Morphology of anatase crystals and their aggregates synthesized hydrothermally from aqueous mixtures of titanium alkoxide and different alkylammonium hydroxides

Abstract

Anatase was hydrothermally synthesized from transparent aqueous sols including layered titanate colloids. The reaction sols were prepared from titanium isopropoxide and different alkylammonium hydroxides (NR4OH). The influence of the type of NR4OH on the morphology of the anatase crystals and their aggregates was examined. We previously reported that although anatase has a tetragonal lattice, six-pointed starlike anatase aggregates were synthesized from the sols prepared using N(CH3)4OH. With increasing the alkyl chain length of NR4OH, the number of the starlike aggregates decreased, and their arms became thicker and shorter. When N(C4H9)4OH was used, needlelike anatase crystals elongated along the c-axis were formed rather than starlike aggregates. The use of NR4OH with long alkyl chains were expected to retard stacking of the layered titanate during hydrothermal synthesis. The stacking and exfoliation of the layered titanate colloids may play an important role in the morphology of the resulting anatase crystals and their aggregates. © 2009 The Ceramic Society of Japan. All rights reserved.