A sealing material for solid oxide fuel cells and its preparation method and application

Abstract

The present application discloses a sealing material for solid oxide fuel cells, its preparation method, and application, and relates to the field of solid oxide fuel cell technology. A sealing material for solid oxide fuel cells comprises mica and barium aluminosilicate-based glass; the components of the barium aluminosilicate-based glass, calculated by mass percentage, include: BaO 10%-15%, Al2O3 5%-10%, B2O3 15%-25%, CaO 6%-13%, La2O3 ≤5%, and the balance SiO2. The sealing material obtained by adjusting the component ratio in the present application achieves a thermal expansion coefficient of ≥8×10 ‑6 / ℃ and low softening point requirements, improves thermal expansion coefficient matching and chemical stability, has good chemical compatibility with other battery components, ensures long-term durability of the seal, and reduces production costs, meeting the requirements of SOFC cell stack sealing.

Description

Technical Field

[0001] The present application relates to the technical field of solid oxide fuel cells, and in particular to a sealing material for solid oxide fuel cells, a preparation method thereof, and an application thereof. Background Art

[0002] Solid oxide fuel cells (SOFCs) are electrochemical power generation devices with high efficiency and a wide fuel range. In the field of SOFC sealing materials, existing technologies primarily use glass, glass-ceramics, and metal alloys as sealing materials. SOFC sealing materials operate in high-temperature environments and are directly exposed to moist air and reducing fuel gases. They must maintain stability and long-term tight adhesion to adjacent cell components to ensure that fuel gas and oxidizing gas do not mix during SOFC operation and prevent fuel gas leakage. Their primary function is to prevent the mixing of oxygen and fuel gas, thereby avoiding fuel cell failure and even destructive behaviors such as explosion. However, current SOFC sealing materials still have several shortcomings, including thermal stress and cracking risks caused by poor thermal expansion coefficient matching, chemical compatibility issues with other cell components under high temperature conditions, uncertain long-term durability, and high production costs. Furthermore, to ensure the durability of the seal, the manufacturing process of the sealing material is complex. These shortcomings limit the large-scale application and economic viability of SOFC sealing materials. Based on this, the present application proposes a sealing material for solid oxide fuel cells, its preparation method, and its application. Summary of the Invention

[0003] The main purpose of this application is to provide a sealing material for solid oxide fuel cells and its preparation method and application, aiming to solve the technical problem that the performance of existing SOFC sealing materials needs to be improved.

[0004] To achieve the above-mentioned object, the present application proposes a sealing material for a solid oxide fuel cell, comprising mica and barium aluminosilicate-based glass;

[0005] The components of the barium aluminosilicate-based glass include, by mass percentage, BaO 10%-15%, Al2O3 5%-10%, B2O3 15%-25%, CaO 6%-13%, La2O3≤5% and the balance SiO2.

[0006] Optionally, the mass ratio of the mica to the barium aluminosilicate-based glass is 1:9.

[0007] Optionally, the mass ratio of the mica to the barium aluminosilicate-based glass is 1:4.

[0008] This application also proposes a method for preparing a sealing material for a solid oxide fuel cell, comprising the following steps:

[0009] The mica is heated to remove crystal water, cooled, and then ball-milled to obtain mica powder;

[0010] BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 are mixed in proportion, heated to form glass and then kept warm to obtain glass paste; the glass paste is quenched and formed, annealed, crushed, ball-milled and sieved to obtain glass powder;

[0011] The mica powder and the glass powder are mixed, and a solvent is added to mix them evenly to obtain a finished sealing material.

[0012] Optionally, the step of heating the mica to remove crystal water comprises:

[0013] The mica is placed in an electric furnace and heated at a temperature of 800° C. to 900° C. for 5 h to 7 h to remove crystal water.

[0014] Optionally, the step of uniformly mixing BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 according to a proportion, heating to form glass and then keeping the mixture warm to obtain a glass paste comprises:

[0015] BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 powder raw materials with purity ≥99.5% are mixed according to the proportion, placed in an electric furnace and heated to 1450℃-1650℃ at a heating rate of 4℃ / min-6℃ / min. After forming glass, keep warm for 9h-11h to obtain glass paste.

[0016] Optionally, the step of annealing the glass paste after quenching and forming the glass paste comprises:

[0017] After the glass paste is quenched and formed on a graphite plate, it is immediately placed in an annealing furnace and kept at 580° C.-780° C. for 7 h-9 h, and then cooled to room temperature.

