TY - JOUR
T1 - The thermodynamics and kinetics of the dehydration of CsH 2PO 4 studied in the presence of SiO 2
AU - Ikeda, Ayako
AU - Haile, Sossina M.
N1 - Funding Information:
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 ).
PY - 2012/4/16
Y1 - 2012/4/16
N2 - The thermodynamic and kinetics of the dehydration and hydration of CsH 2PO 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 2PO 4 to accelerate both dehydration and hydration. When dehydrated in the presence of SiO 2, CsH 2PO 4 has a fine microstructure (~ 200 nm feature size), and no reaction between CsH 2PO 4 and SiO 2 is observed. By making use of the enhanced kinetics afforded by SiO 2, the phase boundary between CsH 2PO 4, CsPO 3 and dehydrated liquid was precisely determined. The triple point connecting these phases is located at p H2O = 0.35 ± 0.2 atm and T = 267.5 ± 1.0°C. The stability of CsH 2PO 4 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 CsPO 3(s) to CsH 2PO 4(s) occur over a period of several hours, depending on temperature, water partial pressure, and morphology of the metaphosphate. High p H2O 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.
AB - The thermodynamic and kinetics of the dehydration and hydration of CsH 2PO 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 2PO 4 to accelerate both dehydration and hydration. When dehydrated in the presence of SiO 2, CsH 2PO 4 has a fine microstructure (~ 200 nm feature size), and no reaction between CsH 2PO 4 and SiO 2 is observed. By making use of the enhanced kinetics afforded by SiO 2, the phase boundary between CsH 2PO 4, CsPO 3 and dehydrated liquid was precisely determined. The triple point connecting these phases is located at p H2O = 0.35 ± 0.2 atm and T = 267.5 ± 1.0°C. The stability of CsH 2PO 4 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 CsPO 3(s) to CsH 2PO 4(s) occur over a period of several hours, depending on temperature, water partial pressure, and morphology of the metaphosphate. High p H2O 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.
KW - Cesium dihydrogen phosphate
KW - Dehydration
KW - Differential scanning calorimetry
KW - Hydration
KW - Phase diagram
KW - Thermogravimetric analysis
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U2 - 10.1016/j.ssi.2011.09.018
DO - 10.1016/j.ssi.2011.09.018
M3 - Article
AN - SCOPUS:84859423582
VL - 213
SP - 63
EP - 71
JO - Solid State Ionics
JF - Solid State Ionics
SN - 0167-2738
ER -