JP2014048175A - Graphite analysis sample and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a graphite sample suitable for analysis and a method for manufacturing the same.SOLUTION: A method for manufacturing a graphite analysis sample includes: a processing step for obtaining at least one plane on the surface of a porous graphite material; a polishing step for polishing plane using a polishing agent made of carbon-based powder or organic powder after the processing step and then obtaining the polished surface; a cleaning step for cleaning the polished surface using liquid; and a drying step for vaporizing the liquid.

Description

  The present invention relates to a porous graphite analysis sample for analyzing a surface.

  Graphite materials are known to have chemical inertness, high thermal conductivity, and high heat resistance, and are basic materials used in various industrial fields such as chemical plants and industrial furnaces. .

  For such a carbon material, various atomic level observations and material surface analyzes are performed on the surface using a scanning tunneling microscope (STM), a scanning probe microscope, or the like. As an example, Patent Document 1 discloses that a voltage is applied between a probe of a scanning tunneling microscope and a sample to measure a minimum voltage necessary for extracting atoms or atomic groups from the sample surface. A surface analysis method for obtaining the binding energy or sublimation energy of atoms on the surface is described.

  Specifically, HOPG (Highly Oriented Pyrolytic Graphite) is used as a sample, the sample is reacted with water, and a reaction for oxidizing carbon of graphite is caused directly under the STM probe. The graphite is cleaved to give a clean surface before the experiment, and pure water is dropped on the surface. Then, an STM probe is brought close to HOPG until a tunnel current flows, and a threshold voltage Vt at which atoms are removed from the surface is measured.

JP-A-6-347468

  HOPG used in Patent Document 1 is special graphite oriented so that the crystal network plane spreads in the plane direction, and since a uniform smooth surface can be easily obtained, the surface state can be obtained with an AFM (atomic force microscope) or the like. Many analyzes and evaluations have been conducted, and various knowledge has been accumulated.

However, industrially, a porous graphite material is overwhelmingly used rather than HOPG having an orientation close to the theoretical density of 2.25 g / cm ³ of the graphite material. The porous graphite material is an isotropic graphite material, an artificial graphite electrode, or the like obtained by using coke and binder pitch as raw materials, kneading and forming, then firing and graphitizing.

  Such isotropic graphite materials and artificial graphite electrodes are widely used in chemical plant piping, heat exchangers, fluorine gas electrolytic electrodes, electrolytic refining materials, etc., utilizing the chemical stability of graphite. On the other hand, using high heat resistance, it is also used in various fields of industry such as graphite members for single crystal pulling devices, fusion reactor first walls, and electrodes for electric discharge machining.

  From such a background, in order to analyze the realistic microscopic reactivity, consumption, etc. of graphite, it is desired to evaluate not with HOPG close to an ideal graphite crystal but with a porous graphite material.

  An object of the present invention is to provide a porous graphite analysis sample suitable for analysis and a method for producing the same.

  The method for producing a porous graphite analysis sample of the present invention uses a processing step of obtaining at least one plane on the surface of a porous graphite material, and an abrasive comprising a carbon-based powder or an organic powder after the processing step. A polishing step of polishing the flat surface to obtain a polishing surface, a cleaning step of cleaning the polishing surface with a liquid, and a drying step of volatilizing the liquid.

  The polishing step is performed by, for example, a wet method using a liquid.

  The polishing step is performed by a wet method using, for example, water.

  In the cleaning step, for example, the abrasive is left inside the pores of the porous graphite material.

  In the washing step, for example, water is used.

  In the cleaning step, for example, ultrasonic cleaning is not performed, or ultrasonic cleaning is performed with a weak output that does not generate bubbles due to the cavitation effect of ultrasonic cleaning.

  The carbon-based powder is at least one selected from the group consisting of diamond powder, coke powder, graphite powder, anthracite, pyrolytic carbon powder, and glassy carbon.

  A graphite analysis sample obtained by the above method for producing a graphite analysis sample is also included in the present invention.

  The graphite analysis sample of the present invention has at least one plane, the arithmetic average roughness Ra measured on the plane is 0.2 μm or less, and contains at least a carbon-based powder inside the pores exposed on the plane. Further, the pores contain abrasives made of carbon-based powder, abrasives made of organic powder, or carbides of abrasives made of organic powder.

