JPH0240027B2 - HISANKABUTSUSERAMITSUKUSUYOSETSUCHAKUZAISHIITOOYOBI HISANKABUTSUSERAMITSUKUSUYOSETHICHAKUTSUUSERAMITSUKUSUNOSETSUCHAKUHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an adhesive for sheet-shaped non-oxide ceramics and a method for bonding non-oxide ceramics.

Conventional technology and its problems Non-oxide ceramics such as silicon nitride and silicon carbide have superior high-temperature strength, corrosion resistance, and wear resistance compared to metals, so they are attracting attention as high-temperature components, and are used in gas turbines. , car engine,
Application development for heat exchangers, etc. is underway.

In order for non-oxide ceramics to fully exhibit their excellent functions in the various uses mentioned above, it is necessary to bond these non-oxide ceramics together during the manufacturing process. In particular, it is difficult to mold and process non-oxide ceramic molded bodies into complex shapes, so it is necessary to assemble simple-shaped members into complex shapes, and it is essential to develop adhesive technology for mutually bonding non-oxide ceramic parts. It is.

However, non-oxide ceramics generally have extremely poor affinity for molten materials, so-called wettability, and unlike oxide ceramics such as alumina and magnesia, they have strong covalent bonds.
Furthermore, since the reactivity to various substances is extremely low, adhesion is extremely difficult.

Conventionally, non-oxide ceramics have been bonded by interposing an adhesive between the members to be bonded, or by hot pressing at high temperature and pressure without intervening any adhesive. However, the hot press method requires high temperature and pressure, so
Bonding complex or large components is extremely difficult. Similar problems also exist in the hot isostatic pressing method, so-called HIP method, which has recently been in the spotlight.

Therefore, in order to assemble large, complex-shaped members, it is desired to develop an adhesive that can be easily bonded by simply heating without requiring pressure. Conventionally, adhesives for non-oxide ceramics include -A group oxide alone, alumina-silica-alkaline earth metal oxide system, calcium fluoride-kaolin system, or adhesives with a small amount of rare earth oxide added thereto. is used. However, these are all adhesives based on oxide glass, and due to differences in coefficient of thermal expansion with non-oxide ceramics, their adhesive strength is generally low, and the excellent properties of non-oxide ceramic molded products cannot be fully demonstrated. I haven't gotten to the point where I can take advantage of it.

In view of the current situation, the present inventors have conducted various studies and have completed an adhesive for non-oxide ceramics containing silicon nitride, magnesium oxide, and two or more rare earth oxides as active ingredients ( special request
59-82712). This adhesive has the strength of pressureless sintered products of commercially available non-oxide ceramics (for example, about 53 Kg/mm ² for silicon nitride and about 50 Kg/mm 2 for silicon carbide).
Kg/mm ² ), and the strength is approximately
It has excellent performance of maintaining up to 900℃. However, since this adhesive is in the form of powder, pellets, or paste, when it is used to join members with complex shapes such as curved surfaces or uneven parts, it is necessary to apply the adhesive to the desired bonding area during work. It is extremely difficult to apply it thickly and uniformly. Therefore, there is still room for improvement in terms of improving workability and preventing variations in adhesive properties.

Means for Solving the Problems As a result of continued research to further improve the excellent properties of the adhesive for non-oxide ceramics disclosed in Japanese Patent Application No. 59-82712, the inventor discovered that the adhesive When adding a binder component to and forming this into a sheet, the desired thickness of adhesive can be applied uniformly and easily to any bonding site, regardless of the shape of the members to be bonded. It has been found that as a result, variations in adhesive properties are suppressed. That is, the present invention provides an adhesive sheet for non-oxide ceramics, which is formed by uniformly mixing and molding an adhesive component containing silicon nitride, magnesium oxide, and two or more rare earth oxides as active ingredients and a binder. .

The present invention further provides a sheet formed by uniformly mixing and molding an adhesive component containing silicon nitride, magnesium oxide, and two or more rare earth oxides and a binder as active ingredients, and interposing the sheet between the non-oxide ceramics. The present invention also provides a method for bonding non-oxide ceramics, characterized by heating at a temperature of 1400 to 1800° C. in a non-oxidizing atmosphere.

Non-oxide ceramics to which the adhesive of the present invention is applied include, for example, silicon nitride, silicon carbide, sialon, aluminum nitride, etc., and can be made by hot pressing, pressureless sintering, reaction sintering, etc. There are no particular limitations on the shape or size, and the members to be bonded may have the same shape or different shapes.

