JP2014191928A - Manufacturing method of inter-cell connection member, inter-cell connection member, and cell for solid oxide type fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for attaining improvement of durability by suppressing diffusion of Cr by forming a more uniform and dense protective film than conventional ones.SOLUTION: A manufacturing method of an inter-cell connection member for forming a protective film from a metal oxide over a base material formed from an alloy or an oxide containing Cr and Mn includes: a coating forming step of forming a non-sintered coating containing metal oxide fine particles as a main component on the base material; a calcination step of calcinating the coating under a condition that Mn contained in the base material reacts with a coating component; and a step of forming a dense layer which is generated by reacting the coating component and Mn, within the coating adhesively with a CrOlayer formed on a surface of the base material and growing the dense layer to thickness of 1 μm or more.

Description

  The present invention relates to a method for producing an inter-cell connecting member for forming a protective film made of a metal oxide on a base material made of an alloy or oxide containing Cr and Mn, an inter-cell connecting member, and a solid oxide fuel cell. Regarding cells.

Such a SOFC cell has a single cell in which an air electrode is joined to one surface side of an electrolyte membrane and a fuel electrode is joined to the other surface side of the electrolyte membrane, and electrons are transferred to the air electrode or the fuel electrode. It has the structure pinched | interposed by a pair of electron conductive base material (inter-cell connection member) which performs.
And in such a cell for SOFC, for example, it operates at an operating temperature of about 700 to 900 ° C., and with the movement of oxide ions through the electrolyte membrane from the air electrode side to the fuel electrode side, the pair of electrodes An electromotive force is generated in the meantime, and the electromotive force can be taken out and used. The inter-cell connecting member corresponds to an interconnector or a member that electrically connects cells via the interconnector.

The interconnector is a member that serves as a partition wall for fuel and air.
With the progress of development in recent years, the operating temperature of SOFC is decreasing. The conventional operating temperature is about 1000 ° C., and metal oxides typified by lanthanum chromite have been used as a base material from the viewpoint of heat resistance, but recently the operating temperature has dropped to 700 ° C. to 800 ° C., Alloys have become available. By using an alloy as a base material, cost reduction and improvement in robustness can be expected.

As the alloy, ferritic stainless steel is often used because of its consistency with the thermal expansion coefficient of the metal oxide to be joined, but an Fe-Cr-Ni alloy which is an austenitic stainless steel superior in heat resistance. In addition, a Ni-Cr alloy that is a nickel-based alloy may be used. In addition, instead of an alloy, a metal oxide typified by (La, Ca) CrO ₃ (calcium dopeplank chromite) may be used.

These alloys and the like almost always contain Cr, and an oxide film of Cr ₂ O ₃ or MnCr ₂ O ₄ is formed on the surface in a high-temperature air atmosphere that is an operating environment. It is known that this oxide film increases in thickness over time, increases electrical resistance, evaporates as a hexavalent chromium compound in a high-temperature atmospheric atmosphere, which is the working environment, and poisons the air electrode to cause deterioration. (Referred to as Cr poisoning). Further, even when (La, Ca) CrO ₃ (calcium dope lanthanum chromite) is used, Cr poisoning may occur although it is less than when an alloy is used. Therefore, an attempt has been made to suppress deterioration by protecting a metal oxide material having excellent heat resistance on the surface of an alloy, (La, Ca) CrO ₃ (calcium dopeplank chromite). In addition, a material containing Mn may be generally used as such an alloy.
In addition, ferritic stainless steel is often used for the alloy in order to ensure consistency in thermal expansion coefficient with other constituent materials of SOFC. (Example: ZMG232L manufactured by Hitachi Metals, Ltd.) Ferritic stainless steels often contain 0.1 to 1% by weight of Mn in addition to Fe and Cr.

  In addition, in the manufacturing process of the SOFC cell, in order to minimize the contact resistance between the base material for the inter-cell connecting member and the air electrode and the fuel electrode, the operating temperature is increased. In some cases, a baking treatment is performed in which baking is performed at a higher baking temperature of about 1000 ° C. to 1250 ° C. (see, for example, Patent Documents 1 and 2).

