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We report an approach to fabricate high conductivity graphite sheets based on a heat-and-current treatment of filtrated, exfoliated graphite flakes. This treatment combines heating (~ 900 °C) and in-plane electrical current flow (550 A·cm−2) to improve electrical conductivity through the reduction of crystalline defects. This process was shown to require only a 1-min treatment time, which resulted in a 2.1-fold increase in electrical conductivity (from 1088 ± 72 to 2275 ± 50 S·cm−1). Structural characterization by Raman spectroscopy and X-ray diffraction indicated that the improvement electrical conductivity originated from a 30-fold improvement in the crystallinity (Raman G/D ratio increase from 2.8 to 85.3) with no other observable structural transformations. Significantly, this treatment was found to act uniformly across a macroscopic (10 mm) sheet surface indicating it is on the development of applications, such as electrodes for energy generation and storage and electromagnetic shielding, as well as on the potential for the development of large-scale treatment technologies. [ABSTRACT FROM AUTHOR]

Studies on confined water are important not only from the viewpoint of scientific interest but also for the development of new nanoscale devices. In this work, we aimed to clarify the properties of confined water in the cylindrical pores of single-walled carbon nanotubes (SWCNTs) that had diameters in the range of 1.46 to 2.40 nm. A combination of x-ray diffraction (XRD), nuclear magnetic resonance, and electrical resistance measurements revealed that water inside SWCNTs with diameters between 1.68 and 2.40 nm undergoes a wet-dry type transition with the lowering of temperature; below the transition temperature Twd, water was ejected from the SWCNTs. Twd increased with increasing SWCNT diameter D. For the SWCNTs with D = 1.68, 2.00, 2.18, and 2.40 nm, Twd obtained by the XRD measurements were 218, 225, 236, and 237 K, respectively. We performed a systematic study on finite length SWCNT systems using classical molecular dynamics calculations to clarify the effect of open ends of the SWCNTs and water content on the water structure. It was found that ice structures that were formed at low temperatures were strongly affected by the bore diameter, a = D - σOC, where σOC is gap distance between the SWCNT and oxygen atom in water, and the number of water molecules in the system. In small pores (a < 1.02 nm), tubule ices or the so-called ice nanotubes (ice NTs) were formed irrespective of the water content. On the other hand, in larger pores (a > 1.10 nm) with small water content, filled water clusters were formed leaving some empty space in the SWCNT pore, which grew to fill the pore with increasing water content. For pores with sizes in between these two regimes (1.02 < a < 1.10 nm), tubule ice also appeared with small water content and grew with increasing water content. However, once the tubule ice filled the entire SWCNT pore, further increase in the water content resulted in encapsulation of the additional water molecules inside the tubule ice. Corresponding XRD measurements on SWCNTs with a mean diameter of 1.46 nm strongly suggested the presence of such a filled structure. [ABSTRACT FROM AUTHOR]

Understanding the fundamental mechanisms and limiting processes of the growth of single-walled carbon nanotube (SWCNT) would serve as a guide to achieve further control on structural parameters of SWCNT. In this paper, we have studied the growth kinetics of a series of SWCNT forests continuously spanning a wide range of diameters (1.9-3.2 nm), and have revealed an additional fundamental growth limiting process where the mass of the individual SWCNT is determined by the individual catalyst volume. Calculation of the conversion rate of carbon atoms into CNTs per Fe atom is 2 × 10² atoms per second. This rate limiting process provides an important understanding where the larger diameter SWCNT would grow faster, and thus be more suited for mass production. [ABSTRACT FROM AUTHOR]

Electron density of single wall carbon nanotubes (SWCNT) is effectively modified by hexaiodobenzene (HIB) molecules using liquid-phase adsorption. UV-Vis-NIR absorption spectra of the HIB-adsorbed SWCNT, especially in the NIR region, showed a disappearance of S11 transitions between the V1 valance band and the C1 conduction band of van Hove singularities which can be attributed to the effective charge transfer between HIB and the SWCNT. The adsorption of HIB also caused significant peak-shifts (lower frequency shift around 170 cm-1 and higher shift around 186 cm-1) and an intensity change (around 100-150 cm-1 and 270-290 cm-1) in the radial breathing mode of Raman spectra. The charge transfer from SWCNT to HIB was further confirmed by the change in the C1s peak of X-ray photoelectron spectrum, revealing the oxidation of carbon in SWCNT upon HIB adsorption. [ABSTRACT FROM AUTHOR]

