Superconducting tape microstructure sampling method

Abstract

The present invention provides a method for sampling the microstructure of a superconducting tape, comprising: step 1: encapsulating the superconducting tape with a metal layer; step 2: separating the metal layers encapsulated on both sides of the superconducting tape with a preset length; step 3: fixing the superconducting tape and the metal layer close to the superconducting layer, and separating the metal layer close to the base band layer of the superconducting tape; step 4: separating the superconducting layer and the buffer layer of the superconducting tape from the superconducting tape; step 5: sampling the superconducting layer or buffer layer of the separated combined layer; step 6: observing the sampled superconducting layer or buffer layer with a detection device. Compared with the prior art, the present invention is dissected, and each film layer structure is well preserved, which is conducive to later analysis.

Description

[0001] This application is a divisional application of the following original application:

[0002] Filing date of original application: March 8, 2022

[0003] Application number of the original application: 202210227165.7

[0004] Title of the invention originally applied for: Method for analyzing the microstructure of superconducting tapes Technical Field

[0005] The present invention relates to the field of superconducting materials, and in particular to a method for sampling a microstructure of a superconducting tape. Background Art

[0006] Since Professor Kamerlingh Onnes of Leiden University in the Netherlands first discovered the superconductivity phenomenon in his laboratory in 1911, superconducting materials and their applications have been one of the most active frontier research areas in contemporary science and technology. In the past decade, research on superconducting power devices based on superconductivity has developed rapidly, and remarkable results have been achieved in the fields of superconducting energy storage, superconducting motors, superconducting cables, superconducting current limiters, superconducting transformers, superconducting magnetic levitation, and nuclear magnetic resonance. The second-generation superconducting tape made of REBCO, also known as coated conductor, has good application prospects in many fields such as medicine, military, and energy due to its strong current carrying capacity, high magnetic field performance, and low material cost. The second-generation high-temperature superconducting material composed of rare earth (Rare Earth, Re), barium (Ba), copper (Cu) and oxygen (O) elements is collectively written as ReBCO.

[0007] The second generation superconducting tape is generally produced by a multi-layer coating process on a nickel-based alloy substrate because its REBCO as the superconducting current carrier core is hard and brittle, so it is also called a coated conductor. The second generation superconducting tape is generally composed of a base tape, a buffer layer (transition layer), a superconducting layer and a protective layer. The role of the metal substrate is to provide excellent mechanical properties for the tape. On the one hand, the role of the transition layer is to prevent the mutual diffusion of elements between the superconducting layer and the metal substrate. On the other hand, the top transition layer needs to provide a good template for the epitaxial growth of the superconducting layer and improve the arrangement quality of the YBCO grains. To prepare a coated conductor with excellent superconducting performance, the superconducting layer needs to have a consistent biaxial texture. Biaxial texture refers to the grains having almost consistent arrangement in both the a / b axis and the c axis (the c axis is perpendicular to the a / b plane). Since the degree of arrangement of the YBCO film in the a / b axis direction (in-plane texture) is relatively difficult to achieve, poor in-plane texture will seriously reduce the superconducting performance. Therefore, it is necessary to epitaxially grow yttrium barium copper oxide (YBCO) superconducting film on a transition layer that already has a biaxial texture and a matching lattice. There are two mainstream technical routes for preparing biaxial textures, one is the rolling-assisted biaxial texture base tape technology, and the other is the ion beam assisted deposition technology. There are many common technologies for preparing ReBCO superconducting layers, including pulsed laser deposition, metal organic chemical vapor deposition, reactive co-evaporation, etc. The protective layer is mainly used to protect the superconducting film layer, and generally a 1-5um silver layer is plated on the surface of the superconducting tape. Subsequently, the surface is copper-plated, that is, a 1-30um copper layer is electroplated on the surface of the superconducting tape that has been silver-plated.

[0008] Shanghai Superconducting uses the IBAD+PLD process. The strip is prepared by coating Al on the base strip. 2 O 3 / Y 2 O 3 / MgO / LaMnO 3 / CeO 2 / REBCO / Ag / Cu layer. Different REBCO components are selected according to the actual working temperature range and magnetic field strength.

[0009] Al 2 O 3 / Y 2 O 3 / MgO / LaMnO 3 / CeO 2 In this article, all of them are classified as buffer layers. Ag / Cu are all classified as protective layers. Encapsulated stainless steel, brass or copper are all classified as metal layers.

[0010] It can be seen that such a coating structure is still very complex, so the strip dissection analysis is of great significance when abnormal conditions occur. For example, if the yield rate is poor, it can be examined whether there are scratches along the width of the film layer that eventually block the current of the strip. After being damaged by a high-field magnet, the edge cracks of the film layer can be studied to find the crack propagation mechanism.

