A new method of fullerene production: pyrolysis of acetylene in high-frequency thermal plasma

Yiming Chen a,*, Haiyan Zhang a, Yanjuan Zhu b, Ding Yu b, Zhenfang Tang c,Yanyang He b, Chunyan Wu b, Jinhua Wang b

a Faculty of Material and Energy, Guangdong University of Technology, Guangzhou 510643, Chinab Department of Applied Physics, Guangdong University of Technology, Guangzhou 510090, China

c National Guangzhou Center of Analysis and Testing, Guangzhou 510076, China

Received 4 December 2001; accepted 14 March 2002

Abstract

Carbon soot that contains fullerene was continuously produced by pyrogenic process of acetylene in high-frequency plasma. The

characterization of the carbon soot was analyzed by the transmission electron microscopy X-ray diffraction, UV/visible and IR

spectra. The fullerene yield in carbon soot is about 2.5 g h�1. # 2002 Elsevier Science B.V. All rights reserved.

Keywords: Pyrolysis method of plasma; Fullerene; Acetylene

1. Introduction

Fullerene has attracted much attention since its

discovery, because of its remarkable electronic and

mechanical properties, as an important raw material of

semiconductor, superconductor, photoelectric material,

catalyst, nonlinear optic material and so on. Since

fullerene of milligram magnitude has been first synthe-

sized by electric arc discharge method [1] extensive

research has been done for the synthesis of fullerene,

and many methods have been found such as resistance

pyrogenation [2], flame method [3], laser ablation [4],

and solar energy method [5]. Currently the most widely

used technique to produce fullerene is the electric arc

discharge. But electric arc discharge cannot fulfill the

increasing demand of application, because of the

discontiguous technics and limited output. So many

scientists try to find a new method to produce fullerene.

Theodora et al. have used halogenated hydrocarbons

(C2Cl4, C2Cl2F2), to produce fullerene by thermal

plasma [6]. Wang et al. also report to produce fullerene

by direct evaporation of carbon powder injected into the

thermal plasma [7]. In this paper, we report a method to

produce fullerene using high-frequency plasma, which

can be used to produce carbon soot containing fullerene

continuously in volume.

Thermal plasma is one of the common technics used

to produce nanomaterial in volume. It is widely used to

produce many kinds of powder, such as metal oxide,metal nitride, carbide, and boride [8]. Also it is a kind of

flexible method to produce fine powder, with relatively

simple preparation technics, and extensive sources

which can be gas, liquid or solid grain. Compared

with direct current plasma, the purity of the powder

produced by high-frequency thermal plasma is higher

because there is no electrode so that no impurity can be

induced in the production process.

2. Experiment

The high-frequency plasma system consists of high-

frequency power, plasmareactor, high-temperature

chamber, quencher, dust-collector, feeding apparatus,

measuring and controlling system, and exhaust-gas

treatment device. The structure sketch of the system isshown in Fig. 1. By using different feedstock and

thermal reaction condition, many kinds of inorganic

fine powder can be prepared. The experiment was* Corresponding author.

E-mail address: mpcyjs@gdut.edu.cn (Y. Chen).

Materials Science and Engineering B95 (2002) 29�/32

www.elsevier.com/locate/mseb

0921-5107/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.

PII: S 0 9 2 1 - 5 1 0 7 ( 0 2 ) 0 0 1 3 0 - 7

carried out in atmosphere pressure, using argon gas

(purity 99%) as dilution gas, and high pure acetylene as

reactant gas. Acetylene was ripped into the outer plasma

flame vertically, and then decomposed into carbon soot

and hydrogen. After quencher, carbon soot and hydro-

gen were drawn out, and then a collector collected the

carbon soot.

The typical preparation parameters for carbon soot

synthesis are plasma power 30 W, frequency 4 MHz, Ar

gas flow rate 10 m3 h�1, and acetylene flow rate 0.25

m3 h�1. In our experiment, the yield of carbon soot is

about 0.25 g h�1, depending on the flow rate of reactant

gas.

3. Results and discussions

The carbon soot was examined by transmission

electron microscopy (TEM) and X-ray diffraction

(XRD). The specimens for ultraviolet (UV)/visible

optical absorption spectroscopy analysis and infrared

(IR) absorption spectra were prepared by extracting the

carbon soot with toluene. After decompression filtra-

tion, red extraction was obtained and then divided into

two parts. A part of the extraction was diluted with

toluene and then checked by UV/visible optical absorp-

tion spectroscopy. Solid powder was obtained from the

other part of the toluene extraction by rotary evapora-

tion. Then the solid powder was washed by aether so as

to get pure fullerene powder. The carbon soot and the

fullerene powder was checked individually by IR.

