Glass bonding material and its use

Abstract

To provide a glass bonding material for a solid oxide reversible fuel cell, capable of exhibiting favorable water resistance.SOLUTION: According to the technology disclosed herein, a glass bonding material for a reversible fuel cell, which can be used under high-temperature steam conditions, is provided. The glass bonding material contains borosilicate glass as a main component, and the glass composition substantially contains no alkali metal elements, P, Pb, Bi, Te, V, or As. When the total of the glass composition is 100 mol%, 95 mol% or more of the composition, in terms of oxide molar ratio, consists of the following components: first metal oxide: 30-75 mol%, Al2O3: 0.7-5 mol%, SiO2: 5-30 mol%, and ZnO: 1-12 mol%, and further contains B2O3: 15-25 mol% and second metal oxide: 1-8 mol%. The first metal element oxide includes at least one oxide of a Group 2 element, and the second metal element oxide includes at least one selected from the group consisting of TiO2 and Fe2O3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to glass bonding materials and their uses. [Background technology]

[0002] Inorganic members, such as ceramic members primarily composed of ceramic materials such as alumina and zirconia, and metal members primarily composed of metal materials such as stainless steel, are widely used in various fields. Various bonding materials are used to bond such inorganic members depending on the application, bonding conditions, etc. For example, in a reversible solid oxide fuel cell (R-SOC), an example of an electrochemical cell, a solid electrolyte and a metal member are bonded together, and a sealing joint is formed to prevent mixing of fuel gas and air gas. A glass bonding material is used to form this sealing joint. Such a glass bonding material contains a glass composition as a main component, and a dense bonding joint is formed by fusing and solidifying the glass composition through a firing process at a predetermined temperature.

[0003] An example of this type of glass sealing material is described in Patent Document 1. Patent Document 1 discloses a glass sealing material having a glass composition containing BaO, ZnO, SiO2, Al2O3, and BO3 in a predetermined ratio, and substantially free of alkali metals, Pb, As, P, Bi, Te, and V. The glass sealing material described in Patent Document 1 can suitably bond objects by low-temperature firing at 650°C or less, and the bonded portion exhibits suitable heat resistance after firing. This can greatly contribute to improving the performance of the bonded portion of low-temperature operating SOFCs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7232106 Summary of the Invention [Problem to be solved by the invention]

[0005] One example of an electrochemical cell is the solid oxide electrolysis cell (SOEC). This SOEC is an electrochemical cell that generates hydrogen gas from water (water vapor), which is the opposite reaction to that of the SOFC. In recent years, reversible solid oxide fuel cells (R-SOCs) have also been proposed as electrochemical cells that can selectively perform the functions of both SOFCs and SOECs. In these SOECs and R-SOCs, the joints that join the solid electrolyte and the metal members and prevent mixing of fuel gas and air gas are exposed to high concentrations of water vapor, so the joints require high water resistance. However, the glass bonding material for SOFCs described in Patent Document 1 is not a glass bonding material designed with water resistance in mind, making it difficult to use it directly in SOECs or R-SOCs.

[0006] The present disclosure has been made in consideration of the above circumstances, and its main purpose is to provide a glass bonding material that can form a suitable bonding joint with excellent water resistance that can be used directly in SOECs and R-SOCs. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the glass bonding material disclosed herein is provided.

[0008] The glass bonding material disclosed herein is a glass bonding material for bonding inorganic members. The glass bonding material contains a glass composition as a main component. The glass composition is substantially free of alkali metal elements, P, Pb, Bi, Te, V, and As, and when the entire glass composition is taken as 100 mol %, 95 mol % or more of the glass composition contains, in terms of oxide, First metal element oxide: 30~75mol%, Second metal element oxide: 1~8mol%, B2O3: 25 mol% or less, Al2O3: 0.7 to 5 mol%, SiO2: 5 to 30 mol%, ZnO: 1 to 12 mol%, It is composed of the following ingredients. Here, the first metal element oxide is an oxide of at least one metal element selected from Group 2 elements (beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra), and the second metal element oxide is an oxide of at least one metal element selected from Ti and Fe.

[0009] The glass bonding material having the above-described structure can form a bonded joint exhibiting high water resistance. Furthermore, since the glass bonding material does not substantially contain alkali metal elements such as P, Pb, Bi, Te, V, and As, various problems such as adverse effects on the environment and human body, deterioration of insulation properties, and chemical deterioration of electrochemical systems can be prevented.

[0010] In a preferred embodiment of the glass bonding material disclosed herein, the glass composition contains 2 mol % or more of Ti oxide (typically TiO2), which can improve the water resistance of the bonded portion after firing.

[0011] In a preferred embodiment of the glass bonding material disclosed herein, the glass composition further contains 2 mol% or more of Fe oxide (typically Fe2O3), which can improve the water resistance of the bonded part after firing.

[0012] In a preferred embodiment of the glass bonding material disclosed herein, the thermal expansion coefficient from 30°C to 500°C is 8.5 × 10 -6 K -1 ~10.2×10 -6 K -1 From the viewpoint of preventing damage to the joint, it is generally considered preferable to make the thermal expansion coefficient of the glass joining material similar to that of the inorganic member to be joined. According to this embodiment, the thermal expansion coefficient can be made similar to that of an inorganic member (e.g., a metal member) having a relatively high thermal expansion coefficient, so that damage to the joint after firing can be suitably prevented.

[0013] In this specification, the term "thermal expansion coefficient" refers to the average expansion coefficient (average linear expansion coefficient) measured using a thermomechanical analysis (TMA) in the temperature range of 30°C to 500°C, and refers to the value obtained by dividing the change in sample length relative to the initial length of the sample by the temperature difference. The thermal expansion coefficient can be measured in accordance with JIS R 3102 (1995).

