Influence of silica nanoparticles on the crystallization behavior of and proton relaxation in cesium hydrogen sulfate

Mikhail Kislitsyn, Sossina M. Haile

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8 Scopus citations

Abstract

The influence of nanoparticulate SiO2 on the crystallization behavior of CsHSO4 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 SiO2 induces amorphization of a portion of CsHSO4 and crystallization of the otherwise metastable phase II form of CsHSO4. The fraction of amorphized CsHSO4 (as determined from an evaluation of the XRD peak intensity) was found to increase from 0% in the absence of SiO2 to fully amorphized in the presence of 90 mol % (∼70 wt %) SiO2. Within the crystalline portion of the composites, the weight fraction of CsHSO4 phase III was observed to fall almost monotonically from 100% in the absence of SiO2 to about 40% in the presence of 70 mol % SiO2 (from both XRD and NMR analysis). These results suggest a crystallization pathway in which SiO2 particles incorporate an amorphous coating of CsHSO4-like material and are covered by nanoparticulate CsHSO4-II, which coexists with independently nucleated particles of CsHSO4-III. In composites with small molar fractions of CsHSO4, the entirety of the acid salt is consumed in the amorphous region. At high CsHSO4 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 SiO2 has on phase II of CsHSO4.

Original languageEnglish (US)
Pages (from-to)2417-2426
Number of pages10
JournalChemistry of Materials
Volume22
Issue number8
DOIs
StatePublished - Apr 27 2010

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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