WO2024121901A1 - C/C COMPOSITE, AND MEMBER FOR Si SINGLE CRYSTAL PULLING-UP FURNACE - Google Patents

Abstract

Provided is a C/C composite which can effectively reduce reactivity with gas such as SiO gas.　This C/C composite contains a carbon fiber, wherein, in the diffraction peak in a 002 plane of the C/C composite, as measured by an X-ray diffraction method, when the 2θ of the peak center at a height corresponding to 2/3 of the peak height is d0, the 2θ of the low angle side at a height corresponding to 1/3 of the peak height is d1, and the 2θ of the high angle side at a height corresponding to 1/3 of the peak height is d2, the asymmetry parameter P represented by expression (1) is 1.0-2.0 and the bulk density is 1.70 g/cm³ to 2.00 g/cm³.　Expression (1): P=(d0-d1)/(d2-d0)

Description

C/C composites and silicon single crystal pulling furnace components

The present invention relates to a C/C composite. The present invention also relates to a component for a Si single crystal pulling furnace that uses the above-mentioned C/C composite.

Traditionally, the production of silicon single crystals using the Czochralski method (CZ method) involves the use of a quartz crucible for melting silicon (Si) inside it, and a carbon crucible to house it and support it from the outside. During use, the quartz crucible softens when exposed to the heat of molten silicon, and its outer surface comes into close contact with the inner surface of the crucible. If it is cooled in this state, large stress is generated in the carbon crucible, which has a larger thermal expansion coefficient than the quartz crucible.

Therefore, it has been proposed to manufacture crucibles for silicon single crystal pulling furnaces out of carbon fiber reinforced carbon composite material (C/C composite), which has the mechanical strength to withstand such stresses and can be easily made larger. C/C composites are easy to handle, lightweight, and less prone to cracking or chipping. In particular, silicon single crystal pulling furnace components made of C/C composites have attracted attention because of their features such as long life, safe operation, light weight, and energy saving.

For example, the following Patent Document 1 discloses a C/C composite crucible for pulling single crystals with pyrolytic carbon formed on the surface. The following Patent Document 2 discloses a C/C composite crucible for pulling single crystals in which not only the cylindrical body but also the bowl-shaped bottom is reinforced by the filament winding method.

JP 2000-219592 A JP 2007-297276 A

The inside of a silicon single crystal pulling furnace is as hot as 1500°C, and the atmosphere contains silicon vapor and SiO gas, making it an extremely harsh environment for the carbon used as a component of the silicon single crystal pulling furnace. If carbon components are used in such an environment, the carbon may be gasified by the SiO gas, causing a decrease in thickness, or may become SiC, causing a change in volume and reducing mechanical strength.

In order to reduce such deterioration due to SiO gas, in Patent Documents 1 and 2, the surface of the C/C composite is coated with pyrolytic carbon. However, there is a problem in that it is difficult to sufficiently reduce reactivity with gases such as SiO gas by simply coating the surface with pyrolytic carbon, as in the C/C composites of Patent Documents 1 and 2.

The object of the present invention is to provide a C/C composite that can effectively reduce reactivity with gases such as SiO gas, and a component for a Si single crystal pulling furnace that uses the C/C composite.

The C/C composite according to the present invention is a C/C composite containing carbon fibers, characterized in that, in a diffraction peak in a 002 plane of the C/C composite measured by an X-ray diffraction method, when 2θ at the peak center at 2/3 of the peak height is defined as d0, 2θ on the low-angle side at 1/3 of the peak height is defined as d1, and 2θ on the high-angle side at 1/3 of the peak height is defined as d2, an asymmetry parameter P represented by the following formula (1) is 1.0 or more and 2.0 or less, and a bulk density is 1.70 g/ ^cm3 or more and 2.00 g/ ^cm3 or less.

P = (d0 - d1) / (d2 - d0) ... Equation (1)

In the present invention, the true density of the C/C composite is preferably 2.05 g/cm ³ or more and 2.20 g/cm ³ or less.

In the present invention, it is preferable that the open porosity of the C/C composite is 16.5% or less.

