Method for inspecting membrane electrode assembly

Abstract

Provided is a method for inspecting a membrane-electrode assembly that prevents erroneous detection of cerium oxide as a foreign object. The method for inspecting a membrane-electrode assembly containing cerium oxide includes: a magnetic field distribution map acquisition step of applying an external magnetic field to the membrane-electrode assembly and acquiring a magnetic field distribution map of the membrane-electrode assembly by using a magnetic resonance method using diamond having NV centers; and a magnetic foreign object inspection step of inspecting a magnetic foreign object in the membrane-electrode assembly based on whether or not magnetic flux is concentrated, with respect to the acquired magnetic field distribution map.

Description

Technical Field

[0001] This invention relates to a method for inspecting membrane electrode assemblies, and more particularly to a method for inspecting membrane electrode assemblies containing cerium oxide. Background Technology

[0002] Cerium oxide-containing membrane electrode assemblies are widely used in fuel cells, water electrolysis for hydrogen production, and other technologies. During the manufacturing process, particulate iron or iron-based foreign matter such as SUS may be introduced, therefore, it is necessary to inspect the manufactured membrane electrode assemblies.

[0003] Patent Document 1 describes a method in which X-rays are irradiated onto a membrane electrode assembly, and the iron-based foreign matter is detected by distinguishing it from the cerium oxide in the X-ray transmission image of the membrane electrode assembly by utilizing the intensity difference between the X-rays transmitted through the membrane electrode assembly and the X-rays of the iron-based foreign matter.

[0004] Patent Document 1: Japanese Patent No. 7221895 Summary of the Invention

[0005] However, cerium oxide also absorbs X-rays, so it is sometimes detected as a foreign substance. Therefore, the method described in Patent Document 1 has the problem of misdetecting cerium oxide as a foreign substance.

[0006] This invention was made to solve this technical problem, and its purpose is to provide an inspection method for membrane electrode joints that can prevent cerium oxide from being mistakenly detected as a foreign object.

[0007] The present invention relates to a method for inspecting a membrane electrode assembly containing cerium oxide. The method includes: a magnetic field distribution map acquisition step, wherein an external magnetic field is applied to the membrane electrode assembly, and a magnetic field distribution map of the membrane electrode assembly is acquired using a magnetic resonance method with diamond having NV color centers; and a magnetic foreign object inspection step, wherein magnetic foreign objects in the membrane electrode assembly are inspected based on the acquired magnetic field distribution map and the presence or absence of magnetic flux concentration.

[0008] Magnetic foreign materials such as iron have relatively high relative permeability and are easily magnetized. On the other hand, cerium oxide has relatively low relative permeability and is not easily magnetized. Therefore, if an external magnetic field is applied to the membrane electrode assembly, the magnetic foreign materials within the assembly will be magnetized. Magnetization of the magnetic foreign material results in a concentration of magnetic flux around it, leading to relatively large magnetic field disturbances. Conversely, cerium oxide in the membrane electrode assembly is not easily magnetized, so no magnetic flux concentration occurs around it, and the magnetic field disturbances around cerium oxide are relatively small or almost nonexistent. Thus, a difference in the occurrence of magnetic field disturbances arises between the magnetic foreign material with relatively high permeability and the cerium oxide with relatively low permeability.

[0009] In the inspection method for membrane electrode assemblies according to the present invention, firstly, an external magnetic field is applied to the membrane electrode assembly, and a magnetic field distribution map of the membrane electrode assembly is obtained using a diamond magnetic resonance method with NV color centers. Next, based on the obtained magnetic field distribution map, the presence or absence of magnetic flux concentration is checked to determine whether magnetic foreign matter is mixed into the membrane electrode assembly. That is, in the inspection method for membrane electrode assemblies according to the present invention, the difference in the disturbance of the magnetic field generated by the aforementioned magnetic foreign matter and cerium oxide is utilized to selectively detect only magnetic foreign matter. As a result, it is possible to prevent the misdetection of cerium oxide as a foreign matter, as has been done in the past.

[0010] In the inspection method of the membrane electrode assembly involved in this invention, preferably, the magnetic field distribution map acquisition step includes: a frequency determination step, in which, under the condition of applying the external magnetic field, the diamond is irradiated with excitation light and microwave, and the frequency of the microwave with the largest change in the emission from the diamond is determined by photodetector magnetic resonance; a emission intensity acquisition step, in which the frequency of the microwave is fixed to the determined frequency, the external magnetic field is applied to the membrane electrode assembly, and under the condition of irradiating the diamond with the excitation light and microwave, the membrane electrode assembly is scanned in two dimensions, and the emission from the diamond is detected to obtain an emission intensity distribution map; and a conversion step, in which the obtained emission intensity distribution map is converted into the magnetic field distribution map.

