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Tytuł:
Temperature Effect on the Structure of Transformer Oil Based Magnetic Fluids Using Acoustic Spectroscopy
Autorzy:
Kúdelčík, J.
Bury, P.
Drga, J.
Kopčanský, P.
Závišová, V.
Timko, M.
Powiązania:
https://bibliotekanauki.pl/articles/1427527.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Mm
75.75.Jn
Opis:
The changes in structural arrangement in transformer oil based magnetic fluids upon the effect of an external magnetic field and temperature were studied by acoustic spectroscopy. The attenuation of acoustic waves was measured as a function of an external magnetic field in the range of 0-300 mT, parallel to the direction of the field and as a function of temperature in the range of 15-35°C for various magnetic nanoparticles concentrations. The strong influence of the steeped magnetic field on the acoustic wave attenuation was detected and its hysteresis was observed, too. When a magnetic field is swept at a constant rate, the dominant interactions between the external magnetic field and the magnetic moment of the nanoparticles occur, leading to the aggregation of magnetic nanoparticles and clusters formation. However, the temperature of magnetic fluids has very important influence on the obtained dependences, where the mechanism of thermal motion acts against the cluster creation. The observed influences of magnetic field and temperature on the investigated magnetic liquids structure are discussed.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1169-1171
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Temperature on the Magneto-Dielectrics Effect of Oil-Based Ferrofluid
Autorzy:
Kúdelčík, J.
Hardoň, Š.
Bury, P.
Timko, M.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1030417.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.65.Cb
77.22.Gm
77.22.Ch
Opis:
The effect of temperature on the magneto-dielectrics behavior was studied by dielectric spectroscopy in the transformer oil-based ferrofluid with magnetic nanoparticles upon the effect of an external magnetic field. The frequency dependence of complex permittivity and dissipation factor were measured within the frequency range from 1 mHz to 10 kHz at different temperatures by a capacitance method. The dielectrics parameters were measured as a function of the external magnetic field in the range of 0-200 mT, parallel to the direction of the electric field as a function of temperature in the range of 15-35°C. The interaction between magnetic field and magnetic moments of nanoparticles led to the aggregation of magnetic nanoparticles to new structures which had influence on dielectric parameters. The dependence of these parameters at constant magnetic field on angle between the direction of the electric and magnetic fields (anisotropy) has been measured, too.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 483-485
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of Structural Changes of Water-Based Magnetic-Fluid by Acoustic Spectroscopy
Autorzy:
Kúdelčík, J.
Hardoň, Š.
Bury, P.
Timko, M.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1032248.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Mm
75.75.Jn
Opis:
The effect of an external magnetic field on the changes in structural arrangement of magnetic nanoparticles in water based magnetic fluid was studied by acoustic spectroscopy. When a magnetic field is increased, the interaction between the magnetic field and the magnetic moments of nanoparticles leads to the orientation of magnetic nanoparticles and their following aggregation to long chains that cause the increase of acoustic attenuation. The attenuation of acoustic waves measured for jump changes of the magnetic field to 100, 200, and 300 mT at temperature 20°C showed that the changes of acoustic attenuation increased slowly to a stabilized state that after switching off the magnetic field decreased immediately to initial value. The dependence of attenuation of acoustic waves at constant magnetic field on angle between the wave vector and direction of the applied magnetic field (attenuation anisotropy) has been measured, too. The measured anisotropy of acoustic attenuation attested structural changes of magnetic fluid in the magnetic field.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 919-921
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural Changes in Liquid Crystals Doped with Rod-Like Magnetic Particles Studied by Surface Acoustic Waves
Autorzy:
Bury, P.
Veveričík, M.
Kúdelčík, J.
Kopčanský, P.
Timko, M.
Závišová, V.
