JP2013235651A - Assembly and solid oxide fuel battery with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assembly arranged so that the deterioration of a brazing filler metal can be prevented by means of suppressing the occurrence of void even when being used in an atmosphere such that void is produced; and a solid oxide fuel battery having the assembly used therein.SOLUTION: The assembly 41 has: a first member made of metal, which is composed of an isolation separator 37; a second member composed of a cell main body 5 including ceramic as one primary component; and a bonding part 39 having a first bonding layer 67 on the side of a hydrogen atmosphere and a second bonding layer 69 on the side of an oxygen atmosphere, and bonding between the first and second members. The oxygen diffusion coefficient of the second bonding layer 69 is smaller than that of the first bonding layer 67. Therefore, in a case where the assembly 41 is used at a high temperature, even if hydrogen diffuses into the first bonding layer 67 from the side of the hydrogen atmosphere, oxygen is hard to diffuse from the side of the oxygen atmosphere into the second bonding layer 69. Hence, the occurrence of void owing to the reaction between hydrogen and oxygen in the assembly 41 can be suppressed, and the occurrence of void can be prevented from deteriorating a brazing filler metal.

Description

  The present invention relates to ceramics, a joined body obtained by joining ceramics and metal, or metals, and a solid oxide fuel cell using the joined body.

  Conventionally, in a solid oxide fuel cell that operates at a high temperature such as 500 to 1000 ° C., a ceramic joined body in which a ceramic substrate and a metal frame are joined by a brazing material has been used as the structure. .

  The ceramic substrate that is this ceramic joined body is a laminate of a fuel electrode, a solid electrolyte layer, and an air electrode. In this ceramic substrate, a metal frame that is a separator is brazed to the surface of the solid electrolyte layer.

As the brazing described above, vacuum brazing in which brazing is performed in a vacuum and atmospheric brazing in which brazing is performed in the air using a flux are known.
In recent years, the reactive air brazing method has been performed as a method of brazing in the atmosphere. In this method, ceramics and a refractory metal (which forms an Al oxide layer in the air) are joined in air using a brazing material in which CuO is added to Ag, and the main component of the brazing material is Ag or the like. Therefore, there is an advantage that brazing can be performed without using a flux.

However, in the above-described solid oxide fuel cell, as shown in FIG. 11, the cell body (P1) and the separator (P2), which are the laminates, are joined by a brazing material (P3), One (fuel electrode side) is a hydrogen atmosphere and the other (air electrode side) is an oxygen atmosphere through the brazing material. Therefore, when the solid oxide fuel cell is operated at the high temperature, hydrogen (H ⁺ ions) and oxygen (O ²⁻ ions) diffuse into the Ag of the brazing filler metal, respectively. in hydrogen and oxygen are reacted, hollow and is void consisting of H ₂ O (H ₂ O voids) is disadvantageously generated.

When this void is generated, the brazing material is deteriorated, and a decrease in bonding strength and a gas leak are undesirable.
As a countermeasure, Patent Document 1 below discloses a technique using a brazing material in which Ge or Cr is added to Ag as a main component. With this technology, for example, by using a brazing material having a composition of Ag-2Ge-1Cr, Ge and Cr are preferentially reacted with oxygen, thereby suppressing generation of voids by combining oxygen and hydrogen. It is something to try.

JP 2010-207863 A

  However, in the above-described conventional technology, most of the Ge and Cr in Ag are scattered as oxides and consumed by brazing in the air, and thereafter, when the solid oxide fuel cell is operated, Furthermore, Ge and Cr react with oxygen and are consumed, and the brazing material has a composition of almost Ag only.

Therefore, when the operation of the solid oxide fuel cell continues, there is a problem that voids are generated in the brazing material and the brazing material is deteriorated.
The present invention has been made to solve the above-described problems, and even when used in an atmosphere in which voids are generated, the bonded body capable of suppressing the generation of voids and preventing the deterioration of the brazing material and the bonding thereof An object of the present invention is to provide a solid oxide fuel cell using the body.

  (1) The present invention is used in a gas separation structure for separating an oxygen atmosphere side containing oxygen gas and a hydrogen atmosphere side containing hydrogen gas as a first embodiment (joined body), and is made of ceramics or metal. In the joined body in which the first member and the second member made of ceramics or metal are joined by the joint having the brazing material, the joint has the first joining layer made of the brazing material on the hydrogen atmosphere side. A second bonding layer is provided on the oxygen atmosphere side, and an oxygen diffusion coefficient in the second bonding layer is smaller than an oxygen diffusion coefficient in the first bonding layer.

  In the joined body of this aspect, the first member and the second member are joined by the joint portion having the first joining layer on the hydrogen atmosphere side and the second joining layer on the oxygen atmosphere side, and the second joining. The oxygen diffusion coefficient of the layer is set smaller than the oxygen diffusion coefficient of the first bonding layer.

Therefore, when this joined body is used at a high temperature such as 700 ° C. or higher, even when hydrogen diffuses into the first joining layer from the hydrogen atmosphere side, oxygen enters the second joining layer from the oxygen atmosphere side. Difficult to diffuse (and therefore difficult to diffuse into the joint). Therefore, it is possible to suppress the generation of voids (H ₂ O voids) due to the reaction between hydrogen and oxygen in the joint, and the effect of preventing the deterioration of the brazing material due to the generation of voids is achieved.

