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Wyświetlanie 1-15 z 15
Tytuł:
Mechanochemical Preparation and Magnetic Properties of Fe₃O₄/ZnS Nanocomposite
Autorzy:
Bujňáková, Z.
Zorkovská, A.
Kováč, J.
Powiązania:
https://bibliotekanauki.pl/articles/1032141.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Bc
81.20.Ev
81.20.Wk
Opis:
Powder nanocomposite of Fe₃O₄/ZnS was prepared by mechanochemical synthesis in a planetary ball mill. In this reaction natural magnetite mineral Fe₃O₄ was used, together with zinc acetate (CH₃COO)₂Zn·2H₂O and sodium sulfide Na₂S·9H₂O, as precursors for the zinc sulfide ZnS. X-ray diffraction revealed that the sample is composed of small nanocrystalline particles, containing Fe₃O₄ and ZnS. The non-milled magnetite showed distinctive Verwey transition at around 120 K, this becomes suppressed after milling, as a consequence of structural disorder and presence of defects. Moreover, the reduction of saturation magnetization from 91 A m²/kg to 69.2 A m²/kg was observed, as a consequence of the milling process. The magnetization of the Fe₃O₄/ZnS nanocomposite was the lowest (34.5 A m²/kg), due to the milling and to the decreased weight fraction of the ferrimagnetic component. Nevertheless, the Fe₃O₄/ZnS sample demonstrates ferrimagnetic behavior as well, and its structure is less perturbed by milling, the Verwey transition, although less impressive, but is preserved.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1120-1122
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic and Magnetotransport Properties of High Quality $Na_{0.77}CoO_{2}$ Single Crystals
Autorzy:
Baran, A.
Zorkovská, A.
Kajňaková, M.
Lin, C.
Feher, A.
Powiązania:
https://bibliotekanauki.pl/articles/1371577.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
75.40.Cx
75.47.-m
Opis:
Heat capacity and electrical resistivity of high-quality $Na_{0.77}CoO_{2}$ single crystals was systematically studied as a function of temperature and magnetic field. Anomalies at 20 K have been observed both in the heat capacity and the electrical resistivity. The broad bump in the heat capacity indicates a smeared magnetic phase transition. Magnetic fields up to 9 T, oriented perpendicularly to the ab plane, reduce the temperature of this anomaly in accordance with the assumption of A-type antiferromagnetic ordering. The low temperature upturn observed in resistivity below 20 K for slow cooling is also suppressed by the magnetic field. This anomaly is probably the consequence of the interplay of several different mechanisms, including the Kondo effect, electron-electron interactions, and electron-phonon scattering.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 360-361
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Annealing Treatment on the Structure and Magnetic Properties of Fe-Al-Cu-Nb-Si-B Alloys
Autorzy:
Pavlík, G.
Matta, P.
Sovák, P.
Zorkovská, A.
Konč, M.
Powiązania:
https://bibliotekanauki.pl/articles/2013354.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.16.Bg
75.50.Kj
75.80.+q
81.40.Rs
Opis:
In this paper we present experimental results on influence of Al content on the structure and saturation magnetostriction of Fe-Al-Cu-Nb-Si-B alloys after heat treatment. Transmission electron microscopy observations confirmed the existence of nanocrystalline structure after annealing at 490°C and 550°C for all samples. The crystallization temperature of FeSi phase and the temperature at which the polycrystalline transformation starts were determined from temperature dependence of electrical resistivity. Aluminium slightly decreases the first crystallization temperature and considerably decreases the saturation magnetostriction in as-quenched state.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 741-744
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of Mechanochemically Synthesized Mixed Oxides
Autorzy:
Kostova, N.
Zorkovská, A.
Kováč, J.
Velinov, N.
Baláž, P.
Powiązania:
https://bibliotekanauki.pl/articles/1372521.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Bw
75.60.-d
76.80.+y
61.05.cp
81.07.Wx
Opis:
The mixed oxides $Fe_{2}O_{3}-ZnO$ have been obtained in nanocrystalline state by reactive milling in a high-energy planetary mill, from a stoichiometric mixture of hematite and ZnO. The magnetic properties of samples were evaluated by magnetization measurements and Mössbauer spectrometry. A post milling annealing promotes the solid state reaction and improves the zinc ferrite formation, paramagnetic $ZnFe_{2}O_{4}$ phase is formed. Further mechanical activation leads to structural transformation into Wüstite-type (FeZn)O mixed oxide, with ferromagnetic hysteresis and increased magnetization.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 411-412
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermopower and Surface Magnetic Characterization of Ni Thin Layers
Autorzy:
Szabo, A.
