Metal oxide reduction

Abstract

The present invention relates to a process for the production of a metal or an alloy comprising the metal from a metal precursor. The process comprises reacting the metal precursor with a reducing agent in a self-sustaining exothermic reaction and separating the metal or the alloy comprising the metal from a slag produced during the reaction. The invention also relates to the use of an intermetallic compound defined by the chemical formula Ca8(Al 3‑x M x ) as a reducing agent in the reduction of a metal precursor to produce a metal or a metal alloy.

Description

Technical Field

[0001] This invention relates to a method for preparing a metal or metal alloy from a metal precursor containing an oxide of a metal, and the use of intermetallic compounds for reducing the metal precursor. Background Technology

[0002] Metals such as titanium and zirconium, as well as refractory metals, actinides, and rare earth metals (such as neodymium), are now essential in many technological fields. These elements are extracted from refined ores using various processes. Titanium is commercially extracted from refined ores using the Kroll process, in which liquid titanium tetrachloride (TiCl4) is obtained from the refined ores and then reduced with magnesium.

[0003] Other reduction methods for extracting these elements from refined ores are also known in the art. However, these methods are expensive because they require specific reaction conditions and strong reducing agents. For example, the aluminothermic reduction method uses aluminum as the active metal, mixed with metal oxides from refined ores, to achieve a reaction in which oxygen is removed from the metal oxides. However, the aluminothermic reduction of refractory metal oxides and rare earth metal oxides suffers from the problem that the extracted metal, although reduced and deoxygenated, typically remains in the form of an alloy with aluminum. For example, the aluminothermic reduction of titanium results in the obtained titanium alloying with aluminum and forming intermetallic titanium aluminides. This is certainly undesirable if the goal is to produce pure titanium. Therefore, when the goal is to prepare pure metals, aluminothermic reduction can be performed using an active metal mixture that further contains calcium. Such active metal mixtures limit the amount of aluminum remaining in the obtained metal. The prior art provides some examples of such active metal mixtures that even contain other metals, such as magnesium, sodium, or barium. For example, US 2006 / 0107788 discloses a method for preparing refractory metals or rare earth metals from metal compounds, wherein the method uses a reducing agent comprising at least one of calcium, magnesium, sodium, barium, or potassium to reduce these metal compounds. Similarly, US 7,354,472 discloses a method for preparing refractory metals from refractory metal oxides, or refractory metal alloys from mixtures of refractory metal oxides, wherein the method uses magnesium, calcium, aluminum, or mixtures thereof to reduce these refractory metal oxides or mixtures of these refractory metal oxides. Furthermore, US Patent 4,373,947 discloses a method for preparing refractory metal alloy powder, comprising the steps of: mixing a precursor metal oxide with a basic oxide or carbonate, calcining the mixture, and then reducing the mixture with metallic calcium.

[0004] The active metal mixture used in the reduction should preferably contribute not only to the reduction of metal oxides during the reduction process. Another key aspect of the reaction mixture is that it should achieve an exothermic reaction that is stable, self-sustaining, or requires at most a moderate heat input to initiate and sustain the reaction thereafter. Some of these aspects are facilitated by presenting the reaction mixture in powder form. Therefore, it is desirable to prepare the reaction mixture using metals in powder form. However, alkali metals or alkaline earth metals (such as calcium) are known to be volatile and require careful handling and storage conditions, especially when in powder form. Furthermore, the powdered form of calcium metal reduces the stability of the reaction, which is undesirable. Therefore, calcium metal in reaction methods disclosed in the prior art is typically added as larger flakes or blocks.

[0005] In view of the above conditions, the object of the present invention is to provide an improved method for reducing metal oxides, which overcomes or at least alleviates some of the disadvantages of the prior art. Summary of the Invention

[0006] The present invention is set forth in the appended claims. This summary is provided to introduce, in a simplified form, some concepts that will be further described in the following detailed description.

[0007] The object of this invention is to provide solutions to at least some of the problems associated with reduction methods using calcium metal (i.e., calcium thermal reduction methods).

[0008] According to a first aspect, the present invention relates to a method for preparing a metal or an alloy containing the metal from a metal precursor, the method comprising: obtaining a reaction mixture by mixing the metal precursor with a reducing agent; reacting the metal precursor with the reducing agent in a self-sustaining exothermic reaction; and separating the metal or the alloy containing the metal from slag generated during the reaction, wherein the metal is selected from a list consisting of Ti, Zr, Hf, V, Nd, Nb, Sc, U, Th, and Ta, and the metal precursor contains an oxide of the metal, and the reducing agent contains an intermetallic compound Ca8(Al) 3-x M x ), where 0 ≤ x ≤ 1.5, and element M is selected from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn and Si.

[0009] According to a second aspect, the present invention relates to a chemical formula Ca8(Al) 3-x M xThe use of an intermetallic compound as a reducing agent in reducing a metal precursor to prepare a metal or metal alloy, wherein the metal is selected from the list consisting of Ti, Zr, Hf, V, Nd, Nb, Sc, U, Th and Ta, and the metal precursor contains an oxide of the metal, and 0 ≤ x < 1.5, and the element M is selected from the list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn and Si.

[0010] Because the reducing agent in this invention mainly contains calcium and is stable under atmospheric conditions, calcium thermal reduction methods can now be performed more easily and safely compared to existing technologies.

[0011] This method and its uses can be further applied to the preparation of other metals or alloys containing such metals besides those listed above.

[0012] The further scope of application will become clear from the specific implementation methods given below. However, it should be understood that the specific implementation methods and examples are given by way of illustration only. Attached Figure Description

[0013] The above and other aspects will now be described in more detail with reference to the accompanying drawings. The drawings should not be considered restrictive; rather, they are for explanation and understanding.

[0014] As shown in the accompanying drawings, some aspects of the elements depicted may be exaggerated for illustrative purposes and are therefore provided to show the overall picture. Throughout the text, the same reference numerals refer to the same elements.

[0015] Figure 1 This is a schematic flowchart of the steps of a method for preparing a metal or alloy, including methods according to aspects of the present invention.

[0016] Figure 2 This is a schematic diagram of the triclinic crystal structure of Ca8Al3 according to an embodiment of the present invention.

[0017] Figure 3 This is an XRD pattern of Ca8Al3 produced according to an embodiment of the present invention.

[0018] Figure 4 This is an XRD pattern of titanium metal produced after leaching according to an embodiment of the present invention.

[0019] Figure 5 This is a cross-sectional micrograph of titanium metal particles embedded in CaO-Al2O3 slag produced according to various aspects of the present invention.

[0020] Figure 6Titanium-niobium Ti embedded in a leached slag matrix of CaO-Al2O3 slag, produced according to various aspects of the present invention. 50 Nb 50 Micrograph of the cross-section of the particle.

[0021] Figure 7 Titanium-niobium Ti produced after leaching according to an embodiment of the present invention 50 Nb 50 XRD pattern of the alloy. Detailed Implementation

[0022] It should be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be restrictive. It must be noted that, unless the context clearly specifies otherwise, the articles “a / an,” “the,” and “said,” as used in this specification and the appended claims, are intended to indicate the presence of one or more elements. Thus, for example, references to “unit” or “the unit” can include several devices, etc. Furthermore, the words “comprising,” “including,” “containing,” and similar expressions do not exclude other elements or steps.

[0023] The problems encountered by known calcium thermal reduction methods in this art involve not only the handling of metallic calcium but also the balancing of reaction rates to ensure a stable yet still self-propagating reaction. A reaction that is too volatile will produce excess gas, which is dangerous in a closed reaction vessel. This excess gas production is detrimental, both in terms of the overall yield of the reduction process.

[0024] Therefore, as Figure 1 As shown, the present invention relates to a method for preparing a metal or an alloy containing a metal from a metal precursor. The method includes the step of reacting the metal precursor with a reducing agent in a self-sustaining exothermic reaction S1. In this respect, self-sustaining means a reaction that, once activated, generates sufficient heat during the reaction to allow the reaction to propagate without the need for additional heat from an external source (e.g., a furnace).

[0025] Following reaction step S1, the method includes an additional step S2 of separating the metal or an alloy containing the metal from the slag produced during the reaction. The metal is selected from a list consisting of Ti, Zr, Hf, V, Nd, Nb, Sc, U, Th, and Ta, and therefore, the metal precursor comprises an oxide of the same metal. The metal precursor is not limited to containing an oxide from a single metal, as it can contain multiple metal oxides, and optionally, a pure metal may be added for alloying purposes.

[0026] The metal oxide can be selected from TiO2, TiFeO3, ZrO2, HfO2, Nd2O3, Nb2O5, Ta2O5, V2O5, Sc2O3, UO2, ThO2, and combinations thereof.

[0027] Depending on the appropriate composition of the reducing agent and / or the elements present in the metal precursor, this method can be used to produce pure metals. Alternatively, this method can be used to produce alloys of metals, such as those selected from Ti. 18 Zr7, Ti 22 V4, Ti 23 Fe4, and Ti 50 Nb 50 alloy.

[0028] The reducing agent contains a single-phase intermetallic compound Ca8(Al) 3-x M x The compound can be denoted as Ca8Al3, where 0 ≤ x ≤ 1.5, and element M is selected from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn, and Si. This compound can also be described as Ca8Al3, where up to half of the aluminum is optionally substituted by element M.

[0029] Ca8Al3 has a triclinic crystal structure and belongs to a phase group known as the Zintl phase, characterized by intermediate metal-ion bonding. The inventors have discovered that up to half of the aluminum in triclinic single-phase intermetallic Ca8Al3 can be substituted by elements M selected from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn, and Si. The atomic radii of these elements make them suitable for substituting aluminum in Ca8Al3 compounds.

[0030] The calcium-aluminum phase diagram indicating the Ca8Al3 compound has been shown in reference [1]. Figure 3 middle.

[0031] Figure 2 The diagram schematically illustrates the triclinic crystal structure of Ca8Al3, where aluminum atoms are light gray and calcium atoms are dark gray. The molar mass of Ca8Al3 is 401.57 g / mol.

[0032] Ca8(Al 3-x M xThe intermetallic compound is brittle and therefore easily pulverized into powder form, which is the preferred form of the reducing agent of the present invention. The brittleness can be attributed to the low Poisson's ratio (< 0.25) of the intermetallic compound. Preferably, the reducing agent is provided in powder form, more preferably in powder having a particle size in the range of 1-1000 micrometers, preferably 10-100 micrometers, as determined by, for example, sieving. The reducing agent may be provided in powder form, wherein at least 95% by weight of the particles in the powder have a particle size in the range of 1-1000 micrometers, preferably 10-100 micrometers.

[0033] It has also been found to be essentially inert under normal atmospheric conditions. This is attributed to the formation of a thin Al2O3 nanolayer, which protects the powder particle surface from hydrolysis and spontaneous combustion in air. Air stability is crucial for industrial applications and scale-up.

[0034] Through the unexpected discoveries of the inventors, Ca8(Al) has been discovered. 3-x M x It is an excellent compound for reduction methods for a variety of reasons.

[0035] First, Ca8Al3 has a low congruent melting point of 575°C. Compared to metallic calcium, which has a melting point of 850°C, Ca8Al3 requires a lower ignition energy to initiate a thermally self-sustaining reaction with the metallic precursor.

[0036] Furthermore, the reaction is more stable compared to using metallic calcium. Ca8(Al) 3-x M x It does not evaporate under high temperature and vacuum conditions, resulting in a more stable, efficient, and less explosive thermal reaction. This is important from a health and safety perspective.

[0037] Furthermore, compared to metallic calcium, Ca8(Al) 3-x M x It exhibits improved wetting properties in the molten state. Furthermore, Ca8(Al) 3-x M x The chemical properties of the alloy can be customized as needed. This customization can be used to determine the composition of the alloy being prepared, as described below.

[0038] As an example, when x = 0, Ca8(Al) 3-x M x It can be represented as Ca8Al3. Ca8Al3 can be called an undoped compound and contains Ca and Al as its two main components. In this case, the compound is basically composed of Ca and Al.

[0039] In the case where x > 0, the compound can be referred to as a doped compound containing calcium, aluminum, and a third metal element M, where the third metal element M replaces aluminum in Ca8(Al 3-x M x ). The x in Ca8(Al 3-x M x ) can be 0 < x ≤ 1.0, preferably 0 < x ≤ 0.6, or even more preferably 0 < x ≤ 0.3. The x in Ca8(Al 3-x M x ) can be 0.1 < x ≤ 1.0, preferably 0.1 < x ≤ 0.6, or even more preferably 0.1 < x ≤ 0.3.

[0040] The reducing agent can contain at least 95% by weight of the reducing agent, such as at least 96% by weight of the reducing agent, such as at least 97% by weight of the reducing agent, such as at least 98% by weight of the reducing agent, such as at least 99% by weight of the reducing agent, such as at least 99.5% by weight of the reducing agent, of single-phase Ca8(Al 3-x M x ). The reducing agent can consist essentially of single-phase Ca8(Al 3-x M x ).

[0041] The optional remainder in the reducing agent can preferably contain or consist of the following: a naturally formed alumina layer and / or unavoidable impurities.

[0042] The unavoidable impurities can be present in an amount up to 1.0% by weight of the reducing agent, such as in an amount up to 0.5% by weight of the reducing agent, such as in an amount up to 0.1% by weight of the reducing agent.

[0043] Before the reaction step can be the step of preparing the reducing agent Ca8Al 3-x M x by melting calcium metal and aluminum metal in a crucible (such as a stainless steel crucible). The relative amounts of calcium metal and aluminum metal are selected such that the stoichiometric relationship between Ca and Al in the Ca8(Al 3-x M x ) single-phase compound is favored. In the case where x = 0, that is, when preparing the undoped compound, the relative amounts of Ca and Al in the crucible during the preparation will be 72.73 atomic-% and 27.27 atomic-% for calcium metal and aluminum metal, respectively. In the case of preparing a doped compound where x > 0, preparing the reducing agent Ca8(Al 3-x M xThe steps involve melting calcium metal, aluminum metal, and a third metallic element M in a crucible. The relative amounts of calcium metal, aluminum metal, and the third metallic element M are chosen to favor Ca8(Al) 3-x M x The stoichiometric relationships between Ca, Al, and M in a single-phase compound. For example, if x = 1, the relative amounts of Ca, Al, and the third element M in the crucible during the preparation process will be 72.73 atomic-%, 18.18 atomic-%, and 9.09 atomic-%, respectively, for calcium metal, aluminum metal, and the third metallic element M. The reducing agent Ca8(Al) is obtained. 3-x M x After the step of ), you can proceed with the process of converting Ca8(Al) into Ca8(Al). 3-x M x The compound is further pulverized into powder by a further step. The particle size of the resulting powder can be determined by sieving, which produces powder particles in the range of 1-1000 micrometers, preferably 10-100 micrometers.

[0044] In a preferred embodiment of this method, the reducing agent is provided in powder form. Therefore, as described above, the reducing agent Ca8(Al) is prepared... 3-x M x After the step of ), you can proceed with the process of converting Ca8(Al) into Ca8(Al) 3-x M x The additional step of pulverizing the material into powder having a particle size in the range of 1-1000 micrometers, preferably 10-100 micrometers.

[0045] The metal precursor can also be provided in powder form. It can be ready for use in powder form, or it can be pulverized prior to the reaction.

[0046] The metal precursor is preferably provided as a powder having a particle size in the range of 1-1000 micrometers, preferably 10-100 micrometers, as determined by sieving. Compared to molten calcium metal, molten Ca8(Al) 3-x M x Improved wetting of Ca8(Al) allows 3-x M x This wets a larger proportion of the particle surface. Therefore, metal oxide particles can be supplied at the micrometer scale and are still molten Ca8(Al) 3-x M x Moisten appropriately.

[0047] In some embodiments, both the reducing agent and the metal precursor are provided in powder form. In such embodiments where both the reducing agent and the metal precursor are provided in powder form, the reaction mixture may be prepared prior to the reaction step by mixing the powder of the metal precursor with the powder of the reducing agent using means known to those skilled in the art. The mixing means may include, but are not limited to, using a ball mill, a drum, or a mortar and pestle. Generally, mixing the metal precursor and the reducing agent is beneficial for achieving a complete and homogeneous reaction between the reducing agent and the metal precursor. The step of obtaining the reaction mixture may also be performed when only one or neither of the reducing agent or the metal precursor is provided in powder form. In other embodiments, when using, for example, a ball mill as the means of mixing, the crushing and pulverization of the metal precursor and / or the reducing agent can be performed during the step of obtaining the reaction mixture. Unlike when using pure calcium metal, when using the reducing agent disclosed in this invention, the preparation of the reaction mixture can be carried out under atmospheric conditions in the presence of oxygen at atmospheric levels. This is a significant advantage compared to the prior art. In addition to the above, it has been unexpectedly found that the reducing agent Ca8(Al) 3-x M x It exhibits self-crushing properties when exposed to normal environmental conditions. Therefore, the reducing agent can be obtained in powder form without the need for a crushing process.

[0048] In some embodiments, the reaction mixture is compressed or briquetteed into a blank prior to the reaction step. This compression or briquetting of the reaction mixture can be achieved by any means known to those skilled in the art, including but not limited to the use of molds and plungers, and hydraulic presses for applying an appropriate amount of force. In this regard, the term "appropriate force" means the force required to obtain a powder blank that remains together after removal from, for example, a mold.

[0049] The reaction step is achieved by heating. In some embodiments, the heating can be uniform, so that the entire reaction mixture or billet is heated evenly to initiate the reaction. However, the heating can also be localized, so that only a portion of the reaction mixture or billet is heated. In the case of localized heating, due to the exothermic nature of the reaction, the reaction will propagate throughout the entire reaction mixture or billet, i.e., a self-propagating reaction. Heating can be achieved, for example, by vacuum induction melting (VIM). In a preferred embodiment, the reaction step is achieved by heating the reaction mixture in an inert atmosphere, thereby initiating the self-sustaining exothermic reaction. Heating in an inert atmosphere can be achieved, for example, by vacuum induction melting (VIM).

[0050] In some embodiments, the metal precursor may comprise additional oxides selected from the list of the following: TiO2, TiFeO3, ZrO2, HfO2, Nd2O3, Nb2O5, Ta2O5, V2O5, Sc2O3, UO2, ThO2, and combinations thereof. For example, the metal precursor may comprise both TiO2 and V2O5. The metal precursor may also comprise three or more oxides, such as TiO2, V2O5, and ZrO3. These two examples are provided by way of illustration only and should not be considered limiting, as any combination of the previously listed oxides is possible. The metal precursor may further comprise pure metals (i.e., non-oxidized metals) selected from the list of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn, and Si, in an amount less than 10% of the total weight of the metal precursor. The alloying of the prepared alloy can be determined by combining different oxides and pure metals in the metal precursors used in the reaction, through the molar ratio between the metal and / or metal oxide present in the metal precursors.

[0051] In other embodiments, the alloying of the prepared alloy can be achieved using a reducing agent Ca8(Al) 3-x M x The element M in ) is determined, where M is a metal atom from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn and Si, which replaces Al in the intermetallic Ca8Al3 phase.

[0052] In addition, in another embodiment of the method, the alloying of the prepared alloy can be determined by the combination of oxides and metals contained in the metal precursor, as well as the metals that replace the reducing agent.

[0053] The relative amounts of the metal precursor and the reducing agent in the reaction are in equilibrium, resulting in a matching molar ratio, as illustrated in the following equilibrium reaction:

[0054] 25TiO2 + 4Ca8Al3 → 25Ti + 32CaO-6Al2O3(I)

[0055] 18TiO2 + 7ZrO2 + 4Ca8Al3 → Ti 18 Zr7 + 32CaO-6Al2O3(II)

[0056] 22TiO2 + 4Ca8Al2V → Ti 22 V4 + 32CaO-4Al2O3(III)

[0057] 19TiO2 + 4TiFeO3 + 4Ca8Al3 → Ti23 Fe⁴⁺ + 32CaO → 6Al₂O₃(IV)

[0058] 25Nd2O3 + 6Ca8Al3 → 50Nd + 48CaO-9Al2O3(V)

[0059] 50TiO2 + 25Nb2O5+ 18Ca8Al3 → Ti 50 Nb 50 + 144CaO-26Al2O3(VI)

[0060] 25UO2 + 4Ca8Al3 → 25U + 32CaO-6Al2O3(VII)

[0061] 25ThO2 + 4Ca8Al3 → 25 Th + 32CaO-6Al2O3(VIII)

[0062] 25Sc2O3+ 6Ca8Al3 → 50Sc + 48CaO-9Al2O3(IX)

[0063] Therefore, as illustrated by equilibrium reaction (I), the molar ratio between the metal precursor (TiO2) and the reducing agent (Ca8Al3) is at least 25:4. In a preferred embodiment, the amount of reducing agent may be higher than the ratio indicated by the equilibrium reaction to ensure complete reduction of the precursor metal.

[0064] In some embodiments, the step of separating the metal or metal-containing alloy from the slag produced during the reaction includes leaching in a dilute acid or alkaline solution.

[0065] According to a second aspect of the invention, a material of the chemical formula Ca8(Al) is also provided. 3-x M x The term "intermetallic compound" is defined as the use of a reducing agent in reducing a metal precursor to prepare a metal or metal alloy, wherein the metal is selected from the list consisting of Ti, Zr, Hf, V, Nd, Nb, Sc, U, Th, and Ta, and the metal precursor contains an oxide of the metal, and 0 ≤ x < 1.5, and element M is selected from the list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn, and Si. In the case of x = 0, the intermetallic compound can be referred to as undoped, where Ca8(Al) 3-x M x () is Ca8Al3. Alternatively, in some implementations, Ca8(Al) 3-x M xIn the given information, x is 0 < x ≤ 1.0, preferably 0 < x ≤ 0.6, or even more preferably 0 < x ≤ 0.3.

[0066] The implementation plan described in the first aspect also applies to the implementation plan in the second aspect.

[0067] Elements can be represented interchangeably by their element names and their symbols in the periodic table.

[0068] Example

[0069] The embodiments of the invention are provided below. These embodiments should be interpreted as examples only and are not intended to limit the scope of the invention in any way.

[0070] Example 1: Preparation of undoped reducing agent

[0071] The undoped reducing agent Ca8Al3 was prepared by melting 72.73 atomic-% calcium metal and 27.27 atomic-% aluminum in a crucible. The XRD pattern of the obtained undoped reducing agent is provided below. Figure 3 middle.

[0072] Example 2: Preparation of a vanadium-doped reducing agent

[0073] The vanadium-doped reducing agent is prepared by melting 72.73 atomic-% of metallic calcium, 18.18 atomic-% of metallic aluminum and 9.09 atomic-% of metallic vanadium in a crucible.

[0074] In the following Examples 3-11, all metal precursors and reducing agents are provided in powder form. "Parts" refers to molar parts.

[0075] Example 3: Pure titanium metal

[0076] The preparation of pure Ti metal is achieved by mixing 25 parts TiO2 (metal precursor) with 4 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture is then pressed into granules (bulks). The granules are heated in a vacuum-induced melting (VIM) furnace to initiate a self-propagating reaction according to the following:

[0077] 25TiO2 + 4Ca8Al3 → 25Ti + 32CaO-6Al2O3(I)

[0078] The reaction material was then crushed, and the CaO-Al₂O₃ slag was removed by leaching in 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain a powder. Subsequent XRF analysis indicated that the powder contained 99.17 wt% titanium, 0.58 wt% iron, and 0.25 wt% nickel, the latter two attributed to carryover from the stainless steel reaction vessel. The XRD pattern of the obtained hexagonal close-packed (hcp) titanium metal is provided in [the original text is missing]. Figure 4 The cross-sectional micrograph is shown in the image. Figure 5 The image shows pure Ti powder particles embedded in a leached slag matrix of 32CaO-6Al2O3 prior to acid leaching.

[0079] Example 4: Ti-Zr alloy

[0080] The Ti-Zr alloy was prepared by mixing 18 parts TiO2 (metal precursor), 7 parts ZrO2 (metal precursor), and 4 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture was then pressed into granules (bulks). The granules were heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0081] 18TiO2 + 7ZrO2 + 4Ca8Al3 → Ti 18 Zr7 + 32CaO-6Al2O3(II)

[0082] The reactants were then crushed and the CaO-Al₂O₃ slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain a powder. Subsequent XRF analysis indicated that the powder contained 56.4 wt% titanium, 42.3 wt% zirconium, and 1.2 wt% hafnium as an impurity in ZrO₂.

[0083] Example 5: Ti-V alloy

[0084] The Ti-V alloy was prepared by mixing 22 parts TiO2 (metal precursor) with 4 parts Ca8Al2V (reducing agent) to obtain a reaction mixture. The reaction mixture was then pressed into granules (bulks). The granules were heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0085] 22TiO2 + 4Ca8Al2V → Ti 22 V4 + 32CaO-4Al2O3(III)

[0086] The reactants were then crushed and the CaO-Al2O3 slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain Ti-V alloy powder.

[0087] Example 6: Ti-Fe alloy

[0088] The Ti-Fe alloy was prepared by mixing 19 parts TiO2 (metal precursor), 4 parts TiFeO3 (metal precursor), and 4 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture was then pressed into granules (bulks). The granules were heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0089] 19TiO2 + 4TiFeO3 + 4Ca8Al3 → Ti 23 Fe⁴⁺ + 32CaO → 6Al₂O₃(IV)

[0090] The reactants were then crushed and the CaO-Al2O3 slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain Ti-Fe alloy powder.

[0091] Example 7: Nd metal

[0092] The preparation of Nd metal is achieved by mixing 25 parts of Nd₂O₃ (metal precursor) and 6 parts of Ca₈Al₃ (reducing agent) to obtain a reaction mixture. The reaction mixture is then pressed into granules (bulks). The granules are heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0093] 25Nd2O3 + 6Ca8Al3 → 50Nd + 48CaO-9Al2O3(V)

[0094] The reactants were then crushed and the CaO-Al2O3 slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain Nd metal powder.

[0095] Example 8: TiNb superconductor alloy

[0096] The TiNb superconductor alloy was prepared by mixing 50 parts TiO2 (metal precursor), 25 parts Nb2O5 (metal precursor), and 18 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture was then pressed into granules (bulks). The granules were heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0097] 50TiO2 + 25Nb2O5+ 18Ca8Al3 → Ti 50 Nb 50 + 144CaO-26Al2O3(VI)

[0098] The reactants were then crushed and the CaO-Al2O3 slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain a powder. Subsequent XRF analysis indicated that the powder contained 70.9 wt% Nb and 29.0 wt% titanium, which is roughly equivalent to an equiatomic TiNb composition.

[0099] Cross-sectional micrographs are shown in Figure 6 The image shows Ti embedded in a leached slag matrix of 144CaO-26Al2O3 prior to acid leaching. 50 Nb 50 Powder particles.

[0100] The obtained body-centered cubic (bcc) titanium-niobium metal XRD patterns are provided in Figure 7 middle.

[0101] Hypothetical Example 9: Uranium Metal

[0102] The preparation of uranium metal is achieved by mixing 25 parts UO2 (metal precursor) and 4 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture is then pressed into pellets (bulks). The pellets are heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0103] 25UO2 + 4Ca8Al3 → 25U + 32CaO-6Al2O3(VII)

[0104] The reactants were then crushed and the CaO-Al₂O₃ slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain uranium metal powder.

[0105] Assume Example 10: Thorium metal

[0106] Thorium metal is prepared by mixing 25 parts ThO2 (metal precursor) and 4 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture is then pressed into granules (bulks). The granules are heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0107] 25ThO2 + 4Ca8Al3 → 25 Th+ 32CaO-6Al2O3(VIII)

[0108] The reactants were then crushed and the CaO-Al2O3 slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain thorium metal powder.

[0109] Example 11. Scandium metal

[0110] The preparation of Sc metal is achieved by mixing 25 parts Sc2O3 (metal precursor) and 6 parts Ca8Al3 (reducing agent) to obtain a reaction mixture. The reaction mixture is then pressed into granules (bulks). The granules are heated in a VIM furnace to initiate a self-propagating reaction according to the following:

[0111] 25Sc2O3 + 6Ca8Al3 → 50Sc + 48CaO-9Al2O3(IX)

[0112] The reactants were then crushed and the CaO-Al2O3 slag was removed by leaching in a 3 M HCl solution for 6 hours. The material was then washed, filtered through a Buchner filter, and air-dried to obtain Sc metal powder.

[0113] References

[0114] [1]Ozturk, K., Zhong, Y., Chen, LQ. Et al. Linking first-principlesenergetics to CALPHAD: An application to thermodynamic 18odelling of the Al-Ca binary system. Metall Mater Trans A 36, 5-13 (2005).

Claims

1. A method for preparing a metal or an alloy containing the metal from a metal precursor, the method comprising: - A reaction mixture is obtained by mixing the metal precursor with a reducing agent; - The metal precursor is reacted with the reducing agent in a self-sustaining exothermic reaction; as well as - Separate the metal or alloy containing the metal from the slag produced during the reaction; in: The metal is selected from a list consisting of Ti, Zr, Hf, V, Nd, Nb, Sc, U, Th, and Ta; The metal precursor contains an oxide of the metal; and The reducing agent contains intermetallic compounds. Ca8(Al 3-x M x ), where 0 ≤ x ≤ 1.5, and element M is selected from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn and Si.

2. The method according to claim 1, wherein, The reducing agent is provided in powder form.

3. The method according to claim 1 or 2, wherein, The metal precursor is provided in powder form.

4. The method according to claim 3, wherein, The step of obtaining the reaction mixture includes mixing the powder of the metal precursor with the powder of the reducing agent.

5. The method according to claim 4, wherein, The reaction step is preceded by a step of compressing the reaction mixture into a bulk material.

6. The method according to any one of claims 1 to 5, wherein, The reaction step is achieved by heating the reaction mixture or preform to initiate the self-sustaining exothermic reaction.

7. The method according to any one of claims 1 to 6, wherein, The reducing agent is a single-phase compound.

8. The method according to any one of claims 1 to 7, wherein, The reducing agent is Ca8Al3.

9. The method according to any one of claims 1 to 7, wherein, Ca8(Al 3-x M x In ), x is 0 < x ≤ 1.

0.

10. The method according to any one of claims 1 to 9, wherein, The metal precursor contains additional oxides.

11. The method according to claim 10, wherein, The additional oxides are selected from the list of the following: TiO2, TiFeO3, ZrO2, HfO2, Nd2O3, Nb2O5, Ta2O5, V2O5, Sc2O3, UO2, and ThO2, and combinations thereof.

12. The method according to any one of claims 1 to 11, wherein, The metal precursor comprises a metal selected from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn, and Si, in an amount less than 10% of the total weight of the metal precursor.

13. The method according to any one of claims 1 to 12, wherein, The step of separating the metal or an alloy containing the metal from the slag produced during the reaction includes leaching in a dilute acid or alkaline solution.

14. The method according to any one of claims 1 to 13, wherein, Prior to the reaction step, Ca8(Al) was prepared by melting calcium metal, aluminum metal, and optionally a third element M in a crucible. 3-x M x The steps are as follows.

15. From the chemical formula Ca₈(Al₂O₃) 3-x M x The use of intermetallic compounds as reducing agents in the reduction of metal precursors to prepare metals or metal alloys, as defined herein. The metal is selected from a list consisting of Ti, Zr, Hf, V, Nd, Nb, Sc, U, Th, and Ta; The metal precursor contains an oxide of the metal; and 0 ≤ x < 1.5, where element M is selected from a list consisting of Fe, Cu, Co, Ni, V, Mn, Mo, Nb, Ta, W, Cr, Sn and Si.

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