2025-05-03
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Optical spectra of thin intrinsic and Al doped nanocrystalline zno thin layers deposited by pulsed laser deposition on fused silica glass substrates
Remeš, Zdeněk ; Neykova, Neda ; Jain, N. ; Sharma, K.R. ; Holovský, Jakub ; Ukraintsev, E. ; Míčová, J. ; Hsu, S.S.
Zinc oxide (ZnO) is a low-cost and environmentally friendly material with unique optical properties and a variety of nano and microstructures imposing challenges for energy conversion, scintillators, photocatalytic wastewater treatment, electrochemical energy storage, or sensing applications. In this work, the nominally undoped and Al-doped nanocrystalline ZnO thin layers were pulsed laser deposited (PLD) on fused silica glass. The samples were characterized by photothermal deflection (PDS) and photoluminescence (PLS) spectroscopy. Excitons were observed at low temperature in both samples at about 3.4 eV. The intrinsic samples show the red PL in near infrared region at about 1.9 eV related to zinc vacancies. The results show that optical properties can be evaluated from optical spectra of very thin nanocrystalline ZnO layers with the thickness below 100 nm.
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2025-05-03
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Wet chemistry treatment and surface modification of recycled glass particles for sustainable construction applications
Babčenko, Oleg ; Beranová, Klára ; Remeš, Zdeněk ; Kolářová, Kateřina ; Lörinc, Jakub ; Volf, Jakub ; Prošek, Z. ; Tesárek, P.
The soda-lime glass is recognized as one of the best recyclable materials. However, surface contamination of glass waste or bulk impurities in the glass matrix can significantly alter glass properties limiting its direct reuse in the glass industry. As an alternative utilization strategy, the incorporation of waste glass as a partial replacement for sand or binder in concrete-based materials for sustainable construction applications has shown promise. Nevertheless, impurities in glass that may affect the alkalinity of concrete or calcium-silicate-hydrate formation must be carefully considered. For example, when the glass waste is in the form of shards or small fragments (particles), the potential diffusion of metal ions into the environment (e.g., through reaction with rainwater) becomes an important issue. In this work, we perform wet chemistry treatment on the recycled glass particles obtained from the commercial source. The resulting changes in glass particle properties were analyzed using microscopic and spectroscopic techniques. In particular, changes in the concentrations of Mg, Al, Ca and Na near the particle surfaces were detected, indicating potential to elements release to the environment via leaching. The observed results can be helpful in the explanation of processes at interfacial transition zones in waste glass containing concrete-based materials.
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2025-05-03
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Metallic and semiconductor nanoparticles integrated into thin layers of hydrogenated amorphous silicon or silicon carbide
Stuchlík, Jiří ; Kupčík, Jaroslav ; Čermák, Jan ; Stuchlíková, The-Ha ; Remeš, Zdeněk
The combination of PECVD - plasma enhanced chemical vapor deposition and VE - vacuum evaporation at one vacuum chamber is in situ method how to integrate semiconductor (Ge) and metallic (Sn) nanoparticles into amorphous hydrogenated thin films and their structures on the base of a-Si:H or a-SiC:H. In this work we focus our effort to deposit a-SiC:H thin films from monomethylsilane (MMS = SiH3-CH3) diluted by hydrogen in the ratio 2/100 sccm. The Ge evaporates at vacuum higher than 2E-5 Pa. The TEM - transmission electron microscopy and AFM - atomic force microscopy are used for microscopical characterization of thin films while PDS - photothermal deflection spectroscopy and PL – photoluminescence spectroscopy are used for their spectroscopical characterization.
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2025-05-03
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Nanocomposites of ZnO-decorated HPHT Nanodiamond as a perspective green photocatalysts
Mičová, J. ; Košutová, T. ; Jerigová, M. ; Remeš, Zdeněk
Electrical and optical properties of zinc oxide, in particular the relatively wide direct band gap of ~3.3 eV predetermines ZnO as a photocatalytic material at room temperature. ZnO itself is non-toxic and the hydrothermal growth method we use to prepare its nanostructures is environmentally friendly. These facts contribute to the attractiveness of this material. Recently, we have focused on studying the influence of doping or of plasma surface treatment on the photocatalytic efficiency of ZnO. However, the main disadvantages are the high recombination rate of charge carriers and the poor use of visible light. The solution is the use of ZnO as part of nanocomposites. In the past, ZnO-detonation nanodiamons (DND) composites were studied. The disadvantage of DND is the formation of clusters of different sizes, therefore we focused our attention on the use of HPHT nanodiamonds (NDs). We modified the surface of commercial HPHT NDs by oxidation in order to increase the concentration of hydroxyl-, carbonyl- and carboxyl- functional groups. The resulting ZnO-HPHT NDs composites were synthesized using a dehydration-condensation process between oxygen-containing functional groups on the NDs surface and hydroxyl groups on the ZnO surface. The prepared nanocomposites were characterized by SEM, AFM, FTIR and PL and tested by photocatalytic dye degradation.
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2025-05-03
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VIS, UV and DUV wavelength extension of Yb:YAG diode-pumped thin-disk laser
Šatra, Šimon ; Novák, Ondřej ; Turčičová, Hana ; Mužík, Jiří ; Smrž, Martin ; Mocek, Tomáš
Application possibilities of picosecond diode-pumped Yb:YAG thin-disk laser have been expanded by installation of harmonics generation system. Fundamental, second, third, fourth, and fifth harmonic frequencies are now available for users at output powers of 70 W, 40 W, 20 W, 10 W, and 2 W, respectively. Nonlinear crystals used for the conversions are LBO (SHG, THG), BBO (FHG, FiHG), and CLBO (FHG, FiHG). The users profit from all the harmonic frequencies. Recent results on harmonics and its applications will be presented.
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2025-02-22
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Some aspects of elasic and plastic deformation of Cu–Ag metastable metal-matrix composites
Lejček, Pavel ; Strakosova, Angelina ; Průša, F. ; Dvorský, Drahomír ; Koller, Martin ; Seiner, Hanuš
Metal-matrix composites (MMCs) are usually characterized by soft matrix and hard reinforcement. In contrast, we focused in this work on the production and properties of metastable MMCs formed by pure Ag matrix and pure Cu particulates. To conserve the metastable character of these MMCs, they were produced by spark plasma sintering of the Cu@Ag core-shell powders with the volume ratios Cu:Ag being 55:45 and 82:18. These m-MMCs exhibit specific mechanical properties. Some of them, Young modulus and the shape of the curves of plastic deformation, are discussed in this work.
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2025-02-01
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2025-02-01
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2025-01-19
00:08 |
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2025-01-19
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