Composite material

Abstract

To provide a composite material which can be precisely processed.SOLUTION: The cross section SA of the composite material 10 includes a plurality of silicon-containing first regions S1 and a silicon-carbide-containing second region S2. When S1, which is the length of the short axis MN of the largest inscribed ellipse E that can be arranged inside the first area S1, is individually calculated for each of the plurality of first areas L1 included in the cross section SA, and a graph showing the relationship between the value of L1 and the frequency is drawn, the value of P1 corresponding to the first peak L1 having the highest frequency in the graph is 1.5 μm or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to composite materials comprising silicon and silicon carbide. [Background technology]

[0002] A composite material containing silicon and silicon carbide is also called "SiSiC" and is known as a material having high corrosion resistance, heat resistance, etc. As described in Patent Document 1 below, the composite material can be obtained, for example, by reactive sintering a molded body made of powdered carbon and silicon carbide while impregnating it with molten silicon.

[0003] The composite material is relatively lightweight yet highly rigid, and also has high thermal conductivity, making it promising for use in a variety of fields, including semiconductor manufacturing equipment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-348288 Summary of the Invention [Problem to be solved by the invention]

[0005] As shown in the figures in the above patent documents, when a composite material containing silicon and silicon carbide is cut, a cross section shows multiple regions that are cross sections of silicon carbide particles and regions containing silicon arranged in a matrix so as to fill the spaces between them. It is known that in conventional composite materials, the silicon carbide particles contained in the raw materials before sintering hardly grow during the sintering process. Therefore, the silicon carbide particle regions that appear in the cross section remain separated into multiple regions while generally maintaining their original size, with relatively large gaps between them. As a result, the area of ​​silicon filling the gaps between the silicon carbide particles in the cross section is relatively large.

[0006] The silicon portion of the composite material is weaker than the silicon carbide portion, and as a result, conventional composite materials have a tendency to be over-cut during processing due to the relatively large silicon area in the cross section, making it difficult to perform the precision processing required for semiconductor manufacturing equipment, etc.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a composite material that can be precisely processed. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a composite material containing silicon and silicon carbide, wherein a cross section of the composite material cut along a plane includes a plurality of first regions containing silicon and a second region containing silicon carbide. For each of the first regions included in the cross section, L1, which is the length of the minor axis of the largest ellipse that can be placed inside the first region, is calculated individually. When a graph is plotted showing the relationship between the L1 value and frequency, the L1 value corresponding to the first peak, which has the highest frequency, is 1.5 μm or less.

[0009] In a cross section of a composite material having such a configuration, if a graph showing the distribution of the L1 values ​​calculated individually for each first region is drawn, the L1 value corresponding to the most frequent first peak in the graph will be 1.5 μm or less. In other words, many of the multiple first regions appearing in the cross section of the composite material are distributed as small regions that can only encompass ellipses with minor axes of 1.5 μm or less. As a result, the proportion of the first regions in the cross section is relatively small. Because the proportion of the first regions, which are low-strength parts, is small, "overcutting" during processing is suppressed, making it possible to process the composite material more precisely than before.

[0010] Furthermore, in the composite material according to the present invention, it is also preferable that in addition to the first peak, a second peak with the second highest frequency is present in the graph. Experiments conducted by the present inventors have shown that adjusting the manufacturing conditions to make the first region containing silicon smaller than conventionally results in the appearance of a second peak (the second peak) in the graph showing the relationship between the L1 value and frequency. By making each first region smaller to the extent that the second peak appears, it is possible to improve processability significantly compared to conventionally possible.

[0011] In the composite material according to the present invention, it is also preferable that the value of L1 corresponding to the second peak is greater than 1.5 μm and not greater than 2.5 μm. By distributing the first regions in the cross section so that the second peak appears in the L1 value range of 1.5 μm to 2.5 μm, the processability of the composite material can be significantly improved.

[0012] Furthermore, in the composite material according to the present invention, when L2, which is the length of the major axis of the largest ellipse that can be arranged inside the first region, is calculated individually for each of the multiple first regions included in the cross section, and a graph showing the relationship between the L2 value and frequency is plotted, it is also preferable that the L2 value corresponding to the first peak, which has the highest frequency in the graph, is 1.5 μm or more and 3.0 μm or less.

[0013] The distribution of L2 values, which is the length of the major axis of the largest ellipse that can be placed inside the first region, was also measured for the composite material samples, and new findings were obtained regarding this distribution. Specifically, it was confirmed that if the L2 value corresponding to the most frequent first peak in the graph showing the distribution of L2 values ​​calculated individually for each first region falls within the range of 1.5 μm to 3.0 μm, the processability of the composite material will be improved.

[0014] Furthermore, the composite material according to the present invention preferably has a three-point bending strength of 500 MPa or more. By making the three-point bending strength 500 MPa or more, the processability of the composite material can be further improved.

[0015] In order to solve the above problems, the present invention provides a composite material containing silicon and silicon carbide, wherein a cross section of the composite material cut along a plane includes a plurality of first regions containing silicon and a second region containing silicon carbide. For each of the first regions included in the cross section, L2, which is the length of the major axis of the largest ellipse that can be placed inside the first region, is calculated individually. When a graph is plotted showing the relationship between the L2 value and frequency, the L2 value corresponding to the first peak, which has the highest frequency in the graph, is 1.5 μm or more and 3.0 μm or less.

[0016] In a cross section of a composite material having such a configuration, if a graph showing the distribution of the L2 values ​​calculated individually for each first region is drawn, the L2 value corresponding to the most frequent first peak in the graph will be in the range of 1.5 μm or more and 3.0 μm or less. In other words, since most of the multiple first regions appearing in the cross section of the composite material are distributed as small regions that satisfy the above condition, the proportion of the first regions in the cross section is relatively small. Since the proportion of the first regions, which are low-strength parts, is small, "over-cutting" during processing is suppressed, and therefore the composite material can be processed more precisely than before. [Effects of the Invention]

[0017] According to the present invention, a composite material that can be precisely processed can be provided. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing a cross section of a composite material according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing a cross section of a composite material according to an embodiment of the present invention. [Figure 3] FIG. 10 is a diagram for explaining a method for calculating L1 and L2. [Figure 4] 1 is a graph showing the relationship between the value of L1 and frequency in a cross section of a composite material according to the present embodiment. [Figure 5] 1 is a graph showing the relationship between the value of L2 and frequency in a cross section of a composite material according to the present embodiment. [Figure 6] FIG. 10 is a diagram showing a cross section of a composite material according to a comparative example. [Figure 7] 10 is a graph showing the relationship between the value of L1 and frequency in a cross section of a composite material according to a comparative example. [Figure 8] 10 is a graph showing the relationship between the value of L2 and frequency in a cross section of a composite material according to a comparative example. [Figure 9] FIG. 10 is a diagram showing the evaluation results of a composite material. [Figure 10] FIG. 10 is a diagram showing the evaluation results of a composite material. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0020] The composite material 10 according to this embodiment is a solid material containing silicon and silicon carbide, and is also known as "SiSiC," etc. The composite material 10 is used, for example, as a material for components constituting semiconductor manufacturing equipment, but its specific use, final shape, etc. are not particularly limited.

[0021] As will be explained later, composite material 10 is a molded body made of powdered carbon and silicon carbide that is impregnated with molten silicon and then reactively sintered. In this respect, it is similar to conventional SiSiC. However, composite material 10 according to this embodiment differs from conventional SiSiC in the shape of each region that appears in a cross section when cut.

[0022] The image shown in FIG. 1 was obtained by observing a cross section SA, which was revealed by cutting the composite material 10 along a plane, with a scanning electron microscope (SEM). The area of ​​the cross section SA is 500 μm × 350 μm, and the magnification is 250 times. Each of the white regions scattered across the cross section SA has been confirmed to be a region primarily containing silicon (Si). These regions will also be referred to as "first region S1" below. The black region of the cross section SA surrounding the first region S1 has been confirmed to be a region primarily containing silicon carbide (SiC). These regions will also be referred to as "second region S2" below.

[0023] The first region S1 may be a region that is 100% silicon, or may be a region that contains components other than silicon. Similarly, the second region S2 may be a region that is 100% silicon carbide, or may be a region that contains components other than silicon carbide.

[0024] It has been confirmed that the cross section SA also contains scattered regions that do not fall into either the first region S1 or the second region S2. Examples of such regions include regions containing carbon particles, which are one of the raw materials used in molding.

