동결건조 공정에서 동결제의 응고조건이 기공특성에 미치는 영향

초록

The present study demonstrates the effect of solidification condition on the pore structure in freeze dryingprocess using the slurries of CuO/sublimable vehicles. Camphene and Camphor-45 wt% naphthalene based slurries with14 vol% CuO powder were frozen into a mold at -25oC, followed by sublimation at room temperature. The green bodieswere hydrogen-reduced and sintered at 500oC for 1 h. The porous Cu specimen, frozen the CuO/camphene slurryinto the heated mold of the upper part, showed large pores with unidirectional pore channels and small pores in theirinternal wall. Also, it was observed that the size of large pores was decreasing near the bottom part of specimen. Thechange of pore structure depending on the freezing condition was explained by the nucleation behavior of camphenecrystals and rearrangement of solid powders during solidification. In case of porous Cu prepared from CuO/Camphornaphthalenesystem, the pore structure exhibited plate shape as a replica of the original structure of crystallized vehicleswith hypereutectic composition.

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