U.S. patent application number 10/040160 was filed with the patent office on 2003-06-12 for method for manufacturing indium-tin-iron catalyst for use in production of carbon nanocoils.
This patent application is currently assigned to YOSHIKAZU NAKAYAMA. Invention is credited to Harada, Akio, Nakayama, Yoshikazu.
Application Number | 20030109382 10/040160 |
Document ID | / |
Family ID | 27806863 |
Filed Date | 2003-06-12 |
United States Patent
Application |
20030109382 |
Kind Code |
A1 |
Nakayama, Yoshikazu ; et
al. |
June 12, 2003 |
METHOD FOR MANUFACTURING INDIUM-TIN-IRON CATALYST FOR USE IN
PRODUCTION OF CARBON NANOCOILS
Abstract
A method for manufacturing an indium-tin-iron type catalyst that
is used to obtain carbon nanocoils that have an external diameter
of 1000 nm or less, the method comprising a first process that
forms an organic solution by mixing an indium-containing organic
compound and a tin-containing organic compound with an organic
solvent, a second process that forms an organic film by coating a
substrate with the thus obtained organic solution, a third process
that forms an indium-tin film by baking this organic film, and a
fourth process that forms an iron film on the surface of this
indium-tin film.
Inventors: |
Nakayama, Yoshikazu;
(Hirakata-shi, JP) ; Harada, Akio; (Osaka-shi,
JP) |
Correspondence
Address: |
KODA & ANDROLIA
Suite 3850
2029 Century Park East
Los Angeles
CA
90067-3024
US
|
Assignee: |
YOSHIKAZU NAKAYAMA
DAIKEN CHEMICAL CO., LTD.
|
Family ID: |
27806863 |
Appl. No.: |
10/040160 |
Filed: |
October 26, 2001 |
Current U.S.
Class: |
502/336 |
Current CPC
Class: |
B01J 37/348 20130101;
Y10S 977/843 20130101; C01B 32/05 20170801; B01J 37/0219 20130101;
Y10S 977/746 20130101; B01J 23/825 20130101; D01F 9/127 20130101;
B01J 23/835 20130101; B01J 37/0244 20130101; B82Y 30/00
20130101 |
Class at
Publication: |
502/336 |
International
Class: |
B01J 023/825 |
Claims
1. A method for manufacturing an indium-tin-iron type catalyst
which is used to manufacture carbon nanocoils that have an external
diameter of 1000 nm or less, said manufacturing method comprising
the steps of: forming an organic solution by mixing an
indium-containing organic compound and a tin-containing organic
compound with an organic solvent, forming an organic film by
coating a substrate with said organic solution, forming an
indium-tin film by baking said organic film, and forming an iron
film on a surface of said indium-tin film.
2. The method according to claim 1, wherein said indium-tin film is
a mixed film of an indium oxide and a tin oxide.
3. The method according to claim 1, wherein said iron film is
formed on said surface of said indium-tin film by
electroplating.
4. A method for manufacturing an indium-tin-iron type catalyst
which is used to manufacture carbon nanocoils that have an external
diameter of 1000 nm or less, said manufacturing method comprising
the steps of: forming an organic solution by mixing an
indium-containing organic compound, a tin-containing organic
compound and an iron-containing organic compound with an organic
solvent, forming an organic film by coating a substrate with said
organic solution, and forming an indium-tin-iron film by baking
said organic film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for manufacturing
an indium-tin-iron type catalyst which is used for producing carbon
nanocoils that have an external diameter of 1000 nm or less and
more particularly to a method for manufacturing an indium-tin-iron
type catalyst for use in the production of carbon nanocoils which
allows inexpensive mass production by utilizing metal-containing
organic compounds and an organic solvent.
[0003] 2. Prior Art
[0004] The history of carbon nanocoils in which the external
diameter of the coil is on the order of nanometers is relatively
brief.
[0005] In 1994, Amelinckx et al. (Amelinckx, X. B. Zhang, D.
