U.S. patent application number 15/366391 was filed with the patent office on 2017-06-22 for thermal insulation material and production method thereof.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA, Toyota School Foundation. Invention is credited to Yohei KINOSHITA, Ryosuke MAEKAWA, Tsunehiro TAKEUCHI, Takeo YAMAGUCHI, Hideo YAMASHITA, Taizo YOSHINAGA.
Application Number | 20170175232 15/366391 |
Document ID | / |
Family ID | 58994101 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170175232 |
Kind Code |
A1 |
YOSHINAGA; Taizo ; et
al. |
June 22, 2017 |
THERMAL INSULATION MATERIAL AND PRODUCTION METHOD THEREOF
Abstract
A thermal insulation material containing an Al--Cu--Fe-based
alloy, wherein at least part of the Al--Cu--Fe-based alloy
comprises a quasicrystalline phase, wherein the Al--Cu--Fe-based
alloy contains one or more transition elements selected from the
group of Ru, Rh, Pd, Ag, Os, Jr, Pt, and Au, and wherein the total
of the transition elements is from 0.25 to 0.75 atom % when the
whole of the Al--Cu--Fe-based alloy is 100 atom %.
Inventors: |
YOSHINAGA; Taizo;
(Susono-shi, JP) ; MAEKAWA; Ryosuke; (Tahara-shi,
JP) ; KINOSHITA; Yohei; (Shizuoka-shi, JP) ;
YAMAGUCHI; Takeo; (Susono-shi, JP) ; YAMASHITA;
Hideo; (Mishima-shi, JP) ; TAKEUCHI; Tsunehiro;
(Nagoya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA
Toyota School Foundation |
Toyota-shi
Nagoya-shi |
|
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
Toyota School Foundation
Nagoya-shi
JP
|
Family ID: |
58994101 |
Appl. No.: |
15/366391 |
Filed: |
December 1, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2998/10 20130101;
B22F 2999/00 20130101; C22C 21/12 20130101; C23C 4/08 20130101;
C22C 1/0416 20130101; B22F 2999/00 20130101; B22F 3/10 20130101;
B22F 2201/01 20130101; B22F 2201/02 20130101; B22F 2201/10
20130101; B22F 2998/10 20130101; B22F 1/0003 20130101; B22F 3/10
20130101; B22F 9/04 20130101; B22F 2999/00 20130101; C22C 1/0416
20130101; C22C 2200/06 20130101 |
International
Class: |
C22C 21/12 20060101
C22C021/12; C23C 4/08 20060101 C23C004/08; C22C 1/04 20060101
C22C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 2015 |
JP |
2015-245288 |
Claims
1. A thermal insulation material containing an Al--Cu--Fe-based
alloy, wherein at least part of the Al--Cu--Fe-based alloy
comprises a quasicrystalline phase, wherein the Al--Cu--Fe-based
alloy contains one or more transition elements selected from the
group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au, and wherein
the total of the transition elements is from 0.25 to 0.75 atom %,
when the whole of the Al--Cu--Fe-based alloy is 100 atom %.
2. The thermal insulation material according to claim 1, wherein
the Al--Cu--Fe-based alloy has a composition represented by
AlaCubFecXd (wherein X is one or more members of the transition
elements, 20.0.ltoreq.b.ltoreq.28.0, 10.0.ltoreq.c.ltoreq.14.0,
0.25.ltoreq.d.ltoreq.0.75, and a+b+c+d=100).
3. The thermal insulation material according to claim 2, wherein b
is from 23.5 to 26.0 and c is from 11.7 to 13.0.
4. A method for producing the thermal insulation material according
to claim 1, comprising: weighing and mixing raw material powder,
and heating the mixed raw material powder in a non-oxidizing
atmosphere to mutually solid-phase diffuse respective elements
contained in the raw material powder, wherein the raw material
powder contain powder of respective metals or alloys of Al, Cu and
Fe and powder of metals or alloys of one or more transition
elements selected from the group consisting of Ru, Rh, Pd, Ag, Os,
Ir, Pt, and Au.
5. The method according to claim 4, wherein the raw material powder
contain an Al powder, a Cu powder, an Fe powder, and powder of
metals of one or more transition elements selected from the group
consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au.
6. The method according to, claim 4 wherein the heating temperature
is from 550 to 800.degree. C.
