JP2006225184A - Manufacture of carbon nanotube and carbon nanohorn, manufacture of arc soot containing carbon nanotube or carbon nanohorn and carbon material used for manufacturing raw material for synthesizing carbon nanoballoon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon material for manufacturing a carbon nanotube and a carbon nanohorn capable of increasing a yield of the carbonnanotube and the carbon nanohorn and also capable of obtaining a high-purity product and to provide the carbon material used for manufacturing an arc soot containing the carbon nanotube or the carbon nanohorn and used for manufacturing a raw material for synthesizing a nanoballoon. <P>SOLUTION: In a graphitized material obtained by treating at a high temperature a formed body obtained by compounding a coal-based coke powder having an average particle size of 2-15 μm as an aggregate and pitch or resin as a binder and forming the mixture or a formed body obtained by forming the aggregate composed of a mesophase, a specific resistance of the graphitized material at room tempereture is ≤20-8 μΩm, a bulk density is 1.85-1.95 g/cm<SP>3</SP>, a bending strength is ≥50 MPa and a gas transmittance is ≤0.10 cm<SP>2</SP>/sec. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a carbon material used for production of carbon nanotubes and carbon nanohorns by arc discharge, production of arc soot containing carbon nanotubes or carbon nanohorns, and production of carbon nanoballoon synthesis raw materials.

  In recent years, graphite materials with nanometer-scale microstructures have attracted attention as single-walled or multi-walled carbon nanotubes or carbon nanohorns, and these nanostructured graphite materials are used for conductive fillers, scanning probe microscope probes, field Applications in various fields such as emission displays, fuel cells, and hydrogen storage are expected.

  Conventionally, the nanostructured graphite material has been produced by an arc discharge method in which a high energy heat source such as arc discharge or laser irradiation is applied to a carbon material, a laser evaporation method, etc. In these production methods, usually, Fe, The production condition is to co-evaporate a metal catalyst such as Ni or Co (see Patent Document 1).

  However, carbon nanotubes synthesized by the arc discharge method or laser evaporation method are excellent in crystallinity, but have a drawback that the amount of synthesis is small. In addition, the metal catalyst is mixed into the carbon nanotube, so that there is a problem that the purity is lowered. There is also a technique for obtaining carbon nanotubes by a CVD method. According to this technique, the synthesis amount of carbon nanotubes increases, but there is a problem that structural defects increase.

When carbon nanotubes are synthesized by the arc discharge method, the carbon material used as the raw material is a material with specified electrical resistance and thermal conductivity, and the carbon nanotube synthesis ratio is increased to increase the yield and crystallinity. It has also been proposed to obtain excellent carbon nanotubes (see Patent Documents 2 and 3).
JP 2002-201014 A JP 2004-149335 A JP 2004-189533 A

  In the production of carbon nanotubes and carbon nanohorns by the arc discharge method, the present invention can increase the synthesis ratio of carbon nanotubes and carbon nanohorns, increase the yield, and increase the purity of carbon nanotubes and carbon nanohorns in the product. In order to obtain carbon nanotubes and carbon nanohorns that can be produced, the results of further examination and examination of the relationship between physical properties such as electrical resistance values and the synthesis ratio, in particular, based on the above-mentioned proposals. It is an object of the present invention to provide a carbon material for producing carbon nanotubes and carbon nanohorns that can produce a large amount of carbon nanotubes and carbon nanohorns with high purity. Another object of the present invention is to provide a carbon material used for production of arc soot containing carbon nanotubes or carbon nanohorns, and production of a raw material for carbon nanoballoon synthesis.

In order to achieve the above object, the carbon material used for the production of carbon nanotubes and carbon nanohorns according to claim 1, the production of arc soot containing carbon nanotubes or carbon nanohorns, and the production of carbon nanoballoon synthesis raw materials, High-temperature treatment of coal-based coke powder having an average particle size of 2 to 15 μm, a molded product obtained by molding pitch or resin as a binder and molding, or a molded product obtained by molding an aggregate made of mesophase The graphitized material has a specific resistance at room temperature of 20 to 8 μΩm, a bulk density of 1.85 to 1.95 g / cm ³ , a bending strength of 50 MPa or more, and a gas permeability of 0.10 cm ² / sec. It is characterized by the following.

