Hierarchically Porous Ceramics via Direct Writing of Binary Colloidal Gel Foams

Hierarchically porous ceramics with a high specific surface area and interconnected porosity may find potential application as particulate filters, catalyst supports, and battery electrodes. We report the design and programmable assembly of cellular ceramic architectures with controlled pore size, volume, and interconnectivity across multiple length scales via direct foam writing. Specifically, binary colloidal gel foams are created that contain entrained bubbles stabilized by the irreversible adsorption of attractive alumina and carbon (porogen) particles at their air-water interfaces. Composition effects on foam ink rheology and printing behavior are investigated. Sintered ceramic foams exhibited specific permeabilities that increased from 2 × 10^-13 to 1 × 10^-12 m² and compressive strengths that decreased from 40 to 1 MPa, respectively, with increasing specific interfacial area. Using direct foam writing, 3D ceramic lattices composed of open-cell foam struts were fabricated with tailored mechanical properties and interconnected porosity across multiple length scales.