JP2000203816A - Intercalation compound and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intercalation compound into which various kinds of metal atoms are inserted and which permits the control in the kinds and selectivity of the elements inserted into the laminar space. SOLUTION: This intercalation compound 8 is prepared by disposing ultrafine metal particles 2 as the first raw material substance on an amorphous carbon support film 1, disposing the second raw material substance 7 containing the second metal element different from the ultrafine metal particles 2 at their near places, irradiating electron beams 4 on the first raw material substance and the amorphous carbon support film 1 under a high vacuum atmosphere to induce a graphite-like substance such as an onion-like fullerene 5, and then further irradiating the first and second raw material substances 2, 7 and electron beams on the induced onion-like fullerence 5 to insert the first metal atoms 2' and the second metal atoms 7 into the laminar spaces of the onion-like fullerene 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an interlayer compound in which two or more different kinds of metal atoms are inserted into a layered space of a graphite-like substance, and a method for producing the same.

[0002]

2. Description of the Related Art Intercalation compounds are prepared by introducing different kinds of substances into a layered space such as graphite having a layered structure, and have functions such as a catalyst utilizing the property of improving electric conductivity and properties of an intercalating substance. Research on synthesis, physical properties, applications, and the like of various intercalation compounds has been conducted since they can be applied to materials.

[0003] Examples of the foreign substance inserted into the layered space of graphite include alkali metal elements such as Li, Na and K, alkaline earth metal elements such as Ca, Sr, and Ba;
rare earth elements such as m, Eu, Yb, Mn, Fe, Ni,
Transition metals such as Co, Zn and Mo, Br ₂ , ICl, I
Halogen elements such as Br and its compounds, HNO ₃ , H ₂
Acids such as SO ₄ , HF, HBF ₄ , MgCl ₂ , FeC
l ₂ , FeCl ₃ , NiCl ₂ , AlCl ₃ , SbCl
Compounds such as ₅ have been reported.

[0004] The graphite intercalation compound in which a different substance is inserted into a layered space as described above can be prepared by the following methods: (a) contacting graphite with a gaseous or liquid intercalation substance;
(b) It is manufactured by applying a method of electrolyzing an electrolytic solution containing an insertion material using a graphite electrode.

For example, a graphite intercalation compound using an alkali metal can be obtained by coexisting an alkali metal and graphite under vacuum and heating. Graphite intercalation compounds using halogen include Br ₂ , I
It can be produced by bringing a liquid phase or vapor such as Cl or IBr into contact with graphite. Ca, Sr,
A graphite intercalation compound using an alkaline earth metal such as Ba or a rare earth element such as Sm, Eu, or Yb is prepared by mixing these metal powders with a graphite fine powder, and forming a mixture of 1-2 MPa.
It is synthesized by a method of baking under normal pressure after pressurizing at about the same level.

On the other hand, with respect to graphite intercalation compounds using transition metals such as Fe, Co, Mo, etc., intercalation compounds of chlorides of these metals are first synthesized, and then they are converted to Na.
There has been reported an example of synthesis by slow reduction at room temperature or lower using BH ₄ , LiAlH ₄ , Na, or the like. However, such a reduction method has low reproducibility,
There is a disadvantage that it is difficult to obtain a transition metal graphite intercalation compound stably.

[0007] In addition, the above-mentioned conventional methods for producing a graphite intercalation compound all employ ordinary synthesis methods such as powder sintering, powder-gas / liquid phase reaction, and electrolytic generation. Although it is suitable for synthesizing a graphite intercalation compound as a body, a graphite intercalation compound is produced after satisfying a controlled shape, distribution, state, etc., for example, forming an intercalation compound in a very small area of graphite. It is impossible, and there is a need to make these feasible. Further, in order to expand the range of application of the graphite intercalation compound, it is required that the type of element inserted into the layered space such as graphite and its selectivity can be controlled.

[0008]

As described above, in the conventional graphite intercalation compound, the reproducibility of inserting the transition metal into the layered space of graphite is poor, and the usable transition metal is limited. There was a drawback.

