Brazing filler metal for atmospheric joining, joined body, and method for producing joined body

Abstract

A brazing filler metal for atmospheric joining, which comprises 94-97 wt% of Ag, 1-5 wt% of Ge or an oxide of Ge, and 1-3 wt% of Cr or an oxide of Cr, with the balance being made up of unavoidable impurities, wherein: the total of these components is adjusted to be 100 wt%; and with respect to the Cr or the oxide of Cr, the proportion of the number of particles having a particle diameter of 10 µm or more is 10% or less in the particle size distribution determined by a laser diffraction scattering method.

Description

Brazing material for atmospheric bonding, bonded body, and method for manufacturing a bonded body

[0001] This invention relates to a brazing material for atmospheric bonding, a bonded body, and a method for manufacturing a bonded body.

[0002] Fuel cells, which generate electricity through a chemical reaction between hydrogen and oxygen, are attracting attention as a highly efficient and clean power generation device. Fuel cells operate, for example, in the atmosphere at 600°C to 800°C. Fuel cells are manufactured by sealing components made of, for example, metal or ceramics, to prevent hydrogen from leaking into the atmosphere.

[0003] Reactive air brazing is a known method for joining base materials such as metals and ceramics. In reactive air brazing, the base materials can be joined by heating and cooling a brazing material in the atmosphere.

[0004] For example, Patent Document 1 discloses a method of joining metals and ceramics using a brazing material which is a mixture of silver powder and copper powder in a reactive air brazing method. According to the air brazing material of Patent Document 1, a reaction layer containing copper oxide is formed at the bonding interface of the ceramics.

[0005] Patent No. 4486820

[0006] However, with a joint made using the atmospheric brazing material described in Patent Document 1, for example, when placed in the operating environment of a fuel cell, hydrogen can enter from one end face of the silver-based layer (brazed layer), and oxygen can enter from the other end face. When hydrogen diffuses into the brazed layer, it can react with oxygen to produce water, which may cause voids. Furthermore, it may reduce copper oxides in the reaction layer, potentially causing delamination. In other words, the atmospheric brazing material described in Patent Document 1 had problems with the durability of joints made by the reactive atmospheric brazing method.

[0007] Therefore, one of the objectives of the present invention is to provide a brazing material for atmospheric bonding that improves the durability of the bonded body. Another objective of the present invention is to provide a bonded body with improved durability. Another objective of the present invention is to provide a method for manufacturing a bonded body that improves the durability of the bonded body.

[0008] The atmospheric bonding brazing material according to one embodiment of the present invention consists of 94 to 97 wt% Ag, 1 to 5 wt% Ge or Ge oxide, 1 to 3 wt% Cr or Cr oxide, and the remainder being unavoidable impurities, adjusted so that the total of these is 100 wt%, and the proportion of particles with a particle size of 10 μm or more in the particle size distribution measured by laser diffraction and scattering method is 10% or less.

[0009] In the atmospheric bonding brazing material according to one embodiment of the present invention, the Cr or Cr oxide may have a maximum peak in the particle size distribution measured by laser diffraction and scattering at a particle diameter of 5 μm or less.

[0010] A joint according to one embodiment of the present invention comprises a first base material, a second base material, and a joining material for joining the first base material and the second base material, wherein the joining material has a first reaction layer in contact with the first base material, a second reaction layer in contact with the second base material, and a brazing layer interposed between the first reaction layer and the second reaction layer, the brazing layer contains Ag, an oxide of Ge, an oxide of Cr, and a composite oxide of Ge and Cr dispersed in the Ag, and in the brazing layer, the proportion of the number of particles of the composite oxide of Ge and Cr with a particle diameter of 10 μm or more is 10% or less.

[0011] In a joint according to one embodiment of the present invention, the first base material is a ceramic, the second base material is a metal, the first reaction layer contains an oxide of Ge, and the second reaction layer contains an oxide of Cr and a composite oxide of Ge and Cr, and the proportion of the volume occupied by the Cr oxide in the second reaction layer may be higher than that of the composite oxide of Ge and Cr.

