WO2004089821A1

WO2004089821A1 - Carbon particle and method for preparation thereof

Info

Publication number: WO2004089821A1
Application number: PCT/JP2004/004953
Authority: WO
Inventors: Masatoshi Takagi; Jun Enda
Original assignee: Mitsubishi Chemical Corporation; Frontier Carbon Corporation
Priority date: 2003-04-07
Filing date: 2004-04-06
Publication date: 2004-10-21

Abstract

A carbon particle, characterized in that it has a graphite thin film formed on the surface thereof; and a method for preparing the carbon particle which comprises heating fullerene or its derivative in a hydrogen atmosphere. In a preferred embodiment, the graphite thin film is a thin film formed by the lamination of 5 to 50 layers of a graphene sheet structure, the graphite thin film occupies a space of a thickness of 10 to 1000 nm, and the carbon particle has a BET surface area of 50 to 3000 m2/g. The above carbon particle is a novel substance which has a fine structure of a nano-size and is useful as a functional material.

Description

Description Carbon particles and production method

The present invention relates to a carbon particle and a method for producing the same, and more particularly, to a novel carbon particle having a nano-sized microstructure and a method for producing the same. The carbon particles of the present invention are useful as novel functional materials used for field emission displays, capacitors of lithium secondary batteries, and the like. Background art

In recent years, fullerenes, single-walled or multi-walled carbon nanotubes, and carbon nanohorns have been reported as new nano-sized carbon materials, and carbon nanowalls (Carbon Nanowa 1 Is) have also been produced (for example, , Nano Lette rs 2002, 2, 355-359, Advanced Materials 2002, 14, 64). These new carbon materials are expected to be applied as new electronic materials, catalysts, optical materials, etc. as nanostructured materials.

However, in practice, there are fields where the above-mentioned new carbon materials do not yet meet the required performance, and if a carbon material with a new nanostructure is provided, the field of application will be greatly expanded . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a SEM photograph (magnification: 100 times) of a drawing of an example of the carbon particles of the present invention.

Fig. 2 is an SEM photograph (magnified photograph of the A particle in Fig. 1 at a magnification of 10,000 times) of an example of the carbon particles of the present invention, instead of a drawing.

Fig. 3 is an SEM photograph as a substitute for a drawing of an example of the carbon particles of the present invention. Large photo: 30,000 times magnification).

FIG. 4 is a SEM photograph (magnification: 500 ×) of a cut surface of an example of the carbon particles of the present invention, which is used as a drawing substitute.

FIG. 5 is an SEM photograph (magnification: 50,000 times) of a cut surface of an example of the carbon particles of the present invention, which is used as a drawing.

FIG. 6 is a SEM photograph (magnification: 3,000 times) of a space existing in a cut surface of an example of the carbon particles of the present invention, which is a drawing substitute.

FIG. 7 is an SEM photograph (SEM in a non-deposited state: magnification of 100,000 times) of an example of the carbon particles of the present invention.

FIG. 8 is a TEM photograph (magnification: 60,000 times) of an example of the pulverized carbon particle product of the present invention, which is a drawing substitute.

FIG. 9 is a TEM photograph (magnification: 60,000 times) of another example of the pulverized carbon particle product of the present invention, which is used as a drawing substitute.

FIG. 10 is a TEM photograph (magnification: 300,000 times) of the pulverized carbon particle product of the present invention as a substitute for a drawing.

FIG. 11 is a TEM photograph (magnification: 1.2 million times) of a pulverized carbon particle product of the present invention as a substitute for a drawing.

FIG. 12 is a TEM photograph (magnification: 1) of another example of the pulverized carbon particle product of the present invention, which is used as a drawing substitute.

200,000 times).

FIG. 13 is an X-ray powder measurement chart of the carbon particles of the present invention.

FIG. 14 is a SEM photograph (magnification: 500 ×) of a drawing of an example of the carbon particles of the present invention.

FIG. 15 is an SEM photograph (magnification: 50,000 times) of a drawing of an example of the carbon particles of the present invention. Disclosure of the invention

The present invention has been made in view of the above circumstances, and its purpose is to provide a functional material The present invention provides a novel carbon particle having a nano-sized fine structure and a method for producing the same.

As a result of intensive studies, the present inventors have obtained the knowledge that by treating fullerenes under specific conditions, it is possible to obtain a carbon material having a nanostructure that has not been known until now. Completed.

That is, the first gist of the present invention resides in carbon particles having a graphite thin film on the particle surface, and the second gist of the present invention is to heat fullerenes in a hydrogen atmosphere. The present invention resides in the above-mentioned method for producing carbon particles. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist.

The carbon particles of the present invention are carbon particles having a graphite thin film on the particle surface. Aforementioned carbon nano-wall is by treating the CH ₄ and H ₂ at a microwave plasma CVD (MPEC VD) method, but was allowed to adult long graphite film on one side of the substrate. On the other hand, in the case of the present invention, a graphite thin film is grown on the surface of carbon particles. In addition, the carbon particles of the present invention usually have a G ′ peak observed around 270 cm- ¹ in Raman spectrum, and a peak is not observed around 220 cm− ^1. The graphite thin film of the carbon particles according to the present invention has a difference in graphite structure as compared with carbon nanowalls described in “Advanced Materials 2002, 14, 64”. The carbon particles of the present invention are more useful industrially because they can be used in various applications as particles in comparison with the carbon nanowalls formed on a substrate. In addition, mass production is possible without using special equipment.

The carbon particles of the present invention contain carbon as a main component. As long as carbon is the main component, a functional group such as a hydroxyl group or a carboxyl group may be present on the particle surface, or a low molecular compound such as water may be adsorbed on the surface or in the pores. Specifically, in elemental analysis, The proportion of carbon is usually at least 90% by weight, preferably 98% by weight. Further, the inside of the carbon particle of the present invention may have any structure, and the inside may be composed of a graphite thin film.

The size of the carbon particles of the present invention differs depending on the raw material and manufacturing method, and cannot be unconditionally specified. However, the particle size of the spherical particles observed with a scanning electron microscope (hereinafter referred to as SEM) (for non-spherical particles, Length), usually in the range of 10 nm to 5 cm, preferably l O Onm to 0.5 cm.

The graphite thin film on the surface of the carbon particles of the present invention can be observed by SEM. The graphite thin film preferably covers substantially the entire surface of the carbon particles. The graphite thin film may be chemically bonded to the carbon structure inside the particles, or may be simply physically added to the carbon particles. However, from the viewpoint that peeling due to external force is unlikely to occur, it is preferable that they are chemically bonded. The layer structure of the graphite thin film can be confirmed from the shape of the end face of the graphite thin film by observing a sample obtained by crushing the carbon particles of the present invention with a transmission electron microscope (hereinafter referred to as TEM). According to this, the layer structure of a graphite thin film is a structure in which a single-layer (hereinafter referred to as a graph ensheet) graphite structure is formed by laminating two or more layers. About a layer. In addition, in the graphite thin film, in addition to the portion where the graph ensheet is beautifully linear, the bent portion or the portion where the number of the graph encapsulation layer changes on the way and a defect is formed on the surface. Are also often observed. In the carbon particles of the present invention, a peak near 2700 cm- ¹ normally observed in Raman spectrum is considered to be a peak peculiar to a graphite structure having a defect (for example, Physical Review B) , vol. 61, p. 4542 (2000)), which is in good agreement with the TEM observation results described above.

The thickness of the above graphite thin film is mainly determined by the number of laminated graphite sheets. Usually, this thickness is confirmed by SEM or TEM observation without vapor deposition, and is usually 1 to 15 nm. Also, the size of the graphite thin film Confirmed by T EM observation sample, as a plane portion of one graphite film, mainly from 0.0005 to 5; is a thin film of m ² is observed. Such a graphite thin film exists densely on the particle surface with a space. When the surface of carbon particles is observed by SEM, 50 to 500 sheets of graphite thin film are usually observed in a visual field of 1 m square. The thickness of the space occupied by the graphite thin film on the carbon particles is usually 10 to: L 000 nm.

