EP4691669A1

EP4691669A1 - Metal fiber structure

Info

Publication number: EP4691669A1
Application number: EP24784946.6A
Authority: EP
Inventors: Hideki Moriuchi; Kimiaki Shiratori
Original assignee: Tomoegawa Corp
Current assignee: Tomoegawa Corp
Priority date: 2023-04-05
Filing date: 2024-04-04
Publication date: 2026-02-11
Also published as: CN120897813A; WO2024210164A1; TW202502468A; JPWO2024210164A1

Abstract

Provided is a metal fiber structure (1) in which a plurality of metal fibers (2) are bonded to each other, the metal fiber structure (1) including a porous metal body (3) that is in contact with the plurality of metal fibers (2) to connect the plurality of metal fibers (2).

Description

TECHNICAL FIELD

The present invention relates to a metal fiber structure.

BACKGROUND ART

Conventionally, various types of metal fiber sheets have been known. For example, Japanese Laid-Open Patent Publication No. H7-258706 ( JPH7-258706A ) discloses a method for producing a sintered metal fiber sheet to be used as a filter material, a heat-resistant material, a conductive material, an electrostatic shielding material, and the like.

SUMMARY OF THE INVENTION

In the production method for a sintered metal fiber sheet disclosed in Japanese Laid-Open Patent Publication No. H7-258706 , a slurry consisting solely of metal fibers is formed into a sheet using a specific wire mesh. A three-layer structure is then formed by placing a flexible porous ceramic sheet on each side, which is subsequently dried. The metal fibers are then sintered at a temperature equal to or lower than their melting point in an argon or hydrogen atmosphere. In this method, the solid cores of the metal fibers are sintered together. Therefore, there is a need for a new metal fiber structure that is different from this conventional structure.
The present invention has been made in view of such circumstances, and an object of the present disclosure is to provide a metal fiber structure having a new structure.
A metal fiber structure of the present disclosure is a metal fiber structure in which a plurality of metal fibers are bonded to each other, and includes a porous metal body that is in contact with the plurality of metal fibers to connect the plurality of metal fibers.
In the metal fiber structure of the present disclosure, the porous metal body may be disposed between the metal fibers.
In the metal fiber structure of the present disclosure, the metal fiber structure may have a structure in which the metal fibers are covered by the porous metal body.
In the metal fiber structure of the present disclosure, an area percentage of metal in a cross section of the porous metal body may be within a range of 20% to 80%.
In the metal fiber structure of the present disclosure, an area percentage of metal in a cross section of the metal fiber structure may be within a range of 30% to 80%.
In the metal fiber structure of the present disclosure, an average fiber diameter of the metal fibers may be within a range of 10 µm to 3000 µm.
A thickness of the metal fiber structure of the present disclosure may be within a range of 0.01 mm to 50.0 mm.
In the metal fiber structure of the present disclosure, a material of the porous metal body may include a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C.
In the metal fiber structure of the present disclosure, a material of the metal fibers may include a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C.
In the metal fiber structure of the present disclosure, a material of the porous metal body may include a metal having a Young's modulus of 150 to 450 GPa.
In the metal fiber structure of the present disclosure, a material of the metal fibers may include a metal having a Young's modulus of 150 to 450 GPa.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of a metal fiber structure according to an embodiment of the present disclosure.
FIG. 2 is another conceptual diagram of the metal fiber structure according to the embodiment of the present disclosure.
FIG. 3 is an illustrative micrograph of the metal fiber structure according to the embodiment of the present disclosure.
FIG. 4 is a micrograph showing a cross section of a metal fiber structure of Example 1.
FIG. 5 is a micrograph showing a cross section of a metal fiber structure of Comparative Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 and FIG. 2 are each a conceptual diagram of a metal fiber structure according to the embodiment of the present disclosure. FIG. 3 is an illustrative micrograph (obtained using a scanning electron microscope manufactured by JEOL Ltd. at 1000× magnification) of the metal fiber structure according to the embodiment of the present disclosure.

