Ti-Fe-Ce-Mn-Zr-Al-Co based hydrogen storage alloy easy to activate and preparation method thereof

Abstract

The invention relates to a Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy and a preparation method thereof, belongs to the technical field of hydrogen storage alloy materials, and solves at least one of the problems of high activation condition, long activation period, poor hydrogen absorption and desorption performance and the like of the traditional TiFe hydrogen storage alloy in the prior art. The invention provides a Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy which is characterized in that the specific composition of the alloy is Ti < 1.05 > Ce < 0.05 > Fe < 1.15-x-y-z-m > Mn < x > Zr < y > Al < z > Com, x, y, z and m are atomic ratios, x is larger than or equal to 0.1 and smaller than or equal to 0.25, y is larger than or equal to 0.05 and smaller than or equal to 0.2, z is larger than or equal to 0.02 and smaller than or equal to 0.1, and m is larger than or equal to 0.02 and smaller than or equal to 0.1. The hydrogen storage alloy has good activation performance and hydrogen absorption and desorption performance, the hydrogen storage capacity is larger than or equal to 1.70 wt.%, the hydrogen absorption plateau pressure is larger than or equal to 0.41 MPa, and the hydrogen desorption plateau pressure is larger than or equal to 0.31 MPa; activation can be completed at a time under the conditions that the temperature is 30 DEG C and the initial hydrogen pressure is 3 MPa, and the solid hydrogen storage material can be widely applied to hydrogen fuel cells and other scenes as a solid hydrogen storage material.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage alloy materials, and relates to a Ti-Fe-Mn-Zr-Al-Co-based hydrogen storage alloy and a preparation method thereof, and particularly relates to an easily activated Ti-Fe-Mn-Zr-Al-Co-based hydrogen storage alloy and a preparation method thereof. Background Art

[0002] In recent years, fuel cell vehicles (FCVs) powered by hydrogen have been considered a viable technology to address the environmental and energy problems caused by the excessive consumption of fossil fuels. At present, lightweight high-pressure hydrogen storage tanks (35 MPa) are one of the main technologies for on-vehicle hydrogen storage in fuel cell vehicles. On the other hand, hydrogen fuel cells require high-purity hydrogen. Therefore, the development of efficient hydrogen purification and compression technologies is of great significance. As is well known, hydrogen storage alloys have the dual functions of purifying and compressing hydrogen. Therefore, metal hydride hydrogen compressors (MHHCs) have many advantages compared with traditional compressors. For example, it combines compression and purification functions, covers a wide pressure range, allows quiet operating conditions, and promotes the utilization of low-grade energy. For metal hydride hydrogen production compressors, it is desirable for the hydrogen storage alloy to have a large hydrogen storage capacity, good pressure plateau characteristics, good activation and kinetic characteristics. Most of the reported hydrogen storage alloys in the literature are AB5-type alloys.

[0003] Among all solid-state hydrogen storage materials, TiFe alloy has the advantages of high capacity, being able to absorb and release hydrogen at room temperature, low cost, and rich resources, and is the most attractive and promising hydrogen storage candidate material. Therefore, a large number of researchers at home and abroad have systematically studied its hydrogen absorption performance.

[0004] Up to now, the existing TiFe hydrogen storage alloys in the prior art still generally have problems such as high activation conditions (i.e., difficult to activate at room temperature), long activation periods, and poor hydrogen absorption and release performance. Summary of the Invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide an easily activated Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy and a preparation method thereof to solve at least one of the problems of high activation conditions (i.e., difficult to activate at room temperature), long activation periods, and poor hydrogen absorption and release performance of the existing TiFe hydrogen storage alloys.

[0006] The present invention discloses a Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy, and the specific composition of the alloy is Ti 1.05 Ce 0.05 Fe 1.15-x-y-z-m Mn x Zr y Al z Co m, where x, y, z, and m are atomic ratios, and 0.1 ≤ x ≤ 0.25, 0.05 ≤ y ≤ 0.2, 0.02 ≤ z ≤ 0.1, 0.02 ≤ m ≤ 0.1.

[0007] Preferably, the ratio of x:y:z:m is x:y:z:m = 0.15:0.1:0.05:0.05.

[0008] Specifically, the hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50 - 200 nm, and there are grain boundary and phase boundary defects.

[0009] Specifically, the hydrogen storage alloy has a multiphase structure and contains TiFe phase, ZrMn2 phase, CeCo2 phase, and Al4Mn phase.

[0010] The present invention also provides a preparation method of the hydrogen storage alloy, which specifically includes the following steps:

[0011] S1: Weigh the raw materials according to the chemical formula composition, and add an appropriate burning loss amount for Mn and Ce;

[0012] S2: Place the prepared raw materials in a zirconia crucible, cover the furnace lid, heat the raw materials to the molten state and keep them warm for a period of time, then pour the liquid alloy into a copper casting mold to obtain a master alloy ingot;

[0013] S3: Mechanically crush the master alloy ingot and screen it. Ball mill the alloy powder after screening to obtain the finished hydrogen storage alloy powder.

[0014] Furthermore, the burning loss amount of Mn and Ce added in step S1 is 8% - 10% of the calculated dosage.

[0015] Furthermore, the placement order and specific operation of each raw material in step S2 are as follows: Place the pure iron rod vertically along the crucible wall. The order of adding other metal raw materials is as follows: Place the massive rare earth Ce at the bottom of the crucible, place the sponge Ti and Zr above the rare earth Ce, place the metal Co on the sponge Ti and Zr, place the electrolytic Mn on the metal Co, and place the electrolytic Al on the top.

[0016] Furthermore, the specific operation of melting the raw materials in step S2 is as follows: Evacuate to 1×10 -2 ~5×10 -5 Pa, then fill with pure argon gas at a pressure of 0.01 - 0.1 MPa as the protective gas, and the melting temperature is 1550 - 1650 °C and keep it warm for 3 - 5 minutes.

[0017] Furthermore, the screening operation in step S3 is to screen the alloy fragments after mechanical crushing through a 200 - mesh sieve, obtain alloy powder with a diameter ≤ 75 μm, and then conduct ball milling.

[0018] Further, the ball milling operation in step S3 is specifically as follows: Load the alloy powder and stainless steel grinding balls into a stainless steel ball milling tank, evacuate and then fill with high-purity argon gas, and ball mill in an all-round planetary high-energy ball mill for 0.5 - 2 h, with a ball-to-material ratio of 1:18 - 22 and a rotation speed of 300 - 400 revolutions per minute.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] 1. The Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy provided by the present invention has low activation conditions, a short activation period, and good hydrogen absorption and desorption performance.

[0021] The present invention combines chemical modification (formula optimization) and microstructure improvement (smelting + short-time ball milling). First, transition elements Ce, Mn, Zr, Al, and Co elements are added to the TiFe alloy, and an excessive amount of Ti element is added. While generating the TiFe phase, α-Ti or β-Ti phases are generated, significantly reducing the fracture toughness of the TiFe alloy and generating a large number of defects such as grain boundaries and phase boundaries, providing a fast channel for hydrogen diffusion; Multi-element alloying can significantly improve the activation performance of the TiFe alloy. In particular, adding a small amount of rare earth Ce can significantly improve the activation performance of the alloy while maintaining the hydrogen absorption capacity, significantly shortening the incubation time during alloy activation. This is because rare earth elements are prone to form rare earth hydrides CeH 2.73 , becoming the catalytic active center of the alloy; The substitution of Fe by Ti and Mn results in an increase in the unit cell volume of the TiFe phase, improving the hysteresis of the alloy and reducing the plateau pressure, and can also improve the activation performance; The addition of Zr significantly improves the activation performance and plateau characteristics of the TiFe alloy; The addition of Al can cause more defects in the crystal lattice; 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 substitution of Fe by Co changes the composition of the surface oxide layer, which is beneficial to the activation of the alloy at room temperature.

[0022] Then, the as-cast sample is ball milled for a short time, improving its microstructure, overcoming the drawbacks of the Ti-Fe-based hydrogen storage alloy and retaining its advantages, resulting in a significant improvement in the comprehensive performance of the novel hydrogen storage alloy. Mechanical ball milling significantly reduces the grain size of the alloy and forms a large number of crystal defects, increasing the hydrogen nucleation points and diffusion channels, further reducing the thermal stability of the hydride and improving the hydrogen absorption and desorption kinetic performance of the alloy.

[0023] The Ti-Fe-Ce-Mn-Zr-Al-Co based hydrogen storage alloy provided by the present invention has good activation performance and hydrogen absorption and desorption performance, with a hydrogen storage capacity of ≥1.70wt.%, a hydrogen absorption platform pressure of ≥0.41MPa, and a hydrogen desorption platform pressure of ≥0.31MPa; the activation can be completed at one time under the conditions of 30°C and 3MPa.

[0024] 2. The hydrogen storage alloy provided by the present invention has a multiphase structure. In addition to the main phase TiFe phase, there are also intermetallic compounds such as ZrMn2 phase, CeCo2 phase and Al4Mn phase (see Figure 1 and Figure 3 ); among them, Zr and Mn can form ZrMn2 phase, Ce and Co can form CeCo2 phase, Al and Mn can form Al4Mn phase, these intermetallic compounds significantly improve the activation ability of the alloy and increase the hydrogen storage capacity. The ratio of each phase is TiFe: ZrMn2: CeCo2: Al4Mn = 0.75-0.85: 0.06-0.08: 0.02-0.03: 0.01-0.015. ZrMn2 phase can combine with hydrogen to form ZrMn2H3, improving the hydrogen storage capacity of the alloy; CeCo2 phase can inhibit the formation of Ti2Fe and TiFe2 phases; Al4Mn phase can produce more defects, providing channels for the entry of hydrogen.

[0025] In addition, thanks to the unique composition design of the alloy, the polycrystalline structure formed by multiple elements causes a higher defect density in the alloy, providing a fast channel for hydrogen diffusion and reducing the conditions for hydrogen absorption and desorption reactions.

[0026] 3. The hydrogen storage alloy preparation method provided by the present invention has a simple process flow, and the raw materials and equipment are easily available. The process conditions are relatively mild, and the operation difficulty is relatively low, which is suitable for large-scale production and wide promotion. Furthermore, the preparation method provided by the present invention can better introduce crystal defects into the hydrogen storage alloy by optimizing the process parameters and specific operations, increase the nucleation points and diffusion channels of hydrogen, and significantly improve the surface state of the alloy, further reduce the thermal stability of the alloy and improve its hydrogen absorption and desorption kinetics.

[0027] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0029] Figure 1 XRD diffraction patterns of as-cast alloys in Examples 1 - 6;

[0030] Figure 2 SEM micrographs of ball-milled alloy powders in Examples 1 - 6;

[0031] Figure 3 XRD patterns of ball-milled alloy powders in Examples 1 - 6;

[0032] Figure 4 HRTEM micrographs of ball-milled alloys in Examples 1 - 6 (red line segments indicate lattice defect positions). Detailed implementation manners

[0033] The following will specifically describe the preferred embodiments of the present invention in conjunction with the accompanying drawings, where the accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, and are not used to limit the scope of the present invention.

[0034] The present invention discloses a Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy, and the specific composition of the alloy is Ti 1.05 Ce 0.05 Fe 1.15-x-y-z-m Mn x Zr y Al z Co m , where x, y, z, and m are atomic ratios, and 0.1 ≤ x ≤ 0.25, 0.05 ≤ y ≤ 0.2, 0.02 ≤ z ≤ 0.1, 0.02 ≤ m ≤ 0.1.

[0035] The functions and the determination basis of the contents / atomic ratios of each component / element are as follows:

[0036] Ti and Fe: In the TiFe alloy, the mass ratio of Ti to Fe has a significant impact on the hydrogen storage performance of the TiFe alloy. When the Ti content is less than 49.5%, while the TiFe phase is formed, an iron-rich TiFe2 phase will be formed. The TiFe2 phase does not absorb hydrogen, so the hydrogen storage capacity of the iron-rich TiFe-based hydrogen storage alloy is significantly low. When the Ti content is between 49.5% and 52.5%, a uniform TiFe phase is formed. When the Ti content is greater than 52.5%, while the TiFe phase is formed, an α-Ti or β-Ti phase will be formed. α-Ti or β-Ti reacts with hydrogen to form titanium hydrides such as TiH and TiH2. Therefore, the alloy rich in Ti has a significantly higher hydrogen storage capacity during the first activation hydrogen absorption. However, titanium hydrides are difficult to decompose at low temperatures. Therefore, during the cyclic hydrogen absorption and desorption at room temperature, the stable hydrogen absorption capacity is significantly lower than the hydrogen absorption amount during the first activation. However, the presence of the α-Ti or β-Ti phase will significantly reduce the fracture toughness of the TiFe alloy, causing the sample to crack faster in a hydrogen atmosphere. These cracks provide an interface for the nucleation and growth of hydrides, thus significantly improving the activation performance of the TiFe alloy.

[0037] Ce: Multi-element alloying can significantly improve the activation performance of the TiFe alloy. In particular, adding a small amount of rare earth Ce can significantly improve the activation performance of the alloy while maintaining the hydrogen storage capacity, and significantly shorten the incubation time during alloy activation. This is because rare earth elements are prone to form rare earth hydrides CeH 2.73 , becoming the catalytic active center of the alloy;

[0038] Mn: The substitution of Fe by Ti and Mn results in an increase in the unit cell volume of the TiFe phase. It improves the hysteresis of the alloy, reduces the plateau pressure, and can improve the activation performance;

[0039] Zr: The addition of Zr significantly improves the activation performance and plateau characteristics of the TiFe alloy;

[0040] Al: The addition of Al can cause more defects in the lattice; 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;

[0041] Co: The substitution of Fe by Co changes the composition of the surface oxide layer, which is beneficial to the activation of the alloy at room temperature.

[0042] In the present invention, by combining chemical modification (formulation optimization) and microstructure improvement (smelting + short-time ball milling), first, transition elements Ce and elements Mn, Zr, Al, and Co are added to the TiFe alloy, and an excessive amount of Ti element is added, so that while the TiFe phase is formed, an α-Ti or β-Ti phase is formed, significantly reducing the fracture toughness of the TiFe alloy and generating a large number of defects such as grain boundaries and phase boundaries, providing a fast channel for the diffusion of hydrogen.

[0043] By comparing the activation performance and kinetic performance of alloy materials with a series of parameters, it was found that the most preferred ratio of x, y, z, and m is x:y:z:m=0.15:0.1:0.05:0.05.

[0044] Specifically, the hydrogen storage alloy has a nanocrystalline structure, an average grain size of 50 to 200 nm, and has grain boundary and phase boundary defects ( Figure 4 The red dotted line in the middle is the position of the lattice defect). The presence of a large number of nanocrystals and crystal defects can effectively inhibit the growth of grains during the process of hydrogen absorption and desorption, provide a fast channel for hydrogen diffusion, and provide nucleation sites for hydrogen absorption and desorption reactions, thereby improving the activation performance and hydrogen absorption and desorption kinetics of the alloy.

[0045] The hydrogen storage alloy provided by the present invention has a multiphase structure. In addition to the main phase TiFe phase, there are also intermetallic compounds such as ZrMn2 phase, CeCo2 phase and Al4Mn phase (see Figure 1 and Figure 3 ); among them, Zr and Mn can form ZrMn2 phase, Ce and Co can form CeCo2 phase, Al and Mn can form Al4Mn phase, these intermetallic compounds significantly improve the activation ability of the alloy and increase the hydrogen storage capacity. The ratio of each phase is TiFe: ZrMn2: CeCo2: Al4Mn = 0.75-0.85: 0.06-0.08: 0.02-0.03: 0.01-0.015. ZrMn2 phase can combine with hydrogen to form ZrMn2H3, improving the hydrogen storage capacity of the alloy; CeCo2 phase can inhibit the formation of Ti2Fe and TiFe2 phases; Al4Mn phase can produce more defects, providing channels for the entry of hydrogen.

[0046] Specifically, the Ti-Fe-Ce-Mn-Zr-Al-Co based hydrogen storage alloy provided by the present invention has good activation performance and hydrogen absorption and desorption performance, with a hydrogen storage capacity of ≥1.70wt.%, a hydrogen absorption platform pressure of ≥0.41MPa, and a hydrogen desorption platform pressure of ≥0.31MPa; activation can be completed at one time under the conditions of 30°C and 3MPa, and can be widely used as a solid hydrogen storage material in scenarios such as hydrogen fuel cells.

[0047] The present invention also provides a method for preparing the hydrogen storage alloy, which specifically comprises the following steps:

[0048] S1: The dosage is calculated according to the chemical formula composition, and the appropriate amount of burn-off of Mn and Ce is added;

[0049] S2: placing the prepared raw materials in a zirconia crucible, covering the furnace cover, heating the raw materials to a molten state and keeping the temperature for a period of time, then pouring the liquid alloy into a copper casting mold to obtain a master alloy ingot;

[0050] S3: Mechanically crush and screen the master alloy ingot, and ball mill the screened alloy powder to obtain the finished hydrogen storage alloy powder.

[0051] The Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy and its preparation method provided by the present invention achieve the corresponding technical effects through the method of "composition design + mechanical ball milling". Scientific composition design combined with appropriate ball milling process can obtain alloy powder with special structure, so that the alloy can maintain excellent activation performance in air medium for a long time. By mechanical ball milling, the grain size of the alloy is greatly reduced. At the same time, the grain boundary and defect density of the alloy are greatly increased, which provides a diffusion channel for the rapid diffusion of hydrogen atoms inside the alloy. Therefore, while improving the activation performance, the hydrogen absorption / desorption kinetics of the alloy is significantly improved.

[0052] Further, the burning loss of Mn and Ce added in step S1 is 8% - 10% of the calculated dosage. Since elements such as Mn and Ce are volatile, it is necessary to add an appropriate burning loss amount additionally to ensure that the final alloy composition reaches the preset value. According to experimental verification, when the burning loss amount is 8% - 10% of the calculated dosage, it is appropriate. Too little burning loss amount will lead to insufficient content of this component in the alloy; too much will lead to material waste and excessive content.

[0053] Further, the placing order and specific operations of each raw material in step S2 are as follows: the pure iron rod is placed vertically along the crucible wall, and the adding order of other metal raw materials is as follows: the massive rare earth Ce is placed at the bottom of the crucible, the sponge Ti and Zr are placed above the rare earth Ce, the metal Co is placed on the sponge Ti and Zr, the electrolytic Mn is placed on the metal Co, and the electrolytic Al is placed on the top. This placing order is determined according to the melting point and solid solubility of the metals, which can make the metals melt in the order of Fe, Ce, Ti, Zr, Co, Mn, Al in turn, effectively reducing the burning loss of elements such as Mn and Ce, making the alloy composition more stable and the element distribution more uniform.

[0054] Further, the specific operation of melting the raw materials in step S2 is: evacuate to 1×10 -2 ~5×10 -5 Pa, then fill with pure argon gas with a pressure of 0.01 - 0.1 MPa as the protective gas, and the melting temperature is 1550 - 1650 °C and keep it warm for 3 - 5 minutes. Among them, the vacuum degree, protective gas and pressure are common technical parameters, and the melting temperature and heat preservation time are determined according to the phase diagram. At this melting temperature and heat preservation time, the alloy can be in a molten state, and the volatilization amount is less, which can save costs and improve the stability of the alloy composition.

[0055] Further, the screening operation in step S3 is to screen the alloy fragments after mechanical crushing through a 200-mesh sieve. After obtaining alloy powder with a diameter ≤ 75 μm, ball milling is carried out. Selecting this particle size can not only ensure the ball milling effect but also reduce the cost of mechanical crushing.

[0056] Further, the ball milling operation in step S3 is specifically as follows: Load the alloy powder and stainless steel grinding balls into a stainless steel ball milling tank, evacuate and then fill with high-purity argon gas, and carry out ball milling in an all-round planetary high-energy ball mill for 0.5 - 2 h, with a ball-to-material ratio of 1:18 - 22 and a rotation speed of 300 - 400 revolutions per minute. The setting of the ball milling parameters here can not only ensure the ball milling effect but also shorten the ball milling time and reduce the ball milling cost. If the ball milling time is extended, the ball-to-material ratio is increased, or the ball milling rotation speed is increased, an excessive amount of amorphous phase will appear in the alloy, reducing the hydrogen storage capacity and hydrogen storage kinetic performance of the alloy; if the ball milling time is shortened, the ball-to-material ratio is reduced, or the ball milling rotation speed is reduced, the grain size in the alloy will increase and the defect density will decrease, damaging the hydrogen storage kinetic performance of the alloy.

[0057] According to the above composition design and preparation method, the present invention sets the specific compositions of the examples and comparative examples as follows:

[0058] Example 1: Ti 1.05 Ce 0.05 Fe 0.8 Mn 0.15 Zr 0.1 Al 0.05 Co 0.05

[0059] Example 2: Ti 1.05 Ce 0.05 Fe 0.85 Mn 0.1 Zr 0.1 Al 0.05 Co 0.05

[0060] Example 3: Ti 1.05 Ce 0.05 Fe 0.7 Mn 0.25 Zr 0.1 Al 0.05 Co 0.05

[0061] Example 4: Ti 1.05 Ce 0.05 Fe 0.7 Mn 0.15 Zr 0.2 Al 0.05 Co 0.05

[0062] Example 5: Ti 1.05 Ce0.05 Fe 0.75 Mn 0.15 Zr 0.1 Al 0.1 Co 0.05

[0063] Example 6: Ti 1.05 Ce 0.05 Fe 0.75 Mn 0.15 Zr 0.1 Al 0.05 Co 0.1

[0064] Comparative Example 1: Ti 1.1 Fe 0.8 Mn 0.2 (As-cast)

[0065] Select rare earth metal Ce, sponge Ti and Zr, high-purity Fe, metal Co, electrolytic Mn and metal Al according to the chemical formula composition of each example. The surface oxide layer of the high-purity iron rod is removed by sanding. An 8-10 wt.% burn loss is added to rare earth metal Ce and electrolytic Mn during batching. The technical parameters at each stage are as follows: The vacuum induction melting furnace is evacuated to 1×10 -2 ~5×10 -5 Pa before heating; then an inert gas argon with a pressure of 0.01-0.1 MPa is filled into the furnace as the protective gas; the temperature during induction heating is 1550-1650 °C; the liquid alloy is kept at a molten state for 3-5 minutes; the ingot alloy is mechanically crushed and then passed through a 200-mesh sieve, with a particle size of about 75 μm. The alloy powder and stainless steel grinding balls are loaded into a stainless steel ball milling tank and ball milled for 0.5-2 hours with a ball-to-material ratio of 1:18-22 and a rotation speed of 300-400 revolutions per minute.

[0066] It should be emphasized that all process parameters can be appropriately selected within the above ranges to prepare the hydrogen storage alloy powder described in the patent. Therefore, although only a typical example is given in the present invention, this example is applicable to preparation methods with different parameters.

[0067] Process technical parameters of Example 1:

[0068] According to the chemical formula Ti 1.05 Ce 0.05 Fe 0.8 Mn 0.15 Zr 0.1 Al 0.05 Co 0.05, bulk rare earth metal Ce, sponge Ti and Zr, pure Fe, electrolytic Mn, metal Co and Al were selected. The purity of these metals was 99.5%. They were weighed according to the stoichiometric ratio. Among them, sponge Ti was 406.6 g, sponge Zr was 73.8 g, pure Fe was 361.5 g, rare earth Ce was 59.5 g, metal Co was 23.8 g, electrolytic Mn was 70.0 g, and metal Al was 10.9 g. The weighed bulk metals were placed in a zirconia crucible of an intermediate frequency induction furnace according to the designed process. The pure iron rod was placed vertically along the crucible wall. The massive rare earth Ce was placed at the bottom of the crucible. Sponge Ti and Zr were placed above rare earth Ce. Metal Co was placed on sponge Ti and Zr. Electrolytic Mn was placed on metal Co. Electrolytic Al was placed on the top. Then the furnace lid was covered, and it was evacuated for about 30 minutes until the vacuum degree reached above 5×10 -2 Pa, and then high-purity argon protective gas was filled until the air pressure reached -0.04 MPa. The heating temperature was adjusted to about 1650 °C to melt all the raw material metals. The molten liquid metal was kept warm for 5 minutes to make it uniform. Subsequently, the uniformly mixed liquid metal was poured into a cylindrical copper mold with a diameter of 30 mm and a depth of 80 mm. After cooling to room temperature in the furnace, it was taken out to obtain the master alloy ingot.

[0069] The alloy Ti 1.05 Ce 0.05 Fe 0.8 Mn 0.15 Zr 0.1 Al 0.05 Co 0.05 After the ingot was mechanically crushed and passed through a 200-mesh sieve, 20 g of the sieved alloy powder and 400 g of stainless steel grinding balls were loaded into a 250-ml stainless steel ball milling jar together. It was evacuated and filled with high-purity argon and then sealed. It was ball milled in an all-round planetary high-energy ball mill for 45 minutes.

[0070] The raw materials of Examples 2 to 6 and the comparative example were weighed according to the chemical formula, and the other preparation process parameters were the same as those in Example 1.

[0071] The phase structure of the as-cast and ball-milled powders was tested by XRD. The morphology and microstructure of the ball-milled alloy particles were observed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), and the crystal state of the alloy was determined by selected area electron diffraction (SAED).

[0072] Figure 1The XRD diagrams of the cast alloys of Examples 1 to 6 show that the alloys have a multiphase structure when rare earth Ce and metal elements Mn, Zr, Co and Al are added for alloying. In addition to the main phase TiFe, there are also intermetallic compounds such as ZrMn2 phase, CeCo2 phase and Al4Mn phase. The ratio of each phase is TiFe: ZrMn2: CeCo2: Al4Mn = 0.8: 0.06875: 0.025: 0.0125.

[0073] Figure 2 The SEM morphologies of the ball-milled alloys of Examples 1 to 6 show that the particles of the alloys after ball milling have good dispersion and no obvious agglomeration is formed.

[0074] Figure 3 The XRD patterns of the ball-milled alloys of Examples 1 to 6 show that ball milling significantly broadens the diffraction peaks of the alloys. Analysis shows that this phenomenon is caused by the lattice stress and grain refinement generated after ball milling.

[0075] Figure 4 The HRTEM morphologies of the ball-milled alloys of Examples 1 to 6 show that the alloys have a nanocrystalline structure with a grain size of 50 to 200 nm.

[0076] The fully automatic Sieverts equipment was used to test the hydrogen absorption activation performance, hydrogen storage capacity and hydrogen absorption and desorption kinetics of the alloy powder. The hydrogen absorption temperature was 30°C and the initial hydrogen pressure was 3MPa; the hydrogen desorption temperature was 30°C and the hydrogen desorption was at 1×10 -4 MPa pressure.

[0077] Table 1 Solid-state hydrogen storage properties of alloys from different embodiments

[0078]

[0079] The Ti-Fe-Ce-Mn-Zr-Al-Co based hydrogen storage alloy provided by the present invention has good activation performance and hydrogen absorption and desorption performance, with a hydrogen storage capacity of ≥1.70wt.%, a hydrogen absorption platform pressure of ≥0.41MPa, and a hydrogen desorption platform pressure of ≥0.31MPa; and activation can be completed at one time under the conditions of 30°C and an initial hydrogen pressure of 3MPa.

[0080] The above results show that the ball-milled alloy powder has excellent activation performance and high hydrogen absorption capacity. Obviously, the alloy preparation process of the present invention is simple and easy to operate, and is completely suitable for large-scale production. Its performance meets the requirements of hydrogen storage materials for various purposes. Compared with similar alloys at home and abroad, the hydrogen storage performance of the alloy of the present invention has been significantly improved, which has obvious advantages.

[0081] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A Ti-Fe-Ce-Mn-Zr-Al-Co-based hydrogen storage alloy, characterized in that: The specific composition of the alloy is Ti 1.05 Ce 0.05 Fe 1.15-x-y-z-m Mn x Zr y Al z Co m , where x, y, z, and m are atomic ratios, and 0.1 ≤ x ≤ 0.25, 0.05 ≤ y ≤ 0.2, 0.02 ≤ z ≤ 0.1, 0.02 ≤ m ≤ 0.

1.

2. The hydrogen storage alloy according to claim 1, characterized in that: The ratio of x, y, z, and m is x:y:z:m = 0.15:0.1:0.05:0.

05.

3. The hydrogen storage alloy according to claim 1, characterized in that: The hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50 - 200 nm, and there are grain boundary and phase boundary defects.

4. The hydrogen storage alloy according to claim 1, wherein: The hydrogen storage alloy has a multiphase structure, containing TiFe phase, ZrMn2 phase, CeCo2 phase, and Al4Mn phase.

5. A method for preparing the hydrogen storage alloy according to any one of claims 1 to 4, characterized in that, Specifically, it includes the following steps: S1: Calculate the dosage according to the chemical formula composition for batching, and add an appropriate burn loss amount for Mn and Ce. S2: Place the prepared raw materials in a zirconia crucible, cover the furnace lid, heat the raw materials to the molten state and keep them warm for a period of time, then pour the liquid alloy into a copper casting mold to obtain a master alloy ingot. S3: Mechanically crush and screen the master alloy ingot, and ball mill the alloy powder after screening to obtain the finished hydrogen storage alloy powder.

6. The preparation method according to claim 5, characterized in that: In step S1, the burn loss amount added for Mn and Ce is 8% - 10% of the calculated dosage.

7. The preparation method according to claim 5, characterized in that: In step S2, the placement order and specific operation of each raw material are as follows: Place the pure iron rod vertically along the crucible wall. The order of adding other metal raw materials is as follows: Place the massive rare earth Ce at the bottom of the crucible, place the sponge Ti and Zr above the rare earth Ce, place the metal Co on the sponge Ti and Zr, place the electrolytic Mn on the metal Co, and place the electrolytic Al on the top.

8. The preparation method according to claim 5, characterized in that: The specific operation of raw material melting in step S2 is as follows: evacuate to 1×10 -2 ~5×10 -5 Pa, then fill with pure argon gas at a pressure of 0.01~0.1MPa as the protective gas, keep the melting temperature at 1550~1650℃ and hold for 3~5 minutes.

9. The preparation method according to claim 5, characterized in that: The screening operation in step S3 is to screen the alloy fragments after mechanical crushing through a 200 - mesh sieve, and ball mill after obtaining alloy powder with a diameter ≤ 75 μm.

10. The preparation method according to claim 5, characterized in that: The specific ball milling operation in step S3 is as follows: Load the alloy powder and stainless steel grinding balls into a stainless steel ball milling tank, evacuate and then fill with high - purity argon gas, and ball mill in an all - around planetary high - energy ball mill for 0.5 - 2 h, with a ball - to - material ratio of 1:18 - 22 and a rotation speed of 300 - 400 revolutions per minute.

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