Papers by Author: Jeong Jung Oak

Abstract: Carbon Nano Tube (CNT) reinforced AZ91 metal matrix composites (MMC) were fabricated by the squeeze infiltrated method. Properties of magnesium alloys have been improved by impurity reduction, surface treatment and alloy design, and thus the usage for the magnesium alloys has been extended recently. However there still remain barriers for the adaption of magnesium alloys for engineering materials. In this study, we report light-weight, high strength heat resistant magnesium matrix composites. Microstructural study and tensile test were performed for the squeeze infiltrated magnesium matrix composites. The wear properties were characterized and the possibility for the application to automotive power train and engine parts was investigated. It was found that the squeeze infiltration technique is a proper method to fabricate magnesium matrix composites reducing casting defects such as pores and matrix/reinforcement interface separation etc. Improved tensile and mechanical properties were obtained with CNT reinforcing magnesium alloys

Abstract: Recently, Ti-based metallic glasses aim at biomaterials with their high specific strength and superior corrosion resistance. Their high workability also shows a good performance for mass production under the energy saving environment. In this study, we started investigation of the design of Ti-based metallic glasses with the restricted alloying elements for biocompatibility and characteristic evaluation of the optimized Ti-based metallic glasses with higher glass forming ability for dental implants. These Ti-based metallic glasses do not contain Al, V and Ni elements which are well known to be neurotoxicity and cytotoxicity for human body. Current medical reports of impracticability by these elements have been a hot issue in biomaterials science. Newly designed Ti-based metallic glasses exhibit good performances. Especially, the optimized Ti-based metallic glass has high corrosion resistance with better passivity in a wide passivation range in simulated body fluids at 310K. In addition, biocompatibility of Ti-based metallic glass was also evaluated by cell culture in vitro. Excellent biocompatibility of Ti-based metallic glass show high potentials to be applied as biomaterials that necrosis of osteoblast (SaOS2) was not detected in this study.

Abstract: We started investigation of new Ti-based bulk metallic glass (BMG) alloys with higher glass forming ability (GFA) for dental implants for medical market. These Ti-based BMG alloys do not contain Ni, Al and Be elements which are well known to be harmful for human body. In particular, cylindrical rod specimens of newly designed Ti-based BMG alloys with produced by copper mold casting exhibit compressive strength of above 1800 MPa. Ti-based BMG alloys also have high corrosion resistance that is passivated at the lower passive current densities of approximately 10-2Am-2 in 1 mass% lactic acid, 10-2~10-3Am-2 in PBS (-) at 310K which are lower than those of pure Titanium and Ti-6Al-4V alloy. These BMG alloys have high potentials to be applied as biomaterials in various forms, such as melt spun ribbons and cylindrical rods.