Single-walled tube

Single-wall tubes. Following the synthesis studies of stuffed nanocapsules, single-wall (SW) tubes were discovered in 1993(9,10]. SW tubes are found in chamber soot when iron[9] and cobalt[10] were used as catalysts, and for nickelfl 1,40] they grow on the surface of the cathode slag. For iron catalyst. 

Fig. 12. TEM picture of single-wall tubes growing radially from a Ni-carbide particle.

The amount of hydrogen that can be stored on these tubes has been debated. One report shows that maximum storage capacity for a single-walled carbon nanotube (SWCNT) [7] and multiwalled carbon nanotubes [8] is approximately 8% by weight [9], Multiwalled carbon nanotubes are a collection of concentric single-walled nanotubes [10] versus the one-dimensional single-walled tubes [11], SWCNTs have very high surface-to-volume ratios as well as uniform pores, which allow for capillary action and thus the ability to be filled by condensation. 

Therefore, multiwalled carbon nanotubes may henceforward be assumed normally to consist of concentric single-walled tubes. These are largely independent of one another and may belong to different structural types even within an individual MWNT. However, this does not mean that alternative structures do not exist. At least partially coiled species have been observed in some cases, and rolled up graphene layers play an important role in some hypotheses on the mechanism of nanotube formation. 

The ways of tube termination and further defects like kinks are another essential aspect of MWNT structure. Like in the single-walled tubes, five-membered rings are crucial to the formation of these domains. As for the asymmetric conical structure, a single pentagon defect at the end of the innermost tube is presumed to cause the generation of such a cap. Sometimes the inner tubes end at a considerable distance from the actual tip. This gives rise to larger voids. 

If graphite/Co-Ni mixtures are used as a target during laser vaporisation at 1200°C, bundles or ropes of single-walled nanotubes are produced [13]. These usually appear to contain mainly (10,10) nanotubes (armchair tubes 13.8 A diameter see section 2.1.2) packed in a crystalline form. X-ray powder diffraction reveals that these ropes or bundles consist of 100-500 single-walled tubes... 

Fignre 7.12 displays the diffraction patterns and calculated structures for AU24T that present evidence for the emergence of an empty single-walled tube-like... 

Each steam generator was of single-wall tube-in-shell design. The evaporators were of the forced-circulation type, with each of the three circuits having a steam drum and a boiler circulating pump. Superheated steam from the three circuits flowed to a common header to drive a 300MW turbo-alternator. The main feed was via a 100% duty steam-driven pump with... 

Carbon nanotubes (CNTs) have two main variants, as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). SWNTs are the tubes of graphite which have a single cylindrical wall whereas MWNTs are larger and consist of many single walled tubes stacked inside the other (Fig. 1). 

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