KR102420277B1 - Carbon composite material - Google Patents

Abstract

[Solution] A carbon composite member (1) in which a pyrolytic carbon layer (3) is formed on a graphite substrate (2), wherein the pyrolytic carbon layer (3) is in the vicinity of the interface between the thermally decomposed carbon layer (3) and the graphite substrate (2) , has a region in which the pores 4 are present.

Description

Carbon composite member {CARBON COMPOSITE MATERIAL}

The present invention relates to a carbon composite member.

BACKGROUND ART Carbon materials such as graphite are used in many fields, such as semiconductor manufacturing, chemical industry, machinery, and nuclear power, because of their excellent chemical stability, heat resistance, and mechanical properties. Moreover, since graphite itself is a porous body, it is easy to adsorb|suck gas, moisture, an impurity, etc. inside a pore, and the inside of a pore is easy to be contaminated. Therefore, there is known a technique for reducing the adverse effect of graphite by coating the pyrolytic carbon so that these contaminants are not re-emitted from the pores.

However, since thermally decomposed carbon and graphite as a coating layer have different coefficients of thermal expansion, deformation or stress due to heat is likely to occur at the interface between the two when heat is applied. Therefore, in Patent Document 1, a graphite substrate having an average coefficient of thermal expansion at 20° C. to 400° C. of 1.3×10 ^-6 /° C. to 6.0×10 ^-6 /° C. is used, and a film of pyrolytic carbon is formed on the surface. Electrodes for electrolytic processing made of graphite have been proposed.

Japanese Patent Laid-Open No. 5-285735

Here, the electrode for electrolytic processing made of graphite described in Patent Document 1 is premised on being used in a substantially constant temperature environment. On the other hand, in the above-described applications such as semiconductor manufacturing, since heating and cooling are repeatedly performed, a severe heat cycle is applied between the graphite substrate and the pyrolytic carbon layer. For this reason, about peeling, it is exposed under a more severe environment.

In view of the above problems, an object of the present invention is to provide a carbon composite member in which a pyrolytic carbon layer is formed on a graphite substrate, in which the pyrolytic carbon layer is hardly peeled even when a heat cycle with a large temperature difference is applied.

The carbon composite member which concerns on this invention for solving the said subject is as follows.

(1) A carbon composite member in which a pyrolytic carbon layer is formed on a graphite substrate,

The carbon composite member according to claim 1, wherein the pyrolytic carbon layer has a region in which pores exist in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate.

According to the carbon composite member according to the present invention, the pyrolytic carbon layer has a region in which pores exist in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate, so that the crystal direction of the pyrolytic carbon around the pores is disturbed. As a result, in the planar direction of the pyrolytic carbon layer, the thermal expansion coefficient in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate is affected by the influence of the thermal expansion coefficient in the c-axis direction of the pyrolytic carbon layer and acts to increase the thermal expansion coefficient. gets smaller By the above, even if a heat cycle with a large temperature difference is applied, peeling of the thermally decomposed carbon layer from a graphite base material can be suppressed.

Further, the carbon composite member according to the present invention preferably has the following aspects (2) to (6).

(2) The pores are unevenly distributed in the vicinity of the interface.

While the pores are unevenly distributed in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate, the difference in the coefficient of thermal expansion in the vicinity of the interface is alleviated. The permeability can be sufficiently ensured, and contamination of the carbon composite member can be prevented.

(3) The pores have a maximum pore diameter of 0.5 to 3.0 µm.

When the maximum pore diameter of the pores is 0.5 µm or more, it is possible to sufficiently secure the components of pyrolytic carbon having different orientations of orientation occurring around the pores, and the difference in thermal expansion coefficient between the graphite substrate and the pyrolytic carbon layer is alleviated by the generation of pores. effect can be sufficiently exerted. In addition, when the maximum pore diameter of the pores is 3.0 µm or less, stress concentration around the pores can be reduced, and it is possible to prevent the strength from lowering due to the presence of pores.

