High-uniformity ti-fe-based hydrogen storage alloy and preparation method thereof

Abstract

The application provides a high-uniformity TiFe-based hydrogen storage alloy and a preparation method thereof. The chemical composition of the alloy is Ti a Fe b Mn c N d The alloy is prepared by accurately controlling the component ratio of titanium, iron and manganese elements and adopting a melt rapid quenching technology, manganese element segregation is effectively inhibited, and the core problem of the serious inclination of the pressure curve of the titanium-rich TiFe-Mn alloy platform is solved. The alloy has low cost and short process flow, and is particularly suitable for fixed hydrogen storage systems.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage alloys, specifically relating to a highly uniform TiFe-based hydrogen storage alloy and its preparation method. Background Technology

[0002] Hydrogen storage alloys are among the key materials for achieving safe and efficient hydrogen storage, transportation, and utilization. Among various hydrogen storage alloys, TiFe-based alloys have attracted widespread attention due to their high hydrogen storage capacity (theoretical capacity approximately 1.86 wt%), abundant resources, and relatively low cost, and are considered potential materials to replace high-pressure gas cylinders in stationary hydrogen storage scenarios. However, a major problem with traditional TiFe alloys is their extremely difficult activation process, requiring multiple hydrogen absorption and desorption cycles at high temperatures (above approximately 450°C) and high pressures (e.g., 5 MPa) to initiate the hydrogenation reaction.

[0003] To improve the activation and kinetic properties of TiFe alloys, those skilled in the art commonly use elements such as Mn, Cr, V, and Ni to partially replace Fe. Among these, Mn is considered one of the most effective substitutes. The introduction of Mn can significantly improve activation and hydrogen absorption / desorption kinetics. However, the introduction of Mn brings a new and serious technical problem: the hydrogen absorption / desorption plateau pressure curve of the alloy becomes significantly skewed (Non-Patent Literature 1: Int J Hydrogen Energy, 2021, 46, 34830). This skewed plateau means that during hydrogen absorption / desorption, the equilibrium hydrogen pressure of the alloy varies greatly with the hydrogen concentration. This not only reduces the effective hydrogen storage capacity but also makes precise control of the hydrogen pressure extremely difficult, severely restricting its practical application. In addition, Ti is the main hydrogen-absorbing element in the alloy composition. Increasing the Ti content can improve the hydrogen storage capacity of the alloy. However, studies have shown that the alloy composition is located in the two-phase region at this time, and there are two or more phases (such as Ti4Fe2O, β-Ti, etc.) in the equilibrium state. Although this is beneficial to improving the activation and hydrogen absorption and desorption kinetics of the alloy to a certain extent, it will also reduce the hydrogen storage capacity and further aggravate the micro-segregation of Mn and Fe elements.

[0004] Therefore, there is an urgent need in this field for a new method that can fundamentally solve the problem of Mn element segregation in TiFe-Mn alloys, especially Ti-rich alloys, in order to prepare hydrogen storage alloys with small plateau slope and excellent performance. Summary of the Invention

[0005] In order to solve the above-mentioned problems, the inventors have discovered, after repeated research, a highly uniform TiFe-based hydrogen storage alloy with high hydrogen storage capacity, good hydrogen absorption and desorption kinetics, and a small slope of the hydrogen absorption and desorption plateau.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A highly uniform TiFe-based hydrogen storage alloy, characterized in that the chemical composition of the alloy is Ti a Fe b Mn c N d Where 50.8≤a≤54.6, 38.5≤b≤44.2, 5.1≤c≤10.3, d≤1.0, and a+b+c+d=100, and N is one or more selected from V, Zr, Al, Cu, B, Si, Mo, Sn, and Cr;

[0008] When observed under backscattered electron mode of a scanning electron microscope, the alloy showed uniform surface distribution of manganese with no obvious segregation or enrichment of the second phase. In SEM-EDS line analysis, the count rate of Mn within a 30 μm length range between any two points did not fluctuate by more than ±15% of the average value.

