Sample holder and observation device
The sample holder with a flow path and protrusion efficiently introduces hydrogen into metal samples, preventing bubble accumulation and enabling real-time observation of hydrogen permeation paths, addressing inefficiencies in existing electrochemical methods.
Patent Information
- Application Number
- JP2024198772
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-12-12
- Filing Date
- 2024-11-14
- Publication Date
- 2025-06-24
AI Technical Summary
Existing methods for introducing hydrogen into metal samples using electrochemical reactions face inefficiencies due to hydrogen bubble accumulation, which hinders effective hydrogen permeation and real-time observation.
A sample holder with a flow path member, protrusion, and electrodes is designed to efficiently introduce hydrogen into metal samples. The protrusion generates turbulent flow, expelling hydrogen bubbles and promoting hydrogen permeation, while the optical microscope observes the silver decoration for hydrogen permeation paths.
This solution enables efficient hydrogen introduction into metal samples, preventing bubble accumulation and allowing for real-time observation of hydrogen permeation paths, thereby improving the accuracy and duration of hydrogen introduction and observation.
Smart Images
Figure 2025093873000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a sample holder and an observation device.
Background Art
[0002] Hydrogen is attracting attention as a clean energy for realizing a decarbonized society. Hydrogen is a clean energy that does not emit carbon dioxide, but there is a risk of leakage from metal tanks due to hydrogen embrittlement. In order to address this problem, a method for identifying from which part of the metal tank or which part of the material constituting the metal tank hydrogen is leaking is required. One such method is a method called silver decoration (Non-Patent Document 1). In silver decoration, hydrogen is introduced from the back surface to the front surface of a plate-shaped metal sample while a silver solution is stored on the front surface of the metal sample. At this time, when hydrogen permeates from the back surface to the front surface of the metal sample, silver ions in the silver solution react with hydrogen on the surface of the metal sample and precipitate as silver. The distribution of the precipitated silver generally coincides with the hydrogen permeation path in the metal sample. Therefore, by knowing the distribution of the precipitated silver, it is possible to identify which part of the metal sample hydrogen has permeated through.
[0003] As a method for introducing hydrogen into a metal sample in silver decoration, for example, there is a method that utilizes an electrochemical reaction (Non-Patent Document 2). In this method, the back surface side of the metal sample is immersed in an electrolyte such as sulfuric acid, saline, and sodium hydroxide solution. Then, in this state, hydrogen is generated on the back surface of the metal sample by water electrolysis, and hydrogen is introduced into the metal sample. There is also a method in which the entire metal sample is immersed in a hydrogen-containing solution, and then the metal sample is taken out of the solution, and the hydrogen remaining in the metal sample is observed by silver decoration.
[0004] In addition to silver decoration, there is also a method in which a layer of a metal ion complex is formed on the front surface side of a metal sample, and hydrogen is introduced from the back surface side of the metal sample using an electrochemical reaction (Non-Patent Document 3). In this method, since the color of the metal ion complex changes at the part where hydrogen has permeated in the metal sample, the hydrogen permeation path can be grasped by capturing the change in the color.
[0005] However, in the method of introducing hydrogen using an electrochemical reaction, there is room for improvement in terms of further promoting the introduction of hydrogen into the metal sample.
Prior Art Documents
Non-Patent Documents
[0006]
Non-Patent Document 1
Non-Patent Document 2
Non-Patent Document 3
Summary of the Invention
Problems to be Solved by the Invention
[0007] In one aspect, an object of the present invention is to efficiently introduce hydrogen into a metal sample.
Means for Solving the Problems
[0008] According to one aspect, the sample holder includes a flow path member having an inner surface that defines a flow path through which an electrolytic solution flows, a protrusion provided on the inner surface, a first surface that closes a second surface to be observed among a plurality of surfaces of the metal sample and faces the protrusion, a first opening formed in the flow path member at a portion facing the protrusion, a first electrode provided in the flow path, and a second electrode connected to the metal sample and having a potential difference applied therebetween.
[0009] In the above sample holder, the protrusion may have a hollow portion, and the electrolytic solution may be ejected from the hollow portion toward the first surface.
[0010] In the above sample holder, the flow path has an upstream portion into which the electrolytic solution flows toward the metal sample and a downstream portion from which the electrolytic solution flows out of the metal sample, and the hollow portion may be connected to the flow path of the upstream portion.
[0011] In the above sample holder, the first electrode may be provided in the electrolytic solution in the downstream portion.
[0012] In the above sample holder, the first electrode is a metal wire, and a hole through which the metal wire passes may be provided at a connection portion between the hollow portion and the upstream portion.
[0013] In the above sample holder, the width of the flow path in the upstream portion may become narrower toward the hollow portion.
