Effect of calcination temperature on the morphology and surface properties of TiO2 nanotube arrays

Well-ordered TiO2 nanotube arrays were prepared by electrochemical anodization of titanium in aqueous electrolyte solution of H3PO4 + NH4F at a constant voltage of 20 V for 3 h, followed by calcined at various temperatures. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Xray photoelectron spectroscopy (XPS) and Photoluminescence (PL) were used to characterize the samples. The results showed that the as-prepared nanotube arrays before being calcined were amorphous and could transform to anatase phase at a heat treatment temperature higher than 400 degrees C. As the calcination temperatures increased, crystallization of anatase phase enhanced and rutile phase appeared at 600 degrees C. However, further increasing the calcination temperature would cause the collapse of nanotube arrays. PL intensity of the nanotube arrays annealed at 500 degrees C was the lowest, which was probably ascribed to better crystallization together with fewer surface defects of the nanotube arrays. Crown Copyright (C) 2009 Published by Elsevier B. V. All rights reserved.