U.S. patent application number 10/455628 was filed with the patent office on 2003-11-13 for highly activated hydrogen containing material and method for producing the material.
This patent application is currently assigned to The Japan Steel Works, Ltd.. Invention is credited to Aono, Fumiaki, Izumi, Hiroto, Kikuyama, Hirohisa, Kosuge, Akiyoshi, Tabata, Toshiharu.
Application Number | 20030209296 10/455628 |
Document ID | / |
Family ID | 18100685 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030209296 |
Kind Code |
A1 |
Aono, Fumiaki ; et
al. |
November 13, 2003 |
Highly activated hydrogen containing material and method for
producing the material
Abstract
A hydrogen containing material comprises a first compound
including hydrogen containing material and fluoride, and a second
compound including a metal which becomes highly reactive with
hydrogen when the metal becomes a compound including fluorine, and
a compound including fluorine. The first compound and the second
compound are integrally formed into a one-piece layer on the
surface of the hydrogen containing material. The metal which
becomes highly reactive with hydrogen when the metal becomes a
compound including fluorine is at least one metal selected from a
rare earth metal, rare earth alloy, Fe, Al, Mg, Ca, Mn, Zn, Zr, Li,
or alloys comprising these elements.
Inventors: |
Aono, Fumiaki; (Tokyo,
JP) ; Tabata, Toshiharu; (Tokyo, JP) ; Kosuge,
Akiyoshi; (Tokyo, JP) ; Kikuyama, Hirohisa;
(Osaka, JP) ; Izumi, Hiroto; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
The Japan Steel Works, Ltd.
Stella Chemifa Corporation
|
Family ID: |
18100685 |
Appl. No.: |
10/455628 |
Filed: |
June 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10455628 |
Jun 6, 2003 |
|
|
|
09699423 |
Oct 31, 2000 |
|
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Current U.S.
Class: |
148/421 ;
420/900 |
Current CPC
Class: |
C01B 3/0078 20130101;
Y02E 60/32 20130101 |
Class at
Publication: |
148/421 ;
420/900 |
International
Class: |
C22C 014/00; C22C
016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 1999 |
JP |
11-318576 |
Claims
What is claimed is
1. A hydrogen containing material comprising: a first compound
including hydrogen containing material and fluoride; a second
compound including a metal which becomes highly reactive with
hydrogen when the metal becomes a compound including fluorine, and
a compound including fluorine, wherein the first compound and the
second compound are integrally formed into a one-piece layer on the
surface of the hydrogen containing material.
2. The material according to claim 1 wherein the hydrogen
containing material comprises a material or intermediate product or
finished product of an alloy selected from the group consisting of
a zirconium alloy, titanium alloy, vanadium alloy, rare earth
alloy, and magnesium alloy.
3. The Material according to claim 1 wherein the metal which
becomes highly reactive with hydrogen when the metal becomes a
compound including fluorine is at least one metal selected from a
rare earth metal, rare earth alloy, Fe, Al, Mg, Ca, Mn, Zn, Zr, Li,
or alloys comprising these elements.
Description
BACKGROUND OF THE INVENTION
[0001] 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).
[0002] 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.
[0003] 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.degree. 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.degree. 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.sub.2, O.sub.2, H.sub.2O, NH.sub.3 and
others.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] At present, a hydrogen containing alloy is used for the
negative pole material of the small secondary battery, and almost
all alloys are AB.sub.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.sub.5, MmNi.sub.2.5, LaNi.sub.4.7Al.sub.0.3 and
MmNi.sub.4.5Mn.sub.0.3Al.sub.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.
[0009] The reason why the rare earth AB.sub.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.degree. C.
[0010] 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.sub.2O, O.sub.2, H.sub.2S). As a result, these alloys can
not exercise their inherent performance, and hence have problems in
treatment thereof.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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 metal on the surface or in a surface
layer of the hydrogen containing material.
[0015] Furthermore in the Japanese Patent Application Laid Open
Publication 10-219301, there is a disclosed highly activated
hydrogen containing material and a method for producing the
material, wherein a metal which becomes high active with hydrogen
when fluorinated is preliminarily coated in the-hydrogen containing
material, thereafter the coating metal is fluorinated or treated so
as to become fluoride. As a result, the hydrogen containing
material becomes active with hydrogen.
[0016] In accordance with the method described in the Japanese
Patent No. 2835327, it is possible to highly activate and stabilize
the hydrogen containing material without a large installation and
complicated steps. Therefore, the method has an advantage in
mass-producing. However, there also exists a hydrogen containing
material wherein a fluoride layer can not be formed on the
material, or even if a fluoride layer can be formed on the
material, the fluoride layer is impossible to become high active
with hydrogen, because of the kind of the hydrogen containing
material.
[0017] The former highly activated material and the producing
method described in the Japanese Patent Publication 10-219301, has
the same advantage as that of the Japanese Patent Publication No.
