JP2002284581A - Method for firing cylindrical ceramic formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for firing a cylindrical ceramic formed body capable of baking large quantities of the same simultaneously and easily. SOLUTION: The method is characterized by firing the ceramic formed body on the condition of abutting the side face of the cylindrical ceramic formed body 1 on a base plate 9 and pressing the both end portions of the cylindrical ceramic formed body 1 toward the base plate. It is preferable that a presser bar pressure of the cylindrical ceramic formed body 1 toward the base plate is 0.2 to 0.8 times as high as a radial crushing strength after calcining the cylindrical ceramic formed body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing a cylindrical ceramic molded body, and more particularly, to a method for firing a cylindrical ceramic molded body used for a solid oxide fuel cell (SOFC) or the like.

[0002]

2. Description of the Related Art Conventionally, cylindrical ceramics have been prepared by preparing a ceramic compound using ceramic powder and a binder as raw materials, adding water to the ceramic compound, drying the formed ceramic compound, and placing it horizontally on a base plate (setter). 1
It was manufactured by firing at a high temperature of 000 ° C to 2000 ° C.
However, there has been a problem that warpage occurs due to uneven firing shrinkage during firing and the yield decreases.

Therefore, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-218892, a method of firing an unfired cylindrical ceramic molded body in a suspended state has been adopted. Further, as disclosed in JP-A-7-103661, in a state where a cylindrical ceramic molded body is suspended,
Further, a method of firing while rotating is adopted.

Further, as disclosed in JP-A-6-72772, a method is employed in which a cylindrical ceramic compact is placed on an inclined setter and fired.

[0005] According to such a method, warpage during firing of the cylindrical ceramic molded body can be reduced.

[0006]

However, the sintering method disclosed in the above-mentioned publication is basically a method of sintering while suspending a cylindrical ceramic molded body, which is effective for small-quantity production. Although it is conceivable, it is not suitable as a method for simultaneously producing a large number of cylindrical ceramic molded bodies having a fixed shape, and in order to obtain a large amount of cylindrical ceramics, firing must be performed many times, and the production cost is increased. However, there has been a problem that the cost is high and the production takes a long time. In addition, a special jig for hanging is required, and there is a problem that it takes a long time to set the jig on such a special jig.

Further, when firing a large cylindrical ceramic molded body having an outer diameter of about 10 mm or more, it is easy to attach it to a hanging jig. In the hanging firing, there are problems that a long time is required for hanging and that a part of the cylindrical ceramic molded body is broken during jig setting.

An object of the present invention is to provide a method for firing a cylindrical ceramic molded body which can be fired simultaneously in a large amount and can be easily fired.

[0009]

According to the method of firing a cylindrical ceramic molded body of the present invention, the side surface of a cylindrical ceramic molded body (including a calcined body; the same applies hereinafter) is brought into contact with a base plate. The firing is performed in a state where both ends of the cylindrical ceramic molded body are pressed toward the base plate.

According to such a firing method, the cylindrical ceramic molded body is fired in a state where both ends are pressed toward the base plate, thereby suppressing deformation of the ceramic during firing in the length direction. As a result, the warp in the radial direction of the fired cylindrical ceramic (warp in the direction orthogonal to the axis of the cylindrical ceramic 2) can be reduced. Thus, a cylindrical ceramic having a small warpage can be obtained without suspending and firing the cylindrical ceramic molded body as in the related art.

Here, the pressing force of the cylindrical ceramic molded body toward the base plate is preferably 0.2 to 0.8 times the radial crushing strength of the cylindrical ceramic molded body. By optimizing the pressing force of the cylindrical ceramic molded body to the base plate in this way, it is possible to obtain a cylindrical ceramic having a small warpage, and to reduce the deformation rate of the external shape of the cylindrical ceramic after firing. be able to.

Further, in the present invention, the plate-shaped ceramic is placed on the upper surface of the cylindrical ceramic molded body, or the plate-shaped ceramic is leaned on the cylindrical ceramic molded body, and pressed against the base plate. Is desirable. By such a method, the pressing force of the cylindrical ceramic molded body toward the base plate can be optimized.

