Preparation and Characterisation of TiO2 Thick Films by Gel Oxidation
Titanium foils were subjected to soaking in NaOH aqueous solutions in the concentration range 0.1 M to 10.0 M, followed by oxidation in the range 400°C to 800°C. The samples were characterised by glancing angle X-ray diffraction and Raman microspectroscopy. The results showed that the corrosion by NaOH solution resulted in: • Partial dissolution of the anatase passive oxidation layer • Partial dissolution of the underlying titanium foil • Formation of a TiO2-rich sodium titanate hydrogel (Na2O·mTiO2·nH2O) The subsequent oxidation of the hydrogel on the titanium substrate resulted in: • Recrystallisation of sodium titanate (Na2O·5TiO2) • Recrystallisation of the rutile polymorph of TiO2 The concentration of the NaOH solution was important in that it affected the dissolution or retention of the anatase passive oxidation layer, where lower concentrations (0.5 M and 1.0 M NaOH) resulted in a lower degree of dissolution in comparison to where higher concentrations (5.0 M and 10.0 M NaOH) were used.
Young Won Chang, Nack J. Kim and Chong Soo Lee
H.Z. Abdullah and C. C. Sorrell, "Preparation and Characterisation of TiO2 Thick Films by Gel Oxidation", Materials Science Forum, Vols. 561-565, pp. 2167-2170, 2007