JP3182780B2 - Method of forming dense ceramic layer - 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 forming a dense ceramic layer acting as a sealing layer or the like.

[0002]

2. Description of the Related Art A ceramic product is obtained by firing an unfired ceramic compact. For this reason, many ceramic products are porous, and it is often necessary to seal necessary portions to seal liquids and gases. As this sealing material, a rubber or resin-based material is generally used, and in addition to these, sealing by a glass layer (enamel) or metallization is performed.

[0003]

The sealing material made of rubber or resin is inferior in heat resistance and chemical resistance. In the glass layer, the corrosion resistance to alkali is weak, and when the temperature exceeds about 600 ° C., softening starts. Metallization has problems in acid resistance and alkali resistance, and also has problems in durability at high temperatures.

Therefore, it is conceivable to form a dense ceramic layer on the surface of the porous substrate by a vapor deposition method such as PVD or CVD, sputtering or ion plating. However, these methods exhibit a sealing effect. It is unsuitable for forming a dense layer of such a thickness, and since corrosive raw materials are often used, it is necessary that the base material itself has corrosion resistance, and furthermore, the equipment becomes large. It is disadvantageous in terms of cost.

[0005]

In order to solve the above-mentioned problems, the present invention provides a method of forming a porous base material by repeating a process of dipping a porous base material in a ceramic slurry for a predetermined time, then pulling up and drying the porous base material a plurality of times. A green ceramic layer was formed on the surface, and then the green ceramic layer was fired.

[0006]

When the porous substrate is immersed in the ceramic slurry, the slurry containing the ceramic particles enters the pores of the porous substrate to reduce the pore diameter. Then, by repeating this, for example, a gas-tight dense film is formed on the surface of the porous substrate.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a sectional view of a fuel cell power generator using a dense ceramic layer formed by the method of the present invention as a seal layer, FIG. 2 is a sectional view of a fuel cell element, and FIG. is there.

In the fuel cell power generation device, a porous partition wall 2 is formed by casting a ceramic material in a housing 1, for example.
At 3 and 4, an oxidizing agent introduction chamber S1 such as air as a first fuel gas, a combustion preheating chamber S2, a power generation chamber S3, and a hydrogen gas introduction chamber S4 as a second fuel gas are defined. S3
The fuel cell elements 5 are arranged at the same time.

As shown in FIGS. 2 and 3, this fuel cell element 5 has a porous first substrate made of a conductive complex oxide or the like on the surface of a porous substrate 51 made of a zirconia or the like through which a gas can pass. the electrode layer 52 is formed, the gas tight solid electrolyte layer 53 made of stabilized zirconia or the like is formed on the surface of the first electrode layer 52, the second the surface of the solid electrolyte layer 53
And a sealing layer 55 made of a ceramic dense layer formed by the method of the present invention is provided on the outer peripheral surface of the base end of the porous substrate 51, and the combustion preheating chamber S2 and the power generation chamber S3 are provided.
Seals in gas tight between.

The tip of the porous substrate 51 is closed,
An oxygen gas introduction pipe 6 is introduced from the base end. Then, an oxygen gas (air) is caused to flow inside the porous base material 51 from the hole 6a formed at the tip of the oxygen gas introduction pipe 6, and the hydrogen gas is caused to flow outside the battery element 5 via the hydrogen gas introduction chamber S4. , Oxygen gas permeates into the first electrode layer 52, hydrogen gas permeates into the second electrode layer 54, and the following reactions occur in the first and second electrode layers.

[0011] The first _{electrode; H 2 O + 1 / 2O} 2 + 2e → 2OH - a second ^{_{electrode; H 2 + 2OH - → 2H}} 2 O + 2e

Then, 2e is supplied to the load. O
H ⁻ moves in the solid electrolyte layer 53.

In order to form the sealing layer 55 made of the dense ceramic layer, as shown in FIG. 4, a plug 7 is inserted into the base end of the porous base material 51, and is slightly shifted toward the center from the base end. The mask 8 is wound around the outer peripheral surface, and the base end of the porous substrate 51 is immersed in the ceramic slurry 10 in the dipping layer 9 in this state.

Then, after immersing for a predetermined time, it is pulled up and dried, and by repeating this step a plurality of times, an unsintered ceramic layer is formed on the surface of the porous base material. To form the desired ceramic dense layer.

Here, the ceramic slurry 10 has a ceramic raw material dispersed in a solvent.
A binder and a surfactant are added. Stabilized zirconia (ZrO ₂ +8 mol% Y)
₂ O ₃ ) or alumina is used. The particle size of the ceramic raw material is smaller than the pore size of the porous substrate.

As the solvent, α-terpineol, acetic acid n
-Butyl carbitol, ethyl alcohol or the like is used, ethyl cellulose or the like is used as a binder, and xylene or ethanol is used as a surfactant. Further, since the viscosity of the ceramic slurry 10 affects the denseness of the ceramic layer, it is preferable to make the viscosity as low as possible.

FIG. 5 is a graph showing the relationship between the thickness of the dense ceramic layer, the pore diameter of the porous substrate, and the amount of nitrogen gas permeation. If a dense ceramic layer having a thickness of 48 μm is formed on the surface of the porous substrate, gas sealing can be completely performed.

In the embodiment, the example in which the ceramic dense layer as the sealing layer is formed on the surface of the porous support held by the partition wall has been described, but the solid electrolyte is formed on the surface of the first electrode layer. When the layer is formed, the method of the present invention may be applied.

[0019]

As described above, according to the present invention, a ceramic dense layer having an excellent sealing property, heat resistance and chemical resistance can be formed on a surface of a porous substrate to a required thickness.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fuel cell power generator using a dense ceramic layer formed by a method of the present invention as a sealing layer.

FIG. 2 is a cross-sectional view of a fuel cell element.

FIG. 3 is an enlarged view of a main part of FIG. 2;

FIG. 4 is a view showing a dipping step of the present invention.

FIG. 5 is a graph showing a relationship between a film thickness, a pore diameter of a porous substrate, and a nitrogen gas permeation amount.

[Explanation of symbols]

1: Case of fuel cell power generator, 2, 3, 4 ... Partition wall, 5
... fuel cell element, 51 ... porous substrate, 52, 54 ... porous electrode, 55 ... dense ceramic layer.

Continuation of the front page (72) Inventor Haruo Nishiyama 2-7-1, Motomura, Chigasaki-shi, Kanagawa Prefecture Tochiki Co., Ltd. Chigasaki Plant (56) References JP-A-1-131089 (JP, A) JP-A-60 -1880979 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 41/87

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the particle diameter is smaller than the pore diameter of the porous substrate.
Adjust by dispersing ceramic particles below μm in solvent
Porous substrate immersed in ceramic slurry for specified time
After that, a process of lifting and drying the porous substrate
By firing after repeating multiple times, the surface of the porous substrate
The surface has a pore diameter after firing of 7 μm or less and a thickness of 40 μm or more.
Characterized by forming a gastight ceramic dense layer
Of forming a dense ceramic layer for a fuel cell. 2. The method according to claim 1, wherein the particle diameter is smaller than the pore diameter of the porous substrate.
Adjust by dispersing ceramic particles below μm in solvent
Porous substrate immersed in ceramic slurry for specified time
After that, a process of lifting and drying the porous substrate
By firing after repeating multiple times, the surface of the porous substrate
Gas tie with a thickness of at least 48 μm after firing on the surface
Characterized by forming a dense ceramic dense layer
A method for forming a ceramic dense layer for a battery.