JP2766756B2 - Conductive hollow flat plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate made of a conductive material and having a through hole serving as a flow passage for flowing a fluid such as gas or cooling water therein. The present invention relates to a conductive hollow flat plate that allows current to flow through another surface. As a specific application field, there is a solid oxide fuel cell, and there is an application as a substrate of a self-supporting fuel cell having a gas supply passage therein.

[0002]

2. Description of the Related Art A fuel cell is composed of an oxidizing gas and a fuel gas.
It is a general term for generating electricity by using a kind and supplying it to an oxidant electrode and a fuel electrode. There are several kinds depending on the material constituting the kind. The solid oxide fuel cell described here (hereinafter abbreviated as SOFC)
Is a material that is made up of all solid materials.Specifically, ceramics obtained by molding powder composed of the following substances by various methods and sintering them are the main material. ing.

Electrolyte Yttria stabilized zirconia (hereinafter abbreviated as YSZ) Fuel electrode Nickel zirconia cermet (hereinafter N)
Oxidant electrode Lanthanum manganite (hereinafter abbreviated as LSM) Basically, one cell is formed by arranging two electrodes on both sides of the electrolyte. The output voltage is less than 1 V even with an open circuit voltage. Therefore, in order to obtain a practical output, it is necessary to have a structure in which such cells are stacked in multiple layers. FIG. 4 shows an example of a structure of an SOFC in which a plurality of cells are stacked. In FIG. 4, 1 is a solid electrolyte, 2 is a fuel electrode, 3 is an oxidant electrode, 4 is an interconnector, 5 is a fuel gas flow path, 6 is an oxidant gas flow path, and 7 is a unit cell. By supplying each gas to the SOFC having such a structure, an electrical output of a predetermined voltage and current can be obtained. In the SOFC having such a structure, in order to perform predetermined power generation, each supplied gas is effectively distributed to each reaction surface, and unreacted gas is discharged from an outlet except for an end of an electrode. It is necessary to stack the layers so that there is no leakage from the area to the periphery. From this point of view, the SOFC having the structure shown in FIG. 4 is considered to be effective in terms of the design concept. However, when the stacking is actually performed, the airtightness between each unit cell 7 and the interconnector 4 is considered. There is a problem that it is extremely difficult to secure the quality. This is because all the materials are composed of solid ceramics as described above, and it is impossible to obtain gas tightness at the joint surface between the ceramics. This is difficult even if the flatness of the member is extremely improved, while considering that a certain degree of warpage or the like is generated when a single cell of an SOFC is actually manufactured by sintering. The more they say, the more impossible.

[0004] Therefore, as one method for solving such a gas tightness problems, with the oxidant gas flow path 6 on the inside at one electrode material e.g. oxidant electrode 3 in which either As shown in FIG. 5 It is conceivable to fabricate a base body and form a unit cell 7 therein (Japanese Patent Application No. 3-114261).
issue). In FIG. 5, 1 is a solid electrolyte, 2 is a fuel electrode, 4
Is an interconnector, and 8 is a dense film. In this manner, the gas that has become the material of the base is supplied to the gas passage 6 in the base.
Therefore, the gas tightness of the gas can be significantly improved by securing the gas tightness at both ends of the base. However, in this case, in addition to the fact that the base of the electrode has the strength to support the unit cell 7,
It is necessary to withstand the compressive force generated when a plurality of cells are connected in series, and a certain degree of mechanical strength is required. On the other hand, in addition to ensuring such strength, it is necessary to allow gas to flow through the inside of the base and to flow an electric current in the thickness direction of the base. It was necessary to design the base such that the electrical resistance of the base itself was suppressed as much as possible. Unless such a design is performed, even if a hollow substrate is used, the gas required for the reaction cannot be supplied sufficiently, or the inlet pressure increases due to the gas supply, which hinders gas sealing performance. Or the electrical resistance of the substrate increases, and the output voltage per unit cell decreases.
Nevertheless, in the conventional hollow substrate, since the gas flow path was not properly designed, there was a serious disadvantage that the characteristics of the unit cell could not be sufficiently exhibited despite the use of the hollow substrate. .

