Startseite Direct formation of the γ-CaSO4 phase in dehydration process of gypsum: In situ FTIR study
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Direct formation of the γ-CaSO4 phase in dehydration process of gypsum: In situ FTIR study

  • P.S.R. Prasad EMAIL logo , V. Krishna Chaitanya , K. Shiva Prasad und D. Narayana Rao
Veröffentlicht/Copyright: 28. März 2015
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American Mineralogist
Aus der Zeitschrift American Mineralogist Band 90 Heft 4

Abstract

The dehydration mechanism of natural single crystals of gypsum was investigated in the temperature range 300-430 K by in situ infrared (FTIR) spectroscopy. The thermal evolution of the second-order modes of H2O and SO4 groups in gypsum, in the wavenumber range 4850.5450 cm-1 and 2050.2300 cm-1 respectively, were used to probe the dehydration and rehydration sequence. A total disappearance of the combination modes of H2O and the replacement of four SO-24 bands (2245, 2200, 2133, and 2117 cm-1) observed at room temperature by three bands (2236, 2163, and 2131 cm-1) observed at 390 K indicates the direct formation of γ-CaSO4 upon heating. Upon cooling water re-enters into the γ-CaSO4 structure at around 363 K to form bassanite. This observation, that the dehydration of gypsum directly yields γ-CaSO4 (anhydrite) without the intermediate formation of hemi-hydrate (bassanite), is further corroborated by the dehydration behavior of bassanite. The second-order SO4 modes of bassanite observed around 2218, 2136, and 2096 cm-1 were replaced with the bands of γ-CaSO4 at about 378 K upon heating.

Received: 2004-6-7
Accepted: 2004-10-19
Published Online: 2015-3-28
Published in Print: 2005-4-1

© 2015 by Walter de Gruyter Berlin/Boston

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  1. Analytical perils (and progress) in electron microprobe trace element analysis applied to geochronology: Background acquisition, interferences, and beam irradiation effects
  2. Contributions to precision and accuracy of monazite microprobe ages
  3. Electron-microprobe age mapping of monazite
  4. Isotopic age constraints from electron microprobe U-Th-Pb dates, using a three-dimensional concordia diagram
  5. Monazite ages in the Chesham Pond Nappe, SW New Hampshire, U.S.A.: Implications for assembly of central New England thrust sheets
  6. Electron-microprobe dating as a tool for determining the closure of Th-U-Pb systems in migmatitic monazites
  7. Comparative isotopic and chemical geochronometry of monazite, with implications for U-Th-Pb dating by electron microprobe: An example from metamorphic rocks of the eastern Wyoming Craton (U.S.A.)
  8. Re-examination of the hydrogarnet structure at high pressure using neutron powder diffraction and infrared spectroscopy
  9. Anomalous elastic behavior and high-pressure structural evolution of zeolite levyne
  10. Crystal chemistry of the hydrothermally synthesized Na2(Mn1-xFex 2+)2Fe3+(PO4)3 alluaudite-type solid solution
  11. Thermodynamic properties of uvarovite garnet (Ca3Cr2Si3O12)
  12. Post-aragonite phase transformation in CaCO3 at 40 GPa
  13. Direct formation of the γ-CaSO4 phase in dehydration process of gypsum: In situ FTIR study
  14. The order-disorder character of FeOHSO4 obtained from the thermal decomposition of metahohmannite, Fe3+2(H2O)4[O(SO4)2]
  15. Temperature and composition dependence of structural phase transitions in Ca(TixZr1-x)OGeO4
  16. Low-T neutron powder-diffraction and synchrotron-radiation IR study of synthetic amphibole Na(NaMg)Mg5Si8O22(OH)2
  17. Charge contrast imaging of fine-scale microstructure and compositional variation in garnet using the environmental scanning electron microscope
  18. Piston-cylinder experiments on H2O undersaturated Fe-bearing systems: An experimental setup approaching fO₂ conditions of natural calc-alkaline magmas
  19. Environmentally important, poorly crystalline Fe/Mn hydrous oxides: Ferrihydrite and a possibly new vernadite-like mineral from the Clark Fork River Superfund Complex
  20. The true structure of wonesite, an interlayer-deficient trioctahedral sodium mica
  21. Clinoholmquistite discredited: The new amphibole end-member fluoro-sodic-pedrizite
  22. XRMapAnal: A program for analysis of quantitative X-ray maps
  23. Letter. Growth zoning and strain patterns inside diamond crystals as revealed by Raman maps
  24. Letter. Differentiation of commercial vermiculite based on statistical analysis of bulk chemical data: Fingerprinting vermiculite from Libby, Montana U.S.A.
  25. Letter. Crystal structure of single-crystal CaGeO3 tetragonal garnet synthesized at 3 GPa and 1000 °C
  26. Letter. Iron isotope exchange kinetics at the nanoparticulate ferrihydrite surface
  27. Letter. Cation distribution in MgFe2O4 vs. pressure and temperature: Experiments in a piston-cylinder apparatus
https://doi.org/10.2138/am.2005.1742

