KR20220069213A - Glass ceramic composite sealant for solid oxide fuel cell with low shrinkage - Google Patents

Abstract

Provided is a glass ceramic composite sealant for a solid oxide fuel cell with a low shrinkage rate, comprising: 91 to 96 wt% of a BaO-B_2O_3-SiO_2-Al_2O_3-based a glass composition; 3 to 4 wt% of 8YSZ; and 0.5 to 5 wt% of expanded vermiculite. The glass ceramic composite sealant for a solid oxide fuel cell according to the present invention includes 8YSZ and expanded vermiculite in the glass composition to prevent the glass ceramic composite sealant from shrinking under a sealing heat treatment condition at a high temperature of 750 to 900 ℃.

Description

Glass ceramic composite sealant for solid oxide fuel cell with low shrinkage

The present invention relates to a sealing material used in a solid oxide fuel cell (SOFC), which contains 8YSZ and expanded vermiculite in a glass composition, and a solid capable of suppressing shrinkage under sealing heat treatment conditions at a high temperature of 750 to 900 ° C. It relates to a glass-ceramic composite sealing material for an oxide fuel cell.

In general, the encapsulant has two functions in the flat SOFC stack. First, it serves to prevent air and fuel gas from mixing inside the stack during SOFC operation and to block fuel gas from leaking out of the stack. Mixing of fuel gas and air or external leakage of fuel gas causes loss of fuel gas due to combustion reaction of fuel prior to power generation by electrochemical reaction of fuel, lowering energy efficiency of SOFC stack, and overheating due to combustion reaction It seriously impairs the durability of the stack.

Second, the sealing material is a mechanical adhesive or a gas leakage preventing film in constructing the stack, and also serves as a buffer against thermal and mechanical shocks given to the stack at the same time. In other words, the sealing material has considerable required properties, such as being able to withstand the pressure applied to the stack or the pressure difference inside and outside the stack in order to enhance the sealing effect, and to relieve thermal and mechanical stress generated during the manufacturing stage and operation of the stack. Complex.

As such, the basic conditions of the sealing material required for the smooth operation of the SOFC are summarized as follows. The sealing material must adhere well to the stack's core component materials that are in physical contact, and especially, the bonding area must not be weakened by the heat cycle given during SOFC operation. Since the difference in coefficient of thermal expansion with other components is not large, there should be no destruction due to thermal stress even if a thermal cycle is given, and it should be able to be used without chemical decomposition and evaporation under the two extreme oxygen partial pressures of fuel gas and air. .

In addition, it must be a stable material that does not undergo chemical reaction with other components at the SOFC stack operating temperature, and has no electrical conductivity at the SOFC operating temperature and can maintain electrical insulation.

As such, the sealing material used in SOFC must first perform sealing bonding with the material to be adhered, and also satisfy all of the physical properties mentioned above.

Representative glass compositions developed as sealants for SOFCs so far include SrO- La ₂ O ₃ -Al ₂ O ₃ -B ₂ O ₃ -SiO ₂ , BaO-Al ₂ O ₃ -SiO ₂ -B ₂ O ₃ , MgO-Al ₂ O ₃ -P ₂ O ₅ type, BaO -Al ₂ O ₃ -SiO ₂ -ZnO type, CaO-TiO ₂ -SiO ₂ type, etc. In the studies for this purpose, it is difficult to develop a sealing material using only glass material due to the intensifying requirements for a rapid thermal cycle, so studies are continuing to overcome the limitations through the composition of a composite using additives.

1. Korean Patent Publication No. 10-21119318 2. Korean Patent Publication No. 10-1182379

An object of the present invention is to provide a glass-ceramic composite sealing material for a solid oxide fuel cell that can suppress shrinkage in a sealing heat treatment condition at a high temperature of 750 to 900° C. by including 8YSZ and expanded vermiculite in a glass composition as a sealing material for a solid oxide fuel cell.

In addition, the glass ceramic composite sealing material for a solid oxide fuel cell according to the present invention increases the thermal expansion coefficient of the glass ceramic composite sealing material by the addition of expanded vermiculite, thereby reducing the difference in the thermal expansion coefficient when applied between the cell frame and the metal separator.

However, these tasks are exemplary, and the technical spirit of the present invention is not limited thereto.

