Nanocarbon effects

Huczko, A. et al. (2005) Pulmonary toxicity of 1-D nanocarbon materials. Fullerenes, Nanotubes, and Carbon Nanostructures, 13 (2), 141—145. Grubek-Jaworska, H. et al. (2006) Preliminary results on the pathogenic effects of intratracheal exposure to onedimensional nanocarbons. Carbon,... 

In situ growth via covalent binding of a hybridizing component to a nanocarbon can be achieved in the case of polymers, dendrons and various other macromolecules which are synthesized in a stepwise manner. The in situ synthesis of such macromolecules potentially increases binding site density while steric effects of the nanocarbon can lead to increased variation in average polymer chain length (polydispersity) [101 103]. 

Hierarchical composites produced by the addition of nanocarbons to standard FR-PCs have tremendous potential. First, because the role of the nanocarbon is to produce only moderate improvements in the absolute properties of the material or to give it additional functionality, these effects being potentially attainable with low mass fraction of nanocarbons. Second, because the ethos itself of hierarchical composites means that rather than competing with well-established composites, nanocarbons are integrated into them to improve their performance and extend their application range. 

Nanocarbon emitters behave like variants of carbon nanotube emitters. The nanocarbons can be made by a range of techniques. Often this is a form of plasma deposition which is forming nanocrystalline diamond with very small grain sizes. Or it can be deposition on pyrolytic carbon or DLC run on the borderline of forming diamond grains. A third way is to run a vacuum arc system with ballast gas so that it deposits a porous sp2 rich material. In each case, the material has a moderate to high fraction of sp2 carbon, but is structurally very inhomogeneous [29]. The material is moderately conductive. The result is that the field emission is determined by the field enhancement distribution, and not by the sp2/sp3 ratio. The enhancement distribution is broad due to the disorder, so that it follows the Nilsson model [26] of emission site distributions. The disorder on nanocarbons makes the distribution broader. Effectively, this means that emission site density tends to be lower than for a CNT array, and is less controllable. Thus, while it is lower cost to produce nanocarbon films, they tend to have lower performance. 

The activity of elemental carbon as a metal-free catalyst is well established for a couple of reactions, however, most literature still deals with the support properties of this material. The discovery of nanostructured carbons in most cases led to an increased performance for the abovementioned reasons, thus these systems attracted remarkable research interest within the last years. The most prominent reaction is the oxidative dehydrogenation (ODH) of ethylbenzene and other hydrocarbons in the gas phase, which will be introduced in a separate chapter. The conversion of alcohols as well as the catalytic properties of graphene oxide for liquid phase selective oxidations will also be discussed in more detail. The third section reviews individually reported catalytic effects of nanocarbons in organic reactions, as well as selected inorganic reactions. 

There are thus multiple effects by which the properties of the nanocarbon-semiconductor hybrid material can be different from the simple physical mixture of the two components [1] The nanocarbon offers an effective way for an efficient dispersion of the semiconductor, thus preventing agglomeration, but also providing a hierarchical structure [15] for efficient light harvesting and eventually easy access from gas/liquid phase components (in photocatalytic reactions) or electrolyte (in DSSC). 

Nanocarbon hybrids have recently been introduced as a new class of multifunctional composite materials [18]. In these hybrids, the nanocarbon is coated by a polymer or by the inorganic material in the form of a thin amorphous, polycrystalline or single-crystalline film. The close proximity and similar size domain/volume fraction of the two phases within a nanocarbon hybrid introduce the interface as a powerful new parameter. Interfacial processes such as charge and energy transfer create synergistic effects that improve the properties of the individual components and even create new properties [19]. We recently developed a simple dry wrapping method to fabricate a special class of nanocarbon hybrid, W03 /carbon nanotube (CNT) coaxial cable structure (Fig. 17.2), in which W03 layers act as an electrochromic component while aligned... 

In mechanochemical activation it would be the action of several of the aforementioned parameters, and their relative importance is often difficult to separate. There may be also other phenomena and synergetic effects too, which have not been elucidated yet. Whatever are the mechanisms, mechanochemical activation works amazingly well, and presents an attractive alternative to thermal activation. It also provides easy, top-bottom method for manufacturing nanostructured hydrides and nanocarbons. 

Abstract. Nanocarbon materials and method of their production, developed by TMSpetsmash Ltd. (Kyiv, Ukraine), are reviewed. Multiwall carbon nanotubes with surface area 200-500 m2/g are produced in industrial scale with use of CVD method. Ethylene is used as a source of carbon and Fe-Mo-Al- mixed oxides as catalysts. Fumed silica is used as a pseudo-liquid diluent in order to decrease aggregation of nanotubes and bulk density of the products. Porous carbon nanofibers with surface area near 300-500 m2/g are produced from acetylene with use of (Fe, Co, Sn)/C/Al203-Si02 catalysts prepared mechanochemically. High surface area microporous nanocarbon materials were prepared by activation of carbon nanofibers. Effective surface area of these nanomaterials reaches 4000-6000 m2/g (by argon desorption method). Such materials are prospective for electrochemical applications. Methods of catalysts synthesis for CVD of nanocarbon materials and mechanisms of catalytic CVD are discussed. 

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