JP5526315B2 - Method for producing carbon nanotubes - Google Patents

Description

  The present invention relates to a method for producing carbon nanotubes. More specifically, the present invention relates to a method for producing carbon nanotubes in a short time using an inexpensive heating device such as a household microwave oven. The term “carbon nanotubes” used in the present specification, claims, and the like includes not only carbon nanotubes but also carbon nanocapsules.

  Carbon nanotubes are generally produced by an arc discharge method, a laser ablation method, a chemical vapor deposition method (CVD method), or the like. In addition to these methods, a method for producing carbon nanotubes from nickel stearate using an electric furnace has been reported (see Non-Patent Document 1).

  This method is a method for producing carbon nanotubes by heating nickel stearate from 800 ° C. to 1000 ° C. in an electric furnace under an argon atmosphere.

Junfeng Geng, 2 others, "Journal of Materials Chemistry", 2005, Vol. 15, p.844-849

  According to the method described in Non-Patent Document 1, carbon nanotubes can be produced under mild conditions using an inexpensive apparatus as compared with the arc discharge method, laser ablation method, and CVD method. However, when an electric furnace is used, it takes an extremely long time of several hours until the temperature is increased from room temperature to the temperature at which carbon nanotubes are generated, and after the carbon nanotubes are generated, the temperature is decreased to room temperature. Moreover, the advent of a method for producing carbon nanotubes using a heating device that is cheaper than an electric furnace is desired.

  This invention is made | formed in view of such a situation, and it aims at providing the method of manufacturing carbon nanotubes in a short time using an inexpensive heating apparatus.

  As a result of intensive efforts to achieve the above-mentioned object, the present inventors have applied electromagnetic waves to metal-containing nanofibers having nanofibers and carbon nanotube-forming catalysts in an environment where electromagnetic wave energy is converted into thermal energy. It has been found that carbon nanotubes can be produced in an extremely short time of about 10 minutes using an inexpensive heating device by irradiating energy, and the present invention has been completed.

[1] The method for producing carbon nanotubes of the present invention includes a metal-containing nanofiber preparation step of preparing a metal-containing nanofiber having a nanofiber made of an organic polymer and a metal having a carbon nanotube production catalytic action, and electromagnetic energy The metal-containing nanofibers are heated by irradiating the heat-generating container with electromagnetic energy and heating the heat-generating container in a state where the metal-containing nanofibers are placed in a heat-generating container provided with a substance that converts the heat into heat energy. As a result, the method includes a carbon nanotube generation step of generating carbon nanotubes including the metal using the nanofiber as a carbon source.

  According to the method for producing carbon nanotubes of the present invention, carbon nanotubes can be produced in a short time using an inexpensive heating device. Moreover, according to the method for producing carbon nanotubes of the present invention, since the nanofiber contained in the metal-containing nanofiber is used as a carbon source, no carbon source is required in addition to the metal-containing nanofiber, thereby simplifying the production process. There is also an effect that can be done.

[2] In the method for producing carbon nanotubes according to the present invention, the metal-containing nanofibers that house the metal-containing nanofibers in the heating container between the metal-containing nanofiber preparation step and the carbon nanotubes generation step. It is preferable to further include a fiber accommodation step.

[3] In the method for producing carbon nanotubes of the present invention, in the metal-containing nanofiber housing step, the metal-containing nanofiber is accommodated by housing a reaction container containing the metal-containing nanofiber in the heat-generating container. Is preferably accommodated in the exothermic container.

[4] In the carbon nanotube production method of the present invention, in the carbon nanotube production step, the metal-containing nanofibers are in a state where the heat-generating container is heated by irradiating the heat-generating container with electromagnetic wave energy. It is preferable to heat the metal-containing nanofibers by gradually passing through the space in the exothermic container.

[5] In the carbon nanotube production method of the present invention, in the carbon nanotube production step, the metal-containing nanofibers are put in a state in which a predetermined portion in the longitudinal direction of the heat-resistant tube is disposed in the heating container. It is preferable that the metal-containing nanofibers gradually pass through the space in the heat generating container by gradually moving the reaction container along the longitudinal direction inside the heat-resistant tube.

[6] In the method for producing carbon nanotubes of the present invention, the metal is preferably at least one metal selected from the group consisting of iron, cobalt, and nickel.

[7] In the method for producing carbon nanotubes of the present invention, the metal is preferably nickel.

