C / C composites and silicon single crystal pulling furnace components

Abstract

To provide a C / C composite that can effectively reduce reactivity with gas such as a SiO gas.SOLUTION: The C / C composite is a C / C composite containing carbon fibers. When a peak center 2θ at 2 / 3 height of a peak height is represented as d0, a low angle side 2θ at 1 / 3 height of a peak height is represented as d1, and a high angle side 2θ at 1 / 3 height of a peak height is represented as d2, on a diffraction peak at a (002) plane of the C / C composite measured by an X-ray diffraction method, an asymmetric parameter P represented by a 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. The formula (1) is given by P=(d0-d1) / (d2-d0).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a C / C composite and also to a furnace component for pulling a Si single crystal, which uses the C / C composite. [Background technology]

[0002] Conventionally, the Czochralski method (CZ method) for producing silicon single crystals uses a quartz crucible for melting silicon (Si) inside it, and a carbon crucible for housing and supporting it from the outside. During use, the quartz crucible softens due to the heat of molten silicon, and its outer surface comes into close contact with the inner surface of the crucible. If the crucible is cooled in this state, large stresses will be generated in the carbon crucible, which has a larger thermal expansion coefficient than the quartz crucible.

[0003] Therefore, it has been proposed to manufacture crucibles for Si single crystal pulling furnaces out of carbon fiber reinforced carbon composite materials (C / C composites), which have 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, C / C composite components for Si single crystal pulling furnaces are attracting attention because of their long life, safe operation, light weight, and energy savings.

[0004] For example, Patent Document 1 below discloses a crucible for pulling single crystals made of a C / C composite with pyrolytic carbon formed on the surface. Also, Patent Document 2 below discloses a crucible for pulling single crystals made of a C / C composite in which not only the cylindrical body but also the bowl-shaped bottom is reinforced by a filament winding method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-219592 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-297276 Summary of the Invention [Problem to be solved by the invention]

[0006] The inside of a Si single crystal pulling furnace is as high as about 1500°C, and the atmosphere contains Si vapor and SiO gas, making it an extremely harsh environment for the carbon used as components in the Si single crystal pulling furnace. When carbon components are used in such an environment, the carbon may be gasified by the SiO gas, causing a decrease in thickness, or the volume may change as the carbon turns into SiC, reducing its mechanical strength.

[0007] In order to reduce such deterioration due to SiO gas, the surface of the C / C composite is coated with pyrolytic carbon in Patent Documents 1 and 2. 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.

[0008] An 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 Si single crystal pulling furnace component that uses the C / C composite. [Means for solving the problem]

[0009] The C / C composite according to the present invention is a C / C composite containing carbon fibers, wherein, 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, the asymmetry parameter P represented by the following formula (1) is 1.0 or more and 2.0 or less, and the bulk density is 1.70 g / cm 3 More than 2.00g / cm 3 It is characterized by the following:

[0010] P=(d0-d1) / (d2-d0)...Equation (1)

[0011] In the present invention, the true density of the C / C composite is 2.05 g / cm 3 More than 2.20g / cm 3 It is preferable that:

[0012] In the present invention, the open porosity of the C / C composite is preferably 16.5% or less.

[0013] In the present invention, the true density of the carbon fiber is 2.00 g / cm 3 More than 2.20g / cm 3 It is preferable that:

[0014] In the present invention, the carbon fibers may be short fibers having a length of 1 mm or more and 50 mm or less.

[0015] In the present invention, the C / C composite may be a C / C composite obtained from a molded article formed by a filament winding molding method.

[0016] The Si single crystal pulling furnace component according to the present invention includes a C / C composite constructed according to the present invention.

[0017] In the present invention, the Si single crystal pulling furnace component is preferably a crucible made of the C / C composite. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a C / C composite that can effectively reduce reactivity with gases such as SiO gas, and a Si single crystal pulling furnace component that uses the C / C composite. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing an example of the diffraction peak of the 002 plane in the X-ray diffraction spectrum of a C / C composite. [Figure 2] FIG. 2 is a schematic cross-sectional front view showing a furnace member for pulling a Si single crystal according to one embodiment of the present invention. [Figure 3] FIG. 3 shows the X-ray diffraction spectrum of the 002 plane of the C / C composite of Example 1. [Figure 4] FIG. 4 shows the X-ray diffraction spectrum of the 002 plane of the C / C composite of Example 4. [Figure 5] FIG. 5 shows the X-ray diffraction spectrum of the 002 plane of the C / C composite of Comparative Example 1. [Figure 6] FIG. 6 shows the X-ray diffraction spectrum of the 002 plane of the C / C composite of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below.

