Estimation of the structure of an anhydrous 2:1-Na layer silicate synthesized from talc by intercalation procedure.

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The structure of an anhydrous 2: 1-Na layer silicate (NLS), which was synthesized by heating a mixture of talc and Na2SiF6 at 800°C for 2 h, was estimated by MD simulation based on a 1 M mica structure (C2/m). The results of MD simulation showed that the top and bottom silicate layers moved in mutually opposite direction along the a- and b-axes, and the silicate layer stacking of NSL was similar to that of talc structure. The trajectory of the Na+ ions in the NLS structure from the MD simulation clearly shows two different movements as follows: one Na+ ion near the Mg2+ vacant site in the octahedral sheet was especially localized in the upper silicate layers, but the other Na+ ion apart from the Mg2+ vacant site in the octahedral sheet was placed in the middle position between the silicate layers. The 23Na MAS NMR spectra of the NLS and Mg2+ ion-exchanged NLS also showed that the NLS had two different kinds of Na+ ions, one was exchangeable and the other was nonexchangeable. However, the MD simulation could not explain quantitatively the mass balance of the exchangeable and non-exchangeable Na+ ions in the NLS structure.
日本粘土学会の論文