Sungmo Moon

Immobilization of pamidronic acids on the nanotube surface of titanium discs and their interaction with bone cells

Self-assembled layers of vertically aligned titanium nanotubes were fabricated on a Ti disc by anodization. Pamidronic acids (PDAs) were then immobilized on the nanotube surface to improve osseointegration. Wide-angle X-ray diffraction, X-ray photoelectron microscopy, and scanning electron microscopy were employed to characterize the structure and morphology of the PDA-immobilized TiO2 nanotubes. The in vitro behavior of osteoblast and osteoclast cells cultured on an unmodified and surface-modified Ti disc was examined in terms of cell adhesion, proliferation, and differentiation. Osteoblast adhesion, proliferation, and differentiation were improved substantially by the topography of the TiO2 nanotubes, producing an interlocked cell structure. PDA immobilized on the TiO2 nanotube surface suppressed the viability of the osteoclasts and reduced their bone resorption activity.

Faradaic Reactions and Their Effects on Dissolution of the Natural Oxide Film on Pure Aluminum During Cathodic Polarization in Aqueous Solutions

Abstract Faradaic reactions and their effects on dissolution of the natural oxide film on pure aluminum during cathodic polarization were investigated in aqueous 0.5 M sulfuric acid (H2SO4) and 0.5...

Effects of Hydroxide and Silicate ions on the Plasma Electrolytic Oxidation of AZ31 Mg Alloy

Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was studied in aqueous solutions containing various concentrations of hydroxide ion (OH ? ) and silicate ion (SiO 3 2? ) by voltage-time curves, and corrosion resistance of the PEO film-covered specimen was investigated by immersion test in 0.5 M NaCl solution. From the analyses of the voltage-time curves, it is suggested that two different types of anions are essentially needed for the formation of PEO films on AZ31 Mg alloy: film formation agent and local film breakdown agent. SiO 3 2? ion acts only as a film formation agent but OH - ion acts not only as a film formation agent but also film breakdown agent. The PEO films prepared on AZ31 Mg alloy in alkaline silicate solution showed very good corrosion resistance without any pitting or filiform corrosions up to 480 h of immersion in 0.5 M NaCl.

Formation Behavior of Anodic Oxide Films on Al7075 Alloy in Sulfuric Acid Solution

Dongjin Metal.Co., Ltd(Received July 9, 2014 ; revised August 4, 2014 ; accepted August 4, 2014)AbstractThe present work is concerned with the formation behavior of anodic oxide films on Al7075 alloy undera galvanostatic condition in 20 vol.% sulfuric acid solution. The formation behaviour of anodic oxide filmswas studied by the analyses of voltage-time curves and observations of colors, morphologies and thicknessesof anodic films with anodization time. Hardness of the anodic oxide films was also measured with anodizationtime and at different positions in the anodic films. Six different stages were observed with anodiziation time: barrier layer formation (stage I), pore formation (stage II), growth of porous films (stage III), abnormalrapid oxide growth (stage IV), growth of non-uniform oxide films (stage V) and breakdown of the thickoxide films under high anodic voltages (stage VI). Hardness of the anodic oxide films appeared to decreasewith increasing anodization time and with the position towards the outer surface. This work provides usefulinformation about the thickness, uniformity, imperfections and hardness distribution of the anodic oxide filmsformed on Al7075 alloy in sulfuric acid solution.

Formation of Anodic Oxide Films on As-Cast and Machined Surfaces of Al-Si-Cu Casting Alloy

The anodic oxidation behaviour of a cast component of AC2A Al alloy with machined surface and ascast surface was investigated in sulfuric acid solution. The anodized specimen showed relatively uniform and thick anodic oxide films on the as-cast surface, while non-uniform and very thin oxide films were formed on the machined surface. Non-anodized as-cast surface was observed to be covered with thick oxide scales and showed a number of second-phase particles containing Si, while non-anodized machined surface showed no oxide scales and relatively very small number of Si particles. Thus, the very limited growth of anodic oxide films on the as-cast surface was attributed to the presence of thick oxide scales and Si-containing second-phase particles on its surface.

Morphological Studies on TiO 2 Nanotubes Formed by Anodizing in Aqueous and Non-Aqueous Solutions

nanotubes were formed on Ti by anodizing in 1 M + 0.3 M HF and 0.1 M + 2% in ethylene glycol, and their surface and cross-sectional morphologies were observed using FE-SEM as a function of anodizing time and applied voltage. The cross-section of the nanotubes was readily observed from the small pieces of nanotubes remaining near the scratch lines after scratching of the anodized surface. nanotubes was observed to grow faster and thicker in non-aqueous solution than in aqueous solution. Diameter of nanotubes was proportional to the applied voltage, irrespective of the type of the electrolyte, and it is recommended to use non-aqueous solutions for the preparation of larger diameter of nanotubes.