Although the conventional method for producing a graphite intercalation compound is suitable for synthesizing a graphite intercalation compound as an aggregate, it is not possible to produce a graphite intercalation compound satisfying a controlled shape, distribution, state and the like. It was impossible. In order to expand the range of application of the graphite intercalation compound, for example, it is possible to produce an intercalation compound whose formation state can be controlled, such as an intercalation compound selectively formed in a very small region of graphite. It is required to be able to control the type of element inserted into the space and its selectivity.

The present invention has been made in order to address such problems, and it is possible to control the type of element inserted into a layered space, its selectivity, and the like, and to provide an interlayer compound into which various metal atoms are inserted, and a method for producing the same. It is intended to provide.

[0011]

According to the first aspect of the present invention, there is provided a graphite intercalation compound having a layered structure having crystal planes corresponding to (001) and (002) planes of graphite. And two or more different kinds of metal atoms inserted in a layered space between the crystal planes of the graphite-based material.

In the intercalation compound of the present invention, the graphite-based material is, for example, a graphite-based material having a multilayer concentric structure, more specifically, an onion-like material as described in claim 3. Fullerene is used. The metal atom inserted into the layered space between the crystal planes of the graphite-based material may be, for example,
And Al atoms and Cu atoms.

In the method for producing an intercalation compound according to the present invention, as described in claim 5, ultrafine metal particles composed of a first metal element are disposed as a first raw material on an amorphous carbon support film. Disposing a second source material containing a second metal element different from the first metal element in the vicinity of the amorphous carbon support film; By irradiating the amorphous carbon support film with an electron beam in a vacuum atmosphere, the graphite-like substance having a layered structure having crystal planes corresponding to the (001) plane and the (002) plane of graphite is formed at the nucleation point of the metal ultrafine particles. And irradiating the induced graphite-like substance with an electron beam together with the first and second raw materials to obtain the graphite-like substance. Inserting a first metal atom constituting the first raw material and a second metal atom contained in the second raw material into the layered space between the crystal planes. And

In the method for producing an intercalation compound according to the present invention,
As described in claim 6, the amorphous carbon support film is disposed on a mesh-like support member made of, for example, a second raw material, and the second metal atoms evaporated from such a second raw material are removed by the second raw material. It is inserted into the layered space of the graphite-like substance together with one metal atom.

[0015] The intercalation compound of the present invention is formed of graphite.
In the layered space between the (001) plane and the crystal plane corresponding to the (002) plane,
Two or more heterogeneous metal atoms are inserted by electron beam irradiation. Examples of the graphite-like substance used here include giant fullerenes whose interlayer distance is equal to that of graphite, such as onion-like fullerene as described above. Onion-like fullerenes are obtained by irradiating an electron beam in a state where metal ultrafine particles made of a first metal element are present on such an onion-like fullerene and a substance containing a second metal element is arranged in the vicinity thereof. Of (00
The first and second metal atoms can penetrate into the layered space between the (1) plane and the (002) plane, respectively, whereby the intercalation compound of the present invention is formed.

[0016]

Embodiments of the present invention will be described below.

FIG. 1 is a cross-sectional view schematically showing a process for producing the interlayer compound of the present invention. First, as shown in FIG. 1A, metal ultrafine particles 2 made of a first metal element are arranged on an amorphous carbon support film 1 as a first raw material. As the metal ultrafine particles 2 as the first raw material,
Any material capable of inducing a graphite-like substance in the amorphous carbon support film 1 below and around the lower portion may be used. For example, ultrafine particles of pure Al having no surface oxide film are used. The constituent element of the metal ultrafine particles 2 is not limited to Al, but may be another metal such as Pt or Au.

The diameter of the ultrafine metal particles 2 is preferably in the range of 5 to 100 nm. 100nm diameter of ultrafine metal particles 2
If it exceeds 3, the lower amorphous carbon support film 1 may not be sufficiently activated, and the graphite-like substance may not be induced. On the other hand, if the diameter of the ultrafine metal particles 2 is less than 5 nm, the activated region of the amorphous carbon support film 1 becomes insufficient, and there is a possibility that a graphite-like substance having a sufficient size cannot be induced. The more preferred diameter of the ultrafine metal particles 2 is in the range of 5 to 20 nm.

