JP2012174674A - Alkali-free glass seal material for solid oxide fuel battery cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali-free glass seal material for a solid oxide fuel battery cell.SOLUTION: An alkali-free glass seal material 10 comprises a glass composition including 50-85 wt% of BaO, 4-20 wt% of SiO, and 1-15 wt% of AlOas essential constituents, and at least one of 0-20 wt% of BOand 0-30 wt% of TiO. The alkali-free glass seal material 10 is arranged to: have at least one of barium silicate crystallines, BaSiO, BaSiO, and BaSiOin its glass matrix; have a high melting/softening point, and therefore have the difficulty in melting/softening in the operating temperature region of a SOFC 12, 700-1200°C approximately; include no alkaline component; have a thermal expansion coefficient of 9-13×10/K; and allow the SOFC 12 to be joined to a peripheral member such as a gas pipe 24 at a joining temperature of 700-900°C approximately.

Description

  The present invention relates to a sealing material used for joining components of a solid oxide fuel cell, and more particularly to an alkali-free glass-based sealing material for a solid oxide fuel cell that does not contain an alkali component.

  Solid oxide fuel cells (SOFCs), also called solid electrolyte fuel cells, are operated at relatively high temperatures and do not require reaction promoters such as catalysts, reducing costs. Since the high-temperature exhaust gas can be reused, the overall efficiency can be increased, and the output density is high, so that the size can be reduced.

A solid oxide fuel cell includes a dense solid electrolyte made of an oxygen ion conductive ceramic body that functions as an oxide ion conductor, and an air electrode (porous layer) that is provided on one side and functions as a cathode. And a fuel electrode (porous layer) provided on the other surface and functioning as an anode. A fuel gas containing hydrogen is supplied to the fuel electrode side, and a gas containing oxygen is supplied to the air electrode side. As a result, in the battery cell, oxygen is electrochemically reduced at the cathode to oxygen ions and reaches the anode through the electrolyte membrane. At the anode, hydrogen is oxidized by the oxygen ions and electrons are released to the external load to be electrically charged. Energy is output. That is, when the fuel gas is electrochemically oxidized, the chemical energy of the fuel gas is directly converted into electric energy and taken out. Therefore, it has high theoretical efficiency, excellent quietness, and low emissions of NO _X , SO _X , particulate matter (PM), etc. that cause air pollution. Has been. For example, it is expected to be used as a distributed power source or a thermoelectric supply system for homes.

  In the solid oxide fuel cell thus configured, for example, yttria stabilized zirconia (YSZ) having a good balance of ion conductivity, stability and price is widely used as the solid electrolyte membrane. Further, as the solid electrolyte membrane becomes thinner, the ion permeation rate tends to increase and the performance tends to improve. For this reason, in recent years, development of anode-supported solid oxide fuel cells in which a solid electrolyte membrane is formed as a thin film on a fuel electrode functioning as an anode has been progressing. A fuel electrode that functions as an anode is generally a mixture of NiO and YSZ. In order to reduce the difference in thermal expansion from the solid electrolyte membrane while taking advantage of the conductivity of Ni, it is reduced at the time of use and Ni + YSZ. Is done.

  By the way, as research on practical application of solid oxide fuel cells progresses, it has been required to reduce gas leakage as much as possible in order to improve durability, reliability, and efficiency. . In a conventional small-scale evaluation, even if a gas leak occurs in a solid oxide fuel cell, there is no problem in obtaining basic data because the fuel gas reacts with oxygen in the air. However, since gas leaks cause a reduction in fuel gas utilization efficiency and local heat distribution unevenness, they have had a great impact on long-term practical use. Therefore, as a fuel gas leak prevention, attention has been paid to the problem of sealing of the fuel gas between the solid oxide fuel cells and between the solid oxide fuel cells and the gas pipe. It was.

  On the other hand, Patent Documents 1 and 2 propose a sealing material in which leucite or cristobalite crystals are precipitated in a glass matrix. Such a glass-based sealing material has a thermal expansion coefficient close to that of a solid oxide fuel cell or a ceramic gas pipe, and is difficult to flow at an operating temperature of, for example, 800 to 1000 ° C. Sealing performance can be obtained. However, with such a glass-based sealing material, stack evaluation of fuel cells has become possible. However, since the glass matrix contains an alkali metal component such as Na and K, depending on the bonding structure, a solid at the bonding interface can be obtained. It easily reacts with oxide fuel cells and metal gas pipes, and may cause deterioration.

In addition to the glass-based sealing material in which leucite and cristobalite crystals are precipitated in the glass matrix, sealing materials having a thermal expansion coefficient of 9 to 13 × 10 ⁻⁶ / K are disclosed in Patent Documents 3, 4, 5 In addition, an alkali metal component such as Na or K that easily reacts with a metal gas pipe is included as an essential component, and when the reaction occurs, the thermal expansion coefficient of the reaction portion is different from that of other portions. In addition to being a cause of peeling degradation during heat cycles, there is a risk that reactants with high environmental impact such as potassium dichromate may be generated by the reaction of chromium and alkali metal components in stainless steel. .

JP 2009-199970 A JP 2009-127804 A JP 2004-039573 A Special table 2008-527680 Special table 2008-529256

On the other hand, it is conceivable that a special stainless alloy having high reaction durability is used for gas piping such as a separator or an interconnector. However, such a special stainless alloy is expensive and difficult to be practically used. However, the problem that the reaction proceeds by using for a long time has not been sufficiently solved. Therefore, an alkali-free glass-based sealing material having low reactivity with respect to, for example, ferritic stainless steel represented by SUS430, which is relatively inexpensive and widely used, is desired. That is, it has a thermal expansion coefficient of 9 to 13 × 10 ⁻⁶ / K, does not contain an alkali metal component such as Na and K, and can be suitably joined at a joining temperature of about 700 to 900 ° C. A material is desired.

