JPS5928625B2 - Mitsushimetal-Nickel based ternary alloy manufacturing method for hydrogen storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing a Mitshu metal-nickel based ternary alloy for hydrogen storage, and in particular, to improve the hydride composition in the flat region of hydrogen storage and dissociation pressure characteristics at a constant temperature, the so-called plateau region. The present invention relates to a method for producing an alloy having characteristics that show little change in hydrogenation pressure.

It has been well known that certain metals or alloys react with hydrogen under appropriate pressure and temperature to produce metal hydrides.

Compared to other solid-gas reactions, this reaction has good reversibility, a fast reaction rate, and a large amount of heat storage per unit weight or unit volume, so metal hydrides are used in various energy conversion materials. It is being considered for use in systems such as

By the way, in the case of such uses, one of the extremely important properties in practice is the hydrogen absorption and dissociation properties at a constant temperature.
In particular, it is required that the plateau region be flat and that the pressure change with respect to the hydride composition be small.

However, multi-component alloys for hydrogen storage are generally produced by directly melting the component metals in an argon arc furnace, high frequency furnace, etc.
Because it is manufactured by mixing, a rapid change from liquid to solid occurs during the cooling process, and it solidifies with unstable lattice gaps, resulting in a single-phase alloy. The disadvantage was that it became larger.

Therefore, the present invention aims to eliminate such conventional drawbacks, and because the obtained alloy is single-phase and the interstitial distance of the crystals is almost constant, it is more effective than conventional alloys. It has the advantage that the pressure change in the plateau region is extremely small, and the amount of hydrogen that can be used for practical purposes is large.Moreover, the reaction rate with hydrogen during the hydrogen absorption and release process is fast, so the reaction completion time is shortened. It has the following.

That is, the present invention has developed a Mitshu metal (hereinafter abbreviated as Mm)-nickel based ternary alloy by treating it under various conditions and examining the effect on the pressure change in the plateau region. It was discovered that the above-mentioned conventional drawbacks could be overcome by heat treatment for a short time at a temperature below the melting temperature of , and this was completed.
This is a method for producing a Mitshu metal-nickel based ternary alloy for hydrogen storage, which is characterized by heating to a temperature of 00 to 1000°C and then cooling.

However, the lion in the ceremony represents Mitsushmetal, A is A6,
An element selected from the group consisting of Cr, Si, and Co, and when A is Ae, Cr, or Si, X is 0
．． It is a number in the range of 01 to 2, and when A is Co, X is 0,
The number ranges from 1 to 4.9.

The raw material alloy used in the present invention is a Mitshu metal-nickel based ternary alloy consisting of Mm, nickel and an element selected from the group consisting of An, Cr, Si and Co, and has the general formula rVIrnNt5-xA.
This is indicated by x.

And X is 0 when A is A6, Cr and Si
．． The number ranges from 01 to 2.

When X is less than 0.01, the properties are only close to those of MmNi 5 and the effect of adding metal A (AI, Cr, Si) cannot be achieved.

That is, since MrnNi5 hydride has a high dissociation pressure, activation requires applying high pressure hydrogen after sufficient degassing, maintaining low temperature in a hydrogen atmosphere, or a combination of both. It gives rise to a certain point.

When X is 2 or more, the ease of activation is maintained, but the hydrogen storage capacity is significantly reduced, making it difficult to release the stored hydrogen, resulting in the problem of requiring high-temperature heating and sometimes combining this with depressurization. .

Further, when A is Co, X is a number in the range of O51 to 4,9.

When X is less than 0.1, the properties only close to those of MmNi 5 are exhibited, and the effect of Co addition cannot be achieved.

That is, activation requires the application of high-pressure hydrogen, maintenance at low temperatures in a hydrogen atmosphere, or a combination of both, which is a disadvantage.

When X is 4.9 or more, it exhibits characteristics close to MITICo5,
A problem arises in that the amount of hydrogen storage is approximately half that of MmNi5.

The present invention is carried out by heating the Mitshu metal-nickel based ternary alloy to 500 to 100° C. and cooling it.

