Apparatus and method for monitoring diffusion of hydrogen atoms across grain boundaries using skpfm

Abstract

The application provides a device and a test method for monitoring diffusion of hydrogen atoms across a grain boundary by using SKPFM, and relates to the technical field of hydrogen energy utilization. The device for monitoring diffusion of hydrogen atoms across a grain boundary by using SKPFM comprises a target grain boundary to be researched, a cantilever, an electrolytic cell, a platinum wire and a direct current power supply. The method is as follows: for a columnar crystal material after directional solidification, a certain grain boundary is determined as the research grain boundary, then a sample of the cantilever connected with the electrolytic cell is prepared, hydrogen atoms diffuse to the research grain boundary and gradually cross the grain boundary during the electrolysis process, and continuous scanning is performed on the grain boundary position by using SKPFM, so that the behavior of hydrogen crossing the grain boundary can be observed in real time. Compared with other traditional methods, the method of the application realizes the diffusion behavior of hydrogen atoms across the target grain boundary, high-throughput research and real-time monitoring research through the design of the device structure and the test method, improves the hydrogen embrittlement resistance of the material, and the conclusion is real, reliable and guaranteed, and is beneficial to industrial popularization and use.

Description

Technical Field

[0001] This invention relates to the technical field of hydrogen energy utilization, and in particular to a device and testing method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM. Background Technology

[0002] Hydrogen energy, as a renewable and clean energy source, is generally regarded as an effective solution to the current global energy and environmental crisis, and also an important measure for my country to achieve its carbon peaking and carbon neutrality goals. However, unfortunately, hydrogen energy will almost inevitably come into contact with metallic materials during storage, transportation, and use. Metallic materials exposed to hydrogen environments often suffer from hydrogen embrittlement failure, which has become a key factor restricting the utilization of hydrogen energy.

[0003] Hydrogen from the environment enters metallic materials in atomic form, existing in interstitial spaces or defects. Hydrogen atoms undergo diffusion transport within the metallic material, leading to a high concentration of hydrogen at these defects. Under stress, these hydrogen atoms interact with the material itself, reducing its toughness and causing hysteresis fracture—a phenomenon known as hydrogen embrittlement. It is evident that the diffusion transport of hydrogen atoms within metallic materials is a necessary step in the hydrogen embrittlement process. Therefore, clarifying the diffusion behavior of hydrogen atoms within metallic materials is crucial for a deeper understanding of the hydrogen embrittlement mechanism and for the further development of hydrogen-resistant materials.

[0004] Grain boundaries, as the most common two-dimensional defects in metallic materials, contribute significantly to the diffusion and transport of hydrogen atoms. However, given the complexity of grain boundary structures and the diversity of grain boundary types, the interaction between hydrogen atoms and grain boundaries is difficult to measure directly experimentally.

[0005] The inventor's research team previously used SKPFM hydrogen measurement technology to creatively study the diffusion behavior of hydrogen atoms along target grain boundaries, discovering that different types of grain boundaries have different effects on hydrogen diffusion. Inspired by this, hydrogen atoms inevitably diffuse across grain boundaries during transport. Could two-dimensional grain boundaries act as a diffusion barrier, thus hindering hydrogen atom diffusion? To address this question, a review of relevant literature revealed that there are currently no experimental studies reported on hydrogen atom diffusion across grain boundaries, both domestically and internationally; the vast majority of studies focus on the diffusion behavior of hydrogen atoms along grain boundaries.

[0006] Chinese patent CN113884411A discloses a method for testing the local hydrogen diffusion coefficient of materials using SKPFM. This method involves using a sheet-like sample made of metallic material as the working electrode of an electrochemical hydrogen-charging tank, immersing its lower surface in an electrochemical hydrogen-charging solution. Under conditions of maintaining a level sample and a nitrogen atmosphere, the upper surface of the sample is observed using an atomic force microscope. The hydrogen-charging tank is then activated to induce a hydrogen-charging reaction on the lower surface of the sample. The change in contact potential difference is recorded over time, and the hydrogen diffusion coefficient of the material used in the sample is calculated. However, this method cannot detect the diffusion of hydrogen atoms across target grain boundaries; it only macroscopically measures the local hydrogen diffusion coefficient and cannot detect the influence of different types of grain boundaries on hydrogen diffusion.

