Preparation of carbon micro-beads via an ethanol-thermal route

Article abstract of DOI:10.1246/cl.2005.846

Carbon micro-beads (CMB) with regular and perfect shape, high yields, and narrow size distributions were obtained via an ethanol-thermal reduction process in a stainless steel autoclave at 500°C. In this process, LaNi₅ alloy was used as a catalyst. The products were characterized with X-ray powder diffractometer (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. There were two types of carbon micro-beads, spherical and spindle-like, in the sample. The spherical microbeads have diameters ranging from 2 to 5 μm. The spindle-like micro-beads had diameters ranging from 2 to 4 μm and lengths ranging from 5 to 10 μm. Copyright

Full text of DOI:10.1246/cl.2005.846

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Chemistry Letters Vol.34, No.6 (2005)
Preparation of Carbon Micro-beads via an Ethanol-thermal Route
ꢀ
Yuanzhu Mi, Yingliang Liu, Dingsheng Yuan, and Jingxian Zhang
Department of Chemistry, Jinan University, Guangzhou, 510632, P. R. China
(Received March 16, 2005; CL-050353)
Carbon micro-beads (CMB) with regular and perfect shape,
high yields, and narrow size distributions were obtained via an
ethanol-thermal reduction process in a stainless steel autoclave
Structure characterization was performed by X-ray diffrac-
tion (XRD) on a MSAL-XD2 X-ray diffractometer using Cu Kꢀ
ꢀ
radiation (40 kV, 20 mA, ꢁ ¼ 1:54051 A). The morphologies of
ꢁ
at 500 C. In this process, LaNi5 alloy was used as a catalyst.
the sample were characterized with Philips XL-30 scanning
electron microscopy. The Raman spectrum of as-prepared
samples was recorded at ambient temperature on a Renishaw
RM2000 Raman microspectrometer with an argon-ion laser at
an excitation wavelength of 514.5 nm.
The products were characterized with X-ray powder diffractom-
eter (XRD), scanning electron microscopy (SEM) and Raman
spectroscopy. There were two types of carbon micro-beads,
spherical and spindle-like, in the sample. The spherical micro-
beads have diameters ranging from 2 to 5 mm. The spindle-like
micro-beads had diameters ranging from 2 to 4 mm and lengths
ranging from 5 to 10 mm.
Figure 1 shows the X-ray diffraction pattern of the as-
ꢁ
ꢂ1
prepared samples. A scanning rate of 0.08 s has been used
ꢁ
to record the pattern in the range of 20–55 . The XRD pattern
ꢀ
shows that the presence of two peaks at d ¼ 3:4169 A and d ¼
ꢀ
:0249 A, which are reflections from the 002 planes and
from the 101 planes, respectively. The peaks can be indexed to
2
The discovery of a number of novel carbon materials with
1
2
ꢀ
unique structures, such as carbon nanotubes, carbon onions,
a hexagonal graphite lattice with cell constant a ¼ 2:448 A
3
4
ꢀ
cone-shaped graphitic structures, carbon micro-trees, carbon
hollow spheres,5 and carbon micro-coils, depending on the
techniques and the carbon precursors used has led to a wide
research interest. Micro-bead carbon materials attract many
researchers due to their unique applications, which include
and c ¼ 6:834 A. The deviation was lower than 1% compared
6
ꢀ
ꢀ
with the reported values a ¼ 2:470 A and c ¼ 6:790 A (JCPDS
No.75-1621).
2
2
500
000
7
,8
high-density and high-strength carbon artifacts, lithium-ion
secondary battery,9 and their unique spherical shape with a
diameter of approximately 1 to 40 mm being appreciated. The
preparation and properties of these carbon materials have attract-
ed considerable attention, because their applications significant-
ly depend on the shape and size of the particles.
–14
1500
1
000
5
00
Qiu et al.15 reported a ball-like carbon material obtained by
arc discharge evaporation of composite carbon rods made from
coal and nickel particles. The carbon micro-balls were observed
in various forms such as mono-dispersed individual balls, net-
like and plate-like materials. It is well known that carbonaceous
spheres or mesocarbon micro-beads (MCMB) can be prepared
from pitch or polymeric materials in large quantities with
2
0
30
40
50
2 θ / degree
Figure 1. X-ray diffraction pattern of the products, using
