WO2019226661A1

WO2019226661A1 - Devices and methods for in situ hydrogen-charging

Info

Publication number: WO2019226661A1
Application number: PCT/US2019/033331
Authority: WO
Inventors: Jinwoo Kim; Cemal Cem TASAN
Original assignee: Massachusetts Institute Of Technology
Priority date: 2018-05-21
Filing date: 2019-05-21
Publication date: 2019-11-28

Abstract

A hydrogen-charging apparatus that can be applied to high vacuum-based systems for material characterization, such as scanning electron microscopes, is disclosed. The device can include an inner chamber, an electrode disposed within the inner chamber, and apertures each formed through the inner chamber, where the apertures are configured to provide access to an electric cable and an electrolyte substance into and out of an interior of the inner chamber, and the inner chamber is configured to receive a sample, the sample being positioned to seal the opening of the inner chamber. Embodiments enable high-resolution microstructural analysis during electrochemical hydrogen permeation. In one non-limiting example, a hydrogen source is isolated from an objective sample surface and simultaneous microstructural observation and mechanical testing is performed during hydrogen charging using a mechanical tester compatible with vacuum systems.

Description

DEVICES AND METHODS FOR IN SITU HYDROGEN-CHARGING

RELATED APPLICATIONS

[0001] The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/674,516, filed May 21, 2018, and entitled“DEVICES AND METHODS FOR IN SITU HYDROGEN CHARGING,” the contents of which is hereby incorporated by reference in its entirety.

FIELD

[0002] The present disclosure relates to devices and methods for in situ hydrogen-charging, and more particularly to in situ hydrogen-charging setups that enable microstructural and mechanical analyses during electrochemical hydrogen permeating of samples such as those made of metallic materials.

BACKGROUND

[0003] Hydrogen embrittlement is a common phenomenon in materials such as high strength metallic materials, leading to critical and long-pending problems across numerous industries including energy, automotive and marine industries. Due to the small size and high mobility of hydrogen atoms in metals, it has traditionally been challenging to identify correlations between hydrogen distribution and microstructural and mechanical responses and effects. Conventional systems and methods for performing mechanical and microstructural analyses to identify hydrogen-induced defects, including in situ techniques, are susceptible to a number of limitations. For example, direct high-pressure hydrogen charging requires an immense facility and resources to ensure safety, making such an approach inaccessible. Electrochemical nanoindentation does not allow for microstructural analysis during testing, since this technique requires the displacement of an electrolyte substance on an objective surface of the material, thereby obstructing the area for analysis. Environmental scanning electron microscopy and transmission electron microscopy are limited to nano-sized samples.

[0004] There is a need therefore for devices and methods for in situ hydrogen charging, and related setups, that enable microstructural and mechanical analyses during electrochemical hydrogen permeation. There is also a need for such devices and methods to enable such analyses of hydrogen-charged samples without any obstruction of the sample.

SUMMARY

[0005] Many configurations of the devices and methods are made possible by the disclosures herein. Some non-limiting, exemplary embodiments of the devices and methods are summarized and claimed below.

[0006] The present disclosure relates to in-situ hydrogen-charging devices and methods that enable micro structural and mechanical analyses during electrochemical hydrogen permeation.

As discussed above, conventional devices and methods for testing and identifying hydrogen permeation, including those that employ in situ hydrogen charging, require the use of large and expensive facilities that make that less accessible or inaccessible; do not allow for

microstructural and mechanical analyses due to, for instance, obstructions caused by an electrolyte substance; and can only be implemented on small, nano-sized samples. The present disclosure reduces and/or alleviates such shortcomings, among other benefits.

[0007] By way of non-limiting example, a device can be provided for in situ hydrogen charging using electrochemical permeation. The device can include a chamber for receiving and holding an electrolyte or electrolyte substance. The chamber can include an inner chamber and an outer chamber. The inner chamber can be made of a chemically inert polytetrafluoroethylene (PTFE) polymer to prevent chemical reactions between the chamber surface and the electrolyte, and to isolate the electrolyte therein. In some embodiments, the inner chamber can be used to hold a gaseous hydrogen that is absorbed by the sample, rather than hydrogen produced by the electrochemical process in which the electrolyte substance is charged. In such embodiments, when hydrogen gas is used, the hydrogen gas need not to be circulated continuously from inlet to outlet. Instead, in some embodiments, the outlet may be used for controlling hydrogen gas pressure. As known to those of skill in the art, like the electrolyte substance described herein, gaseous hydrogen can also obstruct the observation or analysis of a sample because it cannot be compatible with vacuum environment and, therefore, the use of an inner chamber to hold the gaseous hydrogen and cause hydrogen to be absorbed by a bottom surface can likewise obviate a number of the shortcomings of current techniques described herein. [0008] The outer chamber can be made of stainless steel to reinforce the inner chamber. A sample of a material such as a metal can be received or placed at an open end of the inner chamber, covering the open end. Sealers such as O-rings can be provided between the chamber and the sample, and pressure can be applied by an additional steel cover to confine the electrolyte inside the inner chamber and under the sample. A counter electrode, which can be made of platinum, for example, can be placed within the inner chamber and connected to a power supply. Electrical potential can be applied by the power supply to the electrode disposed within the inner chamber, causing the production of atomic hydrogen therein. The produced hydrogen can be adsorbed on, by, or through the bottom surface of the sample. The adsorbed hydrogen can be absorbed into the sample and permeate to the upper surface of the sample. The upper surface, which is free of any contamination from the electrolyte, can be analyzed, for example, using microstructural and mechanical testing techniques that can be employed simultaneously.

