U.S. patent application number 10/931435 was filed with the patent office on 2005-02-10 for carbonaceous nanotube, nanotube aggregate, method for manufacturing a carbonaceous nanotube.
This patent application is currently assigned to Nikkiso Co., Ltd.. Invention is credited to Ohsaki, Takashi.
Application Number | 20050031527 10/931435 |
Document ID | / |
Family ID | 32923148 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050031527 |
Kind Code |
A1 |
Ohsaki, Takashi |
February 10, 2005 |
Carbonaceous nanotube, nanotube aggregate, method for manufacturing
a carbonaceous nanotube
Abstract
A carbonaceous nanotube has a hollow part with an inner diameter
of, at most, 5 nm, and a thickness part of, at most, 10 nm. The
thickness part is formed of carbon atoms and hydrogen atoms,
optionally containing at least one transition metal atom. Such a
carbonaceous nanotube has excellent conductivity and excellent
wettability.
Inventors: |
Ohsaki, Takashi; (Shizuoka,
JP) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Nikkiso Co., Ltd.
Tokyo
JP
|
Family ID: |
32923148 |
Appl. No.: |
10/931435 |
Filed: |
September 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10931435 |
Sep 1, 2004 |
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09615104 |
Jul 13, 2000 |
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6790426 |
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Current U.S.
Class: |
423/447.3 |
Current CPC
Class: |
B82Y 30/00 20130101;
C01B 2202/22 20130101; D01F 9/127 20130101; C01B 2202/36 20130101;
Y10S 977/742 20130101; C01B 32/16 20170801; B82Y 40/00 20130101;
C01B 32/162 20170801 |
Class at
Publication: |
423/447.3 |
International
Class: |
D01F 009/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 1999 |
JP |
11-198731 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10: A method for manufacturing a carbonaceous nanotube, comprising:
mixing a transition metal compound, containing at least one
transition metal atom, a sulfur compound, containing at least one
sulfur atom, an organic compound containing a hydrocarbon, and a
carrier gas, to obtain a raw material mixture; supplying said raw
material mixture to a reaction region maintained at a temperature
of about 900.about.1,300.degree. C. inside a reaction tube;
adjusting said raw material mixture supply so that the
concentration of said transition metal atom in said raw material
mixture is in the range from about 0.025.about.0.5 mol %, and the
concentration of said hydrocarbon in said raw material mixture is
in the range represented by
(273/(T-1000)).sup.4.about.10((73/T-1000)) mol %, wherein T
represents the absolute temperature (K) of the reaction region.
11: The method for manufacturing a carbonaceous nanotube according
to claim 10, wherein said transition metal compound is
ferrocene.
12: The method for manufacturing a carbonaceous nanotube according
to claim 10, wherein said sulfur compound is thiophene.
Description
BACKGROUND TO THE INVENTION
[0001] The present invention relates to a carbonaceous nanotube,
nonotube aggregate, and a method for manufacturing a carbonaceous
nanotube. Described in further detail, the present invention
relates to a carbonaceous nanotube, nanotube aggregate, and
manufacture method for a carbonaceous nanotube, having excellent
conductivity and excellent wettability.
[0002] A conventional method, known as the fluidized vapor method,
is recognized for the manufacture of vapor grown carbon fiber. In
this method, at least one type selected from the group consisting
of organic metal compounds and inorganic metal compounds, and an
organic compound, and a carrier gas are transported to a reaction
region heated to around 1000.degree. C.
[0003] In the fluidized vapor method, very small metal particles
are generated in the vapor phase. The organic compounds on the
metal particles suspended in the vapor phase decompose, allowing
carbon to be deposited on these metal particles. By the growth in
one direction of the deposited carbon, a vapor grown carbon fiber
is obtained.
[0004] According to the conventional fluidized vapor method, a
vapor grown carbon fiber having a constant aspect ratio with an
outer perimeter diameter of 0.05 .mu.m.about.10 .mu.m and a length
of 0.2 .mu.m.about.2000 .mu.m is easily manufactured industrially
(M. Hatano, T. Ohsaki, K. Arakawa; 30th National SAMPE Symposium
preprint 1467 (1985), Japanese Examined Patent Publication Number
62-49363).
[0005] According to the fluidized vapor method, a highly
crystalline carbonaceous fiber with a diameter of 0.05.about.2
.mu.m (Japanese Examined Patent Publication Number 3-61768), highly
crystalline carbonaceous fiber with a diameter of 0.01.about.0.5
.mu.m (Japanese Examined Patent Publication Number 5-36521), a
vapor grown carbon fiber with a diameter of 3.5.about.70 nm
(Japanese Examined Patent Publication Number 3-64606, Japanese
Examined Patent Publication Number 3-77288), and the like, can be
manufactured.
[0006] Another conventional method for the manufacture of graphite
nanotubes is through arc discharge between graphite electrodes.
[0007] According to this conventional method, a plurality of
graphite layers are layered from the inner perimeter surface to the
outer perimeter surface. Its outer perimeter diameter is 10 nm or
less, and its inner perimeter diameter is a few nanometers. A
graphite nanotube which does not contain hydrogen atoms is
obtained.
