JP3088784B2 - C60 manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a method for manufacturing a soot containing C _60, relates to the use of gas as the particular starting material.

[0002] The present invention relates to a method for manufacturing a soot containing C _60, relates to the particular cooling portion for generating soot.

[0003] The present invention relates to a method for manufacturing a soot containing C _60, relates to the use of the interaction of the magnetic field and microwave for particular activating a material gas.

[0004]

2. Description of the Related Art Conventionally, for example, by a method as shown in FIG.
It can be obtained soot containing large amounts C ₆₀ by resistive heating of graphite in an inert gas atmosphere.

In FIG. 1, an inert gas is supplied to a gas introduction system 1.
The graphite 12 is brought into point contact by the force of a spring 13. The graphite is supported by a support which can flow a coolant 14, by applying an electric current to the graphite, the soot containing C ₆₀ to inner wall of the reactor allowed to exotherm sublimating graphite in point contact portions obtained about 10g Can be.

Helium is often used as an inert gas, but argon may be used in some cases. Atmospheric pressure is 50-100 Torr.

The soot adheres to the inner wall of the deposition chamber.
Soot is extracted with benzene. Thereafter, kill is possible to obtain a C ₆₀ by separating the several components by alumina column chromatography using hexane as a developing solvent. When C ₆₀ is actually produced by the above method, the extraction solvent liquid is a dark purple solution, and after the solvent evaporates, a black-brown solid weighing 7% of the total soot weight can be obtained. To give the pure C ₆₀ 15% of the extract by separation by chromatography on alumina. That is, it is possible to obtain a C ₆₀ approximately 1.2% of the total soot.

[0008] C ₆₀ is of a mustard color, if you like a film becomes brown or black as the thickness of the film increases. _C60 is soluble in common organic solvents. In particular, it dissolves well in aromatic hydrocarbons. This solvent exhibits a beautiful reddish purple color.

[0009]

In the method of generating soot containing C ₆₀ by resistance heating the graphite THE INVENTION An object you try solving ## exhibits the same tendency as the most arcing, heating portion and the periphery thereof becomes high Because it is quite dangerous.

Furthermore, in the method of generating soot containing C ₆₀ by resistance heating the graphite, C ₆₀ content in the soot is not more than 2%. Therefore, the _C60 production efficiency is reduced.

[0011] To improve the electrical properties of the C ₆₀ purified from soot generated from the graphite, it may be performed or doped with an impurity to C _60, a compound with other materials. By heating the above graphite by resistance heating, C
After that caused soot containing _60, in the method for purifying C _60, to then purifying the C _60, further or doped with an impurity, in order shall perform the compound with other materials 2 It becomes troublesome. Therefore, if _C60 is produced using a gas, doping of impurities and compounding with other substances can be performed very easily and with good reproducibility.

[0012]

SUMMARY OF THE INVENTION Considerable high temperatures are required to evaporate very high melting solids by heating. Therefore, by using a gas instead of a solid, it is possible to lower the temperature. However, since there is no gas containing only carbon, a gas containing carbon atoms is used, and by applying sufficient energy (electric power) to the gas,
Dissociates carbon from other atoms. At this time, it is preferable that a large amount of a C ₂ radical to which two carbon atoms are bonded is contained. Therefore, by setting the condition that does not deposit other atom other than carbon, it is possible to obtain a soot containing a C _60. In this case, it is possible to obtain better soot simultaneously introducing Kuuenchigasu to cool the plasma radical carbon containing a C ₆₀ rapidly cooling efficiency. Since the quench gas is preferably a gas that efficiently cools only carbon radicals, helium or argon having low reactivity is preferable as the quench gas.

The quenching gas may be a gas that does not react with carbon but reacts with atoms other than carbon. For example, if a hydrocarbon is used as a gas containing carbon atoms, a gas which reacts with hydrogen and extracts hydrogen from carbon may be one in which hydrogen is dissociated into atoms. That is, if a hydrocarbon is used as a raw material, hydrogen may be used as a quench gas. However, in the method using hydrogen as a quenching gas, diamond may be synthesized. That is, it becomes that the soot containing a C ₆₀ are not generated. Incidentally, the synthesis of diamond is closely related to the temperature of the substrate, and the minimum temperature at which diamond is synthesized is about 200 ° C. Also, when synthesizing diamond, it must be sufficiently diluted with hydrogen to remove non-diamond components. In addition, OH groups can be generated by adding water or oxygen to remove non-diamond components. Therefore, in order to produce a soot containing a C ₆₀ using hydrogen as Kuuenchigasu it is a soot generation portion was cooled to 200 ° C. or less, it is necessary to increase the concentration of the gas containing carbon.