A glass ceramic composite sealing material for a solid oxide fuel cell having a low shrinkage rate according to the technical idea of the present invention for achieving the above technical problem is BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ based glass composition: 91 to 96 wt% , 8YSZ: 3 to 4% by weight and expanded vermiculite: 0.5 to 5% by weight.

In some embodiments of the present invention, the BaO may include 50 to 60% by weight, B ₂ O ₃ 5 to 12% by weight, SiO ₂ 25 to 35% by weight, and Al ₂ O ₃ 2 to 6% by weight. .

In some embodiments of the present invention, the glass composition may include 91 to 96 wt%, 3 to 4 wt% of 8YSZ, and 0.5 to 5 wt% of expanded vermiculite.

In some embodiments of the present invention, the glass composition may include 92 to 95.7 wt%, 3.5 to 4 wt% of 8YSZ, and 0.8 to 4.5 wt% of expanded vermiculite.

In some embodiments of the present invention, the weight ratio of the (8YSZ + expanded vermiculite)/glass composition is 0.05 to 0.08 or less, and the shrinkage rate after heat treatment at 750 to 900° C. for 1 hour may be 11% or less.

In some embodiments of the present invention, the weight ratio of the (8YSZ + expanded vermiculite)/glass composition is 0.06 to 0.08 or less, and the shrinkage rate after heat treatment at 750°C to 900°C for 1 hour may be 8% or less.

In addition, the present invention is a glass-ceramic composite sealing material for a solid oxide fuel cell as described above; and a sealing paste including an organic binder.

In addition, the present invention is a glass-ceramic composite sealing material for a solid oxide fuel cell as described above; and a sealing molding sheet including an organic binder.

As a sealing material for a solid oxide fuel cell according to the present invention, it is possible to provide a glass-ceramic composite sealing material for a solid oxide fuel cell that contains 8YSZ and expanded vermiculite in a glass composition to suppress shrinkage under a sealing heat treatment condition at a high temperature of 750 to 900 ° C and has a low shrinkage rate have.

In addition, the glass ceramic composite sealing material for a solid oxide fuel cell according to the present invention increases the thermal expansion coefficient of the glass ceramic composite sealing material by the addition of expanded vermiculite, thereby reducing the difference in the thermal expansion coefficient when applied between the cell frame and the metal separator.

The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.

1 is a graph illustrating a comparison of shrinkage rates of sealing materials for SOFCs according to Examples and Comparative Examples of the present invention.
2 is a cross-sectional view of a specimen for comparative analysis of the shrinkage rate and adhesive strength of the plate-shaped sealant molded with the sealant for SOFC according to Examples and Comparative Examples of the present invention.
3 is a graph showing a comparison of shrinkage rates of plate-shaped sealing materials molded with SOFC sealing materials according to Examples and Comparative Examples of the present invention.
4 is a diagram illustrating a method for evaluating the bonding strength of a plate-shaped sealing material molded with a sealing material for SOFC according to Examples and Comparative Examples of the present invention.
5 is a result of measuring the load change according to the displacement of the upper metal plate (STS460FC).
6 is a graph showing the measurement and comparison of bonding strength of plate-shaped sealing materials molded with SOFC sealing materials according to Examples and Comparative Examples of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided in order to more fully and complete the present disclosure, and to fully convey/completely the technical spirit of the present invention to those skilled in the art. As used herein, the term “and/or” includes any one and all combinations of one or more of those listed items. The same symbols refer to the same elements from time to time. Furthermore, various elements and regions in the drawings are schematically drawn. Therefore, the technical spirit of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.

The sealing material used in Solid Oxide Fuel Cell (SOFC) is a key material that prevents mixing and leakage of air and fuel by bonding ceramic cells, cell frames, and metal separators, which are core components of SOFC stacks, at high temperatures. .

In the manufacturing stage of the stack for SOFC, mechanical pressure is applied as well as heat treatment at a high temperature of 750~900℃ to bond the sealing material and minimize the contact resistance of the components. However, under excessive heat treatment temperature and pressure conditions, the glass sealant may flow into and out of the stack. The leakage of these sealants to the outside lowers the adhesive strength or generates electricity, and in severe cases blocks the air and fuel gas passages, making it impossible to operate the stack stably as a result. Therefore, the most ideal sealing material for SOFC needs to have basic properties and to suppress shrinkage as much as possible during the sealing process.

