Formation of titanium oxide nanotubes using chemical treatments and their characteristic properties |
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Authors: | Tomoko Kasuga |
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Affiliation: | Energy Application R&D Center, Chubu Electric Power Co., Inc., Odaka, Midori-ku, Nagoya 459-8522, Japan |
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Abstract: | Needle-shaped titanium oxide crystals with a diameter of 8 nm were obtained when titania nanopowders were treated chemically with NaOH aqueous solution and subsequently with HCl aqueous solution under various conditions (e.g., at 110 °C for 20 h). Transmission electron microscopy showed that the needle-shaped products have a tube structure with an inner diameter of approximately 5 nm and an outer diameter of approximately 8 nm. TiO2 nanotubes with a large specific surface area of ≈ 400 m2/g are expected to have great potentials for use as high-performance photocatalysts or adsorbents. The amount of residual Na+ ions in the nanotubes can be controlled by HCl treatment, resulting in the formation of Na-Ti-O titanate nanotubes. The titania and titanate nanotubes can also be modified during the treatment. When calcium acetate solution was used for the treatment, a new type of bioactive nanotube was prepared. An apatite layer was formed on a compact composed of the nanotubes within 1 day of soaking in simulated body fluid. An animal test using rats showed that new-bone-tissue formation around the nanotube compact started 3 days after implantation. When oxoacid solutions, such as perchloric acid, phosphoric acid or sulfuric acid, were used in the treatment, new types of nanotube showing proton conduction were prepared; one of the nanotube compacts showed a high electrical conductivity of 8 × 10− 2 S/cm at 150 °C. These nanotubes are expected to have applications in the fields of medicine and energy generation, as well as photocatalytic applications. |
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Keywords: | Titania Titanate Nanotube Chemical process Bioactivity Proton conductivity |
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