U.S. patent application number 11/376856 was filed with the patent office on 2007-05-17 for method for manufacturing nano-carbon substances.
This patent application is currently assigned to Daiken Chemical Co., Ltd.. Invention is credited to Akio Harada, Xu Li, Yoshikazu Nakayama, Takashi Okawa, Youchang Wang.
Application Number | 20070111885 11/376856 |
Document ID | / |
Family ID | 27640520 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070111885 |
Kind Code |
A1 |
Li; Xu ; et al. |
May 17, 2007 |
Method for manufacturing nano-carbon substances
Abstract
A catalyst for manufacturing carbon substances, such as carbon
nanotube that has a diameter of 1000 nm or less, the catalyst
containing at least iron, cobalt or nickel of a first element group
and tin or indium of a second element group. The catalyst can be
formed by at least tin and indium in addition to cobalt or nickel.
The former catalyst provides a 2-component type catalyst and a
multi-component type catalyst that is composed on the basis of the
2-component type catalyst, and the later catalyst provides a
3-component type catalyst and a multi-component type catalyst that
is composed on the basis of the 3-component type catalyst.
Inventors: |
Li; Xu; (Osaka-shi, JP)
; Wang; Youchang; (Osaka-shi, JP) ; Okawa;
Takashi; (Osaka-shi, JP) ; Harada; Akio;
(Osaka-shi, JP) ; Nakayama; Yoshikazu;
(Hirakata-city, JP) |
Correspondence
Address: |
KODA & ANDROLIA
2029 CENTURY PARK EAST
SUITE 1140
LOS ANGELES
CA
90067
US
|
Assignee: |
Daiken Chemical Co., Ltd.
Yoshikazu Nakayama
|
Family ID: |
27640520 |
Appl. No.: |
11/376856 |
Filed: |
March 16, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10328105 |
Dec 23, 2002 |
|
|
|
11376856 |
Mar 16, 2006 |
|
|
|
Current U.S.
Class: |
502/325 ;
502/332; 502/335; 502/336 |
Current CPC
Class: |
B01J 37/082 20130101;
C01B 32/162 20170801; B82Y 40/00 20130101; B01J 37/0219 20130101;
B01J 23/835 20130101; B01J 23/825 20130101; C01B 2202/36 20130101;
C01B 32/18 20170801; B82Y 30/00 20130101 |
Class at
Publication: |
502/325 ;
502/332; 502/335; 502/336 |
International
Class: |
B01J 23/00 20060101
B01J023/00; B01J 23/56 20060101 B01J023/56; B01J 23/74 20060101
B01J023/74; B01J 23/70 20060101 B01J023/70 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2001 |
JP |
2001-403233 |
Claims
1-7. (canceled)
8. A method for manufacturing nano-carbon substances consisting
essentially of carbon atoms, said method comprising the steps of:
exposing a hydrocarbon to a catalyst, said catalyst comprising at
least one element of a first element group and one element of a
second element group, wherein said first element group consists of
cobalt and nickel, and said second element group consists of tin
and indium; heating said catalyst and hydrocarbon to a catalytic
decomposition temperature of hydrocarbons; cooling the catalyst and
nano-carbon substance; and recovering the nano-carbon
substance.
9. The method of manufacturing nano-carbon substances consisting
essentially of carbon atoms according to claim 8, wherein said
first element consists of cobalt and said second element consists
of tin, and said nano-carbon substances comprise carbon nanocoils
that have a coil diameter of 1000 nm or less.
10. The method of manufacturing nano-carbon substances consisting
essentially of carbon atoms according to claim 8, wherein said
first element consists of nickel and said second element consists
of indium, and said nano-carbon substances comprise carbon
nanocoils that have a coil diameter of 1000 nm or less.
11. A method for manufacturing nano-carbon substances consisting
essentially of carbon atoms, said method comprising the steps of:
exposing a hydrocarbon to a catalyst, said catalyst comprising at
least tin and indium and at least one selected from the group
consisting of cobalt and nickel; heating said catalyst and
hydrocarbon to a catalytic decomposition temperature of
hydrocarbons; cooling the catalyst and nano-carbon substance; and
recovering the nano-carbon substance.
12. The method of manufacturing nano-carbon substances consisting
essentially of carbon atoms according to claim 8 or 11, wherein
said cobalt and said nickel are respectively cobalt oxide and
nickel oxide.
13. The method of manufacturing nano-carbon substances consisting
essentially of carbon atoms according to claim 11, wherein said tin
and said indium are in the form of an ITO film.
14. A method for manufacturing nano-carbon substances consisting
essentially of carbon atoms, said method comprising the steps of:
exposing a hydrocarbon to a catalyst, said catalyst being a
two-component catalyst, wherein said two-component catalyst
consists of iron and one element selected from the group consisting
of tin and indium; heating said catalyst and hydrocarbon to a
catalytic decomposition temperature of hydrocarbons; cooling the
catalyst and nano-carbon substance; and recovering the nano-carbon
substance.
15. The method of manufacturing nano-carbon substances consisting
essentially of carbon atoms according to claim 14, wherein said
two-component catalyst consists of iron and tin, and said
nano-carbon substances comprise carbon nanocoils that have a coil
diameter of 1000 nm or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to catalysts for manufacturing
carbon substances which are carbon nanocoils having an external
diameter of 1000 nm or less, or carbon nanotubes having a sectional
diameter of nanosize, etc. More specifically, the present invention
relates to the catalysts for manufacturing carbon substances which
effectively cause the carbon substances to grow on the surface of
the catalysts while a raw-material gas is under pyrolysis by means
of a catalyst which contains at least more than two components,
that is, which contains at least both a first element group
including iron, cobalt and nickel and a second element group
including tin and indium.
