JP2001192277A - Ceramic joined body and its manufacturing process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a joining technique for strongly joining two ceramic sintered bodies, or a ceramic sintered body and a nonmetallic inorganic compound single crystal, to each other so as to attain expected high functionality of the resulting joined body. SOLUTION: The manufacturing process for this ceramic joined body comprises: interposing, between the surfaced to be joined of two ceramic sintered bodies or those of a ceramic sintered body and a nonmetallic inorganic compound single crystal, a layer of a nonmetallic inorganic compound powder having a <=5 μm average particle size, so as to form such dihedral angles between the powder and these ceramic bodies or the like at contact points of the powder with the surfaces to be joined, that >=50% by number of the angles are >=90 deg.; subjecting the interposed layer to pressure bonding to the ceramic bodies or the like; and sintering the layer to join the ceramic bodies or the like to each other with the layer. The layer is sintered as a temperature the numerical value of which is 0.5-1 time as much as that of the melting point of the powder. The powder is preferably formed from a powder-liquid mixture prepared beforehand by mixing the powder, together with at least one agent selected from binders, dispersants and plasticizers, with a liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joined body having improved functions by joining ceramics and ceramics or joining ceramics and a single crystal, and a method for producing the same. More specifically, the present invention relates to a precision ceramic joined body having a fine hole therein or a sharp cut, which is difficult to form by a usual method, and a method for producing the same.

[0002]

2. Description of the Related Art The development of ceramics which can be precisely combined and ceramics having bent holes inside has been required by the development of industrial technology. Since ceramics are hard and brittle, they are difficult to roll or cut like metals. Therefore, in ceramics, the powder of the nonmetallic inorganic compound to be used as a sintering raw material is preliminarily formed into a shape to be used, and the formed body is sintered to obtain the mechanical, electrical, and magnetic properties required for the product. The property is given. In the production of ceramics, it is essentially difficult to produce a product that requires dimensional accuracy or a product that has a bent hole inside because a powder compact shrinks due to sintering.

[0003] Conventional joining methods include thermal spraying, brazing, and hot pressing by hot isostatic pressing (HIP) or hot pressing. Among these techniques, the thermal spraying is a technique of joining by spraying a melted ceramic on a surface of a metal or the like, and is mainly performed for producing a corrosion resistant material at a high temperature or a normal temperature. This technique has a drawback in that it is not possible to manufacture a material that requires dimensional accuracy in order to spray molten ceramic.

[0004] The brazing method is a method in which an appropriate substance is interposed between joints to join the joints. In this method, a low melting point substance is used as an intervening substance, so that a material having excellent high temperature properties is used. There was a drawback that manufacturing was difficult. HIP
Compression at high temperature by hot pressing or hot pressing has the advantage of producing a high-purity, high-performance bonded body with good dimensional accuracy, but the workability is poor and the cost is high because a pressure device is used for bonding. There were drawbacks.

Further, the decrease in high-temperature strength can be ignored,
Techniques have been developed for bonding at normal pressure that does not impair high functionality such as negligible light scattering. However, at present, bonding by this technique is limited to materials capable of flattening surface irregularities to the atomic order. For example, ultra-precisely polished glasses can be joined together, and materials utilizing the joining are already commercially available. In addition, when a single crystal of a nonmetallic inorganic compound can be polished flat even to irregularities on the order of atoms, bonding without pressure has already been successful. On the other hand, in the case of ceramics that are an aggregate of many single crystals,
When polishing, the polishing speed is different for each particle, so it is difficult to polish with irregularities suppressed to the atomic order. For this reason, there are many unsolved technical issues in joining without applying pressure in joining ceramics and ceramics, which is expected to have high functionality, or joining ceramics and a single crystal of a nonmetallic inorganic compound.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by providing a structure between a bonding surface between ceramics and ceramics or a bonding surface between ceramics and a single crystal of a nonmetallic inorganic compound. The dihedral angle with these ceramics or single crystals is 90 ^° or more and the average particle size is 5
Provided is a ceramic joined body characterized by being joined by a layer obtained by pressing and sintering powder of a nonmetallic inorganic compound having a particle size of μm or less.