[0014] In the above sample holder, a second opening that includes an optical axis of an optical microscope for observing the second surface may be formed, and a liquid reservoir for storing a light-transmissive silver solution may be further provided by the second opening and the second surface.
[0015] In the above sample holder, at least a part of the flow path member may have light transmissivity.
[0016] In the above sample holder, the liquid reservoir is a light-transmissive plate in which the second opening is formed, and the part may be a peripheral portion of the first opening.
[0017] In the above sample holder, a first seal ring provided between the flow path member around the first opening and the first surface and in close contact with each of the flow path member and the first surface, and a second seal ring provided between the liquid reservoir around the second opening and the second surface and in close contact with each of the liquid reservoir and the second surface may be further included.
[0018] In the above sample holder, a gas reservoir for accumulating hydrogen bubbles generated in the electrolytic solution may be provided in the middle of the flow path.
[0019] In the above sample holder, a light-transmissive tube constituting the flow path may be further included.
[0020] In the above sample holder, a circulation pump for circulating the electrolytic solution through the flow path may be provided in the middle of the flow path.
[0021] In the above sample holder, the circulation pump may operate intermittently or periodically.
[0022] In the above sample holder, a current measurement unit for measuring the current value flowing between the first electrode and the second electrode, and a control unit for operating the circulation pump when the current value becomes less than a threshold value may be further included.
[0023] In the above sample holder, a metal member fixed to the flow path member may be further included.
[0024] In the above sample holder, the first electrode may be provided at a position in the flow path opposite to the first opening.
[0025] According to another aspect, the observation device is an observation device having a sample holder and an optical microscope, wherein the sample holder includes a flow path member having an inner surface defining a flow path through which an electrolytic solution flows, a protrusion provided on the inner surface, and a first surface of the plurality of surfaces of the metal sample that faces a second surface to be observed by the optical microscope and closes the flow path member at a portion facing the protrusion. The flow path member may be formed with a first opening, a first electrode provided in the flow path, and a second electrode connected to the metal sample and having a potential difference applied therebetween.
[0026] In the above observation device, a second opening enclosing the optical axis of the optical microscope may be formed, and a liquid reservoir for storing a light-transmissive silver solution may be further provided by the second opening and the second surface.
[0027] In the above observation device, a gas reservoir for storing hydrogen bubbles generated in the electrolytic solution may be provided in the middle of the flow path.
Advantages of the Invention
[0028] According to the present invention, hydrogen can be efficiently introduced into the metal sample.
Brief Description of the Drawings
[0029]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Embodiments for Carrying Out the Invention
[0030] Prior to the description of this embodiment, matters considered by the inventor of the present application will be described. When introducing hydrogen from the back surface of a metal sample using an electrochemical reaction, depending on the type of metal sample and the intensity of the electrochemical reaction, etc., hydrogen bubbles may accumulate on the back surface of the metal sample during the introduction of hydrogen. Due to these bubbles, the electrolyte and the back surface of the metal sample are prevented from coming into contact, and the introduction of hydrogen from the back surface is inhibited. To avoid this, it is conceivable to arrange the metal sample vertically in the electrolyte so that the in-plane direction of the metal sample is the vertical direction. According to this, since the hydrogen bubbles escape vertically upward along the back surface of the metal sample, it is possible to prevent the bubbles from accumulating on the back surface. However, in this case, the surface of the metal sample is also immersed in the electrolyte, so the state of the surface cannot be observed in real time with an optical microscope from directly above.
[0031] The inventor of the present application came up with the following embodiment that can prevent hydrogen bubbles from accumulating on the back surface of the metal sample while observing the state of the surface of the metal sample in real time.
[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same reference numerals are given to the same elements, and the description thereof will be omitted.
[0033] (First Embodiment) Figure 1 is a configuration diagram of an observation apparatus 1 according to this embodiment. The observation apparatus 1 is an apparatus for observing the hydrogen permeation path by silver decoration, and includes a sample holder 3, an optical microscope 4, a tube 5, a gas reservoir 6, a circulation pump 7, and a control unit 8.
[0034] The sample holder 3 is a holder that holds a metal sample (not shown) to be observed. The optical microscope 4 is a microscope for observing the distribution of silver deposited on the surface of the metal sample with visible light by silver decoration. Note that the user may visually observe the distribution of silver, or the user may capture a visible light image showing the distribution of silver.
[0035] The tube 5 is a pipe for supplying an electrolytic solution to the metal sample held by the sample holder 3.
[0036] The gas reservoir 6 is a bellows tube for removing hydrogen bubbles generated in the electrolytic solution in the tube 5. The circulation pump 7 is an electric pump for circulating the electrolytic solution between the sample holder 3 and the tube 5. For example, an electric pump for circulating water in a water tank can be used as the circulation pump 7.
[0037] The control unit 8 is an electronic circuit that controls the on / off of the circulation pump 7 and the rotation speed of the circulation pump 7. The control entity of the control unit 8 may be the user or a computer.
[0038] In this example, a path 2 through which the electrolytic solution circulates is formed by the sample holder 3, the tube 5, and the circulation pump 7.
[0039] FIG. 2 is a top view of the sample holder 3 according to the present embodiment. As shown in FIG. 2, the sample holder 3 includes a flow path member 10, a liquid reservoir 11, a metal member 12, a reference electrode 13, a sample electrode 14, and a voltage application unit 15.
[0040] The flow path member 10 is a member that defines the inner surface of the flow path 2. The material of the flow path member 10 is not particularly limited, but in order to insulate the electrolytic solution in the flow path 2, it is preferable to adopt an insulating polymer material such as acrylic or vinyl chloride as the material of the flow path member 10. Also, in this example, the flow path member 10 is fixed to the metal member 12 by screws 17.
[0041] The liquid reservoir 11 is a plate that is substantially circular in top view, and a substantially circular second opening 11a for storing a light-transmissive silver solution is formed near the center thereof. In this example, by tightening the screw 18 with the metal sample S interposed between the flow path member 10 and the liquid reservoir 11, each of the metal sample S and the liquid reservoir 11 is fixed to the flow path member 10.
[0042] The metal member 12 is a vibration-proof member for suppressing displacement of the positional relationship between the sample holder 3 and the optical microscope 4 by suppressing vibration of the flow path member 10 due to vibration of the circulation pump 7 (see FIG. 1). For example, a stainless steel plate having a thickness of about 5 mm can be used as the metal member 12.
[0043] The reference electrode 13 is an example of the first electrode and is provided in the flow path 2. For example, a metal wire such as a platinum wire having a diameter of about 0.5 mm can be adopted as the reference electrode 13. The reference electrode 13 is drawn out from the flow path 2 to the outside of the flow path member 10 through a pore (not shown) formed in the flow path member 10.
[0044] The sample electrode 14 is an example of the second electrode and is connected to the metal sample S through the gap between the flow path member 10 and the liquid reservoir 11. For example, a metal foil such as a copper foil having a thickness of about 0.075 mm and a width of about 8 mm can be adopted as the reference electrode 13.
[0045] The voltage application unit 15 is a potentiostat for applying a potential difference between the reference electrode 13 and the sample electrode 14. Note that the voltage application unit 15 also serves as a current measurement unit for measuring the current flowing between the electrodes 13 and 14. The control main body of the voltage application unit 15 may be a user or a computer.
[0046] FIG. 3 is a cross-sectional view taken along the line I-I of FIG. 2. As shown in FIG. 3, the flow path 2 is filled with the electrolytic solution 9. The type of the electrolytic solution 9 is not particularly limited, and for example, sulfuric acid, saline, sodium hydroxide solution, etc. can be adopted as the electrolytic solution 9.
[0047] Further, the metal sample S is a metal plate having opposing first and second surfaces 21 and 22. The first surface 21 is a hydrogen charging surface into which hydrogen is introduced from the electrolytic solution 9. On the other hand, the second surface 22 is a surface on which silver is deposited by hydrogen that has passed through the metal sample S, and is the surface to be observed by the optical microscope 4. In this example, by making each of the surfaces 21 and 22 parallel to the horizontal plane and making the optical axis C of the optical microscope 4 parallel to the vertical direction, the second surface 22 is observed with the optical microscope 4 from directly above. The metal sample S is, for example, a thin plate made of a material for a metal tank that stores hydrogen. Such materials include, for example, any one of vanadium, palladium, iron, chromium, nickel, aluminum, stainless steel, and duralumin, or an alloy thereof. Further, a layered structure in which a hydrogen permeation prevention film is formed on a substrate made of these materials may be employed as the metal sample S. Examples of the hydrogen permeation prevention film include any one of a plating film, a vapor deposition film, and an oxide film.
[0048] The thickness of the metal sample S is not particularly limited, but in this example, it is set to be 0.1 mm or more and 3 mm or less. The lower limit of the thickness is set to 0.1 mm because if it is thinner than this, it is difficult for the thin plate to stand on its own, and there is a risk of damaging the metal sample S during handling. Further, by making the metal sample S thinner, hydrogen easily permeates through the metal sample S, but in order to reduce the possibility that the metal sample S expands and is damaged due to hydrogen permeation, the lower limit of the thickness of the metal sample S is preferably set to 0.1 mm. Also, the upper limit of the thickness is set to 3 mm because if it is thicker than this, it takes time for hydrogen to permeate through the metal sample S, and the advantage of being able to observe in real time the permeation of hydrogen through the metal sample S is lost.
