Abstract
Carbon aerogels are highly porous materials with a large inner surface area. Due to their high electrical conductivity they are excellent electrode materials in supercapacitors. Their brittleness, however, imposes certain limitations in terms of applicability. In that context, novel carbon aerogels with varying degree of flexibility have been developed. These highly porous, light aerogels are characterized by a high surface area and possess pore structures in the micrometer range, allowing for a reversible deformation of the aerogel network. A high ratio of pore size to particle size was found to be crucial for high flexibility. For dynamic microstructural analysis, compression tests were performed in-situ within a scanning electron microscope allowing us to directly visualize the microstructural flexibility of an aerogel. The flexible carbon aerogels were found to withstand between 15% and 30% of uniaxial compression in a reversible fashion. These findings might stimulate further research and new application fields directed towards flexible supercapacitors and batteries.
Highlights
Carbon aerogels are open-porous materials with a three-dimensional micro- and mesoporous network
Several research teams have shown the influence of the pH value of the sol [7,14], the molar ratio of resorcinol to catalyst (R/Cat) [15], the catalyst type [16,17], and the drying method [18,19] on the morphology of RF aerogels and, of carbon aerogels
We utilized scanning electron microscope (SEM) to observe in-situ the microscopic structural evolution of flexible carbon aerogels during compression-release tests in order to probe the mechanism of their elasticity
Summary
Carbon aerogels are open-porous materials with a three-dimensional micro- and mesoporous network. Due to many excellent properties, such as a large surface area, a tunable, high porosity, and a low bulk density, carbon aerogels are promising materials for hydrogen storage or as a radiation adsorption material [2,3]. Pekala et al investigated the influence of microstructure on the mechanical properties of carbon aerogels [23] They observed that the compressive modulus and the compressive strength of aerogels are both strongly dependent on the bulk density. Carbon aerogels are consistently described as robust, glassy, and brittle They are reported to possess a great stiffness and strength, yet no ductility. Our research group has recently succeeded in preparing RF gels with varying degree of stiffness, spanning from brittle, to rubber-like, to super flexible [24,25]. In this study we visualize, with the help of this technique, the deformation of individual pores (pore size in the range of 2–20 μm) in the 3D network
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