Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Cellulose aemgels are potential alternatives to silica aerogels with advantages in cost, sustainability and mechanical properties. However, the density dependence of thermal conductivity (lambda) for cellulose aerogels remains controversial. Cellulose aerogels were produced by gas-phase pH induced gelation of TEMPO-oxidized cellulose nanofibers (CNF) and supercritical drying. Their properties are evaluated by varying the CNF concentration (5-33 mg.cm(-3)) and by uniaxial compression (9-115 mg.cm(-3)). The aerogels are transparent with specific surface areas of similar to 400 m(2).g(-1), mesopore volumes of similar to 2 cm(3).g(-1) and a power-law dependence of the E-modulus (alpha similar to 1.53, and the highest reported E of similar to 1 MPa). The dataset confirms that A. displays a traditional U-shaped density dependence with a minimum of 18 mW.m(-1).K-1 at 0.065 g.cm(-3). For a given density, lambda is similar to 5 mW.m(-1).K-1 lower for compressed aerogels due to the alignment of nanofibers, confirmed by small angle X-ray scattering (SAXS).

Automated summary

Cellulose aerogels have the potential to be alternatives to silica aerogels with advantages in cost, sustainability, and mechanical properties. However, the density dependence of thermal conductivity for cellulose aerogels remains controversial. Experimental results show that the density of cellulose aerogels affects the thermal conductivity, with compressed aerogels having lower thermal conductivity due to the alignment of nanofibers.