JPH06279119A - Highly heat conductive sic ceramics and its production - Google Patents

Abstract

PURPOSE:To enhance heat conductivity and toughness by compacting a powdery mixture of specified beta-SiC powder with a binder for compacting and heating the resulting compact without applying pressure. CONSTITUTION:A powdery mixture of beta-SiC powder having <=5wt.% B content, <=5wt.% C content and <=0.5mum particle diameter with a binder for compacting is compacted and the resulting compact is heated at 2,100-2,500 deg.C for 5-60min in inert gas or in an inert gas-gaseous H2 mixture to obtain the objective highly heat conductive SiC ceramics having <=5% porosity. In this SiC ceramics, >=50% of the SiC component is beta-SiC and beta-SiC particles having >=20 aspect ratio have been dispersed by >=20vol.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SiC ceramic having high thermal conductivity and high toughness obtained by pressureless sintering.

[0002]

2. Description of the Related Art Recently, heat-resistant materials having high thermal conductivity have been required as materials for parts for high temperature gas turbines, first wall of fusion reactor, channel walls for MHD power generation and the like.

In general, as engineering ceramics suitable for structural materials such as engines and turbines, SiC and Si ₃ N ₄ having excellent heat resistance are known. S
iC is one of the materials with excellent chemical stability and thermal conductivity.
High strength at high temperature and excellent oxidation resistance. In particular, commercially available SiC powder and Be can be used as high thermal conductivity materials.
A material having a thermal conductivity of 267 W / mK at room temperature, which is larger than that of metallic aluminum, has been developed by adding O and performing hot press sintering.

[0004]

The hot press sintering is not suitable for forming long products or products having complicated shapes because a mold material is required. Further, since SiC is a compound having a strong covalent bond, it is difficult to sinter by itself. In order to obtain the SiC sintered body by the pressureless sintering method, it is necessary to add a large amount of a sintering aid such as B or C to the SiC powder. However, since these additives become impurities and impede the conduction of phonons, a high thermal conductive material cannot be obtained.

For the above reason, Si produced by pressureless sintering is used.
Development of manufacturing technology of C sintered body is desired.

An object of the present invention is to provide SiC ceramics having high thermal conductivity and high toughness by a pressureless sintering method.

[0007]

Means for Solving the Problems The gist of the present invention for solving the above problems is as follows.

(1) β-Si having an aspect ratio of 20 or more
A high thermal conductive SiC ceramics, characterized by comprising a sintered body in which C particles are dispersed in an amount of 20 vol% or more.

(2) 5 of the SiC component in the SiC sintered body
High thermal conductivity SiC ceramics characterized in that 0% or more is β-SiC, and β-SiC particles having an aspect ratio of 20 or more are dispersed in 20 vol% or more.

(3) 50 μm to 5 m from the surface of the sintered body
The m layer has 2 β-SiC particles with an aspect ratio of 20 or more.
A high thermal conductive SiC ceramics, which is formed of a SiC sintered body in which 0 vol% or more is dispersed.

(4) High thermal conductivity SiC ceramics in which the porosity of the sintered body is 5% or less.

(5) A molded body is formed by mixing powder of β-SiC powder having a B content of 5 wt% or less and a C content of 5 wt% or less and a particle size of 0.5 μm or less, and a molding binder, and molding the molded body. Is heated in an inert gas or an inert gas + hydrogen at 2100 to 2500 ° C. for 5 to 300 minutes without pressurization.

(6) (A) 100 parts by weight of SiC powder having a particle size of 5 μm or less and B, C, B ₄ C, B as a sintering aid.
A step of producing a molded body from a mixed powder in which 1 to 5 parts by weight of at least one of N, Al ₂ O ₃ and BeO is mixed with a molding binder; and (B) a B content of 5 wt% on the surface of the molded body.
% Or less, C content 5 wt% or less and a particle size of 0.5 μm or less β-SiC powder and a layer made of a mixed powder of a molding binder, and formed in an inert gas or an inert gas + hydrogen 2
A method for producing a high thermal conductive SiC ceramics, which comprises a step of integrally heating at 100 to 2500 ° C. for 5 to 300 minutes.

