JP2006199564A - Method of manufacturing carbon onion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical method of manufacturing carbon onion more simply and inexpensively than before by an easy technique. <P>SOLUTION: The carbon onion is synthesized on an iron group or iron group alloy base body which is a catalyst by using, as a raw material gas, a single gas or a gaseous mixture having an elemental composition containing C and H as primary components or a single gas or a gaseous mixture having an elemental composition containing C, O and H as primary components and activating the gas with heating or discharge plasma. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a carbon onion excellent in mass productivity.

Carbon onion is also called carbon onion, carbon onion, nano-sized spherical graphite, onion graphite, onion fullerene, etc. Nested and overlapped.
Such carbon onions are light and stable, and have excellent resistance to radiation and resistance at high temperatures. In addition, high elasticity is expected from its shape, and application as a solid lubricant that can be used in a vacuum or non-lubricated environment is considered. Applications for hydrogen storage carbon materials for pharmaceuticals, cosmetics, and fuel cells are also considered.
However, carbon onion has a big problem in productivity, and various production methods have been proposed in the past. However, any method has a problem for practical use.

  That is, as a method for synthesizing carbon onion, for example, as shown in JP-A-5-208805, a molded body made of glassy carbon is treated at 2000 to 3000 ° C. and 1000 to 3000 atm by hot isostatic pressing. The method of manufacturing by performing is shown. This method requires expensive equipment corresponding to high-pressure synthesis of diamond, and the production cost is considered to be comparable to that of synthetic diamond, and is not versatile.

JP-A-11-157818 discloses a method for producing onion graphite by heating diamond fine powder at 1600 to 1800 ° C. in an inert gas atmosphere. JP-A-2002-80212 discloses a method for producing diamond fine powder. Is disclosed in which an onion fullerene is obtained by heating to 1700 ° C. or higher using an infrared lamp in an inert gas. These methods have a problem that onion graphite is more expensive than the raw material powder because the raw material powder is expensive.

Japanese Patent Application Laid-Open No. 11-310406 discloses a method for producing onion-like carbon by irradiating polyin with light, an electron beam or an ion beam, or by subjecting it to a heat treatment. Similarly, JP-A-11-349307 discloses a method for obtaining onion-like carbon by irradiating polytetrafluoroethylene, polyvinylidene chloride or polyvinylidene fluoride with light, an electron beam or an ion beam. The publication discloses a method of irradiating a cage carbon with a high energy beam such as an electron beam, a gamma ray, an X-ray or an ion beam to convert it into a carbon onion.

Japanese Patent Application Laid-Open No. 2000-109310 discloses a method for producing onion-like carbon containing a hollow or metal by irradiating a carbon material having a double bond or a triple bond with one or more of X-rays, microwaves and ultrasonic waves. It is shown. Japanese Patent Laid-Open No. 2000-16806 describes a method for producing a carbon onion by irradiating a material having a double bond or a triple bond with light, an electron beam or an ion beam.
All of these methods have a limited amount of energy input to the target raw material, and there is a limit to mass production.

Japanese Patent Application Laid-Open No. 2002-105623 discloses a method for producing a carbon onion film by an unbalanced magnetron sputtering method. Since this method is a thin film method, there is a limit to the production of carbon onion powder.
Japanese Patent Application Laid-Open No. 2003-137518 discloses a method of generating a compression molded body of SiC powder and Cu powder by applying a compression impact of 350,000 atmospheres or more and 2700 ° C. or more to ultrahigh pressure / high temperature. This technology needs to create an extreme environment of high temperature and high pressure, and there are still problems in separation and purification after synthesis.
JP-A-5-208805 JP-A-11-157818 Japanese Patent Laid-Open No. 2002-80212 JP-A-11-310406 JP-A-11-349307 Japanese Patent Laid-Open No. 2001-48508 JP 2000-109310 A JP 2000-16806 A JP 2002-105623 A JP 2003-137518 A

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a practical method capable of producing a carbon onion with a simple technique and at a lower cost than conventional techniques. It is in.

In order to achieve the above object, the method for producing a carbon onion of the present invention activates a single or mixed gas whose element constitution is mainly composed of C and H by heating or discharge plasma, and produces an iron group or iron group. The basic feature is the synthesis of carbon onions on an alloy substrate.
In addition, the basic element is to synthesize a carbon onion on an iron group group or iron group group alloy substrate by activating a single or mixed gas containing C, O, and H as main components by heating or discharge plasma. Characteristic.

