Preparation method of metal copper

Abstract

The invention relates to the technical field of metal preparation. The invention provides a preparation method of metal copper. The preparation method comprises the following steps: S1, preparing a copper oxide thin film; s2, preparing a metal aluminum film on the surface of at least one side of the copper oxide thin film; and S3, the thin film containing the copper oxide thin film and the metal aluminum film is placed in an alkaline solution to be soaked, and metal copper is obtained. The method can be used for preparing the metal copper at room temperature, and is simple and convenient.

Description

Technical Field

[0001] The invention relates to the technical field of metal preparation, and in particular to a method for preparing metallic copper. Background Art

[0002] Copper (Cu) is a metal with excellent performance and extremely wide application. Due to its excellent conductivity and chemical activity, it has irreplaceable uses in power equipment, semiconductor chips, energy and chemical industries. As a high-value metal, Cu has very limited mineral reserves and is unevenly distributed. The slow oxidation of Cu in the air is the main reason for the failure of copper devices. As the use of Cu increases rapidly, the accumulation of copper oxide waste will also increase accordingly. Therefore, the development of efficient copper reduction technology is the fundamental way to cope with the arrival of the "copper shortage" era. Traditional gas phase reduction methods using hydrogen (H2) as a reducing agent often require heating conditions, which inevitably brings explosion hazards. At the same time, the storage and transportation of H2 are also difficult, which greatly increases the cost of gas phase reduction. Aluminum (Al), as an active metal with abundant reserves and low prices, has strong reducing ability, and its solid state characteristics are also convenient for storage and transportation. However, the reduction of copper oxide by Al, namely the aluminothermic reaction, is limited by the slow ion migration rate in the solid phase and requires high temperature activation. The reaction is extremely violent, and its product is a complex solid mixture, which is extremely inconvenient to separate. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a method for preparing metallic copper, which can prepare metallic copper at room temperature and is simple and convenient.

[0004] To this end, the first aspect of the present invention provides a method for preparing metallic copper, comprising: S1, preparing a copper oxide film; S2, preparing a metal aluminum film on the surface of at least one side of the copper oxide film; S3, immersing a film containing the copper oxide film and the metal aluminum film in an alkaline solution to obtain metallic copper.

[0005] The method for preparing metallic copper proposed by the present invention realizes efficient reduction of copper oxide to obtain metallic copper and eliminates residual solid impurities through the reaction process of active hydrogen released by metallic aluminum in an alkaline solution and active hydrogen and copper oxide, thereby solving the problem of recycling metallic copper at room temperature and having the advantages of high efficiency, high conversion rate, no pollution, no danger, etc., does not require the use of catalysts and heating conditions, completely dissolves metallic aluminum without solid residue, and obtains single metallic copper.

[0006] In some embodiments of the present invention, the copper oxide thin film includes at least one of CuO and Cu2O.

[0007] In some embodiments of the present invention, the copper oxide film comprises CuO, and the thickness of the copper oxide film is 350 nm-1000 nm.

[0008] In some embodiments of the present invention, the copper oxide thin film comprises Cu2O, and the thickness of the copper oxide thin film is greater than or equal to 1 μm.

[0009] In some embodiments of the present invention, the copper oxide thin film comprises a polycrystalline CuO thin film.

[0010] In some embodiments of the present invention, the copper oxide thin film is prepared by magnetron sputtering.

[0011] In some embodiments of the present invention, step S1 includes: preparing a Fe2O3 buffer layer on a substrate, and preparing a copper oxide thin film on the Fe2O3 buffer layer.

[0012] In some embodiments of the present invention, the substrate includes at least one of Al2O3, Si and SiO2.

[0013] In some embodiments of the present invention, the thickness of the Fe2O3 buffer layer is 0.5nm-2nm.

[0014] In some embodiments of the present invention, the Fe2O3 buffer layer is prepared by magnetron sputtering.

[0015] In some embodiments of the present invention, step S1 includes: annealing the copper foil in air to form a Cu2O film on the surface of the copper foil.

[0016] In some embodiments of the present invention, the annealing temperature is 400°C-450°C.

