KR20170111066A - Thermoelectric material and preparation method thereof - Google Patents

Abstract

The present invention relates to carbon nanotube fibers that have been subjected to metal doping treatment or acid treatment; And a conductive polymer coated on the carbon nanotube fibers. The thermoelectric material according to the present invention has an effect of significantly improving thermoelectric properties through acid treatment or doping treatment at an appropriate concentration and conductive polymer coating. The present invention also provides a method for fabricating a carbon nanotube fiber, comprising the steps of (1) conducting metal doping treatment of carbon nanotube fibers; And applying a conductive polymer to the carbon nanotubes on which step 1 is performed (step 2). The present invention also provides a method of manufacturing a carbon nanotube based thermoelectric material based on carbon nanotubes. The method of manufacturing a thermoelectric material according to the present invention is advantageous in that a thermoelectric material applicable to thermoelectric elements of various shapes and sizes can be manufactured without a substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a thermoelectric material and a preparation method thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric material and a method of manufacturing the same, and relates to a thermoelectric material including metal-doped or acid-treated carbon nanotube fibers and a conductive polymer coated on the carbon nanotube fibers, and a method for manufacturing the same.

Thermoelectric phenomenon refers to the phenomenon of reversible and direct energy conversion between heat and electricity. It is a phenomenon that electrons and holes move inside the material, which is the phenomenon of electric energy generation (Seebeck effect) Refers to a heat generation phenomenon or an endothermic phenomenon (Peltier effect) of a substance generated by an electric energy to be loaded. When thermoelectric conversion is used, it is possible to produce electric power using various heat sources such as industrial waste heat, natural heat, body heat, etc., and it is possible to convert future future environmentally friendly energy that can perform precision and rapid cooling. In addition, a thermoelectric device using this is used to directly convert thermal energy into electrical energy and electrical energy into thermal energy, and it is energy-saving technology that best meets the needs of the times.

Researches on thermoelectric materials and devices have been developed since the 1950s and have developed thermoelectric properties two to three times higher than those of existing ones over a period of years. Bi-Te, Pb-Te, Si-Ge And Fe-Si-based alloys are the most widely used materials. However, the thermoelectric performance index showing the energy conversion efficiency of these thermoelectric materials showed a value of less than 1 at room temperature, and the maximum cooling efficiency obtained through this was about 8%, which limits the use to various electronic devices. Although the improvement of the thermoelectric performance index has been technically limited since the 1960s, the development of nanotechnology has enabled independent adjustment of the three parameters of the thermoelectric performance index, which can greatly improve the thermoelectric performance index in the 2000s there was. In the 2000s, Bi ₂ Te ₃ , PbTe, ZnSb ₃ , SiGe, BeSi ₂ , MSb ₃ (M = Co, Rb, In), CoFe ₃ Sb, Ba ₈ Si ₄₆ , NaCo ₂ O _x , CaCo ₄ O _{9 and} other ceramics have been studied. Recent researches have been focused on the fabrication of superlattices using these materials, the reduction of thermal conductivity by phonon glass-electron crystal, And structural control technology such as heavy fermion has been proposed, and the thermoelectric performance index is continuously improved.

Most efficient thermoelectric elements are manufactured using inorganic materials including the above-mentioned rare elements, and there are difficulties in utilizing them as high price, brittleness, large area production, that is, industrialization technology.

On the other hand, organic materials are less expensive than inorganic materials, can be manufactured in a large area, have high toughness, elasticity and low thermal conductivity. In addition, the application of the solution process can reduce the process cost and can be mixed with a variety of organic / inorganic materials. Recently, researches on thermoelectric devices using organic materials have been actively conducted.

Unlike most organic polymers having an insulating property, the conductive polymer is an organic polymer having conductivity capable of conducting electricity, and it can exhibit conductivity equivalent to a metal or exhibit semiconductor characteristics. Therefore, one of the important factors in evaluating the thermoelectric performance, a conductive polymer having a metal or semiconductor level value of electric conductivity, can be a very good thermoelectric material. Particularly, polypyrrole, polyaniline (PANi), polycarbazole, polythiophene, poly (3,4-ethylenedioxythiophene) (PEDOT), poly (3,4- The thermoelectric properties of conductive polymers such as poly (4-styrenesulfonate) and poly (4-styrenesulfonate) (PSS) have been attracting interest from many researchers. However, since the electrical conductivity is still lower than that of inorganic materials, .

The thermoelectric performance index (figure of merit, Z or ZT) is determined by three variables such as electromotive force (Jeffreck coefficient), thermal conductivity and electrical conductivity with temperature difference, and is expressed as Z = a ² · s / κ. Where Z is the figure of merit (1 / K), a is the Seebeck coefficient (V / K), s is the electrical conductivity (S / cm), k is the thermal conductivity (W / mK) . In general, the heat transfer coefficient of thermoelectric materials with a high value of the Seebeck coefficient and electrical conductivity is low and the thermal conductivity is low, and the energy conversion efficiency by thermoelectric conversion is high.

Therefore, researches for increasing the electric conductivity and the Seebeck coefficient of the conductive polymer have been carried out in various ways, and studies have been actively conducted to fabricate a thermoelectric device using the same and to improve the thermoelectric performance of the thermoelectric device 10-2014-0095199).