[0011] In some cases, when there are problems with the quality of the strip or problems occur in the application scenario, it is often very difficult to analyze the specific film layer when going back to analyze the strip.

[0012] The silver layer of the superconducting silver-plated tape is made of 25% NH 3 and 30% H 2 O 2 The solution is mixed in a ratio of 1:1 for etching, and the superconducting layer will be better preserved. Usually the surface of the strip is a copper layer, and FeCl 3 Corrosion of copper layer, copper layer is generally thicker, corrosion is not uniform; silver layer with NH 3 +H 2 O 2 The solution will corrode and introduce a lot of impurities into the superconducting layer, which is not conducive to the subsequent dissection and analysis. We must find a way to carry out the dissection work quickly and effectively. Summary of the invention

[0013] In view of the defects in the prior art, an object of the present invention is to provide a method for sampling a superconducting tape microstructure.

[0014] A superconducting tape microstructure sampling and analysis method provided by the present invention comprises:

[0015] Step 1: Encapsulating the superconducting tape with a metal layer;

[0016] Step 2: Separating a preset length of metal layers encapsulated on both sides of the superconducting tape;

[0017] Step 3: Fix the superconducting tape and the metal layer close to the superconducting layer, and separate the metal layer close to the base tape layer of the superconducting tape;

[0018] Step 4: separating the superconducting layer and the buffer layer of the superconducting tape from the superconducting tape;

[0019] Step 5: Sampling the superconducting layer or buffer layer of the separated combined layer;

[0020] Step 6: Use detection equipment to observe the superconducting layer or buffer layer of the sample.

[0021] Preferably, before step 1, the method further comprises:

[0022] Step 0: Perform critical current test on superconducting tape to obtain critical current distribution data and determine the specific location of critical current degradation point for sample analysis.

[0023] Preferably, after step 6, the method further includes:

[0024] Step 7: Etching the buffer layer and superconducting layer of the sample;

[0025] Step 8: Use detection equipment to observe the superconducting layer and buffer layer of the sample.

[0026] Preferably, the detection equipment in step 6 and step 8 includes one or more of: an optical microscope, a scanning electron microscope, a transmission electron microscope, an atomic force microscope, an ellipsometer, a profilometer, an X-ray diffractometer and a reflection high energy diffractometer.

[0027] Preferably, the method of separating the metal layers of a preset length encapsulated on both sides of the superconducting tape in step 2 comprises:

[0028] The preset position of the superconducting tape is bent repeatedly until the packaged metal layer is broken, and the packaged metal layers on both sides are torn off from the broken part.

[0029] Preferably, in step 3, the superconducting tape and the metal layer close to the superconducting layer are fixed, and when the metal layer close to the base tape layer of the superconducting tape is separated, it is ensured that there is no tearing between the superconducting layer and the buffer layer.

[0030] Preferably, in step 4, the superconducting layer and the buffer layer of the superconducting tape are separated by gently pulling apart in opposite directions, ensuring that the superconducting layer and the buffer layer are detached from the interface.

[0031] Preferably, in the separated metal layer, the inner surface of the metal layer close to the superconducting tape base layer has no coating, and the inner surface of the metal layer close to the superconducting layer has the coating of the superconducting layer.

[0032] Preferably, the etching method in step 7 includes: etching the superconducting layer with about 3-10% dilute hydrochloric acid.

[0033] Preferably, the corrosion method in step 7 includes:

[0034] Corrosion of the buffer layer by chemical etching;

[0035] Among them, 5%-20% NaOH is used to corrode Al 2 O 3 ;

[0036] During corrosion, ultrasonic vibration is used to oscillate the corrosion solution.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. In the present invention, the superconducting tape is dissected, and after the dissection, the film structure of each layer of the superconducting tape is well preserved, which is conducive to the subsequent analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0040] Figure 1 The structure of the original superconducting tape;

[0041] Figure 2 The structure of the strip after step 1;

[0042] Figure 3 The structure of the strip after step 3;

[0043] Figure 4 The structure of the strip after step 4;

[0044] Figure 5 To place samples and observe the superconducting layer;

[0045] Figure 6 Buffer layer for sample placement and observation;

[0046] Figure 7 To observe the etched superconducting layer for sample placement;

[0047] Figure 8 To observe the corroded buffer layer for sample placement;

[0048] Fig. 9 To observe the corroded base band for sample placement;

[0049] Fig.10 The surface cracks of the superconducting layer were observed by scanning electron microscope;

[0050] Fig.11 The scratches on the base tape surface observed by optical microscope;

[0051] Fig.12 This is the diffraction pattern of the superconducting layer observed by an X-ray diffractometer.

