Papers by Naděžda Pizúrová
Theoretical and Applied Fracture Mechanics, Feb 1, 2019
Mechanical properties of prospective Fe-Al-based alloys were investigated using miniature specime... more Mechanical properties of prospective Fe-Al-based alloys were investigated using miniature specimens. This enables testing of material from experimental heats that did not allow preparation of standard specimens. Small punch test and mini-tensile test were applied for estimation of the mechanical properties of Fe-22 Al and Fe-22Al-7Ti (at. %) at high temperatures. It is shown that the force applied in the small punch test can be successfully converted into the equivalent applied stress using the empirical formula suggested by the new European standard for small punch testing. The minimum deflection rate can be converted into the minimum creep strain rate as well. The improvement of the latter conversion based on the Monkman-Grant relationship is proposed. The small punch testing enables evaluation of rupture properties including the creep rupture strength. This can effectively complement previous investigations of Fe-Al-Ti alloys performed predominantly in uniaxial compression. It is shown that a significant increase in creep resistance is achieved by addition of titanium and a two-phase microstructure analogical to that in -strengthened nickel-based superalloys is observed.
Journal of Photochemistry and Photobiology A-chemistry, Sep 1, 2023
Kombinaci teoretických metod a experimentů se snažime najit nove superslitiny na bazi Fe-Al.
We synthesized iron nanoparticles, mainly of alpha-Fe type, in microwave plasma. The paper delas ... more We synthesized iron nanoparticles, mainly of alpha-Fe type, in microwave plasma. The paper delas with deposition process and analysis of the deposit.
Bulletin of the American Physical Society, Oct 5, 2010
in microwave plasma. Due to a small size of the nanoparticles causes unique properties of the mat... more in microwave plasma. Due to a small size of the nanoparticles causes unique properties of the material, including magnetic properties. We used two types of microwave discharges-atmospheric plasma torch and low pressure surface wave plasma. Using XRD (X-ray diffraction), HR-TEM (high resolution transmission electron microscope), Raman spectroscopy and Mossbauer spectroscopy we identified the elemental and phase composition of the nanoparticles. The magnetic properties of the prepared nanoparticles were measured, too. During the plasma synthesis process we carried out a plasma diagnostics using optical emission spectroscopy. Finally, we correlated the external and internal parameters of the plasma synthesis process with the properties and composition of the nanoparticulate product.
Iron-based nanoparticles in powder form were synthesised by plasmochemical method. Surface-wave d... more Iron-based nanoparticles in powder form were synthesised by plasmochemical method. Surface-wave discharge was sustained in low-pressure argon atmosphere by 2.45 GHz microwaves. Properties of the discharge were analysed by optical emission spectroscopy and digital photography. The nanopowder captured on filters was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The powder consisted of nanoparticles containing mainly ferrite alpha-Fe and magnetite Fe3O4. Size of synthesised nanoparticles was between 9 and 14 nm.
ZnO rods were grown via aerosol-assisted chemical vapor deposition on Si-based micromachined plat... more ZnO rods were grown via aerosol-assisted chemical vapor deposition on Si-based micromachined platforms. The photo- and thermo-activated sensor characteristics were evaluated towards carbon monoxide, ethanol and toluene. Results proved photo-activated response at room temperature with improved response and selectivity compared to the thermo-activated response at 250 °C. This property becomes significantly advantageous as it allows for the sensor to operate without heating.
Analyst, 2020
Photon-upconversion barcodes are compatible with simultaneous fluorescence detection.
Springer eBooks, Aug 2, 2007
Springer eBooks, 2004
Phase composition of the Mg-Fe powder prepared by spark erosion is investigated using Mössbauer s... more Phase composition of the Mg-Fe powder prepared by spark erosion is investigated using Mössbauer spectroscopy and X-ray diffraction. The results are compared with the phase analysis of MgO single crystal wafer implanted by 57 Fe.
