XVIII IMEKO WORLD CONGRESS Metrology for a Sustainable Development September, 17 – 22, 2006, Rio de Janeiro, Brazil TITANIUM OXIDE FILMS PRODUCED BY MICRO-ARC OXIDATION FOR HIGH PERFORMANCE TITANIUM IMPLANTS J.T. Filho 1 ,2* , L.R. Lidízio 1 , L.A. Sena 1 , J.C. Damasceno 1 and C.A. Achete 1,2 1 Materials Metrology Division, National Institute of Metrology, Standardization and Industrial Quality, RJ, Brazil 2 Department of Metallurgy and Materials Engineering, Federal University of Rio de Janeiro, RJ, Brazil *jtfilho@inmetro.gov.br Abstract: The growth of titanium oxide layer on titanium surface by the micro-arc oxidation technique was investigated. Ca(CH 3 COO) 2 (0.3M), Na 2 CO 3 (0.6M) and Na 2 HPO 4 (0.1M) solutions were employed as electrolytes. SEM and EDS microanalysis were used for morphology, composition characterization and low-angle X-ray diffraction to describe titanium oxide crystallographic orientation. TiO 2 films formed by using 0.3M Ca(CH 3 COO) 2 and 0.1M Na 2 HPO 4 solutions showed a porous, homogeneous surface structure, with presence of phosphorous and after an hydrothermical treatment using a Ca(OH) 2 suspension during 24h at 60ºC was observed phosphorous and calcium. Keywords: titanium oxide, micro-arc oxidation, titanium implants. 1. INTRODUCTION Titanium and titanium alloys are currently used as base materials for surgical implants in biomedicine as for example in artificial joint replacements, maxillofacial reconstruction, audiological applications or dental implants. Success has been related to their good mechanical properties and excellent biocompatibility [1]. However, alternative approaches to produce bioactive, porous and nano- crystallized titanium implant surfaces are being studied [2]. An attractive option is to induce the growth of a natural, bio- inert titanium oxide film [3]. The micro-arc oxidation (MAO) is a particular interesting process to produce such oxide layers due its versatility and cost-effectivity [4]. This technique can electrochemically produce porous and uniformly coated oxides on metal surfaces. In order to produce high performance implants it is very important to measure some film properties such as thickness, chemical composition and surface morphology. The morphology and pore configuration of titanium oxide films seems to be related to its biological performance [5]. The presence of the allotropic phase anatase in the oxide structure is also important because it is responsible for the biocompatibility of the material [6]. However, the anatase is a meta-stable phase, so that the synthesis conditions must be carefully controlled. Production of implants with adequate surface finishing is extremely important for biocompatibility and osseointegration, contributing for a high quality product. In addition, the development of reference substrates that induce specific cellular responses bridge the gap between fundamental knowledge and the product development needs in industry, specially in developing measurement methodologies and reference materials to asses interactions in complex systems of living cells with synthetic materials. In this work, pure titanium samples were coated using MAO to produce TiO 2 layers. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectrometry (EDS) microanalysis were used respectively for morphology and composition characterization. X-ray diffraction was used for crystallographic characterization of titanium oxide. 2. MATERIALS AND METHODS Pure titanium (ASTM grade 2) samples of 1 x 1 cm 2 and 5 x 3 cm 2 were carefully grounded in SiC paper, polished and submitted to the electrochemical treatment using two configurations of the MAO process to produce porous TiO 2 layers. In the first experimental setup, a very simple 60Hz, AC power supply was used to apply 140 V between the sample and a pure Pt electrode during approximately 3 minutes for each sample. Ca(CH 3 COO) 2 (0.3M) and Na 2 CO 3 (0.6M) solutions were used separately as electrolytes. In another MAO experimental setup a 60Hz, pulsed DC power supply was used to apply 110 V between the sample and a stainless steel cube during approximately 10 minutes for each sample. In this case, a Na 2 HPO 4 (0.1M) solution was used as electrolyte and a stainless steel cube as counter- electrode. Generation of sparks was observed in all experiments. An hydrothermical treatment using a Ca(OH) 2 suspension during 24h at 60ºC was employed on samples anodized with phosphate solution to produce a surface rich in calcium and phosphorous. The presence of calcium and phosphorous on sample surface can provide biologic advantages for surgical and odontological applications [7]. SEM and EDS microanalysis were employed for morphology and composition characterization, respectively.