JPS5822536B2 - Alloy for hydrogen storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrogen storage alloy, and more particularly to a hydrogen storage alloy that can easily store and desorb hydrogen at relatively low temperatures, preferably at a temperature around room temperature, and that can easily store and desorb hydrogen at relatively low temperatures, preferably at temperatures around room temperature. The present invention relates to hydrogen storage alloys that are stable, reversible and usable on an industrial scale.

Conventionally, as an alloy for hydrogen storage, for example, LaNi5
tMg2N+ j TiFe and the like are known.

The hydrides of these alloys can release hydrogen at a lower temperature than the hydrides of simple metals such as La and Mg 5 Ti.

However, LaNi5 is expensive, the dissociation equilibrium pressure of hydrogen in Mg2Ni hydride is not very high, and TiFe
However, these alloys have drawbacks such as difficulty in activation, making it difficult to use these alloys for industrial-scale hydrogen storage.

On the other hand, it was discovered that an alloy with a composition of TiMn1.5 can absorb hydrogen well, and various applications of this alloy as a hydrogen storage alloy were investigated.
Several proposals have been made to use an alloy having the composition (Ti, -xZrx)M (where M represents a metal) as a hydrogen storage material.

The analogy is JP-A-52-100319.52-12440
7.53-48011, 54-68702 etc., M
As Mn, Cu, Co.

Using Cr, Mo, Fe, etc., and M as 1
Generally ternary to five-component alloys are disclosed that use two or three metals rather than one metal.

It is said that the hydrides of these alloys have a high hydrogen equilibrium pressure at temperatures around room temperature, and that the equilibrium pressure can be adjusted by changing the types and proportions of the alloy components.

Therefore, the present invention aims to develop hydrogen that can be further developed and manufactured at lower cost, and can be used on an industrial scale to absorb and release hydrogen more stably and reversibly. This was made to develop a storage alloy, and it provides a four-component hydrogen storage alloy that is made of relatively inexpensive metals such as Ti+Zr5Mn and Fe and can absorb and release hydrogen at relatively low temperatures. .

That is, the hydrogen storage alloy of the present invention has the general formula Z r x
T I ]-x(F eyMn ]-ρ, where X is 0.2≦X≦o, s, y are 0
．． 2≦y≦0.8. It is characterized in that z is a number in the range of 1.3≦2≦1.7.

Of the four types of metals constituting the hydrogen storage alloy of the present invention, Ti and Zr form a solid solution over the entire composition range of the above general formula, Ti and Mn, Ti and Fe.

There are some intermetallic compounds in binary systems such as Z r and Mn, and Zr and Fe.

In addition, there are no intermetallic compounds in the binary system of Mn and Fe, and there is a wide solid solution range at high temperatures, but at temperatures below 700°C, α-Fe phase, ε-Fe phase, γ single phase, α-Mn There are phases etc.

Therefore, these four types of metals are likely to form alloys with each other, and even if there are four components, a single four-component intermetallic compound may be formed within a certain range of components.

Zr and Ti that constitute the hydrogen storage alloy of the present invention.

The composition range of Fe and Mn is determined by the existence range of such single-phase quaternary intermetallic compounds, those that absorb hydrogen among these four-component metal compounds, and those that absorb hydrogen and, after releasing the occluded hydrogen, the four-component alloy phase. This indicates the range in which four-component alloys exist, where the alloy completely returns to the alloy phase before hydrogen storage and no metal elements or binary or ternary alloys appear, and alloys in this composition range are suitable as hydrogen storage materials. This is what I discovered.

The structure of the hydrogen storage alloy of the present invention is hexagonal.

When X, Y, and Z are within the above ranges, as X increases, both the a and c axes of the unit cell of the crystal become dog, and as y increases, a
Both the axis and the C-axis become smaller.

When X is less than 0.2 or more than 0.8, or 2
When 2 is smaller than 1.3 or 1.7, hydrogen absorption and release properties become poor, and especially when 2 approaches 2.0, the amount of absorbed hydrogen decreases.

Also, when y is smaller than 0.2, the behavior is essentially the same as that of y = o, and when y is 0.8 or more, the behavior is essentially the same as that of y = = l. will be the same.

The hydrogen storage alloy of the present invention can be produced by melting the raw metal in the above composition range by a normal alloy manufacturing method, such as a method using a high frequency furnace or an arc melt method, in an atmosphere of an inert gas such as argon. It can be easily manufactured.

The metal material used may be of industrial grade with a purity of 97 to 98% or less, but in consideration of increasing the effective hydrogen amount of the alloy hydride, it is preferably a metal material with a purity of 99% or more.

As mentioned above, the alloy of the present invention is a four-component single phase, does not contain metal elements, or binary or ternary alloy phases, and is easy to crush.

In addition, the alloy of the present invention does not need to be finely pulverized for the initial hydrogen storage, and it is only necessary to crush the alloy into an appropriate size and store it in a container.

Further, there is no need to exhaust the inside of the container at a high temperature, and hydrogen can be occluded by introducing hydrogen into the container at a pressure of about 0.1 to 4 MPa at room temperature after exhausting the inside of the container at room temperature.

An alloy that absorbs hydrogen becomes a hydride, but when this hydride is heated to a relatively low temperature, preferably around room temperature, or under reduced pressure, hydrogen is released and the metallographic structure returns to the original alloy. .

That is, the alloy of the present invention can stably and reversibly absorb and release hydrogen at relatively low temperatures.

