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On the mechanism of exfoliation of 'Vermiculite'

Hillier, Stephen and Rice, C.M and Marwa, E.M.M (2013). On the mechanism of exfoliation of 'Vermiculite'. Clay minerals. 48:4, 563-582
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Official URL: http://claymin.geoscienceworld.org/content/48/4/56...

Abstract

Six samples of 'Vermiculite' have been studied to investigate the mechanism of its well known but poorly understood property to exfoliate. The samples were analysed quantitatively by XRD to determine their precise mineralogical composition. Electron microprobe methods, including elemental mapping of native potassium and of caesium (introduced by cation exchange) were used to examine variation in the chemical composition of the particles. Most of the samples examined show heterogeneous mineralogical compositions which occur as distinct zones within the volume of individual particles, presenting a mosaic texture. Exfoliation is related to this mosaic distribution of the different mineral phases within the particles. Lateral phase boundaries between vermiculite and mica layers, or vermiculite and chlorite layers are postulated to prevent or impede the escape of gas from a particle, resulting in exfoliation when the pressure exceeds the interlayer bonding forces that hold the layers together. This mechanism provides a common explanation for the exfoliation of 'Vermiculite' by thermal methods or by treatment with H2O2. Paradoxically, one sample which consists of pure vermiculite, in the mineralogical sense of the term, demonstrates that pure vermiculite does not and should not exhibit the property of exfoliation. Our explanation of the mechanism of exfoliation explains the commonly observed particle size dependence of exfoliation and the tendency for obviously poly-phase 'Vermiculite' samples to show the largest coefficients of expansion.

Authors/Creators:Hillier, Stephen and Rice, C.M and Marwa, E.M.M
Title:On the mechanism of exfoliation of 'Vermiculite'
Series/Journal:Clay minerals (0009-8558)
Year of publishing :2013
Volume:48
Number:4
Page range:563-582
Number of Pages:20
Publisher:The Mineralogical Society
ISSN:0009-8558
Language:English
Publication Type:Journal article
Refereed:Yes
Article category:Scientific peer reviewed
Version:Published version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Geosciences, Multidisciplinary
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Geochemistry
Keywords:vermiculite, hydrobiotite, phlogopite, exfoliation, hydrogen peroxide
URN:NBN:urn:nbn:se:slu:epsilon-e-1936
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-1936
Additional ID:
Type of IDID
Web of Science (WoS)000325594200001
DOI10.1180/claymin.2013.048.4.01
ID Code:11169
Faculty:NL - Faculty of Natural Resources and Agricultural Sciences (until 2013)
Department:(NL, NJ) > Dept. of Soil and Environment
(S) > Dept. of Soil and Environment
Deposited By: SLUpub Connector
Deposited On:28 May 2014 08:58
Metadata Last Modified:08 May 2015 15:06

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