Cu-Ni alloys with unidirectionally aligned pores were prepared by freeze-drying process of CuO-NiO/cam-phene slurry. Camphene slurries with dispersion stability by the addition of oligomeric polyester were frozen at -25˚C,and pores in the frozen specimens were generated by sublimation of the camphene during drying in air. The green bod-ies were hydrogen-reduced at 300˚C and sintered at 850˚C for 1h. X-ray diffraction analysis revealed that CuO-NiOcomposite powders were completely converted to Cu-Ni alloy without any reaction phases by hydrogen reduction. Thesintered samples showed large and aligned parallel pores to the camphene growth direction, and small pores in the inter-nal wall of large pores. The pore size and porosity decreased with increase in CuO-NiO content from 5 to 10 vol%.The change of pore characteristics was explained by the degree of powder rearrangement in slurry and the accumulationbehavior of powders in the interdendritic spaces of solidified camphene.

Freeze drying for porous Mo was accomplished by using MoO3 powder as the source and camphor-naph- thalene eutectic system as the sublimable material. Eutectic composition of camphor-naphthalene slurries with the initial MoO3 content of 5 vol%, prepared by milling at 55o C with a small amount of oligomeric dispersant, was frozen at -25o C. The addition of dispersant showed improvement of dispersion stability in slurries. Pores were generated subse- quently by sublimation of the camphor-naphthalene during drying in air for 48 h. To convert the MoO3 to metallic Mo, the green body was hydrogen-reduced at 750o C, and sintered at 1100o 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.

Porous Ti-systems with unidirectionally aligned channels were synthesized by freeze-drying and a heat treatment process. TiH2 powder and camphene were used as the source materials of Ti and sublimable vehicles, respectively. Camphene slurries with TiH2 content of 10 and 15 vol% were prepared by milling at 50˚C with a small amount of oligomeric polyester dispersant. Freezing of the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled at -25˚C while unidirectionally controlling the growth direction of the camphene. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green body was heat-treated at 1100˚C for 1 h in a nitrogen and air atmosphere. XRD analysis revealed that the samples composed of TiN and TiO2 phase were dependent on the heat-treatment atmosphere. The sintered samples showed large pores of about 120 mm which were aligned parallel to the camphene growth direction. The internal wall of the large pores had relatively small pores with a dendritic structure due to the growth of camphene dendrite depending on the degree of nucleation and powder rearrangement in the slurry. These results suggest that a porous body with an appropriate microstructure can be successfully fabricated by freeze-drying and a controlled sintering process of a camphene/TiH2 slurry.