KR20180007700A - Cu composite reinforced by 3D graphite or graphene network and preparing method thereof - Google Patents

Abstract

The present invention relates to a method for producing a copper composite material reinforced by three-dimensional (3D) graphite or a graphene network structure formed in a copper sample by undergoing the following steps: processing 99% pure copper into a green compact sample having a specific volume; and carrying out chemical vacuum deposition. The present invention further relates to a copper composite material produced thereby. The copper composite material reinforced by the 3D graphite or the graphene network structure ensures excellent features such as electroconductivity, thermal conductivity, corrosion resistance, hardness, tensile strength, and yield strength, and thus can be applied in various industrial fields.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper composite material reinforced with a three-dimensional graphite or graphene network structure,

The present invention relates to a copper composite reinforced with a three-dimensional graphite or graphene network structure and a method of manufacturing the same, and more particularly, to a reinforced copper composite by forming a three-dimensional graphite or graphene network structure on copper, .

Graphene is a two-dimensional crystalline material identified and analyzed in 2004 (Novoselov et al., 2004). Graphene is a material with an atomic structure made of carbon atoms, made of graphite (graphite) as a raw material.

Graphene is the most excellent material among the existing materials. It has a thickness as small as 0.2 nm, high transparency, and a very large specific surface area. Graphene has very good electrical conductivity and can deliver 100 times more current at 100 times faster than silicon at room temperature. In addition, it has been proved that it has a very high intrinsic thermal conductivity that exceeds that of carbon nanotubes (CNTs) in 2008 (Balandin et al., 2008 Balandin, 2011; Ghosh et al., 2009). The electrical conductivity and thermal conductivity of graphene are known to be 150 and 10 times higher than OFHC Cu, respectively. Also, graphene is more than 200 times stronger in mechanical strength than steel, but it is stretchable and does not lose its electrical conductivity even when stretched or folded.

Because of these excellent properties, graphene has attracted a great deal of attention in a variety of scientific and technical fields and is being used as fillers in microelectronic devices, transparent conductors, bio-chemical sensors, electrodes for energy storage and conversion devices, and conductive polymeric composites And is widely used (Huan et al., 2013).

In solid-state physics, it is well known that the properties of polycrystalline materials are often determined by the size of these grains and the atomic structure at the boundary of these particles. This effect is particularly well known for two-dimensional materials in which line defects can divide and destroy crystals. It is also reported that the electrical properties of graphene do not change much even when the mechanical strength of the graphene film is severely weakened by the boundaries of the grains (Yazyev and Louie. 2010; Huang et al., 2011).

Graphene-polymer composites that exploit the excellent properties of graphene, such as thermal conductivity, electrical conductivity, have many potential applications in the polymer industry. By modifying this, incorporating graphene as a filler or additive in the polymer matrix results in the formation of a new material known as a graphene-polymer composite (Stankovich et al., 2006; Ramanathan et al., 2008; Lee et al., 2009; Xu et al., 2009; Quan et al., 2009). However, the graphene-polymer composite has a limitation that the polymer can be used only in a stable region.

Conventional graphene research has focused primarily on two-dimensional (2D) graphene and graphene oxide nanosheets, where graphene oxide structures can be effectively dispersed in aqueous solutions and converted to structures with specific functional groups It can be reduced.

Recently, much research has been done on three-dimensional (3D) porous graphene nanostructures (Chen et al., 2011; Fan et al., 2012). Three-dimensional graphene has been reported to have a large surface area, unique morphological features and porous structure, very sensitive to chemical environments, and a thermal conductivity ranging from 150 K to about 1600 W m ^-1 K ^-1 (Pettes et al., 2012).

In the field of 3D graphene, there are filters such as gas filters, composites of graphene and metal, heat sinks and radiators, motor cores, catalysts, photovoltaics, and biotechnology.

Various studies have been conducted on composite materials of graphene and metal. However, since graphene and metals have different densities, they are not easily mixed with each other. Most of metals are stable at a temperature of 400 ° C. or more, It is not easy to produce a graphene-metal composite.

Japanese Patent Application Laid-Open No. 10-2011-0115085 discloses a graphene / metal nanocomposite powder containing graphene dispersed in base metal and base metal and used as a reinforcing agent of a matrix metal. In the graphene / metal nanocomposite powder, graphene binds to the metal particles interposed between the metal particles of the base metal in a thin film form.

Japanese Patent Registration No. 10-1636001 discloses a thermoelectric material containing graphene having a three-dimensional nano foam structure. In this patent, graphene having a three-dimensional nano foam structure is produced by coating a solution containing a solid carbon source for graphene growth and a metal precursor on a substrate to prepare a thin film, and the thin film is heated to 700 to 1,200 ° C Heating to form a nano-foam graphene structure containing the metal, and removing the metal in the graphene structure of the nano foam structure.

In Patent No. 10-1427885, a hydrophobic solution is injected into a hydrophilic solution containing a graphene oxide and a metal catalyst precursor solution or a metal catalyst solution to prepare droplets, and the resulting droplets are heat-treated to form a three-dimensional graphene- And a metal catalyst bonded to the surface of the three-dimensional graphene carrier, wherein the three-dimensional graphene comprises a plurality of wrinkled graphene sheets in the form of compressed three-dimensional graphene - metal catalyst complexes.

Japanese Patent Registration No. 10-1490693 discloses a process for producing a three-dimensional graphene foam by growing graphene on a foamed foam having a three-dimensional structure by a CVD method and then dissolving the casting component to prepare a three-dimensional graphene foam, A method of preparing a three-dimensional graphene composite by adsorbing nickel-cobalt hydroxide formed by immersing the three-dimensional graphene foam by a chemical solution growing method (CBD) on a surface of the three-dimensional graphene foam, , A three-dimensional graphene composite having a three-dimensional structure, an average pore diameter of 100 to 200 mu m, and a nickel-cobalt hydroxide impregnated and impregnated in the graphene foam.

Copper (Cu) is a representative non-ferrous metal and has excellent electrical conductivity and thermal conductivity, so it is used as a basic material for electric industry. It is also widely used for chemical industry, craft decoration, heating device, money, machine parts, vacuum tube, printing, water supply, etc. It is manufactured in the form of plates, rods, sashes and tubes with excellent corrosion resistance and plasticity.

Oxygen Free High Conductivity Copper (OFHC Cu, C10100), which has excellent thermal conductivity and electrical conductivity, is widely used in various industrial fields. However, oxygen-free high-conductivity copper (OFHC Cu) is not superior in physical properties such as corrosion resistance and oxidation resistance, physical properties such as hardness, strength, and wear resistance compared to other materials, and has a high purity .

Composites in which copper is combined with three-dimensional graphite or graphene can be very useful in a variety of applications where copper is used, but such techniques are not yet known.

Korea Patent Publication No. 10-2011-0115085 Korean Patent No. 10-1427885 Korean Patent No. 10-1490693 Korean Patent No. 10-1636001