  The carbon material for use in the production of carbon nanotubes and carbon nanohorns according to claim 2, the production of arc soot containing carbon nanotubes or carbon nanohorns, and the production of carbon nanoballoon synthesis raw materials is the carbon material used in claim 1, wherein the high temperature treatment is 2000 It is performed at ˜3000 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon material for carbon nanotube and carbon nanohorn manufacture which can increase the yield of a carbon nanotube and carbon nanohorn and can obtain a highly purified product is provided. The carbon material can also be suitably used for the production of arc soot containing carbon nanotubes or carbon nanohorns, and for the production of carbon nanoballoon synthesis raw materials. (Japanese Patent Application No. 2004-097875)

  The carbon material according to the present invention includes coal-based coke powder having an average particle diameter of 2 to 15 μm as an aggregate, pitch or resin as a binder, and is molded into a molded body (first molded body), or made of mesophase. It is a graphitized product obtained by forming an aggregate into a molded body (second molded body) and subjecting these molded bodies to a high temperature treatment.

  The first molded body is formed, for example, by kneading an aggregate and a binder, pulverizing the kneaded material, and cold isostatic pressing. As the aggregate, coal-based coke powder having an average particle diameter of 2 to 15 μm is preferably used. When the average particle size of coal-based coke exceeds 15 μm, it is difficult to evaporate uniformly during arc discharge, and particles that have not been completely evaporated fall off. Therefore, carbon fragments of several μm in the obtained soot (product) And the content of carbon nanotubes and carbon nanohorns in the product are significantly reduced. On the other hand, when the average particle diameter of coal-based coke is less than 2 μm, oxidation consumption increases during arc discharge, and the amount of soot recovered decreases.

  The second molded body is formed by, for example, cold isotropic pressure molding of an aggregate made of mesophase such as mesocarbon microbeads alone. The first molded body and the second molded body are subjected to high-temperature treatment, for example, high-temperature firing, and then heated to a higher temperature in an inert atmosphere to be graphitized to obtain a graphitized product. In this case, the high temperature treatment for graphitization is desirably performed at 2000 to 3000 ° C.

About the obtained graphitized material, the specific resistance at room temperature is 20 to 8 μΩm, the bulk density is 1.85 to 1.95 g / cm ³ , the bending strength is 50 MPa or more, and the gas permeability is 0.10 cm ² / sec or less. It is preferable to provide the carbon material used for the production of carbon nanotubes and carbon nanohorns according to the present invention, the production of arc soot containing carbon nanotubes or carbon nanohorns, and the production of carbon nanoballoon raw materials.

  When the specific resistance exceeds 20 μΩm, a higher voltage is required in the production of carbon nanotubes and carbon nanohorns by the arc discharge method, so that a large amount of electric power is required, leading to an increase in production costs of the carbon nanotubes and carbon nanohorns. The use of high voltages can be dangerous during manufacturing. On the other hand, if the specific resistance is less than 8 μΩm, arc discharge is difficult to occur, the heat generation amount is reduced, and the evaporation amount of soot is reduced. When the high-temperature treatment temperature for graphitization is less than 2000 ° C., the specific resistance of the graphitized material becomes high, the arc discharge becomes unstable, and a sufficient molded product (soot) cannot be recovered. Moreover, since the crystallinity of the carbon material itself is poor, the yield of carbon nanotubes and carbon nanohorns in the soot is reduced.

When the bulk density is less than 1.85 g / cm ³ , there are many voids between the graphitized particles, and cracks are likely to occur during arc discharge, and a large number of carbon pieces of several μm are generated in the generated soot. It mixes and the content rate of the carbon nanotube and carbon nanohorn in a soot is reduced. On the other hand, when the bulk density exceeds 1.95 g / cm ³ , the propagation speed of cracks is increased during arc discharge, and long cracks are likely to occur.