Further, the present invention provides the above-mentioned ceramic bonded body, wherein the structure of the bonding layer and the structure of the ceramics are integrated and an apparent bonding phase is not recognized.

A dihedral angle between the ceramic and the single crystal is 90 ^° or more on a surface for bonding the ceramic and the ceramic or a surface for bonding the ceramic and the single crystal of the nonmetallic inorganic compound, and Average particle size is 5μ
m or less, wherein the non-metallic inorganic compound powder is sandwiched and pressed, and the powder is sintered and joined at a temperature between 0.5 times the melting point and the melting point of the powder. Provided is a method for manufacturing a ceramic joined body.

Further, the present invention provides the above-mentioned method for producing a ceramic joined body, characterized by using a powder kneaded with a liquid together with one or more of a binder, a dispersant, and a plasticizer.

At present, the term "ceramics" is used not only for sintered bodies but also for non-metallic inorganic compound materials such as single crystals, thin films and cements.
It meant a sintered body of the compound. In this specification, the term ceramic is used in its original meaning.

In the present invention, the powder sandwiched between the joining surfaces of the ceramics and the ceramics or between the joining surfaces of the ceramics and the single crystal of the nonmetallic inorganic compound is a powder having a particle size of 5 μm or less. .

The present invention utilizes the property that fine powder is chemically active. For this reason, in principle, it is preferable that the average particle size of the basic particles of the powder be smaller. However, when the basic particles become smaller, strong cohesive force acts between the particles to form hard aggregated particles. The sinterability of the powder is governed by the size of the hard agglomerated particles. For this reason, in the present invention, it is necessary to use a powder having an average particle diameter of hard aggregated particles of 10 μm or less. Here, the basic particles refer to primary particles or particles in which the primary particles are densely aggregated, and substantially no pores are recognized in the aggregate. Aggregated particles are particles in which basic particles are aggregated while including pores.

On the other hand, as the size of the basic particles increases, the sinterability rapidly decreases. Therefore, the average particle size of the basic particles is 5 μm.
m. If a powder larger than the average particle diameter is used, it is not practical because bonding at a very high temperature is required. The powder used in the present invention is not particularly limited as long as the size satisfies the above conditions,
It may be obtained as a commercial product.

In the present invention, the powder that can be used for bonding has a dihedral angle between the powder and the substance to be bonded. In the present invention, the dihedral angle refers to the angle between the surfaces at the intersection of the interface between the powder particles used for bonding and the material to be bonded and the surfaces in contact with each other. The dihedral angle decreases when the interface free energy becomes relatively large as compared with the surface free energy.

As a method for measuring the dihedral angle, the following method (G. Ac
hutaramayya and WDScott.J.Am.Ceram.Soc., 56 [4] 230-31
(1973)). After mirror-polishing the bonded sample, hot corrosion is performed at a temperature between 1/2 of the melting point of the bonded sample and the melting point. The sample is set horizontally on the sample stage of the SEM. The electron beam of the SEM is line-scanned at right angles to the hot corrosion groove at the grain boundary formed between the powder particles used for bonding and the bonded object. Carbon and the like generated by decomposition of the organic vapor colliding with the electron beam are deposited along the scanned line. This linearly deposited material is used as a marker.

If the sample is horizontal, the SEM image obtained from this marker will be a straight line. When the sample is tilted, the marker shows a dimple with a corner at the grain boundary. The angle β of this angle
Is measured. When the angle of inclination of the test slope and the dihedral angle are represented by α and θ, respectively, tan (θ / 2) becomes sin (α / 2) and t
equal to the product of an (β / 2). Since α and β are known, 2θ can be calculated from this equation. Further, by using a recently developed atomic force microscope, the dihedral angle of a grain boundary groove can be directly measured.

In the present invention, the bonding phenomenon is that atoms at an interface formed between a powder particle used for bonding and a substance to be bonded are diffused on the particle surface or the surface of the substance to increase the area of the interface. At the same time, it is a phenomenon that reduces the area of those surfaces. Interfacial free energy is excess energy, similar to surface free energy. For this reason, a large interface free energy means that a large amount of energy is required to increase the area of the interface, and conversely, the driving force causing the bonding is reduced accordingly. According to theoretical calculations, bonding does not proceed when the dihedral angle is 60 ^° or less.

