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Metallic single-wall carbon nanotubes, synthesized through a pulsed-laser vaporization process, were selectively reacted with dodecyl-oxybenzene-diazonium tetrafluoroborate to yield tetrahydrofuran (THF) suspensions of nanotubes enriched in metallic content. The nanotube material that did not suspend in THF displayed a lower D/G ratio in Raman spectroscopy indicating less covalent functionalization and corresponds to an increase in semiconducting nanotube population. After the THF suspendable nanotubes were extracted from the unsuspendable nanotube material, the two separate nanotube populations were stripped of the dodecyloxybenzene functional groups through an annealing process. In this way, the functionalization process was made to be reversible whereby the nanotubes from both semiconducting and metallically enriched populations could have their original band gap properties restored.

Pulsed laser vaporization synthesis of single-wall carbon nanotubes on Co/Ni and Rh/Pd catalysts was explored with respect to variations in the production temperature. The nanotube type populations were determined via photoluminescence, UV-Vis-NIR absorption and Raman spectroscopy. It was found that lowered production temperature leads to smaller nanotube diameters and exceptionally narrow (n, m) type distributions, with marked preference towards large chiral angles for both catalysts. Interestingly, larger nanotube diameters tend to be associated with larger chiral angles. These results demonstrate that PLV production technique can provide at least partial control over the nanotube (n, m) populations. In addition, these results have implications for the understanding the nanotube nucleation mechanism in the laser oven. SWCNT synthesized at lower temperatures appear quite attractive as a starting material for nanotube type separation experiments.

In the interest of developing a highly sensitive, low power radiation dosimeter, a series of tests were performed on single-wall carbon nanotube (SWCNT)-based nanomaterials to monitor their respons...

Metal impurities within as-produced single-walled carbon nanotubes (SWCNTs) are generally coated with thick shells of graphitic carbon, which prevent the acid treatments commonly used in SWCNT purification from attacking the metals. The purpose of this study was to determine a more effective and efficient means for the removal of metal impurities from SWCNTs produced by pulsed laser vaporization (PLV). The method investigated was a modified version of a soft-bake purification procedure developed at Rice University, and in the current work, the soft-bake temperature suitable for PLV-produced SWCNTs was determined, and several samples were purified. The quality of material was determined using the standard protocol developed at NASA Johnson Space Center (JSC), and data was collected for several samples in order to determine the consistency and reproducibility of the purification yield and purity. The properties and quality of soft-bake purified material were compared with those of several equivalent materia...

Samples from nanotubes produced by various methods are analyzed by laser desorption-ionization ion mobility time-of-flight mass spectrometry (LDI-IM-TOF-MS). The measurements find mostly positive f...

Single-walled carbon nanotubes (SWCNTs) were added to aluminium using friction stir processing (FSP). The SWCNTs survived the thermal and stress cycles involved with friction stir processing. The Raman spectroscopy and SEM results are presented. Potential applications of nanotubes inserted into metals by this method are discussed.

Challenges associated with damage tolerance in polymer matrix composites must be successfully addressed in order to ensure highly reliable structures with significant weight savings. Self-healing materials provide a viable means to surmount damage tolerance concerns, thereby allowing for the realization of the mass reduction such structures have promised but not yet achieved. Introduction of multifunctional properties into self-healing composites can further extend their usefulness. This study examines the incorporation of carbon nanotubes into a self-healing composite in order to achieve this. Composite panels were fabricated with carbon fibers, a bismaleimide tetrafuran (2MEP4F) polymer resin, and various carbon nanotube materials. The composites exhibit enhancement in electrical, mechanical, and thermal properties. The healing mechanism is a thermally activated reversible polymerization of the 2MEP4F resin. The proposed method of heating exploits the enhanced microwave absorption inherent to carbon nanotubes to provide the thermal energy required for the reversible polymerization. Microwave testing demonstrated that the heating efficiency is increased, allowing uniform heating to the required temperature for polymer healing. Impacted composites show localized heating at the damage site, which implies that microwave heating can also be used as a means for damage detection and potential structural health monitoring.

Many potential applications of carbon nanotubes are expected to benefit from the availability of single-walled carbon nanotube materials enriched in metallic species, and specifically armchair nanotubes. The present work focuses on the modification of the pulsed laser vaporization (PLV) technique to selectively produce certain carbon nanotube structures. Nanotube nuclei were “warmed-up” with an additional laser pulse, timed to coincide approximately with the nucleation event. The effect of the second laser on the carbon vapor temperature was studied by emission spectroscopy. Nanotube type populations with and without warm-up were compared by means of absorption, photoluminescence, and Raman spectroscopy. It was found that the warm-up of nanotube nuclei with a laser pulse has a noticeable, albeit small, effect on the nanotube population. The intensity of spectral features associated with (9,7) nanotube and its large chiral angle neighbors increased, while small chiral angle nanotubes decreased, with exception of the (15,0) tube. This experiment demonstrates that nanotube population during PLV synthesis can be manipulated in a controlled fashion.

Single wall carbon nanotubes (SWCNT) have previously been considered potential catalyst supports in proton exchange membrane fuel cells (PEMFC) [1]. Earlier research and development of SWCNT for PEMFC catalyst supports has been advanced by utilizing differing SWCNT purities and carbon blacks in differing ratios. This study validates the performance of SWCNT and introduces new concepts for SWCNT membrane fabrication.