A comparative study of synthetic tubular kaolinite nanoscrolls and natural halloysite nanotubes

Abstract

Kaolinite (Kaol) nanoscrolls with a diameter of ~20 to 100 nm and length of ~0.25 to 2 μm were prepared from the exfoliation of Kaol precursor. New interlayer space and lumens could be obtained by delamination and exfoliation of platy Kaol while forming nanoscrolls. The morphological and structural differences between synthetic Kaol nanoscrolls and natural halloysite (Hal) nanotubes were invesigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential scanning calorimetry (TG-DSC), nitrogen adsorption-desorption techniques. TEM showed that Kaol nanoscrolls are thinner and longer than Hal nanotubes. Kaol nanoscrolls exhibited nitrogen adsorption-desorption isotherms and pore size distribution curves similar to those of Hal but the specific surface area and pore volume of the Kaol nanoscrolls were found to be 2 times higher than those of natural tubular Hal. Both the TG and DTA curves of Kaol nanoscrolls and Hal nanotubes indicated that small amount of adsorbed water was lost below 140 °C. The dehydroxylation of Kaol nanoscrolls occurred at 463 °C, which is between the dehydroxylation temperature of Kaol and that of Hal. The current comparative study of Kaol nanoscrolls and Hal nanotubes suggests that the former could possibly be substituted for the latter for improving some applications because of the higher surface area and different types of pore space of the Kaol nanoscrolls.