Titanium foams with aligned, elongated pores produced by freeze casting

Directional freeze-casting - a process used in order to produce foams with elongated, aligned pores applied so far exclusively for ceramics - is demonstrated for a titanium foam. An aqueous slurry of <45 μm titanium powders is directionally solidified, resulting in a preform with elongated, aligned, dendrites of 0.2 wt% agar solution, separated by interdendritic regions with high powdercontent. The preform is freeze-dried to remove the ice dendrites and sintered. The resulting titanium foams show 60 vol% aligned pores (̃0.1 mm width and several millimeters long) replicating theice dendrites and separated by walls constructed by partially-sintered titanium powders. On the other hand, when large size powder (<125 μm) was applied, their larger size inhibits the formationof pure ice dendrites, in agreement with a theoretical model.