JP7306324B2 - Fuel cell separator and fuel cell separator manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel cell separator and a method for manufacturing a fuel cell separator.

Patent Document 1 discloses a fuel cell separator in which a carbon material is dispersed in a resin. The separator is manufactured by heating and pressurizing a mixture of expanded graphite powder and thermosetting resin or thermoplastic resin using a mold.

Such a separator has a plurality of ridges that abut on the power generating section of the fuel cell, and a plurality of gas flow path portions that are provided between two adjacent ridges and form flow paths through which reaction gases flow. ing.

Between the separator on the anode side and the power generating section, a gas flow path for supplying the fuel gas is formed which is partitioned by the protrusion and the gas flow path section. Between the separator on the cathode side and the power generating section, a gas flow path for supplying an oxidizing gas is formed which is partitioned by the protrusion and the gas flow path section. The fuel gas supplied through the anode-side gas flow channel and the oxidizing gas supplied through the cathode-side gas flow channel undergo an electrochemical reaction in the power generation unit to generate power and water.

JP-A-11-354138

By the way, the water produced by the electrochemical reaction (hereinafter referred to as produced water) flows into the gas flow path on the cathode side. Such generated water is discharged to the outside by the pressure of the oxidizing gas flowing through the gas flow path. However, when the amount of generated water increases, the gas flow path may be clogged with the generated water, or the pressure loss of the oxidizing gas may increase excessively.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel cell separator and a method for manufacturing a fuel cell separator that can improve the dischargeability of generated water.

A fuel cell separator for achieving the above object is a fuel cell separator that includes a base material and is provided in contact with a power generation part of a fuel cell, wherein the base material is a conductive first carbon material, and a resin material; a conductive second carbon material; a second conductive layer formed to constitute the surface of the base material, wherein the second carbon material has first carbon particles and an average particle size smaller than that of the first carbon particles. and second carbon particles, and the first carbon particles and the second carbon particles are exposed from the resin material of the second conductive layer.

According to this configuration, the surface of the resin material of the second conductive layer has a portion where the first carbon particles are exposed and a portion where the second carbon particles are exposed. In addition, a plurality of second carbon particles having an average particle diameter smaller than that of the first carbon particles are bonded via the resin material to the surface of the first carbon particles exposed from the surface of the resin material. In this way, the first carbon particles and the second carbon particles form a large number of fine irregularities on the surface of the second conductive layer that contacts the power generating section.

As described above, the generated water generated in the power generation section can be easily discharged from the surface of the second conductive layer along the gaps between the numerous fine irregularities and the power generation section. Therefore, it is possible to improve the dischargeability of the generated water.

Further, according to the above configuration, a conductive path is formed through the first conductive layer and the second conductive layer inside the separator. Therefore, an increase in contact resistance of the separator can be suppressed.
In the above fuel cell separator, the second conductive layer is preferably formed on both sides of the first conductive layer in the thickness direction.

According to this configuration, the conductive path is formed on both sides in the thickness direction of the first conductive layer. Therefore, an increase in contact resistance of the separator can be further suppressed.
Further, a method for manufacturing a fuel cell separator for achieving the above object is a method for manufacturing a fuel cell separator provided in contact with a power generation part of a fuel cell, comprising: A first plate is formed from a first mixture of dispersed materials, and a second plate is formed from a second mixture of a second conductive carbon material dispersed in a resin material, and the thickness of the first plate is A laminated body forming step of forming a laminated body by laminating the second plate material on at least the surface on the power generation part side in the direction, and heating and pressing the laminated body to form the first conductive layer from the first plate material and a conductive layer forming step of forming a second conductive layer from the second plate material adjacent to the first conductive layer on the power generation part side in the thickness direction of the first conductive layer. , as the second mixture, the content of the resin material is less than the content of the second carbon material, and as the second carbon material, the first carbon particles and the average particle diameter of the first carbon particles and second carbon particles having an average particle size smaller than the above.