Materials Science Forum, Mar 1, 2005
We present magnetic and morphological characterization of iron- and iron-carbide- based nanopowde... more We present magnetic and morphological characterization of iron- and iron-carbide- based nanopowder obtained by the laser synthesis from sensitized gas phase mixture containing acetylene and iron pentacarbonyl vapors. The analysis was performed on the as-prepared material and the annealed material. The results of TEM, XRD, Mössbauer and magnetic measurements are reported. Phase transformations taking place during annealing of the nanopowder when core-shell nanoparticles appear are discussed.
Journal of Visualized Experiments, Sep 14, 2017
Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized pr... more Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid-or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/ or high processing temperatures exceeding 900 °C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 °C with zinc chloride (ZnCl 2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-theart microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide. Video Link The video component of this article can be found at https://www.jove.com/video/56127/ 17. The use of localized heating, for instance, has been shown feasible previously for the non-catalyzed aerosol-assisted CVD of tungsten oxide rods 18. The growth of columnar ZnO structures with controlled morphology, that allow for their easy integration into different substrate and microfabrication processes, is of common interest in areas such as chemical sensing, photocatalysis, photonics and energy harvesting, amongst others.
Passivation of iron nanoparticles synthesized in microwave plasma was achieved by hydrocarbons ad... more Passivation of iron nanoparticles synthesized in microwave plasma was achieved by hydrocarbons addition or slow oxidation.
Journal of Alloys and Compounds, Feb 1, 2021
Nanoparticle materials have become a promising candidate for a new kind of storage media based on... more Nanoparticle materials have become a promising candidate for a new kind of storage media based on thermally induced memory effects due to the possibility to tailor their magnetic properties and behaviour. In this study, we have investigated whether the magnetic memory effects could appear at high, industry accessible temperatures including the possibility of thermal data inscription. Investigated iron oxide nanoparticles were synthesized by poliol method, which has been modified in order to allow control of particle agglomeration and consequently magnetic properties. Structure, morphology and the degree of nanoparticle agglomeration were studied by X-Ray diffraction, Transmission Electron Microscopy and Dynamic Light Scattering techniques, while magnetic properties as well as memory effects were measured on a commercial SQUID-based magnetometer. Results of the study confirmed that in super spin glass magnetite nanoparticles, magnetic memory effects can be observed up to 200 K which represents much higher temperatures in comparison to those achieved in spin glasses and other glassy materials. Procedures of writing and reading (inscribing and retrieving) of digital information in such a material were demonstrated and discussed in details.
Intermetallics, Jun 1, 2012
ABSTRACT DSC and thermomagnetic measurements of Fe 75 Ni 2 Si 8 B 13 C 2 amorphous alloy investig... more ABSTRACT DSC and thermomagnetic measurements of Fe 75 Ni 2 Si 8 B 13 C 2 amorphous alloy investigated in 298e973 K temperature range show that alloy remains amorphous up to around 773 K, when it undergoes multi-step structural transformation. As thermomagnetic measurements provided more complete information , the alloy ribbon was successively annealed at temperatures chosen on the basis of these measurements and its microstructure was investigated after each annealing cycle using X-ray diffraction and SEM. XRD and microstructural analysis of the as-prepared and the annealed sample showed there is no difference between shiny and matte side of the ribbon. Two stable, a-Fe(Si) and Fe 2 B, and one metastable, Fe 3 B, crystalline phases were identified after annealing. Microstructural analysis showed that Fe 3 B probably acts as an intermediate in the formation of Fe 2 B, which formed later than the other two phases. Si and B in the alloy show a tendency to separate into different phases, exhibiting complementary fluctuations in concentration in chemical depth profile. Analysis of microstructure, combined with chemical composition, showed that after the final annealing at 973 K, alloy ribbon is composed of interdispersed nanocrystals of a-Fe(Si) and Fe 2 B less than 90 nm in size, with no observable larger domains of either phase.
NANOCOM ..., 2022
Cerium oxide nanoparticles (nanoceria) are currently one of the most investigated nanomaterials b... more 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 Ce 3+ and Ce 4+ valency state ratio. In the nanoparticle form, cerium oxides contain a mixture of Ce 3+ and Ce 4+ 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 Ce 4+ and Ce 3+ 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 ultrasmall 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 Ce 3+ content.
Physics Procedia, 2013
Microwave torch discharge ignited in Ar at 1 bar was used for the synthesis of-Fe 2 O 3 nanoparti... more Microwave torch discharge ignited in Ar at 1 bar was used for the synthesis of-Fe 2 O 3 nanoparticles. A doublewalled nozzle electrode enabled to introduce gases separately: Ar flowed in the central channel, whereas the mixture of H 2 /O 2 /Fe(CO) 5 was added into the torch discharge through an outer channel. The composition and properties of the synthesized nanopowders were studied by TEM, XRD, Raman and Mössbauer spectroscopies. Basic magnetic measurements at low/high temperatures were performed. The-Fe 2 O 3 phase with the mean crystallite size of 24 nm was identified by XRD in the representative sample. The measured Raman spectrum matched well those reported for-Fe 2 O 3 powders in the literature. In the transmission Mössbauer spectrum measured at 5 K the two sextets characteristic for-Fe 2 O 3 were clearly identified. No change in specific magnetic moment typical of Fe 3 O 4 at its Verwey temperature was observed on the zero field curve, which smoothly increased with temperature. Neither Fe 3 O 4 nor-Fe 2 O 3 were present in the sample. We also report on the high-temperature magnetic properties of the representative sample and describe its structural changes and phase transformations up to 1073 K.
Journal of Magnetism and Magnetic Materials, Dec 1, 2018
The influence of Ti substituting partially Fe in Fe-22 at.%Al alloy on the structure and magnetic... more The influence of Ti substituting partially Fe in Fe-22 at.%Al alloy on the structure and magnetic properties is investigated experimentally by electron microscopy, X-ray diffraction, Mössbauer spectrometry, and by magnetic measurements at room and low temperatures. The samples in a form of discs prepared by cutting the arc-melted button-type ingots have yielded a coarse-grained structure in the Fe-22 at.%Al sample and fine Fe-Al-Ti cuboids embedded in Fe-Al(Ti) matrix in the Fe-22 at.%Al-7 at.%Ti alloy. The mean cuboids' size was 45 nm and the mean composition was determined to be close to Fe 2 TiAl. The as-prepared Fe-Al-Ti samples exhibited substantially reduced saturation magnetization and markedly higher remanent magnetization and coercivity as compared to the as-prepared Fe-Al sample. The thermal treatment of the Fe-Al sample at 1073 K/168 h has changed its magnetic behaviour only slightly, whereas the treatment of the Fe-Al-Ti sample at 1273 K/168 h resulted in remarkable softening of its magnetic properties.
Journal of Visualized Experiments, Sep 14, 2017
Optical Materials, Jun 1, 2019
Cerium oxide (CeO 2) nanoparticles present an interesting material for various applications in bi... more Cerium oxide (CeO 2) nanoparticles present an interesting material for various applications in biotechnology and medicine. The mechanism of CeO 2 nanoparticles activity is supposed to be related to the presence both Ce 3+ and Ce 4+ ions on the surface of the nanocrystal. Due to the Ce 3+ ions, the charge deficiency of a crystal is compensated by oxygen vacancies in the lattice. The present work is devoted to study the cerium oxide defects by optical and luminescence spectroscopy methods. The CeO 2 nanoparticles was produced by the method of pulsed electron evaporation of ceramic oxide targets with condensation of the vapors in a vacuum. The strong nonequilibrium conditions of this method could lead to higher oxygen non-stoichiometry of cerium oxide. The results of work show the cerium nanocrystal manifests an emission provided by intracenter transitions in the Ce 3+ ions, F 0-centers and Ce 4+-O 2complexes with charge transfer. The band gap E g of the CeO 2 nanoparticles for direct and indirect transitions was estimated. The cerium oxide was found to demonstrate catalase-mimic activity, as well as differential cytotoxicity in relation to tumor and healthy cell cultures.
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Papers by Naděžda Pizúrová