Microstructure of porous Cu fabricated by freeze-drying process of CuO/camphene slurry

Porous Cu with macroscopically aligned channels was synthesized using a freeze-drying process. Camphene-based CuO slurry was prepared by milling at 60 °C with a small amount of dispersant. Freezing of a slurry was done at −25 °C while unidirectionally controlling the growth direction of the camphene. Pores were generated subsequently by sublimation of the camphene during drying. The green body was hydrogen-reduced at 300 °C for 30 min, and sintered in the furnace at 700 °C for 1 h under a hydrogen atmosphere. Microstructural observation reveals that all of the sintered samples are composed of only Cu phase and show macroscopic open pores with an average size of 100 μm which are aligned along its macroscopic growth direction. The internal wall of the macroscopic aligned pore shows relatively small pores due to the traces of the camphene left between the concentrated Cu particles on the internal wall. Increase in the porosity and pore size with increasing camphene content was explained by the change of the growth behavior of the camphene crystals.