Powiązania:
https://bibliotekanauki.pl/articles/1032787.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Gd
75.50.Mm
43.35.Bf
Opis:
The effect of rod-like magnetic particles on liquid crystal (6CHBT) structural changes in electric and weak magnetic fields were studied by means of the attenuation of surface acoustic wave of frequency 30 MHz propagating along ferronematic liquid crystals. Three low volume concentrations (Φ=1×10¯⁵, 1×10¯⁴ and 1×10¯³) of rod-like magnetic particles were added to liquid crystal during its isotropic phase. Several measurements including the investigation of the effects of electrical and magnetic fields applied both separately and in conjunction as well as the influence of temperature on the surface acoustic wave attenuation were performed. The distinctive surface acoustic wave attenuation responses induced by both electric and magnetic fields in studied ferronematic liquid crystals have been observed suggesting both structural changes and the orientational coupling between magnetic moments of magnetic particles and the director of the liquid crystal. Obtained results confirmed the significant influence of the presence of magnetic particles on the structural properties and resulting behavior of 6CHBT liquid crystal.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 913-915
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Response of a Magnetic Fluid to Radio Frequency Electromagnetic Field
Autorzy:
Dolník, B.
Rajňák, M.
Cimbala, R.
Kolcunová, I.
Kurimský, J.
Balogh, J.
Džmura, J.
Petráš, J.
Kopčanský, P.
Timko, M.
Briančin, J.
Fabián, M.
Powiązania:
https://bibliotekanauki.pl/articles/1032825.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
41.20.Jb
41.20.Gz
75.50.Mm
81.70.Ex
07.50.Hp
Opis:
Electromagnetic pollution generated by the electrical devices has been regarded as a new form of pollution, harmful to the society as air and water pollution. The operation of electronic devices in a polluted electromagnetic environment has caused electromagnetic interference to become important concerns. Devices that are vulnerable to interference must often be shielded to protect them from the effects of electromagnetic interference. In this work we describe an interaction of a magnetic fluid based on transformer oil with alternating magnetic field. The magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Among the wide range of topics covered, we pay attention to an important field related to the absorption of electromagnetic field by magnetic fluid as a suitable candidate for applications where it is necessary to electrically isolate, remove excess of heat, and to shield electromagnetic fields. We present a method for the determination of shielding effectiveness of the magnetic fluid under high-frequency excitation conditions from 750 MHz to 3 GHz by means of magnetic near field measurements and analysis. Herein, we report the effect of magnetic volume fraction in the magnetic fluid and the effect of the sample thickness on the shielding effectiveness. We have found that the magnetic fluid has a frequency dependent "windows", characterized that either absorb the magnetic field, or facilitate penetration of the magnetic field through the barrier.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 946-948
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Polymer Immobilization on Magnetic Properties of Magnetosomes
Autorzy:
Timko, M.
Džarová, A.
Kovač, J.
Kopčanský, P.
Gojzewski, H.
Powiązania:
https://bibliotekanauki.pl/articles/1535115.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Cr
75.30.Gw
75.50.Mm
75.50.Tt
75.60.Ej
Opis:
The anisotropy of several PVA/magnetosomes magnetically textured films has been investigated from the point of view of magnetic properties. The thin film synthesized under the influence of a magnetic field (99 mT) shows the typical behavior of an anisotropic material. On sample textured in magnetic field the magnetisation loop measurements were performed in dependence on the direction of the external magnetic field with respect to the texture axis. The results of hysteresis measurements show that the magnetic field applied during the synthesis promotes an orientation of the chains of magnetosomes and permanently textured film is obtained after solidification. The obtained values for magnetic remanence and coercivity were dependent on the external magnetic field orientation and the alignment effect of particle moments may be clearly seen which is in agreement with the theoretical model of magnetic particle chains.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 995-997
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of Magnetic Fredericksz Transition in Ferronematics
Autorzy:
Kopčanský, P.
Koneracká, M.
Jadżyn, J.
Czechowski, G.
Żywucki, B.
Powiązania:
https://bibliotekanauki.pl/articles/1964799.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
61.30.Gd
Opis:
The magnetic Fredericksz transition in ferronematics (thermotropic nematic liquid crystals 7CB and MBBA combined with fine magnetic particles of a size 10 nm) as a function of concentration of magnetic particles was studied by using simple dielectric measurements. The increase of the threshold magnetic field is observed in 7CB based ferronematic while the decrease of threshold field in MBBA based ferronematic is observed when the concentration of magnetic particles is increased. Experimental results are discussed in the framework of Brochard, de Gennes and Burylov, Raikher theories.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 437-440
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Shielding Effectiveness of a Magnetic Fluid in Radio Frequency Range
Autorzy:
Dolník, B.
Rajňák, M.
Cimbala, R.
Kolcunová, I.
Kurimský, J.
Džmura, J.
Petráš, J.
Zbojovský, J.
Kosterec, M.
Kopčanský, P.
Timko, M.
Powiązania:
https://bibliotekanauki.pl/articles/1030481.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
41.20.Jb
41.20.Gz
75.50.Mm
81.70.Ex
07.50.Hp
Opis:
This article builds on the previous work and describes the interaction of transformer oil-based magnetic fluid (MF) with the radio frequency (RF) magnetic near-field. Three prepared samples of the MF used as a barrier to magnetic near-field, consist of transformer oil and dispersed magnetite nanoparticles coated with oleic acid. We pay attention to the important area related to the electromagnetic field shielding by the MF. Such sample of the MF may be a good candidate for applications where it is necessary to simultaneously electrically isolate, remove the excess of heat and to shield electromagnetic interference (EMI). We present a method for the determination of shielding effectiveness (SE) of the MF under RF excitation conditions ranging from 500 MHz to 3 GHz. We report the effect of magnetic volume fraction in the MF and the effect of the sample thickness on the SE.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 585-587
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Magnetic Particles on the Nematic Droplets Formation in Liquid Crystal
Autorzy:
Majorošová, J.
Gdovinová, V.
Tomašovičová, N.
Juríková, A.
Závišová, V.
Jadzyn, J.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1032205.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Mm
61.30.Gd
67.30.Hm
Opis:
In this work the thermotropic nematic liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) was dissolved in phenyl-isothiocyanate and doped with spherical magnetic particles with volume concentration ϕ₁=10¯⁴ and ϕ₂=10¯³. The influence of the volume concentration on the phase transitions from isotropic to nematic phase was studied by three experimental methods: optical microscopy, differential scanning calorimetry, and dielectric measurements. The obtained results confirmed the coexistence of isotropic and nematic phase, i.e. nematic or ferronematic droplets in isotropic phase in a wide temperature range between nematic and isotropic phase.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 955-957
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Viscosity Dependence of a Magnetic Fluid Nanoparticles Concentration
Autorzy:
Tóthová, J.
Kováč, J.
Kopčanský, P.
Rajňák, M.
Paulovičová, K.
Timko, M.
Józefczak, A.
Powiązania:
https://bibliotekanauki.pl/articles/1201929.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
07.55.Jg
75.50.Mm
83.85.Jn
Opis:
In this work we have studied the effect of temperature on the viscosity of magnetic fluids (MFs) based on the transformer oil ITO 100. The volume concentration of suspended magnetic particles (MPs) changed from 0.25 to 1%. Rheological characterization of MFs was performed using a vibroviscometer at working frequency of 30 Hz. The temperature dependence of the viscosity was measured in the temperature range from 20 up to 50 °C. The magnetization of different concentrations of MPs in MFs was determined by using the vibrating sample magnetometer.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 278-279
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
Tytuł:
Study of Composites Consisting of High-T$\text{}_{c}$ Superconductor and Fine Magnetic Particles
Autorzy:
Timko, M.
Kopčanský, P.
Kováč, J.
Koneracká, M.
Plecháček, V.