JP 2004-259634 A International Publication WO2009 / 131180 Pamphlet

From the above situation, protecting the SOFC alloy interconnector from a metal oxide material that exhibits conductivity in the vicinity of the SOFC operating temperature typified by spinel oxides ensures the long-term durability of the SOFC. It has become an essential technology. Since the spinel oxide has a particularly dense structure, it is considered that the effect of suppressing the scattering of Cr is particularly high.
As the protective film material, Co—Mn spinel, Zn—Co spinel, Zn—Co—Mn spinel, Zn—Mn spinel, ZnO or the like that is not a spinel oxide is used.

  However, even with a protective film made of such a material, further improvements have been desired for suppressing Cr scattering and improving long-term durability.

  In view of the above, the present invention has an object to provide a technique for suppressing the scattering of Cr and improving the durability by forming a more uniform and dense protective film.

[Configuration 1]
A characteristic configuration of the present invention for achieving the above object is a method for manufacturing an inter-cell connection member, in which a protective film made of a metal oxide is formed on a base material made of an alloy or oxide containing Cr and Mn. ,
On the base material, a coating film forming step for forming an unsintered coating film containing metal oxide fine particles as a main component is performed, and the Mn contained in the base material reacts with the coating film component. A baking step of baking the coating film is performed, and a Mn-containing dense layer (hereinafter simply referred to as a dense layer) generated by the reaction between the coating film component and Mn is formed in the coating film. The dense layer is formed in close contact with the Cr ₂ O ₃ layer, and the thickness of the dense layer is grown to 1 μm or more.

[Operation effect 1]
When the coating film forming step is performed on the substrate, an unsintered coating film containing metal oxide fine particles as a main component is formed. When the coating film is heat-treated, a dense film is formed between the Cr ₂ O ₃ oxide film formed on the stainless steel surface and the protective film by the heat treatment, and the dense layer is formed. It is known that the heat treatment can be performed also in the manufacturing process of the protective film, and proceeds naturally due to heat generated during actual use.

Since this dense layer is a layer formed by mutual diffusion and reaction of the Mn component and the protective film component in the base material, it is considered to be very dense and have a high oxygen barrier property. Due to the presence of the dense layer, it is possible to reduce the deterioration of the air electrode by suppressing the scattering of Cr (Cr poisoning), and to suppress the increase in ohmic resistance by suppressing the film thickness increase rate of the Cr ₂ O ₃ oxide film.
Therefore, it is considered that the durability of SOFC can be extended by sufficiently functioning this dense layer. Therefore, as a result of the study by the present inventors, the dense layer is sufficiently formed by forming the dense layer with a thickness of 1 μm or more by closely forming the Cr ₂ O ₃ layer formed on the substrate surface. It can be seen that Cr can be prevented from being scattered and resistance increase can be suppressed, and a suitable durability improvement effect can be expected.

Incidentally, by the firing step, the substrate surface is Cr ₂ O ₃ layer derived from the Cr contained in the base material is formed. This Cr ₂ O ₃ layer usually has high adhesion to the dense layer, and also exhibits an effect of preventing delamination between the dense layer and the substrate.

[Configuration 2]
Further, it is preferable that the protective film contains at least one metal oxide selected from Co, Zn, and Mn.

[Operation effect 2]
As the protective film material, at least one metal oxide selected from Co, Zn, Mn, such as Co—Mn spinel, Zn—Co spinel, Zn—Co—Mn spinel, Zn—Mn spinel, ZnO, etc. Those containing are effectively used.
When these metal oxide components are used, the adhesion to various materials used as the base material is high, the durability against heat reception is high, and when the dense layer is formed, the oxygen barrier property of the spinel structure is high, It is preferable that it is formed on a protective film having a high Cr scattering prevention effect. The present inventors have made Zn-Co based materials such as (Zn _x Co _1-x ) Co ₂ O ₄ (0.45 ≦ x ≦ 1.00) and Mn—Co based such as Co _1.5 Mn _1.5 O _4. It has already been found that those typified by materials are particularly advantageously used. Furthermore, when various compounds were examined as a composite oxide, Zn _x (Co _y Mn _(1-y) ) _(3-x) O ₄ (0 <x <1, 0 <y × (3-x) ≦ The protective film containing 2) has a small mismatch (difference) in the thermal expansion coefficient with the base material, the air electrode, etc., and is particularly exposed to 800 ° C. to 1000 ° C. once during the manufacturing process (when the protective film is baked). It has been found that even in an environment, the thermal expansion coefficient mismatch (difference) with the base material, the air electrode, etc. is small, and the effect of suppressing Cr scattering is extremely high.