  According to the present invention, a porous graphite material is polished, cleaned and dried using an abrasive made of a carbon-based powder or an organic powder, so that even if the abrasive remains in the pores, the graphite sample There is no effect on the analysis of the above, or it can be reduced. This makes it possible to obtain a porous graphite analysis sample suitable for various analyses.

The figure which shows the analysis result by AFM of the surface of the porous graphite material of Example 2. FIG. The figure which shows the analysis result by the AFM of the surface of the porous graphite material of the comparative example 2. The figure which shows the analysis result by SEM (scanning electron microscope) of the surface of the porous graphite material of Example 1. FIG. The figure which shows the analysis result by SEM of the surface of the porous graphite material of Example 2. FIG. The figure which shows the analysis result by SEM of the surface of the porous graphite material of the comparative example 2. The figure which shows the analysis result by SEM of the same location before and after performing the ion irradiation test on the surface of the porous graphite material of Example 2. FIG.

  HOPG (Highly Oriented Pyrolytic Graphite) is a high-purity graphite crystal in which a hydrocarbon gas is precipitated as carbon by pyrolysis from a gas phase, and is a material that is strongly oriented in one direction. HOPG is provided so that the a-axis direction in which the hexagonal network surface of carbon atoms spreads becomes the surface of the sample. In HOPG, it is known that graphene can be obtained by applying an adhesive tape to the surface of a sample having a hexagonal network surface of carbon atoms spread and peeling it off. By removing the surface layer with the pressure-sensitive adhesive tape in this manner, the newly exposed sample surface can be repeatedly obtained by expanding the hexagonal network surface of carbon atoms.

  On the other hand, in the present invention, it is generally used in the industry and targets a porous graphite material. Porous graphite materials include isotropic graphite materials, artificial graphite electrodes, and the like.

  Isotropic graphite material is pulverized coke powder and binder pitch with heat to knead, pulverize the resulting mass kneaded material again, cold isostatically pressurize the resulting powder, fired Obtained by graphitization. Specifically, IBIDEN Co., Ltd. ET-10, T-5, etc. are mentioned.

  The artificial graphite electrode is obtained by applying heat to kneaded pulverized needle coke powder and a binder, extrusion-molding the resulting kneaded material, firing, and graphitizing. The artificial graphite electrode thus obtained is used, for example, as an electrode for an electric steelmaking furnace.

  The analysis sample of the present invention is made of a porous graphite material. The graphite crystal constituting the porous graphite material is a hexagonal crystal, and the a-axis direction is connected by a strong covalent bond and is connected by a weak van der Waals force in the c-axis direction. For this reason, graphite is a material that is easy to cleave and is widely used for pencil leads, solid lubricants, and the like because of its ease of cleavage.

  Porous graphite materials such as isotropic graphite materials and artificial graphite electrodes are generally used in industry, and are more preferable than materials such as HOPG for industrial use. However, in the porous graphite material sample, it was difficult to obtain a smooth surface like the HOPG sample. This is considered as follows.

The bulk density of the porous graphite material is significantly below the theoretical density was ^{1.6~1.9g / cm 3 (2.25g / cm} 3). This is because it is produced by firing and graphitizing using fine particles as raw materials, and thus has many pores. In addition, graphite has a partially disordered amorphous region in the crystal structure where crystallization does not proceed sufficiently even when the heat treatment temperature is raised, and a hard portion and a soft portion are mixed. Further, the crystalline region has a great difference in hardness depending on the direction. That is, the following factors cause the bulk density of the porous graphite material to be much lower than the theoretical density.

-The porous graphite material is a porous material in which fine particles are bonded.
-The porous graphite material is a mixture of a hard amorphous part and a soft crystalline part.
-The soft crystalline parts that make up the porous graphite material vary greatly in hardness depending on the direction and are easy to cleave.

  The cause of the low bulk density as described above is a cause of difficulty in obtaining a smooth surface at the same time. For this reason, conventionally, it has been difficult to obtain a flat sample of a porous graphite material, and it has been difficult to analyze the plane microscopically such as corrosion resistance and heat resistance. In the present invention, a smooth surface can be obtained in the graphite material by using the following method, and various evaluation tests can be performed.

  That is, this invention is a manufacturing method of a graphite analysis sample, Comprising: The following processes (1)-(4) are included.

