JP7168570B2 - Carbyne-containing composite material - Google Patents

Description

The present invention relates to carbyne-containing composites.
This application claims priority based on Japanese Patent Application No. 2017-162599 filed on August 25, 2017, the entire contents of which are incorporated herein by reference.

A carbyne is a carbon allotrope in which the carbon atoms (C) are linked in one dimension. Although the existence of carbyne was pointed out in 1885, it was not identified until the 1960s because it is unstable in the atmosphere. Last year, it was reported that by using double-walled carbon nanotube (DWNT) as a nanoreactor, it was possible to stably generate a very long carbyne in the internal space of DWNT (see Non-Patent Document 1). ).

Lei Shi et al., "Confined linear carbon chains as a route to bulk carbyne", NATURE MATERIALS, vol. 15, 634-639, 2016 Mingjie Liu et al., "Carbyne from First Principles: Chain of C Atoms, a Nanorod or a Nanorope", ACS Nano, 2013, 7(11), pp10075-10082

Non-Patent Document 1 discloses that by heating DWNT at a high vacuum of 8×10 ⁻⁵ Pa and a high temperature of 1460° C., carbyne can be suitably formed inside DWNT. In addition, it is described that carbyne can be grown only with DWNT having an inner tube diameter in the range of 0.62 to 0.85 nm, and that 90% or more of the DWNT with this inner diameter is filled with carbyne. However, according to the authors of Non-Patent Document 1, even if the DWNT preparation conditions were optimized, DWNTs with the above tube diameter could only be obtained in about 25% of the prepared DWNT aggregates. do not have. It is also reported that only 24% of the DWNTs in the prepared DWNT population were loaded with carbyne.

The present invention has been made in view of the above points, and its main object is to provide a carbyne-containing composite material that is an aggregate of carbon nanotubes encapsulating carbyne at a higher filling rate.

The carbyne-containing composite material provided by the present invention includes a CNT aggregate formed by assembling a plurality of carbon nanotubes (CNT, hereinafter sometimes simply referred to as "CNT"), and carbyne. 30% or more of the plurality of CNTs is filled with the carbyne.

That is, the carbyne-containing composites disclosed herein contain carbynes within the CNTs at a higher packing factor than previously known. It has been reported that even when CNTs inherently have semiconducting properties based on their crystal structure, introduction of carbynes into the CNTs can impart metallic properties to the CNTs. From this, for example, even if the CNT aggregate contains a large amount of CNTs exhibiting semiconducting properties, the introduction of carbyne at a high filling rate results in overall high metallic properties (e.g., high electrical conductivity). can be provided. Thus, the carbyne-containing composite material can realize a material that reflects the properties of carbyne more strongly than conventional CNTs or CNTs containing carbyne. The carbyne property provided in the carbyne-containing composite material can be a variety of properties, not limited to electrical conductivity.

In a preferred embodiment of the carbyne-containing composite material disclosed herein, the relative intensity of the peak based on the LCC band is 0 when the intensity of the peak based on the G band is 1 in the Raman spectrum measured by Raman spectroscopic analysis. .4 or more. Such a configuration also realizes a carbyne-containing composite material into which a large amount of carbyne is introduced.

In a preferred embodiment of the carbyne-containing composite material disclosed herein, at least a portion of the carbon nanotube encapsulating the carbyne is a single-walled carbon nanotube (SWNT, hereinafter simply referred to as "SWNT"). There is a case.) including. More preferably, the CNTs encapsulating the carbyne contain 10% or more of SWNTs. Non-Patent Document 1 mentioned above discloses that SWNT cannot form carbyne inside because of its relatively low thermal stability compared to DWNT and the like. However, in the carbyne-containing composite material disclosed herein, carbyne can be stably included even in SWNTs. In other words, the carbyne-containing composites disclosed herein can comprise novel carbyne-encapsulated SWNTs (carbine@SWNTs). Such a carbyne-containing composite material is preferable because it can more effectively increase the proportion of carbyne in the entire composite material. This is also useful in that the material can strongly reflect the characteristics of SWNT and carbyne.

In addition, the ratio of CNTs having a specific structure in the CNT aggregate can be grasped by observation with a transmission electron microscope (TEM), for example. Specifically, for example, the ratio of SWNTs in a CNT aggregate can be obtained by calculating the ratio (number %) of the total number of SWNTs to the total number of CNTs observed in the field of view in TEM observation. can. The number of CNTs may be measured, for example, for CNTs with a length of 500 nm or longer that can be confirmed in the observed image. For the number of CNTs, a value measured based on an observation image at a magnification of about 50,000 to 500,000 times can be preferably adopted.

In a preferred embodiment of the carbyne-containing composite material disclosed herein, at least some of the CNTs contain two or more carbynes in a direction orthogonal to the axial direction of the CNTs. That is, a CNT can contain two or more carbynes aligned in the transverse direction. It is known that carbynes are intermittently formed inside the CNT along the longitudinal direction (axial direction). That is, multiple carbines can be encapsulated within the CNT along the longitudinal direction. However, no report has been made on CNTs containing two carbynes bundled together. The carbyne-containing composite material disclosed herein can include such novel carbyne-encapsulated CNT (carbine@CNT).

As described above, the technology disclosed herein provides a novel carbyne-containing composite material that has never existed before. This carbyne-containing composite material can have the properties of both CNT aggregates and carbyne. For example, carbyne is reported to theoretically have twice the tensile strength of graphene, twice the stiffness of graphene and CNTs, and about three times the stiffness of diamond. Thus, for example, carbyne-containing composites can have significantly improved tensile strength and stiffness relative to CNT aggregates.

On the other hand, as mentioned above, carbyne may have the function of converting semiconducting CNTs into metallic properties. Thus, for example, carbyne-containing composites can result in enhanced electrical conductivity of CNT aggregates. Thus, the carbyne-containing composites disclosed herein provide new materials with enhanced or modified properties of CNT aggregates. This novel material can be used in applications similar to conventional CNTs, or in novel applications never before seen. Accordingly, the technology disclosed herein can provide various articles including carbyne-containing composites.

In another aspect, the technology disclosed herein also provides a method for producing a carbyne-containing composite material. This manufacturing method includes preparing a carbon nanotube aggregate having a G/D ratio of 25 or more, which is formed by assembling a plurality of carbon nanotubes, and applying a voltage that causes at least field electron emission to the carbon nanotube aggregate. ,including. This allows the carbyne-containing composite material to be produced under relaxed conditions of significantly lower temperature and lower vacuum than disclosed, for example, in Non-Patent Document 1. Thereby, the carbyne-containing composite material can be easily produced.

