Rapid and continuous preparation method of single-crystal copper foil

Abstract

The invention provides a rapid and continuous preparation method of a single crystal copper foil. The method comprises the following steps: firstly, rolling the polycrystalline copper foil to generate internal stress in the copper foil, then enabling the rolled copper foil to sequentially pass through a temperature gradient area and a constant temperature area in a reducing atmosphere or an inert atmosphere, and increasing the temperature of the temperature gradient area along the advancing direction of the copper foil, and forming a plurality of abnormal crystal grains with the same orientation under the combined action of the temperature gradient and the internal stress, and growing and splicing the plurality of abnormal crystal grains with the same orientation in the constant-temperature region to obtain the single-crystal copper foil. When the method is used for preparing the single-crystallized copper foil, the preparation speed is not limited by the grain boundary migration rate, the efficiency is high, and the prepared single-crystallized copper foil is large in size and is prepared continuously.

Description

Technical Field

[0001] The invention belongs to the field of materials, and in particular relates to a method for quickly preparing a single crystal copper foil. Background Art

[0002] Compared with commercial polycrystalline copper foil, single crystal copper foil has many excellent properties such as high electrical and thermal conductivity, corrosion resistance, oxidation resistance, and good flexibility, which makes it have important application prospects in the fields of power transportation and battery current collectors. In addition, single crystal copper foil is a good substrate material and also plays a key role in thin film preparation. For example, it is easier to grow high-quality graphene on single crystal copper foil, especially the Cu (111) plane, which matches the symmetry of graphene and has a high lattice constant match (only 3%-4% mismatch), making it the most suitable crystal plane for epitaxial growth of graphene. However, the high preparation cost, low preparation efficiency, and small size of single crystal copper foil have hindered its application and industrial development. Previously, researchers have developed a series of methods to prepare single crystal copper foil, such as temperature gradient annealing, pre-oxidation annealing, contactless annealing, strong texture induced annealing, electrochemical polishing (Chinese patent CN 110273176 A), etc. The key technology is to form a single abnormal grain at high temperature, and under a certain driving force, the grain boundary of the abnormal grain begins to migrate and swallow up other grains, eventually forming a single crystal copper foil. This kind of static annealing method for preparing single crystal copper foil by nucleation of a single abnormal grain has a single crystalization speed restricted by the grain boundary migration rate, low preparation efficiency, and a preparation time of several or even dozens of hours. In addition, the size of the single crystal copper foil is also restricted by the size of the high temperature furnace chamber, and the size of the obtained single crystal copper foil is only in the centimeter or decimeter level. The roll-to-roll dynamic continuous preparation method has achieved a breakthrough in the size of single-crystal copper foil (Chinese patent CN 107904654 A). The key technology is to cut one end of the copper foil into a sharp tip to form a single abnormal grain. During the roll-to-roll rotation process and driven by high temperature, the grain boundary of the abnormal grain migrates, and finally a large-sized single crystal coil is obtained. Although this method has a relatively simple process and can produce large-sized single-crystal copper foil, its low preparation efficiency (the speed of single crystalization is restricted by the grain boundary migration rate) has not been solved.

[0003] Based on the above problems, we have developed a method for rapid and continuous preparation of single crystal copper foil. The key technology is that multiple abnormal grains nucleate at the same time, and under the drive of the internal stress of the copper foil after rolling, they grow and splice into single crystal copper foil in the high temperature zone. This method not only breaks the restriction of grain boundary migration rate on the single crystal speed of copper foil, significantly improves the preparation efficiency of single crystal copper foil, but also realizes the roll-to-roll dynamic continuous preparation of single crystal copper foil, laying the foundation for the low-cost industrial production of single crystal copper foil. Summary of the invention

[0004] The purpose of the present invention is to provide a method for rapidly and continuously preparing single crystal copper foil. The present invention proposes a method for simultaneously nucleating, growing and finally splicing a plurality of abnormal grains into a complete single crystal copper foil under specific process conditions, thereby overcoming the limitation of the single crystal rate of copper foil by the grain boundary migration speed. This method can be used in a roll-to-roll furnace to achieve ultra-rapid, continuous and large-scale preparation of single crystal copper foil. The present invention lays a foundation for the low-cost industrial production of single crystal copper foil.