(1) A processing step of obtaining at least one plane on the surface of the porous graphite material.
(2) A polishing step of polishing a flat surface using a polishing agent made of carbon-based powder or organic powder after the processing step to obtain a polished surface.
(3) A cleaning step of cleaning the polished surface with a liquid.
(4) A drying step for volatilizing the liquid.

<Processing process>
The method for producing a graphite analysis sample of the present invention has a processing step of obtaining at least one plane prior to the polishing step. Since the polishing agent made of carbon powder or organic powder used in the polishing step has a low processing speed, the surface of the graphite material is first processed to be flat to obtain at least one flat surface.

  Any method may be used to obtain one plane in the processing step. Any method such as cutting with a band saw, cutting with a mill, or polishing with a grindstone may be used. By performing the processing step, the polishing amount in the polishing step can be reduced and the polishing time can be shortened, so that the polishing step can be easily performed. When the processing step is performed by polishing with a grindstone, it is desirable to polish using abrasive grains that are sufficiently larger than the pore diameter of the porous graphite. If the abrasive grains are sufficiently larger than the pore diameter of the porous graphite, it is difficult to remain in the pores of the graphite material, so the material of the abrasive grains is not particularly limited. The grindstone used in the processing step is preferably a grindstone using abrasive grains having a size of # 1000 or more. Since the # 1000 abrasive has a median diameter of 16 μm, it can be made difficult to remain in the pores of the porous graphite. The grindstone used in the processing step is more preferably a grindstone using abrasive grains having a size of # 400 or more. Since the # 400 abrasive has a median diameter of 40 μm, it can be made more difficult to remain in the pores of the porous graphite.

<Polishing process>
In the polishing step, the flat surface obtained in the processing step is polished with an abrasive made of carbon-based powder or organic powder to obtain a polished surface.

  Examples of the carbon powder include diamond powder, coke powder, anthracite, graphite powder, pyrolytic carbon powder, and glassy carbon powder. Since the main component is carbon, other elements are not detected or difficult to detect even when used as an analysis sample, and can be suitably used as a graphite analysis sample. Moreover, since these abrasive | polishing agents consist of carbon, these abrasive | polishing agents do not react with a graphite analysis sample, but can be used suitably as an analysis sample.

  Which abrasive (carbon-based powder) should be selected from these carbon-based powders can be appropriately selected depending on the analysis target.

  When carrying out a surface analysis on the contained elements, the carbon content of the abrasive used is important. A high-purity abrasive is preferably used. For example, graphite powder, coke powder, pyrolytic carbon powder, glassy carbon powder and the like that are heated in a halogen-based gas atmosphere and processed to high purity can be suitably used. By heating in a halogen-based gas atmosphere and performing high-purity treatment, a high-purity carbon-based material powder having an impurity content on the order of ppm can be obtained.

  For example, it is preferable to use a coke powder having a hexagonal mesh surface connected with a six-membered ring, anthracite, graphite powder, pyrolytic carbon powder, or glassy carbon as the abrasive, as with the porous graphite material. In these carbon-based material powders, the valence electrons of carbon atoms take SP2 hybrid orbits like graphite, so that the measured value of the graphite analysis sample is hardly affected.

  In order to reduce the influence of the diamond powder remaining in the pores of the graphite analysis sample on the measurement when diamond powder in which valence electrons of carbon atoms have SP3 hybrid orbitals is used as the abrasive made of carbon powder. After polishing, heating is performed to change the cubic crystal to a stable hexagonal crystal so that the valence electrons of the carbon atoms take SP3 hybrid orbits, thereby suppressing the influence of the diamond powder of the abrasive.

  The Mohs hardness of graphite is 0.5 to 2.0 and is very soft. Graphite has a hexagonal crystal structure and becomes softer as crystallization progresses. A porous graphite material obtained by processing at a high temperature is one of the softest forms among materials composed of carbon atoms. For this reason, it is not necessary to use diamond powder (Mohs hardness 10) as an abrasive, and various carbon-based powders such as anthracite (Mohs hardness 2.2) and coke powder can be used as an abrasive.

  Next, as an abrasive | polishing agent which consists of organic type powder, a resin-type abrasive | polishing agent, a plant-type abrasive | polishing agent, etc. are mentioned.

