JPH06211510A - Method for producing metal-containing carbon cluster and device therefor - Google Patents

Abstract

PURPOSE:To easily mass-produce a metal-contg. carbon cluster by incorporating desired atom, molecule or ion into a basket-shaped hollow carbon cluster represented by C60, the so-called fullerenes. CONSTITUTION:The metal-contg. carbon cluster forming device 1 with the outer wall covered with 'Pyrex(R)' contains the upper electrode 2 and lower electrode 3 for producing plasma. A compression-molded target 4 of graphite, into which the metal oxides or halides contg. metal elements in an appropriate ratio are mixed, is mounted on the lower electrode. Meanwhile, gaseous argon for producing sputtering plasma is supplied at the pressure of about 100mTorr. A high-frequency power and a DC power are impressed on the electrodes to produce argon plasma between the electrodes of a reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a novel carbon compound or a novel metal compound or an apparatus for producing them, and more specifically, to a magnetic recording medium such as a magnetic disk or a magnetic tape and an insulator, a semiconductor, The present invention relates to a method and an apparatus for manufacturing an electronic material such as a conductor or a superconductor, or a chemical material such as a catalyst and gas storage.

[0002]

2. Description of the Related Art Cletchmer et al.
A cage-like hollow carbon cluster represented by 60,
So-called full-scale synthetic method of so-called fullerene (Kletschmer et al., Nature (W.Kratshmer et al., Natu
re), 347 (1990) 354), carbon cluster research has been actively carried out on a global scale, including research on various physical properties of C60 crystals as well as on their own. In particular, K3 obtained by Heberd et al.
Report that C60 showed superconductivity at critical temperature Tc = 18K (AFHebard e.
T. al., Nature), 350 (1991) 600) attracted attention as a discovery of a new superconductor. Since then, many research institutes have conducted research aimed at raising the superconducting transition temperature, and now Cs2RbC60 has reached Tc = 33K.
(Tanigaki et al., Nature, 352
(1991) 222). Most recently, the synthesis of organic ferromagnets composed of tetrakis (dimethylamino) ethylene and C60
(Armand et al., Science (PM Allemand et
al., Science), 253 (1991) 301), carbon tube like graphite (S.Iijima, Nature, 354 (1991) 56), and molecular size lubrication. We are beginning to show various developments such as the synthesis of fluorinated fullerene C60F60, which is expected to be applied as an agent. In this way, carbon clusters and fullerenes have received great attention as new industrial materials such as electronics. Hereinafter, carbon clusters are used as a general term for the above fullerenes, carbon tubes, and general carbon aggregates.

On the other hand, since such a carbon cluster has a cage structure, even for a metal-encapsulated carbon cluster having an atom, a molecule or an ion encapsulated therein, it is a novel compound or new material which has never existed before. There are great expectations. To date, a small group of La @ C82 containing La was obtained by a group of Rice University Smalley et al. (Yan Chai et al., J. Phys. Ch.
em.), 95 (1991) 7564), and a report of C82 containing 3 Sc by the group of Shinohara et al. in Mie University (H. Shinohara et al., Nature), 357 (1992).
52) etc.

[0004]

The following laser evaporation method and electric heating method are used for producing the metal-containing carbon clusters. (1) In the laser vaporization method, metal-encapsulated carbon clusters are vaporized and generated by irradiating the graphite impregnated with the metal halide to be confined with laser with laser. Therefore, the production quantity is 10 per pulse.
Only ⁴ to 10 ⁵ can be obtained, and collection is difficult. On the other hand, in the (2) energization heating method, La ₂ O ₃ is put in a carbon rod used for arc discharge in advance, and a DC current of about 25 V and 100 A is applied to generate it in the same manner as in the ordinary fullerene mass synthesis method. . Even in that case, La @ C82 is only slightly obtained.

As described above, according to the current method, the amount of the metal-encapsulated carbon clusters obtained is also small and it is difficult to collect, and the kinds of metal compounds that are impregnated in graphite are limited, so that the desired metal is confined in the carbon clusters. Was difficult.

An object of the present invention is to propose a method and an apparatus for producing a metal-encapsulated carbon cluster that can avoid or improve the above problems, and provide a metal-encapsulated carbon cluster in which a desired metal element is confined inside the carbon cluster. Especially.

