Porous metal structure and preparation method therefor

Abstract

The present application discloses a porous metal structure and a preparation method therefor. The preparation method for the porous metal structure comprises the following steps: performing first dealloying treatment on an alloy foil to form holes, then performing reduction annealing treatment in a reducing gas atmosphere, and then performing second dealloying treatment to obtain the porous metal structure. According to the preparation method for the porous metal structure provided in the present application, the residual amount of relatively active metal in the porous metal structure can be reduced.

Description

Porous metal structure and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311862485.0, filed on December 29, 2023, entitled “Porous Metal Structure and Preparation Method Thereof,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a porous metal structure and a preparation method thereof. Background Art

[0004] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in consumer electronics, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. The negative electrode is an important component of the battery, which affects the performance of the battery. At present, the negative electrode of the battery is usually formed by arranging a negative electrode film layer including negative electrode active materials such as graphite on a copper foil. However, with the continuous expansion of battery application fields, people are more and more demanding on batteries with high energy density. Metal batteries and negative electrode-free batteries can have high energy density because they do not use negative electrode film layers. However, the uneven deposition of metals and dendrite problems restrict the development of metal batteries and negative electrode-free batteries. As an important component of metal batteries and negative electrode-free batteries, the negative electrode current collector is expected to alleviate the uneven deposition of metals and dendrite problems by improving it.

[0005] Porous metal structures offer advantages such as light weight and large surface area. When used in batteries, they can increase energy density and improve reliability. In particular, using porous metal structures in the negative electrodes of metal batteries and anode-free batteries can reduce uneven metal deposition and dendrite problems.

[0006] Dealloying alloy foil is an effective method for creating porous metal structures. Alloys are typically composed of relatively active and relatively inactive metals. Dealloying selectively dissolves the relatively active metal in the alloy to form pores. However, current methods for preparing porous metal structures often suffer from incomplete dealloying and high levels of relatively active metal residue. Excessive levels of relatively active metal residue can affect the flexibility of the prepared porous metal structure. Furthermore, relatively active metals are more susceptible to oxidation, which can lead to more side reactions.

[0007] The above statements are only used to provide background information related to the present application and do not necessarily constitute prior art.

[0008] Summary of the Invention

[0009] The present application provides a porous metal structure and a preparation method thereof, which can reduce the residual amount of relatively active metal in the porous metal structure.

[0010] In a first aspect, the present application provides a method for preparing a porous metal structure, comprising the following steps: subjecting an alloy foil to a first dealloying treatment to form pores, then subjecting the alloy foil to a reduction annealing treatment in a reducing gas atmosphere, and then subjecting the alloy foil to a second dealloying treatment to obtain a porous metal structure.

[0011] The preparation method provided in the embodiment of the present application is subjected to a reduction annealing treatment on the obtained porous metal structure after the first dealloying treatment. When the porous metal structure obtained by the first dealloying treatment is subjected to a reduction annealing treatment, the relatively inactive metal oxide on the surface of the ligament of the porous metal structure is reduced to a metal element under a reducing gas atmosphere, and the thermal diffusion capacity of the metal element is better; at the same time, the relatively active metal atoms and the relatively inactive metal atoms in the porous metal structure will both be heated and diffuse. In the porous metal structure obtained by the first dealloying treatment, the relatively active metal is a poor metal (i.e., the content is lower than that of the relatively inactive metal), and thus there is a tendency to diffuse to the high surface energy area, i.e., the ligament surface, thereby reducing the surface energy of the porous metal structure as a whole. Therefore, after the porous metal structure obtained by the first dealloying treatment is subjected to a reduction annealing treatment, some of the relatively active metal will diffuse from the inside to the ligament surface of the porous metal structure, and then the metal on the ligament surface can be removed by a second dealloying treatment, thereby reducing the residual amount of relatively active metal in the porous metal structure obtained.

[0012] In some embodiments, the process of the first dealloying treatment includes a free corrosion dealloying process or an electrochemical corrosion dealloying process, and the process of the second dealloying treatment includes a free corrosion dealloying process; optionally, the process of the first dealloying treatment includes a free corrosion dealloying process, and the process of the second dealloying treatment includes a free corrosion dealloying process.

[0013] In some embodiments, the first dealloying process includes a free corrosion dealloying process, the second dealloying process includes a free corrosion dealloying process, and the etching solutions used in the first dealloying process and the second dealloying process are both acidic solutions.

[0014] Optionally, the acidic solution includes an acidic aqueous solution, and more optionally includes one or a mixed acid of hydrochloric acid, sulfuric acid, phosphoric acid, and acetic acid.

[0015] In some embodiments, the concentration C1 of the acidic solution used in the first dealloying treatment is greater than the concentration C2 of the acidic solution used in the second dealloying treatment.

[0016] During the first dealloying treatment, the alloy contains a high concentration of relatively active metals, so using a higher concentration of acidic solution can help reduce the amount of relatively active metal residue. During the second dealloying treatment, the relatively active metal content has been greatly reduced, so using a lower concentration of acidic solution can improve the stability of the porous metal structure and reduce corrosion of the relatively inactive metal.

[0017] In some embodiments, the treatment temperature T1 of the first dealloying treatment is greater than the treatment temperature T2 of the second dealloying treatment. Optionally, T1 is 40°C-80°C, and T2 is 20°C-30°C.

[0018] During the first dealloying treatment, the alloy contains a high content of relatively active metals, so a higher treatment temperature is beneficial for reducing the amount of relatively active metal residue. During the second dealloying treatment, the content of relatively active metals in the alloy has been greatly reduced, so a lower treatment temperature is beneficial for improving the stability of the porous metal structure and reducing corrosion of relatively inactive metals.

[0019] In some embodiments, the processing time t1 of the first dealloying treatment is greater than the processing time t2 of the second dealloying treatment. Optionally, t1 is greater than or equal to 24 hours, and t2 is less than or equal to 12 hours.

[0020] During the first dealloying treatment, the alloy contains a high content of relatively active metals, so a longer treatment time is beneficial for reducing the amount of relatively active metal residue. During the second dealloying treatment, the content of relatively active metals in the alloy has been greatly reduced, so a shorter treatment time is beneficial for improving the stability of the porous metal structure and reducing corrosion of relatively inactive metals.

[0021] In some embodiments, the reducing gas used in the reduction annealing process includes ammonia or a mixture of hydrogen and an inert gas.

[0022] In some embodiments, the reducing gas used in the reduction annealing treatment includes a mixture of hydrogen and an inert gas, and the inert gas includes one or more of nitrogen, argon, and helium.

[0023] In some embodiments, the flow rate of the reducing gas used in the reduction annealing treatment is 100 SCCM-2000 SCCM.

[0024] In some embodiments, the reduction annealing treatment is performed in a tube furnace, and the heating rate of the tube furnace is 2° C. / min-10° C. / min.

[0025] In some embodiments, the reduction annealing treatment is performed in a tube furnace, and the heating rate of the tube furnace is 5° C. / min-10° C. / min.