[Configuration 3]
When the protective film contains Zn _x (Co _y Mn _(1-y) ) _(3-x) O ₄ (0 <x <1, 0 <y × (3-x) ≦ 2), In the firing step, the coating film is preferably fired at 1000 ° C. to 1100 ° C. for 2 hours or longer.

[Operation effect 3]
In order to grow the dense layer to 1 μm or more, it is thought that the coating film needs to be baked for a long time at a certain high temperature. While no formation was observed, the formation of a dense layer was observed at 1000 ° C. or higher. Furthermore, it has been confirmed that a dense layer grows in a relatively short time even at 1100 ° C. As a matter of course, it is expected that a dense layer can be grown in a shorter time at a temperature exceeding 1100 ° C., but the temperature exceeds the upper limit of the heat resistance of the stainless steel member of the substrate, and oxidative deterioration during firing occurs. Since it becomes remarkable, it is desirable to set it as 1100 degrees C or less.
In addition, when it is 1000 degreeC or more, while the dense layer of 1 micrometer or more grows by heating for 2 hours or more, and the whole coating film can be baked uniformly, it is preferable. Although it does not prevent further baking for a long time, if the entire coating film grows into a dense layer, further heating only promotes oxidative deterioration of the stainless steel member of the substrate. It is preferable to appropriately set the heating time in consideration of the thickness of the film and the thickness of the target dense layer.

[Configuration 4]
Further, the protective film, if it contains Mn-Co-based material such as Co _1.5 Mn _1.5 O _4, in the firing step, the coating film 1100 degrees below 1050 ° C. or more, is preferably fired.

[Operation effect 4]
In order to grow the dense layer to 1 μm or more, it is considered that the coating film needs to be baked for a long time at a certain high temperature. However, in reality, the dense layer is formed at 1000 ° C. × 2 hr from the following embodiment. It was possible to form the layer only with an insufficient thickness of 0.9 μm. On the other hand, in the firing at 1050 ° C. × 5 hr, formation of a 1.7 μm dense layer was observed.
Further, it is considered that a thick dense layer can be expected in a shorter time at a high temperature of 1100 ° C.
As a matter of course, it is expected that a dense layer can be grown in a shorter time at a temperature exceeding 1100 ° C., but the temperature exceeds the upper limit of the heat resistance of the stainless steel member of the substrate, and oxidative deterioration during firing occurs. Since it becomes remarkable, it is desirable to set it as 1100 degrees C or less.
In addition, when it is 1050 degreeC or more, while the dense layer of 1 micrometer or more grows by heating for 5 hours or more, and the whole coating film can be baked uniformly, it is preferable. Although it does not prevent further baking for a long time, if the entire coating film grows into a dense layer, further heating only promotes oxidative deterioration of the stainless steel member of the substrate. It is preferable to appropriately set the heating time in consideration of the thickness of the film and the thickness of the target dense layer.

[Configuration 5]
Moreover, the coating film formed on the said base material can be formed by the anion electrodeposition coating method.

[Operation effect 5]
As a general film forming method, for example, it can be formed by a wet coating method or a dry coating method. Examples of the wet coating method include a screen printing method, a doctor blade method, a spray coating method, an ink jet method, a spin coating method, a dip coating, an electroplating method, an electroless plating method, and an electrodeposition coating method. Examples of dry coating methods include vapor deposition, sputtering, ion plating, chemical vapor deposition (CVD), electrochemical vapor deposition (EVD), ion beam, laser ablation, and atmospheric pressure plasma. Examples thereof include a film forming method, a low pressure plasma film forming method, and a thermal spraying method. However, the dry coating method is recommended because the manufacturing apparatus is complicated and the manufacturing cost is high.
When a metal oxide film is formed by a wet coating method, the metal oxide itself has almost no binding property, so a mixed solution of metal oxide fine particles and a resin composition is used to form metal oxide fine particles and a resin. A method in which a metal oxide is used as a main component is employed by performing a film forming step for forming a film made of and removing a resin component from the film. In particular, according to the electrodeposition coating method, a film in which a mixed liquid of metal oxide fine particles and a resin composition is attached to the surface of the substrate is formed by performing anion electrodeposition. This coating film is formed by the metal oxide fine particles and the resin composition as main components, and the metal oxide fine particles are aggregated and integrated as the resin component is polymerized. By removing the resin component from the coating, a protective film in which the metal oxide fine particles aggregate to form a coating can be formed. Then, since the obtained protective film can obtain a comparatively thin and uniform coating film compared with dip coating, for example, it is preferable.
Therefore, anion electrodeposition coating is desirable because the coating film is uniformly formed on the entire area of the substrate.