As silicon nitride, which is an active ingredient in the adhesive sheet of the present invention, any commercially available silicon nitride can be used, and its manufacturing method, particle size, purity, etc. are not particularly limited. Furthermore, not only those in powder form but also those in whisker form can be used. In order to increase adhesive strength, it is desirable to use a material with high purity.

Further, as magnesium oxide, any commercially available magnesium oxide can be used, and its purity and particle size are not particularly limited, but in order to increase adhesive strength, it is desirable to have as high a purity as possible and a particle size as small as possible.

Further, as the rare earth oxide which is another active ingredient of the adhesive sheet of the present invention, it is necessary to use two or more kinds of rare earth oxides. If only one type of rare earth oxide is used, sufficient adhesive strength cannot be obtained because sufficient wettability with respect to non-oxide ceramics cannot be obtained.
The combination of rare earth oxides is not particularly limited, but a combination of yttrium oxide and lanthanum oxide is optimal. The purity and particle size of the rare earth oxide used are not particularly limited, but in order to increase adhesive strength, it is desirable to have as high a purity as possible and a small particle size.

Among the active ingredients of the adhesive of the present invention, the blending ratio of silicon nitride and rare earth oxide is 35 to 65 mol% of silicon nitride and 35 to 65 mol% of silicon nitride and rare earth oxide. It is preferable that one of the oxides is yttrium oxide, the content of which is 10 to 35 mol %, and the remainder is at least one other rare earth oxide. especially,
40-55 mol% silicon nitride, yttrium oxide
Very strong adhesive strength can be obtained when the amount is 15 to 30 mol % and the remainder is at least one other rare earth oxide.

Further, the optimum amount of magnesium oxide to be added is 10 to 80 wt%, based on the above-mentioned mixture of silicon nitride and rare earth oxide. 10wt%
If it is less than 80wt% or more than 80wt%, the adhesive will not wet the non-oxide ceramics sufficiently;
A satisfactory adhesive effect cannot be obtained.

The reason why the effective composition range in the present invention is set to the above range is that within this range, the active ingredients of the adhesive will melt and good wetting will be obtained, and since it will contain an appropriate amount of silicon nitride, the adhesive will This is because the coefficient of thermal expansion is close to that of the non-oxide ceramic molded body to be adhered, and there is almost no residual strain in the adhesive layer after bonding.

In the present invention, the binder used to form the adhesive component containing silicon nitride, magnesium oxide, and two or more rare earth oxides as active ingredients into a sheet shape is An elastomer that generates a small amount and does not produce a residue that inhibits adhesion after decomposition is suitable. Such elastomers include ethylene-propylene copolymer, ethylene-propylene copolymer,
Examples include synthetic rubbers such as dienterpolymer, polyisobutylene, polyisoprene, styrene-butadiene copolymer, natural rubbers, and synthetic resins such as ethylene-vinyl acetate copolymer, and one or two of these. Use the above. The molecular weight of the binder is not particularly limited, but in order to maintain good sheet formability, the average molecular weight is preferably about 50,000 to 1,000,000. If necessary, these elastomers may be combined with one or more of alkylphenol-based, coumaron-indene-based, polyterpene-based, rosin-based, petroleum-based, and polyvinyl ether-based resins for the purpose of improving adhesion. Furthermore, a xylene resin, paraffin wax, process oil, abiethyl alcohol, etc. may be added as a softening agent.

In addition, the binder made of the above elastomer or the elastomer and other combined components should be used at a temperature of 0.1 to 50% at 25°C to prevent the adhesive sheet from cracking due to bending or curving when bonding parts with complex shapes.
It is desirable to select one having an elastic modulus of about Kg/mm ² , more preferably about 0.5 to 40 Kg/mm ² . Here, the elastic modulus refers to the tangential modulus expressed by the following formula when a sample is stretched at a speed of 300 mm/min with a chuck distance of 50 mm at a temperature of 25°C.

