JP2009215120A - Nanocarbon material composite, method for producing the same, and electron emission element using nanocarbon material composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nanocarbon material composite which is suitable as a practical material and has a constriction structure, a method for producing the same, and an electron emission element using the nanocarbon material composite. <P>SOLUTION: The nanocarbon material composite 1 comprises a substrate 2 and a nanocarbon material 3 with a constriction structure grown on the substrate 2. The method for producing the same includes a first step of forming a thin film of palladium or a compound thereof on the substrate 2, and a second step of heating the palladium-bearing substrate at a temperature in a range of 650-950°C in octanol. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nanocarbon material composite expected to be applied as a strength reinforcing material, an electron-emitting device material, a battery electrode material, an electromagnetic wave absorbing material, a catalyst material, or an optical material, and a manufacturing method suitable for the production And an electron-emitting device using the same.

The nanocarbon material has a nanometer (nm) -sized fine shape composed of sp ² hybrid orbitals of carbon atoms, and therefore has characteristics superior to those of conventional materials and characteristics that are not found in conventional materials. Therefore, it is expected to be applied as a next-generation functional material such as a strength reinforcing material, an electron-emitting device material, a battery electrode material, an electromagnetic wave absorbing material, a catalyst material, or an optical material.

  In addition, cathode ray tubes are widely used as electronic display devices. However, the cathode ray tubes require a large volume in addition to a large energy consumption in order to emit thermal electrons from the cathode of the electron gun. There were issues such as. For this reason, there has been a demand for a flat display that can use cold electrons instead of thermal electrons, reduce energy consumption as a whole, and reduce the size of the device itself. Realization of high-speed response and high resolution for the display is also strongly demanded.

As a structure of such a flat display using cold electrons, a high-vacuum flat plate cell in which minute electron-emitting devices are arranged in an array is promising, and an electron-emitting device used for this purpose In particular, field emission type electron-emitting devices utilizing the field emission phenomenon have been attracting attention. In this field emission type electron-emitting device, when the strength of the electric field applied to the substance is increased, the width of the energy barrier on the surface of the substance is gradually reduced according to the strength, and the electric field strength is 10 ⁷ V / cm or more. This makes use of the phenomenon that electrons in a substance can break through its energy barrier by the tunnel effect, and thus electrons are emitted from the substance. In this case, since the electric field follows Poisson's equation, if a member that emits electrons, that is, a portion where the electric field concentrates on the emitter, cold electrons can be emitted efficiently with a relatively low extraction voltage (non- (See Patent Documents 1 and 2).

  In recent years, nanocarbon materials have attracted attention as emitter materials. The most typical carbon nanotube among nanocarbon materials is a hollow cylinder made by rolling a graphene sheet in which carbon atoms are regularly arranged. The outer diameter is on the order of nm, and the length is usually 0.5 to several. It is a fine substance with a very high aspect ratio of 10 μm. For this reason, an electric field tends to concentrate on the tip portion, and high electron emission ability is expected. In addition, carbon nanotubes are characterized by high chemical and physical stability, so that adsorption and reaction of residual gas in an operating vacuum are difficult to occur, and are not easily damaged by heat generated by ion bombardment or electron emission. It has characteristics.

  When carbon nanotubes are used as emitters, they are often made into a paste and applied onto a substrate by a printing method. For example, Patent Document 1 discloses an emitter forming method by screen printing. First, the cathode electrode is formed in stripes on the substrate at a predetermined pitch, and the paste containing the carbon nanotubes is formed on the cathode electrode in the form of a square or a circle in the same pitch as the cathode electrode by screen printing. To do. Next, an insulating layer is screen-printed between the resin layers containing carbon nanotubes, and then baked in an air atmosphere. Thereby, the resin component of the resin layer containing the carbon nanotube is decomposed, and the carbon nanotube is exposed to form an electron emission portion. Finally, a grid electrode is formed on the insulating layer to produce an emitter.

  In general, the paste used for manufacturing the emitter as described above is added to a carbon nanotube by adding a solvent, a dispersant, a glass frit as an adhesive, a filler, etc., and mixing them so that their distribution state is uniform. To disperse. After mixing, the mixture is filtered and mixed in a vehicle composed of a solvent and a resin to form a paste. This paste is mixed well to enhance the dispersion state and then filtered to complete the carbon nanotube paste. The carbon nanotube paste obtained by the above process is printed on a substrate, and the vehicle is oxidatively decomposed by drying and baking to obtain a carbon nanotube film.