A single or mixed gas whose elemental composition is mainly composed of C and H, or a single or mixed gas whose structural elements are mainly composed of C, O and H, using an iron group group or an iron group group alloy as a catalyst. Activated by heating or discharge plasma, carbon onion is synthesized directly on the substrate from the above gas, so that carbon onion is easily produced at a relatively low activation temperature condition with an easily available and inexpensive gas and catalyst. In addition, since no special device is required, the cost can be reduced.

The present invention includes the following aspects, and by applying these, the object can be achieved more effectively.
1) The atomic ratio of C: H in the case of using a single or mixed gas mainly composed of C and H is 0.001 to 0.5: 1. When a single or mixed gas containing C, O and H as main components is used, the atomic ratio of C: O: H is (0.001 to 0.5): (0.001 to 0.5): 1 and the number of O atoms is less than the number of C atoms.
2) The iron group group or iron group group alloy substrate is selected from those containing a simple substance of iron, nickel, and cobalt, or an alloy containing them in a ratio of 1% or more in the base material.
3) The temperature of the substrate for carbon onion synthesis is 1000 ° C. or lower.
4) The activation method of the raw material gas for producing carbon onion is a filament heated by energization.
5) The activation method of the raw material gas for producing carbon onion is any one of direct current discharge, alternating current discharge, high frequency discharge, and microwave discharge.
6) The method for activating the raw material gas for producing carbon onion is incomplete combustion of a gas containing C and H.
7) The carbon onion is synthesized under atmospheric pressure, increased pressure or reduced pressure.

The present invention also includes the case where the carbon onion is formed as a layer on the substrate and the case where it is easily obtained as an independent powder. Examples of the latter embodiment include the following.
1) A carbon onion-containing product synthesized on an iron group or iron group alloy substrate is scraped from the substrate continuously or intermittently.
2) Carbon onion is continuously synthesized on a plurality of substrates by a fluidized bed method, and the synthesized product is continuously removed from the substrate by friction and collision between the substrates or by friction and collision by applying vibration; Get a carbon onion.

  In the following, the present invention will be described in detail. The process of producing carbon onions is not well understood, but conventionally disclosed methods include methods for imparting thermal energy to carbon or carbon compounds, ion beams, etc. There are a method of bombarding with high energy particles, a method of applying excitation energy such as X-rays and microwaves, a method of forming a film by a sputtering method, etc., all of which are methods of transforming by applying energy to a carbon compound.

On the other hand, by placing fine diamond in a high temperature atmosphere and transforming from a diamond structure to a carbon onion structure, or holding diamond and graphite at high pressure and high temperature conditions outside the region where diamond is synthesized, There is a method for transforming these raw materials into carbon onions.

The present inventors have found a method for producing carbon onion by a process completely different from these methods. The elemental composition is a single or mixed gas mainly composed of C and H, or the constituent elements are C and O. A basic feature is that a single or mixed gas containing H and H as main components is activated by heating or discharge plasma to synthesize a carbon onion on an iron group or iron group alloy substrate.
That is, as shown in FIG. 1, the present inventors arrange a support base 2 that is rotatable by a rotary shaft 3 in a vacuum vessel 5 having a gas supply port 6 and an exhaust port 7, and confront this support base 2. Using a device having a cathode 4 at a position, in an attempt, a substrate 1 made of an iron group material for carbon onion generation is mounted on the support base 2, and the inside of the vacuum vessel 5 is made hydrocarbon with the gas supply port 6. A mixed gas atmosphere of hydrogen was used, and discharge plasma 8 was generated in the atmosphere using the support 2 as an anode. As a result, it was found that a cage-like carbon onion 9 was generated on the surface of the substrate 1.

In more detail, in addition to a hydrocarbon-based single or mixed gas composed of C and H as constituent elements, a hydrocarbon-based gas composed of C, H, and O as well as carbon is formed on the iron substrate. It was found to produce onions.
C is essential because it is an element that is a raw material for carbon onion, and H and O are said to have an action of etching carbon having an unsaturated carbon chain, and this effectively produces carbon onion. It seems to play a role.

In the single or mixed gas containing C and H as main components, carbon onions are generated in a C: H atomic ratio in the range of 0.001 to 0.5: 1, and other C-rich regions. Then, amorphous carbon was the center, and nothing was generated in the H-rich region.
Moreover, in the single or mixed gas which has C, H, and O as a main component, the atomic ratio of C: O: H is (0.001-0.5) :( 0.001-0.5): A carbon onion is synthesized in a range where the number of O atoms is less than the number of C atoms, and amorphous carbon is generated in a region with a large amount of C outside the range, a region with a large amount of O and H, and a small amount of C. Nothing was generated in the region.
Typical examples of the former gas include CH ₄ alone or a mixed gas of H ₂ and this, and examples of the latter gas include a mixed gas of H ₂ , CO, and CH ₄ .

