Dual-Scale Porosity Alumina Structures Using Ceramic/Camphene Suspensions Containing Polymer Microspheres

Abstract

This study demonstrates the utility of thermo-regulated phase separable alumina/camphene suspensions containing poly(methyl methacrylate) (PMMA) microspheres as porogens for the production of multi-scale porosity structures. The homogeneous suspension prepared at 60 °C could undergo phase separation during freezing at room temperature. This process resulted in the 3D networks of camphene crystals and alumina walls containing PMMA microspheres. As a consequence, relatively large dendritic pores with several tens of microns size could be created as the replica of frozen camphene crystals. In addition, after the removal of PMMA microspheres via heat-treatment, micron-sized small spherical pores could be generated in alumina walls. As the PMMA content with respect to the alumina content increased from 0 vol% to 40 vol%, while the camphene content in the suspensions was kept constant (70 vol%), the overall porosity increased from 45.7 ± 0.5 vol% to 71.4 ± 0.5 vol%. This increase in porosity is attributed to an increase in the fraction of spherical pores in the alumina walls. Thus, compressive strength decreased from 153 ± 18.3 MPa to 33 ± 7.2 MPa. In addition, multi-scale porosity alumina objects with a honeycomb structure comprising periodic hexagonal macrochannels surrounded by dual-scale porosity walls were constructed using a 3D plotting technique.

Ceramic Foams with Controlled Geometries Through 3D‐Printed Sacrificial Templates

“…Poly(methyl methacrylate) (PMMA) is frequently used because of its lowtemperature burn-out, low ash content, and biocompatibility. [24][25][26] Porous materials achieved using PMMA with the sacrificial templating method have yielded a wide range of nanoscale pores, finding applications in catalyst materials, [27][28][29][30][31][32][33] films, [34,35] membranes, [36,37] oxides, [38][39][40] carbon-based structures, [41][42][43][44] bioactive glass, [45] electrode materials, [46,47] and scaffolds and foams. [48,49] In addition, microscale pores have been successfully fabricated using packed PMMA beads (5-800 μm) as pore-forming agents, resulting in porosities ranging from 7% to 80%.…”