[0026] In some embodiments, the average cooling rate of the cooling process after the reduction annealing is less than or equal to 2° C. / min.

[0027] In some embodiments, the temperature reduction process is a furnace cooling process.

[0028] Using a slow cooling process can reduce the stress of the porous metal structure, making it less likely to curl.

[0029] In some embodiments, the cooling treatment after the reduction annealing treatment is cooling to below 50° C. This can reduce the risk of surface oxidation during the transfer of the porous metal structure out of the furnace.

[0030] In some embodiments, the alloy foil is a copper alloy foil, and the copper alloy foil includes a Cu element and a non-Cu metal element, and the standard electrode potential of the non-Cu metal element is lower than the standard electrode potential of the Cu element.

[0031] Optionally, the non-Cu metal elements include one or more of Mn, Zn, Ni, Al, and Fe.

[0032] Optionally, the atomic content of the non-Cu metal element in the copper alloy foil is greater than 60 at.%, and can be optionally 65 at.%-80 at.%.

[0033] In some embodiments, the reduction annealing treatment is performed at a holding temperature of 700° C. to 900° C.; and / or the holding time at the reduction annealing treatment temperature is 20 min to 60 min.

[0034] By adjusting the holding temperature and / or holding time of the reduction annealing treatment within the above-mentioned range, the relatively inactive metal oxides on the surface of the ligament of the porous metal structure obtained by the first dealloying treatment are reduced to metal elements, which is beneficial to the thermal diffusion of relatively active metal atoms and relatively inactive metal atoms in the porous metal structure, and is beneficial to the diffusion of relatively active metal atoms to the ligament surface of the porous metal structure, thereby helping to reduce the amount of relatively active metal residues; in addition, the porous metal can also have a stable structure to avoid the problem of structural collapse.

[0035] In some embodiments, before the alloy foil is subjected to the first dealloying treatment, the steps are further included: providing a cold-rolled alloy foil; subjecting the alloy foil to a recrystallization annealing treatment, and then subjecting the alloy foil to a first cooling treatment to obtain an alloy foil having a first component phase; subjecting the alloy foil having the first component phase to a phase separation heat treatment, and then subjecting the alloy foil to a second cooling treatment to precipitate the second component phase and obtain an alloy foil having both the first component phase and the second component phase, wherein the temperature of the phase separation heat treatment is lower than the temperature of the recrystallization annealing treatment, and the average cooling rate of the second cooling treatment is lower than the average cooling rate of the first cooling treatment.

[0036] By performing recrystallization annealing treatment on the alloy foil after cold rolling, an alloy foil with a first component phase and good plastic processing ability can be obtained, and the grains in the alloy foil are mainly equiaxed crystals; then, by adopting a phase separation heat treatment with a lowered temperature, an alloy foil with both the first component phase and the second component phase can be obtained, thereby making the dealloyed porous metal structure self-supporting.

[0037] After the first dealloying treatment, reduction annealing is performed, a higher cooling rate is used in the first cooling process after the recrystallization annealing treatment, and a lower cooling rate is used in the second cooling process after the phase separation heat treatment. The intergranular corrosion cracks formed by the dealloying treatment can be partially or even completely repaired, and the prepared porous metal structure can also have better strength and toughness.

[0038] In some embodiments, the average cooling rate of the first cooling treatment is greater than or equal to 100°C / min, and can be optionally greater than or equal to 200°C / min. This helps reduce element segregation at grain boundaries and facilitates diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing intergranular corrosion cracks and imparting better toughness to the prepared porous metal structure.

[0039] In some embodiments, the average cooling rate of the second cooling treatment is less than or equal to 2°C / min. This helps reduce the interphase stress between the first component phase and the second component phase in the phase-separated alloy, facilitates the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing intergranular corrosion cracks, and also improves the toughness of the prepared porous metal structure.

[0040] In some embodiments, the first cooling process is a water cooling process, which helps reduce element segregation at grain boundaries and facilitates diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing process, thereby better repairing intergranular corrosion cracks and improving the toughness of the prepared porous metal structure.

[0041] In some embodiments, the second cooling process is a furnace cooling process, which helps reduce the interphase stress between the first component phase and the second component phase in the phase-separated alloy, facilitates the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing process, thereby better repairing intergranular corrosion cracks and improving the toughness of the prepared porous metal structure.

[0042] In some embodiments, the first cooling treatment is cooling to below 50° C. This can reduce the risk of surface oxidation of the alloy foil during the process of being transferred out of the furnace.

[0043] In some embodiments, the second cooling treatment is cooling to below 50° C. This can reduce the risk of surface oxidation of the alloy foil during the process of being transferred out of the furnace.

[0044] In some embodiments, the recrystallization annealing process is performed in a muffle furnace.

[0045] In some embodiments, the phase separation heat treatment is performed in a tube furnace. Optionally, the heating rate of the tube furnace is 2°C / min-10°C / min, optionally 5°C / min-10°C / min.

[0046] In some embodiments, the temperature of the recrystallization annealing treatment is 720°C-850°C.

[0047] In some embodiments, the holding time at the recrystallization annealing temperature is 10 min-60 min.

[0048] Adjusting the temperature and / or time of the recrystallization annealing treatment within the above range is beneficial for obtaining an alloy foil having a first component phase with good plastic working ability, and is also beneficial for precipitating the second component phase during the phase separation heat treatment.

[0049] In some embodiments, the temperature of the phase separation heat treatment is 620°C-700°C.

[0050] In some embodiments, the holding time at the phase separation heat treatment temperature is 60 min-360 min.

[0051] By adjusting the temperature of the phase separation heat treatment and / or keeping it within the above range, it is beneficial to precipitate the second component phase during the phase separation heat treatment, and it is also beneficial to obtain a micron-level porous metal structure after the subsequent reduction annealing treatment.

[0052] In some embodiments, the first component phase includes a gamma phase; and / or, the second component phase includes an alpha phase.

[0053] In a second aspect, the present application provides a porous metal structure prepared by the preparation method of the first aspect of the present application.

[0054] In some embodiments, the porous metal structure is a porous copper structure, and the porous copper structure includes non-Cu metal elements, and the atomic content of the non-Cu metal elements is less than 0.3 wt %, and optionally less than 0.2 wt %. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG1 is a surface Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment in Comparative Example 1.

[0056] FIG2 is a cross-sectional Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment in Comparative Example 1.

[0057] FIG3 is a surface Mn element distribution diagram of the porous copper structure after reduction annealing treatment in Example 1 and before the second dealloying treatment.

[0058] FIG4 is a surface Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment in Example 1.

[0059] FIG5 is a cross-sectional Mn element distribution diagram of the porous copper structure after reduction annealing treatment and before the second dealloying treatment in Example 1.

[0060] FIG6 is a cross-sectional Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment in Example 1.

[0061] FIG7 is the surface morphology of the porous copper structure obtained after the second dealloying treatment in Example 1.