[0007] This is mainly due to the two-dimensional size characteristics of grain boundaries, which makes lateral measurement very difficult.

[0008] Furthermore, how to introduce a hydrogen concentration gradient only on one side of the grain boundary, so that hydrogen atoms can spontaneously diffuse across the grain boundary under the drive of the concentration gradient, is also an unsolved problem.

[0009] Therefore, designing a device and testing method to monitor the diffusion of hydrogen atoms across grain boundaries using SKPFM, so as to directly observe the diffusion behavior of hydrogen atoms across target grain boundaries and further study the influence of different types of grain boundaries on the lateral diffusion of hydrogen atoms, is an urgent problem to be solved by technicians in the fields of hydrogen embrittlement and hydrogen energy. Summary of the Invention

[0010] The technical problem to be solved by this invention is that there is currently no technology that can monitor the diffusion of hydrogen atoms across grain boundaries. The focus of the existing technology is on detecting the behavior of hydrogen atoms diffusing along grain boundaries and the distribution of the diffused hydrogen atoms in the material, without considering the behavior of hydrogen atoms diffusing across grain boundaries and the impact of this behavior on the toughness of the material. The transport and distribution behavior of hydrogen atoms in metallic materials is difficult to predict.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0012] A device for monitoring hydrogen atom diffusion across grain boundaries using SKPFM is disclosed. The device includes a target grain boundary under study, a cantilever beam, an electrolytic cell, a platinum wire, and a DC power supply. The target grain boundary under study spans the cantilever beam. The electrolytic cell includes a cell wall A and a cell wall B, which are connected to the cantilever beam. The platinum wire is connected to the positive terminal of the DC power supply via a wire, and the target grain boundary under study is connected to the negative terminal of the DC power supply via a wire.

[0013] Preferably, the target grain boundary being studied can be one or more; when there are multiple target grain boundaries, the same target grain boundary or different target grain boundaries can be selected.

[0014] A test method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, based on the above-mentioned method, comprises the following steps:

[0015] S1. Determine a specific grain boundary of the columnar crystalline material after directional solidification as the target grain boundary to be studied.

[0016] S2, Prepare a sample of a cantilever beam connected electrolytic cell, wherein the target grain boundary studied in S1 is located on the cantilever beam;

[0017] S3. Electrolyte is added to the electrolytic cell and hydrogen is electrolyzed to introduce hydrogen atoms into the entire sample of S2.

[0018] After the S4 and S3 electrolysis hydrogen charging begins, driven by the concentration gradient, hydrogen atoms diffuse towards the target grain boundary on the cantilever beam and gradually cross the target grain boundary.

[0019] After the electrolytic hydrogen charging of S5 and S4 is completed, the target grain boundary under study is continuously scanned at room temperature using SKPFM to observe the behavior of hydrogen crossing the grain boundary in real time.

[0020] Preferably, in S1, a specific grain boundary of the columnar crystal material after directional solidification is identified as the target grain boundary for study: First, the type of grain boundary to be studied in the columnar crystal must be determined, which can be achieved by electron backscatter diffraction (EBSD) technique in scanning electron microscopy; second, the sample needs to be electropolished before this test to remove the surface strain layer and improve the calibration rate.

[0021] Preferably, the target grain boundary under study located on the cantilever beam in S2 can be a single grain boundary or a variety of different grain boundaries.

[0022] Preferably, in S2, a sample is prepared with a cantilever beam connected to an electrolytic cell. In order to shorten the measurement time, the thickness of the two electrolytic cell walls connected to the cantilever beam needs to be adjusted according to the diffusion rate of hydrogen atoms in different materials.

[0023] Preferably, the diffusion coefficient of hydrogen atoms in S2 in pure nickel is 10. -14 m 2 / s, at which point the thickness of electrolytic cell wall A and electrolytic cell wall B is 0.15mm.

