Hierarchical porous ceramics via two-stage freeze casting of preceramic polymers

Abstract

Freeze-cast porous ceramics are of interest due to a broad range of applications such as filters, bioscaffolds, and catalyst supports. However, achieving the desired mechanical strength while retaining sufficient functionality, such as permeability, has been challenging. In this work, hierarchical structures of bridged lamellar pores were created via two-stage freeze casting of a preceramic polymer to enhance compressive strength of the resulting SiOC. It has been shown that the bridge density can be controlled by changing the concentration of preceramic polymer in solution and compressive strength increased approximately threefold while permeability constants ranged from 9.63 × 10^(−13) to 3.96 × 10^(−12) m^2.