If a hydrocarbon is used as the gas containing a carbon atom as described above, sufficient energy must be applied to decompose the hydrocarbon. However, degraded by energy applied from the outside, than activated ions, radicals had a large kinetic energy, can not be obtained C ₆₀ is an object of the present invention. That is, in order to obtain the C ₆₀ is must give the (hydrocarbon gas in the present invention) reactive gas greater energy in order to perform sufficient ionic or activation, the reactive ionized or activated We must create a state where the gas does not have a large kinetic energy.

As a method for creating such a state, a method using quench gas is effective as described above.
The problem the case for cooling the fully activated reactive gas, since it required in order to obtain C _60, cooling the reaction gas in a state where sufficient activated C ₂ radicals are produced in large quantities Configuration is important.

[0016] By this cooling such activated reactive gas, a method of obtaining a C ₆₀ has the following three methods are roughly.

First, as a first method, a reactive gas (in the present invention, a gas containing carbon) is converted into a plasma state, and at the same time, a plasma is formed, that is, the activated reactive gas is cooled to obtain C _60. It is. In the present invention, the conversion of the reactive gas into plasma and the activation of the reactive gas are synonymous.

As an example of this method, there is a method in which C ₆₀ is obtained by introducing a quench gas to cause activated carbon atoms to collide with molecules of the quench gas and depriving the kinetic energy. A method that does not use a quench gas is to provide a cooled substrate or an obstacle (preferably an insulator so as not to affect the plasma) in a place where the plasma is generated,
This substrate surface there is a method to produce a soot containing C _60.

[0019] As a second method of obtaining the C ₆₀ is at a different location than providing electromagnetic energy to plasma reactive gas, by cooling the plasma, reactive gases, to obtain a C ₆₀ There is a way. Also in this method, there are a method of cooling a reactive gas converted into plasma using a quench gas, and a method of cooling the reactive gas converted to plasma using a substrate or a wall surface of a reaction furnace (plasma generation chamber).

As a third method of obtaining C ₆₀ , a method of intermittently introducing C gas into a plasma-forming reactive gas to thereby obtain C ₆₀ intermittently (hereinafter referred to as a third method). It is). This is a modification of the first method, in which a high activation rate of the reactive gas can be maintained, and at the same time, the reactive gas that has been made into plasma (having a high activation rate) can be cooled efficiently. It is.

A variation of this method is to spray an intermittently activated reactive substrate against a cooled substrate.

[0022] To improve the electrical properties of the C _60, C ₆₀
In or doped with an impurity, in performing a chemical with other substances, after purification of the C ₆₀ from the soot by the purification process, it is necessary to carry out the synthesis or reaction with other substances in addition some way.

In this case, if C ₆₀ is obtained from a gas containing carbon by a gas phase chemical reaction instead of purifying C ₆₀ from graphite, when the gas containing carbon is introduced into the plasma generation chamber, A doping material can be introduced as an additive gas, and doping or compounding can be performed easily and with good reproducibility.

In order to collect soot as much as possible when collecting soot adhering to the plasma generation chamber inner wall, the plasma generation chamber is similar to the plasma generation chamber and smaller than the plasma generation chamber inner wall by 2 to 3 mm. By installing a possible material in the plasma generation chamber, after the soot was formed, the similar shaped material was taken out and divided, so that it became easier to collect soot.

This solves the problem that soot cannot be collected without disassembling the plasma generation chamber when the plasma generation chamber is small.

The lower the pressure in the plasma generation chamber, the more the plasma spreads and a large amount of soot is generated on the inner wall of the plasma generation chamber. Therefore, a magnetic field microwave plasma CVD method can be considered as a method for applying high power at a low pressure. The method albeit in a way are used in diamond synthesis can be the content of C ₆₀ is mass produced high soot by varying the conditions. Plasma generation chamber pressure is 1Torr or less, the gas concentration containing carbon when 5% or more, most of the high C ₆₀ yields were obtained. Naturally, in this case, it is important to cool the plasma generation chamber.