[0003] 2. Prior Art
[0004] Diamond and graphite have been known as substances made from
carbon (hereafter called "carbon substance"). The crystal structure
of a diamond is stereo-structure and the crystal structure of the
graphite is a two dimensional layer-structure. The utility of these
two carbon substances is extremely limited due to the difficulty of
technical treatment for them.
[0005] In order to utilize the heat resisting property and the
strength of carbon, a research and development of carbon filament
started actively in 1960. By weaving carbon filaments to form a
woven sheet, and further by combining the woven sheet and resin to
make a compound fiber, a compound fiber can be utilized in a wide
region.
[0006] Since the method of manufacturing carbon filaments was
established in the decade of 1980, it is succeeded to give car
bodies lightness and strength by means of making car bodies from
the carbon filaments. Furthermore, golf equipment and fishing rods
which are formed with compound fibers have been brought into
practical use. Thus many kinds of carbon goods have been used.
[0007] There are two methods for manufacturing carbon filaments,
one is to remove the organic substance by means of calcinating
organic fibers such as acrylic fiber, etc, another is a vapor-phase
catalytic decomposition method in which the growth of carbon
filaments is stimulated by means of decomposing hydrocarbon in gas
phase by using catalytic particles.
[0008] Specifically, in the vapor-phase catalytic decomposition
method, the fine powder of ferromagnetic metal such as Fe, Ni and
Co is used. In this method the carbon filament is grown at the
tip-end on which this catalytic powder adheres, while pyrolizing
hydrocarbon at the tip end portion. Besides, a method that uses the
catalytic powder of Fe.Co alloy is developed. However, most of the
carbon filaments which are manufactured in these methods are curved
in the middle portion, and it was difficult to grow carbon
filaments with high linearity.
[0009] In such a situation, a discovery of fullerene was reported
in the Nature magazine, Vol. 318 (1985) 162, by H. W. Kroto, J. R.
Heath, S. C. O'Brien, R. F. Curl, and R. E. Smalley, which is
expressed by C.sub.60 and a carbon molecule of a soccer ball shape.
This fullerene is a new type of the carbon substances.
[0010] Nest, S. Iijima reported in 1991, in the Nature magazine;
Vol. 354 (1991) 56-58 that he succeeded in the synthesis of a
carbon nanotube with high linearity by means of an arc discharge
method. The characteristic point of his method was to find carbon
filaments with very high linearity in carbon substances heaped up
on the cathode, which were produced by the ordinary arc discharge
without using any catalyst. He named helical micronanotube the
carbon filament, but at present, it is called a carbon
nanotube.
[0011] Though the use of fullerene is not so much, the development
for use of the carbon nanotube has been rapidly extended. In this
circumstance, a carbon nanocoil, in addition, was discovered as a
further new carbon substance. The carbon nanocoil was discovered in
the process of researching carbon microcoil.
[0012] The fact that carbon fibers grow in a vapor phase, while
being twisted in the manner of a rope, was first reported by Davis
et al. (W. R. Davis, R. J. Slawson and G. R. Rigby, Nature, Vol.
171, 756 (1953)). Since the external diameter of such carbon ropes
is micro-size, such ropes are ordinarily referred to as carbon
microcoils. Subsequently, various reports appeared concerning
carbon nanocoils: however, since there was strong element of
randomness involved in the production of such coils, the coils
lacked reproducibility, and reminded in a state that was inadequate
for industrial production.
[0013] In 1990, Motojima et al. (S. Motojima, M. Kawaguchi, K.
Nozaki, and H. Iwanaga, Appl. Phys. Lett., 56 (1990) 321)
discovered an efficient method for manufacturing carbon microcoils,
and as a result of subsequent research, they established a
manufacturing method that showed reproducibility. In this method, a
graphite substrate which is coated with a powdered Ni catalyst is
placed inside a horizontal type externally heated reaction tube
made of transparent quartz, and a raw-material gas is introduced
perpendicularly onto the surface of the substrate from a
raw-material gas introduction part located in the upper part of the
reaction tube. This raw-material gas is a mixed gas of acetylene,
hydrogen, nitrogen and thiophene. The exhausted gas is discharged
from the bottom part of the reaction tube.
[0014] In this manufacturing method, impurities such as sulfur and
phosphorous, etc., are indispensable; and if the amounts of these
impurities are too large or too small, carbon microcoils will not
grow. For example, the coil yield reaches maximum, at a value of
approximately 50%, in a case where thiophene-containing sulfur is
added at the rate of 0.24% relative to the total gas flow. The
reaction temperature is approximately 750 to 800.degree. C.
[0015] Diameter of fibers constituting such carbon microcoils is
0.01 to 1 .mu.m, the external diameter (outside diameter) of the
coil is 1 to 10 .mu.m, the coil pitch is 0.01 to 1 .mu.m, and the
coil length is 0.1 to 25 mm. It is characteristic that these carbon
microcoils are of micro-size and have an amorphous structure. In
another ward, the carbon microcoils are substances that amorphous
fibers grow up in a coil shape without a hole.
[0016] In 1991, carbon nanocoils were discovered. Spurred by this
discovery, research concerning carbon coils on the nanometer scale,
i.e., carbon nanocoils was initiated. The reason for this was that
on the nanometer scale, there was a possibility that a new physical
property might be discovered, so that such nanocoils showed promise
as new materials in electronics and engineering, etc., in nanometer
region.
[0017] In 1994, Amelinckx et al. (Amelinckx, X. B. Zhang, D.
