JPH01294512A - Novel silicon carbide powder and calcined silicon carbide compact - Google Patents

Abstract

PURPOSE:To provide a calcined silicon carbide compact having a high mechanical strength with a small dispersion thereof by adding boron and carbon as a calcining assistant to specific silicon carbide powder as a raw material, forming the resultant mixture and calcining the obtained compact. CONSTITUTION:Silicon carbide powder to be a raw material has 5-30m<2>/g specific surface area and 0.05-0.4mu average particle diameter. The crystal form is hexagonal and 3-30% stacking fault is contained therein. The silicon carbide powder is used to form a calcined compact by the following method. That is, 0.05-0.5 pt.wt. boron and 0.5-3.0 pts.wt. carbon are added and mixed with 100 pts.wt. silicon carbide powder and the resultant mixture is formed and calcined at a temperature within the range of 1900-2150 deg.C. The resultant calcined compact has >=3.10g/ml density and 3-15mu average particle diameter and 5-20 aspect ratio of a microstructure. The crystal form is cubic and 0.5-5.0% stacking fault is contained therein.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a novel easily sinterable silicon carbide powder and a novel silicon carbide sintered body having excellent physical properties.

(Prior Art) Ceramic sintered bodies obtained by sintering fine powder of silicon carbide are expected to have expanded uses as high-temperature structural materials.

A notable advantage of silicon carbide sintered bodies is that they do not tend to lose strength at high temperatures. Further examples include excellent corrosion resistance, high thermal conductivity, and low coefficient of thermal expansion. Therefore, silicon carbide sintered bodies that have both these advantages are being actively researched and developed for applications such as automobile gas turbine parts and engine parts, high-temperature heat exchangers, bearings, and burners for combustion furnaces. There is.

The reason why the strength is less likely to deteriorate under such high temperatures is said to be that silicon carbide is a compound with strong covalent bonding, and therefore atoms form strong bonds with each other in the sintered body.

The fact that silicon carbide is a compound with such strong covalent bonding properties means that it is a material that is difficult to sinter. The reasons for this are, firstly, that the diffusion rate of atoms is slow, and secondly, that the conditions under which new bonds are established during the sintering process are limited.

A pressureless sintering method is suitable for industrially producing ceramic sintered bodies with complex shapes.

However, since silicon carbide powder is a material that is difficult to sinter, special measures are required to enable pressureless sintering. Several reports, including patents, have been introduced regarding methods for sintering silicon carbide. Representative methods include the following two U.S. patents and a corresponding Japanese patent that use boron and carbon as sintering aids.

(1) U.S. Patent No. 4,004,934 (equity + M
(No. 57-32035) (2) U.S. Patent No. 4,32
No. 1,954 (Japanese Patent Publication No. 59-34147) The method (1) above uses 0.3
After adding and mixing an amount of a boron compound corresponding to ~3.0% by weight of elemental boron and an amount of a carbon source equivalent to 0.1 to 1.0% by weight of elemental carbon, this mixture is molded to form an inorganic material. This is a method of obtaining a silicon carbide sintered body by heating to a high temperature of 1900 to 2100°C in an active atmosphere without applying pressure.

Method (2) is based on silicon carbide powder containing 5% by weight or more of α-products, and a boron compound in an amount equivalent to 3.0% by weight of elemental boron and 0.5 to 5.0% by weight. of carbon compound in an amount equivalent to the elemental carbon and heated to high temperature,
This is a method for obtaining a silicon carbide sintered body without substantially changing the crystal form of the silicon carbide powder and the sintered body.

(Problems to be Solved by the Invention) By using these methods, it is possible to obtain a dense silicon carbide sintered body having a density of 95% or more of the theoretical density. However, the silicon carbide sintered bodies obtained by these methods have problems such as low mechanical strength and too large variations in strength for applications that require heavy mechanical loads such as gas turbines for automobiles. This poses an obstacle to industrial application.

