JP3064069B2 - Manufacturing method of cylindrical electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cylindrical electrode used for a solid oxide fuel cell, an oxygen sensor, or the like.

[0002]

2. Description of the Related Art Conventionally, for example, a cylindrical electrode used for a solid electrolyte fuel cell, an oxygen sensor, or the like, as shown in FIG.
Forming an electrode material film 13 on the outer surface of the porous substrate tube 11;
It is formed by firing this. As a method of manufacturing such a cylindrical electrode, for example, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 11569 and Japanese Patent Application Laid-Open No. 64-2259 are known.

[0003] In these publications, an electrode material of a solid oxide fuel cell is suspended in a liquid, and this suspension is sprayed on a porous substrate tube using a spray or the like, or a suspension containing the electrode material is used. The suspension is applied to a porous substrate tube with a brush or the like,
Alternatively, a method (dipping method) of immersing a porous substrate tube in a suspension containing the electrode material to allow the electrode material to naturally adhere to the outer surface of the porous substrate tube to form an electrode material film (dipping method) and the like are disclosed. Then, by firing such an electrode material film together with the porous base tube, a cylindrical electrode having a porous base tube inside is formed.

A fuel cell is formed by sequentially forming a solid electrolyte and an electrode on the surface of a cylindrical electrode in the same manner as described above.

[0005]

However, in the conventional method of manufacturing a cylindrical electrode, when the electrode material film and the porous substrate tube have different coefficients of thermal expansion, the electrode material film has a thermal stress during firing. This causes a problem that cracks occur in the electrode material film, resulting in defective electrodes. In order to prevent such cracks from occurring, it is necessary to adjust the coefficient of thermal expansion of the electrode material film and the porous substrate tube to be almost the same, but there is a problem that it is difficult to adjust the coefficient of thermal expansion. Was.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a cylindrical electrode capable of reliably preventing cracks due to thermal stress during firing.

[0007]

Means for Solving the Problems As a result of a detailed study on the above problems, the present inventor has found that after using a porous substrate tube only to form an electrode material film on the outer surface, the porous substrate is used. It has been found that when the tube is volatilized during firing, a cylindrical electrode composed of a single layer is formed, and no thermal stress occurs.

That is, according to the method of manufacturing a cylindrical electrode of the present invention, an electrode material film is formed by depositing an electrode material on the outer surface of a porous substrate tube made of a material which is volatilized by heat, and thereafter, this is fired. In this way, only the porous substrate tube is volatilized to produce a cylindrical electrode.

[0009]

According to the method of manufacturing a tubular electrode of the present invention, an electrode material is attached to an outer surface of a porous substrate tube made of a material which is volatilized by heat, and an electrode material film is formed on the outer surface of the porous substrate tube. Since the tubular electrode was manufactured by firing, the porous substrate tube was baked, for example, thermally decomposed or oxidized and volatilized, and only the outer electrode material film remained to form a single-layer tubular electrode during firing. Thermal stress during firing does not occur in the cylindrical electrode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an electrode material film forming apparatus used in the method for producing a cylindrical electrode according to the present invention. Reference numeral 31 denotes a suspension containing an electrode material dispersed therein. This suspension 31
Is obtained by adding an electrode material such as a composite oxide composed of La, Sr, and Mn having an average particle size of 1 to 5 μm to an aqueous solution containing, for example, PVA (polyvinyl alcohol) as a binder. The suspension 31 is a container 33
Housed within.

In the suspension 31 of the container 33, for example, a porous base tube 35 for a solid oxide fuel cell is immersed. The porous substrate tube 35 is formed of a material that evaporates during firing, such as porous carbon or a porous thermosetting resin. The porous carbon used as the porous base tube 35 is crushed by mixing, for example, carbon black or coke with coal tar or pitch, kneading while heating, and crushing again. Then, the powder is sieved to a desired particle size, a molded body is prepared by CIP, and fired at 1000 to 1500 ° C. to obtain porous carbon. The porous thermosetting resin used as the porous base tube 35 may be, for example, a phenol resin, formalin, a catalyst, or the like, and after reacting in a reaction vessel, dehydrating and adding a solvent, and forming a molded article by CIP. Is obtained.

