title: Multi-scale cellulose based new bio-aerogel composites with thermal super-insulating and tunable mechanical properties.
abstract: Bio-composite aerogels based on bleached cellulose fibers (BCF) and cellulose nanoparticles having various morphological and physico-chemical characteristics are prepared by a freeze-drying technique and characterized. The various composite aerogels obtained were compared to a BCF aerogel used as the reference. Severe changes in the material morphology were observed by SEM and AFM due to a variation of the cellulose nanoparticle properties such as the aspect ratio, the crystalline index and the surface charge density. BCF fibers form a 3D network and they are surrounded by the cellulose nanoparticle thin films inducing a significant reduction of the size of the pores in comparison with a neat BCF based aerogel. BET analyses confirm the appearance of a new organization structure with pores of nanometric sizes. As a consequence, a decrease of the thermal conductivities is observed from 28mWm(-1)K(-1) (BCF aerogel) to 23mWm(-1)K(-1) (bio-composite aerogel), which is below the air conductivity (25mWm(-1)K(-1)). This improvement of the insulation properties for composite materials is more pronounced for aerogels based on cellulose nanoparticles having a low crystalline index and high surface charge (NFC-2h). The significant improvement of their insulation properties allows the bio-composite aerogels to enter the super-insulating materials family. The characteristics of cellulose nanoparticles also influence the mechanical properties of the bio-composite aerogels. A significant improvement of the mechanical properties under compression is obtained by self-organization, yielding a multi-scale architecture of the cellulose nanoparticles in the bio-composite aerogels. In this case, the mechanical property is more dependent on the morphology of the composite aerogel rather than the intrinsic characteristics of the cellulose nanoparticles.
authors.affiliation: Université de Bretagne Sud, Laboratoire Ingénierie des Matériaux de Bretagne, BP 92116, 56321 Lorient Cedex, France.
authors.forename: Bastien
authors.initials: B
authors.lastname: Seantier
authors.affiliation: Université de Bretagne Sud, Laboratoire Ingénierie des Matériaux de Bretagne, BP 92116, 56321 Lorient Cedex, France; Cadi Ayyad University, Faculty of Sciences and Technologies, Laboratory of Organometallic and Macromolecular Chemistry, Avenue AbdelkrimElkhattabi, B.P. 549, Marrakech, Morocco.
authors.forename: Dounia
authors.initials: D
authors.lastname: Bendahou
authors.affiliation: Université de Bretagne Sud, Laboratoire Ingénierie des Matériaux de Bretagne, BP 92116, 56321 Lorient Cedex, France.
authors.forename: Abdelkader
authors.initials: A
authors.lastname: Bendahou
authors.affiliation: Université de Bretagne Sud, Laboratoire Ingénierie des Matériaux de Bretagne, BP 92116, 56321 Lorient Cedex, France. Electronic address: yves.grohens@univ-ubs.fr.
authors.forename: Yves
authors.initials: Y
authors.lastname: Grohens
authors.affiliation: Cadi Ayyad University, Faculty of Sciences and Technologies, Laboratory of Organometallic and Macromolecular Chemistry, Avenue AbdelkrimElkhattabi, B.P. 549, Marrakech, Morocco. Electronic address: h.kaddami@uca.ma.
authors.forename: Hamid
authors.initials: H
authors.lastname: Kaddami
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D057139:Nanofibers / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry; D016062:Porosity; D017550:Spectroscopy, Fourier Transform Infrared; D013814:Thermal Conductivity; D014961:X-Ray Diffraction
chemical_list: D005782:Gels; D002482:Cellulose
keywords: Cellulose; Cellulose nanocrystals (CNC); Freeze-drying; Mechanical properties; Multi-scale architecture; Nanofibrillated cellulose (NFC); Super-insulation; porosity