JP2019110138A - Joint body and joint method - Google Patents

Abstract

To provide a joint method capable of effectively jointing various materials as compared to the conventional anode joint method.SOLUTION: A joint body comprises: an oxygen ion conductor; a first jointed material arranged to one surface of the oxygen ion conductor, to which an oxide layer is provided to the surface, and which includes conductivity; and a second jointed material arranged onto the other surface of the oxygen ion conductor, and including an electron conductivity. In a contact interface between the oxide layer of the first jointed material and the oxygen ion conductor, a covalent binding is formed. In a contact interface between the second jointed material and the oxygen ion conductor, the covalent binding is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bonding method.

  Conventionally, an anodic bonding method is known as one of methods of bonding materials by an electrochemical reaction (see, for example, Patent Document 1). The anodic bonding method is a method in which glass and a material to be bonded are brought into contact, and bonding is performed by applying a DC voltage between the material to be bonded as an anode and the glass side as a cathode.

JP 2007-83436A

  The materials can be strongly bonded by the above-described anodic bonding method. However, the materials to be joined are limited to glass, metal, semiconductor and the like, and their applications have been limited.

  Furthermore, in the case of joining members having a three-layer structure by the conventional anodic bonding method, two layers are joined, and after the jig holding the joined two layers is detached, the third layer is mounted, and then There is also a problem that the process is bulky because it is necessary to reattach the jig, change the polarity of the applied voltage, and apply the voltage.

  The present invention has been made in view of the above problems, and the object of the present invention is to propose a bonding method capable of bonding various materials more efficiently than the conventional anodic bonding method. It is.

In order to solve the above-mentioned subject, the zygote concerning the 1st viewpoint is an oxygen ion conductor,
A conductive first bonding material provided with an oxide layer on the surface, disposed on one surface of the oxygen ion conductor;
A second bonding material having electron conductivity disposed on the other surface of the oxygen ion conductor;
Equipped with
A covalent bond is formed at the contact interface between the oxide layer of the first material to be joined and the oxygen ion conductor.
A bonded body, wherein a covalent bond is formed at a contact interface between the second bonding material and the oxygen ion conductor.

  According to the present invention, more diverse materials can be joined more efficiently than the conventional anodic bonding method.

3 is a flow chart of the bonding method according to the invention. It is a figure explaining the method to join an oxygen ion conductor and two to-be-joined materials. It is a figure explaining the Example which joins an oxygen ion conductor and two metals. It is a figure explaining the example which connects two piping via the packing of an oxygen ion conductor. It is a figure explaining the example which connects two piping using the tape for joining sealing. It is a figure explaining the Example which forms the single cell of a solid oxide fuel cell (SOFC). It is a figure explaining the Example which produces a cell stack. FIG. 7 is a diagram illustrating an example of producing another cell stack.

  Hereinafter, the bonding method according to the present invention will be described with reference to the drawings. FIG. 1 shows a flow chart of the bonding method according to the invention. In the bonding method according to the present invention, the first bonding material having conductivity provided with an oxide layer on one surface of the oxygen ion conductor is disposed such that the oxide layer is in contact with the first bonding material. An arrangement step (step S1) of arranging a second bonding material having electron conductivity on the other surface of the oxygen ion conductor, and connecting the first bonding material to the negative electrode side of the voltage application device A connecting step (step S2) of connecting the second material to be bonded to the positive electrode side of the voltage application device, and a voltage applying step of applying a voltage between the first material to be bonded and the second material to be bonded And step S3).

  The present inventors attempted to join various materials under various conditions in order to establish a bonding method capable of bonding various materials more efficiently than the conventional anodic bonding method. As a result, the oxygen ion conductor and the conductive material provided with the oxide layer on the surface are disposed so as to be in contact with each other via the oxide layer, and the oxygen ion conductor is conducted on the positive electrode side of the voltage application device When materials were respectively connected to the negative electrode side of the voltage application device and a DC voltage was applied, it was discovered that both were firmly joined.

  The reason why the above-mentioned strong bond is formed is that, when a voltage is applied between the oxygen ion conductor and the conductive material, between the oxygen ion conductor (X-O) and the oxide layer (R-O) It is considered that a reduction reaction as shown in the following formula (1) occurs.

X-O + R-O + 2e → X-O-R + O ^2- (1)

According to the above-mentioned reduction reaction, the oxide constituting the oxide layer (R-O) of the conductive material is reduced, and between the reduced oxide material (R) and the oxygen ion conductor (X-O) A bond (X-O-R) is formed on the surface, and the oxygen ion conductor and the conductive material are firmly joined at the contact surface. On the other hand, O ²⁻ ions generated in the reduction reaction move in the oxygen ion conductor, move to the anode side, and are discharged. Thus, as a result of the reduction reaction occurring in the member on the cathode side, it is considered that a strong bond is formed between the oxygen ion conductor and the conductive material.

  The reduction reaction represented by the above formula (1) is considered to be a reaction in contrast to the electrochemical reaction which occurs in the conventional anodic bonding method. That is, when, for example, glass (X-O-Na) and metal (M) are bonded by anodic bonding, the following formula (2) is formed between glass (X-O-Na) and metal (M) It is considered that the oxidation reaction as shown in (4) to (4) occurs.

^{X-O-Na → X-} O - + Na + (2)
^{X-O - + M → X} -O-M + e (3)
Na ⁺ + e → Na (4)

The above reaction formula (2) and (3) is a reaction taking place at the anode side (the contact interface), Na is X-O disengaged ionized ^- has generated, bonding and bonded to M is formed Be done. On the other hand, the reaction of the formula (4) is a reduction reaction which occurs on the negative electrode side, and Na ⁺ which has moved toward the cathode side in the glass receives an electron and is reduced to Na.

  Thus, the bonding method according to the present invention based on the reduction reaction at the cathode is a novel bonding method in contrast to the conventional anodic bonding method based on the oxidation reaction at the anode, and compared to the conventional anodic bonding method It shall be called “junction method”. Various materials can be firmly bonded by this cathode bonding method.

Moreover, as is clear from the above formulas (2) to (4), it is Na ⁺ that carries electricity in the glass, and no single O ^{2 −} is present. Since Na is deposited on the cathode side, it becomes a source of contamination or causes peeling of plating at the interface when there is a plating surface on the glass. In this respect, in the present invention, since oxygen ion conduction is borne by O ²⁻ , a junction corresponding to both oxidation and reduction is formed. Since oxygen is a gas, the problems of contamination and peeling off that occur in the reaction in the glass do not occur.

  The present inventors further process the formation of a member having a three-layer structure, which requires a complicated process when using the conventional anodic bonding method by combining the above-mentioned cathode bonding method and the conventional anodic bonding method. It has been found that it can be done efficiently. That is, as shown in FIG. 2, the oxide layer 2 a corresponds to the first material to be joined 2 having the oxide layer 2 a provided on the surface on one surface of the oxygen ion conductor 1. And the second to-be-joined material 3 having electron conductivity is disposed on the other surface of the oxygen ion conductor 1, and the first to-be-joined material 2 is connected to the negative electrode side of the voltage application device. When the second bonding material 3 is connected to the positive electrode side of the voltage application device and a DC voltage is applied between the first bonding material 2 and the second bonding material 3, one time The first bonding material 2 and the second bonding material 3 can be bonded by applying a voltage.

  As described above, according to the bonding method of the present invention, various materials can be bonded to each other as compared with the conventional anodic bonding method. In addition, the first bonding material 2 and the second bonding material 3 can be efficiently bonded via the oxygen ion conductor 1 and the oxide layer 2 a of the first bonding material 2. Hereinafter, each process of this invention is demonstrated.

  First, in step S1, the first bonding material 2 having conductivity provided with the oxide layer 2a on one surface of the oxygen ion conductor 1 is disposed such that the oxide layer 2a abuts At the same time, the second material to be joined 3 having electron conductivity is disposed on the other surface of the oxygen ion conductor 1 (arrangement step). For example, as shown in FIG. 2, the first bonding material 2 is brought into contact with one surface of the oxygen ion conductor 1 via the oxide layer 2a, and the second bonding material 3 is made an oxygen ion conductor. Contact the other surface of 1

The oxygen ion conductor 1 is a layer having the property of transmitting oxygen ions. The material of the oxygen ion conductor 1 is not particularly limited as long as it allows oxygen ions to permeate, but an oxide ion conductor is preferable. For example, stabilized zirconia (YSZ) doped with yttria (Y ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), samaria (Sm ₂ O ₃ ), gadolia (Gd ₂ O ₃ ), scandia (Sc ₂ O ₃₎ Etc. can be used. Also, bismuth oxide (Bi ₂ O ₃ ), cerium oxide (CeO), zirconium oxide (ZrO ₂ ), lanthanum gallate oxide (LaGaO ₃ ), indium barium oxide (Ba ₂ In ₂ O ₅ ), nickel lanthanum oxide (La ₂ O ₃ ) ₂ NiO ₄ ), nickel potassium fluoride (K ₂ NiF ₄ ), or the like can also be used.

  In addition, the material of the oxygen ion conductor 1 is not limited to said thing, Another well-known oxygen ion conductor material can be used. These materials may be used alone or in combination of two or more.

  Typically, the oxygen ion conductor 1 is obtained by mixing the powder of the raw material with an organic binder, applying pressure and stretching thinly, and using a hot press method of pressure sintering in a high temperature furnace. be able to. The thinner oxygen ion conductor 1 can be produced by a sol-gel method.

  The first bonding material 2 can be used in the present invention as long as it is a material having conductivity and capable of forming a covalent bond with oxygen of the oxide layer 2a. For example, metals or semiconductors (Si, SiC, GaN, etc.) can be used. As the metal, for example, various metals such as SUS can be used. Here, the bonded body of the oxygen ion conductor 1 and the first bonding material 2 is a single cell of a solid oxide fuel cell (Solid Oxide Fuel Cell, hereinafter also referred to as "SOFC" or "fuel cell"). A portion of the oxygen ion conductor 1 may be a solid electrolyte made of YSZ or the like, and the first material to be joined 2 may be an electrode material for an air electrode or a fuel electrode connected to both sides of the solid electrolyte. it can. Since SOFCs are usually operated at a high temperature of 800 ° C. or higher, it is preferable to select a material that can withstand this temperature and is not electrodeposited by the redox reaction during power generation. The first bonding material 2 as an electrode material in this case is well known as, for example, a stable electrode material of SOFC, and is high as a barrier metal for suppressing alloy reaction in a high temperature environment between multilayer materials. It is possible to use a metal (including SUS) coated with nickel or Si which has a track record.

  The oxide layer 2 a is a layer provided on the surface of the first bonding material 2 and made of an oxide. The oxide layer 2a is, for example, a thermal oxide film formed by subjecting the surface of the first bonding material 2 to a thermal oxidation treatment, a chemical vapor deposition (CVD) method, a physical vapor phase, or the like. An oxide film formed on the surface of the first workpiece 2 can be obtained by a physical vapor deposition (PVD) method. Also, a natural oxide film formed on the surface of the first bonding material 2 can be used.

  The oxide layer 2a preferably has electron conductivity. Thereby, the oxide which comprises the oxide layer 2a can be reduce | restore efficiently. An N-type oxide semiconductor can be used as the oxide layer 2a having such electron conductivity. That is, in the n-type oxide semiconductor, electrons of the n-type dopant are excited to the conduction band at a temperature lower than the intrinsic temperature to have electron conductivity. Therefore, it is preferable to form the oxide layer 2a of an N-type oxide semiconductor that exhibits electronic conductivity at the temperature at the time of bonding. As such an N-type doped oxide semiconductor, ZnO (zinc oxide: zinc oxide), ITO (indium tin oxide), TiO (titanium oxide), or the like can be used.

  Further, even when the oxide layer 2a is an insulating film not having electron conductivity, the oxide layer 2a should be thin enough to allow electrons to pass through in the thickness direction of the oxide layer 2a. Thus, the oxide layer 2a can be made to have electron conductivity. The specific thickness of the oxide layer 2a in this case depends on the oxide constituting the oxide layer 2a, and thus can not be generally defined. For example, when the conductive material 2 is formed of a metal, it is about 50 Å If the thermal oxide film has a thickness of, it is possible for electrons to pass through in the thickness direction.

  The second bonding material 3 is a material capable of forming a stable covalent bond with oxygen, and preferably has electron conductivity. Thereby, the 2nd to-be-joined material 3 can be oxidized efficiently. Here, as a material having electron conductivity and forming a stable bond with oxygen, for example, Ni (nickel), Ti (titanium), W (tungsten) or the like can be used as the metal. An N-type semiconductor can be used as a material having similar properties to those of metals. In an N-type semiconductor, electrons at the donor level rise to the conduction band at relatively low temperatures and exhibit electron conduction. For example, Si or SiC can be used as such a semiconductor.

  Furthermore, as a material of the second bonding material 3, an intrinsic semiconductor having electron conductivity at a temperature at the time of bonding can be used. Specifically, this is an intrinsic semiconductor with a small band gap, and at the junction temperature, electrons in the valence band are excited to the conduction band to have high electron conductivity. As such an intrinsic semiconductor, Si can be used, for example, when the working temperature is 400 ° C. or higher. The conductivity type at room temperature may be either P-type or N-type.

In addition, even when the second bonding material 3 is an oxide film of an insulator having no electron conductivity, electrons can tunnel through the second bonding material 3 in its thickness direction. The second bonding material 3 can be made to have electron conductivity by being thin to a certain extent. The specific thickness of the second material to be joined 3 in this case depends on the material constituting the second material to be joined 3 and thus can not be specified indiscriminately, but for example, the second material to be joined 3 is SiO _{In the case of (2)} , if the thickness is effectively about 50 Å, electrons can pass through in the thickness direction. Here, "effectively" is because the effective barrier thickness of the oxide film is changed by the electric field. It is well known that the higher the voltage applied, the thinner the effective barrier thickness that can be penetrated. That is, when the voltage is very low (about 1 V), the current flows if the thickness of the insulator is about 50 Å, but does not flow if the thickness is 100 Å. However, when the voltage is increased, the electric field of the insulator is increased, and a phenomenon called "Furanaudheim tunnel" occurs, and a current flows in the insulator. This indicates that the effective thickness of the insulator has been reduced to 50 Å.

  In the present invention, by applying a high voltage of several hundred volts, the contact surfaces between the oxygen ion conductor 1 and the first material to be joined 2 and the oxygen ion conductor 1 and the second object to be joined The contact surfaces of the material 3 are strongly drawn together by electrostatic attraction. When the abutting surfaces approach each other to an interatomic distance, covalent bonds are formed between the atoms of the adjacent abutting surfaces by the above-described electrochemical reaction. Therefore, the flatness of the planned bonding surface is important, and it is desirable to finish as mirror surface as possible. Specifically, at least one of the contact surface between the oxygen ion conductor 1 and the first bonding material 2 and the contact surface between the oxygen ion conductor 1 and the second bonding material 3 is mirror-polished. Thus, at least one of the oxygen ion conductor 1 and the first bonding material 2 and at least one of the oxygen ion conductor 1 and the second bonding material 3 can be in close contact with each other. It is preferable to be thinly configured. Thereby, the bonding strength of at least one of the contact surface between the oxygen ion conductor 1 and the first bonding material 2 and the contact surface between the oxygen ion conductor 1 and the second bonding material 3 is increased. it can.

  Next, in step S2, while connecting the 1st to-be-joined material 2 to the negative electrode side of the voltage application apparatus V, the 2nd to-be-joined material 3 is connected to the positive electrode side of the voltage application apparatus V (connection process). For example, as shown in FIG. 2, the electrode plate P connected to the negative electrode of the voltage application device V is brought into contact with the surface of the first bonding material 2 opposite to the oxide layer 2a, and the second bonding is performed. An electrode plate P connected to the positive electrode of the voltage application device V is brought into contact with the surface of the material 3 opposite to the oxygen ion conductor 1.

  In this connection step, it is intended that “directly” connect the second bonding material 3 to the positive electrode side of the voltage application device V and connect the first bonding material 2 to the negative electrode side of the voltage application device V. It is not something to do. That is, in this connection step, in step S3 described later, a voltage is applied such that a voltage is applied between the two in a state where the potential of the second material 3 to be joined is higher than the potential of the first material 2 It is intended to be connected to the device V.

  Subsequently, in step S3, a voltage is applied between the first bonding material 2 and the second bonding material 3 (voltage application step). Specifically, as shown in FIG. 2, the electrode plate P on the positive electrode side and the electrode plate on the negative electrode side are heated while heating the oxygen ion conductor 1, the first bonding material 2 and the second bonding material 3 Apply a DC voltage between P and P. In the oxygen ion conductor 1, the oxygen ion conductivity increases as the temperature rises, and electricity flows. As a result, the oxygen ion conductor 1 and the oxide layer 2a, and hence the first bonding material 2 are bonded by cathode bonding, and the oxygen ion conductor 1 and the second bonding material 3 are bonded by anodic bonding. It is joined. As described above, the first bonding material 2 and the second bonding material 3 disposed on both sides of the oxygen ion conductor 1 can be efficiently applied to the oxygen ion conductor 1 only by one voltage application. And it can be joined firmly.

  The voltage applied between the first bonding material 2 and the second bonding material 3 has an optimum range according to the temperature because the resistance value of the oxygen ion conductor changes depending on the working temperature. It is selected according to the application in consideration of the material characteristics of the oxygen ion conductor 1 and the use condition after bonding. If the working temperature or voltage is too low, the oxygen ion conduction current of the oxygen ion conductor 1 decreases, and the time required for forming a junction becomes long. On the other hand, when the temperature is high, the time required for forming a bond becomes short, but the residual stress after bonding becomes large, which is unsuitable from the viewpoint of durability. If the voltage is too high, discharge to other than the junction occurs and the junction becomes difficult. Typically, it is preferable to select an optimum value in the range of voltage 50 V or more and 500 V or less under the temperature condition of 300 ° C. or more and 500 ° C. or less. Thereby, the first bonding material 2 and the second bonding material 3 disposed on both surfaces of the oxygen ion conductor 1 can be more efficiently and strongly bonded to the oxygen ion conductor 1 .

  Next, the time for applying a voltage between the first bonding material 2 and the second bonding material 3 will be described. In the contact surface between the first bonding material 2 to be the negative electrode and the oxygen ion conductor 1, the oxide constituting the oxide layer 2a of the first bonding material 2 is reduced and reduced A strong covalent bond is formed between the material and the oxygen ion conductor 1. Thus, the first bonding material 2 and the oxygen ion conductor 1 are chemically bonded.

  On the other hand, a strong bond is formed between the second bonding material 3 on the positive electrode side and the oxygen ion conductor 1 by an oxidation reaction by oxygen ions. The supply of oxygen ions is performed by the reduction reaction on the negative electrode side, that is, the oxygen ions generated by the reduction of the oxide layer 2a and the oxygen ions in the air which are ionized by receiving electrons from the electrode plate P on the negative electrode side. Both can be involved. Thus, oxygen ions generated on the negative electrode side of the oxygen ion conductor 1 move in the oxygen ion conductor 1 and pass electrons to the second member 3 at the interface with the second member 3 Thus, a strong covalent bond is formed with the constituent atoms of the oxygen ion conductor 1 and the second bonding material 3. Thus, the second bonding material 3 and the oxygen ion conductor 1 are chemically bonded. At this time, oxygen ions generated by the reduction reaction of the oxide layer 2a move in the oxygen ion conductor 1 and are used for the above-mentioned oxidation reaction, and the surplus is discharged to the atmosphere.

  Next, the standard of joining time is explained. In the present invention, since two junctions are simultaneously formed, it is possible to determine the optimum time reference by paying attention to the change of the current value. Shortly after the start, while the bonding area of the first bonding material 2 (including the oxide layer 2a) and the oxygen ion conductor 1 and the second bonding material 3 is expanded, the current value is slightly small. The average current shows an increasing trend while repeating the When the bonding on both the positive electrode side and the negative electrode side is almost complete, the average current turns to decrease. It is preferable that the point at which the current value starts to decrease is used as an indication for stopping the application of the voltage. Thereby, the oxygen ion conductor 1 and the conductive material 2 can be firmly bonded over the entire bonding surface.

  Depending on the chemical properties and combinations of the materials to be joined, there may be a portion where the reduction of the oxide layer 2a and the oxidation of the second material 3 to be joined are incomplete only by performing the DC voltage application step. In such a case, it is possible to improve by applying an alternating voltage between the first material to be joined 2 and the second material to be joined 3 after the voltage applying step of step S3 (AC voltage applying step).

  By repeated application of forward and reverse voltage by this AC voltage, the incompletely reduced part is once reduced and then reduced again. In addition, the incompletely oxidized portion is reoxidized after being reduced once.

  Unreacted or unbonded in the joint portion between the oxygen ion conductor 1 and the oxide layer 2 a and the joint portion between the oxygen ion conductor 1 and the second bonding material 3 by these rereduction and reoxidation reactions. It is possible to make atoms in incomplete arrangement transition to more stable states. Thereby, the first bonding material 2 and the second bonding material 3 disposed on both surfaces of the oxygen ion conductor 1 can be more efficiently and strongly bonded to the oxygen ion conductor 1 .

  The frequency of the AC voltage is set low enough that incomplete bonding at the junction surface causes reoxidation and rereduction.

  Thus, the first bonding material 2 and the second bonding material 3 disposed on both surfaces of the oxygen ion conductor 1 can be efficiently and firmly bonded to the oxygen ion conductor 1. In addition, according to the bonding method of the present invention, more various materials can be bonded than the conventional anodic bonding method.

  Further, at the time of performing the disposing step, at least one of the contact surface between the oxygen ion conductor 1 and the first bonding material 2 and the contact surface between the oxygen ion conductor 1 and the second bonding material 3 However, by processing so as to be in close contact with each other, the contact surface between the oxygen ion conductor 1 and the first bonding material 2 and the contact surface between the oxygen ion conductor 1 and the second bonding material 3 At least one bonding strength can be increased.

  Moreover, the oxide layer 2a can reduce the oxide which comprises the oxide layer 2a efficiently by having electronic conductivity. An N-type oxide semiconductor can be used as the oxide layer 2a having such electron conductivity. Further, even in the case where the oxide layer 2a is an insulating film having no electron conductivity, the oxide layer 2a may be formed as thin as possible so that electrons can pass through in the thickness direction. 2a can be made to have electron conductivity.

  Moreover, when the 2nd to-be-joined material 3 has electron conductivity, the to-be-joined material 3 can be oxidized efficiently. The second bonding material 3 having such electron conductivity can be made of either a metal, an N-type semiconductor, or an intrinsic semiconductor having electron conductivity at the temperature at the time of bonding. In addition, even in the case where the second bonding material 3 is an oxide film of an insulator having no electron conductivity, electrons can pass through the second bonding material 3 in the thickness direction thereof. By making it thin, the second bonding material 3 can be made to have electron conductivity.

In addition, since the oxygen ion conductor 1 is an oxide ion conductor, the O ²⁻ ions can be favorably moved in the oxygen ion conductor 1, moved to the anode side, and discharged.

  In addition, after the (direct current) voltage application step, by applying an alternating voltage between the first and second members 2 and 3, the incompletely reduced portion is once oxidized again. A portion which has been reduced and which is incompletely oxidized is once reduced and then reoxidized, and the first material to be joined 2 and the second material to be joined 3 disposed on both sides of the oxygen ion conductor 1 It can be more firmly bonded to the conductor 1.

  Hereinafter, some examples of the present invention will be specifically described, but the present invention is not limited thereto.

Example 1: Joining Two Metals
In the present embodiment, two metals are joined via an oxygen ion conductor. FIG. 3A shows the oxygen ion conductor 11 and the two metals 12 and 13 to be bonded. An oxidation process is applied to one surface of the metal 12 to form an oxide layer 12a. These metals 12 and 13 are disposed on both surfaces of the oxygen ion conductor 11 as shown in FIG. 3 (b).

  Next, as shown in FIG. 3C, the metal 13 is connected to the electrode plate P on the positive electrode side of the voltage application device V, and the metal 12 is connected to the electrode plate P on the negative electrode side. Then, a DC voltage is applied between the metal 12 and the metal 13 while heating the oxygen ion conductor 11 and the metals 12 and 13. Thus, the oxygen ion conductor 11 and the metal 13 are joined (joined 1), and the oxygen ion conductor 11 and the oxide layer 12a of the metal 12 are joined (joined 2). Thus, the junction 10 in which the two metals 12 and 13 are joined can be formed by one voltage application.

(Example 2: Connection of two pipes by packing)
In the present embodiment, two pipes for high temperature gas and liquid in which packing of resin or rubber material can not be used are connected. FIG. 4A shows a cross section of the two pipes 22 and 23 to be connected. As shown in this figure, the end 22a of one of the pipes 22 is tapered toward its tip. On the other hand, the end 23a of the other pipe 23 is expanded in diameter toward its tip. Then, an oxide layer 23 b is formed on the inner peripheral surface of the end 23 a of the pipe 23 by oxidation treatment.

  As shown in FIG. 4B, the end 22a of the pipe 22 and the end 23a of the pipe 23 are connected via the packing 21 made of an oxygen ion conductor. Thus, the outer surface 22b of the end 22a of the pipe 22 is in contact with the packing 21, and the oxide layer 23b of the end 23a of the pipe 23 is in contact with the packing 21.

  Then, as shown in FIG. 4C, the pipe 22 is connected to the positive electrode side of the voltage application device V and the pipe 23 is connected to the negative electrode side, and the whole of the packing 21 and the pipes 22 and 23 is heated. A DC voltage is applied between the pipe 23 and the pipe 23. Thereby, the end 22 a of the pipe 22 and the packing 21 are joined, and the packing 21 and the oxide layer 23 b of the end 23 a of the pipe 23 are joined. Thus, the piping 22 and the piping 23 are integrated, and a connected piping 20 as shown in FIG. 4C can be obtained.

(Example 3: Connection of two pipes by bonding sealing tape)
In the present embodiment, two pipes for high temperature gas and liquid in which packing of resin or rubber material can not be used are connected using a joint sealing tape having high temperature durability. FIG. 5A shows a cross section of a joint sealing tape used for connecting two pipes. The bonding and sealing tape 31 has an oxygen ion conductor thin film 31 b formed on one surface of a flexible metal tape 31 a by a CVD method or a PVD method.

FIG. 5B shows a cross section of the two pipes 32 and 33 to be connected. These pipes 32 and 33, the outer diameter D _o of the inner diameter D _i and the pipe 33 of the pipe 32 is configured to substantially coincide. As shown in FIG. 5C, the end 33a of the pipe 33 is inserted into the end 32a of the pipe 32, and the pipe 32 and the pipe 33 are connected. Then, the surfaces of the connected pipes 32 and 33 are subjected to oxidation treatment to form oxide layers 32 c and 33 c on the outer surface thereof.

  Subsequently, as shown in FIG. 5D, at least a part of the bonding sealing tape 31 overlaps the bonding sealing tape 31 on the connecting portion 34 between the piping 32 and the piping 33, and an oxygen ion conductor The oxide layers 32c and 33c on the outer surface of the pipes 32 and 33 connected to 31b are wound so as to be in contact with each other. In FIG. 5D, the bonding sealing tape 31 is wound twice so as to completely overlap each other. Thereby, a laminated structure of the tape as shown in FIG. 5 (e) is formed.

  Then, as shown in FIG. 5 (e), the metal tape material 31a on the outermost surface of the laminated structure of the tape is connected to the positive electrode side of the voltage application device V and the pipe 33 is connected to the negative side. A direct current voltage is applied between the metal tape material 31 a on the outermost surface of the laminated structure and the pipe 33 while heating the entire structure 32 and 33. Thereby, in the laminated structure of the bonding sealing tape 32, the metal tape material 31a of the bonding sealing tape 31 on the lower layer side and the oxygen ion conductor thin film 31b of the bonding sealing tape 31 on the upper layer side are bonded by anodic bonding. Also, the oxygen ion conductor thin film 31b of the lower layer side bonding sealing tape 31 and the oxide layer 33c of the pipe 33 are bonded by cathode bonding, and the pipe 32 and the pipe 33 are integrated. Thus, the pipe 32 and the pipe 33 are connected to obtain the pipe 30 as shown in FIG. 5 (e).

Example 4 Preparation of Solid Electrolyte Fuel Cell (SOFC)
In this embodiment, SOFC which is a fuel cell using a solid electrolyte is manufactured. FIG. 6 (a) shows a fuel cell (single cell) which is a power generation unit in SOFC. The unit cell 40 shown in FIG. 6A has a configuration in which the anode material 42 is provided on one surface of the solid electrolyte layer 41 and the cathode material 43 is provided on the other surface.

The solid electrolyte layer 41 is an oxygen ion conductor such as YSZ. Further, in the present embodiment, the anode material 42 is made of an oxide material having electron conductivity so that the unit cell 40 finally formed is an oxygen ion conductor as a whole. For example, it can be composed of a mixture (cermet) of Ni and a solid electrolyte layer material. Further, the cathode material 43 is made of an oxide material having oxygen ion conductivity and electron mixed conductivity. As such an oxide material, La (Sr) MnO ₃ , La (Sr) FeO ₃ , La (Sr) CoO ₃ , LaNiO ₄ or the like can be used.

The unit cell 40 shown in FIG. 6A is, for example, paste printed on the material of the anode material 42 on one surface of the solid electrolyte layer 41 and the material of the cathode material 43 on the other surface, and then fired. It can be formed by Alternatively, the anode material 42, the solid electrolyte layer 41, and the cathode material 43 can be stacked and formed as a thin film by a PVD method.
As described above, since the anode material 42 and the cathode material 43 have an oxide structure having both oxygen ion conductivity and electron conductivity, the voltage polarity is switched depending on the bonding surface with each solid electrolyte layer 41. Alternatively, they can be integrally formed by applying voltage twice (anodic bonding or cathodic bonding). Further, the combination of the anodic bonding and the cathodic bonding can form the single cell 40 by applying a voltage once.

  When the unit cell 40 is formed by combination of anodic bonding and cathodic bonding, as shown in FIG. 6A, the anode material 42 and the cathode material 43 are disposed on both surfaces of the solid electrolyte layer 41. Next, as shown in FIG. 6B, the cathode material 43 is connected to the electrode plate P on the positive electrode side of the voltage application device V, and the anode material 42 is connected to the electrode plate P on the negative electrode side. Then, a direct current voltage is applied between the anode material 42 and the cathode material 43 while heating the oxygen ion conductor 41, the anode material 42, and the cathode material 43. As a result, the oxygen ion conductor 41 and the cathode material 43 are anodically bonded (bonded 1), and the oxygen ion conductor 41 and the anode material 42 are cathodic bonded (bonded 2). Thus, by single application of voltage, the anode material 42 and the cathode material 43 disposed on both sides of the oxygen ion conductor 41 are firmly joined to the oxygen ion conductor 41 to form a single cell 40. Can.

  FIG. 7A shows a cell stack in which a plurality of single cells are stacked via a separator. The cell stack 50 shown in FIG. 7A includes a plurality of unit cells formed of a solid electrolyte layer 51, an anode material 52, and a cathode material 53, and a plurality of separators 54. In the cell stack 50, the anode material 52 functions as a fuel electrode, and the cathode material 53 functions as an air electrode. The separator 54 is made of metal, has a trapezoidal cross section by press molding, and has a flat plate portion 54a and an upright plate portion 54b. Further, the separator 54 is subjected to oxidation treatment, and an oxide layer 54 c is provided on one surface. Then, an anode material 52 is disposed on one surface of the solid electrolyte layer 51, and a cathode material 53 is disposed on the other surface to constitute a single cell, and the single cells are connected in series in the stacking direction to form a cell. A stack 50 is configured.

  The solid electrolyte layer 51 and the anode material 52 or the cathode material are formed by laminating the separator 54 having such trapezoidal cross section shape, the solid electrolyte layer 51, the anode material 52, and the cathode material 53 to form a laminate. An oxidant gas flow channel 55 and a fuel gas flow channel 56 are formed between them and 53. In the cell stack 50 shown in FIG. 7A, the phases of the trapezoidal waves of the separator 54 facing each other across the stacked body of the solid electrolyte layer 51, the anode material 52, and the cathode material 53 are configured to be mutually inverted. There is. As a result, the fuel gas flow channel 56 is disposed immediately below the oxidant gas flow channel 55, and oxygen ions generated in the cathode material (air electrode) 53 are directly transmitted through the solid electrolyte layer 51 to the fuel gas. It can move to the flow path 56 to react with the fuel gas, and the resistance of ion conduction can be reduced.

  The cell stack 50 shown in FIG. 7A is obtained as follows. First, a laminate of the solid electrolyte layer 51, the anode material 52, and the cathode material 53 is formed. This can be formed, for example, by paste-printing the material of the anode material 52 on one surface of the solid electrolyte layer 51 and the material of the cathode material 53 on the other surface, followed by firing. Alternatively, the anode material 52, the solid electrolyte layer 51, and the cathode material 53 may be stacked as thin films by PVD to form a stacked body. The materials of the solid electrolyte layer 51, the anode material 52, and the cathode material 53 are the same as those of the unit cell 40 shown in FIG. 6 (a). Thereby, the whole laminated body (single cell) formed becomes an oxygen ion conductor.

  Next, the laminate and the separator 54 are laminated as shown in FIG. 7 (a). As described above, the oxide layer 54 c is provided on one surface of the separator 54, and the separator 54 is disposed such that the oxide layer 54 c is in contact with the cathode material 53. Subsequently, while heating the whole, as shown in FIG. 7B, all cathode materials 53 are connected to the negative electrode side of the voltage application device V, and all anode materials 52 are connected to the positive electrode side to apply DC voltage. Do. Then, a junction 1 by cathode bonding is formed between the oxide layer 54 c of the separator 54 and the cathode material 53, and a junction 2 by anode bonding is formed between the separator 54 and the anode material 52. In this way, the laminate composed of the solid electrolyte layer 51, the anode material 52, and the cathode material 53 and the separator 54 are joined together and the whole is integrated to obtain the cell stack 50.

  Here, the operation of the obtained cell stack 50 will be described. First, an oxidant gas such as air is circulated in the oxidant gas flow channel 55, and a fuel gas such as hydrogen is circulated in the fuel gas flow channel 56. Then, the cell stack 50 is heated. Then, in the cathode material (air electrode) 53, oxygen contained in the oxidant gas receives electrons from an external circuit (not shown) and becomes oxygen ions. The generated oxygen ions pass through the solid electrolyte layer 51, move to the anode material (fuel electrode) 52, and react with the fuel gas. At that time, electrons are emitted and supplied to an external circuit. Thus, power generation is performed.

  In the cell stack 50, since power generation is performed between the anode material 52 and the cathode material 53 facing each other with the solid electrolyte layer 51 interposed therebetween, the area utilization rate of the solid electrolyte layer 51 is about 100%.

Example 5 Preparation of Solid Electrolyte Fuel Cell (SOFC)
FIG. 8 shows a cell stack 60 having a structure similar to that of FIG. In FIG. 8, the same components as those of the cell stack 50 shown in FIG. 7 are denoted by the same reference numerals. The difference between the cell stack 60 shown in FIG. 8 and the cell stack 50 shown in FIG. 7 is that, in the cell stack 60 of FIG. 8, the anode material 52 and the cathode material 53 have a plurality of holes 52a and 53a, respectively. The flat plate portion 54 a of the separator 54 is disposed in the holes 52 a and 53 a and is in direct contact with the oxide layer 54 c of the separator 54 and the solid electrolyte layer 51. The anode material 52 and the cathode material 53 are low in compactness in order to impart gas diffusivity, and under severe operating conditions where repetitive operation is repeated, problems may occur in bonding strength and sealability. In this embodiment, by bonding the separator 54 directly to the dense solid electrolyte layer 51, it is possible to realize a strong and highly sealing bond, and improve the durability under the above-described severe conditions. be able to.

  In the case of paste printing, the holes 52a of the anode material 52 and the holes 53a of the cathode material 53 are holes 52a, 53a by using a mask so as not to apply the paste in a portion where the holes are formed. Can be formed. Further, in the case of the PVD method, the holes 52a and 53a can be formed by photoetching after forming the single cell.

  The cell stack 60 shown in FIG. 8 can be produced in the same manner as the cell stack 50 shown in FIG. 7, but a laminate of a solid electrolyte layer 51, an anode material 52 and a cathode material 53 and a separator are laminated. At this time, the flat plate portion 54 a of the separator 54 is disposed in the hole 52 a of the anode material 52 or in the hole 53 a of the cathode material 53 so as to be in contact with the solid electrolyte layer 51. At this time, in the hole 53 a of the cathode material 52, the oxide layer 54 c of the separator 54 is disposed in direct contact with the solid electrolyte layer 51. Then, as in the cell stack 50 of FIG. 7, a DC voltage is applied once between the separators 54 facing each other across the stacked body. Thereby, a junction 1 by cathode bonding is formed between the oxide layer 54 c of the separator 54 and the solid electrolyte layer 51, and a junction 2 by anode bonding is formed between the separator 54 and the solid electrolyte layer 51. Thus, the laminate composed of the solid electrolyte layer 51, the anode material 52, and the cathode material 53 is joined to the separator 54, and the whole is integrated, whereby the cell stack 60 is obtained.

  Also in the cell stack 60, power generation is performed between the anode material 52 and the cathode material 53 opposed to each other with the solid electrolyte layer 51 interposed therebetween, and the area utilization rate of the solid electrolyte layer 51 is about 100%.

DESCRIPTION OF SYMBOLS 1, 11 oxygen ion conductor 2 1st to-be-joined material 2a, 12a, 23b, 32c, 33c, 54c oxide layer 3 2nd to-be-joined material 10 laminated body 12, 13 metal 20, 22, 23, 30, 32, 33 Piping 21 Packing 22a, 23a, 32a, 33a End 22b Outer surface 31 Bonding sealing tape 31a Metal tape material 31b Oxygen ion conductor thin film 34 Connecting part 40 Fuel cell (single cell)
41, 51 solid electrolyte layer 42, 52 anode material 43, 53 cathode material 50, 60 cell stack 51 solid electrolyte layer 52a, 53a hole 54 separator 54a flat plate 54b standing plate 55 oxidant gas flow path 56 fuel gas flow path

Claims (14)

An oxygen ion conductor,
A conductive first bonding material provided with an oxide layer on the surface, disposed on one surface of the oxygen ion conductor;
A second bonding material having electron conductivity disposed on the other surface of the oxygen ion conductor;
Equipped with
A covalent bond is formed at the contact interface between the oxide layer of the first material to be joined and the oxygen ion conductor.
A bonded body, wherein a covalent bond is formed at a contact interface between the second bonding material and the oxygen ion conductor.   At least one of the contact surfaces of the oxygen ion conductor and the first bonding material and the contact surfaces of the oxygen ion conductor and the second bonding material are processed to be in close contact with each other. The joined body according to claim 1.   The joined body according to claim 1, wherein the oxide layer has electron conductivity.   The joined body according to claim 3, wherein the oxide layer is composed of an N-type semiconductor.   The joined body according to claim 3, wherein the oxide layer is an insulating film capable of passing electrons in the thickness direction.   The joined body according to any one of claims 1 to 5, wherein the second material to be joined has electron conductivity.   The joined body according to claim 6, wherein the second material to be joined is made of a metal, an N-type semiconductor, or an intrinsic semiconductor having electron conductivity at a temperature at the time of joining.   The joined body according to claim 2, wherein the second material to be joined is formed of an insulating film capable of passing electrons in the thickness direction.   The assembly according to any one of claims 1 to 8, wherein the oxygen ion conductor is an oxide ion conductor. The first bonding material and the second bonding material are pipes,
The joined body according to any one of claims 1 to 9, wherein the two pipes are joined to each other via a packing made of the oxygen ion conductor. The first material to be joined comprises two pipes connected, and an oxide layer is provided on the outer surface thereof;
The second bonding material is a flexible metal tape material, and the metal tape material and a thin film made of the oxygen ion conductor provided on one surface of the metal tape are for bonding and sealing. Composed of tape,
The bonding and sealing tape is wound around the connection portion of the two pipes so that at least a part of the bonding and sealing tape is overlapped and the oxygen ion conductor is in contact with the oxide layer on the outer surface. The joined body according to any one of claims 1 to 9, wherein The oxygen ion conductor has a solid electrolyte layer, an anode material disposed on one surface of the solid electrolyte layer, and a cathode material disposed on the other surface of the solid electrolyte layer,
The first bonding material and the second bonding material are separators, and have the oxide layer only on one surface of them.
The plurality of oxygen ion conductors and the plurality of separators are stacked alternately so that the oxide layer of the separator and the cathode are in contact with each other. Zygote. The cathode material and the anode material each have a plurality of holes,
The joined body according to claim 12, wherein the oxide layer of the separator is in contact with the solid electrolyte layer in each of the plurality of holes. A conductive first bonding material having an oxide layer provided on the surface is disposed on one surface of the oxygen ion conductor such that the oxide layer is in contact with the first bonding material, and the oxygen ion conductor An arrangement step of arranging a second bonding material having electron conductivity on the other surface;
Connecting the first material to be bonded to the negative electrode side of the voltage application device and connecting the second material to be bonded to the positive electrode side of the voltage application device;
A voltage application step of applying a DC voltage between the first bonding material and the second bonding material;
Including
In the voltage application step,
The application of the DC voltage between the first bonding material and the second bonding material is performed until at least the average current flowing between the two materials starts to decrease.
Reductive reaction at the contact interface between the oxide layer of the first bonding material and the oxygen ion conductor to cause covalent bonding
An oxidation reaction is carried out at the contact interface between the second material to be joined and the oxygen ion conductor to cause covalent bonding.

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