Publikační činnost Katedry fyziky / Publications of Department of Physics (717)

Permanent URI for this collectionhttp://hdl.handle.net/10084/111463

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry fyziky (717) v časopisech registrovaných ve Web of Science od roku 2003 do roku 2017.
Katedra byla zrušena jako celoškolský subjekt a převedena pod 480 - Katedru fyziky na Fakultě elektrotechniky a informatiky.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 32 results

Experimental demonstration of magnetoplasmon polariton at InSb(InAs)/dielectric interface for terahertz sensor application
(Springer Nature, 2017) Chochol, Jan; Postava, Kamil; Čada, Michael; Pištora, Jaromír
We experimentally demonstrate surface plasmon resonance (SPR) in the terahertz range in InSb and InAs. The surface plasmon is excited on the interface between a thin polymer film and the semiconductor using a silicon prism in Otto configuration. The low effective mass of InSb and InAs permits tuning of the SPR by an external magnetic field in the transversal configuration. The data show a good agreement with a model. Strong excitation of the surface plasmon is present in both materials, with a shifting of resonance position by more than 100 GHz for the field of 0.25 T, to both higher and lower energies with opposite orientation of the magnetic field. Applicability of the terahertz SPR sensor is discussed, along with modeled design for the Kretschmann configuration.
Synthesis and properties of nanocomposites of WO3 and exfoliated g-C3N4
(Elsevier, 2017) Praus, Petr; Svoboda, Ladislav; Dvorský, Richard; Reli, Martin; Kormunda, Martin; Mančík, Pavel
The nanocomposites of WO3 nanoparticles and exfoliated graphitized C3N4 (g-C3N4) particles were prepared and their properties were studied. For this purpose, common methods used for characterization of solid samples were completed with dynamic light scattering (DLS) method and photocatalysis, which are suitable for study of aqueous dispersions. The WO3 nanoparticles of monoclinic structures were prepared by a hydrothermal method from sodium tungstate and g-C3N4 particles were prepared by calcination of melamine forming bulk g-C3N4, which was further thermally exfoliated. Its specific surface area (SSA) was 115 m(2) g(-1). The nanocomposites were prepared by mixing of WO3 nanoparticles and g-C3N4 structures in aqueous dispersions acidified by hydrochloric acid at pH = 2 followed by their separation and calcination at 450 degrees C. The real content of WO3 was determined at 19 wt%, 52 wt% and 63 wt%. It was found by the DLS analysis that the g-C3N4 particles were covered by the WO3 nanoparticles or their agglomerates creating the nanocomposites that were stable in aqueous dispersions even under intensive ultrasonic field. Using transmission electron microscopy (TEM) the average size of the pure WO3 nanoparticles and those in the nanocomposites was 73 nm and 72 nm, respectively. The formation of heterojunction between both components was investigated by UV Vis diffuse reflectance (DRS) and photoluminescence (PL) spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photocatalysis and photocurrent measurements. The photocatalytic decomposition of phenol under the LED source of 416 nm identified the formation of Z-scheme heterojunction, which was confirmed by the photocurrents measurements. The photocatalytic activity of the nanocomposites decreased with the increasing content of WO3, which was explained by shielding of the g-C3N4 surface by bigger WO3 agglomerates. This study also demonstrates a unique combination of various characterization techniques working in solid and liquid phase.