Bernaerts, X. F. Zhang, V. Ivanov and J. B. Nagy, SCIENCE, 265
(1994) 635) succeeded in producing carbon nanocoils. While carbon
microcoils discovered in the past have an amorphous structure, it
has been ascertained that carbon nanocoils have a graphite
structure. Various types of carbon nanocoils have been prepared,
and the smallest coil external diameter achieved so far is
extremely small, i.e., approximately 12 nm. However, the coil yield
is small, and such a method cannot be utilized in industrial
production. Accordingly, there has been a demand for a more
efficient method of manufacture of nanocoils.
[0006] In the manufacturing method used by the above researchers, a
metal catalyst such as Co, Fe or Ni is formed into a very fine
powder, the area in the vicinity of this catalyst is heated to a
temperature of 600 to 700.degree. C., an organic gas such as
acetylene or benzene is caused to flow through so that the gas
contacts the catalyst, and then the organic molecules are broken
down. The carbon nanocoils that are produced have various shapes,
and these shapes are merely produced at random.
[0007] 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 anew in producing carbon nanocoils. In the method used by
these researchers, a catalyst formed by covering the surface of a
graphite sheet with iron particles is placed in the center of the
reaction vessel, and the area in the vicinity of this catalyst is
heated to 700.degree. C. by means of a nichrome wire. A mixed gas
consisting of 10% acetylene and 90% nitrogen by volume is then
caused to flow through so that the gas contacts the catalyst.
However, in this manufacturing method as well, the rate of coil
production is small, and thus this method is extremely inadequate
as an industrial mass production method.
[0008] Under such conditions, the present inventors discovered a
method for the mass production of carbon nanocoils at the end of
1999. This method is disclosed in Japanese Patent Application No.
11-377363.
[0009] In this method, an indium-tin-iron type catalyst is placed
inside a reaction vessel, the area in the vicinity of this catalyst
is heated to a temperature that is equal to or greater than the
temperature at which a hydrocarbon gas is broken down by the
catalyst, and a hydrocarbon gas is caused to flow through so as to
contact the catalyst, thus causing the growth of carbon nanocoils
on the surface of the catalyst. The production rate of this method
is a maximum of 95% or greater. Thus, this method allows the mass
production of carbon nanocoils.
[0010] The core of the above-described manufacturing method lies in
the indium-tin-iron type catalyst. The lowering of the
manufacturing cost of carbon nanocoils is determined by how
inexpensively the indium-tin-iron type catalyst can be provided.
The present inventors prepared an indium-tin-iron type catalyst by
vacuum-evaporating an iron film on a commercially marketed ITO
(indium-tin-oxide) substrate. Since the ITO substrate is expensive,
and since the catalyst is prepared by the vacuum evaporation of
iron, which is a method unsuited to mass production, the resulting
indium-tin-iron type catalyst is extremely expensive.
[0011] ITO substrates are transparent substrates which consist of
an indium oxide and tin oxide and possess electrical conductivity
and a high light transmissivity. Such substrates have been adapted
for practical use as industrial materials which are indispensable
in opto-electronics, etc. The high cost of such ITO substrates is
attributable to the method used to manufacture these substrates.
There are three main manufacturing methods.
[0012] The first method is a spray method. In this method, a mixed
solution consisting of InCl.sub.3, SnCl.sub.4, H.sub.2O, HCl and an
alcohol is sprayed onto a substrate, and this substrate is then
baked at approximately 500.degree. C. In this method, chlorine type
gases are generated in the baking process. Thus, problems such as
contamination of the environment and corrosion of the apparatus,
etc. occur.
[0013] The second method is a CVD (chemical vapor deposition)
method. In this method, an In chelate and dibutyltin diacetate are
used as raw materials, and manufacture is accomplished by CVD
method using N.sub.2 gas as a carrier at a substrate temperature of
approximately 500.degree. C. Since this method is performed inside
a sealed vessel, it is unsuitable for mass production.
