JPH0135769B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel graphite intercalation compound. More particularly, the present invention relates to a ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine, which is not only stable against moisture but also has excellent electrical conductivity. The present invention also relates to a method for producing a ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine. The present invention also relates to a conductive material comprising a ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine. In recent years, fluoride graphite intercalation compounds have been attracting attention because of their excellent electrical conductivity. However, most of the conventionally known graphite intercalation compounds are unstable to moisture and therefore decompose immediately when left in air. Therefore, it is impossible to put it into practical use. Fluorides, which have been used as intercalating substances to create graphite intercalation compounds, have low melting and boiling points and are gaseous or liquid at room temperature.
Therefore, it has been generally accepted that fluoride as an interstitial substance needs to have a relatively low temperature and high vapor pressure. Therefore, no attempt has been made to produce a fluoride graphite intercalation compound having a high melting point or boiling point. In fact, a binary graphite intercalation compound of magnesium fluoride and graphite that exhibits no vapor pressure even at high temperatures is not produced. The present inventors have conducted extensive research to develop a practically usable fluoride graphite intercalation compound that not only has excellent conductivity but is also extremely stable against moisture, and as a result, has the formula C _x F ( _{MgF 2} ) A ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine (hereinafter often simply referred to as "ternary graphite intercalation compound") represented by y has a yield of 100% based on the raw material graphite. I found that it can be obtained at a lower rate.
The obtained three-component graphite intercalation compound is not only stable against moisture but also has high heat resistance and excellent electrical conductivity. The electrical conductivity of the ternary graphite intercalation compound of the present invention is one order of magnitude higher than that of the raw material graphite. The present invention has been made based on such new knowledge. Therefore, an object of the present invention is to provide a novel three-component graphite intercalation compound that is not only stable against moisture but also has high heat resistance and excellent electrical conductivity. Another object of the present invention is to provide a method for producing this novel ternary graphite intercalation compound. Another object of the present invention is to provide a novel electrically conductive material comprising the novel ternary graphite intercalation compound as described above. These and other objects, features and benefits of the present invention will become apparent from the following detailed description and accompanying drawings. According to one embodiment of the invention, the formula C _x F(MgF ₂ )
A ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine represented by _y is provided. Generally, the _ternary graphite intercalation compound represented by _{the formula C} Obtained by contact. The present invention will be explained in more detail below. The ternary graphite intercalation compound of the present invention represented by the formula C _x F (MgF ₂ ) _y may have a first stage, a second stage, a third stage, a fourth stage, or more stages. The number of stages of the ternary graphite intercalation compound is determined by measuring the periodic distance (I _c ) obtained from X-ray diffraction. The number of stages of the obtained ternary graphite intercalation compound is influenced not only by the reaction temperature and time but also by the crystallinity and thickness (in the C-axis direction) of the raw graphite. For the first stage, x = approximately 3.0 ~ 20, y = approximately 0.03 ~
It is 0.20. For the second stage, x = approximately 11~
50, y=about 0.01-0.15. For the third stage and above, x=approximately 30 to 60 and y=10 ^-4 to 10 ^-2 . Generally, in a ternary graphite intercalation compound represented by the formula C _x F (MgF ₂ ) _y , x = 3 to 100 and y
= approximately 0.0001 to 0.20. For each of the first stage, second stage, third stage and fourth stage or higher stage compounds, the values of x and y are within the ranges mentioned above, as well as the reaction temperature and time. It varies depending on the crystallinity and the thickness in the C-axis direction. As the graphite raw material used in the present invention, in addition to natural graphite, artificial graphite obtained by heat treating petroleum coke or the like can also be used. Particle size is not critical, flake-like or powder-like, approximately 20 to
50 meshes, 50 to 400 meshes, or more than 400 meshes (Tyler) can be used.
