JP5231316B2 - Carbon fiber reinforced carbon composite material, member for single crystal pulling apparatus, and method for producing carbon fiber reinforced carbon composite material - Google Patents

Description

The present invention, pyrolytic carbon is impregnated, coated carbon fiber reinforced carbon composite material, the carbon fiber reinforced carbon single crystal pulling apparatus for a member formed of a composite material, and method of manufacturing the carbon fiber reinforced carbon composite material About.

  A single crystal pulling apparatus used for the Czochralski method (hereinafter referred to as CZ method) tends to increase in size as the diameter of the single crystal increases. As a member used in a high-temperature atmosphere in the apparatus, an isotropic, high-density and high-purity graphite having excellent mechanical strength and heat resistance has been conventionally used. And with the enlargement of the equipment, the graphite member also becomes larger, so the graphite member also has to be thickened, which leads to a decrease in handling performance due to an increase in the weight of the graphite member and consequently a decrease in the effective dimension in the furnace. There's a problem.

  Accordingly, carbon fiber reinforced carbon composite materials (hereinafter referred to as C / C materials) that are lighter than graphite members and have mechanical strength equal to or higher than that of the graphite members have been attracting attention, and requested as an alternative to graphite high temperature members for single crystal pulling equipment. Has been.

  However, since the C / C material has a large specific surface area and large pores, it easily reacts with SiO gas generated from molten silicon filled in the apparatus, and has a problem that the rate of progress of SiC conversion is higher than that of graphite. is there.

  Therefore, as a method for suppressing the reaction with the SiO gas, the present applicant has proposed a method of impregnating and coating pyrolytic carbon on the C / C material by the CVI method as a crucible for a CZ apparatus (see Patent Document 1 below). ing. However, when impregnated and coated with pyrolytic carbon only by the CVI method, the impregnated layer can be formed deep, but the coating layer formed on the surface is thin, the surface has a large specific surface area, and there are no pores. SiC conversion was insufficient. Further, when the pyrolytic carbon is coated and impregnated only by the CVD method, contrary to the CVI method, the surface coating layer can be formed thick and the SiC resistance is improved. However, when the pyrolytic carbon coating layer on the surface is worn out, the impregnated layer inside is thin, so there is a risk that the C / C material will be converted to SiC at a stretch. Uncertainties remain in application.

International Publication No. 1997/49844

An object of the present invention performs a pyrolytic carbon CVI, the CVD continuously, impregnate the C / C material, coated, C / C material can exhibit excellent SiC reduction, formed by Re their The object is to provide a member for a single crystal pulling apparatus and a method for producing the C / C material .

  In order to solve the above problems, the present inventors have made use of the advantages of both the CVI method and the CVD method, that is, CVI treatment, followed by continuous CVD treatment, impregnated and coated with pyrolytic carbon. As a result, it was found that the peel resistance of the coating layer was improved, and the present invention was completed.

That is, the carbon fiber reinforced carbon composite material according to the first aspect of the present invention carbonizes a molded body formed by heating and curing a prepreg in which carbon fiber is impregnated with a resin in a reducing atmosphere, and pitch and / or Alternatively, after performing densification treatment by repeatedly impregnating and baking the resin a plurality of times, high-purification treatment is performed, and then a pyrolytic carbon impregnation layer is formed by CVI, and CVD is performed on the impregnation layer. By forming a coating layer of pyrolytic carbon, the average surface roughness of the coating layer is 5 μm or less.
The carbon fiber reinforced carbon composite material according to the second aspect of the present invention is obtained by carbonizing a molded body formed by heating and curing a prepreg obtained by impregnating a carbon fiber with a resin in a reducing atmosphere, thereby producing a pitch and / or resin. After performing the densification treatment by repeating the impregnation and firing several times, a graphitization treatment is performed, and then a pyrolytic carbon impregnation layer is formed by CVI, and further pyrolysis by CVD is performed on the impregnation layer. A carbon coating layer is formed, and the coating layer has an average surface roughness of 5 μm or less.
When the pyrolytic carbon is impregnated by the CVI method, pores in the vicinity of the surface layer portion and steps due to the fibers are filled, and a smooth surface can be formed when the pyrolytic carbon is coated on the surface by the CVD method.

