Large-scale Synthesis Of Carbon Nanotubes Research Articles

Synthesis of Vertically Aligned Carbon Nanotube Arrays from Premade Bimetallic Aluminum-Iron Oxide Nanoparticles Monolayer

: Carbon Nanotubes (CNTs) are excellent materials because of their unique physical and chemical properties. Though catalyst nanoparticles preparation from thin film catalysts are common but premade catalysts nanoparticles in liquid phase has control over the size and composition which control the diameter and length of CNTs. Here, we report the synthesis of vertically aligned (VA) CNTs on metal oxide substrates including silicon oxide and stainless-steel using aluminum-iron oxides Al2O3-Fe2O3 nanoparticles monolayer. Oleic acid functionalized Al2O3-Fe2O3 nanoparticles were assembled onto metal oxide substrate as a monolayer using 11-phousnoundecanoic acid (PNDA) linker molecule where phosphonate group bind to the substrate and terminal carboxylic group of PNDA bind to the surface of bimetallic oxide catalysts. Homogenous catalyst nanoparticles distribution from monolayer assembly can reduce the aggregation of catalyst particles which can increases the catalyst lifetime during CNTs growth. Synthesis of VA-CNTs require Al2O3 catalyst support on substrate surface, but our bimetallic Al2O3-Fe2O3 nanoparticles contain both catalyst support (Al2O3) and catalyst (Fe) in the same particle. The successful VA-CNTs synthesis were achieved by chemical vapor deposition (CVD) process using acetylene as carbon precursor in atmospheric pressure. We envision that our catalyst preparation for VA-CNTs growth can be a cost-efficient method for large scale synthesis of CNTs. Further, the VA-CNTs growth on conductive stainless-steel substrate can facilitate the electrochemical application of this hybrid materials for biomolecule sensing and heavy metals detection.

Synthesis and Characterized of Carbon Nanotubes from Fermented Tapioca

Carbon nanotubes (CNT) has been synthesized by pyrolysing fermented tapioca liquid using an immersed heater. It was made single-walled carbon nanotubes (SWCNT) through heating at 700, 800 and 900 °C by the chemical vapour deposition (CVD) method and characterized by using Raman spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy (FESEM). The synthesized SWCNT demonstrated larger diameters at 700 °C which decreased at 800 and 900 °C, respectively. The SWCNTs were indicated based on the radial breathing mode (RBM) peak present between 200 - 300 raman shift (cm-1). The diameters of synthesized CNTs ranged between 54 - 200 nm. Raman spectrum revealed that the G-bands were 1569, 1582 and 1576 cm-1, respectively, whereas the D-bands were 1346, 1350 and 1358 cm-1 for SWCNT synthesis at 700, 800 and 900 °C, respectively. The modified CVD method set up in the present study was successfully used for large scale synthesis of CNTs from an aqueous precursor such as fermented tapioca liquid.

Evaporated Ethanol as Precursor for Carbon Nanotubes Synthesis

Single-walled carbon nanotubes (SWCNT) were synthesized by using a simple evaporating method and a double furnace system. Ethanol was chosen as a carbon precursor because it has an evaporating temperature of 78 °C and was reported to produce a high purity of CNTs. Evaporated ethanol can be used as a precursor for carbon nanotubes (CNTs) synthesis. Ethanol was evaporated at 80 °C and channeled directly into a double furnace system. Furnace 1 was maintained at 180 °C and furnace 2 was set at 700 °C, 800 °C and 900 °C. The CNTs were then characterized by thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and Raman spectroscopy. Helical CNTs were observed at 700°C, webs of hollow tubes at 800 °C, and long tube structures at 900 °C based on FESEM. The diameter of CNTs that were synthesized ranged between 54 - 200 nm. Raman spectrum revealed that the G-band was 1590 cm-1 and the D-band was about 1350 cm-1. SWCNT was determined by RBM (radial breathing mode) to be between 200 - 300 raman shifts (cm-1). The modified CVD (chemical vapor deposition) system set up in the present study is successfully used for large scale synthesis of CNTs from an aqueous precursor such as ethanol.

