NANOCERIA PREPARED BY ELECTRON BEAM EVAPORATION
Pizúrová, Naděžda; Hlaváček, A.; Kavčiaková, Zuzana; Roupcová, Pavla; Kuběna, Ivo; Buršík, Jiří; Sokovnin, S. Y.
2022 - English Cerium oxide nanoparticles (nanoceria) are currently one of the most investigated nanomaterials because of their attractive properties used in biomedical applications, catalysis, fuel cells, and many others. These attractive properties are connected with the Ce3+ and Ce4+ valency state ratio. In the nanoparticle form, cerium oxides contain a mixture of Ce3+ and Ce4+ on the nanoparticle surfaces. Switching between these two states requires oxygen vacancies. Therefore, nanoceria's inherent ability to act as an antioxidant in an environmentally-dependent manner and a “redox switch” to confer auto-regenerating capabilities by automatically shifting between Ce4+ and Ce3+ oxidation states is significantly affected by surface morphology. Regarding this demanded behavior, we aimed to characterize synthesized nanoparticle surface quality and its influence on the cerium oxidation states. The received results were used to evaluate the synthesis method's suitability for suggested utilization. We used nanoparticles prepared by electron beam evaporation. This unique physical method includes nanoparticle creation through the fast cooling process followed by breaking radiation damaging nanoparticle surfaces to create surface off-stoichiometry. We prepared a sample containing clusters of a mixture of ultra-small nanoparticles and approximately 100 nm particles. X-ray diffraction confirmed the CeO2 phase in both components. To extract the finest component, we used centrifugal size fractionation. We received 200 nm clusters of 2-10 nm nanoparticles. Nanoparticle shapes and facet types were analyzed using transmission electron microscopy methods. We found out most nanoparticles were formed with truncated octahedrons containing {1,1,1} and {1,0,0} facet types and truncated cuboctahedrons containing {1,1,1}, {1,0,0}, and additional {1,1,0} facets. No octahedron (without truncation) containing only {1,1,1} facets was observed. Nanoparticle shapes containing {1,1,0} and {1,0,0} are suitable for redox activity. Some amount of irregular shapes, beneficial for redox activity, was also observed. Spectroscopy methods confirmed Ce3+ content. Keywords: Ce3+ and Ce4+; electron beam evaporation; facet types; hrtem; Nanoceria Available at various institutes of the ASCR NANOCERIA PREPARED BY ELECTRON BEAM EVAPORATION

Cerium oxide nanoparticles (nanoceria) are currently one of the most investigated nanomaterials because of their attractive properties used in biomedical applications, catalysis, fuel cells, and many ...

Pizúrová, Naděžda; Hlaváček, A.; Kavčiaková, Zuzana; Roupcová, Pavla; Kuběna, Ivo; Buršík, Jiří; Sokovnin, S. Y.
Ústav fyziky materiálů, 2022

INFLUENCE OF THE DEPOSITION PARAMETERS ON MICROSTRUCTURE AND PROPERTIES OF HVOF SPRAYED WC-CRC-NI COATING
Vražina, Tomáš; Šulák, Ivo; Poloprudský, Jakub; Zábranský, K.; Gejdoš, P.; Hadraba, Hynek; Čelko, L.
2022 - English This paper investigates the influence of thermal spray parameters of the high-velocity oxygen fuel (HVOF) process on the properties of cermet coatings prepared from commercially available Amperit 551 WC-CrC-Ni powder. Three different processing parameters were applied to optimize the production process with the aim to achieve preeminent mechanical properties and fully dense material without microstructural defects. The deposition was carried out by a GLC5 gun. The velocity and temperature of powder particles in the spray stream were monitored by Accuraspray Tecnar diagnostic tool. The quality of deposited coatings was analyzed by means of light microscopy, scanning electron microscopy, and X-ray diffraction. The chemical composition of the used powder and sprayed WC-CrC-Ni coating was determined by energy dispersive spectroscopy. It was found that the spray parameters have a negligible effect on the resulting microstructure and phase composition of the coating. However, the porosity and surface roughness were significantly affected by the variation in process parameters. To assess the basic mechanical properties of HVOF sprayed coating instrumented Vickers hardness measurements were utilized. The coating hardness reached mean values over 1400 HV 0.1 and the indentation modulus varied from 152-279 GPa. Keywords: hvof; microhardness; WC-CrC-Ni Available at various institutes of the ASCR INFLUENCE OF THE DEPOSITION PARAMETERS ON MICROSTRUCTURE AND PROPERTIES OF HVOF SPRAYED WC-CRC-NI COATING

This paper investigates the influence of thermal spray parameters of the high-velocity oxygen fuel (HVOF) process on the properties of cermet coatings prepared from commercially available Amperit 551 ...