[0025] Figure 2 shows the distribution of second regions S2 on the cross section SA. In Figure 2, each second region S2 is displayed as a black region by performing image processing (binarization) on the cross section SA of Figure 1. In Figure 2, the white region surrounding the second region S2 roughly coincides with the first region S1.

[0026] As shown in Fig. 2, in the cross section SA of the composite material 10, a plurality of first regions S1 are present, and these are spaced apart and dispersed in a substantially uniform manner. Most of the first regions S1 are surrounded from the outside and over the entire periphery by second regions S2. In an image obtained by observation at a magnification of 250 times or less, as in Fig. 1, the second regions S2 are observed to be a single continuous region without any intervening grain boundaries.

[0027] The second region S2 can be observed as a "single continuous region without grain boundaries" at least when observed with a scanning electron microscope at a magnification of 250x or less. When the second region S2, which completely surrounds the first region S1, is observed in detail at a magnification of more than 250x, grain boundaries dividing the second region S2 or boundaries equivalent thereto may be observed.

[0028] Furthermore, if each of the first regions S1 is distributed as a small region that satisfies the conditions described below, grain boundaries that divide the second region S2 into multiple regions may be observed in an image obtained at a magnification of 250 times or less, such as that shown in Figure 1.

[0029] FIG. 3(A) shows one of the multiple first regions S1 in the cross section SA, and is a schematic drawing of only the first region S1 indicated by the arrow AR in FIG. 2. FIG. 3(B) shows the same first region S1 as in FIG. 3(A) superimposed with the corresponding inscribed ellipse E. The "inscribed ellipse E" is the largest ellipse that can be arranged so that it fits entirely within the first region S1. The lengths of the major axis MJ and minor axis MN of the inscribed ellipse E and their ratio can be freely set as long as the inscribed ellipse E does not extend beyond the first region S1. The inscribed ellipse E can also be said to be an ellipse obtained by adjusting the major axis MJ and minor axis MN so that its area is maximized within the range that does not extend beyond the first region S1. The shape of the inscribed ellipse E is uniquely determined corresponding to the shape of each first region S1.

[0030] The length of the minor axis MN of the inscribed ellipse E will be referred to as "L1" below. The length of the major axis MJ of the inscribed ellipse E will be referred to as "L2" below.

[0031] By individually calculating the length L1 of the minor axis MN of the corresponding inscribed ellipse E for each of the multiple first regions S1 included in the cross section SA in Figure 2, a graph showing the distribution of L1 can be drawn. Such a graph can be drawn, for example, as the histogram shown in Figure 4. The horizontal axis of the graph in Figure 4 represents the "classes" into which the L1 values ​​are divided into predetermined ranges. The unit of values ​​is "μm." The vertical axis of the graph in Figure 4 represents, for each of the above classes, the "frequency" of the first regions S1 to which L1 belongs, i.e., the frequency of L1 in the cross section SA.

[0032] The graph showing the relationship between the L1 value and frequency may be drawn as a histogram as shown in Figure 4, or as another graph. For example, a graph showing the frequency of L1 may be drawn as a continuous curve, like a normal distribution graph.

[0033] As shown in FIG. 4, when a graph showing the frequency of L1 for cross section SA is drawn, two peaks P1 and P2 appear on the graph.

[0034] Peak P1 is the peak with the highest frequency in the graph of FIG. 4. Peak P1 corresponds to the "first peak" in the graph of FIG. 4. The L1 value corresponding to peak P1 is approximately 1.15 μm. When the graph is depicted as a histogram as in this embodiment, the "L1 value corresponding to peak P1" refers to any value within the range of the class to which peak P1 belongs. For example, it can be set to the median value of the range of the class to which peak P1 belongs. In the example of FIG. 4, peak P1 belongs to the class of 0.981 to 1.311, so the L1 value corresponding to peak P1 is (0.981 + 1.311) / 2 = 1.146 μm.

[0035] Peak P2 is the peak with the second highest frequency in the graph of FIG. 4. Peak P2 corresponds to the "second peak" in the graph of FIG. 4. The L1 value corresponding to peak P2 is approximately 2.14 μm. The "L1 value corresponding to peak P2" is defined in the same way as the "L1 value corresponding to peak P1" described above, so explanation will be omitted. In the example of FIG. 4, peak P2 belongs to the class of 1.971 to 2.301, so the L1 value corresponding to peak P2 is (1.971 + 2.301) / 2 = 2.136 μm.

