Delamination of Kaolinite by Intercalation of Urea

Abstract

In order to delaminate kaolinite so as to improve its plasticity which is an essential factor as a porcelain material, intercalation of urea along with grinding was applied to kaolinite. In this process, kaolinite was ground with addition of various amounts of urea by using a ball-mill, a mechanical mortar or the combination of a mechanical mortar and a ball-mill. The ratio of intercalation was evaluated by X-ray diffractometry and the degree of delamination was estimated by the surface area and X-ray diffraction measurements. The results are summarized as follow: (1) Grinding using the mechanical mortar markedly accelerated the intercalation of urea into kaolinite. When a mixture of kaolinite and urea without the grinding treatment was stood in a humidity-controlled vessel, the urea intercalation took place, but its ratio was small. The ball-milling was ineffective in the urea intercalation. (2) The 00l and hkl reflections of kaolinite became broad after grinding a mixture of kaolinite and urea first by the mechanical mortar and then by the ball-mill. The specific surface areas of the kaolinite samples ground with addition of urea by 0, 5 and 10wt% were 20.8, 34.4 and 36.5m²/g, respectively. These results suggest that the urea intercalation accelerates the delamination of kaolinite when combined with grinding.