JPH0597418A - Production of highly oriented graphite - Google Patents

Abstract

PURPOSE:To produce highly oriented graphite by improving conditions in treatment at a high temp. at the time of producing graphite. CONSTITUTION:Plural polymer films or plural carbonaceous films obtd. from polymer films are laminated, set in an electric furnace, heated from room temp. to >=2,600 deg.C and treated under pressure in a temp. range of >=2,600 deg.C. After cooling to a temp. range of <=1,500 deg.C, the films are treated under no pressure in a temp. range above that of the initial treatment under pressure. After cooling to a temp. range of <=1,500 deg.C again, the films are heated to a temp. range above that of the initial treatment under pressure and treatment under pressure is carried out to obtain objective highly oriented graphite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing highly oriented graphite which can be used as a radiation optical element such as an X-ray monochromator, a neutron beam monochromator, a neutron beam filter and the like.

[0002]

2. Description of the Related Art In recent years, highly oriented graphite has excellent spectral and reflection characteristics with respect to X-rays and neutron rays.
Monochrome meters or filters for X-rays and neutrons
Etc. are used as radiation optical elements. Natural graphite is the most suitable as highly oriented graphite for this purpose, but high-quality natural graphite has such problems that the production amount is very limited, and that it is powdery or scaly and difficult to handle. Therefore, as an alternative to this, artificial production of graphite has been carried out, and this artificial graphite has begun to be used.

Conventionally, as a method for producing artificial graphite, there is a method by high-temperature decomposition and deposition of hydrocarbon gas in a gas phase and hot working thereof, which is 3400 while applying pressure.
It is manufactured by a process of re-annealing for a long time at around ℃. The graphite produced in this manner is called highly oriented graphite (HOPG) and has excellent properties comparable to natural single crystal graphite. However, this method has a problem that the manufacturing process is extremely complicated and the yield is extremely low, and as a result, HOPG becomes extremely expensive and is not suitable for practical use.

Therefore, as a method for producing graphite that can solve such problems, a method has been developed in which a high-quality graphite is produced easily and at low cost by firing a polymer film at a high temperature. It has been considered that a polymer compound generally belongs to a difficult graphite material and is not converted into good quality graphite even when heated at a high temperature of 3000 ° C. However, as a result of recent research, it has been found that some of the high molecular compounds can be converted into good quality graphite by appropriate heat treatment.

Examples of the polymer compound which can be converted into good quality graphite include polyoxadiazol, aromatic polyimide, aromatic polyamide, polybenzobisthiazole, polybenzoxazol, polythiazole, and the like. And polyparaphenylene vinylene.

A plurality of polymer films or a plurality of carbonaceous films obtained from the polymer films are laminated with these polymers, and pressure treatment is performed at a temperature range of 2600 ° C. or higher to obtain a graphite block. Methods are known (JP-A-63-235218, JP-A-63-2).
35219 gazette).

[0007]

However, it has been found that the above-mentioned conventional method for producing graphite does not provide a completely satisfactory one. It is not possible to obtain highly oriented block-shaped graphite simply by laminating a plurality of films and pressurizing them in a high temperature range. In order to be an excellent block-shaped highly oriented graphite, the inside of each graphitized layer is in a state where crystals in which carbon atoms are regularly arranged in a predetermined manner are properly oriented (highly oriented state). The layers must be firmly adhered to form a block. Simply by applying pressure at a high temperature and heat-treating, wrinkles and internal strain can be generated in the film, and the growth of crystallites can be hindered depending on the degree of pressure applied, making it difficult to form highly oriented graphite. There was a problem that it would end up.

The present invention is to solve the above-mentioned conventional problems. After the pressure treatment in the high temperature region, the pressureless treatment is performed, and the pressure treatment is performed again to obtain highly oriented graphite. The purpose is to provide a method.

[0009]

In order to achieve the above object, a method for producing highly oriented graphite according to the present invention comprises a plurality of polymer films or a plurality of carbonaceous films obtained from the polymer films laminated together. After performing pressure treatment in the temperature range of 2600 ° C or higher, once lowering the temperature range to 1500 ° C or lower, performing pressureless heat treatment again in the temperature range of the initial pressure treatment or higher, and then again 1500 ° C. It can be easily achieved by lowering the temperature to the following temperature range, raising the temperature again to the initial pressure treatment temperature range or higher, and performing the pressure treatment.

Further, as the polymer film for starting material in the present invention, as described in claim 2, polyoxadiazol, aromatic polyimide, aromatic polyamide, polybenzobisthiazole, polybenzoxazole. Examples thereof include a film made of at least one of zole, polythiazole, and polyparaphenylene vinylene, but not limited to this, any polymer film that can be converted into good quality graphite by heat treatment at high temperature may be used. It goes without saying that it can be used as a raw material film. The thickness of the film is preferably 400 μm or less. This is because if the thickness is 400 μm or more, the internal structure of the film is destroyed due to the gas generated inside the film, and high orientation becomes difficult.

