JP2002255526A - CARBON NANOTUBE, CARBON NANOTUBE FILM, SiC SUBSTRATE WITH CARBON NANOTUBE FILM, AND WHISKER WITH CARBON NANOTUBE AND ITS PRODUCING METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon nanotube film produced from polycrystalline SiC, porous SiC and SiC whisker and having large area and arranged in a specific direction, carbon nanotube arranged in a specific direction, an SiC substrate with the carbon nanotube film, and a whisker with the carbon nanotube and its producing method. SOLUTION: The carbon nanotube film is formed on the surface of a sintered body by removing silicon atom from SiC when the polycrystalline or porous sintered body composed of SiC is heated to the temperature at which silicon atom is lost from the surface of the sintered body by SiC decomposition under vacuum condition and consists of carbon nanotubes arranged in the specific direction. A carbon nanotube 2 is generated on the peak of an SiC whisker 3 and in the direction of whisker elongation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbon nanotube, a carbon nanotube film, a SiC substrate with a carbon nanotube film, a whisker with a carbon nanotube, and a method for producing the same. The carbon nanotubes, carbon nanotube films, SiC substrates with carbon nanotube films, and whiskers with carbon nanotubes of the present invention are widely used as electronic materials, electron sources, energy sources, and the like.

[0002]

2. Description of the Related Art In recent years, in the field of electronic materials such as electronic devices,
Investigate carbon nanotubes and carbon nanotube films for applications in the field of electron sources such as field emission type electron sources and flat panel displays, and in the field of energy such as hydrogen storage and nano cylinders. Investigations on a method for producing the product stably with a high yield are being actively conducted. Japanese Patent Application Laid-Open No. 10-265208 describes a carbon nanotube and a method for producing the carbon nanotube.
It is known from Japanese Patent Publication No. However, there is a demand for a carbon nanotube film in which carbon nanotubes are reliably grown in a large area and oriented in a predetermined direction. Also,
It is a fact that neither the growth of carbon nanotubes nor the formation of carbon nanotube films is known for porous SiC and SiC whiskers.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances.
Provided are a carbon nanotube film manufactured from iC and SiC whiskers, having a large area and oriented in a predetermined direction, a carbon nanotube oriented in a predetermined direction, a SiC substrate with a carbon nanotube film, a whisker with carbon nanotubes, and a method of manufacturing the same. With the goal.

[0004]

According to a first aspect of the present invention, there is provided a carbon nanotube film comprising a polycrystalline sintered body made of SiC under a vacuum, wherein the polycrystalline sintered body is decomposed at a vacuum degree of the vacuum. By heating to a temperature at which silicon atoms are lost from the surface of the body, the silicon atoms are removed from the SiC, and formed of a large number of carbon nanotubes formed on the surface of the polycrystalline sintered body and oriented in a predetermined direction. It is characterized by the following.

[0005] The crystal phase of the polycrystalline sintered body is α-SiC
However, β-SiC may be used, but those made of cubic β-SiC having high symmetry are preferable. Also, the shape of the sintered body is not particularly limited, such as a plate shape (a circle, a square, an L shape, etc.), a linear shape (a straight line, a curve, etc.), a lump shape (a cube, a rectangular parallelepiped, a sphere, a substantially spherical shape, etc.). Further, the degree of roughness of the surface of the polycrystalline sintered body on which the carbon nanotube film is formed is not particularly limited, and may be any of a smooth surface and an uneven surface. In order to surely obtain a carbon nanotube film, it is preferable to use a smooth surface.

The surface of the above-mentioned polycrystalline sintered body has a state in which crystal faces are oriented in various directions. Cubic β-
Since SiC has eight kinds of (111) planes, if this is heated under vacuum, silicon atoms are easily removed from the (111) plane, so that carbon nanotubes are [111].
The orientation is high, that is, in the direction perpendicular to the (111) plane.
When the polycrystalline sintered body is heated under vacuum, eight (1)
When only one (111) plane of the 11) planes is exposed parallel to the surface of the sintered body, the carbon nanotube grows perpendicular to the (111) plane. Also, 2
When two (111) planes are simultaneously exposed in different directions, the carbon nanotubes grow perpendicularly in the respective [111] directions, so that a carbon nanotube film having a zigzag structure is formed on the surface of the sintered body. On the other hand, α-SiC
Has the highest orientation in the (0001) plane, for example, (1)
Since the carbon nanotubes are oriented on the surface of the 12￣0) system, the carbon nanotube film can be formed on almost the entire surface of the sintered body.

