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1.
A mixture of as-grown single-wall carbon nanotubes (SWNTs) and a monochlorobenzene (MCB) solution of polymethylmethacrylate (PMMA) was sonicated and homogenized. As a result, SWNTs were separated from carbonaceous impurities and metal particles, which enabled us to purify the SWNTs by filtration. We also found that the number of short (about 1-μm) SWNTs and thin bundles of SWNTs increased. The thin bundles contained one to three SWNTs. These short, thin SWNTs suspended in the MCB solution of PMMA were spin-coated onto a Si wafer, and could be dispersed on it. Received: 18 July 2000 / Accepted: 20 July 2000 / Published online: 6 September 2000  相似文献   

2.
Single-walled carbon nanotubes (SWNTs) were synthesized by disproportionation of carbon monoxide on an aerogel-supported Fe/Mo catalyst. A simple acidic treatment followed by an oxidation process produced a high purity (>99%) of SWNTs. The nanotubes obtained are bundled SWNTs and free of amorphous-carbon coating. Several factors that affect the yield and the quality of the SWNTs were also studied. This method shows great promise for large-scale production of SWNTs. Received: 30 August 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002  相似文献   

3.
Field emission from single-walled carbon nanotubes (SWNTs) aligned on a patterned gold surface is reported. The SWNT emitters were prepared at room temperature by a self-assembly monolayer technique. SWNTs were cut into sub-micron lengths by sonication in an acidic solution. Cut SWNTs were attached to the gold surface by the reaction between the thiol groups and the gold surface. The field-emission measurements showed that the turn-on field was 4.8 V/μm at an emission current density of 10 μA/cm2. The current density was 0.5 mA/cm2 at 6.6 V/μm. This approach provides a novel route for fabricating CNT-based field-emission displays. Received: 3 May 2002 / Accepted: 6 May 2002 / Published online: 4 December 2002 RID="*" ID="*"Corresponding author. Fax: +82-54/279-8298, E-mail: ce20047@postech.ac.kr  相似文献   

4.
Activated multi-walled carbon nanotubes were prepared with appended vanadium as a hydrogen storage medium. The pore structure was significantly improved by an activation process that was studied using Raman spectroscopy, field emission transmission electron microscopy and pore analysis techniques. X-ray photoelectron spectroscopy and X-ray diffraction results reveal that the vanadium catalyst was introduced into the carbon nanotubes in controlled proportions, forming V8C7. The improved pore structure functioned as a path through the carbon nanotubes that encouraged hydrogen molecule adsorption, and the introduced vanadium catalyst led to high levels of hydrogen storage through the dissociation of hydrogen molecules via the spill-over phenomenon. The hydrogen storage behavior was investigated by electrical resistance measurements for the hydrogen adsorbed on a prepared sample. The proposed mechanism of hydrogen storage suggests that the vanadium catalyst increases not only the amount of hydrogen that is stored but also the speed at which it is stored. A hydrogen storage capacity of 2.26 wt.% was achieved with the activation effects and the vanadium catalyst at 30 °C and 10 MPa.  相似文献   

5.
Hydrogen storage using carbon adsorbents: past, present and future   总被引:8,自引:0,他引:8  
Interest in hydrogen as a fuel has grown dramatically since 1990, and many advances in hydrogen production and utilization technologies have been made. However, hydrogen storage technologies must be significantly advanced if a hydrogen based energy system, particularly in the transportation sector, is to be established. Hydrogen can be made available on-board vehicles in containers of compressed or liquefied H2, in metal hydrides, via chemical storage or by gas-on-solid adsorption. Although each method possesses desirable characteristics, no approach satisfies all of the efficiency, size, weight, cost and safety requirements for transportation or utility use. Gas-on-solid adsorption is an inherently safe and potentially high energy density hydrogen storage method that could be extremely energy efficient. Consequently, the hydrogen storage properties of high surface area “activated” carbons have been extensively studied. However, activated carbons are ineffective in storing hydrogen because only a small fraction of the pores in the typically wide pore-size distribution are small enough to interact strongly with hydrogen molecules at room temperatures and moderate pressures. Recently, many new carbon nanostructured absorbents have been produced including graphite nanofibers and carbon multi-wall and single-wall nanotubes. The following review provides a brief history of the hydrogen adsorption studies on activated carbons and comments on the recent experimental and theoretical investigations of the hydrogen adsorption properties of the new nanostructured carbon materials. Received: 16 October 2000 / Accepted: 15 November 2000 / Published online: 9 February 2001  相似文献   