In the present invention, it is desirable that the diameter of the cylindrical ceramic molded body is 5 mm or less. In the case of such a small-diameter cylindrical ceramic molded body, it takes time and effort to set in hanging firing, and the cylindrical ceramic molded body may be broken at the time of setting. Therefore, it is particularly significant to use the firing method of the present invention. .

Further, in the present invention, it is preferable that a groove is formed in the base plate, and the cylindrical ceramic molded body is accommodated in the groove. By using such a base plate, the cylindrical ceramic molded body can be held at a predetermined position without rotating, and, for example, a plate-shaped ceramic can be easily leaned.

In the present invention, it is preferable that a molded body made of a material different from that of the cylindrical ceramic molded body is laminated on the cylindrical ceramic molded body. In such a case, the amount of shrinkage in firing of the molded body laminated with the cylindrical ceramic molded body during firing is different, and warpage is likely to occur.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The firing method of the present invention will be described with reference to a cylindrical solid oxide fuel cell as an example of a cylindrical ceramic. According to the method for firing a cylindrical ceramic molded body of the present invention, first, a cylindrical ceramic molded body 1 as shown in FIG. 1 is produced.

The cylindrical ceramic molded body 1 is prepared by, for example, extruding a cylindrical air electrode molded body having a function as a self-supporting tube, and thereafter producing the cylindrical air electrode molded body.
Binder removal and calcination are performed at a temperature of 00 ° C. for about 5 to 20 hours to produce a cylindrical air electrode calcined body 2.

Next, a solid electrolyte molded body 3a of a material constituting the solid electrolyte is formed on the surface of the air electrode calcined body 2. This solid electrolyte molded body 3 has a mean particle diameter of 0.5 to 3 μm stabilized by a known stabilizer such as Y ₂ O _3.
A slurry is prepared using a powder of rO ₂ , and then a green sheet is prepared by a doctor blade method or the like, and the air electrode calcined body ₂ is prepared so that both ends of the green sheet are separated at a predetermined interval. It is formed by wrapping around the surface.

Then, the air electrode calcined body 2 / solid electrolyte molded body 3a is calcined at a temperature of 1000 to 1300 ° C. for about 1 to 5 hours, and thereafter, the solid electrolyte calcined body 3a to be a laminated portion of the current collector Is polished to expose the air electrode calcined body 2, and the current collector molded body 4 is laminated on the exposed surface of the air electrode calcined body 2 and both ends of the solid electrolyte calcined body 3a. The current collector molded body 4 is made of a LaCrO ₃ -based material, and is formed by laminating green sheets in the same manner as the solid electrolyte calcined body 3a.

A green sheet to be a thin solid electrolyte molded body 3b is prepared by screen printing using the same material as the solid electrolyte molded body 3a, and Ni metal and Y ₂ O ₃ etc. are formed on the surface of the green sheet. A conductive paste containing a mixed powder with ZrO ₂ stabilized by a well-known stabilizer is applied, dried, and the fuel electrode molded body 5 is formed on a green sheet.
Is formed, and a green sheet (solid electrolyte molded body 3b) on which the fuel electrode molded body 5 is formed is laminated on the surface of the solid electrolyte calcined body 3a, whereby the cylindrical ceramic molded body 1 is produced. You.

Next, as shown in FIG. 2, a cylindrical ceramic molded body 1 is placed on a base plate 9 having a groove 8 having a triangular cross section so that the current collector molded body 4 faces downward. In other words, the fuel electrode molded body 5 is housed so as to have the upper surface, and the side surface of the cylindrical ceramic molded body 1 is brought into contact with the groove 8 of the base plate 9. The base plate 9 is preferably made of zirconia that has been heat-treated at a firing temperature or higher because it does not react with the cylindrical ceramic molded body 1 during firing and does not diffuse impurities. The shape of the groove 8 is such that the upper portion of the cylindrical ceramic molded body 1 slightly protrudes from the upper surface of the base plate 9.

Thereafter, ceramic is placed on the upper surface of the cylindrical ceramic molded body 1 in order to press both ends of the cylindrical ceramic molded body 1 toward the base plate. At this time, as shown in FIG. It is desirable to interpose a ceramic molded body 11 between the ceramic and the cylindrical ceramic molded body 1 so that the ceramic does not react with the cylindrical ceramic molded body 1. The ceramic molded body 11 is desirably made of a solid electrolyte material having a large particle diameter in view of low reactivity with the solid electrolyte at both ends of the cylindrical ceramic molded body 1 and no diffusion of impurities. .

