Cellulose-based aerogels are reported that were generated using cellulose
nanofibril (CNF) gels in an ambient drying process. These nancellulose
aerogels were inspired by the preparation of a traditional Chinese
food, frozen tofu, which undergoes significant toughening after freezing
and thawing. It is this toughening mechanism that allows for the formation
of nanocellulose aerogels which ordinarily would collapse upon ambient
drying. By freezing hydrated CNF gel dispersions, solvent exchanging,
and drying at ambient pressure, monolithic nanocellulose aerogels
with high porosity (>98%), low density (as low as 0.018 g cm–3), and high surface area (>30 m2 g–1) were readily generated. Moreover, since no special
reactors are
required, these structures can be easily created over large areas.
For example, a hydrated CNF gel was frozen at −72 °C,
and then, the frozen gel was immersed directly in a 2-propanol bath
to allow solvent exchange. The resulting alcohol-infused gel was dried
at ambient pressure to fabricate monolithic CNF aerogels, enabling
the scalable fabrication of nanocellulose aerogels in an energy-efficient
and cost-effective manner.
Layered zeolite precursors were successfully exfoliated by brief shearing or sonication with the assistance of commercially available telechelic liquid polybutadienes at room temperature. The exfoliated zeolite nanosheets can form a stable suspension in an organic solvent, providing exciting potential for the fabrication of zeolite membranes, composite materials and hierarchical zeolites.
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