29Si and 27Al NMR study of amorphous and paracrystalline opals from Australia

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dc.contributor.author Brown, Leslie en_US
dc.contributor.author Ray, Abhi en_US
dc.contributor.author Thomas, Paul en_US
dc.date.accessioned 2009-12-21T02:32:30Z
dc.date.available 2009-12-21T02:32:30Z
dc.date.issued 2003 en_US
dc.identifier 2003000478 en_US
dc.identifier.citation Brown Leslie, Ray Abhi, and Thomas Paul 2003, '29Si and 27Al NMR study of amorphous and paracrystalline opals from Australia', Elsevier Science Bv, vol. 332, no. 1-3, pp. 242-248. en_US
dc.identifier.issn 0022-3093 en_US
dc.identifier.other C1 en_US
dc.identifier.uri http://hdl.handle.net/10453/4273
dc.description.abstract Four opal-AG (amorphous) and two opal-CT (paracrystalline) samples obtained from various regions in Australia were investigated with 29Si NMR and 27Al NMR. The proton cross-polarization 29Si NMR technique was used and the resulting spectra consisted of two main resonances: -102.0 and -111.2 ppm for opal-AG; and -102.5 and -112.2 ppm for opal-CT. These peaks were assigned to the Q3(1OH) and Q4 resonances, respectively. Using very short contact times, a third, very weak peak at -94 ppm was resolved in an opal-CT specimen, which was assigned to silicon in the Q2(2OH) arrangement (i.e. a silicon with twin hydroxyl groups). It was found that the opal-CT samples contained a higher proportion of both geminal and vicinal silanol groups (Q2 and Q3) than the opal-AG samples. The geminal silanol groups present in opal-AG and opal-CT are not restricted to opal-AN. The full-width at half-maximum (FWHM) values were 9.5 ppm for the opal-AG samples, and 6.5 ppm for both opal-CT samples, a result which confirms that opal-CT has a higher degree of short-range structural order than opal-AG. The 27Al NMR spectra of the opals all showed a single resonance at +52 ppm, indicating that the aluminium exists in a tetrahedral arrangement incorporated within the opal structure. en_US
dc.publisher Elsevier Science Bv en_US
dc.relation.isbasedon http://dx.doi.org/10.1016/j.jnoncrysol.2003.09.027 en_US
dc.title 29Si and 27Al NMR study of amorphous and paracrystalline opals from Australia en_US
dc.parent Journal Of Non-crystalline Solids en_US
dc.journal.volume 332 en_US
dc.journal.number 1-3 en_US
dc.publocation Amsterdam, Netherlands en_US
dc.identifier.startpage 242 en_US
dc.identifier.endpage 248 en_US
dc.cauo.name Dept of Material Science en_US
dc.conference Verified OK en_US
dc.for 091200 en_US
dc.personcode 95054538 en_US
dc.personcode 860311 en_US
dc.personcode 960405 en_US
dc.percentage 100 en_US
dc.classification.name Materials Engineering en_US
dc.classification.type FOR-08 en_US
dc.description.keywords Angle-spinning Nmr; Noncrystalline Silica Minerals; Nuclear-magnetic-resonance; Cross-polarization; Mas-nmr; Water; Microcrystalline; Aluminum; Surface; Xrd en_US
dc.staffid 960405 en_US

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