Lightweight and stiff cellular ceramic structures by ice templating

Porous, strong, and stiff ceramic materials are required for a range of technical applications, involving for instance, liquid or gas flow. Natural materials such as wood can provide useful structural guidelines for the optimal microstructural design, although only few processing routes are able to turn these guidelines into actual materials. We illustrate here, how ice templating of anisotropic particle suspensions can be modified to obtain a honeycomb structure with pores of 30 mu m diameter. The growth of ice crystals in the slurry induces self-assembly of the anisotropic particles, leading to relatively thin walls (10 mu m). Because large anisotropic particles are difficult to sinter, a glassy phase was introduced to facilitate this densification step and then to further reduce the walls' porosity. Young's modulus and compressive strength were both improved by the addition of a glassy phase by an order of magnitude due to the denser walls. These macroporous materials are more robust and stiff than materials with an equivalent morphology, while offering a simple alternative to the current wood replica processing routes.