JP3085589B2 - Method for bonding silicon carbide molded body - 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 bonding a silicon carbide-based molded product, and more particularly, to a method for bonding a silicon carbide-based molded product having a high adhesive strength and its adhesive strength does not decrease even at a high temperature. .

[0002]

2. Description of the Related Art When a silicon carbide (hereinafter referred to as SiC) molded body has a complicated shape or a large bulk, it is often expensive to manufacture it as an integral body. Depending on the case, molding and processing may not be possible. Therefore, a technique for bonding molded articles to each other with an adhesive has been conventionally developed and put to practical use.

As adhesives for bonding SiC molded bodies to each other, an organic adhesive such as an epoxy adhesive and an inorganic adhesive mainly containing silica or alumina are known. When bonding SiC compacts using these adhesives, apply an adhesive to the bonding surfaces of both compacts, then press and adhere both bonding surfaces together, and then cure the adhesive to bond. I do.

[0004]

SUMMARY OF THE INVENTION With the above conventional adhesive, S
When the iC compacts are bonded to each other, a sufficiently high adhesive density cannot be obtained, so that there is a problem that cracks occur during heat treatment such as drying and baking, and the bonding strength is lower than the strength of the bulk SiC compacts. However, there is a problem that the adhesive strength is lowered at a high temperature.

Accordingly, an object of the present invention is to provide a SiC-based molded article which is free from cracks at the time of bonding and has an adhesive strength close to the strength of a bulk SiC molded article, and whose adhesive strength hardly decreases even at a high temperature. It is to provide a bonding method.

[0006]

According to the method of bonding a SiC-based molded body of the present invention, an organic binder and a solvent are added to a SiC powder containing a sintering aid, and the mixture is kneaded and deaerated to obtain a viscosity of 10 ³ to 10 ³ . A method for bonding an SiC-based molded body using an adhesive adjusted to 10 ⁵ Poise, wherein the adhesive is interposed between the bonding surfaces of a plurality of SiC-based molded bodies to be bonded, and the adhesive is applied. The heat treatment is performed after or during pressurization.

The particle size of the SiC powder can be arbitrarily set, but is preferably the same as that of the SiC material to be bonded.

As a sintering aid, boron (B), carbon (C), and alumina (AlO ₂ ) can be used.
Preferably, it is the same as the sintering aid of the SiC material to be bonded. The mixing amount of the sintering aid is appropriately adjusted according to the particle size of the SiC powder, etc.
It is preferably the same as that of the C-shaped molded body.

As the organic binder, both water-soluble and organic solvent-soluble binders can be used. Examples of the water-soluble binder include hydroxyethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyrate, polyethylene glycol, and glucose. Examples of the organic solvent-soluble binder include ethyl cellulose, acetyl cellulose, polyvinyl acetate, ethyl silicate, liquid paraffin, and phenol resin.

A water-soluble binder is easier to adjust the viscosity of an adhesive than a highly volatile organic solvent.
preferable. Among the water-soluble binders, methyl cellulose is preferable from the viewpoint of cost.

The compounding amount of the binder is 100% of SiC powder.
5-15% by weight, preferably 10% by weight
Is particularly preferred. If the amount is less than 5% by weight, the amount of the binder is not sufficient, the binder coat on the surface of the SiC particles after kneading becomes uneven, and sufficient strength cannot be obtained after heat treatment. If it exceeds 15% by weight, the amount of the binder becomes excessive, segregation occurs, and the density after the heat treatment becomes rather small.

As the solvent, any known solvent may be used depending on the binder used, but water or alcohol is preferred. The compounding amount of the solvent is appropriately adjusted so that the viscosity of the adhesive becomes 10 ³ to 10 ⁵ Poise after the kneading and degassing treatment.

The kneading and deaeration of the SiC powder containing the sintering aid, the organic binder and the solvent can be performed, for example, by a known kneader in a vacuum. By kneading in a vacuum, the air contained in these mixtures is degassed. The pressure in the container during kneading is appropriately set in consideration of the degassing situation, viscosity, and the like, and is preferably 1 to 20 Torr. Further, the temperature in the container is preferably set to 10 ° C. or less. The processing time and the like are appropriately set.

During the kneading and deaeration, the viscosity of the adhesive is adjusted to 1
0 ³ to 10 ⁵ Poise, preferably 10 ³ to 10 ⁴ Poi
Adjust to the range of se. Viscosity of 10 ³ to 10 ⁵ Poise
If it is larger than 10 ⁵ or smaller than 10 ³ , the same or similar adhesive strength as that of the bulk SiC molded body cannot be obtained, or cracks occur in the SiC molded body during drying or firing. Because.

