JP6547163B2 - Thermoelectric conversion material and thermoelectric conversion element - Google Patents

Description

  The present invention relates to a thermoelectric conversion material and a thermoelectric conversion element, and more specifically, a thermoelectric conversion that has high power generation efficiency, high formability, flexibility, a large amount of resources, and does not use a high environmental load material such as heavy metal. The present invention relates to a material and a thermoelectric conversion element using the same.

In recent years, in order to recover heat that has not been used and was discarded, waste heat is converted into electrical energy and recovered using a thermoelectric conversion element that generates an electromotive force due to a temperature difference.
For example, Patent Document 1 discloses a thermoelectric conversion material and a thermoelectric conversion element in which the mechanical strength is improved while keeping the performance index of a Bi-Te-based thermoelectric material high, and the solidification or solidification of the Bi-Te-based thermoelectric conversion material During hot pressing, when cooling is applied with a uniaxial temperature gradient, the X-ray diffraction intensity ratio of the reflection of a specific surface measured on a plane perpendicular to the direction of the temperature gradient indicates a specific value, and the performance index is greatly improved. A thermoelectric conversion element with improved power generation efficiency has been proposed.
Further, for example, Patent Document 2 discloses a thermoelectric conversion material compatible with flexibility and high thermoelectric conversion ability, a thermoelectric conversion element using the material, an electronic device using the element, exhaust heat of an automobile, etc. As a device utilizing a carbon nanotube, carbon nanotube fine particles are dispersed on a film substrate, having flexibility, preferably composed of an organic material having a high glass transition temperature, and a low thermal conductivity, and an organic material There have been proposed a thermoelectric conversion element having a layer in which the mass ratio of carbon nanotubes to the material is 50 to 90 mass%, and an apparatus in which the thermoelectric conversion element is installed in the exhaust heat section of the device.
Further, for example, Non-Patent Document 1 discloses a thermoelectric conversion element having flexibility and high conversion efficiency, and controlling the fine structure in the carbon nanotube-polymer composite material through control of the drying and baking process etc. A pattern of carbon nanotube-polymer composite material is formed on a 20 μm-thick plastic film substrate by stencil printing using an ink as a carbon nanotube-polymer composite material, which is intended to be stabilized, and then dried and fired. Flexible thermoelectric conversion elements have been proposed.

JP 2007-013000 A

International Publication No. 2012/55333

AIST press release "soft thermoelectric conversion element made by printing", September 30, 2011, National Institute of Advanced Industrial Science and Technology website (http://www.aist.go.jp/aist_j/press_release/pr2011/ pr20110930 / pr20110930.html)

However, the thermoelectric conversion element according to Patent Document 1 uses a rare metal such as Bi ₂ Te ₃ as a material, and there is concern from the viewpoint of the supply of resources. In addition, there are problems such as that it can not be properly mounted on the surface or movable part of a complex heating element because it is an inorganic solid and has poor formability and poor flexibility.
Moreover, the thermoelectric conversion elements according to Patent Document 2 and Non-Patent Document 1 have a problem that although they have flexibility, power generation efficiency (Seebeck coefficient) is low.
Therefore, there is a demand for development of a thermoelectric conversion material that has high power generation efficiency, high formability, flexibility, a large amount of resources, and is not a high environmental load material such as heavy metals, and a thermoelectric conversion element using the same. ing.

  Therefore, an object of the present invention is to provide a thermoelectric conversion material which has high power generation efficiency, high moldability, flexibility, a large amount of resources, and does not use a high environmental load material such as heavy metal, and thermoelectric conversion using the same. It is in providing an element.

As a result of intensive studies to solve the above problems, the present inventors examined carbon nanotubes as a thermoelectric conversion material, and found that a semiconductor-type carbon nanotube is a thermoelectric conversion material having a high electromotive force, and the present invention It came to complete.
That is, the present invention provides the following inventions.
1. A thermoelectric conversion material comprising a carbon nanotube mixture containing a semiconductor type with a purity of 70% or more based on the sum of the metal type and the semiconductor type.
2. The thermoelectric conversion material according to 1, wherein the carbon nanotube mixture is a semiconductor type rich mixture in which the semiconductor type purity is 70% or more by purifying the carbon nanotube mixture in which the semiconductor type and the metal type are mixed.
The thermoelectric conversion element which comprises the thermoelectric conversion member which consists of a thermoelectric conversion material of 3.1.
4. The above-mentioned thermoelectric conversion member,
The thermoelectric conversion element according to 3, wherein the thermoelectric conversion material is formed by electrically contacting a second thermoelectric conversion member made of a second thermoelectric conversion material having different thermoelectric conversion capabilities.
5. 4. The thermoelectric conversion element according to 4, wherein the second thermoelectric conversion material contains a metal type with a purity of 33% or more based on the total of the metal type and the semiconductor type.
6. 3. The thermoelectric conversion element according to 3, wherein the thermoelectric conversion member is formed using a semiconductor-type rich carbon nanotube composite obtained by uniformly mixing the semiconductor-type rich mixture with a polymer.
It is a manufacturing method of a thermoelectric conversion element given in 7.3,
Equipped with a thermoelectric conversion member molding process,
The above-mentioned thermoelectric conversion member molding process
Purifying the carbon nanotube mixture in a state in which the semiconductor type and the metal type are mixed to produce a semiconductor type rich dispersion,
The above purification is
A process of dispersing carbon nanotubes to form carbon nanotubes in an isolated state, separating the separated carbon nanotubes by ultracentrifugation after the dispersion process, and removing precipitates, and ultracentrifugation A method of manufacturing a thermoelectric conversion element, comprising the step of performing re-separation processing by density gradient ultracentrifugation after the step c).

The thermoelectric conversion material and the thermoelectric conversion element of the present invention have high power generation efficiency, high moldability, flexibility, a large amount of resources, and do not use a high environmental load material such as heavy metal.
In addition, the thermoelectric conversion element of the present invention does not require a miniaturization process, and the performance of the thermoelectric conversion element of the present invention is easily dispersed by dispersing the thermoelectric conversion material in a medium such as a polymer and coating it. It is a thermoelectric conversion element that can
In addition, since the thermoelectric conversion element of the present invention can obtain a p-type or n-type element, various thermoelectric conversion elements having different power generation methods due to thermal gradient can be configured.
In addition, the thermoelectric conversion element of the present invention can obtain a high power generation efficiency (Seebeck coefficient) comparable to that of a bismuth-based thermoelectric conversion element considered to be promising at present.