[0012] The assembly according to one embodiment of the present invention may be used in a fuel cell.

[0013] In the assembly according to one embodiment of the present invention, the fuel cell may be a solid oxide fuel cell.

[0014] A method for manufacturing a bond according to one embodiment of the present invention comprises 94 to 97 wt% of Ag, 1 to 5 wt% of Ge or Ge oxide, 1 to 3 wt% of Cr or Cr oxide, and the remainder being unavoidable impurities, adjusted so that the total of these amounts to 100 wt%, wherein the proportion of particles with a particle size of 10 μm or more in the particle size distribution measured by laser diffraction and scattering method is 10% or less, and an atmospheric bonding brazing material is placed between a first base material and a second base material, the brazing material is heated in the atmosphere to dissolve the Ag, and the heated brazing material is cooled in the atmosphere to solidify the Ag.

[0015] In a method for manufacturing a joint according to one embodiment of the present invention, arranging the atmospheric bonding brazing material between the first base material and the second base material may be done by applying the atmospheric bonding brazing material to the first base material and arranging the second base material on the atmospheric bonding brazing material applied to the first base material.

[0016] According to one embodiment of the atmospheric bonding brazing material, the durability of the bonded body can be improved. According to one embodiment of the bonded body, the durability is improved. According to one embodiment of the manufacturing method for the bonded body, the durability of the bonded body can be improved.

[0017] This is a cross-sectional view showing the outline of a joint according to one embodiment of the present invention. This is a flowchart showing the outline of a method for manufacturing a joint according to one embodiment of the present invention. Cr used in the atmospheric bonding brazing material of Example 1 ２ O ３This graph shows the particle size distribution when measured by laser diffraction and scattering. This graph shows the particle size distribution when measured by laser diffraction and scattering for the Cr used in the atmospheric bonding brazing material of Example 2. This graph shows the particle size distribution when measured by laser diffraction and scattering for the Cr used in the atmospheric bonding brazing material of Reference Example. This is an image of the cross-section of the joint of Reference Example observed using a scanning electron microscope. This is an image of the cross-section of the joint of Example 1 observed using a scanning electron microscope. This is an image of the cross-section of the joint of Example 2 observed using a scanning electron microscope. This is an image of the joint of Reference Example when elemental analysis was performed using an electron probe microanalyzer. This is an image of the joint of Example 1 when elemental analysis was performed using an electron probe microanalyzer. This is an image of the joint of Example 2 when elemental analysis was performed using an electron probe microanalyzer. This graph shows the results of the He leak test performed on the fabricated joint.

[0018] Embodiments of the present invention will be described below with reference to the drawings. While the drawings may schematically represent the width, thickness, shape, etc., of parts in order to clarify the explanation, they are merely examples and do not limit the interpretation of the present invention. In this specification and in the drawings, elements similar to those described above in previous drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0019] <Brazing material for atmospheric bonding> A brazing material for atmospheric bonding according to one embodiment of the present invention will be described. The brazing material for atmospheric bonding can be used mainly in reactive atmospheric brazing. The brazing material for atmospheric bonding consists of 94 to 97 wt% Ag, 1 to 5 wt% Ge or Ge oxide, 1 to 3 wt% Cr or Cr oxide, and the remainder being unavoidable impurities, and is adjusted so that the total of these is 100 wt%. Unavoidable impurities refer to impurities that could not be removed during the manufacturing process of the raw materials Ag, Ge or Ge oxide and Cr or Cr oxide.

[0020] For atmospheric bonding, a mixture of Ag powder, Ge or Ge oxide powder, and Cr or Cr oxide powder can be used as is. Alternatively, the mixture of these powders can be compressed into pellets for use. Another method is to add an organic solvent or organic binder to the mixture to form a paste for use. Examples of organic solvents include terpineol. Examples of organic binders include acrylic polymers (such as Oricox KC). From the viewpoint of uniform application, it is preferable to use the atmospheric bonding brazing material in paste form.

[0021] For example, as the Ag powder, a powder with a median diameter in the range of 2 μm to 100 μm, as measured by laser diffraction / scattering, can be used.

