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VerlagUniversitätsverlag Karlsruhe, Karlsruhe
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The characteristic feature of phyllosilicates like muscovite (KAl2[Si3AlO10(OH)2] is their layered structure. Due to the resulting anisotropic optical and electrical properties this mineral is an important raw material in paint industries and polymer composites.
Crucial for many of these properties is on one hand a high aspect ratio of the stacks, which will be enhanced by delamination of the mineral. On the other hand the exchange of the interlayer cations like potassium changes the chemical properties of the muscovite, its refraction behaviour and surface properties. But these interlayer cations are difficult to access and are not exchangeable under normal conditions.
Thus a process for the intercalation of cations like Cu2+, Mg2+ or Zn2+ from super saturated nitrate solutions in autoclaves was developed to reveal a chemically modified mica phase.
The extensive modification of the muscovite structure, due to the intercalation is monitored by X-ray diffractometry and several spectroscopic methods. The XRD results strongly suggest the formation of an intercalated irregular mixed-layer phase. This is proven by far infrared spectroscopy which show the simultaneous occurrence of both K+ and Cu2+ in the interlayer region, strongly increasing the interlayer space.
1Investigations in the mid infrared region using diffuse reflectance spectroscopy (DRIFT) suggest a further migration of the intercalated cations deep into the ditrigonal holes of the tetrahedral sheet and their fixation within these holes close to the OH groups.