In the vicinity of the amorphous carbon support film 1, a second raw material containing a second metal element different from the first metal element constituting the metal ultrafine particles 2 is further disposed. In this embodiment, a mesh-shaped support member 3 is used as the second raw material, and the amorphous carbon support film 1 is disposed on the mesh-shaped support member 3. Second
May be formed on the back surface of the amorphous carbon support film 1 as a thin film or the like.

The second raw material may be located in a region where the electron beam is irradiated together with the ultrafine metal particles 2 and the amorphous carbon support film 1 in the later-described interlayer compound formation step. Therefore, not only on the rear surface side of the amorphous carbon support film 1 but also on the side of the amorphous carbon support film 1 where the metal ultrafine particles 2 are disposed, the second
Fine particles or the like made of the above raw material may be arranged.

The constituent material of the second raw material is not particularly limited, but may be any material that evaporates, for example, when irradiated with an electron beam in a vacuum atmosphere in a later-described interlayer compound forming step. Examples of such a second raw material include:
Various metals and alloys or compounds containing them can be used. It is preferable to use Cu as the second raw material in consideration of evaporability at the time of electron beam irradiation and subsequent insertability into a layered space. The mesh-like support member 3 is made of, for example, Cu.

In this manner, the metal ultrafine particles 2 as the first raw material are arranged, and the amorphous carbon support film 1 in which the mesh-like support member 3 as the second raw material is disposed in the vicinity. As shown in FIG. 1B, an electron beam 4 is irradiated together with the ultrafine metal particles 2 in a high vacuum atmosphere.

When the electron beam 4 is irradiated to the amorphous carbon support film 1 together with the active metal ultrafine particles 2, the atomic arrangement of the amorphous carbon existing in the lower layer of the active metal ultrafine particles 2 changes, for example, as shown in FIG. As shown in a), a graphite-like substance is induced below and around the metal ultrafine particles 2 with the metal ultrafine particles as nucleation points. Examples of such a graphite-like substance include giant fullerenes such as an onion-like fullerene 5 having a multilayer concentric structure. The bead-like fullerenes 5 induced by the irradiation with the electron beam 4 can be obtained in an independent state, and can be easily irradiated with the electron beam continuously. It is suitable as a graphite-like substance to be used.

The onion-like fullerenes 5 has a multi-layer concentric structure, those having a carbon layer formed structure of a multilayer structure around the nucleus fullerene such as C ₆₀ existing in the center. Although the onion-like fullerene 5 does not have a planar structure like general graphite, the interlayer distance between the carbon layers on the outer shell side is about 0.35 nm, which corresponds to the interlayer distance of graphite. Since the carbon layer (crystal plane) on the outer shell side of the onion fullerene 5 has an interlayer distance of about 0.35 nm, it corresponds to the (001) plane and the (002) plane of graphite. Van der Waals space) is formed.

When producing a graphite-like substance such as an onion-like fullerene 5, the intensity of the electron beam 4 applied is 10 ¹⁹
It is preferably at least e / cm ² · sec. If the intensity of the electron beam 4 to be irradiated is less than 10 ¹⁹ e / cm ² · sec, the amorphous carbon support film 1 may not be activated to the extent that the onion fullerene 5 can be generated. In other words, the electron beam 4 having an intensity of 10 ¹⁹ e / cm ² · sec or more
A local heating effect and an atomic displacement induction (knock-on) effect of the metal ultrafine particles 2 and the amorphous carbon are provided, and the onion fullerene 5 is induced by these effects.

The irradiation of the electron beam 4 is preferably performed in a vacuum atmosphere of 10 ^-5 Pa or less. If the vacuum atmosphere at the time of irradiation with the electron beam 4 exceeds 10 ⁻⁵ Pa, adsorption of residual gas atoms and the like may occur, and the generation of the onion fullerene 5 may be hindered.