Artikel in diesem Heft

  1. Analytical perils (and progress) in electron microprobe trace element analysis applied to geochronology: Background acquisition, interferences, and beam irradiation effects
  2. Contributions to precision and accuracy of monazite microprobe ages
  3. Electron-microprobe age mapping of monazite
  4. Isotopic age constraints from electron microprobe U-Th-Pb dates, using a three-dimensional concordia diagram
  5. Monazite ages in the Chesham Pond Nappe, SW New Hampshire, U.S.A.: Implications for assembly of central New England thrust sheets
  6. Electron-microprobe dating as a tool for determining the closure of Th-U-Pb systems in migmatitic monazites
  7. Comparative isotopic and chemical geochronometry of monazite, with implications for U-Th-Pb dating by electron microprobe: An example from metamorphic rocks of the eastern Wyoming Craton (U.S.A.)
  8. Re-examination of the hydrogarnet structure at high pressure using neutron powder diffraction and infrared spectroscopy
  9. Anomalous elastic behavior and high-pressure structural evolution of zeolite levyne
  10. Crystal chemistry of the hydrothermally synthesized Na2(Mn1-xFex 2+)2Fe3+(PO4)3 alluaudite-type solid solution
  11. Thermodynamic properties of uvarovite garnet (Ca3Cr2Si3O12)
  12. Post-aragonite phase transformation in CaCO3 at 40 GPa
  13. Direct formation of the γ-CaSO4 phase in dehydration process of gypsum: In situ FTIR study
  14. The order-disorder character of FeOHSO4 obtained from the thermal decomposition of metahohmannite, Fe3+2(H2O)4[O(SO4)2]
  15. Temperature and composition dependence of structural phase transitions in Ca(TixZr1-x)OGeO4
  16. Low-T neutron powder-diffraction and synchrotron-radiation IR study of synthetic amphibole Na(NaMg)Mg5Si8O22(OH)2
  17. Charge contrast imaging of fine-scale microstructure and compositional variation in garnet using the environmental scanning electron microscope
  18. Piston-cylinder experiments on H2O undersaturated Fe-bearing systems: An experimental setup approaching fO₂ conditions of natural calc-alkaline magmas
  19. Environmentally important, poorly crystalline Fe/Mn hydrous oxides: Ferrihydrite and a possibly new vernadite-like mineral from the Clark Fork River Superfund Complex
  20. The true structure of wonesite, an interlayer-deficient trioctahedral sodium mica
  21. Clinoholmquistite discredited: The new amphibole end-member fluoro-sodic-pedrizite
  22. XRMapAnal: A program for analysis of quantitative X-ray maps
  23. Letter. Growth zoning and strain patterns inside diamond crystals as revealed by Raman maps
  24. Letter. Differentiation of commercial vermiculite based on statistical analysis of bulk chemical data: Fingerprinting vermiculite from Libby, Montana U.S.A.
  25. Letter. Crystal structure of single-crystal CaGeO3 tetragonal garnet synthesized at 3 GPa and 1000 °C
  26. Letter. Iron isotope exchange kinetics at the nanoparticulate ferrihydrite surface
  27. Letter. Cation distribution in MgFe2O4 vs. pressure and temperature: Experiments in a piston-cylinder apparatus
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