By the kneading and degassing treatment, the adhesive used in the present invention is produced. The generated adhesive is a plastic solid, and is easier to handle than a liquid adhesive. However, in order to further facilitate the bonding operation, it is preferable to form the solid adhesive into a shape (for example, a sheet) suitable for the bonding operation in a vacuum.

For example, when bonding an SiC molded body using an adhesive formed in the form of a sheet, the same solvent (a different solvent may be used) on the surface of the adhesive as used for forming the adhesive.
Is applied, and is brought into close contact with each bonding surface of the SiC molded body to be bonded. Thereafter, a uniaxial pressing force is applied to the SiC molded body to press the adhesive. In addition, pressurization is
Pressurization may be performed by CIP (Cold Isostatical Press). In the case of uniaxial pressing, it is preferable to apply an adhesive to each bonding surface of the SiC molded body. In the case of CIP pressurization, only one adhesive is required for one bonding point.

The heat treatment of the adhesive may be performed after pressurizing as described above, or may be performed while pressurizing. By the heat treatment, the adhesive is dried, cured and fired.

In the adhesive drying step, the solvent contained in the adhesive is removed. The heating temperature and the heating time are set in consideration of the amount of the adhesive and the like. The heating temperature is appropriately set according to the type of the medium. When water is used as the medium, the heating temperature is preferably about 100 ° C., and the heating time is preferably about 4 hours.

In the step of curing the adhesive, the SiC compacts are heated at a slightly higher temperature than in the drying step. In this step, the adhesive is cured, and the SiC molded bodies are bonded to each other. The heating temperature and the heating time are appropriately set in consideration of the amount of the adhesive and the like, and it is preferable that the heating temperature is 100 to 200 ° C. and the heating time is about 4 hours.

In the step of firing the adhesive, the SiC compacts are heated at a much higher temperature than in the curing step. The heating temperature and the heating time are appropriately set in consideration of the amount of the adhesive and the like, and it is preferable that the heating temperature is 1850 to 2300 ° C. and the heating time is about 5 hours.

It is preferable that the density of the adhesive after firing is the same as the density of the bonded SiC material. This is because the adhesive strength increases as the structure of the adhesive after sintering resembles the structure of the SiC material to be bonded. It is best that the structure of the adhesive after sintering matches the structure of the bonded SiC compact.

[0022]

According to the method of bonding an SiC-based molded body of the present invention, since the degassing process is performed at the time of generation of the adhesive, pores are not easily generated in the adhesive at the time of bonding. Since the main component of the adhesive is SiC, the material of the adhesive is the same as the material of the molded body. Therefore, by bonding in this manner, bulk Si
Adhesive strength close to that of the C molded body is obtained, and the adhesive strength is hardly reduced at high temperatures.

[0023]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Embodiment 1) FIG. 1A is a flowchart showing an adhesive generation step, and FIG. 1B is a flowchart showing an adhesion step using the adhesive.

First, a SiC powder (particle size: 0.5 mm) 10
To 0% by weight, 0.8% by weight of boron powder and 3.5% by weight of carbon powder were added as sintering aids and mixed. On the other hand, 10% by weight of hydroxypropyl methylcellulose was dissolved in water as an organic binder, and the water content was 27.5%.
It adjusted so that it might become weight%.

Next, the aqueous solution of hydroxypropylmethylcellulose was added to the SiC powder to which the boron powder and the carbon powder had been added, and the mixture was kneaded in a vacuum at room temperature to adjust the viscosity of the mixture to 10 ⁵ Poise. Kneading time is 15
And the pressure during kneading was about 10 Torr.

Next, the obtained mixture was formed into a sheet having a thickness of about 0.2 mm under the same vacuum to obtain an adhesive sheet.

Then, using the obtained adhesive sheet,
Bonding of the SiC molded body was performed as follows. First, two adhesive sheets were prepared, and both surfaces of the sheets were wetted with water, and then they were brought into close contact with the bonding surfaces of the two SiC molded bodies to be bonded. Then, the surfaces of the two adhesive sheets that are not in close contact with the SiC molded body are brought into close contact with each other, and then the SiC is placed in a direction orthogonal to the adhesive sheet.
The adhesive sheet was pressed by applying a pressing force to the molded body. The magnitude of the pressing force was 5 kg / cm ² .