[0014] The third method is a vacuum evaporation method. In this
method, In and Sn are used as evaporation sources, and vacuum
evaporation for formation is performed at a substrate temperature
of approximately 400.degree. C. Since the operation is performed
inside a vacuum apparatus, it is not suitable for mass
production.
[0015] Thus, since conventional indium-tin-iron type catalysts are
manufactured by the vacuum evaporation of iron on an expensive ITO
substrate, the manufacturing cost is high, and then mass production
is impossible. As a result, the inexpensive mass production of
carbon nanocoils is considered impossible.
SUMMARY OF THE INVENTION
[0016] Accordingly, the object of the present invention is to
realize the mass production of carbon nanocoils and a reduction in
the cost of carbon nanocoils by establishing an inexpensive method
for the mass production of an indium-tin-iron type catalyst.
[0017] The above object is accomplished by the unique manufacturing
method of the present invention for manufacturing an
indium-tin-iron type catalyst which is used to produce carbon
nanocoils that have an external diameter of 1000 nm or less,
wherein the manufacturing method comprises:
[0018] a first process that forms an organic solution by mixing an
indium-containing organic compound and a tin-containing organic
compound with an organic solvent,
[0019] a second process that forms an organic film by coating a
substrate with the thus obtained organic solution,
[0020] a third process that form an indium-tin film by baking this
organic film, and
[0021] a fourth process that forms an iron film on the surface of
the indium-tin film.
[0022] In the above method, the indium-tin film is a mixed film of
an indium oxide and a tin oxide.
[0023] Furthermore, in the above fourth process, the iron film on
the surface of the indium-tin film is formed by electroplating.
[0024] The above object is further accomplished by another unique
manufacturing method of the present invention for manufacturing an
indium-tin-iron type catalyst which is used to produce carbon
nanocoils that have an external diameter of 1000 nm or less,
wherein the manufacturing method comprises:
[0025] a first process that forms an organic solution by mixing an
indium-containing organic compound, a tin-containing organic
compound and an iron-containing organic compound with an organic
solvent,
[0026] a second process that forms an organic film by coating a
substrate with the thus obtained organic solution, and
[0027] a third process that forms an indium-tin-iron film by baking
the organic film.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The inventors of the present application conducted diligent
research in order to realize an inexpensive indium-tin-iron type
catalyst. As a result, the inventors created a method in which an
indium-tin-iron type catalyst is firmly formed and carried on a
substrate by way of dissolving metallo-organic compounds in an
organic solvent, coating the substrate with the resulting organic
solution and then baking this coating.
[0029] The method of the present invention for manufacturing an
indium-tin-iron type catalyst is in fact comprised of two
methods.
[0030] The first method comprises a first process in which an
organic solution is formed by mixing an indium-containing organic
compound and a tin-containing organic compound with an organic
solvent, a second process in which an organic film is formed by
coating a substrate with this organic solution, a third process in
which an indium-tin film is formed by baking this organic film, and
a fourth process in which an iron film is formed on the surface of
this indium-tin film.
[0031] The second method comprises a first process in which an
organic solution is formed by mixing an indium-containing organic
compound, a tin-containing organic compound and an iron-containing
organic compound with an organic solvent, a second process in which
an organic film is formed by coating a substrate with this organic
solution, and a third process in which an indium-tin-iron film is
formed by baking this organic film.
[0032] As the indium-containing organic compound, tin-containing
organic compound and iron-containing organic compound used in the
present invention, known organo-metallic compounds are employed.
Examples of such compounds include, among others, trimethylindium,
triphenylindium, indium octylate, indium carboxylate, triethyltin,
trimethyltin, tetraphenyltin, tin octylate, tin carboxylate, iron
carboxylate, iron carbonyl, iron carbonyl derivatives, iron
nitrosyl and iron nitrosyl derivatives. Various other types of
known organo-metal complexes, etc. may also be used.
Metallo-organic compounds that are soluble in organic solvents are
especially useful.
