Morphology of Kaolinite Crystals Synthesized Under Hydrothermal Conditions

Saverio Fiore1, F. Javier Huertas2, Francisco Huertas2 and José Linares2
1 Istituto di Ricerca sulle Argille, CNR, P.O. Box 27, 85050 Tito (PZ), Italy
2 Estación Experimental del Zaidín, CSIC Profesor Albareda, 1, 18008 Granada, Spain

Abstract: Scanning electron microscopy has revealed the presence of spherical, lath and platy kaolinite in gels with Si/Al 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 of the starting gel. Products from starting material with Si/Al ≈ 1 yield the highest quantity of these particles. Being metastable, sphere dissolution controls the chemistry of the solution and consequently the morphology of the precipitating crystals thus producing more elongated, curved and irregular outlines when gels with Si/Al ≈ 1 are hydrotherrnally treated.

Key Words: Crystal growth • Electron microscopy • Kaolinite • Laths • Morphology • Plates • Spherules • Synthesis

Clays and Clay Minerals; June 1995 v. 43; no. 3; p. 353-360; DOI: 10.1346/CCMN.1995.0430310
© 1995, The Clay Minerals Society
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