JPH10130056A - Silicon carbide ceramic and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat resistance, toughness and high-temp. strength by compacting and calcining a mixture of SiC with C and specified polytitanocarbosilane and infiltrating molten Si. SOLUTION: A powdery mixture is prepd. by mixing SiC with C, 5-20vol.% polytitanocarbosilane having a mol.wt. of >=2,500 based on the total amt. of the SiC and C, and org. binder and an org. solvent. This mixture is compacted under about 1 ton/cm<2> pressure and the resultant compact is heat-treated at 800-1,700 deg.C in a vacuum of about 0.01Torr or in an inert gaseous atmosphere to form a temporary sintered compact having about 70% relative density. About 2 times (weight) as much Si as the temporary sintered compact is put on the compact and heat-treated at 1,450-1,700 deg.C for >=0.5hr in a vacuum of 3-0.01Torr. By this heat treatment, molten Si is infiltrated and the objective SiC ceramic having SiC grains of 10-100nm grain diameter and SiC grains of >100nm grain diameter and not contg. free atomic Si is obtd. In the ceramic, Si, C and O elements account for >=99.9wt.% of the constituent elements of the sintered compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide ceramic and a method for producing the same, and more particularly, to 750 to 1,57.
The present invention relates to a silicon carbide ceramic having excellent heat resistance at an intermediate temperature of 3 ° K, near-net shape having excellent toughness and high-temperature strength at a temperature of 1,500 ° C or higher, and a method for producing the same.

[0002]

2. Description of the Related Art One of the conventional sintering methods for ceramics is a reaction sintering method. According to this method, it is possible to manufacture a ceramic having a near net shape in which the dimensions at the time of the molded body and the dimensions after sintering hardly change, so that the ceramic as a precision part having a complicated shape is sintered. This is a very advantageous method as a sintering method for industrially mass-producing ceramics because it can be sintered at low cost.

As an example of such a reaction sintering method, for example, Japanese Patent Publication No. 45-38061 discloses that a compact formed from a mixture of SiC powder and carbon is formed at 1,600 to 1,700 °.
A reaction sintering method has been disclosed in which molten silicon is impregnated at a temperature of C and the molten silicon is reacted with carbon in a compact to form a SiC sintered body. Although this reaction sintering method has the above-mentioned excellent characteristics, the strength of silicon carbide ceramics obtained by this method is generally as low as about 300 to 500 MPa, and the strength is high at a high temperature of 1,200 ° C. or more. It also has the disadvantage that it drops sharply. this is,
Since about 10% of the unreacted atomic silicon (metallic silicon) impregnated remains in the sintered body, the strength at room temperature is controlled by the brittle silicon fracture behavior, and becomes lower. Is because the melting point of silicon is 1,412 ° C., and the softening phenomenon of the sintered body starts around 1,200 ° C., and the strength sharply decreases.

In order to solve such disadvantages, the method disclosed in Japanese Patent Application Laid-Open No. 5-163065 discloses a method of reacting molybdenum, tungsten, molybdenum carbide, tungsten carbide, molybdenum silicide, tungsten silicide, and mixtures thereof. By impregnating the powder into the compact, free metallic silicon is prevented from remaining in the sintered body.

[0005]

The problem to be solved by the present invention is disclosed in Japanese Patent Laid-Open No. 5-163.
In the method disclosed in Japanese Patent No. 065, the silicon melt-impregnated in the molded body reacts with the reactive powder, and the residual amount of atomic metallic silicon in the sintered body after sintering is reduced. Molybdenum silicide, tungsten silicide, etc. are generated by the reaction between silicon and the reactive powder and remain in the sintered body, deteriorating the oxidation resistance of the sintered body, thereby deteriorating the heat resistance. Occurs. That is, the oxidation resistance of these substances in the sintered body greatly changes depending on the use environment of the sintered body, that is, the temperature and the oxygen partial pressure, but at a temperature of about 750 to 1,573 ° K, silicon And the oxidation of molybdenum or tungsten proceeds simultaneously,
In addition to SiO, MoO ₃ or WO ₃ is generated and evaporated,
The so-called "pest" phenomenon occurs. For this reason, in these temperature ranges, the heat resistance of the sintered body is extremely deteriorated.