(7) (A) 100 parts by weight of SiC powder having a particle size of 5 μm or less and B, C, B ₄ C, B as a sintering aid.
A molded body is prepared from a mixed powder in which 1 to 5 parts by weight of at least one of N, Al ₂ O ₃ and BeO is mixed with a molding binder, and the molded body is subjected to 2100 in an inert gas or an inert gas + hydrogen. A step of producing a primary sintered body by heating at 2,500 ° C. for 5 to 300 minutes, and (B) a B content of 5 wt% or less and a C content of 5 w by plasma spraying on the surface of the primary sintered body.
A layer made of β-SiC having a particle size of t% or less and a particle size of 0.5 μm or less is formed.
A method for producing a highly heat-conductive SiC ceramic, comprising a step of secondary heating at 00 to 2500 ° C. for 5 to 60 minutes.

The high thermal conductive SiC ceramics of the present invention are
SiC raw material powder, B content 5 wt% or less, C content 5
High-purity β-SiC having a particle size of 0.5 μm or less at wt% or less
A compact containing the powder is heated in an inert gas or an inert gas + hydrogen at 2100 to 2500 ° C. for 5 to 300 minutes to obtain 20 β-SiC particles having an aspect ratio of 20 or more in the sintered body.
Thermal conductivity of 13% by generating and dispersing more than vol%
High thermal conductivity S of 0 W / mK or more and porosity of 5 vol% or less
iC ceramics can be obtained.

The sintering atmosphere is preferably an inert gas or an inert gas + hydrogen. In a vacuum, B in the B-containing β-SiC powder decomposes and hinders sintering, which is not preferable.

The high-purity B-containing β-SiC powder of the present invention is
It can be produced by plasma treatment, sol-gel treatment, or the like.

Conventionally, the sintering conditions for suppressing the grain growth of SiC particles have been studied for the purpose of increasing the strength. In the present invention, conversely, by promoting the growth of β-SiC particles having a large aspect ratio, S of high thermal conductivity and high toughness is obtained.
It has become possible to obtain an iC sintered body.

In order to obtain a dense high thermal conductivity SiC sintered body by the pressureless sintering method, plasma-synthesized β-SiC powder of 0.5 μm or less is required. In particular, in order to obtain high thermal conductivity, it is desirable that the SiC powder contains a small amount of impurities such as free silicon, Fe and Al, and a sintering aid.

For high thermal conductivity, the total amount of metal impurities must be 1500 ppm or less, preferably 100 ppm or less. Further, it is preferable that the amorphous phase is hardly contained. This is because the amorphous phase is likely to combine with oxygen during the sintering process, and a small amount of oxide resulting therefrom is present as an impurity, which causes a decrease in thermal conductivity.

Next, crystallization β-of the present invention is performed by plasma treatment.
The method of synthesizing SiC powder is described below.

By reacting SiH ₄ , B ₂ H ₆ and CH ₄ gas in plasma, boron (B) is reduced to 0.5 μm.
A β-SiC powder of m or less is obtained.

By reacting SiH ₄ gas and CH ₄ gas in plasma, β-SiC powder of 0.5 μm or less can be obtained.

Commercially available SiC powder having a metal impurity content of more than 1 wt% is dropped into plasma, and once decomposed into Si and C and reacted with CH ₄ gas to synthesize excess C β-SiC powder, and then in hydrogen. 0.5 by removing excess C at
A high-purity β-SiC powder having a particle size of μm or less is obtained.

Commercially available SiC powder having a metal impurity amount of more than 1500 ppm and B powder are dropped into plasma, and once decomposed into Si, C and B, and reacted with C-containing CH ₄ gas to contain excess C and B. 0.5 was obtained by synthesizing β-SiC powder to be treated and heat-treating in hydrogen to remove excess C.
A B-containing high-purity β-SiC powder having a particle size of μm or less is obtained.

