Low-temperature microcrystalline glass sealing material and preparation method thereof, and PCFC electric pile packaged by using low-temperature microcrystalline glass sealing material

Abstract

The invention relates to a low-temperature microcrystalline glass sealing material, a preparation method thereof and application of the sealing material to packaging of a PCFC (Poly Crystal Fuel Cell) electric pile, and aims to solve the problems of high use temperature, insufficient crystallization at low temperature and the like when the existing microcrystalline glass brazing filler metal is used for sealing a fuel cell. The preparation method comprises the following steps: 1, taking BaCO3, SiO2, B2O3, MgCO3, SrCO3, Al2O3 and TiO2 as raw materials, and carrying out ball milling; 2, melting the mixed powder at high temperature, and pouring glass melt into deionized water for water quenching to obtain glass particles; and 3, carrying out high-energy ball milling on the glass particles, and screening and drying to obtain the microcrystalline glass sealing material. By adding a certain amount of titanium dioxide, the crystal phase distribution, the microstructure and the use temperature range are effectively improved. The microcrystalline glass prepared by the invention has excellent compactness, chemical stability, thermal cycling stability and reliable sealing performance, and improves the long-term operation life and efficiency of a PCFC cell stack.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and in particular relates to the packaging materials for proton ceramic fuel cell (PCFC) stacks and their preparation and application methods. Background Technology

[0002] Proton ceramic fuel cells (PCFCs) are a novel, highly efficient, and clean energy conversion device operating in the intermediate temperature range (typically 500-700℃), and have become a research hotspot. They not only possess high energy conversion efficiency and environmental friendliness, but also offer advantages such as wide fuel adaptability (directly compatible with hydrocarbon fuels) and low precious metal requirements, effectively filling the technological gap between traditional high-temperature solid oxide fuel cells (SOFCs) and low-temperature proton exchange membrane fuel cells (PEMFCs). Compared to SOFCs, PCFCs operate at lower temperatures, significantly mitigating material compatibility issues and high-temperature corrosion; compared to PEMFCs, they exhibit higher energy density and stronger tolerance to fuel impurities.

[0003] However, the practical industrial application of PCFC stacks still faces many engineering challenges, with sealing technology being one of the core challenges. A PCFC stack consists of multiple individual cells (including electrolyte and electrodes) connected in series with metal interconnects. To ensure stable and efficient stack operation, it is necessary to prevent the mixing and leakage of fuel gas (such as wet hydrogen or hydrocarbon fuels) and oxidant gas (such as air) between different flow areas, and to provide the stack with necessary mechanical support and electrical isolation. Therefore, the selection of sealing materials is crucial. Sealing failure is one of the main causes of fuel cell stack performance degradation, shortened lifespan, and even catastrophic failure.

[0004] Ideal sealing materials for PCFCs must meet the following stringent requirements:

[0005] 1. High airtightness: Under the operating temperature and atmosphere conditions of PCFC, a long-term stable, dense, and leak-free sealed structure must be formed. Gas leakage can lead to fuel cross-contamination, reduce battery efficiency, and even cause safety hazards.

[0006] 2. Coefficient of Thermal Expansion (CTE) Matching: The CTE must match the electrolyte of the PCFC (e.g., BaCeO3-based or BaZrO3-based matrix electrolyte conductors, whose CTE is typically 9-11 × 10⁻⁶). -6 / K) and metal interconnects (e.g., chromium-rich ferritic stainless steel or high-temperature alloys, whose CTE is typically 10-12×10 -6 / K) has good CTE matching. CTE mismatch can generate huge thermal stress during heating and cooling, which can lead to interface cracking, material peeling or damage to the sealing layer.

