Aluminum fiber structures and aluminum composites

Abstract

This aluminum composite material (1, 2, 3, 4, 5) is obtained by combining an aluminum fiber structure (10) and a composite material (70, 80, 110). With respect to the aluminum fiber structure (10), aluminum fibers (20) are partially bonded with each other, and an alumina layer 30 is formed on the surface of each one of the aluminum fibers (20). A plurality of alumina projections (40), each of which has a height that is greater than the thickness of the alumina layer (30), is formed on the surfaces of the aluminum fibers (20) or the alumina layer (30). The alumina projections (40) and at least a part of the composite material (70, 80, 110) are in contact with each other.

Description

Technical Field

[0001] The present invention relates to an aluminum fiber structure and an aluminum composite material.

Background Art

[0002] Conventionally, a metal fiber structure formed from metal fibers may be used as a medium for heat transfer in a heat exchanger. Japanese Patent Laid-Open Publication No. JP2011-007365A shows an example in which an aluminum fiber structure formed from aluminum fibers is used as the metal fiber structure.

[0003] The aluminum fiber structure disclosed in Japanese Patent Laid-Open Publication No. JP2011-007365A is produced by filling aluminum fibers with an average fiber thickness of 50 to 200 μm and an average fiber length of 20 to 1000 mm into a mold of a predetermined shape, compressing the filled aluminum fibers to form a compression molded body with a bulk density of 30% or more, heating the compression molded body at 600 to 650 °C in an inert gas atmosphere to diffusion bond the entangled aluminum fibers to form a porous sintered molded body, and then hydrophilizing the surface of the aluminum fibers.

Summary of the Invention

[0004] The aluminum fiber structure disclosed in Japanese Patent Laid-Open Publication No. JP2011-007365A has a large linear expansion coefficient. Therefore, when it is combined with, for example, glass or ceramic, since the linear expansion coefficients of these glass and ceramic are relatively small, there is a problem that peeling may occur due to the difference in the linear expansion coefficients of the two when the temperature of the surrounding environment changes greatly.

[0005] The present invention has been made in consideration of such points, and an object thereof is to provide an aluminum fiber structure having a small linear expansion coefficient, and an aluminum composite material in which peeling hardly occurs between the aluminum fiber structure and the composite material even when the temperature of the surrounding environment changes greatly. [Means for solving the problem]

[0006] The aluminum fiber structure of the present invention is An aluminum fiber structure in which aluminum fibers are partially bonded to each other, An alumina layer is formed on the surface of the aforementioned aluminum fiber, The aluminum fiber or the alumina layer is characterized by having a plurality of alumina protrusions formed on its surface, the protrusions having a height greater than the thickness of the alumina layer.

[0007] The aluminum composite material of the present invention is An aluminum composite material formed by combining the above-mentioned aluminum fiber structure with a composite material, The alumina is characterized in that the protrusions and at least a portion of the composite material are in contact. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram illustrating a first example of the configuration of an aluminum composite material according to an embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating a second example of the configuration of an aluminum composite material according to an embodiment of the present invention. [Figure 3] This is a schematic diagram illustrating a third example of the configuration of an aluminum composite material according to an embodiment of the present invention. [Figure 4] This is a schematic diagram illustrating a fourth example of the configuration of an aluminum composite material according to an embodiment of the present invention. [Figure 5] This is a schematic diagram illustrating a fifth example of the configuration of an aluminum composite material according to an embodiment of the present invention. [Figure 6] This is a photograph of the surface of an aluminum fiber structure made of an aluminum composite material according to an embodiment of the present invention. [Figure 7] Figure 6 shows a photograph of the cross-section of the aluminum fiber structure after it has been cut. [Figure 8] Figure 7 is a photograph showing a magnified portion of the cross-section of the aluminum fiber structure. [Figure 9] This is a schematic diagram illustrating a method for manufacturing an aluminum fiber structure of an aluminum composite material according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Figures 1 to 5 are schematic diagrams illustrating various examples of the configuration of the aluminum composite material according to embodiments of the present invention. Figure 6 is a photograph of the surface of the aluminum fiber structure of the aluminum composite material according to this embodiment. Figure 7 is a photograph showing the cross-section when the aluminum fiber structure shown in Figure 6 is cut, and Figure 8 is a photograph showing a magnified portion of the cross-section of the aluminum fiber structure shown in Figure 7. Figure 9 is an explanatory diagram illustrating a method for manufacturing the aluminum fiber structure of the aluminum composite material according to this embodiment.

