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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.
An Electrochemical Study of Cathodic Protection of Steel Used for Marine Structures
Kim, Seong-Jong,Okido, Masazumi,Moon, Kyung-Man 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.3
Impressed current cathodic protection can result in hydrogen embrittlement, which can cause trouble with high-strength steels, particularly at welds. Therefore, the limiting for hydrogen embrittlement should be examined in detail as a function of the cathodic protection potential. This study investigated the effects of post-weld heat treatment (PWHT) on marine structural steels from an electrochemical viewpoint. In addition, the slow strain rate test (SSRT) was used to investigate both the electrochemical and mechanical effects of PWHT on impressed current cathodic protection. According to the SSRT, the optimum cathodic protection potential was 700 mV [with a saturated calomel electrode (SCE)]. SEM fractography analysis showed that the fracture morphology at an applied cathodic protection potential of-770-850 mV (SCE) was a dimpled pattern with ductile fractures, while a transgranular pattern was seen at potentials below-875 mV (SCE). Therefore, the cathodic protection potential range should be-770~-850 mV (SCE).
The Electrochemical Properties and Mechanism of Formation of Anodic Oxide Films on Mg-Al Alloys
Kim, Seong-Jong,Okido, Masazumi Korean Chemical Society 2003 Bulletin of the Korean Chemical Society Vol.24 No.7
The electrochemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH)₂ in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH)₂ was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in α phase, which had a lower Al content. In the anodic polarization test in 0.017 mol·$dm^{-3}$ NaCl and 0.1 mol·$dm^{-3}$ Na₂SO₄ at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the α phase is a non-compacted film. The anodic film on the α phase at 30 min was a compact film as compared with that at 10 min.