Furthermore, in the configuration of the present invention, by generating soot containing a C ₆₀ to the plasma generating chamber wall, so it is characterized by obtaining a C _60, as much as possible to expand the plasma throughout the plasma generating chamber It is important to cause a gas phase reaction. Therefore, a magnetic field microwave gas phase reaction method, which is a gas phase reaction method capable of activating a reactive gas at a low pressure of 10 ^-2 Torr or less, and a gas phase reaction method using ECR conditions are preferable.

The content of C ₆₀ obtained by the configuration of the present invention is defined as the ratio of the mass of C ₆₀ contained in the soot to the mass of the resulting soot. The C ₆₀ as a method for separating from the soot, laden substance C ₆₀ and C ₇₀ by first dissolving the soot benzene performed initially separating from the soot. At this time, although such C ₈₀ is also included in addition to C ₆₀ and C _70, it can be largely ignored since very small. Furthermore, separating the C ₆₀ and C ₇₀ This material by chromatography alumina is a known method. The mass of C ₆₀ obtained by as described above and the molecular content of the C ₆₀ the mass of the original soot calculation that the denominator is defined.

The confirmation that C ₆₀ has been obtained can be made by measuring the mass spectrum and NMR of the substance. In particular, when measuring the mass spectrum can know the mass number of the substance, it is possible to identify the C _60.
Also, by measuring NMR (nuclear magnetic resonance),
Information is obtained on the molecular structure and chemical bonding, it is possible to specify the C ₆₀ based on this information. A process of manufacturing a C ₆₀ using the configuration of the present invention showed the following examples will be described.

[0030]

[Embodiment] This example was carried out until the produced soot containing mainly C _60. From Preparation soot in this embodiment, a method of extracting only C ₆₀ are common in all the following examples, was extracted with benzene soot, the separation of C ₆₀ and C ₇₀ of alumina chromatography Pure C ₆₀ with low impurity content
I got

Example 1 FIG. 2 shows an apparatus used in this experiment. This apparatus is a parallel plate type RF plasma CVD apparatus. 13.56 MHz for high frequency power supply 29
However, it goes without saying that other frequencies may be used.

The apparatus shown in FIG. 2 is the same as an apparatus conventionally used for forming hydrogenated amorphous silicon or an insulating oxide film. In this experiment, soot attached to the chamber inner wall 8 and the substrate holder 27 was used without mounting a substrate.

In the present embodiment, a quench gas was introduced from 21 and exhausted from 25 simultaneously with the reactive gas. Helium was used as the quench gas.

Therefore, the gas phase reaction was performed without providing a special cooling mechanism or the like in the plasma generation chamber (reaction chamber).

[0035] Hereinafter, the basic condition for generating soot containing C _60. As the introduced gas, methane 10 sccm and helium 200 sccm were used. The pressure in the plasma generation chamber was 0.01 Torr. RF power output is 40
Assuming 0 W, matching was performed so that there was almost no reflection. The soot generation time was 5 hours. With such a method, even if the soot generation time is lengthened, the process can be performed continuously as long as the raw material gas is not exhausted. Therefore, the efficiency is higher than that of generating soot by resistance heating graphite.

Under the above production conditions, about 35 g of soot could be obtained. The amount of soot is slightly lower than conventionally, but becomes C ₆₀ content of soot is 5.5%, eventually it has become possible to get a lot of C ₆₀ conventionally.

Example 2 FIG. 3 shows an apparatus used in this experiment. This apparatus is a microwave plasma CVD apparatus using a microwave power supply of 2.45 GHz.
The chamber 33 is made of quartz and has an inner diameter of 5 to 6 cm.
It is. Conventionally, this apparatus is often used as a diamond film generation apparatus.

In FIG. 3, a mixed gas of methanol and hydrogen, which is a reactive gas containing carbon, was introduced from a gas introduction system 31 and exhausted from 35. The reactive gas was activated at the portion 39 by introducing the microwave 30 into the waveguide 32.

In this embodiment, a cooling device 34 and a substrate holder 37 are provided in order to cool the reactive gas at a location away from the portion 33 where the reactive gas is activated.
The activated reactive gas in this part is cooled, it urged soot containing C _60. As a cooling device, a water cooling system was used, and efforts were made to keep the reactive gas at 200 ° C. or lower.
Of course, liquid nitrogen, liquid helium, or the like can be used as another cooling method.

