Synthesis of porous Cu-Sn using freeze-drying process of CuO-SnO ₂/camphene slurries

Porous Cu-Sn with controlled pore characteristics was synthesized by a freeze-drying and sintering process. CuO and SnO₂ powders were selected as the source material, which are hydrogen-reduced to metallic Cu-Sn in the sintering stage. Camphene-based CuO-SnO₂ slurries were prepared by milling at 60 °C with a small amount of dispersant. Freezing of a slurry was done at -40 °C with unidirectional control of the growth direction of the camphene. Pores were generated by sublimation of the camphene. The green bodies were sintered at 650 °C under a hydrogen atmosphere. The sintered bodies with Cu₃Sn, Cu₆Sn₅ and β-Sn phases showed macroscopic aligned pores with an average size of 200 μm. The internal wall of the macroscopic pores is also porous, and there are a number of many small pores in it. The formation of macroscopic and microscopic pores was discussed in terms of solidification behavior of the liquid with foreign particles.