JP2826080B2 - Silicon nitride / silicon carbide composite sintered body and method for producing composite powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon nitride / silicon carbide composite sintered body and a composite powder.
It is excellent in toughness, thermal shock resistance, corrosion resistance, static fatigue resistance, wear resistance, etc., it can use inexpensive raw materials and the manufacturing process is simple, so it can be used for high temperature structural materials such as gas turbines and automobile engines. An object of the present invention is to provide a method suitable as a low-cost method for manufacturing a sliding material such as a rocker arm.

[0002]

2. Description of the Related Art Silicon nitride-based ceramic sintered bodies are required to be used at high temperatures in view of high strength, high heat resistance, high thermal shock resistance, high abrasion resistance and oxidation resistance. It is expected to be used as structural ceramics that are used under severe conditions. Various components are added for the purpose of improving the mechanical strength. Among them, silicon carbide is a ceramic component capable of exhibiting good mechanical strength, and a ceramic sintered body in which silicon carbide is mixed with silicon nitride has been proposed. However, in a sintered body obtained by simply mixing a silicon nitride powder and a silicon carbide powder, silicon carbide particles (size on the order of microns) exist only at the grain boundaries of silicon nitride, or have a nanocomposite structure. As
The ratio of the silicon carbide particles to be compounded in the silicon nitride particles is small, and a sufficient compounding effect cannot be obtained. Therefore, various methods have been proposed to obtain a sintered body having a nanocomposite structure in which silicon carbide is finely dispersed in silicon nitride.

Japanese Patent Application Laid-Open No. Hei 2-160669 discloses that silicon carbide having an average particle size of 1 μm or less is dispersed in grain boundaries, and fine particles of silicon carbide having a size of several nanometers to several hundred nanometers are dispersed in silicon nitride particles. A composite silicon nitride-silicon carbide sintered body having a microstructure is disclosed. This composite sintered body uses an amorphous silicon nitride-silicon carbide composite powder or a silicon nitride-silicon carbide mixed powder that generates fine silicon carbide having an average particle diameter of 0.5 μm or less in a liquid phase sintering system, 15 in the presence of sintering aids
It is manufactured by sintering at a temperature of 00-2300 ° C. However, the amorphous silicon nitride-silicon carbide composite powder is obtained by a gas phase reaction method of an organic silicon compound, and is very expensive and inferior in mass productivity. Further, there is a problem that the amorphous powder is inferior in moldability.

Japanese Patent Application Laid-Open No. 3-103361 discloses that a silicon nitride powder is used as a base material, and a reinforcing material having a size of 1 μm or less and 5 to 20 μm is used.
A composite sintered body containing silicon carbide particles covering both ranges of μm is disclosed, but this composite sintered body is a sintered body obtained by mixing silicon nitride powder and silicon carbide powder, and the silicon carbide is fine. Does not have a nanocomposite structure dispersed in
There is a problem that a combined effect cannot be sufficiently obtained.

Japanese Patent Application Laid-Open No. 3-261611 discloses a method for producing a silicon nitride composite powder for producing a silicon nitride / silicon carbide composite sintered body, comprising mixing a metal Si powder and a carbonaceous powder, The resulting mixture in a nitrogen-containing inert gas atmosphere,
A method is disclosed in which heating is performed at a temperature of 1400 ° C. or lower to simultaneously perform a carbonization reaction and a nitridation reaction of metal Si powder. However, since this composite powder grows during the reaction, the resulting powder has a large particle size, and since the starting material does not contain a sintering aid, the silicon nitride produced by the heat treatment is β
There is a problem that the mold is easily formed and the sinterability is poor.

Accordingly, an object of the present invention is to provide good strength,
An object of the present invention is to provide a method for producing a silicon nitride / silicon carbide composite sintered body having static fatigue resistance, wear resistance and hardness at low cost.

[0007]

As a result of intensive studies in view of the above objects, the present inventors have used silicon powder, carbonaceous powder, and a sintering aid as starting materials, and performed a nitriding reaction of silicon by heat treatment. The present inventors have found that a composite powder and a composite sintered body of silicon nitride and silicon carbide which are excellent in sinterability can be obtained by causing a carbonization reaction with silicon carbide.

That is, in the method of the present invention for producing a composite sintered body of silicon nitride and silicon carbide, a carbon powder and a sintering aid are mixed with silicon powder, and the resulting mixed powder or a mixture formed therefrom is obtained. The molded body is heat-treated in an atmosphere containing nitrogen gas to cause a nitridation reaction and a carbonization reaction of silicon, and thereafter, is sintered in an atmosphere containing nitrogen gas. Further, the method of the present invention for producing a composite powder of silicon nitride and silicon carbide comprises mixing a silicon powder with a carbonaceous powder and a sintering aid, and subjecting the resulting mixed powder to a heat treatment in a nitrogen gas-containing atmosphere. , to Oko the carbonization reaction and nitriding reaction of silicon, containing the α-silicon nitride
A composite powder of silicon nitride and silicon carbide .

Hereinafter, the present invention will be described in detail. [1] Starting material (a) Silicon powder The silicon powder used in the present invention has an average particle size of 0.2 to 20 µm.
m, particularly preferably 0.3 to 10 μm. Average particle size
If it is smaller than 0.2 μm, the oxidation of the powder surface is large, and if it is larger than 20 μm, uniform dispersion becomes difficult and reactivity becomes poor.

[0010] The silicon powder may be selected from relatively low-purity and inexpensive materials as defined in JIS G 2312.
A wide range of materials can be used, including high-purity materials obtained by pulverizing broken materials of semiconductor silicon wafers. When high-purity silicon powder is used, Fe, Cr, Co
The reaction can be promoted by adding a compound such as described above or a simple substance.

When the total amount of the silicon powder and the carbonaceous powder in the starting material is 100% by weight, the content of the silicon powder is 81.2%.
997.6% by weight is preferred, and 84.2-93.2% by weight is more preferred. If the silicon powder is less than 81.2% by weight, the sintered body is hard to be densified, and a desired composite sintered body cannot be obtained. Also
If it exceeds 97.6% by weight, the combined effect of silicon carbide will not be sufficient.

(B) Carbonaceous powder The carbonaceous powder used in the present invention is not particularly limited as long as it is fine, but graphite powder or carbon black powder such as acetylene black or Ketjen black is preferred. The carbonaceous powder has an average particle size of 20 μm or less, particularly
It is preferably 10 μm or less. If the average particle size is larger than 20 μm, uniform dispersion becomes difficult.

When the total amount of the silicon powder and the carbonaceous powder in the starting material is 100% by weight, the content of the carbonaceous powder is 2.
It is preferably from 4 to 18.8% by weight, more preferably from 6.8 to 15.8% by weight. If the carbonaceous powder is less than 2.4% by weight, the composite effect cannot be obtained, and if it is more than 18.8% by weight, the sintered body will not be densified.

(C) Silicon nitride powder In order to improve the moldability of the mixed powder and to make it a nucleus for silicon nitride formation, 0.1 to 5 μm, preferably 0.1 to 3 μm.
A silicon nitride powder having an average particle size of m may be added.
The addition amount of the silicon nitride powder is 0 to 100% by weight of the total of the silicon nitride formed by the heat treatment and the added silicon nitride.
The content is preferably 10% by weight, more preferably 0 to 5% by weight. If the addition amount of the silicon nitride powder is too large (if the ratio of the silicon nitride powder to the silicon powder is too high), Si
Is insufficient in reaction sintering, and a combined effect cannot be obtained.

(D) Silicon Carbide Powder The silicon carbide powder may be added in a small amount for the same purpose as the silicon nitride powder, that is, to improve the moldability of the silicon powder mixture and to serve as a core for silicon carbide formation. . The preferable addition amount of silicon carbide powder is 0% with respect to the total amount of silicon carbide formed by heat treatment and silicon carbide to be added being 100% by weight.
-10% by weight, more preferably 0-5% by weight. If the addition amount of silicon carbide is too large, the reaction sintering of silicon becomes insufficient, and a combined effect cannot be obtained.