[0049] In this example, a first opening 10a is formed in the flow path member 10, and the first opening 10a is closed by the first surface 21 of the metal sample S. Also, the second opening 11a of the liquid reservoir 11 is coaxial with the first opening 10a, and the optical axis C of the optical microscope 4 is included in each of the openings 10a and 11a.
[0050] Note that the diameters of the first opening 10a and the second opening 11a are not particularly limited, but can be, for example, diameters of 1 mm or more and 15 mm or less. The lower limit of the diameter is set to 1 mm because if the diameter is smaller than this, the aspect ratio of the first opening 10a becomes too large, and when the hydrogen bubbles generated in the electrolytic solution 9 get stuck in the first opening 10a, it becomes difficult for the bubbles to escape from the first opening 10a. Also, the upper limit of the diameter is set to 15 mm because if the diameter is larger than this, a slight pressure difference between the atmospheric pressure and the electrolytic solution 9 causes distortion in the thin metal sample S, and this distortion is excluded as an extra parameter in the experiment for observing permeated hydrogen.
[0051] Furthermore, between the flow path member 10 around the first opening 10a and the first surface 21, a first seal ring 23 that is in close contact with each of the flow path member 10 and the first surface 21 is provided. The first seal ring 23 is a ring-shaped elastic body for sealing the electrolytic solution 9 in the flow path member 10. Here, as the first seal ring 23, an O-ring made of highly corrosion-resistant ester rubber is adopted.
[0052] And between the liquid reservoir 11 around the second opening 11a and the second surface 22, a second seal ring 24 that is in close contact with each of the liquid reservoir 11 and the second surface 22 is provided. The second seal ring 24 is a ring-shaped elastic body for sealing the silver solution 28 stored by the second opening 11a and the second surface 22. In this example, similar to the first seal ring 23, an O-ring made of ester rubber is adopted as the second seal ring 24.
[0053] The silver solution 28 is a light-transmissive solution containing silver ions. Such a solution includes, for example, an aqueous solution of potassium dicyanoargentate (K[Ag(CN)2]). The user adjusts the amount of the silver solution 28 and drops it into the second opening 11a so that the entire second surface 22 exposed from the second opening 11a is immersed in the silver solution 28.
[0054] Furthermore, the flow path member 10 includes an inner surface 10b that defines the flow path 2. The inner surface 10b is the bottom surface of the flow path 2 and is provided at an interval D of 2 mm or more and 5 mm or less from the ceiling surface 10c of the flow path 2. The reason for setting the lower limit of the interval D to 2 mm is to ensure a cross-sectional area that provides sufficient conductance to obtain a sufficient flow rate with the pressure generated by the small circulation pump 7 (see FIG. 1). Also, the reason for setting the upper limit of the interval D to 5 mm is to sufficiently move the electrolytic solution 9 on the first surface 21 side of the metal sample S with the flow rate generated by the small circulation pump 7.
[0055] A protrusion 16 is provided at a portion of the inner surface 10b that faces the first opening 10a. The protrusion 16 is a structure for generating a turbulent flow of the electrolytic solution 9. The height of the protrusion 16 is not particularly limited, but it is preferably 50% or more and 90% or less of the distance between the first surface 21 of the metal sample S and the inner surface 10b. The reason for setting the lower limit to 50% is that if the protrusion 16 is lower than this, it becomes difficult to generate a turbulent flow of the electrolytic solution. Also, the reason for setting the upper limit to 90% is that if the protrusion 16 is higher than this, the flow of the electrolytic solution 9 will be obstructed by the protrusion 19. In this example, the height of the protrusion 16 is set to 4 mm or more and 5 mm or less.
[0056] In this example, the protrusion 16 is cylindrical. The diameter φ of the protrusion 16 is preferably 30% or more and 80% or less of the diameter of the first opening 10a. The reason for setting the lower limit of the diameter φ to 30% is that if the diameter φ is smaller than this, it becomes difficult for a turbulent flow of the electrolytic solution 9 to occur. Also, the reason for setting the upper limit of the diameter φ to 80% is that if the diameter φ is larger than this, the conductance becomes small and the flow of the electrolytic solution 9 is obstructed. In this example, the diameter φ of the protrusion 16 is 3 mm.
[0057] Note that the shape of the protrusion 16 is not limited to a cylindrical shape and may be a prismatic shape. Furthermore, in this example, only one protrusion 16 is provided on the inner surface 10b, but a plurality of protrusions 16 may be provided.
[0058] Further, the aforementioned reference electrode 13 is wound around the periphery of the protrusion 16 and is provided at a position in the flow path 2 that faces the first opening 10a. As a result, the reference electrode 13 is positioned near the metal sample S, so that the electric field between the reference electrode 13 and the metal sample S is strengthened, and hydrogen can be efficiently introduced from the electrolytic solution 9 into the metal sample S.
[0059] Next, an observation method using this observation apparatus 1 will be described with reference to FIG. 4.
