JP2013246887A - Insulation sealing structure, formation method thereof, and fuel cell stack structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation sealing structure capable of exerting an excellent gas sealing property and an excellent electric insulation property, a formation method thereof, and a fuel cell stack structure.SOLUTION: A insulation sealing structure is formed between a pair of opposite members of a fuel cell stack structure, seals a gas between the pair of opposite members, and performs electric insulation. The insulation sealing structure has: an insulation layer positioned on one opposite member side; a metal sealing layer positioned on the other opposite member side; and a metal diffusion restraining layer positioned between the insulation layer and the metal sealing layer. The fuel cell stack structure has the insulation sealing structure. In a method for forming the insulation sealing structure, the insulation sealing structure is formed using the metal sealing layer with the metal diffusion restraining layer having the metal diffusion restraining layer formed using a plating method and/or a vapor deposition method on the metal sealing layer made of a metal foil.

Description

  The present invention relates to an insulating seal structure, a method for forming the same, and a fuel cell stack structure. More specifically, the present invention relates to an insulating seal structure capable of exhibiting excellent gas sealing properties and electrical insulation, a method for forming the same, and a fuel cell stack structure.

  Conventionally, in order to obtain an insulating seal structure that more reliably seals and insulates between two members facing each other, an insulating gasket is sandwiched between a pair of facing members and the space between the facing members is sealed. In addition, an insulating seal structure for insulating is proposed (see Patent Document 1).

  The insulating seal structure includes a core portion made of a material whose main component is an insulating material, and a metal covering portion that is formed on the surface of the core portion by vapor deposition and abuts against a facing member, and is opposed to the metal covering portion. A sealing member different from the insulating gasket is sandwiched between the members.

Japanese Patent No. 4389718

  However, when the present inventors examined, even with the insulating seal structure described in Patent Document 1, there was room for improvement in electrical insulation in long-term operation.

  The present invention has been made in view of such problems of the prior art. An object of the present invention is to provide an insulating seal structure capable of exhibiting excellent gas sealability and electrical insulation, a method for forming the same, and a fuel cell stack structure.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, an insulation having an insulating layer located on one opposing member side, a metal seal layer located on the other opposing member side, and a metal diffusion suppression layer located between the insulating layer and the metal seal layer The inventors have found that the above object can be achieved by forming a seal structure, and the present invention has been completed.

  That is, the insulating seal structure of the present invention is formed between a pair of opposing members in the fuel cell stack structure, and gas-seals and electrically insulates between the pair of opposing members. In the insulating seal structure of the present invention, the insulating layer located on one opposing member side, the metal sealing layer located on the other opposing member side, and the insulating layer and the metallic sealing layer are located. A metal diffusion suppression layer.

  The fuel cell stack structure according to the present invention includes the insulating seal structure according to the present invention.

  Furthermore, the method for forming the insulating seal structure of the present invention is an example of the method for forming the insulating seal structure of the present invention. And in the formation method of the insulation seal structure of this invention, the metal seal layer with a metal diffusion suppression layer which has the metal diffusion suppression layer formed in the metal seal layer which consists of metal foil using the plating method and / or the vapor deposition method Is used.

According to the present invention, the insulating layer located on one opposing member side, the metal seal layer located on the other opposing member side, the metal diffusion suppression layer located between the insulating layer and the metal seal layer, It was decided to form an insulating seal structure having
Therefore, it is possible to provide an insulating seal structure capable of exhibiting excellent gas seal performance and electrical insulation performance, a method for forming the structure, and a fuel cell stack structure.

1 is a schematic perspective view showing an example of a solid oxide fuel cell stack structure according to an embodiment of the present invention. It is sectional drawing along the II-II line of the fuel cell stack structure shown in FIG. It is the elements on larger scale of the part shown by the surrounding line III in FIG. It is explanatory drawing explaining the point of a seal performance evaluation test. It is the photograph (b) which shows the reflected electron image (a) in the cross section of the insulation seal structure of Example 1, and the analysis result by an electron probe microanalyzer by the scanning electron microscope. It is the photograph (b) which shows the reflected electron image (a) in the cross section of the insulation seal structure of the comparative example 1, and the analysis result by an electron probe microanalyzer by the scanning electron microscope.