[0008] However, with the arc discharge method, there are several
problems. For example, (a) the manufacturing method is complex
because the reaction must be conducted under a vacuum or reduced
pressure, and it is difficult to supply the graphite which is
consumed by the arc discharge between the electrodes; (b) because
the manufactured graphite nanotube is formed with graphite that
does not contain hydrogen and because the manufactured graphite
nanotube has few fullerene structure active sites, the chemical
reactivity of the graphite nanotube is poor, (c) with the composite
material obtained by combining the graphite nanotube and a resin,
the mechanical strength of the composite material can not be
improved because of poor wettability of the graphite nanotube with
respect to the resin.
[0009] With the above highly crystalline carbon fiber (Japanese
Examined Patent Publication Number 5-36521), there are also
problems. The chemical reactivity is poor because the highly
crystalline carbon fiber is a graphite with high crystallinity. A
composite material obtained by combining the highly crystalline
carbon fiber and a resin has poor wettability due to the highly
crystalline nature carbon fiber. This results in a composite with
poor mechanical strength which cannot be improved.
[0010] With the carbon fibers of the above highly crystalline
carbon fiber (Japanese Examined Patent Publication Number 5-36521)
and vapor grown carbon fibers with diameters of 3.5.about.70 nm
(Japanese Examined Patent Publication Number 3-64606, Japanese
Examined Patent Publication Number 3-77288), and the like, they are
made into a more complete graphite crystal through heat treatment
of the carbon fiber to make a graphitized carbon fiber. A further
chemical stabilization of its surface is also performed.
[0011] With the above graphitized carbon fibers, because the
graphite structure is well developed, the conductivity is very
high. At the same time, because the fiber surface is chemically
stable, the chemical reactivity is poor. For example, when a
conductive coating material, obtained by mixing this carbon fiber
and an adhesive, is coated on a coating target, there are problems
of peeling of the coating film, and the like, because the affinity
of the carbon fiber and the adhesive is low, or because the
affinity of the carbon fiber and the coating target is low.
OBJECT AND SUMMARY OF THE INVENTION
[0012] It is an object of the present invention is to provide a
carbonaceous nanotube, nanotube aggregate, and a method for
manufacturing a carbonaceous nanotube which solves the foregoing
problems.
[0013] It is a further object object of the present invention to
provide a carbonaceous nanotube, nanotube aggregate, and
manufacture method for carbonaceous nonotube which has excellent
conductivity and excellent wettability.
[0014] Briefly stated, the present invention provides a
carbonaceous nanotube having a hollow part with an inner diameter
of, at most, 5 nm, and a thickness part of, at most, 10 nm. The
thickness part is formed of carbon atoms and hydrogen atoms,
optionally containing at least one transition metal atom. Such a
carbonaceous nanotube has excellent conductivity and excellent
wettability.
[0015] According to an embodiment of the present invention, there
is provided a carbonaceous nanotube, comprising a hollow part
having an inner diameter of, at most, 5 nm, a thickness part having
a thickness of, at most, 10 nm, and the thickness part being a
carbon material comprising hydrogen atoms and carbon atoms.
[0016] According to another embodiment of the present invention,
there is provided a fiber aggregate, comprising carbonaceous
nanotubes having a hollow part having an inner diameter of, at
most, 5 nm, a thickness part, comprising carbon atoms and hydrogen
atoms, having a thickness of, at most, 10 nm, the carbonaceous
nanotubes being present at a ratio of at least 70 weight % with
respect to the fiber aggregate, hydrogen atoms at a content ratio
of 0.1.about.1 weight % with respect to the fiber aggregate, and
carbon atoms at a content ratio of at least 98.5 weight % with
respect to the fiber aggregate.
[0017] According to a further embodiment of the present invention,
there is provided a method for manufacturing a carbonaceous
nanotube, comprising mixing a transition metal compound, containing
at least one transition metal atom, a sulfur compound, containing
at least one sulfur atom, an organic compound containing a
hydrocarbon, and a carrier gas, to obtain a raw material mixture,
supplying the raw material mixture to a reaction region maintained
at a temperature of about 900.about.1,300.degree. C. inside a
reaction tube, adjusting the raw material mixture supply so that
the concentration of the transition metal atom in the raw material
mixture is in the range from about 0.025.about.0.5 mol %, and the
concentration of the hydrocarbon in the raw material mixture is in
the range represented by (273/(T-1000)).sup.4.about.10((73/T-1000))
mol %, wherein T represents the absolute temperature (K) of the
reaction region.
[0018] A first feature of the present invention, for solving the
above objects, is a carbonaceous nanotube, comprising a hollow
part, having an inner diameter of, at most, 5 nm. A thickness part,
the portion with the thickness from the outer perimeter surface to
the inner perimeter surface, which is, at most, 10 nm, and
preferably, at most, 5 nm. This thickness part is formed of carbon
material, comprising hydrogen atoms and carbon atoms.
[0019] A second feature of the present invention, for solving the
above objects, is a carbonaceous nanotube of the above feature,
comprising, in addition, transition metal atoms.
