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 (phi=20 vol%). The warm slurry was prepared at 55 degrees C by ball milling and cast into a mold at 25 degrees 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 (phi > 50 vol%) on the top layer, while maintaining a low solid loading with solidified camphene (phi similar to 20 vol%) in the inner region. The sintered sample showed a dense 125-mu m-thick ceramic layer on a highly porous layer with a thickness of similar to 1.7 mm and three-dimensionally interconnected pore channels that were representative of entangled dendritic growth of the solidified camphene.