Mechanical Energy Storage in Carbon Nanotube Springs

Compression of purified, unoriented, highly crystalline single-wall carbon nanotube material reveals an exceptionally large and reversible volume reduction. Density increases rapidly with increasing pressure, approaching that of graphite, and recovers completely upon pressure release. The reversible work done in compressing to 29thinspthinspkbar is 0.18 eV/C atom. We attribute this effect to crushing, or flattening the tube cross section from circular to elliptical. {copyright} {ital 1999} {ital The American Physical Society}