[8] In the method for producing carbon nanotubes of the present invention, the metal-containing nanofibers are preferably those in which the metal is coated on the surface of the nanofibers.

[9] In the method for producing carbon nanotubes of the present invention, the metal-containing nanofibers are preferably those in which the metal nanoparticles are encapsulated in nanofibers.

[10] In the method for producing carbon nanotubes of the present invention, the metal-containing nanofiber is produced by an electrospinning method using a solution or a suspension containing the metal and a material resin of the nanofiber as a raw material. It is preferable.

[11] In the carbon nanotube production method of the present invention, the carbon nanotube production step is preferably performed in an inert gas atmosphere.

[12] In the method for producing carbon nanotubes of the present invention, the carbon nanotube generation step includes a step of maintaining the inside of the heat generating container at a temperature of 600 ° C. to 900 ° C. for 5 minutes to 20 minutes. preferable.

[13] In the method for producing carbon nanotubes of the present invention, in the carbon nanotube generation step, the inside of the heat generating container is heated to a temperature of 600 ° C. or higher and 900 ° C. or lower, and the metal-containing nanofiber is heated to the heat generating container. It is preferable to pass through the space gradually over a period of 5 minutes to 20 minutes.

[14] The method for producing carbon nanotubes of the present invention comprises a metal-containing nanofiber preparation step of preparing a metal-containing nanofiber having a nanofiber made of an organic polymer and a metal having a catalytic action for producing carbon nanotubes, And a carbon nanotube generation step of generating carbon nanotubes including the metal by heating the metal-containing nanofiber using the nanofiber as a carbon source.

  The carbon nanotubes can be produced in a short time also by the method for producing carbon nanotubes of the present invention. Moreover, according to the method for producing carbon nanotubes of the present invention, since the nanofiber contained in the metal-containing nanofiber is used as a carbon source, no carbon source is required in addition to the metal-containing nanofiber, thereby simplifying the production process. There is also an effect that can be done.

  In addition, in the method for producing carbon nanotubes described in [14], the features described in [6] to [11] are the same as in the method for producing carbon nanotubes described in [1]. It is preferable to have.

1 is a schematic cross-sectional view of a carbon nanotube production apparatus according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of an electrospinning apparatus according to Embodiment 1. FIG. It is a figure shown in order to demonstrate the manufacturing apparatus of carbon nanotubes concerning Embodiment 2. FIG. 2 is a TEM image of carbon nanotubes manufactured in Example 1. FIG. 2 is a TEM image of carbon nanocapsules manufactured in Example 1. FIG. 3 is a TEM image of carbon nanotubes produced in Example 2. FIG.

  Hereinafter, the method for producing carbon nanotubes of the present invention will be described based on the embodiments shown in the drawings.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view of a manufacturing apparatus 10 used in the method for manufacturing carbon nanotubes according to the first embodiment. As shown in FIG. 1, the manufacturing apparatus 10 includes an outer container 12, an electromagnetic wave source 14, a heat generating container 16, a thermocouple 22, and a control unit 24.

  The electromagnetic wave source 14 is a device that generates an electromagnetic wave. In the present embodiment, the electromagnetic wave source 14 includes a magnetron and a waveguide. The manufacturing apparatus 10 shown in FIG. 1 has one electromagnetic wave source on each of the left and right sides of the outer container 12 in order to spatially equalize the intensity of the electromagnetic waves to be irradiated. However, in order to simplify the configuration, only one of the left and right electromagnetic wave sources may be used. Moreover, when the electromagnetic wave source 14 is made into one, the electromagnetic wave source 14 may be attached to the upper part of the outer container 12 like the example of a household microwave oven.

  At the time of the production of carbon nanotubes, a metal-containing nanofiber 28 having nanofibers made of an organic polymer and a metal having a carbon nanotube production catalytic action is prepared, and then a quartz test in which the metal-containing nanofibers 28 are put. A tube (reaction vessel) 40 is installed in the exothermic vessel 16. The metal-containing nanofiber 28 is a raw material for producing carbon nanotubes. Examples of the metal having a carbon nanotube production catalytic action include at least one metal selected from the group consisting of iron, cobalt, and nickel.

  The quartz test tube 40 may be made of a material other than quartz, such as ceramics, as long as it is a heat resistant material.