Towards the Large-Scale Synthesis of Carbon Nanotubes in Fluidised Beds

Carbon nanotubes (CNTs) are a form of crystalline carbon with extraordinary properties, making them valuable in a broad range of applications. However, the lack of suitable large-scale manufacturing techniques, which we define as being of the order 10000 tonnes per annum, continues to inhibit their widespread use. Of the three established synthesis methods for CNTs: (i) chemical vapour deposition (CVD), (ii) laser ablation, and (iii) arc discharge, CVD techniques show the greatest promise for economically viable, large-scale synthesis. In particular, the fluidised bed CVD (FBCVD) technique, where the CVD reaction occurs within a fluidised bed of catalyst particles, has the potential to produce high quality CNTs, inexpensively, in large quantities. In this work we report on the development of a catalytic chemical vapour deposition process, using batch fluidised bed reactors, for the synthesis of straight and spiral carbon nanotubes at pilot scale (up to 1 kg/hr). We believe this to be the first report of the synthesis of spiral carbon nanotubes using fluidised bed CCVD. Iron, nickel and cobalt transition metal catalysts supported on non-porous alumina substrates were fluidised in a mixture of nitrogen, hydrogen and ethylene at temperatures between 550 and 800 degrees C for between 15 and 90 minutes. Nanotube yield was inferred from thermogravimetric analysis and the quality and size of the CNTs from transmission electron microscopy. Conflicting information in the literature about the influence of synthesis parameters on CNT properties suggests that further investigation is necessary to understand the synthesis process at a fundamental level, i.e., independent of reactor design and operation.

Growing carbon nanotubes in a microscope

Great advances have been achieved recently in producing carbon nanotubes (CNTs). By the same token, precisely controlling the growth of both multiwalled and single-walled carbon nanotubes (MWNTs and SWNTs) to generate desired structures remains a major challenge. The importance of this deficiency cannot be underestimated because some of the most promising applications of CNTs in next-generation electronics and optical devices depend strongly on nanotube diameter size and specific chirality (i.e., whether the tube winds left or right). For this reason, better understanding of the initial stages and mechanisms of CNT growth could be key to developing practical, large-scale synthesis of CNTs. Generating nanotubes involves reacting a gaseous carbon source onmetal catalyst particles in a process known as chemical vapor deposition (CVD). Observation of the gas–solid interactions is possible using an ‘environmental’ transmission electron microscope (TEM) fitted out with gas injectors and cells. Indeed, several groups have carried out in situ observations of carbon nanofiber and nanotube growth.1, 2 But nucleation—the first and most important step of nanotube production—is still a puzzle, mainly because the environmental TEM images are blurred by vibrations caused by the chemical reaction or electrical currents. In order to get around this problem, we observed the formation of CNTs in an entirely condensed phase (solid) process. Moreover, we were able to monitor, at atomic resolution, the birth of both SWNTs and MWNTs in a standard TEM.3 To grow a CNT inside the TEM, we subject anMWNT containing a catalytically active metal particle core to electron irradiation. This causes carbon from the graphitic shells of the MWNT to be injected into the body of the metal core and subsequently to emerge as an SWNT or MWNT inside the host nanotube (see Figure 1). This process differs from previous in situ studies because it does not involve a gaseous source of carbon, and elecFigure 1. The sequence of images shows the growth of an MWNT from a metal catalyst particle. The process is driven by the injection of carbon atoms, produced by electron irradiation, into the metal particle.

A Comparison of Different Preparation Methods of Fe-Mo-Mg-O Catalyst for the Large-Scale Synthesis of Carbon Nanotubes

Carbon nanotubes (CNTs) in a high yield were synthesized by the decomposition of the methane gas with CCVD, in which two different reaction routes of sol-gel method prepared Fe-Mo- Mg-O catalyst. The two different routs influenced the wall number and defects of CNTs and the formation of CNTs. The concentration of Mo in the catalyst played a very important role in the yield of CNTs.

Synthesis of carbon nano-tubes by pulsed laser ablation at normal pressure in metal nano-sol

A novel method has been developed for large-scale synthesis of carbon nano-tubes (CNTs) under normal temperature and pressure, using pulsed laser ablation of a graphite target in metal nano-sol. The metal nano-sol was prepared by laser ablation of metal target in ethanol and used as catalyst. The synthesized CNTs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy and Fourier-transformed infrared (FT-IR) absorption spectroscopy. The nanotube surface was revealed to be modified by the - C = O , - CH 2 , - CH 3 and - OH functional groups.

(Mg,Co)O Solid-Solution Precursors for the Large-Scale Synthesis of Carbon Nanotubes by Catalytic Chemical Vapor Deposition

Single- and double-walled carbon nanotubes were produced in high yield using the selective reduction of solid solutions of Mg1–xCoxO in a methane and hydrogen atmosphere at 1000°C. The solid solutions were prepared using combustion synthesis with urea as the fuel. The BET surface areas ranged from 10 to 65 m2/g depending on the fuel content. A single crystalline phase was obtained only for fuel-rich compositions. Increased fuel content increased the surface area by a factor of 6. However, very high fuel contents (>4 times the stoichiometric amount) caused a demixed solid solution. Surface-area measurements and Raman spectra showed that the quantity of nanotubes formed depended on the surface area and composition of the precursor oxide.