Alternatively, if block-shaped graphite is desired, hydrocarbons such as methane, propane, benzene, and/or acetylene are brought into contact with a substrate (generally made of artificial graphite) heated to about 2100°C. The graphite material obtained by thermal decomposition is deposited on a base material, and then the deposited graphite material is heat-treated, which can be used. In that case, block-shaped graphite having different degrees of graphitization can be obtained depending on the heat treatment temperature. Pyrotechnic carbon is obtained by heat treatment at approximately 2400°C. Approximately 2600℃~3000℃
When the heat treatment is carried out at .degree. C., pyrotechnic graphite having higher crystallinity than pyrotechnic carbon can be obtained. Raw material graphite is placed in a fluorine atmosphere at a temperature of 0 to 400°C for at least a period of time to cause the graphite to increase in weight.
carried out by contacting with MgF ₂ ,
Regarding the production of a ternary graphite intercalation compound represented by the formula C _x F (MgF ₂ ) _y , desirable reaction conditions are as follows. Fluorine pressure is not particularly critical, but
Usually about 0.5 to 10 atm is used. The reaction temperature is 0
-400°C, preferably 15-350°C. As mentioned above, the formula C _x has the desired x and y values.
The reaction time to obtain the compound represented by F(MgF ₂ ) _y depends on the crystallinity of the raw graphite, the thickness in the C-axis direction,
It also depends on the reaction temperature. However, reaction times generally range from 1 hour to 10 days, more typically from 1 day to 8 days. The weight ratio of raw graphite to MgF ₂ depends on the desired number of stages of the ternary graphite intercalation compound, but is usually 1:0.4 to 1:10. What should be noted about the reaction conditions is that the temperature of the reaction system is 100℃.
If the temperature is raised to a higher temperature, the temperature will rise to 100% in the process of cooling the heated reaction system.
The point is that an increase in weight of graphite is observed when the temperature drops below ℃. The thickness of the raw graphite in the C-axis direction is 1
When thicker than mm, the product is more likely to be a second stage than a first stage compound or a higher stage number compound rather than the first stage. To obtain first stage compounds, usually
It is preferable to use graphite material having a thickness (in the C-axis direction) of up to 0.8 mm. After the reaction is completed, if the temperature of the reaction system has been raised to a temperature higher than room temperature, the temperature of the reaction system is lowered to room temperature. Unreacted MgF ₂ is separated using a sieve or tweezers to obtain the desired ternary graphite intercalation compound having the formula C _x F (MgF ₂ ) _y . The periodic distance (I _c ) of C _x F(MgF ₂ ) _y is 9.3 to 9.4 Å for the first stage, 12.7 to 12.8 Å for the second stage, and 16.0 to 16.0 for the third stage. 16.1 Å, and 19.4-19.5 Å for the fourth stage. Formula C _x F
In the case of a ternary graphite intercalation compound represented by (MgF ₂ ) _y , the first, second, third and fourth stage compounds all exhibit black color. _All of the ternary graphite intercalation compounds according _to the invention with the formula _C Even if it is X
No change is seen in the line diffraction pattern. Table 1 shows the results of elemental analysis and X-ray diffraction of some examples of the ternary graphite intercalation compound of the present invention represented by the formula C _x F (MgF ₂ ) _y .

[Table] Figure 1 shows C ₉ F (MgF ₂ ) _0.08 and C ₅ F (MgF ₂ ) _0.1.
The X-ray diffraction pattern of ₀ (Cu-K) is shown in contrast to that of fluorinated graphite consisting of 71% by weight of (C ₂ F) _o and 29% by weight of (CF) _o . When considering the X-ray diffraction pattern of the above-mentioned ternary graphite intercalation compound, broad diffraction lines are sometimes observed. Shown in Figure 1
The periodic distances (I _c ) for two of the compounds represented by C _x F (MgF ₂ ) _y are calculated from the (00l) diffraction line and are 9.37 Å and 9.34 Å, respectively. Figure 2 shows C ₇ F (MgF ₂ ) _0.14 and C ₉ F (MgF ₂ ) _0.08.
The DTA curve (measured in air at a heating rate of 20°C/min) is shown in comparison to that of fluorinated graphite consisting of 59% by weight of (C ₂ F) _o and 41% by weight of (CF) _o . .
For C ₉ F(MgF ₂ ) _0.08 and C ₇ F(MgF ₂ ) _0.14 , respectively, a broad exothermic peak first starts around 90° C., as shown in FIG. Also at these points a weight loss is observed by thermogravimetry. In FIG. 2, a peak derived from the oxidation reaction of residual graphite is observed around 830°C. For graphite fluoride, there are two temperatures: 573℃ and 697℃.