[0017] In some embodiments of the present invention, the annealing time is 30 min-60 min.

[0018] In some embodiments of the present invention, the thickness of the metal aluminum film is 200nm-600nm.

[0019] In some embodiments of the present invention, the metal aluminum film is prepared by electron beam evaporation.

[0020] In some embodiments of the present invention, the metal aluminum film is prepared by electron beam evaporation, and the growth rate of the metal aluminum film is

[0021] In some embodiments of the present invention, the alkaline solution includes at least one of a KOH solution and a NaOH solution.

[0022] In some embodiments of the present invention, in the alkaline solution, OH - The concentration of ions is 0.01mol / L-0.1mol / L.

[0023] In some embodiments of the present invention, step S3 includes: S31, soaking the film containing the copper oxide film and the metal aluminum film in an alkaline solution, and continuously replenishing the concentrated alkaline solution during the soaking process to maintain the alkali concentration in the alkaline solution until red copper metal is generated; S32, washing the red copper metal with water and ethanol respectively to obtain metallic copper.

[0024] In some embodiments of the present invention, in the concentrated alkali solution, OH - The concentration of ions is 0.1mol / L0.3mol / L.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0027] Figure 1 A schematic diagram showing the reaction mechanism of the method for preparing metallic copper according to an embodiment of the present invention;

[0028] Figure 2 The pictures showing various stages of the method for preparing metallic copper according to Example 1 of the present invention are shown;

[0029] Figure 3 The pictures of each stage of the method for preparing metallic copper according to Example 2 of the present invention and the scanning electron microscope image of the cross section of the copper foil after calcination are shown;

[0030] Figure 4 The pictures showing the various stages of the method for preparing metallic copper according to Example 3 of the present invention;

[0031] Figure 5 The XRD graph, XPS graph and IV curve graph of the metallic copper obtained in Example 3 of the present invention are shown;

[0032] Figure 6 The pictures of various stages of the method for preparing metallic copper according to Example 4 of the present invention are shown;

[0033] Figure 7 The pictures of various stages of the method for preparing metallic copper according to Example 5 of the present invention are shown. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0035] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0036] In a first aspect of the present invention, the present invention provides a method for preparing metallic copper, comprising:

[0037] S1. Prepare copper oxide thin film.

[0038] In some embodiments of the present invention, the copper oxide film includes at least one of CuO and Cu2O. The copper oxide film of the above material is relatively common, easy to achieve efficient reduction, obtain metallic copper, eliminate the residual solid impurities, can solve the problem of recycling metallic copper at room temperature, has the advantages of high efficiency, high conversion rate, no pollution, no danger, etc., does not require the use of catalysts and heating conditions, the metallic aluminum is completely dissolved without solid residue, and a single metallic copper can be obtained.

[0039] In some embodiments of the present invention, the copper oxide film includes CuO, and the thickness of the copper oxide film is 350nm-1000nm, for example, it can be 350nm, 500nm, 800nm, 1000nm, etc. Controlling the thickness of the copper oxide film within the above range is conducive to sufficient reduction of CuO.

[0040] In some embodiments of the present invention, the copper oxide film includes a polycrystalline CuO film, thereby obtaining metallic copper with better morphology.

[0041] In some embodiments of the present invention, the copper oxide film is prepared by magnetron sputtering. Magnetron sputtering deposition has the characteristics of high sputtering rate, low substrate temperature rise, and good uniformity.

[0042] In some embodiments of the present invention, step S1 comprises:

[0043] S11, preparing an Fe2O3 buffer layer on a substrate, and preparing a copper oxide thin film on the Fe2O3 buffer layer.

[0044] Therefore, before preparing the copper oxide film, a Fe2O3 buffer layer is prepared first. Fe2O3 is a seed layer that can induce the crystal growth of the copper oxide film above it.

[0045] In some embodiments of the present invention, the thickness of the Fe2O3 buffer layer is 0.5nm-2nm, for example, it can be 0.5nm, 1nm, 1.5nm, 2nm, etc. Controlling the thickness of the buffer layer within the above range can better induce the crystal growth of the copper oxide film thereon.

