Hydrogen storage alloy containing composite phase and method for producing same

Abstract

The present invention relates to a hydrogen storage alloy containing a composite phase and having a uniform microstructure and excellent hydrogen storage properties, wherein an optimal alloy structure can be formed by adjusting the temperature of a melt with reference to a nickel content-dependent phase diagram. In the case of a hydrogen storage alloy containing a composite phase according to the present invention, additive elements such as tin (Sn), zinc (Zn), neodymium (Nd), yttrium (Y), or gadolinium (Gd) can be added to improve hydrogen absorption and release rates. In addition, according to the present invention, high-quality chip-shaped alloys can be produced through casting and turning processes, and the production of high-quality chip-shaped alloys is expected to enable the efficient production of hydrogen storage alloys suitable for various industrial applications.

Description

Hydrogen storage alloy including composite phase and method for manufacturing same

[0001] The present invention relates to a hydrogen storage alloy comprising a composite phase including magnesium, nickel and an additive element, and also to a method for producing a hydrogen storage alloy comprising such a composite phase.

[0002] The share of renewable energy generation is increasing, and it's projected to reach 20% by 2030. Solar and wind power are playing a significant role in this process. According to projections for renewable energy generation by source, solar and wind power are projected to account for over 85% of total renewable energy by 2030. However, renewable energy generation efficiency is significantly affected by regional variations in wind speed and solar irradiance. Furthermore, renewable energy's intermittency, with its power output varying significantly depending on the season and cycle, makes it difficult to ensure a stable energy supply.

[0003] To address this, various energy storage technologies are needed. Energy storage technologies include chemical storage, electromagnetic storage, thermodynamic storage, and physical storage. Among these, hydrogen storage technology is receiving particular attention. Hydrogen possesses superior characteristics compared to batteries, enabling long-term and large-scale storage. Green hydrogen is produced using renewable energy, allowing electricity to be stored and used when needed. Hydrogen energy storage can be implemented in various forms, including gaseous, liquid, and solid, each with its own advantages and disadvantages. Therefore, hydrogen-based energy storage technology is necessary to address the intermittency of renewable energy and ensure a stable energy supply.

[0004] In hydrogen-based energy storage technology, magnesium-based metal hydride storage materials offer promise due to their high storage density and fast reaction rates. However, existing materials suffer from high manufacturing costs and low storage densities per unit weight. To address these issues, powder manufacturing technology is needed, which increases surface area and thus reaction efficiency. Representative commercial metal hydride storage materials include the AB5 (LaNi5) and AB (FeTi, FeMn) series, but their storage densities are significantly lower than those of high-pressure gas and liquid hydrogen storage. Continued research is needed to develop optimal hydrogen storage materials.

[0005] Figure 1 illustrates a conventional method for manufacturing a magnesium-based hydrogen storage alloy. This conventional method, as shown in Figure 1, involves gas atomizing, mixing Mg and Ni powders, sintering in a vacuum at 600°C, and ball milling for 40 hours. This method has the advantage of maintaining a fine powder size, allowing for similar hydrogen storage capacity even at high magnesium ratios. However, several problems exist. First, the difficulty of manufacturing gas atomized powder increases costs. Industry, in particular, tends to be reluctant to manufacture powders for magnesium alloys. Second, the sintering and ball milling processes require significant time, resulting in additional costs. Third, hydrogen storage properties are sensitive to powder size, making it difficult to manufacture and maintain fine powders smaller than 50 μm. Fourth, finer powders increase the difficulty of storing and handling the powder, and some magnesium alloys are susceptible to ignition and explosion. For these reasons, commercial AB5-based hydrogen storage alloys are currently manufactured using this method, resulting in significant costs.

[0006] The present invention is intended to solve the problems of the method for manufacturing a magnesium-based hydrogen storage alloy according to the prior art described in the background art.

[0007] The present invention aims to confirm the synergistic effect of a Mg / Mg2Ni composite phase and to provide a Mg + Mg2Ni composite phase metal hydrogen storage alloy by utilizing the same, and in particular, to provide a hydrogen storage alloy including a composite phase through an added element.