[0062] FIG8 is a cross-sectional morphology of the porous copper structure obtained after the second dealloying treatment in Example 1. DETAILED DESCRIPTION

[0063] Hereinafter, embodiments of the porous metal structure and preparation method thereof of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0064] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0066] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0067] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0068] In this application, the terms "plurality" and "multiple" refer to two or more.

[0069] In the description of the embodiments of the present application, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0070] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0071] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0072] The embodiments of the present application provide a method for preparing a porous metal structure.

[0073] The preparation method comprises the following steps: subjecting the alloy foil to a first dealloying treatment to form pores, then subjecting the alloy foil to a reduction annealing treatment in a reducing gas atmosphere, and then subjecting the alloy foil to a second dealloying treatment to obtain a porous metal structure.

[0074] Alloys are typically composed of relatively active and relatively inactive metals. During dealloying, the content of the relatively active metal decreases as the reaction proceeds. However, once the content reaches a low level, even aggressive reaction conditions such as heating, electrolysis, and concentrated acid etching are difficult to effectively reduce the residual relatively active metal. This is because, in the later stages of dealloying, the relatively active metal remains within the alloy, requiring it to undergo more dissolution pathways. Furthermore, in addition to the residual contribution from the undissolved relatively active metal, some relatively active metal ions that have already dissolved within the alloy may also contribute. This is because the diffusion pathways of the relatively active metal ions that have already dissolved within the alloy are larger than those at the surface. During the washing process, it is not guaranteed that the dissolved metal ions will be completely replaced by the detergent. Therefore, some of the metal ions that have already dissolved within the alloy may also contribute to the residual content. Excessive residual relatively active metal can easily affect the flexibility of the prepared porous metal structure. Furthermore, relatively active metals are more susceptible to oxidation, which can lead to more side reactions.

[0075] The preparation method provided in the embodiment of the present application is subjected to a reduction annealing treatment on the obtained porous metal structure after the first dealloying treatment. When the porous metal structure obtained by the first dealloying treatment is subjected to a reduction annealing treatment, the relatively inactive metal oxide on the surface of the ligament of the porous metal structure is reduced to a metal element under a reducing gas atmosphere, and the thermal diffusion capacity of the metal element is better; at the same time, the relatively active metal atoms and the relatively inactive metal atoms in the porous metal structure will both be heated and diffuse. In the porous metal structure obtained by the first dealloying treatment, the relatively active metal is a poor metal (i.e., the content is lower than that of the relatively inactive metal), and thus there is a tendency to diffuse to the high surface energy area, i.e., the ligament surface, thereby reducing the surface energy of the porous metal structure as a whole. Therefore, after the porous metal structure obtained by the first dealloying treatment is subjected to a reduction annealing treatment, some of the relatively active metal will diffuse from the inside to the ligament surface of the porous metal structure, and then the metal on the ligament surface can be removed by a second dealloying treatment, thereby reducing the residual amount of relatively active metal in the porous metal structure obtained. In addition, after the porous metal structure obtained by the first dealloying treatment is subjected to reduction annealing treatment, the relatively inactive metal element formed by the reduction of metal oxides on the ligament surface will undergo a recrystallization process and can also self-diffusion into an alloy phase (relatively active metal content is lower, relatively inactive metal content is higher) or a pure relatively inactive metal element phase.

[0076] In some embodiments, the alloy foil may be a copper alloy foil, which may include Cu and non-Cu metal elements. The standard electrode potential of the non-Cu metal elements is lower than that of Cu, i.e., the non-Cu metal elements are more active than Cu. Optionally, the non-Cu metal elements may include one or more of Mn, Zn, Ni, Al, and Fe.

[0077] The content of Cu and non-Cu metal elements is not particularly limited. In some embodiments, the atomic content of non-Cu metal elements in the copper alloy foil can be greater than 60 at.%, optionally ranging from 65 at.% to 85 at.%, and from 65 at.% to 80 at.%. This facilitates the application of the porous copper structure in battery negative electrodes.

[0078] In some embodiments, the copper alloy foil may further include a small amount of non-metallic element impurities, such as C, Si, etc.

[0079] In some embodiments, the first dealloying process includes a free-etch dealloying process or an electrochemical-etch dealloying process.

[0080] In some embodiments, the first dealloying process may include a free etch dealloying process, and the second dealloying process may include a free etch dealloying process.

[0081] The second dealloying process includes a free etch dealloying process to reduce metal oxidation. Optionally, the processing temperature of the second dealloying process is lower than the processing temperature of the first dealloying process.

[0082] Both the free corrosion dealloying process and the electrochemical corrosion dealloying process can adopt technologies known in the art. The washing process after dealloying can include water washing and alcohol washing. Water washing can reduce the metal ion content in the porous metal structure, and alcohol washing can reduce the moisture in the pores of the porous metal structure. Deionized water can be used for water washing. The number of water washings can be 3 to 6 times, which is not limited in the embodiments of the present application. Anhydrous ethanol can be used for alcohol washing. The number of alcohol washings can be 3 to 6 times, which is not limited in the embodiments of the present application. The drying process after the washing process is completed can be carried out in a vacuum drying oven, and the drying temperature can be 30°C to 50°C, thereby reducing metal oxidation.

[0083] In some embodiments, the first dealloying process includes a free-etching dealloying process, the second dealloying process includes a free-etching dealloying process, and the etching solutions used in the first dealloying process and the second dealloying process may both be acidic solutions.

[0084] Alternatively, the acidic solution may comprise an acidic aqueous solution.

[0085] Alternatively, the acidic solution may include one of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, or a mixture of multiple thereof. Alternatively, the acidic solution may include an aqueous hydrochloric acid solution.

[0086] The etching solution (also called electrolyte) used in the electrochemical etching dealloying process may include an acidic (such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, etc.) aqueous solution, a neutral salt (such as sodium chloride, etc.) aqueous solution, or a mixed aqueous solution of the above components.

[0087] In some embodiments, the first dealloying process includes a free-etch dealloying process, the second dealloying process includes a free-etch dealloying process, and the concentration C1 of the acidic solution used in the first dealloying process may be greater than the concentration C2 of the acidic solution used in the second dealloying process.

[0088] During the first dealloying treatment, the alloy contains a high concentration of relatively active metals, so using a higher concentration of acidic solution can help reduce the amount of relatively active metal residue. During the second dealloying treatment, the relatively active metal content has been greatly reduced, so using a lower concentration of acidic solution can improve the stability of the porous metal structure and reduce corrosion of the relatively inactive metal.

[0089] In some embodiments, the etching solutions used in the first dealloying treatment and the second dealloying treatment are both acidic solutions, and the treatment temperature T1 of the first dealloying treatment may be greater than the treatment temperature T2 of the second dealloying treatment.

[0090] During the first dealloying treatment, the alloy contains a high content of relatively active metals, so a higher treatment temperature is beneficial for reducing the amount of relatively active metal residue. During the second dealloying treatment, the content of relatively active metals in the alloy has been greatly reduced, so a lower treatment temperature is beneficial for improving the stability of the porous metal structure and reducing corrosion of relatively inactive metals.

[0091] Optionally, T1 may be 40°C-80°C.