[0005] The method for rapidly and continuously preparing a single crystal copper foil provided by the present invention comprises the following steps: 1) Using polycrystalline copper foil as raw material, rolling it to generate internal stress inside the copper foil; 2) High temperature heat treatment of the copper foil after rolling In a reducing atmosphere or an inert atmosphere, the copper foil after roller pressing is sequentially passed through a temperature gradient zone and a constant temperature zone for high-temperature heat treatment; along the moving direction of the copper foil, the temperature of the temperature gradient zone increases gradually, and under the joint action of the temperature gradient and internal stress, a plurality of abnormal grains with the same crystal orientation are formed, and in the constant temperature zone, the plurality of abnormal grains with the same crystal orientation are grown and spliced ​​to obtain the single crystal copper foil.

[0006] In step 1) of the above method, the rolling is performed by continuous rolling with upper and lower rollers, and the pressing rate does not exceed 40%, specifically 20-40%, and more specifically 30%; In step 2) of the above method, the copper foil is treated at a relatively low temperature before entering the temperature gradient zone, wherein the relatively low temperature is a temperature ranging from room temperature to a lower temperature limit of the temperature gradient zone.

[0007] In step 2), the lower limit of the temperature in the temperature gradient zone is not less than 850°C, and the upper limit is not more than 1080°C; the temperature in the constant temperature zone is 1000°C-1080°C; The copper foil travel speed v and the temperature gradient value m of the temperature gradient zone satisfy the relationship: m=a / v, wherein the unit of v is cm / min, the unit of m is °C / cm, 0.5 °C / min ≤a≤10 °C / min, specifically a=3 °C / min; The temperature zone length l of the constant temperature zone and the copper foil travel speed v satisfy the relationship: l≥kv, where the unit of l is cm, and k=20 min.

[0008] In one embodiment of the present invention, v = 1 cm / min, and the temperature gradient value m of the temperature gradient zone is 3°C / cm; In one embodiment of the present invention, v = 2 cm / min, and the temperature gradient value m of the temperature gradient zone is 1.5°C / cm; In one embodiment of the present invention, v = 3 cm / min, and the temperature gradient value m of the temperature gradient zone is 1°C / cm; In an embodiment of the present invention, v=1 cm / min, and the temperature zone length l of the constant temperature zone is ≥20 cm; In an embodiment of the present invention, v=2 cm / min, and the temperature zone length l of the constant temperature zone is ≥40 cm; In an embodiment of the present invention, v=3 cm / min, and the temperature zone length l of the constant temperature zone is ≥60 cm; The reducing atmosphere is hydrogen, or a mixture of hydrogen and an inert gas; The high temperature heat treatment can be achieved by a roll-to-roll dynamic continuous system; Furthermore, the operation of the high-temperature heat treatment is: fastening the polycrystalline copper foil obtained after rolling to an unwinding shaft, and then adhering the starting end of the copper foil to a winding shaft, wherein the unwinding shaft is located on a side of the temperature gradient zone away from the constant temperature zone, and the winding shaft is located on a side of the constant temperature zone away from the temperature gradient zone; raising the temperature so that the temperature gradient zone and the constant temperature zone reach a preset temperature, introducing a reducing gas or an inert gas so that the pressure of the chamber is maintained between 500 Pa-1 KPa, maintaining the pressure and temperature, starting the winding system, and allowing the copper foil to pass through the temperature gradient zone and the constant temperature zone of the furnace body in turn until all the polycrystalline copper foils are converted into single crystal copper foils and wound into coils.

[0009] The single crystal copper foil coil produced by the above method also belongs to the protection scope of the present invention.

[0010] The single crystal copper foil coil has a relatively large size, with an unfolded width of 0.1 m and a length of more than 13 m.

[0011] In one embodiment of the present invention, the single crystal copper foil has a Cu(111) crystal plane and a rolling direction of <110> .

[0012] In the method of the present invention, the polycrystalline copper foil is rolled to generate certain internal stress in the rolling direction (RD) and transverse direction (TD). Figure 3), these internal stresses appear as parallel lines along the RD direction, and under a suitable temperature gradient, multiple abnormal Cu(111) grains will be formed. Cu(111) grains are arranged anisotropically in different directions, such as <110> and <211> The interplanar spacing of the crystal directions is different, and the internal stress inside the copper foil plays a key role in the crystallographic orientation screening of the Cu(111) grain plane, and the X direction (corresponding to the RD direction) of the grain can be screened out. <110> Under continuous high temperature annealing in the constant temperature zone, the Cu(111) with a preferred orientation <110> Abnormal grain growth is achieved by splicing to obtain a whole piece of single crystal Cu(111) foil.