Precision comparison of analytical and statistical-regression models for AWJ cutting
(Elsevier, 2017) Hlaváč, Libor; Krajcarz, Daniel; Hlaváčová, Irena; Spadło, Sławomir
The article is focused at the comparison of results calculated using analytical model for determination of abrasive water jet cutting and equations prepared via application of the statistical-regression approach. The statistical-regression model (SRM) is based on measurement of a set of column holes cut in a plan parallel brass plate according to Box-Behnken design. The material and respective range of factors were selected so that they cover the largest possible scale of varying kerf shapes; brass 2.0402 (CuZn4OPb2), water pressure from 280 to 380 MPa, abrasive mass flow rate from 150 to 450 g/min and variable traverse speed from 25 to 75 mm/min. The main results arising from the experiments were the ideal diameters of the holes' sections in several selected depths of material and the cylindricity, i.e. the difference of the real shape of the "column" hole from the ideal one represented by a column with ideal diameter. The statistical-regression equations for calculation of the selected parameters were set-up. The comparison of the analytical model and the one created via statistical-regression was performed for bottom diameters of the produced holes. The reliability of the statistical-regression model is high within the tested scope of factors. However, its precision can be significantly reduced beyond the selected range of factors or by changes that cannot be involved in the regression (change of material wear character, etc.). Statistical processing of the measured data yields interesting relations between certain factors (abrasive mass flow rate, pressure) and respective results (diameters of holes, cylindricity). Therefore, the respective statistical-regression equations are also presented graphically. The comparison proved that the analytical model also has a very high accuracy and, moreover, its application is not limited by the selected ranges of factors.
Free-space characterization of magneto-optical hexaferrites in the submillimeter-wave range
(IEEE, 2017) Horák, Tomáš; Ducournau, Guillaume; Mičica, Martin; Postava, Kamil; Ben Youssef, Jamal; Lampin, Jean-François; Vanwolleghem, Mathias
We present the quasi-optical free-space characterization of magneto-optical hexagonal ferrites-crystalline BaFe12O19 and both ceramic and crystalline SrFe12O19-in the range between 325 and 500 GHz using a vector network analyzer. This method provides us the full complex spectrum of the 2 x 2 S-matrix element of the sample. Transmission through free air and reflection of a perfect mirror have been used as references. We determined the complex optical indices, permittivities, and permeabilities of all samples by fitting a calculated model to the measured data. The perturbing effects of multiple reflections between setup components were filtered out by inverse fast Fourier transform of the measured signal and subsequent time gating in the obtained time-domain signal. The results presented in this paper show that this processing method reliably deals with all perturbing effects in free-space measurement and therefore can be applied for characterization of various types of magneto-optical samples with different sizes and significant surface roughness as well. Furthermore, it provides convincing indications regarding the usefulness of the different types of hexaferrites for nonreciprocal devices (such as isolators) for submillimeter applications.
In-situ Mueller matrix ellipsometry of silicon nanowires grown by plasma-enhanced vapor-liquid-solid method for radial junction solar cells
(Elsevier, 2017) Mrázková, Zuzana; Foldyna, Martin; Misra, Soumyadeep; Al-Ghzaiwat, Mutaz; Postava, Kamil; Pištora, Jaromír
In-situ Mueller matrix spectroscopic ellipsometry was applied for monitoring the silicon nanowire growth by plasma-enhanced vapor-liquid-solid method. The technique is proposed as a real-time, non-destructive, and non-invasive characterization of the deposition process in a plasma-enhanced chemical vapor deposition reactor. The data have been taken by spectrally resolved Mueller matrix ellipsometer every 1 min during the 8-10 min long nanowire growth process. We have developed an easy-to-apply optical model to fit the experimental data, which enables to study the evolution of the parameters of the structure during initial stages of the growth. The first results provide information about the effective deposition rate determined from the linear increase of the deposited silicon volume with the deposition time.
Spectral phase shift of surface plasmon resonance in the Kretschmann configuration: theory and experiment
(Springer, 2017) Hlubina, Petr; Ciprian, Dalibor
The spectral phase shift of surface plasmon resonance (SPR) in the Kretschmann configuration is modeled for aqueous solutions of NaCl (analytes) and an SPR structure consisting of gold and chromium layers deposited on an SF10 glass slide. Using the material dispersion of the SPR structure and the analyte, the SPR phase shift, its spectral derivative, and the spectral dependence of the ratio of the reflectances of p- and s-polarized waves are determined for aqueous solutions of NaCl when the concentration of NaCl in water and the refractive index range from 0 to 10 weight percent (wt%) and from 1.3334 to 1.3515 RIU, respectively. In addition, theoretical modeling is accompanied by experiment and the position of a sharp maximum in the measured spectral derivative of the SPR phase shift changes in a range from 596 to 626 nm. From the measurements, a sensitivity to concentration of 3.83 nm/wt% and a detection limit of 7.3 x 10(-7) RIU at a wavelength of 612.36 nm are obtained, and very good agreement between theory and experiment is confirmed.
