JP2010070397A - Method for joining pressure moldings of ceramic raw material powder and method for producing ceramic sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for joining pressure moldings to produce a unified pressure molding which has high joining strength, where the defect of a joining part, the unevenness of density and the like are little to the same degree as a base material and where mechanical processing similar to that for the pressure moldings which are not joined can be performed. <P>SOLUTION: The method for joining the pressure moldings of ceramic raw material powders in which a plurality of pressure moldings obtained by press-molding a mixture of the ceramic raw material powders and a binder are joined includes : a step to sandwich a molding containing the same or different kind of the ceramic raw material powders as a joining intermediate layer between the joining surface of a first pressure molding and the joining surface of a second pressure molding; and a step to join the first pressure molding and the second pressure molding by pressure via the molding of the joining intermediate layer. The molding to be the joining intermediate layer has smaller elastic modulus than those of the first pressure molding and the second pressure molding. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a pressure-formed body and sintered body of ceramic raw material powder, and joins a plurality of pressure-formed bodies of ceramic raw material powder to obtain a complex shape product, a thick product, and a long product. The present invention relates to a method and a method for producing a ceramic sintered body obtained by firing a bonded pressure-formed body.

  Conventionally, as a method of joining and producing a plurality of parts (parts) to obtain a ceramic sintered body of a desired shape, after joining the pressure-formed bodies of ceramic raw material powders that are parts, firing and joining are performed. There is a first method for performing the above, and a second method for preparing a sintered compact of a pressure-formed body that is a part in advance and joining the sintered body of the part.

  As a second method for joining the sintered bodies, a method using a metal brazing material, glass or the like as a joining material is common. However, since the material of the bonding layer between the sintered bodies after bonding is different from that of the ceramic that is the base material (sintered body), the characteristics inherent to the base material (ceramics) are impaired.

  On the other hand, as a joining method in which a joining layer using the joining member cannot be formed, diffusion joining or the like in which a plurality of sintered bodies are brought into direct contact with each other is known. However, since the diffusion of ceramics occurs at a high temperature, there is a problem that a high temperature treatment is required for bonding of sintered bodies by the diffusion bonding method. In addition, the joining method has a problem that unjoined voids are likely to remain even if the joined surfaces of the sintered bodies are processed with high precision so as to closely contact each other.

On the other hand, since the 1st method joins the parts which are the pressure forming bodies of ceramic raw material powder after joining, it can reduce the gap of a joined part to some extent in a firing process, and more There is a possibility that a highly reliable joint can be obtained.
For example, Patent Document 1 discloses a method of directly joining a plurality of pressure-formed bodies by CIP (cold isostatic pressing). However, since the pressure-molded bodies are directly aligned and joined, a gap is likely to remain between the joining surfaces of the two pressure-molded bodies (joint portion), and it is difficult to completely remove the gap during the firing process. . In order to reduce the voids in the sintered body, it is necessary to perform processing with high accuracy so that the joint surfaces of the pressure-molded bodies are in close contact so that no gaps are formed on the joint surfaces. However, unlike a sintered body, it is generally difficult to process the shape of the joint surface with high accuracy in a pressure-formed body including voids.

  Patent Document 2 discloses a technique in which two pressure-formed bodies are joined after a slurry made of ceramic raw material powder and a solvent is applied to the joint surface of the pressure-formed body. When applying a slurry to a joining surface, the density | concentration of the raw material powder of the ceramics contained in a slurry and the density | concentration of the said raw material powder contained in a molded object differ greatly. That is, since the raw material powder concentration (filling density) of the part where the slurry is applied (that is, the joining intermediate layer) is low, the density of the joining part is obtained when two or more pressure-formed bodies are joined and fired through the slurry. Tends to be low and voids are likely to remain. Furthermore, when using a slurry with a low concentration of the raw material powder, the precision is adjusted so that the joint surface of the pressure-formed body is closely attached so that no gap remains in the joint, as in the case of directly joining the pressure-formed body. It is necessary to finish it high.