[0060] FIG. 4 is a cross-sectional view showing an observation method using the observation apparatus 1 according to the present embodiment.
[0061] To perform the observation, first, the control unit 8 (see FIG. 1) turns on the circulation pump 7 to generate a flow A of the electrolytic solution 9 in the flow path 2.
[0062] Next, the voltage application unit 15 (see FIG. 2) applies a positive voltage to the reference electrode 13 and a negative voltage to the sample electrode 14. As a result, hydrogen ions in the electrolytic solution 9 are attracted to the metal sample S, and hydrogen can be introduced from the electrolytic solution 9 into the metal sample S.
[0063] A part of the hydrogen introduced into the metal sample S permeates through the metal sample S and reaches its second surface 22. At the second surface 22, Ag + +H→Ag ad +H + By this reaction, silver ions in the silver solution 28 are reduced by hydrogen, and silver (Ag ad ) is deposited along the hydrogen permeation path.
[0064] Then, the user observes the distribution of the silver deposited on the second surface 22 with the optical microscope 4. Since the silver solution 28 has translucency with respect to visible light, the second surface 22 can be observed with visible light through the silver solution 28.
[0065] At this time, if a voltage is continuously applied between each of the electrodes 13 and 14 over a long period of time, hydrogen bubbles 9a may be generated on the first surface 21 of the metal sample S, making it difficult to introduce hydrogen into the metal sample S due to the bubbles 9a. In the present embodiment, since the turbulator 16 generates a turbulent flow in the electrolytic solution 9 near the first surface 21, the turbulent flow can expel the bubbles 9a from the first surface 21, suppressing the bubbles 9a from staying on the first surface 21. As a result, by efficiently introducing hydrogen into the metal sample S over a long period of time, hydrogen can be promoted to permeate through the metal sample S, and the second surface 22 of the metal sample S can be observed in real time with the optical microscope 4 over a long period of time.
[0066] Also, in order to enable the user to visually recognize the generation of the bubbles 9a, a part of the flow path member 10 may be formed of a light-transmissive material. For example, a light-transmissive plate may be adopted as the liquid reservoir 11, and the flow path member 10 in the peripheral portion of the first opening 10a may be formed of a light-transmissive material. Thereby, the user can visually recognize the bubbles 9a through both the transparent liquid reservoir 11 and the flow path member 10. Examples of the light-transmissive material include transparent acrylic. Further, a light-transmissive resin tube may be adopted as the tube 5 (see FIG. 1) so that the user can visually recognize the bubbles 9a discharged into the tube 5.
[0067] By enabling the visual recognition of the bubbles 9a in this way, when the bubbles 9a are generated, for example, the user can take measures such as increasing the rotation speed of the circulation pump 7 or stopping the observation.
[0068] Note that it is not necessary to always operate the circulation pump 7 during the observation. For example, when a voltage is applied to each of the electrodes 13 and 14, the circulation pump 7 may be stopped, and when a situation where the bubbles 9a are likely to be generated on the first surface 21 of the metal sample S or a situation where the bubbles 9a of a size that inhibits the introduction of hydrogen into the metal sample S are generated on the first surface 21 occurs, the control unit 8 may operate the circulation pump 7.
[0069] In these situations, the current value flowing between the electrodes 13 and 14 decreases. Therefore, for example, the voltage measurement unit 15 may measure the current value flowing between the electrodes 13 and 14 and notify the control unit 8 of it, and when the current value becomes less than the threshold value, the control unit 8 may operate the circulation pump 7. The threshold value is not particularly limited. For example, when the current value flowing between the electrodes 13 and 14 decreases by about 10% from the initial value when the voltage is applied, the control unit 8 may operate the circulation pump 7.
[0070] Also, in this embodiment, the vibration of the circulation pump 7 is suppressed by the metal plate 12. However, when observing at a high magnification with the optical microscope 4, etc., the visual field may shake even with minute vibrations. In such a case, the control unit 8 may temporarily stop the circulation pump 7 and perform the observation in this state.
[0071] Furthermore, the control unit 8 may operate the circulation pump 7 intermittently or periodically. Thereby, it is possible to observe without being affected by vibration during the period when the circulation pump 7 is stopped, and furthermore, it is possible to remove the bubbles 9a from the metal sample S during the period when the circulation pump 7 is operating.
[0072] Also, during the period when the circulation pump 7 is stopped and the electrolytic solution 9 is not flowing, the voltage application unit 15 may apply a potential difference between the electrodes 13 and 14 to introduce hydrogen from the electrolytic solution 9 into the metal sample S. Thereby, it becomes unnecessary to take into account the flow rate of the electrolytic solution 9 when calculating the amount of hydrogen introduced into the metal sample S per unit time, and the calculation becomes easier.
