Ikeda, Ayako (2013) Superprotonic solid acids : thermochemistry, structure, and conductivity. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:09142012-115522353
In this work, in order to investigate the thermochemistry and property of the superprotonic solid acid compounds, the measurement methods were established for
The thermodynamic and kinetics of the dehydration and hydration of CsH2PO4 is investigated by TG, DSC, and XRD analysis. By making use of the enhanced kinetics afforded by SiO2, the phase boundary between CsH2PO4, CsPO3, and dehydrated liquid was precisely determined. The stability of CsH2PO4 and the liquid dehydrate, CsH2(1-x)PO4-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) occurs over a period of several hours, depending on temperature, water partial pressure, and morphology of the metaphosphate. High and small particles favor rapid dehydration, whereas the temperature dependence of the rehydration kinetics is nonmonotonic, reaching its fastest rate in the vicinity of the superprotonic transition.
Doping Rb and K into CDP was examined and the stable region of Cs1-xRbxH2PO4 and Cs1-xKxH2PO4 are determined by in situ XRD and DSC measurement. Then the effects of doping to the structure and conductivity are discussed. It was found that Rb has whole-range solubility for both cubic and monoclinic CDP. Ts increases and Td decrease with Rb content. K has 27% solubility for cubic CDP, Ts and Td decrease with K content. The eutectic temperature is 208 ± 2°C. The lattice size of Rb- or K- doped CDP depends on the averaged cation size. Conductivity linearly decreases by dopant concentration. The impact of K doping is deeper than that of Rb for the equivalent averaged cation size.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Subject Keywords:||solid acid;thermochemistry;X-ray diffraction;phase transition;proton conduction|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Materials Science|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||10 August 2012|
|Author Email:||ikedashome (AT) yahoo.co.jp|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ayako Ikeda|
|Deposited On:||15 Nov 2012 17:20|
|Last Modified:||12 Apr 2013 18:31|
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