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High-porosity aerogels of high specific surface area prepared from nanofibrillated cellulose (NFC)
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
KTH, School of Biotechnology (BIO), Glycoscience.ORCID iD: 0000-0001-9832-027X
KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.ORCID iD: 0000-0001-5818-2378
2011 (English)In: Composites Science And Technology, ISSN 0266-3538, Vol. 71, no 13, 1593-1599 p.Article in journal (Refereed) Published
Abstract [en]

Low-density aerogels based on nanofibrillated cellulose (NFC) from wood pulp were prepared from NFC aqueous dispersions using solvent exchange from water to tert-butanol followed by tert-butanol freeze-drying. In the present study, the dispersion of NFC nanofibers in the hydrocolloid was very well preserved in the aerogels. The "effective" diameter of the NFC nanofibers in the aerogels is around 10-18 nm corresponding to specific surface areas as high as 153-284 m(2) g(-1). Aerogels based on different NFC nanofibers were studied by FE-SEM, BET analysis (nitrogen gas adsorption), and mechanical properties were measured in compression for different densities of aerogels. The properties are compared with polymer foams and inorganic aerogels. Compared with cellular NFC foams, the present nanofibrous aerogels have lower modulus and show lower stress in compression for a given strain. Tert-butanol freeze-drying can therefore be used to create "soft" aerogels.

Place, publisher, year, edition, pages
2011. Vol. 71, no 13, 1593-1599 p.
Keyword [en]
Mechanical properties, Nano composites, Cellulose nanofibers, Freeze drying
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-45601DOI: 10.1016/j.compscitech.2011.07.003ISI: 000295864000010ScopusID: 2-s2.0-80051939439OAI: diva2:454466
QC 20111107 This article is a revised version of the manuscript "High-porosity aerogels of high specific surface area prepared by new routeusing nanofibrillated cellulose (NFC) disintegrated from the wood cell wall" which is a part of the thesis "Nanofiber networks, aerogels and biocomposites based on nanofibrillated cellulose from wood"Available from: 2011-11-07 Created: 2011-10-31 Last updated: 2011-11-11Bibliographically approved
In thesis
1. Nanofiber networks, aerogels and biocomposites based on nanofibrillated cellulose from wood
Open this publication in new window or tab >>Nanofiber networks, aerogels and biocomposites based on nanofibrillated cellulose from wood
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanofibrillated cellulose (NFC) from wood is an interesting material constituent of high strength and high aspect ratio, which easily forms networks through interfibril secondary bonding including hydrogen bonds. This has been exploited in preparation of new materials, which extend the range of properties for existing cellulosic materials. The objective is to explore processing-structure and structure-property relationships in NFC materials.

Dense networks of NFC, referred to as “nanopaper” having a random-in-the-plane orientation of the fibrils have been successfully prepared by a papermaking-like process involving vacuum filtration and water evaporation using laboratory papermaking equipment. Large, flat and transparent nanopaper sheets have thus been prepared in a relatively short time. Using the same preparation route, NFC was used to reinforce pulped wood fibers in dense network structures. NFC networks formed in the pore space of the wood fiber network give an interesting hierarchical structure of reduced porosity. These NFC/wood fiber biocomposites have greater strength, greater stiffness and greater strain-to-failure than reference networks of wood fibers only. In particular, the work to fracture (area under the stress-strain curve) is doubled with an NFC content of only 2%.

The papermaking preparation route was extended to prepare nanocomposites of high NFC content with a cellulose derivative matrix (hydroxyethyl cellulose, HEC) strongly associated to the NFC. Little HEC was lost during filtration. The NFC/HEC composites have high work to fracture, higher than that of any reported cellulose composite. This is related to NFC network characteristics, and HEC properties and its nanoscale distribution and association with NFC.

Higher porosity NFC nanopaper networks of high specific surface area were prepared by new routes including supercritical drying, tert-butanol freeze-drying and CO2 evaporation. Light-weight porous nanopaper materials resulted with mechanical properties similar to thermoplastics but with a much lower density and a specific surface area of up to 480 m2/g.

Freeze-drying of hydrocolloidal NFC dispersions was used to prepare ultra-high porosity foam structures. The NFC foams have a cellular foam structure of mixed open/closed cells and “nanopaper” cell wall. Control of density and mechanical properties was possible by variation of NFC concentration in the dispersion. A cellulose I foam of the highest porosity ever reported (99.5%) was prepared. The NFC foams have high ductility and toughness and may be of interest for applications involving mechanical energy absorption. Freeze-drying of NFC suspended in tert-butanol gave highly porous NFC network aerogels with a large surface area. The mechanical behavior was significantly different from NFC foams of similar density due to differences in deformation mechanisms for NFC nanofiber networks.


Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 74 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2011:024
Nanofibrillated cellulose, nanopaper, nanofiber, biocomposites, aerogel, foam
National Category
Materials Engineering
urn:nbn:se:kth:diva-32079 (URN)978-91-7415-931-8 (ISBN)
Public defence
2011-04-27, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
QC 20110406Available from: 2011-04-06 Created: 2011-04-05 Last updated: 2011-11-11Bibliographically approved

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