[0008] A method for manufacturing a hydrogen storage alloy including a composite phase according to one embodiment of the present invention comprises the steps of: melting a magnesium ingot to make it into a liquid state; adding nickel to the melted magnesium and melting the nickel; charging at least one additional element selected from Nd, Zn, Gd, Sn, and Y into the molten metal and melting the additional element; lowering the temperature of the molten metal by controlling the temperature with reference to a phase diagram according to the nickel content; and pouring the molten metal into a preheated iron mold for casting.

[0009] The step of melting the above magnesium ingot to make it into a liquid state is to melt the magnesium at a temperature of 700 to 900°C under a mixed protective gas of CO2 and SF6 to prevent the magnesium from being oxidized.

[0010] The step of adding nickel to the above-mentioned molten magnesium and dissolving nickel is to dissolve nickel by 1 cm 3 (or 1,000mm 3 ) and add it and wait for 1 to 2 hours for the nickel to melt.

[0011] The step of adding at least one additive element among Nd, Zn, Gd, Sn, and Y to the above molten metal and melting the additive element includes adding the additive element while maintaining the temperature of the molten metal above the melting point of the additive element and maintaining the molten metal so that the additive element can be dissolved in the molten metal.

[0012] The step of pouring molten metal into the above preheated iron mold and casting is to prepare an iron mold preheated to about 200°C, pour molten metal into the mold, cool it, and solidify it.

[0013] After the step of pouring molten metal into the above preheated iron mold and casting, the step of turning or crushing the cast alloy is additionally included.

[0014] A hydrogen storage alloy including the above composite phase contains 12 to 31 at% of nickel.

[0015] A hydrogen storage alloy including the above composite phase contains 15 to 30 at% of nickel.

[0016] A hydrogen storage alloy comprising the above composite phase contains 20 at% of nickel.

[0017] The above-mentioned additive element is included in a hydrogen storage alloy including the above-mentioned composite phase in an amount of more than 0 and less than 1.1 at%.

[0018] A hydrogen storage alloy including a composite phase according to one embodiment of the present invention is an alloy composed of magnesium (Mg), nickel (Ni) and an additive element, wherein the nickel content is 12 to 31 at%, and the additive element is at least one of Nd, Zn, Gd, Sn, and Y.

[0019] The content of nickel is 15 to 30 at%, and preferably, the content of nickel is 20 at%.

[0020] The above-mentioned additive element is included in a hydrogen storage alloy including the above-mentioned composite phase in an amount of more than 0 and less than 1.1 at%.

[0021] According to the present invention, a hydrogen storage alloy comprising a composite phase with a uniform microstructure and excellent hydrogen storage properties can be produced. In this case, the melt temperature can be adjusted by referring to the phase diagram according to nickel content, thereby forming an optimal alloy structure.

[0022] In the case of a hydrogen storage alloy including a composite phase according to the present invention, the hydrogen absorption and release rate is improved by adding additive elements such as tin (Sn), zinc (Zn), neodymium (Nd), yttrium (Y), and gadolinium (Gd).

[0023] In addition, according to the present invention, it is expected that a high-quality chip-shaped alloy can be manufactured through casting and turning processes, thereby efficiently producing a hydrogen storage alloy suitable for various industrial applications.

[0024] Figure 1 illustrates a method for manufacturing a magnesium-based hydrogen storage alloy according to a conventional technique.

[0025] FIG. 2 illustrates a flowchart of a method for manufacturing a hydrogen storage alloy including a composite phase according to one embodiment of the present invention.

[0026] Figure 3 shows a phase diagram of a magnesium and nickel alloy.

[0027] Figure 4 is data theoretically predicting the hydrogen storage capacity according to the phase fraction after calculating the Mg / Mg2Ni fraction by thermodynamic calculation.

[0028] Figure 5 shows a comparison between experimental results and theoretical values ​​of hydrogen storage capacity according to nickel content in a magnesium-nickel binary hydrogen storage alloy.

[0029] Figure 6 shows the change in microstructure according to the increase in the amount of Ni added in a magnesium-nickel binary hydrogen storage alloy.

[0030] Figures 7a-7c show the hydrogen storage capacity according to the Ni content and temperature in a magnesium-nickel binary hydrogen storage alloy.