(4) in the cross-section along the lamination direction of the graphite substrate and the pyrolytic carbon layer,

The maximum pore diameter is at the top and bottom of the irregularities of the interface with the pyrolysis carbon layer of the graphite substrate in any straight line section of 50 μm along the entire interface with the pyrolysis carbon layer of the graphite substrate. 30% or less of the maximum height difference.

When the pores in the pyrolytic carbon layer are arranged in a line, the pyrolytic carbon layer is easily peeled off from the graphite substrate, but when the maximum pore diameter satisfies the above conditions, suitable undulations are provided on the surface of the graphite substrate, and the surface of the graphite substrate Since pores are formed so as not to be arranged in a line according to the undulations in the , a pyrolytic carbon layer that is difficult to peel can be obtained.

(5) The thickness of the pyrolytic carbon layer is 5 to 200 µm.

When the thickness of the pyrolytic carbon layer is 5 µm or more, it is possible to sufficiently cover the unevenness of the graphite substrate, which is a porous body, and to ensure gas impermeability. In addition, when the thickness of the pyrolytic carbon layer is 200 µm or less, warpage or peeling due to thermal deformation between the graphite substrate and the pyrolytic carbon layer can be prevented.

(6) The graphite substrate is an isotropic graphite material.

Since isotropic graphite has small anisotropy in properties and high uniformity, the difference in thermal expansion coefficient with the pyrolytic carbon layer is small depending on location and direction, so that it is difficult to peel.

According to the carbon composite member according to the present invention, the pyrolytic carbon layer has a region in which pores exist in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate, so that the crystal direction of the pyrolytic carbon around the pores is disturbed. As a result, in the planar direction of the pyrolytic carbon layer, the thermal expansion coefficient in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate is affected by the influence of the thermal expansion coefficient in the c-axis direction of the pyrolytic carbon layer and acts to increase the thermal expansion coefficient. gets smaller By the above, even if a heat cycle with a large temperature difference is applied, peeling of the thermally decomposed carbon layer from a graphite base material can be suppressed.

1 is a schematic cross-sectional view of a carbon composite member according to an embodiment of the present invention.
2 is an explanatory view for explaining the relationship between the maximum difference in height between the top and bottom of the graphite substrate and the maximum pore diameter of the pores when viewed in a cross section along the lamination direction of the graphite substrate and the pyrolytic carbon layer.
3 is a schematic diagram for explaining a method for manufacturing a carbon composite member according to an embodiment of the present invention.
4 is a polarization microscope photograph of a cross section of the carbon composite member obtained in Example 1. FIG.
FIG. 5 is a schematic diagram of FIG. 4 .
6 is a polarization microscope photograph of a cross section of the carbon composite member obtained in Comparative Example 1. FIG.

(Detailed Description of the Invention)

In the carbon composite member 1 according to the present embodiment, as schematically shown in FIG. 1 , a pyrolytic carbon layer 3 is formed on a graphite substrate 2 , and the pyrolytic carbon layer 3 is , has a region in which pores 4 exist in the vicinity of the interface between the pyrolytic carbon layer 3 and the graphite substrate 2 . In addition, in the region where the pores 4 exist, a plurality of pores 4 having non-uniform pore diameters are present at random.

The pyrolytic carbon has the characteristic of very high anisotropy in which the hexagonal mesh plane spreads in the plane direction. In addition, pyrolytic carbon is oriented so that it may become the a-axis direction of the hexagonal crystal of a graphite structure in the plane direction, and the c-axis direction in the thickness direction, and is a material with high anisotropy in both strength and thermal expansion. The coefficient of thermal expansion is 1.7 × 10 ^-6 /°C in the plane direction and 2.7 × 10 ^-5 /°C in the thickness direction (all average values), and there is very large anisotropy. Also, in terms of strength, the hexagonal mesh planes are strongly bonded in the plane direction, and only connected by Van Der Waals bonding in the thickness direction, and the strength in the thickness direction is significantly lower than the strength in the plane direction.

