194 Letters to the Editor / Carbon 41 (2003) 179 198
make the interlayer spacing difficult to decrease even if the
graphitization is proceeding. We showed that the extrapo-
lated interlayer spacing, d, increased a little with increasing
HTT in Figs. 3 5. If the volume change, DV is caused by
the broadening of interlayer spacing, the volume change is
shown by Eq. (2)
DV5 (d3 2 d3 )/d3 (2)
t 1000 1000
where d1000 and dt are the extrapolated interlayer spacing
at HTT 1000 8C and t 8C, respectively. In the case of
volume change at HTT 2800 8C, DV50.045 is obtained
from Eq. (2). This value almost agrees with that of volume
change from 1000 to 2800 8C in Fig. 1a. The result
supports that the volume expansion comes from the
broadening of mean interlayer spacing of the stacking
layers.
References
Fig. 5. Effect of heat treatment times, 1 h and 9 h on the
extrapolated interlayer spacing, d.
[1] Jenkins GM, Kawamura K, Ban LL. Formation and structure
of polymeric carbons. Proc R Soc Lond 1972;A327:501 17.
[2] Mochida I. Review on the structural concepts of carbons.
Molecular, nano, meso and micro-scopic views of mesophase
determine the mean interlayer spacing of the stacking
pitch/graphitized fiber including nano phased fibers as
carbon layers in the three-dimensional entangling structure.
models of carbons. TANSO 2001;200:206 16.
Information about carbon layer arrangement can be [3] Klug HP, Alexander LE. In: X-ray diffraction procedures,
New York: John Wiley, 1973, pp. 111 490.
obtained from the lattice image directly using a high-
[4] Azároff LV, Buerger MJ. In: The powder method in X-ray
resolution electron microscope. The micrograph of glass-
crystallography, New York: McGraw-Hill, 1958, pp. 210 39.
like carbon heat-treated at low temperature shows that
[5] Mehrotra BN, Bragg RH, Rao AS. Effect of heat treatment
small carbon layers gather at random in dense clusters [1].
temperature (HTT) on density, weight and volume of glass-
This observation is consistent with the high density of the
like carbon (GC). J Mater Sci 1983;18:2671 8.
glass-like carbon heat-treated at 1000 8C as shown in Fig.
[6] Saxena RR, Bragg RH. Kinetics of graphitization in glassy
1b. During high temperature heat treatment the carbon
carbon. Carbon 1978;16(5):373 6.
layers grow, and a structure is established, which is
[7] Kawamaura K, Bragg RH. Graphitization of pitch coke:
proposed as a model by Jenkins et al. or Shiraishi. The
change in mean interlayer spacing, strain and weight. Carbon
winding and tangling arrangements of stacking layers 1986;24(3):301 9.
Catalytic formation of carbon nanotubes during detonation of
m-dinitrobenzene
Yi Lu, Zhenping Zhu*, Weize Wu, Zhenyu Liu
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China
Received 13 May 2002; accepted 1 October 2002
Keywords: A. Carbon nanotubes; B. Catalyst; C. Transmission electron microscopy; Raman spectroscopy; X-ray diffraction
*
Corresponding author. Tel.: 186-351-404-8310; fax: 186- Owing to unique electrical, mechanical, gas-storing, and
351-404-1153.
catalytic properties, as well as a variety of significant
E-mail address: zpzhu@sxicc.ac.cn (Z. Zhu).
potential applications [1,2], carbon nanotubes (CNTs) have
0008-6223/03/$ see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0008-6223(02)00335-4
Letters to the Editor / Carbon 41 (2003) 179 198 195
Fig. 3. Cone-shaped metal particles existing at ends of MWCNTs.
Fig. 1. TEM image of a typical detonation product. The molar
ratio of DNB to Co is 6:1 and loading density of DNB is 0.4
g/ml.
these methods are high energy- and hardware-intensive,
which leads to high cost of CNTs and thus constrains their
been an area of intense research since their discovery in practical applications.
1991 [3]. At present, syntheses of CNTs are normally Recently, Boese et al. [10] and Kroke et al. [11] reported
conducted via arc-discharge [3 6], laser ablation [7] and the formation of tubular products after explosive decompo-
catalytic decomposition of hydrocarbons [8,9]. However, sition. This detonation approach may arouse an energy-
Fig. 2. Raman spectrum of the sample shown in Fig. 1.