[0040] Hereinafter, the basic condition for generating soot containing C ₆₀ is present embodiment. As the introduction gas, methanol 50 sccm and hydrogen 100 sccm were used. The pressure in the quartz chamber was 1 Torr, and the microwave output was 1.2 kW. The soot generation time was 5 hours. Note that hydrogen in this case is a diluent gas for the reactive gas containing carbon and also has a role as a quench gas.

Under the above generation conditions, soot adhered to the substrate holder 37 and the inner wall of the quartz chamber in the vicinity thereof. However, since the diameter of the quartz tube is 5 to 6 cm, there is a problem that it is very difficult to collect soot. Therefore, as shown in FIG. 4, a structure was used in which a quartz tube having an outer diameter of 1 to 2 mm smaller than the inner diameter of the quartz tube was divided into two in the direction perpendicular to the diameter. When the splittable quartz tube 41 was inserted into the quartz chamber, the soot was easily collected by removing the splittable quartz tube from the quartz chamber after soot generation. The other parts have the same configuration as that of FIG.

At this time, about 55 g of soot could be obtained. C ₆₀ content of soot is 6.3%, the conventional 3
~ ₆₀ times of C60 can be obtained.

Example 3 In this experiment, the same apparatus as that used in Example 2 was used, but a KBr substrate was introduced into the plasma, and the substrate was further cooled by water cooling. it is obtained so as to generate a large amount of soot containing a C _60. The soot generation conditions in this example were also set to the same conditions as in Example 2.

Also in this embodiment, the quartz chamber was cooled by the cooling device 34.

[0045] In this embodiment, the soot containing C ₆₀ are most often produced was substrate. Soot containing C ₆₀ are generated in a unit area on the substrate was 4 times the soot containing C ₆₀ are generated in the quartz chamber unit area inner wall. Further, the _C60 content was higher on the low temperature substrate. This shows that it is possible to generate soot containing C ₆₀ in large quantities by cooling.

Example 4 FIG. 5 shows an apparatus used in this experiment. FIG. 5 shows a magnetic field microwave CVD apparatus that generates high-density plasma by utilizing the interaction between a magnetic field and microwaves. In this experiment, the substrate
By heating to 0 ° C. and optimizing the reaction gas ratio, reaction pressure, microwave output, and magnetic field strength, it can be used as a diamond film synthesizer. In this experiment, SU
Because it aims to produce a soot containing a C ₆₀ to S-made plasma generation chamber 56 inner wall, the substrate and the substrate holder is not installed. With inborn magnetic field microwave CVD apparatus as in which soot generation apparatus containing C _60, to produce a soot entire plasma generation chamber walls it is possible to obtain a high plasma active rate even at a low pressure It is very important in that it can do this.

In this embodiment, 52 is a coil for generating a magnetic field, 51 is a gas introduction system, 55 is a gas exhaust system, and 57 is a waveguide for introducing the microwave 50. is there.

In this embodiment, the plasma generation chamber is cooled by a water-cooled cooling device so that the wall of the plasma generation chamber is reduced by 20 cm.
It was kept below 0 ° C. By doing so, it was possible to generate a soot containing a large amount of C ₆₀ into the plasma generation chamber walls.

The structure of this embodiment is characterized in that to cool the reaction made the gas for generating soot containing the location and C ₆₀ to HatsuNaru plasma elsewhere.

[0050] Hereinafter, the basic condition for generating soot containing the C _60. As an introduced gas, ethylene 100 scc
m and 50 sccm of hydrogen were used. The pressure in the plasma generation chamber was 0.05 Torr, and the microwave output was 4 kW.
And The soot generation time was 4 hours. The maximum of the magnetic field strength (the center of the two coils) was 2 kGauss.

At this time, about 60 g of soot could be obtained on the wall of the plasma generation chamber. C ₆₀ content of soot stood 7.5%, it has become possible to obtain a conventional 10 times more C _60.

Example 5 This experiment was performed using the same magnetic field microwave CVD apparatus as in FIG. This experiment was performed for the purpose of producing C ₆₀ doped with potassium.

Ethanol in which KOH (potassium hydroxide) is dissolved is used as a raw material gas for producing a soot containing C ₆₀ doped with potassium. Ethanol 100
10 g of KOH was dissolved per g. This solution will be referred to as a KOH ethanol solution.

