Development of Fabrication
Te c h n o l o g y o f C a r b o nNanotube by Fluidized-bed
ReactorTOSHIHIKO SETOGUCHI* 1

MIO NOZAKI* 2

HIDEAKI HASHIMOTO* 3

TAKASHI FUJII* 4

The features of single-wall CNT given in Table 1 are:high electro-conductivity, high mechanical strength, highheat resistance and so on. The single-wall CNT has now
become one of the key materials for new products in thefields of display application, semiconductor application,etc. in addition to the application as a substitute to conventional carbon materials such as elecrtro-conductive
filler to the resin, etc.

1. Introduction
Various applications are proposed for single-wall carbon nanotube (CNT: carbon nanotube) bacause of its
remarkable physical properties such as high electro-conductivity, strength and so on. However, with the present
fabrication method using laser abrasion method, arc discharge method and pneumatic transportation reactor, it
is hard to scale up their fabrication processs. As a result, the high-purity single-wall CNT (low in cost andstable in quality) was not easily available, so that its
application was limited. Hence, a mass-production technology for single-wall CNT was developed in this researchby using fluidized-bed reactor suitable for continuous
mass fabrication.

2. CNT and the fabrication method
2.1 CNT and its application
CNT is a tube-like substance with the tube wall madeFig.. 1
up of hexagonal carbon network (graphen sheet)(1). Fig
shows the model diagram of CNT. There are different
types of CNT with the tube wall ranging from singlewall to several-wall, say dozens of wall. The one withsingle wall in Fig. 1 is called single-wall CNT, and theone with more than two walls is called multi-wall CNT.

Carbon nanotube model diagram
Side-wallstructure
Hexagonal
carbon network

CarbonatomFig. 1 CNT model diagram
CNT has the structure of hexagonal carbon network(graphen sheet) rolled into the shape of a tube.

Table 1 Features and applications of CNT
Application

Features for use

Merit

Development level

Electro-conductive
filler for resin-structurematerialFormation of high-conductivity network
Nano size

High electro-conductive performanceby slight addition
Maintenance of base metal physicalproperties and improvement
in resin recycling

CommercializedElectron emissionsource for FED
application, etc.

High-conductivity
Extra-fine (easy electron emission)

Electron emission possible at low voltage
and low temperature
Reduction of power consumption

Trial-manufacture

Battery electrodematerialFormation of high-conductivity network
High specific surface area(for support of catalyst)

Low resistance and low-temperature
operation
Improvement of battery output

In actual use(Li-ion battery)
Trial-manufacture(fuel cell)

Field-effecttransistor (FET)High electron mobility (10 times that of Si)

High-speed, high current density
transistor to replace Si

Basic development

LSI veer wireHigh electro-conductivity and current density
High thermal-conductanceRestriction of heat generation at highintegration

Basic development*1 Nagasaki Research & Development Center, Technical Headquarters*2 Advanced Technology Research Center, Technical Headquarters*3 Kobe Shipyard & Machinery Works*4 Power Systems Headquarters

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 1 (Jan. 2006)1

2.2 Fabrication method
Fabrication technology for single-wall CNT using fluidized-bed reactor was developed, with the model
fluidized-bed reactor shown in Fig. 2
2. The fluidized-bed
reactor is formed by supplying CNT raw material (hydrocarbon gas) into the catalyst particles through thebottom of the reactor. When reacted at specified temperature, the single-wall CNT grows starting from theactive metal of the catalyst. The high purity single-wall
CNT powder can be obtained by removing the catalyst.
The fluidized-bed reactor has the features givenbelow.
(1) It is easy to control the catalyst particle diameter on
the catalyst support and to manage the selectivity ofthe single-wall CNT growth.
(2) The particles mix well, the reaction atmosphere ishighly uniform and the quality of single-wall CNT ishighly stable.
(3) It is easy to handle the supply and discharge of solid
particles.

Fluidized-bedreactor

These features of the fluidized-bed reactor enable continuous production of CNT, ensuring stable and highproductivity of high-purity single-wall CNT.

3. Production test results of single-wall CNT using fluidized-bed reactor
Study was conducted on the fabrication of single-wall
CNT using fluidized-bed reactor with the test conditions
for fluidized-bed reactor summed up in Table 2
2. The catalyst was supplied continuously at the rate of 6.4 kg/h,
continuously discharging the catalyst particles adheredwith single-wall CNT from the catalyst particle removing hopper, with the single-wall CNT production rate
being 140 - 250 g- CNT/h.
Fig. 3 shows the image of scanning electron microscope (SEM) of the obtained sample, indicating theconfirmed growth of extra-fine fibers on the catalyst surface. An observation using transmission electron
microscope proved that these fine fibers were single-wallFig. 44).
CNT with diameter 1 - 3 nm (Fig.

