THE STRUCTURE AND PROPERTIES OF NANOPOROUS ANODIC OXIDE FILMS ON TITANIUM ALUMINIDE

Abstract

Purpose. The paper presents a structural analysis of nanoporous oxide fi lms formed by anodizing γTiAl (Тi-40 wt. %Al) samples in fl uoride containing water and waterless electrolytes. Methods and methodology. Two groups of samples produced from (1) ingots and (2) sintered powder were used for anodizing. X-ray diffraction, X-ray electron spectroscopy, and scanning electron microscopy were used to analyse the structure of the fi lms. The band gap values of anodized powder samples were estimated based on their UV-vis absorption spectra. The reaction of degradation of methyl orange under UV-vis irradiation was used to examine the photocatalytic activity of anodized TiAl powder. Results. Anodizing performed under optimal conditions in a 10 % H2SO4+0.15 % HF water electrolyte for both groups of samples results in the formation of self-organized nanoporous fi lms of about 350 nm thickness with effective pore diameter = (70±10) nm. All the studied oxide fi lms are heterogeneous, consist mostly of TiO2 : Al2O3 in a ratio of approximately 1:1, and have an X-ray amorphous structure. The optical band gap value of anodized powders determined by their UV absorption was Eg~2.5 eV. It is much less than Eg of nanotubular titanium dioxide (Eg~3.4 eV). The study also found that the concentration of methyl orange decreases under visible light irradiation in the presence of anodized TiAl powder. Conclusion. Photocatalytic activity of the developed eterogeneous fi lms might be initiated by the visible light irradiation (λ~480-510 nm). In other words, the new composite “TiAl powder/TiO2-Al2O3 nanoporous oxide” exhibits activity under the visible light radiation which results in the photocatalytic degradation of methyl orange. The obtained results can be successfully used for the production of new powder nanomaterials which show photocatalytic activity under visible light irradiation

Keywords

• anodizing
• nanoporous
• oxide fi lms
• powder alloy
• titanium aluminide
• heterogeneous
• photocatalytic activity.