In practice, at least 50% of the dihedral angle at the place where the powder particles used for bonding come into contact with the object to be bonded is 90 °.
When it becomes less, the driving force for joining becomes very small,
Joining hardly proceeds. Therefore, it is necessary that 50% or more of the dihedral angle is 90 ^° or more. It is already known that the properties of the surface and interface of a solid vary greatly with trace impurities. If the dihedral angle between the powder and the substance used for bonding is small and bonding does not proceed, add a substance that does not impair the practical characteristics of the bonded body and reduce the dihedral angle of 90 ° or more by 50%.
With the above, joining can be performed by the technique of the present invention.

For example, the bond of SiC has a strong covalent bond, and a dihedral angle of less than 90 ° is not negligible in two planes or sections between the powder particles of SiC and the particles of the sintered body of SiC. Appear. In this case, boron (B) added Si
When C powder is used, most dihedral angles become 90 ° or more, and bonding becomes possible.

In the present invention, a preferable result can be obtained even if the powder is sandwiched between the substances to be bonded, but there is a disadvantage that technical skill is required to obtain a good bonding surface. Therefore, it is preferable that the kneaded material of the powder and the liquid is sandwiched between the substances to be joined, because the action of the liquid increases the joining strength and facilitates the joining operation. In addition, it is more preferable to use a liquid containing a deflocculant or a lubricant at the time of kneading, since the powder sandwiched between the substances to be bonded can be densely filled. In addition, it is preferable to add a binder to the liquid because the bonding strength before firing is improved and the bonding operation is facilitated.

In the present invention, after the powder used for bonding is sandwiched between the objects to be bonded, the adhesion between the powder and the object is improved, or the bulk density of the powder is increased. Further, in order to remove excess powder that does not directly contribute to adhesion, pressure is applied to the object at room temperature to compress the powder. The compression pressure is preferably at least 10 MPa, particularly preferably 30 MPa.

In the present invention, if the joining temperature is 0.5 times or less of the melting point of the powder used for joining, the mass transfer rate is so small that the joining cannot be performed substantially. Necessary, and preferably 0.7 times or more. Above the melting point of the powder or above the melting point of the compound formed by the reaction of the powder with the ceramic to be joined, the grain growth of the ceramic is abnormally promoted. This abnormal grain growth is not preferable because it reduces practically important properties such as mechanical strength of the ceramic. On the other hand, even if a melt is generated in the early stage of bonding, if the melt dissolves in the material to be bonded before the abnormal grain growth occurs or reacts and does not remain after bonding, the function of the bonded body is reduced. There is no problem because it does not lower.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, non-metallic inorganic compounds include iron (Fe) and copper (C) among solid inorganic substances.
u), a substance excluding a simple substance such as a metal such as aluminum (Al), a semimetal such as carbon (C) or silicon (Si), or an intermetallic compound. Examples of the compound include compounds of metals such as alumina (Al ₂ O ₃ ) and aluminum nitride (AlN) and nonmetals such as oxygen and nitrogen, and compounds of semimetals such as silicon carbide (SiC). is there.

In the present invention, the sera to be joined
The mix is a sintered body of a non-metallic inorganic compound,
As the inorganic compound, alumina (Al_TwoO_Three),Stabilization
And high toughness zirconia (Zr containing various additives)
O_Two), Perovskite ceramics, yttrium
・ Aluminum Garnet (YAG), Titania (T
iO _Two), Zinc oxide (ZnO), yttria (Y
_TwoO_Three), Silicon nitride (Si_ThreeN_Four), Sialon (SI
ALON), silicon carbide (SiC), aluminum nitride
Any substance suitable for the purpose of the present invention, such as (AlN),
Is not particularly limited. With these simple sintered bodies
Alternatively, a composite sintered body obtained by mixing a plurality of sintered bodies may be used.