[0013] The present invention first performs rolling before annealing the commercial polycrystalline copper foil, and provides internal stress for the copper foil through rolling. The internal stress is also the driving force for the "abnormal grains" to be spliced ​​into large-sized single crystals with the same orientation; the method of the present invention that multiple "abnormal grains" are simultaneously nucleated and spliced ​​into large-sized single crystals with the same orientation breaks the limitation of the single crystalization speed by the grain boundary migration speed, and improves the single crystalization efficiency. The present invention designs the temperature gradient zone and the constant temperature zone temperature, and gives the relationship between the single crystal coverage and the rotation speed and the constant temperature zone length. The rotation speed and the temperature zone length process parameters can be flexibly matched to prepare large-sized single crystal copper foil.

[0014] The present invention has the following advantages over the prior art: 1. The prepared single-crystal copper foil is large in size and is prepared continuously, which can be industrialized.

[0015] 2. This method is used to prepare single-crystal copper foil. The preparation speed is not restricted by the grain boundary migration rate and has high efficiency.

[0016] 3. The preparation process is simple and does not require the use of chemical reagents for cleaning and polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a schematic diagram of the rapid and continuous preparation of single crystal copper foil according to the present invention.

[0018] FIG. 2 is a schematic diagram showing the temperature design of the high temperature heat treatment of the present invention.

[0019] FIG. 3 is a microstructure photograph of the surface of the copper foil after rolling in Example 1 of the present invention.

[0020] FIG. 4 is a photograph of the single crystal copper (111) foil obtained in Example 1 of the present invention.

[0021] FIG. 5 is an XRD graph of five random positions of the single crystal copper (111) foil obtained in Example 1 of the present invention.

[0022] FIG. 6 is an EBSD image of five random positions of the single crystal copper Cu(111) foil obtained in Example 1 of the present invention.

[0023] FIG7 is a morphology characterization diagram of the sample prepared in Comparative Example 1, wherein a is a macroscopic morphology diagram of the sample; b is an EBSD diagram of the Cu (111) region in the sample; and c is an EBSD diagram of the non-Cu (111) region in the sample.

[0024] FIG8 is a morphology characterization diagram of the sample prepared in Comparative Example 2, wherein a is a macroscopic morphology diagram of the sample; b is an EBSD diagram of the Cu (111) region in the sample; and c is an EBSD diagram of the non-Cu (111) region in the sample.

[0025] FIG9 is an EBSD image of the single crystal copper (111) foil prepared in Example 2, wherein a is a macroscopic image of the sample; and b is an EBSD image of the sample.

[0026] Fig.10 These are morphology characterization images of the sample prepared in Comparative Example 3, where a is the macroscopic morphology image of the sample; b is the EBSD image of the Cu (111) region in the sample; and c is the EBSD image of the non-Cu (111) region in the sample.

[0027] Fig.11 These are morphology characterization images of the sample prepared in Comparative Example 4, where a is the macroscopic morphology image of the sample; b is the EBSD image of the Cu (111) region in the sample; and c is the EBSD image of the non-Cu (111) region in the sample.

[0028] Fig.12 These are morphology characterization images of the sample prepared in Comparative Example 5, wherein a is the macroscopic morphology image of the sample; b is the EBSD image of the Cu (111) region in the sample; and c is the EBSD image of the non-Cu (111) region in the sample.

[0029] Fig.13 This is the EBSD image of the sample prepared in Comparative Example 6.

[0030] Fig.14 These are morphology characterization images of the sample prepared in Comparative Example 7, wherein a is the macroscopic morphology image of the sample; b is the EBSD image of the Cu (111) region in the sample; and c is the EBSD image of the non-Cu (111) region in the sample. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0032] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0033] Example 1. Preparation of single crystal Cu (111) foil according to Figure 1 The preparation flow chart shown in the figure is used to prepare single crystal Cu (111) foil. The specific operations are as follows: 1. The commercial polycrystalline copper foil was subjected to a continuous rolling process (the rolling material was an ultra-thin copper (C1100) strip with a thickness of 50 μm, a thickness of 35 μm after rolling, and a reduction rate of 30%); Figure 3 This is a microstructure photo after calendering (taken by an industrial microscope). Figure 3 In the process, intermittent horizontal lines parallel to the rolling direction are formed on the surface of the copper foil, which are called rolling lines; 2. The polycrystalline copper foil obtained after rolling is fastened to the unwinding shaft of the unwinding chamber. The thickness of the polycrystalline copper foil is 35 μm. Then the starting end of the copper foil passes through the high-temperature furnace and adheres to the winding shaft in the winding chamber. Under the copper foil is a graphite carrier as a supporting material. 3. Pump the gas in the high-temperature furnace to near vacuum (<10 Pa); 4. Introduce argon (500 sccm) into the high-temperature furnace and heat the furnace at the same time. Switch the gas and introduce hydrogen (500 sccm) into the furnace while continuing to heat the furnace until the highest temperature in the temperature gradient zone of the high-temperature furnace rises to 1050 °C and the temperature in the constant temperature zone (temperature zone length 40 cm) rises to 1045 °C. During this process, the chamber pressure is maintained at 500 Pa; The lower limit of the temperature gradient zone is 1005°C, the temperature gradient value is 1.5°C / cm, and the length of the temperature gradient zone is 30 cm. 5. Maintain the atmosphere, pressure and temperature in step 4, start the winding system, set the speed of the winding and unwinding ends to 2 cm / min, and make the copper foil pass through the temperature gradient zone and constant temperature zone of the high temperature furnace in turn.