[Configuration 6]
The characteristic configuration of the inter-cell connecting member of the present invention is that it is manufactured by the above-described method for manufacturing the inter-cell connecting member.

[Operation effect 6]
As described above, the inter-cell connection member manufactured by the method for manufacturing an inter-cell connection member is formed by growing a dense layer by firing on a uniform and stable coating film by 1 μm or more. Since it is derived from the coating film, it is highly integrated with the coating film and strongly adheres to the Cr ₂ O ₃ on the substrate surface, so it has high durability against heat reception, and its dense layer suppresses the increase in resistance, Cr scattering Long-term durability can be expected.

[Configuration 7]
The base material may be ferritic stainless steel containing Mn.

[Operation effect 7]
In addition, a combination of using stainless steel containing Mn as the base material and using a spinel type oxide as the main material as a protective film can form a dense layer with high adhesion to the base material, which is stable. Thus, a protective film can be formed and Cr scattering can be suppressed.
In addition, by making Mn content 0.3% or more of the alloy of the base material, it is possible to prevent scattering of Cr by reliably diffusing Mn and forming a dense layer, but the Mn content is high. The base material is preferably 1% or less because it is considered that the oxidation resistance is low.

[Configuration 8]
Moreover, the characteristic structure of the cell for solid oxide fuel cells of this invention exists in the point formed by joining the above-mentioned connection member between cells with an air electrode.

[Operation effect 8]
As described above, the inter-cell connection member manufactured by the method for manufacturing an inter-cell connection member is formed by growing a dense layer by firing on a uniform and stable coating film by 1 μm or more. Since it is derived from the coating film, it is highly integrated with the coating film and strongly adheres to the Cr ₂ O ₃ on the substrate surface, so it has high durability against heat reception, and its dense layer suppresses the increase in resistance, Cr scattering Long-term durability can be expected. Therefore, it is considered that the solid oxide fuel cell using such an inter-cell connecting member can stably expect long-term durability.

  Therefore, since the inter-cell connection member mainly used for the solid oxide fuel cell can be provided with extremely high durability, it is possible to provide an SOFC that can operate stably even after long-term use.

Schematic diagram of solid oxide fuel cell The figure which shows the usage condition of the cell connection member of a solid oxide fuel cell Sectional view of cell connection member test piece with protective film formed Schematic showing the layer structure after firing the coating film formed on the substrate

  Hereinafter, a protective film forming method, a SOFC cell connecting member, and a SOFC cell for forming a protective film on the surface of a base material made of an alloy or oxide containing Cr used in the SOFC of the present invention will be described. Preferred examples are described below, but these examples are described in order to more specifically illustrate the present invention, and various modifications can be made without departing from the spirit of the present invention. The present invention is not limited to the following description.

<Solid oxide fuel cell>
Embodiments of a cell connection member for SOFC and a method for manufacturing the same according to the present invention will be described with reference to the drawings.
The SOFC cell C shown in FIG. 1 and FIG. 2 has an air electrode made of an oxide ion and an electron conductive porous body on one side of an electrolyte membrane 30 made of a dense oxide oxide conductive solid oxide. 31 and a single cell 3 formed by joining a fuel electrode 32 made of an electron conductive porous body to the other surface side of the electrolyte membrane 30.