[0014] In a preferred embodiment of the glass bonding material disclosed herein, when exposed to heat at 650°C or higher for 100 hours or more in an air atmosphere, the change in thermal expansion coefficient between before and after heat exposure is 10% or less, thereby forming a bonded joint that can maintain high airtightness for a long period of time and has excellent high-temperature durability.

[0015] Another aspect of the technology disclosed herein provides an inorganic member bonded body. The inorganic member bonded body includes two or more inorganic members and a bonding portion bonding the two or more inorganic members. The bonding portion of the inorganic member bonded body is substantially free of alkali metal elements, P, Pb, Bi, Te, V, and As, and contains, when the entire glass constituting the bonding portion is taken as 100 mol %, 95 mol % or more of the following elements in terms of oxides: First metal element oxide: 30~75mol%, Second metal element oxide: 1~8mol%, B2O3: 25 mol% or less, Al2O3: 0.7 to 5 mol%, SiO2: 5 to 30 mol%, ZnO: 1 to 12 mol%, It is composed of the following ingredients. wherein the first metal element oxide is an oxide of at least one metal element selected from Group 2 elements (beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra), The second metal element oxide is an oxide of at least one metal element selected from Ti and Fe.

[0016] The inorganic member bonded body has a bonded portion (also called a sealing portion) that achieves favorable water resistance using the glass bonding material disclosed herein, and can therefore be favorably used even in water vapor. Furthermore, the bonded portion is substantially free of alkali metal elements such as P, Pb, Bi, Te, V, and As, thereby preventing various problems such as adverse effects on the environment and human body, deterioration of insulation properties, and chemical deterioration of electrochemical systems.

[0017] In a preferred embodiment of the inorganic member joined body disclosed herein, the joint contains 2 mol % or more of Ti oxide (typically TiO) when the entire glass constituting the joint is taken as 100 mol %, thereby improving the water resistance of the inorganic member joined body after firing.

[0018] In a preferred embodiment of the inorganic joining member disclosed herein, the joining portion contains 2 mol % or more of Fe oxide (typically Fe2O3) when the entire glass constituting the joining portion is taken as 100 mol %, thereby improving the water resistance of the inorganic member joined body after firing.

[0019] In a preferred embodiment of the inorganic member joined body disclosed herein, the joint contains at least one crystal selected from the group consisting of BaMgSiO4, BaAl2O4, BaZnSiO4, BaAl2Si2O8, and MgSiO3. The presence of this component can improve the water resistance of the inorganic member joined body after firing. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a portion of an R-SOC system according to one embodiment. [Figure 2] FIG. 2 is a top view of an R-SOC system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Preferred embodiments of the technology disclosed herein are described below. Matters necessary for implementing the technology disclosed herein (e.g., a typical manufacturing process for an R-SOC system) other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on conventional technology in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. In the following description, "A to B (where A and B are any values)" includes the values ​​of A and B (upper and lower limits). In the drawings described in this specification, components and parts that perform the same function are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified. The dimensional relationships (length, width, thickness, etc.) in each drawing do not necessarily reflect the actual dimensional relationships.

[0022] <Glass bonding material> The glass bonding material disclosed herein forms a bonding portion (which may also be called a sealing portion) with excellent water resistance, and therefore is suitable for use in a water vapor atmosphere. As will be described in detail later, the term "inorganic member" in this specification is a concept that encompasses both a ceramic member made primarily of a ceramic material and a metal member made primarily of a metal material.

[0023] 1. Glass composition The glass bonding material disclosed herein contains a glass composition as a main component. Typically, the content of the glass composition, when the entire glass bonding material is taken as 100% by mass, is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The upper limit of the content of the glass composition is not particularly limited, and may be 100% by mass, 99% by mass or less, or 95% by mass or less. The glass composition disclosed herein comprises 95 mol% or more of a first metal element oxide, an aluminum component (Al2O3), a silicon component (SiO2), a zinc component (ZnO), a boron component (BO3), and a second metal element oxide. Each component is described below.

[0024] (1) First metal element oxide The first metal element oxide is an oxide of a Group 2 element (a metal element selected from Be, Mg, Ca, Sr, Ba, and Ra) and is a component that can improve the thermal stability of the glass composition (adjusting the thermal expansion coefficient and improving heat resistance after firing). It is particularly preferable that oxides of one or more metal elements selected from Mg, Ca, Sr, and Ba coexist, more preferably two or more metal elements. For example, it is preferable that two or three of MgO, CaO, and BaO coexist. Furthermore, the oxide of the Group 2 element can contribute to improving the water resistance of the joint due to the mixed alkaline earth effect. The "mixed alkaline earth effect" here refers to the irregular change in the glass network structure caused by adding a relatively large amount of alkaline earth metal. From the viewpoint of optimally achieving these effects, in the glass bonding material disclosed herein, the proportion of the Group 2 element component in the entire glass bonding material (hereinafter simply referred to as the "content of the Group 2 element component") is preferably 30 mol% or more, more preferably 35 mol% or more, and even more preferably 45 mol% or more, in terms of the molar ratio of oxide. Furthermore, from the viewpoint of improving physical stability by adding other components, the upper limit of the proportion of the first metal element oxide is set to 75 mol% or less, preferably 72 mol% or less, more preferably 70 mol% or less, and even more preferably 65 mol% or less. The lower and upper limits of the content of the Group 2 element component can be combined without any particular restrictions. Furthermore, by adding these components, the glass composition becomes a multi-component system, thereby improving physical stability.