Bernerts, X. F. Zhang, V. Ivanov and J. B. Nagy, Science, 265
(1994) 653) succeeded in producing carbon nanocoils. It was also
demonstrated that while carbon microcoils are amorphous, carbon
nanocoils have a graphite structure. Various types of carbon
nanocoils were manufactured, and the minimum external diameter of
these nanocoils was extremely small, i.e., approximately 12 nm.
[0018] The manufacturing method used by the above mentioned
researchers was a method in which a metal catalyst such as Co, Fe
or Ni is formed into a fine powder, the area around this catalyst
is heated to a temperature of 600 to 700.degree. C., and an organic
gas such as acetylene or benzene is caused to flow through so that
this gas contacts the catalyst, thus breaking down these organic
molecules. The substance-produced as a result consists of carbon
nanotubes with a graphite structure, and the shapes of these
nanotubes are linear, curvilinear, planar spiral and coil form,
etc.
[0019] In 1999, Li et al. (W. Li, S. Xie, W. Liu, R. Zhao, Y.
Zhang, W. Zhou, and G Wang; J Material Sci., 34 (1999) 2745)
succeeded again in producing carbon nanocoils. In the manufacturing
method used by these researchers, a catalyst formed by covering the
outer circumference of a graphite sheet with iron particles was
placed in the center, and the area around this catalyst was heated
to 700.degree. C. by means of a nichrome wire. This catalyst is a
2-component type catalyst consisting of graphite and iron. However,
as the carbon nanocoils are carbon substance, the graphite is used
as a basic material, so that this catalyst can be regarded as a
1-component Fe catalyst combined with graphite. This manufacturing
method also showed a small coil production rate and was extremely
inadequate as an industrial production method.
[0020] As described above, the catalysts for manufacturing carbon
filaments and carbon nanocoil are limited to a one component type
catalyst for which ferromagnetic metal such as Fe, Co or Ni is used
as simple substance, to a two component type catalyst which is an
alloy consisting of two ferromagnetic metals such as Fe.Co, or to a
two component catalyst combining ferromagnetic metal and
graphite.
[0021] In the course of analyzing such a conventional catalyst, the
present inventors investigated a possibility of two and three
component type catalyst and multi (more than three) component type
catalysts which are constructed by adding non-ferromagnetic metals
to the ferromagnetic metal such as Fe, Co, or Ni. As a result, the
inventors reached to the invention which was published in Japanese
Patent Application Laid-Open (Kokai) No. 2002-192204. This
invention disclosed a 3-component type catalyst comprising indium,
tin and iron.
[0022] In more concrete terms, the 3-component type catalyst is
formed by vacuum-evaporating an iron thin film on the surface of an
ITO substrate which is a thin film being mixture of indium-oxide
and tin-oxide. ITO is an abbreviation of Indium-Tin-Oxide. The ITO
substrate is widely used as a raw material of semi-transparent
electrodes in the field of semiconductor. It was found in a study
that, when hydrocarbon gas is pyrolyzed in a reaction apparatus, a
large amount of carbon nanocoils grow on the surface of the
3-component type catalyst.
[0023] The study shows that there is a possibility of synthesis of
a large amount of carbon substances such as carbon nanotubes or
carbon nanocoils by using adequate catalysts. There, however, might
still exist unknown catalysts. Therefore, it would be very
significant to consider again the construction of catalysts.
SUMMARY OF THE INVENTION
[0024] Accordingly, the object of the present invention is to
provide a catalyst that can produce different types of carbon
substances with various structures, by developing a 2-component
type catalyst constructed by adding a non-ferromagnetic metal to a
ferromagnetic metal such as Fe, Co or Ni, and by developing a
multi-component type catalyst constructed by adding further other
components to the 2-component type catalyst.
[0025] More specifically, the present invention provides a catalyst
for manufacturing carbon substances which is characterized in that
the catalyst contains at least one of first element and one of
second element wherein the first element comprises iron, cobalt
nickel and the second element comprises tin and indium.
[0026] The present invention provides a catalyst for manufacturing
carbon substances wherein the catalyst contains at least tin and
either iron or cobalt, and this catalyst is used for manufacturing
carbon substances which are carbon nanocoils, the diameter of the
nanocoils being equal to or less than 1,000 nm.
[0027] The present invention provides a catalyst for manufacturing
carbon substances wherein the catalyst contains at least nickel and
indium, and this catalyst is used for manufacturing carbon
substances that are carbon nanocoils, the diameter of the nanocoils
being equal to or less than 1,000 nm.
[0028] The present invention provides a catalyst for manufacturing
carbon substances which is characterized in that the catalyst
contains at least both tin and indium in addition to cobalt or
nickel.
[0029] In the present invention that provides a catalyst for
manufacturing carbon substances, the above-mentioned iron, cobalt
and nickel can be iron-oxide, cobalt-oxide and nickel-oxide,
respectively.
