A preparation method of high performance AB2 type hydrogen storage alloy

Abstract

The present invention relates to the technical field of hydrogen storage materials, and discloses a preparation method of a high-performance AB2-type hydrogen storage alloy, which includes the following steps: (1) mixing various metal raw materials constituting the AB2-type hydrogen storage alloy and then melting to obtain an alloy ingot; (2) crushing the alloy ingot and preparing alloy flakes by strip casting melting; (3) mixing graphene with the alloy flakes and then performing high-energy ball milling to obtain the AB2-type hydrogen storage alloy; wherein the metal raw materials of the hydrogen storage alloy are two or three of Ti, Cr, and Mn; the linear speed of strip casting melting is 5-20 m / s; the rotation speed of high-energy ball milling is 600-900 r / min. The preparation of the present invention significantly reduces the activation temperature of the hydrogen storage alloy, improves the hydrogen absorption / desorption rate and heat transfer coefficient of the hydrogen storage alloy, expands the application scenarios of the AB2-type hydrogen storage alloy, and moreover, the preparation method has a simple process flow, low cost, is conducive to large-scale production, and has good industrial application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen storage materials, and in particular to a method for preparing a high-performance AB2 type hydrogen storage alloy. Background Art

[0002] Hydrogen storage alloys can achieve solid-state storage of hydrogen. The principle is to catalytically decompose hydrogen molecules into hydrogen atoms on the surface of the alloy. After the hydrogen atoms enter the alloy, they occupy the vacant positions in the lattice to form metal hydrides. When the alloy is heated, hydrogen is released in the form of hydrogen molecules, which is manifested as a large amount of hydrogen being absorbed by the metal alloy and stored inside the metal alloy. Common hydrogen storage alloys include AB (TiFe series), AB5 (LaNi5 series), AB2 (TiMn2 series), A2B (Mg2Ni series), BCC (V series), etc. AB2 type hydrogen storage alloys are considered to be one of the most promising hydrogen storage alloys due to their high platform pressure, small enthalpy change during the absorption / desorption of hydrogen, and low cost.

[0003] Hydrogen storage alloys need to be activated before hydrogen storage, that is, the hydrogen storage alloy is exposed to hydrogen at a certain activation temperature and pressure, and then vacuumed, and its ability to absorb and release hydrogen is gradually improved through repeated cycles. The activation temperature of AB2 type hydrogen storage alloys is generally 100-300°C. Although it is significantly lower than AB type, A2B type, and BCC type, it is still 20-100°C higher than AB5 type. The high activation temperature brings technical difficulties to the application of AB2 type hydrogen storage alloys. Most of the research on improving the activation performance of hydrogen storage alloys focuses on rare earth doping to improve its hydrogen absorption / desorption capacity, such as Chinese patents CN106801177A, CN112961996A, etc., but rare earths are easily oxidized, and high melting point rare earth oxides cause low melting Mn to volatilize severely, making smelting more difficult. Therefore, how to reduce the activation temperature of AB2 type hydrogen storage alloys has always been a difficulty in the field of hydrogen storage alloys.

[0004] In addition, AB2 type hydrogen storage alloys also have problems such as easy Ti segregation during the melting process and low heat transfer coefficient after alloy hydrogenation. On the one hand, Ti segregation during the melting process will lead to uneven alloy composition, which seriously affects the effective hydrogen release and cycle stability of the alloy; on the other hand, hydrogen storage alloys are accompanied by heat release and heat absorption during hydrogen absorption and desorption, that is, hydrogen storage alloys release heat when absorbing hydrogen, and need to absorb heat when desorbing hydrogen, such as LaNi5 (AB5 type) hydrogen storage alloy desorption reaction enthalpy change of about -30kJ / mol; AB2 hydrogen storage alloy desorption reaction enthalpy change of about -20kJ / mol, BCC hydrogen storage alloy desorption reaction enthalpy change of about -40kJ / mol. In addition, since the desorption process is an endothermic reaction, with the increase of desorption time, the temperature of the alloy system decreases significantly, resulting in a decrease in the effective desorption of hydrogen. It is usually necessary to heat the alloy system additionally, but the heat transfer coefficient of the alloy after hydrogenation is low (about 1W / (m·K)), and additional heating does not significantly improve the desorption rate of the alloy. Therefore, it is very necessary to further improve the heat transfer coefficient of the alloy. However, there are few reports on the improvement of the heat transfer coefficient of the alloy. Summary of the invention

[0005] In view of the problem that the high activation temperature of AB2 type hydrogen storage alloys affects their application, the purpose of the present invention is to provide a method for preparing high-performance AB2 type hydrogen storage alloys. The prepared AB2 type hydrogen storage alloy has a low activation temperature and can be activated at room temperature, thereby improving the application prospects of AB2 type hydrogen storage alloys.

[0006] The present invention provides the following technical solutions:

[0007] A method for preparing a high-performance AB2 type hydrogen storage alloy comprises the following steps:

[0008] (1) mixing various metal raw materials constituting the AB2 type hydrogen storage alloy and then smelting them to obtain an alloy ingot;

[0009] (2) crushing the alloy ingot and preparing alloy flakes by strip melting;

[0010] (3) The graphene and alloy flakes are mixed and then subjected to high-energy ball milling to obtain an AB2 type hydrogen storage alloy.

[0011] In the technical solution of the present invention, for the AB2 type hydrogen storage alloy, an alloy ingot is first obtained by suspension melting, and then the alloy uniformity is further improved by belt melting and rapid quenching, and alloy flakes that are easy to be crushed by ball milling are obtained, and then high-energy ball milling is performed with graphene with a large specific surface area. The graphene is loaded on the surface of the hydrogen storage alloy powder without changing the crystal structure of the alloy itself, providing a channel for hydrogen atoms to enter and exit the alloy matrix. The AB2 type hydrogen storage alloy obtained in this way can be activated at room temperature, and has a faster hydrogen absorption / desorption rate and a higher heat transfer coefficient. The room temperature mentioned here is not less than 20°C, and further 25°C.

[0012] As a preferred embodiment of the method of the present invention,

[0013] The metal raw materials of the hydrogen storage alloy are two or three of Ti, Cr and Mn;

[0014] The atomic ratio of Ti, Cr and Mn is 1-1.2:0.8-1:1-1.2. The preparation method of the present invention is suitable for preparing hydrogen storage alloys using two or three of Ti, Cr and Mn as raw materials.

[0015] As a preferred embodiment of the method of the present invention, the smelting in step (1) is suspension smelting;

[0016] The power of suspension smelting is 10-20kW;

[0017] The suspension smelting time is 5 to 20 minutes;

[0018] The number of suspension smelting is 3 to 5 times.

[0019] As a preferred embodiment of the method of the present invention, the belt-swinging smelting power in step (2) is 10 to 20 kW;

[0020] The time of belt smelting is 3 to 10 minutes;

[0021] The linear speed of the belt melting is 5 to 20 m / s. The linear speed of the belt melting is one of the key steps to obtain the room temperature activated AB2 type hydrogen storage alloy. The titanium-rich phase in the alloy structure is eliminated by belt melting, so that the alloy structure exists in the form of a uniform C14 Laves phase, and the thin alloy flakes can be fully broken in the high-energy ball milling process and mixed with graphene.

[0022] As a preferred embodiment of the method of the present invention, the mass ratio of graphene to alloy flakes in step (3) is 2 to 5:100.

[0023] As a preferred embodiment of the method of the present invention, the ball-to-material ratio in the high-energy ball milling in step (3) is 20 to 40:1;

[0024] The speed of high energy ball mill is 600~900r / min;

[0025] The time of high energy ball milling is 6 to 12 hours;

[0026] The atmosphere of high-energy ball milling is either argon or nitrogen. High-energy ball milling achieves full crushing of alloy flakes and full mixing with graphene. In this process, controlling the rotation speed of high-energy ball milling is the most critical. If the rotation speed is low, it is difficult for the alloy to mix with the finer-grained graphene, and the sample is severely stratified, which fails to achieve the expected effect.

[0027] As a preferred method of the present invention, the high-energy ball milling is a three-stage variable speed ball milling, and the three-stage ball milling speeds are: 600-700r / min, 800-900r / min, 600-700r / min, and the time is 1-3h, 4-7h, and 1-2h. The mixing effect of graphene and alloy powder is improved by low-speed pre-grinding to break alloy flakes and avoid graphene powder adhesion, high-speed ball milling to fully mix the two, and low-speed buffer ball milling.

[0028] The present invention also provides an AB2 type hydrogen storage alloy obtained by the above preparation method. The AB2 type hydrogen storage alloy can be activated at room temperature, has a faster hydrogen absorption and desorption rate, and has a high heat transfer coefficient.

[0029] The present invention further provides a fuel cell comprising the above AB2 type hydrogen storage alloy.

[0030] The beneficial effects of the present invention are as follows:

[0031] The preparation method of the present invention is aimed at AB2 type hydrogen storage alloys. Through the optimized design of each component, suspension melting, belt melt rapid quenching and high-energy ball milling with graphene, the activation temperature of the hydrogen storage alloy is significantly reduced while maintaining a suitable hydrogen absorption capacity of the hydrogen storage alloy. The hydrogen storage alloy can be activated at room temperature, which solves the technical problems faced by the AB2 type hydrogen storage alloys, and improves the hydrogen absorption / desorption rate and heat transfer coefficient of the hydrogen storage alloy, expanding the application scenarios of the AB2 type hydrogen storage alloys. In addition, the preparation method has a simple process flow, low cost, is conducive to large-scale production, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a SEM scanning electron microscope image of the alloy ingot obtained in step (1) of the present invention.

[0033] Figure 2 This is a SEM scanning electron microscope image of the alloy ingot obtained in step (2) of the present invention.

[0034] Figure 3 It is a mechanism diagram of room temperature activation of the AB2 type hydrogen storage alloy of the present invention.

[0035] Figure 4 It is the activation kinetic curve diagram of the hydrogen storage alloys of Examples 1-2 and Comparative Examples 1-4 at 25°C. DETAILED DESCRIPTION

[0036] The specific implementation modes of the present invention are further described below.

[0037] Unless otherwise specified, the raw materials used in the present invention can be purchased from the market or are commonly used in the art. Unless otherwise specified, the methods in the following embodiments are all conventional methods in the art.

[0038] An embodiment of the present invention provides a method for preparing a high-performance AB2-type hydrogen storage alloy, comprising the following steps:

[0039] (1) mixing various metal raw materials constituting the AB2 type hydrogen storage alloy and then smelting them to obtain an alloy ingot;

[0040] In the embodiment provided by the present invention, the metal raw materials of the hydrogen storage alloy can be two or three of Ti, Cr and Mn; the atomic ratio of Ti, Cr and Mn is 1-1.2:0.8-1:1-1.2, for example, 1:0.8:1, 1:1:1, 1.2:0.8:1, 1.2:1:1.2 or 1:1:1.2, etc. Figure 1 As shown, the obtained alloy ingot contains titanium-rich phase and C14Laves phase, and the internal structure uniformity of the alloy is poor;

[0041] (2) crushing the alloy ingot and preparing alloy flakes by strip melting;

[0042] like Figure 2 As shown, the alloy ingot is subjected to belt melting. By controlling the appropriate melting conditions, on the one hand, fragile flakes are formed, and on the other hand, the rich phase disappears, and the alloy forms a uniform and complete C14 Laves phase;

[0043] (3) mixing graphene and alloy flakes and then subjecting them to high-energy ball milling to obtain an AB2 type hydrogen storage alloy;

[0044] like Figure 3 As shown in Figure 2, under appropriate high-energy ball milling conditions, the alloy flakes are fully broken and fully mixed with graphene. Graphene is loaded on the alloy flakes, especially destroying or incorporating the surface oxide layer, providing a channel for hydrogen atoms to enter the alloy matrix, such as Figure 3 As shown. Based on the combined effect of various factors, the prepared AB2 type hydrogen storage alloy has a room temperature activation temperature.

[0045] In the embodiment provided by the present invention, the smelting in step (1) is suspension smelting.

[0046] Furthermore, the power of the suspension smelting is 10-20 kW, preferably 12 kW, 14 kW, 16 kW, 18 kW or 20 kW.

[0047] Furthermore, the suspension smelting time is 5 to 20 minutes, preferably 6 minutes, 8 minutes, 10 minutes, 12 minutes or 15 minutes.

[0048] Furthermore, the number of suspension smelting is 3 to 5 times, preferably 4 times.

[0049] In the embodiment provided by the present invention, the belt-spinning smelting power in step (2) is 10 to 20 kW, preferably 6 kW, 8 kW, 10 kW, 12 kW or 15 kW.

[0050] Furthermore, the time for strip melting is 3 to 10 minutes, preferably 3 minutes, 4 minutes, 5 minutes, 7 minutes or 10 minutes.

[0051] Furthermore, the linear speed of the belt-spinning smelting is 5 to 20 m / s, preferably 5 m / s, 7 m / s, 10 m / s, 15 m / s or 20 m / s.

[0052] In the embodiment provided by the present invention, the mass ratio of graphene to alloy sheet in step (3) is 2 to 5:100, preferably 2:100, 3:100, 4:100 or 5:100.

[0053] In the embodiment provided by the present invention, the ball-to-material ratio in the high-energy ball milling in step (3) is 20 to 40:1, preferably 20:1, 23:1, 34:1 or 40:1.

[0054] Furthermore, the rotation speed of the high energy ball mill is 600-900 r / min, preferably 600 r / min, 700 r / min, 800 r / min or 900 r / min.

[0055] Furthermore, the time of high energy ball milling is 6 to 12 h, 6 h, 7 h, 8 h or 12 h, etc.

[0056] Furthermore, the atmosphere of high energy ball milling is argon or nitrogen.

[0057] In the embodiment provided by the present invention, an AB2 type hydrogen storage alloy is provided, which is obtained by the above-mentioned preparation method.

[0058] In the embodiment provided by the present invention, a fuel cell comprising the above-mentioned AB2 type hydrogen storage alloy is provided.

[0059] Example 1

[0060] A method for preparing a high-performance AB2 type hydrogen storage alloy, wherein the AB2 type hydrogen storage alloy has a chemical formula of Ti 1.2 CrMn, the preparation method is as follows: (1) in a glove box according to Ti 1.2 The CrMn component was designed and mixed, and then suspension smelting was carried out at 10 kW for 10 min, and the alloy ingot was turned over and smelted three times;

[0061] (2) Mechanically crushing the alloy ingot, then smelting it in a 10 kW belt-spinning smelting furnace for 3 min, and then rapidly quenching the melt at a speed of 10 m / s to obtain alloy flakes;

[0062] (3) The alloy flakes and graphene were mixed in a ratio of 100:5 and placed in a planetary ball mill. In an argon atmosphere, high-energy ball milling was performed for 10 h at a ball-to-material ratio of 30:1 and a rotation speed of 900 r / min to obtain D 50 =300nm hydrogen storage alloy.

[0063] Example 2

[0064] A method for preparing a high-performance AB2 type hydrogen storage alloy, wherein the chemical formula of the AB2 type hydrogen storage alloy is TiCrMn, and the preparation method is as follows: (1) preparing the ingredients in a glove box according to the designed proportion of TiCrMn components, then suspension smelting for 8 minutes under 12 kW conditions, and flipping the alloy ingot to repeat the smelting for 3 times;

[0065] (2) The alloy ingot is mechanically crushed, and then smelted in an 8 kW belt smelting furnace for 4 min, and the alloy flakes are obtained at a melt quenching speed of 20 m / s;

[0066] (3) The alloy flakes and graphene were mixed at a ratio of 100:3, and high-energy ball milling was performed for 8 h in an argon atmosphere at a ball-to-material ratio of 25:1 and a rotation speed of 600 r / min to obtain D 50 =200nm hydrogen storage alloy.

[0067] Example 3

[0068] The difference from Example 1 is that the high-energy ball milling in step (3) is carried out in stages: first ball milling at 600 r / min for 1 h, then ball milling at 900 r / min for 8 h, and then ball milling at 600 r / min for 1 h.

[0069] Comparative Example 1

[0070] Compared with Example 1, only suspension smelting is used, and belt-throwing type melt rapid quenching is not used.

[0071] Comparative Example 2

[0072] Compared with Example 1, the ball milling speed in step (3) is 400 r / min.

[0073] Comparative Example 3

[0074] Compared with Example 1, high-energy ball milling is performed alone in step (3) without adding graphene.

[0075] Comparative Example 4

[0076] Compared with Example 1, the belt-spinning speed in step (2) is 3 m / s.

[0077] The hydrogen storage performance and heat transfer coefficient of the hydrogen storage alloys obtained by the preparation methods of the above embodiments and comparative examples were tested. Figure 1 As shown in Table 1, Figure 1 Activation kinetic curves of various hydrogen storage alloys when activated at 25°C.

[0078] Table 1 shows the hydrogen storage performance and heat transfer coefficient of each hydrogen storage alloy

[0079]

[0080]

[0081] from Figure 1 As can be seen from Table 1, the maximum hydrogen absorption capacity of the hydrogen storage alloys prepared in the embodiments and comparative examples is basically similar, but the hydrogen storage alloys obtained in Examples 1 to 3 can all be activated at room temperature of 25°C, and the heat transfer coefficient is also significantly improved.