  Further, the SOFC cell C exchanges electrons with the single cell 3 with respect to the air electrode 31 or the fuel electrode 32, and at the same time, a pair of electronically conductive elements in which grooves 2 for supplying air and hydrogen are formed. The cell connecting member 1 in which the protective film 12 is formed on the base material 11 made of an alloy or oxide (a schematic diagram in the case where the shape is a simple shape having a rectangular cross section is shown in FIG. 3) is appropriately gas at the outer peripheral edge. It has a structure in which the sealing body is sandwiched. And the said groove | channel 2 by the side of the air electrode 31 functions as the air flow path 2a for supplying air to the air electrode 31, because the air electrode 31 and the cell connection member 1 are closely_contact | adhered, on the other hand, fuel The groove 2 on the electrode 32 side functions as a fuel flow path 2 b for supplying hydrogen to the fuel electrode 32 by arranging the fuel electrode 32 and the cell connecting member 1 in close contact with each other.

In addition, when a general material used in each element constituting the SOFC cell C is described, for example, the material of the air electrode 31 is LaMO ₃ (for example, M = Mn, Fe, Co). A perovskite oxide of (La, AE) MO ₃ in which a part of La of Al is substituted with an alkaline earth metal AE (AE = Sr, Ca) can be used. And yttria-stabilized zirconia (YSZ) can be used, and yttria-stabilized zirconia (YSZ) can be used as the material of the electrolyte membrane 30.

  Further, in the SOFC cell C described so far, as the material of the cell connection member 1, an alloy or oxide containing Cr and Mn is used.

In a state where a plurality of SOFC cells C are arranged in a stacked manner, a pressing force is applied in the stacking direction by a plurality of bolts and nuts to form a cell stack.
In this cell stack, the cell connecting members 1 disposed at both ends in the stacking direction may be any one as long as only one of the fuel flow path 2b or the air flow path 2a is formed, and the cells disposed in the other middle. The connecting member 1 may be one in which the fuel flow path 2b is formed on one surface and the air flow path 2a is formed on the other surface. In the cell stack having such a laminated structure, the cell connecting member 1 may be called a separator.
An SOFC having such a cell stack structure is generally called a flat-plate SOFC. In this embodiment, a flat-plate SOFC is described as an example, but the present invention is applicable to SOFCs having other structures.

When the SOFC having such a SOFC cell C is operated, air is supplied through the air flow path 2a formed in the cell connection member 1 adjacent to the air electrode 31, as shown in FIG. In addition, hydrogen is supplied through the fuel flow path 2b formed in the cell connection member 1 adjacent to the fuel electrode 32, and the fuel electrode 32 operates at an operating temperature of, for example, about 800 ° C. Then, the air electrode 31 O ₂ electrons e ^- are reacting with O ^2- is generated, the O ^2- passes through the electrolyte membrane 30 to move to the fuel electrode 32, H ₂ supplied in the fuel electrode 32 Reacts with the O ²⁻ to generate H ₂ O and e ⁻ , so that an electromotive force E is generated between the pair of cell connecting members 1, and the electromotive force E is taken out and used. Can do.

<Cell connection member>
As shown in FIGS. 1 and 3, the cell connection member 1 is configured by providing a protective film 12 on the surface of a substrate 11 for a cell connection member. And it forms in the shape of a groove plate which can be connected, forming the air flow path 2a and the fuel flow path 2b between each said single cell 3. As shown in FIG.

  The protective film 12 is formed as a thick film by electrodeposition coating a base material 11 with a coating film-forming material containing a conductive ceramic material.

<Protective film>
The protective film 12 is formed, for example, on the surface of the base 11 made of ferritic stainless steel (ZMG232L made by Hitachi Metals) containing 22% Cr and about 0.5% Mn, for example, a metal oxide such as ZnCoMnO ₄ . Liquid mixture containing fine particles and anionic resin such as polyacrylic acid in a mass ratio of (metal oxide fine particles: anionic resin) = (0.5: 1) to (1.7: 1) A coating film forming step of forming an unsintered coating film containing metal oxide fine particles as a main component by an anionic electrodeposition coating method, and baking the coating film to resin components in the coating film The fired film is burned off, and the fired film is further fired under the condition that Mn contained in the base material reacts with the paint film component to form Cr ₂ O ₃ formed on the surface of the base material 11. From the metal oxide in close contact with the layer 11a It forms by performing the baking process which forms the protective film 12 which becomes.