The single crystal of the nonmetallic inorganic compound which is the object of the joined body of the present invention includes alumina (Al ₂ O ₃ ), yttrium aluminum garnet (YAG), yttria (Y ₂ O ₃ ), and magnesia. An oxide-based inorganic compound single crystal such as (MgO) or calcia (CaO) is exemplified, but the type is not particularly limited as long as it is a substance suitable for the purpose of the present invention. Even if non-oxide-based inorganic compounds such as silicon carbide (SiC) and aluminum nitride (AlN) can be used to synthesize large single crystals, demand for high-performance bonded bodies will increase. The technology of the present invention can be applied.

If the powder used for bonding and the material to be bonded are different, a chemical reaction occurs during sintering. In the present invention, there are some favorable chemical reactions and some unfavorable chemical reactions. For example, Si ₃ N ₄ or SIALON and Ca
When O is combined, the low-melting substance generated during sintering remains after joining, so that it is technically similar to conventional brazing. For this reason, such a case is not suitable as the powder used in the present invention. However, Si ₃ N ₄ and Y ₂ O ₃
In a system where a low-melting substance is generated in the early stage of bonding, but changes to a high-melting substance as the bonding proceeds, the low-melting substance promotes the bonding, and the low-melting substance is present after the bonding is completed. This is a preferred combination in the present invention.

If the difference in the coefficient of thermal expansion between the bonding phase formed after the sintering of the powder and the ceramic or single crystal used for bonding is 2 × 10 ⁻⁶ / ° C. or more, the thermal expansion during cooling after the bonding will occur. Thermal stress due to the difference in expansion occurs and breaks. Also, when the materials to be joined are different or when the same material is used to join the ceramic and the single crystal, if the difference in the coefficient of thermal expansion is 2 × 10 ⁻⁶ / ° C. or more, the materials are broken during cooling after joining. For this reason, it is necessary to suppress not only the difference in the coefficient of thermal expansion between the joining phase and the material to be joined but also the difference in the coefficient of thermal expansion between the materials to 2 × 10 ⁻⁶ / ° C. or less.

In the present invention, the liquid used for kneading the powder is exemplified by water, alcohols, and the like. If the liquid is suitable for the above-mentioned purpose of use and does not lower the purity of the joint portion, The type is not particularly limited.

In the present invention, examples of the deflocculant used for kneading the powder include diethylamine, pyridine, and methylcellulose. The type of the substance is not particularly limited as long as it is a substance suitable for the purpose of use of the present invention, ie, for relaxing.

In the present invention, the binder used for kneading the powder is to make the state in which the powder is sandwiched between the substances to be joined firm, thereby facilitating the joining operation, and at the same time, the particles are produced during firing for joining. Used to prevent uneven sintering. As the binder, polyethylene glycol, polyvinyl alcohol, polyacrylamide, etc. are exemplified.If the substance does not reduce the purity of the joint after joining, and is a substance suitable for the purpose of use of the present invention as the binder, the binder may be used. The type is not particularly limited.

In the present invention, the lubricant used for kneading the powder improves the slip between the particles of the powder sandwiched by the substances to be joined, and eliminates the uneven packing density of the powder. Used to increase the packing density. Examples include diglycol stearate and carbowax,
The type of the lubricant is not particularly limited as long as it does not reduce the purity of the bonded portion after the bonding and is suitable for the purpose of use of the present invention as a lubricant.

In the present invention, the type and amount of the deflocculant, the binder, and the lubricant that exhibit the purpose of use differ depending on the type and size of the powder. The science of determining these types and amounts is not well developed and must be determined empirically. Since these additives also exert an effect on the molding of ceramic powder, they have been studied in detail in the past as assistants for the production of ceramics. Therefore, in practice, these research results (for example, “organic additives for molding”, TI Co., Ltd.)
C 1993, "Ceramics Manufacturing Process", Yoichi Sogi, Gihodo Shuppan Co., Ltd. (1982), etc.), it is necessary to examine the types and amounts of additives.

There are voids in the powder layer between the substances to be joined. In the present invention, the voids are removed by sintering the particles of the powder layer at a high temperature. If there are irregular and large irregularities on the surface to be joined, densification by sintering becomes uneven, and if the filling state of the powder particles is not strictly controlled, large voids grow by firing. If the surfaces to be joined are smoothed, the densification becomes one-dimensional and the generation of large voids is reduced. For the above reasons, it is preferable to polish with a polishing material of 15 microns or less, and particularly preferable to polish with a polishing material of 3 microns or less.

