U.S. patent application number 12/223168 was filed with the patent office on 2009-08-06 for carbon nanohorn carried material and process for producing carbon nanotube.
Invention is credited to Sumio Iijima, Jin Miyawaki, Masako Yudasaka.
Application Number | 20090196993 12/223168 |
Document ID | / |
Family ID | 38327402 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090196993 |
Kind Code |
A1 |
Iijima; Sumio ; et
al. |
August 6, 2009 |
Carbon Nanohorn Carried Material And Process For Producing Carbon
Nanotube
Abstract
A carbon nanohorn carried material for producing a carbon
nanotube by a chemical vapor deposition (CVD) method, including a
catalytic metal or a compound thereof contained inside carbon
nanohorns or supported on exterior walls of the carbon nanohorns is
provided. A carbon nanotube is produced by a CVD reaction using the
carbon nanohorn carried material. A novel technical means for
producing a carbon nanotube which does not use any noncarbon type
carrier, can easily collect and purify the carbon nanotube and can
control the length of the carbon nanotube can be provided.
Inventors: |
Iijima; Sumio; (Minato-ku,
JP) ; Yudasaka; Masako; (Minato-ku, JP) ;
Miyawaki; Jin; (Ibaraki, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
38327402 |
Appl. No.: |
12/223168 |
Filed: |
January 30, 2007 |
PCT Filed: |
January 30, 2007 |
PCT NO: |
PCT/JP2007/051438 |
371 Date: |
November 14, 2008 |
Current U.S.
Class: |
427/255.28 ;
502/152; 502/182; 502/183; 502/185; 977/742 |
Current CPC
Class: |
B01J 23/42 20130101;
C01B 2202/06 20130101; C01P 2004/13 20130101; B01J 23/74 20130101;
C01B 32/162 20170801; C01B 2202/04 20130101; B01J 23/24 20130101;
Y10T 428/2991 20150115; B82Y 40/00 20130101; C01B 2202/02 20130101;
B01J 37/0207 20130101; B01J 21/185 20130101; Y10S 977/773 20130101;
B82Y 30/00 20130101; B01J 23/745 20130101 |
Class at
Publication: |
427/255.28 ;
502/182; 502/183; 502/185; 502/152; 977/742 |
International
Class: |
C23C 16/00 20060101
C23C016/00; B01J 21/18 20060101 B01J021/18; B01J 23/02 20060101
B01J023/02; B01J 23/42 20060101 B01J023/42; B01J 23/74 20060101
B01J023/74; B01J 31/12 20060101 B01J031/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2006 |
JP |
2006-023800 |
Claims
1. A carbon nanohorn carried material used for producing a carbon
nanotube by a chemical vapor deposition method, wherein a catalytic
metal for producing a carbon nanotube or a compound thereof is
contained inside carbon nanohorns or supported on exterior walls of
the carbon nanohorns.
2. The carbon nanohorn carried material as recited in claim 1,
wherein the catalytic metal or the compound thereof is one or two
or more members selected from the group consisting of Fe, Ni, Co,
Pt, Mo, W, Mg, alloys of these metals and compounds of these
metals.
3. The carbon nanohorn carried material as recited in claim 2,
wherein the compound is in the form of an inorganic acid salt, an
organic acid salt, a complex or an organometallic compound.
4. The carbon nanohorn carried material as recited in claim 1,
wherein the carbon nanohorns have openings at least either side
parts or top parts thereof.
5. A carbon nanohorn carried material used for producing a carbon
nanotube by a chemical vapor deposition method, wherein a catalytic
metal for producing a carbon nanotube or a compound thereof and a
carbon source compound for producing a carbon nanotube are
contained inside carbon nanohorns or supported on exterior walls of
the carbon nanohorns.
6. The carbon nanohorn carried material as recited in claim 5,
wherein the catalytic metal or the compound thereof is one or two
or more members selected from the group consisting of Fe, Ni, Co,
Pt, Mo, W, Mg, alloys of these metals and compounds of these
metals.