Here, when the oxygen atmosphere side and the hydrogen atmosphere side are compared, the oxygen atmosphere side has a higher oxygen partial pressure than the hydrogen atmosphere side, and the hydrogen atmosphere side has a higher hydrogen partial pressure than the oxygen atmosphere side.
(2) As a second aspect, the present invention is characterized in that the oxygen diffusion coefficient in the second bonding layer is 3.48 × 10 ⁻¹⁸ m ² / s or less at 800 ° C.

  In this aspect, a preferable oxygen diffusion coefficient in the second bonding layer is illustrated. That is, as will be apparent from the experimental examples described later, the above-described oxygen diffusion coefficient has the advantage that the generation of voids is extremely small.

(3) In the present invention, as a third aspect, the second bonding layer is an alloy layer containing Ni as a main component and containing at least one of Cr, Al, and Si.
As described above, Ni has a characteristic of suppressing the movement of oxygen (that is, a characteristic of an oxygen diffusion barrier), but, for example, it is oxidized and deteriorates in the condition of joining the Ag brazing filler metal in the atmosphere. On the other hand, in this aspect, the second bonding layer contains Cr, Al, and Si in addition to Ni, and these are alloyed. Thereby, since Ni continues in the state of Ni metal, the effect of the oxygen diffusion barrier can be maintained.

(4) In the present invention, as a fourth aspect, the second bonding layer includes an oxide film including at least one of Cr, Al, and Si oxides.
In the fourth aspect, the second bonding layer includes the above-described oxide film. Since this oxide film has oxygen diffusion barrier properties, generation of voids can be suitably suppressed.

In addition, by providing this oxide film on the oxygen atmosphere side of the second bonding layer, generation of voids can be suitably suppressed.
(5) In the present invention, as a fifth aspect, the Cr content in the second bonding layer is 10 to 30% by weight.

  When the content of Cr in the second bonding layer is less than 10% by weight, it becomes difficult to form the above-described oxide film. On the other hand, if the Cr content exceeds 30% by weight, the amount of components other than Ni becomes excessive, and the precipitate of the second phase (that is, the intermetallic compound) has a weak effect on the oxygen diffusion barrier exceeding the solid solubility limit. Since the volume ratio increases, the effect as an oxygen diffusion barrier is weakened. Therefore, this Cr content range is suitable (as is clear from the experimental examples described later).

(6) In the present invention, as a sixth aspect, the content of Al in the second bonding layer is 1 to 10% by weight.
When the Al content in the second bonding layer is less than 1% by weight, it is difficult to form the above-described oxide film. On the other hand, if the Al content exceeds 10% by weight, the amount of components other than Ni increases too much, exceeding the solid solubility limit and increasing the volume fraction of the second phase precipitate, so that it is effective as an oxygen diffusion barrier. Is weakened. Therefore, this Al content range is suitable (as is clear from the experimental examples described later).

(7) In the present invention, as a seventh aspect, the Si content in the second bonding layer is 1 to 10% by weight.
When the content of Si in the second bonding layer is less than 1% by weight, it is difficult to form the above-described oxide film. On the other hand, if the Si content exceeds 10% by weight, the amount of components other than Ni increases too much, exceeding the solid solubility limit and increasing the volume fraction of the second phase precipitates, so that it is effective as an oxygen diffusion barrier. Is weakened. Therefore, this Si content range is suitable (as is clear from the experimental examples described later).

  (8) In the present invention, as an eighth aspect, in addition to the first bonding layer and the second bonding layer, the bonding member includes the first member and the second bonding layer closer to the oxygen atmosphere than the second bonding layer. An adhesion layer is provided that is in close contact with the second member and has a smaller oxygen diffusion coefficient than the second bonding layer.

  In this aspect, in addition to the second bonding layer, an adhesion layer (having an oxygen diffusion coefficient smaller than that of the second bonding layer) is provided, so that oxygen diffusion can be further suppressed. Therefore, there is a remarkable effect that the generation of voids can be further prevented.

(9) The present invention is characterized in that the joined body according to any one of claims 1 to 8 is provided as a ninth aspect (solid oxide fuel cell).
Since the solid oxide fuel cell is used at a high temperature of, for example, 500 to 900 ° C., for example, when the above-described joined body is used as the structural material, generation of voids can be suitably suppressed.

(10) In the present invention, as a tenth aspect, the joined body is obtained by joining a solid electrolyte body and a metal member.
This aspect illustrates a joined body. By providing the solid electrolyte body with a fuel electrode and an oxygen electrode, a ceramic substrate which is a cell main body for generating power described later can be configured. Moreover, as a metal member, the separator joined to the cell main body (separating the hydrogen atmosphere side and the oxygen atmosphere side) is mentioned.