[0046] In some embodiments of the present invention, the Fe2O3 buffer layer is prepared by magnetron sputtering. Magnetron sputtering deposition has the characteristics of high sputtering rate, low substrate temperature rise, and good uniformity.

[0047] In some embodiments of the present invention, the growth parameters of the Fe2O3 buffer layer are: back vacuum 10 -7 Torr, substrate stage temperature 550°C, gas flow rate Ar (20sccm):O2 (2sccm), total pressure 3mTorr, radio frequency (RF) magnetron sputtering (power 120W), time 120s.

[0048] The parameters for preparing copper oxide films by magnetron sputtering are as follows: the substrate stage is cooled to below 100°C and then heated to 400°C, direct current (DC) magnetron sputtering is used for CuO target material, the gas flow rate is Ar (20sccm):O2 (2sccm), the total pressure is 3mTorr, for thinner CuO films (thickness 350nm), a power of 12W is used, and for thicker CuO films (thickness>1μm), a power of 30W is used.

[0049] In some embodiments of the present invention, the substrate comprises at least one of Al2O3, Si and SiO2, a sapphire Al2O3 (0001) substrate is selected, and the grown CuO film is The oriented strong texture film will also have a (111) oriented part as the thickness increases; a silicon wafer (Si / SiO2) substrate is selected, and the grown CuO film has a polycrystalline structure.

[0050] In some embodiments of the present invention, the copper oxide film includes Cu2O, and the thickness of the copper oxide film is greater than or equal to 1 μm. For example, the thickness of the copper oxide film can be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 20 μm, etc. Controlling the thickness of the copper oxide film within the above range is conducive to sufficient reduction of the copper oxide.

[0051] In some embodiments of the present invention, step S1 comprises:

[0052] The copper foil is annealed in air to form a Cu2O film on the surface of the copper foil.

[0053] In this way, a uniform black Cu2O film can be generated on the surface of the copper foil, and metallic copper with good morphology can be obtained after reduction.

[0054] In some embodiments of the present invention, the annealing temperature is 400°C-450°C, for example, it can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, etc., thereby accurately controlling the thickness of the Cu2O film and reducing the peeling of the Cu2O film.

[0055] In some embodiments of the present invention, the annealing time is 30 min-60 min, for example, 30 min, 40 min, 50 min, 60 min, etc., thereby accurately controlling the thickness of the Cu2O film and reducing the peeling of the Cu2O film.

[0056] In some embodiments of the present invention, copper foil (thickness 0.2 mm) is cut into square pieces with a side length of 1 inch, placed in a tubular annealing furnace for annealing, kept connected to the air, and annealed at 400°C or 450°C for 15 minutes to form a relatively uniform black oxide layer, the main component of which is Cu2O, with a thickness between 1 micron and several microns.

[0057] S2. Preparing a metal aluminum film on at least one side of the copper oxide film.

[0058] In some embodiments of the present invention, the thickness of the metal aluminum film is 200nm-600nm, for example, 200nm, 300nm, 400nm, 500nm, 600nm, etc. The thickness of the metal aluminum film is controlled within the above range, which is sufficient to reduce copper oxides but not too thick to cause excessive metal aluminum, thereby affecting the purity of the obtained metal copper.

[0059] In some embodiments of the present invention, the thickness of the corresponding metal aluminum film is determined according to the thickness of the copper oxide film, such as CuO (350nm) / Al (200nm), CuO (1000nm) / Al (600nm); the thickness of the Al film deposited on the copper foil thermal oxide layer (Cu2O film) is 600nm.

[0060] In some embodiments of the present invention, the metal aluminum film is prepared by electron beam evaporation. Electron beam evaporation can accurately achieve the use of high-energy electrons to bombard the target material with the cooperation of electromagnetic fields, so that it melts and then deposits on the substrate. Electron beam evaporation can deposit high-purity and high-precision thin films.

[0061] In some embodiments of the present invention, the metal aluminum film is prepared by electron beam evaporation, and the growth rate of the metal aluminum film is For example it could be Etc. Specifically, the growth rate of the metal aluminum film can be determined according to its thickness. The greater the thickness, the higher the growth rate.