Exothermic peaks are observed at points, which correspond to the decomposition of fluorinated graphite and the oxidation reaction of residual graphite, respectively. ESCA is one of the most useful means to obtain valuable information about the chemical bonds between host graphite and interloping substances. Figure 3 shows the first stage compound [C ₇ F
(MgF ₂ ) _0.14 and C ₅ F (MgF ₂ ) _0.10 ] and C _x F (MgF ₂ ) _y
The ESCA spectrum of the second stage compound of
It is shown in comparison with that of fluorinated graphite consisting of 59% by weight of (C ₂ F) _o and 41% by weight of (CF) _o . For the first stage compounds, the 1s peak of contamination carbon is observed at 284 eV, whereas
A strong peak is observed at 289eV. The position of this peak is almost the same as that of fluorinated graphite, and this is because the chemical interaction between the penetrating fluorine and carbon atoms of graphite is similar to that of fluorinated graphite, which has a covalent bond between carbon and fluorine. This indicates that the In addition to the peaks mentioned above, for the first stage compound, a strong peak originating from the C--C covalent bond is observed at 284 eV. This means that there are many carbon atoms that have no interaction with fluorine. For the second stage compound, a peak derived from the C--C bond is observed at 284 eV, and a broad shoulder is observed in the range from 286 eV to 291 eV. In ESCA considerations, the kinetic energy of photoelectrons emitted from the inner shell of each atom is measured. Since the mean free path of photoelectrons in a solid is on the order of several tens of angstroms at most, only a few graphite layers can be analyzed in graphite intercalation compounds. Afterwards,
Chemical bonds near the surface of a compound appear strongly in the ESCA spectrum. A comparison of the peak intensities of the analyzed chemical compositions reveals that a small amount of graphite fluoride is produced near the surface of the first stage compound. Regarding the formation of the three-component graphite intercalation compound represented by the formula C _x F (MgF ₂ ) _y , the following may be considered. The gaseous species (MgF ₂ ) _n ′·(F ₂ ) _o ′ is first generated by the reaction between MgF ₂ and fluorine expressed by the following equation. m′MgF ₂ +n′F ₂ (MgF ₂ ) _n ′・(F ₂ ) _o ′ The above gaseous species then penetrate the graphite. As the temperature increases, the chemical equilibrium shifts to the left, and gaseous complexes decompose at high temperatures. Special application No. 56-157807
As described in the specification, when AlF ₃ is used as the intercalating substance and a graphite intercalation compound having the formula C _x F (AlF ₃ ) _y is produced, the gaseous species (AlF ₃ )
_n .(F ₂ ) _o is first produced by the reaction of AlF ₃ with fluorine, represented by the formula mAlF ₃ +nF ₂ (AlF ₃ ) _n .(F ₂ ) _o . From the experimental results, (MgF ₂ ) _n
′·(F ₂ ) _o ′ is found to have higher stability and vapor pressure over a wide temperature range than (AlF ₃ ) _n ·(F ₂ ) _o . In addition, the size of (MgF ₂ ) _n ′·(F ₂ ) _o ′ is considered to be smaller than (AlF ₃ ) _n ·(F ₂ ) _o . Because the periodic distance of C _x F (MgF ₂ ) _y is C _x F
This is because it is smaller by about 0.1 Å compared to that of (AlF ₃ ) _y . Furthermore, aluminum halides tend to form dimers in the gas phase. because of these reasons,
It is believed that MgF ₂ and F ₂ can penetrate graphite more easily than AlF ₃ and F ₂ . As mentioned above, even if the ternary graphite intercalation compound according to the present invention is left in the air for several weeks and then analyzed by X-ray diffraction, the X-ray diffraction result is almost the same as that obtained when it was not left in the air. A pattern is obtained. The ternary graphite intercalation compound according to the present invention is stable against moisture, unlike conventional fluoride-graphite intercalation compounds which decompose immediately when left in air. Next, a of the ternary graphite intercalation compound according to the present invention.
The electrical conductivity in the axial direction (direction parallel to the graphite layer) will be explained. Generally, those skilled in the art will understand that the second
that there is virtually no difference in conductivity between the stage compound and the third stage compound;
It is known that the conductivity of stage and third stage compounds is superior to that of other stage compounds [D. Billand, A. Herold, and F. Fogel, Synthetic Metals No. 3 (1981 ), pp. 279-288 (D. Billand, A.
