Středoevropský technologický institut VUT
Browse
Recent Submissions
Now showing 1 - 5 of 25
- ItemHigh-Temperature Creep Resistance of FeAlOY ODS Ferritic Alloy(MDPI, 2024-10-01) Dymáček, Petr; Jarý, Milan; Bártková, Denisa; Luptáková, Natália; Gamanov, Štěpán; Bořil, Petr; Georgiev, Vjačeslav; Svoboda, JiříA significant effort in optimizing the chemical composition and powder metallurgical processing led to preparing new-generation ferritic coarse-grained ODS alloys with a high nano-oxide content. The optimization was aimed at high-temperature creep and oxidation resistance at temperatures in the range of 1100-1300 degrees C. An FeAlOY alloy, with the chemical composition Fe-10Al-4Cr-4Y2O3 (wt. %), seems as the most promising one. The consolidation of the alloy is preferably conducted by hot rolling in several steps, followed by static recrystallization for 1 h at 1200 degrees C, which provides a stable coarse-grain microstructure with homogeneous dispersion of nano-oxides. This represents the most cost-effective way of production. Another method of consolidation tested was hot rotary swaging, which also gave promising results. The compression creep testing of the alloy at 1100, 1200, and 1300 degrees C shows excellent creep performance, which is confirmed by the tensile creep tests at 1100 degrees C as well. The potential in such a temperature range is the target for possible applications of the FeAlOY for the pull rods of high-temperature testing machines, gas turbine blades, or furnace fan vanes. The key effort now focuses on expanding the production from laboratory samples to larger industrial pieces.
- ItemGreen synthesis and the stablization of selenium nanoparticles using carboxylmethyl starch(Tanger, 2020-12-28) Vishakha, Vishakha; Abdellatif, Abdelmohsen Moustafa; Jančář, JosefThe growing interest in biodegradable products paves the way for the safest sustainable earth. Starch is an extensively studied, cost-effective, easily accessible, and highly trusted resource to produce biodegradable products in the present and future. However, the exploitation of these starch in several fields requires substantial changes in its chemical functionalities and related properties. Here, we investigated the conditions (pH, temperature, the concentration of starch, concentration of chloroacetate, time, the ratio between starch/sodium hydroxide, etc.) that affect the preparation of carboxymethyl starch (CMS). The chemical structure and degree of substitution of native starch and CMS were confirmed by Fourier transform infrared ( FTIR), X-ray powder diffraction (XRD), Thermogravimetric analysis (TGA), potentiometric titration, Scanning electron microscope (SEM), and Nuclear magnetic resonance spectroscopy (NMR ). CMS's rheological properties show that CMS's intrinsic viscosity increased with increased degrees of substitutions (DS) from CMS (0.05 to 0.45). The CMS with different DS (0.05 to 0.45) was used for the first time to stabilize selenium nanoparticles (Se-NPs), showing spherical shape with a high homogenous size of Se-NPs (approx. 50 nm). The NPs shape and size stability were investigated and confirmed by different techniques like Dynamic light scanning (DLS), SEM, and Transmission electron microscope (TEM)
- ItemSecond-order Simple Multiphase Oscillator Using Z-Copy Controlled-Gain Voltage Differencing Current Conveyor(Kaunas University of Technology, 2014-11-19) Šotner, Roman; Jeřábek, Jan; Petržela, Jiří; Herencsár, Norbert; Prokop, Roman; Vrba, KamilInteresting type of the second-order electronically controllable multiphase oscillator is introduced in this paper. Modified voltage differencing current conveyor, so-called z-copy controlled gain voltage differencing current conveyor (ZC-CG-VDCC), offers interesting features for synthesis of this type of multiphase oscillator. Available controllable parameters of the ZC-CG-VDCC (intrinsic resistance, transconductance and current gain) are fully utilized for independent adjusting of oscillation condition and oscillation frequency. Specific matching condition allows linear control of oscillation frequency that is not so typical in such simple types of oscillators. Available phase shifts are 45, 90, 135 and 180 degree. Simulation results based on CMOS model of active element confirms intentions of the proposal in the bandwidth of several MHz.
- ItemZ-Copy Controlled-Gain Voltage Differencing Current Conveyor: Advanced Possibilities in Direct Electronic Control of First-Order Filter(Kaunas University of Technology, 2014-06-13) Šotner, Roman; Herencsár, Norbert; Jeřábek, Jan; Prokop, Roman; Kartci, Aslihan; Dostál, Tomáš; Vrba, KamilA modified version of voltage differencing current conveyor (VDCC) and its performance in detail is presented in this paper. Modified VDCC, so-called z-copy controlled gain voltage differencing current conveyor (ZC-CG-VDCC), offers interesting features from adjustability point of view. The active element allows independent electronic control of three adjustable parameters: intrinsic resistance of current input terminal, transconductance and current gain of the output stage which is not possible in case of conventional VDCC. The characteristics of proposed CMOS implementation designed using TSMC LO EPI 0.18 um technology process parameters are shown and discussed. Simple application in reconfigurable reconnection-less first-order voltage-mode multifunctional filter is shown and verified by SPICE simulations and experimentally. The filter tuning and change of the transfer function type is allowed by the controllable parameters of the ZC-CG-VDCC.
- ItemInvestigation into the Effect of Molds in Grasses on Their Content of Low Molecular Mass Thiols(MDPI, 2012-10-24) Skládanka, Jiří; Adam, Vojtěch; Zítka, Ondřej; Kryštofová, Olga; Beklová, Miroslava; Kizek, René; Havlíček, Zdeněk; Sláma, Petr; Nawrath, adamThe aim of this study was to investigate the effect of molds on levels of low molecular mass thiols in grasses. For this purpose, the three grass species Lolium perenne, Festulolium pabulare and Festulolium braunii were cultivated and sampled during four months, from June to September. The same species were also grown under controlled conditions. High-performance liquid chromatography with electrochemical detection was used for quantification of cysteine, reduced (GSH) and oxidized (GSSG) glutathione, and phytochelatins (PC2, PC3, PC4 and PC5). Data were statistically processed and analyzed. Thiols were present in all examined grass species. The effect of fungicide treatments applied under field conditions on the content of the evaluated thiols was shown to be insignificant. Species influenced (p < 0.05) PC3 and GSSG content. F. pabulare, an intergeneric hybrid of drought- and fungi-resistant Festuca arundinacea, was comparable in PC3 content with L. perenne and F. braunii under field conditions. Under controlled conditions, however, F. pabulare had higher (p < 0.05) PC3 content than did L. perenne and F. braunii. Under field conditions, differences between the evaluated species were recorded only in GSSG content, but only sampling in June was significant. F. pabulare had higher (p < 0.05) GSSG content in June than did L. perenne and F. braunii.