Generally, it is known that there is a strong relationship between the mechanical properties of a ceramic sintered body and the microstructure of the sintered body, and in order to obtain a sintered body with high strength, its microstructure must be determined by the following (a) ~ (
It is necessary to satisfy the three conditions C). Here, the microstructure of a sintered body refers to a three-dimensional structure of particles and defects (voids) that constitute the sintered body.

(a) The defects contained in the sintered body are few and small.

(b) The particle size of the single particles constituting the sintered body is small.

(c) There are no specifically grown coarse particles exceeding 50 g in the sintered body.

Moreover, what has recently become an established theory is that the following condition (d) is satisfied.

(d) The shape of the particles constituting the sintered body has anisotropy.

The presence of anisotropy in the shape of the particles, which is the condition (d), means that the fracture surface that occurs when the sintered body breaks increases. It is presumed that this is to increase the energy required for destruction. In other words, the sintered body is difficult to break.

Here, the anisotropy of particle shape refers to the presence of three-dimensional anisotropy in the shape of particles, such as plate-like or rod-like shape. Needless to say, the sintered body as a whole needs to have no grain orientation in a specific direction.

Conventional techniques have not produced a silicon carbide sintered body that satisfies all of the conditions (a) to (d) in F. (Method of Japanese Patent Publication No. 57-32035) cannot overcome the drawback that coarse particles are easily generated, and method (2) (method of Japanese Patent Publication No. 59-34147)
However, there is a problem in that the single grain of the sintered body has no anisotropy and a sintered body with high strength cannot be obtained.

(Another Means to Solve the Problem) The present inventors aimed to obtain a silicon carbide sintered body with high mechanical strength and small variation, and the present inventors have developed a sintered body that has been proposed in the past as a guideline. This is the result of intensive research aimed at obtaining a sintered body in which the fine structure of the particles constituting the body satisfies all of the conditions (a) to (d) above.

Using a new and unprecedented silicon carbide powder as a raw material,
By specifying the sintering conditions, the above (a) to (d)
It has been found that a microstructure satisfying the conditions (a) to (d) can be obtained with good reproducibility, and furthermore, a sintered body having a microstructure satisfying the conditions (a) to (d) actually has high mechanical strength and small variations in mechanical strength. This has been confirmed and the present invention has been completed.

That is, the first aspect of the present invention has a specific surface area of 5 to 30 crn.
'/g, an average particle size of 0.05-0.4g, and a cubic crystal shape containing 3-30% stacking irregularity. The second invention is the above-mentioned novel silicon carbide powder 1.
0.05 to 0.5 parts by weight of boron and 0.00 parts by weight.
After adding and mixing 5 to 3 Oi parts of carbon, the mixture is molded and sintered at a temperature in the range of 1900 to 2150"C to obtain a density of 3.10 g/d or more and a fine structure. Carbonized material having an average particle size of 3 to 15 g, an aspect ratio of 5 to 20, and a cubic crystal shape containing 0.5 to 5.0% lamination irregularity. This invention is a silicon sintered body.

The present invention will be explained in detail below.

The silicon carbide powder of the present invention must satisfy the following three conditions.

First, the first condition is that the specific surface area of the powder is 5~aorn'
/g range. The reason is that the specific surface area is less than 5rtf/g.

The density of the silicon carbide sintered body (hereinafter simply abbreviated as sintered body) obtained by heating and sintering the powder is 3.10 g/ml.
This is because it is difficult for the specific surface area to exceed 30 m
This is because if the value exceeds ``/g, the driving force during heating and sintering is too large, or coarse particles are likely to be generated in the resulting sintered body.

The second condition is that the average particle diameter ρ of silicon carbide powder is 0.0.
It requires 5 to 0.4 g.

The reason for this is that when ρ is less than o, 05=, the density of the compact before heating and sintering is low, or the resulting sintered compact tends to contain large defects, such as 10p or more. On the other hand, if ρ exceeds 0.4p,
This is based on the experimental findings of the present inventors that the density of the obtained sintered body is unlikely to exceed 3.10 g/d, and more preferably ρ is approximately 0.1 to 0.2.
In addition, it is more preferable because the standard deviation of ρ is ρ × 0.8 or less, which is a narrow particle size distribution, and because the heating temperature during sintering can be lowered. As described in detail in [Particle Size Measurement Method] below, the method used was to obtain the particle size from an electron microscope image.