[0024] Preferably, the target grain boundary studied in S3 is located on the cantilever beam and needs to be set in a direction perpendicular to the spontaneous diffusion of hydrogen atoms, so that the diffusion behavior of hydrogen atoms when crossing this grain boundary can be observed in real time.

[0025] Preferably, in S3, the electrolytic hydrogen charging requires the addition of an acidic or alkaline electrolyte to the electrolytic cell. To improve the hydrogen charging efficiency, a hydrogen atom composite poisoning agent is added to the solution.

[0026] Preferably, in step S3, an acidic or alkaline electrolyte, such as a 0.1 mol / L NaOH solution, is added to the electrolytic cell. To improve hydrogen charging efficiency, a hydrogen atom recombination poison, such as 0.22 g / L thiourea, can be added to the solution. Adding thiourea to the electrolyte can prevent the hydrogen atoms obtained from electrolysis in the solution from recombinating into hydrogen molecules and escaping, thereby allowing more hydrogen atoms to enter the sample.

[0027] Preferably, in step S4, the sample is electrolyzed and charged with hydrogen. During charging, a platinum wire is inserted into the electrolyte, and the positive terminal of a DC power supply is connected. The hydrogen charging current density is selected to be 10 mA / cm². 2 The hydrogen charging current is calculated based on the inner wall area of ​​the electrolytic cell and set on the DC power supply.

[0028] Preferably, the hydrogen charging time in S4 should not be too long, so as to prevent hydrogen atoms from diffusing across the grain boundaries during the charging process, thus making it impossible to observe using SKPFM. For pure nickel, a charging time of 2 hours can be selected.

[0029] Preferably, the target grain boundary studied in S5 needs to be pretreated: the surface is polished with sandpaper of varying grit sizes, up to 3000 grit, and then the surface is mechanically polished and electrolytically polished.

[0030] Preferably, during electropolishing in S5, the sample is connected to the positive terminal of a DC power supply, and the negative terminal is connected to stainless steel, generally in an acidic solution.

[0031] Preferably, the SKFPM test in S5 is performed at room temperature, and the potential is measured using the tapping mode and lift technique. The probe used is a double-sided platinum-plated silicon probe.

[0032] Preferably, S2 consists of multiple single grain boundaries, and S1 involves selecting different types of grain boundaries within the directionally solidified columnar crystalline material using EBSD technology. Through S2-S5, the various behaviors of hydrogen across different types of grain boundaries are observed in real time, obtaining high-throughput sample diffusion of hydrogen atoms across different types of grain boundaries. This further provides theoretical and experimental support for studying the transport and distribution behavior of hydrogen atoms in metallic materials.

[0033] The testing principle of this invention:

[0034] When hydrogen atoms enter a metallic material, they cause a decrease in the work function of the material surface. The SKPFM measurement module of an atomic force microscope can measure the contact potential difference (V) between the probe tip and the sample surface using the Kelvin method. CPDThe relationship between the contact potential difference and the work function of the sample surface can be expressed as:

[0035]

[0036] In the formula, Let represent the surface work functions of the probe tip and the sample, respectively, and e be the electron charge number. It can be seen that hydrogen atoms lower the surface work function of the sample, thereby altering the contact potential difference between the probe tip and the sample. Therefore, the distribution of hydrogen atoms on the material surface can be visualized using SKPFM.

[0037] The above technical solution has at least the following advantages compared with the existing technology:

[0038] The present invention proposes a device and testing method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, which can solve the problem of difficulty in monitoring hydrogen atom diffusion across grain boundaries in the prior art, and enable the monitoring of hydrogen atom diffusion across grain boundaries.

[0039] This invention allows for the observation of hydrogen atom diffusion across arbitrary target grain boundaries using a device, thereby providing theoretical and experimental support for a deeper understanding of hydrogen atom transport behavior in metallic materials and further realizing the hydrogen embrittlement resistance design of materials.

[0040] This invention is the first of its kind in China and abroad to propose an experimental apparatus and method for directly measuring the diffusion behavior of hydrogen atoms across target grain boundaries. It is original, simple to implement, and yields intuitive and reliable results.