[0022] As for the Ge powder, those with a median diameter in the range of 2 μm to 50 μm in the particle size distribution measured by laser diffraction / scattering can be used. Ge oxides (e.g., GeO) ２ As for the powder, those with a median diameter in the range of 2 μm to 50 μm in the particle size distribution measured by laser diffraction and scattering methods can be used.

[0023] For Cr powder, the proportion of particles with a particle size of 10 μm or larger in the particle size distribution measured by laser diffraction / scattering method shall be 10% or less. Note that 0% is included in 10% or less. Furthermore, for Cr powder, the median diameter in the particle size distribution measured by laser diffraction / scattering method shall be in the range of 0.5 μm to 5 μm. In addition, for Cr powder, the maximum peak in the particle size distribution measured by laser diffraction / scattering method shall be 5 μm or smaller in particle size.

[0024] Cr oxides (e.g., Cr ２ O ３As for the powder, we use one in which the proportion of particles with a particle size of 10 μm or larger in the particle size distribution measured by laser diffraction and scattering method is 10% or less. Note that 0% is also included in 10% or less. In addition, Cr oxides (e.g., Cr ２ O ３ As for the powder, those with a median diameter in the particle size distribution measured by laser diffraction and scattering methods, ranging from 0.5 μm to 5 μm, can be used. Furthermore, as for the Cr oxide, those with a maximum peak at a particle size of 5 μm or less, as measured by laser diffraction and scattering methods, can be used.

[0025] <Jointed Body> A jointed body according to one embodiment of the present invention will now be described. Figure 1 is a schematic cross-sectional view of a jointed body according to one embodiment of the present invention. As shown in Figure 1, the jointed body 100 comprises a first base material 111, a second base material 112, and a joining material 120 that joins the first base material 111 and the second base material 112. The jointed body 100 can be used, for example, as a component of a fuel cell, particularly a solid oxide fuel cell.

[0026] Examples of the first base material 111 and the second base material 112 include metals and ceramics. Examples of metals include stainless steel, heat-resistant stainless steel, and FeCrSi alloy. Examples of ceramics include oxide ceramics such as zirconia, stabilized zirconia, magnesia, ceria, gadolina-doped ceria, steatite, mullite, titania, silica, and sialon, as well as nitride ceramics such as aluminum nitride.

[0027] The joint material 120 is formed by a reactive air brazing method using an air-bonding brazing material containing 94 to 97 wt% Ag, 1 to 5 wt% Ge or Ge oxide, and 1 to 3 wt% Cr or Cr oxide. The thickness of the joint material 120 is set to, for example, a range of 20 μm to 100 μm.

[0028] The bonding material 120 includes a first reaction layer 121 in contact with the first base material 111, a second reaction layer 122 in contact with the second base material 112, and a brazing layer 123 interposed between the first reaction layer 121 and the second reaction layer 122. The first reaction layer 121, the second reaction layer 122, and the brazing layer 123 will be described below in the case where the first base material 111 is a ceramic and the second base material 112 is a metal.

[0029] The first reaction layer 121 is formed when the brazing material for atmospheric bonding is heated, causing the Ag contained in the brazing material to dissolve and the oxide of Ge to precipitate on the surface of the first base material 111. The thickness of the first reaction layer 121 is set to, for example, a range of 100 nm to 1200 nm. Because the first reaction layer 121 contains the oxide of Ge, the bonding between the brazed layer 123 and the first base material 111, which is made of ceramics, can be improved.

[0030] The second reaction layer 122 is formed when the Ag contained in the atmospheric bonding brazing material is dissolved by heating the brazing material, causing Cr oxide and a composite oxide of Ge and Cr to precipitate on the surface of the second base material 112. The thickness of the second reaction layer 122 is set to, for example, a range of 100 nm to 12000 nm. Because the second reaction layer 122 contains a composite oxide of Ge and Cr, the bonding between the brazed layer 123 and the metallic second reaction layer 122 can be improved. In the second reaction layer 122, the volume proportion occupied by Cr oxide may be higher than that of the composite oxide of Ge and Cr.

