Synthesis And Characterization Of Hollow Titania And Calcuim Titanate&Investigation On Their Properties

In recent years, hollow materials with nanostructures have attracted much attention because these materials have low densities and high surface areas as well as hollow cores, in which a large amount of guest molecules can be contained for encapsulation. Therefore, hollow spheres constitute an important class of materials that can be potentially used in various fields.The stable TiO2gel was prepared by a sol-gel method with Tetrabutoxytitanium (TBOT) as precursor, acetic acid (or acetyl acetone) as stabilizer and absolute ethanol as solvent. The main factors influencing gel time included:the addition of stabilizer, the different addition modes of water, the amount and ratio of ethanol and water, pH value and temperature of the hydrolysis.Titania hollow spheres (TiHSs) and nanotubes (TiNTs) have been fabricated by adopting CaCO3nanoparticles as core templates through the hydrolysis of TBOT, titania crystal nucleus were deposited on the surface of CaCO3nanoparticles, followed by aggregation condensation of TiO2gel and the removal of CaCO3with dilute acid. SEM, TEM, XRD and nitrogen adsorption have been employed to characterize morphologies and structures of TiHSs and TiNTs. The experimental results indicated that TiHSs had a diameter of60-100nm and a wall thickness of10nm, while TiNTs have a uniform tubular hollow structure with one or two big openings ends, the inner diameters of100-150nm and200""300nm, respectively, the length of about2.5-4μm, and a wall thickness of20"30nm.Titania nanotubes (and hollow spheres) with mesostructured walls (TiNTMs and TiHSMs) have also been prepared using a double-template method, in which calcium carbonate nanoparticles were employed as core templates and surfactants as mesostructure-directing agents at room temperature in nonaqueous system. TiHSMs had a similar morphology with titania hollow spheres, which had a peak pore diameter at4.26nm and a pore volume of0.72cm3/g. TiNTMs had a high surface area of328.01m2/g, a pore volume of0.847cm3/g and the maximum pore size centered at7.45nm. From HRTEM photos, it could be found that worm-like holes were arrayed in the walls in a disordered way.The formation mechanism of hollow titania nanotubes (or spheres) materials with mesostructured using a double-template method has been discussed, it could be suggested that in the presence of neutral surfactants hydrogen bonding interactions between non-ionic surfactants(S0) and inorganic species (I0) play a crucial role in the formationof hollow titania with a mesostructed wall.CaTiO3nanoparticles with a hollow structure were first synthesized by a facile method at a relatively low temperature (≤600℃). TEM and XRD were employed to characterize the as-prepared samples. The results showed that the hollow spheres samples had a diameter of80"100nm and homogeneous wall thickness, the nanotubes samples had a uniform tubular hollow structures with a length of2～3μm, an average inner diameter at150～250nm and a controllable wall thickenss.