WO2021132189A1 - 複合材料、複合材料の製造方法、および熱電変換材料 - Google Patents

複合材料、複合材料の製造方法、および熱電変換材料 Download PDF

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WO2021132189A1
WO2021132189A1 PCT/JP2020/047768 JP2020047768W WO2021132189A1 WO 2021132189 A1 WO2021132189 A1 WO 2021132189A1 JP 2020047768 W JP2020047768 W JP 2020047768W WO 2021132189 A1 WO2021132189 A1 WO 2021132189A1
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composite material
fibrous carbon
thermoelectric conversion
bite
nanoplate
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PCT/JP2020/047768
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English (en)
French (fr)
Japanese (ja)
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内田　秀樹
雅之 高尻
隼人 矢吹
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日本ゼオン株式会社
学校法人東海大学
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Publication of WO2021132189A1 publication Critical patent/WO2021132189A1/ja

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/855—Thermoelectric active materials comprising inorganic compositions comprising compounds containing boron, carbon, oxygen or nitrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B19/00—Selenium; Tellurium; Compounds thereof
    • C01B19/04—Binary compounds including binary selenium-tellurium compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/174—Derivatisation; Solubilisation; Dispersion in solvents
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/01—Manufacture or treatment
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/857—Thermoelectric active materials comprising compositions changing continuously or discontinuously inside the material

Definitions

  • the present invention relates to composite materials, methods for producing composite materials, and thermoelectric conversion materials.
  • thermoelectric conversion element is an element that utilizes the "Zebec effect" that a voltage is generated when a temperature difference is generated at both ends of a substance, and is usually an n (negative) type thermoelectric conversion material and a p (positive) type. It is constructed in combination with the thermoelectric conversion material of.
  • thermoelectric conversion materials that can be used for the thermoelectric conversion element
  • a bismuth tellurium (Bi 2 Te 3 ) nanoplate (hereinafter, also referred to as “BiTe nanoplate”) is known (non-).
  • Patent Document 1 BiTe nanoplates are attracting attention as n-type thermoelectric conversion materials having a large absolute value of Seebeck coefficient.
  • the BiTe nanoplate has a problem that the electric conductivity is low and the resistance of the thermoelectric conversion element increases when it is used as a thermoelectric conversion material.
  • thermoelectric conversion material a mixture of BiTe nanoplates and a conductive substance such as carbon nanotubes (hereinafter, also referred to as “CNT”) as a thermoelectric conversion material.
  • CNT carbon nanotubes
  • an object of the present invention is to provide a composite material having both thermoelectric conversion characteristics and conductivity at a high level. Another object of the present invention is to provide a method for producing a composite material, which can produce a composite material having both thermoelectric conversion characteristics and conductivity at a high level. Furthermore, an object of the present invention is to provide a thermoelectric conversion material containing a composite material having both thermoelectric conversion characteristics and conductivity at a high level.
  • the present inventors have conducted diligent studies to achieve the above object. As a result, if the BiTe nanoplates are synthesized by the sorbothermal method in the presence of fibrous carbon nanostructures such as CNTs, the BiTe nanoplates and the fibrous carbon nanostructures are integrated. We have found that a composite material having both thermoelectric conversion characteristics and conductivity at a high level can be obtained, and have completed the present invention.
  • the present invention advantageously solves the above problems, and the composite material of the present invention is characterized in that a bismuth tellurium nanoplate and a fibrous carbon nanostructure are integrated.
  • the composite material of the present invention can be suitably used as a thermoelectric conversion material.
  • the content of the fibrous carbon nanostructures is preferably 7% by mass or more and 15% by mass or less.
  • the thermoelectric conversion characteristics and the conductivity can be compatible at a higher level.
  • the content of the fibrous carbon nanostructures in the composite material can be measured by the method described in the examples of the present specification.
  • the fibrous carbon nanostructure is a carbon nanotube. If the fibrous carbon nanostructure is a carbon nanotube, thermoelectric conversion characteristics and conductivity can be compatible at a higher level.
  • the present invention aims to advantageously solve the above problems, and the method for producing a composite material of the present invention includes a bismuth source, a tellurium source, a fibrous carbon nanostructure, and a solvent.