  On the other hand, as a method for synthesizing nanocarbon materials such as carbon nanotubes, an arc discharge method, a laser ablation method, a plasma chemical vapor deposition method, a thermal chemical vapor deposition method, and the like are known. Among these methods, arc discharge method, laser ablation method and plasma chemical vapor deposition method are non-equilibrium reactions, so it is easy to generate amorphous components, and generally the yield of carbon nanotubes to be generated is low. It is also known that the thickness and type of the produced carbon nanotubes are not uniform.

  Patent Document 2 and Patent Document 3 disclose a thermal chemical vapor deposition method for producing carbon nanotubes by thermally decomposing hydrocarbon gas using a catalyst. The thermal chemical vapor deposition method is known to have a relatively high yield because it uses a chemical equilibrium reaction. In this method, carbon fibers grown using catalyst particles such as ultrafine iron and nickel as the core are used. can get. The obtained carbon fiber has a carbon net layer grown concentrically and hollowly.

  Patent Document 4 discloses a method of synthesizing high-purity carbon nanotubes that do not require purification. Since the method disclosed in Patent Document 4 is based on a unique interfacial decomposition reaction that occurs when a solid substrate and an organic liquid come into contact with each other with a rapid temperature difference, a solid-liquid interfacial catalytic decomposition method in an organic liquid. is called.

The solid-liquid interface catalytic decomposition method described in Patent Document 4 will be described below.
FIG. 7 schematically shows a synthesis apparatus used in the solid-liquid interface catalytic decomposition method in an organic liquid. The synthesizer used in the solid-liquid interface catalytic cracking method includes a liquid tank 61 containing an organic liquid 60 such as methanol, and a water cooling means provided so as to surround the outside of the liquid tank 61 in order to keep the organic liquid 60 below the boiling point. 62, a substrate holder 65 having an electrode 64 for holding a conductive substrate 63 and allowing an electric current to flow through the substrate 63, and water cooling for cooling and condensing the organic liquid vapor evaporated from the liquid tank 61 and returning it to the liquid tank 61. It comprises a condensing means 67 comprising a pipe 66, a nitrogen gas introduction valve 68 for introducing nitrogen gas to prevent contact between the organic liquid vapor and air, and a lid 69 for sealing the liquid tank 61.

  When performing solid-liquid interface catalytic decomposition in an organic liquid using the synthesis apparatus shown in FIG. 7, a transition metal thin film such as Fe, Co, Ni, etc. is laminated on a conductive silicon substrate, and this transition metal thin film is laminated. By exposing the substrate 63 to hydrogen plasma or thermally oxidizing the transition metal thin film, the catalyst fine particles are supported on the substrate 63 so as to be distributed at a high density. Next, the base 63 is held by the base holder 65, and the base 63 is heated by passing an electric current through the base 63 through the base holder 65. As a result, the base 63 and the organic liquid 60 come into contact with each other with an abrupt temperature difference, so that a unique interfacial decomposition reaction occurs, and carbon nanotubes are synthesized on the catalyst fine particles.

JP 2003-272517 A JP 2002-255519 A JP 2002-285334 A JP 2003-12312 A C. A. Spindt: J. Appl. Phys., 39, 3504 (1968) K. Betsui: Tech. Dig. IVMC., (1991) p26

  However, in the above-described method, it is difficult to control the particle size and chemical state of the metal used as a catalyst, so that it is difficult to control the shape and thickness of the nanocarbon material, and it is difficult to control. It was inevitable that the rate would decline. So far, crystalline nanocarbon materials have been obtained. However, the aggregates in gram units were disordered aggregates and were low-density powder or cluster solids. In order to apply such a nanocarbon material as a practical material, it must be mixed with other materials such as pasting or resin, and since it is a disordered and low-density assembly, uniform mixing is possible. It was not easy.

  Depending on the use of the nanocarbon material, a nanocarbon material having a large surface area or an uneven structure may be required. For example, in the case of a secondary battery, a capacitor, or a fuel cell in which activated carbon that is an amorphous carbon material is used, a carbon material having high crystallinity and a large surface area is preferable. Further, even when a nanocarbon material is used for an electron-emitting device, the configuration having a more uneven structure facilitates electric field concentration and enables low-voltage operation. However, as described above, since it is difficult to produce a nanocarbon material having a desired structure, a nanocarbon material having a structure or form suitable for the application, that is, a highly practical nanocarbon material has been found. Absent.