The porosity of the porous base tube 35 is 20 to
It is 40%, particularly preferably 30-35%. The pore size is 0.5 to 5 μm, especially 0.5 μm.
It is desirable that the thickness be about 2 μm. 20-40% porosity
The reason for this is that the base tube 35 has the necessary strength and the fuel cells need to smoothly diffuse the gas. In addition, the pore size is 0.5 to 5μ.
The reason for setting m is that if it is in this range, the electrode material does not pass through the holes of the porous base tube 35, and the film formation rate can be increased.

Since the lower end of the porous base tube 35 is open, a rubber cap 37 is attached to the lower end of the porous base tube 35 to prevent the suspension 31 from entering from the lower end.
Is attached. If the lower end of the porous base tube 35 is not open, it is not necessary to attach the cap 37. On the other hand, the upper part of the porous base tube 35 is
9 supported. The holding device 39 includes a housing member 41 that houses the upper portion of the porous base tube 35 and a fastening member 43 that is screwed to the housing member 41. An O-ring 45 is provided at a required location to prevent intrusion into the vehicle. A vacuum device 47 for reducing the pressure inside the porous base tube 35 is connected to the housing member 41 of the holding device 39.

In the electrode material film forming apparatus configured as described above, the inside of the porous base tube 35 is depressurized by the vacuum device 47, and the porous base tube 35 is gently immersed in the suspension 31 in this state. As a result, the suspension 31 around the porous substrate tube 35 is forcibly sucked toward the porous substrate tube 35, and the electrode material in the suspension 31 is removed from the porous substrate tube 35.
On the outer surface of the electrode material, and an electrode material film is quickly formed. When the electrode material film is generated, the porous base tube 35 is pulled up, dried, and fired at a predetermined temperature to form a cylindrical electrode.

In the method of manufacturing a cylindrical electrode according to the present invention, since the porous base tube 35 is formed of a material that volatilizes during firing, the porous base tube 35 volatilizes during firing and only the outer electrode material film is formed. Remain to produce a single-layer cylindrical electrode.

Next, an experiment was conducted using the above-described electrode material film forming apparatus. Hereinafter, experimental examples will be described.

Experimental Example 1 La _0.85 Sr _0.15 having an average particle size of 5 μm as an electrode material powder
200 g of MnO ₃ powder is added to a 500 cc aqueous solution containing 3% by weight of PVA (polyvinyl alcohol, polymerization degree 500) to form a suspension 31. The electrode material powder is contained at a ratio of 40% by weight based on the aqueous solution. A porous base tube 35 made of carbon and having a porosity of 35% and a pore diameter of 1.5 μm, the inside of which is reduced to about 25 torr, is immersed in the suspension 31 and allowed to stand for 3 minutes.
An electrode material film is formed on the outer surface of the porous base tube 35.

After drying this, in the air (oxidizing atmosphere)
Then, the temperature was raised to 400 ° C. at 150 ° C./hr, kept at 400 ° C. for 5 hours, and then raised to 1400 ° C. at 200 ° C./hr to obtain a sintered body of a cylindrical electrode. The carbon porous base tube 35 begins to volatilize at 350 to 450 ° C.,
Disappeared completely. The thickness of the obtained cylindrical electrode is 2 mm
Was a uniform film.

Experimental Example 2 An electrode material film was formed on the outer surface of a porous base tube 35 made of a thermosetting resin by the same method as described above.
Sintering was carried out in the same manner as above except that the holding time at 00 ° C. was 3 hours, to obtain a sintered body of a cylindrical electrode. The temperature of the porous base tube 35 made of a thermosetting resin is 350 to 450 ° C.
At 500 ° C. The thickness of the obtained cylindrical electrode was a uniform film of 2 mm.

