High-quality Single-walled Carbon Nanotubes Research Articles

Synthesis of high quality single-walled carbon nanotubes at large scale by electric arc using metal compounds

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Synthesis and Purification of Single-Walled Carbon Nanotubes by AC Arc Discharge

Single-walled carbon nanotubes (SWNTs) were synthesized in a mixed gas of H2 and Ar by AC arc discharge. The catalyst used in the synthesis was a single Fe catalyst. SWNTs containing a negligible number of nanoparticles were obtained. A novel purification method, in which synthesized soot is heated and oxidized in situ, was adopted. As a result, high-quality SWNTs with excellent crystallinity containing very few coexisting nanoparticles and fine particles from the catalyst were obtained.

Mass production of high-quality single-wall carbon nanotubes by H 2–N 2 arc discharge

High-crystalline single-wall carbon nanotubes (SWNTs) have been produced by dc arc discharge evaporation of carbon electrode including 1 at.% Fe catalyst in H 2–N 2 mixture gas. The yield of as-grown SWNTs reaches higher than 70 at.%, and the form of SWNTs takes like a huge web. Raman scattering studies suggest that the diameter distribution of SWNTs can be controlled by varying the mixing ratio of H 2 and N 2 gas. Moreover, we can easily remove the coexisting Fe catalyst nanoparticles and obtain purified SWNTs. This new method for producing gram order of quantities of high-quality SWNTs will accelerate the studies of physical properties and practical applications of bulky SWNTs.

Controlling the diameters in large-scale synthesis of single-walled carbon nanotubes by catalytic decomposition of CH 4

High-quality single-walled carbon nanotubes (SWNTs) are synthesized in gram amount on Fe–Mo/MgO catalysts by catalytic decomposition of CH 4 in H 2 or N 2. Raman data reveal that the as-prepared SWNTs have a diameter of about 0.74–1.29 nm. It is found that the diameter of the as-prepared SWNTs can be controlled mainly by adjusting the molar ratio of Fe–Mo versus the MgO support. Several other factors that potentially influence the growth of SWNTs have been studied in detail. The experimental results show that the nature of the catalyst determines the diameter of the as-prepared SWNTs.

Saturable absorbers incorporating carbon nanotubes directly synthesized onto substrates and fibers and their application to mode-locked fiber lasers.

We present novel carbon-nanotube-based saturable absorbers. Using the low-temperature alcohol catalytic chemical-vapor deposition method, high-quality single-walled carbon nanotubes (SWNTs) were directly synthesized on quartz substrates and fiber ends. We successfully applied the SWNTs to mode lock a fiber laser producing subpicosecond pulses at a 50-MHz repetition rate.

Large‐Scale Synthesis of High‐Quality Single‐Walled Carbon Nanotubes by Catalytic Decomposition of Ethylene.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Large-Scale Synthesis of High-Quality Single-Walled Carbon Nanotubes by Catalytic Decomposition of Ethylene

High-quality single-walled carbon nanotubes (SWNTs) have been synthesized over Fe−Mo/MgO catalyst by catalytic decomposition of ethylene at 800 °C. The produced carbon material primarily consists of a SWNT bundle with few defects and a very small amount of amorphous carbon coating. The diameter of an individual SWNT is in the range of 0.7−2.8 nm. The as-synthesized SWNTs have a high yield of over 550% relative to the weight of Fe−Mo metal in the Fe−Mo/MgO catalyst. Our results show that ethylene can be a very ideal carbon source for the synthesis of SWNTs. We suggest that catalytic decomposition of ethylene over Fe−Mo/MgO catalyst can promise a large-scale production of high-quality SWNTs.

Growth of high-quality single-wall carbon nanotubes without amorphous carbon formation

We report an alternative way of preparing high-quality single-wall carbon nanotubes (SWCNTs). Using a triple-layer thin film of Al/Fe/Mo (with Fe as a catalyst) on an oxidized Si substrate, the sample is exposed to a single short burst (5 s) of acetylene at 1000 °C. This produced a high yield of very well graphitized SWCNTs, as confirmed by transmission electron microscopy and Raman spectroscopy. We believe that the high temperature is responsible for the high crystallinity/straightness of the nanotubes, and the rapid growth process allows us to achieve a clean amorphous carbon (a-C) free deposition which is important for SWCNT device fabrication. The absence of a-C is confirmed by Auger electron spectroscopy, Raman spectroscopy, and electrical measurements.

Chemical Vapor Depositions of Single Walled Carbon Nanotube thin films and their applications for sensors in aqueous solutions

AbstractHigh-density and high-quality single walled carbon nanotubes are directly grown on surface by Chemical Vapor Depositions. We found that those SWNT thin films could be used to fabricate thin film field-effect transistors. Those transistors are very sensitive to surface charges changes in aqueous solutions and could be used tobuild chemical sensors.

Single-walled carbon nanotubes produced by catalytic chemical vapor deposition of acetylene over Fe–Mo/MgO catalyst

High-quality single-walled carbon nanotubes (SWNTs) with few defects and very small amount of amorphous carbon coating have been produced by catalytic decomposition of C 2H 2 over MgO supported Fe–Mo bimetallic catalyst at 800 °C. The diameters of SWNTs are in the range of 0.80–2.43 nm from Raman analysis. The use of MgO support facilitates a large-scale synthesis of SWNTs with a smaller diameter compared with Al 2O 3 support material. This work indicates that MgO is useful support material to realize the synthesis of high-quality SWNTs at high yield using C 2H 2 carbon source.