  The outer container 12 has a function of confining the electromagnetic wave energy irradiated from the electromagnetic wave source 14 therein. The electromagnetic wave source 14 emits electromagnetic wave energy corresponding to the intensity and irradiation time of the electromagnetic wave energy controlled by the control unit 24. The home microwave oven includes an outer container 12, an electromagnetic wave source 14, and a control unit 24. Therefore, in the method for manufacturing carbon nanotubes according to Embodiment 1, a household microwave oven can be used. If a household microwave oven is used, the carbon nanotube production apparatus becomes inexpensive. The type of electromagnetic wave irradiated from the electromagnetic wave source 14 is not particularly limited, but microwave is preferable in order to increase the rate of temperature rise, that is, the rate of generation of carbon nanotubes.

The heat generating container 16 has a function of converting electromagnetic energy into heat energy and heating a member disposed inside the heat generating container 16.
The heat generating container 16 has a substantially hollow cylindrical shape, a hole is formed in the top plate, and a substance that converts electromagnetic wave energy into heat energy is coated on the inner surface of the side wall made of a heat insulating material (not shown). Examples of the substance that converts electromagnetic wave energy into thermal energy include alumina, mullite, ferrite, silicon nitride, and silicon carbide. Instead of coating the inner surface of the heat generating container 16 with a substance that converts electromagnetic wave energy into heat energy, the heat generating container 16 itself may be made from a substance that converts electromagnetic wave energy into heat energy, or the electromagnetic wave energy is converted into heat energy. The substance to be converted may be dispersed or filled in the wall of the heating container 16.

  The control unit 24 controls the intensity and irradiation time of electromagnetic wave energy irradiated from the electromagnetic wave source 14. In the method for producing carbon nanotubes according to the first embodiment, the temperature at which the carbon nanotubes are generated based on the temperature information in the heating container 16 measured by the thermocouple 22, for example, a constant temperature of 600 ° C. or more and 900 ° C. or less. The controller 24 controls the temperature so as to maintain the temperature for a predetermined time, for example, 5 minutes or more and 20 minutes or less.

  A metal-containing nanofiber 28 having nanofibers made of an organic polymer and at least one metal selected from the group consisting of iron, cobalt, and nickel is placed in a quartz test tube 40, and the inside of the heat generating container 16. Is housed in. Nanofibers made of organic polymer in metal-containing nanofibers 28 function as a carbon source for carbon nanotubes, and at least one metal selected from the group consisting of iron, cobalt, and nickel functions as a catalyst for producing carbon nanotubes. To do.

  As the metal-containing nanofiber 28, for example, the surface of the nanofiber is coated with at least one metal selected from the group consisting of iron, cobalt, and nickel by a vapor deposition method or the like, or the nanofiber is coated with iron. , Cobalt, and nickel, and those containing at least one metal nanoparticle selected from the group consisting of nickel and cobalt.

  The nanofiber is formed by a general nanofiber forming method, for example, an electrospinning method, a melt blown method, or the like. Examples of nanofiber materials include polyethylene, polystyrene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyamide, polyurethane, polyvinyl alcohol, polyacrylonitrile, polyether imide, polycaprolactone, polylactic acid, and polylactic acid glycolic acid. Etc.

  Metal-containing nanofibers in which a metal is coated on the surface of the nanofibers are manufactured by coating the nanofibers with metal by a general metal coating method, for example, vacuum deposition. In addition, metal-containing nanofibers in which metal nanoparticles are encapsulated in nanofibers are suspensions containing metal nanoparticles and nanofiber material resin, for example, in a solution in which nanofiber material resin is dissolved in a solvent. It is manufactured by an electrospinning method using a suspension in which metal nanoparticles are dispersed. A method for producing nanofibers and metal-containing nanofibers in which metal nanoparticles are encapsulated in the nanofibers will be described later.

  The quartz test tube 40 can withstand the temperature at which carbon nanotubes are produced. A gas introduction tube 44 is inserted into the opening of the quartz test tube 40 through a plug 42. An inert gas, for example, a rare gas such as helium or argon, or a nitrogen gas is supplied from the gas introduction tube 44 before and after the generation of the carbon nanotubes, and the quartz test tube 40 is supplied by the supplied inert gas. The inside is replaced. The reason why the inside of the quartz test tube 40 is replaced with an inert gas is to generate carbon nanotubes while preventing an oxidation reaction.

  The method for producing carbon nanotubes according to Embodiment 1 is performed by the following steps. First, the metal-containing nanofibers 28 are put in the quartz test tube 40, and then the opening of the quartz test tube 40 is sealed with a stopper 42 into which the gas introduction tube 44 is inserted. Next, the quartz test tube 40 is passed through the hole provided in the top plate of the outer container 12, and the quartz test tube 40 is fixed at a position where the metal-containing nanofibers 28 are disposed inside the heating container 16.

