Method for manufacturing nanocarbon threads or strips

Abstract

To provide a simple method for producing a nanocarbon filament or strip having an N-type conductive region and a P-type conductive region. [Solution] A method for manufacturing a nanocarbon filament or strip having a P-type conductive region and an N-type conductive region, comprising a heating step of heating a part of the N-type conductive region of a nanocarbon filament or strip having an N-type conductive region.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a filamentous or带状 nano-carbon material.

Background Art

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

[0003] For example, Patent Document 1 discloses "a functional device in which a spun yarn made of a conductive fibrous material is sewn into a sheet-like or带状 insulating base material, and the spun yarn is sewn so as to alternately penetrate the front and back surfaces of the insulating base material, and a cell series structure of a π-type thermoelectric conversion device is formed, and the spun yarn has P-type characteristics and N-type characteristics alternately repeated in the longitudinal direction, and when folded back in the thickness direction of the base material, P-type and N-type are switched." Patent Document 1 also discloses that "the spun yarn is made of a composite material of one or more conductive nanofibers selected from the group consisting of carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, graphene nanoribbons, fullerene nanowhiskers, and inorganic semiconductor whiskers, and an insulating or conductive flexible polymer."

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Conventionally, including Patent Document 1, the main methods for producing nanocarbon filaments or strips having N-type conductive regions and P-type conductive regions are to partially dope the nanocarbon filaments or strips with an N-type dopant, or to partially dope the nanocarbon filaments or strips treated with a protective agent with an N-type dopant by immersing them in a solution containing an N-type dopant. However, the method of partially doping nanocarbon filaments or strips with N-type dopants is difficult because it involves applying a liquid N-type dopant to only certain parts of the material. Furthermore, the method of doping N-type dopants onto filamentous or strip-like nanocarbon materials that have been partially treated with a protective agent is time-consuming because it requires partial pretreatment with the protective agent.

[0006] Therefore, the object of this disclosure is to provide a simple method for producing a nanocarbon filament or strip having an N-type conductive region and a P-type conductive region. [Means for solving the problem]

[0007] The means for solving the problem include the following: [Effects of the Invention]

[0008] According to this disclosure, a method for easily producing a nanocarbon filament or strip having an N-type conductive region and a P-type conductive region can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a process diagram showing an example of a method for producing the nanocarbon filamentous or strip-like material according to the present disclosure. [Modes for carrying out the invention]

[0010] The following describes an example of an embodiment of this disclosure. These descriptions and examples are illustrative and do not limit the scope of the invention. In the numerical ranges described stepwise within this specification, one numerical range is described. The upper or lower limits may be replaced with the upper or lower limits of other stepped numerical ranges. Furthermore, within the numerical ranges described herein, the upper or lower limits of those ranges may be replaced with the values ​​shown in the examples. Each component in the composition may contain multiple types of the relevant substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple substances present in the composition.

[0011] <Method for manufacturing nanocarbon threads or strips> The method for producing a nanocarbon filament or strip according to the present disclosure includes a heating step of heating a portion of the N-type conductive region of the nanocarbon filament or strip having an N-type conductive region.

[0012] In the method for manufacturing nanocarbon filaments or strips described herein, it is believed that heating a portion of the N-type conductive region of the nanocarbon filament or strip causes the N-type dopant to detach or break down in the heated area. As a result, the heated area of ​​the N-type conductive region of the nanocarbon filament or strip becomes a P-type conductive region. On the other hand, the unheated area remains an N-type conductive region with the N-type dopant dopant present. Therefore, the method for manufacturing nanocarbon filaments or strips according to this disclosure allows for the simple production of nanocarbon filaments or strips having N-type conductive regions and P-type conductive regions.

[0013] In addition, since the heating part can be made into a P-type conductive region only by heating a part of the N-type conductive region, it is also possible to simply and finely distinguish between the N-type conductive region and the P-type conductive region. Therefore, in the nanofiber or ribbon of nanocarbon, a fine and clear PN junction structure can be formed. As a result, in the method for producing a nanofiber or ribbon of nanocarbon of the present disclosure, a nanofiber or ribbon of nanocarbon having high thermoelectric power generation characteristics can be obtained.

[0014] Hereinafter, the details of the steps will be described.

[0015] (Heating step) In the heating step, a part of the N-type conductive region of the nanofiber or ribbon of nanocarbon having an N-type conductive region is heated. Specifically, a nanofiber or ribbon of nanocarbon having an N-type conductive region is prepared (see Fig. 1(A)). Then, a part of the N-type conductive region of the nanofiber or ribbon of nanocarbon having an N-type conductive region is heated (see Fig. 1(B)). Here, in Figs. 1(A) and 1(B), 10A represents a nanofiber or ribbon of nanocarbon having an N-type conductive region, and 12 represents a heating part.