Next, as shown in FIG. 1 (c), the ultrafine metal particles 2 as the first raw material and the graphite-like material 2 such as onion-like fullerene 5 induced in the amorphous carbon support film 1 are used. The electron beam 6 is further irradiated together with the mesh-like support member 3 as the raw material material of No. 2. The irradiation area of the electron beam 6 is adjusted so that the mesh-shaped support member 3 is irradiated with the electron beam 6 together with the ultrafine metal particles 2 and the onion-like fullerene 5. The intensity of the electron beam 6 at this time is preferably 10 ²¹ e / cm ² · sec or more.

As described above, the active ultrafine metal particles 2
10 ²¹ e / for onion-like fullerenes 5 in the presence of
When the electron beam 6 having a high intensity of not less than cm ² · sec is irradiated, the onion-like fullerene 5 shrinks and the diameter of the ultrafine metal particles 2 is reduced, and as shown in FIGS.
As shown in (b), the first metal atoms (for example, Al atoms) constituting the metal ultrafine particles 2 shrink as an atom group (for example, Al atom group) 2 ′ and a metal atom (for example, Al atom) 2 ″. It enters the layered space of the onion-like fullerene 5 '.

At this time, since the electron beam 6 is also applied to the mesh-like support member 3 existing below the onion-like fullerene 5, the metal atoms (for example, Cu atoms) constituting the mesh-like support member 3 are formed. ) Evaporates. Since the onion-like fullerene 5 is activated by the irradiation of the electron beam 6, the layered space has the second metal atom such as Cu atom together with the first metal atom 2 ', 2 "such as Al atom. 7 invades.

In this way, the onion-like fullerene 5
Layered space (van der Waals space) of graphite-like materials such as (001) plane of graphite and
An interlayer compound 8 is obtained in which a first metal atom 2′2 ″ such as an Al atom and a second metal atom 7 such as a Cu atom are inserted into a layered space between crystal planes corresponding to the (002) plane. The layered space of the onion fullerene 5 contains Al atoms and C atoms.
The insertion of u atoms or the like can be confirmed by, for example, increasing the layer interval of the onion fullerene 5.

The intensity of the electron beam 6 irradiated in the step of forming the interlayer compound 8 is preferably 10 ²¹ e / cm ² · sec or more. If the intensity of the electron beam 6 to be irradiated is less than 10 ²¹ e / cm ² · sec, the carbon atoms cannot be activated to the extent that the onion-like fullerene 5 can be shrunk, and the second raw material located in the vicinity thereof cannot be activated. There is a possibility that the mesh-shaped support member 3 cannot be evaporated.

In other words, the electron beam 6 having the above intensity
Brings about a local heating effect of the onion-like fullerene 5, an atomic displacement induction (knock-on) effect, a local heating effect of the mesh-like support member 3 as a second raw material, and the like.
These make it possible to shrink the onion-like fullerene 5 and insert the first metal atoms 2 ', 2 "and the second metal atoms 7 into the layered space. The irradiation of the electron beam 6 is 10 ^-5 Pa. It is preferable to perform the treatment in the following vacuum atmosphere: If the vacuum atmosphere at the time of irradiation with the electron beam 6 exceeds 10 ⁻⁵ Pa, the metal atoms 2 ′, There is a possibility that intrusion of 2 ″ and 7 may be inhibited.

As described above, the intercalation compound 8 of the present invention comprises two or more different kinds of metal atoms 2 ′, 2 ″ in a layered space between crystal planes corresponding to the (001) plane and the (002) plane of graphite. ,
7 is inserted. Thus, by inserting two or more kinds of metal atoms 2 ′, 2 ″, 7 into a layered space of a graphite-like substance such as an onion-like fullerene 5,
It is expected that characteristics that cannot be obtained with an intercalation compound in which only a single metal atom is inserted can be obtained. Each metal atom 2 ', 2 ", 7 inserted into the layered space is an active metal A
Since it has properties as l and metal Cu, an interlayer compound 8 having excellent properties can be obtained.