[0073] Also, in this embodiment, the gas reservoir 6 (see FIG. 1) can suppress the bubbles 9a from circulating in the flow path 2.
[0074] FIG. 5 is an enlarged cross-sectional view of the gas reservoir 6 according to this embodiment and its surroundings. As the gas reservoir 6, for example, a bellows tube provided in the middle of the drip route can be adopted.
[0075] As shown in Fig. 5, when the bubble 9a moves along the flow A to the gas reservoir 6, the bubble 9a accumulates in the internal space 6a of the gas reservoir 6, so that the outflow of the bubble 9a downstream of the gas reservoir 6 can be suppressed. Thereby, since the circulation of the bubble 9a through the flow path 2 can be suppressed, hydrogen can be introduced more efficiently into the metal sample S.
[0076] Also, even when the bubble 9a is not generated, when using a metal sample S such as aluminum or copper into which hydrogen is difficult to introduce, by exposing the first surface 21 to the turbulent flow of the electrolytic solution 9 generated by the protrusion 16, hydrogen can be continuously introduced into the metal sample S over a long period of time. As a result, it is possible to observe the metal sample S into which hydrogen is difficult to introduce without stopping the introduction of hydrogen.
Example
[0077] Next, the example will be described. In this example, a vanadium plate having a diameter of 16 mm and a thickness of 0.5 mm was used as the metal sample S. And, as the electrolytic solution 9, a sodium hydroxide (NaOH) solution having a specified concentration of 0.1 N was used. Also, as the silver solution 28, an aqueous potassium dicyanoargentate solution having a concentration of 4.3 mM (mmol / L) and a volume of 3 mL was used. Immediately after applying a voltage to each of the electrodes 13 and 14, the current density of the current flowing between the electrodes 13 and 14 was 5.3 A / m 2 or so.
[0078] After about 1 hour has elapsed since the voltage was applied between the electrodes 13 and 14, bubbles 9a accumulated on the first surface 21 of the metal sample S, and the current density began to decrease. Therefore, the circulation pump 7 was intermittently operated to remove the bubbles 9a from the first surface 21 before the bubbles 9a grew large and became difficult to remove. The period during which the circulation pump 7 was operated was set to 1 to 2 minutes. When the circulation pump 7 was operating, the flow rate of the electrolytic solution 9 was 30 cc / min, and the total amount of the circulated electrolytic solution 9 was 5.5 mL. As the metal sample S, a vanadium plate that can be expected as a hydrogen filter material was used. And, as the optical microscope 4, a VHX-1000 manufactured by Keyence Corporation was used, and a visible light image of the second surface 22 of the metal sample S was taken.
[0079] Figs. 6(a) to 6(c) are visible light images captured by the optical microscope 4 in this embodiment.
[0080] In this embodiment, visible light images were acquired at each elapsed time after applying a voltage to each of the reference electrode 13 and the sample electrode 14. Fig. 6(a) is a visible light image immediately after applying the voltage. Fig. 6(b) is a visible light image 30 minutes after applying the voltage, and Fig. 6(c) is a visible light image 90 minutes after applying the voltage. Note that the diamond-shaped image near the center of each visible light image is a mark attached to the metal sample S for alignment of the optical microscope 4 and the metal sample S.
[0081] As shown in Figs. 6(a) to 6(c), a black pattern indicating silver deposited on the second surface 22 of the metal sample S appears in each visible light image. Since silver deposits along the hydrogen permeation path in the metal sample S, the user can identify the hydrogen permeation path based on the black pattern.
[0082] Also, in this embodiment, since the hydrogen bubbles 9a can be removed from the metal sample S as described above, hydrogen can be introduced into the metal sample S even after 90 minutes have elapsed since applying the voltage, and the observation could be continued in real time over a long period.
[0083] Note that when using a vanadium plate as the metal sample S as in this embodiment, the circulation pump 7 is operated at a frequency of once every 15 minutes, and the period during which the circulation pump 7 is operated is set to about 30 seconds to 1 minute, so that the bubbles 9a can be removed from the metal sample S and hydrogen can be stably introduced into the metal sample S.
[0084] As described in detail above, although this embodiment has been described in detail, this embodiment is not limited to the above. For example, in the above, the sample holder 3 was used for observing hydrogen by silver decoration, but the sample holder 3 may be used for observing hydrogen by KPFM (Kelvin probe Force Microscopy). Furthermore, the sample holder 3 may be used for observing the hydrogen permeation path using a metal ion complex (Non-Patent Document 3).
