JPH0336784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to 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 materials. bottle, 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 ( Tokukai Akira
No. 60-226463). Furthermore, by adding a binder component to this adhesive and forming it into a sheet,
We have discovered that regardless of the shape of the parts to be joined, it is possible to uniformly and easily apply an adhesive of a desired thickness to any bonding site, and as a result, variations in adhesive properties are suppressed. . (Special application 1986-
No. 147234).

However, in this method, since the adhesive sheet is simply interposed between the joining members, misalignment between the joining members is likely to occur. Especially when bonding flat surfaces, there is a very high possibility that misalignment will occur.

Means for Solving the Problems The present inventor has continued to conduct research in order to further improve the excellent characteristics of the bonding method using the adhesive sheet for non-oxide ceramics disclosed in Japanese Patent Application No. 147234/1982. As a result of stacking, it is possible to prevent misalignment between the joining members by uniformly applying adhesive to one or both sides of the adhesive sheet, temporarily attaching both joining members with the adhesive sheet, and then heat-treating them. Moreover, it has been found that the adhesive properties are no different from the method shown in Japanese Patent Application No. 147234/1982. That is, the present invention provides a non-oxide product obtained by uniformly mixing and molding an adhesive component containing silicon nitride, magnesium oxide and/or calcium oxide, and two or more rare earth oxides as active ingredients, and a binder. It is characterized by uniformly applying an adhesive to one or both sides of an adhesive sheet for ceramics, interposing the sheet between non-oxide ceramics, and heating it at a temperature of 1400 to 1800°C in a non-oxidizing atmosphere. A method for bonding non-oxide ceramics is provided.

Non-oxide ceramics to which the adhesive used in the present invention is applied include, for example, silicon nitride, silicon carbide, sialon, aluminum nitride, etc., and are processed by hot pressing, pressureless sintering, or reaction sintering. It may be obtained by any method such as, and there are no particular limitations on its shape or size.
Furthermore, the members to be bonded may have the same shape or different shapes.

As silicon nitride, which is an active ingredient in the adhesive 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.

In addition, as magnesium oxide and calcium oxide, any commercially available ones can be used, and their purity and particle size are not particularly limited, but in order to increase adhesive strength, those with as high purity and small particle size as possible are recommended. desirable.

Further, as the rare earth oxide which is another active ingredient of the adhesive of the present invention, it is necessary to use two or more kinds of rare earth oxides. 1 rare earth oxide
If only seeds are used, sufficient adhesive strength cannot be obtained because sufficient wettability 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.

In addition, the amount of magnesium oxide and calcium oxide to be added is 10 to 10% when added alone or in combination to the above mixture of silicon nitride and rare earth oxide.
It is optimal to add 80wt%. If it is less than 10 wt% or more than 80 wt%, the adhesive will not wet the non-oxide ceramics sufficiently and a satisfactory adhesive effect will not be obtained.

The reason why the effective composition range in the present invention is set to the above range is that in this range, the active ingredients of the adhesive melt and good wetting is obtained, and since it contains an appropriate amount of silicon nitride, the thermal expansion of the adhesive This is because the coefficient is close to the coefficient of thermal expansion 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/or calcium oxide, and two or more rare earth oxides as active ingredients into a sheet shape is It is preferable to use an elastomer that generates a small amount of gas during the temperature raising process and does not produce a residue that inhibits adhesion after decomposition. Such elastomers include synthetic rubbers such as ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, polyisobutylene, polyisoprene, styrene-butadiene copolymer, natural rubbers, and ethylene-vinyl acetate copolymer. Synthetic resins such as coalescent resins are exemplified, and one or more of these may be used. 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. These elastomers may contain alkylphenol-based or
One of the resins such as coumaron-indene, polyterpene, rosin, petroleum, and polyvinyl ether.
A species or two or more species may be used in combination, and xylene resin, paraffin wax, process oil, abiethyl alcohol, etc. may be further blended as a softening agent.