  Furthermore, when processing the synthesized nanocarbon material into a use form, for example, when processing into the shape of a battery electrode, in the reaction product containing carbon impurities other than the nanocarbon material such as graphite particles and amorphous carbon. Nanocarbon material must be purified from the carbon nanotubes, and it is necessary to collect the required amount of carbon nanotubes by scraping off the carbon nanotubes grown on the substrate. It was not possible to manufacture a member using a nanocarbon material having

In view of the above problems, the first object of the present invention is to provide a nanocarbon material composite having a structure suitable for various applications.
The second object of the present invention is to provide a method for producing a nanocarbon material composite capable of controlling the shape and thickness of the nanocarbon material.
A third object of the present invention is to provide a high-performance and practical electron-emitting device using the nanocarbon material composite.

In order to achieve the first object, the present invention provides a nanocarbon material composite comprising a substrate and a nanocarbon material having a constricted structure grown on the substrate.
Here, the constricted structure refers to a structure in which the fibers of the nanocarbon material are constricted or twisted to have an uneven structure. By integrally forming a nanocarbon material having a constricted structure on a substrate, it can be easily applied to practical devices such as battery electrode materials and electron-emitting devices. In addition, by using a nanocarbon material with a constricted structure, the surface area per unit volume is increased compared to the most common nanocarbon material, carbon nanotubes, and because it has a constricted structure and an uneven shape, it is practical. When applied as a material, the efficiency and reliability of various elements can be improved.

In order to achieve the second object, the present invention provides a first step in which a thin film selected from palladium or a compound thereof is formed on a substrate as a substrate, and the substrate carrying palladium is 650 ° C. or higher and 950 ° C. or higher in octanol. The manufacturing method of a nanocarbon material composite including the 2nd process heated in the range below ° C is provided.
As described above, Patent Document 4 discloses a method of producing carbon nanotubes in a methanol solution using a metal catalyst selected from iron, cobalt, or nickel. The phase components are different. This difference affects the formation of a constricted nanocarbon material on the substrate. That is, in a combination of a metal other than palladium or a compound thereof and a liquid phase other than octanol, a nanocarbon material having a constricted structure is not formed on the substrate.

  In order to achieve the third object, the present invention provides an electron-emitting device using a nanocarbon material composite comprising a nanocarbon material having a constricted structure grown on a substrate.

Since the nanocarbon material composite of the present invention is integrated with the base and the nanocarbon material having a constricted structure, it can be applied as it is as a member and is excellent in practical process suitability.
Moreover, since it has a constricted structure, it has high mechanical strength and a large surface area. Therefore, when the nanocarbon material composite of the present invention is used as an electrode material of a structural material, an electron emission material, an electric double layer capacitor / battery, a fuel cell, or a general secondary battery, it has good practical physical properties. In addition, the process suitability is shown, and the manufacturing cost can be reduced.

  In the case of carbon nanotubes, there is no electron emission from the wall surface, but the nanocarbon material composite with a constricted structure has fine edges in the nanocarbon fiber, which increases the number of electron emission points, which is different from carbon nanotubes. The range of use as an electron-emitting device of various variations becomes wide.

  According to the method for producing a nanocarbon material composite of the present invention, as described above, the constricted nanocarbon material can be integrally formed on the substrate, and the temperature at which the metal-supported substrate is heated in octanol is controlled. Thus, it is possible to control the thickness of the nanocarbon material having a constricted structure. For this reason, the nanocarbon material composite which has the nanocarbon material of the constriction structure without the variation of high electron emission ability between lots can be manufactured easily.

Hereinafter, embodiments of the present invention will be described in detail.
First, the nanocarbon material composite of the present invention will be described.
FIG. 1 is a schematic cross-sectional view showing the configuration of the nanocarbon material composite of the present invention. The nanocarbon material composite 1 of the present invention comprises a base 2 and a nanocarbon material 3 having a constricted structure grown on the base 2. Although FIG. 1 shows a case where the nanocarbon material 3 having a constricted structure is present directly on the substrate 2, the nanocarbon material 3 having a constricted structure may be present on the substrate 2 through a metal. is there.

  In addition to single crystal silicon, the substrate 2 is formed by forming a thin film of palladium or a compound thereof on a semiconductor substrate such as germanium, gallium arsenide, phosphorus gallium arsenide, gallium nitride, or silicon carbide, or a substrate such as glass, ceramics, or quartz. Obtainable. The thickness of the substrate 2 is not particularly limited, but a normal thickness of 100 to 1500 μm is desirable.

