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Title: Microporous titanosilicate AM-2: Rb-exchange and thermal behaviour

Abstract

Rb-exchange and thermal stability of the microporous titanosilicate AM-2 were analysed by powder X-ray diffraction, thermo-gravimetric analysis, and chemical analysis of the mother liquid after exchange. The dehydration and thermal stability of the exchanged structure were monitored with in situ high temperature powder X-ray diffraction. Crystal structures were refined with Rietveld methods at 25 and 400 deg. C. The AM-2 structure was found to incorporate Rb{sup +} by replacing K{sup +}. After four exchange cycles and 166 h reaction time at 90 deg. C, the chemical composition was refined to K{sub 0.18}Rb{sub 1.82}TiSi{sub 3}O{sub 9}.H{sub 2}O. Extrapolation suggests that higher exchange ratios may be obtained after further cycles. H{sub 2}O was expelled by heating, leading to a dehydrated structure at 360 deg. C. Dehydration was associated with a change of space group symmetry from orthorhombic P2{sub 1}2{sub 1}2{sub 1} to monoclinic P2{sub 1}, which proved to be reversible after rehydration. This change of symmetry leaves the AM-2 characteristic structural topology uninfluenced and causes only minor distortions. The monoclinic AM-2 structure breaks down above 600 deg. C to become X-ray amorphous, and at 750 deg. C a wadeite-type phase (K {sub x}Rb{sub 2-x}TiSi{sub 3}O{sub 9}) crystallises. This transformation is irreversible andmore » leads to immobilisation of Rb{sup +}.« less

Authors:
 [1];  [2]
  1. Laboratorium fuer chemische und mineralogische Kristallographie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland). E-mail: nicola@doebelin.org
  2. Laboratorium fuer chemische und mineralogische Kristallographie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland)
Publication Date:
OSTI Identifier:
20902499
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 42; Journal Issue: 1; Other Information: DOI: 10.1016/j.materresbull.2006.05.006; PII: S0025-5408(06)00204-2; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CHEMICAL PREPARATION; DEHYDRATION; EXTRAPOLATION; GRAVIMETRIC ANALYSIS; HEATING; MONOCLINIC LATTICES; ORTHORHOMBIC LATTICES; POTASSIUM IONS; POWDERS; RUBIDIUM IONS; SPACE GROUPS; STABILITY; SYMMETRY; X-RAY DIFFRACTION

Citation Formats

Doebelin, Nicola, and Armbruster, Thomas. Microporous titanosilicate AM-2: Rb-exchange and thermal behaviour. United States: N. p., 2007. Web. doi:10.1016/j.materresbull.2006.05.006.
Doebelin, Nicola, & Armbruster, Thomas. Microporous titanosilicate AM-2: Rb-exchange and thermal behaviour. United States. doi:10.1016/j.materresbull.2006.05.006.
Doebelin, Nicola, and Armbruster, Thomas. Thu . "Microporous titanosilicate AM-2: Rb-exchange and thermal behaviour". United States. doi:10.1016/j.materresbull.2006.05.006.
@article{osti_20902499,
title = {Microporous titanosilicate AM-2: Rb-exchange and thermal behaviour},
author = {Doebelin, Nicola and Armbruster, Thomas},
abstractNote = {Rb-exchange and thermal stability of the microporous titanosilicate AM-2 were analysed by powder X-ray diffraction, thermo-gravimetric analysis, and chemical analysis of the mother liquid after exchange. The dehydration and thermal stability of the exchanged structure were monitored with in situ high temperature powder X-ray diffraction. Crystal structures were refined with Rietveld methods at 25 and 400 deg. C. The AM-2 structure was found to incorporate Rb{sup +} by replacing K{sup +}. After four exchange cycles and 166 h reaction time at 90 deg. C, the chemical composition was refined to K{sub 0.18}Rb{sub 1.82}TiSi{sub 3}O{sub 9}.H{sub 2}O. Extrapolation suggests that higher exchange ratios may be obtained after further cycles. H{sub 2}O was expelled by heating, leading to a dehydrated structure at 360 deg. C. Dehydration was associated with a change of space group symmetry from orthorhombic P2{sub 1}2{sub 1}2{sub 1} to monoclinic P2{sub 1}, which proved to be reversible after rehydration. This change of symmetry leaves the AM-2 characteristic structural topology uninfluenced and causes only minor distortions. The monoclinic AM-2 structure breaks down above 600 deg. C to become X-ray amorphous, and at 750 deg. C a wadeite-type phase (K {sub x}Rb{sub 2-x}TiSi{sub 3}O{sub 9}) crystallises. This transformation is irreversible and leads to immobilisation of Rb{sup +}.},
doi = {10.1016/j.materresbull.2006.05.006},
journal = {Materials Research Bulletin},
number = 1,
volume = 42,
place = {United States},
year = {Thu Jan 18 00:00:00 EST 2007},
month = {Thu Jan 18 00:00:00 EST 2007}
}