Heat Treatment at 1000 °C under Reducing Atmosphere of Commercial Vermiculites

Abstract

With the purpose of obtaining synthetic materials from other natural sources for industrial and technological applications, a thermal alteration study was carried out with commercial vermiculites of different purity and origin. For this objective, samples were subjected to 1000 °C in a furnace both at ambient and reduced (N2/Ar) atmospheres. The thermal behavior and physicochemical properties of the different vermiculites were investigated by X-ray diffraction (XRD), thermal analysis (TG and DTG), and scanning electron microscopy (SEM), and their textural parameters were analyzed by BET treatment. The transformations undergone by the investigated commercial vermiculites subjected to heating treatments caused textural and structural changes in them. There was a decrease in the specific surface area, adsorption capacity, and pore volume values for the samples treated with in situ heating at 1000 °C, both at ambient and reduced atmospheres, and the samples were treated with ex situ abrupt heating at 1000 °C at ambient conditions. There was a decrease in the specific surface area, adsorption capacity, and pore volume values for the samples treated with in situ heating at 1000 °C, both in ambient and reduced atmospheres, which was not observed in the samples treated with an ex situ abrupt heating at 1000 °C at ambient conditions. This corroborated with our findings that the expansion in the first type of thermal treatment produced less separation of the exfoliation sheets than the expansion in the second type of thermal treatment. These textural changes, together with the structural ones, could play a fundamental role in the choice of industrial and technological applications for which these materials could be used.