The third condition requires that the crystal form of the silicon carbide powder be cubic, and that it contains 3 to 30% lamination irregularity. The reason for this is based on the inventors' experimental findings that only silicon carbide powder that satisfies this condition has a strong tendency for the microstructure of the sintered body to exhibit anisotropy when sintered. It is based on

Silicon carbide powder that satisfies the above three requirements can be produced by the method previously proposed by the present inventors in JP-A No. 59-83922, that is, silicon oxidation is carried out by a chemical reaction between a decomposable silicon compound and a decomposable carbon compound. A powder containing an extremely fine mixture of carbon and elemental carbon is produced, and then this powder is mixed with O,
After tightening to a bulk density of 15 g/d or more, 1600-19
It can be obtained by heating to a temperature of 00''c.

To describe in more detail the method for producing the powder of finely mixed silicon oxide and elemental carbon described above, first, as the decomposable silicon compound, SiC or 4, HSj (413, (CL)2) is used.
SiCfL2, CIIJiCJls, 5i(
Silicon compound molecules such as OC2HJn are used. Next, examples of decomposable carbon compounds include LPG and naphtha.

Petroleum products such as gasoline, fuel oil, kerosene, diesel fuel oil, lubricating oil, and liquid paraffin; methane, ethane, propane, butane, pentane, methanol, ethanol, propatool, ethylene, acetylene, n-paraffin, butadiene, isoprene , isobutylene, benzene, toluene, xylene.

Petroleum such as cyclohexane, cyclohexene, dicyclopentadiene, ethylbenzene, styrene, kyrene, pseudocumene, mesitylene, alkylbenzene, α-methylstyrene, dicyclododecatriene, diisobutylene, vinyl chloride, chlorobenzene, Cs fraction mixture, ethylene bottoms, etc. A suitable method is to select a chemical product that is mutually soluble with the decomposable silicon compound, mix the two, and inject the mixture into hot gas containing water vapor at 700° C. or higher.

As for other methods for producing fine silicon carbide powder mainly composed of cubic crystals, the following two methods are generally known as representative methods. That is, (a) after mechanically mixing silicon oxide and carbon or silicon and carbon, heating to a temperature of 2000″C or less,
A method of pulverizing the produced carbon silicon.

(b) A silicon compound such as SiH,,5i(CHi)4 and a carbon compound such as C114, Czfl, etc.
A method of producing silicon carbide through a gas phase reaction in an atmosphere heated to a temperature of 0°C or higher.

However, according to the results of follow-up experiments conducted by the present inventors on the above two methods (a) and (b), although the crystal shape of the silicon carbide powder obtained by the method (a) is mainly cubic,
The rest are 2H type hexagonal high shapes, and the content of stacking irregularities is 1
% or less. In addition, although the silicon carbide powder obtained by the method (b) has a single particle of about 0.1 part, the particles are bonded together, and the average particle diameter according to the present invention is 0.1 part. The crystal size is 41L or more, and the crystal shape is a cubic crystal with an extremely fine crystal grain size, and the content of lamination irregularities is 1% or less. Therefore, the above (
The silicon carbide powder obtained by methods (a) and (b) does not meet all the requirements of the present invention.

Silicon carbide sintered bodies are made by heating and molding silicon carbide powder.
It is obtained by sintering, but in the present invention, prior to molding, it is necessary to add and mix a small amount of elemental boron or a boron compound and elemental carbon as a sintering aid to promote sintering to silicon carbide powder. . The amount added is 0.05 to 0.5 parts of the former in terms of elemental boron, and 0.5 to 3.0 parts of the latter in terms of elemental boron, per 100 parts by weight of silicon carbide powder (parts by weight is hereinafter simply abbreviated as parts). It is 0 copies.