The glass ceramic composite sealing material for a solid oxide fuel cell having a low shrinkage rate according to the present invention contains 8YSZ and expanded vermiculite in a glass composition. The 8YSZ is zirconia (Y ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 in which the 8 mol% yttria stabilizer is dissolved, and the expanded vermiculite refers to vermiculite expanded by crushing and calcining vermiculite.

8YSZ and expanded vermiculite are included in the glass composition to suppress shrinkage under high temperature sealing heat treatment conditions (temperature and pressure) of 750~900°C. When only 8YSZ is added, the shrinkage rate increases, but when it is added together with expanded vermiculite, the shrinkage rate of the sealing material may decrease. It also shows a decrease in the shrinkage rate as the content of expanded vermiculite increases.

The sealing material is used for sealing the ceramic cell and the cell frame and sealing the cell frame and the metal separator, and in reality, the amount used for sealing the cell frame and the metal separator is relatively large. In addition, most of the cell frame and metal separator materials are STS400-based materials, and most have a thermal expansion coefficient of 12×10 ^-6 K ^-1 or higher, whereas glass encapsulants 10-11×10 ^- similar to the thermal expansion coefficient of 8YSZ, a cell electrolyte material for SOFC. It is designed to have a coefficient of thermal expansion of about ⁶ K ^-1 .

Therefore, the addition of expanded vermiculite increases the thermal expansion coefficient of the glass-ceramic composite sealing material, thereby reducing the difference in the thermal expansion coefficient when applied between the cell frame and the metal separator.

The glass composition may include BaO, B ₂ O _3, SiO ₂ and Al ₂ O ₃ , the BaO 50 to 60% by weight, B ₂ O ₃ 5 to 12% by weight, SiO ₂ 25 to 35% by weight, and Al ₂ O ₃ 2 to 6% by weight.

Since the glass composition having the above composition ratio exhibits excellent fluidity at 850° C. or higher, it can be manufactured at the same temperature as the manufacturing temperature of the solid oxide fuel cell, and has a physically strong characteristic due to high bonding strength. In addition, the glass composition does not soften at about 700° C., which is the operating temperature of the solid oxide fuel cell, and has little reactivity with the electrolyte, so that it is physically and chemically stable.

The BaO is a network modifier and is a major component forming a glass structure, and serves to increase chemical durability and thermal conductivity. However, if BaO is contained too high, phase separation may easily occur, making it difficult to melt and form glass, or may decrease devitrification properties and chemical resistance and increase viscosity. If BaO is contained too low, thermal conductivity may decrease. have. Therefore, the content of BaO is preferably in the range of 50 to 60% by weight. When the content of BaO is less than 50% by weight or exceeds 60% by weight, a phase separation phenomenon may occur during glass manufacturing, and a phenomenon in which the glass composition does not melt may occur.

The B ₂ O ₃ serves as a network former similar to that of SiO ₂ , but has a two-dimensional structure and thus contributes to increasing the glass stability of the glass material and lowering the viscosity. However, if the content of B ₂ O ₃ is more than 12 wt%, the coefficient of thermal expansion may decrease and phase separation may occur. In addition, when the content of B ₂ O ₃ is less than 5% by weight, there is a problem in that a phase separation phenomenon easily occurs, thereby making it difficult to melt and form a glass. Therefore, the content of B ₂ O ₃ is preferably in the range of 5 to 12% by weight.

The SiO ₂ is an oxide that forms a network structure as a main component of glass that increases heat resistance and thermal shock resistance, and when the content is high, the melting point of the glass is raised, while the increase in the content of SiO ₂ also increases the thermal conductivity can increase Therefore, the content of SiO ₂ is preferably in the range of 25 to 35% by weight. When the content of SiO ₂ is less than 25% by weight or exceeds 35% by weight, a phase separation phenomenon may occur during glass manufacturing, and a phenomenon in which the glass composition is not melted may occur.

The Al ₂ O ₃ may be included in an amount of 2 to 6 wt%. Al ₂ O ₃ may improve the stability of the glass, and may increase the average coefficient of thermal expansion of the glass composition when included in the above category. If Al ₂ O ₃ is contained in an amount of more than 6 wt% in the glass composition, crystallization of the glass may occur, thereby reducing fluidity.