According to this method, the first conductive layer and the second conductive layer are formed by heating and pressurizing a laminate obtained by laminating a first plate material made of the first mixture and a second plate material made of the second mixture. They are formed adjacent to each other in the thickness direction. Here, the content of the resin material in the second mixture is less than the content of the second carbonaceous material. Therefore, by heating and pressurizing the laminate, the first carbon particles and the second carbon particles contained in the second carbon material are easily exposed from the resin material on the surface of the second conductive layer. According to the separator manufactured in this way, since the function and effect corresponding to the function and effect of the separator for a fuel cell are exhibited, the discharge property of the generated water can be improved. Also, an increase in the contact resistance of the separator can be suppressed.

In the method for manufacturing a fuel cell separator, in the laminate forming step, the second plate member is laminated on both sides of the first plate member in the thickness direction, and in the conductive layer forming step, the first conductive layer Preferably, the second conductive layer is formed on both sides of the.

According to this method, the conductive paths are formed on both sides in the thickness direction of the first conductive layer. Therefore, an increase in contact resistance of the separator can be further suppressed.
In the method for manufacturing a fuel cell separator, in the laminate forming step, the laminate is formed inside a multi-manifold die to which the first mixture and the second mixture are separately supplied, and the laminate is formed. Extrusion from the multi-manifold die is preferred.

According to this method, since the first mixture and the second mixture are individually supplied to the inside of the multi-manifold die, their viscosities can be adjusted by individually adjusting their temperatures. Then, a laminate of a first plate made of the first mixture whose viscosity is individually adjusted and a second plate made of the second mixture is extruded from a multi-manifold die. Thereby, variations in the thickness of the first plate member and variations in the thickness of the second plate member can be suppressed. Therefore, manufacturing variations of the separator can be suppressed.

According to the present invention, it is possible to enhance the discharge of generated water.

FIG. 2 is a cross-sectional view of a fuel cell stack centering on a single cell having the separator of one embodiment of the fuel cell separator. Sectional drawing of the separator for fuel cells of the same embodiment. The schematic of the extruder of the same embodiment. The perspective view of the multi-manifold die|dye of the same embodiment. The schematic of the press apparatus of the same embodiment.

An embodiment of a fuel cell separator and a method for manufacturing a fuel cell separator will be described below with reference to FIGS. 1 to 5. FIG.
In each drawing, part of the configuration may be exaggerated or simplified for convenience of explanation. Also, the dimensional ratio of each part may differ from the actual one.

As shown in FIG. 1, the fuel cell separator (hereinafter referred to as separator 20) of this embodiment is used in a stack 100 of polymer electrolyte fuel cells. Note that the separator 20 is a general term for the first separator 30 and the second separator 40, which will be described later.

A stack 100 has a structure in which a plurality of unit cells 10 are laminated. The single cell 10 has a power generation section 11 . The power generation unit 11 is sandwiched between a first separator 30 on the anode side and a second separator 40 on the cathode side.

The power generation section 11 is composed of a membrane electrode assembly 12, and an anode-side gas diffusion layer 15 and a cathode-side gas diffusion layer 16 that sandwich the membrane electrode assembly 12 therebetween. The anode-side gas diffusion layer 15 is provided between the membrane electrode assembly 12 and the first separator 30 . The cathode-side gas diffusion layer 16 is provided between the membrane electrode assembly 12 and the second separator 40 . Both the anode-side gas diffusion layer 15 and the cathode-side gas diffusion layer 16 are made of carbon fiber.

The membrane electrode assembly 12 includes an electrolyte membrane 13 made of a solid polymer material having good proton conductivity in a wet state, and a pair of electrode catalyst layers 14 sandwiching the electrolyte membrane 13 . Each electrode catalyst layer 14 carries a catalyst such as platinum in order to promote the electrochemical reaction of the reaction gas in the fuel cell.

The first separator 30 has a plurality of ridges 31 and a plurality of gas channel portions 32 through which reaction gas flows. Each ridge 31 extends in parallel with each other at intervals. Each gas flow path portion 32 extends along the ridges 31 between two adjacent ridges 31 . Each ridge 31 is in contact with the anode-side gas diffusion layer 15 . Note that the ridges 31 and the gas flow path portion 32 extend in a direction orthogonal to the plane of FIG. 1 .

The second separator 40 has a plurality of ridges 41 and a plurality of gas channel portions 42 through which reaction gas flows. Each ridge 41 extends in parallel with each other at intervals. Each gas flow path portion 42 extends along the ridges 41 between two adjacent ridges 41 . Each ridge 41 is in contact with the cathode-side gas diffusion layer 16 . The ridges 41 and the gas flow path portion 42 extend in a direction orthogonal to the plane of FIG. 1 .