[0031] The brazed layer 123 contains Ag as the main component, and Ge oxide, Cr oxide, and Ge-Cr composite oxide dispersed in Ag. The Ge-Cr composite oxide has a particle size of 10 μm or larger, with a proportion of 10% or less. Therefore, the Ge-Cr composite oxide can be uniformly dispersed in the Ag of the brazed layer 123. As a result, the diffusion of hydrogen that enters the brazed layer 123 is suppressed, and the generation of voids and peeling of the second reaction layer 122 can be suppressed.

[0032] <Method for manufacturing a bonded body> A method for manufacturing a bonded body according to an embodiment of the present invention will be described. FIG. 2 is a flowchart showing an outline of a method 200 for manufacturing a bonded body according to an embodiment of the present invention. As shown in FIG. 2, the method includes a step S210 of preparing a brazing filler metal for air brazing, a step S220 of disposing the brazing filler metal for air brazing, a step S230 of heating the brazing filler metal for air brazing, and a step S240 of cooling the brazing filler metal for air brazing.

[0033] In the step S210 of preparing the brazing filler metal for air brazing, powders of Ag, Ge or an oxide of Ge, and Cr or an oxide of Cr are weighed respectively to prepare a brazing filler metal for air brazing containing 94 to 97 wt% of Ag, 1 to 5 wt% of Ge or an oxide of Ge, and 1 to 3 wt% of Cr or an oxide of Cr. The Cr or the oxide of Cr is such that the ratio of the number of particles having a particle diameter of 10 μm or more in the particle size distribution measured by the laser diffraction / scattering method is 10% or less. The brazing filler metal for air brazing can be made into a paste by adding an organic solvent or an organic binder.

[0034] In the step S220 of disposing the brazing filler metal for air brazing, the brazing filler metal for air brazing is disposed between the first base material 111 and the second base material 112. The step S220 of disposing the brazing filler metal for air brazing may include a step of applying the brazing filler metal for air brazing to the first base material 111 and a step of disposing the second base material 112 on the brazing filler metal for air brazing applied to the first base material 111. In the case of the paste-like brazing filler metal for air brazing, it can be applied to the first base material 111 using a dispenser. Also, it can be printed on the first base material 111 by screen printing.

[0035] In the step S220 of disposing the brazing filler metal for air brazing, a workpiece including the first base material 111, the brazing filler metal for air brazing, and the second base material 112 in this order is produced. The workpiece may be pressurized at a constant pressure from the viewpoint of uniform bonding. The pressure for pressurizing the workpiece is set, for example, in the range of 5 kPa or more and 30 kPa or less.

[0036] In the step S230 of heating the brazing material for air brazing, in the atmosphere, the brazing material for air brazing is heated to dissolve Ag contained in the brazing material for air brazing. Examples of heating the brazing material for air brazing include heating the workpiece in a heating furnace in an air atmosphere. The heating temperature is set, for example, in the range of 961°C or higher and 1200°C or lower from the viewpoint of preventing abnormal oxidation of the melting point of Ag and the metal (for example, SUS) as the base material, and preferably in the range of 970°C or higher and 1100°C or lower. The holding time of the set heating temperature is set, for example, in the range of 5 minutes or more and 300 minutes or less.

[0037] In the step S240 of cooling the brazing material for air brazing, in the atmosphere, the heated brazing material for air brazing is cooled to solidify the dissolved Ag. Thereby, the first base material 111 and the second base material 112 can be joined. Examples of cooling the brazing material for air brazing include cooling it as it is in a heating furnace in an air atmosphere. The cooling in the heating furnace is set, for example, to cool at a cooling rate of 3 to 10°C / min to room temperature.

[0038] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereby.

