U.S. patent application number 15/550474 was filed with the patent office on 2018-02-01 for method for producing nickel alloy porous body.
This patent application is currently assigned to SUMITOMO ELECTRIC INDUSTRIES, LTD.. The applicant listed for this patent is SUMITOMO ELECTRIC INDUSTRIES, LTD., SUMITOMO ELECTRIC TOYAMA CO., LTD.. Invention is credited to Tomoyuki AWAZU, Takahiro HIGASHINO, Masatoshi MAJIMA, Junichi NISHIMURA, Kazuki OKUNO, Hidetoshi SAITO, Hitoshi TSUCHIDA, Kengo TSUKAMOTO.
Application Number | 20180030607 15/550474 |
Document ID | / |
Family ID | 56688791 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180030607 |
Kind Code |
A1 |
OKUNO; Kazuki ; et
al. |
February 1, 2018 |
METHOD FOR PRODUCING NICKEL ALLOY POROUS BODY
Abstract
A method for producing a nickel alloy porous body includes a
step of applying a coating material that contains a nickel alloy
powder of nickel and an added metal, the nickel alloy powder having
a volume-average particle size of 10 .mu.m or less, onto a surface
of a skeleton of a resin formed body having a three-dimensional
mesh-like structure; a step of plating with nickel the surface of
the skeleton of the resin formed body onto which the coating
material has been applied; a step of removing the resin formed
body; and a step of diffusing the added metal into the nickel by a
heat treatment.
Inventors: |
OKUNO; Kazuki; (Itami-shi,
JP) ; HIGASHINO; Takahiro; (Itami-shi, JP) ;
AWAZU; Tomoyuki; (Itami-shi, JP) ; MAJIMA;
Masatoshi; (Itami-shi, JP) ; NISHIMURA; Junichi;
(Osaka, JP) ; TSUKAMOTO; Kengo; (Imizu-shi,
JP) ; TSUCHIDA; Hitoshi; (Imizu-shi, JP) ;
SAITO; Hidetoshi; (Imizu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO ELECTRIC INDUSTRIES, LTD.
SUMITOMO ELECTRIC TOYAMA CO., LTD. |
Osaka-shi, Osaka
Imizu-shi, Toyama |
|
JP
JP |
|
|
Assignee: |
SUMITOMO ELECTRIC INDUSTRIES,
LTD.
Osaka-shi, Osaka
JP
SUMITOMO ELECTRIC TOYAMA CO., LTD.
Imizu-shi, Toyama
JP
|
Family ID: |
56688791 |
Appl. No.: |
15/550474 |
Filed: |
January 22, 2016 |
PCT Filed: |
January 22, 2016 |
PCT NO: |
PCT/JP2016/051784 |
371 Date: |
August 11, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2301/15 20130101;
C25D 1/08 20130101; C25D 5/56 20130101; B22F 1/00 20130101; C25D
5/50 20130101; C22C 1/08 20130101; B22F 2304/10 20130101 |
International
Class: |
C25D 1/08 20060101
C25D001/08; C25D 5/56 20060101 C25D005/56; C22C 1/08 20060101
C22C001/08; C25D 5/50 20060101 C25D005/50 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 2015 |
JP |
2015-029654 |
Claims
1. A method for producing a nickel alloy porous body comprising: a
step of applying a coating material that contains a nickel alloy
powder of nickel and an added metal onto a surface of a skeleton of
a resin formed body having a three-dimensional mesh-like structure;
a step of plating with nickel the surface of the skeleton of the
resin formed body onto which the coating material has been applied;
a step of removing the resin formed body; and a step of diffusing
the added metal into the nickel by a heat treatment.
2. The method for producing a nickel alloy porous body according to
claim 1, wherein the added metal is at least one metal selected
from the group consisting of Cr, Sn, Co, Cu, Al, Ti, Mn, Fe, Mo,
and W.
3. The method for producing a nickel alloy porous body according to
claim 1, wherein at least a surface of the nickel alloy powder is
oxidized.
4. The method for producing a nickel alloy porous body according to
claim 1, wherein the coating material that contains the nickel
alloy powder further contains a carbon powder.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing a
nickel alloy porous body that is usable, for example, as a current
collector for a battery, filter, or catalyst carrier, that is
excellent in terms of strength and toughness, and that is produced
at a low cost and from a wide range of materials.
BACKGROUND ART
[0002] Porous metal bodies have been used in various applications,
such as current collectors for batteries, filters, and catalyst
carriers. Accordingly, there are many known documents regarding
production techniques for porous metal bodies, as described
below.
[0003] Japanese Unexamined Patent Application Publication No.
7-150270 (PTL 1) proposes a porous metal body having high strength,
which is obtained by applying a coating material containing
reinforcing fine particles of an oxide, carbide, or nitride of an
element selected from Groups II to VI of the periodic table onto a
surface of a skeleton of a three-dimensional mesh-like resin having
interconnected pores; forming a metal plating layer of a Ni alloy
or Cu alloy on the coating film of the coating material; and
dispersing the fine particles in the metal plating layer by
performing a heat treatment. However, since the reinforcing fine
particles are dispersed in the metal plating layer which is a base
layer, the porous metal body has low elongation at break although
its breaking strength is high. The porous metal body is vulnerable
to processing that involves plastic deformation, such as bending or
pressing, and breaks when subjected to such processing, which is a
problem.
[0004] Japanese Examined Patent Application Publication No.