Elastic modulus = F/S However, F: Force at the intersection of the point where the sample is stretched 100% and the tangent line (Kg/mm ² ) S: Cross-sectional area of the sample (mm ² ) The blending ratio of the binder to the adhesive component is:
While minimizing the effects of gas generation and decomposition residue on adhesive properties during heat bonding, it also provides good sheet formability and a flexible adhesive sheet (elastic modulus).
0.3 to 45 Kg/mm ² and radius of curvature of 10 mm or less), the latter is approximately 3 to 50 parts by weight per 100 parts by weight of the former.
More preferably, the amount is about 5 to 25 parts by weight. Furthermore, it is preferable that the blending ratio of the binder is determined in consideration of the particle size of the adhesive component (if whiskers are used, their diameter and length). Generally, the larger the particle size of the adhesive component, the more
Although it becomes possible to reduce the amount of binder blended, the wettability of the adhesive on the other side decreases. Therefore, in order to obtain an adhesive sheet with excellent adhesive properties and moldability, when the average particle size of the adhesive component is about 1 to 10 μm, the amount of binder blended is 10 to 20 parts by weight per 100 parts by weight of the adhesive component. It is best to

The adhesive sheet of the present invention can be manufactured by various methods. For example, after dissolving the binder in an organic solvent such as acetone, toluene, or methyl ethyl ketone, an adhesive component is added and kneaded uniformly. Next, the kneaded product is poured onto a mold covered with release paper, and after the solvent is evaporated, the molded product is passed through rolling rolls and formed into a sheet, film, or other shape. It goes without saying that the shaping can also be carried out by any other method such as extrusion, press rolling, and doctor blasting.

In order to bond non-oxide ceramics using the adhesive sheet of the present invention, the adhesive sheet cut or processed into a predetermined shape is interposed between the surfaces of the non-oxide ceramic members to be bonded. Heating is performed. The thickness of the adhesive sheet is determined appropriately depending on the composition of the adhesive component, heating conditions, shape of the member, etc., but usually the amount of adhesive component applied is about 0.01 to 1 g per 1 cm ² of adhesive area, or more. Preferably
The amount may be adjusted to about 0.05 to 0.3 g.

In the bonding method of the present invention, the temperature at which the adhesive sheet is heat-treated with the adhesive sheet interposed between the non-oxide ceramic molded members is in the range of 1400 to 1800°C.
If the heating temperature is less than 1400℃, the adhesive component will not melt and the adhesive effect will not be exhibited;
If it exceeds the above range, the non-oxide ceramic molded member to be adhered may be deformed or deteriorated, and the active ingredients of the adhesive may also evaporate, which is also undesirable from the standpoint of thermal efficiency.

As the heat treatment atmosphere, a non-oxidizing atmosphere such as a vacuum, an inert gas, or a nitrogen gas is used, and it is particularly preferable to perform the heat treatment in a vacuum or a nitrogen atmosphere.

Function The reason why the adhesive sheet of the present invention exhibits an excellent adhesive effect is not yet clear, but it is presumed as follows.

That is, the adhesive component of the adhesive sheet of the present invention is:
and has a melting point of 1,400 to 1,800°C, so when a non-oxide ceramic molded member with an adhesive sheet interposed is heated to 1,400°C or higher, the adhesive component melts and the surface of the non-oxide ceramic molded member is sufficiently heated. It is thought that some kind of reaction occurs between the non-oxide ceramic molded body parts and the non-oxide ceramic molded body parts are firmly bonded to each other. When the adhesive active ingredient is a combination of magnesium oxide and two or more rare earth oxides, adhesion is possible to some extent by a similar mechanism, but sufficient strength cannot be obtained. From this, by including silicon nitride as an adhesive active ingredient, the coefficient of thermal expansion of the adhesive becomes close to that of the non-oxide ceramic molded member, and as a result, the residual strain in the adhesive layer after bonding is reduced. It is thought that high adhesive strength can be obtained.

Effects of the Invention According to the present invention, large, complex, and irregularly shaped non-oxide ceramic members, which have been difficult to bond using conventional methods, can be easily and strongly bonded to each other. Also,
The adhesive layer formed after adhesion is chemically stable,
Has sufficient heat resistance up to 900℃. Furthermore, since the adhesive sheet of the present invention can be rolled to a uniform thickness of approximately 0.05 to 5 mm, the adhesive thickness formed by heat treatment is also constant, and there is little variation in adhesive properties. Furthermore, since the adhesive sheet of the present invention can be cut and deformed, it is also possible to join members with complicated shapes, greatly improving workability. Therefore, non-oxide ceramics can exhibit its excellent functions even further.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on examples.

Example 1 Silicon nitride whiskers (diameter 0.5 to 2 μm, length 50
~300μm) 45mol%, yttrium oxide 27.5mol
% and lanthanum oxide 27.5mol%
30 parts by weight of magnesium oxide was added to 100 parts by weight to form an adhesive component. Then the adhesive component
To 100 parts by weight, 20 parts by weight of butyl rubber (molecular weight approximately 250,000) as a binder and 30 parts by weight of toluene as a solvent were added and mixed, and then thoroughly kneaded with rolls heated to approximately 50°C while vaporizing the toluene. , and rolled at room temperature to obtain an adhesive sheet of the present invention having a thickness of 100 μm. The obtained adhesive sheet had an elastic modulus of 3.6 Kg/mm ² and a radius of curvature of 0.5 mm or less.

