JP2896433B2 - Magnesium hydrogen storage alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesium-based hydrogen storage alloy, and more particularly to a magnesium-based hydrogen storage alloy having a high hydrogen release pressure, which can reduce the temperature for storing and releasing hydrogen and having a large hydrogen storage amount. About.

[0002]

2. Description of the Related Art In the background of environmental problems and energy problems,
Recently, attention has been paid to hydrogen energy. Among them, a hydrogen storage alloy is considered as one of the means for easily storing and transporting hydrogen. Important properties required of a hydrogen storage alloy include a large amount of hydrogen storage and the ability to store and release hydrogen at an appropriate temperature. These as conditions to satisfy some extent alloys, for example, there are ₅ type alloy and TiMn _{1. 8} based alloys LaNi, it has also been used in hydrogen vehicle or the like has been developed until now. In particular, the former alloy has been put to practical use in Ni-H secondary batteries. However, these alloys have the fatal drawback of low hydrogen storage capacity. For this reason, the battery has a shortage of capacity, and the car has a problem such as a short cruising distance. As means for solving these problems, use of a magnesium-based hydrogen storage alloy having a larger hydrogen storage amount than these alloys has been studied. However, this magnesium-based hydrogen storage alloy has a problem that it hardly stores and releases hydrogen near room temperature.

[0003]

Accordingly, an object of the present invention is to provide a magnesium-based hydrogen storage alloy having a high hydrogen release pressure.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the above object can be surely achieved by a magnesium-based hydrogen storage alloy having the following composition. Is reached. _{Mg 2-x A x Ni 1} -y B y ( where, A is boron, silicon, shows an element selected from the group consisting of aluminum and zinc, B is selected from the group consisting of copper, manganese and zinc In this case, when A is aluminum and zinc, B
Is not manganese and zinc. Also, 0 <x ≦ 0.4 and 0 <y ≦ 0.5. )

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The magnesium-based hydrogen storage alloy of the present invention is an alloy represented by the above formula. Component A used in this alloy
Is selected from boron, silicon, aluminum and zinc. These elements are smaller than the atomic radius of Mg and can form a hydride. By substituting a part of Mg, the volume of the crystal lattice (lattice volume) is reduced, and nickel described later is substituted. Combined with the component B, the hydrogen release pressure of the resulting magnesium-based hydrogen storage alloy can be increased as compared with the conventional magnesium-based hydrogen storage alloy. As the A component element, boron and aluminum are particularly preferable. Component B element is copper,
Selected from manganese and zinc. These elements, in combination with the A component, are believed to manifest the potential for enhancing the hydrogen release pressure created by the reduced lattice volume. However, when the B component is manganese and zinc, among the elements that can be used as the A component, even in combination with aluminum and zinc, the hydrogen release pressure cannot be improved. Copper is particularly preferred as the B component element.

The amount (x) of the component A which substitutes magnesium in the above composition formula is 0 <x <0.4, and preferably satisfies 0.05 ≦ x ≦ 0.2. When the amount of the component A is within this range, the hydrogen release pressure of the obtained magnesium-based hydrogen storage alloy can be improved. On the other hand, the amount (y) of the component B substituting nickel in the above composition formula is 0 <
y ≦ 0.5, preferably 0.2 ≦ x ≦ 0.5.
When the amount of the component B is within this range, the hydrogen release pressure of the obtained magnesium-based hydrogen storage alloy can be improved. The magnesium-based hydrogen storage alloy of the present invention is, for example, in an inert atmosphere such as argon, in a calculated amount, together with magnesium and nickel, A component element and B component element so that the composition of the obtained magnesium-based hydrogen storage alloy. Into a crucible, heated and melted by a heating means such as high frequency melting, and then cooled. However, when boron is used as the component A, the melting point of boron is very high. For example, a compound of nickel and boron (melting point: 1031 ° C.) such as Ni ₄ B ₃ is preferably used.
Further, since the vapor pressure of magnesium is high, the inert gas pressure as an atmosphere is, for example, 0.1 Mpa or more, especially 0.2 Mpa.
The pressure is preferably set to 0.4 MPa.

