JP6388515B2 - Method for producing pyrolytic carbon-coated graphite member - Google Patents

Description

    The present invention relates to a method for producing a pyrolytic carbon-coated graphite member.

Graphite materials are used in various industrial fields such as semiconductor manufacturing equipment, high-temperature furnaces, metal melting crucibles, and jigs because of their high heat resistance and chemical stability.
As such a graphite material, a porous graphite material obtained by molding into a block using a powder such as coke as a raw material, and firing and graphitizing is widely used.
However, since such porous graphite material easily reacts with oxygen, water, etc., there is a problem that it reacts with a small amount of oxygen, water, etc. during heating and is rapidly consumed. There is known a technique for reducing the consumption rate by reducing the surface area.

In Patent Document 1, in order to further reduce the consumption rate, a pyrolytic carbon having a bulk density of 2.0 g / cm ³ or more is coated on a graphite substrate at a temperature of 1600 to 2200 ° C., and then the pyrolytic carbon coating is applied. A method for producing a pyrolytic carbon-coated graphite material characterized by heat-treating a graphite substrate at a temperature of 2500 ° C. or higher is described.
According to such a manufacturing method, it is described that a pyrolytic carbon-coated graphite material having excellent oxidation resistance can be obtained.

  On the other hand, in Non-Patent Document 1, pyrolytic carbon (PG) has its crystal a-plane (layer surface) oriented almost parallel to the deposition surface of the substrate, but the properties differ considerably depending on the deposition conditions. In particular, it is described that the density becomes minimum at a deposition temperature of around 1600 ° C., and takes a value close to the theoretical density of graphite at 2000 ° C. or higher or 1200 ° C. or lower.

Japanese Unexamined Patent Publication No. 63-210088

Toshiyoshi Ishikawa, Tsutomu Nagaoki, “New Carbon Industry”, published by Modern Editing Co., Ltd., October 20, 1980, p93

  That is, a pyrolytic carbon film obtained under film forming conditions of 1200 to 2000 ° C. centering on 1600 ° C. has a disordered crystal structure with a low density, and the rate of oxidation consumption is increased. For this reason, it is understood that the purpose of Patent Document 1 is to increase the density of the pyrolytic carbon film and increase the crystallinity by performing a heat treatment at 2500 ° C. or higher after film formation.

Here, it is known that the graphite material generally becomes noticeable creep at a temperature of 2000 ° C. or higher (Junichi Kim, “Mechanical properties of carbon”, Carbon, No. 66, edited by the Carbon Materials Society of Japan, 1971, p99-106). For this reason, when heat of 2000 ° C. or higher is applied to a precisely processed graphite member, creep deformation occurs and dimensional accuracy is lowered. When the dimensional accuracy is lowered, the positioning accuracy of the jig is deteriorated, and the graphite member rotating at a high speed causes vibration due to runout.
For this reason, as in the technique described in Patent Document 1, heating at 2000 ° C. or higher, or even 2500 ° C. or higher to slow the consumption rate of pyrolytic carbon may cause creep deformation of the graphite member and cause various problems. become.

The present invention provides a method for producing a pyrolytic carbon-coated graphite member capable of forming a pyrolytic carbon film having a high degree of crystallinity on a graphite member while suppressing creep deformation without exposing the graphite member to a high temperature. For the purpose.
Another object of the present invention is to provide a pyrolytic carbon-coated graphite member having a pyrolytic carbon film having a high degree of crystallinity on the graphite member and having high dimensional accuracy and wear resistance.