For that purpose, it is desirable to mix the sintering aid with the silicon carbide powder as uniformly as possible, and elemental boron or boron compounds should have a specific surface area of 3 m"/g or more, and elemental carbon should have a specific surface area of 30 rn"/g. The above fine powders are preferred.

The above mixing is performed using a ball mill, vibration mill, etc., but in order to obtain a more homogeneous mixture, water or an organic solvent such as methanol or ethanol is added and the mixture is wet-mixed using a ball mill, vibration mill, etc. Preferably, the method of
This is a method in which water or an organic solvent is added to and mixed with elemental carbon fine powder and silicon carbide fine powder, and then the water or organic solvent is removed by evaporation.

Note that the boron compounds that can be used in the present invention include:
Examples include fine powder 84C, ON, BP, and A-mon 8□. Further, examples of fine powdered elemental carbon include carbon black and acetylene black.

The thus obtained silicon carbide powder containing a small amount of sintering aid is then molded into a desired shape, and then molded under no pressure in a vacuum or an inert gas atmosphere such as argon or helium, that is, a molded body. The silicon carbide sintered body of the present invention can be obtained by heating the surface of the silicon carbide without applying mechanical pressure, but the heating temperature is 1.
It is necessary to set it as 900-2150 degreeC. The reason for this is that at a heating temperature of less than 1,900°C, the density of the obtained sintered body decreases. This is because it is difficult for the temperature to exceed tOg/mi, and conversely, at a temperature exceeding 2150°C, coarse particles are likely to be generated in the obtained sintered body. Note that the amount of lamination irregularities in the sintered body is smaller than that contained in the silicon carbide powder that is the raw material. And the higher the sintering temperature, the smaller the amount. However, the microstructure of a sintered body obtained using the silicon carbide powder specified in the present invention as a raw material at a sintering temperature such that the lamination irregularity in the sintered body is 0.5 to 50% is specified in the present invention. The average particle size is 3 to 15 l, and the aspect ratio is 5.
It is possible to have a range of 20 to 20.

As described in detail above, the novel silicon carbide powder of the present invention is usually produced by the first method described above, that is, by chemically reacting a monodegradable silicon compound and a decomposable carbon compound, silicon oxide and elemental carbon are made into extremely fine particles. It was obtained by producing a mixed powder, then compressing this powder to a bulk density of 0.15 g/Trt1 or more, and then heating it to 1,600 to 1,900°C. 30C
Go/g. (b) The average particle diameter is 0.05 to 0.4. (c) The crystal form is cubic, and there are 3
Contains ~30% lamination irregularity. It has this characteristic.

The sintered body of the present invention obtained by heating and sintering this silicon carbide powder by the method specified in the present invention has the following three characteristics.

That is, firstly, the density of the sintered body is 3.10 g/ml or more. Second, the average grain size of the microstructure is 3-15, and the aspect ratio is 5-20.

Thirdly, the crystal form is a cubic crystal form, in which 0.5~
Contains 5.0% lamination irregularity.

Here, the microstructure refers to the three-dimensional structure of the particles and defects that make up the sintered body, as described above, but the average particle diameter and aspect ratio are measured by smoothing the surface of the sintered body and It is determined from an image magnified with a mirror (usually 100 to 1000 times), and the particle size is the average value of the maximum length (L) and minimum length (D) of each particle in this image. is the arithmetic mean value of the particle diameter, and the aspect ratio is the arithmetic mean value of L/D. It is usually sufficient to determine these for 300 or more particles.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in the examples, the standard deviation of the average particle diameter per particle diameter, the ratio of stacking irregularities, and the crystal form were quantified and measured by the methods described below.

Examples 1 to 3 Powders 1 to 3 in Table 1 were obtained using the method previously proposed by the present inventors in JP-A-59-83922, that is, using (CH3)JiC as a decomposable silicon compound, A heavy oil is used as the decomposable carbon compound, and these are mixed in advance and injected into the flame obtained by burning kerosene with air.
A sooty, extremely fine mixture containing 1.8% by weight of SiO□ and 68.1% by weight of elemental carbon was obtained.