Further, since the intercalation compound 8 of the present invention is obtained by irradiating individually controllable giant fullerenes such as onion-like fullerenes 5 having the metal ultrafine particles 2 on the top with the electron beam 6, for example, graphite State, such as being able to be formed in an extremely small area of
The controllability such as the shape and the distribution can be greatly improved, and the reproducibility can be obtained. In addition, since the intercalation compound 8 can be prepared independently under controlled conditions, various operations and control of the intercalation compound 8 and grasp of physical properties thereof can be easily realized.

[0035]

Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1 First, spherical θ-Al ₂ O ₃ particles having a diameter of about 100 nm (purity
= 99.8%), disperse this in alcohol,
It was applied on an amorphous carbon support film made of i-carbon and dried. The amorphous carbon support film on which the θ-Al ₂ O ₃ particles were placed was placed on a support member made of Cu mesh, and in this state, it was placed on a room temperature stage placed in a vacuum chamber of an FE-TEM device.

After the vacuum chamber was evacuated to a degree of vacuum of 1 × 10 ⁻⁵ Pa, the θ-Al ₂ O ₃ particles disposed on the amorphous carbon support film were exposed to 1.3 × 10 ²⁰ e / cm ² · sec electrons. The line was irradiated. By irradiating the θ-Al ₂ O ₃ particles with an electron beam, Al ultrafine particles having a diameter of about 5 to 15 nm were formed on the amorphous carbon support film.

Next, while maintaining the state (including the degree of vacuum) in the vacuum chamber of the FE-TEM apparatus on which the amorphous carbon support film (including the Cu mesh) having the generated ultrafine Al particles is placed, the amorphous carbon The Al ultrafine particles on the support film were irradiated with an electron beam of 1 × 10 ²² e / cm ² · sec together with the underlying amorphous carbon. On this occasion,
The irradiation region of the electron beam was set so that a part of the Cu mesh was present in the irradiation region of the electron beam.

The state of the ultrafine particles of Al and the amorphous carbon were measured in-situ (in-
situ) Observed. This observation result will be described with reference to the schematic diagram of FIG. About 300 seconds after the start of electron beam irradiation, as shown in FIG.
A carbon structure having an elliptical concentric circle was induced below the ultrafine particles 2. Since the carbon structure having the elliptical concentric circles has a layer interval of about 0.35 nm, the onion fullerene 5
Was confirmed. In addition, the periphery of the onion fullerene 5 maintained the state of amorphous carbon.

Further, when the electron beam was continuously irradiated, the onion-like fullerene 5 gradually became concentric while shrinking, and the diameter of the Al ultra-fine particles 2 was similarly reduced.
About 800 to 1000 seconds after the start of the electron beam irradiation, as shown in FIG. 2B, the onion-like fullerene 5 'shrinks concentrically, and the Al ultrafine particles 2' decrease to a diameter of about 2 nm. Was.

After the above-mentioned electron beam irradiation is continued for 3000 seconds,
The portion where the onion-like fullerenes 5 'are present (specifically, the region A in FIG. 2B) was measured by an energy dispersive X-ray analyzer (EDS). The result is shown in FIG. FIG. 4 shows EDS measurement results before electron beam irradiation. As is clear from FIG. 3, it can be seen that Cu exists together with Al in the onion-like fullerene. These Al and Cu are the onion-like fullerene (001)
It penetrates into the layered space between the (002) plane and the (002) plane to form an intercalation compound.

That is, as the diameters of the onion-like fullerene and the Al ultrafine particles described above are reduced, the Al atoms constituting the Al-like ultrafine particles are changed to the (001) plane of the onion-like fullerene and the (002) plane in an atomic state or in an atomic state. The Cu mesh existing underneath is also activated by an electron beam at the same time as it enters the layered space between the) surface and the Cu atoms constituting this Cu mesh have entered the layered space of the onion fullerene. it is conceivable that. These Al atoms and Cu
It was confirmed that the atoms were dispersed in each part of the onion fullerene 5 '.