Fig. 2 is the TEM image of carbon soot. The carbon

soot particles exhibit a sphere nanoparticle, with dia-

meter of 20�/30 nm. The morphology of the carbon soot

particles in this experiment is similar to that of those

produced by other methods [9]. The main ingredients of

the carbon soot are amorphous carbon, graphite and

fullerene. Fig. 3 is the TEM image of C60 crystal

extracted from carbon soot by toluene.

Fig. 4 shows the XRD pattern of the carbon soot (X-

ray wavelength 1.54). We can observe a broad diffrac-

tion peak. This is the typical polycrystalline structure of

carbon soot characteristic of the fullerene.

Fig. 5 is the UV/visible absorption spectrum. Because

the wavelength limit of UV/visible absorption spectrum

is 285 nm [10] (the solution absorption can not be

ignored if the wavelength is lower than that), the test

wavelength should be above 285 nm. The wavelength of

the sorption peak is 337 and 407 nm. Compared with the

Fig. 1. The structure sketch of the high-frequency plasma system.

Fig. 2. TEM image of carbon soot.

Fig. 3. TEM image of C60 crystal*/toluene extract from carbon soot.

Fig. 4. XRD of the carbon soot.

Y. Chen et al. / Materials Science and Engineering B95 (2002) 29�/3230

previous report [11] (329, 404 nm), there is a little red

shift.Fig. 6A and B are the IR spectrum of carbon soot and

fullerene powder. Four characteristic absorption peaks

are shown obviously in the spectrum, with wavenumber

1425, 1178, 571 and 522 cm�1. Compared with spectra

B, background absorption of spectra A is stronger, but

the four characteristic absorption peaks are weaker, and

some sundry peaks were observed. Because there were

not only a lot of amorphous carbon and graphite, but

also some hydrocarbon compounds. The sundry peaks

were the reflection of the strong absorption of �/CH2�/

and �/C�/C�/C�/ radicle. In spectra B, amorphous

carbon, graphite and hydrocarbon have been removed,

so that the four characteristic absorption peaks stand

out obviously.In our experiment, by extracting from the carbon

soot’s toluene solution, the yield of fullerene is 2.5 g h�1

measured by weight. Compared with arc discharge

method, the best advantage of the acetylene thermal

plasma method is that it can be performed in atmo-

sphere pressure, and it is easy to be magnified in

technical application. The technics of this method is

very simple, and the technics process can be controlled

easily.

In Table 1, we compared the yield of carbon soot and

fullerene produced by thermal plasma method with that

by arc discharge method. The typical preparation

parameters for carbon soot synthesis by arc discharge

method are diameter of graphite electrode 6 mm, electric

current 60 A, and voltage 20 V. It can be seen that by

thermal plasma method, fullerene can be produced

continuously in a large scale, with a large feed. So the

yield of fullerene by thermal plasma method will be at

least an order of magnitude larger than that by arc

discharge method.

According to our previous work, inert gas is a very

important factor that affects the yield of fullerene [12]

and He gas is better than Ar gas for fullerene prepara-

tion. So that if we use He gas instead of Ar gas, the yield

of fullerene may be increased largely. In addition,

pyrolysis of acetylene in high-frequency thermal plasma

can produce fullerene. It can be inferred that using other

hydrocarbon gas such as ethylene or methane also can

produce fullerene. So this method can be popularized to

produce fullerene in a large scale, using different

hydrocarbon gas as carbon source.

4. Conclusion

The carbon soot containing fullerene produced in

pyrolysis of acetylene in the thermal plasma, consist of

amorphous carbon, graphite and fullerene. The yield of

fullerene is about 2.5 g h�1. The best advantage of this

method is that it can use the simple instrument device to

produce fullerene, easy to be magnified and the technical

process is very simple. By improving technical condi-

tion, this method can be applied to produce fullerene in

volume, providing a foundation for the wide application

of fullerene.

Fig. 5. UV/visible absorption spectrum of the carbon soot extraction.

Fig. 6. IR spectrum of carbon soot (A) and the fullerene powder.

Table 1

Yield of carbon soot and fullerene in Ar atmosphere by arc discharge method and thermal plasma method

Arc discharge method Thermal plasma method

Ar pressure (kPa) 10.7 20.0 30.7 40.0 50.7 61.3 70.7 81.3 90.7 100

Yield of carbon soot (g h�1) 8.4 5.0 5.2 3.5 3.3 3.6 3.7 3.4 3.3 250

Yield of fullerene (g h�1) 0.27 0.01 0.03 0.06 0.06 0.09 0.08 0.15 0.88 2.5

Y. Chen et al. / Materials Science and Engineering B95 (2002) 29�/32 31

Acknowledgements

This work is supported by Guangdong Provincal

Natural Science Foundation of China.

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