 K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Bubonos, I.V. Grigorieva and A.A. Firsov: Science, 2004, 306, pp. 666-9.  A.K. Geim: Science, 2009, 324, pp. 1530-4.  A.K. Geim and K.S. Novoselov: Nature Mater., 2007, 6, pp. 183-91.  Y. Zhang, Y.W. Tan, H.L. Stormer and P. Kim: Nature, 2005, 438, pp. 201-4.  A.A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, F. Miao and C.N. Lau: Nano Lett., 2008, 8, pp. 902-7.  M.D. Stoller, S. Park, Y. Zhu, J. An and R.S. Ruoff: Nano Lett., 2008, 8, pp. 3498-502.  C. Lee, X.D. Wei, J.W. Kysar and J. Hone: Science, 2008, 321, pp. 385-8.  L. Huan, X. Shen, W. Xinwei and M. Ning: Nanotechnology, 2013, 24, pp. 1-10.  H.G.P Kumar and M.A. Xavior: Procedia Eng., 2014, 97, pp. 1033-40.  Y. Kim, J. Lee, M.S. Yeom, J.W. Shin, H. Kim, Y. Cui, J.W. Kysar, J. Hone, Y. Jung, S. Jeon and S.M. Han: Nat. Commun., 2013, 4, pp. 1-7.  G.A. Lopez and E. J. Mittemeijer: Scr. Mater., 2004, 51, pp. 1-5.  S. Nazarpour and S.R. Waite: Graphene Technology - from Laboratory to Fabrication, Wiley-VCH, 2016.  R. Blume, P.R. Kidambi, B.C. Bayer, R.S. Weatherup, Z.J. Wang, G. Weinberg, M.G. Willinger, M. Greiner, S. Hofmann, A. Knop-Gericke and R. Schl ogl: Phys. Chem. Chem. Phys., 2014, 16, pp. 25989 {6003.  T.J. Nacken, C. Damm, H. Xing, A. Ruer and W. Peukert: Nano Res., 2015, 8, pp. 221, 1865-81.

It is an object of the present invention to provide an excellent copper composite material having enhanced chemical and physical properties by depositing graphite or graphene in a three-dimensional network structure between copper particles.

In order to achieve the above object, the present invention provides a method for producing a copper alloy powder, comprising: preparing copper powder having a purity of 99% or more as a sample of a green compact having a predetermined volume; Charging the copper sample into a chemical vacuum deposition system; Making the inside of the system into a hydrogen gas atmosphere; Setting a pressure inside the system to a first pressure (P1) within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr) and introducing hydrogen gas at a flow rate of 5 to 15 sccm; Heating the furnace in the system to a set temperature within the range of 400 to 1000 占 폚; Annealing for 20 to 40 minutes after reaching the set temperature; The inside pressure of the system is set to a second pressure (P2) within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr), and a source gas for supplying carbon is supplied at a flow rate of 4 to 10 sccm, Growing a graphene network structure; And cooling the mixture to room temperature. The present invention also provides a method for producing a copper composite material reinforced with a three-dimensional graphite or graphene network structure.

In the above manufacturing method, the first pressure P1 is preferably set to 200 to 400 mTorr.

In the above manufacturing method, the second pressure (P2) is preferably set to 350 to 550 mTorr.

In the above production method, the time for which the furnace reaches the set temperature is preferably 40 to 70 minutes.

In the above production method, it is preferable that the source gas for supplying carbon is methane or ethane.

In the above production method, the growth time of the network structure is preferably 30 to 60 minutes.

In the above manufacturing method, it is preferable that the cooling is carried out at a rate of 25 to 45 DEG C / min to room temperature.

In the above production method, it is preferable that the cooling is carried out at a cooling rate of 150 to 250 DEG C / min to room temperature.

The present invention also provides a copper composite material reinforced with a three-dimensional graphite or graphene network structure, wherein graphite or graphene forms a three-dimensional mesh structure between the compacted copper particles.

It is preferable that the composite material is produced by the above method.

The three-dimensional graphite of the present invention or the copper composite reinforced by the graphene network structure (3D composite material of graphite or graphene network, 3DGr-Cu) The size and shape of the graphite or graphene structure can be controlled and the thickness or layer of the graphite or graphene in the 3DGr-Cu composite can be controlled according to the growth conditions of the graphite or graphene. In addition, a desired 3DGr-Cu composite material, such as a 3DGr-Cu composite material having a regular three-dimensional structure or a wide area, can be economically and easily mass-produced.

The 3DGr-Cu composite material of the present invention has a problem in that heat transfer problem in electric devices and electronic devices in which heat generation is a problem is caused by the characteristics of graphene having electric conductivity about 150 times better than copper and about 13 times higher thermal conductivity than oxygen- And can be reinforced with a three dimensional network structure to improve the mechanical properties of copper such as hardness, tensile strength and yield strength. Therefore, it can be applied to a variety of structural materials requiring excellent electrical / thermal conductivity, excellent mechanical strength and excellent corrosion resistance. Also, 3D graphene itself can be applied in various fields such as sensors and filters.

