Cellular materials such as foams or aerogels of nanofibrils of cellulose (NFC) constitute novel low density bio-based materials with high mechanical and insulation properties, and thus have a great potential in several engineering fields. They can be used in the automotive industry as heat/sound insulation systems, cores of structural sandwich composite panels, or for biomedical applications such as filters, scaffolds for tissues. NFC cellular materials can be obtained by ice templating, i.e., by freezing colloidal and concentrated NFC aqueous suspensions (or gels) and sublimation of the formed ice crystals (freeze-drying). The ice templating process has received considerable attention in recent years owing to its simplicity and to the wide variety of porous materials that this technique can provide. However, in the case of NFC gels, growth mechanisms of ice crystals formed during the freezing phase, i.e., when they squeeze and consolidate the remaining NFC gels up to very high NFC concentrations, are complex and still poorly understood. This severely hinders the optimisation of the microstructure of NFC cellular materials. The main objective of this project is to better understand them.
3D microstructure of a frozen NFC suspension observed with X-ray tomography.
On left, the ice phase and on right the NFC phase (sample size: 358x358x554 µm)
For that purpose, various experimental analyses are carried out to better understand the rheology of concentrated NFC gels and the growth of ice crystals in such gels:
This project involves a collaboration between the 3SR lab, the Centre National de Recherche Météorologique, the Institut des Géosciences et de l’Environnement, and the Laboratoire de Mécanique des Structures et des Contacts.
PI: Laurent Orgéas ; PhD Student: Shubham Gupta