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Search Results: 1 - 10 of 87 matches for " Rastislav Dosoudil "
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Microwave measurements of ferrite polymer composite materials
Rastislav Dosoudil,Jaroslav Franek,Marianna Usakova
Advances in Electrical and Electronic Engineering , 2004,
Abstract: The article focuses on the microwave measurements performed on the nickel-zinc sintered ferrite with the chemical formula Ni0.3Zn0.7Fe2O4 produced by the ceramic technique and composite materials based on this ferrite and a non-magnetic polymer (polyvinyl chloride) matrix. The prepared composite samples had the same particle size distribution 0-250um but different ferrite particle concentrations between 23 vol% and 80 vol%. The apparatus for measurement of the signal proportional to the absolute value of scattering parameter S11 (reflexion coefficient) is described and the dependence of measured reflected signal on a bias magnetic field has been studied. By means of experiments, the resonances to be connected with the geometry of microwave experimental set-up were distinguished from ferromagnetic resonance arising in ferrite particles of composite structure. The role of local interaction fields of ferrite particles in composite material has been discussed.
Influence of Substituion on Barium Ferrite Properties
Vladimir Jancarik,Maria Papanova,Darina Kevicka,Rastislav Dosoudil
Advances in Electrical and Electronic Engineering , 2004,
Abstract: BaFe12-2x(Ni, Zn)xSnxO19 M - type compounds processed by citrate precursor method with substitution level 0.0
The Dispersion Characteristics of the Complex Permeability of NiZnCu Ferrite and its Composite Materials
Rastislav Dosoudil,Marianna Usakova,Elemir Usak,Vladimir Jancarik
Advances in Electrical and Electronic Engineering , 2004,
Abstract: The paper deals with the frequency dependence of complex permeability for the Ni0.27Zn0.63Cu0.1Fe2O4 sintered ferrite produced by conventional ceramic method and its composite materials made of this ferrite (in the form of powder) and non-magnetic polymer matrix (polyvnyl chloride - PVC). The experimental and theoretical curves of the complex permeability were compared. The contribution of both domain wall motion and spin rotational mangetisation processes on th complex permeability in high-frequency region (up to 1 GHz) is discussed. In the case of composite materials, the simple magnetic circuit approach is taken into account. In composites, the real part of the complex permeability in the frequency region above 100 MHz is larger than that of the prepared sintered ferrite. This is attibuted to the shift of the spin and domain wall resonance frequencies toward the higher frequency region by introducing demagnetising fields of magnetic particles in the composite.
The Influence of Particle Size and Substituent Contents on the Magnetic Properties of Be or Cu Substituted NiZn Ferrites
Jozef Slama,Elemir Usak,Rastislav Dosoudil,Anna Gruskova
Advances in Electrical and Electronic Engineering , 2006,
Abstract: Polycrystalline NiZn ferrites with the chemical formula (Ni0.3Zn0.7)1 xMexFe2O4 where Me being Be or Cu andx=0.05, 0.1 and 0.25 have been prepared by a ceramic method. Certain magnetic properties such as the coercivity Hc, initialpermeability mi, real part of the complex permeability m’ and saturation magnetization Ms of the ferrites have been measuredand discussed from the point of view of the substituting element type and contents as well as the average particle size.
Characteristics of Magnetic Properties of Substituted Hexagonal Ferrites
Vladimir Jancarik,Anna Gruskova,Jozef Slama,Rastislav Dosoudil
Advances in Electrical and Electronic Engineering , 2006,
Abstract: The samples of barium hexaferrite BaFe12-2x(Me1Me2)xO19 with x from 0.0 to 0.6 were prepared by variousmethods. The cationic preference of mainly divalent Me1 = Zn, Co, Ni, Sn ions and tetravalent Me2 = Ti, Zr, Ir, Sn, Ru ionsand their combinations in substituted Ba ferrites was investigated. The substitutions were performed to reduce the grain sizeand high magnetic uniaxial anisotropy field of the M-type Ba ferrite without affecting the magnetic polarisation. The goal isto reach the properties of ferrite proper for high-density magnetic recording and microwave absorption devices. Magneticproperties were determined as a function of the substitution level x. The specific saturation magnetic polarisation Js–m andremanence Js–rincreased with small x due to the substitution of non-magnetic and less magnetic ions in 4f1 and 4f2 sites. Thesteep decrease of coercivity Hc with increasing x may be caused by the Co2+ preference of 4f2 site and Ti4+or Zr4+ions preference of 2b and slightly in 4f1 sites. The temperature coefficient of the coercivity TKHc was very low (0.01kA.m-1.°C-1)for the Co-Zr substitutions and positive for the rest of samples.
High-Frequency EMI Noise Suppression by Polymer-Based Composite Magnetic Materials
Rastislav Dosoudil,Jaroslav Franek,Marianna Usakova,jozef Olah
Advances in Electrical and Electronic Engineering , 2008,
Abstract: The complex permeability and EM-wave absorption properties of hybrid polymer-based composite magneticmaterials (with MnZn and LiZn ferrite fillers and PVC matrix) prepared with constant total filler content (65 vol%) andparticle size (0-250 mm) have been investigated in the 1-1000 MHz frequency range. Within this filler concentrationthe permeability of composites changed continuously with the change of ferrite filler content ratio between two types offerrite fillers. The observed relaxation type of permeability dispersion was due to the domain wall and natural ferromagneticresonance phenomena and was also attributed to the high damping of spin motion. Measured values of permeability wereused to determine the EM-wave absorption properties (return loss RL, matching frequency fm, matching thickness dm andbandwidth Df for RL £ -20 dB). The calculation of these properties was based on a model of single-layered absorber backedby a perfect conductor using transmission-line and EM-field theory. The composite with the volume fraction ratio of hybridMnZn:LiZn ferrite filler set to 0.5:0.5 has shown a return loss of -57 dB (> 99 % power absorption) at fm = 714 MHz with the-20 dB bandwidth of Df = 232 MHz for an absorber thickness of 7.79 mm.
