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1
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X-ray powder diffraction study of chromium-vanadium oxide compounds prepared by “soft chemistry” methods

100%
Pozdnyakova O., Megyeri J., Kuzmann E., Szirtes L.
Open Chemistry
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2006
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vol. 4
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issue 4
760-772
EN
A novel aqueous method was used to synthesise mixed chromium-vanadium oxide hydrates with various chromium content, via the reaction of peroxo-polyacids of chromium and vanadium. The resulting materials are gelatinous. The dehydration of the gels result in a brown coloured amorphous powder. Depending on the chromium content, the compounds have a different characteristic crystallisation temperature upon the further heating. The crystalline compounds, except for the low chromium ones, go on a phase transition and decompose with increasing temperature. By refining the XRPD measurement data of the compounds, the type and parameters of the unit cells were determined. The experimental data were in concordance with the calculated values, using the PWC code. The lattice parameters and the crystalline structure were changed with the variation of chromium content.
2
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Synthesis, characterization and bioevaluation of partially stabilized cements for medical applications

88%
Voicu G., Bădănoiu A., Andronescu E., Chifiruc C.
Open Chemistry
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2013
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vol. 11
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issue 10
1657-1667
EN
Materials for dental applications, i.e., white mineral trioxide aggregate (WMTA) and partial stabilized cements (PSC) were obtained using the sol-gel method. The presence of ZnO or/and CaF2 additions in the starting mixture induced changes in the composition, morphology and grindability of PSCs as compared with WMTA. The presence of foreign elements (Zn or F) in the crystalline lattice of mineralogical phases, increased their grindability. Thermal analysis (TG&DTA) was used to assess the kinetics of hydration process in binding systems based on WMTA/PSCs. The presence of foreign elements in PSCs systems increases the reactivity vs. water of these materials and consequently, the compressive strength developed after 28 days of hardening at 37°C are higher as compared with WMTA. The in vitro bioevaluation results (trypan blue staining, eukaryotic cells cycle assay by flowcytometry) accounted for a high biocompatibilty of the obtained materials demonstrating their potential use for biomedical applications. [...]
3
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Influence of ThO2 on the photocatalytic activity of TiO2

88%
Kralchevska R., Milanova M., Kovacheva P., Kolev J., Avdeev G., Todorovsky D.
Open Chemistry
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2011
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vol. 9
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issue 6
1027-1038
EN
Microcomposites consisting of TiO2 (or Ce-doped TiO2) and ThO2 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of ThO2. X-ray diffraction study reveals the effects of ThO2 (compared to the ThO2-free TiO2, obtained by the same method) on the anatase interplanar distances, crystallites size and phase composition. The photocatalytic tests in presence of the composites under UV irradiation reveal an increase of the Malachite Green degradation rate constant. The effect depends on the Th relative content, temperature of annealing of the catalyst and addition of other doping agent. The highest photocatalytic activity is observed for TiO2 obtained at 550°C and containing 1% ThO2. The composite exhibits activity in dark, also. The presence of Ce4+ ions is not an obligatory requirement for the realization of the ThO2 effect. The reported results suggest that the radioactivity of the Th and/or its decay products is one of the main factors responsible for the increased photocatalytic activity of TiO2. [...]
4
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Silica hybrid biomaterials containing gelatin synthesized by sol-gel method

88%
Chernev G., Borisova B., Kabaivanova L., Salvado I.
Open Chemistry
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2010
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vol. 8
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issue 4
870-876
EN
This work reports the sol-gel synthesis of silica hybrids. We determined the effect of the type and quantity of silica precursors and organic compounds on the resulting structure, surface area, nanostructure design and size, and potential applications. The structure of the synthesized hybrids was analyzed using FT-IR, XRD, BET-Analysis, SEM, and AFM. We demonstrate the immovilization of whole living thermophilic bacterial cells with cyanocompound degradation activity in the synthesized silica hybrid biomaterials by entrapment, chemical binding, and adsorption.
5
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The radioactivity and the chemical nature of additives as factors determining the photocatalytic activity of TiO2

88%
Milanova M., Kovacheva P., Kralchevska R., Kolev J., Zaharieva J., Todorovsky D.
Open Chemistry
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2012
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vol. 10
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issue 6
1850-1858
EN
Microcomposites consisting of TiO2 and ThF4 or UO3 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of the respective additives. X-ray diffraction study reveals small effect of the latter on TiO2 phase composition and cell parameters and significant influence on the crystallite size and UV/Vis reflectance spectra. The photocatalytic tests in presence of TiO2-ThF4 microcomposites under UV and solar irradiation show a non-monotonic increase of the Malachite Green degradation rate constant with the increase of ThF4-content. No changes in the photocatalytic activity are observed in the presence of UO3 but the latter composites exhibit activity in darkness. The results are compared with previously reported data on the performance of TiO2-ThO2 photocatalyst with the same radioactivity and suggest that both radioactivity and the chemical nature of the dopants are responsible for the photocatalytic performance of TiO2-based composites containing radioactive substances. [...]
6
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Sol-gel preparation and characterization of non-substituted and Sr-substituted lanthanum cobaltates

88%
Cizauskaite S., Kareiva A.
Open Chemistry
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2008
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vol. 6
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issue 3
456-464
EN
This paper reports on the results concerning the sol-gel preparation and characterization of Sr-substituted perovskite lanthanum cobaltates La1−xSrxCoO3−δ (x = 0.0, 0.25, 0.5 and 0.75). The metal ions, generated by dissolving starting materials in diluted acetic acid were complexed by 1,2-ethanediol to obtain the precursors for the non-substituted and Sr-substituted LaCoO3. The influence of the synthesis temperature, heating time and the amount of substituent on the phase purity of La1−xSrxCoO3−δ were investigated. The phase transformations, composition and micro-structural features in the gels and polycrystalline samples were studied by thermal analysis (TG/DTA), infrared spectroscopy (IR), powder X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). [...]
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