The present invention has been made against the background of the above circumstances, and the object is to have a thermal expansion coefficient of 9 to 13 × 10 ⁻⁶ / K and an alkali metal component such as Na or K. It is providing the alkali-free glass-type sealing material for solid oxide fuel cells which can be joined suitably at the joining temperature of about 700-900 degreeC.

In order to achieve such an object, the subject matter of the first invention is (a) an alkali-free glass-based sealing material for solid oxide fuel cells for airtightly joining solid oxide fuel cells. (B) 50 to 85 wt% (wt%) BaO, 4 to 20 wt% SiO ₂ and 1 to 15 wt% Al ₂ O ₃ as essential components, and 0 to 20 wt% It includes a glass having a composition having at least one of B ₂ O ₃ and 0 to ₃₀ wt% of TiO ₂ .

  The gist of the second invention is that, in the first invention, (c) the glass matrix of the glass contains barium silicate crystals.

The gist of the third invention is that, in the first or second invention, (d) the glass has a thermal expansion coefficient of 9 to 13 × 10 ⁻⁶ / K.

  The gist of the fourth invention is the use of the alkali-free glass-based sealing material according to any one of the first to third inventions, and the solid oxide fuel cell and the solid oxide fuel. It is a solid oxide fuel cell characterized in that peripheral members of battery cells are joined.

  Further, the gist of the fifth invention is that the sealing material according to any one of the first invention to the third invention is used, and the periphery of the solid oxide fuel cell and the solid oxide fuel cell. The present invention resides in a method for manufacturing a solid oxide fuel cell, characterized in that members are joined.

According to the alkali-free glass-based sealing material for a solid oxide fuel cell of the first invention, 50 to 85 wt% BaO, 4 to 20 wt% SiO ₂ and 1 to 15 wt% Al ₂ O ₃ are essential components. The Ba-based alkali-free glass having a composition and having at least one of 20 wt% or less of B ₂ O ₃ and 0 to ₃₀ wt% of TiO ₂ constitutes a thermal expansion coefficient of 9 to 13 × 10 6. ⁻⁶ / K, which does not contain alkali metal components such as Na and K, and can obtain a sealing material capable of joining the solid oxide fuel cell and its peripheral members at a joining temperature of about 700 to 900 ° C. It is done. Moreover, since alkali metal components such as Na and K are not included, there is an advantage that reaction with peripheral members such as a stainless steel gas pipe and a separator is suppressed.

  According to the second invention, the glass matrix of the glass contained in the alkali-free glass-based sealing material contains barium silicate crystals, so that while maintaining high thermal expansion, a stainless steel gas pipe or There is an advantage that the reaction with the separator is suppressed.

According to the third invention, the glass contained in the alkali-free glass-based sealing material has a high coefficient of thermal expansion of 9 to 13 × 10 ⁻⁶ / K. The difference in thermal expansion coefficient of the fuel cell is reduced, and the phenomenon of peeling deterioration at the joint between the solid oxide fuel cell and its peripheral members is preferably eliminated.

  Moreover, 4th invention uses the alkali-free glass-type sealing material of any one of the said 1st invention thru | or 3rd invention, and the peripheral member of the said solid oxide fuel cell and its solid oxide fuel cell Are joined by a non-alkali glass-based sealing material that does not contain an alkali component, and for example, with a peripheral member such as a stainless steel gas pipe or a separator. There is an advantage that the reaction at the junction between the two is suppressed.

  Further, a fifth invention is a solid that joins the solid oxide fuel cell and a peripheral member of the solid oxide fuel cell using the sealing material according to any one of the first to third inventions. Since it is a manufacturing method of an oxide fuel cell, it is joined by a non-alkali glass-based sealing material that does not contain alkali metal components such as Na and K. For example, peripheral members such as stainless steel gas pipes and separators There is an advantage that the reaction at the joint between the two is suppressed.

Here, it is preferable that the alkali-free glass-based sealing material be hermetically bonded to at least one solid oxide fuel cell and a gas pipe in a solid oxide fuel cell or a stacked battery pack. This is a glass composition having a composition in which barium silicate crystals BaSi ₄ O ₉ , Ba ₂ Si ₃ O ₈ and / or Ba ₃ Si ₅ O ₁₃ can be precipitated in a glass matrix. The amount of precipitation of the barium silicate crystals can be appropriately adjusted depending on the content (composition ratio) of essential constituents in the glass composition.

BaO and SiO ₂ in the glass composition of the alkali-free glass-based sealing material are components constituting the barium silicate crystals BaSi ₄ O ₉ , Ba ₂ Si ₃ O ₈ , and Ba ₃ Si ₅ O ₁₃ , and a glass matrix Is a main component constituting the skeleton. An excessively high content of BaO and SiO ₂ is not preferable because the melting point or softening point is lowered. On the other hand, if the content of BaO and SiO ₂ is too small, the amount of barium silicate crystals deposited decreases and water resistance and chemical resistance decrease. BaO is 50 to 85 wt% of the content is preferably SiO ₂ is the content of 4～20Wt%, BaO is 55～85Wt% of content, that SiO ₂ is the content of 8～20Wt% Further preferred.

Al ₂ O ₃ in the glass composition of the alkali-free glass-based sealing material is a component that contributes to glass fluidity and adhesion stability. If its content is too small, glass fluidity and adhesion stability are reduced. It becomes difficult to form a glass layer having a uniform thickness, that is, a glass matrix. On the other hand, if the amount is too large, the chemical stability of the joint is impaired. After all, the content of Al ₂ O ₃ is preferably 1 to 15 wt%.

