Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Abstract

Cellulose aerogels are potential alternatives to silica aerogels with advantages in cost, sustainability and mechanical properties. However, the density dependence of thermal conductivity () 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 mgcm -3 ) and by uniaxial compression (9-115 mgcm -3 ). The aerogels are transparent with specific surface areas of ~400 m 2 g -1 , mesopore volumes of ~2 cm 3 g -1 and a power-law dependence of the E-modulus ( ~ 1.53, and the highest reported E of ~1 MPa). The dataset confirms that displays a traditional U-shaped density dependence with a minimum of 18 mWm -1 K -1 at 0.065 gcm -3 . For a given density, is ~5 mWm -1 K -1 lower for compressed aerogels due to the alignment of nanofibers, confirmed by small angle X-ray scattering (SAXS).