[0034] The Cu(111) ratio of the single crystal copper foil was 100% (the rolling crystal direction was <110> , the same below). The unfolded width of the obtained single crystal Cu(111) foil is 0.1 m and the length is 13.4 m.

[0035] FIG. 4 is a photograph of the single crystal Cu (111) foil obtained.

[0036] FIG5 shows XRD patterns of the prepared single crystal Cu (111) foil at five random positions.

[0037] FIG6 shows the EBSD images of the single crystal Cu (111) foil at five random positions.

[0038] Comparative Example 1 The rest is the same as in Example 1, except that the temperature gradient value of the temperature gradient zone is set to 6°C / cm, and the length of the temperature gradient zone is 30 cm. Detection of non-Cu(111) regions in single crystal copper foil, such as Figure 7 As shown in a.

[0039] Figure 7 b is the EBSD of Cu(111) area. Figure 7 (c) is the EBSD map of the non-Cu(111) area.

[0040] Comparative Example 2 The rest is the same as Example 1, the temperature gradient value of the temperature gradient zone is set to 4 °C / cm, the length of the temperature gradient zone is 30 cm, the rotation speed of the winding and unwinding ends is set to 3 cm / min, and the temperature zone length of the constant temperature zone of the high temperature furnace is 60 cm.

[0041] Detection of non-Cu(111) regions in single crystal copper foil, such as Figure 8 As shown in a.

[0042] Figure 8 b is the EBSD of Cu(111) area. Figure 8 (c) is the EBSD map of the non-Cu(111) area.

[0043] Example 2 The rest is the same as Example 1, the temperature gradient value of the temperature gradient zone is set to 3 °C / cm, the length of the temperature gradient zone is 30 cm, the rotation speed of the winding and unwinding ends is set to 3 cm / min, and the temperature zone length of the constant temperature zone of the high temperature furnace is 60 cm.

[0044] The Cu(111) ratio of the single crystal copper foil obtained is 100%. Fig. 9 As shown in a, Fig. 9 (b) is the EBSD of the Cu(111) area.

[0045] Comparative Example 3 The rest is the same as Example 1, the temperature gradient is set to 3 °C / cm, the length of the temperature gradient zone is 30 cm, the speed of the winding and unwinding ends is set to 3 cm / min, and the high temperature furnace is set to a constant temperature zone (temperature zone length 40 cm).

[0046] Detection of non-Cu(111) regions in single crystal copper foil, such as Fig.10 As shown in a.

[0047] Fig.10 b is the EBSD of Cu(111) area. Fig.10 (c) is the EBSD map of the non-Cu(111) area.

[0048] Comparative Example 4 The rest is the same as in Example 2, the temperature gradient value of the temperature gradient zone is 3°C / cm, the length of the temperature gradient zone is 30 cm, the rotation speed of the winding and unwinding ends is set to 3 cm / min, and no constant temperature zone is set.

[0049] Detection of non-Cu(111) regions in single crystal copper foil, such as Fig.11 As shown in a.

[0050] Fig.11 b is the EBSD of Cu(111) area. Fig.11 (c) is the EBSD map of the non-Cu(111) area.

[0051] Comparative Example 5 The rest is the same as in Example 2, except that the constant temperature zone of the high temperature furnace is raised to 950°C.

[0052] Detection of non-Cu(111) regions in single crystal copper foil, such as Fig.12 As shown in a.