Description
TECHNICAL FIELD
[0001] The present invention relates to a thermal insulation
material, in particular, a thermal insulation material containing
an alloy with at least part being a quasicrystalline phase.
BACKGROUND ART
[0002] As an alloy usable as a thermal insulation material, an
alloy comprising a quasicrystalline phase is attracting attention.
The quasicrystalline phase is a phase having a long-range order but
no translational symmetry.
[0003] The electrical conduction and thermal conduction of a metal
and an alloy are derived from the periodicity in crystal. However,
the quasicrystalline phase does not have perfect periodicity, and
therefore an alloy comprising a quasicrystalline phase has low
electrical conduction and thermal conducting properties.
[0004] Patent Document 1 discloses a thermal barrier consisting of
a refractory oxide having low thermal diffusivity and an alloy
comprising 80 vol % or more of a quasicrystalline phase. As the
alloy comprising 80 vol % or more of a quasicrystalline phase, an
Al.sub.aCu.sub.bFe.sub.cY.sub.eI.sub.g alloy (wherein Y is one or
more elements selected from V, Mo, Ti, Zr, Nb, Cr, Mn, Ru, Rh, Ni,
Mg, W, Si, and rare earth elements, I is an avoidable impurity,
0.ltoreq.g.ltoreq.2, 14.ltoreq.b.ltoreq.30, 7.ltoreq.c.ltoreq.20,
0.ltoreq.e.ltoreq.10, 10.ltoreq.c+e, and a+b+c+e+g=100) is
disclosed.
[0005] Patent Document 2 discloses a quasicrystalline alloy thin
film. As the quasicrystalline alloy, an
Al.sub.aCu.sub.bFe.sub.cX.sub.dY.sub.e alloy (wherein X is one or
more members selected from B, C, P, S, Ge, and Si, Y is one or more
selected from V, Mo, Ti, Zr, Nb, Cr, Mn, Co, Ru, Rh, Pd, Ni, La,
Hf, Re, Y, W, Os, Ir, Pt, Ta, and rare earth elements,
14.ltoreq.b.ltoreq.30, 0.ltoreq.c.ltoreq.20, 0.ltoreq.e.ltoreq.20,
0.ltoreq.d.ltoreq.5, 21.ltoreq.b+c+e.ltoreq.45, and a+b+c+d+e=100)
is disclosed.
[0006] Non-Patent Document 1 discloses an Al--Cu--Fe-based alloy
containing 0.25 atom % of Re and comprising a quasicrystalline
phase.
CITATION LIST
Patent Document
[0007] [Patent Document 1] Japanese Unexamined Patent Publication
No. H7-3359
[0008] [Patent Document 2] Japanese National Patent Publication No.
H11-503106
Non-Patent Document
[0009] [Non-Patent Document 1] Tsunehiro Takeuchi, "Engineering
Application of Solid State Physics: Very large thermal
rectification effect generated from the unusual electron thermal
conductivity of quasicrystal", Solid Physics, AGNE Gijutsu Center
Inc., 2015, Vol. 50, No. 1, pp. 33-42
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0010] The alloy disclosed in Patent Document 1 is used as a
material of a thermal barrier, and the property most strongly
required of the alloy is refractory performance.
[0011] The alloy disclosed in Patent Document 2 is used as an
electrically insulating material, and the property most strongly
required of the alloy is electrical insulation performance.
[0012] In the alloy disclosed in Non-Patent Document 1, the thermal
conductivity is decreased, compared with a conventional
Al--Cu--Fe-based alloy comprising a quasicrystalline phase, but the
thermal insulation performance thereof is still insufficient.
[0013] The present inventors have found that all of the alloys
disclosed in Patent Documents 1 and 2 and Non-Patent Document 1
have a problem that, when used as a thermal insulation material,
the thermal conductivity of the alloy must be more reduced in order
to enhance the thermal insulation performance.
[0014] The present invention has been made to solve the problem
above, and an object of the present invention is to provide a
thermal insulation material containing an alloy with at least part
of which comprising a quasicrystalline phase, wherein the thermal
conductivity of the alloy is more reduced, and a production method
thereof.
Means to Solve the Problems
[0015] The present inventors have conducted many intensive studies
to attain the above-described object and have completed the present
invention. The gist of the present invention is as follows.
