Three-dimensional Patterning Super-Black Silica-Based Nanocomposite Aerogels

Aerogels are ultra-lightweight, porous materials defined by a complex network of interconnected pores and nanostructures, which effectively suppress heat transfer, making them exceptional for thermal insulation. Furthermore, their porous architecture can trap and scatter light via multiple internal reflections, extending the optical path within the material. When combined with suitable light-absorbing materials, this feature significantly enhances light absorption (darkness). To validate this concept, mesoporous silica aerogel particles were incorporated into a resorcinol-formaldehyde (RF) sol, and the silica-to-RF ratio was optimized to achieve uniform carbon compound coatings on the silica pore walls. Notably, increasing silica loading raised the sol viscosity, enabling formulations ideal for direct ink writing processes with excellent shape fidelity for super-black topographical designs. The printed silica-RF green bodies exhibited remarkable mechanical strength and ultra-low thermal conductivity (15.8 mW m^-1 K^-1) prior to pyrolysis. Following pyrolysis, the composites maintained structural integrity and printed microcellular geometries while achieving super-black coloration (abs. 99.56% in the 280-2500 nm range) and high photothermal conversion efficiency (94.2%). Additionally, these silica-carbon aerogel microcellulars demonstrated stable electrical conductivity and low electrochemical impedance. The synergistic combination of 3D printability and super-black photothermal features makes these composites highly versatile for multifunctional applications, including on-demand thermal management, and efficient solar-driven water production.