Article
Chemistry, Multidisciplinary
Akari Hiji, Takao Hanawa, Taishi Yokoi, Peng Chen, Maki Ashida, Masakazu Kawashita
Summary: This study utilized X-ray photoelectron spectroscopy to characterize the mechanism of calcium phosphate formation on commercially pure titanium, revealing that different crystal facets of rutile TiO2 have varying abilities to adsorb and incorporate calcium and phosphate ions, with the adsorption rate of phosphate ions changing over time.
Article
Materials Science, Multidisciplinary
Hla Htoot Wai Cho, Atsushi Takaichi, Yuka Kajima, Hein Linn Htat, Nuttaphon Kittikundecha, Takao Hanawa, Noriyuki Wakabayashi
Summary: This study found that a high cooling rate during post-heat treatment can reduce the grain and precipitate sizes of CoCrMo alloys, resulting in improved ductility and fatigue life.
Article
Materials Science, Multidisciplinary
Oktay Yigit, Burak Dikici, Mosab Kaseem, Masaaki Nakai, Mitsuo Niinomi
Summary: This work investigated the formation of a hybrid composite coating composed of strontium-doped hydroxyapatite (HA) and graphene oxide (GO) on the surface of beta-type TiNbTaZr (TNTZ) alloy using a green hydrothermal method. The addition of GO resulted in a decrease in the crystallinity of the HA/Sr coating and the formation of dense homogeneous nanocrystalline structures. Electrochemical measurements demonstrated that the composite coating prepared from a solution with 4.5 wt% GO exhibited the lowest corrosion density and the highest polarization resistance, indicating its potential as a candidate material in orthopedic applications.
JOURNAL OF MATERIALS RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
Seong-Cheol Kim, Takao Hanawa, Tomoyo Manaka, Hiroaki Tsuchiya, Shinji Fujimoto
Summary: This study evaluated the band structures and band gap energies of passive films formed on titanium in simulated bioliquids. The polarization of titanium and the composition of the solution had an impact on the band structure of the passive film. The passive film on titanium exhibited n-type semiconductor characteristics with two layers, where the inner layer had a larger band gap energy and the outer layer had a smaller band gap energy. Calcium phosphate and hydroxyl groups also influenced the band gap energy of the passive film.
SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS
(2022)
Article
Chemistry, Physical
Yuzuki Eda, Tomoyo Manaka, Takao Hanawa, Peng Chen, Maki Ashida, Kazuhiko Noda
Summary: Titanium is always covered by a thin passive film, and the valence band spectra obtained by XPS are the combination of passive film and metallic Ti substrate. In this study, the passive film on Ti was found to consist mainly of a very thin TiO2 layer and exhibits the properties of an n-type semiconductor.
SURFACE AND INTERFACE ANALYSIS
(2022)
Article
Metallurgy & Metallurgical Engineering
Qiang Li, Qi Huang, Jun-jie Li, Qian-feng He, Masaaki Nakai, Ke Zhang, Mitsuo Niinomi, Kenta Yamanaka, Akihiko Chiba, Takayoshi Nakano
Summary: In this study, Zr was added to develop low elastic modulus and high strength beta-Ti alloys for biomedical applications. The results showed that Zr and Fe had a significant solid-solution strengthening effect on the alloys, resulting in high yield and ultimate tensile strengths. Additionally, twinning in the deformed alloys contributed to both strength and plasticity.
TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA
(2022)
Article
Materials Science, Multidisciplinary
Norain Binti Abdullah, Daisuke Miyazaki, Ei Yamamoto, Kosuke Ueki, Masaaki Nakai
Summary: This study investigated the effect of a low-rigidity titanium alloy plate on bone formation during the early stage of fracture healing. The results showed that low-rigidity titanium alloys could improve bone formation, suggesting potential clinical applications. The use of TNTZ implant plate resulted in a smaller and harder callus compared to the Ti-64 implant plate.
JOURNAL OF MATERIALS RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
Takao Hanawa
Summary: Among metals, Ti and its alloys exhibit excellent biocompatibility due to factors such as corrosion resistance, surface charge balance, low electrostatic force, and optimal reactivity. The passive oxide film of Ti plays a crucial role in achieving the optimal balance between high corrosion resistance and appropriate reactivity, leading to its excellent biocompatibility.
SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS
(2022)
Article
Nanoscience & Nanotechnology
Yuka Kajima, Atsushi Takaichi, Hein Linn Htata, Takao Hanawa, Noriyuki Wakabayashi
Summary: The influence of heat treatment time on the recrystallization process in Co-Cr-Mo alloys fabricated by selective laser melting (SLM) was evaluated. The results showed that when the heat treatment time was less than 45 minutes, the yield strength decreased and elongation increased. However, heat treatments longer than 60 minutes resulted in coarse grains and precipitates along the grain boundaries, which decreased the strength and ductility of the alloys.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Chemistry, Physical
Satoshi Omori, Arata Ebihara, Keiko Hirano, Yuka Kasuga, Hayate Unno, Taro Nakatsukasa, Shunsuke Kimura, Keiichiro Maki, Takao Hanawa, Takashi Okiji
Summary: This study evaluated the influence of various rotational modes on the torque/force production and shaping ability of ProTaper Universal and ProTaper Gold nickel-titanium instruments. The results showed that R240/120 and OTR reduced the screw-in force in ProTaper Gold and improved the canal centering ability in ProTaper Universal.
Article
Nanoscience & Nanotechnology
Shunsei Takeda, Kosuke Ueki, Kyosuke Ueda, Masaaki Nakai, Takayoshi Nakano, Takayuki Narushima
Summary: This study investigates the microstructure and mechanical properties changes of the Co-20Cr-15W-10Ni alloy tube, which is used as a balloon-expandable stent after heat treatment. It is the first report on improving mechanical properties through microstructure control in CCWN alloy tubes. Optimized heat treatment conditions are proposed for the development of small-diameter stents. The strength and plastic elongation of the alloy tube increased with decreasing grain size.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Crystallography
Hakan Yilmazer, Ihsan Caha, Burak Dikici, Fatih Toptan, Murat Isik, Mitsuo Niinomi, Masaaki Nakai, Alexandra Cruz Alves
Summary: This study investigated the influence of high-pressure torsion (HPT) processing parameters and solution treatment (ST) on the corrosion and tribocorrosion behavior of CoCrMo (CCM) alloys for potential biomedical applications. The corrosion behavior was evaluated using potentiodynamic scanning and electrochemical impedance spectroscopy tests, while tribocorrosion tests were conducted in a reciprocating ball-on-plate tribometer. The results showed that HPT and ST processes had minimal effect on the corrosion resistance of the samples, but ST-treated samples exhibited higher material loss during sliding in standard phosphate-buffered saline at body temperature compared to HPT-treated samples.
Article
Materials Science, Multidisciplinary
Kosuke Ueki, Ryo Hirano, Masaaki Nakai
Summary: The development of an Fe-Mn-Mg alloy by MA and SPS was reported for the first time to improve the corrosion rate of Fe-based alloys for biodegradable materials. The 10Mg alloy exhibited the highest compressive strength and a lower corrosion rate compared to the 0Mg alloy.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Masaaki Nakai, Kengo Narita, Koichi Kobayashi, Keisuke Sasagawa, Mitsuo Niinomi, Kazuhiro Hasegawa
Summary: This paper introduces the concept and fabrication process of titanium alloy rods for spinal fixation. The rod for the lower side of the lumbar vertebra is strengthened, while the rod for the upper side has low stiffness. Finite element analysis reveals that a rod with partially lowered Young's modulus has higher flexibility and fixity. Ti-29Nb-13Ta-4.6Zr alloys with different oxygen contents were used to fabricate rods with different Young's moduli, and the aging and induction heating treatments were utilized to obtain desired properties.
MATERIALS TRANSACTIONS
(2023)
Article
Engineering, Mechanical
Norain Binti Abdullah, Daisuke Miyazaki, Ei Yamamoto, Kosuke Ueki, Masaaki Nakai
Summary: This study investigates the effect of titanium plate stiffness on bone formation during the early stage of healing in rabbit femurs. It is found that an overly flexible fixation system results in excessive callus formation and delayed union. Suitable implant characteristics can enhance bone healing and improve bone properties such as hardness.
MECHANICAL ENGINEERING JOURNAL
(2022)