[0041] This invention utilizes EBSD technology to select different types of grain boundaries within directionally solidified columnar crystalline materials. Through S2-S5, the behavior of hydrogen atoms crossing different types of grain boundaries is observed in real time, obtaining the diffusion of hydrogen atoms across different types of grain boundaries. This provides theoretical and experimental support for studying the transport and distribution behavior of hydrogen atoms in metallic materials.

[0042] The device structure of this invention can conduct high-throughput studies on the diffusion behavior of hydrogen atoms across target grain boundaries, thereby providing a theoretical basis for adjusting the overall transport and distribution of hydrogen atoms in metallic materials and improving the hydrogen embrittlement resistance of metallic materials.

[0043] In summary, compared with other traditional methods, the method of this invention, through the design of the device structure and testing method, makes it possible to study the diffusion behavior of hydrogen atoms across the target grain boundary, conduct high-throughput research, and monitor it in real time. This improves the hydrogen embrittlement resistance of materials, provides theoretical basis and experimental research for expanding the application fields of metallic materials, and its device and process are simple, the conclusions are true and reliable, and it is conducive to industrial promotion and use. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of a device for monitoring hydrogen atom diffusion across grain boundaries using SKPFM according to the present invention; in the figure: 1-platinum wire, 2-cantilever beam, 3-the target grain boundary under study, 4-electrolytic cell connected to the cantilever beam, 5-DC power supply;

[0046] Figure 2 This invention provides an example of obtaining the inverse pole figure of the grain boundary under study in an embodiment of the invention using EBSD technology in a test method based on a SKPFM device for monitoring hydrogen atom diffusion across grain boundaries.

[0047] Figure 3 This is a hydrogen atom distribution map at the studied grain boundary at different times after electrolysis and hydrogen charging, obtained by a test method based on a hydrogen atom diffusion monitoring device across grain boundaries using SKPFM, according to Embodiment 1 of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0049] like Figure 1 As shown, this invention provides a device for monitoring hydrogen atom diffusion across grain boundaries using SKPFM. The device includes a target grain boundary 3, a cantilever beam 2, an electrolytic cell 4 connected to the cantilever beam, a platinum wire 1, and a DC power supply 5. The target grain boundary 3 spans the cantilever beam 2. The electrolytic cell 4 connected to the cantilever beam includes an electrolytic cell wall A and an electrolytic cell wall B, which are connected to the cantilever beam 2. The platinum wire 1 is connected to the positive terminal of the DC power supply 5 via a wire, and the target grain boundary 3 is connected to the negative terminal of the DC power supply 5 via a wire.

[0050] Among them, the target grain boundary 3 to be studied can be one or more, and when there are multiple, the same target grain boundary or different target grain boundaries can be selected.

[0051] Example 1

[0052] A test method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, taking pure nickel material as an example, includes the following steps:

[0053] S1. First, for pure nickel material after directional solidification, it is necessary to determine the type of grain boundary to be studied in columnar crystals. This requirement can be achieved by electron backscatter diffraction (EBSD) technique in scanning electron microscopy.

[0054] Secondly, the sample needs to be electropolished before this test to remove the surface strain layer and improve the calibration rate.

[0055] The electrolytic polishing process for pure nickel material is as follows: the electrolytic polishing solution is a mixture of perchloric acid, glacial acetic acid and ethanol, with a volume fraction ratio of 1:3:4; the electrolytic polishing voltage is 30V; the temperature is 0℃; and the time is 20s.

[0056] Therefore, the random grain boundaries with an orientation difference of 45° in the directionally solidified columnar crystalline material were identified as the target grain boundaries to be studied, and the results are as follows: Figure 2 As shown;

[0057] S2. Prepare a sample of a cantilever beam-connected electrolytic cell, wherein the target grain boundary studied in S1 is located on and across the cantilever beam, and is perpendicular to the direction of spontaneous hydrogen diffusion; and since the diffusion coefficient of hydrogen atoms in pure nickel is 10... - 14 m 2 / s, therefore the thickness of electrolytic cell wall A and electrolytic cell wall B is selected as 0.15mm; since the outer surface of electrolytic cell wall A and the surface of cantilever beam need to be tested by SKPFM, pretreatment is required: select sandpaper with grit from large to small to polish the surface until 3000 grit, and then perform mechanical polishing and electrolytic polishing on this surface.

