Onion-like structure

Nested fullerene-type structures with other inorganic layered materials have been investigated recently. Tenne et al (1992) have shown that MoSj is formed in a nested (onion-like) structure when MoOj is reduced by HjS in the gas phase at 1070-1220K (Feldman et al, 1995). Similar results have been obtained with WSj. The idea seems to be more general, being applicable to other inorganic layered structures, as... 

Other onion-like structures reported recently include those built of tungsten sulphide and other inorganic materials [26e]. 

Alternatives to impregnation procedures coating procedures are another possibility for the application of different chemical compositions to a carrier -body. A sequential procedure can though lead to an onion like structure of the deposited components, which may not always be desirable, but for some applications one may also exploit this concept. In combination with impregnation procedures, coating procedures may prove to be most powerful and efficient... 

Zhang, J., Ekstrom, T.C., Gordeev, S.K., and Jacob, M. Carbon with an onion-like structure obtained by chlorinating aluminum carbide. J. Mater. Chem. 10, 2000 1039-1041. 

Onion-like structures analogous to nested fullerenes were also obtained in considerable yields (Fig. 5). The heating arrangement with a tubular furnace employed for the preparation of MoS2 nanotubes is shown in Fig. 7. MoOj being sublimable, the Furnace ... 

In this review we shall focus on some of these new forms of solid carbon. The emphasis is on the physical properties of electrically conducting fullerides, fulleride polymers and nanotubes, but the neutral fullerene polymers, dimers and onion-like structures are also included for completeness. This paper is by no means a review of all important work in the domain. We fully realize that in choosing the material we had to be subjective and we selected material best known to us. A few other short reviews have been published recently on fullerene polymers on the optical properties of polymeric fullerenes [15] and on the physical properties of conducting fullerenes [16,17]. There are extensive recent reviews on the pressure and heat induced polymers [18]. We did not include in the paper the physical and chemical properties of alkali fullerides with variously charged monomer ions. These are the subject of other reviews and are described in detail in a recent monograph [19]. In particular, there are comprehensive reviews [20,21] on experiments and theories aimed at the understanding of the mechanism of superconductivity. 

Figure 4.21 A sufficiently smooth surface provided, electron irradiation can cause the formation of a graphitic layer on diamond. Irregularities, on the other hand, give rise to onion-like structures ( Elsevier 1996).

Apart from the methods described so far, there are several other procedures mainly or partly leading to the formation of nano-onions or onion-like structures. Some of these experiments will be presented below. 

A nanoparticle is generally defined as a particle whose diameter is between 1 and 100 nm. No distinction is made according to the material nanoparticles can be metals, metal compounds, organic compounds, and polymers. A composite nanoparticle is a nanoparticle which has a composite stmcmre, including core-shell structure, onion-like structure, or gladiate composition. 

Quantity of atoms Nj in consecutive shells of onion like structures with an interlayer spacing of 0.3373 nm and an atom surface density of 37.77 atoms/nm ... 

When two metals are combined within a nanoparticle, potentially they could mix in different patterns called as nanostructures. A few commonly nanostructures are (a) core-shell, (b) sub-cluster segregated, (c) homogeneous (ordered or random) alloy and (d) multi-shell or onion like structure. In the case of supported AuPd catalysts, homogeneous... 

The same basic structures can be expected in melts that consist of 50% A and 50% B homopolymers (Fig. 58a) or even AB diblock copolymers (Fig. 58b). The situation changes somewhat for AB diblocks if the typical length of the polymer (as, e.g., expressed by its radius of gyration) is much smaller than the radius of the confining sphere. Now, the system is essentially forced to form additional interfaces as it can, e.g., no longer form a core-shell strucmre due to spatial constraints. Consequently, additional layers and onion-like structures emerge (Fig. 58c). 

In summary, the light sphere of the dumbbeU-like scission configuration possesses an onion-like structure with two shells that are progressively difficult to break into the total mass... 

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