Vražina, Tomáš; Šulák, Ivo; Poloprudský, Jakub; Zábranský, K.; Gejdoš, P.; Hadraba, Hynek; Čelko, L.
Ústav fyziky materiálů, 2022

Problematics of aerodynamic damping calculation from measured data of 5-blade cascade
Šnábl, Pavel; Pešek, Luděk; Prasad, Chandra Shekhar; Chindada, Sony
2022 - English Aerodynamic damping as a function of inter-blade phase angle (IBPA), so called S-curve, is crucial for assessment of aeroelastic stability of blade cascades, e.g. turbines, compressors, etc.\nFor constructing the S-curve, the motion-induced controlled flutter is introduced to the bladesof the cascade. As decribed in [1], two testing methods exist: aerodynamic influence coefficient\n(AIC) approach and travelling wave mode (TWM) approach. In TWM approach, all blades in a row oscillate with the same frequency and amplitude with various IBPAs. The response is\nmeasured only on the reference blade. With this approach, several measurements with different IPBAs are needed to construct the S-curve. On the other hand, AIC uses single oscillating\nblade and principle of linear superimposition of aerodynamic influence responses measured on all blades in a cascade. The result of one single measurement can be used for estimation of\naerodynamic damping for any IBPA. In the past year a new 5-blade cascade with rotating symmetrical NACA 0010 profiles was designed and built. The blades of the cascade were placed further apart and thus we are now able to reach stall flutter. Also, the suspension of the blades and sensors were significantly improved. Now, our goal is to evaluate S-curves using AIC approach for different flow conditions and oscillation frequencies. Keywords: aerodynamic damping; S-curve; blade cascade Available at various institutes of the ASCR Problematics of aerodynamic damping calculation from measured data of 5-blade cascade

Aerodynamic damping as a function of inter-blade phase angle (IBPA), so called S-curve, is crucial for assessment of aeroelastic stability of blade cascades, e.g. turbines, compressors, etc.\nFor ...

Šnábl, Pavel; Pešek, Luděk; Prasad, Chandra Shekhar; Chindada, Sony
Ústav termomechaniky, 2022

Interaction of triazole fungicides in agriculture
Kovač, Ishak; Jakl, M.; Šolínová, Veronika; Kašička, Václav; Jaklová Dytrtová, Jana
2022 - English Keywords: capillary electrokinetic chromatography; triazole fungicides; quantitative analysis Available at various institutes of the ASCR Interaction of triazole fungicides in agriculture

Kovač, Ishak; Jakl, M.; Šolínová, Veronika; Kašička, Václav; Jaklová Dytrtová, Jana
Ústav organické chemie a biochemie, 2022

Long term optical monitoring technique of displacement fields based on ArUco markers
Kunecký, Jiří
2022 - English In structural engineering it is often needed to measure tiny displacements of parts of the structure extremely precisely. For such a purpose it is often needed to use some type of sensor attached to the surface of the structure. This paper presents a new technique which simply uses computer vision libraries to measure displacement of markers originally developed for robotics. Such analysis can be under specific circumstances (2D planar movement) valid if we compare two images taken at different times with the same camera. Main advantage of this method is simplicity of use and low cost of markers, which can be printed in a standard office laser printer. The resolution (error) can be for standard cameras around 0.1 pixel. The method is especially developed for research of timber frames/joints behavior in real structures, because displacements of joints in creep or under load can reach an amplitude which is perfectly detectable by this method. Keywords: displacement measurement; long-term monitoring; ArUco markers Available at various institutes of the ASCR Long term optical monitoring technique of displacement fields based on ArUco markers

In structural engineering it is often needed to measure tiny displacements of parts of the structure extremely precisely. For such a purpose it is often needed to use some type of sensor attached to ...