(E) Sintering aid powder Al ₂ O ₃ , MgO, HfO ₂ , Al
N, and _{Y 2 O 3, Yb 2 O} 3, Lu 2 O 3, Tm 2 O
_At least one selected from compounds of rare earth elements such as ₃ is added. Among them, Y ₂ O ₃ is preferable, and Y ₂ O ₃ may be used in combination with the sintering aid powder described above.

The content of the sintering aid powder is preferably 5 to 20% by weight, more preferably 7 to 15% by weight, based on 100% by weight of the total amount of the composite powder produced by the heat treatment. If the amount of the sintering aid powder is less than 5% by weight, the sinterability is insufficient, and if it is more than 20% by weight, the high-temperature strength of the sintered body is low.

[2] Manufacturing method of composite sintered body (1) Preparation of molded body First, the respective components are blended so as to have the above-mentioned blending ratio, and are sufficiently mixed by a ball mill, a kneader or the like. Mixing may be dry or wet. In the case of wet mixing, a dispersion medium such as water, ethanol, or butanol is added to the powder mixture. The obtained mixed powder is molded into a desired shape. As a molding method, press molding, slip casting molding, injection molding or the like can be used.

In the case of press molding, molding is performed using a desired press mold after removing the dispersion medium. In the case of slip casting, it is poured into a hygroscopic mold together with the dispersion medium. In the case of injection molding, an appropriate organic or inorganic binder is added and the mixture is injected into a mold. Examples of the organic binder include ethyl silicate, polyethylene glycol, polyvinyl alcohol (PVA), acrylic emulsion, and polyurethane emulsion. An inorganic binder can also be added. To produce a molded article having a complicated shape, slip casting or injection molding is preferred.

(2) Nitriding / Carburizing Treatment The molded body is heated in a nitrogen-containing atmosphere to perform a nitriding reaction and a carbonizing reaction of the silicon powder in the molded body. The nitriding rate and carbonization rate are determined by the amount of the carbonaceous powder in the starting material. That is,
Since substantially all of the carbon is combined with silicon to form silicon carbide, substantially all of the unreacted silicon is converted to silicon nitride. For example, if silicon and carbon are mixed at a molar ratio of 100: 7, the molar ratio of silicon nitride to silicon carbide is 31: 7.

The conditions of the nitriding / carbonizing treatment need to be slightly changed depending on the thickness of the compact, the particle size of the starting material powder, etc., but the temperature is set to 1450 ° C. or less. Heating to a temperature exceeding 1450 ° C. is not preferable because silicon elutes. Nitriding /
The lower limit of the carbonization temperature is preferably set to 1000 ° C. 1000
If the temperature is lower than 0 ° C, the nitriding / carbonizing reaction does not occur, or the reaction rate is too low even if it occurs. A more preferred reaction temperature is 12
00-1400 ° C.

The pressure of the nitrogen-containing atmosphere is preferably 1 kg / cm ² or more, more preferably 5 to 2000 kg / cm ² . If the pressure of the nitrogen-containing atmosphere is less than 1 kg / cm ² , the nitriding does not proceed well. The time for the nitriding / carbonizing treatment varies somewhat depending on the thickness of the compact, the particle size of the starting raw material powder, the nitriding treatment temperature, and the like, but is generally preferably about 1 to 10 hours. Note that the nitrogen-containing atmosphere is an atmosphere of a nitrogen-containing gas, and examples of the nitrogen-containing gas include a nitrogen gas, a mixed gas of nitrogen and hydrogen, or a mixed gas of nitrogen and ammonia.

When the nitriding / carburizing treatment is performed under the above conditions, the silicon particles in the compact are nitrided to form silicon nitride containing α-silicon nitride finer than the starting material silicon particles, and to form carbon and carbon nitrides. It reacts to produce silicon carbide particles finer than the starting silicon particles and carbon particles.

