Three‐dimensional Ceramic/Camphene‐based Coextrusion for Unidirectionally Macrochanneled Alumina Ceramics with Controlled Porous Walls

Abstract

We report the utility of three‐dimensional ceramic/camphene‐based 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 three‐dimensionally 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.

Porous alumina ceramic scaffolds with biomimetic macro/micro-porous structure using three-dimensional (3-D) ceramic/camphene-based extrusion

“…We herein demonstrate the versatility of 3-dimensional ceramic/ camphene-based extrusion (3D-Ex) [22] for the production of porous ceramic scaffolds comprised of 3-dimensionally interconnected ceramic frameworks with an aligned microporous structure ( Fig. 1(A) and (B)).…”

“…4(D)-(F)). This finding suggests that the camphene phase can be extensively elongated through the extrusion of a frozen alumina/camphene body, thus creating aligned micropores in ceramic frameworks [22].…”

“…Straight alumina frameworks without noticeable distortion or large defects were constructed in a 3-D periodic pattern. This finding suggests that the camphene phase used as a temporary binder can effectively hold alumina powders, thus imparting high green strength to the alumina/camphene filaments [22]. In addition, the camphene phase can be easily removed by conventional freeze drying, thus eliminating a time-consuming, troublesome binder burnout process.…”

“…However, all of the porous scaffolds had 3-dimensionally interconnected macropores with pore sizes of 4 $ 150 μm  600 μm, which would be highly beneficial to bone ingrowth when used as a bone scaffold [1,21]. In addition, good bonding between the alumina frameworks was achieved for all the scaffolds, which was attributed to the excellent adhesive property of the camphene phase [22,28]. These findings demonstrate that a frozen ceramic/camphene body can be successfully used as a feedstock to create porous ceramic scaffolds with controlled macropores, as is often the case with conventional SFF techniques.…”

“…3(D)-(F) shows representative FE-SEM images of the crosssections of the alumina frameworks obtained using various alumina contents (15 vol%, 20 vol%, and 25 vol%). Micropores with sizes of tens of microns were vigorously created as the replica of the camphene dendrites that had been developed normal to the direction of extrusion [22]. In addition, the alumina frameworks became more porous with a decrease in alumina content.…”