[0062] In some embodiments of the present invention, the metal Al layer is deposited by electron beam evaporation technology, and the backing is vacuum 10 - 8 Torr, and the film growth rate was monitored by a quartz crystal oscillator.

[0063] S3, soaking the film containing the copper oxide film and the metal aluminum film in an alkaline solution to obtain metallic copper.

[0064] Specifically, the reaction mechanism of the present invention is as follows Figure 1 As shown, the double-layer membrane is immersed in an alkaline solution, and the active hydrogen generated by aluminum can be used to reduce the copper oxide to metallic copper in situ at room temperature. The present invention has the advantages of high efficiency, high conversion rate, no pollution, no danger, etc., and metallic copper can be obtained in a few minutes. No catalyst and heating conditions are required. The metallic aluminum is completely dissolved without solid residue, and a single metallic copper can be obtained. The by-product hydrogen of the reaction can be collected and still used as fuel. In theory, 100% utilization of metallic aluminum can be achieved, and a way is also provided for the recycling of waste alkali liquid generated in large quantities in industry. At the same time, the present invention can achieve selective reduction of specific areas and specific shapes of copper oxide films, and has better controllability than gas phase reduction.

[0065] In some embodiments of the present invention, the alkaline solution includes at least one of a KOH solution and a NaOH solution. The alkaline solution is an aqueous solution of a strong base, which reacts rapidly with the aluminum metal film and can reduce the copper oxide to metallic copper in situ at room temperature.

[0066] In some embodiments of the present invention, in the alkaline solution, OH - The concentration of ions is 0.01mol / L-0.1mol / L, for example, 0.01mol / L, 0.03mol / L, 0.05mol / L, 0.07mol / L, 0.09mol / L, 0.1mol / L, etc. - The concentration of the ions is controlled within the above range, which is sufficient to react with the aluminum metal film to produce sufficient active hydrogen, and the copper oxide can be reduced to metallic copper in situ at room temperature.

[0067] In some embodiments of the present invention, step S3 comprises:

[0068] S31, soaking the film containing the copper oxide film and the metal aluminum film in an alkaline solution, and continuously replenishing the concentrated alkaline solution during the soaking process to maintain the alkali concentration in the alkaline solution until red copper metal is generated;

[0069] S32. Wash the red copper metal with water and ethanol respectively to obtain metallic copper.

[0070] Specifically, the CuO / Al double-layer film was immersed in the solution. As the Al film continued to dissolve (the whole process took about a few minutes), a red metallic film appeared on the lower layer. After the Al film was completely dissolved, the reduced metal Cu film on the lower layer was washed with deionized water and ethanol respectively, and then allowed to dry naturally.

[0071] With OH - The solution concentration decreases due to the consumption of alkali, and concentrated alkali solution can be added appropriately to maintain the alkali concentration and reaction rate.

[0072] In some embodiments of the present invention, in the concentrated alkali solution, OH - The concentration of ions is 0.1mol / L-0.3mol / L. For example, it can be 0.1mol / L, 0.15mol / L, 0.2mol / L, 0.25mol / L, 0.3mol / L, etc. The OH of concentrated alkali solution - The concentration of ions is higher than the initial alkaline solution. - When the concentration of ions is 0.1 mol / L, the OH - The concentration of ions needs to be higher than 0.1 mol / L. A higher alkali concentration will significantly accelerate the reaction rate, but will reduce the conversion rate. Some active hydrogen will combine to form H2. Within the above-mentioned concentrated alkali solution concentration range, the reaction rate can be increased and the conversion rate can be guaranteed.

[0073] In some embodiments of the present invention, the method of the present invention can also realize a method for local reduction of copper oxide film and visualization of active hydrogen migration, comprising the following steps:

[0074] (1) The surface of the copper oxide film is covered by a mechanical mask to deposit a metal aluminum film on a specific area of ​​the film surface. The pattern on the mask can be used to prepare a metal aluminum film with a specific pattern (circle, square, triangle, five-pointed star, letter pattern, etc.), and its characteristic size is about 1 mm.