The carbon nanotube film of the present invention is made of Si
The degree of vacuum and the heating temperature can be obtained without any particular limitation as long as silicon atoms can be removed by decomposition of C. The preferred degree of vacuum is 10 ^-1 to 10 ^-10 Torr
(More preferably 10 ^-2 ~10 ^{- 9} Torr, more preferably 10 ^-4 ~10 ^-7 Torr) in the range of, also, the preferred heating temperature is 800-2,200 ° C. (more preferably 1000 to 2000 ° C., further Preferably 1200 to 19
00 ° C.). If the degree of vacuum and heating temperature are too high, the rate at which silicon atoms are lost from SiC is high,
The orientation of the carbon nanotubes is likely to be disturbed and the diameter tends to be large, the carbon itself also becomes CO and evaporates, the carbon nanotube film thickness becomes thinner and further disappears, and a disturbed graphite layer is formed, which is not preferable. . The means for heating the polycrystalline sintered body is not particularly limited, and includes an electric furnace, laser beam irradiation,
Means such as direct current heating and infrared irradiation heating can be used.

In the carbon nanotube film according to the second aspect of the present invention, the porous sintered body made of SiC is vacuum-decomposed, and the silicon atoms are lost from the surface of the porous sintered body due to decomposition of SiC at the vacuum degree. By heating to a temperature
It is characterized by comprising a number of carbon nanotubes formed on the surface of the porous sintered body by removing silicon atoms from iC and oriented in a predetermined direction.

The porous sintered body is not particularly limited as long as it has a structure having a high porosity. Further, the shape of the pore may be spherical or irregular, and may be a closed pore or a pore communicating with the outside. Further, the shape of the sintered body is not particularly limited. The carbon nanotube film according to claim 2 can be manufactured under preferable conditions for manufacturing the carbon nanotube film according to claim 1, and a carbon nanotube film can be formed on any part of a sintered body having irregularities. . That is, since the carbon nanotube film can be formed on almost the entire surface of the internal pores of the porous sintered body, it has a very high density and a large area.
And, in practice, it is possible to utilize the high-density characteristics as compared with the carbon nanotube film formed on the powder SiC,
At the same time, handling becomes easy.

[0010] The carbon nanotube film according to claim 4 is characterized in that after polishing the surface of a shaped body made of a polycrystalline sintered body made of cubic SiC, the shaped body is evacuated to a vacuum degree. By heating to a temperature at which SiC is decomposed and silicon atoms are lost from the polished surface of the shaped body,
It is characterized by comprising a large number of carbon nanotubes formed on the polished surface of the shaped body by removing silicon atoms from SiC and oriented in the [111] direction.

The shape of the above-mentioned shaped body is not particularly limited since the surface on which the carbon nanotubes are grown is polished, and may be plate-like, linear, or massive. The surface may be flat or curved. Further, the size is not particularly limited. When the surface of the above-mentioned shaped body is polished, eight (111) planes of cubic SiC are easily exposed, and carbon nanotubes are surely grown from all the exposed (111) planes by heat treatment. A film can be formed. If the surface of the shaped body is not polished, the formed carbon nanotubes are shortened or a carbon layer which is hardly called a carbon nanotube is formed, which results in a disordered film, which is not preferable. Further, when the polycrystalline sintered body is made of α-SiC, if the surface of the shaped body is polished, more crystal planes will appear than cubic SiC. No (0
Except for the (001￣) -Si plane and the (11￣00) plane, there are six (112￣0) planes, so that oriented carbon nanotubes are formed on almost the entire surface. At this time, if the surface of the shaped body is not polished, it becomes an undesired film, which is not preferable. The method for obtaining the polished surface of the shaped body is not particularly limited, and can be a known method. Also,
Preferred production conditions are the same as those described in claim 1.

According to a fifth aspect of the present invention, the SiC substrate provided with a carbon nanotube film comprises a polycrystalline sintered SiC substrate and a polycrystalline sintered SiC substrate which are decomposed under vacuum to a degree of vacuum. By heating to a temperature at which silicon atoms are lost from the surface of the sintered SiC substrate, silicon atoms are removed from the SiC, and a large number of carbon nanotubes oriented in a predetermined direction from the surface of the sintered SiC substrate are formed. , Is provided.