[0011]

By this method, pressure treatment is performed in the temperature range where there is almost no change in the film size to suppress the generation of wrinkles and internal structural strains. With this pressure treatment, wrinkles and internal strains are completely removed. It is difficult to do, and it also hinders the growth of crystallites depending on the condition of pressure, so after pressure treatment, heat treatment is performed under no pressure to completely remove internal strain and further promote crystallite growth. By carrying out the pressure treatment again, highly oriented ones can be obtained. Since the present invention can be carried out by controlling the temperature and pressure in the firing step, it can be carried out extremely easily without any difficulty.

[0012]

EXAMPLES Examples of the present invention will be described below.

First, the case where the polymer film is a polyimide film will be described as an example with reference to the drawings.

As a starting material, a polyimide film (D
The product name, Kapton thickness 25 μm, manufactured by Upon Co. was used. FIG. 1 shows the expansion and contraction of the surface area of this polyimide film as the heat treatment temperature rises, and the graphitization rate (by measurement using X-ray diffraction) as the heat treatment temperature rises.

As shown in the film dimension curve A of FIG. 1, this polyimide film only slightly expands at 450 to 500 ° C., but sharply shrinks in the polymer decomposition temperature range of 500 to 700 ° C. Is about 75% of the length. And, the temperature above this polymer decomposition temperature is 2000 ℃
In the meantime, the film does not expand or contract, and dimensional change hardly occurs. However, at 2000-2600 ° C., the film reversely stretches back to 90% of its original size. The elongation of the film in this temperature region is closely linked to the progress of graphitization, and as seen in the graphitization rate curve B of FIG. 1, the graphitization rate sharply increases as the film stretches. Thus, the film size changes in the temperature range of 2600 ° C. or lower. On the other hand, 26
In the temperature range of 00 ° C. or higher, as can be seen in FIG. 1, the film size hardly changes.

A film which exhibits the above-mentioned dimensional changes with respect to temperature changes is subjected to heat treatment as follows.

First, in the temperature range where the dimensional change is large due to thermal decomposition to the temperature range where the dimensional change is large along with the progress of graphitization (from 0 ° C. to 2600 ° C.), substantially pressureless treatment is performed, and the next graphitization is almost completed. In addition, pressure treatment of 200 kg / cm ² is performed in a temperature range of 2600 ° C. or higher where there is almost no dimensional change.

After that, the temperature is once lowered to 1500 ° C. or lower. When lowering the temperature, it is desirable to maintain the pressure applied up to at least 1500 ° C., and the temperature may be lowered to room temperature. After the temperature is lowered, the temperature is raised again to 2600 ° C. It is desirable to raise the temperature again to a temperature higher than the previous processing temperature. After the temperature is raised, heat treatment is performed in a pressureless state to promote distortion of the internal structure and growth of crystallites.
After this, the temperature is lowered again to 1500 ° C and then to 2600 again.
The temperature is raised to ℃ or higher and the same pressure treatment as in the initial stage is performed.

The above is not limited to the polyimide film, of course, and is generally applicable to all polymer films which can be converted into excellent graphite by heat treatment.

(Example 1) Length 7 cm, width 7 cm, thickness 5
0 μm polyoxadiazol (POD) film 10
0 sheets were piled up and set on a jig made of graphite, and fired in a hot press electric furnace as follows.

First, in an argon gas atmosphere, 10 ° C./m
The temperature was raised to 2600 ° C. at a rate of in. During this time, only 100 g / cm ² of the jig weight was applied to the film. 200kg / after the temperature reaches 2600 ℃
A pressure of cm ² was applied, and the pressure was maintained as it was for 4 hours while maintaining the pressure of 200 kg / cm ² . Then, the temperature was lowered to 1500 ° C with pressure applied, the pressure was released during the holding time of 30 minutes, the temperature was raised again to 2800 ° C at a rate of 10 ° C / min, and then 1 hour under no pressure. After heat treatment, the temperature is lowered to 1500 ° C. again and kept for 30 minutes.
It was maintained for 4 hours while applying a pressure of 0 kg / cm ² , to obtain highly oriented block-shaped graphite.

(Example 2) Length 7 cm, width 7 cm, thickness 2
100 pieces of 5 μm aromatic polyimide (PI) films were stacked and set on a jig made of graphite, and baked in a hot press electric furnace as follows.

