JPH06100366A - Method for manufacturing ceramic-carbon composite material - Google Patents

Abstract

(57) [Summary] [Object] To provide an industrial manufacturing method for obtaining a ceramic-carbon composite material of high density and high strength and having a homogeneous structure with high productivity. [Structure] Silicon carbide powder is mixed with mesophase pitch powder having a carbonization yield of 65% or more at 1000 ° C., quinoline-soluble content of 2 to 15%, and mesophase content of 40% or more, and dispersed in ethanol to form a slurry. Turn into. The slurry is thoroughly wet-milled by a planetary ball mill until the average particle size becomes 5 μm or less. The treated slurry is dried and then pressure-molded, and then 800-2 in a non-oxidizing atmosphere.
Baking is performed in a temperature range of 300 ° C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production method for efficiently obtaining a high density and high strength ceramic-carbon composite material using mesophase pitch powder which is a carbon precursor and ceramic powder as raw materials.

[0002]

2. Description of the Related Art Carbonaceous materials composed of carbon or graphite have a high degree of heat resistance, thermal shock resistance, and chemical stability.
Since it has excellent heat and electric conductivity and is easy to machine, it is useful in a wide industrial field as an industrial member. However, the carbonaceous material has a defect peculiar to the material such as lack of properties such as mechanical strength and oxidation resistance. For this reason, research and development has been actively pursued to compensate for the material defects of the carbonaceous material and improve the characteristics. Among them, the method of improving the structure by compounding ceramics is considered to be a practical means. ing.

Conventionally, as an example of producing a ceramic-carbon composite material, for example, a method in which raw coke and ceramic powder (particularly silicon carbide) are pressure-molded without a binder and then fired (JP-A-56-14005) ), In order to further improve this to achieve high density and high strength, a method in which boron carbide is added to the above-mentioned raw coke-silicon carbide powder material and ground and then pressed and sintered by hot pressing (special feature Kaisho 60-11
No. 8671) is known. However, the raw coke used as a raw material in these methods has a drawback that electrical resistance and other appropriate characteristics cannot be imparted due to its non-graphitizing property. In the latter method, although the grinding process effectively works to increase the mechanical strength, a pressure of ² tf / cm ² or more is required at the time of molding, and the sintering process is performed under pressure, so it is not suitable for the production of large products. In addition to the equipment restrictions, the grinding time can reach 20 hours or more, so mixing of impurities is unavoidable,
It is also disadvantageous in terms of cost.

As a compounding means that does not require grinding treatment, ceramic powder is suspended in a tar fraction of a self-sintering mesophase precursor and heat-treated (into mesophase) while blowing an inert gas. Then, a method of molding and firing (Japanese Patent Laid-Open No. 61-136906) has been proposed. Although this method does not have the above-mentioned disadvantages associated with the grinding treatment, it has a drawback that the steps from the homogeneous dispersion step of the ceramic powder to the molding powder containing the mesophase precursor are complicated, which makes it an industrial production method. Is poorly qualified. In addition, the production of ceramic-carbon composite materials by the self-combustion method in which the graphite material having an appropriate porosity is heated to melt the metallic silicon placed on the upper part, and the heat of reaction heats the graphite pores into silicon carbide. A method (Japanese Patent Laid-Open No. 60-118671) has also been proposed, but a sufficiently homogeneous composite structure cannot be obtained by this method.

[0005]

As described above, the prior art has not developed a method capable of industrially producing a ceramic-carbon composite material having a homogeneous structure by a simple process. The present inventor, as a result of earnestly advancing research to solve such a problem, uses a specific mesophase pitch as a carbon-based raw material and improves mixing and pulverization with a ceramic powder in a short period of time as compared with the prior art. It was confirmed in the process that a high-density, high-strength ceramic-carbon composite material can be manufactured inexpensively.

The present invention was developed on the basis of the above findings, and its purpose is to industrially manufacture a ceramic-carbon composite material having a homogeneous structure having high density and high strength with high productivity. To provide a method.

[0007]

The method for producing a ceramic-carbon composite material according to the present invention for achieving the above object has a carbonization yield of 65% or more at 1000 ° C. and a quinoline-soluble content of 2-15. %, The mesophase pitch powder having a mesophase content of 40% or more is mixed with ceramic powder,
After being dispersed in an organic solvent to form a slurry, a wet pulverization treatment is sufficiently performed, and after drying, a pressure-molded compact is fired in a temperature range of 800 to 2300 ° C. in a non-oxidizing atmosphere. It is a feature of.

