Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2000-10-31
2003-10-14
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S242000, C148S247000, C148S273000, C148S283000, C427S419100
Reexamination Certificate
active
06632293
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hydrogen containing material and to a method for producing the material, and more particularly relates to a hydrogen containing absorbing material which is highly activated with hydrogen so as to be used as the negative pole material of the nickel-hydride cell, medium for storing and transporting hydrogen, catalyst for hydrogenizing carbon oxide and for converting it to hydrocarbon, medium for energy conversion, medium for recovering hydrogen gas from low concentration hydrogen gas and for purifying the hydrogen gas, and others, and to have the protective effect against the poison of the poisonous material (hereinafter called poisoning restraining effect).
The hydrogen containing (absorbing) material reversibly absorbs and discharges hydrogen by the treatment of heating, cooling, decompressing or pressuring thereof. Therefore, the hydrogen containing material is expected to become a storing material of hydrogen as a future secondary energy. Recently, the hydrogen containing alloy is used as the negative pole material of nickel-hydride cell and expected as a future high quality battery for the electric motor vehicle.
In order to stably cause the hydrogen containing material to absorb and discharge the hydrogen, it is necessary to carry out the initial hydrogenation treatment at high temperature, or high pressure, or high vacuum. For example, in the case of Mg—Ni alloy as the hydrogen containing material, the reaction vessel is evacuated at 350° C., and the absorbing and discharging of hydrogen must be repeated over 10 times at 2-5 MPa. In the case of La—Ni alloy or La—Ni—Al alloy as the hydrogen containing material, the reaction vessel is evacuated at 80-100° C., and the absorbing and discharging of hydrogen is repeated over 10 times at 1-3 MPa. In order to keep the surface of the hydrogen containing alloy in very high active condition, the alloy must not be contacted with air. If the alloy is exposed to the air, the alloy is immediately oxidized so that the dissociation from hydrogen element to hydrogen atom is inhibited. Further, the hydrogen activity characteristic of the hydrogen containing alloy is remarkably reduced by a particle impurity gases included in the hydrogen gas such as CO, CO
2
, O
2
, H
2
o, NH
3
and others.
Japanese Patent Publication 3-12121 discloses a microcapsule method of copper or nickel by the electroless plating in order to improve the thermal conductivity of the hydrogen containing material and to protect the material from impurity gases other than the hydrogen gas.
The Japanese Patent Application Laid Open Publication 5-213601 discloses treatment methods for highly activating and stabilizing the hydrogen containing material by treating the surface of the material using the supersaturation aqueous solution consisting of the fluoride metallic compound including alkali metal.
The Japanese Patent Application Laid Open Publication 8-9504 discloses material for hydrogen containing alloy which material is coated with electroconductive powder and cuprous oxide powder and with oxidation inhibitor by mixing the powder for hydrogen containing alloy, conductive powder, and cuprous oxide powder with a high energy mixer, in order to improve the initial hydrogenation characteristic and to maintain the characteristic for a long term, and discloses a method for producing the material.
However, none of the materials and method is proper for mass production on account of the installation cost, production efficiency and production cost. Although it is confirmed that the material has a protective effect against impurity gases other than the hydrogen of the hydrogen containing material, there are problems in stability and durability of the surface treatment layer at the absorbing and discharging of hydrogen.
At present, a hydrogen containing alloy is used for the negative pole material of the small secondary battery, and almost all alloys are AB
5
alloys of the rare earth. As typical alloys, polyatomic alloys wherein the element A is La or rare earth metal alloys Mm (Misch-metall) and the element B is alloy produced by substituting Ni and a part of Ni with other elements (Co, Al, Mn, Si, Cr, Zr and others) are used. For example, there is alloys NaNi
5
, MmNi
2.5
, LaNi
4.7
Al
0.3
and MmNi
4.5
Mn
0.3
Al
0.2
. The composing elements and composition ratio are selected in accordance with the using conditions. The hydrogen containing alloy is used not only for the secondary battery, but also for the chemical heat pump which uses the storage and the purification of hydrogen gas and the reaction heat of the alloy.
The reason why the rare earth AB
5
alloy is substantially used is that the alloy can be initially activated with ease, has a great poisoning restraining effect, and can be easily treated compared with other alloys. However, the alloy is poor in durability. More specifically, the absorbing quantity of hydrogen reduces as the absorbing and discharging cycle increases. The alloy can not be used more than several thousand times. Therefore, although the alloy has a durability necessary for the negative pole material of the secondary battery, it is difficult to use the alloy for other fields which require much longer durability. Furthermore, there is a problem that the reduction rate of durability of the alloy further increases in the atmosphere at a temperature more than 150° C.
As hydrogen containing alloys having at least one of the durability and a high hydrogen containing capacity, and having a possibility for highly balancing both the characteristics, there is titanium-base hydrogen containing alloy, zirconium-base hydrogen containing alloy, and vanadium-base hydrogen containing alloy, and others. However in spite of the fact that these alloys have the above described characteristic and do not deteriorate at high temperature, there are considerable number of alloys having difficulty in initial activation and sensitivity influenced by poisoning (atmosphere exposure, impurity gases in hydrogen gas such as CO, H
2
O, O
2
, H
2
S). As a result, these alloys can not exercise their inherent performance, and hence have problems in treatment thereof.
In order to improve reactivity, durability, hydrogen dissociation pressure-composition isothermal characteristic, and initial hydrogenation characteristic, polyatomic alloys are developed, which alloy is produced by substituting a part of a basic hydrogen containing alloy with another element. For example, a part of an alloy such as rare earth-base alloy, magnesium-base alloy, titanium-base alloy, zirconium-base alloy, or calcium-base alloy is substituted with another single element such as Al, Mn, Cr, Fe, or Cu, or with plural elements. However, an alloy having a remarkable protective effect against an impurity other than hydrogen is not developed.
In order to resolve the above described problems in the conventional alloys, the inventors of the present invention proposed highly activated hydrogen containing materials and the method for producing the materials, wherein on a surface of hydrogen containing alloy such as rare earth-base alloy, magnesium-base alloy, titanium-base alloy, zirconium-base alloy, or calcium-base alloy, a compound layer including fluorine is formed so as to highly activate the hydrogen containing alloy with hydrogen.
For example, in Japanese Patent Publication No. 2835327, there is disclosed a method for highly activating and for stabilizing the hydrogen containing material, wherein a hydrogen containing material and a hydrofluoric anhydride solution are contacted with each other so that a metallic fluoride film of the metal composition of the hydrogen containing material itself is formed on the material.
In the Japanese Patent Application Laid Open Publication 10-219301, there is disclosed a highly activated hydrogen containing material and a method for producing the material, wherein a hydrogen containing material including at least one of elements Al, Fe, Mg, Ca, Mn, Zn, Zr, and Li is fluorinated, thereby forming a fluoride of the meta
Aono Fumiaki
Izumi Hiroto
Kikuyama Hirohisa
Kosuge Akiyoshi
Tabata Toshiharu
Birch & Stewart Kolasch & Birch, LLP
Oltmans Andrew L.
Sheehan John
The Japan Steel Works Ltd.
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