Controllable Preparation, Modificaiton And Properties Of Graphene Aerogels

Graphene aerogels represent a new form of monolithic carbon strcture with high porosity, low density and excellent conductivity that can serve as promising candidates in fields such as energy storage, environment remediation and catalyst support. The idea of controllable preparation of graphene aerogels with desired properties and the establishment of strategies that can modulate the properties of graphene aerogels leading to high performance composite remain great challenges. In the present thesis, an approach that combines colloid chemistry and microwave chemistry to the fabrication of ultralight and highly compressible graphene aerogels has been established after the investigation of the formation process of graphene aerogels. Then, strategies that can modify the properties of graphene aerogels have been proposed to achieve a serials of composites with special applications. Some progresses in the thesis are briefly summarized as follows.By means of manipulating the oxygen content in graphite oxides (GO) and/or graphene-based materials, we demonstrated that the microwave absorption capacity of carbon materials is highly dependent on their chemical composition and structure. The increase of oxygen in GO remarkably decreases its microwave absorption capacity due to the size decrease of the π-π conjugated structure in these materials and vice versa. The addition of a small amount graphene to GO leads to avalanche-like deoxygenation reaction of GO under microwave irradiation (MWI) and graphene formation.The interaction between microwaves and graphene or graphene-based materials may be used for the fabrication of a variety of graphene-based nanocomposites with exceptional properties and a wealth of practical applications.Chemically converted graphene aerogels with ultralight density and high compressibility have been prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as3mg/cm3show excellent resilience and can completely recover after more than90%compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials.An ultrafast microwave-mediated approach has been proposed for the production of carbon nanotube (CNT) and graphene hybrid aerogels, where CNTs are vertically anchored on the surface of cell walls of graphene aerogels. The hybrid aerogels show superhydrophobicity and superoleophilicity, high pore volume, large pore size and excellent compressibility demonstrating outstanding performance for recyclable oil sorption.Two kinds of polymer/graphene composites have been proposed by utilization of the graphene aerogels as substrate. One of them containg the graphene aerogel with pores fully occupied by expoxy resin show excellent conductivity even with ultralow graphene loading. The other hybrid strucutre consists of the graphene aerogel where the surface of cellular wall has been coated unfiromly with polydimethylsiloxane, the corrseponding structure delievers excellent compressibility, outstanding electromechanical performance and "sticky" superhydrophobicity.