  Examples of the resin-based abrasive include polymethyl methacrylate, polycyanomethyl acrylate, polyacrylonitrile, nylon, polycarbonate, urea resin, melamine resin, unsaturated polyester resin, phenol resin, and epoxy resin. These resins are mainly composed of carbon and further contain hydrogen, nitrogen, oxygen and the like. When used as an abrasive for a graphite analysis sample, it can be suitably used except when carbon, nitrogen, oxygen, or the like is an analysis target. When elements such as carbon, nitrogen, and oxygen adversely affect the analysis, the graphite analysis sample may be heated to carbonize or depolymerize the resin-based abrasive. Elements other than carbon can be almost removed by carbonization or depolymerization.

  Since polymethyl methacrylate and polymethyl cyanoacrylate are depolymerized resins, they can be easily removed by heating to 200 to 400 ° C. in air. When the heating temperature is 250 ° C. or higher, depolymerization is promoted and can be removed quickly. If the heating temperature is 400 ° C. or lower, the graphite is difficult to oxidize, and a good surface of the graphite analysis sample can be obtained. In the case of a resin that is not depolymerized, it is preferably carbonized by heating to 700 to 2000 ° C. in a reducing atmosphere, inert atmosphere, or vacuum. When the carbonization temperature is 700 ° C. or higher, the carbonization can be sufficiently advanced, and most of elements such as carbon, nitrogen, and oxygen can be removed. When the carbonization temperature is 2000 ° C. or less, crystallization or sublimation hardly occurs on the surface of the graphite sample due to heat, and the sample surface is less deteriorated.

  As the plant-based abrasive, corn cobs, plant seed shells, and the like can be used. As the seed shell of the plant, walnuts, apricots, quince, etc. can be used. Since the Mohs hardness of the graphite material is about 0.5 to 1.0, if it is a harder abrasive than this, it can be easily polished. For example, corn cobs (Mohs hardness 2.0), walnut husk (Mohs hardness 3.0), apricot husk (Mohs hardness 3.5), peach seeds (Mohs hardness 4.0) etc. are used as abrasives Is possible.

  Since the plant-based abrasive is mainly composed of celluloses, it can be carbonized similarly to the resin-based abrasive. When the plant abrasive is carbonized, hydrogen, oxygen, etc. contained in the abrasive can be volatilized and removed. Carbonization can be performed by heating to 700 to 2000 ° C. in a reducing atmosphere, inert atmosphere, or vacuum. When the carbonization temperature is 700 ° C. or higher, the carbonization can be sufficiently advanced, and most of elements such as carbon, nitrogen, and oxygen can be removed. When the temperature is 2000 ° C. or lower, crystallization or sublimation hardly occurs on the surface of the graphite sample due to heat, and the sample surface hardly deteriorates.

  The median diameter of the abrasive used in the embodiment of the present invention is preferably 0.1 to 10.0 μm. If the median diameter of the abrasive is 0.1 μm or more, it can be efficiently polished because it is difficult to be taken into the pores of graphite. If the median diameter of the abrasive is 10.0 μm or less, it is difficult to damage the surface of the porous graphite analysis sample, so that a graphite analysis sample suitable for surface analysis can be easily obtained. The median diameter of the abrasive can be measured with a laser diffraction particle size analyzer using water as a dispersion medium.

  The polishing step is preferably performed by a wet method using a liquid. According to wet polishing, the graphite fine powder obtained by polishing is dispersed in the liquid and has fluidity, so that it becomes easy to prevent clogging of the graphite fine powder formed by polishing in the pores of graphite. .

  In addition, unlike the ion milling method or the like, wet polishing is difficult to heat during polishing, and thus has an effect that the surface of the graphite analysis sample is not easily altered. The ion milling method is a processing method using a focused ion beam. Although such a method can polish the surface flatly, it is difficult to polish a large area because it is polished while scanning little by little, and it is polished while repelling atoms on the sample surface with high energy, so that the surface is polished. A thin altered layer is formed. With wet polishing, polishing of a large area is easy and polishing can be performed without forming a deteriorated layer on the surface, so that a graphite analysis sample suitable for surface analysis of a porous graphite material can be obtained.