[0011] In the inspection method for membrane electrode assemblies according to this invention, the frequency of the microwave with the largest change in light emission from the diamond is determined by photodetector magnetic resonance. The diamond is then irradiated with the determined microwave frequency, and the membrane electrode assembly is scanned in two dimensions to obtain a light emission intensity distribution map from the diamond. This increases the amount of change in light emission intensity caused by magnetic field variations, thereby improving the sensing sensitivity of the diamond. Consequently, the inspection accuracy of magnetic foreign objects can be improved. Furthermore, by converting the obtained light emission intensity distribution map into a magnetic field distribution map, a magnetic field distribution map of the membrane electrode assembly with high sensitivity can be obtained.

[0012] In the inspection method for membrane electrode assemblies according to the present invention, it is preferable that, in the magnetic field distribution map acquisition step, the direction in which the external magnetic field is applied to the membrane electrode assembly is aligned with the NV axis direction of the diamond. This improves the magnetic sensitivity of the NV color center, thus enabling the acquisition of the magnetic field distribution map with higher sensitivity. Therefore, even minute magnetic foreign objects can be detected at high speed. As a result, the inspection accuracy of magnetic foreign objects in the membrane electrode assembly is improved, and the inspection speed is increased.

[0013] Furthermore, in the inspection method for the membrane electrode assembly according to the present invention, it is preferable that the membrane electrode assembly has a flat surface, and in the magnetic field distribution map acquisition step, when using a diamond with the diamond (100) facet as the main surface, the angle between the direction of application of the external magnetic field and the normal direction of the surface of the membrane electrode assembly is set to 54.7°. Thus, when using a diamond with the diamond (100) facet as the main surface, by tilting the direction of application of the external magnetic field by 54.7° relative to the normal direction of the surface of the membrane electrode assembly, the sensitivity of the detection magnetic field can be intentionally adjusted, making the disturbance of the magnetic field caused by magnetic foreign objects greater. Therefore, since the sensitivity can be improved, magnetic foreign objects of various shapes can be detected. As a result, missed detections can be prevented, and the inspection speed can be improved.

[0014] Furthermore, in the inspection method for the membrane electrode assembly involved in this invention, it is preferable that the membrane electrode assembly has a flat surface. When one direction on the surface of the membrane electrode assembly is designated as the X direction, and the direction orthogonal to the X direction is designated as the Y direction, in the luminescence intensity acquisition step, after scanning along the X direction from one end to the other of the membrane electrode assembly, the position is offset from the Y direction, and scanning is performed again along the X direction from one end to the other to acquire the luminescence intensity distribution map. In the conversion step, the luminescence intensity distribution map is corrected to keep the luminescence intensity constant at all scanning starting points in the X direction, and then converted to the magnetic field distribution map. This suppresses the influence of medium- to long-term luminescence fluctuations, thus obtaining a magnetic field distribution map with good sensitivity. As a result, the inspection accuracy of magnetic foreign objects can be further improved.

[0015] Invention Effects

[0016] According to the present invention, it is possible to prevent cerium oxide from being mistakenly detected as a foreign object. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the structure of the inspection device used in the inspection method for the membrane electrode assembly according to the embodiment.

[0018] Figure 2 This is a schematic diagram used to illustrate the magnetic field disturbance of a magnetic foreign object when an external magnetic field is applied.

[0019] Figure 3 This is a schematic diagram used to illustrate the direction in which an external magnetic field is applied.

[0020] Figure 4 (a) is a graph showing an example of the detected luminescence intensity. Figure 4 (b) is a diagram used to illustrate the determination of microwave frequency.

[0021] Figure 5 (a) is a diagram showing the surface of the membrane electrode assembly. Figure 5 (b) is a diagram showing the magnetic field distribution of the membrane electrode assembly.

[0022] Figure 6 (a) is a graph showing the luminous intensity distribution involved in the embodiment. Figure 6 (b) is a graph showing the luminescence intensity distribution after correction (differentiation). Detailed Implementation

[0023] Hereinafter, embodiments of the inspection method for membrane electrode assemblies according to the present invention will be described with reference to the accompanying drawings. Before describing the embodiments, the structure of the membrane electrode assembly and the inspection apparatus used in the inspection method for the membrane electrode assembly will be described.

