Structures including embedded devices and associated devices and methods for forming such structures

Abstract

A method of forming a structure includes positioning a sensor within a mold. The method further includes depositing particles of a material having a high-temperature melting point in the mold and around the sensor. The method also includes applying pressure to the material having the high-temperature melting point in the mold while heating the material having the high-temperature melting point in the mold to a sintering temperature of the particles of the material having the high-temperature melting point in the mold. The method further includes forming a fully dense solid structure from the particles of the material having the high-temperature melting point in the mold with the sensor disposed in the fully dense solid structure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a national phase entry under 35 U.S.C. § 371 of International Patent Application PCT / US2024 / 017520, filed Feb. 27, 2024, designating the United States of America and published as International Patent Publication WO 2024 / 182421 A2 on Sep. 6, 2024, which claims the benefit of the filing date under Article 8 of the Patent Cooperation Treaty of U.S. Provisional Patent Application Ser. No. 63 / 487,327, filed Feb. 28, 2023, for “EMBEDDED FIBER OPTIC SENSORS FOR REAL TIME IN-SITU SENSING IN EXTREME ENVIRONMENTS,” the disclosure of which is hereby incorporated herein in its entirety by this reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Contract No. DE-AC07-05-ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention.TECHNICAL FIELD

[0003] Structures and the methods for forming such structures are disclosed. More specifically, structures including embedded devices and associated devices and the methods for forming such structures are disclosed.BACKGROUND

[0004] Many structures utilize sensors on the structure to collect information about the structure and surrounding environment, such as temperature, strain, movement, etc. Collecting information about the structure and the surrounding environment may facilitate detecting faults early to substantially prevent unexpected failures and / or to make changes to the environment or operating conditions. The information collected may also facilitate determining when maintenance on the structure needs to be performed to extend a service life of the structure and associated components.

[0005] Sensors are often embedded into structures using ultrasonic additive manufacturing and laser-based additive manufacturing. These techniques are difficult to use with high-temperature materials due to the high melting temperature of the high-temperature material that can result in damage to the sensors, or large gaps and voids around the sensor.BRIEF SUMMARY

[0006] Embodiments of the disclosure include a method of forming a structure. The method includes positioning a sensor within a mold. The method further includes depositing particles of a material having a high-temperature melting point in the mold and around the sensor. The method also includes applying pressure to the material having the high-temperature melting point in the mold while heating the material having the high-temperature melting point in the mold to a sintering temperature of the particles of the material having the high-temperature melting point in the mold. The method further includes forming a fully dense solid structure from the particles of the material having the high-temperature melting point in the mold with the sensor disposed in the fully dense solid structure.

[0007] Other embodiments of the disclosure include a structure including a fully dense solid material comprising an outer surface. The structure further includes a sleeve positioned in the outer surface. The structure also includes an optical fiber at least partially disposed in the fully dense solid material and through the outer surface within the sleeve, the optical fiber substantially bonded to the fully dense solid material.

[0008] Another embodiment of the disclosure includes a sintering assembly. The sintering assembly includes a mold defining a cavity. The sintering assembly further includes a passage defined through a wall of the mold, the passage configured to secure a sleeve at least partially extending into the cavity. The sintering assembly also includes a ram forming a moving wall of the mold, the ram configured to apply a pressure to a material within the cavity of the mold.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] While the specification concludes with claims particularly pointing out and distinctly claiming embodiments of the disclosure, the advantages of embodiments of the disclosure may be more readily ascertained from the following description of embodiments of the disclosure when read in conjunction with the accompanying drawings in which:

[0010] FIG. 1 illustrates a schematic view of a sintering assembly in accordance with embodiments of the disclosure;

[0011] FIGS. 2-4 illustrate schematic views of structures formed in accordance with embodiments of the disclosure;

[0012] FIGS. 5 and 6 illustrate microscopic views of a cross-section of a structure formed in accordance with embodiments of the disclosure;

[0013] FIG. 7 illustrates a plot of a material composition of a structure formed in accordance with embodiments of the disclosure; and

[0014] FIG. 8 illustrates a flow chart representative of a method of forming a structure in accordance with embodiments of the disclosure.DETAILED DESCRIPTION

[0015] The following description provides specific details, such as material compositions, shapes, and sizes, in order to provide a thorough description of embodiments of the disclosure. However, a person of ordinary skill in the art would understand that the embodiments of the disclosure may be practiced without employing these specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional techniques employed in the industry.

[0016] Drawings presented herein are for illustrative purposes only and are not meant to be actual views of any particular material, component, structure, device, or system. Variations from the shapes depicted in the drawings as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes or regions as illustrated, but include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as box-shaped may have rough and / or nonlinear features, and a region illustrated or described as round may include some rough and / or linear features. Moreover, sharp angles that are illustrated may be rounded, and vice versa. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shape of a region and do not limit the scope of the present claims. The drawings are not necessarily to scale. Additionally, elements common between figures may retain the same numerical designation.

[0017] As used herein, the terms “configured” and “configuration” refers to a size, a shape, a material composition, a material distribution, orientation, and arrangement of at least one feature (e.g., one or more of at least one structure, at least one material, at least one region, at least one device) facilitating use of the at least one feature in a pre-determined way.

[0018] As used herein, the term “substantially” in reference to a given parameter means and includes to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0 percent met, at least 95.0 percent met, at least 99.0 percent met, at least 99.9 percent met, or even 100.0 percent met.

[0019] As used herein, “about” in reference to a numerical value for a particular parameter is inclusive of the numerical value and a degree of variance from the numerical value that one of ordinary skill in the art would understand is within acceptable tolerances for the particular parameter. For example, “about” in reference to a numerical value may include additional numerical values within a range of from 90.0 percent to 110.0 percent of the numerical value, such as within a range of from 95.0 percent to 105.0 percent of the numerical value, within a range of from 97.5 percent to 102.5 percent of the numerical value, within a range of from 99.0 percent to 101.0 percent of the numerical value, within a range of from 99.5 percent to 100.5 percent of the numerical value, or within a range of from 99.9 percent to 100.1 percent of the numerical value.

[0020] As used herein, relational terms, such as “below,”“lower,”“bottom,”“above,”“upper,”“top,” and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the drawings. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures. For example, if materials in the figures are inverted, elements described as “below” or “under” or “on bottom of” other elements or features would then be oriented “above” or “on top of” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below, depending on the context in which the term is used, which will be evident to one of ordinary skill in the art. The materials may be otherwise oriented (e.g., rotated 90 degrees, inverted, flipped) and the spatially relative descriptors used herein interpreted accordingly.

[0021] As used herein, the singular forms “a,”“an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0022] As used herein, the term “and / or” means and includes any and all combinations of one or more of the associated listed items.

[0023] As used herein, the terms “vertical,”“longitudinal,”“horizontal,” and “lateral” are in reference to a major plane of a structure and are not necessarily defined by earth's gravitational field. A “horizontal” or “lateral” direction is a direction that is substantially parallel to the major plane of the structure, while a “vertical” or “longitudinal” direction is a direction that is substantially perpendicular to the major plane of the structure. The major plane of the structure is defined by a surface of the structure having a relatively large area compared to other surfaces of the structure.

[0024] As used herein, the terms “a fully dense solid material” and “a fully dense solid structure” mean and include a material or structure substantially free of individual or unbonded particles and gaps (e.g., voids, pores) between particles. For example, a fully dense material may exhibit a density greater than about 80%, such as greater than about 95%, greater than about 98%, or even about 100%.

[0025] Many structures utilize sensors on or in the structure to collect information about the structure and surrounding environment, such as temperature, strain, movement, etc. Some structures, such as those used in nuclear and aerospace fields, operate in extremely harsh environments over extended periods of time. The harsh environments may include extreme temperatures (e.g., extremely high temperatures or extremely low temperatures), caustic environments, corrosive environments, high pressures, low pressures, radioactive environments, etc. The harsh environments may restrict the types of sensors that can be used to withstand the harsh environments. This may limit the information that can be collected during use and operation of the structure. The capability of in-situ real-time collection of information may facilitate detecting faults (e.g., defects, cracks) in the structure early to substantially prevent unexpected failures and / or to make changes to the environment or operating conditions before failure occurs. The information collected may also facilitate determining when maintenance on the structure needs to be performed to extend a service life of the structure and associated components. Structures operating in harsh environments stand to benefit from information collection to a greater degree than structures operating in less harsh environments at least due to the added stresses of the harsh environments. Therefore, forming structures according to embodiments of the disclosure that are capable of including a greater variety of sensors in harsh environments may improve the ability to predict and / or prevent catastrophic failures of the structures. The structures according to embodiments of the disclosure may be continuously monitored and evaluated during their use to prevent failure.

[0026] Disposing or embedding sensors within the materials of the structure may substantially protect the sensors from the harsh environments. However, many conventional procedures that have previously been used to embed the sensors in the structures result in weakening the structure or damaging the sensors. For example, ultrasonic additive manufacturing and laser-based additive manufacturing, which are used for embedding sensors in low-temperature materials, may not be effective for high-temperature materials commonly used in extreme environments. The high melting temperature of high-temperature materials may result in damage to the sensor or in large gaps and voids around the sensor. A good fiber-matrix bond facilitates a bond that is substantially free of gas or liquid leaks as well as improved temperature sensing and strain coupling. In other cases, the sensors fail to bond to the material of the structure, such that the properties that are being measured by the sensors are not efficiently transferred from the structure to the sensor and the sensors do not accurately capture the data. Furthermore, failure to bond the sensor to the material of the structure may result in a fluid (e.g., gas or liquid) leaking through the gaps between the sensor and the structure.

[0027] A process of forming structures using sintering to include sensors substantially bonded within the structure is disclosed herein. The sensor is bonded to a material of the structure, providing good mechanical properties to the structure without decreasing integrity or functionality of the sensor. The mechanical properties may include, but are not limited to, strength or hardness of the structure. Structures formed using these processes may facilitate capturing a greater variety of data from the structure when used in a harsh environment, which may facilitate improvements in predicting and preventing failures of the associated structures.

[0028] FIG. 1 illustrates a sintering assembly 100 for forming a structure with a sensor 112 embedded in a material 108 of the structure. The sintering assembly 100 may be a conventional sintering assembly configured to heat materials while applying a pressure to the materials to form a solid material. In some embodiments, the sintering assembly 100 is an electric field assist sintering (EFAS) assembly configured to apply a pressure to a material while heating the material and sintering assembly 100 by passing an electric current through the sintering assembly 100 and the material.

[0029] The sintering assembly 100 includes a mold 102 defining a cavity 106 within the mold 102 configured to receive the material 108 to be sintered. The sintering assembly 100 also includes one or more rams 104 configured to apply pressure to the material 108 in the cavity 106 of the mold 102. For example, the rams 104 may form a movable surface of the mold 102 that moves to apply pressure to the material 108 within the cavity 106 of the mold 102. In the embodiment illustrated in FIG. 1, the sintering assembly 100 includes two opposing rams 104 positioned on opposing sides of the mold 102 and configured to apply a pressure to the material in the cavity 106 defined in the mold 102 and between the two rams 104. In an EFAS assembly, a voltage is applied between the two rams 104 to induce an electric current from the first ram 104, through the mold 102 and the material 108 in the cavity 106, and out the second ram 104. The electrical current passing through the mold 102 and the material 108 in the cavity 106 generates heat in the mold 102 and the materials 108 in the cavity 106 based on the resistance of the material of the mold 102 and the material 108 in the cavity 106 to the electrical current.

[0030] In a sintering process, the materials 108 to be sintered are disposed in the cavity 106 in a powdered or granulated form. A pressure is then applied to the cavity 106 through the rams 104 and a temperature of the mold 102 is raised to a sintering temperature of the material 108 within the cavity 106. The sintering temperature is less than the melting temperature of the material but high enough that the individual particles in the powdered or granulated material 108 fuse together under pressure to form a fully dense, solid material.

[0031] A sensor 112 is disposed in the material 108 in the cavity 106. The sensor 112 may be a sensor fiber 110 (e.g., a glass fiber, silica fiber, sapphire fibers, etc.) configured to form a fiberoptic sensor 112. Fiberoptic sensors may be used to measure strain, temperature, pressure, light, radiation, orientation, etc. As illustrated in FIG. 1, the sensor fiber 110 extends axially through the material 108 in the cavity 106. As discussed above, through the sintering process, the sensor 112 will be exposed to temperatures that are less than the melting temperature of the material 108. Therefore, the temperatures experienced by the sensor 112 are less than what would be experienced through other processes of embedding the sensor 112 into the material 108 that involve melting the material 108, such as additive manufacturing or welding.

[0032] One or more components of the sintering assembly 100 may include a passage to facilitate the sensor fiber 110 passing into and out of the cavity 106. For example, in the embodiment illustrated in FIG. 1, the rams 104 include channels 118 defined therein to facilitate the passage of the sensor fiber 110. As illustrated in FIG. 1, the channels 118 in the upper ram 104 and the lower ram 104 are substantially axially aligned. In other embodiments, the channels 118 may not be axially aligned. For example, in some embodiments, the channels 118 are axially offset. In another embodiment, channel 118 may extend in different directions. For example, a first channel 118 may extend axially through one of the rams 104, and a second channel 118 may extend radially through the mold 102.

[0033] The sintering assembly 100 may also include a component configured to support and secure the sensor fiber 110 to the material 108 once the material is formed into a fully dense solid structure. In the embodiment illustrated in FIG. 1, a sleeve 114 extends through the channel 118 and through an outer portion 116 of the material 108. The sleeve 114 does not extend completely through the material 108. Rather, the sleeve 114 stops a short distance into the material 108 extending past the end of the associated ram 104. For example, the sleeve 114 may extend a distance 120 from the associated ram 104 that is less than about ¼ of a total distance 122 between the rams 104, such as less than about ⅛ of the total distance 122 or less than about 1 / 10 the total distance 122. Thus, at least a portion of the sensor fiber 110 remains exposed to (e.g., is in contact with) the material 108 in the cavity 106 to form the sensor 112 and be bonded to the material 108 during the sintering process when the material 108 becomes the fully dense solid structure.

[0034] The material 108 may be a material configured to withstand exposure and operation in a harsh environment. For example, materials used in harsh environments are typically high-temperature materials, such as stainless steel (SS), nickel alloys, high-strength steel, or titanium alloys. The material 108 may be configured to provide mechanical structure to the resulting structure. The sleeve 114 may be formed from a similar material configured to bond to the material 108 during sintering, such that the sleeve 114 forms a unitary part of the fully dense solid structure after the sintering process.

[0035] FIG. 2 illustrates a schematic view of a structure 200 formed through the sintering process described above. The structure 200 includes a fully dense solid material 204 with a sensor 208 embedded in the fully dense solid material 204 and bonded to the fully dense solid material 204. The fully dense solid material may have a Vickers hardness (HV) measurement greater than about 100 HV, such as greater than about 140 HV or greater than about 160 HV. The fully dense solid material 204 may also have a grain size smaller than about 50 μm, such as less than about 30 μm, or less than about 20 μm. In the embodiment illustrated in FIG. 2, the sensor 208 is a portion of a sensor fiber 202 extending through the fully dense solid material 204. As discussed above, the structure 200 includes sleeves 206 on opposing axial ends of the structure 200. The sleeves 206 extend through outer surfaces 210 of the structure 200 and into an interior portion of the structure 200.

[0036] The sensor 208 may be exposed to (e.g., in contact with) the fully dense solid material 204 between the sleeves 206. After the sintering process, the sensor 208 is substantially bonded to the fully dense solid material 204 of the structure 200. Substantially bonding the sensor 208 to the fully dense solid material 204 may facilitate the sensor 208 detecting properties of the structure 200. For example, the properties of the fully dense solid material 204, such as the strain, temperature, or pressure of the fully dense solid material 204 may be transferred to the sensor 208 through the bonds, such that the sensor 208 can detect the strain, temperature, and pressure of the fully dense solid material 204. In other cases, the presence of other elements, such as light or radiation in the fully dense solid material 204, may be detected by the sensor 208 through the bonds between the sensor 208 and the fully dense solid material 204.

[0037] The sensor 208 may transmit a signal to a processor 212 through the sensor fiber 202 based on the properties detected by the sensor 208. The processor 212 may then interpret the signal provided by the sensor 208 to provide sensor measurements to a user, such as through a user interface, a database, a printout, an alert, etc. In some embodiments, the sensor 208 generates a signal based on the properties detected in the structure 200. For example, scintillating fibers are configured to emit photons when excited by the presence of specific elements, such as radiation.

[0038] In other embodiments, the processor 212 provides a signal to the sensor 208 through the sensor fiber 202, and the sensor 208 modifies the signal based on the properties detected in the structure 200 and sends the signal back to the processor 212. For example, the processor 212 may provide a light signal through the sensor fiber 202. A strain sensor may alter the light passing through the sensor 208 based on a strain experienced by the sensor 208. Similarly, a temperature sensor may modify the light passing through the sensor 208 based on a temperature of the fully dense solid material 204 surrounding the sensor 208. For example, a fiber Bragg grating (FBG) sensor is configured to monitor spatially dependent temperature and strain by reflecting some wavelengths of light and transmitting other wavelengths of light depending on the strain or temperature detected by the FBG sensor.

[0039] In some embodiments, a source 214 provides a signal (e.g., a light signal) to the sensor 208 through the sensor fiber 202, and the sensor 208 modifies the signal based on the properties detected in the structure 200 before the signal passes to the processor 212. In other embodiments, such as those described above, where the sensor 208 generates the signal or the processor 212 provides a source signal, the source 214 may not be present.

[0040] FIG. 3 illustrates a schematic view of another structure 300 formed through the sintering process described above. The structure 300 includes a fully dense solid material 304 with a sensor 308 embedded in the fully dense solid material 304 and bonded to the fully dense solid material 304. In the embodiment illustrated in FIG. 3, the sensor 308 is a portion of the sensor fiber 302 extending through the fully dense solid material 304. The structure 300 includes sleeves 306 on opposing axial ends of the structure 300. The sleeves 306 extend through outer surfaces 310 of the structure 300 and into an interior portion of the structure 300. The sensor 308 is exposed to the fully dense solid material 304 between the sleeves 306 and is substantially bonded to the fully dense solid material 304 of the structure 300.

[0041] The sensor 308 may have a non-linear shape, such as the spiral shape illustrated in FIG. 3. In the embodiment illustrated in FIG. 3, the sensor 308 includes multiple loops 312 forming a spiral configuration through the fully dense solid material 304. The multiple loops 312 may be formed from the sensor fiber 302 within the granulated material (e.g., material 108 (FIG. 1)) when being arranged in the mold (e.g., mold 102 (FIG. 1)). The loops 312 may increase a surface area of the sensor 308 that is bonded with the fully dense solid material 304 of the structure 300. In some embodiments, the arrangement of the loops 312 may facilitate capturing different properties of the fully dense solid material 304. For example, the loops 312 may facilitate detecting changes in shape of the structure 300, such as stretching or shrinking of the structure 300, at least through the changes in the arrangement of the loops 312 that would be caused by such changes in the shape of the structure 300.

[0042] FIG. 4 illustrates a schematic view of another structure 400 formed through the sintering process described above. The structure 400 includes a fully dense solid material 404 with a sensor 408 embedded in the fully dense solid material 404 and bonded to the fully dense solid material 404. In the embodiment illustrated in FIG. 4, the sensor 408 is a portion of the sensor fiber 402 extending through the fully dense solid material 404. The structure 400 includes sleeves 406 extending through a first outer surface 410 and a second outer surface 412 of the structure 400 and into an interior portion of the structure 400. The sensor 408 is exposed to the fully dense solid material 404 between the sleeves 406 and is substantially bonded to the fully dense solid material 404 of the structure 400.

[0043] In the embodiment illustrated in FIG. 4, the sleeves 406 are not positioned on opposite ends of the structure 400. Rather, the sleeves 406 are positioned on adjacent sides of the structure 400. In the embodiment illustrated in FIG. 4, a first sleeve 406 extends through the first outer surface 410 of the structure 400 and a second sleeve 406 extends through the second outer surface 412 of the structure 400. The first outer surface 410 is connected to the second outer surface 412 at a corner 414 of the structure 400. The sensor fiber 402 forming the sensor 408 includes a curve 416 within the fully dense solid material 404 changing an orientation of the sensor fiber 402, such that the sensor fiber 402 exits the structure 400 with an orientation that is substantially perpendicular to the associated surface (e.g., the first outer surface 410 or the second outer surface 412). For example, the sensor fiber 402 and the associated sleeve 406 are oriented in a direction substantially perpendicular to the first outer surface 410 where the sleeve 406 and the sensor fiber 402 pass through the first outer surface 410 and the sensor fiber 402 and the associated sleeve 406 are oriented in a direction substantially perpendicular to the second outer surface 412 where the sleeve 406 and the sensor fiber 402 pass through the second outer surface 412.

[0044] FIGS. 5 and 6 illustrate enlarged views of a structure 500 including an embedded fiber 502 in a fully dense solid material 504 of the structure 500. A transition zone 506 is defined between the fiber 502 and the fully dense solid material 504. The transition zone 506 is characterized by a change in material makeup between the fully dense solid material 504 and the embedded fiber 502. For example, if the fully dense solid material 504 is stainless steel (e.g., SS316), which includes iron (Fe), chromium (Cr), and nickel (Ni), and the fiber 502 is sapphire, which includes aluminum (Al) and oxygen (O), the material makeup of the stainless steel in the transition zone 506 includes elevated levels of aluminum and oxygen and may include lower levels of iron, chromium, and / or nickel, indicating the interdiffusion of elements between the fully dense solid material 504 and the fiber 502. Interdiffusion of the elements in a zone between the fully dense solid material 504 and the fiber 502 indicates a strong metallurgical bond has formed between the fully dense solid material 504 and the fiber 502, which may be beneficial for detecting different properties of the fully dense solid material 504 with the fiber 502, such as temperature and strain.

[0045] The transition zone 506 may have a width in a range from about 3 μm to about 10 μm, such as in a range from about 3 μm to about 6 μm. As illustrated in FIG. 6, the transition zone 506 may include small gaps 602, such as having a size less than about 10 μm, such as less than about 8 μm or less than about 6 μm. The fiber 502 may remain fully bonded to the fully dense solid material 504 if the transition zone 506 still evidences an interdiffusion of the elements where a portion of the material includes all of the elements of both the fiber 502 and the fully dense solid material 504 in reduced percentages illustrating that the elements of the two materials are diffusing through the transition zone 506. In some cases, the gap 602 may be in a middle portion of the transition zone 506, such that interdiffusion is found on both sides of the gap 602. In other embodiments, the transition zone 506 may begin in the gap 602 and extend on only one side of the gap 602, such that the interdiffusion is found in the fiber 502 or the fully dense solid material 504 but not in both. The combination of a small gap 602 (e.g., less than 10 μm) and a transition zone 506 may result in a bond that is sufficient to substantially prevent leaks and to efficiently transmit properties of the fully dense solid material 504 to the fiber 502, such that the fiber 502 may detect and transmit signals based on the properties.

[0046] FIG. 7 illustrates a plot 700 representative of a simplified material composition percentage 702 of the structure 500 represented by the Y-axis in different positions 704 across the structure 500 represented by the X-axis. The lines in the plot 700 each represent individual elements in the structure 500. A left portion of the plot 700 illustrates the material composition percentage 702 of the fully dense solid material 504 and a right portion of the plot 700 illustrates the fiber 502. In the embodiment illustrated by FIG. 7, the fully dense solid material 504 is formed primarily from three elements iron 706, chromium 708, and nickel 710 and the fiber 502 is formed primarily from two elements aluminum 712 and oxygen 714. The vertical broken lines in the plot 700 represent the bounds of the transition zone 506 between the fiber 502 and the fully dense solid material 504. As illustrated in the plot 700, the iron 706, chromium 708, and nickel 710 of the fully dense solid material 504 gradually reduce to zero or near zero values within the transition zone 506 as the position 704 within the structure 500 advances in the X direction. Similarly, the aluminum 712 and the oxygen 714 of the fiber 502, begin at zero or near zero values throughout the fully dense solid material 504 and gradually increase through the transition zone 506 to reach the associated material composition percentages 702 of the aluminum 712 and oxygen 714 in the fiber 502. Within the transition zone 506 each of the elements of both the fully dense solid material 504 and the fiber 502 have non-zero values as the elements either gradually increase or decrease within the transition zone 506.

[0047] The structure 200, 300, 400, or 500 may be configured as a component that is capable of withstanding a harsh environment, such as the environment in a nuclear reactor or in an aeronautical vehicle. The structure 200, 300, 400, or 500 may be used in extreme temperature environments, caustic environments, corrosive environments, high-pressure environments, low-pressure environments, or radioactive environments. For example, the structure 200, 300, 400, or 500 may be an internal structure of a nuclear reactor, such as a control rod, control drum, flow control device, heat exchanger, etc. In another example, the structure 200, 300, 400, or 500 may be part of a support structure on aerospace equipment, such as an aircraft, a rocket, a satellite, terrestrial landing equipment, etc.

[0048] FIG. 8 illustrates a flow chart representative of a method 800 of forming a structure, such as the structure 200, 300, 400, or 500. The structure is formed using a sintering process, which utilizes a sintering assembly, such as sintering assembly 100, configured to form a fully dense solid structure by applying heat and pressure to a granulated or powdered material in a mold (such as mold 102).

[0049] A sensor is positioned in a mold in act 802. The sensor is positioned within a cavity (e.g., cavity 106) in the mold. The sensor may be arranged or oriented in a desired manner. For example, the sensor may extend through the cavity in a substantially linear arrangement as illustrated in FIGS. 1 and 2, in a spiraled arrangement as illustrated in FIG. 3, or a curved arrangement as illustrated in FIG. 4. In other examples, the sensor may be arranged in other shapes or orientations as desired for the end structure.

[0050] A sleeve (e.g., sleeve 114, 206, 306, 406) is positioned over a portion of the sensor in act 804. The sleeve is secured to a portion of the mold, such that the sleeve extends at least partially into the cavity defined in the mold. The sleeve extends through a wall of the mold. For example, in the sintering assembly 100 described in FIG. 1, the sleeve 114 extends through the rams 104 that form two walls of the mold 102. In other cases, the sleeve may extend through other walls of the mold. The sleeve may be configured to secure and position the sensor in the cavity. For example, the sensor may be an optical fiber sensor as discussed above and the sensor fiber may pass into the cavity through the sleeve. In other embodiments, the sensor may have different configurations, such as a sensor configured to communicate through an optical fiber or a sensor configured to receive power or send signals through wires. The sleeve may be configured to secure the optical fiber or wires communicably coupled to the sensor. In such instances, the sleeve may be positioned to cover the wires or optical fiber up to the sensor, such that the sleeve may shield the optical fiber or the wires from the temperatures and pressures of the sintering process.

[0051] A granulated or powdered material is deposited in the cavity of the mold around the sensor and the portion of the sleeve in act 806. The powdered or granulated material may be a material configured to withstand harsh environments, such as a material having a high melting point or a material having high corrosion resistance. For example, the granulated or powdered material may be a stainless steel (e.g., SS316, SS304, SS308), tungsten, nickel alloys, or titanium alloys. The granulated or powdered material may conform to the shape of the sensor, filling in spaces created by the shape of the sensor, such that the sensor is substantially surrounded by the granulated or powdered material and the cavity is substantially filled with the granulated or powdered material.

[0052] After the cavity of the mold is filled with the granulated or powdered material and the sensor and sleeves are positioned in the mold, the sintering assembly applies pressure to the granulated or powdered material in the mold in act 808. In some embodiments, the pressure is applied in stages, such as a pressure gradient or a stepwise increase in pressure. In some embodiments, a single pressure is applied. For example, an initial pressure may be applied to pre-consolidate the granulated or powder material to facilitate the rearrangement of the powder for initial densification. After the initial pressure is applied, the pressure may be incrementally increased. The pressure may be held at each increment for a specified dwell time. The times and pressure may vary based on the type of material being sintered. For example, stainless steel may be incremented by 10 MPa every 5-10 minutes, such that 10 MPa of pressure is applied for between 5 minutes and 10 minutes and then 20 MPa is applied for between 5 minutes and 10 minutes up to about 50 MPa. The pressure may be applied through a ram (e.g., ram 104) or press that forms part of the sintering assembly.

[0053] Heat is applied to the mold while the pressure is being applied in act 810. In some embodiments, the heat may be applied after the initial pressure is applied, e.g., during the incremental pressure. The heat may be gradually increased until a sintering temperature of the material is reached. For example, stainless steel may be heated at a rate of about 100° C. per minute to a temperature in a range from about 1000° C. and about 1200° C. The temperature may be applied by heating the sintering assembly, such as in a furnace or by applying an electrical current to the sintering assembly to increase the temperature through the heat generated by the electrical resistance of the assembly.

[0054] The individual particles in the powdered or granulated material begin to fuse to adjacent particles while being heated under pressure to form a solid material in act 812. The individual particles of the material that are adjacent to the sensor may also fuse to the sensor. Thus, after the pressure and temperature are released a fully dense solid structure is formed that is fused to the sensor embedded therein.Example

[0055] Eleven structures of stainless steel 316 including an embedded sapphire fiber were formed through an electron field assist sintering process at different pressures, temperatures, and dwell times. Each of the eleven structures passed an initial continuity test demonstrating that the sapphire fiber was undamaged. The sapphire fiber was tested by sending light through the sapphire fiber on a first side of the associated structure and observing that the light was transmitted through the structure by the sapphire fiber on the opposite side of the associated structure. After confirming that the light was transmitted, the structures were cut in a plane perpendicular to a longitudinal axis of the sapphire fiber and subjected to further testing to test different properties of the structures, such as the hardness, density, grain sizes and structures, and material compositions and to observe the bond through a microscope to verify that the sapphire fibers were fully bonded to the associated structure. The following table provides the temperatures, pressures, and dwell time used to form each structure and the density and hardness measured for each structure during the testing.DwellRelativelySampleTemperaturePressuretimedensityHardnessNo.(° C.)(MPa)(min)(%)(HV)1100010588.8105.72100020594.9112.83100050597.7170.341000501098.8174.15105050598.4172.161050501099.0171.87110010590.5104.98110020595.7124.79110050598.8164.210115020596.5139.411115050598.9153.4

[0056] As illustrated, each of the structures had a Vickers hardness number (HV) greater than 100 and a relative density greater than 85%. The grain sizes in the sintered stainless steel 316 were in a range from about 3.7 μm to about 10.4 μm and demonstrated an equiaxed grain structure. It was noted that grain sizes began to grow larger at higher temperatures, such that higher temperatures may result in larger grain sizes and a reduction in micro hardness.

[0057] Non-limiting example embodiments include:

[0058] Embodiment 1: A method of forming a structure, the method comprising: positioning a sensor within a mold; depositing particles of a material having a high-temperature melting point in the mold and around the sensor; applying pressure to the material having the high-temperature melting point in the mold while heating the material in the mold to a sintering temperature of the particles of the material having the high-temperature melting point in the mold; and forming a fully dense solid structure from the particles of the material having the high-temperature melting point in the mold with the sensor disposed in the fully dense solid structure.

[0059] Embodiment 2: The method of embodiment 1, wherein positioning the sensor within the mold comprises positioning an optical fiber within the mold.

[0060] Embodiment 3: The method of embodiment 2, wherein positioning the optical fiber within the mold comprises positioning a sapphire fiber within the mold.

[0061] Embodiment 4: The method of any one of embodiments 1 through 3, further comprising positioning a sleeve around a portion of the sensor and at least partially within a cavity defined in the mold.

[0062] Embodiment 5: The method of embodiment 4, further comprising forming the fully dense solid structure from the particles of the material having the high-temperature melting point in the mold and the sleeve with the sensor disposed in the fully dense solid structure.

[0063] Embodiment 6: The method of any one of embodiments 4 or 5, wherein positioning the sleeve around the portion of the sensor comprises positioning the sleeve of a material configured to bond to the particles of the material having the high-temperature melting point during a sintering process.

[0064] Embodiment 7: The method of any one of embodiments 1 through 6, further comprising applying an initial pressure before heating the material having the high-temperature melting point.

[0065] Embodiment 8: The method of embodiment 7, wherein applying the initial pressure is configured to rearrange the particles of the material having the high-temperature melting point for initial densification.

[0066] Embodiment 9: The method of any one of embodiments 1 through 8, wherein depositing the particles of the material having the high-temperature melting point in the mold comprises depositing particles of a material formulated to withstand harsh environments.

[0067] Embodiment 10: A structure comprising: a fully dense solid material comprising an outer surface; a sleeve positioned in the outer surface; and an optical fiber at least partially disposed in the fully dense solid material and through the outer surface within the sleeve, the optical fiber substantially bonded to the fully dense solid material.

[0068] Embodiment 11: The structure of embodiment 10, wherein the fully dense solid material comprises a material formulated to withstand harsh environments.

[0069] Embodiment 12: The structure of embodiment 11, wherein the material formulated to withstand the harsh environments has at least one of a high melting point or a high corrosion resistance.

[0070] Embodiment 13: The structure of any one of embodiments 11 or 12, wherein the material formulated to withstand the harsh environments includes at least one of a stainless steel, a tungsten alloy, a nickel alloy, and a titanium alloy.

[0071] Embodiment 14: The structure of any one of embodiments 10 through 13, wherein the fully dense solid material comprises a transition zone surrounding the optical fiber.

[0072] Embodiment 15: The structure of embodiment 14, wherein the transition zone includes a different material makeup than the fully dense solid material outside the transition zone.