Then, as shown in FIG. 4, the ceramic molded bodies 1 arranged at both ends of the cylindrical ceramic molded body 1 are formed.
On one upper surface, an arcuate plate-shaped ceramic 15 obtained by dividing a cylindrical ceramic into 1/3 is placed and fired. Ceramic 1
FIG. 5 shows a vertical cross-sectional view of a state in which No. 5 is placed. As shown in FIG. 5, the ceramic 15 does not come into contact with the fuel electrode molded body 5 by the ceramic molded body 11, so that both ends of the cylindrical ceramic molded body 1 Pressed to the side. The arc-plate-shaped ceramic 15 is desirably made of zirconia because there is no diffusion due to impurities.

As shown in FIGS. 6A and 6B, the load may be applied by leaning the plate-shaped ceramic of the cylindrical ceramic molded body 1.

The weight of the arcuate plate-shaped ceramic 15 is 0.2 to 0.8 times the radial crushing strength of the calcined body of the cylindrical ceramic molded body 1 at both ends thereof. Is adjusted so as to apply a load. As described above, the crushing strength of the cylindrical ceramic molded body 1 after calcining the cylindrical ceramic molded body 1 on both ends of the cylindrical ceramic molded body 1 is 0.2 to 0.1 mm.
In this range, the load of 8 times is applied, because the pressing force of the cylindrical ceramic molded body 1 on the base plate 9 side is optimized, so that a cylindrical ceramic with a small warpage can be obtained. This is because the deformation rate of the outer diameter of the cylindrical ceramic after firing can be reduced.

On the other hand, when the load is smaller than 0.2 times the radial crushing strength, the cylindrical ceramic molded body 1 moves in the axial direction, is easily deformed in the direction perpendicular to the axial length, and warpage is easily generated. On the other hand, when it is larger than 0.8 times, the cylindrical ceramic molded body 1 is deformed in the radial direction, the portion to which the load is applied is easily crushed, and the roundness is reduced.

Since the thickness of the air electrode calcined body is much larger than that of the solid electrolyte molded body and the fuel electrode molded body, the radial crushing strength of the cylindrical ceramic molded body 1 is the same as that of the air electrode calcined body. Dominated by strength.

The diameter of the cylindrical ceramic molded body 1 is desirably 5 mm or less. Such a small-diameter cylindrical ceramic molded body 1 is suitable because it takes time and effort to set in a conventional hanging firing, and requires a large amount of firing. This diameter refers to the maximum outer diameter of the cylindrical ceramic molded body 1.

Next, both ends of the cylindrical ceramic molded body 1 are simultaneously fired at a temperature of 1300 to 1600 ° C. for about 1 to 10 hours in an oxidizing atmosphere such as the air while applying a predetermined load. Sintering is performed to produce a cylindrical solid oxide fuel cell.

In the above-described method for firing the cylindrical ceramic molded body, the cylindrical ceramic molded body 1 is fired in a state where both ends are pressed against the base plate 9 so that the cylindrical ceramic molded body 1 is fired during firing. In the state where the deformation in the longitudinal direction is suppressed, the warp in the radial direction of the fired cylindrical ceramics (the warp in the direction perpendicular to the axis of the cylindrical ceramics) is reduced. Can be. Thus, a cylindrical ceramic having a small warpage can be obtained without suspending and firing the cylindrical ceramic molded body as in the related art.

In the above embodiment, the cylindrical ceramic molded body 1 is provided on the surface of the air electrode calcined body 2 with the solid electrolyte calcined body 3
a, the example in which the solid electrolyte molded body 3b, the fuel electrode molded body 5, and the current collector molded body 4 are formed has been described. However, the present invention is not limited to the above example. The present invention may be used when only the air electrode calcined body 2 or the air electrode formed body is fired. Further, the solid electrolyte calcined body 3a is provided on the surface of the cylindrical air electrode calcined body 2, or the solid electrolyte calcined body 3a, the solid electrolyte molded body 3b is provided on the surface of the cylindrical air electrode calcined body 2. The solid electrolyte calcined body 3 a and the current collector molded body 4 may be formed on the surface of the molded body 5 or the cylindrical air electrode calcined body 2.