[0030] Furthermore, in the present invention that provides a
catalyst for manufacturing carbon substances, the above-mentioned
tin and indium can be in the form of an ITO film (indium-tin-oxide
film), respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic structural diagram of a carbon
substance manufacturing apparatus of the present invention;
[0032] FIG. 2 is an electron microscope image of carbon substances
grown by the catalyst Fe.sub.2O.sub.3.Sn;
[0033] FIG. 3 is an electron microscope image of carbon substances
grown by the catalyst Fe.sub.2O.sub.3.In;
[0034] FIG. 4 is an electron microscope image of carbon substances
grown by the catalyst Co.Sn;
[0035] FIG. 5 is an electron microscope image of carbon substances
grown by the catalyst Co.In;
[0036] FIG. 6 is an electron microscope image of carbon substances
grown by the catalyst CoO.Sn;
[0037] FIG. 7 is an electron microscope image of carbon substances
grown by the catalyst CoO.In;
[0038] FIG. 8 is an electron microscope image of carbon substances
grown by the catalyst Ni.Sn;
[0039] FIG. 9 is an electron microscope image of carbon substances
grown by the catalyst Ni.In;
[0040] FIG. 10 is an electron microscope image of carbon substances
grown by the catalyst NiO.Sn;
[0041] FIG. 11 is an electron microscope image of carbon substances
grown by the catalyst NiO.In;
[0042] FIG. 12 is a distribution graph of the external diameter of
carbon nanocoils grown by the catalyst CoO.Sn;
[0043] FIG. 13 is a distribution graph of the external diameter of
carbon nanocoils grown by the catalyst Ni.In;
[0044] FIG. 14 is an electron microscope image of carbon substances
grown by the catalyst Fe.sub.2O.sub.3.ITO;
[0045] FIG. 15 is an electron microscope image of carbon substances
grown by the catalyst Co.ITO; and
[0046] FIG. 16 is an electron microscope image of carbon substances
grown by the catalyst NiO.ITO.
DETAILED DESCRIPTION OF THE INVENTION
[0047] The present inventors, as a result of diligent research
concerning 2-component type catalysts and multicomponent type
catalysts for manufacturing carbon substances, reached to the
conclusion that carbon substances produced by the catalysts are
classified mainly into carbon nanocoils (called "CNC" below),
carbon nanotubes (called "CNT" below) and carbon nanoparticles
(called "CNP" below).
[0048] Here, the CNC is a carbon substance formed in a helical
configuration (coil form) with a regular rotation period, the CNT
is a carbon substance formed in a fiber configuration and the CNP
is a carbon substance formed in a particle shape. In particular,
the CNTs comprise not only a linear (not curved) carbon substance,
but also carbon substances of an irregularly curved fiber and/or of
an irregular helical form.
[0049] The carbon substance produced by the method of the present
invention may be called nano-carbon-substance, since the size is
nanoscale. Concretely saying, the CNC means a small carbon coil
which has an external diameter of the cross section equal to or
less than 1,000 nm, the CNT means a carbon nanotube which has a
diameter of the tube cross section of 1 to several 100 s nm, and
the CNP means a small carbon particle with a diameter equal to or
less than 1,000 nm.
[0050] In observation by an electron microscope, carbon substances
appearing in a range of vision are ordinarily expressed as CNC, CNT
and CNP. Since a CNC is often mixing with a CNT, the expression CNC
(large)+CNT means the state that a small quantity of CNT mixes with
a large quantity of CNC, and the expression CNC (small)+CNT means a
state that a large quantity of CNT exists, mixing with a small
quantity of CNC. When simply written as CNT or CNP, it means that
only the same carbon substance exists in a range of vision.
[0051] Though a catalyst by which only the CNT is produced is a
catalyst for manufacturing CNT, a catalyst by which CNC+CNT are
produced work not only as the catalyst for manufacturing CNC, but
also as the catalyst for manufacturing CNT. In a case where a
single catalyst produces a mixing state of CNC and CNT, the
technique to divide the CNC and the CNT is necessary. Needless to
say, the catalyst by which only a CNC is produced is used as the
catalyst for manufacturing CNC. It is same for the catalyst for
manufacturing CNT.
[0052] The two component type catalysts related to the present
invention contain at least any one of iron, cobalt or nickel of the
first element group and any one of tin or indium of the second
element group. Accordingly, there exist six kinds of the
2-component type catalysts related to the present invention, and
those are expressed by the element symbol as Fe.Sn, Fe.In, Co.Sn,
Co.In, Ni.Sn, and Ni.In.
[0053] The 2-component type catalysts were discovered on the basis
of the next two facts. Namely, the first is the fact that in order
to manufacture CNC, Amelinckx et al. discovered a 1-component type
catalyst by, which consists of iron, cobalt or nickel, and also
that the one component type catalyst of iron, cobalt or nickel is
used even in the case of producing carbon filaments. The second is
the discovery of the 3-component type catalysts comprising indium,
tin and iron, by the present inventors.
[0054] By the formers, ferromagnetic metals such as iron, cobalt
and nickel have been used for necessary components to synthesize
CNC or CNT. By the later, it is shown that a large quantity of CNC
is synthesized by the indium-tin-iron type catalyst, if indium and
tin are added to the ferromagnetic metal iron.
[0055] The idea of the present inventors is based on a verification
of which of indium and tin more contributes to the growth of CNC.
In order to verify it, the researchers of the present invention
tried experiments synthesizing carbon substances by constructing
2-component type catalysts of iron-indium and iron-tin. As a result
of the experiment, it was founded that the iron-tin catalyst caused
CNC to grow intensively, while the iron-indium catalyst caused
almost only CNP to grow.
[0056] Similar synthesis experiments were performed for catalysts
of other ferromagnetic metals such as cobalt and nickel. Though a
cobalt-nickel catalyst caused both a CNC and a CNT to synthesize, a
cobalt-indium catalyst caused almost only CNT to synthesize. On the
contrary; a nickel-tin catalyst caused almost only CNT to
synthesize, while a nickel-indium catalyst caused to synthesize
both a CNC and CNT.