[0024] [About membrane electrode assembly]

[0025] The membrane electrode assembly 100 described in this embodiment (reference) Figure 1 For example, it can be used in fuel cells, and may be plate-shaped with a flat surface. The membrane electrode assembly 100 is, for example, a membrane electrode assembly (MEA) having a plate-shaped electrolyte membrane, an anode catalyst layer disposed on one side of the electrolyte membrane, and a cathode catalyst layer disposed on the other side of the electrolyte membrane. The electrolyte membrane is, for example, a solid polymer membrane formed by a fluorinated sulfonic acid polymer. The anode catalyst layer and the cathode catalyst layer are, for example, formed of a catalyst support carbon loaded with catalyst particles such as platinum and an electrolyte resin, respectively.

[0026] Alternatively, the membrane electrode assembly 100 may be a membrane electrode and gas diffusion layer assembly (MEGA) having a MEA and gas diffusion layers respectively disposed on both sides of the MEA. The gas diffusion layers are formed, for example, of porous carbon materials such as carbon paper or carbon cloth, or porous metal materials such as metal mesh or foamed metal, which are permeable and conductive.

[0027] Furthermore, in the membrane electrode assembly 100 having the structure described above, cerium oxide is contained in order to render the hydrogen peroxide free radicals that occur during power generation harmless and to suppress the deterioration of the electrolyte membrane caused by the hydrogen peroxide free radicals.

[0028] [Regarding the structure of the inspection device]

[0029] The inspection device 1 used in the inspection method for membrane electrode assemblies is a so-called diamond quantum sensor, which is used for two-dimensional scanning of the membrane electrode assembly 100 as the object of inspection and to check for the presence of magnetic foreign matter in the membrane electrode assembly. The diamond quantum sensor utilizes the nitrogen-vacancy complexes (i.e., NV (Nitrogen-Vacancy) color centers) present inside diamond (see reference). Figure 3 Sensors that sensitively detect changes in the quantum state due to environmental changes are used as highly sensitive sensors for magnetic fields, electric fields, temperature, strain, etc.

[0030] Figure 1 This is a schematic diagram showing the structure of the inspection apparatus used in the inspection method for the membrane electrode assembly according to the embodiment. Figure 1 In the diagram, the magnet depicted on the membrane electrode assembly 100 represents a magnetic foreign object 101 that has been magnetized by the application of an external magnetic field 8.

[0031] like Figure 1 As shown, the inspection apparatus 1 mainly comprises an excitation light irradiation unit 2, a sensor head 3, a microwave source 4, a diamond 5, an external magnetic field 8, a stage 6, and a detection unit 7. The excitation light irradiation unit 2 includes: a laser source 21 that generates excitation light that irradiates the diamond 5; and a first optical fiber 22 and a second optical fiber 23 that guide the excitation light from the laser source 21 to the diamond 5. The laser source 21 outputs, for example, green excitation light (i.e., laser light). The first optical fiber 22 and the second optical fiber 23 are connected via a coupler (not shown).

[0032] The sensor head 3 includes: a first lens 31 and a second lens 32, which are optically connected to a second optical fiber 23; and a microwave antenna 33, which is positioned near the diamond 5 and applies microwaves to the diamond 5. The microwave source 4 irradiates the diamond 5 with microwaves of variable frequency through the microwave antenna 33 and scans it.

[0033] Diamond 5 possesses NV color centers, which emit fluorescence (in other words, luminescence) when exposed to excitation light. These NV color centers are formed within the diamond lattice and therefore have four axial orientations (see reference). Figure 3 ).

[0034] The external magnetic field 8, for example, is composed of a permanent magnet or an electromagnet, and enhances the responsiveness to magnetic fields by applying a magnetic field to the diamond 5. Furthermore, the magnetic field applied to the membrane electrode assembly 100 based on the external magnetic field 8 may or may not be perpendicular to the membrane electrode assembly 100. Specifically, for example, when using a diamond 5 with the diamond (100) facet as its main surface, the direction of the applied magnetic field of the external magnetic field 8 is not perpendicular to the surface of the membrane electrode assembly 100; however, when using a diamond 5 with the diamond (111) facet as its main surface, the direction of the applied magnetic field of the external magnetic field 8 is perpendicular to the surface of the membrane electrode assembly 100.

