The effects of structure and morphology on lithium storage in single-wall carbon nanotube (SWNT) bundles were studied by electrochemistry and nuclear magnetic resonance techniques. SWNTs were chemically etched to variable lengths and were intercalated with Li. The reversible Li storage capacity increased from LiC(6) in close-end SWNTs to LiC(3) after etching, which is twice the value observed in intercalated graphite. All the nanotubes became metallic upon intercalation of Li, with the density of states at the Fermi level increasing with increasing Li concentration. The enhanced capacity is attributed to Li diffusion into the interior of the SWNTs through the opened ends and sidewall defects.

Single-walled carbon nanotubes were studied by (13)C nuclear magnetic resonance (NMR). Two types of (13)C nuclear spins were identified with different spin-lattice relaxation rates. The fast-relaxing component, assigned to metallic tubes, followed the relaxation behavior expected in metals, and the density-of-states at the Fermi level increased with decreasing tube diameter. The slow-relaxing component has a significantly lower density-of-states at the Fermi level. Exposure to oxygen has a substantial effect on relaxation rates of both components.

X-ray radiation is widely used in medical and industrial applications. The basic design of the x-ray tube has not changed significantly in the last century. In this paper, we demonstrate that medical diagnostic x-ray radiation can be generated using a carbon nanotube (CNT) based field-emission cathode. The device can readily produce both continuous and pulsed x-ray with a programmable waveform and repetition rate. A total emission current of 28 mA was obtained from a 0.2 cm 2 area CNT cathode. The x-ray intensity is sufficient to image human extremity at 14 kVp and 180 mAs. Pulsed x-ray with a repetition rate greater than 100 kHz was readily achieved by programming the gate voltage. The CNT-based cold-cathode x-ray technology can potentially lead to portable and miniature x-ray sources for industrial and medical applications.

Chemically functionalized carbon nanotubes (see Figure) are shown to produce composites with improved uniformity and dispersion. At low nanotube loading, a significant enhancement of the mechanical properties can be obtained. Moreover, the polymer/nanotube composites show efficient load transfer between the fillers and the matrix.

Films of single‐walled carbon nanotubes have been obtained by simple evaporation of suspended nanotubes on a glass substrate. The technique has also been used to create patterned structures (see Figure) by treating the substrate before evaporation and thus creating hydrophobic and hydrophilic areas. The films showed orientational ordering, which could be useful for optical applications.