[Metal fiber structure 1]

As shown in FIG. 1 and FIG. 2, a metal fiber structure 1 according to the present embodiment includes a plurality of metal fibers 2 and a porous metal body 3 in contact with the metal fibers 2, and the porous metal body 3 serves to connect and bond the metal fibers 2 to each other. As used herein, the term "bonded" between metal fibers means that the metal fibers are physically fixed to each other, and a portion where the metal fibers are physically fixed is also referred to as bonding portion. In the metal fiber structure 1, the metal fibers 2 are indirectly fixed to each other via the porous metal body 3 (i.e., the bonding portion) (see FIG. 1, for example).
As described below, compared to a case where no porous metal body is interposed (e.g., the metal fibers are connected to each other via a solid material), the entire metal fiber structure 1 can exhibit excellent flexibility (stress-relaxation property, pliability, bendability) and other physical properties, due to the porous metal body 3 being in contact with the metal fibers 2.
In the metal fiber structure 1, a structure in which the porous metal body 3 is connected to the metal fibers 2 is not particularly limited. The metal fibers 2 may be covered by the porous metal body 3 (FIG. 1, FIG. 2), and the porous metal body 3 may be disposed in part between the metal fibers 2. That is, the area percentage of the entire metal fiber structure 1 may also vary depending on the relative position of the porous metal body 3 with respect to the metal fibers 2.
Specifically, the area percentage of metal (metals in the metal fibers 2 and the porous metal body 3) in the cross section of the metal fiber structure 1 is preferably within the range of 30% to 80% and more preferably within the range of 40% to 70%. The lower the area percentage of the metal fiber structure 1 is, the better the flexibility tends to be. The higher the area percentage of the metal fiber structure 1 is, the better other physical properties such as specific resistivity or strength tend to be. When the area percentage is within the range, a balance between the flexibility and the other physical properties can be achieved.
The term "area percentage" refers to the proportion of solid portions (such as metal fibers and metal particles) present in a specific area of the metal fiber structure 1.
The metal fiber structure 1 is perpendicularly cut, and using a scanning electron microscope (SEM) and known image analysis software on the resulting cross-section, the average of the values calculated using the following equation can be obtained as the area percentage of the metal fiber structure 1.
Area percentage (%) = area occupied by metal in metal fiber structure 1 / (area occupied by metal in metal fiber structure 1 + area occupied by non-metal in metal fiber structure 1) × 100
The dimensions of the metal fiber structure 1 are appropriately adjusted according to the application and thus are not particularly limited. However, the thickness of the metal fiber structure 1 is preferably within the range of 0.01 mm to 50.0 mm and more preferably within the range of 0.01 mm to 20.0 mm. When the thickness is within the above range, a balance between the flexibility and other physical properties such as specific resistivity or strength can be achieved. Due to individual differences, arrangements, production processes, or the like of the metal fibers 2 which are components of the metal fiber structure 1, the surface of the metal fiber structure 1 may include irregularities (surface roughness).

(Metal fiber 2)

The metal fibers 2 are fibrous metal members. The metal fibers 2 are preferably sintered. Since the metal fibers 2 are sintered, the thermal conductivity and the homogeneity of the metal fiber structure 1 are easily stabilized.
The average fiber diameter of the metal fibers 2 is preferably within the range of 10 µm to 3000 µm, more preferably within the range of 10 µm to 200 µm, and further preferably within the range of 10 µm to 50 µm. The smaller the average fiber diameter of the metal fibers 2 is, the better the flexibility of the resulting metal fiber structure 1 tends to be. The larger the average fiber diameter of the metal fibers 2 is, the better the specific resistivity or the strength of the resulting metal fiber structure 1 tends to be. When the average fiber diameter is within the above range, a balance between the flexibility and other physical properties can be achieved. As used herein, the term "average fiber diameter" refers to the average of area-equivalent diameters (e.g., for 20 fibers), which are calculated as the diameters of circles having the same areas as the cross-sectional areas of the metal fibers 2, the cross-sectional areas being calculated (e.g., using known software) at arbitrary cross sections perpendicular to the longitudinal direction of the metal fibers 2 imaged using a microscope. In addition, the metal fibers 2 may become rounded due to sintering. In this case, the average fiber diameter of the metal fibers 2 is also calculated in the same manner.
The average fiber length of the metal fibers 2 is not particularly limited, and is preferably within the range of 1 mm to 50 mm and more preferably within the range of 1 mm to 20 mm. For example, when the metal fiber structure 1 is used as a metal fiber nonwoven fabric, it is preferable that the average fiber length of the metal fibers 2 is shorter, since it is easy to enhance the homogeneity of the metal fiber nonwoven fabric. As used herein, the term "average fiber length" refers to the average of the values obtained by measuring 20 fibers with a microscope.
As a material of the metal fibers 2, a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C may be included. Examples of such metals include silver, copper, gold, aluminum, and alloys thereof. The metal fiber structure 1 may include two or more of such metals as the metal fibers 2.
In addition, as a material of the metal fibers 2, a metal having a Young's modulus (23°C) of 150 to 450 GPa may be included. Examples of such metals include iron, nickel, chromium, beryllium, tungsten, molybdenum, and alloys thereof. The metal fiber structure 1 may include two or more of such metals as the metal fibers 2.