This fine mixture was then compressed to a bulk density of 6 g/ml at 1700 °C, 1800 °C, and 19 °C, respectively.
It was obtained by heating to 00° C. to generate silicon carbide according to the reaction formula shown in equation (1) below, and then burning off excess carbon.

SiO, + 3C → SiC + 2CO... (1) 1st
As shown by the values in the table, powders 1 to 3 obtained in Examples 1 to 3 satisfy the physical property conditions as silicon carbide powder of the present invention.

Incidentally, a powder X-ray diffraction image of the powder material is shown in FIG.

Comparative Example 1.2 Powder 4 was 5i)1. , C114, and H2 in a direct gas phase reaction, and can be obtained by a conventionally known method [e.g.

It was produced at a reaction temperature of 1400° C. according to Journal of the Chemical Society of Japan, Su, 188-193 (1980)].

Powder 5 is a commercially available product, and its microscopic image shows that it was made by mixing silicon dioxide or silicon with elemental carbon and heating it to obtain coarse particles of silicon carbide, which were then ground for a long time using a vibrating mill or the like to become fine powder. It was estimated that

Table 1 As shown in the numerical values in Table 1, powders 1 to 1 obtained in Examples 1 to 3
As mentioned above, Powder 4 satisfies the physical property conditions for the silicon carbide powder of the present invention, but in comparison, the crystal form of Powder 4 obtained in Comparative Example 1 is mainly cubic, but there is no stacking irregularity. The crystal form of powder 5, which is a commercially available product, is similar to the cubic crystal form as its main component;
The rest is a 2H type hexagonal crystal, and the content of stacking irregularities is 1
% or less.

Examples 4 to 6 To 100 g of each of powders 1 to 3 shown in Table 1, 0.25 g of 11, c powder with a specific surface area of 10.4 rn'/g as a boron source, and 0.25 g of c powder with a specific surface area as a simple carbon source were added. 120.
2 g of carbon black of 5 m''/g and 50 mfi of ethanol were added and mixed in a resin ball mill for 20 hours. The resulting mixture was heated to remove the ethanol by evaporation. After putting it in a cylindrical container and compressing it on the l-axis with a load of 0.5T/cnf, it was compressed to 2T/c.
It was molded by rubber pressing under a hydrostatic pressure of tn'.

Next, these powder compacts were heated in a high-frequency heating furnace for 10-
1950°C in a nitrogen atmosphere under a vacuum of ~l Torr
A silicon carbide sintered body was obtained by heating at a temperature of 30 minutes.

Table 2 shows the density, average particle diameter of microstructure, aspect ratio, and crystal shape of the obtained sintered body.

Twenty test pieces were cut out from each of the silicon carbide sintered bodies, and the bending strength was measured according to the method of JIS R1601. Similarly, xte was measured using the Vickers indentation method from each of the 20 test pieces. These measured values are shown in Table 2.

As shown by the values in Table 2, any silicon carbide sintered body produced using silicon carbide powder having physical properties that meet the conditions of the present invention and sintered under the conditions specified by the present invention meets the objectives of the present invention. It had satisfactory characteristics. In addition, the sintered body of the present invention has high bending strength and small variation, and
It can be seen that tC is also high.

Comparative Example 3.4 Using powders 4 and 5 shown in Table 1, a silicon carbide sintered body was obtained by the same method and under the same conditions as in the example. The density of the obtained sintered body was measured. As shown in Table 2, the results are all well below the target value of 3.1 og/m or more of the present invention.

Table 2 Comparative Examples 5 to 7 Using powders 4 and 5 shown in Table 1, sintering conditions etc. were searched to increase the density of the compacts, and the combustion conditions were changed to those shown in Table 3 (3 A silicon carbide sintered body was obtained under the same conditions as in Examples 4 to 6 except for the conditions listed in the table. The density of the obtained sintered body is as shown in Table 3, and for powder 4 (comparative example 5)
) It could be increased by increasing the amounts of B and C added, and for Powder 5 (Comparative Examples 6 and 7) it was possible to increase by increasing the heating temperature.