[0073] Embodiment 16: The structure of any one of embodiments 10 through 15, wherein the optical fiber has a non-linear shape within the fully dense solid material.

[0074] Embodiment 17: The structure of any one of embodiments 10 through 16, wherein the fully dense solid material has a Vickers hardness number (HV) greater than about 100.

[0075] Embodiment 18: A sintering assembly comprising: a mold defining a cavity; a passage defined through a wall of the mold, the passage configured to secure a sleeve at least partially extending into the cavity; and a ram forming a moving wall of the mold, the ram configured to apply a pressure to a material within the cavity of the mold.

[0076] Embodiment 19: The sintering assembly of embodiment 18, wherein the passage is defined through the moving wall formed by the ram.

[0077] Embodiment 20: The sintering assembly of any one of embodiments 18 or 19, wherein the sintering assembly comprises an electric field assist sintering assembly configured to heat the sintering assembly through resistance to an electric current applied to the sintering assembly.

[0078] Embodiments of the disclosure may facilitate forming structures including embedded sensors. Embedding sensors in a structure configured for use in a harsh environment may facilitate measuring properties of the structure and the environment with the sensor. The properties of the structure may be measured while shielding the sensor from the harsh environment by the material of the structure. Measuring properties of the structure and environment may facilitate detecting faults early to substantially prevent unexpected failures and / or to make changes to the environment or operating conditions. The information collected may also facilitate determining when maintenance on the structure needs to be performed to extend a service life of the structure and associated components.

[0079] The embodiments of the disclosure described above and illustrated in the accompanying drawing figures do not limit the scope of the invention, since these embodiments are merely examples of embodiments of the invention, which is defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be within the scope of this disclosure. Indeed, various modifications of the present disclosure, in addition to those shown and described herein, such as alternative useful combinations of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims and their legal equivalents.

Claims

1. A method of forming a structure, the method comprising:positioning a sensor within a mold;depositing particles of a material having a high-temperature melting point in the mold and around the sensor;applying pressure to the material having the high-temperature melting point in the mold while heating the material in the mold to a sintering temperature of the particles of the material having the high-temperature melting point in the mold; andforming a fully dense solid structure from the particles of the material having the high-temperature melting point in the mold with the sensor disposed in the fully dense solid structure.

2. The method of claim 1, wherein positioning the sensor within the mold comprises positioning an optical fiber within the mold.

3. The method of claim 2, wherein positioning the optical fiber within the mold comprises positioning a sapphire fiber within the mold.

4. The method of claim 1, further comprising positioning a sleeve around a portion of the sensor and at least partially within a cavity defined in the mold.

5. The method of claim 4, further comprising forming the fully dense solid structure from the particles of the material having the high-temperature melting point in the mold and the sleeve with the sensor disposed in the fully dense solid structure.

6. The method of claim 4, wherein positioning the sleeve around the portion of the sensor comprises positioning the sleeve of a material configured to bond to the particles of the material having the high-temperature melting point during a sintering process.

7. The method of claim 1, further comprising applying an initial pressure before heating the material having the high-temperature melting point.

8. The method of claim 7, wherein applying the initial pressure is configured to rearrange the particles of the material having the high-temperature melting point for initial densification.

9. The method of claim 1, wherein depositing the particles of the material having the high-temperature melting point in the mold comprises depositing particles of a material formulated to withstand harsh environments.

10. A structure comprising:a fully dense solid material comprising an outer surface;a sleeve positioned in the outer surface; andan optical fiber at least partially disposed in the fully dense solid material and through the outer surface within the sleeve, the optical fiber substantially bonded to the fully dense solid material.

11. The structure of claim 10, wherein the fully dense solid material comprises a material formulated to withstand harsh environments.

12. The structure of claim 11, wherein the material formulated to withstand the harsh environments has at least one of a high melting point or a high corrosion resistance.

13. The structure of claim 11, wherein the material formulated to withstand the harsh environments includes at least one of a stainless steel, a tungsten alloy, a nickel alloy, and a titanium alloy.

14. The structure of claim 10, wherein the fully dense solid material comprises a transition zone surrounding the optical fiber.

15. The structure of claim 14, wherein the transition zone includes a different material makeup than the fully dense solid material outside the transition zone.

16. The structure of claim 10, wherein the optical fiber has a non-linear shape within the fully dense solid material.

17. The structure of claim 10, wherein the fully dense solid material has a Vickers hardness number (HV) greater than about 100.

18. A sintering assembly comprising:a mold defining a cavity;a passage defined through a wall of the mold, the passage configured to secure a sleeve at least partially extending into the cavity; anda ram forming a moving wall of the mold, the ram configured to apply a pressure to a material within the cavity of the mold.

19. The sintering assembly of claim 18, wherein the passage is defined through the moving wall formed by the ram.

20. The sintering assembly of claim 18, wherein the sintering assembly comprises an electric field assist sintering assembly configured to heat the sintering assembly through resistance to an electric current applied to the sintering assembly.

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