As a result of intensive studies, the present inventor forms a pyrolytic carbon film by coating pyrolytic carbon on a graphite member in a chemical vapor deposition (CVD) furnace in a specific temperature range and in the presence of oxygen. Thus, the inventors have found that the above problems can be solved, and have completed the present invention.
That is, the present invention is as follows.
1. In the method for producing a pyrolytic carbon-coated graphite member in which a graphite member is coated with pyrolytic carbon by a CVD method using a hydrocarbon gas,
The temperature of the graphite member in the CVD method is less than 2000 ° C.,
The method for producing a pyrolytic carbon-coated graphite member, wherein the CVD method is performed in the presence of oxygen.
2. 2. The method for producing a pyrolytic carbon-coated graphite member according to item 1, wherein the temperature of the graphite member in the CVD method is 1200 ° C. or higher.
3. 3. The method for producing a pyrolytic carbon-coated graphite member according to item 1 or 2, wherein the partial pressure of oxygen is 1000 to 17000 ppm relative to the partial pressure of the hydrocarbon gas.
4). 4. The method for producing a pyrolytic carbon-coated graphite member according to any one of the preceding items 1 to 3, wherein the oxygen is mixed and supplied in advance to the hydrocarbon gas.
5. 5. The method for producing a pyrolytic carbon-coated graphite member according to any one of the preceding items 1 to 4, wherein the hydrocarbon gas is methane gas.
6). A pyrolytic carbon-coated graphite member produced by the production method according to any one of 1 to 5 above.

According to the present invention, there is provided a method for producing a pyrolytic carbon-coated graphite member capable of forming a pyrolytic carbon film having a high degree of crystallinity on a graphite member while suppressing creep deformation without exposing the graphite member to a high temperature. Can be provided.
According to the present invention, pyrolytic carbon is coated on a graphite member using a hydrocarbon gas in a CVD furnace having a temperature of less than 2000 ° C., and then the pyrolytic carbon is coated in the presence of oxygen. It is characterized by that. According to this configuration, even if the temperature at which the graphite member is coated with pyrolytic carbon is a low temperature of less than 2000 ° C., since oxygen exists in the atmosphere, the crystallinity of the pyrolytic carbon can be increased. it can. The reason is not clear, but the source gas is not directly oxidized by oxygen, but after the source gas is once deposited as pyrolytic carbon, there is a process in which part of the pyrolytic carbon is oxidized by oxygen. it is conceivable that. Pyrolytic carbon is not a perfect graphite crystal, but has a portion in which the crystal structure is disordered and has grown. If dilute oxygen is contained, it is presumed that the crystallinity of pyrolytic carbon can be rapidly increased because the disorderly grown portion is selectively oxidized and removed.

FIG. 1 is a diagram showing a temperature and pressure profile in a CVD reactor in an example. FIG. 2 is a graph showing the results of Raman R values measured in the examples. FIG. 3 is an enlarged photograph of a cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 1. 4 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 1. FIG. FIG. 5 is an enlarged photograph of the cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 2. FIG. 6 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 2. FIG. 7 is an enlarged photograph of a cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 3. FIG. 8 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 3. FIG. 9 is an enlarged photograph of the cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 4. FIG. 10 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 4. FIG. 11 is an enlarged photograph of the cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 5. FIG. 12 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 5.

Hereinafter, the present invention will be described in more detail.
As the graphite member used in the present invention, general artificial graphite can be used, and its specific size, shape and the like can be variously selected according to the application, and is not particularly limited. In addition, the surface roughness Ra of the graphite member before coating with pyrolytic carbon is preferably 0.1 μm to 10 μm, and more preferably 0.3 μm to 3 μm. If surface roughness Ra is 0.1 micrometer or more, there exists an effect that the adhesiveness of a pyrolytic carbon film increases. Moreover, if surface roughness Ra is 10 micrometers or less, a more precise shape will be obtained and dimensional accuracy can be made high. The surface roughness Ra can be measured according to JIS B 0601.
Moreover, it is preferable that the thermal expansion coefficient of a graphite member is 3.0-5.0 * 10 < ^-6 > / degreeC. When the thermal expansion coefficient is within this range, a strong adhesion between the graphite member and the pyrolytic carbon film can be obtained, and the peeling can be made difficult.
Furthermore, the bulk density of the graphite member is preferably 1.6 to 1.8 g / cm ³ . If the bulk density is 1.6 g / cm ³ or more, since there are few pores that cause defects in the strength of the graphite member, a high-strength pyrolytic carbon-coated graphite member can be obtained. If the bulk density is 1.8 g / cm ³ or less, pores serving as anchors of the pyrolytic carbon coating can be sufficiently secured, so that the pyrolytic carbon can be made difficult to peel off. The bulk density of the pyrolytic carbon coating can be determined by an underwater substitution method.