  The wet polishing is preferably performed using water as a medium. When water is used as a medium, the medium is less likely to volatilize and the fine carbon powder clogged in the pores is less likely to be concentrated, so that it can be easily removed. In addition, water can be suitably used at room temperature because the reaction rate with the carbon material is extremely slow to the extent that it has no reactivity and is not observed.

<Washing process>
In the cleaning process, any volatile oil, alcohol, water, ether or the like can be used as a cleaning medium. Among these, water or a water-soluble solvent such as alcohol or ether is preferable. Since water is used as a medium in wet polishing, when water or a water-soluble solvent is used, graphite powder forming a slurry with water can be easily dispersed, and cleaning can be facilitated.

  In the cleaning step, the abrasive is removed by cleaning the obtained polished surface with a liquid. Graphite is porous, and it is difficult to completely remove the abrasive easily in the pores. The cleaning is preferably performed using friction caused by organic fibers or organic foams or a fluid flow along the polishing surface.

  Various organic fibers such as brushes, brushes, cloths, and absorbent cotton can be used, and the organic foam is, for example, a sponge. The cleaning using the flow of fluid may be any method that uses the flow of liquid used for cleaning, such as a jet of liquid, stirring, and collision of bubbles.

  Conventionally, in porous bodies such as graphite, foreign substances in pores such as abrasives have been removed by ultrasonic cleaning after polishing. Since the graphite sample cleaves the surface graphite crystal by ultrasonic cleaning, it is desirable to clean without using ultrasonic waves. Even when ultrasonic cleaning is performed, it is preferable to perform cleaning under weak conditions. Weak cleaning is described below.

  Ultrasonic cleaning is characterized in that cleaning is performed using the cavitation effect of ultrasonic waves. When the liquid is vibrated with ultrasonic waves, a place where the pressure is high and a place where the pressure is low is created locally. In the place where the pressure is low, a cavity (bubble) is formed in the liquid, and a shock wave is generated when the formed cavity breaks. generate. Since the shock wave has an action of removing foreign substances in the pores and washing them, it is used for washing in various fields and is also frequently used for washing porous materials such as graphite materials. The shock wave generated by the ultrasonic cavitation effect cuts the bond due to van der Waals force in the c-axis direction of the graphite crystal, so that the sample surface becomes rough. For this reason, when performing ultrasonic cleaning, it is preferable to perform it on the conditions which do not produce a cavitation effect. When the cavitation effect occurs, a shock wave is generated when the generated bubbles disappear, and the powder clogged inside the pores of the graphite material is knocked out and the surface of the graphite sample is roughened. It is preferable not to do so.

  Bubbles generated by ultrasonic cleaning newly generate fine bubbles that vibrate vigorously when ultrasonic vibration is applied to the liquid. For this reason, if it is the ultrasonic cleaning of the intensity | strength which does not generate the bubble by a cavitation effect, the surface of a favorable graphite analysis sample can be obtained.

<Drying process>
Any method may be used for the drying step. For example, the liquid used for the grinding | polishing and washing | cleaning contained inside can be volatilized from a grinding | polishing surface by putting in a dryer and exposing to 70-300 degreeC.

  In addition, the graphite analysis sample of the present invention has at least one plane, the arithmetic average roughness Ra measured on the plane is 0.2 μm or less, and at least carbon-based powder is contained in the pores exposed on the plane. Further, the pores contain particles of resin-based abrasive or plant-based abrasive or carbide of resin-based abrasive or plant-based abrasive. The arithmetic average roughness can be measured based on JIS B 0601: 2001.

  According to the graphite analysis sample of the present invention, the abrasive particles of the carbon-based material powder are contained inside the pores, and further the abrasive particles made of organic powder or the carbide particles of the abrasive made of organic powder. contains.

  Since these particles have the same main component as the graphite analysis sample to be analyzed, other elements are not detected or difficult to detect even when used as an analysis sample, and therefore can be suitably used as a graphite analysis sample. . Moreover, since these abrasive | polishing agents consist of carbon, these abrasive | polishing agents can be used suitably as an analysis sample, without reacting with a graphite analysis sample.

  Especially when the pores contain abrasive particles of carbon material powder and carbide particles of abrasive powder made of organic powder, the abrasive particles exist as carbon or graphite, so they can be used as analysis samples. Other elements are not detected. Therefore, it can be suitably used as a graphite analysis sample.