  Moreover, by making average surface roughness 5 micrometers or less, a contact area with SiO gas can be made small and SiC-ized can be suppressed.

In the present invention, when the density difference between the impregnated layer and the coating layer is within 0.2 g / cm ³ , preferably within 0.1 g / cm ³ , there is no clear boundary between the impregnated layer and the coating layer, and the coating layer The peel resistance of the is improved.

Before SL impregnated layer and the coating layer is continuously formed in the same furnace preferably Rukoto. In this case , since the surface of the impregnation layer is not exposed to the outside air, the formation of a clear boundary between the impregnation layer and the coating layer is suppressed without interposition of impurities or the like between the impregnation layer and the coating layer. Can do.

The single crystal pulling apparatus according to the present invention is formed by the carbon fiber reinforced carbon composite material according to the present invention. Further, the method for producing a carbon fiber reinforced carbon composite material according to the first aspect of the present invention is a method of carbonizing a molded body formed by heating and curing a prepreg obtained by impregnating carbon fiber with a resin in a reducing atmosphere. And impregnating layer formation step of forming a pyrolytic carbon impregnation layer by CVI after performing densification treatment by repeating impregnation and firing of pitch and / or resin a plurality of times , and then performing purification treatment And a coating layer forming step of forming a coating layer of pyrolytic carbon on the impregnated layer by CVD. The method for producing a carbon fiber reinforced carbon composite material according to the second aspect of the present invention comprises carbonizing a molded body formed by heating and curing a prepreg impregnated with a resin in carbon fiber in a reducing atmosphere, An impregnation layer forming step of performing a densification treatment by repeatedly performing impregnation and firing of pitch and / or resin a plurality of times, followed by graphitization treatment, and then forming an impregnation layer of pyrolytic carbon by CVI; And a coating layer forming step of forming a pyrolytic carbon coating layer on the impregnated layer by CVD.

  In the present invention, the coating layer formed by the CVD layer is thicker than the conventional one, and has excellent characteristics in terms of SiC resistance. Further, since the coating layer is coated on the surface of the impregnated layer by the CVI method, the peeling resistance is also combined. It has the effect of having. In addition, even when the coating layer is eroded by the SiO gas, the impregnation layer can also have an effect of preventing the progress of SiC formation. In addition, since the surface roughness of the surface can be smoothed, the progress of SiC formation can be reliably suppressed. Further, by continuously performing CVI and CVD, the boundary between the impregnated layer and the coating layer is not clarified, and the effect of improving the peel resistance of the coating layer on the surface is obtained. In addition, the process can be simplified and the quality can be stabilized.

The relationship diagram of the generation temperature and density of pyrolytic carbon.

  The C / C material in the present invention is, for example, UD or 2-D starting from pitch-based or PAN-based carbon fibers, impregnated with resin, laminated and cured, or filament-winding the carbon fibers. The molded body is formed by a method of winding and heating and curing, or impregnating a 3-D or n-D fabric with a resin and heating and curing. Here, the carbon fiber of the innermost layer has a finer fiber density than that of a single piece of 3K cloth, and multi-layer attachment of 1K cloth is advantageous in order to reduce oxidation due to permeation of SiO gas. This molded body is carbonized in a reducing atmosphere. Next, the process of impregnating and baking the pitch or thermosetting resin is repeated several times to perform densification. Then, after the densification treatment, heat treatment is continued at a high temperature to perform graphitization treatment. Next, a high purity treatment is performed by reacting with a halogen gas at a high temperature (about 2000 ° C.). Note that the graphitization treatment and the high-purification treatment may be performed simultaneously in the same furnace. Further, densification may be performed by using a pitch and a thermosetting resin in combination.

