JP3991157B2 - Carbon nanotube production equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing apparatus of carbon nanotubes. A carbon nanotube is a very fine single-layer or multi-layered tube (tube) substance formed by bonding carbon atoms in a network. An electron-emitting device using carbon nanotubes is applied to a field emission flat panel display (FED), an X-ray source, electron beam lithography, a display / lighting device, a gas decomposition apparatus, a sterilization / disinfection apparatus, and the like.
[0002]
[Prior art]
Compared with conventional electron emission materials such as Spindt-type emitters and diamond thin films made of silicon or molybdenum, carbon nanotubes are comprehensively superior in characteristics such as current density, drive voltage, robustness, and lifetime. It is currently the most promising electron source. This is because carbon nanotubes have a large aspect ratio (length-to-diameter ratio) and sharp tip, are chemically stable and mechanically tough, and have excellent stability at high temperatures. This is because it has advantageous physicochemical properties as a material for the emitting element.
[0003]
As a method for producing carbon nanotubes, a method in which carbon nanotubes are oriented perpendicular to the surface of the substrate by plasma chemical vapor deposition has been proposed (see Patent Document 1). However, the plasma chemical vapor deposition apparatus used in this method needs to be provided with a vacuum / pressurizing chamber in which a carbon nanotube is first grown in a vacuum state and then grown in a pressurized state of the raw material gas. Therefore, this apparatus becomes a large-scale apparatus, and the amount of carbon nanotubes produced at a time in a vacuum / pressurization chamber is limited, which is not suitable for mass production.
[0004]
In addition, a belt that rotates while a plurality of substrates are sequentially placed thereon, a rotating unit that rotates the belt, a stacking unit that sequentially mounts the substrates on the belt, and a mounting unit that faces the stacking unit A recovery unit for recovering the substrate moved by the rotation of the belt, a source gas supply unit for supplying a source gas for synthesizing the carbon nanotubes on the substrate moving along the belt, and on the belt There has also been proposed a thermal chemical vapor deposition apparatus including a substrate heating unit that heats a placed substrate for a thermal reaction of the source gas and an exhaust unit that exhausts the source gas (Patent Document 2). reference). However, in this apparatus, the stacking unit needs to include a robot arm that sequentially loads and collects substrates on a rotating belt, and the structure is complicated.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-48512
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-234341
[Problems to be solved by the invention]
An object of the present invention has been made in view of the circumstances described above, provides or vacuum-pressure chamber, there is no need to provide a robot arm for substrate loading, carbon nanotube production equipment installation cost is inexpensive structure is simple There is to do.
[0010]
[Means for Solving the Problems]
An apparatus for producing carbon nanotubes according to the present invention includes a catalyst thin film that is rotated by a driving drum and a driven drum and that is formed of an endless belt composed of a large number of adjacent substrates, and a thin film made of catalytic metal particles on the substrate surface. An apparatus for producing a carbon nanotube, comprising: a forming part; and a carbon nanotube forming part that is provided downstream of the forming part and grows carbon nanotubes on a thin film by chemical vapor deposition. A generating device , the plasma generating device is arranged at the bottom of the frame of the device, and is composed of a horizontal electrode made of a mesh plate or a perforated plate, and a plurality of vertical electrodes erected on the electrode it is made of is characterized in.
In the device of the present invention, the plasma generator preferably generates plasma under atmospheric pressure.
[0011]
In the apparatus of the present invention, the substrate constituting the endless belt is preferably made of stainless steel.
[0012]
As an electrode of the plasma generator, a plate-like electrode, a rod-like electrode or a needle-like electrode can be appropriately selected and used.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0014]
First, a thin film made of catalytic metal particles is formed on the surface of the substrate, and carbon nanotubes are grown on the thin film by chemical vapor deposition using the catalyst particles of the thin film as nuclei. for line cormorant Manufacturing method using a plasma, it will be described.
[0015]
In order to form a thin film made of catalytic metal particles on the substrate surface, a liquid containing a catalyst metal compound is sprayed on the substrate surface by ultrasonic vibration or by spraying with ultrasonic waves, and the formed spray layer is heated. Is preferred. As other methods, after applying a liquid containing a catalyst metal compound to the substrate with a spray or brush, a method of plasma irradiation or heating, a method of striking the catalyst with a cluster gun, drying, and heating if necessary, A method of chemical vapor deposition of metal, a method of heating the coating film or vapor deposition film after depositing metal on a substrate by electron beam can be employed. The catalyst metal is iron, cobalt, nickel, and the like, and can take the form of a complex such as an iron carbonyl complex (pentacarbonyliron or the like), a metal alkoxide (Fe (OEt) ₃ or the like), or the like. The metal complex or metal alkoxide may be supplied in a solution. The solvent may be acetone, alcohol or the like. The concentration of the metal complex or metal alkoxide in the solution may be, for example, 1 to 5% by weight. The thickness of the thin film is preferably 1 to 100 nm because it is difficult to form metal particles by heating if it is too thick.