1 is a perspective view showing a solid oxide fuel cell of Example 1. FIG. It is explanatory drawing which expands and shows typically the cross section (AA cross section of FIG. 1) of the solid oxide fuel cell of Example 1. FIG. FIG. 2 is an explanatory diagram schematically showing an enlarged cross section (cross section BB of FIG. 1) of the solid oxide fuel cell of Example 1. 1 is a perspective view showing a joined body of Example 1. FIG. It is a perspective view which expands and schematically shows the cross section (CC cross section of FIG. 4) of the joined body of Example 1. It is explanatory drawing which expands and shows typically the cross section (CC cross section of FIG. 4) of the junction part vicinity of the conjugate | zygote of Example 1. FIG. FIG. 3 is an explanatory diagram showing a procedure for manufacturing the joined body of Example 1. FIG. 10 is an explanatory diagram illustrating a manufacturing procedure of a modified example of the joined body of Example 1. (A) is explanatory drawing which shows typically the cross section of the conjugate | zygote vicinity of the conjugate | zygote of Example 2, (b) is explanatory drawing which shows typically the cross section of the conjugate | zygote vicinity of the modification of the conjugate | zygote of Example 2. (C) is explanatory drawing which shows typically the cross section of the conjugate | zygote vicinity of the conjugate | zygote of Example 3, (d) is explanatory drawing which shows typically the cross section of the conjugate | zygote vicinity of the conjugate | zygote of Example 4. . It is explanatory drawing which shows an experiment method. It is explanatory drawing of a prior art.

Various forms (examples) for carrying out the present invention will be described below.
[Embodiment]
<Composition of joined body>
As combinations of the first member and the second member, there are ceramic members, ceramic members and metal members, and metal members.

The material of the ceramic member is not particularly limited, and examples thereof include oxide ceramics, nitride ceramics, carbide ceramics, and silicide ceramics.
Examples of oxide ceramics include zirconia, magnesia, alumina, and titania. Moreover, the ceramic which consists of complex oxide containing 2 or more types of elements is mentioned. Examples of nitride ceramics include silicon nitride, titanium nitride, boron nitride and the like. Examples of the carbide ceramics include silicon carbide and tungsten carbide. Examples of silicide ceramics include molybdenum silicide. These ceramics can be selected according to the application of the ceramic joined body.

As said metal member, metal plates, such as a metal frame, are mentioned, Arbitrary metals can be selected according to a use.
As the metal member, a metal that can be isolated so as not to mix the hydrogen-containing gas on the hydrogen atmosphere side and the oxygen-containing gas on the oxygen atmosphere side without deteriorating in the temperature range during use can be selected. Examples of such metals include stainless steel, nickel-based alloys, and chromium-based alloys.

Examples of the stainless steel include ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. Examples of ferritic stainless steel include SUS434 and SUS405 in addition to SUS430. Examples of martensitic stainless steel include SUS403, SUS410, and SUS431. Examples of austenitic stainless steel include SUS201, SUS301, and SUS305. Further, examples of the nickel-based alloy include Inconel 600, Inconel 718, Incoloy 802, and the like. Examples of the chromium-based alloy include Ducrloy CRF (94Cr5Fe1Y ₂ O ₃ ).

The brazing material for the first bonding layer is not particularly limited, and various brazing materials mainly composed of Ag, Au, or the like can be employed. For example, Ag brazing material (Ag—Cr ₂ O ₃ brazing material) containing Cr ₂ O ₃ (for example, 1 to 5% by weight) or Pd (for example, 2 to 30% by mass, preferably 3 to 10% by mass) The contained Ag brazing material (Ag—Pd brazing material) can be used.

  The material of the second bonding layer can be appropriately selected according to the material of the first bonding layer (and hence the oxygen diffusion coefficient), and examples thereof include Ni, Pt, and Au. Of these, Ni and Pt are suitable because of their large oxygen diffusion barrier properties. In particular, Pt is more suitable as an oxygen diffusion barrier because oxidation does not proceed under the condition of joining the Ag brazing filler metal in the atmosphere.

Examples of Cr, Al, and Si oxides that form the oxide film include Cr ₂ O ₃ , Al ₂ O ₃ , and SiO ₂ .
The material of the adhesion layer can be appropriately selected according to the material of the second bonding layer (accordingly, the oxygen diffusion coefficient), and examples thereof include Pt and oxide glass.
<Atmosphere in which the joined body is arranged>
Examples of the gas on the hydrogen atmosphere side include a fuel gas used in a solid oxide fuel cell.

  As this fuel gas, hydrogen, a hydrocarbon serving as a hydrogen source, a mixed gas of hydrogen and hydrocarbons, a fuel gas obtained by passing these gases through water at a predetermined temperature and humidifying them, and water vapor mixed with these gases Examples include fuel gas. The hydrocarbon is not particularly limited, and examples thereof include natural gas, naphtha, and coal gasification gas. Further, the main components are saturated hydrocarbons having 1 to 10, preferably 1 to 7, more preferably 1 to 4 carbon atoms such as methane, ethane, propane, butane and pentane, and unsaturated hydrocarbons such as ethylene and propylene. Those having a saturated hydrocarbon as a main component are more preferable. These fuel gas may use only 1 type and can also use 2 or more types together. Moreover, you may contain inert gas, such as nitrogen and argon of 50 volume% or less.

Examples of the gas on the oxygen atmosphere side include a combustion-supporting gas used in a solid oxide fuel cell.
Examples of the combustion-supporting gas include air, a mixed gas of oxygen and another gas, and the like. The mixed gas may contain 80% by volume or less of an inert gas such as nitrogen and argon. Among these combustion-supporting gases, air (containing about 80% by volume of nitrogen) is preferable because it is safe and inexpensive.
<Configuration of solid oxide fuel cell>
Examples of the solid oxide fuel cell in which the joined body is used include a structure in which a fuel electrode, a solid electrolyte body, and an air electrode are laminated in this order, and the fuel electrode and the air electrode are separated by an isolation separator. Note that any of the fuel electrode, the solid electrolyte body, and the air electrode can be used as a support, but the fuel electrode support type is preferable because it is easy to manufacture.

