Formation of expandable mica from talc using the intercalation procedure

To investigate the transformation process from talc to expandable micas, mixtures of talc and Na2SiF6 were heated from 600 degrees to 900 degrees C and air-quenched at 50 degrees C intervals, The air-quenched product at 800 degrees C mainly consisted of expandable micas with a basal spacing of 1.25 nm, nonexpandable materials with a basal spacing of 0.96 nm, and a small amount of talc used as the starting material, A lattice fringe image by HRTEM of the product shows that the layer spacing at the edges surfaces is about 1.2 nm, but the layer spacing inside of the particles is close to that of talc, Such a nanostructure indicates a topotactic reaction from talc to expandable micas and confirms that Na+ ions intercalate into the structure from the edge to the core.