Layered H2K2Nb6O17 exfoliation promoted by n-butylamine

We have been exploring experimental conditions to achieve the exfoliation of the layered niobate phase K4Nb6O17 using alkyl amines. In this work, the exfoliation process of the niobate acidic form H2K2Nb6O17 was evaluated in aqueous solution media using n-butylamine. Different amine/H+-niobate molar ratios were used and for each one, two fractions were isolated: one that corresponds to the deposited solid (or sediment) and the second one that consists of an aqueous colloidal dispersion. Fractions were characterized by X-ray powder diffraction, electronic absorption spectroscopy and, scanning and transmission electron microscopies. It was observed that the hexaniobate exfoliation is very dependent on the amine/H+-niobate molar ratio utilized. The highest amount of exfoliated niobate particles was achieved by using a butylamine/H+-niobate molar ratio around 0.5. High molar ratios promote the intercalation preferred to the delamination, indicating that the interlayer region saturation precludes the hexaniobate sheets exfoliation. TEM images of delaminated sample showed nanosized particles with flat and tubular morphologies. (C) 2004 Elsevier Ltd. All rights reserved.