  Hereinafter, an insulating seal structure, a forming method thereof, and a fuel cell stack structure according to an embodiment of the present invention will be described in detail. In addition, the dimension ratio of drawing quoted by the following embodiment is exaggerated on account of description, and may differ from an actual ratio.

First, an insulating seal structure and a fuel cell stack structure according to an embodiment of the present invention will be described in detail with reference to the drawings, taking as an example the case of application to a solid oxide fuel cell stack structure.
FIG. 1 is a schematic perspective view showing an example of a solid oxide fuel cell stack structure according to an embodiment of the present invention, and FIG. 2 is taken along line II-II of the fuel cell stack structure shown in FIG. Sectional drawing and FIG. 3 are the elements on larger scale of the part shown by the surrounding line III in FIG.

  As shown in FIGS. 1 and 2, the solid oxide fuel cell stack structure (hereinafter referred to as “cell stack”) A of the present embodiment is referred to as a plurality of solid oxide fuel cells (hereinafter referred to as “cell units”). ) B are laminated via a seal member (end plates 51 and 51 are arranged on the upper and lower surfaces), and a gas inlet and a gas outlet are arranged inside and outside the cell unit B. Electric power is generated by separating and circulating two kinds of reaction gases through the holders 50 and 50 having the above-described configuration.

  In the present embodiment, one reaction gas is a fuel gas such as hydrogen or hydrocarbon, and the other reaction gas is an oxidant gas such as oxygen or air. One reaction gas may be air and the other reaction gas may be hydrocarbon, depending on the relative arrangement of the electrode and the air electrode.

  The cell unit B mainly includes a solid electrolyte type single cell 40, a thin channel component 10, a channel formation body 30, and a separator 20.

  The unit cell 40 has the above-described fuel electrode (anode electrode) and air electrode (cathode electrode) opposed to each other on the upper and lower sides of the electrolyte, and is formed in an annular shape with a through hole as the center. .

The separator 20 is a metal plate having an outer diameter larger than the outer diameter of the single cell 40, and a circular hole is formed in the center thereof, and an outer peripheral edge inner and outer surfaces (upper and lower surfaces in the drawing) of the middle portion thereof. The metal porous body 21 for current collection that contacts the fuel electrode of the single cell 40 and the metal porous body 22 that elastically contacts the air electrode or the end plate 51 of the other cell unit B are disposed. .
An annular spacer 23 is fixed to the outer peripheral edge of the separator 20 over the entire circumference thereof, and an annular inner peripheral plate 24 extends inwardly on the lower surface of the spacer 23. It is fixed with.
Further, the upper surface of the inner peripheral plate 24 and the lower surface of the outer peripheral edge of the electrolyte of the unit cell 40 are bonded and fixed by a glass adhesive 36 interposed therebetween.

  The flow path forming body 30 has flow path parts 31 and 32, which have flow paths 34 and 35 for supplying or discharging any of the above reaction gases to the gas circulation space β. They are formed in common communication.

The flow path component 31 has a cylindrical shape whose outer diameter is slightly smaller than the inner diameter of the through hole of the single cell 40.
The flow path component 32 has a gas flow groove 32a formed on the lower surface thereof to allow the flow path 35 and the gas flow space β to communicate with each other, and has a slightly larger outer diameter than the thin flow path component 10 described later. It is formed in a plate shape.

The thin flow path component 10 is a metal plate that has an annular shape with an outer diameter larger than the through-hole of the single cell 40.
That is, by forming an annular shape having an outer diameter larger than the through-hole of the single cell 40, it is overlapped with the inner peripheral edge of the single cell 40 in a plan view, and this overlapped portion is inserted through the glass adhesive 36. The unit cell 40 is bonded to the upper surface of the inner peripheral edge.
The flow path forming body 30, the thin flow path component 10, and the separator 20 are all arranged concentrically around the axis O.

