High-capacity easy-to-activate AB2 type hydrogen storage alloy and preparation method thereof

Abstract

The invention relates to a high-capacity easy-to-activate AB2 type hydrogen storage alloy and a preparation method thereof, belongs to the technical field of hydrogen storage alloy materials, and solves the problems of high activation condition, long activation period, overhigh hydrogen absorption platform pressure, high batch preparation smelting difficulty and the like of the traditional Ti-Mn based hydrogen storage alloy in the prior art. The hydrogen storage alloy is characterized in that the specific composition of the alloy is (Ti < 1-x-y > Zr < x > Scy) < 1.1 > Mn < 1.15 > Cr < 0.85-z-m > Fe < z > Mo < m >, x, y, z and m in the formula are atomic ratios, x is larger than or equal to 0.10 and smaller than or equal to 0.30, y is larger than or equal to 0.01 and smaller than or equal to 0.05, z is larger than or equal to 0.05 and smaller than or equal to 0.15, and m is larger than or equal to 0.02 and smaller than or equal to 0.10. The hydrogen storage alloy has good activation performance and hydrogen absorption and desorption performance, the hydrogen storage capacity is larger than or equal to 1.85 wt.%, the hydrogen absorption and desorption platform pressure can be adjusted according to application scene requirements, activation can be completed through one-time hydrogen absorption and desorption circulation under the conditions that the temperature is 20 DEG C and the initial hydrogen pressure is 3 MPa, and the hydrogen storage alloy can serve as a solid hydrogen storage material to be widely applied to various scenes such as hydrogen fuel cells. The smelting and rapid quenching process of the alloy industrial preparation process has the advantages of being simple and easy to operate, high in yield and the like, and the problem of component segregation of the casting process is fundamentally solved.

Description

TECHNICAL FIELD

[0001] A high capacity easily activated AB2-type hydrogen storage alloy and a method for preparing the same. BACKGROUND

[0002] Hydrogen is considered as an ideal energy carrier in the future due to its high energy density and environmental friendliness. Among the existing different hydrogen storage systems, metal hydrides have attracted much attention due to their high volumetric energy density. Many researchers have conducted in-depth and extensive research on the hydrogen storage performance of various metal hydrides such as AB, AB2, AB3, AB5, and Mg-based alloys. Among the many metal hydrides, Ti-Mn-based AB2-type hydrogen storage alloys have good hydrogenation / dehydrogenation kinetics, high hydrogen storage capacity, and relatively low cost, and are one of the most promising solid-state hydrogen storage materials for application in various scenarios. However, there are still some key defects that limit its practical application, including high activation conditions, high hydrogen absorption and desorption plateau pressure (more than 2 MPa at room temperature), large hysteresis, and low cycle stability. In order to overcome these obstacles and improve the overall hydrogen storage performance of the alloy, researchers have applied a series of strategies to improve the hydrogen storage performance of the alloy, such as changing the structure of the alloy or optimizing the composition of the alloy by substituting / doping elements on the A or B side. With the in-depth research, element substitution is considered to be the most feasible and effective method to improve the hydrogen storage performance of the alloy. For example, partial substitution of Ti and Mn with other metal elements can significantly improve the performance of the alloy. There are also reports that the thermodynamics, crystallography, and hydrogen storage performance of the alloy are simulated by theoretical calculation to guide the design of Ti-Mn-based alloys. It is found that with the increase of Zr content in the alloy, the hydrogen storage platform decreases sharply, and the platform hysteresis decreases slightly. At the same time, the addition of V is beneficial to improve the hydrogen absorption capacity and kinetics of the alloy, and improve the thermodynamic performance of the alloy. However, due to the high price of V, its large-scale use is limited. It is reported that the addition of rare earth elements (such as La, Ce, Y, Pr, Sm, etc.) can make the alloy exhibit good activation performance, and the addition of rare earth elements is beneficial to improve the nucleation rate and grain refinement of the alloy, thereby improving the hydrogen absorption kinetics of the alloy. The disadvantage is that a high content of rare earth elements usually leads to an increase in the absolute value of the hydrogen absorption enthalpy of the alloy, resulting in poor hydrogen desorption kinetics. At the same time, the use of rare earth elements will increase the raw material cost of the alloy. It is also reported that the doping of Cu makes the unit cell volume of Ti-Mn-based alloy slightly increase, thereby improving the hydrogen storage performance of the alloy. At the same time, it improves the activation performance of the alloy.

[0003] So far, smelting has been the most commonly used method for preparing AB2-type alloys. In particular, for industrialized preparation of AB2-type alloys, there seems to be no other choice but smelting. For steel ingots produced by traditional methods such as induction melting (VIM) and arc melting (VAR), segregation inevitably occurs during the cooling process, which seriously affects the overall hydrogen storage performance of the alloy. High-temperature diffusion annealing of the ingot under vacuum is considered to effectively eliminate the segregation produced during solidification. Although this method is very effective, it is time-consuming and labor-intensive, and the power consumption is huge, which greatly increases the cost of alloy preparation SUMMARY

[0004] The main purpose of the present application is to provide a high-capacity easy-activated AB2-type hydrogen storage alloy and a preparation method thereof, which solves the problems of high activation condition (i.e. not easy to activate at room temperature), long activation period, excessively high plateau pressure, unstable product performance and high cost of existing AB2-type hydrogen storage alloys.

[0005] The present application adopts A-side over-stoichiometric ratio, uses Zr to partially replace A-side Ti, and uses Cr, Fe and Mo elements to partially replace B-side Mn elements, and adds a small amount of rare earth element Sc in the component design. The most prominent feature of the component design is that the alloy does not contain noble metal V element, and the hydrogen storage performance of the alloy is improved by adding a small amount of rare earth Sc. In the preparation technology, vacuum induction melting-quenching integrated technology is adopted, which avoids the composition segregation of the alloy during solidification, and obtains a microstructure with ultra-fine grains, so that the overall hydrogen storage performance of the alloy is greatly improved, which meets the application requirements of different use scenarios, especially the application requirements of vehicle-mounted fuel cells.

