JPS60135538A - Manufacture of hydrogen storing alloy - Google Patents

Abstract

PURPOSE:To manufacture a hydrogen storing alloy which is not finely powdered during use by mixing an intermetallic compound undergoing a hydrogenation reaction with a ductile metal having catalytic action in the hydrogenation reaction, melting the mixture, and carrying out directional solidification. CONSTITUTION:An intermetallic compound undergoing a hydrogenation reaction such as LaNi5, Mg2Ni or CaSi5 for the 1st phase is mixed with a ductile metal having catalytic action in the hydrogenation reaction such as Ni, Co, Cu or Mn for the 2nd phase in a prescribed ratio, and the mixture is melted in vacuum or an atmosphere of an inert gas such as Ar. This melt is cooled while regulating the temp. gradient and the rate of solidification to carry out directional solidification. A eutectic structure consisting of the 1st phase of the intermetallic compound and the 2nd phase of the metal having catalytic action is formed as at least a part of the solidified structure. A hydrogen storing alloy which is not finely powdered by repeating the absorption and release of hydrogen is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a hydrogen storage alloy, and more particularly to a method for producing a hydrogen storage alloy in which pulverization is suppressed or prevented.

BACKGROUND OF THE INVENTION Hydrogen is likely to be at the core of future clean energy, and its storage and transportation forms include high pressure gas, liquid hydrogen, and solidification with metal hydrides. Among these methods, methods using metal hydrides are attracting attention because of their safety and ease of handling. The reasons for this are: +l) The hydrogen storage density per unit volume is high, more than 7000 times that of gaseous hydrogen, and comparable to that of liquid hydrogen.

(2) Hydrogen storage does not require a high-pressure container, so there are no problems in terms of container pressure resistance or hydrogen embrittlement. (3) Metal hydrides are thermodynamically stable, so they can be used as liquid hydrogen. (4) The dissociation pressure of metal hydrides is almost constant, and hydrogen gas at a constant pressure can be obtained by determining the dissociation temperature. Therefore, a wide range of applications are being considered, including hydrogen storage containers using metal hydrides, fuel cells, cylinders for internal combustion engines, hydrogen purification equipment, air conditioners, compressors, and refrigerators, improving safety and equipment. It has many advantages over conventional ones in terms of simplification and improved customization.

As described above, hydrogen solidification using metal hydrides is attracting attention as a form of hydrogen storage and transportation, but in order to be put to practical use as a hydrogen storage material, (1) An alloy that absorbs and releases hydrogen must be (2) It is inexpensive; (3) It is easy to activate; (4) It has excellent hydrogen storage capacity; (5) It has the following characteristics: (6) The equilibrium pressure for the production and dissociation of metal hydrides near room temperature is a diffuse pressure; (7) The hysteresis of the equilibrium pressure for production and dissociation of metal hydrides is small. (8) Various hydrogen storage materials have been proposed in the past, including the fact that the equilibrium pressure curve has a clear plateau. Furthermore, among these practical problems, the problem of material becoming pulverized due to repeated use of hydrogen absorption and release is
The current situation is the biggest barrier to practical application, and solving it is a major challenge.

The pulverization of alloys is not only directly related to performance deterioration, but also makes the alloy container design more complicated due to a decrease in thermal conductivity, as well as scattering of the alloy from the container due to the absorption and release of hydrogen, and problems with filters and pulp. Many studies have focused on the development of alloys that are difficult to pulverize, as they are also related to maintenance issues such as blind spots. However, it is difficult to avoid pulverization with current alloy manufacturing methods, and it is necessary to research methods for manufacturing materials from a different perspective.

In view of this trend, the present inventors have discovered that it is possible to produce a hydrogen storage alloy that is difficult to pulverize by applying a technology for controlling the structure through a eutectic reaction to the production of a hydrogen storage alloy.

Summary of the invention That is, the present invention uses a metal or an intermetallic compound that absorbs and releases a large amount of hydrogen (hydrogenation reaction) as a component or composition of the first phase, and catalyzes the hydrogenation reaction of the component or composition of the first phase. A metal having ductility and ductility is used as a component of the first phase, and in the process of blending a predetermined amount of the components constituting the first phase and the components constituting the first phase, melting, and solidifying, the metal has a ductility that is less susceptible to eutectic reaction. This is a method for producing a hydrogen storage alloy, characterized in that both parts have a eutectic structure of two first phases.

detailed description of the invention The manufacturing method of the present invention will be explained below.

The basic technical idea of the present invention is that the first phase consists of a metal or intermetallic compound that absorbs and releases a large amount of hydrogen (hydrogenation reaction), and the first phase that does not absorb or release hydrogen but acts as a catalyst for the hydrogenation reaction. The purpose is to suppress the pulverization of the FIN/phase due to the eutectic structure with the first phase made of a ductile metal.