Direct synthesis of high-quality single-walled carbon nanotubes on silicon and quartz substrates

A new technique of synthesizing high-quality single-walled carbon nanotubes (SWNTs) directly on the surface of silicon and quartz substrates has been developed by means of the low-temperature catalytic CVD method using ethanol. The proposed method does not employ conventional deposition/sputtering for the mounting of catalytic metals on the substrates, but it adopts an easy and costless liquid-based dip-coat approach without need of support/underlayer materials that were often used in previous studies. The substrate surface is blackened with a uniform layer of SWNTs after the CVD at an optimum condition. The optical absorption of ‘as-grown’ SWNTs has first been measured using thereby prepared SWNT-synthesized quartz substrate.

Synthesis of High Quality Single-Walled Carbon Nanotube Silks by the Arc Discharge Technique

We have modified the conventional arc discharge method for the synthesis of high quality single-walled carbon nanotube (SWNT) silks with high purity (over 70%) by using a hollow cathode that can collect SWNTs effectively.Characterizations of these SWNT materials by XRD, UV-vis-near-IR, Raman were taken. Finally a simple process involving subsequent acid treatment to align the SWNTs locally in the thin silks was introduced.

Synthesis of high-quality single-walled carbon nanotubes by catalytic decomposition of C2H2.

High-quality single-walled carbon nanotubes free of defects and amorphous carbon coating have been produced by catalytic decomposition of C2H2 over Fe-Mo/Al2O3 catalyst.

Production of high quality single-walled carbon nanotubes in a nano-agglomerated fluidized bed reactor

ABSTRACTSSingle-walled carbon nanotubes (SWNTs) have attracted much attention due to their unique structural, mechanical, chemical, and electrical properties. Catalytic chemical vapor deposition (CCVD) through decomposition of hydrocarbons is one of the most challenging synthesis methods to produce SWNTs in large scale. In this paper, high quality SWNTs prepared in a nano-agglomerated fluidized bed reactor (NAFBR) was reported. The reactor is a vertical quartz tube with the inner diameter of about 50 mm. Catalysts nanoparticles used for the production of SWNTs were prepared with Fe metal nanoparticles carried on the surface of MgO. About 150g catalysts powders were loaded on the gas distribution grid. The reaction temperature was controlled at not less than 1123 K. The carrier gas of argon was used to maintain turbulent fluidization of the catalysts powders in FBR. The hydrogen gas was used to reduce the catalysts and to synergize the growth of SWNTs with methane. The powder products were spherical agglomerates of SWNTs bundles tangling with the catalysts particles. By optimizing the process parameters of CCVD, the products of SWNTs with the diameter about 0.9 ∼ 1.8 nm were prepared, without any multi-walled carbon nanotubes (MWNTs) or amorphous carbon. The microstructure of SWNTs products were characterized by the methods of high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectra, etc. The NAFBR is a commercially viable (effective and continuous production at a low cost) process for the production of SWNTs.

High-quality single-walled carbon nanotubes from arc-produced soot

High-quality single-walled carbon nanotubes (SWNTs) were obtained from arc-produced soot using a three-step purification process consisting of soft oxidation, air oxidation, and a high-temperature vacuum treatment. Firstly an oxide layer was formed on the surface of the metal catalyst, which prevents the SWNTs from undergoing metal-assisted dissociation during the process. After the final step, about 20% of the weight of the initial raw soot remained and the final product contained less than 1% metal. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy were used to characterize the SWNTs obtained.

Synthesis, integration, and electrical properties of individual single-walled carbon nanotubes

High-quality single-walled carbon nanotubes (SWNTs) are synthesized by chemical vapor deposition (CVD) of methane on silicon-dioxide substrates at controlled locations using patterned catalytic islands. With the synthesized nanotube chips, microfabrication techniques are used to reliably contact individual SWNTs and obtain low contact resistance. The combined chemical synthesis and microfabrication approaches enable systematic characterization of electron transport properties of a large number of individual SWNTs. Results of electrical properties of representative semiconducting and metallic SWNTs are presented. The lowest two-terminal resistance for individual metallic SWNTs (≈5 μm long) is ≈16.5 kΩ measured at 4.2 K.

Large Scale CVD Synthesis of Single-Walled Carbon Nanotubes

The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane. A series of catalysts are derived by systematically varying the catalytic metal compounds and support materials. The optimized catalysts consist of Fe/Mo bimetallic species supported on a novel silica−alumina multicomponent material. The high SWNT yielding catalyst exhibits high surface-area and large mesopore volume at elevated temperatures. Gram quantities of SWNT materials have been synthesized in ∼0.5 h using the optimized catalyst material. The nanotube material consists of individual and bundled SWNTs that are free of defects and amorphous carbon coating. This work represents a step forward toward obtaining kilogram scale perfect SWNT materials via simple CVD routes.

Chemical vapor deposition of methane for single-walled carbon nanotubes

We report the synthesis of high-quality single-walled carbon nanotubes (SWNT) by chemical vapor deposition (CVD) of methane at 1000°C on supported Fe2O3 catalysts. The type of catalyst support is found to control the formation of individual or bundled SWNTs. Catalysts supported on crystalline alumina nanoparticles produce abundant individual SWNTs and small bundles. Catalysts supported by amorphous silica particles produce only SWNT bundles. Studies of the ends of SWNTs lead to an understanding of their growth mechanism. Also, we present the results of methane CVD on supported NiO, CoO and NiO/CoO catalysts.