The carbon particles of the present invention usually have a high specific surface area, as easily inferred from their structure. Specifically, the BET specific surface area, normally 50~3000m ² Zg, preferably 100-2000 m ² Zg. The carbon particles of the present invention usually have high electrical conductivity, as easily inferred from their structure. Specifically, the value of the volume resistivity is usually 0.005 to 1. OQcm, preferably 0.01 to 0.1 Qcm. Further, the carbon particles of the present invention may have very sharp distribution of pores at 1 to 10 nm.

The carbon particles of the present invention can be produced by heating fullerenes in a hydrogen atmosphere. The reaction conditions are usually as follows.

The lower limit of the hydrogen partial pressure (room temperature: initial pressure before heating) is usually lMPa, preferably 3MPa, more preferably 5MPa, particularly preferably 10MPa, and the upper limit is usually 200MPa, preferably Is 150 MPa, more preferably 100 MPa, particularly preferably 8 OMPa. If the hydrogen partial pressure is too low, the reaction will be slow and the reaction may not proceed. On the other hand, when the hydrogen partial pressure is too high, a thick reaction vessel having sufficient pressure resistance is required. The hydrogen used here is not limited to pure hydrogen, but may be hydrogen diluted with an inert gas or the like as long as the formation of the carbon particles of the present invention is not hindered. The lower limit of the reaction temperature is usually 520 ° C, preferably 550 ° C, and the upper limit is usually 1000 ° C, preferably 900 ° C, more preferably 800 ° C. If the reaction temperature is too low, the reaction will be slow and the reaction may not proceed. On the other hand, if the reaction temperature is too high, the reaction vessel will be severely deteriorated, so an expensive vessel is required. Reaction time is typically a few minutes From 10 hours to 10 hours, preferably from 10 minutes to 5 hours. If the reaction time is too short, carbonization of the fullerenes will be insufficient, and if it is too long, the production efficiency will decrease. The Fe—Ni—Cr alloy is usually used for the material of the reactor. Since the reaction is generally performed at a high temperature, a heat-resistant steel having excellent high-temperature strength, particularly, SCH22 and SCH24 are suitable.

The raw material fullerenes have a closed-shell fullerene skeleton formed by arranging carbon atoms in a spherical or rugby pole shape. Specifically, carbon clusters represented by the general formula C _n (n usually represents an integer of 6120), derivatives thereof, and the like. Examples of carbon classes include, for example, C ₆₀ (so-called buckmins_______________________________________________________________________0 and the like. these may be a single, those which may be. single mixture of two or more, since the C ₆ o and C ₇ o produces much during production, availability Examples of the carbon cluster derivative include a hydrogenated compound, a hydroxylated compound, an epoxidized compound, an alkylated compound, and an arylated compound of the above-mentioned carbon cluster. The number of the groups is not particularly limited, and the number of the groups may be one or more.The procedure for introducing hydrogen gas during the reaction is as follows. Is not particularly limited as long as they coexist in the reactor. It may have been sealed by introducing hydrogen gas, the hydrogen gas may be passed through the reactor during the reaction. Among the former is preferable from ease of device.

In the production method of the present invention, usually, fullerenes are hydrotreated in a solid state. The particle size of the raw material fullerenes is not particularly limited, but the carbon particle size of the product is mainly controlled by the particle size of the fullerene raw material. Therefore, in the carbon particles having a graphite thin film of the present invention, fullerenes having a smaller particle size are used in order to obtain carbon particles having a large proportion (surface area per unit weight) of the graphite thin film. Is preferred. Particle size of fullerenes is as follows: Fullerene is finely pulverized with agate mortar, ball mill, jet mill, etc. Or by crystallization.

