Multiwalled structure

By varying the process parameters and precursors, it is possible to select and control the resulting nanostructures. For example, by introducing the proper concentration of hydrogen into the chlorine-treatment process of SiC, it is possible to induce the formation of nanodiamond (5-10 nm) at fairly low temperatures (<1000°C) and ambient pressures. The choice of carbide may dictate the propensity of the CDC to form a specific carbon structure. Nanobarrels were observed to form in significant fraction in AI4C3CDC. These multiwalled structures were observed by various researchers. " ... 

Figure 2.9 HRTEM (high-resolution TEM) micrographs of IF-WS2 showing the multiwall stmcture. They have a more faceted shape. Due to their larger diameter, their multiwall structure is more difficult to observe...

To resume, IF-M0S2 and IF-WS2 used in this study can be described as quasi-spherical and multiwall structures. Several analyses (EELS, TOF-SIMS) show their purity. Closed structures present the advantage to be chemically inert. Few sulfate forms are detected by TOF-SIMS or XANES. 

Lamellar structures are often used but adhere easily to surfaces by their flexibility, leading them to conform easily to the topography of asperities. IF structures, due to the two properties indicated previously, do not adhere easily to surfaces [11]. Moreover, their hollow and multiwall structure gives them great elasticity. These particles can also be used as separators between two surfaces, thus preventing direct contact between them [11]. 

WS2 nanotubes tested were synthesized at Johannes Gutenberg Universitat of Mainz [70]. These tubes have a multiwall structure and an average diameter of 30 nm for a length of... 

Plots summarising the relationship between (a) tensile modulus and (b) yield stress of melt-spun polyamide-12 nanocomposites and nanoscale filler weight fraction for CNFs, arc-grown (aMWCNT) entangled (eMWCNT) and aligned (aMWCNT) multiwall structures. (Tensile tests were based on a constant force ramp. )... 

Muller, J. et al. (2008) Structural defects play a major role in the acute lung toxicity of multiwall carbon nanotubes toxicological aspects. Chemical Research in Toxicology, 21 (9), 1698-1705. 

To some extent the cobalt particles in Figure 2.1(c) seem to be distributed within the tubular structure of the multiwalled nanotubes. TEM analysis could not fully clarify if this is an artifact or if the particles are truly situated inside the hollow space of the tubes. However, Tavasoli et al.14 observed Co particles captured inside the tubes after incipient wetness impregnation. Thus, it can be assumed that this is the case here as well. 

X-ray diffraction studies have shown an expansion of 2-4% in the c axis of multiwall IF structures (including inorganic nanotubes) (4,11,12). Figure 16 shows a comparison between the (0002) peak of WS2 platelets (bulk 2H) (a), and IF... 

Zhang Q, Zhang L, Li JH (2007) DNA-hemoglobin-multiwalls carbon nanotube hybrid material with sandwich structure Preparation, characterization, and application in bioelectrochemistry. J. Phys. Chem. C 111 8655-8660. 

E. Raymundo-Pinero, P. Azais, T. Cacciaguerra, D. Cazorla-Amoros. A. Linares-Solano, and F. Beguin, KOH and NaOH activation mechanisms of multiwalled carbon nanotubes with different structural organisation, Carbon, 43, 786-795 (2005). 

Bhandari, S. Deepa, M. Srivastava, A. K. Joshi, A. G. Kant, R., Poly (3, 4-Ethylene-dioxythiophene)- multiwalled carbon nanotube composite films structure-directed amplified electrochromic response and improved redox activity./. Phys. Chem. B2009,113, 9416-9428. 

Figure 3.1 (a) Roll-up of a graphene sheet leading to three different types of SWNTs. Reprinted with permission from Ref [25]. Copyright Wiley-VCH Verlag. (b) Different structures of multiwalled CNTs. 

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