Carbon Nanotubes--the Route Toward Applications
02 Aug 2002-Science (American Association for the Advancement of Science)-Vol. 297, Iss: 5582, pp 787-792
TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
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TL;DR: This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology.
Abstract: This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4.
273 citations
TL;DR: These binder-free Cathodes with excellent flexibility and conductivity are obtained by constructing a continuous three-dimensional super-aligned carbon nanotube (SACNT) framework with embedded LiCoO(2) particles.
Abstract: Binder-free LiCoO(2) -SACNT cathodes with excellent flexibility and conductivity are obtained by constructing a continuous three-dimensional super-aligned carbon nanotube (SACNT) framework with embedded LiCoO(2) particles. These binder-free cathodes display much better cycling stability, greater rate performance, and higher energy density than classical cathodes with binder. Various functional binder-free SACNT composites can be mass produced by the ultrasonication and co-deposition method described in this paper.
272 citations
TL;DR: In this article, the 1,3-dipolar cycloaddition of azomethine ylides onto carbon nanotube (CNT) networks may play a relevant role towards this direction.
Abstract: The organic functionalization of carbon nanotubes has opened new avenues with opportunities to fabricate novel nanostructures by improving both their solubility and processibility. The 1,3-dipolar cycloaddition of azomethine ylides onto carbon nanotube (CNT) networks may play a relevant role towards this direction. CNT-based materials have been synthesized possessing differently functionalized solubilizing chains and hold strong promise as useful building blocks for the construction of novel hybrids for nano- and bio-technological applications.
271 citations
TL;DR: The fabrication of a novel continuous yarn of CNTs with a multiple-layer structure by the CVD spinning process, which combines superior mechanical properties, electrical conductivities, and surface structures, and have potential applications as structural fibers, composites, woven fabrics, catalyst supports, energy storage materials, artificial tissue, and so on.
Abstract: 2010 WILEY-VCH Verlag Gm Carbon nanotubes (CNTs) have ultrahigh strength, high electrical conductivities, high thermal conductivities, electric field emissions, gas sensitivities, and other functional properties. These outstandingmechanical, physical, andmultifunctional properties of CNTs, in combination with their unique 1D nanostructures with high specific areas, allow for a wide range of potential applications such as structural fibers, composites, multifunctional fabrics, and devices. The fabrication of CNTs into a continuous multifunctional CNT yarn is an important step towards these macroscopic applications. Several processes are under development to fabricate macroscopic CNT fibers, including wet spinning of CNTs from polymer dispersions or acid dispersions, dry spinning from aligned CNT matrices, and direct spinning from chemical vapor deposition (CVD) reactions. While the development of a continuous and weavable pure CNT yarn remains a major challenge in the fabrications, CNT yarns so far obtained from the different processes are monolithic in structure, although a hollow yarn was demonstrated from a wet drawing process. One the other hand, CNT sheets or films have been fabricated by drying CNT dispersions, drawing [19,20] or infiltrating of CNT arrays, and by CVD spinning. These 2D CNT assemblies have demonstrated applications as catalyst supports, molecular sieves, infiltrators, conductors, electromagnetic shields, capacitors, and artificial tissues. If CNTs can be made into continuous yarns with a layered structure, they will combine the weavable property of fibers and the structural characteristic of films and can be adopted for numerous applications. In the present work, we report the fabrication of a novel continuous yarn of CNTs with a multiple-layer structure by the CVD spinning process. The yarn consists of multiple monolayers of CNTs concentrically assembled in seamless tubules along the yarn axis. This layered structure is assembled from CNTs produced in a gas flow from the CVD reaction with a mixed acetone and ethanol carbon source. The development of a water-densification and spinning process allows us to spin the CNT yarn continuously with a yarn length of over several kilometers and a yarn quality close to conventional textile yarns. The CNTyarn can be controlled to be either hollow or monolithic with compacted or detached CNTmonolayers by controlling the spinning process. This layered multifunctional CNT yarns combine superior mechanical properties, electrical conductivities, and surface structures, and have potential applications as structural fibers, composites, woven fabrics, catalyst supports, energy storage materials, artificial tissue, and so on. The fabrication of a CNT yarn by the CVD spinning process relies on the assembly of CNTs in the gas flow by van der Waals interactions. The CNTs assemble in the gas flow when produced in a sufficiently high yield with a high purity such that interaction occurs. Their assembly is, therefore, greatly dependent on the chemistry of the carbon sources. The assembly of CNTs in the gas flow forms a continuous sock-like CNT integrate, which can be mechanically spun out into a CNT yarn. This process was first demonstrated with ethanol as a carbon source and a twisting spinning performed inside the reactor. Recent work reports that a CNT yarn spun from this process possesses ultrahigh strength after densification of the yarn with an acetone vapor. The spinning of multilayered CNT yarns in this work is based on our discovery that CNTs can self-assemble into a multilayered CNT ‘sock’ in the gas flow when a mixture of acetone and ethanol is used as the carbon source. The synthesis was conducted by the injection of the carbon source dispersed with ferrocene and thiophene into a heated gas-flow reactor in flowing hydrogen (Fig. 1a). The CNT layers in the sock, which can be clearly seen in the gas flow, are continuous, concentric, and discrete (Fig. 1b). The CNTsock was initiated from the upper gas flow and produced continuously, traveling downstream with the gases. The assembly of the CNTs is believed to be associated with the interaction of gas molecules, which drive the CNTs towards the outer circumference of the gas flow where they interact mechanically. The formation of the multilayer structure may result from the higher concentration of CNTs in the gas flow because the CNT yield ( 240mg h ) from the mixed carbon source is double that from ethanol alone ( 110mg h ). The layered CNT sock was densified with water after it came out of the reactor. This is realized by connecting a water tank to the end of the CVD reactor (Fig. 1a). The water tank simultaneously encloses the gas-flow system and provides a soft connection between the reactor and air. This configuration allows the CNT assembly to be drawn out continuously from the high-temperature, hydrogen-containing reactor into the open air in a safe and controlled manner. The CNT sock shrinks immediately into a fiber upon arriving at the water surface (Fig. 1c). The fiber is directed around a rotator in the water and is pulled out into air from the other side (Fig. 1d). It is then directed onto the second spool that rotates in acetone for washing and
271 citations
References
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TL;DR: The nanotubes sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature and the mechanisms of molecular sensing with nanotube molecular wires are investigated.