The binder made of the above elastomer or the elastomer and other combined components has a temperature of 0.1 to 0.1 at 25°C to prevent cracks from occurring due to bending or curving of the adhesive sheet when bonding members with complex shapes.
It is desirable to select one having an elastic modulus of about 50 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. Further, the blending ratio of the binder is preferably determined by taking into account 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 set it at a certain level.

The adhesive sheet used in the present invention can be manufactured by various methods. For example, after dissolving the binder in an organic solvent such as acetone, Tortone, or methyl ethyl ketone, an adhesive component is added and kneaded uniformly. Next, the kneaded product is poured onto a mold covered with a release paper, and after the solvent is evaporated, the molded part is passed through rolling rolls to be molded 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, doctor blade method, etc.

In order to bond non-oxide ceramics using the adhesive sheet of the present invention, the adhesive sheet is cut or processed into a predetermined shape, and then the adhesive is uniformly applied to one or both sides of the adhesive sheet. The member may be heated with the sheet interposed between the surfaces of the non-oxide ceramic member to be adhered. The thickness of the adhesive sheet depends on the composition of the adhesive components,
Although it is determined as appropriate depending on the heating conditions, the shape of the member, etc., the amount of adhesive component applied should generally be about 0.01 to 1 g, more preferably about 0.05 to 0.3 g, per 1 cm ² of adhesive area. .

In the bonding method of the present invention, the temperature at which an adhesive sheet having one or both surfaces uniformly coated with an adhesive is interposed between non-oxide ceramic molded members and heat-treated is in the range of 1400 to 1800°C. If the heating temperature is less than 1,400°C, the adhesive component will not melt and the adhesive effect will not be exhibited. On the other hand, if the heating temperature exceeds 1,800°C, the non-oxide ceramic molded member to be adhered may be deformed or deteriorated. arise or
Further, the evaporation of the adhesive's active ingredients also progresses, which is also unfavorable from the standpoint of thermal efficiency.

As the adhesive to be applied to the surface of the adhesive sheet, it is preferable to use an elastomer that, like the binder used to create the sheet, generates a small amount of gas during the heating process up to the adhesive operation temperature, and does not produce any residue that inhibits adhesion after decomposition. It is. Examples of such elastomers include ethylene-propylene copolymers, ethylene-propylene copolymers, and ethylene-propylene copolymers.
Examples include synthetic rubbers such as propylene-dien terpolymer, polyisobutylene, polyisoprene, styrene-butadiene copolymer, natural rubbers, and synthetic resins such as ethylene acetic acid copolymer.
One or more of these may be used. The molecular weight of the pressure-sensitive adhesive is not particularly limited, but in order to maintain good adhesive properties, the average molecular weight is preferably about 50,000 to 1,000,000. The adhesive coating thickness is not particularly limited, but is preferably about 5 to 50 microns.
If it exceeds 50μ, it will cause voids and foaming during adhesion, while if it is less than 5μ, the adhesive force will decrease.

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:
It has a melting point of approximately 1400 to 1800°C, so when a non-oxide ceramic molded member with an adhesive sheet interposed is heated to 1400°C or higher, the adhesive component melts and sufficiently covers the surface of the non-oxide ceramic molded member. 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 or calcium oxide and two or more rare earth oxides, adhesion is possible due to 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,
It has sufficient heat resistance up to about 900℃. Furthermore, since the adhesive sheet of the present invention can be rolled to a uniform thickness of about 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. Moreover, by applying the adhesive to the surface of the adhesive sheet, the occurrence of misalignment, gaps, etc. between the objects to be adhered is prevented, and the workability and reliability of the work are greatly improved. 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%
35 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, 25 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 a roll 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.

This adhesive sheet was cut into 10×10 mm ^{2 pieces} , and 2 mg of a 40% butyl rubber toluene solution was uniformly applied to both sides of the sheet. This sheet was sandwiched between two silicon nitride molded bodies of 10×10×15 mm ³ , and after drying the toluene, it was heat-treated at 1600° C. for 1 hour in a nitrogen atmosphere.

The resulting bonded body did not have any displacement between the bonded bodies, which occurs when heating is performed without applying an adhesive to the sheet surface.