The above steps (1) and (2) may be reversed. That is, first, a nitriding / carbonizing treatment may be performed to produce a composite powder, and then the composite powder may be pulverized and then molded and sintered. For the composite powder produced in this case,
Details are described in [3].

(3) Sintering The compact after nitriding is sintered at a temperature of 1600 to 2200 ° C., preferably at a temperature of 1800 to 2000 ° C. If the sintering temperature is lower than 1600 ° C., the densification of the sintered body becomes insufficient, and desired characteristics cannot be obtained. If the sintering temperature exceeds 2200 ° C., decomposition of silicon nitride starts, which is not preferable. Sintering is performed in an atmosphere containing nitrogen gas. At this time, the atmospheric gas pressure is 5 to 20
It is preferable to be about 00 kg / cm ² . The sintering time is preferably about 1 to 5 hours. Hot pressing or HIP is preferred in order to achieve a good sintered body density.

(4) Silicon nitride / silicon carbide composite sintered body The silicon nitride / silicon carbide composite sintered body obtained by the above method is:
It has a so-called nanocomposite structure in which fine silicon carbide particles are dispersed in silicon nitride particles. Since silicon carbide particles have a larger coefficient of thermal expansion than silicon nitride particles, it is considered that residual stress acts on the silicon nitride particles. It is also considered that fine silicon carbide particles dispersed in the silicon nitride grain boundaries act like a wedge that suppresses grain boundary sliding of silicon nitride.

Therefore, when the ratio of silicon carbide / silicon nitride is small, the above effects cannot be sufficiently obtained. On the other hand, silicon carbide /
If the ratio of silicon nitride is too large, too many silicon carbide particles are dispersed, so that grain growth of silicon nitride is suppressed, and the density of the sintered body does not sufficiently increase. From the above points, the weight ratio of silicon carbide / silicon nitride is preferably 5/95 to 50/50, and 15/85 to 40/50.
/ 60 is more preferred.

[3] Production method of composite powder After mixing each component with the same material and method as described in the above section [2] Production method of composite sintered body, nitriding / carbonizing treatment is performed without molding. I do. Nitriding / carbonization conditions are as above
[2] The same as described in (2) may be used, but in the case of powder, the nitriding / carbonization reaction tends to occur at a slightly lower temperature than the heat treatment of the molded body. Therefore, the temperature of the nitridation / carbonization reaction is 11
The temperature is more preferably set to 00 to 1380 ° C.

After the nitriding / carbonization reaction, the mixture is ground to obtain a composite powder. The average particle size of the composite powder is preferably about 0.1 to 5 μm. The composite powder can be molded and sintered by the same method as described in the above [2] (1) and (3).

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited thereto.

Example 1 71.7% by weight of silicon powder having an average particle diameter of 0.5 μm (JIS MSi 1) and 11.9% of carbon black powder having an average particle diameter of 0.2 μm
Wt%, 3.9 wt% of silicon nitride powder having an average particle size of 0.1 μm, and 2.1 wt% of silicon carbide powder having an average particle size of 0.2 μm
And 10.4% by weight of Y ₂ O ₃ powder having an average particle size of 1.4 μm were weighed so that a total of 300 g was obtained when 100% of the reaction had proceeded, and a ball mill was used to weigh 18 g of ethanol as a solvent.
Mix for hours and dry.

The obtained raw material powder 1 is filled in a graphite die 2 having a diameter of 50 mm as shown in FIG. 1 and kept at 1400 ° C. for 4 hours in an atmosphere containing nitrogen gas at 9 atm to cause a nitriding / carbonization reaction. Then, the temperature was increased to a maximum of 1800 ° C. under a load of 5 t in a nitrogen gas atmosphere, and hot press sintering was performed for 4 hours. Observation of the structure of the obtained sintered body with an electron microscope revealed that it had a nanocomposite structure schematically shown in FIG. In the figure, A indicates silicon nitride particles, B indicates silicon carbide particles, and C indicates a phase composed of Si-YO. After measuring the density of the sintered body by the Archimedes method, the silicon carbide content and the hardness were measured. The results are as follows.

