KR20130138568A - A carbon hybrid structure comprising a graphene layer and hollow carbon tubes - Google Patents

Abstract

Disclosed is a carbon hybrid structure which includes at least one graphene layer and hollow carbon tubes, wherein the end of the hollow carbon tubes is combined with at least one graphene layer. A manufacturing method of the carbon hybrid structure includes: a step of heating a substrate including a catalyst layer; a step of supplying gas to the heated substrate under water, wherein the gas is a gas supply source; a step of forming the graphene layer in corresponding to gas supply; a step of creating the hollow carbon tubes on the graphene layer by increasing the amount of gas: and a step of cooling the substrate.

Description

Carbon hybrid structure comprising graphene layer and hollow carbon tube {A CARBON HYBRID STRUCTURE COMPRISING A GRAPHENE LAYER AND HOLLOW CARBON TUBES}

The present disclosure relates to carbon hybrid structures, their various applications, and the manufacture of carbon hybrid structures.

In recent years, sp ² hybridized carbon structures such as fullerene, carbon nanotubes (CNT) and graphene have attracted much scientific interest because of the useful properties retained by their structures. Fullerene is an example of a 0-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.

 CNTs are examples of unique one-dimensional systems. Vertically oriented carbon nanotube forests grown by catalytic chemical vapor deposition (CVD) have received enormous attention due to their suitability in increasingly important technical applications. CNTs showed excellent thermal conductivity at room temperature, while graphene showed good thermal conductivity at room temperature. Graphene, on the other hand, is a quasi-2-dimensional (2D) material. Graphene has attracted great attention because of its unique band structure and physical properties. In addition to electrical and mechanical properties, these materials have excellent thermal properties.

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

It is an object of the present invention to provide new carbon hybrid structures having more economically 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 graphene can transport phonons and electrons only in two dimensions along its base.

The present disclosure relates to a carbon hybrid structure comprising at least one graphene layer and a hollow carbon tube, wherein the ends of the hollow carbon tube are bonded to at least one graphene layer. In some embodiments, the hollow carbon tube comprises carbon nanotubes. The present disclosure also provides methods of making carbon hybrid structures, and heat dissipation stages for, but not limited to, Li-ion secondary cells, hydrogen-storage devices, super capacitors, solar cells, and integrated chips. Relates to various applications.

According to one aspect of the present disclosure, the carbon hybrid structure consists of CNTs and graphene 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 two graphene layers and a hollow carbon tube interposed between the two graphene layers. In one aspect of the present disclosure, the length of the sub-structures is in the range of 100 nm to 10 mm, more specifically 150 to 1000 nm.

In some embodiments, the length of the CNTs 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 for the synthesis. The area of the graphene layer is about 1 μm ² to 1 mm ² , and in some embodiments, the area may be 25 μm ² to 25000 mm ² . The number of graphene layer (s) is 1-100.

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

In some embodiments, the method of making a carbon hybrid structure further includes (d ') reducing the amount of gas supplied before cooling the substrate, and in response, creating a graphene layer on the end of the hollow carbon tube. Include. In some embodiments, the method comprises the steps of (d) increasing the supply amount of gas, thereby creating a hollow carbon tube on the graphene layer and (d ') reducing the supply amount of gas prior to cooling the substrate. It further comprises one or more repetitions.

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 At least one hydrocarbon from the group consisting of:

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, the carbon hybrid structure is utilized in a variety of applications including, but not limited to, electrode compositions, Li-ion secondary cells, hydrogen-storage devices, supercapacitors, heat dissipation stages for integrated chips, and the like.

The example will now be described with reference to the various embodiments shown in the accompanying drawings. 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 skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well known methods, procedures, systems, and elements are not described in detail so as not to unnecessarily obscure aspects of the various embodiments.

In this description, plural and singular are used interchangeably. Thus, it should be understood that the plural also includes the singular and vice versa.

In addition to various thermal, electrical and mechanical properties, the carbon hybrid structure can be configured to utilize unique thermal properties, wide specific surface area, and inherent capacitive properties, as disclosed herein.

Graphene includes polycyclic aromatic molecules in which a plurality of carbon atoms are covalently bonded to each other to form an expanded and fused polycyclic structure. Covalently bonded carbon atoms can not only form 6-membered rings in repeating units, but also have rings of other numbers, such as carbon atoms can also form 5-membered and / or 7-membered rings. It is possible. Thus, in graphene, covalently bonded carbon atoms can form a single layer (typically 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 graphene has an expanded two-dimensional structure, graphene is referred to herein as graphene sheets. The carbon hybrid structure of the present disclosure may include such graphene sheets and may also include a plurality of sheets having a total thickness of about 100 nm or less. In general, the side ends (edges) of graphene may be saturated with hydrogen atoms that are end or edge-terminated atoms.

