ÚMVI-odbor keramiky a polymerů
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- ItemSintering activation energies of anisotropic layered and particle alumina/zirconia-based composites and their mechanical response(Elsevier, 2024-08-27) Drdlík, Daniel; Sokolov, Ilya; Hadraba, Hynek; Chlup, Zdeněk; Drdlíková, Katarina; Maca, KarelInformation on the sintering activation energy is currently focused on evaluation of single-phase ceramic systems. This work shows the results of high-temperature dilatometry measurements of layered and particle composites based on alumina and zirconia. Layered composites with different layer thickness ratios and particle composites with variable composition in the entire concentration range were prepared by electrophoretic deposition allowing manufacturing composites with precious design and strongly bonded interfaces. The phenomena observed during the high-temperature dilatometry measurements are discussed, and the data were used to calculate the sintering activation energies of composites using the modified Master Sintering Curve concept. By covering a wide range of composite designs, it was possible to determine differences in activation energies and to show their dependence on the direction in the case of laminate composites given by the directionally dependent sintering behaviour. Sintering activation energies of layered composites were always higher than for monoliths due to constrained sintering showing maximum sintering activation energies at lower volumes of zirconia in the layers for longitudinal and transversal orientation of the samples. A similar trend was identified in particle composites due to slowed down alumina densification by the pinning effect. Additionally, mechanical properties represented by Vickers hardness and indentation elastic modulus were related to the microstructure developed during sintering. The effects of interconnectivity of phases present in the composites together with other parameters of the microstructure were described.
- ItemPorous silica-doped calcium phosphate scaffolds prepared via in-situ foaming method(ELSEVIER SCI LTD, 2024-11-01) Šiška Virágová, Eliška; Novotná, Lenka; Chlup, Zdeněk; Šťastný, Přemysl; Šárfy, Pavlína; Cihlář, Jaroslav; Kučírek, Martin; Benák, Leoš; Streit, Libor; Kocanda, Jan; Sklenský, Jan; Filipovič, Milan; Repko, Martin; Hampl, Aleš; Koutná, Irena; Částková, KláraThe effect of silica (SiO2) addition (0 wt%-20 wt%) on the microstructural and mechanical properties, as well as the in vitro response of calcium phosphate scaffolds for potential application in bone tissue engineering (BTE) was investigated in this research. Scaffolds characterized by high porosity (77%-88 %) and interconnected spherical pores with a broad range of pore sizes (5-600 mu m) were fabricated using in-situ foaming method. Incorporated silica affected the phase transformation of hydroxyapatite (HA) to beta-tricalcium phosphate (beta-TCP) and led to the development of new crystalline silica-rich phases like silicocarnotite and wollastonite. The reinforcement of silica became apparent during the tests of mechanical properties. Scaffolds with 5 wt% of SiO2 exhibited compressive strength (1.13 MPa) higher than pure HA scaffolds (0.93 MPa). Bone bonding potential of the materials was tested in simulated body fluid (SBF), demonstrating this potential in silica-doped samples. Additionally, degradation experiments showed gradual material degradation, making it suitable for BTE applications. Furthermore, cell culture studies using human mesenchymal stromal cells (MSC) confirmed the scaffold's non- toxicity and provided insights into how the silica content influences cell viability, morphology, and osteogenic potential. The findings of this study offer valuable insights into the design and development of advanced scaffolds with tailored properties for effective BTE applications.
- 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.
- ItemDilatometric and microstructural study of particle and functionally graded composites based on hydroxyapatite and crystalline bioglass(2023-10-23) Drdlík, Daniel; Drdlíková, Katarina; Maca, KarelHydroxyapatite (HA) and bioglass (BG) ceramics have become of prime importance in bone tissue engineering. Besides the appropriate composition, the microstructure of bone replacement plays a crucial role. In the present work, particle composites and functionally graded material (FGM) based on HA and BG prepared by electrophoretic deposition were thoroughly characterised in terms of the preparation method, sintering process, phase composition and microstructure. The sintering was monitored by high-temperature dilatometry in two directions, the sintering rates were calculated, and the overall sintering process was discussed. The SEM showed the continuous change in the microstructure of FGM with gradual interconnected porosity favourable for bio-applications. The fundamental fractographic analysis proved the crack development in FGM related to the sintering process, and the recommendations for the reduction of the crack development were given. The phase transformations during thermal treatment were analysed using X-ray diffraction analysis and deeply discussed.
- ItemMicrostructure and Phase Composition Of Steatite Ceramics Sintered by Traditional and Spark Plasma Sintering(International Institute for the Science of Sintering, Beograd, 2018-03-01) Terzić, Anja; Obradović, Nina; Pouchlý, Václav; Stojanović, Jovica; Maca, Karel; Pavlović, Vladimir B.The influence of the sintering method on the mineral phase transformations and development of the crystalline microstructure of steatite ceramics was investigated. The steatite samples were fabricated from talc and bentonite as low-cost raw materials. Feldspar and barium carbonate, as fluxing agents, were altered in the steatite composition. Dilatometric analysis was applied in the monitoring of the dimensional changes and thereby densification of steatite during the traditional sintering (TS) procedure up to 1200 °C. Spark plasma sintering (SPS) method was used under the following sintering conditions: 100 °C/min heating rate, uniaxial pressure of 50 MPa; sintering temperature 800 °C/1 min or 1000 °C/2 min. Crystallinity changes and mineral phase transition during sintering were observed by X-ray diffraction technique. Microstructural visualization of the samples and the spatial arrangements of individual chemical elements were achieved via scanning electron microscopy equipped with the EDS mapping. It was found that SPS sintering facilitated all microstructural changes during high temperature treatment and shifted them to lower temperatures. SPS treatment conducted at 1000 °C resulted in maximum densification of the steatite powder compacts and the formation stabilized protoenstatite structure