According to a recent report by the Physicist Organization Network, researchers at Carnegie Mellon University in Pittsburgh, PA, covered a graphene coating on a fragile carbon nanotube aerogel, making it look like a superman's cloak. The strength and pressure are changed to a collapsed state and become tough and withstand pressure, and when the load is removed, the original state can be completely restored. The results of the study were published in the journal Nature·Nanotechnology. The researchers said that the carbon nanotube mesh they demonstrated changed from fragility to superelasticity, only through graphene coatings, which provide superelasticity and fatigue resistance that will make carbon nanotube aerogels It is widely used in various fields including electrode materials, artificial muscles and other mechanical structures. Under normal circumstances, the coating increases the material's corrosion resistance, lubrication, aesthetics, surface chemical changes, sealing and other characteristics, but is not conducive to changes in mechanical properties. The researchers said: "Normal gels are mostly composed of a network of liquid materials whose surfaces are interlaced. The aerogel replaces the liquid material in the gel with a gas. The gel is dried at a critical temperature. The resulting aerogel is a lightweight material consisting of 99.9% air, but also has the characteristics of being dry, rigid, and solid as solid." In the current study, researchers used carbon nanotubes that had been added with air. An aerogel consisting of dispersed carbon nanotubes approximately 1 micron long. Carbon nanotube aerogels retain their shape under pressure because of the intermolecular interactions at the nodes, the carbon nanotubes will cross each other at various points. However, when these aerogels are compressed up to 90% on the basis of their original size, they collapse or cause permanent deformation, thereby limiting their potential applications. In an uncoated aerogel, after strong compression, the struts supporting the aerogel network at the nodes can be bent and freely rotated, thereby increasing the contact area between the carbon nanotubes and the new nodes formed. When the load is removed, restoring these nodes to their original state requires more force than applying pressure. It is precisely because the carbon nanotube aerogel does not have the power to recover to break through the new nodes formed during the compression process, and thus does not return to the original shape. To overcome this lack of flexibility, the researchers applied 1 to 5 layers of graphene coating on carbon nanotube aerogels. Researchers believe that graphene coatings can strengthen the node pillars and give them superelastic properties. In contrast, when the nodes are strongly compressed, the graphene-coated carbon nanotube aerogel has strong pillars that are not easily rotated, and the graphene on the nodes is compressed and crumpled, and such graphene sheets provide Resilience, breaking the new node formed like a spring. Studies have shown that graphene-coated carbon nanotube aerogels can withstand high compression and then bounce back to their original shape. It can withstand more than 1 million compression cycles and return to its original shape after pressure is released. This not only enables the aerogel to resist strong compression into a superelastic material, but also maintains its properties such as porosity and electrical conductivity. Obviously, this feature opens the door to new aerogel applications in the future.
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