[0009] The teachings of the present disclosure can be used in a variety of different contexts and across a variety of industries, such as those that use hydrogen containing sources that contact metallic structural materials. By way of non-limiting examples, the present disclosures can be applied to energy, automotive, and marine industries, including to natural gas pipelines, thermoelectric/nuclear power plants, automotive steels, hydrogen-powered cars, offshore plants, vessel steels, and the like. Likewise, while the present disclosure provides for a limited number of configurations ( e.g ., size, shape, design, characteristics, deployable microstructural, mechanical analyses, etc.) of the device and methods, a person skilled in the art will recognize other configurations that can be realized in view of the present disclosures.

[0010] In one exemplary embodiment of a device configured to hold a sample, the device includes an inner chamber, an electrode, and one or more apertures. The inner chamber has a floor, one or more walls extending from the floor, and an opening formed opposite the floor.

The electrode is disposed within the inner chamber. The one or more apertures are each formed through one of the one or more walls or the floor of the inner chamber. The one or more apertures are configured to provide access to an electric cable and an electrolyte substance into and out of an interior of the inner chamber. The inner chamber is configured to receive a sample such that the sample is positioned to seal the opening of the inner chamber and prevent leakage of the electrolyte substance supplied into the interior of the inner chamber.

[0011] The device can include an outer chamber having a floor, one or more walls extending from the floor, and an opening formed opposite the floor of the outer chamber. The outer chamber can have the inner chamber positioned within it. The outer chamber can be formed of a metal material and can be configured to protect the electrolyte substance from an environment external to the outer chamber.

[0012] In some embodiments, the device can include a cover extending at least between opposite ones of the one or more walls of the outer chamber. The cover can be configured to be fixed to an upper end of the outer chamber. The cover, when fixed to the upper end of the outer chamber, can prevent movement of the sample positioned at the opening of the inner chamber. The cover can include an opening formed through its upper surface and lower surface. In some embodiments, the sample can be disposed between the cover and the outer chamber. The opening of the cover can enable observation and analysis of the sample.

[0013] The device can include one or more seals. The seal(s) can be configured to fix the sample the upper end of the outer chamber and/or an upper end of the inner chamber, such as to seal the opening of the inner chamber and prevent leakage of the electrolyte substance. In some embodiments, the seal(s) can be configured to fix the sample to the upper end of the inner chamber. The seal(s) can include an O-ring(s).

[0014] In some embodiments, the one or more apertures of the device can provide access into and out of the interior of the inner chamber from and toward a position external to the outer chamber. The one or more apertures can include an inlet tube and an outlet tube, the inlet tube forming a flow path for the electrolyte substance into the interior of the inner chamber, and the outer tube forming a flow path for the electrolyte substance out of the interior of the inner chamber.

[0015] The electrolyte substance can be circulated into and out of the interior of the inner chamber by an external pump system. In some embodiments, the inner chamber, the seal(s), and the aperture(s) can be made of polytetrafluoroethylene and can be configured to electrically isolate the electrolyte substance. The electric cable can be positioned through the one or more apertures and can be connected to the electrode at the interior of the inner chamber and to a power supply at the exterior of the outer chamber.

[0016] The device can include a copper contact positioned between the cover and the sample. In some embodiments, the sample can be a metal. In some embodiments, the thickness of the sample can be larger than approximately 10 nm, and in some further embodiments, the thickness of the sample can be smaller than approximately 1 cm.

[0017] The observation and analysis of the sample performed via the opening of the cover can include micro structural and mechanical analyses. In some embodiments, the electrolyte substance can be disposed within the interior of the inner chamber.

[0018] A system for analyzing a sample can include a material characteristic analysis device and the device as described in various embodiments provided for herein. The material characteristic analysis device can be configured to execute one or more analysis processes on the sample. In some embodiments, a scanning electron microscope (SEM) can include the device as provided for herein. The SEM can be configured to image the sample held by the device.

[0019] In one exemplary embodiment of a method for analyzing a metallic sample, the method includes disposing a metallic sample in a sample holder, pumping an electrolyte substance into and out of the sample holder, and electrically charging an electrolyte substance to cause hydrogen to be produced within the sample holder. The hydrogen is absorbed by a lower surface of the metallic sample.

[0020] In some embodiments, the hydrogen absorbed by the lower surface of the metallic sample can be diffused toward the upper surface of the metallic sample. Further, one or more of microstructural analysis and/or mechanical analysis processes can be performed on the metallic sample. In some such embodiments, the microstructural analysis and/or mechanical analysis processes can include nanoindentation or hydrogen mapping. In some other such embodiments, the microstructural analysis and/or mechanical analysis processes can include X-ray

crystallography, Fourier-transform infrared spectroscopy, raman spectroscopy, X-ray

fluorescence, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis, laser ablation inductively coupled plasma mass spectrometry, secondary ion mass spectrometry, micro X-ray fluorescence, micro particle induced X-ray emission, X-ray photoelectron spectroscopy, scanning electron microscopy, auger electron microscopy, and nano secondary ion mass spectrometry. The microstructural analysis and/or the mechanical analysis processes can be configured to enable the identification of defects in the metallic sample. In some such embodiments, the defects in the metallic sample can include one or more of microcracks, grain or phase boundaries, and dislocations and twin boundaries. An area on which the microstructural analysis and/or the mechanical analysis process can be performed can include one or more pillars.