6.
The sorption of hydrogen on carbon structures and nanostructures offers a way to reduce the storage pressure of hydrogen with respect to compression storage while achieving interesting gravimetric storage densities. The most readily available carbon structures, activated carbons, can achieve reproducible, high gravimetric storage densities under cryogenic operating conditions: 5–6% at 35 bar and 77 K, in excess of the normal density that would be present in the pore volume under compression at the same temperature and pressure. We discuss and compare the adsorption of hydrogen on high specific surface activated carbons, nanofibres and nanotubes from experimental and theoretical considerations. In particular, we present gravimetric and volumetric hydrogen sorption measurements on single-walled carbon nanotubes (SWNTs) at (1 bar, 77 K) and (1 bar, 295 K) within the context of our ongoing work on the storage of hydrogen on activated carbon and carbon nanostructures. BET surface area and XRD characterization results on SWNTs are also presented. The experiments were performed on as received, chemically treated and metal-incorporated SWNT samples. Hydrogen sorption capacities measured on treated samples ranged from 0 to about 1 wt.% at 1 bar and 295 K and reached about 4 wt.% at 1 bar and 77 K. Our results show that under certain conditions, SWNTs have better hydrogen uptake performance than large surface area activated carbons. PACS 81.07.de; 81.05.Uw; 68.43.h  相似文献   

7.
In this paper we review the existing theoretical literature on hydrogen storage in single-walled nanotubes and carbon nanofibers. The reported calculations indicate a hydrogen uptake smaller than some of the more optimistic experimental results. Furthermore the calculations suggest that a variety of complex chemical processes could accompany hydrogen storage and release. Received: 24 August 2000 / Accepted: 15 November 2000 / Published online: 9 February 2001  相似文献   

8.
Single-walled carbon nanotubes (SWNTs) encapsulating C70s, so-called C70 peapods, were synthesized in high yield by a vapor-phase doping method. Raman spectra, high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) measurement indicate that the tube diameter is one of the important factors to determine the orientation of C70 molecules inside the SWNTs. SWNTs with different diameters give different alignment of C70 molecules. The lying orientation is favorable over the standing orientation in thin nanotube, i.e. 1.36 nm nanotubes, whereas the standing orientation is favorable in thick nanotubes, i.e. 1.49 and 1.61 nm nanotubes.  相似文献   

9.
Optical properties of fullerene and non-fullerene peapods   总被引:1,自引:0,他引:1  
Single-wall carbon nanotubes (SWNTs) encapsulating fullerenes, so-called fullerene peapods, were synthesized in high yield by using diameter-selected nanotubes as pods. Transmission electron microscopy revealed high-density fullerene chains inside the nanotubes. X-ray-diffraction measurements indicate 85% filling for C60 and 72% filling for C70 molecules as a total yield. Interestingly, C60 peas do not show any thermal expansion while C70 peas show normal behavior. Room-temperature Raman spectra show one-dimensional photopolymerization of C60 inside nanotubes by blue-laser irradiation, suggesting molecular rotation inside them. In C70 peapods, no photopolymerization was observed but the relative Raman intensity of each peak is different from the C70 3D crystal. This is probably caused by mixing of two different crystal structures in C70 peas. Furthermore, we synthesized Zn-diphenylporphyrin peapods. Optical absorption and Raman spectra suggest that the encapsulated molecules are deformed by interaction with the SWNT. Received: 12 November 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002  相似文献   

10.
Single-wall carbon nanotubes (SWNTs) were synthesized by the irradiation of 20-ms CO2 laser pulses onto a graphite–Co/Ni target at room temperature. We investigated the effect of laser power density (10–150 kW/cm2) and ambient Ar gas pressure (150–760 Torr) on the abundance of SWNTs with lengths of up to about 200 nm in soot-like carbonaceous deposits. For a constant power density (30 kW/cm2), depending on the Ar gas pressure, SWNTs with diameters of 1.2–1.4 nm were synthesized. Expansion behavior and temperature-fall rates of clusters and/or particles in laser plumes were also analyzed by high-speed video imaging and temporally and spatially resolved emission spectroscopy. The temperature-fall rates were estimated to be 171–427 K/ms. The SWNT growth on the time scale of a few milliseconds appeared to be related to some features of condensing clusters and/or particles, including resident densities, collision frequencies and temperatures. Received: 16 July 2001 / Accepted: 23 July 2001 / Published online: 30 August 2001  相似文献   

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