Abstract
Cellulose aerogel is an advanced thermal insulating biomaterial. However, the application of cellulose aerogel in thermal insulation still faces critical problems, for instance, the relatively low strength and large pore size without Knudsen effect. In this study, a silica areogel made from olivine silica rather than traditional tetraethoxysilane or water glass is employed to synthesize silica-cellulose composite aerogel applying a facile one-pot synthesis method. The silica aerogel nanoparticles are formed inside the cellulose nanofibrils by using sol-gel method and freeze-drying. The developed silica-cellulose composite aerogel has an obviosuly lowered thermal conductivity and is significantly stronger compared to plain cellulose aerogel. The microstructure of silica-cellulose aerogel was characterized by SEM, TGA, FTIR and N2 physisorption tests. The developed silica-cellulose aerogel had a bulk density of 0.055 ~ 0.06 g/cm3, compressive strength of 95.4 kPa, surface area of 900 m2/g and thermal conductivity of 0.023 W/(m·K). The thermal stability of the composite aerogel was also improved and showed the higher cellulose decomposition temperature. Furthermore, the composite aerogel is modified by trimethylchlorosilane making it hydrophobic, reaching a water contact angle of ~ 140°, enhancing its volumetric and thermo-phycial stability when applied in a humid environment. In conclusion, the resulting green silica-cellulose aerogel is a promising candidate for utilization as a high performance insulation material.
Highlights
Aerogel was first invented in 1931 by extracting the solvent in a silica gel without collapsing the silica gel structure [1]
The silica-cellulose composite aerogel (SCA) shows a random distribution of silica and cellulose fibers, due to the heterogenous nature of cellulose fibers and because silica aerogel was attached to these randomly distributed fibers
For SS-CNF1, the nanofibers were crossly linked within the silica aerogel structures; the silica surface was very smooth and showed a more homogeneous structure
Summary
Aerogel was first invented in 1931 by extracting the solvent in a silica gel without collapsing the silica gel structure [1]. Applying olivine-derived sodium silicate as a precursor instead of organic silica source (TEOS or TMOS) or commercial water glass can help to significantly reduce the energy consumption to produce aerogel. It was demonstrated that the novel composite aerogel had low thermal conductivity and improved mechanical strength Most of these studies prepared silica-cellulose aerogel by forming cellulose aerogel first and with organic silica source. Most of the studies investigate the cellulose hydrogel immersed in commercial water glass with a high modulus (3.3) and used acid to form silica nanoparticles, followed by supercritical drying. A facile synthesis of silica-cellulose aerogel (SCA) is presented by incorporating renewable cellulose nano-fibrils into the low-cost silicate sol-gel process and freeze-drying the composite gel.
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