  Patent Document 3 discloses a bonding method using a paste of ceramic raw material powder as a bonding agent. In the case of the paste, since the ceramic raw material powder concentration can be higher than that of the slurry, the processing accuracy of the joint surface of the pressure-formed body may be lower than when the pressure-formed bodies are directly joined or when the slurry is used. Good bonding with few voids is possible. However, the ceramic paste also has a problem that voids are likely to remain because the concentration of the ceramic raw material powder is low, and the density of the joint portion is liable to be lower than when the processed compact is directly joined.

In the present application, ceramic means a material or substance such as Al ₂ O ₃ , ZrO ₂ , SiC or Si ₃ N _4, and a ceramic sintered body (or simply referred to as a sintered body) means a ceramic powder. The member obtained by sintering is represented.
JP 59-108801 A JP 54-144407 A JP-A-57-88201

  As described above, the conventional method of directly bonding the pressure-formed bodies of ceramic raw material powders may obtain a homogeneous bonded body. However, in reality, since it is difficult to join the pressure-molded bodies with the joint surfaces completely adhered to each other, defects are likely to remain in the joint portion, and the strength of the joint portion is significantly lower than that of the base material. There was a problem such as.

  In addition, when a slurry or paste using raw material powder having the same composition as the pressure molded body is used as the bonding intermediate layer, the bonding intermediate layer has a low concentration of raw material powder (low packing density), and is fired. Since voids remain in the joined portion of the obtained ceramic sintered body or the density of the base material portion and the joint portion is different, the mechanical properties such as strength of the joint portion are different from the base material of the pressure-formed body itself. It was difficult to get the same thing.

  Thus, when defects such as voids remain in the joint after sintering, or the density of the joint is lower than the base material of the pressure-formed body itself, the reliability related to the mechanical strength, etc. of the joint The properties are significantly impaired. In general, ceramic is a material having low toughness as compared with a metal material, and is therefore a material sensitive to defects such as voids and density, and breakage easily occurs from such defects and inhomogeneous portions. In addition, the pressure-formed body produced by joining a plurality of pressure-formed bodies by the above-mentioned joining method is not sufficient in the strength of the joint before firing. However, there is a problem that it is difficult to perform processing by the same method.

  The present invention has been made in view of the problems of the prior art in which a plurality of parts that are pressure-formed bodies of ceramic raw material powder as described above are joined and then fired to produce a sintered body of a desired shape. Is. In other words, the present invention has a joint strength with high strength capable of performing mechanical processing similar to that of a pressure-molded body that is not joined, and has as few defects and non-uniformity in density as the base material. The first object is to provide a method of joining a pressure-molded body for producing an integrated pressure-molded body, and the strength of the joint is obtained by firing the pressure-molded body joined by the joining method. A second object is to provide a method for producing a ceramic sintered body that is as large as the base material.

The above problems are solved by the present invention. The gist of the present invention is as follows.
(1) The method of joining the pressure-formed body of the ceramic raw material powder of the present invention is as follows:
A step of sandwiching a molded body containing a ceramic raw material powder of the same or different kind as the ceramic as a bonding intermediate layer between the bonding surface of the first pressure-molded body and the bonding surface of the second pressure-molded body; and the bonding Including pressurizing and bonding the first pressure-molded body and the second pressure-molded body through the molded body of the intermediate layer,
The molded body as the joining intermediate layer has an elastic modulus smaller than that of the first pressure molded body and the second pressure molded body.
(2) The method for bonding a pressure-molded body of ceramic raw material powder according to the present invention is characterized in that, in (1), an elastic modulus of the molded body as the bonding intermediate layer is 150 MPa or less.
(3) The method for bonding a pressure formed body of ceramic raw material powder according to the present invention is characterized in that, in (1) or (2), the elastic modulus of the pressure formed body is more than 150 MPa and not more than 300 MPa. To do.
(4) The method for joining the pressure-formed bodies of the ceramic raw material powder of the present invention is the method according to any one of (1) to (3), wherein the first pressure-formed body, the second pressure-formed body, and the joining intermediate. The molded body as a layer contains a binder,
Wherein the first binder content of the molded body pressed compact and a binder content of C _b1 of the second pressed compact and the intermediate joining layer C _b2 is the relationship of 2 × C _{b1 <C b2} It is characterized by satisfying.
(5) The method for bonding a pressure-formed body of ceramic raw material powder according to the present invention is the method according to any one of (1) to (4), wherein the first pressure-formed body, the second pressure-formed body, and The ceramic raw material powders of the compacts to be used as the joining intermediate layer have the same composition.
(6) The method for bonding a pressure-formed body of ceramic raw material powder according to the present invention is characterized in that in any one of (1) to (5), the ceramic raw material powder is alumina.
(7) A method for manufacturing a ceramic sintered body according to the present invention includes joining a plurality of pressure-formed bodies by the method for joining pressure-formed bodies of ceramic raw material powders according to any one of (1) to (6). And a step of producing an integrated pressure molded body, and a step of firing the integrated pressure molded body to obtain a sintered body.