In the present invention, 10 carbon source materials are used.
The carbonization yield at 00 ° C is at least 65%, the quinoline-soluble content is 2 to 15%, and the mesophase content is 40%.
A mesophase pitch powder having a property of not less than% is selectively used. This raw material selection is a requirement for obtaining a high-density and high-strength ceramic-carbon composite material without structural defects. If the above properties and composition range are not satisfied, will cracks or cracks occur in the structure during the firing stage? The bulk density and material strength of the finally obtained composite are extremely low. The mesophase pitch powder has an average particle size of 1 to 1.
It is finely pulverized to a size of 5 μm before use, but the maximum particle size is preferably 10 μm or less.

There are no particular restrictions on the ceramic powder. For example, oxide-based, carbide-based, nitride-based, boride-based,
One type or a mixture of two or more types such as a silicide type is used. Among these, silicon carbide and silicon nitride can be mentioned as ceramics suitable for the purpose of the present invention. The average particle size of the ceramic powder is 0.5.
It is preferable to adjust to a range of 10 μm.

The compounding ratio of the mesophase pitch powder and the ceramic powder is appropriately set according to the target characteristics of the composite material, but the range is generally 5 to 300 parts by weight of the ceramic powder to 100 parts by weight of the mesophase pitch powder. It is preferable that When the compounding ratio of the ceramic powder is less than 5 parts by weight, the reinforcing composite effect cannot be obtained, and conversely, when it exceeds 300% by weight, the effect imparting effect of the carbonaceous material is reduced and the initial purpose cannot be achieved.

The mesophase pitch powder and the ceramic powder mixed in a predetermined ratio are dispersed in an organic solvent to form a slurry. The reason why the organic solvent is used as the dispersion medium is that the low boiling point component contained in the mesophase pitch is extracted into the solvent in the process from slurry formation to wet pulverization, and it is effective in preventing firing cracking. As the organic solvent, alcohol, acetone or the like having a small surface tension is preferably used, and the mixture is stirred and mixed in the range of 30 to 100 parts by weight with respect to 100 parts by weight of the blended raw material powder to form a slurry.

The slurry-form mixed raw material is then subjected to a wet pulverization treatment. This treatment is carried out using a rotary stirring device such as a ball mill. As for the ball mill used, a planetary ball mill is more effective than a rotation type ball mill because homogenous dispersion and pulverization proceed in a short time. In the case of using the planetary ball mill, the preferable crushing condition is to set both the revolution number and the revolution number in the range of 50 to 500 rpm. The crushing time varies depending on the amount of the raw material slurry charged, but it is desirable that the crushing time be the time until the average particle size after treatment becomes 5 μm or less. By this wet pulverization process, the raw material powder is pulverized to an average particle size of 5 μm or less,
At the same time, it becomes a homogeneous slurry with excellent dispersion stability.

The slurry after the wet pulverization treatment has a thickness of 80 to 200.
The mixture is heated to a temperature of ℃, volatilizes the dispersion medium component, is dried, and is then pressure-molded into a predetermined shape. A normal pressure molding method using a uniaxial press or an extrusion press can be applied to the molding means, but it is preferable to use a cold isostatic press (CIP) in order to make the material into an isotropic and dense structure. . A molding pressure of about 1 tf / cm ² is sufficient, but a molding pressure of up to 2.5 tf / cm ² can be applied to impart a high level of mechanical strength.

The molded body is set in a heating furnace which is replaced with an inert gas such as nitrogen or argon, or the surroundings are covered with a carbonaceous packing such as coke powder and placed in a firing furnace under a non-oxidizing atmosphere. The mesophase pitch component is carbonized by the firing treatment. The firing temperature is usually 800 to 1000 ° C., but if necessary, the temperature is raised to 2300 ° C. to convert the carbonaceous component into a semi-graphitized state. However, when the temperature becomes higher than this, the ceramic component decomposes, so that the upper limit temperature must be 2300 ° C.