The glass ceramic composite sealing material for a solid oxide fuel cell having a low shrinkage according to the present invention may consist of 91 to 96 wt% of the glass composition, 3 to 4 wt% of 8YSZ, and 0.5 to 5 wt% of expanded vermiculite. In particular, the glass composition may be comprised of 92 to 95.7 wt%, 3.5 to 4 wt% of 8YSZ, and 0.8 to 4.5 wt% of expanded vermiculite.

The glass ceramic composite sealing material according to the present invention may include 3 to 4 wt% of 8YSZ in the glass composition. Since the sealing material is used for bonding the cell frame and the metal separator as well as bonding the cell electrolyte surface to the cell frame, the same ZrO ₂ electrolyte as the electrolyte material can be used as an additive. When the amount added is small, the effect of inhibiting melting and spreading is too insignificant, and when the amount is excessive, it is preferable to satisfy the above range because the adhesive strength is lowered. When a CeO ₂ -based electrolyte is added, the thermal expansion coefficient of the CeO ₂ -based electrolyte is about 13×10 ^-6 K ^-1 , which is advantageous in increasing the thermal expansion coefficient of the glass composite. However, the CeO ₂ -based electrolyte exhibits electron conductivity in a reducing atmosphere. There is a disadvantage that it may be difficult to insulate the stack.

The glass ceramic composite sealing material according to the present invention may further include 0.5 to 5 wt% of expanded vermiculite in the glass composition. When only 8YSZ is added to the glass composition, the shrinkage rate increases, but when added together with expanded vermiculite, the shrinkage rate of the sealing material may decrease. It also shows a decrease in the shrinkage rate as the content of expanded vermiculite increases. In addition, the addition of expanded vermiculite increases the thermal expansion coefficient of the glass ceramic composite sealing material, thereby reducing the difference in the thermal expansion coefficient when applied between the cell frame and the metal separator. When expanded vermiculite is added in an amount of less than 0.5 wt %, the effect of suppressing the shrinkage of the sealing material is not exhibited, and when it is added in an amount exceeding 5 wt %, crystallization may occur during the manufacture of the sealing material, and NiO+8YSZ ceramic substrate used as an anode support for a cell for SOFC adhesion may be poor.

In the glass ceramic composite sealing material for a solid oxide fuel cell according to the present invention, when the weight ratio of (8YSZ + expanded vermiculite)/glass composition is 0.05 to 0.08 or less, after heat treatment at 750 ° C. to 900 ° C. for 1 hour, the shrinkage rate of 11% or less have

1 is a graph showing the comparison of the shrinkage ratio of sealing materials for SOFC according to Examples and Comparative Examples of the present invention, and Table 3 is a table showing the weight ratio and shrinkage ratio (%) of (8YSZ+expanded vermiculite)/glass. The higher the content of expanded vermiculite, the higher the weight ratio of (8YSZ + expanded vermiculite)/glass composition decreased, resulting in excellent results. After that, the adhesion to the NiO+8YSZ ceramic substrate is deteriorated and separation can occur, so it is preferable to satisfy the above range.

In particular, the weight ratio of the (8YSZ + expanded vermiculite)/glass composition is 0.06 to 0.08 or less, and the shrinkage rate after heat treatment at 750°C to 900°C for 1 hour may be 8% or less, in particular, the (8YSZ + expanded vermiculite)/glass composition A weight ratio of 0.07 to 0.08 or less, after heat treatment at 750 ° C. to 900 ° C. for 1 hour, the shrinkage rate may have an excellent shrinkage rate of 4% or less.

The present invention relates to the above-described glass-ceramic composite sealing material for a solid oxide fuel cell; and a sealing paste including an organic binder. In addition, the present invention is a glass-ceramic composite sealing material for a solid oxide fuel cell as described above; and a sealing molding sheet including an organic binder. When the glass-ceramic composite sealing material is applied by dispensing after manufacturing the sealing paste, the cost is low and the manufacturing yield is high. One sealing layer can be secured.

The organic binder may be a thermoplastic resin. As a specific and non-limiting example, the organic binder may include ethyl cellulose, an acrylate-based polymer, and the like.