2835327. However, the metal which becomes high active is included
in the hydrogen containing material itself. Therefore, only metals
exposed on the surface of the hydrogen containing material are
effective. If a small amount of a high active fluoride exists on
the surface of the hydrogen containing material, the material has
an effect though the amount is small. However, in the absorption
and discharge reaction which accompanies a surface reaction, and in
the methanization reaction which reacts H.sub.2 with CO, CO.sub.2
and others to them to hydrocarbon gas such as CH.sub.4, it is more
preferable that a large amount of active portion exists on the
surface. The hydrogen containing alloy is made into an alloy
corresponding to the using condition of the alloy by adding another
element to a basic composition element or substituting, with
another element in accordance using temperature and pressure
condition. Therefore, it is difficult to compose the hydrogen
containing alloy only by metal which is highly activated by
becoming fluoride. Consequently, such a hydrogen containing
material can not be highly activated by the above described
producing method.
[0018] In the latter hydrogen containing material and the producing
method, since the hydrogen containing material is coated with a
fluoride of high activity with hydrogen regardless of the
composition element, the hydrogen containing material has a high
reactivity with hydrogen. However, the hydrogen containing material
as the matrix and the fluoride coating the material are basically
different from each other in kind. Consequently, there may occur
that the fluoride layer on the surface of the hydrogen containing
material peels off because of expansion and contraction of the
material at the absorption and discharge of hydrogen.
SUMMARY OF THE INVENTION
[0019] Accordingly, an object of the present invention is to
resolve the above described problems in the prior arts, more
particularly to provide a hydrogen containing material having a
hydride layer on the surface, which hydride layer has a high
reactivity with hydrogen,,so that the hydrogen containing material
is highly activated with hydrogen more than the inherent reactivity
of the material despite a poisoning environment.
[0020] Another object of the present invention is to provide a
hydrogen containing material having a fluoride layer which is not
peeled off from the surface so that it is possible to maintain a
high reactivity with hydrogen for a long term, while at least one
of characteristics that is the durability of the hydrogen
containing material itself and the high hydrogen absorbing capacity
is maintained.
[0021] According to the present invention, there is provided a
hydrogen containing material the surface of which has layers
comprising a first compound including the hydrogen containing
material and fluorine, and a second compound including a metal
which becomes high reactive with hydrogen when the metal becomes a
compound including fluorine and a compound including fluorine,
wherein the first compound and the second compound are integrally
formed into a one-piece layer on the surface of the hydrogen
containing material.
[0022] The hydrogen containing material comprises an ingot, or
powder of a material or intermediate product or finished product of
an alloy selected from a zirconium alloy, titanium alloy, vanadium
alloy, rare earth alloy, and magnesium alloy.
[0023] Furthermore, the metal which becomes high reactive with
hydrogen when the metal becomes a compound including fluorine is at
least one metal selected from a rare earth metal, rare earth alloy,
Fe, Al, Mg, Ca, Mn, Zn, Zr, Li, or alloys comprising these
elements.
[0024] The metal is melted in the fluorinating treatment liquid in
a metal ion condition or in an ultrafine grain condition.
[0025] The fluorinating treatment liquid contacted with the
hydrogen containing material is heated so as to vaporize the liquid
to dry the hydrogen containing material.
[0026] The metal which becomes high reactive with hydrogen when the
metal becomes a compound including fluorine is at least one metal
selected from a rare earth metal, rare earth alloy, Fe, Al, Mg, Ca,
Mn, Zn, Zr, Li, or alloys comprising these elements.
[0027] The fluorinating treatment liquid is a hydrofluoric acid
aqueous solution or hydrofluoric anhydride solution, or solution
composed by at least one of organic compounds such as piridine,
triethlamine and isopopyl alcohol, and hydrofluoric anhydride.
[0028] It is possible to select a desired thickness of the metal
fluoride layer on the surface of the hydrogen containing material
so as to extend to a desired depth in accordance with the use of
the hydrogen containing material.
[0029] In the hydrogen containing material of the present
invention, in the cases that a large amount of metals which become
high active when fluorinated are included in the basic composition
elements, that a small amount of metals which become high active
are included in the composition elements, or that highly activated
metal is not included, in any case, it is possible to form a large
amount of very highly activated fluoride layers, compared with a
hydrogen containing material which is simply treated by fluorine,
on the surface of the hydrogen containing material.
[0030] In the boundary surface between the hydrogen containing
material as the matrix and the fluoride, a compound layer in which
the concentration of elements composing the matrix and the
concentration of the fluoride are changed in inclined conditions is
formed. The surface of the material is in the condition the
fluoride of the matrix and the fluoride of the highly activated
metal are mingled.
[0031] In another case, in the boundary surface between the
hydrogen containing material as the matrix and the fluoride, a
compound layer in which the concentration of elements composing the
matrix and the concentration of the fluoride are gradually changed
in inclined conditions is formed, and the fluoride of the matrix is
formed on the outer surface of the compound layer, and further on
the outside of the outer surface, the fluoride of the highly
activated metal is formed.
[0032] By forming the fluoride layer of metal the concentration of
which changes in inclined condition, it is possible to prevent the
metallic fluoride from exfoliating from the hydrogen containing
material. Therefore, it is possible to maintain high activity with
hydrogen for a long term in spite of a poisoning environment, while
maintaining at least one of durability of the hydrogen containing
material itself and a large capacity for absorbing hydrogen.
[0033] Furthermore, in accordance with the method for producing
hydrogen containing material of the present invention, by
contacting the treatment liquid for fluorinating the metal and the
hydrogen containing material with each other, the metallic fluoride
is formed on the surface or on the surface portion of the hydrogen
containing material. Therefore, it is possible to produce the
hydrogen containing material by a simple device with ease, and to
correspond to the mass production.