  Then, through the holes (both not shown) provided in the top plate of the outer container 12 and the heating container 16 from the outside of the manufacturing apparatus 10, the tip 22 a of the thermocouple 22 is placed near the metal-containing nanofiber 28. Move closer. Next, an inert gas is supplied to the gas introduction tube 44, and when the quartz test tube 40 is sufficiently replaced with the inert gas, the controller 24 is operated to irradiate the electromagnetic wave energy from the electromagnetic wave source 14.

  The electromagnetic wave energy irradiated from the electromagnetic wave source 14 is irradiated to the heat generating container 16 and converted into heat energy. The heat energy rapidly increases the temperature in the heat generating container, and the temperature in the heat generating container generates carbon nanotubes. A desired constant temperature of, for example, 600 ° C. or higher and 900 ° C. or lower is reached, for example, within 5 minutes from the start of heating. Subsequently, the inside of the heat generating container 16 is maintained at a constant temperature at which the carbon nanotubes are generated using the control unit 24 for several minutes, for example, 5 minutes or more and 20 minutes or less.

  Thereafter, the irradiation of electromagnetic wave energy from the electromagnetic wave source 14 is stopped. When a few minutes have passed since the irradiation of electromagnetic energy was stopped, the inside of the heating container 16 descends to near room temperature. Then, the quartz test tube 40 is taken out from the outer container 12. In this way, carbon nanotubes encapsulating metal are generated from the metal-containing nanofibers 28. In this manner, carbon nanotubes are produced in a short time by storing metal-containing nanofibers having a metal catalyst and nanofibers, and irradiating the heat generating container with electromagnetic wave energy to maintain the generation temperature of the carbon nanotubes. be able to.

  FIG. 2 is a schematic cross section of the electrospinning apparatus 50 used in the first embodiment. The nanofiber used in Embodiment 1 is manufactured by the following process using the electrospinning apparatus 50. First, the nanofiber material resin is supplied to the tank 52 in a state dissolved in a solvent. Next, the base material 54 is fed out from the feeding-side roll 56 around which the base material 54 is wound.

  When the substrate 54 passes over the counter electrode 70 via the feed roller 58, the valve 76 is opened with a high voltage applied by the high voltage power source 72 between the nozzle 74 and the counter electrode 70. Then, the resin solution 78 is blown off from the nozzle 74 toward the base material 54. The resin solution 78 jumping out from the nozzle 74 becomes nanofibers on the substrate 54.

  The solvent evaporates in the middle of the resin solution 78 from the nozzle 74 toward the substrate 54. Further, even if the counter electrode 70 is heated by a heater (not shown) and the solvent remains in the nanofiber, the solvent evaporates due to heat from the heater. Thus, a nanofiber laminated sheet 80 composed of the base material 54 and the nanofiber layer is obtained. Thereafter, the nanofiber laminated sheet 80 is wound around the winding-side roll 84 via the feed roller 58.

  Further, when the metal-containing nanofibers 28 in which metal nanoparticles are encapsulated in the nanofibers are produced, a suspension in which the metal nanoparticles are dispersed in a solution in which the nanofiber material resin is dissolved is tanked. 52. Except this point, it is the same as the case of producing nanofibers.

[Embodiment 2]
FIG. 3 is a view for explaining the production apparatus 110 used in the method for producing carbon nanotubes according to the second embodiment. 3A is a cross-sectional view of the manufacturing apparatus 110 as viewed from above, FIG. 3B is a cross-sectional view of the manufacturing apparatus 110 as viewed from the front, and FIG. 3C is a cross-sectional view of FIG. FIG. 3D is an enlarged view of a portion indicated by reference numeral A1, and FIG. 3D is an enlarged view of a portion indicated by reference numeral A2 in FIG. In FIG. 3, the inside of the manufacturing apparatus 110 in the middle of manufacturing carbon nanotubes is shown.

  As shown in FIG. 3, the manufacturing apparatus 110 includes an outer container 112, an electromagnetic wave source 114, a heating container 116, a thermocouple 122, a control unit 124, and a quartz glass tube 132 as a heat resistant tube. The quartz glass tube 132 is attached so that a predetermined portion in the longitudinal direction is located in the heat generating container 116.

