KR102696253B1 - Metal oxide nanoparticle embedded carbon nanotube based thermoelectric materials and method for manufacturring the same - Google Patents

Abstract

The present invention provides a thermoelectric material comprising a substrate including carbon nanotubes and metal oxide nanoparticles supported on the substrate. The thermoelectric material according to the present invention forms a p-type thermoelectric material by introducing the metal oxide nanoparticles, and the thermal conductivity of the thermoelectric material is controlled by introducing the metal oxide nanoparticles, so that the thermoelectric performance is significantly improved. In addition, the present invention provides a method for producing a thermoelectric material including a step of producing a metal oxide precursor solution including a solvent and a metal oxide precursor; a step of immersing the metal oxide precursor solution in a substrate including carbon nanotubes; and a step of heat-treating the substrate containing the metal oxide precursor solution.

Description

Thermoelectric material including carbon nanotubes supported with metal oxide nanoparticles and method for manufacturing the same {METAL OXIDE NANOPARTICLE EMBEDDED CARBON NANOTUBE BASED THERMOELECTRIC MATERIALS AND METHOD FOR MANUFACTURRING THE SAME}

The present invention relates to a thermoelectric material based on carbon nanomaterials and a method for manufacturing the same, and more specifically, to a thermoelectric material having controlled thermal conductivity through the introduction of metal oxide nanoparticles into carbon nanotubes and a method for manufacturing the same.

Thermoelectric effect is a reversible and direct energy conversion phenomenon between heat and electricity, and is a phenomenon that occurs by the movement of electrons and/or holes inside a thermoelectric material. Thermoelectric effect includes the Peltier effect, in which heat is released or absorbed at the contact point of two dissimilar materials connected by a contact point when an external current is applied to the dissimilar materials; the Seebeck effect, in which an electromotive force is generated from the temperature difference between the two dissimilar materials connected by a contact point; and the Thomson effect, in which heat is released or absorbed when an electric current flows through a material having a predetermined temperature gradient.

A thermoelectric material with high energy conversion efficiency is good, and the high energy conversion efficiency is obtained from the high Seebeck constant, electrical conductivity, and low thermal conductivity of the thermoelectric material. That is, the energy conversion efficiency of a thermoelectric material is evaluated by the thermoelectric figure of merit ( ZT ), and is expressed by the following equation.

Here, a is the Seebeck coefficient, σ is electrical conductivity, k is thermal conductivity, and T represents the absolute temperature (K).

Therefore, in order to obtain high energy conversion efficiency, attention is being paid to thermoelectric materials with high Seebeck constant and electrical conductivity but low thermal conductivity, or the development of such thermoelectric materials is being focused on.

Up to now, inorganic thermoelectric materials based on bismuth tellurium (Bi ₂ Te ₃ ), which have high Seebeck constant and electrical conductivity and low thermal conductivity, resulting in a thermoelectric figure of merit (ZT) of close to 1 at room temperature, have been used in various commercial applications. However, they are composed of rare metal elements with limited reserves, have high processing temperatures, are brittle, and are difficult to freely change shape, and have high manufacturing process costs.

To solve the problems of these inorganic thermoelectric materials, carbon nanotubes and inorganic composite thermoelectric materials are being developed, but the problems of inorganic thermoelectric materials have not yet been solved, except for improved flexibility.

Therefore, there is an urgent need to develop organic thermoelectric materials that have high energy conversion efficiency while lowering thermal conductivity and improving Seebeck constant or electrical conductivity, and have high flexibility and economy.

Republic of Korea Patent Publication No. 10-1982279 (Publicly Announced on August 28, 2019)

The present invention was invented to solve the problems of the prior art as described above, and aims to provide a thermoelectric material having controlled thermal conductivity by introducing metal oxide nanoparticles into carbon nanotubes, a method for manufacturing the same, and a thermoelectric element including the same.

In addition, the present invention aims to provide a thermoelectric material having p-type characteristics, excellent thermoelectric performance, and high energy conversion efficiency, and a thermoelectric element including the same.

To achieve the above purpose, a thermoelectric material including a substrate including carbon nanotubes and metal oxide nanoparticles supported on the substrate can be provided.