The crystal phase of SiC of the polycrystalline sintered SiC substrate is not particularly limited, but is preferably made of cubic SiC. The surface of the polycrystalline sintered SiC substrate is preferably a smooth surface. Preferred conditions for growing a carbon nanotube film on the polycrystalline sintered SiC substrate and the reasons therefor are the same as those in the first or second aspect.

[0014] The carbon nanotube film and the substrate with the carbon nanotube film of the present invention include a gas separation film, hydrogen storage,
It can be applied to negative electrode materials of lithium ion batteries.

[0015] The carbon nanotube according to claim 6 is:
It is characterized in that it is formed at the tip of the SiC whisker in the direction of the extension of the whisker. The SiC whisker may be either α-SiC or β-SiC as long as it is a whisker-like single crystal. When the SiC whiskers are α-SiC, the growth direction of the whiskers is [0
001] direction, the end surface of the whisker tip is (0
001) plane, and in the case of β-SiC, since the growth direction of the whiskers is the [111] direction, the end face at the tip tends to be the (111) plane.
Carbon nanotubes tend to grow in the direction of the extension of the SiC whiskers. Further, carbon nanotube-like materials may grow on the side surfaces of the SiC whiskers. For example, in the case of β-SiC, the graphite layer corresponds to the surface farthest from the (111) plane, so that the graphite layer is parallel to the surface. Remains formed.

In the carbon nanotube of the present invention, the SiC whisker having the above-mentioned crystal plane is formed by reducing the degree of vacuum to preferably 10 ^-1 to 10 ^-10 Torr (more preferably 10 ^-2 to 1 Torr).
0 ^-9 Torr, more preferably 10 ^-4 to 10 ^-7 Torr
r) and the heating temperature is preferably from 800 to 2
It can be manufactured by treating at a temperature in the range of 200 ° C (more preferably 1000 to 2000 ° C, further preferably 1200 to 1900 ° C). Under the above conditions, the carbon nanotube of the present invention is easily formed in the direction of the extension of the SiC whisker.

According to a seventh aspect of the present invention, there is provided a whisker with a carbon nanotube, comprising: a SiC whisker main body; and a carbon nanotube formed at a tip of the whisker main body and in an extension direction of the whisker main body. In the method for manufacturing a whisker with carbon nanotubes according to claim 8, the SiC whisker is heated under vacuum to a temperature at which SiC is decomposed at the vacuum degree and silicon atoms are lost from the tip of the SiC whisker. With this, the Si
The method is characterized in that silicon atoms are removed from C, and carbon nanotubes are grown from the tip of the whisker in the extension direction of the whisker.

The whisker with carbon nanotubes of the present invention can be manufactured by the same method as described in the carbon nanotube of claim 6. In this case, SiC
It can be manufactured regardless of the size of the whisker. Further, according to the above manufacturing method, not only one carbon nanotube is formed at the tip of the SiC whisker,
It can also be obtained as an aggregate of two or more. FIG. 9 shows a cross-sectional view of the whisker with carbon nanotubes of the present invention. The whisker 1 with carbon nanotubes is composed of a SiC whisker 3, a carbon nanotube 2 grown in an extension direction from the tip thereof, and a graphite layer 4 formed on the side surface of the SiC whisker 3 and covering the side surface of the SiC whisker 3.

