WO2003004411A1

WO2003004411A1 - Method for preparing carbon nano-horn aggregate

Info

Publication number: WO2003004411A1
Application number: PCT/JP2001/010449
Authority: WO
Inventors: Daisuke Kasuya; Sumio Iijima; Fumio Kokai; Kunimitu Takahashi; Masako Yudasaka
Original assignee: Japan Science And Technology Corporation; Institute Of Research And Innovation; Nec Corporation
Priority date: 2001-07-03
Filing date: 2001-11-29
Publication date: 2003-01-16
Also published as: JP2003020215A

Abstract

A method for preparing a carbon nano-horn aggregate, which comprises vaporizing a solid carbon simple substance in an inert gas atmosphere under a controlled pressure corresponding to the atomic or molecular weight of the inert gas to release a carbon vapor into the inert gas, thereby forming a carbon nano-horn aggregate with tips of carbon nano-horns being positioned in the periphery thereof. The method allows each of bud-like and dahlia-like carbon nano-horn aggregates to be prepared individually in high yield.

Description

Description Manufacturing method of carbon nanohorn aggregate Technical field

The invention of this application relates to a method for producing a carbon nanohorn aggregate. More specifically, the invention of this application relates to a method for producing a carbon nanohorn aggregate that can individually obtain bud-shaped and dary-shaped carbon nanohorn aggregates with a high purity of 80 to 90% or more. Concerns. Background art

In recent years, carbon materials having a nanometer-scale fine structure have been attracting attention as single- or multi-walled carbon nanotubes, carbon nanohorns, fullerenes, nanocapsules, and the like.

Of these, a single carbon nanohorn has a single graphite sheet that is rounded into a cylindrical shape with a diameter of about 2 nm to 3 nm, and the tip has a tip angle of about 20. Has a conical shape. A large number of such carbon nanohorns are assembled and connected to each other with the conical tip outside, forming a dahlia flower-like aggregate. The dahlia (dah Iia—Iike) carbon nanohorn We call it an aggregate. This Dary-like carbon nanohorn aggregate is superior in the amount of ethanol adsorbed on the market to activated carbon.In addition, it is possible to selectively adsorb various gases by partially burning it with oxygen or the like to form holes. In addition to the Darrier-like carbon nanohorn aggregate, the bud-like shape (bu d—I ike) The existence of carbon nanohorn aggregates is known. The bud-shaped carbon nanohorn aggregate has a diameter of 0.3 n rr! It is a spherical body with a large number of almost tubular carbon nanohorns of about 3 nm to about 3 nm in length and about several nm to 50 nm in length. Unlike the Dahlia-like carbon nanohorn aggregate, no horn-like protrusions are seen on its surface, it has a fairly smooth surface, and is described as a bud-like shape for Dahlia flowers. And, like the dahlia-shaped one, these carbon nanohorn aggregates, which are expected to have better adsorption characteristics than conventional activated carbon, are used, for example, in an atmosphere of Ar760T0rr. in, Daria like carbon nanohorn aggregate by irradiating C 0 ₂ laser as a carbon source is known to be obtained. For example, under these conditions, the diameter of the obtained Darier-like carbon nanohorn aggregate is about 8 O nm, and the yield is about 75%. Although this yield can be optimized to some extent by controlling the laser intensity, the practical limit was about 75%. In addition, it was impossible to control the diameter (size) of the carbon nanohorn aggregate.

The bud-like carbon nanohorn aggregate is obtained as a mixture with the Darier-like carbon nanohorn aggregate and amorphous carbon, so the yield is even lower, and the combined yield of both is as low as 60%. It was hot. For this reason, it is difficult to produce a bunch of carbon nanohorn aggregates by themselves, and little research has been done on their properties and applications.

Thus, for carbon nanohorn aggregates, there is a need for a search for the unique nanoscale microstructure itself and a more vigorous study of the relationship between the formation method, conditions, and structure. And, beyond the knowledge that has been obtained so far, There is a need to open up the technical possibilities and prospects for the clusters of energy. Accordingly, the invention of this application has been made in view of the circumstances described above, and solves the problems of the conventional art. Thus, the bud-shaped and dary-shaped carbon nanohorn aggregates are individually and individually provided. It is an object of the present invention to provide a method for producing a carbon nanohorn aggregate that can be obtained in a high yield. Disclosure of the invention

Thus, the invention of this application provides the following inventions to solve the above problems.