On the other hand, the graphite used as the graphite base material 2 has a coefficient of thermal expansion of 3 to 6 x 10 ^-6 /°C, which is larger than the coefficient of thermal expansion in the plane direction of the pyrolytic carbon layer 3 formed thereon. For this reason, the graphite base material 2 and the thermally decomposed carbon layer 3 are easy to generate|occur|produce thermal deformation, and it becomes easy to produce delamination by a difference in thermal expansion.

Therefore, in the carbon composite member 1 according to the present embodiment, by providing a region in which the pores 4 exist in the vicinity of the interface with the graphite substrate 2 in the pyrolytic carbon layer 3, the pores ( In the vicinity of 4), the crystal direction of the pyrolytic carbon is disturbed, and it acts so as to alleviate the anisotropy of the thermal expansion coefficient and strength. Concomitantly, in the plane direction of the pyrolytic carbon layer 3, it is affected by the thermal expansion coefficient in the c-axis direction and acts to increase the thermal expansion coefficient, and in the thickness direction of the pyrolytic carbon layer 3, the graphite structure Influenced by the strength in the a-axis direction of the hexagonal crystal, the strength increases. For this reason, even if it forms on the graphite base material 2 with a large coefficient of thermal expansion, even if the thermally decomposed carbon layer 3 which originally has a small coefficient of thermal expansion in a plane direction, it can make it difficult to generate|occur|produce delamination.

It is preferable that the pores 4 are unevenly distributed in the vicinity of the interface. When the pores 4 are unevenly distributed in the vicinity of the interface between the pyrolytic carbon layer 3 and the graphite substrate 2, the difference in the coefficient of thermal expansion in the vicinity of the interface is alleviated, while the graphite substrate in the pyrolytic carbon layer 3 is The portion separated from (2) can sufficiently secure the gas impermeability of the pyrolytic carbon, thereby preventing contamination from the carbon composite member (1).

In the present embodiment, "near the interface" refers to a region from the interface between the pyrolytic carbon layer 3 and the graphite substrate 2 to 25% of the thickness of the pyrolytic carbon layer.

The maximum pore diameter of the pores 4 is preferably 0.5 to 3.0 µm. When the maximum pore diameter of the pores 4 is 3.0 μm or less, stress concentration around the pores 4 can be reduced, and the strength can be prevented from lowering due to the presence of the pores 4 . On the other hand, if the maximum diameter of the pores 4 is 0.5 μm or more, it is possible to sufficiently secure the components of pyrolytic carbon having different orientations generated around the pores 4, and the graphite substrate 2 and the The effect of alleviating the difference in the coefficient of thermal expansion of the thermally decomposed carbon layer 3 can be sufficiently exhibited.

For this reason, when the maximum diameter of the pores 4 is 0.5 to 3.0 μm, the difference in the coefficient of thermal expansion between the pyrolytic carbon layer 3 and the graphite substrate 2 due to the presence of the pores 4 is reduced, The stress concentration in the periphery of the pores 4 can be reduced, and a decrease in strength due to the presence of the pores 4 can be prevented. Moreover, in order to exhibit these effects more favorably, as for the largest pore diameter of the pore 4, 0.8-2.5 micrometers is more preferable, and 1.0-2.0 micrometers is still more preferable. In addition, the size of the pore 4 can be obtained by observation with an electron microscope, and the dimension of the cross section of the largest pore 4 in the observation field is measured. In addition, irregular pores are identified in the longest direction.

In addition, referring to FIG. 2 , the maximum pore diameter is the pyrolysis carbon layer 3 of the graphite substrate 2 when viewed in a cross section along the lamination direction of the graphite substrate 2 and the pyrolysis carbon layer 3 . It is preferable that it is 30% or less of the maximum height difference ΔH of the top and bottom portions of the unevenness of the interface with the pyrolytic carbon layer 3 of the graphite substrate 2 in all linear sections of 50 μm along the entire interface. When the pores 4 in the pyrolytic carbon layer 3 are arranged in a line, the pyrolytic carbon layer 3 is easily peeled off from the graphite substrate 2, but when the maximum pore diameter satisfies the above conditions, the graphite substrate ( Since suitable undulations are provided on the surface of 2) and pores 4 are formed so as not to be arranged in a line along the undulations on the surface of the graphite substrate 2, a pyrolytic carbon layer 3 that is difficult to peel can be obtained. have.