[0052] Reference numerals:

[0053] 1 is baseband

[0054] 2 is the buffer layer

[0055] 3 is the superconducting layer

[0056] 4 is the protective layer

[0057] 5 is the metal layer DETAILED DESCRIPTION

[0058] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0059] The present invention provides a method for sampling a superconducting tape microstructure, comprising the following steps:

[0060] Step 1: Encapsulate the superconducting tape with a metal layer.

[0061] Specifically, the superconducting tape is packaged with metal, and the type of metal is not limited in the present application, and can be, for example, stainless steel, brass or copper. After the packaging is completed, the layer where the metal is located is the metal layer.

[0062] Optionally, the superconducting tape is packaged with a copper tape.

[0063] For example, Figure 1 For the structure of the original superconducting tape, such as Figure 1 As shown, the superconducting tape includes: a base tape 1, a buffer layer 2, a superconducting layer 3 and a protective layer 4. Figure 2 The structure of the strip after step 1, such as Figure 2 As shown, the metal layer Figure 1 After the superconducting tape is packaged, Figure 2 The structure in FIG. 1 is that a metal layer 5 is added to the outside of the protective layer 4 to complete the packaging of the superconducting tape.

[0064] Furthermore, before step 1, the method further includes: step 0: performing a critical current test on the superconducting tape to obtain critical current distribution data and determine the specific location of the critical current degradation point for sample analysis.

[0065] Specifically, in the present invention, a critical current test is performed on the disassembled superconducting tape, and critical current distribution data is obtained through the critical current test to determine the specific location of the critical current degradation point for sample analysis.

[0066] Among them, the critical current refers to the time when a superconductor in a superconducting state is in a state where a DC current increases to a critical value and the sample turns into a normal state. Experiments have found that when a current flows through a superconductor, the superconductor remains unresistance with an upper limit of current, which we call the critical current Ic of the superconductor. As long as the current I is greater than or equal to Ic, the superconductor will have resistance. The critical current is the critical current degradation point in the present invention.

[0067] Step 2: Separate the metal layers of a predetermined length encapsulated on both sides of the superconducting tape.

[0068] There is no limitation on the setting of the preset length in the present application. For example, it can be set to 1-2 cm from one end of the strip.

[0069] Specifically, the method for separating the metal layers of preset length packaged on both sides of the superconducting tape in step 2 includes: repeatedly bending the preset position of the superconducting tape until the packaged metal layer breaks, and tearing it apart from the broken part to obtain the metal layers packaged on both sides.

[0070] Exemplarily, the superconducting tape is clamped at 1-2 cm with needle-nosed pliers, and the superconducting tape is twisted repeatedly until the metal layer is broken.

[0071] Among the separated metal layers, the inner surface of the metal layer close to the superconducting tape base layer has no coating, while the inner surface of the metal layer close to the superconducting layer has the coating of the superconducting layer.

[0072] Specifically, the inner surface of the metal layer close to the superconducting tape base layer has no coating, has a metallic color and has brushed stripes, and the inner surface of the metal layer close to the superconducting layer has a coating of the superconducting layer and is bright black in color.

[0073] Step 3: Fix the superconducting tape and the metal layer close to the superconducting layer, and separate the metal layer close to the base tape layer of the superconducting tape.

[0074] Figure 3 The structure of the strip after step 3, such as Figure 3 As shown, in step 3, the superconducting tape and the metal layer close to the superconducting layer are fixed, and when the metal layer close to the base tape layer of the superconducting tape is separated, it is ensured that there is no tearing between the superconducting layer and the buffer layer.

[0075] Step 4: Separating the superconducting layer and the buffer layer of the superconducting tape from the superconducting tape.

[0076] Figure 4 The structure of the strip after step 4, such as Figure 4 As shown, in step 4, the superconducting layer and the buffer layer of the superconducting tape are gently pulled apart in opposite directions to ensure that the superconducting layer and the buffer layer are detached from the interface, wherein: Figure 4 The front direction in the figure indicates the direction of pulling.

[0077] Specifically, press the metal layer connecting the superconducting tape and the YBCO surface, tear off the superconducting surface at the back, and gently tear open the interface between the superconducting layer and the buffer layer.

[0078] The interface is the surface between the superconducting layer and the buffer layer.

[0079] Step 5: Sample the superconducting layer or buffer layer of the separated combined layer.

[0080] The combined layer consists of a superconducting layer, a protective layer and a metal layer, or the combined layer consists of a buffer layer, a base band and a protective layer.

[0081] Step 6: Use detection equipment to observe the superconducting layer or buffer layer of the sample.

[0082] Specifically, Figure 5 To observe the superconducting layer, Figure 5 As shown, the superconducting layer is sampled and observed using detection equipment. Further, Figure 6 For sample observation buffer layer, Figure 6 As shown, the buffer layer is sampled and observed using detection equipment.