[0092] Alternatively, T2 may be 20°C-30°C.

[0093] In some embodiments, the etching solutions used in the first dealloying treatment and the second dealloying treatment are both acidic solutions, and the processing time t1 of the first dealloying treatment may be greater than the processing time t2 of the second dealloying treatment.

[0094] During the first dealloying treatment, the alloy contains a high content of relatively active metals, so a longer treatment time is beneficial for reducing the amount of relatively active metal residue. During the second dealloying treatment, the content of relatively active metals in the alloy has been greatly reduced, so a shorter treatment time is beneficial for improving the stability of the porous metal structure and reducing corrosion of relatively inactive metals.

[0095] Optionally, t1 may be greater than or equal to 24 hours, and may be 24 hours to 60 hours, or 32 hours to 48 hours.

[0096] Optionally, t2 may be less than or equal to 12 hours, and may be 4 hours to 12 hours, or 6 hours to 10 hours.

[0097] In some embodiments, the reducing gas used in the reduction annealing process may include ammonia or a mixture of hydrogen and an inert gas. Alternatively, the inert gas may include one or more of nitrogen, argon, and helium.

[0098] Optionally, the reducing gas used in the reduction annealing treatment may include a mixture of hydrogen and an inert gas, and the volume fraction of hydrogen in the reducing gas may be greater than or equal to 2%, and more preferably 2% to 10%. This can reduce the metal oxides on the ligament surface to metal elements with better diffusion ability while ensuring operational safety.

[0099] In some embodiments, the flow rate of the reducing gas used in the reduction annealing process may be 100 SCCM-2000 SCCM.

[0100] The reduction annealing treatment can adopt a programmed heating process, which includes a heating stage, a holding stage, and a cooling stage.

[0101] In some embodiments, the reduction annealing process may be performed in a tube furnace.

[0102] Optionally, the heating rate of the tube furnace may be 2°C / min-10°C / min, optionally 5°C / min-10°C / min.

[0103] In some embodiments, the holding temperature of the reduction annealing treatment can be 700°C-900°C, for example, it can be 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, or a range consisting of any of the above values, and can be optionally 720°C-900°C, 750°C-880°C, or 750°C-850°C.

[0104] In some embodiments, the holding time at the reduction annealing temperature can be 20 min-60 min, for example, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range consisting of any of the above values, and can be optionally 25 min-55 min, 30 min-50 min.

[0105] By adjusting the holding temperature and / or holding time of the reduction annealing treatment within the above-mentioned range, the relatively inactive metal oxides on the surface of the ligament of the porous metal structure obtained by the first dealloying treatment are reduced to metal elements, which is beneficial to the thermal diffusion of relatively active metal atoms and relatively inactive metal atoms in the porous metal structure, and is beneficial to the diffusion of relatively active metal atoms to the ligament surface of the porous metal structure, thereby helping to reduce the amount of relatively active metal residues; in addition, the porous metal can also have a stable structure to avoid the problem of structural collapse.

[0106] When the holding temperature of the reduction annealing treatment is low and / or the holding time is short, the thermal diffusion of relatively active metal atoms and relatively inactive metal atoms is slow, and the thermal diffusion effect is poor, which is not conducive to the full diffusion of relatively active metal atoms to the ligament surface, and further not conducive to reducing the relatively active metal residue.

[0107] When the holding temperature of the reduction annealing treatment is high, the relatively inactive metal atoms on the ligament surface diffuse violently, which greatly promotes the reduction of surface free energy of the porous metal structure. As a result, the pore structure of the porous metal structure is prone to shrinkage or even sintering, and the porosity of the porous metal structure decreases, which is not conducive to reducing the relatively active metal residue.

[0108] When the holding time of the reduction annealing treatment is long, the relatively active metal atoms and the relatively inactive metal atoms diffuse thermally faster, more fully, and have a better diffusion effect. At this time, the pore structure of the porous metal structure is prone to shrinkage, and the porosity of the porous metal structure decreases, which is not conducive to reducing the relatively active metal residue.

[0109] In some embodiments, the average cooling rate of the cooling process after the reduction annealing treatment may be less than or equal to 2° C. / min. Using a slow cooling process can reduce the stress of the porous metal structure and make it less likely to curl.

[0110] In some embodiments, the temperature reduction process may be a furnace cooling process, which refers to a process in which the porous metal structure is not removed from the high-temperature furnace body, but is slowly cooled naturally together with the furnace body.

[0111] In some embodiments, the temperature reduction treatment after the reduction annealing treatment may be cooling to below 50° C. This can reduce the risk of surface oxidation during the transfer of the porous metal structure from the furnace.

[0112] In some embodiments, before the alloy foil is subjected to a first dealloying treatment, the preparation method further includes the steps of: providing a cold-rolled alloy foil; subjecting the alloy foil to a recrystallization annealing treatment, and then subjecting the alloy foil to a first cooling treatment to obtain an alloy foil having a first component phase; subjecting the alloy foil having the first component phase to a phase separation heat treatment, and then subjecting the alloy foil to a second cooling treatment to precipitate a second component phase and obtain an alloy foil having both the first component phase and the second component phase, wherein the temperature of the phase separation heat treatment is lower than the temperature of the recrystallization annealing treatment, and the average cooling rate of the second cooling treatment is lower than the average cooling rate of the first cooling treatment.

[0113] The thickness of the alloy foil used to prepare battery-grade porous metal structures is usually very small, for example, mostly at the micron level (for example, typically tens of microns to hundreds of microns), and thus, the preparation process of the alloy foil usually requires multiple cold rollings. However, the alloy is prone to problems such as rolling orientation, element segregation, and stress accumulation after repeated cold rolling thinning, which can reduce the structural strength of the alloy foil. An alloy with good plastic processing ability can be obtained by carrying out recrystallization annealing treatment on the alloy foil after cold rolling. However, when preparing a porous metal structure with high porosity by carrying out dealloying treatment on the alloy foil, the volume shrinkage of the alloy foil is serious, resulting in the porous metal structure prepared being unable to be self-supporting, and very likely to produce intergranular corrosion cracks, thereby affecting the practical application of the porous metal structure.

[0114] By performing recrystallization annealing treatment on the alloy foil after cold rolling, an alloy foil with a first component phase and good plastic processing ability can be obtained, and the grains in the alloy foil are mainly equiaxed crystals; then, by adopting a phase separation heat treatment with a lowered temperature, an alloy foil with both the first component phase and the second component phase can be obtained, thereby making the dealloyed porous metal structure self-supporting.