PVA is reinforced with SWCNTs using green tea extract as a dispersant to achieve good dispersion of the SWCNTs in an organic solvent and finally high-performance composite fibers. A combination of green tea extract/DMSO/SWCNT/PVA is found to disperse larger aggregates of SWCNTs to individual or thin bundles of a few nanotubes. Incorporation of 0.5 wt% SWCNTs into PVA fibers yields a tensile strength of 2.42 GPa, a Young's modulus of 46 GPa, toughness of 105 J · g−1 at a failure strain of 11%, and a loop strength of 245 MPa, much higher than the values of commercial PVA fibers. The incorporation of highly dispersed SWCNTs suppresses the fibrillation tendency of the PVA fibers. The applied load is effectively transferred from the matrix to the SWCNTs. [ABSTRACT FROM AUTHOR]

Green tea has recently been reported to be a good dispersant of single-walled carbon nanotubes (SWCNTs) in aqueous media. In the current work, green tea extract powder was examined for dispersion of SWCNTs in organic solvents. Dimethyl sulfoxide (DMSO) was found to be a good solvent of green tea extract for dispersing SWCNTs. A combination of green tea (dispersant)/DMSO (solvent)/polyvinyl alcohol (PVA) (nanotube wrap) was obtained that resulted in the dispersion of SWCNTs almost to individual nanotubes or to very thin nanotube bundles. The reinforcing ability of highly dispersed SWCNTs was explored in a PVA matrix producing PVA-SWCNT gel-spun fibers. Extraordinary reinforcing effects on the tensile and dynamic mechanical properties of the composites were observed by incorporating a minute amount of SWCNTs (∼1 wt% to PVA). The analysis revealed effective stress transfer through the PVA crystalline interfaces surrounding the nanotubes. [ABSTRACT FROM PUBLISHER]

Among all known materials, we found that a forest of vertically aligned single-walled carbon nanotubes behaves most similarly to a black body, a theoretical material that absorbs all incident light. A requirement for an object to behave as a black body is to perfectly absorb light of all wavelengths. This important feature has not been observed for real materials because materials intrinsically have specific absorption bands because of their structure and composition. We found a material that fan absorb light almost perfectly across a very wide spectral range (0.2-200 μm). We attribute this black body behavior to stem from the sparseness and imperfect alignment of the vertical single-walled carbon nanotubes. [ABSTRACT FROM AUTHOR]

In order to be useful as microelectromechanical devices, carbon nanotubes with well-controlled properties and orientations should be made at high density and be placed at predefined locations. We address this challenge by hierarchically assembling carbon nanotubes into closely packed and highly aligned three-dimensional wafer films from which a wide range of complex and three-dimensional nanotube structures were lithographically fabricated. These include carbon nanotube islands on substrates, suspended sheets and beams, and three-dimensional cantilevers, all of which exist as single cohesive units with useful mechanical and electrical properties. Every fabrication step is both parallel and scalable, which makes it easy to further integrate these structures into functional three-dimensional nanodevice systems. Our approach opens up new ways to make economical and scalable devices with unprecedented structural complexity and functionality. [ABSTRACT FROM AUTHOR]

We present a rational and general method to fabricate a high-densely packed and aligned single-walled carbon-nanotube (SWNT) material by using the zipping effect of liquids to draw tubes together. This bulk carbon-nanotube material retains the intrinsic properties of individual SWNTs, such as high surface area, flexibility and electrical conductivity. By controlling the fabrication process, it is possible to fabricate a wide range of solids in numerous shapes and structures. This dense SWNT material is advantageous for numerous applications, and here we demonstrate its use as flexible heaters as well as supercapacitor electrodes for compact energy-storage devices. [ABSTRACT FROM AUTHOR]

We have succeeded in synthesizing vertically aligned doubled-walled carbon nanotube (DWNT) forests with heights of up to 2.2 mm by water-assisted chemical vapour deposition (CVD). We achieved 85% selectivity of DWNTs through a semi-empirical analysis of the relationships between the tube type and mean diameter and between the mean diameter and the film thickness of sputtered Fe, which was used here as a catalyst. Accordingly, catalysts were engineered for optimum DWNT selectivity by precisely controlling the Fe film thickness. The high efficiency of water-assisted CVD enabled the synthesis of nearly catalyst-free DWNT forests with a carbon purity of 99.95%, which could be templated into organized structures from lithographically patterned catalyst islands. [ABSTRACT FROM AUTHOR]

Temperature dependence on synthesis of carbon nanotube by thermal catalytic decomposition of hydrocarbon was investigated. Benzene, thiophene, and iron(III)phthalocyanine are used for synthesis. As a result, the thickness of 20 nm, 5 to 10 layers solid structured carbon nanotube was obtained. [ABSTRACT FROM PUBLISHER]

This is an investigation on the storage of hydrogen at 288∼308 K on ultra-fine particles. We studied the pore structure by nitrogen adsorption at 77 K on thermal-treated ultra-fine particles with CO 2 and pristine ultra-fine particles. [ABSTRACT FROM PUBLISHER]

Temperature dependence on synthesis of carbon nanotube by thermal catalytic decomposition of hydrocarbon was investigated. Benzene, thiophene, and iron(III)phthalocyanine are used for synthesis. As a result, the thickness of 20 nm, 5 to 10 layers solid structured carbon nanotube was obtained. [ABSTRACT FROM AUTHOR]

This is an investigation on the storage of hydrogen at 288∼308 K on ultra-fine particles. We studied the pore structure by nitrogen adsorption at 77 K on thermal-treated ultra-fine particles with CO 2 and pristine ultra-fine particles. [ABSTRACT FROM AUTHOR]

The sp2 C2 species, C2H3/C2H4, has been found as a key precursor for the efficient growth of single-wall carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) from hydrocarbons. [ABSTRACT FROM AUTHOR]

An in situ telecentric height monitoring system was employed as a standard characterization tool for in situ height monitoring of nanotube forests. We demonstrated that the system possesses a wide dynamic range beyond the centimeter scale, high resolution of 1 μm, free from routine maintenance, simple installation, and use in contrast to previous methods. These features were highlighted by the monitoring of a 5 mm tall forest, the examination of the effect of gas species on growth rates, and the automatic control forest height. [ABSTRACT FROM AUTHOR]

We report on site-selective growth of multiwalled carbon nanotubes (MWNTs) from a Co nanoparticle catalyst patterned by an ink-jet printing (IJP) technique. The dispersion of the Co nanoparticles was employed as "catalyst ink" for the IJP, and the catalyst pattern was subjected to chemical vapor deposition of acetylene gas. The patterned array of MWNTs was obtained with a dot size around 5-30 µm and showed field emission of electrons corresponding to the printed pattern. The present method offers a simple and powerful means to pattern carbon nanotubes at desired positions with any patterns. [ABSTRACT FROM AUTHOR]

The potentiality of optical absorption spectroscopy (OAS) for the estimation of mean diameter of single-wall carbon nanotubes (SWCNTs) from electronic transition energies has been explored. The observed dependence of electronic transition energies of both metallic and semiconducting SWCNTs on their mean diameters clearly showed that transition energies scale inversely with the tube diameter. In the present study, the applicability of this estimation method has been experimentally confirmed for the diameter range of 1–2 nm and is expected to be useful for the characterization of wide range of diameters of SWNCTs. [ABSTRACT FROM AUTHOR]

The science and technology of carbon nanotubes are very interesting topics in the field of nanotechnology. It is considered that such nanotubes have excellent properties of electrical conduction, tensile strength, and thermal conduction. However, these properties are not well understood yet. Techniques for handling a nanotube and measuring these properties have not yet been established. Recently, a technique for synthesizing supergrowth carbon nanotubes, which form a highly pure single-walled carbon nanotube (SWNT) forest, has been developed. These supergrowth carbon nanotubes grow to as long as a millimeter scale. As-grown supergrowth carbon nanotubes include about 5×1011 SWNTs per square centimeter. The solid of supergrowth carbon nanotubes is prepared by reducing the distance between SWNTs. We have investigated the thermal conduction of such carbon nanotubes and were successful in measuring the thermal diffusivity of self-standing samples of as-grown supergrowth carbon nanotubes and their solid using the laser flash method. It was found that the carbon nanotube samples show a comparable thermal diffusivity to isotropic graphite. We have also measured the temperature dependence of the thermal diffusivity of the supergrowth carbon nanotube samples. [ABSTRACT FROM AUTHOR]

We report that Co metal nanoparticles (an average diameter of 4 nm) chemically synthesized by a reverse micelle method catalyzes the growth of multiwall carbon nanotubes (MWNTs) aligned perpendicular to a substrate. The surface of the nanoparticles is covered with surfactants so that the nanoparticles can be dispersed in organic solvent. The dispersion of the nanoparticles was cast directly onto a plane Si substrate for thermal pyrolysis of acetylene. We have found that the pretreatment of the metal nanoparticles with hydrogen sulfide before the pyrolysis straightens the MWNTs, suggesting sulfurization of the nanoparticle catalyst plays an important role in regular growth of the MWNTs. The dispersion of the nanoparticles offers a conventional and processible approach to synthesize large area aligned MWNT arrays. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]