons X mous et un environnement ultra-vide sur la ligne de lumière DEIMOS (SOLEIL) qui est toujours en développementFerrofluids are colloidal suspensions of magnetic nanoparticles dispersed in a carrier liquid. The intimate interaction between the magnetic nanoparticles and the liquid provides a unique system, from both fundamental and industrial application point of views, whose flow and properties can be precisely controlled using an external magnetic field. Magnetic nanoparticles of spinel ferrites MFe2O4 (M = Fe2+, Co2+, Mn2+…) are of particular scientific interest and have been extensively studied for their electrical and magnetic properties. Spinel ferrites find potential applications, notably in storage devices, for computers, or hyperthermia, for cancer treatment, where high magnetic anisotropy energies are required at the nanoscale. However, deeper knowledges of the fine mechanisms playing a significant role on the magnetic anisotropies existing in the nanospinels are necessary to help the creation of rationalized materials with controlled magnetic anisotropies for the requirement of the system. In this thesis, we have used X-ray Magnetic Circular Dichroism (XMCD) as an original approach for probing the magnetic anisotropies and magnetic couplings of nanospinels obtained in ferrofluids. The nanoparticles are iron bearing spinels for which cobalt ions have been introduced in the spinel structure of the nanoparticles as a true makers of magnetic anisotropy. First, magnetic nanospinels have been synthesized by tuning their size and composition and using different synthesis processes. XMCD investigations revealed that the coercive field of the nanospinels is governed by the concentration of Co2+ ions sitting in octahedral sites of the spinel structure, and this can be directly linked to some synthesis parameters. Then, we have investigated core@shell nanoparticles, which can be synthesized with an appropriate choice of magnetic anisotropies for the core and the shell in order to tailor optimal magnetic properties. In the case of MnFe2O4@CoFe2O4, our findings reveal that the very thin CoFe2O4 shell imposes a strong magnetic anisotropy to the otherwise very soft MnFe2O4 core. The other class of ferrofluids that has been investigated during this thesis are binary ferrofluids that are constituted of two different types of magnetic nanoparticles. For such systems, the carrier liquid must be preserved to understand the magnetic interactions in the ferrofluid as they are. Another motivation of this thesis was thus to extend XMCD to the in situ investigation of the nanospinels dispersed in ferrofluids. We have been started a liquid cell development in the DEIMOS beamline at SOLEIL. The setup is still in progress and is aimed at being compatible with soft X-Rays short penetration depth and ultra-high vacuum environment. Hard X-ray photon-in/photon-out spectroscopy coupled to XMCD (1s2p RIXS-MCD) can be a very valuable alternative to soft X-ray XMCD at K-edge of 3d elements when liquid cell sample environment is required. The instrumental development of a liquid cell used with 1s2p RIXS-MCD spectroscopy allowed us to investigate the nanoparticles directly in the ferrofluids revealing interparticles magnetic couplings in binary ferrofluids
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Khelfallah, Malika. "Magnetic properties of ferrofluids of self-assembled nano-magnets." Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS502.
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Cette thèse a pour objectif principal d'explorer les effets de l’assemblage créé par les interactions magnétiques dipolaires entre des nanoparticules magnétiques en suspension colloïdales dans un liquide (ferrofluide) sur les propriétés magnétiques de ce ferrofluide. Ce travail se base sur la caractérisation approfondie de ferrofluides constitués de nanoparticules en forme de fleurs composées de matériaux magnétiques durs tels que la ferrite de cobalt (CoFe2O4), ou de matériaux magnétiques mous comme la ferrite de manganèse (MnFe2O4) et la maghémite (γ-Fe2O3). Les propriétés magnétiques de ces ferrofluides ont été mesurées à l'aide de magnétométrie classique, mettant en évidence l'influence significative de la composition chimique des nanoparticules sur les caractéristiques macroscopiques du ferrofluide. De plus, je me suis intéressée à la structuration des nanoparticules dans le ferrofluide liquide, en observant des particules isolées ainsi que la formation d'assemblages et d'agrégats, grâce à une méthode de Microscopie Electronique en Transmission cryogénique, avec un protocole développé spécifiquement pendant la thèse. L'impact de la morphologie des nanoparticules sur leurs propriétés magnétiques a été exploré grâce à la tomographie, imagerie en trois dimensions des nanoparticules, en collaboration avec le laboratoire IPCMS de Strasbourg. À l'échelle nanométrique, les propriétés magnétiques des assemblages ont été mesurées au moyen de l'holographie électronique, en collaboration avec le laboratoire CEMES de Toulouse. L'introduction des ferrofluides binaires, définis comme des mélanges de ferrofluides composés de nanoparticules de matériaux magnétiques durs et mous, a permis d'explorer de nouvelles interactions magnétiques dipolaires. Ces matériaux permettent de créer des ferrofluides aux