The present invention has been made to solve the above-mentioned drawbacks of the conventional silicon carbide ceramics and the method of manufacturing the same. In particular, there is no material deterioration due to a decrease in heat resistance at an intermediate temperature, and high-temperature strength and It is an object of the present invention to provide a silicon carbide ceramic having excellent toughness and near-net shape, and a method for producing the same.

[0007]

The silicon carbide ceramic of the present invention has a crystal group of silicon carbide having a particle size of about 10 nm to 1,000 nm and a crystal group of silicon carbide having a larger particle size. At least 99.9% by weight of the elements constituting the sintered body is occupied by the Si element, the C element and the O element, and the sintered body does not substantially contain free atomic Si. That is, since the sintered body does not contain an easily oxidizable element such as silicon, molybdenum, or tungsten, there is no decrease in heat resistance at an intermediate temperature, and high-temperature strength and toughness, and a near-net-shaped carbonized material. A silicon ceramic is obtained.

Further, it has a crystal group of silicon carbide having a particle diameter of about 10 nm to 1,000 nm and a crystal group of silicon carbide having a particle diameter larger than that, and is composed of Si element, C element, O element and Ti element. 99.9% by weight of the elements constituting the sintered body
The above is occupied, and the atomic S
i does not substantially contain i. That is, similarly, since the sintered body does not contain an easily oxidizable element such as silicon, molybdenum, or tungsten, there is no decrease in heat resistance at an intermediate temperature, high strength at high temperature and toughness, and near net shape property. Is obtained.

Further, the sintered body further contains 60% by volume or less of continuous carbon fiber, continuous silicon carbide fiber or silicon carbide whisker. The mechanical strength of the silicon carbide ceramic is further enhanced by these carbon continuous fibers, silicon carbide continuous fibers, or silicon carbide whiskers.

The method for producing silicon carbide ceramics according to the present invention is characterized in that silicon carbide, carbon and polycarbosilane having an average molecular weight of 2,500 or more are added to silicon carbide and carbon in an amount of 5 to 2 parts.
A step of mixing and molding at a ratio of 0% by volume, a step of calcining the molded mixture to form a temporary sintered body, and a step of infiltrating the temporary sintered body with molten silicon while heating. It is provided. That is, polycarbosilane having a molecular weight of 2,500 or more is decomposed into β-SiC and amorphous carbon by crystallization, and the excess carbon reacts with atomic silicon to sinter the liberated silicon. Residuals in the body are prevented. If the volume ratio of polycarbosilane to silicon carbide and carbon is less than 5%, free silicon cannot be completely removed and remains in the sintered body, resulting in deterioration of the strength of the sintered body.
%, The amorphous carbon remains in the sintered body and also deteriorates the properties such as strength and toughness of the sintered body.
By satisfying the above requirements, it is possible to obtain a silicon carbide ceramic which does not contain metallic silicon or amorphous carbon, has no decrease in heat resistance at an intermediate temperature, has excellent high-temperature strength and toughness, and has near net shape. Can be

A step of mixing and molding silicon carbide, carbon and polytitanocarbosilane having an average molecular weight of 2,500 or more with respect to silicon carbide and carbon at a ratio of 5 to 20% by volume; And a step of infiltrating the pre-sintered body with molten silicon while heating the pre-sintered body. Polytitanocarbosilane having a molecular weight of 2,500 or more also decomposes into β-SiC and amorphous carbon by crystallization similarly to polycarbosilane, and this excess carbon reacts with atomic silicon. As a result, the remaining silicon in the sintered body is prevented. On the other hand, if the volume ratio of polytitanocarbosilane to silicon carbide and carbon is less than 5%, free silicon cannot be completely removed and remains in the sintered body, resulting in deterioration of the strength of the sintered body. If it is more than 20%, amorphous carbon remains in the sintered body, and also deteriorates properties such as strength and toughness of the sintered body. By satisfying the above requirements, it is possible to obtain a silicon carbide ceramic which does not contain metallic silicon or amorphous carbon, has no decrease in heat resistance at an intermediate temperature, has excellent high-temperature strength and toughness, and has near net shape. Can be