In two unit cells 10 adjacent to each other, the bottom portion of the gas channel portion 32 of the first separator 30 in one unit cell 10 and the bottom portion of the gas channel portion 42 of the second separator 40 in the other unit cell 10 are abutting each other.

A portion of the first separator 30 defined by the gas flow path portion 32 and the anode-side gas diffusion layer 15 is formed with a fuel gas flow path through which the fuel gas as the reaction gas flows. A portion of the second separator 40 defined by the gas flow path portion 42 and the cathode-side gas diffusion layer 16 is formed with an oxidizing gas flow path through which an oxidizing gas as a reaction gas flows. The fuel gas in this embodiment is hydrogen and the oxidizing gas is air.

A cooling water flow path through which cooling water flows is formed in a portion defined by the back surface of the ridge 31 of the first separator 30 and the back surface of the ridge 41 of the second separator 40 .
As shown in FIG. 2, the separator 20 has a plate-shaped base material 21 . The base material 21 includes a first conductive layer 50 and second conductive layers 60 formed adjacent to the first conductive layer 50 on both sides of the first conductive layer 50 in the thickness direction.

The first conductive layer 50 includes a conductive first carbon material 51 and a resin material 52 .
The second conductive layer 60 includes a conductive second carbon material 61 and a resin material 62 .
The first carbon material 51 and the second carbon material 61 in this embodiment are the same type of carbon material. Examples of the first carbon material 51 and the second carbon material 61 include natural graphite such as spherical graphite.

The resin material 52 and the resin material 62 in this embodiment are the same kind of resin material. Examples of the resin material 52 and the resin material 62 include thermoplastic resin such as polypropylene resin.
The second carbon material 61 includes first carbon particles 63 and second carbon particles 64 having an average particle size smaller than that of the first carbon particles 63 .

The term "average particle size" as used herein refers to the particle size when the integrated value in the volume-based particle size distribution measured by a laser diffraction/scattering method or the like is 50%, that is, the median size. In FIG. 2, for the sake of convenience, among the first carbon particles 63, carbon particles having the median diameter of the first carbon particles 63 and among the second carbon particles 64, the median diameter of the second carbon particles 64 are and carbon particles having

The first carbon particles 63 and the second carbon particles 64 are exposed from the resin material 62 on the surface of each second conductive layer 60 . Therefore, in the second conductive layer 60 facing the power generation section 11 , the first carbon particles 63 and the second carbon particles 64 exposed from the resin material 62 of the second conductive layer 60 come into contact with the power generation section 11 . there is

Next, an extruder 200 and a press device 300 for manufacturing the separator 20 will be described.
<Extruder 200>
As shown in FIG. 3 , the extruder 200 includes one first extruder 201 and two second extruders 202 . The first extruder 201 produces a first mixture 50 a in which the first carbon material 51 is dispersed in the resin material 52 . The second extruder 202 produces a second mixture 60 a in which the second carbon material 61 is dispersed in the resin material 62 .

Each extruder 201 , 202 is connected to a multi-manifold die 230 via a channel 220 .
The first extruder 201 and the second extruder 202 in this embodiment have the same configuration. Therefore, the configuration of the first extruder 201 will be described below, and the description of the configuration of the second extruder 202 will be omitted.

The first extruder 201 includes a cylinder 211, a screw 212 accommodated in the cylinder 211, a first hopper 213 that supplies the resin material 52 into the cylinder 211, and a first carbon material 51 that is supplied into the cylinder 211. It has a second hopper 214 to do. The second hopper 214 is provided closer to the tip side of the cylinder 211 than the first hopper 213 is.

A heater 215 for heating the inside of the cylinder 211 is provided on the outer periphery of the cylinder 211 . Heating the inside of the cylinder 211 by the heater 215 melts the resin material 52 supplied into the cylinder 211 . Therefore, the viscosity of the resin material 52 is adjusted by adjusting the temperature of the resin material 52 with the heater 215 .

The screw 212 is connected to a driving device 216 having a motor (not shown) and is rotatably provided within the cylinder 211 . By rotating the screw 212, the resin material 52 supplied from the first hopper 213 and the first carbonaceous material 51 supplied from the second hopper 214 are mixed to generate the first mixture 50a.

The first mixture 50 a is conveyed toward the tip of the cylinder 211 by the rotation of the screw 212 . After that, the first mixture 50 a is supplied to the interior of the multi-manifold die 230 through the channel 220 .

As shown in FIG. 4, the multi-manifold die 230 has a substantially rectangular parallelepiped shape. Inside the multi-manifold die 230, one first manifold 231 and two second manifolds 232 are arranged side by side. Each second manifold 232 is provided on the opposite side with the first manifold 231 interposed therebetween.

The first mixture 50 a is supplied from the first extruder 201 to the first manifold 231 through the flow path 220 . Each second manifold 232 is supplied with the second mixture 60 a from each second extruder 202 through the flow path 220 . Therefore, the multi-manifold die 230 is separately supplied with the first mixture 50a and the second mixture 60a.

A first slit 233 is continuously provided in the first manifold 231 . A second slit 234 is provided in a row in each second manifold 232 .
The end of the first slit 233 opposite to the first manifold 231 and the end of each second slit 234 opposite to the second manifold 232 communicate with the junction 235 .

The confluence portion 235 has a plate-like space. The confluence portion 235 communicates with a discharge port 236 opening at the end face of the multi-manifold die 230 .
<Press device 300>
As shown in FIG. 5, the press device 300 includes a lower die 301 and an upper die 305 that is movable forward and backward with respect to the lower die 301 .

A protruding portion 302 protruding toward the upper mold 305 is provided in the central portion of the lower mold 301 . A die 303 for forming the protrusions 31 and 41 and the gas flow path portions 32 and 42 is provided on the projecting portion 302 . A heating wire 304 is incorporated inside the lower mold 301 .

A projecting portion 306 projecting toward the lower mold 301 is provided at the center of the upper mold 305 . The projecting portion 306 is provided with a punch 307 for forming the ridges 31 and 41 and the gas passage portions 32 and 42 . Note that the punch 307 and the die 303 are provided facing each other. A heating wire 308 is incorporated inside the upper mold 305 .

Next, a method for manufacturing the separator 20 will be described.
As shown in FIG. 3, first, a first extruder 201 and a second extruder 202 are used to produce a first mixture 50a and a second mixture 60a, respectively. Then, the first mixture 50 a and the second mixture 60 a are supplied to the multi-manifold die 230 .

In this embodiment, the first extruder 201 and the second extruder 202 individually adjust the temperature of the first mixture 50a and the temperature of the second mixture 60a.
When generating the second mixture 60a, the amount of the resin material 62 supplied to the first hopper 213 and the second The amount of supply of the second carbon material 61 to the hopper 214 is adjusted.

As shown in FIG. 4 , the first mixture 50 a supplied to the first manifold 231 flows through the first slits 233 into the confluence portion 235 . The second mixture 60 a supplied to the second manifold 232 flows through the second slit 234 into the confluence portion 235 . Therefore, the first mixture 50 a and the second mixture 60 a join together at the junction 235 . As a result, a first plate member 50b made of the first mixture 50a is formed, and a second plate member 60b made of the second mixture 60a is formed.

In the confluence portion 235, the second mixture 60a is merged from both sides in the thickness direction of the first mixture 50a. As a result, the laminate 70 is formed by laminating the second plate member 60b on both sides in the thickness direction of the first plate member 50b at the confluence portion 235 . After that, the laminate 70 is discharged from the discharge port 236, that is, extruded from the multi-manifold die 230 (laminate forming step).

Next, the laminate 70 is cut into a predetermined shape by a cutting device (not shown).
As shown in FIG. 5, the lower mold 301 and the upper mold 305 are then heated to a predetermined temperature by supplying current to the heating wires 304 and 308 . After that, the laminate 70 is placed on the die 303 of the lower mold 301 and the laminate 70 is sandwiched between the lower mold 301 and the upper mold 305 . Thereby, the laminated body 70 is heated and softened.

Next, the laminate 70 is pressed by the lower mold 301 and the upper mold 305 . As a result, the laminate 70 is deformed in accordance with the shapes of the die 303 and the punch 307 , thereby forming the ridges 31 and 41 and the gas passage portions 32 and 42 in the laminate 70 .

After that, the resin materials 52 and 62 are cured by cooling the laminate 70 . Thus, the first conductive layer 50 is formed from the first plate material 50b, and the second conductive layers 60 are formed from the second plate material 60b on both sides of the first conductive layer 50 in the thickness direction so as to be adjacent to the first conductive layer 50. (conductive layer forming step).

Thus, the separator 20 is manufactured.
The operation of this embodiment will be described.
The surface of the resin material 62 of the second conductive layer 60 has a portion where the first carbon particles 63 are exposed and a portion where the second carbon particles 64 are exposed. Further, a plurality of second carbon particles 64 having an average particle diameter smaller than that of the first carbon particles 63 are bonded via the resin material 62 to the surface of the first carbon particles 63 exposed from the surface of the resin material 62 . . In this manner, the first carbon particles 63 and the second carbon particles 64 form a large number of fine irregularities on the surface of the second conductive layer 60 that contacts the power generation section 11 .

As described above, the generated water generated in the power generation unit 11 is easily discharged from the surface of the second conductive layer 60 through the gaps between the numerous fine irregularities and the power generation unit 11 .
Effects of the present embodiment will be described.

(1) The base material 21 includes a first conductive layer 50 and second conductive layers 60 formed adjacent to the first conductive layer 50 on both sides of the first conductive layer 50 in the thickness direction. . The second carbon material 61 of the second conductive layer 60 includes first carbon particles 63 and second carbon particles 64 having an average particle size smaller than that of the first carbon particles 63 . The first carbon particles 63 and the second carbon particles 64 are exposed from the resin material 62 .

According to such a configuration, since the above-described effects are exhibited, the discharge of generated water can be enhanced.
Moreover, according to the above configuration, a conductive path is formed inside the separator 20 through the first conductive layer 50 and the second conductive layer 60 . Therefore, an increase in contact resistance of the separator 20 can be suppressed.

(2) In the laminate forming step, the first plate material 50b is formed from the first mixture 50a, and the second plate material 60b is formed from the second mixture 60a. A laminate 70 is formed by laminating the second plate members 60b. In the conductive layer forming step, the stacked body 70 is heated and pressed to form the first conductive layer 50 from the first plate material 50b, and the second plate material 60b is formed on both sides of the first conductive layer 50 in the thickness direction. A second conductive layer 60 is formed adjacent to the first conductive layer 50 . As the second mixture 60a, a mixture in which the content of the resin material 62 is less than the content of the second carbon material 61 is used. As the second carbon material 61, one containing first carbon particles 63 and second carbon particles 64 having an average particle size smaller than that of the first carbon particles 63 is used.

According to such a method, by heating and pressurizing the laminate 70, the first conductive layer 50 and the second conductive layer 60 are formed adjacent to each other in the thickness direction. Here, the content of the resin material 62 in the second mixture 60 a is less than the content of the second carbon material 61 . Therefore, by heating and pressurizing the laminate 70, the first carbon particles 63 and the second carbon particles 64 included in the second carbon material 61 are exposed from the resin material 62 on the surface of the second conductive layer 60. easier to do. According to the separator 20 manufactured in this way, since the above effect (1) is exhibited, the discharge property of the generated water can be improved. Also, an increase in the contact resistance of the separator 20 can be suppressed.

(3) In the laminate forming step, the laminate 70 is formed inside the multi-manifold die 230 and the laminate 70 is extruded from the multi-manifold die 230 .
According to this method, since the first mixture 50a and the second mixture 60a are individually supplied to the interior of the multi-manifold die 230, the viscosities thereof can be adjusted by individually adjusting their temperatures. can. Then, the laminate 70 of the first plate material 50b made of the first mixture 50a whose viscosity is individually adjusted and the second plate material 60b made of the second mixture 60a is extruded from the multi-manifold die 230. Thereby, variations in the thickness of the first plate member 50b and variations in the thickness of the second plate member 60b can be suppressed. Therefore, manufacturing variations of the separator 20 can be suppressed.