The carbon nanotubes and whiskers with carbon nanotubes of the present invention are characterized in that a graphite layer is formed on the side surfaces of the whiskers, so that electrical conductivity can be obtained. Can be used. In this case, there is an advantage that handling is easy because SiC whiskers thicker than carbon nanotubes are handled. In addition, nano-processing with the tip of a scanning probe microscope has been attempted,
Since the length of the carbon nanotube of the present invention can be controlled, it is also possible to control the strength for processing.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. Example 1 (Production of carbon nanotube film) β-SiC powder having an average particle diameter of 1 μm (trade name “MSC-
20β-SiC powder ”, manufactured by Mitsui Toatsu Co., Ltd.
The resultant was fired at 50 ° C. for 0.5 hour to obtain a polycrystalline sintered body having a length of 5 mm, a width of 5 mm, and a thickness of 5 mm. The surface of this polycrystalline sintered body was mirror-polished using a φ0.3 μm alumina slurry. The above sintered body was placed in a high-temperature vacuum heating furnace (High Multi 1
0000, manufactured by Fuji Denki Kogyo Co., Ltd.)
Heated at ^0-4 Torr, 1600 ° C. for 0.5 hour. The carbon nanotube film formed on the sintered body was observed from a cross-sectional direction using a high-resolution transmission electron microscope (200 KV-002B, manufactured by Topcon Corporation). TEM showing the interface between the carbon nanotube film and the sintered body when the (111) plane of SiC is substantially parallel to the sample surface
FIG. 1 shows a photograph, and FIG. 2 shows a TEM photograph when two (111) planes of SiC are simultaneously exposed in different directions.
FIG. 3 shows a TEM photograph when the (111) plane of iC is exposed but the outermost surface is the Si plane, and a TEM photograph when the (111) plane of SiC is not exposed in the sintered body. 4
Shown in

FIG. 1 shows that carbon nanotubes having uniform length and tube diameter were grown in the [111] direction with good orientation to form a carbon nanotube film. From FIG. 2, two carbon nanotubes (11
1) It can be seen that a carbon nanotube film having a zigzag structure was formed by growing vertically on the respective surfaces. Further, as shown in FIG. 3, since the surface of the sintered body is a Si surface, it is not formed in a direction perpendicular to the (111) plane confirmed by electron beam diffraction, and is not shown in the electron beam diffraction image. (111) on the C plane
It can be seen that they were formed in a direction perpendicular to the plane. FIG.
Is the case where the (111) plane does not appear in the electron beam diffraction image of the surface of the sintered body, and the growth direction of the carbon nanotube is contrast (striped pattern) corresponding to the lamination of the (111) plane seen in SiC. Is expected to be related to
Since the (111) plane is inclined with respect to the plane of the paper, it is observed that the (111) plane, which is seen in SiC as a result of the projection, deviates from the perpendicular to the stacking contrast. As described above, a carbon nanotube film can be formed on the surface of the polycrystalline sintered body made of β-SiC. The carbon nanotubes to be produced differ particularly depending on the crystal planes of the exposed SiC. When the (111) plane is arranged in parallel to the surface of the sintered body, a carbon nanotube film having the best orientation was formed. In β-SiC, (11
1) Since there are eight planes, there is a very high possibility that any one of the (111) planes will appear on the surface of the sintered body, particularly when the surface is made smooth by polishing or the like, and the polycrystalline sintered body It is considered that the carbon nanotube film was formed on almost the entire surface of the substrate.

Example 2 (Preparation of Carbon Nanotube on SiC Whisker Tip) β-SiC whisker (trade name “SiC whisker”,
(Tokai Carbon Co., 0.3μm in cross-section, several μm in length)
Using a high-temperature vacuum heating furnace (High Multi 10000 type, manufactured by Fuji Denki Kogyo KK) at a pressure of 1 × 10 ⁻⁴ Torr, 150
After heating at 0 ° C. for 2 hours, the carbon nanotubes growing in the extension direction of the whiskers were observed using the high-resolution transmission electron microscope. FIGS. 5 to 8 show the carbon nanotubes formed at the tips of the whiskers. FIGS. 5 and 7 are general views, and FIGS. 6 and 8 are enlarged views of the formed carbon nanotubes.

FIG. 5 and FIG. 7 show that the carbon nanotube was formed at the tip of the SiC whisker in the direction of its extension. 6 and 8 are examples in which one carbon nanotube is formed, but it is considered that a large number of carbon nanotubes can be formed depending on conditions.

The present invention is not limited to the above embodiment, but can be variously modified within the scope of the present invention. For example, a polycrystalline sintered body made of SiC bonded to a substrate made of ceramics, metal, or the like can be used as a substrate having a carbon nanotube film by heat treatment. In this case, the carbon nanotube film, SiC
It may have a three-layer structure of a sintered body and a substrate, or may completely decompose SiC to form a two-layer structure of a carbon nanotube film and a substrate.
It may have a layered structure. The substrate is not particularly limited as long as it is not deformed by heat during the formation of the carbon nanotube and does not hinder the formation of the carbon nanotube film. In addition, the form may be any of a plate shape, a film shape, a tubular shape, and the like, and the surface may be a smooth surface or an uneven surface.