[0034] These and other objects and features of the present
invention will become more apparent from the following detailed
description with reference to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0035] FIG. 1 is a graph showing the relationship between the time
necessary for absorbing hydrogen and the hydrogen concentration in
the example I;
[0036] FIG. 2 is a graph showing the change of the amount of
hydrogen absorption in the example I;
[0037] FIG. 3 is a graph showing the relationship between the time
necessary for absorbing hydrogen and the hydrogen concentration in
the example II;
[0038] FIG. 4 is a graph showing the relationship between the time
necessary for absorbing hydrogen and the hydrogen concentration in
the example III;
[0039] FIG. 5 is a photograph showing a surface condition of a
hydrogen containing material in the example I; and
[0040] FIG. 6 is a photograph showing a surface condition of a
hydrogen containing material in the comparative example 1C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] Hydrogen containing materials used in the present invention
are hydrogen containable metals or alloys, in particular titanium
alloys (titanium-base alloys), zirconium alloys, rare earth alloys,
and magnesium alloys. Specifically, for example, here is given as
titanium alloys, TiFe, TiCo, TiNi, TiMn.sub.2, TiCr.sub.2, TiV, as
zirconiumalloys, ZrV.sub.2, Zrcr.sub.2, ZrMn.sub.2, ZrFe.sub.2,
ZrCo.sub.2, as rare earth alloys, LaNi.sub.5, MmNi.sub.2.5Co2.5,
LaNi.sub.4.7Al.sub.0.3, MmNi4.5Mn.sub.0.3Al0.2,
MmNi.sub.4.7Al.sub.0.2Zr.- sub.0.1,
LaNi.sub.4.5Cr.sub.0.25Mn.sub.0.25, M.sub.0.5Ca.sub.0.5Ni.sub.5, as
magnesium alloys, Mg.sub.2Ni, Mg.sub.2Cu.
[0042] In order to adjust and improve the dissociation pressure
characteristic, plateau, hysteresis of the hydrogen containing
material, polyelement alloys which are formed by addition or
substitution of other elements can be used.
[0043] Although the above described hydrogen containing materials
are intermetallic compounds, vanadium alloys called as the solid
solution hydrogen containing alloy can be used. There are various
alloys such as (V.sub.0.9Ti.sub.0.1).sub.0.8Fe.sub.0.2,
(V.sub.0.9Ti.sub.0.1).sub.0.9Al.- sub.0.1,
(V.sub.0.85Ti.sub.0.15).sub.0.8Mn.sub.0.2, V.sub.0.8Ti.sub.0.2,
V.sub.3Mn.sub.0.4Ni.sub.0.6.
[0044] As the metal which is formed on the surface of the hydrogen
containing material as the fluoride and has a high reactivity with
hydrogen, there is given rare earth metal, alloy including rare
earth metal, Fe, Al, Mg, Ca, Mn, Zn, Zr, Li and alloys including
these metals. As the rare earth metal, La and Mm are preferable. As
alloy including rare earth metal, AB.sub.5 type alloy, which is
hydrogen containing alloy, such as LaNi.sub.5, and polyelement
alloy in which a part Ni is substituted with another element (Al,
Mn, Co, Cr, Si, Zr and others) can be used.
[0045] The rare earth alloy is not limited to above described
composition for the object of the present invention, and alloys of
non-stoichiometry composition may be used.
[0046] As the A in the AB.sub.5 type alloy, rare earth metal or
rare earth metal alloy other than La may be used, and as the B,
elements other than Ni may be used. The alloy which has not
hydrogen containing performance may be used. Catalyst having a high
reactivity with hydrogen excels in catalytic activity in proportion
to the increasing of the surface activity. As fluoride having a
high surface acidity, there is given FeF.sub.2, AlF.sub.3,
MgF.sub.2, CaF.sub.2, LiF.sub.2. Forming of such a fluoride on the
surface of the hydrogen containing material is effective in
increasing of activity thereof.
[0047] As treating solution for forming a metallic fluoride layer
on the surface of the hydrogen containing material, hydrofluoric
acid aqueous solution or hydrofluoric anhydride solution, or
solution composed by at least one of organic compounds such as
piridine, triethlamine and isopopyl alcohol, and hydrofluoric
anhydride is used. The above described metal is contacted with the
treating solution or added at a temperature between -200.degree. C.
and 200.degree. C., preferably between -40.degree. C. and
100.degree. C., thereby melting ultrafine particles of the metal
ion into the solution in a described amount at least one of the
conditions.
[0048] The hydrogen containing material is immersed in the treating
solution including the metal to fluorinate the material. If the
surface of the hydrogen containing material is excessively
fluorinated, the inherent characteristics of the hydrogen
containing material is deteriorated. Therefore, in order to
restrain the reaction, it is preferable to use a solution
containing a small amount of water. In the case of the hydrofluoric
acid aqueous solution, it is preferable to use the solution having
a molality of 70% or more. When the above described other solutions
are used, the molality is the same as the hydrofluoric acid aqueous
solution.