[0020] A third feature of the present invention, for solving the
above objects, is a fiber aggregate, comprising carbonaceous
nanotubes, described in the above first feature, at a ratio of at
least 70 weight % with respect to the whole. Hydrogen atoms are
present at a content ratio of 0.1.about.1 weight % with respect to
the whole. Carbon atoms are present at a content ratio of at least
98.5 weight % with respect to the whole. Transition metal atoms are
present at a content ratio of 0.005.about.1 weight % with respect
to the whole.
[0021] A fourth feature of the present invention, for solving the
above objects, is a method for manufacturing a carbonaceous
nanotube, wherein a raw material mixture is obtained by mixing a
transition metal compound which contains transition metal atoms, a
sulfur compound which contains sulfur atoms, an organic compound
which contains a hydrocarbon, and a carrier gas. The raw material
mixture is supplied to a reaction region which is maintained at a
temperature of 900.about.1,300.degree. C. inside a reaction tube.
The raw material mixture is supplied so that the concentration of
the transition metal atoms in the raw material mixture is in the
range of 0.025.about.0.5 mol % and the concentration of the
hydrocarbon in the raw material mixture is in the range represented
by (273/(T-1000)).sup.4.about.10(273/(T-1000)) mol %, wherein T
represents the absolute temperature (K) of the reaction region.
[0022] The above, and other objects, features, and advantages of
the present invention will become apparent from the following
description read in conjunction with the accompanying drawings, in
which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic diagram of a vertical vapor grown
carbon fiber manufacturing device used for the manufacturing method
of a carbonaceous nanotube according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Carbonaceous Nanotube
[0025] The carbonaceous nanotube of the present invention has a
hollow part with an inner diameter of, at most, 5 nm, a thickness
part of, at most, 10 nm, preferably a thickness part of, at most, 5
nm. The carbonaceous nanotube is formed from carbon material
containing hydrogen atoms and carbon atoms.
[0026] The size of the inner diameter in the above hollow part and
the thickness of the thickness part are determined, for example, by
observing an arbitrary 100 samples by a transmission microscope and
measuring the inner diameters and thicknesses. Therefore, the
hollow part inner diameters and the thicknesses reported herein
generally refer to an average values of a statistical sample.
[0027] The above carbonaceous nanotubes preferably have an average
outer perimeter diameter of about 3.about.12 nm, and an inner
perimeter diameter of about 2.about.5 nm.
[0028] When the thickness part is at the maximum of 10 nm, the
average inner perimeter diameter is 2.about.5 nm, and the average
outer perimeter diameter becomes 22 nm.about.25 nm. If the
thickness is any thicker, the mechanical properties, electrical
properties, and the like become inferior. Therefore, this thickness
approximates an upper thickness limit.
[0029] When the carbonaceous nanotube of the present invention is
observed by a transmission electron microscope, it is confirmed
that the carbon material which forms the carbonaceous nanotube is
an imperfect graphite layer, having a partially disordered layer
construction.
[0030] Furthermore, by elemental analysis of the carbonaceous
nanotube, it is confirmed that the carbon material that forms the
carbonaceous nanotube contains hydrogen atoms and carbon atoms.
[0031] With the present invention, by having the carbon material
which forms the carbonaceous nanotubes have a disordered layer
construction and by having it contain hydrogen atoms, the
disordered layer construction portions act as active sites,
increasing the chemical reactivity of the carbon material. For
example, with a composite material of this carbonaceous nanotube
and a resin, the wettability of the carbonaceous nanotube is
greatly increased.
[0032] With the present invention, the problem of the chemical
stability arising from the carbon fiber of the prior art being of
graphite material, or stated differently, the problems of the lack
of activity of the carbon fiber of the prior art, are solved.
Stated differently, because the carbonaceous nanotube of the
present invention has hydrogen atoms, there is a disturbance in the
hexagonal lattice surface construction of graphite. This
disturbance in the hexagonal lattice surface construction generates
a disordered layer construction part, generating chemical active
sites. In addition, despite having a disordered layer construction,
there is little decline in the mechanical construction.
[0033] The carbonaceous nanotube of the present invention can
further contain a transition metal atom. In most cases, this
transition metal atom is contained as particles in the tube ends.
However, the transition metal atom can also be contained as atoms
or clusters inside the carbon layer forming the tube. As with the
hydrogen atoms contained in the carbon material, the transition
metal atom has chemical activity. Furthermore, after the
carbonaceous tube is formed, if the tube is cut, the resulting
carbonaceous tube is a mixture of ones that have transition metal
particles in the tube end and those that do not have transition
metal particles in the tube end.
[0034] The carbon material which forms the carbonaceous nanotube of
the present invention, normally, has a content ratio of the
hydrogen atom about 0.1.about.1 weight %. The content ratio of
carbon atom is at least 98.5 weight %. The content ratio of the
transition metal atom is about 0.005.about.1 weight %. Preferably,
the content weight ratio of the hydrogen atom is 0.15.about.0.7
weight %, the content ratio of carbon is at least 99 weight %, and
the content ratio of the transition metal is 0.01.about.0.7 weight
%. Even more preferably, the content ratio of hydrogen is
0.2.about.0.5 weight %, the content ratio of carbon is at least 99
weight %, and the content ratio of the transition metal is
0.02.about.0.5 weight %.