As the first phase intermetallic compound, LaNi, Mg2N
i.

Cadi, etc. In addition, seventh phase metals include V, Nb, Pa, Mg, Oa, etc.; second phase metals include Ni, co, Ou, Mn, etc.; therefore, systems that cause eutectic reactions include LaNi, -Ni-based 1Mg
, Ni-Ni system, Mgz (!utoQX0aN i *
There are Oa etc.

7. According to the present invention. The blending ratio of the components or composition of the phase and the components of the first phase is determined in consideration of the ability to absorb and release hydrogen and the ability to suppress pulverization of the hydrogen-absorbing metal. That is, it is desirable to crystallize as much of the first phase that has the ability to absorb and release hydrogen as possible, but if the amount is too large, the first phase's ability to suppress pulverization will decrease, causing pulverization of the first phase. The desired effect according to the invention cannot be achieved. Therefore, it is preferable to include the eutectic point in the composition on the seventh phase side.

Melting in the method of the invention can be carried out in vacuum or in an inert gas (e.g. argon) to prevent oxidation, using any melting furnace capable of raising the temperature above the melting point of the alloy, but only the hydrogen storage alloy itself. The selection of the material for the crucible is an important key point, as it is extremely sensitive to impurities, especially oxygen. For example, this is carried out using a water-cooled steel crucible.

If the melted alloy components are solidified, the amount of primary crystals and eutectic structures that crystallize during the solidification process will be the same as the components (composition) of the first phase.
It is determined by the blending ratio with the other components. By performing directional solidification, which consists of adjusting the temperature gradient and solidification rate, which are solidification parameters, as one mode of solidification, the first phase or first set shown in FIG. 1 is grown in an aligned structure,
The spacing and size of the first phase or first set of aligned tissue phases can be varied arbitrarily.

Examples of the invention The present invention will be explained below based on Examples.

Example 1 Purity de9.g% Lanthanum (La) and purity? W, De S% nickel (Ni) using intermetallic compound LaNi, and N1
A eutectic alloy with (symbol / in Table 1) and an alloy having a partial eutectic structure (symbol - to 6 in Table 1) were melt-produced. La
(components of the first phase intermetallic compound LaNi) and Ni
The relationship between the blending ratio of (first set of components) and alloy composition is shown in Table 1 below.

First, the raw material soog prepared in various proportions was put into a water-cooled copper crucible, and after exhausting the gas until
It was melted in a plasma arc (in Ar gas). Next, when the molten metal was cooled, the composition and composition ratio (primary crystal/eutectic structure) of each sample after solidification were as shown in Table 1.

Each alloy sample obtained in this way was divided into small pieces of /σ angle, set in an automatic balance device that can automatically control temperature and pressure in a high-temperature, high-pressure hydrogen gas atmosphere, and after exhausting with purity? De, 1st adventure? ? - After introducing hydrogen and holding it for 30 minutes, it was evacuated again. From the change in alloy weight due to the hydrogenation reaction when hydrogen was then pressurized at lio atmospheric pressure at room temperature,
The amount of hydrogen absorbed and released by the alloy is shown in Table 1.

Furthermore, (1
) ff Hydrogen absorption amount at room temperature, hydrogen absorption rate, and 100% after hydrogen is absorbed at room temperature under IO atmospheric conditions
The operation to release hydrogen under the conditions of hydrogen pressure of 70 atm at ℃ is performed using SO
Table 1 shows the state of pulverization of the samples that were repeated several times.

/ / (It can be seen that the hydrogen absorption rate of the alloys manufactured by the method of the present invention is faster than that of the comparative materials in all cases, and the pulverization does not stop except for alloy 3. Hydrogen absorption amount of crystal composition (3,0 hydrogen atoms/metal atom (H/M)
) is the comparison material LaNis (A, j H/M)
Although it is small at about s0% compared to that of La
The amount of hydrogen absorption increases as it shifts to the 1JiB side, for example, the alloy of the code (La2r weight % - Ni 7 - weight %)
The hydrogen absorption amount (41.9H/M) of LaNi5 is significantly improved compared to the eutectic composition, and the hydrogen absorption rate is faster than that of the comparative material, and considering that it does not become pulverized, the hydrogen The disadvantage in absorption amount is not a practical problem.

Example 2 La and N1 prepared in the same manner as in Example 1 were set in the directional coagulation apparatus shown in FIG. 2, and exhaust gas was discharged to 10 to 10 μl. While cooling the bottom side with water to create a temperature gradient, the furnace consisting of the SIA heating element is slowly pulled up to the top, and while the hemorrhoid melting part moves continuously from the bottom to the top, the LaNi, 1st phase and 2nd of N1
A directional solidification alloy consisting of a set was obtained.