[0010] The aluminum composite materials 1, 2, 3, 4, and 5 according to this embodiment are formed by combining an aluminum fiber structure 10 with a composite material composed of a material other than aluminum. Various examples of such aluminum composite materials 1, 2, 3, 4, and 5 will be explained with reference to Figures 1 to 5.

[0011] As shown in Figure 1, the first example of aluminum composite material 1 is one in which resin 70 is completely impregnated into an aluminum fiber structure 10. The material of the resin 70 is not particularly limited, but examples include epoxy, polyolefin, styrene polymer, polyether, polyurea, acrylic polymer, polyurethane, polyester, polyamide, polysiloxane, polysaccharide, polypeptide, polynucleotide, polyvinyl alcohol, polyacrylamide, etc., and mixtures thereof. Specifically, by completely impregnating the two aluminum fiber structures 10 with resin 70, the aluminum fiber structures 10 are positioned near the front and back sides of the resin 70, respectively. The aluminum fiber structures 10 do not protrude outward from the front and back surfaces of the resin 70.

[0012] As shown in Figure 2, the second example of aluminum composite material 2 is one in which resin 70 is partially impregnated into an aluminum fiber structure 10. Specifically, by partially impregnating two aluminum fiber structures 10 with resin 70, the aluminum fiber structures 10 are positioned near the front and back surfaces of the resin 70, respectively, and the aluminum fiber structures 10 protrude outward from the front and back surfaces of the resin 70.

[0013] As shown in Figure 3, the third example of aluminum composite material 3 is one in which two aluminum fiber structures 10 are bonded together by an adhesive layer 80 composed of an adhesive made of a metal paste other than aluminum, such as silver paste, copper paste, nickel paste, silver solder, copper solder, tin, solder, etc.

[0014] As shown in Figure 4, the fourth example, the aluminum composite material 4, is formed by bonding a metal part 90, such as a copper plate, to one surface of an aluminum fiber structure 10 using an adhesive layer 80 made of an adhesive such as a metal paste other than aluminum.

[0015] As shown in FIG. 5, as a fifth example, the aluminum composite material 4 has a metal component 90 adhered to one surface of the aluminum fiber structure 10 by an adhesive layer 80 composed of an adhesive such as a metal paste other than aluminum, and an alumina plate 100 adhered to the other surface of the aluminum fiber structure 10 by an adhesive layer 110 composed of an adhesive such as glass (for example, water glass, frit glass, glass paste).

[0016] Next, the configuration of the aluminum fiber structure 10 will be described. As shown in FIGS. 6 to 8, the aluminum fiber structure 10 according to the present embodiment has aluminum fibers 20 partially joined together, and an alumina layer 30 is formed on the surface of the aluminum fibers 20. Further, as shown in FIG. 8, a plurality of alumina protrusions 40 having a height greater than the thickness of the alumina layer 30 are formed on the surface of the aluminum fibers 20 or the alumina layer 30. In FIG. 8, a portion where the alumina layer 30 and the protrusions 40 are not formed on the surface of the aluminum fibers 20 is indicated by reference numeral 22.

[0017] In such an aluminum fiber structure 10, the portion where the alumina layer 30 is formed is likely to expand or contract due to temperature changes, while the portion where the plurality of alumina protrusions 40 are formed is less likely to expand or contract due to temperature changes. Thus, since there is a partial bias in the linear expansion coefficient throughout the aluminum fiber structure 10, the overall linear expansion coefficient can be reduced.