[0025] (2) Aluminum content The aluminum component (Al2O3) stabilizes the glass bonding material and improves its chemical durability. As the proportion of the aluminum component increases, the heat resistance, chemical resistance, and adhesion stability tend to improve. Furthermore, the aluminum component is an essential component for forming crystals of BaAl2O4 and BaAl2Si2O8 produced by heat treatment. By favorably precipitating these crystals, the water resistance of the bonded joint can be improved. From this perspective, in the glass bonding material disclosed herein, the proportion of Al2O3 in the entire glass composition is set to 0.7 mol% or more (preferably 1 mol% or more, more preferably 2 mol% or more). On the other hand, if the Al2O3 content is increased too much, Al-based crystals become extremely likely to precipitate, increasing the glass viscosity and potentially impairing low-temperature bondability. From this perspective, the upper limit of the proportion of Al2O3 is set to 5 mol% or less (preferably 4 mol% or less, more preferably 3.5 mol% or less, and even more preferably 3 mol% or less).

[0026] (3) Silicon component Silicon (SiO2), together with boron oxide (BO3), described below, is a major ingredient of the glass composition. The glass composition disclosed herein is based on borosilicate glass. The silicon (silicon oxide) component constitutes the framework of the glass after firing and also functions to reduce viscosity during firing. Heat resistance also tends to improve as the SiO2 content increases. Furthermore, because the silicon component contributes to the framework of the glass, a higher content increases the degree of SiO2 bonding, which can contribute to the water resistance of joints. Therefore, the SiO2 content in the overall glass composition is set to 5 mol% or more, in terms of the molar ratio of oxide, preferably 8 mol% or more, more preferably 10 mol% or more, and even more preferably 14 mol% or more. To ensure a certain viscosity during firing, the upper limit of the SiO2 content is set to 30 mol% or less, preferably 27 mol% or less, more preferably 25 mol% or less, and even more preferably 23 mol% or less. Furthermore, the silicon component is said to be able to improve chemical resistance and thermal shock resistance.

[0027] (4) Zinc The zinc component (zinc oxide (ZnO)) adjusts the viscosity of the glass bonding material during firing and improves the airtightness and stability of the bonded joint after firing. Furthermore, it can prevent the formation of SiO crystals (cristobalite crystals) in the bonded joint after firing, which would otherwise reduce heat resistance. Furthermore, the zinc component is stable in water at a pH between 6 and 14, and therefore can contribute to improving the water resistance of the bonded joint. From this perspective, the proportion of ZnO in the entire glass composition, in terms of oxide molar ratio, is set to 1 mol% or more, preferably 3 mol% or more, more preferably 3.5 mol% or more, and even more preferably 4 mol% or more. On the other hand, if the ZnO content is too high, Zn-based crystals are likely to precipitate excessively, which may increase the glass viscosity and impair low-temperature bondability. From this perspective, the upper limit of the ZnO content is set to 12 mol% or less, preferably 9 mol% or less, more preferably 8 mol% or less, and even more preferably 7 mol% or less. Furthermore, by including ZnO in the above proportion, the water resistance and thermal shock resistance of the bonded joint can be improved.

[0028] (5) Boron component The boron component (boron oxide (BO)) contributes to increasing fluidity during firing, so increasing its content tends to improve bondability. On the other hand, excessive BO content has been shown to decrease the water resistance of the joint. This is presumably due to the generation of tricoordinated boron, which makes the joint more reactive with water. For this reason, the technology disclosed herein sets the upper limit of the BO content in the entire glass composition to 25 mol% or less. To more effectively suppress the decrease in water resistance, the BO content is preferably 23 mol% or less, more preferably 21 mol% or less, and even more preferably 20 mol% or less. To improve bondability, the BO content is preferably 15 mol% or more, more preferably 16 mol% or more, even more preferably 17 mol% or more, and particularly preferably 18 mol% or more.

[0029] (6) Second metal element oxide The second metal element oxides in this specification are titanium (typically TiO2) and iron (typically Fe2O3) components. Experiments have surprisingly confirmed that the inclusion of a certain amount of these second metal element oxides significantly improves the water resistance of the joint after firing. In the technology disclosed herein, the content of the second metal element oxide is set to 1 mol% or more (preferably 1.5 mol% or more, more preferably 2 mol% or more). On the other hand, adding too much of the second metal element oxide may significantly reduce the thermal expansion coefficient. It is believed that this effect occurs due to the precipitation of crystals during glass firing. From this perspective, the content of the second metal element oxide is set to 8 mol% or less (preferably 7.5 mol% or less, more preferably 7 mol% or less).

[0030] Among the second metal element oxides, titanium (typically TiO) can particularly effectively improve the water resistance of the joint. While not intending to limit the technology disclosed herein, this effect is presumably due to TiO's stability in water, which makes the resulting glass structure less reactive with water. Therefore, the proportion of titanium in the entire glass joining material (hereinafter simply referred to as the "titanium content") is preferably 2 mol% or more, more preferably 2.5 mol% or more, and even more preferably 3 mol% or more, when the entire glass joining material is taken as 100 mol%. Meanwhile, taking into consideration a decrease in the thermal expansion coefficient of the joint, the upper limit is set to 8 mol% or less (preferably 7.5 mol% or less, more preferably 7 mol% or less).

