ARTICLES FOR CONTAINING A MOLTEN MATERIAL AND METHODS OF PRODUCING THE SAME

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 63/727,385, filed Dec. 3, 2024, the disclosure of which is hereby incorporated herein in its entirety by this reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Contract Number DE-AC07-05-ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention.

TECHNICAL FIELD

Embodiments of the disclosure relate generally to articles for containing and handling molten materials. More specifically, embodiments relate to composite-coated articles that can be used to contain and handle molten metals, molten metal salts, molten metal alloys, or a combination thereof.

BACKGROUND

Problems exist in the handling and containment of highly reactive molten materials such as molten metals, molten metal salts, molten slags, and molten metal alloys. For example, most metals display a higher degree of reactivity when they are in molten states. Particular problems relate to the crucible (i.e., vessel) used to contain the highly reactive molten materials during processing. The crucibles should be resistant to thermal and physical shocks and exhibit chemical resistance to the highly reactive molten materials. Furthermore, the manufacturing of the crucibles should be achieved at an acceptable cost on a large scale.

Ceramic, refractory-lined and graphite crucibles are commonly used to contain the highly reactive molten materials, such as molten uranium (U), molten titanium (Ti), and molten titanium-based alloys. However, uncoated graphite may not be entirely inert toward the highly reactive molten materials. For example, graphite may react with molten uranium (forming uranium carbide) and thereby resulting in a loss of the graphite crucible material into the melt. A titanium-based alloy (e.g., a titanium aluminide alloy) may dissolve large quantities of carbon from the graphite crucible into the titanium-based alloys, resulting in contamination that jeopardizes the mechanical properties of the titanium-based alloys. Therefore, not only does the graphite crucible physically deteriorate with time (and eventually becomes unusable), but also the resulting molten material becomes contaminated. This latter problem is particularly important when the molten materials must be of very high purity, e.g., for nuclear fuel application.

SUMMARY

In the first aspect, an article for containing a molten material is disclosed. The article includes a crucible, and a composite coating having a first surface adjacent an inner surface of the crucible and a second surface opposite the first surface. The second surface of the composite coating defines an exposed interior surface of the article. The composite coating comprises at least one carbide of a transition metal. The composite coating includes a gradient of carbon across a thickness of the composite coating between the first surface and the second surface of the composite coating.

In the second aspect, an article for containing a molten material is disclosed. The article includes a crucible, and a composite coating including one side adjacent to an inner surface of the crucible and another side defining an exposed interior surface of the article. The composite coating includes one or more layers of at least one carbide of a transition metal proximal to the inner surface of the crucible, and at least one layer of the transition metal distal from the inner surface of the crucible. The article further includes at least one layer of an oxide of the transition metal adjacent to the another side of the composite coating.

In the third aspect, a method of producing an article for containing a molten material is disclosed. The method includes electroplating a transition metal on a surface of a crucible from a molten salt electrolyte to form a coated crucible. The method further includes annealing the coated crucible under an inert atmosphere to form an annealed crucible comprising a composite coating on the surface of the annealed crucible. The composite coating comprises at least one carbide of the transition metal.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed understanding of the disclosure, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view of an article in accordance with some embodiments of the disclosure;

FIG. 2A is a schematic cross-sectional view of an article in accordance with some other embodiments of the disclosure;

FIG. 2B is a schematic cross-sectional view of an article in accordance with some further embodiments of the disclosure;

FIG. 3 is a simplified schematic illustration of a system for electroplating a transition metal onto a substrate, in accordance with some embodiments of the disclosure;

FIG. 4 is a simplified schematic illustration of the article, in accordance with some embodiments of the disclosure; and

FIG. 5 is a scanning electron microscope (SEM) image showing the formation of Y₂O₃ phase on the phases of YC and Y₂C, after anodization.

DETAILED DESCRIPTION

Embodiments described herein generally relate to articles for containing and handling molten metals, molten metal salts, molten slags, or molten metal alloys, and methods for producing such articles. The disclosed articles may exhibit an improved inertness toward chemical reaction with the highly reactive molten materials (e.g., metals, metal salts or metal alloys), an enhanced resistance to thermal and physical shock, and an extended use life of the article compared to conventional articles.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown, by way of illustration, specific example embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable a person of ordinary skill in the art to practice the disclosure. However, other embodiments may be utilized, and structural, material, and process changes may be made without departing from the scope of the disclosure.

The illustrations presented herein are not meant to be actual views of any particular method, system, device, or structure, but are merely idealized representations that are employed to describe the embodiments of the disclosure. The drawings presented herein are not necessarily drawn to scale. Similar structures or components in the various drawings may retain the same or similar numbering for the convenience of the reader; however, the similarity in numbering does not mean that the structures or components are necessarily identical in size, composition, configuration, or any other property.