  In addition, the overall structure of the solid oxide fuel cell includes various structures, in which a power generation layer (cell) that is a plurality of power generation units is stacked via a metal intercell separator. It is done. In this solid oxide fuel cell, each cell has a substrate-like cell body, and each cell has a solid electrolyte body, a fuel electrode provided on one surface of the solid electrolyte body, and an air electrode provided on the other surface. The thing which has these. In this case, the cell body corresponds to the first member, and the isolation separator corresponds to the second member.

  Further, the fuel electrode and air electrode of each cell and the inter-cell separator can be electrically connected by a fuel electrode side current collector and an air electrode side current collector, respectively. Each cell includes an isolation separator for isolating the flow path of the fuel gas from the flow path of the air that is the combustion-supporting gas. Further, in order to electrically insulate the respective cells, an insulating plate made of an insulator such as ceramic may be disposed at a predetermined portion in the stacking direction.

The solid electrolyte body is preferably made of at least one of ZrO ₂ , BaCeO ₃ -based oxide, and LaGaO ₃ -based oxide. Of these, a solid electrolyte using a ZrO ₂ oxide is particularly preferable.

The fuel electrode can be formed of Ni, YSZ, or the like. This fuel electrode is in contact with a fuel gas serving as a hydrogen source and functions as a negative electrode in the cell.
The material used for forming the fuel electrode is not limited to Ni and YSZ, and can be appropriately selected depending on the use conditions of the solid oxide fuel cell. Examples of this material include metals such as Pt, Au, Ag, Cu, Pd, Ir, Ru, Rh, Ni, and Fe. These metals may be used alone or in an alloy of two or more metals.

  Further, a mixture (including cermet) of these metals and / or alloys and zirconia ceramics such as zirconia stabilized by at least one of Y and rare earth elements, ceria ceramics, and ceramics such as manganese oxide. ).

Furthermore, the mixture etc. of the oxide of metals, such as Ni and Cu, and at least 1 sort (s) of the said ceramic are mentioned.
The air electrode can be formed of, for example, La _1-x Sr _x MnO ₃ composite oxide. This air electrode is in contact with a combustion-supporting gas serving as an oxygen source and functions as a positive electrode in the cell.

The material used for forming the air electrode is not limited to the La _1-x Sr _x MnO ₃ composite oxide, and can be appropriately selected depending on the use conditions of the solid oxide fuel cell 1. Examples of this material include metals such as Pt, Au, Ag, Pd, Ir, Ru, and Rh. These metals may be used alone or in an alloy of two or more metals.

Further, oxides such as La, Sr, Ce, Co, and Mn (for example, La ₂ O ₃ , SrO, Ce ₂ O ₃ , Co ₂ O ₃ , MnO _2, FeO, etc.) can be mentioned.
In addition, various composite oxides containing at least one of La, Sr, Ce, Co, Mn, and the like (for example, La _1-x Sr _x FeO ₃ composite oxide, La _1-x Sr _x Co _{1). -y} Fe _y O ₃ composite oxide, Pr _1-x Ba _x Co _{1 -y} Fe _y O ₃ composite oxide, Sm _1-x Sr _x Co _1-y Fe _y O ₃ composite oxide, etc.) Is mentioned.

Examples of the joined body of the present invention and a solid oxide fuel cell using the same will be specifically described below.
a) First, the configuration of the solid oxide fuel cell of this example will be described.

  As shown in FIG. 1, a solid oxide fuel cell 1 according to the present embodiment is a device that generates power by being supplied with a fuel gas (for example, hydrogen) and a combustion-supporting gas (for example, air). The oxide fuel cell 1 is formed by laminating a plurality of layers (here, for example, three layers 3a, 3b, and 3c) of a power generation layer (that is, a solid oxide fuel cell: hereinafter simply referred to as a cell) 3 that is a basic configuration of power generation. Is.

  As schematically shown in FIGS. 2 and 3, the cell 3 includes a substrate-like cell main body 5 that is a main part for generating power, and in the cell main body 5, fuel in contact with (for example, hydrogen). The electrode 7, the solid electrolyte body 9 having oxygen ion conductivity, and the air electrode 11 in contact with the oxidizing gas (for example, oxygen in the air) are stacked in this order.

Although not shown, a reaction preventing layer for preventing a reaction between the solid electrolyte body 9 and the air electrode 11 is formed between the solid electrolyte body 9 and the air electrode 11.
Further, in this embodiment, the so-called fuel electrode support membrane type cell 3 in which the fuel electrode 7 serves as a support base is cited, but the present invention is not limited to this. For example, an air electrode support membrane type cell or a solid electrolyte is used. The present invention can be applied to a self-supporting membrane cell whose body is a supporting base.

  Further, as shown in detail in FIGS. 2 and 3, in the solid oxide fuel cell 1, the cells 3 are arranged in the stacking direction (up and down in both figures) via a metal interconnector (inter-cell separator) 13. Direction).

