Abstract

Freeze drying for porous Mo was accomplished by using MoO_3 powder as the source and camphor-naphthalene eutectic system as the sublimable material. Eutectic composition of camphor-naphthalene slurries with the initial MoO_3 content of 5 vol%, prepared by milling at 55°C with a small amount of oligomeric dispersant, was frozen at -25°C. The addition of dispersant showed improvement of dispersion stability in slurries. Pores were generated subsequently by sublimation of the camphor-naphthalene during drying in air for 48 h. To convert the MoO_3 to metallic Mo, the green body was hydrogen-reduced at 750°C, and sintered at 1100°C for 2 h. The sintered samples, frozen by heated Teflon cylinder, showed large pores with the size of about 40 µm which were aligned parallel to the sublimable vehicles growth direction. The formation of unidirectionally aligned pores is explained by the rejection and accumulation of solid particles in the serrated solid-liquid interface.

• Keywords: MoO_3/camphor-naphthalene slurry;Freeze-drying;Hydrogen reduction;Pore characteristics;