The method may further include a step of filling the mixture into the carbon continuous fiber, the silicon carbide continuous fiber, or the silicon carbide whisker. Thereby, these carbon continuous fibers,
The sintered body is compounded by the silicon carbide continuous fibers or the silicon carbide whiskers, and the mechanical strength of the silicon carbide ceramic is further enhanced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is a crystal structure diagram showing a crystal structure of one embodiment of the silicon carbide ceramics of the present invention. The silicon carbide ceramics of the present embodiment is composed of a silicon carbide crystal group having three types of average particle sizes. Reference numeral 1 denotes a silicon carbide crystal group having the largest average particle diameter, reference numeral 2 denotes a silicon carbide crystal group having an intermediate size, and reference numeral 3 denotes a silicon carbide crystal group having the smallest average particle diameter. The average particle size of the silicon carbide crystal groups denoted by reference numerals 1 and 2 is approximately 0.3 μm to 10 μm.
m, and the average particle size of the silicon carbide crystal group denoted by reference numeral 3 is 10 n.
m to 1,000 nm. The silicon carbide crystal groups denoted by reference numerals 1 and 2 are formed on the surface of SiC powder particles used as a starting material when manufacturing the silicon carbide ceramics of the present embodiment.
The SiC particles are SiC particles grown and applied by reaction, and the silicon carbide crystal group denoted by reference numeral 3 is composed of polycarbosilane or polytitanocarbosilane added when manufacturing the silicon carbide ceramics of the present embodiment. These are SiC fine particles generated by decomposition or reaction between amorphous carbon and residual Si.

In a silicon carbide ceramic according to another embodiment of the present invention, long fibers or whiskers containing carbon or silicon carbide as a main component are mixed so as to be 60% or less by volume in the sintered body, and the composite is mixed. Has been In this way, the mechanical strength is further increased. The volume ratio of long fibers or whiskers containing carbon or silicon carbide as a main component is 60%.
If it is larger, the heat resistance properties of the SiC matrix,
Characteristics such as oxidation resistance cannot be sufficiently exhibited, resulting in a silicon carbide ceramic having poor durability.

Next, an embodiment of the method for producing a silicon carbide ceramic of the present invention will be described. In this embodiment, polycarbosilane is used as the organic silicon polymer to be added to silicon carbide and carbon.However, even when polytitanocarbosilane is used, substantially the same effect as when polycarbosilane is used is obtained. Can be

In the manufacturing method of the present embodiment, the polycarbosilane changes from an amorphous state to a crystalline state with an increase in temperature. Since polycarbosilane having an average molecular weight as low as 800 to 2,000 is completely melted at 80 to 245 ° C., infusibility in the air is required to obtain a sound sintered body. It is known that a typical chemical composition of the polycarbosilane subjected to the infusibilization treatment is Si ₃ C ₄ O ₁ . At a temperature of about 1,600 ° C. at which the formed body is impregnated with Si, Si ₃ C ₄ O ₁ is decomposed to generate SO or CO gas and change to SiC.