When the maximum pore diameter with respect to ΔH exceeds 30%, the pores 4 are too large, and the pyrolytic carbon layer 3 tends to peel off. The maximum pore diameter with respect to ΔH is more preferably 25% or less, and still more preferably 20% or less. In addition, in order to provide a predetermined height difference on the surface of the graphite base material 2, it can consider roughening the graphite base material 2 suitably so that it may become predetermined roughness, for example.

It is preferable that the thickness of the thermal decomposition carbon layer 3 is 5-200 micrometers. If the thickness of the pyrolytic carbon layer 3 is 5 μm or more, the unevenness of the graphite substrate 2 which is a porous body can be sufficiently covered, and it becomes difficult to adsorb gas, moisture, impurities, etc. into the pores, and the impermeability of these gases and impurities can be obtained On the other hand, when the thickness of the pyrolytic carbon layer 3 is 200 μm or less, it is possible to prevent warping and peeling due to thermal deformation of the pyrolytic carbon layer 3 .

In order to exhibit these effects more favorably, as for the thickness of the pyrolytic carbon layer 3, 10-100 micrometers is more preferable, and 20-50 micrometers is still more preferable.

In addition, the thickness of the thermally decomposed carbon layer 3 can be measured using a polarization microscope, a scanning electron microscope, etc. from comparison with a standard scale. When a standard scale is already displayed with a scanning electron microscope or the like, it can be used to calculate the thickness.

Moreover, as the graphite base material 2 in the carbon composite member 1 concerning this embodiment, it is preferable that it is an isotropic graphite material. Since isotropic graphite has small characteristic anisotropy and high uniformity, the difference in thermal expansion coefficient with the pyrolytic carbon layer 3 is small depending on the location and direction, so that it is difficult to peel.

Subsequently, the carbon composite member 1 according to the present embodiment can be obtained, for example, as follows. 3 : is a schematic diagram for demonstrating the process.

First, the graphite base material 2 of the target shape is prepared (FIG.3(a)). When the pyrolytic carbon layer 3 is formed on the graphite substrate 2, it becomes larger by the thickness, so it is preferable to process it relatively thinly according to the size of the carbon composite member 1 and the thickness of the pyrolytic carbon layer 3 to be formed. do. Moreover, in order to improve the adhesiveness with the pyrolysis carbon layer 3, or to make the maximum pore diameter with respect to the said ΔH be 30% or less, the surface of the graphite substrate 2 may be roughened.

Then, the graphite base material 2 is placed in the CVD furnace, and the raw material gas is introduced after raising the temperature to the film formation temperature. Although the film-forming temperature is not specifically limited, For example, it can be 800-2000 degreeC. The raw material gas for obtaining the pyrolysis carbon layer 3 will not be specifically limited if it is a hydrocarbon. For example, alkanes such as methane, ethane, propane, and butane, alkenes such as ethylene and propylene, alkynes such as acetylene, and aromatic raw material gases such as benzene and toluene may be used.

Then, a very thin pyrolytic carbon layer 3 is formed on the surface of the graphite substrate 2 by maintaining the film-forming temperature and introducing the source gas for a certain period of time (FIG. 3(b)). In addition, as the carrier gas, an inert gas such as Ar can be used. In addition, this very thin pyrolytic carbon layer is arbitrary and does not need to be formed.

Subsequently, at a stage in which the pyrolysis carbon layer 3 has a very thin predetermined thickness, clusters of pyrolysis carbon are generated on the surface of the pyrolysis carbon layer 3 . Clusters of pyrolytic carbon are generated when particles (fine lumps) of pyrolytic carbon generated in the air settle on the surface of the very thin pyrolytic carbon layer 3 and are deposited (that is, deposited).