The electromagnetic wave source 114 is a device that generates an electromagnetic wave. In the present embodiment, the electromagnetic wave source 114 includes a magnetron and a waveguide. The manufacturing apparatus 110 shown in FIG. 2 has one electromagnetic wave source on each of the left and right sides of the outer container 112 in order to spatially equalize the intensity of the electromagnetic waves to be irradiated. However, in order to simplify the configuration, only one of the left and right electromagnetic wave sources may be used. Further, when the number of the electromagnetic wave sources 114 is one, the electromagnetic wave source 114 may be attached to the upper portion of the outer container 112 as in the example of a home microwave oven.
The quartz glass tube 132 may be made of a material other than quartz, such as ceramics, as long as it is a heat resistant material.

  When producing carbon nanotubes, first, metal-containing nanofibers 128 (for example, non-woven fabric) having nanofibers made of an organic polymer and a metal having a carbon nanotube production catalytic action are prepared. Thereafter, the quartz vessel (reaction vessel) 136 in which the metal-containing nanofibers 128 are put is placed along the longitudinal direction inside the quartz glass tube 132 in a state where the heating vessel 116 is irradiated with electromagnetic wave energy to generate heat. Move gradually. As a result, the metal-containing nanofibers 128 gradually pass through the space in the heat generating container 116, whereby the metal-containing nanofibers 128 can be efficiently heated. The quartz boat 136 is moved by placing the quartz boat 136 on a quartz conveyor 134 that gradually moves in the direction of the arrow by a driving means (not shown). The metal-containing nanofiber 128 is a raw material for producing carbon nanotubes. Examples of the metal having a carbon nanotube production catalytic action include at least one metal selected from the group consisting of iron, cobalt, and nickel.

  The quartz boat 136 and the conveyor 134 may be made of materials other than quartz, such as ceramics, as long as they have heat resistance.

  The outer container 112 has a function of confining the electromagnetic wave energy irradiated from the electromagnetic wave source 114 inside. The electromagnetic wave source 114 irradiates the electromagnetic wave energy corresponding to the intensity and irradiation time of the electromagnetic wave energy controlled by the control unit 124. The type of electromagnetic wave irradiated from the electromagnetic wave source 114 is not particularly limited, but microwave is preferable in order to increase the rate of temperature rise, that is, the rate of generation of carbon nanotubes.

The heat generating container 116 has a function of converting the electromagnetic wave energy into heat energy and heating a member disposed inside the heat generating container 116.
The exothermic container 116 has a substantially hollow cylindrical shape, holes are formed on both sides, and a substance that converts electromagnetic wave energy into heat energy is coated on the inner surface of the wall made of a heat insulating material (not shown). Examples of the substance that converts electromagnetic wave energy into thermal energy include alumina, mullite, ferrite, silicon nitride, and silicon carbide. Instead of coating the inner surface of the heat generating container 116 with a substance that converts electromagnetic wave energy into heat energy, the heat generating container 116 itself may be made from a substance that converts electromagnetic wave energy into heat energy, or the electromagnetic wave energy is converted into heat energy. The substance to be converted may be dispersed or filled in the wall of the heating container 116.

  The control unit 124 controls the intensity and irradiation time of electromagnetic wave energy irradiated from the electromagnetic wave source 114. In the method for producing carbon nanotubes according to the second embodiment, based on the temperature information in the heating container 116 measured by the thermocouple 122, the temperature in the heating container 116 is the temperature at which the carbon nanotubes are generated, for example, 600. It is controlled by the control unit 124 so as to be maintained at a constant temperature of not less than 900 ° C and not more than 900 ° C.

  A metal-containing nanofiber 128 having nanofibers made of an organic polymer and at least one metal selected from the group consisting of iron, cobalt, and nickel is placed in a quartz boat 136 and is moved in the direction of the arrow in FIG. It is placed on a quartz conveyor 134 that gradually advances. Nanofibers made of an organic polymer function as a carbon source for carbon nanotubes, and at least one metal selected from the group consisting of iron, cobalt, and nickel functions as a catalyst for producing carbon nanotubes.

  The structure, material, and manufacturing method of the metal-containing nanofiber 128, the nanofiber, and the metal nanoparticle are as exemplified in Embodiment 1, for example.

  The quartz glass tube 132 can withstand the temperature at which the carbon nanotubes are produced. The quartz glass tube 132 is provided with an inert gas introduction tube, and an inert gas, for example, a rare gas such as helium or argon, or nitrogen gas is introduced into the quartz glass tube 132 before and after the generation of carbon nanotubes. By doing so, the inside of the quartz glass tube 132 is replaced by these inert gases. The reason why the inside of the quartz glass tube 132 is replaced with an inert gas is to generate carbon nanotubes while preventing an oxidation reaction.