  Among these, as shown in FIG. 2, on the outer peripheral side of the solid oxide fuel cell 1 (left and right direction in FIG. 2), a rectangular cylindrical shape is formed so as to airtightly surround the fuel electrode 7, the air electrode 11, and the like. The frame portion 15 is provided in a space (fuel gas flow path) 17 on the fuel electrode 7 side of each cell 3 so as to penetrate a part of the frame portion 15 in the vertical direction of the figure. A fuel gas supply passage 19 for supplying fuel gas and a fuel gas discharge passage 21 for discharging the fuel gas after power generation from each fuel gas passage 17 to the outside are provided.

  Similarly, as shown in FIG. 3, the frame portion 15 has an air supply passage 25 for supplying air to the air flow passage 23 of each cell 3 so as to penetrate a part of the frame portion 15 in the vertical direction of the figure. An air discharge path 27 is provided for discharging the air after power generation from each air flow path 23 to the outside.

  The fuel electrode 7 of each cell 3 is electrically connected to each cell separator 13 and the like by a fuel electrode side current collector 29, and each air electrode 11 is joined by an air electrode side current collector 31 made of an Ag brazing material. It is electrically connected to the other inter-cell separator 13 or the like via the layer 33.

  The uppermost and lowermost interconnectors are referred to as a lid 35 and a bottom 36, respectively. The uppermost air electrode 11 is electrically connected to the lid 35, and the lowermost fuel electrode 7 is electrically connected to the bottom 36. Has been.

  Each cell 3 includes an isolation separator (in-cell separator) 37 for isolating the fuel gas flow path 17 and the air flow path 33, and the isolation separator 37 is connected to a joint portion 39 as will be described in detail later. Is joined to the surface of the solid electrolyte body 9 (and hence the cell body 5).

The substrate-like joined body 41 in which the isolation separator 37 and the cell main body 5 are joined by the joining portion 39 corresponds to the joined body of the present invention.
In addition, in the frame portion 15, in order to electrically insulate the cells 3 from each other, a rectangular frame-shaped ceramic frame 43 which is an insulator is disposed in a predetermined portion in the stacking direction. In order to increase the strength, rectangular frame-shaped metal frames 45 and 47 are arranged in the stacking direction. Note that they are integrally bonded to the upper and lower members by bonding layers 49, 51, 53, 55, 57 made of Ag brazing material.

  That is, in the frame portion 15 of the solid oxide fuel cell 1, the lid 35, the bonding layer 49, the metal frame 45, the bonding layer 51, the ceramic frame 43, the bonding layer 53, and the isolation from above in FIGS. 2 and 3. The separator 37, the bonding layer 55, the metal frame 47, the bonding layer 57, the inter-cell separator 13, and the like are stacked in this order, and each member is bonded and integrated by bonding layers 49 to 57 made of an Ag brazing material therebetween.

  Here, as the material of the inter-cell separator 13, the lid 35, the bottom 36, and the metal frames 45, 47 that are metal members, similarly to the isolation separator 37, heat resistance such as stainless steel, nickel base alloy, chromium base alloy, etc. Alloys can be used.

Further, as the Ag brazing material constituting the bonding layers 33, 49 to 57, oxidation of each element of Ni, Co, Cr, Ti, Ce, Sr, Mn, La, Sm and Y in the Ag brazing material An Ag brazing material containing at least one of the materials can be used. Examples of the oxide include NiO, Co ₃ O ₄ , Cr ₂ O ₃ , TiO ₂ , CeO ₂ , Sr ₂ O ₃ , MnO ₂ , La ₂ O ₃ , Sm ₂ O ₃ , and Y ₂ O _3. .

  Further, the material of the fuel electrode side current collector 29 is preferably a metal, and can be formed of, for example, Ni or a Ni-based alloy. The fuel electrode side current collector 29 preferably has elasticity, and examples thereof include felts or meshes made of porous bodies, foams, and metal fibers.

  On the other hand, the material of the air electrode side current collector 31 can be a metal and a conductive ceramic. As this metal, the same material as the fuel electrode side current collector 29 can be used, but an inelastic dense plate-like body may be used.

b) Next, the joined body 41 which is a main part of the present embodiment will be described.
As shown in FIG. 4, the joined body 41 is joined to a square frame-shaped isolation separator 37 having a square opening 61 at the center so that the square plate-shaped cell body 5 is airtightly covered with the opening 61. It has been done.

  Specifically, as schematically shown in an enlarged view in FIG. 5, the joined body 41 is isolated in an exposed portion 63 where the solid electrolyte body 9 is exposed (planar shape is a square frame shape) in the upper part of the cell body 5. An edge portion 65 (planar shape is a square frame shape) on the opening 61 side of the separator 37 is joined by a joint portion 39 (a planar shape is a square frame shape).

  FIG. 6 schematically shows an enlarged view of the vicinity of the joint portion 39 of the joined body 41. The joined body 41 includes a separation separator 37, which is a first metal member, and a second main component composed of ceramics. A first bonding layer 67 made of Ag brazing material is provided on the fuel gas flow path 17 side, which is the hydrogen atmosphere side in the cell 3, between the cell main body 5 (specifically, the solid electrolyte body 9) as a member, and oxygen A second bonding layer 69 made of Ni is provided on the air flow path 23 side which is the atmosphere side.