As described above, the glass-ceramic composite sealing material for a solid oxide fuel cell according to the present invention is a sealing material for a solid oxide fuel cell and contains 8YSZ and expanded vermiculite in the glass composition to suppress shrinkage under the sealing heat treatment conditions at a high temperature of 750 to 900 ° C.

In addition, the addition of expanded vermiculite increases the thermal expansion coefficient of the glass-ceramic composite sealing material, thereby reducing the difference in the thermal expansion coefficient when applied between the cell frame and the metal separator.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense.

Content not described here will be omitted because it can be technically inferred sufficiently by a person skilled in the art.

Production of disk-shaped molded body

A composite powder obtained by mixing 8YSZ (8 mol% Y ₂ O ₃ stabilized ZrO ₂ ) and vermiculite with a glass powder of BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ composition used as a glass sealing material for SOFC. was prepared and the compounding ratio (wt%) is summarized in Table 1 below.

The glass powder is BaO 54 wt%, B ₂ O ₃ 8.8 % by weight, SiO ₂ 29% by weight Al ₂ O ₃ A composition of 3.1 wt% was prepared using BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ glass powder.

Sample comparative example Example comparative example One 2 3 4 5 6 7 Glass 100 96.15 95.24 94.34 93.46 92.60 91.74 8YSZ 3.85 3.81 3.77 3.74 3.70 3.67 Vermiculite 0.95 1.89 2.80 3.70 4.59

After uniaxial pressure molding of pure glass powder (sample 1) and uniformly mixed composite powder (sample 2-7) into a disk-shaped molded body with a diameter of 27 mm, the molded bodies are placed on the NiO+8YSZ ceramic substrate used as the anode support of the SOFC cell, and 850 It was heat-treated at ℃ for 1 hour to confirm the change in diameter and adhesion to the substrate. As shown in Table 2, all but sample 7 maintain good adhesion to the NiO+8YSZ ceramic substrate.

Sample comparative example Example comparative example One 2 3 4 5 6 7 adhesion state Good Good Good Good Good Good error

Evaluation of Shrinkage Rate of Disc-shaped Molded Body

1 is a graph illustrating a comparison of shrinkage rates of sealing materials for SOFCs according to Examples and Comparative Examples of the present invention. As a sealing material for SOFC, glass powder with BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ composition (sample 1), composite powder with 8YSZ added to glass powder (sample 2), and glass powder with 8YSZ and expanded vermiculite at the same time The added composite powder (samples 3 to 7) was prepared into a disk-shaped molded body, placed on a NiO+8YSZ ceramic substrate, and the shrinkage rates of specimens heat-treated at 850° C. for 1 hour were compared and shown.

The shrinkage ratio according to the change in diameter was measured and compared. Sample 1, which is pure glass, showed a shrinkage of 11.44%, but sample 2 with only 8YSZ added showed a higher shrinkage of 12.44%. Composite sealing materials in which 8YSZ and expanded vermiculite were added at the same time showed a decrease in shrinkage as the content of expanded vermiculite increased, and in particular, the shrinkage inhibitory effect in samples 3 to 5 showed a tendency to occur rapidly.

The sealing material is used for sealing the ceramic cell and the cell frame and sealing the cell frame and the metal separator, and in reality, the amount used for sealing the cell frame and the metal separator is relatively large. In addition, most of the cell frame and metal separator materials are STS400-based materials, and most have a thermal expansion coefficient of 12×10 ^-6 K ^-1 or higher, whereas glass encapsulants 10-11×10 ^- similar to the thermal expansion coefficient of 8YSZ, a cell electrolyte material for SOFC. It is designed to have a coefficient of thermal expansion of about ⁶ K ^-1 . Therefore, it can be expected that the addition of expanded vermiculite increases the thermal expansion coefficient of the composite sealing material, thereby reducing the difference in thermal expansion coefficient when applied between the cell frame and the metal separator.

Molding of plate-shaped sealing material

2 is a cross-sectional view of a specimen for comparative analysis of the shrinkage rate and adhesive strength of the plate-shaped sealant molded with the sealant for SOFC according to Examples and Comparative Examples of the present invention. As a sealing material for SOFC, a glass powder (sample 1) having a composition of BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ and a composite powder (sample 4) in which 8YSZ and expanded vermiculite are simultaneously added to the glass powder (sample 4) are molded into a plate-shaped sealing material. The cross section of the specimen for comparative analysis of the shrinkage rate and adhesive strength of this plate-shaped sealing material is shown.

