| Graphene, a two-dimensional (2D) mesh of carbon atoms, has received widespread attention due to its exceptional mechanical, electrical, and thermal properties. Integration of individual graphene sheets into macroscopic structures is essential for the application of graphene. And 3D aerogel has drawn great attention due to its low density, high porosity, large specific surface area and other advantages. Although many achievements of graphene aerogel have been made recently, there are still a number of important issues greatly restricting its large scale preparation, performance improvements and applications. For example, How to realize the large scale preparation of graphene aerogel with a facile non-template method? How to simultaneously achieve ultra-flyweight and high elastic aerogel through structural design? What is the ultimate apparent density of the aerogel with graphene as building blocks? Accordingly, this dissertation presented systemic studies on the fabrication of ultra-flyweight aerogel with graphene and carbon nanotubes as building blocks, and the explorations of its potential applications in areas such as adsorption, energy storage, phase change materials and others.The philosophy of’long span structures’in building architecture amazedly works in the micro world. We designed ultralight all-carbon aerogel from atomically thin graphenes as "walls", and extended the ultralight solids to their limit in density by utilizing the newly discovered graphene. Their ultralight graphene aerogel has extremely low density, down to 0.16 mg/cm3, obviously lower than that of plastic foams in our daily life, even only 15%that of air at room temperature, setting a new Guinness World Record as "the least dense solid". Also by the analogy of "enforcing ribs" in buildings, they implanted another carbon nanomaterial, one-dimensional carbon nanotube, onto the graphene "walls". The cooperative effect between graphene and carbon nanotube provides super elasticity to the graphene ultralight aerogel. After compression to the extent of 20%, this all-carbon aerogel is able to recover its shape, even for thousands times. More favorably, it can maintain the super elasticity in extreme temperature surroundings, even at high 900℃ and low -190℃ in liquid nitrogen.The aerogels possess super-high absorption capacities for organic solvents and oils, and can handle 900 times its weight in oil. In addition, paraffin can also be absorbed into the UFAs by melting infiltration to prepare phase-change energy storage materials. We found that the melting latent heat and freezing latent heatfor the paraffinn-filled UFAs are 7.8% and 28.7% higher than those of neat paraffin, rarely found in previous reports where the latent heat of composite is generally lower than that of neat phase-change materials. Additionally, the porous aerogel exhibited higher capacitance (86.1 F/g) than carbon nanotubes aerogel and better stability than graphene aerogle. The remarkable properties, such as outstanding temperature-invariant elasticity, ultralow density, excellent thermal stability, extremely high absorption capacities make the new stuff receive tremendous attention from both academia and mass media.In summary, a template-free, synergistic assembly strategy have been developed for the scalable fabrication of ultra-flyweight elastic aerogel with cell walls of giant graphene sheets and CNTs ribs. The ideal combination of giant size of constituent graphene sheets and their cooperative effect between graphene and CNTs offers the as-prepared aerogels integrated properties of outstanding temperature-invariant elasticity, ultralow density, excellent thermal stability, extremely high absorption capacities for organic liquids and PCMs, and good electrical conductivity. These charming multifunctional attributes would enable the UFAs many applications including elastic and flexible conductors, high-performance conductive polymer composites, organic absorbents, environmental remediation materials, phase-change energy storage, sensors, supercapacitors and catalyst beds. |
