Abstract
In the present work, titanium dioxide (TiO2) coatings were deposited on wood surfaces by an atmospheric pressure plasma jet using titanium tetraisopropoxide (TTIP) as a precursor to improve the wood’s stability against ultraviolet (UV) light and its moisture resistance capability. The surface topology and morphology of the wood specimens were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface chemical compositions of the specimens were characterized by X-ray photoelectron spectroscopy (XPS) and by Fourier transform infrared (FTIR) spectroscopy. The wettability of the coated wood was investigated by measuring the sessile contact angle. SEM and AFM showed the presence of small globules of TiO2 with some areas agglomerated on the coated wood surface. The coated surface roughness increased with increasing deposition time. FTIR analysis showed the existence of a Ti–O–Ti band at 800–400 cm−1 on the coated wood surfaces. The results obtained from FTIR were confirmed by XPS measurements. The hydrophilic wood surfaces were transformed to become hydrophobic or superhydrophobic after coating with TiO2, depending on the deposition parameters. The changes of colour during UV-exposure for both uncoated and coated wood specimens were measured using the CIELab colour system. The TiO2 coated wood became more resistant to colour change after UV radiation exposure than did untreated wood.
Highlights
Wood is an organic material, consisting mainly of three compounds: cellulose, lignin and hemicelluloses [1]
scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that TiO2 thin films have been successfully deposited on wood surfaces using a plasma polymerization method by atmospheric pressure plasma jet (APPJ)
The analysis of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectra of the coated and uncoated wood demonstrates that the wood surface was covered with TiO2 particles
Summary
Wood is an organic material, consisting mainly of three compounds: cellulose, lignin and hemicelluloses [1]. When wood materials are used in outdoor applications, they are generally subjected to many weathering factors that affect their aesthetic appearance and mechanical performance, such as moisture, sunlight (especially ultraviolet (UV) radiation), and temperature (heat/cold). The untreated wood surface can be affected by the influence of sunlight in combination with rain, which leads to an initial discolouration followed by the destruction of mechanical and physical properties. Lignin, which is responsible for the characteristic colour changes, is the component most sensitive to UV light, since it undergoes structural changes in the presence of solar UV light and leads to discolouration and degradation of wood [2]. The discolouration of untreated wood surfaces is a serious aesthetic problem for many outdoor applications of wood such as garden furniture and facades [2,3]. In order to improve the colour stability of wood, it is necessary to deposit thin protective barrier films on wood surfaces
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