[0075] (2) Soaking the above film in an alkaline solution.

[0076] The reduction reaction starts from the edge of the Al pattern, and most of the copper oxide film covering it is reduced. The original boundary expands evenly outward, so that the reduced metal Cu has a shape basically consistent with the original metal aluminum film pattern, that is, the local selective reduction of the copper oxide film is achieved.

[0077] (3) When the boundary of the metal aluminum film pattern is naturally uneven due to defects, the rate of active hydrogen migration outward is also inconsistent. The original straight boundary becomes a curve after expansion. The new boundary represents the end point of active hydrogen migration. The dynamic change of the boundary visualizes the migration path of active hydrogen and can be observed under an optical microscope.

[0078] The scheme of the present disclosure will be explained below in conjunction with the examples. Those skilled in the art will appreciate that the following examples are only used to illustrate the present disclosure and should not be considered to limit the scope of the present disclosure. Where specific techniques or conditions are not indicated in the examples, the techniques or conditions described in the literature in this area or the product instructions are used. Where the manufacturers of reagents or instruments are not indicated, they are all conventional products that can be obtained commercially.

[0079] Example 1

[0080] Magnetron sputtering was used to grow CuO thin films on sapphire Al2O3 (0001) and silicon wafers. First, an ultra-thin Fe2O3 buffer layer was grown on the substrate surface to induce the crystallization of CuO above. The growth temperature was 550°C, the gas flow was controlled at Ar (20sccm): O2 (2sccm), and the total pressure was 3mTorr. Then the temperature was lowered to below 100°C, and then raised to 400°C to grow the CuO thin film. The gas flow was Ar (20sccm): O2 (2sccm), and the total pressure was 3mTorr. For thinner CuO films (thickness 350nm), a power of 12W was used.

[0081] For the preparation of the metal Al layer, electron beam evaporation technology was used to deposit the metal Al, and the backing was vacuum 10 -8 Torr, the film growth rate is monitored by a quartz crystal oscillator, and the control rate is The thickness of each layer is CuO (350 nm) / Al (200 nm).

[0082] The CuO (350nm) / Al (200nm) double-layer film was immersed in a KOH solution with a concentration of 0.01mol / L and allowed to stand at room temperature for about 5 minutes. The metal Al layer gradually dissolved. When it was completely dissolved, that is, the silvery white metallic luster disappeared, the film was taken out and placed in ethanol to wash off the surface aqueous solution. Then it was taken out and the ethanol was allowed to evaporate naturally in the air to obtain a complete metal Cu layer.

[0083] The pictures of each stage of Example 1 are as follows Figure 2 As shown, it can be seen that after the CuO (350nm) / Al (200nm) double-layer film is immersed in a KOH solution with a concentration of 0.01mol / L, the silvery white metal Al layer gradually turns into red metal copper.

[0084] Example 2

[0085] Cut the copper foil with a thickness of 0.2mm into square pieces with a side length of 1 inch, place them on a refractory substrate, put them into a tubular annealing furnace for annealing, keep them connected to the air, and anneal them at 400℃ or 450℃ for 15min to form a relatively uniform black oxide layer. X-ray diffraction identified its main component as Cu2O, and the scanning electron micrograph of the cross section showed that its thickness was between 1 micron and several microns. The metal Al layer with a thickness of 600nm was prepared by electron beam evaporation process. The thermally oxidized copper foil after Al plating was immersed in a KOH solution with a concentration of 0.01mol / L, and left to stand at room temperature for about 5 minutes. The metal Al layer gradually dissolved. When it was completely dissolved, the copper foil was taken out, the surface aqueous solution was washed off in ethanol, and then taken out, and the ethanol was naturally volatilized in the air to obtain a copper foil with a basically reduced oxide layer.

[0086] The pictures of each stage of Example 2 and the scanning electron microscope images of the cross section of the copper foil after calcination are as follows: Figure 3 As shown, it can be seen that after the copper foil is annealed, a relatively uniform black oxide layer is formed on the surface. X-ray diffraction identifies that its main component is Cu2O. The scanning electron micrograph of the cross section shows that its thickness is 2.07 microns. After the Al-plated thermally oxidized copper foil is immersed in a KOH solution with a concentration of 0.01 mol / L, the silvery-white metal Al layer gradually turns into red metal copper.

