JPH0364472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a powder or sheet adhesive for 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, essential oxide ceramics generally have extremely poor affinity for molten materials, so-called wettability, and unlike oxide ceramics such as alumina, zirconia, and magnesia, they have strong covalent bonds, making them highly reactive to various substances. Also very bad. Furthermore, since its coefficient of thermal expansion is extremely low compared to other materials, it is extremely difficult to bond it.

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 their adhesive strength is generally low due to differences in coefficient of thermal expansion with non-oxide ceramics, making it difficult to take full advantage of the excellent properties of non-oxide ceramic molded bodies. It hasn't gotten better.

In view of the current situation, the present inventor conducted research to develop an adhesive technology for non-oxide ceramics that can have the necessary strength when using non-oxide ceramic molded bodies as mechanical parts, etc. We have completed an adhesive and bonding method suitable for oxide ceramics (Japanese Patent Application Laid-open No. 226463/1983).

Furthermore, by adding a certain type of binder component to this adhesive component and kneading and rolling it, it became possible to use it on uneven and curved surfaces, expanding the range of use and also reducing variations in adhesive properties. (Japanese Patent Publication No. 62-7678). This adhesive and bonding method are based on the strength of commercially available pressureless sintered non-oxide ceramics (for example, about 53
Kg/mm ² , approximately 50 Kg/mm ² for silicon carbide), and has the ability to maintain this strength up to approximately 900°C.

However, non-oxide ceramics such as silicon nitride and silicon carbide have excellent properties even at high temperatures of 1000°C or higher, and the adhesive and bonding method do not take full advantage of the high-temperature properties of these non-oxide ceramics. The current situation was that I couldn't do it.

Means for Solving the Problems The present inventors have proposed
In order to further improve the excellent properties of the adhesive for non-oxide ceramics shown in No. 7678, we continued to research adhesives and bonding conditions, and as a result, we discovered an adhesive active ingredient with even better high-temperature properties. I've reached it.

That is, the present invention provides an adhesive for non-oxide ceramics containing silicon nitride, calcium oxide, and two or more rare earth oxides as active ingredients, and silicon nitride,
To provide an adhesive sheet for non-oxide ceramics, which is formed by uniformly mixing and molding an adhesive component containing calcium 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 forming an adhesive component containing silicon nitride, calcium oxide, and two or more kinds of rare earth oxides and a binder as active ingredients, 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 and adhesive sheet of the present invention, any commercially available silicon nitride can be used, and there are no particular limitations on its manufacturing method, particle size, purity, etc. 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 calcium oxide, any commercially available calcium 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.

In addition, the rare earth oxide which is another active ingredient of the adhesive and adhesive sheet of the present invention includes:
It is necessary to use two or more 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 85 mol% of silicon nitride, and 35 to 85 mol% of silicon nitride and 100 mol% of the total of silicon nitride and rare earth oxide. It is preferable that one of the oxides is yttrium oxide in a content of 5 to 30 mol %, and the remainder is at least one rare earth oxide. In particular, silicon nitride is 50 to 70 mol% and yttrium oxide is 10 to 70 mol%.
Very strong adhesive strength can be obtained when the amount is 25 mol % and the balance is at least one other rare earth oxide.

In addition, the amount of calcium oxide added is determined by multiplying the amount of calcium oxide added to the above mixture of silicon nitride and rare earth oxide.
It is optimal to add 20 to 80 wt%. If the amount is less than 20 wt% or more than 80 wt%, the adhesive will not wet the non-oxide ceramics sufficiently and a satisfactory adhesive action will not 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, calcium 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-
Examples include synthetic rubbers such as propylene copolymer, ethylene-propylene-diene terpolymer, polyisobutylene, polyisoprene, and styrene-butadiene copolymer, and natural rubber.
Use one species or two or more species. The molecular weight of the binder is not particularly limited, but in order to maintain good sheet formability, it is desirable that the average molecular weight is about 50,000 or more. If necessary, these elastomers may be combined with one or more of alkylphenol-based, coumaron-indene-based, polyterpene-based, rosin-based, petroleum-based, polyvinyl ether-based resins, etc., for the purpose of improving adhesion. In addition, as a softening agent, xylene resin, paraffin wax,
Process oil, abiethyl alcohol, etc. may also be blended.