  In addition, in the state which adhered to the inner peripheral part lower surface of the single cell 40 via the glass adhesive agent 36, flow-path components so that a space | gap may be produced between the upper surface of the fuel electrode of the single cell 40, and the flow-path component 32. A height of 31 is set.

  As shown in FIG. 3, the seal member 60 has an annular shape having the same outer diameter as the flow path component 31, and includes an insulating layer 61, a metal seal layer 62, and a metal diffusion suppression layer 63 positioned therebetween. It is what has. The separator 20 which is one of a pair of opposing members of the cell stack has an insulating layer on the surface thereof, and the flow path component 31 which is the other of the opposing members has a metal seal layer on the surface thereof. Is provided with a metal diffusion suppression layer. The insulating seal structure insulates the opposing members from each other by the action of a fastening load that elastically presses (clamps) the stacked cell units B from the upper and lower sides of the figure.

  Examples of the insulating layer 61 include those made of an electrically insulating material. This may be a single-layer structure or a multi-layer structure (laminated structure). When the insulating layer is used, the risk of breakage due to the effect of the fastening load can be reduced as compared with the case where the core member is applied. Moreover, as a suitable form of an insulating layer, the sprayed film formed by spraying an electrically insulating material on an opposing member can be mentioned. For example, an electrically insulating ceramic is preferably used as the electrically insulating material. As an electrically insulating ceramic, for example, alumina can be cited as a suitable example.

  As the metal seal layer 62, a material whose main constituent material is made of silver, copper, stainless steel or the like can be cited as a suitable example. Moreover, it is preferable to apply what consists of metal foil. This may be a single-layer structure or a multi-layer structure (laminated structure). In the present invention, for example, “silver is the main constituent material” means that 90% by mass or more of the metal seal layer is silver.

  The metal diffusion suppression layer 63 preferably has a vapor pressure at the fuel cell operating temperature of the main constituent material higher than the vapor pressure at the fuel cell operating temperature of the main constituent material of the metal seal layer. If this relationship is not satisfied, the constituent metal of the metal seal layer is likely to evaporate and diffuse into the insulating layer, and the electrical insulation may be reduced. As the metal diffusion suppression layer, a material whose main constituent material is made of gold, silver, copper, chromium, iron, cobalt, platinum or the like can be cited as a suitable example. This may be a single-layer structure or a multi-layer structure (laminated structure). In the present invention, for example, “gold is the main constituent material” means that 90% by mass or more of the metal diffusion suppression layer is gold (the same applies hereinafter).

  Moreover, the metal diffusion suppression layer 63 can use suitably what consists of a highly malleable material. For example, a material in which the main constituent material is made of a highly malleable material such as gold, silver, copper, platinum, aluminum, lead and the like can be cited as a suitable example. With such a highly malleable material, even when a fastening load is applied, the gas sealability between the insulating layer and the insulating layer can be maintained by the malleability.

  Further, the metal diffusion suppressing layer 63 has a main constituent material having oxidation resistance such as gold, platinum, aluminum or the like (in the Ellingham diagram showing the relationship between the standard free energy of oxide formation and temperature, the fuel cell operating temperature). (It can be defined by referring to (700 ° C.)) and those that form a non-moving body coating (for example, can be defined by referring to those having a small oxidation rate constant). be able to.

  From the various viewpoints described above, a metal diffusion suppression layer made of gold or platinum can be cited as a more preferable example.

Next, a method for forming an insulating seal structure according to an embodiment of the present invention will be described in detail.
A method for forming an insulating seal structure according to an embodiment of the present invention is an example of a method for forming an insulating seal structure according to an embodiment of the present invention.
In the method for forming an insulating seal structure of the present embodiment, a metal seal layer with a metal diffusion suppression portion having a metal diffusion suppression layer formed using at least one of a plating method and a vapor deposition method on a metal seal layer made of a metal foil. Is preferably used. In addition, as a plating method or a vapor deposition method, a conventionally known film formation method such as electrolytic plating, electroless plating, chemical vapor deposition such as plasma chemical vapor deposition or thermal chemical vapor deposition, or physical vapor deposition such as vacuum vapor deposition, sputtering, or ion plating. The law can be applied.
When such a metal seal layer with a metal diffusion suppression portion is used, the metal diffusion suppression layer can be densely formed and the number of parts can be reduced as compared with the case where the metal diffusion suppression layer is formed on the insulating layer. There is an advantage that you can.
However, the insulating seal structure of the present invention is not limited to the one obtained by such a forming method as long as it has the above-described configuration.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.

