Shielding-enhanced steel for application in neutron environments

Abstract

The present disclosure is directed to a multicomponent composite (or structural steel composite) for mixed neutron and electromagnetic shield application. The multicomponent composite includes a matrix and a secondary phase, where the matrix is composed of an iron-based steel alloy and the secondary phase is composed of one or more neutron and electromagnetic radiation absorbing metal-hydrides (MH). As metal hydrides are typically thermal unstable at common metals processing temperatures, and the release of hydrogen from the MH results in a less effective shield, a resulting method which avoids hydrogen release is desired and disclosed in the present disclosure.

Description

050-9482_PCT_Application.docxSHIELDING-ENHANCED STEEL FOR APPLICATION IN NEUTRON ENVIRONMENTSCROSS REFERENCE TO RELATED APPLICATION

[0001] The present invention claims the benefit of U. S. Provisional Patent Application No.63 / 733,811 filed December 13, 2024, the entire content and disclosure of which is incorporated herein by reference.GOVERNMENT SUPPORT

[0002] This invention was made with government support under DE-AR0001381 awarded by the Department of Energy ARPA-E and under DE-SC0018332 awarded by the Department of Energy. The government has certain rights in the invention.FIELD OF THE INVENTION

[0003] The present disclosure relates to a multicomponent composite (or composited structural steel) for application in high-radiation environments of neutron and electromagnetic (e.g., gamma-ray / X-ray) environments, and a method of forming such a multicomponent composite. The application of the multicomponent composite includes, without limitation, fission and fusion reactor core internals or other systems that require radiation shielding.BACKGROUND

[0004] The harmful radiation emanating from or contained within nuclear systems is often managed through the use of shielding to limit absorbed dose to workers and / or system components. The shielding can take the form of solid or liquid materials, with the two general radiation threats being electromagnetic radiation (gamma-rays or X-rays) and neutrons.Electromagnetic radiation has a range of sources in nuclear systems, and, as example, can span energies from a few KeV to tens of MeV as released in the fission of U-235. As high-energygamma-ray irradiation and X-ray irradiation strongly interact with electrons, the most efficient shielding materials are those providing high electron (and atomic) density. Materials such as lead and tungsten are therefore common and effective shielding materials for electromagnetic irradiation. Neutron irradiation, which is often coincident with production of gamma-rays, require a different shielding approach as they are best slowed with very light mass materials such as, for example, water or polyethylene, and then must be absorbed by special materials with large neutron absorption cross-sections. Those absorbers are materials such as isotopes of boron, hafnium, cadmium, etc.

[0005] Within central core and core-surrounds of both fission and fusion power systems, electromagnetic and neutron radiation threats coexist. Functionally and practically these forms of radiation are mitigated in different ways. As an example, gamma irradiation is typically shielded through placement and interaction with the very high-density shield materials. In these instances, the electromagnetic radiation primarily interacts with the high density of electrons in the heavy material depositing its energy through a number of channels such as electron excitation, Compton scattering, or pair production. To first order, the effectiveness of gamma ray shielding increases in direct proportion to material density, explaining the popularity of materials such as lead for gamma-ray shielding. In certain special applications, depleted uranium, thorium, and tungsten are also used, as are a range of specialty (relatively low cost) concrete mixtures with heavy aggregates, such as Baryte or Magnetite, to enhance density.However, even this high-density concrete (of about 3.5 g / cc) would need to be many times thicker than lead (11.35 g / cc) to achieve an equivalent shielding effectiveness.

[0006] There are numerous ways to judge and compare the effectiveness of shielding, including resulting heat deposition, nuclear damage, or through comparing equivalent thickness of a material required to reduce ionizing dose levels (i.e., X-ray dose) by half. As example, the normalized X-ray half-value-layer of normal concrete would be 44.5 mm, steel 12.7 mm, lead 4.8 mm, tungsten 3.3 mm, and uranium 2.8 mm. In many practical applications, space limitation necessitate the use of the more shielding-effect high density materials

[0007] As neutrons are electrically neutral, they undergo only weak interaction as they pass through matter. With a mass similar to that of protons, the primary’ reaction of neutrons with material are elastic, or billiard-ball-type collisions, in which some fraction of their energy is lost in every collision. This reaction is referred to as an elastic scattering reaction for which the maximum energy per collision is lost when the neutron collides with material atoms of similar weight, the most similar being hydrogen, and the least similar being those of highly dense materials. For this reason, the metrics for selecting optimal shield materials for combined X-ray and neutron radiation are in direct opposition, with very light (hydrogenous) materials such as water being ideal for neutrons, and very heavy materials such as lead being ideal for X-rays.

[0008] The neutrons emanating from fusion and fission reactions are borne at different, but very high energies: 14.1 million electron volts (MeV) and approximately 2 MeV, respectively. As these neutrons pass through matter, they can interact in an elastic scatter or “billiard-ball” reaction and slowly lose energy. However, as they slow down within the material a second atomic reaction becomes increasingly important. Specifically, a material-dependent neutron capture reaction may occur whose by-product may be either stable or unstable (radioactive), and in some cases may immediately release one or more neutrons. In the event no secondary neutron is emitted, the neutron is effectively shielded.

[0009] The probability of a neutron having an elastic scattering reaction as it passes through a material is defined by a parameter known as the elastic scattering cross section. This process favors materials of high atomic number density and low atomic mass such as water, concrete, beryllium, and hydrocarbons as example. The probability of a neutron being absorbed as it interacts with the material, otherwise known as the neutron absorption cross section, is also a material dependent phenomenon and a strong function of the energy (velocity) of the incident neutron, which has a complex dependency on the nuclear structure complex with different elements and isotopes of elements having vastly different absorption cross sections. As an example, hydrogen and iron, two commonly used nuclear materials, have low-energy neutron absorption cross-sections of 0.2 and 3 barns, respectively. However, materials such as hafnium, boron, and europium have average neutron absorption cross sections of 104, 200, and 4530barns, respectively. Within a specific element, the isotopic absorption cross-sectional dependency can be dramatic. As an example, the respective isotopic low neutron energy absorption cross-sections for gadolinium are 735b for152Gd, 85b for154Gd, 61100b for155Gd, 1.5 b for156Gd, 259000b for157Gd, 2.2 b for158Gd, and 1b for160Gd.

[0010] Biological and internal functional shielding is currently and widely used in both fission and fusion systems. Within fusion systems, one important function of shielding is to provide adequate suppression of both neutron and gamma flux emanating from the plasma core such that the superconducting magnets are not overheated or succumb to physical damage. The most commonly investigated configuration of fusion device, the so-called Tokamak, is geometrically a toroid, with the radiation-generating plasma held within the torus. Tokamak shielding must mitigate threats to the superconducting coils: neutron cascade damage, heat deposition, and organic insulator damage due to X-rays and neutrons emanating from the toroid into the Tokamak structure. Current shield solutions use a combination of boronated steel with a separate shield of flowing water. The water serves the function of slowing the neutrons to an energy at which the neutron can be effectively absorbed by the boron atom. The steel host for the boron is a relatively good electromagnetic shielding material. In this way the heterogeneous combination of water and boronated steel mitigates the neutron and electromagnetic radiation threat. Such an approach is known both in the fusion and fission industries, though can be considered relatively inefficient in terms of space and performance.SUMMARY

[0011] The present disclosure is directed to a multicomponent composite (or structural steel composite) for mixed neutron and electromagnetic shield application. The multicomponent composite includes a matrix and a secondary phase, where the matrix is composed of an iron¬ based steel alloy and the secondary phase is composed of one or more neutron and electromagnetic radiation absorbing metal-hydrides (MH). In some embodiments, the multicomponent composite can also include a steel enhancement element. As metal hydrides are typically thermal unstable at common metals processing temperatures, and the release ofhydrogen from the MH results in a less effective shield, a resulting method which avoids hydrogen release is desired and disclosed in the present disclosure.

[0012] In one aspect of the present disclosure, a multicomponent composite is provided. In one embodiment, the multicomponent composite comprises, consists essentially of, or consists of, a secondary phase composed of at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity.

[0013] In some embodiments of the present disclosure, the at least one neutron and electromagnetic radiation absorbing metal hydride of the multicomponent composite is present in the steel matrix in an amount from about 5 volume percent to about 70 volume percent.