Next, a method for producing the nanocarbon material composite of the present invention will be described.
FIG. 2 shows an example of an apparatus for producing the nanocarbon material composite of the present invention. This apparatus includes a water cooling means 12 for cooling the liquid tank 11 outside the liquid tank 11, an electrode 13 for holding the base 2 and for passing a current through the base 2, and an organic that evaporates from the liquid tank 11. A lid 17 holding a condensing means 15 comprising a water-cooled pipe 14 for cooling and condensing the liquid vapor and returning it to the liquid tank 11, and a valve 16 for introducing an inert gas when air in the apparatus is removed. The liquid octanol 10 is hermetically sealed and held by the liquid tank 11 and the lid 17.

  According to this apparatus, the temperature of the liquid octanol can be maintained below the boiling point, and the substrate temperature can be maintained at a temperature at which the thickness of the nanocarbon fiber is formed. In addition, since the organic liquid phase is condensed, the raw organic liquid is not wasted, and there is no risk of explosion or flame due to mixing of the organic gas phase and air.

Next, the method for producing the nanocarbon material composite of the present invention will be described in detail. First, the substrate is cleaned, and palladium or a compound thereof is deposited on the substrate.
As described above, a semiconductor substrate such as germanium, gallium arsenide, phosphorus gallium arsenide, gallium nitride, and silicon carbide, glass, ceramics, quartz, or the like can be used for the substrate as described above.
As the catalyst, palladium or a compound thereof is used. In the case of other than palladium or its compound, for example, Fe and Ni, the nano-carbon fibers are not formed on the substrate 2 but nanotubes are formed.
The means for depositing these metals on the substrate is a sputtering method or adding a predetermined amount of metal salt, then evaporating excess water, drying and firing in an air stream at 400 to 500 ° C. Decomposition and oxidation may be performed to convert the metal salt to an oxide. Although the thickness of the metal thin film to deposit is not specifically limited, What is necessary is just to select suitably in the range of 2-10 nm which is normal thickness. The thickness of the substrate 2 is not particularly limited, but a normal thickness of 100 to 1500 μm is desirable.

  Subsequently, the surface of the substrate 2 on which the metal thin film is deposited is disposed on the electrode 13 of the manufacturing apparatus so as to be parallel and downward with respect to the apparatus bottom surface, so that the liquid octanol 10 is filled in the apparatus. The liquid phase filled in the apparatus is octanol, and in the case of methanol, ethanol or octane, nanocarbon fibers having a constricted structure are not formed on the substrate 2.

  From the viewpoint of safety, it is preferable to introduce an inert gas into the apparatus through the valve 16 and replace the residual air in the apparatus with an inert gas or nitrogen gas. An electric current is passed through the electrode 13 to heat the substrate 2. Heating is performed at a temperature of the substrate 2 in the range of 650 ° C to 950 ° C. At temperatures outside this range, nanocarbon fibers having a constricted structure are not formed on the substrate 2. When the substrate temperature is in the range of 650 ° C. to less than 750 ° C., the diameter of the nanocarbon fiber is less than 50 nm, the diameter is 50 nm or more and less than 300 nm at 750 ° C. to 880 ° C., and the thickness is 300 nm or more at 880 ° C. to 950 ° C. A nanocarbon fiber having a constricted structure is formed. Thus, by controlling the temperature of the substrate 2, it is possible to control the thickness of the nanocarbon fiber having a constricted structure. The nanocarbon material 3 is formed on the lower surface of the base 2.

  During production, octanol bubbles are generated from the surface of the substrate 2 and the substrate surface is covered with the bubbles. At this time, it is necessary to keep the temperature of the octanol below the boiling point, and the water cooling means 12 is used for cooling. Further, the octanol that has become a gas phase is returned to the liquid by the condensing means 15 and returned to the liquid tank 11. By maintaining the substrate 2 at a constant temperature for a certain period of time according to the length of the nanocarbon fiber having a desired constricted structure, a nanocarbon fiber having a constricted structure having a desired length can be formed.

  The nanocarbon material having a constricted structure has a rough surface and a large number of edge structures. For this reason, unlike the carbon nanotube, the number of electron emission portions is increased, and the electron emission ability of the variation different from that of the carbon nanotube can be obtained. In the manufacturing process, the thickness of the fiber can be made uniform by controlling the temperature of the substrate 2, so that an electron-emitting device having excellent electron emission stability can be obtained.

Hereinafter, the present invention will be described in more detail based on examples.
Palladium was formed on a Si (100) substrate (n-type, low resistance) using magnetron sputtering. The palladium formed on the substrate was 4 nm in terms of the weight of the substrate converted into a film thickness. The obtained substrate (hereinafter also referred to as “palladium-supported substrate” or “palladium-supported body”) was placed on the electrode of the production apparatus shown in FIG. 2, and the apparatus was filled with liquid octanol.
Next, the palladium-supported substrate was heated at 700 ° C., 800 ° C., 850 ° C., and 900 ° C. for 10 minutes, respectively, to form a nanocarbon material on the palladium-supported substrate.
The surface structure of the obtained nanocarbon material composite was observed with a field emission scanning electron microscope (FE-SEM). The results are shown in FIGS.

