JP2000204471A - Metallic fine wire and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fine wire stock having a specified diameter and a specified ratio of the diameter to the major axis length and having a uniform crystal structure in which major axis length is long and axial ratio is high by forming cylindrical carbon on the inner walls of fine pores each having an almost rectangular shape in an inorganic material and precipitating metal on the inside. SOLUTION: An inorganic material 2 consisting of an anodically oxidized film of aluminum, zeolite or the like having fine pores 1 of an almost rectangular shape is prepared as a formwork. Next, a cylindrical carbon tube 3 is formed on the inner wall of the fine pore 1. This carbon tube 3 is formed by coating the inner wall of the fine pore with an organic compd., thereafter executing heating to carbonize it, or carbonizing gaseous hydrocarbon in vapor phase into the fine pore. Into the carbon tube 3, transition metal such as nickel is precipitated by using an organometallic compd. such as nickelocene to form a metallic fine wire 4, and after that, the inorganic material 2 is melted away. In this way, the metallic fine wire of 1 to 100 nm diameter, in which the ratio of the diameter to the major axis is >=50 and coated with the carbon tube 3 of 10 nm to 1 μm diameter and 1 to 100 μm major axis length can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thin metal wire and a method for producing the same.

[0002]

2. Description of the Related Art Fine metal wires having a large axial ratio are made of various materials such as electrically conductive materials, quantum wire devices, ultra-high-speed electrical devices, ultra-high-density magnetic recording media, and nonlinear optical materials due to their special shapes. It is expected to be used in the field.

[0003] On the other hand, similar to such a thin metal wire, a fine tube made of carbon is expected to have various applications due to its special shape. Such a carbon tube is manufactured by arc discharge of a graphite electrode, a gas phase pyrolysis method, or the like, but only a tube having a very small size such as a diameter can be manufactured. Further, in order to produce a carbon tube having a large diameter, a carbon tube in which a flame-retardant polyacrylonitrile (hereinafter referred to as PAN) -based carbon fiber is heat-treated to be hollow is also known ("Carbon", 1992, 155). No. 307, etc.).

[0004] Then, for the purpose of imparting new characteristics, attempts have been made to deposit a thin wire-like foreign substance in a carbon tube and to include the foreign substance in the carbon tube.

[0005]

However, when such a carbon tube is manufactured by an arc discharge or a gas phase pyrolysis method, it is difficult to obtain a tube having a uniform diameter, and it is necessary to increase the diameter of the tube. It is difficult. Furthermore, since the carbon tube manufactured by this method is obtained in a state where both ends of the tube are closed, it is necessary to deposit foreign substances after opening both ends or one end of the carbon tube by an oxidation treatment or the like.

When a carbon tube is manufactured by heat-treating a flame-resistant PAN-based carbon fiber, PA
Since the diameter of the N-based carbon fiber itself is on the order of microns, the resulting carbon tube can only be obtained on the order of microns, and the obtained carbon tube can only be obtained with knots.

[0007] Then, even if the metal as the foreign substance is precipitated in such a carbon tube to obtain a metal thin wire in which a metal thin wire material is included in the carbon tube, the above-described method is used. It is difficult to deposit the metal uniformly throughout the carbon tube, and the resulting fine wire material also has knots and breaks,
The major axis length was short and very fine.

[0008] Further, when this metal wire is used for the above-mentioned applications, the crystal structure of the wire material is considered to have a great influence on its characteristics, but a material having a uniform crystal structure has not yet been obtained. Did not.

The present invention has been proposed in view of such conventional circumstances, and has a long major axis length, a large axial ratio, and a thin metal wire using a thin wire material having a uniform crystal structure and its production. The aim is to provide a method.

[0010]

According to the present invention, there is provided a thin metal wire having a diameter of a cross section substantially perpendicular to the major axis direction of 1 nm to 100 nm and a ratio of the diameter of the cross section to the major axis length of 50 or more. Material is used. The fine metal wire according to the present invention as described above has a very large axial ratio despite being fine, and can provide advantageous characteristics.

Further, the method for producing a thin metal wire according to the present invention comprises a first step of forming a tubular carbon on the inner wall of a pore of an inorganic substance having a substantially straight pore, and a step of forming the tubular carbon in the first step. A second step of depositing a metal inside the carbon formed into a shape
At least.

In the method for manufacturing a thin metal wire according to the present invention as described above, the thin wire material can be uniformly and stably deposited in the tubular carbon.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a thin metal wire and a method for manufacturing the same according to the present invention will be described.

