Preparation And Applications Of Three-dimensional Carbon Nanomaterials

Carbon nanotubes,graphene,porous carbon and other carbon nanomaterials are tagged with the excellent mechanical,electrical and thermal properties due to their structural features such as high aspect ratio,dirac point and high specific surface area.Carbon nanomaterials,with their intrinsic properties,could be the building blocks for various materials applied in energy dissipation,energy storage and flexible electronic devices,in which the performance is highly linked with the interaction between these nano-sized building blocks.Our strategy to make the three-dimensional carbon materials was to assemble these building blocks in a proper route for specific use,where their interaction was tailored to optimize the macro properties.The main research contents and results are listed as follows:(1)The one-dimensional carbon nanotube was chosen as the building block for energy dissipative material through water-assisted chemical vapor deposition.It exhibited the damping ability with the specific dissipated energy up to 0.82 J/kg at the impact velocity from 1 to 3 m/s,which was 4.3 times of that of polyurethane sponge.Microscopic investigation revealed an intertube structure where the wavy carbon nanotubes traversed laterally,making van der Waals interconnections with the vertical aligned carbon nanotubes bundles.The vertical aligned carbon nanotube bundles resembled the scaffolds,which not only improved the mechanical strength of the material,but favored the tube-tube interactions to be parallel to the impact during collisions.The interacted tubes were found to be separated to dissipate the impact by overcoming these van der Waals attraction.(2)The two-dimensional graphene was chosen as the building block for three-dimensional partially overlapped graphene networks by the chemical reduction method with the reduction time being controlled.The stretchable strain sensor based on the graphene network was made,which exhibited the durability up to 300,000 cycles,the temperature stability over-45～180 ℃ and frequency stability ranged from 0.1 to 5Hz.The in-situ transmission electron microscope observation revealed that the partially overlapped graphene sheets produced relative slipping under the applied strain.Their overlapping area varied with the applied strain,thereby producing the change of the material resistance.The three-dimensional graphene network is the key for the extra-ordinary stability of the strain sensor by controlling the electrical resistance variation within the local slippage.(3)The three-dimensional porous carbon materials with uniform size were chosen as the building blocks,and the drop-casting method was used to fabricate the stretchable strain sensor.Not only exhibiting the high stretchability,high sensitivity and fast response,the material possessed the high durability as well that demonstrated over 10,000 stretching cycles at 80%strain.The structural evolution of conductive pathway was investigated under both optical and microscopic observation throughout the loading/unloading cycle.It revealed that the material possessed the cracking-repairing ability by minimizing stress concentrations at large strains due to the exceptionally uniform distribution of three-dimensional porous carbon materials.(4)The three-dimensional porous carbon materials with the nitrogen and sulfur doped were chosen as the building blocks for the electrode materials for supercapacitors,which exhibited an excellent capacitive performance(high specific capacitance of 360 F/g,excellent cycling stability with capacitance retention of 92%over 10,000 cycles at 5 A/g).The X-ray photoelectron spectroscopy analysis showed that the defects on carbon lattices through self-contained heteroatoms could act as the reactive sites with the lowered binding energy to introduce more heteroatoms during the following high-temperature "external-doping",leading to the improvement of capacitive performance.