  According to the present invention, it is possible to obtain a pressure-formed body of ceramic raw material powder having a joint portion having a density and mechanical properties equivalent to those of the base material. Furthermore, by sintering this, a ceramic sintered body having the same characteristics as the base material can be obtained at the joint portion, and a ceramic material having a complicated shape and a large size and high reliability can be provided.

An embodiment for carrying out a method for joining a pressure-formed body of ceramic raw material powder and a method for producing a ceramic sintered body according to the present invention will be described in detail.
In order to obtain a ceramic sintered body having a desired shape, a ceramic raw material powder is pressure-molded in advance to produce a pressure-formed body which is two or more parts (joined bodies). Next, as will be described in detail below, the pressure-formed bodies of the respective bonded bodies are joined to produce a pressure-formed body having a desired shape, and then the pressure-formed body is fired to sinter the ceramic sintered body. Get.

The material for the ceramic raw material powder for producing the press-formed body that is the joined body is not particularly limited. For example, known or well-known oxide-based ceramic raw material powders such as alumina, zirconia, cordierite, and mullite, and non-oxide-based ceramic raw material powders such as silicon nitride and silicon carbide are used as materials for producing ceramics. It is possible. In the examples described later, an example of using an oxide-based ceramic raw material powder is shown.
As the press-molded body that is the joined body (part), a ceramic raw material powder produced by a press-molding method such as die press molding, CIP (cold isostatic pressing), or uniaxial pressure molding can be used. .

  And between the joining surfaces of two to-be-joined bodies, the same kind or different type | mold of ceramic raw material powder is pinched | interposed as a joining intermediate | middle layer, two to-be-joined bodies are joined, and one press-molded body is obtained. obtain. A schematic diagram of pressure bonding is shown in FIG. FIG. 1 shows an arrangement of each member when two cuboid shaped objects 1 and 2 are bonded by applying uniaxial pressures 7 and 8 with a bonding intermediate layer 3 interposed therebetween. In FIG. 1, reference numeral 6 denotes a joint portion composed of two joint surfaces 4 and 5 and a joint intermediate layer 3 therebetween.

  It is preferable that the raw material of the pressure-formed body of the joined body contains a binder. One of the reasons is that after bonding, the bond between the pressure formed body that is the bonded body and the ceramic raw material powder formed body used as the bonding intermediate layer is strengthened, and the bonded pressure formed body is processed or the like. This is because it becomes possible to have a sufficient bonding strength when handling.

  Another reason is that the elastic modulus of the press-molded body of the joined body can be adjusted mainly by changing the amount (content ratio) of the binder. That is, by reducing the elastic modulus of the pressure-formed body that is the joined body, it is possible to eliminate a gap with the joining intermediate layer at the time of joining and to strengthen the bond with the joining intermediate layer. However, if the amount of the binder added is too large, the ceramic raw material powder and the binder are uniformly mixed and pressure-molded to produce a pressure-molded body, which is then degreased by removing the binder by decomposition and volatilization by heating. There are cases where cracking occurs in the pressure-formed product during the process, making it difficult to obtain a sound joined product. If the added amount of the binder added to the pressure-molded product exceeds 10% by mass in terms of solid content, cracking tends to occur during degreasing. Therefore, the addition amount of the binder is more preferably 10% by mass or less with respect to the ceramic raw material powder.