[0049] Therefore, the hydrogen containing material is dried at a
temperature between the room temperature and 500.degree. C.,
preferably between 100.degree. C., and 250.degree. C., purging with
a gas such as Ar, N.sub.2, He which has not a bad influence upon
the fluorination treatment. Further, after the atmosphere of the
hydrogen fluoride is discharged, the hydrogen containing material
undergoes heat treatment at the dry temperature or more to
stabilize the fluoride layer formed on the surface of the hydrogen
containing material. By the heat treatment, the fluoride of the
metal composing the hydrogen containing material itself and the
metallic fluoride included in the treating solution are integrated,
on the surface of the hydrogen containing material.
[0050] In the above described process, the treating solution in the
reaction vessel is vaporized by the heating of the solution,
without separating an excessive solution. If it takes long time for
vaporizing the treating solution having a low concentration of the
ultrafine particles of the metal ion and it is preferable to
separate the treating solution. However, there may be occurred that
the metal included in the treating solution is formed on the
surface of the hydrogen containing material as a fluoride,
dependent on the kind of the metal. Therefore it is preferable to
select the concentration and to separate the excessive solution in
dependency on the kind of the hydrogen containing material and the
kind of the metal included in the treating solution.
[0051] The hydrogen containing material having the fluoride film on
the surface thereof by the above described process has a high
activity to the hydrogen molecule. Furthermore, even in the
poisonous environment, the hydrogen containing material stably
keeps the activity to the hydrogen.
[0052] There is difference in the form of the metal fluoride film
formed on the surface of the hydrogen containing material in
dependency on the kind of the hydrogen containing material and the
kind of the metal included in the treating solution, as following
examples.
[0053] (1) The fluoride of the metal composing the hydrogen
containing material is formed on the surface of the material, and
the metal included in the treating solution becomes fluoride, the
fluoride film is formed in the condition that both fluorides are
mingled together.
[0054] (2) After the fluoride of the metal composing the hydrogen
containing material has been formed on the surface of the material,
the metal included in the treating solution becomes fluoride which
is formed on the metal fluoride.
[0055] (3) The metal of the surface of the hydrogen containing
material is fluorinated and melted in the treating solution, and
the melted metal fluoride is formed again on the surface of
containing material as a fluoride film together with the metal in
the treating solution when the solution is dried.
[0056] Although it is preferable that the all surface of the
hydrogen containing material is coated with the fluoride of the
metal, it is allowable that the,hydrogen containing materials are
contacted with each other so that the contacted surfaces are not
covered by the fluoride. If the active fluoride exists only on a
part of the surface of the hydrogen containing material, it is
possible to maintain high reactivity.
[0057] The depth and other conditions of the fluoride of the metal
of the hydrogen containing material can be properly adjusted by
adjusting the treatment period of time, treating temperature and
others in accordance with the use of the hydrogen containing
material. Further, there is a case that metals other than fluorine,
the hydrogen containing material and metals included in the
treating solution are included in the fluoride film formed on the
hydrogen containing material. For example, treated in such an
environment as atmosphere where the surface of the hydrogen
containing material is oxidized and hydroxided, oxide and hydroxide
are formed. Therefore, in the compound layer formed on the surface
of the hydrogen containing material, compounds such as M, O--M,
F--M, F--O--M (F: fluorine, O: oxygen, M: metal) are mingled in a
stoichiometrically stable condition or in a stoichrometrically
unstable (non-stoichiometric composition). There may be a case
where other elements other than metals included in the treating
solution are included in the fluoride film on the surface of the
hydrogen containing materials.
[0058] Although there is a case where the fluoride film is formed
in substantially uniform thickness, there is a case that partial
projections are formed on the film. In either case, the hydrogen
containing material as the matrix becomes fluoride and a gradient
diffusion layer of the hydrogen containing material and the
fluoride is formed in the boundary layer between the hydrogen
containing materials and the fluoride. (In the boundary layer, the
fluorine concentration reduces toward the inside and the
concentration of the metal composing the hydrogen containing
material increases in reverse.)
[0059] Therefore, the fluoride on the hydrogen containing material
is kept in a stable condition without peeling off despite the
expansion and contraction caused by the containing and discharging
of the hydrogen. The surface of the hydrogen containing materials
is finely powdered by the containing and discharging of the
hydrogen. Therefore if the containing and discharging is repeated a
neo-surface (metal surface) is exposed. However, if a fluoride
having a high activity exists on a part of the hydrogen containing
material, it is possible to maintain a high reactivity.
[0060] As described above, a film consisting a metal fluoride as a
main component on the surface of the hydrogen containing material
by treating with the hydrofluoric acid aqueous solution or
hydrofluoric anhydride solution or solution composed by at least
one of organic compounds such as piridine, triethlamine and
isopopyl alcohol, and hydrofluoric anhydride. Therefore, the
hydrogen containing material has a high activity with the hydrogen
element. In the prior art, in order to initially activate the
hydrogen containing material, the material must be treated,at a
high temperature and a high pressure and in a high vacuum.
[0061] In accordance with the present invention, the hydrogen
containing materials can be initially activated without high
temperature, high pressure, and high vacuum. Furthermore, since the
fluoride film formed on the surface is a stable compound layer,
there is no danger of ignition of the hydrogen containing material
in the atmosphere. Since the hydrogen containing material having
the fluoride film has a poisoning restraining effect other than the
hydrogen element, the danger problem at the treatment of the
hydrogen containing material is solved. As a result, the upkeep for
installations, production and transportation can be largely
reduced. Since the fluoride film is formed by the reaction in the
solution of high concentration or in the anhydride solution, a
large installation and complicated technique in the reaction
treatment are not necessary. Both of the high activation and the
stabilization treatment of the hydrogen containing material which
can be mass produced can be carried out at the same time.