[0005]

As described above, as an application example of a flat plate made of a conductive substance provided with a flow path for flowing a fluid such as a gas therein, an SOFC unit cell is supposed. It is considered effective to use a hollow base made of an electrode material and form cells on one side of this base in terms of improving the shape, but such hollow shapes have not been appropriately designed until now. . Therefore, there is a problem that the cell performance cannot be sufficiently exhibited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conductive hollow flat plate that clarifies a method of arranging flow paths and thereby reduces the electric resistance of the flat plate.

[0007]

According to the present invention, there is provided a flat plate having a hollow structure which is made of a conductive material and has a plurality of through-holes arranged substantially in parallel therein. The position of the mouth is provided at a distance of less than 1/10 of the thickness of the entire flat plate from one surface of the flat plate. Application example 1 of such a flat plate having a hollow structure
One example is an SOFC. However, there has been little use of a conductive hollow plate, and no study has been made on a method of arranging the internal through-holes.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the structure of an embodiment of the present invention.
(A) is a cross-sectional view of a hollow flat plate, (b) is a prism that is a component of the hollow flat plate, and (c) is an overall perspective view of the hollow flat plate.
The present embodiment is a flat plate 21 made of a conductive material and having a hollow structure in which a plurality of through-holes 20 are arranged substantially parallel to each other. The through-hole 20 is based on one surface 22 of the flat plate 21. It is formed. Wherein the installation position of the through hole 20 and the one surface 22 of the hollow flat plate 21 as a reference, and a portion spaced a distance less than t _u from this surface 22. Here, the distance t _u, when the total thickness of the hollow flat plate 21 was set to t, t _u ≦
This value satisfies 1 / 10t. Although the electric resistance of the flat plate increases when a hollow portion such as a through hole is provided inside, the increase in the electric resistance can be suppressed by providing the flat portion at such a position. FIG. 2 shows the electric resistance between the upper and lower surfaces of the hollow prismatic body (FIG. 1B) (corresponding to the opposing surfaces in the hollow flat plate 21), which is a component of the hollow flat plate 21, and the internal through-hole 20. Is obtained as a parameter. For the calculation, the circuit analysis software “SPIC
E ”was used. In a specific calculation, the cross section of the hollow prismatic body which is a component of the hollow flat plate 21 shown in FIG. 2 was divided into a plurality of grid-like units 40 as in the example of FIG. The calculation was made assuming that the lattice-shaped unit 40 did not exist in the through-hole 20. At the time of calculation, the depth of the hollow flat plate 21 was arbitrary, but was typically 1 cm.
In the analysis by CE, sub-circuits are set,
The whole is analyzed as a combination of the sub-circuits. Here, the lattice unit 40 described above is used as a sub-circuit, and the resistance of one surface of the sub-circuit is approximated to a resistor having DC resistances arranged on four sides. I asked. Then, the resistance change when the position of the through-hole 20 was variously changed was calculated by variously changing the electrical connection state of the sub-circuit. As a result, the electric resistance of the prism increases with the provision of the through-hole 20 and as the opening area of the through-hole 20, that is, the opening width ts increases, but it is better to arrange the position closer to one surface. It can be seen that the increase is suppressed. From this figure, it can be seen that the electrical resistance of the prismatic body can be reduced by bringing the through hole 20 close to a distance of 1/10 of the plate thickness t from one surface regardless of the size of the through hole 20. It turns out that it is possible. Since the hollow flat plate 21 shown in FIG. 1A can be regarded as an aggregate of prisms as constituent elements of FIG. 1B, a shape having a small resistance in FIG. 1B is most advantageous. Therefore, it can be said that an arrangement method in which one surface 22 is brought close to at least a distance of 1/10 of the total thickness t of the plate is also preferable for the hollow flat plate 21. In addition, as for the distance of 1/10 or less of the total thickness t of the plate, the thickness t of the entire plate is at most 5 to 15 mm in consideration of the usage in which the current flows in the thickness direction of the hollow flat plate 21.
1/10 is 0.5 to 1.5 mm, so that it is considered that an interval of about 1/10 of the total thickness t of the plate is sufficient for practical use.