[0087] Example 3

[0088] A CuO film (350nm thick) was prepared by magnetron sputtering, and the surface of the CuO film was covered with a mechanical mask with a hollow pattern. A metal Al layer (200nm thick) was deposited by electron beam evaporation, so that Al was deposited in a specific shape area on the surface of the film, thereby preparing an Al film (five-pointed star) with a specific pattern, and its characteristic size was about 1mm. The above film was immersed in a KOH solution with a concentration of 0.01mol / L, and the reduction reaction started from the edge of the Al pattern. Most of the CuO covered below was reduced, and the original boundary expanded evenly outward, so that the metal Cu formed after reduction had a shape that was basically consistent with the Al film pattern above it.

[0089] For large Al patterns with a side length of 2 mm, the reduction is uneven due to defects at the boundary, and the rate of active hydrogen migration outward is also inconsistent. The original straight boundary becomes a curve after expansion, and the new boundary represents the end point of active hydrogen migration. The dynamic change of the boundary visualizes the migration path of active hydrogen and can be observed under an optical microscope.

[0090] The images of the CuO film / Al film of Example 3 at different time periods after being placed in a KOH solution are as follows: Figure 4As shown, it can be seen that the reduction reaction starts from the edge of the Al pattern. After 5 minutes, most of the CuO is reduced, and the original boundary expands evenly outward, so that the metal Cu formed after reduction has a shape that is basically consistent with the Al film pattern above it.

[0091] The XRD graph, XPS graph and IV curve graph of the metallic copper obtained in Example 3 of the present invention are as follows: Figure 5 As shown, the IV curve is tested using the four-terminal method, with voltage applied to measure current. Figure 5 The (a) XRD, (b) XPS and (c) IV curves can prove that it is metallic Cu. According to the comparison of the peak intensity between the initial and reduced phases in Figure (b), it can be seen that after the final reduction, the unconverted CuO content is close to zero, and the active hydrogen utilization efficiency can be inferred to be 95%.

[0092] Example 4

[0093] A CuO film (350nm thick) was prepared by magnetron sputtering, and the surface of the CuO film was covered with a mechanical mask of a hollow pattern. A metal Al layer (200nm thick) was deposited by electron beam evaporation, and Al was deposited in a specific shape area on the surface of the film, thereby preparing an Al film (square) with a specific pattern, and its characteristic size was about 1mm. The above film was immersed in a KOH solution with a concentration of 0.01mol / L, and the reduction reaction started from the edge of the Al pattern. Most of the CuO covered below was reduced, and the original boundary expanded evenly outward, so that the metal Cu formed after reduction had a shape that was basically consistent with the Al film pattern above it.

[0094] For large Al patterns with a side length of 2 mm, the reduction is uneven due to defects at the boundary, and the rate of active hydrogen migration outward is also inconsistent. The original straight boundary becomes a curve after expansion, and the new boundary represents the end point of active hydrogen migration. The dynamic change of the boundary visualizes the migration path of active hydrogen and can be observed under an optical microscope.

[0095] Depend on Figure 6 It can be seen that the reduction reaction starts from the edge of the Al pattern. Finally, most of the CuO is reduced and the original boundary expands evenly outward, so that the metal Cu formed after reduction has a shape that is basically consistent with the Al film pattern thereon. Figure 6 The far right is an optical microscope image of the metal Cu edge formed after the final reduction. Data such as 297.52μm represent the edge diffusion width. It can be seen that the edge diffusion width of the square is smaller. Edge diffusion represents edge clarity, that is, the smaller the edge diffusion width, the clearer the resolution, which is more conducive to the construction of the graphic.