Substrate 1 is a catalyst for carbon onion production, and iron can be used as the substrate material, but as a result of subsequent experiments, in addition to iron, iron, cobalt, nickel, and other iron groups such as iron, cobalt, nickel, etc. The synthesis of carbon onions was also confirmed on iron group based alloys containing one or more metals. Even if the iron group metal is contained in the substrate in an amount of 1% or more, it is sufficiently effective. For example, it has been confirmed that carbon onion is synthesized on a cemented carbide containing tungsten carbide as a main component. For these reasons, the substrate is an iron group or iron group alloy base.

  The temperature of the substrate 1 on which carbon onions are generated rises upon exposure to plasma, but this is not possible because carbon onions are difficult to be generated particularly in the region where the substrate temperature exceeds 1000 ° C. This is presumably because C generated by gas decomposition was dissolved in the iron group metal of the substrate due to high temperature. Since the substrate temperature is passively changed by the heating means for activating the raw material gas or the discharge plasma, if the output is reduced, the substrate temperature is also lowered. However, substantially at a temperature of about 200 ° C. or less, the rate of carbon onion formation decreases, making it impractical. Therefore, the substrate temperature is preferably in the range of 200 ° C to 1000 ° C.

  Various methods can be used to activate the raw material gas for producing carbon onion. As a typical one, a filament is disposed at a position facing the substrate and activated by bringing the source gas into contact with a filament heated to 2000 ° C. or higher, or DC discharge, AC discharge, high frequency discharge. And microwave discharge, or a method of activation in a discharge plasma atmosphere generated by combining one or more of them. The raw material gas can also be activated by burning hydrocarbon gas containing C and H, and the carbon onion is synthesized in an incomplete combustion region in an oxygen-deficient state.

  Carbon onion can be synthesized under atmospheric pressure, under pressure, or under reduced pressure. However, practically, the method using the electrically heated filament is suitable for synthesis under atmospheric pressure, pressure and reduced pressure, the combustion method is suitable for synthesis under atmospheric pressure, and the method using various discharges is under reduced pressure. Suitable for synthesis.

In the method of the present invention, carbon onions are synthesized on an iron group-based or iron group-based alloy substrate. However, as the carbonaceous film containing carbon onions becomes thicker, the catalytic function of the substrate containing iron group metals decreases, so that mass production is possible. Problems remain in terms of conversion.
As a countermeasure against this, the present invention physically removes a carbonaceous film containing carbon onions synthesized on an iron group or iron group alloy substrate continuously or intermittently from the substrate during the synthesis. .
FIG. 2 shows this example. A disk-shaped or columnar substrate 1 is arranged in a vacuum vessel 5 with or without a support base so as to be rotatable around a horizontal axis, and a required range of the substrate 1 is shown. For example, the heating or discharge plasma generating means (cathode in this example) 4 is disposed at a position facing the half-circumferential region, and at a position away from the carbon onion generation region of the substrate 1, in this example on the opposite side in the circumferential direction, Scraping or scraping means 12 that is stationary or reverse to the rotation direction of the substrate is disposed, and means 14 for housing the bowl-shaped carbon onion 13 scraped from the surface of the substrate is disposed below the scraping means 12. ing. A suction / discharge hose may be used instead of the means for containing the carbon onion. Thus, the product can be separated and collected from the substrate continuously or intermittently while synthesizing the carbon onion.

In the present invention, the carbon onion is continuously synthesized on a plurality of substrates by a fluidized bed method, and the synthesized product is continuously subjected to friction and collision between substrates, or friction and collision by applying vibration. It includes a method of removing from and obtaining a carbon onion.
FIG. 3 shows an example, in which an endless conveyor 16 is arranged in the vacuum vessel 5, and heating or discharge plasma generating means (cathode in this example) 4 is arranged at a position facing the tension side of the conveyor. A plurality of box-shaped partition walls 18 are arranged on the conveyor 16, and a base 15 having a rollable shape such as a sphere made of the iron group group or iron group group alloy is loaded in the space in the partition wall. On the loose side (lower side) of the conveyor 16, a porous member (plate or wire mesh) 17 that also serves as a means for preventing the base 15 from dropping is disposed, and a means 14 for accommodating carbon onions is disposed below the porous member. ing. The conveyor 16 may be equipped with vibration generating means such as a vibrator.

