Systems, devices, and methods for non-destructive quantification of hydrogen content

Abstract

Systems, devices, and methods for non-destructive quantification of hydrogen in conductive materials are provided. In some embodiments, a gauge can be placed in proximity to a conductive material such as a metal or alloy to non-destructively detect and / or measure a hydrogen content thereof. The gauge can include an interface layer having a compound on a surface thereof that is configured to contact an object to facilitate extraction of hydrogen therefrom, a hydrogen sensitive layer that is configured to change resistivity or other measurable properties based on the concentration of hydrogen, and a pair of terminals configured to support an electrical potential therebetween for mobilizing, pumping, collecting, concentrating, storing, and / or detecting hydrogen content in the extracted hydrogen. The gauge can provide a fast, portable, and non-destructive method to quantify hydrogen and address the risk of hydrogen embrittlement in infrastructure, identifying potential hazards before they lead to structural failures.

Description

Attorney Docket No. MIT 26274 PCT | 88212-432506SYSTEMS, DEVICES, AND METHODS FOR NON DESTRUCTIVE QUANTIFICATION OF HYDROGEN CONTENT CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] The present disclosure claims priority to and the benefit of U.S. Provisional Application No. 63 / 753,437, entitled “Systems, Devices, and Methods for Non-Destructive Quantification of Hydrogen Content,’’ filed on February 3, 2025, the content of which is incorporated by reference herein in its entirety.FIELD

[0002] The present disclosure relates to systems, devices, and methods for non-destructive quantification of hydrogen content, and more particularly relates to systems, devices, and methods for detecting and measuring solute hydrogen content within metals and alloys without damaging the structural integrity of the object being measured.BACKGROUND

[0003] Hydrogen is a versatile energy carrier that can be produced from various sources and used across multiple sectors, including transportation, power generation, and industrial processes. As global efforts to reduce carbon emissions intensify, hydrogen infrastructure has expanded to include pipelines for hydrogen gas transport, storage tanks, fuel systems for fuel cell electric vehicles, and equipment for hydrogen production and processing. Metals and alloys are commonly employed in the construction of such infrastructure due to their mechanical strength and durability. However, when metals are exposed to hydrogen environments, hydrogen atoms can diffuse into the metal structure over time, a phenomenon that can lead to degradation of mechanical properties.

[0004] Hydrogen embrittlement is a well-documented phenomenon in which hydrogen atoms that have permeated into a metal can cause a reduction in ductility and load-bearing capacity, potentially leading to premature failure of structural components. Hydrogen within metals can exist in various forms, including diffusible hydrogen that moves through the lattice structure, trapped hydrogen that accumulates at defects such as grain boundaries and dislocations, and bonded hydrogen that reacts to form compounds such as hydrides. The accumulation of hydrogen in any of these forms can compromise the integrity of metal infrastructure, making it desirable to monitor hydrogen content within metals to assess the risk of embrittlement before structural damage occurs.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0005] Conventional approaches to hydrogen detection in metals have various limitations. Many existing techniques rely on measuring hydrogen flux, which focuses on diffusible hydrogen passing through a material, but such approaches may not capture trapped or bonded hydrogen that also contributes to embrittlement. Liquid electrolyte-based systems can present challenges related to electrolyte containment and leakage, particularly in field applications where portability is desired. Additionally, some detection methods can only identify hydrogen-related damage after it has manifested as cracks or leaks, rather than providing early warning of hydrogen accumulation. This reactive approach results in high costs of repair and does not allow for preemptive detection, which can prolong system shutdown times and increase capital costs of equipment maintenance. For example, periodic inspections and overhauls to mitigate failure risks represent some of the most significant cost contributors in gas turbine plants. Direct measurement of hydrogen flux without concentration or amplification can result in low signal-to-noise ratios, reducing measurement sensitivity and accuracy. Further, destructive testing methods that require sample extraction from the structure being evaluated are impractical for in-service monitoring of infrastructure components.

[0006] Accordingly, there is a need for systems, devices, and methods for monitoring and detecting hydrogen levels in metals and alloys that can provide non-destructive measurement of hydrogen content, including diffusible, trapped, and bonded forms of hydrogen, with improved sensitivity and portability for field applications.SUMMARY

[0007] The presently disclosed embodiments generally relate to systems, devices, and methods for non-destructive quantification of hydrogen content in metals and alloys. Such systems enable detection and measurement of solute hydrogen content within conductive materials using a gauge having a sol-gel interface and a hydrogen-sensitive layer to electrochemically extract, concentrate, and quantify hydrogen without damaging the structural integrity of the object being measured. These systems address the risk of hydrogen embrittlement in infrastructure by identifying potential hazards before they lead to structural failures, thereby shifting the focus from damage detection to damage prevention.

[0008] In accordance with some embodiments, the ability to electrochemically pump, collect, concentrate, store, and / or detect hydrogen content from an object may present advantages in measuring diffusible hydrogen, trapped hydrogen, and bonded hydrogen. Also,Attorney Docket No. MIT 26274 PCT | 88212-432506being able to position a gauge proximate to a conductive material such as a metal or alloy without destructively penetrating, invading, or otherwise deforming the object may present advantages in providing a fast, portable, and non-destructive method to quantify hydrogen within metals used in hydrogen infrastructure.

[0009] In an aspect, embodiments relate to a hydrogen content measuring device. The device includes an interface layer having a compound on a surface thereof that is configured to contact an object non-destructively to facilitate extraction of hydrogen therefrom. The device includes a hydrogen-sensitive layer that is configured to change one or more measurable properties based on a concentration of hydrogen. The device includes a first terminal and a second terminal configured to support an electrical potential therebetween. The device is configured to one or more of electrochemically pump, collect, concentrate, or store hydrogen content from the object to non-destructively measure a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen.

[0010] One or more of the following features may be included. The compound can comprise a sol-gel having a paste-like consistency. The sol-gel can include an acid-in-clay electrolyte. The acid-in-clay electrolyte can comprise sepiolite clay and phosphoric acid. The object can comprise a conductive material comprising at least one of a metal or an alloy. The hydrogen-sensitive layer can comprise at least one of palladium, palladium-based alloys, platinum-based alloys, transition metal alloys, or composite of metal oxide and metalceramic. The hydrogen-sensitive layer can comprise palladium having a purity of at least 99.99% trace metals basis. The object can comprise one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines. The one or more measurable properties can comprise one or more of resistivity, impedance, elastic modulus, absorptivity, reflectivity of electromagnetic radiation, residual stress, expansion, contraction, or magnetic properties. The device can further comprise an insulation layer that separates the first terminal from the second terminal. The first terminal can be configured as an outer ring terminal and the second terminal can be configured as an inner ring terminal in a concentric arrangement. The device can be configured to achieve a limit of detection of less than or equal to 10 ppm for hydrogen content. The device can be configured to preserve an operational capability of the object during and after measurement of the hydrogen content. The hydrogen-sensitive layer can be configured to be discharged to remove hydrogen therefrom to allow the hydrogen-sensitive layer to be reused for subsequent measurements.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0011] In another aspect, embodiments relate to a method of non-destructively measuring hydrogen content. The method includes non-destructively placing a gauge adjacent to an object. The method includes applying an electrical potential between the first terminal and the second terminal to deliver an electric current therebetween. The method includes electrochemically extracting hydrogen from the object through the interface layer into the hydrogen-sensitive layer. The method includes measuring a content of the hydrogen extracted into the hydrogen-sensitive layer non-destructively.

[0012] One or more of the following features may be included. Electrochemically extracting hydrogen from the object can further comprise one or more of mobilizing, pumping, collecting, concentrating, or storing hydrogen content from the object. Measuring the content of the hydrogen can further comprise measuring a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen. The compound can be a sol-gel having a paste -like consistency that conforms to a surface of the object. The sol-gel can include an acid-in-clay electrolyte comprising sepiolite clay and phosphoric acid. The object can be a conductive material comprising a metal or an alloy. The object can comprise one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines. The applied electrical potential can lead to extraction of hydrogen atoms from the object using one or more charge carriers in the gauge to form an ion channel. The method can further comprise preserving an operational capability of the object during and after measurement of the hydrogen content by maintaining the gauge adjacent to the object without deforming the object throughout the measuring step. The method can further comprise discharging the hydrogen-sensitive layer to remove hydrogen therefrom after measuring the content of the hydrogen, thereby allowing the hydrogen-sensitive layer to be reused for subsequent measurements.

[0013] In another aspect, embodiments relate to a non-destructive hydrogen sensing system. The system includes a gauge configured to be positioned on an outer surface of a conductive object non-destructively. The gauge comprises a sol-gel interface comprising an acid-in-clay electrolyte configured to conform to the outer surface of the conductive object and to transport hydrogen ions extracted from the conductive object. The gauge comprises a hydrogen-sensitive layer comprising palladium disposed adjacent to the sol-gel interface and configured to receive and store hydrogen transported through the sol-gel interface. The gauge comprises a first terminal and a second terminal arranged in a concentric configuration and configured to establish an electrical potential for electrochemically driving hydrogenAttorney Docket No. MIT 26274 PCT | 88212-432506from the conductive object through the sol-gel interface and into the hydrogen-sensitive layer. The system includes a measurement system configured to measure a change in resistivity of the hydrogen-sensitive layer to quantify hydrogen content extracted from the conductive object.

[0014] One or more of the following features may be included. The acid-in-clay electrolyte can comprise sepiolite clay and phosphoric acid. The system can be configured to non-destmctively measure a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen extracted from the conductive object. The system can be configured to achieve a limit of detection of less than or equal to 10 ppm for hydrogen content. The hydrogen-sensitive layer can be configured to be discharged to remove hydrogen therefrom via electrolytic charging to allow the hydrogen-sensitive layer to be reused for subsequent measurements. The conductive object can comprise one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines, and the gauge can be configured to preserve an operational capability of the conductive object during and after measurement of the hydrogen content. The system can further comprise an insulation layer that separates the first terminal from the second terminal.BRIEF DESCRIPTION OF DRAWINGS

[0015] This disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0016] FIG. 1 A is a schematic perspective view of one embodiment of an object and a gauge for measuring a hydrogen content of the object, the object being a high pressure pipeline;

[0017] FIG. IB is a schematic perspective view of the gauge of FIG. 1A attached to an outer surface of the high pressure pipeline of FIG. 1 A;

[0018] FIG. 2A is a perspective bottom view of the gauge of FIG. 1 A showing a distribution of charges thereon;

[0019] FIG. 2B is a cross-sectional schematic view about the line A-A in FIG. 2A of the gauge of FIG. 2A proximate to the object having hydrogen flowing therethrough;

[0020] FIG. 2C is a cross-sectional schematic view about the line A-A in FIG. 2A of the gauge of FIG. 2B contacting the object of FIG. 2B during operation to extract hydrogen therefrom;Attorney Docket No. MIT 26274 PCT | 88212-432506

[0021] FIG. 3 is a cross-sectional schematic view of the object of FIG. 2B during electrochemical hydrogen extraction showing hydrogen atoms and hydrogen ions migrating through a sol-gel interface of the gauge of FIG. 2A;

[0022] FIG. 4A is a front perspective view of a sensor prototype assembly for hydrogen content measurement;

[0023] FIG. 4B is a rear perspective view of the sensor prototype assembly of FIG. 4A; and

[0024] FIG. 5 is a graph illustrating palladium resistivity as a function of hydrogen insertion time, according to aspects of the present disclosure.DETAILED DESCRIPTION

[0025] Certain embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems, devices, related components (e.g., gauges, sol-gel interfaces, hydrogen-sensitive layers, insulation layers, terminals, and cables), 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. Further, to the extent features, layers, sides, objects, steps, or the like are described as being "first," "second," "third," etc., and / or "lower," "upper," "middle," "inner," "outer," etc., such numerical and / or location ordering / identification is generally arbitrary, and thus such numbering can be interchangeable unless indicated or otherwise understood by those skilled in the art to not be interchangeable. While terms like "proximal" and "distal" are used herein, they are primarily used as a point of reference for describing two portions or ends of an instrument, tool, component, device, system, location on a structure, etc. Accordingly, no meaning should be attributed to a specific location with respect to "proximal" or "distal" beyond distinguishing one side from another unless explicitly indicated. For example, what is referred to herein as a proximal portion or end may be considered distal in operation, and thus, likewise, what is referred to herein as a distal portion or end may be considered proximal in operation.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0026] The figures provided herein are not necessarily to scale, although a person skilled in the art will recognize instances where the figures are to scale and / or what a typical size is when the drawings are not to scale. Further, to the extent that linear or circular dimensions or shapes are used or described herein, such dimensions are not intended to limit the types of shapes or sizes of such devices, components, etc. A person skilled in the art will recognize that an equivalent to such linear and / or circular dimensions or shapes can be easily determined for any geometric shape (e.g., references to widths and diameters being easily adaptable for circular and linear dimensions, respectively, by a person skilled in the art). While in some embodiments movement of one component is described with respect to another, a person skilled in the art will recognize that other movements are possible. Further, to the extent arrows are used to describe a direction a component can expand or move, these arrows are illustrative and in no way limit the direction the respective component can expand or move. A person skilled in the art will recognize other ways and directions for creating the desired tension or movement.

[0027] Still further, in the present disclosure, like -numbered components of various embodiments generally have similar features when those components are of a similar nature and / or serve a similar purpose, unless otherwise noted or otherwise understood by a person skilled in the art. To the extent the present disclosure includes prototypes, mock-ups, bench models, or the like, a person skilled in the art will recognize how to rely upon the present disclosure to integrate the techniques, systems, devices, and methods into a product, such as a portable hydrogen sensing gauge for field deployment on hydrogen infrastructure. A number of terms may be used throughout the disclosure interchangeably but will be understood by a person skilled in the art. By way of non-limiting example, the terms "gauge," "sensor," and "device" may be used interchangeably with one another, as may the terms "sol-gel," "solgel," "solid electrolyte," and "acid-in-clay electrolyte." Moreover, it will be appreciated that although features may be discussed with respect to one embodiment within the present disclosure, these features can be applied to every embodiment of the present disclosure where such feature would be supported.

[0028] To the extent terms like "approximately," "about," and "substantially" are used herein, a person skilled in the art will appreciate the scope those words convey in the context of their usage. In the context of hydrogen content measurement and electrochemical extraction, obtaining a certain degree of resistivity measurement, hydrogen concentration, voltage application, and / or terminal positioning, among other parameters and the like, may beAttorney Docket No. MIT 26274 PCT | 88212-432506difficult, and thus use of terms like "approximately," "about," and "substantially" is intended to address this difficulty. A person skilled in the art will understand what constitutes how close a particular dimension or placement should be to still fall within the spirit of the quantification and description provided for herein. Even in instances where such terminology is not used, and a dimension or measurement just includes the number or term (e.g., "parallel" is used instead of "substantially parallel"), a person skilled in the art will appreciate that, unless explicitly indicated otherwise, terms like "approximately," "about," and "substantially" are applicable to those dimensions and terms as well. The foregoing notwithstanding, a person skilled in the art will appreciate that terms like "approximately," "about," and "substantially" at least encompass dimensions, quantities, resistivity values, voltage levels, and concentrations that are ±10%, 10°, etc. of the provided amount, or encompass dimensions that are ±5%, 5°, etc. of the provided amount, unless indicated otherwise or otherwise known to those skilled in the art. The present disclosure appreciates that a person skilled in the art, in view of the present disclosure, understands suitable placements for various features of the disclosed systems, devices, and gauges, and related components of any of the same, and thus to the extent a particular dimension, voltage, resistivity, or concentration is described, unless it is explicitly indicated that such parameter is required, a person skilled in the art will appreciate other parameters that are possible without impacting the overall system, device, or gauge.

[0029] The present disclosure generally provides for systems, devices, and methods for nondestructive quantification of hydrogen content in compounds, and more specifically within metals and alloys. As mentioned above, hydrogen embrittlement in metal infrastructure poses a serious safety risk, as hydrogen atoms can diffuse into metals and alloys, accumulate at grain boundaries and other microstructural features, and ultimately lead to degradation of mechanical properties and structural failures. This phenomenon affects a wide range of applications, including pipelines for blending hydrogen gas, storage tanks, storage cylinders and fuel systems for fuel cell electric vehicles, vessels, pipes, welds, hydrogen gas turbines, hydrogen production and processing equipment such as methane pyrolysis reactors, purification systems, separators, coolers, and hydrogen storage and transportsystems. Conventional technologies for detecting hydrogen-related damage in metal infrastructure either detect hydrogen damage after damage has occurred, such as through structural cracks or hydrogen leaks, or via ultrasonic testing, which are only reliable at a limited range of temperatures, material thicknesses, and materialAttorney Docket No. MIT 26274 PCT | 88212-432506geometries. Inhomogeneous materials, such as coated materials or materials with welds, cause sound waves to travel unpredictably, limiting the use of ultrasonic testing in many applications.

[0030] The present disclosure addresses these limitations by providing a hydrogen content measuring device or gauge 100 having a sol-gel interface and a hydrogen-sensitive layer to electrochemically extract, concentrate, and quantify hydrogen accumulation before crack formation, enabling preventative maintenance and reducing material and replacement costs. The device 100 can be adaptable to a wide range of material sizes, geometries, and temperatures, thereby increasing safety across diverse applications. The device 100 can also be compatible with a wider range of materials and applications than conventional methods, allowing new materials to be used in hydrogen infrastructure and opening new market potential. The device 100 can be operated both continuously for real-time monitoring and periodically for scheduled inspections.

[0031] In some embodiments, the device 100 can function analogously to a stethoscope for metal, where the device 100 can be placed against a metal surface to collect and quantify hydrogen content within the metal. Unlike conventional methods that measure hydrogen flux or detect hydrogen gas in the atmosphere, the device 100 of the present disclosure can electrochemically extract hydrogen from within the metal structure, concentrate the extracted hydrogen into a hydrogen-sensitive material, and quantify the hydrogen content based on measurable property changes in the hydrogen-sensitive material. This approach shifts the focus from damage detection to damage prevention by identifying solute hydrogen levels at an early stage, providing a proactive safety measure before hydrogen-induced structural failures occur.

[0032] Referring to FIG. 1A, the gauge 100 can non-destructively measure hydrogen content of an object 10 in proximity therewith. In the illustrated embodiment, the object 10 can include a high pressure pipeline extending horizontally across a terrain, though other forms of piping can also accommodate placement of the gauge 100. In use, the gauge 100 can be mounted on an outer surface of the object 10, positioned to interface with the pipeline non-destructively with respect to the structure of the object 10. It will be appreciated that the term "non-destructive" as used throughout this disclosure refers to the ability of the gauge 100 to measure hydrogen content of an object without penetrating, entering, invading, or otherwise deforming the object 10 or meaningfully changing a structural integrity of a surface of the object. As mentioned above, the gauge 100 can function analogously to a stethoscopeAttorney Docket No. MIT 26274 PCT | 88212-432506in that can be applied to a metal surface to measure and / or collect data therefrom. For example, the gauge 100 can be applied to the surface of the object, or adjacent to a surface of the object 10, to collect hydrogen data that can be used to determine the extent of hydrogen content within the material.

[0033] With continued reference to FIG. 1 A, the gauge 100 can have multiple visible layers arranged in a stacked configuration and connected via a cable 110 that extends from the gauge 100 for electrical connection to external measurement equipment or power sources. The gauge 100 can be configured to preserve the operational capability of the object 10 during and after measurement by enabling measurement of hydrogen content within the pipeline material while maintaining the structural integrity of the infrastructure.

[0034] FIG. 1 B illustrates the gauge 100 attached to an outer surface of the object 10, which in this embodiment is a high pressure gas line. As shown, the gauge 100 can be positioned on the exterior surface of the object 10 to enable non-destructive measurement of hydrogen content within the metal of the pipeline. This configuration demonstrates the portable and field-deployable nature of the gauge 100, which can be applied to infrastructure such as pipelines to detect and quantify hydrogen levels without damaging the structural integrity of the object 10. In use, the gauge 100 can contact the outer surface of the pipeline to facilitate extraction and measurement of hydrogen content from the metal, providing an early warning system to prevent hydrogen-induced structural failures in hydrogen infrastructure applications.

[0035] The object 10 to which the gauge 100 can be applied can be a conductive material, such as a metal or an alloy. Some additional non-limiting examples of the object 10 to which the gauge 100 can be applied can include hydrogen tanks, cars, nuclear reactors, submarines, or any object that may suffer from hydrogen embrittlement, where hydrogen atoms diffuse into the metal structure and cause degradation of mechanical properties over time. In some embodiments, the object 10 can include hydrogen gas turbine blades, which face changing gradients of pressure and temperature that make hydrogen embrittlement unpredictable, methane pyrolysis reactors used in hydrogen production, where equipment is exposed to hydrogen-rich environments during operation, as well as hydrogen purification systems, separators, and coolers used in hydrogen processing. The gauge 100 can further be applied to welds and valves, which represent areas where hydrogen is difficult to detect using conventional methods. Welds in particular can be susceptible to hydrogen accumulation due to microstructural variations introduced during the welding process. Valves in hydrogenAttorney Docket No. MIT 26274 PCT | 88212-432506infrastructure can also experience hydrogen ingress during operation. The gauge 100 can be adapted to interface with these various geometries and surface configurations to provide nondestructive hydrogen content measurement across diverse applications.

[0036] Referring to FIGS. 2A-2C, the gauge 100 includes several components arranged in a concentric configuration for non-destructive hydrogen content measurement. FIG. 2A illustrates a perspective view of the gauge 100, and FIGS. 2C illustrate a cross-sectional view of the gauge 100 before and after being applied to the object 10. As shown, the gauge 100 can include a sol-gel interface 102 positioned on a surface of the gauge 100 and configured to contact the object 10 to facilitate extraction of hydrogen therefrom. The sol-gel interface 102 can have a compound on a surface thereof that ensures effective contact with the metal, thereby facilitating hydrogen extraction from the object into the gauge 100. It will be appreciated that the terms "sol-gel interface," "interface layer," and "solgel" can be used interchangeably throughout this disclosure to refer to the compound-bearing layer that contacts the object and facilitates hydrogen extraction.

[0037] The sol-gel interface 102 can include a compound having a paste-like consistency that resembles the gel used in ultrasound diagnostics. The paste-like consistency of the solgel can enable the sol-gel to conform to a surface of the metal or alloy being measured, thereby ensuring effective contact between the gauge and the object 10. This conformable nature of the sol-gel can accommodate surface irregularities, curvatures, and textures present on the object, which can facilitate hydrogen extraction across diverse surface conditions encountered in field applications. The compound can be a sol-gel having a paste -like consistency that can be applied to the gauge prior to placement on the object, or the compound can be pre-applied to the gauge during manufacturing.

[0038] In some embodiments, the sol-gel includes an acid-in-clay electrolyte. The acid-inclay electrolyte can be composed of sepiolite clay mixed with phosphoric acid and water. In some embodiments, the acid-in-clay electrolyte comprises specific proportions of sepiolite clay, phosphoric acid, and water, such as approximately 1000 milligrams (mg) sepiolite clay, approximately 3756 mg phosphoric acid, and approximately 1180 mg water. The sepiolite clay can provide a structural matrix that retains the phosphoric acid while maintaining the paste-like consistency of the sol-gel. The phosphoric acid can function as a proton electrolyte that enables transport of hydrogen ions through the sol-gel during the electrochemical extraction process.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0039] With continued reference to FIGS. 2A-2C, the gauge 100 can include a hydrogensensitive layer 104 disposed adjacent to the sol-gel interface 102. The hydrogen-sensitive layer 104 can be configured to change one or more measurable properties based on the concentration of hydrogen. When hydrogen is extracted from the object and transferred through the sol-gel interface 102, the hydrogen can enter the hydrogen-sensitive layer 104 and cause a change in resistivity or other measurable properties of the hydrogen-sensitive layer 104. The change in measurable properties can be correlated to the hydrogen content, and calibration of the gauge 100 can reveal a quantity of hydrogen being measured.

[0040] The hydrogen-sensitive layer 104 can include at least one of palladium, palladiumbased alloys, platinum-based alloys, transition metal alloys, or metal oxide and metal-ceramic composites. Palladium can be selected for the hydrogen-sensitive layer due to the ability of palladium to absorb hydrogen and exhibit measurable property changes based on hydrogen concentration. Palladium-based alloys can include palladium alloyed with other metals to modify the hydrogen absorption characteristics, response time, or operating temperature range of the hydrogen-sensitive layer. Platinum-based alloys can similarly be employed in the hydrogen-sensitive layer to provide hydrogen sensitivity with different performance characteristics than pure palladium. Transition metal alloys can include alloys of metals from the transition metal series that exhibit hydrogen sensitivity through various mechanisms including hydride formation, lattice expansion, or electronic structure changes. Metal oxide and metal-ceramic composites can provide hydrogen sensitivity through surface reactions, changes in electrical conductivity, or other mechanisms that produce measurable property changes in response to hydrogen concentration.

[0041] In some embodiments, the hydrogen-sensitive layer 104 can include palladium with a thickness of approximately 50 micrometers. In some embodiments, the hydrogen-sensitive layer 104 can include palladium with a thickness of approximately 228 micrometers. The thickness of the hydrogen-sensitive layer 104 can be selected based on the desired sensitivity, response time, and hydrogen storage capacity for a particular application. A thinner hydrogen-sensitive layer 104 can provide faster response times due to reduced diffusion distances for hydrogen within the layer. A thicker hydrogen-sensitive layer 104 can provide greater hydrogen storage capacity and can accommodate higher hydrogen concentrations without saturation effects that could affect measurement accuracy.

[0042] In some embodiments, the hydrogen-sensitive layer 104 can include palladium foil with 99.99% purity (trace metals basis). High purity palladium can provide consistent andAttorney Docket No. MIT 26274 PCT | 88212-432506reproducible hydrogen absorption behavior, which can facilitate calibration of the device and correlation of measurable property changes to hydrogen content. The trace metals basis purity specification can indicate that the palladium contains minimal impurities from other metallic elements, which can affect the baseline properties and hydrogen response characteristics of the hydrogen-sensitive layer. Impurities in the palladium can alter the baseline resistivity, hydrogen diffusion rate, and hydride formation behavior, and thus high purity palladium can provide more predictable and consistent performance across multiple devices and measurements.

[0043] The hydrogen-sensitive layer can have a baseline resistivity of approximately 1.045 X 10-5+ 2.081 X 10~7fl ■ cm. This baseline resistivity value can be measured prior to hydrogen exposure and can serve as a reference point for quantifying hydrogen content based on resistivity changes. The baseline resistivity can be slightly lower than literature values for pure palladium, which can reflect the presence of trace impurities in the palladium material. The uncertainty in the baseline resistivity measurement can be accounted for during calibration of the device to ensure accurate hydrogen content quantification.

[0044] As further shown in FIGS. 2A-2C, the gauge 100 can include a terminal layer 108 disposed adjacent to one or more of the sol-gel interface 102 or the hydrogen-sensitive layer 104. The terminal layer 108 can include a first terminal 108a and a second terminal 108b configured to support an electrical potential therebetween. The first terminal 108a and the second terminal 108b can be connected to the cables 110 for delivering an electric current to the first terminal 108a and the second terminal 108b to establish an electric potential therebetween. The cables 110 can extend from the gauge 100 and can be configured for connection to external measurement equipment or power sources, as described further below.

[0045] The gauge 100 can further include an insulation layer 106 that separates the first terminal 108a from the second terminal 108b. The insulation layer 106 can prevent electrical shorting between the first terminal 108a and the second terminal 108b, thereby maintaining the electrical potential therebetween during operation of the gauge 100. As shown, the insulation layer 106 can be positioned between the first terminal 108a and the second terminal 108b to electrically isolate the terminals from one another while permitting the electrochemical extraction process to proceed.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0046] In the illustrated embodiment shown in FIG. 2A, the first terminal 108a is configured as an outer ring terminal and the second terminal 108b is configured as an inner ring terminal in a concentric arrangement. The first terminal 108a is shown marked with positive symbols, and the second terminal 108b is shown marked with a negative symbol. These positive and negative charges can then be transferred to the adjacent sol -gel interface 102 disposed adjacent to the first terminal 108a and the second terminal 108b in anticipation of an electric potential applied therebetween, as discussed with respect to FIGS. 2B-2C below. This concentric ring configuration can provide a defined interaction volume for hydrogen extraction from the object. The distance between the first terminal 108a and the second terminal 108b, as well as the configuration of the first terminal 108a and the second terminal 108b relative to the metal surface, can have minimal margin of error from one surface to another when viewed locally, which can ensure straightforward gauge and material calibration.

[0047] It will be appreciated that the first terminal 108a and the second terminal 108b can be interchanged, such that the positive and negative terminals can be reversed from that shown in the figures. For example, the first terminal 108a can be configured as the inner ring terminal and the second terminal 108b can be configured as the outer ring terminal in alternative embodiments. Consistent positioning of the first terminal 108a and the second terminal 108b can be maintained to ensure a consistent hydrogen extraction process, where the interaction volume of hydrogen in the metal with the terminals remains constant. Flexible terminal positioning can be possible if supported by simulation and modeling data.

[0048] In a method of measuring hydrogen content, the gauge 100 can be placed adjacent to an object to extract and measure hydrogen content without destructively penetrating, invading, or otherwise deforming the object. It will be appreciated that for the purposes of the present disclosure, the term “adjacent” can refer to the gauge 100 being disposed on, in contact with, or at a small enough distance relative to an object to allow extraction and / or measurement of hydrogen content from the object via, for example, application of an action potential.. FIGS. 2B-2C illustrate the process of measuring the hydrogen content in greater detail. For example, FIG. 2B shows the gauge 100 positioned proximate to the object 10 prior to hydrogen extraction, with the sol -gel interface 102 in proximity, but not yet in contact, with the surface of the object 10. That is, when the gauge 100 is positioned proximate to the object 10, an electric potential is not yet applied between the first terminal 108a and the second terminal 108b to initiate the electrochemical extraction process. In thisAttorney Docket No. MIT 26274 PCT | 88212-432506proximate position, the sol-gel interface 102 disposed proximate to the first terminal 108a can have positive charge and the sol-gel interface 102 disposed proximate to the second terminal 108b has a negative charge, as shown in FIGS. 2A-2B.

[0049] FIG. 2C shows the gauge 100 during operation, e.g., when the gauge 100 is in contact with the surface of the object 10. In this orientation, an electric potential can be applied between the first terminal 108a and the second terminal 108b to initiate the electrochemical extraction process, causing hydrogen atoms to be driven from the object 10 through the sol-gel interface 102 as hydrogen ions and into the hydrogen-sensitive layer 104 as hydrogen atoms, as indicated by the H+ symbols and directional arrows, while the positive and negative charges transfer to the object 10.

[0050] The electrochemical extraction process employed by the gauge 100 can remove hydrogen from a localized portion of the metal while simultaneously measuring the hydrogen content in a defined interaction volume. For example, the device 100 of the present disclosure employs electrochemical pumping to extract and store hydrogen, including trapped and bonded hydrogen, rather than relying solely on diffusion-based extraction. This electrochemical storage approach is distinct from conventional methods that use direct chemical reaction, gas-phase storage, or mechanical reaction to store hydrogen. By mobilizing, pumping, collecting, concentrating, storing, and detecting hydrogen content, the device 100 can measure not only diffusible hydrogen but also trapped hydrogen and bonded hydrogen, which yields more comprehensive and accurate results than conventional sensors that measure hydrogen flux alone. Conventional flux-based measurements focus on diffusible hydrogen and perform direct measurement, but if the flux is not high enough, the measurement becomes less sensitive due to a low signal-to-noise ratio where noise overtakes the signal. The device 100 of the present disclosure overcomes this limitation by concentrating hydrogen into the hydrogen-sensitive material 104 and amplifying the signal brought by the hydrogen, thereby achieving higher sensitivity and more accurate measurements.

[0051] The measurement of trapped and bonded hydrogen increases measurement accuracy at least because hydrogen can bond or react to form various compounds, such as hydrides, within the conductive material, which would be undetectable by conventional sensors that measure hydrogen flux. Conventional methods based on diffusion equations are designed to detect diffusible hydrogen, but in many cases, hydrogen does not diffuse freely because the hydrogen becomes bonded and forms different chemical compounds inside the metal.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0052] The sol-gel of the present disclosure differs from conventional liquid electrolytes, such as those used in Devanathan-Stachurski (DS) cells. Conventional DS cells employ liquid electrolytes that measure hydrogen flux, which is the rate at which hydrogen diffuses through a material. These liquid electrolytes can measure hydrogen content in a substance flowing through an object, but cannot accurately quantify hydrogen in the object itself because conventional means lack the ability to extract and concentrate hydrogen from the metal. The hydrogen flux measurement performed by conventional DS cells focuses on measuring diffusible hydrogen, which is integrated with time and taken as a direct measurement. However, the flux concentration is often not high enough to make an accurate measurement, resulting in decreased sensitivity, inaccurate values, and a low signal-to-noise ratio where noise overtakes the signal.

[0053] The electrochemical hydrogen extraction process of the present disclosure differs from conventional Devanathan-Stachurski (DS) cell technology in that the device 100 applies voltage to actively extract hydrogen atoms 112 from the object 10, rather than relying on natural diffusion processes. For example, the sol-gel of the present disclosure can enable hydrogen extraction and concentration rather than merely measuring hydrogen flux. By collecting, concentrating, and storing hydrogen in the hydrogen-sensitive layer 104 before measurement, the device 100 can achieve enhanced signal-to-noise ratio and increased sensitivity compared to conventional flux-based measurements. The electrochemical pumping approach can also extract trapped and bonded hydrogen by providing sufficient electrochemical driving force to break the bonds holding the hydrogen at trapping sites or in hydride compounds, providing more comprehensive hydrogen content measurement than conventional diffusion-based methods.

[0054] As mentioned above, when voltage is applied to the gauge 100, a positive potential can be created that extracts hydrogen atoms from the object 10. The hydrogen atoms in the metal can be oxidized to form hydrogen ions (H+) at the interface between the object 10 and the sol-gel. As discussed above with respect to FIG. 2C, the sol-gel can function as an ion channel that transports the hydrogen ions from the object toward the hydrogen-sensitive layer 104. This electrochemical extraction process can mobilize, pump, collect, and concentrate hydrogen from the object into the hydrogen-sensitive layer 104, where the hydrogen content can be quantified based on measurable property changes.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0055] The sol-gel can be optimized for hydrogen extraction by adjusting the composition, consistency, and application parameters. In some embodiments, the sol-gel can have varying consistency ranging from more gel-like to more liquid depending on the application. A more gel-like consistency can be suitable for vertical or overhead applications where the sol-gel should remain in place against gravity. A more liquid consistency can be suitable for applications where the sol-gel should flow into surface features or conform to complex geometries. The consistency of the sol-gel can be adjusted by varying the proportions of sepiolite clay, phosphoric acid, and water in the acid-in-clay electrolyte formulation.

[0056] In some embodiments, the sol-gel can be housed in a disposable cartridge (not shown) that is attached to the gauge 100. The disposable cartridge can contain a premeasured quantity of the sol-gel, which can simplify field deployment of the gauge by eliminating the need for manual preparation and application of the sol-gel. The disposable cartridge can be replaced after each measurement or after a predetermined number of measurements, depending on the application requirements. This cartridge-based configuration can facilitate consistent sol-gel application across multiple measurements and can reduce variability introduced by manual sol-gel preparation.

[0057] In the hydrogen content measuring device 100, the one or more measurable properties that can change based on hydrogen concentration can include one or more of impedance, elastic modulus, absorptivity, reflectivity of electromagnetic radiation, residual stress, expansion / contraction, or magnetic properties. Resistivity can represent one measurable property that changes as hydrogen enters the hydrogen-sensitive layer 104, where the resistivity of palladium can increase with increasing hydrogen content due to scattering of conduction electrons by hydrogen atoms in the palladium lattice. Impedance can change with hydrogen concentration due to alterations in the electrical characteristics of the hydrogensensitive layer 104 at various frequencies.

[0058] In some embodiments, elastic modulus of the hydrogen-sensitive layer 104 can change with hydrogen concentration as hydrogen atoms occupy interstitial sites in the crystal lattice and modify the bonding characteristics of the material. Absorptivity and reflectivity of electromagnetic radiation can change with hydrogen concentration due to modifications in the electronic structure and optical properties of the hydrogen-sensitive layer. Residual stress in the hydrogen-sensitive layer can change with hydrogen concentration as hydrogen absorption can cause lattice expansion and introduce internal stresses in thematerial. Expansion and contraction of the hydrogen-sensitive layer 104 can occur asAttorney Docket No. MIT 26274 PCT | 88212-432506hydrogen enters or exits the material, causing dimensional changes that can be measured using appropriate techniques. Magnetic properties of the hydrogen-sensitive layer can change with hydrogen concentration in materials where hydrogen absorption affects the magnetic susceptibility or other magnetic characteristics.

[0059] The selection of which measurable property to monitor can depend on the application requirements, available measurement equipment, and desired sensitivity and response characteristics. Resistivity measurement using a four-point probe technique can provide a straightforward and reliable method for quantifying hydrogen content in the hydrogen-sensitive layer. Other measurable properties can be monitored using appropriate sensors and measurement techniques, and multiple measurable properties can be monitored simultaneously to provide redundant measurements or to characterize different aspects of the hydrogen absorption process.

[0060] Referring to FIG. 3, the electrochemical hydrogen extraction process from the object 10 is illustrated schematically. FIG. 3 depicts a cross-sectional view of the object 10 during operation, showing the extraction of hydrogen atoms 112 from the object 10, e.g., a hydrogen-containing alloy, and the transport of hydrogen ions 114 through the sol-gel interface 102. As shown, the hydrogen-containing alloy can serve as a working electrode positioned at an upper portion of the object 10. The sol-gel interface 102, identified as an acid-in-clay electrolyte, can be disposed beneath the hydrogen-containing alloy. The hydrogen-sensitive layer, or counter electrode 104 as pertaining to an electrochemical cell, can be positioned at a bottom portion of the object 10, below the sol-gel interface 102.

[0061] With continued reference to FIG. 3, the hydrogen atoms 112 are represented as solid dots distributed throughout the hydrogen-containing alloy 10 at grain boundaries and other microstructural features. A power source 118 can be connected to the object 10, with a positive terminal 108a connected to the hydrogen-containing alloy 10 and being associated with a positive (+) source of the power source 118 via a first wire 110b (see FIG. 2B), and a negative terminal 108b connected to the counter electrode 104 and being associated with a negative (-) source of the power source 118 via a second wire 110a (see FIG. 2B). When an electric potential is applied between the positive terminal 108a and the negative terminal 108b, the electric potential creates positive and negative portions of the sol-gel interface 102. The applied electric potential can establish an electrochemical driving force that extracts the hydrogen atoms 112 from the hydrogen-containing alloy 10 and drives the hydrogen atoms 112 toward the sol -gel interface 102.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0062] As further shown in FIG. 3, the applied electric potential can lead to the negative terminal 108b extracting the hydrogen atoms 112 from the object 10 using one or more charge carriers in the sol-gel interface 102 to form an ion channel. At the interface between the hydrogen-containing alloy 10 and the sol-gel interface 102, the hydrogen atoms 112 can be oxidized to form the hydrogen ions 114, represented as circled dots in FIG. 3. The hydrogen ions 114 can migrate from the hydrogen-containing alloy 10 through the sol-gel interface 102 toward the counter electrode 104 under the influence of the applied electric potential. The sol-gel interface 102 can function as an ion channel that transports the hydrogen ions 114 from the object 10 toward the hydrogen-sensitive layer 104, where the hydrogen ions 114 can be reduced back to hydrogen atoms and stored within the hydrogensensitive layer 104.

[0063] In a method of measuring hydrogen content, an electric potential can be applied to the first terminal 108a and the second terminal 108b to initiate the electrochemical extraction process. Hydrogen can be extracted from the object 10 into the hydrogen-sensitive layer 104 as the applied electric potential drives the hydrogen atoms 112 out of the object 10 and through the sol-gel interface 102. The hydrogen content can be measured by monitoring changes in one or more measurable properties of the hydrogen-sensitive layer 104 while the gauge 100 remains in contact with the object 10.

[0064] In the method of measuring hydrogen content, extracting hydrogen from the object can further comprise each of mobilizing, pumping, collecting, concentrating, storing, or detecting hydrogen content in the extracted hydrogen. The electrochemical extraction process can mobilizes hydrogen atoms 112 from their locations within the metal structure, pump the hydrogen atoms 112 out of the object 10, collect and concentrate the hydrogen in the hydrogen-sensitive layer 104, and store the hydrogen for subsequent detection and measurement. In some embodiments, the device 100 can be configured to one or more of pump, collect, concentrate, store, or detect the hydrogen content from the object 10 to measure a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen.

[0065] The electrochemical extraction process employed by the device 100 can extract all three types of hydrogen by providing sufficient electrochemical driving force to overcome the binding energies of trapped and bonded hydrogen in addition to diffusible hydrogen. For example, in the method of measuring hydrogen content, measuring the content of the hydrogen can further include measuring a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen. By applying an appropriate electric potential for aAttorney Docket No. MIT 26274 PCT | 88212-432506sufficient duration, the electrochemical extraction process can extract hydrogen from various binding sites within the metal. The total hydrogen content measured by the device 100 can therefore represent the sum of diffusible hydrogen, trapped hydrogen, and bonded hydrogen extracted from the interaction volume defined by the gauge 100 configuration.

[0066] The hydrogen sensing device 10 can operate with an applied voltage of about 1.5 V for hydrogen extraction from the object into the hydrogen-sensitive layer 104. The hydrogen extraction process can be performed for a duration of approximately 3 hours. The time, size, and voltage of extraction can be controlled for consistent measurements across different objects and applications. By controlling the extraction time, the interaction volume from which hydrogen can be extracted can be defined. By controlling the applied voltage, the electrochemical driving force for hydrogen extraction can be adjusted to optimize extraction efficiency for different materials and hydrogen binding states. Moreover, by controlling the size of the gauge 100 and the terminal configuration, the area from which hydrogen is extracted can be defined.

[0067] In the method of measuring hydrogen content, optimizing the sol-gel interface 102 for hydrogen extraction can comprise adjusting the composition, consistency, and application parameters of the sol-gel. The sol-gel interface 102 can be optimized to provide efficient ion transport while maintaining effective contact with the object surface. The ionic conductivity of the sol-gel interface 102 can be adjusted by varying the concentration of phosphoric acid in the acid-in-clay electrolyte formulation. The mechanical properties of the sol-gel interface 102 can be adjusted by varying the proportion of sepiolite clay to achieve the desired consistency for a particular application. The sol-gel interface 102 can be optimized to minimize electrical resistance in the extraction circuit, which can enable efficient hydrogen extraction at the applied voltage of 1.5 V.

[0068] Referring to FIGS. 4A-4B, a sensor prototype assembly 200 for hydrogen content measurement is illustrated. FIG. 4A shows a front perspective view of a circular sensor body 201, and FIG. 4B shows a rear perspective view of the sensor assembly 200. The sensor prototype 200 can demonstrate a portable and field-deployable design for non-destructive hydrogen content quantification, where the compact configuration of the sensor prototype 200 allows for application to metal surfaces in field environments without use of laboratory equipment or destructive sampling of the object being measured.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0069] With continued reference to FIG. 4A, the main body 201 can be made of 6061 aluminum. The 6061 aluminum body can provide structural support for the sensor components and serve as part of the electrode assembly. The main body 201 can feature a disc-shaped configuration with a central recessed area that can accommodate the hydrogensensitive layer 204 and sol-gel interface 202 during operation. With continued reference to FIGS. 4A-4B, the cables 210 can include 16-gauge solid copper wiring for electrical connections with two terminals a visible on the sensor body, including a negative terminal 208b and a positive terminal 208a, which are configured to support an electrical potential therebetween for driving the electrochemical hydrogen extraction process. Two wires 210 can extend from the sensor body, with a first wire 210b connected to the negative terminal 208b and a second wire 210a connected to the positive terminal 210a for forming connection with corresponding positive and negative terminals of a power source. The 16-gauge solid copper wiring can provide sufficient current-carrying capacity for the electrochemical extraction process while maintaining flexibility for field deployment applications.

[0070] As further shown in FIG. 4B, the gauge includes an acrylic insulation backing 206. The acrylic insulation backing 206 can separate the positive and negative terminals 208a, 208b to prevent electrical shorting during operation of the gauge 200. The insulation backing 206 can appear as a white disc-shaped component positioned at the rear of the sensor assembly. The acrylic material 206 can provide electrical isolation between the terminals 208a, 208b while maintaining structural integrity of the gauge assembly 200. The insulation backing 206 can be secured to the aluminum main body to form an integrated sensor unit that can be handled and positioned on a surface of the object 10 for hydrogen content measurement.

[0071] The hydrogen-sensitive layer 204 can be attached to the gauge body 201 using conductive adhesives. The conductive adhesives can provide both mechanical attachment and electrical connection between the hydrogen-sensitive layer 204 and the terminal structure 208 of the gauge 200. The conductive adhesives can conform to the surface of the hydrogensensitive layer 204 and the gauge body 201 to establish reliable electrical contact for resistivity measurement using a four-point probe technique. The use of conductive adhesives for attachment can facilitate replacement of the hydrogen-sensitive layer 204 between measurements or after the hydrogen-sensitive layer 204 has been saturated with hydrogen from previous extraction operations. In some embodiments, the conductive adhesives can include a copper tape.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0072] The components of the gauge 100, 200 can work together to electrochemically extract, concentrate, and quantify hydrogen content from the object 10. This coordinated operation enables fast, portable, and non-destructive quantification of hydrogen within metals used in hydrogen infrastructure. The prototype fabrication demonstrates that the gauge 200 can be constructed from readily available materials at relatively low cost compared to conventional hydrogen sensing equipment. The 6061 aluminum main body 201, acrylic insulation backing 206, 16-gauge solid copper wiring 210, and copper tape attachment method represent materials and fabrication techniques that can be implemented without specialized manufacturing equipment. The compact design of the prototype 200 can allow for portable application to metal surfaces for non-destructive hydrogen content quantification in field environments such as pipeline inspection sites, hydrogen storage facilities, and industrial processing plants.

[0073] Referring to FIG. 5, a graph illustrates palladium resistivity as a function of hydrogen insertion time, demonstrating the measurable property changes that occur in the hydrogen-sensitive layer as hydrogen content increases. The vertical axis represents palladium resistivity measured in ohm-centimeters multiplied by ten to the negative fifth power, with values ranging from approximately 1.050 to 1.225. The horizontal axis represents time of hydrogen insertion measured in hours, with values ranging from 0 to 6 hours. The graph includes two data series distinguished by different markers, where circular markers represent hydrogen charged using liquid electrolyte and diamond markers represent hydrogen transferred into palladium using solgel.

[0074] With continued reference to FIG. 5, an initial data point is labeled near the origin at approximately 1.050 x 105ri • cm at time zero, representing the baseline resistivity of the palladium prior to hydrogen exposure. The circular markers show resistivity values at approximately 1 hour, 2 hours, and 6 hours of hydrogen insertion, demonstrating an increasing trend in palladium resistivity with increasing hydrogen insertion time. The resistivity can increase from the baseline value of approximately 1.050 x 10-5 / 2 • cm to approximately 1.225 x 10-512 • cm after 6 hours of hydrogen charging. The diamond marker appears at approximately 3 hours, showing a resistivity value that falls between the 2-hour and 6-hour measurements from the liquid electrolyte charging method. The data demonstrates that palladium resistivity increases with hydrogen content regardless of the hydrogen insertion method employed, confirming that the sol-gel based extraction method produces comparable results to liquid electrolyte charging methods.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0075] As further shown in FIG. 5, the resistivity increased approximately linearly with hydrogen content during the first two hours of charging. The 6-hour data point deviates from this linear trend, which can be attributed to hydride formation within the palladium at higher hydrogen concentrations. This behavior suggests an upper hydrogen concentration limit beyond which resistivity is no longer a reliable proxy for hydrogen content. Below this limit, however, resistivity can provide a robust and predictable measure of hydrogen concentration in palladium, enabling quantitative correlation between resistivity changes and hydrogen content in the object being measured.

[0076] The device 100, 200 can include a four-point probe measurement system for measuring resistivity changes in the hydrogen-sensitive layer 104, 204. The four-point probe measurement technique can employ four electrical contacts arranged in a linear or other geometric configuration on the surface of the hydrogen-sensitive layer. A current can be passed through the outer two contacts, and a voltage can be measured across the inner two contacts. The resistivity can be calculated from the measured voltage, applied current, and geometric factors related to the probe spacing and sample thickness. The four-point probe technique can eliminate contact resistance effects that would otherwise introduce measurement errors, thereby providing accurate resistivity measurements of the hydrogensensitive layer.

[0077] In some embodiments, a separate resistance detection circuit can be connected directly to the hydrogen-sensitive layer to monitor resistivity changes in real-time. The resistance detection circuit can be integrated into the gauge assembly or can be provided as external measurement equipment connected to the gauge via the cable. Real-time monitoring of resistivity changes can enable continuous tracking of hydrogen extraction progress during the measurement process. The resistance detection circuit can provide feedback that indicates when sufficient hydrogen has been extracted into the hydrogen-sensitive layer for accurate quantification, or can indicate when the hydrogen-sensitive layer is approaching saturation and should be discharged before further measurements.

[0078] The device 100, 200 can achieve a limit of detection of less than or equal to 10 ppm for hydrogen content. This limit of detection can represent a minimum hydrogen concentration that can be reliably distinguished from baseline noise in the measurement system. The limit of detection of less than or equal to 10 ppm can be achieved through the concentration of hydrogen from the object into the hydrogen-sensitive layer, which amplifies the signal produced by the extracted hydrogen. The concentration process can increase theAttorney Docket No. MIT 26274 PCT | 88212-432506effective hydrogen concentration in the hydrogen-sensitive layer relative to the hydrogen concentration in the object 10, thereby enabling detection of lower hydrogen concentrations than would be possible with direct flux measurement methods.

[0079] The limit of detection of less than or equal to 10 ppm can represent a significant improvement over conventional palladium-based hydrogen sensors, which can have limits of detection of 700 ppm or higher. The improved limit of detection can enable earlier detection of hydrogen accumulation in metal infrastructure, providing additional time for preventative maintenance before hydrogen concentrations reach levels that could cause hydrogen embrittlement or structural failures. The limit of detection can be affected by factors including the sensitivity of the resistivity measurement system, the noise floor of the measurement electronics, the efficiency of hydrogen extraction from the object 10, and the hydrogen absorption characteristics of the hydrogen-sensitive layer material 104, 204.

[0080] The device 100, 200 can be calibrated using thermal desorption spectroscopy (TDS) to establish a quantitative relationship between palladium resistivity change and hydrogen concentration. TDS can be employed to determine the absolute hydrogen concentration in a metal sample after the gauge has been applied to the sample for a fixed duration and voltage. In the calibration process, the gauge can be applied to a hydrogen-charged metal sample, and the resistivity change in the hydrogen-sensitive layer can be measured. The metal sample can then be analyzed using TDS to determine the absolute hydrogen concentration that was present in the sample. By performing multiple trials with metal samples having different hydrogen contents, a quantitative relationship between palladium resistivity change and hydrogen concentration can be established.

[0081] Metals with different hydrogen contents can be tested to calibrate and align the hydrogen content with the palladium resistivity increase. The calibration process can involve preparing a series of metal samples with known or controlled hydrogen concentrations, applying the gauge 100, 200 to each sample under consistent operating conditions, measuring the resulting resistivity change in the hydrogen-sensitive layer, and correlating the resistivity change to the hydrogen concentration determined by TDS. This calibration can enable direct calculation of hydrogen content in a metal based on resistivity measurements obtained from the gauge. The calibration can be repeated with different materials of interest to establish material-specific relationships between resistivity change and hydrogen concentration, as different metals and alloys can exhibit different hydrogen absorption and release characteristics that affect the extraction efficiency.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0082] The hydrogen charging of the object for testing purposes can be performed using an aqueous electrolyte consisting of about 30 g / L NaCl and about 3 g / L NH4SCN in distilled water. The metal sample can serve as the cathode and a platinum electrode can serve as the anode during the charging process. A negative current density of — 5A / m2can be applied to reduce hydrogen at the metal surface and drive hydrogen into the sample. This electrochemical charging method can introduce controlled amounts of hydrogen into the metal sample for calibration purposes. The charging duration can be varied to produce samples with different hydrogen concentrations, where longer charging times can result in higher hydrogen concentrations in the metal.

[0083] Operating parameters including voltage and time can be adjusted for reliable measurements with different materials and prototype configurations. The operating voltage can be adjusted based on the electrical resistance of the sensor assembly and the electrochemical characteristics of the material being measured. Higher applied voltages can be employed when additional electrical resistance is introduced by the sensor assembly, which can occur in certain prototype geometries or when measuring materials with different surface conditions. The operating time can be adjusted based on the hydrogen concentration in the material being measured and the desired sensitivity of the measurement. Longer extraction times can enable more complete extraction of hydrogen from the interaction volume, while shorter extraction times can be sufficient for materials with higher hydrogen concentrations.

[0084] The hydrogen-sensitive layer can be discharged to remove hydrogen via electrolytic charging in 0.1 M NaOH solution, allowing the sensor to be reused multiple times. In the discharge process, the hydrogen-sensitive layer 104 can serve as the anode and a platinum electrode can serve as the cathode. A voltage of 1.5 V can be applied for approximately 7 hours to drive hydrogen out of the hydrogen-sensitive layer, where the hydrogen can recombine into H2 gas at the platinum surface. Following the discharge process, the resistivity of the hydrogen-sensitive layer can return to approximately the baseline value, with a small increase that can be attributed to hydrogen trapped at grain boundaries or other defects within the hydrogen-sensitive layer. This small residual increase in resistivity can be accounted for during subsequent measurements by establishing a new baseline resistivity value after each discharge cycle.Attorney Docket No. MIT 26274 PCT | 88212-432506

[0085] The reversibility of the hydrogen uptake process can allow a single hydrogensensitive layer to be reused multiple times, providing perpetual use of the gauge with minimal maintenance costs. The gauge 100, 200 can be operated without frequent calibration or consumable replacement, as the hydrogen-sensitive layer can be discharged and reused rather than replaced after each measurement. The sol-gel 102, 202 used in the gauge can be durable and can resist repeatable charging cycles, further contributing to the reusability of the gauge 100, 200. This reusability can reduce the cost per measurement and can make the gauge economically viable for applications requiring frequent or continuous hydrogen content monitoring.

[0086] The device 100, 200 can be fabricated as a MEMS (microelectromechanical systems) device or semiconductor device where the sensor and paste are integrated in a silicon wafer. It will be appreciated that MEMS refers to miniaturized mechanical and electromechanical elements that are made using microfabrication techniques. In a MEMS-based implementation, the hydrogen-sensitive layer 104, 204, the sol-gel interface 102, 202, the terminals 108, 208, and the insulation layer 106, 206 can be fabricated on a silicon substrate using semiconductor manufacturing processes such as thin film deposition, photolithography, and etching. The integration of the sensor and paste in a silicon wafer can enable a conformal interface for pumping hydrogen to the hydrogen-sensitive material 104, where the conformal interface can conform to surface features of the object being measured and can maintain effective contact for electrochemical hydrogen extraction.

[0087] The MEMS-based or semiconductor-based implementation can provide several capabilities for hydrogen content measurement applications. The miniaturization achievable through MEMS fabrication can enable deployment of multiple sensors across a structure for distributed hydrogen content monitoring. The semiconductor manufacturing processes used for MEMS fabrication can enable batch production of multiple devices on a single wafer, which can reduce per-unit manufacturing costs for high-volume applications. The integration of the sensor and paste in a silicon wafer can also enable incorporation of additional electronic components, such as signal conditioning circuits, analog-to-digital converters, and communication interfaces, on the same substrate as the hydrogen sensing elements.

[0088] The device 100, 200 can operate both continuously for real-time monitoring and periodically for scheduled inspections. In continuous operation mode, the device 100, 200 can remain in contact with the object 10 and can perform ongoing extraction and measurement of hydrogen content to track changes in hydrogen concentration overAttorney Docket No. MIT 26274 PCT | 88212-432506time. Continuous operation can be suitable for applications where hydrogen accumulation rates are high or where early detection of hydrogen ingress is desired, such as in hydrogen gas turbines where turbine blades face changing gradients of pressure and temperature that make hydrogen embrittlement unpredictable. In periodic operation mode, the device 100, 200 can be applied to the object 10 at scheduled intervals to perform discrete measurements of hydrogen content. Periodic operation can be suitable for applications where hydrogen accumulation rates are lower or where continuous monitoring is not practical due to access constraints or operational considerations.

[0089] The measurement process also removes hydrogen from the localized portion of the metal, thereby prolonging the life of that region against hydrogen damage if hydrogen removal is desired. The electrochemical extraction process that transfers hydrogen from the object into the hydrogen-sensitive layer simultaneously depletes the hydrogen content in the interaction volume of the object. This hydrogen removal can reduce the local hydrogen concentration in the metal, which can slow or prevent hydrogen embrittlement processes that would otherwise degrade the mechanical properties of the metal over time. In applications where hydrogen removal is desired in addition to hydrogen content measurement, the device can be operated for extended durations or at higher applied voltages to extract greater quantities of hydrogen from the object. The dual functionality of hydrogen measurement and hydrogen removal can provide both diagnostic information about current hydrogen levels and therapeutic benefit by reducing hydrogen concentrations in the measured region.

[0090] The device 100, 200 can provide several advantages over conventional systems for hydrogen content measurement. As mentioned above, the device 100 can measure all forms of hydrogen, including diffusible, trapped, and bonded hydrogen. Moreover, the device 100, 200 can enable proactive safety measures to prevent hydrogen-induced structural failures by detecting hydrogen accumulation before crack formation or hydrogen leakage occurs.

[0091] The ability to monitor hydrogen levels using the device can enable use of less expensive alloys with reduced coating and maintenance requirements in hydrogen infrastructure applications. Conventional approaches to managing hydrogen embrittlement risk can involve using more expensive alloys that are resistant to hydrogen embrittlement, applying protective coatings to prevent hydrogen ingress, and performing frequent maintenance to detect and repair hydrogen-related damage. When hydrogen levels can be monitored using the device, less expensive alloys can be employed because hydrogen accumulation can be detected before reaching levels that would cause embrittlement orAttorney Docket No. MIT 26274 PCT | 88212-432506structural failure. Coating requirements can be reduced because hydrogen ingress can be monitored directly rather than relying solely on coatings to prevent hydrogenentry. Maintenance intervals can be optimized based on actual hydrogen content measurements rather than conservative schedules designed to account for uncertainty in hydrogen accumulation rates. These capabilities can reduce material costs, coating costs, and maintenance costs for hydrogen infrastructure while maintaining or improving safety through proactive hydrogen content monitoring.