Sintered body density: 3.3 g / cm ³ Silicon carbide content ^* : 35% by weight Hardness (Hv) ^** : 2197 kg / mm ² Note *: Quantitative analysis of Si, C and N elements in the sintered body It was calculated from the results. [SiC / (SiC + Si ₃ N ₄ )] × 100% **: The surface of the sample was polished with diamond and measured with a Vickers hardness tester at 500 g × 10 seconds.

Further, the sintered body was cut into a size of 3 mm × 4 mm × 40 mm to obtain a test piece, and a three-point bending strength test (room temperature and 1400 ° C.) and a static fatigue test were performed under the following conditions.
The results are as shown in Table 1 below. (1) Three-point bending strength test: At room temperature, the test is performed under the conditions of a span of 30 mm and a crosshead speed of 0.5 mm / min. I went in. (2) Static fatigue test: The test piece was set in a three-point bending jig having a span of 30 mm, heated to 1300 ° C., held for 1 hour, and measured for the time required to break by applying a predetermined stress. The test was stopped if the sample did not break after a certain period of time. During the test, the displacement of the test piece was observed with a high-resolution CCD camera.

Table 1 Three-point bending strength Room temperature: 580 MPa 1400 ° C .: 591 MPa Static fatigue test (load stress 396 MPa, 160 hours) No breakage, maximum displacement 0.15 mm or less

Examples 2-3, Comparative Example 1 Silicon powder (JIS MSi 1) having an average particle size of 0.5 μm, carbon black powder having an average particle size of 0.2 μm,
The proportions of the silicon nitride powder having a particle diameter of 0.1 μm, the silicon carbide powder having an average particle diameter of 0.2 μm, the Y ₂ O ₃ powder having an average particle diameter of 1.4 μm, and the AlN powder having an average particle diameter of 2 μm are shown in Table 2. (However, the total amount is 300 g when 100% reaction has progressed.)
Mix for 18 hours and dry. The obtained raw material powder was used in Example 1.
After hot press sintering under the same conditions as above, the characteristics were evaluated. Table 2 shows the results.

Table 2 Composition of raw material powder (% by weight) Example 2 Example 3 Comparative Example 1 Silicon powder 72.9 69.9 80.6 Carbon black powder 10.4 11.3-Silicon nitride powder 4.3 3.9 7.1 Silicon carbide powder 1.8 2.0-Y ₂ O ₃ powder 10.6 9.0 12.3 AlN powder-3.9- Characteristic sintered body density (g / cm ³ ) 3.2 3.2 3.0 Silicon carbide content (% by weight) ⁽¹⁾ 30 340 Hardness (Hv) ⁽²⁾ 2012-1062 Three-point bending strength Room temperature 570 328 170 (MPa) 1400 ℃ 584 252- ^* Static fatigue characteristics No break ^{(3) No} break ⁽⁴⁾ - ^* Maximum displacement (mm) ⁽⁵⁾ 0.14 or less 0.21 or less-Note: (1) Example 1 It was calculated in the same way as in. (2) Measurement was performed in the same manner as in Example 1. (3) The test piece did not break even after 140 hours at a load stress of 368 MPa, and the test was stopped. (4) The test piece did not break even after 90 hours at a load stress of 190 MPa, and the test was stopped. (5) Maximum displacement under each static fatigue test condition. * High temperature properties were not measured due to silicon elution.

Comparative Examples 2 and 3, silicon nitride powder having an average particle size of 1.2 μm (direct nitriding method, α /
α + β = 92%), a silicon carbide powder having an average particle diameter of 1.2 μm, and a Y ₂ O ₃ powder having an average particle diameter of 1.4 μm were weighed at the ratio shown in Table 2 (the total amount was 300 g), and were weighed using a ball mill. For 18 hours using ethanol as a solvent and dried. The obtained raw material powder was filled in a graphite die having a diameter of 50 mm as shown in FIG. 1, heated to a maximum of 1800 ° C. under a load of 5 t in a nitrogen gas, and subjected to hot press sintering for 4 hours. The characteristics of the obtained sintered body were evaluated in the same manner as in Example 1. Table 3 shows the results.

