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Sol-gel synthesis of a LAS glass ceramics and influence of additives on a phase transformation and crystallization.
Kalinová, Helena ; Opravil, Tomáš (referee) ; Ptáček, Petr (advisor)
Course of synthesis of Li2O – Al2O3 – SiO2 (LAS) ceramic via sol – gel process made precursor was investigated. Powder precursor containing LAS components in molar ratio 1:1:4 were prepared by polycondensation technique in aqueous medium using lithium chloride (LiCl), hydrated aluminium nitrate (Al(NO3)39H2O) and silica sol (tosil), respectively. Heated sol was transformed into gel. The resulting gel was dried at temperature 105 °C and xerogel was next calcinated at 750°C. Further was evaluated influence of sintering additives (MgO, ZnO, Ca5(PO4)3OH) on the length of sintering interval. All of them have been stabilized spodumene in the solid solution. The properties of ceramic body prepared by sintering of precursor and grinded Li2CO2, Al2O3 a SiO2 powders were compared. Simultaneous thermogravimety and differential thermal analysis (TG-DTA), X-ray diffractions and heating microscopy were used to study sintering process of LAS ceramic.
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Photoelectrochemical Oxidation of Carboxylic Acids on the Sol-Gel Thin TiO2 Layer Electrode
Morozová, Magdalena ; Klusoň, Petr ; Krýsa, Josef ; Šolcová, Olga
Heterogeneous photocatalysis is based on the reaction between the light excitated semiconductor and oxidizable compound adsorbed on the catalytic surface. This work reports the photoelectrocatalytic oxidation characteristics of carboxylic acids on the TiO2 sol-gel thin-film electrode by using electrochemical techniques. The influence of the thickness of the films on photoactivity and the various concentrations of oxalic, formic and acetic acid in the supporting electrolyte were investigated. The effect of the used mono- and dicarboxylic acids on the electrode behaviour for possible application as sensors has been also studied. The surface characteristics of TiO2 films were determined by XRD, SEM and AFM analyses and the photoexcitation properties of nanoparticulate layer electrode were determined by cyclic and linear voltammetry, amperometry and open circuit potential (OCP).
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Fyzikální metody ke stanovení struktury povrchové vrstvy funkcionalizovaných mesoporézních silik
Zub, Yu.L. ; Šolcová, Olga
The given report is an attempt to summary the results of composition and structure studying of functionalized mesoporous silicas surface. These results have been received with the help of a number of physical methods (electronic microscopy, the thermal analysis, IR and Raman spectroscopy, solid-state (CP/MAS) NMR spectroscopy (on such nucleus as 1H, 13C, 29Si, 31P), MALDI, metal microprobe method) and also quantum chemistry.
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Příprava TiO2 pro fotokatalytické aplikace
Matějová, Lenka ; Cajthaml, Tomáš ; Matěj, Z. ; Strýhal, Z. ; Benada, Oldřich ; Šolcová, Olga
Powder nanoporous TiO2 with narrow monodisperse pore-size distribution in the range from 2 to 30 nm were prepared by self-assemble micelle system in nonpolar and polar solvents at laboratory temperature and pressure. Nonionic surfactants Triton X-102, 100, 114, 45, 15 were used for preparation of micelle systems. Various approaches were applied for removing of residual organic matter from prepared titania gels: a) calcination, b) improved extraction by supercritical (CO2) and subcritical fluids (H2O, CH3OH) and c) the combination of both forenamed approaches.
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