[0018] Optionally, the particle size of the glass powder is less than 45 μm.

[0019] Optionally, the solvent is a mixture of 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate in a mass ratio of (3.5-7.5): (4-6): (3.5-7.5): (4-6).

[0020] The present application also proposes an application of a sealing material for a solid oxide fuel cell, wherein the sealing material is used for sealing a metal connector of a solid oxide fuel cell.

[0021] This application has at least the following beneficial effects:

[0022] This application uses barium aluminosilicate-based glass as a sealing matrix material for SOFCs. By changing the composition ratio and adding elements that can lower the melting point and increase fluidity, the composition and content of the barium aluminosilicate-based glass are optimized to: BaO 10%-15%, Al2O3 5%-10%, B2O3 15%-25%, CaO 6%-13%, La2O3 ≤5%, and the balance SiO2. This reduces the SiO2 content in the barium aluminosilicate-based glass, optimizes the B2O3 composition and reduces the BaO ratio, increases the B2O3 content, and adjusts the ratio of CaO and La2O3.

[0023] Since SiO2 is the main skeleton component of glass, although it provides excellent mechanical strength and chemical stability, its melting point is relatively high, about 1710℃. If its content is too high, the melting point of the entire glass will be too high, affecting the melt fluidity and sintering properties during the preparation process. By appropriately reducing the SiO2 content, the melting point of the glass can be significantly reduced, making it easier to sinter at a lower temperature while maintaining sufficient structural stability; B2O3 can be used as a glass network flux, which has a lower melting point (about 450℃) and can improve the fluidity of the glass. Increasing the B2O3 content can effectively lower the melting point of the glass, making it more suitable for the melting process; BaO may cause chemical instability at high temperatures, especially when in contact with other materials (such as electrolytes or electrodes), which may trigger reactions or form unfavorable phases. By reducing the proportion of BaO, these instabilities can be reduced and the long-term stability of the sealing material can be enhanced. Excessive BaO content may cause thermal expansion mismatch, thereby inducing stress and cracks during thermal cycling. Optimizing the composition of B2O3 and reducing BaO can better match the thermal expansion characteristics of the sealing material and other components, reduce stress concentration, and reducing the BaO content can also help improve the overall mechanical properties and electrical insulation properties of the sealing material; La2O3 has a high melting point and CaO has a relatively low melting point. By reducing the proportion of La2O3 and increasing CaO, the overall melting point of the glass can be effectively lowered. Both La and Ca can act as glass network modifiers, destroying the Si-O network, reducing viscosity and increasing the fluidity of the glass material when molten. Both can combine with oxygen to form stable compounds. Adjusting the La / Ca molar ratio within a certain range will not significantly change the basic properties of the glass. Their effects on thermal stability and thermal expansion coefficient can offset each other, so that the overall glass performance is still suitable for SOFC use conditions after the change. The increase in CaO makes the glass easier to flow at high temperatures, ensuring its good sealing performance and uniform filling effect. At the same time, it can also reduce the use of rare earth raw material La2O3 and save costs.

[0024] By adding mica, a mixture of inorganic particles, glass and mica form a glass-ceramic composite, which can enhance the rigidity and compressive strength of the sealing material, effectively fill the micropores of the glass, reduce gas permeation, improve the high-temperature stability and filling capacity of the sealing material, thereby reducing the stress caused by thermal expansion and improving the durability of the sealing material in the battery environment;

[0025] The sealing material obtained by adjusting the composition ratio in this application finally achieves a thermal expansion coefficient of ≥8×10 -6 / ℃ and low softening point (690℃) requirements, improves thermal expansion coefficient matching and chemical stability, has good chemical compatibility with other battery components, ensures long-term durability of the seal, and reduces production costs, meeting the requirements of SOFC cell stack sealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0027] Figure 1 This is a cross-sectional microstructure diagram of the sealing material after sintering and crystallization according to an embodiment of the present application;

[0028] Figure 2 Schematic diagram of thermal expansion curves of the sealing material sample and other SOFC components described in the embodiments of the present application;

[0029] Figure 3 Schematic diagram of a curve showing changes in viscosity and height of a sealing material sample according to an embodiment of the present application as a function of temperature;

[0030] Figure 4 Schematic diagram of the resistance change curve of the sealing material sample described in the embodiment of the present application;

[0031] Figure 5 This is a schematic diagram of the high-temperature cycle leakage rate of the sealing material sample described in the embodiment of the present application.

