title: Superior mechanical performance of highly porous, anisotropic nanocellulose-montmorillonite aerogels prepared by freeze casting.
abstract: Directionally solidified nanofibrillated cellulose (NFC)-sodium-montmorillonite (MMT) composite aerogels with a honeycomb-like pore structure were compared with non-directionally frozen aerogels with equiaxed pore structure and identical composition and found to have superior functionalities. To explore structure-property correlations, three different aerogel compositions of 3wt% MMT, and 0.4wt%, 0.8wt%, and 1.2wt% NFC, respectively, were tested. Young׳s modulus, compressive strength and toughness were found to increase with increasing NFC content for both architectures. The modulus increased from 25.8kPa to 386kPa for the isotropic and from 2.13MPa to 3.86MPa for the anisotropic aerogels, the compressive yield strength increased from 3.3kPa to 18.0kPa for the isotropic and from 32.3kPa to 52.5kPa for the anisotropic aerogels, and the toughness increased from 6.3kJ/m(3) to 24.1kJ/m(3) for the isotropic and from 22.9kJ/m(3) to 46.2kJ/m(3) for the anisotropic aerogels. The great range of properties, which can be achieved through compositional as well as architectural variations, makes these aerogels highly attractive for a large range of applications, for which either a specific composition, or a particular pore morphology, or both are required. Finally, because NFC is flammable, gasification experiments were performed, which revealed that the inclusion of MMT increased the heat endurance and shape retention functions of the aerogels dramatically up to 800°C while the mechanical properties were retained up to 300°C.
authors.affiliation: Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 USA.
authors.forename: Amalie E
authors.initials: AE
authors.lastname: Donius
authors.affiliation: Wallenberg Wood Science Center, KTH-Royal Institute of Technology, Teknikringen 56-58, S-10044 Stockholm Sweden.
authors.forename: Andong
authors.initials: A
authors.lastname: Liu
authors.affiliation: Wallenberg Wood Science Center and Department of Fiber and Polymer Technology, KTH- Royal Institute of Technology, Teknikringen 56-58, S-10044 Stockholm Sweden.
authors.forename: Lars A
authors.initials: LA
authors.lastname: Berglund
authors.affiliation: Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA. Electronic address: ulrike.wegst@dartmouth.edu.
authors.forename: Ulrike G K
authors.initials: UG
authors.lastname: Wegst
mesh_terms: D016880:Anisotropy; D001546:Bentonite / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D005615:Freezing; D005782:Gels; D006358:Hot Temperature; D055595:Mechanical Phenomena; D057139:Nanofibers / Q000737:chemistry*; D036103:Nanotechnology; D016062:Porosity
chemical_list: D005782:Gels; D001546:Bentonite; D002482:Cellulose
keywords: Directional solidification; Foams; Honeycombs; Nanoclay; Structure-property correlations