[0057] Accordingly, since Fe.Sn, Co.Sn and Ni.In, expressed in term
of the element symbol, cause to synthesize CNC+CNT, these act as
the catalysts for manufacturing CNC and CNT. When the yield of CNC
is improved to be more than 90%, CNC is obtained almost as simple
substance, but if the yield of CNC is reduced, the technique to
collect by separating the CNC from the CNT is necessary. On the
other hand, it was founded that Fe.In was available for the
catalyst for manufacturing CNP, and Co.In and Ni.Sn were available
for the catalysts for manufacturing CNT.
[0058] From the results above, it was found that when manufacturing
CNC, iron, cobalt and nickel strongly depend on the selection of
tin or indium. However, the reason why the ferromagnetic metal is
available for the catalyst and has a strong selection tendency for
their combinations is unknown at present.
[0059] The next problem is to make it clear whether or not the
2-component type catalysts, to which third components added, are
available for the catalyst. In order t solve the problem, a
synthesis experiment of carbon substances was executed using ITO
(Indium-Tin-Oxide) substrates added ferromagnetic metals. As
above-mentioned, this ITO is a mixture of indium-oxide and
tin-oxide.
[0060] As a result, it was found that all of the iron ITO, cobalt
ITO and nickel ITO synthesize carbon nanocoils at a high yield
rate. Since metal components ordinarily work as catalyst, these
3-component type catalysts are expressed as Fe.In.SN, Co.In.Sn and
Ni.In.Sn in terms of the element symbol. As described above, the
3-component type catalyst of Fe.In.Sn has been disclosed by the
present inventors.
[0061] Fe.In.Sn obviously contains at least Fe.Sn. Similarly,
Co.In.Sn contains at least Co.Sn, and Ni.In.Sn contains at least
Ni.In. These facts show that even the 2-component type catalyst, to
which another element is added, can be used as a catalyst for
manufacturing CNC.
[0062] Saying straightforwardly, it means that if the
above-mentioned 2-component type catalyst is available for the
catalyst for manufacturing CNC, a multi-component type catalyst
which is constructed by adding other element to the 2-component
type catalyst also work well as a catalyst for manufacturing CNC.
Furthermore, the 3-component type catalyst of Fe.In.Sn has a
tendency to produce the yield of CNC more than the 2-component type
catalyst, but the detail of the reason is unclear at present.
[0063] Next, both cases of catalysts constructed with pure metals
and with metal oxides were examined. More specifically, as a result
of the experiment examination, in the respective cases of Fe.Sn,
Co.Sn, and Ni.In, whether the effects as the 2-component type
catalysts of for manufacturing CNC are different or not, depending
on chemical states of metal elements contained in the catalysts, it
was found that both a pure metal state and a metal-oxide state are
available for a catalyst.
[0064] For example, in the case of Fe.Sn, a catalyst of the
vacuum-evaporated Fe film piled on the vacuum-evaporated Sn film is
effective and an alloy calcinating the mixture of an Fe fine powder
and an Sn fine powder is also effective. Furthermore, a catalyst
calcinating the mixture of a Fe.sub.2O.sub.3 powder and SnO.sub.2
powder, and also a catalyst calcinating the mixture of an
Fe.sub.2O.sub.3 powder and an Sn powder are effective. From these
facts, it is inferred that the co-existence state of an Fe-atom and
an Sn-atom contributes to the growth of CNC. This is similar for
the catalysts of Co.Sn and Ni.In.
[0065] It was confirmed that also in 3-component type catalysts,
both cases where the constituting element is a pure metal and a
metal-oxide are effective as the catalyst for manufacturing CNC.
That is, an ITO substrate is a thin film mixed of In.sub.2O.sub.3
with SnO.sub.2, and the ITO substrate on which a vacuum evaporated
iron film is formed turns into a strong catalyst. This fact has
been already published in the above-mentioned open laid
publication.
[0066] It was also confirmed that the thin film made of a mixing
powder of Fe.sub.2O.sub.3, In.sub.2O.sub.3 and SnO.sub.2, and the
thin film of an In and Sn alloy on which a vacuum-evaporated Fe
film is formed, are likewise effective as the catalyst.
Accordingly, it can be regarded that a substance that contains at
least Fe-atoms and Sn-atoms works as a catalyst for manufacturing
CNC, even in cases where In-atoms and further other atoms are added
to it. This fact is also true at least for a multi-component type
catalyst containing Co-atoms and Sn-atoms, and also a
multi-component type catalyst containing Ni-atoms and In-atoms.
[0067] Even organic-metallic compounds containing organic-metallic
complexes as a metallic-source material are effective as the
catalysts for manufacturing carbon substances. For example, in the
case of a 2-component type catalyst of Fe.quadrature.Sn, a thin
film of a mixture of an organic-iron compound and an organic-tin
compound is formed on the surface of a substrate, and next the film
is broken down to remove organic components therefrom by means of
calcination method, thus obtaining a thin film of the mixture of
iron and tin. By calcination in the air, Fe and Sn are oxidized and
turned into Fe.sub.2O.sub.3 and SnO.sub.2. The Fe.Sn catalyst thus
produced works well as the catalyst for manufacturing carbon
nanocoils. It is same for another 2-component type catalysts.
Furthermore, from an organic-iron compound and an organic-cobalt
compound, a mixing catalyst of Fe.sub.2O.sub.3 and CoO is formed by
calcination method in the air.
[0068] Organic-metallic compounds containing organic-metallic
complexes may be used as raw materials in the composition of
3-component type catalysts. For example, in the composition of
3-component type catalysts consisting of Fe.Sn.In, a thin film is
formed on the surface of a substrate, using the mixture of an
organic-iron compound, an organic-tin compound and an
organic-indium compound. By calcinating the substrate and by
breaking down to remove all organic components from the substrate,
a metallic catalyst of the mixture of residual iron, tin and indium
is obtained. It was found that this 3-component type catalyst
composed of Fe.Sn.In also acts as the catalyst for manufacturing
CNC.