[0031] The iron component (typically Fe2O3) of the second metal element oxide can also favorably improve the water resistance of the joint. While not intending to limit the technology disclosed herein, it is believed that this effect is due to Fe2O3 being stable to water and the glass structure formed during bonding being less reactive with water. Therefore, the proportion of the iron component in the entire glass bonding material (hereinafter simply referred to as the "iron component content") is preferably 2 mol% or more, more preferably 2.5 mol% or more, and even more preferably 3 mol% or more, when the entire glass bonding material is taken as 100 mol%. Meanwhile, taking into consideration a decrease in the thermal expansion coefficient of the bonded portion, the upper limit is set to 8 mol% or less (preferably 7.5 mol% or less, more preferably 7 mol% or less). Compared to titanium, iron has a superior effect of improving the water resistance of the bonded portion. This is believed to be due to the stable chemical durability of crystals containing titanium.

[0032] Furthermore, it has been confirmed that the mixture of titanium and iron components provides both a higher level of water resistance and a higher thermal expansion coefficient than when these components are used alone. 3+ The ions are Ti 4+ This is presumably because the presence of ions results in a stable four-way coordination in the glass structure. The content of the iron component (i.e., the mixing ratio of the iron component to the titanium component) when the titanium component is taken as 100% is preferably 50% to 150%, more preferably 75% to 125%, even more preferably 85% to 115%, and particularly preferably 90% to 110%.

[0033] (7) Other ingredients The glass composition disclosed herein may contain optional components other than the six major components described above, as long as the effects of the technology disclosed herein are not significantly impaired. Examples of such optional components include La2O3, NiO, ZrO2, Nb2O5, SnO, SnO2, CeO2, and Cu2O. Adding these optional components to form a multi-component glass composition can improve the physical stability of the joint after firing. For example, the glass composition is preferably composed of a multi-component system containing six or more components. This improves the physical stability of the joint. From the standpoints of workability and cost, it is also preferable that the glass composition be composed of 10 or fewer components. When these optional components are added, the proportion of the optional components in the entire glass composition is preferably 0.01 mol% to 1 mol% or less, more preferably 0.05 mol% to 0.75 mol%, and even more preferably 0.1 mol% to 0.5 mol% or less.

[0034] (8) Prohibited ingredients The glass bonding material disclosed herein specifies components that are substantially free of (prohibited components) in order to prevent the occurrence of the following problems. First, the glass composition of the glass bonding material disclosed herein is substantially free of alkali metal elements. Examples of such alkali metal elements include Li, Na, K, Rb, Cs, and Fr. Glass bonding materials containing these alkali metal elements (particularly Na and K) may generate substances that adversely affect the environment during firing. For example, when a glass bonding material containing alkali metal elements is used to bond ferritic stainless steel, hexavalent chromium, an environmentally restricted substance, may be generated. In contrast, the glass bonding material disclosed herein is substantially free of alkali metal elements, and therefore can prevent the generation of environmentally restricted substances during firing. Next, the glass composition of the glass bonding material disclosed herein is substantially free of lead (Pb) and arsenic (As). This prevents Pb and As from adversely affecting the human body and the environment. Furthermore, the glass bonding material disclosed herein is substantially free of phosphorus (P). This prevents chemical deterioration of electrochemical systems (e.g., R-SOC) due to phosphorus poisoning. Furthermore, the glass composition of the glass bonding material disclosed herein is also substantially free of bismuth (Bi), tellurium (Te), and vanadium (V). This prevents the glass (bonding portion) from becoming electrically conductive after firing.

[0035] In this specification, the term "substantially free" means that the prohibited components described above are not intentionally added. Therefore, when a component that can be interpreted as a prohibited component is contained in a small amount due to raw materials, a manufacturing process, or the like, this is included in the concept of "substantially free" in this specification. For example, when the content of the prohibited component relative to the entire glass composition is 0.01 mol% or less (preferably 0.005 wt% or less, more preferably 0.001 wt% or less, even more preferably 0.0005 wt% or less, and particularly preferably 0.0001 wt% or less), it can be said to be "substantially free."

[0036] Furthermore, it is more preferable that the components of the glass composition described above are appropriately adjusted so that the thermal expansion coefficients of the glass composition and the inorganic members to be joined are similar. For example, the thermal expansion coefficient of the glass joining material is 8. 5×10 -6 K -1 ~10.2×10 -6 K -1 (preferably 9.5 x 10 -6 K -1 ~10.1×10 -6 K -1) range. This can prevent damage to the joint due to differences in the amount of expansion between the materials being joined. In this specification, the "thermal expansion coefficient" refers to the average expansion coefficient (average linear expansion coefficient) measured using a thermomechanical analysis (TMA) in the temperature range of 30°C to 500°C, and refers to the value obtained by dividing the change in sample length relative to the initial length by the temperature difference. The thermal expansion coefficient can be measured, for example, in accordance with JIS R3102:1995 or the like.

[0037] Furthermore, the glass bonding material disclosed herein exhibits a difference in thermal expansion coefficient between before and after thermal exposure of 100 hours at 650°C or higher in the air atmosphere of 10% or less. Thus, the glass bonding material, which is prevented from decreasing in thermal expansion coefficient due to thermal exposure, can form a bonding part with suitable heat resistance.

[0038] 2. Materials other than glass compositions In addition to the glass composition described above, the glass bonding material disclosed herein may contain, as appropriate, conventionally known materials that can be added to this type of glass bonding material. Examples of such additives include organic materials such as organic binders and organic solvents. Examples of organic binders include various binders typically used in this type of glass paste. Examples include cellulose-based polymers such as methyl cellulose, ethyl cellulose, and nitrocellulose, as well as acrylic resins, epoxy resins, and amine resins. Similarly, examples of organic solvents include various organic solvents typically used in this type of glass paste. Examples include terpineol, ether-based solvents, ester-based solvents, and various glycols.

