Method for producing multicomponent alloy nanostructure, multi-component alloy nanostructure, and aluminum-based composite containing same

Abstract

This method for producing a multi-component alloy nanostructure includes a production step in which a composition containing a plurality of types of metal elements, an ionic liquid, and water is electrolyzed to electrodeposit the metal elements in pores of a nanoporous electrolysis electrode thereby producing a multi-component alloy nanostructure that comprises the plurality of types of metal elements. The composition has a polar domain volume of 10 or less when the volume of the non-polar domain is 1.

Description

Method for producing multi-component alloy nanostructure, multi-component alloy nanostructure, and aluminum-based composite containing the same

[0001] The present disclosure relates to methods for producing multi-component alloy nanostructures, as well as multi-component alloy nanostructures and aluminum-based composites containing the same.

[0002] Unlike conventional alloys containing trace amounts of secondary metal elements in the matrix of a primary metal element, multi-component alloys containing multiple primary metal elements have been attracting attention in recent years. Due to differences in the content ratios of the constituent metal elements, multi-component alloys are expected to have physical and / or mechanical properties different from those of conventional alloys. Multi-component alloys can be, for example, alloys in which multiple metal elements are mixed at the elemental level by being arranged in a crystal lattice, resulting in a high entropy state. Known examples of such alloys include medium entropy alloys (MEAs) containing three or more primary metal elements in roughly equal proportions, and high entropy alloys (HEAs) containing five or more primary metal elements in roughly equal proportions.

[0003] Until now, research into methods for producing bulk MEAs and HEAs has been the mainstream, but in recent years, plating films of multi-component alloys have also begun to be investigated, as disclosed in, for example, Non-Patent Document 1. Non-Patent Document 1 describes the production of a CoNiCu MEA film by using a water-in-oil emulsion containing water droplets in the oil phase as a plating solution.

[0004] Y.Murakami et al., Electrochem.Commun., 128,107057(2021)

[0005] By further forming a nanostructure from a multi-component alloy, a material with a large specific surface area can be realized, and a material with even better properties than conventional materials can be provided. However, with conventional techniques such as those disclosed in Non-Patent Document 1, it has been difficult to obtain a multi-component alloy nanostructure.

[0006] The present disclosure has been made in light of the above circumstances, and one of its objectives is to provide a novel method for producing a multi-component alloy nanostructure, and another objective is to provide a novel multi-component alloy nanostructure obtained by the method, and an aluminum-based composite containing the same.

[0007] A first aspect of the present invention is a method for producing a multi-component alloy nanostructure, which comprises a production step of electrolyzing a composition containing multiple metal elements, an ionic liquid, and water, and electrodepositing the metal elements inside the pores of a nanoporous electrolytic electrode, thereby producing a multi-component alloy nanostructure containing the multiple metal elements, wherein the volume of the polar domain of the composition is 10 or less when the volume of the non-polar domain is 1.

[0008] A second aspect of the present invention is the method for producing a multi-component alloy nanostructure according to the first aspect, wherein the producing step comprises performing the electrodeposition by pulse electrolysis based on pulse potential control.

[0009] A third aspect of the present invention is the method for producing a multi-component alloy nanostructure according to the first aspect, wherein the electrodeposition is carried out by constant potential electrolysis in the producing step.

[0010] A fourth aspect of the present invention is the method for producing a multi-component alloy nanostructure according to any one of the first to third aspects, wherein the nanoporous electrolytic electrode is subjected to a hydrophobic treatment.

[0011] A fifth aspect of the present invention is the method for producing a multi-component alloy nanostructure according to any one of the first to fourth aspects, wherein the composition further contains hydrochloric acid.

[0012] A sixth aspect of the present invention is a multi-component alloy nanostructure containing a plurality of metal elements and having a portion that satisfies the following formulas (1) to (3): ｎ ≧2.0 (atomic %) ... (1) Σa ｎ ≧25 (atomic %) (2) a ｍｉｎ ≧0.1a ｍａｘ ... (3) where a ｎ is the atomic fraction (atomic %) of the nth metal element (n is an integer of 2 or more), and Σa ｎis the total atomic fraction (atomic %) of n kinds of metal elements, and a ｍｉｎ Haa ｎ is the minimum value of a ｍａｘ Haa ｎ is the maximum value of

[0013] A seventh aspect of the present invention is the multi-component alloy nanostructure according to the sixth aspect, wherein n is an integer of 3 or more.

[0014] An eighth aspect of the present invention is an aluminum-based composite comprising the multi-component alloy nanostructure according to the sixth or seventh aspect in a matrix of aluminum or an aluminum alloy.

[0015] According to the present embodiment, it is possible to provide a novel method for producing a multi-component alloy nanostructure, as well as a novel multi-component alloy nanostructure obtained by the method and an aluminum-based composite containing the same.

[0016] FIG. 1 is a schematic diagram illustrating the structure of an example of an ionic liquid according to the present production method. FIG. 2 is a flowchart illustrating an example of the flow of the present production method. FIG. 3 is a schematic diagram of a molecular structure used in a molecular dynamics simulation of an example. FIG. 4 is a schematic diagram illustrating an outline of a method and apparatus for producing a multi-component alloy nanostructure of an example. FIG. 5 is an example of a TEM image of a multi-component alloy nanostructure of Example 1. FIG. 6 is an electron diffraction image of a multi-component alloy nanostructure of Example 1. FIG. 7 is another example of a TEM image of a multi-component alloy nanostructure of Example 1. FIG. 8 is an example of a TEM image of a multi-component alloy nanostructure of Example 2. FIG. 9 is another example of a TEM image of a multi-component alloy nanostructure of Example 2. FIG. 10 is an example of a TEM image of a multi-component alloy nanostructure of Example 3-1. FIG. 11 is an example of a TEM image of a multi-component alloy nanostructure of Example 3-2. FIG. 12 is an example of a TEM image of a multi-component alloy nanostructure of Example 3-3. FIG. 13 is an example of a TEM image of a multi-component alloy nanostructure of Example 3-4. FIG. 14 is an example of a TEM image of a multi-component alloy nanostructure of Example 4-1. 1 is an example of a TEM image of the multi-component alloy nanostructure of Example 4-2. 2 is a surface SEM image of the aluminum-based composite obtained in Example 5.

[0017] The present inventors have investigated from various angles in order to realize a novel method for producing multi-component alloy nanostructures.

[0018] Multi-component alloys, especially MEAs and HEAs, are generally known to be difficult to produce with the desired composition by depositing all of the constituent metal elements at approximately the same time due to the different redox potentials of the constituent metal elements, and producing nanostructures of these alloys can be even more difficult.

[0019] In response to the above, the present inventors conducted extensive research into compositions that would primarily serve as plating solutions. While compositions typically comprised of polar solvents are used as plating solutions, the present inventors came up with the idea of ​​using a composition having nonpolar and polar domains as the plating solution. They then discovered that by setting the volume of the polar domains to 10 or less, relative to the volume of the nonpolar domains, the composition can undergo nanometer-scale phase separation. Furthermore, by using this composition in conjunction with an electrolytic electrode having nanoporous portions on at least a portion of its surface (hereinafter also referred to as a "nanoporous electrolytic electrode"), multiple metal elements with different redox potentials are intermittently supplied to the pores of the nanoporous portion of the electrolytic electrode during electrodeposition (i.e., the continuous supply of a specific metal element is suppressed), resulting in the realization of a multi-component alloy nanostructure. Note that the above mechanism does not limit the technical scope of this embodiment.

[0020] The details of each requirement stipulated in this embodiment are given below.

[0021] [1. Method for Producing Multi-component Alloy Nanostructures] The method for producing a multi-component alloy nanostructure according to this embodiment (hereinafter also referred to as "the present production method") includes a production step of electrolyzing a composition containing multiple metal elements, an ionic liquid, and water to electrodeposit the metal elements into the pores of a nanoporous electrolytic electrode, thereby producing a multi-component alloy nanostructure containing the multiple metal elements, wherein the volume of the polar domain of the composition is 10 or less when the volume of the non-polar domain is taken as 1. This allows for the provision of a novel multi-component alloy nanostructure. Furthermore, the present production method allows for a high degree of freedom in the types of metal elements used, enabling the production of multi-component alloy nanostructures with controlled compositions at practical processing speeds. Furthermore, while physical vapor deposition methods such as ion plating require large equipment (e.g., a vacuum chamber and an electron gun (or ion gun) are required), the present production method can be performed using relatively simple equipment.

[0022] (Metal element) In this specification, "multiple types of metal elements" refers to two or more types of metal elements, and may be three or more types, four or more types, or five or more types of metal elements. The combination of "multiple types of metal elements" is not particularly limited and can be appropriately set depending on the purpose.

[0023] The metal element used in this production method is a metal element that constitutes a multi-component alloy nanostructure, and can be a metal element that can be plated at a potential of -1.63 V or higher (i.e., a potential of -1.63 V or higher) relative to the standard hydrogen electrode potential. Examples of such metal elements include Cr, Co, Ni, Fe, Cu, Mn, and Zn. There is no particular upper limit to the potential, but it may be, for example, +1.50 V or lower.

[0024] When the metal elements described above are contained in the composition according to the present production method, they may be dissolved as metal salts. The metal salts may be metal halides containing the metals described above, such as CrCl. ３ , CoCl ２ , NiCl ２ , FeCl ２ , CuCl, MnCl ２ , ZnCl ２ And so on.

[0025] (Ionic Liquid) Ionic liquid is a liquid consisting of only ions. In the present production method, the ionic liquid preferably consists of organic cations and inorganic anions. This makes it easier to obtain a composition having desired non-polar domains and polar domains. Examples of cations constituting the ionic liquid include imidazolium ions, pyridinium ions, ammonium ions, and phosphonium ions. Examples of anions constituting the ionic liquid include Br － , Cl － , NO ３ － , B.F. ４ － , P.F. ６ － , AlCl ４ － , Al ２ Cl ７ － , C.H. ３ CO ２ － , N(SO ２ CF ３ ) ２ － And so on.

[0026] Fig. 1 is a schematic diagram illustrating the structure of an example of an ionic liquid according to the present production method. For convenience of explanation, Fig. 1 shows the polar domain 1 extracted from an ionic liquid containing a polar domain 1 and a non-polar domain 2, and shows the portion where the non-polar domain 2 exists as a void. As shown in Fig. 1, the ionic liquid according to the present production method may have a three-dimensional network structure (sponge-like structure).

[0027] An example of an ionic liquid used in this production method is an ionic liquid containing a cation having an alkyl group with four or more carbon atoms. By using an ionic liquid containing a cation having an alkyl group with four or more carbon atoms, it becomes easier to obtain a composition having the desired non-polar domains and polar domains, and multi-component alloy nanostructures can be suitably produced.

[0028] Imidazolium-based ionic liquids, which are an example of ionic liquids used in this production method, have a structure separated into polar domains consisting of polar moieties such as imidazolium rings and nonpolar domains consisting of alkyl groups. In imidazolium-based ionic liquids with ethyl groups containing two carbon atoms, the alkyl chains are short, so the nonpolar domains have a smaller volume than the polar domains. Therefore, imidazolium-based ionic liquids with ethyl groups containing two carbon atoms have a globular structure in which the nonpolar domains are surrounded by polar domains. On the other hand, imidazolium-based ionic liquids with alkyl chains longer than the butyl groups containing four carbon atoms have a larger volume ratio of the nonpolar domains, and are not surrounded by polar domains. Therefore, they form a three-dimensional network structure in which multiple nonpolar domains are at least partially connected to each other.

[0029] The ionic liquid used in this production method preferably contains an imidazolium ion in which the alkyl group constituting the non-polar domain has 4 or more carbon atoms, and more preferably contains an imidazolium ion in which the alkyl group constituting the non-polar domain has 4 or more carbon atoms. Examples of ionic liquids containing an imidazolium ion in which the alkyl group constituting the non-polar domain has 4 or more carbon atoms include the 1-butyl-3-methylimidazolium ion and the 1-hexyl-3-methylimidazolium ion.

[0030] (Water) The water may be, for example, ion-exchanged water, ultrafiltered water, distilled water, pure water, or ultrapure water.

[0031] (Composition) The composition according to the present production method contains multiple metal elements, an ionic liquid, and water, and the volume of the polar domains is 10 or less when the volume of the nonpolar domains is 1. Preferably, the volume of the polar domains is 2 or more, and more preferably, the volume of the polar domains is 6 or less. This facilitates phase separation of the composition on a nanometer scale, making it easier to obtain a multi-component alloy nanostructure. In the present production method, the volumes of the nonpolar and polar domains of the composition can be determined using the method described in the Examples below.

[0032] The mole fraction of each metal element in the composition (b １ , b２ ...b ｍ ) (m is an integer of 2 or more, preferably 3 or more, more preferably 5 or more) are preferably in a substantially equal ratio, and preferably satisfy, for example, the following formula (4): ｍｉｎ ≧0.1b ｍａｘ ... (4) where b ｍｉｎ Ha b ｍ is the minimum value of b ｍａｘ Ha b ｍ is the maximum value of b ｍ is preferably 2.0 mol % or more.

[0033] The amount of ionic liquid in the composition is expressed as a molar ratio, and is the maximum molar fraction b of each metal element in the composition. ｍａｘ is set to 1, the ratio is preferably 2 or more and 10 or less, more preferably 3 or more and 9 or less, even more preferably 4 or more and 8 or less, and most preferably 6. This makes it easier for each metal element to be intermittently supplied to the inside of the pores of the nanoporous portion of the electrolytic electrode because the ratio of nonpolar domains is appropriate.

[0034] The molar ratio of ionic liquid to water in the composition is preferably 1:45 or more and 12:45 or less, more preferably 3:45 or more and 9:45 or less, even more preferably 4:45 or more and 8:45 or less, and particularly preferably 6:45, which makes it easier to obtain a composition having the desired non-polar domains and polar domains.

[0035] The composition according to the present production method may contain an acid as needed to prevent the precipitation of oxides and / or hydroxides. The composition according to the present production method preferably further contains hydrochloric acid. The amount (molar ratio) of hydrochloric acid added to the composition is determined based on the maximum molar fraction b of each metal element in the composition. ｍａｘ is set to 1, the ratio is preferably 0.01 or more and 1 or less. By mixing hydrochloric acid into the composition, the oxygen content and / or carbon content in the resulting nanostructure can be reduced.

[0036] The composition according to the present production method preferably further contains boric acid. The amount (molar ratio) of boric acid mixed into the plating solution is set to be equal to or less than the maximum molar fraction b of each metal element in the composition. ｍａｘ is set to 1, it is preferable that the ratio is 1 or more and 2 or less. By mixing boric acid into the composition, it is possible to suppress the generation of hydrogen in the composition and prevent hydroxides from being generated in the obtained nanostructure.

[0037] (Nanoporous Electrode) The nanoporous electrolysis electrode according to the present production method is an electrolysis electrode (cathode electrode) having a nanoporous portion on at least a portion of its surface so that the nanostructure described below can be produced. The nanoporous portion may have a circular equivalent diameter of 1 nm or more but less than 1000 nm in a top perspective view where the circular equivalent diameter of the pore is at its smallest. For example, the electrode may be one in which a nanoporous portion is formed by processing at least a portion of the surface of a known electrode (conductive material substrate). Alternatively, a known electrode may be one in which a structure having a known nanoporous portion, such as anodized aluminum oxide (AAO), is provided on at least a portion of the surface, or one in which a conductive material is provided by vapor deposition or the like on the surface of a structure having a known nanoporous portion, such as anodized aluminum oxide.

[0038] The nanoporous electrolytic electrode used in this production method is preferably hydrophobized. This makes it easier for the composition used in this production method to be supplied to the vicinity of the electrode, thereby improving the rate at which nanostructures are produced. The hydrophobization method can be performed using known methods, such as immersion in a solution of a silane coupling agent having a hydrophobic group such as an alkyl group or an aryl group. A hydrophobized nanoporous electrolytic electrode can have a larger static water contact angle than one that has not been hydrophobized. A hydrophobized nanoporous electrolytic electrode can exhibit a static water contact angle of, for example, 90° or more.

[0039] An example of the flow of the present production method will be described with reference to FIG. 2. FIG. 2 is a flowchart showing an example of the flow of the present production method. As shown in FIG. 2, the present production method may include a mixing step of an ionic liquid and water (step S11), a composition preparation step (step S12), and a production step of producing a nanostructure (step S13). An example of the present production method is a method that will be described in detail in the Examples below, but is not limited to this example.

[0040] (Step S11) In the step of mixing the ionic liquid and water, the ionic liquid and water are mixed to produce a solvent for the composition. When a metal element to be dissolved later is dissolved as a hydrated metal salt, the ionic liquid and water are preferably mixed so that the ratio of the ionic liquid to water in the resulting composition is the above-mentioned ratio, taking into account the water of crystallization of the metal salt.

[0041] (Step S12) In the composition preparation process, multiple metal elements are dissolved in a solvent mixture of ionic liquid and water. The composition may be prepared by dissolving multiple metal elements in the water solvent, or by mixing an aqueous solution in which multiple metal elements are dissolved into the solvent. In the composition, the metal elements are present primarily as ions in the water, not in the ionic liquid. In the multi-component alloy nanostructure production process, by using a composition whose solvent is a mixture of ionic liquid and water, multiple metal elements, which are solutes, are each precipitated by electrodeposition, thereby producing a multi-component alloy nanostructure.

[0042] Dissolving multiple metal elements in a solvent can be carried out, for example, by adding metals or metal salts to the solvent and stirring for at least one minute while heating to a temperature of 0° C. or higher and 120° C. or lower.

[0043] In the process of producing a multi-component alloy nanostructure, electrodeposition using the prepared composition is carried out using a nanoporous electrolytic electrode. By electrolyzing the composition in the electrodeposition process, metal elements are reduced and precipitated inside the pores of the nanoporous electrolytic electrode, thereby producing a multi-component alloy nanostructure.

[0044] The electrolysis of the composition may be constant-potential electrolysis, but pulse electrolysis is preferred. Pulse electrolysis suppresses phase separation (bias in the composition of the constituent metal elements) in the resulting multi-component alloy nanostructure, allowing for the production of a uniform multi-component alloy nanostructure. Furthermore, in TEM images of multi-component alloy nanostructures obtained by pulse electrolysis, changes in brightness at regular intervals (also called "streaks") due to pulse electrolysis can be observed.

[0045] In pulse potential control, it is preferable to apply a potential of -2.0 V or more and +1.5 V or less relative to a reference electrode (Ag / AgCl in 3.33 M KCl) for 0.1 to 5 seconds, and then hold the potential as an open circuit (current I = 0) for 0.1 to 5 seconds, and repeat this process. The potential is more preferably -1.6 V or more and -1.0 V or less, and even more preferably greater than -1.4 V and -1.1 V or less. This makes it possible to further suppress phase separation in the multi-component alloy nanostructure. The number of cycles is not particularly limited, but can be, for example, 100 cycles or more.

[0046] When the electrolysis of the composition is constant-potential electrolysis, the controlled potential is preferably −2.5 V or more and +1.5 V or less relative to the reference electrode (Ag / AgCl in 3.33 M KCl), more preferably −2.0 V or more and −1.0 V or less, and even more preferably −1.6 V or more and −1.1 V or less. Constant-potential electrolysis has the advantages of a faster nanostructure formation rate and easier potential control compared to pulse electrolysis.

[0047] The temperature during electrodeposition may be, but is not limited to, 20° C. or higher and 200° C. or lower. Electrodeposition may be carried out until a multi-component alloy nanostructure having a desired length is obtained.

[0048] The present production method may further include an annealing step in which the multi-component alloy nanostructure obtained in the production step is annealed. While the multi-component alloy nanostructure obtained immediately after electrodeposition in the production step has the advantage of having a low elastic modulus and suppressed warping, its small crystal grain size may result in insufficient hardness. By performing an annealing step after the production step, the crystal grain size of the multi-component alloy nanostructure can be increased, thereby improving its hardness. Furthermore, the improved hardness of the multi-component alloy nanostructure after the annealing step further improves its wear resistance.

[0049] In the annealing step, for example, the multi-component alloy nanostructure is annealed at 350°C or higher and 700°C or lower. The temperature in the annealing step is more preferably 400°C or higher and 550°C or lower, and even more preferably 500°C or higher and 550°C or lower. Furthermore, the time for annealing the multi-component alloy nanostructure in the annealing step may be 5 minutes or higher and 60 minutes or lower, and is preferably 25 minutes or higher and 30 minutes or lower. Other annealing conditions in the annealing step can be appropriately selected from conventionally known conditions.

[0050] [2. Multi-component alloy nanostructure] The above-described production method can provide a multi-component alloy nanostructure according to this embodiment (hereinafter also referred to as "the present multi-component alloy nanostructure"). The present multi-component alloy nanostructure is a multi-component alloy nanostructure that contains multiple types of metal elements (preferably three or more types, more preferably five or more types) and has a portion that satisfies the following formulas (1 to (3): a ｎ ≧2.0 (atomic %) ... (1) Σa ｎ ≧25 (atomic %) (2) a ｍｉｎ ≧0.1a ｍａｘ ... (3) where a ｎ is the atomic fraction (atomic %) of the nth metal element (n is an integer of 2 or more, preferably 3 or more, more preferably 5 or more), and Σa ｎ is the total atomic fraction (atomic %) of n kinds of metal elements, and a ｍｉｎ Haa ｎ is the minimum value of a ｍａｘ Haa ｎis the maximum value of . Since the present multi-component alloy nanostructure is produced by electrodeposition using a composition (plating solution) as described above, it is possible to easily form structures (e.g., nanofibers) with curved surfaces that are difficult to form by physical vapor deposition such as ion plating. One preferred aspect of the present multi-component alloy nanostructure is that it has a curved surface, which makes it easier to apply to various uses.

[0051] The left side of the formula (1) is preferably 2.5 atomic % or more, and more preferably 3.0 atomic % or more. This can improve the properties of the multi-component alloy nanostructure. The left side of the formula (2) is preferably 30 atomic % or more, 40 atomic % or more, 50 atomic % or more, 60 atomic % or more, and more preferably 70 atomic % or more. This can improve the properties of the multi-component alloy nanostructure. The left side of the formula (3) is preferably 0.2a ｍａｘ Above, 0.3a ｍａｘ Above, 0.4a ｍａｘ or more, and 0.5a ｍａｘ The above are preferred in order of order, as this can improve the properties of the multi-component alloy nanostructure.

[0052] The multi-component alloy nanostructure may also contain carbon, for example as an impurity derived from the ionic liquid. The carbon content is preferably 60 atomic % or less, 50 atomic % or less, 40 atomic % or less, 30 atomic % or less, 20 atomic % or less, and 10 atomic % or less, in order of preference. This can improve the properties of the multi-component alloy nanostructure.

[0053] The multi-component alloy nanostructure may contain oxygen due to metal oxides, etc. The oxygen content is preferably 40 atomic % or less, 30 atomic % or less, 20 atomic % or less, and 10 atomic % or less, in order of preference, which can improve the properties of the multi-component alloy nanostructure.

[0054] In one example of the multi-component alloy nanostructure, the remainder is preferably unavoidable impurities. Affected impurities include elements introduced due to the conditions of raw materials, materials, and manufacturing equipment. While elements such as C and O are generally considered unavoidable impurities, their composition ranges are separately defined as described above. Therefore, the term "unavoidable impurities" used herein excludes elements whose composition ranges are separately defined. Examples of unavoidable impurities include elements that can be contained in ionic liquids, such as Cl and S, and elements such as Au and Al that can be contained in nanoporous electrolytic electrodes. Metal elements present at low concentrations that do not satisfy the above formula (1) are considered impurity elements. The amount of unavoidable impurities may be, for example, less than 2.0 atomic %, preferably less than 1.0 atomic %, and more preferably less than 0.5 atomic %. The total amount of unavoidable impurities is preferably 10 atomic % or less, more preferably 5 atomic % or less. The content of each of the above elements can be measured using the method described in the Examples below.

[0055] Here, the thermodynamic mixing entropy ΔS ｍｉｘ The MEA and HEA are defined as follows: ΔS ｍｉｘ is given by the following equation (5): In equation (5), ln is the natural logarithm, R is the gas constant, x ｉ where σ represents the atomic concentration (molar fraction) of each component, and n represents the number of components. The MEA is defined by the following formula (6) in a single-phase solid solution state. The HEA is defined by the following formula (7) in a single-phase solid solution state. For example, in the case of a ternary alloy containing three metal elements, these metal elements are mixed in equal proportions (X ｉ = 0.33), then ΔS ｍｉｘ = 1.099R, and the ternary alloy is an MEA. In other words, the multi-element alloy nanostructure has a structure in which 1.0R≦ΔS ｍｉｘ The MEA nanostructure may have a solid solution phase with a ΔS≦1.5R. ｍｉｘ The HEA nanostructure may have a solid solution phase with R≧1.5.

[0056] When viewed from above so that the circle-equivalent diameter of the multi-component alloy nanostructure is at its smallest, the circle-equivalent diameter may be 1 nm or more and less than 1000 nm. The multi-component alloy nanostructure may be, for example, nanoparticles, nanofibers, etc. In the case of nanofibers, the diameter (circle-equivalent diameter) may be 1 nm or more and less than 1000 nm, and the length may be more than 1.0 times, 1.5 times or more, 2.0 times or more, or 3.0 times or more longer than the diameter. The length may be, for example, 100 μm or less, 50 μm or less, or 10 μm or less.

[0057] The present multi-component alloy nanostructure is a nanostructure of a multi-component alloy plating film having excellent mechanical properties (low elastic modulus, reduced warpage, high hardness, and excellent wear resistance), as disclosed in, for example, PCT / JP2024 / 005719, and clearly possesses the same excellent mechanical properties as the multi-component alloy plating film. Because of its excellent mechanical properties, the present multi-component alloy nanostructure can be applied to a variety of applications (e.g., electrode catalysts, etc.). Furthermore, the present multi-component alloy nanostructure may have an FCC structure, as described in the examples below. The FCC structure can maintain high toughness even at low temperatures compared to a BCC structure, in which dislocation motion can be induced by thermal energy. Therefore, the present multi-component alloy nanostructure can have good low-temperature toughness.

[0058] The present multi-component alloy nanostructure is one embodiment of a multi-component alloy nanostructure produced by the present production method detailed in Section 1. Therefore, the explanations of the metal elements, multi-component alloys, multi-component alloy nanostructures, and production methods in Section 1 above are incorporated herein by reference as appropriate in the description of the present multi-component alloy nanostructure.

[0059] [3. Aluminum-based composite] The aluminum-based composite according to this embodiment contains the multi-component alloy nanostructure in an aluminum or aluminum alloy matrix. The aluminum-based composite according to this embodiment contains the multi-component alloy nanostructure, which has excellent mechanical properties, and as a result, the mechanical properties (for example, strength such as Vickers hardness, crack resistance, etc.) are improved.

[0060] The aluminum or aluminum alloy matrix (hereinafter also simply referred to as "matrix") may be bulk or a thin film (e.g., 0.2 to 200 μm thick). Generally, the higher the aluminum content in the matrix, the lower the mechanical properties such as strength. In such cases, the effect of improving the mechanical properties when the multi-component alloy nanostructure is contained in the matrix becomes more significant. The aluminum content may be 50% by mass or more, 75% by mass or more, 90% by mass or more, or 95% by mass or more. There is no particular upper limit, and it may be 100% by mass or less.

[0061] The content of the multi-component alloy nanostructure in the matrix is ​​preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more. This further improves the mechanical properties of the aluminum-based composite. There is no particular upper limit to the content, but it is preferably, for example, 20% by mass or less.

[0062] The aluminum-based composite according to this embodiment can be produced, for example, by dispersing the multi-component alloy nanostructure in an aluminum or aluminum alloy plating solution (electrolytic solution for aluminum or aluminum alloy electroplating) and then electroplating. Alternatively, the aluminum-based composite according to this embodiment may be produced by adding the multi-component alloy nanostructure to a molten aluminum or aluminum alloy and casting the resultant, or by adding the multi-component alloy nanostructure to aluminum or aluminum alloy powder and forming it into a bulk by powder metallurgy (further rolling or extruding the bulk as necessary).

[0063] The following examples are provided to more specifically describe the embodiments of the present invention. The embodiments of the present invention are not limited to the following examples, and may be modified as appropriate within the scope of the above-described and below-described aims, and all such modifications are within the technical scope of the embodiments of the present invention.

[0064] [1. Example of pulse electrolysis, no hydrophobic treatment of nanoporous electrolysis electrode, and no hydrochloric acid in the composition] (Preparation of composition) 1-butyl-3-methylimidazolium chloride (C ４ 3 g of C stored in a dry chamber was used. ４ mimCl, C ４ mimCl:H ２ Ultrapure water was added with a pipette so that the molar ratio of CrCl was 6:45. ３ ・6H ２ O, CoCl ２ ・6H ２ O, NiCl ２ ・6H ２ Considering the amount of water of crystallization in the crystals of O, at this point, ４ mimCl:H ２ O = 6: (45 - 6 x 3) = 6:27 of H ２ O was added.

[0065] Next, C ４ mimCl: CrCl ３ : CoCl ２ : NiCl ２ : H ３ BO ３ = 6:1:1:1:2 (molar ratio) ３ ・6H ２ O, CoCl ２ ・6H ２ O, NiCl ２ ・6H ２ O and H ３ BO ３ , C ４ mimCl and H ２ The mixture was added to O.

[0066] H due to evaporation ２ To avoid changes in the O ratio, the container containing the mixed solution was sealed with a stopper and then stirred at 500 rpm on a hot plate at 80°C for 30 minutes or more to stabilize the complex, producing the composition used in Example 1. The volumes of the nonpolar and polar domains of this composition were determined by molecular dynamics simulation as follows.

[0067] (Identification of the volumes of non-polar and polar domains by molecular dynamics simulation) Molecular dynamics (MD) simulations were performed using GROMACS-2023 software. １） In order to align the simulation box (length of the periodic boundary condition), the number of molecules was determined so that the total number of atoms inside the box was approximately 100,000. In this example, to model an imidazolium-based ionic liquid, CL&P ２） The OPLS-AA force field reported by

[1999] was selected. The SPC / E model was used to model water molecules. ３） The van der Waals (VdW) interaction was performed using the 12-6 Lennard-Jones (LJ) potential, and the LJ parameters of the metal ions were based on the IOD parameter set reported by Merz et al. ４～５） The molecular structure used in this simulation is shown in Figure 3, and the parameters used are summarized in Table 1. The cutoff distance for VdW interactions was set to 12 Å. Electrostatic interactions were simulated using the SPME method. ６） The equation of motion was calculated using the Velocity Verlet method. The relative permittivity was set to 1, and the time step was 1 fs in all simulations. The initial configuration was PACKMOL. ７） and fftool ８） The molecules were randomly placed in a sufficiently large box using the steepest descent method. ９） followed by energy minimization using a V-rescale thermal bath. １０） Next, we performed a 2 ns NVT ensemble at 423 K using the V-rescale thermal bath and the C-rescale pressure bath. １１） The pressure was adjusted to 1 bar by the NPT ensemble and held at 423 K for 4 ns. １２）Using a C-rescale pressure bath, equilibration was performed using the NPT ensemble for 4 ns at 343 K, the temperature at which electrodeposition is actually performed. After confirming that the energy, density, pressure, and temperature had reached equilibrium, a 20 ns actual simulation was performed using the NVT ensemble with a Nose-Hoover heat bath. The trajectory was saved every 2 ps. The number of molecules inside the box for each mixed solution and the side length of the cube finally obtained are summarized in Table 2. To quantitatively evaluate the mesoscopic phase separation of the mixed solution, domain analysis was performed using Travis software. １３）１４）This allowed us to examine the number and shape of connected domains inside the box for a total of 10,000 frames every 2 ps. We used the Q value, expressed by the following equation, as an index of domain shape: Q = {(r_sphere(V)) / (r_sphere(A))}^6, where rsphere(V) and rsphere(A) are the radii calculated from the volume and area of ​​each domain obtained in the domain analysis, assuming a spherical shape. The Q value ranges from 0 to 1; values ​​closer to 1 indicate a more spherical domain, while values ​​closer to 0 indicate a more complex shape with a high specific surface area. [References] 1) MJ Abraham, T. Murtola, R. Schulz, S. Pall, JC Smith, B. Hess, E. Lindah, SoftwareX 2015, 1-2, 19. 2) JN Canongia Lopes, J. Deschamps, AAH Padua, J. Phys. Chem. B 2004, 108, 2038. 3) HJC Berendsen, JR Grigera, TP Straatsma, J. Phys. Chem. 1987, 91, 6269. 4) P. Li, BP Roberts, DK Chakravorty, KM Merz, J. Chem. Theory Comput. 2013, 9, 2733. 5) P. Li, LF Song, KM Merz, J. Phys. Chem. B 2015, 119, 883. 6) U. Essmann, L. Perera, ML Berkowitz, T. Darden, H. Lee, LG Pedersen, J. Chem. Phys. 1995, 103, 8577. 7) L. Martinez, R. Andrade, EG Birgin, JM Martinez, J. Comput. Chem. 2009, 30, 2157. 8) A. Padua, fftool, https: / / github.com / paduagroup / fftool, accessed: August 2023. 9) MC Payne, MPTeter, DC Allan, TA Arias, JD Joannopoulos, Rev. Mod. Phys. 1992, 64, 1045. 10) G. Bussi, D. Donadio, M. Parrinello, J. Chem. Phys. 2007, 126, 014101. 11) M. Bernetti, G. Bussi, J. Chem. Phys. 2020, 153, 114107. 12) S. Nose, Mol. Phys. 1984, 52, 255. 13) M. Brehm, B. Kirchner, J. Chem. Inf. Model. 2011, 51, 2007. 14) M. Brehm, M. Thomas, S. Gehrke, B. Kirchner, J. Chem. Phys. 2020, 152, 164105.

[0068]

[0069]

[0070] According to the MD simulation, the composition used in Example 1 had a polar domain volume of 4.3 when the non-polar domain volume was taken as 1.

[0071] FIG. 4 shows a schematic diagram outlining the method and apparatus 10 for producing a multi-component alloy nanostructure according to the present invention. The working electrode (WE) 11 consisted of an anodized aluminum oxide (AAO) (manufactured by Alliance Biosystems) with gold deposited on one side. The electrode 11 was positioned with the AAO facing the composition. The hotplate temperature was set to 90°C, and the entire cell was covered with aluminum foil for uniform heating. Pulse electrolysis was then performed. Specifically, a potentiostat was used to set the counter electrode (CE) 12 to a platinum (Pt) reference electrode (RE, Ag / AgCl in 3.33 M KCl) 13 at a potential of -1.3 V, held for 1 second, followed by an open circuit (current I = 0) for 3 seconds. This cycle was repeated 1,800 times. After pulse electrolysis, the AAO was removed by immersion in a 3 M NaOH aqueous solution, yielding a multi-component alloy nanostructure.

[0072] The obtained multi-component alloy nanostructure was subjected to elemental analysis by TEM-EDS (JEM-2100F manufactured by JEOL Ltd., accelerating voltage 200 kV).

[0073] Figure 5A shows an example of a TEM image of the multi-component alloy nanostructure of Example 1. As shown in Figure 5A, the multi-component alloy nanostructure of Example 1 had less phase separation (unevenness in the TEM image) than Examples 3 and 4, which were produced by constant-potential electrolysis, as described below. The results of elemental analysis of the area indicated by the square in Figure 5A are shown in Table 3.

[0074]

[0075] The following can be seen from Table 3: In Example 1, a multi-component alloy nanostructure was produced according to the production method of the present invention, and as a result, a multi-component alloy nanostructure that satisfied the requirements of this embodiment was obtained.

[0076] Figure 5B shows an electron beam diffraction image of Example 1. From the electron beam diffraction image of Figure 5B, it was found that the multi-component alloy nanostructure of Example 1 had an FCC structure.

[0077] Figure 5C shows another example of a TEM image of the multi-component alloy nanostructure of Example 1. As shown in Figure 5C, the multi-component alloy nanostructure of Example 1 exhibited light-dark changes (streaks) at regular intervals (about 21 nm) due to pulse electrolysis.

[0078] [2. Example of pulse electrolysis, nanoporous electrolysis electrode hydrophobized, composition not containing hydrochloric acid] Tests were conducted in the same manner as in Example 1, except that the nanoporous electrolysis electrode was hydrophobized as follows. [Hydrophobization procedure] 1. Dissolve 40 μL of octadecyltrichlorosilane in 1.5 mL of n-hexadecane. 2. Immerse anodized aluminum oxide (AAO) with Au vapor-deposited on one side in the above solution for 5 minutes. 3. Immerse in 100 mL of chloroform for 5 minutes (washing). 4. Immerse in 100 mL of ethanol for 5 minutes (washing). 5. Anneal at 100°C for 2 hours.

[0079] Figure 6A shows an example of a TEM image of the multi-component alloy nanostructure of Example 2. As shown in Figure 6A, the multi-component alloy nanostructure of Example 2 had less phase separation (uneven light and dark in the TEM image) than Examples 3 and 4, which were produced by constant-potential electrolysis, as described below. Furthermore, when an electron diffraction image was obtained in the same manner as in Example 1, it was found that the multi-component alloy nanostructure of Example 2 had an FCC structure, similar to Example 1. The results of elemental analysis of the area indicated by the square in Figure 6A are shown in Table 4.

[0080]

[0081] The following can be seen from Table 4: In Example 2, a multi-component alloy nanostructure was produced according to the production method of the present invention, and as a result, a multi-component alloy nanostructure that satisfied the requirements of this embodiment was obtained.

[0082] Figure 6B shows another example of a TEM image of the multi-component alloy nanostructure of Example 2. Figure 6B shows that the streak spacing is longer (approximately 120 nm) compared to Example 1, which is thought to be due to the improved nanostructure production rate per pulse. This is thought to be due to the hydrophobic treatment of the nanoporous electrolytic electrode, which makes it easier for the composition to be supplied to the electrode.

[0083] 3. Examples of constant-potential electrolysis, nanoporous electrolysis electrode not hydrophobized, and composition not containing hydrochloric acid: Tests were conducted in the same manner as in Example 1, except that pulse electrolysis was changed to constant-potential electrolysis. The applied potentials were −1.2 V (Example 3-1), −1.3 V (Example 3-2), −1.4 V (Example 3-3), and −1.5 V (Example 3-4).

[0084] Figures 7 to 10 show examples of TEM images of the multi-component alloy nanostructures of Examples 3-1 to 3-4. Furthermore, electron beam diffraction images were obtained in the same manner as in Example 1, and it was found that the multi-component alloy nanostructures of Examples 3-1 to 3-4 had an FCC structure, similar to Example 1. The results of elemental analysis of the squared areas in Figures 7 to 10 are shown in Tables 5 to 8.

[0085]

[0086]

[0087]

[0088]

[0089] The following can be seen from Tables 5 to 8: In Examples 3-1 to 3-4, multi-component alloy nanostructures were produced according to this production method, and as a result, multi-component alloy nanostructures that satisfied the requirements of this embodiment were obtained.

[0090] [4. Example of constant potential electrolysis, nanoporous electrolysis electrode not hydrophobized, and composition containing hydrochloric acid] Example 4-1 was tested in the same manner as Example 3-3, except that hydrochloric acid was contained in the composition. Example 4-2 was tested in the same manner as Example 3-2, except that hydrochloric acid was contained in the composition, the entire cell was not covered with aluminum foil, and the hot plate temperature during electrolysis was set to 70°C. Note that the hydrochloric acid content was CoCl in both Examples 4-1 and 4-2. ２ The molar ratio was 0.06 when the volume of the nonpolar domains of the compositions of Examples 4-1 and 4-2 was taken as 1. Because the content of hydrochloric acid was extremely small, the volume of the polar domains when the volume of the nonpolar domains of the compositions of Examples 4-1 and 4-2 was taken as 1 is thought to be around the value of Example 1 (4.3) (i.e., within the range of 2 to 6).

[0091] Figures 11 and 12 show examples of TEM images of the multi-component alloy nanostructures of Examples 4-1 and 4-2. Furthermore, electron beam diffraction images were obtained in the same manner as in Example 1, and it was found that the multi-component alloy nanostructures of Examples 4-1 and 4-2 had an FCC structure, similar to Example 1. The results of elemental analysis of the squared areas in Figures 11 and 12 are shown in Tables 9 and 10.

[0092]

[0093]

[0094] The following can be seen from Tables 9 and 10. In Examples 4-1 and 4-2, multi-component alloy nanostructures were produced according to this production method, and as a result, multi-component alloy nanostructures that satisfied the requirements of this embodiment were obtained. Furthermore, compared to Examples 1 to 3, no carbon was detected in Examples 4-1 and 4-2. This may be due, for example, to the fact that the composition contained hydrochloric acid. Furthermore, Example 4-1 had a reduced oxygen content of 10 atomic % or less compared to Example 4-2. This is thought to be due to the fact that the applied potential in Example 4-1 was more negative than in Example 4-2, making it easier for reductive precipitation of chromium to occur.

[0095] The multi-component alloy nanostructures of Examples 1 to 4 are nanostructures of multi-component alloy plating films that have excellent mechanical properties (low elastic modulus, reduced warping, high hardness, and excellent wear resistance), as disclosed in, for example, PCT / JP2024 / 005719, and it is clear that they have the same excellent mechanical properties as the multi-component alloy plating films.

[0096] [5. Aluminum-based composite] The working electrode 11 was made of a 1 cm diameter (electrode area: 0.785 cm ２ The aluminum alloy nanostructure was obtained by the same test as in Example 2. ３ A solution (molar ratio 1:1.5) was prepared, and 1 mL of it was taken and placed in a centrifuge tube, where it was dispersed by ultrasonic treatment. This procedure was repeated three times to prepare 3 mL of electrolyte. All of the multi-component alloy nanostructures obtained as described above were added to the electrolyte. Electroplating was performed using a Si substrate / Au film as the working electrode, an Al plate as the counter electrode, and an Al wire as the reference electrode, to obtain an aluminum-based composite with a thickness of approximately 100 μm on the working electrode (on the Au film). The electrolysis conditions were -10 mA / cm ２ for 1 s, and the open circuit voltage (OCV, 0 mA / cm ２ ) for 1 second was repeated 36,000 times (the net current application time was 5 hours, and ultrasonic treatment was not performed during current application).

[0097] A surface SEM image of the obtained aluminum-based composite is shown in Figure 13. As shown in Figure 13, a multi-component alloy nanostructure (white portion) was confirmed in the aluminum matrix.

[0098] For comparison with the obtained aluminum-based composite, electroplating was carried out in the same manner as above without adding the multi-component alloy nanostructure, and an Al plating film with a thickness of about 100 μm was obtained on the working electrode (on the Au film).

[0099] The Vickers hardness (arithmetic mean value of 10 randomly selected points) of the aluminum matrix composite and the Al plating film was measured using a Vickers hardness tester (Shimadzu Corporation, HMV-2). The Al plating film without the multi-component alloy nanostructure had a Vickers hardness of 205.1 (HV), whereas the aluminum matrix composite containing the multi-component alloy nanostructure had a Vickers hardness of 327.7 (HV), demonstrating improved strength. Furthermore, while the Al plating film showed cracks when tensile stress was applied in a bending test, the aluminum matrix composite showed no cracks in a similar test, demonstrating improved crack resistance.

[0100] This application claims priority from Japanese Patent Application No. 2024-085023, filed May 24, 2024. Japanese Patent Application No. 2024-085023 is incorporated herein by reference.

[0101] 1 Polar domain 2 Non-polar domain 10 Device 11 Working electrode 12 Counter electrode 13 Reference electrode 14 O-ring (φ8)

Claims

1. A method for producing a multi-component alloy nanostructure, comprising the steps of electrolyzing a composition containing multiple metal elements, an ionic liquid, and water, and electrodepositing the metal elements inside the pores of a nanoporous electrolytic electrode, thereby producing a multi-component alloy nanostructure containing the multiple metal elements, wherein the volume of the polar domain of the composition is 10 or less when the volume of the non-polar domain is taken as 1.

2. A method for producing a multi-component alloy nanostructure according to claim 1, wherein in the producing step, the electrodeposition is carried out by pulse electrolysis based on pulse potential control.

3. The method for producing a multi-component alloy nanostructure according to claim 1 or 2, wherein the nanoporous electrolytic electrode has been subjected to a hydrophobic treatment.

4. The method for producing a multi-component alloy nanostructure according to claim 1, wherein the electrodeposition is carried out by constant potential electrolysis in the production step.

5. A method for producing a multi-component alloy nanostructure according to claim 1 or 4, wherein the composition further contains hydrochloric acid.

6. A multi-component alloy nanostructure containing multiple metal elements and having a portion that satisfies the following formulas (1) to (3): ｎ ≧2.0 (atomic %) ... (1) Σa ｎ ≧25 (atomic %) (2) a ｍｉｎ ≧0.1a ｍａｘ ... (3) where a ｎ is the atomic fraction (atomic %) of the nth metal element (n is an integer of 2 or more), and Σa ｎ is the total atomic fraction (atomic %) of n kinds of metal elements, and a ｍｉｎ Haa ｎ is the minimum value of a ｍａｘ Haa ｎ is the maximum value of 7. The multi-component alloy nanostructure according to claim 6, wherein n is an integer of 3 or more.

8. An aluminum-based composite comprising the multi-component alloy nanostructure according to claim 6 or 7 in an aluminum or aluminum alloy matrix.

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