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7
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84916315838
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Präparative Trennung von C60 und C70 an Polystyrol-Gel
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(1992)
Angewandte Chemie
, vol.104
, pp. 666
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Gügel, A.1
Becker, M.2
Hammel, D.3
Mindach, L.4
Räder, J.5
Simon, T.6
Wagner, M.7
Müllen, K.8
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14
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84989525039
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This remains true despite the most recent reports on metal‐catalyzed production processes, since a selective synthesis is still not possible.
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(1993)
Chem. Eng. News
, vol.71
, pp. 6
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Dagani, R.1
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15
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84989525027
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The yield of soluble fullerenes is a sensitive and complex function of the helium vapor pressure (used for quenching), the electrode diameter, and the distance between the electrodes, which also influences the selectivity of formation of the various fullerenes: hot plasmas with a small electrode separation give increased quantities of higher fullerenes at lower overall yields. Graphitic tubules can be found within the carbon slag formed on the negative electrode used in the arc discharge with direct current. Graphitic onionlike spheres apparently arise only when fullerene black is intensively bombarded with electrons; however, the desired structure is not obtained in every batch, even when conditions are identical. It has not been proved beyond doubt whether graphitic onionlike spheres can be produced by other thermal processes, since transmission electron microscopy has, up to now, been the only possible means of identification.
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18
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84989600585
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(1993)
Nature
, vol.363
, pp. 60
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23
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0001787275
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(1992)
Chem. Phys. Lett.
, vol.34
, pp. 62
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Werner, H.1
Herein, D.2
Blöcker, J.3
Henschke, B.4
Tegtmeyer, U.5
Schedel‐Niedrig, T.6
Keil, M.7
Bradshaw, A.M.8
Schlögl, R.9
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24
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84989559178
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Modified ULVIC BUCKY II apparatus equipped with graphite rods for spectroscopy (6 mm, 3 mm apart); alternating current of 150 A; distance between electrodes adjusted to give a constant current.
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25
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84989505452
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Diode array spectrophotometer BECKMANN DU 7000; spectra were recorded with the help of a quartz optical fiber and a quartz window directly in front of the center of the electric arc.
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28
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84989534580
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In plasmas, a large number of charged particles are also formed. The electrical charge can influence the formation of fullerenes, and this source of building blocks could give rise to additional selectivity. However, the fact that fullerenes are also produced under conditions in which charged species are absent suggests that electrically charged building blocks are helpful but not essential.
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29
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84989537581
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All samples were investigated supported on amorphous carbon films after deagglomeration in an ultrasonic bath of acetone. Siemens (Elmiskop 102, 120 kV, double tilt, side entry), Jeol (CX 200, 200 kV, double tilt, top entry), and Phillips (CM 20, modified with a cryoprojection lens, ultrahigh vacuum in the sample chamber, single tilt, side entry) instruments were used.
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33
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84989598458
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The layered character of the objects, shown with continuous contrast, also follows from powder X‐ray diffraction data, which show a clear peak corresponding to the interlayer separation of 341 pm and a complex, modulated background [13]. This material can be distinguished from the electrode graphite, which may contaminate the product, by its much lower combustion temperature [12].
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34
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84989559167
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Since the apparatus was designed for the manufacture of large amounts of fullerenes, we operated with a regulated electrode separation and continuous external adjustment of the graphite rods, which led to a leak rate of the same order as the residual pressure. This factor could only be eliminated if the whole apparatus was placed in a glove box with an inert atmosphere.
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35
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0039215559
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Presumably, this material is always formed when the apparatus is in operation and acts as a “getter” to the vapor‐phase contaminants (helium 5.0). Moreover, such particles may well act as nuclei for the condensation of large fullerenes.
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(1991)
Chem. Phys. Lett.
, vol.184
, pp. 310
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Goeres, A.1
Sedelmayer, E.2
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40
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84989569892
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This is determined by the thermal conductivity and partial pressure of the quench gas, as well as by a steep temperature gradient in the gas chamber, which was achieved by placing a metal plate around the plasma chamber to provide efficient cooling of the quench gas.
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