Hemisphere-like caps

Flard spherocylinders (cylinders witli hemispherical end caps) were studied using computer simulations [118]. In addition to a nematic phase, such particles also display a smectic-A phase, in which tire particles are arranged in liquid-like layers. To observe tliis transition, ratlier monodisperse particles are needed. The smectic-A phase was indeed observed in suspensions of TMV particles [17]. 

Regarding a historical perspective on carbon nanotubes, very small diameter (less than 10 nm) carbon filaments were observed in the 1970 s through synthesis of vapor grown carbon fibers prepared by the decomposition of benzene at 1100°C in the presence of Fe catalyst particles of 10 nm diameter [11, 12]. However, no detailed systematic studies of such very thin filaments were reported in these early years, and it was not until lijima s observation of carbon nanotubes by high resolution transmission electron microscopy (HRTEM) that the carbon nanotube field was seriously launched. A direct stimulus to the systematic study of carbon filaments of very small diameters came from the discovery of fullerenes by Kroto, Smalley, and coworkers [1], The realization that the terminations of the carbon nanotubes were fullerene-like caps or hemispheres explained why the smallest diameter carbon nanotube observed would be the same as the diameter of the Ceo molecule, though theoretical predictions suggest that nanotubes arc more stable than fullerenes of the same radius [13]. The lijima observation heralded the entry of many scientists into the field of carbon nanotubes, stimulated especially by the un-... 

At a concentration close to the CMC, the micelles are generally spherical or close to spherical (see Fig. 2). As the concentration is increased, the micelles may remain spheroidal or grow and become oblate (disk-like) or prolate (rod-like). The giant worm-like or thread-like micelles represent an extreme case of growth into elongated micelles. The worm-like micelles can be linear or branched (see Fig. 2). The hemispherical end caps of thread-like micelles have a larger diameter than the cylindrical body," a result correctly predicted by theory. Micelles can also be ring-like. " ... 

The coimection between carbon nanotubes and other fullerenes has been defined by the observation that the nanotubes were closed by fullerene-like caps or hemispheres. It is interesting to observe that the smallest reported carbon nanotube diameter is the same as the diameter of C60. This is important in evaluating the minimum dimension of carbon nanostructures. It is necessary to identify all types of nanoparticles and nanostructures of the fullerene family (multiwall and/or single-wall nanotubes, carbon-encapsulated metal nanoparticles, fullerene black and soot, carbon onion, nanowhiskers, etc.). For each nanostructure it is possible to define a set of physical and chemical properties and subsequent applications. It is also interesting to explore the interrelationships between the various nanostructured carbon forms, as well as their relation to the traditional forms of ordered carbon atoms such as diamond and graphite. Carbon is a unique material and can be a good metallic... 

Another important group of fullerene-related compounds are the carbon nanotubes, the reference compounds of the carbon nano-science. They may be obtained by convenient variations of the preparation procedure mentioned. These are long tubular fullerenes with a concentric shell structure a few nanometres wide and often capped with C60-like hemisphere or faceted tips. They are mechanically very strong and either metallic conducting or semiconducting types have been obtained. 

Fig. 4 a-c. Various caps for carbon nanotubes a,b hemispherical - headed arrows denote likely pentagon sites c triangular cap (interlayer spacing ca. 0.34 nm)... 

A recent study reported the formation of bamboo nanostructures with different morphologies from turpentine oil by the aerosol route at 1000 °C. FcH was used as a catalyst source and sulfur as a promoter [40]. These structures have sharp tips, bamboo shapes, open ends, hemispherical caps, pipe-like morphology, and metal particles trapped inside the wide hollow cores. 

The model of Custodio et al. [74] describes every crystallite as a cylinder with a hemispherical cap at each end. The length of the cylindrical part then determines whether the crystallite will look more like a spherulite or more like a shish-kebab. In Figure 14.11, this concept for the morphological development is illustrated. The growth mechanisms for isotropic (spherulites) and ori-... 

Rod-like polymers may be represented by rods or rods capped with hemispheres at both ends. In rod-like molecules, anisotropic translational diffusion arising from the airisotropic particle shape is coupled with rotational diffusion to appear in a < i dependence of the initial decay rate of DLS, which has experimentally been observed for the tobacco mosaic vims. °° By finding a proper model, we can characterize the particle shape and size through Rg, Rh, and Rg/Rh, along with P(g) and r(g], which could contain more information. 

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