[0007]

The above object of the present invention is to:
The target is formed by compression-molding a carbon on which a desired metal element or metal oxide or metal chloride mixed with the desired inclusion is sputtered with plasma, and a rare gas flow is generated in the vicinity of the target to cool it, and the synthesized carbon is synthesized. This is accomplished by conveying and collecting clusters in the gas stream.

[0008]

According to the method of the present invention as described above, a target obtained by compression-molding a carbon powder mixed with an oxide or a halide containing a desired metal element to be encapsulated in a carbon cluster is exposed to a plasma such as a rare gas. By sputtering, metal-encapsulated carbon clusters containing metal in addition to ordinary fullerenes can be efficiently obtained. Although the clear reason for this has not been clarified, it is considered as follows. That is, the conventional manufacturing method basically promotes the generation of active species such as carbon clusters, metal atoms, or metal ions by using electric current heating of carbon or laser sputtering.

However, in these conventional methods, the active species as described above are in a situation of spatially diverging, and there is a high possibility that a sufficient collision probability cannot be obtained to generate a desired metal-containing carbon cluster. Conceivable. On the other hand, in the present invention,
The probability of collision of the active species can be increased by positively performing generation of the active species, control of lifetime by re-excitation, and spatial confinement of the active species by using plasma such as rare gas. It is considered possible to improve the production efficiency of carbon clusters.

The target to be used may be produced by a simple compression molding, or a high temperature sintering step for increasing the strength may be added. At that time, a polymer material such as phenol resin or tar pitch may be mixed as a binder for sintering. In addition, the mixing ratio of the metal oxide or metal halogen compound mixed is 5% or more by weight and 50%.
The following is desirable. The reason is that, when the content is 5% or less, the supply of metal atoms is extremely reduced, so that the yield of the metal-encapsulated fullerene is drastically reduced. On the other hand, when the content is 50% or more, the supply of carbon clusters is reduced and the yield of the metal-encapsulated fullerene is decreased. The reason is that

Further, a rare gas is basically preferable as the plasma source, and particularly argon or xenon gas is suitable. Depending on the case, an appropriate amount of a gas such as a metal halide or an organometallic compound containing a metal atom to be included may be mixed. This is because these metal compounds can generate active metal atoms or metal ions in plasma and take them into carbon clusters.

Further, the noble gas as the plasma source not only promotes the efficient generation of fullerenes, carbon clusters, metal atoms and ions as plasma, but also serves to suppress the deactivation by constantly exciting these active species. To do. Furthermore, it also has an advantage of absorbing and relaxing excessive thermal energy generated in these processes by gas collision.

The suitable pressure of such rare gas is 1 mTorr.
A range of 1 Torr or less is desirable. Because 1mT
When the pressure is lower than orr, sufficient plasma is not generated and the sputtering efficiency is reduced. On the other hand, when the pressure of the rare gas as the plasma source is 1 Torr or more, the density is high and the momentum possessed by the rare gas plasma decreases, which in turn increases the possibility of lowering the sputtering efficiency.

However, when such a plasma of a rare gas having a pressure of 1 Torr or less is used, there is a possibility that the above-mentioned absorption and relaxation of excessive thermal energy may not be sufficiently achieved. In such a case, it is possible to avoid it by mixing an appropriate amount of helium gas having a large mean free path.

Further, in the facing target plasma system using two facing targets of the present invention, the components in the two targets can be freely controlled. For example, in the case of molding a carbon target containing a metal compound as the starting material described above, if sufficient mechanical strength cannot be imparted due to the compatibility between the respective components or the ratio of the components, it is sufficient. This can be avoided by separating the respective components so as to obtain a combination of components that can have various mechanical strengths and adjusting to two targets.

Further, in metal-encapsulated fullerenes such as La @ C82, it has been pointed out that C60 may be involved as an intermediate during the formation thereof, and therefore the following combinations of targets are also possible. . That is, when one target is a carbon target containing graphite as the main component, and the other target is a target containing a metal compound containing a desired metal element as the main component, C60 is provided on one side by performing plasma sputtering, On the other hand, it is also possible to efficiently generate reaction active species such as metal atoms and ions, and to produce a target metal-encapsulating carbon cluster in a space where they are in contact with each other.

Since the metal-encapsulated carbon clusters produced as described above are diffused as they are in the entire reaction vessel and attached to the internal partition walls, their recovery is a very difficult work. Therefore, according to the present invention, by providing a gas flow containing a rare gas as a main component in the above-mentioned reaction system, that is, in the vicinity of the plasma target, it is possible to efficiently convey and recover the generated metal-encapsulated carbon clusters. Become.