[0021] (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 X-ray diffraction spectrum of the C / C composite, the asymmetry parameter P, expressed by the following formula (1), is 1.0 or more and 2.0 or less in the diffraction peak of the 002 plane. The bulk density of the C / C composite is 1.70 g / cm. 3 More than 2.00g / cm 3 The following is the result.

[0022] P=(d0-d1) / (d2-d0)...Equation (1)

[0023] Note that d0, d1, and d2 in the above formula (1) can be explained as follows with reference to FIG.

[0024] FIG. 1 is a diagram showing an example of the diffraction peak of the 002 plane in the X-ray diffraction spectrum of a C / C composite.

[0025] As shown in Figure 1, in the X-ray diffraction spectrum of a C / C composite, the 2θ of the peak center at 2 / 3 of the peak height for the diffraction peak of the graphite 002 plane (hereafter referred to as graphite) is d0. The 2θ of the peak position on the low-angle side at 1 / 3 of the peak height is d1. The 2θ of the peak position on the high-angle side at 1 / 3 of the peak height is d2.

[0026] The C / C composite of the present invention has the asymmetry parameter P and bulk density within the above ranges, and therefore can effectively reduce reactivity with gases such as SiO gas. This point will be explained in detail below.

[0027] When using carbon components for single crystal pulling furnaces, SiO gas resistance is an important characteristic. In this case, it is important to reduce the surface area of the components to reduce reactivity, and reducing the porosity is effective for this purpose.

[0028] Furthermore, carbon members with high true density tend to have a high degree of graphitization, and because they have fewer edges of graphite crystals that act as reaction initiation points in terms of their crystal structure, they are less likely to be reactive with SiO gas.

[0029] 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 degree of graphitization of such C / C composites. The lattice constant C0 and crystallite size Lc can be calculated from the position and half-width of the diffraction lines, allowing for a quantitative evaluation of the degree of graphitization. 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 this method particularly suitable for measuring C / C composites.

[0030] 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 fiber.

[0031] Since carbon fibers often have a lower degree of graphitization than the carbon matrix, the carbon fiber peaks in XRD are often located at lower angles than the carbon matrix peaks, and as a result, the composite profile often shows asymmetric peaks with a tail on the low angle side.

[0032] For example, when determining C0(002) and Lc(002) from a composite profile obtained by the method specified by the JSPS method, C0(002) and Lc(002) are 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 with a large tailing 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.

[0033] As a result of extensive investigations, the present inventors have found that an asymmetry parameter P highly correlated with the average degree of graphitization of the carbon fiber and carbon matrix can be obtained even in a C / C composite having a composite profile that significantly tails toward the low-angle side. As described above, the asymmetry parameter P is determined 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 that is 1 / 3 of the peak height of the profile, when the peak center position is set to 2θ at the center in the width direction at a height that is 2 / 3 of the peak height.

[0034] 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, a parameter P between 1.0 and 2.0, can effectively reduce reactivity with gases such as SiO gas.

[0035] Furthermore, the inventors focused on the bulk density of the C / C composite and calculated the bulk density of the C / C composite to be 1.70 g / cm 3 More than 2.00g / cm 3 It has been found that the reactivity with gases such as SiO gas can be effectively reduced by the following:

[0036] The C / C composite of the present invention can effectively reduce the reactivity with gases such as SiO gas in a Si single crystal pulling furnace, and therefore can be suitably used as a component for a Si single crystal pulling furnace, and can be particularly suitably used as a crucible for a Si single crystal pulling furnace.

[0037] 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 more effectively reduced.

[0038] The asymmetry parameter P of a C / C composite can be reduced by using mesophase pitch carbon fibers as the carbon fibers or by using carbon fibers that have been pre-treated at high temperatures.

[0039] The densifying substance is not particularly limited, and may be carbon derived from CVI treatment, pitch, a carbonaceous substance derived from a thermosetting resin, metal silicon, silicon carbide, etc. These may be used alone or in combination.

[0040] The X-ray diffraction measurement of the C / C composite can be performed using CuKα radiation (wavelength 1.541 Å) by wide-angle X-ray diffraction. For example, the X-ray diffraction measurement device "SmartLab" manufactured by Rigaku Corporation can be used.