That is, first of all, the invention of this application is to evaporate the solid carbon simple substance in an atmosphere in which the pressure is controlled in accordance with the atomic weight or molecular weight of the inert gas and to convert the carbon vapor into the inert gas. The present invention provides a method for producing a carbon nanohorn assembly, characterized in that the shape and size of the carbon nanohorn assembly are obtained by controlling the shape and the size of the carbon nanohorn by assembling the carbon nanohorn with the tip being an outer peripheral surface.

Secondly, the size of the invention of this application is reduced by evaporating the solid carbon substance in an atmosphere in which the temperature of the inert gas is controlled and releasing carbon vapor into the inert gas. The method for producing a carbon nanohorn aggregate is characterized by obtaining a controlled carbon nanohorn aggregate.Third, the carbon nanohorn aggregate is characterized in that the evaporation of the solid carbon simple substance is performed by laser irradiation. A method for producing a body is provided.

Fourth, the invention of this application is directed to any of the above-described production methods, wherein, fourth, by controlling the inert gas atmosphere at room temperature to Ar700 to 900 Torr, Darrie-like carbon is obtained. Fifth, a method for producing a carbon nanohorn aggregate characterized by obtaining a nanohorn aggregate is as follows. In an inert gas atmosphere at room temperature, He 300 nm or more, N ₂ 300 Tor or more Or A method for producing a carbon nanohorn aggregate, wherein a bud-like carbon nanohorn aggregate is obtained by controlling the temperature to Ar 150 to 700 Torr. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view exemplifying an electron microscope image of a dary-like carbon nanohorn aggregate obtained in an example.

FIG. 2 is a view exemplifying an electron microscope image of the bud-like carbon nanohorn aggregate obtained in the example.

FIG. 3 is a diagram illustrating the relationship between the yield of the carbon nanohorn aggregate and the atmospheric gas pressure in the example, with respect to the gas type and the shape of the carbon nanohorn aggregate.

FIG. 4 is a diagram exemplifying the pressure of the atmospheric gas and the diameter of the obtained carbon nanohorn aggregate in each example for each type of the atmospheric gas and the shape of the carbon nanohorn aggregate. BEST MODE FOR CARRYING OUT THE INVENTION

The invention of this application has the features described above, and the embodiment will be described below.

First, the method of manufacturing a carbon nanohorn aggregate provided by the invention of this application is based on evaporating solid carbon simple substance in an atmosphere in which the pressure is controlled according to the atomic weight or molecular weight of an inert gas. By discharging carbon vapor into the inert gas, the force of carbon nanohorns gathered with the tip on the outer peripheral surface—bon nanohorn aggregates is obtained by controlling the shape and size. As a known method for producing a carbon nanohorn aggregate, a method of controlling only the intensity of a laser for evaporating carbon in order to increase the yield. However, the method of the invention of the present application provides a completely new method with a different purpose and means. That is, by controlling the conditions of the inert gas atmosphere for producing the carbon nanohorn aggregate with respect to the atomic weight or molecular weight of the inert gas (that is, the type of the inert gas), and the pressure and temperature, the carbon nanohorn aggregate is manufactured. Can be obtained in any shape and size in the shape of a dahlia or bud. The expression “dahlia-like” in the invention of this application refers to a spherical body in which a large number of carbon nanohorns are gathered with the conical tip outside as in the aggregate of carbon nanohorns obtained by the conventional method. It expresses what looks like a dahlia flower. In addition, the term “bud-shaped” refers to a bud before the formation of the Darya petal protrusions, which is smoother than the dahlia-shaped one without any angular protrusions on the surface of the aggregate. It is expressed in such a way because it can be taken.

In the method of the invention of this application, as the solid carbon simple substance, for example, round rod-shaped sintered carbon, compression molded carbon, or the like can be used. By evaporating the solid carbon substance, carbon vapor, which is a source of carbon nanohorns, is released into the inert gas. As a means for evaporating the solid carbon simple substance, for example, the solid carbon simple substance is heated to a high temperature of about 3,000 to 200,000 ° C by irradiating a laser beam, an arc, or the like. This is shown as an example.

When laser light is used in the evaporation of carbon, in the output 2 0 W or more, the pulse width is 2 0~ 5 0 0 ms, for example it is used a high-power laser, such as C 0 ₂ gas laser beam it can. Preferably, it is a continuous wave laser. In the invention of this application, it is of course effective to control the laser intensity as in a known method. However, if the laser intensity is higher than the optimum range, the purity of the obtained carbon nanohorn aggregate is low. It should be noted that if the temperature is lower than the optimum range, the amount of carbon evaporation decreases. The laser beam is applied to the surface of the solid carbon substance at an appropriate angle. Specifically, for example, the irradiation angle of one laser beam is 100 to 170 °, more preferably 120 to 170 °, as the angle between the surface of the solid carbon simple substance and the irradiation laser beam. The spot diameter of the laser beam on the surface of the solid material during irradiation is, for example, about 0.5 to 5 mm.