  It is desirable that the graphite analysis sample of the present invention has at least one plane, and the arithmetic average roughness Rz measured on the plane is 0.2 μm or less. When the arithmetic average roughness Rz is 0.2 μm or less, the cross section of the graphite sample can be observed regardless of the stacking direction of the graphite particles, so that a graphite analysis sample suitable for the surface analysis of graphite can be obtained. A graphite analysis sample having an arithmetic average roughness Rz of 0.2 μm or less can be obtained by washing so that abrasive particles remain in the pores as described above.

  Hereinafter, based on an Example and a comparative example, the manufacturing method of a graphite analysis sample is demonstrated in detail.

(Processing process)
As a graphite analysis sample, IBIDEN Co., Ltd. porous graphite material ET-10 was prepared. ET-10 was appropriately cut using a metal tooth metal band saw, and porous graphite was cut out to obtain an unpolished sample. The size of the obtained graphite analysis sample was 40 × 40 × 3 mm. Furthermore, using a grindstone using # 240 abrasive grains, the sawtooth irregularities generated by the cutting process were previously removed. The pore size of the porous graphite was on the order of microns. On the other hand, the abrasive grain of # 240 has a median diameter of 74 to 88 μm, and the particle diameter is sufficiently larger than the pores of graphite and hardly remains inside the pores. The material of the grindstone at this stage is not particularly limited. May be.

(Polishing process)
Next, an aqueous slurry containing diamond powder having a median diameter of 4 μm (polished with SYNP3 SYP3-5. Polishing was performed with a general-purpose high-precision polishing apparatus (model FAM32BTAW / GPAW) manufactured by SPEED FAM). Was 60 rpm, the load applied to the polished surface was 6.37 × 10 ⁻³ kgf / cm ² , and the polishing time was 15 minutes.

(Washing process)
About the obtained porous graphite analysis sample, the abrasive | polishing agent which remains on the surface was wash | cleaned with the water flow which falls from a tap. At this time, it is considered that most of the abrasive remaining in the pores flows out together with the liquid constituting the slurry, but thereafter the pores were not cleaned by ultrasonic cleaning. Since ultrasonic cleaning is not performed, it is considered that some abrasives remain in the pores.

(Drying process)
The porous graphite analysis sample that had undergone the washing step was dried in a dryer. The drying temperature was 120 ° C. for 60 minutes.

  A porous graphite analysis sample was produced in the same manner as in Example 1 except that the porous graphite material IG-11 manufactured by Toyo Tanso Co., Ltd. was used as the graphite analysis sample.

Comparative Example 1

  A porous graphite analysis sample was produced in the same manner as in Example 1 except that ultrasonic cleaning was performed in the cleaning step. In the washing step, water was put into a washing tank using an ultrasonic washing machine manufactured by Nippon Emerson, and ultrasonic washing was performed for 2 minutes. The output of the ultrasonic transducer was 500W.

  When ultrasonic cleaning was started, bubbles due to the cavitation effect were generated around the porous graphite analysis sample, and the periphery of the porous graphite analysis sample began to become black and turbid. It is considered that the graphite particles in the pores and the graphite particles destroyed by the ultrasonic cleaning began to drift, the abrasive in the pores was removed, and a part of the graphite analysis sample surface was destroyed.

Comparative Example 2

  A porous graphite analysis sample was produced in the same manner as in Comparative Example 1 except that Toyo Carbon Co., Ltd. porous graphite material IG-11 was used as the graphite analysis sample. When ultrasonic cleaning was started, bubbles due to the cavitation effect were generated around the porous graphite analysis sample, and the periphery of the porous graphite analysis sample began to become black and turbid. It is considered that the graphite particles in the pores and the graphite particles destroyed by the ultrasonic cleaning began to drift, the abrasive in the pores was removed, and a part of the graphite analysis sample surface was destroyed.

Comparative Example 3

(Processing process)
As a graphite analysis sample, IBIDEN Co., Ltd. porous graphite material ET-10 was prepared. ET-10 was appropriately cut using a metal tooth metal band saw, and porous graphite was cut out to obtain an unpolished sample. The size of the obtained graphite analysis sample was 40 × 40 × 3 mm. Furthermore, using a grindstone using # 240 abrasive grains, the irregularities of the sawtooth generated by the cutting process were removed in advance. The pore size of the porous graphite was on the order of microns. On the other hand, the abrasive grain of # 240 has a median diameter of 88 to 74 μm and is larger than the pores of graphite and hardly remains inside the pores. Therefore, the material of the grindstone at this stage is not particularly limited. good.

