JPS6154748B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an adhesive for ceramics and a bonding method thereof, and in particular to an adhesive suitable for bonding non-oxide ceramics such as silicic nitride, silicic carbide, and sialon to each other or to other ceramic materials, and the like. Regarding the adhesion method. Non-oxide ceramics such as silicic acid carbide, silicic nitride, and sialon have excellent strength, thermal shock resistance, and chemical resistance, especially at high temperatures, and are therefore being used as new high-temperature heat-resistant materials that are different from metal oxide ceramic materials. It has been in the spotlight in recent years, and development in various fields of application is progressing. For example, these materials are
The development of its use in high-temperature equipment, high-precision mechanical parts, heat exchangers, etc., as well as in porcelain parts that become instantly hot and special high-temperature insulators, is being considered. In order to utilize these non-oxide ceramics and fully demonstrate their characteristics, it is necessary to combine these non-oxide ceramics with each other or with other materials during the manufacturing process of various types of equipment and their parts. In particular, it is essential to develop bonding technology for non-oxide ceramics molded into various shapes. However, non-oxide ceramics generally have very poor compatibility with melts, so-called demand, and unlike metal oxide ceramic materials such as alumina and magnesia, they have strong covalent bonding properties, and they are difficult to bond with other compounds. The reactivity of alumina is also very low, and its coefficient of thermal expansion is less than half that of alumina, making it extremely difficult to bond. In fact, conventionally, the only known method for bonding non-oxide ceramics is the hot press method, which is performed under high temperature and high pressure.Since the hot press method requires operation under high temperature and high pressure, it is difficult to bond large, complex, irregularly shaped materials. This is extremely difficult, and even if it can be bonded, the adhesive strength is still insufficient. In view of the above-mentioned current situation, the present inventor has made various efforts to develop a new adhesive and bonding method that can easily bond large, complex, and irregularly shaped materials with sufficient bonding strength without using the hot press method under milder conditions. I did a lot of research. However, the above-mentioned adhesive for non-oxide ceramics not only has the feature of being able to bond with sufficient adhesive force, but also that the adhesive layer itself that is formed is chemically stable. There is a demand for excellent heat resistance, thermal shock resistance, etc. to a degree that does not impair the properties of the non-oxide ceramics mentioned above, and currently known adhesives and their active ingredients are unlikely to meet the above requirements. It wasn't. In subsequent research, the present inventors found that sodium fluoride and/or calcium fluoride in particular meet the above requirements and are suitable for bonding not only non-oxide ceramics but also oxide ceramics. He discovered that this is the case, completed an invention based on this, and has already filed an application. The adhesive according to the present invention is extremely excellent, and in the process of further examining its application fields, the following new facts were discovered. That is, (a) alkali metal fluorides and alkaline earth metal fluorides other than the above-mentioned sodium fluoride and calcium fluoride exhibit similar effects, and (b) alkali metal fluorides (including sodium fluoride) ) as an active ingredient,
As the content increases, the processing temperature can be lowered, which is a great advantage, but on the other hand, there is a tendency for some minute pinholes to occur in the resulting adhesive layer, and depending on the place of use, the pinholes may It cannot be said that there are always cases where holes have an unexpected adverse effect on the adhesive, and (c) the occurrence of the above pinholes can be effectively prevented by coexisting with itria and at least one kind of alkaline earth metal compound. I discovered what I could do. The present invention has been completed based on these new discoveries, namely, the present invention combines 20 to 80% by weight of at least one of yttria and alkaline earth metal compounds (excluding fluorides) and an alkali. An adhesive for bonding ceramics containing a mixture of 80 to 20% by weight of a metal fluoride as an active ingredient, and at least one kind of ittria and alkaline earth metal compounds (excluding fluorides) and an alkali metal fluoride, or An adhesive containing a mixture of these and kaolin as an active ingredient is interposed between non-oxide ceramics, between oxide ceramics, or between non-oxide ceramics and oxide ceramics. The present invention relates to a ceramic bonding method characterized by heating to a temperature higher than the decomposition temperature of the fluoride. The adhesive of the present invention contains at least one of yttoria and alkaline earth metal compounds (excluding fluorides) and an alkali metal fluoride as active ingredients. The amounts of these components to be used are within the above specified ranges in order to obtain the desired effects of the present invention. Moreover, the adhesive of the present invention can further contain kaolin and/or an alkaline earth metal fluoride. The amount used is not particularly limited, but is usually 0 to 60% by weight. The adhesive of the present invention is prepared by simply interposing the adhesive between non-oxide ceramics, between oxide ceramics, or between non-oxide ceramics and oxide ceramics, usually at a temperature of about 1000 to 1500°C, preferably about 1000°C. Ceramics can be easily bonded by simply heating to ~1300°C without applying any pressure and without generating any pinholes. At this time, as the proportion of alkali metal fluoride in the adhesive increases, it becomes possible to bond at a lower temperature within the above heating range. The adhesive of the present invention has the great advantage of being able to bond non-oxide ceramics in particular, and the adhesive strength in this case is usually over 400Kg/cm, in fact 600Kg/cm.
