Pn-controlled carbon nano-tube-cellulose composite material and method for manufacturing the same

Abstract

To provide a CNT-cellulose composite material in which a P / N type is controlled, and provide a method for manufacturing the same.SOLUTION: A CNT-cellulose composite material is composed of an aggregation of a nano-carbon material and a cellulose material, and contains an n-type dopant component or a p-type dopant component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a PN-controlled carbon nanotube-cellulose composite material and a method for manufacturing the same.

Background Art

[0002] Due to advantages such as low cost, light weight, flexibility, large area, and low resource constraints, electronic devices and energy devices using molecular compounds are expected. Among them, nanocarbon materials such as carbon nanotubes (CNT) and graphene have high carrier mobility and mechanical strength advantages, so there is high expectation for practical application.

[0003] In order to operate devices such as transistors, solar cells, thermoelectric conversion elements, temperature sensors, and infrared sensors with high efficiency, both p-type and n-type materials are required. Generally, a material in which the majority carriers are holes is used as a p-type material, and a material in which the carriers are electrons is used as an n-type material. Nanocarbon materials are usually known to exhibit p-type in the atmosphere. In order to construct high-performance devices, it is necessary to convert the polarity to an n-type that pairs with the p-type. That is, an operation to change the majority carriers from holes to electrons is essential. Thus, the technology for controlling the carriers of a material is called doping, and the substance used for this purpose is called a doping agent or dopant. In recent years, research has been conducted on doping agents for converting the polarity of nanocarbon materials from p-type to n-type, that is, n-type doping agents.

[0004] Patent Document 1 discloses an n-type nanocarbon material that can maintain n-type characteristics for a long time even under high-temperature conditions in the atmosphere and enables stable operation of molecular devices. Specifically, it discloses an n-type composite material composed of a nanocarbon material or an aggregate of nanocarbon materials using at least one compound selected from amidine compounds and guanidine compounds.

[0005] In addition to the above-mentioned nanocarbon materials, in recent years, composite fibers that make use of the respective advantages of fiber materials different from nanocarbon materials have been developed. Examples of such composite fibers include cellulose composite fibers containing CNTs and polyvinyl alcohol (PVA) composite fibers containing CNTs. For example, Patent Document 2 discloses a method for producing carbon nanotube-containing fibers using cellulose fibers or PVA fibers as fiber raw materials.

[0006] Devices such as heat flux sensors are composed of a combination of p-type and n-type semiconductors as described above. Although methods for controlling CNT fibers and CNT yarns to be n-type, such as those in Patent Document 1, are known, there have been no reports on techniques for PN control after spinning CNT-cellulose composite fibers. For example, the technique for n-type conversion of the CNT yarn in Patent Document 1 is only effective for 100% CNT yarns and cannot be applied to composite yarns spun from CNTs and cellulose, and n-type CNT-cellulose composite yarns could not be obtained. On the other hand, a method of spinning with cellulose fibers using n-type CNT fibers obtained by the method of Patent Document 1 or the like is also conceivable. However, since the strength of n-type CNT fibers containing an n-type dopant compound is low, there has been a problem that spinning with cellulose fibers is difficult. Also, even if an n-type CNT-cellulose composite material could be produced by this method, the entire composite material would become n-type, resulting in an increase in resistance at the PN junction when used together with a p-type composite material, and a problem that the device performance would deteriorate. These circumstances have hindered the device development using CNT-cellulose composite materials.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In view of the above problems, an object of the present invention is to provide a CNT-cellulose composite material in which P-type and N-type are controlled, and a method for producing the same.

Means for Solving the Problems

[0009] In order to solve the above problems, the present inventors conducted various studies on the doping method of CNT-cellulose composite materials. The present inventors tried to dope a doping compound into a CNT-cellulose composite yarn by ultrasonic penetration, but the penetration method of the dopant compound by ultrasonic waves could not be applied because it destroyed the fiber shape of the CNT-cellulose composite yarn (Comparative Example 1 below). Therefore, the present inventors focused on the vacuum infiltration method and conducted studies. As a result, they succeeded in infiltrating the N-type dopant liquid into the inside of the composite material without destroying the fiber shape of the CNT-cellulose composite yarn. As a result, it became possible to perform postnatal PN control even after spinning the CNT-cellulose composite material. The method can be used not only for N-type dopant compounds but also for the infiltration of P-type dopant compounds. In this way, the present inventors have first found a CNT-cellulose composite material in which P-type or N-type is controlled and a method for producing the same. The present invention has been completed based on the above findings and includes the following aspects:

[0010] One aspect of the present invention is 〔1〕A CNT-cellulose composite material composed of an aggregate of a nanocarbon material and a cellulose material and containing an n-type dopant compound or a p-type dopant compound. Here, in one embodiment, the CNT-cellulose composite material of the present invention is 〔2〕The CNT-cellulose composite material according to the above 〔1〕, characterized by including at least two regions selected from the group consisting of a region having an N-type semiconductor polarity, a region having a P-type semiconductor polarity, or an insulating region. Also, in one embodiment, the CNT-cellulose composite material of the present invention is 〔3〕The CNT-cellulose composite material according to the above 〔1〕 or 〔2〕, Comprising at least one region of said N-type and at least one region of said P-type, and characterized by comprising at least one region in which the N-type region and the P-type region are joined to each other. Also, in one embodiment, the CNT-cellulose composite material of the present invention 〔4〕The CNT-cellulose composite material according to 〔2〕 or 〔3〕 above, Characterized by including a plurality of each of said at least two regions. Also, in one embodiment, the CNT-cellulose composite material of the present invention 〔5〕The CNT-cellulose composite material according to any one of 〔1〕 to 〔4〕 above, Characterized in that the nanocarbon material is selected from any one of carbon nanotubes, graphene, or graphite. Also, in one embodiment, the CNT-cellulose composite material of the present invention 〔6〕The CNT-cellulose composite material according to any one of 〔1〕 to 〔5〕 above, The CNT-cellulose composite material, wherein the aggregate of the nanocarbon material and the cellulose material is in the form of a fiber, a film, a thread, or a cloth. Also, in one embodiment, the CNT-cellulose composite material of the present invention 〔7〕The CNT-cellulose composite material according to any one of 〔1〕 to 〔6〕 above, Characterized in that the n-type dopant compound is at least one compound selected from a crown ether complex, an amidine compound, and a guanidine compound. Also, in one embodiment, the CNT-cellulose composite material of the present invention 〔8〕The CNT-cellulose composite material according to any one of 〔1〕 to 〔7〕 above, Characterized by having an n-type region with a Seebeck coefficient of -10 μV / K or less.

[0011] Also, in another aspect, the present invention 〔9〕Relates to a thermoelectric conversion element, a temperature sensor, an infrared sensor, a field effect transistor, a PN junction diode, a thermopile, or a solar cell, comprising the CNT-cellulose composite material described in the above 〔1〕 to 〔8〕.

[0012] Here, in another aspect of the present invention, 〔10〕A method for producing the CNT-cellulose composite material according to any one of the above 〔1〕 to 〔8〕, (i) A step of infiltrating the dopant compound into a part or the whole of the aggregate of the nanocarbon material and the cellulose material by vacuum infiltration Relates to a production method including this. Also, in one embodiment, the method for producing the CNT-cellulose composite material of the present invention 〔11〕The production method according to the above 〔10〕, after the vacuum infiltration step of (i), (ii) A step of infiltrating a different dopant compound into a region different from the region containing the dopant compound in the aggregate of the nanocarbon material and the cellulose material by vacuum infiltration Characterized by further including this. Also, in one embodiment, the method for producing the CNT-cellulose composite material of the present invention 〔12〕The production method according to the above 〔11〕, (iii) Characterized by repeating the step of (ii) at least one more time. Also, in one embodiment, the method for producing the CNT-cellulose composite material of the present invention 〔13〕The production method according to the above 〔10〕, The vacuum infiltration step of (i) is a step of simultaneously infiltrating at least two or more dopant compounds into the aggregate of the nanocarbon material and the cellulose material by vacuum infiltration, Characterized by including a step of infiltrating each of the two or more dopant compounds into different regions on the aggregate of the nanocarbon material and the cellulose material. Another aspect of the present invention is, Relates to a CNT-cellulose composite material produced by the production method according to any one of the above

[10] to

[13] .

Advantages of the Invention

[0013] According to the PN-controlled CNT-cellulose composite material of the present invention, since it contains a cellulose material, the thermal conductivity of the composite material decreases, and thus it becomes easier to create a temperature difference within the composite material, enabling excellent performance to be imparted to devices such as thermoelectric elements. This effect can be represented, for example, by the value of the figure of merit ZT [= (Seebeck coefficient)2 × (conductivity) × (absolute temperature) ÷ (thermal conductivity)]. Also, according to the PN-controlled CNT-cellulose composite material of the present invention, since it contains cellulose, the mechanical strength of the composite material itself is improved. A certain level of mechanical strength is required for the mechanical knitting process, and the PN-controlled CNT-cellulose composite material according to the present invention can contribute to its use in the mechanical knitting process for large-area production. This contributes to an increase in power generation and higher sensitivity of sensors when used in devices such as thermoelectric elements. Further, according to the PN-controlled CNT-cellulose composite material of the present invention, since seamless PN control can be achieved within a single CNT-cellulose composite material (especially a composite yarn), compared to devices that use a combination of p-type and n-type composite materials, an increase in resistance at the PN junction can be suppressed, improving the performance of the device. Additionally, according to the PN-controlled CNT-cellulose composite material of the present invention, since cellulose raw materials are relatively inexpensive compared to CNT raw materials, the manufacturing cost of CNT-cellulose composite materials and devices using them can be suppressed.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0015] In one aspect, the present invention provides a CNT-cellulose composite material composed of an aggregate of a nanocarbon material and a cellulose material and containing an n-type dopant compound or a p-type dopant compound.