B ₂ O ₃ and TiO _{2 in} the glass composition of the alkali-free glass-based sealing material need to contain at least one of them, and the other is an optional additive component that may be 0 wt%. B ₂ O ₃ is considered to contribute to glass fluidity, adhesion stability, or wettability in the same manner as Al ₂ O _3, and contributes to the multi-component and improved meltability of the glass matrix. If the content of B ₂ O ₃ is too large, the acid resistance is lowered. Therefore, a content in the range of 0 to 20 wt%, that is, 20 wt% or less is preferable. If the content of TiO ₂ is too large, the coefficient of thermal expansion decreases and the occurrence of cracks is caused. Therefore, a content in the range of 0 to 30 wt%, that is, 30 wt% or less is preferable.

Also, components other than the above oxide components that are not essential for the practice of the present invention, such as ZnO, Li ₂ O, Bi ₂ O ₃ , SrO, SnO, SnO ₂ , CuO, Cu ₂ O, ZrO ₂ , La _2. O ₃ can be appropriately added as necessary. Preferably, the thermal expansion coefficient of the glass of the alkali-free glass-based sealing material approximates the thermal expansion coefficient between the objects to be joined, for example, the gas tube and the fuel electrode and / or the solid electrolyte membrane of the solid oxide fuel cell. Thus, the crystal-containing glass can be adjusted by adjusting the content of any of the above components. For example, when the gas pipe and the solid electrolyte are composed of a dense body of zirconia oxide such as YSZ and the gas pipe and the solid electrolyte are joined in an airtight manner, the thermal expansion of the zirconia oxide is performed. The composition may be adjusted to approximate the coefficient. For example, the composition is such that the average value of the thermal expansion coefficient from room temperature (25 ° C.) to the glass softening point (eg, 450 ° C.) based on the differential expansion method (TMA) is 9 to 12 × 10 ⁻⁶ / K. Can be adjusted.

  The alkali-free glass-based sealing material is melted after the various oxide components capable of precipitating barium silicate crystals are mixed at a predetermined ratio and maintained at a predetermined temperature after pulverization to precipitate barium silicate crystals in the glass matrix. The crystallization treatment is performed, and then the powdered glass composition having a predetermined average particle diameter of, for example, 0.1 to 10 μm is obtained by pulverization and sieving, and fine powder is obtained by pulverization and drying using a ball mill. Is obtained. The alkali-free glass-based sealing material thus obtained is kneaded with a binder and a solvent to form a paste having a predetermined viscosity suitable for the coating operation.

  The said binder consists of cellulose or its derivative (s), for example, and is contained in 5-20 wt% of the whole paste. This binder is, for example, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, carboxyethylcellulose, carboxymethylethylcellulose, cellulose, ethylcellulose, methylcellulose, ethylhydroxyethylcellulose, and salts thereof.

  Moreover, the said solvent consists of an ether solvent, an ester solvent, a ketone solvent, or another organic solvent, for example, and is contained in 1-40 wt% of the whole paste. This solvent is, for example, ethylene glycol and diethylene glycol derivatives, high-boiling organic solvents such as toluene, xylene, terpineol, or a mixture of two or more thereof.

  The alkali-free glass-based sealing material is used in the same manner as a conventional bonding material. For example, the paste is applied in a paste-like state to the joined portion where the solid oxide and / or the fuel electrode and the gas pipe of the solid oxide fuel cell that is the object to be joined are brought into contact with each other. After the drying, the operating temperature range of the solid oxide fuel cell or higher temperature range where the glass does not flow out. For example, when the operating temperature range is 700 to 1000 ° C, it is 1200 to 1300 ° C. By firing, the joined portions of the solid electrolyte and / or the fuel electrode and the gas pipe that are brought into contact with each other are airtightly joined. In the joined portion joined in this way, the fuel gas is supplied to the fuel electrode of the solid oxide fuel cell without leaking in the gas pipe. In addition, since the alkali-free glass-based sealing material used for this bonding exhibits flexibility in the operating temperature range of the solid oxide fuel cell, stress is applied to the above-mentioned joint due to reductive expansion associated with the contact with the fuel gas. Even if it occurs, the airtightness and durability of the joint are enhanced.

  The alkali-free glass-based sealing material can be applied to various structures such as a flat plate type, a cylindrical type, or a flat tubular type solid oxide fuel cell, regardless of their shape or size. This alkali-free glass-based sealing material can also be applied to objects to be bonded that are difficult to perform pressure sealing or diffusion bonding. For example, the present invention can also be suitably applied to an anode-supported solid oxide fuel cell in which a fuel electrode is used as a support substrate and a thin solid electrolyte of about 100 μm is formed on the fuel electrode.

The solid electrolyte may be composed of a material that can form a dense layer having high oxygen ion conductivity and no gas permeability in any of an oxidizing atmosphere, that is, an air atmosphere and a reducing atmosphere, that is, a fuel gas atmosphere. What consists of a thing is used suitably. Examples of such zirconia-based oxides include zirconia (YSZ) stabilized with yttria (Y ₂ O ₃ ), zirconia (CSZ) stabilized with calcia (CaO), and scandia (Sc ₂ O ₃ ). A typical example is zirconia (SSZ).

The materials of the fuel electrode and the air electrode are the same as those of the conventional solid oxide fuel cell, and are not particularly limited. As the fuel electrode, for example, a cermet of nickel (Ni) and zirconia (YSZ), a cermet of ruthenium (Ru) and zirconia (YSZ), or the like is preferably used. As the air electrode, a lanthanum cobaltate (LaCoO ₃ ) -based or lanthanum manganate (LaMnO ₃ ) -based perovskite oxide is preferably used. A layered porous body made of these materials and having gas permeability is used as a fuel electrode and an air electrode.