Varga, R.
Ujhelyi, F.
Komanicky, V.
Zorkovska, A.
Lovas, A.
Powiązania:
https://bibliotekanauki.pl/articles/1201858.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.15.Jf
73.50.Lw
75.70.-i
68.55.jm
Opis:
Thermoelectric power and surface magnetic characterization of Ni evaporated layers will be presented, with the comparison with the bulk Ni material. The bulk electrical and magnetic properties are developed gradually, approaching the bulk properties, as the layer thickness increases. Below the thickness of 180 nm, the evaporated layers are amorphous. The epitaxial stresses can appear in both, the anomaly observed in the thermopower and the surface coercivity measurements.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 204-205
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetotransport Properties of $CaTi_xRu_{1-x}O_3$ (x=0, 0.07)
Autorzy:
Zorkovská, A.
Baran, A.
Feher, A.
Šebek, J.
Šantavá, E.
Bradarić, I.
Powiązania:
https://bibliotekanauki.pl/articles/1813683.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Pq
73.43.Qt
75.47.-m
Opis:
Electrical resistance, transversal magnetoresistance and the Hall effect were studied on polycrystalline $CaTi_xRu_{1-x}O_3$ (x=0, 0.07) samples using a conventional Quantum Design PPMS-9 equipment in the temperature range 2-300 K and magnetic field up to 9 T. Substantial differences were found between the two samples: (i) opposite to the metallic character of $CaRuO_3$, the substituted sample has insulating-like electrical resistance;(ii) the magnetoresistance of the substituted sample changes the sign from negative to positive values with increasing temperature. The magnetoresistance of $CaRuO_3$ is negative, the sign reversal is induced by magnetic field and only at temperatures below 15 K, such a behaviour is predicted for clustered systems;(iii) the Hall voltage in pure $CaRuO_3$ also changes sign from negative to positive values above 35 K. This temperature coincides with the observed magnetic transition temperature, indicating that the magnetic state and the carrier character interrelate.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 351-354
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetics of Solid-State Synthesis of Quaternary Cu₂FeSnS₄ (Stannite) Nanocrystals for Solar Energy Applications
Autorzy:
Baláž, P.
Baláž, M.
Zorkovská, A.
Škorvánek, I.
Bujňáková, Z.
Trajić, J.
Powiązania:
https://bibliotekanauki.pl/articles/1032135.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
81.05.Hd
61.46.Hk
Opis:
In this study we demonstrate the use of elemental precursors (Cu, Fe, Sn, S) to obtain stannite forms by a solid-state one-pot mechanochemical synthesis. In the processing route, we report the kinetics of the synthesis. For the characterization of the unique nanostructures, X-ray diffraction, specific surface area measurements and SQUID magnetometry methods were applied. CFTS polymorphs with the tetragonal body-centered structure with the average crystallite size 18-19 nm were obtained. The weak ferromagnetic properties of the quaternary nanocrystals after maximum milling time were also documented.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1153-1155
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanochemical Dechlorination of PVC by Utilizing Eggshell Waste
Autorzy:
Baláž, M.
Baláž, P.
Bujňáková, Z.
Pap, Z.
Kupka, D.
Zorkovská, A.
Powiązania:
https://bibliotekanauki.pl/articles/1375093.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Lg
81.20.Wk
88.20.dr
Opis:
Within this work, the dechlorination of polyvinylchloride (PVC) chemical as a model by co-milling with eggshell was performed in a planetary ball mill in order to show that mechanochemistry can be utilized for the simultaneous treatment of two wastes, while the products of the treatment can be used in further applications. The products of the reaction are water-soluble calcium chloride ($CaCl_2$), which can be used e.g. for de-icing of roads in winter and organic residue on the basis of ethylene, which can be recovered as energy source. The highest dechlorination yield (almost 97%) was achieved under following milling conditions: molar ratio between Ca and Cl: 2.34, ball-to-powder ratio: 65, rotation speed of the planet carrier: 550 rpm, milling time: 4 h and material of milling media: tungsten carbide. The optimum conditions were then applied for the removal of chlorine from industrial waste - the abandoned PVC window parapet. In this case, 95% dechlorination was evidenced.