[0031] Figures 8 to 13 illustrate the microstructure of ternary alloys with Y, Sn, Gd, Ag, Nd, and Zn added as additive elements, respectively.

[0032] Figures 14a-14c illustrate the hydrogen storage capacity according to the added elements and temperature in a hydrogen storage alloy including a composite phase.

[0033] Figure 15 shows the degree of hydrogen activation and hydrogen storage capacity according to the content of Ni and the added element over time.

[0034] Figure 16 shows the hydrogen concentration over time for each element added to Ni.

[0035] Various embodiments are now described with reference to the drawings, wherein like reference numerals are used throughout the drawings to designate like elements. For purposes of explanation, various descriptions are provided herein to facilitate an understanding of the present invention. However, it will be apparent that these embodiments may be practiced without these specific descriptions. In other instances, well-known structures and devices are presented in block diagram form to facilitate the description of the embodiments.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention is susceptible to various modifications and variations, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Throughout the description of each drawing, similar reference numerals have been used to designate similar components.

[0037] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, steps, operations, components, parts, or combinations thereof.

[0038] The present invention relates to a hydrogen storage alloy comprising a composite phase having a uniform microstructure and excellent hydrogen storage properties, wherein an optimal alloy structure can be formed by controlling the melt temperature with reference to a phase diagram according to nickel content. In the case of the hydrogen storage alloy comprising a composite phase according to the present invention, the hydrogen absorption and release rate can be improved by adding additive elements such as tin (Sn), zinc (Zn), neodymium (Nd), yttrium (Y), and gadolinium (Gd).

[0039] In the case of a hydrogen storage alloy including a composite phase according to the present invention, the synergistic effect of the Mg / Mg2Ni composite phase was confirmed, and a Mg + Mg2Ni composite phase metal hydrogen storage alloy (magnesium-nickel binary hydrogen storage alloy) was designed using this, and a hydrogen storage alloy including a composite phase was designed by adding an additional element to this magnesium-nickel binary hydrogen storage alloy.

[0040] Therefore, below, a magnesium-nickel binary hydrogen storage alloy will be described, while at the same time, a hydrogen storage alloy including a composite phase according to an embodiment of the present invention will be described.

[0041] In the case of a magnesium-nickel binary hydrogen storage alloy, the manufacturing method is as follows: melting a magnesium ingot to make it liquid, adding nickel to the molten magnesium, melting the nickel, lowering the temperature of the molten metal by referring to the phase diagram according to the nickel content, and pouring the molten metal into a preheated iron mold for casting. Using this method for manufacturing a magnesium-nickel binary hydrogen storage alloy, the present invention describes a method for manufacturing a hydrogen storage alloy including a composite phase as follows.

[0042] FIG. 2 illustrates a flowchart of a method for manufacturing a hydrogen storage alloy including a composite phase according to one embodiment of the present invention.

[0043] As illustrated in FIG. 2, a method for manufacturing a hydrogen storage alloy including a composite phase according to one embodiment of the present invention includes a step of melting a magnesium ingot to make it into a liquid state (S 210); a step of adding nickel to the melted magnesium and melting the nickel (S 220); a step of charging at least one additional element among Nd, Zn, Gd, Sn, and Y into the molten metal and melting the additional element (S 230); a step of lowering the temperature of the molten metal by controlling the temperature with reference to a phase diagram according to the nickel content (S 240); and a step of pouring the molten metal into a preheated iron mold for casting (S 250).

[0044] In step S 210, the magnesium ingot is melted to a liquid state. Pure magnesium ingot is used, and the magnesium is melted at a temperature of 800 to 900°C under a mixed protective gas of CO2 and SF6 to prevent oxidation of the magnesium. In this case, CO2 and SF6 Mix in a ratio of 10:1 and use as a protective gas.

[0045] In step S 220, nickel is added to the molten magnesium and the nickel is dissolved. Nickel is added to 1 cm 3 (or 1,000mm 3 ) Prepare in the form of a small size below, insert nickel into the magnesium molten metal, and wait for 1 to 2 hours to allow the nickel to sufficiently melt in the magnesium molten metal.