In this apparatus, while the conveyor 16 is driven to move the rollable base 15, a single or mixed gas mainly composed of C and H is activated by the heating or discharge plasma 8. During the movement, carbon onions 9 are respectively synthesized on the surfaces of the plurality of bases 15, and the bases with the carbon onion films rub against each other and collide with each other in the conveyor end region, or are subjected to friction and collisions due to vibration application. The carbon onion 13 is detached from the base body 15 by impact and is accommodated in the accommodating means 14 through the hole of the porous member 17. Therefore, carbon onions can be mass-produced easily and inexpensively.

Carbon onion was synthesized using an apparatus having a schematic configuration shown in FIG.
1) A mixed gas of 99% hydrogen and 1% methane was used as a raw material for producing carbon onion, and a steel alloy SKD11 disc having a diameter of 36 mm and a thickness of 7 mm was used as a base for synthesizing carbon onion.
2) In the synthesis, first, the inside of the vacuum vessel is evacuated to 1 × 10 ⁻² Pa or less using a vacuum evacuation device not shown, and then the source gas is supplied from the gas supply port 6 into the vacuum vessel up to a pressure of 2000 Pa. Introduced and heated a 0.75 mm diameter tungsten filament cathode using an AC power source 10 to 2000 to 2500 ° C. as measured by a pyrometer, and an iron alloy disk substrate serving as the cathode and anode using the DC power source 1 was performed according to the procedure for discharging the substrate 1 with the substrate support 2 mounted thereon. At this time, the discharge current between the cathode and the anode was 4A. The temperature of the substrate at this time was 850 ° C. in the high temperature part and 700 ° C. in the low temperature part.

3) As a result, a bowl-shaped substance 9 was synthesized on the iron alloy disk substrate 1. When this cage-like substance 9 was observed with an electron microscope, a structure in which spherical carbon molecules were concentrically multilayered as shown in FIG. 4 was formed, the layers did not cross each other, and the carbon onion was 0.34 nm between layers. I found out. When observed with a transmission electron microscope, the size was several tens to several hundreds nano as shown in FIG.
4) Carbon onion was synthesized in the same manner even when the substrate was changed to stainless steel SUS304 (Fe-18Cr-8Ni) and ultrafine cemented carbide (WC-12% Co) and synthesized in the same manner. Carbon onions were also synthesized when synthesis was performed in the same manner using a gas mixture of 80% hydrogen, 18% carbon monoxide, and 2% methane.
5) A pin-on-disk test was performed using the disc obtained by synthesizing the rod-shaped material obtained in 1) and 2), and the friction between the pin steel bearing steel SUJ2 and the disc-shaped material was synthesized. The coefficient was investigated. FIG. 6 shows the coefficient of friction in a vacuum, and it can be seen that a low coefficient of friction is obtained despite the non-lubricated state test. This is considered to reflect the low friction characteristic predicted from the spherical shape of the carbon onion.

Using the apparatus shown in FIG. 2, carbon onions were generated using a rotating anode having a diameter of 250 mm as a base.
1) Cast iron FC250 was used as a base material. A tungsten wire for welding having a diameter of 1 mm was used for the cathode 4, and discharge was performed between the cathode 4 and the rotating anode 1, and a carbon onion 9 was synthesized on the rotating anode serving as a substrate.
2) The synthesis procedure is as follows. First, the inside of the vacuum vessel 5 is evacuated to 1 × 10 ⁻² Pa or less, and then a mixed gas composed of 70% hydrogen, 27% carbon monoxide, and 3% methane is supplied from the gas supply port 6 to the total flow rate. Supply was performed at a flow rate of 300 cc / min, and discharge was started between a filamentary cathode (not shown) and the anode 1, and this discharge was transferred between the cathode 4 and the rotary anode substrate 1 as a start auxiliary discharge. The raw material gas was activated using the plasma 8 generated thereby, and the carbon onion 9 was synthesized on the rotating anode.
3) At this time, the discharge current between the cathode and the rotating anode is 10 A, the rotation speed of the rotating anode is 1 rpm, and the composite 9 is continuously applied using the scrubber plate 12 on the side opposite to the side where the discharge plasma is generated. Thus, the rotary anode 1 was scraped off and the composite powder 13 was collected on a tray 14 placed below the scraper plate.
After the operation for 24 hours under the above conditions, the scraped bowl-shaped composite powder was observed with an electron microscope. As a result, synthesis of carbon onion was confirmed. The synthesis rate of the rod-like substance was about 1 g / hour.