  The coating of pyrolytic carbon on the graphite member is performed in a CVD furnace. As is well known, a CVD furnace includes a reaction chamber for coating pyrolytic carbon, a gas introduction pipe connected to the reaction chamber and introducing hydrocarbon gas and other purge gas, an exhaust pipe for discharging exhaust gas, and a graphite member. A heating means for heating and a vacuum pump for reducing the pressure of the reaction chamber as necessary are provided. Specifically, a graphite member is placed in the reaction chamber, and while the inside of the CVD furnace is heated to a temperature of less than 2000 ° C. by a heating means, hydrocarbon gas is supplied from the gas introduction tube to the reaction chamber, and exhaust gas is discharged from the exhaust tube. A pyrolytic carbon film is formed on the surface of the graphite member in the presence of oxygen while discharging and depressurizing the reaction chamber with a vacuum pump as necessary.

  As described above, the coating of pyrolytic carbon on the graphite member is performed in a CVD furnace at a temperature of less than 2000 ° C. When the temperature is lower than 2000 ° C., the graphite member is unlikely to undergo creep deformation, and high dimensional accuracy can be maintained even if the graphite member once processed precisely is coated with pyrolytic carbon.

  Further, the pyrolytic carbon coating on the graphite member is preferably performed in a CVD furnace having a temperature of 1200 ° C. or higher. When the temperature is 1200 ° C. or higher, thermal decomposition of the hydrocarbon gas is promoted, and a sufficient film formation rate can be obtained. A more preferable temperature range is 1300 to 1800 ° C. When the temperature is 1300 ° C. or higher, thermal decomposition of the hydrocarbon gas is further promoted, and a further sufficient film formation rate can be obtained. When the temperature is 1800 ° C. or lower, the graphite member is less prone to creep deformation, and even if the graphite member once processed precisely is coated with pyrolytic carbon, higher dimensional accuracy can be maintained.

  The hydrocarbon gas is not particularly limited, and examples thereof include methane gas, ethane gas, propane gas, ethylene gas, acetylene gas, and mixtures thereof. Among them, it is preferable to use methane gas because the number of carbon atoms contained in one molecule is the smallest. If the number of carbon atoms contained in one molecule is small, the number of carbon atoms attached in one decomposition reaction can be reduced, so that it is considered that the growth of a pyrolytic carbon film having a disordered structure can be suppressed. . Moreover, inert gas, such as nitrogen gas and argon gas, can also be supplied with hydrocarbon gas as needed.

The pressure in the CVD furnace at the time of thermal decomposition is, for example, 100 to 3000 Pa, and more preferably 200 to 1000 Pa. If the pressure in the CVD furnace is lower than 100 Pa, the generation rate of the pyrolytic carbon film is slowed, and the oxygen pressure is also reduced at the same time. Therefore, it is considered that the ability to repair the disordered crystal structure by oxygen is also lowered. When the pressure in the CVD furnace during pyrolysis exceeds 3000 Pa, the mean free path of the hydrocarbon gas is shortened, pyrolyzing before the hydrocarbon gas molecules collide with the graphite member, and soot is easily generated. It becomes easy to form a pyrolytic carbon film having a disordered structure. Further, it is considered that oxygen is consumed by the reaction with the hydrocarbon gas before the pyrolytic carbon film is formed, and the action of removing crystal defects is reduced.
If the pressure in the CVD furnace is 200 Pa or higher, the generation rate of the pyrolytic carbon film can be increased, and the oxygen pressure is also increased at the same time. Therefore, it is considered that the ability to repair the crystal structure disturbed by oxygen is improved. If the pressure in the CVD furnace during pyrolysis is 1000 Pa or less, the mean free path of the hydrocarbon gas becomes long, so it is difficult to pyrolyze before the hydrocarbon gas molecules collide with the graphite member, and the structure of the turbulent structure Pyrolytic carbon coating can be made difficult. Further, it is considered that oxygen is consumed by the reaction with the hydrocarbon gas before the pyrolytic carbon film is formed, and the action of removing crystal defects by oxygen can be increased.