[0032] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] In view of the technical problems existing in the above-mentioned prior art, the embodiments of the present application provide a sealing material for a solid oxide fuel cell, comprising mica and barium aluminosilicate-based glass;

[0035] The components of the barium aluminosilicate-based glass include, by mass percentage, BaO 10%-15%, Al2O3 5%-10%, B2O3 15%-25%, CaO 6%-13%, La2O3≤5% and the balance SiO2.

[0036] In view of the current trend of solid oxide fuel cells developing towards medium and low temperature (<800°C) operating temperatures, and in order to match medium and low temperature solid oxide fuel cells, this application is based on barium aluminosilicate-based glass as the SOFC sealing matrix material. By changing the component ratio and adding elements that can lower the melting point and increase fluidity, the composition and content of the barium aluminosilicate-based glass are optimized to: BaO 10%-15%, Al2O3 5%-10%, B2O3 15%-25%, CaO 6%-13%, La2O3≤5% and the balance SiO2. This reduces the SiO2 content in the barium aluminosilicate-based glass, optimizes the B2O3 composition and reduces the BaO ratio, increases the B2O3 content, and adjusts the ratio of CaO and La2O3. SiO2 is the main skeleton component of glass. Reducing its proportion can lower the melting point, but still maintain the strength and stability of the glass; BaO can keep the thermal expansion coefficient of the sealing material matching, and reducing a certain proportion can lower the melting point of the sealing material; Al2O3, as an inorganic particle, can increase the mechanical strength and chemical resistance of the sealing material; B2O3 can provide fluxing effect, lower the melting point and improve fluidity. Increasing the B2O3 content can effectively lower the melting point of the glass, making it more suitable for the melting process; CaO can provide thermal shock resistance and adjust the melting point of the glass. La2O3 can enhance the reduction resistance and high-temperature stability of the sealing material. La and Ca have similar chemical properties and Function, by reducing the proportion of La2O3 and increasing CaO, the overall melting point of the glass can be effectively reduced, and its effects on thermal stability and thermal expansion coefficient can offset each other, so that the overall glass performance is still suitable for the use conditions of SOFC after the change; at the same time, increasing B2O3 and CaO can effectively improve the fluidity of the glass in the molten state, ensuring that the material can better fill the contact interface during the sintering process and improve the sealing; reducing SiO2 and increasing B2O3 and CaO will reduce the overall melting point of the glass, allowing it to be sintered at a lower temperature, which will help save energy and reduce consumption in actual production and avoid thermal damage to other components of the SOFC battery stack. Adding mica, an inorganic particle mixture, the glass and mica form a glass-ceramic composite, which can enhance the rigidity and compressive strength of the sealing material, effectively fill the micropores of the glass, reduce gas permeation, and improve the high-temperature stability and filling capacity of the sealing material, thereby reducing the stress caused by thermal expansion and improving the durability of the sealing material in the battery environment. The sealing material obtained by adjusting the component ratio in this application ultimately achieves a thermal expansion coefficient of ≥8×10 -6 / ℃ and low softening point (690℃) requirements, which solves the problems of thermal expansion coefficient mismatch, poor chemical compatibility with other battery components, uncertain long-term durability and high production cost, and has good applicability in medium and low temperature (<800℃) SOFC sealing applications.

[0037] Specifically, the mica is phlogopite, whose molecular formula is KMg3(AlSiO10 )(OH)2.

[0038] As an implementation method of the present application, the mass ratio of the mica to the barium aluminosilicate-based glass is 1:9.

[0039] Specifically, mica as ceramic particles can provide excellent thermal stability and good mechanical properties. A reasonable glass / ceramic ratio can lower the melting point, ensure good fluidity and filling capacity at high temperatures, effectively improve the high-temperature stability of the sealing material, and adapt to the working conditions of SOFC. Mica has good chemical stability and can improve the durability of the sealing material in the battery environment.

[0040] When the mass ratio of mica to glass is 1:9, the toughness of SOFC sealing materials can be improved to a certain extent, and the thermal expansion coefficient can reach ≥8×10 -6 / ℃ and softening point 690℃, can match well with other SOFC components, avoid sealing failure due to thermal expansion mismatch, and have suitable high-temperature viscosity, and its high-temperature resistance value meets the conductivity requirements of SOFC high-temperature sealing materials.