The production of a gas flow of a rare gas can also be achieved by introducing a rare gas from one place of a reaction vessel and exhausting it from the opposite side so as to form a simple rare gas flow. Alternatively, a method of introducing a rare gas such as helium into the above reaction system using a pipe having an orifice having a small diameter and injecting it from the orifice can be easily produced. At that time, by appropriately adjusting the conditions of the pressure of the rare gas to be introduced, the diameter of the orifice, and the pressure of the reaction system, it is possible to produce a molecular jet having a high flow rate. By guiding the gas flow of the rare gas created in this way to the vicinity of the reaction system, in addition to transporting the metal-encapsulated carbon clusters, it is possible to efficiently reduce the excessive thermal energy generated during the reaction described above. Can also be added.

Further, by providing a recovery substrate in the downstream direction of the gas flow, it is possible to efficiently recover the target metal-containing carbon clusters. The material of the substrate used for recovery does not pose any particular problem, but a mesh-like material is preferable so as not to obstruct the flow of gas. Further, by controlling the temperature of the recovery substrate, it becomes possible to improve the trapping efficiency of the metal-containing carbon clusters. Furthermore, it is possible to easily purify the trapped species by once controlling the temperature of the substrate after capturing the metal-encapsulated carbon clusters. Therefore, the overall work efficiency can be significantly improved.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Example 1 The structure of an apparatus for producing metal-containing carbon clusters is shown in FIG. This device 1 has an outer wall covered with Pyrex glass, and is equipped with an upper electrode 2 and a lower electrode 3 for generating plasma inside.
On the lower electrode, a graphite compression molding target 4 in which Y ₂ O ₃ having a weight ratio of about 10% was premixed was attached. Argon gas was supplied at a pressure of about 100 mTorr as a plasma generating gas for sputtering.

When a high frequency power of 50 MHz was applied to the above electrodes for 3 kW, argon plasma was formed between the electrodes of the reactor, and black soot adhered to the inner wall of the Pyrex glass after about 30 minutes. When a part of the soot thus obtained was analyzed by a mass spectrometer FT-ICR using Fourier transform ion cyclotron resonance, it corresponded to Y @ C82 metal-encapsulated carbon clusters in addition to fullerenes such as C60 and C70. A strong peak was confirmed at 1073 amu. Further, a peak corresponding to Y @ C82 was also observed in the result of mass spectrometry of the filtrate obtained by filtering the soot benzene solution.

Therefore, from the above results, it was found that the soot after the recovery contained the metal-encapsulated carbon cluster Y @ C82.

(Example 2) As in Example 1, an apparatus 5 for producing metal-encapsulated carbon clusters kept at an argon gas pressure of about 100 mTorr was used. A target disk 7 made of graphite is provided on the upper electrode 6 side as a raw material target.
On the lower electrode 8 side was arranged in a facing target format using a disk 9 of yttrium oxide Y ₂ O ₃ .

Similarly to Example 1, when 3 kW of high frequency power of 100 MHz was applied to the electrodes, argon plasma was formed between the electrodes, and after about 30 minutes, black soot adhered to the inner wall of the Pyrex glass. A part of the soot thus obtained was analyzed by a mass spectrometer FT-ICR using Fourier transform ion cyclotron resonance, and found to be C60 and C7.
In addition to fullerenes such as 0, a strong peak was confirmed at 1073 amu corresponding to the metal-encapsulated carbon cluster of Y @ C82. Further, a peak corresponding to Y @ C82 was also observed in the result of mass spectrometry of the filtrate obtained by filtering the soot benzene solution.

Therefore, from the above results, it was found that the soot after the recovery contained the metal-encapsulated carbon cluster Y @ C82.

Example 3 The structure of an apparatus for producing metal-encapsulated carbon clusters is shown in FIG. The interior of this device 12, made of stainless steel, is filled with argon gas and its gas pressure is kept at about 500 mTorr. In addition, two sets of plasma generators are arranged facing each other inside, and targets 14 for producing carbon clusters are attached to the respective electrodes 13 side. Further, by disposing the permanent magnets 15 on the back surfaces of the two plasma generators facing each other, a magnetic field in one direction is created so that the plasma generated therebetween can be confined. Although not shown in the figure, a viewing window was formed on a part of the stainless steel wall of the device.