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:
In order to minimize the effects of gas generation and decomposition residues on the adhesive properties during heat bonding and at the same time obtain good sheet formability, the latter is preferably about 3 to 50 parts by weight per 100 parts by weight of the former. 5~
It is desirable that the amount be about 25 parts by weight. Furthermore, it is preferable that the blending ratio of the binder is determined by taking into account the particle size of the adhesive component (if whiskers are used, their diameter and length). Generally, as the particle size of the adhesive component increases, it becomes possible to reduce the amount of binder blended, but the wettability of the adhesive on the other side decreases. Therefore, in order to obtain an adhesive sheet with excellent adhesive properties and moldability, it is necessary to
The optimum amount of binder to be added to 100 parts by weight is about 10 to 20 parts by weight.

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, an 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 appropriately determined depending on the composition of the adhesive component, the heating conditions, the shape of the non-oxide ceramic member, etc., but usually the amount of the adhesive component applied is 0.01 to 1 cm2 per ¹ cm2 of adhesive area. 1g
What is necessary is just to make it about 0.05-0.4g more preferably.

In the bonding method of the present invention, the temperature at which the adhesive sheet is interposed between the non-oxide ceramic molded members and heat-treated is in the range of 1400 to 1800°C. If the heating temperature is less than 1400°C, the adhesive component will not melt and the adhesive effect will not be exhibited. On the other hand, if the heating temperature exceeds 1800°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 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 and adhesive sheet of the present invention exhibit excellent adhesive effects is not yet clear, but it is presumed as follows.

That is, since the adhesive of the present invention and the adhesive component of the adhesive sheet have a melting point of approximately 1400 to 1800°C, when the non-oxide ceramic molded member with the adhesive sheet interposed is heated to 1400°C or higher, The adhesive component melts and sufficiently wets the surface of the non-oxide ceramic molded body, and some reaction occurs with the non-oxide ceramic molded body to strengthen the non-oxide ceramic molded body members. It is thought that it is attached to the When the adhesive active ingredient is a combination of calcium 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 conventionally been difficult to bond without pressure, can be easily and strongly bonded to each other. Furthermore, the adhesive layer formed after adhesion is chemically stable and has sufficient heat resistance up to 1000°C. Further, since the adhesive sheet of the present invention can be rolled to a uniform thickness of about 0.05 to 5 mm, the thickness of the adhesive layer formed by heat treatment is also constant, and there is little variation in adhesive properties. Furthermore, the adhesive sheet of the present invention is
Since it can be cut and deformed, it is also possible to join members with complex 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 65mol%, yttrium oxide
60 parts by weight of calcium oxide was added to 100 parts by weight of a mixed powder consisting of 17.5 mol % and 17.5 mol % lanthanum oxide to obtain an adhesive of the present invention.

0.2 g of the obtained adhesive was applied a pressure of approximately 150 kg/cm ² to form a pellet with a thickness of 0.5 mm, which was sandwiched between two silicon nitride molded bodies measuring 10 x 10 x 15 mm, and heated at 1600°C in a nitrogen atmosphere. The mixture was heat-treated for 1 hour.

A square bar of 3 x 3 x 30 mm ³ was cut out from the obtained adhesive sample, and a three-point bending test was performed under conditions of a span of 20 mm and a loading rate of 0.5 mm/min. As a result, it was 39.4 kg/
An intensity of mm ² was obtained.

In addition, in a test of the same sample under a high temperature range, 900℃
22.5Kg/mm ² at 1000℃, 15.6Kg/mm ² at 1050℃
It was 13.8Kg/ ^mm2 .

Example 2 Silicon nitride powder 55mol%, yttrium oxide
50 parts by weight of calcium oxide was added to 100 parts by weight of a mixed powder consisting of 22.5 mol% and 22.5 mol% of lanthanum oxide to obtain an adhesive of the present invention.

The thickness of the obtained adhesive was adjusted in the same manner as in Example 1.
The pellets were made into 0.5 mm pellets, sandwiched between two silicon carbide molded bodies of 10 x 10 x 15 cm ³ , and heat-treated at 1650° C. for 1 hour in an argon atmosphere.

