JPH05327038A - Method and apparatus for manufacturing metallofullerene - Google Patents

Abstract

PURPOSE:To improve generating efficiency of metallofullerene by reaction of fullerene molecules with metal atoms in a microwave discharging, and synthesizing fullerenes doped with the atoms. CONSTITUTION:Fullerene molecules are reacted with metal atoms in a microwave discharging to synthesize fullerene doped with the atoms. The apparatus comprises a microwave oscillator 9, a waveguide 10 for propagating microwave oscillated by the oscillator 9, a cavity resonator 1 connected to the waveguide 10, and a discharge tube 2 inserted into the resonator 1. Further, the apparatus comprises means for heating fullerene powder 3 to molecules and supplying it from one end of the tube 2, and means for heating metal 4 to atoms and supplying it from the other end of the tube 2. The molecules are reacted with the metal element in the tube 2 to synthesize fullerenes 12 doped with the atoms. A pressure of helium gas 6 in the tube 2 is desirably set to about 1-10Torr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing metallofullerenes (in which spherical carbon clusters composed of C60, C70 and the like have metal atoms incorporated therein) used as catalyst carriers and electronic materials.

[0002]

2. Description of the Related Art A conventional metallofullerene manufacturing apparatus will be described with reference to FIG. FIG. 3 is a front view of a conventional device. In a vacuum vessel 15, a graphite rod 14 mixed with an alkali metal such as Rb or a metal oxide such as lanthanum oxide is used as an electrode in an atmosphere of helium gas 6 of about 100 Torr, and a voltage and current of 50 V and 100 A are directly applied by a power source 16. The graphite is vaporized and turned into plasma by arc discharge. At this time, metal atoms are vaporized together with graphite from the graphite, and the metal atoms are taken into the inside of the spherical molecule when the graphite becomes a fullerene in the plasma to cause dissociation and binding reaction. After discharging for about 1 hour, the soot containing the metallofullerene adhering to the inner wall of the vacuum container and the water-cooled copper pipe 17 can be recovered. An example of the yield of metallofullerene according to the prior art is shown in FIG.

[0003]

In the prior art, metallofullerenes produced by arc discharge are scattered throughout the vacuum vessel, so that the recovery rate is lowered and impurities are easily mixed, and the heating method by arc discharge is used. Therefore, since the discharge current is localized at one part of the graphite surface, the surface temperature of graphite is high only in a partial area and the evaporation amount of metal atoms cannot be well controlled. Also, because of local heating. However, since the amount of sublimation of graphite is small and constant, there is a drawback that the reaction efficiency of incorporating metal atoms into the interior decreases. Further, since the graphite rod as a raw material also serves as an electrode for arc discharge, there is a drawback that the evaporation of graphite causes a large temporal change in the electrode shape, and a stable reaction condition cannot be obtained.

In view of the above-mentioned state of the art, the present invention is to provide a method and apparatus for producing metallofullerene capable of improving the production efficiency of metallofullerene.

[0005]

The present invention provides (1) a method for producing a metallofullerene, which comprises reacting a fullerene molecule and a metal atom in a microwave discharge to synthesize a fullerene doped with a metal atom.

(2) A microwave oscillator, a waveguide for propagating while being oscillated by the microwave oscillator, a cavity resonator connected to the waveguide, and a discharge tube inserted in the cavity resonator. ,
A means for heating and atomizing fullerene powder to supply it from one end of the discharge tube and a means for heating and atomizing a metal to supply it from the other end of the discharge tube are provided. An apparatus for producing a metallofullerene, which comprises reacting to synthesize a fullerene doped with a metal atom. Is.

[0007]

According to the method and apparatus of the present invention, since plasma generated by microwave discharge is used, manufactured fullerenes can be used, and the production efficiency of metallofullerenes is improved as compared with the case of DC arc discharge. Furthermore, since the microwave electric field distribution and strength can be variously selected according to the reaction conditions, the reaction efficiency can be improved.