1 is a diagram schematically showing the crystal structure of carbyne encapsulated in SWNTs contained in a carbyne-containing composite material according to one embodiment. FIG. 1 is a Raman spectrum of CNTs containing 100% carbyne disclosed in Non-Patent Document 1. FIG. 1 is a Raman spectrum for a carbyne-containing composite material according to one embodiment; It is an example of a Raman spectrum for a CNT sheet containing no carbynes. Fig. 10 is an SEM image showing Raman spectrum measurement positions (a) to (c) of a carbyne-containing composite material according to another embodiment. FIG. 5B is a Raman spectrum of the carbyne-containing composite material at the measurement positions (a) to (c) shown in FIG. 5A. (A) to (C) are TEM images of SWNTs in a CNT sheet containing no carbyne, and (D) is a diagram showing the results of gradation profile analysis of (A). 1 is a TEM image of SWNTs included in a carbyne-containing composite according to one embodiment. 1 is a TEM image of other SWNTs included in a carbyne-containing composite according to one embodiment. 7A and 7B are diagrams showing the results of gradation profile analysis of the boxed regions in FIGS. 7A and 7B, respectively; FIG. (A) and (B) are TEM images of DWNTs included in a carbyne-containing composite material according to one embodiment. 9A and 9B are diagrams showing the results of gradation profile analysis of the areas enclosed by squares in FIGS. 9A and 9B, respectively; FIG. (A) is a TEM image of MWNTs contained in a carbyne-containing composite material according to one embodiment, and (B) is a diagram showing the results of tone profile analysis of the boxed area. (A) is a TEM image of DWNTs contained in a carbyne-containing composite material according to one embodiment, and (B) is a diagram showing the results of tone profile analysis of the boxed area.

Preferred embodiments of the present invention are described below. In addition to matters specifically mentioned in the present specification (e.g., structure of carbyne-containing composite material), matters necessary for carrying out the present invention (e.g., a method for producing a CNT aggregate as a starting material, etc.) can be grasped as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be implemented based on the contents disclosed in the specification and drawings, and the common general technical knowledge in the field. In this specification, the notation "X to Y" indicating a numerical range means "X or more and Y or less" unless otherwise specified.

[Carbyne-containing composite material]
The carbyne-containing composite material disclosed herein includes a CNT aggregate formed by assembling a plurality of CNTs, and carbyne. Carbyne is filled (encapsulated) in the CNT. Each component of the carbyne-containing composite material will be described below.

[CNT aggregate]
CNT aggregates are the main component of the carbyne-containing composites disclosed herein. And it has a role as a protective case that holds Calbyne stably. The CNT aggregate also functions as a reactor for carbyne in the production of a carbyne-containing composite material, which will be described later. The structure of the CNT aggregate is not particularly limited, and various CNT aggregates in which a plurality of CNTs are aggregated separately or integrally can be considered. From the viewpoint of ease of handling, a plurality of CNTs may be aggregated integrally. Also, the CNT aggregate may be composed of, for example, a group of a plurality of CNTs grown in a direction perpendicular to the substrate. Here, the number of CNTs constituting the "CNT aggregate" is not strictly limited. can be considered as consisting of sets. However, it can be said that it is not realistic to define a CNT aggregate by the number of CNTs that constitute it. Although it is not necessarily limited to this, for example, from the viewpoint of facilitating industrial handling, the "CNT aggregate" may be grasped as an aggregate of 1 μg or more of CNTs. A CNT aggregate may be an aggregate of 10 μg or more of CNTs, may be 100 μg or more, and may be, for example, 1000 μg or more. There is no upper limit on the mass of CNTs forming the CNT aggregate.

The CNT aggregate may be composed of SWNTs in which one graphene sheet is rolled into a cylindrical shape, or may be composed of DWNTs in which two SWNTs having different diameters are nested. Alternatively, it may be composed of a multi-walled carbon nanotube (MWNT) in which three or more SWNTs with different diameters are nested. Also, the CNT aggregate may be composed of a mixture of two or more of these SWNTs, DWNTs and MWNTs. In the present specification, CNTs having three or more layers are collectively referred to as MWNTs, and unless otherwise specified, the values of the MWNTs as a whole are also referred to as their ratios. MWNTs are, for example, generally CNTs with about 3 to 200 layers, and typically can be CNTs with about 3 to 60 layers. CNTs can also have different layer structures, such as partial single layer, double layer, or triple layer, even in one tube. In such a case, the number of layers occupying the largest proportion in the CNT may be adopted as the number of layers of the CNT.

The CNT aggregate is not necessarily limited to this, but the ratio of SWNTs to the total of SWNTs, DWNTs and MWNTs is preferably 10% or more (10% or more based on number). By increasing the ratio of SWNTs constituting the CNT aggregate, it is possible to increase the amount of carbyne contained per unit weight of the CNT aggregate, which is preferable. The proportion of SWNTs in the CNT aggregate is more preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, and may be, for example, 50% or more. The proportion of SWNTs may be 60 number % or more, 70 number % or more, 80 number % or more, 90 number % or more, or substantially 100 number %. There may be.

In recent years, methods for synthesizing SWNTs have been greatly improved, and methods for synthesizing SWNTs with higher quality in terms of purity and degree of graphitization have been proposed. Moreover, in a CNT aggregate containing such SWNTs, the content of SWNTs may be evaluated on a mass basis. Therefore, for example, the CNT aggregate is not necessarily limited to this, but the ratio of SWNTs to the total of SWNTs, DWNTs and MWNTs is preferably 30% by mass or more, and more preferably 40% by mass or more. It is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. This also makes it possible, for example, to effectively reduce the mass proportion of CNTs in the entire carbyne-containing composite material. The upper limit of the proportion of SWNTs is not particularly limited, and may be, for example, substantially 100% by mass (eg, 95% by mass or less).

On the other hand, DWNT is known to easily form carbyne in its interior. From this point of view, in the CNT aggregate, the ratio of DWNTs to the total of SWNTs, DWNTs and MWNTs may be 10% by mass or more, may be 15% by mass or more, and may be, for example, 20% by mass or more. good too. However, in the carbyne-containing composite material disclosed herein, it is not necessary to increase the proportion of DWNTs in order to enclose a high proportion of carbynes in CNTs. From this point of view, the CNT aggregate is not necessarily limited to this, but for example, the ratio of DWNT to the total of SWNT, DWNT and MWNT may be 70% by mass or less, or 60% by mass or less. For example, it may be 50% by mass or less. The ratio of MWNTs to the total of CNTs is preferably 30% by mass or less, more preferably 20% by mass or less, and may be, for example, 10% by mass or less.