On the other hand, in the present embodiment, polycarbosilane having an average molecular weight of 2,500 or more is added to silicon carbide and carbon and mixed, and such a polycarbosilane having an average molecular weight of 2,500 or more is mixed. Although is partially melted by heating, it is not completely melted, and the infusibilizing treatment in the air is not required. The chemical composition of the polycarbosilane not subjected to the infusibilization treatment after thermal decomposition is Si ₃ C ₄ . This chemical composition does not contain an oxygen element as compared with the chemical composition Si ₃ C ₄ O ₁ of the polycarbosilane subjected to the infusibilizing treatment.
Therefore, even if heat treatment up to 1,700 ° C. is performed, S
Since O or CO gas is not generated, the weight change is 2-3.
%, And most of the excess carbon remains after the pyrolysis, resulting in a mixed state of β-SiC and amorphous carbon (T.
Shimoo, T .; Hayato, M .; Taked
a, H .; Ichikawa, T .; Seguchi,
K. Okamura, "Journal of the
heCeramic Society of Japan
n ", 102, pp. 1, 141-47 (199
4)). For this reason, the melting temperature of silicon (1,410 °
C) The silicon impregnated in the preliminary sintered body as described above first reacts with the carbon contained in the starting material, and when the carbon in the starting material disappears, the remaining silicon is decomposed by polycarbosilane, Reacts with the resulting amorphous carbon. That is,
At a temperature of about 1,600 ° C., the organosilicon polymer is decomposed into β-SiC and amorphous carbon by crystallization, and the reaction between the excess amorphous carbon and the atomic metallic silicon in the compact is performed. It will happen. Therefore, the use of polycarbosilane having a large average molecular weight makes it possible to remove residual Si from the sintered body for the first time. The same is true for polytitanocarbosilane.

In the method for producing silicon carbide ceramics of the present embodiment, silicon carbide powder, carbon black as a carbon source, and polycarbosilane powder having an average molecular weight of 2,500 or more are mixed, and Phenolic resin is added, and mixed powder is obtained by ball mill mixing in a xylene solvent. This mixed powder is subjected to CIP molding under a pressure of about 1 ton / cm ² , and heat-treated at 800 to 1,700 ° C. for several hours in a vacuum of about 0.01 Torr or in an inert gas atmosphere, so that the relative density is about 70% pre-sintered body. The mixing and molding are not limited to the ball mill and the CIP, respectively. About twice the weight of metal Si is placed on the pre-sintered body and heat-treated at 1,450 to 1,700 ° C for 0.5 to several tens of hours in a vacuum of 3 to 0.01 Torr. Impregnation with Si is performed. Here, the mixing amount of the polycarbosilane with respect to the silicon carbide powder and carbon black or another carbon source is desirably 5 to 20% by volume. 5% polycarbosilane
If the amount is too small, the metallic silicon remains in the sintered body and the strength of the sintered body at room temperature and high temperature decreases, and if it is more than 20%, the carbon formed by decomposition of the organic silicon compound is sintered. This is because they remain in the body and deteriorate mechanical properties such as strength and toughness of the sintered body. Note that the above description also applies to the case where polytitanocarbosilane is used.

Since the silicon carbide ceramics obtained by the above-described method for manufacturing silicon carbide ceramics of the present embodiment does not contain molybdenum and tungsten, there is no deterioration in heat resistance in an intermediate temperature range and the fracture toughness value Is
The 4-point bending strength at about 6 MPa · √m and 1,500 ° C. becomes 800 MPa. Characteristic values of SiC ceramics manufactured by the conventional reaction sintering method (four-point bending strength 200 to
(400 MPa, fracture toughness value of 3 to 4 MPa · √m), considerably improved characteristics are obtained.

Next, another embodiment of the method for producing a silicon carbide ceramic of the present invention will be described. Fiber bundle is 500 ~
Using about 3,000 continuous fibers of silicon carbide or carbon fiber, the fibers are arranged one-dimensionally, two-dimensionally, and three-dimensionally to perform shaping. In one-dimensional arrangement, one-dimensional orientation of fibers is preferable, in two-dimensional arrangement plain weave, satin weave, and entanglement weave, and in three-dimensional arrangement, orthogonal weave and entanglement weave are desirable. When whiskers are used, it is desirable to use a mat-shaped non-woven body. Fiber content V ₁ of the this time to use not more than 60%. The fibrous structure is filled with a tissue powder for forming a silicon carbide matrix. As a filling method, a method of making a slurry and filling is simple, but not limited to this. That is, a powder containing silicon carbide powder, carbon black, and a polycarbosilane powder or a polytitanocarbosilane having a balance average molecular weight of 2,500 or more is added, and the powder slurry is mixed by ball milling in a xylene solvent, for example. And The slurry is impregnated with the slurry by pressure impregnation. This impregnated body is 800-1700 ° in a vacuum of about 0.01 Torr or in an inert gas atmosphere.
C. A heat treatment is performed for several hours to form a pre-sintered body. On the pre-sintered body, about twice the weight of metal Si is placed, and 3 to 0.01 T
0.5-1 at 1,450-1700 ° C in a vacuum of orr
Heat treatment is performed for several tens of hours to perform Si impregnation. Thus, silicon carbide ceramics reinforced by long fibers or whiskers can be obtained. This silicon carbide ceramic has a four-point bending strength of about 800 MPa, which is almost the same as that containing no long fiber, but has a fracture toughness of about 20 M.
As large as about Pa · √m can be obtained.

Using the above-described silicon carbide ceramics according to the present invention and the silicon carbide ceramics manufactured by the method for manufacturing silicon carbide ceramics according to the present invention, high-temperature heat-resistant members such as moving blades, stationary blades, and combustors for gas turbines, and nuclear fusion. A counter plasma member for a furnace, and a heat sink for semiconductors can be manufactured, and when using silicon carbide ceramics compounded using long fibers or whiskers, the high temperature heat-resistant member, the counter plasma member and By matching the main stress direction applied to the heat sink with the main direction of the fiber axis, it is possible to function as a member having higher strength and high durability and a heat sink.

[0022]

Example 1 An α-type silicon carbide powder having an average particle size of 2 μm, carbon black having an average particle size of 0.01 μm, and a polycarbosilane powder having an average molecular weight of 3,400 were prepared as shown in Table 1 by sample numbers 1 to 5. It was weighed so that it might become a composition, and the whole was 100 g. 1 g of a phenol resin as a binder and 140 cc of xylene were added, and the mixture was mixed in a ball mill using SiC balls to obtain a mixed powder. This mixed powder is 1,000
After molding at a pressure of kg / cm ² , heat treatment was performed at 1,000 ° C. for 1 hour in a vacuum of 0.01 Torr to obtain a temporary sintered body. At this time, the relative density of the temporary sintered body was about 70%. About twice the weight of metallic silicon is placed on the pre-sintered body, and is placed in a vacuum of 0.01 Torr at 1,600 ° C. for 1 hour.
Heat treatment was performed for a long time, and the temporary sintered body was impregnated with Si to obtain a sintered body.

As a result of ICP analysis, the sum of the weights of the (Si + C + O) elements of all the samples was 99.
It was found to account for more than 9% by weight. Further, in order to examine the presence or absence of residual metallic silicon, the silicon carbide ceramic impregnated with the silicon was polished, and then heated to 1,500 ° C., which was about 1,000 ° C. higher than the melting point of metallic silicon, and the surface of the sample was removed. The histological changes were observed. Sample No. 1 showed traces of silicon elution, while Sample Nos. 2 to 5 showed no trace of silicon elution, and no substantial silicon residue was observed.