Heating may be carried out in the presence of air, but if the surface layer of the alloy is oxidized, heating may be carried out under reduced pressure, or in an inert atmosphere such as in the presence of an inert gas such as argon, or a combination of both. It is preferable to do so.

Heating may be performed by any method, for example, using a siliconite or nichrome heating element electric furnace.

The heating temperature depends on the combination with the heating time, but is usually in the range of 500 to 1000°C, preferably 600°C.
The temperature range is from 1000°C to 1000°C, more preferably from 700°C to 1000°C, and most preferably from 800°C to 1000°C.

If the heat treatment is carried out for a long time at 500° C. or lower, the same effect as the treatment in the above temperature range can be obtained, but this is not practical for mass production of alloys.

Furthermore, at temperatures above 1000°C, if the alloy contains Ae, Cr, etc., which have relatively high vapor pressures, some of them will volatilize, increasing the dissociation pressure of hydrides, and making it difficult to obtain an alloy with the desired composition. It disappears.

The heating time is determined from the relationship with the heating temperature, and the heating time is 1000°C within the range of 500 to 1000°C.
If the temperature is close to 500°C, it may take a short time; if the temperature is close to 500°C, it may take a long time, but generally it is in the range of 0.25 to 6 hours.

If it is less than 0.25 hours, the effect of the alloy heat treatment tends to decrease, and if it is more than 6 hours, there is no difference in the heat treatment effect.

For cooling after heating the alloy, it may be rapidly cooled in ice water immediately after heating, or it may be slowly cooled in air.

Note that Mm, which is a component of the alloy used in the present invention, is generally 25 to 35% lanthanum (by weight, the same hereinafter) and 40% cerium.
~70%, Praseodymium 1-15%, Neodymium 4-
15%, samarium + gadolinium 1 to 7, iron 0.1
~5%, silicon 0.1-1%, magnesium 0.1-2
It contains 0.1 to 1 grade of Hiroshi aluminum and can be easily and inexpensively made by hand.

Further, the alloy (1) nN + 5-

That is, the metals of nickel and A component are respectively powdered or shaped into appropriate shapes so as to have the alloy composition described above.
For example, after mixing in the form of a rod, it is press-formed into an arbitrary shape, the molded product is charged into an argon arc furnace, and the composition is homogenized by repeating heating, melting, and cooling several times in an inert atmosphere. , taken out from the furnace and used as a raw material alloy.

According to the method of the present invention, excellent effects can be imparted to the MmNi5-xAx alloy through relatively simple operations.

In other words, by heat-treating the raw material alloy at 500 to 1000°C and cooling it, the unstable lattice gaps that occur during alloy production disappear and a single-phase alloy is obtained, and the interstitial distance between the crystals also decreases. Since it remains almost constant, it has the advantage that compared to conventional alloys, the pressure changes in the flat or plateau region of the hydrogen storage and dissociation pressure characteristics at a constant temperature are extremely small, and the amount of hydrogen that can be used for practical purposes is large. are doing.

Moreover, since the reaction rate with hydrogen during the hydrogen absorption and desorption process is fast, the reaction completion time is shortened, and the hydrogen absorption reaction is completed in a short time.

Furthermore, no matter how many times the hydrogen storage and release reactions are repeated, there is virtually no deterioration of the alloy itself, and therefore it can be used for a long period of time, making it extremely excellent as a hydrogen storage alloy.

Furthermore, the method of the present invention can be applied not only to a ternary Ni-nickel alloy, but also to a ternary or higher hydrogen storage multi-component alloy containing 1 and Ni as main components, such as MfTll-XAXNi5. Shil-XA3Nl5-yBy.

Mml xAx-2C2Ni5゜ Mml-xAx-2C2N15-yB,.

Mml-XAxNi5-yB, -202 (both A,
B and different elements) can also be used in the same way.

Examples of the present invention will be described below.

Example 1 Conventional alloy manufactured by argon arc furnace melting method, t4,5 Ae6.5, MmN t2,5
Co2.5.

1'v1mN i4.5 CrO,5 and MmNi4
．． 5S io and 5 were each placed in a quartz container, and after introducing argon to sufficiently replace the gas in the container, the inside of the container was maintained at a pressure of 1 torr using a vacuum device.