The fullerenes may not be pure, and may contain other liquid or solid organic substances as long as they do not prevent the production of the carbon particles of the present invention. Examples of the organic substance here include general organic compounds such as benzene, toluene, and n-hexane in addition to the carbon material. Organic substances composed of carbon, hydrogen and oxygen are preferable because other elements do not remain in the carbon material after the reaction.

The thickness and size of the thin film, the density of the thin film on the particle surface, the thickness of the thin film portion in the particle, the specific surface area of the carbon particles, the particle size, and the like can be adjusted by the properties of the raw material and the presence or absence of additives. The yield of carbon particles produced by the production method of the present invention is usually at least 80%, and is preferably at least 90% under preferable reaction conditions. The absence of fullerenes as raw materials in the product can be attributed to, for example, (1) changes in color or UV absorption and liquid chromatography (UV) when the product is dispersed in toluene and irradiated with ultrasonic waves. (HPLC) analysis confirms that fullerenes do not elute in the liquid phase, and (2) the product is measured by IR and no absorption derived from fullerenes is observed.

The carbon material of the present invention usually has a high specific surface area, and has a unique structure in which a graphite thin film having a nano-level thickness occupies a space on the particle surface. Therefore, the carbon material of the present invention is a useful material which is easy to handle and can be widely applied to various uses requiring a graphite surface. On the other hand, the porous nanowall described in the above-mentioned “Advanced Materials 2002, 14, 64” has a graphite thin film formed only on one surface of the substrate. Even if the particles are dropped, they can only be obtained by forming a graphite thin film on one surface.

Specific uses of the carbon material of the present invention include, for example, a gas absorbent utilizing a high specific surface area, a fuel cell utilizing a defect and a bent portion of a graphite thin film, and a general chemical industry. Supported catalysts, and capacitors for lithium ion batteries. Further, the carbon particles of the present invention are applied after pulverization. By doing so, patterning on the substrate is also possible. Furthermore, since the structure has a high-density Daraphite end face, it is useful, for example, as a material for a field emission display. Further, since the carbon material of the present invention does not require a special production apparatus, it can be produced in a large size (kg order).

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1:

The pressure vessel F e -N i -C r alloy having an inner volume of 6 OML, placed Furontaka one carbon manufactured by C ₆₀ fullerene (particle size 20~200 m) 10. 0 g, was replaced three times with hydrogen gas Thereafter, the container was sealed and pressurized to 2 IMPa with hydrogen gas at room temperature. The reactor was heated to 600 ° C and held there for 2 hours. Thereafter, the reactor was cooled and then purged with hydrogen gas, and the contents were taken out. 9.2 g of a black solid were obtained. This value corresponds to 92% at a yield in the case of the 100% pure C ₆₀ fullerene and 100% charcoal material fee purity was obtained.

Since the above product was insoluble in toluene, not a C ₆₀ fullerene material was confirmed. As a result of elemental analysis, oxygen was 0.28% by weight, hydrogen was less than 0.3% by weight, and carbon was 98.1% by weight. Result of IR measurement, including peaks corresponding to C ₆₀ fullerenes, at all, since the peak was not observed was presumably carbide was One to put under the conditions of the above follow.

Using "NR 1800 (F single ZG4)" manufactured by JASCO Corporation, Raman spectrum was measured at an excitation wavelength of Ar + 514.5 nm and a Raman irradiation diameter of 100 m. As a result, the size of each peak changes depending on the measurement position, but in any case, it is as large as 1350 cm-i (D), 1583 cm-i (G), and 2704 cm- ¹ (G '). This peak was observed, and small peaks were observed at 1617 cm- ¹ , 2452 cm (D "+ D), 2935 cm-i (D + G), and 3243 cm (2D,). In the carbon nanostructure, it is stated that peaks are observed at 220 cm-i, 1350 cm-1583 cm, and 1617 cm- ^1. (Advanced Materials 2002, 14, 64). Comparing the two, the carbon particles of the present invention have no peak at 220 cm-1 and a G 'peak at 2704 cm-i. The measurement result of the BET specific surface area of the carbon particles of the present invention was 175 m ² / g. 1 to 3 show SEM photographs instead of drawings of an example of the carbon particles of the present invention. According to Figure 1 (100x magnification), the diameter of the particles is about 50-200 im. Figure 2 is an enlarged photograph (magnification 10,000x) of Figure 1. According to FIG. 2, it can be seen that almost the entire surface of the particle is covered with flakes. Figure 3 is a further enlarged image of Figure 1 (magnification 30,000). According to FIG. 3, it can be seen that the thickness of the dense flakes is about several nm to several tens nm.

