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    Tobermorite synthesis under hydrothermal conditions
    (Elsevier, 2016-08-03) Dlabajová, Lucie; Másilko, Jiří; Solný, Tomáš; Štěpánková, Eva
    The influence of different hydrothermal conditions and starting materials on a preparation of tobermorite was examined. Tobermorite is a mineral, which, thanks to its composition and properties, is an important phase in aerated concrete and it can be also used as an ion exchanger. Tobermorite crystallizes together with other calcium silicate hydrates from the system CaO–SiO2–H2O during hydrothermal reactions. Paper deals with the key role of starting materials pre-treatment and its influence on the hydrothermal synthesis process. The other important parameters for a synthesis of pure tobermorite as conditions of the reaction, especially the temperature of hydrothermal reaction and curing time were also studied. Phase composition of prepared samples was characterized by XRD and was confirmed by TG-DTA. For overall product characterization, the SEM was used.
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    The influence of starting materials´ solubility on tobermorite structure formation under the hydrothermal conditions
    (IOP Publishing, 2018-07-12) Dlabajová, Lucie; Bartoníčková, Eva; Opravil, Tomáš; Tkacz, Jakub; Ptáček, Petr
    Overall, the tobermorite mineral crystallises under the hydrothermal conditions from the CaO-SiO2-H2O system. The system of calcium hydrosilicates species is extremely complex and many factors play an important role. The solubility of starting materials belongs to one of the most important factors. Dissolution rates of SiO2 source are significantly affected by their particle size distribution. Also the starting cation´s concentration in the aqueous solution affects the yield of the hydrothermal reaction. The main aim of this contribution is to study the influence of water-to-solid ratio on tobermorite crystallization. The effect of particle size of various sources of SiO2 was also studied. The cost effective Ca and Si sources was primarily favoured. The C/S ratio of the experiments was set to 0.83. All syntheses were performed at 180 °C in laboratory steel autoclaves. The prepared powdered samples were characterized in order to determine the phase composition by using of X-Ray diffractometry. The thermal behaviour of prepared samples was studied by TG-DTA analyser. Morphology and particle size of synthetized powdered products was studied by scanning electron microscopy.
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    Determination of Critical Parameters of Drug Substance Influencing Dissolution: A Case Study
    (Hindawi Publishing Corporation, 2014-09-15) Bojňanská, Erika; Kalina, Michal; Pařízek, Ladislav; Bartoníčková, Eva; Opravil, Tomáš; Veselý, Michal; Pekař, Miloslav; Jampílek, Josef
    The purpose of this study was to specify critical parameters (physicochemical characteristics) of drug substance that can affect dissolution profile/dissolution rate of the final drug product manufactured by validated procedure from various batches of the same drug substance received from different suppliers.The target was to design a sufficiently robust drug substance specification allowing to obtain a satisfactory drug product. For this reason, five batches of the drug substance and five samples of the final peroral drug products were analysed with the use of solid state analysis methods on the bulk level. Besides polymorphism, particle size distribution, surface area, zeta potential, and water content were identified as important parameters, and the zeta potential and the particle size distribution of the drug substance seem to be critical quality attributes affecting the dissolution rate of the drug substance released from the final peroral drug formulation.
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    Potential use of blast furnace slag for filtration membranes preparation: A pilot study
    (IOP Publishing, 2018-07-12) Bílek, Vlastimil; Bulejko, Pavel; Kejík, Pavel; Hajzler, Jan; Másilko, Jiří; Bednárek, Jan; Tkacz, Jakub; Kalina, Lukáš
    This paper investigates the possibilities of the use of sodium hydroxide activated blast furnace slag for preparation of filtration barriers. The motivation for this research is searching for cheaper and more eco-friendly alternative to sintering, which is commonly used for filtration membranes preparation. Such an alternative could be alkaline activation, which is able to bind slag particles together. Low amount of activator, low water to slag (w/s) ratio together with pressure compaction was used to obtain microstructure with preserved continuous porosity. To confirm this presumption scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses were carried out.
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    Possibilities of elimination of ammonia slip from technological water in power plants
    (IOP Publishing, 2018-07-12) Hajzler, Jan; Opravil, Tomáš; Pořízka, Jaromír; Ptáček, Petr
    The purpose of this study is to find new possibilities of elimination or separation of ammonium compounds from technological water produced by powerplants and incinerators, in which the secondary flue gas denitrification methods have been implemented (SCR, SNCR). This paper seeks for a new method of ammonium slip elimination from technological water due to the absence of industrially applicable method and thus fixation of ammonium ions in composite cement eventually in binder containing fly ash. The experiments confirmed the validity of the complex compound utility in given issue. The new method consists in adding a soluble cobalt compound to get an insoluble cobalt complex, the processing conditions were optimized during laboratory testing.