The thin metal wire according to the present invention is a thin wire material having a diameter of a cross section substantially perpendicular to the long axis direction of 1 nm to 100 nm and a ratio of the diameter of the cross section to the long axis length of 50 or more. ing. And this fine wire material is included in the carbon tube. This carbon tube is disclosed in JP-A-8-151207 according to the invention of the present inventors.

That is, the carbon tube containing the fine wire material has a diameter of 10 nm to 1 μm and a length of 1 μm.
１００100 μm. The carbon tube is manufactured using an inorganic substance 2 having substantially linear pores 1 as a mold as shown in FIG.

As described above, the inorganic substance 2 having substantially linear pores 1 serving as a mold for a carbon tube includes:
Examples include anodized films of various metals, clay minerals such as zeolite and sepiolite. As the zeolite, those of type L are suitable. Particularly preferable examples of the above substances include an anodized aluminum film. The diameter of the pores of the aluminum anodic oxide film may be controlled according to a conventional method. For example, the condition is such that the higher the voltage (higher current density), the larger the diameter of the pores. Further, as an electrolytic solution used for forming the aluminum anodic oxide film, any of an acidic electrolytic solution and an alkaline electrolytic solution may be used. As the acidic electrolyte, sulfuric acid, oxalic acid, chromic acid, phosphoric acid, etc. are mainly used,
In this order, the diameter of the pores 1 increases.

Then, as shown in FIG. 1B, carbon is formed on the inner wall of the pores 1 of the inorganic substance 2 to form a carbon tube 3 inside the pores 1. As a method of forming carbon on the inner wall of the pores 1 of the inorganic substance 2, a method of coating the inner wall of the pores 1 with an organic compound and then carbonizing the organic compound by heating is used.

In this case, the organic compound used must be capable of liquefaction. Examples of the liquefaction method include raising the temperature and dissolving in a solvent. Specifically, as the solvent for dissolving the organic compound,
Furfuryl alcohol, polyvinyl alcohol, polyacrylonitrile, vinyl acetate, a partial polymer thereof, pitch of coal and petroleum, acenaphthylene, and the like can be mentioned.

The organic compound is brought into contact with the above-mentioned inorganic substance 2 to fill the pores 1 of the inorganic substance 2. When the organic compound is filled in the pores 1 of the inorganic substance 2, it is preferable to reduce the pressure in advance so that the organic compound can easily enter the pores.

Then, the inorganic substance 2 filled with the organic compound is heated to carbonize the organic compound, whereby a carbon tube 3 is formed on the inner wall of the pore 1. The heating temperature at the time of carbonizing the organic compound may be selected within a range where carbonization of the organic compound occurs, but there is no possibility that the inorganic substance 2 is destroyed or the inorganic substance 2 reacts with the organic compound. When an aluminum anodic oxide film is used as the inorganic substance 2, the temperature is preferably 500 ° C. to 1300 ° C., and when zeolite or sepiolite is used, 5 ° C.
00 ° C to 1000 ° C is preferred. If the temperature is lower than this range, carbonization of the organic compound does not easily progress.

As another method for forming carbon on the inner wall of the pores 1 of the inorganic substance 2, a gaseous hydrocarbon is carbonized in a gas phase, and a chemical vapor deposition (CVD) method is used.
a method of depositing a carbon film on the inner wall of the pore 1 by apor deposition.

In this case, the inorganic substance 2 used as the mold of the carbon tube 3 is a plate-like or thin-film-like inorganic substance, and the substantially linear pores 1 are continuous in the thickness direction. It is preferable to use one in which both ends of the hole 1 are open to the outside. By using the inorganic substance 2 having such a shape,
The gaseous hydrocarbon can be easily passed through the inside of the pores 1.
As such an inorganic substance 2, for example, "Anodis
c "(aluminum anodic oxide film manufactured by Whatman Paper Co., Ltd.) and the like.

As the gaseous hydrocarbon, it is preferable to use gaseous hydrocarbons at normal temperature, such as methane, ethane, propane, propylene, benzene and ethylene.
Such a gaseous hydrocarbon is usually circulated so as to be in contact with the inorganic substance 2 together with the carrier gas. The flow rate at this time is not particularly limited because it differs depending on the length of the pores 1 (thickness of the thin film) and the diameter of the pores 1. However, when the concentration of the gaseous hydrocarbon is high, or when the residence time is long, etc. Since the carbon tube may not be obtained, it is preferable to appropriately adjust the gaseous hydrocarbon flow conditions.

As described above, carbon is deposited on the inner wall of the pores 1 of the inorganic substance 2 to obtain the carbon tube 3. Then, as shown in FIG. 1 (c), by depositing a metal material in the carbon tube 3 formed in the pores 1 of the inorganic substance 2, the thin wire material 4 is included in the carbon tube 3.