Commercially available SiC powder having a metal impurity content of more than 1500 ppm was dropped into plasma to temporarily remove Si,
0.5 μm or less by decomposing into C, reacting with B ₂ H ₆ and CH ₄ gas to synthesize β-SiC powder containing excess C and B, and removing excess C by heat treatment in hydrogen. A B-containing high-purity β-SiC powder is obtained.

Molten Si is doped with B, B-doped S
i lump is made, crushed and dropped into plasma, S
i is reacted with CH ₄ gas to obtain B-containing high-purity β-SiC powder.

Among the above, the B-containing β-SiC powder obtained by the methods of ,, and is particularly suitable for obtaining a high thermal conductive SiC ceramics without pressure.

Depending on the application, it may not be necessary to use the high thermal conductive ceramics of the present invention in the entire bulk.
In that case, it is effective to increase the thermal conductivity of only the surface layer by the following method from the viewpoint of cost reduction.

(A) SiC powder 1 having a particle size of 5 μm or less
00 parts by weight and B, C, B ₄ C, BN, A as a sintering aid
1 to 5 parts by weight of at least one of l ₂ O ₃ and BeO, and a step of producing a molded body using a mixed powder of a molding binder, (B) the surface of the above-mentioned molded body is synthesized in plasma B Covered with a mixture of β-SiC powder having a content of 5 wt% or less and a C content of 5 wt% or less and a particle size of 0.5 μm or less, and a binder necessary for molding, and then 2100 in an inert gas.
A step of heating at 2,500 ° C. for 5 to 300 minutes to integrate them,
As a result, 20 μ% or more of β-SiC particles having an aspect ratio of 20 or more are dispersed in 50 μm to 5 mm of the surface layer of the SiC sintered body, and the surface layer portion has a thermal conductivity of 130 W / m · K or more and pressureless sintering. Method for producing high thermal conductive SiC ceramics.

(A) SiC powder 1 having a particle size of 5 μm or less
00 parts by weight and B, C, B ₄ C, BN, A as a sintering aid
1 to 5 parts by weight of at least one of l ₂ O ₃ and BeO and a molding binder are used to prepare a molded body, and the molded body is stored in an inert gas at 2100 to 2500 ° C. for 5 to 30 parts.
Step of producing a primary sintered body by heating for 0 minutes, (B) B content of 5 wt% synthesized on the surface of the above sintered body in plasma
%, A C content of 5 wt% or less and a particle size of 0.5 μm or less of β-SiC powder and a binder necessary for molding, and the mixture is covered with a mixture of 5 to 5 ° C. at 2100 to 2500 ° C. in an inert gas.
By the step of performing secondary sintering for 60 minutes, a layer of 50 μm to 5 mm from the surface of the SiC sintered body is β having an aspect ratio of 20 or more.
-SiC particles are dispersed in an amount of 20 vol% or more, and the thermal conductivity of the surface layer portion is 130 W / mK or more.
Method of making iC ceramics.

By the above method or method, a member having excellent thermal shock resistance can be obtained. The pressureless sintered high thermal conductive SiC ceramics of the present invention can be applied to parts used in an ultrahigh temperature region such as gas turbine parts and the first wall of a fusion reactor.

Further, since the sintered body of the present invention can be sintered without pressure, its molding method is injection molding, press molding, cast molding, rubber press molding, extrusion molding, die powder molding, or the like. Various molding methods can be selected according to the required characteristics, and it is extremely convenient for obtaining highly heat-conductive and high-toughness ceramics with complicated shapes.

It is also possible to obtain a composite material having higher toughness by dispersing other ceramic particles or short fibers or long fibers in the high thermal conductive SiC ceramics.

[0035]

In order to prevent deterioration of the mechanical properties of the high thermal conductive SiC ceramics of the present invention, Si in the obtained sintered body is
It is important that 50% or more of the C composition is composed of β-SiC. By dispersing 20 vol% or more of β-SiC particles having an aspect ratio of 20 or more, a SiC sintered body having high thermal conductivity and high toughness can be obtained. This is because the dispersed β-SiC particles having an aspect ratio of 20 or more reduce the driving force for cracking and crack development.