[0041] In the present invention, the bulk density of the C / C composite is preferably 1.70 g / cm 3 More preferably, 1.80 g / cm 3 or more, preferably 2.00 g / cm 3 or less, more preferably 1.90 g / cm 3 When the bulk density of the C / C composite is within the above range, the reactivity with gases such as SiO gas can be reduced more effectively.

[0042] 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 the dimensions and mass.

[0043] In addition, the bulk density of the C / C composite can be increased by using mesophase pitch carbon fiber as the carbon fiber, or by performing a densification step, increasing the heat treatment temperature, or extending the heat treatment time in the manufacturing method described below.

[0044] In the present invention, the true density of the C / C composite is preferably 2.05 g / cm 3 More preferably, 2.07 g / cm 3 or more, preferably 2.20 g / cm 3 or less, more preferably 2.18 g / cm 3 When the true density of the C / C composite is within the above range, the reactivity with gases such as SiO gas can be reduced more effectively.

[0045] The true density of a C / C composite can be measured, for example, by crushing the C / C composite to be measured and then subjecting it to a liquid phase immersion method using butanol.

[0046] 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 more effectively reduced. The lower limit of the open porosity of the C / C composite is not particularly limited, but can be, for example, 0.1%.

[0047] 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 of pores with pore radii of 68.7 μm to 0.0074 μm. The open porosity is then calculated from this and the bulk density.

[0048] In the present invention, the carbon fibers constituting the C / C composite are not particularly limited, and pitch-based carbon fibers or polyacrylonitrile-based carbon fibers (PAN-based carbon fibers) can be used. When PAN-based carbon fibers are used, mechanical strength can be further increased. However, mesophase pitch-based carbon fibers are preferably used from the viewpoint of excellent carbon mesh plane orientation and further increasing true density. Mesophase pitch-based carbon fibers have less exposed edges that are the starting point of reactions, and therefore have better chemical stability. Therefore, reactivity with gases such as SiO gas can be more effectively reduced. Furthermore, when mesophase pitch-based carbon fibers are used, thermal conductivity can also be further increased.

[0049] In the present invention, the carbon fibers constituting the C / C composite may be short fibers. In this case, molding may be performed by impregnating short fibers with resin to obtain a sheet-shaped prepreg (sheet molding compound, hereinafter abbreviated as SMC), laying the SMC in a female mold, and then inserting a male mold, applying pressure, and heating. 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 can be obtained that has excellent moldability and mechanical properties due to the flow of the fibers.

[0050] 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).

[0051] In the present invention, the true density of the carbon fiber constituting the C / C composite is preferably 2.00 g / cm 3 More preferably, 2.07 g / cm 3 or more, preferably 2.20 g / cm 3 or less, more preferably 2.18 g / cm 3 When the true density of the carbon fiber is within the above range, the reactivity with gases such as SiO gas can be reduced more effectively.

[0052] (C / C composite manufacturing method) The C / C composite of the present invention can be produced, for example, as follows.

[0053] First, a molded body is obtained by impregnating carbon fibers with a thermosetting resin, and molding the impregnated carbon fibers with a thermosetting resin such as a phenol resin, a furan resin, or a polycarbodiimide resin.

[0054] The method for forming the molded body is not particularly limited, but includes a method in which a 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 Si single crystal pulling furnace described later, a molded body can be formed by winding a carbon fiber impregnated with a thermosetting resin around a crucible-shaped mandrel and molding it.

[0055] Alternatively, carbon fibers may be cut to a predetermined length, impregnated with a thermosetting resin, and the resulting SMC may be molded into a molded article having a crucible-like shape or the like.

[0056] Next, the molded body is fired to carbonize the thermosetting resin, thereby obtaining a C / C composite.

[0057] The firing process is preferably carried out in a non-oxidizing atmosphere such as a nitrogen gas atmosphere to prevent oxidation of the C / C composite during normal manufacturing.

[0058] The firing temperature is not particularly limited, but can be, for example, 700° C. to 1300° C. The firing time is not particularly limited, but can be, for example, the maximum temperature holding time is 30 minutes to 600 minutes.

[0059] Furthermore, the pitch impregnation / sintering process 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.

[0060] The present invention may further include a densification step of densifying at least a portion of the open pores in the C / C composite, which can further reduce the open porosity of the C / C composite and further increase its density.

[0061] The densification step may be, for example, a step of impregnating open pores of a C / C composite with pitch or a thermosetting resin and carbonizing the composite.

[0062] The densification step may be a step of carrying out a CVI treatment.

[0063] The densification step may be a step of impregnating open pores of the C / C composite with molten silicon to convert it into silicon carbide.