Therefore, for the sintered bodies obtained in Comparative Examples 5 and 7, in which the sintered body density reached 3.10 g/711 iJ or more, the average particle diameter of the microstructure, crystal shape, bending strength, etc. were measured and shown in Table 4.

As a result, a sintered body having a large average particle size and satisfying the requirements of the present invention could not be obtained. Furthermore, it can be seen that the sintered bodies have lower bending strength and greater variation in bending strength than those obtained in Examples 4 to 6, and are inferior in KIC.

Table 3 Table 4 [Particle size measurement method] The particle size of silicon carbide powder in the present invention is measured using a mirror image using a microscope, which is the only method to directly observe a single particle.The microscope is a transmission electron microscope.

Use an IIA microscope.
1. As is well known, powder particles are used as sample supports in an electron microscope.
1. When supporting the particles on the carrier, agglomeration and organization of the particles may occur.
However, it is quite difficult to prepare a sample that is representative of the entire powder. In order to prevent this problem, many studies have been carried out in the past (for example, "Powder Particle Size Measurement Method" published by Yokendo, published by Powder Engineering Research Association, 1972).
Various methods are described in Chapter 4.

The present inventors have intensively studied these various methods. As a result, a slurry in which powder particles are dispersed is sprayed using a nebulizer onto a sheet mesh using collodion as a support film, and the powder particles are supported on the collodion film. It was determined that the best results could be obtained with the sample prepared using the following methods.
1 The particle size of the powder shall be determined from an electron microscope image of a sample obtained by this spraying method.

The slurry preferably uses isobutanol as a dispersion medium, and the powder slurry concentration is preferably in the range of 0.3 to 0.7%. In order to disperse the powder, a powerful A method using an ultrasonic disperser for several minutes is preferred.

The particle size of the powder is determined from the microscopic image of the sample thus obtained, and here the particle size is assumed to be the equivalent circle diameter. This equivalent circle diameter is a value expressed by the diameter of a circle that is assumed to have the same area as the particle image after determining the area of the particle image.

In the present invention, in order to eliminate the possibility of arbitrariness in whether a certain image is regarded as a single particle or as a plurality of particles, for example, in the case of a gourd-shaped image, even partially connected are all considered to be a single particle. In addition,
As the amount of powder supported on the supporting film increases, the probability that multiple particles will appear to be a single particle will increase, so the particle size at the time of the main image is determined by the proportion of the particle image in the entire image. It shall be determined from a sample prepared such that the area is in the range of 5 to 15%. Note that the average particle diameter is the arithmetic mean value of the five diameters of the circular phase.

[Lamination irregularity determination method] In the present invention, the lamination irregularity in silicon carbide powder and sintered body is determined by minimizing the difference between the X-ray diffraction intensity value of the powder obtained by the step scan method and the theoretical value using parameters. It was determined by the profile method. (Reference, J.
Kakinoki and Y, Komura,
J, Phys, Soe, Japan,
7. 30-35 (+952)) [Crystal form determination method] Low-temperature α crystal (2H) contained in silicon carbide powder and sintered body
) and high-temperature α crystals (4H, 6H, 15R) are determined by C
It is determined from a pattern obtained by powder X-ray diffraction using a uKa ray as a light source and a monochromator on the receiving side. The method of calculating each component from the height of each peak of the figure is described in the Ceramics Association Journal.
Danyu.

576-582 (+979) shall be followed.

(Operations and Effects of the Invention) Although the present invention has been considered ideal for some time, a manufacturing method thereof has not been established. A method for producing a silicon carbide sintered body with an excellent microstructure was established by using a new raw material silicon carbide powder and by specifying the sintering conditions.

The results of measuring the mechanical strength of the sintered body obtained by the method of the present invention show that, as shown in the examples, the strength is clearly higher than that of the conventional sintered body, the variation is small, and the fracture toughness value is (Kxc) was also confirmed to be high.