196 Letters to the Editor / Carbon 41 (2003) 179 198
and hardware-saved method for CNT synthesis, since the diameter, 70 mm in length) equipped with a pressure
needed high temperature is spontaneously produced from gauge, under an inert gas (Ar) of 0.1 MPa. Before the
the detonation. However, the employed experiment, DNB and cobalt acetate (or nickel formate)
1,2:5,6:11,12:15,16-tetrabenzo-3,7,9,13,17,19-hexadehydro were mixed in an appropriate molar ratio (DNB:metal
annulene [10] and 2,4,6-triazido-s-triazine [11] were spe- salt58:1 1:2), ground physically and then loaded into the
cially synthesized, and the obtained products contained pressure vessel to a desired loading density (the amount of
only 2% of CNTs [11]. Here we present a more effective explosive employed for the detonation in a given volume,
synthesis of CNTs using m-dinitrobenzene (DNB) as a 0.02 0.4 g/ml) for DNB. The detonation was induced by
starting explosive and cobalt (or nickel) as a catalyst for heating (20 8C/min) to 420 8C and evidenced by a sudden
CNTs growth. Such a detonation system can produce pressure rise (shock wave, from 0 to 20 40 MPa, depend-
CNTs with purity of 30 40%. ing on the loading density of DNB). After the detonation,
The detonation experiments were performed in a her- the reactor was cooled to room temperature naturally,
metic stainless steel pressure vessel (14 mm in inner argon and the gaseous products were vented. The solid
Fig. 4. XRD patterns of detonation products. The molar ratio of DNB to metal is 6:1 and loading density of DNB is 0.4 g/ml, cobalt (a) and
nickel (b) are the catalysts.
Letters to the Editor / Carbon 41 (2003) 179 198 197
products, very voluminous black powders, were collected pounds and subsequent reduction by carbon species re-
for further characterization. Transmission electron micro- sulting from detonation. Such a procedure resembles those
scopy (TEM; Hitachi H-600), X-ray diffraction (XRD; of the catalysis-assisted arc-discharge [5,6] and laser
Rigaku X-ray diffractometer using Cu Ka radiation) and ablation [7] approaches and is superior to catalytic de-
Raman scattering (Renishaw Micro-Raman 2000 equipped composition of hydrocarbons unless the alignment of
with a 209 objective and 632.8 nm line of helium neon synthesized nanotubes is requested. Furthermore, most of
laser as excitation resource) were employed to investigate the metal particles located at the tube ends show a cone
the as-synthesized solid products. shape, suggesting that the metal particles are likely in a
Fig. 1 is a typical TEM image of the solid products from quasi-liquid phase or fluxion state during the tube growth,
detonation of a mixture containing DNB and cobalt acetate which may be important to understand the carbon metal
at a molar ratio of 6:1. The loading density of DNB is 0.4 interaction. Cobalt exhibits high catalytic activity in con-
g/ml. It reveals that the products mainly consist of multi- trast to nickel, which may be related to the difference in
wall carbon nanotubes (MWCNTs) and carbon-encapsu- structure. XRD patterns indicate that in the solid products,
lated metal nanoparticles. The MWCNTs are separated the cobalt particles show cubic structures (Fig. 4a) while
from each other with inner diameters of 12 30 nm and nickel particles show both cubic and hexagonal structures
outer diameters of 20 40 nm. The tube length is between (Fig. 4b).
0.5 and 8 mm. Most of the MWCNTs are coiled to In conclusion, the detonation of nitro-containing organic
different extents. Based on the TEM images, it is estimated explosives as common as m-dinitrobenzene can be used to
that the sample contains 30 40% MWCNTs. Higher synthesize CNTs in the presence of a catalyst. The
loading densities of DNB and appropriately higher molar approach is simple, low-cost and universal. From the
ratios of DNB to the metal salt are preferable to yield experimental observation, it is estimated that some other
CNTs-rich products, possibly due to larger heat release nitro-containing organic explosives possessing higher
[12] and slower local heat diffusion, which are very chemical energy than DNB, such as picric acid and
important for the nucleation and thermal annealing of trinitrotoluene, may be more effective for CNTs growth
CNTs [12,13]. In the experiments where DNB loading because their detonations can generate higher tempera-
density is lower than 0.05 g/ml and/or the molar ratio of tures. In addition, a further increase in CNTs selectivity
DNB/metal salt is lower than 1:1, no CNTs are found in and tailoring of structure defects may be available by
the products, carbon-encapsulated metal nanoparticles and elaborate design of detonation experiments.
amorphous carbon particles are the main products.
Fig. 2 is a Raman spectrum of the sample shown in Fig.
1. There are two main peaks in the region between 200 and
Acknowledgements
2000 cm21. The one located at 1595 cm21 (G-band [14])
can be designated as the stretching vibration mode of
The authors thank the National Scientific Foundation of
graphite crystals indicating the formation of graphitized
China for partial support (No. 59872047) and Profs. Bing
CNTs. The one located at 1329 cm21 (D-band [14]) can be
Zhong and Yongwang Li for some valuable discussions.
designated as disorder-induced mode. Kang et al. [15]
attributed the D-band to the carbonaceous particles existing
near CNTs or adhering to the walls of CNTs. The
relatively low intensity of the G-band with respect to that
References
of the D-band is presumably due to the structure defects of
MWCNTs [16] as well as a large amount of carbonaceous
[1] Subramoney S. Novel nanocarbons structure, properties
particles in the sample [15], which agrees with the
and potential applications. Adv Mater 1998;10(15):1157 71.
estimated purity of MWCNTs of 30 40%, based on TEM
[2] Ajayan PM. Nanotubes from carbon. Chem Rev
observation.
1999;99(7):1787 99.
Metal particles are often capped at one of the two ends
[3] Iijima S. Helical microtubules of graphitic carbon. Nature
of MWCNTs with sizes close to the diameters of the 1991;354(6348):56 8.