It will be readily understood that the components of the embodiments as described herein and illustrated in the drawings may be arranged and designed in a wide variety of different configurations. Thus, the following description of various embodiments is not intended to limit the scope of the disclosure but is merely representative of various embodiments. While the various aspects of the embodiments may be presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The following description may include examples to help enable one of ordinary skill in the art to practice the disclosed embodiments. The use of the terms “exemplary,” “by example,” and “for example,” means that the related description is explanatory, and though the scope of the disclosure is intended to encompass the examples and legal equivalents, the use of such terms is not intended to limit the scope of any embodiments or this disclosure to the specified components, acts, features, functions, or the like.

Thus, specific implementations shown and described are only examples and should not be construed as the only way to implement the disclosure unless specified otherwise herein. Elements, apparatuses, and methods may be shown in block diagram form in order not to obscure the disclosure in unnecessary detail. Conversely, specific implementations shown and described are exemplary only and should not be construed as the only way to implement the disclosure unless specified otherwise herein. It will be readily apparent to one of ordinary skill in the art that the disclosure may be practiced by numerous other applications.

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

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

As used herein, the term “may” with respect to a material, structure, feature, or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure, and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other compatible materials, structures, features, and methods usable in combination therewith should or must be excluded.

As used herein, the term “about” used 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.

As used herein, the term “substantially” in reference to a given parameter, property, or condition 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% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met.

As used herein, the term “comprise(s),” “comprising,” “include(s),” “including,” “having,” “has,” “contain(s),” “containing,” and variants thereof, are open-ended transitional phrases, terms, or words that are meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

As used herein, “molten material” means and includes a molten metal, a molten metal salt, a molten metal alloy, a molten slag, or a combination thereof.

As used herein, “metal alloy” means and includes a substance that combines more than one metal, or a substance that mixes a metal with other non-metallic elements. For example, brass is a metal alloy made of copper and zinc.

The disclosed article includes a crucible and a composite coating on the inner surface of the crucible. The composite coating has a first surface adjacent to the inner surface of the crucible, and a second surface opposite the first surface that defines an exposed interior surface of the article. The composite coating comprises at least one carbide of a transition metal. The composite coating includes a gradient of carbon across a thickness of the composite coating between the first surface and the second surface of the composite coating. As a non-limiting example, the first surface of the composite coating may have a greater carbon content than the second surface of the composite coating.

FIG. 1 is a schematic cross-sectional view of an article 100 in accordance with some embodiments of the disclosure. The article 100 includes a crucible 102 having an interior portion 120 configured for containing the material (e.g., the metal, the metal salt, or the metal alloy) to be melted. The crucible 102 has an outer surface 104 and an inner surface 106. The article 100 also includes a composite coating 108 having a first surface 110 adjacent the inner surface 106 of the crucible 102, and a second surface 112 defining an exposed interior surface of the article 100.

The crucible 102 may be formed of and include graphite. The composite coating 108 comprises at least one carbide of a transition metal. In some embodiments, the transition metal comprises niobium (Nb), tantalum (Ta), titanium (Ti), tungsten (W), molybdenum (Mo), hafnium (Hf), vanadium (V), zirconium (Zr), or a combination thereof. In some embodiments, the composite coating 108 further includes the transition metal, an oxide of the transition metal, or both.

The composite coating 108 may exhibit excellent compatibility with the crucible (e.g., graphite crucible). In some embodiments, a thermal expansion coefficient of the composite coating 108 is substantially similar to that of the crucible 102.

A concentration of the carbon in at least one transition metal carbide is a gradient along a thickness of the composite coating 108 between the first surface 110 and the second surface 112 of the composite coating 108. In some embodiments, the composite coating 108 comprises multiple layers of the at least one carbide of transition metal. In some embodiments, the composite coating 108 comprises multiple layers of at least one carbide of the transition metal, and at least one layer of the transition metal, at least one layer of an oxide of the transition metal, or both.

In some embodiments, the composite coating 108 includes tantalum (Ta) and at least one metal carbide is chosen from TaC and Ta₂C. As a non-limiting example, the composite coating 108 may comprise layers of TaC, Ta₂C, and Ta (i.e., TaC-Ta₂C—Ta).

In some embodiments, the composite coating 108 includes niobium (Nb) and at least one metal carbide is chosen from NbC and Nb₂C. As a non-limiting example, the composite coating 108 may comprise layers of NbC, Nb₂C, and Nb (i.e., NbC—Nb₂C—Nb).