[0085] Furthermore, the sample holder 3 may be used in a hydrogen microscope that desorbs hydrogen transmitted through a metal sample disposed in a vacuum vessel by the ESD (Electron Stimulated Desorption) method and measures the transmission position. In this case, in order to prevent the electrolytic solution 9 from flowing out into the vacuum vessel, it is preferable to use double O-rings as the seal rings 23 and 24. Also, in order to suppress degassing to the vacuum vessel, it is preferable to form the flow path member 10 from a metal that is less likely to generate degassing compared to resin. Furthermore, in order to electrically insulate the electrolytic solution 9 and the inner surface of the flow path member 10, it is preferable to coat the inner surface of the flow path member 10 with an insulating film. And as the screws 17 and 18, it is preferable to employ insulating ceramic bushings or the like.
[0086] (Second Embodiment) In this embodiment, air bubbles 9a are efficiently removed from the metal sample S as follows.
[0087] FIG. 7 is a top view of the sample holder according to this embodiment. As shown in FIG. 7, in this embodiment, the protrusion 16 has a hollow portion 16a. The upper surface shape of the hollow portion 16a is not particularly limited, but in this example, the hollow portion 16a is circular in top view.
[0088] FIG. 8 is a cross-sectional view taken along line II-II of FIG. 7. In FIG. 8, as in the first embodiment, the case where the flow A of the electrolytic solution 9 is generated by the circulation pump 7 (see FIG. 1) will be described as an example.
[0089] As shown in FIG. 8, the flow path 2 has an upstream portion 2a into which the electrolytic solution 9 flows toward the metal sample S and a downstream portion 2b from which the electrolytic solution 9 flows out of the metal sample S. And the hollow portion 16a is connected to the upstream portion 2a. The material of the hollow portion 16a is not particularly limited, but for example, the hollow portion 16a can be formed of a resin such as acrylic.
[0090] The hollow portion 16a is cylindrical with the extending direction being perpendicular to the first surface 21 of the metal sample S. As a result, the electrolytic solution 9 supplied from the upstream portion 2a is ejected from the hollow portion 16a toward the first surface 21. Therefore, the bubbles 9a that tend to stay on the first surface 21 are washed away by the electrolytic solution 9, and the bubbles 9a can be efficiently removed from the first surface 21.
[0091] Note that the dimensions of each part are not particularly limited. In this example, the diameter B of the hollow portion 16a is set to be 1.5 mm or more and 2 mm or less. The lower limit is set to 1.5 mm because if the diameter B is smaller than this, the conductance inside the hollow portion 16a decreases and it becomes difficult for the electrolytic solution 9 to flow through the hollow portion 16a. Also, the upper limit is set to 2 mm because if the diameter B is larger than this, the reference electrode 13 wound around the periphery of the protrusion 16 moves away from directly below the center of the metal sample S, making it difficult to uniformly introduce hydrogen into the plane of the metal sample S. Furthermore, in order to facilitate the flow of the electrolytic solution 9 around the protrusion 16, it is preferable that the diameter B of the hollow portion 16a be 2 mm or less.
[0092] Also, the wall thickness of the hollow portion 16a is 1.5 mm or more and 2 mm or less in this example. In this case, if the diameter B of the hollow portion 16a is 1.5 mm or more and 2 mm or less as described above, the diameter φ of the protrusion 16a is 3 mm or more and 4 mm or less. It is preferable to design each part so that this diameter φ is 50% or more and 80% or less of the diameter of the first opening 10a. The reason for setting the lower limit to 50% is the same as that for setting the lower limit of the diameter B to 1.5 mm. Also, the reason for setting the upper limit to 80% is the same as that for setting the upper limit of the diameter B to 2 mm.
[0093] Furthermore, the distance between the tip 16b of the hollow portion 16a and the first surface 21 of the sample S is preferably 1 mm or more and 2 mm. The lower limit is set to 1 mm because if the distance is narrower than this, there is a risk that the bubbles 9a will be trapped between the tip 16b and the first surface 21. Also, the upper limit is set to 2 mm because if the distance is wider than this, the flow of the electrolytic solution 9 along the in-plane direction of the first surface 21 becomes weaker, making it difficult to remove the bubbles 9a from the first surface 21.
[0094] Also, in this example, a reference electrode 13 is provided in the electrolytic solution 9 in the downstream portion 2b of the flow path 2, and no reference electrode 13 is provided in the upstream portion 2a of the flow path 2. Since bubbles 9a are often generated on the surface of the reference electrode 13, by providing the reference electrode 13 in the downstream portion 2b, the bubbles 9a can be flushed in the direction away from the metal sample S, and the stay of the bubbles 9a on the surface of the reference electrode 13 can be suppressed.
[0095] Furthermore, a hole 2c through which the reference electrode 13 passes is provided at the connection portion between the hollow portion 16a and the upstream portion 2a. Thereby, it is possible to prevent the reference electrode 13 wound around the periphery of the protrusion 16 from floating up in the electrolytic solution 9. Furthermore, since the reference electrode 13 can be passed through the hole 2c, the number of turns of the reference electrode 13 wound around the periphery of the protrusion 16 can also be increased.