[0035] When the hydrogen content ratio of the carbon material
forming the carbonaceous nanotube of the present invention is
0.1.about.1 weight %, a composite material of this carbonaceous
nanotube with a resin has improved wettability of the carbonaceous
nanotube with respect to the resin. This improvement in wettability
is thought to be based on the increased chemical active sites on
the surface of the carbonaceous nanotube resulting from the
presence of the hydrogen atoms.
[0036] The content ratio of hydrogen atoms, the content ratio of
carbon atoms, and the content ratio of the transition metal atoms
can be measured by known elemental analysis methods.
[0037] When the carbonaceous nanotube of the present invention is
heat treated by heating to more than 2000.degree. C., preferably
2500.about.3000.degree. C., it becomes a graphite nanotube.
[0038] Manufacturing Method of the Carbonaceous Nanotube
[0039] The manufacturing method for the carbonaceous nanotube of
the present invention, as long as it has the properties of the
carbonaceous nanotube of the present invention, is not limited to
any one particular method.
[0040] The manufacturing method of the present invention is
well-suited for manufacturing a carbonaceous nanotube which
contains hydrogen atoms, transition metal atoms, carbon atoms, and
which has a hollow part with an inner diameter of, at most, 5 nm
and a thickness part of, at most, 10 nm.
[0041] In the manufacturing method for the carbonaceous nanotube of
the present invention, a raw material mixture is obtained by mixing
a transition metal compound containing transition metal atoms, a
sulfur compound containing sulfur atoms, an organic compound
containing hydrocarbons, and a carrier gas. This raw material
mixture is supplied to a reaction region which is maintained at a
temperature of 900.about.1,300.degree. C. inside a reaction
tube.
[0042] Transition Metal Compound
[0043] The transition metal compound in the present invention
contains transition metal atoms. By decomposing the transition
metal compound inside the reaction tube, it generates transition
metal particles as catalysts.
[0044] The decomposition temperature of the transition metal
compound is normally 50.about.900.degree. C., preferably
70.about.800.degree. C., and more preferably 100.about.700.degree.
C.
[0045] The above transition metal compound is preferably supplied
as a gas to the reaction region which is maintained at a
temperature of 900.about.1300.degree. C. inside the reaction tube.
However, even if the above transition metal compound is supplied to
a zone, in this same reaction container, slightly upstream from the
reaction region and at a slightly lower temperature, for example
400.about.900.degree. C., essentially the same results are
achieved. The above transition metal compounds are ideally ones
that are vaporized completely before the temperature is raised to
the specified reaction temperature.
[0046] As the above transition metal atoms, examples include metals
in the periodic table group VIII. Suitable transition metal atoms
include iron, nickel, cobalt, and the like. Concrete examples of
other transition metal atoms include scandium, titanium, vanadium,
chromium, manganese, and the like. Among these, group VIII metals
of iron, cobalt, nickel, and the like are preferred.
[0047] As the transition metal compounds, examples include organic
transition metal compounds and inorganic transition metal
compounds.
[0048] As the above organic transition metal compounds, examples
include ferrocene, nickelocene, cobaltcene, iron carbonyl, iron
acetylacetonato, iron oleate, and the like. As the above inorganic
transition metal compound, examples include iron chloride and the
like. Among these, metallocenes of metals in the periodic table
group VIII, particularly ferrocene and nickelocene, are
preferred.
[0049] Sulfur Compounds
[0050] Sulfur compounds in the present invention contain sulfur
atoms and interact with the transition metal as a catalyst to
accelerate the generation of the carbonaceous nanotube.
[0051] Examples of the above sulfur compounds include organic
sulfur compounds, inorganic sulfur compounds and the like.
[0052] Examples of the above organic sulfur compounds include
sulfur-containing heterocyclic compounds, such as thianaphthene,
benzothiophene, thiophene, and the like. As the above inorganic
sulfur compounds, examples include hydrogen sulfide, and the
like.
[0053] Organic Compounds
[0054] The organic compound of the present invention can be used as
the carbon source for the carbon material which forms the
carbonaceous nanotube. Preferably, the organic compound contains a
hydrocarbon.
[0055] Concrete examples of the above organic compound include
aromatic hydrocarbons such as benzene, toluene, xylene,
naphthalene, anthracene, and the like; aliphatic hydrocarbons, such
as methane, ethane, propane, butane, heptane, hexane, ethylene,
propylene, acetylene, and the like; mixtures, such as gasoline, gas
oil, kerosene, oil fuel, anthracene oil, creosote oil, and the
like; oxygen containing organic substances such as alcohol, furan,
and the like; nitrogen containing organic substances such as amine,
pyridine, and the like. If there are free carbons contained in the
above organic compound, it is preferable to remove the free carbons
beforehand.
[0056] If the above organic compound is a liquid at room
temperature, for example at 20.degree. C., this is preferable from
the standpoint of ease of handling. Furthermore, if the above
organic compound is solid or a viscous liquid at room temperature,
this organic compound can be used dissolved in a low viscosity
solvent such as toluene, hexane, and the like. When using oxygen
containing organic substances or nitrogen containing substances for
the above organic compound, these are preferably used together with
hydrocarbons.