[0033] The organic solvents that are used in the present invention
include known organic solvents such as acetone, toluene, benzene
and alcohols. Organic solvents that can dissolve indium-containing
organic compounds, tin-containing organic compounds and
iron-containing organic compounds are especially useful.
[0034] In the present invention, an indium-containing organic
compound and a tin-containing organic compound, or an
indium-containing organic compound, a tin-containing organic
compound and an iron-containing organic compound, are dissolved in
an organic solvent. Then, this solution is applied as a coating to
the surface of a substrate such as a plate or tube, etc.,
consisting of a glass, ceramic, etc., and the solvent is evaporated
so that an organic film is formed on the substrate.
[0035] Coating methods that can be used in the present invention
include various types of methods such as dipping of the substrate
in the organic solution, brush coating of the substrate, spraying
onto the substrate, and spin-coating on the substrate, etc.
[0036] Furthermore, a method such as heat-drying, natural air draft
drying, warm air draft drying or hot air draft drying is used in
the present invention to dry the substrate following the coating
process.
[0037] Next, the above-described organic film is baked so that the
organic component is broken down and dispersed, thus forming an
indium-tin film or indium-tin-iron film on the surface of the
substrate. The baking temperature is set at a temperature that is
equal to or greater than the decomposition temperatures of the
metallo-organic compounds. Accordingly, the baking temperature
depends on the types of metallo-organic compounds used. Generally,
a temperature of 400.degree. C. to 800.degree. C. is desirable.
[0038] In one case, the indium-tin film is constructed from
metallic indium and metallic tin; and in another case, it is
constructed from an indium oxide and a tin oxide. The former film
is comprised of a metallic body, while the latter case results in a
so-called ITO substrate.
[0039] In the indium-tin-iron film, there may be cases in which
this film is comprised of a metallic body constructed from metallic
indium, metallic tin and metallic iron and cases in which the film
comprises a mixed metal oxide body constructed from an indium
oxide, tin oxide and iron oxide. Such an indium-tin-iron film
functions "as is" as an indium-tin-iron type catalyst.
[0040] The indium-tin-iron type catalyst is completed by forming an
iron film on the surface of the indium-tin film. Methods that can
be used to form this iron film include various types of known
methods such as physical vacuum evaporation, CVD and sputtering.
Among such methods, however, electroplating, which is efficient and
inexpensive, is especially effective. Furthermore, the iron film in
the present invention may also be formed by way of coating the
surface of the indium-tin film with an organic solution of an
iron-containing organic compound and then baking the resulting
film. In other words, such a method is a two-stage baking method
that involves the indium-tin film and the iron film.
[0041] There are no particular restrictions on the thickness of the
indium-tin film. For instance, the thickness may range from 10 nm
to several microns. It is also preferable that the thickness of the
iron film that is formed on top of the indium-tin film be small so
that the underlying indium-tin film can contribute to the formation
of the carbon nanocoils. For instance, the iron film has a
thickness of 5 nM to 100 nM though the thickness is not limited to
this range of numerical values. In the case of an indium-tin-iron
film, the surface of the film contributes to the formation of
carbon nanocoils. Accordingly, there are no restrictions on the
thickness of the film. In other words, the thickness may range, for
example, from 10 nm to several microns (m).
[0042] Below, examples of the method of the present invention for
manufacturing an indium-tin-iron type catalyst for use in the
production of carbon nanocoils will be described in detail.
FIRST EXAMPLE
Catalyst Consisting of Indium-Tin Film and Iron Film
[0043] 8.1 g of indium octylate and 0.7 g of tin octylate were
mixed with 100 ml of toluene, and these were uniformly dissolved by
way of applying an ultrasonic vibration. This organic solution was
applied to a glass plate with a brush and then dried with a warm
air draft, thus forming an organic film. The obtained organic film
was baked by placing this glass substrate in a heating furnace at
500.degree. C. for 20 minutes. The organic component was thus
pyrolyzed, and an indium-tin film was formed. The thickness of this
indium-tin film was 300 nm. Furthermore, with this glass substrate
used as a cathode, the surface of the indium-tin film was
electroplated with iron, thus producing an indium-tin-iron type
catalyst. The thickness of the iron film that was formed was 50
nm.