Carbon nanotubes (CNTs) include nanotubes that are members of the fullerene structure family, which also includes spherical buckyballs, and the ends of the nanotubes can be capped with hemispheres of the buckyball structure. The nanotubes can be single-walled nanotubes (SWNTs) or multi-walled nanotubes (MWNTs). In some embodiments, the carbon hybrid structure includes a sub-structure comprising two graphene layers and a hollow carbon tube interposed between the two graphene layers. This sub-structure provides many various advantages that can exploit its sp ² hybridized carbon properties. For example, CNTs can transport phonons and electrons only in one dimension (along their length) and graphene can transport phonons and electrons only along two dimensions (along their base). The hybrid structure can transport phonons (thermal) and electrons (electric) in three dimensions. The carbon hybrid structure possesses unique properties that are combinations of properties from its elements, namely CNTs and graphene.

In some embodiments, the thickness of each graphene layer can vary depending on its use and can be about 0.1 to about 100 nm, about 0.1 to about 20 nm, about 0.1 to about 10 nm, or still thinner about 0.1. To about 5 nm. The thickness of the single layered graphene is about 0.1 nm; The thickness of the sub-structures is in the range of 100 nm to 10 mm, more specifically 150 to 1000 nm. The carbon hybrid structure may have any shape, such as, for example, spherical, cubic, oval, etc., as long as it includes a carbon tube and one or more graphene layers to which the ends of the carbon tube are bonded.

In some embodiments, the carbon hybrid structure includes more than one graphene layer. The number of graphene layers can be 1 to 100, less than 80, less than 50, or 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 micromechanical methods and SiC thermal decomposition methods. According to the micromechanical method, graphene sheets separated from graphite can be prepared by attaching a graphite sample to the tape at the surface of a SCOTCH ^™ tape (purchased from 3M Corporation) and detaching from the tape. In this case, the separated graphene sheets do not contain a uniform number of layers and do not have a uniform shaped strip. In another method using silicon carbide (SiC) thermal decomposition, SiC single crystals are heated to decompose SiC at their surface to remove Si, after which the remaining carbon C forms a graphene sheet. However, SiC single crystals, which are the starting material for SiC thermal decomposition, are very expensive and do not readily produce wide-area graphene sheets.

In order to produce significant amounts of carbon tubes, several techniques have been developed, including arc discharge, laser ablation, high pressure carbon monoxide (HiPco) and chemical vapor deposition (CVD). Most of these processes are carried out in vacuo or using a process gas. According to the arc discharge technique, a carbon tube such as CNT was created with the carbon soot of the graphite electrode during the arc discharge by using electron current. In this case, the yield is 30% by weight or less, producing both single- and multi-walled 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 an inert gas is introduced into the chamber, which yields about 70% yield and has an adjustable diameter determined by the reaction temperature. Mainly produces single-walled carbon nanotubes with However, it is more expensive than other methods. Thus, the most common method for producing carbon tubes is chemical vapor deposition (CVD), a technique for depositing thin solid films on substrates from vapor species through chemical reactions, because of their price / unit ratio, and nanotubes CVD is most promising for industrial-scale deposition because it can grow nanotubes directly on the desired substrate, although it must be collected by other growth techniques. Chemical reactions play an important role and are therefore one of the unique features of CVD compared to other film deposition techniques.

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

1 shows a schematic diagram of a tube-furnace CVD system for CNT and graphene growth. It consists of a gas transport system, a reactor 5 and a gas removal system. During the CVD process, the reactive gas types are varied uniformly before entering the required valve (1), pressure regulating valve (3), mass flow regulator (4) (MFC), and reactor (5) to control the flow rate of gas passing therethrough. It is introduced into the reactor by a gas transport system consisting of a gas-mixing unit responsible for mixing the gases. The reactor is where the chemical reaction takes place and where the solid material is deposited on the substrate during the reaction step. Heater 2 is positioned surrounding the reactor to raise the temperature of the reaction. As a result, the side products of the reaction and the non-reactant gas consist of one or more pumps and are removed by a gas transport system that is unnecessary for CVD not operating under vacuum conditions.

Carbon hybrid structures 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 gas, which is a carbon source, to the heated substrate in the presence of water; (c) in response to the gas supply, forming a graphene layer; (d) increasing the amount of gas supplied thereby creating a hollow carbon tube on the graphene layer, and (e) cooling the substrate. In some embodiments, prior to cooling the substrate, the supply amount of gas is reduced and, in response, a graphene layer is produced on the end of the hollow carbon tube.

