Biomaterials

Biography

Biography: Hyun-Do Jung

Abstract

Freeze casting has recently received increasing interest, as it can endow porous ceramics with well-defined pore structures, such as a controlled pore size, perfect interconnections between pores. Particularly, the use of camphene as the freezing vehicle makes it possible to freeze a ceramic slurry at near room temperature, thus allowing for more flexible processing. However, camphene-based freeze casting can only be applied to ceramic powders because dispersant can be activated by electrostatic effect when using ceramic powders. So it suffers from the considerable sedimentation of relatively large metal powders during solidification, resulting in an inhomogeneous porous structure. Therefore, this study reports how porous Ti scaffolds can be produced with a uniform porous structure by freezing a Ti/camphene slurry in rotation, which is denoted as “dynamic freeze casting”. Ti/camphene slurries with Ti powder content (15vol.%) were prepared by stirring at 60 °C for 30 min. Prepared slurries were poured into cylindrical molds and frozen at 44 °C dynamically in order to avoid segregating powder from camphene. During this process, camphene crystals can nucleate and grow extensively until the slurry has solidified completely, while preserving the walls made of Ti powders, particularly due to freezing in rotation. After de-molding, the green bodies were pressed using a cold isostatic press to produce the green compact specimens. They were freeze dried to remove the frozen camphene. The 3-dimensionally interconnected large pores can be created after removing the camphene crystals. Thereafter, the samples were heated up to 1300°C, and heat treated for 2 h. The porous structures and morphology of the samples were characterized using scanning electron microscopy (SEM) and a micro–computed tomography (micro-CT). In order to evaluate their mechanical properties, their compressive stress–strain behaviors were also monitored.