[0053] Fig.12 b is the EBSD of Cu(111) area. Fig.12 (c) is the EBSD map of the non-Cu(111) area.

[0054] Comparative Example 6 The rest is the same as Example 2, except that step (1) is removed, i.e., the rolling process is not performed.

[0055] Detection of rolling non-uniformity of single crystal copper foil <110> .

[0056] Fig.13 This is the EBSD image of the single crystal copper foil rolled.

[0057] Example 3 The rest is the same as in Example 1, except that the temperature zone length of the constant temperature zone is set to 50 cm. The Cu(111) ratio of the obtained single crystal copper foil was detected to be 100%.

[0058] Comparative Example 7 The other aspects are the same as those in Example 3, except that the temperature gradient value of the temperature gradient zone is 0.2°C / cm, and the length of the temperature gradient zone is 30 cm.

[0059] Detection of non-Cu(111) regions in single crystal copper foil, such as Fig.14 As shown in a.

[0060] Fig.14 b is the EBSD of Cu(111) area. Fig.14 (c) is the EBSD map of the non-Cu(111) area.

[0061] Example 4 The rest is the same as in Example 2, the rotation speed of the winding and unwinding ends is set to 1 cm / min, and the temperature zone length of the constant temperature zone of the high temperature furnace is 30 cm. The Cu(111) ratio of the obtained single crystal copper foil was detected to be 100%.

[0062] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principles of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departure from the disclosed scope in the application, and changes made with conventional techniques known in the art.

Claims

1. A method for rapidly and continuously preparing a single crystal copper foil, comprising the following steps: 1) Using polycrystalline copper foil as raw material, rolling it to generate internal stress inside the copper foil; 2) High temperature heat treatment of the copper foil after rolling In a reducing atmosphere or an inert atmosphere, the copper foil after roller pressing is sequentially passed through a temperature gradient zone and a constant temperature zone for high-temperature heat treatment; along the moving direction of the copper foil, the temperature of the temperature gradient zone increases gradually, and under the joint action of the temperature gradient and internal stress, a plurality of abnormal grains with the same crystal orientation are formed, and the plurality of abnormal grains with the same crystal orientation are grown and spliced ​​in the constant temperature zone to obtain the single crystal copper foil.

2. The method according to claim 1, characterized in that: The copper foil is treated at a lower temperature before entering the temperature gradient zone, wherein the lower temperature is a temperature ranging from room temperature to a lower temperature limit of the temperature gradient zone.

3. The method according to claim 1, characterized in that The rolling process uses upper and lower rollers to perform continuous rolling, and the pressing rate does not exceed 40%.

4. The method according to claim 1, characterized in that: In step 2), the lower limit of the temperature in the temperature gradient zone is not less than 850 °C, and the upper limit is not more than 1080 °C; the temperature in the constant temperature zone is 1000 °C-1080 °C.

5. The method according to any one of claims 1 to 4, characterized in that: The copper foil travel speed v and the temperature gradient value m of the temperature gradient zone satisfy the relationship: m=a / v, wherein the unit of v is cm / min, the unit of m is °C / cm, 0.5 °C / min ≤a≤10 °C / min; The temperature zone length l of the constant temperature zone and the copper foil travel speed v satisfy the relationship: l≥kv, where the unit of l is cm, and k=20min.

6. The method according to claim 1, characterized in that The reducing atmosphere is hydrogen or a mixed gas of hydrogen and an inert gas.

7. The method according to any one of claims 1 to 6, characterized in that: The operation of the high-temperature heat treatment is as follows: fasten the polycrystalline copper foil coil obtained after rolling to an unwinding shaft, and then adhere the starting end of the copper foil to a winding shaft, wherein the unwinding shaft is located on a side of the temperature gradient zone away from the constant temperature zone, and the winding shaft is located on a side of the constant temperature zone away from the temperature gradient zone; increase the temperature so that the temperature gradient zone and the constant temperature zone reach a preset temperature, introduce a reducing gas or an inert gas so that the pressure of the chamber is maintained between 500 Pa and 1 KPa, maintain the pressure and temperature, start the winding system, and allow the copper foil to pass through the temperature gradient zone and the constant temperature zone of the furnace body in turn until all the polycrystalline copper foils are converted into single crystal copper foils and wound into coils.

8. A single crystal copper foil coil, wherein the single crystal copper foil coil is prepared by the method according to any one of claims 1 to 7.

9. The single crystal copper foil coil according to claim 8, characterized in that: The single crystal copper foil has a Cu(111) crystal plane and a rolling direction of <110> .

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