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1258-R05-11

Carbon Nanomaterials in Silica Aerogel Matrices Christopher E. Hamilton1, Manuel E. Chavez1, Juan G. Duque2, Gautam Gupta3, Stephen K. Doorn3, Andrew M. Dattelbaum3, and Kimberly A. DeFriend Obrey1 1 Polymers and Coatings Group, Materials Science and Technology Division, 2 Physcial Chemistry and Applied Spectroscopy Group, Chemistry Division, 3 Center for Integrated Nanotechnology, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos NM 87545, U.S.A. ABSTRACT Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWNTs and graphenebased materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications. INTRODUCTION Silica aerogels are typically produced by sol-gel polymerization of alkoxysilane precursors followed by supercritical solvent extraction (usually methanol, ethanol, or CO2).[1] Aerogels have been examined for numerous applications owing to their low density, high porosity, and thermal insulating properties.[2] Perhaps the most serious limitation of these materials is their poor mechanical strength. Previous efforts toward reinforcing silica aerogels have been focused on simple gel aging (Ostwald coarsening), the addition of filler materials (typically organic polymers), or surface treatments.[3–5] Carbon nanomaterials (SWNTs and graphene) have been widely investigated for use in composites. Two typical problems encountered with these materials are 1) poor homogeneity arising from insolubility of the nanomaterials and 2) poor interfacial adhesion between filler and matrix materials. Although SWNTs in carbon aerogel matrices have been frequently reported, there is very little in the literature pertaining to carbon nanotubes within silica aerogels and nothing regarding graphene-based silica aerogel composites.[6,7] We have addressed the solubility issue described above by using heavily oxidized carbon filler materials. Both ultrashort single-walled carbon nanotubes (US-SWNTs) and graphene oxide (GO) are dispersible in methanol,[8,9] allowing production of homogeneous alcogels. Methanol is a common solvent for silica gel preparation; hydrolysis and condensation of tetramethoxysilane (TMOS) leave methanol as the byproduct (Figure 1). Moreover, methanol can be supercritically extracted under reasonably safe conditions (80 atm, 239 °C), avert