[0039] (Example 1) Powders of Ag, Ge, and Cr ２ O ３ were mixed to prepare a brazing material for air brazing (Ag-2Ge-1Cr) containing 97 wt% of Ag, 2 wt% of Ge, and 1 wt% of Cr ２ O ３ (Cr ２ O ３The particle size distribution of the powder was measured by laser diffraction / scattering in accordance with JIS Z8825. For the measurement of particle size distribution by laser diffraction / scattering, a laser diffraction / scattering particle size distribution analyzer (Malvern Panalytical, LMS-3000) was used. The measurement method by laser diffraction / scattering involved first performing a blank measurement using only the dispersion medium, and then placing the pre-ultrasonically dispersed sample into the dispersion tank and performing the measurement in a circulating manner. The measurement conditions were: measurement range of 0.010 to 3500.00 μm, dispersion medium of I.P.A., and ultrasonic dispersion time of 1 minute. Cr ２ O ３ As shown in Figure 3, the particle size distribution of the powder showed that the proportion of particles with a diameter of 10 μm or larger was approximately 7%, and less than 10%. The median diameter was approximately 1.78 μm. Furthermore, the maximum peak was observed between particle diameters of 1 μm and 2 μm. A paste was made by adding terpionol, an organic solvent, and Oricox KC, an organic binder, to the atmospheric bonding brazing material.

[0040] As the first base material, a plate-shaped zirconia ceramic (manufactured by Kyocera Corporation, 3YSZ) was prepared. As the second base material, a cylindrical ferritic stainless steel (manufactured by Proterial Co., Ltd., ZMG232L) with an outer diameter of Φ20 mm and an inner diameter of Φ15 mm was prepared. An atmospheric bonding brazing material was screen printed onto the first base material, and the second base material was placed on top so that its outer diameter was in contact with the first base material. A pressure of 12 kPa was applied, and the mixture was heated in a heating furnace under atmospheric conditions at a heating temperature of 970°C for a heating time of 1 hour. After that, the mixture was cooled to room temperature in the heating furnace at a cooling rate of 3°C / min to produce a bonded body.

[0041] (Example 2) In Example 1, Cr ２ O ３An atmospheric bonding brazing material (Ag-2Ge-1Cr) was prepared in the same manner as in Example 1, except that Cr powder was mixed in instead of the Cr powder. The particle size distribution of the Cr powder was measured by laser diffraction / scattering in accordance with JIS Z8825, using the same equipment, measurement method, and measurement conditions as in Example 1. As shown in Figure 4, the proportion of particles with a particle size of 10 μm or more was 0%, and less than 10%. The median diameter was approximately 2.06 μm. The maximum peak was observed between particle sizes of 2 μm and 3 μm (around 2 μm). A bonded body was fabricated under the same conditions as in Example 1.

[0042] (Reference example) In Example 1, Cr ２ O ３ An atmospheric bonding brazing material (Ag-2Ge-1Cr) was prepared in the same manner as in Example 2, except that a different Cr powder was mixed in place of the powder used in Example 1. The particle size distribution of the Cr powder was measured by laser diffraction / scattering in accordance with JIS Z8825, using the same equipment, measurement method, and measurement conditions as in Example 1. As shown in Figure 5, the proportion of particles with a particle diameter of 10 μm or more was approximately 59%. The median diameter was approximately 12.82 μm. The maximum peak was observed between particle diameters of 20 μm and 30 μm (around 20 μm). A bonded body was fabricated under the same conditions as in Example 1.

[0043] <Evaluation Tests> The fabricated joint was observed in cross-section using a scanning electron microscope (Evaluation Test 1). Elemental analysis was performed on the fabricated joint using an electron probe microanalyzer (Evaluation Test 2). The fabricated joint was heated to 800°C in a heating furnace under an atmospheric environment while hydrogen was injected through an opening in the second base material. With this test method, one end face of the brazed joint (inside the second base material) is exposed to hydrogen, and the other end face (outside the second base material) is exposed to the atmosphere. He leak tests were performed on the joint before heating (0h), and at 25h, 50h, and 100h after heating (Evaluation Test 3). In the He leak test, a He leak detector (HELIOT-701W1, manufactured by ULVAC, Inc.) was used to evaluate the leak by evacuating the internal space of the joint from an opening in the second base material while simultaneously blowing He gas onto the joint from the outside of the second base material, and detecting the amount of He gas that entered the internal space of the joint.