Cut this adhesive sheet into 10 x 10 mm ² and 10 x 10
It was sandwiched between two silicon nitride molded bodies measuring 15 mm ³ and heat-treated at 1600° C. for 1 hour in a nitrogen atmosphere.

A square bar of ³ x 3 x 30 mm was cut out from the obtained adhesive sample, with a span of 20 mm and a loading rate of 0.5 mm/min.
As a result of a three-point bending test under the conditions of 32.5
A strength of Kg/mm ² was obtained.

Example 2 Silicon nitride powder (average particle size 15 μm) 45 mol%,
Yttrium oxide 27.5mol% and lanthanum oxide
30 parts by weight of magnesium oxide was added to 100 parts by weight of a mixed powder consisting of 27.5 mol % to form an adhesive component.

25 parts by weight of acrylic rubber as a binder and 30 parts by weight of toluene as a solvent were added to 100 parts by weight of the adhesive component, and the thickness was determined by the same method as in Example 1.
An adhesive sheet of the present invention having a diameter of 300 μm, an elastic modulus of 2.4 Kg/mm ² and a radius of curvature of 0.5 mm or less was obtained.

This adhesive sheet was cut to a predetermined size, sandwiched between silicon nitride molded bodies, and placed in a nitrogen atmosphere.
Heat treatment was performed at 1650°C for 1 hour.

The three-point bending strength of the obtained adhesive sample was 32.4 kg/
It was warm in ^mm2 .

Example 3 Silicon nitride powder (average particle size 15 μm) 55 mol%,
Ittrim oxide 22.5mol% and lanthanum oxide
20 parts by weight of magnesium oxide was added to 100 parts by weight of mixed powder consisting of 22.5 mol%, and the total average particle size was about 3.
~7μm adhesive active ingredient.

100 parts by weight of the above active ingredient, 15 parts by weight of butadiene rubber as a binder and 30 parts by weight of toluene as a solvent.
After adding parts by weight and thoroughly kneading, the adhesive of the present invention was dried at 50°C for 180 minutes, rolled at room temperature to form a sheet with a thickness of about 1 mm, and the obtained sheet was further pressed to have a thickness of 300 μm. Got a sheet.

The adhesive sheet had an elastic modulus of 1.4 Kg/mm ² and a radius of curvature of 0.5 mm or less.

Cut this adhesive sheet into 10 x 10 mm ² pieces,
Sandwiched between 10 x 15 mm ³ silicon carbide molded bodies,
Heat treatment was performed at 1700°C for 30 minutes in an argon atmosphere.

A square bar ^of 3 x 3 x 30 mm was cut out from the obtained adhesive sample, and the span was 20 mm and the loading speed was 0.5 mm/
When a three-point bending test was conducted under conditions of min.
A strength of 28.5Kg/mm ² was obtained.

Example 4 Silicon nitride whiskers (diameter 0.5 to 20 μm, length 50
~300μm) 55mol%, yttrium oxide 22.5mol
30 parts by weight of magnesium oxide was added to 100 parts by weight of a mixed powder of 22.5 mol% of lanthanum oxide and 22.5 mol% of lanthanum oxide to form an adhesive active ingredient.

For 100 parts by weight of the above active ingredient, 5 parts by weight of butyl rubber as a binder and toluene as a solvent.
After adding 30 parts by weight and thoroughly kneading, a film-like adhesive composition of the present invention having a thickness of about 50 μm and a radius of curvature of 0.5 mm or less was obtained by a doctor blade method.

This film adhesive also showed excellent adhesive properties.

Claims (1)

[Scope of Claims] 1. An adhesive sheet for non-oxide ceramics formed by uniformly mixing and molding an adhesive component containing silicon nitride, magnesium oxide, and two or more rare earth oxides as active ingredients and a binder. 2. A sheet formed by uniformly mixing and molding an adhesive component containing silicon nitride, magnesium oxide, and two or more rare earth oxides and a binder as active ingredients is interposed between non-oxide ceramics and placed in a non-oxidizing atmosphere. A method for bonding non-oxide ceramics characterized by heating at a temperature of 1400 to 1800℃.