Direct Ink Writing of Multifunctional Silica-Reinforced Zirconia Aerogels via Electrostatic Attraction-Assisted Co-Gelation

ZrO₂ aerogels are renowned for their exceptional stability and high positive charge, positioning them as promising candidates for various applications. However, the inherent frangibility and contractibility of ZrO₂ aerogels pose significant challenges in processing and drying intactly. In this study, we introduce a novel approach to fabricate 3D-printed ZrO₂-based aerogels through electrostatic attraction-assisted cogelation process, utilizing a silica reinforcement and rheological adjustment strategy. Under the dispersion and coordination effects of a silica sol with opposite charges, crack-free 3D-printed ZrO₂-based aerogels were successfully prepared. These 3D-printed samples exhibit a low filament density of 221 mg cm^-3 and an impressive specific surface area of up to 535.6 m² g^-1, showcasing superior performance in high-temperature insulation (withstanding temperature up to 1300 °C) and phosphate adsorption (with an adsorption capacity reaching 88.78 mg g^-1). It is revealed that incorporated SiO₂ is uniformly dispersed even at the primary structure level, forming a homogeneous hybrid skeleton. The zeta-potential results indicate that the uniform dispersion is due to the electrostatic attraction between positively charged ZrO₂ sol and negatively charged SiO₂ sol during the cogelation process. This innovative strategy paves the way for the development of ceramic-based inks suitable for 3D printing applications.