KR101956920B1 - A carbon hybrid structure comprising a graphene layer and hollow carbon tubes - Google Patents

Abstract

At least one graphene layer and a hollow carbon tube, wherein the end of the hollow carbon tube is bonded to at least one graphene layer. A method of making a carbon hybrid structure includes: (a) heating a substrate comprising a catalyst layer; (b) supplying a carbon source gas to the heated substrate in the presence of water; (c) forming a graphene layer in response to the gas supply; (d) generating a hollow carbon tube on the graphene layer by increasing the amount of gas supplied; And (e) cooling the substrate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a carbon hybrid structure including a graphene layer and a hollow carbon tube,

This disclosure relates to carbon hybrid structures, their various applications, and the fabrication of carbon hybrid structures.

Recent years have attracted a lot of scientific interest due to their useful properties such as sp ² hybridized carbon structures such as fullerene, carbon nanotubes (CNT) and graphene retained by their structure. Fullerene is an example of a zero-dimensional system, CNT is an example of a one-dimensional system, and graphene is an example of a two-dimensional system of sp ² hybridized carbon.

 CNT is an example of a unique one-dimensional system. Vertically oriented carbon nanotube forests grown by catalytic chemical vapor deposition (CVD) have received considerable attention due to their suitability in many important technical applications. CNT showed excellent thermal conductivity at room temperature, while graphene showed excellent thermal conductivity at room temperature. While graphene is a quasi-2-dimensional (2D) material. Graphene has attracted great interest due to its unique band structure and physical properties. Besides electrical and mechanical properties, these materials have excellent thermal properties.

However, despite the advantages of these CNTs and graphene materials, each of these also has disadvantages and limitations. CNT can transport phonons and electrons only in one dimension (along its length), while graphene can transport phonons and electrons only in two dimensions only along its bottom surface. Thus, it would be desirable to have a single carbon hybrid structure that could have the advantages of both a one-dimensional nature of CNT and a two-dimensional nature of graphene.

It is an object of the present invention to provide a new carbon hybrid structure with improved electrical and thermal properties while maintaining the advantages of each material. CNTs can transport phonons and electrons only in one dimension (along their length), while graphenes can transport phonons and electrons only in two dimensions only along its basal plane.

The present disclosure relates to a carbon hybrid structure comprising at least one graphene layer and a hollow carbon tube, wherein the end of the hollow carbon tube is bonded to at least one graphene layer. In some embodiments, the hollow carbon tube comprises carbon nanotubes. The present disclosure also relates to a method of making a carbon hybrid structure and to a method of manufacturing the same, including but not limited to a Li-ion secondary cell, a hydrogen-storage device, a supercapacitor, a solar cell, And to various applications.

According to one aspect of the present disclosure, the carbon hybrid structure is composed of CNTs and graphenes, and enables transport of phonons, heat, and electrons in three dimensions.

According to some aspects of the present disclosure, the carbon hybrid structure may comprise a sub-structure comprising a hollow carbon tube interposed between two graphene layers and two graphene layers. In one aspect of the disclosure, the length of the sub-structure may be in the range of 100 nm to 10 mm, and more specifically, 150 to 1000 nm.

In some embodiments, the length of the CNT is 100 nm to 5 mm, more specifically 200 nm to 2 mm, which may vary depending on various factors including the size of the substrate used in the synthesis. The area of the graphene layer is from about 1 μm ² to 1 mm ² , and in some embodiments, the area may be from 25 μm ² to 25000 mm ² . The number of graphene layer (s) is 1 to 100.

In another embodiment, the disclosure is directed to a method of making a carbon hybrid structure comprising: (a) heating a substrate comprising a catalyst layer; (b) supplying a carbon source gas to the heated substrate in the presence of water; (c) forming a graphene layer in response to the gas supply; (d) generating a hollow carbon tube on the graphene layer by increasing the amount of gas supplied; And (e) cooling the substrate. In some embodiments, the carbon source gas is supplied during step (a) above. In another embodiment, during step (c), water is present in the form of a vapor. In another embodiment, the substrate is heated to 500 to 1000 占 폚 during step (a), or alternatively to 700 to 950 占 폚.

