N-type nanocarbon yarn manufacturing method

Abstract

To provide an N-type nanocarbon yarn manufacturing method capable of manufacturing an N-type nanocarbon yarn at low cost.SOLUTION: An N-type nanocarbon yarn manufacturing method comprises: a first step to dope nanocarbon by adding N-type dopant to nanocarbon dispersion liquid; and a second step to generate a nanocarbon yarn by extruding the nanocarbon dispersion liquid after being doped.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing N-type carbon nanotube yarns.

Background Art

[0002] In recent years, thermoelectric power generation elements are known as solid elements that convert thermal energy into electrical energy. Thermoelectric power generation elements have been applied, for example, to power sources for space use and thermoelectric conversion modules (such as wristwatches and wearable devices) that operate at body temperature. And, for thermoelectric conversion elements, carbon nanotube yarns such as carbon nanotube yarns may be used, and various studies have been made on carbon nanotube yarns.

[0003] For example, Patent Document 1 discloses "a step (a) of preparing a dispersion liquid in which carbon nanotubes are dispersed in a first solvent which is either only water or a mixed solvent containing an organic solvent and water by a surfactant, and a step (b) of injecting the dispersion liquid in which the carbon nanotubes are dispersed into a coagulation liquid which is a second solvent different from the first solvent to coagulation-spin the carbon nanotubes, and a method for manufacturing a coagulation-spun structure characterized by including the above steps."

[0004] Patent Document 2 discloses "a carbon nanotube composite yarn having a carbon nanotube composite yarn obtained by impregnating or coating a part or all of a filamentous substrate with a dispersion liquid containing carbon nanotubes having semiconductor properties and drying it, and a conductive yarn having conductivity, and characterized in that the semiconductor carbon nanotube composite yarn and the conductive yarn are woven so as to be electrically connected to each other." Patent Document 3 discloses "a method for manufacturing carbon nanotube spun yarns by spinning a carbon nanotube dispersion liquid containing a carbon nanotube dispersion, wherein the spherical equivalent size of the carbon nanotube dispersion measured by a disk-type frequency-specific centrifugal sedimentation device is 25 nm to 1.3 μm." Patent Document 4 discloses "a thermal transport device having a series connection body of single-layer and multi-layer heterogeneous composite yarns, which is formed by impregnating or coating a natural-derived yarn, a synthetic fiber yarn, or a mixed yarn thereof with a dispersion containing single-walled carbon nanotubes to obtain a single-walled carbon nanotube composite yarn as a first composite yarn, impregnating or coating the mixed yarn with a dispersion containing multi-walled carbon nanotubes to obtain a multi-walled carbon nanotube composite yarn as a second composite yarn, and connecting the first and second composite yarns in series in the order of the second composite yarn - the first composite yarn - the second composite yarn or the first composite yarn - the second composite yarn - the first composite yarn, and passing a direct current through the series connection body to cause a temperature difference between one connection point and the other connection point by the Peltier effect."

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventionally, including Patent Documents 1 to 4, the mainstream method for manufacturing N-type nanocarbon yarn is to dope a completed nanocarbon yarn with an N-type dopant. However, doping an N-type dopant into a completed nanocarbon yarn requires a large number of steps, and these steps include a time-consuming vacuum heating step for mass production.

[0007] Therefore, an object of the present invention is to provide a method for manufacturing an N-type nanocarbon fiber that can manufacture an N-type nanocarbon fiber at low cost. **Means for Solving the Problems**

[0008] The means for solving the problems include the following aspects. <1> A first step of adding an N-type dopant to a nanocarbon dispersion to dope the nanocarbon; A second step of extruding the nanocarbon dispersion after the doping to produce a nanocarbon fiber; A method for manufacturing an N-type nanocarbon fiber having the above steps. <2> The method for manufacturing an N-type nanocarbon fiber according to <1>, wherein the nanocarbon dispersion is an aqueous dispersion, and the N-type dopant is a nonionic compound. <3> The method for manufacturing an N-type nanocarbon fiber according to <2>, wherein the nonionic compound is polyalkyleneimine. **Advantages of the Invention**

[0009] According to the present disclosure, there is provided a method for manufacturing an N-type nanocarbon fiber that can manufacture an N-type nanocarbon fiber at low cost. **Embodiments for Carrying Out the Invention**

[0010] Hereinafter, embodiments which are examples of the present disclosure will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the invention. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerically described range. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. Each component in the composition may contain a plurality of the corresponding substances. When referring to the amount of each component in a composition, in the case where there are multiple substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the multiple substances present in the composition.

[0011] <Method for manufacturing N-type nanocarbon yarn> The method for manufacturing an N-type nanocarbon yarn according to the present disclosure includes a first step of adding an N-type dopant to a nanocarbon dispersion liquid to dope the nanocarbon, and a second step of extruding the doped nanocarbon dispersion liquid to produce a nanocarbon yarn.

[0012] In the method for manufacturing an N-type nanocarbon yarn according to the present disclosure, before producing the nanocarbon yarn, an N-type dopant is added to the nanocarbon dispersion liquid to dope the nanocarbon. Then, a nanocarbon yarn is manufactured from the doped nanocarbon. Therefore, in the method for manufacturing an N-type nanocarbon yarn according to the present disclosure, steps such as a heating step under vacuum can be simplified, and an N-type nanocarbon yarn can be manufactured at low cost.

[0013] Further, in the method for manufacturing an N-type nanocarbon yarn according to the present disclosure, since a nanocarbon yarn is manufactured from the doped nanocarbon, the N-type dopant penetrates into the inside of the nanocarbon yarn. Therefore, there is little change in the conductivity type over time, and a stable N-type nanocarbon yarn can be obtained. Specifically, for example, there is little change in the electrical resistivity and the Seebeck coefficient, and a stable N-type nanocarbon yarn can be obtained.

[0014] Here, the dimensionless performance index ZT, which is one of the indexes for evaluating the thermoelectric conversion performance of the nanocarbon yarn, will be described. ZT is represented by the following formula (1). Dimensionless performance index ZT = S2 × σ × T / κ (1) In formula (1), S (V / K) represents the Seebeck coefficient, σ (S / m) represents the electrical conductivity, κ (W / mK) represents the thermal conductivity, and T (K) represents the absolute temperature.

[0015] Hereinafter, the details of the method for manufacturing the nanocarbon yarn according to the present embodiment will be described.

[0016] (First step) In the first step, an N-type dopant is added to the nanocarbon dispersion liquid to dope the nanocarbon.

[0017] -Dispersion medium- From the perspective of reducing environmental load, the dispersion medium of the nanocarbon dispersion liquid preferably contains water as a main component. That is, the nanocarbon dispersion liquid is preferably an aqueous dispersion liquid. The aqueous dispersion liquid may contain a water-soluble organic solvent such as alcohol (methanol, ethanol, propanol, etc.). Note that the fact that water is the main component means that, for example, the proportion of water is 50% by mass (preferably 70% by mass or 90% by mass) or more based on the total dispersion medium. However, the main component of the dispersion medium of the nanocarbon may be an organic solvent. Examples of the organic solvent include alcohol (ethanol, propanol, etc.), acetone, methyl ethyl ketone, butyl acetate, etc. The fact that the organic solvent is the main component means that, for example, the proportion of the organic solvent is 50% by mass (preferably 70% by mass or 90% by mass) or more based on the total dispersion medium.

[0018] -Nanocarbon- Examples of the nanocarbon include carbon nanotubes (CNT). The carbon nanotube may be a single-walled carbon nanotube (SWCNT) in which a single carbon film (graphene sheet) is wound cylindrically. The carbon nanotube may be a multi-walled carbon nanotube (MWCNT) such as a double-walled carbon nanotube, a triple-walled carbon nanotube, or a quadruple-walled carbon nanotube in which two graphene sheets are wound concentrically. Considering the thermoelectric characteristics, the carbon nanotube preferably has 10 layers or less. A single-walled carbon nanotube is preferable because high thermoelectric characteristics can be easily obtained. A multi-walled carbon nanotube is preferable because it is inexpensive and has excellent mass productivity. A single-walled carbon nanotube and a multi-walled carbon nanotube can also be mixed and used. Further, the carbon nanotube may be a metallic carbon nanotube, a semiconducting carbon nanotube may be used, or they may be mixed and used. The method for manufacturing carbon nanotubes is not particularly limited. Carbon nanotubes can be manufactured by an arc discharge method, a chemical vapor deposition method (CVD, Chemical Vapor Deposition), a laser ablation method, etc. Alternatively, commercially available carbon nanotubes may be used.

[0019] The nanocarbon may be graphene. By introducing carriers between two layers of overlapping graphene, graphene can be used as a semiconductor material.

[0020] Other examples of nanocarbons include carbon nanorods, carbon nanowires, graphene, and fullerenes.

[0021] -N-type dopant- Examples of N-type dopants include non-ionic compounds or ionic compounds. In particular, when the nanocarbon dispersion is an aqueous dispersion, non-ionic compounds are preferred as N-type dopants. On the other hand, when the nanocarbon dispersion is an organic solvent-based dispersion, ionic compounds are preferred as N-type dopants.

[0022] Preferred non-ionic compounds include polyalkyleneimines. Preferred polyalkyleneimines are those having structural units with alkylene groups having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms), and polyethyleneimine is more preferred.

[0023] Examples of ionic compounds include alkali metal salts (such as salts of lithium, sodium, potassium, or cesium), and alkylammonium salts (such as salts of tetraethylammonium ions or tetrabutylammonium ions). Among these, halogenated alkylammonium salts are preferred as ionic compounds, and the following compounds are exemplified.

[0024]

Chemical

[0025] The addition amount of the N-type dopant is preferably 2 to 20% by mass, more preferably 5 to 15% by mass, based on the nanocarbon.

[0026] -Other components- The nanocarbon dispersion (nanocarbon dispersion before adding the N-type dopant) may contain well-known additives such as surfactants.

[0027] (Second step) In the second step, the doped nanocarbon dispersion is extruded to produce a nanocarbon yarn. Specifically, for example, the doped nanocarbon dispersion is extruded into a coagulating liquid to aggregate the nanocarbon, followed by spinning to produce a nanocarbon yarn.

[0028] The coagulating liquid is selected according to the dispersion medium of the nanocarbon dispersion. When the main component of the dispersion medium of the nanocarbon dispersion is water, examples of the coagulating liquid include N-methylpyrrolidone, N,N-dimethylacetamide, propylene carbonate, formamide, N-methylformamide, etc. When the main component of the dispersion medium of the nanocarbon dispersion is an organic solvent, examples of the coagulating liquid include water and alcohols (such as methanol, ethanol, propanol, etc.).

[0029] (Applications) The N-type nanocarbon yarn obtained by the method for producing an N-type nanocarbon yarn of the present disclosure can be applied to various applications. For example, the N-type nanocarbon yarn can be suitably applied as an N-type nanocarbon yarn connecting between thermoelectric conversion elements of a thermoelectric conversion module. In addition, the N-type nanocarbon yarn can also be suitably applied to semiconductor applications.

Examples

[0030] Examples will be described below, but the present disclosure is not limited to these examples in any way. In the following description, unless otherwise specified, all "parts" and "%" are based on mass.

[0031] <Example 1> To a 0.2 mass% carbon nanotube (CNT) aqueous dispersion, 5 mass% of polyethyleneimine was added to the CNTs and mixed by ultrasonic treatment. Thereafter, the CNT aqueous dispersion was extruded into an aggregate of propanol to aggregate and spin the CNTs. In this way, an N-type carbon nanotube yarn was produced.

[0032] <Comparative Example 1> A 0.2 mass% carbon nanotube (CNT) aqueous dispersion was extruded into an aggregate of propanol to aggregate and spin the CNTs. Thereafter, the CNT yarn subjected to vacuum heating was immersed in the following chloroalkylammonium aqueous solution with a concentration of 1000 mmol / L and then dried. In this way, an N-type carbon nanotube yarn was produced.

Chemical formula

[0033] <Evaluation> The following evaluations were performed on the N-type carbon nanotube yarns obtained in each example.

[0034] (Electrical resistivity) The electrical resistivity of the N-type carbon nanotube yarn was measured. The measurement method is as follows. Four electrodes were brought into contact with the N-type carbon nanotube yarn, and the resistance value was measured using the four-terminal measurement method. Thereafter, the distance between the electrodes and the sample cross-sectional area were measured, and the electrical resistivity was calculated using them.

[0035] (Seebeck coefficient / Conduction type) The Seebeck coefficient of the N-type carbon nanotube yarn was measured. The measurement method is as follows. One end of the N-type carbon nanotube yarn was heated to generate a temperature difference across the sample, and the generated thermoelectromotive force was measured and calculated using a thermoelectric property measurement device.

Table 1

[0036] From the above results, it can be seen that in this example, an N-type nanocarbon yarn can be obtained at low cost.

Claims

1. A first step of adding an N-type dopant to a nanocarbon dispersion to dope the nanocarbon; A second step of extruding the nanocarbon dispersion after doping to produce a nanocarbon thread; A method for manufacturing an N-type nanocarbon thread having the above steps.

2. The method for manufacturing an N-type nanocarbon thread according to Claim 1, wherein the nanocarbon dispersion is an aqueous dispersion, and the N-type dopant is a nonionic compound.

3. The method for manufacturing an N-type nanocarbon thread according to Claim 2, wherein the nonionic compound is a polyalkyleneimine.

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