EXAMPLE I
[0062] The alloy TiFe.sub.0.8Mn.sub.0.2 as the hydrogen containing
material was mechanically powder and classified into less than 250
.mu.m by a screen. The alloy powdered of 100 g was put in a first
reaction vessel. On the other hand, the alloy
LaNi.sub.4.7Al.sub.0.3 was mechanically powdered and classified
into less than 38 .mu.m, and the alloy powder of 100 g was put in a
second reaction vessel. More than 9N high-purity hydrofluoric
anhydride solution of 100 cc was poured in the second reaction
vessel and kept for three minutes at a temperature of about
80.degree. C. Thereafter, while the powder LaNi.sub.4.7Al.sub.0.3
was filtered by a filter paper, the hydrofluoric anhydride solution
was transferred to the first reaction vessel in which the powder of
TiFe.sub.0.8Mn.sub.0.2 is put. The first reaction vessel was put in
a constant temperature tank heated at 100.degree. C. and N.sub.2
gas was flowed in the first reaction vessel to vaporize the
hydrofluoric anhydride solution, thereby drying the vessel. After
the drying, the temperature of the constant temperature tank was
increased to 150.degree. C. and kept for one hour to heat-treat the
alloy. Thereafter, the hydrogen containing material was cooled to
approximately room temperature, while N.sub.2 gas was flowed in the
first reaction vessel. The hydrogen containing material was taken
out from the first reaction vessel. Thus, the alloy powder
TiFe.sub.0.8Mn.sub.0.2 having a fluoride film in which F, La, Al
and Ni are formed on the surface of the powder in the mingled
condition was obtained.
[0063] According to the observation of the surface of the alloy
TiFe.sub.0.8 Mn.sub.0.2 with a scanning electron microscope,
protrusive product of about 0.1-0.3 .mu.m, was formed on the
surface. It was confirmed that there is existed F, La, Al, Ni which
do not exist in the untreated alloy on the surface in the mingled
condition, as a result of the element analysis of the surface of
the alloy after the treatment with an energy dispersion type X-ray
analysis device. The elements melted in the hydrofluoric anhydride
solution in the second reaction vessel were analyzed with an
inductive coupling plasma light emitting analyzing device.
[0064] The Table 1 shows the result of the analysis and proportions
of the molten elements. As a result, La and Al are melted more than
the ratio by mass of the original alloy LaNi.sub.4.7Al.sub.0.3. The
proportions are approximately equal to the proportions of
quantitative analysis result of La, Ni, Al where Ti, Fe, Mn are
removed by the energy dispersion type X-ray analysis device.
Therefore, it is considered that the metal ion of the molten
LaNi.sub.4.7Al.sub.0.3 in the hydrofluoric anhydride becomes a
compound with fluorine and is finally stuck on the alloy powder
TiFe.sub.0.8Mn.sub.0.2 in the treatment of the vaporizing of the
hydrofluoric anhydride.
1 TABLE 1 Analysis Proportion of Proportion Proportion
LaNi.sub.4.7A1.sub.0.3 (ppm) (%) La 32.8 24.0 42.3 Ni 65.2 30.7
54.0 A1 1.9 2.1 3.8
COMPARATIVE EXAMPLE 1a
[0065] A hydrofluoric anhydride in which alloy powder
LaNi.sub.4.7Al.sub.0.3 is not melted was used for highly activating
the alloy TiFe.sub.0.8Mn.sub.0.2 in the same method and condition
as the example I.
COMPARATIVE EXAMPLE 1b
[0066] The alloy TiFe.sub.0.8Mn.sub.0.2 was mechanically powdered
and classified into less than 250 .mu.m and the fluoridization was
not carried out.
[0067] Evaluation
[0068] Initial activation characteristics of TiFe.sub.0.8Mn.sub.0.2
of the example I, comparative examples 1a and 1b were evaluated in
the same conditions and compared. The transverse of FIG. 1 shows
time necessary for containing hydrogen, and the vertical line shows
the quantity of contained hydrogen, in the case that a maximum
containing quantity of an untreated alloy is set to 100%.
[0069] As the reaction conditions, the air in the reaction vessel
was discharged by the evacuation at the alloy temperature of
constant 80.degree. C. until the inside pressure becomes 1 Pa, and
the vacuum discharge was further continued for thirty minutes, and
then hydrogen was introduced at the initial pressure of 2.5 MPa. On
the other hand, all test pieces were left in the atmosphere
controlled at the temperature of 25.degree. C. and the humidity of
30% for 24 hours. The results are as follows.
[0070] The untreated alloy TiFe.sub.0.8Mn.sub.0.2 of the
comparative example 1b did not absorb the hydrogen despite the
passage of 6 hours.
[0071] The alloy of the comparative example 1a started to absorb
the hydrogen at the time of one-hour passages and contained
quantity of about 100% of the hydrogen after 5 hours.
[0072] On the other hand, the alloy of the example I started to
absorb the hydrogen after 30 minutes, and contained quantity of
almost 100% of the hydrogen after 2.5 hours.