  The production of the solid oxide fuel cell and the stack thereof is performed in the same process as the conventional solid oxide fuel cell, and no special process is required. A solid electrolyte, a fuel electrode, and an air electrode can be formed from the above materials by various conventional methods.

  The gas pipe connected to the solid oxide fuel cell is made of a material similar to the conventional one for guiding the fuel gas, and has a shape and dimension corresponding to the joining with the fuel electrode, for example, a straight tube or an arc tube. Composed. For example, the gas pipe is made of a dense body of ceramics made of the same material as the fuel electrode and the solid electrolyte, for example, a zirconia-based oxide such as YSZ, in order to enhance the ease of joining.

An anode-supported solid oxide fuel cell to which an alkali-free glass-based sealing material according to an embodiment of the present invention is applied, and a gas pipe hermetically joined to the anode-supported solid oxide fuel cell Is a perspective view schematically showing. It is the side view seen from the gas pipe side of the anode support type solid oxide fuel cell of FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2 for explaining the configuration of the anode-supported solid oxide fuel cell in FIG. 2. It is a figure explaining the manufacturing process of the alkali free glass-type sealing material of this invention. It is a figure explaining the manufacturing process of the anode support type solid oxide fuel cell of Drawing 1 thru / or Drawing 3 to which the alkali free glass system sealing material of the present invention was applied. It is sectional drawing explaining the structure of the anode support type solid oxide fuel cell used for evaluation of sealing material paste, ie, SOFC for evaluation. FIG. 7 is a chart showing evaluations when ten types of evaluation SOFCs of FIG. 6 are prepared and leakage tests are performed. Another anode-supported solid oxide fuel cell to which an alkali-free glass-based sealing material according to an embodiment of the present invention is applied, and the anode-supported solid oxide fuel cell are hermetically bonded to the anode-supported solid oxide fuel cell It is sectional drawing which shows a gas pipe typically, Comprising: It is a figure corresponded in FIG. Another anode-supported solid oxide fuel cell to which an alkali-free glass-based sealing material according to an embodiment of the present invention is applied, and the anode-supported solid oxide fuel cell are hermetically bonded to the anode-supported solid oxide fuel cell It is a perspective view which shows a gas pipe typically, Comprising: It is a figure corresponded in FIG.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are simplified or modified schematic diagrams as appropriate, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a perspective view showing a configuration of a solid oxide fuel cell (hereinafter referred to as “SOFC”) 12 to which an alkali-free glass-based sealing material 10 according to an embodiment of the present invention is applied. FIG. 2 is a sectional view for explaining the structure of the SOFC 12. 3 is a sectional view taken along line III-III in FIG. In FIGS. 1 and 2, the sealing material 10 is not shown in order to clearly show the structure of the SOFC 12.

  The SOFC 12 is formed into a flat box shape having an internal space 14 through which a fuel gas FG containing well-known hydrogen such as hydrogen gas, methane gas, natural gas, or a reformed gas thereof circulates, and is porous. A fuel electrode 16 composed of a conductive ceramic body that can function as an anode, that is, a sintered body, and a pair of upper and lower surfaces 16a and 16b in opposite directions of the fuel electrode 16 are fixed to each other in layers by sintering. A dense layered solid electrolyte membrane 18 made of an oxygen ion conductive ceramic body functioning as an ion conductor, and fixed to each of the solid electrolyte membranes 18 by sintering, and is porous and serves as a cathode The air electrode 20 is composed of a conductive ceramic body capable of functioning. The air electrode 20 is exposed to the outside or is positioned in an air duct (not shown) so as to be always in contact with air. The pair of upper surface 16a and lower surface 16b of the fuel electrode 16 having a flat box shape has a rectangular shape, and the pair of solid electrolyte membranes 18 has a rectangular pattern slightly smaller than the pair of upper surface 16a and lower surface 16b. The air electrode 20 is fixed on the pair of solid electrolyte membranes 18 in a rectangular pattern slightly smaller than the pair of solid electrolyte membranes 18.

  In the SOFC 12, the solid electrolyte membrane 18 has a tendency that the ion permeation rate increases and the performance improves as the thickness of the solid electrolyte membrane 18 becomes thinner. And formed as a thin film and supported by the fuel electrode 16. That is, the SOFC 12 of this example is an anode-supported solid oxide fuel cell.

  The fuel electrode 16 is made of, for example, a mixture of NiO and YSZ and is porous. In order to reduce the difference in thermal expansion from the solid electrolyte membrane 18 while taking advantage of the conductivity of Ni, the fuel electrode 16 is subjected to reduction treatment at the time of use and Ni + YSZ. It is said. As the fuel electrode 16, for example, a cermet of nickel (Ni) and zirconia (YSZ), a cermet of ruthenium (Ru) and zirconia (YSZ), or the like is preferably used.

The solid electrolyte membrane 18 may be made of a material that can form a dense layer having high oxygen ion conductivity and no gas permeability in any of an oxidizing atmosphere, that is, an air atmosphere and a reducing atmosphere, that is, a fuel gas atmosphere. A dense sintered body having a low density of gas permeability and high ion permeability is preferably used. For example, yttria-stabilized zirconia (YSZ) having a good balance of ion conductivity, stability and price is preferably used. Further, as the zirconia-based oxide, for example, stabilized with zirconia (YSZ) stabilized with yttria (Y ₂ O ₃ ), zirconia (CSZ) stabilized with calcia (CaO), or scandia (Sc ₂ O ₃ ). Zirconia (SSZ) is used.

The air electrode 20 is composed of a lanthanum cobaltate (LaCoO ₃ ) -based or lanthanum manganate (LaMnO ₃ ) -based perovskite oxide, as in the conventional solid oxide fuel cell, and is 100 μm or less, for example 10 to 10 μm. It is used as a layered porous sintered body having a gas permeability and a film thickness of about 50 μm.

