A study on the structure and thermal stability of titanate nanotubes as a function of sodium content

• Published in: Solid state sciences 2006-08, Vol.8 (8), p.888-900
• Main Authors: Morgado, Edisson, de Abreu, Marco A.S., Pravia, Oscar R.C., Marinkovic, Bojan A., Jardim, Paula M., Rizzo, Fernando C., Araújo, Antonio S.
• Format: Article
• Language: English
• Subjects: Chemical synthesis methods; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Hydrothermal synthesis; Materials science; Methods of nanofabrication; Nanoscale materials and structures: fabrication and characterization; Nanotube; Nanotubes; Phase transformation; Physics; Sodium; Thermal stability; TiO 2; Titanate
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2006.02.039

TiTanate NanoTubes (TTNT) were synthesized by hydrothermal treatment of TiO 2 anatase in 10 M NaOH at 120 °C followed by repeated water washing, with and without ion exchanging by HCl 0.1 M. Samples with different contents of remnant sodium in nanotubes were characterized, as synthesized and after heat-treatment, by X-ray diffraction, transmission electron microscopy, thermal analysis and N 2 adsorption. It was demonstrated that TTNT consisted of a trititanate structure with general formula Na x H 2− x Ti 3O 7⋅ nH 2O, where 0 < x < 2 and n < 1.2 , depending on the degree of proton exchange after washing. As-synthesized nanotubes retained interlayer water in its multi-walled structure. The removal of sodium reduced the amount of this intercalated water and increased the specific surface area, while thermal stability was reduced. The mechanism through which TTNT dehydrated and converted into their condensed titanates and/or TiO 2 polymorphs after thermal treatment as a function of the sodium content was discussed and a schematic picture of the thermal transformations was proposed.