Next, a specific example of manufacturing such a hollow flat plate will be described. In the present invention, such a plate is manufactured using an electrode material, and a hollow flat plate is manufactured using an electrode material, assuming an SOFC cell in which an electrolyte and another electrode are formed on one surface. The electrode material of the SOFC includes an oxidant electrode and a fuel electrode, and as shown in the following examples, it was possible to produce the material using any material.

(1) Oxidizer electrode material (La _1-x Sr _x ) _Y MnO ₃ having a perovskite structure is generally widely used as an oxidizer electrode material of the SOFC. Therefore, this material is taken up and the composition;
a _0.8 Sr _0.2 MnO ₃ and La _0.9 Sr _0.1 MnO
_3. Raw material powder having a particle size of 1 to ₃ μm was used. Then, for the production of the hollow flat plate, a method of heat-sealing the sheet molded body was used, and the heat-sealed green body was sintered to obtain a hollow object. The sheet compact was prepared by a doctor blade method, and the slurry required for this was prepared at the following mixing ratio (weight).

Raw material powder 100 Binder 10-15 Plasticizer 5-10 Solvent 200 Polyvinyl butyral was used as the binder, butyl phthalate was used as the plasticizer, and isobutyl alcohol was used as the solvent. As the solvent, isobutyl alcohol alone can be used, but it was also used as a mixture to which toluene was added as necessary. The range of the amount of the binder and the amount of the plasticizer is that if the amount used is different, for example, the particle size is different and the surface area is also different, so a difference occurs in the properties of the slurry, so that the amount is appropriately adjusted. It is. In addition, a small amount of a dispersant and a defoamer were also added depending on the properties of the slurry. After stirring such a mixture with a ball mill for about 24 to 48 hours, the mixture was degassed under reduced pressure to remove the solvent and adjust the viscosity, and then a sheet molded body was obtained with a doctor blade device. Such a molded sheet was cut into a predetermined size, and then heated and pressed to produce a fused sheet. The heating / pressing conditions at this time need to be changed depending on the softness of the sheet.
C., 30 to 70 kg / cm ² . At this stage, the shape of the hollow portion of the hollow body can be changed to an arbitrary shape by changing the number of sheets to be stacked on each layer. A hollow flat plate having a surface having a thickness of 1/10 of the total thickness on one side was obtained. What should be considered at this time is the contraction rate of the sheet molded body. Shrinkage occurs during the forming and firing of the sheet, but in this example,
Shrinkage during molding was mainly observed only in the thickness direction, approximately 60%, and approximately 10% during firing. Therefore, in consideration of such shrinkage, the number of sheets and the size of the fused body were selected so that the sintered body after firing had a predetermined size. The hollow flat plate thus fused was degreased at about 400 ° C., and then baked at 1250 to 1350 ° C. for 5 to 10 hours to produce an oxidant electrode hollow flat plate. Regarding the size of the hollow flat plate, a plate having a size of about 100 to 150 mm square and a thickness of about 5 to 10 mm could be produced. The progress of sintering is affected by the particle size of the raw material powder used and the amounts of the binder and plasticizer added. Therefore, in consideration of these effects, the temperature and time were appropriately selected according to the raw materials used. Raw materials having a small particle size have a large surface area, so that sintering starts from a low-temperature region.
1250 ° C, 2 hours). Thus, by appropriately selecting the firing conditions in accordance with the amount of the raw material powder, the binder, and the like, and firing, a sintered body having a porosity of 20 to 30% could be obtained even when the raw material powder was changed. . Although the conductivity of the oxidant electrode is affected to some extent by the porosity, the net conductivity of the sintered body at 1000 ° C. was about 100 S / cm.