[0115] The porous metal structure obtained after the first dealloying treatment is prone to intergranular corrosion cracks. This is because there is a certain atomic diffusion phenomenon in the cooling process after the recrystallization annealing treatment. The relatively active metal atoms in the alloy are easily enriched at the grain boundaries, while the relatively inactive metal atoms are easily enriched on both sides of the grain boundaries. When the dealloying treatment is carried out, the relatively active metal components are preferentially corroded, while the diffusion capacity of the components that are not corroded is poor, which easily leads to intergranular corrosion cracks. In addition, the diffusion power of the metal atoms on the surface of the alloy is relatively strong, so a relatively uniform pore structure can be formed on the surface by diffusion. However, the diffusion power of the metal atoms inside the alloy is weaker due to its lower surface energy. Therefore, after the dealloying treatment, the metal atoms at the grain boundaries inside the alloy tend to remain in their original positions. At this time, the cracks left by the dealloying treatment cannot be filled, and the porous metal structure prepared has a large amount of intergranular corrosion cracks. At the same time, the toughness of the porous metal structure prepared is also very poor, and larger cracks are easily generated after bending.

[0116] The reduction annealing treatment is performed after the first dealloying treatment. The metal atoms near the grain boundaries (mainly relatively inactive metal atoms, and also relatively active metal atoms that have not been completely corroded) are allowed to diffuse due to heat, and the grain boundary corrosion cracks formed in the first dealloying treatment can be repaired. Thus, the prepared porous metal structure can have better toughness.

[0117] A relatively high cooling rate is used in the first cooling process after the recrystallization annealing treatment. This is because the recrystallization annealing treatment is a high-temperature heat treatment, and there is a certain atomic diffusion phenomenon in the cooling process after the high-temperature heat treatment. The relatively active metal atoms in the alloy tend to be enriched at the grain boundaries, while the relatively inactive metal atoms tend to be enriched on both sides of the grain boundaries, which will affect the effect of the subsequent dealloying treatment and reduction annealing treatment. After the recrystallization annealing treatment, the use of a rapid cooling process can quickly reduce the internal temperature of the alloy foil to a lower temperature, shorten the cooling time, thereby avoiding the formation of more serious element segregation problems at the grain boundaries as much as possible, and is also conducive to the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing the grain boundary corrosion cracks and making the prepared porous metal structure have better toughness.

[0118] A slower cooling rate was used in the second cooling process after the phase separation heat treatment. This is because the phase separation alloy has interphase stress between the first component phase and the second component phase. A slow cooling process can reduce the interphase stress, thereby facilitating the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing intergranular corrosion cracks and making the prepared porous metal structure have better toughness.

[0119] Therefore, the preparation method provided in the embodiment of the present application can also partially or even completely repair the intergranular corrosion cracks formed by the dealloying treatment, and can also make the prepared porous metal structure have better strength and toughness.

[0120] In some embodiments, the cold-rolled alloy foil can be directly purchased from a commercial source, or can be obtained according to a preparation process known in the art, for example, through processes such as melting, cutting, annealing, and cold rolling.

[0121] In some embodiments, the average cooling rate of the first cooling treatment can be greater than or equal to 100°C / min, and can be optionally greater than or equal to 200°C / min. This helps reduce the problem of element segregation at the grain boundaries and facilitates the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing intergranular corrosion cracks and improving the toughness of the prepared porous metal structure.

[0122] In some embodiments, the first cooling process can be a water cooling process. This helps reduce the problem of element segregation at the grain boundaries and facilitates the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing process, thereby better repairing intergranular corrosion cracks and making the prepared porous metal structure have better toughness. The water cooling process refers to the process of removing the alloy foil from a high temperature state and then immersing it in water for rapid cooling. Optionally, the temperature of the water used can be 20°C-30°C.

[0123] In some embodiments, the first cooling treatment may cool the alloy foil to a temperature below 50° C. This can reduce the risk of surface oxidation during the transfer of the alloy foil out of the furnace.

[0124] In some embodiments, the average cooling rate of the second cooling treatment can be less than or equal to 2°C / min. This helps reduce the interphase stress between the first component phase and the second component phase in the phase-separated alloy, facilitates the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing intergranular corrosion cracks and improving the toughness of the prepared porous metal structure.

[0125] In the present application, average cooling rate = (temperature before cooling - temperature after cooling) / total cooling time.

[0126] In some embodiments, the second cooling process can be a furnace cooling process. This helps reduce the interphase stress between the first component phase and the second component phase in the phase-separated alloy, facilitates the diffusion of metal atoms near the grain boundaries during the subsequent reduction annealing treatment, thereby better repairing intergranular corrosion cracks and improving the toughness of the prepared porous metal structure. The furnace cooling process refers to a process in which the alloy foil is not removed from the high-temperature furnace body, but is slowly cooled naturally from the high-temperature state along with the furnace body.

[0127] In some embodiments, the second cooling process can cool the temperature of the alloy foil to below 50° C. This can reduce the risk of surface oxidation of the alloy foil during the process of transferring the alloy foil out of the furnace.

[0128] In some embodiments, the recrystallization annealing process may be performed in a muffle furnace.

[0129] In some embodiments, the temperature of the recrystallization annealing treatment can be 720°C-850°C, for example, it can be 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, or a range consisting of any of the above values, and can be optionally 760°C-820°C.

[0130] In some embodiments, the holding time at the recrystallization annealing treatment temperature can be 10 min-60 min, for example, it can be 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range consisting of any of the above values, and can be optionally 15 min-45 min.

[0131] Adjusting the temperature and / or time of the recrystallization annealing treatment within the above range is beneficial for obtaining an alloy foil having a first component phase with good plastic working ability, and is also beneficial for precipitating the second component phase during the phase separation heat treatment.

[0132] In some embodiments, before the recrystallization treatment, some anti-oxidation materials may be coated on the surface of the alloy foil to reduce surface oxidation problems. For example, the anti-oxidation material may be made of a high-purity silicate solution, added with ultrafine inorganic metal oxides and finely processed.

[0133] In some embodiments, the phase separation heat treatment may be performed using a programmed heating process, which includes a temperature rise stage, a temperature holding stage, and a temperature drop stage.

[0134] In some embodiments, the phase separation heat treatment may be performed in a tube furnace. Optionally, the heating rate of the tube furnace may be 2° C. / min-10° C. / min, or alternatively 5° C. / min-10° C. / min.

[0135] In some embodiments, the phase separation heat treatment may be performed under the protection of an inert gas, wherein the inert gas may include one or more of nitrogen, argon, and helium.

[0136] In some embodiments, the temperature of the phase separation heat treatment can be 620℃-700℃, for example, it can be 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, or a range consisting of any of the above values, and can be optionally 640℃-680℃.

[0137] In some embodiments, the holding time at the phase separation heat treatment temperature can be 60 min-360 min, for example, 60 min, 90 min, 120 min, 150 min, 180 min, 210 min, 240 min, 270 min, 300 min, 330 min, 360 min, or a range consisting of any of the above values.

[0138] By adjusting the temperature of the phase separation heat treatment and / or keeping it within the above range, it is beneficial to precipitate the second component phase during the phase separation heat treatment, and it is also beneficial to obtain a micron-level porous metal structure after the subsequent reduction annealing treatment.

[0139] In some embodiments, the first component phase may include a γ phase. Taking a Mn-Cu alloy foil as an example, the first component phase may include a γ phase Mn-Cu alloy.

[0140] In some embodiments, the second component phase may include an α phase. Taking a Mn-Cu alloy foil as an example, the second component phase may include an α phase Mn.