38-17554 (PTL 2), Japanese Unexamined Patent Application
Publication No. 9-017432 (PTL 3), and Japanese Unexamined Patent
Application Publication No. 2001-226723 (PTL 4) each propose a
porous metal body which is obtained by applying or spraying a
slurry composed of a metal or metal oxide powder and a resin onto a
three-dimensional mesh-like resin, followed by drying, and
performing a sintering treatment. However, in the porous metal body
produced by the sintering process, since the skeleton is formed by
sintering between metal or metal oxide powder particles, even if
the powder particle size is decreased, voids occur in considerable
numbers in the skeleton in cross section. As a result, even when a
body having high breaking strength is obtained by designing a
single metal or alloy species, since the elongation at break is
low, the body is vulnerable to processing that involves plastic
deformation, such as bending or pressing, and breaks when subjected
to such processing, which is a problem, as in the case described
above.
[0005] Japanese Unexamined Patent Application Publication No.
8-013129 (PTL 5) and Japanese Unexamined Patent Application
Publication No. 8-232003 (PTL 6) each propose a porous metal body
obtained by a diffusion coating process in which a Ni porous body
formed by a plating process, with a three-dimensional mesh-like
resin to which conductivity has been imparted being used as a
substrate, is buried in powder of Cr or Al and NH.sub.4Cl, and is
subjected to a heat treatment in an Ar or H.sub.2 gas atmosphere.
However, the low productivity of the diffusion coating process
results in a high cost, and the element capable of forming an alloy
with the Ni porous body is limited to Cr and Al, all of which are
problems.
[0006] Japanese Unexamined Patent Application Publication No.
2013-133504 (PTL 7) proposes a method for producing a porous body
in which, when an electrical conduction treatment is performed on a
surface of a resin formed body having a three-dimensional mesh-like
structure, a carbon coating material to which a metal powder has
been added is applied to the surface, and then electroplating with
a desired metal and a heat treatment are performed, thereby
obtaining a homogeneous alloy porous body.
CITATION LIST
Patent Literature
[0007] PTL 1: Japanese Unexamined Patent Application Publication
No. 7-150270
[0008] PTL 2: Japanese Examined Patent Application Publication No.
38-17554
[0009] PTL 3: Japanese Unexamined Patent Application Publication
No. 9-017432
[0010] PTL 4: Japanese Unexamined Patent Application Publication
No. 2001-226723
[0011] PTL 5: Japanese Unexamined Patent Application Publication
No. 8-013129
[0012] PTL 6: Japanese Unexamined Patent Application Publication
No. 8-232003
[0013] PTL 7: Japanese Unexamined Patent Application Publication
No. 2013-133504
SUMMARY OF INVENTION
Technical Problem
[0014] According to the method described in PTL 7, it is possible
to produce a porous metal body that is suitable for use, for
example, as a current collector for a battery, filter, or catalyst
carrier, that is excellent in terms of strength and toughness, and
that is produced at a low cost and from a wide range of
materials.
[0015] However, as a result of diligent studies by the present
inventors, it has been found that in the method described in PTL 7,
in the case where the content of the metal added is small (e.g.,
about 5% by mass or less), there is room for improvement from the
viewpoint of facilitating control of the concentration. As a result
of further studies on this matter, it has been found that, when the
resin formed body is removed by burning, some metal particles
remain on the surface of the resin formed body and are not
incorporated in the metal plating layer. In such a phenomenon, the
contraction of the resin formed body on which metal particles are
held proceeds faster than the diffusion of metal particles into the
metal plating layer, and some metal particles separate from the
metal plating layer without being diffused and remain on the inner
surface of the skeleton. In particular, the phenomenon is markedly
observed in the heat treatment of Cr-based oxide particles.
[0016] The phenomenon described above will be described in detail
with reference to FIGS. 3A to 3C.
[0017] FIGS. 3A to 3C are schematic diagrams, each showing a cross
section of a skeleton of a resin formed body during a production
step when a porous metal body is produced by the method described
in PTL 7.
[0018] First, in order to perform an electrical conduction
treatment on the surface of a resin formed body 1, a carbon coating
material containing a metal powder 2 is applied onto the surface of
the resin formed body 1 (refer to FIG. 3A). Thereby, the surface of
the resin formed body 1 is made conductive. Subsequently, coating
with a desired metal is performed by electrolytic plating. Thereby,
as shown in FIG. 3B, a metal plating layer 3 is formed on the
surface of the resin formed body 1. Subsequently, in order to
remove the resin formed body 1, a heat treatment is performed. In
this process, a phenomenon is observed in which, as shown in FIG.
3C, the resin formed body 1 contracts, and some of the metal
particles 2 which have been adhering to the surface of the resin
formed body 1 remain adhering to the resin formed body 1 and are
not incorporated in the metal plating layer 3.
[0019] This necessitates that metal particles should be added in an
amount larger than that required for the desired alloy
concentration of the porous metal body.
[0020] Accordingly, it is an object of the present invention to
provide a method for producing a nickel alloy porous body, in
which, even in the case where the concentration of the metal added
to nickel is low, control of the concentration is facilitated, and
the added metal can be uniformly diffused into the porous body.
Solution to Problem
[0021] A method for producing a nickel alloy porous body according
to an embodiment of the present invention is as follows:
[0022] (1) A method for producing a nickel alloy porous body
includes:
[0023] a step of applying a coating material that contains a nickel
alloy powder of nickel and an added metal onto a surface of a
skeleton of a resin formed body having a three-dimensional
mesh-like structure;
[0024] a step of plating with nickel the surface of the skeleton of
the resin formed body onto which the coating material has been
applied;
[0025] a step of removing the resin formed body; and
[0026] a step of diffusing the added metal into the nickel by a
heat treatment.
