JPH11106265A - Method for sintering alternate ceramic laminates - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To eliminate cracking and peeling during sintering of a ceramic alternating laminate. A method of sintering a ceramic alternate laminate, in which ceramic tapes made of different materials having different physical properties are alternately stacked and integrally formed, the laminate having three directions orthogonal to each other during a sintering step. Is measured continuously, and the temperature rise rate is controlled in accordance with the contraction rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sintering a ceramic alternate laminate having a high tolerance to strain and stress and a high toughness.

[0002]

2. Description of the Related Art When ceramics are used as a structural material, for example, a combination structure with a metallic material is required. In such a combination structure, a difference in strain occurs due to a difference in thermal and mechanical properties between the ceramic and another material. In particular, the stress applied to a stationary part with severe restraint conditions and the resulting fracture are caused by this strain difference. In order to avoid the destruction of this type of ceramics, it is effective to increase the breaking strain of the material.

[0003] From such a viewpoint, lamination of ceramics has been performed. In particular, in the case of an increase in breaking strain and an increase in toughness due to the laminated structure, the more the difference in physical properties between layers, the more the characteristics of the laminated body are improved. For example, J.Am.Ceram.So
c., 75 [12] 3396-400 (1992) and J.Am.Ceram.Soc., 77 [3] 689-
As seen in 96 (1994), the greater the difference in the coefficient of thermal expansion between layers and the greater the difference in the elastic modulus, the more the strength and toughness of the laminate improve. These laminates are usually manufactured by laminating tapes obtained by extrusion molding, centrifugal casting, and tape molding, and sintering them integrally.

[0004]

However, the above-mentioned manufacturing method has the following problems, and there has been a strong demand for its solution.

[0005] Differences in physical properties between layers, which help to improve the properties of the laminate, cause a number of problems during the manufacturing process. In particular, the problem has been that, after molding, the laminated body cracked or peeled off during sintering. This is because the difference in physical properties (difference in firing shrinkage, etc.) between the respective layers is greatly different, so that when the integrated sintering shrinks during heating, a very large shear stress acts on the interface between the layers, resulting in cracking and peeling. That is the cause. For example, as seen in J. Am. Ceram. Soc., 72 [8] 1511-13 (1989), after sintering, peeling may occur mainly at the interface between layers in the laminate. Until now, J. Am. Ceram. Soc., 74 [12] 2979-87 (199
As can be seen in 1), a method is used in which the chemical composition is intentionally graded between layers to absorb the difference in firing shrinkage.
As seen in m. Ceram. Soc., 75 [10] 2907-909 (1992), efforts were needed to alternately laminate very thin layers to reduce the shear stresses generated. However, these monolithic sintering methods have a problem of an increase in cost and a lack of reproducibility, and have been a great limitation in industrial use.

Under these circumstances, the present inventors have studied in view of the above-mentioned prior art to develop an integrated sintering method that does not cause cracking or peeling of an alternate laminated body composed of layers having different physical properties. As a result, it was found that cracking and peeling occurring in the laminated body during sintering can be prevented by devising a heating process during sintering.

The present invention has been devised based on the findings obtained from the research results made in view of the above-mentioned problems of the prior art. When firing a ceramic alternate laminate made of different kinds of materials, An object of the present invention is to provide a method for sintering a ceramic alternating laminate, which can prevent cracks and peeling occurring in the laminate and can improve productivity.

[0008]

In order to achieve the above object, a method of sintering a ceramic alternate laminate according to the present invention comprises alternately stacking and integrally forming ceramic tapes of different materials having different physical properties. This is a method for sintering a ceramic alternate laminated body, in which shrinkage rates in three orthogonal directions are continuously measured during a sintering step, and a heating rate is controlled in accordance with the shrinkage rates.

It is preferable to control the heating rate to be low when the shrinking rate is high.

[0010] The ceramic tape is extruded,
It is preferable to produce by a technique such as centrifugal casting or tape molding.

Next, the operation of the present invention will be described. Cracks and peeling occurring during sintering are caused by differences in the shrinkage behavior of each layer during sintering. A molded body made of ceramic powder shows a shrinkage behavior according to each material as the temperature rises. The temperature dependence of the amount of shrinkage varies greatly depending on the material, and a shear stress acts on the interface due to the difference in strain between the layer that shrinks quickly and the layer that does not shrink, resulting in cracks and peeling of the laminate. In this case, cracking and peeling are considered to occur at a temperature at which the difference in the amount of shrinkage between the layers during sintering is greatest. Therefore, the temperature is slowly increased near this temperature. By doing so, cracking and peeling between layers can be prevented.

In the present invention, the shrinkage in three orthogonal directions is measured during the sintering process, and when any one of the shrinkage speeds starts to increase, the temperature is increased slowly to increase the temperature slowly. And to prevent cracks and peeling between layers.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a ceramic alternating laminate during sintering by the method for sintering a ceramic alternating laminate of the present invention. As shown in the drawing, the ceramic alternating laminate 1 is placed on a stand (not shown) in a sintering apparatus, and two orthogonal side surfaces (for example, a left side surface and a back side surface in the figure) are fixed so as not to move. Then, three contact rods 2a, 2b and 2c are brought into contact with the two side surfaces (the front side surface and the right side surface in the figure) and the upper surface of the laminate, respectively, from outside the furnace of the sintering apparatus. The three contact rods 2a, 2b, 2c are respectively connected to three-axis displacement meters, and the contact rods 2a, 2b,
The movement in the X, Y, and Z directions of 2c is measured by a displacement meter. By the measurement, the shrinkage behavior of the laminate 1 during sintering can be monitored. When heating the sintering furnace,
At a temperature at which the movement of one of the contact bars of this displacement meter becomes intense, the temperature rises slowly. In other words, the rate of shrinkage of the laminate can be controlled by controlling the temperature, and cracks generated during sintering of the laminate,
Peeling can be prevented.

[0014]

EXAMPLES The results of two experiments performed to demonstrate the present invention will be described below as Examples I and J. Example I (1) Preparation of Tape As Tape A, 5 wt% yttrium oxide and 2 wt% aluminum oxide were added as a sintering aid to α-type silicon nitride powder, and a toluene / butanol mixed solution (4/1)
Was used as a dispersion medium together with a dispersant and a binder to form a slurry. Using this slurry, 100μ thick by tape forming
m of tape were produced. Further, as the tape B, β-type silicon nitride columnar particles (short diameter: 1 μm, aspect ratio: 30) were used as a slurry using a toluene / butanol mixed solution (4/1) as a dispersion medium together with a dispersant and a binder. Was used to produce a tape having a thickness of 50 μm.

(2) Production of Laminate A total of 100 produced tapes were alternately laminated and pressed to produce a laminate. After the CIP treatment, the laminate was degreased.

(3) Sintering Sintering was performed at a holding temperature of 1850 ° C. for 6 hours in a nitrogen atmosphere using a sintering apparatus capable of measuring the amount of shrinkage in three directions. The sintering apparatus is equipped with a three-axis displacement meter that inserts a contact rod from the outside of the furnace and makes contact with the object to be sintered. Can be monitored. When the temperature of the displacement meter is increased when the temperature of the sintering furnace is increased, the temperature is slowly increased. That is, the rate of shrinkage of the laminate can be controlled by controlling the temperature, and cracking and peeling during sintering of the laminate can be prevented.

The heating rate during sintering was controlled so that the shrinkage did not exceed 0.1% per minute. FIG.
The following is a comparison between a controlled heating pattern of the present invention and a conventional heating pattern. In the present invention, the most severe shrinkage is 1
From around 600 ° C., the temperature rises slowly.

(4) Cracking in Laminated Body According to the sintering method of the present invention, no cracking or peeling was observed near the interface, and a sound laminated body was produced. On the other hand, when sintering was performed without measuring the usual amount of shrinkage, cracks were observed at the interface.

Example J (1) Production of Tape As a raw material, a tape C was made of alumina (average particle size: 0.5 μm), and a tape D was made of zirconia stabilized by 3 mol% yttria (average particle size: 0.2 μm). A tape was produced in the same manner as in Example I. The thickness of the tape was 10 μm.

(2) Production and sintering of laminate A total of 1,000 produced tapes were laminated, and a laminate having a thickness of about 10 mm after pressure bonding was produced. At this time, the ratio of the number of sheets to be laminated was changed at the ratio shown in Table 1. This molded body is C
After the IP treatment, the material was degreased and sintered at 1500 ° C. in the atmosphere for 1 hour. The same apparatus as in Example I was used for the sintering.

[0021]

[Table 1]

(3) Cracking in the laminated body As shown in Table 1, in the ordinary sintering method in which the amount of shrinkage is not measured, no cracking occurs when the laminating ratio is 1: 1 but cracks occur when the laminating ratio is other. occured. This means that the stacking ratio is 1: 1 to 50
As the ratio increases to 0: 500, the shear stress generated at the interface of the laminated structure increases.
Cracks will occur at high lamination ratios. On the other hand, in the sintering method according to the present invention, it is notable that cracking did not occur at any lamination ratio, and in particular, cracking did not occur even in a laminate of a thick layer having a lamination ratio of 500: 500. The lamination ratio refers to the ratio of the number of tapes in a layer of the same substance, and is 1: 1:
1 is a material obtained by alternately laminating different substances one by one,
10:10 means that after ten tapes of the same substance are laminated, ten tapes of another substance are laminated, and this is repeated alternately.

The present invention is not limited to the embodiments and examples described above, and various changes can be made without departing from the gist of the invention.

[0024]

As described above, the method for sintering a ceramic alternating laminate according to the present invention provides a method for sintering a ceramic alternating laminate obtained by alternately laminating ceramic tapes of different materials. Since the rate of temperature rise is controlled in accordance with the rate of shrinkage, cracking and peeling do not occur during sintering, and there are excellent effects such as improvement in productivity.

[Brief description of the drawings]

FIG. 1 is a perspective view of a ceramic alternating laminate during sintering by a sintering method of the present invention.

FIG. 2 is a graph of a temperature rise curve in the sintering method of the present invention and a conventional sintering method.

[Explanation of symbols]

 1 alternate ceramic laminate 2 contact rod

Claims (3)

[Claims] 1. A method of sintering a ceramic alternating laminate in which ceramic tapes made of different materials having different physical properties are alternately stacked and integrally formed, and laminated in three directions orthogonal to each other during a sintering step. A method for sintering a ceramic alternate laminated body, comprising continuously measuring a shrinkage speed of a body and controlling a heating rate according to the shrinkage speed. 2. The method for sintering a ceramic alternate laminate according to claim 1, wherein the temperature raising rate is controlled to be lower when the shrinking rate is high. 3. The method according to claim 1, wherein the ceramic tape is formed by extrusion molding, centrifugal casting or tape molding.