He〓rold and F.Vogel, SYNTHETIC
METALS, 3 (1981) 279-288). Pyrotics Graphite (manufactured by Nippon Carbon Co., Ltd.) and C ₃₈ F (MgF ₂ ) _0.03 (1st stage and 2nd stage)
The specific resistance in the a-axis direction of the mixed stage compound) is determined by Materials Science and
Engineering, No. 31 (1977), pp. 255-259 [Materials Science and Engineering, 31
(1977) 255-259] by the four-point DC-Bridge method. The results are shown in Table 2. Table 2 Compound Specification Low Resistance (25℃), (Ω・cm) Pyrotake Carbon 3.5×10 ^-5 C ₃₈ F (MgF ₂ ) _0.03 2×10 ^-6 As is clear from Table 2, C ₃₈ F( _MgF2 ) _0.03
The specific resistance of the material is one order of magnitude lower than that of the raw material, pyrotechnic carbon. The ternary graphite intercalation compound according to the invention is not only stable against moisture but also has high electrical conductivity. The ternary graphite intercalation compound according to the present invention can be used as a conductive material by wrapping it in copper foil or incorporating it into epoxy or the like. The ternary graphite intercalation compound according to the present invention is not only useful as a conductive material, but also can be used as a catalyst in various organic reactions. Next, examples of the present invention will be described, but the scope of the present invention is not limited to the examples. Example 1 Flaky natural graphite from Madagascar (297~
840 μm) and 0.6 g of powdered MgF ₂ were mixed.
Place in a prepared reaction tube and evacuate. Fluorine gas was introduced into this at a temperature of 25℃ to create a pressure of 1 atm, and after leaving it for 30 minutes.
The temperature was raised to 300°C at a rate of 4°C/min, and the reaction was allowed to proceed for 45 hours. The reaction tube was then cooled to 25°C. Fluorine gas was replaced with nitrogen. After the reaction was completed, the product and unreacted MgF ₂ were separated using a 297 μm sieve to obtain a black graphite intercalation compound C ₇ F (MgF ₂ ) _0.10 . Example 2 Flaky natural graphite from Madagascar (297~
840 μm) and 0.6 g of powdered MgF ₂ were mixed.
Place in a prepared reaction tube and evacuate. Fluorine gas was introduced into this at a temperature of 25°C to create a pressure of 1 atmosphere, and the temperature was increased to 320°C.
The temperature was raised at a heating rate of °C/min, and the reaction was carried out for 58 hours.
The reaction tube was then cooled to 25°C. Fluorine gas was replaced with nitrogen. After the reaction is complete, the product and unreacted
MgF ₂ was separated using a 297 μm sieve to obtain a black graphite intercalation compound C ₉ F (MgF ₂ ) _0.08 . Example 3 42.9 mg of pyrolytic graphite (manufactured by Nippon Carbon Co., Ltd., thickness in the C-axis direction 0.671 mm, width 4.445 mm, and length 5.012 mm) and 100 g of powdered MgF ₂ were mixed,
Place in a Ni reaction tube and evacuate. This has a temperature of 25
Fluorine gas was introduced at 0.degree. C. to create a pressure of 1 atm, and the reaction system was allowed to react at that temperature for 8 days. Fluorine gas was replaced with nitrogen. After the reaction is complete, the product and unreacted
MgF ₂ was separated using a sieve to obtain a black graphite intercalation compound C ₁₁ F (MgF ₂ ) _0.05 . The specific resistance of the product was 4×10 ^-6 Ω·cm, while the specific resistance of the raw material pyrolytic carbon was 3.5×10 ⁻⁵ Ω·cm. The product was from the first stage. Example 4 51.0 mg of pyrolytic graphite (manufactured by Nippon Carbon Co., Ltd., thickness in the C-axis direction 0.928 mm, width 4.457 mm, and length 5.125 mm) and 100 g of powdered MgF ₂ were mixed,
Place in a Ni reaction tube and evacuate. The reaction system was heated to 232°C at a heating rate of 4°C/min, and at that temperature fluorine gas was introduced to bring the pressure to 1 atmosphere. The reaction system was allowed to react at that temperature for 8 days. Fluorine gas was replaced with nitrogen. After the reaction is complete, the product and unreacted
MgF ₂ was separated using a sieve to obtain a black graphite intercalation compound C ₃₈ F (MgF ₂ ) _0.03 . The specific resistance of the product was 2×10 ^-6 Ω·cm, while that of the raw material pyrolytic carbon was 3.5×10 ⁻⁵ Ω·cm. The product was of a mixed stage of the first stage and the second stage. Example 5 66.7 mg of pyrolytic graphite (manufactured by Nippon Carbon Co., Ltd., thickness in the C-axis direction 0.950 mm, width 5.081 mm, and length 5.237 mm) and 100 g of powdered MgF ₂ were mixed,
Place in a Ni reaction tube and evacuate. This has a temperature of 25
Fluorine gas was introduced at 0.degree. C. to create a pressure of 1 atmosphere, and the reaction system was allowed to react at that temperature for 2 days. Fluorine gas was replaced with nitrogen. After the reaction is complete, the product and unreacted
MgF ₂ was separated using a sieve to obtain a black graphite intercalation compound C ₃₀ F (MgF ₂ ) _0.19 . The specific resistance of the product was 2×10 ^-6 Ω·cm, while that of the raw material pyrolytic carbon was 3.5×10 ⁻⁵ Ω·cm. The products are first stage, second stage, third stage
It was a mixed stage of stage and fourth stage. Example 6 Mix 80.4 mg of pyrolytic graphite (manufactured by Nippon Carbon Co., Ltd., thickness in the C-axis direction 0.950 mm, width 5.427 mm, and length 6.175 mm) and 100 g of powdered MgF ₂ .