[0035] like Figure 1 As shown, in this embodiment, an external magnetic field 8 applies a magnetic field to the membrane electrode assembly 100 placed on the mounting stage 6 from the upper left direction of the diamond 5. Furthermore, by adjusting the orientation of its polarity, the external magnetic field 8 can apply a magnetic field to the membrane electrode assembly 100 placed on the mounting stage 6 in a predetermined direction. For example, when using a diamond 5 with the diamond (100) face as its main surface, the external magnetic field 8 is aligned with one NV axis of the diamond 5 and applies a magnetic field to the membrane electrode assembly 100 at an angle of 54.7° relative to the normal direction of the surface of the membrane electrode assembly 100. This 54.7° is based on results determined by crystallography and other methods of the diamond 5.

[0036] The stage 6, used to mount and fix the membrane electrode assembly 100, is disposed below the diamond 5. The stage 6 may have, for example, an XY stage capable of moving along the X and Y axes. The upper surface of the XY stage is planar, serving as the mounting surface for the membrane electrode assembly 100. The membrane electrode assembly 100 is mounted on the upper surface of the stage 6 with its flat surface parallel to the upper surface of the stage 6.

[0037] Furthermore, when one direction on the surface of the membrane electrode assembly 100 is designated as the X direction and the direction orthogonal to that direction is designated as the Y direction, the membrane electrode assembly 100 is preferably placed on the upper surface of the mounting stage 6 such that the X direction is along the X-axis of the XY stage and the Y direction is along the Y-axis of the XY stage. Additionally, when placed on the mounting stage 6, the distance from the upper surface of the membrane electrode assembly 100 to the bottom surface of the diamond 5 is, for example, 0.6 mm.

[0038] The detection unit 7 includes an optical fiber 71 connected to the second optical fiber 23 via an optical fiber coupler (not shown), a photodetector 72 that detects fluorescence guided by the optical fiber 71 (i.e., light emitted from the diamond 5), a current-to-voltage converter 73, a lock-in amplifier 74, and a voltmeter 75.

[0039] Optical fiber 71 is connected, for example, to a filter that transmits only the red fluorescence emitted from diamond 5 and no other light, and guides the red fluorescence transmitted through the filter to photodetector 72. Photodetector 72 detects the fluorescence guided by optical fiber 71, converts the detected luminescence intensity into an electrical signal (e.g., alternating current), and outputs it to current-to-voltage converter 73.

[0040] The current-to-voltage converter 73 converts the alternating current from the photodetector 72 into an alternating voltage and outputs it to the lock-in amplifier 74. The lock-in amplifier 74 is a device for reducing noise in the detected fluorescence by frequency modulation of the microwaves applied to the diamond 5 and synchronizing them with the obtained signal. For example, the lock-in amplifier 74 converts the alternating voltage from the current-to-voltage converter 73 into a direct current voltage by multiplying it by a reference signal and outputs it to the voltmeter 75.

[0041] The voltmeter 75 converts the DC voltage signal (analog signal) from the lock-in amplifier 74 into a digital signal and outputs the converted digital signal to the control unit (not shown). The control unit performs various processes based on the results output from the voltmeter 75. For example, the control unit creates a luminous intensity distribution map or converts the luminous intensity distribution map into a magnetic field distribution map based on the input results.

[0042] [History of the Invention]

[0043] Here, the formation process of the present invention will be described.

[0044] To address the problem of misdetecting cerium oxide as a foreign object, the inventors of this application conducted in-depth research. First, they investigated how to better distinguish between cerium oxide and magnetic foreign objects to avoid misdetection. Therefore, they focused on the difference between the relative permeability of magnetic foreign objects and that of cerium oxide. Specifically, magnetic foreign objects such as iron have relatively high relative permeability and are easily magnetized. On the other hand, cerium oxide has relatively low relative permeability and is not easily magnetized. Furthermore, relative permeability refers to the difference between the permeability of a material and the vacuum permeability (4π × 10⁻⁶) used as a reference. -7 The ratio of [H / m] is used to determine the magnetic permeability. It is said that the closer the relative permeability is to 1, the less easily it can be magnetized.

[0045] like Figure 2As shown, if an external magnetic field, such as that of a magnet, is applied, a magnetic foreign object such as iron will be magnetized. This results in a concentration of magnetic flux around the magnetic foreign object, causing relatively large disturbances in the magnetic field. In contrast, as mentioned above, cerium oxide is not easily magnetized, therefore no concentration of magnetic flux occurs around it, and the disturbances in the magnetic field around cerium oxide are very small. Thus, a difference in the disturbances in the magnetic field arises between a magnetic foreign object with high relative permeability and cerium oxide with low relative permeability.