To produce one or more sub-structures comprising a hollow carbon tube sandwiched between two graphene layers and two graphene layers, (d) increasing the supply amount of gas, thereby increasing the hollow carbon tube on the graphene layer. And (d ') reducing the amount of gas supplied before cooling the substrate is repeated one or more times.

In the production of carbon hybrid structures, a substrate comprising a catalyst layer is used. Any substrate known in the art, for example silicon oxide, can be used. As the catalyst layer used in the preparation of the carbon hybrid structure, any suitable catalyst used for synthesizing graphite, inducing carbonization or for preparing 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 may be selected, including but not limited to Ti, V, Cr, Mn and Cu.

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 cannot be easily obtained on the substrate.

In the described process, the flow rate of the gas which is the carbon source used can be 50 to 500 cm ³ / min, 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 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 during step (a). . However, other flow rates are possible.

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

During at least some of the steps of the process for producing the described carbon hybrid structure, the deposition is generally performed in the presence of water. Water is generally supplied as a mixture of water vapor and an inert gas such as nitrogen, argon, helium, etc., which has a flow rate of inert gas (carrier) of 100 to 200 cm ³ / min, 150 to 200 cm ³ / min, 180 to 200 cm ^It is advantageous to adjust to a value of 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 can be used. Hydrocarbon species are typically used as precursors for graphene growth. Carbon sources include, but are not limited to, include one or more hydrocarbons selected from C _{1 -10} alkane, C _{2 -10} alkylene, C _{2 -10} alkenylene, and the group consisting of aromatic. 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 (ie low pyrolysis rate) simple atomic structure at high temperatures (eg 800-1000 ° C. for most graphene growth). Hydrocarbons, which have very high pyrolysis rates at high temperatures and cause large amounts of carbon deposition, may be undesirable for graphene below nanometers. In some embodiments, the gas that is a carbon source is also supplied during step (a).

In other aspects of the present disclosure, the carbon hybrid structure is, for example, but not limited to, supercapacitors, high hydrogen storage capacity devices, novel solar cells, which are aimed at high surface area, high electron mobility and high thermal conductivity, It can be used for various electronic devices including novel electronic devices.

In some embodiments, membranes comprising carbon hybrid structures are utilized in such electronic devices. Membranes of graphite nanostructures use the flat geometry of the graphene portion of the carbon hybrid structure, which is easily incorporated into the device structure to facilitate and / or improve its applicability to various devices.

In another embodiment, electrode compositions comprising carbon hybrid structures are utilized in various electronic devices. Still 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 because of its large surface area and improves interfacial contact and high specific capacity. Additionally, graphene / CNT hybrids can be used with inorganic materials to form composite materials for improving the circulation stability and capacity of the anode material. In view of this advantage of carbon hybrid structures according to the present disclosure, the use of carbon hybrid structures in electrode compositions for Li-ion secondary cells is described.

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

In yet another embodiment, the supercapacitor may comprise the carbon hybrid structure described. Since the carbon hybrid structure of the present disclosure exhibits an accessible large surface area, high porosity, and excellent properties such as no or reduced micropores, and pseudo-capacitance effects such as redox charge transfer, the carbon hybrid structure is expensive It can be used as electrode material in super capacitors at lower cost than CNT materials.

In yet another embodiment, the present disclosure relates to a heat dissipation stage for an integrated chip comprising a carbon hybrid structure according to the present disclosure. Devices and device elements, such as, but not limited to, heat removal from reduced electronic devices, integrated circuits, high-power electronics, light emitting optical devices, or high speed electronic or optoelectronic devices, are key to further development of these technologies. This is a problem. Since graphene is characterized by extremely high thermal conductivity in the carbon hybrid structure described above, it can be utilized for better thermal management of electronic and optoelectronic devices and circuits, and can be used to reduce power consumption.

By using a carbon hybrid structure according to various disclosures, it has the ability to transport phonons (thermal) and electrons (electricity) in three dimensions, has a more economical manufacturing method, and improves electrical and thermal properties in various conditions. It is possible to produce new carbon hybrid structures that result in performance stability.

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

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

In the event that the disclosure of a document cited herein by the following reference conflicts with the description of the disclosure to the extent that the term is unclear, the present disclosure will prevail.