[0016]
Next, when this thin film is heated preferably at 650 to 800 ° C., preferably under reduced pressure or in a non-oxidizing atmosphere, metal catalyst particles having a diameter of about 1 to 50 nm are formed. In the process of growing carbon nanotubes on a thin film by chemical vapor deposition, the source gas is usually acetylene (C ₂ H ₂ ) gas, but may be other aliphatic hydrocarbon gas such as methane gas or ethane gas. . In the case of acetylene, carbon nanotubes having a multilayer structure and a thickness of 12 to 38 nm are formed in the shape of brush hairs on the substrate surface. The source gas may be supplied to the reaction zone through a source gas supply pipe in a state diluted with an inert gas such as helium, argon or xenon. The gas supply may be performed continuously or intermittently. The operating conditions of the chemical vapor deposition method are preferably a temperature of 650 to 800 ° C. and a time of 1 to 10 minutes under atmospheric pressure.
[0017]
The plasma generated in the carbon nanotube growth process is, for example, atmospheric pressure plasma generated by a high frequency power source or a direct current power source, and is preferably in the range of transition plasma to arc plasma. When the diluting gas of the source gas is argon, it is preferable to generate the plasma upward from the bottom of the substrate, and for helium, the plasma is generated downward from the top of the substrate. The length and thickness of the carbon nanotubes to be grown are controlled by the power consumption required for plasma generation, the supply amount of the mixed gas of the source gas and the dilution gas, the mixing ratio of the source gas and the dilution gas, the carbon nanotube formation operation time, etc. Can do.
[0018]
The plasma generation method and conditions may be in accordance with conventional methods. As the plasma generating gas, an inert gas such as argon, helium or xenon is often used. The distance between the electrode and the carbon nanotube is 1 mm or less, preferably 100 to 400 μm. The high frequency power is preferably 500 to 1000 W.
[0019]
An electron-emitting device using carbon nanotubes manufactured by the above method is particularly suitable as an FED device.
[0020]
The length of the carbon nanotube is preferably 1 to 10 μm, the diameter is preferably 20 to 30 nm, and the distance between the carbon nanotubes is preferably 100 to 150 nm.
[0021]
Next, an endless belt rotated by a driving drum and a driven drum, a catalyst thin film forming portion for forming a thin film made of catalytic metal particles on the surface of a large number of substrates constituting the belt, and a downstream of the forming portion are provided. The carbon nanotube manufacturing apparatus of the present invention provided with a carbon nanotube forming part for growing carbon nanotubes on a thin film by chemical vapor deposition will be described. In the carbon nanotube production apparatus according to the present invention, a plasma generator is provided in the carbon nanotube formation portion.
[0022]
The endless belt is composed of a large number of adjacent substrates. The substrate is not particularly limited as long as it supports the catalyst particles, and is preferably one in which the catalyst particles are not easily wetted, and may be a silicon substrate, a glass substrate, or a stainless steel substrate. Preferably, it is made of stainless steel. The substrate is preferably grounded.
[0023]
The catalyst thin film forming section includes a tank for storing a liquid containing a catalyst metal compound, an ultrasonic oscillator or an ultrasonic oscillator provided in the tank, a spray device, and a heater for heating the spray layer formed on the substrate surface. It has. A mask plate made of a slit or mesh may be interposed between the catalyst thin film forming portion and the substrate. The spray droplets can be made finer by the mask plate.
[0024]
The carbon nanotube forming unit includes a plasma generator, a heater for chemical vapor deposition, and a gas supply pipe that feeds a raw material gas of carbon nanotubes to the plasma generator. The plasma generator includes a mesh electrode made of a mesh plate arranged in parallel with the substrate. This mesh electrode can uniformly pass the mixed gas of the source gas and the dilution gas through the entire electrode. The plasma generator comprises a horizontal electrode arranged on the bottom of the frame of the apparatus and made up of a mesh plate or a perforated plate, and a plurality of vertical electrodes standing on the electrode. Also good. In this electrode configuration, the vertical electrode may be a plurality of plate-like bodies, a plurality of rod-like bodies, a plurality of needle-like objects and the like standing in parallel. The plurality of plate-like bodies, the plurality of rod-like bodies, the plurality of needle-like objects and the like are preferably arranged in an aligned manner. By appropriately selecting the vertical electrode having such a shape, the carbon nanotubes can be provided only on a necessary portion of the substrate.