[0006] An important finding of the present application is that the combination of element substitution and rapid quenching process can more effectively improve the activation performance of Ti-Mn-based AB2-type alloy, adjust its plateau pressure, improve its plateau characteristics, and improve the hydrogen absorption and desorption kinetics and cycle stability of the alloy, which meets the application requirements of vehicle-mounted fuel cells and other various scenarios.

[0007] The first aspect of the present application provides a high-capacity easy-activated AB2-type hydrogen storage alloy, which specifically comprises (Ti 1-x-y Zr x Sc y ) 1.1 Mn 1.15 Cr 0.85-z-m Fe z Mo m , wherein x, y, z and m are atomic ratios, and 0.10≤x≤0.30, 0.01≤y≤0.05, 0.05≤z≤0.15, 0.02≤m≤0.10. The preferred ratio of x, y, z and m is x: y: z: m = 0.25:0.03:0.10:0.04.

[0008] Specifically, the hydrogen storage alloy has a nanocrystalline structure, and the average grain size is 50-200 nm. The hydrogen storage alloy has a single-phase structure, contains a C14-type Laves phase, and has an MgZn2 structure. C14 is a Strukturbericht (structure report) classification symbol proposed by German crystallographers in the 1930s for systematizing the naming of crystal structure types. The letter C represents a binary compound (AB2 type). The number 14 represents the 14th specific variant in this type of structure. The Laves phase is named after Fritz Laves for his pioneering research on AB2 close-packed structures. He first systematically studied the crystal geometry of AB2 intermetallic compounds in the 1930s-1940s. In memory of his pioneering work, such structures are collectively referred to as Laves Phases. The C14 Laves phase is a hexagonal intermetallic compound and is typically represented by MgZn2, hence also known as the MgZn2-type structure. The chemical formula is AB2, where A atoms are larger-sized metal atoms (such as Mg, Ti, Zr, V), and B atoms are smaller-sized metal atoms (such as Zn, Mn, Cr, Fe). Its crystal structure: crystal system: hexagonal (Hexagonal); space group: P63 / mmc; unit cell parameters: a typical unit cell contains 12 atoms (4 A atoms + 8 B atoms). A atoms occupy the vertices and bottom center positions of the hexagonal lattice, with a coordination number of 16 (surrounded by 16 B atoms), and B atoms form a distorted tetrahedral network with a coordination number of 12 (6 A atoms + 6 B atoms). The atomic layer stacking sequence is arranged in a specific sequence (such as ABACABAC...), which reflects the derived characteristics of hexagonal close packing (HCP).

[0009] The application also provides a preparation method of the hydrogen storage alloy, specifically comprising the following steps: S1: according to the calculated dosage of the chemical formula composition, the ingredients are prepared, and the appropriate loss on ignition of Mn and Sc is added; S2: place the prepared raw materials in an Al2O3 crucible, cover the furnace cover, and after the vacuum reaches the preset vacuum degree, fill in a certain pressure of high-purity Ar gas as a protective gas, heat the raw materials to a molten state by a medium-frequency induction heating method, and after a certain period of heat preservation, obtain a liquid master alloy with uniform composition; S3: Liquid master alloy is poured directly from a crucible nozzle into an upper tundish (200 x 40 mm) with a narrow opening at the bottom. Liquid alloy then flows through the opening at the bottom of the upper tundish into a lower tundish made of high-temperature mullite. The high-temperature liquid alloy evenly covers the bottom plate of the lower tundish, and rotating copper rollers carry the liquid alloy directly to its surface. Centrifugal force throws thin alloy flakes out, a process known as strip throwing on the production site. The rapidly quenched alloy flakes that escape the copper rollers fall directly onto a water-cooled bed below them, where they cool to room temperature to form a rapidly quenched alloy strip.

[0010] Furthermore, the burn-off amount of Mn and Sc in step S1 is 3%-5% of the calculated dosage.

[0011] Further, in step S2, each raw material is placed and concrete operation is as follows: all raw materials Ti, Sc, Zr, Mn, Cr, Fe and Mo are removed surface impurities and oxide scale with special raw material surface cleaning equipment. Crucible must be cleaned with high-purity Fe before smelting alloy, to remove impurities on the crucible surface. Prepared raw materials are placed in order in sequence in Al2O3 crucible, wherein, the spongy Ti of about half the addition amount is evenly spread to the crucible bottom, metallic Fe and metallic Mo and half of the electrolytic Mn are placed above the spongy Ti at intervals, and metallic Cr, spongy Zr, metallic Sc ​​and the other half of the spongy Ti are mixed and placed above Fe, Mo and Mn, and the electrolytic Mn of about half is placed on the top.

[0012] Furthermore, the smelting in step S2 adopts a power-incremental melting and refining process, and the specific parameters are shown in Table 1: Table 1 Induction melting process parameters Melting begins at a power of 100 kW for approximately 10 minutes, then the power is increased by 50 kW every 5 minutes until it reaches 550 kW. Once all raw materials have melted, the molten alloy is held at approximately 1550°C for 3-5 minutes to achieve complete homogenization of the liquid alloy composition. This power ramping process generates variable electromagnetic stirring forces within the molten raw materials, enhancing the stirring effect, improving melting efficiency, and promoting homogenization of the alloy composition. Most importantly, this process significantly increases the yield of the molten alloy.

