JPS5946294B2 - Method for manufacturing hydrogen storage material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a hydrogen storage material, and in particular to a method for producing a hydrogen storage material.
The present invention relates to a method for producing a hydrogen storage material composed of an intermetallic compound of Zr, Hf or a rare earth metal and Fe, Co or Ni or several such intermetallic compounds.

Such intermetallic compounds have the property of being able to absorb and store a large amount of hydrogen, and conventional hydrogen storage methods using hydrogen storage materials constructed using these intermetallic compounds store hydrogen as a highly compressed gas or as liquefied hydrogen. These hydrogen storage materials have recently attracted particular attention because they have significantly greater hydrogen storage capacity (they are safer and easier to handle) than conventional hydrogen storage methods.

When using the above-mentioned hydrogen storage material to store hydrogen, for example, it is placed in a reaction vessel, the inside of this vessel is evacuated, and then hydrogen is charged into the vessel at an appropriate temperature and under high pressure. Introduce.

This operation is called activation, and it causes a large amount of hydrogen to be stored in the hydrogen storage material in the container in the form of hydrogenated intermetallic compounds.

Thereafter, the hydrogen storage material can absorb or release hydrogen as needed and desired simply by changing temperature or pressure conditions.

However, in the above-mentioned intermetallic compound hydrogen storage material manufactured by conventional manufacturing methods, for example, by melting and solidifying raw materials in an Ar atmosphere, Ti, Zr, etc.
, Hf or rare earth metals are extremely active, so an oxide film is formed on the surface of the material by a trace amount of oxygen gas contained as an impurity in the Ar gas.

This oxide film significantly blocks the ingress and egress of hydrogen and greatly impedes the hydrogen storage function of the hydrogen storage material.

Therefore, the aforementioned intermetallic hydrogen storage materials made by conventional manufacturing methods require heat treatment to remove the oxide layer prior to their activation.

However, this heat treatment is a very troublesome, time-consuming and expensive operation, such as maintaining the material at 450° C. for an extended period of time in a hydrogen atmosphere of 100 kg/cm.

The object of the present invention is to provide a novel method for producing a hydrogen storage material that eliminates such conventional drawbacks.

To achieve this objective, the method for producing a hydrogen storage material of the present invention includes a first raw material consisting of one or more of Ti, Zr, Hf, and metals belonging to rare earths, and Fe, Co, etc.
and a second car consisting of one or more types of Ni.
The raw materials are melted and solidified together in a hydrogen atmosphere or a mixed atmosphere of hydrogen and a rare gas to form an intermetallic compound of the metal contained in the first raw material and the metal contained in the second raw material, with a slight amount of hydrogen. The method is characterized by producing a hydrogen storage material that absorbs hydrogen.

It is already known that in this method, a hydrogen storage material composed of the above-mentioned intermetallic compound can be obtained by melting and solidifying the first raw material and the second raw material together.

However, achieving such dissolution and solidification in a hydrogen atmosphere or a mixed hydrogen and rare gas atmosphere is a novelty that significantly improves the properties of the resulting hydrogen storage material.

According to the method of the invention, during melting and solidification, ie while still hot, hydrogen in the atmosphere is absorbed into the material to be melted and combines with the intermetallic compound.

It has been found that such pre-absorbed hydrogen enhances the hydrogen absorption action upon activation.

In addition, an oxide film is not actually formed, and even if a film such as an oxide film is formed, when it is melted and solidified in a hydrogen atmosphere, this film is extremely permeable to hydrogen due to the action of hydrogen. Remains porous.

Although the above explanation regarding the action of hydrogen is conceptual, it has actually been found that the hydrogen storage material produced by the production method according to the present invention can be made by combining this and raw materials,
It has a better occlusion ability than a hydrogen storage material manufactured by a manufacturing method using the same melting method but using an atmosphere different from that used in the present invention, for example, an Ar atmosphere.

Specifically, it has the same storage capacity as a conventional hydrogen storage material without heat treatment.

In fact, the hydrogen storage material obtained by the method of the present invention can be sufficiently activated even without heat treatment.

As is clear from the above, the atmosphere may consist solely of hydrogen, since hydrogen in the atmosphere provides excellent properties to the hydrogen storage material.

However, as is well known, hydrogen has a very high risk of exploding, so it is desirable and practical to dilute the hydrogen to some extent by employing a mixed atmosphere of hydrogen and a rare gas.

As is well known, the gas does not substantially react with the substances in the pond and therefore does not interfere with the action of hydrogen.

A mixed atmosphere of gases other than rare gases and hydrogen cannot be used because this gas is thought to act on the material to be dissolved and interfere with the action of hydrogen.

Melting in the process of this invention can be accomplished in a variety of ways, but preferred are induction heating melting and non-consumable electrode arc melting.

Both of these dissolving methods are suitable for dissolving the above-mentioned raw materials employed in the dissolving method of the present invention, and are also suitable for dissolving in a closed tank in which a specific atmosphere is maintained.

Of course, solidification must also be carried out in the above-mentioned specific atmosphere, but in the case of arc melting, there is generally no problem in this regard because the crucible itself used for melting is exposed to the mold.

In the case of induction heating melting, both the crucible and the mold must be placed in a specific atmosphere, so measures such as housing the crucible, mold, and pouring mechanism in a closed tank that maintains a specific atmosphere are required. Requires.

Note that the above-mentioned melting and solidification in a specific atmosphere is not limited to cases in which the crucible and mold are placed in a specific atmosphere; Means melting and solidification while in contact with.

To describe an embodiment of the method of the present invention, a closed type non-consumable electrode arc melting furnace using a tungsten non-consumable electrode and a copper water-cooled crucible is used. , argon (Ar), a rare gas
Pure iron (F
e) A mixture of 50% pure titanium (Ti) and 50% pure titanium (Ti) was melted, and after the melting was completed, the arc power was turned off to solidify the molten metal in the crucible.

The thus obtained lump of intermetallic compound consisting of Fe and Ti was crushed and its hydrogen storage properties were investigated.

As a result, the intermetallic compounds obtained by this method are
The intermetallic hydrogen storage material produced using the same melting equipment and the same raw materials but with an argon atmosphere had hydrogen storage properties after heat treatment, without heat treatment.

A similar operation is also carried out by using an induction heating crucible, a mold, and a pouring mechanism in a closed tank instead of a non-consumable electrode arc melting furnace, so that melting and solidification are achieved in the atmosphere inside the closed tank. The process was carried out using an induction heating melting furnace with a mixed atmosphere of hydrogen and argon in the closed tank.

Furthermore, with both of the melting and solidification methods mentioned above, tests were conducted by changing the types of the first raw material and the second raw material or by changing the mixing ratio of hydrogen and argon, and in each case, it was found that the hydrogen storage properties were substantially improved. A hydrogen storage material is obtained that can be activated without the need for heat treatment.

It is clear that similar effects can be obtained by performing melting and solidification in an atmosphere of pure hydrogen or in a mixed atmosphere of hydrogen and a rare gas other than argon.

Claims (1)

[Claims] A first raw material consisting of one or more of Ti, Zr, Hf, and rare earth metals, and Fe, Co
and a second raw material consisting of one or more kinds of Ni in a hydrogen atmosphere or a mixed atmosphere of hydrogen and a rare gas, and solidify them together to dissolve the metal contained in the first raw material and the second raw material. 1. A method for producing a hydrogen storage material, which comprises producing a hydrogen storage material that is composed of an intermetallic compound with a metal contained therein and has absorbed a certain amount of hydrogen.