[0014] In some embodiments of the present disclosure, the at least one neutron and electromagnetic radiation absorbing metal hydride is present in the steel matrix in an amount from about 10 volume percent to about 55 volume percent.

[0015] In some embodiments of the present disclosure, the at least one neutron and electromagnetic radiation absorbing metal hydride comprises a transition metal hydride, a lanthanide hydride or any combination thereof.

[0016] In some embodiments of the present disclosure, the at least one neutron and electromagnetic radiation absorbing metal hydride comprises hafnium hydride, gadolinium hydride, europium hydride or any combination thereof.

[0017] In some embodiments of the present disclosure, the steel matrix is a structural steel, a high-strength, low alloy steel that contains Mn levels up to 2%, or a cryogenic steel.

[0018] In some embodiments of the present disclosure, the secondary phase of the multicomponent composite further comprises a steel enhancing element.

[0019] In some embodiments of the present disclosure, the steel enhancing element is present in the secondary phase in an amount from about 10 volume percent to about 40 volume percent.

[0020] In some embodiments of the present disclosure, the steel enhancing element is present in the secondary phase in an amount from about 20 volume percent to about 60 volume percent.

[0021] In some embodiments of the present disclosure, the steel enhancing element comprises an elemental metal, a metal carbide, a metal boride or any combination thereof.

[0022] In some embodiments of the present disclosure, the steel enhancing element comprises tungsten, tungsten carbide, tungsten boride, boron carbide or any combination thereof.

[0023] In some embodiments of the present disclosure, the multicomponent composite contains substantially no intermetallic phases.

[0024] In another aspect of the present disclosure, a reactor is provided that includes a composite steel wall surrounding a reactor core, where the composite steel wall is composed of a multicomponent composite that comprises, consists essentially of, or consists of, at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity.

[0025] In some embodiments of the present disclosure, the reactor core is a fission reactor core.

[0026] In some embodiments of the present disclosure, the reactor core is a fusion reactor core.

[0027] In some embodiments of the present disclosure, the composite steel wall slows and absorbs neutrons and electromagnetic rays emitted by the reactor core.

[0028] In some embodiments of the present disclosure, the electromagnetic rays emitted by the reactor core comprises gamma-rays, X-rays or a combination thereof.

[0029] In yet another aspect of the present disclosure, a method of forming a multicomponent composite is provided that includes forming a green body comprises, consists essentially of, or consists of, a steel powder and at least one least electromagnetic radiation and neutron absorbing metal hydride-containing powder; and sintering the green body to provide a multicomponent composite comprising a secondary phase composed of at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity. In accordance with the present disclosure, the sintering is performed at a temperature in which the at least one neutron and electromagnetic radiation absorbing metal hydride does not dissociate. Sintering can include any consolidation process including, but not limited, to hot pressing or direct current sintering.

[0030] In some embodiments of the present disclosure, the temperature of the sintering achieves full density from about 850°C to about 900°C, below the dissociation temperature of many metal hydrides of shielding interest.

[0031] In some embodiments of the present disclosure, the green body further includes a steel enhancing element-containing powder.BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a graph illustrating fast neutron dose reduction in MH -composited steel.

[0033] FIG. 2 is a scanning electron microscopy (SEM) microgram of hafnium hydride 304 Matrix MH-composited Steel.

[0034] FIG. 3A shows the die displacement as a function of temperature for a Fe-25% HfH₂ multicomponent composite in accordance with the present disclosure.

[0035] FIG. 3B shows the measured vacuum pressure during the sintering process, including sintering temperature, for the Fe-25% HfH₂ multicomponent composite in accordance with the present disclosure.

[0036] FIG. 3C shows the relative density of specimens sintered with varying volume % of HfH2, with an inset of a 25 nm compact.

[0037] FIG. 4A is a SEM microgram collected in backscattered secondary electron (BSE) mode for a Fe-25% HfH₂ multicomponent composite in accordance with the present disclosure.

[0038] FIG. 4B is a SEM microgram collected in BSE mode for a Fe-40% HfH2 multicomponent composite in accordance with the present disclosure.

[0039] FIG. 4C is a SEM microgram collected in BSE mode for a Fe-55% HfH₂ multicomponent composite in accordance with the present disclosure.

[0040] FIG. 4D is a SEM microgram collected in BSE mode for a Fe-70% HfH₂ multicomponent composite in accordance with the present disclosure.

[0041] FIG. 5A shows the XRD results of Fe-n% HfH₂ series where n = 25, 40, 55 and 70.

[0042] FIG. 5B shows XRD phase fraction vs. sample composition.

[0043] FIG. 6A is a X-ray fluorescence (XRF) map collected of the Hf LIII-edge of a Fe-25% HfH₂ lamellae.

[0044] FIG. 6B is a XRF map collected for Location 1 shown in FIG. 6A.

[0045] FIG. 6C is a XRF map collected for Location 2 shown in FIG. 6A.

[0046] FIG. 7 is a FEFF generated Hf LIII-edge X-ray absorption near-edge structure (XANES) of relevant reference materials.

[0047] FIG. 8A shows the analysis of nano-XANES at Location 1; Specific positions were probed linearly across each location from A1 to A6 for Location 1.

[0048] FIG. 8B shows the analysis of nano-XANES at Location 2; Specific positions were probed linearly across each location from Bl to B6 for Location 2.

[0049] FIG. 9A is a XRF map of a particle of the Hf LIII-edge of the Fe-25% HfH₂ sample taken at Location 1.

[0050] FIG. 9B is a XRF map showing the edge correlation of the Fe-25% HfH₂ sample taken at Location 1.

[0051] FIG. 9C is a graph of Absorption vs. Energy for various samples.DETAILED DESCRIPTION

[0052] The present disclosure will now be described in greater detail by referring to the following discussion and drawings that accompany the present disclosure. In the following description, numerous specific details are set forth, such as particular structures, components, materials, dimensions, processing steps and techniques, in order to provide an understanding of the various embodiments of the present disclosure. However, it will be appreciated by one of ordinary skill in the art that the various embodiments of the present disclosure may be practiced without these specific details. As used throughout the present disclosure, the term “about” generally indicates no more than ±10 %, ±5 %, ±2 %, ±1 % or ±0.5 % from a number. When a range is expressed in the present disclosure as being from one number to another number (e.g., 20 to 40), the present disclose contemplates any numerical value that is within the range (i.e., 22,24, 26, 28.5, 31, 33.5, 35, 37.7, 39 or 40) or any in amount that is bounded by any of the two values that can be present within the range (e.g., 28.5-35).

[0053] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. 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. It will be further understood that the terms “comprises” and / or “comprising”, when used in this disclosure, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0054] The present disclosure provides a multicomponent composite (i.e., structural steel composite) in which specific functions of the composite constituents are selected to interact synergistically thus providing an effective nuclear shield. For example, where the primary purpose of the H of the MH is the slowing of the neutrons, and the function of the M is to both absorb that neutron, retain the H, and to aid in shielding any electromagnetic radiation present. Additionally, the metal, M, of the MH can convey structural purpose and integrity to the steel matrix.

[0055] Notably, the present disclosure provides a multicomponent composite (i.e., structural steel composite) that comprises, consists essentially of, or consists of, a secondary phase composed of at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix. Stated in other terms, the present disclosure provides a two phase composite including an entrained (i.e., secondary) phase composed of at least one neutron and electromagnetic radiation absorbing metal hydride contained within a host matrix which is a steel matrix. Both the secondary (i.e., entrained) phase and the steel matrix of the multicomponent composite of the present disclosure are solid materials. In the present disclosure, the steel matrix of the multicomponent composite has less than 1 %, preferably less than 0.5 %, more preferably less than 0.1 % interconnected porosity. The low percentage ofinterconnected porosity in the steel matrix of the multicomponent composite of the present disclosure limits any substantial migration of chemical species through, or out of, the multicomponent composite of the present disclosure. The steel matrix is dense and provides a rigid structure for the secondary phase. In some embodiments of the present disclosure, the steel matrix has a density of from about 7.6 g / cc to about 8 g / cc.

[0056] The at least one neutron and electromagnetic radiation absorbing metal hydride of the multicomponent composite is present in the steel matrix in an amount that is sufficient to provide enhanced neutron and gamma-ray / X-ray shielding to the steel matrix without adversely affecting the physical and / or mechanical properties of the steel matrix. In some embodiments, the at least one neutron and electromagnetic radiation absorbing metal hydride of the multicomponent composite is present in the steel matrix in an amount from about 5 volume percent to about 70 volume percent with an amount from 10 volume percent to about 55 volume percent being more preferred. In some embodiments, the secondary phase is distributed randomly in the steel matrix. In yet other embodiments, the secondary phase is distributed in an ordered manner in the steel matrix.

[0057] In the present disclosure, the at least one neutron and electromagnetic radiation absorbing metal hydride, MH, includes metal, M, that functions to both absorb neutrons and electromagnetic (including both gamma-ray and X-ray) radiation, and hydrogen, H, that slows the neutron and electromagnetic radiation. The metal in the metal hydride can also convey structural properties to the steel matrix. In some embodiments of the present disclosure, the at least one neutron and electromagnetic radiation absorbing metal hydride comprises a transition metal hydride, a lanthanide hydride or any combination thereof, the metal in each case must absorb neutron and electromagnetic (including both gamma-ray and X-ray) radiation. The transition metal hydride includes a transition metal from Group 4 to Group 12 of the Periodic Table of Elements. Illustrative examples of transition metals that can provide the transition metal hydride that can be employed in the present disclosure include, but are not limited to, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium ( Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), manganese (Mn), rhenium (Re), osmium (Os) or nickel (Ni).A single transition metal hydride or a combination of two or more metal hydrides can be used in the present disclosure. In one preferred embodiment, the transition metal hydride that can be employed as the at least one neutron and electromagnetic radiation absorbing metal hydride is hafnium hydride.

[0058] The lanthanide hydride includes a lanthanide metal. A lanthanide metal is one of the 14 metallic chemical elements with atomic numbers 57-70, i.e., from lanthanum to ytterbium. A single lanthanide hydride or a combination of two or more lanthanide hydrides can be used in the present disclosure. In one preferred embodiment of the present disclosure, the lanthanide hydride that can be employed as the at least one neutron and electromagnetic radiation absorbing metal hydride is gadolinium hydride, europium hydride or a combination thereof.

[0059] In some embodiments of the present disclosure, the least one neutron and electromagnetic radiation absorbing metal hydride comprises hafnium hydride, gadolinium hydride, europium hydride or any combination thereof.

[0060] The steel matrix is composed of steel. Steel is an alloy of iron (Fe) and carbon (C) in which the carbon content is typically from about 0.02 to 2.15 % by weight of the alloy. Steel can contain alloy elements including, but not limited to, Mn, Ni, Cr, Mo, B, Ti, V, W, Co and Nb. Steel can also include P, S, Si as well as trace amounts of O, N and Cu. The steel matrix is formed using a steel powder that includes at least Fe and C. In some embodiments, the steel powder used in providing the steel matrix can also contain alloy elements including, but not limited to, Mn, Ni, Cr, Mo, B, Ti, V, W, Co and Nb; P, S, Si as well as trace amounts of O, N and Cu.

[0061] In some embodiments of the present disclosure, the steel matrix is composed of a structural steel. Structural steel is a carbon steel in which no other alloying element is present, Cu content does not exceed 0.4 to 0.6%, Mn does not exceed 1.6%, and Si does not exceed 0.6%.

[0062] In some embodiments, the steel matrix is a high-strength, low alloy steel that contains Mn levels up to 2%. Trace amounts of Cr, Ni, Mo, N, V, Nb, and Ti may be used to alter the properties of this type of steel.

[0063] In other embodiments of the present disclosure, the steel matrix is composed of a cryogenic steel. Cryogenic steel is steel as example used as in superconducting magnet structural and function application for fusion reactor systems.

[0064] In some embodiments of the present disclosure, the steel enhancing element is present in the secondary phase in an amount from about 10 volume percent to about 40 volume percent, with an amount from 20 volume percent to 60 volume percent being more preferred. In many cases the lower hydride product occurs in conjunction with other non-hydride shielding additives to the base steel matrix. The steel enhancing element is any element or compound that can be added into steel to enhance the shielding effectiveness of the body working in concert with the metal hydride additive. The steel enhancing element can include, but is not limited to, a metal carbide (such as, for example, WC and / or boron carbide), a metal boride (such as, for example, WB) or any combination thereof. In one preferred embodiment of the present disclosure, the steel enhancing element includes tungsten, tungsten carbide, tungsten boride, boron carbide or any combination thereof.

[0065] In some embodiments of the present disclosure, the multicomponent composite of the present disclosure contain substantially no intermetallic phases. The term “substantially no intermetal phases” denotes that the multicomponent composite of the present disclosure contains no (i.e., is free of) intermetallic phases, or it contains a trace amount (less than 100 ppm, even more preferably less than 50 ppm, and most preferably less than 1 ppm) of intermetallic phases. Intermetallic phases in the multicomponent composite of the present disclosure are undesirable since they can change the properties of the steel matrix of the multicomponent composite of the present disclosure. The intermetallic phases can include, for example, α-HfFe2and λ-HfFe2.

[0066] The multicomponent composite of the present disclosure can be used in various applications in which shielding of neutrons and electromagnetic radiation is needed. In one example, the multicomponent composite can be used in a reactor. In such an embodiment, a reactor is provided that includes a composite steel wall surrounding a reactor core, where the composite steel wall is composed of a multicomponent composite in accordance with the present disclosure. Notably, the composite steel wall is composed of a multicomponent composite that comprises, consists essentially of, or consists of, at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity. In some embodiments of the present disclosure, the reactor core is a fission reactor core. In some embodiments of the present disclosure, the reactor core is a fusion reactor core.

[0067] In some embodiments of the present disclosure, the composite steel wall slows and absorbs neutrons and electromagnetic rays emitted by the reactor core. In some embodiments of the present disclosure, the electromagnetic rays emitted by the reactor core comprises, gamma¬ rays, X-rays or a combination thereof.

[0068] The multicomponent composite of the present disclosure can be provided by first forming a green body that comprises, consists essentially of, or consists of, a steel powder and at least one neutron and electromagnetic radiation absorbing metal hydride, as defined above. In some embodiments, the green body can also include a steel enhancing element, as defined above.

[0069] The term “green body” is used herein to denote a consolidation of a powder mixture through low- temperature pressing. That powder mixture may contain steel powder, at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder, and optionally a steel enhancing element-containing powder. Prior to forming the green body, any of the steel powder, the at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder, and the optional steel enhancing element-containing powder can be dried (i.e., kiln-dried) in an inert gas environment (e.g., He, Ar and / or Ne) and at a temperature from about 100°C to about 200°C.

[0070] The mixture of the steel powder, the at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder, and optionally the steel enhancing element- containing powder that provides the green body, can be formed by adding, in any order, the steel powder, the at least one neutron and electromagnetic radiation absorbing metal hydride- containing powder, and optionally the steel enhancing element-containing powder to a mixer, such as for example, a bladeless dual-asymmetric-centrifugal mixer. Mixing may be performed during, and / or after each addition step. In one embodiment, the mixture that is used in forming the green body comprises first adding the steel to the mixer, followed by second adding the at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder to the mixer containing the steel powder and thereafter adding any steel enhancing element¬ containing powder to the mixer containing both the steel powder and the at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder. In such an embodiment, mixing can be performed during and / or after each of the three addition steps. In one embodiment, the mixture used in forming the green body can contain from about 5 volume percent to about 70 volume percent of the at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder, from about 3 volume percent to about 20 volume percent of the optional steel enhancing element-containing powder, with the balance being the steel powder. In some embodiments, the mixture can be pressed at a pressure of about 100 MPa to about 200 MPa to provide the green body. In other embodiments, the mixture can be pressed at a pressure of about 50 MPa.