Synthesis and crystallinity of carbon nanotubes produced by a vapor-phase growth method

We have studied the effect of temperature on the growth and crystallinity of carbon nanotubes (CNTs), synthesized by a vapor-phase growth method using a catalytic reaction of iron pentacarbonyl (Fe(CO)5) and acetylene (C2H2) gas. By increasing the growth temperature from 750 °C to 950 °C, both the growth rate and the diameter of the CNTs increase. Moreover, the crystallinity of the graphite sheets improves progressively with increasing growth temperature. Adjustment of the growth temperature gives potential for controlled growth of CNTs in a large-scale synthesis of CNTs.

カーボンナノチューブの大量合成と触媒効果

Carbon nanotubes have potential applications in a variety of fields, such as composites, field-emission displays, electrodes, gas adsorbent, and catalyst supports. For putting these applications into industry, it is very important to establish the mass production of nanotubes. Here, we introduce our recent progress on the large-scale synthesis of carbon nanotubes, in particular, single-wall carbon nanotubes (SWNTs), based on the gas-phase flow reaction. By spraying the Co-Mo nanoparticles dissolved in toluene to the vertical furnace, we succeeded in selectively obtaining SWNTs and multi-wall carbon nanotubes (MWNTs). It was found that the structure and quality of nanotubes depend on the concentration of the thiophene additives, the hydrogen gas flow rate, and the injection rate of the colloidal solution. The growth mechanism of SWNTs and MWNTs are discussed in terms of catalytic effects. Other large-scale synthetic methods for SWNTs, such as high pressure CO disproportionation (HiPco) and the supported catalysts-based fluidized bed reactions are also introduced.

Large-Scale Synthesis of Carbon Nanotubes by an Ethanol Thermal Reduction Process

The bamboo-shaped carbon nanotubes were synthesized on a large scale through an ethanol thermal reduction process, in which ethanol was used as the carbon source and magnesium was used as the reductant. The toxic or corrosive reagents have been completely avoided. Furthermore, Y-junction carbon nanotubes obtained from our experiment can be used as the building blocks of nanoelectronics. Because of the simplicity and high yield of this route, it may potentially be applied on the scale of industrial production.

Single-source precursor route to carbon nanotubes at mild temperature

Carbon nanotubes were synthesized via a single-source precursor route at 500 °C, using iron carbonyl both as carbon source and catalyst. The X-ray power diffraction pattern indicates that the products are hexagonal graphite. Transmission electron microscope (TEM) images of the sample reveal carbon nanotubes with an average inner (outer) diameter of 30 nm (60 nm). High-resolution TEM indicates that fabrication of the carbon nanotube walls was composed of ca. 40 graphene layers. The Raman spectrum shows two strong peaks at 1587 and 1346 cm −1, corresponding to the typical Raman peaks of graphitized carbon nanotubes. This method avoids the separation of raw material from solvent and simplifies the operation process. At the same time, the research provides a new route to large-scale synthesis of carbon nanotubes.

Large scale synthesis of carbon nanotubes by plasma rotating arc discharge technique

The large-scale synthesis of carbon nanotubes is achieved by plasma rotating arc discharge. The graphite anode is rotated at a high velocity for the synthesis of carbon nanotubes. Conventional arc discharge is an unstable process because of the cathode spot phenomena, which induces an inhomogeneity of the electric field distribution and a discontinuity of the current flow. The rotation of the anode distributes the microdischarges uniformly and generates a stable plasma. The centrifugal force by the rotation generates the turbulence and accelerates carbon vapor perpendicular to the anode. It is not condensed at the cathode surface but collected on the graphite collector that was placed at the periphery of the plasma. The nanotube yield increases as the rotation speed of the anode increases and the collector becomes closer to the plasma. The reason for this is because two conditions are optimized. One is the high density of carbon vapor that is created by uniform and high temperature plasma for nucleation and the other is the sufficient temperature of collectors for nanotube growth. The plasma rotating electrode process is a continuous process of the stable discharge and it is expected to perform the mass production of high quality nanotubes.

Large-scale synthesis of carbon nanotubes

INTEREST in carbon fibres1,2 has been stimulated greatly by the recent discovery of hollow graphitic tubules of nanometre dimensions3. There has been much speculation about the properties and potential application of these nanotubes4–8. Theoretical studies predict that their electronic properties will depend on their diameter and degree of helicity4,5. Experimental tests of these ideas has been hampered, however, by the lack of macroscopic quantities of the material. Here we report the synthesis of graphitic nanotubes in gram quantities. We use a variant of the standard arc-discharge technique for fullerene synthesis under a helium atmosphere. Under certain conditions, a carbonaceous deposit forms on one of the graphite rods, consisting of a macroscopic (diameter of about 5 mm) cylinder in which the core comprises pure nanotubes and nanoscale particles in high yield. The purity and yield depend sensitively on the gas pressure in the reaction vessel. Preliminary measurements of the conductivity of the bulk nanotube material indicate a conductivity of about 100 S cm–11.