[0018] The aluminum fibers 20 have a length within the range of 0.2 to 15 mm and a diameter within the range of 0.01 to 0.100 mm. The length of the aluminum fibers 20 can be confirmed by actual measurement through photographic observation using an SEM, an optical microscope, or the like.

[0019] The alumina layer 30 is formed by oxidizing the aluminum fibers 20 in an air atmosphere. The alumina layer 30 is generally formed uniformly on the surface of the aluminum fibers 20. The thickness of such an alumina layer 30 is in the range of 10 nm to 10 μm, preferably 100 nm to 7 μm, and more preferably 1 μm to 5 μm.

[0020] The protrusions 40 are formed from what has been eluted from the aluminum fibers 20 by sintering the aluminum fibers 20 at 700 °C or higher. A method for manufacturing the aluminum fiber structure 10 by sintering the aluminum fibers 20 will be described later. When the sintering temperature for the aluminum fibers 20 is less than 700 °C, a sufficient amount of alumina cannot be eluted from the aluminum fibers 20, and protrusions 40 with a sufficient height cannot be obtained.

[0021] Also, as described above, the height of the protrusions 40 with respect to the surface of the aluminum fibers 20 or the alumina layer 30 is greater than the thickness of the alumina layer 30. Specifically, the height of the protrusions 40 with respect to the surface of the aluminum fibers 20 or the alumina layer 30 is in the range of 10 nm to 10 μm, preferably 100 nm to 7 μm, and more preferably 1 μm to 5 μm. This increases the adhesion strength between the aluminum fibers 20 and the protrusions 40. Here, when the height of the protrusions 40 with respect to the surface of the aluminum fibers 20 or the alumina layer 30 is too small, specifically, less than 10 nm, the difference between the thickness of the alumina layer 30 and the height of the protrusions 40 does not increase, and there is a problem that a partial bias in the linear expansion coefficient cannot be formed in the aluminum fiber structure 10. Also, when the height of the protrusions 40 with respect to the surface of the aluminum fibers 20 or the alumina layer 30 is too large, specifically, greater than 10 μm, there is a problem that large voids are formed between the aluminum fibers 20.

[0022] In the cross-section of the aluminum fiber structure 10 as shown in Figures 7 and 8, the coverage rate of the areas covered by the protrusions 40 on the surface of the aluminum fibers 20 is preferably 20% or more, and more preferably 40% or more. The surface of the aluminum fibers 20 is almost entirely covered with an alumina layer 30, and the protrusions 40 are partially formed in this alumina layer 30. The coverage rate of the areas covered by the protrusions 40 on the surface of the aluminum fibers 20 can be calculated by dividing the length of the alumina layer 30 in the area covered by the protrusions 40 (specifically, the area from the point where the peak of the protrusion 40 begins to descend to the point where it ends) by the total length of the alumina layer 30 in the cross-section of the aluminum fiber structure 10. If the coverage rate of the protrusions 40 on the surface of the aluminum fibers 20 is less than 20%, the proportion occupied by the protrusions 40 in the aluminum fiber structure 10 is relatively small, which presents a problem in that the coefficient of linear expansion of the aluminum fiber structure 10 does not decrease.

[0023] Furthermore, at least some of the multiple protrusions 40 are in contact with the alumina layer 30 of the multiple aluminum fibers 20. In this case, the aluminum fibers 20 are connected to each other by the protrusions 40, making it difficult for the aluminum fibers 20 to move relative to each other, and thus the coefficient of thermal expansion of the aluminum fiber structure 10 can be made even smaller. In addition, when the aluminum fiber structure 10 is composited with a composite material (for example, the resin 70, adhesive layer 80, adhesive layer 110, etc. mentioned above), the composite material that has entered the gaps in the aluminum fiber structure 10 will come into contact with the protrusions 40.