  As described above, it is preferable to increase the amount of binder added to the pressure molded body to lower the elastic modulus, but there is an upper limit of the amount of binder added that does not cause the degreasing crack, and the pressure molded body at that time The elastic modulus is a desirable lower limit of the elastic modulus. That is, the addition amount of the binder can be determined using the elastic modulus of the pressure-formed body as an index. In the present invention, as the elastic modulus, the value calculated by the equation (1) from the bending load and the amount of displacement obtained by the three-point bending test of the molded body is used using the bending elastic modulus E calculated from the equation (1).

E = 9.8 × P × L ³ / (4 × b × h ³ × x) (1)
Where E: elastic modulus (MPa)
P: Bending load (kgf)
L: Distance between fulcrums (mm)
b: Sample width (mm)
h: Sample thickness (mm)
x: displacement (mm).

  Specifically, it is desirable that the elastic modulus of the pressure-molded body exceeds 150 MPa. In other words, in order to make the elastic modulus of the pressure-formed body 150 MPa or less, it is necessary to increase the amount of binder added, and degreasing cracks may occur. On the other hand, the upper limit of the elastic modulus of the pressure-molded body is desirably 300 MPa or less from the viewpoint that the pressure-molded body is deformed at the time of pressure welding and the joined body and the joining intermediate layer can be joined without a gap.

Typical examples of the binder include polyvinyl alcohol and polyacrylate. However, according to the type of the ceramic raw material powder of the pressure-formed body of the joined body, any binder that can impart elasticity when mixed with the ceramic raw material powder is appropriately selected and used. Can do.
In addition, the elastic modulus of the pressure-formed body may be adjusted by the type, particle size, shape, etc. of the ceramic raw material powder.

  As the molded body of the ceramic raw material powder used as the bonding intermediate layer, a known ceramic raw material powder whose type and shape are optimized so as to obtain a desired elastic modulus may be used. However, a mixture of the same ceramic raw material powder and binder as the object to be joined, in addition to the pressure forming method such as die press molding, CIP, uniaxial pressure molding, etc., like the object to be joined, injection molding, injection molding, It is preferable to use one produced by a molding method such as a doctor blade (sheet molding). This is because the elastic modulus can be easily adjusted. The elastic modulus of the molded body of the bonding intermediate layer is made smaller than the elastic modulus of the pressure molded body that is the bonded body. By making the elastic modulus of the bonding intermediate layer smaller than the elastic modulus of the object to be bonded, defects in the bonded portion can be eliminated and a strong bonded portion can be formed.

  The bonding intermediate layer preferably has a modulus of elasticity calculated by the above formula (1) from a load displacement curve in a bending test smaller than the modulus of elasticity of the bonded body, and further uses a molded body having a modulus of elasticity of 150 MPa or less. Is preferred. When a molded body having an elastic modulus greater than 150 MPa is used as a bonding intermediate layer, it is difficult for the bonding intermediate layer to be deformed in accordance with the shape of the bonding surface of the bonded body during bonding by pressurization. In some cases, voids are easily generated, and a defect-free joint cannot be obtained.

  As a method of obtaining a molded product having an elastic modulus of 150 MPa or less, there is a method of controlling the amount of a binder to be added. Typical examples of the binder include polyvinyl alcohol and polyacrylic acid ester. However, any binder that can impart elasticity when mixed with the ceramic raw material powder can be used. When binders such as polyvinyl alcohol and polyacrylic acid esters are used, increasing the amount added (content ratio) decreases the elastic modulus of the molded body that becomes the bonding intermediate layer, so that the molded body is bonded during bonding. It becomes possible to deform | transform according to the joint surface shape of a body (pressure-molded body).

  The appropriate amount of binder to be added varies depending on the shape and size of the ceramic raw material powder used. For example, in the case of using an alumina raw material powder, when using a ceramic raw material powder having an average particle size of 0.5 μm, the amount of binder added should be 2.4% by mass or more based on the ceramic raw material powder in terms of the solid equivalent of the binder. Further, it is possible to obtain a molded article having a low elastic modulus having an elastic modulus of 150 MPa or less.

  In addition, there is no lower limit to the modulus of elasticity of the molded body used as the bonding intermediate layer, and even a molded body that is deformed by its own weight and cannot be measured by a bending test can be sandwiched and held between the bonded bodies. If possible, it can be used as an intermediate layer. However, an elastic modulus of about 5 MPa or more is more preferable in view of the ease of the work of sandwiching the formed body as a bonding intermediate layer and the object to be bonded.

And the ratio of the binder of the pressure-molded body which is a to-be-joined body, and the binder of the molded body used as a joining intermediate layer is the binder content Cb1 of a pressure-molding body, and the binder content of the molded body used as a joining intermediate _| middle layer. By making the ratio with the rate C _b2 satisfy the relationship of 2 × C _b1 <C _b2 , a better bonded body can be obtained. The ratio of the binder content, in the case of 2 × C _b1 ≧ C _b2, because the elastic modulus of the intermediate joining layer is not sufficiently low, it becomes likely to occur a gap at the joint surface, it may not be possible to obtain a sound conjugate is there.
Binder content C _b1 of pressed compact is defined in mass% of the binder in the molded body. Similarly, the binder content _Cb2 of the molded body used as the bonding intermediate layer is also defined by mass% of the binder in the molded body.
Incidentally, pressed compact is object to be bonded are normally there are multiple, in this case, it is preferable that the binder content C _b1 of all pressed compact is the same.

  When two objects to be bonded are bonded, the above-mentioned low elastic modulus bonded intermediate layer molded body is sandwiched between the bonding surfaces of the pressure-molded body that is the bonded object, and pressed (bonded). Pressure bonding). As a pressurizing method used for joining, uniaxial pressurization or hydrostatic pressurization can be applied. The pressure applied at the time of joining in the case of joining the joined bodies produced by pressure molding is preferably equal to or higher than the pressure at the time of pressure molding of the joined bodies. For example, an integrated pressure molded body produced by bonding a bonded body obtained by pressure molding at 98 MPa at a pressure of 98 MPa or more can sufficiently withstand the stress applied during normal processing. Has strength.

  The thickness of the joining intermediate layer sandwiched between two joined bodies (pressure-formed bodies) before pressure joining varies depending on the size of the joined body and the processing accuracy of the joining surface, and is appropriately set based on these. For example, in the case of general surface accuracy of a press-molded body that is a joined body, it is often preferable to set the range of 10 μm to 5 cm. It is sufficient that the bonding intermediate layer after the pressure bonding has a thickness that can eliminate defects and voids in the bonded portion. Therefore, the thickness of the bonding intermediate layer after pressure bonding is preferably 0.5 μm or more. However, in order to sufficiently maintain the strength of the bonded portion, the thickness of the bonded intermediate layer after pressure bonding is more preferably 0.8 μm or less.

  The ceramic raw material powder of the molded body used as the bonding intermediate layer is desirably a raw material powder made of a ceramic component having the same composition as the pressure-formed body of the bonded body. The bonded sintered body after firing of the pressure-formed body that has been pressure-bonded thereby becomes a bonded sintered body having a joint portion of the same composition as the base material obtained by firing each pressure-formed body. It becomes possible to obtain a joint having mechanical properties such as equivalent strength. In addition, by using the powder having the same composition, shrinkage at the time of firing of the pressure-formed body and the pressure-bonded body of the joining intermediate layer occurs in the same manner. .

  Further, the two pressure-formed bodies to be joined are more preferably pressure-formed bodies of ceramic raw material powder having the same composition. This is because, as in the case of joining the joined body (press-molded body) and the joining intermediate layer, peeling of the joining surface during firing hardly occurs.

  In addition, by applying a binder added to the molded body or another type of binder having an equivalent function directly or with a solution dissolved in a solvent such as water on the bonding surface of the bonded intermediate layer molded body and the joined body. Thus, it is possible to obtain a bonded body with higher bonding strength. As a result, the strength of the bonded portion before firing is increased, handling becomes easy, and the effect of preventing breakage during processing is obtained when the bonded pressure-formed body is machined.

  It is preferable to process the bonding surfaces of the pressure-formed body of the body to be bonded and the molded body used as the bonding intermediate layer into a shape that is in close contact with each other. After sandwiching a molded body as a joining intermediate layer between the joining surfaces of the joined bodies and joining them by uniaxial pressing or CIP, the sintered body is fired under firing conditions in which the base ceramic is densified to the desired density. obtain. In particular, when used as a structural material, it is desirable that the density of the bonded portion of the sintered body after firing is densified to 95% or more of the theoretical density.

  By the method described above, a bonding intermediate layer made of the same kind of ceramic raw material powder as the pressure-formed body of a plurality of objects to be joined or ceramic powder that can be firmly bonded to the ceramic raw material after firing is prepared. And adjusting the elastic modulus appropriately as described above, and press-bonding the joined bodies with the joining intermediate layer sandwiched therebetween to obtain a ceramic sintered body, whereby the strength of the joint portion is the strength of the base material. Compared with conventional products, complex shaped sintered products, thick sintered products, and long sintered products that are not inferior to those of conventional products can be easily manufactured at a low cost.

Examples where the effects of the present invention are particularly remarkable include the following cases. (1) When the ceramic sintered body to be finally processed has a complicated shape, it is easy to concentrate stress on the joint portion of the pressure-formed body, and there is a high demand for improving the joint strength at that portion. (2) When the dimensions of the container or apparatus for pressure molding including CIP are the same.
According to the present invention, the first pressure-molded body and the second pressure-molded body can be newly pressure-bonded through the bonding intermediate layer in a state after pressure-shrinkage. Is limited only to the bonding intermediate layer, it is possible to produce a larger-sized pressure-molded body as compared with the case where the pressure-formed body is produced in one step.
The present invention is particularly useful for the production of ceramic sintered bodies used for parts of various precision equipment such as electrostatic chucks, stage devices, and semiconductor manufacturing devices, which have recently been increasing in demand for larger size and higher defect-free strength. However, the present invention is not limited to these objects and can be widely applied to the production of ceramic sintered bodies.

  Hereinafter, as an example of a method for joining a pressure-formed body of a ceramic raw material powder according to the present invention and a method for producing a ceramic sintered body, a pressure-formed body is produced using the ceramic raw material powder, and two pressure-formed bodies are produced. A pressure bonded body was produced by pressure bonding, and further sintered to obtain a sintered body. Below, the sintered compact produced with the manufacturing method of this invention is described as an "Example." And the sintered compact produced on the manufacturing method different from the manufacturing method of this invention or the conditions remove | deviated from the conditions of the manufacturing method of this invention is described as a "comparative example."

(Example)
Alumina powder (average particle size 0.6 μm) is used as the ceramic raw material powder of the pressure-formed body, and the alumina powder and polyvinyl alcohol as the binder (binder) are shown in Table 1 in terms of solid content in the pressure-formed body. Distilled water was mixed as a solvent so that the binder addition amount shown for each sample was obtained to obtain a mixture. After the mixture was dried, two pressure-molded bodies were produced by pressure-molding at 98 MPa on a rectangular parallelepiped having a size of 50 mm (W) × 50 mm (L) × 20 mm (T).

  Similarly, polyvinyl alcohol was mixed with the alumina powder as a joining intermediate layer together with an aqueous solvent so that the binder addition amount shown for each sample in Table 1 in terms of solid matter in the molded body was obtained. The powder obtained by drying this mixture was molded into a size of 50 mm (W) × 50 mm (L) × 5 mm (T).