cm, and approximately 300 kg/cm using known methods.
Compared to cm, which was the limit, it is possible to achieve an improvement of about 30% or more. Furthermore, pinholes do not occur in the adhesive layer. Furthermore, the adhesive of the present invention can be easily applied to bonding non-oxide ceramic materials of large size, complicated irregular shapes, which cannot be bonded by known methods, and can also strongly bond such materials. In addition, the adhesive layer of the present invention is chemically stable and has heat resistance and thermal shock resistance comparable to those of non-oxide ceramics. The reason why the above-mentioned various outstanding effects are exhibited by the use of the adhesive of the present invention is not clear at present, but it is thought to be as follows. That is, the alkali metal fluoride or the alkaline earth metal fluoride constituting the adhesive of the present invention may be used between non-oxide ceramics, between oxide ceramics, or between non-oxide ceramics and oxide ceramics. When heated to a temperature higher than the decomposition temperature of the ceramic material, it decomposes and generates fluorine gas, which corrodes the surface of the ceramic material while alkali metals or It is thought that the reactants of kaolin and alkaline earth metals, or these and kaolin, penetrate into the material eroded by the above and form an adhesive layer with excellent adhesive strength between the adhered materials. . In the case of the adhesive of the present invention in which kaolin is used in combination, the kaolin activates the alkali metals and/or alkaline earth metals generated by the heating and further promotes their penetration into the ceramic material. Seem. In this case, in the present invention, the presence of ittria and/or alkaline earth metal compounds can effectively prevent the formation of pinholes caused by the use of large amounts of alkali metal fluoride, but the mechanism is still unclear. In any case, the present invention provides a new adhesive technology for ceramics. Examples of non-oxide ceramics to which the adhesive of the present invention is applied include silicon carbide, silicon nitride, and sialon. Sialon is a nitride of silicon and aluminum. Examples of adhesion between these non-oxides include silicon carbide monosilicon carbide,
Examples include adhesion between silicon nitride and silicon nitride, silicon nitride and silicon carbide, silicon nitride and Sialon, silicon carbide and Sialon, and Sialon and Sialon.
Further, the adhesive of the present invention can be applied to the above-mentioned non-oxide ceramics and oxide ceramics such as alumina, mullite ceramics, zirconia, beryllia,
It can also be suitably used for adhesion with cordierite, magnesia, etc., or adhesion between the above oxide ceramics. Furthermore, it is also possible to bond metal to non-oxide ceramics via the oxide ceramics. In this case, since non-oxide ceramics and metal have significantly different coefficients of expansion, oxide ceramics are placed between them. If the thickness of this oxide-based ceramic is 5 mm or less, only one type of oxide-based ceramic may be used, but if the thickness is greater than 5 mm, two or more types of oxide-based ceramics with different expansion coefficients may be used. Preferably, they are used in combination. The metal in this case includes a wide variety of metals. These non-oxide-based, oxide-based, or metallic materials are not particularly limited in shape or size; they may be plate-like,
It may have any shape such as columnar, pipe-like, block-like, etc., and the materials to be bonded may have the same shape or different shapes. Examples of the alkali metal fluorides used as active ingredients in the adhesive of the present invention include lithium fluoride, potassium fluoride, sodium fluoride, rubidium fluoride, etc.Alkaline earth metal fluorides used as necessary include is beryllium fluoride,
Examples include calcium fluoride, magnesium fluoride, strontium fluoride, barium fluoride, and the like. The purity of these fluorides is not particularly limited, but in order to increase adhesive strength, it is preferable that the purity is as high as possible. In addition, alkaline earth metal compounds used in the present invention include oxides such as calcium oxide, magnesium oxide, beryllium oxide, barium oxide, and strontium oxide, and calcium carbonate, magnesium carbonate, beryllium carbonate, barium carbonate, and strontium carbonate. Specific examples include carbonate compounds and the like. These alkali metal fluorides, alkaline earth metal fluorides, itria and alkaline earth metal compounds are advantageously used in their commonly available powdered forms. Moreover, as the kaolin that can be used in combination, any commercially available kaolin can be used, and there are no particular limitations on its production area (type of raw stone), crystal size, history, etc.
