Thermoelectric conversion element and heat insulation structure of piping

Abstract

A thermoelectric conversion element 1 includes an element body 2 made of an insulating material, a first conductive member 3 made of a metal, and a second conductive member 4 containing a carbon material as a conductive material and electrically connected to the first conductive member 3. The first conductive member 3 has, on the surface thereof, a metal layer 32 made of a pure metal capable of forming an oxide film, or is made of an alloy.

Description

Thermoelectric conversion element and heat insulation structure of piping

[0001] The present invention relates to a thermoelectric conversion element and a heat insulation structure of piping.

[0002] A thermoelectric conversion element including a heat insulating material and a filamentous thermoelectric conversion member sewn into the heat insulating material has been proposed (see Patent Document 1 below).

[0003] International Publication No. 2023 / 127590

[0004] In the thermoelectric conversion element as described in Patent Document 1 above, when a metallic conductive member is used instead of the P-type thermoelectric conversion member or the N-type thermoelectric conversion member, there is a possibility that the conductive member may be corroded by moisture in the heat insulating material.

[0005] The present invention provides a thermoelectric conversion element capable of suppressing corrosion of a first conductive member in a thermoelectric conversion element including a first conductive member made of metal and a second conductive member containing a carbon material, and a heat insulation structure of piping including the thermoelectric conversion element.

[0006] The present invention [1] includes a body made of an insulating material extending in a first direction, a first conductive member made of metal, at least a part of which is disposed in the body, and a second conductive member containing a carbon material as a conductive material and electrically connected to the first conductive member, at least a part of which is disposed in the body, and the first conductive member includes a thermoelectric conversion element having a metal layer made of a pure metal capable of forming an oxide film on the surface or made of an alloy.

[0007] The present invention [2] includes the thermoelectric conversion element according to [1] above, in which the first conductive member has a core and the metal layer covering the core.

[0008] The present invention [3] includes the thermoelectric conversion element according to [2] above, in which the core is made of a pure metal different from the metal layer.

[0009] The present invention [4] includes the thermoelectric conversion element according to any one of [1] to [3] above, in which the metal layer is made of aluminum, titanium, nickel, cobalt, zinc, or tin.

[0010] The present invention [5] includes any one of the thermoelectric conversion elements described in [1] to [4] above, wherein the first conductive member is thread-like and the diameter of the first conductive member is 400 μm or less.

[0011] The present invention [6] includes any one of the thermoelectric conversion elements described in [1] to [5] above, wherein the difference between the Seebeck coefficient of the first conductive member and the Seebeck coefficient of the second conductive member is 10 μV / K or more.

[0012] The present invention [7] includes any one of the thermoelectric elements described in [1] to [6] above, wherein the second conductive member is a P-type thermoelectric member or an N-type thermoelectric member.

[0013] The present invention [8] includes a pipe insulation structure comprising a pipe, an insulating material covering the pipe, and one of the thermoelectric conversion elements described in [1] to [7] above, wherein the base body is a part of the insulating material.

[0014] The present invention [9] includes a pipe insulation structure comprising a pipe, an insulating material covering the pipe, and one of the thermoelectric conversion elements described in [1] to [7] above embedded in the insulating material, wherein the base body is made of a thermosetting resin or a thermoplastic resin.

[0015] The present invention

[10] includes the thermal insulation structure for the piping described in [9], further comprising a second thermal insulation material placed on top of the thermal insulation material and covering the thermoelectric conversion element.

[0016] The present invention

[11] further includes an exterior member that covers the heat insulating material, wherein the exterior member has an opening, and the thermoelectric conversion element is disposed within the opening, and the heat insulating structure for the pipe described in

[10] is further provided.

[0017] The present invention

[12] includes the piping insulation structure of

[11] , further comprising a cover that closes the opening of the exterior member.

[0018] According to the thermoelectric conversion element of the present invention, the first conductive member has a metal layer on its surface made of a pure metal capable of forming an oxide film, or is made of an alloy.

[0019] Therefore, if the first conductive member has a metal layer on its surface made of a pure metal capable of forming an oxide film, the formation of an oxide film on the metal layer can suppress corrosion from progressing to the interior of the first conductive member.

[0020] Furthermore, if the first conductive member is made of an alloy, corrosion of the first conductive member can be suppressed by selecting an alloy that is resistant to corrosion.

[0021] As a result, in a thermoelectric conversion element comprising a first conductive member made of metal and a second conductive member containing a carbon material, corrosion of the first conductive member can be suppressed.

[0022] Furthermore, the thermal insulation structure for piping according to the present invention uses a thermoelectric conversion element in which corrosion of the first conductive member is suppressed. Therefore, abnormalities in the thermal insulation material around the piping can be reliably detected.

[0023] Figure 1 is a plan view of a thermoelectric element as one embodiment of the present invention. Figure 2 is a cross-sectional view taken along line A-A of the thermoelectric element shown in Figure 1. Figure 3 is a cross-sectional view taken along line B-B of the first conductive member shown in Figure 1. Figure 4 is a cross-sectional view showing the thermal insulation structure of the piping. Figure 5 is a perspective view of the thermal insulation material shown in Figure 4. Figure 6 is a cross-sectional view of a modified example (2) of the thermoelectric element. Figure 7 is a cross-sectional view showing the thermal insulation structure of the piping when the thermoelectric element shown in Figure 6 is used.