In some embodiments, the method of making the carbon hybrid structure further comprises the steps of (d ') reducing the amount of gas supplied prior to cooling the substrate and, in response, creating a graphene layer on the end of the hollow carbon tube . In some embodiments, the method comprises the steps of: (d) creating a hollow carbon tube on the graphene layer by increasing the amount of gas supplied, and (d ') reducing the amount of gas supplied before cooling the substrate. One or more iterations.

In some embodiments, the carbon supply source gas is C _{1 -10} alkane, C _{2 -10} alkylene, C _{2 -10} alkenylene, and at least one hydrocarbon selected from the group consisting of aromatic, or methane, ethylene, acetylene, or benzene ≪ / RTI >

In some embodiments, the catalyst layer comprises a transition metal, such as, but not limited to, iron. In some embodiments, the thickness of the catalyst layer may be less than 20 nm, less than 15 nm, or less than 12 nm. In some embodiments, the thickness of the catalyst layer may be greater than 8 nm, greater than 9 nm, or greater than 10 nm.

In some embodiments, carbon hybrid structures are utilized in a variety of applications including, but not limited to, electrode compositions, Li-ion secondary batteries, hydrogen-storage devices, supercapacitors, thermal dissipation stages for integrated chips, and the like.

The examples will now be described with reference to the various embodiments shown in the accompanying drawings in detail. In this detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. However, it will be apparent to one of ordinary skill in the art that the present disclosure can be practiced without these specific details. In other instances, well-known methods, procedures, systems, and elements have not been described in detail so as not to unnecessarily obscure aspects of various embodiments.

In the present specification, pluralities and singularities are used interchangeably. It is therefore to be understood that the plural includes also the singular and vice versa.

In addition to a variety of thermal, electrical, and mechanical properties, carbon hybrid structures can be configured to utilize specific thermal properties, wide specific surface area, and inherent capacitance properties, as disclosed herein.

Graphene comprises polycyclic aromatic molecules in which a plurality of carbon atoms are covalently bonded together to form a fused polycyclic structure. Covalently bonded carbon atoms not only can form a 6-membered ring in repeated units, but also have ring structures with other numbers of configurations, such that the carbon atoms can also form a 5-membered ring and / or 7-membered ring It is possible. Thus, in graphene, covalently bonded carbon atoms can form a single layer (usually with sp ² bonds). Graphene can be any one of a variety of structures, for example, a three-dimensional configuration such as a spherical or cylindrical configuration. Other structures may also be possible. If the graphene has an extended two-dimensional structure, the graphene is referred to herein as a graphene sheet. The carbon hybrid structure of the present disclosure may include such a graphene sheet and may also include a plurality of sheets having a total thickness of about 100 nm or less. Generally, the lateral edges (edges) of graphene can be saturated with hydrogen atoms that are end or edge-terminating atoms.

Carbon nanotubes (CNTs) include nanotubes that are members of a fullerene structure family that also includes spherical buckyballs, and the ends of the nanotubes can be capped with a hemisphere of a buckyball structure. The nanotubes may be single-walled nanotubes (SWNTs) or multi-walled nanotubes (MWNTs). In some embodiments, the carbon hybrid structure comprises a sub-structure comprising a hollow carbon tube interposed between two graphene layers and two graphene layers. This sub-structure provides a number of different advantages that can exploit its sp ² hybridized carbon properties. For example, a CNT can only transport phonons and electrons in one dimension (along its length) and graphene can transport phonons and electrons in only two dimensions (along its basal plane) , The hybrid structure can transport phonons (heat) and electrons (electrons) three-dimensionally. Carbon hybrid structures possess unique properties that are a combination of their elements, i.e., properties from CNT and graphene.

