Development of tunable porous alumina monolith using hollow microspheres via extrusion-based 3D printing

Hierarchical cellular ceramics have attracted considerable interest due to their versatility and unique physico-mechanical effectiveness for advanced applications. Tailorable alumina foams with low shrinkage were fabricated through an innovative combination of 3D printing and sacrificial templating with low environmental footprint. The viscoelastic pastes were formulated using the aqueous-based solution of binder, dispersant, and plasticizer with different volumes of α-alumina and lightweight hollow microspheres (HMs) as a template. The solid-to-liquid ratio increased 53 to 80 vol. % with the inclusion of HMs for printable rheology. Cellular architectures of alumina were structured through a material extrusion-based technique and then thermally treated at 1200°C. Finally, the alumina monoliths achieved a ∼55-93% porosity with three different types of adjustable pores, produced by combining 3D printing, burning of templates, and inter-particle voids. The HMs generated spherical pores (7-47 µm) in the printing struts with reduced CO2 emissions compared to conventional sacrificial porogens during the burnout process.