Pokročilé keramické materiály
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- ItemEffect of atmosphere on thermal debinding of DLP-printed ceramics(2026-03-01) Šťastný, Přemysl; Man, Ondřej; Brouczek, Dominik; Schwentenwein, Martin; Trunec, MartinThis study investigates the effect of the gas atmosphere on the size limit for defect-free thermal binder removal in 3D-printed alumina bodies fabricated using digital light processing (DLP). Binder removal from cylindrical specimens with diameters ranging from 5mm to 15mm was carried out in either nitrogen or air atmospheres under different heating schedules. In nitrogen, defect-free debinding was achieved for specimens up to 15mm in diameter. In contrast, defect-free binder removal in air was limited to specimens as small as 5mm. Thermogravimetric analysis and microstructural characterization were employed to elucidate the role of the atmosphere in binder removal and defect formation. Microstructural differences between debinding in air and nitrogen were identified. Based on these results, mechanisms of binder removal in ceramic DLP printed bodies with acrylate-based crosslinked binder systems are proposed, and critical steps for achieving defect-free processing are discussed.
- ItemLuminescent Er3+doped transparent alumina ceramics(Elsevier, 2017-07-01) Drdlíková, Katarina; Klement, Róbert; Drdlík, Daniel; Spusta, Tomáš; Galusek, Dušan; Maca, KarelWe report on successful preparation of Er3+doped transparent alumina (0.1–0.17 at.%) exhibiting visible light photoluminescence using wet shaping method and hot isostatic pressing. The effects of dopantamount, type of doping powder and powder pre-treatment on final microstructure, real in-line transmittance and photoluminescence characteristics were studied.The real in-line transmittance ranged between 28 and 56%, depending on processing parameters. The transparency decreased with increased amount of dopant. The decrease is dependent on the type ofdoping powder and its pre-treatment. The photoluminescence spectra measured in both visible and NIR region showed typical emissionbands due to the presence of Er3+ions. The decay profiles of the 4S3/24I15/2 transition were fitted with a 2-exponential function, with faster component in the range of 360–700 ns and slower component around 1.6-2.4 us. The intensity of emissions and lifetime of the 4S3/2 level decrease significantly with increasingconcentration of Er3+ions.
- ItemMachinability and properties of zirconia ceramics prepared by gelcasting method(TAYLOR & FRANCIS LTD, 2020-08-17) Kaštyl, Jaroslav; Chlup, Zdeněk; Šťastný, Přemysl; Trunec, MartinThe machinability of newly developed zirconia ceramics for computer numerically controlled milling (CNC) was investigated. The zirconia blanks were prepared by the gelcasting method and tested in the green and two pre-sintered states. All blanks exhibited uniform sintering shrinkage in all directions. The blanks were investigated from the viewpoint of surface milling roughness, quality of milled edges and sharp tips, and machinability of thin structures. The best milling results were obtained for the blanks pre-sintered at 900?C/1?h. Mechanical properties of zirconia blanks, such as biaxial flexural strength, microhardness, indentation elastic modulus, and fracture toughness were determined in the green and pre-sintered states (900 and 1100?C/1?h) and the correlation with the milling results was discussed. The biaxial strength tests of sintered discs showed the advantage of optimised surface milling over conventional polishing.
- ItemPreserving Metamagnetism in Self-Assembled FeRh Nanomagnets(AMER CHEMICAL SOC, 2023-02-15) Motyčková, Lucie; Arregi Uribeetxebarria, Jon Ander; Staňo, Michal; Průša, Stanislav; Částková, Klára; Uhlíř, VojtěchPreparing and exploiting phase-change materials in the nanoscale form is an ongoing challenge for advanced material research. A common lasting obstacle is preserving the desired functionality present in the bulk form. Here, we present self-assembly routes of metamagnetic FeRh nanoislands with tunable sizes and shapes. While the phase transition between antiferro-magnetic and ferromagnetic orders is largely suppressed in nanoislands formed on oxide substrates via thermodynamic nucleation, we find that nanomagnet arrays formed through solid-state dewetting keep their metamagnetic character. This behavior is strongly dependent on the resulting crystal faceting of the nanoislands, which is characteristic of each assembly route. Comparing the calculated surface energies for each magnetic phase of the nanoislands reveals that metamagnetism can be suppressed or allowed by specific geometrical configurations of the facets. Furthermore, we find that spatial confinement leads to very pronounced supercooling and the absence of phase separation in the nanoislands. Finally, the supported nanomagnets are chemically etched away from the substrates to inspect the phase transition properties of self-standing nanoparticles. We demonstrate that solid-state dewetting is a feasible and scalable way to obtain supported and free-standing FeRh nanomagnets with preserved metamagnetism.
- ItemStudy of the Synthesis of Multi-Cationic Sm-Co-O, Sm-Ni-O, Al-Co-O, Al-Ni-O, and Al-Co-Ni-O Aerogels and Their Catalytic Activity in the Dry Reforming of Methane(MDPI, 2024-05-01) Cihlář, Jaroslav; Tkachenko, Serhii; Bednaříková, Vendula; Cihlář, Jaroslav; Částková, Klára; Trunec, Martin; Čelko, LadislavDense multi-cationic Sm-Co-O, Sm-Ni-O, Al-Co-O, Al-Ni-O, and Al-Ni-Co-O oxide aerogels were prepared by epoxide-driven sol-gel synthesis. Catalysts for dry reformation of methane, Sm2O3/Co, Sm2O3/Ni, Al2O3/Co, Al2O3/Ni, Al2O3/Co, and Ni were prepared by reduction of aerogels with hydrogen and their catalytic activities and C-deposition during dry reformation of methane were tested. Catalytic tests showed high methane conversion (93-98%) and C-deposition (0.01-4.35 mg C/gcat.h). The highest content of C-deposits after catalytic tests was determined for Al2O3/Co and Al2O3/Ni catalysts, which was related to the formation of Al alloys with Co and Ni. A uniform distribution of Co0 and Ni0 nanoparticles (in the form of a CoNi alloy) was found only for the Al2O3/Co and Ni catalysts, which showed the highest activity as well as low C deposition.