propriétés nouvelles pouvant présenter un intérêt pour des applications biomédicales. Ces ferrofluides binaires ont révélé des propriétés magnétiques globales originales qui diffèrent de la simple addition des propriétés individuelles des ferrofluides originels. En outre, l'organisation des nanoparticules dans le ferrofluide binaire a été minutieusement étudiée en utilisant la spectroscopie chimiquement sélective et résolue spatialement par microscopie à rayons X en transmission sur la ligne HERMES du synchrotron SOLEIL, permettant d'obtenir des cartographies chimiques d’assemblages de nanoparticules de CoFe2O4 et de MnFe2O4. La séparation des contributions magnétiques des deux types de nanoparticules composant le ferrofluide binaire a été réalisée à l'aide d’une technique de magnétométrie appelée diagramme de FORC (First Order Reversal Curve), en collaboration avec le laboratoire IPGP. Les diagrammes de FORC ont permis d’identifier et d’évaluer l’influence des nanoparticules de CoFe2O4 sur le comportement magnétique des nanoparticules de MnFe2O4 dans le ferrofluide binaire. De plus, des mesures de courbes d’aimantation chimiquement sélective par spectroscopie ont été réalisées grâce à une cellule liquide permettant une mesure in-situ des ferrofluides, avec des expériences menées sur la ligne GALAXIES du synchrotron SOLEIL. Enfin, une comparaison des propriétés magnétiques de différents ferrofluides binaires a été entreprise, en variant le ratio entre matériau magnétique dur et mou, la composition du matériau mou ainsi que la taille des nanoparticules, offrant ainsi une perspective complète sur les possibilités de conception et d'optimisation de ces matériaux magnétiques avancés. Cette thèse établit une relation significative entre la structuration des nanoparticules dans le ferrofluide et leurs propriétés magnétiquesThe main objective of this thesis is to explore the effects of the assembly caused by dipolar magnetic interactions between magnetic nanoparticles suspended in a liquid (so-called ferrofluid) on the magnetic properties of this ferrofluid. It is based on the in-depth characterization of ferrofluids made up of flower-shaped nanoparticles composed of hard magnetic materials such as cobalt ferrite (CoFe2O4), or soft magnetic materials such as manganese ferrite (MnFe2O4) and maghemite (γ- Fe2O3). The magnetic properties of these ferrofluids were measured using standard magnetometry methods, highlighting the significant influence of the chemical composition of the nanoparticles on the macroscopic characteristics of the ferrofluid. In addition, this research focused on the structuring of nanoparticles in liquid ferrofluid, by observing isolated particles, as well as the formation of assemblies and aggregates, using a cryogenic Transmission Electron Microscopy method, with a protocol developed specifically during the thesis. The impact of nanoparticle morphology on their magnetic properties was explored using tomography, three-dimensional imaging of nanoparticles, in collaboration with the IPCMS laboratory in Strasbourg. At the nanoscale, the magnetic properties of the assemblies were measured using electron holography, in collaboration with the CEMES laboratory in Toulouse. The study of binary ferrofluids, defined as ferrofluid mixtures composed of nanoparticles of hard and soft magnetic materials, has enabled new dipolar magnetic interactions to be explored. These new materials allow creating ferrofluids with novel properties that may be of interest for biomedical applications. These binary ferrofluids have revealed original bulk magnetic properties that differ from the simple addition of the individual properties of the original ferrofluids. In addition, the organization of nanoparticles in the binary ferrofluid has been meticulously studied using chemically selective and spatially resolved transmission X-ray microscopy on the HERMES beamline at the SOLEIL synchrotron, yielding chemical mappings of CoFe2O4 and MnFe2O4 nanoparticle assemblies. The separation of the magnetic contributions of the two types of nanoparticles composing the binary ferrofluid was achieved using a magnetometry technique known as the FORC (First Order Reversal Curve) diagram, in collaboration with the IPGP laboratory. FORC diagrams were used to assess the influence of CoFe2O4 nanoparticles on the magnetic behavior of MnFe2O4 nanoparticles in the binary ferrofluid. In addition, spectroscopic measurements of chemically selective magnetization curves were carried out using a liquid cell for in-situ ferrofluid measurements, with experiments carried out on the GALAXIES beamline at the SOLEIL synchrotron. Finally, a comparison of the magnetic properties of different binary ferrofluids was undertaken, by varying the ratio between hard and soft magnetic components, the composition of the soft material as well as the size of the nanoparticles, thus providing a comprehensive perspective on the design and optimization possibilities of these advanced magnetic materials. This thesis establishes a significant relationship between the structuring of nanoparticles in ferrofluid and their magnetic properties
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Daffé, Niéli. "Anisotropies and Magnetic Couplings of Texturable Ferrofluids." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066640.pdf.