[0071] The green body thus formed is then sintered to provide a multicomponent composite in accordance with the disclosure. Sintering is performed at a temperature in which the at least one neutron and electromagnetic radiation absorbing metal hydride does not dissociate. Sintering is typically, but not always, carried out under vacuum on the green body in the range of from about 10 MPa to about 50 Pa with initiation of sintering starting at a temperature from about 750°C to about 900°C. Sintering temperatures greater than 900°C should be avoided since at such high sintering temperatures the metal hydride can dissociate. This dissociation of the metal hydride can lead to the formation of undesirable intermetallic phases.

[0072] The term “sintering” is used throughout the present disclosure to denote a process of compacting and forming a solid mass by pressure or heat without melting it the point of liquification. Since the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points. The sintering process can include any consolidation process such as, for example, direct current sintering or hot pressing.

[0073] Examples have been set forth below for the purpose of further illustrating the present disclosure. The scope of the present disclosure is not limited to any of the examples set forth herein.

[0074] EXAMPLE 1

[0075] In this example, the effectiveness of an iron matrix containing secondary phase hafnium hydride, HfH2, (in accordance with the present disclosure) is provided and contrasted with common shield materials utilized as superconducting magnet shield materials in fusion reactor systems. The effectiveness is shown in FIG. 1 which is a graph of fast neutron flux (neutrons / cm2, E >0.1 MeV) vs. percent of HfH2in steel matrix. Here the effect of variable MH (in the case M being the high neutron absorbing hafnium) on the reduction in damaging fast neutron flux is provided. For all cases above, a few percent MH in the composited shield outperforms the common shield materials of water, combined boronated steel, steel / water, and boron carbide. Similar performance can be seen for radiation dose, or nuclear heating.

[0076] EXAMPLE 2

[0077] FIG. 2 provides an SEM image of a 304 matrix steel processed with approximately 50% hafnium hydride in accordance with the present disclosure. As seen in the image and confirmed by high-resolution tomography the steel matrix is of full density. Moreover, X-ray diffraction analysis indicates that the structure of the MH phase has undergone little decomposition suchthat the retained hydrogen fraction is high. The material of FIG. 2 and similar structure are formed in thick plate geometry at relatively low temperature and pressure utilizing an advanced manufacturing process of direct current sintering, as described in the present disclosure. Starting¬ materials for matrix and MH are powders, with levels of MH variable from 5% to 55% MH. Based on application need, additional electromagnetic shielding can be gained through inclusion of heavy elements of tungsten within the steel matrix, or tungsten boride.

[0078] EXAMPLE 3

[0079] The structural interactions of an Fe-HfH2metal matrix composite (MMC) are studied across multiple length scales to elucidate the Fe-Hf-H interactions at work during direct current sintering. Fe-HfH2composites were formed with increasing as-mixed hydride content: Fe-25% HfH2, Fe-40% HfH2, Fe-55% HfH2, and Fe-70% HfH2to demonstrate the ability to achieve target final hydrogen content. Samples were probed across multiple length scales with X-ray diffraction, scanning electron microscopy and segmentation analysis, and hard X-ray fluorescence mapping and nanoprobe X-ray absorption near-edge structure. Under these relatively aggressive sintering temperature and pressure conditions hydrogen evolution is seen to evolve through parallel paths: thermal decomposition from original HfH2to HfHx<2 and through reaction leading to intermetallic phase formation. Specifically, HfFe and HfFe2 intermetallic formation occurs leading to the release of hydrogen with a subsequent HfCh phase forming at grain boundaries. For this composite system, the consumption or loss of hydrogen can be considerable in compacts with 25-40% HfH 2 initial powder volume loadings, with as much as 83% hydrogen lost for the lower volume fraction composites, with maximum retained hydrogen content found to be 53% for the Fe-70% HfH2material.

[0080] I. Materials Fabrication

[0081] Sample specimens were prepared via direct current sintering (DCS) as follows. Fe powder (Alfa Aesar, USA, 325 mesh, 98% purity) was mixed with 25, 40, 55, or 70 vol% HfH2powder (Stanford Advanced Materials, USA, 200 mesh, 99% purity) via speed-mixing(FlackTek DAC-1100) at 800 rpm for 1 min. 20 g of each powder charge was loaded into a 25 mm-diameter graphite die inlayed with graphite foil and wrapped in carbon felt to reduce thermal losses. A thermocouple (K-type) inserted into the graphite die was utilized to monitor the temperature during sintering. Samples were sintered using a SinterLand LABOX-3010KF DCS system. Electrical contact was maintained during the displacement of the graphite die assembly by placing the sample under a 50 MPa static uniaxial compressive pressure. Each sample was heated at a rate of 100°C / min and held at 1000°C for 5 min prior to cooling at ambient temperatures. Vacuum pressure was set at 10 Pa throughout the sintering process to promote densification. After sintering, each sample was sandblasted to remove the graphite foil and potential contaminants. Prior to characterization, samples were mirror-polished to eliminate surface imperfections, roughness, and scratches using a standard set of SiC abrasive sheets and diamond suspension.

[0082] II. Materials Characterization

[0083] Density was determined using the water displacement method based on Archimedes1Principle (See, for example, M. Kires, Archimedes’ principle in action, Physics Education 42(5) (2007)). Relative density was determined via normalizing by the rule-of-mixture density, which accounted for the concentration of HfFfo in each composite. X-ray diffraction patterns (XRD; Bruker D8 Ad vance) were collected to assess phase content and degree of hydrogen retention post-sintering. After phase identification, the lattice parameters, weight fractions, and grain sizes for each phase were allowed to be refined. Each XRD pattern was analyzed using Rietveld refinement (See, for example, H. M. Rietveld, A profile refinement method for nuclear and magnetic structures, J. Appl. Cryst. 2 (1969) 65-71) with the TOP AS software (Bruker) with instrument-based broadening parameters fixed (fundamental parameters approach) and a four component polynomial background function. The crystallographic data from Dottor (See, for example M. Dottor, J.-C. Crivello, L. Laversenne, J.-M. Joubert, Experimental determination of the H-Hf phase diagram using in situ neutron diffraction, Journal of Alloys and Compounds 937 (2023)) for the HfH2(I4 / mmm) and HfH1.44(Ibam) phases were included in refinements with atom positions and atomic displacement parameters fixed. The Fe-Hf intermetallic phases HfFe2(α-HfFe2Fd-3m), HfFe2(λ-P6_3 / mmc) and HfO2 (P21 / c) were also included atom positions and atomic displacement parameters fixed values reported within literature (See, for example, R. Ruh, P. W. R. Corfield, Crystal Structure of Monoclinic Hafnia and Comparison with Monoclinic Zirconia, Journal of the American Ceramic Society 53(3) (1970) 126-129; A. Jain, S. P. Ong, G. Hautier, W. Chen, W. D. Richards, S. Dacek, S. Cholia, D. Gunter, D. Skinner, G. Ceder, K. A. Persson, Commentary: The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1(1) (2013) 011002; and B. Cekic, B. Prelesnik, S. Koicki, D. Rodic, M. Manasijevic, N. Ivanovic, Refinement of the crystal structure of Hf2Fe, Journal of the Less Common Metals 171(1) (1991) 9-15).