The evaporation of the solid carbon simple substance is performed under a controlled inert gas atmosphere, which is characteristic of the method of the present invention.

In the invention of this application, as the inert gas, a rare gas typified by Ar (argon), He (helium) or the like, or a reaction inert gas such as N ₂ (nitrogen) gas is used alone. Alternatively, it can be used as a mixture of two or more gases. In addition, the pressure of the inert gas atmosphere cannot be unambiguously shown because it affects the shape of the carbon nanohorn aggregate in correlation with the type of the inert gas, but is approximately 150 Torr or more. Various adjustments can be made within the range. These inert gas is preferably introduced after venting by reducing the pressure in the container, single The one vaporization of carbon is carried out once below 1 0- ² P a.

By controlling the type and pressure of the inert gas within the above range, the carbon nanohorn aggregate can be obtained as any one of a Darrie or bud. It is considered that such control of the shape of the carbon nanohorn aggregate is realized by controlling the two factors of the atmospheric gas, in particular, the atomic weight or molecular weight and the pressure in a correlated manner. The size of the carbon nanohorn aggregate can be controlled by controlling the atomic weight or molecular weight of the inert gas and the pressure. More surprisingly, in the method of the invention of this application, The yield of the hollow carbon nanohorn aggregate can be increased to about 80 to 90% or more, which has not been seen before.

More specifically, for example, by using Ar as an inert gas and controlling the atmospheric pressure to 700 or more, more preferably in the range of about 700 to 900 Torr, the Darrie-like carbon nanohorn aggregate can be used alone. And a yield of 90% or more. Even when Ar is used as the inert gas, the bud-shaped carbon nanohorn aggregate can be obtained alone by controlling the atmospheric pressure as low as about 150 to 700 Torr. By controlling the atmospheric pressure in the range of about 400 to 600 Torr, a bud-like carbon nanohorn aggregate can be obtained alone with a yield of 80% or more.

Also, if the molecular weight (atomic weight) of the inert gas is too small, it tends to be difficult to obtain a Dary-like carbon nanohorn aggregate alone. For example, in the case of He (atomic weight 4) other than Ar (atomic weight 40), the atmospheric pressure is controlled to about 700 T 0 rr, and in the case of N ₂ (molecular weight 28), the atmospheric pressure is controlled. The bud-like carbon nanohorn aggregate can be obtained with a yield of 80% by setting the pressure to about 400 to 600 Torr. The above pressure range by Li is low, A r 1 50 T 0 rr below, H e 300 T orr below, when N ₂ 1 50 T orr following pressure becomes Rukoto amorphous carbon obtained.

Therefore, even in the case of an inert gas having a small molecular weight (atomic weight), it is possible to obtain a Dary-like carbon nanohorn aggregate by controlling the atmospheric pressure sufficiently high. In addition, an inert gas having a larger molecular weight (atomic weight) is obtained. If it is a gas, it is expected that a Dary-like carbon nanohorn aggregate can be obtained even if the atmospheric pressure is controlled to be low.

The size (diameter) of the carbon nanohorn aggregate is the same as the shape In addition, it changes depending on the molecular weight (atomic weight) and pressure of the inert gas, the diameter decreases when the pressure of the inert gas is reduced, and also when the molecular weight (atomic weight) of the inert gas is reduced. Decrease.

Also, in the invention of this application, it is possible to control the size of the carbon nanohorn aggregate by controlling the temperature of the inert gas atmosphere. In the production of the carbon nanohorn aggregate, the temperature of the inert gas atmosphere may be generally room temperature of about 15 to 35 ° C. However, in the invention of this application, the temperature of the inert gas atmosphere is set lower. It is possible to increase the size of the carbon nanohorn aggregate by increasing the temperature. More preferably, by setting the temperature in the range of about 100 ° C. to about 200 ° C., a dary-shaped or bud-shaped carbon nanohorn aggregate having a diameter of about 2 to 3 times as compared with the case of room temperature is used. Can be obtained.

According to the invention of the present application as described above, the shape and diameter of the carbon nanohorn aggregate can be controlled, and a sample having a required structure and size can be appropriately manufactured.