[0013] Furthermore, the rapid quenching operation in step S3 is as follows: the power of the smelting furnace is adjusted to about 300 kW, the temperature of the liquid alloy is maintained at about 1550°C, the liquid master alloy is directly injected into the upper tundish with a leak at the bottom, and the liquid alloy is injected into the lower tundish made of mullite through the leak. The bottom plate of the lower tundish is connected to the rapid quenching copper roller. The high-temperature liquid alloy has good fluidity and will be evenly spread on the entire bottom plate of the lower tundish. The rotating copper roller brings the molten steel to the roller surface, and after cooling, a rapid quenching alloy thin strip is formed. The entire rapid quenching process is as follows: Figure 1 As shown. Figure 1It can be seen that the molten steel flows out of the pouring nozzle of the inclined crucible, is injected into the upper tundish, and is injected into the lower tundish through the bottom narrow leakage opening of the upper tundish. Two tundishes are mainly used to control the flow of molten steel, so that the molten steel can be uniformly laid on the bottom plate of the lower tundish. The bottom plate is in direct contact with the copper roller, and the rotation of the copper roller can bring the molten steel to the surface of the copper roller and spin out under the action of centrifugal force. The pouring nozzle of the crucible is relatively small, and the molten steel will be dispersed when passing through the upper tundish. The function of the upper tundish is to gather the dispersed molten steel to the bottom narrow leakage opening, so as to ensure that the molten steel flowing into the lower tundish is uniformly spread on the bottom plate. Controlling the flow of molten steel of the pouring nozzle to remain constant is the key to the rapid quenching technology. The crucible can be freely inclined in the range of 0-90 degrees, and the inclination rate of the crucible determines the flow of molten steel. During the operation, an automatic control system can be used to realize accurate control of the inclination rate of the crucible, so that the flow of the pouring nozzle of the crucible remains constant. The linear speed of the surface of the rotating copper roller is 1-15 m / s, and the water inflow of the copper roller is greater than or equal to 36 m 3 / h, and the water temperature is 18-20℃. The alloy sheet separated from the copper roller falls onto a rotating water cooling bed below the copper roller, the rotating speed of the water cooling bed is 1 rpm, and the alloy is cooled to room temperature to obtain a rapid quenching alloy sheet with a thickness of 100-300μm. Determining the appropriate rapid quenching cooling speed (mainly determined by the linear speed of the surface of the copper roller) is a key technical parameter, and appropriate quenching speed can ensure that the rapid quenching alloy thin strip has almost complete nanocrystalline structure, and the grain size is between 50-200 nm.

[0014] The technical scheme of the application has the following technical effects: Compared with the prior art, the advantages of the application lie in that the A side is designed to be over-stoichiometric, which can significantly improve the hydrogen storage capacity of the alloy and improve the activation performance of the alloy. Alloying with metal elements Sc, Zr, Cr and Fe can significantly improve the activation performance and platform characteristics of the alloy, significantly reduce the platform hysteresis, and make the hydrogen absorption and desorption platform pressure of the alloy meet the application requirements of various scenes such as fuel cells. Especially, the addition of a small amount of rare earth element Sc to the alloy can significantly improve the hydrogen storage capacity of the alloy, improve the room temperature activation performance, and significantly reduce the platform pressure and improve the platform characteristics of the alloy. In the preparation technology, the vacuum induction melting-rapid quenching integrated technology is adopted. The advantage of this technology is that melting and rapid quenching are completed at one time, which can completely inhibit the composition segregation during solidification. At the same time, rapid quenching can produce internal stress state and microcrystalline defects that are beneficial to activation in the alloy, so that the hydrogen storage performance of the alloy is significantly improved. The complicated process of alloy melting-casting-annealing is omitted, the yield of the alloy preparation is significantly improved, the stability of the product performance is improved, and the preparation cost is further reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0016] Figure 1 Schematic diagram of the vacuum rapid quenching process.

[0017] Figure 2 Phase diagrams of four different binary alloy systems.

[0018] Figure 3 This is the rapidly quenched alloy sheet of Example 1.

[0019] Figure 4 XRD diffraction spectrum of the rapidly quenched alloy of Example 1-6.

[0020] Figure 5 This is the SEM morphology of the horizontal cross section of the quenched strip in Example 1.

[0021] Figure 6 This is the SEM morphology of the longitudinal section of the rapidly quenched ribbon in Example 1.

[0022] Figure 7 The SEM morphology and EDS element distribution diagram of the rapidly quenched alloy. DETAILED DESCRIPTION

[0023] The design concept and mechanism of the present invention are further described in detail with reference to the accompanying drawings, comparative examples and embodiments to make the technical solution of the present invention clearer.