[0036] Similarly to the above, by individually calculating the length L2 of the major axis MJ of the corresponding inscribed ellipse E for each of the multiple first regions S1 included in the cross section SA in Figure 2, it is possible to plot a graph showing the distribution of L2. Such a graph can be plotted, for example, as the histogram shown in Figure 5. The definitions of the horizontal and vertical axes of the graph in Figure 5 are the same as those in Figure 4, so further explanation will be omitted. The graph showing the distribution of L2 may also be plotted as a continuous curve, for example, like a normal distribution graph.

[0037] As shown in FIG. 5, only a single peak P11 appears in the graph showing the frequency of L2. Peak P11 is the peak with the highest frequency in the graph. Peak P11 corresponds to the "first peak" in the graph of FIG. 5. The L2 value corresponding to peak P11 is approximately 2.18 μm. The "L2 value corresponding to peak P11" is defined in the same way as the "L1 value corresponding to peak P1" described above, so further explanation will be omitted. In the example of FIG. 4, peak P11 belongs to the class of 1.828 to 2.528, so the L2 value corresponding to peak P11 is (1.828 + 2.528) / 2 = 2.178 μm.

[0038] To compare with the composite material 10 having the above-described configuration, a comparative composite material 11 will be described. The image in FIG. 6(A) is an image obtained by observing a cross section SB, which appears when the composite material 11 according to the comparative example is cut along a plane, with a scanning electron microscope (SEM). As in FIG. 1, the area of ​​the cross section SB is 500 μm × 350 μm, and the magnification is 250 times. FIG. 6(B) is a schematic redrawing of a portion of FIG. 6(A) that has been enlarged.

[0039] The region marked with the symbol "S11" in Fig. 6(B) is a region that mainly contains silicon, similar to the first region S1 in Fig. 2. The region marked with the symbol "S12" in Fig. 6(B) is a region that mainly contains silicon carbide, similar to the second region S2 in Fig. 2.

[0040] In the comparative example of Figure 6, the regions S12 (silicon carbide) exist as relatively large particles, and there are multiple such particles in the cross section SB. Some of the multiple regions S12 are in contact with each other, but the regions S12 are separated by grain boundaries. Furthermore, because each region S12 is relatively large, each of the multiple regions S11 (silicon) in the gaps between them is relatively wide.

[0041] In this comparative example as well, an inscribed ellipse E can be drawn for each region S11, and the distribution of the lengths L1 of the minor axes MN and the distribution of the lengths L2 of the major axes MJ can be calculated.

[0042] The graph shown in FIG. 7 shows the distribution of L1 at cross section SB (FIG. 6) in a manner similar to that shown in FIG. 4. As shown in FIG. 7, only a single peak P1 appears in the graph showing the frequency of L1 in this comparative example. Peak P1 is the peak with the highest frequency in the graph of FIG. 7 and corresponds to the "first peak" in the graph. The L1 value corresponding to peak P1 is approximately 2.33 μm, which is larger than the value in this embodiment (1.15 μm as mentioned above).

[0043] The graph shown in FIG. 8 shows the distribution of L2 at cross section SB (FIG. 6) in the same manner as FIG. 5. As shown in FIG. 8, only a single peak P11 appears in the graph showing the frequency of L2 in this comparative example. Peak P11 is the peak with the highest frequency in the graph of FIG. 8, and corresponds to the "first peak" in the graph. The L2 value corresponding to peak P11 is approximately 3.83 μm, which is larger than the value in this embodiment (2.18 μm mentioned above).

[0044] As described above, in the composite material 10 of this embodiment, each of the first regions S1 on the cross section SA is made smaller so that the peak of the distribution of L1 calculated for each of the first regions S1 appears at a smaller value than in the comparative example.

[0045] In composite material 10 having such a configuration, the proportion of first region S1 in cross section SA is relatively small. As is generally known, silicon contained in first region S1 has lower strength than silicon carbide contained in second region S2. In composite material 10, the proportion of first region S1, which is a portion with lower strength, is small, which suppresses "excessive cutting" during processing, making it possible to perform more precise processing than conventional methods.