Źródło:
Acta Physica Polonica A; 2014, 126, 4; 884-887
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanochemically Synthesized CuFeSe₂ Nanoparticles and Their Properties
Autorzy:
Dutková, E.
Škorvánek, I.
Sayagués, M.
Zorkovská, A.
Kováč, J.
Baláž, P.
Powiązania:
https://bibliotekanauki.pl/articles/1032137.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Hd
81.07.Wx
81.20.Wk
Opis:
The mechanochemical synthesis of nanocrystalline CuFeSe₂ particles prepared by high-energy milling in a planetary mill in an argon atmosphere from copper, iron, and selenium for 60 min is reported for the first time. The CuFeSe₂ nanoparticles crystallize in tetragonal structure with mean crystallite size of about 32±1 nm. High resolution transmission electron microscopy measurements confirmed the presence of agglomerates which are formed by small nanocrystalline domains (5-40 nm). The magnetic data revealed that paramagnetic CuFeSe₂ nanoparticles coexist with a small amount of ferromagnetic impurities at room temperature. The magnetic transition towards a weak ferromagnetic or ferrimagnetic behavior occurs in CuFeSe₂ at approximately 79 K. The band gap of the CuFeSe₂ particles is 0.95 eV which is wider than the band gap in bulk materials (0.16 eV), which could be in many aspects of application more beneficial.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1156-1158
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The influence of Al doping on microstructure and hyperfine interactions in FINEMET
Autorzy:
Brzózka, K.
Szumiata, T.
Gawroński, M.
Górka, B.
Zorkovská, A.
Sovák, P.
Powiązania:
https://bibliotekanauki.pl/articles/147216.pdf
Data publikacji:
2004
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer spectroscopy
FINEMET
nanocrystalline alloys
Al-dopped FINEMET
Opis:
Structure and hyperfine interactions of amorphous and nanocrystalline FINEMET were investigated by means of Mössbauer spectrometry. It was found that substitution of x iron atoms with aluminum ones causes changes in the properties of both amorphous and nanocrystalline alloys as well as in the structure of individual phases. The reduction of hyperfine magnetic field caused by atom substitution is a non-linear function of x, unlike the linear dependence expected because of dilution. Temperature studies reveal a double magnetic phase transition at 250°C and 330°C as well as point to the variety of phases in the examined material.
Źródło:
Nukleonika; 2004, 49,suppl.3; 59-62
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ti-Induced Ferromagnetism and the Specific Heat of $CaTi_xRu_{1-x}O_3$ (x=0, 0.005, 0.03)
Autorzy:
Zorkovská, A.
Baran, A.
Kajňaková, M.
Feher, A.
Šebek, J.
Šantavá, E.
Bradarić, I.
Powiązania:
https://bibliotekanauki.pl/articles/1813685.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Pq
75.40.Cx
72.80.Ga
Opis:
The influence of Ti substitution on the specific heat of the $CaTi_xRu_{1-x}O_3$ system at low concentrations x=0, 0.005, and 0.03 was studied in the temperature range of 2-300 K at magnetic fields up to 9 T. Small peak was revealed in the C/T vs. $T^2$ dependence at around 3 K, which are field sensitive (the electronic specific heat coefficient γlinearly decreases with the increase in magnetic field), and might be connected to some kind of magnetic ordering. The coefficient γis suppressed also by Ti substitution.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 355-358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanochemical Reduction of Chalcopyrite CuFeS₂: Changes in Composition and Magnetic Properties
Autorzy:
Baláž, P.
Zorkovská, A.
Baláž, M.
Kováč, J.
Tešinský, M.
Osserov, T.
Guseynova, G.
Ketegenov, T.