In this connection, a carbon material such as carbon nanotube (CNT) and graphene having excellent electrical conductivity is added to a conductive polymer solution, and chemical treatment is performed using a hydrazine solution to obtain an electrical conductivity of the polymer / carbon composite material Research is actively being carried out. These methods have also been reported to improve the conductivity of a conductive polymer having a conductivity of several S / cm to a conductivity level of several hundreds S / cm. In recent years, in order to improve the thermoelectric properties of such a polymer / carbon composite material to the same level as inorganic materials, the charge mobility of the polymer is improved by forming a polyaniline polymer aligned on carbon nanotubes by in-situ polymerization Carbon nanotube / polyaniline composite thermoelectric material with improved electrical conductivity and Seebeck coefficient have been reported.

In order to improve the thermoelectric properties of the conductive polymer, there have been a lot of studies to add a carbon material to the conductive polymer. In order to improve the thermoelectric properties of the conductive polymer, the carbon material to be added must be uniformly dispersed in the polymer matrix, The added carbon materials should be properly connected. However, in the polymer / carbon composite material prepared by the conventional method, the carbon material is aggregated due to the high temperature exposure, and thus the electric conductivity of the composite material is sharply lowered to improve the thermoelectric properties.

Accordingly, the present inventors have studied a method for improving the existing method of adding a carbon material to a polymer matrix in order to produce a thermoelectric material having improved thermoelectric properties, and have found that the electrical conductivity of the porous carbon nanotube fiber And then the organic polymer material is coated on the surface of the porous carbon nanotube fiber to improve the thermoelectric properties efficiently, and the present invention has been completed.

Korean Patent Publication No. 10-2014-0095199

An object of the present invention is to provide a thermoelectric material having improved thermoelectric properties and a method of manufacturing the same.

In order to achieve the above object,

Metal-doped carbon nanotube fibers; And

And a conductive polymer coated on the carbon nanotube fibers.

In addition,

Acid treated carbon nanotube fibers; And

And a conductive polymer coated on the carbon nanotube fibers.

Further,

Metal doping the carbon nanotube fibers (step 1); And

And applying a conductive polymer to the carbon nanotubes on which step 1 is performed (step 2).

Further,

Acid treating the carbon nanotube fibers (step a); And

And a step (b) of applying the conductive polymer to the carbon nanotubes on which step 1 is performed.

Furthermore,

A thermoelectric element including the thermoelectric material is provided.

The thermoelectric material according to the present invention has an effect of significantly improving thermoelectric properties through acid treatment or doping treatment at an appropriate concentration and conductive polymer coating.

In addition, the method of manufacturing a thermoelectric material according to the present invention is advantageous in that a thermoelectric material applicable to thermoelectric elements of various shapes and sizes can be manufactured without a substrate.

1 is a schematic view showing an example of a thermoelectric element including a thermoelectric material according to the present invention,
2 is a graph showing the whiteness coefficient, the electric conductivity, the thermal conductivity and the thermoelectric performance index of Example 2, Example 10, Example 11, and Comparative Example 9 according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described as follows. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. In addition, "including" an element throughout the specification does not exclude other elements unless specifically stated to the contrary.

In order to improve the thermoelectric properties of the conductive polymer, it is necessary to uniformly disperse the carbon material in the polymer matrix and to add the conductive polymer to the conductive polymer. There is a difficulty in finely adjusting the amount of the carbon material, and there is a limit in forming a uniform thin film according to the characteristics of the carbon material.

In the present invention, the carbon nanotube fibers are subjected to an acid treatment or a metal doping treatment to improve the electrical conductivity, the surface of the carbon nanotube fibers is coated with the conductive polymer to reduce the thermal conductivity, and the thermoelectric material having improved thermoelectric properties is provided I want to.

The present invention

Metal-doped carbon nanotube fibers; And

And a conductive polymer coated on the carbon nanotube fibers to provide a thermoelectric material based on a carbon nanotube fiber.

Hereinafter, the carbon nanotube fiber-based thermoelectric material according to the present invention will be described in detail.

In the carbon nanotube fiber-based thermoelectric material according to the present invention, the metal doping treatment may be performed using metals such as gold, silver, palladium, platinum, nickel, and chromium. However, It is not limited.

The metal doping treatment may be performed by dipping the carbon nanotube fibers in a solution containing metal ions, but the present invention is not limited thereto.

The metal ion concentration of the metal ion-containing solution may be 0.5 mM to 20 mM, may be 0.7 mM to 18 mM, may be 0.9 mM to 16 mM, may be 1.0 mM to 15 mM, May be from 1.0 mM to 10 mM.

At this time, if the concentration of the metal ion is less than 0.5 mM, the electrical conductivity of the carbon nanotube fiber may not be improved, and if the concentration of the metal ion is more than 20 mM, the thermal conductivity of the carbon nanotube fiber becomes excessively high There is a possibility that the thermoelectric properties are remarkably reduced.

Next, in the carbon nanotube fiber-based thermoelectric material according to the present invention, the carbon nanotube fibers may be directly spinned, coagulated spinning, liquid-crystalline spinning, brush spinning, spinning and the like, and it is preferable that they are produced by direct spinning.

In addition, the carbon nanotube fibers are preferably porous.

Next, in the carbon nanotube fiber-based thermoelectric material according to the present invention, the conductive polymer may be at least one selected from the group consisting of polypyrrole, polyaniline, polycarbazole, polythiophene, (PEDOT): poly (styrenesulfonate) (PSS), and the like can be used as the poly (3,4-ethylenedioxythiophene) (PTHOT) A mixture of the conductive polymer and the inorganic material may be used. However, the conductive polymer or mixture is not limited to the conductive polymer or the mixture coated on the carbon nanotube fibers.