Advantageous Effects of Invention
[0027] According to the invention, it is possible to provide a
method for producing a nickel alloy porous body, in which, even in
the case where the concentration of the metal added to nickel is
low, control of the concentration is facilitated, and the added
metal can be uniformly diffused into the porous body.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1A is a schematic diagram showing a cross section of a
skeleton in a state in which a coating material is applied onto the
surface of the skeleton of a resin formed body in a method for
producing a nickel alloy porous body according to an embodiment of
the present invention.
[0029] FIG. 1B is a schematic diagram showing a cross section of a
skeleton in a state in which the surface of the skeleton of the
resin formed body is plated with nickel in the method for producing
a nickel alloy porous body according to the embodiment of the
present invention.
[0030] FIG. 1C is a schematic diagram showing a cross section of a
skeleton in a step of removing the resin formed body in the method
for producing a nickel alloy porous body according to the
embodiment of the present invention.
[0031] FIG. 2A is a photograph showing a cross section of a
skeleton of a nickel alloy porous body 1 produced in Example 1 when
observed with an electron microscope.
[0032] FIG. 2B is a photograph showing a cross section of a
skeleton of a nickel alloy porous body 2 produced in Example 1 when
observed with an electron microscope.
[0033] FIG. 2C is a photograph showing a cross section of a
skeleton of a nickel alloy porous body 3 produced in Example 1 when
observed with an electron microscope.
[0034] FIG. 2D is a photograph showing a cross section of a
skeleton of a nickel alloy porous body 4 produced in Example 1 when
observed with an electron microscope.
[0035] FIG. 2E is a photograph showing a cross section of a
skeleton of a nickel alloy porous body 9 produced in Comparative
Example 1 when observed with an electron microscope.
[0036] FIG. 2F is a photograph showing a cross section of a
skeleton of a nickel alloy porous body 10 produced in Comparative
Example 1 when observed with an electron microscope.
[0037] FIG. 2G is photograph showing a cross section of a skeleton
of a nickel alloy porous body 11 produced in Comparative Example 1
when observed with an electron microscope.
[0038] FIG. 2H is photograph showing a cross section of a skeleton
of a nickel alloy porous body 12 produced in Comparative Example 1
when observed with an electron microscope.
[0039] FIG. 3A is a schematic diagram showing a cross section of a
skeleton in a state in which a coating material is applied onto the
surface of the skeleton of a resin formed body in an existing
method for producing an alloy porous body.
[0040] FIG. 3B is a schematic diagram showing a cross section of a
skeleton in a state in which the surface of the skeleton of the
resin formed body is plated with nickel in the existing method for
producing an alloy porous body.
[0041] FIG. 3C is a schematic diagram showing a cross section of a
skeleton in a step of removing the resin formed body in the
existing method for producing an alloy porous body.
[0042] FIG. 4 is a schematic diagram showing an existing water
decomposition device.
[0043] FIG. 5 is a schematic diagram showing a water decomposition
device which uses porous metal bodies according to an embodiment of
the present invention.
DESCRIPTION OF EMBODIMENTS
Description of Embodiments of the Present Invention
[0044] First, the embodiments of the present invention will be
enumerated and described below.
[0045] (1) A method for producing a nickel alloy porous body
according to an embodiment of the present invention includes:
[0046] a step of applying a coating material that contains a nickel
alloy powder of nickel and an added metal onto a surface of a
skeleton of a resin formed body having a three-dimensional
mesh-like structure;
[0047] a step of plating with nickel the surface of the skeleton of
the resin formed body onto which the coating material has been
applied;
[0048] a step of removing the resin formed body; and
[0049] a step of diffusing the added metal into the nickel by a
heat treatment.
[0050] According to the invention described in (1), it is possible
to provide a method for producing a nickel alloy porous body, in
which, even in the case where the concentration of the metal added
to nickel is low, control of the concentration is facilitated, and
the added metal can be uniformly diffused into the porous body.
[0051] (2) In the method for producing a nickel alloy porous body
according to (1), preferably, the added metal is at least one metal
selected from the group consisting of Cr, Sn, Co, Cu, Al, Ti, Mn,
Fe, Mo, and W.
[0052] According to the invention described in (2), at least one
added metal selected from the group consisting of Al, Ti, Cr, Mn,
Fe, Co, Cu, Mo, Sn, and W can be uniformly distributed in the
nickel porous body, and the concentration thereof can be easily
controlled.
[0053] (3) In the method for producing a nickel alloy porous body
according to (1) or (2), preferably, at least a surface of the
nickel alloy powder is oxidized.
[0054] According to the invention described in (3), by decreasing
the particle size of the nickel alloy powder, the added metal can
be easily diffused into the nickel layer.
[0055] (4) In the method for producing a nickel alloy porous body
according to any one of (1) to (3), preferably, the coating
material that contains the nickel alloy powder further contains a
carbon powder.
[0056] According to the invention described in (4), the
conductivity of the surface of the resin formed body is improved,
and nickel plating can be performed easily.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION
[0057] Specific examples of a method for producing a nickel alloy
porous body according to the embodiments of the present invention
will be described in detail below. The present invention is not
limited to the examples, but is defined by the appended claims, and
is intended to include all modifications within the meaning and
scope equivalent to those of the claims.
[0058] A method for producing a nickel alloy porous body according
to an embodiment of the present invention will be described in
detail with reference to FIGS. 1A to 1C.
[0059] FIGS. 1A to 1C are schematic diagrams, each showing a cross
section of a skeleton of a resin formed body during a production
step when a nickel alloy porous body is produced by the method for
producing a nickel alloy porous body according to the embodiment of
the present invention.