[0069] In a case where a pure metal or an organic-metallic compound
is used as a raw material, since the metals contained in the raw
materials are not oxidized by calcination in an inactive gas, a
mixed catalyst of pure metals is produced. However, in a case of
calcination in the air, the metals are finally oxidized, then a
mixed catalyst of metallic-oxides is obtained. As described above,
both of the mixed catalyst of pure metals and the mixed catalyst of
metallic-oxides act as the catalyst for manufacturing carbon
substances such as CNC, CNT or CNP.
[0070] In order to pile up metal films in layers, various
well-known methods may be used, such as a vacuum evaporation
method, a spattering method, an ion-plating method, a chemical
vapor deposition (CVD) method, an electric plating method, an
electroless plating method, etc.
[0071] Most simple method to form films is a paste painting method.
In this method, first, a metallic paste containing metallic raw
materials is made, next the paste is painted on a substrate by
means of a screen-printing method. Finally, by calcinating the
substrate to break down and to remove out unnecessary organic
components, a metallic film or a metallic oxide film is thus
produced.
[0072] In this paste method, metallic powders, metal-oxide powders
and organic-metallic compound powders (organic-metallic complex
powders are also included) are used as metallic raw materials, and
these materials are mixed with resin and organic solvent in order
to make the metallic paste with suitable viscosity. Subsequently,
by painting the metallic paste on substrates and by calcinating
them, metallic films or metallic oxide films are formed.
[0073] A 2-component type catalyst can be straightforwardly
produced by calcinating a substrate painted with metallic paste
which is mixed together with two metallic raw materials. However,
even in the case where making two kinds of pastes for each
metallic, and painting the two pastes to pile up in layers on a
substrate, after that, by calcinating it, a 2-component type
catalyst can be produced. These two methods or the modified methods
can be applied to production of 3-component and multi (more than
3)-component type catalysts.
EMBODIMENTS
First Embodiment
[0074] Production of 2-component type catalysts and experiments of
synthesis of carbon substances
[0075] In this embodiment, twelve kinds of 2-component type
catalysts were produced on the surfaces of substrates, and next,
carbon substances were formed on the surfaces of the twelve kinds
of catalysts by means of a vapor phase growth method. Subsequently,
the effect of the catalysts was evaluated by observing the grown
carbon substances by an electron microscope.
[0076] The above-mentioned twelve kinds of the 2-component type
catalysts comprises a first component (Fe, Co or Ni) and a second
component (Sn or In), where the first component is pure a metallic
powder or a metallic oxide powder, and the second component is also
a pure metallic powder or a metallic oxide powder. For example, Co
is a pure metallic powder, and Fe.sub.2O.sub.3 is a metallic oxide
powder. The discrimination of a pure metal and a metallic oxide is
shown in the catalyst symbol in the case of Fe.Co.Ni.
TABLE-US-00001 TABLE 1 Composition of 2-component type catalysts
Fist component Second component Catalyst symbol Fe Sn or SnO.sub.2
Fe.cndot.Sn Fe In or In.sub.2O.sub.3 Fe.cndot.In Fe.sub.2O.sub.3 Sn
or SnO.sub.2 Fe.sub.2O.sub.3.cndot.Sn Fe.sub.2O.sub.3 In or
In.sub.2O.sub.3 Fe.sub.2O.sub.3.cndot.In Co Sn or SnO.sub.2
Co.cndot.Sn Co In or In.sub.2O.sub.3 Co.cndot.In CoO Sn or
SnO.sub.2 CoO.cndot.Sn CoO In or In.sub.2O.sub.3 CoO.cndot.In Ni Sn
or SnO.sub.2 Ni.cndot.Sn Ni In or In.sub.2O.sub.3 Ni.cndot.In NiO
Sn or SnO.sub.2 NiO.cndot.Sn NiO In or In.sub.2O.sub.3
NiO.cndot.In
[0077] By dispersing the mixed powders of the first component and
the second component in an organic solvent, further to which some
amount of resin was added, then a metallic paste with suitable
viscosity was made. The component ratio of the metallic paste was
arranged so that the first component:the second component:the
resin:the organic solvent=1:1:1:6 (weight ratio).
[0078] The metallic paste thus made was painted on an alumina
substrate to make a 0.5 mm thick film, and was desiccated at a
temperature 150.degree. C. for one hour. Subsequently the metallic
paste was calcinated in the air at a temperature 580.degree. C. for
three hours. By this calcination, unnecessary organic substances
was removed, a thin film of the mixed composition of the first
component and the second component was formed. This thin film
composition is the 2-component type catalyst related to the present
invention.
[0079] The next experiment was to grow carbon substances on the
surfaces of the twelve kinds of the substrates. FIG. 1 is a
schematic structural diagram of the carbon nanocoil manufacturing
apparatus of the present invention. This manufacturing apparatus 2
is a flow reactor placed under atmospheric pressure, a reaction
chamber 4 is surrounded by a quartz tube 6 which has a diameter of
130 mm and a length of 150 mm.
[0080] A tube-form heater 8 having a length of 1100 mm is installed
around the outer circumference of the central portion of the quartz
tube 6, and the center of the reaction chamber 4 is set in an
isothermic region 10 over a length of approximately 200 mm. A
quartz boat 14 is disposed in this isothermic region 10; and on the
upper surface of the quartz, a growth substrate 12 is disposed.
