Transparent, Conductive Carbon Nanotube Films

Department of Physics, University of Florida, Gainesville, FL 32611, USA.
Science (Impact Factor: 33.61). 09/2004; 305(5688):1273-6. DOI: 10.1126/science.1101243
Source: PubMed


We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting
films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance,
the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far
superior transmittance in the technologically relevant 2- to 5-micrometer infrared spectral band. These characteristics indicate
broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used
to construct an electric field–activated optical modulator, which constitutes an optical analog to the nanotube-based field
effect transistor.

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Available from: Zhihong Chen, Jul 16, 2014
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    • "Microscopy images of CNT membranes show that the CNTs are distributed randomly in the membrane plane (Li et al., 2013; Wu et al., 2004), and the 2D simulation model is accordingly established, as shown in Fig. 3. In the representative area element of CNT network in Fig. 3(a), CNTs are simplified as line segments with the length l CNT , and the position and orientation of the CNTs are determined by the midpoint (X 1 , X 2 ) and the angle θ. "
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    ABSTRACT: For carbon nanotube (CNT) networks, with increasing network density, there may be sudden changes in the properties, such as the sudden change in electrical conductivity at the electrical percolation threshold. In this paper, the change in stiffness of the CNT networks is studied and especially the existence of stiffness threshold is revealed. Two critical network densities are found to divide the stiffness behavior into three stages: zero stiffness, bending dominated and stretching dominated stages. The first critical network density is a criterion to judge whether or not the network is capable of carrying load, defined as the stiffness threshold. The second critical network density is a criterion to measure whether or not most of the CNTs in network are utilized effectively to carry load, defined as bending–stretching transitional threshold. Based on the geometric probability analysis, a theoretical methodology is set up to predict the two thresholds and explain their underlying mechanisms. The stiffness threshold is revealed to be determined by the statical determinacy of CNTs in the network, and can be estimated quantitatively by the stabilization fraction of network, a newly proposed parameter in this paper. The other threshold, bending–stretching transitional threshold, which signs the conversion of dominant deformation mode, is verified to be well evaluated by the proposed defect fraction of network. According to the theoretical analysis as well as the numerical simulation , the average intersection number on each CNT is revealed as the only dominant factor for the electrical percolation and the stiffness thresholds, it is approximately 3.7 for electrical percolation threshold, and 5.2 for the stiffness threshold of 2D networks. For 3D networks, they are 1.4 and 4.4. And it also affects the bending–stretching transitional threshold, together with the CNT aspect ratio. The average intersection number divided by the fourth root of CNT aspect ratio is found to be an invariant at the bending–stretching transitional threshold, which is 6.7 and 6.3 for 2D and 3D networks, respectively. Based on this study, a simple piecewise expression is summarized to describe the relative stiffness of CNT networks, in which the relative stiffness of networks depends on the relative network density as well as the CNT aspect ratio. This formula provides a solid theoretical foundation for the design optimization and property prediction of CNT networks.
    Journal of the Mechanics and Physics of Solids 11/2015; 84(C):395–423. DOI:10.1016/j.jmps.2015.07.016 · 3.60 Impact Factor
    • "Theoretical fundamentals of heat transfer in MWCNT nanocomposite foams Since their discovery by Iijima in 1991, carbon nanotubes (CNTs) with unique thermal, electrical, and mechanical properties have been widely studied [14] [15] [16] [17]. The superior properties of CNTs makes them potential design candidates for novel materials [18] [19]. "
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    ABSTRACT: We report the heat-transfer characteristics of polystyrene (PS)/multi-walled carbon nanotube (MWCNT) nanocomposite foams with a large expansion ratio (18-fold) and a microcellular cell size (5 μm) that have never been achieved before. These PS/MWCNT foams exhibited excellent thermal insulation performance even without insulation gas. The 5 μm-sized cells in these PS/MWCNT foams are small enough to induce Knudsen effect, and also lead to a distinct radiation behavior that has never been reported; that is, because of the unique synergy of the small cells and the MWCNTs, the short wavelength radiation below the cell size is 100% blocked while the long wavelength radiation over the cell size is strongly attenuated. We made an in-depth analysis of the heat transfer through the PS/MWCNT foams using models. Adding 2 wt% MWCNTs into the PS matrix, 86% of the radiative thermal conductivity was effectively blocked, and the radiative contribution was reduced to 3.5% of the total thermal conductivity. However, the MWCNTs increased the solid conductivity of the PS/MWCNT foams due to their inherently high thermal conductivity. So, a compromised content of 1 wt% MWCNTs was added to optimize solid conduction and radiation, and thereby to minimize the total thermal conductivity to 32.8 mW/m.K.
    Carbon 06/2015; 93. DOI:10.1016/j.carbon.2015.06.003 · 6.20 Impact Factor
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    • "On the other hand, electronic- EAP based actuators, or electrothermal actuators (ETAs), can be manipulated in air and own a short response time but need a high operating voltage or electric field ($MV/m), which constrains their applications [12]. Carbon nanotubes (CNTs) with excellent mechanical, electrical and thermal properties [13] [14] [15] have been used in various fields including being as fillers to improve the mechanical, electrical or other properties [16] [17] [18] [19] [20]. In order to overcome the high voltage constraints in ETAs and improve the actuation performance, CNTs and other conductive fillers are used as additives into the polymer matrices, and are http://dx.doi. "
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    ABSTRACT: Multi-walled carbon nanotubes are used to fabricate a type of environment-friendly electrothermal bimetallic actuators with the matrix of waterborne polyurethane or silicone rubber. Even under a relatively low DC driven voltage of 7 V, the actuator can achieve a bending displacement up to 28 mm, or a curvature up to 0.29 cm−1, which are greater than most of other electrothermal actuators reported. The actuator has considerable controllability, large mechanical output and long life-time, and the working power can be reduced down to 25 mW/mm3 in the atmospheric environment. The actuation mechanisms owe not only to the mismatch in the coefficients of thermal expansion, but also to the unique negative temperature coefficient effect of nanotube composites. Furthermore, the bimetallic actuators based on various polymer matrices are supposed to provide revelations for electrothermal bimorph actuators.
    Carbon 04/2015; 84(1). DOI:10.1016/j.carbon.2014.12.012 · 6.20 Impact Factor
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