  In the present invention, pyrolytic carbon coating is performed in the presence of oxygen. The partial pressure of oxygen is preferably 1000 to 17000 ppm relative to the partial pressure of the hydrocarbon gas. If the partial pressure of oxygen relative to the partial pressure of the hydrocarbon gas is 17000 ppm or less, it is considered that the pyrolytic carbon film is not excessively oxidized and only the crystal defect portion of the pyrolytic carbon can be selectively removed. It is considered that a sufficient film formation rate of the pyrolytic carbon film can be obtained. Moreover, since oxygen and hydrocarbon gas which is combustible gas will be mixed, if it is this range, it can keep away from the combustion range of hydrocarbon gas, Therefore Abrupt reaction can be prevented. On the other hand, if the partial pressure of oxygen with respect to the partial pressure of the hydrocarbon gas is 1000 ppm or more, it is considered that the crystal structure portion in which the pyrolytic carbon that is generated is disturbed can be efficiently removed. It is considered that a pyrolytic carbon coating can be easily obtained. Moreover, it is preferable that oxygen is mixed with hydrocarbon gas in advance and supplied into the CVD furnace. According to this embodiment, since the concentration of oxygen is less likely to occur, the ability to remove the crystal structure portion disturbed by oxygen is less likely to be biased, so that it is possible to easily obtain a pyrolytic carbon film having less disordered crystal structure. It is considered possible.

  The thickness of the pyrolytic carbon coating is preferably 3 μm to 200 μm. When the thickness of the pyrolytic carbon coating is 3 μm or more, it is difficult to form a thin portion, so that the graphite member as a base material can be hardly exposed. When the thickness of the pyrolytic carbon coating is 200 μm or less, delamination of the pyrolytic carbon coating in which crystals have a layer structure can be made difficult to occur. Furthermore, the thickness of the pyrolytic carbon coating is more preferably 5 μm to 50 μm. When the thickness of the pyrolytic carbon coating is 5 μm or more, it is difficult to form a portion with a thinner thickness, so that the graphite member as the base material can be hardly exposed. When the thickness of the pyrolytic carbon coating is 50 μm or less, delamination of the pyrolytic carbon coating in which crystals have a layer structure can be further prevented. The method for measuring the thickness of the pyrolytic carbon film can be obtained by breaking the pyrolytic carbon-coated graphite member and observing the fracture surface with a scanning electron microscope (SEM). Specifically, the scale having a known length can be obtained by observing the scale by the same method and comparing the interval between the scales and the thickness of the pyrolytic carbon coating.

  Thus, the pyrolytic carbon-coated graphite member of the present invention can be produced. Since the pyrolytic carbon-coated graphite member can form a pyrolytic carbon film having a high degree of crystallinity on the graphite member without being subjected to creep deformation, it has high dimensional accuracy and wear resistance.

As described above, according to the present invention, a pyrolytic carbon-coated graphite member capable of forming a pyrolytic carbon film having a high degree of crystallinity on a graphite member while suppressing creep deformation without exposing the graphite member to a high temperature. The manufacturing method of can be provided.
Further, according to the present invention, it is possible to provide a pyrolytic carbon-coated graphite member having a pyrolytic carbon film having a high degree of crystallinity on the graphite member and having high dimensional accuracy and wear resistance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not restrict | limited to the following example.