[0057] Carrier Gas
[0058] As the carrier gas of the present invention, hydrogen and
the like can be used favorably. Other than hydrogen, non-reactive
gases which do not affect the generative reaction for the
carbonaceous nanotube, reaction accelerating gases which accelerate
the generative reaction for the carbonaceous nanotube, and reaction
inhibiting gases which inhibit the carbonaceous nanotube generating
reaction can be added to the carrier gas.
[0059] As the above non-reactive gas, examples include noble gases
of helium, neon, argon, and the like, and nitrogen and the like. As
the reaction accelerating gas, examples include carbon monoxide,
carbon dioxide, methane, and the like. Examples of reaction
inhibiting gases include oxygen, air, and the like.
[0060] At least one type of gas selected from the group consisting
of non-reactive gases and reaction accelerating gases can be added
at 50 volume % or less to the carrier gas. Preferably, the gas is
added in the range of 5.about.40 volume %, and more preferably, in
the range of 10.about.30 volume %.
[0061] The above reaction inhibiting gas can be added to the
carrier gas at 30 volume % or less, preferably 20 volume % or less,
and more preferably in the range of 1.about.10 volume %.
[0062] Raw Material Mixture
[0063] The raw material mixture of the present invention can be
obtained by mixing the above transition metal compound, the above
sulfur compound, the above organic compound, and the above carrier
gas.
[0064] With the above raw material mixture, the above transition
metal compound is mixed into the raw material mixture so that the
concentration of the transition metal atoms in the raw material
mixture is in the range of 0.025.about.0.5 mol %. The above organic
compound is mixed in the raw material mixture so that the
concentration of the above hydrocarbon in the raw material mixture
is in the range of (273/(T-1000)).sup.4.about.10- (273/T-1000)) mol
%, wherein T represents absolute temperature (K) in the reaction
region.
[0065] In the present invention, by adjusting the concentration of
the transition metal atoms in the above material mixture within a
range of 0.025.about.0.5 mol %, a carbonaceous nanotube, in which a
hollow part with a specified inner diameter is formed along the
axial direction of the carbonaceous fiber, is effectively
manufactured.
[0066] If the concentration of the above transition metal atom
exceeds 0.5 mol %, the yield of the resulting carbonaceous nanotube
is decreased. If the concentration of the above transition metal
atom is less than 0.025 mol %, the carbonaceous nanotube is not
generated.
[0067] The inner diameter of the hollow part formed in this
carbonaceous nanotube, or stated another way, the inner perimeter
diameter of the carbonaceous nanotube, is related to the particle
diameter of the transition metal particles generated in the
reaction tube by the decomposition of the above transition metal
compound. It is thought that the larger the particle diameter of
the transition metal particles, the larger the inner diameter of
the hollow part. In other words, the larger the inner perimeter
diameter of the carbonaceous nanotube.
[0068] Judging from the results of observing the transition metal
particles contained at the ends of the generated carbonaceous
nanotubes, when the particle diameter of the above transition metal
particles generated inside the reaction tube has a particle
diameter of 1.5.about.6 nm, and preferably 2.about.5 nm,
carbonaceous nanotubes having an average outer perimeter diameter
of 3.about.12 nm and an average inner perimeter diameter of
2.about.5 nm are manufactured effectively. Therefore, by
appropriately selecting the above transition metal atom
concentration and the following hydrocarbon concentration and
temperature, transition metal having a suitable particle diameter
is generated. As a result, the carbonaceous tube of the present
invention can be obtained.
[0069] With the present invention, the above organic compound can
be mixed in the above raw material mixture so that the
concentration of the above hydrocarbon in the above raw material
mixture is in the range of
(273/(T-1000)).sup.4.about.10(273/T)-1000)) mol %, wherein T
represents the absolute temperature (K) of the reaction region.
[0070] The concentration of the above hydrocarbon in the raw
material mixture can be decided, for example, by the relationship
with the carbon ratio with respect to the above transition metal
atoms, the organic material concentration in the above raw material
mixture, and the temperature of the reaction region.
[0071] Furthermore, the concentration of the above hydrocarbon in
the raw material mixture can be decided while taking into
consideration the decomposition temperature, reaction temperature,
and the like, for each type of hydrocarbon that is used.
[0072] Particularly when the reaction temperature is in the range
of 1,000.about.1,200.degree. C., it is preferable to mix the above
organic compound in the above raw material mixture so that the
concentration of the above hydrocarbon in the raw material mixture
is in the range of
(273/(T-1000)).sup.3.about.10(273/(T-1000)).sup.2 mol %, wherein T
represents the absolute temperature (K) of the reaction region.
[0073] If the concentration of the above hydrocarbon in the above
raw material mixture exceeds 10(273/(T-1000)) mol %, the distance
between the inner perimeter surface to the outer perimeter surface
of the carbonaceous nanotube, or stated differently, the thickness
of the thickness part of the carbonaceous nanotube, can become
unnecessarily thick, or the hydrogen content ratio in the carbon
material which forms the carbonaceous nanotube can exceed 1%. If
the hydrogen atom content ratio in the above carbon material
exceeds 1%, there can be problems such as reduced
electroconductivity in the carbonaceous nanotube.