[0007] 3. Excellent chemical stability: The fuel cell must not undergo harmful chemical reactions with any of the stack components (electrolyte, electrodes, interconnects) in the reducing atmospheres commonly found in PCFCs (e.g., wet hydrogen, dry hydrogen, reformed hydrocarbon fuels) or oxidizing atmospheres (e.g., air). Specifically, corrosion, element migration, byproduct formation, and interfacial reaction layer formation must be avoided, as these phenomena can impair the sealing layer performance and the overall stability of the stack.

[0008] 4. Excellent electrical insulation: It must maintain excellent electrical insulation performance under high temperature operating conditions to prevent current short circuits inside the fuel cell stack and ensure stable output of the series voltage of the fuel cell stack.

[0009] 5. Sufficient mechanical strength: It must have sufficient mechanical strength and creep resistance in high-temperature environments to withstand the internal pressure and its own weight during long-term operation of the fuel cell stack, and resist external vibration and impact.

[0010] 6. Excellent thermal cycling stability: PCFCs undergo frequent start-stop cycles during actual operation, leading to significant temperature fluctuations. The sealing material must be able to withstand hundreds or even thousands of thermal cycles to maintain seal integrity and prevent fatigue failure.

[0011] Currently, glass and glass-ceramics (also known as glass-ceramics) have been widely used in fuel cell sealing due to their excellent sealing performance, adjustable coefficient of thermal expansion, good chemical stability, and relatively low cost. Compared to pure glass, glass-ceramics, through a controlled crystallization process, transforms amorphous glass into a composite material consisting of fine crystals and a small amount of residual glass. This structure endows glass-ceramics with higher mechanical strength, better creep resistance, and more stable high-temperature characteristics, making it the preferred material for high-temperature fuel cell sealing. Other sealing technologies (such as metal compression sealing, welding, or brazing) generally suffer from defects such as creep, oxidation, corrosion, and poor high-temperature compatibility, making it difficult to meet the long-term operation requirements of PCFC stacks.

[0012] Among various glass-ceramic systems, BaO-MgO-B2O3-SiO2 glass-ceramics have become a research hotspot due to the good high-temperature stability and tunable crystallization transition (CTE) of their main crystalline phases (such as barium silicate and barium magnesium silicate). The CTE of these crystalline phases is at a moderate level, making them easy to match with the electrolyte and interconnect materials of PCFCs. However, it should be noted that existing research mainly focuses on SOFCs, and the reported glass-ceramic solders generally suffer from problems such as high operating temperatures and insufficient crystallization at low temperatures. Therefore, to better adapt this type of barium-magnesium-borosilicate glass-ceramic to the stringent requirements of PCFC stacks, especially to achieve long-term stable operation under complex conditions, it is urgent to develop a method that can precisely control its crystallization behavior and optimize its final performance. Summary of the Invention

[0013] The present invention aims to address the problems of high operating temperature, insufficient crystallization at low temperatures, and uneven distribution of crystalline phases in the use of existing microcrystalline glass brazing fillers for sealing fuel cells. The invention provides a method for preparing a low-temperature microcrystalline glass sealing material and its application in encapsulating PCFC stacks.

[0014] The low-temperature microcrystalline glass sealing material of the present invention is composed of 45-60 wt% BaO, 20-35 wt% SiO2, 10-20 wt% B2O3, 5-15 wt% MgO, 0.5-2 wt% SrO, 0.5-2 wt% Al2O3 and 1-10 wt% TiO2 by mass percentage.

[0015] The preferred TiO2 content in the microcrystalline glass sealing material of this invention is 2-5 wt%.

[0016] The preparation method of the low-temperature microcrystalline glass sealing material of the present invention is carried out according to the following steps:

[0017] Step 1: Use BaCO3, SiO2, B2O3, MgCO3, SrCO3, Al2O3 and TiO2 as raw materials, mix the raw materials and ball mill them to obtain mixed powder;

[0018] Step 2: Melt the mixed powder at high temperature to obtain glass melt, pour the glass melt into deionized water for water quenching, and obtain glass particles;

[0019] Step 3: High-energy ball milling is performed on the glass particles, followed by sieving and drying to obtain microcrystalline glass sealing material.

