On the Mechanical Modeling, Visco-Elasticity and Application of Aerographite, a 3D Carbon Nano-Material
A three dimensional carbon network material of seamless interconnected and hollow tubes, featuring a graphitic structure and an extremely low density has been designed and fabricated in cm3 volumes. The synthesis of this foam like material, named Aerographite, is based on highly-porous three dimensional networks from zinc oxide (ZnO) which are utilized as sacrifcial templates in a chemical vapor deposition (CVD) process. Such type of ZnO templates are produced by the flame transport synthesis (FTS) and allow free control over the template pore size, porosity and structure sizes. By consequent minimization of the applied carbon masses and tailored template porosity of 97%, the density of Aerographite was reduced to 180 mg/cm3 which had broken the record for lightest solid and remains up to date among the lightest materials in literature. The challenge to measure the mechanical response of super light materials has been tackled by a self built mechanical test set-up for an automated cyclic stress strain measurement. Highest specific moduli under tensile stress has been revealed. The microscopic deformation mechanisms of Aerographite networks are identified by detailed in situ studies in the scanning electron microscope and an analytical model is established to interpret the elastic properties of the bulk Aerographite. Further, the visco elastic properties of Aerographite are discussed and based on the findings in the in situ experiments, a first theory for the visco-elastic mechanisms in Aerographite is introduced. Finally the functional application of Aerographite as electrode material is demonstrated by the construction of two prototypes: an electrical double-layer capacitor equipped with Aerographite electrodes and a rechargeable lithium-sulfur battery with sulfur infiltrated Aerographite cathode. The capacity fading of the lithiumsulfur battery has been studied by cyclic voltammetry and the specific capacity of the electrical double-layer capacitor was measured.