[0024] 1. Thermoelectric Conversion Element As shown in Figure 1, the thermoelectric conversion element 1 comprises a base body 2, a first conductive member 3, and a second conductive member 4.

[0025] (1) As shown in Figure 2, the base body 2 has a predetermined thickness. The base body 2 has one surface S1 and the other surface S2 in the thickness direction of the base body 2. In the following description, the thickness direction of the base body 2 will be referred to as the "thickness direction". The one surface S1 and the other surface S2 extend in the surface direction. The surface direction intersects with the thickness direction. Preferably, the surface direction is perpendicular to the thickness direction.

[0026] The element 2 is made of an insulating material. The insulating performance of element 2 can be defined by its resistance value. The resistance value of element 2 is not limited as long as it can prevent short circuits between the first conductive member 3 and the second conductive member 4.

[0027] Examples of insulating materials include thermal insulation materials. The thermal insulation performance of a thermal insulation material can be defined by its thermal conductivity.

[0028] The thermal conductivity of the insulating material is, for example, 1 W / m·K or less, preferably 0.5 W / m·K or less. When the thermal conductivity of the insulating material is below the above upper limit, a temperature difference can be secured in the thickness direction, and the resulting electromotive force can be increased.

[0029] There is no lower limit to the thermal conductivity of the insulation material. The thermal conductivity of the insulation material is, for example, 0.01 W / m·K or higher.

[0030] Examples of insulating materials include glass wool, rock wool, calcium silicate, polystyrene, polyethylene, urethane resin, melamine resin, phenolic resin, foamed glass, perlite, cellulose fiber, alumina fiber, ceramic fiber, carbon fiber, fumed silica, and alkali earth silicate. Preferably, glass wool, rock wool, and calcium silicate are used as insulating materials, and glass wool is preferred.

[0031] The base body 2 may consist of only one of the above-described insulating materials. The base body 2 may contain two or more of the above-described insulating materials. The base body 2 includes at least one of glass wool, rock wool, and calcium silicate. When the base body 2 includes at least one of glass wool, rock wool, and calcium silicate, the insulating properties of the base body 2 can be improved. This makes it possible to secure a temperature difference in the thickness direction and increase the electromotive force obtained. Preferably, the base body 2 includes a layer made of at least one of glass wool, rock wool, and calcium silicate. More preferably, the base body 2 consists of glass wool.

[0032] The thickness of the base body 2 is, for example, 10 mm or more, preferably 30 mm or more. If the thickness of the base body 2 is greater than or equal to the above lower limit, a temperature difference can be secured in the thickness direction, and the resulting electromotive force can be increased.

[0033] There is no upper limit to the thickness of base body 2. The thickness of base body 2 is, for example, 300 mm or less.

[0034] (2) First conductive member At least a portion of the first conductive member 3 is placed inside the base body 2. In this embodiment, the first conductive member 3 is thread-like.

[0035] The diameter of the first conductive member 3 is, for example, 50 μm or more, preferably 100 μm or more. If the diameter of the first conductive member 3 is greater than or equal to the above lower limit, the durability of the first conductive member 3 can be ensured. In addition, for example, when sewing the first conductive member 3 into the base body 2, the breakage of the first conductive member 3 can be suppressed.

[0036] The "diameter of the first conductive member 3" refers to the minimum length of the first conductive member 3 in the direction perpendicular to the direction in which the first conductive member 3 extends (the radial direction of the first conductive member 3). Specifically, if the cross-section of the first conductive member 3 in the radial direction is circular, the "diameter of the first conductive member 3" refers to the diameter of the circle. If the cross-section of the first conductive member 3 in the radial direction is elliptical, the "diameter of the first conductive member 3" refers to the length of the minor axis of the ellipse. If the first conductive member 3 is ribbon-shaped, the "diameter of the first conductive member 3" refers to the thickness of the first conductive member 3.

[0037] The diameter of the first conductive member 3 is, for example, 400 μm or less, preferably 300 μm or less. When the diameter of the first conductive member 3 is less than or equal to the above upper limit, the flexibility of the first conductive member 3 can be ensured, and the first conductive member 3 can be sewn into the base body 2.

[0038] In this embodiment, the first conductive member 3 is sewn into the base body 2. The first conductive member 3 penetrates the base body 2. The first conductive member 3 has a first connecting portion 3A, a second connecting portion 3B, and a main body portion 3C. The first connecting portion 3A is located outside the base body 2. The first connecting portion 3A is located on one surface S1 of the base body 2. The second connecting portion 3B is located outside the base body 2. The second connecting portion 3B is located on the other surface S2 of the base body 2. The main body portion 3C is located between the first connecting portion 3A and the second connecting portion 3B in the thickness direction. The main body portion 3C is located inside the base body 2. The main body portion 3C extends in the thickness direction of the base body 2. The main body portion 3C may extend along the thickness direction. The main body portion 3C may be inclined with respect to the thickness direction.

