title: Kaolinite-urea complexes obtained by mechanochemical and aqueous suspension techniques--a comparative study.
abstract: Intercalation compounds of low- and high-defect kaolinites have been prepared by direct reaction with urea aqueous solution as well as by co-grinding with urea in the absence of water (mechanochemical intercalation). The complexes formed were studied by X-ray diffraction, thermal analysis, DRIFT spectroscopy, and scanning electron microscopy. In aqueous solution the degree of intercalation for the low- and high-defect kaolinites was found to be 77 and 65%, respectively. With mechanochemical intercalation, both kaolinites were almost fully expanded after 1 h of grinding. Based on the results of DRIFT spectroscopy, a structural model for the bonding of urea to the siloxane surface is proposed. The kaolinite-urea intercalation compounds produced by mechanochemical intercalation have crystallite sizes lower than those obtained by the aqueous solution method.
authors.affiliation: Institute for Materials Engineering, University of Pannonia, H-8201 Veszprém, P.O. Box 158, Hungary. makoe@almos.vein.hu
authors.forename: Eva
authors.initials: E
authors.lastname: Makó
authors.forename: János
authors.initials: J
authors.lastname: Kristóf
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Horváth
authors.forename: Veronika
authors.initials: V
authors.lastname: Vágvölgyi