[0024] The key bottlenecks of Ti-Mn based AB2 type alloys for practical applications are difficult activation, high hydrogen absorption / desorption plateau pressure, serious hysteresis and high cost of raw materials. It is found that the activation process includes the removal of the surface protective oxide film, the dissociation of hydrogen molecules on the metal surface, the diffusion of dissociated hydrogen atoms to the alloy interior through the surface and the interaction with the metal to form hydride. Among these steps, the dissolution and removal of the oxide film is usually the most difficult, which generally requires the application of high-pressure hydrogen and / or high temperature for a long time. It is found that the activation process of Ti-Mn based AB2 type alloys is a hydrogen-induced cracking process. These alloys are generally brittle materials. After the introduction of Sc and Zr on the A side and Cr, Fe and Mo elements on the B side, the micro-cracks and lattice stress in Ti-Mn based alloys are increased. These cracks can provide deeper diffusion channels under the action of internal stress and a certain hydrogen pressure, ensuring the initial dissociation and adsorption of hydrogen on the relatively fresh surface at the crack tip, leading to the lattice expansion of the material at the crack tip, followed by the generation of new cracks, the explosive appearance of a large number of fresh surfaces, the accelerated diffusion of hydrogen through the new channels, and then the dissociation and adsorption of hydrogen on the deeper crack surfaces of the alloy. The room temperature activation performance is affected by the reactivity between hydrogen molecules and the surface oxide layer, and the hydrogen reactivity varies according to the composition of the oxide layer. The partial substitution of Ti by Sc and Zr and the partial substitution of Mn by Cr, Fe and Mo changes the composition of the surface oxide layer, promotes the reaction between hydrogen molecules and the oxide layer, accelerates the dissolution and removal of the surface oxide layer, and thus improves the activation performance of the alloy at room temperature. On the composition design, the addition of trace rare earth Sc can significantly improve the activation performance of the alloy, reduce the plateau pressure and improve the plateau characteristics. Since Sc itself is a hydrogen-absorbing element, the addition of Sc is beneficial to improve the hydrogen storage capacity of the alloy, and the alloy has ultra-strong hydrogen activation performance comparable to that of metallic palladium. At the same time, the integrated vacuum induction melting and rapid quenching technology is used to prepare the alloy, which can obtain a special microstructure, so that the alloy has activation performance and plateau characteristics that meet the application requirements of various scenarios such as vehicle fuel cells. The rapid quenching can produce a large lattice stress in the alloy, accelerate the cracking of the alloy during the activation process, promote the formation of a large number of fresh surfaces, and thus greatly improve the activation performance. The excessively high hydrogen absorption plateau pressure of Ti-Mn based AB2 type alloys is another defect that hinders their wide application. It is known that the hydrogen absorption reaction is an exothermic reaction, and the maximum hydrogen absorption capacity of the alloy decreases with the increase of temperature, and the hydrogen absorption / desorption plateau pressure of the alloy increases with the increase of temperature. It is found that with the increase of valence electron concentration, the phase transition of metal hydride is inhibited, and the plateau pressure is increased. This is because in the process of forming hydrogen solid solution, the 1s orbital electrons of hydrogen interact with the electrons on the d orbital of transition metal. When the valence electron concentration increases, the vacancies in the orbital decrease, which increases the energy consumption of the 1s electrons of hydrogen occupying the unoccupied sites in the orbital, thereby increasing the plateau pressure.The present application partially replaces Ti elements on the A side with Sc and Zr, because the atomic radius of Sc and Zr is much larger than that of Ti, so the addition of Sc and Zr increases the lattice constant of the alloy, thus reducing the platform pressure, and the hydrogen storage performance of the alloy is obviously improved. The increase in the unit cell volume reduces the volume expansion and contraction of the alloy during hydrogen absorption and desorption cycles, thereby improving the cycle stability of the alloy. Partially replacing the Mn elements on the B side with Cr, Fe and Mo can significantly improve the comprehensive hydrogen storage performance of the alloy, adjust the hydrogen absorption and desorption platform pressure of the alloy, and make the platform characteristics significantly better, and the hysteresis significantly smaller. When the atomic ratio A / B of the A side and the B side deviates from 1:2, it is called a non-stoichiometric ratio. Research has found that when the A / B atomic ratio changes within a certain range, the alloy can still obtain a single Laves phase structure. Compared with the stoichiometric ratio alloy, the non-stoichiometric ratio alloy has obvious advantages in hydrogen storage capacity. As the non-stoichiometric ratio A / B value increases, the hydrogen storage capacity of the alloy increases, the unit cell volume increases, the platform pressure and the inclination decrease, and the activation performance is obviously improved. This is due to the change of the chemical environment of the interstitial site and the increase of the atomic ratio of the hydrogen absorption elements Ti and Zr. The advantage of the rapid quenching process is to obtain ultra-fine grains, which produces a large number of grain boundaries, providing a channel for hydrogen atom diffusion, and greatly improving the hydrogen absorption and desorption kinetics of the alloy. Due to the extremely fast cooling rate (>1000℃ / s) of rapid quenching, the composition segregation during solidification cooling is inhibited, and the hydrogen storage performance is improved. At the same time, rapid quenching can also increase the unit cell volume of the alloy, increase the platform length, reduce the hydrogen absorption and desorption platform pressure, and reduce the platform hysteresis. In addition, due to the increase of the stress in the lattice of the alloy caused by rapid quenching, the alloy is broken during hydrogen absorption, and the activation performance of the alloy is improved.

[0025] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this application and serve to explain the principles of the embodiments of the present application, but are not intended to limit the scope of the present application.

[0026] The present application discloses a Ti-Zr-Sc-Mn-Cr-Fe-Mo-based AB2-type hydrogen storage alloy, wherein the alloy specifically comprises (Ti 1-x-y Zr x Sc y ) 1.1 Mn 1.15 Cr 0.85-z-m Fe z Mo m , wherein x, y, z, m are atomic ratios, and 0.10≤x≤0.30, 0.01≤y≤0.05, 0.05≤z≤0.15, 0.02≤m≤0.10.

[0027] The functions and content / atomic ratios of each component / element are determined as follows: Ti: In the Ti-Mn-based alloy, the mass ratio of Ti to Mn has a decisive influence on the hydrogen storage performance of the Ti-Mn-based alloy. It is found that when the Ti-Mn alloy has a single C14-type Laves phase, the alloy has good comprehensive hydrogen storage performance. From the Ti-Mn binary phase diagram, Figure 2 a) It can be found that although the Ti / Mn atomic ratio can form a single C14-type Laves structure in a wide range, too high or too low Ti content will cause the hydrogen storage performance of the alloy to decrease sharply. It is found that when the Ti content is less than 36 mol%, the Ti-Mn-based alloy hardly absorbs hydrogen. Only when the Ti content is greater than 36 mol%, the alloy begins to absorb hydrogen. However, the alloy with high Ti content can react with hydrogen without activation treatment at room temperature, but too high Ti content will form α-TiMn phase or even β-Ti phase, which will significantly reduce the hydrogen storage performance of the alloy.

[0028] Zr: In order to improve the hydrogen storage performance of the AB2-type alloy and optimize the hydrogen storage alloy with more excellent performance, the addition of Zr element can change the binding force between hydrogen and metal, thereby improving the hydrogen storage capacity of the alloy. Adjusting the Ti / Zr ratio in the alloy can control the platform pressure of the alloy to meet the requirements of the platform pressure of the application scene. With the increase of Zr content in the alloy, the Ti / Zr ratio decreases, the platform pressure decreases, and the hydrogen storage capacity increases, which is due to the fact that the atomic radius of Zr is larger than that of Ti, and the partial substitution of Ti by Zr increases the cell volume. In addition, since the affinity of Zr for hydrogen is greater than that of Ti, more stable hydride can be formed during hydrogen absorption, so the hydrogen absorption capacity of the alloy increases. It should be noted that from the Zr-Mn binary phase diagram, Figure 2 b) It can be seen that the Zr content in the alloy cannot be too high, and too high Zr content will form ZrMn2 phase in the alloy, which will reduce the reversible hydrogen storage performance of the alloy, especially the activation performance will be significantly reduced.

