Synthesis Of Graphene Aerogel & Aerogel Enhanced Composite And Their Applications

Graphene is considered a two-dimensional carbon nanofiller with a one-atom-thick planar sheet of sp2 bonded carbon atoms that are densely packed in a honeycomb crystal lattice, possesses a unique two-dimensional(2D) structure, high Conductivity(108 S/m) and charge carrier mobility(15000 cm2?V-1?s-1), great mechanical strength(130 GPa). In addition, the huge specific surface area of graphene is up to 2630m2/g.Therefore, when graphene was first discovered in 2004,it quickly became a hot scientific spot all over the world.The goal of this paper is to prepare graphene aerogel by freeze-drying method and apply graphene aerogels to the field of electromagnetic wave absorbing and shape memory composites. The conclusions of this research work are as follows:First, graphene aerogels were successfully prepared by freeze-drying method. By changing the content of polyvinyl alcohol(PVA) and graphene oxide(GO) and heat treatment method. We find that if the weight ratio between PVA and water is less than 1:250, no GO/PVA compound aerogel will form after freeze-drying. If the weight ratio between graphene oxide and water in the mixture is less than 1:500, graphene aerogel will not be obtained after pyrolysis. Compared with the aerogel fabricated by one-step annealing under 1050 ℃,aerogel gained by two-step(600 ℃ and 1050 ℃) annealing possess more flexibility.Second, the wave absorbing properties of aerogels were tested using the appropriate network analyzer. We found that the microwave absorbing performance of graphene aerogel will change according to the load of carbon nanotube in the aerogel. The maximum reflection loss will first increase from-35.49 dB to-43.97 dB then decreased to-37.14 d B with the in increasing load of carbon nanotube. At the same time, along with the increase of the load of carbon nanotubes, the reflection loss peak aerogel of the same thickness will be moved to the low frequency region.Third, we also probes into the application of aerogel in the field of composite materials. Using the method of vacuum casting, a shape memory aerogel/epoxy composite structure composed of a reduced carbon nanotubes and graphene compound aerogel as scaffold and epoxy resin as matrix was prepared. By applying dynamic mechanical analysis, we found that the glass transition temperature(Tg) as prepared composite and the corresponding matrix was close to each other, and the diminution of Tg for composite material will decrease with increasing the content of carbon nanotubes in the aerogel. Through the characterization of shape memory properties, we found that the composite material can recover its original shape by directly connect to a circuit with a voltage of 60 volts without the presence of outside heater.