7. The carbon nanohorn carried material as recited in claim 6,
wherein the compound is in the form of an inorganic acid salt, an
organic acid salt, a complex or an organometallic compound.
8. The carbon nanohorn carried material as recited in claim 5,
wherein the carbon source compound is one or two or more members
selected from the group consisting of fullerenes, phthalocyanines
and carbon compounds with low vapor pressure.
9. The carbon nanohorn carried material as recited in claim 5,
wherein the carbon nanohorns have openings at least either side
parts or top parts thereof.
10. A process for producing a carbon nanotube, comprising
subjecting a carbon source compound to a chemical vapor deposition
reaction at a temperature in a range of 500 to 1,200.degree. C. in
an inert gas atmosphere or in a mixed gas atmosphere containing an
inert gas and hydrogen in the presence of a carbon nanohorn carried
material according to claim 1, so that the carbon nanotube is
produced.
11. A process for producing a carbon nanotube, comprising
conducting a chemical vapor deposition reaction at a temperature in
a range of 500 to 1,200.degree. C. in an inert gas atmosphere or in
a mixed gas atmosphere containing an inert gas and hydrogen in the
presence of a carbon nanohorn carried material according to claim
5, so that the carbon nanotube is produced.
12. The process for producing a carbon nanotube as recited in claim
11, wherein the chemical vapor deposition reaction is performed in
the coexistence of a carbon source compound.
13. The process for producing a carbon nanotube as recited in claim
11, wherein a form of the carbon source compound contained inside
the carbon nanohorns or supported on exterior walls of the carbon
nanohorns is varied to control the length of the carbon nanotube
produced.
14. The process for producing a carbon nanotube as recited in claim
13, wherein the form of the carbon source compound is a solid.
15. The process for producing a carbon nanotube as recited in claim
10, wherein a kind of the catalytic metal or the compound thereof
is varied to control the number of layers of the carbon nanotube
produced.
Description
TECHNICAL FIELD
[0001] The present invention relates to catalyst-carrying carbon
nanohorns (NHs) capable of realizing a novel process for producing
carbon nanotubes and to a process for producing a carbon nanohorn
(NT) using the catalyst-carrying carbon nanohorns.
BACKGROUND ART
[0002] For the production of a carbon nanotube (NT) by a chemical
vapor deposition (CVD) method, Si, SiO.sub.2, MgO, Al.sub.2O.sub.3
or the like has been hitherto used as a carrier of a catalytic
metal such as Fe, Ni, Co, Pt, W and Mo. As a carbon source, an
organic gas, such as methane, ethane, acetylene, benzene or an
alcohol, or a CO gas is used. Such a carbon source is heated at a
high temperature in the presence of the above catalyst to produce a
single walled carbon nanotube (SWNT) by a CVD reaction.
[0003] With the above conventional method, however, it is necessary
to remove the catalyst carrier after the formation of the carbon
nanotubes because the carrier is an inorganic substance other than
carbon (see, for example, Patent Documents 1 and 2). Thus, a burden
is imposed by the recovery and refinement of carbon nanotubes,
which poses a serial problem in practical application.
[0004] In conventional CVD methods, there is also a problem because
it is difficult to control the length of carbon nanotubes.
[0005] Patent Document 1: Published Japanese Translation of PCT
International Application No. 2005-532976
[0006] Patent Document 1: Unexamined Japanese Patent Application
Publication No. 2005-126323
SUMMARY OF THE INVENTION
[0007] With the foregoing background in view, it is an object of
the present invention to solve the above described problems of the
conventional technology and to provide a novel technical means for
producing a carbon nanotube which does not use any noncarbon type
carrier, can easily collect and purify the carbon nanotube and can
control the length of the carbon nanotube.
[0008] As means for accomplishing the above object, the present
invention has the following features.