[0016] <1> A thermal insulation material containing an
Al--Cu--Fe-based alloy,
[0017] wherein at least part of the Al--Cu--Fe-based alloy
comprises a quasicrystalline phase,
[0018] wherein the Al--Cu--Fe-based alloy contains one or more
transition elements selected from the group consisting of Ru, Rh,
Pd, Ag, Os, Ir, Pt, and Au, and
[0019] wherein the total of the transition elements is from 0.25 to
0.75 atom %, when the whole of the Al--Cu--Fe-based alloy is 100
atom %.
[0020] <2> The thermal insulation material according to item
<1>, wherein the Al--Cu--Fe-based alloy has a composition
represented by Al.sub.aCu.sub.bFe.sub.cX.sub.d (wherein X is one or
more of the transition elements, 20.0.ltoreq.b.ltoreq.28.0,
10.0.ltoreq.c.ltoreq.14.0, 0.25.ltoreq.d.ltoreq.0.75, and
a+b+c+d=100).
[0021] <3> The thermal insulation material according to item
<2>, wherein b is from 23.5 to 26.0 and c is from 11.7 to
13.0.
[0022] <4> A method for producing the thermal insulation
material according to any one of items <1> to <3>,
including:
[0023] weighing and mixing raw material powder, and
[0024] heating the mixed raw material powder in a non-oxidizing
atmosphere to mutually solid-phase diffuse respective elements
contained in the raw material powder,
[0025] wherein the raw material powder contain powder of respective
metals or alloys of Al, Cu and Fe and powder of metals or alloys of
one or more transition elements selected from the group consisting
of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au.
[0026] <5> The method according to item <4>, wherein
the raw material powder contain an Al powder, a Cu powder, an Fe
powder, and powder of metals of one or more transition elements
selected from the group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt,
and Au.
[0027] <6>The method according to item <4> or
<5>, wherein the heating temperature is from 550 to
800.degree. C.
Effects of the Invention
[0028] According to the present invention, a thermal insulation
material containing an alloy at least part of which comprises a
quasicrystalline phase, wherein the thermal conductivity of the
alloy is more reduced, and a production method thereof can be
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 A pseudo-binary phase diagram of Al--Cu--Fe.
[0030] FIG. 2 A graph illustrating the relationship between the
content of Ru or Ir and the thermal conductivity, with respect to
the Al--Cu--Fe-based alloy.
[0031] FIG. 3 A view illustrating the X-ray diffraction results of
each of the samples of Examples 1 to 3 and Reference Example 1.
[0032] FIG. 4 A view enlarging the range of the diffraction angle
2.theta. being from 42.6 to 43.1.degree. in FIG. 3.
[0033] FIG. 5 A view illustrating the X-ray diffraction results of
alloys having compositions of Al.sub.61.5Cu.sub.26.5Fe.sub.12 and
Al.sub.61.5Cu.sub.26.5Fe.sub.12-xRe.sub.x (wherein x is 0.25, 0.5,
and 0.75) for the sake of comparison with the samples illustrated
in FIG. 4.
MODE FOR CARRYING OUT THE INVENTION
[0034] The embodiments of the thermal insulation material according
to the present invention and the production method thereof are
described in detail below. However, the present invention is not
limited the following embodiments.
[0035] First, the thermal insulation material of the present
invention is described.
[0036] The thermal insulation material of the present invention
contains an Al--Cu--Fe-based alloy. The thermal insulation material
of the present invention may contain a thermal insulation material
other than the Al--Cu--Fe-based alloy within the range not
impairing the effects of the present invention.
(Al--Cu--Fe-Based Alloy)
[0037] The Al--Cu--Fe-based alloy is not particularly limited in
respective contents of Al, Cu and Fe as long as at least part of
the alloy comprises a quasicrystalline phase. The Al--Cu--Fe-based
alloy may also contain, in addition to unavoidable impurities, an
optional element other than Al, Cu, Fe and the later-described
transition elements. The optional element includes W, Re and
Ta.
[0038] The contents of Al, Cu and Fe may be determined by referring
to the phase diagram. The phase diagram illustrates a state of the
phase at equilibrium. The Al--Cu--Fe-based alloy may have a phase
that develops at non-equilibrium, and therefore is not bound by the
Al, Cu and Fe contents determined from the phase diagram.
[0039] FIG. 1 is a pseudo-binary phase diagram of Al--Cu--Fe. FIG.
1 is quoted from Materials Science and Engineering, Volume 133, 15
Mar. 1991, Pages 383-387. The i phase is a quasicrystalline phase,
the .omega. phase, .beta. phase and .lamda. phase are a crystalline
phase, and the L phase and Liq. phase are a liquid phase.
[0040] Referring to FIG. 1, the Al--Cu--Fe-based alloy may have a
composition represented by Al.sub.aCu.sub.bFe.sub.cX.sub.d (wherein
20.0.ltoreq.b.ltoreq.28.0, 10.0.ltoreq.c.ltoreq.b 14.0,
0.25.ltoreq.d.ltoreq.0.75, and a+b+c+d=100). Each of a, b, c and d
corresponds to the atom % when Al.sub.aCu.sub.bFe.sub.cX.sub.d is
100 atom %. X is a transition element described later. The degree
of purity of Al.sub.aCu.sub.bFe.sub.cX.sub.d is preferably 97.0
mass % or more, more preferably 98.0 mass % or more, still more
preferably 99.5 mass % or more, when the whole of
Al.sub.aCu.sub.bFe.sub.cX.sub.d is 100 mass %.
[0041] Referring to FIG. 1, when 20.0.ltoreq.b.ltoreq.28.0 and
10.0.ltoreq.c.ltoreq.14.0, the Al--Cu--Fe-based alloy comprises at
least partially i phase (quasicrystalline phase). When
23.5.ltoreq.b.ltoreq.26.0 and 11.7c13.0, the alloy comprises much
more i phase.
(One or More Transition Elements Selected from the Group Consisting
of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au)
[0042] The Al--Cu--Fe-based alloy contains one or more transition
elements selected from the group consisting of Ru, Rh, Pd, Ag, Os,
Ir, Pt, and Au. When the whole of the Al--Cu--Fe-based alloy is 100
atom %, the total of the transition elements is from 0.25 to 0.75
atom %.
[0043] In the case where the composition of the Al--Cu--Fe-based
alloy is represented by Al.sub.aCu.sub.bFe.sub.cX.sub.d, X is the
one or more transition elements selected from the group consisting
of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au.
[0044] FIG. 2 is a graph illustrating the relationship between the
content of Ru or Ir and the thermal conductivity, with respect to
the Al--Cu--Fe-based alloy.
[0045] It is generally well known that in an alloy comprising a
quasicrystalline phase, the thermal conductivity of the
quasicrystalline phase is smaller than the thermal conductivity of
the crystalline phase. For example, regarding the Al--Cu--Fe-based
alloy, at room temperature, the thermal conductivity of the i phase
(quasicrystalline phase) is 1.4 W/mK, and the thermal conductivity
of the .beta. phase (crystalline phase) is 2.5 W/mK.
[0046] As shown in FIG. 2, when the Ir content of the
Al--Cu--Fe-based alloy reaches 0.25% or more, the thermal
conductivity of the Al--Cu--Fe-based alloy starts falling below the
thermal conductivity of the i phase. For this reason, the Ir
content in the Al--Cu--Fe-based alloy in the thermal insulation
material of the present invention is 0.25 atom % or more. The
content is more preferably 0.35 atom % or more.
[0047] When the Ir content is about 0.50 atom %, the thermal
conductivity of the Al--Cu--Fe-based alloy shows a minimum value.
After reaching the minimum value, the thermal conductivity of the
Al--Cu--Fe-based alloy increases along with an increase in the Ir
content. When the Ir content reaches 0.75 atom %, the thermal
conductivity of the Al--Cu--Fe-based alloy becomes equivalent to
the thermal conductivity of the i phase. For this reason, the Ir
content of the Al--Cu--Fe-based alloy in the thermal insulation
material of the present invention is 0.75 atom % or less. The Ir
content is more preferably 0.65 atom % or less.
[0048] As shown in FIG. 2, Ru shows the same thermal conductivity
behavior as Ir. Without being bound by theory, the reason for such
a change in the thermal conductivity is considered as follows.
[0049] Phonon (lattice vibration) transport participates in thermal
conduction. The more phonon transport is, the more easily heat is
transferred. Phonon transport through the quasicrystalline phase is
reduced compared with the crystalline phase, and therefore, an
alloy comprising a quasicrystalline phase exhibits a small thermal
conductivity.
[0050] When the Al--Cu--Fe-based alloy contains Ir, the crystal
lattice of the Al--Cu--Fe-based alloy contracts. Contraction of the
crystal lattice suppresses the transport of a low frequency phonon.
The phonon participating in thermal conduction is known to have a
broad frequency range. The transport of the phonon participating in
thermal conduction is suppressed as much as the transport of a low
frequency phonon is suppressed due to contraction of the crystal
lattice, as a result, the thermal conduction is more suppressed,
i.e., the thermal conductivity lowers. On the other hand, when the
Ir content in the Al--Cu--Fe-based alloy is increased, the
quasicrystalline phase can be hardly maintained in the
Al--Cu--Fe-based alloy, as a result, the thermal conductivity
rises.
[0051] If the discussions above are applied to the phenomenon
illustrated in FIG. 2, this leads to the following. When the Ir
content in the Al--Cu--Fe-based alloy has reached 0.25%, the
crystal lattice undergoes significant contraction, and the
transport of a low frequency phonon is more reduced. As a result, a
decrease in the thermal conductivity of the Al--Cu--Fe-based alloy
is notably recognized.
[0052] Until the Ir content reaches about 0.50 atom %, the increase
of the effect brought about by the contraction of the crystal
lattice (the effect of lowering the thermal conductivity) is larger
than the increase of the effect brought about by becoming difficult
to maintain the quasicrystalline phase (the effect of raising the
thermal conductivity). In other words, until the Ir content reaches
about 0.50 atom %, the difference between the effect brought about
by the contraction of the crystal lattice (the effect of lowering
the thermal conductivity) and the effect brought about by becoming
difficult to maintain the quasicrystalline phase (the effect of
raising the thermal conductivity) continues increasing. This
difference is maximized when the Ir content is about 0.50 atom
%.
[0053] If the Ir content is further increased, the effect brought
about by becoming difficult to maintain the quasicrystalline phase
(the effect of raising the thermal conductivity) grows, and the
difference between the effect brought about by becoming difficult
to maintain the quasicrystalline phase (the effect of raising the
thermal conductivity) and the effect brought about by the
contraction of the crystal lattice (the effect of lowering the
thermal conductivity) turns to decrease. If the Ir content has
reached 0.75 atom %, the thermal conductivity becomes equivalent to
that at the time of the Ir content being 0.25 atom %. More
specifically, when the Ir content is 0.75 atom % or less, the
significant effect obtained by the contraction of the crystal
lattice (the effect of lowering the thermal conductivity) can be
enjoyed by negating the effect brought about by becoming difficult
to maintain the quasicrystalline phase (the effect of raising the
thermal conductivity).
[0054] Such a phenomenon is recognized not only in the case of Ir
but also in the case of one or more transition elements selected
from the group consisting of Ru, Rh, Pd, Ag, Os, Pt, and Au.
Without being bound by theory, the reason is considered as
follows.
[0055] Any of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au have more total
electron numbers than Fe and is a heavier element (the atomic
weight is larger). The larger the sum of atomic weights of
respective atoms is and the more the sum of total electron numbers
of respective atoms is, the more the bonding force between atoms is
strengthened. In addition, since Rh, Pd, Ag, Ir, Pt, and Au have
more outermost electrons than Fe, the bonding force between atoms
is particularly large. When the bonding force between atoms is more
strengthened, the crystal lattice composed of those atoms readily
contracts due to the bonding force between atoms.
[0056] Maintaining the quasicrystalline phase is considered to be
also related to the bonding force between atoms. Accordingly, Ru,
Rh, Pd, Ag, Os, Pt, and Au provide the same effect as that of
Ir.
[0057] The bonding force between atoms is considered to rely on the
content (atom %) of Ru, Rh, Pd, Ag, Os, Ir, Pt or Au in the
Al--Cu--Fe-based alloy. In the case where the transition element
selected from the group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt,
and Au is two or more elements, the total content (atom %) of the
atoms may be set in the same manner as the content (atom %) of Ru
in the case of Ru alone.
(Production Method)
[0058] The production method of the thermal insulation material of
the present invention is described below.
[0059] The production method of the thermal insulation material of
the present invention comprises weighing and mixing raw material
powder, and heating the mixed raw material powder to mutually
solid-phase diffuse respective elements contained in the raw
material powder.
(Weighing and Mixing of Raw Material Powder)
[0060] As the raw material powder, powder of respective metals or
alloys of Al, Cu and Fe and powder of metals or alloys of one or
more transition elements selected from the group consisting of Ru,
Rh, Pd, Ag, Os, Ir, Pt, and Au are prepared.
[0061] For example, an Al powder, a Cu powder, an Fe powder, and
powder of metals of one or more transition elements selected from
the group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au are
prepared.
[0062] In the case of preparing an alloy powder instead of a metal
powder, for example, an Al-Cu alloy powder may be prepared in place
of an Al powder and a Cu powder.
[0063] The particle diameter of the raw material powder is not
particularly limited as long as it does not inhibit mutual
solid-phase diffusion of respective elements contained in the raw
material powder. The particle diameter of the raw material powder
may be, for example, from 0.5 to 100 .mu.m. In the following,
unless otherwise indicated, the average particle is a 50% average
value of median diameters.
[0064] In the case where the raw material powder is an Al powder, a
Cu powder, an Fe powder, and a powder of a metal of a transition
element selected from the group consisting of Ru, Rh, Pd, Ag, Os,
Ir, Pt, and Au, the particle diameters of the powder are preferably
as follows.
[0065] The particle diameter of the Al powder is preferably from 1
to 5 .mu.m. When the particle diameter of the Al powder is 1 .mu.m
or more, the Al powder is prevented from being oxidized with trace
oxygen. The particle diameter is more preferably 2 .mu.m or more.
On the other hand, when the particle diameter of the Al powder is 5
.mu.m or less, mutual solid-phase diffusion of Al with other
elements easily and rapidly proceed. The particle diameter is more
preferably 4 .mu.m or less. Heating of the raw material powder for
solid-phase diffusion is described later.
[0066] The particle diameter of the Cu powder is preferably from
0.5 to 3 .mu.m. When the particle diameter of the Cu powder is 0.5
.mu.m or more, the Cu powder is prevented from being oxidized with
trace oxygen. The particle diameter is more preferably 1 .mu.m or
more. On the other hand, when the particle diameter of the Cu
powder is 3 .mu.m or less, mutual solid-phase diffusion of Cu with
other elements easily and rapidly proceed. The particle diameter is
more preferably 2 .mu.m or less.
[0067] The particle diameter of the Fe powder is preferably from 3
to 7 .mu.m. When the particle diameter of the Fe powder is 3 .mu.m
or more, the Fe powder is prevented from being oxidized with trace
oxygen. The particle diameter is more preferably 4 .mu.m or more.
On the other hand, when the particle diameter of the Fe powder is 7
.mu.m or less, mutual solid-phase diffusion of Fe with other
elements easily and rapidly proceed. The particle diameter is more
preferably 6 .mu.m or less.
[0068] The particle diameter of the powder of a metal of a
transition element selected from the group consisting of Ru, Rh,
Pd, Ag, Os, Ir, Pt, and Au is determined by referring to the case
of the Fe powder.
[0069] In the case where the raw material powder is an alloy
powder, the particle diameter of the alloy powder may be
appropriately determined by referring to the ratio of respective
elements constituting the alloy and the particle diameter of the
metal powder of each element.
[0070] In all of the case of preparing a metal powder, the case of
preparing an alloy powder, and the case of preparing a metal powder
and an alloy powder in combination, each raw material powder is
weighed so as to obtain a desired composition of the
Al--Cu--Fe-based alloy.
[0071] In the case where the Al--Cu--Fe-based alloy contains an
optional element other than Al, Cu, Fe, Ru, Rh, Pd, Ag, Os, Ir, Pt,
and Au within the range not impairing the effects of the present
invention, a raw material powder of the accessory element is
prepared and weighed in a predetermined amount. The particle
diameter of the raw material powder of the optional element may be
appropriately determined in view of ease of oxidization and
solid-phase diffusion of the element.
[0072] The weighed raw material powder is thoroughly mixed. This
mixing makes the microstructure of the obtained Al--Cu--Fe-based
alloy uniform. In the case of using an alloy powder, the powder is
preferably subjected to a solid solution treatment in advance. By
this treatment, even when the alloy powder is segregated, the
microstructure of the obtained Al--Cu--Fe-based alloy can be made
uniform.
(Heating of Raw Material Powder)
[0073] The mixed raw material powder is heated in a non-oxidizing
atmosphere to mutually solid-phase diffuse respective elements
contained in the raw material powder.
[0074] The heating temperature is not particularly limited as long
as it is a temperature capable of mutually solid-phase diffusing
respective elements contained in the raw material powder. The
melting points of Al, Cu and Fe are 660.degree. C., 1,085.degree.
C. and 1,538.degree. C., respectively, and the heating temperature
may be appropriately determined by referring to these melting
points.
[0075] The heating temperature is preferably from 550 to
800.degree. C. When the heating temperature is 550.degree. C. or
more, Cu rapidly diffuses into the Al powder as a result, an Al-Cu
alloy powder is formed and the Al powder is not melted. The heating
temperature is more preferably 650.degree. C. or more. On the other
hand, when the heating temperature is 800.degree. C. or less, the
Al powder is not melted before Cu rapidly diffuses into the Al
powder to form an Al--Cu alloy powder. The heating temperature is
more preferably 750.degree. C. or less.
[0076] Heating of the raw material powder is performed in a
non-oxidizing atmosphere. If the surface of the raw material powder
is oxidized, respective elements contained in the raw material
powder cannot be mutually solid-phase diffused. Out of the raw
material powder, the Al powder is particularly easy to be oxidized.
In order to prevent oxidation of the Al powder, the oxygen
concentration in the heating atmosphere must be very low.
Accordingly, the heating atmosphere may be even a reducing
atmosphere.
[0077] The non-oxidizing atmosphere includes an inert gas
atmosphere, a nitrogen gas atmosphere, and a hydrogen gas
atmosphere. The atmosphere may also be a mixed gas atmosphere
produced by adding a hydrogen gas to an inert gas and/or a nitrogen
gas.
[0078] The pressure in the atmosphere is not particularly limited
as long as respective elements contained in the raw material powder
can be mutually solid-phase diffused, but the pressure is
preferably from 0.9 to 1.1 atm. When the pressure is 0.9 atm or
more, air is prevented from entering the heating vessel to oxidize
the Al powder, Cu powder and Fe powder. On the other hand, when the
pressure is 1.1 atm or less, the raw material powder can be heated
without using a pressure-resistant vessel for the heating
vessel.
[0079] The heating time is preferably from 0.5 to 24 hours. As long
as the particle diameter of each raw material powder is in the
range above, when the heating time is from 0.5 to 24 hours,
respective elements contained in the raw material powder can be
mutually solid-phase diffused.
(Additional Step)
[0080] When respective elements contained in the raw material
powder are mutually solid-phase diffused, an aggregated thermal
insulation material is obtained. The aggregated thermal insulation
material may be used as it is. Alternatively, the aggregated
thermal insulation material may be pulverized into a thermal
insulation material powder and then thermally sprayed to a metal
plate, etc.
EXAMPLES
[0081] The present invention is described more specifically below
by referring to Examples. However, the present invention is not
limited to the conditions employed in the following Examples.
(Preparation of Sample)
[0082] An Al powder, a Cu powder, an Fe powder, and an Ir powder
were weighed to provide a desired composition, mixed and housed in
a vessel. In addition, an Al powder, a Cu powder, an Fe powder, and
an Ru powder were weighed, mixed and housed in another vessel.
[0083] As for the Al powder, Cu powder and Fe powder, the powders
produced by Kojundo Chemical Laboratory Co., Ltd. were used. The
particle diameter of the Al powder was 3 .mu.m, the particle
diameter of the Cu powder was 1 .mu.m, and the particle diameter of
the Fe powder was 5 .mu.m. The particle diameters of Al powder, Cu
powder and Fe powder are a 50% average value of median diameters.
As for the Ir powder and the Ru powder, the powders produced by
Furuya Metal Co., Ltd. were used. The Ir powder and the Ru powder
were screened using a sieve having an opening of 100 .mu.m.
[0084] The inside of each vessel was set to have a hydrogen
atmosphere at 1 atm, and the raw material powder was heated at
700.degree. C. during 2 hours to obtain an aggregated thermal
insulation material. The aggregated thermal insulation material was
pulverized into a thermal insulation material powder.