[0092] Examples of the above-described embodiments can include the following:1. A hydrogen content measuring device, comprising:an interface layer having a compound on a surface thereof that is configured to contact an object non-destructively to facilitate extraction of hydrogen therefrom;a hydrogen-sensitive layer that is configured to change one or more measurable properties based on a concentration of hydrogen; anda first terminal and a second terminal configured to support an electrical potential therebetween,wherein the device is configured to one or more of electrochemically pump, collect, concentrate, or store hydrogen content from the object to non-destructively measure a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen.2. The device of example 1, wherein the compound comprises a sol-gel having a pastelike consistency.3. The device of example 2, wherein the sol-gel includes an acid-in-clay electrolyte. 4. The device of example 3, wherein the acid-in-clay electrolyte comprises sepiolite clay and phosphoric acid.5. The device of any of examples 1 to 4, wherein the object comprises a conductive material comprising at least one of a metal or an alloy.6. The device of any of examples 1 to 5, wherein the hydrogen-sensitive layer comprises at least one of palladium, palladium-based alloys, platinum-based alloys, transition metal alloys, or composite of metal oxide and metal-ceramic.7. The device of example 6, wherein the hydrogen-sensitive layer comprises palladium having a purity of at least 99.99% trace metals basis.8. The device of any of examples 1 to 7, wherein the object comprises one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines.Attorney Docket No. MIT 26274 PCT | 88212-4325069. The device of any of examples 1 to 8, wherein the one or more measurable properties comprises one or more of resistivity, impedance, elastic modulus, absorptivity, reflectivity of electromagnetic radiation, residual stress, expansion, contraction, or magnetic properties. 10. The device of any of examples 1 to 9, further comprising an insulation layer that separates the first terminal from the second terminal.11. The device of any of examples 1 to 10, wherein the first terminal is configured as an outer ring terminal and the second terminal is configured as an inner ring terminal in a concentric arrangement.12. The device of any of examples 1 to 11, wherein the device is configured to achieve a limit of detection of less than or equal to 10 ppm for hydrogen content.13. The device of any of examples 1 to 12, wherein the device is configured to preserve an operational capability of the object during and after measurement of the hydrogen content.14. The device of any of examples 1 to 13, wherein the hydrogen-sensitive layer is configured to be discharged to remove hydrogen therefrom to allow the hydrogen-sensitive layer to be reused for subsequent measurements.15. A method of non-destructively measuring hydrogen content, comprising:non-destructively placing a gauge adjacent to an object;applying an electrical potential between the first terminal and the second terminal to deliver an electric current therebetween;electrochemically extracting hydrogen from the object through the interface layer into the hydrogen-sensitive layer; andmeasuring a content of the hydrogen extracted into the hydrogen-sensitive layer non-destructively.16. The method of example 15, wherein electrochemically extracting hydrogen from the object further comprises one or more of mobilizing, pumping, collecting, concentrating, or storing hydrogen content from the object.17. The method of example 16, wherein measuring the content of the hydrogen further comprises measuring a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen.18. The method of any of examples 15 to 17, wherein the compound is a sol -gel having a paste-like consistency that conforms to a surface of the object.Attorney Docket No. MIT 26274 PCT | 88212-43250619. The method of example 18, wherein the sol-gel includes an acid-in-clay electrolyte comprising sepiolite clay and phosphoric acid.20. The method of any of examples 15 to 19, wherein the object is a conductive material comprising a metal or an alloy.21. The method of example 20, wherein the object comprises one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines.22. The method of any of examples 15 to 21, wherein the applied electrical potential leads to extraction of hydrogen atoms from the object using one or more charge carriers in the gauge to form an ion channel.23. The method of any of examples 15 to 22, further comprising preserving an operational capability of the object during and after measurement of the hydrogen content by maintaining the gauge adjacent to the object without deforming the object throughout the measuring step.24. The method of any of examples 15 to 23, further comprising discharging the hydrogen-sensitive layer to remove hydrogen therefrom after measuring the content of the hydrogen, thereby allowing the hydrogen-sensitive layer to be reused for subsequent measurements.25. A non-destructive hydrogen sensing system, comprising:a gauge configured to be positioned on an outer surface of a conductive object non-destructively, the gauge comprising:a sol-gel interface comprising an acid-in-clay electrolyte configured to conform to the outer surface of the conductive object and to transport hydrogen ions extracted from the conductive object;a hydrogen-sensitive layer comprising palladium disposed adjacent to the solgel interface and configured to receive and store hydrogen transported through the sol-gel interface;a first terminal and a second terminal arranged in a concentric configuration and configured to establish an electrical potential for electrochemically driving hydrogen from the conductive object through the sol-gel interface and into the hydrogen-sensitive layer; anda measurement system configured to measure a change in resistivity of the hydrogen-sensitive layer to quantify hydrogen content extracted from the conductive object.Attorney Docket No. MIT 26274 PCT | 88212-43250626. The system of example 25, wherein the acid-in-clay electrolyte comprises sepiolite clay and phosphoric acid.27. The system of example 25 or example 26, wherein the system is configured to non-destructively measure a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen extracted from the conductive object.28. The system of example 27, wherein the system is configured to achieve a limit of detection of less than or equal to 10 ppm for hydrogen content.29. The system of any of examples 25 to 28, wherein the hydrogen-sensitive layer is configured to be discharged to remove hydrogen therefrom via electrolytic charging to allow the hydrogen-sensitive layer to be reused for subsequent measurements.30. The system of any of examples 25 to 29, wherein:the conductive object comprises one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines, andthe gauge is configured to preserve an operational capability of the conductive object during and after measurement of the hydrogen content.31. The system of any of examples 25 to 30, further comprising an insulation layer that separates the first terminal from the second terminal.

[0093] Although the procedures provided for herein are described in conjunction with performing non-destractive quantification of hydrogen content in metals and alloys, the instruments and procedures provided for herein can also be used and applied in monitoring hydrogen levels in other conductive materials, assessing hydrogen embrittlement risk in various infrastructure components, and extracting hydrogen from localized regions to prolong material life. A person skilled in the art, in view of the present disclosures, will understand how monitoring hydrogen levels in other conductive materials, assessing hydrogen embrittlement risk in various infrastructure components, and extracting hydrogen from localized regions to prolong material life can be implemented in view of the present disclosures.

[0094] 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. By way of example, the hydrogen sensing gauge described herein can be adapted for use with different hydrogen-sensitive materials, alternative sol-gel formulations, or modifiedAttorney Docket No. MIT 26274 PCT | 88212-432506terminal configurations to accommodate specific measurement requirements or environmental conditions. A person skilled in the art, in view of the present disclosures, will be able to adapt some or all of the various systems, devices, and methods disclosed herein for monitoring hydrogen content in fuel cell components, assessing hydrogen accumulation in aerospace structures, evaluating hydrogen levels in chemical processing equipment, or detecting hydrogen ingress in offshore and marine infrastructure. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

Claims

Attorney Docket No. MIT 26274 PCT | 88212-432506CLAIMSWhat is claimed is:

1. A hydrogen content measuring device, comprising :an interface layer having a compound on a surface thereof that is configured to contact an object non-destructively to facilitate extraction of hydrogen therefrom;a hydrogen-sensitive layer that is configured to change one or more measurable properties based on a concentration of hydrogen; anda first terminal and a second terminal configured to support an electrical potential therebetween,wherein the device is configured to one or more of electrochemically pump, collect, concentrate, or store hydrogen content from the object to non-destructively measure a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen.

2. The device of claim 1, wherein the compound comprises a sol-gel having a paste -like consistency.

3. The device of claim 2, wherein the sol-gel includes an acid-in-clay electrolyte.

4. The device of claim 1, wherein the object comprises a conductive material comprising at least one of a metal or an alloy.

5. The device of claim 1, wherein the hydrogen-sensitive layer comprises at least one of palladium, palladium-based alloys, platinum-based alloys, transition metal alloys, or composites of metal oxide and metal-ceramic.

6. The device of claim 5, wherein the hydrogen-sensitive layer comprises palladium having a purity of at least 99.99% trace metals basis.

7. The device of claim 1, wherein the object comprises one or more of pressure lines, hydrogen tanks, hydrogen gas turbines, nuclear reactors, or submarines.

8. The device of claim 1, wherein the one or more measurable properties comprises one or more of resistivity, impedance, elastic modulus, absorptivity, reflectivity of electromagnetic radiation, residual stress, expansion, contraction, or magnetic properties.

9. The device of claim 1, further comprising an insulation layer that separates the first terminal from the second terminal.Attorney Docket No. MIT 26274 PCT | 88212-43250610. The device of claim 1, wherein the first terminal is configured as an outer ring terminal and the second terminal is configured as an inner ring terminal in a concentric arrangement.

11. The device of claim 1 , wherein the device is configured to achieve a limit of detection of less than or equal to 10 ppm for hydrogen content.

12. The device of claim 1, wherein the device is configured to preserve an operational capability of the object during and after measurement of the hydrogen content.

13. The device of claim 1, wherein the hydrogen-sensitive layer is configured to be discharged to remove hydrogen therefrom to allow the hydrogen-sensitive layer to be reused for subsequent measurements.

14. A method of non-destructively measuring hydrogen content, comprising:non-destructively placing a gauge adjacent to an object;applying an electrical potential between the first terminal and the second terminal to deliver an electric current therebetween;electrochemically extracting hydrogen from the object through the interface layer into the hydrogen-sensitive layer; andmeasuring a content of the hydrogen extracted into the hydrogen-sensitive layer non-destructively.

15. The method of claim 14, wherein electrochemically extracting hydrogen from the object further comprises one or more of mobilizing, pumping, collecting, concentrating, or storing hydrogen content from the object.

16. The method of claim 15, wherein measuring the content of the hydrogen further comprises measuring a content of each of diffusible hydrogen, trapped hydrogen, and bonded hydrogen.

17. The method of claim 14, wherein the applied electrical potential leads to extraction of hydrogen atoms from the object using one or more charge earners in the gauge to form an ion channel.

18. The method of claim 14, further comprising preserving an operational capability of the object during and after measurement of the hydrogen content by maintaining the gauge adjacent to the object without deforming the object throughout the measuring step.Attorney Docket No. MIT 26274 PCT | 88212-43250619. The method of claim 14, further comprising discharging the hydrogen-sensitive layer to remove hydrogen therefrom after measuring the content of the hydrogen, thereby allowing the hydrogen-sensitive layer to be reused for subsequent measurements.

20. A non-destructive hydrogen sensing system, comprising:a gauge configured to be positioned on an outer surface of a conductive object non-destructively, the gauge comprising:a sol-gel interface comprising an acid-in-clay electrolyte configured to conform to the outer surface of the conductive object and to transport hydrogen ions extracted from the conductive object;a hydrogen-sensitive layer comprising palladium disposed adjacent to the solgel interface and configured to receive and store hydrogen transported through the sol-gel interface;a first terminal and a second terminal arranged in a concentric configuration and configured to establish an electrical potential for electrochemically driving hydrogen from the conductive object through the sol-gel interface and into the hydrogen-sensitive layer; anda measurement system configured to measure a change in resistivity of the hydrogen-sensitive layer to quantify hydrogen content extracted from the conductive object.

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