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    Wyświetlanie 1-3 z 3
    Tytuł:
    Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids
    Autorzy:
    Rajňák, M.
    Kurimský, J.
    Dolník, B.
    Cimbala, R.
    Paulovičová, K.
    Kopčanský, P.
    Timko, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032784.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    47.65.Cb
    77.22.Ch
    77.22.Gm
    82.70.Dd
    Opis:
    In this paper, we report on the temperature dependent broadband dielectric response of a ferrofluid based on transformer oil and magnetite nanoparticles covered with oleic acid molecules. For that purpose the method of dielectric spectroscopy has been chosen in the frequency range from 20 Hz up to 100 kHz. The experiments were carried out on thin film ferrofluid samples confined in a glass plate capacitor containing indium tin oxide (ITO) plate electrodes. The obtained complex permittivity spectrum shows a pronounced dielectric dispersion in the low frequency range. Taking into account the ferrofluid composition we associate this relaxation with ion impurity polarization at the nanoparticle-oil interface. The strong temperature dependence of the relaxation process has been found when conducting the experiments in the temperature range from 298 K to 358 K. The relaxation time of the revealed process exhibits a typical Arrhenius behavior. Based on the conducted experiments and analysis, we propose some reasonable practical applications of the studied ferrofluid in the field of electrical engineering.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 943-945
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Generation of Fe₃O₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field
    Autorzy:
    Kurimský, J.
    Rajňák, M.
    Cimbala, R.
    Paulovičová, K.
    Timko, M.
    Kopčanský, P.
    Kolcun, M.
    Kosterec, M.
    Kruželák, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032151.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    47.57.J-
    47.65.Cb
    77.22.Jp
    77.22.Ch
    82.70.Dd
    Opis:
    In the paper the experimental study of magnetic nanoparticle aggregation in a transformer oil based ferrofluid driven by an external electric field is reported. The studied ferrofluid was composed of the magnetite nanoparticles, oleic acid surfactant, and transformer oil. Generally, it is considered that superparamagnetic nanoparticles do not interact in the absence of external magnetic field. In the paper we present an experimental observation of the particle assembly formation in a direct current external electric field by optical microscopy. During the observation no external magnetic field was applied. A diluted low-polarity ferrofluid drop on a glass surface was exposed to the external static inhomogeneous electric field. It is assumed that induced dipole-dipole interaction and subsequent dielectrophoretic motion give rise to the electrohydrodynamic flow in the fluid after a certain time period. As a result, a visible particle chain was formed at the drop electrical equator. This demonstration is expected to contribute to the understanding of the streamer formation and electrical breakdown in transformer oil based ferrofluids.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 907-909
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ultrasound Frequency Analysis of a Magnetic Fluid in Low-Intensity External Magnetic Field
    Autorzy:
    Kurimský, J.
    Rajňák, M.
    Cimbala, R.
    Dolník, B.
    Tóthová, J.
    Paulovičová, K.
    Timko, M.
    Kopčanský, P.
    Kolcunová, I.
    Petráš, J.
    Džmura, J.
    Balogh, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1032764.pdf
    Data publikacji:
    2017-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.58.+z
    43.60.+d
    47.65.Cb
    82.70.Dd
    83.80.Hj
    Opis:
    This work deals with an interaction of a magnetic fluid of a dielectric nature with a magnetic field by means of ultrasound waves measurements and analysis. Ultrasound analysis is known as a non-destructive inspection tool often used in technical diagnostics, moreover, it has numerous applications in medicine and biology, too. We report the low-frequency ultrasound analysis of a dielectric magnetic fluid in a low-intensity external static magnetic field. The studied magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Experiments were carried out by using an ultrasonic testing cell. The cell was exposed to a magnetic field of 50 mT in both parallel and perpendicular direction to the waves propagation. A through-transmission mode measurement was applied, where two fixed narrow-band transducers with completely shielded crystal for maximum RFI/EMI immunity (Physical Acoustic R15I-AST, the resonant frequency 150 kHz) served as a transmitter and a receiver. In this way we carried out the measurement of the frequency-dependent ultrasonic response to a rectangle calibrating signal of 5 μs pulse width. Digitized signals were recorded for further analysis. We present the frequency domain analysis of the low-frequency ultrasound in magnetic fluid. The frequency spectrum in magnetic fluid colloidal system was calculated by the Fourier transformation method. Results show that there is a frequency shift in the amplitude-frequency spectrum caused by the step-up magnetic field. The higher the magnetic field, the higher the frequency of the peaks. The effect of particle aggregation in magnetic field on the ultrasound wave propagation is discussed in the paper.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 4; 910-912
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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