Ikeda, Ayako and Haile, Sossina M. (2012) The thermodynamics and kinetics of the dehydration of CsH_(2)PO_(4) studied in the presence of SiO_2. Solid State Ionics, 213 . pp. 63-71. ISSN 0167-2738 http://resolver.caltech.edu/CaltechAUTHORS:20120525-095306573
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The thermodynamic and kinetics of the dehydration and hydration of CsH_(2)PO_(4) is investigated by thermogravimetric, differential scanning calorimetry and X-ray diffraction analysis in the temperature range of 200 to 400 °C, water partial pressure range of 0.06 to 0.90 atm. SiO_(2) powder was added to CsH_(2)PO_(4) to accelerate both dehydration and hydration. When dehydrated in the presence of SiO_(2), CsH_(2)PO_(4) has a fine microstructure (~200 nm feature size), and no reaction between CsH2PO4 and SiO_(2) is observed. By making use of the enhanced kinetics afforded by SiO_(2), the phase boundary between CsH_(2)PO_(4), CsPO_(3) and dehydrated liquid was precisely determined. The triple point connecting these phases is located at pH2O = 0.35 ± 0.2 atm and T = 267.5 ± 1.0 °C. The stability of CsH2PO4 and the liquid dehydrate, CsH_(2(1−x))PO_(4−x)(l), were confirmed by the complete reversal of dehydration to recover these phases in the appropriate temperature and water partial pressure ranges. Rehydration and conversion of CsPO3(s) to CsH2PO4(s) occur over a period of several hours, depending on temperature, water partial pressure, and morphology of the metaphosphate. High pH2O and small particles favor rapid dehydration, whereas the temperature dependence of the rehydration kinetics is non-monotonic, reaching its fastest rate in the vicinity of the superprotonic transition.
|Additional Information:||© 2011 Elsevier B.V. Received 17 April 2011; Received in revised form 11 September 2011; Accepted 20 September 2011; Available online 19 October 2011. The authors gratefully acknowledge Dr. Shu Yamaguchi for valuable discussions. Financial support has been provided by the U.S. National Science Foundation (DMR-0906543 and DMR-0520565) and the Army Research Office (W911NF-07-1-0410). Selected experimental facilities utilized in this study were additionally supported by the NSF through the Caltech Center for the Science and Engineering of Materials, a Materials Research Science and Engineering Center (DMR-052056).|
|Subject Keywords:||Cesium dihydrogen phosphate; Dehydration; Hydration; Phase diagram; Thermogravimetric analysis; Differential scanning calorimetry|
|Official Citation:||Ayako Ikeda, Sossina M. Haile, The thermodynamics and kinetics of the dehydration of CsH2PO4 studied in the presence of SiO2, Solid State Ionics, Volume 213, 16 April 2012, Pages 63-71, ISSN 0167-2738, 10.1016/j.ssi.2011.09.018.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||25 May 2012 18:40|
|Last Modified:||25 May 2012 18:41|
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