Hollow core

The earliest observations of carbon nanotubes with very small (nanometer) diameters [151, 158, 159] are shown in Fig. 14. Here we see results of high resolution transmission electron microscopy (TEM) measurements, providing evidence for m-long multi-layer carbon nanotubes, with cross-sections showing several concentric coaxial nanotubes and a hollow core. One nanotube has... 

Fig. 4. Coexisting vapour-grown carbon fiber, with thicker diameter and hollow core, and carbon nanolubes, with thinner hollow core, (as-grown samples).

Fig. 8. The lip of PCNTs with continuous hollow core (a) and the cone-like shape (b) (T indicates the toroidal structure shown in detail in Fig. 11).

Fig. 13. HRTEM image of an as-grown thick PCNT. 002 lattice image demonstrates the innermost hollow core (core diam. 2.13 nm) presumably corresponding to the as-formed nanotube. The straight and continuous innermost two fringes similar to Fig. 5 are seen (arrow).

No superconductivity has yet been found in carbon nanotubes or nanotube arrays. Despite the prediction that ID electronic systems cannot support supercon-ductivity[33,34], it is not clear that such theories are applicable to carbon nanotubes, which are tubular with a hollow core and have several unit cells around the circumference. Doping of nanotube bundles by the insertion of alkali metal dopants between the tubules could lead to superconductivity. The doping of individual tubules may provide another possible approach to superconductivity for carbon nanotube systems. 

VGCFs have typical diameters of 100 nm - 100 pm with hollow cores [9]. Thus VGCFs are 10 - lO times thicker than CNTs. A preparation method for VGCFs was first developed by Endo [10,11] wbo decomposed benzene at 1150-1.300°C in an electric furnace in the presence of H2 (99.9% pure) as the carrier gas (see Fig. 1). Ultra-fine particles of Fe (ca. 10 nm diameter) or its compounds, such as Fe(N03)3 or ferrocene, were introduced into the chamber as a catalyst. 

Fig. 3. Heat-treated PCNT two concentric layers and a hollow core (2.4 nm diameter) [18. ...

PCNTs are marketed commercially by Hyperion Catalyst International Inc. (Cambridge, Mass. USA), based on a patent [22] Graphite Fibrils. The method of production appears to be essentially the same as that used for Endo PCNTs. The material consists of MWCNTs, 10-20 nm in diameter and 10-12 j,m long, with ca. 10 coaxial layers within each tube. The tubes have hollow cores of ca., 2 nm diameter. The Brunauer-Emmett-Teller (BET) analysis characteristically shows a surface area of 250 m /g, true density 2.0 g/cm- and bulk density of less than 0.1 g/cm (95% void vol). 

HRTEM picture (Fig. 1(a)) shows that CNF-R is estimated of a diameter of 30 40 nm and has a hollow core. The graphene layers are about 15-20 inclining to the axis. After heat treatment, CNF-HT, the structure remained, but graphene layers stack more regularly. 

It has been suggested (Bozzi et ah, 1997 Grant et ah, 1998) that Dps and E. inocua ferritin represent examples of a family of ancestral dodecameric protein which had as function to trap, but not to mineralize, metal ions, and that the ability to oxidize and mineralize iron efficiently and to form fourfold interactions came later. The hollow-cored dodecameric motif exemplified by Dps and E. inocua ferritin has clearly been adapted to a number of functions, since in addition to DNA binding and iron storage, other family members include a novel pilin, a bromoperoxidase and several other proteins of unknown function (Grant et ah, 1998). 

Wilson S.J., Hollow core glass waveguides, Proc. SPIE 799 (1987), pp.54-60. 

Benabid, F. Couny, F. Knight, J. C. Birks, T. A. Russell, P. S. J., Compact, stable and efficient all fibre gas cells using hollow core photonic crystal fibres, Nature. 2005, 434,... 

Fig. 18.1 ARROW waveguides, (a) Side view of light ray propagating in original solid state ARROW19 (b) side view of ray propagating in hollow core ARROW (c) hollow core cross section with light polarization...

Fig. 18.7 Scanning electron microscope images showing interfaces between solid core and hollow core waveguides, (a) Top view of the interface at the end of a hollow core waveguide, (b) Side view of a solid core waveguide intersecting a hollow core waveguide...

Yin, D. Barber J. P. Hawkins A. R. Schmidt H., Low loss integrated optical sensors based on hollow core ARROW waveguides, Proc SPIE 2005, 5730, 218 225... 

Renn, M. J. Pastel, R. Lewandowski, H. J., Laser guidance and trapping of mesoscale particles in hollow core optical fibers, Pkys. Rev. Lett. 1999, 82, 1574 1577... 

Measor, P. Kuhn, S. Lunt, E. J. Phillips, B. S. Hawkins, A. R. Schmidt, H., Hollow core waveguide characterization by optically induced particle transport, Opt. Lett. 2008, 33, 672 674... 

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