FIGS. 4 to 6 show SEM photographs as substitutes for drawings on cut surfaces of an example of the carbon particles of the present invention. As shown in Fig. 4 (500x magnification), the inside of the particle is basically less uneven and has a different structure from the particle surface. Figure 5 is a photograph (magnification: 50,000 times) of the cut surface enlarged. According to Fig. 5, the thickness of the part where the graphite thin film exists is 50-

It seems to be around 200 nm. Fig. 6 is an enlarged photograph (magnification: 3000x) of the concavo-convex portion seen on the surface of the cut surface in Fig. 4, where the state of being covered with the graphite thin film is also observed.

FIG. 7 is a SEM photograph (magnification 100,000) of the surface of the carbon particles of the present invention measured in a non-evaporated state. From Fig. 7, it can be seen that the thinnest thickness of the graphite thin film is about 5 nm.

8 to 12 show TEM photographs instead of drawings of an example of the pulverized carbon particle product of the present invention. These are photographs obtained by pulverizing carbon particles and observing them with a TEM in order to confirm a finer structure of the carbon particles of the present invention. In Figs. 8 to 10, a number of flakes are observed on the particle surface. Many flakes have a length of about 50-30 Onm. Figure 11 is a photograph (magnification: 1.2 million times) of a portion where the thin sections are densely enlarged. FIG. 11 confirms a laminated structure of thin films, which is considered to be the end face of the flake. This indicates that the flake has a graphite structure. Graph Entries 5 ~

Many graphite thin films (thickness: 3 to 15 nm) with about 30 layers laminated are observed. You. The photograph shown in Fig. 12 (magnification: 1.2 million times) is considered to be the structure inside the carbon particles, but it is basically amorphous although the graphite structure is growing slightly.

When the volume resistivity of the carbon particles of the present invention was measured, it showed a very small value of 0.039 Qcm, indicating that the carbon particles exhibited high conductivity. Figure 13 shows the results of powder X-ray measurement of the carbon particles of the present invention. This is probably due to the small size of the graphite flakes, but no peak corresponding to the graphite was observed.The pore distribution of the carbon particles of the present invention was measured. Distribution.

Example 2:

In Example 1, in place of the C 60, with C ₆ 0, C 70 and other higher order fullerene mixture of emission (weight ratio, C ₆ Q: C _7:. Other higher fullerenes = 6 2: 2 3: 1 5) The reaction was carried out in the same manner as in Example 1 except that a fullerene mixture 100.Og manufactured by Frontier Carbon Co., Ltd. was used. As a result, 9. O g of a black product was obtained. This value corresponds to a yield of 90% when a carbon material having a purity of 100% was obtained from a fullerene mixture having a purity of 100%. Since this product was insoluble in toluene, it was confirmed that it was not a fullerene mixture as a raw material. FIGS. 14 and 15 show SEM photographs of this product as substitutes for drawings. The carbon particles obtained in Example 2 are smaller than the product of Example 1, and the surface thereof has the same structure as that of the product of Example 1, but the flakes observed in Example 1 Smaller flakes were covered.

