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 %.

Description

TECHNICAL FIELD

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

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.

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.

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_aCu_bFe_cY_eI_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≦g≦2, 14≦b≦30, 7≦c≦20, 0≦e≦10, 10≦c+e, and a+b+c+e+g=100) is disclosed.

Patent Document 2 discloses a quasicrystalline alloy thin film. As the quasicrystalline alloy, an Al_aCu_bFe_cX_dY_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≦b≦30, 0≦c≦20, 0≦e≦20, 0≦d≦5, 21≦b+c+e≦45, and a+b+c+d+e=100) is disclosed.

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

[Patent Document 1] Japanese Unexamined Patent Publication No. H7-3359

[Patent Document 2] Japanese National Patent Publication No. H11-503106

Non-Patent Document

[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

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.

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.

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.

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.

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

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.

<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 item <1>, wherein the Al—Cu—Fe-based alloy has a composition represented by Al_aCu_bFe_cX_d (wherein X is one or more of the transition elements, 20.0≦b≦28.0, 10.0≦c≦14.0, 0.25≦d≦0.75, and a+b+c+d=100).

<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.

<4> A method for producing the thermal insulation material according to any one of items <1> to <3>, including:

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 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.

<6>The method according to item <4> or <5>, wherein the heating temperature is from 550 to 800° C.

Effects of the Invention

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

FIG. 1 A pseudo-binary phase diagram of Al—Cu—Fe.

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.

FIG. 3 A view illustrating the X-ray diffraction results of each of the samples of Examples 1 to 3 and Reference Example 1.

FIG. 4 A view enlarging the range of the diffraction angle 2θ being from 42.6 to 43.1° in FIG. 3.

FIG. 5 A view illustrating the X-ray diffraction results of alloys having compositions of Al_61.5Cu_26.5Fe₁₂ and Al_61.5Cu_26.5Fe_12-xRe_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

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.

First, the thermal insulation material of the present invention is described.

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)

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.

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.

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 ω phase, β phase and λ phase are a crystalline phase, and the L phase and Liq. phase are a liquid phase.

Referring to FIG. 1, the Al—Cu—Fe-based alloy may have a composition represented by Al_aCu_bFe_cX_d (wherein 20.0≦b≦28.0, 10.0≦c≦b 14.0, 0.25≦d≦0.75, and a+b+c+d=100). Each of a, b, c and d corresponds to the atom % when Al_aCu_bFe_cX_d is 100 atom %. X is a transition element described later. The degree of purity of Al_aCu_bFe_cX_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_aCu_bFe_cX_d is 100 mass %.

Referring to FIG. 1, when 20.0≦b≦28.0 and 10.0≦c≦14.0, the Al—Cu—Fe-based alloy comprises at least partially i phase (quasicrystalline phase). When 23.5≦b≦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)

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 %.

In the case where the composition of the Al—Cu—Fe-based alloy is represented by Al_aCu_bFe_cX_d, X is the one or more transition elements selected from the group consisting of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au.

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.

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 β phase (crystalline phase) is 2.5 W/mK.

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.

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.

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.

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.

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.

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.

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 %.

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).

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.

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.

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.

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)

The production method of the thermal insulation material of the present invention is described below.

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)

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.

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.

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.

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 μm. In the following, unless otherwise indicated, the average particle is a 50% average value of median diameters.

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.

The particle diameter of the Al powder is preferably from 1 to 5 μm. When the particle diameter of the Al powder is 1 μm or more, the Al powder is prevented from being oxidized with trace oxygen. The particle diameter is more preferably 2 μm or more. On the other hand, when the particle diameter of the Al powder is 5 μm or less, mutual solid-phase diffusion of Al with other elements easily and rapidly proceed. The particle diameter is more preferably 4 μm or less. Heating of the raw material powder for solid-phase diffusion is described later.

The particle diameter of the Cu powder is preferably from 0.5 to 3 μm. When the particle diameter of the Cu powder is 0.5 μm or more, the Cu powder is prevented from being oxidized with trace oxygen. The particle diameter is more preferably 1 μm or more. On the other hand, when the particle diameter of the Cu powder is 3 μm or less, mutual solid-phase diffusion of Cu with other elements easily and rapidly proceed. The particle diameter is more preferably 2 μm or less.

The particle diameter of the Fe powder is preferably from 3 to 7 μm. When the particle diameter of the Fe powder is 3 μm or more, the Fe powder is prevented from being oxidized with trace oxygen. The particle diameter is more preferably 4 μm or more. On the other hand, when the particle diameter of the Fe powder is 7 μm or less, mutual solid-phase diffusion of Fe with other elements easily and rapidly proceed. The particle diameter is more preferably 6 μm or less.

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.

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.

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.

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.

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)

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.

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° C., 1,085° C. and 1,538° C., respectively, and the heating temperature may be appropriately determined by referring to these melting points.

The heating temperature is preferably from 550 to 800° C. When the heating temperature is 550° 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° C. or more. On the other hand, when the heating temperature is 800° 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° C. or less.

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.

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.

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.

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)

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

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)

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.

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 μm, the particle diameter of the Cu powder was 1 μm, and the particle diameter of the Fe powder was 5 μm. 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 μm.

The inside of each vessel was set to have a hydrogen atmosphere at 1 atm, and the raw material powder was heated at 700° 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)

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° C.

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 1
	Blending Amount of Raw Material	Thermal
	Powder (atom %)	Conductivity
	Target Composition	Al	Cu	Fe	Ru	Ir	(Wm−1K−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

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 2θ being from 42.6 to 43.1° in FIG. 3. FIG. 5 is a view illustrating the X-ray diffraction results of alloys having compositions of Al_61.5Cu_26.5Fe₁₂ and Al_61.5Cu_26.5Fe_12-xRe_x (wherein x is 0.25, 0.5, and 0.75) for the sake of comparison with the samples illustrated in FIG. 4.

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.

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.

On the other hand, the peak of Al_61.5Cu_26.5Fe_{12 x}Re_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_61.5Cu_26.5Fe₁₂. 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.

From these results, the fact that the present invention provides remarkable effects, as well as the reasons therefor, could be confirmed.

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≦b≦28.0, 10.0≦c≦14.0, 0.25≦d≦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° C.