[0016] In the present invention, the "nanocarbon material" is carbon nanotube (CNT), graphene, or graphite. When using CNT as the nanocarbon material, the CNT mixed with the cellulose material can be used without particular limitation, and single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used. However, the CNT is preferably a single-walled carbon nanotube. By using single-walled carbon nanotubes, the strength and elastic modulus of the CNT-containing fiber can be further improved as compared with the case of using multi-walled carbon nanotubes.

[0017] The CNT used in the present invention is not limited to the following. For example, the CNT disclosed in Japanese Patent No. 6316577 can be used. The production of CNT can be efficiently carried out, for example, in the production method of carbon nanotube bulk structures (super growth method) described in Japanese Patent No. 4621896 (European Patent Application Publication No. 1787955) and Japanese Patent No. 4811712 (US Patent Application Publication No. 2009 / 297846), by forming a catalyst layer on the substrate surface by a wet process and using a raw material gas mainly composed of acetylene (for example, a gas containing 50% by mass or more of acetylene).

[0018] In the present invention, as the "cellulose material", known cellulose fibers can be used as raw materials. The cellulose fiber raw material is not particularly limited, and the cellulose fibers may be used as they are. Alternatively, a material prepared by dissolving or dispersing cellulose fibers in a solvent in the presence of an arbitrary dispersant can be used. As the solvent, for example, organic solvents such as DMSO (dimethyl sulfoxide), N-methyl-2-pyrrolidone, N-methylmorpholine-N-oxide, or water can be used. Further, as the dispersant, known dispersants can be used. Furthermore, it is preferable to add an antioxidant such as propyl gallate, for example. By adding an antioxidant, fibers with less discoloration and excellent mechanical properties can be obtained.

[0019] The cellulose fibers are not particularly limited, and cellulose-based regenerated fibers such as rayon, polynosic rayon, cupra, Tencel (trademark), and lyocell (trademark), and cellulose-based natural fibers such as cotton, linen, ramie, banana, bamboo, kenaf, shell ginger, hemp, kapok, etc. can be used. From the viewpoint of obtaining high-strength fibers, it is preferable to use rayon made from high-quality pulp with a relatively high molecular weight (degree of polymerization of about 1000 to 1400) and high physical properties as the cellulose fibers.

[0020] In this specification, the "aggregate of nanocarbon material and cellulose material" refers to an aggregate of a nanocarbon material and a cellulose material. The method for producing the aggregate of nanocarbon material and cellulose material is known, and for example, the aggregate of nanocarbon material and cellulose material can be produced according to the methods described in Japanese Patent No. 6316577 and Japanese Patent No. 7224256. The aggregate of nanocarbon material and cellulose material can be obtained, for example, by uniformly mixing CNT and cellulose fibers while stirring, kneading, etc. to obtain a fiber raw material, and spinning the fiber raw material by a wet coagulation method or the like.

[0021] The CNT-cellulose composite material according to the present invention is composed of an aggregate of the aforementioned nanocarbon material and cellulose material, and contains an n-type dopant compound or a p-type dopant compound. The form of the CNT-cellulose composite material is not particularly limited, and for example, it can be in the form of fibers, films, threads, or cloth. In addition, the CNT-cellulose composite material may further optionally contain components other than the nanocarbon material and cellulose material (other components). There is no particular limitation on the components other than the nanocarbon material and cellulose material. For example, it may contain a dispersant such as sodium dodecyl sulfate, a dispersion stabilizer (a water-soluble polymer such as polyvinyl alcohol), alcohols and water used in the production of the CNT-cellulose composite material. Further, the CNT-cellulose composite material of the present invention may contain various polymers other than the above-described cellulose fibers, dispersant, and dispersion stabilizer.

[0022] In this specification, the "n-type dopant compound" refers to a compound used to convert the polarity of the aggregate of the nanocarbon material and cellulose material from p-type to n-type or insulating type. Also in this specification, the "p-type dopant compound" refers to a compound used to enhance the p-type polarity of the aggregate of the nanocarbon material and cellulose material.

[0023] The n-type dopant compound used in the present invention is not limited as long as it can convert the polarity of the aggregate of the nanocarbon material and the cellulose material from p-type to n-type, and known n-type dopant compounds can be used. Examples of the n-type dopant compound include amidine compounds, guanidine compounds, imidazolium salts, supramolecular complexes, polyethyleneimine, alkali metal ions (such as potassium and sodium), and crown ether complexes in which these alkali metal ions are arranged at the center of a cyclic molecule. Preferably, the n-type dopant compound is at least one compound selected from crown ether complexes containing a benzene ring, amidine compounds, and guanidine compounds. For the crown ether complex as the n-type dopant compound and its doping method, for example, Patent 6704577 can be referred to, and for the amidine compound or guanidine compound and their doping methods, for example, JP-A-2022-135933 can be referred to.

[0024] Examples of the crown ether complex include a crown ether, a crown ether having an arylene group, or a complex of an azacrown ether. Examples of the arylene group include a phenylene group, a tolylene group, a xylylene group, and a naphthylene group. Further, the crown ether having an arylene group is not limited to the following, but preferably includes a benzo crown ether or a dibenzo crown ether. By using a crown ether having an arylene group, it is possible to produce a CNT-cellulose composite material having more excellent durability, which is preferable. When the crown ether complex has a benzene ring, it is considered that the adhesion rate increases because the benzene ring and the CNT have the same six-membered ring structure. Specific examples of the crown ether complex include, but are not limited to, complexes of 12-crown-4-ether, 15-crown-5-ether, 18-crown-6-ether, and benzo-18-crown-6-ether. Preferably, it is a complex of benzo-18-crown-6-ether. The metal ion constituting the complex can be selected according to the structure of the crown ether, and examples thereof include potassium ion, sodium ion, and lithium ion. In a preferred embodiment, the crown ether complex is a complex of benzo-18-crown-6-ether and potassium hydroxide. The complex of benzo-18-crown-6-ether and potassium hydroxide is preferred in terms of high doping performance.

[0025] Examples of the amidine compound include 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) having the structure of the following (1).

Chemical formula

[0026] Examples of the guanidine compound include guanidine, 1,1,3,3-tetramethylguanidine (TMG) having the structure of the following (2), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) having the structure of the following (3), or 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (Me-TBD) having the structure of the following (4).

Chemical formula

Chemical formula

Chemical formula

[0027] Amidine compounds and guanidine compounds containing nitrogen as an atom having a lone pair of electrons, especially when they are cyclic, can define the steric position of the lone pair of electrons in the compound and can be used as effective bases (n-type doping reagents) for nanocarbons. Further, by using a substance containing both π-bonds and σ-bonds in the molecule, the structure of the conjugate acid after electron donation to the nanocarbon can be resonance-stabilized, and the negative charge of the n-type nanocarbon material, which is the conjugate base, can be stabilized. By n-type doping a nanocarbon material using the above-described amidine compound or guanidine compound, the heat resistance of the doping function of the nanocarbon material can be improved.

[0028] The p-type dopant compound used in the present invention is not limited as long as it can enhance the p-type polarity of the aggregate of the nanocarbon material and the cellulose material, and known p-type dopant compounds can be used. Examples of the p-type dopant compound include polyacrylic acid, onium salts, organic electron-accepting compounds (TCNQ), nitric acid, hydrochloric acid, metal halogen compounds (AuCl3, FeCl3), and the like.

[0029] In one embodiment, the CNT-cellulose composite material according to the present invention includes at least two regions selected from the group consisting of a region having an N-type semiconductor polarity, a region having a P-type semiconductor polarity, or an insulating region. The at least two regions selected from the group consisting of a region having an N-type semiconductor polarity, a region having a P-type semiconductor polarity, or an insulating region are specifically any one of a combination of a P-type region and an N-type region, a combination of a P-type region and an insulating region, a combination of an N-type region and an insulating region, and a combination of a P-type region, an N-type region, and an insulating region. As described above, the CNT-cellulose composite material in this embodiment has at least two regions selected from the group consisting of an N-type region, a region with a P-type semiconductor polarity, or an insulating region in one CNT-cellulose composite material (for example, in one CNT-cellulose composite yarn). Note that the upper limit of the number of each region of the CNT-cellulose composite material is not limited as long as conditions such as the size of the CNT-cellulose composite material permit.

[0030] In one embodiment, the CNT-cellulose composite material according to the present invention includes at least one N-type region and at least one P-type region, and includes at least one region where the N-type region and the P-type region are continuously and directly joined to each other. A CNT-cellulose composite material having a seamless PN junction region is very advantageous for device applications such as a heat flux sensor as compared with, for example, using a combination of individual n-type composite materials and p-type composite materials.

[0031] In one embodiment, the CNT-cellulose composite material according to the present invention has an n-type region with a Seebeck coefficient of -10 μV / K or less. In a preferred embodiment, the Seebeck coefficient in the n-type region is -15 μV / K or less, -20 μV / K or less, -25 μV / K or less. When the Seebeck coefficient in the n-type region of the CNT-cellulose composite material is -10 μV / K or less, the value of the relative Seebeck coefficient at the PN junction point increases, which is preferable. The measurement of the Seebeck coefficient can be carried out according to the method described in Example 2 below.

[0032] The CNT-cellulose composite material according to the present invention can be applied to various fields, and is not limited to the following, but can be used, for example, as a field effect transistor, a PN junction diode, a solar cell, a thermocouple, a thermoelectric conversion element, a temperature sensor, an infrared sensor, and the like.

[0033] In another aspect, the present invention provides a method for manufacturing a CNT-cellulose composite material. The manufacturing method includes the step of (i) infiltrating a dopant compound into a part or the whole of an aggregate of a nanocarbon material and a cellulose material by means of reduced-pressure infiltration. To infiltrate a dopant compound into an aggregate of a nanocarbon material and a cellulose material by means of reduced-pressure infiltration, a dopant solution containing the dopant compound is brought into contact with a desired region where the electron energy level on the aggregate of the nanocarbon material and the cellulose material is to be controlled. The electron energy level of the doped composite yarn is determined depending on the electron-hole injection ability of the dopant solution. The method of bringing the aggregate of the nanocarbon material and the cellulose material into contact with the dopant solution is arbitrary. For example, there are a method of dropping the dopant solution onto a desired part or the whole of the aggregate of the nanocarbon material and the cellulose material, and a method of immersing a desired part or the whole of the aggregate of the nanocarbon material and the cellulose material in the dopant solution.

[0034] As the solvent used for the dopant solution, a known solvent corresponding to the dopant compound to be used can be used. A person skilled in the art can select a solvent corresponding to the dopant compound to be used. For example, polar solvents such as water, butanol, toluene, acetone, N,N-dimethylformamide and the like can be used. The concentration of the dopant compound contained in the dopant solution can be any concentration at which a desired semiconductor polarity can be obtained. For example, the concentration of the dopant compound in the dopant solution may be 0.001 to 10 mol / L, or may be 0.01 to 0.1 mol / L.

[0035] Next, a pressure reduction treatment is performed while the aggregate of the nanocarbon material and the cellulose material is in contact with the dopant solution. By performing the pressure reduction treatment, the dopant compound can be impregnated into the interior of the aggregate of the nanocarbon material and the cellulose material. A known pressure reduction device such as a desiccator can be used for the pressure reduction treatment. The degree of vacuum is desirably -0.1 MPa or less in gauge pressure, and the pressure reduction time is desirably 1 hour or more. The temperature in the pressure reduction treatment is not particularly limited, and can be appropriately set, for example, in the range of 0 to 50 °C, preferably 4 to 30 °C, more preferably 10 to 25 °C. The required pressure and time depend on the physical property values and temperature conditions of the dopant solution. After the dopant compound is infiltrated by the pressure reduction treatment, the pressure in the pressure reduction device is returned to atmospheric pressure, and the aggregate of the nanocarbon material and the cellulose material containing the dopant compound is recovered from the dopant solution. In this way, a CNT-cellulose composite material with controlled semiconductor polarity can be obtained.

[0036] The CNT-cellulose composite material after the pressure reduction infiltration treatment is preferably dried. That is, in one embodiment, the method for producing the CNT-cellulose composite material according to the present invention includes a step of drying the CNT-cellulose composite material after the pressure reduction treatment step. The method for drying the CNT-cellulose composite material is not limited as long as the dopant compound is contained in the CNT-cellulose composite material and the solvent in the CNT-cellulose composite material can be removed. For example, a hot plate or the like can be used to perform the drying treatment. The conditions of the hot plate for the drying treatment can be, for example, 120 °C for 10 minutes.

[0037] In one embodiment, the method for producing the CNT-cellulose composite material according to the present invention further includes a step of infiltrating a different dopant compound by pressure reduction into a region different from the region containing the dopant compound in the aggregate of the nanocarbon material and the cellulose material after the pressure reduction infiltration step (i). The step (ii) is performed to control the semiconductor polarity in a region different from the region where the dopant compound has penetrated by the pressure reduction treatment step in (i). The different dopant compounds are preferably compounds different from the dopant compound used in the step (i), and are either an n-type dopant compound or a p-type dopant compound. By the step (ii), the polarity of a region different from the region containing the dopant compound used in the step (i) can be controlled. In one embodiment, after the pressure reduction treatment step in (ii), a step of drying the CNT-cellulose composite material may further be included.

[0038] In one embodiment, the method for manufacturing the CNT-cellulose composite material according to the present invention includes a step of repeating the step (ii) at least one more time in (iii). Thereby, the polarity of the CNT-cellulose composite material can be controlled using three or more types of dopant compounds. In one embodiment, after each step of the pressure reduction treatment in (iii), a step of drying the CNT-cellulose composite material may further be included.

[0039] In one embodiment, the pressure reduction infiltration step in (i) is a step of simultaneously infiltrating at least two or more dopant compounds into an aggregate of a nanocarbon material and a cellulose material by pressure reduction infiltration, each of the two or more dopant compounds can be a step of infiltrating into different regions on the aggregate of the nanocarbon material and the cellulose material.

[0040] In this embodiment, each of two or more dopant liquids containing different dopant compounds is brought into contact with two or more different regions in advance, and then pressure reduction treatment is performed, whereby it is possible to simultaneously control the polarities of two or more regions in the CNT-cellulose composite material.

Examples

[0041] (Example 1. Vacuum infiltration doping of CNT - cellulose composite yarn 1) In this example, an n - type dopant solution was infiltrated into CNT - cellulose composite yarns of various grades (10 S / cm, 100 S / cm, and 1000 S / cm) and CNT spun yarns (CNT 100%) by vacuum infiltration. Each sample length was 5 mm, and two elements each were used for the doping test. As the dopant compound, a crown ether - potassium complex (B18C6 + KOH) was used and dissolved in pure water as the solvent to a concentration of 0.5 mol / L to prepare the n - type dopant solution. Each sample was placed so that its entire body was immersed in the n - type dopant solution and left standing in a vacuum desiccator (AS ONE, Vacuum Polycad Desiccator 240GA type) in that state. Then, degassing was carried out by reducing the pressure to - 0.1 MPa for 10 minutes, and the n - type dopant solution was infiltrated into each sample. After the vacuum infiltration treatment, each sample was transferred onto a hot plate, the temperature condition was set to 120 °C, and a drying treatment was carried out for 10 minutes. In this way, CNT - cellulose composite yarns and CNT spun yarns in which the n - type dopant compound was completely infiltrated were produced.

[0042] (Example 2. Evaluation of n - type doping 1) It was clarified whether the CNT - cellulose composite yarn and the CNT spun yarn after doping produced in Example 1 were p - type or n - type by measurement using the Seebeck effect. The Seebeck effect is a phenomenon in which the temperature difference applied to a substance is converted into voltage. The generated voltage per unit temperature difference applied to the sample is called the Seebeck coefficient and is defined as follows. Seebeck coefficient (S)= - generated voltage (ΔV) / temperature difference (ΔT) The polarity of the material can be judged by the sign of the Seebeck coefficient. If the sign of the Seebeck coefficient is plus, it is judged as p - type, and if it is minus, it is judged as n - type. That is, if the sign of the Seebeck coefficient is minus, it indicates that the n - type dopant has infiltrated and the semiconductor polarity has become n - type.

[0043] The Seebeck coefficient of each sample was measured using a measurement system combined with a K-type thermocouple under the condition of a 27°C atmospheric atmosphere. Also, for comparison, the Seebeck coefficients of each sample before immersion in the doping solution (before doping) and each sample impregnated with the doping solution without depressurization (after impregnation doping) were also measured. Each sample with the doping solution infiltrated without depressurization was prepared by impregnating it in an n-type dopant solution at room temperature for 10 minutes. The results are shown in Table 1. The values of the Seebeck coefficients in Table 1 represent the average values of each sample (n = 2).

[0044]

Table 1

[0045] As shown in Table 1, the CNT-cellulose composite yarn did not show n-type polarity as the doping solution did not penetrate when it was simply immersed in the doping solution without depressurization. However, by applying depressurization, the dopant solution could be made to penetrate the CNT-cellulose composite yarn, and the n-type polarity could be significantly enhanced. Also, for any grade of CNT-cellulose composite yarn, the n-type polarity could be enhanced by depressurization infiltration.

[0046] (Example 3. Vacuum infiltration doping of CNT-cellulose composite yarn 2) In this example, it was verified whether doping by vacuum infiltration was possible even with a dopant compound different from that in Example 1. In this example, TBD (1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene) was used as the dopant compound and dissolved in N,N - dimethylformamide, which is a solvent, to a concentration of 0.1 mol / L to prepare an n - type dopant solution. As the sample, a CNT - cellulose composite yarn of 1000 S / cm grade was used. The CNT - cellulose composite yarn was placed so that the whole was immersed in the n - type dopant solution and left in a vacuum desiccator (AS ONE, Vacuum Poly Cad Desiccator 240GA type) in that state. Then, degassing was carried out by reducing the pressure to - 0.1 MPa for 10 minutes to 2 days, and the n - type dopant solution was infiltrated into each sample. In this way, a CNT - cellulose composite yarn in which the n - type dopant compound was completely infiltrated was produced.

[0047] (Example 4. Evaluation 2 of n - type doping) The Seebeck coefficients of the samples produced in Example 3 with reduced - pressure infiltration for 10 minutes, 30 minutes, 1 day, or 2 days (TBD 10 - minute reduced - pressure infiltration, TBD 30 - minute reduced - pressure infiltration, TBD 1 - day reduced - pressure infiltration, and TBD 2 - day reduced - pressure infiltration) were measured. The measurement of the Seebeck coefficient was carried out under the same conditions as in Example 2. Also, for comparison, the Seebeck coefficients of each sample before immersion in the doping solution (before doping) and the samples impregnated with the doping solution without reducing the pressure (TBD 10 - minute impregnation and TBD 1 - day impregnation) were also measured. Each sample with the doping solution infiltrated without reducing the pressure was prepared by leaving it in the n - type dopant solution at room temperature for 10 minutes or 1 day. The results are shown in Table 2.

[0048] [Table 2]

[0049] As shown in Table 2, when TBD was used as the dopant compound, the obtained CNT-cellulose composite yarn exhibited n-type polarity by impregnating the CNT-cellulose composite yarn in the dopant solution for one day. However, in the impregnation into the dopant solution, the Seebeck coefficient value did not show below -10 μV / K even after more than one day, and the absolute value of the n-type Seebeck coefficient did not show a value sufficient for practical use. On the other hand, when TBD was infiltrated into the CNT-cellulose composite yarn by vacuum infiltration, the Seebeck coefficient became about twice that of the non-vacuum impregnated section after one day of vacuum infiltration. Also, by two days of vacuum infiltration, the n-type polarity could be significantly enhanced. Further, when the doping compound was infiltrated by one day of vacuum infiltration, the linear resistance of the obtained n-type CNT-cellulose composite yarn showed a lower value compared to the section where the doping compound was infiltrated by impregnation without vacuum for the same time. Furthermore, the value of the linear resistance of the n-type CNT-cellulose composite yarn obtained by vacuum infiltration for one day or more showed a lower value than the value of the linear resistance of the CNT-cellulose composite yarn before doping. Thus, even when changing the type of dopant compound, the semiconductor polarity of the CNT-cellulose composite yarn could be converted to n-type by vacuum infiltration.

[0050] (Comparative Example 1. Ultrasonic infiltration doping into CNT-cellulose composite yarn) In this example, when infiltrating the dopant compound into the CNT-cellulose composite yarn, it was verified whether infiltration was possible by other infiltration methods other than vacuum infiltration. In this example, a crown ether-potassium complex (B18C6 + KOH) was used as the dopant compound and dissolved in pure water as the solvent to a concentration of 0.5 mol / L to prepare an n-type dopant solution. As the sample, a 1000 S / cm grade CNT-cellulose composite yarn was used. The prepared n-type dopant solution was filled in an ultrasonic generator (Tokyo Glass Kikai, FINE ultrasonic cleaner FU-10C), and the CNT-cellulose composite yarn was immersed so that its entire body was in the n-type dopant solution. Then, ultrasonic waves were generated for 10 minutes under normal temperature and pressure conditions to attempt infiltration of the dopant solution. As a result, due to the influence of ultrasonic waves, the CNT-cellulose composite yarn after treatment could not maintain the shape of the yarn as the fibers unraveled (Figure 1). It was found that the method of infiltrating the dopant compound with ultrasonic waves cannot be applied because it destroys the shape of the yarn and fibers of the CNT-cellulose composite yarn.

[0051] (Example 5. Prototype example of a seamless CNT-cellulose composite yarn (thermoelectric conversion element) with PN control) The CNT-cellulose composite material produced by the present invention can be applied to various devices by combining it with a p-type material. In this example, a prototype example of a CNT-cellulose composite yarn (thermoelectric conversion element) having a plurality of seamless undoped p-type regions and n-type regions obtained by doping is shown.

[0052] The thermoelectric conversion element using the CNT-cellulose composite yarn can be fabricated as follows. The flow of the fabrication example is shown in Figure 2. As the dopant compound, a crown ether - potassium complex (B18C6 + KOH) is used and dissolved in pure water as the solvent to a concentration of 0.5 mol / L to prepare an n - type dopant solution. Next, the undoped CNT - cellulose composite yarn is wound around a glass plate as shown in Fig. 2. A part of the CNT - cellulose composite yarn wound around the glass plate (a plurality of regions where the dopant compound is to penetrate) is impregnated and fixed in the above - mentioned crown ether - potassium complex solution. Since the dopant compound does not penetrate into the CNT - cellulose composite yarn just by impregnating the CNT - cellulose composite yarn in the dopant solution, the contact between the CNT - cellulose composite yarn and the dopant solution is preferably achieved by immersing the CNT - cellulose composite yarn in the dopant solution. By adopting the method of immersing the CNT - cellulose composite yarn in the dopant solution, the dopant compound can be made to penetrate into a plurality of desired regions at once, which is preferable. Also, this method is preferable in that it is easy to control the regions where the dopant compound penetrates. Next, the CNT - cellulose composite yarn and the crown ether - potassium complex solution are left standing in a vacuum desiccator (AS ONE, Vacuum Poly Cad Desiccator 240GA type). Degassing is carried out by reducing the pressure to - 0.1 MPa for 1 hour or more, so that the n - type dopant solution penetrates only into a part of the CNT - cellulose composite yarn. Then, the glass plate around which the CNT - cellulose composite yarn is wound is transferred onto a hot plate, and a drying treatment is carried out at a temperature condition of 120 °C for 10 minutes. After the drying treatment, the CNT - cellulose composite yarn is removed from the glass plate. In this way, p - type regions and n - type regions are seamlessly joined alternately so as to be p - type region, n - type region, p - type region, n - type region, ···, and a CNT - cellulose composite yarn with continuously repeated PN control can be produced using the same single CNT - cellulose composite yarn. By knitting a fiber with the above - mentioned CNT - cellulose composite yarn with continuously repeated PN control, a thermoelectric conversion clothing capable of generating electricity from the temperature difference between body temperature and outside air temperature can be made.

Claims

1. A CNT-cellulose composite material composed of an aggregate of a nanocarbon material and a cellulose material and containing an n-type dopant compound or a p-type dopant compound.

2. The CNT-cellulose composite material according to Claim 1, including at least two regions selected from the group consisting of a region having an N-type semiconductor polarity, a region having a P-type semiconductor polarity, or an insulating region. CNT-cellulose composite material.

3. The CNT-cellulose composite material according to Claim 2, including at least one region having an N-type region and at least one region having a P-type region, and at least one region where the N-type region and the P-type region are joined to each other.

4. The CNT-cellulose composite material according to Claim 2, including a plurality of each of the at least two regions. CNT-cellulose composite material.

5. The CNT-cellulose composite material according to any one of Claims 1 to 4, wherein the nanocarbon material is selected from any one of carbon nanotubes, graphene, or graphite.

6. The CNT-cellulose composite material according to any one of Claims 1 to 4, wherein the aggregate of the nanocarbon material and the cellulose material is in the form of a fiber, a film, a thread, or a cloth.

7. The CNT-cellulose composite material according to any one of Claims 1 to 4, wherein the n-type dopant compound is at least one compound selected from a crown ether complex, an amidine compound, and a guanidine compound.

8. The CNT-cellulose composite material according to any one of Claims 1 to 4, having an n-type region with a Seebeck coefficient of -10 μV / K or less.

9. A thermoelectric conversion element, a temperature sensor, an infrared sensor, a field effect transistor, a PN junction diode, a thermopile, or a solar cell including the CNT-cellulose composite material according to any one of Claims 1 to 4.

10. A method for manufacturing the CNT-cellulose composite material according to Claim 1, including the step of (i) infiltrating the dopant compound into a part or the whole of the aggregate of the nanocarbon material and the cellulose material by vacuum infiltration. Manufacturing method.

11. The manufacturing method according to claim 10, wherein after the reduced-pressure impregnation step of (i), (ii) a step of impregnating a different dopant compound into a region different from the region containing the dopant compound in the aggregate of the nanocarbon material and the cellulose material by reduced-pressure impregnation is further included.

12. The manufacturing method according to claim 11, wherein (iii) the step of (ii) is repeated at least one more time.

13. The manufacturing method according to claim 10, wherein the reduced-pressure impregnation step of (i) is a step of simultaneously impregnating at least two or more dopant compounds into the aggregate of the nanocarbon material and the cellulose material by reduced-pressure impregnation, including a step of impregnating each of the two or more dopant compounds into different regions from each other on the aggregate of the nanocarbon material and the cellulose material The manufacturing method.

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