Next, pyrolytic carbon is impregnated by the CVI method for the purpose of suppressing reaction with SiO gas. As a result, pores remaining in the surface layer portion can be filled. The impregnation of pyrolytic carbon by the CVI method is usually performed at a temperature of 800 to 1300 ° C. and 10 to 100 Torr (13.3 × 10 ^{2 to} 13.3 × 10 ³ Pa) in a hydrocarbon gas having 1 to 8 carbon atoms. Supply is performed at a flow rate of 10 to 100 l / min, and the holding time is adjusted to form a desired thickness. This impregnated layer has a role as a buffer layer for preventing peeling of the coating layer, and at least 5 to 20 μm in order to prevent the C / C material from becoming SiC when the coating layer on the surface is eroded or worn. Is preferably 5 to 10 μm. The carbon structure of the impregnated layer thus formed is mainly a columnar fine carbon structure (RC structure).

The surface pyrolytic carbon coating layer is formed by a CVD method in order to suppress reaction with SiO gas and prevent penetration of SiO gas into the interior. The CVD process is performed at a higher temperature and lower pressure than the processing temperature during the CVI process in order to increase the deposition rate. Here, it is known that the higher the temperature, the closer to the ideal density of carbon, but in the case of such a reactor, the higher the temperature, the higher the manufacturing cost. Since this is contrary to one of the objects of the present invention, the processing temperature in the present invention is 1500 to 2200 ° C., which is an industrially feasible temperature, and the processing pressure is ^{1 to} 10 Torr (13.3 × 10 ^{1 to} 13 In the range of 3 × 10 ² Pa), a hydrocarbon gas having 1 to 8 carbon atoms is supplied at a flow rate of 5 to 50 l / min, and the holding time is adjusted to form a desired thickness. If this coating layer is too thick, it may peel off, and it may not be too thin in order to prevent the penetration of SiO gas into the interior, and at least a thickness of 10 to 100 μm in order to delay the reaction to turn into SiC, Furthermore, it is preferable that it is 20-80 micrometers.

  Further, the surface coating layer is filled with pyrolytic carbon by the CVI method, and further, the surface step formed by the carbon fiber is filled. Therefore, by performing the CVD process, the surface roughness of the pyrolytic carbon coated on the surface can be set to 5 μm or less, and further to 4 μm or less. For this reason, the specific surface area of a surface becomes small and it becomes possible to suppress SiC-ization.

The pyrolytic carbon that forms the impregnation layer and the coating layer varies in density and shape depending on manufacturing conditions such as heating method, substrate temperature, gas concentration, gas type, and flow rate. As an example, FIG. 1 (Chemistry and Physics of Carbon, Vol. 5, P. 47) shows the relationship between density and pyrolytic carbon production temperature. As shown in the figure, the density of pyrolytic carbon is about 2.2 g / cm ³ in the low temperature range (800-1300 ° C.), but the density decreases in the temperature range of 1300-1700 ° C. The density begins to increase again in the temperature range exceeding ^1, and becomes about 2.2 g / cm ³ which is close to the ideal density of carbon. This is due to the synergistic effect of the nucleation rate and the growth rate. Both the nucleation rate and the growth rate increase as the temperature increases. Therefore, in the high temperature region, the nucleus is grown and oriented along with the precipitation of the nucleus and the deposition on the base material, and the crystallites are large, regularly oriented, and high density. On the other hand, since the substrate temperature is not sufficient for the nucleus growth in the low temperature region, the nuclei hardly grow, and the nuclei precipitated in the gas phase are deposited on the substrate and become high density. Further, in the middle temperature range, new nuclei are deposited before the nuclei on the base material are sufficiently grown and oriented, and are deposited on the nuclei, thereby causing a phenomenon of density reduction and re-increase. That is, in the generation mechanism of pyrolytic carbon, the deposition of nuclei generated in the gas phase on the base material is dominant in the low temperature range, but the growth and orientation of nuclei deposited on the base material in the high temperature range. Becomes dominant.