(Polishing process)
Next, it grind | polished with the aqueous slurry containing the alumina abrasive | polishing agent (WA2000 by Fujimi Incorporated Co., Ltd.) with a median diameter of 6.90 ± 0.60 μm (catalog value). Polishing was performed manually for about 5 minutes on a glass plate covered with gauze.

(Washing process)
The obtained porous graphite analysis sample was cleaned of the abrasive remaining on the surface with a water flow falling from the faucet. At this time, it is considered that most of the abrasive remaining in the pores flows out together with the liquid constituting the slurry, but thereafter the pores were not cleaned by ultrasonic cleaning. There is a partial white area on the surface of the porous graphite analysis sample, and it is considered that the alumina abrasive remains in the pores.

(Drying process)
The porous graphite analysis sample that has undergone the washing step is dried in a dryer. The drying temperature is 120 ° C. for 60 minutes. Even after the drying process, the white portion remains, and it is considered that the alumina abrasive remains in the pores.

Comparative Example 4

  A porous graphite analysis sample was produced in the same manner as in Comparative Example 3 except that ultrasonic cleaning was performed in the cleaning step. In the washing step, water was put into a washing tank using an ultrasonic washing machine manufactured by Nippon Emerson, and ultrasonic washing was performed for 2 minutes. The output of the ultrasonic transducer was 500W.

  When ultrasonic cleaning was started, bubbles due to the cavitation effect were generated around the porous graphite analysis sample, and the periphery of the porous graphite analysis sample began to become black and turbid. It is thought that graphite particles in the pores and graphite particles destroyed by ultrasonic cleaning began to drift.

  Before the ultrasonic cleaning, there was a partial white area on the surface of the sample, and it was considered that the alumina abrasive remained in the pores, but the partial white area disappeared by the ultrasonic cleaning. It is considered that the alumina abrasive was removed by ultrasonic cleaning.

  The results are summarized in Table 1 below for the examples and comparative examples described above.

  1 and 2 show the results of analysis by AFM (Atomic Force Microscope) of Example 2 and Comparative Example 2, respectively. The device used was a VN-8000 model manufactured by Keyence Corporation, and the OP75042 model manufactured by Keyence Corporation was used as the cantilever. The measurement was performed at room temperature (about 25 ° C.), and the scanning speed was 2.2 sec / time. The measurement range was defined as a square area of 0.2 mm square.

  3 to 5 show the results of analysis by SEM (scanning electron microscope) of Example 1, Example 2, and Comparative Example 2, respectively. SEM used the ULTRAplus type made by SII Nanotechnology. The scale was 20 μm in FIG. 3 and 10 μm in FIGS. 4 and 5. In the figure, a marker formed by FIB (focused ion beam) is formed on the surface of the graphite sample.

  The following matters are derived from the AFM analysis results.

  In Comparative Example 2 (FIG. 2) in which ultrasonic cleaning is performed, there is a region that cannot be measured by AFM because the surface unevenness is large (a band-like portion in the center portion sideways). From the AFM results, it can be confirmed that Example 2 (FIG. 1) where ultrasonic cleaning is not performed is flatter than Comparative Example 2 (FIG. 2) where ultrasonic cleaning is performed. In Comparative Example 2 (FIG. 2) in which ultrasonic cleaning is performed, there is a region that cannot be measured by AFM because the surface unevenness is large (a band-like portion in the center portion sideways).

  From the SEM analysis results, the following can be understood. In Comparative Example 2 where ultrasonic cleaning is performed, a large dent is formed (FIG. 5). From the results of SEM, Examples 1 and 2 (FIGS. 3 and 4) in which ultrasonic cleaning was not performed are flatter than Comparative Example 2 (FIG. 5) in which ultrasonic cleaning is performed, and ultrasonic waves are not generated. It is confirmed that the graphite particles on the surface of the graphite analysis sample are dropped by the cleaning.

  Moreover, it is confirmed from the measurement result of the surface roughness of the porous graphite sample that the surface roughness is increased by ultrasonic cleaning (see Table 1).