According to the temperature and pressure profile shown in FIG. (Experimental Examples 1-5)
In a reaction chamber of a CVD furnace, a graphite member made of rectangular isotropic graphite of 150 mm × 150 mm × 5 mm (ETU-10 manufactured by Ibiden Co., Ltd., surface roughness Ra = 0.6 μm, thermal expansion coefficient 4.2 × 10 ⁻⁶ / ° C.) (furnace packing), vacuuming was performed, and the pressure in the furnace was set to 100 Pa or less. Subsequently, the temperature in the CVD furnace was raised from room temperature to 1500 ° C. over 2 hours.
Next, while maintaining the temperature in the CVD furnace, methane gas as a source gas and hydrogen as a carrier gas were introduced, and a pyrolytic carbon coating process was performed for a time (film formation). The flow rate of hydrogen was 1.6 L / min and the flow rate of methane gas was 5.0 L / min. When the introduction was started, the furnace pressure increased to 500 Pa. The concentration of oxygen with respect to methane gas was adjusted in advance with a mixer outside the CVD furnace and used as a raw material gas. Table 1 shows the oxygen concentration relative to methane gas in Experimental Examples 1 to 5. After film formation, the introduction of methane gas and hydrogen was stopped. Then, it cooled to room temperature over 4 hours, maintaining the pressure in a CVD furnace at 100 Pa or less. After the cooling was completed, the pressure inside the CVD furnace was restored, and the pyrolytic carbon-coated graphite member was taken out from the CVD furnace (furnace out).
About the obtained pyrolytic carbon covering graphite member, the cross section and the surface were observed using SEM.
FIG. 3 is an enlarged photograph of a cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 1. 4 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 1. FIG. FIG. 5 is an enlarged photograph of the cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 2. FIG. 6 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 2. FIG. 7 is an enlarged photograph of a cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 3. FIG. 8 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 3. FIG. 9 is an enlarged photograph of the cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 4. FIG. 10 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 4. FIG. 9 is an enlarged photograph of the cross section of the pyrolytic carbon-coated graphite member obtained in Experimental Example 5. FIG. 10 is an enlarged photograph of the surface of the pyrolytic carbon-coated graphite member obtained in Experimental Example 5.

<Evaluation method of crystallinity>
About each manufactured pyrolytic carbon covering graphite member, Raman R value was measured. The Raman R value is an index indicating the number of edges of the crystal, and the smaller the index is, the fewer structural defects and the higher the crystallinity (graphitization degree). The R value is the intensity ratio of two Raman bands (I ₁₃₆₀ / I ₁₅₈₀ ). When disturbed graphite structure occurs, it becomes Raman band is observed at 1360 cm ^-1 and 1620 cm ^-1 in addition to the Raman band at 1580 cm ^-1, the Raman of 1580 cm ^-1 of these bands with structural disorder increases It is known that the relative strength with respect to the band increases and the overall shape becomes broader. The band of 1360 cm ^-1 and 1620 cm ^-1 as being due to the structural disorder (Disorder), with respect to graphite (Graphite) original G band (1580cm ^-1), D-band ^(1360cm -1), D 'band Abbreviated as (1620 cm ⁻¹ ). Thus, it is known that the Raman spectrum of graphite is extremely sensitive to structural defects as no other compound has, and is useful as a method for evaluating carbon materials.
FIG. 2 is a graph showing the results of Raman R values measured in the examples.
The measurement equipment and measurement conditions of Raman R value are shown below.
Measuring equipment: HORIBA HR800
Measurement conditions: measurement light wavelength 632.81 nm
No filter
Measuring range 1250-1750cm ^-1
Measurement time x number of measurements 5 seconds x 10 times

<Evaluation method of film thickness>
The film thickness was measured by simultaneously folding a test piece (7 × 7 × 20 mm) for film thickness measurement placed in a CVD furnace, and measuring the thickness of the pyrolytic carbon film that appeared on the fracture surface.