In some embodiments, the composite coating comprises TaC, Ta₂C, NbC, Nb₂C, and Nb. As a non-limiting example, the composite coating 108 may comprise layers of TaC, Ta₂C, NbC, Nb₂C, and Nb (i.e., TaC—Ta₂C—NbC-Nb₂C—Nb).

In some embodiments, the composite coating 108 includes hafnium (Hf) and hafnium carbide (HfC). As a non-limiting example, the composite coating 108 may comprise layers of HfC and Hf (i.e., HfC—Hf).

In some embodiments, the composite coating 108 includes molybdenum carbides MoC and Mo₂C. As a non-limiting example, the composite coating 108 may comprise layers of MoC and Mo₂C (i.e., MoC—Mo₂C).

In some embodiments, the composite coating 108 includes YC, Y₂C, and YC₂. As a non-limiting example, the composite coating 108 may comprise layers of Y₂C, YC₂, and YC (i.e., Y₂C—YC₂—YC).

In some embodiments, the composite coating 108 includes YC, Y₂C, YC₂, and Y₂O₃. As a non-limiting example, the composite coating 108 may comprise layers of YC, Y₂C, YC₂, and Y₂O₃ (i.e., YC-Y₂C—YC₂—Y₂O₃).

In some embodiments, the composite coating 108 includes tungsten (W) and at least one metal carbide is chosen from WC and W₂C. As a non-limiting example, the composite coating 108 may comprise layers of WC, W₂C, and W (i.e., WC—W₂C—W).

In some embodiments, the composite coating 108 of the article 100 is in direct contact with the inner surface 106 of the crucible 102 (i.e., the first surface 110 of the composite coating 108 is in direct contact with the inner surface 106 of the crucible 102, as shown in FIG. 1).

FIG. 2A is a schematic cross-sectional view of an article 100′ in accordance with some other embodiments of the disclosure. The article 100′ includes a crucible 102′ having an interior portion 120′ configured for containing the highly reactive material to be melted (e.g., a metal, a metal salt, a molten slag, or a metal alloy). The crucible 102′ has an outer surface 104′ and an inner surface 106′. The crucible 102′ may be formed of and include graphite. The article 100′ also includes a composite coating 108′ having a first surface 110′ adjacent the inner surface 106′ of the crucible 102′, and a second surface 112′ opposite the inner surface 106′ of the article 100′. The composite coating 108′ may include one of the materials described above for the composite coating 108. Furthermore, the article 100′ includes a topcoat 114 on the second surface 112′ of the composite coating 108′. Therefore, the article 100′ includes the topcoat 114 in addition to the multiple layers of the composite coating 108′.

In some embodiments, the topcoat 114 comprises a metal, a metal alloy, a metal oxide, a metal nitride, a metal boride, or a combination thereof. Non-limiting examples of the metal oxide are magnesium oxide, calcium oxide, aluminum titanium oxide (Al₂TiO₃), scandium oxide, yttrium oxide, hafnium oxide, zirconium oxide, an oxide of a lanthanide metal, or a combination thereof. The oxide of the lanthanide metal includes at least one oxide of lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu). In some embodiments, the topcoat 114 comprises scandium oxide, yttrium oxide, hafnium oxide, an oxide of the lanthanide metal, or a combination thereof. In some embodiments, the topcoat 114 comprises hafnium nitride, hafnium boride, molybdenum boride, niobium boride, nickel boride, tantalum (Ta), tungsten (W), tantalum boride, thorium oxide, titanium nitride, titanium boride, vanadium boride, zirconium nitride, zirconium boride, or a combination thereof.

FIG. 2B is a schematic cross-sectional view of an article 100″ in accordance with some further embodiments of the disclosure. The article 100″ includes a crucible 102″ having an interior portion 120″ configured for containing the highly reactive material to be melted (e.g., a metal, a metal salt, a molten slag, or a metal alloy). The crucible 102″ has an outer surface 104″ and an inner surface 106″. The crucible 102″ may be formed of and include graphite, such as high-density graphite. The article 100″ also includes a composite coating 108″ having a first surface 110″ adjacent the inner surface 106″ of the graphite crucible 102″, and a second surface 112″ defining an exposed interior surface of the article 100″. The composite coating 108″ may include one of the materials described above for the composite coating 108. Furthermore, the article 100″ includes a basecoat 116 positioned between the first surface 110″ of the composite coating 108′ and the inner surface 106″ of the crucible 102″. Therefore, the article 100″ includes the basecoat 116 in addition to the multiple layers of the composite coating 108″.