As a result of measuring the Ram spectrum in the same manner as in Example 1, it was found to be as large as 1352 cm-1 (D), 1583 cm- ¹ (G), and 2698 cmi (G '). Three peaks were observed, and small peaks were observed at 1615 cm-2900 cm (D + G) and 3240 cm- ¹ (2D '). The BET specific surface area was 184 cm-i, and the volume resistivity was 0.038 Qcm, all of which showed the same value as the carbon particles of Example 1. Example 3:

The 10. 0 g which a C ₆₀ fullerene used was ground in an agate mortar for 10 minutes in Example 1 except that the raw material, the reaction was carried out in the same manner as in Example 1. As a result, 9.3 g of a black product was obtained. This value corresponds to 93% at a yield in the case of the 100% pure C ₆₀ fullerene with 100% pure carbon material is obtained. Since this product was insoluble in toluene, it was confirmed that it was not the raw material fullerene. The carbon particles obtained in Example 3 were smaller than the product of Example 1, and the surface was covered with flakes having the same structure and size as the product of Example 1.

As a result of measuring the Ram spectrum in the same manner as in Example 1, three large peaks were found at 1351 cmi (D), 1583 cm-i (G), and 2704 cm- ¹ (G '). observed, 1615 cm_i, 2460 cm-i (D "+ D), 2 940 cm -. 1 (D + G), 3243 cm- 1 small peak (2D ') was observed BET specific surface area 316m ² Zg, which was larger than that of the carbon particles of Example 1. This indicates that the surface structure of the carbon particles affected the BET specific surface area.

Example 4:

The reaction was carried out in the same manner as in Example 1 except that 10.0 g of the fullerene mixture manufactured by Frontier Carbon Co., Ltd. used in Example 2 was crushed in an agate mortar for 10 minutes as a raw material. As a result, 9.7 g of a black product was obtained. This value is equivalent to 97% of the yield when 100% pure carbon material is obtained from a 100% pure fullerene mixture. Since this product was insoluble in toluene, it was confirmed that it was not a fullerene mixture as a raw material. The carbon particles obtained in Example 4 were smaller than the product of Example 2, and the surface thereof was covered with flakes having the same structure and size as the product of Example 2. The BET specific surface area was 229 m ² Zg, which was larger than that of the carbon particles of Example 2. This suggests that the surface structure of the carbon particles affects the BET specific surface area. Example 5:

The reaction was carried out in the same manner as in Example 2 except that the partial pressure of hydrogen introduced was changed to 10.5 MPa. As a result, 9.4 g of a black product was obtained. This value corresponds to a yield of 94% when a 100% pure carbon material is obtained from a 100% pure fullerene mixture. Since this product was insoluble in toluene, it was confirmed that it was not a raw material fullerene mixture. In the carbon particles obtained in Example 5, flakes having the same structure and size as the product of Example 2 covered the particle surface.

Example 6:

The reaction was carried out in the same manner as in Example 2 except that the partial pressure of hydrogen introduced was changed to 3.5 MPa. As a result, 9.0 g of a black product was obtained. This value corresponds to a yield of 90% when a 100% pure carbon material is obtained from a 100% pure fullerene mixture. Since this product was insoluble in toluene, it was confirmed that it was not a fullerene mixture as a raw material. In the carbon particles obtained in Example 6, fine flakes having a side of about 20 to 40 nm covered the particle surface. Industrial applicability

According to the present invention, there is provided a carbon particle having a unique nanostructure in which the particle surface is covered with flaky graphite. Also, a method for selectively producing the carbon particles from fullerenes by a simple method without using a special apparatus is provided.

Claims

The scope of the claims

1. A carbon particle having a graphite thin film on the particle surface.

2. The carbon particles according to claim 1, wherein the graphite thin film is a thin film formed by laminating 5 to 50 layers of a graph ensheet structure.

3. The carbon particles according to claim 1, wherein the thickness of the space occupied by the graphite thin film on the carbon particles is 10 to 100 Onm.

4. The carbon particles according to any one of claims 1 to 3, wherein the BET surface area is 50 to 3000 m2g.

5. The method for producing carbon particles according to claim 1, wherein the fullerenes are heated in a hydrogen atmosphere.

6. The production method according to claim 5, wherein the hydrogen partial pressure is 1 MPa or more.

7. The method according to claim 5, wherein the reaction temperature is in a range of 520 to 1000 ° C.