Pure glass sealing material (Sample 1) and composite sealing material (Sample 4) powder were molded into a plate-shaped sealing material having a length of 60 mm, a width of 10 mm, and a thickness of 0.5 mm using a tape casting process. As shown in Figure 2 below, one upper metal plate (STS460FC) having a length of 60mm, a width of 10mm, and a thickness of 2mm, and two lower metal plates (STS430) having a length of 29mm, a width of 10mm, and a thickness of 1.5mm A plate-shaped sealing material was laminated in between. The two laminated specimens were placed on an alumina plate, and an alumina sintered body was placed on the upper metal plate to give a load (62 g/cm ² ), and the experimental conditions were set to be as similar as possible to the actual SOFC stack lamination process.

Evaluation of shrinkage rate of plate-shaped sealing material

3 is a graph showing a comparison of shrinkage rates of plate-shaped sealing materials molded with SOFC sealing materials according to Examples and Comparative Examples of the present invention. As a sealing material for SOFC, a glass powder (Sample 1) having a composition of BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ and a composite powder (Sample 4) in which 8YSZ and expanded vermiculite are simultaneously added to the glass powder (Sample 4) are molded into a plate-shaped sealing material. , shown by comparing the shrinkage rate of the plate-shaped sealing material heat treated by applying a load of 64 g / cm ² for 1 hour at 850 ℃. In the sealing heat treatment, the temperature was maintained at 850° C. for 1 hour at a temperature increase rate of 5° C. per minute, and then cooled.

Sample 1 and Sample 4 plate-shaped sealing material was applied and the thickness of the specimens sealed at 850°C for 1 hour was measured to calculate the shrinkage of the sealing material.

① Thickness of plate-shaped sealing material before heat treatment

② Thickness of plate-shaped sealing material after heat treatment = thickness of specimen after heat treatment - (STS460FC+STS430 thickness)

③ Shrinkage (%) = (①-②)/① × 100

The plate-shaped sealant of Sample 1 showed a shrinkage rate of 29.8%, while the plate-shaped sealant of Sample 4 showed a relatively low shrinkage rate of 10.9%. Therefore, it was confirmed that the shrinkage ratio results obtained by measuring the change in the thickness of the sealing material after heat treatment under a load were similar to the results of comparison of the shrinkage ratio calculated by measuring the diameter change after heat treatment in the unloaded state of FIG. 1 .

Table 3 is a table showing the weight ratio and shrinkage (%) of (8YSZ + expanded vermiculite)/glass of the sealing material for SOFC according to Examples and Comparative Examples of the present invention.

Sample comparative example Example comparative example One 2 3 4 5 6 7 (8YSZ+expanded vermiculite)/glass 0.00 0.04 0.05 0.06 0.07 0.08 0.09 Shrinkage (%) 11.44 12.44 10.56 7.7 4 3.07 1.85

As shown in Table 3, when the weight ratio of (8YSZ + expanded vermiculite)/glass composition is 0.05 to 0.08 or less in the glass ceramic composite sealing material for solid oxide fuel cell, as shown in Table 3, after heat treatment at 750 ° C. to 900 ° C. for 1 hour, the shrinkage rate of 11% or less have

The weight ratio of the (8YSZ + expanded vermiculite)/glass composition is 0.06 to 0.08 or less, and the shrinkage rate after heat treatment at 750°C to 900°C for 1 hour may be 8% or less, in particular, the (8YSZ + expanded vermiculite)/glass composition The weight ratio is 0.07 to 0.08 or less, and the shrinkage rate after heat treatment at 750° C. to 900° C. for 1 hour may have an excellent shrinkage ratio of 4% or less.