(2) Fuel electrode material For the fuel electrode material, nickel is contained in an amount of 40 to 50 by volume%.
% Ni-YSZ was used as a starting material. This powder is made of nickel oxide (# 200 mesh or less) and YSZ
(TZ-8Y, manufactured by Tosoh Corporation). Each powder was weighed so that nickel had a predetermined volume%, and then mixed. Ethanol was added to the powder and mixed by a ball mill for 24 to 48 hours. As in the case of the oxidant electrode material,
According to a method in which a sheet molded body is thermally fused and sintered. The sheet molding used as the material of the hollow flat plate was again produced by the doctor blade method, and the slurry required for this was set at the following mixing ratio (weight).

Raw material powder 100 Binder 10-15 Plasticizer 5-10 Solvent 200 The method for producing the sheet molded body and the hollow flat plate is the same as that for the oxidant electrode material. Also, by appropriately selecting the number and size of the sheets to be laminated at the time of heating and pressurizing, a fused body of a hollow flat plate having an arbitrary size was obtained. The hollow fused body thus produced is degreased at about 400 ° C.
It was fired at a temperature of 250 to 1400 ° C. for 5 to 10 hours to obtain a hollow flat plate sintered body made of a fuel electrode material. Here also, the firing conditions were selected according to the particle size of the raw material powder used. However, when the temperature and temperature are increased, the conductivity after reduction increases, but the porosity decreases. Therefore, firing was performed with the aim of achieving a conductivity after reduction of about 1000 S / cm at 1000 ° C.

It should be noted that the shrinkage ratio of the sheet compact must be taken into account when producing the compact, as in the case of the oxidizer electrode material. However, in the case of this fuel electrode material, the shrinkage during molding was about 60%, which was almost equal to that of the oxidizer electrode material.
Since the value at the time of firing was approximately 20%, the number and size of the sheets of the fused body were selected in consideration of the shrinkage.

[0016]

As described above, in the present invention, a method of arranging the through-holes in a flat plate having a plurality of through-holes through which a fluid such as a gas flows is specifically clarified. As a specific application example of the hollow flat plate as shown in the present invention, an SOFC in which such a flat plate is formed from an electrode material and an electrolyte and another electrode are formed on one surface thereof is considered. In the configuration, there is a specific effect that the electric resistance of the flat plate can be reduced, which can reduce the internal resistance of the SOFC, and finally has a great effect in realizing a high-performance SOFC. . Further, as shown in the specific contents of the invention, such a hollow flat plate can be produced very easily by a thermocompression bonding method of a sheet molded body, and is excellent in terms of economical efficiency without production cost. Things.

Although the present invention has been described by taking an SOFC as an example, the present invention can be applied to an application in which a current flows from one surface of a flat plate to another surface and a cooling medium flows in the flat plate. A predetermined object can be achieved while suppressing electric resistance as much as possible, and application to a wide variety of applications is possible. In this way, it can be widely applied to the general industry and has many advantages.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of a resistance characteristic of a prism serving as a component of the hollow flat plate according to the present invention.

FIG. 3 is an explanatory view showing a sectional state of a rectangular column constituting a hollow flat plate according to the present invention during resistance analysis.

FIG. 4 is an exploded perspective view of a conventional flat fuel cell in an assembled state.

FIG. 5 is a perspective view of a conventional fuel cell using a base having a gas flow path inside.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte, 2 ... Fuel electrode, 3 ... Oxidant electrode, 4 ... Interconnector, 5 ... Fuel gas flow path, 6 ... Oxidant gas flow path, 7 ... Unit cell, 8 ... Dense membrane, 20 ... Through-hole , 21 ...
Hollow flat plate, 22: one surface of the hollow flat plate, 40: lattice unit.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-68562 (JP, A) JP-A-4-230954 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/86 H01M 8/00-8/24

Claims (1)

(57) [Claims] 1. A hollow flat plate made of a conductive material and having a plurality of through-holes disposed substantially in parallel therein,
The through-hole is formed with reference to one of the surfaces of the flat plate, and the position thereof is set at 1/1 of the entire plate thickness from the reference surface.
A conductive hollow flat plate arranged at a distance of less than 0.