Further, in the above example, the method of firing a cylindrical ceramic molded body for a cylindrical fuel cell has been described. However, the present invention may be applied to, for example, a method of firing a cylindrical ceramic molded body for a cylindrical oxygen sensor. good.

The groove 8 has a triangular cross section.
It may be square, and is not particularly limited.
It is desirable to make a line contact on the inner surface of the.

Further, the present invention may be applied to firing of an air electrode molded body. In this case, the pressing force on the base plate is desirably 0.2 to 0.8 times the radial crushing strength after calcining the air electrode molded body since the binder removal step is performed.

[0035]

EXAMPLE A commercially available powder having a purity of 9 as a powder forming an air electrode.
La of 9.9% or more_TwoO_Three, CaCO _Three, Mn_TwoO_ThreeDeparts
As a raw material, this is La_0.8Ca_0.2MnO_ThreeThe composition of
And calcined at 1500 ° C for 3 hours
This was crushed to obtain a solid solution powder having an average particle size of 5 μm.

Further, a binder was added to the solid solution powder, and cylindrical air electrode molded articles having different outer diameters were produced by an extrusion molding method. The air electrode molded body is dried at 1250 ° C.
Debinding and calcining for 10 hours at
An air electrode calcined body having a cylindrical shape of not less than mm was produced.

Next, toluene and a binder were added to ZrO ₂ powder having an average particle diameter of 1 μm and containing Y ₂ O ₃ at a ratio of 8 mol% obtained by a coprecipitation method to prepare a slurry. A solid electrolyte sheet having a thickness of 100 μm was prepared by a blade method.

Next, commercially available La _{2 having} a purity of 99.9% or more is used.
Starting from O ₃ , Cr ₂ O ₃ , and CaCO ₃ ,
a _0.8 Ca _0.22 CrO ₃ were weighed and mixed to obtain a composition, then calcined at 1500 ° C. for 3 hours and pulverized to obtain an average particle size of 2
A μm solid solution powder was obtained. Toluene and a binder were added to the solid solution powder to prepare a slurry, and a current collector sheet having a thickness of 100 μm was prepared by a doctor blade method.

As the powder forming the fuel electrode, Ni powder having an average particle diameter of 1 μm and ZrO having an average particle diameter of 0.5 μm are used.
₂ (containing 8 mol% Y ₂ O ₃ ) at a ratio of 7: 3 to prepare a mixed powder. A binder was added to the mixed powder to prepare a conductive paste. A thin solid electrolyte sheet having a thickness of 20 μm was prepared in the same manner as the solid electrolyte sheet described above, and a conductive paste was applied to the upper portion thereof by screen printing so as to have a thickness of 30 μm.

The solid electrolyte sheet was wound into a roll around the cylindrical air electrode calcined body so that both ends were separated at a predetermined interval, and calcined at 1100 ° C. for 3 hours. After calcining, the surface between both ends of the solid electrolyte calcined body, which is a laminated portion of the current collector sheet, is flat-polished on the surface until the air electrode calcined body is exposed. The current collector sheets were laminated in a belt shape. Further, a thin solid electrolyte sheet coated with the conductive paste was wound around the surface of the calcined solid electrolyte body to produce a cylindrical ceramic molded body.

Then, the cylindrical ceramic compact was placed sideways in the groove of the alumina base plate, and the average particle diameter containing 8 mol% of Y ₂ O ₃ obtained by the coprecipitation method was 10 μm.
m and ZrO ₂ powder were mixed with toluene and a binder to prepare a slurry.
A solid electrolyte sheet having a thickness of 0 μm is prepared, and the solid electrolyte sheet is disposed on the upper surfaces of both ends of the cylindrical ceramic molded body.
A ceramic obtained by halving a zirconia tube was placed on this solid electrolyte sheet, and co-sintering was attempted at 1500 ° C. in air for 6 hours. Note that the radial crushing strength of the cylindrical ceramic molded body was defined as the radial crushing strength of the air electrode calcined body because the thickness of the air electrode calcined body was very large.

