Electric heating – Metal heating – By arc
Reexamination Certificate
2003-07-28
2004-09-21
Hoang, Tu Ba (Department: 3742)
Electric heating
Metal heating
By arc
C373S062000
Reexamination Certificate
active
06794599
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This patent application claims priority to Japanese Patent Document No. P2001-056330 filed on Mar. 1, 2001, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method and a manufacturing apparatus of a carbonaceous material. More particularly, for the present invention relates to a manufacturing method and apparatus for single-walled carbon nanotubes or other carbonaceous materials by using arc discharge.
Carbon nanotubes are new materials first reported by S. Iijima in Nature, Vol. 354 (1991) 56 in 1991. Especially, single-walled carbon nanotubes (SWNT) have been figured out theoretically to change in electronic physicality from a metallic nature to a semiconductive nature, depending upon the way of winding of its helix, i.e. so-called chirality, and it is remarked as a hopeful electronic material of the next generation. Actually, there are various proposals of its applications to nanoelectronics materials, field electron emission emitters, highly directional radiation sources, soft X-ray sources, one-dimensional conduction materials, high-heat conduction materials, hydrogen storage materials, and others. Additionally, binding functional groups on surfaces, metal coating or containment of foreign substances will further expand the range of application of carbon nanotubes.
As a method of manufacturing single-walled carbon nanotubes and other carbonaceous materials, it has been proposed to compound a large mass of such materials by a so-called arc discharge process making use of arc discharge from a carbon rod as an electrode. This method produces carbonaceous materials by generating arc discharge in an arc discharge portion composed of juxtaposed anode and cathode.
An example of manufacturing apparatus of carbonaceous materials relying on an arc discharge process is shown in FIG.
1
. The manufacturing apparatus
101
includes a cylindrical reaction tube
111
in which an anode
113
and a cathode
114
are juxtaposed via a light distance. The anode
113
is electrically connected to a positive-pole current inlet terminal
142
, and the cathode
114
is electrically connected to a negative-pole current inlet terminal
141
. These two current inlet terminals
141
,
142
are electrically connected to a current supply portion
112
located outside the reaction tube
111
such that a voltage can be applied to the anode
113
and the cathode
114
. The arc discharge portion is defined by distal ends where the anode
113
and the cathode
114
are opposed. The arc discharge portion is located approximately in the center of the reaction tube
111
in its axial direction, and an electric furnace
124
for heating the arc discharge portion is provided outside the portion of the reaction tube
111
aligned with the art discharge portion.
The anode
113
is a carbon electrode made of carbon added with a metal functioning as a catalyst such as iron, cobalt, nickel, lanthanum, or the like. The catalyst is used upon manufacturing carbonaceous materials such as single-walled carbon nanotubes by arc discharge. The cathode
114
is a pure carbon electrode containing no catalyst.
Caps
111
C,
111
D covering end portions of the reaction tube
111
are provided at opposite ends of the reaction tube
111
to be able to seal the interior of the reaction tube
111
from the atmospheric air. The cap
111
C have a through hole
111
a
that penetrates it in the axial direction and permits communication between the interior and the exterior of the reaction tube
111
. Connected to the through hole
111
a
is an inactive gas injector
143
via a hose
117
. The inactive gas injector
143
can supply inactive gas such as He or Ar into the reaction tube
111
. A flowmeter
118
is interposed in the hose
117
such that the velocity of the inactive gas injected into the reaction tube
111
can be changed.
The cap
111
D has a through hole
111
b
penetrating it in the radial direction from its circumferential surface to permit communication between the interior and the exterior of the reaction tube
111
. A pump
121
is connected to this through hole
111
b
via a hose
119
. The pump
121
can discharge gas inside the reaction tube
111
to the exterior thereof by making use of a reduced pressure. A flowmeter
120
is interposed in the hose
119
such that the velocity of inactive gas, or the like, discharged from inside the reaction tube
111
.
The cap
111
D has another through hole
111
c
that penetrates it in the axial direction, and receives a double tube
122
penetrating and extending beyond it. Therefore, part of the double tube
122
resides in the reaction tube
111
. On one of opposite end portions of the double tube
122
residing in the double tube
122
, a capturer
123
for capturing carbonaceous materials produced in the arc discharge portion is mounted. The capturer
123
defined therein a space communicating with a space defined by the inner periphery of an outer tube and the outer periphery of an inner tube of the double tube
122
, and a space communicating with a space defined by the inner periphery of the inner tube of the double tube
122
. These two spaces are communicating with each other. In this configuration, when cooled water is supplied to the space defined by the inner periphery of the inner tube from one end of the double tube
122
opposite from the said end having the capturer
123
, the cooled water passes through the space defined by the inner periphery of the inner tube, then reaches the inside of the capturer
123
, cools the capturer
123
there, thereafter flows into the space defined by the inner periphery of the outer tube of the double tube
122
and the outer periphery of the inner tube thereof, and exits from the other end of the double tube
122
.
Next explained is a method of manufacturing carbonaceous materials like single-walled carbon nanotubes. The anode
113
is made by crushing carbon to powder, then preparing a mixture of the powder carbon and powder of a catalyst such as iron, nickel, cobalt or lanthanum, shaping the mixture into the form of the anode
113
, and sintering and/or machining it. The cathode
114
is made by directly shaping carbon into the form of the cathode
114
. After that, the anode
113
and the cathode
114
are set in a carbonaceous material manufacturing apparatus
101
, and the interior of the reaction tube
111
is once evacuated to a vacuum. After that, under the condition where an inactive gas injector
143
supplies inactive gas into the reaction tube and the pump
121
discharges the inactive gas from the reaction tube
111
, that is, under the condition where a gas flow is made in the arc discharge portion, arc discharge is executed to produce a carbonaceous material such as single-walled carbon nanotubes from the carbon composing the anode
113
by catalysis of the catalyst. More specifically, in the arc discharge portion, metal and carbon simultaneously vaporize from the anode
113
, and the vaporizing carbon appears as soot. The soot obtained contains graphite, amorphous carbon, catalytic metal, oxides of the catalytic metal, and others in addition to single-walled nanotubes. The soot containing carbonaceous materials such as single-walled carbon nanotubes produced in the arc reaction portion is transported to the capturer
123
located downstream by the flow of the supplied inactive gas.
In order to increase the recovery percentage of single-walled carbon nanotubes and other carbonaceous materials produced by the above-explained arc discharge method, various techniques have been disclosed heretofore.
According to Japanese Patent Laid-Open Publications Nos. hei 6-157016 and hei 6-280116, it is appreciated that the recovery percentage of single-walled carbon nanotubes by the arc discharge method largely depends upon the partial pressure of gas in the reaction tube where the single-walled carbon nanotubes are produced. Japanese Patent Laid-Open Publication No. hei 6-280116 discloses that the r
Hirano Yoshiyuki
Kajiura Hisashi
Miyakoshi Mitsuaki
Tsutsui Shigemitsu
Bell Boyd & Lloyd LLC
Hoang Tu Ba
Sony Corporation
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