[0041] As one possible implementation method of the present application, the mass ratio of the mica to the barium aluminosilicate-based glass is 1:4. When the mica-to-glass mass ratio is 1:4, the toughness of the SOFC sealing material is significantly improved, while also having a good thermal expansion coefficient, enabling good compatibility with other SOFC components. Furthermore, when the mica-to-glass mass ratio is 1:4, the SOFC sealing material has an optimal high-temperature viscosity, ensuring good adhesion between the sealing material and adjacent components and maintaining structural integrity during high-temperature operation, thereby forming a good seal. Furthermore, its high-temperature resistance and average leakage rate meet the requirements for SOFC cell stack sealing.

[0042] The present invention also provides a method for preparing a sealing material for a solid oxide fuel cell, comprising the following steps:

[0043] The mica is heated to remove crystal water, cooled, and then ball-milled to obtain mica powder;

[0044] BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 are mixed in proportion, heated to form glass and then kept warm to obtain glass paste; the glass paste is quenched and formed, annealed, crushed, ball-milled and sieved to obtain glass powder;

[0045] The mica powder and the glass powder are mixed, and a solvent is added to mix them evenly to obtain a finished sealing material.

[0046] The present application adopts a melting process to prepare the sealing material, with Al2O3, La2O3 and mica as ceramic components, BaO, B2O3, SiO2, etc. as glass components, and CaO as inorganic particles. During the heat treatment process, the bonding and interaction between the particles can be promoted, the porosity in the sealing material can be reduced, the overall density and strength can be improved, and the microstructure of the sealing material can be made more uniform, thereby improving the performance stability. Mica is then mixed with glass to form a glass-ceramic composite, so that the mica particles can effectively fill the micropores of the glass, further improving the good fluidity and filling capacity of the sealing material at high temperatures.

[0047] As an embodiment of the present application, the step of heating the mica to remove crystal water includes:

[0048] The mica is placed in an electric furnace and heated at a temperature of 800° C. to 900° C. for 5 h to 7 h to remove crystal water.

[0049] As an implementation method of the present application, the step of uniformly mixing BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 according to a proportion, heating and forming glass, and then maintaining the temperature to obtain a glass paste includes:

[0050] BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 powder raw materials with purity ≥99.5% are mixed according to the proportion, placed in an electric furnace and heated to 1450℃-1650℃ at a heating rate of 4℃ / min-6℃ / min. After forming glass, keep warm for 9h-11h to obtain glass paste.

[0051] Preferably, heating to 1550°C at a heating rate of 5°C / min and keeping warm for 10 hours after forming glass helps to combine and interact with each component, reduce the porosity in the material, improve the density, make the microstructure of the glass more uniform, improve the performance stability, and enhance its filling capacity in sealing applications.

[0052] As an implementation method of the present application, the step of annealing the glass paste after quenching and forming the glass paste includes:

[0053] After the glass paste is quenched and formed on a graphite plate, it is immediately placed in an annealing furnace and kept at 580° C.-780° C. for 7 h-9 h, and then cooled to room temperature.

[0054] Preferably, annealing is performed at 680° C. for 8 hours to release internal stress and make the microstructure of the sealing material more uniform, thereby improving performance stability.

[0055] As an embodiment of the present application, the particle size of the glass powder is less than 45 μm. By controlling the particle size of the glass powder, the sealing material can flow more easily at high temperatures, which helps it achieve better filling effects in sealing applications.

[0056] As an implementation method of the present application, the solvent is a mixture of 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate in a mass ratio of (3.5-7.5): (4-6): (3.5-7.5): (4-6).

[0057] An embodiment of the present application further provides an application of a sealing material for a solid oxide fuel cell, wherein the sealing material is used to seal a metal connector of a solid oxide fuel cell.

[0058] The above technical solutions of the present application are described in detail below with reference to specific embodiments.

[0059] Example 1

[0060] A sealing material for a solid oxide fuel cell is prepared by the following steps:

[0061] The mica was placed in an electric furnace and heated at 850°C for 6 hours to remove crystal water, and then cooled and ball-milled to obtain mica powder.