[0082] Compared with Example 1, Comparative Example 1 cannot be activated at 25°C, and the required activation temperature is 200°C. This is because the conventional cooling speed is slow, which leads to the segregation of Ti during the cooling process, making the composition uneven; in addition, due to the high hardness of the hydrogen storage alloy itself, the conventionally cooled cast alloy is more difficult to ball mill than the alloy flakes obtained by belt spinning, and it is difficult to obtain the expected particle size, especially when mixed with finer-grained graphene, the sample is severely stratified, resulting in the alloy requiring high-temperature activation at 200°C, and the hydrogen absorption rate and heat transfer coefficient are also lower than those of the melt quenching.

[0083] Compared with Example 1, Comparative Example 2 cannot be activated at 25°C, and the conventional activation temperature is 150°C. This is because the hydrogen storage alloy itself has a large hardness, and the low ball milling speed makes it difficult for the alloy to mix with the finer-grained graphene. The sample is severely stratified and does not achieve the expected effect. The alloy needs high-temperature activation, and the heat transfer coefficient of the alloy cannot be significantly improved.

[0084] Compared with Example 1, Comparative Example 3 cannot be activated at 25°C, and the conventional activation temperature is 200°C. This is because no graphene is added to provide a channel for hydrogen atoms to enter the alloy matrix. In addition, since the heat transfer coefficient of the hydrogen storage alloy is low after hydrogenation (0.9W / (m·K)), even on the basis of an external power supply, the dehydrogenation process of the alloy cannot effectively transfer heat due to a large amount of heat absorption, resulting in a low temperature of the alloy system, and thus unable to effectively dehydrogenate at low temperatures.

[0085] Compared with Example 1, Comparative Example 4 cannot be activated at 25° C., and the conventional activation temperature is 150° C. This is because the belt spinning speed is low, resulting in a thicker alloy sheet, poor ball milling effect, and no significant improvement in the performance of the alloy system.

[0086] It can be seen from the above embodiments and comparative examples that the preparation method of the present invention prepares an AB2 type hydrogen storage alloy with excellent performance, room temperature activation and high thermal conductivity through suspension melting, belt melting, graphene doping and high-energy ball milling. The alloy can be activated at a temperature not exceeding 30°C, the maximum hydrogen absorption capacity of the hydrogen storage alloy is ≥1.8wt%, the thermal conductivity is not less than 2W / (m·K), and the saturated hydrogen absorption time is not more than 120s. At the same time, the preparation method of the present invention has a simple process flow, low cost, is conducive to large-scale production, and has good industrial application prospects.

Claims

1. A method for preparing a high-performance AB2 type hydrogen storage alloy, characterized in that: The following steps are involved: (1) Mixing various metal raw materials constituting a high-performance AB2 type hydrogen storage alloy and then smelting them to obtain an alloy ingot; the metal raw materials are two or three of Ti, Cr, and Mn, and the atomic ratio of Ti, Cr, and Mn is 1-1.2:0.8-1:1-1.2; (2) crushing the alloy ingots and preparing alloy flakes by belt melting at an online speed of 5 to 20 m / s; (3) After mixing graphene and alloy flakes, high-energy ball milling is performed at a speed of 600-900 r / min to obtain a high-performance AB2 type hydrogen storage alloy.

2. The method for preparing the high performance AB2 type hydrogen storage alloy according to claim 1, characterized in that: The smelting in step (1) is suspension smelting; The power of suspension smelting is 10-20kW; The suspension smelting time is 5 to 20 minutes; The number of suspension smelting is 3 to 5 times.

3. The method for preparing the high performance AB2 type hydrogen storage alloy according to claim 1, characterized in that: The belt-swinging smelting power in step (2) is 10 to 20 kW; The time for belt melting is 3 to 10 minutes.

4. The method for preparing the high performance AB2 type hydrogen storage alloy according to claim 1, characterized in that: In step (3), the mass ratio of graphene to alloy flakes is 2 to 5:

100.

5. The method for preparing a high performance AB2 type hydrogen storage alloy according to claim 1 or 4, characterized in that: In step (3), the ball-to-material ratio of high-energy ball milling is 20 to 40:1; The time of high-energy ball milling is 6 to 12 h; The atmosphere of high energy ball milling is argon or nitrogen.

6. The method for preparing the high performance AB2 type hydrogen storage alloy according to claim 5, characterized in that: The high energy ball mill is a three-stage variable speed ball mill. The three-stage ball mill speeds are: 600-700 r / min, 800-900 r / min, 600-700 r / min, and the time is 1-3h, 4-7h, and 1-2h.

7. A high performance AB2 type hydrogen storage alloy obtained by the preparation method as described in any one of claims 1 to 6.

8. A fuel cell comprising the high performance AB2 type hydrogen storage alloy as claimed in claim 7.

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