In the present invention, the true density of the carbon fiber is preferably 2.00 g/cm ³ or more and 2.20 g/cm ³ or less.

In the present invention, the carbon fibers may be short fibers having a length of 1 mm or more and 50 mm or less.

In the present invention, the C/C composite may be composed of a C/C composite obtained from a molded body formed by a filament winding molding method.

The silicon single crystal pulling furnace component of the present invention includes a C/C composite constructed according to the present invention.

In the present invention, it is preferable that the Si single crystal pulling furnace component is a crucible made of the C/C composite.

The present invention provides a C/C composite that can effectively reduce reactivity with gases such as SiO gas, and a silicon single crystal pulling furnace component that uses the C/C composite.

FIG. 1 is a diagram showing an example of a diffraction peak of the 002 plane in an X-ray diffraction spectrum of a C/C composite. FIG. 2 is a schematic front sectional view showing a Si single crystal pulling furnace member according to one embodiment of the present invention. FIG. 3 is an X-ray diffraction spectrum of the 002 plane of the C/C composite of Example 1. FIG. 4 is an X-ray diffraction spectrum of the 002 plane of the C/C composite of Example 4. FIG. 5 is an X-ray diffraction spectrum of the 002 plane in the C/C composite of Comparative Example 1. FIG. 6 is an X-ray diffraction spectrum of the 002 plane in the C/C composite of Comparative Example 2.

The details of the present invention are explained below.

(C/C composite)
The C/C composite of the present invention is a carbon fiber reinforced carbon composite material. The C/C composite contains carbon fibers. In the diffraction peak of the 002 plane in the X-ray diffraction spectrum of the C/C composite, an asymmetry parameter P represented by the following formula (1) is 1.0 or more and 2.0 or less. In addition, the bulk density of the C/C composite is 1.70 g/ ^cm3 or more and 2.00 g/ ^cm3 or less.

P = (d0 - d1) / (d2 - d0) ... Equation (1)

Note that d0, d1, and d2 in the above formula (1) can be explained as follows, with reference to Figure 1.

Figure 1 shows an example of a diffraction peak of the 002 plane in the X-ray diffraction spectrum of a C/C composite.

As shown in Figure 1, in the diffraction peak of the graphite 002 plane (hereafter referred to as graphite) in the X-ray diffraction spectrum of a C/C composite, the 2θ of the peak center at 2/3 of the peak height is d0. The 2θ of the peak position on the low angle side at 1/3 of the peak height is d1. Additionally, the 2θ of the peak position on the high angle side at 1/3 of the peak height is d2.

The C/C composite of the present invention has the asymmetry parameter P and bulk density within the above ranges, so it can effectively reduce reactivity with gases such as SiO gas. This point will be explained in detail below.

When using carbon components for single crystal pulling furnaces, SiO gas resistance is an important characteristic. In that case, it is important to reduce the surface area of the components to reduce reactivity, and reducing the porosity is an effective way to achieve this.

In addition, carbon components with high true density tend to have a high degree of graphitization, and because the crystal structure has fewer edges of graphite crystals that serve as reaction initiation points, reactivity with SiO gas can be reduced.

C/C composites, which are carbon components, are composed of a carbon matrix made from starting materials such as resin and pitch, and carbon fibers. X-ray diffraction (XRD) can be used to measure the graphitization degree of such C/C composites, and the lattice constant C0 and crystallite size Lc can be calculated from the position and half-width of the diffraction lines, allowing the graphitization degree to be quantitatively evaluated. In particular, C0(002) and Lc(002) using the 002 diffraction line can be measured even in samples with a low degree of graphitization, making it particularly suitable for measuring C/C composites.

Analysis of C/C composites using X-ray diffraction (XRD) reveals a composite profile of the carbon matrix, which is made from starting materials such as resin and pitch, and the carbon fibers.

Since carbon fibers often have a lower degree of graphitization than the carbon matrix, the carbon fiber peaks in XRD often lie at lower angles than the carbon matrix peaks. For this reason, the composite profile often shows an asymmetric peak that tails on the lower angle side.

