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  • Author or Editor: E. Večerníková x
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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Földesová
,
P. Lukáč
,
P. Dillinger
,
E. Klosová
,
Z. Málek
,
E. Večerníková
, and
V. Balek

Abstract  

Zeolites from Nižný Hrabovec (Slovak Republic) were, modified with solutions of NaOH. The changes of zeolites in the temperature range 20–1200 °C were studied by thermal analysis (DTA, TG, ETA), X-ray analysis and REM analysis. Thermal analysis showed that the process of dehydration started between temperatures 20 and 600 °C, over this temperature the dealumination and structural changes have taken place. X-ray analysis and REM analysis showed the structural changes of natural zeolites and gradual loss of cristallinity of the chemically modified zeolites.

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Journal of Thermal Analysis and Calorimetry
Authors:
V. Balek
,
N. Todorova
,
C. Trapalis
,
V. Štengl
,
E. Večerníková
,
J. Šubrt
,
Z. Malek
, and
G. Kordas

Summary Titania-based photocatalytic materials were prepared by sol-gel method using Fe3+ and polyethyleneglycol (PEG600) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe3+ containing titania gels. The microstructure development of the Fe2O3/TiO2 gel samples with and without PEG600 admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120°C and the samples preheated for 1 h to 300 and 500°C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600°C.

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Abstract

A new method for the preparation of titania photocatalyst was proposed. Precursors of the photoactive titania were prepared from TiOSO4·nH2O solution by precipitation with ammonia and addition of H2O2 or HNO3, respectively. Methods of TG, DTA, ETA, EGA/MS detection and FTIR were used to characterize the thermal degradation of the titania precursor and to determine the optimal temperature to obtain the photoactive titania. ETA made it possible to characterize the microstructure development of the samples in the heating conditions.

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Abstract  

Thermogravimetry-differential thermal analysis, emanation thermal analysis, mass spectrometry detection, Fourier transform infrared and XRD were used to characterize thermal behaviour of titanium dioxide photocatalyst precursors prepared by precipitation at various conditions from peroxotitanic acid sols. The transmission electron microscopy HRTEM technique was used to characterize the surface microstructure. The sols contained TiO2 anatase particles of approximately 10 nm in diameter. During heating of the air dried samples, their chemical degradation took place giving rise to anatase. On further heating, the crystallization of anatase and formation of rutile phase was observed. To test the photocatalytic activity of the samples, the decomposition of 4-chlorophenol (4-CP) under ultraviolet and visible irradiation was monitored. It was shown that photocatalytic activities of the samples are comparable to the Degussa P25 photocatalyst reference material.

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Journal of Thermal Analysis and Calorimetry
Authors:
A. Kohutova
,
P. Honcova
,
V. Podzemna
,
P. Bezdicka
,
E. Vecernikova
,
M. Louda
, and
J. Seidel

Abstract  

Thermal decomposition and structural characterization of three human kidney stones (KS1–KS3) extracted from patients of Eastern Bohemia have been carried out using X-ray powder diffraction systems (XRD), scanning electron microscope with energy dispersive X-ray micro analyser (SEM-EDX) and differential thermal analysis (DTA). The samples KS1 and KS2 solely consisted of calcium oxalate monohydrate (a.k.a. whewellite, CaC2O4·H2O). The third sample, KS3, was formed from calcium oxalate dihydrate (weddellite, CaC2O4·2H2O), calcium oxalate monohydrate, and hydroxyapatite (HA, Ca10(PO4)6(OH)2). Thermal measurements were carried out in the range between room temperature and 1,230 °C. XRD analysis was utilized to investigate the change of phases at 800 and 1,230 °C.

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