Structural and energetical characterization of exfoliated kaolinite surfaces

Abstract

Understanding the surface and structural properties of kaolinite/halloysite nanostructures is of utmost importance from the points of view of nanohybrid preparation. The formation of nano-sized particles depends on the quality and quantity of bonding sites as well as on the required degree of dispersity. The basic goal of this work is the study of the effect of the morphology (as secondary structure) on the surface properties as well as the demonstration of the applicability of inverse gas chromatography (IGC) to characterize exfoliated surfaces. The surface properties of nanostructures made of kaolinites of varying structural order were investigated with N2 adsorption and inverse gas chromatography (IGC). The spectral changes of the OH groups sensitive to the changes in the outer chemical environment were followed by FTIR spectroscopy. The nanostructures made of a highly ordered kaolinite (HI=1.4) were investigated as a function of the way of energy-input, as well. Exfoliation resulted in a mixture of nanoparticles with pseudo-hexagonal and tubular morphology. The pseudo-hexagonal morphology favored the formation of pores with cylindrical symmetry. Structural order can primarily influence the pore size distribution, the dispersion component of surface energy and the acidity parameter. The deformation band of the inner OH groups can be considered as an indicator of the changes in the secondary structure. The relative band intensity of the inner OH groups increased with the increase of the structural order.