For example, when determining C0(002) or Lc(002) from a composite profile obtained by the method specified by the JSPS method, C0(002) or Lc(002) is calculated based on the angle at the center of the peak width at 2/3 of the peak height, or the peak width (half width) at 1/2 of the peak height. Therefore, in the case of a sample that shows a peak that tails significantly on the low angle side, a value that is strongly influenced by the carbon matrix may be calculated, and this value may be inappropriate as a measure of the average degree of graphitization of the carbon fiber and the entire carbon matrix.

After extensive research, the inventors have found that even in C/C composites with a composite profile that tails significantly toward the low angle side, an asymmetry parameter P that is highly correlated with the average degree of graphitization of the carbon fiber and carbon matrix can be obtained. As described above, the asymmetry parameter P is calculated from the ratio of the peak width on the low angle side to the peak width on the high angle side from the angle of the peak center position at a height of 1/3 of the peak height of the profile, when the 2θ at the center of the width direction at a height of 2/3 of the peak height is set as the peak center position.

The inventors then investigated the correlation between the asymmetry parameter P and the properties of C/C composites and found that C/C composites with a small asymmetry, that is, an asymmetry parameter P of 1.0 or more and 2.0 or less, can effectively reduce reactivity with gases such as SiO gas.

In addition, the present inventors focused on the bulk density of the C/C composite and found that by setting the bulk density of the C/C composite to 1.70 g/ ^cm3 or more and 2.00 g/ ^cm3 or less, the reactivity with gases such as SiO gas can be effectively reduced.

The C/C composite of the present invention can effectively reduce reactivity with gases such as SiO gas in a Si single crystal pulling furnace, and is therefore suitable for use in Si single crystal pulling furnace components, and is particularly suitable for use in crucibles for Si single crystal pulling furnaces.

In the present invention, the asymmetry parameter P of the C/C composite is preferably 1.0 or more, more preferably 1.2 or more, and preferably 2.0 or less, more preferably 1.5 or less. When the asymmetry parameter P of the C/C composite is within the above range, the reactivity with gases such as SiO gas can be reduced even more effectively.

The asymmetry parameter P of a C/C composite can be reduced by using mesophase pitch carbon fibers or carbon fibers that have been pretreated at high temperatures.

The densifying material is not particularly limited, and may be carbon derived from CVI processing, pitch, carbonaceous material derived from thermosetting resin, silicon metal, silicon carbide, etc. These may be used alone or in combination.

The X-ray diffraction measurement of the C/C composite can be performed by wide-angle X-ray diffraction using CuKα radiation (wavelength 1.541 Å). For example, the X-ray diffraction measurement device that can be used is Rigaku Corporation's "SmartLab" model.

In the present invention, the bulk density of the C/C composite is preferably 1.70 g/cm ^or more, more preferably 1.80 g/cm ^or more, and preferably 2.00 g/cm ^or less, more preferably 1.90 g/cm ^or less. When the bulk density of the C/C composite is within the above range, the reactivity with gases such as SiO gas can be more effectively reduced.

The bulk density of a C/C composite can be calculated, for example, by mechanically processing the C/C composite to be measured into a rectangular parallelepiped and then measuring its dimensions and mass.

The bulk density of the C/C composite can be increased by using mesophase pitch carbon fiber as the carbon fiber, or by carrying out a densification process, increasing the heat treatment temperature, or lengthening the heat treatment time in the manufacturing method described below.

In the present invention, the true density of the C/C composite is preferably 2.05 g/ ^cm3 or more, more preferably 2.07 g/ ^cm3 or more, and is preferably 2.20 g/ ^cm3 or less, more preferably 2.18 g/ ^cm3 or less. When the true density of the C/C composite is within the above range, the reactivity with gases such as SiO gas can be more effectively reduced.

The true density of a C/C composite can be measured, for example, by crushing the C/C composite to be measured and then performing a liquid phase immersion method using butanol.