However, if β-SiC changes to α-SiC by 50% or more during sintering, a large amount of grain growth of particles having a small aspect ratio occurs, resulting in a decrease in fracture toughness value.

[0037]

EXAMPLES The present invention will be specifically described based on examples.

Example 1 First, plasma treatment β-S
A method for synthesizing iC powder will be described.

Argon gas was introduced at a rate of 20 liters / minute from a gas introduction tube and discharged between the cathode and the anode under the conditions of 30 V and 700 A to generate plasma. Then, silane (SiH ₄ ) and diborane (B ₂ H ₄ ) were introduced to produce molten Si particles containing boron in the first reaction zone, and further reacted with methane (CH ₄ ) in the second reaction zone. Carbonized to a particle size of 0.
A β-SiC powder of 3 μm or less was synthesized.

Next, the above β-SiC powder was taken out into the air and various analyzes were conducted. No amorphous component was detected by X-ray diffraction analysis. The boron content is 0.3w
t%, free carbon amount is 1.5 wt%, oxygen amount is 0.3 wt%
Met. The total amount of metal impurities was 30 ppm or less.

A press forming binder was mixed with the above β-SiC powder in an amount of 2 wt% together with an organic solvent, dried and used as a forming raw material. By press molding, diameter 50 mm x thickness 1
A 0 mm molded body was produced. The obtained molded body was heated to 2200 ° C. in argon and kept for 1 hour to have a porosity of 3%.
The sintered body of was produced. According to X-ray diffraction analysis, 95% of the composition of the sintered body was β-SiC. From image processing and micro X-ray diffraction analysis, β-Si having an aspect ratio of 20 or more was obtained.
It was found that 25 vol% of C was present.

The thermal conductivity of the obtained sintered body at room temperature was 170 as a result of measurement by the laser flash method.
It was found to have W / m · K. Fracture toughness value is IM
As a result of measurement by the method, the average was 4.5 MPa√m.

Here, the B content of the β-SiC powder is set to 0.
3 to 5 wt% and the content of C were changed from 0 to 5 wt%, and molding and sintering were performed in the same manner.
SiC ceramics having a high thermal conductivity of W / m · K or more and a fracture toughness value of 3.5 MPa√m or more were obtained.

Here, when the C content is more than 5 wt%, the S gas having a high heat conductivity of 130 W / m · K or more is obtained by mixing the inert gas with hydrogen gas to remove the C.
An iC ceramic is obtained. Similarly, when the B content is high, by preheating in vacuum,
B can be decomposed and reduced.

Comparative Example 1 3 wt% of B ₄ C powder was added as a sintering aid to a commercially available β-SiC powder, and molding was performed in the same manner as in Example 1 and sintering was performed at 2200 ° C. for 1 hour. Commercial β
-SiC powder contains 0.1 wt% Fe as a metal impurity.
%, Al was 0.02 wt%, and oxide was 0.52 wt%. The thermal conductivity of the obtained sintered body is 105 W / m.
-K, the fracture toughness value was 2.7 MPa√m. From the X-ray diffraction analysis, it was found that 99% of the composition of the sintered body was β-SiC, and from image processing and micro X-ray diffraction analysis, 5 vol% β-SiC having an aspect ratio of 20 or more was present. .

Further, 3 wt% of B ₄ C powder was added to a commercially available β-SiC powder as a sintering aid, the mixture was molded in the same manner as in Example 1, and sintered at 2200 ° C. for 5 hours to promote grain growth. . From the X-ray diffraction analysis, 70% of the composition of the sintered body is β-S
37% by volume of β-SiC composed of iC and having an aspect ratio of 20 or more by image processing and micro X-ray diffraction analysis.
It turns out that it exists. However, the thermal conductivity of the obtained sintered body was 105 W / m · K. Therefore, it was found that the SiC ceramics having both high thermal conductivity and high toughness, which is the object of the present invention, cannot be obtained simply by using the conventional commercially available fine β-SiC powder containing many impurities.