[0029] Sc: Sc atomic radius (161 pm) is much larger than the atomic radius of Ti, therefore, the addition of Sc makes the unit cell volume significantly increased, thus significantly improving the hydrogen storage capacity and hydrogen absorption and desorption platform pressure of the alloy. Since Sc itself is a hydrogen absorbing element, the addition of Sc helps to improve the hydrogen storage capacity of the alloy. In addition, the appropriate amount of Sc addition can significantly improve the activation performance and anti-poisoning performance of the alloy, and significantly improve the hydrogen absorption and desorption hysteresis effect. Sc is considered to be a very effective catalyst, with a performance comparable to Pd, which can significantly improve the hydrogen absorption and desorption kinetics performance of the alloy. In terms of element selection, the abundance of Sc in the earth's crust is comparable to that of La, and since Sc is much lighter than La-based elements, it plays an irreplaceable role in hydrogen storage materials. The application of Sc in hydrogen storage can promote the development of hydrogen storage alloys and exceed La-based elements in future related applications. It should be noted that due to the large atomic radius of Sc, the solid solubility in the alloy is small, and excessive Sc addition will cause the appearance of impurity phases in the alloy, thereby affecting the hydrogen storage performance of the alloy. In addition, the use of excessive Sc will significantly increase the raw material cost of the alloy.

[0030] Mn: The role of Mn in Ti-Mn-based alloys is to shrink the C14 Laves phase unit cell volume, which can significantly reduce the stability of the hydride phase, thereby meeting the thermodynamics required for solid-state hydrogen storage, allowing Ti-Mn-based AB2-type alloys to reversibly absorb and desorb hydrogen at room temperature. Mn in AB2-type alloys mainly plays a catalytic role, similar to Ni in AB5-type alloys, but the catalytic effect of Mn is much smaller than that of Ni. A sufficient amount of Mn content ensures that the AB2-type alloy has a single Laves phase.

[0031] Cr: Partial replacement of B-side Mn elements with metal elements can significantly improve the hydrogen storage performance of the alloy, and the preferred element is Cr. The important reason why Ti-Mn-based AB2-type alloys have attracted high attention in the field of solid-state hydrogen storage applications is the discovery of the important role of Cr. Cr is located between Ti and Mn in the periodic table, and its atomic radius is 125 pm, while the atomic radius of Mn is 124 pm. After Cr replaces part of the Mn elements, larger voids will be formed in the alloy lattice, which is beneficial to the entry of hydrogen atoms. After Cr replaces part of the Mn elements, the hydrogen absorption and desorption performance of the alloy is improved, the activation incubation period of the alloy is shortened, the hydrogen absorption and desorption rate is increased, and the hydrogen desorption amount is also increased to a certain extent. After Cr replaces part of the Mn elements, the dissociation pressure of the alloy is significantly improved with the increase of Cr content. The most significant effect of Cr addition is to adjust the hydrogen absorption and desorption platform pressure of the alloy, and particularly significantly reduce the hydrogen absorption and desorption hysteresis effect, making the alloy suitable for application in more scenarios. In alloy design, the amount of Cr added needs to be strictly controlled. From the Ti-Cr and Zr-Cr binary phase diagrams ( Figure 2It can be known that the addition of excess Cr can form TiCr2 or ZrCr2 with Ti or Zr, and the appearance of these two phases can significantly reduce the hydrogen storage performance of the alloy, especially the activation performance. It should be noted that Cr itself is not a hydrogen absorbing element, and the addition of excess Cr will reduce the hydrogen storage capacity of the alloy.

[0032] Fe: Fe can replace Mn to improve the hydrogen release kinetics of the alloy, and the combined addition of Fe and Cr can improve the activation performance of the alloy. At the same time, the addition of Fe is considered to improve the microstructure stability of the alloy, thereby significantly improving the cycle stability of the alloy. Fe is considered to improve the composition of the surface oxide of the alloy, improve the reactivity of the surface oxide with hydrogen, and thereby improve the activation performance of the alloy. As an important element in the hydrogen storage alloy, Fe does not affect the hydrogen storage performance by directly reacting with hydrogen, but by adjusting the interaction between metal atoms and hydrogen. Partial substitution of Fe for Cr or Mn will cause the platform pressure to rise and the hydrogen storage capacity to decrease. Therefore, the amount of Fe added needs to be strictly controlled. The addition of Fe reduces the hydrogen absorption capacity of the alloy, which can be understood from the occupation of Fe in the interstitial site of the crystal lattice. It is known that in the hexagonal AB2 Laves phase, hydrogen atoms mainly occupy two interstitial sites [A2B2] and [AB3]. After Fe substitution, the two interstitial sites [A2B2] and [AB3] change from [Ti2Mn2] or [TiMn3] to [Ti2MnFe] and [TiMn2Fe] or [TiMnFe2] or [Ti2Fe2] or [TiFe3]. Since Fe has a weak affinity for hydrogen, these last two sites are free of hydrogen. Therefore, the amount of Fe added must be controlled.

[0033] Mo: Studies have shown that appropriate amounts of Mo addition can improve the activation performance and hydrogen storage capacity of Ti-Mn-based AB2-type alloys, and adjust the platform pressure of the hydrogen absorbing and releasing alloy, and reduce the hydrogen absorbing and releasing hysteresis effect. The combined addition of Mo and Fe has a more significant effect on the performance of the alloy, but excessive Mo will significantly increase the cost of the alloy and reduce the hydrogen storage capacity of the alloy.

[0034] After comparing the activation performance and kinetic performance of a series of alloy parameters, the optimal ratio of x, y, z, and m is x: y: z: m = 0.25: 0.03: 0.10: 0.04. Specifically, the hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50-200 nm. A large number of grain boundaries can provide a fast channel for hydrogen diffusion and provide nucleation sites for hydrogen absorption and release reactions, thereby improving the activation performance and hydrogen absorption and release kinetic performance of the alloy. The substitution of multiple metal elements on the A side and the B side, combined with the rapid quenching process, can achieve the regulation of the hydrogen absorption and release platform.

[0035] Specifically, the Ti-Zr-Sc-Mn-Cr-Fe-Mo-based AB2 type hydrogen storage alloy provided by the application has good activation performance and hydrogen absorption and desorption performance, a hydrogen storage capacity of >1.85 wt.%, adjustable hydrogen absorption and desorption plateau pressure, and the ability to complete activation at one time under the condition of 20 DEG C and 3 MPa. After 200 hydrogen absorption and desorption cycles, the capacity retention rate is >98%. The hydrogen storage alloy can be widely used as a solid-state hydrogen storage material in hydrogen fuel cells and various different scenes.