[0141] The embodiment of the present application also provides a porous metal structure prepared by the above-mentioned preparation method, in which the residual amount of relatively active metals in the structure is low.

[0142] In some embodiments, the porous metal structure may be a porous copper structure. The porous copper structure includes non-Cu metal elements. The atomic content of the non-Cu metal elements may be less than 0.3 wt %, and may be less than 0.2 wt %.

[0143] In some embodiments, the porous metal structure may also have fewer intergranular corrosion cracks, and better strength and toughness. Optionally, the porous metal structure has no intergranular corrosion cracks.

[0144] In some embodiments, the pores of the porous metal structure are mostly on the micrometer scale.

[0145] Example

[0146] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0147] Example 1

[0148] (1) Preparation of Mn-Cu alloy foil

[0149] Pure copper (purity ≥ 99.9%) and pure manganese (purity ≥ 99.9%) are used as raw materials to prepare a Mn-Cu alloy through vacuum induction melting. The Mn atomic content in the Mn-Cu alloy is 75 at.%, and the Cu atomic content is 25 at.%. The Mn-Cu alloy prepared by vacuum induction melting is cut and subjected to homogenization annealing and multiple cold rolling processes to obtain a Mn-Cu alloy foil with a thickness of approximately 250 μm.

[0150] The Mn-Cu alloy foil was recrystallized and annealed in a muffle furnace at 800°C for 20 minutes to obtain a single-phase γ Mn-Cu alloy. The γ single-phase Mn-Cu alloy foil was removed and immediately water-cooled to below 50°C. After cleaning and drying with anhydrous ethanol, it was placed in a tube furnace and the gas system installed. The pipeline was first checked for airtightness. Once the airtightness was confirmed, it was evacuated to -1 MPa and nitrogen was introduced to atmospheric pressure, completing a gas exchange to achieve initial oxygen removal. After three gas exchanges, the gas flow was continued for 60 minutes to further remove any residual oxygen from the pipeline system. Subsequently, a heating program was initiated, with the temperature increased at 5°C / min to 660°C under a nitrogen atmosphere for phase separation heat treatment. The temperature was held for 210 minutes, and the foil was cooled to below 50°C in the furnace. The pressure reducing valve and main valve of the gas cylinder were closed, and the sample was removed to obtain an α / γ dual-phase Mn-Cu alloy foil.

[0151] (2) First dealloying treatment

[0152] The Mn-Cu alloy foil after the phase separation heat treatment was cut into 30mm x 30mm samples and then immersed in a 1mol / L hydrochloric acid aqueous solution at 50°C for the first dealloying treatment for 48 hours. After the treatment, the sample was removed and washed five times with deionized water (100ml each time), then three times with anhydrous ethanol (100ml each time), and finally dried in a vacuum drying oven at 35°C and -0.1MPa for 2 hours to obtain a porous copper structure.

[0153] (3) Reduction annealing treatment

[0154] Place the porous copper structure obtained by the first dealloying treatment in the furnace tube of a tubular furnace and install the gas system. First check the airtightness of the pipeline. If there is no problem, evacuate to -1MPa and introduce a mixture of 5% H2 and 95% argon (volume ratio) to normal pressure to complete a gas replacement and achieve the purpose of preliminary oxygen removal. After completing three gas replacements, continue ventilation for 60 minutes to further remove the residual oxygen in the pipeline system; then start the heating program and adjust the gas flow rate of the above-mentioned hydrogen-argon mixture to 500SCCM, the heating rate to 10℃ / min, the insulation temperature to 800℃, and the insulation time to 40min. After the insulation is completed, cool the reduction annealing sample to below 50℃ with the furnace, close the pressure reducing valve and main valve of the gas cylinder, and take out the sample.

[0155] (4) Second dealloying treatment

[0156] The porous copper structure obtained by reduction annealing was immersed in a 0.5 mol / L hydrochloric acid aqueous solution and subjected to a second dealloying treatment at 25°C for 8 hours. Afterward, the sample was removed and washed five times with deionized water (100 ml each time), then three times with anhydrous ethanol (100 ml each time). Finally, it was dried in a vacuum drying oven at 35°C and -0.1 MPa for 2 hours to obtain the final porous copper structure.

[0157] Comparative Example 1

[0158] (1) Preparation of Mn-Cu alloy foil

[0159] Pure copper (purity ≥ 99.9%) and pure manganese (purity ≥ 99.9%) are used as raw materials to prepare a Mn-Cu alloy by vacuum induction melting. The Mn-Cu alloy contains 75% by weight of Mn and 25% by weight of Cu. The Mn-Cu alloy prepared by vacuum induction melting is cut and then subjected to homogenization annealing and multiple cold rolling processes to obtain a Mn-Cu alloy foil with a thickness of approximately 250 μm.

[0160] (2) First dealloying treatment

[0161] The prepared Mn-Cu alloy foil was cut into 30 mm x 30 mm samples and immersed in a 1 mol / L hydrochloric acid solution at 50°C for 48 hours for the first dealloying treatment. The sample was then washed five times with 100 ml of deionized water and three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum oven at 35°C and -0.1 MPa for 2 hours to obtain a porous copper structure.

[0162] (3) Second dealloying treatment

[0163] The porous copper structure obtained from the first dealloying treatment was immersed in a 0.5 mol / L hydrochloric acid solution and then subjected to a second dealloying treatment at 25°C for 8 hours. Afterward, the sample was removed and washed five times with 100 ml of deionized water, then three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum drying oven at 35°C and -0.1 MPa for 2 hours to obtain the final porous copper structure.

[0164] Comparative Example 2

[0165] (1) Preparation of Mn-Cu alloy foil

[0166] Pure copper (purity ≥ 99.9%) and pure manganese (purity ≥ 99.9%) are used as raw materials to prepare a Mn-Cu alloy through vacuum induction melting. The Mn atomic content in the Mn-Cu alloy is 75 at.%, and the Cu atomic content is 25 at.%. The Mn-Cu alloy prepared by vacuum induction melting is cut and subjected to homogenization annealing and multiple cold rolling processes to obtain a Mn-Cu alloy foil with a thickness of approximately 250 μm.

[0167] (2) First dealloying treatment

[0168] The prepared Mn-Cu alloy foil was cut into 30 mm x 30 mm samples and immersed in a 1 mol / L hydrochloric acid solution at 50°C for 48 hours for the first dealloying treatment. The sample was then washed five times with 100 ml of deionized water and three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum oven at 35°C and -0.1 MPa for 2 hours to obtain a porous copper structure.

[0169] (3) Second dealloying treatment

[0170] The porous copper structure obtained from the first dealloying treatment was immersed in a 12 mol / L concentrated hydrochloric acid solution and then subjected to a second dealloying treatment at 25°C for 8 hours. Afterward, the sample was removed and washed five times with 100 ml of deionized water, then three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum drying oven at 35°C and -0.1 MPa for 2 hours to obtain the final porous copper structure.