That is, the dissociation equilibrium pressure of the hydride of this alloy can be changed by changing the composition of the alloy, that is, by changing the values of X and y within the above ranges.

Generally, the dissociation equilibrium pressure at the same temperature becomes lower as X becomes larger, and becomes higher as y becomes larger.

Since the hydrogen storage alloy of the present invention has the above characteristics,
By changing X, y, and z, it is possible to design an alloy that has a practically necessary dissociation equilibrium pressure and a large amount of effective hydrogen.

As described above, according to the hydrogen storage alloy of the present invention,
Since industrial-grade raw metals can be adjusted to within the composition range of the general formula and easily manufactured using known alloy manufacturing methods, alloys can be obtained at extremely low costs, and at relatively low temperatures.
Preferably, it is possible to repeatedly store and release hydrogen stably and reversibly at a temperature around room temperature.

Therefore, the hydrogen storage alloy of the present invention can be preferably used for industrial hydrogen storage, transportation, heat storage, chemical boosters, chemical engines, etc.

Hereinafter, the present invention will be explained in detail based on examples.

Example 1 99.9% purity Ti, 99.7% Zr, 99.9% purity
M, n, 99.9% Fe respectively Z r g
, 2TI 0.8 (F e O, 5M116.5)]
,5 t Z r O,5T l O,5(Fe(1
, G, 5) +, 5=Z to, 3T l □, 2 (
Feo, 5MnO, 5), 5. Zr(1,5Tl
o.

(Fe(1,2MnO,8)], 5tZr
O,5'r l O,5(F eO,3Mn□,2
)] and 5, and Arcmel 1 to 5 were repeated six times in argon to produce five types of intermetallic compounds having the above compositions.

After crushing these alloys into soybean-sized pieces, they are placed in a pressure-resistant container.
After evacuation at room temperature, 0.01MPa to 4.0 at room temperature
When introducing MPa of hydrogen, hydrogen was absorbed immediately or after an induction time of several minutes.

If enough hydrogen is absorbed, the alloy will be finely pulverized.

The figure shows hydrogen equilibrium dissociation pressure isotherms at 150° C. for five types of alloys having these compositions, which were measured after hydrogen absorption and release were repeated several times.

In the figure, the vertical axis shows the dissociation equilibrium pressure of hydrogen (MPa), the horizontal axis shows the composition of the hydride (H atom/1 mole of alloy), and the curve A
is Zr012TIO,B (Feo, 5M, no, 5
), , , curve B is zrO,5TI O,5(Feo
,,Mn,5:),,5,Curve C is Zro, sT Io
,2 (Feo, 5Mno, 5)] ,5, The curve is Z ro,,T I o,5 (Feo, 2Mn0.
3)], 5, curve E is zro, 5'r'0.5 (F
The relationship between the dissociation pressure of hydrogen and the composition of each hydride of e(1,3Mn□,2)1.5 is shown.

As is clear from the figure, the relationship between the dissociation equilibrium pressure of hydrogen and the composition of the hydride shows very characteristic changes depending on the composition of the alloy.

That is, as can be seen from the comparison of curves A, B, and C at y=0.5, as X becomes larger, the dissociation equilibrium pressure of hydrogen becomes lower.

Furthermore, as can be seen from the comparison of curves B and E at x = 0.5, as y increases, the dissociation equilibrium pressure of hydrogen increases.

By changing X and y in this way, the dissociation equilibrium pressure of hydrogen can be adjusted.

Among the alloys with five compositions illustrated here, Zr□, 2
T I □, 3 (F eo, 6Mn o, ri)1.
5 (curve A) has the lowest dissociation equilibrium pressure.

The figure shows the experimental results at 150℃, so Zro
, 2TIo, a (Feo, 5Mn0,5) 1.5 (curve A), IZro, 5T1o, 5 (Feo, 8Mno, 2
) 1.5 (curve E), Zr.

, 5Tlo, 5(F eo, 5”n015) 1.5 (
Curve B) and other curves do not have a plateau, but as the temperature increases, a plateau does exist if the temperature is measured near room temperature.

That is, by changing X and y, a plateau with a desired dissociation equilibrium pressure can be obtained.

When metal hydrides are used for hydrogen storage, transportation, heat storage, chemical boosters, chemical engines, etc., metal hydrides, which have a high equilibrium pressure of hydrogen near room temperature, are advantageous when releasing hydrogen; When storing hydrogen for use, high pressure hydrogen is required, which is disadvantageous.

In this respect, the alloy according to the present invention is advantageous in terms of alloy design because by changing X and y, the equilibrium pressure can be changed by creating a four-component alloy suitable for the operating temperature range.

Moreover, X-ray diffraction shows that the hydride of this alloy completely returns to its original alloy structure after releasing hydrogen, and no change in composition of the alloy or generation of T + H2, Z r H2, etc. is observed.

In other words, these four-component alloys reversibly absorb hydrogen,
It has been confirmed that the material is emitted, and it has become clear that it can be used repeatedly.

[Brief explanation of drawings]

The drawing is a diagram showing the relationship between the dissociation equilibrium pressure of hydrogen at 150° C. and the hydride composition of five types of hydrogen storage alloys according to the present invention.

Claims (1)

[Claims] 1 It has a composition represented by the general formula ZrxTil-x(FeyMnlY)z, where X is 0.2≦X≦0.8.
A hydrogen storage alloy, characterized in that y is a number in the range of 0.2≦y≦0.8 and tz is a number in the range of 1.3≦2≦1.7.