Fabrication and characterization of robust freeze-cast alumina scaffolds with dense ceramic walls and controllable pore sizes

Directionally aligned prismatic and lamellar porous alumina scaffolds with a high strength-to-density ratio were fabricated from submicron Al₂O₃ powders and a tiny quantity of nanoscale TiO₂ sintering aids by freeze casting using TBA and water as solvents. Both freezing temperature (− 10 °C, − 50 °C, − 90 °C) and sintering temperature (1300 °C, 1350 °C, 1400 °C) were varied to adjust pore parameters while a low solid loading (15 vol%) was maintained to ensure high porosity. This paper describes and compares the microstructures, porosity, pore size, wall thickness and compressive behavior of the scaffolds with two typical pore morphologies (lamella and honeycomb), which help to identify their scope of application and to unveil the relationship between pore morphology and mechanical property to optimize the material performance. The failure modes of these two types of scaffolds under compression were simulated. The TBA-based 1 wt% TiO₂-containing alumina scaffolds with dense ceramic walls that were freeze-cast at − 90 °C and sintered at 1400 °C exhibited a compressive strength of 160 MPa with a porosity of 59%, indicating lightweight and high-strength characteristics.