[0096] Example 5

[0097] A CuO film (350nm thick) was prepared by magnetron sputtering, and the surface of the CuO film was covered with a mechanical mask of a hollow pattern. A metal Al layer (200nm thick) was deposited by electron beam evaporation, and Al was deposited in a specific shape area on the surface of the film, thereby preparing an Al film (square) with a specific pattern, and its characteristic size was about 1mm. The above film was immersed in a KOH solution with a concentration of 0.01mol / L, and the reduction reaction started from the edge of the Al pattern. Most of the CuO covered below was reduced, and the original boundary expanded evenly outward, so that the metal Cu formed after reduction had a shape that was basically consistent with the Al film pattern above it.

[0098] For large Al patterns with a side length of 2 mm, the reduction is uneven due to defects at the boundary, and the rate of active hydrogen migration outward is also inconsistent. The original straight boundary becomes a curve after expansion, and the new boundary represents the end point of active hydrogen migration. The dynamic change of the boundary visualizes the migration path of active hydrogen and can be observed under an optical microscope.

[0099] Depend on Figure 7 It can be seen that the reduction reaction starts from the edge of the Al pattern. Finally, most of the CuO is reduced and the original boundary expands evenly outward, so that the metal Cu formed after reduction has a shape that is basically consistent with the Al film pattern thereon.

[0100] In summary, the method for preparing metallic copper proposed in the present invention realizes efficient reduction of copper oxide to obtain metallic copper and eliminates residual solid impurities through the active hydrogen released by metallic aluminum in an alkaline solution and the reaction process between the active hydrogen and copper oxide, thereby solving the problem of recycling metallic copper at room temperature, and has the advantages of high efficiency, high conversion rate, no pollution, no danger, etc., does not require the use of catalysts and heating conditions, and the metallic aluminum is completely dissolved without solid residue, so that a single metallic copper can be obtained.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", "some implementation schemes" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0102] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing metallic copper, characterized in that: include: S1. preparing a copper oxide thin film; S2, preparing a metal aluminum film on at least one side of the copper oxide film; S3, soaking the film containing the copper oxide film and the metal aluminum film in an alkaline solution to obtain metallic copper.

2. The method according to claim 1, characterized in that The copper oxide film comprises at least one of CuO and Cu2O; and / or, The copper oxide film comprises CuO, and the thickness of the copper oxide film is 350nm-1000nm; and / or, The copper oxide film comprises Cu2O, and the thickness of the copper oxide film is greater than or equal to 1 μm; and / or, The copper oxide film comprises a polycrystalline CuO film; and / or, The copper oxide film is prepared by magnetron sputtering.

3. The method according to claim 1 or 2, characterized in that: Step S1 includes: A Fe2O3 buffer layer is prepared on a substrate, and a copper oxide film is prepared on the Fe2O3 buffer layer.

4. The method according to claim 3, characterized in that The substrate comprises at least one of Al2O3, Si and SiO2; and / or, The thickness of the Fe2O3 buffer layer is 0.5nm-2nm; and / or, The Fe2O3 buffer layer is prepared by magnetron sputtering.

5. The method according to claim 1 or 2, characterized in that: Step S1 includes: The copper foil is annealed in air to form a Cu2O film on the surface of the copper foil.

6. The method according to claim 5, characterized in that The annealing temperature is 400°C-450°C; and / or, The annealing time is 30 min-60 min.

7. The method according to claim 1 or 2, characterized in that: The thickness of the metal aluminum film is 200nm-600nm; and / or, The metal aluminum film is prepared by electron beam evaporation; and / or, The metal aluminum film is prepared by electron beam evaporation, and the growth rate of the metal aluminum film is 8. The method according to claim 1 or 2, characterized in that: The alkaline solution comprises at least one of a KOH solution and a NaOH solution; and / or, In the alkaline solution, OH - The concentration of ions is 0.01mol / L-0.1mol / L.

9. The method according to claim 1 or 2, characterized in that: Step S3 includes: S31, soaking the film containing the copper oxide film and the metal aluminum film in an alkaline solution, and continuously replenishing the concentrated alkaline solution during the soaking process to maintain the alkali concentration in the alkaline solution until red copper metal is generated; S32. Wash the red copper metal with water and ethanol respectively to obtain metallic copper.

10. The method according to claim 9, characterized in that In the concentrated alkali solution, OH - The concentration of ions is 0.1mol / L-0.3mol / L.

Images