[0021] In some embodiments, the thickness of the metallic sample can be approximately in the range of about 10 nm and about 1 cm. The electrolyte substance can be electrically charged by applying a charge via a wire connected to an electrode disposed within the inner chamber and a power supply disposed outside of the inner chamber. In some embodiments, the electrolyte substance can be pumped such that it continuously circulates into and out of the inner chamber.

[0022] In some embodiments, the metallic sample can be disposed such that it is sealed to the sample holder and such that an electrolyte substance within an inner chamber of the sample holder is prevented from leaking.

[0023] In another exemplary method for analyzing a metallic sample, the method includes disposing a metallic sample in a sample holder and pumping gaseous hydrogen into and out of the sample holder, which in turn causes hydrogen to be absorbed by a surface of the metallic sample and diffused toward another, opposite surface of the metallic sample.

BRIEF DESCRIPTION OF DRAWINGS

[0024] This disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0025] FIG. 1 is a schematic diagram of a hydrogen-charging apparatus inside an SEM chamber, the hydrogen-charging apparatus being in a cross-sectional view; [0026] FIG. 2 is a perspective view of one exemplary embodiment of an inner chamber part of a main assembly of a hydrogen-charging apparatus;

[0027] FIG. 3A and 3B are exploded perspective views of the main assembly of the hydrogen charging apparatus of FIG. 2;

[0028] FIG. 4 is an exploded perspective view illustration of certain parts of the main assembly of the hydrogen-charging apparatus of FIGS. 3 A and 3B;

[0029] FIG. 5 is an illustration of the main assembly of the hydrogen-charging apparatus of FIG. 2 and exemplary SEM feedthrough components for connecting the main assembly;

[0030] FIG. 6A is a perspective view of the main assembly connected to the feedthrough components of FIG. 5;

[0031] FIG. 6B is a perspective view of the main body of the main assembly of FIG. 6A, showing the inner chamber;

[0032] FIG. 7A is a perspective view of the main assembly of FIG. 5 positioned inside a vacuum chamber of an SEM during operation;

[0033] FIG. 7B is an SEM image of the main assembly of FIG. 7A showing a sample disposed therein;

[0034] FIG. 8A is a top view of the main assembly of FIG. 5 positioned in a miniaturized mechanical tester compatible with high vacuum systems for testing a sample held in the main assembly;

[0035] FIG. 8B is a perspective view of the main assembly and miniaturized mechanical tester of FIG. 8A; and

[0036] FIGS 9A and 9B are SEM images of a sample before and after hydrogen charging using embodiments of the present disclosure. DET AILED DESCRIPTION

[0037] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure.

[0038] Hydrogen storage and embrittlement studies still suffer from experimental difficulties in studying diffusible hydrogen effects. As a consequence of the small size and high diffusivity of hydrogen atoms, it is challenging to detect and confirm hydrogen presence in material volumes, let alone investigate corresponding effects on micro structure or damage evolution. To address this need, a hydrogen-charging setup was developed that can be applied to high vacuum- based systems, such as scanning electron microscopes (SEMs), to enable high-resolution microstructural analysis during electrochemical hydrogen permeation. In some embodiments, a hydrogen source is isolated from the objective sample surface to avoid the contamination problems from the source and enable analyses of the clean surface during hydrogen charging. Using the setup, a clean, fine-polished surface of micrometer-to-millimeter scale can be observed and tested during hydrogen-charging. Accordingly, embodiments provided for herein enable simultaneous microstructural observation and mechanical testing to be performed during hydrogen charging, by, for example, using embodiments of the present disclosure with a miniaturized mechanical tester compatible with high vacuum systems.

[0039] In in-situ techniques, high pressure hydrogen gas or the electrolyte of the

electrochemical cell enables hydrogen charging, acting as hydrogen sources. However, in those techniques, the hydrogen sources can also be obstacles to conducting microstructural observation during hydrogen charging. In fact, neither high pressure hydrogen gas nor the electrolyte of the electrochemical cell can typically be utilized in high vacuum environments required by most high-resolution analysis equipment. Additionally, the use of liquid electrolytes can also render or contaminate sample surfaces by corrosion during the electrochemical process. Certain embodiments of the present disclosure overcome these challenges, while ensuring high resolution and high field-of-view analysis capability, by: (i) enabling hydrogen charging in a scanning electron microscopy; (ii) providing a clean objective sample surface for both microstructural and mechanical probing; and (iii) ensuring the highest quality imaging and analysis possible by not providing a barrier between an objective surface and the microscope pole piece.

[0040] FIG. 1 is a schematic diagram of a hydrogen-charging apparatus 10 disposed inside a high vacuum chamber 12 of an SEM 11. The schematic diagram of FIG. 1 shows the internal structure of the example hydrogen-charging apparatus 10 in cross-section. The hydrogen charging apparatus 10 can include a main assembly 100 that is configured to hold a sample 80 of a material to be tested inside the vacuum chamber 12. The SEM 11 can be any testing apparatus having a vacuum chamber 12. In FIG. 1, the SEM 11 includes an emitter 15 positioned to image an objective surface 81 of the sample 80 held by the main assembly 100.