Conventionally reported carbon nanohorn aggregates have a diameter of 12 O nm or less, typically about 10 O nm, for the Darrie-like carbon nanohorn aggregate, and a diameter of 10 O nm for the bud-like carbon nanohorn aggregate. O nm or less, typically 70 nm, and they were obtained as a mixture of them.However, the invention of this application makes it possible to reliably obtain a sample of the desired structure and size, and It is extremely useful in various applied research on nanohorn assemblies.

Hereinafter, embodiments will be described with reference to the accompanying drawings, and embodiments of the present invention will be described in further detail. Example At room temperature, the graphite raw material was laser-evaporated in a 30 × 30 × 25 cm ³ acrylic chamber in an inert gas atmosphere. As the laser, a wavelength 1 0. 6 μιτκ power density 20 k W / cm ^2, was used C_〇 ₂ laser pulse width 500 ms, 1 H z. He, N ₂ , and Ar were used as the inert gas, and the flow rate was adjusted to about 30 I / min while maintaining a constant pressure in the range of 160 to 760 T 0 rr.

The aggregate of carbon nanohorns as a product was moved inside the transfer tube together with the atmospheric gas, and was captured by a single tube filter.

Fig. 1 shows an electron microscope image of the carbon nanohorn aggregate obtained when the <I> atmosphere gas was Ar760T0rr. It was confirmed that the Darier-like carbon nanohorn aggregate was obtained alone. The yield was 90%. The diameter of the Dary-like carbon naphhorn aggregate was about 100 nm on average.

On the other hand, FIG. 2 shows an electron microscope image of the carbon nanohorn aggregate obtained when the atmosphere gas was He 760 T 0 rr. It was confirmed that the bud-like carbon nanohorn aggregate was obtained alone.

<11> FIG. 3 shows the relationship between the yield of the carbon nanohorn aggregate and the atmospheric gas pressure in this example, with respect to the gas type and the shape of the carbon nanohorn aggregate. As shown in Fig. 3, each bud-shaped carbon nanohorn aggregate can be obtained in high yield even when the pressure of the atmosphere gas is set to N 2 760 T 0 rr and Ar 400 to 600 Torr. Was confirmed.

<III> FIG. 4 shows the pressure of the atmospheric gas and the diameter of the obtained carbon nanohorn aggregate in the example for each type of the atmospheric gas and the shape of the carbon nanohorn aggregate. Bud-like carbon nanohorn aggregate The diameter of the inert gas changes depending on the type and pressure of the inert gas. The diameter decreases when the pressure of the inert gas decreases, and also decreases when the molecular weight (atomic weight) of the inert gas decreases. It has been shown.

Also, when the temperature of the atmosphere was increased to 120 CTC under the conditions of Ar760T0rr and Ar600Torr, the dahlia-like carbon nanohorn having a diameter of about 100 to 150 nm was obtained. An aggregate and a bud-like carbon nanohorn aggregate having a diameter of about 100 to 130 nm were obtained.

Of course, the present invention is not limited to the above-described example, and it goes without saying that various aspects are possible in detail. Industrial applications

As described in detail above, according to the present invention, bud-shaped and dary-shaped carbon nanohorn aggregates can be obtained independently at a high yield of about 90% or more, respectively. A method of making a body is provided.

Claims

The scope of the claims

1. In a gas atmosphere in which the pressure is controlled in accordance with the atomic or molecular weight of the inert gas, the carbon nanohorn is used to evaporate the solid carbon substance and release carbon vapor into the inert gas. Force gathered on the outer peripheral surface—A method for producing a carbon nanohorn assembly, characterized in that a bon nanohorn assembly is obtained by controlling its shape and size.

2. It is possible to obtain a carbon nanohorn aggregate with a controlled size by evaporating solid carbon simple substance in an atmosphere where the temperature of the inert gas is controlled and releasing carbon vapor into the inert gas. The method for producing a carbon nanohorn aggregate according to claim 1, wherein

3. The method for producing a carbon nanohorn aggregate according to claim 1, wherein the evaporation of the solid carbon simple substance is performed by laser irradiation.

4. The method according to any one of claims 1 to 3, wherein the inert gas atmosphere is controlled to Ar 700 to 900 Torr at room temperature to obtain a Darier-like carbon nanohorn aggregate. A method for producing a carbon nanohorn aggregate.

5. In claims 1 to 3 or of the production process, the inert gas Kiri囲air at room temperature, H e 3 0 0 T 0 rr above, N ₂ 3 0 0 T orr above, there have the A rl 5 0 to A method for producing a carbon nanohorn aggregate, wherein a bud-like carbon nanohorn aggregate is obtained by controlling the carbon nanohorn aggregate at 700 Torr.