  In addition, although the said coating-film formation process was based on the anion electrodeposition coating method, it can also be based on other methods, such as a dip coat and a spray coat.

Although the specific manufacturing method of the said protective film 12 is explained in full detail below, this invention is not limited to a following example.
<Example>
By preparing a test piece provided with a coating film made of a spinel type metal oxide on the surface of the substrate 11 for an interconnector made of the stainless steel material, and performing a heat treatment for heating the test piece at various temperatures for a predetermined time. The coating film was baked (baking step) to form a protective film 12. The protective film 12 was subjected to anion electrodeposition under the condition that the thickness of the protective film was about 5 to 10 μm for each test piece, and an adhesive layer was adhered to the surface of the protective film 12 to perform a heat treatment test. . For each test piece, the thickness of the dense layer 12a occupying the protective film 12 was measured by SEM, and changes in the dense layer 12a due to heat treatment were examined.

<Example 1> (B: Reference)
Using ZnCoMnO ₄ as the metal oxide, a coating film was formed on the substrate by anionic electrodeposition coating, and baked at 1000 ° C. for 2 hours to prepare a sample of the protective film 12. When the cross-sectional shape of the protective film 12 was confirmed, as shown in FIG. 4, the Cr ₂ O ₃ layer 11a was formed on the surface of the substrate 11, and the formed coating film was formed on the Cr ₂ O ₃ layer 11a. It turned out that it forms in the protective film 12 which consists of the dense layer 12a (Mn containing dense layer said to this application) which adheres, and the porous layer of the coating-film surface side. The dense layer 12a had a thickness of about 2 μm.

(Energization test)
When the sample was embedded in an air electrode material and a current test at 1000 ° C. × 200 hr was performed, the initial voltage drop was about 55 mV, the voltage drop increase (deterioration amount) after 200 hr was 3 mV or less, and the resistance increase was It was found that long-term durability can be expected while being sufficiently suppressed.

(Measurement of Cr scattering number)
In addition, when the sample was cut and the cross section was observed with EPMA and the scattering state of Cr was examined, the scattering count number was 2945, and a high Cr scattering suppression effect derived from ZnCoMnO ₄ was exhibited. I understand.

<Example 2> (A)
A sample was formed in the same manner as in Example 1 except that the firing time in Example 1 was 200 hours, and an energization test and the number of Cr scattering were measured. The results are shown in Table 1.

<Comparative Example 3> (D)
A sample was formed in the same manner as in Example 1 except that the firing temperature in Example 1 was changed to 800 ° C., and an energization test was performed. The results are shown in Table 1.

<Examples 4 to 7> (C)
A sample was formed in the same manner as in Example 1 except that the firing temperature and firing time in Example 1 were variously changed, and an energization test was performed. The results are shown in Table 1.

<Example 8> (E)
Using Co _1.5 Mn _1.5 O ₄ as the metal oxide, a coating film was formed on the base material by anionic electrodeposition coating, and baked at 1050 ° C. for 5 hours to prepare a sample of the protective film 12, Example 1 The same test was conducted. The results are shown in Table 1.

<Comparative Example 9> (F)
Using Co _1.5 Mn _1.5 O ₄ as the metal oxide, a coating film was formed on the substrate by anionic electrodeposition coating, and the sample was formed by baking at 1000 ° C. for 2 hours to prepare a sample of the protective film 12. The same test was conducted. The results are shown in Table 1.

<Result>
(About firing time)
In Example 2, it was considered that the firing time was sufficiently long, and Mn contained in the base material was sufficiently reacted with the coating film components, and the coating film was all a dense layer, and the thickness thereof was 7 μm. .
The initial voltage drop is about 55 mV, and the voltage drop increase (deterioration amount) after 200 hours is 3 mV or less, showing the same performance as in Example 1, and the Cr scattering amount being 330 (count). Thus, it was found that when the thickness of the dense layer is increased, a higher Cr scattering suppression effect is exhibited.

(About the composition of the dense layer)
In Example 2, the composition of the dense layer was examined by EDX analysis and found to be Zn: Co: Mn = 0.77: 1.0: 1.64 (molar ratio). In addition, since the initial molar ratio is 1: 1: 1, it turns out that Mn which the quantity increases is derived from the outside.
In addition, when the composition of the porous layer was examined in Examples 5 and 7, the composition of the porous layer was not changed so much (the slight change is relatively different due to the dispersion of the composition or the scattering of the Zn and Co components). This is expected to be due to an increase in the amount of the component of), indicating that this Mn is derived from the base material.

