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Nat Nanotechnol. 2015 Mar;10(3):277-83. doi: 10.1038/nnano.2014.248. Epub 2014 Nov 2.

Thermally insulating and fire-retardant lightweight anisotropic foams based on nanocellulose and graphene oxide.

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Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden.
Engineering Ceramics Department, Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
1] Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden [2] Wallenberg Wood Science Centre, Royal Institute of Technology, KTH, 100 44 Stockholm, Sweden.
Politecnico di Torino, Corso Duca degli Abruzzi, 24 10129 Torino, Italy.
Max Planck Institute for Colloids and Interfaces, Potsdam-Golm Science Park, Am Mühlenberg 1, 14476 Potsdam, Germany.


High-performance thermally insulating materials from renewable resources are needed to improve the energy efficiency of buildings. Traditional fossil-fuel-derived insulation materials such as expanded polystyrene and polyurethane have thermal conductivities that are too high for retrofitting or for building new, surface-efficient passive houses. Tailored materials such as aerogels and vacuum insulating panels are fragile and susceptible to perforation. Here, we show that freeze-casting suspensions of cellulose nanofibres, graphene oxide and sepiolite nanorods produces super-insulating, fire-retardant and strong anisotropic foams that perform better than traditional polymer-based insulating materials. The foams are ultralight, show excellent combustion resistance and exhibit a thermal conductivity of 15 mW m(-1) K(-1), which is about half that of expanded polystyrene. At 30 °C and 85% relative humidity, the foams retained more than half of their initial strength. Our results show that nanoscale engineering is a promising strategy for producing foams with excellent properties using cellulose and other renewable nanosized fibrous materials.


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