Hydrothermal Synthesis and Crystal Structure of Titanate Nanotubular

Nanotubular titanates with an external diameter around 10 nm were prepared by hydrothermal processing using commercial anatase-type TiO2 powder as raw material in the NaOH(aq) solution. The products obtained at different conditions were characterized by means of TEM, SEM, XRD, EDS and the thermal stability of the products was tested. The results show that nanotubular titanate formed during hydrothermal treatment rather than in washing or immersing processes. NaxH2-xTi3O7 or mixtures of NaxH2-xTi3O7 and TiO2 nanotubes can be obtained by control the pH values of immersing solutions. The nanotubular titanates are stable with original symmetry crystal structure till 400 ℃ and keeps nanotubular under 500 ℃. At higher heat-treatment temperatures, the anatase structure will change into rutile structure and a new Na2Ti6O13 crystal obtained by the reaction of rutile-type TiO2 with Na2Ti3O7. At 800 ℃, the main crystal Na2Ti6O13 and small quantity of rutile TiO2 is found in the sample.