Example  One

PCB manufacturing

As shown in FIG. 2, a 500 μm thick n-type Si (100) wafer with a 300 nm SiO ₂ layer that is chemically clean is 10 nm thick Fe at a rate of 0.1 μs / s using e-beam deposition. Used to deposit the layer. 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 Forming Graphite Nano-structures

Details of existing WA-CVD methods are described in SP Patole et al., Which is hereby incorporated by reference in its entirety. al . Carbon 46, 1987 (2008). After sample loading, the CVD chamber was evacuated to <0.01 Torr. Ar, H ₂ O steam and C ₂ H ₂ were injected into the CVD reactor at room temperature. A rapid thermal heating system was used to reach the 800 ° 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 feed stock, the growth pressure was further increased to 2.42 Torr, and CNT growth was performed for an additional minute, as shown in step (a) of FIG. 3. Reducing the reactor pressure by lowering the acetylene feed stock again grew graphene on the CNT bottom and on the substrate (shown in step (b) of FIG. 3). Repetition of CNT and graphene growth by changing reactor pressure resulted in a laminated structure (shown in step (c) of FIG. 3). The film of carbon hybrid structure can be detached from the substrate and used for further use.

Example  2

Appearance

As shown in FIG. 4, the carbon hybrid structure obtained in Example 1 was characterized by Raman spectroscopy to confirm graphene and CNT formation. Various literature in this field, for example, MS Dresselhaus, et al . , Physics Reports (2005) 409: 47-99, FIG. 4 shows characteristic peaks of sp ² hybridized carbon, ie, G, D, and 2D bands of graphene-CNT stacked structures. As a result of Raman spectroscopy, it was clearly confirmed that the hybrid structure of graphene and CNT was produced in Example 1.

To further investigate the physical structure of the carbon hybrid structure obtained in Example 1, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used and the graphene layer and the carbon hybrid structure were shown in FIGS. Several SEM / TEM images were obtained. FIG. 5 shows an SEM image of a graphene layer according to the present disclosure, which is deposited on a Fe-coated Si substrate, where CNT adheres to the graphene underneath, and graphene unfolds horizontally on the CNT, while CNT Was identified in the SEM image standing perpendicular to the substrate. 6 is an enlarged TEM image of the carbon hybrid structure, which shows the junction between the CNT and the graphene moiety.

The new structure consists of vertically aligned CNTs connected to graphene at the top and / or bottom. Whereas CNTs can transport phonons and electrons only along one dimension (along their length) and graphene can transport phonons and electrons only along two dimensions (along their base), the hybrid structure of the present invention It can transport phonons (heat) and electrons (electricity) in three dimensions, which can lead to better conductivity.

It is to be understood that the present disclosure has been described in connection with the most feasible embodiments contemplated and that the present disclosure is not limited to the described embodiments. The subject matter described in this specification can be embodied in a variety of other forms or in various combinations; In addition, various omissions, substitutions, combinations, and changes in the forms 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 without departing from the scope and spirit of the disclosure.

Claims (18)

A carbon hybrid structure comprising at least one graphene layer and a hollow carbon tube, wherein an end of the hollow carbon tube is bonded to at least one graphene layer. The carbon hybrid structure of claim 1, wherein the hollow carbon tube comprises carbon nanotubes. The carbon hybrid structure of claim 1, wherein the carbon hybrid structure comprises a sub-structure comprising two graphene layers and a hollow carbon tube interposed between the two graphene layers. 4. The carbon hybrid structure of claim 3, wherein the sub-structures are between 100 nm and 10 mm in length. (a) heating a substrate comprising a catalyst layer;
(b) supplying a gas, which is a carbon source, to the heated substrate in the presence of water;
(c) in response to the gas supply, forming a graphene layer;
(d) increasing the amount of gas supplied thereby creating a hollow carbon tube on the graphene layer, and
(e) cooling the substrate
A method for producing a carbon hybrid structure according to any one of claims 1 to 4, including. 6. The method of claim 5, further comprising (d ') reducing the amount of gas supplied before cooling the substrate and, in response, creating a layer of graphene on the end of the hollow carbon tube. 7. The method of claim 6, further comprising: (d) increasing the amount of gas supplied thereby creating a hollow carbon tube on the graphene layer and (d ') reducing the amount of gas supplied before cooling the substrate. Further comprising repeating over. 6. The method of claim 5, wherein a gas that is a carbon source is supplied while heating a substrate comprising a 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 process of claim 5 wherein the gas being a carbon source comprises one from the group consisting of methane, ethylene, acetylene or benzene. The method of claim 5, wherein the catalyst layer comprises a transition metal. The method of claim 11, wherein the transition metal is Fe. Membrane comprising the carbon hybrid structure according to any one of claims 1 to 4. Electrode composition comprising the carbon hybrid structure according to any one of claims 1 to 4. A Li-ion secondary battery comprising the electrode composition according to claim 14. Hydrogen-storage device comprising the carbon hybrid structure according to any one of claims 1 to 4. A supercapacitor comprising the carbon hybrid structure according to any one of claims 1 to 4. A heat dissipation stage for an integrated chip comprising the carbon hybrid structure according to any one of claims 1 to 4.

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