In the present invention, the open porosity of the C/C composite is preferably 16.5% or less, more preferably 15.0% or less, and even more preferably 14.0% or less. When the open porosity of the C/C composite is equal to or less than the above upper limit, the reactivity with gases such as SiO gas can be reduced even more effectively. The lower limit of the open porosity of the C/C composite is not particularly limited, but can be, for example, 0.1%.

The open porosity of a C/C composite can be determined, for example, as follows. First, the C/C composite to be measured is cut into 5 mm squares to obtain a sample for mercury porosimetry. The cumulative pore volume of the obtained sample is measured using a mercury porosimeter, and the total open pore volume is obtained from the cumulative pore volume with pore radii between 68.7 μm and 0.0074 μm, and the open porosity is calculated from this and the bulk density.

In the present invention, the carbon fiber constituting the C/C composite is not particularly limited, and pitch-based carbon fiber or polyacrylonitrile-based carbon fiber (PAN-based carbon fiber) can be used. When PAN-based carbon fiber is used, the mechanical strength can be further increased. However, it is preferable to use mesophase pitch-based carbon fiber from the viewpoint of excellent orientation of the carbon net surface and further increasing the true density. Mesophase pitch-based carbon fiber has better chemical stability because the edge part that is the starting point of the reaction is less exposed. Therefore, reactivity with gases such as SiO gas can be more effectively reduced. In addition, when mesophase pitch-based carbon fiber is used, the thermal conductivity can be further increased.

In the present invention, the carbon fibers constituting the C/C composite may be short fibers. In this case, as a molding method, a method may be used in which the short fibers are impregnated with resin to obtain a sheet-shaped prepreg (sheet molding compound, hereinafter abbreviated as SMC), the SMC is laid in a female mold, and then a male mold is inserted, pressurized, and heated. The length of the carbon fibers is preferably 1 mm or more, more preferably 6 mm or more, and even more preferably 13 mm or more, and preferably 50 mm or less, more preferably 25 mm or less. The fiber diameter of the carbon fibers is preferably 1 μm or more, more preferably 5 μm or more, and preferably 20 μm or less, more preferably 12 μm or less. When the carbon fibers are such short fibers, a C/C composite with excellent moldability and mechanical properties accompanied by fiber flow can be obtained.

The length and diameter of the carbon fibers can be determined, for example, from the average values of 20 carbon fibers measured using a scanning electron microscope (SEM).

In the present invention, the true density of the carbon fiber constituting the C/C composite is preferably 2.00 g/ ^cm3 or more, more preferably 2.07 g/ ^cm3 or more, and preferably 2.20 g/ ^cm3 or less, more preferably 2.18 g/ ^cm3 or less. When the true density of the carbon fiber is within the above range, the reactivity with gases such as SiO gas can be more effectively reduced.

(Manufacturing method of C/C composite)
The C/C composite of the present invention can be produced, for example, as follows.

First, the carbon fibers are impregnated with a thermosetting resin and molded to obtain a molded body. Examples of the thermosetting resin that can be used include phenol resin, furan resin, and polycarbodiimide resin.

The method for forming the molded body is not particularly limited, but includes a method in which carbon fiber impregnated with a thermosetting resin is wound around a mandrel by a filament winding molding method. For example, when manufacturing a crucible for a silicon single crystal pulling furnace described below, a molded body can be formed by winding carbon fiber impregnated with a thermosetting resin around a crucible-shaped mandrel and molding it.

Also, carbon fibers can be cut to a specified length, impregnated with a thermosetting resin, and the resulting SMC can be molded in a die to obtain a molded body having a crucible-like shape, etc.

Then, the molded body is fired to carbonize the thermosetting resin and obtain a C/C composite.

The firing process is usually carried out in a non-oxidizing atmosphere, such as a nitrogen gas atmosphere, to prevent oxidation of the C/C composite during production.

The firing temperature is not particularly limited, but can be, for example, 700°C or higher and 1300°C or lower. The firing time is not particularly limited, but can be, for example, the maximum temperature holding time is 30 minutes or higher and 600 minutes or lower.