Kunecký, Jiří
Ústav teoretické a aplikované mechaniky, 2022

Analysis of van der Pol equation on slow time scale for combined random and harmonic excitation
Náprstek, Jiří; Fischer, Cyril
2022 - English Vortex shedding represents one of the most important processes that constantly attract the attention of experimental and theoretical research. A number of non-linear effects arise from the fluid-structure interaction. The non-stationary response in the vicinity of the lock-in region has a quasi-periodic character, beating frequency of which varies considerably with the distance from the lock-in frequency. This property is significantly affected by the assumption of combined random and harmonic excitation. This paper describes several details that contribute to the probabilistic characteristics of the system on a time-slow scale using partial response amplitudes. Keywords: SDOF oscillator; slow-time system; Fokker-Planck equation Available at various institutes of the ASCR Analysis of van der Pol equation on slow time scale for combined random and harmonic excitation

Vortex shedding represents one of the most important processes that constantly attract the attention of experimental and theoretical research. A number of non-linear effects arise from the ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2022

Construction of the Lyapunov function reflecting the physical properties of the model
Náprstek, Jiří; Fischer, Cyril
2022 - English Practical experience shows that the random excitation component can affect the system response and its dynamic stability not only negatively but also positively. Such mechanisms are usually developed heuristically and are often not sufficiently justified theoretically. The paper presents a possibility of using the properties of first integrals for the construction of a Lyapunov function for the analysis of a dynamic system stability in the stochastic domain. In such case, the Lyapunov function itself contains information on the examined system and, consequently, it is able to provide a more detailed insight into the system stability properties. The procedure is illustrated by a nonlinear SDOF example. Keywords: Lyapunov function; stability; spherical pendulum Available at various institutes of the ASCR Construction of the Lyapunov function reflecting the physical properties of the model

Practical experience shows that the random excitation component can affect the system response and its dynamic stability not only negatively but also positively. Such mechanisms are usually developed ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2022

Magnetocrystalline anisotropy of Ni-Mn-Ga-Co-Cu martensite
Rameš, Michal; Straka, Ladislav; Sozinov, A.; Heczko, Oleg
2022 - English The martensites of Heusler alloys based on Ni-Mn-Ga exhibit magnetically-induced reorientation resulting in giant field-induced strain. Up to 12% strain was observed in Ni-Mn-Ga-Co-Cu with 4 at.% of Co and Cu. The driving force of the phenomenon is the magnetocrystalline anisotropy. We studied evolution of the anisotropy with temperature and compositions using magnetiyation curve measurements in four different single crystalline Ni-Mn-Ga-Co-Cu and compared with non-doped Ni-Mn-Ga. The anisotropy of martensite decreases with increasing average doping (Co+Cu)/2 but it does not scale with tetragonal ratio or valence electron concentration. Keywords: martensite; magnetocrystalline anisotropy; Heusler alloys; Ni-Mn-Ga Available at various institutes of the ASCR Magnetocrystalline anisotropy of Ni-Mn-Ga-Co-Cu martensite

The martensites of Heusler alloys based on Ni-Mn-Ga exhibit magnetically-induced reorientation resulting in giant field-induced strain. Up to 12% strain was observed in Ni-Mn-Ga-Co-Cu with 4 at.% of ...

Rameš, Michal; Straka, Ladislav; Sozinov, A.; Heczko, Oleg
Fyzikální ústav, 2022

Analysis, separation and characterization of dityrosine diastereomers by capillary electrophoresis
Šolínová, Veronika; Niederhafner, Petr; Šafařík, Martin; Šebestík, Jaroslav; Kašička, Václav
2022 - English Keywords: capillary electrophoresis; diastereomer separation; dityrosine Available at various institutes of the ASCR Analysis, separation and characterization of dityrosine diastereomers by capillary electrophoresis

Šolínová, Veronika; Niederhafner, Petr; Šafařík, Martin; Šebestík, Jaroslav; Kašička, Václav
Ústav organické chemie a biochemie, 2022

Analytical model of joint loaded perpendicular to wooden grain
Hataj, M.; Pošta, J.; Hasníková, Hana; Kunecký, Jiří
2022 - English Computing models for structural behaviour and determination of traditional timber butt joints using analytical relations are presented in this paper. A component method is the base of the computing technique introduced herein. This method is usually used for steel joint design. The component method is based on dividing a joint into individual components. These are defined by partial joint component stiffness. An analytical solution includes a subsidence effect of wooden material close to compressive loading. Analytical computation results are compared with the experimental outputs. A design procedure according to Eurocode 5 for a load capacity determination of perpendicularly loaded structural elements is stated in the paper. Keywords: analytical models; load capacity; butt joint; carpentry; timber structures Available at various institutes of the ASCR Analytical model of joint loaded perpendicular to wooden grain

Computing models for structural behaviour and determination of traditional timber butt joints using analytical relations are presented in this paper. A component method is the base of the computing ...

Hataj, M.; Pošta, J.; Hasníková, Hana; Kunecký, Jiří
Ústav teoretické a aplikované mechaniky, 2022