[0046] In addition to iron, the magnetic foreign matter mentioned in this embodiment also includes strongly magnetic materials such as nickel and cobalt, austenitic stainless steel (e.g., SUS304), ferritic stainless steel (e.g., SUS403), etc.

[0047] Next, the inventors of this application, utilizing the difference in magnetic field disturbance between the aforementioned magnetic foreign matter and cerium oxide, investigated a method capable of distinguishing it from cerium oxide while detecting only the magnetic foreign matter. The results focused on sensing using a diamond quantum sensor. Specifically, the method involves irradiating a diamond with NV color centers with excitation light while an external magnetic field is applied, simultaneously irradiating the diamond with microwaves and scanning it, thereby detecting the intensity of the light emitted from the diamond, and detecting a small magnetic field based on the detected change in light intensity. By using this method, it was discovered that detecting only magnetic foreign matter can prevent false detection of cerium oxide in conventional X-ray irradiation, thus completing this invention.

[0048] [Inspection methods for membrane electrode assemblies]

[0049] Therefore, the inspection method for the membrane electrode assembly according to this embodiment includes a frequency determination step S1, a light intensity acquisition step S2, a conversion step S3, and a magnetic foreign object inspection step S4. Furthermore, the frequency determination step S1, the light intensity acquisition step S2, and the conversion step S3 correspond to the "magnetic field distribution map acquisition step" described in the claims.

[0050] In the frequency determination step S1, while an external magnetic field 8 is applied to the diamond 5, the diamond 5 is irradiated with excitation light and microwaves, and the frequency of the microwave with the largest change in the amount of light emitted from the diamond 5 is determined by optical detection magnetic resonance (ODMR).

[0051] Specifically, firstly, without placing the film electrode assembly 100 on the stage 6, an external magnetic field 8 is applied to the diamond 5. Here, for example, a diamond 5 with the diamond (100) facet as its main surface is used. At this time, as... Figure 3 As shown, the direction of the applied magnetic field of the external magnetic field 8 is aligned with one of the four NV axis directions present in the diamond 5, and is 54.7° relative to the normal direction of the surface of the membrane electrode assembly 100 placed on the mounting stage 6.

[0052] Next, the laser source 21 is activated, and excitation light is irradiated onto the diamond 5. The excitation light is, for example, a 532nm green laser with a power of, for example, 2mW. Then, the green excitation light is guided to the first optical fiber 22 and the second optical fiber 23, and irradiates the diamond 5 (see reference). Figure 1 (The arrow with a dashed line).

[0053] When illuminated with green excitation light, red fluorescence (in other words, luminescence) is emitted from the NV color center of diamond 5. The luminescence from diamond 5 is guided to photodetector 72 via second optical fiber 23 and optical fiber 71 (see reference). Figure 1 (Arrow with a solid line).

[0054] Next, microwave source 4 is activated, and microwaves of variable frequency are irradiated onto diamond 5 via microwave antenna 33 and scanned. When the microwaves are scanned, the electron spins of the NV color center undergo photodetector magnetic resonance, causing the red fluorescence emitted from diamond 5 to rapidly decrease. That is, the intensity of the red fluorescence decreases sharply at the resonance frequency. Detection unit 7 detects the red fluorescence and outputs the intensity of the detected fluorescence (i.e., luminescence intensity) to control unit (not shown).

[0055] Figure 4 (a) is a graph showing an example of the detected luminescence intensity. Figure 4 In (a), the horizontal axis represents the microwave frequency, and the vertical axis represents the detected luminous intensity. The peak value at which the microwave frequency is shifted to the lowest frequency side by applying a magnetic field is shown in [the diagram]. Figure 4 In (a), three peaks appear due to ultrafine interactions with N atoms. Furthermore, as shown by the arrows in the figure, the waveform shifts left and right with changes in the external magnetic field. In this embodiment, if the external magnetic field 8 becomes stronger, the waveform shifts to the left; if the external magnetic field 8 becomes weaker, the waveform shifts to the right. As a result of this waveform shift, the luminescence intensity changes. Moreover, the frequency change can be read from the change in luminescence intensity.

[0056] Next, for the detected emission spectrum (representing the emission intensity spectrum), only the NV color centers with directions aligned with the applied magnetic field are extracted. Within the extracted region, the emission intensity is differentiated relative to the microwave frequency to determine the frequency of the microwave with the largest change in emission intensity. Here, in the steeply sloped region ( Figure 4 (a) The frequency is determined by the three points shown.