(Evaluation of Sample)
[0085] The thermal insulation material powder prepared was analyzed
by X-Ray Diffraction (XRD). In addition, the thermal insulation
material powder was sintered by spark plasma sintering to prepare a
pellet, and the thermal conductivity of the pellet was measured.
The spark plasma sintering temperature was about 700.degree. C.
[0086] The results of thermal conductivity measurement are shown in
Table 1. In Table 1, the target composition of the Al--Cu--Fe-based
alloy and the blending ratios (atom %) of respective raw material
are shown together.
TABLE-US-00001 TABLE 1 Blending Amount of Raw Material Thermal
Powder (atom %) Conductivity Target Composition Al Cu Fe Ru Ir
(Wm.sup.-1K.sup.-1) Example 1 Al63Cu24.5Fe12.25Ir0.25 63.00 24.50
12.25 -- 0.25 0.91 Example 2 Al63Cu24.5Fe12Ir0.5 63.00 24.50 12.00
-- 0.50 0.62 Example 3 Al63Cu24.5Fe11.75Ir0.75 63.00 24.50 11.75 --
0.75 1.10 Example 4 Al63Cu24.5Fe12.25Ru0.25 63.00 24.50 12.25 0.25
-- 1.09 Example 5 Al63Cu24.5Fe12Ru0.5 63.00 24.50 12.00 0.50 --
0.84 Example 6 Al63Cu24.5Fe11.75Ru0.75 63.00 24.50 11.75 0.75 --
1.01 Reference Al63Cu24.5Fe12.5 63.00 24.50 12.50 -- -- 1.40
Example 1
[0087] FIG. 2 is a view illustrating the relationship between the
content of Ru or Ir and the thermal conductivity, with respect to
each sample in Table 1. FIG. 3 is a view illustrating the X-ray
diffraction results of each of the samples of Examples 1 to 3 and
Reference Example 1. FIG. 4 is a view enlarging the range of the
diffraction angle 2.theta. being from 42.6 to 43.1.degree. in FIG.
3. FIG. 5 is a view illustrating the X-ray diffraction results of
alloys having compositions of Al.sub.61.5Cu.sub.26.5Fe.sub.12 and
Al.sub.61.5Cu.sub.26.5Fe.sub.12-xRe.sub.x (wherein x is 0.25, 0.5,
and 0.75) for the sake of comparison with the samples illustrated
in FIG. 4.
[0088] As shown in Table 1 and FIG. 2, in the thermal insulation
materials of Examples 1 to 6 where the content of Ru or Ir is from
0.25 to 0.75 atom %, the thermal conductivity is reduced. On the
other hand, in the thermal insulation material of Reference Example
1 not containing any of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au, the
thermal conductivity is high, in other words, the thermal
insulation performance is poor.
[0089] As shown in FIG. 4, the peaks of the samples of Examples 1
to 3 are shifted to the wide angle side (right side in FIG. 4)
relative to the peak of Reference Example 1. It could be confirmed
from this shift that with respect to the samples of Examples 1 to
3, due to containing from 0.25 to 0.75 atom % of Ir, the crystal
lattice is contracted. The peak of the Al--Cu--Fe-based alloy of
Example 3 is very broad, and it could be confirmed that it is
getting difficult to maintain the quasicrystalline phase. With
respect to Examples 4 to 6, the same tendency as in FIG. 4 is
observed.
[0090] On the other hand, the peak of
Al.sub.61.5Cu.sub.26.5Fe.sub.12 xRe.sub.x (wherein x is 0.25, 0.5,
and 0.75) illustrated in FIG. 5 is shifted to the narrow angle side
(left side in FIG. 5) relative to the peak of
Al.sub.61.5Cu.sub.26.5Fe.sub.12. It could be confirmed from this
shift that when from 0.25 to 0.75 atom % of Re is added to the
Al--Cu--Fe-based alloy, the crystal lattice expands. This suggests
that in the Al--Cu--Fe-based alloy containing 0.25 atom % of Re
disclosed in Non-Patent Document 1, unlike the present invention,
the crystal lattice of the Al--Cu--Fe-based alloy is not
contracted, and therefore the thermal conductivity is not
sufficiently decreased in the alloy of Non-Patent Document 1.
[0091] From these results, the fact that the present invention
provides remarkable effects, as well as the reasons therefor, could
be confirmed.
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