  After grinding the joint surface (50 mm (W) × 50 mm (L)) of these pressure-molded bodies and the joint surface of the molded body as a joining intermediate layer with a # 400 grindstone, A molded body serving as a bonding intermediate layer having a thickness of 5 (mm) was sandwiched therebetween, and pressure bonding was performed at a pressure of 147 MPa. The obtained joined body was fired in air at 1600 ° C. for 8 hours to obtain a ceramic sintered body.

  About the obtained sintered compact (joint sintered compact), the presence or absence of the defect of a junction part was observed visually and with the optical microscope. Moreover, about the sintered compact by which the defect was not looked at by the visual observation or the optical microscope, after carrying out the mirror surface grinding | polishing of the joining cross section, the etching process by phosphoric acid was given and the joining part was observed with the scanning electron microscope. In addition, for samples in which no defect was found in the joint, the sample was processed into a 3 × 4 × 40 mm test piece so that the joint became the center in the length direction of the test piece, and then joined by a four-point bending test method. The strength of the part was measured.

  In Table 1, the description of the press-molded body about the samples 1-19 which are an Example or a comparative example, the description of a joining intermediate | middle layer, and the list of evaluation results are shown. In the evaluation of the bonding state, the case where separation or cracking occurred on the bonding surface was evaluated as x, and the case where an obvious defect such as a gap was observed in the bonding portion by visual observation, optical microscope, or SEM observation was considered to be due to bonding. Those where no defects were found were marked as ○.

  As shown in Table 1, Sample No., which is a comparative example, using a bonding intermediate layer having an elastic modulus not lower than that of the molded body outside the scope of the present invention. Nos. 1, 8 and 9 were separated or cracked from the joint during degreasing or firing, and a joined body could not be obtained.

On the other hand, those using the joining method according to the present invention were able to obtain a joined body without any degreasing or firing without cracking or separation.
After cutting the sintered body from which these healthy bonded bodies were obtained, the bonded cross section was mirror polished, etched with phosphoric acid, and the bonded portion was observed with a scanning electron microscope. It was confirmed that it was composed of crystal grains having a grain size, and it was confirmed that the base material and the joint had a similar structure.

  Among the bonded sintered bodies according to the present invention, the sample No. In 2, 3, and 4, as a result of observation with a scanning electron microscope, pores of several tens of μm are seen at the joint interface, and the strength of the joint is slightly 350 to 370 MPa while the average strength of the base material is 460 MPa. The strength was low. However, sample no. 2, 3, and 4 had a bonding strength sufficient for practical use.

On the other hand, the sample ratio of the binder content _{C b2} of the molded body used as a binder content of _{C b1} of pressed compact intermediate joining layer does not satisfy the relation of 2 × _C b1 _{<C b2} No. In 15 and 16, no conspicuous defects were found in the joint, and the strength of the joint was 380 to 390 MPa.
Sample No. using a pressure-molded article having a high elastic modulus of 310 MPa. In 18 samples, no conspicuous defects were found in the joint, and the strength of the joint was 370 MPa.

  A sample prepared by using the same method as that for other bonding intermediate layers in which magnesium hydroxide is added to the alumina raw material of the pressure-molded body so as to be 0.1% by mass in terms of MgO. No. In No. 19, as a result of observation with a scanning electron microscope, pores of several tens of μm were found at the bonding interface, and the strength of the bonding portion was 370 MPa.

The elastic modulus of the bonding intermediate layer is 150 MPa or less, and the ratio of the binder content C _b1 of the pressure-molded body and the binder content C _b2 of the molded body used as the bonding intermediate layer satisfies 2 × C _b1 <C _b2 Sample No. As a result of observation with a scanning electron microscope, 5-7, 10-14, and 17 showed no noticeable defects at the joint interface, and the joint strength was 380 to 415 MPa.

