Wyniki wyszukiwania - Biblioteka Nauki

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Magnetic properties of magnetostrictive Tb0.3Dy0.7Fe1.9 / polyurethane composite materials

100%

Dobrzański L. , Tomiczek A. , Nabiałek A. , Stokłosa Z.

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2011

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tom Vol. 51, nr 2

97-102

EN

Purpose: The aim of this work was to obtain polyurethane matrix composite materials reinforced with Tb0.3Dy0.7Fe1.9 particles and to observe changes of magnetic properties and magnetostriction of samples with different particle size distributions of Tb0.3Dy0.7Fe1.9 powder and varying volume concentration. Design/methodology/approach: The studies was performed on composite materials with the polyurethane matrix reinforced with Tb0.3Dy0.7Fe1.9 powders. The morphology of powder was examined by scanning electron microscopy (SEM) and analysis of the grain distribution of Tb0.3Dy0.7Fe1.9 powder was made using the Mastersizer 2000 analyser. The changes of magnetostriction and magnetic properties, including hystersis loops and effective permeability with changing applied field are tested. Findings: Analysis establishes a direct connection between magnetic properties and structural characteristics of the Tb0.3Dy0.7Fe1.9 powder size, which was used as reinforcement phase. The increase of particle size distribution of Tb0.3Dy0.7Fe1.9 powder in composite materials amplify the magnetostrictive responses, moreover the change of magnetic properties as a function of volume fraction of Tb0.3Dy0.7Fe1.9 powder were confirmed. Research limitations/implications: Contributes to research on structure and properties of magnetostrictive composite materials with the polymer matrix reinforced with Tb0.3Dy0.7Fe1.9 powders. Practical implications: The polymer matrix in investigated composite materials causes growth of resistivity, limiting this way losses for eddy currents at the high operating frequency of the transducers. In addition the values of permeability of composite materials is nearly constant in investigated frequency range. Originality/value: The obtained results show the possibility of manufacturing the magnetostrictive composite materials based on the Tb0.3Dy0.7Fe1.9 particles, with desired properties in cost effective way in comparison to conventional giant magnetostrictive materials (GMM).

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Crystallisation kinetics and magnetic properties of a Co-based amorphous alloy

100%

Lesz S. , Nowosielski R. , Kostrubiec B. , Stokłosa Z.

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2006

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tom Vol. 16, nr 1-2

35--39

EN

Purpose: In the present paper, the kinetics of crystallization process and its correlation with magnetic properties of the Co80Si9B11 alloy was carefully examined. Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), electrical resistivity in situ measurements (four-point probe), saturation magnetization in situ measurements (magnetic balance) and initial relative magnetic permeability measurements (Maxwell-Wien bridge). Findings: The investigations proved that thermal annealing of amorphous Co80Si9B11 alloy leads to a crystallization process and radical changes of magnetic properties. The activation energy of this process was determined as Ec=3.0±0.2 eV. Research limitations/implications: According to the results presented in the present paper the examined alloys can be used as a very good soft magnetic material. Originality/value: The best soft magnetic properties are observed in as quenched state.

3

Electrophysical properties of the multicomponent PbFe1/2Nb1/2O3 ceramics doped by Li

100%

Bochenek D. , Niemiec P. , Adamczyk M. , Stokłosa Z.

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nr 1

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Influence of structure on soft magnetic properties of Co70Fe5Si15B10 metallic glass ribbons

88%

Babilas R. , Nowosielski R. , Dercz G. , Stokłosa Z. , Głuchowski W.

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2012

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tom Vol. 54, nr 1

37-44

EN

Purpose: The paper presents a structural, thermal and magnetic characterization of Co-based amorphous samples in as-cast state and after annealing process. Design/methodology/approach: The studies were performed on Co70Fe5Si15B10 metallic glass in form of ribbons with different thickness. The amorphous structure and phase analysis of studied samples after annealing process was examined by X-ray diffraction (XRD). The crystallization behaviour of the studied ribbons was also examined by differential scanning calorimetry (DSC). The fracture morphology of the ribbons after heat treatment was analysed using the scanning electron microscopy (SEM). The soft magnetic properties examination contained relative initial magnetic permeability and magnetic permeability relaxation measurements. Findings: The X-ray diffraction investigations revealed that the tested ribbons with different thickness were amorphous. The two exothermic peaks describing crystallization process of Co70Fe5Si15B10 alloy were observed for all studied samples with different thickness. The heat treatment process of ribbon samples involved crystallization of á-Co(Si), Co2Si phases and cobalt borides at temperature above 773 K. The study of fracture morphology of samples after annealing at 623 K shows mixed fractures with “river” patterns, which are characteristic for glassy materials and some areas of scaly morphology. The initial magnetic permeability decreases in function of the increase of annealing temperature, but a local maximum could be determine at 673 K. Practical implications: The soft magnetic properties of studied metallic glasses can be formed by different sample thickness and applying the appropriate conditions of annealing process. Originality/value: The applied investigation methods are suitable to determine the changes of structure and soft magnetic properties of examined Co-based alloy with function of sample thickness and heat treatment conditions.