In some embodiments, the basecoat 116 comprises a metal, a metal alloy, a metal oxide, a metal nitride, a metal boride, or combinations thereof. As non-limiting examples of the metal oxide are magnesium oxide, calcium oxide, aluminum titanium oxide (Al₂TiO₃), scandium oxide, yttrium oxide, hafnium oxide, zirconium oxide, an oxide of a lanthanide metal, or a combination thereof. The oxide of the lanthanide metal includes at least one oxide of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) or lutetium (Lu). In some embodiments, the basecoat 116 comprises scandium oxide, yttrium oxide, hafnium oxide, an oxide of the lanthanide metal, and combinations thereof. In some embodiments, the basecoat 116 comprises hafnium nitride, hafnium boride, molybdenum boride, niobium boride, nickel boride, tantalum (Ta), tungsten (W), tantalum boride, thorium oxide, titanium nitride, titanium boride, vanadium boride, zirconium nitride, zirconium boride, or combination thereof.

The article 100, 100′, 100″ may be produced by forming a coating on an exposed surface of the crucible 102, 102′, 102″, wherein the coating comprises a transition metal. Then, the coated crucible may be annealed to form the composite coating 108, 108′, 108″ on the crucible surface, wherein the composite coating comprises at least one carbide of the transition metal.

During the annealing process, at least one portion of the transition metal in the coating may be converted to one or more carbide of the transition metal. As a result, the composite coating comprising at least one carbide of the transition metal may be formed on the crucible surface. The annealing process may take place under an inert atmosphere at a temperature of less than or equal to about 1000° C. In some embodiments, the annealing process takes place under an inert atmosphere at a temperature of from about 500° C to about 700° C. The annealing process may be performed for up to about 12 hours.

The composite coating 108, 108′, 108″ may be formed on the inner surface 106, 106′ of the crucible 102, 102′ or on the basecoat 116, using any method known to those of ordinary skill in the art. Non-limiting examples of such methods are vapor deposition, air plasma spraying, and electroplating. In some embodiments, the composite coating 108, 108′, 108″ is formed by a molten salt electroplating process. The composite coating 108, 108′, 108″ may adhere to the crucible 102, 102′, 102″ or to other underlying materials. Since the composite coating 108 includes a metal, the article 100 may exhibit a higher thermal conductivity and enhanced heat transfer properties compared to a conventional article (e.g., a graphite crucible that lacks the composite coating). Without being bound by any theory, the composite coating 108, 108′, 108″ is believed to prevent the formation of cracks or pores in the article 100, 100′, 100″. In addition, the composite coating 108, 108′, 108″ may prevent ions, such as hydrogen ions and chloride ions, from passing into the crucible 102, 102′, 102″.

The article 100, 100′, 100″ may be used as a vessel to contain and melt highly reactive metals, highly reactive metal salts, highly reactive metal alloys, or highly reactive molten slags. Non-limiting examples of such metals include uranium (U), titanium (Ti), or a combination thereof. A non-limiting example of such metal salts includes a fluoride salt of uranium (U). Non-limiting examples of highly reactive metal alloys include titanium-based alloys (e.g., titanium aluminide), hafnium-based alloys, iridium-based alloys, rhenium-based alloys, niobium-based alloys (e.g., niobium silicide), nickel-based alloys (e.g., nickel aluminide), or a combination thereof. The article 100, 100′, 100″ including the composite coating 108, 108′, 108″ may have reduced or substantially no contaminants from the crucible 102, 102′, 102″.

In some embodiments, the disclosed article 100, 100′, 100″ is suitable for use in melting a titanium-based alloy (e.g., titanium aluminide alloy), which is generally performed at a temperature of from about 1370° C. to about 1700° C. In some embodiments, the disclosed article 100, 100′, 100″ is suitable for containing, processing and/or casting of molten copper. The molten copper is typically maintained at temperature of about 1100° C.

Although articles 100, 100′, 100″ in FIGS. 1-2B are configured as a crucible (i.e., a vessel) for containing molten materials, the disclosure is not limited. The article 100, 100′, 100″ disclosed herein may be used as a component for a device that is in direct contact with the molten material. As non-limiting examples, the article 100, 100′, 100″ may be a component (e.g., in the form of a plate or a baffle) of a collector for collecting the molten material, a die used for producing/casting products made from the molten material, a sensor for determining an amount of a dissolved gas in the molten material, or an ultrasonic device for reducing gas content (e.g., hydrogen) in the molten material. Articles 100, 100′, 100″ may also be used in other extreme environments, such as high temperature environments, oxidizing and reducing environments, ionizing radiation environments, elevated pressure environments, and/or vacuum environments.

FIG. 3 is a simplified schematic illustration of a system 300 for a molten salt electroplating process to coat the surface of a substrate (e.g., a crucible) with a transition metal, in accordance with some embodiments of the disclosure. The system 300 includes a reservoir 310 dimensioned and configured to receive an amount of a molten salt electrolyte 312. The reservoir 310, in some embodiments, comprises a chemically and/or electrically inert material of construction, so as to minimize (e.g., prevent) interference with the electrochemical reactions occurring therein. Alternatively, at least the liquid contacting surfaces of the reservoir 310 may be lined (e.g., coated) with a chemically and/or electrically inert material to minimize (e.g., prevent) interference with the electrochemical reactions occurring therein.

The system 300 further includes electrodes 302, 304, and an optional electrode 306 disposed below the surface of the electrolyte 312 in the reservoir 310. The electrode 302 is a positively charged anode (e.g., a counter electrode), the electrode 304 is a negatively charged cathode (e.g., a working electrode), and the optional electrode 306 is a reference electrode. In some embodiments, the optional electrode 306 may be separated from electrodes 302, 304 in the electrolyte 312 in the reservoir 310, such as, for example, by a glass frit (not shown). Although the system 300 of FIG. 3 is shown as including only one anode electrode 302 and only one cathode electrode 304, the disclosure is not limited and the system 300 may include more than one anode electrode 302 and/or more than one cathode electrode 304.

The cathode 304 of the system 300 may comprise graphite and/or any other electrically conductive material suitable to be used as a substrate. In some embodiments, the cathode 304 comprises graphite, such as a high-density graphite.

The anode 302 of the system 300 may include one of the materials described above for the composite coating 108. In some embodiments, the transition metal comprises niobium (Nb), tantalum (Ta), titanium (Ti), tungsten (W), molybdenum (Mo), hafnium (Hf), vanadium (Va), Zirconium (Zr), or a combination thereof.

The molten salt electrolyte 312 of the system 300 may comprise, for example, a molten salt, such as an alkali halide salt, an alkaline earth metal halide salt, or combinations thereof. The molten salt electrolyte 312 may be formed of and include lithium chloride (LiCl), sodium chloride (NaCl), calcium chloride (CaCl₂), lithium bromide (LiBr), potassium bromide (KBr), cesium bromide (CsBr), sodium bromide (NaBr), calcium bromide (CaBr₂), potassium chloride (KCl), potassium bromide (KBr), strontium chloride (SrCl₂), strontium bromide (SrBr₂), or a combination thereof. The electrolyte may be a LiCl or a CaCl₂ electrolyte. The calcium chloride may constitute a remainder of the molten salt electrolyte 312.

The molten salt electrolyte 312 may be formulated and configured to exhibit a melting temperature within a range of from about 550° C. to about 950° C., such as from about 550° C. to about 650° C., from about 650° C. to about 750° C., from about 750° C. to about 850° C., or from about 850° C. to about 950° C. The molten salt electrolyte 312 may be maintained at a temperature such that the molten salt electrolyte 312 is, and remains, in a molten state. In other words, the temperature of the molten salt electrolyte 312 may be maintained at or above a melting temperature of the molten salt electrolyte 312.

With continued reference to FIG. 3, the system 300 further comprises a potential source 320 configured to apply an electrical potential across the anode 302 and the cathode 304. When the electrical potential is applied across the anode 302 and the cathode 304, a current is generated between the anode 302 and the cathode 304 and through the electrolyte 312 in the reservoir 310. In some embodiments, the potential source 320 is dimensioned and configured to generate a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². Furthermore, the system 300 may comprise a potential measurement device 322 to monitor the potential difference between the cathode 304 and the optional reference electrode 306.

The molten salt electroplating may be performed until the desired thickness of the coating of transition metal is achieved. In some embodiments, the molten salt electroplating is performed for from about 30 minutes to about 180 minutes. In some embodiments, the molten salt electroplating process is performed at a temperature of less than about 450° C. In some embodiments, the electroplating process is performed at a temperature of from about 350° C. to about 450° C. In some embodiments, the molten salt electroplating process is performed under an inert atmosphere.

FIG. 3 illustrates the system 300 while in use. Upon applying the electrical potential across the anode 302 formed of a transition metal (“a first transition metal”) and the cathode 304 (e.g., a graphite substrate), electroplating of the first transition metal (from the anode 302) occurs to provide a first transition metal-coated structure comprising a layer 330 of the first transition metal electrochemically deposited on an exposed surface of the cathode 304.

After the electroplating process, the first transition metal-plated structure is subjected to an annealing process (i.e., a heat treatment). The annealing process may take place under an inert atmosphere at a temperature of less than or equal to about 1000° C. In some embodiments, the annealing process takes place under an inert atmosphere at a temperature of from about 500° C. to about 700° C. The annealing process may be performed for up to about 12 hours. The annealing process facilitates the diffusion of the first transition metal, as well as the chemical reaction between the diffused first transition metal and the carbon of the substrate, to form a first annealed structure comprising a first composite coating on the substrate surface. The first composite coating comprises at least one carbide of the first transition metal.

Subsequently, the first annealed structure is used as a cathode for a second electroplating process (e.g., using the system 300 as described above) with an anode formed of a second transition metal. In some embodiments, the first transition metal of the anode for the first electroplating process is substantially the same as the second transition metal of the anode for the second electroplating process. In some other embodiments, the first transition metal of the anode for the first electroplating process is different from the second transition metal of the anode for the second electroplating process.

Upon applying the electrical potential across the anode formed of the second transition metal and the cathode (the first annealed structure comprising the first composite coating on the substrate), an electroplating of the second transition metal from the anode occurs to provide a second transition metal-coated structure. The second transition metal-coated structure comprises the first composite coating on the substrate surface, and a layer of the second transition metal on the surface of the first composite coating.

After the second electroplating process, the second transition metal-plated structure is subjected to an annealing process as previously described to form a second annealed structure comprising a second composite coating on the substrate surface.

The second annealed structure may be subjected to an additional electroplating process and the subsequent annealing process as described above. These additional acts may be repeated until the desired thickness of the composite coating is achieved. After the desired thickness of the composite coating is obtained, a final annealing process may optionally be performed to complete the production of the disclosed article. The final annealing process, as previously described, may be performed for several hours or several days. The resulting article may be used, for example, as a crucible for containing a molten material or as another container used in an extreme environment.

The disclosed combination of an electroplating act and a subsequent annealing (a heat treatment) act to produce the article offers a low-temperature fabrication option that results in a lower production cost compared to a conventional method of forming the composite coating on the crucible.

In some embodiments, the disclosed method further includes anodizing the annealed structure to form a metal oxide layer on the exposed surface of the composite coating. The combination of the metal oxide layer and the composite coating may provide a further enhanced resistance of the article from the chemical reaction with the molten materials.

The disclosed article may exhibit enhanced thermal and physical stability at an elevated temperature, as well as an improved degree of chemical inertness, which minimizes the chemical and mechanical degradation of the article while in contact with the molten materials (e.g., uranium, titanium alloy). The chemical and mechanical stability of the article enable long term containment of reactive materials, such as molten materials. Furthermore, the disclosed article may be produced at a relatively lower cost, such as through an electroplating and a subsequent annealing process, compared to the conventional articles, e.g., vapor deposition processes.

Moreover, when a highly reactive material (e.g., metal, metal salt, or metal alloy) is melted in the article, the resulting molten material may contain relatively fewer contaminants compared to the molten material prepared in the conventional article (e.g., graphite crucible without the disclosed composite coating). In some embodiments, the article may be used to contain the molten material at a temperature of up to 1700° C.

The following examples serve to explain embodiments of the disclosure in more detail. These examples are not to be construed as being exhaustive, exclusive, or otherwise limiting as to the scope of the disclosure.

EXAMPLES

Materials

Graphite rods having a diameter of about 5 mm and a length of 100 mm, or graphite rectangular plates (2 cm in length, 0.5 cm in thickness, and 2.5 cm in width) were used as cathode substrates for a molten salt electroplating process. The graphite specimens were heated (inside an argon atmosphere glove box) up to a temperature of 500° C. to remove gaseous and volatile matter followed by a de-dusting operation (inside the glove box). The graphite specimens were subsequently vacuum degassed at 1000° C. and 0.001 mbar for 30 minutes prior to being used as a cathode.

The principal electrolyte was a eutectic composition of LiBr, KBr, and CsBr (56.1% mol LiBr, 18.9% mole KBr, and 25.0% mol CsBr). These salts were anhydrous in nature and sealed in a quartz ampoule. The salts were removed from the quartz tube inside an argon-atmosphere glove box before use.

The functional electrolyte included bromide salts of the selected transition metals (NbBr₅, TaBr₅, RuBr₃, IrBr₃, YBr₃, TaBr₅, TiBr₄, MoBr₃, ZrBr₄, and WBr₅). The bromide salts were anhydrous in nature and were in sealed quartz ampoules prior to removing them from the container for storage in polythene bottles. These salts were stored inside the argon atmosphere glove box.

Three types of materials were used for testing the compatibility and the reactivity of their molten forms with the articles:

• • (1) metal having a low melting-point: aluminum (melting point of 660° C.);
  • (2) metal having a relatively higher melting point: copper (melting point of 1085° C.); and
  • (3) metal alloys: bronze (melting point of 920° C.), and brass (melting point of 915° C.).

Example 1. A Composite Coating Comprising Ta₂C, TaC, and Ta

A ternary salt composition was prepared by heating a mixture of lithium bromide (LiBr), potassium bromide (KBr) and cesium bromide (CsBr) at about 750° C. for about two (2) hours. The salt melt was allowed to cool down to room temperature. To the solidified salt, about 70-80% TaBr₅ was added, and the resulting salt bath was very slowly heated to a temperature of 350° C. until the melt formed a clear liquid. The tantalum (Ta) rod was sand blasted and cleaned with alcohol and acetone. The cleaned Ta rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. A three-electrode set up, including (1) a graphite rod/plate as a working electrode (cathode), (2) a tantalum rod (about 5 mm in diameter and about 100 mm in length) as a counter electrode (anode), and (3) a glassy carbon rod (about 3 mm in diameter and 100 mm in length) as a reference electrode, was used to electrochemically deposit Ta onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting article was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 700° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed article.

The X-ray diffraction analysis of the annealed article showed that the combination of TaC, Ta₂C and Ta phases were formed on the graphite substrate. FIG. 4 is a simplified schematic illustration of the annealed structure based on the X-ray diffraction analysis. As shown in the annealed structure 400, a combination of TaC and Ta₂C 402 was formed between a graphite substrate 404 and a Ta layer 406.

The annealed article was tested for its reactivity and stability toward the following molten metals and molten metal alloy.

Molten Copper: the annealed article was kept immersed in a pool of molten copper at a testing temperature of about 1100° C. for up to 5 hours.

Molten Brass: the annealed article was kept immersed in a pool of molten brass at a testing temperature of about 930° C. for up to 5 hours.

Molten Bronze: the annealed article was kept immersed in a pool of molten bronze at a testing temperature of about 950° C. for up to 5 hours.

At the end of immersion time, the annealed article was removed from the pool of molten material and examined for possible degradation. No degradation was observed on the annealed article when the tested materials were molten copper, molten brass, or molten bronze. Furthermore, no loss of the composite coating (e.g., Ta₂C and/or TaC) was detected when the tested materials were molten copper, molten brass, or molten bronze.

Example 2. A Composite Coating Comprising Nb₂C and NbC

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% NbBr₅ was used instead of about 70-80% TaBr₅. A niobium (Nb) rod was sand blasted and cleaned with alcohol and acetone. The cleaned Nb rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used, except that the cleaned Nb rod (5 mm in diameter and 100 mm in length) was used as the counter electrode (anode), for the electroplating of Nb onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 700° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed article.

The reactivity and stability of the annealed article (NbC-Nb₂C-coated graphite rod) was tested by immersing in a molten copper pool at a testing temperature of about 1100° C. for up to 5 hours. After the testing period, the annealed article was examined for any degradation, damage, or loss due to the reactivity with the molten copper. No degradation, damage, or loss of the coated component (NbC-Nb₂C-coated graphite rod) was detected.

Example 3. A Composite Composition Comprising TaC, Ta₂C, NbC, Nb₂C, and Nb

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% NbBr₅ was used instead of about 70-80% TaBr₅. A tantalum (Ta) rod was sand blasted and cleaned with alcohol and acetone. The cleaned Ta rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used for electroplating tantalum onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 1000° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed Ta-coated article.

The annealed Ta-coated article was subjected to an electroplating process as described above with the annealed Ta-coated article as a cathode, and a niobium (Nb) as an anode, in order to form a layer of Nb on the exposed surface of the annealed Ta-coated article. An annealing process as described above was performed after the electroplating process to provide an annealed tantalum and niobium-coated graphite rod having a composite coating on the surface of the graphite substrate. The composite coating included layers of TaC, Ta₂C, NbC, Nb₂C, and Nb.

The reactivity and stability of the annealed tantalum and niobium-coated graphite rod was tested by immersing in a molten pool of aluminum at a testing temperature of about 700° C. for a duration up to 5 hours. After the testing period, the annealed tantalum and niobium-coated graphite rod was examined for any degradation, damage, or loss due to the reactivity with the molten aluminum. No degradation, damage, or loss of the annealed tantalum and niobium-coated graphite rod was detected.

Example 4. A Composite Composition Comprising HfC and Hf

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% HfBr₄ was used instead of about 70-80% TaBr₅. The hafnium (Hf) rod was sand blasted and cleaned with alcohol and acetone. The cleaned Hf rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used, except that the cleaned Hf rod (5 mm in diameter and 100 mm in length) was used as the counter electrode (anode), for electroplating Hf onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 1000° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed Hf-coated article that included layers of HfC and Hf.