As a material of the fine wire material 4, a transition metal is used. In particular, it is preferable to use an iron group metal among the transition metals. Here, the iron group metal is a metal belonging to the first transition series among the group VIII elements in the periodic table, and specifically, iron (Fe), cobalt (C
o) and nickel (Ni). Among them, it is particularly preferable to use nickel. By using nickel as the material of the fine wire material 4, nickel (111)
Surface is oriented substantially parallel to the longitudinal direction of the fine wire material 4,
The characteristics when the thin wire material 4 is used as a magnetic material or an electrically conductive material can be improved.

As a method of inserting the fine wire material 4 into the carbon tube 3, a metal material is made into a gaseous state by heat or the like, and a metal organic chemical vapor deposition (MOCVD) method is used.
(rganic chemical vapor deposition) to deposit the metal material in the carbon tube 3. In such a case, for example, a metal carbonyl complex or metallocene is used. Specifically, when obtaining the fine wire material 4 made of nickel, nickelocene is used as the material.

In addition to the above-described method, the metal material as a raw material is made into a liquid state,
And inserting it into the inside of the carbon tube 3. Examples of a method for bringing the metal material into a liquid state include a method of dissolving in a solvent and a method of melting.

When the metal material is dissolved in a solvent, examples of the metal material used include metal salts such as lead sulfate, nitrate and chloride. The solvent for dissolving the metal salt is appropriately selected depending on the kind of the salt used, such as water or an organic solvent. In this case, when inserting the solution of the metal salt into the carbon tube 3, if the inside of the carbon tube 3 is previously depressurized, the solution can be easily inserted into the carbon tube 3.

When the metal material is melted, it is necessary that the metal material be melted at such a temperature that the carbon tube 3 (or the inorganic substance 2 coexisting as a mold) is not denatured.

Then, the molten metal material is brought into contact with the carbon tube 3 and the metal material is inserted into the carbon tube 3. As a method of inserting a metal material into the inside of the carbon tube 3, a pre-pressurized state is used.
A method in which the carbon tube 3 and the molten metal material are brought into contact with each other and inserted into the pores 1 is exemplified.

Further, in order to improve the contact between the metal material and the carbon tube 3, a metal material to be inserted is previously deposited on the carbon tube 3 by vapor deposition, sputtering or the like. A method in which the metal material is inserted into the carbon tube 3 by capillary action by increasing the temperature can also be used.

Finally, as shown in FIG. 1D, the inorganic substance 2 serving as the mold of the carbon tube 3 is dissolved and removed with a solvent capable of dissolving the inorganic substance 2.
Specifically, for example, when an aluminum anodic oxide film is used as the inorganic substance 2, sodium hydroxide (NaOH)
The aluminum anodic oxide coating can be dissolved and removed by the aqueous solution. Here, it is necessary that the solvent does not affect the carbon tube 3 and the thin wire material 4.

In this manner, a thin metal wire in which the thin wire material 4 is included in the carbon tube 3 is obtained.

The state of the thin wire material 4 contained in the carbon tube 3 may be changed by post-processing.
The post-treatment is appropriately performed depending on the intended final inclusion. For example, when the final inclusion is to be obtained in a metal state, when it is difficult to easily obtain a metal in a liquid state, for example, first insert in a state of a metal compound such as a metal salt, and then perform a reduction treatment. This changes the state to a metallic state. When the final inclusion is to be a metal carbide or a carbon solid solution, the inserted metal compound or metal reacts with the surrounding carbon, or the carbon dissolves in the metal, and the carbide or the carbon is dissolved. Heat treatment is performed at a predetermined temperature, for example, in a non-oxidizing atmosphere so as to become a solid solution of carbon.

The thin wire material 4 thus obtained has no nodes or breaks and is uniformly deposited inside the carbon tube 3. The fine wire material 4 has a diameter of a cross section substantially perpendicular to the long axis direction of 1 nm to 100 nm, a ratio of the diameter of the cross section to the long axis length of 50 or more, and has a very large axis while being fine It has a ratio. When nickel is used as the thin wire material, the crystal orientation is controlled, and an excellent metal thin wire can be obtained.

Here, in the above description, the step of inserting the fine wire material 4 into the carbon tube 3, the step of dissolving and removing the inorganic substance 2 serving as a mold, and the process of changing the state of the inserted fine wire material 4 Although the case of performing the processing steps in this order has been described as an example, the present invention is not limited to this, and the order and the contents of post-processing can be appropriately changed depending on the state of the target fine wire material 4. preferable.