[0044] (Evaluation Test 1) Figures 6, 7, and 8 are images of the fabricated joints observed in cross-section using a scanning electron microscope. Figure 6 is the joint of the reference example. Figure 7 is the joint of Example 1. Figure 8 is the joint of Example 2. As shown in Figures 6, 7, and 8, it can be seen that the joints of Examples 1 and 2 have fine particles more uniformly dispersed compared to the joint of the reference example.

[0045] (Evaluation Test 2) Figures 9, 10, and 11 are images of the fabricated joints after elemental analysis using an electron probe microanalyzer. Figure 9 is a reference example joint. Figure 10 is the joint from Example 1. Figure 11 is the joint from Example 2.

[0046] As shown in Figure 9, in the joint of the reference example, Ag accounts for the majority of the brazed layer, indicating that silver is the main component of the brazed layer. Furthermore, since Ge, Cr, and O are simultaneously present in the parts of the brazed layer other than silver, it can be seen that the brazed layer contains a composite oxide of Ge and Cr within the Ag. In the elemental analysis image using an electron probe microanalyzer, the proportion of particles with a particle size of 10 μm or larger is greater than 10%. It can be said that coarse Ge and Cr composite oxides are dispersed in the Ag within the brazed layer. The first reaction layer contains Ge oxide, as Ge and O are simultaneously present. The second reaction layer contains Ge and Cr composite oxide, as Ge, Cr, and O are simultaneously present.

[0047] As shown in Figure 10, the brazed layer of the joint in Example 1 is mainly composed of Ag, similar to the joint in the Reference Example. Furthermore, the brazed layer contains a composite oxide of Ge and Cr within the Ag, similar to the joint in the Reference Example. However, in the elemental analysis images using an electron probe microanalyzer, the proportion of particles with a particle size of 10 μm or larger is less than 10%. Also, compared to the joint in the Reference Example, the fine Ge and Cr composite oxide is more uniformly dispersed within the Ag in the brazed layer. The first reaction layer contains an oxide of Ge, similar to the joint in the Reference Example. The second reaction layer contains a composite oxide of Ge and Cr, similar to the joint in the Reference Example. Furthermore, in the second reaction layer, there is Cr present that is not present at the same time as Ge, and its proportion is higher than the proportion of Cr present at the same time as Ge. Therefore, it can be seen that the second reaction layer contains Cr oxide, and that the volume proportion occupied by Cr oxide is higher than the volume proportion occupied by the combined oxide of Ge and Cr.

[0048] As shown in Figure 11, the brazed layer of the joint in Example 2 is mainly composed of Ag, similar to the joint in the Reference Example. Furthermore, the brazed layer contains a composite oxide of Ge and Cr within the Ag, similar to the joint in the Reference Example. However, in the elemental analysis image using an electron probe microanalyzer, the proportion of particles with a particle size of 10 μm or larger is less than 10%. Also, in the brazed layer, the fine Ge and Cr composite oxide is more uniformly dispersed within the Ag compared to the joint in the Reference Example. The first reaction layer contains an oxide of Ge, similar to the joint in the Reference Example. The second reaction layer contains a composite oxide of Ge and Cr, similar to the Reference Example. Furthermore, in the second reaction layer, there is Cr present that is not present at the same time as Ge, and its proportion is higher than the proportion of Cr present at the same time as Ge. Therefore, it can be seen that the second reaction layer contains Cr oxide, and that the volume proportion occupied by Cr oxide is higher than the volume proportion occupied by Ge and Cr oxide.

[0049] (Evaluation Test 3) Figure 12 is a graph showing the results of a leak test performed on the fabricated joint. In Figure 12, the horizontal axis represents the heating time of the joint, and the vertical axis represents the amount of He leak. As shown in Figure 12, the amount of leak in the reference example joint increased slightly in proportion to the heating time. In contrast, the amount of leak in the joint of Example 1 began to increase after 50 hours of heating, and the amount of leak was less than that of the reference example joint. Furthermore, the amount of leak in the joint of Example 2 did not increase even after 100 hours of heating. The reason why the joint of Example 2 yielded better results than the joint of Example 1 is that the Cr used in the joint of Example 1 was different. ２ O ３ The particle size distribution of the powder has another peak on the side with larger particle sizes compared to the particle size distribution of the Cr powder used in the composite of Example 2, and the specific surface area of ​​the Cr powder of Example 2 is the same as that of the Cr powder of Example 1. ２ O ３Since the specific surface area tends to be larger than that of the powder, it can be inferred that the specific surface area of ​​the Ge-Cr composite oxide in the brazed layer of the joint in Example 2 was larger than that of the brazed layer of the joint in Example 1, thus increasing the area that is attacked by hydrogen. Furthermore, an increase in the area that is attacked by hydrogen in the brazed layer of the joint suppresses the diffusion of hydrogen entering the brazed layer.