Carbon onions were continuously produced using a fluidized bed system apparatus shown in FIG. This apparatus has a mechanism for circulating a spherical base body 15 made of bearing steel SUJ2 having a diameter of 20 mm, on which a carbon onion is synthesized by a conveyor 16.
1) Carbon onion is synthesized by evacuating the inside of the vacuum vessel 5 to 1 × 10 ⁻² Pa through the exhaust port 7 and then through a hole in the tantalum tube 4 serving as a cathode, a mixed gas in a ratio of 97% hydrogen gas and 3% methane gas. At a flow rate of 500 cc / min., Then, using a filament (not shown) as a cathode and a conveyor 16 loaded with a spherical substrate 15 as an anode, a discharge is started. The discharge was transferred between conveyors loaded with spherical substrates, and the main discharge was started. In the plasma 8 thus generated, the source gas was excited to synthesize carbon onion on the spherical substrate.
2) The carbon onion synthesized on the spherical substrate is moved away from the synthesis region by the conveyor 16 and dropped from the substrate by the collision of rolling, sliding and dropping of the substrate while the substrate is dropped downward. It dropped through the perforated plate 17 placed below and collected in the tray 14 below the perforated plate.
3) By this method, it was confirmed that the powder 13 containing carbon onion (synthetic powder) was deposited in the tray by continuous operation for 24 hours. Although the synthesis rate was not accurately determined due to the large amount of residue remaining on the substrate or structure, it was estimated that the powder containing carbon onion was synthesized at 1 to 2 g / hour.

It is explanatory drawing which shows the outline of the synthesis | combining method of the carbon onion by this invention, and the apparatus used for it. It is explanatory drawing which shows the outline of the other example of the synthesis method of the carbon onion by this invention, and the apparatus used for it. It is explanatory drawing which shows the outline of the other example of the synthesis method of the carbon onion by this invention, and the apparatus used for it. (A) is the electron micrograph of the carbon onion obtained in the Example of this invention, (b) is the partially expanded photograph of (a). It is a transmission electron micrograph of the carbon onion obtained in the Example of this invention. It is a diagram which shows the friction test result in the vacuum of the carbon onion obtained in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base 2 ... Base support 3 ... Substrate support rotating shaft 4 ... Cathode 5 ... Vacuum container 6 ... Gas supply port 7 ... Exhaust port 8 ··· Plasma 9 ··· Carbon onion 10 ··· AC power source 11 ··· DC power source 12 ··· Scraping plate 13 ··· Composite powder 14 ··· Tray 15 ··· Spherical substrate 16 ··· Conveyor 17 ··· Perforated plate

Claims (12)

  A carbon onion characterized in that a single or mixed gas whose elemental composition is C and H as main components is activated by heating or discharge plasma to synthesize carbon onion on an iron group or iron group alloy substrate. Production method.   A single or mixed gas whose constituent elements are C, O and H as main components is activated by heating or discharge plasma, and carbon onions are synthesized on an iron group or iron group alloy substrate. Production method of carbon onion.   2. The carbon onion according to claim 1, wherein the atomic composition is a C: H atomic ratio in a single or mixed gas mainly composed of C and H of 0.001 to 0.5: 1. Production method.   The atomic ratio of C: O: H in a single or mixed gas whose main constituents are C, O and H is 0.001 to 0.5: 0.001 to 0.5: 1; and The method for producing a carbon onion according to claim 2, wherein the number of O atoms is smaller than the number of C atoms.   The iron group-based or iron group-based alloy substrate contains iron, nickel, and cobalt alone or an alloy containing them in a ratio of 1% or more in the base material. A method for producing a carbon onion according to claim 1. The method for producing a carbon onion according to any one of claims 1 to 5, wherein the temperature of the substrate for carbon onion synthesis is 1000 ° C or lower. The method for producing a carbon onion according to claim 1 or 2, wherein the method for activating the raw material gas for producing the carbon onion is an electrically heated filament.   The method for producing a carbon onion according to claim 1 or 2, wherein the method for activating the raw material gas for producing carbon onion is any one of direct current discharge, alternating current discharge, high frequency discharge, and microwave discharge.   The method for producing a carbon onion according to claim 1 or 2, wherein the activation method of the raw material gas for producing the carbon onion is incomplete combustion of a gas containing C and H.   The method for producing a carbon onion according to any one of claims 1 to 9, wherein the synthesis of the carbon onion is carried out under atmospheric pressure, under pressure or under reduced pressure.   The carbon onion production product according to any one of claims 1 to 10, wherein the carbon onion-containing product synthesized on the iron group group or iron group group alloy substrate is scraped from the substrate continuously or intermittently. Method.   The carbon onion is continuously synthesized on a plurality of substrates by a fluidized bed method, and the synthesized product is continuously removed from the substrate by friction and collision between the substrates or by friction and collision by applying vibration. The method for producing a carbon onion according to any one of claims 1 to 10, wherein: