Publikační činnost Institutu fyziky / Publications of Institute of Physics (516)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64768

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Institutu fyziky (516)v časopisech registrovaných ve Web of Science od roku 2003 do roku 2019. Institut byl na fakultě zrušen.
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.

Browse

Now showing 1 - 20 out of 295 results

Evidence of tetrahedrally coordinated nickel cations in nanostructured NiFe2O4
(American Scientific Publishers, 2019) Fabián, Martin; Harničárová, Marta; Valíček, Jan; Da Silva, Klebson L.; Hahn, Horst; Šepeľák, Vladimír; Lesňák, Michal; Kušnerová, Milena
Nanostructured nickel ferrite (NiFe2O4) is prepared via high-energy ball milling of the bulk counterpart at ambient temperature. The structure of the as-prepared nanoferrite is characterized by Raman spectroscopy and Fe-57 Mossbauer spectroscopy. Due to the ability of these spectroscopic techniques to probe the local environment of ions, valuable complementary insight into the nature of the local structural disorder of nanosized NiFe2O4, is provided. For the first time, evidence is given of the tetrahedrally coordinated nickel cations in the nanomaterial.
Magnetic sorbents biomineralization on the basis of iron sulphides
(Taylor & Francis, 2018) Jenčárová, Jana; Luptáková, Alena; Vítkovská, Nikola; Matýsek, Dalibor; Jandačka, Petr
Biomineralization means mineral formation under the influence of organisms. Sulphate-reducing bacteria (SRB) constitute an essential role of iron sulphide minerals precipitation. Their composition involves amorphous, non-stoichiometric or crystalline iron sulphides, weakly or strongly magnetic. Variation in environmental conditions can alter the reactive iron species within the mineral, potentially modifying their magnetic properties. Biogenic iron sulphide minerals can be used as heavy metals and toxic ions adsorbents in soil or water remediation. For these reasons, a series of laboratory-scale iron sulphide synthesis experiments with the aim to study the chemical composition, mineralogy and magnetic properties of iron sulphide precipitates were carried out using SRB under various cultivation mode and nutrient medium composition. Energy-dispersive X-ray analysis (EDX) showed formation of iron sulphides in all biogenic samples and iron phosphates in abiotic controls. Results of X-ray diffraction analysis (XRD) in biomineralized samples confirmed nanocrystalline greigite, mackinawite and sulphur alpha. Magnetic measurements showed that sample prepared by static cultivation without addition of fresh nutrient medium was the most magnetic, magnetic hysteresis of sample formed under semicontinuous mode without any nutrient supply was the lowest. Abiotic samples contained only vivianite and they did not prove any significant response to magnetic field.
Design of MO-SPR sensor element with photonic crystal
(Elsevier, 2018) Otipka, Petr; Vlček, Jaroslav; Lesňák, Michal; Sobota, Jaroslav
Magneto-plasmonic response in planar multilayer with prism coupling composed from Fe/Au bi-layer supplied by photonic crystal (Ta2O5/SiO2 bi-layers) is studied. Modeled structure is intended as a sensor unit combining magneto-optical (MO) and surface-plasmon-resonance (SPR) effects. The sensitivity of MO-SPR system by small variations of analyte refractive index is tested to obtain optimal resolution ability. The non-reciprocal MO-SPR response is studied by means of the function p(phi) = (R-p((+))- R-p((-)))/(R-p((+)) + R-p((-))), where the reflectance Rp depends on the incidence angle phi and external magnetic field orientation by a fixed wavelength. The detection ability is characterized by the angular shift Delta phi(o) between the null-points of the function p that corresponds to the change Delta n(a) of analyte refractive index. Besides the key role of metallic layers thicknesses the number and size of Ta2O5/SiO2 bi-layers of photonic crystal are discussed. The magneto-plasmonic response in planar multilayer with prism coupling composed from Fe and Au bilayer supplied by photonic crystal (Ta2O5/SiO2) is studied. Modeled structure is intended as a sensor unit combining MO and SPR effects.