[0046] In step S 230, one or more additive elements among Nd, Zn, Gd, Sn, and Y are added to the molten metal and the additive elements are melted. The additive elements are added while maintaining the temperature of the molten metal above the melting point of the additive elements and the molten metal is maintained so that the additive elements can be dissolved into the molten metal.

[0047] At step S240, the temperature of the molten metal is adjusted and lowered by referring to the phase diagram according to the nickel content. Once it is determined that the nickel has sufficiently melted, the temperature of the molten metal is adjusted and lowered by referring to the phase diagram according to the desired nickel content. Figure 3 illustrates the phase equilibrium diagram of a magnesium and nickel alloy.

[0048] In step S 250, molten metal is poured into a preheated iron mold for casting. An iron (Fe) mold preheated to approximately 200°C is prepared, and molten metal is poured into the mold, cooled, and solidified.

[0049] After step S250, a turning process (S260) may be additionally included for the cast alloy. The cast alloy undergoes a turning process (lathe processing) to obtain the desired thickness (<300 μm) and surface quality. The remaining material after processing is stored in bulk for further processing when necessary.

[0050] Turning (lathe machining) is a manufacturing process that rotates a workpiece made of a material such as metal or plastic and moves a fixed cutting tool accordingly to machine it into a desired shape.

[0051] When predicting the hydrogen storage characteristics according to the existing powder manufacturing method when manufacturing a magnesium-nickel binary hydrogen storage alloy, theoretically, it is predicted that the hydrogen storage amount will decrease as the Ni content increases, as shown in Fig. 4. Fig. 4 is data theoretically predicted for the hydrogen storage amount according to the phase fraction after calculating the Mg / Mg2Ni fraction by thermodynamic calculation. However, in the case of the magnesium-nickel binary hydrogen storage alloy according to the present invention, contrary to this theoretical prediction, an increase in the hydrogen storage amount according to the Ni content was also confirmed. Hereinafter, the hydrogen storage capacity according to the Ni content will be examined.

[0052] Below, the content of nickel in a magnesium-nickel binary hydrogen storage alloy will be explained. The content of nickel in this magnesium-nickel binary hydrogen storage alloy can be equally applied to a hydrogen storage alloy including a composite phase with an added element, and this part will be further explained in Example 2 below.

[0053] In the case of a hydrogen storage alloy including a composite phase according to the present invention, in order to exhibit hydrogen storage capacity, it may include 12 to 31 at% of nickel, may include 12 to 31 at% of nickel, preferably may include 15 to 30 at% of nickel, and more preferably may include 20 at% of nickel. In this case, the additional element may be included in the hydrogen storage alloy including a composite phase in an amount of more than 0 and less than 1.1 at%.

[0054] Figure 5 shows a comparison between the experimental results and theoretical values ​​of the hydrogen storage capacity according to the nickel content in a magnesium-nickel binary hydrogen storage alloy. As shown in Figure 5, the hydrogen storage capacity in the magnesium-nickel binary hydrogen storage alloy began to appear when the nickel content was 12 at% (or exceeding 12 at%), and broadly in the range of 12 to 31 at% and 15 to 30 at%. In this case, as shown in Figure 5, the highest hydrogen storage capacity was observed at 20 at%, in particular.

[0055] The magnesium-nickel binary hydrogen storage alloy exhibited hydrogen storage capability at an Ni content of 12 at% or more (excess), in which case the alloy contained a primary Mg2Ni phase. One possible reason for this is that when the Ni content is less than 12 at% (less than), the primary α-Mg phase appears, which can be interpreted as impeding the hydrogen storage activation (first activation) process. Therefore, at an Ni content of 12 at% or more (excess), reduction and hydrogenation were easy, which resulted in good hydrogen storage activation and excellent hydrogen storage characteristics. This will be described in more detail in Example 1 below with reference to FIG. 6.

[0056] Example 1 describes a magnesium-nickel binary hydrogen-storage alloy. First, the magnesium-nickel binary hydrogen-storage alloy will be described, followed by a hydrogen-storage alloy including a composite phase in Example 2.