[0062] 25 g of BaO, 15 g of Al2O3, 40 g of B2O3, 19 g of CaO, 10 g of La2O3, and 90 g of SiO2 powders with a purity of ≥99.5% were mixed in a proportion, placed in an electric furnace, and heated to 1550°C at a heating rate of 5°C / min. After forming glass, the mixture was kept warm for 10 hours to obtain a glass paste; the glass paste was quenched and formed on a graphite plate, and then immediately placed in an annealing furnace and kept warm at 680°C for 8 hours, cooled to room temperature, crushed, ball-milled, and sieved to obtain a glass powder with a particle size of less than 45 μm;

[0063] The mica powder and the glass powder are mixed in a mass ratio of 1:9, and a solvent is added and mixed evenly, wherein the solvent is 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate mixed in a mass ratio of 5.5:5:5.5:5 to obtain a finished sealing material.

[0064] Example 2

[0065] A sealing material for a solid oxide fuel cell is prepared by the following steps:

[0066] The mica was placed in an electric furnace and heated at 850°C for 6 hours to remove crystal water, and then cooled and ball-milled to obtain mica powder.

[0067] 25 g of BaO, 15 g of Al2O3, 40 g of B2O3, 19 g of CaO, 10 g of La2O3, and 90 g of SiO2 powders with a purity of ≥99.5% were mixed in a proportion, placed in an electric furnace, and heated to 1550°C at a heating rate of 5°C / min. After forming glass, the mixture was kept warm for 10 hours to obtain a glass paste; the glass paste was quenched and formed on a graphite plate, and then immediately placed in an annealing furnace and kept warm at 680°C for 8 hours, cooled to room temperature, crushed, ball-milled, and sieved to obtain a glass powder with a particle size of less than 45 μm;

[0068] The mica powder and the glass powder are mixed in a mass ratio of 1:4, and a solvent is added and mixed evenly, wherein the solvent is 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate mixed in a mass ratio of 5.5:5:5.5:5 to obtain a finished sealing material.

[0069] Example 3

[0070] A sealing material for a solid oxide fuel cell is prepared by the following steps:

[0071] The mica was placed in an electric furnace and heated at 850°C for 6 hours to remove crystal water, and then cooled and ball-milled to obtain mica powder.

[0072] 20 g of BaO, 10 g of Al2O3, 40 g of B2O3, 22 g of CaO, 8 g of La2O3, and 100 g of SiO2 powder raw materials with a purity of ≥99.5% were mixed in a proportion, placed in an electric furnace, and heated to 1550°C at a heating rate of 5°C / min. After forming glass, the mixture was kept warm for 10 hours to obtain a glass paste; the glass paste was quenched and formed on a graphite plate, and then immediately placed in an annealing furnace and kept warm at 680°C for 8 hours, cooled to room temperature, crushed, ball-milled, and sieved to obtain a glass powder with a particle size of less than 45 μm;

[0073] The mica powder and the glass powder are mixed in a mass ratio of 1:9, and a solvent is added and mixed evenly, wherein the solvent is 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate mixed in a mass ratio of 5.5:5:5.5:5 to obtain a finished sealing material.

[0074] Example 4

[0075] A sealing material for a solid oxide fuel cell is prepared by the following steps:

[0076] The mica was placed in an electric furnace and heated at 850°C for 6 hours to remove crystal water, and then cooled and ball-milled to obtain mica powder.

[0077] 22g of BaO, 20g of Al2O3, 42g of B2O3, 26g of CaO, 10g of La2O3, and 80g of SiO2 powder raw materials with a purity of ≥99.5% were mixed in a proportion, placed in an electric furnace, and heated to 1550°C at a heating rate of 5°C / min. After forming glass, the mixture was kept warm for 10 hours to obtain a glass paste; the glass paste was quenched and formed on a graphite plate, and then immediately placed in an annealing furnace and kept warm at 680°C for 8 hours, cooled to room temperature, crushed, ball-milled, and sieved to obtain a glass powder with a particle size of less than 45μm;

[0078] The mica powder and the glass powder are mixed in a mass ratio of 1:4, and a solvent is added and mixed evenly, wherein the solvent is 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate mixed in a mass ratio of 5.5:5:5.5:5 to obtain a finished sealing material.

