Graphene can support 50,000 times its own weight and can spring back into shape after being compressed by up to 80%. Graphene also has a much lower density than comparable metal-based materials. A new super-elastic, three-dimensional form of graphene can conduct electricity, and will probably pave the way for flexible electronics.
The scientists published their findings in the journal Nature Communications. Dan Li, a materials engineer at Monash University in Clayton, Australia, was able to coax 1-centimeter-high graphene blocks from tiny flakes of graphene oxide using ice crystals as templates.
Graphene is a two-dimensional form of carbon that was first discovered less than a decade ago. It has exceptional strength and electrical conductivity, but being able to use these properties implies that scientists need to find ways to scale graphene up from nano-sized flakes.
Li and his colleagues used a technique called freeze casting, which involves growing layers of graphene oxide, an oxygen-coated soluble version of grapheme, between forming ice crystals. A thin layer of nanomaterial becomes trapped between the growing crystals, forming a continuous network that retains its structure once the ice is thawed.
This method was used before, but the resulting material has poor mechanical strength. In this study, researchers have shown that partially stripping the oxygen coating before freeze casting could enhance the bonding between adjacent flakes in the network.
The honeycomb-like network retained its shape after the ice was removed. The scientists chemically converted the graphene oxide into graphene, strengthening the inter-sheet bonding. These properties were attributed to the material’s structure, which forms an ordered network of hexagonal pores.
The structure could be used as a scaffold for flexible battery electrodes or form the basis of many composite materials. This super-elastic graphene has the potential to be used in biomedical applications as well.
Reference: “Biomimetic superelastic graphene-based cellular monoliths” by Ling Qiu, Jeffery Z. Liu, Shery L.Y. Chang, Yanzhe Wu and Dan Li, 4 December 2012, Nature Communications.