  The method for producing carbon nanotubes according to Embodiment 2 is performed by the following steps. First, by flowing an inert gas through the inert gas introduction tube, the inside of the quartz glass tube 132 is sufficiently replaced with the inert gas. Thereafter, the heat generating container 116 is irradiated with electromagnetic wave energy to cause the heat generating container 116 to generate heat, and the predetermined region of the quartz glass tube 132 is heated to a desired constant temperature of, for example, 600 ° C. or more and 900 ° C. or less. At this time, the tip 122a of the thermocouple 122 is placed in a predetermined region in the quartz glass tube 132, and the output of the control device 124 is controlled based on the temperature information of the thermocouple 122. Thereafter, with this temperature maintained, a quartz boat 136 (reaction vessel) in which the metal-containing nanofibers 128 are placed is placed on a quartz conveyor 134 that gradually advances in the direction of the arrow in FIG.

  As a result, the metal-containing nanofibers 128 gradually pass through the space in the heat generating container 116, and thus the metal-containing nanofibers 128 can be heated for a necessary time. The quartz boat 136 that has passed through a predetermined region of the quartz glass tube 132 is gradually cooled, and when it reaches the outlet of the quartz glass tube 132, it is cooled to near room temperature. In the method for producing carbon nanotubes according to the second embodiment, a plurality of quartz boats 136 are prepared, and the carbon boats are produced with high productivity by sequentially placing these quartz boats 136 on a conveyor. Can do.

  In the following examples, carbon nanotubes were manufactured using the manufacturing apparatus 10 according to Embodiment 1 described above.

1. Carbon Nanotube Manufacturing Apparatus A household microwave oven (Elephant Mahobin Co., Ltd. ES-HA196) was modified for the manufacturing apparatus 10 and used. That is, the thermocouple 22 is provided in a microwave oven so that the inside of the heating container 16 can be maintained at a constant temperature, and the output of electromagnetic wave energy (microwave energy) can be adjusted based on temperature information from the thermocouple 22. The range operation unit (corresponding to the control unit 24) was modified. The exothermic container 16 used was a calciner (generic name: microwave oven; trade name “Art Box”) in which the internal temperature was increased by microwaves in a microwave oven. In addition, this baking machine is comprised from two bodies of a bottom part and a container main-body part .

2. Production of carbon nanotubes [Example 1]
Example 1 is an example using a metal-containing nanofiber in which a metal is coated on the surface of the nanofiber.

(1) Preparation of nanofibers A nonwoven fabric of polystyrene nanofibers was produced on the base material 54 by an electrospinning method using a DMF solution of polystyrene (about 30% by weight) as a raw material. The resulting nanofiber nonwoven fabric had a thickness of 1 to 10 μm and a nanofiber diameter of 500 to 2000 nm. The diameter of the nanofiber was determined by measuring the fiber width of a large number of nanofibers shown in the electron micrograph.

(2) Coating of metal on the nanofiber surface Nickel was coated on the surface of the nanofiber produced on the substrate 54 by vacuum deposition. The thickness of the nickel coating layer was 10 to 300 nm. The thickness of the nickel coating layer was determined by measuring the thickness of the nickel layer in the cross-sectional micrograph of the metal-containing nanofiber.

(3) Generation of carbon nanotubes The metal-containing nanofibers 28 (exfoliated from the base material) obtained in the above process are placed in a quartz test tube 40 having a diameter of 15 mm and a length of 180 mm, and placed in a microwave oven. The quartz test tube 40 was accommodated in the fired oven, and the inside of the quartz test tube 40 was replaced with nitrogen gas for 10 minutes. And the microwave energy (output 600W) was irradiated to the baking machine for 5 minutes in the state where the inside of the quartz test tube 40 was nitrogen gas atmosphere, and the temperature in a baking machine was raised to 800 degreeC. Subsequently, microwave energy was continuously irradiated to the calciner and the temperature in the calciner was maintained at 800 ° C. for 10 minutes, and then the microwave energy irradiation was stopped. After 5 minutes from the stop of microwave energy irradiation, the temperature inside the calciner dropped to near room temperature. Thereby, carbon nanotubes were obtained.

