Papers by Author: Takamasa Onoki

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Authors: Takamasa Onoki, Xin Min Wang, Sheng Li Zhu, Yasuto Hoshikawa, Naota Sugiyama, Masaru Akao, Eiichi Yasuda, Masahiro Yoshimura, Akihisa Inoue
Abstract: Apatite forming and bonding ability of Ti based bulk metallic glass ((Ti0.40Zr0.10Cu0.36Pd0.14)99Ca1: BMG) were investigated as a new type of biomaterials. Powder mixture of CaHPO4・2H2O and Ca(OH)2 and the BMG disks were treated with autoclave for hydrothermal hot-pressing simultaneously (150°C, 40MPa). And then the BMG disks were soaked in simulated body fluid (SBF, Kokubo solution). Apatite were deposited and covered on the surface of the BMG. It was firstly demonstrated that surface of Ti based bulk metallic glass could be revealed apatite forming ability.
Authors: Takamasa Onoki, Kazuyuki Hosoi, Toshiyuki Hashida
Authors: Takamasa Onoki, Toshiyuki Hashida
Abstract: A new hydrothermal method is proposed which enables us to prepare thin hydroxyapatite (HA) ceramic coatings on Ti substrates with a curved surface at low temperatures. The method uses double layered capsules in order to produce a suitable hydrothermal condition; the inner capsule encapsulates the coating materials and a Ti substrate, and the outer capsule is subjected to isostatic pressing under the hydrothermal condition. In this study, it is demonstrated that a pure HA ceramic layer with the thickness of 50 µm could be coated to a Ti cylindrical rod at the low temperature as low as 135°C under the confining pressure of 40 MPa. Pull-out tests were conducted to obtain an estimate for the adhesion properties of the HA coating prepared by the double layered capsule method. The shear strength obtained from the pull-out tests was in the range of 4.0-5.5 MPa. It was also shown that the crack propagation occurred within the HA coating layer, not along the HA/Ti interface in the pull-out tests.
Authors: Yasuto Hoshikawa, Eiichi Yasuda, Takamasa Onoki, Masaru Akao, Yasuhiro Tanabe
Abstract: Titanium (Ti) and its alloy have sufficient mechanical properties to be utilized as artificial hip joints and article teeth. However, they have no bioactivity. In this work, we prepared bioactive coatings on Ti by sol-gel techniques. The coatings had a double layered structure. Underlying layer was methylsiloxane (MS) consisted of methyltriethoxysilane (MTES). Top layer was MS-Ca-Nb-Ta hybrid composed of MTES, calcium nitrate tetrahydrate, pentaethoxy-niobium and pentaethoxy-tantalum. The coating exhibited formation of bone-like apatite in SBF immersion test. Adhesive strength of the coating was found to be 1.8 MPa.
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