Abstract: Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO 2 or NH 3 , the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.
5,908 citations
TL;DR: In this paper, the fabrication of a three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics and has attracted much interest, particularly because it could lead to new miniaturization strategies in the electronics and computer industry.
Abstract: The use of individual molecules as functional electronic devices was first proposed in the 1970s (ref 1) Since then, molecular electronics2,3 has attracted much interest, particularly because it could lead to conceptually new miniaturization strategies in the electronics and computer industry The realization of single-molecule devices has remained challenging, largely owing to difficulties in achieving electrical contact to individual molecules Recent advances in nanotechnology, however, have resulted in electrical measurements on single molecules4,5,6,7 Here we report the fabrication of a field-effect transistor—a three-terminal switching device—that consists of one semiconducting8,9,10 single-wall carbon nanotube11,12 connected to two metal electrodes By applying a voltage to a gate electrode, the nanotube can be switched from a conducting to an insulating state We have previously reported5 similar behaviour for a metallic single-wall carbon nanotube operated at extremely low temperatures The present device, in contrast, operates at room temperature, thereby meeting an important requirement for potential practical applications Electrical measurements on the nanotube transistor indicate that its operation characteristics can be qualitatively described by the semiclassical band-bending models currently used for traditional semiconductor devices The fabrication of the three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics
5,258 citations
TL;DR: X-ray diffraction and electron microscopy showed that fullerene single-wall nanotubes (SWNTs) are nearly uniform in diameter and that they self-organize into “ropes,” which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms.
Abstract: The major part of this chapter has already appeared in [1], but because of the length restrictions (in Science), the discussion on why we think this form is given in only brief detail. This chapter goes into more depth to try to answer the questions of why the fullerenes form themselves. This is another example of the very special behavior of carbon. From a chemist’s standpoint, it is carbon’s ability to form multiple bonds that allows it to make these low dimensional forms rather than to produce tetrahedral forms. Carbon can readily accomplish this and it is in the mathematics and physics of the way this universe was put together, that carbon is given this property. One of the consequences of this property is that, if left to its own devices as carbon condenses from the vapor and if the temperature range is just right, above 1000°C, but lower than 1400°C, there is an efficient self-assembly process whose endpoint is C60.
5,215 citations
TL;DR: In this paper, the Young's modulus, strength, and toughness of nanostructures are evaluated using an atomic force microscopy (AFM) approach. And the results showed that the strength of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical values.
Abstract: The Young's modulus, strength, and toughness of nanostructures are important to proposed applications ranging from nanocomposites to probe microscopy, yet there is little direct knowledge of these key mechanical properties. Atomic force microscopy was used to determine the mechanical properties of individual, structurally isolated silicon carbide (SiC) nanorods (NRs) and multiwall carbon nanotubes (MWNTs) that were pinned at one end to molybdenum disulfide surfaces. The bending force was measured versus displacement along the unpinned lengths. The MWNTs were about two times as stiff as the SiC NRs. Continued bending of the SiC NRs ultimately led to fracture, whereas the MWNTs exhibited an interesting elastic buckling process. The strengths of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical values. Because of buckling, the ultimate strengths of the stiffer MWNTs were less than those of the SiC NRs, although the MWNTs represent a uniquely tough, energy-absorbing material.
4,627 citations
TL;DR: The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device and shows linear temperature dependence with a value of 80 microV/K at room temperature.
Abstract: The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device. The observed thermal conductivity is more than 3000 W/K m at room temperature, which is 2 orders of magnitude higher than the estimation from previous experiments that used macroscopic mat samples. The temperature dependence of the thermal conductivity of nanotubes exhibits a peak at 320 K due to the onset of umklapp phonon scattering. The measured thermoelectric power shows linear temperature dependence with a value of 80 microV/K at room temperature.
3,166 citations