Yield Of Single-walled Carbon Nanotubes Research Articles

Production of Single-Wall Carbon Nanotubes at High Pressure

Using a graphite rod with a hole filled with the powder of a mixture of Y−Ni alloy and graphite as anode, single-wall carbon nanotubes (SWCNTs) with 50%−70% purity were produced in quantity of tens of grams a day under the arc conditions of 40−60 A d.c. and helium pressure of 2 atm. If calcium−nickel was used as catalyst instead of yttrium−nickel, high yields of SWCNTs can also be produced in large quantities, although the yield was slightly less than that of yttrium−nickel. The samples were characterized by SEM, HREM, and Raman spectroscopy. The results showed that the SWCNTs produced with yttrium−nickel as catalyst had the same structures as those obtained from laser-ablation with Co−Ni as catalyst. SWCNTs with smaller diameters were found when calcium−nickel was used as catalyst, proving that the diameter of SWCNTs is dependent on the properties of the metal catalysts. Furthermore, high helium pressure can lead to a high yield of SWCNTs. Our results suggested a formation mechanism of SWCNTs and the rol...

Purification of single-wall carbon nanotubes

With Y–Ni alloy and CaC 2–Ni as catalyst, large-scale single-wall carbon nanotubes (SWCNTs) were produced by d.c. arc-discharge method. The yield of SWCNTs and the composition of the raw-soot was quantified with thermogravimetric analysis (TGA). The burning temperature of SWCNTs in air was also determined. On these bases, 350°C was chosen for the first step purification of SWCNTs. Combining with the micro-filtration method, larger than 90% purity of SWCNTs and high purity of carbon nanoparticles were obtained.

Mechanism of the Effect of NiCo, Ni and Co Catalysts on the Yield of Single-Wall Carbon Nanotubes Formed by Pulsed Nd:YAG Laser Ablation

We revealed that the yield of SWNTs formed by Nd:YAG laser ablation depends on the target composition with yields following the order CxNiyCoy > CxNiy ≫ CxCoz. The SWNT bundles in the web formed when using the CxNiyCoy target (web-CxNiyCoy) is thicker and longer than those in the web-CxNiy. The diameters of the SWNTs in the web-CxNiyCoy were larger and more uniform than those of the SWNTs in the web-CxNiy. The NiCo particles in the web-CxNiyCoy and the Ni particles in the web-CxNiy were nanometer sized and were embedded in the amorphous carbon flakes that were dispersed throughout the weblike deposits. Filmlike deposits were formed when using the CxCoz targets, and nanometer-sized Co particles in these deposits were localized within sub-millimeter-sized areas. Examination of the target surfaces revealed that Ni emits from the CxNiy target more efficiently than NiCo from the CxNiyCoy target or Co from the CxCoz target during the laser ablation. On the basis of these results, we provide an explanation of ho...

Growth Dynamics of Single-Wall Carbon Nanotubes Synthesized by CO2 Laser Vaporization

Single-wall carbon nanotubes (SWNTs) were synthesized by the irradiation of a 20-ms CO2 laser pulse (1-kW peak power) onto a graphite−Co/Ni composite target at 25−1200 °C. Characterization of carbonaceous deposits using Raman scattering, scanning electron microscopy, and transmission electron microscopy showed that SWNTs were formed by laser irradiation even at room temperature. At 1100−1200 °C, the SWNT yield significantly increased (> 60%). A high-speed video imaging technique was used to observe the expanding vaporization plume and the emerging carbonaceous materials in an Ar atmosphere. Carbonaceous materials containing SWNTs became visible after ∼3 ms from the initiation of laser irradiation of the target. At 1000−1200 °C, blackbody emission from large carbon clusters and/or particles was observed for more than 1 s after the end of the laser pulse. We suggest that the growth of the SWNTs occurs from a liquidlike carbon−metal particle via supersaturation and segregation. A continuous supply of hot car...

Effect of environment temperature for synthesizing single-wall carbon nanotubes by arc vaporization method

The generation rate of single-wall carbon nanotubes (SWNTs) via arc burning of a Ni–Y (0.6–0.6 at%) catalyzed carbon pellet is investigated by varying the environment temperature ( T env). The yield of SWNTs indicates a maximum in the T env range between 400 and 600°C. At 600°C, the yield reaches >70 wt%, while the yield is ∼30–40 wt% for the sample prepared at room temperature. In this study, it is found that the T env plays an important role for the high yield synthesis of SWNTs as well as to select the metal catalysts.

High yield of single-wall carbon nanotubes by arc discharge using Rh–Pt mixed catalysts

Single-walled carbon nanotubes (SWNT) were produced using binary mixtures of the platinum-group metals as catalysts by arc evaporation in helium gas. Transmission electron microscopy and Raman scattering spectroscopy revealed that the production yield of SWNTs was remarkably enhanced when a Rh–Pt mixture was used as a catalyst. The density of SWNTs in raw soot was as high as that obtained from Fe–Ni and Y–Ni. The distribution of diameters of SWNTs was narrow (1.28±0.07 nm). The merit of this catalyst is that it is free from magnetic metals.

Large-scale and low-cost synthesis of single-walled carbon nanotubes by the catalytic pyrolysis of hydrocarbons

Rope-like bundles of single-walled carbon nanotubes (SWNTs) similar to those obtained by laser vaporization and electric-arc techniques were synthesized on a relatively large scale and at low cost by the catalytic decomposition of hydrocarbons at a temperature of about 1200 °C using an improved floating catalyst method. The SWNTs thus obtained have larger diameters and are self-organized into ropes. The addition of thiophene was found to be effective in promoting the growth of SWNTs and in increasing the yield of either SWNTs or multiwalled carbon nanotubes under different growth conditions.

Single-wall carbon nanotube formation by laser ablation using double-targets of carbon and metal

During laser ablation to form single-wall carbon nanotubes, the composition at the surface of a target composed of C, Ni and Co became metal-rich and the yield of single-wall carbon nanotubes decreased. This problem was solved by applying double-target laser ablation where separate carbon and metal-alloy targets were simultaneously irradiated by the laser light.

Large-scale production of single-walled carbon nanotubes by the electric-arc technique

Single-walled carbon nanotubes (SWNTs) offer the prospect of both new fundamental science and useful (nano)technological applications1. High yields (70–90%) of SWNTs close-packed in bundles can be produced by laser ablation of carbon targets2. The electric-arc technique used to generate fullerenes and multi-walled nanotubes is cheaper and easier to implement, but previously has led to only low yields of SWNTs3,4. Here we show that this technique can generate large quantities of SWNTs with similar characteristics to those obtained by laser ablation. This suggests that the (still unknown) growth mechanism for SWNTs must be independent of the details of the technique used to make them. The ready availability of large amounts of SWNTs, meanwhile, should make them much more accessible for further study.