JPH04310580A - Bonding of formed silicon carbide - Google Patents

Abstract

PURPOSE:To provide a process for bonding a formed SiC material capable of attaining an adhesive strength close to the strength of bulk SiC material and keeping the adhesive strength almost to the original level even at a high temperature. CONSTITUTION:SiC powder containing a sintering assistant is kneaded with an organic binder (e.g. methylcellulose) and a solvent (e.g. water). The kneaded mixture is deaerated and the viscosity is adjusted to 10<3> to 10<5> poise to obtain an adhesive. The adhesive is applied to the bonding faces of plural SiC articles to be bonded, the articles are joined together and the assembly is heated after or during the application of pressure to the adhesive to effect the drying, curing and baking of the adhesive.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a method for adhering silicon carbide molded bodies, and more specifically, to a method for bonding silicon carbide molded bodies that have high adhesive strength and do not decrease in adhesive strength even at high temperatures. .

0002

[Prior Art] Molded bodies of silicon carbide (hereinafter referred to as SiC) are often expensive to manufacture as a single piece when the shape is complex or bulky. In some cases, molding and processing may not be possible. Therefore, techniques for bonding molded bodies to each other using an adhesive have been developed and put into practice.

[0003] As adhesives for bonding SiC molded bodies together, organic adhesives such as epoxy adhesives and inorganic adhesives containing silica or alumina as main components are known. When bonding SiC molded bodies together using these adhesives, the adhesive is applied to the bonding surfaces of both molded bodies, and then both bonding surfaces are pressed and brought into close contact with each other.Then, the adhesive is cured and bonded. do.

0004

[Problem to be solved by the invention] With the above conventional adhesive, S
When iC molded bodies are bonded together, a sufficiently high adhesive density cannot be obtained, so there is a problem that cracks occur during heat treatment such as drying and firing, and the adhesive strength is lower than that of bulk SiC molded bodies. Moreover, there is a problem that the adhesive strength decreases at high temperatures.

[0005] Therefore, an object of the present invention is to create a SiC molded product that does not cause cracks during adhesion, has an adhesive strength close to that of a bulk SiC molded product, and has almost no decrease in adhesive strength even at high temperatures. An object of the present invention is to provide an adhesive method.

[0006]

[Means for Solving the Problems] The method for adhering SiC molded bodies of the present invention involves adding an organic binder and a solvent to SiC powder containing a sintering aid, kneading and degassing the mixture, and reducing the viscosity to 103 to 105. A method for adhering SiC molded bodies using an adhesive adjusted to poise, the adhesive being interposed between each bonding surface of a plurality of SiC molded bodies to be bonded, and the adhesive being pressurized. The feature is that heat treatment is performed after or while applying pressure.

[0007] The particle size of the SiC powder can be set arbitrarily, but it is preferably the same as that of the SiC molded body to be bonded.

[0008] As the sintering aid, boron (B), carbon (C
), alumina (AlO2) can be used, preferably the same as the sintering aid of the SiC compact to be bonded. The blending amount of the sintering aid is appropriately adjusted depending on the particle size of the SiC powder, etc., but it is preferably the same as that of the SiC molded body to be bonded.

As the organic binder, both water-soluble and organic solvent-soluble binders can be used. Water-soluble binders include, for example, hydroxyethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyrate, polyethylene glycol, and glycose. Examples of binders soluble in organic solvents include ethyl cellulose, acetyl cellulose, polyvinyl acetate, ethyl silicate, liquid paraffin, and phenolic resin.

[0010] Water-soluble binders are easier to adjust the viscosity of adhesives than highly volatile organic solvents;
preferable. Furthermore, among water-soluble binders, methylcellulose is preferred from the viewpoint of cost.

[0011] The blending amount of the binder is SiC powder 100
Preferably 5 to 15% by weight, 10% by weight
is particularly preferred. If the amount is less than 5% by weight, the amount of binder is insufficient and the binder coating on the surface of the SiC particles after kneading becomes non-uniform, making it impossible to obtain sufficient strength after heat treatment. If it exceeds 15% by weight, the amount of binder becomes excessive,
Segregation occurs and the density after heat treatment becomes smaller.

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

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

During the kneading and degassing process, the viscosity of the adhesive was reduced to 1
03-105 Poise, preferably 103-104P
Adjust to the oise range. Viscosity 103~105Po
ise is greater than 105 or 10
If it is smaller than 3, adhesive strength comparable to or close to that of the bulk SiC molded body may not be obtained, or cracks may occur in the SiC molded body during drying or firing.

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

For example, when bonding a SiC molded body using an adhesive formed into a sheet, the surface of the adhesive is coated with the same solvent (a different solvent may be used) as used to form the adhesive.
After coating, it 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 pressurize the adhesive. In addition, pressurization is
CIP (Cold Isostatic Pres)
Pressure may be applied by s). In the case of uniaxial pressure, Si
It is preferable to apply an adhesive to each adhesive surface of the C molded body. In the case of CIP pressurization, one adhesive is sufficient for one adhesive location.

[0017] The adhesive may be heat-treated after being pressurized as described above, or may be performed while being pressurized. The heat treatment dries, hardens, and bakes the adhesive.

[0018] In the process of drying the adhesive, the solvent contained in the adhesive is removed. The heating temperature and heating time are set in consideration of the amount of adhesive and the like. The heating temperature is appropriately set depending on the type of medium, but when water is used as the medium, it is preferably about 100° C. and the heating time is about 4 hours.

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

[0020] In the adhesive firing step, these SiC compacts are heated at a much higher temperature than in the curing step. The heating temperature and heating time are appropriately set in consideration of the amount of adhesive, etc., but it is preferable that the heating temperature is 1850° to 2300°C and the heating time is about 5 hours.