[0057] In step S2, while fixing the frequency of the microwave to a predetermined frequency (hereinafter referred to as "specific frequency"), an external magnetic field 8 is applied to the diamond 5 and the film electrode assembly 100. Under the condition of irradiating the diamond 5 with excitation light and microwave, the film electrode assembly 100 is scanned in two dimensions to detect the light emission from the diamond 5, thereby obtaining a light emission intensity distribution map.

[0058] Specifically, firstly, the membrane electrode assembly 100, which is to be inspected, is placed on the upper surface of the stage 6 with its surface parallel to the upper surface of the stage 6 and then fixed. At this time, the distance from the upper surface of the membrane electrode assembly 100 to the diamond 5 is set to approximately 0.6 mm.

[0059] Next, the frequency of the microwave emitted from the microwave source 4 is fixed to the aforementioned specific frequency, and an external magnetic field 8 is applied to the membrane electrode assembly 100 (that is, the external magnetic field 8 is applied to the membrane electrode assembly 100 in the same direction as the NV axis of the diamond, and the angle between the external magnetic field 8 and the normal direction of the surface of the membrane electrode assembly 100 is 54.7°), thereby irradiating the diamond 5 with excitation light and microwaves.

[0060] Next, the stage 6 is moved along the X-axis and Y-axis directions to change the relative positions of the membrane electrode assembly 100 and the diamond 5. At the same time, the light emitted from the diamond 5 is detected while the membrane electrode assembly 100 is scanned in two dimensions by excitation light.

[0061] At this time, the excitation light is scanned from one end of the membrane electrode assembly 100 to the other along the X-axis direction of the stage 6. Then, after reaching the other end of the membrane electrode assembly 100, the position of the membrane electrode assembly 100 is adjusted using the stage 6 in a manner that the excitation light is deflected along the Y-axis direction of the stage 6 and returned to one end of the membrane electrode assembly 100. Then, the excitation light is scanned again from one end of the membrane electrode assembly 100 to the other along the X-axis direction of the stage 6. By repeating this operation, the entire membrane electrode assembly 100 is continuously scanned using the excitation light, and the luminescence from the diamond 5 is detected. As a result, the luminescence intensity of the entire membrane electrode assembly 100 can be mapped, and a luminescence intensity distribution map can be obtained.

[0062] In conversion step S3, the acquired luminescence intensity distribution map is converted into a magnetic field distribution map of the membrane electrode assembly 100. Here, firstly, according to Figure 4 The change in luminous intensity described in (a) is a change in the reading frequency. For example, based on Figure 4The resonant frequency shift Δf is determined from the peak frequency (i.e., the resonant frequency) of the spectrum shown in (a). Next, the magnetic field strength B is calculated based on B = Δf / γ (where γ represents the gyrometry of the electron spin). The magnetic field strength B is the magnetic flux density, which represents the strength of the magnetic field. In this way, the obtained luminescence intensity distribution map can be converted into a magnetic field distribution map of the membrane electrode junction 100.

[0063] Furthermore, it is preferable to convert the obtained luminescence intensity distribution map into a magnetic field distribution map after correcting the luminescence intensity of all scanning starting points in the X direction (i.e., the X-axis direction of the stage 6) of the membrane electrode assembly 100 to be constant.

[0064] In the magnetic foreign object inspection step S4, based on the acquired magnetic field distribution map, magnetic foreign objects 101 in the membrane electrode assembly 100 are inspected according to whether magnetic flux is concentrated or not. In other words, based on the acquired magnetic field distribution map, the presence or absence of magnetic foreign objects 101 is checked by utilizing the difference in magnetic field disturbance generated by magnetic foreign objects with high relative permeability and cerium oxide with low relative permeability. Moreover, if magnetic flux concentration exists (i.e., if the magnetic field disturbance is relatively large), it is determined that magnetic foreign objects 101 are mixed in with the membrane electrode assembly 100; if magnetic flux concentration does not exist (i.e., if the magnetic field disturbance is relatively small or almost non-existent), it is determined that no magnetic foreign objects 101 are mixed in with the membrane electrode assembly 100.

[0065] Figure 5 This is the result of actually inspecting the magnetic foreign object using the above-mentioned inspection methods. Figure 5 middle, Figure 5 (a) is a diagram showing the surface of the membrane electrode assembly. Figure 5 (b) is a diagram showing the magnetic field distribution of the membrane electrode assembly. For example... Figure 5 As shown in (b), according to the magnetic field distribution diagram, magnetic flux concentration occurs at the location of the magnetic foreign object (SUS304), resulting in relatively large magnetic field disturbances. On the other hand, no magnetic flux concentration occurs at the location of cerium oxide (Ce oxide). Therefore, SUS304 is detected as a foreign object, but cerium oxide is not detected as a foreign object.

[0066] In the membrane electrode assembly inspection method according to this embodiment, the difference in the disturbance of the magnetic field generated by the magnetic foreign object and cerium oxide is utilized to selectively detect only the magnetic foreign object. Therefore, it is possible to prevent the misdetection of cerium oxide as a foreign object as in the past. Furthermore, the frequency of the microwave with the largest change in the emission of diamond 5 is determined by photodetector magnetic resonance, and diamond 5 is irradiated with the determined microwave frequency. The membrane electrode assembly 100 is then scanned in two dimensions to obtain a emission intensity distribution map from diamond 5. In this way, the amount of change in emission intensity caused by magnetic field fluctuations can be increased, thereby improving the sensing sensitivity of diamond 5. That is, by determining the frequency of the microwave with the largest change in the emission of diamond 5 in photodetector magnetic resonance and fixing the microwave frequency to a specific frequency, even a small spectral shift caused by a small magnetic field will result in a large change in emission intensity. Therefore, since the sensitivity can be further improved, the inspection accuracy of magnetic foreign object 101 can be improved.

[0067] Furthermore, by converting the acquired luminescence intensity distribution map into a magnetic field distribution map, a magnetic field distribution map of the membrane electrode assembly 100 with high sensitivity can be obtained. Moreover, before converting the luminescence intensity distribution map into a magnetic field distribution map, a correction is performed on the acquired luminescence intensity distribution map to keep the luminescence intensity of all scanning starting points in the X direction of the membrane electrode assembly 100 constant. This suppresses the influence of mid- to long-term luminescence fluctuations, thus obtaining a magnetic field distribution map with good sensitivity. As a result, the inspection accuracy of magnetic foreign objects can be further improved.

[0068] Furthermore, by aligning the direction of the external magnetic field 8 applied to the membrane electrode assembly 100 with the NV axis of the diamond 5, the magnetic sensitivity of the NV color center can be improved, thus enabling the acquisition of a magnetic field distribution map with higher sensitivity. Therefore, even minute magnetic foreign objects can be detected at high speed. As a result, the inspection accuracy of magnetic foreign objects 101 in the membrane electrode assembly 100 can be improved, and the inspection speed can be increased.

[0069] Furthermore, by setting the direction of the external magnetic field 8 to an angle of 54.7° relative to the normal direction of the surface of the membrane electrode assembly 100, the sensitivity of the detection magnetic field can be intentionally adjusted, thereby increasing the disturbance of the magnetic field caused by magnetic foreign objects. This prevents missed detections and improves inspection speed.

[0070] The inspection method for membrane electrode assemblies described in this embodiment is not limited to Fe or SUS304, but is also applicable to the detection of materials such as Ni with a relative permeability of at least 1.04. Furthermore, the sensitivity of the detection magnetic field can be intentionally adjusted by adjusting an external magnetic field, etc., as needed, thereby enabling the selection of materials to be detected and materials not to be detected.

[0071] Furthermore, in the aforementioned conversion step S3, the average value of the data points above, below, left, and right can be taken. This suppresses the effects caused by variations in light emission, thus improving inspection accuracy.

[0072] In order to verify the effectiveness of the inspection method for the membrane electrode assembly involved in the embodiments, the inventors of this application conducted the following embodiments using the above-described inspection device 1 and inspection method.

[0073] [Example]

[0074] In an embodiment, such as Figure 1 The diamond is configured with an NV color center and the diamond (100) facet is set as the main surface. A laser with a wavelength of 532nm is irradiated on the diamond, and the magnetic field strength of the external magnetic field 8 is set to 3mT near the surface of the membrane electrode assembly 100.

[0075] In the embodiment, firstly, in a state where the membrane electrode assembly 100 is not mounted, the above-described... Figure 4 (a) shows the optically detected magnetic resonance spectrum. Next, for the acquired spectrum, only the NV color centers with the direction aligned with the applied magnetic field were extracted. The luminescence intensity was differentiated relative to the microwave frequency in the extracted region to determine the microwave frequency with the largest change in luminescence. Then, the microwave was fixed at the determined frequency.

[0076] Furthermore, in this embodiment, as Figure 1 As shown, a lock-in amplifier 74 is used to reduce noise. That is, noise removal is achieved by modulating the microwave frequency applied to the diamond 5 and synchronizing it with the obtained signal. Here, the microwave modulation is set to 2.5 kHz.