The conditions for producing a soot containing C ₆₀ doped with potassium are as follows. KO as the introduced gas
H ethanol solution 100sccm, hydrogen 50scc
m. The pressure inside the quartz chamber is 0.01 To
rr and the microwave output was 4 kW. The soot generation time was 4 hours. The maximum of the magnetic field strength (the center of the two coils) was 2 kGauss.

The manufacturing conditions were the same as in Example 4, and the inner wall of the plasma generating chamber was cooled to 200 ° C. or less.

At this time, about 45 g of soot could be obtained. C ₆₀ content of potassium soot is doped was 3.5%. When the electrical characteristics at a low temperature were examined using this sample, the Meissner effect was confirmed at 18k. From this, potassium doping C ₆₀ (K
_x C ₆₀ ) was found to have superconducting properties.

[0057] As described above, can be manufactured of various compounds of C ₆₀ using this method. In addition, impurities can be easily added, and C ₆₀
Can be used. In this embodiment, doped with potassium, the reactive gas or solid contain other elements, the use of the liquid as a gas source, be doped in the form that is easily controlled impurities into materials consisting of C ₆₀ it can.

[0058]

As described above, according to the present invention, C ₆₀
Can be produced in a larger amount than before.

According to the present invention, the carbon soot
_{The 60} content could be increased to 5% or more.

Further, it has become possible to easily produce a compound with C ₆₀ .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a graphite resistance heating device.

FIG. 2 is a schematic diagram of an RF plasma CVD apparatus.

FIG. 3 is a schematic diagram of a microwave plasma CVD apparatus.

FIG. 4 is a schematic diagram of a microwave plasma CVD apparatus.

FIG. 5 is a schematic view of a magnetic field microwave CVD apparatus.

[Explanation of symbols]

 11, 21, 31, 40, 51 Gas introduction system 12 Graphite electrode 13 Spring 14 Cooling water 15, 25, 35, 45, 55 Gas exhaust system 26 Electrodes 27, 37, Substrate holder 28.33, 56 Plasma generation chamber 29 RF power supply 41 Splittable quartz tube 30, 55 Microwave 52 Magnetic field coil 32, 57 Waveguide

Claims (10)

(57) [Claims] (1) The pressure is maintained at 10 ⁻² Torr from the atmospheric pressure.
A gaseous mixture containing carbon atoms into a heated plasma generation chamber
Process and externally applying electric power to the gas mixture,
Generating a plasma containing elemental active species, and introducing a quench gas to cool the plasma.
And the plasma generation chamber wall or the plasma generation chamber
Depositing soot containing C ₆₀ in the interior of the obstacle or the substrate
_{C 60} manufacturing method has a step of, the. 2. A plasma generating chamber maintained in a reduced pressure state.
Introducing a gas mixture containing carbon atoms, and applying a magnetic field and microwave power to the gas mixture from outside.
Generate high-density plasma containing active carbon species
Process and introducing a quench gas to cool the plasma
And the plasma generation chamber wall or the plasma generation chamber
Depositing soot containing C ₆₀ in the interior of the obstacle or the substrate
_{C 60} manufacturing method has a step of, the. 3. The pressure in the plasma generation chamber is 1 Torr.
r or less.
_{C 60} manufacturing method of mounting. 4. The active species of carbon includes a C ₂ radical.
C ₆₀ Preparation sides according to any one of the continuously claims 1 to 3
Law. 5. Further the step of separating the C ₆₀ from the soot
C ₆₀ Preparation according to any one of claims 1 to 4 having
Method. Wherein said _soot, child contains _{C 60} 5% or more
C according to any one of claims 1 to 5, characterized in that:
₆₀ manufacturing methods. 7. The quench gas includes helium and rare gas.
Gas or nitrogen gas is used.
C ₆₀ Preparation method according to any one of Motomeko 1 to 6. 8. The gas containing a carbon atom has an OH group.
Alcohols or hydrocarbons, and
Wherein hydrogen is used as the chigas.
_{C 60} Preparation method according to any one of 1 to 7. 9. The plasma generation chamber wall or the plastic
A cooling mechanism is provided for obstacles or substrates inside the
9. The method according to claim 1, wherein
C described in one ₆₀ Production method. 10. Inside the plasma generation chamber, the pump
Splittable similar material slightly smaller than inside the plasma generating chamber
10. A method according to claim 1, further comprising:
C described in one ₆₀ Production method.