  In the present invention, fine high-density pyrolytic carbon of crystallites generated at a low temperature is impregnated, and large high-density pyrolytic carbon of crystallites generated continuously at a high temperature is coated thereon. At this time, the peel resistance of the coating layer is improved by making the densities of the both substantially the same. Here, the density is adjusted by adjusting the gas concentration in the furnace during the coating process. That is, the furnace temperature, gas flow rate, processing pressure, etc. are adjusted.

  In addition, when the CVI and CVD processes are performed separately, the boundary between pyrolytic carbon layers generated by both may appear clearly. For example, when the conditions at the time of each treatment are performed without considering the above-mentioned pyrolytic carbon generation mechanism, or when the CVD treatment is performed again after being taken out of the furnace and exposed to the outside air in the CVD furnace Etc. Once exited from the furnace after the CVI process is completed, impurities in the outside air are adsorbed on the surface, and impurities remaining on the surface during heating during the CVD process cause abnormal growth of nuclei during the CVD process. For example, the orientation of the nucleus may be hindered, such as not being oriented. These are considered to be one of the causes that the boundary between the impregnated layer and the coating layer to be formed clearly appears. When such a boundary is formed, the coating layer formed on the surface by the CVD method easily peels off or cracks due to thermal shock or the like. Therefore, even if both the impregnation layer and the coating layer are formed, the effect is halved.

Therefore, the structures of both the impregnation layer and the coating layer are aligned, the density difference is within 0.2 g / cm ^3, and a continuous layer is formed without clarifying the boundary. In order to have the combined characteristics, it is preferable to perform the impregnation and coating treatment continuously in the same furnace while adjusting the treatment conditions. Thereby, the pyrolytic carbon of the outermost core of the impregnated layer formed by the CVI method becomes a nucleus during the CVD process without being inhibited by impurities, and it is possible to form a new coating layer. it is conceivable that.

  In addition, since the CVI and CVD processes are continuously performed, it is possible to make the impregnation layer and the coating layer thicker than before. This is because peeling is less likely to occur. The surface roughness of the C / C material depends on the type of fiber forming the C / C material and the forming method, but the surface roughness can be controlled by CVI or CVD treatment. When the surface roughness is 5 μm or less, the specific surface area of the surface is reduced, that is, the surface contact area with the outside air is reduced, and the SiC resistance characteristics can be improved. Furthermore, by performing CVI and CVD processes continuously, the process can be simplified and the quality can be stabilized, and the high temperature for a single crystal pulling apparatus formed of a C / C material having excellent SiC resistance. A member can be provided.

Hereinafter, the present invention will be specifically described with reference to examples.
Example 1
A carbon fiber sheet (Toray, 6K plain weave) was impregnated with a phenol resin, the carbon fiber sheet was laminated, and then heat-treated in a 200 ° C. oven for 10 hours to cure the resin. Next, baking was performed at 1000 ° C. in a nitrogen atmosphere in an electric furnace. Further, pitch impregnation-firing was repeated three times for densification. Thereafter, heat treatment at 2000 ° C. was performed, and then processing into a shape of 60 × 10 × 3 (mm) was performed, and a high purity treatment was performed by reacting with halogen gas at 2000 ° C. Next, impregnation with pyrolytic carbon was carried out by supplying a CH ₄ gas at a flow rate of 10 l / min at 1100 ° C. and 10 Torr (13.3 × 10 ² Pa) and holding it for 100 hours. After the CVI treatment, it is continuously heated to 2000 ° C. in the same furnace, depressurized to 5 Torr (6.67 × 10 ² Pa), and CH ₄ gas is supplied at a flow rate of 5 l / min, and maintained for 3 hours. A thermal decomposition carbon layer having an average surface roughness of 1.9 μm and a thickness of 50 μm was formed by the CVD process to obtain a test sample.