Full textAbstract:
Les ferrofluides sont des suspensions colloïdales de nanoparticules magnétiques dispersées dans un liquide porteur. La possibilité de moduler les propriétés des ferrofluides in situ en appliquant un champ magnétique externe leur procure un fort potentiel d’étude, à la fois d’un point de vue fondamental ou pour des applications industrielles variées. En particulier, les nanospinels de ferrite ferrimagnétiques MFe2O4 (M = Fe2+, Co2+, Mn2+…) sont largement étudiés pour leurs propriétés électriques et magnétiques. Plus spécifiquement, une forte énergie d’anisotropie de ces matériaux à l’échelle nanométrique est requise pour des applications dans le stockage de l’information ou l’hyperthermie pour lesquels ils sont considérés. Une connaissance fine des mécanismes régissant ces propriétés d’anisotropies magnétiques est ainsi primordiale pour la création de nouveaux objets aux propriétés magnétiques contrôlées à l’échelle nanométrique. L’originalité de notre approche consiste à utiliser une technique fine du magnétisme, le dichroïsme magnétique circulaire des rayons X (XMCD) à l’étude des anisotropies et couplages magnétiques des nanospinels composants les ferrofluides. Au cours de cette thèse, nous nous sommes intéressés à différentes stratégies possibles pour induire une forte énergie d’anisotropie aux nanospinels de ferrite par l’utilisation de cobalt. Des nanoparticules de tailles et compositions variées ont été obtenues par différentes voies de synthèse, et nous démontrons que l’anisotropie magnétique de ces systèmes est fortement gouvernée par la symétrie de site du Co2+ en structure spinel qui peut être directement corrélé au processus de synthèse utilisé. Nous nous sommes aussi intéressés à l’ordre et au couplage magnétique de ferrite spinels structurés en coeur-coquille, dont le cœur et la coquille sont réalisés à partir de matériaux aux propriétés magnétiques intrinsèques différentes. Nous montrons ainsi que pour des nanospinels MnFe2O4@CoFe2O4, la très fine coquille formée de CoFe2O4 impose une forte anisotropie magnétique au cœur doux de MnFe2O4. Enfin, nous nous sommes intéressés à une troisième classe de ferrofluide à base de nanospinels, les ferrofluides binaires, constitué d’un mélange physique de ferrofluides aux propriétés magnétiques intrinsèques différentes. Pour de tels systèmes, il est essentiel de préserver le liquide porteur du ferrofluide pour ne pas dénaturer les interactions entre particules existantes. L’un des objectifs de cette thèse fut donc d’étendre la technique du XMCD à l’étude d’échantillons de ferrofluides in situ, dans leur phase liquide ou gelée. Nous avons débuté la conception d’une cellule liquide compatible avec les rayons X mous et un environnement ultra-vide sur la ligne de lumière DEIMOS (SOLEIL) qui est toujours en développementFerrofluids are colloidal suspensions of magnetic nanoparticles dispersed in a carrier liquid. The intimate interaction between the magnetic nanoparticles and the liquid provides a unique system, from both fundamental and industrial application point of views, whose flow and properties can be precisely controlled using an external magnetic field. Magnetic nanoparticles of spinel ferrites MFe2O4 (M = Fe2+, Co2+, Mn2+…) are of particular scientific interest and have been extensively studied for their electrical and magnetic properties. Spinel ferrites find potential applications, notably in storage devices, for computers, or hyperthermia, for cancer treatment, where high magnetic anisotropy energies are required at the nanoscale. However, deeper knowledges of the fine mechanisms playing a significant role on the magnetic anisotropies existing in the nanospinels are necessary to help the creation of rationalized materials with controlled magnetic anisotropies for the requirement of the system. In this thesis, we have used X-ray Magnetic Circular Dichroism (XMCD) as an original approach for probing the magnetic anisotropies and magnetic couplings of nanospinels obtained in ferrofluids. The nanoparticles are iron bearing spinels for which cobalt ions have been introduced in the spinel structure of the nanoparticles as a true makers of magnetic anisotropy. First, magnetic nanospinels have been synthesized by tuning their size and composition and using different synthesis processes. XMCD investigations revealed that the coercive field of the nanospinels is governed by the concentration of Co2+ ions sitting in octahedral sites of the spinel structure, and this can be directly linked to some synthesis parameters. Then, we have investigated core@shell nanoparticles, which can be synthesized with an appropriate choice of magnetic anisotropies for the core and the shell in order to tailor optimal magnetic properties. In the case of MnFe2O4@CoFe2O4, our findings reveal that the very thin CoFe2O4 shell imposes a strong magnetic anisotropy to the otherwise very soft MnFe2O4 core. The other class of ferrofluids that has been investigated during this thesis are binary ferrofluids that are constituted of two different types of magnetic nanoparticles. For such systems, the carrier liquid must be preserved to understand the magnetic interactions in the ferrofluid as they are. Another motivation of this thesis was thus to extend XMCD to the in situ investigation of the nanospinels dispersed in ferrofluids. We have been started a liquid cell development in the DEIMOS beamline at SOLEIL. The setup is still in progress and is aimed at being compatible with soft X-Rays short penetration depth and ultra-high vacuum environment. Hard X-ray photon-in/photon-out spectroscopy coupled to XMCD (1s2p RIXS-MCD) can be a very valuable alternative to soft X-ray XMCD at K-edge of 3d elements when liquid cell sample environment is required. The instrumental development of a liquid cell used with 1s2p RIXS-MCD spectroscopy allowed us to investigate the nanoparticles directly in the ferrofluids revealing interparticles magnetic couplings in binary ferrofluids
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Odenbach, Stefan. "Biodistribution magnetischer Nanopartikel in der Krebstherapie." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1223717775507-68325.
