Fabrication of TiO2 Films by Anodisation of Ti-Foils in Oxalic Acid
TiO2 thin films were fabricated on titanium substrates by the anodisation method. Different anodisation parameters, such as anodising voltage, electrolyte concentration and anodising time, have been investigated in order to explore their effects on the photocatalytic performance of the films. Regarding the effect of anodisation voltage, GAXRD analysis showed that anatase was the only oxide phase in the samples anodised at voltages from 100 to 200 V (at 10 min for 0.2 M oxalic acid and current density 60 mA / cm^2). Data from Raman showed that anatase was present in all films and its intensity increased with increasing voltage. FESEM images showed that, at anodisation voltages of 10-20 V, a flat layer was formed, which became rougher with increasing voltage in the range 50-100 V. With further increase in the voltage to 120-200 V, increased porosity resulted. Transmission electron microscopy (TEM) confirmed an increase in film thickness with increasing anodisation voltage. The photocatalytic performance showed that the activities increased with increasing anodisation voltage and hence thickness and roughness. With regard to the effect of varying electrolyte concentration, mineralogical analysis showed that anatase was the only phase present in the films (at 10 min for 0.2, 0.4 and 0.6 M oxalic acid at 120 V and current density 60 mA / cm^2). However, there was an increase in the intensity of the Raman anatase peaks with increasing electrolyte concentration, which was confirmed by TEM analysis, which showed that the film thickness increased with increasing electrolyte concentration. FESEM analysis showed that the areal density of the pores and cracks increased with increasing electrolyte concentration. The photocatalytic performance showed that the activities with increasing electrolyte concentration. With regard to the effect of anodising time, GAXRD and Raman analysis showed that anatase was the only phase in all the films fabricated at different anodisation times (5, 10 and 20 minfor 0.2 M oxalic acid at 200 V and current density 60 mA / cm^2). Further, the data showed that anatase peaks for both types of analysis increased with increasing anodising time. FESEM analysis showed that the diameter and areal density of the pores increased with increasing anodising time formed. Correspondingly there was an increase in the photocatalytic performance with increasing anodising time for the reasons mentioned above.
Titanium., Oxalic acid., Anodisation., Titanium dioxide., Anatase., Rutile.
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