Plasmonic behavior of III-V semiconductors in far-infrared and terahertz range
(European Optical Society, 2017) Chochol, Jan; Postava, Kamil; Čada, Michael; Vanwolleghem, Mathias; Mičica, Martin; Halagačka, Lukáš; Lampin, Jean-François; Pištora, Jaromír
Background: In this article, III-V semiconductors are proposed as materials for far-infrared and terahertz plasmonic applications. We suggest criteria to estimate appropriate spectral range for each material including tuning by fine doping and magnetic field. Methods: Several single-crystal wafer samples (n, p-doped GaAs, n-doped InP, and n, p-doped and undoped InSb) are characterized using reflectivity measurement and their optical properties are described using the Drude-Lorentz model, including magneto-optical anisotropy. Results: The optical parameters of III-V semiconductors are presented. Moreover, strong magnetic modulation of permittivity was demonstrated on the undoped InSb crystal wafer in the terahertz spectral range. Description of this effect is presented and the obtained parameters are compared with a Hall effect measurement. Conclusion: Analyzing the phonon/free carrier contribution to the permittivity of the samples shows their possible use as plasmonic materials; the surface plasmon properties of semiconductors in the THz range resemble those of noble metals in the visible and near infrared range and their properties are tunable by either doping or magnetic field.
The effect of cryo-rolling and annealing on magnetic properties in non-oriented electrical steel
(Polish Institute of Physics, 2017) Kvačkaj, Tibor; Bella, Peter; Bidulský, Róbert; Kočiško, Róbert; Petroušek, Patrik; Fedoriková, Alica; Bidulská, Jana; Jandačka, Petr; Lupták, Miloslav; Černík, Martin; Pernis, Rudolf
The goal of the present work is to compare progressive technology - rolling at cryogenic temperature and classical rolling at ambient temperature followed by an investigation of their impact on the final microstructure and the magnetic properties of non-oriented electrical steel. Non-oriented electrical steel is characterized by high magnetic induction, low magnetic losses, and low coercivity. The best magnetic properties are achieved using preferable texture and optimal grain size. In this paper there is analyzed the percentage of different textural components after cryo-rolling and after rolling at ambient temperature. To obtain maps of inverse pole figures, the electron backscatter diffraction method was used. The main contribution of this study was that the samples rolled at cryo conditions and after final annealing reached better magnetic properties than at ambient temperature, which was reflected by low magnetic losses and coercivity.
Magnetic and Mössbauer study of cerium-based reactive sorbent
(Polish Institute of Physics, 2017) Jirásková, Yvonna; Buršík, Jiří; Životský, Ondřej; Luňáček, Jiří; Janoš, Pavel
A new kind of magnetically separable composite consisting initially of magnetite and cerium carbonate nanograins was investigated using magnetic and Mossbauer methods at room and low temperatures. Various stages of calcination treatment in air resulted in a transformation of the cerium carbonate into cerium dioxide and magnetite into more complicated iron oxide compositions. The final CeO2 nanograins on the surface of alpha-Fe2O3 were obtained after calcination at 973 K.
Co2FeSi Heusler alloy prepared by arc melting and planar flow casting methods: microstructure and magnetism
(Polish Institute of Physics, 2017) Titov, Andrii; Životský, Ondřej; Hendrych, Aleš; Janičkovič, Dušan; Buršík, Jiří; Jirásková, Yvonna
This paper is devoted to studies of the structural and magnetic properties of Co2FeSi Heusler alloy produced by arc melting resulting in samples with large grains compared to finer-grained ribbon type samples prepared by planar flow casting. The scanning electron microscopy completed by energy dispersive X-ray spectroscopy, X-ray diffraction, and magnetic methods sensitive to both bulk and surface were applied. The chemical composition inside the grains was found to be in agreement with the nominal one while at the grain boundaries enrichment on Co and Si at expense of Fe was observed. The magnetic parameters derived from the bulk hysteresis curves resulted in nearly the same values of coercivity, about 1 kA/m, for both technological procedures while magnetization was of about 15 A m(2)/kg higher at ribbons compared with sample prepared by arc melting, 145 A m(2)/kg. The surface magnetic characteristics were visibly influenced by a surface magnetic anisotropy. The smooth polished surface of the sample prepared by arc melting has allowed visualizing the magnetic domain structure inside the grains and at grain boundaries by the magneto-optical Kerr microscopy and magnetic force microscopy.
Preparation of sorbent with a high active sorption surface based on blast furnace slag for phosphate removal from wastewater
(Wroclaw University of Technology. Department of Environmental Engineering, 2017) Kostura, Bruno; Dvorský, Richard; Kukutschová, Jana; Študentová, Soňa; Bednář, Jiří; Mančík, Pavel
A new method has been presented, which leads to a significant improvement of the adsorption ability of blast furnace slag (BFS). An ultra-high pressure water jet mill cavitation disintegrator and a controlled vacuum freeze dryer were used to disintegrate amorphous BFS. Specific surface areas of both BFS and disintegrated slag (BFS-D) were measured using the SBET method. BFS-D was obtained with an average particle size of 198 nm and with 27-times bigger free specific surface area than that of original BFS. The BFS-D was tested as an adsorbent of phosphate from aqueous solutions. Adsorption data were analysed using the Freundlich and Langmuir adsorption isotherms. The BFS-D after phosphate adsorption was characterized using FTIR. The theoretical adsorption capacity of the BFS-D was 30.49 mg P/g, which represents an increase by 126.7% compared to the original BFS. Surface precipitation of hydroxyapatite was dominant retention mechanism.
Impact of pressure of surrounding medium on plain water jet cutting of rocks
(Springer, 2017) Poláček, Josef; Janurová, Eva
The goal of this contribution is to investigate problems connected with the application of plain water jets in surroundings between jet outlet and target differing from standard atmosphere. Two cases are especially interesting from the practical viewpoint. Application of water jets under the water level, i.e., in pressurized water: it is sometimes necessary to perform certain reparations on dam walls, bridge pillars, and other structures under the water level without emptying the dam or changing the river flow. The second case particularly involves water jets used for cleaning of chemical or radioactive facilities, which is much safer if done in underpressure. By these reasons, behavior of plain water jets on several different rock materials was tested inside the pressure vessel with the application of normal air pressure, air underpressure, and water overpressure. The effectiveness of rock material disintegration by water jet in various environmental conditions has been described. The depth of penetration decreases with increasing water overpressure, approximately with the second degree of the overpressure value. The cut depth decreases with the increasing value of certain material characteristics. The cut depth decreases also with decreasing pressure of air between nozzle outlet and sample surface. The dependence seems to be linear within the experimental range.
Abrasives for water-jet cutting of high-strength and thick hard materials
(Springer, 2017) Hlaváčová, Irena; Geryk, Vladan
The paper discusses abrasive water-jet cutting of hard-to-cut materials represented by high carbon steel DIN norm No.1.2436 (CSN EN 19437) plate 61-mm-thick and high-strength concrete cube sized 150 mm. Four relatively hard minerals with different densities not commonly used in water-jet technology were tested and their cutting results compared to those of three types of almandine garnets: Ukraine, Australian, and sorted Australian. Cutting efficiency was evaluated utilizing declination angle. Dependence of cutting efficiency on abrasive density and hardness was investigated. High density of abrasive appeared to be disadvantageous in our experiment. Cutting efficiency dependence on hardness exhibited nearly linear course, the increase was much more significant for concrete than for steel. Evaluation of experimental results led to the conclusion that cutting mechanism in case of very thick samples is different from common abrasive waterjet cutting. The limit declination angle for thick samples is significantly smaller, it was found to be approximately 22A degrees. This result represents entirely new finding. The most promising finding from the economical point of view appears to be behavior of corundum, when cutting concrete. Our experimental results promise 20 % increase in cutting speed for brittle materials.
