동결주조로 제조한 텅스텐의 기공구조에 미치는 camphene 및 tert-butyl alcohol 동결제의 영향

Camphene and tert-butyl alcohol (TBA) crystals are used as sublimable vehicles in a freeze casting process to fabricate porous W with distinctive pore structures. The WO₃ raw powder was subjected to ball milling for 5 h to eliminate large agglomerates and achieve a uniform particle size distribution. Homogeneous slurries with dispersion stability were prepared by incorporating 1 wt% Hypermer KD-4 for camphene, and 5 wt% polyethylene glycol along with 1 wt% citric acid for TBA as dispersants. The slurries containing 10 vol% WO₃ were subjected to freezing within a mold at a temperature of-20 °C at the bottom. Pore formation occurred via sublimation of the vehicles, and the resulting green bodies were subjected to sintering at 1500 °C in a hydrogen atmosphere. The sintered bodies exhibited macroscopic pores that were aligned parallel to the direction of freeze-casting. The porous W prepared using the sublimable vehicles of camphene and TBA showed distinct pore morphologies of dendritic and hexagonal structures, respectively, corresponding to their crystal structures. All sintered porous bodies exhibited larger pore sizes in the upper region compared to the lower region, which can be mainly explained by changes in the solidification rate and the degree of rearrangement of solid particles.