Strategies for Robust Porous Ceramics

Reference Presenter Authors
17-035 Katherine T Faber Faber, K.T.(California Institute of Technology); Arai, N.(California Institute of Technology); Kuo, T.C.(California Institute of Technology); One of the greatest challenges for porous ceramics is to ensure the necessary mechanical strength and toughness while providing the functionality derived from pores, such as high permeability or high surface area for chemical reactions. Here we use solution-based directional freeze casting of preceramic polymers to explore methods for enhanced mechanical behavior of porous SiOC. Two strategies are considered. First, bridges between lamellar SiOC walls are created using a two-stage freeze casting method. The bridge density is controlled by the concentration of the preceramic polymer, polymethylsiloxane, in solution. Second, reinforcing fillers are incorporated into the freeze-casting process. Multiwall carbon nanotubes or SiC whiskers are dispersed in casting solutions, and are retained through pyrolyzation. The carbon nanotubes are preserved within SiOC walls, while the SiC whiskers both reinforce walls and form bridges. For both two-stage freeze casting and filler reinforcement, permeability, compressive strength, and microstructure are assessed to verify the efficacy of these approaches.
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