[0039] The form of the glass bonding material disclosed herein is not particularly limited, and any form can be adopted depending on the application. For example, it can be in the form of cullet, powder, frit, pellet, sheet, paste, etc. For example, in the case of a paste-like glass bonding material, by appropriately adjusting the viscosity, it can be easily applied to the bonding target (inorganic member) by a method such as coating or printing. From the viewpoint of operational convenience, a form can also be adopted in which a sheet-like bonding material is preformed and then attached to the bonding target. The method for dispersing and mixing the paste is not particularly limited, and can be performed using, for example, a conventionally known three-roll mill. In this manner, the glass bonding material can be prepared.

[0040] <Glass bonding material manufacturing method> An example of a method for producing the glass bonding material disclosed herein will be described. For example, first, a glass raw material powder is prepared. Next, the glass raw material powder is melted and then rapidly cooled to prepare a glass composition (i.e., a glass intermediate). In this manner, the glass bonding material disclosed herein can be prepared. Note that the description of this manufacturing method is not intended to limit the glass bonding material disclosed herein. Each step will be described in detail below.

[0041] When manufacturing the glass bonding material disclosed herein, first, a raw material powder is prepared, the main components of which are the above-mentioned first metal element oxide, Al2O3, SiO2, ZnO, BO3, and second metal element oxide (the six main components occupy 95 mol% or more in terms of molar ratio of oxides). For example, industrial products, reagents, or various mineral raw materials containing oxides, carbonates, nitrates, composite oxides, etc. containing the various components described above are prepared and mixed to achieve the desired composition ratio. The mixing and preparation of this raw material powder can be performed, for example, by charging the raw materials into a mixer such as a ball mill and mixing for several hours to several tens of hours.

[0042] Next, the obtained glass raw material powder is dried and then heated under a predetermined temperature condition (typically 900°C to 1200°C) to melt the glass raw material powder. The molten glass is then cooled (preferably rapidly cooled) to obtain a glass composition having the above-mentioned configuration. The obtained glass composition is then crushed and classified (sieved) to a desired size (particle size), thereby obtaining a glass powder in the form of cullets or powder. The average particle size of such glass powder is preferably, for example, 0.5 μm to 50 μm (typically 1 μm to 10 μm). In this specification, the term "average particle size" may refer to the particle size corresponding to the 50% cumulative value from the smallest particle size in a volume-based particle size distribution based on a laser diffraction / scattering method.

[0043] The obtained glass powder is then processed into a desired shape to obtain a glass bonding material. The means for processing the glass bonding material into a desired shape can be any conventionally known method without particular limitation, as long as it does not impair the effects of the technology disclosed herein. For example, a pellet-shaped glass bonding material can be obtained by compression-molding the glass powder into a desired shape and then calcining it. Alternatively, a paste-shaped glass bonding material can be obtained by mixing the glass powder with an organic material such as an organic binder or an organic solvent.

[0044] ≪Joining method≫ As described above, the inorganic members to be joined in the technology disclosed herein are a concept that encompasses metal materials and ceramic members. That is, the glass joining material disclosed herein can be widely used for joining metal members (between similar members) or joining a metal member and a ceramic member (between different members). The metal is not particularly limited as long as the effects of the technology disclosed herein are exhibited. For example, members made of various metal materials with thermal expansion coefficients relatively close to that of the glass joining material disclosed herein can be used. For example, it is preferable to use members made of metal materials with thermal expansion coefficients similar to or slightly higher than that of the glass joining material disclosed herein. A rough guide to the thermal expansion coefficient of a metal material is, for example, a thermal expansion coefficient of 10.0 × 10 from 30°C to 500°C. -6 K -1 ~22.0×10 -6 K -1 Examples of such joining targets include stainless steel, aluminum, chromium, iron, nickel, copper, silver, manganese, and alloys thereof. More specifically, the joining targets may include ferritic or austenitic stainless steel, pure aluminum, aluminum alloys (duralumin, aluminum bronze, etc.), silver, silver alloys (nickel silver, etc.), copper, and copper alloys (phosphor bronze, etc.). Examples of ceramic members include zirconia, alumina, forsterite, titania, yttria, beryllia, boron nitride (BN), aluminum nitride (AlN), silicon nitride (Si3N4), and boehmite (AlOOH). The glass joining material disclosed herein can ensure favorable water resistance in a high-concentration water vapor atmosphere, as described above, and therefore can be suitably used to form joining parts for SOEC and R-SOC system components.

[0045] Furthermore, when forming a joint using the glass bonding material disclosed herein, firing is performed after the glass bonding material is applied to the above-mentioned bonding objects (inorganic members). As described above, the firing temperature is appropriately changed. Specifically, the temperature of the low-temperature firing may be 500°C to 750°C, 550°C to 670°C, or 600°C to 750°C. The firing atmosphere is set to, for example, an oxidizing atmosphere. The firing time is set to 0.5 hours to 10 hours (for example, 2 hours). As a result, the glass composition in the glass bonding material is fused and solidified, forming a dense joint mainly composed of glass.

[0046] Note that crystals selected from the group consisting of BaMgSiO4, BaAl2O4, BaZnSiO4, BaAl2Si2O8, and MgSiO3 may be generated in the joint after firing. The generation of these crystals further improves the thermal stability of the joint, resulting in better heat resistance and durability. However, the inventors have confirmed through experiments that joints formed using the glass joining material disclosed herein have a certain level of heat resistance and durability even when the above-mentioned crystals are not generated. Therefore, the presence or absence of crystal generation does not limit the technology disclosed herein. Joints may be formed under conditions that prevent crystal generation, taking into account manufacturing costs and bonding performance during firing.