(Porous metal body 3)

As described above, in the metal fiber structure 1, the porous metal body 3 is the bonding portion that bonds the metal fibers 2 to each other.
The area percentage of metal in the cross section of the porous metal body 3 is preferably within the range of 20% to 80% and more preferably within the range of 30% to 70%. The lower the area percentage of the porous metal body 3 is, the better the flexibility of the resulting metal fiber structure 1 tends to be. The higher the area percentage of the porous metal body 3 is, the better the specific resistivity or the strength of the resulting metal fiber structure 1 tends to be. When the area percentage is within the above range, a balance between the flexibility and other physical properties can be achieved.
The area percentage of the porous metal body 3 can also be determined as an area ratio by using a scanning electron microscope (SEM) and known image analysis software. Specifically, the average of the values calculated, using the following equation, from cross-sectional samples (e.g., 20 samples) of the porous metal body 3 in SEM images can be obtained as the area percentage of the porous metal body 3.
Area percentage (%) = area occupied by metal in porous metal body 3 / (area occupied by metal in porous metal body 3 + area occupied by non-metal in porous metal body 3) × 100
As a material of the porous metal body 3, a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C may be included. Examples of such metals are as described above.
In addition, as a material of the porous metal body 3, a metal having a Young's modulus (23°C) of 150 to 450 GPa may be included. Examples of such metals are as described above.
In order to allow the resulting metal fiber structure 1 to exhibit excellent flexibility and specific resistivity, the metal fibers 2 and the porous metal body 3 are preferably formed of copper, silver, or aluminum. In addition, in order to allow the resulting metal fiber structure 1 to exhibit excellent flexibility and strength, the metal fibers 2 and the porous metal body 3 are preferably formed of stainless steel, tungsten, nickel, or iron. The material of the porous metal body 3 and the material of the metal fibers 2 may be the same or different from each other.

(Method for producing metal fiber structure 1, application thereof)

As a method for producing the metal fiber structure 1, for example, a slurry solution including metal particles or metal fibers to form the porous metal body 3 is first prepared. Next, this solution is applied to the metal fibers 2 prepared as a base, and the metal fibers 2 are dried at a predetermined temperature. Here, in order to prevent the porous metal body 3 formed on the metal fibers 2 from melting (liquefying), it is necessary to adjust the drying and heating temperature according to the melting point of the metal used. The metal fiber structure 1 according to the present disclosure can be obtained by performing appropriate separation and selection on the resulting structures, based on the structure in which the porous metal body 3 is connected to the metal fibers 2 and the above-described characteristics (area percentage, diameter, thickness, etc.). The diameter of the metal particles and the diameter of the metal fibers are preferably 0.001 µm to 10.0 µm.
The metal fiber structure 1 is a structure that can be molded into a shape such as a plate or a sheet due to the pliability. Depending on the application, the metal fiber structure 1 may be further coated with a resin film. The thickness of the resin film may be 1 to 1000 times that of the metal fiber structure 1, and a known resin material having insulating properties and pliability can be used as the material of the resin film. Examples of the material include acrylic resin, polyvinylpyrrolidone resin, polyester resin, polypropylene resin, fluororesin, polyimide resin, and silicone resin. In addition, depending on the material (properties) of the metal fibers 2, the metal fiber structure 1 can be used as a filter material, a heat-resistant material, a conductive material, a heat-dissipating material, a heat-transfer material, or an electrostatic shielding material.
The metal fiber structure 1 of the present embodiment having the above-described configuration is the metal fiber structure 1 in which the plurality of metal fibers 2 are bonded to each other, and includes the porous metal body 3 that is in contact with the plurality of metal fibers 2 to connect the plurality of metal fibers 2. Unlike conventional techniques in which entangled portions of solid metal fibers are melted by sintering to bond the metal fibers together, according to the metal fiber structure 1, as described above, the plurality of metal fibers 2 are connected via the porous metal body 3, and thus the entire metal fiber structure 1 can exhibit excellent flexibility and other physical properties.
In addition, in the metal fiber structure 1 of the present embodiment, the porous metal body 3 may be disposed between the metal fibers 2, as described above. Alternatively, the metal fiber structure 1 may have a structure in which the metal fibers 2 are covered by the porous metal body 3.
In addition, in the metal fiber structure 1 of the present embodiment, the area percentage of metal in the cross section of the porous metal body 3 may be within the range of 20% to 80%. Thus, a more favorable balance between the flexibility and another physical property of the metal fiber structure 1 can be achieved.
In addition, in the metal fiber structure 1 of the present embodiment, the area percentage of metal in the cross section of the metal fiber structure 1 may be within the range of 30% to 80%. Thus, a more favorable balance between the flexibility and another physical property of the metal fiber structure 1 can be achieved.
In addition, in the metal fiber structure 1 of the present embodiment, the average fiber diameter of the metal fibers 2 may be within the range of 10 µm to 3000 µm. Thus, a favorable balance between the flexibility and another physical property of the metal fiber structure 1 can be achieved.
In addition, the thickness of the metal fiber structure 1 of the present embodiment may be within the range of 0.01 mm to 50.0 mm. Thus, a favorable balance between the flexibility and another physical property of the metal fiber structure 1 can be achieved.
In addition, in the metal fiber structure 1 of the present embodiment, the material of the porous metal body 3 may include a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C. Thus, the metal fiber structure 1 having excellent flexibility and specific resistivity can be obtained.
In addition, in the metal fiber structure 1 of the present embodiment, the material of the porous metal body 3 may include a metal having a Young's modulus of 150 to 450 GPa. Thus, the metal fiber structure 1 having excellent flexibility and strength can be obtained.
In addition, in the metal fiber structure 1 of the present embodiment, the material of the metal fiber 2 may include a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C. Thus, the metal fiber structure 1 having excellent flexibility and specific resistivity can be obtained.
In addition, in the metal fiber structure 1 of the present embodiment, the material of the metal fibers 2 may include a metal having a Young's modulus of 150 to 450 GPa. Thus, the metal fiber structure 1 having excellent flexibility and strength can be obtained.
The metal fiber structure 1 according to the present embodiment is not limited to the above-described mode or combination.
For example, the porous metal body 3 may form a thin coating over the surface of each metal fiber 2. At the connection points between the metal fibers 2, the porous metal body 3 may be more abundantly (thickly) interposed so as to serve as the bonding portion between the metal fibers 2 (FIG. 2, FIG. 3). In other words, the amount (volume) of the porous metal body 3 in the metal fiber structure 1 may change depending on the positions of the metal fibers 2.
In addition, in the metal fiber structure 1 of the present embodiment, when the materials of the metal fibers 2 and the porous metal body 3 include a metal having high thermal conductivity, the metal fiber structure 1 having excellent flexibility and thermal conductivity can be obtained. Examples of the metal having high thermal conductivity include silver, copper, gold, aluminum, and alloys thereof.
In addition, a non-metal component may be used as a part of each metal fiber 2, and such a component may be covered by a metal component as described above.

EXAMPLES

Hereinafter, the present disclosure will be described in detail using Examples and Comparative Examples.

Metal fiber structures were produced using materials shown in Tables 1 to 2. That is, a slurry solution (solid content: 50%, solvent: glycerin) including copper particles (average primary particle diameter: 25 nm, manufactured by loLiTec) was applied to copper fibers as a base shown in Tables 1 and 2, and the copper fibers were heated at 250°C for 1 hour under an N₂ atmosphere. FIG. 4 is a micrograph (at 3000× magnification) showing a cross section of the metal fiber structure of Example 1.

A metal fiber structure was produced using materials shown in Table 2. That is, a slurry solution (solid content: 50%, solvent: glycerin) including copper particles (average primary particle diameter: 25 nm, manufactured by loLiTec) was applied to aluminum fibers as a base shown in Table 2, and the aluminum fibers were heated at 250°C for 1 hour under an N₂ atmosphere.

Metal fiber structures were produced using materials shown in Tables 3 to 4. That is, a slurry solution (solid content: 50%, solvent: glycerin) including stainless steel SUS316L particles (average primary particle diameter: 70 nm, manufactured by loLiTec) was applied to stainless steel fibers (SUS304) as a base shown in Tables 3 and 4, and the stainless steel fibers were heated at 250°C for 1 hour under an N₂ atmosphere.

A metal fiber structure was produced using materials shown in Table 4. That is, a slurry solution (solid content: 50%, solvent: glycerin) including stainless steel SUS316L particles (average primary particle diameter: 70 nm, manufactured by loLiTec) was applied to tungsten fibers as a base shown in Table 4, and the tungsten fibers were heated at 250°C for 1 hour under an N₂ atmosphere.

Metal fiber structures of Comparative Examples 1, 2 were each obtained by using the same metal fibers as the copper fibers or the stainless steel fibers used in Examples 1, 18, followed by heating treatment at 250°C for 1 hour under an N₂ atmosphere. FIG. 5 is a micrograph (at 3000× magnification) showing a cross section of the metal fiber structure of Comparative Example 1.

(Specific resistivity (volume resistivity))

The specific resistivity (volume resistivity) of each metal fiber structure of Examples 1 to 17 and Comparative Example 1 was measured and evaluated as follows. The specific resistivity (volume resistivity) of the metal fiber structure was measured by using Loresta-GP which is a low resistivity meter manufactured by Nittoseiko Analytech Co., Ltd., based on the four-terminal method. The measurement sample was cut to an appropriate size according to the measurement range so as to have a uniform thickness. If the value was greater than 1.7×10^-8 Ω·m and equal to or less than 3.4×10^-8 Ω·m, it was rated as Excellent, if the value was greater than 3.4×10^-8 Ω·m and equal to or less than 5.1×10^-8 Ω·m, it was rated as Good, if the value was greater than 5.1×10^-8 Ω·m and equal to or less than 6.8×10^-8 Ω·m, it was rated as Fair, and if the value was greater than 6.8×10^-8 Ω·m, it was rated as Poor.

(Stress-relaxation property)

The stress-relaxation property (flexibility) of each metal fiber structure of Examples 1 to 34 and Comparative Examples 1, 2 was measured and evaluated as follows. The metal fiber structures except for those of Examples 15 and 32 were each cut into a doughnut shape (outer diameter: 50 mmφ, inner diameter: 30 mmφ) to have a thickness that was approximately one-tenth of the original thickness (e.g., thickness: 1.1 mm in Example 1). In addition, a doughnut-shaped alumina plate (outer diameter: 55 mmφ, inner diameter: 35 mmφ, thickness: 0.5 mm) having a purity of 95% was prepared, and a two-component epoxy adhesive (1500, manufactured by CEMEDINE CO., LTD.) was uniformly applied to one surface of the alumina plate at a thickness of 10 µm. Then, the metal fiber structure cut into a doughnut shape or the doughnut-shaped metal fiber structure of each of Examples 15, 32 was adhered to the surface, to which the two-component epoxy adhesive had been applied, of the alumina plate, and the sample was allowed to stand for 24 hours under conditions of 23°C and 65% RH to obtain a test piece. The obtained test piece was placed in a temperature chamber (PV-212, manufactured by ESPEC CORP.) set at 150°C, and the amount of warpage of the test piece during heating was measured and used as the evaluation result of stress-relaxation property. If the amount of warpage was less than 0.05 mm, it was rated as Excellent, if the amount of warpage was equal to or greater than 0.05 mm and less than 0.20 mm, it was rated as Good, if the amount of warpage was equal to or greater than 0.20 mm and less than 0.50 mm, it was rated as Fair, and if the amount of warpage was equal to or greater than 0.50 mm, it was rated as Poor.

(Strength)

The strength of each metal fiber structure of Examples 18 to 34 and Comparative Example 2 was measured and evaluated as follows. The metal fiber structure was cut into a Type No. 4 test piece in accordance with JIS Z2241, and a tensile test was performed by using a tensile tester (UH-1000kNI, manufactured by Shimadzu Corporation). The obtained Young's modulus (23°C) was used as the strength. If the Young's modulus was equal to or greater than 20.0 GPa, it was rated as Excellent, if the Young's modulus was equal to or greater than 15.0 GPa and less than 20.0 GPa, it was rated as Good, if the Young's modulus was equal to or greater than 10.0 GPa and less than 15.0 GPa, it was rated as Fair, and if the Young's modulus was less than 10.0 GPa, it was rated as Poor.

The results and overall evaluations are shown in Tables 1 to 4. For the overall evaluation, if two individual items were rated as Excellent, the overall evaluation was rated as "Excellent". If one or more individual items were rated as Good and no items were rated as Fair or Poor, the overall evaluation was rated as "Good". If any one individual evaluation item was rated as Fair and the others were rated as Excellent or Good, the overall evaluation was rated as "Fair". In addition, if any one individual evaluation item was rated as Poor, the overall evaluation was rated as "Poor".

[Table 1]

		Ex. 1	Ex. 2	Ex. 3	Ex. 4	Ex. 5	Ex. 6	Ex. 7	Ex. 8	Ex. 9
Metal fiber (Cu, Al)	Material	Copper C1020	Copper C1100	Copper C1100	Copper C1100	Copper C1020	Copper C1020	Copper C1020	Copper C1020	Copper C1020
	Volume resistivity (1.0×10^-8 Ω·m)	1.55	1.55	1.55	1.55	1.55	1.55	1.55	1.55	1.55
	Average diameter (µm)	17	17	17	17	17	17	17	17	17
	Average length (mm)	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
Slurry solution (porous metal body)	Metal type	Copper	Copper	Copper	Copper	Copper	Copper	Copper	Copper	Copper
Slurry solution (porous metal body)	Area percentage (%) (after production)	61	60	57	57	59	58	55	22	77
Metal fiber structure	Thickness (mm)	12	10	11	11	12	11	12	13	12
Metal fiber structure	Area percentage (%)	60	27	83	31	76	42	69	55	61
Evaluation	Specific resistivity (10^-8 Ω·m)	2.3 Excellent	6.7 Fair	1.8 Excellent	5.8 Fair	1.9 Excellent	5.0 Good	2.1 Excellent	5.4 Fair	2.0 Excellent
	Stress-relaxation property (mm)	0.03 Excellent	0.02 Excellent	0.42 Fair	0.02 Excellent	0.30 Fair	0.03 Excellent	0.21 Fair	0.03 Excellent	0.26 Fair
	Overall evaluation	Excellent	Fair	Fair	Fair	Fair	Good	Fair	Fair	Fair

[Table 2]

		Ex. 10	Ex. 11	Ex. 12	Ex. 13	Ex. 14	Ex. 15	Ex. 16	Ex. 17	Comp. Ex. 1
Metal fiber (Cu, Al)	Material	Copper C1020	Copper C1020	Copper C1020	Copper C1020	Copper C1020	Copper C1020	Copper C1020	Aluminum	Copper C1020
	Volume resistivity (1.0×10^-8 Ω·m)	1.55	1.55	1.55	1.55	1.55	1.55	1.55	2.50	1.55
	Average diameter (µm)	17	17	7	11	42	17	17	17	17
	Average length (mm)	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
Slurry solution (porous metal body)	Metal type	Copper	Copper	Copper	Copper	Copper	Copper	Copper	Copper	-
Slurry solution (porous metal body)	Area percentage (%) (after production)	31	67	62	60	61	63	60	58	-
Metal fiber structure	Thickness (mm)	12	12	11	12	12	0.2	45	12	12
Metal fiber structure	Area percentage (%)	57	63	60	64	59	54	60	60	60
Evaluation	Specific resistivity (10^-8 Ω·m)	4.2 Good	2.2 Excellent	5.2 Fair	3.1 Excellent	2.0 Excellent	2.2 Excellent	2.3 Excellent	3.5 Good	10.2 Poor
	Stress-relaxation property (mm)	0.03 Excellent	0.11 Good	0.02 Excellent	0.02 Excellent	0.10 Good	0.01 Excellent	0.09 Good	0.03 Excellent	0.03 Excellent
	Overall evaluation	Good	Good	Fair	Excellent	Good	Excellent	Good	Good	Poor

[Table 3]

		Ex. 18	Ex. 19	Ex. 20	Ex. 21	Ex. 22	Ex. 23	Ex. 24	Ex. 25	Ex. 26
Metal fiber (SUS, W)	Material	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304
	Young's modulus (GPa)	202	202	202	202	202	202	202	202	202
	Average diameter (µm)	17	17	17	17	17	17	17	17	17
	Average length (mm)	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
Slurry solution (porous metal body)	Metal type	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L
Slurry solution (porous metal body)	Area percentage (%) (after production)	62	60	61	61	57	58	55	18	81
Metal fiber structure	Thickness (mm)	11	10	11	10	11	11	12	11	13
Metal fiber structure	Area percentage (%)	58	18	83	31	76	44	69	52	63
Evaluation	Strength (GPa)	26.9 Excellent	10.9 Fair	35.2 Excellent	12.1 Fair	32.1 Excellent	13.5 Fair	30.2 Excellent	14.6 Fair	33.4 Excellent
	Stress-relaxation property (mm)	0.04 Excellent	0.02 Excellent	0.33 Fair	0.02 Excellent	0.24 Fair	0.03 Excellent	0.22 Fair	0.03 Excellent	0.28 Fair
	Overall evaluation	Excellent	Fair	Fair	Fair	Fair	Fair	Fair	Fair	Fair

[Table 4]

		Ex. 27	Ex. 28	E. 29	Ex. 30	E. 31	Ex. 32	Ex. 33	Ex. 34	Comp. Ex. 2
Metal fiber (SUS, W)	Material	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	SUS 304	Tungsten	SUS 304
	Young's modulus (GPa)	202	202	202	202	202	202	202	397	202
	Average diameter (µm)	17	17	7	11	47	17	17	17	17
	Average length (mm)	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0
Slurry solution (porous metal body)	Metal type	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	SUS 316L	-
Slurry solution (porous metal body)	Area percentage (%) (after production)	32	69	61	64	55	58	54	61	-
Metal fiber structure	Thickness (mm)	12	13	10	12	10	0.2	44	10	10
Metal fiber structure	Area percentage (%)	61	62	60	64	59	54	60	60	60
Evaluation	Strength (GPa)	19.6 Good	30.5 Excellent	14.9 Fair	19.8 Good	27.3 Excellent	26.6 Excellent	26.5 Excellent	51.3 Excellent	8.2 Poor
	Stress-relaxation property (mm)	0.03 Excellent	0.10 Good	0.02 Excellent	0.02 Excellent	0.10 Good	0.01 Excellent	0.09 Good	0.08 Good	0.03 Excellent
	Overall evaluation	Good	Good	Fair	Good	Good	Excellent	Good	Good	Poor