This catalyst substrate 12 comprises an almina substrate 16 and a
catalyst layer 18 that is formed in a form of a thin film on the
surface of the almina substrate 16.
[0081] First, the interior of the quartz tube 6 is filled with
helium gas, and the temperature of the growth substrate is raised
to 700.degree. C. at a temperature rising rate of 15.degree. C. per
minute. This helium gas is introduced in order to prevent the metal
from being oxidized inside the reaction chamber. After the
temperature reached at 700.degree. C., a part of the helium gas is
replaced with acetylene, and the mixed gas of a flow rate 5.0 SLM
of helium and a flow rate 1.5 SLM of acetylene is flowed for 30
minutes.
[0082] The acetylene is pyrolyzed on the surface of the catalyst
substrate 12, and a carbon component grows as a carbon substance 20
by catalysis. In FIG. 1, CNC is shown as the carbon substance 20.
After the reaction time 30 minutes, the acetylene is cut off, so
that only helium is caused to flow, and the catalyst substrate is
gradually cooled to room temperature in this helium atmosphere.
[0083] Though acetylene was used as the gas for manufacturing the
carbon substance, various gases may be available such as not only
methane, ethane, but also alkane, alkene, alkine, aromatic
hydrocarbon, etc. In particular, acetylene, alkylene, benzene, etc.
are valid, and among them, acetylene is especially suitable.
[0084] As for heating temperature, a temperature higher than the
catalytic decomposition temperature of hydrocarbon is effective.
Though the pyrolysis temperature of acetylene is approximately
400.degree. C., the suitable temperature for synthesis of carbon
nanocoils is approximately 600-800.degree. C. However, the
synthesis temperature is not necessarily limited in the region but
can be freely set according to a production rate, provided that the
temperature being higher than the catalytic decomposition
temperature of hydrocarbon.
[0085] The catalyst substrate 12 taken out from the reaction
chamber was observed by a scanning type electron microscope
(JSM-T20, made by Nihon Densi Co.). The magnification rate of the
electron microscope always was 10,000 in all the observations.
Since the carbon substances produced by the present invention are
of nanosize (nanocarbon substance), a 1000 nm scale is shown in
Figures for comparison. Since the results of the observations of
Fe.Sn and Fe.In are almost same as the results of
Fe.sub.2O.sub.3.Sn and Fe.sub.2O.sub.3.In, the microscope images
are omitted.
[0086] FIGS. 2 through 11 show the images of the carbon substances
observed by the magnification 10,000 electron microscope and each
one of the Figures is accompanied by a 1000 nm scale. FIG. 2 shows
the image of the carbon substances by the catalyst
Fe.sub.2O.sub.3.Sn; FIG. 3, by the catalyst Fe.sub.2O.sub.3.In;
FIG. 4, by the catalyst Co.Sn; FIG. 5, by the catalyst Co.In; FIG.
6, by the catalyst CoO.Sn; FIG. 7, by the catalyst CoO.In; FIG. 8,
by the catalyst Ni.Sn; FIG. 9, by the catalyst Ni.In; FIG. 10, by
the catalyst NiO.Sn; and FIG. 11, by the catalyst NiO.In,
respectively.
[0087] As seen from these electron microscope images, CNC (large)
and CNT were mainly produced by the catalyst Fe.Sn; CNP, by the
catalyst Fe.In; CNC (large) and CNT, by the catalyst
Fe.sub.2O.sub.3.Sn; CNP, by the catalyst Fe.sub.2O.sub.3.In; CNC
(small) and CNT, by the catalyst Co.Sn; CNT, by catalyst Co.In; CNC
(large) and CNT, by the catalyst CoO.Sn; CNT, by CoO.In; CNT, by
the catalyst Ni.Sn; CNC and CNT, by the catalyst Ni.In; CNT, by the
catalyst NiO.Sn; CNT and CNT, by the catalyst NiO.In, respectively.
These results are summarized in Table 2. TABLE-US-00002 TABLE 2
2-component type catalysts and carbon substances Catalyst symbol
Produced carbon substance Fe.cndot.Sn CNC (large) + CNT Fe.cndot.In
CNP Fe.sub.2O.sub.3.cndot.Sn CNC (large) + CNT
Fe.sub.2O.sub.3.cndot.In CNP Co.cndot.Sn CNC (small) + CNT
Co.cndot.In CNT CoO.cndot.Sn CNC (large) + CNT CoO.cndot.In CNT
Ni.cndot.Sn CNT Ni.cndot.In CNC + CNT NiO.cndot.Sn CNT NiO.cndot.In
CNC + CNT
[0088] As seen from Table 2, the catalyst for manufacturing CNC are
Fe.Sn, Fe.sub.2O.sub.3.Sn, Co.Sn, CoO.Sn, Ni.In and NiO.In, and as
the 2-component type catalysts, there exist three groups of Fe.Sn,
Co.Sn and Ni.In. At the present stage, CNC and CNT grow together in
a mixing state, and 100% yield of CNC alone is difficult. It is
necessary in future to research and develop the 100% production
method and the isolation method of CNC from CNT.
[0089] On the other hand, since CNP grows up by Fe.In and
Fe.sub.2O.sub.3.In at the yield rate of 100%, the group of Fe.In
becomes the catalyst for manufacturing CNP. Beside, since CNT grows
up by Co.In, CoO.In, Ni.Sn, NiO.Sn at the yield rate of 100%, the
two groups of Co.In and Ni.Sn can be the catalyst for manufacturing
CNT.
[0090] FIG. 12 is a graph showing different external diameters of
carbon nanocoils which grow by the catalyst CoO.Sn. The external
diameters differ in a range of 0.1-0.9 .mu.m, i.e., 100-900 nm and
the maximum frequency value is 0.3 .mu.m, i.e., 300 nm.
[0091] FIG. 13 is a graph showing different external diameters of
carbon nanocoils which grow by the catalyst Ni.In. The external
diameters differ in a range of 0.25-0.40 .mu.m, i.e., 250-400 nm
and the maximum frequency value is 0.30 .mu.m, i.e., 300 nm.
Second Embodiment
[0092] Production of 3-component type catalysts and experiments of
synthesis of carbon substances
[0093] In this second embodiment, six kinds of 3-component type
catalysts were produced on the surface of substrates. Next, carbon
substances were formed on the surfaces of the six kinds of these
catalysts. Then, the grown carbon substances were observed by an
electron microscope in order to evaluate the effect of the
catalysts.
[0094] The above-mentioned six kinds of 3-component type catalysts
comprise a first component, a second component and a third
component. An IOT substrate is used as the second component and the
third component, where the IOT is an abbreviation of
Indium-Tin-Oxide and is the mixed catalyst of In.sub.2O.sub.3 and
SnO.sub.2. Namely, the second component is In.sub.2O.sub.3 and the
third component is SnO.sub.2, so that both of In and Sn are
contained in the ITO.
[0095] The first component is a pure metallic powder or a
metallic-oxide powder. Metallic paste containing the first
component was painted on the ITO substrate. Afterward, by
calcinating the substrate, the 3-component type catalyst of the
first component thin film was formed on the ITO substrate. Since
the paste treatment method and the calcination method are same as
those of the first embodiment, the detail explanation will be
omitted. The catalysts are shown in Table 3. TABLE-US-00003 TABLE 3
Compositions of 3-component type catalysts. First component
Second-third components Catalyst symbols Fe ITO Fe.cndot.ITO
Fe.sub.2O.sub.3 ITO Fe.sub.2O.sub.3.cndot.ITO Co ITO Co.cndot.ITO
CoO ITO CoO.cndot.ITO Ni ITO Ni.cndot.ITO NiO ITO NiO.cndot.ITO
[0096] Next, these 3-component type catalysts are disposed in a
reaction chamber, and carbon substances was grown on the surface of
the catalysts by means of the same method as the first embodiment.
Then, the growing manner of nanocoils was observed by imaging the
catalyst surfaces by the scanning type electron microscope.
[0097] The respective images of the electron microscope are shown
in Figures; and the case of the catalyst Fe.sub.2O.sub.3.ITO is
shown in FIG. 14, the case of the catalyst Co.ITO in FIG. 15, the
case of the catalyst NiO.ITO in FIG. 16. The electron microscope
images for Fe.ITO, CoO.ITO and Ni.ITO are almost same as those in
FIGS. 14, 15 and 16, respectively, and these Figures are omitted.
The magnifications of all observations are set at 10,000 times, and
the 1000 nm scale is shown in each one of Figures.
[0098] As shown in FIGS. 14-16, a large quantity of CNC was
observed on all surfaces of the 3-component type catalysts, but
only a small quantity of CNT was seen. The external diameter of
observed carbon coils are less than 1000 nm, and all of these
carbon coils are regarded as carbon nanocoil. The results are shown
in Table 4 below.
[0099] As seen from Table 4, it seems that the 3-component type
catalysts give more yield of CNC than the 2-component type
catalysts. However, it cannot be concluded at present that the
3-component type catalysts are more effective than the 2-component
type catalysts. TABLE-US-00004 TABLE 4 3-component type catalysts
and carbon substances Catalyst symbol Produced carbon substance
Fe.cndot.ITO CNC (large) + CNT Fe.sub.2O.sub.3.cndot.ITO CNC
(large) + CNT Co.cndot.ITO CNC (large) + CNT CoO.cndot.ITO CNC
(large) + CNT Ni.cndot.ITO CNC (large) + CNT NiO.cndot.ITO CNC
(large) + CNT
[0100] The present invention is not limited to the embodiments
described above. Various modifications and design alternations,
etc. that involve no departure from the technical concept of the
present invention are also included in the technical scope of the
present invention.
[0101] As seen from the above, according to the present invention,
by selecting one of iron, cobalt and nickel of a first element
group and one of tin and indium of a second element group, the
catalyst for manufacturing carbon substances includes is formed
with at least the selected first element and the selected second
element. Accordingly, carbon substances of CNC, CNT, CNP, etc. can
be effectively produced.
[0102] The present invention, the catalyst for manufacturing carbon
substances comprises at least iron and tin or cobalt and tin.
Accordingly, CNC can be effectively produced as a carbon
substance.
[0103] In the present invention, the catalyst for manufacturing
carbon substances comprises at least nickel and indium.
Accordingly, CNC can be effectively produced as a carbon
substance.
[0104] In the present invention, the catalyst for manufacturing
carbon substances comprises at least cobalt, tin and indium or
nickel, tin and indium. Accordingly, CNC or CNT can be produced as
a carbon substance.
[0105] In the present invention, since iron, cobalt or nickel is
employed in oxide-states or in the form of iron-oxide,
cobalt-oxide, or nickel-oxide, respectively, when producing
catalysts for manufacturing carbon substances, these catalysts are
not oxidized any more when used in the air, so that stable
catalysts for manufacturing carbon substances are provided.
[0106] Furthermore, in the present invention, since the 3-component
type catalysts comprise cobalt.cndot.ITO or nickel.cndot.ITO, CNC
can be selectively manufactured with a high efficiency.
* * * * *