[0025]

The carbon nanotube film of the present invention can be a film in which carbon nanotubes are reliably formed in a predetermined direction depending on the crystal plane of SiC constituting a sintered body. Obtainable. Further, according to the substrate with a carbon nanotube film, a carbon nanotube film formed in a large area and in a predetermined direction can be used functionally. The carbon nanotube of the present invention has S
Since it can be manufactured from an iC whisker and can be obtained in a substantially straight state, it can be used as a probe of a scanning probe microscope or the like.

[Brief description of the drawings]

FIG. 1 is a TEM photograph showing a carbon nanotube film.

FIG. 2 is a TEM photograph showing another carbon nanotube film.

FIG. 3 is a TEM photograph showing another carbon nanotube film.

FIG. 4 is a TEM photograph showing another carbon nanotube film.

FIG. 5 is a TEM photograph showing carbon nanotubes, and is an overall view.

FIG. 6 is an enlarged view of a carbon nanotube formed on a SiC whisker.

FIG. 7 is a TEM photograph showing another carbon nanotube, and is an overall view.

FIG. 8 is an enlarged view of a carbon nanotube formed on another SiC whisker.

FIG. 9 is an explanatory sectional view showing a whisker with a carbon nanotube.

[Explanation of symbols]

1; whiskers with carbon nanotubes; 2; carbon nanotubes; 3; SiC whiskers; 4; graphite layers.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsukasa Hirayama 2-4-1 Rokuno, Atsuta-ku, Nagoya City Inside the Fine Ceramics Center (72) Inventor Noriyoshi Shibata 2-4-1, Rokuno, Atsuta-ku, Nagoya No. F-term in the Fine Ceramics Center (Reference) 4G046 CA00 CB03 CC02 CC03

Claims (8)

[Claims] 1. Heating a polycrystalline sintered body made of SiC under a vacuum to a temperature at which SiC is decomposed at a vacuum degree and silicon atoms are lost from the surface of the polycrystalline sintered body. A carbon nanotube film comprising a large number of carbon nanotubes formed on the surface of the polycrystalline sintered body by removing silicon atoms from SiC, and oriented in a predetermined direction. 2. Heating a porous sintered body made of SiC under vacuum to a temperature at which SiC is decomposed at the vacuum degree and silicon atoms are lost from the surface of the porous sintered body, A carbon nanotube film comprising a number of carbon nanotubes formed on the surface of a porous sintered body by removing silicon atoms from SiC and oriented in a predetermined direction. 3. When the SiC is cubic, the carbon nanotubes are oriented in the [111] direction.
3. The carbon nanotube film according to item 1. 4. After polishing the surface of a shaped body made of a polycrystalline sintered body composed of cubic SiC, the shaped body is decomposed under a vacuum at a vacuum degree of the vacuum to form the shaped body. By heating to a temperature at which silicon atoms are lost from the polished surface of the body, the silicon atoms are removed from the SiC to form a large number of carbon nanotubes formed on the polished surface of the shaped body and oriented in the [111] direction. A carbon nanotube film characterized by the above-mentioned. 5. A polycrystalline sintered SiC substrate and the polycrystalline sintered SiC substrate under a vacuum, wherein SiC is decomposed at a vacuum degree, and silicon is decomposed from the surface of the sintered SiC substrate. A plurality of carbon nanotubes oriented in a predetermined direction from the surface of the sintered SiC substrate by removing silicon atoms from the SiC by heating to a temperature at which the atoms are lost. With SiC
substrate. 6. A carbon nanotube formed at the tip of a SiC whisker in the direction of an extension of the whisker. 7. A whisker with carbon nanotubes, comprising: a SiC whisker main body; and a carbon nanotube formed at the tip of the whisker main body and in the direction of the extension of the whisker main body. 8. A method for removing silicon atoms from SiC by heating the SiC whiskers under vacuum to a temperature at which SiC is decomposed at the vacuum degree and silicon atoms are lost from the tips of the SiC whiskers; A method for producing a whisker with carbon nanotubes, comprising growing carbon nanotubes from the tip of the whisker in the direction of the extension of the whisker.