The distribution of the average particle size of the sintered body was measured by polishing the silicon-impregnated sintered body to a mirror surface, and then corroding the silicon body in a boiling solution of red blood potassium and sodium hydroxide to obtain a plasma of SiC. Grain boundaries are highlighted. The area ratio of each crystal grain of this sample was determined by image processing and defined as an average particle size. In addition, in order to examine the decrease in heat resistance in the intermediate temperature range, a temperature of 1,000 ° K
The sample held in the atmosphere for 0 hours was moved to a room temperature state, and the four-point bending strength was measured. The strength and fracture toughness of the sample were determined by JI
It was evaluated by the S4 point bending test method. In addition, the fracture toughness value is determined by pressing a Vickers indenter against the surface of a specimen polished to a mirror surface, generating a crack on the diagonal extension from the four corners of the indentation,
The diagonal length of the indentation was measured, and IF (Indentation
(Fracture) method.

[0025]

[Table 1]

As is clear from Table 1, the silicon carbide ceramics of the present example did not substantially deteriorate in strength up to 1,500 ° C., had a four-point bending strength at room temperature of about 800 MPa,
It has the characteristic that the fracture toughness value is about 6 MPa · √m by the F method.

[0027]

Example 2 Powder was mixed, molded and pre-sintered in the same manner as in the sample No. 3 of Example 1 except that polycarbosilane having an average molecular weight of 2,000 to 5,000 was used. On the pre-sintered body, about twice the weight of metallic silicon was placed.
The silicon impregnation was performed at 1600 ° C. for 10 hours in a vacuum of 01 Torr. The density of the calcined body was evaluated by the Archimedes method, and the strength after reaction sintering was evaluated by the same method as in Example 1.

[0028]

[Table 2]

The average molecular weight of the polycarbosilane is 2,50.
In the case of 0 or less, heating during calcination causes complete melting, foaming phenomenon due to decomposition and evaporation of low molecular weight polymer, etc.,
The relative density does not improve to about 52%. On the other hand, when the average molecular weight is 2,500 or more, complete melting does not occur, and further, decomposition and evaporation are small, so that a material having a relative density of about 70% can be obtained. Therefore, Sample Nos. 7 to 9 according to the present invention were used.
It is also evident from Table 2 that the room temperature strength of the sample No. 6 is significantly higher than that of the sample No. 6 not according to the present invention.

[0030]

Example 3 A silicon carbide ceramic sample was prepared in the same manner as in Example 1 except that polytitanocarbosilane having an average molecular weight of 3,000 was used instead of polycarbosilane. As shown in Table 3, the mixing, molding, and temporary sintering of the powder were performed while changing the content of the polytitanocarbosilane.
On this temporary sintered body, put about twice the weight of metallic silicon,
At a reaction time of 10 hours and a sintering temperature of 1,600 ° C. in a vacuum of 0.01 Torr, a sintered body was obtained while impregnating silicon. As a result of ICP analysis of the sample after sintering, the total weight of the (Si + C + O + Ti) element was
It turned out to account for 99.9% by weight or more of the weight of the whole sample. Presence of residual silicon after reaction sintering, average particle size, strength,
The fracture toughness value was evaluated in the same manner as in Example 1, and is shown in Table 3.

[0031]

[Table 3]

From Table 3, it can be seen that the same effect can be obtained when polytitanocarbosilane is used, as well as when polycarbosilane is used.

[0033]

Example 4 Using a continuous fiber of 500 pieces of silicon carbide fiber bundles, a fibrous structure composed of three types of three-dimensional fabrics having orthogonal structures having different fiber filling rates was manufactured. A slurry was prepared using exactly the same composition powder as the sample of Sample No. 3 of Example 1,
The fiber structure was filled. That is, the average particle size is 2 μm
Α-type silicon carbide powder, carbon black having an average particle diameter of 0.001 μm, and polycarbosilane powder having an average molecular weight of 3,400, and 1 g of a phenol resin as a binder and 140 cc of xylene were added thereto. The mixture was mixed by a ball mill using SiC balls to obtain a slurry. The fiber structure was filled with the slurry by pressure impregnation. After drying the impregnated body, it was subjected to a heat treatment at 1,000 ° C. for 1 hour in a vacuum of 0.01 Torr to obtain a temporary sintered body. About twice the weight of metallic silicon is placed on this temporary sintered body, and heat treatment is performed at 1600 ° C. for 1 hour in a vacuum of 0.01 Torr to impregnate the silicon into the temporary sintered body. Was. The strength and fracture toughness after reaction sintering were evaluated in the same manner as in the sample of Example 1. Table 4 shows the results.

