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: Rice et al. as mentioned in this paper reported a method by which pristine SWNT are solubilized, separated from catalyst particles, and separated from excess dispersant by grafted poly(sodium 4-styrenesulfonate) (PSS) as an aqueous solution that is stable indefinitely.
Abstract: Because of outstanding electrical conductivity, thermal conductivity, and mechanical strength, single-wall carbon nanotubes (SWNT) have enormous potential in field emission displays, supercapacitors, molecular computers, and ultrahigh-strength materials.1,2 For optimal performance in most applications, the SWNT should be separated into individual tubes or bundles of only a few tubes. However, the as-prepared SWNT contain impurities of metal catalyst particles and amorphous carbon, and because of strong van der Waals attraction, the SWNT pack into bundles that aggregate into tangled networks. Dissolution of SWNT in water, which is important because of potential biomedical applications and biophysical processing schemes, has been facilitated by surfactants and polymers and by chemical modification.3-11 Here we report a method by which pristine SWNT are solubilized, separated from catalyst particles, and separated from excess dispersant to produce SWNT with grafted poly(sodium 4-styrenesulfonate) (PSS) as an aqueous solution that is stable indefinitely. The method is illustrated in Scheme 1. As in some other functionalizations of SWNT,12-14 the process requires no pretreatment. Debundling and functionalization of SWNT are achieved in one step with no high shear mixing or heavy sonication, which break down SWNT to shorter lengths.5,15 A mixture of 40 mg of pristine HiPco SWNT, 4.0 g of sodium 4-styrenesulfonate (NaSS), and 40 mg of potassium persulfate as a free radical initiator was stirred at 65 °C for 48 h. Catalyst residues and amorphous carbon were removed by gentle centrifugation, and excess unbound PSS was removed by ultrafiltration and ultracentrifugation. The final solution contained 68 mg of SWNT-PSS in 100 mL of water. A detailed procedure is in the Supporting Information. Elemental analysis (CHS) corresponded to 45 wt % of PSS in the SWNT/PSS composite. The 1H NMR spectra of the PSS in the ultrafiltrate and the SWNT-PSS were the same, which suggests that the molecular weight of the attached PSS is high. In control experiments, stirring pristine SWNT with preprepared PSS or with potassium persulfate and sodium p-toluenesulfonate but no monomer by the method used during the polymerization or sonicating in a cleaning bath failed to disperse the SWNT. SWNT also can be dispersed into water by surfactants and by high shear mixing or sonication with PSS, but large excesses of the surfactants or PSS are required.5,15 We attribute the stability of the SWNT with such a small amount of PSS to covalent bonding of the polymer to the SWNT. One attached polymer coil protects a large area of the SWNT surface from van der Waals attraction to other SWNT. By analogy to the addition of polystyryl radicals at diffusion-controlled rates to aggregates of [60]fullerene in solution,16 bundles of SWNT should also react with polymer radicals, although at lesser rate constants because of the lesser strain of the sidewalls of SWNT than of [60]fullerene. Additions of nonpolymeric radicals to SWNT are well-known.17 The distributions of diameters and lengths of the functionalized SWNT were analyzed by tapping mode atomic force microscopy (AFM). Figure 1 shows contour lengths from several hundred nanometers to several micrometers and a representative diameter of 1.2 nm. The range of diameters of pristine HiPco SWNT is 0.61.3 nm.18 Larger area AFM images and transmission electron microscopy (TEM) images at resolution too low to detect individual tubes show bundles of the SWNTPSS that are much smaller than the bundles of the pristine SWNT (Figures S1 and S2). TEM shows none of the catalyst particles that were abundant in the pristine SWNT (Figures S2a and 2b). The Raman spectrum of the functionalized SWNT in Figure 2a shows a disorder (D) band at 1315 cm-1 in addition to the radial breathing band (180-260 cm-1) and tangential (G) band at 1590 cm-1. The intensity of the D band is indicative of the degree of covalent functionalization of the nanotube framework. The radial breathing bands are shifted an average of 5 cm-1 to higher frequency by functionalization with the PSS, which indicates debundling during the polymerization. † Oklahoma State University. ‡ University of Oklahoma. § Rice University. * Corresponding author: e-mail wtford@okstate.edu. Figure 1. AFM height image of SWNT-PSS (3 μm × 3 μm). The arrows point to a 1.2 nm height difference.
