Alloys or metallic compositions – Zirconium or hafnium base
Patent
1992-04-20
1994-01-25
Wyszomierski, George
Alloys or metallic compositions
Zirconium or hafnium base
420581, 420900, 429 59, 429221, C22C 1600, C22C 3000
Patent
active
052813908
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of
producing a hydrogen-storing alloy which is capable of reversibly storing and releasing large quantity of hydrogen, and also to a storage battery electrode making use of the alloy.
BACKGROUND ART
Hitherto, hydrogen-storing alloys of the kinds containing rare earth elements or Zr(Ti) or Mg have been known as materials used for storage, holding and transportation of hydrogen, heat pumps, alkali storage batteries, and so forth. Among these alloys, alloys of Zr(Ti)-Ni, Zr(Ti)-Fe, Zr(Ti)-V and Zr(Ti)-Sn, as well as alloys containing many elements which are based on these alloys with part of elements replaced with other element or with addition of another element, are attracting attention because these alloys are superior in hydrogen storage capacity, reaction speed, hydrogen-dissociating equilibrium pressure, safety in terms of flammability in air, and electrochemical hydrogen storage and release characteristics. More specifically, Zr-containing Lavas-phase alloys (AB.sub.2 type alloy: A and B representing different elements) are suitable for practical use because they can safely store and release large quantity of hydrogen.
In general, this type of hydrogen-storing alloy is produced by a process which utilizes single substance of Zr or V as the starting material. More specifically, the single substance of the metal as one of the starting material is placed at a predetermined atomic ratio in an aluminum crucible or a water-cooled copper crucible and is directly melted to synthesize the hydrogen-storing alloy in the crucible by placing the crucible in a high-frequency induction heating surface, high-temperature resistance heating oven or an arc melting surface.
When single substance of Zr or V is molten as one of the starting materials, the alloy composition tends to deviate from the expected composition due to such reason that such substance in molten state reacts with the metal of the crucible or due to difference in vapor pressure of such substance from those of other elements at high temperature. It is therefore difficult to obtain homogeneous excellent alloy having the aimed composition. In addition, production of single substance of Zr or V requires a complicated refining process so that the prices of such substances are relatively high. Furthermore, handling of such substances has to be conducted with care to ensure safety, because these single substances generate toxic vapors. Thus, from the view points of practicality, economy and safety, it has been desired that no single substance of Zr or V is used in the production of Zr- or V-type alloys.
Hydrogen-storing alloys produced by processes which do not rely upon single substance of Zr or V are practical in view of both characteristics and cost and, hence, are expected to be promising as materials of electrodes of nickel-hydrogen storage batteries.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a hydrogen-storing alloy which can be produced at low cost with high degrees of reliability and reproducibility and which exhibits superior hydrogenation characteristic, as well as a storage battery electrode making use of the alloy, thereby overcoming the above-described problems encountered with the production of Zr- or V-containing hydrogen storing alloy.
The production method according to the present invention makes use of commercially available ferrozirconium (Zr-Fe) alloy and zircalloy (Zr-Sn alloy) in place of single substance of Zr and ferrovanadium in place of single substance of vanadium, whereby a hydrogen-storing alloy can be produced with reduced material and production costs, high efficiency, reliability and safety in the production. The thus produced hydrogen-storing alloy is homogeneous without segregation and, therefore, is excellent in properties such as hydrogen storage capacity, reaction speed, electrochemical hydrogen storage/release characteristics in an electrolyte, electrode reaction efficiency, and so forth.
When ferrozirconium, zircalloy and f
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Gamo Takaharu
Iwaki Tsutomu
Moriwaki Yoshio
Shintani Akemi
Matsushita Electric - Industrial Co., Ltd.
Wyszomierski George
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