In addition, the average diameter of CNTs in the CNT aggregate is not strictly limited, and may be, for example, 0.43 nm or more and 100 nm or less, typically 0.5 nm or more and 50 nm or less, preferably 0.6 nm. 10 nm or less. The diameter of the CNT aggregate means the tube diameter (diameter) for SWNTs, and the tube system (diameter) for the innermost CNTs for CNTs having two or more layers. Although the carbyne-containing composite material disclosed herein is not necessarily limited to this, it has been confirmed that CNTs having a diameter of 0.6 nm or more, for example, 0.7 nm or more, can preferably enclose carbynes. ing. Therefore, the average inner diameter of the CNTs in the CNT aggregate is preferably 0.6 nm or more, more preferably 0.7 nm or more, and can be, for example, 0.8 nm or more. For CNTs containing carbyne, for example, the average inner diameter of CNTs is preferably 5 nm or less, more preferably 2 nm or less, from the viewpoint that carbyne can exist more stably.

It is suitable that the average length of CNTs is typically 1 μm or more. From the viewpoint of low resistance and increased film strength, the average length of CNTs is preferably 3 μm or more, more preferably 5 μm or more, even more preferably 8 μm or more, particularly preferably 10 μm or more, for example, more than 10 μm. Although the upper limit of the average length of the CNTs is not particularly limited, it is suitable to be approximately 30 μm or less, and may be, for example, 25 μm or less, typically 20 μm or less, for example, 15 μm or less. For example, CNTs having an average length of 5 μm or more and 30 μm or less, preferably 10 μm or more and 25 μm or less, and typically 12 μm or more and 20 μm or less are suitable.

The average value of the CNT aspect ratio (CNT length/diameter) in the CNT aggregate is not particularly limited, but is typically 100 or more. The larger the aspect ratio of the CNTs, the easier it is for the CNTs to be mechanically entangled with each other, and the easier it is for them to form an integral aggregate, which is preferable. Furthermore, it is also preferable in that an aggregate having a desired shape can be formed without including a binder. The average aspect ratio of CNTs is preferably 250 or more, more preferably 500 or more, still more preferably 800 or more, and particularly preferably 1000 or more, from the viewpoint of increasing the low resistance property and strength of the CNT aggregate. The upper limit of the average aspect ratio of CNTs is not particularly limited, but from the viewpoint of ease of handling and production, it is suitable to be approximately 25,000 or less, preferably 20,000 or less, more preferably 15,000 or less, and even more preferably. It is 12,000 or less, particularly preferably 10,000 or less. For example, CNTs having an average aspect ratio of 100 to 10,000 are suitable. For the average aspect ratio (length/diameter of CNTs), average length and average diameter of CNTs, values typically obtained by measurement based on electron microscope observation can be employed.

[Calvin]
In the carbyne-containing composite material disclosed herein, carbyne is encapsulated in CNTs, for example, as shown in FIG. Carbyne and CNT have the same longitudinal direction (axial direction). As described above, carbyne is one of allotropes of carbon, and has a structure in which carbon atoms are sp-bonded in a one-dimensional straight chain. Specifically, as shown in the following formulas (1) and (2), carbyne has a polyyne structure (1) in which adjacent carbon atoms are alternately bonded with triple bonds and single bonds, and a continuous double bond. It can be represented by a resonance structure of a cumulene-type structure (2) connected by a bond. Therefore, carbyne has a thickness (diameter) of one carbon atom and a sufficiently long length (e.g., approximately 9 nm or more) relative to this thickness, so it can be said that carbyne is the ultimate one-dimensional substance. .

-C≡CC≡CC≡CC≡CC≡C- (1)

=C=C=C=C=C=C=C=C=C=C= (2)

In Non-Patent Document 2, precise computer simulations are performed on carbyne represented by formulas (1) and (2), and it is predicted that carbyne is harder than any substance existing in the world. Specifically, the tensile strength is about twice that of graphene, the stiffness is about twice that of graphene and nanotubes, and about three times that of diamond. Carbyne is expected to become a magnetic semiconductor when twisted by 90° with its bonding direction as the axis of rotation, and to store energy and be stable even at room temperature. The phase diagram of carbyne is said to exist in a narrow region surrounded by gas phase, liquid phase, diamond, and graphite. Details have not been disclosed.

However, even such carbyne can exist stably under normal temperature and normal pressure by being encapsulated in CNTs. The fact that the ^{carbyne -} containing composite material disclosed herein contains carbyne indicates that linear carbon chains (LCC ) The presence of carbyne can be confirmed by the presence of a peak based on the band. In other words, by detecting the LCC band, it can be confirmed that carbyne is included in the CNT.

In this specification, unless otherwise specified, the Raman spectrum means a spectrum obtained by Raman spectroscopic analysis using a laser with a wavelength of 532 nm as excitation light. Also, in the Raman spectrum of such a carbyne-containing composite material, a peak based on the G band is observed near 1590 cm ⁻¹ derived from the graphite structure of CNT. Also, in the Raman spectrum of such a carbyne-containing composite material, a peak based on the D band can be observed near 1350 cm ⁻¹ due to defects in the graphite structure.

It should be noted that the carbyne-containing composites disclosed herein contain carbynes in the CNTs in a greater proportion than in the past. As a result, in the Raman spectrum, the relative intensity I _LCC of the peak based on the LCC band when the intensity I _G of the peak based on the G band is "1" (reference), that is, the relative intensity I _LCC /I _G , is 0 .4 or more. The relative intensity I _LCC /I _G is preferably 0.8 or more, more preferably 1.0 or more, still more preferably 1.2 or more, and particularly preferably 1.5 or more. Also, the relative intensity I _LCC /I _G can be 2 or more, more preferably 2.5 or more, and particularly preferably 3.0 or more. The upper limit of the relative intensity I _LCC /I _G is not strictly limited. For example, as described later, the relative intensity I _LCC /I _G for the carvin-encapsulated portion (local) of the CNT disclosed in Non-Patent Document 1 is 6.1, so the upper limit of the relative intensity I _LCC /I _G can be about 6.1.

In the carbyne-containing composite material disclosed herein, the amount of carbyne encapsulated in CNTs can also be evaluated by the carbyne filling rate. In the carbyne-containing composite material disclosed herein, the carbyne filling rate is preferably 30% or more. A CNT assembly containing carbynes at such a high filling rate has not been known so far. The carbyne filling rate can be further increased by adjusting the manufacturing method of the carbyne-containing composite material and the starting materials, which will be described later. For example, the carbyne filling rate may be 32% or more, more preferably 33% or more, particularly preferably 35% or more, even more preferably 37% or more, for example 40% or more.