[0057] [Example 1]

[0058] The material was prepared by sufficiently melting a pure-Mg ingot in a graphite crucible at around 730℃ using an induction furnace, then increasing the temperature of the molten metal to 850-900℃ and adding Ni. After sufficiently dissolving Ni in the molten metal, the molten metal was poured into a cylindrical Fe mold with a diameter of 55 mm, cast into a billet shape, and cooled in the air. To manufacture chips, the cast billet was fixed to a turning machine and turned, and the chip shape was manufactured as the bite passed. These chips were mounted using resin, and the mounted specimen was polished and the microstructure was observed using an SEM.

[0059] Figure 6 shows the change in microstructure according to the increase in the amount of Ni added in a magnesium-nickel binary hydrogen storage alloy.

[0060] Looking at Figure 6, in the case of Pure Mg, it is a pure magnesium microstructure with no nickel added, as in the case of Mg-0Ni. It mainly forms α-Mg crystals, and the microstructure shows uniform α-Mg crystals.

[0061] For Mg-6Ni, the microstructure of a magnesium alloy with 6% nickel added, the magnesium and nickel combine to form a eutectic structure. The eutectic structure can be seen to form between α-Mg crystals, and the eutectic structure gradually increases as nickel is added.

[0062] For Mg-10.1Ni, the microstructure of a magnesium alloy with 10.1% nickel added represents the eutectic composition. Magnesium and nickel exist as a eutectic mixture, and α-Mg and Mg2Ni are uniformly distributed. The eutectic structure becomes more distinct, showing a uniform distribution of α-Mg and the eutectic mixture.

[0063] For Mg-20Ni, this is the microstructure of a magnesium alloy with 20% nickel added. As the nickel content increases, primary Mg2Ni crystals are formed in addition to the eutectic structure. Primary Mg2Ni crystals are distinct and distributed together with the eutectic structure.

[0064] For Mg-30Ni, the microstructure of a magnesium alloy with 30% nickel added forms more Mg2Ni phase. The microstructure mainly includes the primary Mg2Ni phase and the eutectic structure, and the eutectic structure appears as a mixture of Mg and Mg2Ni.

[0065] In the case of the magnesium-nickel binary hydrogen storage alloy, as shown in Fig. 6, as the Ni content increases, the chip size decreases under the same turning processing conditions. In the case of the conventional manufacturing process (gas atomizing + sintering + ball milling), the ball milling process is used to reduce the powder size. However, as the powder size increases, the amount of hydrogenation in the depth direction is limited, which reduces the storage capacity. Therefore, it is predicted that the hydrogen storage characteristics will be improved as the powder is made finer. In order to improve the hydrogen storage characteristics, when manufacturing in the form of chips as in the manufacturing method of the present invention, the hydrogen storage characteristics will be maximized as the chip size is smaller. In addition, since the chip becomes more fragile as the Mg2Ni content increases, the chip can be made finer. For reference, specimens for evaluating the actual hydrogen storage characteristics can be manufactured and evaluated with a thickness of, for example, approximately 200 μm. For reference, specimens for evaluating the actual hydrogen storage characteristics can be manufactured and evaluated with a thickness of, for example, approximately 200 μm.

[0066] As shown in Fig. 6, when primary α-Mg is present, the first activation process does not proceed smoothly, resulting in deterioration of the hydrogen storage properties. This is because primary α-Mg readily forms a stable and thick oxide layer, which hinders the penetration of hydrogen, making the reduction and hydrogenation processes difficult. Because the thick oxide layer makes it difficult for hydrogen to penetrate into the magnesium, the hydrogen storage properties deteriorate.

[0067] On the other hand, in the presence of primary Mg2Ni in Fig. 6, the First Activation process proceeds smoothly, thereby improving the hydrogen storage characteristics. For example, one reason for this is that primary Mg2Ni forms an unstable oxide film, making it easily reducible. This thin and unstable oxide film can be interpreted as providing a path for hydrogen to easily penetrate. For example, this can be interpreted as hydrogen easily penetrating into the interior of Mg2Ni due to the thin and unstable oxide film, allowing the reduction and hydrogenation processes to proceed smoothly.