[0020] In this invention, BaCO3, MgCO3, and SrCO3 in the raw materials are converted into oxides after being melted at high temperature.

[0021] The method for encapsulating a PCFC stack using a low-temperature microcrystalline glass sealing material, as described in this invention, is implemented according to the following steps:

[0022] Step 1: Pre-treat the surfaces of the PCFC electrolyte and ferritic stainless steel to be joined, and dry them to obtain the PCFC electrolyte and ferritic stainless steel to be joined.

[0023] Step 2: Mix the microcrystalline glass sealing material with the adhesive to obtain a glass sealant. Then, apply the glass sealant to the surfaces of the PCFC electrolyte and the ferritic stainless steel to be connected, and assemble the components to be sealed.

[0024] Step 3: Apply welding pressure to the part to be sealed, hold it at 400-450℃ in air, and then heat it to 750-850℃ for welding to complete the sealing of the PCFC electrolyte and the ferritic stainless steel.

[0025] This invention proposes a method for preparing a low-temperature microcrystalline glass sealing material and applying it to encapsulate PCFC stacks. By optimizing the composition of barium magnesium borosilicate microcrystalline glass, a sealing material suitable for PCFC stacks is obtained. This low-temperature microcrystalline glass sealing material reduces the connection temperature and minimizes damage to the base material's properties. Furthermore, it improves the types and distribution of crystalline phases within the glass, shortens the time required for complete internal crystallization, and enhances the stack sealing efficiency. Stack encapsulation can be completed in just 1 hour within a temperature range of 750~850℃.

[0026] The preparation method and application of the low-temperature microcrystalline glass sealing material of this invention for encapsulating PCFC stacks have the following beneficial effects:

[0027] The introduction of TiO2 effectively regulates the nucleation and crystal growth process of the glass and controls the TiO2 content in the mixed powder, resulting in a uniform distribution and refined grains in the final microcrystalline glass, significantly improving the overall uniformity and reliability of the material. Simultaneously, the TiO2-modified microcrystalline glass achieves excellent CTE matching with the PCFC electrolyte and interconnects, minimizing thermal stress during stack operation and start-up / shutdown, and effectively avoiding the risk of interface cracking and delamination. The optimized crystalline phase possesses a higher melting point and thermal stability, ensuring the sealing material maintains stable performance within the typical PCFC operating temperature range of 500–700°C, and also possesses the potential for short-term operation at higher temperatures such as 750°C, significantly broadening its operating temperature range and enhancing high-temperature stability. Furthermore, the dense crystalline structure and optimized crystalline phase composition further enhance the material's corrosion resistance in reducing atmospheres such as wet hydrogen and oxidizing atmospheres such as air, ensuring interface integrity during long-term operation. Based on the above characteristics, the seals made using this microcrystalline glass can form a highly dense and stable sealing interface, reducing the helium leakage rate to an extremely low level. At the same time, during thermal cycling, thanks to the synergistic optimization of the microstructure and CTE, the thermal stress inside the material and at the interface is significantly reduced, and the fatigue resistance and long-term reliability are significantly improved. It can withstand hundreds or even thousands of thermal cycles while maintaining the integrity of the seal, ultimately achieving a significant extension of the PCFC stack's operating life and a comprehensive improvement in overall efficiency and reliability. Attached Figure Description

[0028] Figure 1 Backscattered electron micrograph of the interface microstructure of BZCYYb ceramic / Crofer 22 H stainless steel joint obtained using low-temperature microcrystalline glass sealing material at 775℃ / 30min / 0.2kPa in Example 1;

[0029] Figure 2The image shows a magnified backscattered electron image of the ceramic side interface of a BZCYYb ceramic / Crofer 22 H stainless steel connector obtained using a low-temperature microcrystalline glass sealing material at 775℃ / 30min / 0.2kPa in Example 1.