The conductive polymer is coated on the metal-doped carbon nanotube fibers, thereby reducing the thermal conductivity of the carbon nanotube fibers, and reducing the electrical conductivity to a small extent, and ultimately improving the thermoelectric properties.

In addition,

Acid treated carbon nanotube fibers; And

And a conductive polymer coated on the carbon nanotube fibers to provide a thermoelectric material based on a carbon nanotube fiber.

Hereinafter, the carbon nanotube fiber-based thermoelectric material according to the present invention will be described in detail.

First, in the carbon nanotube fiber-based thermoelectric material according to the present invention, the acid treatment may be performed using sulfuric acid, nitric acid, hydrochloric acid, acetic acid, acetic acid, or a combination thereof, %, May be from 55% to 97%, and may be from 60% to 95%, but is not limited thereto.

At this time, if the concentration of the acid is less than 50%, the doping effect may be deteriorated.

In the acid treatment, an acid mixed with sulfuric acid and nitric acid at a volume ratio of 5 to 9: 3 may be used, and an acid mixed at a volume ratio of 6: 8: 3 may be used. Preferably, a volume ratio of 7: Can be used.

Next, in the carbon nanotube fiber-based thermoelectric material according to the present invention, the carbon nanotube fibers may be directly spinned, coagulated spinning, liquid-crystalline spinning, brush spinning, spinning and the like, and it is preferable that they are produced by direct spinning.

In addition, the carbon nanotube fibers are preferably porous.

Next, in the carbon nanotube fiber-based thermoelectric material according to the present invention, the conductive polymer may be at least one selected from the group consisting of polypyrrole, polyaniline, polycarbazole, polythiophene, (PEDOT): poly (styrenesulfonate) (PSS), and the like can be used as the poly (3,4-ethylenedioxythiophene) (PTHOT) A mixture of the conductive polymer and the inorganic material may be used. However, the conductive polymer or mixture is not limited to the conductive polymer or the mixture coated on the carbon nanotube fibers.

The conductive polymer is coated on the metal-doped carbon nanotube fibers, thereby reducing the thermal conductivity of the carbon nanotube fibers, and reducing the electrical conductivity to a small extent, and ultimately improving the thermoelectric properties.

The thermoelectric performance index (figure of merit, Z or ZT) of a thermoelectric material is determined by the electromotive force (Jeffreck coefficient), thermal conductivity, and electric conductivity according to temperature difference, and expressed as Z = a ² · s / κ. Where Z is the figure of merit (1 / K), a is the Seebeck coefficient (V / K), s is the electrical conductivity (Om), κ is the thermal conductivity (W / mK) and T is the absolute temperature .

In general, the larger the Seebeck coefficient and the electrical conductivity, and the lower the thermal conductivity, the higher the figure of merit of the thermoelectric semiconductor, and the energy conversion efficiency by thermoelectric conversion is improved.

The carbon nanotube fiber-based thermoelectric material according to the present invention can improve the electrical conductivity through acid treatment or metal doping treatment at a proper concentration, improve the Seebeck coefficient and lower the thermal conductivity through the polymer coating, .

Further,

Metal doping the carbon nanotube fibers (step 1); And

And applying a conductive polymer to the carbon nanotubes on which step 1 is performed (step 2). The present invention also provides a method for manufacturing a carbon nanotube based thermoelectric material based on carbon nanotubes.

Hereinafter, a carbon nanotube fiber-based thermoelectric material preparation method according to the present invention will be described in detail.

First, in the method of manufacturing a thermoelectric material based on carbon nanotube fibers according to the present invention, step 1 is a step of metal doping the carbon nanotube fibers.

The carbon nanotubes of step 1 may be prepared by a method such as direct spinning, coagulation spinning, liquid-crystalline spinning, brush spinning, It is preferred that they are prepared by direct spinning.

The carbon nanotube fibers of step 1 are preferably porous.

The metal doping process of step 1 may be performed using a metal such as gold, silver, palladium, platinum, nickel, and chromium, but is not limited to a metal having a high reduction potential.

The metal doping process of step 1 may be performed by dipping the carbon nanotube fibers in a solution containing metal ions, but the present invention is not limited thereto.

The metal ion concentration of the metal ion-containing solution may be 0.5 mM to 20 mM, may be 0.7 mM to 18 mM, may be 0.9 mM to 16 mM, may be 1.0 mM to 15 mM, May be from 1.0 mM to 10 mM.

At this time, if the concentration of the metal ion is less than 0.5 mM, the electrical conductivity of the carbon nanotube fiber may not be improved, and if the concentration of the metal ion is more than 20 mM, the thermal conductivity of the carbon nanotube fiber becomes excessively high There is a possibility that the thermoelectric properties are remarkably reduced.

Next, in the method for manufacturing a thermoelectric material based on carbon nanotube fibers according to the present invention, step 2 is a step of applying a conductive polymer to the carbon nanotubes on which step 1 is performed.

The conductive polymer of step 2 may be at least one selected from the group consisting of polypyrrole, polyaniline, polycarbazole, polythiophene, poly (3-hexylthiophene) (P3HT) (PEDOT): poly (styrenesulfonate) (PSS), and the mixture of the conductive polymer and the inorganic material may be used. However, the present invention is not limited thereto, as long as it is a conductive polymer or a mixture coated on the carbon nanotube fibers in an aligned form.

