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최윤일,Kensuke Kuroda,MasazumiOkido 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5
The effects of solution temperature on the initial corrosion characteristics of wrought AZ61 and die-cast AZ91D Mg alloys in 0.1M NaCl were analyzed. Systematic studies indicate that AZ91D exhibits higher corrosion resistance than AZ61 at room temperature. However, at high temperatures of around 55 °C, we observed contradictory corrosion behavior, as demonstrated by cyclic corrosion tests and electrochemical tests including potentiodynamic polarization, potentiostatic polarization, and elecrochemical impedance spectroscopy. As a result, AZ61 rather showed higher corrosion resistance from the point of view of pit initiation during the immersion at 55 °C resulting from the strengthening of surface passivation. These results can be attributed to the microstructure of AZ61 which contains sub-micron scale β-phase particles dispersed effectively within the α-Mg grains whereas AZ91D has many α-Mg that do not containing any β-phases.
Surface Modification on Titanium Substrate for Osteoconductive Properties
Ryoichi Ichino,Kensuke Kuroda,Masazumi Okido 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
Many kinds of surface modification by wet processes for osteoconductive properties were performed on Ti substrate. Hydroxyapatite, titania, and carbonate apatite ceramics are coated on Ti substrate. Composite coatings with them or with collagen were also coated on Ti substrate. HAp coatings with different morphology were fabricated by wet processes, and those with needle-like morphology had the highest osteoconductivity by in vivo evaluation among the HAp coated Ti samples. The osteoconductivity also improved by adding effective amount of collagen in the HAp coatings. Titania coatings prepared by anodizing also had good osteoconductivities.
Hisao Suzuki,Kensuke Kuroda,Masazumi Okido,Ryoichi Ichino 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
To improve the anti-corrosion property of AZ31 Mg alloy, in the present study we tried to form thin films using electrodeposition, anodizing and thermal oxidation. The flake-like hydroxyapatite (HAp) film was formed by electrodeposition in a solution containing Ca and P ions, the MgO film indicating a white color by anodizing in a solution of NaOH, and the MgO film indicating a interference color by thermal oxidation in air, respectively. From the results of anti-corrosion measurements, we found that these films had the anti-corrosion property in simulated body fluid (SBF).
Surface Treatment on Titanium for the Fabrication of Bone-Compatible Materials
Dai Yamamoto,Kensuke Kuroda,Ryoichi Ichino,Masazumi Okido 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
The aim of this study was to investigate important factors that influence on the osteoconductivity of TiO₂. TiO₂ coatings were fabricated on titanium using anodizing with their surface roughness controlled at micron-level to evaluate the influence of surface roughness. The influence of oxidizing process was also discussed by comparing wetprocess to dry-process; anodizing and high temperature oxidation. In conclusion, TiO₂ coatings improved the osteoconductivity of Ti substrates. TiO₂ coatings indicated high osteoconductivity only when Ra < 0.3 ㎛. Moreover, wet-process was better than dry-process to form osteoconductive TiO₂ coating on titanium substrate.
Kim, Sangjae,Matsunaga, Naoya,Kuroda, Kensuke,Okido, Masazumi The Korean Electrochemical Society 2018 Journal of electrochemical science and technology Vol.9 No.1
Aluminum electrodeposition was carried out in dimethylsulfone ($DMSO_2$) baths containing 6.2-28.3 mol% $AlCl_3$ at 403 K. The electrochemically active species for Al electrodeposition in $DMSO_2$ baths were investigated. Electrochemical behavior of the electrolyte and the deposition mechanism were studied via cyclic voltammetry (CV). Properties of the deposits were assessed by scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction. In addition, structures of the ionic complexes formed with aluminum in the bath were characterized by $^{27}Al$ nuclear magnetic resonance (NMR) spectroscopy. NMR spectra revealed that all baths contained two ionic species: $AlCl_4{^-}$ and $[Al(DMSO_2)_3]^{3+}$. Al electrodeposited when the $[Al(DMSO_2)_3]^{3+}$ concentration was the highest (23.3 mol% $AlCl_3$) exhibited fine grain sizes, relatively smooth surfaces, and high purities.