  The pair of side surfaces 16c and 16d in the opposite directions of the fuel electrode 16 are formed with through holes 22 communicating with the internal space 14, respectively, and a stainless steel or ceramic gas for supplying the fuel gas FG. The tube 24 has its end surface 24a abutted against the pair of side surfaces 16c and 16d and communicates with the inner space 14 of the fuel electrode 16 through the through hole 22, and the end of the gas tube 24 and the side surface 16c of the fuel electrode 16 and The side surfaces 16c and 16d are hermetically bonded and sealed by the non-alkali glass-based sealing material 10 applied and melted between 16d. Similarly, the solid electrolyte membrane 18 fixed on the pair of upper surface 16a and the lower surface 16b of the fuel electrode 16 and the periphery of the fuel electrode 16 and the pair of upper surface 16a and the lower surface 16b are applied and melted there. It is sealed with a non-alkali glass-based sealing material 10. In addition, the gap between the peripheral edge of the fuel electrode 16 and the peripheral edge of the air electrode 20 fixed thereon is sealed with an alkali-free glass-based sealing material 10 applied and melted as necessary. The other surface of the fuel electrode 16 may be sealed with a non-alkali glass-based sealing material 10 applied and melted as necessary.

  In the SOFC 12 configured as described above, the fuel gas FG containing hydrogen is supplied to the internal space 14 of the fuel electrode 16 through the gas pipe 24 in the operating temperature range of about 700 to 1200 ° C., preferably 800 to 1000 ° C. When a gas OG containing oxygen is supplied to the air electrode 20 side, oxygen is electrochemically reduced to oxygen ions at the air electrode 20 that functions as a cathode, and the fuel electrode 16 that functions as an anode through the electrolyte membrane 18. Where hydrogen is oxidized by oxygen ions, electrons are emitted to the external load, and electric energy is output. That is, when the fuel gas FG is electrochemically oxidized, the chemical energy of the fuel gas FG is directly converted into electric energy and extracted.

The alkali-free glass-based sealing material 10 shown in FIG. 3 is shown as molten glass remaining after firing, but is in a paste form before firing. The glass contained in the sealing material 10 has barium silicate crystals BaSi ₄ O ₉ and Ba ₂ Si ₃ O so as to have a high melting point or a high softening point that is difficult to soften or melt in the operating temperature range of SOFC 12 of about 700 to 1200 ° C. ₈ and Ba ₃ Si ₅ O _{13 in} the glass matrix, without any alkali component, having a thermal expansion coefficient of 9 to 13 × 10 ⁻⁶ / K and about 700 to 900 ° C. 50-85 wt% (wt%) BaO, 4-20 wt% SiO ₂ and 1-15 wt% so that the SOFC 12 and the gas pipe 24 as a peripheral member can be joined at the joining temperature. The composition includes Al ₂ O ₃ as an essential component and includes at least one of 20 wt% or less of B ₂ O ₃ and 30 wt% or less of TiO ₂ .

  Below, the manufacturing method of the said sealing material 10 is demonstrated using FIG. 4, and the manufacturing method of the said SOFC12 is demonstrated using FIG.

In FIG. 4, in the glass material preparation step S1, 50 to 85 wt% BaO, 4 to 20 wt% SiO ₂ powder, 1 to 15 wt% Al ₂ O ₃ powder, and 20 wt% or less B ₂ O. _Three powders and at least one of 30 wt% or less TiO ₂ powder are weighed and mixed. Next, in the mixing step S2, the glass material prepared in the glass material preparation step S1 is mixed for several hours to several tens of hours using a wet ball mill, and in the drying step S3, the glass material mixed in the mixing step S2 is dried. Let In the melting step S4, the glass material that has undergone the drying step S3 is heated to 1000 to 1500 ° C. in a crucible to be melted or melted.

Next, in the crystallization treatment step S5, the glass material melted in the melting step S4 is heated very slowly at a temperature increase rate of 1 to 5 ° C./min between room temperature and 100 ° C., and subsequently 800 to 1000 ° C. Is maintained for 30 to 60 minutes in the maximum temperature range, and then a crystallization treatment is performed to cool slowly. As a result, at least one of barium silicate crystals BaSi ₄ O ₉ , Ba ₂ Si ₃ O ₈ , and Ba ₃ Si ₅ O ₁₃ is precipitated in the glass matrix. In the subsequent pulverization step S6, the crystal-containing glass obtained in the crystallization treatment step S5 is pulverized using a dry ball mill and classified using a sieve, and contains powdery crystals having an average particle size of 0.1 to 10 μm. A glass composition is obtained. Further, if necessary, the powdery crystal-containing glass composition is further pulverized using a wet ball mill so that the average particle diameter applicable to the paste is obtained and the basic composition of the alkali-free glass-based sealing material 10 is obtained.

  In the paste material preparation step S7, in order to obtain a pasted alkali-free glass-based sealing material 10, 40 to 94 wt% of the powdery crystal-containing glass composition, cellulose such as hydroxycellulose, ethylcellulose and / or the like Weigh 5 to 20 wt% of a binder, 1 to 40 wt% of a solvent having a high boiling point such as ethylene glycol and diethylene glycol derivatives, toluene, terpineol, or a combination thereof, and an appropriate amount of dispersant. Mix together. In the kneading step S8, for example, using a paste kneader such as a three-roller device, the paste material prepared in the paste material preparation step S7 is kneaded for a predetermined time to be homogenized and pasted into a non-alkali glass-based sealing material. Get 10. Next, in the adjustment step S9, the paste viscosity and the like are adjusted by a well-known method.