[0068] Figures 7a-7c illustrate the hydrogen storage capacity of a magnesium-nickel binary hydrogen storage alloy as a function of Ni content and temperature. The graph in Figure 7 is a PCT (Pressure-Composition-Temperature) graph, which shows how much hydrogen is absorbed and released at a given pressure. The straight line represents the measurement in the direction of hydrogen absorption, and the dotted line represents the measurement in the direction of hydrogen release.

[0069] Hydrogen storage characteristics are measured through hydrogen storage activation (first activation: deoxidation and hydrogenation). For example, magnesium oxide was reduced and hydrogenated in a 60 bar hydrogen atmosphere at 300°C. If hydrogenation was sufficient, there was no change in hydrogen pressure. After sufficient dehydrogenation in a vacuum atmosphere, the hydrogen storage amount was measured at various temperatures and pressures to complete a PCT (Pressure-Composition-Temperature) curve. In this case, when primary α-Mg was present, the first activation did not occur at all, so the 60 bar hydrogen pressure did not decrease at all. This is believed to be because the oxide layer became stable and thick, resulting in little reduction. On the other hand, when primary Mg2Ni was formed, the oxide film was unstable, so reduction occurred easily. One explanation for this could be that hydrogen easily penetrates the oxide film, enabling deoxidation and hydrogenation, thereby realizing hydrogen storage characteristics.

[0070] [Example 2]

[0071] Example 2 was manufactured in the same manner as Example 1. Nickel was added to magnesium, and the molten metal was melted, and the molten metal was added with additional elements, and the molten metal was melted at a temperature higher than the melting point of the additional elements, and the molten metal was poured into a mold to manufacture it. The additional elements were Nd, Zn, Gd, Sn, Y, and Ag. Figures 8 to 13 illustrate the microstructures of ternary alloys with Y, Sn, Gd, Ag, Nd, and Zn added as additional elements, respectively. In this case, the microstructure is the microstructure after casting. After Ni was sufficiently melted, Mg-30Y, Mg-38.43Gd, Mg-15Nd master alloys (wt.%) or pure Ag, Zn, and Sn were added as additional elements to manufacture it. In this case, the Ni content was fixed at 20 at% and the experiment was conducted.

[0072] Figure 8 shows the microstructure of a ternary alloy with Y added as an additional element, confirming that a secondary phase is formed.

[0073] Figure 9 shows the microstructure of a ternary alloy with Sn added as an additional element, confirming that no secondary phase is formed.

[0074] Figure 10 shows the microstructure of a ternary alloy with Gd added as an additive element, confirming the formation of a secondary phase.

[0075] Figure 11 shows the microstructure of a ternary alloy with Ag added as an additive element, confirming the formation of a secondary phase.

[0076] Figure 12 shows the microstructure of a ternary alloy with Nd added as an additional element, confirming that no secondary phase is formed.

[0077] Figure 13 shows the microstructure of a ternary alloy with Zn added as an additional element, confirming that no secondary phase is formed.

[0078] Figures 14a-14c illustrate the hydrogen storage capacity of a hydrogen storage alloy containing a composite phase as a function of added elements and temperature. The graph in Figure 14 is a PCT (Pressure-Composition-Temperature) graph, which shows how much hydrogen is absorbed and released at a given pressure.

[0079] Figure 15 shows the degree of hydrogen activation and hydrogen storage capacity over time depending on the Ni content and added elements. By measuring the decrease in hydrogen pressure over a long period of time under conditions of 300°C and 60 bar of hydrogen, the degree of activation can be determined. It is predicted that materials with faster activation will be more suitable for use. The conditions of 300°C and 60 bar were specific temperatures and pressures established to promote hydrogenation reactions in experiments and applications of hydrogen storage alloys, and the hydrogen storage capacity and characteristics of the alloys were evaluated under these conditions.