In one aspect of the present invention, the metal of the metal oxide may include one or more selected from the group consisting of Fe, Cu, and Co.

In one aspect of the present invention, the thermoelectric material may have a negative surface charge.

In one aspect of the present invention, the metal oxide precursor may be acetylacetate.

In one aspect of the present invention, the substrate may be a carbon nanotube sheet.

In one aspect of the present invention, 0.001 to 10 parts by weight of metal oxide nanoparticles may be included with respect to 100 parts by weight of carbon nanotubes.

In one aspect of the present invention, the average particle diameter of the metal oxide nanoparticles may be 5 to 50 nm.

In one aspect of the present invention, the thermoelectric material may be p-type.

In one aspect of the present invention, the metal oxide nanoparticle may further include an aliphatic amine capped on the surface.

In one aspect of the present invention, the Seebeck constant preservation rate of the thermoelectric material in air can be 90% or more.

In one aspect of the present invention, the thermoelectric material may satisfy the following [Formula 1].

[Formula 1] 2≤(power factor of thermoelectric material/power factor of carbon nanotube sheet)

Another aspect of the present invention relates to a method for producing a thermoelectric material, comprising the steps of preparing a metal oxide precursor solution containing a solvent and a metal oxide precursor, immersing the metal oxide precursor solution in a substrate containing carbon nanotubes, and heat-treating the substrate containing the metal oxide precursor solution.

In one aspect of the present invention, the solvent may be a method for producing a thermoelectric material including a polar solvent.

In one aspect of the present invention, the metal oxide precursor may be a method for producing a thermoelectric material in which the metal oxide precursor is an acetylacetate.

In one aspect of the present invention, the heat treatment may be a method for manufacturing a thermoelectric material performed at 100°C to 300°C.

In one aspect of the present invention, there may be a method for producing a thermoelectric material, wherein the metal oxide precursor solution further includes an aliphatic amine as a capping agent.

In addition, another aspect of the present invention relates to a thermoelectric element including the thermoelectric material described above.

Another aspect of the present invention relates to a thermoelectric module including a first electrode; a second electrode; and the above-described thermoelectric element disposed between the first electrode and the second electrode.

The thermoelectric material according to the present invention exhibits excellent thermoelectric performance and high energy conversion efficiency due to a significantly improved white matter constant compared to a material made of carbon nanotube sheets.

The thermoelectric material according to the present invention maintains a Seebeck constant preservation rate (%) of 90% or more when exposed to air for a long period of time, so that the thermoelectric performance and energy conversion efficiency are also maintained stably.

A thermoelectric element or thermoelectric module including a thermoelectric material according to the present invention has high energy conversion efficiency.

Figure 1 is a schematic diagram of manufacturing a thermoelectric material according to the present invention.
Figure 2 shows an SEM image (right) of a thermoelectric material according to the present invention and a schematic diagram (left) showing aliphatic amine capping on the surface of metal oxide nanoparticles when capped.
Figure 3 is a diagram showing the change in electrical conductivity of a thermoelectric material when the heat treatment temperature is changed after immersing a metal oxide precursor solution containing Cu(AcAc) ₂ , which is a metal oxide precursor, in a substrate containing carbon nanotubes.
Figure 4 is a diagram showing the change in the power factor of a thermoelectric material when the heat treatment temperature is changed after immersing a metal oxide precursor solution containing Cu(AcAc) ₂ , which is a metal oxide precursor, in a substrate containing carbon nanotubes.
Figure 5 shows the conservation rate (%) of the Seebeck constant when the thermoelectric material according to the present invention is exposed to air.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings attached to the present invention. In explaining the present invention, specific descriptions of related known functions or configurations are omitted in order to avoid obscuring the gist of the present invention.

Since the embodiments according to the concept of the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit the embodiments according to the concept of the present invention to a specific disclosed form, and it should be understood that it includes all changes, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Unless otherwise defined herein, all technical and scientific terms have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the present invention is only for the purpose of effectively describing particular embodiments and is not intended to limit the present invention.

Also, when a part is said to “include” a certain component, this does not mean that it excludes other components, unless otherwise specifically stated, but rather that it may include other components. Also, singular expressions include plural expressions unless the context clearly indicates otherwise.

