Characterization of urea-modified Palabora vermiculite

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dc.contributor.author Muiambo, H.F. (Herminio Francisco)
dc.contributor.author Focke, Walter Wilhelm
dc.contributor.author Atanasova, Maria T.
dc.contributor.author Benhamida, Aida
dc.date.accessioned 2015-01-30T08:42:08Z
dc.date.available 2015-01-30T08:42:08Z
dc.date.issued 2015-03
dc.description.abstract Replacing the exchangeable interlayer ions in Palabora vermiculite with magnesium, aluminumor iron (III) ions does not affect the exfoliation onset temperature (456± 11 °C). However, co-intercalation of minor amounts of urea lowers the exfoliation onset temperature to 209 ± 35 °C. This significant decrease is attributed to the low thermal stability of urea which releases ammonia and water as blowing agents. Thermo-mechanical analysis indicates that the expanded vermiculite exhibits spring-like properties. Part of the original expansion is recovered when the applied force is removed. The observed hysteresis is attributed to the progressive flattening ofwarped/buckled sheets that make up the expandedworm-like structure. Provided the expanded flake has not been heated beyond 450 °C, it can be reconstituted by applying a sufficiently high compressive force followed by equilibration with distilled water. Such flakes show the conventional exfoliation behavior when heated again. en_ZA
dc.description.librarian hb2015 en_ZA
dc.description.sponsorship National Research Foundation (NRF) through Research Grant 87453 under the South African/Algeria Research Partnership Programme Bilateral Agreement. en_ZA
dc.description.uri http://www.elsevier.com/locate/clay en_ZA
dc.identifier.citation Muiambo, HF, Focke, WW, Atanasova, M & Benhamida, A 2015, 'Characterization of urea-modified Palabora vermiculite', Applied Clay Science, vol. 105-106, pp. 14-20. en_ZA
dc.identifier.issn 0169-1317 (print)
dc.identifier.issn 1872-9053 (online)
dc.identifier.other 10.1016/j.clay.2014.12.019
dc.identifier.uri http://hdl.handle.net/2263/43509
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2014 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Applied Clay Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Applied Clay Science, vol. 105-106, pp.14-20, 2015. doi : 10.1016/j.clay.2014.12.019. en_ZA
dc.subject Vermiculite en_ZA
dc.subject Urea en_ZA
dc.subject Ion exchange en_ZA
dc.subject Exfoliation en_ZA
dc.subject Thermal mechanical analysis en_ZA
dc.title Characterization of urea-modified Palabora vermiculite en_ZA
dc.type Postprint Article en_ZA


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