Then, the warpage and deformation rate of the obtained cylindrical solid oxide fuel cell were measured. Table 1 summarizes the results of the outer diameter of the obtained fuel cell after molding, the load during firing, the amount of warpage, and the deformation ratio. These deformation rates and warpage will be described below. (A) Deformation rate The inner diameter of the cylindrical ceramic was measured, and the difference between the maximum and the minimum was divided by the maximum value to express the degree of crushing (= degree of distortion). That is, the degree of crushing was represented by a deformation rate = {(maximum inner diameter−minimum inner diameter) / maximum diameter} × 100. (B) Warpage The deflection {(maximum outer diameter−minimum outer diameter) / 2} when the cylindrical ceramics are rotated in the axial direction with both ends fixed is determined at regular intervals in the cell longitudinal direction, and the maximum value is determined. It is divided by the length of the cell. That is, the warpage was calculated from: warpage = maximum value {(maximum outer diameter−minimum outer diameter) / 2} / cell length.
The load at the time of firing was obtained by dividing the weight of the ceramic by the area of the solid electrolyte sheet to obtain loads acting on both ends.

[0043]

[Table 1]

From Table 1, it can be seen that Sample No. in which no load was applied to both ends of the cylindrical ceramic molded body. 6, it can be seen that the warpage is very large. On the other hand, when firing while applying a load to both ends of the cylindrical ceramic molded body,
It can be seen that the warpage becomes smaller. In addition, the deformation ratio is small for a sample whose load is small compared to the radial crushing strength of the calcined cathode, but the warpage tends to be large.On the other hand, when the load is increased, the warpage is suppressed. It can be seen that the deformation ratio tends to increase.

[0045]

As described above, according to the method for firing a cylindrical ceramic molded body of the present invention, the side surface of the cylindrical ceramic molded body is brought into contact with the base plate, and both ends of the cylindrical ceramic molded body are brought into contact with each other. By sintering while being pressed against the base plate, deformation of the ceramic during sintering can be suppressed in the length direction, and warpage of the cylindrical ceramic after sintering in the radial direction can be reduced. Therefore, mass production can be performed as compared with the conventional hanging firing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a cylindrical ceramic molded body of the present invention.

FIG. 2 is a sectional view showing a state in which a cylindrical ceramic molded body is accommodated in a groove of a base plate.

FIG. 3 is a perspective view showing a state in which a cylindrical ceramic molded body is accommodated in a groove of a base plate.

FIG. 4 is a cross-sectional view showing a state where a ceramic is covered on an upper surface of a cylindrical ceramic molded body.

FIG. 5 is a longitudinal sectional view of FIG.

6 (a) is a perspective view, and FIG. 6 (b) is a cross-sectional view showing a state in which ceramic is leaned on a cylindrical ceramic molded body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylindrical ceramic molded body 8 ... Groove 9 ... Base plate 15 ... Ceramics

Claims (6)

[Claims] 1. A cylindrical ceramic molded body characterized in that the cylindrical ceramic molded body is fired in a state in which the side surface of the cylindrical ceramic molded body is brought into contact with a base plate and both ends of the cylindrical ceramic molded body are pressed toward the base plate. Firing method. 2. The pressing force of the cylindrical ceramic molded body toward the base plate is 0.2% of the radial crushing strength of the cylindrical ceramic molded body.
2. The method for firing a cylindrical ceramic molded body according to claim 1, wherein the ratio is up to 0.8 times. 3. A plate-shaped ceramic is placed on an upper surface of a cylindrical ceramic molded body, or a plate-shaped ceramic is leaned on the cylindrical ceramic molded body and pressed against a base plate. A method for firing a cylindrical ceramic molded body according to claim 1 or 2. 4. The firing method for a cylindrical ceramic molded body according to claim 1, wherein the diameter of the cylindrical ceramic molded body is 5 mm or less. 5. The cylindrical ceramic according to claim 1, wherein a groove is formed in the base plate, and the cylindrical ceramic molded body is accommodated in the groove. The method of firing the molded body. 6. The cylindrical ceramic body according to claim 1, wherein a molded body made of a material different from that of the cylindrical ceramic molded body is laminated on the cylindrical ceramic molded body. A method for firing a ceramic molded body.