Three-dimensional ceramic/camphene-based coextrusion for unidirectionally macrochanneled alumina ceramics with controlled porous walls

We report the utility of three-dimensional ceramic/camphenebased coextrusion, newly developed in this study, for the production of unidirectionally macrochanneled alumina ceramics with three-dimensionally interconnected porous alumina walls. In this technique, a continuous ceramic/camphene filament with a diameter of 1 mm, comprised of a pure camphene core and a frozen alumina/camphene shell, was produced by the coextrusion process and then deposited in a layer-by-layer sequence using a computer-controlled 3-axis moving table. Unidirectionally aligned macrochannels (∼400 μm in diameter) and threedimensionally interconnected pores (several tens of micrometers in size) in the alumina walls were created by removing the camphene core and the camphene dendrites formed in the alumina/camphene region, respectively. The sample showed much higher compressive strength in the macrochannel direction than in the perpendicular direction. In addition, the compressive strength of the sample could increase with an increase in initial alumina content owing to a decrease in the total porosity.