For example, when the metal material is changed by post-processing, depending on the processing conditions, the inorganic material 2 of the mold,
When the carbon or the metal material of the carbon tube 3 reacts, after inserting the metal material into the carbon tube 3,
The inorganic substance 2 serving as a mold is dissolved and removed, and then the state of the metal material is changed by post-treatment. That is, in this case, the order is insertion → removal → post processing.

Conversely, if the metal material can be changed to a state in which it does not react with the solution by the post-treatment,
After the fine wire material 4 is inserted into the carbon tube 3, post-processing is performed to change the fine wire material 4 so as not to react with the solution, and then the inorganic substance 2 in the mold is dissolved and removed. That is, in this case, the order is insertion → post-processing → removal.

Regardless of the presence or absence of the post-treatment, the step of dissolving and removing the inorganic substance 2 is performed after the step of inserting the fine wire material 4 or for dissolving the fine wire material 4 and the inorganic material 2. When reacting or dissolving with a solution or the like, it is necessary to cover the openings of the pores 1 with a substance that does not react with the solution. For example, pores 1 are formed by vapor deposition or gas phase carbonization.
Is coated with carbon to prevent the inclusions from dissolving.

When the fine wire material 4 can be inserted with the carbon tube 3 alone, the fine wire material 4 may be inserted after dissolving and removing the inorganic substance 2 of the mold in advance.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments to which the present invention is applied will be described.

First, an aluminum anodic oxide coating was used as an inorganic substance having substantially linear pores, which would be a mold for a carbon tube. This aluminum anodic oxide film was produced as follows using an apparatus as shown in FIG.

First, the aluminum plate 10 to be anodized
The one surface 10a is in contact with the electrolytic solution 11 and the other surface 1
0b was placed in contact with the ion-exchanged water 12. Here, a 20% sulfuric acid aqueous solution was used for the electrolyte solution 11. Further, another aluminum plate 13 was disposed in the electrolytic solution 11 so as to face the aluminum plate 10. Here, the aluminum plate 10 serves as an anode, and the aluminum plate 13 serves as a cathode.

Then, using the device having such a configuration,
The anodic oxidation of the aluminum plate 10 was performed. Anodizing is
DC constant voltage is 20V, temperature is 0 ° C to 5 ° C,
An anodic oxide film was formed on the surface 10a of the aluminum plate 10 by applying a voltage between the positive and negative electrodes for 2 hours. Next, the voltage between the anode and the cathode was reversed, and a voltage was applied between the positive and negative electrodes for 10 minutes so that the constant current became 0.3 A, thereby peeling the anodized film.

The pores in the anodic oxide film at this stage have a shape in which the voltage application side is closed, and the anodic oxide film is immersed in 20% sulfuric acid for 1 hour to make the pores through holes. The closed side was melted and opened to form a through hole.
The diameter of the pores in the obtained anodic oxide coating is approximately 3
It was 0 nm.

Next, carbon was deposited in the pores of the anodic oxide film using an apparatus having the structure shown in FIG. Specifically, one anodic oxide film 20 having an inner diameter of 2
glass fiber assembly 2 arranged in a quartz reaction tube 21 cm in diameter
2 and placed together with the quartz reaction tube 21 in a furnace equipped with a heater 23. The temperature of the heater 23 is 800 ° C.
And

Next, a mixed gas of propylene and nitrogen mixed so that the propylene concentration becomes 1.3% by volume is introduced into the above-mentioned quartz reaction tube 21 at 200 ml / min (standard state) for 3 hours. For gas phase carbonization.

Thereafter, using the apparatus shown in FIG. 3, the anodic oxide film 20 on which carbon was formed was
Pieces (100 mg), placed on a quartz glass fiber assembly 22 placed in a quartz reaction tube 21, and under a hydrogen gas direct current,
The entire quartz reaction tube 21 was placed in a furnace equipped with a heater 23. At this time, the temperature of the heater 23 was 275 ° C.

Then, nickelocene as the reaction raw material 24 of the thin wire material was volatilized by heating in an oil bath 25, and gaseous nickelocene was put on hydrogen of a carrier gas and reacted. At this time, the flow system was heated in the heating zone 26 in order to prevent cooling and precipitation of the reaction material in the flow system. And
The partial pressure of nickelocene was set to 1.95 toor., And the reaction was performed for 2 hours.

Thereafter, autoclaving was carried out, and 150 ° C.
The aluminum anodic oxide film was dissolved by holding for 6 hours under immersion in a 10 N aqueous solution of sodium hydroxide kept at a temperature of 10 ° C. Finally, by performing filtration, washing, and drying, a thin metal wire in which a nickel thin wire material was included in a carbon tube was obtained.