Powiązania:
https://bibliotekanauki.pl/articles/2013009.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.Hs
75.50.Tt
Opis:
The composite systems as a mixture of fine magnetic particles of Fe$\text{}_{3}$O$\text{}_{4}$ and superconducting powder such as Bi$\text{}_{1.8}$Pb$\text{}_{0.2}$Sr$\text{}_{2}$Ca$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{10+x}$ were prepared. The influence of internal magnetic field (generated by magnetic particles) on the superconducting properties of prepared composites were studied as a function of concentration of magnetic particles and their magnetic state. The observed data both of the shielding and the Meissner effect were compared with corresponding linear combination of pure signals of magnetite and superconductor, respectively. The large differences were observed for demagnetized samples. It means that result must be discussed in the frame of the distribution of internal magnetic field created by the magnetic particles.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 389-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis and Characterization of Magnetoferritin
Autorzy:
Mitróová, Z.
Melníková, L.
Kováč, J.
Timko, M.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1429123.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Cr
75.50.Ee
75.60.Ej
75.50.Tt
Opis:
The paper presents detailed experimental study of synthesis and characterization a bioinorganic magnetic molecule - magnetoferritin. Magnetoferritin with loading of iron ions per protein molecule in the range from 300 to 3000 was prepared. Size distribution analysis (transmission electron microscopy, dynamic light scattering) shows spherical nanoparticles with particle size distribution from 2 to 12 nm, and hydrodynamic diameter from 12 to 25 nm. The thermomagnetic curves measured after cooling the sample in zero field (zero-field cooling) and under the presence of the measurement field (field cooling) show superparamagnetic behavior with the blocking temperature $T_{b}$ from 22 to 60 K and the magnetization loops measured below $T_{b}$ (at 2 K) show the hysteresis with coercive field from 20 to 30 kA/m depending on the concentration of the magnetic nanoparticles.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1318-1320
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lysozyme Amyloid Fibrils Doped by Carbon Nanotubes
Autorzy:
Majorošová, J.
Tomašovičová, N.
Mitróová, Z.
Rajňák, M.
Girman, V.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1030498.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.48.De
68.37.Lp
68.37.-d
75.60.Ej
87.14.Ee
Opis:
Production of new composites for the creation of modern materials with desired properties is the key feature of nanotechnology. Despite the well known advantages of magnetic nanoparticles, the aim of the present study was to synthesize lysozyme amyloid fibrils from hen egg white and subsequently doped this solution with single walled carbon nanotubes and with the magnetite Fe₃O₄ labelled single walled carbon nanotubes. Transmission electron microscopy and polarization optical microscopy were used to obtain the structural and dimensional information about samples. Measurements of magnetic properties indicate the considerable increase of the saturation magnetization for solutions included the magnetite nanoparticles.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 588-590
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preparation and Complex Characterization of Magnetic Nanoparticles in Magnetic Fluid
Autorzy:
Kubovčíková, M.
Antal, I.
Kováč, J.
Závišová, V.
Koneracká, M.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1201928.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.75.Fk
78.67.Bf
36.40.Cg
47.65.Cb
75.50.Mm
75.30.Cr
Opis:
This paper deals with the preparation and complex characterization of magnetite nanoparticles (MNPs), stabilized with sodium oleate (SO), by the routine methods such as infrared spectroscopy (FTIR), magnetic measurements, scanning electron microscopy (SEM) and dynamic light scattering (DLS). The FTIR spectra showed that SO molecules were linked to MNPs through chemical bonding. Magnetic measurements proved that the MNPs are superparamagnetic in nature. Four different methods were used to determine the size and size distribution of the MNPs: SEM, DLS, differential centrifugal sedimentation (DCS) and magnetic measurements. SEM analysis showed a relatively narrow size distribution of roughly spherical MNPs with a mean diameter of 61 nm. DLS analysis confirmed monodispersed MNPs production with hydrodynamic diameter of 75 nm. The size distribution determined by DCS was found to be 69 nm. Finally, the calculated magnetic core diameter obtained from magnetization curve was 10 nm. The obtained results demonstrate that SO coated MNPs fulfil the requirements for a useful drug delivery system.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 268-269
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 50

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