In this alloy, the first phase of LaNi was continuous during solidification, and the same appearance was observed even when cut at any vertical cross section.

Even when the alloy thus produced was repeatedly absorbed and released from hydrogen using the above-mentioned high-temperature, high-pressure thermobalance device, no pulverization occurred.

Effects of the Invention According to the manufacturing method of the present invention, pulverization of the water bulk storage alloy is prevented.

Furthermore, by employing directional coagulation, it is possible to obtain a first phase that is continuous over a long range in the coagulation direction, making it possible to apply it to new applications such as hydrogen filters and semipermeable membranes.

[Brief explanation of the drawing]

FIG. 1A is a schematic diagram of a directionally solidified alloy according to the present invention;
Figure B is a photograph showing the cross-sectional structure of the alloy shown in Figure 1A;
The figure is a schematic cross-sectional view of a directional solidification alloy manufacturing apparatus. Patent Applicant Nippon Steel Corporation Prefecture 2 Cooling Water Entrance Procedures Amendment Band December 28, 1937 Mr. Commissioner of the Japan Patent Office 2 Title of Invention Process for Producing Hydrogen Storage Alloy 3 Relationship with the Amendment Person Case Patent Application Name of person (,J/) Japan Steel Works, Ltd. 4, Agent 5, Target of amendment/'--'T-Person (1) Column for detailed explanation of the invention in the specification \・Contents of the Muum amendment (1) ) Page 6 line 7 of the specification ", CaNi, --Cal
is corrected to "caNt.-Ca system". (2) “Composition ratio (primary crystal/eutectic structure)” on page g, line IO
is corrected to “primary crystal amount (primary crystal/total structure)”. (3) Same page 1/? Correct the line "Cross section" to [Matrix]. (2) Procedural amendment (method) % formula % 1. Indication of the case 1982 Patent Application No. 240894 2. Name of the invention Hydrogen storage alloy i! ! Method of submission 3, Relationship with the case of the person making the amendment Patent applicant name (421) Japan Steel Works, Ltd. 4, agent address 4th floor 5, Marunouchi Building, 2-4-1 Marunouchi, Chiyoda-ku, Tokyo, of the amendment order Date March 27, 1980 1-7 Contents of amendment (1) Figure 2 will be corrected as shown in the attached sheet. (2) Supplement the attached power of attorney. Rei 2, et al. Procedural Amendment (Spontaneous) April 26, 1980, Commissioner of the Patent Office], Description of the case, 1982 Patent Application No. 240894 2, Name of the invention Process for manufacturing hydrogen storage alloy 3, Person making the amendment Relationship to the case Patent applicant name (42),) Japan Steel Works Co., Ltd. 4, agent address 4th floor 5, Marunouchi Building, 2-4-1 Marunouchi, Chiyoda-ku, Tokyo, subject of amendment 6, content of amendment ( 1) Page 11, line 16 of the specification [La and Nil [1]
-a and sample 2 consisting of Ni. (2) ``Directional coagulation apparatus'' on page 11, line 17 is corrected to ``1 directional coagulation gold manufacturing apparatus 1''. (3) On page 11, line 18 of the same text, before "exhaust gas.""From the vacuum pump connection pipe 11 using a vacuum pump (not shown)."
join. (4) Add "with cooling water (cooling water population 12 and cooling water outlet 13)" before "while cooling with water" on page 11, line 19 of the same document. (5) Page 11, line 19 [SiC heating element-1]
Heating element 3". (6) Page 12, line 3 [Directional solidification alloy was obtained. ] followed by ``In Figure 2, 4 is an aluminum crucible, 5 is a thermometer, 6 is a refractory wire, 7 is a silica tube, 8 is a ceramic tube, 9 is a copper rod, and 10 is an O-ring.'' join. (7) Add the following to the second line of page 13: ``1. Directional solidification alloy manufacturing device, 2. Sample, 32-... SiC heating element, 4. Aluminum crucible, 5. Temperature. Total, 6... Firebrick, 7... Silica tube, 8...
Ceramic tube, 9...Copper rod, 10...O ring, 11...
・Vacuum pump connection pipe, 12...Cooling water inlet, 13...Cooling water outlet. ”

Claims (1)

[Scope of Claims] l A metal or an intermetallic compound that absorbs and releases a large amount of hydrogen (hydrogenation reaction) is a component or composition of the first phase;
A metal having a catalytic action and ductility for the hydrogenation reaction of the phase component or composition is used as a first set of components, and the components constituting the first phase and the components constituting the first group are blended in predetermined amounts and then melted. 1. A method for producing a hydrogen storage alloy, which comprises forming at least a portion of the alloy into a eutectic structure of a first phase and a first set by a eutectic reaction during the solidification process. The manufacturing method according to claim 1, wherein aligned tissue is grown by performing directional solidification in the solidification process.