Next, an Si sheet with an adhesive sheet interposed is used.
The C molded body was heated at 100 ° C. for 4 hours while maintaining the above-mentioned pressurized state to remove water remaining on the adhesive sheet. Next, the SiC molded body was further heated at 200 ° C. for 4 hours to cure the adhesive sheet from which moisture was removed. Finally, the SiC molded body is subjected to a pressure of 1850-2300 ° C. at normal pressure.
For 5 hours to fire the adhesive sheet. Thus, the bonding of the SiC molded body was completed.

A test was conducted to measure the adhesive strength of the SiC compact bonded as described above. The test was performed by the three-point bending method of the room temperature bending test method of JIS R 1601. As the test piece, one obtained by bonding the end faces of two 5 × 5 × 50 mm rectangular parallelepiped SiC molded bodies by the bonding method described above was used, and the thickness of the adhesive layer was 0.2 to 0.6.
mm. The span between the two fulcrums was 30 mm, and the load point was set on the adhesive layer of the test piece.

As a result, the adhesive strength was 420 MPa. Since the room-temperature bending strength of a bulk (those having no bonded portion) SiC molded article is usually 400 to 450 MPa, it has been found that this adhesive strength is comparable to that of a bulk SiC molded article. When the same adhesive strength test was performed in air at 1200 ° C., the adhesive strength was 430 MPa.

When the obtained adhesive layer was observed with an optical microscope, the structure was almost the same as the structure of the bonded SiC compact, and the density was also substantially the same. The binder was changed to hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyrate, polyethylene glycol, glycolose, ethyl cellulose, acetyl cellulose, polyvinyl acetate, ethyl silicate, liquid paraffin, and phenol resin, and the same adhesion was performed. Was obtained.

(Examples 2 to 6) As in Example 1, Si
0.8% by weight of boron powder and 3.5% by weight of carbon powder as sintering aids were added to 100% by weight of the C powder (particle size: 0.5 mm) and mixed. On the other hand, hydroxypropylmethylcellulose as an organic binder was dissolved in water in the amount shown in Table 1, and the water content was adjusted to the amount shown in Table 1.

Next, the aqueous solution of hydroxypropylmethylcellulose was added to the SiC powder to which the boron powder and the carbon powder had been added, and the mixture was kneaded in a vacuum at room temperature to adjust the viscosity of the mixture to the value shown in Table 1. The kneading time and the pressure during kneading were the same as in Example 1.

Next, using this mixture, an adhesive sheet similar to that of Example 1 was formed.
The molded body was adhered. As a result of the adhesive strength test, Examples 2 to 6
The adhesive strength at room temperature and the adhesive strength at high temperature (1200 ° C.) are as shown in Table 1, and almost the same results as in Example 1 were obtained.

(Comparative Examples 1-2) Using the same binder as in Example 1, the amount of binder, the amount of water and the viscosity were adjusted as shown in Table 2, and the other conditions were the same as in Example 1 to produce an adhesive sheet. . Then, using the adhesive sheet, Example 1
The SiC molded body was bonded in the same manner as described above. In Comparative Example 1,
Cracks occurred in the adhesive sheet during drying. In Comparative Example 2, the adhesive strength at room temperature was as shown in Table 2, and was considerably lower than Examples 1 to 6.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

According to the bonding method of the present invention, cracks do not occur during bonding and bulk SiC
It has an effect that an adhesive strength close to the strength of the molded article can be obtained, and the adhesive strength hardly decreases even at a high temperature.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows one embodiment of a bonding method for a SiC molded body of the present invention, in which (a) is a flowchart showing a process of generating an adhesive used in the method, and (b) is a bonding obtained in (a) 5 is a flowchart showing a bonding step of a SiC molded body performed using an agent.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-149476 (JP, A) JP-A-63-139070 (JP, A) JP-A-62-138370 (JP, A) (58) Investigation Field (Int. Cl. ⁷ , DB name) C04B 37/00 B28B 11/00

Claims (1)

(57) [Claims] 1. A silicon carbide material using an adhesive whose viscosity is adjusted to 10 ³ to 10 ⁵ Poise by adding an organic binder and a solvent to silicon carbide powder containing a sintering aid, kneading and degassing the mixture. A method of bonding molded articles, wherein the adhesive is interposed between respective adhesive surfaces of a plurality of silicon carbide molded articles to be adhered, and a heat treatment is performed after or while the adhesive is pressed. A method for bonding a silicon carbide-based molded body, characterized by comprising: