Papers by Author: T.G. Woo

Abstract: This study examined the effect of the current density, anodizing voltage and time on the surface characteristics of titanium during anodic spark oxidation. Anodic spark oxidation was performed at different concentrations of electrolyte composed of DL-α-glycerophosphate (DL-α-GP) and calcium acetate (CA). The specimens were anodized at various conditions (current density, anodizing voltage, and duration) in a fixed electrolyte concentration. Anodized specimens were treated hydrothermally under high pressure steam using an autoclave. Homogeneous anodic oxide films were produced by anodic spark oxidation on the titanium surface with 1~4 μm diameter pores, and the breakdown voltage was changed by the electrolyte concentration. After the hydrothermal treatment, hydroxyapatite crystals formed as an enlarged polygonal shape in the higher concentration of DL-a-GP group and as thin needles in higher concentration of CA group. The bioactivity and osteoblast growth was good for the anodized surface at 340V compared with the groups applied other parameters.

Abstract: The effect of surface states of substrate and additives on copper electrodeposition for thin film applications was investigated. Titanium substrate states were mechanically and chemically moderated and several additives such as Arabic gum, hydroxyl ethyl cellulose, and chlorine were used during electrodeposition process under a constant current condition with current density of 500 mA/cm2. Results obtained using SEM, X-ray, and AFM for early stage of copper nucleation and growth revealed that substrate conditions and additives appear to be effective in producing uniformly-distributed copper nuclei and their subsequent growth in a regulated manner of surface leveling. The shape of copper nuclei was clearly affected by the surface state of the substrate. It seems to be related with dislocations produced on the titanium cathode during surface moderating. Hardness, growth direction, and resistivity of copper deposits changed with the kind of additives.