[0074] If the concentration of the above hydrocarbon in the above
raw material mixture is less than (273/(T-1000)).sup.4 mol %, the
generation of the carbonaceous nanotube can stop, or the
productivity can be reduced.
[0075] In the present invention, the concentration of sulfur atoms
in the above raw material mixture is preferably in the range of
1/4.about.5 times, particularly 1/2.about.3 times the concentration
of the above transition metal atom. The above sulfur compound is
mixed in the above raw material mixture so that the concentration
of the above sulfur atoms in the above raw material mixture is in
the range of 0.00625.about.2.5 mol %, and preferably in the range
of 0.0125.about.1.5 mol %.
[0076] If the concentration of the sulfur atoms in the above raw
material mixture is in the range of 0.00625.about.2.5 mol %, the
above transition metal particle can decompose the above organic
compound and can maintain its activity as the nucleus for
deposition in one direction of carbon. A tube-shaped carbonaceous
nanotube, which has few twists and turns, can be manufactured
efficiently and easily. Twists and turns are the result of
abnormality of crystal growth. When there are few twists and turns,
the true properties (mechanical properties, electrical properties,
thermal properties, and the like) of the carbonaceous nanotube can
be achieved. Furthermore, carbonaceous nanotubes with few twists
and turns can be easily dispersed in resins and rubbers and can be
dispersed in an arrangement with directionality.
[0077] If the above sulfur atom density exceeds 2.5 mol %, there is
difficulty in generating the carbonaceous nanotube. When the
concentration of the above sulfur atoms is less than 0.00625 mol %,
a large amount of bent carbonaceous nanotubes is generated, and
there is difficulty in generating the carbonaceous nanotube.
[0078] When supplying the above raw material mixture to the
reaction region inside the above reaction tube, the above raw
material mixture can be supplied more stably if, for example, it is
dissolved in a hydrocarbon or other organic solvent or in a small
amount of inorganic solvent and the like.
[0079] The time that the above raw material mixture spends in the
reaction region, based upon the length of reaction region/flow
speed of the raw material mixture at the reaction temperature, is
normally within one minute, and preferably in the range of
0.1.about.30 seconds, and most preferably in the range of
1.about.20 seconds.
[0080] Fiber Aggregate
[0081] According to the method for manufacturing the carbonaceous
nanotube of the present invention, the following fiber aggregate is
achieved. This fiber aggregate contains the above described
carbonaceous nanotube of the present invention at a ratio of about
70 weight % with respect to the whole. The fiber aggregate also
contains 0.1.about.1 weight % of hydrogen atoms with respect to the
whole, carbon atoms at a content ratio of at least 98.5 weight %
with respect to the whole, and transition metal atoms at a content
ratio of 0.005.about.1 weight % with respect to the whole.
[0082] The above fiber aggregates can also contain by-products and
the like, such as soot, tar materials, and non-hollow carbonaceous
fibers, which do not have hollow parts, and the like.
[0083] The above tar material in the above fiber aggregate can be
removed by rinsing with organic solvents such as toluene, acetone
and the like, for example. The above tar material can also be
removed by evaporating in an inert atmosphere of approximately
1,000.degree. C. and decomposing this evaporated tar material.
[0084] The above fiber aggregate normally contains at least 70
weight % of the above thin carbonaceous nanotube, and preferably
contains at least 80 weight %.
[0085] By having the above fiber aggregate contain at least 70
weight % of the above thin carbonaceous nanotube, in a composite
material of the above fiber aggregate and resin, for example, the
mechanical properties of strength, elasticity, and the like,
electrical properties, and thermal properties of this composite
material is effectively improved.
[0086] Furthermore, the above fiber aggregate may also contain
carbon-covered metal particles, which are transition metal
particles of a diameter of several nm, for example 1-10 nm, covered
by carbon material. The above carbon-covered metal particles can be
removed from the above fiber aggregate by acid rinsing and the
like, but by having a content in the above fiber aggregate in a
range not exceeding 1 weight %, in the composite material of the
above fiber aggregate and a resin, for example, the wettability of
the fiber aggregate with respect to the resin is effectively
improved, and the mechanical properties of strength and elasticity
and the like of this composite material is effectively
improved.
EXAMPLES
[0087] Embodiment 1
[0088] Referring to FIG. 1, the manufacture of the carbonaceous
nanotube was conducted using a vertical-type vapor grown carbon
fiber manufacturing device 1.
[0089] Vapor grown carbon fiber manufacturing device 1 has a raw
material tank 2, a raw material pump 3, a raw material vaporizer 4,
a pre-heater 5, a first carrier gas flow meter 6, a second carrier
gas flow meter 7, a third carrier gas flow meter 8, a raw material
mixture gas supply nozzle 9, a reaction tube 10, a flow
straightener 11, a second carrier gas supply nozzle 12, a third
carrier gas supply nozzle 13, an electric furnace 14, a fiber
collector 15, and a gas exhaust opening 16.
[0090] The inner diameter of reaction tube 10 is 8.5 cm.
[0091] The reaction region is from the lower end of flow
straightener 11 to a position at approximately 80 cm towards fiber
collector 15. The temperature inside reaction tube 10 is controlled
so that the reaction region is maintained at 1100.degree. C.