If the bending strength is less than 50 MPa, the strength and thermal shock resistance are inferior, and it becomes difficult to withstand the impact during arc discharge. The gas permeability of the graphitized material is important as a carbon material for producing carbon nanotubes and carbon nanohorns. When the gas permeability exceeds 0.10 cm ² / sec, a lot of continuous bubbles are present. In such a bubble, current does not flow during arc discharge, and micro drift occurs, so that micro arc uniform arc discharge does not occur. Accordingly, uniform carbon nanotubes and carbon nanohorns cannot be obtained, and foreign matters and the like increase, so that the content (yield) of the carbon nanotubes and carbon nanohorns in the product (soot) decreases.

  When the decrease in purity is allowed, metal catalysts such as Fe, Ni, and Co may be co-evaporated during arc discharge. As a method for adding the metal catalyst, a method of mixing metal powder at the time of mixing raw materials, a method of impregnating a carbon material by immersing it in a metal-containing solution, and the like can be applied.

  Examples of the present invention will be described below in comparison with comparative examples. These examples show one embodiment of the present invention relating to the synthesis of carbon nanohorns, and the present invention is not limited thereto. In addition, the result similar to the case of the synthesis | combination of the carbon nanohorn was obtained also about the synthesis | combination of the carbon nanotube according to this invention.

Example 1
60 parts by mass of coal tar pitch (medium pitch, softening point 90 ° C.) was added to 100 parts by mass of coal-based coke (average particle size 10 μm), and kneaded at a temperature of 150 to 200 ° C. The resulting kneaded product was pulverized to an average particle size of 50 μm and then cold isostatically pressed with a pressure of 100 MPa.

  The obtained molded body was fired at a temperature of 1000 ° C., further heated to 3000 ° C. in an inert atmosphere, and graphitized to obtain a graphitized product. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of this graphitized material at room temperature. The crystal lattice spacing (d002) of the graphitized product was 0.3360 nm, and the crystallite thickness (Lc) was 90 nm.

  The arc discharge apparatus used is shown in FIG. As shown in FIG. 1, the graphitized materials 5 and 6 processed into dimensions of 6.4 mm in diameter and 150 mm in length are passed from a gas cylinder 13 through a gas regulator and a flow meter 12 into a reaction chamber 7 filled with an inert gas. The electrodes were set facing each other. Then, two electrodes were made to contact using the motor 8, and direct current was sent using the direct current supply device 10 there. When the two electrodes were separated, an arc was generated between the electrodes, and the anode was evaporated violently by setting the distance between the electrodes to about several mm. The generated evaporant 11 escaped to a wide space via the arc plasma, and then the substance adhering in the chamber 7 was recovered as a product (soot). 1 is a scale screen, 2 is a filter, 3 is a lens, 4 is a pressure gauge, 9 is a water cooling jacket, 14 is a vacuum pump, and 15 is a valve.

  Table 1 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

Example 2
A graphitized product was obtained in the same manner as in Example 1 except that mesocarbon microbeads (average particle size 6 μm) were used as an aggregate, and this was cold isostatically pressed alone. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature.

  The graphitized material was processed into the same dimensions as in Example 1, and this was placed in an arc discharge device to perform arc discharge. Table 1 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

Comparative Example 1
A graphitized product was obtained in the same manner as in Example 1 except that coal-based coke (average particle size: 6 μm) was used as an aggregate. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature. In Table 1, the comparative examples that are outside the conditions of the present invention are underlined.

  The graphitized material was processed into the same dimensions as in Example 1, and this was placed in an arc discharge device to perform arc discharge. Table 2 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

Comparative Example 2
A graphitized material is obtained by treating in the same manner as in Example 1 except that 100 parts by mass of coal tar pitch (medium pitch, softening point 90 ° C.) is added to 100 parts by mass of coal-based coke (average particle diameter 10 μm). It was. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature.

  The graphitized material was processed into the same dimensions as in Example 1, and this was placed in an arc discharge device to perform arc discharge. Table 2 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

Comparative Example 3
A graphitized product was obtained in the same manner as in Example 1 except that petroleum coke (average particle size: 10 μm) was used as the aggregate. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature.