[0058] S3. Electrolyte is added to the electrolytic cell and hydrogen is charged by electrolysis. Electrolysis by hydrogen charging requires acid or base electrolyte to be added to the electrolytic cell. In order to improve the hydrogen charging efficiency, hydrogen atom composite poisoning agent is added to the solution, thereby introducing hydrogen atoms into the entire sample of S2.

[0059] Therefore, an electrolyte solution of 0.1 mol / L NaOH + 0.22 g / L thiourea was added to the sample electrolytic cell. Thiourea was added to prevent the hydrogen atoms obtained by electrolysis from recombinating into hydrogen molecules and escaping, thereby allowing more hydrogen atoms to enter the sample and improving the hydrogen charging efficiency.

[0060] During hydrogen charging, a platinum wire is inserted into the electrolyte, and the positive terminal of a DC power supply is connected. The hydrogen charging current density is selected to be 10 mA / cm². 2The hydrogen charging current is calculated based on the inner wall area of ​​the electrolytic cell and set on the DC power supply.

[0061] After S4 and S3 electrolytic hydrogen charging begins, driven by the concentration gradient, hydrogen atoms diffuse towards the target grain boundary on the cantilever beam and gradually cross the target grain boundary. The electrolytic hydrogen charging time should not be too long, so as to avoid hydrogen atoms having already crossed the grain boundary during the hydrogen charging process, thus making it impossible to observe using SKPFM. For pure nickel, a hydrogen charging time of 2 hours can be selected.

[0062] After the electrolytic hydrogen charging in S5 and S4 is completed, the target grain boundary under study is continuously scanned at room temperature using SKPFM. The potential is measured using tapping mode and lift technology. The probe used is a double-sided platinum-plated silicon probe to observe the behavior of hydrogen crossing the grain boundary in real time. Among them, the target grain boundary under study needs to be pre-treated: the surface is polished with sandpaper of varying grits from large to small until 3000 grit, and then the surface is mechanically polished and electrolytically polished.

[0063] like Figure 3 As shown, with the increase of diffusion time, the hydrogen concentration gradient gradually advances from the right side of the grain boundary to the left side, and during the diffusion process across the grain boundary, this grain boundary acts as a two-dimensional barrier, hindering the diffusion of hydrogen atoms.

[0064] In this embodiment, S2 represents a single grain boundary. In S1, different types of grain boundaries are selected within the directionally solidified columnar crystalline material using EBSD technology. Through S2-S5, the various behaviors of hydrogen across different types of grain boundaries are observed in real time, obtaining the high-throughput sample diffusion of hydrogen atoms across different types of grain boundaries. This further provides theoretical and experimental support for studying the transport and distribution behavior of hydrogen atoms in metallic materials.

[0065] Example 2

[0066] A test method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, taking pure nickel material as an example, includes the following steps:

[0067] S1. First, for pure nickel material after directional solidification, it is necessary to determine the types of grain boundaries to be studied in columnar crystals. There can be 2-3 types. This requirement can be achieved by electron backscatter diffraction (EBSD) technology in scanning electron microscopy.

[0068] Secondly, the sample needs to be electropolished before this test to remove the surface strain layer and improve the calibration rate.

[0069] The electrolytic polishing process for pure nickel material is as follows: the electrolytic polishing solution is a mixture of perchloric acid, glacial acetic acid and ethanol, with a volume fraction ratio of 1:3:4; the electrolytic polishing voltage is 30V; the temperature is 0℃; and the time is 20s.

[0070] S2. Prepare a sample of a cantilever beam-connected electrolytic cell, wherein the target grain boundary studied in S1 is located on and across the cantilever beam, and is perpendicular to the direction of spontaneous hydrogen diffusion; and since the diffusion coefficient of hydrogen atoms in pure nickel is 10... - 14 m 2 / s, therefore the thickness of electrolytic cell wall A and electrolytic cell wall B is selected as 0.15mm; since the outer surface of electrolytic cell wall A and the surface of cantilever beam need to be tested by SKPFM, pretreatment is required: select sandpaper with grit from large to small to polish the surface until 3000 grit, and then perform mechanical polishing and electrolytic polishing on this surface.

