Gradient-Hierarchic-Aligned Porosity SiOC Ceramics

This work describes a simple technique to produce porous ceramics with aligned porosity having very high permeability and specific surface area. SiOC-based compositions were processed from blends of three types of preceramic polymer and a catalyst, followed by curing and pyrolysis. The heating applied from the bottom of molds promoted the nucleation, expansion and rising of gas bubbles, and the creation of a ceramic matrix with axially oriented channels interconnected by small round pores. The samples were analyzed by SEM, tomography, BET, water immersion porosimetry and permeation to gas flow. The resulting bodies presented levels of open porosity (69.9-83.4%), average channel diameter (0.59-1.25 mm) and permeability (0.56-3.83 × 10^-9 m²) comparable to those of ceramic foams and honeycomb monoliths, but with specific surface area (4.8-121.9 m²/g) typical adsorbents, enabling these lotus-type ceramics to be advantageously used as catalytic supports and adsorption components in several environmental control applications.