[0083] Specifically, the detection equipment in step 6 and step 8 includes one or more of: an optical microscope, a scanning electron microscope, a transmission electron microscope, an atomic force microscope, an ellipsometer, a profilometer, an X-ray diffractometer and a reflection high energy diffractometer.

[0084] Wherein, after step 6, the method further includes: step 7: corroding the buffer layer and the superconducting layer of the sample; and step 8: observing the superconducting layer and the buffer layer of the sample by using a detection device.

[0085] Specifically, the etching method in step 7 includes: the superconducting layer is etched with about 3-10% dilute hydrochloric acid. Figure 7 To observe the etched superconducting layer, Figure 7 As shown, the etched superconducting layer is sampled and observed using a detection device.

[0086] Furthermore, the etching method in step 7 also includes: etching the buffer layer by chemical etching; wherein 5%-20% NaOH is used to etch Al2O3; and during etching, ultrasonic oscillation is used to etch the solution. Figure 8 To observe the corroded buffer layer, Figure 8 As shown, the corroded buffer layer is sampled and observed using a detection device.

[0087] Furthermore, Fig. 9 To observe the corroded baseband, Fig. 9 As shown, the baseband is not corroded. Figure 7 and Figure 8 By controlling the concentration of chemical corrosion reagents and the reaction time, the surface structure of the superconducting tape that may be mechanically damaged due to tearing can be partially corroded, so as to observe the part with good crystal structure, observe the surface morphology of the film layer, measure the crystal structure of the film layer, and judge the quality of the sample film layer. Fig. 9 Yes Figure 8After the buffer layer on the upper base tape is completely etched, the surface morphology on the base tape is observed. Figure 7 The superconducting layer is completely corroded to the protective layer. The protective layer is not researchable in the preparation process, so it is not sampled and analyzed. Samples are placed and observed using detection equipment.

[0088] The following is the observation of the superconducting layer and the base layer using the detection equipment.

[0089] Fig.10 The surface cracks of the superconducting layer observed by scanning electron microscope, such as Fig.10 As shown, 300um means the total length of the scale bar on the figure is 300um, and N means the working mode of the scanning electron microscope is the normal mode of 15kv, which can clearly obtain the cracks on the surface of the superconducting layer; Fig.11 The scratches on the surface of the base tape observed by optical microscope, such as Fig.11 As shown, the scratches on the surface of the base layer can be clearly seen; Fig.12 is the diffraction pattern of the superconducting layer observed by an X-ray diffractometer, such as Fig.12 The figure shows the diffraction of the superconducting layer.

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] 1. In the present invention, the superconducting tape is dissected, and after the dissection, the film structure of each layer of the superconducting tape is well preserved, which is conducive to the subsequent analysis.

[0092] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0093] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for sampling a superconducting tape microstructure, characterized in that: include: Step 1: Encapsulating the superconducting tape with a metal layer; Step 2: Separating a preset length of metal layers encapsulated on both sides of the superconducting tape; Step 3: Fixing the superconducting tape and the metal layer close to the superconducting layer, and separating the metal layer close to the base tape layer of the superconducting tape; Step 4: separating the superconducting layer and the buffer layer of the superconducting tape from the superconducting tape; Step 5: Sample the separated superconducting layer or buffer layer.

2. The method for placing a sample of a superconducting tape microstructure according to claim 1, characterized in that: Before step 1, the method further includes: Step 0: Perform critical current test on superconducting tape to obtain critical current distribution data and determine the specific location of critical current degradation point for sample analysis.

3. The method for placing a sample of a superconducting tape microstructure according to claim 1, characterized in that: The method for separating the metal layers of a preset length encapsulated on both sides of the superconducting tape in step 2 comprises: The preset position of the superconducting tape is bent repeatedly until the packaged metal layer is broken, and the packaged metal layers on both sides are torn off from the broken part.

4. The method for placing a sample of a superconducting tape microstructure according to claim 1, characterized in that: In the step 3, the superconducting tape and the metal layer close to the superconducting layer are fixed, and when the metal layer close to the base tape layer of the superconducting tape is separated, it is ensured that there is no tearing between the superconducting layer and the buffer layer.

5. The method for placing a sample of a superconducting tape microstructure according to claim 1, characterized in that: In the step 4, the superconducting layer and the buffer layer of the superconducting tape are separated by gently pulling in opposite directions, and it is ensured that the superconducting layer and the buffer layer are detached from the interface.

6. The method for placing a sample of a superconducting tape microstructure according to claim 1, characterized in that: In the separated metal layer, the inner surface of the metal layer close to the superconducting tape base layer has no coating, and the inner surface of the metal layer close to the superconducting layer has the coating of the superconducting layer.

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