A transmission electron microscop (TEM) of the thin metal wire thus obtained is used.
e) The photographs are shown in FIGS. 4, 5 and 6. In addition, FIG.
FIGS. 5 and 6 are photographs of thin metal wires taken at different magnifications.

As can be seen from FIGS. 4, 5 and 6, the nickel fine wire material obtained according to the present invention is uniformly deposited in the carbon tube and has an extremely large axial ratio.
Further, it was confirmed that the crystal orientation was excellent over a long range and the crystal orientation was excellent. In addition, FIG. 6 shows that the arrangement of the (111) planes of face-centered cubic nickel can be confirmed, and it can be seen that the (111) axis plane of nickel is substantially parallel to the long axis direction of the thin metal wire.

[0053]

According to the present invention, it is possible to realize a fine metal wire using a fine wire material which is fine but has a large axial ratio. The metal wires obtained by the present invention are greatly expected as novel composite materials, electrically conductive materials, quantum wire devices, ultra-high-speed electrical devices, ultra-high-density magnetic recording media, nonlinear optical materials, and the like.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a manufacturing process of a thin metal wire according to the present invention, and FIG. 1 (a) is a view showing an inorganic substance serving as a mold. FIG. 1B is a diagram showing a state in which carbon is formed in the pores of the inorganic substance. Also,
FIG. 1C is a diagram showing a state in which a fine metal wire is inserted into carbon. FIG. 1D is a diagram showing a state in which the inorganic substance of the mold has been dissolved and removed.

FIG. 2 is a diagram showing an example of a production apparatus for producing an inorganic substance as shown in FIG.

FIG. 3 is a diagram showing an example of a manufacturing apparatus for manufacturing a thin metal wire according to the present invention.

FIG. 4 is an electron micrograph showing an enlarged view of a thin metal wire produced according to the present invention.

5 is an electron micrograph showing the fine metal wire shown in FIG. 4 in a further enlarged manner.

FIG. 6 is an electron micrograph showing the fine metal wire shown in FIG. 5 in a further enlarged manner.

[Explanation of symbols]

1 pore, 2 inorganic substance, 3 carbon tube,
4 Metal wire

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 5/02 H01B 5/02 A // C01B 31/02 101 C01B 31/02 101F

Claims (13)

[Claims] 1. A diameter of a cross section substantially perpendicular to a major axis direction is 1 nm.
A thin metal wire, which is made of a thin wire material having a diameter of the cross section and a length of the major axis of 50 to 100 nm or more. 2. The thin metal wire according to claim 1, wherein said thin wire material is made of a transition metal. 3. The thin metal wire according to claim 1, wherein the fine wire material is made of nickel, and a (111) plane of the nickel is substantially parallel to a long axis direction. 4. The thin metal wire according to claim 1, wherein said fine wire material is covered with a carbon tube. 5. The tube has a diameter of a cross section substantially perpendicular to the major axis direction of 10 nm to 1 μm, and a major axis length of 1 μm to 5 μm.
The thin metal wire according to claim 4, wherein the thickness is 100 μm. 6. A first step of forming a tubular carbon on the inner wall of a pore of an inorganic substance having substantially linear pores, and a step of forming a tubular carbon inside the tubular carbon in the first step. At least a second step of depositing a metal. 7. A method according to claim 1, wherein said step (c) is performed between said first step and said second step.
Or a third step of dissolving and removing the inorganic substance after performing the second step.
A method for producing a thin metal wire as described above. 8. In the first step, an organic compound is coated on the inner walls of the pores of the inorganic substance, and the organic compound is carbonized by heating to form carbon on the inner walls of the pores of the inorganic substance. 7. The method for producing a thin metal wire according to claim 6, wherein: 9. In the first step, the gaseous hydrocarbon is gas-phase carbonized in the pores of the inorganic substance, and a carbon thin film is deposited on the inner walls of the pores. 7. The method of claim 6, wherein carbon is formed.
A method for producing a thin metal wire as described above. 10. The method according to claim 6, wherein in the second step, a metal is deposited inside the carbon by a chemical vapor deposition method of an organometallic compound. Method. 11. The method according to claim 10, wherein in the second step, nickelocene is used as the organometallic compound. 12. The method according to claim 6, wherein a transition metal is used in the second step. 13. The method for producing a fine metal wire according to claim 6, wherein the inorganic substance having substantially linear pores is any one of a metal anodic oxide coating, zeolite, and sepiolite.