The reactivity and stability of the annealed article was tested by immersing in a molten pool of aluminum at a testing temperature of about 700° C. for a duration up to 5 hours. After the 5-hour testing period, the annealed article was examined for any degradation, damage, or loss due to the reactivity with the molten aluminum. No degradation, damage, or loss of the annealed article was detected.

Example 5. A Composite Composition Comprising MoC, MO₂C, and Mo

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% MoBr₃ was used instead of about 70-80% TaBr₅. The molybdenum (Mo) rod was sand blasted and cleaned with alcohol and acetone. The cleaned Mo rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used, except that the cleaned Mo rod (6 mm in diameter and 100 mm in length) was used as the counter electrode (anode), for electroplating Mo onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 1000° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed Mo-coated article that included layers of MoC, MO₂C, and Mo.

The reactivity and stability of the annealed article was tested by immersing in a molten pool of brass at a testing temperature of about 925° C. for a duration up to 5 hours. After the testing period, the annealed article was examined for any degradation, damage, or loss due to the reactivity with the molten brass. No degradation, damage, or loss of the annealed article was detected.

Example 6. A Composite Composition Comprising YC, Y₂C, YC₂, and Y

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% YBr₃ was used instead of about 70-80% TaBr₅. The yttrium (Y) rod was sand blasted and cleaned with alcohol and acetone. The cleaned yttrium rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used, except that the cleaned yttrium rod (4 mm in diameter and 100 mm in length) was used as the counter electrode (anode), for electroplating yttrium onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 1000° C, under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed Ta-coated article.

The reactivity and stability of the annealed article component was tested by immersing in a molten pool of aluminum at a testing temperature of about 700° C. for a duration up to 5 hours. After the testing period, the annealed article was examined for any degradation, damage, or loss due to the reactivity with the molten aluminum. No degradation, damage, or loss of annealed article was detected.

Example 7. A composite Composition Comprising YC, Y₂C, YC₂, and Y₂O₃

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% YBr₃ was used instead of about 70-80% TaBr₅. The yttrium rod was sand blasted and cleaned with alcohol and acetone. The cleaned yttrium rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used, except that the cleaned yttrium rod (4 mm in diameter and 100 mm in length) was used as the counter electrode (anode), for electroplating yttrium onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to a heat treatment (annealing) at a temperature of from about 500° C. to about 1000° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed Ta-coated article.

The annealed yttrium-coated graphite rod was anodized in a phosphoric acid solution to grow the yttrium oxide layer (up to about 10 μm in thickness) by polarizing the annealed yttrium-coated graphite rod against a graphite rod for a duration up to 15 minutes. The anodized article was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting anodized article was then dried in the oven, kept inside the argon-atmosphere glove box. FIG. 5 is a scanning electron microscope (SEM) image of the composite coating formed on the graphite rod. The SEM image showed the formation of Y₂O₃ phase on YC+Y₂C phases after the anodization.

Example 8. A Composite Composition Comprising WC, W₂C, and W

The all-bromide salt bath was prepared as described in Example 1, except that about 70-80% WBr₅ was used instead of about 70-80% TaBr₅. The tungsten (W) rod was sand blasted and cleaned with alcohol and acetone. The cleaned W rod was dried overnight in a furnace, situated inside the argon atmosphere glove box. The same three-electrode set up as described in Example 1 was used, except that the cleaned tungsten rod (6 mm in diameter and 80 mm in length) was used as the counter electrode (anode), for electroplating tungsten onto the graphite rod/plate. The electroplating process was performed at a temperature of from about 350° C. to about 450° C. and a plating duration time of from about 30 minutes to about 180 minutes. Furthermore, the electroplating process was performed at a cathode current density of from about 0.1 A. cm⁻² to about 0.5 A. cm⁻². After the electroplating process, the coated cathode was removed from the plating bath, and then thoroughly washed with water, alcohol and acetone. The resulting cathode was then subjected to heat treatment (annealing) at a temperature of from about 500° C. to about 1000° C. under an inert atmosphere (e.g., the argon atmosphere) for up to 12 hours to provide an annealed tungsten-coated article.

The reactivity and stability of the annealed article component was tested by immersing in a molten pool of aluminum at a testing temperature of about 700° C. for a duration up to 5 hours. After the testing period, the annealed article was examined for any degradation, damage, or loss due to the reactivity with the molten aluminum. No degradation, damage, or loss of the annealed article was detected.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the following appended claims and their legal equivalents.