Ultra-low-density silver aerogels via freeze-substitution

Herein is reported a method for fabricating <10 mg/cm3 silver aerogels via the freeze casting of aqueous nanowire suspensions followed by freeze substitution and supercritical drying. This method overcomes the limitations of traditional freeze drying and yields highly uniform, crack-free monoliths that undergo no measurable shrinkage with excellent mold reproduction. Significantly, freeze substitution enables the use of high concentrations of cryoprotectants to control the freezing process and, hence, the pore architecture of the resulting aerogels. Due to its physical nature, this method is applicable to the fabrication of materials with a broad range of compositions.