Powiązania:
https://bibliotekanauki.pl/articles/1032642.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
81.05.Hd
Opis:
High-energy milling of sulphides with a reactive metal in so-called mechanochemical reduction mode can lead to products in nanorange and to composition which simplifies the following metallurgical processing. Chalcopyrite CuFeS₂, a ternary semiconductor with antiferromagnetic properties represents promising candidate as an advanced material for use in inexpensive nanoelectronics (solar cells, magnetic area), as well as copper ore source in metallurgical operations. In this work, the process of mechanochemical reduction of chalcopyrite with elemental iron is studied. The composition and properties of nanopowder prepared by high-energy milling were analyzed by X-ray diffraction and magnetic measurements. Most of the reaction takes place during 30 min with chalcocite Cu₂S and troilite FeS as the only reaction products. The magnetic investigations reveal significant increase of saturation magnetization as a result of milling. Unlike the conventional high-temperature reduction of chalcopyrite, the mechanochemical reduction is fast and ambient temperature and atmospheric pressure are sufficient for its propagation.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1165-1167
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanochemically Synthesized Nanocrystalline $Sb_2S_3$ Particles
Autorzy:
Dutková, E.
Sayagués, M.
Real, C.
Zorkovská, A.
Baláž, P.
Šatka, A.
Kováč, J.
Ficeriová, J.
Powiązania:
https://bibliotekanauki.pl/articles/1375343.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Hd
81.07.Bc
81.20.Wk
Opis:
Nanocrystalline $Sb_2S_3$ particles have been synthesized from Sb and S powders by high-energy milling in a planetary mill using argon protective atmosphere. X-ray diffraction, particle size analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, electron diffraction, high resolution transmission electron microscopy, UV-VIS, and differential scanning calorimetry methods for characterization of the prepared particles were applied. The powder X-ray diffraction pattern shows that $Sb_2S_3$ nanocrystals belong to the orthorhombic phase with calculated crystallite size of about 36 nm. The nanocrystalline $Sb_2S_3$ particles are constituted by randomly distributed crystalline nanodomains (20 nm) and then these particles are forming aggregates. The monomodal distribution of $Sb_2S_3$ particles with the average hydrodynamic parameter 210 nm was obtained. The quantification of energy dispersive X-ray spectroscopy analysis peaks give an atomic ratio of 2:3 for Sb:S. The optical band gap determined from the absorption spectrum is 4.9 eV, indicating a considerable blue shift relative to the bulk $Sb_2S_3$. Differential scanning calorimetry curves exhibit a broad exothermic peak between 200 and 300°C, suggesting recovery processes. This interpretation is supported by X-ray diffraction measurements that indicate a 23-fold increase of the crystallite size to about 827 nm as a consequence of application of high temperature process. The controlled mechanochemical synthesis of $Sb_2S_3$ nanoparticles at ambient temperature and atmospheric pressure remains a great challenge.
Źródło:
Acta Physica Polonica A; 2014, 126, 4; 943-946
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low Temperature Anomalies in the Specific Heat and Magnetic Susceptibility of $Na_{0.7}CoO_2$ Samples
Autorzy:
Baran, A.
Zorkovská, A.
Feher, A.
Šebek, J.
Šantavá, E.
Hejtmánek, J.
Veverka, M.
Bradarić, I.
Ružička, M.
Powiązania:
https://bibliotekanauki.pl/articles/1813849.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
72.80.Ga
Opis:
We present a comparative study of $Na_{0.7}CoO_2$ samples obtained from three different sources and prepared by different methods. The specific heat and magnetic susceptibility measurements in the temperature range 2-300 K show substantial influence on the observed anomalies, which underlines that the system is extremely sensitive to preparation protocols.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 495-498
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Radiation Stability of the BSA Modified Biocompatible Magnetic Fluid
Autorzy:
Tomašovičová, N.
Haysak, I.
Kováč, J.
Kubovčíková, M.
Závišová, V.
Timko, M.
Okunev, A.
Zorkovská, A.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1368667.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Mm
61.30.Gd
64.70.Md
Opis:
The aim of the presented work was to investigate the stability of biocompatible magnetic fluid, i.e. water-based magnetic fluid containing magnetite nanoparticles stabilized by surfactant sodium oleate and modified by bovine serum albumin (BSA) after electron irradiation. Samples with the same concentration of $Fe_{3}O_{4}$ but different mass ratio BSA/$Fe_{3}O_{4}$ (w/w=0.25, 1.0 and 2.5) were studied. The electron irradiation caused about 10% reduction of the saturation magnetization in the samples with w/w BSA/$Fe_{3}O_{4}$ ratio of 0.25 and less than 5% in the samples with w/w BSA/$Fe_{3}O_{4}$ ratio of 1 and 2.5.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 262-263
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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