[0034]

[Table 4]

[0035]

Example 5 A mat of 200 g / m ² was manufactured using a three-dimensional woven fabric having an orthogonal structure with a fiber filling ratio of 41% and a silicon carbide whisker prepared using 500 continuous carbon fibers. These fiber structures were slurried using the same composition powder as the sample No. 3 of Example 1, and each fiber structure was impregnated with the slurry by pressure impregnation. After drying these impregnated bodies, 0.01
Heat treatment is performed at 1,000 ° C. for 1 hour in a vacuum of Torr to form a pre-sintered body. On the pre-sintered body, about twice the weight of metallic silicon is placed, and in a pre-sintered state of 0.01 Torr, 1,
Heat treatment was performed at 600 ° C. for 1 hour to perform reaction sintering. The strength and fracture toughness after reaction sintering were evaluated in exactly the same manner as in Example 1. As a result, in the structure using the continuous carbon fiber, the bending strength was 890 MPa and the fracture toughness value was 18 MPa.
The value of √m is, in the case of the silicon carbide whisker mat structure, a bending strength of 830 MPa and a fracture toughness value of 23 MPa
The value of m was obtained.

From the above data of Examples 4 and 5, the four-point bending strength was approximately 800 MPa by using silicon carbide, carbon continuous fibers, and silicon carbide whiskers.
It can be seen that a fracture toughness value as high as about 20 MPa · √m can be obtained, although the degree of identification does not include long fibers.

[0037]

Embodiment 6 In an orthogonal three-dimensional woven fabric composed of an x-axis, a y-axis, and a z-axis, the x-axis and the y-axis are silicon carbide continuous fibers with 500 fiber bundles, and the z-axis is 500 carbon bundles with carbon fiber bundles. Was used to manufacture a three-dimensional woven fabric having an orthogonal structure having a fiber filling rate of 41%. To this three-dimensional fabric, exactly as in Example 5,
The slurry was impregnated, pre-sintered under the same conditions as in Example 5, and further, as in Example 5, metallic silicon was placed thereon and heat-treated to perform reaction sintering. The strength and fracture toughness after reaction sintering were evaluated in exactly the same manner as in Example 1. As a result, the bending strength was 930 MPa and the fracture toughness value was 23.
A value of MPa · √m was obtained.

[0038]

Embodiment 7 A gas turbine rotor blade shown in FIG. 2 was manufactured by a three-dimensional woven fabric of orthogonal structure using continuous fibers of silicon carbide having a fiber bundle of 500 pieces. The filling factor of the fiber was 45%. A slurry was prepared using exactly the same composition powder as that of Sample No. 3 of Example 1, and the slurry was filled in the fibrous structure. That is, α-type silicon carbide powder having an average particle size of 2 μm, carbon black having an average particle size of 0.01 μm, and an average molecular weight of 3,
400 polycarbosilane powders were weighed so as to have the composition of Sample No. 3 in Table 1, and the total was 100 g. 1 g of phenol resin and 14 g of xylene as a binder
0 cc was added, and a ball mill was mixed using SiC balls to obtain a slurry. This slurry was impregnated into the fibrous structure by pressure impregnation. The impregnated body was heat-treated at 1,000 ° C. for 1 hour in a vacuum of 0.01 Torr to obtain a temporarily sintered body. About twice the weight of metallic silicon was placed on the temporary sintered body, and heat-treated at 1600 ° C. for 1 hour in a vacuum of 0.01 Torr to perform reaction sintering. The ceramic blade thus manufactured has a rated rotation speed of 11,500 ° C at 11,500 ° C.
Its soundness was confirmed under the condition of 000 rpm.