Fabrication of single-wallcarbon nanotube
Removal ofcatalyst + CNT

Supply of raw
gas catalyst
Catalyst particle model
Active metal Fluid material

CNTSolidseparation

Elimination ofWaste solution
catalyst
Growth of CNT
starting at active metal* The diagramshows an image.

Before CNT synthesis*

After CNT synthesis*

Fig. 2 Model diagram of fluidized-bed reactor
CNT is fabricated in processes (1) - (5). Catalyst particles were used as the fluid
material to be fed in the fluidized-bed reactor.

Fig. 4 Transmission electron microscope (TEM)
image of the sample experimentally manufactured by using continuous fabricating
fluidized-bed test equipment (reactor)
Black stripe patterns caused by carbon element areconfirmed, with the space between patterns in correspondence with the tube external shape being 1- 3 nm,
indicating the synthesis of single-wall CNT.

Table 2 Test conditions for continuous fabricating fluidized-bed
test equipment (reactor)
Continuous fabricating fluidized-bed
test equipment (reactor)

Reactor6.4 kg/hMagnesium oxide (MgO)

Supply gas

CH4=20 %, N2=80 %Pressure
CNT fabricating
temperature

Fig. 3 Image of scanning electron microscope (SEM image) of
the sample experimentally manufactured by using continuous fabricating fluidized-bed test equipment (reactor)
After fabrication of CNT, extra-fine fiber with diameter <10 nm is
confirmed on the catalyst surface.

Fe typeCatalyst
Catalyst supply unit
Catalyst support(MPa)0.1800o( C)

Fluidized-bed size (mm)Diameter: 151, bed height: 150

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 1 (Jan. 2006)

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90

100

Amorphous C 5 - 15%

9080

Simple combustion pattern80: Thermogravimetriccurve: Differential thermal
analytic curve

Single-wall CNT 70 - 90%

TG (%)

70605060

No combustive component isfound at temperature 500oC
or over, and no existenceof multi-wall CNT or graphite
content observed.

4030Catalyst 5 - 15%

7050
4030
2020

10100-10
1 000

00

100

200

300

400

500

600

700

800

900oTemp ( C)
Fig. 6 Analysis result of thermogravimetry (TG-DTA) and purity evaluation of the sample experimentally fabricatedby using continuous fabricating fluidized-bed test equipment (reactor)
oThe weight changes at continuous temperature rise recorded the weight reduction of 70 - 90% between 400 - 500 C,othe combustible calcinations 5 - 15% and catalyst residue 5 - 15% at 400 C or under:

4. Conclusion
Mitsubishi Heavy Industries, Ltd. (MHI) has succeeded for the first time in the world in continuous
fabrication of single-wall carbon nanotube, ensuring effective manufacture of single-wall carbon nanotube by
applying catalyst of special structure to MHI fluidizedbed reactor. The productivity at the present stage is 140- 250 g/h and the purity of the single-wall carbonnanotube is 70 - 90%. In the future, MHI plans to demonstrate the annual production of several tons for fiscal
year 2007, and to realize a drastic cost down as compared with the convention sample market price, aiming
at the expansion of application to the business of materials and their applied products.
This research was a part of the advanced nanocarbon
application project consigned by the New Energy andIndustrial Technology Development Organization(NEDO) to the Japan Fine Ceramic Center (JFCC).

CNT diameter (nm)0.9

D-bandRaman signal a. u.

G-bandRaman signal a. u.

Besides, it was confirmed through Raman spectroscopy in Fig. 5 that the radial breathing mode (RBM)
specific to the single-wall tube structure was observedat the region 300 cm-1 or under. The purity of the singlewall CNT was evaluated by thermogravimetry. The result
from Fig. 6 showed a sharp weight reduction of 70 - 90%
to correspond to the single-wall CNT at about 450oC as
well as the subsequent exothermic peak. The combustible calcinations ratio at 400 oC or under was found to
be 5 - 15% and 5 - 15% catalyst residue at 500 o C orover. It was confirmed through these results that singlewall CNT of purity 70 - 90% was continuously producedin the fluidized-bed test equipment for continuous manufacture.

1 700 1 600 1 500 1 400 1 300 1 200 300

Raman shift cm-1

1.0

1.2 1.4 1.6 1.8 2 2.2

Detection of RBM
mode derived fromsingle-wall CNT

250200150100

Raman shift cm-1

Fig. 5 Raman spectroscopy of the sample experimentally manufactured
by using fluidized-bed test equipment (reactor)
Signals from G-band due to graphite and RBM derived from single-wall CNT
were confirmed, indicating the existence of single-wall CNT in the sample.

Toshihiko Setoguchi

Mio Nozaki

Hideaki Hashimoto

Takashi Fujii

References(1) S. Iijima, Helical microtubules of graphitic carbon, Nature,
Vol.354 (1991) p.56

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 1 (Jan. 2006)

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