Organic/inorganic nanocomposite aerogels encompass the superior properties of both, such as flexibility of the organics and thermal stability of the inorganics. In this paper, we demonstrated a facile way of in situ synthesis of silica on TEMPO oxidized cellulose nanofibrils (CNFs) to form CNF/silica aerogels via an aqueous sol-gel process. Transparent hydrogels were obtained by aging sodium silicate and CNFs at varied ratios. The gelation process was monitored by AFM imaging and rheological behaviors. The highest storage modulus G’ was observed at 8/2 CNFs/Na2SiO3 composition, indicating strongest hydrogel possibly due to the more extensive network structures. The hydrogels were solvent exchanged to tert-butanol and then freeze-dried to yield lightweight aerogel with density less than 8 mg/cm3. The obtained aerogels are highly meso-porous, evident by surface pores less than 100 nm observed under SEM and internal mesopores indicated from BET analysis. As the silicate loading contents increased from 10 to 60 wt%, the BET surface area increased from 152-342 m2/g while the mesopores clearly lowered from 50 to 8 nm. EDS mapping showed homogeneously dispersed silica and CNFs in the aerogel without evident phase separation. Increased silica contents from 0.51-19.34 wt% improved the thermal stability of the composite aerogels. Due to the presence of silica, the obtained porous aerogel could be facilely functionalized via silane reactions for practical applications such as oil/water separation, gas and pollutant adsorption, etc.

Sol-gel synthesis of cellulose nanofibrils/silica nanocomposite aerogels

251st National Meeting (2016)

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