[0039]

Embodiment 8 500 fiber bundles, thermal conductivity 600 W / mK
, A one-dimensionally oriented sample having a fiber filling rate of 63% was produced in exactly the same manner as the sample of sample No. 3 in Example 1. Irradiation at a heat flow rate of 20 MW / m ² was sound and thermal conductivity exceeded 300 W / mK. The silicon carbide ceramics of the present embodiment is suitable for a plasma facing member for a nuclear fusion reactor.

[0040]

Example 9 Plates of 80 mm × 60 mm × 3 mm were manufactured by exactly the same manufacturing method as the samples using the continuous carbon fibers of Sample No. 3, Sample No. 8 and Example 5. The thermal conductivity of the continuous carbon fiber is 600 W / mK.
Was used. Table 5 shows the thermal expansion coefficient and the thermal conductivity of these samples. The coefficient of thermal expansion was calculated from the thermal expansion up to 500 ° C., and the thermal conductivity was measured by a laser flash method.

[0041]

[Table 5]

From Table 5, it is clear that the flat plate of this example has a thermal expansion coefficient equal to that of silicon and a thermal conductivity exceeding Mo or W. When used as a heat sink for a large current power module as a substitute for the conventional Mo, no problem occurred at all, and it was found to be suitable.

[0043]

According to the present invention, it is possible to easily obtain a silicon carbide ceramic having excellent high-temperature strength and toughness without deterioration of heat resistance in an intermediate temperature range. It has a great effect on the industrialization of engineering ceramics such as plasma facing members for furnaces and heat dissipation substrates for semiconductors.

[Brief description of the drawings]

FIG. 1 is a crystal structure diagram of a silicon carbide ceramic according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a moving blade for a gas turbine according to an embodiment of the present invention.

[Explanation of symbols]

 1 silicon carbide crystal group having the largest average particle size 2 silicon carbide crystal group having an average size of medium size 3 silicon carbide crystal group having the smallest average particle size

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Sawai 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Yoshiyuki Yasutomi 7-1, Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Kunihiro Maeda 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Ltd. Hitachi Research Laboratory

Claims (6)

[Claims] 1. A sintered body comprising a silicon carbide crystal group having a particle size of about 10 nm to 1,000 nm and a silicon carbide crystal group having a larger particle size, and comprising a Si element, a C element and an O element. Silicon carbide ceramics, wherein 99.9% by weight or more of the elements constituting the silicon carbide are occupied, and the sintered body does not substantially contain free atomic Si. 2. It has a silicon carbide crystal group having a particle size of about 10 nm to 1,000 nm and a silicon carbide crystal group having a larger particle size, and comprises Si element, C element, O element and Ti
99.9% by weight or more of the elements constituting the sintered body is occupied by the element, and the atomic S
A silicon carbide ceramics substantially free of i. 3. The silicon carbide ceramic according to claim 1, wherein the sintered body contains 60% by volume or less of continuous carbon fiber, continuous silicon carbide fiber, or silicon carbide whisker. 4. Silicon carbide, carbon and an average molecular weight of 2.5
A step of mixing and molding polycarbosilane of at least 00 with respect to the silicon carbide and the carbon at a ratio of 5 to 20% by volume, and a step of calcining the molded mixture to form a temporarily sintered body; A step of infiltrating the pre-sintered body with molten silicon while heating the silicon body. 5. Silicon carbide, carbon and an average molecular weight of 2.5
A step of mixing and shaping a polytitanocarbosilane of at least 00 with respect to the silicon carbide and the carbon at a ratio of 5 to 20% by volume, and a step of calcining the molded mixture to form a temporary sintered body And a step of infiltrating the pre-sintered body with molten silicon while heating the silicon body. 6. The method for producing a silicon carbide ceramic according to claim 4, further comprising a step of filling the mixture into a carbon continuous fiber, a silicon carbide continuous fiber, or a silicon carbide whisker.