[0073] Although the alloy of the comparative example 1a also has a
high reactivity with hydrogen compared with the untreated alloy of
the comparative example 1b, the alloy of the example I has a more
higher reactivity than the comparative example 1a.
[0074] As a modification of the example I , the alloy
MmNi.sub.4.5Al.sub.0.5 was used instead of the alloy
LaNi.sub.4.7Al.sub.0.3, and the same treatment as the example I was
carried out. In accordance with the evaluation similar to the
example I, it was confirmed that the same effects as the example I
were achieved.
[0075] FIG. 2 shows the fact that the test piece treated by the
example I has a poisoning restraining effect against the poison of
the poisonous materials other than the hydrogen element, compared
with comparative examples 1a and 1b. The transverse of FIG. 2 shows
the number of the cycles of the containing and discharging of
hydrogen, the vertical line shows the ratio of the change of the
hydrogen containing quantity in the case that the initial hydrogen
containing quantity is set to 100% when the high purity hydrogen of
7N is used.
[0076] As the activation treatment before the test, the air in the
treating vessel, in which the alloys of the example I and of the
comparative examples are contained, was discharged by the
evacuation until 1 Pa at 80.degree. C. Thereafter, the high purity
hydrogen gas of 7N was introduced in the reaction vessel at the
introduction pressure of 3 MPa. The activation treatment was
carried out 5 times. After the activation treatment, in order to
confirm the initial hydrogen containing quantity, the 7D high
purity hydrogen gas including CO of 1,044 ppm was introduced at the
introduction pressure of 3 MPa at 80.degree. C. for 10 minutes, so
that the hydrogen is to be included in the test piece. The obtained
value by the treatment was used as the initial hydrogen containing
quantity. Thereafter, poisoning test was carried out. In the
poisoning test, the same treatment as the above described initial
hydrogen containing treatment was performed. After the poisoning
test, the hydrogen in the reaction vessel was spontaneously emitted
at 80.degree. C. Until the pressure in the vessel becomes 12 MPa,
and the change of the hydrogen containing quantity was confirmed at
every cycle.
[0077] The hydrogen containing quantity of the untreated alloy of
the comparative example 1b decreased to 23% at the first cycle and
to 0% at the second cycle. Although the hydrogen containing
quantity of the comparative example 1a decreased to 56% at the
tenth cycle, the alloy had a poisoning restraining effect compared
with the comparative example 1b.
[0078] On the other hand, the alloy of the example I maintained the
hydrogen containing quantity more than 90% at the tenth cycle. In
other words, the alloy has a great poisoning restraining
effect.
[0079] As a result of the analysis of gas components at the
emission by the gas chromatography, there was confirmed that
CH.sub.4 was included in the emission gas of the example I and CO
was less than the detection lower limit. In the comparative example
1a, both of CH.sub.4 And CO were detected. In the alloy of the
comparative example 1b, it was considered that hydrogen is scarcely
emitted from the alloy. However, it was confirmed that CO having a
higher concentration than the original gas was included in the
hydrogen gas in the reaction vessel. Therefore, it is regarded that
in the poisoning restraining effect of the hydrogen containing
alloy of the present invention, CO as the poisoning element is
hydrogenized to be converted to CH.sub.4 so that the CH.sub.4 is
removed from the surface of the alloy.
EXAMPLE II
[0080] The alloy Zr(Fe.sub.0.75Cr.sub.0.25).sub.2 as the hydrogen
containing material was mechanically powder and classified into
less than 250 .mu.m by a screen. The alloy powder of 100 g was put
in a first reaction vessel. On the other hand, the element Al was
mechanically powdered and classified into less than 100 .mu.m, and
the alloy powder of 100 g was put in a second reaction. More than
9N high-purity hydrofluoric anhydride solution of 200 cc was poured
in the second reaction vessel and kept for three minutes at a
temperature of about 120.degree. C. Thereafter, while the powder Al
was filtered by a filter paper, the hydrofluoric anhydride solution
was transferred to the first reaction vessel in which the powder of
Zr(Fe.sub.0.75Cr.sub.0.25).sub.2 is put. The first reaction vessel
was put in a constant temperature tank heated at 80.degree. C. and
N.sub.2 gas was flowed in the first reaction vessel to vaporize the
hydrofluoric anhydride solution, thereby drying the vessel. After
the drying, the temperature of the constant temperature tank was
increased to 120.degree. C. and kept for one hour to heat-treat the
alloy. Thereafter, the hydrogen containing material was cooled to
approximately room temperature, while N.sub.2 gas was flowed in the
first reaction. The hydrogen containing material was taken out from
the first reaction vessel. Thus, the alloy powder Zr
(Fe.sub.0.75Cr.sub.0.25).sub.2 having a fluoride film of Al on the
surface of the powder was obtained.
[0081] According to the observation of the surface of the alloy
Zr(Fe.sub.0.75Cr.sub.0.25).sub.2, it was confirmed that there is
existed FAl which do not exist in the untreated alloy as a result
of the element analysis of the surface of the alloy Zr
(Fe.sub.0.75Cr.sub.0.25).sub.2 after the treatment with an energy
dispersion type X-ray analysis device.
COMPARATIVE EXAMPLE 2a
[0082] A hydrofluoric anhydride in which alloy powder Al is not
melted was used for highly activating the alloy Zr
(Fe.sub.0.75Cr.sub.0.25).sub.2 in the same method and condition as
the example II.