(Other Comparative Example 1)
Alumina powder (average particle size 0.6 μm) and polyvinyl alcohol binder were mixed at a volume ratio of 45:55 to prepare a paste. After 1.5 g of this paste was placed in a uniform thickness on the joint surface of the molded body of the joined body produced by the same method as in the example, and the other molded body was vacuum-sealed with a vinyl sheet, Bonding was performed at a pressure of 1.5 ton / cm ² . The obtained joined body was degreased at 600 ° C. in the air, and then fired under the conditions of 1600 ° C. × 8 hours in the air to obtain a sintered body.
As a result of optical microscope observation of the joint surface, a long and narrow defect having a length of 100 to 200 μm, which is considered to be a trace of the binder being removed at the joint portion, was observed. Moreover, in the joint strength measurement by the four-point bending test method, the average strength of the bonded body is greatly reduced to 280 MPa with respect to the average strength of the base material, which is 280 MPa, and the failure starts from a defect in the joint. Was confirmed.

(Other Comparative Example 2)
A slurry was prepared by using alumina powder (average particle size 0.6 μm) as a raw material of the molded body, water as a solvent, and a polycarboxylic acid-based dispersant and a polyvinyl alcohol binder added thereto. This slurry was applied to the joint surfaces of the molded bodies of the two joined bodies produced by the same method as in Example 1. Next, the slurry application surfaces of the objects to be joined were bonded together. This was joined by CIP, and the obtained joined body was degreased at 600 ° C. in the atmosphere, and then fired at 1600 ° C. for 8 hours in the atmosphere to obtain a sintered body.
As a result of optical microscope observation of the joint surface, a gap of 10 to 30 μm was observed on the joint surface. In the measurement of the bonding strength by the four-point bending test method, the average strength of the joined body was greatly reduced to 310 MPa as compared to the average strength of the base material of 460 MPa.

Schematic layout diagram for explaining a method for joining pressure-formed bodies of ceramic raw material powder of the present invention

Explanation of symbols

1 1st press-molded body (bonded body)
2 Second pressure-formed body (bonded body)
3 Joining intermediate layer 4 Joining surface of first pressure-molded body 5 Joining surface of second pressure-molded body 6 Joining portion 7, 8

Claims (7)

A method of joining a plurality of pressure-formed bodies obtained by pressure-molding ceramic raw material powder,
A step of sandwiching a molded body containing a ceramic raw material powder of the same or different kind as the ceramic as a bonding intermediate layer between the bonding surface of the first pressure-molded body and the bonding surface of the second pressure-molded body; and the bonding Including pressurizing and bonding the first pressure-molded body and the second pressure-molded body through the molded body of the intermediate layer,
The molded body as the bonding intermediate layer has a modulus of elasticity smaller than that of the first pressure molded body and the second pressure molded body. Joining method.   The method for bonding a ceramic material powder pressure-formed body according to claim 1, wherein an elastic modulus of the formed body as the joining intermediate layer is 150 MPa or less.   The method for joining a pressure-formed body of ceramic raw material powder according to claim 1 or 2, wherein the elastic modulus of the pressure-formed body exceeds 150 MPa and is 300 MPa or less. The first pressure molded body, the second pressure molded body, and the molded body as the bonding intermediate layer include a binder,
The first pressed compact and a binder content of C _b1 of the second pressed compact, the the bonding intermediate layer a binder content C _b2 of the molded body, 2 × C _{b1 <relation} C _b2 The method for bonding a pressure-formed body of ceramic raw material powder according to any one of claims 1 to 3, wherein:   The ceramic raw material powder constituting each of the first pressure-formed body, the second pressure-formed body, and the formed body as the bonding intermediate layer has the same composition. Item 5. A method for bonding a pressure-formed body of ceramic raw material powder according to any one of Items 1 to 4.   The said ceramic raw material powder is an alumina, The joining method of the press-molding body of the ceramic raw material powder of any one of Claims 1-5 characterized by the above-mentioned. The process of producing the press-molded body which joined and integrated the several press-molded body by the joining method of the press-molded body of the ceramic raw material powder according to any one of claims 1 to 6, and A method for producing a ceramic sintered body comprising a step of firing an integrated pressure formed body to obtain a sintered body.

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