(Example 2)
A C / C material having the same shape produced in the same manner as in Example 1 was subjected to high-purity treatment and impregnation treatment under the same conditions as in Example 1. Then, after the CVI treatment in the same manner as in Example 1, the average was continuously obtained by the CVD treatment that was held in the same furnace for 3 hours at 1800 ° C., 5 Torr (6.67 × 10 ² Pa), and CH ₄ gas flow rate of 5 l / min. A pyrolytic carbon layer having a surface roughness of 2.0 μm and a thickness of about 50 μm was formed to obtain a test sample.

(Example 3)
One layer of a PAN-based carbon fiber plain weave cloth (Torayca T-300 6K manufactured by Toray Industries, Inc.) impregnated with a phenol resin was applied to the mandrel surface, and filament winding was performed thereon. Filament winding consists of 5 layers of TORAYCA T-300 12K (manufactured by Toray Industries, Inc.) with 6 filaments impregnated with phenolic resin, level winding and parallel winding with a winding angle of 85 ° to 90 ° with respect to the central axis. I wrapped it. The body has 10 layers of parallel winding and level winding, but only the level winding at the bottom. As a result, a molded body having a layer thickness of 10 mm was obtained. Next, after adjusting the volatile content at 100 ° C. in an oven, the temperature of the oven was raised to 200 ° C. while evacuating the vacuum bag, and the molded body was thermally cured. After thermosetting, the molded body was removed from the mandrel. Next, in order to maintain the roundness of the body, a graphite deformation preventing jig is attached, and the temperature is raised to 1000 ° C. at a temperature rising rate of 10 ° C./hr while nitrogen is injected in an electric furnace. C material was obtained. This was heated to 2000 ° C. in a halogen gas atmosphere and held for 10 hours to perform a purification treatment. Further, pitch impregnation is performed, and the temperature is increased to 1000 ° C. at a temperature increase rate of 10 ° C./hr while nitrogen is injected in an electric furnace to perform firing. This was repeated twice and again heated to 2000 ° C. under normal pressure in a halogen gas atmosphere, and subjected to graphitization and high purification treatment. Thereafter, CVI treatment was performed under the same conditions as in Example 1. After CVI treatment, continuously for 3 hours in the same furnace at 1800 ° C., 5 Torr (6.67 × 10 ² Pa), and CH ₄ gas flow rate of 5 l / min. A pyrolytic carbon layer having an average surface roughness of 5.0 μm and a thickness of about 50 μm was formed by the retained CVD process, and a test sample was obtained.

(Comparative Example 1)
A high purity treatment and an impregnation treatment were performed on the C / C material having the same shape as in Example 1 under the same conditions as in Example 1. Thereafter, a CVD process in which CH ₄ gas is supplied at a flow rate of 5 l / min at 2000 ° C. and 5 Torr (6.67 × 10 ² Pa) as in Example 1 except that the CVI process is not performed. Was carried out to form a pyrolytic carbon layer having an average surface roughness of 5.0 μm and a thickness of 10 μm to obtain a test sample.

(Comparative Example 2)
A high purity treatment and an impregnation treatment were performed on the C / C material having the same shape as in Example 1 under the same conditions as in Example 1. Thereafter, as in Example 1, CH ₄ gas was supplied at a flow rate of 10 l / min at 1100 ° C. and 10 Torr (13.3 × 10 ² Pa), held for 100 hours, and only CVI treatment of pyrolytic carbon was performed. A test sample was obtained. The average surface roughness of the surface was 7.0 μm.

(Comparative Example 3)
A C / C material of the same shape produced in the same manner as in Example 1 was subjected to high-purity treatment and impregnation treatment under the same conditions as in Example 1, and was not subjected to CVI and CVD treatment, and was used as a test sample.