[4] Ebbesen TW, Ajayan PM. Large-scale synthesis of carbon
connected MWCNTs (Fig. 3), which is in agreement with
nanotubes. Nature 1992;358(6368):220 2.
the findings in the literature [17 19]. To validate the
[5] Bethune DS, Kiang CH, de Vries MS, Gorman G, Savoy R,
importance of the metal particles in CNTs formation, an
Vazquez J et al. Cobalt-catalysed growth of carbon nanotubes
experiment employing only DNB (at loading density of 0.4
with single-atomic-layer walls. Nature 1993;363(6430):605
g/ml) was performed. Only spherical carbon nanoparticles
7.
were found in the product, instead of the desired tubular
[6] Journet C, Maser WK, Bernier P, Loiseau A, de la Chapelle
products. These results suggest that the metal particles are
ML, Lefrant S et al. Large-scale production of single-walled
catalysts crucial to the CNTs formation, providing sites for
carbon nanotubes by the electric-arc technique. Nature
CNTs growth. The nano metal catalyst particles were
1997;388(6644):756 8.
formed in situ through decomposition of the metal com- [7] Thess A, Lee R, Nikolaev P, Dai H, Petit P, Robert J et al.
198 Letters to the Editor / Carbon 41 (2003) 179 198
Crystalline ropes of metallic carbon nanotubes. Science [14] Tan PH, Hu CY, Li F, Bai S, Hou PX, Cheng HM. Intensity
1996;273(5274):483 7. and profile manifestation of resonant Raman behavior of
[8] Li WZ, Xie SS, Qian LX, Chang BH, Zou BS, Zhou WY et carbon nanotubes. Carbon 2002;40(7):1131 4.
al. Large-scale synthesis of aligned carbon nanotubes. Sci- [15] Kang HS, Yoon HJ, Kim CO, Hong JP, Han IT, Cha SN et
ence 1996;274(5293):1701 3. al. Low temperature growth of multi-wall carbon nanotubes
[9] Terrones M, Grobert N, Ollvares J, Zhang JP, Terrones H, assisted by mesh potential using a modified plasma enhanced
Kordatos K et al. Controlled production of aligned-nanotube chemical vapor deposition system. Chem Phys Lett
bundles. Nature 1997;388(6637):52 5. 2001;349(3 4):196 200.
[10] Boese R, Matzger AJ, Vollhardt KPC. Synthesis, crystal [16] Tan PH, Kwok TY, Huang FM, Zhang SL, Shi ZJ, Zhou XH
structure, and explosive decomposition of et al. A comparative raman study of carbon nanotubes and
1,2:5,6:11,12:15,16-tetrabenzo-3,7,9,13,17,19-hexadehydro the highly oriented pyrolytic graphite. Chin J Light Scatter-
annulene: formation of onion- and tube-like closed shell ing 1996;8(3):125 30.
carbon particles. J Am Chem Soc 1997;119(8):2052 3. [17] Tang YH, Zheng YF, Lee CS, Wang N, Lee ST, Sham TK.
[11] Kroke E, Schwarz M, Buschmann V, Miehe G, Fuess H, Carbon monoxide-assisted growth of carbon nanotubes.
Riedel R. Nanotubes formed by detonation of C/N pre- Chem Phys Lett 2001;342(3 4):259 64.
cursors. Adv Mater 1999;11(2):158 61. [18] Sinnott SB, Andrews R, Qian D, Rao AM, Mao Z, Dickey
[12] Frank AC, Fischer RA. Detonation chemistry: a new access EC et al. Model of carbon nanotube growth through chemical
to nanocrystalline gallium nitride. Adv Mater vapor deposition. Chem Phys Lett 1999;315(1 2):25 30.
1998;10(12):961 4. [19] Yudasaka M, Kikuchi R, Ohki Y, Ota E, Yoshimura S.
[13] Ugarte D. Curling and closure of graphitic networks under Behavior of Ni in carbon nanotube nucleation. Appl Phys
electron-beam irradiation. Nature 1992;359(6397):707 9. Lett 1997;70(14):1817 8.
Wyszukiwarka
Podobne podstrony:
Development of Carbon Nanotubes and Polymer Composites TherefromLasenby et al New Framework 4 Formation of Invariants (1997) [sharethefiles com]Medicine in the (trans)formation of wrong bodiesSHSpec 074 6111C01 Formation of CommandsFIRST and the Formation of Massive StarsEvidence for the formation of anhydrous zinc acetate and aceticFormation of a new chromosomes as a virulence mechanism in C glabrataGarret Formation of Indoeuropean subgroups, ChronologyF1 Format of financial statementsElectrochemical DNA biosensors based on platinum nanoparticles combined carbon nanotubesInvestigations of White Layer Formation During Machining of Powder Metallurgical Ni Based ME 16 SPassage of a Bubble Detonation Wave into a Chemically Inactive Bubble MediumPhase Diagram of Ultrafine CarbonA Political Economy of Formatted PleasuresPharmacokinetics of intraosseous and central venous drug delivery during cardiopulmonary resuscitatiEvolution of Carbonwięcej podobnych podstron