[0047] <Reversible Solid Oxide Fuel Cell (R-SOC) System> An R-SOC system will be described as a preferred example of the inorganic member bonded body described above. Fig. 1 is a cross-sectional view schematically showing an R-SOC system 100. Note that Fig. 1 shows only the main components of the R-SOC system 100, and omits the peripheral components. Fig. 2 is a top view of the R-SOC system 100.

[0048] The R-SOC system 100 shown in FIG. 1 includes a unit cell 10, a spacer 20, a supporting metal member 30, and a frame 40. In this unit cell 10, a dense layered solid electrolyte 13 made of an oxide ion conductor and a porous air electrode 14 are sequentially formed on the surface of a porous fuel electrode 12. The fuel electrode 12 is a so-called ceramic member, exemplified by a cermet of nickel (Ni) and YSZ. The solid electrolyte 13 is a ceramic member, exemplified by a member made of yttria-stabilized zirconia (YSZ), gadolinia-doped ceria (GDC), or lanthanum gallate (LaGaO). Examples of the air electrode 14 include those made of lanthanum manganate (LaMnO3)-based oxides such as (LaSr)MnO3 and (LaCa)MnO3, lanthanum cobaltate-based oxides such as LaCoO3, (LaSr)CoO3 and (LaSr)(CoFe)O3, and lanthanum titanate-based oxides such as (LaSr)(TiFe)O3.

[0049] The unit cell 10 having the above configuration is sandwiched between a pair of support members 30. The support members 30 are metal plate-shaped members. Each support member 30 has a first gas flow path 31 that penetrates the support member 30 in the stacking direction of the unit cells 10 (the vertical direction in FIG. 1). The upper support member 30 in FIG. 1 is stacked on a frame 40. The frame 40 is a frame body having an opening 42. The air electrode 14 of the unit cell 10 is in contact with the upper support member 30. The frame 40 has a second gas flow path 41 that penetrates the frame 40 in the stacking direction of the unit cells 10. The second gas flow path 41 communicates with the first gas flow path 31 of the support member 30. The frame 40 is a metal member whose main component is a variety of metallic materials. Examples of suitable materials include, but are not limited to, stainless steel, aluminum, chromium, iron, nickel, copper, silver, manganese, and alloys thereof. In particular, metals that are relatively heat-resistant and inexpensive (such as ferritic stainless steel) can be preferably used as the material.

[0050] A spacer 20 is disposed between the frame 40 and the lower support member 30. The spacer 20 is a cylindrical member having an opening 22. The fuel electrode 12 of the unit cell 10 is in contact with the lower support member 30. In the R-SOC system 100 configured as described above, the fuel gas (water vapor) supplied to the fuel electrode 12 is supplied to the space within the opening 22 of the spacer 20 through the first gas flow path 31 and the second gas flow path 41 (see A1 in FIG. 1). The fuel gas then flows through the fuel electrode 12 in the direction of arrow A2.

[0051] 2, an air flow path 33 is formed in the upper support member 30. Although not shown in the figure because it is formed in the depth direction of FIG. 1 (direction perpendicular to the paper surface), the air flow path 33 penetrates the upper support member 30 and communicates with an opening 42 of the frame 40. Air is supplied to the air electrode 14 through the air flow path 33 and the opening 42.

[0052] In this R-SOC system 100, a portion of the solid electrolyte 13 and a portion of the frame 40 are joined. Specifically, in the R-SOC system 100 configured as described above, fuel gas is supplied to the opening 22 of the spacer 20, and air is supplied to the opening 42 of the frame 40. If the fuel gas and air mix at this time, the desired steam electrolysis reaction and power generation reaction will be difficult to occur. Therefore, in this R-SOC system 100, the boundary between the solid electrolyte 13 and the frame 40 is joined at a joint 16. This separates the opening 22 of the spacer 20 from the opening 42 of the frame 40, preventing the fuel gas and air from mixing. This joint 16 is formed by attaching the above-mentioned glass joining material to the interface between the solid electrolyte 13 and the frame 40, performing a degreasing process to remove organic matter, and then performing a firing process to fuse and solidify the glass powder.

[0053] The operation of the R-SOC system 100 will now be described.

[0054] <Steam electrolysis> The R-SOC system 100 can function as an SOEC that performs steam electrolysis to produce hydrogen. In the R-SOC system 100 having such a structure, water vapor is supplied to the anode 12, and the reaction of the following formula (1) proceeds due to external power. H2O+2e - →H2+O 2- Formula (1)

[0055] And oxide ions (O 2- ) is conducted through the solid electrolyte 13, and the reaction shown in formula (2) below proceeds at the air electrode 14. O 2- →1 / 2O2+2e - Formula (2)

[0056] Through the above formulas (1) and (2), water vapor is decomposed to generate hydrogen. At this time, the joint 16 is exposed to a high-concentration water vapor environment supplied through the first gas flow path 31. However, the joint 16 formed using the glass joining material disclosed herein has good water resistance and can therefore be used suitably even in such an environment.

[0057] <Power Generation> The R-SOC system 100 can function as an SOFC that generates electricity based on the principles of solid oxide fuel cells. In the R-SOC system 100 having such a structure, oxygen is supplied to the air electrode 14, causing a reduction reaction, as shown in formula (3) below. 1 / 2O2+2e - →O 2- Formula (3)

[0058] Then, the oxide ions (O 2- ) is conducted through the solid electrolyte 13, and the reaction shown in the following formula (4) proceeds in the fuel electrode 12. H2+O 2- →H2O+2e - Formula (4)

[0059] Power generation by the SOFC is performed through the above formulas (3) and (4). At this time, water generated in the above formula (4) may come into contact with the joint 16. However, the joint 16 formed using the glass joining material disclosed herein has good water resistance and can be used suitably even in such an environment.