In the present invention, the suppression of the surface undulation is also effective, and the undulation is preferably suppressed to within ± 100 μm, particularly preferably within ± 50 μm. In the present invention, it is necessary to suppress the surface waviness to within ± 100 μm in the joining for integrating the structure of the substance to be joined with the joining layer.

In the present invention, the thickness of the powder layer used for bonding between the ceramics to be bonded and the ceramics or between the ceramics and the single crystal depends on the surface roughness or the surface undulation of the bonding surface between the ceramics and the single crystal. Comparing the height of each amplitude with the three of the particle diameters of the powder particles, it is preferably 1 to 100 times, preferably 3 to 50 times the largest one.
Double is particularly preferred. If the thickness of the powder layer is smaller than the above-mentioned value, the ceramics to be bonded or the ceramics and the single crystal are in direct contact with each other, and a good bonded body cannot be obtained. On the other hand, even when the thickness is 100 times or more as described above, the joining characteristics are the same, only the amount of powder used for joining increases. Therefore, it is not preferable to increase the thickness to 100 times or more because it is economically disadvantageous only by increasing the amount of powder used.

[0036]

EXAMPLE 1 Using a commercially available alumina powder having a diameter of 0.4 .mu.m, a plurality of alumina compacts having a diameter of 10 mm and a thickness of 3 mm were prepared by a dry press method, and were vacuum-baked at 1700.degree. C. for 1 hour. Tie. One side of the sintered body is mirror-polished. 0.9 μm in diameter
After adding a little distilled water to the commercially available alumina powder and kneading it well, apply it to the polished surface and paste the polished surfaces together to about 30M.
Pressure bonding was performed at a pressure of Pa. The thickness of the coating layer was about 10 μm.

The bonded sample was dried, and 170
When fired in vacuum at 0 ° C. for 1 hour, a good bonded body was obtained. After mirror-polishing the joined body, it is thermally corroded at 1600 ° C. The electron beam of the SEM is line-scanned at right angles to the hot corrosion groove at the grain boundary formed between the powder particles used for bonding and the bonded object. Along the scanned line, carbon and the like decomposed from the organic vapor colliding with the electron beam are deposited in a linear manner. After tilting the sample by the angle α, the angle β between the surfaces intersecting the grain boundaries is measured. The dihedral angle θ is ta
It was calculated using the equation: n (θ / 2) = sin (α / 2) × tan (β / 2). According to the measurement result, 90 °
No smaller dihedral angle was observed and the average was 135 °
Met. 2 of used alumina powder and alumina sintered body
No surface angle of less than 90 ° was observed, and the average value was 1
35 °.

Example 2 A commercially available alumina powder having a diameter of 0.4 μm and distilled water containing a binder and a dispersing agent were kneaded well, applied to the mirror-polished surface of the test piece prepared in Example 1, and bonded to each other. You. About 3
After pressure bonding at a pressure of 0 MPa, preliminary firing is performed at 1400 ° C. for 2 hours in air to remove a binder and a dispersant. The thickness of the coating layer was about 10 μm. Then, at 1700 ° C, 1
Vacuum firing was performed for a time to obtain a joined body in which the two test pieces were integrated. FIG. 1 is an SEM photograph showing a joining portion of the obtained ceramic joined body.

Arrows shown in FIG. 1 indicate pores formed in the bonding layer. Unless indicated by an arrow, the structure of the bonding layer and the structure of the ceramics are integrated, and it is not known where the bonding layer is. When a three-point bending test was performed on the joined body, the bending strength was 52 kg / mm ² , which was consistent with the bending strength of the test piece having no joint within an experimental error. The dihedral angle was measured by the method described in Example 1. As a result, the dihedral angle showed the same distribution as in Example 1, and the average value was 135 °.

Example 3 Instead of the mirror-polished surface, the surface cut with a diamond cutter is coated with the kneaded material used in Example 2. The thickness of the coating layer was about 100 μm. Crimping is performed under a pressure of about 30 MPa, followed by drying, sintering and bonding under the conditions of Example 2. Although the void could not be sufficiently removed, the three-point bending strength was 15 kg / mm ^2, and a joined body having considerable strength was obtained. The dihedral angle was measured by the method described in Example 1. As a result, the dihedral angles showed the same distribution as that obtained in Example 1.