[0025]
The plasma may be atmospheric pressure plasma by a high frequency power source or a DC power source, for example. It is also preferable to maintain or control the plasma by using high frequency power for plasma ignition between the substrate and the electrode and switching the high frequency power to DC power after the plasma is generated. If the substrate is grounded, the plasma is in the range of transition plasma to arc plasma.
[0026]
A source gas such as acetylene gas is supplied to the plasma generator through a source gas supply pipe in a state diluted with an inert gas such as helium, argon or xenon. When the dilution gas of the source gas is argon, the plasma generator is disposed under the substrate, and the plasma is generated upward. In the case of helium, the plasma generator is disposed on the substrate, and the plasma is generated downward.
[0027]
The apparatus for producing carbon nanotubes according to the present invention is preferably a carbon nanotube peeling part for peeling carbon nanotubes from a substrate constituting an endless belt downstream of the carbon nanotube forming part, and a substrate purification part provided downstream of the peeling part Is provided. The carbon nanotube peeling unit includes, for example, a scraper that peels carbon nanotubes from a substrate, and a suction device that collects the peeled carbon nanotubes.
[0028]
The substrate purification unit includes, for example, a plurality of brushes that clean the surface of the substrate after the separation of the carbon nanotubes, and a cleaning roll disposed downstream thereof.
[0029]
The drive drum is driven by a drive motor, and the endless belt is rotated intermittently. The carbon nanotubes are grown by the above operation when the endless belt is stopped.
[0030]
Next, the present invention will be specifically described based on examples.
[0031]
Example 1
In FIG. 1, an apparatus for producing carbon nanotubes according to the present invention comprises an endless belt (3) rotated by a drive drum (1) and a driven drum (2), and a number of adjacent substrates constituting the belt (3). And a catalyst thin film forming part (4) for forming a thin film made of catalytic metal particles on the substrate surface, and a carbon that is provided downstream of the formation part (4) and that grows carbon nanotubes on the thin film by chemical vapor deposition. Nanotube forming part (5), carbon nanotube separating part (6) provided downstream of the forming part (5), for peeling carbon nanotubes from the substrate, and substrate purification provided downstream of the separating part (6) Part (7).
[0032]
The substrate constituting the endless belt (3) is made of a stainless steel plate having a thickness of 0.5 mm, and is grounded via the drive drum (1). The drive drum (1) is drawn by a tension spring (19) to a drive-side column (18) erected on one end of the bottom of the chamber (21) of the manufacturing apparatus, and the endless belt (3) stretched by heat is the same. Tension is applied by a spring (19). The driven drum (2) is attached to the top of the driven column (20) that is erected on the other end of the bottom of the chamber (21).
[0033]
The catalyst thin film forming section (4) includes a tank (8) for storing the catalyst metal compound-containing liquid, an ultrasonic oscillator (9) provided in the tank, and a coil heater (for heating the spray layer formed on the substrate surface). 10).
[0034]
The carbon nanotube forming part (5) includes a plasma generator (11), a high-frequency power source (22) connected to the apparatus (11), a plurality of heaters (12) for chemical vapor deposition, and a plasma generator (11). And a gas supply pipe (13) for feeding a raw material gas of carbon nanotubes. The plasma generator (11) includes a mesh electrode (15) made of a mesh plate arranged in parallel with the substrate. This mesh electrode can uniformly pass the mixed gas of the source gas and the dilution gas through the entire electrode.
[0035]
FIG. 2 shows a modification of the plasma generator. In this example, the plasma generator (28) includes a vertical rectangular frame (14), a horizontal electrode (16) arranged on the inner bottom of the frame (14) and made of a mesh plate, and the same electrode ( 16) A plurality of vertical electrodes (17) erected on the top. The horizontal electrodes (16) are parallel to the substrate, and the plurality of vertical electrodes (17) are plate-like electrodes that are parallel to the moving direction of the substrate and parallel to each other at a predetermined interval (that is, aligned). The horizontal electrode (16) formed of a mesh plate allows the mixed gas of the source gas and the dilution gas to pass uniformly through the entire electrode, and the carbon nanotubes can be provided only in the necessary portion of the substrate by the plurality of vertical electrodes.
[0036]
The source gas is acetylene gas, which is diluted with argon gas (acetylene gas: argon gas 1: 9) and is supplied to the plasma generator (11) through the source gas supply pipe (13). The gas supply amount is adjusted by a valve (23).