[0039] The first conductive member 3 is made of metal. The first conductive member 3 has a first Seebeck coefficient. The first Seebeck coefficient is, for example, 20 μV / K or less, preferably 10 μV / K or less. The first Seebeck coefficient is, for example, -10 μV / K or more, preferably -5 μV / K or more.

[0040] For example, as shown in FIG. 3, the first conductive member 3 has a core 31 and a metal layer 32.

[0041] The core 31 is made of pure metal. The core 31 is made of a pure metal different from the metal layer 32. Examples of the material of the core 31 include copper, aluminum, beryllium, cadmium, cobalt, erbium, gold, hafnium, holmium, indium, iridium, iron, lanthanum, lead, magnesium, molybdenum, neodymium, nickel, niobium, palladium, platinum, rhenium, rhodium, silver, tantalum, tin, titanium, tungsten, vanadium, zinc, and zirconium. Preferably, copper is mentioned as the material of the core 31.

[0042] The diameter D of the core 31 (the diameter of the core 31 in the radial direction of the first conductive member 3) is, for example, 50 μm or more, preferably 100 μm or more. When the diameter D of the core 31 is equal to or greater than the above lower limit value, the conductivity of the first conductive member 3 can be ensured.

[0043] The diameter D of the core 31 is, for example, 400 μm or less, preferably 300 μm or less. When the diameter D of the core 31 is equal to or less than the above upper limit value, a decrease in the electromotive force of the thermoelectric conversion element 1 due to heat conduction through the first conductive member 3 can be suppressed.

[0044] The metal layer 32 covers the core 31. The first conductive member 3 has the metal layer 32 on its surface. The metal layer 32 is made of a pure metal capable of forming an oxide film. The metal layer 32 protects the core 31. The metal layer 32 suppresses the progress of corrosion to the core 31. The metal layer 32 is preferably made of a metal that is less likely to corrode than the core 31 in a state of being wetted with water. Examples of the material of the metal layer 32 include aluminum, titanium, nickel, cobalt, zinc, or tin. Preferably, tin is mentioned as the material of the metal layer 32.

[0045] The thickness T of the metal layer 32 (the thickness of the metal layer 32 in the radial direction of the first conductive member 3) is, for example, 1 nm (0.001 μm) or more, preferably 1 μm or more. When the thickness T of the metal layer 32 is at least the above lower limit value, corrosion of the core 31 can be suppressed.

[0046] The thickness T of the metal layer 32 is, for example, 100 μm or less, preferably 10 μm or less. When the thickness T of the metal layer 32 is at most the above upper limit value, reduction of material cost can be achieved.

[0047] The first conductive member 3 may be made of an alloy. When the first conductive member 3 is made of an alloy, the first conductive member 3 does not have the metal layer 32. When the first conductive member 3 is made of an alloy, the first conductive member 3 is preferably made of an alloy that is less likely to corrode than iron in a state of being wetted with water. Examples of the alloy include stainless steel, aluminum alloy, nickel alloy, Advance, Alchrom - O, Al - Mg - Si, Al - Si, brass, ceramawire, beryllium copper, dummet, gilding metal, gold antimonide, gold gallium, gold molybdenum, gold palladium, Hastelloy, Inconel, Invar, Super Invar, iron chromium, Kanthal, Kovar, manganin, Molecularoy, Monel, nichrome, permalloy, piano, phosphor bronze, platinum palladium, platinum iridium, platinum rhodium, shape memory alloy, gold solder, silver solder, superconducting material, rhenium tungsten, Alumel - Chromel, constantan, copper constantan, and titanium alloy.

[0048] Preferably, stainless steel is used as the alloy. Examples of stainless steel include SUS630, SUS631, SUS301, SUS301J1, SUS301L, SUS302, SUS302B, SUSXM15J1, SUS303, SUS303Cu, SUS304, SUS304L, SUS304LN, SUS304N1, SUS304N2, SUS304Cu, SUSXM7, and SUS304J 1, SUS304J2, SUS305, SUS305J1, SUS309S, SUS310S, SUS315J1, SUS315J2, SUS316, SUS316L, SU S316N, SUS316LN, SUS316J1, SUS316J1L, SUS317, SUS317J1, SUS317L, SUS321, SUS347, SUS312L , SUS836L, SUS890L, SUS329J1, SUS329J3L, SUS329J4L, SUS430, SUH409, SUH409L, SUS405, SUS 410L, SUS429, SUS430F, SUS430LX, SUS430J1L, SUS443J1, SUS434, SUS436J1L, SUS436L, SUS444 Examples include SUS445J1, SUS445J2, SUSXM27, SUS447J1, SUS410, SUS403, SUS410S, SUS410F2, SUS416, SUS420J1, SUS431, SUS420J2, SUS420F2, SUS440A, SUS420F, SUS440B, SUS440B, and SUS440F.

