Freeze-casting has been wildly exploited to construct
porous ceramics
but usually requires costly and demanding freeze-drying (high vacuum,
size limit, and supercooled chamber), which can be avoided by the
ambient pressure drying (APD) technique. However, applying APD to
freeze-cast ceramic based on an aqueous suspension is still challenging
due to inert surface chemistry. Herein, a modified APD strategy is
developed to improve the drying process of freeze-cast ceramics by
exploiting the simultaneous ice etching, ionic cross-linking, and
solvent exchange under mild conditions (−10–0 °C,
ambient pressure). This versatile strategy is applicable to various
ceramic species, metal ions, and freezing techniques. The incorporated
metal ions not only enhance liquid-phase sintering, producing ceramics
with higher density and mechanical properties than freeze-cast counterparts,
but also render customizable coloration and antibacterial property.
The cost-/time-efficient APD is promising for mass production and
even successive production of large-size freeze-cast ceramics that
exceed the size of commercial freeze-dryers.