This container was placed in an electric furnace previously maintained at 900'C and heat treated.

The heat treatment was stopped after 2 hours, and the mixture was immediately cooled in ice water.

In this way, the heat treatment temperature and treatment time were varied to examine the effects on the heat treatment effect.

The results are shown in Table 1. Note: The heat treatment effect was compared with the effect that appeared under heat treatment conditions of 900° C. and 2 hours as 100.

A: 90-100 ratio 8170-90% C: 50-70% D = 50% or less As is clear from Table 1, heat treatment temperature 500-100
All of the heat-treated alloys obtained under the conditions of 0°C and a treatment time of 0.25 hours (15 minutes), preferably a treatment time of 2 hours, had a remarkable heat treatment effect, as shown in Figures 1 to 3 below. It has good crystallinity, very little pressure change in the plateau region of the hydrogen storage pressure-composition isotherm, and has a fast hydrogen storage rate, making it an excellent hydrogen storage material.

Example 2 Conventional alloy produced by argon arc furnace melting method,
MmN i 4.5 Ae o, i'r 1 torr
Heat treatment was performed at 900°C for 2 hours in an argon gas atmosphere.

FIG. 1 shows the powder X-ray diffraction patterns of this heat-treated alloy and a conventional alloy that was not heat-treated.

As is clear from FIG. 1, the X-ray diffraction pattern of the alloy heat-treated according to the present invention has a sharper shape than the X-ray diffraction pattern A of the alloy that has not been heat-treated, and the half-width of the peak is significantly larger. It can be seen that the crystalline phase becomes much smaller and has a homogeneous crystalline phase.

Example 3 MmN i 4.5AJ O, heat treated in Example 2
5 was heated and degassed at 80°C under reduced pressure, and after being sufficiently activated with hydrogen, MmN i4.5Ae in the hydrogen storage reaction,
The storage pressure car hydride composition isotherm (40° C.) of the 5-H system was compared with that of the alloy without heat treatment.

The results are shown in Figure 2.

It has been known that when some of the nickel in MmNi5 is replaced with other elements, the pressure gradient in the plateau region becomes steeper as the substitution progresses; for example, the MmNi5-XA total alloy , X increases in the range of 0.1 to 2, the slope of the plateau region also increases gradually.

However, as shown in FIG. 2, the pressure change in the plateau region of the hydrogen storage pressure-composition isotherm A of MmN i 4.5 Aeo, 5, which was heat-treated according to the present invention, was in the range of 2.3 to 4.5 atm. G) Mm
The isotherm B of Ni4.5Aeo,5 varies greatly in the range of 1.6 to 6.0 atmospheres, and it is clear that the alloy according to the present invention has extremely excellent properties as a hydrogen storage material.

Example 4 Alloy MmN i4.5 A6o heat treated as in Example 2
, 5 was measured.

NIl′T1Ni4.5A6o without heat treatment,
A comparison with alloy No. 5 is shown in FIG.

As is clear from FIG. 3, the hydrogen storage reaction rate A of the heat-treated alloy completes the reaction in approximately 1/2 the time of the reaction rate B of the non-heat-treated alloy.

[Brief explanation of drawings]

FIG. 1 shows alloys obtained by the method of the present invention and the conventional method, MmNi4. , Aeo, and 5, FIG. 2 is a hydrogen storage pressure-hydride composition isotherm diagram of these alloys, and FIG. 3 is a diagram showing the relationship between hydrogen storage rate and time of these alloys.

Claims (1)

[Claims] 1 Mitshu metal for hydrogen storage, characterized in that an alloy represented by the general formula MITINi5-xAx is heated to a temperature of 500 to 1000°C, and then this alloy is cooled.
A method for producing a nickel-based ternary alloy. However, in the formula, the kite represents Mitsushmetal, A represents an element selected from the group consisting of A#, Cr, Si, and Co, and when A is Ae, Cr, and Si, X is a number in the range of 0.01 to 2. and when A is Co, X is 0
．． The number ranges from 1 to 4.9.