[0021] It is preferable that the density of the adhesive after firing is the same as the density of the bonded SiC molded body. This is because the adhesive strength improves as the structure of the adhesive after sintering resembles the structure of the SiC molded body to be bonded. It is best that the structure of the adhesive after sintering matches the structure of the bonded SiC molded body.

[0022]

[Operation] In the method for adhering SiC molded bodies of the present invention, deaeration treatment is performed during the production of the adhesive, so that pores are less likely to be formed in the adhesive during adhesion. Furthermore, 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, when bonding with this method, the bulk Si
Adhesive strength close to that of the C molded product can be obtained, and there is almost no possibility that the adhesive strength will decrease at high temperatures.

[0023]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto.

(Example 1) FIG. 1(a) is a flowchart showing an adhesive production process, and FIG. 1(b) is a flowchart showing a bonding process using the adhesive.

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

Next, the aqueous solution of hydroxypropyl methylcellulose was added to the SiC powder to which boron powder and carbon powder had been added, and the mixture was kneaded in vacuum at room temperature to adjust the viscosity of the mixture to 105 Poise. The kneading time was 15 minutes, and the pressure during kneading was about 10 Torr.

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

[0028] Therefore, using the obtained adhesive sheet,
Bonding of the SiC molded bodies was carried out as follows. First, two adhesive sheets were prepared, both sides of which were wetted with water, and then the sheets were brought into close contact with the adhesive surfaces of two SiC molded bodies to be bonded. After the sides of the two adhesive sheets that are not in close contact with the SiC molded body are brought into close contact with each other, pressing force is applied to the SiC molded body in a direction perpendicular to the adhesive sheet, thereby removing the adhesive sheet Pressurized. The magnitude of the pressing force was 5 kg/cm2.

Next, Si with an adhesive sheet interposed between
The molded product C was heated at 100° C. for 4 hours while maintaining the above-mentioned pressurized state to remove moisture remaining in the adhesive sheet. Next, the same SiC molded body was further heated at 200° C. for 4 hours to cure the adhesive sheet from which water had been removed. Finally, the same SiC molded body was heated at 1850 to 2300°C at normal pressure.
The adhesive sheet was baked at a temperature of 5 hours. In this way, adhesion of the SiC molded body was completed.

A test was conducted to measure the adhesive strength of the SiC molded bodies bonded as described above. The test was conducted using the three-point bending method of JIS R 1601 room temperature bending test method. The test piece is 5 x 5 x 50 mm.
The end surfaces of two rectangular parallelepiped shaped SiC molded bodies were bonded together using the above bonding method, and the thickness of the adhesive layer was 0.2 to 0.2 mm.
It was set to 6 mm. Also, the span between the two fulcrums is 30mm
The load point was set on the adhesive layer of the test piece.

[0031] As a result, the adhesive strength was 420 MPa. Since the room-temperature bending strength of a bulk (no bonded part) SiC molded body is usually 400 to 450 MPa, it has been found that this adhesive strength is comparable to that of a bulk SiC molded body. Further, when a similar adhesive strength test was conducted in air at 1200°C, the adhesive strength was 430 MPa.

[0032] When the obtained adhesive layer was observed with an optical microscope, it was found that it had almost the same structure and density as that of the bonded SiC molded body. The binder is hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyrate, polyethylene glycol, glycose, ethyl cellulose,
Adhesion was performed in the same manner using acetyl cellulose, polyvinyl acetate, ethyl silicate, liquid paraffin, and phenol resin, but almost the same results were obtained.

(Examples 2 to 6) Similar to Example 1, Si
To 100% by weight of C powder (particle size: 0.5 mm), 0.8% by weight of boron powder and 3.5% by weight of carbon powder as sintering aids were added and mixed. On the other hand, hydroxypropyl methyl cellulose 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 hydroxypropyl methylcellulose was added to the SiC powder to which boron powder and carbon powder had been added, and the mixture was kneaded in vacuum at room temperature to adjust the viscosity of the mixture to the values shown in Table 1. The kneading time and the atmospheric pressure during kneading were the same as in Example 1.

Next, an adhesive sheet similar to that in Example 1 was produced using this mixture, and SiC was bonded in the same manner as in Example 1.
The molded bodies were glued together. Adhesive strength test results, Examples 2 to 6
The adhesive strength at normal temperature and the adhesive strength at high temperature (1200° C.) are shown in Table 1, and results almost the same as in Example 1 were obtained.

(Comparative Examples 1-2) Using the same binder as in Example 1, the binder amount, moisture content and 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 above. In comparative example 1,
Cracks appeared in the adhesive sheet when drying. In Comparative Example 2, the adhesive strength at room temperature was as shown in Table 2, which was considerably lower than in Examples 1 to 6.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Effects of the Invention] The method for adhering SiC molded bodies of the present invention does not cause cracks during adhesion and can provide adhesive strength close to that of bulk SiC molded bodies, and the adhesive strength hardly decreases even at high temperatures. It has the effect of not doing so.

[Brief explanation of drawings]

FIG. 1 shows an example of the bonding method for SiC molded bodies of the present invention, in which (a) is a flowchart showing the process of producing an adhesive used in the method, and (b) is the bond obtained in (a). 2 is a flowchart showing a step of adhering SiC molded bodies using a bonding agent.

Claims (1)

[Claims] Claim 1: A silicon carbide molded body using an adhesive obtained by adding an organic binder and a solvent to silicon carbide powder containing a sintering aid, kneading and degassing the mixture, and adjusting the viscosity to 103 to 105 Poise. A bonding method characterized in that the adhesive is interposed between each bonding surface of a plurality of silicon carbide molded bodies to be bonded, and heat treatment is performed after or while pressurizing the adhesive. A method for adhering a silicon carbide molded body.