[0064] These densification steps may be used alone or in combination.

[0065] (Si single crystal pulling furnace components) FIG. 2 is a schematic cross-sectional front view showing a furnace member for pulling a Si single crystal according to one embodiment of the present invention.

[0066] The Si single crystal pulling furnace component 1 shown in Figure 2 is a crucible made of the C / C composite of the present invention. 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.

[0067] Such a Si single crystal pulling furnace component 1 can be obtained by manufacturing a C / C composite using a crucible-shaped compact formed by winding carbon fibers impregnated with a thermosetting resin around a crucible-shaped mandrel using a filament winding molding method.

[0068] The Si single crystal pulling furnace member 1 may also be obtained by manufacturing a C / C composite using a crucible-shaped compact obtained by molding SMC with a metal mold.

[0069] The thickness of the Si single crystal pulling furnace member 1 can be set to, for example, 5 mm or more and 30 mm or less.

[0070] The furnace component 1 for pulling Si single crystals of this embodiment is made of the C / C composite of the present invention described above, and therefore can effectively reduce reactivity with gases such as SiO gas. As a result, the furnace component 1 for pulling Si single crystals is less likely to suffer from problems such as carbon being gasified by SiO gas, causing wall thinning, or volume change due to conversion to SiC, resulting in reduced mechanical strength, and is therefore highly reliable.

[0071] Next, the present invention will be clarified by showing specific examples and comparative examples of the present invention, but the present invention is not limited to the following examples.

[0072] Example 1 True density is 2.07g / cm 3 A crucible was obtained by forming a crucible using mesophase pitch-based carbon fiber with an elastic modulus of 640 GPa by a filament winding (FW) molding method. Specifically, a predetermined number of tows consisting of 12,000 filaments made of the prepared carbon fiber were aligned and impregnated with uncured phenolic resin, and then wound around a mandrel with a cylindrical straight body and a hemispherical bottom, resulting in a crucible with an inner diameter of 800 mm, a straight body height of 500 mm, and a straight body wall thickness of 10 mm.

[0073] Next, the obtained crucible molded body was heated to 200°C and maintained at that temperature for 1 day to harden the phenolic resin. The crucible molded body with the hardened phenolic resin was treated in a nitrogen atmosphere at 1000°C for 3 hours to carbonize the phenolic resin and obtain a fired body.

[0074] The fired body was then impregnated with 100°C pitch and fired twice in a nitrogen atmosphere at 1000°C for one hour. The body was then heat-treated in a vacuum furnace at 2000°C for three hours to obtain a C / C composite material.

[0075] The resulting C / C composite material was then machined to the desired shape, and then subjected to chemical vapor infiltration (CVI) using CH4 gas as the source gas at a temperature of 2000°C and a pressure of 3.3 kPa for 100 hours to deposit pyrolytic carbon. To achieve high purity, the material was then held in a chlorine gas stream at a temperature of 2000°C and a pressure of 1.3 kPa for 20 hours to remove impurities, yielding a C / C composite crucible.

[0076] The bulk density of the resulting crucible was 1.82 g / cm 3 , true density 2.10g / cm 3 The open porosity was 12.3%.

[0077] The bulk density was calculated by measuring the dimensions and mass after mechanically processing the sample into a rectangular parallelepiped. The true density was measured by pulverizing the C / C composite to be measured and then immersing it in 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.

[0078] 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 of pore radii of 68.7 μm to 0.0074 μm, and the open porosity was calculated from this and the bulk density.

[0079] Example 2 A C / C composite crucible was obtained in the same manner as in Example 1, except that the temperature during heat treatment in the vacuum furnace was set to 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 is 2.18 g / cm 3 The open porosity was 13.6%.

[0080] 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 one. 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 1.70 g / cm. 3 , true density 2.05g / cm 3 The open porosity was 15.3%.

[0081] Example 4 A C / C composite crucible was obtained in the same manner as in Example 3, except that the temperature during 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. The bulk density was 1.75 g / cm 3 The true density is 2.16 g / cm 3 The open porosity was 16.5%.

[0082] Example 5 Carbon fibers prepared in the same manner as in Example 1 were cut to a predetermined length and impregnated with phenolic resin to obtain SMC, which was then molded into a crucible molded body. More specifically, carbon fibers cut to a length of 25 mm were laid out in a tray in a random direction, resol-type phenolic resin was poured over them, and the solvent was evaporated in a 100°C dryer to adjust the volatile content to 5%, yielding a 1 mm thick sheet-like SMC. The obtained SMC was laid out between a male mold and a female mold, heated to 160°C, and then dried under a pressure of 30 kg / cm. 2 A pressure of 1.00 MPa was applied, and the pressure was maintained for 2 hours. After cooling, the crucible was demolded 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. Other points were the same as in Example 1 to obtain a C / C composite crucible. 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 found to be 1.80 g / cm. 3 The true density is 2.10 g / cm 3The open porosity was 13.0%.

[0083] (Comparative Example 1) True density is 1.74g / cm 3 A C / C composite crucible was obtained in the same manner as in Example 1, except that a PAN-based carbon fiber having an elastic modulus of 240 GPa was used. 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 1.58 g / cm 3 The true density is 1.93 g / cm 3 The open porosity was 17.0%.

[0084] (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 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. The bulk density was 1.46 g / cm 3 The true density is 2.02 g / cm 3 The open porosity was 25.6%.

[0085] (Reference example) Isotropic graphite (manufactured by Toyo Tanso Co., Ltd., product number "IG-56") was used after high-purification treatment. The bulk density, true density, and open porosity were measured in the same manner as in Example 1. The bulk density was 1.81 g / cm 3 , true density is 2.18g / cm 3 The open porosity was 15.0%.

[0086] [evaluation] (X-ray diffraction) The C / C composite was measured by X-ray diffraction using wide-angle X-ray diffraction with CuKα radiation (wavelength 1.541 Å). The X-ray diffraction measurement device used was a Rigaku Corporation model "SmartLab."

[0087] 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 Fig. 3 shows the results of Example 1, Fig. 4 shows the results of Example 4, Fig. 5 shows the results of Comparative Example 1, and Fig. 6 shows the results of Comparative Example 2. It can be seen from Figs. 3 to 6 that the asymmetry is reduced in Examples 1 and 4 compared to Comparative Examples 1 and 2.

[0088] 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.

[0089] Furthermore, in 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), where d0 is the central angle 2θ at 2 / 3 of the peak height, d1 is the angle 2θ on the low-angle side at 1 / 3 of the peak height, and d2 is the angle 2θ on the high-angle side at 1 / 3 of the peak height.

[0090] P=(d0-d1) / (d2-d0)...Equation (1)

[0091] The results are shown in Table 1 below.

[0092] (Relative SiC ratio) The SiC conversion ratio was measured for the C / C composite crucibles of Examples 1 to 5 and Comparative Examples 1 and 2, as well as 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 under the same conditions for 10 hours to react with the SiO gas, and the SiC conversion ratio of the carbon was measured from the mass change rate. The obtained SiC conversion ratios are shown in Table 1 below. Table 1 shows the relative SiC conversion ratios, with the SiC conversion ratio of Comparative Example 1 set to 100%.

[0093] [Table 1] [Explanation of symbols]

[0094] 1...Si single crystal pulling furnace components 2...Straight body part 3...Bottom 4…Central axis

Claims

1. 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 a height of ⅔ of the peak height is defined as d0, 2θ on the low-angle side at a height of ⅓ of the peak height is defined as d1, and 2θ on the high-angle side at a height of ⅓ 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, Bulk density: 1.70 g / cm ３ Above, 2.00g / cm ３ is as follows: A C / C composite having an open porosity of 16.5% or less. P=(d0-d1) / (d2-d0)...Formula (1)

2. True density is 2.05 g / cm ３ Above, 2.20g / cm ３ 2. The C / C composite of claim 1, wherein:

3. The true density of the carbon fiber is 2.00 g / cm ３ Above, 2.20g / cm ３ 3. The C / C composite according to claim 1 or 2, wherein:

4. The C / C composite according to any one of claims 1 to 3, wherein the carbon fibers are short fibers having a length of 1 mm or more and 50 mm or less.

5. The C / C composite according to any one of claims 1 to 3, which is formed by a molding formed by a filament winding molding method.

6. A silicon single crystal pulling furnace component comprising a C / C composite containing carbon fiber, 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 a height of ⅔ of the peak height is defined as d0, 2θ on the low-angle side at a height of ⅓ of the peak height is defined as d1, and 2θ on the high-angle side at a height of ⅓ 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, The bulk density of the C / C composite is 1.70 g / cm 3 or more and 2.00 g / cm 3 or less; A crucible for use in a Si single crystal pulling furnace, the crucible being made of the C / C composite. P=(d0-d1) / (d2-d0)...Formula (1)

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