In the present invention, the metals and metal oxides used in the production of metallofullerenes include Ca, Zn, Cu, Pt, Pd, etc. in addition to the above-mentioned alkali metals such as Rb and metal oxides such as lanthanum oxide. Examples include various metals.

[0009]

EXAMPLE An example of the method for producing fullerene by microwave discharge according to the present invention will be described with reference to FIG. Here, a case where a cylindrical resonator is used as the cavity resonator is illustrated, and FIG. 1 shows a front sectional view thereof. The cylindrical cavity 1 has an inner diameter of 86 mm and a length of 100 mm, and an inner diameter of 2
A fullerene 3 and a rubidium metal 4 were installed on both ends of a 5 mm quartz discharge tube 2. First, the helium gas 6 is sealed in the discharge tube 2 at a pressure of 1 Torr, and the heater 5
Is used to evaporate fullerene at 200 ° C. (powdered fullerene breaks out by heating a little) and rubidium is evaporated at 700 ° C. The vaporized substances are guided to the quartz discharge tube 2 in the cavity resonator 1 according to the flow directions 7 and 8, respectively. Therefore, the microwave of frequency 2.45 GHz generated by the microwave oscillator 9 is guided to the cavity resonator 1 using the waveguide 10 to discharge the gas in the discharge tube 2 installed inside. Here, by reacting the fullerene with the rubidium atom, the metallofullerene 12 having the rubidium atom incorporated in the fullerene is deposited. The deviation of the resonance frequency due to vapor and products in the cavity is due to the tuner 1 attached to the end plate of the cavity resonator 1.
The correction was made in step 1 so that a uniform discharge can always be obtained. Three
After discharging for 0 minutes, the black product adhered to the wall of the discharge tube 2 was recovered, and the rubidium atom-doped metallofullerene was recovered by Soxhlet extraction using toluene as a solvent. The results of obtaining the yield of metallofullerene obtained by changing the pressure are also shown in FIG. From this figure, the yield is improved as the pressure is lowered, but in consideration of actual operation, about 10 torr is preferable.

Further, the same result can be obtained by selecting the microwave electromagnetic field mode as the higher order mode of TM (Transvers Magnetic) or the TE (Transvers Electric) mode according to the amount of the product and forming it in the cavity resonator. Is obtained. Further, depending on the metal atoms that are easily taken into the fullerene, it is not necessary to form a standing wave in the cavity resonator, and the vapor may be discharged in a normal traveling wave type waveguide.

The metallofullerene obtained by the above method can be expected to be used as an electric material such as a superconducting material and an electrode material, and as a catalyst.

[0012]

According to the present invention, in the production of fullerenes, it is possible to make the reaction temperature uniform by discharging the fullerene in TM mode and the vapor containing metal atoms to be incorporated, and to optimize the pressure of helium gas. ,
The production rate of metallofullerenes and the production efficiency of metallofullerenes can be improved. Further, it is possible to suppress a decrease in the recovery rate of the soot containing fullerene, which is a drawback of the conventional technique.

[Brief description of drawings]

FIG. 1 is a front view of a metallofullerene manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a chart showing the relationship between the yield of metallofullerene and the helium pressure.

FIG. 3 is a front view of a conventional metallofullerene manufacturing apparatus.

Claims (2)

[Claims] 1. A method for producing a metallofullerene, which comprises reacting a fullerene molecule and a metal atom in a microwave discharge to synthesize a fullerene doped with a metal atom. 2. A microwave oscillator, a waveguide for propagating while being oscillated by the oscillator, a cavity resonator connected to the waveguide, and a discharge tube inserted in the cavity resonator. The fullerene powder has a means for heating and molecularizing and supplying from one end of the discharge tube, and a means for heating and atomizing a metal and supplying from the other end of the discharge tube, and supplying fullerene molecules and metal atoms in the discharge tube. An apparatus for producing a metallofullerene, which comprises reacting to synthesize a fullerene doped with a metal atom.