Mid-infrared supercontinuum generation to similar to 4.7 mu m in a ZBLAN fiber pumped by an optical parametric generator
(IEEE, 2017) Michalska, Maria; Hlubina, Petr; Świderski, Jacek
We present mid-infrared (mid-IR) supercontinuum (SC) generation from a stepindex fluorozirconate fiber pumped at 2.25 mu m. When 70 ps pulses with a peak power of 128 kW were launched into a ZBLAN fiber with a zero dispersion wavelength at 1.603 mu m, SC was extended to 4695 nm, with spectral flatness below 10 dB, in the 2.00-4.56 mu m range. To the best of our knowledge, this is the first time such a broad and flat mid-IR SC spectrum from a ZBLAN fiber pumped with ps pulses has been achieved. The SC evolution as a function of pump wavelength and pump pulse energy was also experimentally demonstrated.
Effect of hydrogen on Fe and Pd alloying and physical properties
(Elsevier, 2017) Jirásková, Yvonna; Buršík, Jiří; Zemanová, Adéla; Čížek, Jakub; Hruška, Petr; Životský, Ondřej
Metastable Fe-Pd powder samples were synthesized by mechanically activated solid-state diffusion using high-energy ball milling. The Fe and Pd alloying and the hydrogen effect on this process were followed by preparation of two samples: the A-sample was a mixture of Fe powder and of Pd powder pre-charged with hydrogen (PdH) and milled under Ar atmosphere, the B-sample was a mixture of the Fe and Pd powders milled under hydrogen atmosphere. The fundamental properties, i.e., chemical and phase composition, lattice parameters, microstructure, morphology, grain size, defect structure, and macro- and micro-magnetic properties, were monitored after several steps of the alloying at room and appropriately at elevated temperatures. The alloying of Fe and Pd in both samples begins already after 5 h of milling and two phases are formed, the dominating bcc-Fe(Pd) phase and a minor fraction of the fcc-Pd(Fe) phase. The occurrence of the fcc phase, not observed previously by solid-state diffusion under argon atmosphere, is ascribed to mainly a positive effect of hydrogen reducing the formation energy of lattice defects and facilitating their formation. Consequently, the moving defects during mechanical alloying make the solid-state diffusion of Pd into bcc-Fe lattice and Fe into fcc-Pd lattice easier. On the other hand, hydrogen used as atmosphere in the milling procedure is adsorbed on the particle surfaces and after the vial opening hydrogen atoms form water molecules with oxygen from air. This exothermic reaction causes a removal of hydrogen atoms from the particle surface which thus becomes more sensitive to oxidation. Nothing similar was observed after mechanical alloying under argon atmosphere having positive impact on the particle surface stability.
Determination of local thickness values of non-uniform thin films by imaging spectroscopic reflectometer with enhanced spatial resolution
(IOP Publishing, 2017) Vodák, Jiří; Nečas, David; Ohlídal, Miloslav; Ohlídal, Ivan
In this paper an imaging spectroscopic reflectometer with enhanced spatial resolution is presented. Main features of its design, experimental data acquisition, i. e. maps of thin film spectral dependencies of local reflectance and the local thickness map determination are described. The ability of this instrument to characterize thin film thickness non-uniformity with high gradients is demonstrated on measurements of thin film edges. A comparison with an older device is also presented.