[0046] FIG. 9 shows the results of an experiment comparing the processability of the composite material 10 according to this embodiment with the processability of the composite material 11 according to the comparative example.

[0047] The "first peak of the minor axis" in the table of Figure 9 refers to the L1 value corresponding to the first peak in a graph showing the distribution of L1 for each cross-section of each sample. In other words, it refers to the L1 value corresponding to peak P1 in Figures 4 and 7. The unit is "μm." In Figure 9, the L1 value corresponding to peak P1 was calculated for each of multiple cross-sections in a single sample, and each obtained value is shown as a range as the "first peak of the minor axis." As in Figure 1, the image of each cross-section to be measured was an image of an area of ​​500 μm × 350 μm, and the magnification was 250x. The range of the cross-section used to measure the L1 distribution may be wider than the above.

[0048] In the composite material 10 according to this embodiment, the first peak of the minor axis was calculated to be in the range of 0.98 μm to 1.3 μm. In this embodiment, it was confirmed that the first peak of the minor axis was always within the range of 1.5 μm or less, regardless of the method of taking the cross section. On the other hand, in the composite material 11 according to the comparative example, the first peak of the minor axis was calculated to be in the range of 0.98 μm to 8.0 μm.

[0049] The "second peak of the minor axis" in the table of FIG. 9 refers to the L1 value corresponding to the second peak in a graph showing the distribution of L1 for the cross-section of the sample of this embodiment. In other words, it refers to the L1 value corresponding to peak P2 in FIG. 4. The unit is "μm." In FIG. 9, the L1 value corresponding to peak P2 is calculated for each of multiple cross-sections in one sample, and each obtained value is shown as a range as the "second peak of the minor axis." The image of each cross-section to be measured is the same as the image used to calculate the first peak of the minor axis.

[0050] In the composite material 10 according to this embodiment, the second peak of the minor axis was calculated to be in the range of 1.9 μm to 2.4 μm. In this embodiment, it was confirmed that the second peak of the minor axis was always greater than 1.5 μm and equal to or less than 2.5 μm, regardless of how the cross section was taken. Note that, since no second peak appeared in the comparative example, the "second peak of the minor axis" was not calculated.

[0051] The "first peak of the major axis" in the table of Figure 9 refers to the L2 value corresponding to the first peak in a graph showing the distribution of L2 for the cross section of each sample. In other words, it refers to the L2 value corresponding to peak P11 in Figures 5 and 8. The unit is "μm." In Figure 9, the L2 value corresponding to peak P11 is calculated for each of multiple cross sections in one sample, and each obtained value is shown as a range as the "first peak of the major axis." The image of each cross section to be measured is the same as the image used to calculate the first peak of the minor axis, etc.

[0052] In the composite material 10 according to this embodiment, the first peak of the major axis was calculated to be in the range of 1.7 μm to 2.7 μm. In this embodiment, it was confirmed that the first peak of the major axis was always in the range of 1.5 μm or more and 3.0 μm or less, regardless of how the cross section was taken. On the other hand, in the composite material 11 according to the comparative example, the first peak of the major axis was calculated to be in the range of 1.1 μm to 16.0 μm.

[0053] In calculating the first peak of the minor axis, the second peak of the minor axis, and the first peak of the major axis as described above, the images of Figures 1 and 6 obtained by observation using a scanning electron microscope were subjected to binarization processing using image analysis software to extract only the second region S2 of each, creating an image like that shown in Figure 2. Then, using the analysis functions of the image analysis software, the inscribed ellipse E for each first region S1 was created, L1 and L2 were calculated, and statistical processing was performed to calculate the first peak of the minor axis, etc.

[0054] The "machining depth" in the table of FIG. 9 refers to the measurement results, expressed in mm, of the depth of the recesses formed on the surface of each sample, measured using a gauge after sandblasting under the same conditions. In the example of FIG. 9, for each of the present embodiment and the comparative example, sandblasting was performed on three portions of one sample, and the machining depth of each portion was measured. The "average machining depth" shown in FIG. 9 is the average value of the machining depths at these three locations. For composite material 10 according to the present embodiment, the measured average machining depth was 2.89 mm. For composite material 11 according to the comparative example, the measured average machining depth was 4.83 mm. Thus, it was confirmed that composite material 10 according to the present embodiment has a smaller average machining depth than the comparative example, making it a material that is easier to precisely machine.