  In order to remove the bare nickel metal particles contained in the crude product of carbon nanotubes obtained in this way, the crude product of carbon nanotubes and concentrated hydrochloric acid are put in a test tube different from the test tube used at the time of production. The test tube was immersed in a water tank of an ultrasonic cleaner (Sharp Corporation UT-105S) for ultrasonic cleaning. Next, after standing overnight in a test tube stand, the supernatant was removed, and the addition of water and the removal of the supernatant were repeated until the wash water became neutral. And this product was dried under reduced pressure and carbon nanotubes were obtained. The yield of carbon nanotubes calculated based on the carbon content of the nanofibers was about 4%.

[Example 2]
Example 2 is an example using metal-containing nanofibers in which metal nanoparticles are encapsulated in nanofibers.

(1) Preparation of metal-containing nanofibers Metal nanoparticles are encapsulated in polystyrene nanofibers by electrospinning using a suspension of nickel particles having a diameter of 10 to 130 nm dispersed in a DMF solution of polystyrene as a raw material. A metal-containing nanofiber nonwoven fabric was prepared. The concentration of polystyrene in the suspension was 30% by weight, and the concentration of nickel particles in the suspension was 1.0% by weight. The thickness of the obtained metal-containing nanofiber layer was 1 to 10 μm, and the diameter of the metal-containing nanofiber was 600 to 2500 nm. The diameter of the metal-containing nanofiber was determined by measuring the fiber width of the metal-containing nanofiber in the electron micrograph.

(2) Generation of Carbon Nanotubes Only the point that metal-containing nanofibers in which metal nanoparticles are encapsulated in nanofibers is placed in quartz test tube 40 is different from Example 1, and except for this point, Example 1 Carbon nanotubes were produced by the same method.

3. Confirmation of carbon nanotubes In Example 1, carbon nanotubes and carbon nanocapsules were obtained. 4A, 4B, and 4C are TEM images of the carbon nanotubes produced in Example 1. FIG. 5A and 5B are TEM images of the carbon nanocapsules produced in Example 1. FIG.

  As shown in FIGS. 4A, 4B, and 4C, it was confirmed that carbon nanotubes were generated by the method of Example 1. The obtained carbon nanotube has a shell thickness of about 42 nm and a hollow portion diameter of about 17 nm as shown in FIG. 4A, and a shell thickness of about 47 nm and a hollow portion diameter as shown in FIG. 4B. The thickness was about 15 nm, the shell thickness as shown in FIG. 4C was about 10 nm, and the diameter of the hollow portion was about 5 nm.

  Moreover, as shown to FIG. 5A and FIG. 5B, it has confirmed that the carbon nanocapsule was produced | generated by the method of Example 1. FIG. The obtained carbon nanocapsule contained nickel fine particles having a shell thickness of about 8 nm to 9 nm and a diameter of about 10 nm in the center. And as shown to FIG. 4A, FIG. 4B, FIG. 4C, FIG. 5A, and FIG. 5B, it turned out that the carbon nanotubes manufactured in Example 1 include nickel (black part of a TEM image). .

  In Example 1, carbon nanotubes encapsulating metal were manufactured using metal-containing nanofibers whose surfaces are coated with metal as raw materials. Despite the presence of nanofibers, which are carbon sources, inside the metal catalyst, carbon nanotubes were formed outside the metal catalyst. It is thought that this was because the vapor of organic matter was ejected, and this vapor became carbon nanotubes around the metal catalyst layer.

  On the other hand, also in Example 2, carbon nanotubes and carbon nanocapsules were obtained. 6A and 6C are TEM images of the carbon nanotubes produced in Example 2. FIG. 6B is a TEM image of the carbon nanotubes and carbon nanocapsules produced in Example 2. FIG. In FIG. 6B, an aggregate of carbon nanocapsules was observed (see the left side of the TEM image). As shown in FIGS. 6A, 6B and 6C, it was confirmed that carbon nanotubes and carbon nanocapsules were produced by the method of Example 2. The obtained carbon nanotubes have a shell thickness and hollow part diameter of about 10 nm to 15 nm as shown in FIGS. 6A and 6B, and a shell thickness and hollow part diameter of about 20 nm to about 20 nm as shown in FIG. 6C. The size was 30 nm and various sizes. Further, as shown in FIGS. 6A, 6B and 6C, it was found that the carbon nanotubes produced in Example 2 contained nickel (black portion of the TEM image).