1 is a scanning electron microscope (SEM) photograph showing the shape and size distribution of copper particles used in the embodiment of the present invention.
2 is a photograph of a copper disk compressed to a diameter of 15 mm and a thickness of about 1 mm.
Fig. 3 shows an example of experimental conditions for the synthesis of the 3DGr-Cu composite of the present invention.
FIG. 4 is a schematic diagram illustrating a process for synthesizing the 3DGr-Cu composite material of the present invention.
Fig. 5 is a SEM photograph showing the mutual bonding of copper particles at a copper disk cut surface. Fig.
6 is a graph showing the EDX analysis results of the 3DGr-Cu composite material.
FIG. 7 shows the structure of a 3D graphene in a 3DGr-Cu composite material, wherein (a) is a photograph of a copper disk after formation of a graphene network structure, and (b) is a three-dimensional graphene network structure in which copper is removed.
Fig. 8 shows the growth of the 3DGr-Cu composite material. Fig. 8 (a) shows the copper alone, Fig. 8 (b) shows the graphite- (E) and (f) are scanning electron microscope (TEM) images showing single-layer graphene formed in the twin boundary of copper in the graphene-copper composite.
9 is a SEM photograph showing a 3D network structure in a 3DGr-Cu composite material, wherein (a) is graphite and (b) is graphene.
10 shows XRD patterns of copper powder, graphite-copper composite and graphene-copper composite.
11 is a Raman spectrum of a graphene structure in a 3DGr-Cu composite.
12 shows the thermal conductivity of 3DGr-Cu composite material and general copper according to the temperature.

The three-dimensional graphite of the present invention or the copper composite material (3DGr-Cu composite material) reinforced by the graphene network structure,

Preparing a copper powder having a purity of 99% or more as a sample of a green compact having a constant volume;

Charging the copper sample into a chemical vacuum deposition system;

Making the inside of the system into a hydrogen gas atmosphere;

Setting a pressure inside the system to a first pressure (P1) within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr) and introducing hydrogen gas at a flow rate of 5 to 15 sccm;

Heating the furnace in the system to a set temperature within the range of 400 to 1000 占 폚;

Annealing for 20 to 40 minutes after reaching the set temperature;

The inside pressure of the system is set to a second pressure (P2) within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr), and a source gas for supplying carbon is supplied at a flow rate of 4 to 10 sccm, Growing a graphene network structure; And

Followed by cooling to room temperature.

Hereinafter, the present invention will be described in detail.

(1) Preparation of copper raw materials

Copper used as a raw material is a copper powder having a certain size and shape and having a purity of 99% or more. The particle shape and size of the copper powder can be selected variously according to need. Examples of the particle shape of the copper powder include an annular shape, a rotation ellipse shape, and the like. The copper powder preferably has a particle size of 5 to 25 mu m, but is not limited thereto.

The shape and size of the three-dimensional structure in the copper composite material can be controlled according to the particle shape and size of the copper powder, thereby obtaining a copper composite material reinforced with various types of three-dimensional graphite or graphene mesh.

(2) Preparation of Copper Samples

Copper is produced from a specimen in the form of a green compact having a constant volume. For example, a copper sample having a predetermined shape can be produced by molding copper particles by a mechanical vertical pressing method which applies a constant pressure using a hydraulic press on or under the mold. In the case of mechanical vertical compression, it is preferable to apply pressure of 1 to 4 tons.

The density of the powder compacts in the copper samples can be varied in various ways depending on the size, shape, particle size distribution, copper sample thickness, and applied pressure of the copper particles to be used. At this time, the size, shape and size distribution of the copper particles control the shape of the three-dimensional graphite or graphene network structure in the copper composite. In addition, since the thickness of the copper sample may affect the thickness of the network structure, the thickness of the copper composite material reinforced with the three-dimensional graphite or graphene network structure can be adjusted by adjusting the thickness of the copper sample.