Downstream from the above reaction region, the temperature becomes
gradually lower. The temperature at fiber collector 15 is around
100.about.300.degree. C.
[0092] A raw material solution of ferrocene:thiophene:toluene with
a mixing ratio of a mole ratio of 0.5:0.2:99.3 was stored in raw
material tank 2.
[0093] The raw material solution was supplied by raw material pump
3 to raw material vaporizer 4 via a raw material supply pipe 17.
After vaporizing the raw material solution and making into a raw
material gas, this raw material gas and a first carrier gas are
mixed so that the concentration of the raw material gas is at 4
volume %.
[0094] The above first carrier gas had a mixing ratio of
hydrogen:nitrogen of a volume ratio of 80:20 and was supplied to
the inside of raw material gas pipe 19 through first carrier gas
supply pipe 18 and was mixed with the raw material gas.
[0095] The raw material mixture gas, which was obtained by mixing
the above raw material gas and the above first carrier gas so that
the raw material gas was 4 volume %, was pre-heated by pre-heater
5. Next, the raw material mixture gas was supplied to raw material
mixture gas supply nozzle 9 via raw material mixture gas supply
pipe 20. This raw material mixture gas corresponds to the raw
material mixture of the present invention.
[0096] The inner diameter of the above raw material mixture gas
supply nozzle 9 was 2 cm. The temperature inside raw material
mixture gas supply nozzle 9 was controlled at approximately
400.degree. C.
[0097] Because, at room temperature, the above raw material mixture
gas was supplied at 2 L/minute, the raw material mixture gas was
blown in from raw material mixture gas supply nozzle 9 at
400.degree. C. at a speed of 24 cm/second.
[0098] The second carrier gas was pure hydrogen, supplied to flow
straightener 11 from second carrier gas supply nozzle 12 via second
carrier gas supply pipe 21.
[0099] Because, at room temperature, the above second carrier gas
was supplied at 7 L/minute, it must have flowed though the space
between the inner perimeter wall surface (inner diameter 7 cm) of
flow straightener cylinder 11 a provided on flow straightener 11
and the outer perimeter wall (outer diameter 4 cm) of raw material
mixture gas supply nozzle 9 at approximately 1100.degree. C. at a
speed of 21 cm/second.
[0100] The third carrier gas was a mixture of nitrogen:air at a
mixing ratio of 80:20 volume ratio. Third carrier gas was supplied
to flow straightener 11 from third carrier gas supply nozzle 13 via
third carrier gas supply pipe 22.
[0101] Because, at room temperature, the above third carrier gas
was supplied at 3 L/minute, it must have flowed through the space
between the outer perimeter wall surface (outer diameter 7.5 cm) of
flow straightener cylinder 11a provided on flow straightener 11 and
the inner perimeter wall (inner diameter 8.5 cm) of reaction tube
10 at approximately 1100.degree. C. at a speed of 19 cm/second.
[0102] With this reaction device, convection flow did not occur,
and there was an air flow approximating a piston flow with a
direction of gas flow from vertically above to vertically
downward.
[0103] By bringing in the surrounding pure hydrogen gas, the raw
material mixture gas, flowing down from raw material mixture gas
supply nozzle 9, flowed down while the raw material gas in the raw
material mixture gas was being dispersed in the hydrogen.
[0104] The above raw material mixture gas and pure hydrogen gas
contacted the third carrier gas, which flowed down along the inner
perimeter wall of reaction tube 10. By having the above third
carrier gas interposed between the above raw material mixture gas
and pure hydrogen gas and the inner perimeter wall surface of
reaction tube 10, the adhesion of products on the inner perimeter
wall surface of reaction tube 10 are prevented.
[0105] The raw material concentration in the reaction region
immediately after blowing out of the nozzle was 4%, but as it
flowed down the reaction tube, it was gradually diluted by mixing
with the second carrier gas. However, because the flow approximated
a piston flow, it can be hypothesized that it was not completely
mixed. Although it was gradually mixed with the third carrier gas
as well, it can be hypothesized that there would be a large amount
of nitrogen/air components near the reaction tube wall, and there
would be a large amount of raw material components/hydrogen in the
reaction tube interior.
[0106] After maintaining this state for 30 minutes, raw material
supply pump 3 was stopped and left standing for 5 minutes.
Afterwards, the inside of reaction tube 10 was substituted with
nitrogen gas.
[0107] From the filter part of gas exhaust opening 16, 0.5 g of
fiber, and from fiber collector 15, 2.2 g of fiber was
collected.
[0108] The fibers collected from the above filter part and the
fibers collected from fiber collector 15 were each observed with a
high resolution transmission electron microscope.
[0109] When the fibers collected from the above filter part were
observed, there was a mixture of fibers of outer perimeter diameter
of 5.about.8 nm. They were hollow carbon fibers with an average
outer perimeter diameter of 6 nm and an average inner perimeter
diameter of 4 nm. These hollow carbon fibers were labeled as Sample
1.
[0110] When the fibers collected from fiber collector 15 were
observed, there was a mixture of fibers of outer perimeter diameter
8.about.30 nm. They were hollow carbon fibers with an average outer
perimeter diameter of 23 nm, and an average inner perimeter
diameter of 4 nm. These hollow carbon fibers were labeled as Sample
2.