FIG. 3 is a field emission scanning electron microscope image of the surface structure of the nanocarbon material composite obtained by heating the palladium-supported substrate to 700 ° C. A nanocarbon fiber having a constricted structure with a thickness of less than 50 nm of the nanocarbon material is formed.
FIG. 4 is a field emission scanning electron microscope image of the surface structure of the nanocarbon material composite obtained by heating the palladium-supported substrate to 800 ° C. Nanocarbon fibers having a constricted structure with a thickness of about 50 to 150 nm of the nanocarbon material are formed.
FIG. 5 is a field emission scanning electron microscope image of the surface structure of the nanocarbon material composite obtained by heating the palladium-supported substrate to 850 ° C. Nanocarbon fibers having a constricted structure with a thickness of about 150 to 300 nm of the nanocarbon material are formed.
FIG. 6 is a field emission scanning electron microscope image of the surface structure of the nanocarbon material composite obtained by heating the palladium-supported substrate to 900 ° C. A nanocarbon fiber having a constricted structure with a thickness of 300 nm or more of the nanocarbon material is formed.

  As shown in FIG. 3 to FIG. 6, when the thickness of the palladium film formed on the palladium-supporting substrate is 4 nm, the nanocarbon fiber has a diameter in the range where the heating temperature of the substrate is 650 ° C. to less than 750 ° C. A nanocarbon fiber having a constricted structure of less than 50 nm is obtained, and a nanocarbon material having a constricted structure with a diameter of 50 nm to 300 nm at 750 ° C. to 880 ° C. is obtained, and a diameter of 300 nm or more is obtained at 880 ° C. to 950 ° C. A nanocarbon material having a constricted structure of thickness was formed. From this, it can be seen that by controlling the heating temperature, the fiber thickness can be controlled and the fiber can be made uniform.

(Comparative Example 1)
As a comparative example of the above examples, the liquid phase solvent was changed to ethanol and methanol, and the same conditions as in the above examples were performed. Even under the conditions of 600 ° C., 700 ° C., 800 ° C., 850 ° C. and 900 ° C. A carbon material having a constricted structure with a diameter of 20 nm or more was not formed on the substrate.

  The nanocarbon material composite of the present invention can be used as, for example, a field emission type electron-emitting device (field emitter) that emits electrons by a strong electric field. More specifically, as an electron generation source or electron gun for an optical printer, an electron microscope, an electron beam exposure apparatus, or the like, or as an ultra-compact illumination source for an illumination lamp, and further, a surface of an arrayed field emitter array constituting a flat display Needless to say, the present invention can be used as an electron-emitting device useful as an electron source, but is not limited thereto.

It is a schematic cross section which shows the structure of the nano carbon material composite_body | complex of this invention. It is a figure which shows an example of the apparatus which manufactures the nano carbon material composite_body | complex of this invention. It is a figure which shows the scanning electron microscope image of the nano carbon material formed when heating at 700 degreeC. It is a figure which shows the scanning electron microscope image of the nano carbon material formed when it heated at 800 degreeC. It is a figure which shows the scanning electron microscope image of the nano carbon material formed when it heated at 850 degreeC. It is a figure which shows the scanning electron microscope image of the nanocarbon material formed when heating at 900 degreeC. It is a figure which shows typically the synthesizing | combining apparatus by the conventional solid-liquid interface contact decomposition method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nano carbon material composite body 2 Base | substrate 3 Nano carbon material 10 Liquid octanol 11 Liquid tank 12 Water cooling means 13 Electrode 14 Water cooling pipe 15 Condensing means 16 Valve | bulb 17 Lid 60 Organic liquid 61 Liquid tank 62 Cooling means 63 Base 64 Electrode 65 Base holder 66 Water-cooled pipe 67 Condensing means 68 Valve 69 Lid

Claims (3)

A first step of forming a thin film selected from palladium or a compound thereof on a substrate as a substrate;
A second step of heating the substrate in octanol in a range of 650 ° C. or higher and 950 ° C. or lower;
The manufacturing method of a nano carbon material composite_body | complex containing.   A nanocarbon material composite comprising a substrate and a nanocarbon material having a constricted structure grown on the substrate.   An electron-emitting device using a nanocarbon material composite made of a nanocarbon material having a constricted structure grown on a substrate.