[0071] S3. Electrolyte is added to the electrolytic cell and hydrogen is charged by electrolysis. Electrolysis by hydrogen charging requires acid or base electrolyte to be added to the electrolytic cell. In order to improve the hydrogen charging efficiency, hydrogen atom composite poisoning agent is added to the solution, thereby introducing hydrogen atoms into the entire sample of S2.

[0072] Therefore, an electrolyte solution of 0.1 mol / L NaOH + 0.22 g / L thiourea was added to the sample electrolytic cell. Thiourea was added to prevent the hydrogen atoms obtained by electrolysis from recombinating into hydrogen molecules and escaping, thereby allowing more hydrogen atoms to enter the sample and improving the hydrogen charging efficiency.

[0073] During hydrogen charging, a platinum wire is inserted into the electrolyte, and the positive terminal of a DC power supply is connected. The hydrogen charging current density is selected to be 10 mA / cm². 2 The hydrogen charging current is calculated based on the inner wall area of ​​the electrolytic cell and set on the DC power supply.

[0074] After S4 and S3 electrolytic hydrogen charging begins, driven by the concentration gradient, hydrogen atoms diffuse towards the target grain boundary on the cantilever beam and gradually cross the target grain boundary. The electrolytic hydrogen charging time should not be too long, so as to avoid hydrogen atoms having already crossed the grain boundary during the hydrogen charging process, thus making it impossible to observe using SKPFM. For pure nickel, a hydrogen charging time of 2 hours can be selected.

[0075] After the electrolytic hydrogen charging in S5 and S4 is completed, the target grain boundary under study is continuously scanned at room temperature using SKPFM. The potential is measured using tapping mode and lift technology. The probe used is a double-sided platinum-plated silicon probe to observe the behavior of hydrogen crossing the grain boundary in real time. Among them, the target grain boundary under study needs to be pre-treated: the surface is polished with sandpaper of varying grits from large to small until 3000 grit, and then the surface is mechanically polished and electrolytically polished.

[0076] As diffusion time increases, the hydrogen concentration gradient gradually moves from the right side of 2-3 grain boundaries to the left side, thus allowing for real-time monitoring of the diffusion of hydrogen atoms across different types of grain boundaries in pure nickel.

[0077] In this embodiment, S2 involves 2-3 types of grain boundaries. In S1, different types of grain boundaries are selected within the directionally solidified columnar crystalline material using EBSD technology. Through S2-S5, multiple behaviors of hydrogen across different types of grain boundaries can be observed at once, obtaining high-throughput sample diffusion of hydrogen atoms across different types of grain boundaries. This further provides theoretical and experimental support for studying the transport and distribution behavior of hydrogen atoms in metallic materials.

[0078] Example 3

[0079] A test method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, taking pure iron material as an example, includes the following steps:

[0080] S1. First, for pure iron materials after directional solidification, it is necessary to determine the type of grain boundary to be studied in columnar crystals. This requirement can be achieved by electron backscatter diffraction (EBSD) technique in scanning electron microscopy.

[0081] Secondly, the sample needs to be electropolished before this test to remove the surface strain layer and improve the calibration rate.

[0082] The electrolytic polishing process for pure iron materials is as follows: the electrolytic polishing solution is a 5% (volume fraction) perchloric acid alcohol solution, the electrolytic polishing voltage is 30V, the current is 0.71A, the electrolyte temperature is 10℃, and the electrolysis time is 20s.

[0083] S2. Prepare a sample of a cantilever beam-connected electrolytic cell, wherein the target grain boundary studied in S1 is located on and across the cantilever beam, and is perpendicular to the direction of spontaneous diffusion of hydrogen atoms; and since the diffusion coefficient of hydrogen atoms in pure iron is 10... - 11 m 2 / s, therefore, the thickness of electrolytic cell wall A and electrolytic cell wall B is selected as 1mm; since the outer surface of electrolytic cell wall A and the cantilever beam surface need to be tested by SKPFM, pretreatment is required: select sandpaper with grit from large to small to polish the surface until 3000 grit, and then perform mechanical polishing and electrolytic polishing on this surface.