Furthermore, the pitch impregnation/sintering may be repeated to obtain a C/C composite with even higher density. The pitch impregnation/sintering process may be repeated, for example, one or more times and up to ten times.

The present invention may further include a densification step for densifying at least a portion of the open pores in the C/C composite. In this case, the open porosity of the C/C composite can be further reduced, and the density can be further increased.

The densification process can be, for example, a process in which pitch or a thermosetting resin is impregnated into the open pores of a C/C composite and then carbonized.

The densification process may be a process of performing CVI treatment.

The densification process may be a process in which molten silicon is infiltrated into the open pores of the C/C composite to convert it into silicon carbide.

These densification processes may be used alone or in combination.

(Si single crystal pulling furnace components)
FIG. 2 is a schematic front sectional view showing a Si single crystal pulling furnace member according to one embodiment of the present invention.

The Si single crystal pulling furnace component 1 shown in FIG. 2 is a crucible made of the C/C composite of the present invention described above. The Si single crystal pulling furnace component 1 comprises a straight body portion 2 and a bottom portion 3. The shape of the straight body portion 2 is not particularly limited, but in this embodiment, it is substantially cylindrical. The shape of the bottom portion 3 is not particularly limited, but in this embodiment, it is substantially hemispherical. In this embodiment, both the straight body portion 2 and the bottom portion 3 are made of a C/C composite.

Such a silicon single crystal pulling furnace component 1 can be obtained by manufacturing a C/C composite using a crucible-shaped body formed by winding carbon fiber impregnated with a thermosetting resin around a crucible-shaped mandrel using a filament winding molding method.

In addition, the Si single crystal pulling furnace component 1 may be obtained by manufacturing a C/C composite using a crucible-shaped molded body formed by molding SMC with a die.

The thickness of the Si single crystal pulling furnace component 1 can be, for example, 5 mm or more and 30 mm or less.

The Si single crystal pulling furnace component 1 of this embodiment is made of the above-mentioned C/C composite of the present invention, so it can effectively reduce reactivity with gases such as SiO gas. Therefore, the Si single crystal pulling furnace component 1 is less likely to have problems such as carbon being gasified by SiO gas and reducing its thickness, or volume change caused by conversion to SiC and reducing its mechanical strength, and is therefore highly reliable.

Next, the present invention will be clarified by presenting specific examples and comparative examples. Note that the present invention is not limited to the following examples.

Example 1
A crucible molded body was obtained by molding mesophase pitch carbon fiber having a true density of 2.07 g/ ^cm3 and an elastic modulus of 640 GPa by a filament winding (FW) molding method. Specifically, a predetermined number of tows each having 12,000 filaments made of the prepared carbon fiber were aligned and impregnated with uncured phenolic resin, and then wound around a mandrel having a cylindrical straight body with a diameter of 800 mm and a hemispherical bottom to obtain a crucible molded body having an inner diameter of 800 mm, a straight body height of 500 mm, and a straight body thickness of 10 mm.

Then, the obtained crucible molded body was heated to 200°C and held for one day to harden the phenolic resin. The crucible molded body with the hardened phenolic resin was treated in a nitrogen atmosphere at a temperature of 1000°C for three hours to carbonize the phenolic resin and obtain a fired body.

Furthermore, the sintered body was impregnated with pitch at 100°C and sintered twice in a nitrogen atmosphere at 1000°C for one hour. This was followed by a heat treatment in a vacuum furnace at 2000°C for three hours to obtain a C/C composite material.

Next, the obtained C/C composite material was machined into a predetermined shape, and then, by chemical vapor infiltration (CVI) using _CH4 gas as the raw material gas, pyrolytic carbon was deposited by holding for 100 hours under the conditions of a temperature of 2000°C and a pressure of 3.3 kPa. Then, in order to highly purify the material, impurities were removed by holding for 20 hours in a chlorine gas flow under the conditions of a temperature of 2000°C and a pressure of 1.3 kPa, and a C/C composite crucible was obtained.

The resulting crucible had a bulk density of 1.82 g/cm ³ , a true density of 2.10 g/cm ³ , and an open porosity of 12.3%.