  • the fibrous carbon nanostructure is a carbon nanotube. If the fibrous carbon nanostructure is a carbon nanotube, thermoelectric conversion characteristics and conductivity can be compatible at a higher level.
  • thermoelectric conversion material of the present invention aims to solve the above problems advantageously, and the thermoelectric conversion material of the present invention is characterized by containing any of the above composite materials. If any of the above composite materials is included in this way, the thermoelectric conversion characteristics and the conductivity of the thermoelectric conversion material can be compatible at a high level.
  • the thermoelectric conversion material of the present invention can be suitably used for manufacturing a thermoelectric conversion element.
  • thermoelectric conversion material having both thermoelectric conversion characteristics and conductivity at a high level. Further, according to the present invention, it is possible to provide a method for producing a composite material capable of producing a composite material having both thermoelectric conversion characteristics and conductivity at a high level. Further, according to the present invention, it is possible to provide a thermoelectric conversion material having both thermoelectric conversion characteristics and conductivity at a high level.
  • thermoelectric conversion material of the present invention is excellent in thermoelectric conversion characteristics and conductivity, it can be suitably used as a thermoelectric conversion material for a thermoelectric conversion element.
  • the method for producing a composite material of the present invention can be used for producing a composite material of the present invention.
  • thermoelectric conversion material of the present invention contains the composite material of the present invention, and can be suitably used for, for example, manufacturing a thermoelectric conversion element.
  • the composite material of the present invention is a composite material in which a BiTe nanoplate and a fibrous carbon nanostructure are integrated. Further, since the composite material of the present invention integrates the BiTe nanoplate and the fibrous carbon nanostructure, it is higher than the case where the BiTe nanoplate and the fibrous carbon nanostructure are simply mixed. It is possible to achieve both thermoelectric conversion characteristics and high conductivity. Here, “high thermoelectric conversion characteristics” means that the absolute value of the Seebeck coefficient is large.
  • the composite material of the present invention usually has a negative Seebeck coefficient and can be used as an n-type thermoelectric conversion material.
  • the composite material of the present invention can be produced by the method for producing a composite material of the present invention, which will be described later.
  • the composite material of the present invention is not particularly limited, but is preferably obtained as a sheet as described later from the viewpoint of handleability and the like. Since the composite material of the present invention has good properties, it is not necessary to perform a treatment such as high-temperature firing after the film formation.
  • BiTe nanoplates are thin plate-like nanostructures composed of bismuth tellurium crystals.
  • the composition of bismuth tellurium is tritellurium dibismuth (Bi 2 Te 3 ).
  • the planar shape of the BiTe nanoplate is typically hexagonal as shown in FIGS. 1 to 3, but is not limited thereto.
  • the average size (size of one side) of the BiTe nanoplate is not particularly limited, and is typically in the range of 500 nm or more and 2000 nm or less.
  • the average size of the BiTe nanoplates is determined by measuring the length of one side of 100 randomly selected BiTe nanoplates from a scanning electron microscope (SEM) photograph of the surface of the composite material and calculating the average value. Obtainable.
  • SEM scanning electron microscope
  • the size of the BiTe nanoplate can be controlled by adjusting various conditions of the solvothermal treatment described later.
  • the size (size of one side) of the BiTe nanoplate is not uniform and varies (Figs. 1 to 3).
  • the size of the BiTe nanoplate typically varies in the range of 500 nm or more and 2000 nm or less. The reason for such variation is not always clear, but in order to synthesize BiTe nanoplates in the presence of fibrous carbon nanostructures, BiTe nanoplates are formed with the fibrous carbon nanostructures as the core as described above. It is presumed that this is because it does.
  • the size of the BiTe nanoplate does not vary and is uniform (Fig. 4). ..
  • the average thickness of the BiTe nanoplate is not particularly limited, but is typically 50 nm or less, for example, about 30 nm.
  • the average thickness of BiTe nanoplates can be obtained by measuring the thickness of 100 randomly selected BiTe nanoplates from scanning electron microscope (SEM) photographs of the cross section of the composite and calculating the average value. it can.
  • the thickness of the BiTe nanoplate can be controlled by adjusting various conditions of the solvothermal treatment described later.
  • BiTe nanoplates are synthesized from bismuth source compounds and tellurium source compounds by the solvothermal method described later.