The gas flow for transporting the generated metal-containing fullerenes is prepared by injecting helium gas of about 3 atm from a nozzle 16 having an orifice having a diameter of about 50 microns at the tip, and an exhaust hole 19 The internal pressure can be adjusted with. The helium gas flow thus created was introduced between the opposed plasma generators and arranged so as to be orthogonal to the confined argon plasma.

Further, after the above gas flow passed through the plasma, the silicon substrate 17 was arranged in the downstream direction for recovering the metal-containing carbon clusters. Both of the targets 14 used were disk-shaped targets obtained by mixing lanthanum oxide La ₂ O ₃ with graphite powder in a weight ratio of about 20% and firing the mixture at about 1000 degrees. At that time, tar pitch was used as a binder for firing.

First, when high frequency power of 100 MHz was applied to the opposed plasma generators, it was confirmed from the observation window that argon plasma was generated between the opposed targets. It was also confirmed that the plasma was confined between the facing targets by a unidirectional magnetic field. While generating the above helium gas flow
When a high frequency of 5 kW was continuously applied for about 1 hour, soot deposition was confirmed on the surface of the recovery silicon substrate. Since soot hardly adhered to the inner wall of the reaction vessel, it was confirmed that the metal-encapsulated carbon clusters produced by this reactor could be efficiently recovered.

A portion of the soot thus recovered was analyzed by a mass spectrometer FT-ICR using Fourier transform ion cyclotron resonance as in Example 1. As a result, C
In addition to fullerenes such as 60 and C70, a strong peak was confirmed at 1123 amu corresponding to the metal-encapsulated carbon cluster of La @ C82. In addition, a peak corresponding to La @ C82 was also observed in the result of mass spectrometry of the filtrate obtained by filtering the soot benzene solution. Therefore, it was found that the soot after recovery contained La @ C82 which is a metal-encapsulated carbon cluster.

Further, when the recovery silicon substrate is cooled to the liquid nitrogen temperature by using the temperature controller 18, the soot collection efficiency is improved as compared with the case of normal temperature, and the soot recovery efficiency is improved. It was peeled off. Since the temperature control range of the substrate 17 by the temperature control device 18 is set to be within a range of 1000 degrees Celsius from the liquid nitrogen temperature depending on the purpose, a pipe for transporting the liquid nitrogen or wiring of an electric heater is provided. However, the illustration is omitted in the figure.

Further, when a copper mesh is used as the recovery substrate 17 instead of the silicon substrate, there is no scattering on the surface of the substrate due to the helium gas flow used for transportation, so that the inside of the device 12 is prevented from being contaminated. Was completed.

[0034]

According to the present invention, carbon powder mixed with a desired metal element or metal oxide or metal chloride to be encapsulated is subjected to plasma spattering on a target compression-molded on a plate. Metal-encapsulated carbon clusters can be efficiently produced. Further, a carbon gas synthesized by forming a rare gas flow in the vicinity thereof can be conveyed by the gas flow and efficiently collected.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a structure of an apparatus used for producing a metal-containing carbon cluster in Example 1 or 2.

FIG. 2 is a conceptual diagram showing the structure of an apparatus used for producing metal-containing carbon clusters in Example 3.

[Explanation of symbols]

1, 5, 12 ... Manufacturing device container, 2, 6 ... Upper electrode for generating plasma, 3, 8 ... Lower electrode for generating plasma, 4, 7, 9, 14 ... For manufacturing metal-encapsulating carbon clusters Compression molded target of 10,1
DESCRIPTION OF SYMBOLS 1 ... Gas introduction hole and exhaust hole for adjusting gas pressure inside a reaction vessel, 13 ... Opposed electrodes for generating plasma, 15 ... Permanent magnet used for confining plasma, 16 ... For generating gas flow Nozzle, 17 ... Substrate for collecting the produced metal-containing carbon clusters,
18 ... Recovery substrate temperature control device, 19 ... Gas exhaust hole for controlling gas pressure inside the reaction vessel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Taniguchi 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Stock company Hitachi Research Laboratory

Claims (20)