[0030] Figure 3 The image shows a magnified backscattered electron image of the stainless steel side interface of a BZCYYb ceramic / Crofer 22 H stainless steel connector obtained using low-temperature microcrystalline glass sealing material at 775℃ / 30min / 0.2kPa in Example 1.

[0031] Figure 4 Backscattered electron micrographs of the interface microstructure of the BZCYYb ceramic / Crofer 22 H stainless steel joint were obtained using low-temperature microcrystalline glass sealing material under the conditions of 800℃ / 60min / 0.2kPa in Comparative Example 1. Detailed Implementation

[0032] Specific Implementation Method 1: The preparation method of the low-temperature microcrystalline glass sealing material in this implementation method is carried out according to the following steps:

[0033] Step 1: Use BaCO3, SiO2, B2O3, MgCO3, SrCO3, Al2O3 and TiO2 as raw materials, mix the raw materials and ball mill them to obtain mixed powder;

[0034] Step 2: Melt the mixed powder at high temperature to obtain glass melt, pour the glass melt into deionized water for water quenching, and obtain glass particles;

[0035] Step 3: High-energy ball milling is performed on the glass particles, followed by sieving and drying to obtain microcrystalline glass sealing material.

[0036] This embodiment effectively improves the crystalline phase distribution, microstructure, and operating temperature range by adding a certain amount of titanium dioxide (TiO2). Specifically, TiO2, as a highly efficient nucleating agent, promotes the precipitation of uniform and fine crystals, optimizes the type and proportion of the main crystalline phases (such as barium silicate and barium magnesium silicate), and eliminates the harmful phase barium aluminum silicate. As a result, the prepared glass-ceramic has a thermal expansion coefficient that is closer to that of the electrolyte and interconnect materials, and broadens its operational stability in the medium temperature range of 500-700°C.

[0037] The microcrystalline glass prepared in this embodiment has excellent compactness, chemical stability, thermal cycling stability and reliable sealing performance; the formed connection structure is free of defects such as pores and cracks, which significantly improves the long-term operating life and efficiency of PCFC battery stacks.

[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that, in step one, 42%-52% of BaCO3, 18-28wt% of SiO2, 5-12wt% of B2O3, 17-20wt% of MgCO3, 1-1.5wt% of SrCO3, 1-1.5wt% of Al2O3 and 1.5-5wt% of TiO2 are weighed as raw materials according to their mass percentages. The raw materials are mixed and ball-milled to obtain a mixed powder.

[0039] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the rotation speed of the ball mill is controlled at 200-400 r / min in step 1, and the ball milling time is 1-3 hours.

[0040] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the high-temperature melting temperature in step two is 1100-1300℃, and the temperature is maintained for 1-3 hours.

[0041] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the rotation speed of the high-energy ball mill is controlled at 300-600 r / min in step 3, and the ball milling time is 6-12 h.

[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the sieving in step three refers to filtering through a 300-mesh sieve, and the drying temperature is 60℃.

[0043] Specific Implementation Method Seven: This implementation method for encapsulating a PCFC stack using low-temperature microcrystalline glass sealing material is carried out according to the following steps:

[0044] Step 1: Pre-treat the surfaces of the PCFC electrolyte and ferritic stainless steel to be joined, and dry them to obtain the PCFC electrolyte and ferritic stainless steel to be joined.

[0045] Step 2: Mix the microcrystalline glass sealing material with the adhesive to obtain a glass sealant. Then, apply the glass sealant to the surfaces of the PCFC electrolyte and the ferritic stainless steel to be connected, and assemble the components to be sealed.

[0046] Step 3: Apply welding pressure to the part to be sealed, hold it at 400-450℃ in air, and then heat it to 750-850℃ for welding to complete the sealing of the PCFC electrolyte and the ferritic stainless steel.

