In situ fabrication of a dense/porous Bi-layered ceramic composite using freeze casting of a ceramic-camphene slurry

Dense/porous bi-layered ceramic composites were fabricated in situ by freeze casting a ceramic/camphene slurry with a low solid content (φ=20 vol%). The warm slurry was prepared at 55°C by ball milling and cast into a mold at 25°C, where the top surface of the cast body was exposed to air to allow for the controlled evaporation of molten camphene. This simple method produced a high solid content with negligible camphene (φ>50 vol%) on the top layer, while maintaining a low solid loading with solidified camphene (φ∼20 vol%) in the inner region. The sintered sample showed a dense 125-μm-thick ceramic layer on a highly porous layer with a thickness of ∼1.7 mm and three-dimensionally interconnected pore channels that were representative of entangled dendritic growth of the solidified camphene.