Although the method for generating this cluster is not specifically limited, For example, by raising the pressure in a CVD furnace, raising the temperature, or raising the partial pressure of hydrocarbon, the balance of a thermal decomposition reaction is temporarily disturbed, and pyrolysis A plurality of clusters of pyrolytic carbon can be formed on the surface of the very thin pyrolytic carbon layer 3 by accelerating the formation of pyrolytic carbon particles in the air and depositing them.

In addition, since particles of pyrolytic carbon not only generate in the upper space of the pyrolysis carbon layer 3 but also grow after falling on the surface of the pyrolysis carbon layer 3, particles of pyrolysis carbon are generated in the pyrolysis carbon layer 3 It is integrated with the pyrolysis carbon layer 3 while being deposited on the surface of the That is, the pyrolytic carbon layer 3 and the cluster of pyrolytic carbon formed on the surface are integrated.

In the thus obtained pyrolytic carbon layer 3 to which particles are attached, pores 4 are formed in the gaps between the clusters, and the crystal direction of the pyrolytic carbon around the pores 4 is disturbed (FIG. 3(c)) . In Fig. 3(c), randomly oriented short straight lines appearing around the pores 4 schematically show a state in which the crystal direction of the pyrolytic carbon is disturbed. In addition, the size of the pores 4 obtained is about the same as the particle size.

As an example of the conditions for generating and depositing this pyrolytic carbon particle, it is mentioned that the pressure in a CVD furnace shall be 10-10000 Pa, and the temperature shall be 800-2000 degreeC.

In addition, in order to deposit more pyrolytic carbon particles on the surface of the pyrolytic carbon layer 3 to form more pores 4, in the CVD furnace, the space above the pyrolytic carbon layer 3 is widened. If the upper space is wide, the amount of generated pyrolytic carbon particles increases, and more pyrolytic carbon particles can be deposited on the surface of the pyrolytic carbon layer 3 to be integrated.

In addition, by applying an electric charge to the graphite substrate 2 or inverting the graphite substrate 2 in a CVD furnace, not only the upper surface of the thermally decomposed carbon layer 3 but also the side surface and the lower surface of the graphite substrate 2 are thermally decomposed. Pores may be formed in the carbon layer 3 .

Subsequently, after the particles of the pyrolytic carbon have reached a certain amount of deposition, the pyrolytic carbon is made constant under the CVD conditions for film formation, and continuously on the pyrolytic carbon layer 3 in which the pores 4 are formed, a further pyrolytic carbon layer (3) is formed (FIG. 3(d)).

Further, a pyrolytic carbon layer 3 that generates particles of pyrolyzed carbon to form pores 4 and a pyrolytic carbon layer 3 that does not generate particles of pyrolytic carbon and does not form pores 4 are continuously formed into a film Therefore, it is possible to form the thermally decomposed carbon layer 3 in which peeling between layers is unlikely to occur. In addition, it is preferable to form the pyrolytic carbon layer 3 after the formation of the particles and the pores 4 at the same time under constant conditions without changing the pressure or temperature in the CVD furnace so as not to generate particles. In this way, the film is formed so that no particles are generated, and the pyrolytic carbon layer 3 having a predetermined thickness is formed to obtain the desired carbon composite member 1 .

(Form for implementing the invention)

Hereinafter, an Example and a comparative example are given and demonstrated further so that the characteristic of the carbon composite member which concerns on this invention may be made clear.

(Example 1)

The isotropic graphite material was processed so that it might become a size of 50x50x5 mm, and it was set as the graphite base material. The obtained graphite substrate is placed in a CVD furnace, heated to 1200° C. or higher while reducing pressure with a vacuum pump, and the raw material gas containing hydrocarbon is supplied at a constant gas partial pressure from the beginning so that the gas pressure in the CVD furnace is 1 kPa or less, The formation of a pyrolytic carbon layer was initiated. Further, since hydrocarbon gas is continuously consumed during film formation, when the gas supplied and the gas in the furnace are compared in a steady state, the gas in the furnace has a lower partial pressure of hydrocarbon gas.