FIG. 1 is a view showing an example of an embodiment of the thermoelectric conversion element of the present invention. FIG. 2 is a view showing an example of another embodiment of the thermoelectric conversion element of the present invention. FIG. 3 is a light absorption spectrum of the purified CNT obtained in Example 1 and Comparative Examples 1 and 2. FIG. 4 is a view showing the relationship between the temperature and the Seebeck coefficient in the thermoelectric conversion elements obtained in Examples 1 and 2 and in the CNT films obtained in Comparative Examples 1 and 2. FIG. 5 is a view showing the Seebeck coefficients at 300 K of the thermoelectric conversion elements obtained in Examples 1 and 2, the CNT films obtained in Comparative Examples 1 and 2, and the CNT sample described in the literature. FIG. 6 is a chart (chart) showing light absorption spectra of the semiconductor-type rich mixture, the metal-type rich mixture, and the unseparated CNT obtained in Examples 4 and 5. FIG. 7 is a plan view showing the thermoelectric conversion element of the present invention obtained in Example 4. FIG. 8 is a diagram showing the state at the time of measurement of the fourth embodiment. FIG. 9 is a diagram showing the state at the time of measurement of the fifth embodiment. FIG. 10 is a plan view showing the thermoelectric conversion element of the present invention obtained in Example 6. FIG. 11 is a diagram showing the state at the time of measurement of the sixth embodiment.

1: Thermoelectric conversion element, 10: Thermoelectric conversion member, 10 ': thermoelectric conversion line, 20: metal block, 30: wiring, 31: copper wire, 40: CNT line, 50: contact point, 60: electrode, 70: flexibility Material, 100: Tester

  Hereinafter, the present invention will be described in more detail. The thermoelectric conversion element of the present invention is characterized by comprising a thermoelectric conversion member made of a specific thermoelectric conversion material.

<Thermoelectric conversion element>
In the present specification, a thermoelectric conversion element is an element that converts heat to electric power, and for example, an element that converts heat and electric power using the Seebeck effect.
Here, the Seebeck effect is a phenomenon in which when a temperature difference is provided at both ends of a substance, a voltage corresponding to the temperature difference is generated at both ends, and the thermoelectromotive force V is represented by the following formula (I) The larger the Seebeck coefficient, the higher the electromotive force.
V = S (T ₂ −T ₁ ) (I)
(Wherein, V represents a voltage, S represents a Seebeck coefficient, and T ₁ and T ₂ represent temperatures at both ends).

  If the thermoelectric conversion element of the present invention comprises a thermoelectric conversion member formed using a thermoelectric conversion material described later, a plurality of types of thermoelectric conversion members such as p-type and n-type having different electric characteristics are electrically Various configurations can be adopted without departing from the scope of the present invention, such as those connected in large numbers, those electrically connected between the thermoelectric conversion member and other members, and those consisting only of the thermoelectric conversion member, etc. An electrode for connection with the electrical material of Preferred embodiments will be described later with reference to the drawings.

<Thermoelectric conversion material>
The thermoelectric conversion material of the present invention comprises a carbon nanotube mixture containing the semiconductor type at a purity of 70% or more based on the total of the metal type and the semiconductor type.
In the present specification, a carbon nanotube mixture refers to a mixture of a large number of carbon nanotubes (a large number of metallic carbon nanotubes and a large number of semiconductive carbon nanotubes, etc.).
The specific purity of the mixture of carbon nanotubes (hereinafter sometimes referred to as CNT) is 70% or more, preferably 87% or more , of the semiconductor type with respect to the total of the metal type and the semiconductor type.
By setting the purity to 70% or more, the Seebeck coefficient of the thermoelectric conversion member formed of the thermoelectric conversion material of the present invention becomes large, and the power generation efficiency of the thermoelectric conversion element of the present invention becomes high. On the other hand, if it is less than 70%, the power generation efficiency of the thermoelectric conversion element is lowered.
Here, “%” means the number of predetermined CNTs in the total number of CNTs.

Here, the purity refers to the ratio of the number of predetermined CNT molecules to the total number of CNTs, and the term "purity of semiconducting CNT" refers to the ratio of the number of semiconductor CNTs to the total number of CNT molecules.
For example, in the case of single-walled carbon nanotubes (hereinafter sometimes referred to as SWCNTs), the above-mentioned purity is determined by light absorption spectroscopy (Nair et al., “Estimation of the (n, m) Concentration Distribution of Single-Walled Carbon Nanotubes from It can measure by methods, such as Photoabsorbtion Spectra ", Analytical Chemistry, 2006, Vol. 78, Issue. 22, p7589-7596.).
The above-mentioned purity can be prepared within the above-mentioned specific range by the purification method described later and the like.
Further, it is more preferable that the carbon nanotube mixture is a semiconductor rich mixture in which the semiconductor nanotube purity is 70% or more by purifying the carbon nanotube mixture in which the semiconductor and metal substrates are mixed.
The manufacturing method and the like will be described later.

<Carbon nanotube (CNT)>
The CNT used in the present specification is a substance in which a six-membered ring network (graphene sheet) made of carbon is a single layer or a multilayer coaxial tube, and if it satisfies the specific purity of the above-mentioned semiconductor type, Layers, two layers, and multiple layers may be used singly or in combination of many, or mixtures thereof. The semiconducting CNT can be used without particular limitation as long as it is semiconducting, and specifically, p-type or n-type semiconducting CNT prepared by doping treatment, CNT having a chemically modified surface, and a cylinder of CNT The CNT etc. which included the atom and molecule | numerator in the cavity are used.
In addition, the diameter of the CNT used in the present invention is typically 0.6 to 5 nm, but is not limited to this range.
In addition, the length of CNT used in the present invention is typically 200 to 20000 nm, but is not limited to this range.

(Semiconductor-type CNT)
The semiconducting CNT used in the present invention can be used without particular limitation as long as it is an electrically semiconducting CNT.
In general, single-walled CNT is uniquely defined by a chiral index consisting of a set of two integers whose structure is (n, m). The semiconducting CNT refers to one in which the chiral index is not a multiple of n−m = 3, and the metallic CNT described later refers to one in which n−m = (a multiple of 3). A two-layered or multi-layered carbon nanotube is composed of a plurality of single-walled CNTs, and depending on the combination thereof, it may have an electrically semiconducting property, and such a CNT is defined as a semiconducting CNT.
As the CNT containing the semiconductor type at a purity of 70% or more, a CNT mixture in which the semiconductor type and the metal type are mixed is refined to make the semiconductor type have a purity of 70% or more, The thing which made the purity of semiconductor type 70% or more etc. can be mentioned by division, etc. can also be used and the CNT mixture made into semiconductor type rich with a commercial item can also be used.

The CNT mixture used when purifying a CNT mixture to obtain CNTs of the above purity used in the present invention is, for example, a mixture of reaction products obtained by the production of CNTs, and the semiconductor type and the metal type are Examples thereof include CNT mixtures in a mixed state, and may contain solvents such as water and organic solvents, various salts, and other components such as surfactants.
The thermoelectric conversion member used in the present invention is a semiconductor-type rich mixture obtained by purifying the CNT mixture, in other words, the purity of the semiconductor-type by purifying a CNT mixture in which a semiconductor-type and a metal-type are mixed. Preferably, it is formed using a semiconductor-type rich mixture of 70% or more.
By the purification, impurities other than metal type CNTs can also be removed, so that a thermoelectric conversion member and a thermoelectric conversion element with higher performance can be manufactured.
The above-mentioned semiconductor-type rich mixture used in the present invention, as long as it is the above-mentioned one, includes solvents such as water and organic solvents, salts, and other constituents such as surfactants within the scope of the present invention. May be.

(Refining)
As the above purification, density gradient ultracentrifugation (DGU) (K. Yanagi et al., Applied Physics Express, 2008, Vol. 1, No. 3, 034003, etc.), agarose gel treatment (electrophoretic separation, agarose gel) Separation with a column packed with water, etc.), NO ₂ ⁺ treatment, H ₂ O ₂ treatment, amine extraction treatment, ion chromatography treatment, treatment using adsorption to resin, etc., and if the semiconductor type can be concentrated Any method may be used.
As an example of purification, the above-mentioned density gradient ultracentrifugation (DGU) method (K. Yanagi et al., Applied Physics Express, 2008, Vol. 1, No. 3, 034003) will be described.
First, CNT dispersion processing is performed.
Dispersion treatment of CNTs is performed by ultrasonication of an aqueous solution of a surfactant such as sodium deoxycholate, sodium dodecylate, sodium cholate, etc., in a mixed solution of CNTs in a mixed state of semiconductor type and metal type obtained by manufacture. Irradiation, etc.
As a solvent used when setting it as a solution, water is mentioned preferably, and it may contain the organic solvent.
Examples of the surfactant include sodium deoxycholate, sodium dodecyl sulfate, sodium cholate and the like.
The surfactant concentration in the surfactant solution is preferably 1.8 to 2.2% by mass, and the amount of the surfactant solution used is 800 to 1200 parts by mass with respect to 1 part by mass of the CNT mixture. It is preferable to do.
In ultrasonication, a glass container containing the CNT dispersion is dispersed for about 30 minutes with a bath-type ultrasonic cleaner to obtain a uniform CNT dispersion and then the chip is immersed in cold water at about 16 ° C. An ultrasonic homogenizer (apparatus name: Digital Sonifier 250 DA, manufactured by BRANSON Co., Ltd.) is inserted into the CNT dispersion, and ultrasonic waves are applied for further dispersion treatment to disperse CNTs in a highly dispersed state. The ultrasonic output of the ultrasonic homogenizer is preferably 0.25 to 0.3 W / cm ³ , and the ultrasonic treatment time is preferably 4 to 8 hours.
As a result, the CNTs aggregated after production become CNTs in an isolated state.
After the dispersion treatment, the above isolated CNTs are separated by ultracentrifugation to remove precipitates.
In the ultracentrifugation method, it is preferable to use a swing type rotor, and the centrifugal acceleration in the centrifugation process is 95,000 to 230,000 g and the rotation speed is 36,000 rpm. Moreover, it is preferable to make processing time into 30 to 60 minutes.
As a result, semiconducting CNTs can be concentrated, and impurity carbons other than CNTs, catalytic metals used at the time of CNT production, tip pieces of ultrasonic homogenizers used at the time of dispersion, bundle-like CNTs not isolated and dispersed And the like can also be removed, so that the power generation efficiency of the thermoelectric conversion element formed using the resulting thermoelectric conversion material is increased.
After ultracentrifugation, re-separation is performed by density gradient ultracentrifugation. Thereby, CNTs having a high proportion of semiconducting CNTs can be separated.
The density gradient ultracentrifugation method uses a solution in which CNTs in isolated state from which precipitates have been removed obtained by the separation process is 2.2 to 2.4 mass of surfactant such as sodium dodecyl sulfate or sodium cholate. The solution obtained by adding a density gradient agent such as iodexanol in an amount of 24 to 32 parts by mass to 100 parts by mass of the aqueous solution is adjusted to five types at different concentrations. The solutions are placed in order from the solution with the highest density so that the density gradient can be obtained, and the solution of each concentration is overlaid to prepare the density gradient solution, which is performed by ultracentrifugation. .
In density gradient ultracentrifugation, it is preferable to use a vertical type rotor, and the centrifugal acceleration of the centrifugation process is 170,000 to 240,000 g. Moreover, it is preferable to make processing time into 6 to 9 hours.
In density gradient ultracentrifugation, the density is different depending on the ratio of the metal type and the semiconductor type of CNT, and therefore, it is possible to separate CNT having different ratio of the metal type and the semiconductor type of CNT by the density gradient solution.

The thermoelectric conversion member may be formed into a sheet using a semiconductor rich dispersion obtained by dispersing the semiconductor rich mixture in a polymer solution.
Thereby, it is possible to manufacture a thermoelectric conversion element having flexibility, excellent moldability, and an arbitrary shape.

<Polymer>
In the present invention, the thermoelectric conversion member can be formed using a semiconductor rich dispersion obtained by dispersing the above-mentioned semiconductor rich mixture in a polymer solution.
The polymer that can be used at this time is not particularly limited as long as it is an insulating polymer, and includes, for example, carboxymethylcellulose, polystyrene, polyvinylcarbazole, polyvinyl alcohol and the like, with preference given to carboxymethylcellulose.
Thereby, it can be made to be a sheet by apply | coating and drying, and the said thermoelectric conversion member of arbitrary shapes can be produced very easily.
The blending ratio of the polymer and the CNT in the case of using the polymer is preferably 20 to 80 parts by mass of CNT per 100 parts by mass of the polymer and CNT from the viewpoint of coexistence of the sheet formability and the thermoelectric conversion efficiency. .

  The solvent used for the semiconductor-type rich dispersion is not particularly limited as long as it is a solvent capable of dissolving a polymer, and, for example, water, toluene or the like can be used. The amount of solvent used is optional depending on the thickness of the sheet to be produced and the application.

As the method of the said dispersion | distribution to a polymer solution, methods, such as ultrasonication and stirring, are mentioned.
As a result, it is possible to produce a thermoelectric conversion member having uniform performance and stable dispersion of CNTs and a thermoelectric conversion element using the same.
The polymer solution in which the above-mentioned CNTs are dispersed may contain other components such as surfactant, oxygen, nitrogen, water and the like within the scope of the present invention.