  • the BiTe nanoplate is an n-type thermoelectric conversion material and has a negative Seebeck coefficient (unit: ⁇ V ⁇ K -1 ).
  • the Seebeck coefficient is an index showing the thermoelectromotive force per 1K of absolute temperature, and the larger the absolute value, the larger the thermoelectromotive force.
  • the Seebeck coefficient can be measured by the method described in the examples.
  • the fibrous carbon nanostructure contained in the composite material of the present invention is not particularly limited as long as it is a conductive nano-sized carbon structure, and examples thereof include carbon nanotubes (CNTs), carbon nanohorns, and carbon nanofibers. Be done. From the viewpoint of achieving both thermoelectric conversion characteristics and conductivity at a higher level, the fibrous carbon nanostructure is preferably CNT.
  • the CNT may be a single-walled carbon nanotube or a multi-walled carbon nanotube, but the CNT preferably contains at least a single-walled CNT.
  • the conductivity of the obtained composite material can be enhanced and the Seebeck coefficient can be sufficiently secured, and the thermoelectric conversion characteristics and conductivity of the composite material can be compatible at a higher level.
  • the ratio of the single-walled CNTs in the CNTs is preferably 50% or more, more preferably 70% or more, and further preferably 90% or more.
  • the "ratio of single-walled CNTs in CNTs" can be determined by counting the number of single-walled CNTs in 100 CNTs randomly selected using a transmission electron microscope.
  • the average diameter of the fibrous carbon nanostructures can be 0.5 nm or more, 1 nm or more, and 2.5 nm or more.
  • the upper limit of the average diameter of the fibrous carbon nanostructure is not particularly limited, but is, for example, 15 nm or less, 10 nm or less, and 6 nm or less.
  • the average length of the fibrous carbon nanostructures is preferably 0.1 ⁇ m or more, preferably 1 cm or less, and more preferably 3 mm or less. If fibrous carbon nanostructures having an average length within the above range are used, the thermoelectric conversion characteristics and conductivity of the composite material can be compatible at a higher level.
  • the average length of the fibrous carbon nanostructures can be determined by measuring the length of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope.
  • the average diameter (Av) and the standard deviation ( ⁇ ) of the diameter satisfy the relational expression: 0.20 ⁇ (3 ⁇ / Av) ⁇ 0.80. If a fibrous carbon nanostructure satisfying the above relationship is used, the thermoelectric conversion characteristics and conductivity of the composite material can be compatible at a higher level.
  • "average diameter of fibrous carbon nanostructures (Av)” and “standard deviation of diameter of fibrous carbon nanostructures ( ⁇ : sample standard deviation)” are determined by a transmission electron microscope, respectively. The diameter (outer diameter) of 100 fibrous carbon nanostructures randomly selected using the nanostructures can be measured and determined.
  • the BET specific surface area of the fibrous carbon nanostructure is preferably 600 m 2 / g or more, and more preferably 800 m 2 / g or more.
  • the thermoelectric conversion characteristics and conductivity of the composite material can be compatible at a higher level.
  • the upper limit of the BET specific surface area of the fibrous carbon nanostructure is not particularly limited, but is, for example, 2600 m 2 / g or less.
  • the "BET specific surface area" of the fibrous carbon nanostructure can be determined by the BET method by measuring the nitrogen adsorption isotherm at 77K.
  • BELSORP registered trademark
  • -max manufactured by Nippon Bell Co., Ltd.
  • the method for producing the fibrous carbon nanostructure used in the present invention is not particularly limited, and is not particularly limited, a method by catalytic hydrogen reduction of carbon dioxide, an arc discharge method, a chemical vapor deposition method (CVD method), and a laser. Examples thereof include an evaporation method, a vapor phase growth method, a vapor phase flow method, and a HiPCO method.
  • the fibrous carbon nanostructure for example, when a raw material compound and a carrier gas are supplied on a substrate having a catalyst layer for producing carbon nanotubes on the surface and CNTs are synthesized by a CVD method, the CNTs are contained in the system.
  • the fibrous carbon nanostructure may have a functional group such as a carboxyl group introduced therein.
  • the functional group can be introduced by a known method such as an oxidation treatment method using hydrogen peroxide or nitric acid, or a contact treatment method with a supercritical fluid, a subcritical fluid or a high-temperature high-pressure fluid.
