Fabrication of elastic silica-bacterial cellulose composite aerogels with nanoscale interpenetrating network by ultrafast evaporative drying

A nanoscale interpenetrating network (IPN) structure comprised of silica gel and bacterial cellulose gel is designed and surface-modified, to enable the fabrication of intact composite aerogels via direct heating to a relatively high temperature (110 °C). Compared to currently employed supercritical drying, freeze drying and ambient pressure drying, this process shortens the drying time of the aerogels from more than a few hours to less than 10 min. Although wet silica gels and bacterial cellulose gels seriously crack and shrink, respectively, when they exist individually, synergic effects between the fragile silica gel skeleton and soft bacterial cellulose gel skeleton ensure structural integrity of the composite gels during ultrafast evaporative drying. In particular, these synergic effects endow the composite aerogels with excellent elasticity so that they could recover their initial shapes even after undergoing 60% deformation. Hence, in addition to their low density (less than 0.12 g cm−3), high specific surface area (823 m2 g−1) and low thermal conductivity (0.032 W m−1 K−1) are well preserved, these synergic effects also aid to overcome some limitations with respect to practical applications of the fragile silica aerogels and soft bacterial cellulose aerogels, particularly when they are used as effective kinetic energy absorbers and recyclable oil absorbents.