In this specification, the filling ratio of carbyne to CNTs is defined as follows. That is, first, it is defined that the carbyne-encapsulated portion of one CNT that encloses one long carbyne without intermittence in the length direction has a carbyne filling rate of 100%. Then, in the Raman spectrum of the carbyne-encapsulated portion with a filling rate of 100%, the intensity I _LCC* of the peak based on the LCC band when the intensity I _G* of the peak based on the G band is set to "1", that is, I _LCC* / Let _IG* be the relative intensity I _LCC/G* (reference) of the LCC band to the G band at a filling rate of 100%. Further, in the Raman spectrum of the carbyne-containing composite material, the intensity I _LCC of the peak based on the LCC band when the intensity IG of the peak based on the _G band is set to "1" is the LCC band for the G band of the carbyne-containing composite material. Let the relative intensity I _LCC/G of At this time, the carbyne filling factor F of CNTs in the carbyne-containing composite material is represented by the following equation.
F (%)= _ILCC/G / _ILCC/G* ×100

The relative intensity _ILCC/G* of the LCC band with respect to the G band when the filling rate is 100% may adopt a value obtained by measurement using carbyne-encapsulated CNTs with a filling rate of 100%. A value of "6.1" calculated based on the Raman spectrum disclosed in Patent Document 1 may be used. FIG. 2 shows the Raman spectrum disclosed in Non-Patent Document 1.

In addition, the carbyne-containing composite material preferably has fewer surface defects in the CNT aggregate portion because the intermolecular force between the CNTs can be effectively enhanced. In addition, when CNTs exhibit metallic properties, electrical conductivity can be increased with fewer surface defects. Therefore, it is preferable that the CNT aggregate has few surface defects. From this point of view, the carbyne-containing composite material disclosed herein has a ratio of the intensity I _G of the peak based on the G band to the intensity I _D of the peak based on the D band (I _G /I _D : G/D ratio) High is preferred. The G/D ratio of the carbyne-containing composite material is, for example, preferably 6 or more, more preferably 7 or more, even more preferably 8 or more, and particularly preferably 10 or more.

[Use]
In the carbyne-containing composite material described above, carbyne is included in the CNT aggregate at an unprecedentedly high ratio. Thus, a carbyne-containing composite material can have properties derived from carbyne in addition to the inherent properties of CNTs. For example, it is possible to provide an article with higher strength compared to conventional CNT sheets and the like. On the other hand, carbyne can bring about changes in the properties of CNTs encapsulating carbyne. For example, SWNTs exhibit metallic properties or semiconducting properties depending on chirality, but DWNTs and MWNTs exhibit metallic properties as a whole by including even one layer of CNTs with metallic properties. It is known that almost all DWNTs and MWNTs can exhibit metallic properties. Since the carbyne-containing composites disclosed herein can suitably include SWNTs, when the SWNTs exhibit semiconducting properties, the carbyne-containing composites can modify the SWNTs to exhibit metallic properties. . As a result, for example, the properties of CNTs in a CNT aggregate in which metal/semiconductor are not completely separated can be matched to metallic properties. An article comprising such a carbyne-containing composite material can be used to replace almost all conventional products using CNTs. For example, articles comprising carbyne-containing composites can be particularly useful as lightweight materials, such as for mechanical or electrical conductor applications. Suitable examples of such articles include, for example, transparent electrodes and transparent conductive films.

[Method for producing carbyne-containing composite material]
Further, according to the technology disclosed herein, a suitable method for producing the carbyne-containing composite material is provided. This manufacturing method includes the following steps (1) to (2). Each step will be described below.
(1) As a starting material, a CNT aggregate having a G/D ratio of 25 or more is prepared.
(2) Applying a voltage that causes at least field emission (FE) to the CNT aggregate.

[1. Preparation of starting materials]
Carbyne-containing composites use CNT aggregates as starting materials. This CNT aggregate may be prepared to have almost the same structure as the desired carbyne-containing composite material. For example, it is preferable to prepare a CNT aggregate having a desired aspect at the stage of the starting material, such as the respective ratios, shapes, and aggregate forms of SWNTs, DWNTs, and MWNTs in the CNT aggregate of the carbyne-containing composite material. From the viewpoint of facilitating the generation of FE in the next step, it is preferable to use a sheet-like CNT aggregate having a substantially flat surface morphology. The CNT aggregate may be held on any base material, or may be prepared as an independent CNT aggregate alone.

As the CNT aggregate, one having a G/D ratio of 25 or more as measured by Raman spectroscopic analysis can be preferably used from the viewpoint of favorably generating FE. A CNT aggregate having a higher G/D ratio can be evaluated as having fewer surface defects and higher crystallinity. As a result, FE can be produced in a suitable state in the next step. In addition, since the CNTs have few surface defects, the intermolecular forces between the CNTs are effectively enhanced. Therefore, in the formation of a CNT aggregate, it is also suitable in that high film strength can be achieved without requiring a binder, for example. The G/D ratio of CNTs is preferably 28 or higher, more preferably 30 or higher, particularly preferably 35 or higher. For example, the G/D ratio of CNTs may be 50 or higher, typically 100 or higher. Although the upper limit of the G/D ratio of the CNT is not particularly limited, it may be, for example, 200 or less, typically 150 or less, for example, 120 or less from the viewpoint of ease of production. The method for producing this CNT aggregate is not particularly limited. For example, it may be a CNT aggregate manufactured by an arc discharge method, a CVD method, or the like. However, a CNT aggregate having a high G/D ratio as described above is preferably produced by, for example, the CVD method.

Also, the purity of the CNT aggregate is not particularly limited, but is typically 85% or higher. The purity here means the ratio of the carbonaceous material (CNT and amorphous carbon) to the CNT aggregate. The purity of the CNT aggregate is preferably 90% or more, more preferably 95% or more, from the viewpoints of suppressing variations in FE, reducing resistance, improving film strength, and the like. The upper limit of the purity of the CNT aggregate is not particularly limited, and may typically be 99% or less, for example, 98% or less from the viewpoint of ease of production. The technology disclosed herein can be preferably practiced, for example, in a mode in which the purity of the CNT aggregate is 85% or more and 100% or less (typically 95% or more and 99% or less). In this specification, the purity of CNTs can be obtained by measurement using a differential thermogravimetry (TG-DTA) device. For example, in the TG/DTA chart, the content of CNTs, which is the sum of SWNTs and amorphous carbon, can be calculated from the weight loss rate due to the combustion of SWNTs at around 683°C and the combustion of amorphous carbon at around 322°C. can be done. If the CNT aggregate contains DWNTs or MWNTs, the weight loss due to their combustion should be taken into consideration.

Furthermore, the bulk density of the CNT aggregate is not particularly limited. For the purpose of obtaining a carbyne-containing composite material containing carbyne at a higher concentration, for example, the bulk density of the CNT aggregate is preferably 0.1 g/cm ³ or more, more preferably 0.3 g/cm ³ or more. More preferably, 0.5 g/cm ³ or more is particularly preferable. The upper limit of the bulk density of the CNT aggregate is not particularly limited. For example, a CNT aggregate with an excessively high density may increase the proportion of CNTs composed of MWNTs or may increase the proportion of CNTs that may break due to compaction. From the viewpoint of avoiding such inconvenience, the bulk density of the CNT aggregate can be typically set to 1 g/cm ³ or less. It is more preferable that this bulk density is a value for CNTs that do not contain catalyst metals, amorphous metals, etc., which will be described later.