[0036] The application further provides a preparation method of the hydrogen storage alloy, specifically comprising the following steps: S1: ingredient calculation according to chemical formula composition, wherein the addition amount of Mn and Sc is appropriately burned; S2: placing the prepared raw materials in an Al2O3 crucible, covering the furnace cover, vacuumizing to a preset vacuum degree, then filling high-purity Ar gas with a certain pressure as a protective atmosphere, using an induction heating method to heat the raw materials to a molten state and keep the molten state for a period of time, and obtaining a liquid-state master alloy with uniform composition; S3: directly injecting the liquid-state master alloy into an upper tundish with a narrow long leakage opening at the bottom through a crucible spout, injecting the liquid alloy from the bottom leakage opening of the upper tundish into a lower tundish, and bringing the molten steel uniformly distributed on the bottom plate of the lower tundish to the surface of the lower tundish by a rotating copper roller, and obtaining a rapidly quenched alloy thin strip after rapid cooling.

[0037] The Ti-Zr-Sc-Mn-Cr-Fe-Mo-based AB2 type hydrogen storage alloy and the preparation method thereof provided by the application, in terms of component design, adopt an A-side superstoichiometric ratio, and Sc and Zr are used to partially replace Ti, and Cr, Fe and Mo are used to partially replace Mn, so that the use of the noble metal V is omitted, and the cost of raw materials is significantly reduced. In terms of process preparation, the corresponding technical effects are achieved by a vacuum induction melting-rapid quenching integrated technology. Scientific component design combined with appropriate rapid quenching process can obtain an alloy thin strip with a special structure, and such an alloy has excellent activation performance and good platform characteristics. In particular, the composition segregation in the solidification process is inhibited by rapid quenching treatment, and the grain size of the alloy is greatly reduced due to rapid quenching, a large number of grain boundaries provide good channels for the rapid diffusion of hydrogen atoms in the alloy, so that the activation performance is improved, and the hydrogen absorption and desorption kinetics of the alloy is significantly improved. In addition, rapid quenching can increase the unit cell volume of the alloy and change the stress state in the crystal lattice of the alloy, which is beneficial to adjusting the hydrogen absorption and desorption plateau pressure of the alloy. The complicated process of traditional melting-casting-annealing is omitted, the yield of the alloy is significantly improved, the stability of the product performance is improved, and the preparation cost is further reduced.

[0038] Further, the loss on ignition of Mn and Sc in step S1 is 3-5% of the calculated amount. Since Mn and Sc are volatile elements, an appropriate loss on ignition is needed to ensure that the final alloy composition reaches the preset value. According to experimental verification, it is appropriate to add 3-5% of the calculated amount. Too little loss on ignition will result in insufficient content of the component in the alloy, and too much will result in waste of material and excessive content.

[0039] Further, the placing order and specific operation of the raw materials in step S2 are as follows: the raw materials with clean surfaces are placed in the Al2O3 crucible in proportion, about half of the added amount of sponge Ti is evenly laid on the bottom of the crucible, metal Fe and metal Mo and half of the electrolytic Mn are placed on the sponge Ti, metal Cr, sponge Zr, metal Sc and about half of the sponge Ti are mixed and placed on Fe, Mo and Mn, and about half of the electrolytic Mn is placed on top. The placing order is determined according to the melting point and electromagnetic induction efficiency of the raw materials. This raw material arrangement can effectively improve the efficiency of metal smelting, make the alloy composition more stable, the element distribution more uniform, and the yield of finished products higher.

[0040] Further, the specific operation of melting the raw materials in step S2 is as follows: vacuum extraction is performed to 5x10 -1 Pa or more, high-purity argon gas with a pressure of 0.01-0.1 MPa is filled as a protective gas, and the alloy is melted by a medium-frequency induction heating method with a power increasing process (parameters are shown in Table 1). The specific operation is as follows: smelting for 10 min at 100 kW, then increasing the power by 50 kW every 5 min until the power reaches 550 kW, so that all raw materials are completely melted, the temperature of the molten alloy is controlled at 1550°C and the temperature is maintained for 3-5 min, so that the alloy composition is completely homogenized. The vacuum degree, protective gas and pressure are common technical parameters, and the melting temperature and holding time are determined according to the phase diagram. Under the melting temperature and holding time, the alloy has good fluidity and less volatilization, which can save cost and improve the stability of the alloy composition.

[0041] Further, the rapid quenching operation in step S3 is as follows: the power of the smelting furnace power supply is adjusted to 300 kW, the liquid alloy with a temperature of about 1550°C is directly injected into the upper tundish with a long and narrow leakage hole (200x40 mm) at the bottom, the liquid alloy is injected from the bottom leakage hole of the upper tundish into the lower tundish made of high-temperature mullite, the liquid alloy has good fluidity and uniformly covers the entire bottom plate of the lower tundish, the liquid alloy (about 1400°C) is directly taken to the surface of the copper roller by the rotating copper roller, and the thin strip is separated from the rapid quenching roller under the action of centrifugal force. The linear speed of the copper roller surface is 1-15 m / s, the water inlet amount of the copper roller is ≥36 m 3 / h, water temperature 18-20 ℃. The thin strip separated from the copper roller directly falls on a rotating water cooling bed with a rotation speed of 1 rpm, so that the melt strip continues to be rapidly cooled. When the alloy is cooled to room temperature, the melt strip is obtained, with a thickness of 100-300 μm and a grain size of 50-200 nm.

[0042] The temperature of the liquid alloy on the roller is very critical. If the temperature is much lower than 1400 ℃, the flowability of the liquid alloy is very poor, and the alloy is unevenly distributed at the bottom of the tundish. Another problem of the low temperature of the roller is that the adhesion to the roller is poor when the liquid alloy contacts the melt strip, which greatly reduces the cooling speed of the alloy, so that the ultra-fine crystal structure cannot be obtained. If the temperature of the roller is much higher than 1400 ℃, the viscosity of the alloy is too low, which makes it difficult for the liquid alloy to be separated from the roller, and reduces the performance of the melt strip. Controlling the temperature of the alloy on the roller and the appropriate quenching speed of the roller (i.e. quenching speed) are key technical parameters to ensure that the melt strip has almost complete nanocrystalline structure. Too high quenching speed will result in more amorphous phase in the alloy, which will result in a decrease in hydrogen storage capacity. Too low quenching speed will cause the grain of the alloy to be significantly coarsened, which will affect the uniform distribution of the alloy composition and reduce the activation and hydrogen absorption and desorption kinetic performance. The water inlet quantity and temperature of the copper roller cooling water also need to meet the requirements, otherwise the microstructure of the melt strip will be affected, and the hydrogen storage performance of the alloy will be affected.