[0041] The main assembly 100 can include a multi-layered construction that secures and seals the sample 80 above an inner chamber 70 containing an electrolyte solution 59. Such a configuration can allow a top surface ( e.g ., the objective surface 81) of the sample 80 to be exposed to be imaged or acted on by an instrument, such as the electron gun column 15 of the SEM 12, and a bottom surface of that to be exposed to the electrolyte solution 59 in the inner chamber 70. The main assembly 100 can allows the objective surface 81 of the sample 80 to be exposed to the vacuum chamber 12 without the electrolyte solution 59 on the bottom surface of the sample 80 contaminating the high vacuum environment of the vacuum chamber 12. This is achieved as shown by the main assembly 100 including an outer housing 40 and an inner housing 30, the inner housing 30 being positioned inside the outer housing 40. The inner housing 30 defines the inner chamber 70 for containing the electrolyte 59. The inner chamber 70 of the inner housing 30 can be open at the top for being covered by the sample 80. The inner housing 30 and the outer housing 40 can be nested together to form a top surface that receives the bottom surface of the sample 80, and the top surface can include O-rings 31, 41 that can be positioned to seal the inner chamber against the bottom surface of the sample 80 when the sample is held against the top surface of the inner and outer housings 30, 40. An upper cover 20 can be positioned above the sample 80 and can be configured to be secured to the main assembly 100 using any techniques known to those skilled in the art for holding one component in a location with respect to another. In the illustrated embodiment, screws 19 are used. The upper cover 20 can include an opening for exposing at least a portion ( e.g ., an objective surface 81) of the sample 80 for observation and testing by, for example, an electron beam 16 from the emitter 15. The upper cover 20, when secured to the main assembly, can force the sample 80 against the O- rings 31, 41, which in turn can seal the inner chamber 70. Below the outer housing 40, a bottom fixture 90 can receive the screws 19 and apply an opposite force against the outer housing 40. For example, four screws can be used for fixing the upper cover 20 to the outer housing 40 for sealing the inner chamber 70 by pressing the sample 80 to the O-rings 31, 41. In some embodiments, the bottom fixture can be integrated into the outer housing 40. The bottom fixture 90 can include an adaptor 92, which can be a separately attached adaptor plate for example, for securing the main assembly 100 to the testing apparatus, e.g., a holding platform inside the vacuum chamber 12.

[0042] In some embodiments, including the embodiment shown in FIG. 1, the main assembly 100 can include a conductive contact plate 51 between the sample 80 and the upper cover 20.

The conductive contact plate can provide an electric contact on the sample 80. In some embodiments, the conductive copper contact 51 is not used, for example, when the upper cover 20 is sufficiently conductive.

[0043] The inner chamber 70 of the inner housing can be connected to an external source of electrolytes 59 by tubing 57, 58. In some embodiments, the external source of electrolytes 59 can include a pump 52 for circulating the electrolytes 59 into and out of the inner chamber 70.

[0044] In operation, the example hydrogen-charging apparatus 10 can use the electrochemical permeation method for hydrogen charging of a portion of the sample 80. This can be achieved, for instance, by using the sample 80 as a working electrode, the platinum wire 50 as a counter electrode, and an acidic or basic aqueous solution as an electrolyte 59 to provide hydrogen to the bottom surface of the sample 80 above the inner chamber 70. The inner chamber 70 can contain the electrolyte 59 inside of the double layers of the inner housing 30 and the outer housing 40. The inner housing 30 can be made of chemically inert polytetrafluoroethylene (PTFE) polymer to prevent chemical reactions between the inner chamber 30 surface and the electrolyte solution 59, and to electrically isolate the electrolyte solution 59. The rigid outer housing 40 can be made of stainless steel to supplement the relatively weaker mechanical reliability of the inner housing 30. A thin plate section of the sample 80 can cover the open-side of the inner chamber 70. The O-rings 31, 41 between the inner chamber 70 and sample 80 and pressure applied by the upper cover 20 can confine the electrolyte 59 inside the inner chamber 70 and under the sample 80.

The platinum counter electrode 50 can be placed in the inner chamber 80 and both electrodes 50, 51 can be connected to an external power supply 54 via wires 55, 56 that pass into the vacuum chamber 12 and into the main assembly 100. When electrical potential is applied across the electrodes 50, 51, the electrochemical reduction process can produce atomic hydrogen 79 in the electrolyte 59, and the hydrogen 79 can be adsorbed on the bottom surface of the sample 80, according to the following:

H⁺ + e Hads (1)

HiO + e H_ads + OH (2) where the adsorbed atomic hydrogen 79 can be absorbed into the sample 80 and permeate to the upper sample surface, including the objective surface 81. After diffusion of the absorbed hydrogen 79 from the bottom surface of the sample ( e.g ., the electrolyte-contacting surface) to the upper surface, a portion of the upper surface that is not occluded by the upper cover 20 can form a hydrogen-charged objective sample surface 81 without any contamination from the hydrogen source (e.g., the electrolyte 59), and this objective surface 81 can be observed, interacted with, tested, and/or analyzed during the hydrogen charging process, even inside the high-vacuum system chamber 12. For example, the objective surface 81 in FIG. 1 shows the sample having both nanoindentations 82 and pillars 83 that can be tested during hydrogen charging without contamination of the vacuum chamber 12.

[0045] During the hydrogen charging process, the liquid electrolyte 59 can be circulated between the inner chamber 70 and outside the vacuum chamber 12 of the SEM 11 through PTFE tubing by an external pump system. This can: (i) supply fresh electrolyte continuously; and (ii) remove molecular hydrogen (H2) bubbles formed by recombination of the adsorbed hydrogen. To prevent the breakage of vacuum by potential leakage from soft PTFE tubing, the tubing 57,

58 for the electrolyte path can be sealed in flexible steel tubing and isolated from the vacuum chamber 12 environment inside the SEM 11, as shown in more detail in FIG. 5.