[0049] (3) Second conductive member As shown in Figure 2, at least a portion of the second conductive member 4 is arranged inside the base body 2. In this embodiment, the second conductive member 4 is thread-like. The shape of the second conductive member 4 is not limited. The second conductive member 4 may be, for example, strip-shaped, needle-shaped, or rod-shaped.

[0050] The diameter of the second conductive member 4 is, for example, 150 μm or more, preferably 300 μm or more. If the diameter of the second conductive member 4 is greater than or equal to the above lower limit, the electromotive force of the second conductive member 4 can be increased.

[0051] The "diameter of the second conductive member 4" refers to the minimum length of the second conductive member 4 in the direction perpendicular to the direction in which the second conductive member 4 extends (the radial direction of the second conductive member 4). Specifically, if the cross-section of the second conductive member 4 in the radial direction is circular, the "diameter of the second conductive member 4" refers to the diameter of the circle. If the cross-section of the second conductive member 4 in the radial direction is elliptical, the "diameter of the second conductive member 4" refers to the length of the minor axis of the ellipse. If the second conductive member 4 is ribbon-shaped, the "diameter of the second conductive member 4" refers to the thickness of the second conductive member 4.

[0052] The diameter of the second conductive member 4 is, for example, 3000 μm or less, preferably 1500 μm or less, and more preferably 1000 μm or less.

[0053] In this embodiment, the second conductive member 4 is sewn into the base body 2. The second conductive member 4 penetrates the base body 2. The second conductive member 4 has a first connecting portion 4A, a second connecting portion 4B, and a main body portion 4C. The first connecting portion 4A is located outside the base body 2. The first connecting portion 4A is located on one surface S1 of the base body 2. The first connecting portion 4A is electrically connected to the first connecting portion 3A of the first conductive member 3 by a bonding material 10. Examples of bonding materials 10 include conductive bonding materials such as silver paste, copper paste, and solder. By electrically connecting the first connecting portion 4A to the first connecting portion 3A, the second conductive member 4 is electrically connected to the first conductive member 3. The second connecting portion 4B is located outside the base body 2. The second connecting portion 4B is located on the other surface S2 of the base body 2. The second connecting portion 4B is electrically connected to the second connecting portion 3B of the first conductive member 3 by a bonding material (not shown). The main body portion 4C is positioned between the first connecting portion 4A and the second connecting portion 4B in the thickness direction. The main body portion 4C is positioned inside the base body 2. The main body portion 4C is positioned separately from the main body portion 3C of the first conductive member 3. The main body portion 4C extends in the thickness direction of the base body 2. The main body portion 4C may extend along the thickness direction. The main body portion 4C may be inclined with respect to the thickness direction.

[0054] The second conductive member 4 is, for example, a P-type thermoelectric conversion member. The second conductive member 4 behaves as a P-type semiconductor. The second conductive member 4 has a second Seebeck coefficient. The second Seebeck coefficient is different from the first Seebeck coefficient. The second Seebeck coefficient is larger than the first Seebeck coefficient.

[0055] The second Seebeck coefficient is, for example, 10 μV / K or more, preferably 20 μV / K or more. The second Seebeck coefficient is, for example, 40 μV / K or less, preferably 30 μV / K or less.

[0056] The difference between the Seebeck coefficient of the first conductive member 3 (first Seebeck coefficient) and the Seebeck coefficient of the second conductive member 4 (second Seebeck coefficient) is, for example, 10 μV / K or more, preferably 20 μV / K or more. If the difference between the first Seebeck coefficient and the second Seebeck coefficient is greater than or equal to the above lower limit, the power generation performance of the thermoelectric conversion element 1 can be ensured. The difference between the first Seebeck coefficient and the second Seebeck coefficient is, for example, 65 μV / K or less, preferably 40 μV / K or less.

[0057] The second conductive member 4 contains a carbon material as a conductive material, and optionally a binder and a P-type dopant.

[0058] The carbon material imparts conductivity to the second conductive member 4. Examples of carbon materials include carbon nanotubes, carbon nanofibers, graphene, graphene nanoribbons, and fullerene nanowhiskers. Preferably, carbon nanotubes are used as the carbon material. In other words, the second conductive member 4 preferably contains carbon nanotubes, and optionally a binder and a P-type dopant. When the carbon material is carbon nanotubes, the electrical properties of the carbon nanotubes as a P-type semiconductor can be utilized to efficiently manufacture the second conductive member 4.

[0059] Furthermore, the second conductive member 4 may contain, in addition to the carbon material described above, a conductive material other than carbon material. Examples of conductive materials other than carbon material include semiconductor materials and conductive polymers.

[0060] Examples of semiconductor materials include bismuth (Bi), tellurium (Te), antimony (Sb), cobalt (Co), zinc (Zn), silicon (Si), germanium (Ge), iridium (Ir), lead (Pb), and their alloys, skutterudite, and constantan. While semiconductor materials may contain metallic elements, their crystal structure or the combination of elements in the alloy can result in higher resistance values ​​than metals, thus behaving as semiconductors. Semiconductor materials may also be semiconductor whiskers.