Rapid mechanochemical synthesis of titanium and hafnium carbides
(Springer, 2018) Lyakhov, Nikolay; Grigoreva, Tatiana; Šepeľák, Vladimír; Tolochko, Boris Petrovich; Ancharov, Aleksey; Vosmerikov, Sergey; Devyatkina, Evgeniya; Udalova, Tatyana; Petrova, Sofia
The mechanically triggered interactions in the Ti-C and Hf-C systems performed in a high-energy planetary ball mill are studied. The formation of carbides (TiC and HfC) in the course of mechanochemical synthesis at the different stages is followed by both conventional and synchrotron X-ray diffraction analyses and high-resolution scanning and transmission electron microscopy. The mechanism of the mechanochemically induced reactions in the Ti-C and Hf-C systems leading to the relatively rapid formation of TiC and HfC, respectively, is proposed. The interaction between metallic Ti (Hf) and C proceeds through the formation of mechanocomposites Ti/C (Hf/C) at the first stage, followed by the melting of titanium (hafnium), the spreading it over the carbon particle surface and the crystallization of titanium (hafnium) carbides. It is demonstrated that the mechanosynthesis of ultra-fine TiC and HfC is completed after 20 and 8 min of mechanical activation, respectively.
Mechanosynthesis of composites in chemically non-reacting and exothermically reacting systems for magnetic abrasive media
(Springer, 2018) Kovaliova, Svetlana A.; Šepeľák, Vladimír; Grigoreva, Tatiana; Zhornik, Victor; Kiseleva, Tatiana; Khomich, Mikalai; Devyatkina, Evgeniya; Vosmerikov, Sergey; Vityaz, Pyotr A.; Lyakhov, Nikolay
Magnetic abrasive machining is one of the advanced finishing processes that produce a high level of surface quality of any type. The productivity of the finishing process and the quality of the treated surfaces are determined by magnetic and abrasive properties of the working media. To synthesize effective magneto abrasive composites with the size range of 1-100 mu m the intensive mechanical treatment of powdered mixtures of chemically inert (Fe:SiC, Fe:B4C and Fe:diamond) and exothermically reacting (Fe2O3:Fe:Me, Me = Al, Zr) systems in high-energy planetary ball mills is performed. It is shown that the formation of composites is the result of intensive processes of grinding and deformation (mechanical alloying) as well as of the mechanically intensified redox reactions (mechanochemical synthesis) leading to the formation of abrasive particles (MexOy) in iron matrix. X-ray diffraction, scanning electron microscopy, Mossbauer spectroscopy and investigations of mechanical properties accompanied by the measurements of the abrasive activity in the finishing process of the surface polishing are used for the characterization of the as-prepared composites. The main parameters and mechanisms of the formation of the optimal structure of composites are revealed. It is demonstrated that the smallest roughness of the machined surface (R-a similar to 1 nm) is achieved in the case of using the mechanically alloyed Fe/diamond composite and the mechanosynthesized Fe/ZrO2 composite.
The formation of Fe–Ga–In nanocomposite particles using mechanochemical interaction of Fe with the Ga–In eutectic
(Springer, 2018) Kiseleva, Tatiana; Levin, Eduard; Novakova, Alla; Ilyushin, Alexander; Grigoryeva, Tatiana; Šepeľák, Vladimír
Mechanochemical interaction of Fe powder with the liquid Ga-In eutectic in the Fe-rich concentration corner of the Fe-Ga-In phase diagram was studied and compared with binary Fe-Ga and Fe-In specimens. Slow formation of diluted solid solutions in the Fe-In system was confirmed. In the Fe-Ga system, the dominant concentrated A2 solid solution is formed with H-eff = 236 kOe, accompanied by ordered D0(3) and L1(2) phases. The Fe-Ga-In system features a stationary equilibrium between the concentrated A2 phase and D0(3) in the iron matrix.
Analysis of signals obtained from surfaces created by abrasive waterjet by means of amplitude-frequency spectra and autocorrelation function
(Sveučilište Josipa Jurja Strossmayera u Osijeku. Strojarski fakultet; Elektrotehnički fakultet; Građevinski fakultet., 2008) Valíček, Jan; Hloch, Sergej; Fabian, Stanislav; Monková, Katarína; Hatala, Michal; Luptáková, Alena; Radvanská, Agáta
The paper deals with the description of contemporary methodology of topography evaluation of surfaces created by the abrasive water jet by using the existing standard and non-standard parameters in combination with an autocorrelation function. The grid projection method was used for measurement of samples prepared from stainless steel AISI 309 by abrasive water jet. The optical signals obtained by means of grid projection method of these surfaces were processed by Fourier transform and the norm autocorrelation function in order to get information about height and longitudinal fluctuations. The obtained results are analysed and interpreted.