(Ion irradiation test)
FIG. 6 shows the analysis result by SEM (scanning electron microscope) of the same part before and after performing the ion irradiation test on the surface of the porous graphite analysis sample of Example 2 of the present invention. b) shows after irradiation. Comparing (a) and (b) before and after ion irradiation in FIG. 6, it can be seen that almost no change is observed in the observed region. However, since the observation surface of the porous graphite analysis sample is flat and no elements other than carbon are present, slight changes can be detected without being affected by the elements contained in the abrasive. It turns out that the porous graphite analysis sample which can be obtained is obtained.

  Specifically, the contents of a specific ion irradiation test for the porous graphite sample obtained in Example 2 will be described below.

A marker formed by FIB (focused ion beam) on the surface of the graphite sample was used as a marker, and changes around the marker accompanying ion irradiation were confirmed. In the ion irradiation test, evaluation was performed by performing ion irradiation for 60 to 400 minutes in an area of 8 mm ² using an acceleration voltage of 5.1 MeV, a current of 4 mA, and a Si ion source in a vacuum chamber.

  Comparing before and after ion irradiation, graphite changes before and after ion irradiation occur in crystal units, (1) generation of grain boundary cracks due to irradiation induced shrinkage or increase in grain boundary crack size, and (2) irradiation induction. It was confirmed that the crack size decreased with expansion.

  In addition, the generation of cracks and an increase in size were observed due to ion irradiation, and under the conditions of ion irradiation this time (porous graphite surface temperature 400 ° C., 3-10 dpa), the irradiated portion contracted almost uniformly without bias, and the sample It was found that there is a possibility that the overall dimensional change can be estimated. Incidentally, dpa (displacements per atom) is a unit of damage amount and represents the number of atoms ejected per atom.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  According to the present invention, a graphite analysis sample having a flat observation surface can be obtained without containing other elements. Therefore, damage evaluation of graphite material due to irradiation with high energy particles such as ion particles, and reactive gas such as SiO can be used. It is expected to provide a porous graphite analysis sample that can be used as various evaluation samples that can detect slight changes such as damage evaluation of graphite materials. Such porous graphite analysis samples are expected to enable various resistance evaluations of industrially useful porous graphite materials.

Claims (9)

A processing step of obtaining at least one plane on the surface of the porous graphite material;
Polishing the flat surface using an abrasive made of carbon-based powder or organic powder after the processing step to obtain a polished surface;
A cleaning step of cleaning the polishing surface with a liquid;
A drying step for volatilizing the liquid;
A method for producing a graphite analysis sample. A method for producing a graphite analysis sample according to claim 1,
The method for producing a graphite analysis sample, wherein the polishing step is performed by a wet process using a liquid. A method for producing a graphite analysis sample according to claim 2,
The said grinding | polishing process is a manufacturing method of the graphite analysis sample performed by the wet process using water. A method for producing a graphite analysis sample according to any one of claims 1 to 3,
The cleaning step is a method for producing a graphite analysis sample, wherein the abrasive is left inside pores of the porous graphite material. A method for producing a graphite analysis sample according to any one of claims 1 to 4,
The washing step is a method for producing a graphite analysis sample using water. A method for producing a graphite analysis sample according to any one of claims 1 to 5,
The method for producing a graphite analysis sample, wherein the cleaning step performs ultrasonic cleaning with a weak output that does not cause ultrasonic cleaning or generates bubbles due to a cavitation effect by ultrasonic cleaning. A method for producing a graphite analysis sample according to any one of claims 1 to 6,
The method for producing a graphite analysis sample, wherein the carbon-based powder is at least one selected from the group consisting of diamond powder, coke powder, graphite powder, anthracite, pyrolytic carbon powder, and glassy carbon.   The graphite analysis sample obtained by the manufacturing method of the graphite analysis sample of any one of Claim 1 to 7. Having at least one plane, the arithmetic average roughness Ra measured in the plane is 0.2 μm or less,
Containing at least a carbon-based powder inside the pores exposed in the plane,
Furthermore, the graphite analysis sample which contains the carbide | carbonized_material of the abrasive | polishing agent consisting of the abrasive | polishing agent which consists of carbon type powder, the abrasive | polishing agent which consists of organic type powder, or the organic type | system | group powder in the said pore.