<Deposition rate>
The film thickness at each level obtained by the above method was divided by the time required for film formation to calculate the film formation rate per hour.

<Peel test>
In the peeling test, the pyrolytic carbon-coated graphite member was heated to 350 ° C. and then dropped in water at 25 ° C. to confirm the presence or absence of peeling.

  Table 1 shows the manufacturing conditions and evaluation results for each experimental example.

  From the results of Table 1 and FIG. 2, the R value of the Raman spectrum was 1.78 in the range where the partial pressure of oxygen with respect to the hydrocarbon gas was 0 ppm (Experimental Example 1), whereas the oxygen value with respect to the hydrocarbon gas. As the partial pressure increases, the R value of the Raman spectrum decreases at 200 to 17000 ppm (Experimental Examples 2 to 5), and the disorder of the crystal structure decreases. In particular, at 1000 to 17000 ppm (Experimental Examples 4 and 5), the R value was significantly reduced. In Experimental Examples 4 and 5, the film formation of the pyrolytic carbon film was slow although the oxygen was mixed in the source gas, but the film formation itself was possible. Further, it was confirmed that Experimental Examples 2 to 5 had no phenomenon of peeling in the peeling test as in Experimental Example 1, and ensured a certain peeling strength.

  From the above results, in the method for producing a pyrolytic carbon-coated graphite member in which a graphite member is coated with pyrolytic carbon by a CVD method using a hydrocarbon gas, even if the temperature of the graphite member is less than 2000 ° C., oxygen It was confirmed that there is an effect of obtaining a pyrolytic carbon-coated graphite member having a high degree of crystallinity by performing in the presence of.

This effect is thought to be because the source gas is not directly oxidized by oxygen, but there is a process in which part of the pyrolytic carbon is oxidized by oxygen after the source gas is once deposited as pyrolytic carbon. Pyrolytic carbon is not a perfect graphite crystal, but has a portion in which the crystal structure is disordered and has grown. If dilute oxygen is contained, it is presumed that the crystallinity of pyrolytic carbon can be rapidly increased because the disorderly grown portion is selectively oxidized and removed.
In addition, since this effect is considered to be obtained by the above mechanism, the conditions of film formation such as the type of hydrocarbon gas, the partial pressure of oxygen with respect to the hydrocarbon gas, the method of mixing, the temperature, etc. are limited to the range of this embodiment. Not applicable.

  As described above, according to the present invention, it is possible to form a pyrolytic carbon film having a high degree of crystallinity on a graphite member while suppressing creep deformation without exposing the graphite member to a high temperature. It has been found that a pyrolytic carbon-coated graphite member having dimensional accuracy and wear resistance can be provided.

Claims (4)

In the method for producing a pyrolytic carbon-coated graphite member in which a graphite member is coated with pyrolytic carbon by a CVD method using a hydrocarbon gas,
The temperature of the graphite member in the CVD method is less than 2000 ° C.,
The CVD method is performed in the presence of oxygen,
The method for producing a pyrolytic carbon-coated graphite member, wherein the oxygen partial pressure is 1000 to 17000 ppm relative to the hydrocarbon gas partial pressure.   The temperature of the said graphite member of the said CVD method is 1200 degreeC or more, The manufacturing method of the pyrolytic carbon covering graphite member of Claim 1 characterized by the above-mentioned.   The method for producing a pyrolytic carbon-coated graphite member according to claim 1 or 2, wherein the oxygen is supplied by being mixed with the hydrocarbon gas in advance.   The said hydrocarbon gas is methane gas, The manufacturing method of the pyrolytic carbon covering graphite member as described in any one of Claims 1-3.