Experimental study of surface topography created by abrasive waterjet cutting
(Uredništvo časopisa Strojarstvo, 2007) Hloch, Sergej; Valíček, Jan; Samardžić, Ivan; Kozak, Dražan; Müllerová, Jana; Gombár, Miroslav
In this work the surface topography of aluminium has been in detail studied with the aim of quantification of morphologically different zones initial, smooth, transition and tough zone by means of surface profile parameters Ra and Rz obtained from 24 depth traces. The surfaces have been measured by means of optical profilometer MicroProf FRT that allows research, especially the initial zone that has not been deeply studied and described. From analyses of the parameters Ra, Rq and Rz obtained by means of optical profilometer - MicroProf FRT, a new way of classification of morphologically different zones on the basis of the quantitative parameters Ra and Rz has been proposed.
Effective spectral optical functions of lamellar nanogratings
(European Optical Society, 2006) Foldyna, Martin; Postava, Kamil; Ossikovski, Razvigor; De Martino, Antonello; Garcia-Caurel, Enric
Spectral properties of lamellar sub-wavelength gratings (nanogratings) are described by effective medium approximation (EMA). Analytical spectral formulae for ordinary and extraordinary effective optical functions are derived for nanogratings consisting of material described by Sellmeier, damped harmonic oscillator, and Drude formulae. Spectral origin for birefringence of dielectric nanogratings and linear dichroism for absorbing ones is discussed for model cases and gratings consisting of real natural materials. Simple approximation by zero-order diffraction is compared with rigorous modeling based on Rigorous Coupled Wave Analysis (RCWA). Limits of applicability of effective medium approximation is discussed in the spectral domain.
Transverse magneto-optical Kerr effect measured using phase modulation
(European Optical Society, 2006) Postava, Kamil; Maziewski, Andrzej; Stupakiewicz, Andrzej; Wawro, Andrzej; Baczewski, Lech T.; Višňovský, Štefan; Yamaguchi, Tomuo
An ellipsometric configuration for measurement of the complex transverse magneto-optical Kerr effect is described that uses a photoelastic modulator (PEM). The real and imaginary parts of the complex transverse Kerr effect are represented as small perturbations of ellipsometric angles psi and Delta. The measurement, based on null ellipsometry and zone averaging, gives high signal typical for modulation techniques and insensitivity to other magnetisation components and system imperfections. The method is demonstrated by the measurement of transverse component during magnetisation reversal in a thin cobalt film.
Measurement of powder surface area using capillary elevation method
(Polskie Towarzystwo Przeróbki Kopalin, 2015) Jandačka, Petr; Dvorský, Richard; Luňáček, Jiří
This contribution presents a neglected method of measuring powder surface area that uses the capillary elevation phenomenon. Such measurement has a potential to distinguish a fine surface texture of measured powder materials. The method has been verified experimentally on smooth steel spheres with diameters of 0.5 mm, 1.0 mm, 1.2 mm, and 1.6 mm, for which the theoretical values of specific surface area can be calculated and compared with the measurement results. The deviation of these experimentally determined values from the reference theoretical ones was less than 1%. New alternative experimental arrangements and related theoretical relations and simulations are presented.
Fabrication and characterisation of porous, calcium enriched coatings on titanium after plasma electrolytic oxidation under DC regime
(De Gruyter, 2017) Rokosz, Krzysztof; Hryniewicz, Tadeusz; Pietrzak, Kornel; Sadlak, P.; Valíček, Jan
The purpose of this work is to produce and characterize (chemical composition and roughness parameters) porous coatings enriched in calcium and phosphorus on the titanium (CP Titanium Grade 2) by plasma electrolytic oxidation. As an electrolyte, a mixture of phosphoric acid H3PO4 and calcium nitrate Ca(NO3)(2)center dot 4H(2)O was used. Based on obtained EDS and roughness results of PEO coatings, the effect of PEO voltages on the chemical composition and surface roughness of porous coatings was determined. With voltage increasing from 450 V to 650 V, the calcium in PEO coatings obtained in freshly prepared electrolyte was also found to increase. In addition, the Ca/P ratio increased linearly with voltage increasing according to the formula Ca/P = 0.035 center dot U+0.176 (by wt%) and Ca/P = 0.03 center dot U+0.13 (by at%). It was also noticed that the surface roughness increases with the voltage increasing, what is related to the change in coating porosity, i.e. the higher is the surface roughness, the bigger are pores sizes obtained.