The obtained adhesive sample was subjected to the same three-point bending test as in Example 1, and its strength was 35.6 kg/kg at room temperature.
mm ² and 20.5 Kg/mm ² at 1000°C.

Example 3 Silicon nitride powder 55 mol%, yttrium oxide
35 parts by weight of calcium oxide was added to 100 parts by weight of a mixed powder consisting of 22.5 mol% and 22.5 mol% of lanthanum oxide to obtain an adhesive of the present invention.

The obtained adhesive was formed into pellets in the same manner as in Example 1, sandwiched between two aluminum nitride molded bodies measuring 10 x 10 x 15 mm, and heat treated at 1600° C. for 1 hour in a nitrogen atmosphere.

The obtained adhesive sample was subjected to the same three-point bending test as in Example 1, and the strength was 36.2 Kg/mm ² .

Example 4 Silicon nitride (average particle size 15 μm) 65 mol%, yttrium oxide 17.5 mol% and lanthanum oxide
60 parts by weight of calcium oxide was added to 100 parts by weight of a 17.5 mol % mixed powder to form an adhesive active ingredient with a total average particle size of about 5 μm.

After mixing 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 to 100 parts by weight of the above active ingredient,
Thoroughly knead the toluene while vaporizing it with rolls heated to about 50℃, roll it at room temperature, and
An adhesive sheet of the present invention having a diameter of 200 μm, an elastic modulus of 3.6 Kg/mm ² and a radius of curvature of 0.5 mm or less was obtained.

Cut the resulting adhesive sheet into 10 x 10 mm ^{2 pieces} , 10
It was sandwiched between two silicon nitride molded bodies measuring 10 x 15 mm and heat-treated at 1600°C for 30 minutes in a nitrogen atmosphere. The three-point bending strength of the obtained adhesive sample was 33.9 Kg/mm ² at room temperature.

Comparative example 1 Silicon nitride 45mol%, yttrium oxide
A comparative adhesive was obtained by adding and mixing 40 parts by weight of magnesium oxide to 100 parts by weight of a mixed powder consisting of 27.5 mol% and 27.5 mol% lanthanum oxide.

As in Example 1, this adhesive was treated and the obtained bonded body sample was subjected to a three-point bending test. As a result, the strength was 53 Kg/mm ² at room temperature and 35 Kg/mm ² at 900°C. However, at 950°C, it significantly decreased to about 2 Kg/mm ² .

Comparative example 2 55 mol% silicon oxide, yttrium oxide
A comparative adhesive was obtained by adding and mixing 60 parts by weight of calcium oxide to 100 parts by weight of a mixed powder consisting of 22.5 mol% and 22.5 mol% lanthanum oxide.

As in Example 1, this adhesive was treated and the obtained bonded body sample was subjected to a three-point bending test. As a result, the strength was 51 Kg/mm ² at room temperature and 1 at 600°C.
It decreased to below Kg/ ^mm2 .

In the same way as above, increase the amount of silicon oxide to 25~
Adhesive strength was measured by changing the amount within a range of 65 mol%, but sufficient heat resistance was not obtained.

Comparative example 3 Silicon oxide 55mol%, yttrium oxide
40 parts by weight of calcium oxide was added to 100 parts by weight of a mixed powder consisting of 22.5 mol% and 22.5 mol% of lanthanum oxide. This mixture was treated in the same manner as in Example 4 to obtain a comparative adhesive sheet.

This adhesive sheet was treated in the same manner as in Example 4,
The obtained joined body sample was subjected to the same three-point bending test as in Example 1, and the strength was 10 Kg/mm ² at room temperature.
Therefore, sufficient heat resistance could not be obtained.

Claims (1)

[Scope of Claims] 1. An adhesive for non-oxide ceramics containing silicon nitride, calcium oxide, and two or more types of rare earth oxides as active ingredients. 2. An adhesive sheet for non-oxide ceramics made by uniformly mixing and molding an adhesive component containing silicon nitride, calcium oxide, and two or more types of rare earth oxides as active ingredients and a binder. 3 A sheet made by uniformly mixing and molding an adhesive component containing silicon nitride, calcium oxide, and two or more types of rare earth oxides and a binder as active ingredients and forming it 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℃.