[0060] First, a resin formed body 1 serving as a base for a nickel
alloy porous body is prepared. In order to impart conductivity to a
surface of a skeleton of the resin formed body 1, a coating
material containing a conductive powder is applied onto the surface
of the skeleton of the resin formed body 1. As the conductive
powder, an alloy powder 4 including a metal to be added to a nickel
porous body and nickel is used (refer to FIG. 1A). Subsequently, a
nickel plating layer 3 is formed on the surface of the skeleton of
the resin formed body 1. Since the surface of the skeleton of the
resin formed body 1 is conductive, the nickel plating layer 3 can
be formed by electrolytic plating. Thereby, as shown in FIG. 1B, a
layer composed of the nickel alloy powder 4 and the nickel plating
layer 3 are formed.
[0061] Then, a heat treatment is performed in order to remove the
resin formed body. At this time, the nickel alloy powder 4 on the
surface of the skeleton of the resin formed body rapidly starts to
diffuse into the nickel plating layer 3. Therefore, when the resin
formed body 1 starts to contract, the nickel alloy powder 4 does
not move without adhering to the surface of the resin formed body
1, but remains incorporated in the nickel plating layer 1 (refer to
FIG. 1C).
[0062] That is, in the existing method, some particles of the metal
powder on the surface of the skeleton of the resin formed body are
pulled to the surface of the skeleton of the resin formed body
before starting to diffuse into the metal plating layer, and are
not incorporated in the metal plating layer (refer to FIG. 3C).
Such a phenomenon does not occur in the method for producing a
nickel alloy porous body according to the embodiment of the present
invention, and all of the nickel alloy powder can be effectively
used.
[0063] As described above, the method for producing a nickel alloy
porous body according to the embodiment of the present invention
includes a step of applying a coating material that contains a
nickel alloy powder onto a surface of a skeleton of a resin formed
body, a step of performing nickel plating, a step of removing the
resin formed body, and a step of diffusing the nickel alloy powder
into nickel.
[0064] Each of the steps will be described in detail below.
[0065] (Step of applying coating material that contains nickel
alloy powder)
[0066] --Resin Formed Body--
[0067] As the resin formed body having a three-dimensional
mesh-like structure, a resin foam, nonwoven fabric, felt, woven
fabric, or the like can be used. As necessary, these may be used in
combination. Furthermore, the material that constitutes the resin
formed body is not particularly limited, but is preferably a
material that can be plated with a metal and then can be removed by
a burning treatment. Furthermore, from the viewpoint of handling of
the resin formed body, in particular, in a sheet-shaped body, a
material having high rigidity may break, and therefore, a material
having flexibility is preferable.
[0068] In the method for producing a nickel alloy porous body
according to the embodiment of the present invention, it is
preferable to use a resin foam as the resin formed body having a
three-dimensional mesh-like structure. The resin foam may be a
known or commercially available resin foam as long as it is porous.
Examples thereof include a urethane foam and a styrene foam. Among
these, in particular, a urethane foam is preferable from the
viewpoint of a high porosity. The thickness, porosity, and average
pore size of the resin foam are not particularly limited and can be
appropriately determined depending on the application.
[0069] --Nickel Alloy Powder--
[0070] A nickel alloy powder having a volume-average particle size
of 10 .mu.m or less is used for performing an electrical conduction
treatment on the surface of the skeleton of the resin formed body.
In order to produce a coating material by adding the nickel alloy
powder into a binder or solvent, the nickel alloy powder preferably
has a smaller volume-average particle size, and more preferably has
a volume-average particle size of 3 .mu.m or less. Furthermore, the
volume-average particle size may be appropriately selected in
accordance with the diameter of the skeleton of a resin formed body
to be used.
[0071] In the nickel alloy powder, the added metal that forms an
alloy with nickel is not particularly limited, and a desired metal
may be selected in accordance with the intended use. For example,
it is preferable to use at least one metal selected from the group
consisting of Cr, Sn, Co, Cu, Al, Ti, Mn, Fe, Mo, and W.
[0072] In the method for producing a nickel alloy porous body
according to the embodiment of the present invention, the nickel
alloy powder may be a powder in which nickel and an added metal
form a completely homogeneous alloy, or may be a mixed-type powder,
a core-shell type powder, or a composite-type powder. In the
present invention, all of these types of powder are referred to as
the nickel alloy powder.
[0073] The term "mixed-type powder" refers to a powder in which a
plurality of single particles of an added metal are present inside
a nickel particle, or a powder in which a layer-shaped added metal
is present inside a nickel particle. Furthermore, the term
"core-shell type powder" refers to a powder in which the surface of
a single particle of an added metal is coated with nickel.
[0074] The term "composite-type powder" refers to, for example, a
powder which has a core-shell structure composed of an added metal
and a nickel alloy, or a powder having a core-shell structure in
which a particle-shaped or layer-shaped added metal is partially
present.
[0075] In any of the nickel alloy powders, a powder in which most
of the surfaces of nickel alloy particles are made of nickel or a
homogeneous nickel alloy is used so that the nickel alloy particles
can be easily diffused into the nickel plating layer.
[0076] Such a nickel alloy powder can be obtained by a
disintegration process for disintegrating a nickel alloy, an
atomization process, or the like.
[0077] Preferably, at least a surface of the nickel alloy powder is
oxidized.
[0078] In the case where a nickel alloy powder is produced by
disintegrating an alloy of nickel and an added metal, a nickel
alloy, i.e., a starting material, in an oxidized state is more
likely to be disintegrated, and it is possible to obtain a nickel
alloy powder having a smaller volume-average particle size. By
using such a nickel alloy powder having a small particle size, the
added metal can be easily diffused into nickel. Furthermore,
regarding the nickel alloy powder obtained by disintegrating the
nickel alloy in an oxidized state, at least a surface of the nickel
alloy powder is in an oxidized state, and the oxidized metal can be
reduced in a heat treatment step in which the added metal is
diffused into nickel. Alternatively, it may be possible to perform,
separately, a step of reducing metal oxides by carrying out a heat
treatment in a reducing atmosphere.
[0079] --Carbon Powder--
[0080] In the case where at least a surface of the nickel alloy
powder is oxidized and the nickel alloy powder is not a conductive
powder, preferably, a carbon powder is further added to the coating
material. Thereby, the conductivity of the coating material can be
enhanced. The volume-average particle size of the carbon powder is
preferably 10 .mu.m or less, and more preferably 3 .mu.m or less,
as in the nickel alloy porous body. Furthermore, the volume-average
particle size may be appropriately selected in accordance with the
diameter of the skeleton of a resin formed body.
[0081] Examples of the material of the carbon powder include
crystalline graphite and amorphous carbon black. Among these,
graphite is particularly preferable from the viewpoint that, in
general, graphite tends to have a small particle size.
[0082] --Coating Material--
[0083] A conductive coating material can be produced by adding the
nickel alloy powder and, if necessary, a carbon powder to a binder,
followed by mixing.
[0084] In order to perform an electrical conduction treatment on
the surface of the resin formed body, the coating material may to
be applied onto the surface of the skeleton of the resin formed
body. The method of applying the coating material is not
particularly limited and, for example, an immersion method or an
application method by using a brush or the like may be used.
Thereby, a conductive coating layer is formed on the surface of the
skeleton of the resin formed body.
[0085] The conductive coating layer may be continuously formed on
the surface of the skeleton of the resin formed body. Furthermore,
the coating weight of the conductive coating layer is not
particularly limited, and is usually about 0.1 to 300 g/m.sup.2,
and preferably about 1 to 100 g/m.sup.2.
[0086] (Step of Performing Nickel Plating)
[0087] In the step of performing nickel plating, a known plating
process can be used, and an electroplating process is preferably
used. Instead of the electroplating treatment, if the thickness of
a plating film is increased by an electroless plating treatment
and/or a sputtering treatment, it may not be necessary to perform
an electroplating treatment. However, this is not desirable from
the viewpoint of productivity and cost. For this reason, as
described above, by employing a method in which a resin formed body
is subjected to an electrical conduction treatment, and then a
nickel plating layer is Ruined by an electroplating process, a
nickel alloy porous body can be produced with high productivity and
at a low cost. Furthermore, it is possible to obtain a highly
stable nickel alloy porous body in which the skeleton, in cross
section, has a void ratio of less than 1%.
[0088] Furthermore, the plating layer may have a multi-layered
structure, and in such a case, a nickel plating layer is fainted as
a first plating layer. Thereby, the nickel alloy particles can be
easily diffused into the nickel plating layer. A metal plating
layer may be appropriately formed on the nickel plating layer in
accordance with the intended use.
[0089] The nickel plating layer may be formed on the conductive
coating layer to such an extent that the conductive coating layer
is not exposed. The coating weight of the nickel plating layer is
not particularly limited, and may be appropriately selected in
accordance with the thickness of the nickel alloy porous body. In
order to achieve both strength and a porosity, the coating weight
per 1 mm thickness may be usually about 100 to 600 g/m.sup.2, and
is more preferably about 200 to 500 g/m.sup.2.
[0090] (Step of Removing Resin Formed Body)
[0091] By subjecting the composite body of resin and metal obtained
through the foregoing steps to a heat treatment in the air, the
resin formed body can be removed.
[0092] The heat treatment temperature is preferably 700.degree. C.
to 1,200.degree. C. When the heat treatment temperature is
700.degree. C. or higher, the resin formed body can be removed and
the nickel alloy powder can be easily diffused into the nickel
plating layer. When the heat treatment temperature is 1,200.degree.
C. or lower, nickel can be suppressed from being excessively
oxidized. From these viewpoints, the heat treatment temperature is
more preferably 750.degree. C. to 1,100.degree. C., and still more
preferably 800.degree. C. to 1,050.degree. C.
[0093] Furthermore, the heat treatment time may be appropriately
changed depending on the heat treatment temperature. For example,
in the case where the heat treatment is performed at 800.degree.
C., the resin formed body can be satisfactorily removed in about 10
to 30 minutes.
[0094] (Step of Diffusing Added Metal by Heat Treatment)
[0095] This step is carried out to more uniformly diffuse the added
metal incorporated in the nickel plating layer.
[0096] The heat treatment temperature and the heat treatment time
may be appropriately selected in accordance with the metal added.
For example, in the case where a nickel alloy porous body is
produced by using a nickel-chromium alloy powder or nickel-tungsten
powder, the heat treatment may be performed at 1,100.degree. C. for
30 minutes or more. In the case where an alloy powder of nickel and
tin, cobalt, copper, aluminum, titanium, manganese, iron, or
molybdenum is used, the heat treatment may be performed at
1,000.degree. C. for 15 minutes or more.
[0097] Furthermore, when the heat treatment is performed in a
reducing atmosphere by using H.sub.2 gas or the like, the nickel
alloy powder or nickel alloy oxide powder and the nickel plating
layer can be reduced. The carbon powder contained in the conductive
coating layer serves as a strong reducing agent at high
temperatures to reduce the nickel alloy powder or nickel alloy
oxide powder and the nickel plating layer.
[0098] Furthermore, the heat treatment at the optimal temperature
for the optimum period of time suitable for the added metal species
allows reduction of the nickel alloy (decrease in the oxygen
concentration in the metal) with the carbon powder when used, alloy
formation due to thermal diffusion, and coarsening of crystal
grains. As a result, the strength and roughness of the nickel alloy
porous body are improved, and it is possible to obtain a strong
nickel alloy porous body that does not break even when subjected to
processing that involves plastic deformation, such as bending or
pressing.
EXAMPLES
[0099] The present invention will be described in more detail below
on the basis of examples. However, the examples are merely
illustrative and the porous metal body of the present invention is
not limited thereto. The scope of the present invention is defined
by the appended claims, and includes all modifications within the
meaning and scope equivalent to those of the claims.
Example 1
[0100] (Electrical Conduction Treatment of Resin Formed Body)
[0101] First, as resin formed bodies having a three-dimensional
mesh-like structure, polyurethane foam sheets (pore size 0.45 mm)
with a thickness of 1.5 mm were prepared. Subsequently, 100 g of
graphite with a volume-average particle size of 10 .mu.m, 20 g of
carbon black with a volume-average particle size of 0.1 .mu.m, and
100 g of a nickel alloy oxide powder with a volume-average particle
size shown in Table 1 were dispersed in 0.5 L of a 10% aqueous
solution of an acrylic ester resin, and a viscous coating material
was produced at this composition ratio.
[0102] As the nickel alloy oxide powder, a nickel-chromium alloy
oxide powder, a nickel-cobalt alloy oxide powder, a nickel-tin
alloy oxide powder, and a nickel-copper alloy oxide powder was
used. The nickel alloy oxide powders were obtained by oxidizing the
corresponding nickel alloy powders and used by disintegrating and
classifying the oxidized powders so that the volume-average
particle size was 0.5 to 1.5.mu.m.
[0103] Subsequently, each of the polyurethane foam sheets was
continuously immersed in the coating material and squeezed with
rolls, followed by drying. In such a manner, the polyurethane foam
sheet was subjected to an electrical conduction treatment. Thereby,
a conductive coating layer was formed on the surface of the resin
formed body having a three-dimensional mesh-like structure. The
viscosity of the conductive coating material was adjusted with a
thickener, and the coating weight of the coating material was set
to be 20 g/m.sup.2 in terms of alloy powder. The coating weight is
shown in Table 1.
[0104] (Nickel Plating Step)
[0105] A nickel plating layer was formed by electroplating with 300
g/m.sup.2 on the surface of the skeleton of the resin formed body
having a three-dimensional mesh-like structure which had been
subjected to the electrical conduction treatment. As the plating
solution, a nickel sulfamate plating solution was used.
[0106] (Step of Removing the Resin Formed Body)
[0107] By performing a heat treatment in the air at 800.degree. C.
for 15 minutes, the resin formed body was removed by burning. The
oxidized porous metal body was reduced by performing a heat
treatment in a reducing hydrogen atmosphere at 1,000.degree. C. for
15 minutes.
[0108] (Step of Diffusing Added Metal)
[0109] By performing a heat treatment in a hydrogen atmosphere at
1,100.degree. C. for 30 minutes, the added metal was sufficiently
diffused into nickel.
[0110] In such a manner, nickel alloy porous bodies 1 to 4 were
produced.
[0111] <Evaluation>
[0112] FIGS. 2A to 2D show the results of observation, by an
electron microscope (SEM), of cross sections of skeletons of the
nickel alloy porous bodies 1 to 4 obtained as described above. As
shown in FIGS. 2A to 2D, in each of the nickel alloy porous bodies
1 to 4, it has been confirmed that the added metal particles do not
remain on the inner surface of the skeleton of the nickel alloy
porous body and that the added metal is uniformly diffused into
nickel.
Example 2
[0113] Nickel alloy porous bodies 5 to 8 were produced as in
Example 1 except that, instead of the nickel-chromium alloy oxide
powder, the nickel-cobalt alloy oxide powder, the nickel-tin alloy
oxide powder, and the nickel-copper alloy oxide powder, a
nickel-chromium alloy powder, a nickel-cobalt alloy powder, a
nickel-tin alloy powder, and a nickel-copper alloy powder were
used. The volume-average particle size and coating weight of the
nickel alloy powders are shown in Table 1.
[0114] Cross sections of skeletons of the nickel alloy porous
bodies 5 to 8 were observed by an electron microscope as in Example
1. As a result, it was confirmed that the added metal particles do
not remain on the inner surface of the skeleton of the nickel alloy
porous body and that the added metal is uniformly diffused into
nickel.
Comparative Example 1
[0115] Nickel alloy porous bodies 9 to 12 were produced as in
Example 1 except that, instead of the nickel-chromium alloy oxide
powder, the nickel-cobalt alloy oxide powder, the nickel-tin alloy
oxide powder, and the nickel-copper alloy oxide powder, a chromium
oxide powder, a cobalt oxide powder, a tin oxide powder, and a
copper oxide powder were used. The metal oxide powders were
obtained by oxidizing the corresponding metal powders and used by
disintegrating and classifying the oxidized powders. The
volume-average particle size and coating weight of the oxidized
metal powders are shown in Table 1.
[0116] FIGS. 2E to 2H show the results of observation, by an
electron microscope, of cross sections of skeletons of the nickel
alloy porous bodies 9 to 12, as in Example 1. As shown in FIGS. 2E
to 2H, in each of the porous metal bodies 9 to 12, it has been
confirmed that some of the added metal particles remain on the
inner surface of the skeleton of the nickel alloy porous body.
Comparative Example 2
[0117] Nickel alloy porous bodies 13 to 16 were produced as in
Example 1 except that, instead of the nickel-chromium alloy oxide
powder, the nickel-cobalt alloy oxide powder, the nickel-tin alloy
oxide powder, and the nickel-copper alloy oxide powder, a chromium
powder, a cobalt powder, a tin powder, and a copper powder were
used.
[0118] Cross sections of skeletons of the nickel alloy porous
bodies 13 to 16 were observed by an electron microscope as in
Example 1. As a result, it was confirmed that some of the added
metal particles remain on the inner surface of the skeleton of the
nickel alloy porous body.
TABLE-US-00001 TABLE 1 Added metal Powder content in Nickel alloy
Volume-average Coating weight nickel alloy porous body particle
size (g/m.sup.2) porous body No. Kind (.mu.m) in terms of metal
(mass %) 1 Nickel-chromium alloy oxide 0.5 21 3.4 2 Nickel-cobalt
alloy oxide 0.7 19 3.1 3 Nickel-tin alloy oxide 0.6 20 3.2 4
Nickel-copper alloy oxide 1.1 22 3.5 5 Nickel-chromium alloy 1.5 23
3.5 6 Nickel-cobalt alloy 1.8 21 3.4 7 Nickel-tin alloy 1.5 20 3.3
8 Nickel-copper alloy 2.3 24 3.7 9 Chromium oxide 0.5 20 3.2 10
Cobalt oxide 0.5 23 3.7 11 Tin oxide 0.6 19 3.1 12 Copper oxide 1.4
18 2.9 13 Chromium 1.4 21 3.3 14 Cobalt 1.5 23 3.7 15 Tin 1.7 20
3.3 16 Copper 2.2 21 3.4
[0119] Besides being used for fuel cells, porous metal bodies which
are nickel alloy porous bodies according to the present invention
can also be suitably used for the production of hydrogen by water
electrolysis.
[0120] FIG. 4 is a schematic diagram showing an existing water
decomposition device. Current collectors 6 are disposed on both
sides of an ion permeable membrane 5. The ion permeable membrane 5
allows mainly hydrogen or oxygen to permeate therethrough.
The current collectors 6 each have a gas channel, which is made of
a corrugated stainless steel plate, carbon structure having
grooves, or the like, on the side thereof in contact with the ion
permeable membrane. Steam is introduced into one of the gas
channels. For example, hydrogen ions generated from decomposition
pass through the ion permeable membrane 5 and are discharged from
the gas channel on the opposite side, and oxygen generated from
decomposition, together with steam that has not been decomposed, is
discharged as is.
[0121] FIG. 5 is a schematic diagram showing a water decomposition
device which uses porous metal bodies according to an embodiment of
the present invention. The water decomposition device has the same
structure as that of the existing water decomposition device shown
in FIG. 4 except that gas channels are made of porous metal bodies
7. By using current collectors 6 whose gas channels are made of
porous metal bodies 7 in such a manner, hydrogen can be efficiently
produced by water decomposition compared with the existing
device.
[0122] (1) In an alkaline electrolysis method, an anode and a
cathode are immersed in a strongly alkaline aqueous solution, and
water is electrolyzed by applying a voltage. By using a porous
metal body as an electrode, the contact area between water and the
electrode increases, and the efficiency of water electrolysis can
be enhanced. The pore size of the porous metal body is preferably
100 to 5,000 .mu.m. When the pore size is less than 100 .mu.m,
removal of bubbles of generated hydrogen/oxygen becomes
unsatisfactory, and the area of contact between water and the
electrode decreases, resulting in a decrease in efficiency.
Furthermore, when the pore size is more than 5,000 .mu.m, the
surface area of the electrode decreases, resulting in a decrease in
efficiency. From the same viewpoint, the pore size is more
preferably 400 to 4,000 .mu.m.
[0123] Since a larger electrode area may cause deflection or the
like, the thickness and metal content of the porous metal body can
be appropriately selected in accordance with the scale of
equipment. In order to secure both removal of bubbles and a
sufficient surface area, a plurality of porous metal bodies having
different pore sizes may be combined for use.
[0124] (2) In a PEM method, water is electrolyzed by using a solid
polymer electrolyte membrane. An anode and a cathode are placed on
both surfaces of the solid polymer electrolyte membrane, and by
applying a voltage while feeding water to the anode side, hydrogen
ions are generated by electrolysis of water. The hydrogen ions are
transported through the solid polymer electrolyte membrane to the
cathode side, and are taken out as hydrogen at the cathode side.
The operating temperature is about 100.degree. C. The PEM
electrolysis device has the same structure as that of a solid
polymer-type fuel cell which produces electricity from hydrogen and
oxygen and discharges water, but is operated in a completely
reverse manner. Since the anode side and the cathode side are
completely separated from each other, hydrogen with a high purity
can be taken out, which is advantageous. In each of the anode and
the cathode, since it is necessary to pass water/hydrogen gas
through an electrode, a conductive porous body is required as the
electrode.
[0125] The porous metal body according to the present invention has
a high porosity and good electrical conductivity, and therefore,
can be suitably used for PEM water electrolysis as well as suitably
used for a solid polymer-type fuel cell. The pore size of the
porous metal body is preferably 100 to 5,000 .mu.m. When the pore
size is less than 100 .mu.m, removal of bubbles of generated
hydrogen/oxygen becomes unsatisfactory, and the area of contact
between water and the solid polymer electrolyte decreases,
resulting in a decrease in efficiency. Furthermore, when the pore
size is more than 5,000 .mu.m, water retention is poor, and water
passes through the porous metal body before fully reacting,
resulting in a decrease in efficiency. From the same viewpoint, the
pore size is more preferably 400 to 4,000 .mu.m.