In the above-mentioned intercalation compound, Al ultrafine particles were formed such that the {002} plane of Al ultrafine particles 2 and the (002) plane of onion-like fullerene 5 were parallel to each other.
1 atomic group 2 'was arranged, and Al atomic group 2' and onion-like fullerene 5 'had an epitaxy relationship. The spacing d between the (001) plane and the (002) plane of the onion fullerene 5 'at the site where the existence of the Al atomic group 2' is clear is 0.40 nm, and the d (200) Al = 0.20 nm
The lattice of the onion fullerenes 5 'was swelled so as to be doubled. It was confirmed from the increase in the interplanar spacing that Al atoms and Cu atoms penetrated into the layered space of the onion-like fullerene 5 '.

Further, when the onion-like fullerene 5 'in which Al and Cu atoms were inserted into the layered space was measured by an electron energy loss spectrometer (EELS), the state of the electrons inside the onion-like fullerene 5' changed. I was From this, the onion fullerene 5 '
It has been confirmed that Al atoms and Cu atoms have penetrated into the layered space of.

As described above, the onion-like fullerene having the Al ultrafine particles present on the upper side and the Cu mesh disposed on the lower side is irradiated with a high intensity electron beam such as 10 ²² e / cm ² · sec. By doing so, an intercalation compound in which Al atoms and Cu atoms are inserted into the layered space between the (001) plane and the (002) plane of the onion fullerene is obtained.

[0046]

As described above, according to the present invention, two or more different kinds of metal atoms can be inserted into a layered space of a graphite-like substance with good reproducibility. Such an interlayer compound of the present invention greatly contributes to expansion of its application range and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a step of producing an interlayer compound according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a change in the state of ultrafine Al particles and onion-like fullerenes in the process of producing an interlayer compound according to Example 1 of the present invention.

FIG. 3 is a diagram showing an EDS measurement result of an onion fullerene after electron beam irradiation according to Example 1 of the present invention.

FIG. 4 is a diagram showing an EDS measurement result of amorphous carbon before electron beam irradiation according to Example 1 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Amorphous carbon support film 2 ... Metal ultrafine particles 2 ', 2 "... First metal atom 3 ... Mesh-like support member 4, 6 ... Electron beam 5 ... Onion-like fullerene 7 ... 2nd Metal atom 8 …… Interlayer compound

Claims (8)

[Claims] 1. A graphite-based material having a layered structure having crystal planes corresponding to the (001) plane and the (002) plane of graphite, and a heterogeneous compound 2 inserted into a layered space between the crystal planes of the graphite-based substance. An intercalation compound comprising at least one kind of metal atom. 2. The intercalation compound according to claim 1, wherein the graphite-based material has a multilayer concentric structure. 3. The intercalation compound according to claim 1, wherein the graphite-based material is an onion-like fullerene. 4. The intercalation compound according to claim 1, wherein a laminar space between the crystal planes of the graphite-based material is
An intercalation compound comprising an Al atom and a Cu atom inserted therein. 5. An ultrafine metal particle comprising a first metal element as a first raw material on an amorphous carbon support film, and a first metal element different from the first metal element in the vicinity of the amorphous carbon support film. Arranging a second raw material containing the second metal element, and irradiating the amorphous carbon support film with an electron beam in a high vacuum atmosphere together with the first raw material to form the amorphous carbon support film on the amorphous carbon support film. A step of inducing a graphite-like substance having a layered structure having crystal planes corresponding to the (001) plane and the (002) plane of graphite as the nucleation points of the metal ultrafine particles, further comprising: An electron beam is irradiated together with the first and second raw materials to form the first raw material in a layered space between the crystal planes of the graphite-like material. Wherein the first metal atom second
And inserting a second metal atom contained in the raw material of (1). 6. The method for producing an intercalation compound according to claim 5, wherein the amorphous carbon support film is disposed on a mesh-like support member made of the second raw material. . 7. The method for producing an intercalation compound according to claim 5, wherein the graphite-based material is an onion-like fullerene. 8. The method for producing an intercalation compound according to claim 5, wherein a laminar space between the crystal planes of the graphite-based material is
A method for producing an intercalation compound, comprising inserting an Al atom and a Cu atom.