[0084] A minimum of 21 and maximum of 28 parameters were refined for each sample (depending on the number of phases), with minimal correlations between the grain size and weight fractions. Slightly higher correlations were observed between the lattice parameters for the HfO phase, and the background. The microstructure of each sample was examined using scanning electron microscopy (SEM; Tescan, Lyra 3) with an accelerating voltage of 10 kV in backscattered electron (BSE) mode. BSE images were analyzed using Fiji image processing software (See, for example, C. A. Schneider, W. S. Rasband, K. W. Eliceiri, NIH Image to Image J: 25 years of image analysis, Nat Methods 9(7) (2012) 671-5) and the trainable Weka Segmentation (See, for example, L Arganda-Carreras, V. Kaynig, C. Rueden, K. W. Eliceiri, J. Schindelin, A. Cardona, H. Sebastian Seung, Trainable Weka Segmentation: a machine learning tool for microscopy pixel classification, Bioinformatics 33(15) (2017) 2424-2426) plugin package to determine the % area of each component. In short, this process involves hand selection of representative pixels and assigning each a ‘class’ designation before running the available code to then classify the entire image. This process is iterative and allows correction for mis -assignment of pixel class through further selection and analysis. Three SEM images for each specimen (from different regions) were analyzed to determine fractions, mean sizes and standard errors. The Fe-25% Hffib sample was further characterized at the Hard X-Ray Nanoprobe (HXN) Beamline at the NSLS-II at Brookhaven National Laboratory (BNL). Two- dimensional scanning X-ray fluorescence (XRF) and spectroscopy measurements were collected to resolve the elemental (See, for example, H. Yan, N. Bouet, J. Zhou, X. Huang, E. Nazaretski,W. Xu, A. P. Cocco, W. K. S. Chiu, K. S. Brinkman, Y. S. Chu, Multimodal hard x-ray imaging with resolution approaching 10 nm for studies in material science, Nano Futures 2(1) (2018) 011001) and chemical structure around nanometer-scale features of interest (See, for example, A. Pattammattel, R. Tappero, M. Ge, Y. S. Chu, X. Huang, Y. Gao, H. Yan, High-sensitivity nanoscale chemical imaging with hard x-ray nano-XANES, Science Advances 6(37) (2020) eabb3615; and D. J. Sprouster, W. Streit Cunningham, G. P. Halada, H. Yan, A. Pattammattel, X. Huang, D. Olds, M. Tilton, Y. S. Chu, E. Dooryhee, G. P. Manogharan, J. R. Trelewicz, Dislocation microstructure and its influence on corrosion behavior in laser additively manufactured 316L stainless steel, Additive Manufacturing 47 (2021) 102263).

[0085] A 10 x 10 x 0.1 pm sample lamella was prepared via focused ion beam (FIB) lift-out techniques in a FEI Helios Nanolab 600 dual-beam focused ion beam / scanning electron microscope (FIB / SEM) located at the Center for Functional Nanomaterials (CFN) at BNL. A nominally one pm-thick cross-sectional lamella was removed from the bulk sample, welded to a copper Omniprobe lift-out grid, and subsequently thinned to approximately 100 nm for analysis. Incident X-rays with a wavelength of 1.3051 A and an energy of 9.5 keV were focused via Fresnel zoneplate nanofocusing optics to a approximately 30 × 30 nm spot size. Two dimension XRF maps were collected employing scanning dwell times of 50 ms. Two-dimensional XRF spectral maps were processed and visualized in PyXRF (See, for example, L. Li, H. Yan, W. Xu, D. Yu, A. Heroux, W.-K. Lee, S. Campbell, Y. Chu, PyXRF: Python-Based X-ray Fluorescence Analysis Package, SPIE2017) and MIDAS (See, for example, A. Pattammattel, R. Tappero, Y. S. Chu, M. Ge, D. Gavrilov, X. Huang, H. Yan, Hard x-ray nano-XANES and implementation deep learning tools for multi-modal chemical imaging, SPIE Optical Engineering + Applications, San Diego, California, USA, 2021).

[0086] Nanoscale X-ray absorption near-edge spectroscopy (nano-XANES) around the Hf LIII-edge (9561 eV) were collected to quantify the atomic structure of Hf atoms located within the XRF maps with 30 nm spatial resolution. Two separate locations were probed with nano-XANES. The graphical user interface JFEFF was utilized to run FEFF9, an implementation of real-space multiple scattering theory, to calculate and model Hf based XANES data at the HfLIII-edge (See, for example, K. Jorissen, J.J. Rehr, New Developments in FEFF: FEFF9 and JFEFF, Journal of Physics: Conference Series 430 (2013)). To date, there are no reported X-ray absorption near edge structure (XANES) measurements of any HfHxor Fe-Hf phases. Of the Hf LIII-edge XANES data reported, the majority are of oxides (See, for example, M. Bauer, S.Muller, G. Kickelbick, H. Bertagnolli, The structures of the precursor Hf(OnBu)4 and its modification in solution: EXAFS-investigation in combination with XANES- and IR- spectroscopy, New Journal of Chemistry 31(11) (2007); M. S. Mathur, The engineering and optimization of the hafnium based metal oxide semiconductor structure, Chemical Engineering, University of California, Los Angeles, 2008; D.-Y. Cho, T.J. Park, K. D. Na, J. H. Kim, C. S. Hwang, Structural disorders in an amorphousHfO2film probed by x-ray absorption fine structure analysis, Physical Review B 78(13) (2008); and D.-Y. Cho, H.-S. Jung, C. S. Hwang, Structural properties and electronic structure ofHfO2-ZrO2composite films, Physical Review B 82(9) (2010)) and silicates (See, for example, Y. Uehara, K. Kawase, J.i. Tsuchimoto, T. Shibano, X- ray absorption and emission spectroscopy at the Hf LI edge of hafnium-(silicon)-oxide ultra-thin films, Journal of Electron Spectroscopy and Related Phenomena 148(2) (2005) 75-79; and J. Morais, L. Miotti, K. P. Bastos, S. R. Teixeira, I. J. R. Baumvol, A. L. P. Rotondaro, J. J. Chambers, M. R. Visokay, L. Colombo, M. C. M. Alves, Environment of hafnium and silicon in Hf-based dielectric films: An atomistic study by x-ray absorption spectroscopy and x-ray diffraction, Applied Physics Letters 86(21 ) (2005)).

[0087] III. Sintering of Fe-HfH2composites

[0088] Iron-hafnium hydride entrained MMCs were produced with increasing volume percent of Hffh: Fe-25% HfH2, Fe-40% HfH2, Fe-55% HfH2, and Fe-70% HfH2via DCS. FIGS. 3A-3C depict the sintering characteristics of a representative Fe-HfH2powder. A positive displacement, i.e., in the direction of the applied compressive force, is observed in FIG. 3A. At temperatures below 370°C, samples undergo densification and concluded at 1000°C, wherein the displacement curve exhibited a consistent and gradual increase in rate.

[0089] Measured vacuum pressure during the sintering cycle is shown in FIG. 3B. An initial surge in vacuum pressure occurred at about 70°C, consistent with the release of any remaining moisture or adsorbed gases within either the sample or the chamber. Notably, distinctive peaks in the vacuum pressure curve were evident at approximately 390°C, 435°C, and 890°C, signifying the release of gaseous substances that alter the observed vacuum pressure (See, H. Wen, Y. Zhao, Z. Zhang, O. Ertorer, S. Dong, E. J. Lavernia, The influence of oxygen and nitrogen contamination on the densification behavior of cryomilled copper powders during spark plasma sintering, Journal of Materials Science 46(9) (2010) 3006-3012). Recent work by Dottor and colleagues developed a Hf-H phase diagram with in-situ neutron diffraction indicates HfHxbegin to decompose and form H2gas between 170 and 300°C (See, M. Dottor, J.-C. Crivello, L. Laversenne, J.-M. Joubert, Experimental determination of the H-Hf phase diagram using in situ neutron diffraction, Journal of Alloys and Compounds 937 (2023)). Above this temperature, HfHxphases are still present. Furthermore, above 800°C Hf metal forms and significant amounts of H2are expected to be lost. These values are supported in other thermal analyses of the Hf-H system (See, for example, Y. Arita, T. Ogawa, B. Tsuchiya, T. Matsui, Heat Capacity Measurement and DSC Study of Hafnium Hydrides, Journal of Thermal Analysis and Calorimetry 92(2) (2008) 403-406; and S. K. Dolukhanyan, A. G. Aleksanian, A. G. Hakobian, Interaction of Hafnium with Hydrogen and Nitrogen in the Combustion Regime, Int. J. Hydrogen Energy 20(5) (1995) 397-395). Additionally, the small amount of iron oxides present on the surface of the feedstock Fe powder release additional O2at 775 and 925°C (See, for example, W. M. Keely, Differential Thermal Analysis Study of the Reduction of Cobalt Oxide, Iron Oxide, and Copper Oxide, J. Chem. Eng. Data 10(2) (1965) 186-188; and A. V. Anupama, W. Keune, B. Sahoo, Thermally induced phase transformation in multi-phase iron oxide nanoparticles on vacuum annealing, Journal of Magnetism and Magnetic Materials 439 (2017) 156-166).