(3) three-dimensional graphite or Grapina  Copper reinforced with mesh structure (3 DGR - Cu ) Manufacture of Composites

A three-dimensional graphite or graphene network structure is formed on the prepared copper sample to prepare a copper composite material (hereinafter referred to as "3DGR-Cu composite material ") reinforced with three-dimensional graphite or a graphene network structure.

As a method of producing a three-dimensional graphite or a graphene network structure, it is preferable to use CVD (Chemical Vapor Deposition). Specific methods are as follows.

First, the prepared copper sample is charged into a chemical vacuum deposition system. At this time, it is charged to the center of the horizontal electric furnace of the chemical vacuum deposition system.

The inside air of the system is replaced with hydrogen (H ₂ ) gas three times or more to make a hydrogen gas atmosphere. Hydrogen gas is used to produce high surface area copper powders that can reduce the surface of copper to remove oxides on the copper surface and react easily with carbonization.

The first pressure P1 is set to set the pressure in the system to a constant pressure, and hydrogen gas at a constant flow rate is supplied. At this time, the pressure is set within a range from 2 atm to a low vacuum (~ 1 × 10 ^-3 Torr), and more preferably, set at 200 to 400 mTorr. The flow rate of the hydrogen gas is preferably set to 5 to 15 sccm, and the hydrogen gas is continuously supplied from the start of the reaction until the subsequent cooling process is terminated.

After setting the first pressure, set the temperature and heat the furnace. At this time, the temperature is preferably set within the range of 400 to 1000 占 폚. The time for reaching the target temperature is preferably about 40 to 70 minutes.

After reaching the set temperature, anneal is performed to remove the stress of the specimen while maintaining the temperature for 20 to 40 minutes. In this process, the copper powders are bonded to each other by diffusion and the voids form a three-dimensional network structure, and this three-dimensional pore network structure plays a role in providing and growing nucleation sites in the production of 3DGR-Cu composite materials.

After the annealing process, the pressure inside the system is set to a second pressure (P2), and a source gas for supplying carbon is introduced into the system to grow a three-dimensional graphite or graphene network structure.

At this time, the pressure is set within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr), and more preferably set at 350 to 550 mTorr.

As the source gas for supplying carbon, various materials capable of supplying carbon can be used. Representative examples of the source gas for supplying carbon include, but are not limited to, methane, ethane, and the like. The flow rate of the source gas for supplying carbon is preferably set to 4 to 10 sccm.

In the above process, carbon in the source gas for supplying carbon is dissolved and deposited in the copper sample, so that the graphite or graphene network structure grows. The growth time of the graphene network structure depends on the thickness and particle size of the copper sample, but it is preferably 30 to 60 minutes.

After the dissolution process of carbon is completed, cool to room temperature. When cooled slowly, it is cooled to room temperature at a rate of about 25 to 45 ° C / min. When it is quenched, it is cooled to room temperature at a rate of about 150 to 250 ° C / min to obtain a 3DGR-Cu composite material.

The solubility of carbon in the copper increases from ~ 1 ppm to ~ 6 ppm at a temperature between the room temperature and the set temperature, so that carbon diffuses into the copper particles, and in the subsequent cooling process, carbon is precipitated on the surface of the copper particles.

At this time, the carbon is in the form of graphite or graphene depending on the condition of the CVD disk and the CVD disk. With respect to the pressure to press the copper powder, it becomes a graphite form when the pressure is low, and a graphen form when the pressure is high. Further, with respect to the cooling rate, in the case of gradual cooling, it is in the form of graphene, and in the case of quenching, it tends to become a sacrificial form. Therefore, by controlling conditions such as pressure and cooling rate during pressing of the copper powder, it is possible to obtain a graphite network structure, a graphene network structure, or a mixed network structure of graphite and graphene.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. These examples and experimental examples are illustrative of the present invention, and the scope of the present invention is not limited thereto.

