JPH03150216A - Production of graphite - Google Patents

Abstract

PURPOSE:To obtain the subject graphite excellent in locking properties and useful for a monochromater, a filter, etc., for X ray or neutron beam by laminating plural sheets of polymer film having a specified surface roughness and applying heat and pressure thereto. CONSTITUTION:Plural sheets of polymer film having a surface roughness of <=10% of film thickness are laminated and treated with heat and pressure (conventionally at >=4kg/cm<2> and >=2000 deg.C, preferably >=2500 deg.C) to obtain the objective graphite having locking properties corresponding to requirements. As the polymer film, one or more selected from polyamide, polyoxadiazole, polyimide, polybenzothiazole, polybenzobisthiazole, polybenzooxazole, polybenzobisoxazole, poly(pyromellitimide), polyphenylene isophthalamide, polyphenylene benzoimidazole, polyphenylene benzobisimidazole and polythiazole are used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for producing graphite used in, for example, X-ray optical elements, XvA monochromators, neutral ray diffraction mirrors, neutron ray filters, etc. be.

Conventional technology Graphite has outstanding heat resistance, chemical resistance, and high conductivity, so it occupies an important position as an industrial material and is widely used in electrodes, heating elements, structural materials, etc. . Among these, single crystal graphite is widely used as a monochromator, filter, or spectroscopic crystal for X-rays and neutron beams.

To obtain such single crystal graphite, it is easy to use naturally occurring graphite, but high-quality natural graphite is produced in very limited quantities, and it is difficult to handle in the form of powder or minute blocks. Because of its shape, its uses are limited.

Therefore, it was considered to produce large nigeraphite having properties equivalent to those of the above-mentioned natural single crystal graphite. As general manufacturing methods, the following two manufacturing methods 1.2 are mainly known.

The first production method is to produce graphite by precipitation from a Pe, Ni/C-based melt, decomposition of carbides such as Si, ^1, or cooling of a carbon melt under high temperature and high pressure. . Graphite obtained by this method is called Kinoche graphite, and exhibits physical properties almost equivalent to natural graphite. However, the first production method only yields graphite in the form of minute flakes, and the production process is difficult. It is complicated and expensive (because of this, it is hardly used industrially).

The second production method involves high-temperature decomposition precipitation of hydrocarbon gas in the gas phase and its hot processing. Graphite is obtained by reannealing at 3400°C for a long time while applying pressure. . The graphite obtained in this manner is called highly oriented pyrographite (HOPG), and its properties are almost the same as those of natural graphite. With this second production method, unlike the above-mentioned Kinoche graphite, it is possible to produce graphite of considerably large size. Graphite produced by the second manufacturing method has good rocking property, which is one of the values representing orientation, and is widely used as an optical element for X-rays and neutron beams.

However, this manufacturing method has the problem that the process is complicated and the overgrowth retention is very low, and as a result, the obtained graphite is expensive and is of little practical use.

On the other hand, as a third manufacturing method that eliminates the drawbacks of the above two manufacturing methods and allows graphite to be easily obtained at low cost,
There is a method of heating various organic substances or carbonaceous substances at 3000° C. or higher to graphitize them. However, with this third manufacturing method, it is difficult to obtain graphite with excellent properties almost equivalent to natural graphite or Quiche graphite. For example, the electrical conductivity in the ah-plane direction, which is the most typical physical property of graphite, is I~2.5X for natural graphite and Kinoche graphite
IOS/cm, whereas the graphite produced by the third manufacturing method only has about 1 to 2XlOS/cm.
This indicates that graphitization can only be performed incompletely in the third manufacturing method.

In the case of the third production method, the carbon structure produced by heating coke or Nayacol as a starting material to about 3000°C varies from one relatively close to a graphite structure to one far from it. There are many kinds of things. Among these carbon structures, carbon that can be relatively easily converted into a graphite-like structure by simple heat treatment is called easily graphitizable carbon, and carbon that does not change into a graphite-like structure is called difficult-to-graphitize carbon. The cause of such structural differences is closely related to the graphitization mechanism, and depends on whether structural defects present in the carbon precursor can be easily removed by heat treatment at a higher temperature. Therefore, the microstructure of the carbon precursor plays an important role in graphitization. This third
In the manufacturing method of , because the carbon precursor has many structural defects,
Graphitization does not progress sufficiently.

Furthermore, as a fourth manufacturing method, there is a method of manufacturing graphite by using a polymer material expected to have few structural defects and heat-treating the polymer material. Some research has already been conducted regarding this method. This fourth production method is a method in which a polymer is heat-treated in a vacuum or an inert gas, converted into a carbonaceous material through decomposition and polycondensation reaction, and this carbonaceous material is further graphitized.