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Journal Article•
TL;DR: In this paper, melt spinning combined with a plasma-activated sintering (MS-PAS) method is employed for commercial p-type zone-melted (ZM) ingots of Bi_0.5Sb_1.5Te_3.
Abstract: Bismuth telluride based thermoelectric materials have been commercialized for a wide range of applications in power generation and refrigeration. However, the poor machinability and susceptibility to brittle fracturing of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with a plasma-activated sintering (MS-PAS) method is employed for commercial p-type zone-melted (ZM) ingots of Bi_0.5Sb_1.5Te_3. This fast synthesis approach achieves hierarchical structures and in-situ nanoscale precipitates, resulting in the simultaneous improvement of the thermoelectric performance and the mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS-PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS-PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in their fracture toughness, combined with an eightfold and a factor of six increase in the compressive and flexural strength, respectively. Accompanied by an excellent thermal stability up to 200 °C for the MS-PAS synthesized samples, the MS-PAS technique demonstrates great potential for mass production and large-scale applications of Bi_2Te_3 related thermoelectrics.
198 citations
TL;DR: In this article, a review of the recent development of inorganic and hybrid nanomaterials for optical limiting applications is presented, together with the synthesis, testing method, optical limiting property and mechanism of several representative classes of nanommaterial, including carbon nanotubes, silver and gold nanocomposites, and selected other conducting and semiconducting nanOMaterials.
Abstract: This paper reviews the recent development of inorganic and hybrid nanomaterials for optical limiting applications. The synthesis, testing method, optical limiting property and mechanism of several representative classes of nanomaterial, including carbon nanotubes, silver and gold nanocomposites, and selected other conducting and semiconducting nanomaterials, are introduced separately. The nonlinear optical mechanisms observed in inorganic nanomaterials, i.e. nonlinear scattering, two-photon absorption, free-carrier absorption, etc, are discussed in conjunction with the influence of the material properties and the laser source on the optical limiting performance.
197 citations
TL;DR: In this article, an overview of polymer and carbon nanotube composite is presented with special emphasis on their applications in technical fields and the general applications of polymer/carbon nanotub...
Abstract: In this review, an overview of polymer and carbon nanotube composite is presented with special emphasis on their applications in technical fields. The general applications of polymer/carbon nanotub...
197 citations
Cites background from "Carbon Nanotubes--the Route Toward ..."
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TL;DR: Carbon nanotubes (CNTs) have been considered as a new promising reinforcement for ceramic matrix composites over the last decade, owing to their exceptional properties as mentioned in this paper, however, gaining further control over challenging CNTs dispersion is still an important issue with the aim of tailoring multifunctional properties of CNT-reinforced CMCs.
Abstract: Carbon nanotubes (CNTs) have been considered as a new promising reinforcement for ceramic matrix composites (CMCs) over the last decade, owing to their exceptional properties. CNT-reinforced CMCs posses a unique microstructure, nanoscale objects dispersed throughout ceramic matrix grain boundaries, which allows tailoring physical properties with an unprecedented combination of remarkable engineered transport properties as well as superior mechanical properties. However, gaining further control over challenging CNTs dispersion is still an important issue with the aim of tailoring multifunctional properties of CNT-reinforced CMCs. This paper reviews the current status of the research and describes all different approaches used to effectively disperse CNTs throughout ceramic matrices, providing an overview of composites microstructure and mechanical, electrical and thermal properties. Besides, all findings reported till date point out a promising approach towards physical properties tailoring of CNT-reinforced ceramic CMCs.
195 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