Evaluation of Fillers Dispersion Degree in Elastomeric Magnetic Composites
Ján Kru?elák,Sybill Ilisch,Ivan Hudec,Rastislav Dosoudil
Smart Materials Research , 2012, DOI: 10.1155/2012/532170
Abstract: Elastomeric magnetic composites were prepared by incorporation of strontium ferrite into polymer matrices based on natural as well as butadiene rubber. Besides the rubber and ferrite, or the combinations of ferrite and carbon black (in case of natural rubber), the model rubber compounds contained only ingredients which support curing process. The study was dedicated to the observation of fillers dispersion degree in the rubber matrices and investigation of physical-mechanical and magnetic properties of prepared composites. The results indicate that the dispersion degree of ferrite in the rubber matrices is not very high, but it can be positively influenced by the addition of carbon black. Despite of the fact that ferrite exhibits only low reinforcing effect on cross-linked elastomeric materials, physical-mechanical properties can be also positively influenced by the mutual change in combinations of both fillers (ferrite and carbon black). The prepared materials seem to have suitable magnetic and elastic properties. 1. Introduction In the recent years, a rapid interest in development of smart materials consisting of rubber matrix and magnetic active particles has been shown [1–4]. The final properties of elastomeric magnetic composites are strongly dependent on the characteristics of polymer matrix especially. However, by integration of magnetic materials, new properties and technological abilities can be provided. The advantage of such type of materials is that their properties can be modified for the requirements of specific applications. Because of their elasticity and easy mouldability, they are suitable for additive devices, where elasticity and flexibility are additional and important parameters. Moreover, they have very good magnetic properties. Rubber magnets can absorb shock and sound, so they can be applied in dc motors, motor parts, memo holders, intelligent tyres, microwave and radar technology, and also in other technological applications. The quality of rubber blends to a large extent depends on the ability of filler or fillers to be well dispersed in the rubber matrix. The mixing process can be characterized by two essential elements of mixing process: the distributive and the dispersion mixing. The distributive mixing ensures the homogenous concentration of ingredients in all rubber volume. The dispersion mixing ensures the dispersion of filler into primary particles or aggregates. The quality of rubber blends, mainly physical properties, depends also on the quality of phases interface, stress on interface, and chemical or physical
The Influence of Strontium Ferrite on Curing and Properties of BR-Composites / Utjecaj stroncijeva ferita na umre ivanje i svojstva kompozita butadienskoga kau uka
Jan KRU?ELáK,Ivan HUDEC,Mariana U?AKOVá,Rastislav DOSOUDIL
Polimeri , 2011,
Abstract: The focus of the work was to prepare elastomeric magnetic composites based on a highly elastic polymer matrix (1,4-cis butadiene rubber). Three modifications of the same type of strontium ferrite SrFe12O19, type FD8/24 were applied as magnetic fillers. The applied ferrites differed in particle size distribution and other structural and magnetic characteristics. The work is focused on the preparation of rubber compounds for making elastomeric magnetic composites and evaluation of magnetic fillers influence on curing characteristics, physical-mechanical and magnetic properties of prepared composites. The study is also dedicated to the cross-link density of vulcanizates. / Cilj rada je pripremiti elastomerne magnetne kompozite na temelju visokoelasti ne polimerne matrice (1,4-cis butadienski kau uk). Tri su modifikacije istog tipa stroncijeva ferita SrFe12O19, tip FD8/24, primijenjene kao magnetna punila. Primijenjeni feriti razlikovali su se po raspodjeli veli ine estica te drugim strukturnim i magnetnim svojstvima. Rad obra uje pripremu spojeva kau uka za izradu elastomernih magnetnih kompozita i daje ocjenu utjecaja magnetnih punila na svojstva umre ivanja, fizi ko-mehani ka i magnetna svojstva pripremljenih kompozita. Ispitivanje tako er obra uje gusto u umre ivanja vulkanizata.
Sequence stratigraphic dictionary
Rastislav Synak
Acta Geologica Slovaca , 2010,
Abstract: Sequence stratigraphy represents the study of cyclic sedimentary patterns within the stratigraphic succession, as they form in response to various factors, such as fluctuations in sea level (fall or rise), tectonics, and variations in sediment supply or space available for sediment to accumulate. Depositional sequence is the fundamental stratal unit of sequence stratigraphy, bounded by subaerial unconformities. It represents the final depositional unit of one full cycle of sea level changes and it consists of subdivisions called systems tracts, which are defined on the basis of internal stratal stacking patterns, position within the sequence and types of bounding surfaces.
Modelling of sedimentary architecture using the SedPak software – a case study of the Upper Badenian sediments (Vienna Basin)
Rastislav Synak
Acta Geologica Slovaca , 2009,
Abstract: SedPak software provides a conceptual framework for modeling the sedimentary fill of basins by visualizing stratal geometries as they are produced between sequence boundaries. It is designed to model and reconstruct clastic and carbonate sediment geometries which are produced as a response to changing rates of tectonic movements, eustasy, and sedimentation. The simulation enables the evolution of the sedimentary fill of a basin to be tracked, defines the chronostratigraphic framework for the deposition of these sediments, and illustrates the relationship between sequences and systems. The possibilities of use the SedPak software to simulate infilling of a sedimentary basin and to demonstrate the basics principles of sequence stratigraphy are shown on the example of Upper Badenian deposits in the Vienna Basin.
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