[0043] According to the above composition design and preparation method, the specific components of the examples and comparative examples are as follows: Example 1: (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 Example 2: (Ti 0.67 Zr 0.3 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 Example 3: (Ti 0.87 Zr 0.1 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 Example 4: (Ti 0.7 Zr 0.25 Sc0.05 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 Example 5: (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.66 Fe 0.15 Mo 0.04 Example 6: (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.65 Fe 0.1 Mo 0.10 Comparative Example 1: (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 (as-cast) Comparative Example 2: (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 ( melt-cast + 1000°C annealing for 8 h) Comparative Example 3: (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 (15 m / s rapid quenching) Sponge Ti and Zr, rare earth Sc, metal Cr, electrolytic Mn, high-purity Fe and metal Mo were selected according to the chemical formula composition of each example. A special raw material cleaning device was used to remove the oxide layer and impurities on the surface of the raw material. The electrolytic Mn and rare earth Sc were increased by 3%-5% of the burning loss during batching, and the technical parameters of each stage were as follows: the vacuum induction melting furnace was vacuumed to 5x10 -1Pa; then, inert gas Ar is filled into the furnace as protective gas at 0.01-0.1 MPa; the temperature of the liquid alloy is inducted to 1550 ℃; the liquid alloy is kept in the melting state for 3-5 min to make the composition of the alloy fully homogenized; the linear speed of the surface of the water-cooled copper roller is 1-15 m / s.

[0044] It is emphasized that all the process parameters can be properly selected within the above range to prepare the hydrogen storage alloy described in the patent. Therefore, although only one typical example is given in the present application, the example is applicable to the preparation method with different parameters.

[0045] Process technical parameters of Example 1: According to the chemical formula (Ti 0.72 Zr 0.25 Sc 0.03 ) 1.1 Mn 1.15 Cr 0.71 Fe 0.1 Mo 0.04 , bulk sponge Ti and Zr, rare earth Sc, electrolytic Mn, metal Cr, high-purity Fe and metal Mo are selected. The purity of these metals is ≥99.5%, and they are weighed according to the chemical dosage ratio, and each furnace is dosed by 350 kg, wherein the sponge Ti is 76.257 kg, the sponge Zr is 50.462 kg, the rare earth Sc is 3.074, the electrolytic Mn is 130.897 kg, the metal Cr is 74.259 kg, the high-purity Fe is 11.233 kg, and the metal Mo is 7.720 kg. The weighed bulk metals are placed in the Al2O3 crucible of the medium-frequency induction furnace in the designed order, wherein about half of the sponge Ti is evenly laid on the bottom of the crucible, the metal Fe and the metal Mo and half of the electrolytic Mn are placed on the sponge Ti, the metal Cr, the sponge Zr, the rare earth Sc and about half of the sponge Ti are mixed and placed on the Fe, Mo and Mn, and about half of the electrolytic Mn is placed on the top. -1 Pa above, high-purity Ar gas is filled as protective gas until the pressure reaches-0.04 MPa, and the alloy is melted by the power incremental process (the parameters are shown in Table 1), that is, the power source is kept at 100 kW for 10 min, and then the power source is increased by 50 kW every 5 min until the power reaches 550 kW, so that the furnace temperature reaches about 1550 ℃, and the alloy is kept for 3-5 min after all the raw material metals are melted to make the composition uniform.

[0046] After the power of the smelting furnace is adjusted to 300 kW, the liquid alloy (about 1550 °C) is directly injected into the upper tundish with a narrow bottom outlet (200 x 40 mm), and the liquid alloy is injected from the outlet at the bottom of the upper tundish into the lower tundish made of high-temperature mullite. Due to the good flowability of the steel liquid, the lower tundish bottom plate is uniformly covered. The lower tundish bottom plate is in direct contact with the rapid quenching roller, and the high-temperature (about 1400 °C) liquid alloy is brought to the surface of the rotating copper roller, which rotates at a speed of 63 rpm, and the surface linear velocity (quenching speed) is 2 m / s. The alloy thin strip separated from the copper roller falls onto a rotating water-cooled bed, and the water-cooled bed rotates at a speed of 1 rpm. After the alloy is cooled to room temperature, the alloy rapid solidification thin sheet with an average thickness of 215-220 μm is obtained, and the average grain size is about 106 nm.

[0047] The raw materials of Examples 2-6 and Comparative Examples are weighed according to the chemical formula, and the other process parameters are the same as those of Example 1.

[0048] The raw materials of Comparative Examples 1-3 are weighed according to the chemical formula, and the other process parameters are basically the same as those of Example 1, except that the alloy of Comparative Example 1 is induction melted and then cast in a copper mold. Comparative Example 2 is vacuum annealed at 1000 °C for 8 h after casting, and Comparative Example 3 has a quenching speed of 15 m / s.

[0049] The phase structure and phase composition of the rapidly quenched alloy are tested by XRD, the morphology and microstructure of the cross-section and longitudinal section of the rapidly quenched alloy thin strip are observed by scanning electron microscopy (SEM), and the element distribution and energy spectrum of the alloy are tested by SEM and EDS.

[0050] Figure 1 A schematic diagram of the vacuum rapid quenching process.

[0051] Figure 2 Phase diagrams of four different binary alloy systems Vacuum induction melting and rapid quenching integrated furnace. Maximum capacity of the crucible: 800 kg; rated power: 600 kW; limit vacuum degree: 4 x 10 -1 Pa; diameter of the water-cooled copper roller for rapid quenching: 610 mm. Due to the small density of sponge Ti and Zr, the maximum alloy loading capacity of the crucible is 350 kg.

[0052] Figure 3 The rapidly quenched alloy thin sheet of Example 1; the thickness of the randomly selected rapidly quenched physical sheet is in the range of 215-220 μm, which fully meets the design requirements.