Example 4 In the same manner as in Example 1, bonding was performed using yttria powder having an average particle size of 0.06 μm instead of commercially available alumina powder having a diameter of 0.9 μm. The thickness of the coating layer was about 10 μm. Since the material to be joined was alumina, the alumina and yttria reacted during sintering for joining to generate a low-melting substance, and the joining proceeded very quickly. The dihedral angle was measured by the method described in Example 1. As a result, the dihedral angle between the low melting point material and the alumina sintered body was between 120 and 150 °.

Example 5 A plurality of yttria compacts having a diameter of 10 mm and a thickness of 3 mm were produced by dry pressing using an easily sinterable yttria powder having a diameter of 0.06 μm, and these were molded at 1700 ° C. for 1 hour. Vacuum sintering. One side of the sintered body is mirror-polished. After the above-mentioned yttria powder and water containing a binder and a dispersing agent are well kneaded, the mixture is applied to a polished surface, the polished surfaces are adhered to each other, and pressed and pressed at a pressure of about 30 MPa, followed by drying. The thickness of the coating layer was about 10 μm. When the bonded sample was vacuum-sintered at 1700 ° C. for 1 hour, a good joined body was obtained. The dihedral angle of the sintered body joined to the powder used for the joining was measured by the method described in Example 1. As a result, the dihedral angle was between 120 and 147 °.

Comparative Example 1 As in Examples 1 and 2, alumina powder having an average particle diameter of 0.4 μm was used and sandwiched between the test pieces manufactured in Example 1 in a powder state without adding a liquid. The sandwiched powder was set in an electric furnace without pressure bonding and vacuum-sintered at 1700 ° C. for 1 hour. FIG. 2 is an SEM photograph showing a joining portion of the obtained ceramic joined body. There were portions where the bonding did not proceed sufficiently, and there were also portions where the bonding was hardly performed. The dihedral angle was measured by the method described in Example 1. As a result, the dihedral angle showed the same value as in Example 1.

Comparative Example 2 The test piece prepared in Example 1 was directly contacted without sandwiching the powder and fired under the conditions of Example 1. However, the bonding between the test pieces was negligible, and the test pieces were I left immediately.

[Brief description of the drawings]

FIG. 1 is an SEM photograph as a substitute for a drawing, showing a joined portion of a ceramic joined body obtained in Example 2.

FIG. 2 is an SEM photograph as a substitute for a drawing, showing a bonded portion of the ceramic bonded body obtained in Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G026 BA02 BA03 BA05 BA14 BA16 BA17 BA19 BB02 BB03 BB05 BB14 BB16 BB17 BB19 BC01 BD12 BF04 BF43 BF44 BG03 BG05 BG23

Claims (4)

[Claims] 1. A dihedral angle of 50 degrees between the joining surfaces of ceramics and ceramics or between the joining surfaces of ceramics and a single crystal of a non-metallic inorganic compound at the point of contact with these ceramics or single crystals. ceramic joined body% or more and wherein the 90 ^o or more and an average particle size are joined with a layer obtained by sintering and bonding a powder of the following non-metallic inorganic compound 5 [mu] m. 2. The ceramic joined body according to claim 1, wherein the structure of the joining layer and the structure of the ceramics are integrated and no apparent joining phase is observed. 3. A surface joining ceramics and ceramics or a surface joining ceramics and a single crystal of a non-metallic inorganic compound, at least 50% of the dihedral angle at the point of contact with these ceramics or single crystals. Is 90 ^° or more and a powder of a non-metallic inorganic compound having an average particle diameter of 5 μm or less is sandwiched and pressed, and the powder is sintered at a temperature between 0.5 times and a melting point of the melting point of the powder. The method for producing a ceramic joined body according to claim 1, wherein the ceramic joined body is joined. 4. The method for producing a ceramic joined body according to claim 3, wherein a powder kneaded with a liquid together with one or more of a binder, a dispersant, and a plasticizer is used.