[0077] Next, under the above conditions, the film electrode assembly 100 containing magnetic foreign matter (Fe) and cerium oxide was placed on the stage 6, and mapping was performed as described in the above embodiment to obtain a light intensity distribution map. Figure 6 (a) is a graph showing the luminous intensity distribution involved in the embodiment. Figure 6 As shown in (a), the change in luminescence intensity is large at the location of the magnetic foreign object (Fe), indicating a large change in the magnetic field. More specifically, strong and weak magnetic fields appear at both ends of the magnetic foreign object. As a result, small iron-based foreign objects can be selectively detected only by their magnified shape compared to their actual size. Furthermore, no change in the magnetic field was observed at the location of cerium oxide. Magnetic foreign objects can be detected based on the magnitude of this change in luminescence intensity.

[0078] from Figure 6 As shown in (a), magnetic foreign objects can be detected by light intensity distribution map alone, without converting them into magnetic field distribution map.

[0079] Furthermore, in this embodiment, regarding the obtained luminous intensity, noise removal and correction were further performed by taking the difference between adjacent data in the X-axis direction and performing differentiation. The noise-removed image is shown below. Figure 6 (b). For example Figure 6 As shown in the differential image (b), it can be seen that by removing noise, and Figure 6 (a) Compared to the former, it can detect magnetic foreign objects more clearly.

[0080] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Various design changes can be made without departing from the spirit of the present invention as set forth in the claims.

[0081] Symbol Explanation

[0082] 1-Inspection device, 2-Excitation light irradiation unit, 3-Sensor head, 4-Microwave source, 5-Diamond, 6-Stage, 7-Detection unit, 8-External magnetic field, 21-Laser source, 22-First optical fiber, 23-Second optical fiber, 31-First lens, 32-Second lens, 33-Microwave antenna, 71-Optical fiber, 72-Photodetector, 73-Current-to-voltage converter, 74-Lock-in amplifier, 75-Voltmeter, 100-Membrane electrode assembly, 101-Magnetic foreign object.

Claims

1. A method for inspecting a membrane electrode assembly, wherein the membrane electrode assembly contains cerium oxide, the method for inspecting the membrane electrode assembly being characterized by comprising: The magnetic field distribution map acquisition step involves applying an external magnetic field to the membrane electrode assembly and acquiring the magnetic field distribution map of the membrane electrode assembly using a diamond magnetic resonance method with NV color centers. and The magnetic foreign object inspection step involves checking for magnetic foreign objects in the membrane electrode assembly based on the obtained magnetic field distribution map and whether the magnetic flux is concentrated.

2. The method for inspecting the membrane electrode assembly according to claim 1, characterized in that, The steps for obtaining the magnetic field distribution map include: The frequency determination step involves irradiating the diamond with excitation light and microwaves while the external magnetic field is applied, and determining the frequency of the microwave with the largest change in the light emitted from the diamond by photodetector magnetic resonance. The step of obtaining luminescence intensity involves fixing the frequency of the microwave to the determined frequency, applying the external magnetic field to the membrane electrode assembly, and scanning the membrane electrode assembly in two dimensions while the diamond is irradiated with the excitation light and the microwave. By detecting the luminescence from the diamond, a luminescence intensity distribution map is obtained. and The conversion step involves converting the obtained luminescence intensity distribution map into the magnetic field distribution map.

3. The method for inspecting the membrane electrode assembly according to claim 1, characterized in that, In the magnetic field distribution map acquisition step, the direction of the external magnetic field applied to the membrane electrode assembly is aligned with the NV axis direction of the diamond.

4. The method for inspecting the membrane electrode assembly according to claim 3, characterized in that, The membrane electrode assembly has a flat surface. In the magnetic field distribution map acquisition step, when using a diamond with the diamond (100) facet as the main surface, the angle between the direction of application of the external magnetic field and the normal direction of the surface of the membrane electrode assembly is set to 54.7°.

5. The method for inspecting the membrane electrode assembly according to claim 2, characterized in that, The membrane electrode assembly has a flat surface. When one direction on the surface of the membrane electrode assembly is designated as the X direction, and a direction orthogonal to the X direction is designated as the Y direction... In the step of acquiring the luminescence intensity, the luminescence intensity distribution map is acquired by scanning along the X direction from one end to the other of the membrane electrode assembly, then shifting away from the Y direction and scanning again along the X direction from one end to the other. In the conversion step, after correcting the luminous intensity distribution map to keep the luminous intensity of all scanning starting points in the X direction constant, the conversion to the magnetic field distribution map is performed.

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