As the weight ratio of the (8YSZ + expanded vermiculite)/glass composition increased, the shrinkage decreased, resulting in excellent results. . In particular, as shown in Table 2, when the weight ratio of (8YSZ + expanded vermiculite)/glass composition is 0.09, it was confirmed that the adhesion state with the NiO + 8YSZ ceramic substrate used as the anode support of the SOFC cell was not good. it's good

Evaluation of joint strength of plate-shaped sealing material

4 is a diagram illustrating a method for evaluating the bonding strength of a plate-shaped sealing material molded with a sealing material for SOFC according to Examples and Comparative Examples of the present invention. As a sealing material for SOFC, a glass powder (Sample 1) having a composition of BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ and a composite powder (Sample 4) in which 8YSZ and expanded vermiculite are simultaneously added to the glass powder (Sample 4) are molded into a plate-shaped sealing material. , the bonding strength of the plate-shaped sealing material heat treated by applying a load of 64 g/cm ² for 1 hour at 850°C was evaluated.

Adhesive strength was compared and evaluated using the specimens that had been evaluated for shrinkage, and a 4-point hardening strength evaluation method was applied as shown in FIG. 4 . Since the lower STS430 plate is not connected in the middle, the actual measured adhesive strength was evaluated as the sum of the hardening strength of the upper STS460FC and the bonding strength of the sealing material placed between the upper and lower plates.

5 is a result of measuring the load change according to the displacement of the upper metal plate (STS460FC) according to the measurement method of FIG. First, a four-point hardening strength evaluation was performed on the STS460FC specimen, which is the upper plate, and it was confirmed that the slope of the load change curve according to the displacement was changed near the displacement of 1.25mm as shown in FIG. The measured load was compared.

FIG. 6 is a graph showing and comparing the joint strength of the plate-shaped sealing material molded with the sealing material for SOFC according to the embodiment and the comparative example of the present invention according to the measurement method of FIG. 4 . As a result of the experiment, the specimen to which the plate-shaped sealant of Sample 1 was applied had a load of 80.7 kgf at a displacement of 1.25 mm, and the specimen to which the plate-shaped sealant of Sample 4 was applied had a higher load of 82.2 kgf under the same conditions. As pure STS460FC showed 75.5 kgf under the same conditions, both specimens reflected the interfacial adhesive force of the sealing material, and thus higher load values were confirmed.

As described above, it was confirmed that the glass ceramic composite sealing material for a solid oxide fuel cell according to the present invention suppresses the shrinkage under the sealing heat treatment condition at a high temperature of 750 to 900 ° C.

In addition, the addition of expanded vermiculite increases the thermal expansion coefficient of the glass-ceramic composite sealing material, thereby reducing the difference in the thermal expansion coefficient when applied between the cell frame and the metal separator.

The technical spirit of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is the technical spirit of the present invention that various substitutions, modifications and changes are possible without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which this belongs.

Claims (7)

BaO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ glass composition: 91 to 96% by weight, 8YSZ: 3 to 4% by weight and expanded vermiculite: 0.5 to 5% by weight of low shrinkage Glass-ceramic composite sealing material for solid oxide fuel cells.
The method of claim 1,
The glass composition comprises BaO: 50 to 60 wt%, B ₂ O ₃ : 5 to 12 wt%, SiO ₂ : 25 to 35 wt%, and Al ₂ O ₃ : 2 to 6 wt% Glass-ceramic composite sealing material for solid oxide fuel cells with low shrinkage.
The method of claim 1,
A glass-ceramic composite sealing material for a solid oxide fuel cell having a low shrinkage rate, comprising 92 to 95.7 wt% of the glass composition, 3.5 to 4 wt% of 8YSZ, and 0.8 to 4.5 wt% of expanded vermiculite.
The method of claim 1,
The weight ratio of the (8YSZ + expanded vermiculite)/glass composition is 0.05 to 0.08 or less, and a glass-ceramic composite sealing material for a solid oxide fuel cell having a low shrinkage rate of 11% or less after heat treatment at 750°C to 900°C for 1 hour.
The method of claim 1,
The weight ratio of the (8YSZ + expanded vermiculite)/glass composition is 0.06 to 0.08 or less, and the glass-ceramic composite sealing material for a solid oxide fuel cell having a low shrinkage rate of 8% or less after heat treatment at 750°C to 900°C for 1 hour.
The glass-ceramic composite sealing material for a solid oxide fuel cell according to any one of claims 1 to 5; and an organic binder.
The glass-ceramic composite sealing material for a solid oxide fuel cell according to any one of claims 1 to 5; and an organic binder.

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