[0046] FIG. 2 is an illustration of a main body 49 of the main assembly 100 of the hydrogen charging apparatus 10, which includes the inner and outer housings 30, 40, as well an electrode 50 ( e.g ., a platinum electrode) and a coupling 71 for connecting the main body 49 to a connection outside of the vacuum chamber 12. FIG. 2 shows the inner chamber 70 without the sample 80 covering the upper opening of the inner chamber 70. The O-rings 31, 41 are shown surrounding the opening of the inner chamber 70, and an additional insulating layer 42 surrounds each of the through-holes in the outer housing to further electrically isolate the upper cover 20 and the sample 80 from the outer housing 40 by preventing electrical contact between the screws 19 and the outer housing 40. As shown, the platinum electrode 50 can be visible at the bottom of the inner chamber 70 and the coupling 71 can carry the tubing 57, 58 and the wire 56 into the inner chamber 70 and the wires 57 to the conductive contact plate 51. The wires 56 can be connected to the electrode 50, and the tubing 57, 58 can circulate the electrolyte 59 into and out of the inner chamber 70.

[0047] FIG. 3A and 3B are exploded view illustrations of the main assembly 100 of the hydrogen-charging apparatus 100. FIG. 3A shows the outer and inner housings 30, 40 of FIG. 2 arranged in the main assembly 100, with the sample 80 positioned above the inner chamber 80, the conductive contact plate 51 positioned above the sample 80, and the upper cover 20 above the conductive contact plate 51 with the screws 19 positioned to secure the upper plate to the outer housing 40. This arrangement can seal the inner chamber 70 with the sample 80 and clamp the conductive contact plate 51 against the sample 80. In the illustrated embodiment, the upper cover 20 and the conductive contact plate 51 both have apertures formed at their center to expose a portion of the top surface of the sample 80, which is the objective surface 81 of the sample 80 to be tested and analyzed. An insulating PTFE layer 89 can be positioned below the bottom surface of the outer housing 40 and a bottom fixture 90 can be below the insulating PTFE layer 89, which can be secured to the outer housing 40 via the screws 19 (or other components known to those skilled in the art for connecting two or more components together) and is insulated from the outer housing 40 by the insulating PTFE layer 89. An insulating PTFE layer 43 can be positioned on the upper surface of the outer housing 40, which insulates the outer housing 40 from the sample 80 and the upper cover 20.

[0048] FIG. 3B shows a bottom-perspective exploded view of the main assembly 100, with the adaptor plate 92 and pin adaptor 93 visible. The bottom fixture 90 is configured to receive the adaptor plate 92 and to secure the adaptor plate 92 to the main assembly 100 via screws 17 (or other components known to those skilled in the art for connecting two or more components together). The adaptor plate 92 can be attached to and removed from the bottom figure 90 without any further disassembly of the main assembly 100 ( e.g ., without undoing screws 19), which enables multiple adaptor plates 92 to be affixed to the main assembly 100 during operation. The use of different adaptor plates 92 can enable the main assembly 100 to be coupled to multiple different testing and holding apparatuses during a single hydrogen-charging operation.

[0049] FIG. 4 is an exploded view illustration of certain parts of the main assembly 100 of the hydrogen-charging apparatus 10. FIG 4 shows the upper cover 20, the conductive contact plate 51, the inner housing 30, the outer housing 40, the bottom fixture 90, and the adaptor plate 92 arranged in one exemplary assembly-order. The conductive contact plate 51 can include an extending tab 451 for connecting the conductive contact plate 51 to the wire 55. While the inner chamber 70 and inner housing 30 are shown to be generally circular in shape, other shapes are considered within the scope of this disclosure. Similarly, while the outer housing 40 is shown to have a generally square external profile and circular inner chamber to receive the inner housing 30, other shapes are considered, for example a curved or circular outer profile and a curved or rectangular inner chamber. While the apertures in the upper cover 20 and the conductive contact plate 51 are shown to be generally rectangular in shape, other shapes are considered, such as, for example, curved or circular apertures.

[0050] FIG. 5 is an illustration of the main assembly 100 of the hydrogen-charging apparatus 10 showing SEM feedthrough components for connecting the main assembly 100 outside of the vacuum chamber 12 of the SEM 11. FIG. 5 shows a feedthrough flange 201 with a flexible steel tube 202 that terminates with a coupling 203 for connecting with the coupling 71 of the main assembly 100. The flexible steel tube 202 can contain portions of the tubing 57, 58 for circulating the electrolyte 59 into and out of the inner chamber 70, as well as the wires 55 and 56 for connecting the electrodes 50, 51 to the power supply 54 outside of the vacuum chamber 12.

[0051] While the upper cover 20, inner housing 30, outer housing 40, conductive contact plate 51, bottom fixture 90, and adaptor plate 92 have each been shown as being separate components of the main assembly 100, embodiments include one or more of the upper cover 20, inner housing 30, outer housing 40, conductive contact plate 51, bottom fixture 90, and adaptor plate 92 being integrally formed with each other to form a whole or part of the main assembly 100.