[0047] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the pretreatment in step one involves first ultrasonic cleaning with anhydrous ethanol, followed by progressive polishing with 400#, 800#, 1200#, 1500#, and 2000# wet sandpaper, and then ultrasonic cleaning with anhydrous ethanol and acetone in sequence, with each cleaning session lasting 5 to 10 minutes.

[0048] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Seven or Eight in that the material of the PCFC electrolyte in step one is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) or BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY); The stainless steel interconnect is made of Crofer 22 H, Crofer 22 APU, AISI 441 or AISI 430.

[0049] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 7 to 9 in that in step 2, a screen printing process is used to coat the glass sealant onto the surface of the PCFC electrolyte and the ferritic stainless steel to be connected, and the coating thickness is controlled to be 50-500μm.

[0050] Specific Implementation Method Eleven: This implementation method differs from Specific Implementation Methods Seven to Ten in that the welding pressure applied in step three is 0.1-1 kPa.

[0051] Specific Implementation Method Twelve: This implementation method differs from Specific Implementation Methods Seven to Eleven in that in step three, the temperature is kept at 400-450°C for 2 hours in an air atmosphere, and then the temperature is raised to 750-850°C for welding for 0.5-2 hours.

[0052] Example 1: The preparation method and application of the low-temperature microcrystalline glass sealing material in this example for encapsulating a PCFC stack are carried out according to the following steps:

[0053] Step 1: Weigh out 48% BaCO3, 19.9wt% SiO2, 8.7wt% B2O3, 18.3wt% MgCO3, 1.1wt% SrCO3, 1.2wt% Al2O3 and 2.8wt% TiO2 as raw materials according to mass percentage. Mix the raw materials and ball mill at 200 rpm for 2 hours to obtain mixed powder.

[0054] Step 2: Melt the mixed powder at high temperature (1200℃, 2h) to obtain glass melt. Quickly pour the glass melt into deionized water at 20℃ for water quenching to obtain glass particles.

[0055] Step 3: High-energy ball milling is performed on the glass particles, with the ball milling speed controlled at 400 rpm and the ball milling time at 10 h. After passing through a 300-mesh sieve and drying (60℃), the microcrystalline glass sealing material is obtained.

[0056] Step 4: The surfaces to be joined between the BZCYYb electrolyte and Crofer 22 H ferritic stainless steel are successively polished with 400#, 800#, 1200#, 1500#, and 2000# wet sandpaper. Then, they are ultrasonically cleaned with anhydrous ethanol and acetone in sequence, with each cleaning time being 10 minutes. After drying, the PCFC electrolyte and ferritic stainless steel to be joined are obtained.

[0057] Step 5: Mix the microcrystalline glass sealing material, ethyl cellulose and terpineol in a mass ratio of 100:5:25 to obtain a glass sealant. Then, apply the glass sealant to the surfaces of the PCFC electrolyte and ferritic stainless steel to be connected using a screen printing process, controlling the coating thickness to be 200μm. Align and stack the surfaces to be connected to obtain the sealing component.

[0058] Step 6: Apply a welding pressure of 0.2 kPa to the part to be sealed, hold it at 400℃ (heating rate of 5℃ / min) in air for 2 hours, then heat it to 775℃ (heating rate of 2℃ / min) and hold it for 0.5 hours, then cool it to room temperature at a rate of 2℃ / min to complete the sealing of the PCFC electrolyte and the ferritic stainless steel.

[0059] The microcrystalline glass sealing material obtained in step three of this embodiment is composed of 47% BaO, 25% SiO2, 11% B2O3, 11% MgO, 1% SrO, 1.5% Al2O3 and 3.5% TiO2 by mass percentage.

