| 1. |
- Kosa, Ladislav, et al.
(författare)
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Phase transitions of K2TaF7 within 680-800 degrees C
- 2008
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 6:1, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680-800 degrees C were investigated by the DSC method. The values determined for the enthalpy change of the individual processes are: Delta H-transII(m)(K2TaF7; 703 degrees C) = 1.7(2) kJ mol(-1), Delta H-transI(m)(K2TaF7; 746 degrees C) = 19(1) kJ mol(-1) and Delta H-transIII(m)(K2TaF7; 771 degrees C) = 13(1) kJ mol(-1). The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654-794 degrees C.
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| 2. |
- Pritula, Ondrej, et al.
(författare)
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Neutron and X-ray Rietveld quantitative phase analysis of industrial Portland cement clinkers
- 2004
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Ingår i: Materials Structure in Chemistry, Biology, Physics and Technology. - 1211-5894. ; 11:1a, s. 181-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Weight fractions of four dominant phases (C3S, C2S, C4AF and C3A) present in five industrial clinkers were estimated by a series of neutron and X-ray Rietveld refinements. Calculated powder patterns were derived from the structural data for triclinic and monoclinic C3S, monoclinic C2S, orthorhombic C4AF and cubic C3A. Neutron diffraction data were collected with the high resolution E9 diffractometer (BENSC) using the wavelengths of 1.797Å and 2.816Å, X-ray diffraction data with a high resolution transmission diffractometer using CoKα1 radiation. Elemental composition of the samples obtained by ESEM/EDX technique were in a good agreement with the data delivered by the producers. Convergence of the refinements was remarkably different for X-ray and for neutron data. Several refinements were not completed due to numerical instabilities. Neutron refinements were found to be more stable than X-ray, but there was not any notable difference in the final estimated phases' compositions. Calculated absolute deviates of phases' weight fractions were mostly within ±10%, which for the less abundant phases corresponded to relative deviations within ±50%.
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| 3. |
- Pritula, Ondrej, et al.
(författare)
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X-ray and neutron Rietveld quantitative phase analysis of industrial Portland cement clinkers
- 2004
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Ingår i: Powder Diffraction. ; 19:3, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- Weight fractions of four dominant phases (C3S, C2S, C4AF, and C3A) present in five industrial clinkers were estimated by a series of neutron and X-ray Rietveld refinements. Calculated powder patterns were derived from the structural data for monoclinic and triclinic C3S, monoclinic C2S, orthorhombic C4AF, cubic C3A and MgO. Neutron diffraction data were collected with the high resolution E9 diffractometer (BENSC) using two different wavelenghts, X-ray diffraction data with a high resolution transmission diffractometer. Elemental composition of the samples obtained by ESEM/EDX technique were in good agreement with the data delivered by the producers. Convergence of the refinements was remarkably different for X-ray and for neutron data. Several refinements were not completed due to numerical instabilities. Neutron refinements were found to be more stable tha X-ray, but there was not any notable difference in the final estimated phases' compositions. Calculated absolute deviates of phases' weight fractions were mostly within +-10%, which for the less abundant phases corresponded to relative deviations within +-50%.
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