(About firing temperature)
In Comparative Example 3, since the firing temperature was low, it was considered that Mn contained in the base material was not in a condition for reacting with the coating film component, and a dense layer could not be observed.
In addition, since the protective film thus obtained is composed of only a porous layer, in the energization test, the initial voltage drop is about 55 to 60 mV, and the voltage drop increase (deterioration amount) after 2500 hours is 5 mV (evaluation) It is considered that it corresponds to a voltage drop of about 41 mV when converted to an evaluation value of 900 ° C. and 1310 hr, and the long-term durability is considered to be lower than that of Examples 4 to 7. It is done.

(About the firing process)
Further, comparing Examples 1, 5, 7 and Comparative Example 3, it can be seen that the higher the firing temperature, the thicker the dense layer, and the higher the firing process, the faster the dense layer is formed. It can be seen that the condition under which Mn contained in the material reacts with the coating film component may be 1000 ° C. or higher.
Further, when Examples 1, 2, and 4 are compared, it can be seen that a dense layer of 1 μm or more is obtained by setting the firing time to 2 hours or more, and a sufficient Cr scattering prevention effect is exhibited.

(About coating composition)
Comparing Example 1 and Comparative Example 9, it can be seen that the firing conditions for the dense layer thickness to be 1 μm or more differ depending on the composition of the coating film. Moreover, when Example 8 and Comparative Example 9 are compared, even if the composition of the coating film is different, a protective film containing at least one metal oxide selected from Co, Zn, and Mn is formed, and the film thickness is 1 μm or more. As a result, it can be seen that voltage drop due to long-term use is suppressed to a low level, and long-term durability can be improved.

Therefore, since the inter-cell connection member mainly used for the solid oxide fuel cell can be provided with extremely high durability, it is possible to provide an SOFC that can operate stably even after long-term use.
1: Cell connection member 2: Groove 2a: Air flow path 2b: Fuel flow path 3: Single cell 11: Base material 11a: Cr ₂ O ₃ layer 12: Protective film 12a: Dense layer 15: Adhesive layer 30: Electrolyte film 31 : Air electrode 32: Fuel electrode C: Cell for SOFC

Claims (8)

A method for producing an inter-cell connecting member, wherein a protective film made of a metal oxide is formed on a base material made of an alloy or oxide containing Cr and Mn,
On the base material, a coating film forming step for forming an unsintered coating film containing metal oxide fine particles as a main component is performed, and under the condition that Mn contained in the base material reacts with the coating film component, A firing step of firing the coating film is performed, and a Mn-containing dense layer formed by the reaction between the coating film component and Mn in the coating film is formed in close contact with the Cr ₂ O ₃ layer formed on the substrate surface. And a method for producing an inter-cell connection member, wherein the thickness of the Mn-containing dense layer is grown to 1 μm or more.   The method for manufacturing an inter-cell connection member according to claim 1, wherein the protective film contains at least one metal oxide selected from Co, Zn, and Mn. In the firing step, the protective film includes Zn _x (Co _y Mn _(1-y) ) _(3-x) O ₄ (0 <x <1, 0 <y × (3-x) ≦ 2). The method for producing an inter-cell connection member according to claim 2, wherein the coating film is baked at 1000 ° C. to 1100 ° C. for 2 hours or more. The method for producing an inter-cell connection member according to claim 2, wherein the protective film contains Co _1.5 Mn _1.5 O ₄ , and the coating film is baked at 1050 ° C. or higher and 1100 ° C. or lower in the baking step.   The method for producing an inter-cell connecting member according to any one of claims 1 to 4, wherein the coating film formed on the substrate is formed by an anionic electrodeposition coating method.   The inter-cell connection member manufactured by the manufacturing method of the inter-cell connection member according to claim 1.   The inter-cell connection member according to claim 6, wherein the base material is ferritic stainless steel containing Mn.   A cell for a solid oxide fuel cell obtained by joining the inter-cell connecting member according to claim 6 or 7 to an air electrode.

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