The nanocomposites synthesis requires the starting precursor materials: silicon dioxide of Aerosil 200, 12 nm particle size with 200 m2/g surface area from EVONIK named ASi and silicon dioxide of 100 nm from AVAN-nanoSil named NSi; the cellulose fibers of 20 micron, named C20, were provided by Aldrich (Saint Louis, MO, USA). The first solvent exchange step was adding water in droplets to the cellulose fibers and gently stirring for 15 min to get a gel, then ethanol was added in droplets at 1:1 volume ratio. Stirring was maintained more than 1 h, and then the second solvent exchange step was applied, adding acetone in droplets at 1:2 volume ratio according to water volume. At this point, the surface modified cellulose by solvent exchange method can be dried and named AG20, while the as-received cellulose is named C20. Stirring was still maintained for 3 h more; nanosilica, previously wet with acetone, was added while stirring for 10 min more and 20 min of an ultrasound bath of 40 kHz was also applied, taking care that the temperature did not exceed 40 °C. Finally, the resultant dough was dried at 60 °C in an oven, in order to obtain a fine powder.