Place in a Ni reaction tube and evacuate. This has a temperature of 25
Fluorine gas was introduced at a temperature of 1 atm, and the reaction system was allowed to react at that temperature for 2 days. Fluorine gas was replaced with nitrogen. After the reaction is complete, the product and unreacted
MgF ₂ was separated using a sieve to obtain a black graphite intercalation compound C ₃₂ F (MgF ₂ ) _0.17 . The specific resistance of the product was 9×10 ^-7 Ω·cm, while the specific resistance of the raw material pyrolytic carbon was 3.5×10 ^-5 Ω·cm. The products are 1st stage, 2nd stage, 3rd stage
It was a mixed stage of stage and fourth stage. By the way, the ESCA study described here was conducted using the Mg-K line using a DuPont 650B electron spectrometer. Regarding DTA, α in the air
_-Al2O3 was used as _a control. Analysis of Al was performed by atomic absorption method. From the above examples, it is clear that the present invention has the formula C _x F(MgF ₂ ) _y
It is clear that the present invention provides a novel graphite intercalation compound having excellent properties and a method for producing the same. The features and benefits of the present invention are also apparent from the extensive experimental data set forth in the foregoing detailed description.

[Brief explanation of drawings]

FIG. 1 shows examples of ternary graphite intercalation compounds according to the present invention, C ₉ F (MgF ₂ ) _0.08 and C ₅ F (MgF ₂ ) _0.10.
The X-ray diffraction pattern of fluorinated graphite is shown in comparison with that of graphite fluoride. Figure 2 shows other examples of ternary graphite intercalation compounds according to the present invention, C ₇ F (MgF ₂ ) _0.14 and C ₉ F.
The DTA curve of (MgF ₂ ) _0.08 is shown in comparison with that of graphite fluoride. FIG. 3 shows the first stage and second stage of the present invention, each containing MgF ₂ as the metal fluoride.
The ESCA spectrum of the stage compound is shown in comparison with that of graphite fluoride.

Claims (1)

[Claims] 1. A ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine represented by the formula C _x F (MgF ₂ ) _y . 2. The ternary graphite intercalation compound according to claim 1, wherein x is about 3 to 100 and y is about 0.0001 to 0.20. 3. The ternary graphite intercalation compound is a mixed stage compound consisting of at least two types selected from the group consisting of a first stage compound, a second stage compound, a third stage compound and a fourth stage compound. A ternary graphite intercalation compound according to claim 1. 4 A formula C _x F characterized in that raw graphite is brought into contact with MgF ₂ in a fluorine atmosphere at a temperature of 0 to 400°C for at least a period of time to cause the graphite to increase in weight.
(MgF ₂ ) A method for producing a ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine, represented by _y . 5. The method according to claim 4, wherein the weight ratio of raw material graphite to magnesium fluoride is 1:0.4 to 1:10. 6. The method according to claim 4, wherein the temperature is 15 to 350°C. 7. The method according to claim 4, wherein the fluorine pressure of the fluorine atmosphere is 0.5 to 10 atm. 8 A conductive material made of a ternary graphite intercalation compound of graphite, magnesium fluoride, and fluorine represented by the formula C _x F (MgF ₂ ) _y .