Cu Kꢀ X-ray as radiation.
Figure 2a shows SEM image of LaNi5 alloy catalyst. The
catalyst have sizes ranging from 10 to 40 mm. Figure 2b shows
many carbon micro-beads grown from the surface of LaNi5
alloy. Low-magnification SEM image (Figure 2c) indicates that
carbon micro-beads with large quantity, narrow size distribu-
tions, regular and perfect shape are achieved by this approach.
Most of carbon micro-beads are spheres with diameters ranging
from 2 to 5 mm. Furthermore, there are many spindle-like carbon
micro-beads (Figure 2d), diameters ranging from 2 to 4 mm and
lengths ranging from 5 to 10 mm. In addition, we could also ob-
serve some hemispheres in the sample via SEM observation
(Figure 2c). All of them are mono-dispersed, and the surfaces
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various methods, such as direct polymerization from pitch,
19
17,18
emulsion method, and suspension method. In the present
study, carbon micro-beads were fabricated with LaNi5 alloy as
a catalyst via an ethanol-thermal reduction process in a stainless
ꢁ
steel autoclave at 500 C. The yield of carbon micro-beads was
estimated through SEM observations of the as-prepared samples
to be about 95%.
All reagents of analytical grade were commercially availa-
ble in our experiment. A lanthanum nickel alloy prepared by
melting method was used as a catalyst to produce carbon mi-
cro-beads. In a typical experiment, an appropriate amount of
LaNi5 alloy (0.5 g), and absolute ethanol (50 mL) were put into
a stainless steel autoclave of 60 mL capacity. The reactor was
8
seem to be rather smooth. Yamada et al. separated mesocarbon
micro-beads by solvent fractionation from heat-treated coal-tar
pitch and from heat-treated asphalt at 430 C. The shapes of
ꢁ
ꢁ
maintained at 400, 500, and 600 C for 12, 24, 36, and 48 h, re-
spectively, and then it was cooled to room temperature naturally.
A dark precipitate was collected and washed with absolute etha-
nol, dilute HCl aqueous solution, distilled water and absolute
ethanol, respectively. The obtained sample was then dried in a
the mesocarbon micro-beads are classified into lemon-like and
spherical in their report. In our experiment, a particular period
of reaction time (48 h) appears to be optimum to give a large
quantity of the carbon micro-beads than other reaction times.
ꢁ
ꢁ
vacuum at 60 C for 4 h.
The optimal reaction temperature is 500 C. There is no carbon
Copyright ꢀ 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.6 (2005)
847
micro-bead in the as-prepared sample when the temperature is
route, compared with the sample prepared through the arc dis-
15
ꢁ
ꢁ
lower than 400 C or higher than 600 C. LaNi5 alloy may be
play a catalytic role in producing carbon micro-beads, because
no carbon micro-beads were obtained when there was not LaNi5
alloy in the reaction process. A study of the growth mechanism
of the carbon micro-beads is underway.
charge method (ID=IG ¼ 0:25) reported by Qiu et al.
In summary, we have successfully synthesized carbon
micro-beads on a large scale through an ethanol-thermal route.
In this process, ethanol was used as the carbon source and
solvent, and LaNi5 alloy prepared by melting method was used
as a catalyst. The optimal reaction time was 48 h, and the most
ꢁ
favorable temperature was 500 C. Two types of carbon micro-
b
a
beads, spindle-like and spherical, are obtained by the approach.
They have narrow size distributions, regular and perfect shape.
Further studies along this line are in progress. Compared with
other methods, this approach was simple and feasible. Further-
more, nontoxic and cheap ethanol was used as carbon source.
Therefore, it may potentially be applied on the scale of industrial
production.
This work was financially supported by the Science and
Technology Project of Guangdong Province (2KM02304G)
and Qian Bai Shi Project of Guangdong Province (Q02059).
c
d
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Figure 3. Raman spectrum of the as-prepared sample.
Published on the web (Advance View) May 21, 2005; DOI 10.1246/cl.2005.846