[Embodiment 2] In the plasma synthesis of Embodiment 1, the total amount of metal impurities (Fe, Al, Ti, etc.) is set to 2
0.5wt% B changed from 0ppm to 3000ppm
A contained β-SiC powder was produced. Then, molding and sintering were performed in the same manner as in Example 1. From the X-ray diffraction analysis, 95% of the composition of all the sintered bodies was β-SiC, and from the image processing and the micro X-ray diffraction analysis, the aspect ratio was 20.
It was found that the above β-SiC was present in an amount of 20 vol% or more.

FIG. 1 shows the relationship between the amount of metal impurities and the thermal conductivity of the sintered body at room temperature. As can be seen from the figure, the thermal conductivity of the sintered body at room temperature is 1500 when the amount of metal impurities is 1500.
It was found that the thermal conductivity was 130 W / m · K or more at ppm or less. Therefore, the amount of metal impurities is 1500ppm
The following is preferable.

Further, in the case of SiC powder having a large amount of metal impurities, it is possible to remove some impurities when the SiC is decomposed by raising the sintering temperature during sintering to a range of 2300 ° C. to 2500 ° C. Is. However, at this time, β to α
Since there is a risk that the particles will become coarse due to the change to, the temperature control must be careful.

Example 3 A 1.2 wt% B-containing β-SiC powder was prepared by the plasma synthesis method of Example 1,
Molding and sintering were performed in the same manner as in Example 1.

Here, the sintering temperature is changed from 1900 ° C. to 220
Sintered bodies having different porosities were prepared by controlling in the range of 0 ° C. FIG. 2 shows the relationship between the sintered body porosity and the fracture toughness value.

It has been found that when the porosity exceeds 5%, the fracture toughness value decreases to 3 MPa√m or less. Therefore, the porosity of the sintered body is preferably 5% or less.

Example 4 A β-SiC powder containing 0.3 wt% B was prepared by the plasma synthesis method of Example 1,
Molding and sintering were performed in the same manner as in Example 1.

Here, the sintering temperature is changed from 2100 ° C. to 250
The temperature and time were controlled in the range of 0 ° C. to prepare sintered bodies having different contents of β-SiC particles having an aspect ratio of 20 or more in the sintered bodies.

FIG. 3 shows the relationship between the content of β-SiC particles having an aspect ratio of 20 or more in the sintered body and the thermal conductivity and the fracture toughness value.

A β-SiC particle having an aspect ratio of 20 or more is 20 vol% or more, has a thermal conductivity of 130 W / mK or more, and has a fracture toughness value of 3.5 MPa√m or more. I understood.

Example 5 Argon gas was introduced at a rate of 20 liters / minute from the gas introduction tube, and the amount of the argon gas between the cathode and the anode was 40%.
Discharge was performed under the conditions of V and 700 A to generate plasma. Then, silane (SiH ₄ ) and methane (CH ₄ ) were reacted and carbonized to synthesize β-SiC powder having a particle size of 0.2 μm or less. The β-SiC powder was taken out in air and various analyzes were performed.

No amorphous substance was detected by X-ray diffraction analysis. Free carbon amount is less than 1.5wt%, oxygen amount is 0.3wt%
%Met. The amount of metal impurities was 100 ppm or less.

B was added to the above β-SiC powder as a sintering aid.
1 wt% of ₄ C powder was added, and 12 wt% of a thermoplastic binder for injection molding was kneaded to obtain a molding raw material. This was injection-molded to prepare a 50 mm square × 10 mm thick molded body.
After degreasing the obtained compact in argon,
It was heated to 200 ° C. and kept for 1 hour to produce a sintered body having a porosity of 4%. The composition of the sintered body is composed of β-SiC 95%, and β-SiC with an aspect ratio of 20 or more is 30 vol.
It turns out that it exists.

The obtained sintered body had a thermal conductivity at room temperature of 140 W / m · K and a fracture toughness value of 4.1 MPa√m on average.
Met.

In the present embodiment, B, C, Al ₂ O ₃ , BN or the like can be used as the β-SiC powder sintering aid.