In some embodiments, the thickness of each graphene layer may vary depending on its use and may range from about 0.1 to about 100 nm, from about 0.1 to about 20 nm, from about 0.1 to about 10 nm, or continuously thinner about 0.1 To about 5 nm. The thickness of the monolayered graphene is about 0.1 nm; The thickness of the sub-structure may be in the range of 100 nm to 10 mm, more specifically 150 to 1000 nm. The carbon hybrid structure may have any shape, for example, spherical, cubical, oval or the like, as long as it includes at least one graphene layer to which the ends of the carbon tube and the carbon tube are bonded.

In some embodiments, the carbon hybrid structure comprises more than one graphene layer. The number of graphene layers may be from 1 to 100, less than 80, less than 50, or from 1 to 10.

Another aspect of the disclosure includes a method of making a carbon hybrid structure.

Methods for producing graphene materials are classified into a micromechanical method and a SiC thermal cracking method. According to a micromechanical method, a graphene sheet separated from graphite can be prepared by attaching a graphite sample to a tape at the surface of a SCOTCH ^TM tape (purchased from 3M Corporation) and separating it from the tape. In this case, the separated graphene sheet does not include a uniform number of layers and has no uniformly peeled portion. In another method using silicon carbide (SiC) thermal decomposition, SiC single crystals are heated to decompose SiC at their surface to remove Si, and then the remaining carbon C forms a graphene sheet. However, SiC single crystals, which are the starting material in SiC thermal decomposition, are very expensive and can not easily produce wide-area graphene sheets.

Several techniques have been developed to produce significant amounts of carbon tubes, including arc discharge, laser welding, high pressure carbon monoxide (HiPco) and chemical vapor deposition (CVD). Most of these processes are carried out in vacuum or using process gases. According to arc discharge techniques, carbon tubes such as CNTs were produced as carbon soot of graphite electrodes during arc discharge by using electron currents. In this case, the yield is 30 wt% or less, producing both single- and multi-wall nanotubes with little structural defects. In another method using a laser ablation process, a pulsed laser vaporizes a graphite target in a high temperature reactor as the inert gas is introduced into the chamber, the process yields an adjustable diameter < RTI ID = 0.0 >Lt; RTI ID = 0.0 > single-walled < / RTI > However, it costs more than other methods. Thus, the most common method of making a carbon tube is chemical vapor deposition (CVD), which is a technique for depositing a thin solid film on a substrate from a vapor species through a chemical reaction, because of its price / unit ratio, Although it must be collected with other growth technologies, CVD is most promising as an industrial-scale deposition method because it can grow nanotubes directly on the desired substrate. Chemical reactions play an important role and are therefore one of the unique features possessed by CVD compared to other film deposition techniques.

In some embodiments, carbon hybrid structures are fabricated by CVD techniques.

Figure 1 shows a schematic view of a tube-furnace CVD system for CNT and graphene growth. It consists of a gas transport system, a reactor (5) and a degassing system. During the CVD process, the reactive gas species is introduced into the reactor 5 in a uniformly variable manner before entry into the reactor 5, with the requisite valve 1, pressure regulating valve 3, mass flow regulator 4 (MFC) Is introduced into the reactor by a gas delivery system consisting of a gas-mixing unit responsible for mixing the gas. The reactor is where the chemical reaction takes place and where the solid material is deposited on the substrate during the reaction step. The heater 2 surrounds the reactor to raise the temperature of the reaction. Eventually, the byproducts of the reaction and the non-reacting gas are constituted by one or more pumps, and are removed by an unnecessary gas transport system for CVD not operating in vacuum conditions.

A carbon hybrid structure having one of a variety of three-dimensional configurations can be formed by forming graphene from a carbon source by: (a) heating a substrate comprising a catalyst layer; (b) supplying a carbon source gas to the heated substrate in the presence of water; (c) forming a graphene layer in response to the gas supply; (d) creating a hollow carbon tube on the graphene layer by increasing the amount of gas supplied, and (e) cooling the substrate. In some embodiments, prior to cooling the substrate, the amount of gas supplied is reduced and, in response, a graphene layer is formed on the end of the hollow carbon tube.