In the fourth production method, the present inventors used, for example, aromatic polyamide (PA), polyoxadiazole (POD), aromatic polyimide (PI), polybenzobisthiazole (PBBT) + poly Benzoxazole (PBO), Polybenzobisoxazole (PB
BO), polythiazole (PT), etc. are proposed (JP-A-61-275114, JP-A-61-275115, JP-A-61-275117).
Furthermore, the present inventors have also disclosed a method for obtaining a graphite block by laminating a large number of these polymer films and subjecting them to heat treatment under pressure (Japanese Patent Application No. 1983).
3-235219).

Problems to be Solved by the Invention The method for obtaining graphite from a polymer film described above is a low-cost, simple, and highly practical method. Furthermore, when a large number of polymer films are laminated and subjected to pressure heat treatment, there is an advantage that it is easy to obtain large graphite blocks. However, the obtained graphite has insufficient locking properties. This rocking characteristic is a diffraction intensity white line obtained by rotating the crystal when a monochromatic and parallel X-ray flux is incident, and is obtained by fixing 20 at the angle at which the (00ffi) diffraction line appears and rotating θ. It is measured by This value is expressed in rotation angle (°), and the smaller this value is, the more precisely the ab-b planes are aligned, indicating that it has excellent rocking properties. Graphite with insufficient rocking properties is used as an optical element for X-rays, etc. Difficult to use.Although it varies depending on the application, normally a monochromator for X-rays or neutron beams requires an angle of 1@ or less, and a filter for neutron beams requires an angle of 3 degrees or less.

In view of the above circumstances, it is an object of the present invention to provide a method for easily obtaining graphite with good rocking properties using a polymer film.

Means for Solving the Problems In order to solve the above problems, in the invention according to claim 1.2, a plurality of polymer films having a surface roughness of 10% or less of the film thickness are laminated and subjected to pressure heat treatment. I have to.

Polymer films used in the production method of this invention include polyamide, polyoxadiazole, polyimide,
Aromatic polyamide, aromatic polyimide, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, poly(pyromellitimide), polyphenylene isophthaloamide, polyphenylenebenzimidazole, polyphenylenebenzobisimidazole, polythiazole Among them, one consisting of at least one polymer is used.

To obtain one graphite, usually only one type of polymer film is laminated, but it is also possible to use and laminate multiple types of polymer films at the same time.
A sheet of polymer film may be formed using a combination of multiple types of polymers.

In addition, in this invention, the surface roughness is determined by l of the film thickness.
The film thickness when the thickness is 0% or less refers to the total thickness including the rough surface portion.

Usually, they are laminated and heat treated at about 1000° C. to make them carbonaceous in advance, and then pressurized heat treatment is performed.

The rougher the surface, the higher the pressure required during the pressure heat treatment, but the pressure is usually 4 kg/d or more.

The heat treatment temperature during pressure heat treatment varies depending on the thickness of the raw material film, etc., but is usually 2000°C or higher, preferably 2000°C or higher.
The temperature is 500°C or higher.

By appropriately selecting lamination and heat treatment conditions depending on the thickness and surface roughness of the raw material polymer film, graphite with rocking properties that meet requirements can be obtained.

It goes without saying that the method for producing graphite of the present invention is not limited to the compounds and materials exemplified above, but may also use equivalent compounds and materials.

Function: In the method for producing graphite according to the present invention, the surface roughness of the polymer film used is 10% of the film thickness.
Since it is as follows, the obtained graphite has excellent locking properties. For example, block-shaped graphite is
It can be used in monochromators, filters, etc. for radiation and neutron beams.

Examples Next, more specific examples of the present invention will be described below.

In order to evaluate the characteristics of the obtained graphite, the lattice constant, graphitization rate, and rocking properties were measured, and the measurement method was as follows.

(1) Lattice constant (C,) Rotaflex RU-2008 xwA manufactured by Rigaku Denki Co., Ltd.
Using a diffractometer, the XvA diffraction line of the graphite sample was measured using CuKa radiation.

C, appears around 2θ=26~27′″ (002)
From the diffraction line, Bragg's equation nλ-2dsinθ (where 2d
=C,). Here, n=1, λ is xm
wavelength.

(2) Graphitization rate The graphitization rate was calculated using the following formula from the value of the interplanar spacing d determined from the (002) diffraction line.

do. == =3.345g+3-44(1g) where g indicates the degree of graphitization, g=1 is complete graphite, g=0
indicates amorphous carbon.

(3) Rocking properties of graphite (002) using a Rotaflex RU-2008 X-ray diffractometer manufactured by Rigaku Denki Co., Ltd.
The rocking characteristics at the peak position of the line were measured. This rocking characteristic is a diffraction intensity curve obtained by rotating the crystal when a monochromatic parallel xvA flux is incident, and is
0041) Fixing 20 at the angle at which the diffraction line appears, θ
It is measured by rotating. The half-width of the intensity curve thus obtained was defined as the rocking characteristic.