In particular, in this embodiment, the oxygen diffusion coefficient of the second bonding layer 69 on the oxygen atmosphere side is set to be smaller than the oxygen diffusion coefficient in the first bonding layer 67 on the hydrogen atmosphere side. For example, Ag—Cr ₂ O ₃ (containing 4% by weight of Cr ₂ O ₃ ) is used as the Ag brazing material constituting the layer 67, and the operating temperature of the solid oxide fuel cell 1 of the first bonding layer 67 is used. The oxygen diffusion coefficient at (for example, 800 ° C.) is 1.56 × 10 ⁻⁸ m ² / s.

On the other hand, Ni constituting the second bonding layer 69 is pure Ni, and the oxygen diffusion coefficient of the second bonding layer 69 at the same operating temperature (for example, 800 ° C.) of the solid oxide fuel cell 1 is 3. 48 × 10 ⁻¹⁸ m ² / s.

  In particular, in this embodiment, it is important that the oxygen diffusion coefficient of the second bonding layer 69 on the oxygen atmosphere side is set smaller than the oxygen diffusion coefficient in the first bonding layer 67 on the hydrogen atmosphere side. Within the range that satisfies the conditions, the material of the brazing material of the first bonding layer 67 and the material (for example, metal material) of the second bonding layer 69 can be appropriately selected.

Table 1 below shows the oxygen diffusion coefficient (m ² / s) at each temperature (° C.) of each material.

c) Next, a method for manufacturing the solid oxide fuel cell 1 will be described.
First, for example, a plate material made of SUS430 was punched out to manufacture the inter-cell separator 13, the isolation separator 37, and the metal frames 45 and 47.

Also, an insulating frame 43 was manufactured from mica.
Furthermore, the cell body 5 was manufactured. Specifically, the material of the solid electrolyte body 9 is printed on one surface (surface side) of the green sheet of the fuel electrode 7 so as to cover the entire surface, and further, on the printed layer of the solid electrolyte body 9. Next, the material of the reaction preventing layer is printed and fired once. Thereafter, the material of the air electrode 13 was printed on the surface of the reaction preventing layer and baked to manufacture the cell body 5.

Next, it arrange | positioned so that the inner edge part of the isolation | separation separator 37 might contact | connect the surface of the peripheral part of each cell main body 5 via Ag brazing material, and it brazed and joined.
Specifically, as shown in FIG. 7A, a square frame (paste-like) Ag brazing is formed along the inner edge of the isolation separator 37 at the position where the first bonding layer 67 of the bonding portion 39 is formed. A brazing material layer 71 made of a material was formed. Similarly, the same (pasty) Ag in the form of a square frame is formed along the peripheral edge of the cell body 5 (specifically, the exposed portion 63 of the solid electrolyte body 9) at the position where the first bonding layer 67 of the bonding portion 39 is formed. A brazing material layer 73 made of a brazing material was formed.

  Next, as shown in FIG. 7 (b), the separator 37 and the cell body 5 were brought close to each other and the brazing filler metal layers 71 and 73 were brought into close contact with each other. Specifically, as is well known, for example, the insulative separator 37 and the cell body 5 are placed on a heat-resistant cushioning material (not shown) made of ceramic, for example, and a weight (see FIG. A predetermined pressure (for example, 500 Pa or more) was applied.

  Then, after heating in the atmosphere (for example, to 1000 ° C.) and cooling to form the first bonding layer 67, the isolation separator 37 and the cell body 5 are brazed and bonded together by the first bonding layer 67. Turned into.

Since an oxide film is formed on the surface of the isolation separator 37 during brazing, the film is removed with hydrochloric acid or sulfuric acid.
Next, as shown in FIGS. 7C and 7D, plating made of Ni is formed on one exposed side surface of the first bonding layer 67 (that is, the side surface on the oxygen atmosphere side: the right side in FIG. 7) by electrolytic plating. A second bonding layer 69 as a layer is formed. Note that the plating layer is not formed on the side surface on the hydrogen atmosphere side by masking. Here, the plating conditions are, for example, an electrolytic plating solution (nickel sulfate 24%, nickel oxide 4.5%, boric acid 3%, ion-exchanged water (remainder)), temperature 20 ° C., and plating time 30 minutes.

As a result, a joined body 41 in which the cell body 5 was joined to the isolation separator 37 by the joining portion 39 was obtained.
Thereafter, the metal frame 45, the ceramic frame 43, the cell body 5, and the metal frame 47 are stacked in this order so as to form the frame portion 15, and further, the solid oxide fuel cell 1 of FIG. The inter-cell separator 13, the air electrode side current collector 31, the fuel electrode side current collector 29, and the like are stacked and assembled using a jig, and joint portions (that is, portions where the joint layers 33 and 49 to 57 are formed) ) Ag brazing material was placed.

Then, the assembled structure was heated in the atmosphere (for example, at 1000 ° C.) and then cooled and integrated by brazing to complete the solid oxide fuel cell 1.
Note that the melting temperature of the Ag brazing material (first Ag brazing material) that joins the separator 37 and the cell body 5 is higher than the melting temperature of the Ag brazing material (second Ag brazing material) of the joining layers 33 and 49 to 57. As such, its composition is selected. For example, as described above, Ag-4 wt% Cr ₂ O ₃ can be used as the first Ag brazing material, and Ag-5 wt% Pd can be used as the second Ag brazing material.

d) Next, the effect of the present embodiment will be described.
In the present embodiment, the joined body 41 includes an isolation separator 37 that is a first metal member and a cell body 5 that is a second member mainly composed of ceramics, and a first joining layer 67 on the hydrogen atmosphere side. The oxygen diffusion coefficient of the second bonding layer 69 is set to be smaller than the oxygen diffusion coefficient of the first bonding layer 67.