[0044] The substrate on which the indium-tin-iron type catalyst was
formed was placed in a quartz tube. The tube was filled with helium
gas, and the temperature in the vicinity of the substrate was
elevated to 700.degree. C. After the temperature reached
700.degree. C., 1/3 of the helium was replaced with acetylene gas,
and the mixed gas was caused to flow through for one hour at a flow
rate of 250 sccm. Afterward, the acetylene was cut off, so that
only helium was caused to flow through, and the reaction system was
cooled to room temperature.
[0045] The glass substrate was observed under a scanning electron
microscope, and countless carbon nanocoils were observed on the
surface of the iron film. It was found from the weight ratio of the
amount of acetylene used and the carbon nanocoils produced that the
coil yield was 90%. Since the maximum yield obtained in
conventional ITO substrate was used was 95%, it is determined that
the indium-tin-iron type catalyst prepared in the First Example can
be used for the inexpensive mass production of carbon
nanocoils.
SECOND EXAMPLE
Catalyst Consisting of Indium-Tin-Iron Film
[0046] 8.1 g of indium octylate, 0.7 g of tin octylate and 0.7 g of
iron octylate were mixed with 100 ml of toluene, and these were
uniformly dissolved by way of applying an ultrasonic vibration.
This organic solution was sprayed onto a glass plate and dried by
means of a natural air draft from a fan, thus forming an organic
film. The obtained organic film was baked by way of placing the
glass substrate in a heating furnace at 450.degree. C. for 30
minutes. The organic component was thus pyrolyzed so that a
catalyst consisting of an indium-tin-iron film was produced. The
thickness of this indium-tin-iron film was 400 nm.
[0047] The substrate on which this indium-tin-iron type catalyst
was formed was placed inside a quartz tube, and carbon nanocoils
were produced by the same method as in the First Example. When the
glass substrate was observed under a scanning electron microscope,
countless carbon nanocoils were observed on the surface of the
film. It was found that the coil yield was 85%. Accordingly, it is
determined that the indium-tin-iron type catalyst prepared in the
Second Example can be used for the inexpensive mass production of
carbon nanocoils.
[0048] The present invention is indeed not limited to the above
Examples. Various modifications, design changes, etc. that involve
no departure from the technical concept of the present invention
are included in the technical scope of the present invention.
[0049] As seen from the above, in the present invention, an
indium-tin film is formed merely by coating a substrate with an
organic solution of an indium-containing organic compound and a
tin-containing organic compound and then by baking this coating.
Consequently, an indium-tin-iron type catalyst can be mass-produced
simply and inexpensively. A reduction in the manufacturing cost of
carbon nanocoils and mass production of such carbon nanocoils are
as a result realized.
[0050] In the present invention, the indium-tin film is a mixed
film of an indium oxide and a tin oxide. Thus, the physical
structure is substantially the same to that of a conventional ITO
substrate. By way of forming an iron film on top of this mixed
film, the conventional maximum yield of 95% obtained using an ITO
substrate can be realized.
[0051] Furthermore, an iron film is formed on the surface of the
indium-tin film by electroplating. Accordingly, an indium-tin-iron
type catalyst can be manufactured very inexpensively and in large
quantities. As a result, the manufacturing cost of carbon nanocoils
is reduced, and mass production of such carbon nanocoils is
realized.
[0052] In addition, an indium-tin-iron film can be formed on a
substrate in a single operation merely by coating the substrate
with an organic solution of an indium-containing organic compound,
a tin-containing organic compound and an iron-containing organic
compound, and then by baking this coating. As a result, an
indium-tin-iron type catalyst is produced inexpensively and in
large quantities. Accordingly, the manufacturing cost of carbon
nanocoils is reduced, and such carbon nanocoils can be
mass-produced.
* * * * *