[0060] The R-SOC system 100 operates by switching between steam electrolysis using the SOEC and power generation using the SOFC. In either case, water may come into contact with the joint 16. However, the joint 16 formed using the glass joining material disclosed herein has good water resistance and can therefore be used favorably in this application.

[0061] [Test example] Test examples relating to the technology disclosed herein will be described below, but it is not intended that the technology disclosed herein be limited to such test examples.

[0062] 1. Sample Preparation In this test, a total of 14 types of glass powders (Examples 1 to 6, Comparative Examples 1 to 8) were prepared with different glass composition components. Specifically, raw material powders of a predetermined composition were first melted at 1000°C to 1200°C for 60 minutes and then rapidly cooled to obtain a glass body. Next, this glass body was crushed and classified to prepare glass bonding materials with an average particle size of approximately 10 to 20 μm. The components of the glass composition in each sample are shown in Table 1. The numerical values ​​in Table 1 are in "mol%."

[0063] [Table 1]

[0064] 2.Evaluation Test (1) Heat resistance evaluation The glass powder thus prepared was press-molded into a disk with a diameter of 15 mm and a thickness of 7 mm and heated at 750°C for 120 minutes. Cylindrical specimens approximately 5 mm in diameter and 20 mm in thickness were cut using a diamond cutter. The thermal expansion coefficient was measured using a thermomechanical analyzer (TMA8311, manufactured by Rigaku Corporation) and used as the thermal expansion coefficient before thermal exposure. Specifically, the thermal expansion coefficient was calculated from the average linear expansion between 30°C and 500°C when the temperature was raised from room temperature (25°C) to 1000°C at a constant rate of 10°C / min. Next, a sample similar to the above was prepared and exposed to temperatures above 650°C for 100 hours. The thermal expansion coefficient was then measured. The thermal expansion coefficient after thermal exposure was then measured. The rate of change in the thermal expansion coefficient before and after thermal exposure was calculated using the following formula. A change of 10% or less was evaluated as "good" for heat resistance, and otherwise was evaluated as "bad." Rate of change in thermal expansion coefficient = | Thermal expansion coefficient before heat exposure - Thermal expansion coefficient after heat exposure | × 100 / Thermal expansion coefficient before heat exposure

[0065] (2) Water resistance The above glass powder compact (approximately φ15 × 7 mm) was prepared by press molding and heated at 750°C for 120 minutes. It was then cut into 10 × 10 × 3 mm samples using a diamond cutter. The samples were dried at 80°C for 60 minutes, after which their weights (weight before testing) were measured, placed in approximately 300 mL of distilled water, and stored in an oven at 90°C for 24 hours. After this, the samples were dried at 90°C for 60 minutes and their weights (weight after testing) were measured. The weight loss rate was calculated using the following formula. An average weight loss rate of 1.00 or more was evaluated as "×", 0.51 to 0.99 as "◯", and 0.50 or less as "◎". Weight loss rate = (weight before test - weight after test) / weight before test

[0066] (3) Evaluation of adhesion The glass powder compact obtained above was placed on a ferritic stainless steel plate such as SUS430 and heated at 750°C for 120 minutes to obtain a bonded body. The bonded body was inverted, and if it did not fall freely it was marked as "Good", and if it fell freely even a little it was marked as "Poor". In this test, three types of inorganic materials were used as the bonding objects: ferritic stainless steel (SUS430), zirconia, and alumina, and the bondability to each inorganic material was evaluated.

[0067] 3. Evaluation Results The results of each of the above-mentioned evaluation tests are shown in Table 2. For the overall evaluation, if there was even one "x" in each evaluation item, it was marked as "x", and if there was no "x", it was marked as "good".

[0068] [Table 2]

[0069] From the above results, it was confirmed that the glass bonding materials (Examples 1 to 6) exhibited good water resistance, bondability, and heat resistance. Comparative Example 1, which contained 42.7 mol% of B2O3, and Comparative Example 2, which did not contain a second metal element oxide and was composed only of the main components of the glass bonding material, exhibited good bondability after firing, but the water resistance was significantly reduced. Furthermore, Comparative Examples 3 to 5, which did not contain a second metal element oxide but contained metal element oxides other than the second metal element oxide, exhibited good water resistance, but the bondability after firing was reduced. Comparative Examples 6 to 8, which contained a relatively large amount of the second metal element, were confirmed to be unable to achieve both good water resistance and bondability. These results confirmed that reducing the amount of B2O3 and adding a second metal element oxide (TiO2 and / or Fe2O3) can achieve both water resistance and bondability after firing. Furthermore, Examples 4 to 6 confirmed that mixing TiO2 and Fe2O3 can further improve water resistance without reducing bondability and heat resistance.

[0070] While specific examples of the technology disclosed herein have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0071] This specification includes the following items 1 to 9. The following items 1 to 9 are not limited to the above-described embodiments.

[0072] Section 1: A glass bonding material for bonding inorganic members, Contains a glass composition as a main component, The glass composition is substantially free of alkali metal elements, P, Pb, Bi, Te, V, and As, and when the entire glass composition is taken as 100 mol %, 95 mol % or more of these elements are contained in a molar ratio calculated as oxides. First metal element oxide: 30~75mol%, Second metal element oxide: 1~8mol%, B2O3: 25 mol% or less, Al2O3: 0.7 to 5 mol%, SiO2: 5 to 30 mol%, ZnO: 1 to 12 mol%, It is composed of the ingredients wherein the first metal element oxide is an oxide of at least one metal element selected from Group 2 elements (beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra), The glass bonding material, wherein the second metal element oxide is an oxide of at least one metal element selected from the group consisting of Ti and Fe.

