Morphology of kaolinite crystals synthesized under hydrothermal conditions. Clays Clay Miner

Abstract--Scanning electron microscopy has revealed the presence of spherical, ath and platy kaolinite in gels with SL/A1 atomic ratio ranging from 1.84 to 0.76 that are hydrothermally treated under different temperature and time conditions. Hemispherical structures and excavated zones, at different stages of evolution, have been observed on the surface of the gel grains, indicating that spherical particles do not precipitate from the solution but are generated from the gels. The quantity of spherical particles depends on temperature, time and the chemical composition ofthe starting el. Products from starting material with Si/A1 ~ 1 yield the highest quantity of these particles. Being metastable, sphere dissolution controls the chemistry of the solution and consequently he morphology of the precipitating crystals thus producing more elongated, curved and irregular outlines when gels with Si/AI ~ 1 are hydrotherrnally treated