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 m²/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

中文翻译：

---

各向同性和定向冰模板纳米纤维素/壳聚糖气凝胶的结构集成热管理

气凝胶是包含分层设计的材料，对于在未来的技术应用中获得基于结构的先进功能具有越来越重要的意义。由于研究人员以前专注于制造气凝胶的单一冷冻铸造策略，因此无法确定加工路线与其综合特征之间的相关性。在此，我们通过采用随机和定向冷冻铸造策略构建了基于纤维素纳米纤维 (CNF)/壳聚糖 (CS) 的复合气凝胶 (CCSA)。这种技术的效果已被探索为集成冷冻浇注干燥多孔结构的来源。随机冷冻干燥气凝胶 (r-CCSA) 表现出各向同性的特性，具有高孔隙率 (99.6%) 和大孔体积 (2.71 mL/g)。然而，^-1  K ^-1 )在径向方向上并且在轴向方向上大约大20％(0.033 Wm ^-1  K ^-1 )。此外，对于这些各向异性气凝胶，观察到高 BET 比表面积 (342 m ^{2 /g) 和 60% 的应变粘附。}考虑到潜在的应用和环境安全，这种复合生物质气凝胶制备方法可以清楚地了解采用正确的方法。

图形概要