Structurally integrated thermal management of isotropic and directionally ice-templated nanocellulose/chitosan aerogels

Aerogels are materials comprising hierarchical designs and are of growing significance to acquire advanced structure-based functionality in future technical applications. Since the researchers have previously focused on a single freeze-casting strategy in the fabrication of aerogels, the correlation between processing routes and their integrated characteristics could not be determined. Herein, we constructed cellulose nanofiber (CNF)/chitosan (CS) based composite aerogels (CCSA) by employing random and directional freeze-casting strategies. The effect of such techniques has been explored as a source of an integrated freeze-cast dried porous structure. Random freeze-dried aerogels (r-CCSA) exhibited isotropic properties with high porosity (99.6%) and large pore volume (2.71 mL/g). Whereas, controlled freeze ice-cast nucleation endowed the directional aerogels with ultra-low thermal conductivity (0.027 Wm −1  K −1 ) in the radial direction and about 20% greater (0.033 Wm −1  K −1 ) in the axial direction. Moreover, high BET-specific surface area (342 m 2 /g) and 60% strain adherence was observed for these anisotropic aerogels. This composite bio-mass aerogel preparation approach can offer a clear insight into the adoption of the right methodology considering the potential applications and environmental safety. Graphical abstract