[0060] pass Figure 1 It can be seen that using microcrystalline glass sealing material to connect the BZCYYb electrolyte and Crofer 22 H stainless steel results in a dense and defect-free interface, with sufficient internal crystallization. Through... Figure 2 Magnified observation of the interface shows that the microcrystalline glass sealing material and the BZCYYb electrolyte form a good bond. Figure 3 A magnified view of the interface structure on the stainless steel side is presented. The figure shows that the microcrystalline glass sealing material forms a direct bond with the oxide layer on the stainless steel surface, and the resulting sealing structure can meet the requirements for service in PCFC stacks.

[0061] In this embodiment, the connection between the BZCYYb electrolyte and Crofer 22 H stainless steel was achieved at 775°C, which is 100-150°C lower than the connection temperature of other existing methods. The microcrystalline glass sealing material did not react violently with the parent materials on both sides, especially since the reaction layer at the electrolyte interface was thin and the damage to its performance was negligible. Moreover, after 0.5 hours of heat preservation, sufficient crystallization occurred inside the sealing material, and the shear strength of the sealing structure reached 20 MPa. This shows that the method of the present invention can achieve efficient sealing between the BZCYYb electrolyte and Crofer 22 H stainless steel, and has significant technical advantages.

[0062] In this embodiment, TiO2 nucleating agent is introduced to promote the formation of a uniform fine grain structure and guide the precipitation of favorable crystalline phases, thereby preparing a microcrystalline glass sealing material and using it to encapsulate the PCFC electrolyte and stainless steel interconnect. This reduces the connection temperature and ensures sufficient crystallization inside the glass, resulting in a well-bonded and defect-free sealing interface.

[0063] Comparative Example: The preparation method and application of the microcrystalline glass sealing material for encapsulating a PCFC stack in this example are carried out according to the following steps:

[0064] Step 1: Weigh out 49.8% BaCO3, 19.9wt% SiO2, 8.7wt% B2O3, 19.3wt% MgCO3, 1.1wt% SrCO3 and 1.2wt% Al2O3 as raw materials according to mass percentage. Mix the raw materials and ball mill at 200 rpm for 2 hours to obtain mixed powder.

[0065] Step 2: Melt the mixed powder at high temperature (1200℃, 2h) to obtain glass melt. Quickly pour the glass melt into deionized water at 20℃ for water quenching to obtain glass particles.

[0066] Step 3: High-energy ball milling is performed on the glass particles, with the ball milling speed controlled at 400 rpm and the ball milling time at 10 h. After passing through a 300-mesh sieve and drying (60℃), the microcrystalline glass sealing material is obtained.

[0067] Step 4: The surfaces to be joined between the BZCYYb electrolyte and Crofer 22 H ferritic stainless steel are successively polished with 400#, 800#, 1200#, 1500#, and 2000# wet sandpaper. Then, they are ultrasonically cleaned with anhydrous ethanol and acetone in sequence, with each cleaning time being 10 minutes. After drying, the PCFC electrolyte and ferritic stainless steel to be joined are obtained.

[0068] Step 5: Mix the microcrystalline glass sealing material, ethyl cellulose and terpineol in a mass ratio of 100:5:25 to obtain a glass sealant. Then, apply the glass sealant to the surfaces of the PCFC electrolyte and ferritic stainless steel to be connected using a screen printing process, controlling the coating thickness to be 200μm. Align and stack the surfaces to be connected to obtain the sealing component.

[0069] Step 6: Apply a welding pressure of 0.2 kPa to the part to be sealed, hold it at 400℃ (heating rate of 5℃ / min) in air for 2 hours, then heat it to 800℃ (heating rate of 2℃ / min) and hold it for 1 hour, then cool it to room temperature at a rate of 2℃ / min to complete the sealing of the PCFC electrolyte and the ferritic stainless steel.

[0070] observe Figure 4 It is known that after removing TiO2 from the raw materials, the microcrystalline glass sealing material cannot complete the sealing of BZCYYb electrolyte and Crofer 22 H stainless steel at 800℃. The resulting sealing structure has many defects such as pores, and the shear strength is only 5MPa.