[0037]
The carbon nanotube peeling part (6) includes a scraper (24) for peeling the carbon nanotubes from the substrate, and a suction device (25) for collecting the peeled carbon nanotubes.
[0038]
The substrate purification unit (7) includes a plurality of brushes (26) for cleaning the substrate surface after carbon nanotube separation, and a cleaning roll (27) disposed downstream thereof.
[0039]
The drive drum (1) is driven by a drive motor, the endless belt (3) is rotated, and the manufacturing apparatus according to the present invention is continuously driven.
[0040]
In the carbon nanotube production apparatus configured as described above, the endless belt (3) was rotated at a feed speed of 12 m / h by the driving drum (1) and the driven drum (2).
[0041]
In the catalyst thin film forming section (4), a 3 wt% acetone solution of Fe (OEt) ₃ in the tank (8) is sprayed onto the lower surface of the substrate by the ultrasonic oscillator (9), and the formed spray layer is applied to the coil heater ( 10) heated to a temperature of 220 ° C. Thus, a thin film made of catalytic metal particles is formed on the substrate.
[0042]
In the carbon nanotube formation part (5) where carbon nanotubes are grown on the thin film by chemical vapor deposition using the catalyst particles of the thin film as nuclei, the raw material gas is acetylene gas, which is diluted with argon gas (acetylene gas: argon gas) 1: 9), and continuously supplied to the plasma generator (11) through the source gas supply pipe (13) at a flow rate of 30 ml / min. The substrate is heated by a coil heater (12). The plasma generator (11) was supplied with 500 w of power from the high frequency power source (22) to generate atmospheric pressure plasma.
[0043]
The plasma generated by the plasma generator (11) is atmospheric pressure plasma from a high frequency power source. Since the substrate is grounded as described above, the generated plasma is in the range of transition plasma to arc plasma (see FIG. 3). The high frequency power source (22) includes a matching circuit, which is also grounded.
[0044]
The operating conditions of the chemical vapor deposition method were set to a temperature of 720 ° C. and a time of 5 minutes under atmospheric pressure.
[0045]
By this operation, the catalyst thin film was made into particles, and brush-like carbon nanotubes were generated using the obtained catalyst particles as nuclei and gradually grown. The grown carbon nanotubes had a multilayer structure with a thickness of 10 to 30 nm and a length of 5 μm.
[0046]
The carbon nanotubes thus grown on the substrate surface were scraped off by the scraper (24) of the carbon nanotube peeling part (6), and this was collected by the suction device (25). Thereafter, the substrate surface after carbon nanotube peeling was washed by rubbing with a plurality of brushes (26) of the substrate purification section (7), and then cleaned with a cleaning roll (27) downstream thereof.
[0048]
【The invention's effect】
In the carbon nanotube production apparatus according to the present invention, since carbon nanotubes are directly grown on an endless belt composed of a large number of adjacent substrates, there is no need to provide a device for loading and collecting substrates, and the structure is simple. An inexpensive carbon nanotube production apparatus can be provided.
[Brief description of the drawings]
1 is a flow sheet showing steps of Example 1. FIG.
FIG. 2 is a flow sheet showing steps of Example 2.
FIG. 3 is a graph showing a relationship between a discharge current and an interelectrode electrode.
[Explanation of symbols]
(1): Driving drum
(2): Followed drum
(3): Endless belt
(4): Catalyst thin film formation part
(5): Carbon nanotube formation part
(6): Carbon nanotube peeling part
(7): Substrate purification unit
(8): Tank
(9): Ultrasonic oscillator
(10): Coil heater
(11): Plasma generator
(12): Heater
(13): Gas supply pipe
(14): Frame
(15): Mesh electrode
(16): Horizontal electrode
(17): Vertical electrode
(21): Chamber
(22): High frequency power supply
(24): Scraper
(25): Suction device
(26): Brush
(27): Cleaning roll
(28): Plasma generator

Claims (2)

Provided downstream of the endless belt, which is rotated by a driving drum and a driven drum and is composed of a large number of adjacent substrates, a catalyst thin film forming portion for forming a thin film made of catalytic metal particles on the substrate surface And a carbon nanotube production apparatus comprising a carbon nanotube forming part for growing carbon nanotubes on a thin film by chemical vapor deposition,
A plasma generating device is provided in the carbon nanotube forming portion, and the plasma generating device is arranged on the bottom of the frame of the device and is erected on the same electrode as a horizontal electrode made of a mesh plate or a porous plate. An apparatus for producing carbon nanotubes, comprising a plurality of vertical electrodes . The apparatus for producing carbon nanotubes according to claim 1, wherein the plasma generator generates plasma under atmospheric pressure.

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