Rensselaer Polytechnic Institute (RPI) researchers discovered that freestanding films of vertically aligned carbon nanotubes exhibit super-compressible, foam-like behavior. Under compression, the nanotubes collectively form zigzag buckles that can fully unfold to their original length upon load release. Compared with conventional low-density flexible foams, the nanotube films show much higher compressive strength, recovery rate, and sag factor, and the open-cell nature of the nanotube arrays gives excellent breathability. The nanotube films present a class of open-cell foam structures, consisting of well-arranged one-dimensional units (nanotube struts).
“Carbon nanotubes display an exceptional combination of strength, flexibility, and low density, making them attractive and interesting materials for producing strong, ultra-light foam-like structures,” says Pulickel Ajayan, former Henry Burlage Professor of Materials Science and Engineering at Rensselaer Polytechnic Institute.
“These nanotubes can be squeezed to less than 15 percent of their normal lengths by buckling and folding themselves like springs,” says Anyuan Cao, who did much of the work as a postdoctoral researcher in Ajayan’s lab and is now assistant professor of mechanical engineering at the University of Hawaii at Manoa. “After every cycle of compression, the nanotubes unfold and recover, producing a strong cushioning effect.”
Applications where strength and flexibility are needed, such as flexible electromechanical systems or coatings for absorbing energy.
When compared with conventional foams designed to sustain large strains, nanotube foams recovered very quickly and exhibited higher compressive strength. The thickness of the nanotube foams decreased slightly after several hundred cycles, but then stabilized and remained constant, even up to 10,000 cycles. Nanotubes also are stable in the face of extreme chemical environments, high temperatures, and humidity.
Pulickel Ajayan, while at Rensselaer, and a team of researchers at the University of Hawaii at Manoa and the University of Florida subjected films of vertically aligned nanotubes to a battery of tests, demonstrating their impressive strength and resilience.
Rensselaer Polytechnic Institute is offering a license for the super-compressible foam-like carbon nanotube films. The carbon nanotube foam and its manufacturing method are protected by U.S. Patent 7,473,411. Parties interested in licensing the technology should contact the RPI Office of Technology Commercialization.
Prof. Ajayan has recently accepted a position at Rice University, Houston, Texas. Some of the graduate students and post-doctoral researchers have joined him at the university. To get further information, connect to Prof. Ajayan's Rice University Website link.
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