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

Example 2 Silicon nitride powder (average particle size 15 μm) 45 mol%,
Yttrium oxide 27.5mol% and lanthanum oxide
Add and mix 35 parts by weight of magnesium oxide to 100 parts by weight of mixed powder consisting of 27.5 mol%, and the total average particle size is approximately
The adhesive component was 5 μm thick.

To 100 parts by weight of the adhesive component, 20 parts by weight of acrylic rubber as a binder and 30 parts by weight of toluene as a solvent were added, and an adhesive sheet was obtained in the same manner as in Example 1.

Cut this adhesive sheet to the specified size and
% acrylic rubber toluene solution was evenly applied to both sides of the sheet. This sheet was sandwiched between silicon nitride molded bodies and heat-treated at 1650° C. for 1 hour in a nitrogen atmosphere.

The obtained bonded body did not come off, and its three-point bending strength was 35.4 Kg/mm ² .

Example 3 Silicon nitride (average particle size 15 μm) 55 mol%, yttrium oxide 22.5 mol% and lanthanum oxide
60 parts by weight of calcium oxide was added to 100 parts by weight of a mixed powder consisting of 22.5 mol%, and the total average particle size was approx.
The adhesive component was 5 μm thick.

To 100 parts by weight of the adhesive component, 20 parts by weight of bruti rubber as a binder and 30 parts by weight of toluene as a solvent were added, and an adhesive sheet was obtained in the same manner as in Example 1.

Cut the adhesive sheet into a predetermined size and reduce 40%
A butyl rubber toluene solution was uniformly applied to both sides of the sheet. This sheet was sandwiched between silicon nitride molded bodies and heat-treated at 1600° C. for 1 hour in a nitrogen atmosphere. The three-point bending strength of the obtained bonded body was 30.5
It was Kg/ ^mm2 .

Example 4 Silicon nitride powder (average particle size 15 μm) 45 mol%,
Yttrium oxide 27.5mol% and lanthanum oxide
Add and mix 35 parts by weight of magnesium oxide to 100 parts by weight of mixed powder consisting of 27.5 mol%, and the total average particle size is approximately
The adhesive component was 5 μm thick.

100 parts by weight of the adhesive component, 20 parts by weight of acrylic rubber as a binder, and 30 parts by weight of toluene as a solvent.
An adhesive sheet was obtained in the same manner as in Example 1 by adding parts by weight.

Cut this adhesive sheet to the specified size and
% acrylic rubber toluene solution was applied uniformly to both sides of the sheet.

As the members to be joined, male and female silicon nitride molded bodies having a cylindrical shape with a diameter of 10 mm and a joint surface with a radius of curvature of 30 mm were used.

The adhesive sheet was temporarily bonded to one of the bonding surfaces of the bonding material and then bonded, followed by heat treatment at 1650° C. for 1 hour in a nitrogen atmosphere.

There is no void at the bonding interface of the obtained bonded body, and 3
The point bending strength was 38.5Kg/ ^mm2 .

Comparative Example 1 The adhesive powder used in Example 4 was uniformly applied to a silicon nitride molded body with an R surface, and the adhesive powder was applied in a nitrogen atmosphere.
Heat treatment was performed at 1650°C for 1 hour. A void was formed at the joint interface of the obtained joint, and the three-point bending strength was 20 kg/
It was warm in ^mm2 .

Comparative Example 2 Example 4 was followed except that silicon oxide was used instead of silicon nitride. The three-point bending strength of the resulting joined body was 10 Kg/mm ² , and sufficient heat resistance was not obtained.

Claims (1)

[Claims] 1. An adhesive sheet for non-oxide ceramics obtained by uniformly mixing and molding an adhesive component containing silicon nitride, magnesium oxide and/or calcium oxide, and two or more rare earth oxides as active ingredients and a binder. of non-oxide ceramics, which is characterized by uniformly applying an adhesive to one or both sides of the sheet, interposing the sheet between non-oxide ceramics, and heating the sheet at a temperature of 1400 to 1800°C in a non-oxidizing atmosphere. Adhesion method.