COMPARATIVE EXAMPLE 2b
[0083] The alloy Zr (Fe.sub.0.75Cr.sub.0.25).sub.2 was mechanically
powdered and classified into less than 250 .mu.m and the
fluoridization was not carried out.
[0084] Evaluation
[0085] Initial activation characteristics of
Zr(Fe.sub.0.75Cr.sub.0.25).su- b.2 of the example II, comparative
examples 2a and 2b were evaluated in the same conditions and
compared. The transverse of FIG. 3 shows time necessary for
containing hydrogen, and the vertical line shows the quantity of
contained hydrogen, in the case that a maximum containing quantity
of an untreated alloy is set to 100%.
[0086] As the reaction conditions, the air in the reaction vessel
was discharged by the evacuation at the alloy temperature of
constant 60.degree. C. until the inside pressure becomes 1 Pa, and
the vacuum discharge was further continued for thirty minutes, and
then hydrogen was introduced at the initial pressure of 1.5 MPa at
60.degree. C. On the other hand, all test pieces were left in the
atmosphere controlled at the temperature of 25.degree. C. and the
humidity of 30% for 24 hours. The results are as follows.
[0087] The untreated alloy Zr(Fe.sub.0.75Cr.sub.0.25).sub.2 of the
comparative example 2b did not absorb the hydrogen despite the
passage of 6 hours.
[0088] The alloy of the comparative example 2a started to absorb
the hydrogen at the time of 1.5-hour passage, and contained
quantity of about 100% of the hydrogen after 4.5 hours.
[0089] On the other hand, the alloy of the example II started to
absorb the hydrogen after one hour, and contained quantity of
almost 100% of the hydrogen after 3 hours.
[0090] Although the alloy of the comparative example 2a also has a
high reactivity with hydrogen compared with the untreated alloy of
the comparative example 2b, the alloy of the example II has a more
higher reactivity than the comparative example 2a.
[0091] As a modification of the example II, Fe, Mg, Ca or Li was
used instead of Al and the same treatment as the example II was
carried out. In accordance with the evaluation similar to the
example II, it was confirmed that the same effects as the example
II were achieved.
[0092] The test of the poisoning restraining effect of the hydrogen
containing material of the example II was carried out in the same
manner as the example I. As a result of the test, it was confirmed
that the hydrogen containing material of the example II has a great
poisoning restraining effect although there are individual
differences, and CH.sub.4 is included in any emitted hydrogen
gases.
EXAMPLE III
[0093] The alloy V(vanadium) as the hydrogen containing material
was mechanically powder and classified into less than 75 .mu.m by a
screen. The V powder of 10 g was put in a first reaction vessel. On
the other hand, Mg was mechanically powdered and classified into
less than 250 .mu.m, and Mm was mechanically powdered and
classified into less than 1 mm and Mg powder 15 g and Mm powder 15
g were put in a second reaction vessel. More than 9N high-purity
hydrofluoric anhydride solution of 100 cc was poured in the second
reaction vessel and kept for three minutes at a temperature of
about 100.degree. C. Thereafter, while the powders Mg and Mm were
filtered by a filter paper, the hydrofluoric anhydride solution was
transferred to the first reaction vessel in which the powder of V
is put. The first reaction vessel was put in a constant temperature
tank heated at 50.degree. C. and N.sub.2 gas was flowed in the
first reaction vessel to vaporize the hydrofluoric anhydride
solution, thereby drying the vessel. After the drying, the
temperature of the constant temperature tank was increased to
120.degree. C. and kept for one hour to heat-treat the powders.
Thereafter, the hydrogen containing material was cooled to
approximately room temperature, while N.sub.2 gas was flowed in the
first reaction. The hydrogen containing material was taken out from
the first reaction vessel. Thus, the V powder having a fluoride
film of Mg and Mm was obtained.
[0094] According to the observation of the surface of V, it was
confirmed that there is existed F which does not exist in the
untreated alloy Mg and La, Ce, Pr, Nd and Sm which are component
elements of Mm, as a result of the element analysis of the surface
of the alloy after the treatment with an energy dispersion type
X-ray analysis device.
COMPARATIVE EXAMPLE 3a
[0095] A hydrofluoric anhydride in which Mg and Mm are not melted
was used for highly activating V powder in the same method and
condition as the example III.
COMPARATIVE EXAMPLE 3b
[0096] The vanadium V was mechanically powdered and classified into
less than 75 .mu.m and the fluoridization was not carried out.
[0097] Evaluation
[0098] Initial activation characteristics of the example III,
comparative examples 3a and 3b were evaluated in the same
conditions and compared. The transverse of FIG. 4 shows time
necessary for containing hydrogen, and the vertical line shows the
quantity of contained hydrogen, in the case that a maximum
containing quantity of an untreated alloy is set to 100%.
[0099] As the reaction conditions, the air in the reaction vessel
was discharged by the evacuation at the alloy temperature of
constant 60.degree. C. until the inside pressure becomes 1 Pa, and
the vacuum discharge was further continued for thirty minutes, and
then hydrogen was introduced at the initial pressure of 1.5 MPa at
60.degree. C. On the other hand, all test pieces were left in the
atmosphere controlled at the temperature of 25.degree. C. and the
humidity of 30% for 24 hours. The results are as follows.