[0171] Comparative Example 3

[0172] (1) Preparation of Mn-Cu alloy foil

[0173] Pure copper (purity ≥ 99.9%) and pure manganese (purity ≥ 99.9%) are used as raw materials to prepare a Mn-Cu alloy through vacuum induction melting. The Mn atomic content in the Mn-Cu alloy is 75 at.%, and the Cu atomic content is 25 at.%. The Mn-Cu alloy prepared by vacuum induction melting is cut and subjected to homogenization annealing and multiple cold rolling processes to obtain a Mn-Cu alloy foil with a thickness of approximately 250 μm.

[0174] (2) First dealloying treatment

[0175] The prepared Mn-Cu alloy foil was cut into 30 mm x 30 mm samples and immersed in a 1 mol / L hydrochloric acid solution at 50°C for 48 hours for the first dealloying treatment. The sample was then washed five times with 100 ml of deionized water and three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum oven at 35°C and -0.1 MPa for 2 hours to obtain a porous copper structure.

[0176] (3) Second dealloying treatment

[0177] The porous copper structure obtained from the first dealloying treatment was immersed in a 0.5 mol / L hydrochloric acid solution and then subjected to a second dealloying treatment at 70°C for 8 hours. Afterward, the sample was removed and washed five times with 100 ml of deionized water, then three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum drying oven at 35°C and -0.1 MPa for 2 hours to obtain the final porous copper structure.

[0178] Comparative Example 4

[0179] (1) Preparation of Mn-Cu alloy foil

[0180] Pure copper (purity ≥ 99.9%) and pure manganese (purity ≥ 99.9%) are used as raw materials to prepare a Mn-Cu alloy through vacuum induction melting. The Mn atomic content in the Mn-Cu alloy is 75 at.%, and the Cu atomic content is 25 at.%. The Mn-Cu alloy prepared by vacuum induction melting is cut and subjected to homogenization annealing and multiple cold rolling processes to obtain a Mn-Cu alloy foil with a thickness of approximately 250 μm.

[0181] (2) First dealloying treatment

[0182] The prepared Mn-Cu alloy foil was cut into 30 mm x 30 mm samples and immersed in a 1 mol / L hydrochloric acid solution at 50°C for 48 hours for the first dealloying treatment. The sample was then washed five times with 100 ml of deionized water and three times with 100 ml of anhydrous ethanol. Finally, it was dried in a vacuum oven at 35°C and -0.1 MPa for 2 hours to obtain a porous copper structure.

[0183] (3) Second dealloying treatment

[0184] The porous copper structure obtained from the first dealloying treatment was subjected to a second dealloying treatment via electrochemical etching. During the electrochemical etching process, the porous copper structure obtained from the first dealloying treatment served as the anode, the Pt sheet served as the cathode, a 0.5 mol / L hydrochloric acid aqueous solution served as the electrolyte, the etching voltage was 0.1 V, the etching temperature was 25°C, and the etching time was 2 hours. After the etching, the sample was removed and washed five times with 100 ml of deionized water, followed by three washes with 100 ml of anhydrous ethanol. Finally, the sample was dried in a vacuum drying oven at 35°C and -0.1 MPa for 2 hours to obtain the final porous copper structure.

[0185] The porous copper structures before the second dealloying treatment in the examples and comparative examples were cut into samples of about 1 cm*1 cm in size, and ICP tests were performed using an ICAP XP inductively coupled plasma emission spectrometer to obtain the residual Mn content.

[0186] The porous copper structures after the second dealloying treatment in the examples and comparative examples were cut into samples of about 1 cm*1 cm in size, and ICP tests were performed using an ICAP XP inductively coupled plasma emission spectrometer to obtain the residual Mn content.

[0187] The test results are shown in Table 1. In Table 1, the symbol "—" indicates that the corresponding treatment was not performed.

[0188] Table 1

[0189] Figure 1 is a surface Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment of Comparative Example 1. Figure 2 is a cross-sectional Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment of Comparative Example 1. Figure 3 is a surface Mn element distribution diagram of the porous copper structure obtained after the reduction annealing treatment and before the second dealloying treatment of Example 1. Figure 4 is a surface Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment of Example 1. Figure 5 is a cross-sectional Mn element distribution diagram of the porous copper structure obtained after the reduction annealing treatment and before the second dealloying treatment of Example 1. Figure 6 is a cross-sectional Mn element distribution diagram of the porous copper structure obtained after the second dealloying treatment of Example 1. Figure 7 is the surface morphology of the porous copper structure obtained after the second dealloying treatment of Example 1. Figure 8 is the cross-sectional morphology of the porous copper structure obtained after the second dealloying treatment of Example 1.

[0190] It can be seen from FIG. 1 to FIG. 8 and the test results in Table 1 that by performing a reduction annealing treatment after the first dealloying treatment and before the second dealloying treatment, the prepared porous copper structure can have a lower residual manganese content.

[0191] The test results of Comparative Examples 1 to 4 also show that after the first dealloying treatment, the residual manganese content has dropped to a relatively low level. At this point, even with very aggressive reaction conditions, such as heating, electrolysis, and concentrated acid corrosion treatment, it is difficult to effectively further reduce the residual manganese content.

[0192] Example 2

[0193] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding temperature of the reduction annealing treatment is 700° C.

[0194] Example 3

[0195] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding temperature of the reduction annealing treatment is 900° C.

[0196] Example 4

[0197] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding temperature of the reduction annealing treatment is 650° C.

[0198] Example 5

[0199] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding temperature of the reduction annealing treatment is 950° C.

[0200] Example 6

[0201] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding time of the reduction annealing treatment is 20 minutes.

[0202] Example 7

[0203] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding time of the reduction annealing treatment is 30 minutes.

[0204] Example 8

[0205] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding time of the reduction annealing treatment is 50 minutes.

[0206] Example 9

[0207] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding time of the reduction annealing treatment is 60 minutes.

[0208] Example 10

[0209] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding time of the reduction annealing treatment is 10 minutes.

[0210] Example 11

[0211] The preparation process of the porous copper structure is the same as that of Example 1, except that the holding time of the reduction annealing treatment is 70 minutes.

[0212] The porous copper structures of Examples 1 to 11 after reduction annealing and before the second dealloying were broken to expose the cross-sections, and EDS surface scanning was performed using a Phenom XL G2 desktop scanning electron microscope to measure the residual Mn content.

[0213] The porous copper structures after the second dealloying treatment in Examples 1 to 11 were broken to expose the cross-sections, and EDS surface scanning was performed using a Phenom XL G2 desktop scanning electron microscope to measure the residual Mn content.

[0214] Table 2

[0215] It can be seen from the test results of Examples 1 to 11 that the residual manganese content in the porous copper structure can be further reduced by further adjusting the holding temperature and / or holding time of the reduction annealing treatment.

