Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Deeptanshu Sivaraman; Gilberto Siqueira; Anjani K Maurya; Shanyu Zhao; Matthias M Koebel; Gustav Nyström; Marco Lattuada; Wim J Malfait

doi:10.1016/j.carbpol.2022.119675

Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Carbohydr Polym. 2022 Sep 15:292:119675. doi: 10.1016/j.carbpol.2022.119675. Epub 2022 Jun 3.

Authors

Deeptanshu Sivaraman¹, Gilberto Siqueira², Anjani K Maurya³, Shanyu Zhao⁴, Matthias M Koebel⁴, Gustav Nyström⁵, Marco Lattuada⁶, Wim J Malfait⁴

Affiliations

¹ Empa - Building Energy Materials and Components, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland; Department of Chemistry, University of Fribourg, Fribourg, Switzerland. Electronic address: deeptanshu.sivaraman@empa.ch.
² Cellulose & Wood Materials Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
³ Empa - Center for X-ray Analytics, Swiss Federal Laboratories for Materials Science and Technology, Empa, St. Gallen, Switzerland.
⁴ Empa - Building Energy Materials and Components, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
⁵ Cellulose & Wood Materials Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland; Department of Health Sciences and Technology, ETH Zürich, 8092 Zürich, Switzerland.
⁶ Department of Chemistry, University of Fribourg, Fribourg, Switzerland.

PMID: 35725170
DOI: 10.1016/j.carbpol.2022.119675

Abstract

Cellulose aerogels are potential alternatives to silica aerogels with advantages in cost, sustainability and mechanical properties. However, the density dependence of thermal conductivity (λ) 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 ~400 m²·g^-1, mesopore volumes of ~2 cm³·g^-1 and a power-law dependence of the E-modulus (α ~ 1.53, and the highest reported E of ~1 MPa). The dataset confirms that λ 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, λ is ~5 mW·m^-1·K^-1 lower for compressed aerogels due to the alignment of nanofibers, confirmed by small angle X-ray scattering (SAXS).

Keywords: Aerogel; CNF; Cellulose nanofibers; E modulus; SAXS; Thermal conductivity.

MeSH terms

Cellulose / chemistry
Gels / chemistry
Nanofibers* / chemistry
Scattering, Small Angle
X-Ray Diffraction

Substances

Gels
Cellulose