[0015]

According to the present invention, the mesophase pitch powder having a specific range of compositional properties selectively used as a carbon source material skillfully balances the densification and shrinkage behavior of the structure during carbonization, and the structure of the firing treatment stage It functions effectively to form a high-density, high-strength composite tissue without causing damage. Then, in the process step of wet-milling the slurry of mesophase pitch powder and ceramic powder, the raw material powder is made finer to 5 μm or less and a stable homogeneous dispersion system is formed.
It effectively contributes to high density and high strength characteristics. Furthermore, at this stage, the low boiling point component contained in the mesophase pitch is extracted into the organic solvent and volatilized and removed at the same time during drying, so that the cause of damage during firing is eliminated in advance.

By such synergistic effects, it becomes possible to efficiently obtain a high density and high strength ceramic-carbon composite material having a homogeneous composite structure at all times through a short process.
Moreover, since the manufacturing process is simple and a large-scale device is not required, it is extremely advantageous for industrial production of large-sized materials.

[0017]

【Example】

Examples 1 to 6, Comparative Examples 1 to 3 Mesophase pitch powder having different composition properties [Kawasaki Steel Co., Ltd., KMFC series] 100 parts by weight of silicon carbide powder [Pacific Random Co., Ltd., GMF-15S] 90
By weight, 200 parts by weight of the dispersion medium was mixed appropriately and made into a slurry. The slurry was placed in a planetary ball mill and wet-milled under the conditions of an orbital speed of 200 rpm and a rotational speed of 400 rpm. The slurry after wet crushing is 20
The dispersion medium component was removed by drying at 0 ° C. for 8 hours.

Table 1 shows the compositional properties of the mesophase pitch powder used, the particle size of the ceramic powder, the type of dispersion medium,
The particle size and the like after wet pulverization are shown. In addition, "C (%)" in the table
Is the carbonization yield (%), "QS (%)" is the quinoline soluble content (%)
, "MP (%)" is the mesophase content (%), "EtO"
"H" means ethanol and the particle size is average.

[0019]

[Table 1]

Then, the dried raw material powder was filled in a molding rubber mold, set in a cold isostatic press and subjected to a hydrostatic pressure of 1 tf / cm ² to mold a molded body having a diameter of 120 mm and a length of 120 mm. This molded body was put into a graphite crucible, and the periphery was covered with coke powder packing and set in a firing electric furnace.
A firing process was performed by heating to 1000 ° C. at a heating rate of ° C./hr. The obtained silicon carbide-carbon composite material (diameter 100
mm, length 100 mm), the state of structure damage (fire cracking) during firing treatment, bulk density, and bending strength were measured, and the results are shown in Table 2.

[0021]

[Table 2]

From the results shown in Tables 1 and 2, according to the examples satisfying the requirements of the present invention, no damage was caused during firing, and the obtained ceramic-carbon composite materials were all high bulk density and bending. It turns out to have strength. In addition, the observation of the structure of the material confirmed that it was an extremely homogeneous composite structure. On the other hand, in the comparative examples that deviate from the requirements of the present invention, firing cracking occurs, or the density and strength of the obtained ceramic-carbon composite material are both extremely low.

Example 7 A silicon nitride-carbon composite material was produced under the same conditions as in Example 3 except that silicon nitride powder having an average particle size of 7 μm was used in place of the silicon carbide powder of Example 3. Also in this case, no material damage occurs during firing, bulk density 1.99 g / cm ³ , bending strength 1
It was confirmed that it had a uniform composite structure of 60 MPa.

[0024]

As described above, according to the present invention, a specific mesophase pitch powder is used as a carbon source, and a wet pulverizing means is used for mixing with a ceramic powder, so that a high density and a high strength can be obtained. A ceramic-carbon composite material having a structure can be stably manufactured. In addition, since the manufacturing process is simple and no large-scale equipment is required, it is useful as an industrial manufacturing means for hot pressing dies and various functional members requiring thermal shock resistance.

Claims (2)

[Claims] 1. The carbonization yield at 1000 ° C. is 65% or more, the quinoline-soluble content is 2 to 15%, and the mesophase content is 4.
Ceramic powder is blended with 0% or more of mesophase pitch powder, dispersed in an organic solvent to form a slurry, and sufficiently wet-pulverized, and then dried, and the pressure-molded compact is molded in a non-oxidizing atmosphere. A method for producing a ceramic-carbon composite material, which comprises performing a firing treatment in a temperature range of 800 to 2300 ° C. 2. The method for producing a ceramic-carbon composite material according to claim 1, wherein the wet pulverization treatment is carried out until the average particle diameter after the treatment becomes 5 μm or less.