[0055] In addition to the present embodiment shown in FIG. 1 and elsewhere, the inventors have produced several types of composite material 10 under different manufacturing conditions, calculating various indices such as the "first peak of the minor axis" and measuring the average processing depth for each sample. These measurements confirmed that if the first peak of the minor axis, such as peak P1 in FIG. 4, is within the range of 1.5 μm or less, the average processing depth is smaller than conventional methods, and processability is significantly improved. Furthermore, if a second peak of the minor axis, such as peak P2 in FIG. 4, appears on the graph and is greater than 1.5 μm and less than 2.5 μm, processability is further improved. Furthermore, if the first peak of the major axis, such as peak P11 in FIG. 5, is within the range of 1.5 μm or more and 3.0 μm or less, processability is significantly improved. The indicator that the first peak of the major axis is within the range of 1.5 μm or more and 3.0 μm or less can be used as an indicator independent of the first peak of the minor axis, etc.

[0056] FIG. 10 shows the results of comparing various physical properties of the composite material 10 according to this embodiment with the same physical properties of the composite material 11 according to the comparative example.

[0057] The "bulk density" in the table of Fig. 10 is the apparent density of each sample, i.e., the mass per unit volume of the composite material including pores, etc., expressed in "g / cm 3 The bulk density of the composite material 10 according to this embodiment is 3.03 g / cm 3 The bulk density of the composite material according to the comparative example is 3.00 g / cm 3 It was.

[0058] 10, the Young's modulus of each sample is measured by the measurement method specified in JIS R 1602, and the obtained value is expressed in units of GPa. The Young's modulus of the composite material 10 according to this embodiment was 371 GPa, and the Young's modulus of the composite material according to the comparative example was 340 GPa.

[0059] 10, the "three-point bending strength" is the value obtained by measuring the three-point bending strength of each sample using the measurement method specified in JIS R 1601, and is expressed in units of "MPa." The three-point bending strength of the composite material 10 according to this embodiment was 844 MPa, and the three-point bending strength of the composite material according to the comparative example was 300 MPa.

[0060] It was confirmed that the composite material 10 according to this embodiment has a sufficiently high three-point bending strength of 844 MPa because the proportion of the first region S1 in the cross section SA, i.e., the proportion of silicon carbide (second region) with relatively high strength, is relatively large. The greater the SiC area ratio in the cross section, the higher the three-point bending strength of the composite material 10. To obtain good processability, the three-point bending strength of the composite material 10 should be at least 500 MPa or higher. A more preferable value is 700 MPa or higher, and even more preferable is 800 MPa or higher as in this embodiment.

[0061] A method for manufacturing the composite material 10 will be described below. In the following, the description of well-known aspects of the manufacturing method for SiSiC will be simplified or omitted as appropriate.

[0062] First, the raw materials, carbon powder and silicon carbide powder, are weighed out in predetermined amounts and dispersed in pure water together with a binder and a dispersant to form a slurry. The carbon powder preferably has a particle size of 0.5 to 5 μm. The silicon carbide powder preferably has a particle size of 0.01 to 0.3 μm.

[0063] The slurry obtained as described above is spray-dried using a spray dryer to produce a granulated powder containing carbon and silicon carbide. At this time, it is preferable that the slurry is made into an agglomerated slurry having a viscosity of about 100 to 200 cp in advance so as to prevent cavities from forming inside the granulated powder or the granulated powder from becoming a so-called "depressed sphere." As a method for producing the granulated powder, various known granulation methods can be used.

[0064] When preparing the slurry, the sphericity of the resulting granulated powder can be increased by appropriately selecting the binder and dispersant in advance. The target sphericity value is preferably set to a value higher than the sphericity of the granulated powder used in conventional SiSiC materials. For example, the sphericity of the granulated powder is preferably 0.8 or higher, and more preferably 0.9 or higher.