Table 3 Raw material powder composition (% by weight) Comparative example 2 Comparative example 3 Silicon nitride powder 92.0 64.4 Silicon carbide powder-27.6 Y ₂ O ₃ powder 8.0 8.0 Characteristic sintered compact density (g / cm ³ ) 3.2 3.0 Silicon carbide Content (% by weight) ⁽¹⁾ 0 30 Hardness (Hv) ⁽²⁾ 1698 1194 Three-point bending strength Room temperature 775 408 (MPa) 1400 ° C 139 123 Static fatigue properties Rupture ⁽³⁾ Rupture ⁽⁴⁾ Note: (1) It was calculated in the same manner as in Example 1. (2) Measurement was performed in the same manner as in Example 1. (3) Fracture in a load stress of 83 MPa for 36 seconds. (4) Breaking load stress 83MPa, 1 second.

As described above, the sintered bodies of Comparative Examples 2 and 3 which are not sintered bodies formed by reaction sintering of silicon powder do not have sufficient mechanical strength and heat resistance. This is presumably because the silicon nitride particles do not have a nanocomposite structure in which silicon carbide particles exist.

Example 4 78.0% by weight of silicon powder (JIS MSi 1) having an average particle size of 3.4 μm and 11.2% by weight of graphite powder having an average particle size of 5 μm
And 10.8% by weight of Y ₂ O ₃ powder having an average particle size of 1.4 μm were weighed so that a total of 300 g when reacted 100% was mixed, mixed by a ball mill using ethanol as a solvent for 18 hours, and dried. The obtained powder was heat-treated at 1380 ° C. in a nitrogen gas atmosphere at 9 atm, and then pulverized together with 200 parts by weight of silicon nitride balls and 200 parts by weight of ethanol in a 500 ml pot for 7 days. Those that passed through the sieve were collected to obtain a composite powder. This composite powder was filled in a graphite die 2 having a diameter of 42 mm as shown in FIG.
The temperature was raised to 50 ° C., and hot press sintering was performed for 4 hours. After measuring the density of the obtained sintered body by the Archimedes method, JIS R 1601
A three-point bending test was performed at room temperature and high temperature (1300 ° C. and 1400 ° C.) according to the above. The results are as follows.

Sintered body density: 3.32 g / cm ³ Silicon carbide content: 30% by weight Three-point bending strength Room temperature: 1084 MPa 1300 ° C .: 1000 MPa 1400 ° C .: 830 MPa

Example 5 The composite powder obtained in Example 4 was put into a mold and press-molded, and further subjected to an isotropic pressure of 4 t / cm ^{2 with} a CIP device to obtain 55%.
A molded body of mm × 35 mm × 6 mm was obtained. 9
Atmospheric pressure sintering at 2000 ° C for 4 hours in a nitrogen gas atmosphere, then HIP at 1850 ° C for 1 hour in a 1000 atmosphere nitrogen gas atmosphere
Sintered. After measuring the density of the obtained sintered body by the Archimedes method, the density is measured at room temperature and high temperature (1400 ° C.) in accordance with JIS R 1601.
A point bending test and a static fatigue test were performed. The results are as follows.

Sintered body density: 3.29 g / cm ³ Silicon carbide content: 30% by weight Three-point bending strength Room temperature: 958 MPa 1400 ° C .: 756 MPa Static fatigue test (load stress 592 MPa, 90 hours) Maximum displacement 0.07mm or less

[0045]

As described in detail above, in the present invention, a mixed powder containing a silicon powder, a carbon powder and a sintering aid is used as a starting material, and a nitriding reaction of silicon is performed by heat treatment in a nitrogen gas-containing atmosphere. Since a carbonization reaction is caused, silicon carbide particles are finely dispersed in silicon nitride particles in the obtained composite sintered body, and have a nanocomposite structure. Therefore, the composite sintered body obtained by the method of the present invention is excellent in room temperature strength, high temperature strength, hardness, toughness, thermal shock resistance, corrosion resistance, static fatigue resistance, wear resistance, and the like. In addition, the method for producing a composite sintered body and composite powder of the present invention can use inexpensive raw materials and the production process is simple. Is suitable as a low-cost manufacturing method.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a graphite die for hot pressing used for manufacturing a molded body for a composite sintered body of the present invention.