For this reason, it is thought that when the partial pressure of hydrocarbon gas is maintained and supplied from the film formation, a state in which the gas partial pressure of the hydrocarbon gas is high in the initial stage of film formation is generated, and clusters forming pores on the surface of the graphite substrate are likely to be formed.

Then, when the time for which the thickness of the thermal decomposition carbon layer grows to 20 micrometers has reached|attained, supply of the source gas was stopped.

The cross section of the carbon composite member thus obtained was confirmed with a polarization microscope. The photographed polarization microscope picture is shown in FIG. 4 , and a schematic diagram of the polarization microscope picture of FIG. 4 is shown in FIG. 5 . In Fig. 5, pores are formed in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate. The maximum pore diameter confirmed in FIGS. 4 and 5 of Example 1 was 1.05 μm.

In addition, when viewed in a cross-section along the lamination direction of the graphite substrate and the pyrolysis carbon layer, the maximum pore diameter is the graphite substrate in a straight section of 50 μm along the interface with the pyrolysis carbon layer, the graphite substrate was 19% of the maximum elevation difference between the top and bottom of the unevenness of the interface with the pyrolytic carbon layer. In addition, the maximum difference in elevation between the top and bottom of the graphite substrate was 5.5 µm (broken line portion in FIG. 5 ).

It was confirmed that this carbon composite member is a slanted functional material whose crystal orientation is aligned from the interface with the graphite substrate toward the surface in the vicinity of the interface due to the presence of pores in the pyrolytic carbon layer.

(Comparative Example 1)

A carbon composite member was formed in the same manner as in Example 1. However, the ratio of the hydrocarbon gas was initially decreased and the flow rate of the hydrocarbon gas was gradually increased, and then, as in Example 1, film formation was performed at a constant partial pressure ratio of the source gas.

As a result of observing the cross section of the carbon composite member obtained in this way with a polarizing microscope, pores were not formed in the vicinity of the interface of the pyrolytic carbon layer with the graphite substrate, and the pyrolytic carbon layer had a directionality from the vicinity of the interface of the graphite substrate to the surface. An aligned film of was obtained (see Fig. 6).

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, etc. of each component in the above-mentioned embodiment are arbitrary, as long as it can achieve this invention, and it is not limited.

In the carbon composite member according to the present invention, since the pyrolytic carbon layer has a region in which pores exist near the interface between the pyrolytic carbon layer and the graphite substrate, the difference in the coefficient of thermal expansion in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate is small. Even when a heat cycle with a large temperature difference is applied, the pyrolytic carbon layer is difficult to peel off, so it is effective in many fields, such as semiconductor manufacturing, chemical industry, machinery, and nuclear power.

1: carbon composite member
2: Graphite substrate
3: Pyrolysis carbon layer
4: Qigong

Claims (10)

A carbon composite member in which a pyrolytic carbon layer is formed on a graphite substrate,
the pyrolytic carbon layer has a region in which pores exist in the vicinity of the interface between the pyrolytic carbon layer and the graphite substrate;
The pores have a maximum pore diameter of 0.5 to 3.0 μm,
When viewed in a cross-section along the lamination direction of the graphite substrate and the pyrolysis carbon layer, the maximum pore diameter is in any linear section of 50 μm along the entire interface of the graphite substrate with the pyrolysis carbon layer. , wherein the carbon composite member is 30% or less of the maximum height difference between the top and bottom of the unevenness of the interface with the pyrolytic carbon layer of the graphite substrate. The carbon composite member according to claim 1, wherein the pores are unevenly distributed in the vicinity of the interface. The carbon composite member according to claim 1 or 2, wherein the pyrolytic carbon layer has a thickness of 5 to 200 µm. The carbon composite member according to claim 1 or 2, wherein the graphite substrate is an isotropic graphite material. delete delete delete delete delete delete

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