Ultralight and Flexible Subnanowire Aerogels for Intrinsically Hydrophobic Thermal Insulation

Aerogels are regarded as the next generation of thermal
insulators; however, conventional
aerogels suffer
from issues such as brittleness, low moisture resistance, and a complex
production process. Subnanowires (SNWs) are emerging materials known
for their exceptional flexibility, toughness, intrinsic hydrophobicity,
and gelling capabilities, making them ideal building blocks for flexible,
tough, hydrophobic, and thermally insulating aerogels. Herein, we
present a simple and scalable strategy to construct SNW aerogels by
freeze-drying hydroxyapatite (HAP) SNW dispersions in cyclohexane.
The resulting aerogels consist of three-dimensional porous flakes
composed of thin layers of SNW bundles. They exhibit numerous outstanding
properties, including ultralow density (12.33 mg·cm–3), high porosity (99.15%), remarkable flexibility and toughness,
and excellent thermal insulation properties (27.53 mW·m–1·K–1). Because the HAP SNWs consist of hydroxyapatite
cores capped with hydrocarbon chains, the aerogels demonstrate intrinsic
hydrophobicity (138° water contact angle) and superior thermal
stability compared to polymer foams. Furthermore, the HAP SNW aerogels
can effectively shield against infrared radiation due to their low
thermal conductivity. This work suggests that SNWs can serve as superior
building blocks for flexible, tough, and intrinsically hydrophobic
aerogels, paving the way for future applications in thermal insulation.