Naslov
High temperature Raman spectroscopy of titanate nanotubes

Autori
Gajović, Andreja ; Friščić, Ivica ; Plodinec, Milivoj ; Iveković, Damir

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
XXXIX European Congress on Molecular Spectroscopy (EUCMOS 2008) : Book of Abstracts / Musić, Svetozar ; Ristić, Mira ; Krehula, Stjepko - Zagreb : Institut Ruđer Bošković, 2008, 143-143

Skup
EUCMOS 2008 XXXIX European Congress on Molecular Spectroscopy

Mjesto i datum
Opatija, Hrvatska, 31.08.2008. - 05.09.2008

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
titanate nanotubes; thermal stability; phase transition; high temperature Raman spectroscopy; transmission electron microscopy

Sažetak
In last few years, properties of titanate nanotubes were extensively studied due to their potential applications in solar cells, electronics, chemical sensors, (photo)catalysis, hydrogen sensing and as mesoporos material for ion exchange. Titanate nanotubes are especially interesting because of their high aspect ratio and high specific surface area. Although there are some ambiguities regarding the exact structure and chemical composition of titanate nanotubes, it is generally accepted that the nanotubes have a layered titanate structure. An interlayer space of about 8 Å ; is occupied by water molecules and alkali metal cations. However, the mechanism of nanotube formation and growth are still the subject of the numerous studies. In this work the formation of titanate nanotubes are discussed in the view of different TiO2 precursors. The thermal stability of prepared nanutubes have been studied in situ at high temperatures. The influence of Na+ content on the thermal stability of titanate nanotubes is also considered in details. Titanate nanotubes were sinthesized by hydrothermaly treating the TiO2 powder with NaOH solution. The starting precursors for nanotube synthesis were anatase or the mixture of anatase, rutile, and high-pressure TiO2II phase (TiO2-II) as a major component. The samples with various Na/Ti ratios were prepared by ion-exchange of interlayer Na+ cations with H+ ions under controlled pH conditions. The structural changes in the nanotubes induced by the thermal treatment were studied in situ by Raman spectroscopy (RS) and transmission electron microscopy (TEM). The morphology and the microstructure of the nanotubes before and after the thermal treatment in heating stage for RS were additionally examined by TEM and selected area electron diffraction (SAED). We found that hydrothermal treatment of mixture of TiO2 phases (anatase, rutile, and TiO2-II) leads to the formation of titanate nanotubes with structure and morphology similar to the nanotubes obtained from pure anatase, as observed both by RS and TEM. However, the temperature stability of nanotubes prepared from mixtures containing TiO2-II was much lower. These nanotubes undergo phase transition to anatase at temperatures lower than 100 °C, while, in the case of nanotubes obtained from anatase precursor, Raman bands characteristic for titanate nanotubes were visible up to 300 º ; C. At 500 º ; C titanate nanotubes in H-form were copletely transformed to anatase. Furthermore, titanate nanotubes in Na-form showed even better thermal stability – tubular structure was preserved to the temperatures as high as 500 °C. Phase transformation temperatures observed for nanotubes prepared from anatase are in good agreement with X-ray diffraction results reported by E. Morgano Jr. et al. [1]. [1] E. Morgado Jr., M. A. S. de Abreu, O. R. C. Pravia, B. A. Marinkovic, P. M. Jardim, F. C. Rizzo, A. S. Araújo, Solid State Sciences 8 (2006) 888.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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