[0090] The change in vacuum pressure around 890°C potentially marks the formation of the intermetallic compound Fe-Hf. These findings align with reports in scientific literature, which suggest that lower initial pressure during DCS results in higher density; See, for example, Z. H. Zhang, F. C. Wang, S. K. Lee, Y. Liu, J. W. Cheng, Y. Liang, Microstructure characteristic, mechanical properties and sintering mechanism of nanocrystalline copper obtained by SPSprocess, Materials Science and Engineering: A 523(1-2) (2009) 134-138; Z.-H. Zhang, F.-C. Wang, L. Wang, S.-K. Li, Ultrafine-grained copper prepared by spark plasma sintering process, Materials Science and Engineering: A 476(1-2) (2008) 201-205; and Z. Zhaohui, W. Fuchi, W. Lin, L. Shukui, S. Osamu, Sintering mechanism of large-scale ultrafine-grained copper prepared by SPS method, Materials Letters 62(24) (2008) 3987-3990. Mechanisms governing densification of the Fe-HfH2MMCs are discussed below.

[0091] IV. Microstructural analysis through SEM analysis

[0092] To understand the distribution of these phases within the microstructure and confirm the phase concentrations determined via XRD, SEM micrographs were collected for each sample in BSE mode (See, FIGS. 4A-4D). FIG. 4A is a SEM micrograph for a multicomponent composite containing 25% HfH contained in the steel matrix, FIG. 4B is a SEM micrograph for a multicomponent composite containing 40% HfH2contained in the steel matrix, FIG. 4C is a SEM micrograph for a multicomponent composite containing 55% HfH2contained in the steel matrix, and FIG. 4D is a SEM micrograph for a multicomponent composite containing 70% HfH2contained in the steel matrix. Contrast variation in BSE images arise from differences in Z (atomic number), and phase density with high-Z elements like Hf appear brighter while low-Z elements appear darker. Similarly, denser phases appear lighter than their less dense counterparts. In these images, the lightest areas are Hf-rich, containing HfHxand HfO2phases, and the darkest areas are Fe-rich. Medium grey areas are the intermetallic phases, α-HfFe2and λ-HfFe2. It is noted that the extremely dark regions viewable in the samples are from pullout areas arising from polishing and are not to be considered.

[0093] BSE images were further analyzed to quantify each area / phase present in the BSE images. Results from the SEM analysis (See, also Table 2) are compared with XRD phase refinement results and independently confirm the phase fraction percent determined by XRD. Qualitative analysis of the micrographs clearly indicates a growing area of the white, Hf-rich zones, consistent with the amount of HfHxphases present. The light gray area, which consists of intermetallic phases, frequently separates the light, Hf-rich hydride, and oxide zone from themuch darker, Fe-rich areas. Considering the starting materials, HfH2and Fe-powder, the intermediate (in-between) intermetallic zone clearly forms as the starting materials interact and the free Hf and Fe atoms combine into intermetallic phases.

[0094] V. Phase determination with XRD

[0095] The behavior of the Fe-Hf-H interactions post -sintering were first probed with XRD (See, FIGS. 5 A and 5B) and Table 1..050-9482_PCT_AppUcadon.docx

[0096] TABLE 1: Results of Rietveld refinement. Uncertainties from the non-linear least squares fitting method are given in parenthesis.a (A) b (A) c (A) beta (°) Weight Fraction Sample Phase Name Space Group Value Value Value Value(%) (Error) (Error) (Error) (Error) (Error)Fe Im-3rn 2.86886(1) - - - 48.8(2) α-HfFe2Fd-3m 6.9978(3) - - - 5.6(3) Fe-25%HfH2λ-HfFe2P6_3 / mmc 4.92842(8) - 8.0241(2) - 40.6(2) HfO2P21 / c 5.1198(5) 5.1717(5) 5.2974(5) 99.169(7) 6.4(1) HfH1.44Ibam 4.650(1) 9.282(3) 4.6272(9) - 4.2(1) Fe Im-3m 2.86918(5) ■■ ■■ - 21.4(2) a-HfFe?. Fd-3m 6.9958(4) ■■ ■■ - 14.7(3) Fe-40%HfH2λ-HfFe2P6_3 / mmc 4.9345(1) - 8.0316(3) - 53.3(2) HfO2P21 / c 5.1189(6) 5.1775(7) 5.2933(6) 99.15(1) 6.3(1) HfH1.44Ibam 4.712(2) 9.418(4) 4.610(2) - 4.2(9) Fe Im-3m 2.8696(1) - - - 4.7(1) Fe-55%HfH2a-HfFe2Fd-3m 7.0262(3) - - - 24.9(3)A-HfFe2P6_3 / mmc 4.9465(3) - 8.0553(8) - 38.5(3) HfO2P21 / c 5.130(1) 5.185(1) 5.282(1) 99.11(1) 4.1(1) HfH1.9I4 / mmm 3.375(8) - 4.78(2) - 4.4(2) HfH144Ibam 4.7332(4) 9.4141(8) 4.6468(2) - 23.3(1) Fe Im-3m 2.8688(1) ■■ ■■ - 2.0(1) α-HfFe2Fd-3m 7.0226(4) - - - 26.5(3) λ-HfFe2P6_3 / mmc 4.9413(8) - 8.027(1) - 14.8(3) Fe-70%HfH2HfO2P21 / c 5.126(1) 5.185(1) 5.285(1) 99.12(1) 4.7(1) HfH1.9I4 / mmm 3.2227(4) - 4.830(1) - 5.4(5)ibam 4.7279(1) 9.3826(5) 4.6914(2) - 46.7(4)050-9482_PCT_Application.docx

[0097] Phase identification revealed each sample consists of body-centered cubic (BCC) Fe metal, Fe-Hf intermetallic phases (a-HfFe2and k-HfFe2), HfO2, and multiple hafnium hydrides (Hffli.99 and 8’-Hffih.44)- Subtle differences in the weight fractions were determined when comparing between the SEM and XRD analysis, due to the different inherent sensitivities and limitations of the two methods: SEM is poor at separating materials with similar Z-contrast (such as HfHx phases and intermetallic phases); while XRD phase quantification can be complicated by overlapping diffraction peaks, and weak scattering due to low-Z elements. The weight fractions and uncertainties reported in Table 1 for the Rietveld refinement are those directly from the non-linear least squares fitting method. The true uncertainty for the XRD weight fraction quantification is about 1-2%.

[0098] Table 2 lists the weight fractions determined from both the XRD and SEM analysis with the realistic weight uncertainties.

[0099] TABLE 2: Results of Weka Segmentation and Comparison to XRD results.Sample Phase SEM % XRD % Fe-25%HfH2Fe-rich 41.6 (1.2) 48.8 (2.0) Intermetallic 53.3 (1.1) 46.2 (2.0)Hf-rich 5.1 (1.0) 10.6 (2.0)Fe-40% HfH2Fe-rich 21.2 (1.5) 21.4 (2.0) Intermetallic 69.5 (2.3) 68.0 (2.0)Hf-rich 9.3 (0.5) 10.5 (2.0)Fe-55%HfH2Fe-rich 6.0 (0.9) 4.7 (2.0) Intermetallic 68.7 (2.9) 63.4 (2.0)Hf-rich 25.7 (1.4) 31.9 (2.0)Fe-70%HfH2Fe-rich 7.1 (1.5) 2.0 (2.0)Intermetallic 46.9 (1.0) 41.3 (2.0)Hf-rich 46.0 (1.3) 56.8 (2.0)

[0100] It is interesting to note that the quantification from the XRD and SEM for the 40 % and 55%' Hffib samples are in agreement within uncertainty ranges, while the extremes (25 and 70 %) show discrepancies. These discrepancies result from a variety of factors, namely the different length scale probed by each technique, and similar Z-contrast limiting isolation of Hf-rich intermetallic and oxide phases. Furthermore, these samples were prone to ‘pullout’ during polishing leading to more dark regions on the sample surface. These dark / black areas were best resolved in the 25% sample and became increasingly difficult to differentiate from the dark, Fe- rich areas in the 70% sample. The differences in the weight fractions from XRD and SEM for the low Fe-rich and Hf-rich are likely the source of this discrepancy. Additionally, the thin nature of the HfO2 phase (as discussed in following sections), potentially hinders the correct incorporation into the Hf-rich phase analysis.

