Dielectric Properties of Magnetic Liquids in High Electric Fields

Herchl, F.; Kopčanský, P.; Τimko, M.; Koneracká, M.; Marton, K.; Kolcunová, Iraida; Tomčo, L.

doi:10.12693/aphyspola.113.569

Cited by 8 publications

(5 citation statements)

References 4 publications

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“…After the last washing, the oleic acid (as surfactant to prevent irreversible aggregation of magnetic particles) and mineral oil ITO 100 (as carrier liquid) were added at 70 • C in the volume ratio 1:1. Subsequently ITO 100 was added dropwise during stirring and heating in order to obtain the appropriate volume concentration of magnetite nanoparticles [14].…”

Section: Sample Preparationmentioning

confidence: 99%

Structuring from nanoparticles in oil-based ferrofluids

Rozynek

Józefczak²,

Knudsen

et al. 2011

Eur. Phys. J. E

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The effect of magnetic field on the structure formation in an oil-based magnetic fluid with various concentrations of magnetite particles was studied. The evaluation of the experimental data obtained from small-angle X-ray scattering and ultrasonic attenuation indicates the formation of chain-like aggregates composed of magnetite particles. The experimental data obtained from ultrasonic spectroscopy fit well with the recent theoretical model by Shliomis, Mond and Morozov but only for a diluted magnetic fluid. In this model it is assumed that a dimer is the main building block of a B -field-induced chain-like structure, thus the estimation of the nematic order parameter does not depend on the actual length of the structure. The scattering method used reveals information about the aggregated structure size and relative changes in the degree of anisotropy in qualitative terms. The coupling constant [Formula: see text] , concentrations [Formula: see text] , average particle size d and its polydispersity [Formula: see text] were initially obtained using the vibrating sample magnetometry and these results were further confirmed by rheometry and scattering methods. Both the particles' orientational distribution and the nematic order parameter S were inferred from the ultrasonic measurements. The investigation of SAXS patterns reveals the orientation and sizes of aggregated structures under application of different magnetic-field strengths. In addition, the magnetic-field-dependent yield stress was measured, and a relationship between the yield stress and magnetic-field strength up to 0.5 T was established.

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Section: Sample Preparationmentioning

confidence: 99%

Structuring from nanoparticles in oil-based ferrofluids

Rozynek

Józefczak²,

Knudsen

et al. 2011

Eur. Phys. J. E

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“…The magnetic particles such as Fe 3 O 4 , Fe 2 O 3 etc., if dispersed in the transformer oil, also enhance the dielectric performance of the suspension. The magneto-dielectric effect due to chain formation as well as reorientation of magnetite influences the particle distribution as well as stability of the suspension [14][15][16][17][18][19]. However, effect of particle size on the dielectric performance of nano insulating oils is rarely reported in the literature experimentally; hence need more attention towards experimentation of such phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Effects of nanostructure permittivity and dimensions on the increased dielectric strength of nano insulating oils

Katiyar

Dhar

Nandi

et al. 2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Theoretical analysis suggested that the heat flux can increase by about 20% while using magnetic oil containing a 1% volume fraction of SPIO-based nanoparticles . Although the subject has been already reported in the literature, − ,− the very promising industrial application of insulating magnetic oils for transformers, expected to provide device extended life at higher efficiency operation profiles while reducing the risk of accidents, is at its infancy.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Molecular Surface Coating on the Stability of Insulating Magnetic Oils

et al. 2009

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Surface functionalization of a series of nanosized iron oxide particles (average diameter around 6 nm) with oleic acid was realized in this study. The aim is to suspend the surface-functionalized nanoparticulated materials in insulating mineral oil and evaluate their colloidal stability as a function of time. Nanoparticulated samples presenting stoichiometry close to maghemite were obtained by oxidation of a freshly precipitated magnetite sample. Systematic variations observed in the Fe3+/Fe2+ ratio, average particle size, and lattice constant were attributed to differences in oxidation route and oxidation condition employed. Morphological, compositional, thermal, optical and magnetic characterization techniques were used in the investigation of native (P, PN1, PN2, POX1, POX3, and POX7) and surface-functionalized (POA, PN1OA, PN2OA, POX1OA, POX3OA, and POX7OA) samples. While suspending the oleic-acid-coated nanosized iron oxide particles in insulating mineral oil, the best colloidal stability was achieved at the oxidation profile of Fe3+/Fe2+ = 40 (5.9 nm average core diameter), leading to a surface grafting coefficient of about 75% of a full monolayer coating of chemisorbed species only and resulting in the smallest observed hydrodynamic radius (8.1 nm). Within the range of our investigation, our findings reveal the characteristics and the chemical protocol used to produce a magnetic fluid sample embodying long-term colloidal stability, thus representing a very much promising material for application as a refrigerating fluid in power transformers and related devices.

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Dielectric Properties of Magnetic Liquids in High Electric Fields

Cited by 8 publications

References 4 publications

Structuring from nanoparticles in oil-based ferrofluids

Structuring from nanoparticles in oil-based ferrofluids

Effects of nanostructure permittivity and dimensions on the increased dielectric strength of nano insulating oils

Investigation of the Molecular Surface Coating on the Stability of Insulating Magnetic Oils

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