[0216] The test results of Examples 1 to 5 also show that as the holding temperature of the reduction annealing treatment increases, the manganese content of the porous copper structure measured by EDS increases after the reduction annealing treatment and before the second dealloying treatment, that is, more manganese atoms diffuse to the ligament surface of the porous copper structure, thereby helping to reduce the residual manganese content of the porous copper structure finally prepared. At the same time, the holding temperature of the reduction annealing treatment should not be too high. At this time, the thermal diffusion of copper element on the ligament surface is intense, which greatly promotes the reduction of the surface free energy of the porous copper structure. As a result, the pore structure of the porous copper structure is prone to shrinkage and even sintering, and the porosity of the porous copper structure decreases, which is not conducive to further reducing the residual manganese content of the porous copper structure.

[0217] The test results of Examples 1, 6, and 11 also show that as the holding time of the reduction annealing treatment increases, the manganese content of the porous copper structure measured by EDS increases after the reduction annealing treatment and before the second dealloying treatment. This means that more manganese atoms diffuse to the ligament surface of the porous copper structure, thereby reducing the residual manganese content of the porous copper structure. At the same time, the holding time of the reduction annealing treatment should not be too long. In this case, due to the faster and more complete thermal diffusion of copper and manganese atoms, the diffusion effect is better, which easily leads to shrinkage of the pore structure of the porous copper structure, accompanied by a decrease in the porosity of the porous copper structure, which is not conducive to further reducing the residual manganese content of the porous copper structure.

[0218] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a porous metal structure, comprising the following steps: Performing a first dealloying treatment on an alloy foil to form pores, then performing a reduction annealing treatment in a reducing gas atmosphere, and then performing a second dealloying treatment to obtain a porous metal structure.

2. The preparation method according to claim 1, wherein the process of the first dealloying treatment includes a free corrosion dealloying process or an electrochemical corrosion dealloying process, and the process of the second dealloying treatment includes a free corrosion dealloying process; Optionally, the process of the first dealloying treatment includes a free corrosion dealloying process, and the process of the second dealloying treatment includes a free corrosion dealloying process.

3. The preparation method according to any one of claims 1-2, wherein, The process of the first dealloying treatment includes a free corrosion dealloying process, and the process of the second dealloying treatment includes a free corrosion dealloying process, and the corrosion liquids used in the first dealloying treatment and the second dealloying treatment are both acidic solutions. Optionally, the acidic solution includes an acidic aqueous solution, and more optionally includes one or a mixture of hydrochloric acid, sulfuric acid, phosphoric acid, and acetic acid.

4. The preparation method according to claim 3, wherein the concentration C1 of the acidic solution used in the first dealloying treatment is greater than the concentration C2 of the acidic solution used in the second dealloying treatment; and / or the treatment temperature T1 of the first dealloying treatment is greater than the treatment temperature T2 of the second dealloying treatment. Optionally, T1 is 40°C - 80°C, and T2 is 20°C - 30°C; and / or the treatment time t1 of the first dealloying treatment is greater than the treatment time t2 of the second dealloying treatment. Optionally, t1 is greater than or equal to 24h, and t2 is less than or equal to 12h.

5. The preparation method according to any one of claims 1-4, wherein, The reduction annealing treatment satisfies at least one of the following conditions (1) to (8): (1) The reducing gas used in the reduction annealing treatment includes ammonia or a mixture of hydrogen and an inert gas; (2) The reducing gas used in the reduction annealing treatment includes a mixture of hydrogen and an inert gas, and the inert gas includes one or more of nitrogen, argon, and helium; (3) The flow rate of the reducing gas used in the reduction annealing treatment is 100 SCCM - 2000 SCCM; (4) The reduction annealing treatment is carried out in a tube furnace, and the heating rate of the tube furnace is 2°C / min - 10°C / min; (5) The reduction annealing treatment is carried out in a tube furnace, and the heating rate of the tube furnace is 5°C / min - 10°C / min; (6) The average cooling rate of the cooling treatment process after the reduction annealing treatment is less than or equal to 2°C / min; (7) The cooling treatment process is a furnace cooling process; (8) The cooling treatment after the reduction annealing treatment is to cool to below 50°C.

6. The preparation method according to any one of claims 1-5, wherein, The alloy foil is a copper alloy foil, the copper alloy foil includes a Cu element and a non-Cu metal element, and the standard electrode potential of the non-Cu metal element is less than the standard electrode potential of the Cu element; Optionally, the non-Cu metal element includes one or more of Mn, Zn, Ni, Al, and Fe; and / or Optionally, the atomic content of the non-Cu metal element in the copper alloy foil is 60 at.% or more, and may be optionally 65 at.% - 80 at.%.

7. The preparation method according to any one of claims 1-6, wherein, The holding temperature of the reduction annealing treatment is 700°C - 900°C; and / or, the holding time at the reduction annealing treatment temperature is 20 min - 60 min.

8. The preparation method according to any one of claims 1 - 7, wherein Before the first dealloying treatment of the alloy foil, the steps further include: Providing a cold-rolled alloy foil; Performing a recrystallization annealing treatment on the alloy foil, and then performing a first cooling treatment to obtain an alloy foil having a first component phase; Performing a phase separation heat treatment on the alloy foil having the first component phase, and then performing a second cooling treatment to precipitate a second component phase and obtain an alloy foil having both the first component phase and the second component phase. The temperature of the phase separation heat treatment is lower than the temperature of the recrystallization annealing treatment, and the average cooling rate of the second cooling treatment is lower than the average cooling rate of the first cooling treatment.

9. The preparation method according to claim 8, wherein, The average cooling rate of the first cooling treatment is greater than or equal to 100°C / min, and may be optionally greater than or equal to 200°C / min; and / or, the average cooling rate of the second cooling treatment is less than or equal to 2°C / min.

10. The preparation method according to any one of claims 8-9, wherein, The first cooling treatment process is a water cooling process; and / or, the second cooling treatment process is a furnace cooling process.

11. The preparation method according to any one of claims 8-10, wherein, The first cooling treatment is to cool to below 50°C; and / or, the second cooling treatment is to cool to below 50°C.

12. The preparation method according to any one of claims 8-11, wherein, The recrystallization annealing treatment is carried out in a muffle furnace; and / or, the phase separation heat treatment is carried out in a tube furnace. Optionally, the heating rate of the tube furnace is 2°C / min - 10°C / min, and may be optionally 5°C / min - 10°C / min.

13. The preparation method according to any one of claims 8 - 12, wherein The temperature of the recrystallization annealing treatment is 720°C - 850°C; and / or, The holding time at the recrystallization annealing treatment temperature is 10 min - 60 min; and / or, The temperature of the phase separation heat treatment is 620°C - 700°C; and / or, The holding time at the phase separation heat treatment temperature is 60 min - 360 min.

14. The preparation method according to any one of claims 8-13, wherein, The first component phase includes a γ phase; and / or, the second component phase includes an α phase.

15. A porous metal structure prepared by the preparation method according to any one of claims 1 - 14.

16. The porous metal structure according to claim 15, wherein, The porous metal structure is a porous copper structure, the porous copper structure includes a non-Cu metal element, and the atomic content of the non-Cu metal element is 0.3 wt% or less, and may be optionally 0.2 wt% or less.

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