[0016] -Preparation of nanofiber or ribbon of nanocarbon having N-type conductive region- The nanofiber or ribbon of nanocarbon having an N-type conductive region can be obtained by doping an N-type dopant into the nanofiber or ribbon of nanocarbon. The nanofiber or ribbon of nanocarbon having an N-type conductive region may be obtained in advance by obtaining a nanofiber or ribbon of nanocarbon doped with an N-type dopant. Note that the nanofiber or ribbon of nanocarbon having an N-type conductive region may be a nanofiber or ribbon of nanocarbon in which the whole is an N-type conductive region, or a nanofiber or ribbon of nanocarbon in which a part is an N-type conductive region.

[0017] As the nanocarbon constituting the filamentous or strip-like nanocarbon, carbon nanotubes (CNTs) are preferred. In other words, the filamentous or strip-like nanocarbon is preferably a filamentous or strip-like form of carbon nanotubes. Carbon nanotubes may be single-walled carbon nanotubes (SWCNTs) in which a single carbon film (graphene sheet) is wound into a cylindrical shape. Carbon nanotubes may also be multi-walled carbon nanotubes (MWCNTs), such as double-walled, triple-walled, or quadruple-walled carbon nanotubes, in which two graphene sheets are wound concentrically. Considering thermoelectric properties, carbon nanotubes with 10 layers or less are preferable. Single-walled carbon nanotubes are preferable because they easily provide high thermoelectric properties. Multi-walled carbon nanotubes are preferable because they are inexpensive and easy to mass-produce. Single-walled and multi-walled carbon nanotubes can also be used in combination. Furthermore, carbon nanotubes may be metallic carbon nanotubes, semiconducting carbon nanotubes, or a mixture of both. The method for producing carbon nanotubes is not particularly limited. Carbon nanotubes can be produced by methods such as arc discharge, chemical vapor deposition (CVD), and laser ablation. Commercially available carbon nanotubes may also be used.

[0018] Nanocarbon may also be graphene. By inserting carriers between two layers of graphene, graphene can be used as a semiconductor material.

[0019] Other examples of nanocarbons include carbon nanorods, carbon nanowires, graphene, and fullerenes.

[0020] One method for doping nanocarbon filaments or strips with an N-type dopant is to immerse the heated nanocarbon filaments or strips in an N-type dopant solution. This method allows for simple and low-cost doping with the N-type dopant. After doping, washing is performed. However, doping with an N-type dopant may be performed by methods such as coating or brushing.

[0021] Examples of N-type dopants include nonionic compounds or ionic compounds. In particular, when the solvent of the N-type dopant solution is water, a nonionic compound is preferred as the N-type dopant. On the other hand, when the solvent of the N-type dopant solution is an organic solvent, an ionic compound is preferred as the N-type dopant.

[0022] As the nonionic compound, polyalkyleneimines are preferred. As the polyalkylene imine, polyalkylene imines having constituent units with alkylene groups having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms) are preferred, and polyethyleneimine is more preferred.

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

[0024] [ka]

[0025] From the viewpoint of reducing environmental impact, the solvent of the N-type dopant solution preferably contains water as its main component. The solvent containing water as its main component may also contain water-soluble organic solvents such as alcohols (methanol, ethanol, propanol, etc.). Note that "water as the main component" means, for example, that the proportion of water is 50% by mass (preferably 70% by mass, or 90% by mass) or more of the total solvent. However, the solvent of the N-type dopant solution may have an organic solvent as its main component. Examples of organic solvents include alcohols (ethanol, propanol, etc.), acetone, methyl ethyl ketone, and butyl acetate. Having an organic solvent as the main component means, for example, that the proportion of the organic solvent is 50% by mass (preferably 70% by mass, or 90% by mass) or more of the total solvent.

[0026] Here, the nanocarbon filament or strip having an N-type conductive region may be coated with an insulating resin coating layer. The insulating resin coating layer is formed after doping nanocarbon filaments or strips with an N-type dopant. Examples of well-known insulating resins for the insulating resin coating layer include polyethylene, polyolefins (polyethylene, polypropylene, etc.), polystyrene, poly(meth)acrylic acid esters, styrene-(meth)acrylic acid ester copolymers, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, straight silicone resin or its modified products, fluororesin, polycarbonate, phenolic resin, epoxy resin, and polyurethane resin.

[0027] -Method of the heating process- In the heating process, for example, a portion of the N-type conductive region of a nanocarbon filament or strip is heated. Specifically, a method for heating a portion of the N-type conductive region of a nanocarbon filament or strip includes, for example, a method of heating a portion of the N-type conductive region of a nanocarbon filament or strip such that heated and unheated portions are alternately arranged in the longitudinal direction of the N-type conductive region of the nanocarbon filament or strip. By performing heating in such a way that alternating heated areas, which become P-type conductive regions where N-type dopants are detached or destroyed, and unheated areas, which remain N-type conductive regions with N-type dopants, a thread-like or strip-like nanocarbon material having a repeated PN junction structure can be easily obtained. The N-type conductive region that is heated can be any region that you want to be a P-type conductive region, depending on the intended use of the resulting nanocarbon filament or strip.

[0028] Heating of a portion of the N-type conductive region of a nanocarbon filament or strip can be performed using, for example, a laser, burner, or hot press. In particular, by using a laser capable of localized heating, filamentous or strip-like nanocarbon materials having a fine PN junction structure can be easily obtained. Furthermore, when using a laser, even if the nanocarbon filament or strip is covered with an insulating resin coating layer, if the insulating resin coating layer is transparent to the wavelength of the irradiated laser light, the heated area can be converted into a P-type conductive region without destroying the insulating resin coating layer.

[0029] The heating temperature for the nanocarbon filamentous or strip-like material should be such that the N-type dopant detaches or breaks down (e.g., 200-300°C).

[0030] Through the above process, a filamentous or strip-like nanocarbon material having an N-type conductive region and a P-type semiconducting region is obtained (see Figure 1(C)). Here, in Figure 1(C), 10 represents a filamentous or strip-like nanocarbon material having an N-type conductive region and a P-type semiconducting region, P represents the P-type conductive region, and N represents the N-type conductive region. Figure 1 shows an example of a method for manufacturing a nanocarbon filament or strip having alternating N-type conductive regions and P-type conductive regions.

[0031] (Application) The nanocarbon filaments or strips having N-type conductive regions and P-type conductive regions obtained by the manufacturing method of this disclosure can be applied to various uses. For example, a nanocarbon filament or strip having an N-type conductive region and a P-type conductive region can be suitably applied as a nanocarbon filament or strip connecting thermoelectric elements in a thermoelectric conversion module. Furthermore, nanocarbon filaments or strips having N-type and P-type conductive regions can also be suitably applied to semiconductor applications. [Examples]

[0032] Examples are described below, but this disclosure is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" all refer to mass.

[0033] <Example 1> Carbon nanotube filaments and an N-type dopant solution (solute: triphenylphosphine, solvent: acetone, concentration: approximately 1 mol / L) were prepared. Carbon nanotube filaments were immersed in an N-type dopant solution and left for more than 24 hours. The carbon nanotube filaments were removed from the N-type dopant solution and washed with acetone. This resulted in N-type carbon nanotube filaments in which the entire structure was an N-type conductive region. A fiber laser was irradiated onto the portion of the N-type carbon nanotube filament where the N-type dopant was to be detached or destroyed (i.e., the portion to be converted into a P-type conductive region). Subsequently, the Seebeck coefficient of the laser-irradiated (heated) section of the obtained carbon nanotube filament was measured and found to be +1.5 (μV / K), indicating P-type semiconductor characteristics. The Seebeck coefficient of the unirradiated (unheated) portion of the obtained carbon nanotube filament was measured to be -70 (μV / K), indicating N-type semiconductor characteristics. This confirmed that by irradiating the material with a laser at regular intervals and heating it, a fine PN junction structure (approximately 1 mm apart) can be formed within a single carbon nanotube filament.

[0034] The Seebeck coefficient was measured as follows: One end of a carbon nanotube filament was heated to create a temperature difference between the two ends of the sample. The resulting thermoelectric voltage was then measured using a thermoelectric property measuring device, and the Seebeck coefficient was calculated. [Explanation of symbols]

[0035] 10. Thread-like or strip-like nanocarbon material having N-type conductive regions and P-type conductive regions 10A N-type conductive region nanocarbon filament or strip 10B Heated nanocarbon filamentous or strip-like material 12 Heating section

Claims

1. A method for manufacturing a nanocarbon filament or strip having a P-type conductive region and an N-type conductive region, comprising a heating step of heating a part of the N-type conductive region of a nanocarbon filament or strip having an N-type conductive region.

2. The method for producing a nanocarbon filament or strip according to claim 1, wherein in the heating step, a portion of the nanocarbon filament or strip is heated such that heated and unheated portions are alternately arranged in the longitudinal direction of the N-type conductive region of the nanocarbon filament or strip.

3. The method for producing a nanocarbon filament or strip according to claim 1 or claim 2, wherein the nanocarbon filament or strip is a carbon nanotube filament or strip.

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