Units used below without special mention are based on weight, and for example, units of % or ratio mean weight% or weight ratio.

In addition, when describing components of the present invention, terms such as first, second, (A), (B), (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by these terms.

Hereinafter, the thermoelectric material of the present invention, the manufacturing method thereof, and the thermoelectric element including the thermoelectric material will be described in detail.

The present invention provides a thermoelectric material, characterized in that the thermoelectric material includes a substrate including carbon nanotubes and metal oxide nanoparticles supported on the substrate.

Carbon nanotubes have a large surface area, high electrical conductivity, high thermal conductivity, uniform pore distribution, high mechanical strength, and chemical stability, and are therefore being applied to various fields such as electronics and information industries. However, they are not suitable as thermoelectric materials due to their high thermal conductivity. Therefore, in order to use carbon nanotubes as thermoelectric materials, it is most important to effectively lower the thermal conductivity of carbon nanotubes.

The substrate including the above carbon nanotubes may be a carbon nanotube sheet formed by irregularly stacking carbon nanotubes, and it is preferable that the substrate has a porous form. The degree of porosity is not particularly limited, but may have a porosity of 20 to 70%, and as it has porosity, the phonon scattering effect is promoted at the interface between the metal oxide nanoparticles and the carbon nanotubes, thereby lowering the thermal conductivity of the carbon nanotubes and at the same time being more effective in improving the electrical conductivity or the Seebeck constant.

The thickness of the substrate including the carbon nanotubes may be from 10 ㎛ to 200 ㎛, preferably from 10 ㎛ to 100 ㎛, and more preferably from 20 ㎛ to 50 ㎛.

The carbon nanotubes used in the present invention may be manufactured by chemical vapor deposition using plasma treatment.

The metal of the metal oxide nanoparticles supported in the above description may include one or more selected from the group consisting of Fe, Cu, and Co, and may preferably be Fe and Cu, but may not be limited thereto.

The above metal oxide nanoparticles are supported within carbon nanotubes and promote phonon scattering at the interface between the carbon nanotubes and the metal oxide, thereby significantly reducing the thermal conductivity of the thermoelectric material while simultaneously increasing the electrical conductivity or Seebeck constant of the thermoelectric material.

The above metal oxide nanoparticles are derived from a precursor, and the metal oxide precursor may be an acetylacetate. Specifically, it may be one or more selected from the group consisting of iron acetylacetate (CAS No. 14024-18-1, hereinafter referred to as Fe(AcAc) ₃ ), copper acetylacetate (CAS No. 13395-16-9, hereinafter referred to as Cu(AcAc) ₂ ), and cobalt acetylacetate (CAS No. 14024-48-7, hereinafter referred to as Co(AcAc) ₂ ), and preferably iron acetylacetate and copper acetylacetate. The metal oxide precursors may form a p-type thermoelectric material by being converted into metal oxide nanoparticles by heat treatment.

The content of the above metal oxide nanoparticles may be 0.001 to 10 parts by weight, preferably 0.01 to 10 parts by weight, and more preferably 1 to 10 parts by weight, based on 100 parts by weight of the carbon nanotubes. Satisfying this is sufficient to reduce the thermal conductivity of the carbon nanotubes.

The above metal oxide nanoparticles can be dispersed and positioned to form a sea-island structure on a substrate including carbon nanotubes. Accordingly, the metal oxide nanoparticles do not form a continuous phase or a bicontinuous phase, and have the shape of an independent nanoparticle by agglomeration of one single nanoparticle or 2 to 3 nanoparticles, and the nanoparticles are dispersed on a substrate including carbon nanotubes to form a bound structure.

The average particle size of the metal oxide nanoparticles may be 5 to 50 nm, preferably 5 to 40 nm, and more preferably 5 to 30 nm. If the average particle size of the metal oxide nanoparticles is less than 5 nm, aggregation may occur between the metal oxide nanoparticles, and the shape in which they are supported within the carbon nanotubes is irregular, which is not effective in reducing thermal conductivity. In addition, if the average particle size of the metal oxide nanoparticles exceeds 50 nm, the size of the aggregation between the metal oxide nanoparticles may be large, thereby blocking the pores of the substrate including the carbon nanotubes, thereby lowering the Seebeck constant.