Example 6 Argon gas was introduced at a rate of 20 liters / minute from a gas introduction tube, and the amount of the argon gas was 30% between the cathode and the anode.
Discharge was performed under the conditions of V and 700 A to generate plasma. Then, a commercially available SiC powder was introduced, decomposed into Si and C in plasma, reacted with methane (CH ₄ ) and carbonized to synthesize β-SiC powder having a particle size of 0.2 μm or less.

No amorphous component was detected in the β-SiC powder by X-ray diffraction analysis. Free carbon amount is 4.5wt
%, And the amount of oxygen was 0.3 wt%. The amount of metal impurities is 5
It was below 00 ppm. This β-SiC powder was treated in a hydrogen stream at 1500 ° C. to remove excess C. This removal treatment was performed while confirming whether excess C was removed by the infrared absorption method. This will reduce the amount of free carbon to 0.5 wt.
% Or less.

B was added to the above β-SiC powder as a sintering aid.
1 wt% of ₄ C powder was added, and 12 wt% of a thermoplastic binder for injection molding was kneaded to obtain a molding raw material. A 50 mm square × 10 mm thick molded body was produced by injection molding this. After degreasing the obtained molded body in argon, it is heated to 2300 ° C. in argon + 5% hydrogen and kept for 1 hour,
A sintered body having a porosity of 2% was produced. The composition of the sintered body is 50
% Consists of β-SiC and has an aspect ratio of 20 or more β-
It was found that SiC was present in an amount of 35 vol%. The thermal conductivity at room temperature was 140 W / m · K, and the fracture toughness value was 4.7 MPa√m on average.

In this embodiment, B, C, Al ₂ O ₃ , BN or the like can be used as the β-SiC powder sintering aid.

Example 7 A 1.2 wt% B-containing β-SiC powder was prepared by the plasma synthesis method of Example 1,
Example 1 was prepared by adding 1 wt% of BeO powder to the SiC powder.
Molded in the same manner as above, and sintered in an argon atmosphere at 2100 ° C. for 2 hours.

The obtained sintered body had a thermal conductivity of 230 W / mK at room temperature and an average fracture toughness value of 4.6 MPa√m.
Met. It was found that the thermal conductivity was further improved when BeO powder was used as a sintering aid.

[Embodiment 8] Argon gas was introduced at a rate of 20 liters / minute from the gas introduction tube, and the amount of the argon gas was 30% between the cathode and the anode.
Discharge was performed under the conditions of V and 700 A to generate plasma. Then, a commercially available SiC powder is introduced, decomposed into Si and C in plasma, and reacted with diborane (B ₂ H ₄ ) to obtain S.
B is solid-dissolved in i and then reacted with methane (CH ₄ ) to be carbonized, and the B content of 0.3 μm or less is 0.2 wt%
Of β-SiC powder was synthesized.

The β-SiC powder was taken out into the air and various analyzes were conducted. No amorphous component was detected by X-ray diffraction analysis. Free carbon amount is 3.5wt%, oxygen amount is 0.3wt
%Met. The amount of metal impurities was 500 ppm or less. This β-SiC powder was treated at 1500 ° C. in a hydrogen stream to remove excess C in the powder. This removal treatment was performed while confirming whether excess C was removed by the infrared absorption method. As a result, the amount of free carbon was reduced to 0.1 wt% or less.

A 0.5 wt% dispersant for slip casting was added to the β-SiC powder to form a slurry. The slurry is slip-cast to a diameter of 50 mm
A molded body having a thickness of 20 mm was produced. The obtained molded body was heated to 2100 ° C. in nitrogen and held for 1 hour to produce a sintered body having a porosity of 4%.

98% of the composition of the above sintered body is β-SiC, and 22 vo of β-SiC having an aspect ratio of 20 or more is used.
It was found that 1% was present.

The obtained sintered body had a thermal conductivity at room temperature of 150 W / m · K and a fracture toughness value of 3.9 MPa√m on average.
Met.