[0052] FIG. 6A shows an image of the main assembly 100 and the feedthrough components of FIG. 5 and FIG. 6B illustrates the main body 49 of the main assembly 100 of FIG. 6A, showing the inner chamber. The main assembly 49 shown in FIG. 6B has an approximate dimension of about 30 mm x about 30 mm x about 10 mm, and the electrical cables for electrodes and PTFE tubing for electrolyte path can be connected to the external power supply 54 and pump system 52, respectively, through the flexible steel tubing 202 and feedthrough 201. A platinum wire 50 is visible in FIG. 6B, where it can be placed in the inner chamber 70 as a counter electrode 50.

[0053] FIG. 7A is an image of the SEM 11 with a main assembly 100 positioned inside the vacuum chamber 12 of the SEM 11 in an operating configuration. Specifically, FIG. 7A shows the main assembly 100 is installed in a Tescan MIRA3 SEM and the chamber 12 is pumped to a high-vacuum state under approximately 1.5 x 10³ Pa of pressure, with complete sealing of the electrolyte 59 inside the inner chamber 70 of the main assembly 100. FIG. 7B is an SEM image of the main assembly 100 showing the objective surface 81 of the sample 80 as recorded by the Tescan MIRA3 SEM.

[0054] FIGS. 8A and 8B are illustrations of the main assembly 100 positioned in a

miniaturized mechanical tester 800 compatible with high vacuum systems for testing the sample 80 held in the main assembly 100. In FIGS. 8A and 8B, the mechanical tester 800 is a Hysitron PI-88 nanoindenter configured to precisely control the application of a probe 801 against the sample 80 to determine mechanical properties before, during, and after hydrogen charging operation. The combination of the main assembly 100 and 800 can installed in a SEM and be used to investigate mechanical properties of the sample 80 by nanoindentation as well as to observe micro structure by the SEM simultaneously.

[0055] Certain embodiments of the present disclosure provide for a hydrogen-charging setup that can charge a metallic specimen with hydrogen inside a vacuum-based system and simultaneously enable microstructural and micro-mechanical investigations on a contamination- free sample surface. Studies conducted using embodiments of the present hydrogen-charging setup combined with, for example, a silver decoration technique, as well as SEM-based techniques, show that: (i) hydrogen can successfully be absorbed from the hydrogen source contacting surface of a sample 80 and diffused to the objective surface 81 so that the hydrogen- affected objective surface 81 can be investigated by analysis tools; (ii) hydrogen-induced microstructural changes can be directly imaged by SEM-based techniques; and (iii) simultaneous mechanical testing can be applied to investigate hydrogen effects on mechanical properties at specific microstructural features of interest during hydrogen charging in real-time.

[0056] Although these example case studies show the compatibility of certain embodiments with SEM-based techniques, embodiments of the present disclosure can be applied to various type of surface analysis techniques that allow a similar sample dimension with that for SEM, regardless of their necessity of vacuum environment. Certain embodiments of the present disclosure can be coupled with surface analysis techniques to allow investigating a wide range of field of view from nanometer to millimeter scale, as well as various types of microstructural features and defects during simultaneous hydrogen charging process. The experimental investigation of bulk-scale materials under hydrogen charging using embodiments of the present disclosure setup can provide improved understanding on hydrogen effects on the mechanical behavior of structural materials.

[0057] Example

[0058] Multiple materials were investigated to demonstrate charging the sample materials with hydrogen, simultaneous microstructural observation, and mechanical testing the materials using embodiments of the hydrogen-charging apparatus disclosed herein. In a representative example, a duplex stainless steel ( e.g ., ferrite + austenite) sample 80 was studied for hydrogen mapping of the objective surface 81 after hydrogen charging by the hydrogen-charging apparatus 10. The thickness of the duplex stainless- steel sample was approximately 750 ± 15 p.m. For hydrogen mapping, silver decoration was carried out using KAg(CN)₂ solution. The solution was applied on the objective surface 81 for approximately one (1) minute after hydrogen charging for approximately four (4) hours from the electrolyte-contacting surface. The sample was prepared as a circular disc shape with an approximately 24 mm-diameter using electrical discharge machining. The material sample was wet-ground and polished before undergoing hydrogen charging using an embodiment of the present disclosure. Colloidal silica was used for final mechano-chemical polishing process. For electrochemical hydrogen-charging, approximately 5 vol% H₂S0₄ + approximately 5 g/L NH₄SCN solution was used as the electrolyte 59, and current density was approximately 5 A/m². SEM observation and electron backscattered diffraction (EBSD) analysis were conducted by Tescan MIRA3 SEM equipped with ED AX EBSD camera.

[0059] Duplex stainless steels (DSS) are often used in power plants, and in the oil and gas industry, sometimes for long periods of time ( e.g ., decades). They are known to be susceptible to hydrogen embrittlement, and their hydrogen embrittlement resistance is strongly

microstructure dependent. Thus, the damage nucleation and evolution process is of interest. In case of hydrogen embrittlement, distribution of hydrogen plays an important role in damage nucleation. In this example, hydrogen distribution in a duplex stainless steel was investigated. This example verifies that hydrogen charging can be carried out efficiently by embodiments disclosed herein and that the diffusion of the hydrogen (absorbed from the electrolyte-contacting surface) towards the upper objective surface 81 occurs. For this purpose, the silver decoration methodology can be employed, which uses the following redox reaction between hydrogen atoms and silver ion:

Ag⁺ (aq) + H (Desorbed from sample surface) Agj, (nanoparticles) + H⁺ (aq) (3)