[0073] Section 2: Item 2. The glass bonding material according to item 1, wherein the second metal element oxide contains 2 mol % or more of Ti oxide.

[0074] Section 3: Item 3. The glass bonding material according to item 2, wherein the second metal element oxide further contains 2 mol % or more of Fe oxide.

[0075] Section 4: The thermal expansion coefficient from 30℃ to 500℃ is 8.5×10 -6 K -1 ~10.2×10 -6 K -1 Item 4. The glass bonding material according to any one of items 1 to 3,

[0076] Section 5: Item 5. The glass bonding material according to any one of items 1 to 4, wherein the rate of change in thermal expansion coefficient before and after thermal exposure to 650°C or higher for 100 hours or more in an air atmosphere is 10% or less.

[0077] Item 6: An inorganic member joined body including two or more inorganic members and a joining portion that joins the two or more inorganic members, The joint is substantially free of alkali metal elements, P, Pb, Bi, Te, V, and As, and contains 95 mol % or more of these elements in terms of oxides when the entire glass constituting the joint is taken as 100 mol %. First metal element oxide: 30~75mol%, Second metal element oxide: 1~8mol%, B2O3: 25 mol% or less, Al2O3: 0.7 to 5 mol%, SiO2: 5 to 30 mol%, ZnO: 1 to 12 mol%, It is composed of the ingredients wherein the first metal element oxide is an oxide of at least one metal element selected from Group 2 elements (beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra), The inorganic member joined body, wherein the second metal element oxide is an oxide of at least one metal element selected from the group consisting of Ti and Fe.

[0078] Section 7: 7. The inorganic member joined body according to item 6, wherein the second metal element oxide contains 2 mol % or more of Ti oxide.

[0079] Section 8: 8. The inorganic member joined body according to item 7, wherein the second metal element oxide further contains 2 mol % or more of Fe oxide.

[0080] Section 9: Item 9. The inorganic member joined body according to any one of items 6 to 8, wherein at least one crystal selected from the group consisting of BaMgSiO4, BaAl2O4, BaZnSiO4, BaAl2Si2O8, and MgSiO3 is present in the joint. [Explanation of symbols]

[0081] 10 single cells 12 Fuel electrode 13 Solid electrolyte 14 Air electrode 16 Joint 20 spacer 22 Spacer opening 30 Support member 31 First gas flow path 33 Air flow path 40 frames 41 Second gas flow path 42 Frame opening 100 R-SOC system

Claims

1. A glass bonding material for bonding inorganic members, Contains a glass composition as a main component, The glass composition is substantially free of alkali metal elements, P, Pb, Bi, Te, V, and As, and when the entire glass composition is taken as 100 mol %, 95 mol % or more of these elements are contained in a molar ratio calculated as oxides. First metal element oxide: 45 to 75 mol%, Second metal element oxide: 2 to 8 mol%, B ２ O ３ :15~25mol%、 Al ２ 9 ３ :0.75%、 SiO ２ :5~30mol%、 ZnO: 1 to 12 mol%, It is composed of the ingredients Here, the first metal element oxide contains at least an oxide of magnesium Mg, calcium Ca, or barium Ba among Group 2 elements (beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra), and contains at least 11 mol% or more of the oxide of magnesium Mg and at least 22 mol% or more of the oxide of Ca, The glass bonding material, wherein the second metal element oxide is an oxide of at least one metal element selected from the group consisting of Ti and Fe.

2. The glass bonding material according to claim 1 , wherein the second metal element oxide contains 2 mol % or more of Ti oxide.

3. The glass bonding material according to claim 2 , wherein the second metal element oxide further contains 2 mol % or more of Fe oxide.

4. The thermal expansion coefficient from 30°C to 500°C is 8.5 x 10 －６ K －１ ~10.2 x 10 -６ K －１ The glass bonding material according to claim 1 ,

5. 4. The glass bonding material according to claim 1, wherein a rate of change in thermal expansion coefficient before and after thermal exposure in an air atmosphere at 650°C or higher for 100 hours or more is 10% or less.

6. An inorganic member joined body including two or more inorganic members and a joining portion that joins the two or more inorganic members, The joining part is substantially free of alkali metal elements, P, Pb, Bi, Te, V, and As, and when the entire glass constituting the joining part is taken as 100 mol %, 95 mol % or more of these elements are contained in a molar ratio calculated as oxides. First metal element oxide: 45 to 75 mol%, Second metal element oxide: 2 to 8 mol%, B ２ O ３ :15~25mol%、 Al ２ 9 ３ :0.75%、 SiO ２ :5~30mol%、 ZnO: 1 to 12 mol%, It is composed of the ingredients wherein the first metal element oxide contains at least an oxide of magnesium Mg, calcium Ca, or barium Ba among Group 2 elements (beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba, and radium Ra), and contains at least 11 mol% or more of the oxide of magnesium Mg and at least 22 mol% or more of the oxide of Ca; The inorganic member joined body, wherein the second metal element oxide is an oxide of at least one metal element selected from the group consisting of Ti and Fe.

7. 7. The inorganic member joined body according to claim 6, wherein the second metal element oxide contains 2 mol% or more of Ti oxide.

8. The inorganic member joined body according to claim 7 , wherein the second metal element oxide further contains 2 mol % or more of Fe oxide.

9. In the joint, BaMgSiO ４ , BaAl ２ O ４ , BaZnSiO ４ , BaAl ２ Si ２ O ８ , MgSiO ３ The inorganic member joined body according to claim 6 , wherein at least one type of crystal selected from the group consisting of:

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