Papers by Author: D.J. Yang

Abstract: Surface morphology and degradation behavior of mechanically mixed and chemically precipitated biphasic calcium phosphate (M-BCP and P-BCP) were compared. For the M-BCP powder, commercial HA and TCP powders were used. In order to prepare P-BCP powder, precipitation method was used. The particle size of P-BCP was smaller than that of M-BCP. The disk-type specimens of each powder were prepared for the morphology comparison and degradation test. The surface morphology of sintered samples was porous in M-BCP and dense in P-BCP. The degradation test was conducted in the revised simulated body fluid (R-SBF) for 1, 7, and 21 days. Surface morphology and degradation rate of two samples were different. The weight gain in both samples increased linearly with immersion period due to apatite-like layer formation. However, the weight gain in M-BCP was much higher than that in P-BCP. The weight gain was related to the surface morphology and degradation with immersion period.

Abstract: Porous calcium metaphosphate granules for bone fillers were prepared by starch consolidation with baking powder and surfactant. Paste for foaming was prepared by the mixing of calcium metaphosphate powder and water with the various amount of starch (10~20㎛ size), where solid contents 30%, 45%, 60% of the paste. In order to obtain the optimum micro/macro porous structure, the appropriate contents of baking powder and surfactant at a fixed content of starch were examined. In order to examine the content of baking powder on pore morphology, the baking powder was added 60, 180, and 300 wt% of the paste at fixed content of starch. And then, in order to investigate the effect of surfactant on porous structure, surfactant was added 0.035, 0.1, and 0.16 wt% of paste weight at fixed content of starch and baking powder. Foaming was conducted using microwave method, and foamed samples were sintered at 900 °C. The sintered porous blocks with starch only showed uneven and closed macro pores without any micro pores. However, the sintered porous blocks with starch, baking powder, and surfactant showed homogeneous micro and macro porous structures ranging 20~60, and 300~1000 ㎛ in pore size, respectively. The porosity was increased with the increase of surfactant up to about 70 %.