Full textAbstract:
Suspensionen magnetischer Nanopartikel – sogenannte Ferrofluide – haben in den vergangenen Jahren große Bedeutung bezüglich ihrer technischen Anwendung gewonnen. Parallel zur Entwicklung des technischen Einsatzes wird auch seit langer Zeit die Möglichkeit einer Verwendung in der Krebstherapie diskutiert. Allerdings haben Tierversuche gezeigt, dass für den erfolgreichen Übergang in klinische Studien noch wesentliche offene Fragen geklärt werden müssen, wobei die Biodistribution der magnetischen Partikel im Tumor und im gesamten behandelten Organismus eine der zu klärenden Kernfragen darstellt. Normalerweise werden hierfür histologische Schnitte durchgeführt, die jedoch nur lokale, zweidimensionale Informationen liefern. Einen detaillierten Einblick in die Verteilung bietet die Röntgen-Mikrotomografie, deren Einsatz bereits eine Reihe wesentlicher Erkenntnisse in diesem Zusammenhang erbracht hatSuspensions of magnetic nanoparticles – commonly called ferrofluids – are nowadays widely used in technical applications. Parallel to this development, it has been discussed for a long time whether these fluids could be used in cancer treatment. In this context, animal experiments have shown that there are still a number of fundamental questions to be clarified before proceeding to clinical tests. One of these points concerns determination of the biodistribution of the magnetic particles, both in the tumour tissue and in the organism as a whole. The standard determination method involves histological sections, but this provides only local, two-dimensional information. A much more detailed insight into the distribution of the particles can be obtained by means of x-ray microtomography, a method which has meanwhile already provided extensive and valuable information in this context
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Bentley, Caroline. "Optical and microwave properties of ferrofluids." Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290411.
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Лютий, Тарас Володимирович, Тарас Владимирович Лютый, Taras Volodymyrovych Liutyi, Олександр Юрійович Поляков, Александр Юрьевич Поляков, Oleksandr Yuriiovych Poliakov, S. Denisov, and P. Hanggi. "Technique of the Fast Ferrofluids Simulation." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35341.
Full textAbstract:
We present a highly-parallel implementation of the Langevin simulation method for modeling ferrofluids
on Graphical Processor Units (GPU). Our method is based on the Barnes-Hut algorithm. As a benchmark
we use the straightforward 'all-to-all interaction' algorithm. The obtained results are in good agreement
with known theoretical model. With the proposed method we were able to follow the evolution of a
system of one million interacting particles over long time-scales, the task hitherto is out of reach with the
standard, CPU-based numerical schemes.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35341
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Arantes, Fabiana Rodrigues. "Sistemas de nanopartículas magnéticas: estudos experimentais e simulações Monte Carlo." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26012015-111206/.