[0007] The composition of the obtained magnesium-based hydrogen storage alloy can be easily measured by combining chemical analysis and X-ray diffraction analysis. In particular, zinc is a component A element that replaces magnesium, and a component B element that replaces nickel. When manufacturing a magnesium-based hydrogen storage alloy using zinc, whether to replace Mg or Ni,
This will be confirmed by analyzing the actually obtained magnesium hydrogen storage alloy. Particularly preferred examples of the magnesium-based hydrogen storage alloy of the present invention include, for example, the following magnesium-based hydrogen storage alloys. Mg _1.9 B _0.1 Ni _0.8 Cu _0.2 Mg _1.8 B _0.2 Ni _0.8 Cu _0.2 Mg _1.9 Si _0.1 Ni _0.8 Cu _0.2 Mg _1.8 Si _0.2 Ni _0.8 Cu _0.2 Mg _1.9 Al _0.1 Ni _0.8 Cu _0.2 Mg _1.8 Al _0.2 Ni _0.8 Cu _0.2

[0008]

The present invention will be described below in more detail with reference to examples. Example 1 In this Example 1, characteristics of an alloy obtained by substituting a part of Mg of Mg ₂ Ni with another element were examined. Composition formula: Mg _1.9
Magnesium, an A component element (excluding boron) and nickel are charged into a crucible in such an amount as to form an alloy represented by A _0.1 Ni (A = boron, silicon, zinc or aluminum), and placed in an argon atmosphere at 0.1 MPa. , Heat and dissolve by high frequency dissolving means and then at room temperature (25
C) to produce an alloy having the above composition. When the A component was boron, an alloy was produced by mixing Ni ₄ B ₃ as the boron component. In the above composition formula, A = Mg when no component A was used. The composition and lattice constant of the obtained alloy were calculated by X-ray diffraction.
In addition, the hydrogen storage characteristics of the alloy were determined by activating at a reaction temperature of 300 ° C. and a hydrogen pressure of 30 Kg / cm ² , and then proceeding to a pressure composition isotherm at 250 ° C.
Calculated by measuring T).

FIG. 1 shows an A component element that replaces a part of Mg.
Radius calculated from the X-ray diffraction peak and the atomic radius (horizontal axis) of
The relationship with the child volume is shown. Figure 2 shows the PCT of an alloy of the above composition
The curve is shown. From FIG. 1, the atomic radius of the component A decreases.
The lattice volume of the resulting alloy can
I understand. From FIG. 2, it can be seen that 250 ° C.
To form a release plateau, at which time the plateau release pressure is
About 1Kg / cm^TwoMet. This release pressure is Mg_TwoAlmost Ni
Were identical. Therefore, from the above results, Mg_1.9A
_0.1In Ni-based alloys, the volume effect of the crystal lattice is
It turns out that it does not contribute to the improvement of the hydrogen release pressure. Example 2 This example 2 uses Mg_1.9A_0.1Ni_0.8Cu_0.2A component of
When the element is boron, silicon, aluminum or zinc
It is a result of examining the properties of the alloys obtained. Manufacture of this alloy
Was performed in the same manner as in Example 1. Also, the obtained alloy set
The composition, lattice volume and hydrogen storage properties were measured in the same manner as in Example 1.
Specified. When A is Mg, that is, when Mg is_TwoNi
_0.8Cu_0.2In the same manner for the ternary alloy
And examined its characteristics. FIG. 3 shows the atomic half of the A component element.
The lattice calculated from the diameter and the X-ray diffraction peak of the obtained alloy
This shows the relationship with the volume. Mg_1.9A_0.1For Ni-based alloy
In the same way as above, place Mg with the A component element having a small atomic radius.
In other words, the lattice volume of the resulting alloy decreases.
Call FIG. 4 shows the lattice volume for an alloy of the above composition and water
The relationship with the elementary release pressure is shown. The vertical axis is from the PCT curve of the alloy.
The logarithmic value of the obtained plateau discharge pressure is shown, and the horizontal axis is the grid.
Indicates the volume. As can be seen from FIG. 4, the smaller the lattice volume, the more hydrogen
It can be seen that the discharge pressure increases.