[0126] The thickness and metal content of the porous metal body can
be appropriately selected in accordance with the scale of
equipment. When the porosity is excessively small, the pressure
loss during feeding of water increases. Therefore, the thickness
and metal content are preferably adjusted so that the porosity is
30% or more. Furthermore, in this method, since the electrical
conduction between the solid polymer electrolyte and the electrode
is performed by pressure bonding, it is necessary to adjust the
metal content such that the increase in electrical resistance due
to deformation/creeping during application of pressure is within a
range that causes no problem in practical use. The metal content is
preferably 400 g/m.sup.2 or more. Additionally, in order to secure
the porosity and to achieve electrical connection, a plurality of
porous metal bodies having different pore sizes may combined for
use.
[0127] (3) In an SOEC method, water is electrolyzed by using a
solid oxide electrolyte membrane, and the structure is different
depending on whether the electrolyte membrane is protonically
conductive or oxygen ion-conductive. In an oxygen ion-conductive
membrane, since hydrogen is generated at the cathode side into
which steam is fed, the hydrogen purity decreases. Therefore, from
the viewpoint of hydrogen production, a protonically conductive
membrane is preferable. An anode and a cathode are placed on both
sides of a protonically conductive membrane, and by applying a
voltage while introducing steam to the anode side, hydrogen ions
are generated by electrolysis of water. The hydrogen ions are
transported through the solid oxide electrolyte membrane to the
cathode side, and hydrogen alone is taken out at the cathode side.
The operating temperature is about 600.degree. C. to 800.degree. C.
The SOEC electrolysis device has the same structure as that of a
solid oxide fuel cell which produces electricity from hydrogen and
oxygen and discharges water, but is operated in a completely
reverse manner. In each of the anode and the cathode, since it is
necessary to pass steam/hydrogen gas through an electrode, a porous
body that is conductive and that can withstand a high-temperature
oxidizing atmosphere, in particular, at the anode side is required
as the electrode.
[0128] The porous metal body according to the present invention has
a high porosity, good electrical conductivity, high oxidation
resistance, and high heat resistance, and therefore, can be
suitably used for SOEC water electrolysis as well as suitably used
for a solid oxide fuel cell. It is preferable to use a Ni alloy to
which a metal having high oxidation resistance, such as Cr, is
added for the electrode on the side subjected to an oxidizing
atmosphere. The pore size of the porous metal body is preferably
100 to 5,000 .mu.m. When the pore size is less than 100 .mu.m, flow
of steam or generated hydrogen becomes unsatisfactory, and the area
of contact between steam and the solid oxide electrolyte decreases,
resulting in a decrease in efficiency. Furthermore, when the pore
size is more than 5,000 .mu.m, since the pressure loss excessively
decreases, steam passes through the porous metal body before fully
reacting, resulting in a decrease in efficiency. From the same
viewpoint, the pore size is more preferably 400 to 4,000.mu.m.
[0129] The thickness and metal content of the porous metal body can
be appropriately selected in accordance with the scale of
equipment. When the porosity is excessively small, the pressure
loss during feeding of steam increases. Therefore, the thickness
and metal content are preferably adjusted so that the porosity is
30% or more. Furthermore, in this method, since the electrical
connection between the solid oxide electrolyte and the electrode is
performed by pressure bonding, it is necessary to adjust the metal
content such that the increase in electrical resistance due to
deformation/creeping during application of pressure is within a
range that causes no problem in practical use. The metal content is
preferably 400 g/m.sup.2 or more. Additionally, in order to secure
the porosity and to achieve electrical connection, a plurality of
porous metal bodies having different pore sizes may combined for
use.
Appendixes
[0130] (Water Decomposition Device)
[0131] A water decomposition device including:
[0132] a current collector including a nickel alloy porous
body,
[0133] the nickel alloy porous body being produced through a step
of applying a coating material that contains a nickel alloy powder
of nickel and an added metal onto a surface of a skeleton of a
resin formed body having a three-dimensional mesh-like structure, a
step of plating with nickel the surface of the skeleton of the
resin formed body onto which the coating material has been applied,
a step of removing the resin formed body, and a step of diffusing
the added metal into the nickel by a heat treatment; and
[0134] an ion permeable membrane having the current collector on
each of two sides thereof.
[0135] (Water Decomposition Method)
[0136] A water decomposition method including:
[0137] a step of preparing a current collector including a nickel
alloy porous body,
[0138] the nickel alloy porous body being produced through a step
of applying a coating material that contains a nickel alloy powder
of nickel and an added metal onto a surface of a skeleton of a
resin formed body having a three-dimensional mesh-like structure, a
step of plating with nickel the surface of the skeleton of the
resin formed body onto which the coating material has been applied,
a step of removing the resin formed body, and a step of diffusing
the added metal into the nickel by a heat treatment;
[0139] a step of forming an ion permeable membrane having the
current collector on each of two sides thereof; and
[0140] a step of introducing steam into the current collector and
taking out hydrogen that has passed through the ion permeable
membrane.
INDUSTRIAL APPLICABILITY
[0141] Nickel alloy porous bodies according to the present
invention have excellent mechanical properties and high corrosion
resistance and can be produced at a reduced cost. Therefore, the
nickel alloy porous bodies can be suitably used as current
collectors for secondary batteries, such as lithium-ion batteries,
capacitors, and fuel cells, and water decomposition devices.
REFERENCE SIGNS LIST
[0142] 1 cross section of resin formed body [0143] 2 metal powder
[0144] 3 nickel plating layer [0145] 4 alloy powder [0146] 5 ion
permeable membrane [0147] 6 current collector [0148] 7 porous metal
body
* * * * *