The silicon carbide sintered body obtained by the method of the present invention has an excellent microstructure as described above, and the reason for this is presumed to be as follows.

(a) Lamination irregularities contained in the raw material powder tend to create new bonds during the sintering process. That is, the silicon carbide powder of the present invention is easily sinterable.

(b) Since the raw material powder is easily sinterable, sintering can be performed with the added amount of boron, which is a sintering aid, of 0.05 to 0.3 parts by weight, which is smaller than the conventional technology. Therefore, generation of coarse particles in the sintered body is suppressed.

(c) Since an easily sinterable raw material powder is used, the sintering temperature is 1
It is possible to lower the temperature to 900 to 2150° C. than in the past, thereby suppressing enlargement of the sintered particles.

(d) The crystal form of the raw material powder is cubic, and since it contains 3 to 30% lamination irregularity, the microstructure of the sintered body exhibits anisotropy.

[Brief explanation of the drawing]

FIG. 1 shows a powder X-ray diffraction diagram of Powder 1 in Example. Procedure 7 City ■ Sansho (voluntary) 1. Display of the case 1986 Patent Application No. 125487 2 Title of the invention New silicon carbide powder and silicon carbide sintered body 3 Person making the amendment Relationship to the case Patent applicant address 3-2 Kasumigaseki, Chiyoda-ku, Tokyo No. 5 name (3
12) Mitsui Toatsu Kagaku Co., Ltd. Representative: Haruo Sawamura 4, Agent Address: 5th Floor, 7th Floor, Midoriya Building 2, 3-7-3 Shinbashi, Minato-ku, Tokyo 105, Date of Amendment Order Voluntary Action 6, Claims Increased by Amendment Number of paragraphs 07. Subject of amendment: "Claims column" and "Detailed explanation of the invention column" of the specification. 8. Contents of amendment (1) The description of the claims of the specification is as shown in the attached sheet. I will correct it. (2) r3 on page 7, line 19, page 16, lines 1-2 of the same book
Correct 0cm'/gJ to r30rn''/gJ. (3) In the same book, page 3, line 6, change "equivalent" to "correspond"
I will correct it. (4) In the same book, page 15, line 10, “50%” was changed to “5.0%.”
” will be corrected. (5) r K , c (K N/
m3/2)" to r K1(: (M N/ m""
) Correct to J. (6) “Nebulizer” in the same book, page 25, lines 16-17
to "nebulizer". (or more) (1) Specific surface area is 5 to 30 m''/g, average particle diameter is 0.
05 to 0.41L, and the crystal form is a cubic crystal form, and the silicon carbide powder is characterized in that it contains 3 to 30% of lamination irregularity. (2) Silicon carbide powder io according to claim 1. Parts by weight include O, OS~0.5 parts by weight of boron and 0.5~
After adding and mixing 3.0 parts by weight of carbon, the mixture is molded and sintered at a temperature in the range of 1900 to 2150°C, resulting in a density of 3.1 Og/m or more and an average particle size of the microstructure. 3 to 15p, an aspect ratio of 5 to 20, and a cubic crystal shape containing 0.5 to 5.0% lamination irregularity. .

Claims (2)

[Claims] (1) The specific surface area is 5 to 30 cm^2/g, the average particle diameter is 0.05 to 0.4 μ, and the crystal form is cubic, which contains 3 to 30% stacking irregularity. Silicon carbide powder characterized by: (2) After adding and mixing 0.05 to 0.5 parts by weight of boron and 0.5 to 3.0 parts by weight of carbon to 100 parts by weight of the silicon carbide powder according to claim 1, the mixture is molded. 19
The density obtained by sintering at a temperature in the range of 00 to 2150 ° C is 3.10 g / ml or more, and the average particle size of the microstructure is 3 to 2150 ° C.
A carbon-silicon sintered body having an aspect ratio of 5 to 20 in 15 prefectures, a cubic crystal shape, and containing 0.5 to 5.0% lamination irregularity therein.