  FIG. 5 is a diagram for explaining a manufacturing process of the SOFC 12 that is the anode-supported solid oxide fuel cell shown in FIGS. 1 to 3. In the anode forming step S11, for example, zirconia (YSZ) powder having an average particle diameter of about 0.1 to 10 μm, NiO powder having an average particle diameter of about 1 to 10 μm, a binder, a dispersant, and a solvent are mixed at a predetermined ratio. The prepared slurry-like fuel electrode forming material is adjusted. Then, a flat plate having a predetermined thickness is formed from the slurry-like fuel electrode forming material by dehydration using a filter press, and the flat plate is assembled to form a hollow box-shaped molded body, or directly by hollow molding. A shaped molded body is formed. And this molded object is dried as needed.

  Next, in the solid electrolyte membrane forming step S12, for example, a slurry-like solid electrolyte forming material in which zirconia (YSZ) powder having an average particle diameter of about 0.1 to 10 μm, a binder, a dispersant, and a solvent is mixed is prepared. The slurry-like solid electrolyte forming material is not applied to the surface of the fuel electrode having the predetermined shape by coating or printing on the upper and lower surfaces of the hollow box-shaped molded body with a film thickness of 100 μm or less, for example, about 10 to 50 μm. A fired solid electrolyte membrane is formed in layers with a predetermined area. And this unbaked solid electrolyte membrane is dried as needed. Subsequently, in the fuel electrode firing step S13, a molded body of the fuel electrode and an unfired solid electrolyte membrane formed in a film shape on the molded body are subjected to a predetermined firing temperature, for example, a temperature of about 1200 to 1400 ° C. Bake in the atmosphere. As a result, a dense solid electrolyte membrane 18 is formed on the upper surface 16 a and the lower surface 16 b of the porous fuel electrode 16.

In the subsequent air electrode forming step S14, for example, a slurry-like air electrode forming material in which a lanthanum manganate (LaMnO ₃ ) powder having an average particle diameter of about 1 to 10 μm, a binder, a dispersant, and a solvent is mixed in a predetermined ratio is prepared. To do. By applying or printing the slurry-like air electrode forming material on the solid electrolyte membrane 18 after firing to a thickness of 100 μm or less, for example, about 10 to 50 μm, the unfired air electrode is equivalent to the solid electrolyte membrane 18 or It is formed in a layer with a slightly smaller area. In the air electrode firing step S15, the air electrode thus formed on the solid electrolyte membrane 18 is air dried at a firing temperature lower than the firing temperature of the solid electrolyte membrane, for example, about 1000 to 1200 ° C. after predetermined drying. Bake in. As a result, a porous and conductive air electrode 20 is formed on the dense solid electrolyte membrane 18, and the SOFC 12, which is an anode supported solid oxide fuel cell shown in FIGS. Is done.

  In the assembling step S16, the end surface 24a of the gas pipe 24 for guiding the fuel gas FG is brought into contact with the pair of side surfaces 16c and 16d of the fuel electrode 16 of the SOFC 12 and through the through hole 22 with the internal space 14 of the fuel electrode 16. Positioning and assembling are performed by appropriately using an assembly jig (not shown) so as to communicate with each other. The gas pipe 24 is composed of a ceramic made of the same material as the fuel electrode and the solid electrolyte, for example, a dense body of a zirconia-based oxide such as YSZ, in order to enhance the ease of joining. Other materials may be used.

  In the sealing material application step S17, among the assemblies thus assembled, the end of the gas pipe 24 and the side surfaces 16c and 16d of the fuel electrode 16 with which the end surface 24a abuts are shown in FIG. The paste-form non-alkali glass-based sealing material 10 manufactured by the process is applied at a predetermined thickness using a coating apparatus such as a dispenser, and the drying process S18 is performed at a temperature of 60 to 100 ° C., and the process is performed at a temperature of 80 ± 10 ° C. The pasted alkali-free glass-based sealing material 10 is dried. Thereby, a substance having a low volatilization temperature, such as a solvent, is removed from the pasted alkali-free glass-based sealing material 10.

  Next, in the sealing material firing step S19, the operating temperature range of the SOFC 12 is operated so that the assembly to which the alkali-free glass-based sealing material 10 is applied is difficult to soften in the operating temperature range of the SOFC 12, that is, the operating temperature range. Firing is performed in a temperature range equal to or higher than the temperature range. For example, when the SOFC 12 is used in a relatively low temperature operating range of 700 to 1000 ° C., it is fired at, for example, 800 to 1200 ° C., and when the SOFC 12 is used in a relatively high operating temperature range of up to 1200 ° C., for example, 1200 Bake at ~ 1300 ° C. As a result, the stainless steel or ceramic gas pipe 24 for supplying the fuel gas FG has its end face 24a in contact with the pair of side faces 16c and 16d and through the through hole 22 with the internal space 14 of the fuel electrode 16. In a state of communication, the non-alkali glass sealing material 10 applied and melted between the end of the gas pipe 24 and the side surfaces 16c and 16d of the fuel electrode 16 is airtightly joined to the side surfaces 16c and 16d, respectively. The