Example 1
An insulating layer b made of an alumina sprayed film having a thickness of 0.5 mm was formed on a substrate a made of stainless steel (SUS430) having a thickness of 1 mm by a thermal spraying method. In order to improve the adhesion between the substrate a and the insulating layer b, the substrate a was previously subjected to sandblasting.

  A metal diffusion suppression layer d made of gold having a thickness of 5 μm was formed on a metal seal layer c made of a ring-shaped silver foil having an inner diameter of φ30 mm, an outer diameter of φ36 mm, and a thickness of 0.2 mm by a vacuum deposition method.

  Two electrodes in which an insulating layer b formed on the substrate a and a metal diffusion suppression layer d formed on the metal seal layer c are arranged to face each other, and a lead wire e for measuring an insulation resistance is joined. The gas seal structure of this example as shown in FIG. 4 was formed by sandwiching with the plate f, further sandwiching with an alumina plate g and a metal plate h for insulation, and fastening with bolts i.

(Example 2)
Implemented except that a ring-shaped silver foil with an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm was used instead of a ring-shaped silver foil with an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm. The same operation as in Example 1 was repeated to form the gas seal structure of this example as shown in FIG.

(Example 3)
Instead of a ring-shaped silver foil having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm, a metal seal layer made of a ring-shaped stainless steel foil (SUS316L) having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm was used. Except for the above, the same operation as in Example 1 was repeated to form a gas seal structure of this example as shown in FIG.

(Comparative Example 1)
An insulating layer made of an alumina sprayed film having a thickness of 0.5 mm was formed on a substrate made of stainless steel (SUS430) having a thickness of 1 mm by a thermal spraying method. In order to improve the adhesion between the substrate and the sprayed film, the substrate was previously subjected to a sandblast treatment.

  An insulating layer formed on the substrate and a metal seal layer made of a ring-shaped silver foil having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm are arranged to face each other, and a lead wire for measuring an insulation resistance is joined. The gas seal structure of this example was formed by sandwiching between two electrode plates, further sandwiching with an alumina plate and a metal plate for insulation, and fastening with bolts. In addition, this example is the same structure as Example 1 except not having formed the metal diffusion suppression layer.

(Comparative Example 2)
Compared to a ring-shaped silver foil having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm, except that a metal seal layer made of a ring-shaped copper foil having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm was used. The same operation as in Example 1 was repeated to form the gas seal structure of this example.

(Comparative Example 3)
Instead of a ring-shaped silver foil having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm, a metal seal layer made of a ring-shaped stainless steel foil (SUS316L) having an inner diameter of 30 mm, an outer diameter of 36 mm, and a thickness of 0.2 mm was used. Except for the above, the same operation as in Comparative Example 1 was repeated to form the gas seal structure of this example.
Table 1 shows a part of the specifications of the seal structure in each of the above examples.

[Performance evaluation]
(Seal performance evaluation test)
With respect to the seal structures of the above examples before and after the following high-temperature exposure treatment, the amount of leakage when pressurized with 10 kPa using helium gas was measured. In addition, only air was supplied when the temperature fell. The obtained results are also shown in Table 1.

<High temperature exposure treatment>
Supply gas: Combustion gas (dry air; 200 L / min (0 ° C., 1 atm), hydrogen; 20 L / min (0 ° C., 1 atm))
Body temperature: 750 ° C
Retention time: 10 hours or more

(High temperature insulation performance evaluation test)
The seal structure of each of the above examples was incorporated in a part of the high-temperature gas pipe, and the insulation resistance value was measured when a 50 V voltage was applied between the electrodes at a main body temperature of 750 ° C. under high-temperature gas supply conditions. The obtained results are also shown in Table 1.