  Therefore, when the joined body 41 is used at a high temperature such as 400 ° C. or higher, oxygen is diffused from the oxygen atmosphere side to the second joining layer even when oxygen diffuses into the first joining layer 67 from the hydrogen atmosphere side. 69 is less likely to diffuse into the joint 69 (and therefore less likely to diffuse into the joint 39). Therefore, since it is possible to suppress the generation of voids due to the reaction of hydrogen and oxygen in the joint portion 39, it is possible to prevent the brazing material from being deteriorated due to the generation of voids.

In particular, in this embodiment, since the oxygen diffusion coefficient in the second bonding layer 69 is 3.48 × 10 ⁻¹⁸ m ² / s at 800 ° C., for example, there is an advantage that generation of voids is extremely small.

As the material of the second bonding layer 69, a material having a small oxygen diffusion coefficient such as Pt other than Ni (as compared to the first bonding layer 67) can be adopted.
Also, as shown in FIG. 8, plated layers 83 and 85 made of Ni may be formed on the hydrogen atmosphere side and the oxygen atmosphere side of the first bonding layer 81 by electrolytic plating. Here, the plating layer 85 on the oxygen atmosphere side is the second bonding layer 85.

Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
As shown in FIG. 9A, in the present embodiment, the first member and the second member are the isolation separator 91 and the cell main body 93 similar to those in the first embodiment.

  The first bonding layer 97 constituting the bonding portion 95 is made of the same Ag brazing material as that of the first embodiment, and the second bonding layer 99 is made of a Ni alloy. As the Ni alloy, for example, Ni-3Al, Ni-20Cr, or Ni-3Si, which is at least one of Ni, Cr, Al, and Si, can be used.

  In addition, as content of Cr in the 2nd joining layer 99, 10 to 30 weight% is employable. Moreover, as content of Al in the 2nd joining layer 99, 1 to 10 weight% is employable. Alternatively, the content of Si in the second bonding layer 99 can be 1 to 10% by weight.

  In particular, when the second bonding layer 99 is made of an alloy having the above-described composition, when the second bonding layer 99 is exposed to a high-temperature oxygen atmosphere, for example, the solid oxide fuel cell as in the first embodiment is used. When used, the oxidation of Ni is suppressed by oxidation of Cr, Al and Si.

Further, as a result of this oxidation, an oxide film 101 corresponding to the composition of the alloy is formed on the oxidation atmosphere side of the second bonding layer 99 as shown in FIG. 9B. For example, an oxide film 101 made of Al ₂ O ₃ , Cr ₂ O ₃ , or SiO ₂ is formed.

Since these oxide films 101 have a smaller oxygen diffusion coefficient than the first bonding layer 97 (for example, Al ₂ O ₃ : 1.14 × 10 ⁻¹⁴ m ² / s at 800 ° C.), generation of voids can be suppressed. There is an advantage.

  That is, Ni in a metal state exhibits the effect of an oxygen diffusion barrier, and the oxide film 101 can also exhibit the effect of an oxygen diffusion barrier, so that there is an advantage that generation of voids can be effectively suppressed.

  The oxide film 101 may be formed when actually used at a high temperature as described above, but may be formed by exposing it to a high-temperature oxidizing atmosphere in advance. Alternatively, for example, it may be formed during manufacture (for example, during brazing).

Next, the third embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
As shown in FIG. 9C, in the present embodiment, the first member and the second member are the isolation separator 111 and the cell body 113 similar to those in the first embodiment.

Further, the first bonding layer 117 and the second bonding layer 119 constituting the bonding portion 115 are made of the same Ag brazing material and Ni as in the first embodiment.
In particular, in this embodiment, an adhesion layer 120 made of oxide glass is formed on the oxygen atmosphere side of the second bonding layer 119. Since the adhesion layer 120 has an oxygen diffusion coefficient smaller than that of the first bonding layer 117, there is an advantage that generation of voids can be greatly suppressed.

  The adhesion layer 120 can be formed by applying a glass paste with a dispenser and then baking it.

Next, the fourth embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
The joined body of the present embodiment can be used for apparatuses other than solid oxide fuel cells. For example, it can be used in devices such as machine cutting tools, inverter ceramic substrates (HV / EV vehicle power devices), and turbine rotors.

As shown in FIG. 9D, in this embodiment, plate-shaped ceramic members 121 and 123 made of alumina, for example, are used as the first member and the second member.
Further, the first bonding layer 127 constituting the bonding portion 125 is formed of the same Ag brazing material as that of the first embodiment, and the second bonding layer 129 has an oxygen diffusion coefficient smaller than that of the first bonding layer 127. It consists of Ni or Pt.

Also in the present embodiment, the same effects as in the first embodiment can be obtained.
Moreover, in the modification of a present Example, the plate-shaped metal member which consists of stainless steel, for example can be used as a 1st member and a 2nd member.
<Experimental example>
Next, experimental examples in which the effect of the present invention has been confirmed will be described.