[0084] S3. Electrolyte is added to the electrolytic cell and hydrogen is charged by electrolysis. Electrolysis by hydrogen charging requires acid or base electrolyte to be added to the electrolytic cell. In order to improve the hydrogen charging efficiency, hydrogen atom composite poisoning agent is added to the solution, thereby introducing hydrogen atoms into the entire sample of S2.

[0085] Therefore, an electrolyte solution of 0.5 mol / L H2SO4 + 0.22 g / L thiourea was added to the sample electrolytic cell. Thiourea was added to prevent the hydrogen atoms obtained by electrolysis from recombinating into hydrogen molecules and escaping, thereby allowing more hydrogen atoms to enter the sample and improving the hydrogen charging efficiency.

[0086] During hydrogen charging, a platinum wire is inserted into the electrolyte, and the positive terminal of a DC power supply is connected. The hydrogen charging current density is selected to be 10 mA / cm². 2 The hydrogen charging current is calculated based on the inner wall area of ​​the electrolytic cell and set on the DC power supply.

[0087] After S4 and S3 electrolytic hydrogen charging begins, driven by the concentration gradient, hydrogen atoms diffuse towards the target grain boundary on the cantilever beam and gradually cross the target grain boundary. The electrolytic hydrogen charging time should not be too long, so as to avoid hydrogen atoms having already crossed the grain boundary during the hydrogen charging process, thus making it impossible to observe using SKPFM. For pure iron, a hydrogen charging time of 1 hour can be selected.

[0088] After the electrolytic hydrogen charging in S5 and S4 is completed, the target grain boundary under study is continuously scanned at room temperature using SKPFM. The potential is measured using tapping mode and lift technology. The probe used is a double-sided platinum-plated silicon probe to observe the behavior of hydrogen crossing the grain boundary in real time. Among them, the target grain boundary under study needs to be pre-treated: the surface is polished with sandpaper of varying grits from large to small until 3000 grit, and then the surface is mechanically polished and electrolytically polished.

[0089] As diffusion time increases, the hydrogen concentration gradient gradually moves from the right side of the grain boundary under study to the left side, thus allowing for real-time monitoring of the diffusion of hydrogen atoms across different types of grain boundaries in pure iron.

[0090] In this embodiment, S2 represents a single grain boundary. In S1, different types of grain boundaries are selected within the directionally solidified columnar crystalline material using EBSD technology. Through S2-S5, various behaviors of hydrogen across different types of grain boundaries can be observed in real time, obtaining high-throughput sample diffusion of hydrogen atoms across different types of grain boundaries in pure iron. This further provides theoretical and experimental support for studying the transport and distribution behavior of hydrogen atoms in metallic materials.

[0091] The present invention proposes a device and testing method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, which can solve the problem of difficulty in monitoring hydrogen atom diffusion across grain boundaries in the prior art, and enable the monitoring of hydrogen atom diffusion across grain boundaries.

[0092] This invention allows for the observation of hydrogen atom diffusion across arbitrary target grain boundaries using a device, thereby providing theoretical and experimental support for a deeper understanding of hydrogen atom transport behavior in metallic materials and further realizing the hydrogen embrittlement resistance design of materials.

[0093] This invention is the first of its kind in China and abroad to propose an experimental apparatus and method for directly measuring the diffusion behavior of hydrogen atoms across target grain boundaries. It is original, simple to implement, and yields intuitive and reliable results.

[0094] This invention utilizes EBSD technology to select different types of grain boundaries within directionally solidified columnar crystalline materials. Through S2-S5, the behavior of hydrogen atoms crossing different types of grain boundaries is observed in real time, obtaining the diffusion of hydrogen atoms across different types of grain boundaries. This provides theoretical and experimental support for studying the transport and distribution behavior of hydrogen atoms in metallic materials.

[0095] The device structure of this invention can conduct high-throughput studies on the diffusion behavior of hydrogen atoms across target grain boundaries, thereby providing a theoretical basis for adjusting the overall transport and distribution of hydrogen atoms in metallic materials and improving the hydrogen embrittlement resistance of metallic materials.

