Target, carbon

SWCNTs have been produced by carbon arc discharge and laser ablation of graphite rods. In each case, a small amount of transition metals is added to the carbon target as a catalyst. Therefore the ferromagnetic catalysts resided in the sample. The residual catalyst particles are responsible for a very broad ESR line near g=2 with a linewidth about 400 G, which obscures the expected conduction electron response from SWCNTs. 

In 1984. scientists (Rohlling. Cox. and Caldor at Exxon Research and Engineering) created clusters of carbon (soot) by the laser vaporization of a carbon target rod in connection with a supersonic nozzle. By means of mass spectroscopy, the researchers determined the relative abundance of the carbon clusters produced. Small, 20- to 40-atom clusters of carbon were expected inasmuch as these had been produced a number of times by earlier investigators working on the soot problem. In such experiments, an interesting but unexplained question always arose—Why were only even-numbered carbon clusters produced in the complete absence of odd-numbered clusters See Fig. 3. 

Consider the reaction 12C(a, n) where the laboratory energy of the incident projectile is 14.6 MeV. What is the excitation energy of the compound nucleus The reaction cross section is 25 millibars. Assuming a carbon target thickness of 0.10 mg/cm2 and a beam current of 25 nA, compute the lsO activity after a 4-min irradiation. 

The synthesis was very short, requiring only ten steps, six of which were C-C bond-forming steps, to prepare the twenty-carbon target 1. 

Figure 6.25. Proposed scheme for the formation of the multishell fullerene C6o C24o- Reproduced from Mordkovich, V. Z. Shiratori, Y Hiraoka, H. Takeuchi, Y. Synthesis of Multishell Fullerenes by Laser Vaporization of Composite Carbon Targets, found onhne at http //www.ioffe.rssi.ru/joumals/ ftt/2002/04/p581-584.pdf.

In Fig. 5 we show, with solid line, the non-linear calculations of the stopping power of carbon for all ions with atomic numbers in the range 1 < Zj < 40, and with a fixed velocity v = 0.8 a.u., together with experimental results from various authors [10,46,47]. We also show the theoretical results obtained from the DFT [32] (which, for the electron density of carbon targets, are available only in the range Zj 17), and the calculations according to the Brandt-Kitagawa model (BK) [15]. This model is based on linear theory and includes a statistical model for the ion stmcture as well as... 

Fig. 5. (a) Stopping power of carbon targets (with = 1-6) for slow ions with velocity v = 0.8 a.u. E/A = 16 keV/u). The solid line is the result of the present non-linear calculations for 1 < Zj <40 the dashed line shows the result of the density functional theory (DFT) for 1 < Zj < 17 (with = 1.5) the dotted line shows the result of the Brandt-Kitagawa model. The symbols show the experimental results from various authors [10,46,47]. (b) Contributions of the main partial wave components, I = 0,1,. ..,4, to the total stopping power shown in part (a). 

Fig. 9. General scaling of the effective charge values Z = [Sio (v)/5p(v)] /2 obtained from the non-linear calculations for all the ions with 1 < Zj < 92 in carbon targets, with energies E/M = 1, 2, 5, and lOMeV/u, assuming q = q. Here the calculated values are shown by symbols, while the solid line shows the empirical fitting to Zgff given by equation (19).

Fig. 10. Effective charge values, Z = Kon(v)/Sp(v)] for and Kr ions in carbon targets, obtained from energy loss calculations using the dielectric function (DF) and the non-linear (NL) models described in the text. The dotted lines separate the regions where Z > q and Z < q.

Abstract. Thermally-assisted grafting of linear alkene molecules either in the liquid phase (ethyl undecylenate) or in the gas phase (perfluorodecene), has been performed on atomically flat amorphous carbon (a-C) films with variable average surface hybridization, sp3/(sp2+ sp3), as obtained from X-ray photoelectron spectroscopy. In contrast with the sp2-rich sputtered a-C, optimized sp3-rich a-C films obtained by Pulsed Laser ablation of a glassy carbon target do not require surface preparation before hquid phase grafting. 

A thermally produced beam of atomic hydrogen was allowed to react on a carbon target at temperatures between 30° and 950° C. The reaction products were isolated on a liquid helium cold finger and then analyzed by gas chromatography. 

The above experiments served to characterize the operation of the H atom reactor. The apparent inability to remove all traces of organic material from reactor surfaces exposed to H atoms was not expected. It is interesting to note that in all previous experimental studies on the H atom-carbon reaction in which hydrocarbon reaction products were analyzed, no reports were made of tests to determine possible hydrocarbon yields in the absence of the carbon target. Sufficient experimental details were given in some of these studies to indicate that H atom attack on O-rings and vacuum greases in the reactor system probably occurred. 

It is also possible that the higher atom temperatures used in this study compared with those previously reported may have resulted in the hydrocarbon-producing reactions occurring closer to the surface of the carbon target. If indeed this is the case, the opportunity for reaction product pyrolysis to occur during diffusion out of the pores in the carbon target would be reduced. 

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