  The carbon nanotubes produced in Example 1 and Example 2 were attracted to the magnet. This phenomenon indicates that the nickel contained in the carbon nanotubes was not removed by the hydrochloric acid treatment. That is, it is considered that the carbon nanotubes produced in Example 1 and Example 2 are chemically stable in a state where nickel particles are included. Therefore, according to the method for producing carbon nanotubes of the present invention, there is an effect that carbon nanotubes having magnetism can be selectively produced. Carbon nanotubes having magnetism can be widely used such as toner for copying machines, magnetic recording / memory materials, magnetic paints and the like. In addition, it can also be used for electrode materials, conductivity imparting agents, additives for tires, and the like.

Claims (14)

A metal-containing nanofiber preparation step of preparing a metal-containing nanofiber having a nanofiber made of an organic polymer and a metal having a carbon nanotube production catalytic action;
In a state where the metal-containing nanofibers are placed in a heat generating container including a substance that converts electromagnetic wave energy into heat energy, the metal-containing nanofibers are heated by irradiating the heat generating container with electromagnetic wave energy to generate heat. And, as a result, a carbon nanotube production process for producing carbon nanotubes encapsulating the metal using the nanofiber as a carbon source. In the manufacturing method of carbon nanotubes of Claim 1,
The carbon nanotubes further comprising a metal-containing nanofiber housing step of housing the metal-containing nanofibers in the heating container between the metal-containing nanofiber preparation step and the carbon nanotubes generating step. Production method. In the manufacturing method of carbon nanotubes of Claim 2,
In the metal-containing nanofiber housing step, the metal-containing nanofibers are housed in the heat-generating container by housing a reaction container containing the metal-containing nanofibers in the heat-generating container. A method for producing nanotubes. In the manufacturing method of carbon nanotubes of Claim 1,
In the carbon nanotube generation step, the metal-containing nanofibers gradually pass through the space in the heat generating container in a state where the heat generating container is heated by irradiating the heat generating container with electromagnetic wave energy. The method for producing carbon nanotubes characterized in that the metal-containing nanofibers are heated. In the manufacturing method of carbon nanotubes of Claim 4,
In the carbon nanotube generation step, the reaction vessel containing the metal-containing nanofibers is placed along the longitudinal direction inside the heat-resistant tube in a state where a predetermined portion in the longitudinal direction of the heat-resistant tube is disposed in the heating container. A method for producing carbon nanotubes, characterized in that the metal-containing nanofibers gradually pass through the space in the heating container by being gradually moved. In the manufacturing method of carbon nanotubes of Claim 1,
The method for producing carbon nanotubes, wherein the metal is at least one metal selected from the group consisting of iron, cobalt, and nickel. In the manufacturing method of carbon nanotubes of Claim 6,
The method for producing carbon nanotubes, wherein the metal is nickel. In the manufacturing method of carbon nanotubes of Claim 1,
The method for producing carbon nanotubes, wherein the metal-containing nanofiber is a nanofiber having a surface coated with the metal. In the manufacturing method of carbon nanotubes of Claim 1,
The method for producing carbon nanotubes, wherein the metal-containing nanofiber is a nanofiber in which the metal nanoparticles are encapsulated. In the manufacturing method of carbon nanotubes according to claim 9,
The method for producing carbon nanotubes, wherein the metal-containing nanofiber is produced by an electrospinning method using a solution or a suspension containing the metal and a material resin of the nanofiber as a raw material. In the manufacturing method of the carbon nanotube of Claim 1,
The carbon nanotube production process is performed in an inert gas atmosphere. In the manufacturing method of carbon nanotubes of Claim 2,
The method for producing carbon nanotubes includes the step of maintaining the inside of the heat generating container at a temperature of 600 ° C. to 900 ° C. for 5 minutes to 20 minutes. In the manufacturing method of carbon nanotubes of Claim 4,
In the carbon nanotube generation step, the inside of the heat generating container is heated to a temperature of 600 ° C. or more and 900 ° C. or less, and the metal-containing nanofibers spend a time of 5 minutes or more and 20 minutes or less in the space in the heat generating container A method for producing carbon nanotubes, wherein the carbon nanotubes are allowed to pass gradually. A metal-containing nanofiber preparation step of preparing a metal-containing nanofiber having a nanofiber made of an organic polymer and a metal having a catalytic action to generate carbon nanotubes;
A method for producing carbon nanotubes, comprising: a step of producing carbon nanotubes by heating the metal-containing nanofibers to produce carbon nanotubes containing the metal using the nanofibers as a carbon source.

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