[0079] Comparative Example 1

[0080] A sealing material for a solid oxide fuel cell is prepared by the following steps:

[0081] 25 g of BaO, 15 g of Al2O3, 40 g of B2O3, 19 g of CaO, 10 g of La2O3, and 90 g of SiO2 powders with a purity of ≥99.5% were mixed in a proportion, placed in an electric furnace, and heated to 1550°C at a heating rate of 5°C / min. After forming glass, the mixture was kept warm for 10 hours to obtain a glass paste; the glass paste was quenched and formed on a graphite plate, and then immediately placed in an annealing furnace and kept warm at 680°C for 8 hours, cooled to room temperature, crushed, ball-milled, and sieved to obtain a glass powder with a particle size of less than 45 μm;

[0082] A solvent is added to the glass powder and mixed evenly, wherein the solvent is 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate mixed in a mass ratio of 5.5:5:5.5:5 to obtain a finished sealing material.

[0083] Experimental example

[0084] (1) Microstructure observation

[0085] The sealing materials in Example 1, Example 2 and Comparative Example 1 were dried at 120°C, and then subjected to ball milling and sieving granulation procedures. The resulting powder was placed in a mold and pressed at a pressure of 270 MPa for 60 seconds to form a cylindrical sample with a diameter of 8 mm and a height of 20 mm. The sample was then placed in a high-temperature furnace, heated to 830°C at a heating rate of 5°C / min, and kept warm for 1 hour for sintering. It was then cooled to 750°C and kept warm for 4 hours for crystallization. The crystallized sample was then cut, ground, and polished. The microstructure of the sample was observed using a metallographic microscope with a 10x objective magnification and the image was recorded by a CCD. The results are shown in FIG. Figure 1 As shown, Figure 1 In the figure, part (a) is the microstructure diagram of the sample in comparative example 1; part (b) is the microstructure diagram of the sample in embodiment 1; and part (c) is the microstructure diagram of the sample in embodiment 2.

[0086] Depend on Figure 1 It can be seen that in parts (b) and (c), mica is uniformly dispersed in the glass matrix, while cracks appear in part (a). This is because glass materials are prone to embrittlement under tensile stress and are therefore prone to cracking. In Examples 1 and 2, by adding a certain amount of mica, the expansion of the cracks is suppressed, and when the mass ratio of mica to glass is 1:4, the toughness of the sealing material is greatly improved.

[0087] (2) Thermal expansion coefficient measurement

[0088] The crystallized sample in Experimental Example (1) was cut and ground into a sample with parallel upper and lower surfaces. The sample was then placed in a high-temperature dilatometer. Argon was used as the protective atmosphere. The sample was heated from room temperature to soften or to 900°C at a heating rate of 5°C / min and a load of 1g. The temperature and elongation of the sample were recorded in real time by a computer. Figure 2 shown.

[0089] Depend on Figure 2As can be seen, the thermal expansion coefficient of each sample gradually increases with increasing temperature, and the thermal expansion curve of the sample in Example 2 exhibits near-linear behavior within the measured temperature range. The curve is smooth and has no obvious inflection points. This near-linear behavior means that within a small temperature range, the thermal expansion coefficient of a material (the rate of volume change under temperature changes) can be approximately constant and does not fluctuate significantly with changes in temperature. Furthermore, the thermal expansion coefficient of the sample in Example 2 ranges from 7.74ppm / °C to 11.8ppm / °C (RT-600°C), showing similar thermal expansion behavior to other SOFC components (bipolar plates and metal interconnects). This indicates that the sample in Example 2 has excellent thermal compatibility with other SOFC components. This demonstrates that by optimizing the glass composition and incorporating a certain amount of mica, the thermal expansion coefficient of the glass can be fine-tuned to a certain extent, ensuring that it still matches well with other SOFC components and avoiding seal failure due to thermal expansion mismatch.

[0090] (3) High temperature viscosity measurement

[0091] High-temperature viscosity is a critical parameter for glass-ceramic sealants used in SOFC sealing. Suitable glass or glass-ceramic sealants for SOFC stacks must provide sufficient viscosity and mechanical strength to ensure good adhesion between the sealant and adjacent components and maintain structural integrity during high-temperature operation. The impact of high-temperature viscosity on SOFC glass sealants includes the following: 1. Sealing performance: Ideal viscosity ensures that the glass sealant is sufficiently fluid when heated to fill the gaps between cell components, thereby forming a good seal. If the viscosity is too high, the glass may not flow sufficiently, resulting in an incomplete seal and the risk of leakage. 2. Thermomechanical matching: The viscosity of the glass sealant affects its thermal expansion behavior. Appropriate viscosity helps the glass match the expansion coefficient of other cell materials during heating and cooling, reducing thermal stress and the possibility of cracking. 3. Processability: Viscosity affects the processing and handling of the glass sealant. Lower viscosity generally means better flowability, facilitating coating and molding during production, but too low a viscosity can lead to loss and an unstable seal structure. 4. Structural integrity: During use, the viscosity of the glass affects its ability to resist corrosion in oxidizing environments. Appropriate viscosity helps maintain the structural integrity of the sealant and extend its service life.