< Example  1>

3 DGR - Cu  Manufacture of composites

(1) Manufacture of copper disks

Copper powder of 99.5% purity having a spheroidal shape with a diameter of 14 ~ 25μm was purchased from Aldrich. A scanning electron microscope (SEM) photograph showing the shape and size distribution of the used copper particles is shown in Fig. 1 (a). Fig. 1 (b) is an enlarged view showing the pores of the surface of the copper particle identified in Fig. 1 (a).

1.3 g of the copper powder was axially compressed by mechanical compression of 4 tons in a mold using a double action oil hydraulic press to prepare a copper disk having a diameter of 15 mm and a thickness of about 1 mm. The green densities of the copper disks produced were 75 to 85% of the theoretical green density of the copper, depending on the thickness of the disc sample and the applied pressure. The manufactured copper disk is shown in Fig.

(2) 3 DGR - Cu  Composite composites

(99.999%) and methane gas (99.995%) into a quartz tube chamber having a length of 1 m and a diameter of 3 cm, which can be heated up to 1,100 ° C., as an apparatus for synthesizing a 3DGR- flow controller, respectively, were used. The gas pressure in the chamber is controlled by a throttling valve with a pressure regulator. The system has a temperature of the furnace at &lt; RTI ID = 0.0 &gt; 5 C, &lt; / RTI &gt; 0.0 &gt; sccm &lt; / RTI &gt; and a system pressure of 330 mTorr or 450 mTorr to +/- 0.01 mTorr.

When the temperature of the furnace was set to 1000 ° C, the temperature profile in the chamber was accurately determined by a single thermocouple transferred along the length of the furnace and measured at intervals of 2 cm. The parabola suitable for temperature data was 0.99 for R ² .

A copper disk was placed on a sample boat located in the middle of the quartz tube chamber. First, the chamber was washed five times with hydrogen gas (99.999%). Then, it was heated to 1000 캜 while raising the temperature to about 17 캜 / min. Hydrogen gas was introduced at a flow rate of 10 sccm, and the first pressure P1 in the quartz tube was maintained at 330 mTorr. When the temperature of the furnace reached 1000 캜, a annealing process was performed to remove the stress of the sample for 30 minutes.

Methane gas (99.995%) was introduced into the source gas at a flow rate of 5 sccm after annealing, and the second pressure (P2) in the quartz tube was set to 450 mTorr. During the reaction for 40 minutes, the carbon atoms of the methane molecules were dissolved in the copper. After the reaction was completed, the temperature was cooled to room temperature. And cooled to room temperature at a cooling rate of about 200 DEG C / min to obtain a 3DGR-Cu composite material. When the temperature of the furnace reached room temperature, the 3DGR-Cu composite material was taken out of the furnace. These experimental conditions are shown in Fig.

FIG. 4 is a schematic view illustrating a process of synthesizing the 3DGR-Cu composite material.

As can be seen in FIG. 4, the copper powder was pressed in the mold without any other additive to produce a copper disk. During the CVD at 1,000 ° C, methane (CH ₄ ) is decomposed into 2H ₂ and C, resulting in an increase in the solubility of carbon in the copper between room temperature and 1,000 ° C from ~ 1 ppm to ~ 6 ppm, (Lopez and Mittemeijer, 2004). In the subsequent cooling process, carbon precipitates on the surface of the copper particles. At this time, the carbon is in the form of graphite or graphene depending on the condition of the CVD disk and the CVD disk.

< Experimental Example  1>

Identify the type of copper particles in the copper disk

The copper disk prepared in Example 1 was cut in half to confirm the shape of the copper particles on the side by a scanning electron microscope. The results are shown in Fig.

In Figure 5 (a), it can be seen that the copper particles are mechanically interconnected after being compressed in the mold at a pressure of 4 tons.

In Fig. 5 (b), it can be seen that the spherical ellipsoidal copper particles turned into slightly angular particles, indicating that the copper particles undergo elastic deformation and plastic deformation during the production of the copper disk. 5 (b), it is also confirmed that the surface of the copper particles is slightly oxidized.