The metal oxide nanoparticles may further include an aliphatic amine capped on the surface. The aliphatic amine capped on the surface of the metal oxide nanoparticles may be a C8-C25 aliphatic amine, and specifically, may be octylamine, decyl amine, dodecyl amine, dodecyl-tetradecyl amine, tetradecyl amine, hexadecyl amine, octadecyl amine, stearyl amine, oleyl amine, or erucyl amine. Although not limited thereto, when oleyl amine is used as a capping agent, the bonding force with the surface of the metal oxide nanoparticles is excellent, so that even when the thermoelectric material is exposed to the air for a long time, the Seebeck constant is maintained at 90% or more, so that high energy conversion efficiency can be maintained for a long time.

The thermoelectric material according to the present invention can satisfy the following [Formula 1].

[Formula 1] 1.5≤(power factor of thermoelectric material/power factor of carbon nanotube sheet)

Drawing 1 is a schematic diagram briefly showing a method for manufacturing a thermoelectric material according to the present invention. Referring to Drawing 1(a), the method for manufacturing a thermoelectric material of the present invention will be described. The method includes the steps of manufacturing a metal oxide precursor solution containing a metal oxide precursor and a solvent on a substrate including carbon nanotubes manufactured by a chemical vapor deposition method, immersing the substrate in the metal oxide precursor solution, and heat-treating the substrate containing the metal oxide precursor solution, thereby manufacturing a thermoelectric material. This manufacturing method can manufacture a good thermoelectric material with high energy conversion efficiency by lowering the thermal conductivity (k) while improving the Seebeck constant (a), thereby increasing the thermoelectric performance figure (ZT).

The above metal oxide precursor may be an acetylacetate. Specifically, it may be one or more selected from the group consisting of Fe(AcAc) ₃ , Cu(AcAc) ₂ , and Co(AcAc) ₂ , and preferably Fe(AcAc) ₃ , Cu(AcAc) ₂ . The above metal oxide precursors may form a p-type thermoelectric material by heat treatment.

The solvent may be a polar solvent. If it is a polar solvent, the type is not particularly limited. Specific examples of the polar solvent may include one or more selected from the group consisting of water, methanol, ethanol, propanol, glycerin, acetic acid, dichloromethane (CH ₂ Cl ₂ ), tetrahydrofuran (THF), ethyl acetate (C ₄ O ₂ H ₈ ), and benzyl alcohol. Benzyl alcohol is preferably effective.

The above metal oxide precursor solution can be prepared at a concentration of 0.1 M to 5 M, and preferably 0.5 M to 2 M. If the concentration of the metal oxide precursor solution is lower than 0.1 M, the amount of metal oxide nanoparticles supported in the carbon nanotubes is small, so that it is not effective in reducing the thermal conductivity and improving the electrical conductivity of the substrate including the carbon nanotubes. In addition, if the concentration of the metal oxide precursor solution exceeds 5 M, the metal oxide nanoparticles may aggregate with each other and block the pores of the substrate including the carbon nanotubes, which may excessively increase the thermal conductivity and lower the energy conversion efficiency.

The above heat treatment step may be performed at 100° C. to 300° C. for 10 to 800 minutes. Preferably, it may be 150° C. to 300° C., and more preferably, it may be 170° C. to 290° C. In order to lower the thermal conductivity of the carbon nanotubes and increase the Seebeck constant by supporting the metal oxide nanoparticles in the carbon nanotubes, the heat treatment may be performed at 180° C. to 280° C. By the heat treatment, the metal oxide precursor immersed in the substrate including the carbon nanotubes is generated as metal oxide nanoparticles, and the anions, for example, Cl ^- , NO3 ^- , SO3 ^- , which are paired with the metal cations of the metal oxide precursor, are generated as acid by-products, such as HCl, HNO ₃ , and H ₂ SO ₄ , by the heat treatment, respectively, and C ₅ H ₇ O ₂ ^- generates acetone and carbon dioxide as by-products by the heat treatment. These byproducts are volatilized through heat treatment. By this reaction mechanism, the thermoelectric material of the present invention may have a negative surface charge.

The above heat treatment step can be performed for 10 to 800 minutes. Preferably, it can be performed for 20 to 800 minutes, and more preferably, it can be performed for 20 to 720 minutes. In the above heat treatment step, the active atmosphere can use air. If the heat treatment is performed in air, only metal oxide nanoparticles can be formed at the interface with the carbon nanotubes.

The above metal oxide precursor solution may further include an aliphatic amine as a capping agent. A step of immersing a sample in a solution in which an aliphatic amine is further added to the metal oxide precursor solution so that the mass ratio of the metal oxide precursor and the aliphatic amine is 1:0.25 to 1:2 and then performing a heat treatment may be performed. Through the heat treatment, the metal oxide precursor is converted into metal oxide nanoparticles, and the capping agent is capped on the surface of the metal oxide nanoparticles.

Since the specific compound used as the aliphatic amine, which is the capping agent, is the same as described above, the specific details are omitted.

The thermoelectric material manufactured by including a capping agent in the above metal oxide precursor solution can maintain a high energy conversion efficiency by maintaining a Seebeck constant of 90% or more even when the thermoelectric material is exposed to air for a long time because the aliphatic amine caps the surface of the metal oxide nanoparticles (Fig. 5).

The present invention provides a thermoelectric element including the thermoelectric material.

The above thermoelectric element may be a thermoelectric element including a substrate including carbon nanotubes and a thermoelectric material including metal oxide nanoparticles supported on the substrate; and an electrode provided on the upper or lower portion of the thermoelectric material.

The present invention provides a thermoelectric module including the thermoelectric element.

The above thermoelectric module may be a thermoelectric module including a first electrode; a second electrode; and the above-described thermoelectric element disposed between the first electrode and the second electrode.

The present invention is described in detail below by the following examples and experimental examples.

However, the following examples and experimental examples are only intended to illustrate the present invention, and the scope of the invention is not limited by the examples and experimental examples.

A carbon nanotube sheet (CNT Web) manufactured by a chemical vapor deposition method was prepared, and copper acetylacetate (CAS No. 13395-16-9, hereinafter referred to as Cu(AcAc) ₂ ) as a metal oxide precursor was added to benzyl alcohol as a solvent so that the concentration was 1 mol/L (1 M), and oleylamine as a capping agent was further added to the benzyl alcohol containing the metal oxide precursor so that the weight ratio with the copper acetylacetate was 1:0.5, and then stirred to prepare a metal precursor solution.

The above carbon nanotube sheet was immersed in the metal precursor solution so that the metal oxide precursor was supported within the carbon nanotube, and then heat-treated at a temperature of 200°C for 20 minutes. Through the heat treatment, the metal oxide precursor supported within the carbon nanotube was converted into metal oxide nanoparticles, and oleylamine was capped on the surface of the metal oxide nanoparticles, so that the capped metal oxide nanoparticles were supported within the carbon nanotube.

A thermoelectric material was manufactured in the same manner as in Example 1, except that iron acetylacetate (CAS No. 14024-18-1, hereinafter referred to as Fe(AcAc) ₃ ) was used as the metal oxide precursor.

A thermoelectric material was manufactured in the same manner as in Example 1, except that cobalt acetylacetate (CAS No. 14024-48-7, hereinafter referred to as Co(AcAc) ₂ ) was used as the metal oxide precursor.

(Comparison Example 1)

A thermoelectric material was manufactured in the same manner as in Example 1, except that the metal oxide precursor and capping agent were not used.

(Comparative Example 2)

A thermoelectric material was manufactured in the same manner as in Example 1, except that ZrCl ₄ was used as the metal oxide in Example 1.

(Comparative Example 3)

A thermoelectric material was manufactured in the same manner as in Example 1, except that Zr(NO ₃ ) ₄ was used as the metal oxide in Example 1.

(Comparative Example 4)

A thermoelectric material was manufactured in the same manner as in Example 1, except that Zr(AcAc) ₄ was used as the metal oxide in Example 1.

(Experimental example)

The electrical conductivity of the thermoelectric materials obtained from the above Examples 1 to 3 and Comparative Examples 1 to 3 was measured using the 4-point probe method, and a thermoelectric element was manufactured by stacking electrodes by applying silver paste on top of the thermoelectric material, and the Seebeck constant was measured. The thermoelectric performance was evaluated from the measured electrical conductivity and Seebeck constant, and the results are shown in Tables 1 and 2.

Table 1

The Seebeck constant of the thermoelectric material manufactured in Comparative Example 1, that is, the thermoelectric material made of carbon nanotube sheets, was 45 μV/K, and it was confirmed that the thermoelectric material into which the metal oxides CuO ₂ and Fe ₂ O ₃ derived from the metal oxide precursors used in Examples 1 and 2 were introduced had an improved Seebeck constant compared to the thermoelectric material of Comparative Example 1. In addition, since the Seebeck constants all showed positive values, it can be seen that the thermoelectric materials of Examples 1 to 3 and Comparative Example 1 were p-type thermoelectric materials. However, in the case where a metal oxide precursor having the same anion ((AcAc) ₃ ) as the metal oxide precursor used in Examples 1 to 3 was used, the thermoelectric material of Comparative Example 4 showed a Seebeck constant of -12 μV/K, which means that an n-type thermoelectric material was manufactured. It can be seen that the properties of the thermoelectric material finally manufactured differ depending on the metal cation of the precursor even if the metal oxide precursor contains the same anion.

Comparative Examples 2 to 4 are supported as ZrO ₂ nanoparticles within carbon nanotubes, although the anion types of the metal oxide precursors are different. It can be seen that the thermoelectric material ultimately manufactured can be p-type or n-type depending on the type of anion bonded to the same metal atom cation of the metal oxide precursor.

Table 2

Normally, the thermoelectric performance of a thermoelectric material is evaluated by the ZT value, but in the case of thin films, it is difficult to measure thermal conductivity, so a perfect performance evaluation is impossible. However, the power factor (ZT) is Here, a ² is the square of the Seebeck constant and σ is the electrical conductivity) is also used as an indicator of thermoelectric performance, so in the present invention, the thermoelectric performance and energy conversion efficiency were evaluated using the power factor.

As shown in Table 2, the Seebeck constant of the thermoelectric material manufactured in Example 1 was higher than that of the thermoelectric material manufactured in Comparative Example 1, confirming excellent thermoelectric performance, and the power factor (thermoelectric performance) of Example 1 was improved by more than 1.5 times compared to the power factor (thermoelectric performance) of the carbon nanotube sheet of Comparative Example 1. It was confirmed that the introduction of metal oxide nanoparticles into the carbon nanotube sheet would improve thermoelectric performance and excellent energy conversion efficiency.

Examples 4 to 6 were performed in the same manner as in Example 1, except that the heat treatment temperature was changed to 280°C (Example 4), 220°C (Example 5), and 180°C (Example 6), thereby producing a thermoelectric material. In addition, Examples 7 to 11 were performed in the same manner as in Example 1, except that the heat treatment temperature and heat treatment time were changed, thereby producing a thermoelectric material.

In addition, Comparative Examples 5 to 7 were performed in the same manner as Comparative Example 1, except that the heat treatment temperature and time were changed, to manufacture a thermoelectric material.

The electrical conductivity and power factor (thermoelectric performance) of these thermoelectric materials are summarized in Table 3, and the change in electrical conductivity according to the heat treatment temperature is shown in Figure 3, and the change in power factor (thermoelectric performance) is shown in Figure 4.

Table 3

It can be seen that the electrical conductivity, Seebeck constant, and power factor (thermoelectric performance) do not increase in proportion to the heat treatment temperature and heat treatment time, that is, it was confirmed that there is an appropriate heat treatment temperature and treatment time that exhibit the best effect. As the metal oxide nanoparticles are supported in the carbon nanotubes, the electrical conductivity is somewhat lowered in the case where the metal oxide nanoparticles are not included (Comparative Examples 5 to 7), but as the Seebeck constant significantly increases, it can be seen that the thermoelectric performance (power factor) in the case where the metal oxide nanoparticles are supported (Examples 4 to 6) is always improved by more than twice that of the thermoelectric materials of Comparative Examples 5 to 7. These results show that the electrical conductivity decreases somewhat because the charge transfer between the carbon nanotubes forming the substrate, where metal oxide nanoparticles are supported within the carbon nanotubes, is limited or because the surface charge of the final thermoelectric material has a negative charge, so that the charge transfer is limited, whereas phonon scattering is promoted between the interface of the nanoparticles and the carbon nanotubes, which significantly increases the Seebeck constant and improves the thermoelectric performance (power factor). In addition, when the heat treatment temperature is the same, the electrical conductivity of the thermoelectric material increases as the heat treatment time increases (Examples 6 to 11), but the Seebeck constant increases and shows a tendency to show a maximum value when the heat treatment time is 120 minutes and then gradually decreases. Accordingly, it can be seen that the power factor (thermoelectric performance) also shows a tendency similar to the Seebeck constant.

Table 4 shows the change in Seebeck constant according to the weight ratio of Cu(AcAc)2 and oleylamine, using Cu(AcAc)2 as a precursor of metal oxide.

Table 4

When the weight ratio of the metal oxide precursor and the capping agent, oleylamine, was 1:0.5, the Seebeck constant was the largest, and when the weight ratio exceeded 1:0.5, the Seebeck constant tended to gradually decrease. In addition, as in Comparative Example 8, it can be seen that when the capping agent is not included on the surface of the metal oxide nanoparticles included in the thermoelectric material, the Seebeck constant decreases compared to when the capping agent is included. That is, it can be seen that the thermoelectric performance is improved as the capping agent is included on the surface of the metal oxide nanoparticles.

The present invention is not limited to the above-described embodiments, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope that does not depart from the technical spirit of the present invention as described in the claims, and this will also fall within the scope of the present invention.

Claims (18)

A thermoelectric material comprising a substrate including carbon nanotubes and metal oxide nanoparticles supported on the substrate, wherein the thermoelectric material has a Seebeck constant retention rate of 90% or higher in air. In the first paragraph,
A thermoelectric material wherein the metal of the metal oxide includes one or more selected from the group consisting of Fe, Cu, and Co. In the first paragraph,
The above thermoelectric material is a thermoelectric material having a negative surface charge. In the first paragraph,
A thermoelectric material in which the precursor of the above metal oxide is an acetylacetate. In the first paragraph,
The above description is a thermoelectric material which is a carbon nanotube sheet. In the first paragraph,
A thermoelectric material comprising 0.001 to 10 parts by weight of metal oxide nanoparticles per 100 parts by weight of the carbon nanotubes. In the first paragraph,
A thermoelectric material having an average particle diameter of the above metal oxide nanoparticles of 5 to 50 nm. In the first paragraph,
The above thermoelectric material is a p-type thermoelectric material. In the first paragraph,
A thermoelectric material further comprising an aliphatic amine capped on the surface of the metal oxide nanoparticles. delete In the first paragraph,
The above thermoelectric material is a thermoelectric material satisfying the following [Formula 1].
[Formula 1]
2≤(power factor of thermoelectric material/power factor of carbon nanotube sheet) In a method for manufacturing a thermoelectric material according to any one of claims 1 to 9 and 11,
A step of preparing a metal oxide precursor solution comprising a solvent and a metal oxide precursor,
A step of immersing the above metal oxide precursor solution into a substrate including carbon nanotubes, and
A method for manufacturing a thermoelectric material, comprising a step of heat-treating the substrate containing the metal oxide precursor solution. In Article 12,
A method for producing a thermoelectric material, wherein the solvent comprises a polar solvent. In Article 12,
A method for manufacturing a thermoelectric material, wherein the precursor of the above metal oxide is an acetylacetate. In Article 12,
A method for manufacturing a thermoelectric material, wherein the above heat treatment is performed at 100°C to 300°C. In Article 12,
A method for producing a thermoelectric material, wherein the metal oxide precursor solution further comprises an aliphatic amine as a capping agent. A thermoelectric element comprising a thermoelectric material according to any one of claims 1 to 9 and 11. First electrode;
second electrode; and
A thermoelectric module comprising a thermoelectric element according to claim 17, arranged between the first electrode and the second electrode.