[0009] The chemical composition of the TiFe-based hydrogen storage alloy is Ti a Fe b Mn c N d Preferably, 51 < a < 53, 39 < b < 44, 5.0 < c < 10, d ≤ 1.0, and a + b + c + d = 100, and N is preferably selected from one or more of V, Zr, Al, Cu, and B;

[0010] The TiFe-based hydrogen storage alloy has a maximum hydrogen absorption capacity of ≥1.90 wt.% at room temperature and 6 MPa hydrogen pressure.

[0011] The hydrogen storage capacity w at a hydrogen pressure of 6 MPa is shown on the hydrogen desorption pressure-composition-isotherm (PCT) curve of the TiFe-based hydrogen storage alloy at room temperature. max The hydrogen content is 90% w max and 10% w max The slope factor F between two points is ≤0.5, where F=log(P 90% / P 10% ) / (90%w max -10%w max ),

[0012] In the formula, P 90% and P 10% The hydrogen content on the hydrogen release curve is equal to 90% w. max and 10% w max The hydrogen pressure at that time is expressed in MPa.

[0013] In the TiFe-based hydrogen storage alloy, its chemical composition must also satisfy the requirement that the atomic ratio of Ti / (Fe+Mn) is between 1.03 and 1.15.

[0014] In the TiFe-based hydrogen storage alloy of the present invention, if the Ti / (Fe+Mn) ratio of the alloy is between 1.03 and 1.15, a high-capacity titanium-rich alloy can be formed, thereby increasing the hydrogen storage capacity of the alloy. However, if it is too high, it will lead to the formation of too many titanium-rich phases in the alloy, which will reduce the reversible hydrogen storage capacity.

[0015] In the TiFe-based hydrogen storage alloy, the content of TiFe main phase is ≥96wt.%.

[0016] The following describes the Ti of the present invention. 、 Fe 、 The roles of each element of Mn and its content range in this invention are explained.

[0017] Ti is the most important hydrogen-absorbing element in the alloy, possessing a strong affinity for hydrogen, which is the basis for the alloy's high hydrogen storage capacity. Fe and Ti together constitute the TiFe main phase, playing an important role in maintaining the structural stability of the TiFe phase and regulating the heat of hydride formation in the alloy (affecting the plateau pressure).

[0018] In this invention, the Ti content ranges from 50.8% to 54.6%. If the Ti content is insufficient, the TiFe2 phase is easily formed, leading to a decrease in hydrogen storage capacity. If the Ti content is too high, even with the use of melt quenching process, the excess Ti is very likely to form a Ti-rich second phase (such as Ti4Fe2O, β-Ti, etc.) during or after solidification, resulting in a decrease in the TiFe main phase content, disrupting phase homogeneity, and causing a significant decrease in hydrogen storage capacity.

[0019] Mn is a key alloying and modifying element, its main function being to replace part of Fe, effectively reducing the activation difficulty of TiFe alloys and improving hydrogen absorption and desorption kinetics. In this invention, the Mn content ranges from 5.1% to 10.3%. If the Mn content is too low, it cannot effectively improve activation and kinetics; while if the Mn content is too high, even with melt quenching, segregation is very likely to occur, leading to uneven distribution in the alloy and an excessively high slope on the PCT curve plateau.

[0020] Another technical solution of the present invention:

[0021] A method for preparing a highly uniform TiFe-based hydrogen storage alloy as described above, characterized by comprising the following steps:

[0022] (1) The ingredients are prepared according to the above chemical composition ratio, and the purity of the metal raw materials is ≥99.5%;

[0023] (2) The raw materials prepared in step (1) are induction melted under an argon protective atmosphere. The melting conditions are: pressure range of 0.01~0.1MPa, melt temperature controlled at 1500℃~1700℃, to obtain alloy melt.

[0024] (3) First, spray the molten liquid obtained in step (2) onto the surface of a high-speed rotating copper roller to rapidly cool the alloy melt, thereby obtaining an alloy sheet with a thickness of 50~100 μm.

[0025] In step (3), in order to achieve a highly uniform distribution of Mn elements, the linear speed of the copper roller is controlled within the range of 15~25 m / s, and the cooling rate is between 4000~8000 K / s.

[0026] The beneficial effects of this invention are:

[0027] The preparation method of this invention combines composition design with rapid melt quenching cooling technology, specifically addressing the problem of non-uniform composition in existing high-capacity titanium-rich TiFe-Mn alloys. Specifically, titanium-rich TiFe-Mn alloys prepared by traditional casting or arc melting methods suffer from slow cooling rates, allowing sufficient time for atomic diffusion and segregation, resulting in a higher proportion of impurity phases and uneven elemental distribution. Furthermore, this invention employs rapid melt quenching technology with a linear velocity of 15-25 m / s and a cooling rate of 4000-8000 K / s. This effectively suppresses the formation of non-hydrogen-absorbing second phases such as β-Ti and Ti4Fe2O, thereby increasing the abundance of the main phase (TiFe main phase content ≥96wt.%). Secondly, it significantly inhibits atomic diffusion during solidification, solving the manganese segregation problem and achieving a high degree of uniformity in microstructure and compositional distribution. This significantly improves hydrogen storage performance, resulting in a high-capacity alloy (maximum hydrogen release capacity can reach over 1.9wt%) and a flat hydrogen absorption / desorption plateau (hydrogen release plateau slope less than 0.5). Furthermore, the cooling rate and strip thickness (50-100 μm) can be precisely controlled by adjusting the linear speed of the copper roller, resulting in strong process controllability and suitability for continuous production. Attached Figure Description

[0028] Figure 1 The scanning electron microscope (SEM) scans of the elemental distributions of Example 1 and Comparative Examples 1 and 2 are shown below.

[0029] Figure 2 X-ray diffraction patterns of Example 1 and Comparative Examples 1 and 2

[0030] Figure 3 The fluctuation of Mn element between two points is shown in Example 1 and the scanning electron microscope line scan.

[0031] Figure 4 To compare the fluctuation of Mn element between two points in the scanning electron microscope line scan of Example 1.

[0032] Figure 5 To compare the fluctuation of Mn element between two points using scanning electron microscopy line scanning in Example 2.

[0033] Figure 6PCT curves at 298K for Example 1 and Comparative Examples 1 and 2 Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 43.6 Mn 5.1 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for approximately 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller at a linear velocity of 15 m / s and a cooling rate of 6000~8000 K / s to obtain rapidly quenched alloy sheets with an average thickness of ~100 μm. The average value of the Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0037] Comparative Example 1

[0038] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 43.6 Mn 5.1 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the molten state for about 5 minutes under the Ar atmosphere to allow the metal elements to fully react, melt, and mix uniformly. The melt was then poured into a metal mold and cooled to room temperature in the furnace under the Ar atmosphere to obtain a cast alloy ingot. The average value of the Mn element strength fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0039] Comparative Example 2

[0040] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 43.6 Mn 5.1The materials were prepared and placed in a water-cooled copper crucible. A vacuum of 10⁻³ Pa was applied, followed by the introduction of high-purity Ar gas (0.01–0.1 MPa). Non-consumable arc melting was then performed under an argon atmosphere. The arc current was adjusted to ensure complete melting of the metal block. Electromagnetic stirring was used during melting to homogenize the alloy composition. The arc was then turned off, allowing the melt to solidify rapidly in the water-cooled copper crucible, resulting in a cast alloy ingot. The average Mn element strength fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0041] The alloy ingot samples obtained above (Example 1, Comparative Examples 1 and 2) were cut to obtain flat observation surfaces, and then the cross-sections were ground and polished using standard metallographic sample preparation procedures. To obtain clear backscattered electron contrast images, a diamond polishing paste with a particle size of 0.1 μm was used for final fine polishing. Subsequently, the prepared samples were observed for microstructure and compositional analysis using a scanning electron microscope equipped with an X-ray energy dispersive spectroscopy (EDS) instrument. First, representative micro-regions were selected in backscattered electron mode, and BSE images were acquired at an accelerating voltage of 15 kV. Surface scanning analysis was performed in the same region to map the elemental distribution of Ti, Fe, and Mn, visually demonstrating the uniformity of elemental distribution within the micro-region and the presence of agglomeration. Figure 1 (As shown). To quantitatively analyze the elemental concentration gradient at a specific location, a 30 μm scanning path was set at any location of impurity phases other than the TiFe main phase. Linear scanning was performed under the same operating conditions, and the continuous variation curve of Mn element X-ray intensity along the scanning path was recorded to assess the magnitude of elemental content fluctuations (as shown). Figure 3-5 ).

[0042] Figure 1 Scanning electron microscopy (SEM) elemental distribution maps of Example 1 and Comparative Examples 1 and 2 are shown. The results indicate that Ti, Fe, and Mn are uniformly distributed in Example 1, while Comparative Examples 1 and 2 show a small number of Ti-rich and Fe- and Mn-poor regions, indicating the presence of a small amount of titanium-rich phase. Therefore, the obtained hydrogen storage alloy sheets or blocks were mechanically crushed after removing the oxide scale, and powder with a mesh size smaller than 400 was selected for X-ray powder diffraction testing. Cu Kα rays were used at a power of 40 kV × 150 mA, with a step scan of 0.02° and a 2θ range of 10°–90°. The scans are shown below. Figure 2 , Figure 2The XRD patterns of Example 1 and Comparative Examples 1 and 2 are shown. As can be seen from the figures, the second phase in Comparative Examples 1 and 2 is mainly composed of β-Ti and Ti4Fe2O phases. The mass percentage of each phase can be obtained through Rietveld refinement, and the mass percentage of the TiFe main phase is listed in Table 1 below. The data in Table 1 show that the proportion of the TiFe phase in Example 1 is close to 100 wt.%, while the proportion of the TiFe phase in Comparative Examples 1 and 2 is ≤95 wt.%. This is because Example 1 uses the melt rapid quenching technology of the present invention, with a copper roller linear speed of 15~25 m / s and a cooling rate of 4000~8000 K / s, which effectively suppresses the formation of non-hydrogen-absorbing second phases such as β-Ti and Ti4Fe2O, thereby increasing the abundance of the main phase (TiFe main phase content ≥96 wt.%). In contrast, in Comparative Examples 1 and 2, which do not utilize the copper roller linear speed and cooling rate of the present invention, the proportion of the TiFe phase is significantly reduced.

[0043] Figure 1 In the region outside the titanium-rich phase, the Mn element spectrum in Example 1 shows uniform color intensity, indicating a uniform distribution of Mn elements without obvious segregation. In contrast, the spectra of Comparative Examples 1 and 2 show significant changes in brightness and color intensity, indicating a significantly non-uniform distribution of Mn elements and the presence of obvious enrichment areas. This proves that the TiFe-based hydrogen storage alloy prepared by the method of the present invention can suppress the formation of the titanium-rich phase and the diffusion and segregation of Mn atoms when the alloy cooling rate is within a certain range, thereby obtaining a single-phase structure with uniform composition.

[0044] Figure 3 , Figure 4 and Figure 5 The scanning electron microscope (SEM) line scan Mn elemental distribution curves for Example 1, Comparative Example 1, and Comparative Example 2 are shown respectively. Three line scan paths were randomly selected in each field of view. Figure 3As can be seen, the Mn element intensity curve of Example 1 fluctuates smoothly and stably throughout the entire scan path, fluctuating within the average range of 10% to 12%, indicating a highly uniform compositional distribution. In stark contrast, the Mn element curves of Comparative Examples 1 and 2 exhibit large and drastic fluctuations, with multiple sharp peaks and valleys. Comparative Examples 1 and 2 fluctuate within the average ranges of 20% to 26% and 19% to 24%, respectively. This indicates that severe microscopic segregation of Mn occurred in both Comparative Examples 1 and 2, resulting in significantly poor compositional uniformity. In contrast, the TiFe-based hydrogen storage alloy obtained using the preparation method of this invention shows a uniform surface distribution of manganese, without obvious segregation or second-phase enrichment. This demonstrates that, compared to the alloys of Comparative Examples 1 and 2 prepared using conventional methods, the combination of the compositional design and melt rapid quenching cooling process of this invention can significantly suppress atomic diffusion during solidification, solve the manganese segregation problem, and achieve a high degree of uniformity in microstructure and compositional distribution.

[0045] In other words, the preparation method provided by this invention effectively reduces the formation of the second phase outside the TiFe main phase by cooling the alloy within a certain range, promoting the solid solution of Mn and suppressing its segregation tendency, thereby obtaining a highly uniform microstructure. In contrast, Comparative Examples 1 and 2 show that due to the slower cooling rate of the alloy ingot after melting, a larger amount of the second phase is easily formed, and Mn segregates, resulting in drastic fluctuations in its distribution curve, with a much larger variation range than in Example 1. This severe compositional fluctuation is direct evidence of microscopic elemental segregation, which inevitably has an adverse effect on the hydrogen storage performance of the alloy.

[0046] Furthermore, the gaseous hydrogen storage performance of the alloys of Example 1 and Comparative Examples 1 and 2 was tested. The gaseous hydrogen storage performance of the hydrogen storage alloy can be represented by the pressure-composition-temperature curve (PCT curve). The hydrogen storage capacity, hydrogen release plateau pressure and hydrogen release plateau slope of the hydrogen storage material can be obtained from the PCT curve.

[0047] To clarify, the PCT curve of the hydrogen storage material in this invention is tested using the Sieverts method. The test procedure is as follows: Take approximately 2g of alloy powder smaller than 100 mesh, vacuum at 200°C for 1 hour, and then cool to 25°C. Introduce 5MPa hydrogen gas for hydrogen absorption activation, then vacuum at 200°C for 1 hour. Repeat this cycle 3-4 times. After cooling to 25°C, perform the PCT curve test. Figure 6 As shown. According to Figure 6 The PCT curve can be used to obtain the hydrogen storage capacity w at a hydrogen pressure of 6 MPa. max The hydrogen content on the hydrogen release curve is 90% w. max and 10% w maxThe slope factor F between two points (F = log(P)) 90% / P 10% ) / (90%w max -10%w max ), where P 90% and P 10% The hydrogen content on the hydrogen release curve is equal to 90% w. max and 10% w max The hydrogen pressure at the time of application is in MPa. The results are shown in Table 1 below. In Comparative Examples 1 and 2, due to the presence of a certain amount of non-hydrogen-absorbing β-Ti phase and Ti4Fe2O phase other than the TiFe main phase, the hydrogen storage capacity decreased from 1.96 wt% in Example 1 to 1.80~1.83 wt%. The uniformly distributed Mn element in Example 1 corresponds to a smaller slope factor (0.43) on its PCT curve platform; while the severely segregated Mn element in Comparative Examples 1 and 2 corresponds to a larger slope factor (0.68 and 0.61). The slope factor of the PCT curve is a key indicator for measuring the flatness of the hydrogen storage alloy platform. Therefore, the smaller the slope factor, the flatter the platform, indicating that the energy distribution of the lattice sites occupied by hydrogen atoms in the alloy is more concentrated, and the better the synergy of the hydrogen absorption and desorption process.

[0048] Specifically, in Example 1, the uniform distribution of Mn resulted in optimal solid solution in the TiFe matrix, forming a highly homogeneous main phase in terms of composition and structure. This provided interstitial sites with consistent energy states for hydrogen atoms. Therefore, during hydrogen absorption and desorption, hydride formation and decomposition could proceed synergistically within a narrow pressure range, manifested as a flat hydrogen absorption / desorption plateau and a small slope factor (0.43). In Comparative Examples 1 and 2, the microscopic segregation of Mn led to inhomogeneity in the alloy's microstructure, forming multiple regions with varying thermodynamic stability. These regions possess different hydride formation enthalpies and react under different equilibrium pressures during hydrogen absorption and desorption. The superposition of multiple microplateaus caused the macroscopic PCT curve plateau to tilt, resulting in larger slope factors (0.68 and 0.61). The increase in slope factor directly led to a decrease in effective hydrogen storage capacity. Thus, compared to Example 1 with its flat plateau, Comparative Examples 1 and 2 showed a significant reduction in reversible hydrogen storage capacity under the same application conditions. Furthermore, a flat platform ensures that the system pressure remains relatively stable during the main hydrogen absorption or release phases, reducing the requirements for external pressure management systems and improving the controllability and safety of system operation. In contrast, a tilted platform results in a wider operating pressure range for the same capacity utilization, increasing compression energy consumption. Frequent pressure fluctuations also exacerbate material pulverization and container fatigue, negatively impacting the long-term cycle life of the device.

[0049] Example 2

[0050] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 41.0 Mn 7.7 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for about 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 15 m / s and a cooling rate of 6000-8000 k / s, resulting in rapidly quenched alloy sheets with an average thickness of ~100 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy sheets are shown in Table 1.

[0051] Example 3

[0052] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 38.5 Mn 10.3 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for approximately 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 15 m / s and a cooling rate of 6000-8000 K / s, resulting in rapidly quenched alloy sheets with an average thickness of ~100 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0053] Example 4

[0054] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 38.5 Mn 10.3 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for approximately 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 20 m / s and a cooling rate of 5000-7000 K / s, resulting in rapidly quenched alloy sheets with an average thickness of ~80 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0055] Example 5

[0056] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 38.5 Mn 10.3 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for about 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 25 m / s and a cooling rate of 4000-6000 K / s, resulting in rapidly quenched alloy sheets with an average thickness of ~50 μm. The average value of the Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0057] Example 6

[0058] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 53.5 Fe 41.2 Mn 5.3 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for about 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 25 m / s and a cooling rate of 4000-6000 K / s, resulting in rapidly quenched alloy sheets with an average thickness of ~50 μm. The average value of the Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0059] Example 7

[0060] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti.54.6 Fe 39.9 Mn 5.5 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for about 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 25 m / s and a cooling rate of 4000-6000 K / s, resulting in rapidly quenched alloy sheets with an average thickness of ~50 μm. The average value of the Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0061] Example 8

[0062] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 50.8 Fe 43.1 Mn 5.1 V 1.0 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for approximately 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 15 m / s and a cooling rate of 6000-8000 k / s, yielding rapidly quenched alloy sheets with an average thickness of ~100 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0063] Example 9

[0064] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.0 Fe 43.4 Mn 5.1 Zr 0.5 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for approximately 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 15 m / s and a cooling rate of 6000-8000 k / s, yielding rapidly quenched alloy sheets with an average thickness of ~100 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0065] Comparative Example 3

[0066] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 51.3 Fe 35.9 Mn 12.8 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for approximately 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 10 m / s and a cooling rate of 3000~4000 K / s, yielding rapidly quenched alloy sheets with an average thickness of ~130 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0067] Comparative Example 4

[0068] Metal raw materials with a purity greater than 99.5% were classified according to their chemical composition Ti. 57.1 Fe 37.1 Mn 5.7 Prepare the ingredients, place them in a crucible, and first evacuate the vacuum to 100°C. -3 The solution was initially charged with high-purity Ar gas at 0.01~0.1 MPa, followed by induction melting. The melt temperature was controlled at 1500℃~1700℃, and the melt was maintained in the Ar atmosphere for about 5 minutes to allow the metal elements to fully react, melt, and mix uniformly. The melt was then sprayed onto the surface of a high-speed rotating water-cooled copper roller with a linear velocity of 25 m / s and a cooling rate of 4000~6000 K / s, resulting in rapidly quenched alloy sheets with an average thickness of ~50 μm. The average Mn element intensity fluctuation range, slope factor F, maximum hydrogen absorption, and TiFe phase content of the obtained alloy are shown in Table 1.

[0069] Table 1

[0070]

[0071] Observing the data in Table 1, Examples 2 and 3 show that, under the condition of a fixed cooling rate (same copper roller rotation speed), the microscopic distribution fluctuation of Mn increases with the gradual increase of Mn content. This confirms that its segregation tendency increases with increasing content. When the Mn content is further increased to the level of Comparative Example 3 (exceeding the content range of the present invention), its distribution fluctuation also exceeds the range of the present invention, directly leading to a decrease in hydrogen storage capacity and an excessively large slope factor of the PCT curve, proving that there is a clear upper limit to the Mn content.

[0072] However, this invention has found that component segregation can be effectively suppressed by optimizing process parameters. As shown in Examples 4 and 5, under conditions of high Mn content, a significant reduction in fluctuation values ​​was successfully achieved by increasing the copper roller speed (i.e., increasing the cooling rate). This demonstrates that increasing the cooling rate can suppress element diffusion and segregation during the solidification process of the alloy melt, and is a key means to obtain a uniform microstructure. Therefore, for the high Mn content alloy formulation in this invention, a suitable copper roller speed must be matched, or in other words, a certain cooling rate is required for the Mn content within the range of this invention, i.e., 4000~8000 K / s.

[0073] Studies in Examples 6 and 7 show that, at a fixed cooling rate, as the Ti / (Fe+Mn) ratio gradually increases to 1.15, the uniformity of elemental distribution is affected, and fluctuations gradually increase. When this ratio is further increased to 1.20 in Comparative Example 4, even with the same cooling rate, excessive fluctuations occur, and excessive precipitation of the second phase occurs. This deterioration of the microstructure manifests macroscopically as a decrease in hydrogen storage capacity and a slope factor exceeding the scope of the claims. This indicates that maintaining the Ti / (Fe+Mn) ratio within a certain range (e.g., not greater than 1.15) in the alloy of the present invention is crucial for avoiding the formation of harmful second phases, ensuring the uniformity of the main phase composition, and maintaining excellent hydrogen storage performance.

[0074] For Comparative Example 4, where the Ti content is higher than the range of the present invention, even though the preparation process conditions are within the range of the present invention, although alloy sheets are obtained, the average value of the Mn element strength fluctuation range is high, and its distribution is uneven, resulting in a large slope silver, poor maximum hydrogen absorption, and poor practicality.

[0075] In Examples 8 and 9 of this invention, 1.0 at.% V (vanadium) and 0.5 at.% Zr (zirconium) were added to the optimized Ti-Fe-Mn base composition, respectively. Experimental data show that both alloys successfully achieved the excellent properties of the base composition alloy: highly uniform Mn element distribution (fluctuations of ±12.1% and ±11.8%, respectively), high TiFe main phase content (98.5 wt.% and 97.6 wt.%, respectively), and exhibited high hydrogen storage capacity (1.94 wt.% and 1.93 wt.%) and low plateau slope (slope factors F of 0.44 and 0.45, respectively). This demonstrates the significant inclusiveness and controllability of the technical solution of this invention. This greatly expands the formulation design space and performance optimization potential of the alloys of this invention, enabling customized development for more specific application requirements (such as higher requirements for kinetics or cycle life).

[0076] Through systematic studies of examples and comparative examples, this invention reveals the synergistic effect of alloy composition (Mn content, Ti / (Fe+Mn) ratio) and preparation process (cooling rate) on microstructure uniformity and final hydrogen storage performance, and thereby determines the optimal process window.

[0077] This invention optimizes the alloy composition and preparation process to achieve uniform distribution of Mn elements in the TiFe matrix and suppress the formation of the second phase. This advantage in microstructure directly translates into a flatter PCT platform and an increased hydrogen storage capacity of the alloy on a macroscopic scale. This not only improves the effective hydrogen storage capacity of the alloy, but also gives it significant advantages in practical hydrogen storage device applications, such as stable operating pressure and long system life.

[0078] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A highly uniform TiFe-based hydrogen storage alloy, characterized in that, The chemical composition of the alloy is Ti a Fe b Mn c N d Where 50.8≤a≤54.6, 38.5≤b≤44.2, 5.1≤c≤10.3, d≤1.0, and a+b+c+d=100, and N is one or more selected from V, Zr, Al, Cu, B, Si, Mo, Sn, and Cr; When observed under backscattered electron mode of a scanning electron microscope, the alloy showed uniform surface distribution of manganese with no obvious segregation or enrichment of the second phase. In SEM-EDS line analysis, the count rate of Mn within a 30 μm length range between any two points did not fluctuate by more than ±15% of the average value.

2. The hydrogen storage alloy according to claim 1, characterized in that, The chemical composition of the TiFe-based hydrogen storage alloy is Ti a Fe b Mn c N d In the given condition, 51 < a < 53, 39 < b < 44, 5.0 < c < 10, d ≤ 1.0, and a + b + c + d = 100, where N is one or more of V, Zr, Al, Cu, and B.

3. The hydrogen storage alloy according to claim 1, characterized in that, The TiFe-based hydrogen storage alloy has a maximum hydrogen absorption capacity of ≥1.90 wt.% at room temperature and 6 MPa hydrogen pressure.

4. The hydrogen storage alloy according to claim 1, characterized in that, The hydrogen storage capacity w at a hydrogen pressure of 6 MPa is shown on the hydrogen desorption pressure-composition-isotherm (PCT) curve of the TiFe-based hydrogen storage alloy at room temperature. max The hydrogen content is 90% w max and 10%w max The slope factor F between two points is ≤0.5, where F=log(P 90% / P 10% ) / (90%w max -10%w max ), In the formula, P 90% and P 10% The hydrogen content on the hydrogen release curve is equal to 90% w. max and 10% w max The hydrogen pressure at that time is expressed in MPa.

5. The hydrogen storage alloy according to claim 1, characterized in that, In the TiFe-based hydrogen storage alloy, its chemical composition must also satisfy the requirement that the atomic ratio of Ti / (Fe+Mn) is between 1.03 and 1.

15.

6. The hydrogen storage alloy according to claim 1, characterized in that, In the TiFe-based hydrogen storage alloy, the content of TiFe main phase is ≥96wt.%.

7. A method for preparing a highly uniform TiFe-based hydrogen storage alloy according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) The ingredients are prepared according to the above chemical composition ratio, and the purity of the metal raw materials is ≥99.5%; (2) The raw materials prepared in step (1) are induction melted under an argon protective atmosphere. The melting conditions are: pressure range of 0.01~0.1MPa, melt temperature controlled at 1500℃~1700℃, to obtain alloy melt. (3) First, spray the molten liquid obtained in step (2) onto the surface of a high-speed rotating copper roller to rapidly cool the alloy melt, thereby obtaining an alloy sheet with a thickness of 50~100 μm.

8. The preparation method according to claim 7, characterized in that, The linear speed of the copper rollers used is controlled within the range of 15~25 m / s, and the cooling rate is between 4000~8000 K / s.

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