<Thermoelectric conversion member>
The thermoelectric conversion element of the present invention comprises a thermoelectric conversion member made of the above-mentioned thermoelectric conversion material.
The thermoelectric conversion member used in the present invention is not particularly limited as long as it is formed using the above-mentioned thermoelectric conversion material, for example, so-called bucky paper (see the embodiment of FIG. 1) made of the above CNT A sheet of CNT and a polymer (a sheet formed using a semiconductor-type rich dispersion described later), a sheet or a tape of CNT and a low-molecular material using a low-molecular material other than the polymer as a binder, A linear member, a sheet, a tape, a linear member (see the embodiment in FIG. 2), etc., in which CNTs are fixed in various shapes to materials such as flexible and insulating resin or paper, etc. may be mentioned.
The method of forming the thermoelectric conversion member is not particularly limited. For example, a method of forming buckypaper from known CNTs, a method of forming a sheet using a dispersion of CNTs dispersed in a polymer used as a binder, A semiconductor rich carbon nanotube which can be formed by dispersing CNTs in resin, paper, low molecular weight material, etc. and press-adhering it for immobilization, etc., and obtained by uniformly mixing the above-mentioned semiconductor rich mixture with a polymer Preferably, they are formed using a composite.
The content of the CNTs in the thermoelectric conversion member is 95 to 100 parts by mass of CNT (total CNT amount) in 100 parts by mass of the thermoelectric conversion member when the sheet is formed only of the CNTs. When the amount is not 100 parts by mass, some impurities and dispersant remain, but even if this amount remains, the thermal power generation effect is not affected.
Although the thickness in particular of the said thermoelectric conversion member is not restrict | limited, 10-500 micrometers is preferable.
Moreover, the size of the above-mentioned thermoelectric conversion member is arbitrary according to the use, and the form of use thereof is not particularly limited and is arbitrary according to the use, but it may be rectangular, circular, linear, curvilinear, etc. Any shape of can be used. Also, columnar CNT blocks formed by stacking sheets can be used.

<Thermoelectric conversion element>
The thermoelectric conversion element of the present invention may be composed only of the above-mentioned thermoelectric conversion member, or may be composed of other components.
Preferred embodiments are described with reference to the drawings.
FIG. 1 is a view showing an example of an embodiment of the thermoelectric conversion element of the present invention.
The thermoelectric conversion element 1 of the present embodiment is configured by stacking three thermoelectric conversion members 10 which are bucky papers made of a so-called CNT mixture of 95% of semiconductor type CNTs. The three thermoelectric conversion members 10 are in close contact with each other and are held by two metal blocks 20. When the two metal blocks 20 are given different temperatures, the temperature difference generates electric power from the thermoelectric conversion member 10. The generated power can be utilized through the wiring 30 connected to the metal block 20.

FIG. 2 is a view showing an example of another embodiment of the thermoelectric conversion element of the present invention.
The thermoelectric conversion element 1 ′ of the present embodiment is an example in which a thermoelectric conversion line is formed on the surface of a flexible material 70 such as paper using a semiconductor-type rich dispersion liquid using a polymer as a binder. A thermoelectric conversion line 10 'consisting of a CNT mixture of 95% type CNT and a polymer, and a CNT line 40 consisting of a CNT mixture of 33% of a semiconductor type 67% metal type and a polymer are immobilized, 10 thermoelectric conversion lines 10'. And ten CNT lines 40 are connected via contact points 50. In addition, an electrode 60 is provided at the end of the line formed by connecting the line 10 'and the line 40.
That is, the thermoelectric conversion element 1 'of this embodiment includes the thermoelectric conversion member made of the thermoelectric conversion material of the present invention, and the second thermoelectric conversion material (CNT line 40) having a thermoelectric conversion ability different from that of the thermoelectric conversion material. The second thermoelectric conversion member is formed in electrical contact with the second thermoelectric conversion member.
Although various things can be used as a 2nd thermoelectric conversion material, Preferably it is a CNT mixture which contains a metal type with a purity of 33% or more with respect to the sum total of a metal type and a semiconductor type like this embodiment. Is used.
By thus connecting the thermoelectric conversion line 10 'and the CNT line 40 as a second thermoelectric conversion member having different electrical characteristics, the power generated by the thermoelectric conversion can be increased without increasing the width or thickness of the element. be able to.
That is, even if the electromotive force is, for example, 0.1 mV in one thermoelectric conversion line 10 ′, ten thermoelectric conversion lines 10 ′ are connected, and as a result, a voltage of 1.0 mV can be obtained. . In this case, if the thermoelectric conversion lines 10 'are connected in a zigzag manner in the same way, a negative electromotive force will be generated in the diagonally connected one and eventually the electric power obtained will disappear, so there is almost no thermoelectromotive force as in this embodiment. By connecting via the CNT line 40, power loss can be almost eliminated, and as a result, large power can be obtained.
When a temperature is applied to the contact point opposite to the electrode with respect to the minor axis direction of the flexible material 70 indicated by an arrow in the figure, a temperature difference occurs at the two ends of the thermoelectric conversion line 10 ' Will occur. The generated power can be utilized through the wiring 30 connected to the electrode 60.
FIG. 7 is a view showing an example of another embodiment of the thermoelectric conversion element of the present invention.
The thermoelectric conversion element 1 ′ ′ of the present invention shown in FIG. 7 has a thermoelectric conversion line 10 ′ consisting of a 95% mixture of semiconductor-type CNTs and a polymer, and a metal-type 95% on the surface of a paper 70 as a flexible material. A CNT line 40 composed of a CNT mixture and a polymer is fixed, and six thermoelectric conversion members 10 ′ and six CNT lines 40 are connected via contact points 50. Also, an electrode 60 is provided at its end. Except this point, it is the same as the embodiment shown in FIG. 2 described above, and as in the embodiment shown in FIG. 2, a large electromotive force can be obtained with a small area.
FIG. 10 is a view showing an example of another embodiment of the thermoelectric conversion element of the present invention.
In the thermoelectric conversion element 1 ′ ′ of the present invention shown in FIG. 10, a thermoelectric conversion line 10 ′ consisting of a 95% semiconductive-type CNT mixture and a polymer is immobilized, and six thermoelectric conversion lines 10 ′ are copper wires 31. It is connected via. Further, an electrode 60 is provided at the end, and the flexible material 70 uses a substrate made of polyethylene terephthalate. Except for this point, the embodiment is the same as the embodiment shown in FIG. 2 and, like the embodiment shown in FIG. 2, a large electromotive force can be obtained with a small area.

<Manufacturing method>
The manufacturing method of the thermoelectric conversion element of this invention is demonstrated.
The thermoelectric conversion element of the present invention is formed from the above-mentioned thermoelectric conversion member, and the above-mentioned thermoelectric conversion member is produced by sheeting semiconductive CNTs having a purity of 70% or more of semiconducting CNT as the above thermoelectric conversion material. be able to.
The method of forming the thermoelectric conversion member is not particularly limited. For example, a method of forming a bucky paper from CNTs, a method of dispersing CNTs in a polymer to form a sheet, and materials such as insulating resin and paper A method of immobilizing and forming a sheet can be used.
The method of forming bucky paper from said CNT can use a well-known method, and it describes it in the Example for details.
The above-mentioned dispersion can be performed by ultrasonic irradiation etc., after mixing the above-mentioned polymer with the above-mentioned semiconductor type rich mixture as the above-mentioned thermoelectric conversion material.
The thermoelectric conversion member can be obtained by sheeting the mixture of the polymer and the semiconductor-type rich mixture after the dispersion.
The method of forming the sheet is not particularly limited, and any known method of forming a sheet can be used. For example, when carboxymethyl cellulose is used, the sheet is formed by applying and drying the mixed liquid after the dispersion. It can be carried out.
Further, the thickness, size and shape of the thermoelectric conversion member are not particularly limited and can be appropriately selected according to the application, and it is possible to obtain an arbitrary shape by performing molding before sheeting or the like. Can.
The thermoelectric conversion member obtained in this manner can be used as the thermoelectric conversion element of the present invention, but connection with thermoelectric conversion members having different electric characteristics or other materials, electrodes as required, etc. May be formed.

Hereafter, the manufacturing method of this invention is demonstrated.
The manufacturing method of this invention is a manufacturing method of a thermoelectric conversion element, Comprising: It can implement by performing a thermoelectric conversion member shaping | molding process.
In the present invention, the CNT production process may be carried out before the above-mentioned thermoelectric conversion member molding process, and the thermoelectric conversion member obtained after the above-mentioned thermoelectric conversion member molding process is used according to a conventional method. An element manufacturing process for manufacturing a thermoelectric conversion element is performed.
Then, in the present invention, “The step of purifying the CNT mixture in a state in which the semiconductor type and the metal type are mixed as the above-mentioned thermoelectric conversion member molding step is carried out to produce a semiconductor type rich dispersion liquid. The step of separating the CNTs into the isolated state, the step of separating the isolated carbon nanotubes by the ultracentrifugation after the dispersion treatment, and removing the precipitate, and the ultracentrifugation After separation, the above-mentioned reseparation process is performed by density gradient ultracentrifugation.
Here, the step of purifying the CNT mixture in a state in which the above-mentioned semiconductor type and metal type are mixed to produce a semiconductor-type rich dispersion is described in the density gradient ultracentrifugation (DGU) method as an example of the above-mentioned purification. It is a process of performing each process.
Thereby, as described above, the impurities in the CNT mixture can be reduced, and a thermoelectric conversion element having high power generation efficiency can be manufactured. Moreover, the ratio of the semiconductor type in the CNT mixture can be increased, and a thermoelectric conversion element with higher power generation efficiency can be manufactured.
After completion of the step of producing the semiconductor rich dispersion, the thermoelectric conversion member production step of molding the thermoelectric conversion member is performed according to the above-described method of forming the thermoelectric conversion member, and the element production step is carried out. An element can be obtained.

<How to use>
The thermoelectric conversion element of the present invention can be applied to various places such as heat generating devices and members, or roofs and walls that carry heat. Then, by utilizing the temperature difference between one surface and the opposite surface, the thermoelectric conversion element of the present invention can be installed by attaching it to a waste heat part of a car or a device, etc. The electricity obtained by the thermoelectric conversion element of the present invention can be stored by connecting with the electronic device of the present invention, and can be used directly.

  EXAMPLES Hereinafter, the present invention will be more specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Example 1] Preparation of thermoelectric conversion element (thermoelectric conversion member (semiconductor type 95%)) and measurement of Seebeck coefficient (production of thermoelectric conversion material)
(Production process of semiconductor type rich dispersion)
An aggregate of SWCNT as a CNT raw material (trade name: SO, manufactured by Meijo Nano Carbon Co., Ltd., semiconductor type: metal type = 67: 33, manufacturing method: arc discharge method) 25 mg, sodium deoxycholate (2 mass% concentration) DOC) The solution was placed in a glass container filled with 25 mL of an aqueous solution, and dispersed by a 200 W bath ultrasonic cleaner for about 1 hour to obtain a uniform CNT dispersion.
A chip type ultrasonic homogenizer (apparatus name: Digital Sonifier 250DA, manufactured by BRANSON) is inserted into the CNT dispersion while the glass container containing the CNT dispersion is immersed in cold water at 16 ° C., and the output 20% Further dispersion treatment was carried out by irradiating ultrasonic waves of (8 W) for 8 hours to make CNTs in a highly isolated dispersed state (step of making CNTs in isolated state).
After dispersion treatment, in order to precipitate and remove impurities, separation treatment was performed by ultracentrifugation under the following conditions (step of removing precipitates).
conditions:
Device name: Device name: himac CP100WX, manufactured by HITACHI Revolution speed: 36,000 rpm (average 160,000 × g)
Temperature: 22 ° C
Time: 1 hour change: ACCEL = 9
Deceleration: DECEL = 9
Rotor: Swing rotor After ultracentrifugation, collect 80% of the separated solution centering on the supernatant part with many isolated SWCNT components, remove unnecessary lower 20% part, remove the precipitate-removed solution of CNT in isolated state Obtained.
The solution in the isolated state from which the obtained precipitate was removed was processed by the density gradient ultracentrifugation (DGU) method (K. Yanagi et al., Applied Physics Express, 2008, Vol. 1, No. 3, 034003).
Sodium dodecyl sulfate (final concentration of 2.2 to 2.4 mass% as a surfactant) in five types of aqueous iodexanol (IO) solution having a concentration of 24 to 32 mass% as a density gradient agent. Adjust the solution (density gradient: 24 to 32% by mass (IO)) to which the aqueous solution is added, and add the solution to 7 mL each for 4 types of high concentration and 6 mL for the thinnest one, and the upper part On the other hand, 6 mL of the solution in which the CNTs from which the precipitates had been removed were in an isolated state was overlaid, and density gradient ultracentrifugation was performed under the following conditions (step of performing re-separation treatment).
conditions:
Centrifuge: Device name: himac CP100WX, manufactured by HITACHI Rotation speed: 50,000 rpm (average: 210,000 × g)
Temperature: 22 ° C
Time: 9 hours Moderate: ACCEL = 3
Deceleration: DECEL = 1
Rotor: Vertical Rotor After completion of density gradient ultracentrifugation, the centrifuge tube was taken out, and the solution after density gradient ultracentrifugation was separated at intervals of about 2 mm from the top.
The solution after density gradient ultracentrifugation contains CNTs in which the proportions of semiconducting CNT and metallic CNT differ depending on the removal position.
Therefore, it separated into CNT containing many semiconducting CNTs according to the position to take out, CNT containing many metallic CNTs, and CNT having an intermediate concentration.
The above operation is repeated three times (8 centrifugal tubes are set at each time) until the required amount of CNT is obtained, and a semiconductor-type rich mixture (semiconductor-type CNT purity 95%) as a thermoelectric conversion material of the present invention is about 200 mL was obtained.
The ratio of metallic CNT and semiconducting CNT is evaluated by measuring the light absorption spectrum of the semiconducting rich mixture with a UV-visible near-infrared spectrophotometer (device name: UV-3600, manufactured by Shimadzu Corporation), and a light absorption spectrum. It evaluated by analyzing the area of. The obtained light absorption spectrum is shown in FIG.

(Creating a thermoelectric conversion element)
Subsequently, a thermoelectric conversion member was produced by the following method.
50 mL of methanol was added to 50 mL of the semiconductor-type rich mixture as a thermoelectric conversion material obtained, and CNT was bundled to obtain a bundle solution.
Next, as a step of condensing the CNTs, the bundle solution was subjected to vacuum filtration, and the CNTs were condensed on a membrane filter (trade name: Omnipore membrane filter JGWP, manufactured by Merck Millipore) to obtain an aggregation liquid.
Thereafter, as a step of washing the CNTs, 50 mL of hot water was poured into this flocculation solution, followed by filtration under reduced pressure to wash out the surfactant and IO contained in the CNT agglomerates.
Finally, as a step of dispersing the CNTs, after washing, the sheet-condensed CNTs are peeled off from the membrane filter, put in a glass bottle containing 30 mL of methanol, and the glass bottle is subjected to ultrasonic cleaning with 200 W output. The CNTs were dispersed in methanol by irradiation with ultrasonic waves for 30 minutes, and a dispersion was obtained again.
The steps from the step of condensing the CNTs to the step of dispersing the CNTs using this dispersion were repeated three more times. The sonication time in these three processes was 10 minutes.
Next, the dispersion obtained by performing the three steps is condensed again in the same manner as the above-mentioned condensing step to obtain the condensed CNT on the membrane filter, and the obtained CNT is washed with toluene, Then, CNTs were dispersed in toluene in the same manner as in the step of dispersing CNTs described above. The toluene dispersion and condensation steps were repeated twice without hot water to obtain condensed CNTs.
Next, the CNTs condensed on the membrane filter were washed with methanol, peeled off from the membrane filter, and dispersed in methanol in the same manner as the above condensation step. The ultrasonic irradiation time was 10 minutes in the above processing. Finally, the CNTs in this methanol solution were condensed on a membrane filter.
The condensed CNTs were peeled off from the membrane filter and recovered to obtain a thermoelectric conversion member made of a disk-shaped 1 cm diameter disc having a thickness of 120 μm (bucky paper) as a thermoelectric conversion element of the present invention. The obtained thermoelectric conversion member was dried by vacuum drying at room temperature.
The thermoelectric conversion element of the present invention was produced using the obtained thermoelectric conversion member in the configuration shown in FIG.

(Seebeck coefficient measurement of thermoelectric conversion element)
The Seebeck coefficient of the surface direction of the thermoelectric conversion member (thermoelectric conversion element) was measured using the Thermal Transport Option of a general-purpose physical property evaluation system (apparatus name: Physical Property Measurement System (PPMS), manufactured by Quantum Design) under the following conditions. .
conditions:
Sample size: 8 mm × 3 mm
Measurement method: 4 terminal method gap between electrodes: 2 mm
Temperature difference given between electrodes: 5 K or less The obtained results are shown in FIG. 4 (Seebeck coefficient at each temperature) and FIG. 5 (Seebeck coefficient at 300 K).

Example 2 Preparation of Thermoelectric Conversion Material and Thermoelectric Conversion Member (Semiconductor Type 87%) and Measurement of Seebeck Coefficient Except that the ratio of the semiconductor type in the semiconductor type rich dispersion obtained by purification was changed to 87% In the same manner as in Example 1, a thermoelectric conversion member comprising the thermoelectric conversion material of the present invention and a CNT film was obtained.
Next, at room temperature (300 K), a nanovoltmeter (apparatus name: Model 2182 nanovoltmeter, manufactured by Keithley) connected via a wire the thermoelectromotive force generated by giving a temperature difference of about 1 K to the thermoelectric conversion member The Seebeck coefficient was obtained by The obtained result is shown in FIG. 4 and FIG.

Comparative Example 1 Preparation of CNT Film (Metal Type) and Measurement of Seebeck Coefficient A CNT film was prepared in the same manner as Example 1, except that the CNT used was changed to a metal type rich CNT (semiconductor type 5% or less). The Seebeck coefficient was obtained. The light absorption spectrum data of the used CNT was measured, and the obtained result is shown in FIG. 3 (light absorption spectrum data). Also, the Seebeck coefficient was measured in the same manner as in Example 1. The results are shown in FIG. 4 and FIG.

Comparative Example 2 Preparation of CNT Film (Semiconductor Type 44%) and Measurement of Seebeck Coefficient A CNT film was obtained in the same manner as Example 1, except that the purified CNT was changed to semiconductor type 44% in the purification of CNT. , Its Seebeck coefficient was measured. The light absorption spectrum data of the used CNT was measured, and the obtained result is shown in FIG. 3 (light absorption spectrum data). Also, the Seebeck coefficient was measured in the same manner as in Example 1. The results are shown in FIG. 4 and FIG.

[Example 3] Thermoelectric conversion in the thickness direction of the thermoelectric conversion element (semiconductor type 87%) The thermoelectric conversion member as the thermoelectric conversion element of the present invention is flexible, so it is formed on the surface of a heating element such as a muffler of an automobile. It is thought that it can be stuck and can be used as a thermoelectric conversion element using waste heat. Therefore, a thermoelectric conversion element that can be arranged as such is actually formed.
After three thermoelectric conversion members (87% of semiconductor type) obtained in Example 2 were stacked, they were sandwiched between two metal blocks to obtain a thermoelectric conversion element shown in FIG.
In order to evaluate the electromotive force by thermoelectric conversion of the obtained thermoelectric conversion element, the thermoelectromotive force generated between the metal blocks by heating one metal block with a heater and giving a temperature difference of about 1 K between the two metal blocks Was measured using a nanovoltmeter (apparatus name: Model 2182 nanovoltmeter, manufactured by Keithley) connected via a wire to calculate the Seebeck coefficient.
As a result, the Seebeck coefficient was 100 μV / K.
In addition, as a metal block, stainless steel with a small Seebeck coefficient was used, and the measurement was performed at room temperature (300 K) vicinity.

[Example 4] Preparation of thermoelectric conversion element using semiconductor type rich dispersion liquid and thermal power generation (Preparation of dispersion liquid of semiconductor type rich and metal type rich mixture)
To 100 mg of HiPco (registered trademark) (Nano Integris, unrefined carbon nanotube, diameter 1.0 ± 0.3 nm), add 1% by mass sodium dodecyl sulfate (SDS) aqueous solution (100 mL) and suspend well. A suspension was obtained. The obtained suspension is sonicated at a power of 30% for 3 hours while cooling in cold water using a tip-type ultrasonic crusher (Sonifera, manufactured by Branson, tip diameter: 0.5 inch) And a dispersion was obtained. The obtained dispersion was subjected to ultracentrifugation (210,000 × g, 1 hour), and then the supernatant corresponding to 80% of the separated liquid was collected, and the collected supernatant was used as a CNT dispersion.

(Preparation and separation of separation container)
A suspension of gel beads (GE Healthcare, trade name "Sephacryl S-200") suspended in water was filled in a plastic container with a volume of 50 mL to prepare a CNT separation container (gel beads after filling) Volume was about 20 mL).
The separation vessel is equilibrated with a 1% by mass aqueous SDS solution, and 2 mL of the above CNT dispersion is added thereto, and then 40 mL of a 1% by mass aqueous SDS solution is added, the non-adsorbed fraction is recovered, and the metal type rich mixture is dispersed A liquid (second thermoelectric conversion material) was obtained.
Next, 40 mL of a 1% by mass aqueous solution of sodium deoxycholate (DOC) was introduced into the separation vessel and CNTs eluted were recovered to obtain a dispersion liquid of the semiconductor rich mixture as the thermoelectric conversion material of the present invention. .
The light absorption spectra of the dispersion liquid of each of the obtained semiconductor-type rich CNT, metal-type rich CNT, and CNT before separation were measured in the same manner as in Example 1.
The results are shown in FIG.
In the figure, "thin line", "grey thick line" and "black thick line" respectively show the respective spectra of dispersion liquid of CNT, metal-type rich mixture, and semiconductor-type rich mixture before separation.
The ratio of the absorption of the metallic rich mixture (M11) in the metallic rich mixture as compared to the ratio of the absorption (S22) of the semiconducting rich mixture in the spectrum in the dispersion of CNTs before separation (S22) to the absorption of the metallic rich mixture (M11) Is significantly increased as compared to the absorption of the semiconducting rich mixture (S22), while the ratio of S22 is significantly increased in the semiconducting rich mixture compared to M11, and the semiconducting CNT is concentrated and the concentration is high. It has been confirmed that it has become.
From the intensity ratio of absorption spectra of S22 and M11, the content of metallic CNT in the dispersion of metallic rich mixture was estimated to be 95%, and the content of semiconducting CNT in the dispersion of semiconductive rich mixture was 95%. .

(Fabrication of thermoelectric conversion element)
A dispersion of metal-type rich CNT (semiconductor type: metal type = 0.5: 9.5) containing 10 mg net amount of CNT obtained by the above purification is filtered to remove the aqueous SDS solution, and the concentration is 0.2 The mixture was mixed with 10 mL of a mass% aqueous solution of carboxymethylcellulose (CMC: Sigma-Aldrich), and uniformly dispersed by stirring with Polytron (manufactured by Polytron) to prepare a metal-type rich dispersion.
Next, a dispersion of a semiconducting rich CNT obtained by purifying HiPco (registered trademark) (Nano Integris, unrefined carbon nanotube) containing a net amount of 10 mg of CNT (a semiconducting type: metallic type = 9.5: 0) .5) was filtered to remove the DOC aqueous solution, and then mixed with 10 mL of a 0.2% by mass aqueous CMC solution and uniformly dispersed by stirring with a polytron to prepare a semiconductor-type rich dispersion.

(Production of a thermoelectric conversion element formed by joining a line formed of a semiconductor-type rich CNT polymer composite formed using a semiconductor-type rich dispersion liquid and a line formed of a metal-type rich CNT polymer composite)
The above-mentioned semiconductor-type rich dispersion and the above-mentioned metal-type rich dispersion are alternately applied six times on paper and dried, thereby forming a line (linear thermoelectric conversion member) and metal composed of a semiconductor-type rich CNT polymer composite The lines (linear second thermoelectric conversion members) made of the mold-rich CNT polymer composite were alternately joined to obtain thermoelectric conversion elements 1 ′ ′ of the present invention shown in FIG.
(Measurement of electromotive force)
A tester was connected to the terminal electrode of the produced thermoelectric conversion element of the present invention, and the electromotive force was measured.
When the lower contact (portion indicated by the arrow in the figure) of the thermoelectric conversion element 1 ′ ′ of the present invention shown in FIG. 7 is warmed with a palm, the room temperature is 1.2 mV at room temperature 24 ° C. and 2.2 mV at 14 ° C. An electromotive force has occurred.
The state at the time of measurement is shown in FIG.
In addition, since the body temperature is about 36 ° C., the temperature difference is about 22 ° C. at 14 ° C. and about 12 ° C. at 24 ° C., respectively.

[Example 5] (Thermoelectric conversion element by the junction of a line composed of a semiconductor-type rich CNT polymer composite and a line composed of an unseparated CNT polymer composite)
In the same manner as in Example 4 using undivided CNTs (Nikkiso Co., Ltd., diameter 1.8 nm, semiconductor type: metal type = 6.7: 3.3) prepared by the eDIPS method, the unseparated CNTs are uniformly converted into a polymer It disperse | distributed and prepared the unseparated CNT dispersion liquid. A line (a line made of a semiconductor-type rich CNT polymer composite is obtained by alternately coating the non-separated CNT dispersion liquid with the semiconductor-type rich CNT dispersion liquid obtained in the same manner as in Example 4 on paper and drying. -Like thermoelectric conversion members) and lines composed of unseparated CNT polymer composites (linear second thermoelectric conversion material members) are alternately joined to form thermoelectric conversion lines on paper, as shown in FIG. The thermoelectric conversion element 1 'of the present invention shown in FIG.
(Measurement of electromotive force)
When the lower contact (portion indicated by the arrow in the figure) of the thermoelectric conversion element 1 'of the present invention shown in FIG. 2 is warmed with a palm, a total room temperature of 1.5mV at 24 ° C and 2.6mV at 14 ° C Power has been generated.
The state at the time of measurement is shown in FIG.

[Example 6]
(Thermoelectric conversion element by the junction of the line consisting of semiconductor type rich CNT polymer composite and copper wire)
The above-mentioned semiconductor type rich dispersion prepared in the same manner as in Example 4 is coated on the entire surface of a substrate made of polyethylene terephthalate and dried, and then unnecessary portions are removed to form a stripe-shaped thermoelectric conversion line (linear thermoelectric conversion line (Conversion member) was formed. Between the stripes of the thermoelectric conversion line are connected by a copper wire (second thermoelectric conversion member) using a conductive paste (Fujikura Kasei Co., Ltd., trade name "Dotite D-362"), and the thermoelectric conversion line is placed on the substrate The thermoelectric conversion element 1 ′ ′ ′ of the present invention shown in FIG. 10 is obtained.
(Measurement of electromotive force)
When the lower contact (portion indicated by the arrow in the figure) of the thermoelectric conversion element 1 ′ ′ ′ of the present invention shown in FIG. 10 is warmed with a palm, the room temperature is 1.9 mV at 24 ° C. and 3.0 mV at 14 ° C. EMF occurred.
The state at the time of measurement is shown in FIG.

The results are discussed below.
FIG. 3 shows the light absorption spectra of the purified CNTs obtained in Example 1 and Comparative Examples 1 and 2.
Note that the spectra in the figure are shown shifted up and down for easy viewing.
The light absorption spectrum of the semiconducting CNT and the metallic CNT is distinctly different, and it is understood that the light absorption spectrum of the mixture of the semiconducting CNT and the metallic CNT is a spectrum in which the semiconducting CNT and the metallic CNT are mixed.
Further, it can be seen that the semiconductor-type rich mixture (semiconductor type: 95%) used in Example 1 has high purity of the semiconductor type.

FIG. 4 shows the relationship between the temperature and the Seebeck coefficient in the thermoelectric conversion elements obtained in Examples 1 and 2 and in the CNT sheet obtained in Comparative Examples 1 and 2.
The Seebeck coefficient is found to increase as the proportion of semiconductor types increases.
In the semiconductor-type rich CNT of 80% or more used in the thermoelectric conversion element of the present invention, it can be seen that a giant Seebeck coefficient comparable to that of the BiTe system is exhibited.

FIG. 5 shows the relationship between the Seebeck coefficient and the ratio of semiconducting CNTs at a temperature of 300 K in the thermoelectric conversion elements obtained in Examples 1 and 2 and the CNT sheets obtained in Comparative Examples 1 and 2. Furthermore, the document values (Semiconductor type 67% semiconducting type rich CNT, literature name: J. Hone et al., Physical Review Letters, 1998, No. 80, pages 1042-1045, values shown in FIG. 2) are combined together. It is shown in FIG.
In addition, the broken line in a figure shows the fitting curve by the polynomial which approximated the Seebeck coefficient of the said Example 1 and 2, the comparative examples 1 and 2, and a literature value.
From FIG. 5, it can be seen that the thermoelectric conversion elements (Examples 1 and 2) of the present invention exhibit a high Seebeck coefficient as compared to the conventional thermoelectric conversion materials (the values in the literature).

In Example 3, the thermoelectric conversion in the thickness direction of the thermoelectric conversion element (semiconductor type 87%) of the present invention was evaluated.
As a result, it is understood that the thermoelectric conversion element of the present invention exhibits a high Seebeck coefficient (100 μV / K) and is a thermoelectric conversion element having a high power generation capacity.

In Examples 4, 5 and 6, a thermoelectric conversion element comprising a semiconductor rich dispersion and a metal rich dispersion, a thermoelectric conversion element comprising a semiconductor rich dispersion and an unseparated CNT dispersion, and a semiconductor rich dispersion Thermal power of thermoelectric conversion elements by copper wire and copper wire was compared.
As a result, in the thermoelectric conversion element of Example 4, an electromotive force of 1.2 mV was generated at a temperature difference of 12 ° C. and 2.2 mV at a temperature difference of 22 ° C. This indicates that the thermoelectromotive force of the thermoelectric conversion element of Example 4 is 0.2 mV at a temperature difference of 12 ° C. and about 0.37 mV at a temperature difference of 22 ° C. per junction.
In the thermoelectric conversion element of Example 5, an electromotive force of 1.5 mV at a temperature difference of 12 ° C. and 2.6 mV at a temperature difference of 22 ° C. was generated as a whole. This indicates that the thermoelectromotive force of the thermoelectric conversion element of Example 5 is 0.15 mV at a temperature difference of 12 ° C. and 0.26 mV at a temperature difference of 22 ° C. per junction.
In the thermoelectric conversion element of Example 6, an electromotive force of 1.9 mV at a temperature difference of 12 ° C. and 3.0 mV at a temperature difference of 22 ° C. was generated as a whole. This indicates that the thermoelectromotive force of the thermoelectric conversion element of Example 6 is 0.32 mV at a temperature difference of 12 ° C. and 0.5 mV at a temperature difference of 22 ° C. per junction.
In addition, thermoelectric elements that use the thermoelectric power generated at the junction of unseparated CNTs and other materials (metallic materials) so far (The 59th Annual Conference of the Association of Applied Physics Conference Conference No. 16p-E7 7) has been developed, but with a temperature difference of about 26 ° C., the EMF is 0.11 mV per junction (about 1/5 to 1/6 of Example 6), which also indicates It can be seen that the thermo-electromotive force is higher in the semiconducting CNT than in the separated CNT.
In addition, by using such a semiconductor type enriched CNT, a thermoelectric conversion element with high power generation efficiency can be easily made.
The thermoelectric conversion element of the present invention can be expected to generate a higher electromotive force by optimizing the other material for producing a junction. Moreover, it can be expected that the generated thermoelectromotive force can be most effectively used by forming an element structure in which p-type and n-type semiconductor-type rich CNT composites are joined.
In addition, by using a polymer liquid in which CNTs in which the ratio of semiconductor type CNTs is dispersed is dispersed, it is possible to manufacture a thermoelectric conversion element only with a polymer liquid in which CNTs are dispersed, without using other conductive materials, It is considered to be applicable to high sensitivity temperature sensors and the like.
In addition, the thermoelectric conversion element of the present invention does not require a miniaturization process, and the thermoelectric conversion material of the present invention is dispersed in a medium such as a polymer and the performance thereof as a thermoelectric conversion element can be easily achieved simply by applying it. It turns out that it is a thermoelectric conversion element which can be demonstrated.

  From the above, it is understood that the thermoelectric conversion element of the present invention is a thermoelectric conversion element having high power generation efficiency, high moldability and flexibility.

  The thermoelectric conversion element of the present invention is important in that it can significantly improve the thermoelectric characteristics by concentrating the semiconducting CNTs, and it is important to use carrier rich doping using semiconducting rich CNTs in the future. It is naturally expected that optimization such as control of thermoelectric properties or improvement of mechanical properties by polymer dispersion is performed. In addition, the separated and purified CNT contains oxygen, water, an organic solvent, and the like, and a semiconducting CNT containing these impurities is also included in the target material.

The thermoelectric conversion element of the present invention has a large Seebeck coefficient, and can be used as a thermo couple as a thermometry element as well as an application as a thermoelectric power generation element by waste heat. The CNT used in the thermoelectric conversion element of the present invention can be made smaller in heat capacity than ordinary metals, and therefore, it can be applied to high-speed, high-precision temperature measurement, temperature measurement of a minute mass material, and the like.

Claims (2)

A thermoelectric conversion member comprising a thermoelectric conversion material for converting heat into electric power which comprises a carbon nanotube mixture containing a semiconductor type with a purity of 70% or more based on the sum of the metal type and the semiconductor type ;
The thermoelectric conversion material is formed by electrically contacting a second thermoelectric conversion member made of a second thermoelectric conversion material having different thermoelectric conversion ability to convert heat into electric power,
The thermoelectric conversion member and the second thermoelectric conversion member are connected alternately through a plurality of contact lines and a plurality of lines of the thermoelectric conversion members and the lines of the second thermoelectric conversion members alternately in a zigzag manner. A thermoelectric conversion element having an electrode at its end,
The thermoelectric conversion element according to claim 1, wherein the second thermoelectric conversion member is a carbon nanotube containing a metal type with a purity of 33% or more with respect to the total of the metal type and the semiconductor type. It is a manufacturing method of the thermoelectric conversion element according to claim 1 ,
Equipped with a thermoelectric conversion member molding process,
The above-mentioned thermoelectric conversion member molding process
Purifying the carbon nanotube mixture in a state in which the semiconductor type and the metal type are mixed to produce a semiconductor type rich dispersion,
A step of dispersing the carbon nanotubes to bring the carbon nanotubes into an isolated state, separating the isolated carbon nanotubes by ultracentrifugation after the dispersion treatment, and removing the precipitates; And a step of performing re-separation treatment by density gradient ultracentrifugation after ultracentrifugation.

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