[0050] Based on the above, it can be said that the bonded bodies of Example 1 and Example 2 did not increase in leakage even when heated, and thus improved durability. This is presumed to be due to the fact that by mixing Cr or Cr oxides with a particle size of 10 μm or larger in the atmospheric bonding brazing material, the proportion of particles with a particle size of 10 μm or larger in the Ge and Cr composite oxide contained in the brazing layer became 10% or less. Furthermore, it is presumed that the Ge and Cr composite oxide was uniformly dispersed in the brazing layer, suppressing the diffusion of hydrogen entering the brazing layer.

[0051] Although this embodiment has been described above, any other effects and advantages brought about by the aspects described in this embodiment that are obvious from this specification or that can be appropriately conceived by those skilled in the art are naturally considered to be brought about by the present invention.

[0052] 100 Joint 111 First base material 112 Second base material 120 Joining material 121 First reaction layer 122 Second reaction layer 123 Brazing layer

Claims

1. A brazing material for atmospheric bonding, comprising 94-97 wt% of Ag, 1-5 wt% of Ge or Ge oxide, 1-3 wt% of Cr or Cr oxide, and the remainder being unavoidable impurities, adjusted so that the total of these is 100 wt%, wherein the proportion of particles with a particle size of 10 μm or larger in the particle size distribution measured by laser diffraction / scattering method is 10% or less.

2. The brazing material for atmospheric bonding according to claim 1, wherein the Cr or Cr oxide has a maximum peak in the particle size distribution measured by laser diffraction and scattering, with a particle size of 5 μm or less.

3. A joint comprising a first base material, a second base material, and a joining material for joining the first base material and the second base material, wherein the joining material has a first reaction layer in contact with the first base material, a second reaction layer in contact with the second base material, and a brazing layer interposed between the first reaction layer and the second reaction layer, the brazing layer contains Ag, an oxide of Ge, an oxide of Cr, and a composite oxide of Ge and Cr dispersed in the Ag, and in the brazing layer, the proportion of the number of particles of the composite oxide of Ge and Cr with a particle diameter of 10 μm or more is 10% or less.

4. The bonded body according to claim 3, wherein the first base material is a ceramic, the second base material is a metal, the first reaction layer contains an oxide of Ge, the second reaction layer contains an oxide of Cr and a composite oxide of Ge and Cr, and in the second reaction layer, the volume proportion of the Cr oxide is higher than that of the composite oxide of Ge and Cr.

5. The assembly according to claim 4, used in a fuel cell.

6. The assembly according to claim 5, wherein the fuel cell is a solid oxide fuel cell.

7. A method for manufacturing a bonded body, comprising: placing an atmospheric bonding brazing material between a first base material and a second base material, the brazing material comprising 94 to 97 wt% of Ag, 1 to 5 wt% of Ge or Ge oxide, 1 to 3 wt% of Cr or Cr oxide, and the remainder being unavoidable impurities, adjusted so that the total of these is 100 wt%, wherein the proportion of particles with a particle size of 10 μm or larger in the particle size distribution measured by laser diffraction and scattering method is 10% or less; heating the brazing material in air to dissolve the Ag; and cooling the heated brazing material in air to solidify the Ag.

8. The method for manufacturing a joined body according to claim 7, wherein placing the atmospheric bonding brazing material between the first base material and the second base material means applying the atmospheric bonding brazing material to the first base material and placing the second base material on the atmospheric bonding brazing material applied to the first base material.

Images