Modeling the temperature dependence of dynamic mechanical properties and visco-elastic behavior of thermoplastic polyurethane using artificial neural network
(MDPI, 2017) Kopal, Ivan; Harničárová, Marta; Valíček, Jan; Kušnerová, Milena
This paper presents one of the soft computing methods, specifically the artificial neural network technique, that has been used to model the temperature dependence of dynamic mechanical properties and visco-elastic behavior of widely exploited thermoplastic polyurethane over the wide range of temperatures. It is very complex and commonly a highly non-linear problem with no easy analytical methods to predict them directly and accurately in practice. Variations of the storage modulus, loss modulus, and the damping factor with temperature were obtained from the dynamic mechanical analysis tests across transition temperatures at constant single frequency of dynamic mechanical loading. Based on dynamic mechanical analysis experiments, temperature dependent values of both dynamic moduli and damping factor were calculated by three models of well-trained multi-layer feed-forward back-propagation artificial neural network. The excellent agreement between the modeled and experimental data has been found over the entire investigated temperature interval, including all of the observed relaxation transitions. The multi-layer feed-forward back-propagation artificial neural network has been confirmed to be a very effective artificial intelligence tool for the modeling of dynamic mechanical properties and for the prediction of visco-elastic behavior of tested thermoplastic polyurethane in the whole temperature range of its service life.
Identification of upper and lower level yield strength in materials
(MDPI, 2017) Valíček, Jan; Harničárová, Marta; Kopal, Ivan; Palková, Zuzana; Kušnerová, Milena; Panda, Anton; Šepelák, Vladimír
This work evaluates the possibility of identifying mechanical parameters, especially upper and lower yield points, by the analytical processing of specific elements of the topography of surfaces generated with abrasive waterjet technology. We developed a new system of equations, which are connected with each other in such a way that the result of a calculation is a comprehensive mathematical-physical model, which describes numerically as well as graphically the deformation process of material cutting using an abrasive waterjet. The results of our model have been successfully checked against those obtained by means of a tensile test. The main prospect for future applications of the method presented in this article concerns the identification of mechanical parameters associated with the prediction of material behavior. The findings of this study can contribute to a more detailed understanding of the relationships: material properties-tool properties-deformation properties.
Thermal and performance analysis of a gasification boiler and its energy efficiency optimization
(MDPI, 2017) Valíček, Jan; Palková, Zuzana; Harničárová, Marta; Kušnerová, Milena; Lukáč, Ondrej
The purpose of this study was to determine a method for multi-parametric output regulation of a gasification boiler especially designed for heating or for hot water heating in buildings. A new method of regulation is offered, namely more parametric regulation via proportional-integral-derivative (PID) controllers that are capable of controlling the calculated values of pressure, temperature and fan speed. These values of pressure, temperature and fan speed are calculated in a completely new way, and calculations of setpoints for determination of optimal parameters lead to an increase in boilers efficiency and power output. Results of measurements show that changes at the mouth of the stack draft due atmospheric influences occur in times with high intensity and high frequency, while power parameters, or boiler power output amplitudes and fan speed automatically "copy" those changes proportionally due to instantaneous fan speed changes. The proposed method of regulation of the gasification boiler power output according to the technical solution enables a simple, cheap, express and continuous maintenance of high power output at low concentrations of the exhaust gases of the gasification boilers from the viewpoint of the boiler user, as well as from the perspective of development and production it allows a continuous control monitoring of these parameters.