Samples obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were placed in a vacuum furnace together with metallic silicon, and conditions of 1800 ° C. and 100 Torr (13.3 × 10 ³ Pa) for 5 hours. A reactivity test was performed. After the test, the weight change of each sample was measured to examine the SiC conversion rate, that is, the reaction rate with SiO gas.

  Further, the samples obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to a rapid heating and quenching test. That is, a sample heated and rapidly heated to 1000 ° C. in 5 minutes was poured into water and rapidly cooled to examine the state of peeling of pyrolytic carbon. The number of samples is 5 each.

  Table 1 summarizes the SiC conversion rate, rapid thermal quench test results, CVI, and the density of pyrolytic carbon after CVD treatment. Here, the density of pyrolytic carbon was calculated by obtaining the degree of orientation from the diffraction intensity ratio of the [002] plane of carbon by X-ray diffraction analysis.

As can be seen from Table 1, impregnation layer, the samples of Examples 1 to 3 density difference is within 0.2 g / cm ³ of the coating layer are excellent peeling resistance, resistance to Si C resistance both . Further, the average surface roughness of the sample formed by the filament winding method as in Example 3 is a little worse than that in Examples 1 and 2, and accordingly, the SiC resistance is slightly worse. Moreover, since the comparative example 1 only coat | covered the pyrolytic carbon on the surface only by CVD, the surface coating layer peeled as a result of the rapid thermal quenching test. Since the sample of Comparative Example 2 is only impregnated with pyrolytic carbon by CVI treatment, the SiC resistance rate is poor.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

Claims (7)

A compact formed by heating and curing a prepreg impregnated with a resin in carbon fiber is carbonized in a reducing atmosphere, and pitch and / or resin impregnation and firing are repeated multiple times for densification treatment. Then , a high-purification treatment is performed, and then an impregnated layer of pyrolytic carbon is formed by CVI , and a coating layer of pyrolytic carbon is further formed on the impregnated layer by CVD,
The carbon fiber reinforced carbon composite material whose average surface roughness of the said coating layer is 5 micrometers or less. A compact formed by heating and curing a prepreg impregnated with a resin in carbon fiber is carbonized in a reducing atmosphere, and pitch and / or resin impregnation and firing are repeated multiple times for densification treatment. After performing the graphitization treatment, a pyrolytic carbon impregnation layer is formed by CVI , and a pyrolytic carbon coating layer is further formed by CVD on the impregnation layer.
The carbon fiber reinforced carbon composite material whose average surface roughness of the said coating layer is 5 micrometers or less. The carbon fiber reinforced carbon composite material according to claim 1 or 2 , wherein a density difference between the impregnation layer and the coating layer is 0.2 g / cm ³ or less. The carbon fiber reinforced carbon composite material according to any one of claims 1 to 3 , wherein the impregnation layer and the coating layer are formed continuously in the same furnace. The member for single crystal pulling apparatuses formed with the carbon fiber reinforced carbon composite material of any one of Claims 1-4 . A compact formed by heating and curing a prepreg with carbon fiber impregnated with resin is carbonized in a reducing atmosphere, and is densified by repeatedly impregnating and firing pitch and / or resin multiple times. After the treatment, an impregnation layer forming step of performing a purification treatment and then forming an impregnation layer of pyrolytic carbon by CVI;
A coating layer forming step of forming a pyrolytic carbon coating layer by CVD on the impregnated layer;
A method for producing a carbon fiber reinforced carbon composite material. A compact formed by heating and curing a prepreg with carbon fiber impregnated with resin is carbonized in a reducing atmosphere, and is densified by repeatedly impregnating and firing pitch and / or resin multiple times. An impregnation layer forming step of performing a graphitization treatment after the treatment, and then forming an impregnation layer of pyrolytic carbon by CVI;
A coating layer forming step of forming a pyrolytic carbon coating layer by CVD on the impregnated layer;
A method for producing a carbon fiber reinforced carbon composite material.

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