The bulk density was calculated by measuring the dimensions and mass after mechanically processing into a rectangular parallelepiped. The true density was measured by pulverizing the C/C composite to be measured and then immersing it in a liquid phase using butanol. The open porosity was measured as follows. First, the obtained C/C composite was cut into 5 mm squares to obtain samples for mercury porosimetry.

The cumulative pore volume of the obtained sample was measured using a mercury porosimeter (Micromeritics, product number: AutoPore IV 9500), and the total open pore volume was obtained from the cumulative pore volume with pore radii of 68.7 μm to 0.0074 μm, and the open porosity was calculated from this and the bulk density.

Example 2
A C/C composite crucible was obtained in the same manner as in Example 1, except that the temperature during the heat treatment in the vacuum furnace was 2500° C. The bulk density, true density, and open porosity of the obtained C/C composite crucible were measured in the same manner as in Example 1. The bulk density was 1.82 g/cm ³ , the true density was 2.18 g/cm ³ , and the open porosity was 13.6%.

Example 3
A C/C composite crucible was obtained in the same manner as in Example 1, except that the number of times of pitch impregnation (the number of times the process of impregnating with pitch and holding and firing in a nitrogen atmosphere at 1000°C for 1 hour) was set to 1. The bulk density, true density and open porosity of the obtained C/C composite crucible were measured in the same manner as in Example 1, and the bulk density was 1.70 g/ ^cm3 , the true density was 2.05 g/ ^cm3 , and the open porosity was 15.3%.

Example 4
A C/C composite crucible was obtained in the same manner as in Example 3, except that the temperature during the heat treatment in the vacuum furnace was 2800° C. Furthermore, the bulk density, true density, and open porosity of the obtained C/C composite crucible were measured in the same manner as in Example 1, and the bulk density was 1.75 g/cm ³ , the true density was 2.16 g/cm ³ , and the open porosity was 16.5%.

Example 5
The carbon fibers prepared in the same manner as in Example 1 were cut to a predetermined length, impregnated with phenolic resin to obtain SMC, and molded to obtain a crucible molded body. More specifically, the carbon fibers cut to a length of 25 mm were laid out in a bat in a random direction, resol-type phenolic resin was poured in, and the solvent was evaporated in a 100°C dryer to adjust the volatile content to 5%, thereby obtaining a sheet-like SMC with a thickness of 1 mm. The obtained SMC was laid out between a male mold and a female mold, heated to 160°C, subjected to a pressure of 30 kg/ ^cm2 , held for 2 hours, cooled, and then demolded to obtain a crucible molded body with an inner diameter of 800 mm, a straight body height of 500 mm, and a straight body thickness of 10 mm. In other respects, a C/C composite crucible was obtained in the same manner as in Example 1. In addition, the bulk density, true density, and open porosity of the obtained C/C composite crucible were measured in the same manner as in Example 1. The bulk density was 1.80 g/ ^cm3 , the true density was 2.10 g/ ^cm3 , and the open porosity was 13.0%.

(Comparative Example 1)
Except for using PAN-based carbon fibers having a true density of 1.74 g/ ^cm3 and an elastic modulus of 240 GPa, a C/C composite crucible was obtained in the same manner as in Example 1. Furthermore, the bulk density, true density, and open porosity of the obtained C/C composite crucible were measured in the same manner as in Example 1, and the bulk density was 1.58 g/ ^cm3 , the true density was 1.93 g/ ^cm3 , and the open porosity was 17.0%.

(Comparative Example 2)
A C/C composite crucible was obtained in the same manner as in Comparative Example 1, except that the pitch impregnation was performed once and the temperature during the heat treatment in the vacuum furnace was set to 2800° C. The bulk density, true density, and open porosity of the obtained C/C composite crucible were measured in the same manner as in Example 1, and the bulk density was 1.46 g/ ^cm3 , the true density was 2.02 g/ ^cm3 , and the open porosity was 25.6%.