[0060] When a solution containing silver ions is applied on the surface of a hydrogen-charged sample, the silver ions can be reduced by hydrogen atoms desorbed from the sample surface and leave silver nanoparticles on the sample surface. With the silver nanoparticles formed from the reaction, hydrogen distribution on the sample surface can be mapped indirectly. In this example, the silver decoration technique can be applied on the objective surface 81 of sample 80 for detecting hydrogen diffusing from the electrolyte-contacting surface. [0061] A duplex stainless- steel consisting of ferrite and austenite phase was chosen as a model alloy, which has a significant difference in hydrogen diffusivity between the two phases. The diffusion rate of hydrogen is higher by a few orders of magnitude in the ferrite phase than in the austenite phase. FIG. 9A shows the duplex micro structure of the sample 80 observed using backscatter electron imaging before hydrogen charging and silver decoration, showing a ferrite matrix 901 with islands of austenite 902. The sample 80 was charged with hydrogen using the hydrogen-charging apparatus 10 for approximately four (4) hours and the objective surface 81 was silver-decorated by KAg(CN)₂ solution. The diffusion length of hydrogen can be estimated by the equation, L = V Dt, where V is diffusion coefficient of hydrogen in sample and Dt is the diffusion time. By the estimation using the diffusion coefficient of hydrogen in polycrystalline pure iron at 295 K ( i.e ., 7.2 x 109 m²/s), the charging time of approximately four (4) hours is enough for hydrogen to diffuse through the ferrite phase in the sample with thickness of approximately 750 pm.

[0062] FIG. 9B shows the silver-decorated objective surface 81 of the duplex stainless steel after hydrogen charging. Fine silver nanoparticles 903 are observed on the surface, which reveals that hydrogen absorbed from the opposite surface successfully diffuses through the whole sample thickness and affects the clean-polished objective surface 81. The silver particles have a population clearly larger in the ferrite phases 901 compared to in the austenite phases 902 and are preferentially formed along the phase boundaries. This reveals that hydrogen can be more easily released from the ferrite 901 than the austenite 902, and at the phase boundary between ferrite 901 and austenite 902 phases compared to grain interior.

[0063] Hydrogen detection via surface reaction products such as silver particles in the silver decoration technique provides the distribution of hydrogen released from the sample surface, but does not directly reflect hydrogen distribution inside the sample because high concentration of hydrogen does not always lead to its high release rate. When the silver decoration is applied to sample surface that did not have direct contact with hydrogen sources (as is the case in this example), however, the distribution of silver nanoparticles 903 reflects the diffusion rate difference of hydrogen, because hydrogen can only react with silver ions after diffusion across the whole sample thickness. The distribution of silver nanoparticles depending on phases in FIG. 9B can be attributed to higher diffusion rate and lower solubility of hydrogen in the ferrite phase than in the austenite phase. Furthermore, the high release rate of hydrogen at the phase boundary corresponds to that the hydrogen-depleted zone is observed by nano-secondary ion mass spectrometry (nano-SIMS) in the vicinity of phase boundary in a duplex stainless steel after a few hours from hydrogen charging. The results show that the phase boundary between ferrite 901 and austenite 902 is a preferred diffusion path and hydrogen is depleted preferentially in the proximity of the phase boundary after stoppage of hydrogen supply.

[0064] Other example sample 80 materials include titanium alloys with a duplex

microstructure (e.g., a-hcp phase + b-bcc phase). Such as, for example, Ti-6Al-4V alloy, where embodiments of the present disclosure can be used to observe hydrogen-induced phase transformation, formation of titanium hydride phases, lattice expansions in both a and b phases and surface cracking in the a phase or along a phase interface. Embodiments can enable real time imaging during hydrogen charging inside a SEM 11 to investigate, for example, internal microstructural evolution of the alloy during room-temperature hydrogenation, and hydrogen diffusion paths in the multi-phase micro structure.

[0065] Embodiments also include nanoindentation tests with SEM 11 imaging during hydrogen-charging to investigate hardening and modulus reduction effects in materials such as steel. For example, a commercial 430 ferritic stainless steel, which has a relatively high diffusion rate of hydrogen compared to austenitic or martensitic steels. Embodiments can enable charging a sample 80 with hydrogen using the hydrogen-charging apparatus 10 and testing the sample 80 using the in situ nanoindenter 800 inside the SEM 11 before and during hydrogen charging.

[0066] ETsing the above-described techniques and others known in the art, embodiments of the present disclosure can provide for analytical detection of hydrogen-charging down to at least lOppt, including detection of dislocations, twin boundaries, grain and phase boundaries, and microcracks in the material sample 80, which can be investigated across analytical areas at least as small as lOnm. Examples of applicable analytical detection techniques include micro- or nano-mechanical tests using a nanoindenter and a focused ion beam system, and hydrogen mapping techniques using mass spectrometry of desorbed H₂ gas or H⁺ ion, such as nano secondary ion mass spectrometry and electron stimulated desorption ion mass spectrometry. [0067] One skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

Claims

What is claimed is:

1. A device for holding a sample, comprising:

an inner chamber having a floor, one or more walls extending from the floor, and an opening formed opposite the floor;

an electrode disposed within the inner chamber; and

one or more apertures each formed through one of the one or more walls or the floor of the inner chamber,

wherein the one or more apertures are configured to provide access to an electric cable and an electrolyte substance into and out of an interior of the inner chamber, and

wherein the inner chamber is configured to receive a sample such that the sample is positioned to seal the opening of the inner chamber and prevent leakage of the electrolyte substance supplied into the interior of the inner chamber.