[0009] First aspect: A carbon nanohorn carried material used for
producing a carbon nanotube by a chemical vapor deposition method,
characterized in that a catalytic metal for producing a carbon
nanotube or a compound thereof is contained inside carbon nanohorns
or supported on exterior walls of the carbon nanohorns.
[0010] Second aspect: The carbon nanohorn carried material as
recited in the first aspect, wherein the catalytic metal or the
compound thereof is one or two or more members selected from the
group consisting of Fe, Ni, Co, Pt, Mo, W, Mg, alloys of these
metals and compounds of these metals.
[0011] Third aspect: The carbon nanohorn carried material as
recited in the second aspect, wherein the compound is in the form
of an inorganic acid salt, an organic acid salt, a complex or an
organometallic compound.
[0012] Fourth aspect: The carbon nanohorn carried material as
recited in any one of the first to third aspects, wherein the
carbon nanohorns have openings at least either side parts or top
parts thereof.
[0013] Fifth aspect: A carbon nanohorn carried material used for
producing a carbon nanotube by a chemical vapor deposition method,
characterized in that a catalytic metal for producing a carbon
nanotube or a compound thereof and a carbon source compound for
producing a carbon nanotube are contained inside carbon nanohorns
or supported on exterior walls of the carbon nanohorns.
[0014] Sixth aspect: The carbon nanohorn carried material as
recited in the fifth aspect, wherein the catalytic metal or the
compound thereof is one or two or more members selected from the
group consisting of Fe, Ni, Co, Pt, Mo, W, Mg, alloys of these
metals and compounds of these metals.
[0015] Seventh aspect: The carbon nanohorn carried material as
recited in the sixth aspect, wherein the compound is in the form of
an inorganic acid salt, an organic acid salt, a complex or an
organometallic compound.
[0016] Eighth aspect: The carbon nanohorn carried material as
recited in any one of the fifth to seventh aspects, wherein the
carbon source compound is one or two or more of members selected
from the group consisting of fullerenes, phthalocyanines and carbon
compounds with a low vapor pressure.
[0017] Ninth aspect: The carbon nanohorn carried material as
recited in any one of the fifth to eighth aspects, wherein the
carbon nanohorns have openings at side parts or top parts
thereof.
[0018] Tenth aspect: A process for producing a carbon nanotube,
comprising subjecting a carbon source compound to a chemical vapor
deposition reaction at a temperature in a range of 500 to
1,200.degree. C. in an inert gas atmosphere or in a mixed gas
atmosphere containing an inert gas and hydrogen in the presence of
a carbon nanohorn carried material according to any one of the
first to fourth aspects, so that the carbon nanotube is
produced.
[0019] Eleventh aspect: A process for producing a carbon nanotube,
comprising conducting a chemical vapor deposition reaction at a
temperature in a range of 500 to 1,200.degree. C. in an inert gas
atmosphere or in a mixed gas atmosphere containing an inert gas and
hydrogen in the presence of a carbon nanohorn carried material
according to any one of the fifth to ninth aspects, so that the
carbon nanotube is produced.
[0020] Twelfth aspect: The process for producing a carbon nanotube
as recited in the eleventh aspect, wherein the chemical vapor
deposition reaction is performed in the coexistence of a carbon
source compound.
[0021] Thirteenth aspect: The process for producing a carbon
nanotube as recited in eleventh or twelfth aspect, wherein a form
of the carbon source compound contained inside the carbon nanohorns
or supported on exterior walls of the carbon nanohorns is varied to
control the length of the carbon nanotube produced.
Fourteenth aspect: The process for producing a carbon nanotube as
recited in the thirteenth aspect, wherein the form of the carbon
source compound is a solid.
[0022] Fifteenth aspect: The process for producing a carbon
nanotube as recited in any one of the tenth to fourteenth aspects,
wherein a kind of the catalytic metal or the compound thereof is
varied to control the number of layers of the carbon nanotube
produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a TEM photograph (1 cm: 20 nm) of NHox containing
therein iron acetate.
[0024] FIG. 2 is a TEM photograph (1 cm: 300 nm in the left-side
drawing; 1 cm: 25 nm in the right-side drawing) of SWNT of Example
1.
[0025] FIG. 3 is Raman spectra of SWNT of Example 1.
[0026] FIG. 4 is a TEM photograph (3 cm: 50 nm in the left-side
drawing; 3 cm: 20 nm in the right-side drawing) of MWNT of Example
2.
[0027] FIG. 5 is a TEM photograph (1 cm: 35 nm in the left-side
drawing; 3 cm: 2 nm in the right-side drawing) of DWNT of Example
3.
[0028] FIG. 6 is a TEM photograph (1 cm: 10 nm in the left-side
drawing; 3 cm: 20 nm in the right-side drawing) of a product of
Example 4.
[0029] FIG. 7 is Raman spectra of the products of Example 4.
BEST MODE FOR CARRYING OUT THE INVENTION
[0030] The features of the present invention are as described
above. The embodiments of the invention will be next described.
[0031] The "carbon nanohorns" in the present invention are
generally intended to include a "dahlia-like" aggregate of a
plurality of horn-shaped bodies with their closed portions oriented
outward, and an assembly of a plural groups each composed of a
plurality of horn-shaped bodies.
[0032] The carbon nanohorns as defined above will be hereinafter
called "NHs" (as a plural) for brevity. Such NHs may have openings
at their side parts or top parts. Namely, each of one or more
horn-shaped bodies from which NHs are formed may be provided with
an opening.
[0033] Carbon nanohorns (NHs) to be used in the present invention
may be obtained by methods developed by the present inventors or by
other various methods. Methods developed by the present inventors
in which oxygen is acted to NHs or other methods may be suitably
used for forming the above-described openings.
[0034] Thus, carbon nanohorns (NHs) to be used in the present
invention may be those which are obtained by the conventional
methods or by various methods and which may have or may not have
openings. Further, the carbon nanohorns (NHs) may contain a
permissive range of functional group or groups bonded thereto.
[0035] A catalytic metal or a compound of the catalytic metal for
producing a carbon nanotube (NT) may be carried on the carbon
nanohorns (Nas) by adhesion thereof on exterior wall surfaces of
each of the horn-shaped bodies constituting the carbon nanohorns
(NHs), by inclusion thereof into the horn-shaped bodies through the
openings, or by insertion thereof into interstices between the
horn-shaped bodies.
[0036] As the catalytic metal, there may be used various kinds of
metals such as those conventional metals that have been hitherto
known to have capabilities of producing carbon nanotubes. Specific
examples of the catalytic metal include Fe, Ni, Co, Pt, Mo, W, Mg
and alloys thereof. The compound of the catalytic metal may be in
any known form such as an inorganic acid salt, an organic acid
salt, a complex or an organometallic compound.
[0037] The catalytic metal or compound thereof may be supported on
the carbon nanohorns by various methods such as a vapor phase
deposition and liquid phase adhesion or precipitation.
[0038] When a carbon source compound is carried on the carbon
nanohorns together with the catalytic metal or compound thereof,
the above-described method may be used similarly. As the carbon
source compound, a carbonic compound having a relatively low vapor
pressure, such as a fullerene, a phthalocyanine or a polycyclic
hydrocarbon compound, may be suitably used.
[0039] The amount of the catalytic metal or compound thereof and
the amount of the carbon source compound carried on the carbon
nanohorns (NHs) may be determined in consideration of the reaction
conditions of the CVD reaction and of the yield, length and shape
of carbon nanotubes (NT) to be produced.
[0040] In carrying out the chemical vapor deposition (CVD method),
the carbon nanohorn carried material supporting thereon the
catalytic metal or compound thereof and, if desired, the carbon
source compound may be used in the form of a layer scattered over a
substrate or in the form of a bed fluidized by or moved through a
gas.
[0041] When the carbon nanohorn carried material which does not
carry the carbon source compound is used, the CVD reaction is
carried out by feeding, a hydrocarbon compound such as methane,
ethane, ethylene, acetylene or benzene, an alcohol such as methanol
or ethanol, or CO, as the carbon source compound, to a reaction
system containing the carbon nanohorn carried material. The
reaction system is heated to a temperature of 500 to 1,200.degree.
C. in the atmosphere of an inert gas such as argon or nitrogen or
of a mixed gas of the inert gas with hydrogen. When the carbon
nanohorn carried material which carries the carbon source such as
fullerenes is used, the reaction is performed without introducing
the above-described hydrocarbon compound, alcohol, CO or the
like.
[0042] In performing the CVD reaction, the amounts of the reactants
may be properly selected in consideration of the conditions similar
to those described above.
[0043] The reaction of the present invention can produce carbon
nanotubes having a single walled or a multi-walled (two or more
walls) structure depending upon the kind of the catalytic metal or
compound thereof. This also applies to the diameter of the carbon
nanotubes produced.
[0044] When the carbon nanohorn carried material which carries the
carbon source compound such as fullerenes is used, carbon nanotubes
having shorter lengths can be produced by using carbon nanohorn
carried material with a shorter length.
[0045] Description will be next made to examples for describing the
invention in more detail. But these examples are not restrictive of
the invention in any way.
Example 1
[0046] Graphite was subjected to CO.sub.2 laser ablation at room
temperature in a stream of Ar (760 Torr) to prepare NHs in
accordance with the method described in Chem. Phys. Lett., 1999,
309, 165. The obtained NHs were treated at 570 to 580.degree. C.
for 10 minutes in a stream of O.sub.2 to obtain carbon nanohorns
(NHox) having openings in accordance with the method described in
Mol. Pharm., 2005, 2, 475.
[0047] Next, 50 mg of iron acetate (manufactured by Sigma-Aldrich
Inc.; purity: more than 99.995%) and 50 mg of the hole-opened
nanohorns (NHox) were mixed with each other in 20 cm.sup.3 ethanol.
The mixture was stirred at room temperature for 24 hours, filtered,
washed with ethanol and dried to obtain iron acetate-carrying NHox
having an iron content of 2 atomic %. The TEM photograph of the
iron acetate-carrying NHox is shown in FIG. 1. The particles seen
in NHox are those of the iron acetate.
[0048] The obtained iron acetate-carrying NHox was placed in a boat
made of alumina and heated to 800.degree. C. in a stream of a mixed
gas of Ar and H.sub.2 (Ar: 300 cm.sup.3/min, H.sub.2: 100
cm.sup.3/min). After a temperature of 800.degree. C. had been
reached, the Ar and H.sub.2 mixed gas stream was bubbled through
ethanol and the resulting stream of a mixed gas containing Ar,
H.sub.2 and ethanol was fed to the reaction system in place of the
Ar and H.sub.2 mixed gas stream. The CVD was thus performed for 15
minutes. After the CVD, the ethanol bubbling was stopped and the
reaction system was cooled to room temperature in the Ar and
H.sub.2 mixed gas stream to obtain single walled carbon nanotubes
(SWNT). The TEM photograph of SWNT is shown in FIG. 2 and the Raman
spectrum thereof is shown in FIG. 3.
[0049] In FIG. 2, SWNT, obtained by CVD at 800.degree. C. using
carbon nanohorns containing therein iron acetate, is seen in a
fibrous form. The spherical substance is the hole-opened nanohorn.
In the right-side enlarged view, the iron oxide particles attached
to the hole-opened nanohorn are seen as black particles. The iron
oxide was formed by alteration of iron acetate during the course of
CVD.
[0050] FIG. 3 shows the Raman spectra of SWNT obtained by CVD at
various temperatures using the nanohorns containing therein iron
acetate. The G and D bands inherent to NHox are seen at 1600
cm.sup.-1 and 1,350 cm.sup.-1, respectively. In the spectra of the
samples after CVD, there are narrow G bands and shoulders in their
low wave number sides, which are characteristic to SWNT. In
addition, peaks are seen near 200 cm.sup.-1. Such peaks are
attributed to breathing mode of SWNT. The fact that the peak
position of the breathing mode varies with the CVD temperature
indicates that the diameter distribution of SWNT varies with the
CVD temperature.
Example 2
[0051] The experiment of Example 1 was conducted in the same manner
as described except that nickel acetate was used in place of the
iron acetate used in Example 1. The TEM photograph of the obtained
multi-walled carbon nanotube (MWNT) is shown in FIG. 4. The TEM
photograph of MWNT, obtained by CVD at 800.degree. C. using carbon
nanohorns containing therein nickel acetate, is seen in the
observed image. In the right-side enlarged view, nickel oxide
particles attached to MWNT are seen as black particles. The nickel
oxide was formed by alteration of nickel acetate during the course
of CVD.
Example 3
[0052] The experiment of Example 1 was conducted in the same manner
as described except that a mixture of cobalt acetate and molybdenum
acetate (weight ratio: 1.1) was used in place of the iron acetate.
The TEM photograph of the obtained double-walled carbon nanotube
(DWNT) is shown in FIG. 5.
Example 4
[0053] Prepared was NHox containing therein C.sub.60
(C.sub.60@NHox) (Preparation method: C.sub.60 is dissolved in
toluene, to which NHox is mixed. The toluene is then evaporated in
a nitrogen stream). C.sub.60@NHox was mixed with an ethanol
solution of iron acetate. Using this mixture, iron acetate-carrying
C.sub.60@NHox was prepared in a manner similar to that of Example
1. The TEM photograph of C.sub.60@NHox and iron acetate-carrying
C.sub.60@NHox is shown in the left side in FIG. 6. e iron
acetate-carrying C.sub.60@NHox was heated at 1,000.degree. C. for
15 minutes in a stream of Ar (300 cm.sup.3/min) to produce SWNT
(right side in FIG. 6). The Raman spectrum of the obtained SWNT is
shown in FIG. 7. The left-side drawing of FIG. 6 shows the TEM
photograph of NHox containing therein iron acetate and C.sub.60.
Seen in the circle is C.sub.60. The grayish particles in NHox are
iron acetate particles. The right-side drawing of FIG. 6 shows the
TEM photograph of the product after the heat treatment at
1,000.degree. C. The produced SWNT having a diameter of 1 nm is
seen.
[0054] FIG. 7 shows a Raman spectrum of the product obtained by
heating the NHox containing therein iron acetate and C.sub.60 at
1,000.degree. C. (upper spectrum) and a Raman spectrum of
C.sub.60@NHox (lower spectrum). In the lower spectrum, peaks
attributed to the G and D bands and a peak (1,460 cm.sup.-1)
inherent to the C.sub.60 contained inside NHox are seen. In the
upper spectrum, the G band at near 1600 cm.sup.-1 has a greater
intensity than that of the D band at 1,350 cm.sup.-1. This suggests
that SWNT is produced. Because the amount of the produced SWNT is
small, no breathing mode was observed.
INDUSTRIAL APPLICABILITY
[0055] As will be appreciated from the foregoing description, since
the nanohorns used as a carrier in the present invention is made of
100% carbon, it is easy to remove the carrier. Therefore, only a
small burden is placed on the recovery and refinement of carbon
nanotubes so that the production efficiency can be improved and
process costs can be reduced.
[0056] Additionally, in the method of the present invention, when a
solid carbon source (such as fullerenes and organic materials
having a low vapor pressure) is included inside nanohorns or
adhered on outer walls of nanohorns, it is possible to prepare
nanotubes having a short length because the amount of the carbon
source is small. The thus obtained short nanotubes may be used as
an electron emitting element such as FED.
* * * * *