To form one or more sub-structures comprising a hollow carbon tube sandwiched between two graphene layers and two graphene layers, (d) forming a hollow carbon tube And (d ') reducing the amount of gas supplied before cooling the substrate is repeated at least once.

In the production of carbon hybrid structures, a substrate comprising a catalyst layer is used. Any substrate known in the art, such as silicon oxide, may be used. As the catalyst layer used in the production of carbon hybrid structures, any suitable catalyst used for synthesizing graphite, inducing carbonization, or producing carbon nanotubes can be used. In some embodiments, the catalyst layer may be derived from one or more transition metals, such as Fe, but other transition metals, including, but not limited to, Ti, V, Cr, Mn, and Cu may be selected.

In other embodiments, the thickness of the catalyst layer may be less than 20 nm, less than 15 nm, or less than 12 nm. The thickness of the catalyst layer may also be greater than 10 nm, greater than 8 nm, or greater than 9 nm. However, other thicknesses are possible. If the catalyst layer is thicker than 20 nm, the desired hybrid structure can not be easily obtained on the substrate.

In the described process, the flow rate of the carbon supply source gas to be used may be from 50 to 500 cm ³ / min, of 100 to 500 cm ³ / min, 200 to 500 cm ³ / min, or 400 cm ³ / min. In some embodiments, the carbon source gas is supplied during step (a) at a flow rate of 10 to 100 cm ³ / min, 20 to 80 cm ³ / min, 30 to 70 cm ³ / min, or 50 cm ³ / min . However, other flow rates are possible.

During at least a portion of the described method of making the carbon hybrid structure, an inert gas such as nitrogen, argon, helium, etc. may be supplied to the CVD chamber along with the carbon source gas. The flow rate of the inert gas used can be adjusted according to various factors such as the size of the CVD chamber, CVD dimensions, and the like. In a specific embodiment, the flow rate of the inert gas used may be from 300 to 800 cm ³ / min, from 400 to 700 cm ³ / min, from 500 to 600 cm ³ / min, or from 500 cm ³ / min.

During at least some stages of the method of making the described carbon hybrid structure, the deposition is generally carried out in the presence of water. Water is typically water vapor and nitrogen, argon, is supplied with a mixture of an inert gas such as helium, which is 100 to 200 cm ³ / min for flow rate of the inert gas (carrier), 150 to 200 cm ³ / min, 180 to 200 cm ³ / min, or 180 cm < ³ > / min. However, other mixtures are possible. In some embodiments, the supply of water vapor occurs during both steps (a) and (b).

Any carbon source known in the art may be used. Hydrocarbon species are typically used as precursors to graphene growth. The carbon source includes, but is not limited to, one or more hydrocarbons selected from the group consisting of C _{1 -10} alkanes, C _{2 -10} alkylenes, C _{2 -10} alkenylene, and aromatics. In some embodiments, the carbon source is methane, ethylene, acetylene, or benzene. CH ₄ is one commonly used precursor because it has a relatively stable (i.e., low thermal decomposition rate) simple atomic structure at high temperatures (e.g., 800-1000 ° C for most graphene growth). Hydrocarbons having very high thermal decomposition rates at high temperatures and causing large amounts of carbon deposition may be undesirable for sub-nanometer graphene. In some embodiments, the carbon source gas is also supplied during step (a).

In other aspects of the present disclosure, the carbon hybrid structures may be used in various applications, including, but not limited to, supercapacitors for high surface area, high electron mobility and high thermal conductivity, high hydrogen storage capacity devices, New electronic devices, and the like.

In some embodiments, a membrane comprising a carbon hybrid structure is utilized in such an electronic device. The film of graphite nanostructures uses the flat geometry of the graphene portion of the carbon hybrid structure, which is easily integrated into the device structure, making its applicability to various devices convenient and / or improved.

