Bonding member, bonded structure, and method for forming hydrophilic film

Abstract

To provide a joint member that can improve hydrophilicity, and to provide a joint structure and a method for forming a hydrophilic film.SOLUTION: A joint member includes: a substrate containing a metal; a film provided at a surface of the substrate and containing a crystal of inorganic flux; and a plurality of linear bodies provided in the film and having hydrophilicity. Some of the linear bodies are exposed from the surface of the film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a bonding member, a bonding structure, and a method for forming a hydrophilic film. [Background technology]

[0002] There are joining members that contain metals such as aluminum and are joined to other members by joining methods such as brazing. There are also joining structures in which multiple members are joined by joining methods such as brazing. Generally, such joining members and joining structures are placed in the atmosphere. Therefore, water droplets formed by condensation of moisture in the atmosphere may form on the surfaces of the joining members and joining structures. If water droplets are present on the surfaces of the joining members and joining structures, corrosion may occur or functions such as heat exchange may be impaired.

[0003] Therefore, a technique has been proposed in which a film containing silica particles is provided on the surface of the bonded structure. The film containing silica particles is hydrophilic, making it easy to drain water droplets that form on the surface of the film. However, there is room for improvement in this technology in terms of improving hydrophilicity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-153343 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a bonded member, a bonded structure, and a method for forming a hydrophilic film that can improve hydrophilicity. [Means for solving the problem]

[0006] The joining member according to the embodiment is A joining member to be joined to another member,The device includes a substrate containing metal, a film containing crystals of inorganic flux provided on the surface of the substrate, and a plurality of linear bodies provided inside the film and having hydrophilic properties, some of the linear bodies being exposed from the surface of the film. The substrate includes aluminum or an aluminum alloy, the inorganic flux crystals are fluoride-based non-corrosive flux crystals, and the linear bodies are carbon nanotubes having polar functional groups on their surfaces or carbon nanofibers having polar functional groups on their surfaces. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view illustrating a joining member according to an embodiment of the present invention; [Figure 2] 1 is a schematic cross-sectional view illustrating a joint structure according to an embodiment of the present invention; [Figure 3] 1(a) to 1(e) are schematic process diagrams illustrating a method for manufacturing a bonded member and a bonded structure. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be illustrated with reference to the drawings. In each drawing, like components are designated by like reference numerals and detailed descriptions thereof will be omitted where appropriate.

[0009] FIG. 1 is a schematic cross-sectional view illustrating a joining member 1 according to the present embodiment. As shown in FIG. 1, the joining member 1 includes, for example, a substrate 2, a film 3, and a plurality of linear members 4. The substrate 2 may be, for example, plate-shaped or block-shaped. There are no particular limitations on the size or shape of the substrate 2. The substrate 2 may be, for example, flat, bent, or have a curved surface. The substrate 2 may contain a metal. The metal may be, for example, aluminum or an aluminum alloy. An example of an aluminum alloy is one in which at least one of copper, manganese, silicon, and magnesium is added to aluminum.

[0010] The film 3 is provided on the surface of the base material 2. The film 3 may contain, for example, an inorganic material. In this case, if the film 3 contains a flux used for joining such as brazing, the workability when joining the joining member 1 to another element can be improved. For this reason, the film 3 may contain crystals of an inorganic flux.

[0011] When the base material 2 contains aluminum or an aluminum alloy, a natural oxide film is formed on the surface of the base material 2, which inhibits the wettability of the brazing filler metal and makes joining difficult. Therefore, when the base material 2 contains aluminum or an aluminum alloy, it is preferable that the flux crystals contained in the film 3 be capable of removing the oxide film on the surface of the base material 2.

[0012] For example, the film 3 can contain crystals of a fluoride-based noncorrosive flux. Brazing using crystals of a fluoride-based noncorrosive flux can stabilize the quality of the joint compared to vacuum brazing, which does not use a flux. In this case, the crystals of the fluoride-based noncorrosive flux are activated when melted and remove the oxide film. Furthermore, the crystals of the fluoride-based noncorrosive flux before melting adhere firmly to aluminum and aluminum alloys. Another advantage is that the crystals of the fluoride-based noncorrosive flux before and after melting are insoluble in water, making them less susceptible to corrosion. Examples of the fluoride-based noncorrosive flux include potassium tetrafluoroaluminate (KAlF4), potassium zinc trifluoroaluminate (KZnF3), and cesium tetrafluoroaluminate (CsAlF4).

[0013] The film 3 can be provided on the entire surface of the substrate 2, on a portion of the surface of the substrate 2, or on a portion of the surface of the substrate 2. For example, if the film 3 contains crystals of a fluoride-based non-corrosive flux, the film 3 may be provided in the area where joining such as brazing is performed. However, the film 3 also has the function of holding a plurality of linear bodies 4 having hydrophilicity, which will be described later. Therefore, it is preferable that the film 3 be provided on the entire surface of the substrate 2. If the film 3 is provided on the entire surface of the substrate 2, the hydrophilicity described later can be imparted to the entire surface of the joining member 1. Furthermore, joining such as brazing can be performed at any position on the joining member 1. This makes it easy to use the joining member 1 for various purposes.

[0014] The plurality of linear bodies 4 are provided inside the membrane 3. Some of the plurality of linear bodies 4 are exposed from the surface of the membrane 3. The plurality of linear bodies 4 are hydrophilic. For example, the linear bodies 4 have polar functional groups such as OH groups (hydroxyl groups) on their surfaces. The linear bodies 4 may also contain carbon. For example, the linear bodies 4 may be carbon nanotubes having polar functional groups on their surfaces, or carbon nanofibers having polar functional groups on their surfaces.

[0015] Carbon nanotubes, carbon nanofibers, and the like are small, with diameters of about several nm and lengths of about several hundred μm. This makes it easy to disperse the linear bodies 4 in the mixed liquid 21 described below. If the linear bodies 4 are uniformly dispersed in the mixed liquid 21, it is possible to prevent the amount of polar functional groups on the surface of the joining member 1 from being distributed in the plane, thereby preventing unevenness in the hydrophilicity of the surface of the joining member 1. Furthermore, carbon nanotubes, carbon nanofibers, and the like have high thermal conductivity, so when the joining member 1 is used in the heat dissipation portion of a heat exchanger, the heat dissipation properties can be improved.

[0016] Here, for example, it is also conceivable to provide hydrophilic particles inside the film 3. However, if the linear bodies 4 are used, the surface area per unit volume can be made larger than that of particles, and therefore more polar functional groups can be provided. Therefore, if the linear bodies 4 are used, the hydrophilicity of the bonding member 1 can be improved compared to that of hydrophilic particles.

[0017] Furthermore, it is considered that the hydrophilicity of the bonding member 1 is positively correlated with the exposed area of ​​the linear bodies 4 on the surface of the membrane 3. In this case, if the particles are hydrophilic, the exposed area of ​​the particles will be small even if the particles are exposed from the surface of the membrane 3. Therefore, if the particles are hydrophilic, the number of polar functional groups on the surface of the bonding member 1 will be reduced.

[0018] In contrast, when the linear bodies 4 are used, the linear bodies 4 can be exposed along the surface of the film 3 or can be exposed so as to protrude from the surface of the film 3. This increases the exposed area of ​​the linear bodies 4, and therefore increases the number of polar functional groups on the surface of the bonding member 1. As a result, when the linear bodies 4 are used with hydrophilicity, the hydrophilicity can be improved compared to hydrophilic particles, etc.

[0019] The exposed area of ​​the linear body 4 can be confirmed, for example, by photographing the surface of the joining member 1 using a scanning electron microscope and then checking the photographed image.

[0020] In this case, by controlling the exposure of the linear bodies 4 by a coating method or the like, the water contact angle on the surface of the joining member 1 can be set to, for example, 1° or more and 30° or less. If the water contact angle is 1° or more and 30° or less, even if water droplets formed on the surface of the joining member 1 due to condensation of moisture in the atmosphere, the water droplets are easily discharged. Therefore, it is possible to prevent corrosion of the joining member 1 and the impairment of functions such as heat exchange.

[0021] Furthermore, if the linear bodies 4 are exposed so as to follow the surface of the membrane 3 or so as to protrude from the surface of the membrane 3, the surface roughness of the joining member 1 increases. In this case, as can be seen from Wenzel's equation, increasing the surface roughness can improve hydrophilicity.

[0022] FIG. 2 is a schematic cross-sectional view illustrating the joint structure 10 according to the present embodiment. 2 is a case where a plurality of second members 12 are provided. For example, the joined structure 10 illustrated in FIG. 2 can be an element provided in a heat dissipation portion of a heat exchanger. As shown in FIG. 2, the bonded structure 10 can have a first member 11, a second member 12, a film 3, a plurality of linear bodies 4, and a bonded portion 13.

[0023] The first member 11 may be, for example, plate-shaped or block-shaped. The first member 11 may have at least one groove 11a. The first member 11 illustrated in FIG. 2 has a plurality of grooves 11a. When a plurality of grooves 11a are provided, the grooves 11a may be arranged parallel to one another at a predetermined interval.

[0024] There are no particular limitations on the size or shape of the first member 11. For example, the shape of the first member 11 may be a plate, a columnar shape such as a cylinder or a cylindrical column, or a block shape such as a cube or a rectangular parallelepiped. The first member 11 may also be bent or have a curved surface.

[0025] The first member 11 may contain a metal. The metal may be, for example, aluminum or an aluminum alloy. For example, if the bonded structure 10 is an element provided in a heat dissipation portion of a heat exchanger, the material of the first member 11 is preferably a material with high thermal conductivity. In such a case, the material of the first member 11 may be, for example, aluminum or an aluminum alloy.

[0026] At least one second member 12 can be provided. For example, the number of second members 12 can be the same as the number of grooves 11a in the first member 11. Note that the joined structure 10 illustrated in FIG. 2 is provided with a plurality of second members 12. The second members 12 can be provided in the first member 11. Each of the plurality of second members 12 is provided in the groove 11a in the first member 11. By providing the vicinity of each end of the plurality of second members 12 inside the groove 11a, the plurality of second members 12 are provided parallel to one another at a predetermined interval.

[0027] The second member 12 may be, for example, a plate-like body. There are no particular limitations on the size or shape of the second member 12. The second member 12 may have, for example, a flat shape, a bent shape, or a curved surface. Furthermore, when multiple second members 12 are provided, the shapes and dimensions of the multiple second members 12 may be the same or different.

[0028] The second member 12 may include, for example, a metal. The metal may be, for example, aluminum or an aluminum alloy. When the bonded structure 10 is an element provided in a heat dissipation portion of a heat exchanger, the second member 12 may be a heat dissipation fin. In this case, the material of the second member 12 is preferably a material with high thermal conductivity. The second member 12 may include, for example, aluminum or an aluminum alloy.

[0029] The film 3 and the plurality of linear members 4 can be similar to those in the case of the joining member 1 described above. Here, when the joined structure 10 is placed in the atmosphere, water droplets formed by condensation of moisture in the atmosphere may form on the surface of the joined structure 10. Furthermore, when the joined structure 10 is an element provided in the heat dissipation portion of a heat exchanger, moisture in the atmosphere is more likely to condense, making water droplets even more likely to form on the surface of the joined structure 10. Water droplets on the surface of the joined structure 10 are more likely to cause corrosion. Furthermore, for example, when water droplets form between the second members 12, the flow of gas between the second members 12 may be obstructed, which may reduce the heat exchange rate.

[0030] As described above, some of the hydrophilic linear bodies 4 are exposed from the surface of the film 3. In this case, as described above, the water contact angle of the region where the film 3 is provided can be set to 1° or more and 30° or less. If the water contact angle is 1° or more and 30° or less, even if water droplets are formed, they are easily discharged. This can suppress the occurrence of corrosion and facilitate the flow of gas between the second members 12.

[0031] Here, since the surface area of ​​the second member 12 is larger than that of the first member 11, water droplets are likely to form on the second member 12. Furthermore, when the bonded structure 10 is an element provided in a heat dissipation portion of a heat exchanger, it is the second member 12 that mainly contributes to heat dissipation. Therefore, the film 3 can be provided at least on the surface of the second member 12.

[0032] Furthermore, as described above, when the first member 11 and the second member 12 are joined by brazing or the like, it is preferable that the film 3 contain crystals of an inorganic material-based flux. For example, as shown in Fig. 2, the film 3 containing crystals of an inorganic material-based flux can be provided so as to cover the first member 11 and the second member 12. In this way, brazing or the like at the joint portion between the first member 11 and the second member 12 becomes easier, and water droplets are more easily discharged from almost the entire surface of the joined structure 10.

[0033] The joint 13 joins the first member 11 and the second member 12. The joint 13 can contain a metal with a lower melting point than the materials of the first member 11 and the second member 12. For example, the joint 13 can be formed when the first member 11 and the second member 12 are brazed together. That is, the joint 13 can contain a metal with a lower melting point than the melting points of the metals contained in the first member 11 and the second member 12. When the materials of the first member 11 and the second member 12 are aluminum or an aluminum alloy, the joint 13 contains an Al-Si alloy, and the film 3 contains crystals of a fluoride-based non-corrosive flux.

[0034] Next, a method for forming a hydrophilic film according to this embodiment will be described. In the following, as an example, a case will be described in which the method for forming a hydrophilic film according to this embodiment is used to manufacture a bonded member 1 and a bonded structure 10. 3(a) to 3(e) are schematic process diagrams illustrating the method for manufacturing the joint member 1 and the joint structure 10. FIG. First, as shown in Fig. 3(a), polar functional groups such as OH groups are provided on the surface of the linear body 4. In the following, as an example, a case where polar functional groups are provided on the surface of a carbon nanotube will be described, but the same can be applied to a carbon nanofiber.

[0035] For example, a plurality of carbon nanotubes can be added to ozone water, and heated under reflux while stirring for a predetermined period of time, thereby providing polar functional groups on the surfaces of the plurality of carbon nanotubes. In this case, for example, the ozone concentration can be about 5 mgh / L, the amount of ozone water can be about 25 mL, the mass of the multiple carbon nanotubes to be added can be about 0.3 g, and the time to leave it while stirring can be 10 to 48 hours. As another example, the ozone concentration is set to about 16.6 mgh / L, the amount of ozone water is set to about 40 mL, and the mass of multiple carbon nanotubes added is set to about 0.04 g. After stirring, the solution is left to stand for 10 to 480 hours, whereby the ozone in the solution is consumed and dissipated, thereby obtaining an aqueous solution of multiple carbon nanotubes having polar functional groups on their surfaces.

[0036] Subsequently, the carbon nanotubes are separated from the ozone water (solution) by filtration, and the separated carbon nanotubes are washed with pure water. It is preferable that the separated carbon nanotubes become neutral after washing. Subsequently, the washed carbon nanotubes are dried to obtain a plurality of carbon nanotubes having polar functional groups on the surface.

[0037] Next, a mixed solution 21 is prepared containing a plurality of carbon nanotubes (linear bodies 4) having polar functional groups on their surfaces, a fluoride-based non-corrosive flux, and at least one of water and a solvent. By preparing the mixed solution 21, it becomes easy to form a film 3 containing a plurality of linear bodies 4 on the surface of objects having various shapes.

[0038] For example, as shown in FIG. 3(b), a mixture 21 can be produced by supplying a plurality of carbon nanotubes (linear bodies 4) having polar functional groups on their surfaces or an aqueous solution thereof, a fluoride-based non-corrosive flux, and at least one of water and a solvent into a container 20 and stirring them. The solvent can be, for example, alcohol. When producing the mixture 21, a surfactant can be further supplied into the container 20 and stirred. When a surfactant is supplied, the surfactant can be, for example, a cationic surfactant, a modified polymer containing a carboxyl group, or the like.

[0039] The mixed solution 21 may further contain a binder resin. The binder resin is preferably one that can adhere the crystals (film 3) of the fluoride-based non-corrosive flux to the surface of the object and is decomposed in the heating step described below. The binder resin may be, for example, an acrylic resin, a urethane resin, or an elastomer resin.

[0040] The mixed solution 21 may contain, for example, 0.02 wt% to 2 wt% carbon nanotubes having polar functional groups on their surfaces, 0.1 wt% to 2.0 wt% fluoride-based non-corrosive flux, 16.0 wt% to 19.87 wt% water, and about 80 wt% ethanol. If a surfactant is further added, it may contain, for example, about 0.0001% to 0.01 wt% of a carboxyl group-containing polymer-modified surfactant.

[0041] 3(c), the mixed liquid 21 is applied to the surface of the substrate 2. In this case, the mixed liquid 21 may be applied to the entire surface of the substrate 2, or may be applied to a predetermined region. 3(d), the mixed liquid 21 is applied to the surface of the structure in which the second member 12 is attached to the first member 11. In this case, the mixed liquid 21 may be applied to the entire surface of the structure, or may be applied to a predetermined area.

[0042] There is no particular limitation on the method for applying the mixed liquid 21. The mixed liquid 21 can be applied to the surface of the object using, for example, a spray method, a coater method, or the like. Alternatively, the mixed liquid 21 can be applied to the surface of the object by, for example, immersing the object in the mixed liquid 21.

[0043] Next, the object coated with the mixed liquid 21 is heated to crystallize the fluoride-based non-corrosive flux contained in the mixed liquid 21, thereby forming a film 3 including a plurality of carbon nanotubes (linear bodies 4) having polar functional groups on the surface. For example, the heating temperature can be about 600°C, and the heating time can be about 30 minutes.

[0044] As shown in FIG. 3(e), multiple carbon nanotubes (linear bodies 4) are provided inside the membrane 3, and some of the carbon nanotubes (linear bodies 4) are exposed from the surface of the membrane 3. This improves the hydrophilicity of the surface of the membrane 3. Furthermore, the membrane 3 contains crystals of a fluoride-based non-corrosive flux, which improves workability in brazing and other processes. For example, when joining the joining member 1 to another element, it is possible to omit the supply of flux.

[0045] In this manner, the bonding member 1 having the substrate 2, the film 3, and the plurality of linear members 4 can be manufactured. When manufacturing the joint structure 10, a brazing paste is supplied to the joints between the multiple second members 12 and the first members 11, and then heated to form the joints 13. In this case, since the film 3 contains crystals of a fluoride-based non-corrosive flux, the supply of flux can be omitted, thereby improving the workability of brazing and other processes.

[0046] Furthermore, in the heating step for forming the film 3 described above, joining such as brazing can also be performed. For example, the applied mixed liquid 21 is dried to a certain extent, and a brazing paste is supplied to the joining portion between the first member 11 and the second member 12. Subsequently, the mixed liquid 21 and the brazing paste are heated simultaneously using a heating furnace or the like, thereby forming the film 3 and the joining portion 13 together. In this way, the productivity of the joined structure 10 can be improved.

[0047] As described above, the method for forming a hydrophilic film according to this embodiment can include the following steps. A step of producing a mixed solution 21 containing a plurality of linear bodies 4 having polar functional groups on the surface, an inorganic flux, and at least one of water and a solvent. A step of applying the mixture 21 to the surface of an object containing metal. A step of heating the object onto which the mixed liquid 21 has been applied. Then, in the process of heating the object, crystals of the inorganic flux are formed, and parts of the plurality of linear bodies 4 are exposed from the surface of the crystals of the inorganic flux.

[0048] In this case, the object may include aluminum or an aluminum alloy, and the inorganic flux may be a fluoride-based non-corrosive flux. The linear body 4 can be a carbon nanotube having a polar functional group on the surface thereof, or a carbon nanofiber having a polar functional group on the surface thereof.

[0049] The object can also have a first member 11 containing a metal and a second member 12 containing a metal. The method can further include a step of applying a paste containing a metal having a melting point lower than the melting point of the metal contained in the first member 11 and the metal contained in the second member 12 to the joint between the first member 11 to which the mixed liquid 21 has been applied and the second member 12. In the step of heating the object, crystals of the inorganic flux are formed and the paste is melted, forming joint 13 that joins first member 11 and second member 12 together.

[0050] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0051] REFERENCE SIGNS LIST 1 Bonding member, 2 Base material, 3 Film, 4 Linear body, 10 Bonding structure, 11 First member, 11a Groove, 12 Second member, 13 Bonding portion, 21 Mixed liquid

Claims

1. A joining member to be joined to another member, a substrate including a metal; a film provided on the surface of the substrate and containing crystals of an inorganic flux; a plurality of linear bodies provided inside the membrane and having hydrophilic properties; Equipped with a portion of the plurality of linear bodies is exposed from the surface of the film; the substrate comprises aluminum or an aluminum alloy; the inorganic flux crystals are fluoride-based non-corrosive flux crystals, The linear body is a joining member that is a carbon nanotube having a polar functional group on the surface thereof, or a carbon nanofiber having a polar functional group on the surface thereof.

2. a first member including a metal; a second member provided on the first member and including a metal; At least a film provided on the surface of the second member and containing crystals of inorganic flux; a plurality of linear bodies provided inside the membrane and having hydrophilic properties; a joining portion that includes a metal having a melting point lower than the melting points of the metal contained in the first member and the metal contained in the second member, and that joins the first member and the second member provided on the first member; Equipped with a portion of the plurality of linear bodies is exposed from the surface of the film; the first member and the second member contain aluminum or an aluminum alloy; the inorganic flux crystals are fluoride-based non-corrosive flux crystals, The linear bodies are carbon nanotubes having polar functional groups on the surface thereof, or carbon nanofibers having polar functional groups on the surface thereof.

3. A step of preparing a mixed solution containing a plurality of linear bodies having polar functional groups on their surfaces, an inorganic flux, and at least one of water and a solvent; applying the mixture to a surface of an object containing metal; heating the object onto which the mixed liquid has been applied; Equipped with the object comprises aluminum or an aluminum alloy; the inorganic flux is a fluoride-based non-corrosive flux, the linear body is a carbon nanotube having a polar functional group on its surface, or a carbon nanofiber having a polar functional group on its surface, A method for forming a hydrophilic film, wherein, in the step of heating the object, crystals of the inorganic flux are formed, and a portion of the plurality of linear bodies is exposed from the surface of the crystals of the inorganic flux.

4. the object has a first member containing a metal and a second member containing a metal; the method further comprises a step of applying a paste containing a metal having a melting point lower than the melting points of the metal contained in the first member and the metal contained in the second member to a joint portion between the first member and the second member to which the mixed liquid has been applied, 4. The method for forming a hydrophilic film according to claim 3, wherein in the step of heating the object, crystals of the inorganic flux are formed and the paste is melted to form a joint that joins the first member and the second member.

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