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KMID : 0362220130400020103
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Journal of The Korean Research Society for Dental Materials
2013 Volume.40 No. 2 p.103 ~ p.110
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Surface characteristics of oxide films on titanium alloys formed by AC-type microarc oxidation combined with hydrothermal treatment
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Min Kyung-Kwan
Lee Dong-Soo
Lim Hoi-Jeong
Park Young-Jun
Song Ho-June
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Abstract
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The purpose of this study was to develop a surface modification method of titanium alloys using AC-type microarc oxidation (MAO) and hydrothermal (HT) treatments. CP-Ti (Ti2), Ti-6Al-4v (Ti64), and Ti-6Al-7Nb (Ti67) metals were used for this study. Disk-shaped as-received metals were wet ground with up to 1200 grit SiC paper, and those were microarc oxidized using AC-type high power supply in electrolyte containing 0.02M β-g1ycerophosphoric acid disodium salt pentahydrate (β-GP) and 0.2M calcium acetate monohydrate for 120 s. Frequency, duty ratio and maximum voltage of AC type-rectangular electric pulses was 500 ㎐, 70% and 200 V, respectively. The MAO-treated groups were hydrothermally treated in alkaline aqueous solution (pH 11.5) containing 0.002M β-GP at 190 ℃ for 8 hours. Surface morphology, chemical compositions, and crystalline structure of oxide films were examined by scanning electron microscopy, X-ray diffractometer, and energy dispersive X-ray analyzer. A porous surface with homogeneously distributed pores approximately 1 ㎛ dia was observed for Ti2-MAO group, and particular structures and variously sized pores under 1 ㎛ dia were observed for Ti64-MAO and Ti67-MAO groups. An anatase TiO₂ (ATO) structure was dominant for Ti2-MAO groups while rutile TiO₂ (RTO) and CaTiO₃ (CTO) structures were observed for Ti64-MAO and Ti67-MAO groups. After HT-treatment, hydroxyapatite (HAp) crystalline structure was observed for all groups. Nanorods were observed on the porous surface and ATO XRD peak intensity increased for HT-treated specimens. On contrary to the formation of only TiO₂ by DC-type MAO treatment, CTO crystallites were concurrently formed by AC-type MAO technique. The RTO crystallites were transformed to ATO, and CTO crystallites were converted to HAp and ATO by HT-treatment. This study showed that the oxide films on titanium alloys fabricated by MAO technique and HT treatment had the desirable properties for improved bioactivity, such as having porous surface and nano-sized HA crystalline particles. Therefore, it could be used as a promising surface modification method for developing titanium implant.
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KEYWORD
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Titanium, surface modification, microarc oxidation, hydrothermal treatment, hydroxyapatite, nanorods
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