< Experimental Example  2>

Of copper disc EDX  analysis

In order to confirm the degree of oxidation of the copper disk prepared in Example 1, it was analyzed by energy-dispersive X-ray spectroscopy (EDX). The results are shown in FIG.

The initial oxygen content of the purchased copper powder was about 0.3%, but EDX analysis of the disk type copper sample showed that copper and carbon together with about 5% oxygen were present. This seems to be due to the oxidation of small copper particles with a high surface area during the process of preparing the copper disc samples or handling the copper powder.

The oxygen content in copper was found to be an important parameter that could influence and control the kinetics of graphene network growth (Nazarpour and Waite, 2016). Copper forms species such as CuOx present on the surface of copper (Blume et al., 2014), and these CuOx species have been found to have a large impact on the kinetics and growth of graphene on copper.

< Experimental Example  3>

Identification of 3D network structure

The structure of the 3D graphene in the 3DGR-Cu composite material was confirmed as follows, and the process and results are shown in FIG.

First, a thin copper disk (0.2 mm thick) was prepared to prevent 3D graphene from collapsing due to the high surface area of the graphene after etching and drying. A graphene network structure was formed on the produced copper disk by CVD. A photograph of the copper disk after the formation of the graphene network structure is shown in Fig. 7 (a).

The copper disk was polished to remove graphene from the disk surface. The abraded sample was immersed in ethanol and ultrasonic cleaning was performed three times or more for 5 minutes to remove foreign substances generated in the polishing process. After washing, copper was immersed in a caustic solution containing 1 mol of FeCl ₃ and 0.1 mol of HCl to remove only the three-dimensional graphene network structure. The three-dimensional graphene network structure in which copper is removed is shown in Fig. 7 (b).

< Example  2 to 4>

3 DGR - Cu  Manufacture of composites

In order to confirm the difference of the 3DGR-Cu composite material according to the inflow gas, the compression pressure and the cooling rate, samples were prepared under the conditions shown in Table 1 below.

Sample number Inflow gas Crimping (Tone) Temperature (℃) Cooling rate Comparative Example 1 Hydrogen 4 1,000 Slow cooling Example 2 Hydrogen + methane One 1,000 Slow cooling Example 3 Hydrogen + methane 4 1,000 Slow cooling Example 4 Hydrogen + methane 4 1,000 Quenching

Comparative Example 1 is a cold copper sample at a cooling rate of 35 DEG C / min after compression with a pressure of 4 tons and heat treatment with hydrogen gas only without methane gas.

Example 2 is a 3DGR-Cu composite material produced by compressing at a pressure of 1 ton, heat-treating it with hydrogen gas and methane gas, and slowly cooling at a cooling rate of 35 ° C / min.

Example 3 is a 3DGR-Cu composite material produced by compression at a pressure of 4 tons, heat treatment with hydrogen gas and methane gas, and gradual cooling at a cooling rate of 35 ° C / min.

Example 4 is a 3DGR-Cu composite material produced by compression at a pressure of 4 tons, heat treatment with hydrogen gas and methane gas, followed by quenching at a cooling rate of 200 ° C / min

< Experimental Example  4>

Conditional 3 DGR - Cu  Identify differences in composites

The 3DGR-Cu composite materials of Examples 2 to 4 and the samples of Comparative Example 1 were used for the samples. The differences of the 3DGR-Cu composite materials according to the inflow gas, compression pressure and cooling rate were as follows.

An OM image of the surface of the sample specimen after etching with a mixed solution of 1 M FeCl ₃ and 0.1 M HCl is shown in FIG. (B) is a graphite-copper composite material of Example 2, (c) is a graphene-copper composite material of Example 3, and (d) is a graphite-copper composite material of Example 4, And a graphene-copper composite. (e) and (f) are scanning electron microscope (TEM) images showing a single-layer graphene formed on the twin boundary of copper in the graphene-copper composite of Example 3. As can be seen from Fig. 8, the copper particles of the samples of Comparative Example 1 and Example 3 were 20 to 40 mu m in size, and the copper particles of the sample of Example 2 and the copper raw material particles (5 to 25 占 퐉). This shows that the copper particles were grown during the CVD and cooling processes in the samples of Comparative Example 1 and Example 3.