Accordingly, in the above-described method of manufacturing a cylindrical electrode, the inside of the porous base tube 35 is depressurized, and the porous base tube 35 is immersed in the suspension 31 in this state. The suspension 31 around the perimeter 35 is forcibly sucked toward the porous base tube 35, and the electrode material in the suspension 31 adheres to the outer surface of the porous base tube 35, thereby shortening the electrode material film. Can be generated on time. Further, the electrode material in the suspension 31 tends to be attracted to a portion of the outer surface of the porous substrate tube 35 where the electrode material film is not clogged, that is, a portion where the electrode material film is thin. An electrode material film can be uniformly formed on the outer surface of the substrate.

Further, in the method of manufacturing a cylindrical electrode according to the present invention, the porous base tube 35 is formed of a material that is volatilized during firing, so that the porous base tube 35 is volatilized during firing and only the outer electrode material film is formed. Is left to produce a cylindrical electrode of a single layer, and no thermal stress is generated in the electrode material film at the time of firing, and the generation of cracks in the cylindrical electrode can be reliably prevented. Thereby, the cylindrical electrode can be easily manufactured without considering the coefficient of thermal expansion between the electrode material film and the porous base tube 35.

The concentration of PVA as a binder is as follows:
Desirably, it is 1 to 5% by weight based on water. Also,
As the binder, for example, an acrylic resin-based binder may be used in addition to PVA. Further, the particle diameter of the electrode material powder is desirably 1 to 10 μm.

The suspension 31 desirably contains the electrode material powder at a ratio of 10 to 80% by weight, particularly 30 to 60% by weight, based on the aqueous solution. Is preferred.

The pressure inside the porous base tube 35 is 10
~ 200 torr is desirable. The firing temperature of the electrode material film is desirably 1300 to 1600 ° C.

Further, in the above embodiment, an example was described in which the porous substrate tube 35 whose inside was in a reduced pressure state was immersed in the suspension 31, but the present invention is not limited to the above embodiment. After the porous substrate tube is immersed in the suspension, the same effect as in the above embodiment can be obtained even if the inside of the porous substrate tube is depressurized.

Also, an example has been described in which the method for producing a cylindrical electrode of the present invention is applied to an electrode material membrane used in a solid electrolyte fuel cell.
For example, it may be applied to an oxygen sensor.

Further, in the above embodiment, the porous substrate tube 3
5 has been described with respect to an example in which porous carbon or a porous thermosetting resin is used. However, the present invention is not limited to the above embodiment, and has a predetermined porosity and a predetermined pore diameter. The same effect as in the above embodiment can be obtained even when a material that volatilizes, for example, a porous substrate tube made of a thermoplastic resin is used. That is, the porous substrate tube may be formed of a material that can maintain a cylindrical shape when the electrode material film is formed, and may be formed of a material that volatilizes by heat.

In the above embodiment, the porous substrate tube 35
Although an example in which an electrode material film is formed on the outer surface by a dipping method has been described, the present invention is not limited to the above-described example.For example, a suspension may be sprayed on a porous substrate tube by spraying or the like, The same effect as in the above embodiment can be obtained by applying a suspension containing an electrode material to a porous substrate tube with a brush or the like to form an electrode material film, and then volatilizing the porous substrate tube.

[0029]

As described above in detail, according to the method for manufacturing a cylindrical electrode of the present invention, the porous substrate tube is volatilized during firing, so that a cylindrical electrode composed of a single layer can be manufactured. Accordingly, in the production of the cylindrical electrode, it is possible to reliably prevent the occurrence of cracks during firing.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an electrode material film forming apparatus used in a method for manufacturing a cylindrical electrode of the present invention and the vicinity thereof.

FIG. 2 is a longitudinal sectional view showing a state where an electrode material film is formed on a porous substrate tube.

[Explanation of symbols]

 31 Suspension 35 Porous substrate tube

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁷ Identification code FI G01N 27/409 G01N 27/58 B

Claims (1)

(57) [Claims] An electrode material film is formed by depositing an electrode material on the outer surface of a porous substrate tube made of a material which is volatilized by heat, and thereafter, the electrode material film is fired to volatilize only the porous substrate tube. A method for manufacturing a cylindrical electrode, comprising: