SOFC high-temperature vermiculite sealing material and preparation method therefor

Abstract

The present invention relates to the technical field of sealing materials. Disclosed are an SOFC high-temperature vermiculite sealing material and a preparation method therefor. The material is prepared from modified chemically-expanded vermiculite and anion high-temperature expanded vermiculite. The modified chemically-expanded vermiculite is positively charged, and the anion high-temperature expanded vermiculite is negatively charged; and the two are mixed to generate electrostatic attraction so as to achieve compounding. The material does not contain any adhesive, and the ignition loss is significantly reduced while the compounding strength of the sealing material is unchanged. A fatty acid salt is used as an intercalation agent of the chemically-expanded vermiculite, and the modified chemically-expanded vermiculite prepared from the fatty acid salt has a 700°C high-temperature-resistant compressive strength. The anion high-temperature expanded vermiculite is produced by treating high-temperature expanded vermiculite with anion air, allowing the high-temperature expanded vermiculite to be loaded with and accumulate negative charges, and treating high-temperature expanded vermiculite with anion air requires no chemical agents, has a simple process, and can be produced on a large scale.

Description

A SOFC high-temperature vermiculite sealing material and its preparation method Technical Field

[0001] This invention relates to the field of sealing materials technology, and in particular to a SOFC high-temperature vermiculite sealing material and its preparation method. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are energy conversion devices that directly convert the chemical energy of fuel into electrical energy. They are not limited by the Carnot cycle, have high energy conversion efficiency, and possess advantages such as wide fuel adaptability, clean and pollution-free operation, all-solid-state structure, and no use of precious metal catalysts. The fuel cell stack is the core component of an SOFC, and it is sealed using stack sealing materials. Currently, the main stack sealing materials in existing technologies are high-temperature glass adhesive and high-temperature ceramic adhesive. However, glass, metal, and solar cells have different coefficients of thermal expansion. Under operating conditions of high temperature, current, and airflow disturbances, the stack sealing structure is easily damaged, leading to performance degradation and severely limiting the number of stack start-ups and shutdowns. Therefore, a new stack sealing material is needed.

[0003] The publication CN112424310 B discloses a sealing material, indicating that high-temperature vermiculite sealing material possesses extremely stable characteristics such as high thermal cycling resistance, high temperature resistance, and corrosion resistance, making it a high-performance SOFC sealing material. Currently, traditional high-temperature vermiculite sealing materials are formed by bonding chemically expanded vermiculite and high-temperature expanded vermiculite using polymer binders. Since the polymer binder is mainly an organic polymer, it carbonizes at high temperatures. This causes the burn-off of the high-temperature sealing material to increase with the amount of polymer binder used. Excessive burn-off can lead to structural collapse and a significant reduction in sealing performance. Therefore, the preparation of high-temperature vermiculite sealing materials requires a balance between bond strength and burn-off to ensure the strength of the sealing material while minimizing burn-off. Summary of the Invention

[0004] To overcome the problems of high binder content and high burn-off in existing high-temperature vermiculite sealing materials, this invention provides a SOFC high-temperature vermiculite sealing material and its preparation method. This material is made of modified chemically expanded vermiculite and negatively charged high-temperature expanded vermiculite. The modified chemically expanded vermiculite carries a positive charge, and the negatively charged high-temperature expanded vermiculite carries a negative charge. When the two are mixed, they generate electrostatic attraction to achieve composite bonding. This material does not use binders and significantly reduces burn-off without changing the composite strength of the sealing material.

[0005] The specific technical solution of the present invention is as follows: A SOFC high-temperature vermiculite sealing material, the raw materials of which include modified chemically expanded vermiculite and negative ion high-temperature expanded vermiculite, wherein the raw materials of the modified chemically expanded vermiculite include stearate and chemically expanded vermiculite, and the mass ratio of stearate to chemically expanded vermiculite is 3-5:1, and the raw materials of the negative ion high-temperature expanded vermiculite are negative ion air and high-temperature expanded vermiculite.

[0006] This invention provides a SOFC high-temperature vermiculite sealing material, which is composed of positively charged modified chemically expanded vermiculite and negatively charged negatively charged high-temperature expanded vermiculite through electrostatic attraction. Compared with traditional high-temperature vermiculite sealing materials that use adhesives, the composite strength remains unchanged while the burn-off is significantly reduced.

[0007] The modified chemically expanded vermiculite of this invention employs stearate intercalation agent to modify the chemically expanded vermiculite. Chemically expanded vermiculite exhibits the characteristic of interlayer charge accumulation; therefore, cation exchangers can be used for intercalation modification. The accumulation of positive charge increases the interlayer spacing of the modified vermiculite. Commonly used cation exchangers include quaternary ammonium salt cation exchangers. However, in practical application, it was found that quaternary ammonium salt cation exchangers used in traditional sealing materials are prone to high-temperature decomposition. This leads to rapid failure of the electrostatically attracted composite modified chemically expanded vermiculite and the negative ion high-temperature expanded vermiculite under high-temperature environments, causing the sealing material structure to collapse. Therefore, to address the above problems, this application selects stearate as the intercalation agent for chemically expanded vermiculite. The modified chemically expanded vermiculite made using stearate exhibits a high-temperature compressive strength of 700℃.

[0008] The negative ion high-temperature expanded vermiculite of the present invention uses negative ion air to treat the high-temperature expanded vermiculite, so that the high-temperature expanded vermiculite is loaded and accumulates negative charge. The high-temperature expanded vermiculite treated with negative ion air does not require the use of chemical agents and the process is simple and can be mass-produced.

[0009] Preferably, the mass ratio of modified chemically expanded vermiculite to negative ion high-temperature expanded vermiculite is 2 to 4:1.

[0010] Preferably, the concentration of negative ions in the negative ion air is 10,000 to 15,000 ions / cm³. 3 .

[0011] Preferably, the chemically expanded vermiculite is 20-50 mesh.

[0012] Preferably, the particle size of the high-temperature expanded vermiculite is 300-325 mesh.

[0013] A method for preparing the above-mentioned SOFC high-temperature vermiculite sealing material includes the following steps: ball milling stearate and chemically expanded vermiculite in a ball milling device to prepare modified chemically expanded vermiculite; passing air into a high-voltage ionization chamber for negative high-voltage ionization treatment to prepare negative ion air; passing the negative ion air into a filter element containing high-temperature expanded vermiculite for filtration treatment to prepare negative ion high-temperature expanded vermiculite; mixing and stirring the modified chemically expanded vermiculite and negative ion high-temperature expanded vermiculite evenly, and then pressing and molding to prepare SOFC high-temperature vermiculite sealing material.

[0014] This invention also provides a method for preparing the aforementioned SOFC high-temperature vermiculite sealing material. In this method, the high-temperature vermiculite containing negative ions is made from negative ion air and high-temperature expanded vermiculite. The negative ion air is produced by ionizing air in a high-voltage electrostatic chamber. After the air undergoes high-voltage electrostatic treatment, negative ions are generated. The negative ion air is then passed into a filter element made of high-temperature expanded vermiculite. Through the filtration effect of the high-temperature expanded vermiculite, the negative ions in the air are loaded onto the high-temperature expanded vermiculite, thereby causing the high-temperature expanded vermiculite to accumulate negative charges. Using this method to prepare the negative ion high-temperature expanded vermiculite does not require the use of chemical agents, and the process is simple and can be mass-produced.

[0015] Preferably, the pressure for the pressure molding is 5-10 MPa and the time is 1-3 hours.

[0016] Preferably, the ball milling time is 50-80 rpm and the milling time is 1-2 hours.

[0017] Preferably, the voltage of the high-voltage ionization treatment is 10000-12000V.

[0018] Preferably, the airflow rate for negative ions is 100–200 cm⁻¹. 3 The filter treatment time is 3-5 hours, and the mass of the high-temperature expanded vermiculite is 0.8-1 kg.

[0019] Compared with the prior art, this application has the following technical effects: (1) The material is made of modified chemically expanded vermiculite and negative ion high-temperature expanded vermiculite. The modified chemically expanded vermiculite has a positive charge, and the negative ion high-temperature expanded vermiculite has a negative charge. After the two are mixed, electrostatic attraction is generated to achieve composite. The material does not use adhesives, and the loss on ignition is significantly reduced without changing the composite strength of the sealing material; (2) As an intercalating agent for chemically expanded vermiculite, the modified chemically expanded vermiculite made using stearate has a high temperature resistance and compressive strength of 700℃; (3) The negative ion high-temperature expanded vermiculite of the present invention uses negative ion air to treat the high-temperature expanded vermiculite so that the high-temperature expanded vermiculite is loaded and accumulates negative charge. The use of negative ion air to treat the high-temperature expanded vermiculite does not require the use of chemical agents and the process is simple and can be mass-produced. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments.

[0021] Example 1: A method for preparing SOFC high-temperature vermiculite sealing material, comprising the following steps: Step 1: Add 1L of anhydrous ethanol, 300g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) to a ball mill. Heat the ball mill to 60°C and ball mill at 50 rpm for 1 hour to prepare a wet material. After cooling, rinse the wet material with deionized water and dry it in an 80°C oven to prepare modified chemically expanded vermiculite; Step 2: Pass air into a high-voltage electrostatic chamber and apply a voltage of 10000V to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.8 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The air flow rate is 100 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 2:1, place the mixture in a mold and pressurize it with a pressure of 5MPa for 3h to make SOFC high temperature vermiculite sealing material.

[0022] Example 2: A method for preparing a SOFC high-temperature vermiculite sealing material, comprising the following steps: Step 1: Add 1L of anhydrous ethanol, 400g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) to a ball mill. Heat the ball mill to 70°C and ball mill at 70 rpm for 1-2 hours to prepare a wet material. After cooling, rinse the wet material with deionized water and dry it in an 80°C oven to prepare modified chemically expanded vermiculite; Step 2: Pass air into a high-voltage electrostatic chamber and apply an 11000V voltage to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 12000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.9 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The airflow rate is 150 cm³ / h. 3 / min, filtration time is 4h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite with a mass ratio of 3:1 are mixed and stirred, the mixture is placed in a mold and pressurized at 8MPa for 2h to make SOFC high temperature vermiculite sealing material.

[0023] Example 3: A method for preparing SOFC high-temperature vermiculite sealing material, comprising the following steps: Step 1: Add 1L of anhydrous ethanol, 500g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) to a ball mill. Heat the ball mill to 80℃ and ball mill at 80rpm for 1-2 hours to prepare a wet material. After cooling, rinse the wet material with deionized water and dry it in an 80℃ oven to prepare modified chemically expanded vermiculite; Step 2: Pass air into a high-voltage electrostatic chamber and apply a voltage of 12000V to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 15000 ions / cm³. 3 Negative ion air is pumped into an air filter via an output pump. The filter element is filled with 1 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter treats the negative ion air to produce negative ion high-temperature expanded vermiculite. The airflow rate is 200 cm³ / h. 3 / min, filtration time is 5h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite with a mass ratio of 5:1 are mixed and stirred, the mixture is placed in a mold and pressurized at 10MPa for 1h to make SOFC high temperature vermiculite sealing material.

[0024] Example 4: A method for preparing SOFC high-temperature vermiculite sealing material, comprising the following steps: Step 1: Add 1L of anhydrous ethanol, 400g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) to a ball mill. Heat the ball mill to 80°C and ball mill at 80 rpm for 1 hour to prepare a wet material. After cooling, rinse the wet material with deionized water and dry it in an 80°C oven to prepare modified chemically expanded vermiculite; Step 2: Pass air into a high-voltage electrostatic chamber and apply a voltage of 10000V to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter via an output pump. The filter element is filled with 1 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The airflow rate is 100 cm³ / h. 3 / min, filtration time is 5h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 3:1, place the mixture in a mold and pressurize it at 10MPa for 1h to make SOFC high temperature vermiculite sealing material.

[0025] Example 5: A method for preparing SOFC high-temperature vermiculite sealing material, comprising the following steps: Step 1: Add 1L of anhydrous ethanol, 400g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) to a ball mill. Heat the ball mill to 80°C and ball mill at 80 rpm for 1 hour to prepare a wet material. After cooling, rinse the wet material with deionized water and dry it in an 80°C oven to prepare modified chemically expanded vermiculite; Step 2: Pass air into a high-voltage electrostatic chamber and apply a voltage of 10000V to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 15000 ions / cm³. 3 Negative ion air is pumped into an air filter via an output pump. The filter element is filled with 1 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter treats the negative ion air to produce negative ion high-temperature expanded vermiculite. The airflow rate is 200 cm³ / h. 3 / min, filtration time is 5h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 3:1, place the mixture in a mold and pressurize it at 10MPa for 1h to make SOFC high temperature vermiculite sealing material.

[0026] Example 6: A method for preparing SOFC high-temperature vermiculite sealing material, comprising the following steps: Step 1: Add 1L of anhydrous ethanol, 400g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) to a ball mill. Heat the ball mill to 60-80℃ and ball mill at 50-80 rpm for 1-2 hours to prepare a wet material. After cooling, rinse the wet material with deionized water and dry it in an 80℃ oven to prepare modified chemically expanded vermiculite; Step 2: Pass air into a high-voltage electrostatic chamber and apply a voltage of 12000V to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 15000 ions / cm³. 3 Negative ion air is pumped into an air filter via an output pump. The filter element is filled with 1 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter treats the negative ion air to produce negative ion high-temperature expanded vermiculite. The airflow rate is 200 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix and stir the modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 3:1, place the mixture in a mold and pressurize it at 10MPa for 1h to make SOFC high temperature vermiculite sealing material.

[0027] Comparative Example 1: Compared with Example 1, Comparative Example 1 uses an organic polymer binder SOFC high-temperature vermiculite sealing material. The organic polymer binder includes the following steps: Step 1: 1L of anhydrous ethanol, 300g of zinc stearate, and 100g of chemically expanded vermiculite (20-50 mesh) are added to a ball mill. The ball mill is heated to 60°C and then ball-milled at 50 rpm for 1 hour to produce a wet material. After cooling, the wet material is rinsed with deionized water and dried in an 80°C oven to produce modified chemically expanded vermiculite; Step 2: Air is introduced into a high-voltage electrostatic chamber, and a voltage of 10000V is applied to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.8 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The air flow rate is 100 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Modified chemical expanded vermiculite, negative ion high temperature expanded vermiculite and binder in mass ratio of 2:1:0.05 are vacuum kneaded and mixed, the mixture is placed in a mold for pre-forming and the blank is dried at 70℃. The blank is placed on a hot press vulcanizing machine for hot press vulcanization to make SOFC high temperature vermiculite sealing material.

[0028] Comparative Example 2: Compared with Example 1, Comparative Example 2 uses a quaternary ammonium salt cation exchanger to modify chemically expanded vermiculite. The quaternary ammonium salt cation exchanger is octadecyltrimethylammonium bromide, and the modification includes the following steps:

[0029] A method for preparing SOFC high-temperature vermiculite sealing material includes the following steps: Step 1: 1L of water, 300g of octadecyltrimethylammonium bromide, and 100g of chemically expanded vermiculite (20-50 mesh) are added to a ball mill. The ball mill is heated to 60℃ and then ball-milled at 50 rpm for 1 hour to produce a wet material. After cooling, the wet material is rinsed with deionized water and dried in an 80℃ oven to produce modified chemically expanded vermiculite; Step 2: Air is introduced into a high-voltage electrostatic chamber, and a voltage of 10000V is applied to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.8 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The air flow rate is 100 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 2:1, place the mixture in a mold and pressurize it with a pressure of 5MPa for 3h to make SOFC high temperature vermiculite sealing material.

[0030] Comparative Example 3: Compared with Example 1, Comparative Example 3 uses a quaternary ammonium salt cation exchanger to modify chemically expanded vermiculite. The quaternary ammonium salt cation exchanger is hexadecyltrimethylammonium bromide. The method includes the following steps: A method for preparing SOFC high-temperature vermiculite sealing material includes the following steps: Step 1: 1L of water, 300g of hexadecyltrimethylammonium bromide, and 100g of chemically expanded vermiculite (20-50 mesh) are added to a ball mill. The ball mill is heated to 60°C and then ball-milled at 50 rpm for 1 hour to prepare a wet material. After cooling, the wet material is rinsed with deionized water and dried in an 80°C oven to prepare modified chemically expanded vermiculite; Step 2: Air is introduced into a high-voltage electrostatic chamber and a voltage of 10000V is applied to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.8 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The air flow rate is 100 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 2:1, place the mixture in a mold and pressurize it with a pressure of 5MPa for 3h to make SOFC high temperature vermiculite sealing material.

[0031] Comparative Example 4: Compared with Example 1, the stearate in Comparative Example 4 is calcium stearate, comprising the following steps: Step 1: 1L of anhydrous ethanol, 300g of calcium stearate, and 100g of chemically expanded vermiculite (20-50 mesh) are added to a ball mill. The ball mill is heated to 60°C and then ball-milled at 50 rpm for 1 hour to produce a wet material. After cooling, the wet material is rinsed with deionized water and dried in an 80°C oven to produce modified chemically expanded vermiculite; Step 2: Air is introduced into a high-voltage electrostatic chamber, and a voltage of 10000V is applied to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.8 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The air flow rate is 100 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 2:1, place the mixture in a mold and pressurize it with a pressure of 5MPa for 3h to make SOFC high temperature vermiculite sealing material.

[0032] Comparative Example 5: Compared with Example 1, the stearate in Comparative Example 5 is barium stearate, comprising the following steps: Step 1: 1L of anhydrous ethanol, 300g of barium stearate, and 100g of chemically expanded vermiculite (20-50 mesh) are added to a ball mill. The ball mill is heated to 60°C and then ball-milled at 50 rpm for 1 hour to produce a wet material. After cooling, the wet material is rinsed with deionized water and dried in an 80°C oven to produce modified chemically expanded vermiculite; Step 2: Air is introduced into a high-voltage electrostatic chamber, and a voltage of 10000V is applied to the electrodes to ionize the air and produce negative ion air. The concentration of negative ions in the negative ion air is 10000 ions / cm³. 3 Negative ion air is pumped into an air filter. The filter element is filled with 0.8 kg of high-temperature expanded vermiculite (300-325 mesh). The air filter processes the negative ion air to produce negative ion high-temperature expanded vermiculite. The air flow rate is 100 cm³ / h. 3 / min, filtration time is 3h, after treatment, negative ion high temperature expanded vermiculite is collected in the air filter element; Step 3: Mix modified chemical expanded vermiculite and negative ion high temperature expanded vermiculite in a mass ratio of 2:1, place the mixture in a mold and pressurize it with a pressure of 5MPa for 3h to make SOFC high temperature vermiculite sealing material.

[0033] Comparative Example 6: Compared with Example 1, the mass ratio of zinc stearate to chemically expanded vermiculite in Comparative Example 6 was 0.5:1, and all other conditions were the same as in Example 1.

[0034] Comparative Example 7: Compared with Example 1, the mass ratio of zinc stearate to chemically expanded vermiculite in Comparative Example 7 was 10:1, and all other conditions were the same as in Example 1.

[0035] Test Examples: The loss on ignition, tensile strength, density, and high-temperature compressive strength of the SOFC high-temperature vermiculite sealing materials prepared in Examples 1 to 6 and Comparative Examples 1 to 7 were tested. The loss on ignition was tested according to the method disclosed in GB / T 27970-2011 Non-metallic Gasket Materials Burn-off Test Method, at a temperature of 800℃ for 4 hours. The tensile strength was tested according to the method disclosed in GB / T 20671.7-2006 Non-metallic Gasket Materials Classification System and Test Methods. The high-temperature compressive strength was tested using a high-temperature compressive strength testing machine to determine the failure temperature of the SOFC high-temperature vermiculite sealing material. The test results are shown in Table 1.

[0036] Table 1 Test Results As shown in Table 1, the SOFC high-temperature vermiculite sealing materials prepared in Examples 1 to 6 exhibit a thermal weight loss of less than 5%, a tensile strength of less than 0.5 MPa, and a density of 1.0 ± 1 g / cm³. 3 The high temperature compressive strength can reach 700℃. The above results show that the SOFC high temperature vermiculite sealing material prepared by the present invention has low loss on ignition and excellent high temperature resistance, and has excellent sealing performance.

[0037] Comparative Example 1 is a SOFC high-temperature vermiculite sealing material prepared by bonding with an adhesive. The loss on ignition of Comparative Example 1 is 6.82%, and the high-temperature compressive strength is 350℃. Compared with Example 1, the loss on ignition of Comparative Example 1 is significantly higher, and the high-temperature compressive strength is significantly lower. The above results show that the SOFC high-temperature vermiculite sealing material prepared by the present invention has significantly reduced loss on ignition and significantly increased high-temperature compressive strength compared with the adhesive composite material. Since the adhesive is usually an organic polymer, the high-temperature resistance of the adhesive is low. Under high temperature environment, the adhesive component will soften or even decompose, leading to problems such as leakage of the sealing material. However, the high-temperature vermiculite material of this application adopts electrostatic attraction and has stronger stability under high temperature environment.

[0038] Comparative Examples 2 and 3 were prepared by treating chemically expanded graphite with quaternary ammonium salt cation exchangers octadecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide, respectively. The results showed that the high-temperature compressive strength of Comparative Example 2 was 250℃, and that of Comparative Example 3 was 180℃. The high-temperature compressive strength of Comparative Examples 2 and 3 was significantly lower than that of Example 1. After analysis, it was found that the quaternary ammonium salt cation exchangers inserted into the vermiculite decomposed at high temperatures. As a result, the electrostatic attraction of vermiculite in SOFC high-temperature vermiculite sealing material rapidly failed due to the decomposition of the quaternary ammonium salt cation exchangers, leading to material collapse.

[0039] Comparative Examples 4 and 5 were treated with calcium stearate and barium stearate, respectively. The results showed that the high-temperature compressive strength of Comparative Example 4 was 400℃, and that of Comparative Example 5 was 300℃. Compared with Example 1, the high-temperature compressive strength of Comparative Examples 4 and 5 was significantly lower. Analysis revealed that calcium stearate and barium stearate also underwent thermal decomposition at high temperatures. However, since the temperature of the fuel cell stack exceeds 500℃, further optimization of the fuel cell stack is necessary to ensure that the high-temperature resistance of the sealing material meets the requirements of the fuel cell stack. As can be seen from the above, when using chemically expanded vermiculite as a cation exchanger for modification, materials that are not easily decomposed at high temperatures should be selected to ensure that the electrostatic attraction of the SOFC high-temperature vermiculite sealing material does not fail due to the decomposition of the cation exchanger. Therefore, the type of cation exchanger can be adjusted according to the actual application requirements.

[0040] Comparative Examples 6 and 7 investigated the dosage of zinc stearate and chemically expanded vermiculite, respectively. The results showed that if the dosage was too small, the number of positively charged modified chemically expanded vermiculite layers would be insufficient, resulting in a decrease in the tensile strength of the SOFC high-temperature vermiculite sealing material. However, if the dosage was too large, the intercalation effect of the intercalating agent would be saturated, and once a certain amount was reached, the intercalating agent would not be able to be inserted into the vermiculite layers. This resulted in the situation where excessive use of zinc stearate did not improve the material performance.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A SOFC high-temperature vermiculite sealing material, characterized in that, The raw materials include modified chemically expanded vermiculite and negative ion high-temperature expanded vermiculite. The modified chemically expanded vermiculite is composed of stearate and chemically expanded vermiculite, with a mass ratio of zinc stearate to chemically expanded vermiculite of 3 to 5:

1. The negative ion high-temperature expanded vermiculite is composed of negative ion air and high-temperature expanded vermiculite.

2. The SOFC high-temperature vermiculite sealing material according to claim 1, characterized in that, The mass ratio of modified chemically expanded vermiculite to negative ion high-temperature expanded vermiculite is 2–4:

1.

3. The SOFC high-temperature vermiculite sealing material according to claim 1, characterized in that, The concentration of negative ions in the air is 10,000–15,000 ions / cm³. 3 .

4. The SOFC high-temperature vermiculite sealing material according to claim 1, characterized in that, The chemically expanded vermiculite is 20-50 mesh.

5. The SOFC high-temperature vermiculite sealing material according to claim 1, characterized in that, The particle size of the high-temperature expanded vermiculite is 300-325 mesh.

6. A method for preparing SOFC high-temperature vermiculite sealing material according to any one of claims 1 to 5, characterized in that, Includes the following steps: Stearate and chemically expanded vermiculite are ball-milled in a ball mill to produce modified chemically expanded vermiculite. Air is passed into a high-voltage ionization chamber for high-voltage ionization to produce negative ion air. The negative ion air is then passed into a filter element containing high-temperature expanded vermiculite for filtration to produce negative ion high-temperature expanded vermiculite. The modified chemically expanded vermiculite and the negative ion high-temperature expanded vermiculite are mixed and stirred evenly, then pressurized and molded to produce SOFC high-temperature vermiculite sealing material.

7. The preparation method according to claim 6, characterized in that, The pressure applied during the pressure molding process is 5–10 MPa.

8. The preparation method according to claim 6 or 7, characterized in that, The pressure molding time is 1 to 3 hours.

9. The preparation method according to claim 6, characterized in that, The ball milling time is 50-80 rpm for 1-2 hours.

10. The preparation method according to claim 6, characterized in that, The voltage for the high-voltage ionization treatment is 10000–12000V, and the flow rate of the negative ion air is 100–200cm³. 3 The filter treatment time is 3-5 hours, and the mass of the high-temperature expanded vermiculite is 0.8-1 kg.

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