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Thermo-physical properties of thin films composed of anatase TiO2 nanofibers

✍ Scribed by X. Feng; X. Wang; X. Chen; Y. Yue


Publisher
Elsevier Science
Year
2011
Tongue
English
Weight
886 KB
Volume
59
Category
Article
ISSN
1359-6454

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✦ Synopsis


In this paper, anatase titanium dioxide (TiO 2 ) thin films $60 lm thick are fabricated using the electrospinning technique. The prepared thin films are composed of interconnected anatase TiO 2 nanofibers. The transient electro-thermal technique, combined with a temperature-resistance calibration procedure, provides a full spectrum study which examines the relationship between the film's thermal diffusivity, density and thermal conductivity. It is found that the annealing process significantly reduces the thermal diffusivity of the sample from 3.73 Γ‚ 10 -5 m 2 s Γ€1 to the order of 10 -6 m 2 s Γ€1 . The effective thermal diffusivity, conductivity and density of the films are 1.35-3.52 Γ‚ 10 -6 m 2 s Γ€1 , 0.06-0.36 W m Γ€1 K Γ€1 and 25.8-373 kg m Γ€3 , respectively. These values are about one order of magnitude or more lower than the bulk property values. This difference is attributed to the loose interior structure and large concentration of vacancies. A microscale physical model is designed to explore the intrinsic thermal conductivity of the discrete TiO 2 nanofibers that compose the films. The calculated intrinsic thermal conductivity of the TiO 2 nanofibers varies from 4.67 to 12.2 W m Γ€1 K Γ€1 , which is comparable with the bulk thermal conductivity of 8.5 W m Γ€1 K Γ€1 . The phonon mean free path calculation demonstrates that the nanofiber size has a negligible impact on the phonon transport. The major restriction on the heat transfer originates from the crystalline structure defect.


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