[0024] Furthermore, the packing ratio of the aluminum fibers 20 in the aluminum fiber structure 10 according to this embodiment is in the range of 20% to 90%. This packing ratio of the aluminum fibers 20 can be determined by calculating the ratio of the area occupied by the aluminum fibers 20 to the area inside the outer edge of the aluminum fiber structure 10 at the cut surface when the aluminum fiber structure 10 is cut. By having a packing ratio of the aluminum fibers 20 in the aluminum fiber structure 10 in the range of 20% to 90%, both lightness and strength of the aluminum fiber structure 10 can be achieved. In other words, if the packing ratio of the aluminum fibers 20 in the aluminum fiber structure 10 is less than 20%, sufficient strength cannot be obtained, and if the packing ratio of the aluminum fibers 20 in the aluminum fiber structure 10 is greater than 90%, there is a problem in that weight reduction cannot be achieved. Also, when the packing ratio of the aluminum fibers 20 in the aluminum fiber structure 10 is 20% or more, a sufficient amount of aluminum fibers 20 is obtained, resulting in appropriate homogeneity. Furthermore, if the packing ratio of the aluminum fibers 20 in the aluminum fiber structure 10 is 90% or less, the desired flexibility can be obtained in addition to appropriate homogeneity.

[0025] Furthermore, in the aluminum fiber structure 10 according to this embodiment, a plasma-resistant layer may be formed on the surfaces of the alumina layer 30 and the protrusions 40. Here, the plasma-resistant layer may contain a metal oxide or aluminum nitride. The metal oxide may include at least one of the following: zirconium oxide, yttrium oxide, magnesium oxide, zinc oxide, sapphire, or quartz glass. In this case, a composite material of the aluminum fiber structure 10 and the plasma-resistant layer can be provided, and the composite material will have excellent plasma resistance. Such a composite material of the aluminum fiber structure 10 and the plasma-resistant layer can be manufactured by applying a glaze containing zirconia, yttria, etc., to the alumina layer 30 and protrusions 40 of the aluminum fiber structure 10 and then heating it at a high temperature.

[0026] As shown in Figure 9(a), the aluminum fibers 20 are formed into a sheet inside the molding container 50 and then pressed. This allows the aluminum fibers 20 to be tightly packed together. Furthermore, as shown in Figure 9(b), the aluminum fibers 20 are sintered by heating them to 700°C or higher inside the sintering equipment 60. This forms the aluminum fiber structure 10. The method for heating the aluminum fibers 20 is to heat the surface of the aluminum fibers 20 with hot air, but is not limited to this method. Electric heating may also be used as the method for heating the aluminum fibers 20. Also, as described above, when the aluminum fibers 20 are sintered to 700°C or higher, alumina dissolves from the aluminum fibers 20, and the dissolved alumina solidifies at room temperature to form the protrusions 40. Furthermore, by placing the aluminum fiber structure 10 in an atmospheric environment, the aluminum fibers 20 oxidize to form the alumina layer 30.

[0027] In summary, according to the aluminum fiber structure 10 of this embodiment, the aluminum fibers 20 are partially bonded to each other, and an alumina layer 30 is formed on the surface of the aluminum fibers 20. In addition, multiple alumina protrusions 40, which are taller than the thickness of the alumina layer 30, are formed on the surface of the aluminum fibers 20 or the alumina layer 30. In such an aluminum fiber structure 10, the parts where the alumina layer 30 is formed are prone to expansion or contraction due to temperature changes, while the parts where the multiple alumina protrusions 40 are formed are less prone to expansion or contraction due to temperature changes. As a result, the coefficient of linear expansion of the aluminum fiber structure 10 as a whole is partially uneven, and the overall coefficient of linear expansion can be reduced.

[0028] Furthermore, in aluminum composite materials 1, 2, 3, 4, and 5, which are formed by combining such an aluminum fiber structure 10 with a composite material made of a different composite material (for example, resin 70, adhesive layer 80, adhesive layer 110, etc.), the alumina protrusions 40 and at least a portion of the composite material are in contact. Even if the ambient temperature changes significantly, delamination between the aluminum fiber structure 10 and the composite material becomes less likely. More specifically, the composite material that has entered the gaps in the aluminum fiber structure 10 catches on the protrusions 40 of the aluminum fiber structure 10, so that even composite materials that are difficult to bond with aluminum can be firmly bonded to the aluminum fiber structure 10.

[0029] For example, in the aluminum composite material 1 according to the first and second examples, the resin 70 that has entered the gaps in the aluminum fiber structure 10 catches on the protrusions 40 of the aluminum fiber structure 10, so that even if the resin 70 does not adhere well to aluminum, the aluminum fiber structure 10 can be firmly bonded to the resin 70.

[0030] Furthermore, in the aluminum composite materials 3 and 4 according to the third and fourth examples, the adhesive that has entered the gaps in the aluminum fiber structure 10 catches on the protrusions 40 of the aluminum fiber structure 10, thereby firmly bonding the aluminum fiber structure 10 to the adhesive layer 80. As a result, in the aluminum composite material 3 according to the third example, two aluminum fiber structures 10 are less likely to peel off from each other. Also, in the aluminum composite material 4 according to the fourth example, the aluminum fiber structure 10 is less likely to peel off from metal parts 90 such as copper plates. In addition, even if the adhesion between the metal part 90 and the adhesive layer 80 is weak, the low coefficient of linear expansion of the aluminum fiber structure 10 makes it less likely for the aluminum fiber structure 10 to peel off from the metal part 90 even if the metal part 90 expands.

[0031] Furthermore, according to the aluminum composite material 5 of the fifth example, the adhesive that has entered the gaps in the aluminum fiber structure 10 catches on the protrusions 40 of the aluminum fiber structure 10, thereby firmly bonding the aluminum fiber structure 10 to the adhesive layers 80 and 110, respectively. As a result, the aluminum fiber structure 10 is less likely to peel off from the metal part 90 and the alumina plate 100. In this case, even if there is a difference in the coefficient of thermal expansion between the metal part 90 and the alumina plate 100, the coefficient of thermal expansion of the aluminum fiber structure 10 is small, so delamination is less likely to occur between the metal part 90 and the aluminum fiber structure 10, or between the alumina plate 100 and the aluminum fiber structure 10, in the aluminum composite material 5 as a whole. [Examples]

[0032] The present invention will be described in more detail below with reference to examples and comparative examples.

[0033] <Example 1> The aluminum fiber structure was manufactured using the following procedure. First, multiple aluminum fibers, made of A1070 material with a fiber diameter of 50 μm and an average length of 2 mm, were formed into a sheet. Then, the aluminum fibers were sintered by heating them at 700°C inside a sintering facility. This produced the aluminum fiber structure.

[0034] Microscopic examination of the cross-section of the fabricated aluminum fiber structure revealed that an alumina layer had formed on the surface of the aluminum fibers, and that multiple alumina protrusions, taller than the thickness of the alumina layer, were formed on either this alumina layer or the surface of the aluminum fibers. Furthermore, the total coverage of the alumina layer and protrusions on the surface of the aluminum fibers in the cross-section of the aluminum fiber structure was 24%, and the packing density of the aluminum fibers in the structure was 75%. The physical properties of this aluminum fiber structure are shown in Table 1 below.

[0035] <Examples 2-4> Aluminum fiber structures were fabricated in the same manner as in Example 1, except that the aluminum fibers were sintered by heating them at 750°C, 800°C, and 850°C, respectively, inside a sintering facility. When the cross-sections of the fabricated aluminum fiber structures of Examples 2 to 4 were examined under a microscope, it was found that an alumina layer had formed on the surface of the aluminum fibers, and that multiple alumina protrusions, greater in height than the thickness of the alumina layer, had formed on this alumina layer or on the surface of the aluminum fibers. The physical properties of the fabricated aluminum fiber structures of Examples 2 to 4 are shown in Table 1 below.

[0036] <Examples 5-8> Table 1 shows the individual fiber diameters and average lengths of multiple aluminum fibers. Except for sintering the aluminum fibers by heating them at the temperatures shown in Table 1 (800°C or 900°C) inside a sintering facility, the aluminum fiber structures were fabricated in the same manner as in Example 1. Microscopic examination of the cross-sections of the fabricated aluminum fiber structures in Examples 5-8 revealed that an alumina layer was formed on the surface of the aluminum fibers, and that multiple alumina protrusions, greater in height than the thickness of the alumina layer, were formed on this alumina layer or on the surface of the aluminum fibers. The physical properties of the fabricated aluminum fiber structures in Examples 5-8 are shown in Table 1 below.

[0037] <Example 9> As in Example 1, aluminum fibers were formed into a sheet, and then sintered by heating the aluminum fibers at 900°C inside a sintering facility. After that, a glaze containing yttria was applied to the surface of the aluminum fiber structure and then heated at a high temperature. When the cross-section of the aluminum fiber structure produced in this way was examined under a microscope, it was found that an alumina layer had been formed on the surface of the aluminum fibers, and that multiple alumina protrusions, greater in height than the thickness of the alumina layer, had been formed on this alumina layer or on the surface of the aluminum fibers. Furthermore, in such an aluminum fiber structure, a plasma-resistant layer containing yttrium oxide was formed on the surface of the alumina layer and the protrusions. The physical properties of the aluminum fiber structure produced in Example 9 are shown in Table 1 below.

[0038] <Example 10> As in Example 1, aluminum fibers were formed into a sheet, and then sintered by heating the aluminum fibers at 900°C inside a sintering facility. After that, a glaze containing zirconia was applied to the surface of the aluminum fiber structure and then heated at a high temperature. When the cross-section of the aluminum fiber structure produced in this way was examined under a microscope, it was found that an alumina layer had been formed on the surface of the aluminum fibers, and that multiple alumina protrusions, greater in height than the thickness of the alumina layer, had been formed on this alumina layer or on the surface of the aluminum fibers. Furthermore, in such an aluminum fiber structure, a plasma-resistant layer containing zirconium oxide was formed on the surface of the alumina layer and the protrusions. The physical properties of the aluminum fiber structure produced in Example 10 are shown in Table 1 below.

[0039] <Comparative Examples 1-2> Aluminum fiber structures according to Comparative Examples 1 and 2 were fabricated in the same manner as in Example 1, except that the aluminum fibers were sintered by heating them at 680°C and 600°C, respectively, inside a sintering facility. When the cut surfaces of the fabricated aluminum fiber structures according to Comparative Examples 1 and 2 were examined under a microscope, it was found that an alumina layer was formed on the surface of the aluminum fibers, but no alumina protrusions were formed on this alumina layer or on the surface of the aluminum fibers. The physical properties of the fabricated aluminum fiber structures according to Comparative Examples 1 and 2 are shown in Table 1 below. <Comparative Example 3> As Comparative Example 3, an aluminum plate made of material A1070 was used.

[0040] <Rating> The coefficient of linear expansion at 40°C was measured for the aluminum fiber structures of Examples 1-10 and Comparative Examples 1-3. The results are shown in Tables 1 and 2 below. In Tables 1 and 2, the coverage rate refers to the coverage rate of the protrusions on the surface of the aluminum fibers in the cross-section when the aluminum fiber structure is cut. This was calculated by dividing the length of the alumina layer in the area covered by the protrusions (specifically, from the point where the peak of the protrusion begins to descend) by the total length of the alumina layer. In Comparative Examples 1-3, the coverage rate is 0%, which means that no alumina protrusions were formed. In Tables 1 and 2, the packing density refers to the packing density of the aluminum fibers in the aluminum fiber structure. This is the ratio of the area occupied by the aluminum fibers to the area inside the outer edge of the aluminum fiber structure in the cross-section when the aluminum fiber structure is cut.

[0041] [Table 1]

[0042] [Table 2]

[0043] Microscopic examination of the cross-sections of the aluminum fiber structures according to Examples 1-10 revealed that an alumina layer was formed on the surface of the aluminum fibers, and that multiple alumina protrusions, greater in height than the thickness of the alumina layer, were formed on this alumina layer or on the surface of the aluminum fibers. On the other hand, microscopic examination of the cross-sections of the aluminum fiber structures according to Comparative Examples 1-3 revealed that an alumina layer was formed on the surface of the aluminum fibers, but no alumina protrusions were formed on this alumina layer or on the surface of the aluminum fibers. Furthermore, the coefficient of linear expansion of the aluminum fiber structures according to Examples 1-10 and Comparative Examples 1-3 was measured. The coefficient of linear expansion of the aluminum fiber structures according to Examples 1-10 was all 22.0 or less, while the coefficient of linear expansion of the aluminum fiber structures according to Comparative Examples 1-3 was all greater than 23.0. From these results, it can be seen that the coefficient of linear expansion of the aluminum fiber structures can be reduced when aluminum fibers are sintered by heating them to 700°C or higher inside a sintering facility.

[0044] <Example 11> An aluminum composite material as shown in Figure 2 was fabricated by bonding two aluminum fiber structures with resin. The aluminum composite material according to Example 11 has resin partially impregnated into the aluminum fiber structures. Specifically, by partially impregnating the two aluminum fiber structures with resin, the aluminum fiber structures are positioned near the front and back surfaces of the resin, respectively, and these aluminum fiber structures protrude outward from the front and back surfaces of the resin. The aluminum fiber structures used were those according to Example 1, with each aluminum fiber structure having a thickness of 3.0 mm and a packing ratio of 75%. Epoxy resin was used as the adhesive layer, and the thickness of this adhesive layer was 125 μm.

[0045] <Example 12> An aluminum composite material, as shown in Figure 3, was fabricated by bonding two aluminum fiber structures with an adhesive layer consisting of silver paste. The aluminum fiber structures used were those described in Example 1, with each aluminum fiber structure having a thickness of 3.0 mm and a packing ratio of 75%. The thickness of the adhesive layer consisting of silver paste was 12 μm.

[0046] <Example 13> An aluminum composite material, as shown in Figure 4, was fabricated by bonding a copper plate to one side of an aluminum fiber structure using an adhesive layer made of copper paste. The aluminum fiber structure used was the one described in Example 3, with each aluminum fiber structure having a thickness of 1.0 mm and a packing ratio of 72%. The thickness of the adhesive layer made of copper paste was 48 μm. The copper plate used was made of C1100, had a thickness of 5.0 mm, and a packing ratio of 100%.

[0047] <Example 14> An aluminum composite material as shown in Figure 5 was fabricated by bonding a copper plate to one side of an aluminum fiber structure using an adhesive layer made of copper paste, and bonding an alumina plate to the other side of the aluminum fiber structure using an adhesive layer made of glass paste. The aluminum fiber structure used was the aluminum fiber structure according to Example 3, with each aluminum fiber structure having a thickness of 1.0 mm and a packing ratio of 72%. The thickness of the adhesive layer made of copper paste was 48 μm. The copper plate used was made of C1100 material, had a thickness of 0.5 mm, and a packing ratio of 100%. The thickness of the adhesive layer made of glass paste was 27 μm. The alumina plate used was 1.0 mm thick and had a packing ratio of 100%.

[0048] <Comparative Example 4> In contrast to Example 14, instead of using an aluminum fiber structure, an aluminum composite material as shown in Figure 5 was fabricated by bonding a copper plate to one side of an aluminum plate with an adhesive layer made of copper paste, and an alumina plate to the other side of the aluminum plate with an adhesive layer made of glass paste. The aluminum plate used had a thickness of 1.0 mm and a packing ratio of 100%. The thickness of the adhesive layer made of copper paste was 43 μm. The copper plate used was made of C1100, had a thickness of 0.5 mm, and a packing ratio of 100%. The thickness of the adhesive layer made of glass paste was 34 μm. The alumina plate used had a thickness of 1.0 mm and a packing ratio of 100%.

[0049] <Comparative Example 5> An alumina composite material was fabricated by bonding a copper plate to one side of an alumina plate using an adhesive layer made of glass paste. The alumina plate used had a thickness of 1.0 mm and a packing density of 100%. The thickness of the adhesive layer made of glass paste was 32 μm. The copper plate used was made of C1100, had a thickness of 0.5 mm, and a packing density of 100%.

[0050] <Rating> The adhesion and adhesive strength of the aluminum composite materials and alumina composite materials of Examples 11-14 and Comparative Examples 4-5 were evaluated. For adhesion, a heat shock test (500 cycles between -40°C and 120°C, with a total holding time of 30 minutes) was performed on the aluminum composite materials and alumina composite materials of Examples 11-14 and Comparative Examples 4-5, and whether or not delamination occurred was visually inspected. If no delamination occurred, it was evaluated as "○", and if partial delamination or lifting of the composite material occurred, it was evaluated as "×". For adhesive strength, the rate of change in adhesive strength was calculated before and after the above heat shock test for the aluminum composite materials and alumina composite materials of Examples 11-14 and Comparative Examples 4-5. This adhesive strength was measured by tensile strength in accordance with JIS K 6854-2:1999 (ISO 8510-2:1990). The change in adhesive strength before and after the heat shock test was evaluated as follows: less than 10% was rated "◎", less than 30% was rated "○", and 30% or more was rated "×". The evaluation results are shown in Table 3 below.

[0051] [Table 3]

[0052] As shown in the evaluation results in Table 3, when an aluminum fiber structure was used as the aluminum composite material, good adhesion and adhesive strength were achieved. Specifically, delamination was less likely to occur, and the adhesive strength did not change easily even with changes in ambient temperature. On the other hand, when an aluminum plate or alumina plate was used as the aluminum composite material instead of an aluminum fiber structure, the adhesion and adhesive strength were inferior compared to when an aluminum fiber structure was used. Thus, when an aluminum fiber structure is used as the aluminum composite material, delamination between the aluminum fiber structure and the composite material is less likely to occur even when the ambient temperature changes significantly.

Claims

1. An aluminum fiber structure in which aluminum fibers are partially bonded to each other, An alumina layer is formed on the surface of the aforementioned aluminum fiber, Multiple alumina protrusions, whose height is greater than the thickness of the alumina layer, are formed on the surface of the aluminum fiber or the alumina layer. The height of the protrusions on the surface of the aluminum fibers or the alumina layer is in the range of 10 nm to 10 μm. An aluminum fiber structure wherein the surface of the aluminum fibers in the cross-section of the aluminum fiber structure is covered with 20% or more of the protrusions.

2. The aluminum fiber structure according to claim 1, wherein at least some of the multiple protrusions are in contact with the alumina layer of the multiple aluminum fibers.

3. The aluminum fiber structure according to claim 1 or 2, wherein the thickness of the alumina layer is in the range of 10 nm to 10 μm.

4. The aluminum fiber structure according to any one of claims 1 to 3, characterized in that the protrusions cover a total of 40% or more of the surface of the aluminum fibers in the cross-section of the aluminum fiber structure.

5. The aluminum fiber structure according to any one of claims 1 to 4, wherein a plasma-resistant layer is formed on the surface of the alumina layer and the protrusions.

6. The aluminum fiber structure according to claim 5, wherein the plasma-resistant layer comprises a metal oxide or aluminum nitride.

7. A method for manufacturing an aluminum fiber structure according to any one of claims 1 to 6, The method for forming the protrusions is one in which the aluminum fibers are sintered at a temperature of 700°C or higher and the material dissolved from the aluminum fibers is used.

8. The aluminum fiber structure according to any one of claims 1 to 7, wherein the packing ratio of the aluminum fibers in the aluminum fiber structure is in the range of 20% to 90%.

9. An aluminum composite material comprising an aluminum fiber structure and a composite material according to any one of claims 1 to 8, An aluminum composite material in which the protrusions of the alumina and at least a portion of the composite material are in contact.

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