[Claims] 1. In the production of a metal-encapsulated carbon cluster containing at least one metal element inside a carbon cluster, a carbon powder mixed with an oxide or a halide containing the metal element is rarely used as a target for compression molding. A method for producing a metal-containing carbon cluster, which comprises producing the metal-containing carbon cluster by sputtering with plasma in the presence of a gas. 2. The mixing ratio of the metal oxide or the metal halide mixed in the target is 5% or more and 50% by weight.
The method for producing a metal-containing carbon cluster according to claim 1, wherein: 3. A target 2 obtained by compression-molding carbon powder in which an oxide or a halide containing at least one kind of metal element to be contained in a carbon cluster is mixed.
An apparatus for producing metal-encapsulated carbon clusters, characterized in that the two are arranged facing each other, and plasma is generated between the facing targets in the presence of a rare gas. 4. The apparatus for producing a metal-encapsulated carbon cluster according to claim 3, wherein the constituent components of the two targets arranged opposite to each other are different. 5. The metal-encapsulated carbon cluster according to claim 4, wherein the two targets arranged opposite to each other are composed of carbon containing at least one kind of metal compound of the same kind, and have different mixing ratios of the metal compounds. Manufacturing equipment. 6. The metal-encapsulated carbon cluster according to claim 1, wherein two targets are arranged to face each other and each target is composed of carbon containing at least one kind of a different kind of metal compound. Production method. 7. The metal according to claim 4, wherein one of the two targets to be opposed to each other is composed of a metal containing no carbon or a metal compound such as a metal oxide or a metal chloride. Equipment for producing endohedral carbon clusters. 8. The method for producing a metal-containing carbon cluster according to claim 1, wherein the pressure of the gas for generating plasma is 1 mTorr to 1 Torr. 9. The gas for generating plasma is argon or xenon, as claimed in claim 1.
9. The method for producing a metal-containing carbon cluster according to any one of 2, 6 and 8. 10. In the production of a metal-encapsulating carbon cluster containing at least one metal element inside a carbon cluster, a rare gas containing the metal element is applied to a target obtained by compression-molding carbon powder not containing the metal element. A method for producing a metal-encapsulated carbon cluster, which comprises producing the metal-encapsulated carbon cluster by forming plasma in the presence and performing sputtering. 11. The gas for generating plasma contains at least one kind of a metal halide or an organometallic compound containing a metal element, according to claim 1, 2, 6, 8 or 10. For producing a metal-encapsulated carbon cluster of: 12. The metal-encapsulated carbon cluster according to claim 1, wherein the produced metal-encapsulated carbon cluster is conveyed or collected using a gas flow containing a rare gas. Manufacturing method. 13. Two targets, which are compression-molded with a carbon powder mixed with an oxide or a halide containing at least one kind of metal element to be contained in a carbon cluster, are arranged so as to face each other, and a plasma of a rare gas is used. The metal-encapsulated carbon clusters are transported or collected by arranging a gas supply / exhaust device so that the gas flow is generated between the opposed targets in the presence of the gas, and the gas flow passes near the target. Metal-encapsulating carbon cluster manufacturing equipment. 14. An air supply / exhaust device is arranged so that a gas flow is orthogonal to a facing direction of a target arranged opposite thereto, and the orthogonal gas flow is at least among respective perimeters of a lower surface, an upper surface or a side surface of the target. The apparatus for producing a metal-encapsulated carbon cluster according to claim 14, wherein the metal-encapsulated carbon cluster is transported or collected by passing through one location. 15. An air supply / exhaust device is arranged so that a gas flow is parallel to a facing direction of a target which is arranged to face the target.
The apparatus for producing metal-encapsulated carbon clusters according to claim 14, wherein the metal-encapsulated carbon clusters are transported or collected by the gas flow passing through at least one location on the outer circumference of the target. 16. The two targets facing each other are arranged substantially horizontally or vertically.
16. The apparatus for producing a metal-containing carbon cluster according to any one of 4 and 15. 17. The metal-encapsulated carbon cluster according to claim 13, further comprising a substrate for adhering and holding the metal-encapsulated fullerenes transported and collected in the downstream direction of the gas flow. Manufacturing equipment. 18. The apparatus for producing a metal-encapsulated carbon cluster according to claim 18, wherein the substrate has a mesh shape. 19. The apparatus for producing metal-encapsulated carbon clusters according to claim 17, wherein the substrate is provided with a temperature control device. 20. The apparatus for producing a metal-encapsulated carbon cluster according to claim 19, wherein the temperature control range of the substrate is within a range of 1000 ° C. from the liquid nitrogen temperature.