5

Właściwości magnetyczne stopów typu nanoperm oraz ich wykorzystanie na ekrany pola elektromagnetycznego.

88%

Haneczok G. , Kwapuliński P. , Stokłosa Z. , Rasek J. , Wroczyński R.

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tom T. 24, nr 4

373-391

PL

W pracy pokazano, że miękkie właściwości magnetyczne amorficznych stopów Fe76X2B22 (X=Cr, Zr, Nb) oraz Fe87Nb2B11 i Fe78B22 mogą być znacznie polepszone przez zastosowanie jednogodzinnego wygrzewania optymalizującego w temperaturach zbliżonych do temperatury krystalizacji. Pokazano, że dodatki stopowe Zr i Nb opóźniają procesy dyfuzyjne zachodzące w materiale i przesuwają pierwsze stadium krystalizacji (nanokrystalizacji) do wyższych temperatur. Obniżenie stężenia boru w stopach z dodatkiem Nb z 22 %at. do 11 %at. prowadzi do obniżenia temperatury wygrzewania optymalizującego o 150 K i obniżeniem temperatury Curie fazy amorficznej o 130 K. Z grupy badanych materiałów najlepszym stopem na ekrany tłumiące pole elektromagnetyczne okazał się stop Fe87Nb2B11. Pokazano, że w tym przypadku tłumienie fali elektromagnetycznej dla częstotliwości 0,2-1 GHz zawiera się w przedziale 30-55 dB.

EN

It was shown that soft magnetic properties of amorphous Fe76X2B22 (X=Cr, Zr, Nb), Fe87Nb2B11, and Fe78B22 alloys can be significantly improved by 1-h thermal annealing at temperatures closed to the crystallisation temperature. Alloying additions of Zr and Nb cause a slowing down of diffusion processes and a shift of the crystallisation temperature as well as the optimisation annealing temperature into high temperature region. A reduction of boron content for alloys with Nb (from 22 at.% to 11 at.%) causes a decrease of the 1h optimisation annealing temperature of about 150 K and the Courie temperature of the amorphous phase of about 130 K. Application of the examined materials as electromagnetic shields shows that the best parameters were obtained for the Fe87Nb2B11 alloy. In this case in the frequency range 0.2-1 GHz damping varies from 30 to 55 dB.

6

Phse stability and structural relaxation in Fe-Nb-B amorphous alloys

75%

Chrobak A. , Kubisztal M. , Chrobak D. , Kwapuliński P. , Stokłosa Z. , Rasek J.

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tom Vol. 51, iss. 4

561-564

EN

In the present paper the phase stability in the Fe86-xNbxB14 (26x68) group of amorphous alloys was examined by applying i) DSC measurements, ii) Young modulus versus temperature and iii) magnetic after effects. It was shown that different physical quantities i.e. i) the optimized magnetic permeability, ii) the heat of amorphous – crystalline transition and iii) the change of Young modulus taking place during structural relaxation of amorphous Fe-Nb-B alloys exhibit the remarkable maximum for x = 6 at.% Nb. The degree of amorphisation measured by the heat transition (energetic difference between amorphous and crystalline state) or by change of the Young modulus (intensity of structural relaxation) is the main reason of structural changes favorable for soft magnetic properties enhancement effect. Intensity of magnetic after effects, corresponding to the free volume content, decreases with increasing Nb content.

PL

W niniejszej pracy badano stabilność fazową w amorficznych stopach Fe86-xNbxB14 (26x68) poprzez zastosowanie takich technik pomiarowych jak pomiary kalorymetryczne DSC, pomiary modułu Younga w funkcji temperatury oraz pomiary przenikalności magnetycznej po rozmagnesowaniu próbki. Z otrzymanych wyników wynika, że różne wielkości fizyczne (zoptymalizowana przenikalność magnetyczna, ciepło krystalizacji, zmiana modułu Younga w trakcie relaksacji strukturalnej) wykazują charakterystyczne maksimum dla próbek o zawartości x = 6% Nb. Na tej podstawie sformułowano wniosek, że stopień amorficzności badanych stopów, mierzony jako ciepło przemiany ze stanu amorficznego do krystalicznego (energia swobodna zamrożona procesie produkcji próbek) oraz zmiana modułu Younga (natężenie relaksacji strukturalnej), jest decydującym czynnikiem dla korzystnych, z punktu widzenia optymalizacji miekkich własciwości magnetycznych, przemian strukturalnych. Zmiana przenikalności magnetycznej po rozmagnesowaniu, odpowiadająca stężeniu mikropustek w strukturze amorficznej, maleje wraz ze wzrostem stężenia niobu.