<Change example>
This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

- In the laminate forming step, instead of the multi-manifold die 230, for example, a coater or a sprayer may be used to form the first plate member 50b and the second plate member 60b. As an example of such a method, first, the second plate material 60b is formed by applying the molten second mixture 60a to the surface of the mold. Next, the first plate member 50b is formed by applying the melted first mixture 50a to the surface of the second plate member 60b. Next, the second plate member 60b is formed by applying the melted second mixture 60a to the surface of the first plate member 50b. As a result, a laminate 70 is formed in which the second plate member 60b is laminated on both sides of the first plate member 50b in the thickness direction.

- The second conductive layer 60 may be formed only on the surface of the first conductive layer 50 on the side of the power generation section 11 in the thickness direction. In this case, in the laminate forming step, the second plate member 60b may be laminated only on the surface of the first plate member 50b on the power generating section 11 side in the thickness direction.

- In the present embodiment, the first carbon material 51 and the second carbon material 61 are the same type of carbon material, but they may be different types of carbon material.
- The first carbon material 51 and the second carbon material 61 may be any conductive carbon material, and may be, for example, artificial graphite or natural graphite other than spherical graphite.

- In addition to the first carbon material 51, the first conductive layer 50 may contain a carbon material different from the first carbon material 51, metallic conductive particles, and the like. In addition to the second carbon material 61, the second conductive layer 60 may contain a carbon material different from the second carbon material 61, metal conductive particles, and the like.

- In the present embodiment, the first carbon particles 63 and the second carbon particles 64 are carbon particles of the same type, but they may be carbon particles of different types.
- In the present embodiment, the resin material 52 and the resin material 62 are the same type of resin material, but they may be different types of resin material.

- The resin material 52 and the resin material 62 may be a thermoplastic resin other than the polypropylene resin, or may be a thermosetting resin such as an epoxy resin.
- The second conductive layer 60 is preferably formed on the entire surface of the portion of the separator 20 that faces the power generation section 11, but does not necessarily have to be formed on the entire surface. For example, the second conductive layer 60 may be formed only on the top surfaces of the ridges 31 and 41 of the separator 20 .

- The separator 20 of the present embodiment may be applied only to the first separator 30 on the anode side, or may be applied only to the second separator 40 on the cathode side.

DESCRIPTION OF SYMBOLS 11... Power generation part 20... Separator 21... Base material 50... First conductive layer 50a... First mixture 50b... First plate material 51... First carbon material 52... Resin material 60... Second conductive layer 60a... Second mixture 60b... Second plate material 61 Second carbon material 62 Resin material 63 First carbon particles 64 Second carbon particles 70 Laminated body 230 Multi-manifold die

Claims (3)

A fuel cell separator comprising a base material and provided in contact with a power generation part of a fuel cell,
The base material is
a first conductive layer including a conductive first carbon material and a resin material;
A second conductive material comprising a conductive second carbon material and a resin material, formed adjacent to the first conductive layer on both sides in the thickness direction of the first conductive layer, and constituting the surface of the base material. comprising a layer and
the first carbon material and the second carbon material are carbon materials of different types;
The second carbon material includes first carbon particles and second carbon particles having an average particle size smaller than the average particle size of the first carbon particles,
The first carbon particles and the second carbon particles are exposed from the resin material of the second conductive layer,
Fuel cell separator. A method for manufacturing a fuel cell separator provided in contact with a power generation portion of a fuel cell, comprising:
A first plate is formed from a first mixture in which a first conductive carbon material is dispersed in a resin material, and a second plate is formed from a second mixture in which a second conductive carbon material is dispersed in a resin material. a laminate forming step of forming a laminate by laminating the second plate material on both sides of the first plate material in the thickness direction;
By heating and pressurizing the laminate, a first conductive layer is formed from the first plate material, and a second conductive layer is formed from the second plate material on both sides of the first conductive layer. A conductive layer forming step formed adjacent to the layer,
As the second mixture, a mixture having a resin material content smaller than the content of the second carbon material is used,
As the second carbon material, one containing first carbon particles and second carbon particles having an average particle size smaller than the average particle size of the first carbon particles is used.
A method for producing a fuel cell separator. In the laminate forming step, the laminate is formed inside a multi-manifold die to which the first mixture and the second mixture are separately supplied, and the laminate is extruded from the multi-manifold die.
3. The method for manufacturing the fuel cell separator according to claim 2 .

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