Environmental Engineering Reference
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RF gel +
Silica particles
Carbon-silica
composite
Nanoporous
Carbon
Silica sol solution
(1)
(3)
(2)
(1): Resorcinol + Formaldehyde, polymerization; (2): Carbonization; (3): Nanoparticle
removal
Figure 10.4
Schematic diagram for the synthesis of nanoporous carbon using silica sol
templates (Han and Hyeon, 1999a).
10.1.4 Other Nanoscale Carbons
To date, except for the three outstanding types of carbonaceous materials above,
only few forms of the numerous remaining nanoscale carbons have shown their
promising applications for environmental fields.
Carbon black is an industrial form of soot produced by hydrocarbon
dehydrogenation and widely used as a filler to modify the mechanical, electrical, and
optical properties of the materials in which they are dispersed (Dresselhaus et al., 1996).
The particle size of carbon black is partially in the nanometer range with average values
between 20 and 300 nm (Sirisinha and Prayoonchatphan, 2001). Carbon blacks are
composed of the concentric organization of small graphite layers (Dresselhaus et al.,
1996; Harris, 1999).
Carbon onions were synthesized in 1992 by Daniel Ugarte, which are perfect
spheres apparently made up of concentric fullerenes (Ugarte, 1992). They were extracted
from cathodic soot following arc-evaporation. They also can be obtained by the
irradiation of 'fullerene soot' (Harris, 1999). Unfortunately, though carbon onions have
a central shell about 0.7-1.0 nm in diameter (very close to the diameter of C
60
), they are
unstable when not being irradiated in an electron beam.
10.2.1 Fullerenes
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