[0080] In the embodiment of Fig. 15, the maximum addition content as the maximum solid capacity in the Mg matrix when Mg-20Ni is Sn is 1.16 at%, Y is 0.98 at%, Zn is 0.76 at%, Ag is 1.07 at%, Gd is 1.13 at%, and Nd is 0.1 at%. Therefore, it is preferable that Sn is more than 0 and less than 1.16 at%, Y is more than 0 and less than 0.98 at%, Zn is more than 0 and less than 0.76 at%, Gd is more than 0 and less than 1.13 at%, and Nd is more than 0 and less than 0.1 at%. In the case of Sn as an example, the wt% is approximately more than 0 and less than 5 wt%, and preferably about 3 wt%. (See Fig. 16)

[0081] As shown in Fig. 15, except for Ag among the additive elements, it was confirmed that the hydrogen activation over time was better for Nd, Zn, Gd, Sn, and Y than when no additive elements were added. Therefore, since the addition of alloying elements enables faster activation than Mg-20Ni, it is expected that much more price competitiveness will be secured even when commercialized. In particular, it was confirmed that Zn and Sn greatly improved the activation and hydrogen storage speed.

[0082] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. A step of melting a magnesium ingot to make it into a liquid state; A step of adding nickel to the above-mentioned molten magnesium and dissolving the nickel; A step of adding one or more additive elements among Nd, Zn, Gd, Sn, and Y to the molten metal and melting the additive elements; A step of lowering the temperature of the molten metal by referring to the phase diagram according to the nickel content; and A step of pouring molten metal into a preheated iron mold for casting, A method for manufacturing a hydrogen storage alloy including a composite phase.

2. In paragraph 1, The step of melting the above magnesium ingot to make it into a liquid state is: Magnesium is dissolved at a temperature of 700 to 900°C under a mixed protective gas of CO2 and SF6 to prevent oxidation of magnesium. A method for manufacturing a hydrogen storage alloy including a composite phase.

3. In paragraph 1, The step of adding nickel to the above-mentioned molten magnesium and dissolving nickel is: 1cm nickel 3 (or 1,000mm 3 ) and add it and wait for 1 to 2 hours so that the nickel can melt. A method for manufacturing a hydrogen storage alloy including a composite phase.

4. In paragraph 1, The step of adding one or more additive elements among Nd, Zn, Gd, Sn, and Y to the above molten metal and melting the additive elements is as follows: Adding the additive element while maintaining the temperature of the molten metal above the melting point of the additive element and maintaining the molten metal so that the additive element can be dissolved in the molten metal. A method for manufacturing a hydrogen storage alloy including a composite phase.

5. In paragraph 1, The step of pouring molten metal into the above preheated iron mold and casting is as follows: Prepare an iron mold preheated to about 200℃, Pour the molten metal into the mold and let it cool to solidify. A method for manufacturing a hydrogen storage alloy including a composite phase.

6. In paragraph 1, After the step of pouring molten metal into the above preheated iron mold and casting, further comprising a step of turning or crushing the cast alloy, A method for manufacturing a hydrogen storage alloy including a composite phase.

7. In paragraph 1, A hydrogen storage alloy comprising 12 to 31 at% of nickel, including the above composite phase. A method for manufacturing a hydrogen storage alloy including a composite phase.

8. In paragraph 1, A hydrogen storage alloy comprising 15 to 30 at% of nickel, including the above composite phase. A method for manufacturing a hydrogen storage alloy including a composite phase.

9. In paragraph 1, A hydrogen storage alloy containing 20 at% nickel including the above composite phase, A method for manufacturing a hydrogen storage alloy including a composite phase.

10. In paragraph 1, The above-mentioned additive element is included in the hydrogen storage alloy including the above-mentioned composite phase in an amount of more than 0 and less than 1.1 at%. A method for manufacturing a hydrogen storage alloy including a composite phase.

11. Manufactured according to any one of the manufacturing methods of Articles 1 to 10, Hydrogen storage alloy containing a composite phase.

12. An alloy composed of magnesium (Mg), nickel (Ni) and additive elements. The nickel content is 12 to 31 at%, The above additive element is at least one of Nd, Zn, Gd, Sn, and Y. Hydrogen storage alloy containing a composite phase.

13. In paragraph 12, The nickel content is 15 to 30 at%, Hydrogen storage alloy containing a composite phase.

14. In paragraph 12, The above nickel content is 20 at%, Hydrogen storage alloy containing a composite phase.

15. In paragraph 12, The above-mentioned additive element is included in the hydrogen storage alloy including the above-mentioned composite phase in an amount of more than 0 and less than 1.1 at%. Hydrogen storage alloy containing a composite phase.

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