[0053] Figure 4XRD diffraction spectrum of the as-quenched alloys of Examples 1-6 was measured. It can be found that the as-quenched alloys have single-phase hexagonal C14-type Laves phase with MgZn2 structure, which is a typical topologically close-packed structure. There is only tetrahedral interstice in the crystal lattice, and the hydride formed is TiMn2H 2.5 The substitution of Zr, Sc, Cr, Fe and Mo does not form new phase, which proves that the element substitution does not exceed its solid solubility in the matrix alloy.

[0054] Figure 5 SEM morphology of the horizontal section of the as-quenched thin ribbon of Examples 1-6 can be found that the as-quenched alloys have almost entirely nanocrystalline structure.

[0055] Figure 6 SEM longitudinal section morphology of the as-quenched ribbon of Examples 1-6 can be found that the longitudinal section of the as-quenched ribbon shows roughly parallel arrangement of columnar crystal structure, which is caused by the temperature gradient in the vertical direction to the roller surface during the rapid quenching. The average grain diameter is about 106 nm.

[0056] Figure 7 SEM morphology and EDS element distribution map and energy spectrum of the as-quenched alloy thin ribbon of Example 1 can be seen that the Ti, Zr, Sc, Mn, Cr, Fe and Mo elements are uniformly distributed, which is due to the fact that the rapid quenching can inhibit the composition segregation during the solidification process and ensure the uniformity of the alloy composition. The element distribution and energy spectrum of different regions of the as-quenched ribbon were tested, and the results showed that there was no obvious composition change between different regions, which cannot be achieved by other preparation processes. It is this uniformity of composition that ensures the excellent hydrogen storage performance of the alloy.

[0057] The hydrogen absorption activation performance, hydrogen storage capacity, hydrogen absorption and desorption kinetics and cycle stability of the as-quenched alloys were tested by using a full-automatic Sieverts device. The hydrogen absorption temperature was 20℃, and the initial hydrogen pressure was 3 MPa; the hydrogen desorption temperature was 20℃, and the hydrogen desorption was carried out at a pressure of 1x10 -4 MPa. S 200 represents the capacity retention rate of the alloy after 200 charge-discharge cycles, i.e. S 200 = C 200 / C max x 100%. C max - saturated hydrogen absorption capacity; C 200 - hydrogen absorption capacity after 200 charge-discharge cycles. The results are shown in Table 2.

[0058] Table 2 Solid-state hydrogen storage performance of the alloys of different examples

[0059] The high-capacity easy-activation AB2 type hydrogen storage alloy provided by the application has good activation performance and hydrogen absorption and desorption performance, the hydrogen storage capacity is greater than or equal to 1.85 wt.%, the hydrogen absorption and desorption plateau pressure is adjustable, and the activation can be completed in one hydrogen absorption and desorption cycle at 20 DEG C and an initial hydrogen pressure of 3 MPa.

[0060] The above results show that the rapidly quenched alloy has excellent activation performance, hydrogen absorption capacity and cycle stability. Obviously, the alloy preparation process of the application is simple and easy to operate, and is completely suitable for large-scale production, and the performance meets the requirements of various application scenarios such as vehicle-mounted fuel cells for hydrogen storage materials. Compared with the same alloys at home and abroad, the hydrogen storage performance of the alloy of the application is significantly improved, and the cost is significantly reduced.

[0061] The above only describes the preferred embodiments of the application and is not used to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A high-capacity, easily activated AB2-type hydrogen storage alloy, characterized in that: The specific composition of the alloy is (Ti 1-x- y Zr x Sc y ) 1.1 Mn 1.15 Cr 0.85-z-m Fe z Mo m , where x , y , z , m is the atomic ratio, 0.10≤x≤0.30, 0.01≤y≤0.05, 0.05≤z≤0.15, 0.02≤m≤0.

10.

2. The hydrogen storage alloy according to claim 1, wherein The atomic ratio of the chemical formula is x : y : z : m = 0.25: 0.03: 0.10: 0.

04.

3. The hydrogen storage alloy according to claim 1, wherein: The hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50 to 200 nm.

4. The hydrogen storage alloy according to claim 1, wherein: The hydrogen storage alloy has a columnar crystal structure arranged substantially in parallel.

5. The hydrogen storage alloy according to claim 1, wherein: The alloy has a single C14 type Laves phase structure.

6. The method for preparing the hydrogen storage alloy according to any one of claims 1 to 5, characterized in that: The specific steps include: S1: The ingredients are prepared according to the chemical formula, and Mn and Sc are added in appropriate amounts of burn-off; S2: Place the prepared raw materials in an Al2O3 crucible, cover the furnace, heat the raw materials to a molten state using a power increase process and keep the temperature for an appropriate time to obtain a liquid master alloy with uniform composition; S3: Liquid master alloy is poured directly into an upper tundish (with a narrow opening at the bottom) through a crucible pouring nozzle. From there, the liquid alloy is poured into a lower tundish (made of high-temperature mullite). The liquid alloy is then carried directly to the surface of a rotating copper roller. Centrifugal force cools and solidifies the alloy, and the resulting alloy flakes separate from the roller. The strips fall onto a rotating water-cooling bed, where they cool to room temperature to form alloy strips with a thickness of 100-300μm.

7. The preparation method according to claim 6, wherein: The amount of Mn and Sc added in step S1 is 3%-5% of the calculated dosage.

8. The preparation method according to claim 6, characterized in that: The order and specific operation of placing the raw materials in step S2 are as follows: about half of the added sponge Ti is evenly spread on the bottom of the crucible, metal Fe and metal Mo and half of the electrolytic Mn are placed on the sponge Ti at intervals, metal Cr, sponge Zr, rare earth Sc and about half of the sponge Ti are mixed and placed on Fe, Mo and Mn, and about half of the electrolytic Mn is placed on the top.

9. The preparation method according to claim 6, wherein: In step S3, the temperature of the liquid alloy upper roller is controlled at about 1400° C., and the surface linear speed of the rotating copper roller is 1-15 m / s.

10. The preparation method according to claim 6, wherein: The rotating copper roller in step S3 is cooled by water, and the water flow rate of the copper roller is ≥36 m 3 / h, water temperature 18-20 degrees Celsius.

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