[0100] The untreated V of the comparative example 3b did not absorb
the hydrogen despite the passage of 6 hours.
[0101] The vanadium V of the comparative example 3a started to
absorb the hydrogen at the time of three-hour passage, and
contained quantity of about 80% of the hydrogen after 6 hours.
[0102] On the other hand, V of the example III started to absorb
the hydrogen after two hours, and contained quantity of almost 100%
of the hydrogen after 5 hours.
[0103] Although the alloy of the comparative example 3a also has a
high reactivity with hydrogen compared with the untreated alloy of
the comparative example 3b, the vanadium of the example III has a
more higher reactivity than the comparative example 3a.
[0104] The test of the poisoning restraining effect of the hydrogen
containing material of the example III was carried out in the same
manner as the example I. As a result of the test, it was confirmed
that the hydrogen containing material of the example II has a great
poisoning restraining effect although there are individual
differences, and CH.sub.4 is included in any emitted hydrogen
gases.
[0105] An additional evaluation was carried out about the condition
of the fluoride layer of the highly activated hydrogen containing
material of the example I. As a comparative example 1c, the highly
activated hydrogen containing material described in the Japanese
Patent Laid Open Publication 10-219301 as an example 5 was
used.
[0106] Fine particle test pieces of LaNi which were obtained by the
hydrogenizing and dehydrogenizing were classified into diameters of
25-50 .mu.m by a filter. As the powder of alumimun fluoride,
alumina powder of purity of 2N and diameter of 1 .mu.m produced by
the High Purity Chemical Laboratory Co. Ltd. was used. The alumina
powder was immersed in the hydrofluoric anhydride solution at the
room temperature for one hour and dried in the atmosphere of
nitrogen gas of 393 K for one hour. The surfaces of LaNi powder
test pieces by the obtained aluminum fluoride powder were improved
by the shock method by the high speed air current using NHS--O type
produced by the Nara Machine Production Co. Ltd. More particularly,
aluminum fluoride powder and LaNi.sub.5 of 20 g were charged in the
mixer in the capacity ratio of 1 to 50, and mixed at the rotating
speed of 1,500 rpm for ten minutes to produce a mixture. The
quality of the mixture of 10 g was improved at the rotating speed
of 15,000 rpm for 15 hours, thereby to produce capsule particles
each of which comprises LaNi.sub.5 with a cover of the aluminum
fluoride.
[0107] In the evaluation, 10 g of each of the alloys of the example
I and comparative example 1a were put in respective reaction
vessels and evacuated up to 0.5 Pa at the temperature of 80.degree.
C., and high purity hydrogen of 7N was supplied to each reaction
vessel at the pressure of 2.5 MPa for 15 minutes. Furthermore, each
reaction vessel was evacuated at the same temperature up to 1 Pa.
Regarding the high purity hydrogen supply and the evacuation as one
cycle, 1,000 cycles of discharge and supply were carried out. As
the result of the observation of the surface condition of the alloy
with the electron microscope, there are released portions of the
fluoride film on the surface of the alloy of the comparative
example 1c as shown in FIG. 6. To the contrary, in the alloy of the
example I although cracks were observed, released portions were not
observed as shown in FIG. 5.
[0108] In accordance with the present invention, in the cases that
a large amount of metals which become high active when fluorinated
are included in the basic composition elements, that a small amount
of metals which become high active are included in the composition
elements, or that highly activated metal is not included, in any
case, it is possible to form a large amount of very highly
activated fluoride layers, compared with a hydrogen containing
material which is simply treated by fluorine, on the surface of the
hydrogen containing material.
[0109] In the boundary surface between the hydrogen containing
material as the matrix and the fluoride, a compound layer in which
the concentration of elements composing the matrix and the
concentration of the fluoride are changed in inclined conditions is
formed. The surface of the material is in the condition the
fluoride of the matrix and the fluoride of the highly activated
metal are mingled.
[0110] In another case, in the boundary surface between the
hydrogen containing material as the matrix and the fluoride, a
compound layer in which the concentration of elements composing the
matrix and the concentration of the fluoride are gradually changed
in inclined conditions is formed, and the fluoride of the matrix is
formed on the outer surface of the compound layer, and further on
the outside of the outer surface, the fluoride of the highly
activated metal is formed.
[0111] By forming the fluoride layer of metal the concentration of
which changes in inclined condition, it is possible to prevent the
metallic fluoride from exfoliating from the hydrogen containing
material. Therefore, it is possible to maintain high activity with
hydrogen for a long term in spite of a poisoning environment, while
maintaining at least one of durability of the hydrogen containing
material itself and a large capacity for absorbing hydrogen.
[0112] Furthermore, in accordance with the method for producing
hydrogen containing material of the present invention, by
contacting the treatment liquid for fluorinating the metal and the
hydrogen containing material with each other, the metallic fluoride
is formed on the surface or on the surface portion of the hydrogen
containing material. Therefore, it is possible to produce the
hydrogen containing material by a simple device with ease, and to
correspond to the mass production. Thus, it is possible to easily
form fluoride having a high activity with hydrogen and having a
characteristic for preventing the exfoliation of the fluoride.
[0113] While the invention has been described in conjunction with
preferred specific embodiment thereof, it will be understood that
this description is intended to illustrate and not limit the scope
of the invention, which is defined by the following claims.
* * * * *