[0092] The sealing materials in Example 1, Example 2, and Comparative Example 1 were dried at 120°C, then ball-milled and sieved to granulate. The resulting powders were placed in a mold and pressed at 270 MPa for 60 seconds to form cylindrical samples with a diameter of 8 mm and a height of 6 mm. The samples were then placed in a high-temperature parallel plate viscometer, loaded with 0.025 MPa, and heated to 850°C at a heating rate of 5°C / min. The changes in sample viscosity and height with temperature were recorded. Figure 3shown.

[0093] Depend on Figure 3 It can be seen that under a specific external load (0.025 MPa), the viscosity and height of each sample change with temperature; all samples show a reflection point when the temperature is close to or exceeds their crystal temperature, which indicates that during the heating process, the two mechanisms of softening and hardening are competing; the viscosity of the sample of Comparative Example 1 decreases significantly when the temperature is higher than the glass transition temperature; compared with Comparative Example 1, the viscosity of the samples of Example 1 and Example 2 is higher, and the viscosity of the sample of Example 2 is higher than that of Example 1, which indicates that by adding a certain amount of mica in Example 1 and Example 2, it is beneficial to improve the viscosity of the sealing material, and when the mass ratio of mica to glass is 1:4, the viscosity of the sealing material is higher.

[0094] (4) High temperature resistance measurement

[0095] The sealing materials in Example 1, Example 2, and Comparative Example 1 were dried at 120°C, then ball-milled and sieved to granulate. The resulting powders were placed in a mold and pressed at 270 MPa for 60 seconds to form sheet samples with a thickness of 1 mm. The sheet samples were then placed in a high-temperature furnace, heated to 830°C at a heating rate of 5°C / min, and kept at that temperature for 1 hour for sintering. Ag paste was coated on both sides of the sintered sheet samples as conductive electrodes, and the samples were placed in a high-temperature furnace at 800°C to maintain the temperature. The two-point four-line method was used to record the changes in their resistance values ​​as the temperature was maintained for a period of time. The results are shown in Figure 2. Figure 4 shown.

[0096] Depend on Figure 4 It can be seen that the resistance of each sample was measured for more than 2700 hours in air at 800°C. The resistance of the samples in Example 2 and Comparative Example 1 increased with the increase in test time. In the long-term test, the resistance values ​​reached 289kΩ and 391kΩ, respectively. The resistance of the sample in Example 1 changed smoothly, with a resistance of approximately 69kΩ, which means that the resistance of each sample is much higher than the resistance of the SOFC metal connector. The sealing material obtained by optimizing the glass composition in this application has good applicability in SOFC sealing applications.

[0097] (5) High temperature thermal cycle seal leakage rate measurement

[0098] The sealing material of Example 2 was applied between upper and lower Crofer 22APU stainless steel substrates (ThyssenKrupp VDM GmbH, Germany). After a high-temperature curing process, a rectangular hollow structure specimen with a sealing area of ​​0.5 mm in height, 7 mm in width, and 45 mm in side length was formed. A pipe was opened in the upper substrate to allow gas to flow in. After applying a stress of 0.031 MPa and passing 2 psi of He gas, the test specimen was repeatedly heated and cooled between room temperature and 800°C at a heating / cooling rate of 2°C / min. The total temperature was maintained at 800°C for more than 1 hour. The change in sealing pressure with the holding time was recorded, and the leakage rate was calculated. The results are shown in Figure 2. Figure 5 shown.

[0099] Depend on Figure 5 It can be seen that after the sealing material in Example 2 and the Crofer22APU stainless steel metal connector were bonded and cured at high temperature, the average leakage rate after 50 thermal cycle (RT-800℃) leakage tests was 2.1×10 -4 mbar·l / s / cm, which is lower than the permissible upper limit of 5.2×10 -4 mbar·l / s / cm, indicating that the sealing material of the present application has good sealing performance and is suitable for sealing SOFC.