Example 9 Commercially available β having a particle size of 0.5 μm
3% by weight of Al ₂ O ₃ powder as a sintering aid to SiC powder
The mixture was added and a press molding binder was mixed to obtain a molding raw material. This is press-formed with a diameter of 50 mm and a thickness of 20 m.
A molded body of m was produced. Next, the plasma-synthesized 2.3 wt% B-containing β-SiC powder prepared in the same manner as in Example 1 was mixed with a press molding binder to obtain a molding raw material. This is press-molded to have a diameter of 50 mm and a thickness of 5 m.
A molded body of m was produced.

The above two molded bodies were laminated and integrally molded.
Then, the obtained integrally molded body is placed at 2200 ° C. in argon.
And heated for 1 hour to prepare a sintered body. This makes it possible to produce a sintered body having SiC having a high thermal conductivity of 150 W / m · K on the surface of the SiC base material having a thermal conductivity of 100 W / m · K.

In the present embodiment, it is possible to wrap the entire surface of the base material with the high thermal conductive material by the slip casting method or the slurry coating method.

Further, in the same manner as described above, it is possible to obtain a structure or a slanted structure in which a plurality of layers of a low thermal conductive material, a high thermal conductive material, a low thermal conductive material, a high thermal conductive material, etc. are laminated.

Example 10 A commercially available α-SiC powder having a particle size of 0.5 μm was added with 4 wt% of B ₄ C powder as a sintering aid.
It was added and mixed with a press molding binder to obtain a molding raw material. This is press-formed with a diameter of 50 mm and a thickness of 20 m.
A molded body of m was prepared, heated to 2200 ° C. in argon and held for 1 hour to prepare a sintered body.

Next, a layer made of β-SiC containing 1.3 wt% B was formed on the surface of the above-mentioned base material sintered body by plasma spraying, heated to 2200 ° C. in argon, and held for 1 hour for firing. The bonded surface layer was densified. Thus, a SiC film having a high thermal conductivity of 150 W / m · K can be formed on the surface of the SiC base material having a thermal conductivity of 100 W / m · K.

As the above-mentioned base material sintered body, not only a pressureless sintered material but also a hot pressed material, a reaction sintered material, a HIP material and the like can be used, and the material is only a SiC matrix. Not limited to.

As a result of an experiment, it was found that a reaction sintered silicon nitride or a reaction sintered silicon nitride binder having a similar thermal expansion coefficient and no sintering aid can be used as the base material.

In the present invention, by forming a SiC film containing few impurities, it becomes possible to improve not only high thermal conductivity and high toughness but also oxidation resistance.

[Embodiment 11] The first wall member of the fusion reactor of the nuclear power plant was examined.

The sintered body obtained in Example 1 was applied as a member of the furnace wall 1 shown in FIG. As a result, it was found that it has sufficient thermal shock resistance to withstand a sudden temperature change due to neutron irradiation.

Further, it can be easily compounded with carbon fiber, and the neutron absorption characteristic can be improved by using the compound SiC.

Since the high-heat-conductivity / high-toughness SiC ceramics of the present invention can be produced by pressureless sintering, the fusion reactor first wall parts of a nuclear power plant, gas turbine moving blade members, stationary blade members, combustion It can be applied as a material for a vessel member and a shroud member.

Example 12 The high thermal conductive ceramics obtained in Example 1 was applied to a liner tube, a reaction tube and a wafer boat of a semiconductor diffusion furnace. As a result, since the thermal shock resistance and the thermal uniformity are excellent as compared with the conventional low thermal conductivity SiC product, the size of the wafer can be increased to 15 inches.

[0087]

Industrial Applicability The present invention relates to SiC ceramics having high heat conduction and high toughness which can be applied to products having complicated shapes.
A green compact made of high-purity β-SiC powder is dispersed with 20 vol% or more of β-SiC particles having an aspect ratio of 20 or more,
High-thermal-conductivity SiC ceramics having a thermal conductivity of 130 W / m · K or more can be obtained by performing pressureless sintering to obtain a sintered body having a porosity of 5 vol% or less.

As described above, in the present invention, highly pure β-
By controlling the structure of the sintered body using the SiC powder, it is possible to obtain SiC ceramics having high heat conductivity and high toughness by the pressureless sintering method.