2. The device of claim 1, further comprising:

an outer chamber having a floor, one or more walls extending from the floor, and an opening formed opposite the floor of the outer chamber, the outer chamber having the inner chamber positioned therein,

wherein the outer chamber is formed of a metal material and is configured to protect the electrolyte substance from an environment external to the outer chamber.

3. The device of claim 2, further comprising:

a cover extending at least between opposite ones of the one or more walls of the outer chamber, the cover being configured to be fixed to an upper end of the outer chamber.

4. The device of claim 3, wherein the cover, when fixed to the upper end of the outer chamber, prevents movement of the sample positioned at the opening of the inner chamber.

5. The device of claim 4, wherein the cover includes an opening formed through its upper surface and lower surface.

6. The device of claim 5,

wherein the sample is disposed between the cover and the outer chamber, and wherein the opening of the cover enables observation and analysis of the sample.

7. The device of claim 3, further comprising one or more seals, the one or more seals being configured to fix the sample to one or more of the upper end of the outer chamber and an upper end of the inner chamber, such as to seal the opening of the inner chamber and prevent leakage of the electrolyte substance.

8. The device of claim 7, wherein the one or more seals are configured to fix the sample to the upper end of the inner chamber.

9. The device of claim 8, wherein the one or more seals comprise an O-ring.

10. The device of claim 7, wherein the one or more apertures provide access into and out of the interior of the inner chamber from and toward a position external to the outer chamber.

11. The device of claim 2, wherein the one or more apertures include an inlet tube and an outlet tube, the inlet tube forming a flow path for the electrolyte substance into the interior of the inner chamber, and the outer tube forming a flow path for the electrolyte substance out of the interior of the inner chamber.

12. The device of claim 11, wherein the electrolyte substance is circulated into and out of the interior of the inner chamber by an external pump system.

13. The device of claim 11, wherein the inner chamber, the one or more seals and the one or more apertures are made of polytetrafluoroethylene and are configured to electrically isolate the electrolyte substance.

14. The device of claim 1, wherein the electric cable positioned through the one or more apertures is connected to the electrode at the interior of the inner chamber and a power supply at the exterior of the outer chamber.

15. The device of claim 1, further comprising a copper contact positioned between the cover and the sample.

16. The device of claim 1, wherein the sample is a conductive material.

17. The device of claim 16, wherein the thickness of the sample is larger than approximately 10 nm.

18. The device of claim 17, wherein the thickness of the sample is smaller than

approximately 1 cm.

19. The device of claim 1, wherein the observation and analysis of the sample performed via the opening of the cover includes micro structural and mechanical analyses.

20. The device of claim 1, further comprising the electrolyte substance disposed within the interior of the inner chamber.

21. The device of claim 1, wherein the inner chamber is formed of a chemical-resistant polymeric material.

22. A system for analyzing a sample, comprising:

a material characterization device; and

the device of claim 1, wherein the material characterization device is configured to execute one or more analysis processes on the sample.

23. A scanning electron microscope (SEM), comprising the device of claim 1, wherein the SEM is configured to image the sample held by the device.

24. A method for analyzing a metallic sample, comprising:

disposing a metallic sample in a sample holder,

pumping an electrolyte substance into and out of the sample holder; and

electrically charging an electrolyte substance, thereby causing hydrogen to be produced within the sample holder,

wherein the hydrogen is absorbed by a lower surface of the metallic sample.

25. The method of claim 24, wherein the hydrogen absorbed by the lower surface of the metallic sample is diffused toward the upper surface of the metallic sample.

26. The method of claim 25, further comprising performing one or more of microstructural analysis and/or mechanical analysis processes on the metallic sample.

27. The method of claim 26, wherein the micro structural analysis and/or mechanical analysis processes include nanoindentation or hydrogen mapping.

28. The method of claim 26, wherein the micro structural analysis and/or mechanical analysis processes include X-ray crystallography, Fourier-transform infrared spectroscopy, raman spectroscopy, X-ray fluorescence, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis, laser ablation inductively coupled plasma mass spectrometry, secondary ion mass spectrometry, micro X-ray fluorescence, micro particle induced X-ray emission, X-ray photoelectron spectroscopy, scanning electron microscopy, auger electron microscopy, nano secondary ion mass spectrometry, and focused ion beam technique.

29. The method of claim 26, wherein the micro structural analysis and/or the mechanical analysis processes are configured to enable the identification of defects in the metallic sample.

30. The method of claim 29, wherein the defects in the metallic sample include one or more of microcracks, grain or phase boundaries, and dislocations and twin boundaries.

31. The method of claim 26, wherein an area on which the microstructural analysis and/or the mechanical analysis processes are performed includes one or more pillars.

32. The method of claim 24, wherein the thickness of the metallic sample is approximately in the range of about 10 nm and about 1 cm.

33. The method of claim 24, wherein the electrolyte substance is electrically charged by applying a charge via a wire connected to an electrode disposed within the inner chamber and a power supply disposed outside of the inner chamber.

34. The method of claim 24, wherein the electrolyte substance is pumped such that it continuously circulates into and out of the inner chamber.

35. The method of claim 24, further comprising disposing the metallic sample such that it is sealed to the sample holder and such that an electrolyte substance within an inner chamber of the sample holder is prevented from leaking.

36. A method for analyzing a metallic sample, comprising:

disposing a metallic sample in a sample holder, and

pumping gaseous hydrogen into and out of the sample holder, thereby causing hydrogen to be absorbed by a surface of the metallic sample and diffused toward another, opposite surface of the metallic sample.