Claims

1. A low-temperature microcrystalline glass sealing material, characterized in that... The low-temperature microcrystalline glass sealing material is composed of 45-60 wt% BaO, 20-35 wt% SiO2, 10-20 wt% B2O3, 5-15 wt% MgO, 0.5-2 wt% SrO, 0.5-2 wt% Al2O3, and 1-10 wt% TiO2 by mass percentage.

2. The method for preparing the low-temperature microcrystalline glass sealing material as described in claim 1, characterized in that... The preparation method of the low-temperature microcrystalline glass sealing material is carried out according to the following steps: Step 1: Use BaCO3, SiO2, B2O3, MgCO3, SrCO3, Al2O3 and TiO2 as raw materials, mix the raw materials and ball mill them to obtain mixed powder; Step 2: Melt the mixed powder at high temperature to obtain glass melt, pour the glass melt into deionized water for water quenching, and obtain glass particles; Step 3: High-energy ball milling is performed on the glass particles, followed by sieving and drying to obtain microcrystalline glass sealing material.

3. The method for preparing the low-temperature microcrystalline glass sealing material according to claim 2, characterized in that... In step one, 42%-52% of BaCO3, 18-28wt% of SiO2, 5-12wt% of B2O3, 17-20wt% of MgCO3, 1-1.5wt% of SrCO3, 1-1.5wt% of Al2O3 and 1.5-5wt% of TiO2 are weighed as raw materials according to mass percentage. The raw materials are mixed and ball-milled to obtain mixed powder.

4. The method for preparing the low-temperature microcrystalline glass sealing material according to claim 2, characterized in that... In step two, the high-temperature melting temperature is 1100-1300℃, and the temperature is maintained for 1-3 hours.

5. The method for preparing the low-temperature microcrystalline glass sealing material according to claim 2, characterized in that... In step three, the rotation speed of the high-energy ball mill is controlled at 300-600 r / min, and the milling time is 6-12 h.

6. A method for encapsulating a PCFC stack using the low-temperature microcrystalline glass sealing material prepared according to claim 2, characterized in that... The method for encapsulating a PCFC stack using low-temperature microcrystalline glass sealing material is implemented according to the following steps: Step 1: Pre-treat the surfaces of the PCFC electrolyte and ferritic stainless steel to be joined, and dry them to obtain the PCFC electrolyte and ferritic stainless steel to be joined. Step 2: Mix the microcrystalline glass sealing material with the adhesive to obtain a glass sealant. Then, apply the glass sealant to the surfaces of the PCFC electrolyte and the ferritic stainless steel to be connected, and assemble the components to be sealed. Step 3: Apply welding pressure to the part to be sealed, hold it at 400-450℃ in air, and then heat it to 750-850℃ for welding to complete the sealing of the PCFC electrolyte and the ferritic stainless steel.

7. The method for encapsulating a PCFC stack using a low-temperature microcrystalline glass sealing material according to claim 6, characterized in that... The material of the PCFC electrolyte in step one is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ or BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ The stainless steel interconnects are made of Crofer 22 H, Crofer 22 APU, AISI 441, or AISI 430.

8. The method for encapsulating a PCFC stack using a low-temperature microcrystalline glass sealing material according to claim 6, characterized in that... In step two, a glass sealant is applied to the surface of the PCFC electrolyte and the ferritic stainless steel to be connected using a screen printing process, with the coating thickness controlled to be 50-500μm.

9. The method for encapsulating a PCFC stack using a low-temperature microcrystalline glass sealing material according to claim 6, characterized in that... The welding pressure applied in step three is 0.1-1 kPa.

10. The method for encapsulating a PCFC stack using a low-temperature microcrystalline glass sealing material according to claim 6, characterized in that... In step three, the temperature is maintained at 400-450℃ in air for 2 hours, and then the temperature is raised to 750-850℃ for welding for 0.5-2 hours.

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