In addition, its composition mainly consists of SiO ₂ and Al ₂ O ₃ , with other
Ordinary materials containing small amounts of Fe ₂ O ₃ , TiO ₂ , CaO, K ₂ O, etc. may be used, but the use of higher purity materials will improve the adhesive strength of alkali metal fluorides and alkaline earth metal fluorides. There is a tendency to increase the Moreover, the physical properties of the adhesive layer can be improved. The adhesive of the present invention can also be used in the form of a powder mixture of at least one of the above-mentioned ittria and alkaline earth metal compounds, an alkali metal fluoride, or these and kaolin or (and) an alkaline earth metal fluoride. , etc. can also be blended with a conventional vehicle (an organic adhesive such as balsam or an organic adhesive and an organic solvent) and used in the form of a paste or the like. When using the thus obtained adhesive of the present invention, it is interposed between materials to be bonded and then heated to a temperature higher than the decomposition temperature of the alkali metal fluoride or alkaline earth metal fluoride. The adhesive of the present invention can be applied between materials depending on the form of the adhesive. For example, if it is in powder form, it can be applied to the surface to be adhered, or if it is in paste form, it can be applied to the surface to be adhered. You can apply it in the same way. The amount to be applied can be determined as appropriate depending on the composition of the adhesive used, especially the amount of kaolin used, the heating conditions after applying the adhesive, the type and shape, especially the thickness, of the material to be bonded, and is not particularly limited. However, in terms of the weight of the active ingredient of the adhesive of the present invention, it is approximately 0.01 to 5% per cm of adhesive area.
g, preferably about 0.1 to 1 g. Further, the adhesive of the present invention may be heated at the temperature mentioned above after application, that is, the temperature at which the alkali metal fluoride or alkaline earth metal fluoride decomposes and releases fluorine. In the present invention, it is not particularly necessary to employ any pressure means during the above-mentioned heating, but a slight pressure may be applied in order to ensure the adhesion of the surfaces to be bonded. In addition, the above heating can generally be easily performed in air,
If there is a risk of oxidation of the material to be bonded due to heating, the bonding may be carried out in a nitrogen atmosphere. Examples will be given below to explain the present invention in more detail. Example 1 A mixed powder consisting of 30% by weight of ittria and 70% by weight of sodium fluoride was removed between a silicon nitride plate and a mullite ceramic plate (manufactured by Nippon Kagaku Ceramics Co., Ltd.) in an amount of 0.5 g per 1 cm ² of adhesive area. A copper plate was placed on a mullite ceramic plate with cloth interposed therebetween, and this was heated in an electric furnace at 1100°C for 20 minutes. The adhesive strength of the obtained bonded body sample was measured at a span of 20 mm.
The bending strength was determined to be 470 Kg/cm ² under the condition of a loading rate of 0.5 mm/mm according to the three-point loading bending strength measurement method. Further, when the fractured surface was examined after the above measurement, it was found that the fracture occurred on the outside of the bonded portion (mullite ceramic plate). Further, the above bonded body sample was immersed in a 48% potassium hydroxide aqueous solution at 70° C. for 70 hours to examine chemical resistance, and no abnormality was observed in the bonded portion. In addition, thermal shock resistance was examined by a rapid cooling test in which the above-mentioned joined body sample was heated to 1100° C. and then rapidly cooled in air, and no abnormality was observed in the bonded portion. Examples 2 to 4 In Example 1, adhesives of the present invention were prepared by varying the blending ratio of ittria powder and sodium fluoride powder, and these were used to prepare silicon nitride plates and mullite ceramic plates in the same manner. - Glued the copper plate. The adhesive strength, chemical resistance, and thermal shock resistance of each of the obtained joined body samples were determined in the same manner as in Example 1, and the results are shown in Table 1 below.

[Table] Example 5 A mixed powder consisting of 30% by weight of ittria and 70% by weight of sodium fluoride was placed between two silicon nitride plates.