  The graphitized material was processed into the same dimensions as in Example 1, and this was placed in an arc discharge device to perform arc discharge. Table 2 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

Comparative Example 4
The same treatment as in Example 1 except that 70 parts by mass of coal tar pitch (medium pitch, softening point 90 ° C.) was added to 100 parts by mass of lamp black (average particle diameter 0.1 μm measured by electron microscope). Thus, a graphitized product was obtained. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature.

  The graphitized material was processed into the same dimensions as in Example 1, and this was tried to be installed in an arc discharge device. However, since the graphitized material was brittle and destroyed at the time of installation, arc discharge could not be performed.

Comparative Example 5
A graphitized product was obtained in the same manner as in Example 1 except that the firing and graphitizing temperature was 1000 ° C. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature. The crystal lattice spacing (d002) of the graphitized product was 0.3340 nm, and the crystallite thickness (Lc) was 5 nm.

  The graphitized material was processed into the same dimensions as in Example 1, and this was placed in an arc discharge device to perform arc discharge. Table 2 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

Comparative Example 6
A graphitized product is obtained by treating in the same manner as in Example 1 except that 50 parts by mass of coal tar pitch (medium pitch, softening point 90 ° C.) is added to 100 parts by mass of coal-based coke (average particle size 10 μm). It was. Table 1 shows the specific resistance, bulk density, three-point bending strength, and gas permeability of the graphitized material at room temperature.

  The graphitized material was processed into the same dimensions as in Example 1, and this was placed in an arc discharge device to perform arc discharge. Table 2 shows arc discharge conditions and power consumption. In addition, Table 2 shows the recovered amount of soot (carbon nanohorn) obtained by arc discharge and the carbon nanohorn content (CNH content) in the soot observed with a transmission electron microscope (TEM).

  As can be seen from Tables 1 and 2, all of Examples 1 and 2 according to the present invention have a large amount of recovered product (soot) and a high content of carbon nanohorns in the soot (CNH content). Indicated.

  On the other hand, in Comparative Example 1, since the average particle diameter of the aggregate is large, the bulk density is small, the gas permeability is large, and the CNH content in the produced soot is low. Since Comparative Example 2 has a large specific resistance, power consumption during arc discharge is large. Since Comparative Example 3 uses petroleum-based coke as an aggregate, the amount of recovered soot is low.

  In Comparative Example 4, lamp black having an average particle diameter of 0.1 μm was used as the aggregate, so that the strength was small and the arc discharge could not be endured. Since Comparative Example 5 has a low graphitization temperature, the CNH content in the soot is low, and the specific resistance is large, and the power consumption during arc discharge is also large. Since Comparative Example 6 has a high gas permeability, the CNH content in the produced soot is low.

FIG. 1 is a schematic view of arc discharge devices used in Examples and Comparative Examples.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scale screen 2 Filter 3 Lens 4 Pressure gauge 5 Cathode 6 Anode 7 Reaction chamber 8 Motor 9 Water-cooling jacket 10 DC supply device 11 Product (煤)
12 Gas regulator and flow meter 13 Gas cylinder 14 Vacuum pump 15 Valve

Claims (2)

A coal-based coke powder having an average particle diameter of 2 to 15 μm as an aggregate, a pitch or a resin as a binder, and a molded body obtained by molding, or a molded body obtained by molding an aggregate made of mesophase is heated to a high temperature. A graphitized material obtained by treatment, wherein the graphitized material has a specific resistance at room temperature of 20 to 8 μΩm, a bulk density of 1.85 to 1.95 g / cm ³ , a bending strength of 50 MPa or more, and a gas permeability of 0.10 cm. ^The carbon material used for manufacture of the carbon nanotube and carbon nanohorn characterized by being ² / sec or less, manufacture of the arc soot containing a carbon nanotube or carbon nanohorn, and manufacture of the raw material for carbon nanoballoon synthesis. The high-temperature treatment is performed at 2000 to 3000 ° C, the production of carbon nanotubes and carbon nanohorns according to claim 1, the production of arc soot containing carbon nanotubes or carbon nanohorns, and the production of raw materials for carbon nanoballoon synthesis Carbon material used for

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