217 Proceedings of ICXRI 2010 International Conference on X-Rays & Related Techniques in Research & Industry June 9 – 10, 2010, Aseania Resort Langkawi, Malaysia ICXRI 2010 Preparation and Characterisation of TiO 2 Thick Films Fabricated by Anodic Oxidation in Sulphuric Acid H.Z. ABDULLAH and C.C. SORRELL Abstract - Anodic oxidation is an electrochemical method for the production of oxide films on metallic substrates. It involves the application of an electrical bias at relatively low currents while the substrate is immersed in an acid bath. The resultant oxide films can be very dense and stable, showing a variety of colours and microstructural characteristics. In the present work, thick films of the anatase and rutile polymorphs of TiO 2 were formed on high- purity Ti foil (50 μm thickness) using sulphuric acid solutions (1.5 M H 2 SO 4 ). The conditions of oxidation involved the application of potentials (5 to 350 V) and current densities (5 to 60 mA.cm -2 ) for 10 min at room temperature. The films were characterised using a digital photography, laser Raman microspectroscopy, and field emission scanning electron microscopy (FESEM). The thicknesses of the oxide films on Ti were measured using a thin film analyser based on optical spectroscopy principles. The phase formation, colours, thicknesses, and microstructures of the films depended strongly on the applied voltage and current density. At a standard bias of 150 V, single-phase anatase was observed to form on Ti at low current density (5 mA.cm - 2 ) but, at higher current densities (up to 60 mA.cm -2 ), increasing rutile formation was observed. Keywords: H. Z. Abdullah is with the Department of Materials and Design Engineering, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, Parit Raja, 86400 Batu Pahat, Johor,Malaysia (e-mail: hasan@uthm.edu.my). C. C. Sorrell, is with School of Materials Science and Engineering, University of New South Wales, NSW 2052, Australia.(e-mail: c.sorrell@unsw.edu.au). I. INTRODUCTION Titanium and anodised titanium are used in a range of applications, including aerospace and chemical industries; they are also important in the biological and dental fields [1,2]. It is well known that titanium invariably has a nanoscale (1.5-10 nm thickness) passivating layer on the surface, which forms spontaneously upon exposure to air [3]. This layer typically consists of oxides and hydroxides that form from reactions between the metal substrate and humid air [4]. A comparable protective layer can be formed under controlled conditions using anodic oxidation, which is a well established method of modifying the surface microstructure and the properties of titanium. This electrochemical approach for protective layer formation can be used to produce much thicker layers on titanium (up to several hundred microns thick) and these layers may be amorphous or crystalline, dense or porous, depending on the electrolyte, its concentration, and applied potential [5]. The most commonly used electrolytes are dilute solutions of sulphuric acids at low (>100 V) or high (~100-250 V) potentials. II. METHODS AND PROCEDURES High-purity Ti foils of dimensions 25 mm x 10 mm x 0.5 mm were wet hand-polished using 1200 grit (~1 μm) abrasive paper, followed by immersion in an ultrasonic bath with acetone, rinsing with distilled water, and drying with compressed air. Anodic oxidation was done in an electrochemical cell containing ~0.4 L aqueous solutions of H 2 SO 4 (Merck, 98 wt%) at ~25°C [6]. These solutions and the associated experimental parameters are shown in Table 1. The anode and cathode were Ti foil and the anodising was done with a programmable power supply (EC2000P, E-