Influence of Silica Nanoparticles on the Crystallization Behavior of and Proton Relaxation in Cesium Hydrogen Sulfate
- Creators
- Kislitsyn, Mikhail
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Haile, Sossina M.
Abstract
The influence of nanoparticulate SiO_2 on the crystallization behavior of CsHSO_4 from aqueous solution has been quantitatively evaluated using powder X-ray diffraction (XRD) and ^1H magic angle spinning nuclear magnetic resonance (NMR) spectroscopy. It is shown that SiO_2 induces amorphization of a portion of CsHSO_4 and crystallization of the otherwise metastable phase II form of CsHSO_4. The fraction of amorphized CsHSO_4 (as determined from an evaluation of the XRD peak intensity) was found to increase from 0% in the absence of SiO_2 to fully amorphized in the presence of 90 mol % (~70 wt %) SiO_2. Within the crystalline portion of the composites, the weight fraction of CsHSO_4 phase III was observed to fall almost monotonically from 100% in the absence of SiO_2 to about 40% in the presence of 70 mol % SiO_2 (from both XRD and NMR analysis). These results suggest a crystallization pathway in which SiO_2 particles incorporate an amorphous coating of CsHSO_(4-)like material and are covered by nanoparticulate CsHSO_(4-II), which coexists with independently nucleated particles of CsHSO_(4-III). In composites with small molar fractions of CsHSO_4, the entirety of the acid salt is consumed in the amorphous region. At high CsHSO_4 content, the extent of amorphization becomes negligible, as does the extent of crystallization in metastable phase II. The phase distribution was found to be stable for over 1 year, indicating the strength of the stabilization effect that SiO_2 has on phase II of CsHSO_4.
Additional Information
© 2010 American Chemical Society. Received March 27, 2009. Revised Manuscript Received February 6, 2010. The authors gratefully acknowledge support from the National Science Foundation (Grant DMR- 0435221) and via the Caltech Center for the Science and Engineering of Materials (Grant DMR-0520565). Dr. Sonjong Hwang of the California Institute of Technology has kindly assisted with the acquisition of NMR data. We also thank Dr. Clare Grey of SUNY Stonybrook for valuable discussions.Additional details
- Eprint ID
- 18576
- DOI
- 10.1021/cm9031495
- Resolver ID
- CaltechAUTHORS:20100607-083648823
- NSF
- DMR-0435221
- NSF
- DMR-0520565
- Created
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2010-06-07Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field