Nanotubes and Nanofibers potx

[...]... chapter by Du and Winey [3]) The minimum diameter of a stable freestanding SWNT is limited by curvature-induced strain to ~0.4 nm [4] MWNT may have outer shells Ͼ30 nm 1 Copyright 2006 by Taylor & Francis Group, LLC Nanotubes and Nanofibers 2 Zigzag Chiral Armchair FIGURE 1.1 Schematic representation of the relation between nanotubes and graphene The three rectangles can be rolled up into seamless nanotubes; ... modulus and strength are highly dependent on the nanotube growth method and subsequent processing, due no doubt to variable and uncontrolled defects Values of Young’s modulus as low as 3 to 4 GPa have been observed in MWNT produced by pyrolysis of organic precursors [57] TEM-based pulling and bending tests gave more reasonable moduli and strength of MWNT of 0.8 and 150 GPa, respectively [58] Multiwall nanotubes. .. in Figure 1.1 Because the length and width of legal strips are “quantized,” so too are the lengths and diameters of the tubes The short side of the rectangle becomes the tube diameter and therefore is “quantized” by the requirement that the rolled-up tube must have a continuous lattice structure Similarly, Copyright 2006 by Taylor & Francis Group, LLC 4 Nanotubes and Nanofibers the rectangle must be... LLC Nanotubes and Nanofibers 8 (a) z Film y x Fiber Substrate Free-standing films (b) Film normal X-ray beam Capillary FIGURE 1.5 Schematic of the experimental setup for measuring out-of-plane mosaic The film plane is parallel to the incident x-ray beam Out-of-plane preferred orientation results in azimuth (χ)-dependent anisotropic scattering within the 2D detector plane; (a) and (b) refer to films and. .. important in science and industry The discovery and rapid evolution of carbon nanotubes has played a major role in triggering the explosive growth of R & D in nanotechnology Many of the early lessons learnt carried over to rapid developments in inorganic semiconductor nanowire science and engineering, in particular, field effect transistor (FET)-like switching devices, and chemical and biological sensors... Group, LLC Carbon Nanotubes: Structure and Properties 23 to a finite value as T approaches zero, and the effective band gap, Ϫdlnρ/dT, vanishes as T approaches zero; examples of this behavior are shown in Figure 1.20 On the insulating side for PVA-rich gel fibers or annealed oleum fibers, ρ diverges as T approaches zero, and the exponential T dependence can be ascribed to strong localization and either 3D... “localized” interband processes, respectively The inset shows the loss function over a wide energy range, in which the plasmons representing collective excitations of the π and π ϩ σ electrons can be clearly seen at 5.2 and 21.5 eV respectively, in agreement with the , theory Features in the loss function at 0.85, 1.45, 2.0, and 2.55 eV are independent of q and are therefore assigned to interband transitions... and any possible energy gap, vanishes, signaling a true metallic state (From Vavro, J et al., Phys Rev B 71, 155410 (2005), with permission.) Copyright 2006 by Taylor & Francis Group, LLC Nanotubes and Nanofibers 24 7 40 6 35 E/ F 5 30 3 25 (mΩ cm) 4 2 20 1 10 T (K) 1 15 100 Empty SWNTs 10 C60@SWNTs 5 0 1 10 100 T (K) FIGURE 1.21 Four-point resistivity vs T for C60@SWNT (filled circles) and empty nanotubes. .. delocalized electrons, and how it evolves with doping Figure 1.25 shows the reflectance of an unoriented undoped film [80] The solid curve is a model fit, including a free carrier Drude term and several interband Lorentz oscillators These results confirm that undoped material consists of a mixture of conducting and semiconducting nanotubes, typical for bulk samples The interband transition energies... ~40× Copyright 2006 by Taylor & Francis Group, LLC Nanotubes and Nanofibers 26 6 4 1 2 0 –2 8 2 6 4 2 0 0.6 8 0.3 6 0 1 2 0.0 3 4 r (Ω cm)–1/103 10 2 0 0 5 10 15 20 Energy (eV) FIGURE 1.23 Real and imaginary parts of the dielectric function (upper panels) and the real part of the optical conductivity for SWNT (solid curves), C60 (dot–dash curves) and graphite (dotted curves) (From Pichler, T et al., . quasi-one-dimensional materials such as nanotubes and nanowires demonstrate many extreme properties that can be tuned by controlling their structure and diameter. Nanotubes, nanowires, and nanofibers are not only. Dimovski and Yury Gogotsi Chapter 4 Inorganic Nanotubes and Fullerene-Like Materials of Metal Dichalcogenide and Related Layered Compounds 135 R. Tenne Chapter 5 Boron Nitride Nanotubes: Synthesis and. in 2 Nanotubes and Nanofibers Zigzag Chiral Armchair FIGURE 1.1 Schematic representation of the relation between nanotubes and graphene. The three rectangles can be rolled up into seamless nanotubes;