[0065] The purpose of increasing the sphericity of the granulated powder is to provide the granulated powder with sufficient fluidity. It is preferable to increase the fluidity of the granulated powder to a level that would have been considered excessive in the past. The fluidity of the granulated powder varies not only depending on the sphericity of the granulated powder but also on the size of the granulated powder. For this reason, for example, when spray-drying a slurry, it is preferable to control the size of the granulated powder by adjusting the flow rate of the supplied air to obtain granulated powder with optimal fluidity. It is preferable to set the particle size of the granulated powder finally obtained to 10 to 50 μm.

[0066] The resulting granulated powder is then placed in a predetermined mold and subjected to dry uniaxial press molding to obtain a molded body. By increasing the fluidity of the granulated powder in advance as described above, the granulated powder is packed sufficiently densely into the mold. As a result, a molded body with a small pore size can be obtained.

[0067] As a molding method, methods other than the dry uniaxial pressing described above may be used as long as they can pack the highly fluid granulated powder sufficiently densely. For example, molding may be performed using cold isostatic pressing (CIP), or a method of forming the shape by laying the powder using a 3D printer may be used.

[0068] After molding is complete, metallic silicon is placed on the resulting molded body and sintered under reduced pressure. The molded body is impregnated with molten silicon and reactively sintered with carbon powder to obtain the composite material 10 shown in Fig. 1 etc.

[0069] In this embodiment, as described above, the fluidity of the granulated powder is increased compared to conventional methods, and the molded body is obtained by filling the molded body sufficiently densely. As a result, the reaction between silicon and carbon powder occurs more uniformly throughout the material, which is thought to be why the second region S2 is formed over a relatively wide area and the first region S1 is smaller than conventional methods.

[0070] If a composite material is formed by a conventional manufacturing method without sufficiently increasing the fluidity of the granulated powder, a composite material having a cross section similar to that of the comparative example shown in Fig. 6 is produced. In producing composite material 11 shown in Fig. 6, a molded body is produced by slip casting in order to make the difference in structure from this embodiment more noticeable.

[0071] Specifically, first, predetermined amounts of carbon powder and silicon carbide powder were weighed and dispersed in pure water together with a binder and a dispersant to form a slurry. The resulting slurry was then poured into a plaster mold and a molded body was obtained by casting. After molding was completed, metal silicon was placed on the resulting molded body and sintered under reduced pressure.

[0072] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise. [Explanation of symbols]

[0073] 10: Composite material SA: Cross section S1: 1st area S2:Second area E: Inscribed ellipse MJ: Long axis MN: Minor axis P1, P11: First peak P2: Second peak

Claims

1. A composite material comprising silicon and silicon carbide, In a cross section of the composite material cut along a plane, a plurality of first regions including the silicon; a second region comprising the silicon carbide; For each of the plurality of first regions included in the cross section, L1, which is the length of the minor axis of the largest ellipse that can be arranged inside the first region, is calculated individually, and a graph showing the relationship between the value of L1 and frequency is plotted. A composite material characterized in that the L1 value corresponding to the first peak, which has the highest frequency in the graph, is 1.5 μm or less.

2. The composite material according to claim 1 , wherein the graph contains, in addition to the first peak, a second peak having the second highest frequency.

3. 3. The composite material according to claim 2, wherein the L1 value corresponding to the second peak is greater than 1.5 μm and less than or equal to 2.5 μm.

4. Further, for each of the plurality of first regions included in the cross section, L2, which is the length of the major axis of the largest ellipse that can be arranged inside the first region, is calculated individually, and a graph showing the relationship between the value of L2 and frequency is plotted.

2. The composite material according to claim 1, wherein the L2 value corresponding to the first peak, which has the highest frequency in the graph, is 1.5 μm or more and 3.0 μm or less.

5. 2. The composite material according to claim 1, characterized in that the three-point bending strength is 500 MPa or more.

6. A composite material comprising silicon and silicon carbide, In a cross section of the composite material cut along a plane, a plurality of first regions including the silicon; a second region comprising the silicon carbide; For each of the plurality of first regions included in the cross section, L2, which is the length of the major axis of the largest ellipse that can be arranged inside the first region, is calculated individually, and a graph showing the relationship between the value of L2 and frequency is plotted. A composite material characterized in that the L2 value corresponding to the first peak, which has the highest frequency in the graph, is 1.5 μm or more and 3.0 μm or less.

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