Here, the leak test conducted for confirming the sealing performance of the alkali-free glass-based sealing material 10 and the results thereof will be described below. FIG. 6 is a cross-sectional view showing the evaluation SOFC 30 created for this leak test. First, a slurry fuel in which a binder, a dispersant, and a solvent are added to and mixed with yttria-stabilized zirconia (YSZ) powder having an average particle diameter of about 1 μm and NiO powder having an average particle diameter of about 3 μm. The electrode forming material was injected into a circular pattern formed on a metal mask, for example, and dried to form a circular sheet-shaped fuel electrode molded body having a thickness of 20 mmφ × 1 mm and dried. Next, a slurry-like solid electrolyte forming material prepared by adding a binder, a dispersant, and a solvent to yttria-stabilized zirconia (YSZ) powder having an average particle size of about 1 μm is mixed with the circular sheet-shaped fuel electrode molded body. On top of this, a circular pattern having a thickness of 16 mmφ × 100 μm or less, for example, 10 to 50 μm, was printed, dried, and then fired at a temperature of 1200 to 1400 ° C. As a result, the solid electrolyte membrane 34 fixed on the disk-shaped fuel electrode 32 is obtained. Next, a slurry-like air electrode forming material prepared by adding a binder, a dispersant, and a solvent to a powder of lanthanum manganate La _0.5 Sr _0.5 CoO ₃ having an average particle diameter of about 1 to 10 μm, Printing is performed in a circular pattern having a thickness of 10 mmφ × 100 μm or less, for example, 10 to 50 μm, on the solid electrolyte membrane 34 after firing, and after drying, at a firing temperature lower than the firing temperature of the solid electrolyte membrane, for example, about 1000 to 1200 ° C. Baking in air. Thus, an anode-supported solid oxide fuel cell having a basic structure similar to that of the SOFC 12 and comprising a sintered body in which the solid electrolyte membrane 34 and the air electrode 36 are sequentially laminated on the disk-shaped fuel electrode 32. The evaluation SOFC 30 is obtained.

  Next, ten types of test sealing materials g1 to g10 having compositions corresponding to the sample numbers 1 to 10 in FIG. 7 were prepared through the same steps as shown in FIG. As shown in FIG. 6, the fuel electrode 32 and the solid electrode are formed at opposite end surfaces of a pair of cylindrical gas pipes 38 and 40 made of stainless steel SUS430 and having the same outer diameter as the disk-shaped fuel electrode 32. With the peripheral edge of the electrolyte membrane 34 sandwiched, the end portions of the cylindrical gas tubes 38 and 40 are applied using the paste-like test sealing materials g1 to g10, dried at 80 ° C., and then 850 ° C. Ten types of test samples T1 to T10 shown as representative in FIG. 7 were prepared by melting and sealing by heating. And the leak test shown below was done about those 10 types of test samples T1 to T10.

In the leak test, nitrogen gas containing 3% by volume of fuel gas (methane gas) FG is supplied to the cylindrical gas pipe 40 on the fuel electrode 32 side for one hour while being heated to 800 ° C. for each of the test samples T1 to T10. Then, the fuel electrode 32 is reduced, and then air (oxidized gas) OG is supplied into the cylindrical gas pipe 38 on the air electrode 36 side at a flow rate of 100 ml / min under a pressure of 0.2 Pa. When helium gas He as a fuel gas is supplied into the cylindrical gas pipe 40 on the fuel electrode 32 side at a flow rate of 100 ml / min under a pressure of 0.2 Pa, the He exhaust gas from the fuel electrode 32 side using gas chromatography. The composition was measured, and it was evaluated from the amount of nitrogen gas N ₂ contained in the He exhaust gas whether or not nitrogen gas N ₂ in the air leaked from the joint. The evaluation results are shown in FIG. In FIG. 7, a nitrogen gas N ₂ leak rate of 1% or less is indicated by ◯, indicating that practical airtightness is satisfied. A case where the leakage rate of nitrogen gas N ₂ exceeds 1% is indicated as x, which indicates that practical airtightness is not satisfied.

Among the 10 types of test samples T1 to T10 corresponding to the sample numbers 1 to 10 in FIG. 7, the test samples T1 to T4 and T7 to T10 have sufficient airtightness and are a pair of stainless steel SUS430. No compound was formed by diffusion of Cr at the joint interface between the cylindrical gas pipes 38 and 40. Therefore, the sealing materials g1 to g4 and g7 to g10 used in the test samples T1 to T4 and T7 to T10 are 50 to 85 wt% BaO, 4 to 20 wt% SiO2, and ₁ to 15 wt%, respectively. and a the _{for Al} 2 _{O 3} essential components, and has a composition comprising at least one of the 20 wt% or less of _B 2 _{O 3} and 30 wt% or less of TiO _2, 9~13 × ^{10 -6} / K has a coefficient of thermal expansion. Further, these sealing materials g2 to g4 and g8 to g10 contain any one of barium silicate crystals BaSi ₄ O ₉ , Ba ₂ Si ₃ O ₈ and Ba ₃ Si ₅ O _{13 in} the glass matrix. g1 and g7 do not contain barium silicate crystals in the glass matrix. This point indicates that it is not essential to include barium silicate crystals in the glass matrix, as is apparent from the comparison between the sealing materials g1 and g2.

Of the sealing materials g5 and g6 used in the test samples T5 and T6 having a nitrogen leak rate exceeding 1%, the sealing material g5 showed insufficient wettability, and cracks were observed in the sealing material g6. The sealing material g5 has a BaO content exceeding 85 wt% and does not contain B ₂ O ₃ and TiO ₂ . BaO of sealant g6 its glass composition is below the 50 wt%, TiO ₂ is over 30 wt%.

As described above, according to the non-alkali glass-based sealing material 10 for the solid oxide fuel cell according to this embodiment, 50 to 85 wt% BaO, 4 to 20 wt% SiO ₂ and 1 to 15 wt% Al _2. Since a Ba-based alkali-free glass having a composition having O ₃ as an essential component and having at least one of 20 wt% or less of B ₂ O ₃ and 0 to ₃₀ wt% of TiO ₂ is formed, Is 9 to 13 × 10 ⁻⁶ / K, does not contain alkali metal components such as Na and K, and joins the solid oxide fuel cell and its peripheral members at a joining temperature of about 700 to 900 ° C. A possible sealing material is obtained. Moreover, since alkali metal components such as Na and K are not included, there is an advantage that reaction with peripheral members such as a stainless steel gas pipe and a separator is suppressed.