[0061] Examples of conductive polymers include polyacetylene, poly(p-phenylenevinylene), polypyrrole, polythiophene, polyaniline, poly(p-phenylene sulfide), a composite of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (PEDOT: PSS), a composite of poly(3,4-ethylenedioxythiophene) and polypropylsulfonic acid methylsiloxane (PEDOT: PSiPS), and a composite of poly(3,4-ethylenedioxythiophene) and p-toluenesulfonic acid (PEDOT: Tos).

[0062] The proportion of conductive material in the second conductive member 4 is, for example, 30% by mass or more, preferably 40% by mass or more, and more preferably 50% by mass or more. If the proportion of conductive material is above the above lower limit, the conductivity of the second conductive member 4 can be ensured.

[0063] There is no upper limit to the proportion of conductive material in the second conductive member 4. The proportion of conductive material in the second conductive member 4 is, for example, 100% by mass or less, preferably 70% by mass or less, and more preferably 60% by mass or less.

[0064] If the second conductive member 4 contains a binder, the proportion of conductive material in the second conductive member 4 is, for example, 40 parts by mass or more, preferably 60 parts by mass or more, per 100 parts by mass of binder. If the proportion of conductive material is above the above lower limit, the conductivity of the second conductive member 4 can be ensured.

[0065] If the second conductive member 4 contains a binder, the proportion of conductive material in the second conductive member 4 is, for example, 250 parts by mass or less, preferably 150 parts by mass or less, per 100 parts by mass of binder. When the proportion of conductive material is below the above upper limit, the proportion of binder can be ensured and the strength of the second conductive member 4 can be ensured.

[0066] The binder binds the conductive material. If the conductive material is carbon nanotubes, the binder binds the carbon nanotubes. Examples of binders include insulating resins and conductive resins.

[0067] Examples of insulating resins include polyethylene glycol, epoxy resin, acrylic resin, urethane resin, polystyrene resin, and polyvinyl resin. Examples of polyvinyl resins include polyvinyl chloride, polyvinylpyrrolidone, polyvinyl alcohol, and polyvinyl acetate.

[0068] Examples of conductive resins include polyacetylene, poly(p-phenylenevinylene), polypyrrole, polythiophene, polyaniline, poly(p-phenylene sulfide), and poly(3,4-ethylenedioxythiophene).

[0069] Preferably, the binder is an insulating resin, and more preferably, polyethylene glycol.

[0070] The proportion of binder in the second conductive member 4 is, for example, 30% by mass or more, preferably 40% by mass or more. If the proportion of binder is above the lower limit mentioned above, the tensile strength of the second conductive member 4 can be ensured.

[0071] The proportion of binder in the second conductive member 4 is, for example, 70% by mass or less, preferably 60% by mass or less. When the proportion of binder is below the above upper limit, the proportion of conductive material can be ensured, and the conductivity of the second conductive member 4 can be ensured.

[0072] The proportion of binder in the second conductive member 4 is, for example, 40 parts by mass or more, preferably 60 parts by mass or more, per 100 parts by mass of conductive material. If the proportion of binder is above the above lower limit, the tensile strength of the second conductive member 4 can be ensured.

[0073] The proportion of binder in the second conductive member 4 is, for example, 250 parts by mass or less, preferably 150 parts by mass or less, per 100 parts by mass of conductive material. When the proportion of binder is below the above upper limit, the proportion of conductive material can be ensured, and the conductivity of the second conductive member 4 can be ensured.

[0074] The p-type dopant imparts the electrical properties of a p-type semiconductor to the second conductive member 4. However, if the carbon material is a carbon nanotube, the second conductive member 4 does not need to contain a p-type dopant, as the carbon nanotube already possesses the electrical properties of a p-type semiconductor.

[0075] The second conductive member 4 may be an N-type thermoelectric conversion member. When the second conductive member is an N-type thermoelectric conversion member, the second conductive member 4 does not contain a P-type dopant, and may contain an N-type dopant if necessary.

[0076] The N-type dopant imparts the electrical properties of an N-type semiconductor to the second conductive member 4. Examples of N-type dopants include 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF). ６), polyethyleneimine (PEI), ethylenediaminetetrakis(propoxylate-block-ethoxylate) tetrol (trade name: Tetronic® 1107), reduced benzyl viologen (reduced BV), diphenylphosphine (dpp), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb), bis(diphenylphosphinomethyl)phenylphosphine (dppp), bis(diphenylphosphinoethyl)phenylphosphine (ppmdp), bis[(diphenylphosphinomethyl)phenylphosphino]methane (dppmpm), triphenylphosphine (tpp), tris(p-fluorophenyl)phosphine (F-tpp), tris(p-chlorophenyl)phosphine (Cl-tpp), tris(p-methoxy) Examples include phenyl)phosphine (MeO-tpp), tris(4-methoxy-3,5-dimethylphenyl)phosphine (tmdp), indole (Id), polyvinylpyrrole (PVPy), polyvinylpyrrolidone (PVP), 1,3-dimethyl-2-(o-methoxyphenyl)benzimidazole (o-MeO-DMBI), hydrazine monohydrate (HH), phenylhydrazine (MPH), 1,2-diphenylhydrazine (DPH), diazabicycloundecene (DBU), 1,5,7-triazabicyclo[4.4.0]deca-5-ene (TBD), and 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene (MTBD). Triphenylphosphine is preferred as the N-type dopant.

[0077] The surface of the second conductive member 4 may be coated. In other words, the second conductive member 4 may have a core containing a conductive material and, if necessary, a binder and a dopant (P-type dopant or N-type dopant), and a coating layer that coats the surface of the core. Examples of materials for the coating layer include resins, carbon fibers, metals, metal oxides, and silicon compounds. Examples of resins include epoxy resins, acrylic resins, urethane resins, fluororesins, polyvinyl alcohol, ethylene vinyl alcohol, polybutylene terephthalate, polyamides, polyimides, polyvinyl acetals, polysilsesquioxanes, polysilazanes, and parylenes. Examples of carbon fibers include carbon nanofibers. Examples of metals include aluminum and chromium. Examples of metal oxides include smectite, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), and zinc tin oxide (ZTO). Examples of silicon compounds include silica nanoparticles, silicon dioxide, and silicon nitride. The coating layer can improve the strength and wear resistance of the second conductive member 4. Furthermore, the coating layer can suppress the deterioration of the second conductive member 4 due to oxygen and moisture.

[0078] 2. Insulation Structure of Piping Next, an example of how the thermoelectric conversion element 1 is used, specifically the insulation structure 100 of the piping, will be described.

[0079] As shown in Figure 4, the pipe insulation structure 100 comprises a pipe 11, an insulating material 12, the thermoelectric conversion element 1 (see Figure 5) described above, and an outer covering member 13. The insulating material 12 covers the pipe 11. The outer covering member 13 covers the insulating material 12.

[0080] As shown in Figure 5, the insulation material 12 has, for example, a cylindrical shape. The insulation material 12 extends in the direction in which the pipe 11 extends.

[0081] The thermoelectric conversion element 1 utilizes a portion of the thermal insulation material 12 as the base body 2 (see Figure 2). In other words, the base body 2 is a portion of the thermal insulation material 12. The first conductive member 3 and the second conductive member 4 are sewn into the thermal insulation material 12.

[0082] 3. Effects (1) In the thermoelectric conversion element 1, the first conductive member 3 has a metal layer 32 on its surface made of a pure metal capable of forming an oxide film (see Figure 3), or is made of an alloy.

[0083] Therefore, as shown in Figure 3, when the first conductive member 3 has a metal layer 32 on its surface, the formation of an oxide film on the metal layer 32 can suppress corrosion from progressing to the interior of the first conductive member 3 (specifically, the core 31).

[0084] Furthermore, if the first conductive member 3 is made of an alloy, corrosion of the first conductive member 3 can be suppressed by selecting a corrosion-resistant alloy such as stainless steel.

[0085] As a result, as shown in Figure 2, in a thermoelectric conversion element 1 comprising a first conductive member 3 made of metal and a second conductive member 4 containing a carbon material, corrosion of the first conductive member 3 can be suppressed.

[0086] (2) According to the piping insulation structure 100, as shown in Figure 5, a thermoelectric conversion element 1 is used in which corrosion of the first conductive member 3 is suppressed. Therefore, as shown in Figure 4, abnormalities in the insulation material 12 around the piping 11 can be reliably detected.

[0087] 4. Modified Examples Modified examples will be described. In the modified examples, the same reference numerals are used for components similar to those in the embodiments described above, and their descriptions are omitted.

[0088] (1) The applications of the thermoelectric element 1 are not limited to the insulation structure 100 of piping. The thermoelectric element 1 can be used, for example, as insulation material for the roofs and exterior walls of houses, vacuum insulation material, insulation material for cooler boxes, insulation material for liquefied gas tanks, and insulation material for fermentation culture tanks.

[0089] (2) The insulating material is not limited to thermal insulation material. As shown in Figure 6, the thermoelectric conversion element 200 may have a resin body 201 as an example of a base body, a first conductive member 3, and a second conductive member 4. Examples of materials for the resin body 201 include thermoplastic resins as an example of an insulating material, and thermosetting resins as an example of an insulating material.

[0090] Examples of thermoplastic resins include polyvinyl chloride (PVC), polystyrene (PS), styrene-based resins (HIPS, SAN, ABS), acrylic resin (PMMA), polyethylene (PE), polypropylene (PP), polycarbonate (PC), modified polyetherphenyl (m-PPE), polyacetal (POM), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polyarylate (PAR), polysulfone (PSU), polyethersulfone (PES), thermoplastic polyimide (TPI, PEI, PAI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), liquid crystal polymer (LCP), and fluororesins (PTFE, PFA, PVDF, ETFE).

[0091] Examples of thermosetting resins include epoxy resin (EP), silicone resin (SI), diallyl phthalate resin (PDAP), phenolic resin (PF), unsaturated polyester resin (UP), polyimide resin (PI), polyurethane resin (PUR), melamine resin (MF), urea resin (UF), and thermosetting acrylic resin (PAR).

[0092] Preferably, the material for the resin base 201 is a thermosetting resin, and more preferably, an epoxy resin.

[0093] Furthermore, the thermoelectric conversion element 200 may also include electrodes 202 and 203.

[0094] The electrode 202 is positioned at one end of the resin body 201 in the thickness direction. The electrode 202 is positioned outside the resin body 201. The electrode 202 is electrically connected to the first conductive member 3. The electrode 202 is electrically connected to one end of the first conductive member 3 via a bonding material such as solder. In this embodiment, the electrode 202 is a lead wire made of metal.

[0095] The electrode 203 is positioned at one end of the resin body 201 in the thickness direction. The electrode 203 is positioned away from the electrode 202. The electrode 203 is positioned outside the resin body 201. The electrode 203 is electrically connected to the second conductive member 4. The electrode 203 is electrically connected to the other end of the second conductive member 4 via a bonding material such as solder. In this embodiment, the electrode 203 is a lead wire made of metal.

[0096] Note that electrodes 202 and 203 are not limited to lead wires. Electrodes 202 and 203 may have a flat plate shape.

[0097] In this modified example, as shown in Figure 7, the thermoelectric conversion element 200 is embedded in the thermal insulation material 12 described above. In this case, the exterior member 13 may have an opening 130. The thermoelectric conversion element 200 is placed inside the opening 130. The thermal insulation structure 100 of the piping may further include a second thermal insulation material 14 and a cover 15.

[0098] The second insulation material 14 is placed inside the opening 130. The second insulation material 14 is placed on top of the insulation material 12. The second insulation material 14 covers the thermoelectric conversion element 200. In the thickness direction of the insulation material 12, the second insulation material 14 is placed on the opposite side of the piping 11 from the thermoelectric conversion element 200. The second insulation material 14 is made of the same material as the insulation material 12, for example. The second insulation material 14 may be made of a different material from the insulation material 12.

[0099] The cover 15 closes the opening 130 of the exterior member 13. The cover 15 can open and close the opening 130. The cover 15 may be removable from the exterior member 13. The cover 15 is made of the same material as the exterior member 13, for example. The cover 15 may be made of a different material than the exterior member 13.

[0100] (3) The same effects and advantages as those of the embodiments described above can be obtained with the modified example (1) or (2).

[0101] The present invention will be further described below with reference to examples and comparative examples. However, the present invention is not limited to the examples and comparative examples. Furthermore, specific numerical values ​​such as the proportions, dimensions, and physical properties used in the examples and comparative examples can be replaced with the corresponding upper limits (numbers defined as "less than or equal to") or lower limits (numbers defined as "greater than or equal to") of the proportions, dimensions, and physical properties described in the "Modes for Carrying Out the Invention" above.

[0102] 1. Manufacturing of Thermoelectric Conversion Elements (1) Manufacturing of the Second Conductive Member A P-type thermoelectric conversion member was manufactured as the second conductive member shown in Figure 2.

[0103] In the production of the second conductive component, a carbon nanotube dispersion was first prepared.

[0104] In preparing the carbon nanotube dispersion, first, 20 g of glycerin and 0.4 g of a 5% by mass aqueous solution of carboxymethylcellulose sodium salt (CMC-Na, medium viscosity) were mixed in a mortar as a dispersant.

[0105] Next, 200 mg of carbon nanotubes was added to the resulting mixture and stirred for 1 minute to obtain a pre-dispersion of carbon nanotubes.

[0106] Next, a thin-film swirling high-speed mixer (FM-40L, manufactured by Primix Corporation) was used to stir the carbon nanotube predispersion at a peripheral speed of 10 m / s for 60 seconds to obtain a carbon nanotube dispersion.

[0107] Next, the resulting carbon nanotube dispersion was dispensed into water (ultrapure water) using a syringe (with an inner diameter of the nozzle of 4 mm).

[0108] In detail, first, the carbon nanotube dispersion was filled into a syringe and centrifuged at 2000 rpm for 3 minutes using a centrifuge to remove air bubbles from the carbon nanotube dispersion in the syringe.

[0109] Next, an aluminum container was placed on a rotating platform, draining equipment was placed inside the container, and ultrapure water was filled into the container. A tube (length: 150 mm) was also connected to a syringe and attached to a syringe pump.

[0110] Next, while the container was rotated at 0.8 rpm by operating the turntable, the carbon nanotube dispersion in the syringe was dispensed into the ultrapure water in the container at a discharge rate of 400 ml / hour using a syringe pump.

[0111] Once the container had completed one rotation, the turntable and syringe pump were stopped, and the discharged carbon nanotube dispersion was left to stand in the container for 24 hours.

[0112] Next, the discharged carbon nanotube dispersion was removed from the container using a draining device and dried at 80°C for 1 hour to obtain the second conductive material (dried carbon nanotube dispersion).

[0113] The diameter of the obtained second conductive member was 250 mm.

[0114] (2) Measurement of Seebeck coefficient The Seebeck coefficient of the obtained second conductive member was measured using a thermoelectric property evaluation device (ZEM-3, manufactured by Advance Engineering Co., Ltd.).

[0115] In detail, the electromotive force of the second conductive member was measured at 25°C, 30°C, 40°C, 50°C, and 60°C, and the Seebeck coefficient was calculated from the measured electromotive force. The Seebeck coefficient of the second conductive member was 35 μV / K.

[0116] (3) Manufacturing of thermoelectric elements A first conductive member made of the material shown in Table 1 and the second conductive member were sewn into a thermal insulation material (material: glass wool, thickness: 40 mm), and as shown in Figure 1, the first conductive member and the second conductive member were bonded together using silver paste. In this way, thermoelectric elements for each example and comparative example were manufactured.

[0117] Table 1 shows the difference in Seebeck coefficients between the first conductive member and the second conductive member.

[0118] 2. Evaluation of Thermoelectric Conversion Elements (1) Corrosion In each example and comparative example, the corrosion susceptibility of the first conductive member was evaluated using the following methods and evaluation criteria.

[0119] After wetting the thermoelectric conversion element with 150 ml of 1% by mass salt water, the surface of the first conductive component was observed with a digital microscope (VHX6000, manufactured by Keyence Corporation) 30 minutes later. <Evaluation Criteria> ○: No change in appearance before and after water injection. ×: Rusting occurs before and after water injection.

[0120] (2) Power generation performance In each example and comparative example, the power generation performance of the thermoelectric conversion element was evaluated by the following method.

[0121] A first thermocouple (1HKN035, manufactured by Chino Corporation) was attached to one side of the thermoelectric conversion element, and a second thermocouple (1HKN035, manufactured by Chino Corporation) was attached to the other side of the thermoelectric conversion element. The first and second thermocouples were connected to a data logger (GRAPHTEC Corporation, GL240).

[0122] Next, the thermoelectric element was placed on the hot plate along with the first and second thermocouples so that the other side of the thermoelectric element was in contact with the hot plate.

[0123] Furthermore, the first conductive member of the thermoelectric conversion element and the data logger were connected using alligator clips and IC clips.

[0124] Next, the hot plate temperature was set to 60°C, 80°C, and 100°C, and the electromotive force (voltage value) generated in the thermoelectric conversion element at each temperature was recorded using a data logger.

[0125] In each example and comparative example, an electromotive force of 0.5 mV or more was generated at each temperature.

[0126]

[0127] The above invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and should not be interpreted restrictively. Modifications of the present invention that are obvious to those skilled in the art are included in the claims below.

[0128] The thermoelectric conversion element and the piping insulation structure of the present invention can be used for detecting abnormalities in the insulation material around the piping.

[0129] 1 Thermoelectric conversion element 2 Base body 3 First conductive member 4 Second conductive member 100 Thermal insulation structure 11 Piping 12 Thermal insulation material 13 Exterior member 130 Opening 14 Second thermal insulation material 15 Cover

Claims

1. A thermoelectric conversion element comprising: a base body made of an insulating material; a first conductive member made of a metal, at least a portion of which is disposed within the base body; and a second conductive member containing a carbon material as a conductive material and electrically connected to the first conductive member, at least a portion of which is disposed within the base body, wherein the first conductive member has a metal layer on its surface made of a pure metal capable of forming an oxide film, or is made of an alloy.

2. The thermoelectric conversion element according to claim 1, wherein the first conductive member comprises a core and the metal layer covering the core.

3. The thermoelectric element according to claim 2, wherein the core is made of a pure metal different from the metal layer.

4. The thermoelectric element according to claim 1, wherein the metal layer is made of aluminum, titanium, nickel, cobalt, zinc, or tin.

5. The thermoelectric conversion element according to claim 1, wherein the first conductive member is thread-like, and the diameter of the first conductive member is 400 μm or less.

6. The thermoelectric conversion element according to claim 1, wherein the difference between the Seebeck coefficient of the first conductive member and the Seebeck coefficient of the second conductive member is 10 μV / K or more.

7. The thermoelectric element according to claim 1, wherein the second conductive member is a P-type thermoelectric member or an N-type thermoelectric member.

8. A thermal insulation structure for piping comprising piping, a thermal insulation material covering the piping, and a thermoelectric conversion element according to any one of claims 1 to 7, wherein the base body is a part of the thermal insulation material.

9. A pipe insulation structure comprising: a pipe; an insulating material covering the pipe; and a thermoelectric conversion element according to any one of claims 1 to 7 embedded in the insulating material, wherein the base body is made of a thermosetting resin or a thermoplastic resin.

10. The piping insulation structure according to claim 9, further comprising a second insulation material placed on top of the insulation material and covering the thermoelectric conversion element.

11. The piping insulation structure according to claim 10, further comprising an exterior member covering the insulation material, wherein the exterior member has an opening, and the thermoelectric conversion element is disposed within the opening.

12. The pipe insulation structure according to claim 11, further comprising a cover that closes the opening of the exterior member.

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