[0101] Of note, the 5’-HfHi.44 phase was recognized as the recently identified 3’-HfHi.44 structure determined by M. Dottor, J.-C. Crivello, L. Laversenne, J.-M. Joubert, Experimental determination of the H-Hf phase diagram using in situ neutron diffraction, Journal of Alloys and Compounds 937 (2023). Overall, sintering of HfH2with Fe powder induces changes to the hydride structure, forming additional phases which have been extensively documented in phase diagrams (See, for example, M. H. Mintz, Hafnium-Hydrogen, Solid State Phenomena 49-50 (1996) 331-356, R. K. Edwards, E. Veleckis, Thermodynamic Properties and Phase Relations in the System Hydrogen-Hafnium, Journal of Physical Chemistry 66(9) (1962) 1657-1661, and C. Boelsma, L. J. Bannenberg, MJ. van Setten, N. J. Steinke, A. A. van Well, B. Dam, Hafnium-an optical hydrogen sensor spanning six orders in pressure, Nature Communications 8 (2017) 15718) and through XRD studies (See, for example, S. S. Sidhu, L. Heaton, D. D. Zauberis, Neutron Diffraction Studies of Hafnium-Hydrogen and Titanium- Hydrogen Systems, Acta Cryst.9 (1955) 607-614, L. J. Bannenberg, H. Schreuders, H. Kim, K. Sakaki, S. Hayashi, K. Ikeda, T. Otomo, K. Asano, B. Dam, Suppression of the Phase Coexistence of the fcc-fct Transition inHafnium-Hydride Thin Films, J Phys Chem Lett 12(45) (2021) 10969-10974, andH. Wang, K. Konashi, Investigation on electronic, mechanical and thermal properties of Hf-H system, Journal of Nuclear Materials 443(1-3) (2013) 99-106). Unfortunately, few works have examined the Hf-H system at temperatures > 800°C, with only a single work noting the system is undefined at 1000°C and 1 atm H2 (See, M. H. Mintz, Hafnium-Hydrogen, Solid State Phenomena 49-50 (1996) 331-356). The concomitant formation of lower ratio hydride phases along with HfO2and Hf-Fe intermetallic phases suggests that the sintering process results in a net loss of detectable hydrogen phases. Dehydrogenation has been noted before in TiHc analogs, starting at the particle or compact surface and progressing inward to the interior, creating a hydrogen concentration gradient (See, G. Chen, K. D. Liss, G. Auchterlonie, H. Tang, P. Cao, Dehydrogenation and Sintering of TiH2: An In Situ Study, Metallurgical and Materials Transactions A 48(6) (2017) 2949-2959).

[0102] A uniform distribution of hydrogen (and hydride) concentration over die hafnium-sample volume is impeded by low mobility of hydrogen in the hafnium hydride and its weak solubility in the metal lattice. Low hydrogen mobility in the Hf-H system has been attributed to vacancy sizing effects necessitating H be first reduced to become mobile. Finally, dissolved oxygen in the Hf lattice tends to decrease H solubility, further reducing mobility and increasing the likelihood H will migrate in alternative paths.

[0103] A comparison of the XRD phase fraction vs sample composition is provided in FIG. 5B. The HfO2phase fraction remains constant across all four samples, suggesting the HfO2phase reaches a stable equilibrium concentration despite the starting composition. It is noted that some percentage of the HfO2formation is related to a surface phenomenon, with HfO2forming upon exposure to air. The 8’-HfI -I1.44 phase shares an inverse relationship with the Fe metal phase traction, suggesting that Hf readily reacts with Fe, preferentially forming the intermetallic phases. Additional free Hf and Fe atoms form intermetallic λ-HfFe2and α-HfFe2phases. Phase diagrams of the Hf-Fe system indicate HfFe2phases are stable at higher atomic percentages of available Hf, nominally 33% (See, for example, H. Okamoto, M. E. Schlesinger, E. M. Mueller, Thermodynamics and Phase Diagrams, ASM Handbook: Alloy Phase Diagrams 2016). Whilethis availability is slightly out of range for the 25%; Hfl h sample, this behavior would be observable at a local level. Interestingly, the λ-Hf2Fe phase is highest in the 25% HfH2sample, with its presence decreasing as the initial amount of HfH2increases. At the same time, the α-HfFe2shows a steady increase before both intermetallic phases reach ~20% phase fractions. There is thus a clear interplay between the intermetallic phases, with the Fe matrix incorporating additional Hf as more is readily available.

[0104] VI. Hard X-ray Nanoprobe

[0105] The 25% HfH2sample was selected for HXN analysis due to the low hydride content representing the extreme case scenario for this sample series. Further characterization was necessary to determine the physio-chemical structure around nanometer-scale features of interest observed through SEM-BSE mapping. 2D XRF mapping was collected of the 25% HfH2sample, shown in FIGS. 6A-6C. Examination of the 2D XRF map collected of the10 x 10 x 0.1 pm sample lamella reveals the presence of two distinct regions: an Fe-rich matrix with Hf-rich particles embedded. Within the Hf-rich particles there are smaller Fe-rich particulates. These results are consistent with the SEM-BSE images in FIG. 4A. Within the XRF map of the 25%-HfH2 lamellae, two locations, as indicated by the colored boxes, were further analyzed using nano-XANES around the Hf LIII-edge. Spectroscopic analysis was performed on this imaging stack to resolve the local atomic structure of the different Hf environments with 30 nm spatial resolution. Both Hf-rich particles exhibit a mottled appearance, with a sizable portion of their bulk consisting of lower Hf concentrations.

[0106] Reference XANES spectra of relevant materials (HfH1.99, HfO2, α-HfFe2, and λ-HfFe2) were generated and are shown in FIG. 7. The Hf LIII-edge XANES of HfO2agrees well with literature (See, for example, M. Bauer, S. Muller, G. Kickelbick, H. Bertagnolli, The structures of the precursor Hf(OnBu)4 and its modification in solution: EXAFS-investigation in combination with XANES- and IR- spectroscopy, New Journal of Chemistry 31(11) (2007), D.- Y. Cho, T. J. Park, K. D. Na, J. H. Kim, C. S. Hwang, Structural disorders in an amorphousHfO2film probed by x-ray absorption fine structure analysis, Physical Review B78(13) (2008), D.-Y. Cho, H.-S. Jung, C. S. Hwang, Structural properties and electronic structure ofHfO2-ZrO2composite films, Physical Review B 82(9) (2010), and L. Both, S. A. Kondrat, R. Navar, D. Padovan, J. S. Martinez-Espin, S. Meier, C. Hammond, Solvent-Activated Hafnium- Containing Zeolites Enable Selective and Continuous Glucose-Fructose Isomerisation, Angew Chem Int Ed Engl 59(45) (2020) 20017-20023), with a strong white-line attributed to transition of a 2p electron to the 5d unoccupied state and a post edge signal arising from multiple-scattering events affected by Hf - O disorder. To the best of Applicant’ s knowledge, there are no prior experimental works of the Hffik or Hf-Fe intermetallic XANES structures. In the modeled spectra, the significant loss of white line intensity from the λ-HfFe2to the α-HfFe2indicates a filling of 5d orbitals. This behavior is also noted in the HfO2, HfH1.99and S’-HfHi 44 phase samples, with the O having additional available electrons to donate. Notably, the difference between the HfCL and HfHi.99 phases is < 1 eV, making their structures difficult to resolve.

[0107] To probe phase differences across the Hf-rich particle, the Fe-rich / Hf-deficient matrix, and the boundary between them, regions of interest were selected at regular intervals in both Location 1 and Location 2 (See, FIGS. 8A and 8B). Fingerprinting analysis of the resultant XANES spectra indicates the Hf-rich region consists of a mixture of HfO? and Hf-Fe intermetallic phases. This analysis was confirmed by fitting the white line peak with two pseudo- V oigt functions (1:1 Lorentzian: Gaussian relationship) centered at 9563.0 eV for HfO2and 9566.6 for HfFe2. The similar peak centroid energies of 9563.0 eV and 9563.7 eV between HfO2and HfH1.99, respectively were a significant hurdle in resolving these structures. Given the open-air environment and the nm-thickness of the sample lamellae, it was concluded that HfO2would dominate the signal and thus a peak centroid of 9563.0 eV was selected to probe. It is noted that the presence of HfHi.99 detected via XRD is minor (within the error of XRD phase quantification) (See, FIG. 5 A); and furthermore, its presence was difficult to confirm with XANES.

[0108] Moving from inside the Hf-rich particle towards the edge, there is a marked change in the white line intensity. Outside the Hf-rich particle, the white line is so intense it is indistinguishable from the background noise found throughout the sample. This is due to thelow-negligible signal from Hf within the Fe-rich matrix. Notably, the signal near the edge of a particle indicates a reasonable increase in white line intensity, particularly in Location 1. This nano-XANES area was probed with cluster analysis, available as a part of the MIDAS package (See, A. Pattammattel, R. Tappero, Y. S. Chu, M. Ge, D. Gavrilov, X. Huang, H. Yan, Hard x-ray nano-XANES and implementation deep learning tools for multi-modal chemical imaging, SPIE Optical Engineering + Applications, San Diego, California, USA, 2021). Analysis confirmed the line scan methodology and indicated 2 predominant regions; the particle core and the particle edge or ‘crust’, as shown in FIGS. 9A-9B. Comparison of the resultant XANES with the JFEFF-generated reference materials in FIG. 9C confirms the Hf-rich particle core is a mixture of HfO2 / HfHxwith Hf-Fe intermetallic phases. Interestingly, the resulting cluster spectra for the edge has a distinct pre-edge shoulder feature, indicating a distinct phase not found within the particle. The energy of this feature most closely resembles the HfO2phase spectra.

[0109] Given the formation of Hf-Fe intermetallic phases, and the low remaining HfHxphases post sintering for the Fe-25% HfH2composite, it is reasonable to conclude that the area probed by the HXN experiments is the boundary between the Hf-Fe intermetallic phase and the Fe-rich matrix phase (with additional confirmation shown in the SEM-BSE and FIG. 4A). The presence of the HfO2between these areas is a striking discovery. During processing, decomposition of the hydride phase is noted by its decreased presence from XRD patterns. Outside of the remaining hydride particles, H atoms unable to leave the structure become trapped along grain boundaries between the growing intermetallic phase and the consumed Fe and HfH2particles. As such, during cooling, the Hf at the surface recombines with any available O to form the HfO2phase, potentially accelerated by free H.

[0110] In the Fe-n% HfH? (n = 25, 40, 55, 70) metal matrix composites, the HfH2undergoes limited decomposition during sintering, mitigated by the short times (5 min) at high temperature (1000 °C), while achieving full matrix density. Atomic hydrogen released from the HfHxphases can potentially have a cleaning effect on the surface of surrounding Fe particles, increasing surface activity, and promoting interactions between the newly available Hf. The Fe and Hf will readily interact at these temperatures to form intermetallic phases. It is interesting to note that atthe higher HfH2loadings (n 40-70), there is significant remaining HfHx, presumably due to the short times at the high processing temperature, and sluggish decomposition, and high surface areas of initial HfH2particles. This points to a potential pathway to engineer Fe-based composites with more hydrogen retention through interface control (i.e. pre-oxidizing HfH2particles). The XANES and XRF results in FIGS. 9A-9C highlight that the HfO2formation between the Fe and HfH2particles could be utilized to enable the former. Alternatively, directly incorporating larger format HfH2inclusions within the Fe host (wires or chopped fibers) where surface effects would be minimized / negligible could be explored.

[0111] VII. Conclusion

[0112] Iron-hafnium hydride entrained metal matrix composites were produced via sintering with increasing volume percent of HfH2: Fe-25% HfH2, Fe-40% HfH2, Fe-55% HfH2, and Fe-70% HfH2. This work focuses on the Fe-Hf-H interactions post-sintering across multiple length scales using XRD, SEM, XRF, and nano-XANES. XRD revealed each sample undergoes a varied degree of decomposition and reaches an equilibrium state of HfH1.99and HfO2, around 3.5 and 5% XRD phase fraction, respectively. A unique hydride phase, 8’-HfHi.44, was identified in each sample. Likewise, the pure Fe metal phase decreases from initial concentration in each sample and decreases to a markedly lower percentage in the 55% and 70% HfH?. samples. This work demonstrates that HfH? and Fe particles, under heat and pressure during SPS processing, form intermetallic phases, HfFe and HfFe2. However, while decomposition and intermetallic formation are simultaneously occurring during processing a significant fraction of hydrogen (as HfH1.44) is retained within the final composite material. The retained hydrogen content is a function of the original HfH2loading with a maximum value of 53% for the initial Fe-70% HfH2compact. Overall composition is confirmed with SEM-BSE which reveals the intermetallic phases form between Hf-rich and Fe-rich areas. Hard X-ray nanoprobe XRF and subsequent nano-XANES reveals the HfO2phase is formed at an intermetallic-Fe boundary.

[0113] While the present disclosure has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoingand other changes in forms and details may be made without departing from the spirit and scope of the present disclosure. It is therefore intended that the present disclosure not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.

Claims

1. CLAIMS2.What is claimed is:

1. A multicomponent composite comprising:4.a secondary phase composed of at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity.

2. The multicomponent composite of Claim 1, wherein the at least one neutron and electromagnetic absorbing metal hydride is present in the steel matrix in an amount from about 5 volume percent to about 70 volume percent.

3. The multicomponent composite of Claim 2, wherein the at least one neutron and electromagnetic absorbing metal hydride is present in the steel matrix in an amount from about 10 volume percent to about 55 volume percent.

4. The multicomponent composite of Claim 1, wherein the at least one neutron and electromagnetic metal hydride comprises a transition metal hydride, a lanthanide hydride or any combination thereof.

5. The multicomponent composite of Claim 1, wherein the at least one neutron and electromagnetic metal hydride comprises hafnium hydride, gadolinium hydride, europium hydride or any combination thereof.

6. The multicomponent composite of Claim 1, wherein the steel matrix is structural steel, a high-strength, low alloy steel that contains Mn levels up to 2%. or a cryogenic steel.

7. The multicomponent composite of Claim 1, wherein the secondary phase further comprises a steel enhancing element.

12.

13.

8. The multicomponent composite of Claim 7, wherein the steel enhancing element is present in the secondary phase in an amount from about 3 volume percent to about 10 volume percent.

9. The multicomponent composite of Claim 8, wherein the steel enhancing element is present in the secondary phase in an amount from about 10 volume percent to about 20 volume percent.

10. The multicomponent composite of Claim 7, wherein the steel enhancing element comprises an elemental metal, a metal carbide, a metal boride or any combination thereof.

11. The multicomponent composite of Claim 7, wherein the steel enhancing element comprises tungsten, tungsten carbide, tungsten boride, boron carbide or any combination thereof.

12. The multicomponent composite of Claim 1, wherein the multicomponent composite contains substantially no intermetallic phases.

13. A reactor comprising:19.a composite steel wall surrounding a reactor core, wherein the composite steel wall comprises a multicomponent composite, the multicomponent composite comprising at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity.

14. The reactor of Claim 13, wherein the reactor core is a fission reactor core.

15. The reactor of Claim 13, wherein the reactor core is a fusion reactor core.

16. The reactor of Claim 13, wherein the composite steel wall slows and absorbs neutrons and electromagnetic rays emitted by the reactor core.

24.

25.

17. The reactor of Claim 16, wherein the electromagnetic rays emitted by the reactor core comprises, gamma-rays, X-rays or a combination thereof.

18. A method of forming a multicomponent composite, the method comprising:27.forming a green body comprising a steel powder and at least one neutron and electromagnetic radiation absorbing metal hydride-containing powder; and28.sintering the green body to provide a multicomponent composite comprising a secondary phase composed of at least one neutron and electromagnetic radiation absorbing metal hydride contained within a steel matrix, the steel matrix having less than 1 % interconnected porosity, wherein the sintering is performed at a temperature in which the at least one neutron and electromagnetic radiation absorbing metal hydride does not dissociate.

19. The method of Claim 18, wherein the temperature of the sintering is from about 750°C to about 900°C.

20. The method of Claim 18, wherein the green body further includes a steel enhancing elementcontaining powder.32.

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