Carbon bamboo-like

Because of the speeial atomie arrangement of the earbon atoms in a carbon nanotube, substitutional impurities are inhibited by the small size of the carbon atoms. Furthermore, the serew axis disloeation, the most eommon defeet found in bulk graphite, is inhibited by the monolayer strueture of the Cfj() nanotube. For these reasons, we expeet relatively few substitutional or struetural impurities in single-wall earbon nanotubes. Multi-wall carbon nanotubes frequently show bamboo-like defects associated with the termination of inner shells, and pentagon-heptagon (5 - 7) defects are also found frequently [7]. 

Abstract. IR pyrolysis of PAN and PAN based composites yields ordered graphitelike structure as well as several carbon nanostructures. Metal-carbon nanocomposites, in which the nanosized metal particles were introduced into the structure of carbon matrix in the course of IR pyrolysis of composite-precursor on the basis of PAN and metal (Gd, Pt, Ru, Re) compounds were prepared. The carbon phase of metal-carbon nanocomposites was shown to include different types of nano structured carbon particles. Bamboo-like CNT were observed in the structure of pyrolized at 910 and 1000°C composite-precursor based on PAN and GdCl3. At T=1200°C the solid carbon spheres with diameter in the range of 50-360 nm and octahedral carbon particles with the size in the range of 300-350 nm were observed. These nanostructured particles consist of carbon only or they include Gd nanoparticles incapsulated in carbon shell. IR pyrolysis of composite-precursor based on PAN as well as H2PtCl6 and RuC13 or NH4Re04 (Pt Ru(Re)=10 l) allows the preparation of Pt-Ru and Pt-Re alloys nanoparticles with 2[Pg.577]

The carbon phase of obtained metal-carbon nanocomposites was shown to contain different types of nanostructured carbon particles in parallel with main graphite-like structures. Bamboo-like carbon nanotubes (CNT) with 14-30 nm in their outer diameter were observed in structured carbon material when GdCl3 was used as a component of composite-precursor (Fig. 4). In this case IR radiation intensity provides the heating of sample to 910 and 1000°C. 

In the course of IR pyrolysis, according to mass spectrometry and gas chromatography data, various gas products of destruction of PAN polymeric chain are present in the reaction chamber, including hydrocarbons such as ethylene and propylene [17, 18], These hydrocarbons provide the carbon source. Catalytic decompositions of hydrocarbons at high intensity IR-radiation in the presence of metallic Gd leads to the formation of carbon nanostructures such as observed bamboo-like CNT. It is well known that Ni, Co Fe have conventionally been used widely as metallic catalysts for high temperature pyrolysis of hydrocarbons. Recently bimetallic components was shown to be more effective than single metals as catalysts. Especially transition metals with addition of rare-earth metals such as Y, Ce, Tb, La and Ho [19]. In this work catalytic activity of single metallic Gd in the IR-pyrolysis of hydrocarbons are found by us for the first time. 

It is important to note that structural transformations of obtained bamboo-like CNT takes place while IR radiation intensity rises. At T=1200°C bamboo-like CNT are converted to solid carbon spheres with diameter in the range of 50-360 nm and octahedral carbon particles with the size in the range of 300-350 nm (Fig. 5). These nanostructured particles consist of carbon only or they contents Gd nanoparticles incapsulated in spherical or octahedral carbon particles. The mechanism of high temperature structural transformations of bamboo-like CNT still needs research. 

Thus, the carbon phase of obtained metal-carbon nanocomposites represents in reality the carbon-carbon nanocomposite of main graphite-like structure with array of carbon nanostructures such as bamboo-like CNT, spherical or octahedral carbon nanoparticles. 

Yu Y, Gu L, Wang C, Dhanabalan A, Van Aken PA, Maier J. Encapsulation of Sn carbon nanoparticles in bamboo-like hollow carbon nanofibers as an anode material in lithium-based batteries. Angew Chem Int Ed. 2009 48 6485-9. 

The conversion of acetylene on an iron catalyst on Si02-support is a typical example. In this process, acetylene is thermally decomposed by leading it over a bed of catalyst within a quartz tube heated at about 700 °C (500-1000 °C, generally). Apart from the desired MWNT, there are also larger, fibrous structures and layers of amorphous graphene observed. These tend to coat the catalyst particles. The bamboo-like nanotubes (Section 3.3.4) usually obtained from this method are often covered with amorphous carbon too and, in parts, they are considerably curved. In addition to these bent species, there is also a spiral or helical structure... 

However, instead of the idealized coaxial layers shown in Figure 13.10a, MWNT prepared by CCVD sometimes exhibit a bamboo-like structure, as that shown in Figure 13.10c (85). This type of MWNT has many more defects than either SWNT or DWNT, and as a result, their intrinsic properties are inferior to those of less defective carbon forms. Also, the variabUity of properties from mbe to mbe is much higher than those seen in SWNT, as demonstrated by direct tensile test measurements conducted in a TEM chamber with AFM capabUity on individual MWNT grown by CCVD (86). 

Figure 13.10 (a) Schematic depiction of a multiwaiied carbon nanotube (MWNT) as formed by a series of coaxial rolled-up graphene layers (b) TEM image of multiwaU coaxial nanotubes reported by lijimain 1991 (3). (c) Bamboo-like multiwaiied carbon nanotube. (Reproduced with permission from C. J. Lee et al., Chem. Phys. Lett. 2000, 323, 560.)... 

Heng, L.Y., Chou, A., Yu, )., Chen, Y, and Gooding, J.J. (2005) Demonstrating the advantages of using bamboo-like nanotubes for electrochemical biosensor applications compared to single walled carbon nanotubes. Electrochem. Commun., 7 (12), 1457-1462. 

Eguilaz, M., Ferreyra, N.E, and Rivas, G.A. (2014) Dispersions of hollow and bamboo-like multi-walled carbon nanotubes in polyethyleneimine critical analysis of the preparation conditions and applications for electrochemical sensing. Electroanalysis, 26 (11), 2434- 2444. 

Cui, H., Zhou, O., Zhu, W. and Stoner, B. R., Deposition of aligned bamboo-like carbon nanotubes via microwave plasma enhanced chemical vapor deposition . Journal of Applied Physics, 2000,88, 6072-6074. 

Acetylene, benzene, and ethylene Fe, Co, Ni 1950-2600 — — Bamboo-like carbon [139]... 

---