  • the content of the fibrous carbon nanostructures is preferably 2% by mass or more, more preferably 5% by mass or more, and further preferably 7% by mass or more.
  • the content of the fibrous carbon nanostructure is preferably 20% by mass or less, more preferably 17% by mass or less, and further preferably 15% by mass or less. If the fibrous carbon nanostructures are present in the composite material within the above abundance ratio, thermoelectric conversion characteristics and conductivity can be compatible at a higher level.
  • the content of the fibrous carbon nanostructure may be 2.7% by mass or more, 4.9% by mass or more, or 6.7% by mass or more. Further, it may be 14.4% by mass or less.
  • the fibrous carbon nanostructures in the composite material is increased, the fibrous carbon nanostructures may be densely packed in the composite material, and uneven density of the fibrous carbon nanostructures may occur. ..
  • a bismuth tellurium nanoplate (BiTe nanoplate) and a fibrous carbon nanostructure are integrated.
  • the bismuth tellurium nanoplate and the fibrous carbon nanostructure are integrated means that the bismuth tellurium nanoplate and the fibrous carbon nanostructure are bonded to the extent that they are not separated.
  • the nanoplate of bismuth tellurium and the fibrous carbon nanostructure are integrated means that one or more fibrous carbon nanostructures and one or more bismuth tellurium nanostructures are integrated.
  • a state in which the plates are entangled and bonded to each other a state in which one or more fibrous carbon nanostructures penetrate one or more bismuth tellurium nanoplates and are bonded to each other, and a combination thereof. It refers to the state. Therefore, in "the bismuth tellurium nanoplate and the fibrous carbon nanostructure are integrated", for example, both are simply mixed by simply mixing the bismuth tellurium nanoplate and the fibrous carbon nanostructure. It does not include the state where it overlaps with and is connected only by a weak bond such as van der Waals force.
  • FIGS. 1 to 4 the structure in which the BiTe nanoplate and the fibrous carbon nanostructure in the composite material of the present invention are integrated and the structure in which both are not integrated are concretely described.
  • FIGS. 1 to 3 are scanning electron microscope (SEM) photographs of the surface of a coating film (sheet) formed using the composite material of the present invention.
  • FIG. 4 is a scanning electron microscope (SEM) photograph of a sheet made from a mixture of BiTe nanoplates and CNTs as fissure carbon nanostructures.
  • SEM scanning electron microscope
  • thermoelectric conversion characteristics and the conductivity can be achieved at a high level by integrating the BiTe nanoplate and the fibrous carbon nanostructure.
  • the BiTe nanoplates and the fibrous carbon nanostructures are simply mixed, the BiTe nanoplates having low electrical conductivity enter between the individual fibrous carbon nanostructures, and the fibrous carbon nanostructures are interleaved with each other. It is presumed that the movement of electrons is hindered and the conductivity decreases.
  • the fibrous carbon nanostructures are inserted between the individual BiTe nanoplates and the BiTe nanoplates are separated from each other, so that the movement of carriers (electrons) is hindered and the thermoelectromotive force is reduced.
  • the BiTe nanoplate and the fibrous carbon nanostructure are integrated, the movement of electrons (carriers) is not hindered, so it is presumed that thermoelectric conversion characteristics and conductivity can be compatible at a high level. Will be done.
  • the composite material of the present invention it is preferable that all of the BiTe nanoplates and the fibrous carbon nanostructures are integrated, but to the extent that the effects of the present invention are not impaired, the unintegrated BiTe nanoplates and / or Fibrous carbon nanostructures may be included in the composite.
  • the composite material of the present invention can be dispersed in a solvent by a general dispersion method used when dispersing CNTs in a solvent, such as an ultrasonic method, an ultrasonic homogenizer method, a jet mill method, or a bead mill method. , It is preferable that the structure in which the BiTe nanoplate and the fibrous carbon nanostructure are integrated remains.
  • the method for producing a composite material of the present invention is a step of preparing a raw material composition containing a bismuth source, a tellurium source, a fibrous carbon nanostructure, and a solvent, and optionally further containing other components (hereinafter, """Preparationstep")and; A step of subjecting the raw material composition to a sorbothermal treatment to form a composite material in which BiTe nanoplates and fibrous carbon nanostructures are integrated (hereinafter referred to as "formation step"). And at least include.