Further, according to the alkali-free glass-based sealing material 10 for SOFC 12 of this example, the glass matrix of the glass contained therein contains barium silicate crystals BaSi ₄ O ₉ , Ba ₂ Si ₃ O ₈ , and Ba ₃ Si _5. from being included either O ₁₃ is, while maintaining the high thermal expansion, there is an advantage that the reaction of the stainless steel of the gas pipe and the separator is suppressed.

Moreover, according to the non-alkali glass-based sealing material 10 for SOFC 12 of the present embodiment, the glass contained therein has a high coefficient of thermal expansion of 9 to 13 × 10 ⁻⁶ / K, so that the stainless steel gas pipe The difference in thermal expansion coefficient between the solid oxide fuel cell and the peripheral member of the solid oxide fuel cell is suitably eliminated.

  In addition, since the solid oxide fuel cell in which the non-alkali glass-based sealing material 10 for SOFC 12 of this embodiment is used for joining the SOFC 12 and the gas pipe 24 that is a peripheral member of the SOFC 12 is configured, Since the solid fuel cell is joined by a non-alkali glass-based sealing material 10 that does not contain an alkali component, for example, a reaction at a joint portion with a peripheral member such as a stainless steel gas pipe or a separator is suppressed. There are advantages.

  In addition, a solid oxide fuel cell in which the SOFC 12 and the gas pipe 24 that is a peripheral member of the SOFC 12 are joined using the non-alkali glass-based sealing material 10 for SOFC 12 of this embodiment is manufactured. Since it is joined by a non-alkali glass-based sealing material that does not contain alkali metal components such as Na and K, for example, the reaction at the joint between peripheral members such as a stainless steel gas pipe and a separator is suppressed. There are advantages.

  FIG. 8 schematically shows another anode-supported SOFC (solid oxide fuel cell) 50 to which the alkali-free glass-based sealing material 10 is applied, and a gas pipe 52 airtightly joined to the SOFC 50. It is sectional drawing shown. The SOFC 50 is an insulating support base material made of a porous material such as zirconia-based oxide or magnesia, and has a hollow box-type support base material 54 having an internal space 53 through which fuel gas flows, Fuel electrode layer 56 formed in layers on upper surface 54 a and lower surface 54 b of support base 54, solid electrolyte membrane 58 laminated on fuel electrode layer 56, and air laminated on solid electrolyte membrane 58 And the polar layer 60. The fuel electrode layer 56, the solid electrolyte membrane 58, and the air electrode layer 60 are made of the same material as the fuel electrode 16, the solid electrolyte membrane 18, and the air electrode 20 shown in the embodiment of FIG. It is a ligation. A pair of side surfaces 54c and 54d in opposite directions of the hollow box-type support base 54 are respectively formed with through holes 62 communicating with the internal space 53, and are made of stainless steel for supplying the fuel gas FG. Alternatively, the end of the gas pipe 52 is in a state where the end face 52a is in contact with the pair of side faces 54c and 54d and communicates with the internal space 53 of the hollow box-type support base 54 through the through hole 62. And the non-alkali glass sealing material 10 applied and melted between the side wall 54c and the side surfaces 54c and 54d of the hollow box-type support base 54, respectively, and sealed and sealed to the side surfaces 54c and 54d, respectively. . Similarly, the gap between the peripheral portion of the solid electrolyte membrane 58 fixed on the pair of upper surface 54a and the lower surface 54b of the hollow box-type support base 54, the fuel electrode layer 56, and the pair of upper surface 54a and the lower surface 54b is there. It is sealed with a non-alkali glass-based sealing material 10 that has been applied and melted.

  FIG. 9 shows an example in which a plurality of anode-supported SOFCs (solid oxide fuel cell) 70 are integrally connected. That is, the solid electrolyte membrane 74 and the air electrode layer 76 are sequentially laminated at four locations on one surface of the square-electrode fuel electrode 72 and the fuel electrode 72, so that 4 on the common fuel electrode 72. SOFCs 70 are formed. The fuel electrode 72, the solid electrolyte membrane 74, and the air electrode layer 76 are sintered in the same manner from the same materials as the fuel electrode 16, the solid electrolyte membrane 18, and the air electrode 20 shown in the embodiment of FIG. Is the body. Then, in a state where a rectangular tube-like gas pipe 78 similar to the fuel electrode 72 is brought into contact with the end surface 72c of the fuel electrode 72, the non-alkali glass-based sealing material 10 causes the fuel electrode 72, the gas pipe 78, Are airtightly joined.

  As mentioned above, although one Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

10: Non-alkali glass-based sealing material for SOFC 12, 12, 50, 70: SOFC (solid oxide fuel cell)
24, 52, 78: Gas pipe (peripheral members)

Claims (5)

A non-alkali glass-based sealing material for solid oxide fuel cells for airtightly joining solid oxide fuel cells,
50 to 85 wt% BaO, 4 to 20 wt% SiO ₂ and 1 to 15 wt% Al ₂ O ₃ as essential components, and 0 to 20 wt% B ₂ O ₃ and 0 to ₃₀ wt% An alkali-free glass-based sealing material for a solid oxide fuel cell, comprising a glass having a composition having at least one of TiO ₂ .   2. The alkali-free glass-based sealing material for a solid oxide fuel cell according to claim 1, wherein the glass matrix of the glass contains barium silicate crystals. The alkali-free glass-based sealing material for a solid oxide fuel cell according to claim 1 or 2, wherein the glass has a thermal expansion coefficient of 9 to 13 x ^10-6 / K.   A solid oxide fuel cell, wherein a solid oxide fuel cell and a peripheral member are joined using the alkali-free glass-based sealing material according to any one of claims 1 to 3.   A method for producing a solid oxide fuel cell, comprising joining the solid oxide fuel cell and a peripheral member using the alkali-free glass-based sealing material according to any one of claims 1 to 3.

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