Furthermore, the CNT aggregate is allowed to contain, for example, catalyst metals used in CNT synthesis and the like. The catalyst metal can be, for example, at least one metal selected from the group consisting of Fe, Co and platinum group elements (Ru, Rh, Pd, Os, Ir, Pt), or an alloy mainly composed of said metal. Such catalytic metals can typically be contained in the CNT aggregates in the form of fine particles (eg, average particle diameter of about 3 nm to 100 nm). In a preferred embodiment of the CNT aggregate as the starting material, 85 atom % or more (more preferably 90 atom % or more) of the carbonaceous material is carbon atoms (C). 95 atom % or more of the carbonaceous material may be carbon atoms, 99 atom % or more may be carbon atoms, or CNTs consisting essentially of carbon atoms may be used. A product obtained by the CNT production method described later may be subjected to any post-treatment (for example, purification treatment such as removal of amorphous carbon and removal of catalyst metal) to be used as the CNT.

The CNT aggregate may contain materials other than the above-described carbonaceous materials and catalyst metals (hereinafter also referred to as additive materials) within a range that does not significantly hinder the generation of FE in the next step. Examples of such additive materials include resin binders, conductive materials, thickeners, and the like. However, the content of these additive materials is suitably, for example, 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, and particularly preferably 5% by mass or less, of the total mass of the CNT aggregate. is 3% by mass or less. Among others, it is preferable that the CNT aggregate does not substantially contain an insulating resin binder.

[2. FE treatment of CNT aggregate]
The carbyne-containing composite material disclosed herein can be obtained by applying a voltage to the CNT aggregates prepared above to induce or equate to FE. The voltage to be applied, the atmospheric conditions, and the like vary depending on the properties of the CNT aggregate (crystallinity, shape, and field emission characteristics), and cannot be generalized. The fact that the CNT aggregate emits electrons due to the action of the electric field can be confirmed, for example, by applying an electric field to the CNT aggregate and causing a weak current (FE current) to flow between the applied electrodes. In general, field emission of metallic materials can be stably generated only in an ultra-high vacuum atmosphere (typically, an atmosphere of 10 ⁻⁸ Pa or less). However, by using the above-described CNT aggregate with high crystallinity as a starting material, FE can be generated in a milder reduced-pressure environment and/or a lower voltage than before. By creating an FE environment in such a CNT aggregate with high crystallinity, it is considered that an environment more suitable for carbyne formation can be prepared.

Such a reduced-pressure environment can be, for example, a pressure exceeding 10 ⁻⁵ Pa (for example, approximately greater than 10 ⁻⁵ Pa and 10 Pa or less). According to JIS Z8126-1:1999, a vacuum of 10 ⁻⁵ Pa or less is defined as “ultra ^- high vacuum”. It can be a “high vacuum” of more than ⁵ Pa and 0.1 Pa ⁻¹ or less, or a “medium vacuum” of more than 0.1 Pa ⁻¹ and 10 Pa or less. From the viewpoint of generating FE in an environment closer to normal pressure, the reduced pressure environment is preferably 10 ⁻⁴ Pa or more, more preferably 10 ⁻³ Pa or more, particularly preferably 10 ⁻² Pa or more, and 10 ^{− 1} Pa or more is more preferable, and for example, it may be 10 ⁰ Pa or more.

Moreover, the voltage conditions for generating an electric field cannot be generalized because they greatly depend on the crystallinity and surface morphology of the CNT aggregate, the distance between the electrodes, and the like. For example, when the inter-electrode distance is 1.6 mm, the voltage exceeds 0 V, preferably about 0.5 kV or more, and more preferably about 1 kV or more, as a rough guideline. Also, the voltage condition for generating the electric field may be, for example, about 3 kV or less, more preferably about 2.8 kV or less, for example, about 2.5 kV or less. There are no strict restrictions on the direction of the electric field. However, from the viewpoint of more preferably exposing the CNTs to a state that can cause FE, it is preferable to apply an electric field in a direction that intersects the tube axis of the CNTs. As a result, it is considered that the energy from the high electric field can be suitably supplied to the CNT aggregate, and the energy can be used for the formation of carbyne without being excessively lost by the FE. For example, when the CNT aggregate is in the form of a sheet, the direction of the electric field is preferably the direction intersecting the surface rather than the direction parallel to the surface, and approaches the direction perpendicular to the surface. is more preferable. Thereby, an electric field can be effectively applied to the entire CNT aggregate.

Although the details are not clear, electrons in the CNT can move smoothly along the tube wall (graphene sheet) with low resistance due to the action of the electric field. Then, in the CNT aggregate, an electron drawing action is exhibited at the portion where the electric field is concentrated. As a result, the bonds of the carbon atoms constituting the CNT are disturbed at the site, and the carbon atoms are arranged one-dimensionally in the center of the inner space of the CNT and form sp bonds to form carbynes. Alternatively, it is thought that vaporization of amorphous carbon contained in the CNT aggregates similarly forms carbynes at the center of the inner space of the CNTs. Note that a discharge phenomenon (dielectric breakdown) is not necessary for field emission. In other words, the electric field may be applied by a non-destructive voltage. However, it is preferable to apply a relatively high voltage to the CNT aggregates for carbyne formation. From this point of view, it is acceptable to cause electric discharge during field emission in order to include more carbyne in the carbyne-containing composite material. In this case, with discharge, the G/D ratio of CNTs in the carbyne-containing composite may decrease as described above. Calvin may be formed inside the CNTs in the vicinity of the field emission of the CNT aggregates. Carbyne is filled in the CNT at a relatively high filling rate of, for example, 30% or more. This allows the carbyne-containing composites disclosed herein to be produced.

Specific examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in such specific examples.

[Test Example 1]
Three types of sheet-like CNT aggregates (hereinafter simply referred to as "CNT sheets") having different G/D ratios were prepared. Specifically, the CNT sheet of Example 1 is a sheet made of SWNT "EC1.5" manufactured by Meijo Nano Carbon Co., Ltd. This EC1.5 is mainly composed of SWNTs produced by the CVD method. The CNT sheet of Example 2 is a sheet made mainly of SWNT manufactured by Meijo Nano Carbon Co., Ltd. by an arc discharge method. The CNT sheet of Example 3 is a "high-purity CNT tape" manufactured by JFE Engineering Corporation. The CNT sheet of Example 3 is a sheet made of MWNT produced by an arc discharge method. All of these CNT sheets are obtained by molding CNT bucky paper into sheets, and none of the sheets contains a binder.

Raman spectroscopic analysis was performed on the prepared CNT sheets of Examples 1 to 3, and the G/D ratio was calculated from the obtained Raman spectrum and shown in Table 1. For Raman spectroscopic analysis, a microscopic Raman spectrometer (inVia Reflex, manufactured by Renishaw) was used, and a laser with a wavelength of 532 nm was used as excitation light. Also, the bulk density of the CNT sheet of each example, the average diameter of the CNTs constituting the sheet, and the thickness of the sheet were measured and shown together. The average diameter of CNTs is the arithmetic mean value of diameters of 10 CNTs measured by observation using a scanning electron microscope (SEM) and TEM. In measuring the diameter, the sheets of Examples 1 and 2 were measured on SWNTs, and the sheet of Example 3 was measured on arbitrary MWNTs. Moreover, the sheet thickness is an arithmetic mean value of thicknesses of three or more points of each CNT sheet measured by cross-sectional observation using SEM.

[Carbyne formation 1]
Next, the CNTs of the CNT sheets of Examples 1 to 3 prepared above were cut into 5 mm squares to obtain measurement samples. Then, the samples of Examples 1 to 3 were placed in a vacuum chamber, and an electric field was applied to cause Field Emission (FE). Specifically, first, the samples of Examples 1 to 3 were fixed to an aluminum holder with silver paste to construct a cathode unit, and placed on a grounded stainless steel stage in the chamber. A voltage was applied between both electrodes with the anode facing parallel to the aluminum holder in the chamber. That is, an electric field was applied in a direction perpendicular to the CNT sheet. The applied voltage was varied between 0 and 2.5 kV until discharge occurred. The pressure in the chamber was set in two ways: (a) about 1×10 ⁻⁵ Pa and (b) about 1×10 ⁻¹ Pa. Insulating ceramic glass was inserted between the electrodes as a spacer to adjust the distance between the electrodes to about 1.6 mm.

[Raman spectroscopic analysis]
The samples of each example after FE were subjected to Raman spectroscopic analysis in the same manner as described above. Note that the Raman spectrum was measured at or near the point where the discharge occurred in the sample of each example. The G/D ratio was calculated from the obtained Raman spectrum and shown in Table 2 below. For reference, Table 2 also shows the initial G/D ratio before FE. Also, when a peak attributed to the LCC band was observed near 1860 cm ⁻¹ , the relative peak intensity of the LCC band with respect to the peak intensity of the G band (LCC/G ratio) was calculated and shown in Table 2. Also, based on this LCC/G ratio, the carbyne filling rate was calculated and shown in Table 2. However, for the sample of Example 3, the Raman spectroscopic analysis was omitted because the FE current itself was not observed when the chamber pressure was about 1×10 ⁻¹ Pa, which was close to normal pressure. As a result of the Raman analysis, the Raman spectrum of the sample of Example 1 obtained is shown in FIG. 3, and the Raman spectra of the samples of Examples 2 and 3 are shown in FIG. In each Raman spectrum, the peak intensity on the vertical axis is adjusted so that the peak intensity of the G band is 1.

[evaluation]
As shown in Table 1, in the Raman spectrum of the initial CNT sheet, CNT-specific D and G bands were observed. I was able to confirm something. From this, it was confirmed that the crystallinity of the CNTs constituting the CNT sheet was higher in the order of Example 1, Example 2, and Example 3.
Moreover, as shown in Table 2, it was found that the G/D ratios of the CNT sheets of Examples 1 and 2 were greatly reduced by the discharge accompanying FE. Since the D band is caused by special vibrations around defects in the crystal structure of CNTs, it was found that the CNT sheets of Examples 1 and 2 had defects introduced into the CNTs by electrical discharge. On the other hand, in the CNT sheet of Example 3, which originally had relatively low crystallinity, the discharge resulted in an increase in the G/D ratio, but the G/D ratio itself was a value close to 1, and the crystallinity was remarkable. No gender change was observed.

Then, for the CNT sheet of Example 1, which has the highest G/D ratio, by discharging with FE, a peak based on the LCC band appears in the Raman spectrum, and the peak based on the LCC band does not appear for the other CNT sheets. was confirmed. From this, it was found that carbynes were formed in the CNTs composed of SWNTs of Example 1. For the CNT sheet of Example 1, the LCC band appeared at both (a) a high vacuum of about 1×10 ⁻⁵ Pa and (b) a low vacuum of about 1×10 ⁻¹ Pa in the chamber pressure. As shown in FIG. 3, the height of the LCC band peak relative to the G band peak (LCC/G ratio) was higher in the (b) low-vacuum FE-discharged sample. Until now, it has been said that carbyne can be produced by heating DWNT to a high temperature in a high vacuum of the order of 10 ⁻⁵ Pa to 10 ⁻⁶ Pa. However, in this test example, it was confirmed that carbyne was produced even at approximately normal pressure of about 1×10 ⁻¹ Pa. In addition, until now, it has been said that carbyne cannot be generated without maintaining stability unless it is in two or more layers of MWNT. However, in this embodiment, it was confirmed that carbyne was also produced in SWNTs.

[Test Example 2]
[Carbyne formation 2]
For the CNT sheet of Example 1 prepared above, (a) under a vacuum condition of about 1×10 ⁻⁵ Pa, a voltage was applied in the same manner as in Test Example 1 to generate FE, and FE was generated before discharge occurred. A discharge-free FE-CNT sheet was prepared by terminating the discharge. Then, Raman spectra were obtained by Raman spectroscopy under the same conditions as above for the three measurement positions a to c shown in FIG. 5A on the prepared FE-CNT sheet. All of the measurement positions a to c are located at the edge of the measurement sample where a part of the CNT sheet is turned up. Although discharge did not occur in the measurement sample of this test example, impurities (e.g. amorphous carbon) heated by the supply of high electric field energy melted and vaporized, and the generated vapor etc. caused part of the surface of the sheet to turn up. It is considered to be The measurement location a is a relatively uniform and flat area of the surface morphology. Measurement positions b and c are raised portions like ridges or walls, and since c appears brighter than b in the SEM image, c is considered to be located higher than the sheet surface. be done. The obtained Raman spectrum is shown in FIG. 5B. The Raman spectrum for each measurement position is shown by adjusting the peak intensity on the vertical axis so that the peak intensity of the G band is 1.

As shown in FIG. 5B, it was found that peaks based on the LCC band were observed at all three Raman-analyzed CNT sheets that were subjected to FE but not discharged. In other words, it turns out that the formation of carbynes is not necessarily triggered by discharge. However, the value of the LCC/G ratio was significantly lower than that of Test Example 1, and the variation was large, and in this test example, the LCC/G ratio was in the range of 0.47 to 1.2. In other words, it was found that the formation of carbyne does not necessarily require discharge, but the discharge creates a situation in which carbyne is likely to be formed. Since the LCC/G ratio increases in the order of measurement positions a, b, and c, it is said that carbynes were formed more easily at positions where the CNT sheet fluctuated more due to the supply of high electric field energy. The three Raman spectra are not significantly different other than the peak heights based on the LCC bands, eg the G/D ratios are not significantly different. From this, it is expected that the destruction of CNTs (increase in defects) due to discharge does not necessarily affect the formation of carbyne. In other words, carbyne is not formed only from the carbon atoms in the defective portion (collapsed portion) of CNT as a carbon source, and it is expected that there is a portion due to the influence of high electric field energy.

[Reference example]
[Starting material]
The CNT sheet of Example 1 used in Test Example 1 was observed with a TEM (CM120, manufactured by PHILIPS). The acceleration voltage of the TEM was set to 80 kV. TEM images obtained as a result are shown in FIGS. Further, for the CNT shown in FIG. 6(A), a line scan was performed in a direction orthogonal to the CNT in the area surrounded by a square in the figure, and the black and white gradation (contrast) of the TEM image was quantified and the gradation was calculated. Line scan analysis processing into profiles was performed. The results are shown in FIG. 6(D).

As a result, the CNTs shown in FIG. 6A were SWNTs composed of a single layer of CNTs. The CNTs shown in (B) were DWNTs in which two different diameter SWNTs were nested. The CNT shown in (C) was a three-layered MWNT in which three SWNTs of different diameters were nested. As shown in FIGS. 6A to 6C, the CNT sheet of Example 1 is mainly composed of (A) SWNT (approximately 70% or more), and partly (B) DWNT and (C) It was confirmed to contain three layers of MWNTs.

In the line scan result of FIG. 6(D), the vertical axis corresponds to the contrast of the TEM image. On the vertical axis, the higher the position, the brighter the corresponding position in the TEM image, and the lower the lower, the darker the corresponding position in the TEM image. As shown in FIG. 6(D), this line scan reveals deep valleys corresponding to the SWNT walls indicated by arrows in FIG. It was confirmed that it was expressed in a mountain shape (hill shape). It was confirmed that the gradation profile was generally flat between the SWNT walls. In the contrast gradation profile of the SWNT TEM image, for example, the difference ΔC The ratio (ΔC _H /ΔC) of the maximum variation ΔC _H of the gradation of the hollow part to the total SWNT, ie, the ratio of the contrast change in the hollow part to the TEM contrast difference of the entire SWNT, was about 0.15. Note that the difference ΔC in gradation between the wall portion and the hollow portion is calculated using a line connecting a pair of points (a1 and b1 in FIG. 6(D)) with the darkest contrast corresponding to the innermost wall as a baseline. , the maximum contrast ΔC, which is the region between this pair of points (a1, b1) and where the distance of the gradation profile from the baseline is maximum. Also, the maximum variation _ΔCH in the gradation of the hollow part is the maximum contrast at which the distance of the gradation profile from the baseline in the region between the pair of points (a1, b1) is the maximum, and The difference between the minimum contrast that minimizes the distance of the gradation profile of . In the case of FIG. 6(D), the set of points (a1, b1) corresponding to the wall are points with scan points of about 1.1 nm and about 3.8 nm. The gradation profile with the furthest distance from the baseline connecting these points is the point where the scan points are about 1.6 nm and about 3.3 nm (the maximum contrast ΔC is both about 8.6 divisions), and the distance is The closest tone profile was at a scan point of about 2.75 nm (minimum contrast of about 7.3 divisions) and their difference ΔC _H was about 1.3 divisions. From these pieces of information, the ratio (ΔC _H /ΔC) is calculated. In the contrast of the CNT TEM image, the boundary between the relatively dark portion corresponding to the tube wall and the relatively bright portion corresponding to the hollow portion is not always clear. Therefore, between the pair of points (a1, b1) corresponding to the innermost tube wall and the peak of the bright part closest to the pair of points (FIG. 6(D), the scan point is The region sandwiched between the maximum points of about 1.6 nm and about 3.3 nm) is conveniently determined to be the portion corresponding to the hollow part of the CNT, and the gradation profile closest to the baseline is a set of these is measured between the maxima of

[Test Example 3]
[Carbyne Formation 3, Carbyne-Containing Composites: SWNT]
Next, the CNT sheet of Example 1 was subjected to plasma generated by a high-frequency voltage, and then under a vacuum condition of about 1×10 ⁻⁵ Pa, a voltage was applied in the same manner as in Test Example 1 to generate FE discharge. caused it. More specifically, after attaching a mask having a predetermined opening to the CNT sheet, reactive ion etching (RIE) was performed to apply plasma to the CNT sheet near the opening of the mask. The conditions for RIE are to apply a high-frequency electric field of 200 W to a reactive gas composed of oxygen (O ₂ ) and argon (Ar) under a reduced pressure atmosphere of 100 Pa to activate the reactive gas, thereby generating radical ions. was used as etching particles to etch the CNT sheet surface. According to the above RIE conditions, the CNT sheet at the openings of the mask is completely eliminated by etching, and reactive plasma can be applied to the CNT sheet near the openings of the mask. Then, the same FE discharge as in Test Example 1 was generated on the CNT sheet after RIE.

SWNTs in the CNT sheet after RIE and FE discharge were observed by TEM, and the results are shown in FIGS. 7A and 7B. Line scan analysis was performed in the direction perpendicular to the SWNTs in the regions indicated by squares in FIGS. 7A and 7B, respectively, and the results are shown in FIGS. 8(A) and 8(B), respectively.

Observation of the SWNTs in FIG. 7A confirmed a faint but deep contrast extending like a streak along the tube axis at the center of the tube wall indicated by arrows a1 and b1. Looking at the gradation profile of FIG. 8A, it was confirmed that one valley was formed in the middle of the positions a1 and b1 corresponding to the pair of tube walls. The grayscale profile confirmed that the diameter of the SWNTs was about 1.9 nm, and the valley in the middle was located approximately at the center (axis) of the SWNTs. Further, for the SWNT in FIG. 7B, intermittent deep contrast along the axis was confirmed at the center of the pair of tube walls indicated by arrows a2 and b2. Also in the gradation profile of FIG. 8B, it was confirmed that one trough was formed in the middle of the positions a2 and b2 corresponding to the tube wall. The grayscale profile confirmed that the diameter of the SWNTs was about 1.4 nm, and the valley in the middle was located approximately at the center (axis) of the SWNTs. From the TEM contrast, what exists in the center of the SWNT is a material composed of light elements. The contrast is also much thinner than the SWNT tube walls. Summarizing the above results, it can be concluded that carbyne, which is a linear carbon allotrope, is formed at the center of SWNTs. It has been said that carbyne is stably formed only in two or more layers of MWNTs. However, in the carbyne-containing composite material disclosed herein, it was confirmed for the first time that carbyne is formed inside SWNTs.

Based on (A) of FIG. 8, the ratio (ΔC _H /ΔC), which is calculated as the contrast change in the hollow portion with respect to the TEM contrast difference of the entire SWNT, is about 0.34. The calculated ratio (ΔC _H /ΔC) was approximately 0.35. Due to the presence of carbyne, for example, the contrast of the hollow part of the CNT in the TEM image clearly changes to dark.

[Carbyne-containing composite material: DWNT]
Two DWNTs found in the prepared CNT sheet after RIE and FE discharge were similarly observed by TEM, and the results are shown in FIGS. 9(A) and 9(B). Line scan analysis was performed in the direction perpendicular to the DWNT in the regions indicated by squares in FIGS. 9A and 9B, respectively, and the results are shown in FIGS. 10A and 10B, respectively.

In FIG. 9(A), the inner tube walls of DWNT are indicated by arrows a1 and b1. Observation of FIG. 9(A) confirmed a dark contrast extending like a streak near the center of the tube wall, although it was also faint. In the DWNT greyscale profile of FIG. 10(A), the double tube walls corresponding to the two layers of CNTs were clearly observed as two pairs of deep valleys. It was also confirmed that one trough was formed near the center of the pair of inner tube walls indicated by arrows a1 and b1. The greyscale profile confirms that the diameter of the inner tube of the DWNT is on the order of about 1.2 nm, with the middle valley approximately centered. Further, in the DWNT of FIG. 9(B), intermittent deep contrast along the axial direction was confirmed at the center of the pair of inner tube walls indicated by arrows a2 and b2. Also in the gradation profile of FIG. 10B, it was confirmed that one trough was formed in the middle of the positions a2 and b2 corresponding to the inner tube wall. The gradation profile confirmed that the diameter of the inner tube of the DWNT was about 1.4 nm, and the valley in the middle appeared slightly off-center. The TEM contrast suggests that the material present in the DWNT tube is composed of light elements. Also, the contrast is much thinner than the SWNT tube wall observed in the same field of view of the TEM image. Based on the above results, it can be concluded that in the carbyne-containing composite material disclosed herein, carbyne, which is a linear carbon allotrope, is also formed in the DWNT tube.

Based on (A) of FIG. 10, the ratio (ΔC _H /ΔC), which is calculated as the contrast change in the hollow portion with respect to the TEM contrast difference of the entire DWNT, is about 0.19. The calculated ratio (ΔC _H /ΔC) was approximately 0.17. The ratio (ΔC _H /ΔC) was slightly smaller due to the observed high wall contrast due to the double walls of DWNTs. It can be said that the contrast ratio (ΔC _H /ΔC) of the part is, for example, 0.16 or more, typically 0.17 or more.

[Carbyne-containing composite material: MWNT]
Furthermore, the results of similar TEM observation of the three-layer MWNTs found in the prepared CNT sheets after RIE and FE discharge are shown in FIG. 11(A) and shown by squares in FIG. FIG. 11B shows the results of line scan analysis performed in the region in the direction orthogonal to the CNTs.
FIG. 11(A) shows a three-layered CNT, and the innermost tube walls are indicated by arrows a1 and b1. In FIG. 11(A), a streak-like deep contrast was clearly confirmed in the middle of the three pairs of tube walls. In the MWNT gradation profile of FIG. 11(B), the triple tube walls corresponding to the three-layered CNTs could be identified as approximately three pairs of valleys. It was also confirmed that one deep valley was formed near the center of the innermost pair of tube walls indicated by arrows a1 and b1. The gradation profile confirms that the diameter of the inner tube of the three-walled CNT is about 0.8 nm, and the middle valley is located almost at its center. From the above results, it can be said that in the carbyne-containing composite material disclosed herein, carbyne, which is a linear carbon allotrope, is formed also in the three-walled CNT tube. Note that the ratio (ΔC _H /ΔC) calculated based on FIG. 11B was about 0.63.

[Carbyne-containing composite material: multiple carbynes]
Furthermore, FIG. 12(A) shows the results of similar TEM observation of the DWNTs found in the CNT sheet after RIE and FE discharge. FIG. 12(B) shows the results of line scan analysis performed in the direction orthogonal to the CNTs in the regions indicated by squares in FIG. 12(A).
FIG. 12(A) shows a bent DWNT, with a pair of inner tube walls indicated by arrows a1 and b1. In this DWNT, about three streaks of bright contrast were confirmed between the inner pair of tube walls. Therefore, when the gradation profile of FIG. 12(B) was checked, it was confirmed that two troughs were formed between positions a1 and b1 corresponding to the inner tube wall. That is, it is considered that the three bright contrast lines in the TEM image appeared due to the formation of two dark contrast lines. From the gradation profile, it is confirmed that the diameter of the inner tube of DWNT is about 1.5 nm, and the two inner troughs are about 0.43 nm apart and appear at the approximate center position of the inner tube. was done. The TEM contrast suggests that the material present in the DWNT tube is composed of light elements. Also, the contrast is much thinner than the SWNT tube wall observed in the same field of view of the TEM image. From these, it was confirmed that in the carbyne-containing composite material disclosed herein, multiple carbynes, which are linear carbon allotropes, can be stably formed in the CNT. Moreover, from this result, it is expected that when the arrangement of carbynes deviates from the center of the innermost CNT, a plurality of carbynes are formed within the CNT, although this is difficult to observe with a TEM.

Although the carbyne-containing composite material according to one embodiment of the present invention has been described above, the carbyne-containing composite material according to the present invention is not limited to the above-described embodiment, and various modifications are possible.

Claims (5)

a carbon nanotube assembly formed by assembling a plurality of carbon nanotubes;
Calvin and
including
The carbyne is filled in 30% or more of the plurality of carbon nanotubes ,
A carbyne-containing composite material , wherein the carbon nanotubes encapsulating carbyne include 10% or more of single-walled carbon nanotubes .
The carbyne filling rate F in the carbon nanotube is determined by the relative intensity _ILCC/G* of the LCC band to the G band of the carbyne-encapsulated carbon nanotube with a filling rate of 100% and the LCC band to the G band of the carbyne-containing composite material. It is calculated based on the following formula from the relative intensity _ILCC/G .
F (%)= _ILCC/G / _ILCC/G* ×100 In the Raman spectrum measured by Raman spectroscopy,
When the intensity of the peak based on the G band is 1,
2. The carbyne-containing composite material of claim 1, wherein the relative intensity of peaks based on LCC bands is 0.4 or greater. 3. The carbyne-containing composite material according to claim 1 , wherein at least part of said carbon nanotube encloses two or more said carbynes in a direction perpendicular to the axial direction of said carbon nanotube. An article comprising a carbyne-containing composite material according to any one of claims 1-3 . preparing a carbon nanotube aggregate having a G/D ratio of 25 or more, which is formed by assembling a plurality of carbon nanotubes;
applying a voltage that causes at least field electron emission to the aggregate of carbon nanotubes;
including
The method for producing a carbyne-containing composite material, wherein the carbon nanotubes contain 10% or more of single-walled carbon nanotubes .

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