[0100] In summary, the present application is based on barium aluminosilicate-based glass. By changing the composition ratio and adding elements that can lower the melting point and increase fluidity, the molar ratio of La / Ca is adjusted, the use of rare earth raw material La2O3 is reduced, the B2O3 composition is optimized and the BaO ratio is reduced, and an inorganic particle mixture mica is added. The sealing material is prepared by a melting process, and the thermal expansion coefficient is ≥8×10 -6 / ℃ and softening point 690℃, and the resistance values ​​of the samples with mica to glass mixing ratio of 1:4 and 1:9 were 289kΩ and 69kΩ respectively in the high temperature (800℃) and long time (>2700 hours) test, which met the conductivity requirements of SOFC high temperature packaging materials. After high temperature bonding and curing with Crofer22APU stainless steel substrate using sealing material with mica to glass mixing ratio of 1:4, the average leakage rate was 2.1×10 -4 mbar·l / s / cm, which is lower than the permissible upper limit (5.2×10 -4 mbar·l / s / cm), which meets the sealing requirements of SOFC cell stack.

[0101] The above description is merely an optional embodiment of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application specification and drawings under the inventive concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A sealing material for a solid oxide fuel cell, characterized in that: including mica and barium aluminosilicate-based glasses; The components of the barium aluminosilicate-based glass are, by mass percentage, BaO 10%-15%, Al2O3 5%-10%, B2O3 15%-25%, CaO 6%-13%, La2O3 ≤ 5%, and the balance SiO2; wherein the thermal expansion coefficient of the sealing material for solid oxide fuel cells is ≥8×10 -6 / ℃, with a softening point of 690℃, and is used in SOFC sealing applications <800℃.

2. The sealing material for solid oxide fuel cells according to claim 1, wherein The mass ratio of the mica to the barium aluminosilicate-based glass is 1:

9.

3. The sealing material for solid oxide fuel cells according to claim 1, wherein The mass ratio of the mica to the barium aluminosilicate-based glass is 1:

4.

4. A method for preparing a sealing material for a solid oxide fuel cell according to any one of claims 1 to 3, characterized in that: The following steps are involved: The mica is heated to remove crystal water, cooled, and then ball-milled to obtain mica powder; BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 are mixed in proportion, heated to form glass and then kept warm to obtain glass paste; the glass paste is quenched and formed, annealed, crushed, ball-milled and sieved to obtain glass powder; The mica powder and the glass powder are mixed, and a solvent is added to mix them evenly to obtain a finished sealing material.

5. The method for preparing a sealing material for a solid oxide fuel cell according to claim 4, wherein: The step of heating the mica to remove crystal water comprises: The mica is placed in an electric furnace and heated at a temperature of 800° C. to 900° C. for 5 h to 7 h to remove crystal water.

6. The method for preparing a sealing material for a solid oxide fuel cell according to claim 4, wherein: The step of mixing BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 in a proportion, heating and forming glass and then keeping the temperature to obtain glass paste includes: BaO, Al2O3, B2O3, CaO, La2O3 and SiO2 powder raw materials with purity ≥99.5% are mixed according to the proportion, placed in an electric furnace and heated to 1450℃-1650℃ at a heating rate of 4℃ / min-6℃ / min. After forming glass, keep warm for 9h-11h to obtain glass paste.

7. The method for preparing a sealing material for a solid oxide fuel cell according to claim 4, wherein: The step of annealing the glass paste after quenching and forming the glass paste comprises: After the glass paste is quenched and formed on a graphite plate, it is immediately placed in an annealing furnace and kept at 580° C.-780° C. for 7 h-9 h, and then cooled to room temperature.

8. The method for preparing a sealing material for a solid oxide fuel cell according to claim 4, wherein: The particle size of the glass powder is less than 45 μm.

9. The method for preparing a sealing material for a solid oxide fuel cell according to claim 4, wherein: The solvent is prepared by mixing 96% ethanol, butanone, polyvinyl butyral and diisononyl phthalate in a mass ratio of (3.5-7.5): (4-6): (3.5-7.5): (4-6).

10. Use of the sealing material for a solid oxide fuel cell according to any one of claims 1 to 3, characterized in that: The sealing material is used for sealing metal interconnects of solid oxide fuel cells.

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