[0096] In summary, compared with other traditional methods, the method of this invention, through the design of the device structure and testing method, makes it possible to study the diffusion behavior of hydrogen atoms across the target grain boundary, conduct high-throughput research, and monitor it in real time. This improves the hydrogen embrittlement resistance of materials, provides theoretical basis and experimental research for expanding the application fields of metallic materials, and its device and process are simple, the conclusions are true and reliable, and it is conducive to industrial promotion and use.

[0097] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A device for monitoring hydrogen atom diffusion across grain boundaries using SKPFM, characterized in that, The SKPFM device for monitoring hydrogen atom diffusion across grain boundaries includes a target grain boundary under study, a cantilever beam, an electrolytic cell, a platinum wire, and a DC power supply. The target grain boundary under study spans the cantilever beam. The electrolytic cell includes cell wall A and cell wall B, which are connected to the cantilever beam. The platinum wire is connected to the positive terminal of the DC power supply via a wire, and the target grain boundary under study is connected to the negative terminal of the DC power supply via a wire.

2. A test method based on the SKPFM device for monitoring hydrogen atom diffusion across grain boundaries according to claim 1, characterized in that, The test method for monitoring hydrogen atom diffusion across grain boundaries using SKPFM is as follows: S1. Determine a specific grain boundary of the columnar crystalline material after directional solidification as the target grain boundary to be studied. S2, Prepare a sample of a cantilever beam connected electrolytic cell, wherein the target grain boundary studied in S1 is located on the cantilever beam; S3. Electrolyte is added to the electrolytic cell and hydrogen is electrolyzed to introduce hydrogen atoms into the entire sample of S2. After the S4 and S3 electrolysis hydrogen charging begins, driven by the concentration gradient, hydrogen atoms diffuse towards the target grain boundary on the cantilever beam and gradually cross the target grain boundary. After the electrolytic hydrogen charging of S5 and S4 is completed, the target grain boundary under study is continuously scanned at room temperature using SKPFM to observe the behavior of hydrogen crossing the grain boundary in real time.

3. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, In S1, a specific grain boundary of the columnar crystal material after directional solidification is identified as the target grain boundary for study. First, the type of grain boundary to be studied in the columnar crystal must be determined, which is achieved by electron backscatter diffraction (EBSD) technique in scanning electron microscopy. Second, the sample needs to be electropolished before this test to remove the surface strain layer and improve the calibration rate.

4. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, In S2, samples were prepared using a cantilever beam connected to an electrolytic cell. To shorten the measurement time, the wall thicknesses of the two electrolytic cells connected to the cantilever beam needed to be adjusted based on the diffusion rate of hydrogen atoms in different materials.

5. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 4, characterized in that, The diffusion coefficient of hydrogen atoms in S2 within pure nickel is 10. -14 m 2 / s, at which point the thickness of electrolytic cell wall A and electrolytic cell wall B is 0.15mm.

6. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, The target grain boundary studied in S3 is located on a cantilever beam and needs to be set in a direction perpendicular to the spontaneous diffusion of hydrogen atoms.

7. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, In S3, electrolytic hydrogen charging requires the electrolytic cell to be filled with an acid or alkali electrolyte. To improve the hydrogen charging efficiency, a hydrogen atom composite poisoning agent is added to the solution.

8. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, In step S4, the sample was electrolyzed and charged with hydrogen. During charging, a platinum wire was inserted into the electrolyte, and the positive terminal of a DC power supply was connected. The charging current density was selected to be 10 mA / cm². 2 The hydrogen charging current is calculated based on the inner wall area of ​​the electrolytic cell and set on the DC power supply.

9. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, The target grain boundaries studied in S5 need to be pretreated: the surface is polished with sandpaper of varying grit sizes, up to 3000 grit, and then the surface is mechanically polished and electrolytically polished.

10. The test method for monitoring hydrogen atom diffusion across grain boundaries using an SKPFM device according to claim 2, characterized in that, In S5, the SKFPM test was performed at room temperature, using tapping mode and lift technology to measure the potential. The probe used was a double-sided platinum-plated silicon probe.

Images