Nanostructured carbon materials

Jurewicz K, Frackowiak E, Beguin F. Towards the mechanism of electrochemical hydrogen storage in nanostructured carbon materials. Appl. Phys. A 2003 in press. 

Carbon nanotubes (CNTs) constitute a nanostructured carbon material that consists of rolled up layers of sp2 hybridized carbon atoms forming a honeycomb lattice. After diamond, graphite and fullerenes, the one-dimensional tubular structure of CNTs is considered the 4th allotrope of carbon (graphene is the 5th). 

Until recently, synthesis of nanostructured carbon materials was usually based on very harsh conditions such as electric arc discharge techniques [1], chemical vapor deposition [2], or catalytic pyrolysis of organic compounds [3]. In addition (excluding activated carbons), only little research has been done to synthesize and recognize the structure of carbon materials based on natural resources. This is somewhat hard to understand, as carbon structure synthesis has been practiced from the beginning of civilization on the base of biomass, with the petrochemical age only being a late deviation. A refined approach towards advanced carbon synthesis based on renewable resources would be significant, as the final products provide an important perspective for modern material systems and devices. 

Modifying the surface characteristics to enhance the charge storage. There is a broad protocol to modify the surface characteristics of carbon materials, especially the nanostructured carbon materials, to have excellent adsorption/desorp-tion behavior ... 

Fig. 15.1 Classification of sp2- and sp3-hybridized nanostructured carbon materials. CNTs are considered as open-end tubes, thus also exposing prismatic edge surfaces.

Kuznetsov V.I. and Butenko Yu.V. (2003) Synthesis and properties of nanostructured carbon materials nano-diamond, onion-like carbon and carbon nanotubes. In Proceedings of NATO Advanced Research Workshop on Nanostructured Materials and Coatings for Biomedical and Sensor Applications , 4-8 August 2002. Eds. Gogotsi Y.G. and Uvarova I.V. V. 102, IOS Press, p. 187-202. 

The distinctive feature of the discussed method for nanostructural carbon material synthesis is that there is a possibility to produce these materials without catalysts owing to a very quick synthesis (competing with velocity of light). An example of such type of process is synthesis of carbon nanotubes by evaporation of pure graphite in liquid media. 

The results given indicate the electrochemical method for the synthesis of nanostructured carbon materials to be promising. In the reaction space, dissipative self-assembly of carbon compounds takes place by the action of electric discharges. In this case, structures of new type can be formed, which are transitional between polycyclic aromatic hydrocarbons and fullerenes, nanotubes. 

Finally, let us move to the investigating of the physical properties of nanostructural carbon materials. As mentioned already the methods of acoustomicroscope defectoscopy are applicable to almost all materials in condensed state. The opportunity of their usage for carbon materials is demonstrated on the graphite PROG, that is chosen as a model. Its main characteristics, determined with the help of acoustomicroscope methods, are illustrated in the Table 1. 

NANOSTRUCTURED CARBON MATERIALS BASED ON IR-PYROLIZED POLYACRYLONITRILE... 

This study shows the possibilities and specific feature of IR-pyrolysis for the formation of nanostructured carbon. In such way PAN, thermal transformations of which have been studied in detail [8-11], was chosen as the precursor for preparation of nanostructured carbon materials by carbonization of PAN and its composites with gadolinium chloride under non-coherent IR radiation. Specific action of IR-radiation on vibrational energy of PAN bands macromolecules allows one to decrease extremely time treatment and as a result to make simple, low energy and cost-effective pyrolitic method. 

Karpacheva G.P., Zemtsov L.M., Bagdasarova K.A., Muratov D.G., Ermilova M.M. and Orekhova N.V. (2005) Nanostructured carbon materials based on IR-pyrolysed polyacrylonitrile, Hydrogen materials scince and chemistry of carbon nanomaterials. ICHMS 2005. IX International Conference, Sevastopol -Crimea - Ukraine, September 05-11, 2005, AHEU, Kiev, 890-891. 

We have analyzed the influence of the annealing temperature, structural disorder, and the frequency of a continuous excitation laser radiation Vl on the first- and the second-order Raman spectra of several nanostructured carbon materials including single-wall carbon nanotubes (SWCNT), SWCNT-polymer composites, and nanostructured single-crystalline graphites. Consideration of the high-order nonlinear effects in Raman spectra and anharmonicity of characteristic Raman bands (such as G, G, and D modes) provides important information on the vibration modes and collective (phonon-like) excitations in such ID or 2D confined systems... 

Ryoo, R. and Joo, S.H. (2004). Nanostructured carbon materials synthesized from mesoporous silica crystals by replication. Stud. Surf. Sci. Catal, 148, 241-60. 

Chapter 14 addresses the special topic of sensors, in which advantage is taken of the unique properties of nanostructured carbon materials such as nanotubes and fullerenes. Finally, applications of carbon-supported precious metal catalysts are reviewed from an industrial perspective in Chapter 15. 

Yuruma, Y, Taralp, A., Veziroglu, T. N. 2009. Review storage of hydrogen in nanostructured carbon materials. Int J. Hydrogen Energy 34 3784-3798. 

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