[0096] Also, as shown within the dotted circle, the inner surface of the upstream portion 2a at the connection portion with the hollow portion 16a is an inclined surface 2d. Thereby, the interval D of the flow path 2 in the upstream portion 2a becomes narrower toward the hollow portion 16a. As a result, the flow of the electrolytic solution 9 can be smoothed in the portion from the upstream portion 2a toward the hollow portion 16a.
Explanation of Signs
[0097] 1... Observation device, 2... Flow path, 2a... Upstream portion, 2b... Downstream portion, 2c... Hole, 2d... Inclined surface, 3... Sample holder, 4... Optical microscope, 5... Tube, 6... Gas reservoir, 7... Circulation pump, 9... Electrolytic solution, 9a... Bubbles, 10... Flow path member, 10a... First opening, 10b... Inner surface, 10c... Ceiling surface, 11... Liquid reservoir, 11a... Second opening, 12... Metal member, 13... Reference electrode, 14... Sample electrode, 16... Protrusion, 16a... Hollow portion, 16b... Tip, 17... Screw, 18... Screw, 21... First surface, 22... Second surface, 23... First sealing ring, 24... Second sealing ring, 28... Silver solution, S... Metal sample, C... Optical axis.
Claims
1. a flow path member having an inner surface defining a flow path through which the electrolyte flows; A protrusion provided on the inner surface; a first opening that is closed by a first surface of the metal sample that faces a second surface to be observed and that is formed in the flow path member at a location facing the protrusion; A first electrode provided in the flow channel; a second electrode connected to the metal sample and having a potential difference applied between the second electrode and the first electrode; A sample holder having
2. The protrusion has a hollow portion, and the electrolyte is sprayed from the hollow portion toward the first surface.
2. The sample holder of claim 1.
3. the flow path has an upstream portion through which the electrolytic solution flows toward the metal sample and a downstream portion through which the electrolytic solution flows out from the metal sample, The hollow portion is connected to the flow path of the upstream portion.
3. The sample holder of claim 2.
4. The first electrode is provided in the electrolytic solution in the downstream portion.
4. The sample holder of claim 3.
5. the first electrode is a metal wire; A hole through which the metal wire is passed is provided at a connection portion between the hollow portion and the upstream portion.
4. The sample holder of claim 3.
6. The width of the flow path in the upstream portion narrows toward the hollow portion.
4. The sample holder of claim 3.
7. 7. A sample holder as described in any one of claims 1 to 6, further comprising a second opening that contains the optical axis of an optical microscope for observing the second surface, and a reservoir for storing a translucent silver solution formed by the second opening and the second surface.
8. 8. The sample holder according to claim 7, wherein at least a part of the flow path member is optically transparent.
9. the liquid reservoir is a light-transmitting plate having the second opening formed therein; 9. The specimen holder of claim 8, wherein the portion is a periphery of the first opening.
10. a first seal ring provided between the flow path member and the first surface around the first opening and in close contact with both the flow path member and the first surface; a second seal ring provided between the reservoir and the second surface around the second opening and in close contact with both the reservoir and the second surface; 8. The sample holder of claim 7 further comprising:
11. 7. The sample holder according to claim 1, further comprising a gas reservoir provided in the flow path for storing hydrogen bubbles generated in the electrolyte.
12. 7. The sample holder according to claim 1, further comprising a light-transmitting tube that constitutes the flow path.
13. 7. The sample holder according to claim 1, further comprising a circulation pump provided midway along the flow path for circulating the electrolyte through the flow path.
14. 13. The sample holder of claim 12, wherein the circulation pump operates intermittently or periodically.
15. a current measuring unit that measures a value of a current flowing between the first electrode and the second electrode; 13. The sample holder according to claim 12, further comprising a control unit that operates the circulation pump when the current value falls below a threshold value.
16. 7. The sample holder according to claim 1, further comprising a metal member fixed to the flow path member.
17. 7. The sample holder according to claim 1, wherein the first electrode is provided at a position in the flow channel opposite to the first opening.
18. An observation device having a sample holder and an optical microscope, The sample holder includes: a flow path member having an inner surface defining a flow path through which the electrolyte flows; A protrusion provided on the inner surface; a first opening that is closed by a first surface of a metal sample that faces a second surface that is an object of observation by the optical microscope and that is formed in the flow path member at a location that faces the protrusion; A first electrode provided in the flow channel; a second electrode connected to the metal sample and having a potential difference applied between the first electrode and the second electrode.
19. 19. The observation device according to claim 18, further comprising: a second opening that contains an optical axis of the optical microscope; and a liquid reservoir that contains a translucent silver solution and is formed by the second opening and the second surface.
20. 20. The observation device according to claim 18 or 19, further comprising a gas reservoir disposed in the flow path for storing hydrogen bubbles generated in the electrolyte.