The conductive polymer of step 2 is coated on the metal-doped carbon nanotube fibers in the step 1, thereby reducing the thermal conductivity of the carbon nanotube fibers, reducing the electrical conductivity to a small extent, and ultimately improving the thermoelectric properties have.

The method of coating the conductive polymer of step 2 may include spin coating, roll coating, spray coating, dip coating, flow coating, doctor blade, printing, printing, dispensing, inkjet printing, offset printing, screen printing, pad printing, gravure printing, flexography printing, stencil printing and imprinting, Imbedding coatings can be used.

Next, the method for manufacturing a thermoelectric material according to the present invention may further include washing and drying the thermoelectric material prepared in the step 2 (step 3c).

At this time, the thermoelectric material prepared in step 2 may be washed using distilled water, 1,2-dichlorobenzene (ODCB), m-cresol, methanol, or the like , But is not limited thereto.

Further, the heat-treated material subjected to the cleaning may be heat-treated at a temperature of 100 ° C to 140 ° C for 5 minutes to 20 minutes, but is not limited thereto.

Further,

Acid treating the carbon nanotube fibers (step a); And

And a step (b) of applying a conductive polymer to the carbon nanotubes on which step 1 has been performed (step b).

Hereinafter, a method for manufacturing a thermoelectric material based on a carbon nanotube fiber according to the present invention will be described in detail.

In the method of manufacturing a thermoelectric material based on carbon nanotube fibers according to the present invention, the acid treatment in step a may be performed using sulfuric acid, nitric acid, hydrochloric acid, acetic acid, acetic acid, or a combination thereof, Can be from 50% to 98%, from 55% to 97%, and from 60% to 95%, but is not limited thereto.

At this time, if the concentration of the acid is less than 50%, the doping effect may be deteriorated.

The acid treatment in step (a) may be carried out using an acid in which sulfuric acid and nitric acid are mixed at a volume ratio of 5: 9: 3, and an acid mixed at a volume ratio of 6: 8: 3 may be used. Lt; RTI ID = 0.0 >% < / RTI > by volume.

Next, in the method of manufacturing a thermoelectric material based on a carbon nanotube fiber according to the present invention, the carbon nanotube fibers of the step a may be directly spinned, coagulated spinning, liquid-crystalline spinning, Brush spinning and the like, and it is preferable that they are produced through direct spinning.

The carbon nanotube fibers of step (a) are preferably porous.

Next, in the method of manufacturing a thermoelectric material based on a carbon nanotube fiber according to the present invention, the conductive polymer of step b may be selected from the group consisting of polypyrrole, polyaniline, polycarbazole, polythiophene, (PEDOT): poly (styrenesulfonate) (PSS), poly (3,4-ethylenedioxythiophene) (PEDOT) ), And a mixture of the conductive polymer and the inorganic material may be used. However, the conductive polymer or mixture is not limited to the conductive polymer or the mixture coated on the carbon nanotube fibers.

The conductive polymer of step (b) may be coated on the carbon nanotube fibers acid-treated in step (a), thereby reducing the thermal conductivity of the carbon nanotube fibers and decreasing the electrical conductivity of the carbon nanotube fibers to some extent and ultimately improving the thermoelectric properties .

The method of coating the conductive polymer of step b may include spin coating, roll coating, spray coating, dip coating, flow coating, doctor blade, dispensing printing, printing, dispensing, inkjet printing, offset printing, screen printing, pad printing, gravure printing, flexography printing, stencil printing and imprinting, Imbedding coatings can be used.

Next, the method for manufacturing a thermoelectric material according to the present invention may further include washing and drying the thermoelectric material manufactured in the step b (step 3c).

At this time, the thermoelectric material prepared in step b may be washed using distilled water, 1,2-dichlorobenzene (ODCB), m-cresol, methanol, or the like , But is not limited thereto.

Further, the heat-treated material subjected to the cleaning may be heat-treated at a temperature of 100 ° C to 140 ° C for 5 minutes to 20 minutes, but is not limited thereto.

Accordingly, the method of manufacturing a thermoelectric material based on carbon nanotube fibers according to the present invention has an advantage that a thermoelectric material applicable to thermoelectric elements of various shapes and sizes can be manufactured without a substrate, Doping improves the electric conductivity and improves the Seebeck coefficient and the thermal conductivity through the polymer coating, thereby producing a thermoelectric material exhibiting high thermoelectric performance.

Furthermore,

A thermoelectric element including the thermoelectric material is provided.

The thermoelectric element

Metal-doped, conductive polymer-coated carbon nanotube fiber based thermoelectric material; And an electrode provided on an upper portion or a lower portion of the thermoelectric material.

Further, the thermoelectric element

Carbon nanotube fiber based thermoelectric material treated with acid and coated with conducting polymer; And an electrode provided on an upper portion or a lower portion of the thermoelectric material.

At this time, an example of the thermoelectric device according to the present invention is shown in Fig.

As shown in FIG. 1, a thermoelectric device in which electrodes are laminated by patterning a film-shaped thermoelectric material formed on a substrate with a predetermined width and width, and then applying silver paste on the thermoelectric material can be manufactured.

Hereinafter, the present invention will be described in detail with reference to the following examples and experimental examples.

It should be noted, however, that the following Examples and Experimental Examples are merely illustrative of the present invention, and the scope of the present invention is not limited by Examples and Experimental Examples.

< Example  1> Metal-doped carbon nanotube fibers 1

Step 1: A porous carbon nanotube prepared by direct spinning is provided in the form of a film, and the carbon nanotube fiber is immersed in a solution containing gold ions at a concentration of 1 mM for 10 minutes to perform gold doping treatment After that, it was washed with distilled water and dried in a nitrogen atmosphere for 1 hour to prepare a gold-doped porous carbon nanotube fiber.

< Example  2> Metal-doped carbon nanotube fiber 2

Doped porous carbon nanotube fibers were prepared in the same manner as in Example 1 except that the gold ion concentration of the gold ion solution was changed to 2 mM in Example 1.

< Example  3> Metal-doped carbon nanotube fiber 3

Doped porous carbon nanotube fibers were prepared in the same manner as in Example 1, except that the gold ion concentration of the gold ion solution was changed to 5 mM in Example 1.

< Example  4> Metal-doped carbon nanotube fiber 4

Doped porous carbon nanotube fibers were prepared in the same manner as in Example 1, except that the gold ion concentration of the gold ion solution was changed to 10 mM in Example 1.

< Example  5> Metal-doped carbon nanotube fiber 5

Doped porous carbon nanotube fibers were prepared in the same manner as in Example 1 except that the solution containing gold ions was changed to a solution containing silver ions at a concentration of 2 mM in Example 1 Respectively.

< Example  6> Metal-doped carbon nanotube fiber 6

The procedure of Example 1 was repeated except that the solution containing gold ions was replaced with a solution containing palladium ions at a concentration of 2 mM in Example 1 to prepare palladium-doped porous carbon nanotube fibers Respectively.

< Example  7> Acid treated carbon nanotube fibers 1

Step a: Porous carbon nanotubes prepared by direct spinning are provided in a film form. The carbon nanotube fibers are immersed in a sulfuric acid solution having a concentration of 95% for 30 minutes to perform acid treatment, and then distilled water And dried in a nitrogen atmosphere for 1 hour to prepare an acid-treated porous carbon nanotube fiber.

< Example  8> Acid-treated carbon nanotube fibers 2

The acid-treated porous carbon nanotube fibers were prepared in the same manner as in Example 7, except that the nitric acid solution was changed to a 60% concentration solution instead of the sulfuric acid solution.

< Example  9> Acid-treated carbon nanotube fibers 3

The acid-treated porous carbon nanotube fibers were prepared in the same manner as in Example 7 except that the sulfuric acid solution and the nitric acid solution were replaced by an acid solution mixed at a volume ratio of 7: 3 .

< Comparative Example  1 > metal doped Grapina

Step 1: Commercialized graphite was peeled by chemical method to prepare a graphene solution, and a graphene film was formed through a vacuum filter. Then, the graphene was immersed in a solution containing gold ions at a concentration of 2 mM for 10 minutes to perform gold doping treatment, followed by washing with distilled water and drying in a nitrogen atmosphere for 1 hour to obtain gold doped graphene .

< Comparative Example  2> Metal-doped carbon nanotubes

Step 1: Commercialized carbon nanotubes were dispersed in a dimethylformamide (DMF) solvent to prepare a carbon nanotube solution, and a carbon nanotube film was formed through a vacuum filter. Thereafter, the carbon nanotubes were immersed in a solution containing gold ions at a concentration of 2 mM for 10 minutes to perform gold doping treatment, followed by washing with distilled water and drying in a nitrogen atmosphere for 1 hour to obtain gold-doped carbon nano- Tube.

< Comparative Example  3> acid treated Grapina

Step a: The commercially available graphite was peeled off chemically to prepare a graphene solution, and a graphene film was formed through a vacuum filter. Thereafter, the graphene was immersed in an acid solution mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3 for 30 minutes to perform an acid treatment, followed by washing with distilled water and drying in a nitrogen atmosphere for 1 hour, Pin.

< Comparative Example  4> Acid-treated carbon nanotubes

Step a: The commercialized carbon nanotubes were dispersed in a dimethylformamide (DMF) solvent to prepare a carbon nanotube solution, and a carbon nanotube film was formed through a vacuum filter. Thereafter, the carbon nanotubes were immersed in an acid solution mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3 for 30 minutes to perform an acid treatment, followed by washing with distilled water and drying in a nitrogen atmosphere for 1 hour, Carbon nanotubes were prepared.

< Example  10> Porosity Carbon nanotube  Fiber-based thermoelectric material 1

Step 1: Porous carbon nanotube fibers prepared by direct spinning were provided in a film form. The carbon nanotube fibers were immersed in a gold ion solution at a concentration of 2 mM for 10 minutes to perform gold doping treatment , Washed with distilled water and dried in a nitrogen atmosphere for 1 hour.

Step 2: The carbon nanotube fibers in which Step 1 was performed were coated with a poly (3-hexylthiophene) (P3HT) conductive polymer.

Step 3c: Carbon nanotube fibers having been subjected to the step 2 were washed with an organic solvent of 1,2-dichlorobenzene (ODCB) and then heat-treated at 120 ° C for 10 minutes to prepare a thermoelectric material based on a porous carbon nanotube fiber .

< Example  11> Porous carbon nanotube fiber based thermoelectric material 2

Same as Example 10 except that polyaniline was used as a conductive polymer in Step 2 of Example 10 and m-cresol was used as an organic solvent in Step 3c of Example 10 above. To produce a porous carbon nanotube fiber based thermoelectric material.

< Example  12> Porous carbon nanotube fiber based thermoelectric material 3

Except that poly (3,4-ethylenedioxythiophene) (PEDOT) was used as a conductive polymer in Step 2 of Example 10 and methanol was used as an organic solvent in Step 3c of Example 10, The porous carbon nanotube fiber-based thermoelectric material was prepared in the same manner as in Example 10.

< Example  13> Porous carbon nanotube fiber based thermoelectric material 4

(3-hexylthiophene) (P3HT) doped with FeCl ₃ as a conductive polymer in Step 2 of Example 10 was used instead of the porous carbon nanotube fiber-based thermoelectric material .

< Example  14> Porous carbon nanotube fiber based thermoelectric material 5

Polyaniline doped with camphorsulfonic acid was used as the conductive polymer in Step 2 of Example 10 and m-cresol (m-cresol) was used as the organic solvent in Step 3c of Example 10 , A porous carbon nanotube fiber-based thermoelectric material was prepared in the same manner as in Example 10.

< Example  15> Porosity Carbon nanotube  Fiber-based thermoelectric material 6

Step a: Porous carbon nanotube fibers prepared by direct spinning in a film form, and the carbon nanotube fibers were immersed in an acid solution mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3 for 30 minutes After acid treatment, it was washed with distilled water and dried in a nitrogen atmosphere for 1 hour.

Step b: The carbon nanotube fibers on which step a was performed were coated with poly (3-hexylthiophene) (P3HT) conductive polymer.

Step 3c: Carbon nanotube fibers having been subjected to the step b) were washed with an organic solvent of 1,2-dichlorobenzene (ODCB) and then heat-treated at 120 ° C for 10 minutes to prepare a thermoelectric material based on a porous carbon nanotube fiber .

< Example  16> Porous carbon nanotube fiber based thermoelectric material 7

The same procedure as in Example 15 was carried out except that polyaniline was used as a conductive polymer in Step b of Example 15 and m-cresol was used as an organic solvent in Step 3c of Example 15 To produce a porous carbon nanotube fiber based thermoelectric material.

< Example  17> Porous carbon nanotube fiber based thermoelectric material 8

Except that poly (3,4-ethylenedioxythiophene) (PEDOT) was used as a conductive polymer in Step b of Example 15 and methanol was used as an organic solvent in Step 3c of Example 15. [ The porous carbon nanotube fiber-based thermoelectric material was prepared in the same manner as in Example 15.

< Comparative Example  5> Grapina  Based thermoelectric material 1

Step 1: Commercialized graphite was peeled by chemical method to prepare a graphene solution, and a graphene film was formed through a vacuum filter. Thereafter, the graphene was dipped in a solution containing gold ions at a concentration of 2 mM for 10 minutes to perform gold doping treatment, followed by washing with distilled water and drying in a nitrogen atmosphere for 1 hour.

Step 2: The graphene obtained in the step 1 was coated with a polyaniline conductive polymer.

Step 3c: The graphene obtained in step 2 was washed with m-cresol organic solvent and heat-treated at 120 ° C for 10 minutes to prepare a graphene-based thermoelectric material.

< Comparative Example  6> Grapina  Based thermoelectric material 2

Step a: The commercially available graphite was peeled off chemically to prepare a graphene solution, and a graphene film was formed through a vacuum filter. Thereafter, the graphene was immersed in an acid solution mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3 for 30 minutes, acid-treated, washed with distilled water, and dried in a nitrogen atmosphere for 1 hour.

Step b: The graphene obtained in step a was coated with a polyaniline conductive polymer.

Step 3c: The graphene obtained in step 2 was washed with m-cresol organic solvent and heat-treated at 120 ° C for 10 minutes to prepare a graphene-based thermoelectric material.

< Comparative Example  7> Carbon nanotube based thermoelectric material 1

Step 1: Commercialized carbon nanotubes were dispersed in a dimethylformamide (DMF) solvent to prepare a carbon nanotube solution, and a carbon nanotube film was formed through a vacuum filter. Then, the carbon nanotubes were immersed in a solution containing gold ions at a concentration of 2 mM for 10 minutes to perform gold doping treatment, followed by washing with distilled water and drying in a nitrogen atmosphere for 1 hour.

Step 2: Carbon nanotubes carrying out the step 1 were coated with a polyaniline conductive polymer.

Step 3c: Carbon nanotubes based on step 2 were washed with an m-cresol organic solvent and then heat-treated at 120 ° C for 10 minutes to prepare a thermoelectric material based on carbon nanotubes.

< Comparative Example  8> Carbon nanotube based thermoelectric material 2

Step a: The commercialized carbon nanotubes were dispersed in a dimethylformamide (DMF) solvent to prepare a carbon nanotube solution, and a carbon nanotube film was formed through a vacuum filter. Thereafter, the carbon nanotubes were immersed in an acid solution mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3 for 30 minutes, acid-treated, washed with distilled water, and dried in a nitrogen atmosphere for 1 hour.

Step b: The carbon nanotubes obtained in the step 1 were coated with a polyaniline conductive polymer.

Step 3c: Carbon nanotubes based on step 2 were washed with an m-cresol organic solvent and then heat-treated at 120 ° C for 10 minutes to prepare a thermoelectric material based on carbon nanotubes.

< Comparative Example  9> Carbon nanotube fiber material

Porous carbon nanotube fibers prepared by direct spinning were provided in a film form.

< Comparative Example  10> Grapina  Material

The commercialized graphite was peeled by a chemical method to prepare a graphene solution, and a graphene film was formed through a vacuum filter.

< Comparative Example  11> Carbon nanotube material

Commercial carbon nanotubes were dispersed in a dimethylformamide (DMF) solvent to prepare a carbon nanotube solution, and a carbon nanotube film was formed through a vacuum filter.

< Experimental Example  1> Comparative analysis of carbon doped or acid-treated carbon materials

In order to confirm the improvement of the electrical conductivity according to the metal doping treatment or the acid treatment in the step 1 or the step a of the method for producing a thermoelectric material according to the present invention, the above Examples 1 to 9, Comparative Examples 1 to 4, The electrical conductivities of the carbon materials prepared in Examples 9 to 11 were measured by the 4-point probe method and the thermal conductivity was measured using a scanning laser heating analyzer (Ulvac-Riko, Inc., Laser PIT) As shown in FIG. 1, a carbon material is patterned to have a predetermined width and area, and a silver paste is applied on the carbon material to form a thermoelectric element. The thermoelectric performance was evaluated from the measured electrical conductivity and the whiteness factor, and it is shown in Table 1.

As shown in Table 1, the Seebeck coefficient of the carbon nanotube fibers prepared in Comparative Example 9 was about 10 It shows high value of double and shows excellent electrical conductivity and thermoelectric performance.

In addition, the carbon nanotube fibers prepared in Examples 1 to 9 had an electric conductivity of about 5 times and a thermoelectric performance of about two times that of Comparative Example 1. [ Compared with the results of the graphene and carbon nanotubes prepared in Comparative Example 10 and Comparative Example 11 and the results of Comparative Examples 1 to 4 in which the metal doping treatment or the acid treatment was applied to the carbon nanotube fibers, It is confirmed that the acid treatment can exhibit a very excellent thermoelectric performance improvement of 100 times or more. Therefore, it was confirmed that not only the superiority of the porous carbon nanotube fibers themselves, but also the metal doping treatment or the acid treatment according to the present invention greatly influenced the improvement of the electrical conductivity and the thermoelectric performance of the carbon nanotube fibers.

That is, as in Example 2, it was confirmed that the electroconductivity of 5134 S / cm and the thermoelectric performance of 3548 μW / mK ² when the gold ion concentration of the solution containing gold ions for gold doping treatment was 2 mM, As shown in Example 9, when the acid was mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3, the electrical conductivity of 5120 S / cm and the thermal conductivity of 3322 μW / mK ² were confirmed.

Raw material Step 1 or step a Electricity
conductivity
(S / cm) Sebek
Coefficient
(μV / K) Thermoelectric performance
(μW / mK ² ) Thermal conductivity
(W / mK) Thermoelectric performance
Index (ZT) Comparative Example 9 CNT fiber - 1090 117.72 1510 5.68 0.079 Comparative Example 10 graphene - 701 10.03 7.05 0.92 0.0023 Comparative Example 11 CNT - 831 15.12 19.00 0.82 0.0069 Example 1 CNT fiber Gold doping
(1 mM) 3500 95.41 3186 7.07 0.135 Example 2 CNT fiber Gold doping
(2 mM) 5134 83.14 3548 7.09 0.150 Example 3 CNT fiber Gold doping
(5 mM) 5270 78.8 3272 7.30 0.134 Example 4 CNT fiber Gold doping
(10 mM) 5556 69.4 2675 7.12 0.112 Example 5 CNT fiber Doping
(2 mM) 5324 86.89 3147 7.13 0.132 Example 6 CNT fiber Palladium doping
(2 mM) 5346 87.56 3215 7.20 0.133 Example 7 CNT fiber Sulfuric acid (95%) 4904 79.32 3085 7.5 0.123 Example 8 CNT fiber Nitric acid (60%) 5030 80.46 3256 7.61 0.128 Example 9 CNT fiber Mixed acid * 5120 80.56 3322 7.65 0.130 Comparative Example 1 graphene Gold doping
(2 mM) 912 9.11 7.57 0.91 0.0024 Comparative Example 2 CNT Gold doping
(2 mM) 1072 14.42 22.29 0.86 0.0077 Comparative Example 3 graphene Mixed acid * 908 9.15 7.44 0.95 0.0024 Comparative Example 4 CNT Mixed acid * 1021 14.56 21.64 0.85 0.0076

(Mixed acid *: acid mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3)

< Experimental Example  2> Comparative analysis of thermoelectric materials

In order to confirm the thermoelectric characteristics of the thermoelectric material according to the present invention, the electrical conductivities of the thermoelectric materials prepared through Examples 11 to 17 and Comparative Examples 5 to 8 were measured by a 4-point probe method, Thermal conductivity was measured using a scanning laser heating analyzer (Ulvac-Riko, Inc., Laser PIT), and a thermoelectric device was fabricated from the carbon material (as shown in FIG. 1, After the carbonization, a silver paste was applied on top of the carbon material, and a thermoelectric element was formed by laminating electrodes. The whiteness coefficient was measured, and the thermoelectric performance was evaluated from the measured electric conductivity and the whiteness coefficient.

As shown in Table 3, the thermoelectric materials prepared in Examples 10 to 12 had higher energy than the carbon nanotube fibers of Example 2, which was performed only in Step 1 of the thermoelectric material manufacturing method of the present invention, As a result of the filtering and phonon scattering effects, the Seebeck coefficient was increased, the electrical conductivity was slightly reduced, and the thermal conductivity was reduced by 4 W / mK max. It was confirmed that the figure of merit (ZT) of Example 11, which is gold doped with a solution containing gold ions at a concentration of 2 mM and which is a polyaniline-coated carbon nanotube fiber-based thermoelectric material, has a high value of 0.209 .

The thermoelectric material prepared in Examples 15 to 17 has a higher shear coefficient due to the energy filtering effect of the conductive polymer layer than the carbon nanotube fiber of Example 9 which was carried out only in the step a of the thermoelectric material manufacturing method according to the present invention But the electrical conductivity decreased. This is because the charge transfer between the carbon nanotube fiber and the fiber was limited by the coating process of the conductive polymer. On the other hand, the thermal conductivity of the carbon nanotubes is controlled by the effect of phonon scattering due to the polymer coating on the surface of the carbon nanotube fibers, and then treated with an acid mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3 and the polyaniline polymer- It was confirmed that the thermoelectric material of Example 16 had a thermoelectric performance index (ZT) of about 0.05 instead of about 3 W / mK lower than that of the carbon nanotube fiber prepared in Example 9.

When the thermoelectric properties of the thermoelectric materials prepared in Examples 11 to 17 and Comparative Examples 5 to 8 were compared, it was found that when the carbon nanotube fibers were used, the graphene and carbon nanotubes It shows a very good thermoelectric property improvement and shows a high thermoelectric performance index.

In addition, the thermoelectric material according to the present invention has an effect of significantly improving the thermoelectric property of the carbon nanotube fiber than the carbon nanotube fiber of the original material through the acid treatment, the doping treatment and the conductive polymer coating with appropriate concentration.

Raw material Step 1 or step a Step 2 or step b Step 3c Example 10 CNT fiber Gold doping (2 mM) P3HT ODCB Example 11 CNT fiber Gold doping (2 mM) PANI m-cresol Example 12 CNT fiber Gold doping (2 mM) PEDOT methanol Example 13 CNT fiber Gold doping (2 mM) FeCl ₃ doped P3HT ODCB Example 14 CNT fiber Gold doping (2 mM) CSA doped PANi m-cresol Example 15 CNT fiber Mixed acid * P3HT ODCB Example 16 CNT fiber Mixed acid * PANI m-cresol Example 17 CNT fiber Mixed acid * PEDOT methanol Comparative Example 5 graphene Gold doping (2 mM) PANI m-cresol Comparative Example 6 graphene Mixed acid * PANI m-cresol Comparative Example 7 CNT Gold doping (2 mM) PANI m-cresol Comparative Example 8 CNT Mixed acid * PANI m-cresol

(Mixed acid *: acid mixed with sulfuric acid and nitric acid at a volume ratio of 7: 3)

Electrical conductivity
(S / cm) Seebeck coefficient
(μV / K) Thermoelectric performance
(μW / mK ² ) Thermal conductivity
(W / mK) Thermoelectric performance index (ZT) Example 10 1100 139.74 2147 3.95 0.163 Example 11 1106 150.86 2454 3.61 0.209 Example 12 1300 135.23 2377 4.01 0.177 Example 13 1372 75 771 5.12 0.045 Example 14 1760 118 2450 6.42 0.114 Example 15 1005 138.74 1934 3.82 0.151 Example 16 1009 148.86 2235 3.9 0.171 Example 17 1011 138.23 1931 4.01 0.144 Comparative Example 5 829 15.92 21.01 0.8 0.0078 Comparative Example 6 750 12.02 10.84 0.86 0.0038 Comparative Example 7 834 16.12 21.67 0.79 0.0082 Comparative Example 8 763 12.32 11.58 0.84 0.0041

The present invention is not limited to the above-described embodiments but is intended to be limited by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

Claims (10)

Metal-doped carbon nanotube fibers; And
And a conductive polymer coated on the carbon nanotube fibers.
Acid treated carbon nanotube fibers; And
And a conductive polymer coated on the carbon nanotube fibers.
The method according to claim 1,
Wherein the metal doping treatment is performed using at least one metal selected from the group consisting of gold, silver, palladium, platinum, nickel, and chromium.
The method according to claim 1,
Wherein the metal doping treatment is performed by dipping the carbon nanotube fibers in a solution containing metal ions, and the metal ion concentration of the solution containing the metal ions is 0.5 mM to 20 mM. Tube fiber based thermoelectric material.
3. The method of claim 2,
Wherein the acid treatment is carried out using at least one acid selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, acetic acid, and combinations thereof.
3. The method according to claim 1 or 2,
The conductive polymer may be selected from the group consisting of polypyrrole, polyaniline, polycarbazole, polythiophene, poly (3-hexylthiophene) (P3HT), poly (3,4-ethylenedioxythiophene Wherein the thermoelectric material is at least one selected from the group consisting of poly (styrene sulfonate) (PEDOT) and poly (3,4-ethylenedioxythiophene) (PEDOT): poly (styrene sulfonate) (PSS).
Metal doping the carbon nanotube fibers (step 1); And
And applying a conductive polymer to the carbon nanotubes on which step 1 is performed (step 2).
Acid treating the carbon nanotube fibers (step a); And
(B) applying a conductive polymer to the carbon nanotubes to which the step (1) has been performed (step b).
10. The method according to claim 8 or 9,
The method of manufacturing a thermoelectric material according to claim 1, further comprising washing and drying the thermoelectric material prepared in the step 2 (step 3c).
A thermoelectric device comprising the thermoelectric material of any one of claims 1 to 3.

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