JP2010055951A - Seal material and electrochemical device using the same - Google Patents

Abstract

In a device using a gas at a high temperature, the performance of sealing the gas is improved while ensuring insulation.
An electrochemical cell including an electrolyte membrane and an oxygen electrode and a hydrogen electrode provided so as to sandwich the electrolyte membrane is a gas space communicating with the oxygen electrode and the hydrogen electrode, respectively. The gas supply grooves 16 and 17 are sandwiched between current collector plates 14 and 15. A sealing material 61 is provided between the electrolyte membrane 11 and the current collector plates 14 and 15 to prevent gas leakage in the gas space. The sealing material 61 stably stabilizes the foamed material such as calcium carbonate that foams between normal temperature and the use temperature, the molten material that exists in a stable molten state at the use temperature, such as glass, and the foamed material and the molten material at normal temperature. And a binder such as methylcellulose to be retained.
[Selection] Figure 1

Description

  The present invention relates to a sealing material and an electrochemical device using the same.

  A solid electrolyte fuel cell (SOFC) is a device that reacts a reducing agent (such as hydrogen or hydrocarbon) with an oxidizing agent (such as oxygen) through an electrolyte membrane having oxygen ion conductivity and extracts the energy as electricity. is there. On the other hand, the high-temperature steam electrolysis method is a method of obtaining hydrogen and oxygen by electrolyzing high-temperature steam, and its operation principle is a reverse reaction of a solid electrolyte fuel cell. The operating temperature of the solid electrolyte fuel cell and the operating temperature of the high-temperature steam electrolysis method are usually around 600 to 900 ° C.

  In an electrochemical cell that performs a battery reaction or an electrolytic reaction, a gas necessary for the electrode reaction is supplied to each of two types of electrodes that perform an oxidation reaction and a reduction reaction, and a gas generated by the electrodes is discharged. For this reason, in putting a solid electrolyte fuel cell and a high-temperature steam electrolysis method into practical use, it is necessary to efficiently supply and discharge gas. Therefore, it is necessary to establish a seal structure that prevents gas leakage from the inside to the outside of the electrochemical cell or from the outside to the inside.

  Electrochemical cells generally comprise multiple layers of ceramics. An electrochemical apparatus is an apparatus provided with a means for supplying gas to the electrochemical cell, discharging the gas, and means for supplying or taking out electricity together with such an electrochemical cell. When joining the electrochemical cell and the connection portion on the casing side of the electrochemical device, it is required to adjust the expansion coefficient, to ensure the sealing property and the joining strength.

In particular, in order to ensure sealing performance and bonding strength, for example, a glass packing having a property of softening and melting at an operating temperature (for example, 800 ° C.) or higher is interposed on the bonding surface, and the melting is performed by heating above the melting point. There is a method of joining the two. Patent Document 1 discloses a method for joining cylindrical cells. Patent Document 2 discloses a method of joining flat cells using glass.
Japanese Patent Laid-Open No. 2005-1000086 JP 2007-287585 A

  In order to operate the fuel cell, it is necessary to supply an oxidizing agent (for example, air) to one electrode and a reducing agent (for example, hydrogen) to the other electrode via an electrolyte. In order to operate the high-temperature steam electrolysis cell, oxygen is discharged from one electrode, and hydrogen is discharged from the other electrode via the electrolyte. In operation of the electrochemical cell, these two kinds of gas should not leak and mix and react with each other without leaking from the peripheral part of the cell or the partition wall of the flow channel in contact with each other without going through the intended electrochemical reaction. It is necessary not to leak from the flow path to the outside of the device and into the atmosphere.

  In addition, since an electrochemical cell having a solid electrolyte is operated under a high temperature condition of 700 to 1000 ° C., when operating an electrochemical device including an electrochemical cell and a seal portion, a temperature increasing / decreasing cycle from normal temperature to an operating temperature is performed. It will go through. The electrochemical cell is formed by laminating a plurality of ceramic thin films including a catalyst and an electrolyte. Such a gas seal structure in contact with the electrochemical cell needs to be in close contact with the electrochemical cell with a minimum necessary pressure. Furthermore, it is necessary to obtain a good gas sealing property while absorbing internal stress generated due to a temperature change due to the difference in the thermal expansion coefficient and the structure of each member and the occurrence of looseness. In the conventional invention, a gas sealing property is ensured by installing a glassy or metal sealing material in contact with, for example, the cell end face and compressing from above and below (see Patent Documents 1 and 2).

  However, in the sealing method for a cylindrical cell described in Patent Document 1, all of the absorption of the difference in thermal expansion coefficient between different members, the mechanical strength of the cell support, and the securing of the gas sealability are all achieved by the joint portion of the device base and the cell. It depends only on the seal part in contact with it, and stability becomes a problem. Moreover, when using a metal sealing material, the electric potential of an adjacent cell cannot be insulated, and depending on the structure of an electrochemical apparatus, the operation of an electrochemical cell having a multilayer structure may not be performed properly.

  Moreover, in the sealing method with respect to the other flat cell described in patent document 2, maintenance of a sealing structure is largely dependent only on the viscosity of the glass which is a sealing member quality. Moreover, since the viscosity of the glass largely changes near the operating temperature, it is difficult to maintain the sealing performance over a wide temperature range and for a long time. In addition, the seal area is limited. For these reasons, the sealing performance may become unstable.

  Therefore, the present invention improves the performance of gas sealing while ensuring insulation in devices that use gas at high temperatures, such as electrochemical cells that perform high-temperature steam electrolysis or solid oxide fuel cell reactions. Objective.

  In order to achieve the above-mentioned object, the present invention uses a reaction that is used at a use temperature higher than normal temperature to electrolyze water vapor to generate oxygen and hydrogen, and a battery reaction that supplies oxygen and hydrogen to discharge water vapor. In an electrochemical device that causes any one of the following reactions: an electrolyte membrane; an oxygen electrode attached to one surface of the electrolyte membrane; and an attachment on a surface opposite to the oxygen electrode across the electrolyte membrane An electrochemical cell comprising: a hydrogen electrode; a structure that forms a gas space communicating with one of the oxygen electrode and the hydrogen electrode; and a foaming material that foams between normal temperature and the use temperature; A molten substance that exists in a stable molten state at the use temperature; and a binder that stably holds the foamed substance and the molten substance at room temperature, and is provided between the electrochemical cell and the structure. Is in and having a, a seal member for preventing leakage of gas in the gas space.

  In addition, the present invention is a sealing material used in equipment used at a use temperature higher than normal temperature, and a foaming substance that foams between normal temperature and the use temperature, and exists in a stable molten state at the use temperature. It contains a molten material and a binder that stably holds the molten material and the molten material at room temperature.

  According to the present invention, it is possible to improve the performance of sealing a gas while ensuring insulation in a device that uses a gas at a high temperature, such as an electrochemical cell that performs high-temperature steam electrolysis or a solid oxide fuel cell reaction. it can.

  Embodiments of an electrochemical device according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a block diagram of an electrochemical device shown together with a longitudinal sectional view in the first embodiment of the electrochemical device according to the present invention.

  The electrochemical device according to the present embodiment includes an electrochemical cell, current collector plates 14 and 15, and a sealing material 61. The electrochemical cell is formed by laminating an electrolyte membrane 11, an oxygen electrode 12, and a hydrogen electrode 13. The electrolyte membrane 11, the oxygen electrode 12 and the hydrogen electrode 13 are all formed in a square flat plate shape, for example. The oxygen electrode 12 is provided in contact with one surface of the electrolyte membrane 11 which is a support base material. The hydrogen electrode 13 is provided in contact with the surface opposite to the oxygen electrode 12 with the electrolyte membrane 11 interposed therebetween. The oxygen electrode 12 and the hydrogen electrode 13 are both smaller than the electrolyte membrane 11, and there are portions that are not covered with these electrodes on the outer periphery of the electrolyte membrane 11.

  The electrolyte membrane 11 is formed by densely forming a solid oxide material having electronic insulating properties and oxygen ion conductivity, such as yttria stabilized zirconia (YSZ). Here, the dense state may be a dense density that allows gas leakage in the electrolyte membrane 11 to be substantially ignored. The oxygen electrode 12 is formed of, for example, a lanthanum / strontium / manganese perovskite oxide (LSM). The hydrogen electrode 13 is formed as a porous body with a cermet of nickel and YSZ, for example.

  The current collecting plates 14 and 15 are arranged so as to sandwich the electrochemical cell from the outside of the oxygen electrode 12 and the hydrogen electrode 13. The two current collector plates 14 and 15 are electrically connected to the oxygen electrode 12 and the hydrogen electrode 13, respectively. The current collecting plates 14 and 15 are formed in a plate shape in order to collect current evenly from the entire surface of the electrode. An external load 25 is connected between the two current collector plates 14 and 15.

  The two current collecting plates 14 and 15 are both formed in a square shape larger than the electrolyte membrane 11. The two current collecting plates 14 and 15 are formed with gas supply grooves 16 and 17 connected to external gas supply means (not shown) in order to supply reaction gas to the respective electrodes. The gas supply groove 16 formed in the current collector plate 14 in contact with the oxygen electrode 12 extends, for example, in a direction perpendicular to the gas supply groove 17 formed in the current collector plate 15 in contact with the hydrogen electrode 13. Oxygen is supplied to the gas supply groove 16 formed in the current collector plate 14 in contact with the oxygen electrode 12. Hydrogen is supplied to the gas supply groove 17 formed in the current collector plate 15 in contact with the hydrogen electrode 13 in the direction indicated by the dotted arrow 71 in FIG. That is, these gas supply grooves 16 and 17 are gas spaces communicating with the oxygen electrode 32 or the hydrogen electrode 33, respectively, and the two current collector plates can be said to be structures that form these gas spaces.

  The outer sides of the two current collecting plates 14 and 15 in the stacking direction are sandwiched between two insulating sheets 18 and 19, and the outer sides are sandwiched between two end plates 20 and 21. A plurality of bolts 22 extend between the two end plates 20 and 21. The two end plates 20 and 21 are tightened in a direction approaching each other by these bolts 22 and nuts 23 screwed into them.

  A sealing material 61 is disposed outside the oxygen electrode 12 and the hydrogen electrode 13 and between the two current collector plates 14 and 15 so as to be in contact with the electrolyte membrane 11. The insulating sheets 18 and 19 and the sealing material 61 can use materials having the same composition.

  A frame 24 is provided between the two current collecting plates 14 and 15 on the outer side of the sealing material 61. The frame 24 is formed of a rigid body such as metal or ceramics. In the case of using a metal frame 24, in order to ensure insulation between the two current collector plates 14 and 15, two frames 24 are used, and a sealing material is also provided between these frames 24. An insulator such as 61 is interposed.

  The sealing material 61 contains at least a foam material, a molten material, and a binder. Here, the foam material is a material that foams between normal temperature and use temperature. A molten material is a substance that exists in a stable molten state at the use temperature. The binder is a material that is mixed with these foamed material and molten material and stably holds them at room temperature.

For example, calcium carbonate (CaCO ₃ ) can be used as the foaming material of the sealing material 61. Calcium carbonate is decomposed into calcium oxide (CaO) and carbon dioxide (CO ₂ ) by heating. For this reason, gaseous carbon dioxide is generated, and bubbles are generated in the sealing material 61. As the foamed material, ceramics containing a component that vitrifies and a component that gasifies into water vapor, carbon dioxide, or the like by performing a heat treatment at a temperature between normal temperature and use temperature can be used. Such foamed materials include pearlite, fly ash, and obsidian. A material foamed by applying heat treatment to obsidian is known as a shirasu balloon.

  If the content of the foaming substance in the sealing material 61 is too small, the volume expansion associated with foaming becomes small, and there is a possibility that the thermal expansion of the electrolysis cell cannot be followed. Moreover, when there is too much quantity of a foaming substance, a bubble may connect and airtightness may not be ensured. Therefore, the content of the foaming substance is, for example, 1 to 20 wt%, more preferably 5 to 10 wt%.

  As the melting material of the sealing material 61, glass having a glass transition temperature of not more than the use temperature, such as sodium silicate and borosilicate glass molded into a powder form or a fiber form, can be used. The content of the molten material in the sealing material 61 is, for example, 30 to 40 wt%.

  As the binder of the sealing material 61, a general organic binder such as methyl cellulose can be used. As the organic binder, it is preferable to use an organic binder that does not contain a poisoning component for electrochemical cells, such as Cr and S. The binder content in the sealing material 61 is, for example, 10 to 30 wt%. If the content of the binder is too small, molding cannot be performed, and if the content is too large, it remains undesirably remaining after decomposition in the temperature raising process. Ceramics such as yttria-stabilized zirconia and alumina may be further contained in the sealing material 61. The content of such ceramics in the sealing material 61 is, for example, 20 to 30 wt%.

  FIG. 2 is a plan view showing a state during the production of the electrochemical device of the present embodiment.

  When manufacturing the electrochemical device of the present embodiment, first, a kneaded material obtained by mixing and kneading these materials is shaped into a sheet shape with a calendar roll or the like. As shown in FIG. 3, the sealing material 61 shaped into a sheet shape is cut out in a shape surrounding the respective electrodes of the oxygen electrode 32 and the hydrogen electrode 33 in a frame shape and attached to both surfaces of the electrochemical cell. At this time, a through hole 26 through which the bolt 22 passes is formed in the sealing material 61. Thereafter, the electrochemical cell to which the sealing material 61 is attached is sequentially sandwiched between the two current collecting plates 14 and 15, the insulating sheets 18 and 19, and the end plates 20 and 21, and tightened with the bolts 22 and the nuts 23.

  The thickness of the sheet-like kneaded material is, for example, 0.1 to 0.5 mm, preferably 0.3 to 0.5 mm. Moreover, in order to ensure gas-sealing property, it is preferable that the width | variety of the sealing material 61 shall be 1-3 cm.

  By supplying oxygen from an external gas supply means to a gas supply groove 16 communicating with the oxygen electrode 12 and supplying hydrogen to a gas supply groove 17 communicating with the hydrogen electrode 13, the electrochemical cell generates electricity, and a current collector plate Electric power is taken out from 14 and 15 and consumed by the external load 25. In addition, a reaction for electrolyzing water vapor can be caused by connecting an external power source instead of the external load 25 and supplying water vapor to the hydrogen electrode 13.

  In such an electrochemical device, when the temperature is raised during the first operation or the like, a gas is generated from the foaming substance contained in the sealing material 61, and bubbles are generated inside the sealing material 61. At this time, the binder in the sealing material 61 is decomposed and disappears. For this reason, even if other components such as the current collector plates 14 and 15 expand due to the temperature rise, the sealing material 61 expands according to the expansion, and the sealing performance can be maintained. In addition, a molten material such as glass contained in the sealing material 61 is melted in the process of increasing the temperature and exists in a stable molten state at the use temperature. For this reason, the sealing material 61 can be deformed following deformation such as thermal expansion of other constituent articles, and the sealing performance can be maintained.

  As described above, the electrochemical device according to the present embodiment obtains an insulating seal structure that suppresses gas leakage while the temperature is raised from room temperature to about 800 to 900 ° C. that is the operating temperature. Further, this insulating seal structure can be obtained, for example, by arranging the sealing material 61 formed in a sheet shape at a necessary place, so that the structure is simple and the electrochemical cell is not damaged. As a result, the electrochemical device can be operated with high efficiency.

  Further, when glass is used as the molten material to be contained in the sealing material 61, it is fused to the current collector plates 14 and 15 and the electrolyte membrane 11 in the temperature rising process such as the first operation and the subsequent temperature falling process. For this reason, appropriate joint strength is securable. Further, in the present embodiment, since the rigid frame 24 is provided, it is possible to prevent the sealing material 61 from melting and flowing down to the outer periphery of the electrochemical device at a high temperature, and to maintain gas sealing performance for a long period of time. . In addition, in order to confine the gas generated from the foamable substance as bubbles, it is necessary to select a composition such as a molten substance so that the fluidity of the sealant 61 at the use temperature does not become too large.

[Second Embodiment]
FIG. 3 is a block diagram of the electrochemical device shown together with a longitudinal sectional view in the second embodiment of the electrochemical device according to the present invention.

  The electrochemical device according to the present embodiment includes a housing 38, an electrochemical cell 30, and a sealing material 61. An opening 81 is formed in the housing 38.

  The electrochemical cell 30 includes an electrolyte membrane 31, an oxygen electrode 32, and a hydrogen electrode 33. The hydrogen electrode 33 is formed in a cylindrical shape with one end closed. The electrolyte membrane 31 is fixed to the hydrogen electrode 33 so as to cover the outer surface of the hydrogen electrode 33 which is a supporting base material. The oxygen electrode 32 is formed so as to extend in a band shape in the circumferential direction of a cylinder formed by the hydrogen electrode 33 and the electrolyte membrane 31, and is fixed to the electrolyte membrane 31.

  A current collecting plate 51 electrically connected to the oxygen electrode 32 is formed on the surface of the oxygen electrode 32 opposite to the electrolyte membrane 31. The current collector plate 51 has conductivity and gas permeability. A part of the electrolyte membrane 31 is provided with a penetrating part that penetrates to the hydrogen electrode 33, and a current collecting part 52 that is electrically connected to the hydrogen electrode 33 is formed in that part. The current collector 52 has conductivity and airtightness. The electrolyte membrane 31 and the current collector 52 have airtightness as a whole. A DC power supply 39 is provided between the current collector plate 51 connected to the oxygen electrode 32 and the current collector 52 connected to the hydrogen electrode 33.

  The electrochemical cell 30 has a support 37 provided at the end of the hydrogen electrode 33 that is not closed. The support 37 is fixed to the hydrogen electrode 33 and the electrolyte membrane 31 via a ring-shaped insulating adhesive layer 36. The support 37 has a portion extending in a cylindrical shape with a diameter substantially the same as that of the hydrogen electrode 33 from a portion in contact with the insulating adhesive layer 36, and a portion extending outward from the cylinder at one end of the cylindrical portion. Yes. The support 37 is preferably formed of a metal or ceramic having substantially the same thermal expansion coefficient as that of the hydrogen electrode 33. The insulating adhesive layer 36 is made of a glass such as sodium silicate or borosilicate glass that is adjusted so as not to melt even at the operating temperature (800 to 900 ° C.) of the electrochemical cell.

  The electrochemical cell 30 is fixed to the housing 38 so that the cylindrical portion communicates with the opening 81. That is, the inside of the housing 38 is a gas space that communicates with the hydrogen electrode 33, and the outside of the housing 38 is a gas space that communicates with the oxygen electrode 32. The housing 38 can be said to be a structure that forms these gas spaces. The sealing material 61 is formed in a ring shape and is interposed between the support 37 and the housing 38.

  The electrochemical cell 30, the sealing material 61, and the housing 38 are tightened by a bolt 22 that penetrates a portion of the support 37 that extends outward from the cylinder and the housing 38, and a nut 23 that is screwed into the bolt 22. It has been. The bonding surface between the support 37 and the housing 38 is smooth. For example, about 4 to 8 bolts 22 are provided around the opening 81 at the same interval. The sealing material 61 has the same composition as in the first embodiment.

  Edges 29 may be formed on the support 37 and the casing 38 at positions facing each other in order to further improve the sealing performance. It is better to use as many bolts 22 as possible as long as workability is not impaired.

  Water vapor is supplied from the inside of the housing 38 through, for example, a water vapor introduction pipe 40 extending coaxially with the electrochemical cell 30 in the direction of the dotted arrow 73 in FIG. 3, and between the oxygen electrode 32 and the hydrogen electrode 33 by a DC power supply 39. When a voltage is applied to the water vapor, an electrolysis reaction of water vapor occurs. Oxygen generated by this electrolysis reaction is exhausted from the oxygen electrode. Hydrogen generated by this electrolysis reaction is discharged from the hydrogen electrode 33 and flows in the direction of the dashed line arrow 74 in FIG. The electrolyte membrane 31 and the current collector 52 are airtight as a whole, and the sealing material 61 prevents gas leakage from the gas space inside and outside the housing 38. Therefore, the atmosphere inside and outside the electrochemical cell 30 is Do not mix in the vicinity of the cell.

  In such an electrochemical device, when the temperature is raised during the first operation or the like, a gas is generated from the foaming substance contained in the sealing material 61, and bubbles are generated inside the sealing material 61. In addition, a molten material such as glass contained in the sealing material 61 is melted in the process of increasing the temperature and exists in a stable molten state at the use temperature. For this reason, as in the first embodiment, an insulating seal structure can be obtained without damaging the electrochemical cell 30.

[Other embodiments]
The above-described embodiments are merely examples, and the present invention is not limited to these. For example, the electrochemical device of the first embodiment can be used for electrolysis. Alternatively, the electrochemical device of the second embodiment can be used as a fuel cell. Moreover, it can also implement combining the characteristic of each embodiment.

It is a block diagram of the electrochemical apparatus shown with the longitudinal cross-sectional view in 1st Embodiment of the electrochemical apparatus which concerns on this invention. It is a top view which shows the state in the middle of manufacture in 1st Embodiment of the electrochemical apparatus which concerns on this invention. It is a block diagram of the electrochemical apparatus shown with the longitudinal cross-sectional view in 2nd Embodiment of the electrochemical apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Electrolyte membrane, 12 ... Oxygen electrode, 13 ... Hydrogen electrode, 14 ... Current collecting plate, 15 ... Current collecting plate, 16 ... Gas supply groove, 17 ... Gas supply groove, 18 ... Insulating sheet, 19 ... Insulating sheet, 20 End plate, 21 End plate, 22 Bolt, 23 Nuts, 24 Frame, 25 External load, 29 Edge, 30 Electrochemical cell, 31 Electrolyte membrane, 32 Oxygen electrode, 33 Hydrogen electrode 36 ... Insulating adhesive layer, 37 ... Support, 38 ... Housing, 39 ... DC power supply, 40 ... Water vapor inlet tube, 51 ... Current collector plate, 52 ... Current collector, 61 ... Sealing material, 81 ... Opening

Claims (12)

In an electrochemical device that is used at a use temperature higher than normal temperature and causes either a reaction of electrolyzing water vapor to generate oxygen and hydrogen or a battery reaction of supplying oxygen and hydrogen to discharge water vapor ,
An electrochemical cell comprising: an electrolyte membrane; an oxygen electrode attached to one surface of the electrolyte membrane; and a hydrogen electrode attached to a surface opposite to the oxygen electrode across the electrolyte membrane; ,
A structure forming a gas space communicating with one of the oxygen electrode and the hydrogen electrode;
A foaming substance that foams between room temperature and the use temperature, a melted substance that exists in a stable molten state at the use temperature, and a binder that stably holds the foaming substance and the melted substance at room temperature. A sealing material provided between the electrochemical cell and the structure to prevent gas leakage in the gas space;
An electrochemical device comprising: The electrolyte membrane is formed in a flat plate shape,
Both the oxygen electrode and the hydrogen electrode are formed in a flat plate shape smaller than the electrolyte membrane,
The structure includes a first current collector plate formed on the opposite side of the oxygen electrode from the side facing the electrolyte membrane and larger than the oxygen electrode, and a side of the hydrogen electrode facing the electrolyte membrane; And a second current collector plate formed on the opposite side and larger than the hydrogen electrode, and a groove is formed on the side of the first current collector plate facing the oxygen electrode, and the second current collector plate is formed. A groove is formed on the side of the electrode plate facing the hydrogen electrode,
The sealing material is filled between the first current collector plate and the electrolyte membrane, and between the second current collector plate and the electrolyte membrane. The described electrochemical apparatus. The structure is a housing in which an opening is formed,
The electrochemical cell is formed so as to cover the opening, and engages with the casing at an edge of the opening,
The electrochemical device according to claim 1, wherein the sealing material is formed so as to surround the opening.   The electrochemical device according to claim 3, wherein the casing and the electrochemical cell are formed with edges that bite into the sealing material at opposing positions. In sealing materials used in equipment used at higher operating temperatures than room temperature,
A foaming material that foams between room temperature and the use temperature;
A molten material present in a stable molten state at the use temperature;
A binder that stably holds the foamed material and the molten material at room temperature;
The sealing material characterized by containing.   The sealing material according to claim 5, wherein the molten material is glass having a glass transition temperature equal to or lower than the use temperature.   The foaming material is one or more materials selected from ceramics containing calcium carbonate and a component that vitrifies when heated and a component that gasifies when heated. The sealing material described.   The sealing material according to any one of claims 5 to 7, wherein the content of the foaming substance is smaller than a ratio in which bubbles generated by foaming are connected so as to communicate the front and back.   9. The binder according to claim 5, wherein the binder is decomposed between normal temperature and the use temperature, and the content thereof is not less than a moldable amount and not more than an amount disappeared by decomposition. 2. The sealing material according to item 1.   The sealing material according to any one of claims 5 to 9, further comprising an insulating material having substantially the same thermal expansion coefficient as the device.   The foaming material content is 1% by weight to 20% by weight, the molten material content is 30% by weight to 40% by weight, and the insulating material content is 20% by weight to 30%. 11. The sealing material according to claim 5, wherein the content of the binder is 10% by weight or more and 30% by weight or less.   The sealing material according to claim 5, wherein the sealing material is formed into a sheet shape.

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