FIG. 2 is a schematic diagram showing the structure of a composite sintered body obtained in Example 1.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01D 5/28 C04B 35/56 101D F01L 1/18 101U F02C 7/00 35/58 102V (72) Inventor Yoshikatsu Higuchi Wako Saitama 1-4-1, Ichichuo, Japan Inside Honda R & D Co., Ltd. (56) References JP-A-3-261611 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/584 C01B 21/068 C04B 35/565

Claims (13)

(57) [Claims] 1. A method for producing a composite sintered body of silicon nitride and silicon carbide, comprising mixing a siliconaceous powder with a carbonaceous powder and a sintering aid, and forming a compact formed from the resulting mixed powder. A method comprising heat-treating in a nitrogen gas-containing atmosphere to cause a nitridation reaction and a carbonization reaction of silicon, and thereafter sintering in a nitrogen gas-containing atmosphere. 2. The method for producing a composite sintered body of silicon nitride and silicon carbide according to claim 1, wherein the content of the sintering aid is 100% by weight of the total amount of the molded body produced by the heat treatment.
A method of 5 to 20% by weight. 3. The method for producing a composite sintered body of silicon nitride and silicon carbide according to claim 1, wherein the mixed powder comprises a silicon powder, a carbonaceous powder, a sintering aid, A method comprising mixing silicon and / or silicon carbide. 4. The method for producing a composite sintered body of silicon nitride and silicon carbide according to claim 1, wherein the weight ratio of silicon carbide / silicon nitride is 5/95 to 50/50. A method comprising: 5. The method for producing a composite sintered body of silicon nitride and silicon carbide according to claim 1, wherein the heat treatment in the nitrogen gas-containing atmosphere is performed at a temperature of 1450 ° C. or less. Features method. 6. The method for producing a composite sintered body of silicon nitride and silicon carbide according to claim 1, wherein the molded body is heated to 1600 ° C. to 2200 ° C. in an atmosphere containing nitrogen gas.
And sintering. 7. A method for producing a composite powder of silicon nitride and silicon carbide, comprising mixing a silicon powder with a carbonaceous powder and a sintering aid, and subjecting the resulting mixed powder to a heat treatment in a nitrogen gas-containing atmosphere. and, to Oko the carbonization reaction and nitriding reaction of silicon, alpha-type nitrogen
Produces composite powder of silicon nitride containing silicon carbide and silicon carbide
Wherein the that. 8. The method for producing a composite powder of silicon nitride and silicon carbide according to claim 7, wherein the content of the sintering aid is such that the total amount of the composite powder produced by the heat treatment is 100% by weight.
A method of 5 to 20% by weight. 9. The method for producing a composite powder of silicon nitride and silicon carbide according to claim 7, wherein the mixed powder comprises silicon powder, carbonaceous powder, a sintering aid, silicon nitride, and silicon nitride. And / or mixing with silicon carbide. 10. The method for producing a composite powder of silicon nitride and silicon carbide according to claim 7, wherein the weight ratio of silicon carbide / silicon nitride is 5/95 to 50/50. Features method. 11. The method for producing a composite powder of silicon nitride and silicon carbide according to claim 7, wherein the heat treatment in the nitrogen gas-containing atmosphere is performed at a temperature of 1450 ° C. or less. how to. 12. A method for producing a composite sintered body of silicon nitride and silicon carbide, wherein the compact formed from the composite powder of silicon nitride and silicon carbide according to claim 7 is nitrogen-coated. A method characterized by sintering in a gas-containing atmosphere. 13. The method for producing a composite sintered body of silicon nitride and silicon carbide according to claim 12, wherein the compact is sintered at 1600 ° C. to 2200 ° C. in an atmosphere containing nitrogen gas. how to.