In another embodiment, an electrode composition comprising a carbon hybrid structure is utilized in a variety of electronic devices. Still further, another embodiment includes a Li-ion secondary battery comprising an electrode composition comprising a carbon hybrid structure. The hybrid structure of the present invention can be useful for applications such as electrodes for Li-ion batteries due to its large surface area, and improves interface contact and high specific capacitance. Additionally, graphene / CNT hybridization can be used with inorganic materials to form a composite material for improved cyclic stability and capacity of the anode material. In view of this advantage of the carbon hybrid structure according to the present disclosure, the use of the carbon hybrid structure in the electrode composition for the Li-ion secondary battery is described.

In yet another embodiment, the carbon hybrid structures described can be utilized in a hydrogen-storage device. Hydrogen storage media is a system for storing hydrogen that is an environmentally clean energy source for convenient and economical use. Because of the large surface area and stable physical properties of graphite nanostructures, hydrogen-storage devices are able to store more hydrogen and are more stable than conventional methods.

In yet another embodiment, the supercapacitor may comprise the carbon hybrid structure described. The carbon hybrid structures of the present disclosure exhibit pseudo-capacitance effects such as large surface area, high porosity, and excellent properties such as no or reduced fine holes, redox charge transfer, etc., Can be used as an electrode material in supercapacitors at a lower cost than CNT materials.

In yet another embodiment, this disclosure is directed to a thermal dissipation stage for an integrated chip comprising a carbon hybrid structure according to the present disclosure. Heat removal from devices and device elements, such as, but not limited to, reduced electronic devices, integrated circuits, high-output electronic devices, luminescent optical devices, or high speed electronic or optoelectronic devices, This is a problem. Graphene in the above-described carbon hybrid structure is characterized by an extremely high thermal conductivity, which can be utilized for better thermal management of electronic and optoelectronic devices and circuits, and can be used to reduce power consumption.

By using carbon hybrid structures according to various disclosures, it is possible to have a more economical manufacturing method, capable of transporting phonons (heat) and electrons (electrons) in three dimensions, and improving electrical and thermal properties, It is possible to fabricate a new carbon hybrid structure that brings performance stability.

1 schematically illustrates an apparatus for chemical vapor deposition (CVD), in accordance with some embodiments.
Figure 2 schematically illustrates the formation of graphene on a substrate, in accordance with some embodiments.
FIG. 3 is an overview of a synthetic reaction scheme for producing a carbon hybrid structure using chemical vapor deposition techniques, in accordance with some embodiments.
Figure 4 graphically illustrates the results of Raman spectroscopic analysis on carbon hybrid structures, in accordance with some embodiments.
Figure 5 shows a scanning electron microscope (SEM) image of a carbon hybrid structure, according to some embodiments.
Figure 6 shows a TEM image of a single structural unit of a carbon hybrid structure (scale size is 10 nm), in accordance with some embodiments.
7 schematically illustrates a thermal spreading system for an integrated circuit comprising a carbon hybrid structure, in accordance with some embodiments.

The following examples are provided for illustrative purposes only and are not intended to limit the scope of the present disclosure.

Where the disclosure of the references cited herein below conflicts with the description of this disclosure to the extent that the terms obscure, the present disclosure will prevail.

Example  One

Substrate Manufacturing

As shown in FIG. 2, a chemically clean 500 μm thick n-type Si (100) wafer with a 300 nm SiO ₂ layer was deposited by e-beam deposition at a rate of 0.1 Å / Layer was used to deposit. The deposition rate was monitored using a quartz crystal sensor fixed inside the e-beam deposition chamber. The e-beam deposition chamber was evacuated to ~ 3 × 10 ^-6 Torr prior to deposition. The substrate was removed from the deposition chamber and cut into several equal-sized pieces for CNT-graphene growth using water assisted (WA) -CVD.