A bonded body was obtained by removing 0.5 g per cm ² and heating it at 1100° C. for 20 minutes in the same manner as in Example 1. The adhesive strength of the resulting joined body sample was measured and found to be 520 Kg/cm ² . Further, chemical resistance and thermal shock resistance were tested in the same manner as in Example 1, and no abnormalities were found. Examples 6 to 8 In Example 5, adhesives of the present invention were prepared by varying the blending ratio of ittria powder and sodium fluoride powder, and two silicon nitride plates could be bonded using these in the same manner. Example 1 The adhesive strength, chemical resistance, and thermal shock resistance of each bonded body sample
The results obtained in the same manner as above are shown in Table 2 below.

[Table] Example 9 A mixed powder consisting of 70% by weight of calcium oxide and 30% by weight of sodium fluoride was used between a silicon nitride plate and a mullite ceramic plate (manufactured by Nippon Kagaku Togyo Co., Ltd.). The three-point bending strength of a similarly prepared sample was measured and found to be 510 Kg/cm ² .
In addition, chemical resistance and thermal shock resistance were tested according to Example 1, and there were no abnormalities. Examples 10 to 13 Adhesives of the present invention were prepared by varying the blending ratio of calcium oxide and sodium fluoride in Example 9, and these were used to bond a silicon nitride plate, a mullite ceramic plate, and a copper plate in the same manner. The adhesive strength, chemical resistance, and thermal shock resistance of each bonded body sample obtained in Example 1 were determined in the same manner as in Example 1.
Shown in the table.

[Table] Example 14 Calcium oxide 30% by weight and sodium fluoride
A mixed powder consisting of 70% by weight was interposed between two silicon nitride plates in an amount of 0.5 g per 1 cm ² and heated in the same manner as in Example 1. The adhesive strength of the resulting bonded body sample was It was 560Kg/ ^cm2 . Further, chemical resistance and thermal shock resistance were tested in the same manner as in Example 1, and no abnormalities were found. Examples 15 to 17 In Example 14, adhesives of the present invention were prepared by varying the blending ratio of calcium oxide and sodium fluoride, and these were used to bond two silicon nitride plates together in the same manner. The adhesive strength, chemical resistance, and thermal shock resistance of each of the obtained bonded body samples were determined in the same manner as in Example 1, and the results are shown in Table 4 below.

[Table] Example 18 Calcium carbonate 80% by weight and lithium fluoride 20%
A mixed powder consisting of 0.5% by weight was applied between a silicon nitride plate and a mullite ceramic plate at a rate of 0.5% ^per cm2 of adhesion area.
A copper plate was placed on the mullite ceramic plate, and this was placed in an electric furnace.
Heated at 1100°C for 20 minutes. The adhesive strength of the obtained bonded body sample was measured according to Example 1 and was found to be 550 Kg/cm ² . Also, Example 1
Chemical resistance and thermal shock resistance were tested in the same manner as above, and no abnormalities were found. No pinholes were observed in the adhesive layers of the bonded body samples obtained in Examples 1 to 18.

Claims (1)

[Claims] 1. Ceramics containing as an active ingredient a mixture of 20 to 80% by weight of at least one of yttoria and alkaline earth metal compounds (excluding fluorides) and 80 to 20% by weight of an alkali metal fluoride. Adhesive for joining. 2. The adhesive according to claim 1, wherein the alkaline earth metal compound is an alkaline earth metal oxide or an alkaline earth metal carbonate. 3. The adhesive according to claim 1, wherein the ceramic is non-oxide based. 4. The adhesive according to claim 3, wherein the non-oxide ceramic is at least one of silicon carbide, silicon nitride, and sialon. 5. The adhesive according to claim 1, wherein the ceramics are oxide-based. 6. An adhesive containing as an active ingredient a mixture of 20 to 80% by weight of at least one of ittria and alkaline earth metal compounds (excluding fluorides) and 80 to 20% by weight of an alkali metal fluoride is used as a non-oxide adhesive. A method for adhering ceramics, characterized by interposing the ceramics between two fluoride-based ceramics, between oxide-based ceramics, or between a non-oxide-based ceramic and an oxide-based ceramic, and heating the fluoride to a temperature higher than the decomposition temperature of the fluoride. . 7. A non-oxide ceramic, an oxide ceramic, and another oxide ceramic having a larger expansion coefficient than the oxide ceramic are laminated in this order with the adhesive interposed between them. The adhesion method according to claim 6. 8. The bonding method according to claim 7, wherein the other oxide ceramic having a large coefficient of expansion has a metal bonded to one surface thereof in advance.