Morphology-controlled Fabrication And Characterization Of TiO₂ Nanostructures

Nanomaterials, which at least have one dimension smaller than 100 nm and have many unique properties compared to general materials, are a new kind of materials. TiO₂ is an important inorganic functional material, and has excellent application potentials in many fields. In the past and recent years, researches all over the world have paid much attention on the synthesis and properties of TiO₂ nanocrystals. Much progress in this field has been demonstrated.In this thesis, we first introduce the fundamental concepts, development histories, properties and characteristic technologies of nanomaterials;as well as the main application potentials and synthetic strategies of TiO₂ nanomaterials. And then, we discuss our research work. The detailed contents are as follows:(1) Rutile TiO₂ were prepared by "two-step method" including low-temperature hydrothermal process and high-temperature calcinations employing TiCl₄ as the source material. The samples prepared at different conditions were investigated by XRD, TEM, BET and UV-VIS absorption spectra. The results showed that the final products, which were firstly treated in higher temperature hydrothermal process, had smaller particle size, better dispersive property and higher specific surface area.(2) Flowerlike rutile titania nanocrystals were prepared via a simple aqueous -phase stirring for 24h at a low temperature of 75℃, employing only TiCl₄, HCl as the starting materials. XRD analyse proved the formation of rutile TiO₂. The observations from TEM and SEM showed that the product were large-scale flower-shaped structures consisted of radial nanorods. Comparative experiments demonstrated that the volume ratio of TiCl₄/H₂O influenced the morphology of the TiO₂ crystals. The growth mechanisms of TiO₂ nanostructures (flowers, pinecones, and needle-like nanorods) prepared under different conditions were also discussed. It was found that the ilowerlike structures exhibited the highest photocatalyticactivity in the photodegradation of aqueous brilliant red X - 3B solution.(3) TiO? nanobelts were successfully prepared by pressure-thermalcrystallization method in alkaline solution(KOH) at the temperature ranging from 180°C to 230°C using the medial product Ti(0H)4 as raw material, which obtained from the industrial synthesized process of TiO2, X-ray diffraction (XRD) results showed that TiO2 is anatase structure;Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations demonstrated the average width of TiC>2 is 10¹5 ran, with the lengths in the range of several tens to several hundreds micrometers. Further studies implied that the pretreatment of raw material and temperature influence the growth of nanocrystal directly. Longer TiOa with uniform size and good quality were obtained when the pH value of solution was 14 and the aged time is 12 hours;the crystallization degree increased with increasing temperature. The formation mechanism of TiO2 nanobelts was interpreted at last.