Heating and graphite nano-structure formation

Details of the conventional WA-CVD method are described in SP Patole et < RTI ID = 0.0 &gt; et &lt; al . Carbon 46, 1987 (2008). After sample loading, the CVD chamber was evacuated to &lt; 0.01 Torr. Ar, H ₂ O vapor and C ₂ H ₂ were injected into the CVD reactor at room temperature. A fast thermal heating system was used to reach 800 [deg.] C temperature in 1 minute and additional graphene growth was performed for 1 minute at 1.9 Torr (as shown in FIG. 2). By increasing the acetylene feedstock, the growth pressure was increased further to 2.42 Torr and CNT growth was performed for an additional 1 minute, as shown in step (a) of FIG. Decreasing the reactor pressure by lowering the acetylene feedstock again caused graphene growth (shown in step (b) of FIG. 3) beneath the CNT and substrate. Repeated CNT and graphene growth by varying the reactor pressure resulted in a laminate structure (shown in step (c) of FIG. 3). The film of the carbon hybrid structure can be detached from the substrate and used for further applications.

Example  2

Confirmation of property

The carbon hybrid structure obtained in Example 1 was confirmed by Raman spectroscopy to confirm formation of graphene and CNT as shown in Fig. Various literature in this field, for example, MS Dresselhaus, et al . , Physics Reports (2005) 409: 47-99], Figure 4 showed characteristic peaks of the sp ² hybridized carbon, i.e. G, D, and 2D bands of the graphene-CNT laminate structure. As a result of Raman spectroscopy, it was clearly confirmed in Example 1 that a hybrid structure of graphene and CNT was generated.

In order to further investigate the physical structure of the carbon hybrid structure obtained in Example 1, a scanning electron microscope (SEM) and a transmission electron microscope (TEM) were used and as shown in FIGS. 5 and 6, Several SEM / TEM images were obtained. Figure 5 shows an SEM image of the graphene layer according to the present disclosure, which is deposited on an Fe-coated Si substrate, in which the CNT is attached to the bottom of the graphene and the graphene is spread horizontally on the CNT, Were identified in SEM images standing perpendicular to the substrate. Figure 6 is an enlarged TEM image of the carbon hybrid structure showing the junction between the CNT and the graphene portion.

The new structure consists of vertically aligned CNTs connected to graphenes at the top and / or bottom. While the CNT is capable of transporting phonons and electrons in only one dimension (along its length) and graphene can transport phonons and electrons in only two dimensions (along its basal plane), the hybrid structure of the present invention Phonons (heat) and electrons (electrons) can be transported in three dimensions, which can lead to better conductivity.

It is to be understood that the present disclosure has been described in connection with what is considered the most feasible embodiment and that the disclosure is not limited to the embodiments described. The subject matter described herein may be embodied in various other forms or in various combinations; In addition, various omissions, substitutions, combinations, and conversions in the form of the various embodiments described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of this disclosure.

Claims (18)

delete delete delete delete (a) heating a substrate comprising a catalyst layer;
(b) supplying a carbon source gas to the heated substrate in the presence of water;
(c) forming a graphene layer in response to the gas supply;
(d) generating a hollow carbon tube on the graphene layer by increasing the amount of gas supplied, and
(e) cooling the substrate
Lt; / RTI &gt;
(d ') reducing the amount of gas supplied prior to cooling the substrate and, in response, creating a graphene layer on the end of the hollow carbon tube,
(d) generating a hollow carbon tube on the graphene layer by increasing the amount of gas supplied, and (d ') reducing the amount of gas supplied before cooling the substrate, Including,
At least one graphene layer and a hollow carbon tube, wherein the end of the hollow carbon tube is bonded to at least one graphene layer. delete delete The method according to claim 5, wherein the carbon-supplying gas is supplied while heating the substrate including the catalyst layer. The method of claim 5, wherein the carbon supply source, which method comprises at least one hydrocarbon gas is selected from C _{1 -10} alkane, C _{2 -10} alkylene, C _{2 -10} alkenylene, and the group consisting of aromatic. 6. The method of claim 5 wherein the carbon source gas comprises one of the group consisting of methane, ethylene, acetylene or benzene. 6. The method of claim 5, wherein the catalyst layer comprises a transition metal. 12. The method of claim 11, wherein the transition metal is Fe. delete delete delete delete delete delete

Images