In this experimental example, using the experimental apparatus shown in FIG. 10, the presence / absence of voids in the joined portion of the joined body was examined.
As shown in FIG. 10, this experimental apparatus 131 is obtained by joining a disk-shaped stainless steel plate 135 to the tip of a cylindrical stainless steel metal pipe 133 so as to close the opening. .

  A through hole 137 is opened at the center of the plate member 135, and a ceramic substrate 139 (made of a solid electrolyte body similar to that of the first embodiment) is joined by the joint portion 141 so as to close the through hole 137 from above. It is joined.

  In other words, the joint 141 surrounds the opening 147 above the through-hole 137 so as to prevent gas from passing from the internal space 143 in the metal pipe 133 to the external space 145 outside (to be airtight). It is arranged to cover.

As in the first and second embodiments, the bonding portion 141 includes a first bonding layer 149 on the hydrogen atmosphere side and a second bonding layer 151 on the oxygen atmosphere side.
In the experiment, as shown in Table 2 below, as the first bonding layer 149, an Ag brazing material having an oxygen diffusion coefficient of 1.56 × 10 ⁻⁸ m ² / s at 800 ° C. (specifically, Ag-4 weight) % Cr ₂ O ₃ ), and various materials having various oxygen diffusion coefficients at 800 ° C. were used as the second bonding layer 151. As shown in Table 2, the oxygen diffusion coefficient when a predetermined amount of another substance is added to Ni includes the second bonding layer and the oxide film formed on the oxygen side of the second bonding layer. The value is smaller than the single unit of 3.48 × 10 ⁻¹⁸ m ² / s.

  The experimental condition is that the temperature is set to 850 ° C., 1 atm of hydrogen is supplied to the internal space 143 and 1 atm of oxygen is supplied to the external space 145, and voids are generated in 20 hours and 200 hours (ie, Ag). The state of deterioration of the brazing material) was investigated.

  The results are shown in Table 2 below. In each durability evaluation in Table 2, “x” indicates the occurrence of a void, and “◯” indicates that no void is generated. Moreover, x, (triangle | delta), (circle) in comprehensive evaluation has shown that durability is excellent in this order.

* 1: The oxygen diffusion coefficient including the second bonding layer and the oxide film formed on the oxygen side of the second bonding layer is a value smaller than 3.48 × 10 ⁻¹⁸ m ² / s.
As is clear from Table 2, it can be seen that the use of a material having a smaller oxygen diffusion coefficient in the second bonding layer than in the first bonding layer can suppress the generation of voids, that is, the durability is excellent.

Further, it can be seen that when Ni contains 10 to 30% by weight of Cr, the durability is higher than other Cr contents.
Similarly, when Al is contained in Ni in an amount of 1 to 10% by weight, it can be seen that durability is higher than other Al contents.

Similarly, it can be seen that when Ni is contained in Ni in an amount of 1 to 10% by weight, the durability is higher than other Si contents.
Needless to say, the present invention is not limited to the above-described embodiments and the like, and can be implemented in various modes without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Solid oxide fuel cell 3, 3a, 3b, 3c ... Electric power generation layer (cell)
5, 93, 113 ... Cell body 7 ... Fuel electrode 9 ... Solid electrolyte body 11 ... Air electrode 37, 91, 111 ... Isolation separator 39, 95, 115, 125, 141 ... Joint part 41 ... Joint body 67, 81, 97 117, 127, 149: first bonding layer 69, 85, 99, 119, 129, 151: second bonding layer 120: adhesion layer

Claims (10)

A gas separation structure for separating an oxygen atmosphere side containing oxygen gas and a hydrogen atmosphere side containing hydrogen gas is used, and a first member made of ceramics or metal and a second member made of ceramics or metal are brazed. In a joined body joined by a joint having a material,
The bonding portion has a first bonding layer made of the brazing material on the hydrogen atmosphere side and a second bonding layer on the oxygen atmosphere side,
A bonded body, wherein an oxygen diffusion coefficient in the second bonding layer is smaller than an oxygen diffusion coefficient in the first bonding layer. 2. The joined body according to claim 1, wherein an oxygen diffusion coefficient in the second joining layer is 3.48 × 10 ⁻¹⁸ m ² / s or less at 800 ° C. 3.   The joined body according to claim 1 or 2, wherein the second joining layer is an alloy layer containing Ni as a main component and containing at least one of Cr, Al, and Si.   The joined body according to claim 3, wherein the second joining layer includes an oxide film containing at least one kind of oxides of Cr, Al, and Si.   The joined body according to claim 3 or 4, wherein a content of Cr in the second joining layer is 10 to 30% by weight.   The joined body according to claim 3 or 4, wherein the content of Al in the second joining layer is 1 to 10% by weight.   The joined body according to claim 3 or 4, wherein the content of Si in the second joining layer is 1 to 10% by weight.   In addition to the first bonding layer and the second bonding layer, the bonding portion is in close contact with the first member and the second member closer to the oxygen atmosphere side than the second bonding layer and the second bonding layer. The joined body according to claim 1, further comprising an adhesion layer having a smaller oxygen diffusion coefficient than the layer.   A solid oxide fuel cell comprising the joined body according to any one of claims 1 to 8.   The solid oxide fuel cell according to claim 9, wherein the joined body is obtained by joining a solid electrolyte body and a metal member.