Full textAbstract:
Nesta tese apresentamos um estudo do comportamento magnético de sistemas de nanopartículas por meio de medidas experimentais e simulações Monte Carlo. Estudamos o papel das interações entre partículas experimentalmente a baixas temperaturas em amostras de ferrofluidos comerciais por meio de curvas ZFC-FC, delta m e diagramas FORC. Observamos nas curvas ZFC-FC o fenômeno de super-resfriamento e transições de fase do estado sólido para o líquido em ferrofluidos. Para amostras de cristais líquidos dopados com nanopartículas magnéticas, observamos a transição entre as fases isotrópica e nemática. Detectamos em amostras de ferrofluidos e em soluções micelares dopadas com nanopartículas um aumento da viscosidade na presença de um campo magnético aplicado, o chamado efeito magnetoviscoso, que surge devido às interações entre partículas. Nas simulações Monte Carlo, vimos que a temperatura crítica (Tc) diminui com o tamanho das partículas, e que esse comportamento pode ser descrito por uma lei de escala. As simulações também mostraram que uma camada morta na superfície das nanopartículas provoca uma pequena diminuição na temperatura crítica, o que não ocorre quando adicionamos uma camada dura, que pode aumentar significativamente Tc. Para simulações de um sistema de nanopartículas interagentes, demos especial atenção a interpretar de que forma as interações magnetizantes e desmagnetizantes se manifestam em diagramas FORC para um conjunto de nanopartículas com distribuição de tamanhos. Observamos que uma interação desmagnetizante está associada a um deslocamento do pico do diagrama FORC para campos locais de interação Hb positivos e que a presença de uma interação magnetizante pode deslocar esse pico para campos Hc , relacionados à distribuição de coercividades do sistema, maiores.In this thesis we present a study of the behavior of a system of magnetic nanoparticles by means of experimental measurements and Monte Carlo simulations. We experimentally study the role of the interactions between particles at low temperatures in commercial samples of ferrofluids through ZFC-FC, delta m curves, and FORC diagrams. We observed the phenomenon of supercooling and phase transitions from solid to liquid states in the ZFC-FC curves of ferrofluids. For the samples of liquid crystal doped with magnetic nanoparticles, we saw the transition between the isotropic and nematic phases. We detected in the samples of ferrofluids and in micellar solutions doped with nanoparticles an increase of the viscosity in the presence of an applied magnetic field, the so-called magnetoviscous effect, which arises due to interactions between particles. In the Monte Carlo simulations, we found that the critical temperature (Tc) decreases with particle size, a behavior that is described well by a scaling law. The simulations also showed that a dead layer on the surface of the nanoparticles causes a slight decrease in the critical temperature value, what does not occur when we add a hard layer, which increases Tc significantly. For simulations of a system of interacting nanoparticles, we paid special attention to interpret how the magnetizing and demagnetizing interactions manifest themselves in FORC diagrams for a set of nanoparticles with size distribution. We observed that demagnetizing interactions is associated with a displacement of the peak of the FORC diagram to positive values of the local field interaction Hb , and that the presence of a magnetizing interaction can shift this peak to larges values of the Hc field, related to the distribution of coercivities.
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Holmes, Mark G. "A study of magnetostatic interactions in ferrofluids." Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278921.
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Sakhnini, Lama Issam. "The microwave, optical and magnetic properties of magnetic fluids." Thesis, Bangor University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385796.
Full textBooks on the topic "Ferrofluids"
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Odenbach, Stefan, ed. Ferrofluids. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5.
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Pant, R. P., Vidya Nand Singh, Komal Jain, and Arvind Gautam. Material Aspects of Ferrofluids. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003274247.
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Odenbach, ed. Colloidal Magnetic Fluids: Basics, Development and Application of Ferrofluids. Berlin: Springer Verlag, 2008.
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Stierstadt, Klaus. Ferrofluide im Überblick. Wiesbaden: Springer Fachmedien Wiesbaden, 2020. http://dx.doi.org/10.1007/978-3-658-32708-8.
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1947-, T͡S︡ebers A. O., and Maĭorov M. M, eds. Magnetic fluids. Berlin: Walter de Gruyter, 1997.
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Magnetoviscous Effects in Ferrofluids. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45544-2.
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Odenbach, Stefan. Magnetoviscous Effects in Ferrofluids. Springer London, Limited, 2003.
Find full textBook chapters on the topic "Ferrofluids"
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Charles, Stuart W. "The Preparation of Magnetic Fluids." In Ferrofluids, 3–18. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_1.
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Odenbach, Stefan, and Steffen Thurm. "Magnetoviscous Effects in Ferrofluids." In Ferrofluids, 185–201. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_10.
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Bossis, G., O. Volkova, S. Lacis, and A. Meunier. "Magnetorheology: Fluids, Structures and Rheology." In Ferrofluids, 202–30. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_11.
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Alexiou, Ch, R. Schmid, R. Jurgons, Ch Bergemann, W. Arnold, and F. G. Parak. "Targeted Tumor Therapy with “Magnetic Drug Targeting”: Therapeutic Efficacy of Ferrofluid Bound Mitoxantrone." In Ferrofluids, 233–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_12.
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Fannin, Paul C. "Magnetic Spectroscopy as an Aide in Understanding Magnetic Fluids." In Ferrofluids, 19–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_2.
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Wiedenmann, Albrecht. "Magnetic and Crystalline Nanostructures in Ferrofluids as Probed by Small Angle Neutron Scattering." In Ferrofluids, 33–58. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_3.
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Rosensweig, Ronald E. "Basic Equations for Magnetic Fluids with Internal Rotations." In Ferrofluids, 61–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_4.
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Shliomis, Mark I. "Ferrohydrodynamics: Retrospective and Issues." In Ferrofluids, 85–111. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_5.
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Müller, Hanns Walter, and Mario Liu. "Ferrofluid Dynamics." In Ferrofluids, 112–23. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_6.
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Blums, Elmars. "Heat and Mass Transfer Phenomena." In Ferrofluids, 124–39. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45646-5_7.
Full textConference papers on the topic "Ferrofluids"
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Xiao, Wenjia, and Steffen Hardt. "The Dynamic Behavior of an Adaptive Liquid Microlens Driven by a Ferrofluidic Transducer." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30353.
Full textAbstract:
Ferrofluids are superparamagnetic suspensions of nanoparticles that can be used as transducers in microfluidic systems, among others. In corresponding setups a microscopic enclosure such as a microchannel is filled with a ferrofluid that is acted on by an external magnetic field. The induced motion of the ferrofluid is utilized to pump or manipulate minute amounts of liquids. Here the dynamic behavior of an adaptive liquid microlens driven by a ferrofluidic transducer is studied. Adaptive microlenses based on that principle promise a number of advantages over existing concepts, such as an increased tuning range of the focal length. It is shown that the delay time of the deformation of the lens surface to the displacement of the magnet producing the external field increases with increasing magnet speed. Dynamic leakage of the lens liquid around the ferrofluid plug, on the other hand, only occurs when the magnet speed exceeds a threshold value and further increases from that point onwards. When the viscosity of the lens liquid increases, both the delay time and the dynamic leakage increase.
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Brahmbhatt, Khushboo, Wujun Zhao, Zhaojie Deng, Leidong Mao, and Eric Freeman. "Magnetically Responsive Droplet Interface Bilayer Networks." In ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/smasis2015-9029.
Full textAbstract:
This work explores incorporating ferrofluids with droplet interface bilayer (DIB) membranes. Ferrofluids contain magnetic nanoparticles in solution with a stabilizing surfactant, providing a magnetically-responsive fluid. These fluids allow for remote mechanical manipulation of ferrofluid droplets through magnetic fields, and will allow for better control over the characteristics of networks of stimuli-responsive cellular membranes created through by DIB technique. This work involves several phases. First, a suitable biocompatible ferrofluid is synthesized, containing a neutral pH and a biocompatible surfactant. Once a proper ferrofluid is identified, it is tested as the aqueous phase for the creation of DIB membranes. Interfacial membranes between ferrofluid droplets are created and compared to non-ferrofluid DIB membranes. The interfacial membrane between two ferrofluid droplets was tested for leakage and stability, and the electrical characteristics of the interfacial membrane were studied and compared to non-ferrofluid DIB membranes. Once it is confirmed that the ferrofluid droplets do not negatively interfere with the formation of the artificial cellular membranes through the electrical measurements, the magnetically-responsive nature of the ferrofluid droplets are used to form large networks of DIB membranes through a simple magnetic field. These networks are easy to assemble and may be remotely manipulated, providing a significant step towards the rapid and simple assembly of DIB networks advancing towards the tissue scale.
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Özbey, Arzu, Mehrdad Karimzadehkhouei, Evrim Kurtoğlu, and Ali Koşar. "Simulation of Magnetic Actuation of Ferrofluids in Microtubes." In ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icnmm2013-73153.
Full textAbstract:
Magnetic actuation of ferrofluids with dynamic magnetic fields is one of the most promising research areas with its wide and different potential application areas such as biomedical and micropumping applications. Ferrofluid has the potential of opening up new possibilities. To have more understanding about various fields of engineering, more research should be conducted by considering both the experimental and modeling aspects. The most important parameters determining the flow property, flow rates and overall system efficiency are the quality and the topology of magnetic fields used in these systems. Therefore, the methods of dynamic magnetic field generation constitute a central problem to obtain desired performance. This study includes modeling and simulation of ferrofluid actuation with dynamic magnetic fields by using the COMSOL software and reports that ferrofluid actuation can be successfully used and the simulation results agree well with the experimental results.
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Gunde, Akshay C., and Sushanta K. Mitra. "Simulation of Microfluidic Flow Using Ferrofluids." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62072.
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Present day microfluidics widely uses electrokinetic effects like eletrosmosis and electrophoresis to achieve flow control. These methods require extensive micromachining processes. Also, the fabrication of valves and valve-seats is difficult, which frequently leads to leakages and eventual breakdown of the system. This paper introduces the use of ferrofluids as an alternative for flow control in microchannels. Numerical simulation of flow through a microchannel using a ferrofluid in the presence of an external magnetic field is performed by coupling the flow and magnetic phenomena. An additional term calculated from the ferrofluid magnetization equations, is introduced in the Navier-Stokes equations to account for the magnetic force. The maximum velocity in a magnetically driven flow is shown to be a linear function of magnitude of magnetization of the permanent magnet. Further, the insertion of micron-size magnetic particles (referred here as magnetic plugs) in the flow field has been discussed. These plugs can be used to provide appropriate barriers to the flow by controlling their movement externally. Using the combination of ferrofluid and magnetic plugs, flow control can be achieved by the variation of external magnetic field alone.
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Asmatulu, R., B. Zhang, and N. Nuraje. "Guiding the Nonmagnetic Particles by Magnetic Nanoparticles in a Microfluidic Device Using External Magnetic Fields." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12340.
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A microfluidic device was fabricated via UV lithography technique to separate nonmagnetic fluoresbrite carboxy microspheres (∼4.5 μm) from the ferrofluids made of magnetic nanoparticles (∼10 nm). A mixture of microspheres and ferrofluid was injected to lithographically developed Y shape micro channels, and then by applying the external magnet field, the fluoresbrite carboxy microspheres and ferrofluids were clearly separated into different channels because of the magnetic force acting on those nonmagnetic particles. During the fabrication, a number of different parameters, such as UV exposure times, UV power level and photoresist thickness were tested to optimize for our needs. In addition, in the magnetic field testing, different pumping speeds, and particle concentrations associated with the various distances between the magnet and the microfluidic system were studied for an efficient separation.
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Mohammadi, Maziar, Mehdi Taslimifar, Mohammad Hassan Saidi, Mohammad Behshad Shafii, Hossein Afshin, and Siamak Kazemzadeh Hannani. "Experimental Investigation of an Open Loop Pulsating Heat Pipe Using Ferrofluid." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75069.
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The present work investigates the thermal performance of a five turn Open Loop Pulsating Heat Pipe (OLPHP). The effects of working fluid namely water and ferrofluid, heat input, ferrofluid concentration, charging ratio, and orientation will be considered. Experimental results show that using ferrofluids can enhance the thermal performance in comparison with the case of distilled water. In addition, applying a magnetic field on the OLPHP charged with ferrofluid reduces its thermal resistance. Variation of the ferrofluid concentration results in different thermal performance of the OLPHP. Best charging ratio for the distilled water and ferrofluid without magnetic field is 60% in most of the cases, while in the case of ferrofluid in the presence of magnetic field at low heat inputs, 20% and at high heat inputs 60% of charging ratios have lowest thermal resistance.
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Taslimifar, Mehdi, Maziar Mohammadi, Ali Adibnia, Hossein Afshin, Mohammad Hassan Saidi, Mohammad Behshad Shafii, and Siamak Kazemzadeh Hannani. "Effects of Surface Coating of Nanoparticles on Thermal Performance of Open Loop Pulsating Heat Pipes." 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/ht2012-58064.
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Homogenous dispersing of nanoparticles in a base fluid is an excellent way to increase the thermal performance of heat transfer devices especially Heat Pipes (HPs). As a wickless, cheap and efficient heat pipe, Pulsating Heat Pipes (PHPs) are important candidates for thermal application considerations. In the present research an Open Loop Pulsating Heat Pipe (OLPHP) is fabricated and tested experimentally. The effects of working fluid namely, water, Silica Coated ferrofluid (SC ferrofluid), and ferrofluid without surface coating of nanoparticles (ferrofluid), charging ratio, heat input, and application of magnetic field on the overall thermal performance of the OLPHPs are investigated. Experimental results show that ferrofluid has better heat transport capability relative to SC ferrofluid. Furthermore, application of magnetic field improves the heat transfer performance of OLPHPs charged with both ferrofluids.
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Alazemi, Saad F., and Mohammed F. Daqaq. "Ferrofluids for Concurrent Vibration Absorption and Energy Harvesting." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3298.
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This paper proposes a novel Tuned Magnetic Fluid Damper (TMFD) with energy harvesting capabilities to concurrently mitigate structural vibrations and harvest vibratory energy. The energy harvesting TMFD consists of a rectangular container carrying a magnetized ferrofluid and mounted on a vibrating structure. The ferrofluids geometric and material properties (height, surface area, magnetization) are tuned such the first modal frequency of the fluid column matches the first modal frequency of the structure. The one-to-one resonant interactions between the structure and the fluid column results in a direct energy transfer mechanism which mitigates the vibration of the structure by channeling energy to the ferrofluid. Consequently, the fluid undergoes a sloshing motion with large-amplitude surface waves that change the orientational order of the magnetic dipoles in the fluid. This creates a time-varying magnetic flux, which induces an electromotive force in a coil wound around the container. The electromotive force transforms a small part of the fluids kinetic energy into electricity by generating a current in the coil. Experimental studies performed on an actual TMFD prototype clearly demonstrate its vibration suppression potential and energy generation capabilities.
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Gutierrez, Gustavo, and Radhames Rodriguez. "Conductivity Measurement of Ferrofluid Using Transient Hot Wire Method." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43365.
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Thermal conductivity of the ferrofluids is a difficult property to predict theoretically. Existing models can not explain the real behavior of such fluids and mismatch the results found in the experiments. Experimentation is then the most reliable way to determine the observed enhancement in thermal conductivity of ferrofluids. The transient hot wire method is an experimental technique in which the thermal conductivity is obtained by measuring a temperature change, respect to time in a thin wire, caused by a constant current passing through it. Some advantages of this method are the almost complete elimination of natural convection effects, its fast implementation and its high accuracy. In order to use the transient hot-wire technique in a ferrofluid a modification must be made because the transient hot-wire method cannot be applied to electrical conducting fluids since part of the current will be conducted by the fluid, generating uncertainties in the current passing through the wire. These uncertainties will affect the voltage measurement over predicting the thermal conductivity. To prevent the current to pass through the fluid the hot wire has to be covered with an electrical insulating coating. Then, it is necessary to calibrate the wire with a calibrating constant in order to correct the effect of the coating in the RTD. For calibration purposes, thermal conductivity measurements of known fluids have been carried out. For this purpose, substances like water, toluene acetone and heptane are used. In this study the transient hot-wire method is implemented to measure the thermal conductivity of different water-based ferrofluids and oilbased ferrofluids. Parametric Studies are carried out numerically to understand the effect of the coating in the technique.
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Gutierrez, Gustavo, Juan Catan˜o, and Oscar Perales-Perez. "Development of a Magnetocaloric Pump Using a Mn-Zn Ferrite Ferrofluid." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13784.
Full textAbstract:
Magnetic fluids or ferrofluids are colloidal dispersions of magnetic nanoparticles in a liquid carrier. These nanoparticles have a specific size range in order to remain suspended in the liquid, about 3 to 15 nm. In this range Brownian motion (thermal molecular motion in the liquid) keeps the particles from settling out. Because magnetic particles tend to aggregate, and aggregates sediment faster than single particles, the particles are coated with a stabilizing dispersing agent. The surfactant must be matched to the carrier type and must overcome the attractive Van der Waals and magnetic forces between the particles to prevent agglomeration even when a strong magnetic field is applied to the ferrofluid. A device that can pump a fluid with no moving mechanical parts represents a very encouraging alternative since such device would be practically maintenance free. A magnetocaloric pump achieves this purpose by providing a pressure gradient to a ferrofluid placed inside a magnetic field while experiencing a temperature change. If the temperature change is produced by extracting heat out of an element that needs refrigeration, coupling this heat via a heat pipe with the magnetocaloric pump will result in a completely passive cooling system. For applications near ambient temperature the ferrofluid must have specific characteristics such as low Curie temperature, high pyromagnetic coefficient, high thermal conductivity and low viscosity. This work presents the detailed description of the synthesis of ferrofluids composed of Mn-Zn ferrite nanoparticles and the characterization of its magnetic and thermal properties. Different composition of Mn-Zn ferrites nanoparticles were produce and evaluated. This ferrite ferrofluid was compared with commercially available magnetite ferrofluid in a magnetocaloric pump prototype. Results of saturation magnetization, pyromagnetic coefficient, Curie temperature, particle size, viscosity and pressure increment inside the magnetocaloric pump are presented.
Reports on the topic "Ferrofluids"
1
Srikanth, Hariharan. Static and Dynamic Magnetic Response in Ferrofluids. Fort Belvoir, VA: Defense Technical Information Center, October 2007. http://dx.doi.org/10.21236/ada482373.
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2
Borglin, S. E., G. J. Moridis, and C. M. Oldenburg. Experimental investigation of magnetically driven flow of ferrofluids in porous media. Office of Scientific and Technical Information (OSTI), August 1998. http://dx.doi.org/10.2172/290810.
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3
Moridis, G. J., S. E. Borglin, C. M. Oldenburg, and A. Becker. Theoretical and experimental investigations of ferrofluids for guiding and detecting liquids in the subsurface. FY 1997 annual report. Office of Scientific and Technical Information (OSTI), March 1998. http://dx.doi.org/10.2172/296663.
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4
Borglin, S., G. Moridis, and A. Becker. Magnetic detection of ferrofluid injection zones. Office of Scientific and Technical Information (OSTI), March 1998. http://dx.doi.org/10.2172/290876.
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5
Knappenberger, Jr, and Kenneth L. Magnetoplasmonic Nanomaterials: A Route to Predictive Photocatalytic, Light-Harvesting and Ferrofluidic Properties. Fort Belvoir, VA: Defense Technical Information Center, October 2013. http://dx.doi.org/10.21236/ada606151.
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