First, in an argon gas atmosphere, 10 ° C./m
The temperature was raised to 2700 ° C. at a rate of in. During this time, only 100 g / cm ² of the jig weight was applied to the film. 200kg / after the temperature reaches 2700 ℃
A pressure of cm ² was applied, and the pressure was maintained as it was for 4 hours while maintaining the pressure of 200 kg / cm ² . Then, the temperature was lowered to 1500 ° C with pressure applied, the pressure was released during the holding time of 30 minutes, the temperature was raised again to 2900 ° C at a rate of 10 ° C / min, and then 1 hour under no pressure. After heat treatment, the temperature is lowered to 1500 ° C. again and kept for 30 minutes.
While maintaining a pressure of 0 kg / cm ² for 4 hours, block-shaped graphite was obtained.

(Example 3) Length 7 cm, width 7 cm, thickness 2
100 sheets of 5 μm aromatic polyamide (PA) films were stacked, set on a jig made of graphite, and baked in a hot press electric furnace as follows.

First, in an argon gas atmosphere, 10 ° C./m
The temperature was raised to 2800 ° C. at a rate of in. During this time, only 100 g / cm ² of the jig weight was applied to the film. 300kg / after the temperature reaches 2800 ℃
A pressure of cm ² was applied, and the pressure was maintained as it was for 4 hours while maintaining the pressure of 200 kg / cm ² . Then, the pressure was released to 1500 ° C, the pressure was released, the temperature was raised to room temperature, the temperature was raised again to 3000 ° C at a rate of 10 ° C / min, and heat treatment was performed for 1 hour under no pressure. After the temperature was lowered to room temperature again, the temperature was raised to 2800 ° C. at 10 ° C./min and held for 4 hours while applying a pressure of 300 kg / cm ^{2 in} the same manner as in the initial treatment to obtain a block-shaped graphite.

Example 4 A block-like graphite was obtained in the same manner as in Example 3 except that a polybenzobisthiazole (PBBT) film was used instead of the PA film.

Example 5 A block graphite was obtained in the same manner as in Example 3 except that a polybenzoxazole (PBO) film was used instead of the PA film.

(Example 6) Block graphite was obtained in the same manner as in Example 3 except that a polythiazole (PT) film was used instead of the PA film.

Example 7 A block graphite was obtained in the same manner as in Example 3 except that a polyparaphenylene vinylene (PPV) film was used instead of the PA film.

The block-shaped graphites obtained in Examples 1 to 7 had a smooth surface with almost no wrinkles.

The locking characteristics according to this embodiment and the conventional locking characteristics are shown in (Table 1). Each rocking characteristic was measured by using a rotor flex RU-200B type X-ray diffractometer manufactured by Rigaku Denki Co., Ltd. Graphite (00
2) The half value width of the diffraction line obtained as a result of the measurement of the rocking characteristic at the peak position of the diffraction line was evaluated.

[0032]

[Table 1]

As is clear from (Table 1), all of the methods for producing highly oriented graphite according to the present embodiment have excellent rocking characteristics as compared with the conventional methods, and the X-ray and core wire monochromatic images are obtained. It turns out that it is most suitable for data.

[0034]

As described above, according to the present invention, a plurality of carbonaceous films obtained from a polymer film are laminated and heated,
After performing the pressure treatment, the temperature is once lowered, and the pressureless heat treatment is again performed in the temperature range higher than the initial pressure treatment, and then the temperature is lowered again and the temperature is raised again to perform the pressure treatment and graphitize. It is possible to easily obtain an excellent highly oriented graphite without wrinkles or internal strain. Further, the polymer film of claim 2 is very suitable for the production method of the present invention, and easily obtains highly oriented graphite.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing temperature-film size and temperature-graphitization rate of a film when baking a polyimide film.

[Explanation of symbols]

 A Film size curve B Graphitization rate curve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mutsumi Murakami 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (2)

[Claims] 1. A plurality of polymer films, or a plurality of carbonaceous films obtained from the polymer films are laminated and subjected to a pressure treatment in a temperature range of 2600 ° C. or higher, and then once heated to 1500 ° C. or lower. After the temperature is lowered to the temperature range, the pressureless heat treatment is performed again in the temperature range above the initial pressurization process, and then 15 times again.
A method for producing highly oriented graphite, characterized in that the temperature is lowered to a temperature range of 00 ° C. or lower, the temperature is raised again to an initial pressure treatment temperature range or higher, and pressure treatment is performed to graphitize. 2. The polymer film is polyoxadiazo-
A highly-oriented graphite according to claim 1, which comprises at least one of the following: a polyimide, an aromatic polyimide, an aromatic polyamide, a polybenzobisthiazole, a polybenzoxazole, a polythiazole, and a polyparaphenylene vinylene. Production method.