Nanotubes from Carbon.

Masses of single-walled carbon nanotubes (SWNTs) with a large mean diameter of about 1.85 nanometers, synthesized by a semicontinuous hydrogen arc discharge method, were employed for hydrogen adsorption experiments in their as-prepared and pretreated states. A hydrogen storage capacity of 4.2 weight percent, or a hydrogen to carbon atom ratio of 0.52, was achieved reproducibly at room temperature under a modestly high pressure (about 10 megapascal) for a SWNT sample of about 500 milligram weight that was soaked in hydrochloric acid and then heat-treated in vacuum. Moreover, 78.3 percent of the adsorbed hydrogen (3.3 weight percent) could be released under ambient pressure at room temperature, while the release of the residual stored hydrogen (0.9 weight percent) required some heating of the sample. Because the SWNTs can be easily produced and show reproducible and modestly high hydrogen uptake at room temperature, they show promise as an effective hydrogen storage material.

https://science.sciencemag.org/content/sci/286/5442/1127.full.pdf

Hydrogen Storage in Single-Walled Carbon Nanotubes at Room Temperature

Conducting polymer artificial muscles

Carbon nanotubes (CNTs), due to their unique electronic and extraordinary mechanical properties, have been receiving much attention for a wide variety of applications. Recently, plasma enhanced chemical vapour deposition (PECVD) has emerged as a key growth technique to produce vertically-aligned nanotubes. This paper reviews various plasma sources currently used in CNT growth, catalyst preparation and growth results. Since the technology is in its early stages, there is a general lack of understanding of growth mechanisms, the role of the plasma itself, and the identity of key species responsible for growth. This review is aimed at the low temperature plasma research community that has successfully addressed such issues, through plasma and surface diagnostics and modelling, in semiconductor processing and diamond thin film growth.

https://iopscience.iop.org/article/10.1088/0963-0252/12/2/312/pdf

Carbon nanotube growth by PECVD: a review

Carbon capture by physical adsorption: Materials, experimental investigations and numerical modeling and simulations - A review

Carbon nanotubes with single-layer walls

Macroscopic quantities of single-layer carbon nanotubes have recently been synthesized by co-condensing atomic carbon and iron group or lanthanide metal vapors in an inert gas atmosphere. The nanotubes consist solely of carbon, sp2-bonded as in graphene strips rolled to form closed cylinders. The structure of the nanotubes has been studied using high-resolution transmission electron microscopy. Iron group catalysts, such as Co, Fe, and Ni, produce single-layer nanotubes with diameters typically between 1 and 2 nm and lengths on the order of micrometers. Groups of shorter nanotubes with similar diameters can grow radially from the surfaces of lanthanide carbide nanoparticles that condense from the gas phase. If the elements S, Bi, or Pb (which by themselves do not catalyze nanotube production) are used together with Co, the yield of nanotubes is greatly increased and tubules with diameters as large as 6 nm are produced. Single-layer nanotubes are anticipated to have novel mechanical and electrical properties, including very high tensile strength and one-dimensional conductivity. Theoretical calculations indicate that the properties of single-layer tubes will depend sensitively on their detailed structure. Other novel structures, including metallic crystallites encapsulated in graphitic polyhedra, are produced under the conditions that lead to nanotube growth.

A reliable source of coherent ns pulses of infrared radiation continuously tunable between 1.4 and 22 μm has been designed and built with the aim of developing a time-resolved infrared vibrational spectroscopy for species adsorbed on surfaces. The system is based on a Nd: YAG-laser and dye-laser combination which drive difference mixing processes in a sequence of nonlinear optical crystals (two LiNbO3, and a CdSe or AgGaS2). The system operates at MW peak power levels above 2500 cm−1, at kW power levels from 1000–2500 cm−1 and at 10–100 W levels down to 450 cm−1. These power levels are certainly sufficient for spectroscopic purposes, and at shorter wavelengths molecular pumping and applications requiring high-power should be possible. Vibrational spectra of a monolayer of CO adsorbed on Pt in an electrochemical cell have been obtained in an initial application of this source.

A laser infrared source of nanosecond pulses tunable from 1.4 to 22 μm

TIME-RESOLVED INFRARED SPECTRAL PHOTOGRAPHY ABSTRACT An intense broadband continuum light pulse of uniform spectral intensity and short time duration is generated, then downconverted in frequency to a region of interest, preferably in the infrared region, by applying it as a pump pulse to a molecular or atomic vapor so as to induce stimu-lated Raman scattering. The resulting uniform spectral intensity distribution Raman Stokes pulse is then used to probe a sample. The sample converts the distribution of the probe pulse into a nonuniform spectral intensity distribu-tion which contains the absorption spectrum of the sample. This spectrum pulse has the same spectral bandwidth and time duration as the Raman Stokes pulse and is finally upconvert-ed in frequency to a region where the spectrum pulse can be conveniently recorded. This is done with a four-wave Raman mixing process in an alkali metal vapor. The vapor is simultaneously pumped with the spectrum pulse and with a second pumping light pulse (or beam) having a frequency in the vicinity of a suitable resonance line of the vapor so as to induce SERS. In the alkali metal vapor, the re-sulting Raman Stokes pulse and spectrum pulse beat to-gether with the second pumping light pulse to produce an upconverted pulse at a higher frequency band, which sur-prisingly also tends to have the same spectral bandwidth, intensity distribution (spectrum) and time duration as the spectrum pulse. The upconverted pulse is then recorded either photographically or photoelectrically with conven-tional spectrographic apparatus.

Time-resolved infrared spectral photography

The theory of second-harmonic generation (SHG) that is due to quadrupole and magnetic-dipole second-order optical susceptibilities is developed for monochromatic, focused beams of arbitrary transverse mode structure and polarization character. The strength of SHG depends sensitively on the polarization character of the beam.

Quadrupole second-harmonic generation for a focused beam of arbitrary transverse structure and polarization.

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Carbon nanotubes with single-layer walls

Carbon nanotubes with single-layer walls

A laser infrared source of nanosecond pulses tunable from 1.4 to 22 μm

Time-resolved infrared spectral photography

Quadrupole second-harmonic generation for a focused beam of arbitrary transverse structure and polarization.