As shown in the above Table 1 to Table 4, it has been confirmed that each metal fiber structure 1 according to Examples 1 to 34 has a (new) structure different from conventional ones (see FIG. 4, FIG. 5), exhibits excellent flexibility (stress-relaxation property), and also exhibits excellent specific resistivity or strength, compared to the metal fiber structures of Comparative Examples 1, 2. Unlike Comparative Examples 1, 2 that have received overall evaluations rated as Poor, it has been found that all Examples can achieve a balance between the specific resistivity or strength and the stress-relaxation property.
In addition, among Examples, from comparisons between Examples 8 and 9 and Examples 10 and 11 and between Examples 25 and 26 and Examples 27 and 28, it has been found that when the area percentage of the porous metal body 3 is within the range of 20% to 80%, the overall evaluation is further improved, and a more favorable balance between the specific resistivity or strength and the stress-relaxation property can be achieved.
Further, as compared to Examples 2 and 3, each of Examples 4 to 7 shows that the lower limit of the specific resistivity is increased and the upper limit thereof is decreased, and the upper limit of the stress-relaxation property is also decreased. Thus, it has been found that these properties are exhibited in a more balanced manner. In addition, as compared to Examples 19 and 20, each of Examples 21 to 24 shows that the lower limit of the strength is increased and the upper limit thereof is decreased, and the upper limit of the stress-relaxation property is also decreased. Thus, it has been found that these properties are exhibited in a more balanced manner. Therefore, it has been found that when the area percentage of the metal fiber structure 1 is within the range of 30% to 80%, a more favorable balance between the specific resistivity or strength and the stress-relaxation property can be achieved.
In addition, from comparisons between Example 12 and Examples 13 and 14 and between Example 29 and Examples 30 and 31, it has been found that when the average fiber diameter of the metal fibers 2 is within the range of 10 µm to 3000 µm, the overall evaluation is further improved, and a more favorable balance between the specific resistivity or strength and the stress-relaxation property can be achieved.
In addition, from each result of Examples 15 and 16 and Examples 32 and 33, it has been found that when the thickness of the metal fiber structure 1 is within the range of 0.01 mm to 50.0 mm, the individual evaluation and the overall evaluation are also rated as "Excellent" or "Good", and a more favorable balance between the specific resistivity or strength and the stress-relaxation property can be achieved.
As described above, the metal fiber structure of the present disclosure is a metal fiber structure in which a plurality of metal fibers are bonded to each other, and includes a porous metal body that is in contact with the plurality of metal fibers to connect the plurality of metal fibers, and the metal fiber structure of the present disclosure has excellent physical properties such as flexibility.

Claims

A metal fiber structure in which a plurality of metal fibers are bonded to each other, the metal fiber structure comprising
a porous metal body that is in contact with the plurality of metal fibers to connect the plurality of metal fibers.
The metal fiber structure according to claim 1, wherein the porous metal body is disposed between the metal fibers.
The metal fiber structure according to claim 1, wherein the metal fiber structure has a structure in which the metal fibers are covered by the porous metal body.
The metal fiber structure according to any one of claims 1 to 3, wherein an area percentage of metal in a cross section of the porous metal body is within a range of 20% to 80%.
The metal fiber structure according to any one of claims 1 to 4, wherein an area percentage of metal in a cross section of the metal fiber structure is within a range of 30% to 80%.
The metal fiber structure according to any one of claims 1 to 5, wherein an average fiber diameter of the metal fibers is within a range of 10 µm to 3000 µm.
The metal fiber structure according to any one of claims 1 to 6, having a thickness within a range of 0.01 mm to 50.0 mm.
The metal fiber structure according to any one of claims 1 to 7, wherein a material of the porous metal body includes a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C.
The metal fiber structure according to any one of claims 1 to 8, wherein a material of the metal fibers includes a metal having a specific resistivity of 1.5×10^-8 Ω·m to 3.0×10^-8 Ω·m at 20°C.
The metal fiber structure according to any one of claims 1 to 9, wherein a material of the porous metal body includes a metal having a Young's modulus of 150 to 450 GPa.
The metal fiber structure according to any one of claims 1 to 10, wherein a material of the metal fibers includes a metal having a Young's modulus of 150 to 450 GPa.