EMANATION THERMAL ANALYSIS OF NATURAL AND CHEMICALLY-MODIFIED VERMICULITE

摘要

Emanation thermal analysis (ETA), based on radon release measurements from previously labeled samples, was used for the first time in the characterization of the thermal behavior of natural Mg~(2+)-vermiculite (Santa Olalla, Huelva, Spain) and of Na~+- and NH_4~+-exchanged vermiculite samples. In addition, vermiculite samples subjected to a chemical treatment with an aqueous solution of (NH_4)_2SiF_6 and partially or totally re-saturated with Na~+ ions were also investigated by ETA. The ETA results of natural Mg~(2+)-vermiculite, Na~+-vermiculite and NH_4~+-vermiculite gave supplementary information about microstructure changes of the samples observed under dynamic heating conditions. The method has proved to be very useful for characterization of microstructure changes due to modification in the interlayer space of samples during the heat treatment. The crystallization of vermiculite into new phases, such as enstatite (for NH_4~+-vermiculite and Mg~(2+)-vermiculite) and forsterite (for Na~+-vermiculite) was also observed by ETA.