TITLE:
Impact of Annealing Treatment on the Behaviour of Titanium Dioxide Nanotube Layers
AUTHORS:
Marie Siampiringue, Christophe Massard, Eric Caudron, Yves Sibaud, Mohammed Sarakha, Komla Oscar Awitor
KEYWORDS:
Titanium Dioxide Nanotubes, In-Situ X-Ray Diffraction, Annealing Treatment, Photo-Degradation
JOURNAL NAME:
Journal of Biomaterials and Nanobiotechnology,
Vol.7 No.3,
June
28,
2016
ABSTRACT: In this work, we study
the influence of the annealing treatment on the behaviour of titanium dioxide
nanotube layers. The heat treatment protocol is actually the key parameter to
induce stable oxide layers and needs to be better understood. Nanotube layers
were prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric
acid solution during 20 minutes and then annealed in air atmosphere. In-situ X-ray diffraction analysis,
coupled with thermogravimetry, gives us an inside on the oxidation behaviour of
titanium dioxide nanotube layers compared to bulk reference samples. Structural
studies were performed at 700°C for 12 h in order to follow the time
consequences on the oxidation of the material, in sufficient stability
conditions. In-situ XRD brought to light that the amorphous oxide layer induced by
anodization is responsible for the simultaneous growths of anatase and rutile phase
during the first 30 minutes of annealing while the bulk sample oxidation leads
to the nucleation of a small amount of anatase TiO2. The initial
amorphous oxide layer created by anodization is also responsible for the delay
in crystallization compared to the bulk sample. Thermogravimetric analysis
exhibits parabolic shape of the mass gain for both anodized and bulk sample; this
kinetics is caused by the formation of a rutile external protective layer, as
depicted by the associated in-situ XRD
diffractograms. We recorded that titanium dioxide nanotube layers exhibit a
lower mean mass gain than the bulk, because of the presence of an initial
amorphous oxide layer on anodized samples. In-situ XRD results also provide accurate information concerning the sub-layers
behavior during the annealing treatment for the bulk and nanostructured layer. Anatase
crystallites are mainly localized at the interface oxide layer-metal and the
rutile is at the external interface. Sample surface topography was characterized
using scanning electron microscopy (SEM). As a probe of the photoactivity of
the annealed TiO2 nanotube layers, degradation of an acid orange 7
(AO7) dye solution and 4-chlorophenol under UV irradiation (at 365 nm) were
performed. Such titanium dioxide nanotube layers show an efficient
photocatalytic activity and the analytical results confirm the degradation
mechanism of the 4-chlorophenol reported elsewhere.