Example 3 This example 3 is based on Mg _1.9 Al _0.1 Ni _0.8 B _0.2
In the alloy represented by the following composition formula, the alloy characteristics when the B component element in the formula was replaced with manganese, copper, cobalt, or zinc were examined. The alloy was produced in the same manner as in Example 1. The composition, lattice volume, and hydrogen storage properties of the obtained alloy were measured in the same manner as in Example 1. In the case where the B component element is Ni, that is, Mg _1.9 A
A ternary alloy of l _0.1 Ni was produced in the same manner, and its characteristics were examined. FIG. 5 shows the relationship between the lattice volume of the obtained alloy and the hydrogen release pressure. In FIG. 5, the vertical axis shows the plateau release pressure obtained from the PCT curve of the alloy, and the horizontal axis shows the lattice volume. According to FIG. 5, when copper is used as the B component element, the hydrogen release pressure is about 1.8.
5 kg / cm ^2, which is much larger than the value near 1 of unsubstituted Mg ₂ Ni. On the other hand, when zinc and manganese are used as the B component elements, the logarithmic value of the hydrogen release pressure is around 1 kg / cm ² , which is not much different from the case of Mg ₂ Ni. , The value when aluminum is used as the A component element,
It is considered that when the A component element is boron, it is considerably larger than in the case of Mg ₂ Ni.

Example 4 An alloy having the following composition was produced. The production method and the method for measuring the properties of the alloy were the same as in Example 1 above. 1) Mg _1.9 B _0.1 Ni _0.8 Cu _0.2 2) Mg _1.8 B _0.2 Ni _0.8 Cu _0.2 Similarly, an alloy having the following composition was similarly produced for reference. 3) Mg _1.9 B _0.1 Ni 4) Mg ₂ Ni The hydrogen release pressure at 250 ° C. of each of the above alloys is as follows.

[0012]

Table 1 Alloy No. Hydrogen release pressure (Kg / cm ² ) 1 1.85 2 1.6 3 1.0 4 From the results of more than 1.0, Alloys 1 and 2 release more hydrogen than Alloy 4. It turns out that pressure is large. Further, alloys 1 and 2 are more alloyed than alloy 3 in which a part of Mg is replaced by boron.
It turns out that it is excellent in hydrogen release pressure. In addition, it can be seen that Alloys 1 and 2 are superior in Mg _0.8 Ni _0.8 Cu _0.2 alloy shown in FIG. 4 in hydrogen release pressure.

[0013]

According to the present invention, in a Mg ₂ Ni-based hydrogen storage alloy, a specific element is used as an A component element that replaces Mg, and at the same time, a specific element is used as a B component element that replaces Ni. By using the alloy, an alloy having a higher hydrogen release pressure than that of a conventional magnesium-based hydrogen storage alloy was obtained. Conventionally, Mg ₂ Ni-based alloys cannot provide a practical hydrogen release pressure of 1 kg / cm ² or more unless the temperature is 250 ° C. or more. On the other hand, according to the present invention, for example, a hydrogen release pressure of 1.8 kg / cm ² or more can be generated at 250 ° C. In particular, when copper is used as the B component, the hydrogen release pressure becomes 1.8 kg / cm ² or more. In other words, if a hydrogen release pressure of 1 kg / cm ² is provided as before, the operating temperature can be lowered further than 250 ° C. Moreover, the magnesium-based hydrogen storage alloy of the present invention is very useful because it has a larger hydrogen storage amount than other hydrogen storage alloys. For example, the magnesium-based hydrogen storage alloy of the present invention can be widely used as a Ni-H battery, a heat pump, and a battery for an automobile.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a substitution element radius and a lattice volume of an obtained alloy.

FIG. 2 is a diagram showing a relationship between a hydrogen storage amount and a logarithmic value of a hydrogen release pressure.

FIG. 3 is a diagram showing a relationship between a substitution element radius and a lattice volume of an obtained alloy.

FIG. 4 is a diagram showing a relationship between a lattice volume and a logarithmic value of a hydrogen release pressure.

FIG. 5 is a diagram showing a relationship between a lattice volume and a logarithmic value of a hydrogen release pressure.

FIG. 6 is a diagram showing a relationship between a lattice volume and a logarithmic value of a hydrogen release pressure.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-268403 (JP, A) JP-A-6-76817 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 23/00 C22C 19/00

Claims (2)

(57) [Claims] 1. The following composition: Mg_2-xA_xNi_1-yB_y  (However, A is boron, silicon, aluminum and zinc
Represents an element selected from the group consisting of
2 shows an element selected from the group consisting of zinc and zinc. this
In case A is aluminum and zinc, B
Is not manganese and zinc. Also, 0 <x ≦ 0.4
And 0 <y ≦ 0.5. )
A magnesium-based hydrogen storage alloy characterized by the following. 2. The magnesium-based hydrogen storage alloy according to claim 1, wherein A is boron and B is copper.