  From Table 1, when Examples 1 to 3 belonging to the scope of the present invention are compared with Comparative Examples 2 and 3 outside the present invention, the gas sealing properties are excellent before and after the high temperature exposure treatment. I understand. Moreover, it turns out that the gas-seal property is falling after the high temperature exposure process of the comparative example 2 and the comparative example 3. On the other hand, in Comparative Example 1 outside the present invention, the gas sealability is comparable before and after the high temperature exposure treatment when compared with Examples 1 to 3 belonging to the scope of the present invention. However, it can be seen that Comparative Example 1 outside the present invention does not have sufficient electrical insulation when compared with Examples 1 to 3 belonging to the scope of the present invention.

  That is, it can be seen that the gas seal structure of the present invention can exhibit excellent gas sealability and electrical insulation. In particular, it can be seen that the gas seal structure according to Example 1 in which a metal seal layer made of silver foil is applied and a metal diffusion suppression layer made of gold is formed thereon is most excellent at the present time. These are because the vapor pressure near the fuel cell operating temperature is lower and the silver diffuses into the insulating layer in the gold constituting the metal diffusion suppression layer compared to silver, copper and stainless steel constituting the metal seal layer. This is thought to be to suppress insulation and maintain insulation performance. Moreover, the gold | metal | money which comprises a metal diffusion suppression layer can be used suitably also in the material mentioned above from a viewpoint that malleability and oxidation resistance are excellent.

  Moreover, about the insulating seal structure of Example 1 and Comparative Example 1, the cross section was observed with the scanning electron microscope and the electron probe microanalyzer. The obtained results are shown in FIG. 5 and FIG. 6 (note that FIG. 5 and FIG. 6 show a portion of the substrate and the insulating layer formed thereon in each example). In Comparative Example 1 shown in FIG. 6, it can be seen that silver (Ag) constituting the metal seal layer is evaporated and diffused, and Ag is deposited in the insulating layer made of the alumina sprayed film. On the other hand, in Example 1 shown in FIG. 5, since the metal diffusion suppression layer traps evaporated silver (Ag), it can be seen that Ag does not deposit in the insulating layer made of the alumina sprayed film. .

  As mentioned above, although this invention was demonstrated with some embodiment and an Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.

  DESCRIPTION OF SYMBOLS 10 ... Thin channel component, 20 ... Separator, 21, 22 ... Metal porous body, 23 ... Spacer, 24 ... Inner peripheral board, 30 ... Channel formation body, 31, 32 ... Channel component, 32a ... For gas distribution Groove, 34, 35 ... flow path, 36 ... glass adhesive, 40 ... single cell, 50 ... holder, 51 ... end plate, 60 ... sealing member, 61 ... insulating layer, 62 ... metal sealing layer, 63 ... metal diffusion suppression Layer, A ... Cell stack, B ... Cell unit, β ... Gas distribution space

Claims (6)

An insulating seal structure is formed between a pair of opposing members in the fuel cell stack structure, and gas-seals and electrically insulates between the pair of opposing members,
An insulating layer located on one opposing member side, a metal seal layer located on the other opposing member side, and a metal diffusion suppression layer located between the insulating layer and the metal seal layer Insulating seal structure. The main constituent material of the metal seal layer is silver,
2. The insulating seal structure according to claim 1, wherein a main constituent material of the metal diffusion suppression layer is gold, copper, chromium, iron, cobalt, or platinum.   The insulating seal structure according to claim 1 or 2, wherein a main constituent material of the metal diffusion suppression layer is gold, copper, platinum, aluminum, or lead.   The main constituent material of the said metal diffusion suppression layer is gold, platinum, or aluminum, The insulating seal structure as described in any one of Claims 1-3 characterized by the above-mentioned.   A fuel cell stack structure comprising the insulating seal structure according to any one of claims 1 to 4. A method of forming an insulating seal structure according to any one of claims 1 to 4,
A method of forming an insulating seal structure, comprising using a metal seal layer with a metal diffusion suppression layer having a metal diffusion suppression layer formed using a plating method and / or vapor deposition method on a metal seal layer made of a metal foil.

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