[0111] Embodiment 2
[0112] The reaction region was maintained at 1150.degree. C., a
solution of ferrocene:thiophene:toluene with a mixing ratio of a
mole ratio of 1.5:0.8:97.7 was used as the raw material solution.
Pure hydrogen gas was used for each of the first carrier gas and
second carrier gas. Pure nitrogen gas was used as the third carrier
gas. The above raw material solution was vaporized and made into
the raw material gas. Next, the raw material gas and the first
carrier gas were mixed so that the raw material gas was 2 volume %,
and a raw material mixture gas was obtained. There was downward
flow of this raw material mixture gas at a speed of 30 cm/second,
and there was downward flow of the second carrier gas at 12
cm/second, and there was downward flow of the third carrier gas at
12 cm/second. In order to manufacture a carbon fiber, all else was
the conducted the same as Embodiment 1.
[0113] From fiber collector 15, 1.5 g of fiber, and from the filter
part of gas exhaust opening 16, 1.0 g of fiber was collected.
[0114] The fibers collected from the above filter part and the
fibers collected from fiber collector 15 were observed with a high
resolution transmission electron microscope.
[0115] When the fibers collected from the above filter part were
observed, there was a mixture of fibers of outer perimeter diameter
5.about.9 nm. They were hollow carbon fibers with an average outer
perimeter diameter of 7 nm and an average inner perimeter diameter
of 3.5 nm. These hollow carbon fibers were labeled as Sample 3.
[0116] When the fibers collected from fiber collector 15 were
observed, there was a mixture of fibers with an outer perimeter
diameter of 7.about.25 nm. They were hollow carbon fibers with an
average outer perimeter of 20 nm and an average inner perimeter
diameter of 4 nm. These hollow carbon fibers were labeled as Sample
4.
Comparative Example 1
[0117] Vapor grown carbon fibers, which have been graphitized and
which have an average outer perimeter diameter of 200 nm and an
average inner perimeter diameter of 3 nm, were prepared. These
vapor grown carbon fibers which have been graphitized were labeled
as Sample 5.
[0118] Evaluation
[0119] Referring to Table 1, spacing of basal graphite plane
(d.sub.002), hydrogen atom content ratio, carbon atom content
ratio, transition metal atom content ratio, specific surface area,
water retention rate, hydrogen absorption amount, and flexural
strength, flexural modulus, and specific resistance of the
composite material when mixed with epoxy resin are shown for the
above Samples 1.about.5.
[0120] In the above composite material, each sample was mixed at 10
volume %.
[0121] Samples 1 and 4 obtained in the above Embodiments 1 and 2
correspond to the carbonaceous nanotube of the present
invention.
1 TABLE 1 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Average
fiber diameter 6 23 7 20 200 (nm) Average hollow 4 4 3.5 4 3
diameter (nm) Average thickness 1 9.5 1.8 8 98 (nm) basal graphite
plane 0.347 0.349 0.345 0.348 0.336 spacing d.sub.002 (nm)
Elemental analysis: Hydrogen (wt %) 0.3 0.5 0.2 0.6 0 Carbon (wt %)
99.6 99.4 99.7 99.8 99.9 Transition metal 0.2 0.1 0.2 0.1 0 (wt %)
Specific surface area 100 250 900 200 5 m.sup.2/g Water retention
rate Large Medium Large Medium Very small Hydrogen absorption Very
large Medium Large Medium Very small amount Properties of epoxy
resin composite material (fiber 10 vol %) flexural strength 9 7 9 6
4 (kg/mm.sup.2) flexural modulus 360 320 390 340 510 (kg/mm.sup.2)
Specific resistance 0.1 1 0.1 1 15 (ohm/cm)
[0122] According to the carbonaceous nanotube of the present
invention, for example, with the composite material obtained by
combining the carbonaceous nanotube with resin, the carbonaceous
nanotube has excellent wettability. As a result, the mechanical
strength of the above composite material is effectively
improved.
[0123] According to the present invention, the carbonaceous
nanotube and the fiber aggregate, which contains a ratio of at
least 70 weight % with respect to the whole of the carbonaceous
nanotube, have excellent conductivity. In addition, there are
active sites on their surfaces. As a result, the problems of
wetting and the like with composite materials of the prior art are
solved. For example, a high performance composite material which
has excellent electrical properties such as specific resistance and
the like, and excellent mechanical properties, such as bending
strength, bending elasticity, and the like, and excellent chemical
properties, such as water retention ability and absorptive ability,
and the like is obtained.
[0124] According to the manufacturing method for the carbonaceous
nanotube of the present invention, the above carbonaceous nanotube
and the above fiber aggregates are obtained easily.
[0125] The carbonaceous nanotube and fiber aggregate of the present
invention have a large specific surface area, many active sites,
and excellent chemical resistance. As a result, for example, they
are effectively used in adsorbents and hold-back agents.
[0126] Having described preferred embodiments of the invention with
reference to the accompanying drawings, it is to be understood that
the invention is not limited to those precise embodiments, and that
various changes and modifications may be effected therein by one
skilled in the art without departing from the scope or spirit of
the invention as defined in the appended claims.
* * * * *