Creation of combined sigma-epsilon graphs for some engineering materials
(Wiley-VCH, 2017) Valíček, Jan; Harničárová, Marta; Kušnerová, Milena; Václavík, Vojtěch; Kopal, Ivan; Koštial, Pavol
This paper presents the characterization of engineering materials according to stress-strain diagrams, according to the basic material, namely partially according to the basic material groups that correspond to the generally applicable division into metals, glasses, ceramics, composites, polymers, and elastomers. These groups of materials are presented using combined graphs obtained from the authors' own method of solving the given problem. For the purpose of generalization, the conception according to the publication by Ashby can be used very well. By the fast development of new materials, the number of available and used materials in technical fields is growing. The concentration of technically used materials in the conception of Ashby can be used to derive an approximate equation of the distribution trend of a parameter of the conventional strength of material. From the graphical processing of these values, it is seen that this trend is concordant with the central line of materials in the diagram according to Ashby.
Measurements of rubber mechanical properties in aged and nonaged state
(Wiley-VCH, 2017) Ružiak, Ivan; Koštial, Pavol; Jančíková, Zora; Krišťák, Ľuboš; Kopal, Ivan; Valíček, Jan; Harničárová, Marta
In this work we study the influence of different types of plasticizers on the mechanical properties of rubber blend mixtures before and after the ageing process. We have used Oleic acid as plasticizer. Reference samples were mixed with an oleic acid content of 1 part of the oleic acid to the 100 parts of rubber and 3 parts of the oleic acid to the 100 parts of rubber with weight percentages of the surfactant ETOXON 2, 4, 6, 8, 10, 20, 30 and basic mechanical properties such as tensile strength, Shore A hardness, ductility, moduli 100, 200, 300 have been measured. Measurements were performed 24 h after blend vulcanization and then 1 month after. We have studied the influence of plasticizers on the measured properties and the influence of ageing on the measured properties. All measured mechanical properties change with chemical composition except Shore A hardness.
Manufacturing technology of composite materials-principles of modification of polymer composite materials technology based on polytetrafluoroethylene
(MDPI, 2017) Panda, Anton; Dyadyura, Kostiantyn; Valíček, Jan; Harničárová, Marta; Zajac, Jozef; Modrák, Vladimír; Pandová, Iveta; Vrábel, Peter; Nováková-Marcinčínová, Ema; Pavelek, Zdeněk
The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer-solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment.
Laserowe pomiary topografii powierzchni narzędzi ściernych z zastosowaniem systemu pomiarowego CLI 2000
(Sigma Not, 2011) Nadolny, Krzysztof; Kapłonek, Wojciech; Łukianowicz, Czesław; Valíček, Jan
W pracy zaproponowano wykorzystanie systemu pomiarowego Talysurf CLI 2000 firmy Taylor-Hobson Ltd,. do oceny topografii powierzchni narzędzi ściernych. Przedstawiono krótką charakterystykę urządzenia oraz pokazano przykładowe wyniki pomiarów powierzchni, wykonywanych metodą triangulacji laserowej. Rezultaty badań potwierdziły dużą użyteczność zastosowanego systemu pomiarowego oraz jego szerokie możliwości oceny tego typu powierzchni.
Combined mechanochemical/thermal synthesis of microcrystalline pyroxene LiFeSi2O6 and one-step mechanosynthesis of nanoglassy LiFeSi2O6-based composite
(Elsevier, 2017) Turianicová, Erika; Witte, Ralf; Da Silva, Klebson L.; Zorkovská, Anna; Senna, Mamoru; Hahn, Horst; Heitjans, Paul; Šepelák, Vladimír
Both, microcrystalline LiFeSi2O6 pyroxene and nanoglassy LiFeSi2O6-based composite are prepared via non-conventional mechanochemical/ thermal processing and one-step mechanosynthesis, respectively. The structural state of the as-prepared materials on the long-range and local atomic scales is characterized by XRD and Fe-57 Mossbauer spectroscopy, respectively. The derived hyperfine interaction parameters indicate that the nanoglassy nature of the mechanosynthesized LiFeSi2O6-based composite is characterized, on the short-range scale, by a broadly distorted geometry of the constituent structural units, and on the long-range scale, by the raptured chains of the edge-sharing FeO6 octahedra and of the corner-sharing SiO4 tetrahedra.

Browse

Recent Submissions