Fiber optic temperature sensing with enhanced sensitivity based on spectral interferometry
(Elsevier, 2017) Militký, Jan; Kadulová, Miroslava; Ciprian, Dalibor; Hlubina, Petr
Temperature sensing with enhanced sensitivity based on the spectral interference of polarization modes in a highly birefringent (HB) fiber is proposed and demonstrated. A temperature sensor employs a tandem configuration of a birefringent quartz crystal and HB fiber placed between an analyzer and a polarizer. In the setup a modified channeled spectrum is generated, which shifts with the temperature change of the sensing part of the HB fiber. We analyze the measurement method theoretically and show that the sensitivity of the temperature sensing based on the wavelength interrogation is enhanced in comparison to a standard method with a fiber interferometer. We also demonstrate the enhancement of the temperature sensitivity for three HB fibers under test. Experimental results show that the temperature sensing can reach a sensitivity of −0.30 nm/K, which is enhanced in comparison to −0.10 nm/K reached for a standard measurement.
Taper of kerfs made in rocks by abrasive water jet (AWJ)
(Springer, 2017) Hlaváč, Libor; Hlaváčová, Irena; Geryk, Vladan
The taper, inclination of cut side walls, is one of the characteristic phenomena of the abrasive water jet (AWJ) cutting. The taper represents a serious problem in shape cutting, especially in corners and curvatures. However, deviation of the side walls occurs even in the straight line parts of trajectories. Some differences from character typical for metal cutting have been noticed when studying the rock materials. This article is aimed at the experimental research of the cut walls taper on several rock materials with different genesis and composition. The topic of this contribution to the common knowledge is pointing out the most important differences compared to previous research made mainly on metals. The widths of slots made in plan-parallel plates of rock materials were measured both on the top and on the bottom. The difference between these widths has been used for evaluation of the taper—the angle of the cut walls inclination. The results were compared with the regression equation obtained from experimental results on metals and presented in past. The discrepancy between new findings and previously determined equation is discussed and the most probable explanations are submitted.
Magneto-optical properties of InSb for terahertz applications
(AIP Publishing, 2016) Chochol, Jan; Postava, Kamil; Čada, Michael; Vanwolleghem, Mathias; Halagačka, Lukáš; Lampin, Jean-François; Pištora, Jaromír
Magneto-optical permittivity tensor spectra of undoped InSb, n-doped and p-doped InSb crystals were determined using the terahertz time-domain spectroscopy (THz-TDS) and the Fourier transform far-infrared spectroscopy (far-FTIR). A Huge polar magneto-optical (MO) Kerr-effect (up to 20 degrees in rotation) and a simultaneous plasmonic behavior observed at low magnetic field (0.4 T) and room temperature are promising for terahertz nonreciprocal applications. We demonstrate the possibility of adjusting the the spectral rage with huge MO by increase in n-doping of InSb. Spectral response is modeled using generalized magneto-optical Drude-Lorentz theory, giving us precise values of free carrier mobility, density and effective mass consistent with electric Hall effect measurement.
High coercivity in Fe-Nb-B-Dy bulk nanocrystalline magnets
(Wiley, 2016) Ziółkowski, Grzegorz; Chrobak, Artur; Klimontko, Joanna; Chrobak, Dariusz; Životský, Ondřej; Hendrych, Aleš; Rak, Jan
The paper refers to structural and magnetic properties of the (Fe80Nb6B14)1−xDyx (x = 0.08, 0.10, 0.12, 0.16) bulk nanocrystalline alloys prepared by making use of the vacuum suction casting technique. The samples are in a form of rods with different diameters d = 1.5, 1, and 0.5 mm. The phase structure was investigated by XRD technique and reveals an occurrence of magnetically hard Dy2Fe14B as well as other relatively soft Dy–Fe, Fe–B, and Fe phases dependently on the Dy content. The alloys show hard magnetic properties with high coercive field up to 5.5 T (for x = 0.12 and d = 0.5 mm). The observed magnetic hardening effect with the increase of cooling rate (decrease of sample diameter d) can be attributed to a formation of ultra-hard magnetic objects as well as increasing role of low dimensional microstructure.

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