Control over the Hierarchical Structure of Titanate Nanotube Agglomerates
journal contributionposted on 03.05.2011, 00:00 by Dmitry V. Bavykin, Alexander N. Kulak, Frank C. Walsh
An alkaline hydrothermal treatment of several types of ordered macroporous TiO2 structures, namely, microtubes, sea urchin shapes, and anodic nanotube arrays, has been investigated under stationary conditions. The effect of the size and geometry of these structures on the morphology of the forming hierarchical agglomerates of titanate nanotubes has been systematically studied. It has been revealed that, at sizes larger than the critical value (ca. 1 μm), the whole geometry of the initial ordered TiO2 structure is maintained under reaction conditions leading to formation of hierarchical structures, in which bulk TiO2 is replaced with titanate nanotube agglomerates. This principle provides a convenient route for the preparation of multiscale micro- and nanostructures of TiO2 based materials. The analysis of critical size suggests that, under reaction conditions, due to the limited transport of dissolved Ti(IV) species, the growth of nanotubes occurs locally.