  • the BiTe nanoplate and the fibrous carbon nanostructure are easily integrated to achieve both thermoelectric conversion characteristics and conductivity at a high level. It is possible to obtain a composite material that can be obtained.
  • the method for producing the composite material of the present invention may optionally include steps other than the preparation step and the forming step (hereinafter, referred to as "other steps"). Hereinafter, each step will be described.
  • the preparation step is a step of preparing a raw material composition containing a bismuth source, a tellurium source, a fibrous carbon nanostructure, and a solvent, and is not particularly limited as long as the raw material composition can be finally prepared.
  • the raw material composition may be purchased, or the above-mentioned components may be mixed to prepare a raw material composition.
  • a raw material composition can be prepared by subjecting a mixed solution containing a predetermined amount of a bismuth source, a tellurium source, a fibrous carbon nanostructure, a solvent, an arbitrary additive, and the like to an arbitrary dispersion treatment. it can.
  • Examples of such a dispersion treatment include the dispersion treatment for obtaining a cavitation effect or the dispersion treatment for obtaining a crushing effect described in International Publication No. 2016/103706.
  • a mixture (precursor solution) containing a predetermined amount of a bismuth source, a tellurium source, a solvent, and an arbitrary additive is prepared, and a fibrous carbon nanostructure dispersion having a predetermined concentration is added to the precursor solution.
  • a raw material composition (dispersion liquid) may be prepared by mixing a predetermined amount.
  • the fibrous carbon nanostructure dispersion liquid can be obtained by mixing the fibrous carbon nanostructures with a solvent so as to have a predetermined concentration and subjecting them to an arbitrary dispersion treatment.
  • the concentration of the fibrous carbon nanostructures in the fibrous carbon nanostructure dispersion is generally 0.02% by mass or more, preferably 0.1% by mass or more, and generally 1.0% by mass. Hereinafter, it is preferably 0.5% by mass or less. If it exceeds 2.0% by mass, the fibrous carbon nanostructures may aggregate and become difficult to integrate with the synthesized BiTe nanoplate.
  • the content of the fibrous carbon nanostructures in the raw material composition is preferably 0.03% by mass or more and 0.12% by mass or less, and 0.05% by mass or more, based on the solvent of the raw material composition. More preferably, it is 0.09% by mass or less. When the content of the fibrous carbon nanostructures with respect to the solvent is within the above range, the fibrous carbon nanostructures can be satisfactorily dispersed.
  • the compound of the bismuth source is not particularly limited as long as it can react with the compound of the tellurium source to synthesize a BiTe nanoplate, and bismuth oxide, bismuth chloride, bismuth fluoride, bismuth hydroxide, and bismuth nitrate. , Bismuth acetate, hydrates thereof and the like.
  • the concentration of the bismuth source compound in the precursor solution is not particularly limited, but is generally 0.005 mol / L or more, preferably 0.01 mol / L or more, and generally 0.1 mol / L or less. , Preferably 0.05 mol / L or less.
  • the tellurium source compound is not particularly limited as long as it can react with a bismuth source compound to synthesize a BiTe nanoplate, and tellurium oxide, tellurium chloride, tellurium fluoride, tellurium hydroxide, and tellurium nitrate are not particularly limited. , Tellurium acetate, hydrates thereof and the like.
  • the concentration of the tellurium source compound in the precursor solution is not particularly limited, but is generally 0.01 mol / L or more, preferably 0.05 mol / L or more, and generally 0.15 mol / L or less. It is preferably 0.09 mol / L or less.
  • Other ingredients include, but are not limited to, additives that help dissolve bismuth and tellurium sources in solvents and control crystal growth.
  • the additive is not particularly limited, but for example, polyvinylpyrrolidone can be added.
  • the concentration of the additive in the precursor solution is not particularly limited, but is generally 0.5% by mass or more, preferably 1.0% by mass or more, and generally 5.0% by mass or more with respect to the solvent. It is mass% or less, preferably 3.0 mass% or less.
  • the solvent contained in the raw material composition is not particularly limited, and either water or an organic solvent can be used.
  • the solvent one type may be used alone, or two or more types may be used in combination.
  • the organic solvent is not particularly limited, and alcohols such as methanol, ethanol and ethylene glycol; toluene, xylene, ethylbenzene, anisole, trimethylbenzene, p-fluorophenol, p-chlorophenol, o-chlorophenol, and purple olo.
  • alcohols such as methanol, ethanol and ethylene glycol; toluene, xylene, ethylbenzene, anisole, trimethylbenzene, p-fluorophenol, p-chlorophenol, o-chlorophenol, and purple olo.
  • Aromatic solvents such as phenol; tetrahydrofuran, dioxane, cyclopentyl monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate , And ethers such as 3-methoxybutyl acetate; ketones such as acetone, cyclohexanone, methylisobutylketone, methylethylketone, and diisobutylketone; N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethyl Formamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N, N, N, N-te
  • Nitrogen-containing polar organic solvents such as acid triamide; ethyl acetate, methyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, n-pentyl acetate, methyl lactate, ethyl lactate, n-butyl lactate, ⁇ -Ethers such as butyrolactone and ⁇ -valerolactone; dimethylsulfoxide can be mentioned.
  • polar organic solvents such as acid triamide
  • ethyl acetate, methyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, n-pentyl acetate, methyl lactate, ethyl lactate, n-butyl lactate, ⁇ -Ethers such as butyrolactone and ⁇ -valerolactone; dimethylsulfoxide can be mentioned.
  • water is preferable from the viewpoint of improving the dispersibility of the fibrous carbon nanostructures.
  • the forming step is a step of subjecting the raw material composition produced in the above preparatory step to a sorbothermal treatment to obtain a composite material in which the BiTe nanoplate and the fibrous carbon nanostructure are integrated.
  • the solvothermal treatment refers to a treatment in which a raw material is reacted in a solvent under high pressure at a temperature higher than the boiling point of the solvent to obtain crystals of the reaction product.
  • the means of the solvothermal treatment is not particularly limited, and any device used for the solvothermal reaction in the technical field such as an autoclave can be used.
  • the raw material composition (dispersion liquid) in which the fibrous carbon nanostructures are dispersed is sealed in a pressure-resistant container such as an autoclave, and stirred under a pressure that does not inhibit crystallization. This is done by heating to a predetermined temperature while or in a stationary state. Heating can be performed using any heating device such as a hot stirrer.
  • Solvothermal treatment is preferably performed in the presence of a base.
  • the base is not limited, but an inorganic compound such as potassium hydroxide or sodium hydroxide can be used.
  • the heating temperature during the solvothermal treatment needs to be higher than the boiling point of the solvent used, and is generally 160 ° C. or higher, preferably 180 ° C. or higher, and generally 240 ° C. or lower, preferably 220 ° C. It is as follows.
  • the heating time is generally 20 minutes or more, preferably 30 minutes or more, and generally 20 hours or less, preferably 8 hours or less.
  • the heating temperature may be constant during the reaction, or may be changed stepwise or continuously.
  • the pressure during the solvothermal treatment depends on the heating temperature and is determined by defining the heating temperature.
  • the other steps that the method for producing the composite material of the present invention can optionally include are not particularly limited.
  • the method for producing a composite material of the present invention can include, for example, a step of performing post-treatment after the above-mentioned forming step (post-treatment step).
  • a composite material (a structure in which a BiTe nanoplate and a fibrous carbon nanostructure are integrated) is obtained in a state of being dispersed in a solvent.
  • the composite material can be recovered from this dispersion (recovery step).
  • the recovery method include known recovery methods such as a centrifugation method.
  • the composite material can be dried after the formation step or recovery step described above (drying step). Examples of the drying method include known drying methods such as vacuum drying. Further, after the above-mentioned drying step, the obtained composite material powder can be used for thinning (sheeting) (thinning step).
  • a printing method (drop casting method) can be used.
  • the drop casting method is more cost effective and simpler than other film forming methods because it does not require its easy scalability, high deposition rate, and vacuum conditions.
  • the powder of the obtained composite material is mixed with a solvent such as ethanol at a predetermined concentration and dispersed by an ultrasonic cleaner or the like.
  • the obtained dispersion liquid is dropped onto the substrate by any dropping means such as a dropper to obtain a coating film.
  • the obtained coating film can be arbitrarily dried to obtain a sheet of composite material.
  • thermoelectric conversion material of the present invention includes the composite material of the present invention described above.
  • the thermoelectric conversion material of the present invention may consist only of the composite material of the present invention, but may include other thermoelectric conversion materials.
  • Other thermoelectric conversion materials are not particularly limited, but are selenium-based compounds; bismastellu-based compounds; antimony-based compounds; silicon-based compounds; metal oxide-based compounds; Whistler alloy-based compounds; polythiophene-based compounds, polyacetylene-based compounds, and polyaniline.
  • Conductive polymer compounds such as system compounds and polypyrrole compounds; fibrous carbon nanostructures such as carbon nanotubes; and composite materials thereof can be used.
  • thermoelectric conversion material of the present invention is excellent in thermoelectric conversion characteristics and conductivity, it can be suitably used as a material for a thermoelectric conversion element. Specifically, the thermoelectric conversion material of the present invention can be suitably used for forming an n-type thermoelectric conversion material layer of a thermoelectric conversion element.
  • thermoelectric conversion element The thermoelectric conversion element is characterized by containing the composite material of the present invention described above.
  • the structure of the thermoelectric conversion element is not particularly limited, but the thermoelectric conversion element can include the composite material of the present invention as an n-type thermoelectric conversion material layer. Further, the thermoelectric conversion element can include a p-type thermoelectric conversion material layer. The thickness of each thermoelectric conversion material layer may be appropriately determined. Examples of the thermoelectric conversion material of the p-type thermoelectric conversion material layer include selenium-based compounds; bismastellu-based compounds; antimony-based compounds; silicon-based compounds; metal oxide-based compounds; Whistler alloy-based compounds; polythiophene-based compounds and polyacetylene-based compounds.
  • thermoelectric conversion element can be manufactured, for example, by attaching two electrodes to the thermoelectric conversion material layer on the base material.
  • the electrode is not particularly limited, and for example, those described in JP-A-2014-199837 can be used. Further, the positional relationship between the thermoelectric conversion material layer and the two electrodes is not particularly limited. For example, electrodes may be arranged at both ends of the thermoelectric conversion material layer, or the thermoelectric conversion material layer may be sandwiched between two electrodes.
  • thermoelectric characteristic evaluation device having the same configuration as the thermoelectric characteristic evaluation device (manufactured by Advance Riko Co., Ltd., "ZEM-3") was manufactured, and the temperature was about 1 to 5 ° C in the atmosphere near room temperature (temperature of 20 ° C to 40 ° C).
  • the Seebeck coefficient S ( ⁇ V ⁇ K -1 ) and conductivity ⁇ (S ⁇ cm -1 ) of the composite material sheet when the temperature difference was added were measured.
  • the CNT ratio in the composite material was determined by AI qualitative analysis (point analysis) using an electron probe microanalyzer (EPMA) (EPMA-1610 manufactured by Shimadzu Corporation).
  • Example 1 ⁇ Preparation of CNT dispersion liquid> According to the description of International Publication No. 2006/011655, by the super growth method, CNT (SGCNT, single-walled CNT ratio: 90%, average diameter: 3.5 nm, average length: 350 ⁇ m, BET specific surface area: 1200 m 2 / g ) was prepared.
  • the obtained CNTs were dispersed in ethanol using an ultrasonic homogenizer (manufactured by Branson, "Model 250 DA”) at an output of 50% for 15 minutes to prepare a 0.2 mass% ethanol dispersion of CNTs.
  • an ultrasonic homogenizer manufactured by Branson, "Model 250 DA
  • the obtained raw material composition (dispersion liquid) was placed in a Teflon (registered trademark) container, which was placed in an autoclave container.
  • the dispersion was heated at 200 ° C. for 24 hours using a hot stirrer while stirring at 500 rpm with a stirrer.
  • the autoclave container was taken out, cooled, and the contents were transferred to a test tube. This was set in a centrifuge and centrifuged at 15,000 rpm to separate an aqueous solution and a precipitate. Next, only the precipitate was taken out into a saucer and dried at a temperature of 60 ° C. for 24 hours using a vacuum dryer (“Vacuum Oven ADP-21” manufactured by Yamato Scientific Co., Ltd.).
  • the obtained composite powder was mixed with ethanol at a concentration of 0.01 mol / L and dispersed by an ultrasonic cleaner. Next, the obtained dispersion liquid was applied onto a polyimide sheet as a substrate to form a film (drop casting method). Then, the obtained coating film was dried at 60 ° C. for 24 hours using a vacuum dryer (“Vacuum Oven ADP-21” manufactured by Yamato Scientific Co., Ltd.) to obtain a sheet of composite material. The obtained sheet of the composite material was observed with a scanning electron microscope, and it was confirmed that the BiTe nanoplate and the CNT were integrated. Moreover, the CNT ratio in the sheet of the composite material was measured by EPMA. In addition, the conductivity and Seebeck coefficient of the composite sheet were measured. The results are shown in Table 1.
  • Example 2 Sheet of composite material in the same manner as in Example 1 except that the amount of 0.2% by mass ethanol dispersion of CNT added was changed to 3.0 mL, 6.0 mL, 9.0 mL, 12.0 mL, and 15.0 mL, respectively.
  • Got The obtained composite material sheet was observed with a scanning electron microscope, and it was confirmed that the BiTe nanoplate and the CNT were integrated.
  • the CNT content in the composite material sheet was measured in the same manner as in Example 1.
  • the conductivity and Seebeck coefficient of the composite sheet were measured. The results are shown in Table 1.
  • the BiTe nanoplate was synthesized by subjecting only the precursor solution of the BiTe nanoplate to the above-mentioned solvothermal treatment without adding the 0.2% by mass ethanol dispersion of CNT. After the synthesis reaction, the autoclave container was taken out, cooled, and the contents were transferred to a test tube. This was set in a centrifuge and centrifuged at 15,000 rpm to separate an aqueous solution and a precipitate. Then, only the precipitate was taken out into a saucer and dried at 60 ° C. for 24 hours using a vacuum dryer (“Vacuum Oven ADP-21” manufactured by Yamato Scientific Co., Ltd.).
  • the obtained BiTe nanoplate powder was mixed with ethanol at a concentration of 0.01 mol / L and dispersed by an ultrasonic cleaner.
  • the obtained dispersion liquid was applied onto a polyimide sheet as a substrate to form a film (drop casting method).
  • the obtained coating film was dried at 60 ° C. for 24 hours using a vacuum dryer (“Vacuum Oven ADP-21” manufactured by Yamato Scientific Co., Ltd.) to obtain a sheet.
  • a vacuum dryer (“Vacuum Oven ADP-21” manufactured by Yamato Scientific Co., Ltd.) to obtain a sheet.
  • heat treatment was performed at 250 ° C. for 1 hour in an atmosphere containing 95% by volume of argon and 5% by volume of hydrogen.
  • the conductivity and Seebeck coefficient of the obtained sheet were measured. The results are shown in Table 1.
  • thermoelectric conversion characteristics and high conductivity have a good balance (Example).
  • Example 4 in which 9 mL of a 0.2 mass% ethanol dispersion of CNTs was added, a composite material having a CNT content of 7.0 mass% was obtained, and the thermoelectric conversion characteristics (Seebeck coefficient) and conductivity were the best. It can be seen that both were achieved at a high level.
  • Example 6 in which 15 mL of a 0.2 mass% ethanol dispersion of CNTs was added, the CNT content was reduced to 2.7 mass%, but this was due to the large amount of CNTs, which aggregated and the BiTe nanoplate. It is probable that it was not fully integrated with.
  • the sheet produced using only the BiTe nanoplate although the BiTe nanoplate has obtained high thermoelectric conversion characteristics, it can be seen that the conductivity is low due to the absence of CNT (Comparative Example 1). Further, in the sheet produced using only CNTs, high conductivity is obtained due to the presence of CNTs, but the Seebeck coefficient takes a positive value due to the absence of BiTe nanoplates and is not n-shaped.
  • thermoelectric conversion material having both thermoelectric conversion characteristics and conductivity at a high level. Further, according to the present invention, it is possible to provide a method for producing a composite material capable of producing a composite material having both thermoelectric conversion characteristics and conductivity at a high level. Further, according to the present invention, it is possible to provide a thermoelectric conversion material containing a composite material having both thermoelectric conversion characteristics and conductivity at a high level.

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CN116855787A (zh) * 2023-07-12 2023-10-10 安徽中航纳米技术发展有限公司 一种制备金属单质及金属复合导热材料的方法

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