Das Industriemineral Vermiculit - Enfluß der Rohstoffmineralogie auf die De- und Rehydratation bei der Herstellung von Hochtemperaturdämmstoffen
Vermiculite is an important clay mineral and due to its exfoliation characteristics also used for industrial processing. Over the past years crystal structure and chemistry of selected samples have been extensively investigated. But so far the in-situ investigation of temperature and humidity influence on the step-wise dehydration behaviour was not possible. A reliable calorimetric quantification of the sudden endothermic exfoliation process has neither been published. Representative analysises have been conducted with material from seven deposits. Based on a mineralogical characterisation the following results are given: * A pH2O- T- stability diagram for Mg- vermiculite was obtained by in-situ XRD.* For the thermal exfoliation process endothermic and exothermic enthalpy changes were quantified calorimetrically. * After artificial weathering of phlogopite and biotite a vermiculite-scroll formation was detected on (00l)-planes. * The industrial application of the given results permits a significant qualitiy improvment of high-temperature isolating materials based on vermiculite; additionally the production process can be optimised. * Basics for consecutive single-crystal investigations have been developed. The goal is an explanation of the structural changes as well as the va-rying H2O- content of pure vermiculite.
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