(Reference example)
Isotropic graphite (manufactured by Toyo Tanso Co., Ltd., product number "IG-56") was used after purification treatment. The bulk density, true density, and open porosity were measured in the same manner as in Example 1, and the bulk density was 1.81 g/cm ³ , the true density was 2.18 g/cm ³ , and the open porosity was 15.0%.

[evaluation]
(X-ray diffraction)
The X-ray diffraction measurement of the C/C composite was performed by wide-angle X-ray diffraction using CuKα radiation (wavelength 1.541 Å). The X-ray diffraction measurement device used was a Rigaku Corporation model number "SmartLab."

Figures 3 to 6 show X-ray diffraction spectra of the 002 plane of the C/C composites of Example 1, Example 4, Comparative Example 1, and Comparative Example 2. Note that Figure 3 shows the results of Example 1, Figure 4 shows the results of Example 4, Figure 5 shows the results of Comparative Example 1, and Figure 6 shows the results of Comparative Example 2. It can be seen from Figures 3 to 6 that asymmetry is reduced in Examples 1 and 4 compared to Comparative Examples 1 and 2.

The lattice constant C0(002) and crystallite size Lc(002) obtained from the 002 diffraction line were measured according to the revised Gakushin method (JIS R7651:2007). According to this method, the baseline is based on 2θ=29°, and the peak position is the central angle at 2/3 of the peak height.

Furthermore, for the C/C composites of Examples 1 to 5 and Comparative Examples 1 and 2, and the isotropic graphite of the Reference Example, the asymmetry parameter P, which represents the asymmetry at 1/3 of the peak height, was calculated using the following formula (1) when the central angle 2θ at 2/3 of the peak height was d0, the angle 2θ on the low angle side at 1/3 of the peak height was d1, and the angle 2θ on the high angle side at 1/3 of the peak height was d2.

P = (d0 - d1) / (d2 - d0) ... Equation (1)

The results are shown in Table 1 below.

(Relative SiC ratio)
The SiC ratio was measured for the C/C composite crucibles of Examples 1 to 5 and Comparative Examples 1 and 2, and the isotropic graphite crucible of the Reference Example. Specifically, _SiO2 and carbon were heated at a temperature of 1800°C and a pressure of 13 kPa to generate SiO gas, and the test piece was held for 10 hours under the same conditions to react with the SiO gas, and the SiC ratio of the carbon was measured from the mass change rate. The obtained SiC ratios are shown in Table 1 below. In Table 1, the relative SiC ratios are shown, with the SiC ratio of Comparative Example 1 taken as 100%.

Reference Signs List 1: Si single crystal pulling furnace member 2: body portion 3: bottom portion 4: central axis

Claims (8)

A C/C composite comprising carbon fibers,
In a diffraction peak in the 002 plane of the C/C composite measured by an X-ray diffraction method, when 2θ at the peak center at 2/3 of the peak height is d0, 2θ on the low angle side at 1/3 of the peak height is d1, and 2θ on the high angle side at 1/3 of the peak height is d2, an asymmetry parameter P represented by the following formula (1) is 1.0 or more and 2.0 or less,
A C/C composite having a bulk density of 1.70 g/ ^cm3 or more and 2.00 g/ ^cm3 or less.
P = (d0 - d1) / (d2 - d0) ... formula (1) 2. The C/C composite according to claim 1, having a true density of 2.05 g/ ^cm3 or more and 2.20 g/cm3 or ^less . The C/C composite according to claim 1 or 2, having an open porosity of 16.5% or less. The C/C composite according to any one of claims 1 to 3, wherein the true density of the carbon fiber is 2.00 g/ ^cm3 or more and 2.20 g/ ^cm3 or less. The C/C composite according to any one of claims 1 to 4, wherein the carbon fibers are short fibers having a length of 1 mm or more and 50 mm or less. The C/C composite according to any one of claims 1 to 4, which is composed of a molded body formed by a filament winding molding method. A component for a Si single crystal pulling furnace, comprising the C/C composite according to any one of claims 1 to 6. The Si single crystal pulling furnace component according to claim 7, which is a crucible made of the C/C composite.

Images