Since the high thermal conductivity and high toughness SiC ceramics of the present invention can be produced by pressureless sintering, it can be applied to complex shaped products, and the fusion reactor first wall member of a nuclear power plant and the gas turbine rotor blade member. , A vane member, a combustor member, a shroud member, a semiconductor wafer manufacturing apparatus, and the like, which are effective as members required to have heat resistance and thermal shock resistance.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the total amount of metal impurities in β-SiC powder and the thermal conductivity of the obtained sintered body.

FIG. 2 is a graph showing a relationship between a porosity of a sintered body and a fracture toughness value.

FIG. 3 β-SiC with an aspect ratio of 20 or more in a sintered body
It is a graph which shows the relationship between content of particles, thermal conductivity, and fracture toughness value.

FIG. 4 is a partial schematic perspective view of a fusion reactor first wall member of a nuclear power plant.

[Explanation of symbols]

1 ... Furnace wall, 2 ... Cooling medium flow furnace, 3 ... Intermediate material, 4 ... Metal coating layer, 5 ... Groove.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Saito 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Jiro Kondo 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Nippon Steel Corporation Advanced Technology Research Center

Claims (8)

[Claims] 1. A high thermal conductive SiC ceramics comprising a sintered body in which 20 vol% or more of β-SiC particles having an aspect ratio of 20 or more are dispersed. 2. 50% or more of the SiC component in the SiC sintered body is β-SiC, and β-SiC particles having an aspect ratio of 20 or more are dispersed in an amount of 20% by volume or more. High thermal conductivity SiC ceramics. 3. A layer of 50 μm to 5 mm from the surface of the sintered body, and 20 vo of β-SiC particles having an aspect ratio of 20 or more.
A high thermal conductive SiC ceramics, which is formed of a SiC sintered body having 1% or more dispersed therein. 4. The high thermal conductive SiC ceramics according to claim 1, wherein the porosity of the sintered body is 5% or less. 5. A B content of 5 wt% or less and a C content of 5 wt%
% Or less of a β-SiC powder having a particle size of 0.5 μm or less and a molding binder to form a molded body, and the molded body is subjected to no pressure in an inert gas or an inert gas + hydrogen in 210
A method for producing a highly heat-conductive SiC ceramic, which comprises heating at 0 to 2500 ° C. for 5 to 300 minutes. 6. The high thermal conductive SiC according to claim 5, wherein the β-SiC powder is a raw material powder synthesized in plasma.
Ceramics manufacturing method. 7. (A) SiC powder 10 having a particle size of 5 μm or less
0 parts by weight and B, C, B ₄ C, BN, Al ₂ as a sintering aid
A step of producing a molded body from a mixed powder in which 1 to 5 parts by weight of at least one of O ₃ and BeO and a molding binder are mixed, and (B) a B content of 5 wt% or less on the surface of the molded body,
Β-Si with a C content of 5 wt% or less and a particle size of 0.5 μm or less
A layer composed of a mixed powder of C powder and a binder for forming is formed, and 2100 to 2100 in an inert gas or an inert gas + hydrogen.
A method for producing a highly heat-conductive SiC ceramic, comprising a step of integrally heating at 2500 ° C. for 5 to 300 minutes. 8. (A) SiC powder 10 having a particle size of 5 μm or less
0 parts by weight and B, C, B ₄ C, BN, Al ₂ as a sintering aid
A molded body is prepared from a mixed powder in which 1 to 5 parts by weight of at least one of O ₃ and BeO and a molding binder are mixed, and the molded body is subjected to 2100 in an inert gas or an inert gas + hydrogen.
A step of producing a primary sintered body by heating at 2,500 ° C. for 5 to 300 minutes, and (B) particles having a B content of 5 wt% or less and a C content of 5 wt% or less by plasma spraying on the surface of the primary sintered body. A layer made of β-SiC having a diameter of 0.5 μm or less is formed and 2100 to 2100 in an inert gas or an inert gas + hydrogen.
A method for producing a high thermal conductive SiC ceramic, comprising a step of secondary heating at 2500 ° C. for 5 to 60 minutes.