Example 1 20 aromatic polyamide films with a thickness of 10 μm and a surface roughness of 0-0111 m were laminated and
The carbonaceous material obtained was heated at a rate of 1000℃ and heat treated at 1000℃ for 1 hour to obtain a carbon award.
The temperature was raised at a rate of 0°C, heat treatment was performed at 3000°C for 1 hour, and then the temperature was lowered at a rate of 20°C per minute to obtain graphite.

Example 2 Graphite was obtained in the same manner as in Example 1, except that the surface roughness of the aromatic polyamide film was 11 um.

Example 3 Graphite was obtained in the same manner as in Example 1, except that the surface roughness of the aromatic polyamide film was 1.0 μm.

Example 4 50 sheets of aromatic polyimide films with a thickness of 255 m and a surface roughness of 0.01 μm were laminated, and the film was heated at 20 inches per minute in a nitrogen atmosphere.
The temperature was raised at a rate of C, and heat treatment was performed at 1000°C for 1 hour.
Carbonaceous material was obtained. The temperature of the obtained carbonaceous material was raised from room temperature at a rate of lOC/min in an argon stream, and when the temperature reached 3000°C, a pressure of 50 kg/a1 was applied. After heat treatment for 1 hour, The temperature was lowered at a rate of C to obtain graphite.

Example 5 Graphite was obtained in the same manner as in Example 4, except that the surface roughness of the aromatic polyimide film was 0.1 pm.

Example 6 Graphite was obtained in the same manner as in Example N4, except that the surface roughness of the aromatic polyimide film was 2.0 μm.

Example 7 POD film 1 with a thickness of 50 μm and a surface roughness of 15 μm
00 sheets were laminated, the temperature was raised at a rate of 20° C. per minute in a nitrogen atmosphere, and heat treatment was performed at 1000° C. for 1 hour to obtain carbonaceous material.

The obtained carbonaceous material was heated at 1 minute per minute from room temperature in an argon stream.
The temperature is raised at a rate of 0°C, and when it reaches 3000°C, the temperature is 100°C.
After applying a pressure of 111 kg/c and heat treatment for 1 hour,
The temperature was lowered at a rate of 20°C per minute to obtain graphite.

Example 8 Graphite was obtained in the same manner as in Example 7, except that the POD film was a PA (aromatic polyamide) film.

Example 9 Graphite was obtained in the same manner as in Example 7, except that the POD film was a PI film (aromatic polyamide).

Example 10 Graphite was obtained in the same manner as in Example 7, except that the POD film was a PBBT film.

Example 11 Example 7 except that the POD film is a PBO film
Graphite was obtained in the same manner.

Example 12 Graphite was obtained in the same manner as in Example 7 except that the POD film was a PBBO film.

Example 13 A graphite was obtained in the same manner as in Example 7 except that the POD film was a PT film.

Example 14 POD film 4A with a thickness of 50 #m and a surface roughness of 0.1 #m
A carbon prize was obtained in the same manner as in Example 1 by laminating 20 sheets of TM. The obtained carbonaceous material was heated to 50 kg/kg in an argon stream.
A heat treatment was performed at 3000° C. while maintaining a pressure of d to obtain graphite.

Example 15 Graphite was obtained in the same manner as in Example 14, except that the surface roughness of the POD film was 0.5 tt m.

Example 16 Graphite was obtained in the same manner as in Example 14, except that the surface roughness of the POD film was 5 μm.

Comparative Example 1 Graphite was obtained in the same manner as in Example 1, except that the surface roughness of the aromatic polyamide film was 25 m.

Comparative Example 2 Graphite was obtained in the same manner as in Example N4, except that the surface roughness of the aromatic polyimide film was 5 μm.

Comparative Example 3 The surface roughness of POD film was 10. Graphite was obtained in the same manner as in Example 14, except that um was used.

The lattice constants, graphitization rates, and rocking properties of Examples and Comparative Examples are shown in Table 1, respectively.

The graphite of each example below has good locking properties. Example 1 and Comparative Example 11 Example 4 and Comparative Example 2,
Comparing Example 14 and Comparative Example 3, it is clear that the rocking properties are sufficient when the film surface roughness is 10% or less of the film thickness.

Effects of the Invention As stated above, in the method for producing graphite according to the present invention, the film surface roughness is 10% of the film thickness.
% or less of polymer film,
Graphite with excellent rocking properties is obtained.

Claims (2)

[Claims] (1) A method for producing graphite in which a plurality of polymer films having a surface roughness of 10% or less of the film thickness are laminated and subjected to pressure heat treatment. (2) The polymer film is polyamide, polyoxadiazole, polyimide, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, poly(pyromellitimide), polyphenylene inphthalamide, polyphenylene benzimidazole 2. The method for producing graphite according to claim 1, comprising at least one of polyphenylenebenzobisimidazole, polythiazole, and polythiazole.