Affiliations: Department of Mechanical Engineering, Ibaraki University, Ibaraki, Japan | Frontier Research Center for Applied Atomic Sciences, Ibaraki, Japan | International Apatite Co., Ltd, Tokyo, Japan
Note: [] Address for correspondence: K. Ozeki, Department of Mechanical Engineering, Ibaraki University, 4-12-1, Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan. Tel.: +81 294 38 5040; Fax: +81 294 38 5047; E-mail: ozeki@mx.ibaraki.ac.jp.
Abstract: Hydroxyapatite (HA) was coated onto a titanium substrate using radio frequency magnetron sputtering. The sputtered film was crystallized using a hydrothermal treatment. The films were observed using X-ray diffractometry, field emission scanning electron microscopy (FE-SEM) and scanning transmission electron microscopy (STEM) equipped with energy dispersive X-ray spectroscopy (EDX). It was observed that the surface of the hydrothermally-treated film was covered with globular particles. The FE-SEM observations indicated that these particles were composed of columnar grains with a grain size of 20–50 nm. In the STEM cross-sectional observation of the HA–Ti interface, HA crystalline phase regions were observed, in part, in the non-crystalline phase layer of the as-sputtered film. After the hydrothermal treatment, the HA layer crystallized; the HA crystallization proceeded to a distance of 30 nm above the titanium surface. From an EDX line scan analysis, the titanium oxide layer was not observed at the HA–Ti interface of the as-sputtered film; however, in the hydrothermally-treated film, the titanium oxide layer, with a 15 nm thickness, was observed between the mixing layer and the titanium substrate. The formation of titanium oxide at the HA–Ti interface would contribute to the adhesion improvement of the sputtered film following the hydrothermal treatment.
