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    MoOx-based high-density nanoarrays on a substrate via smart anodizing as novel 3D electrodes for nano-energy applications
    (Royal Society of Chemistry, 2025-05-27) Mozalev, Alexander; Bendová, Mária; Kalina, Lukáš; Prášek, Jan; Gispert-Guirado, Francesc; Llobet, Eduard
    For the first time, arrays of MoOx-based nanostructures of various sizes and morphologies, vertically aligned on a substrate, have been synthesized self-organized via the PAA-assisted anodization of a Mo layer through a very thin Nb interlayer. Such a smart anodization enabled the nucleation and sustainable growth of fully amorphous MoOx nanostructures within and under the PAA nanopores, which is impossible by direct molybdenum anodizing or other methods. The MoOx-based nanoarrays revealed the potential for applications in semiconductor nanoelectronics where the intensive and localized at the nanoscale electron transport, reversible redox reactions, high population density of nanochannels, and tailored crystallinity are in demand. The disclosed intercalation pseudocapacitance behavior of the rods' cores and the competitive performance metrics make the films promising as nanostructured electrodes for on-chip energy-related applications. The works to improve the electron-transport properties of the shells, explore field-emission and memristive potentials of the nanoarrays, and design relevant device configurations are in progress and will be reported in due course.
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    Chlorine determination in cement paste samples using laser-induced breakdown spectroscopy and non-matching matrix calibration samples
    (Royal Society of Chemistry, 2025-06-05) Kratochvilová, Lucie; Prochazka, David; Opravil, Tomáš; Pořízka, Pavel; Kaiser, Jozef
    This paper deals with determining the chlorine content in cement matrixes using non-matching calibration samples made from microsilica and potassium chloride. We aimed to make easy-to-prepare calibration samples and determine the chlorine content in cement paste samples. To create proper cement paste samples, it is necessary to allow the concrete to mature for 28 days. Also, this methodology enables faster calibration and higher throughput in routine analysis. To suppress the matrix effect, we tested several strategies of signal normalization and then compared the reference (known) and the predicted chlorine content. Best results were obtained when we normalized the intensity of the chlorine line by a parameter proportional to the particle number density which was a priori determined by the intensity of the hydrogen emission line (H alpha) and full width at half-maximum (FWHM). With this parameter, we obtained a high-reliability coefficient for the calibration curve (R2 = 0.99) and the best prediction for total chloride content in cement paste, with a sum of mean squares of the prediction error of 0.22 wt%.
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    CORROSION BEHAVIOUR OF AZ31 ALLOY IN AN ALKALINE ENVIRONMENT OF 0.1 M NACL IN THE PRESENCE OF LIGNITIC HUMIC ACID
    (Tanger, 2024-01-08) Horák, Tomáš; Buchtík, Martin; Wasserbauer, Jaromír; Březina, Matěj; Doskočil, Leoš
    Magnesium alloys are characterized by high corrosion rates. This undesirable phenomenon can be slowed down by corrosion inhibitors. Particularly environmentally friendly molecules are in the spotlight. A possible candidate for a green inhibitor may be humic acid isolated from lignite. In this work, the corrosion behavior of AZ31 was investigated in 0.1 M NaCl with and without humic acid at pH 9. Surface analysis was performed using a scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS) and Fourier--transform infrared (FTIR) spectroscopy. Corrosion behavior was investigated using potentiodynamic polarization (PDP) measurements. The results showed that lignitic humic acid accelerates corrosion in 0.1 M NaCl at pH 9 and this effect was concentration dependent.
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    Filling of Chitosan Film with Wax/Halloysite Microparticles for Absorption of Hydrocarbon Vapors
    (WILEY-V C H VERLAG GMBH, 2024-02-24) Caruso, Maria Rita; D’Agostino, Giulia; Wasserbauer, Jaromír; Šiler, Pavel; Cavallaro, Giuseppe; Milioto, Stefana; Lazzara, Giuseppe
    The effect of the preparation protocol of chitosan (CHI) based films filled with wax microparticles stabilized by halloysite nanotubes (HNTs) in Pickering emulsions (PE) is investigated. The obtained results show that the addition of acetic acid (before or after the preparation of wax/HNT microspheres) affects the properties of the composite films as well as the colloidal stability of PE. The colloidal behavior of CHI/HNT/wax PE by optical microscopy and sedimentation tests are studied. On the other hand, the corresponding composite films (prepared by solvent casting method) are characterized through several techniques, including Scanning Electron Microscopy, UV-vis spectrometer, water permeability, and contact angle measurements. Dynamic Mechanical Analysis allows this to estimate the effect of wax microparticles on the tensile performances of CHI-based films. As a general consideration, the filling of the CHI matrix with wax/HNT improves the physicochemical properties of the films. Finally, the efficacy of the films as adsorbents of n-dodecane vapors is explored. Due to the presence of hydrophobic domains (wax embedded in CHI), the composite films possess higher adsorption efficiencies compared to pristine CHI. Accordingly, it can be stated that the combination of CHI with wax/HNT microparticles is promising to obtain biocompatible composite films useful for remediation purposes. Chitosan films filled with hydrophobic microparticles are successfully prepared by solvent casting of wax/halloysite Pickering emulsions. The addition of wax microparticles within chitosan generated the surface hydrophobization of the film. Due to hydrophobic attractions, the presence of microwax improved the absorption capacity toward n-dodecane vapors. The filled film is promising as a sustainable material for capturing organic pollutants, such as hydrocarbons. image
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    CONDUCTOMETRY ANALYSIS - BENEFICIAL METHOD FOR DETERMINING THE CHEMICAL COMPOSITION OF ALKALINE SILICATE SOLUTIONS
    (Institute of Metals and Technology, 2024-04-12) Kalina, Lukáš; Bílek, Vlastimil; Flídrová, Michaela; Markusík, David; Topolář, Libor; Fládr, Josef
    The study deals with the methodology for determining the chemical composition of alkaline silicate solutions. Nowadays, the most widely used method in industry is titration, using the color change of an acid -base indicator. This technique is very accurate for the determination of the total alkalinity (i.e., Na2O, K2O, or Li2O). However, a problem arises in the determination of the SiO2 content, since the color change of the methyl red indicator is very slow and therefore the equivalence point is unclear. The main aim of this work is to present the benefits of conductometric titration, where the equivalence point is indicated by a sudden change in the conductivity. The applicability of the method was verified with other analytical techniques, such as ICP-OES and gravimetric analyses. Their results confirmed the values of the obtained silicate module (the molar ratio of SiO2 and alkaline oxide) in the cases of sodium, potassium and lithium water glasses. Based on the obtained results, one can say that conductometry is a very promising method providing an accurate, fast and instrumentally undemanding chemical characterization of alkaline silicate solutions, usable even in a manufacturing process.