Further, in FIG. 8, the sample of Example 2 shows large gaps between the copper particles and the black color is filled with graphitic carbon. This means that the disk pressure is low and the disk specimen has a density of about 60%, which means that the copper particles of this specimen are relatively wider than the other specimens. In the sample of Example 2, relatively large and large gaps were filled with carbon. As a result, the copper particles did not grow beyond the carbon boundary, resulting in smaller particles than the copper particles in the sample of Example 3.

It can be seen that the grain boundaries with dark black lines in the sample of Example 3 are mostly multilayer graphene or graphite formed in grain boundaries and twins. The small black dots (one of which is indicated by arrow # 1) seen in the inner particles in the sample of Example 3 are derived mostly from the small holes in the copper raw material particles. However, in the sample of Example 3, small loops (two of which are indicated by arrows # 2 and # 3) visible in the inner particles and additional loops at the grain boundaries, B and C) are probably formed as a result of the growth of copper particles during CVD and slow cooling. Large copper particles will grow while small copper particles shrink (Oswald Ripening). During cooling, small gaps (or grain boundaries) between the small holes on the surface of the copper particles and the copper particles with a high surface area act as carbon nuclei and growable catalyst sites to form graphene . Small points or loops of graphene inside the copper particles can act as obstacles to dislocation movement. Therefore, copper particles with dots or loops have higher mechanical strength than copper particles without dots or loops. Also, graphene or graphite in a copper matrix may have better machinability due to the lubrication effect of carbon. Also, due to the graphene coating on the copper particles, the graphene-copper composite can have better corrosion resistance.

The copper particles in the sample of Example 4 did not grow sufficiently as compared with the sample of Example 3 which was cooled slowly by quenching. Due to the quenching, there is not enough time for the copper particles to grow (spread), resulting in a large gap between the copper particles, which becomes a site where carbon grows and forms graphite during the cooling process.

Some copper particles are bonded together, but copper particles with a relatively large gap between the particles are sintered at a CVD process at 1,000 ° C. leaving a 3D mesh structure with open pores. The 3D mesh structure of these open holes serves as nucleation and growth sites for graphite or graphene during CVD and cooling processes.

< Experimental Example  5>

3 DGR - Cu  Identification of mesh structure of composite material

The 3D network structure of 3DGR-Cu composites was confirmed as follows.

In order to confirm the three-dimensional network structure of graphene or graphite, the samples of Example 2 and Example 3 were immersed in an etching solution containing 1 M FeCl ₃ and 0.1 M HCl to remove copper. When the copper is removed, a three-dimensional network structure of graphene or graphite is revealed, which is shown in Fig.

9 (a) is an SEM image showing the three-dimensional network structure of the graphite-copper composite material after removing the copper from the sample of the second embodiment.

FIG. 9 (b) is an SEM image showing the three-dimensional network structure of the graphene-copper composite after removing the copper from the sample of Example 3. FIG. Most three-dimensional graphene mesh structures collapse due to capillary forces exerted by small holes and the high surface area of graphene during the drying of the ethanol used to clean the etchant after etching. However, when the collapsed 3D graphene sample is immersed again in ethanol, graphene swells up to its original 3D mesh structure. FIG. 9 (b) is a view taken near the edge of the collapsed sample. After removing the copper particles, the holes on the surface are mutually bonded to form a three-dimensional network structure.

< Experimental Example  6>

3 DGR - Cu  Composite XRD  Check Pattern

The XRD (X-ray diffraction) patterns of the copper powder as the raw material, the graphite-copper composite material of Example 2 and the graphene copper composite material of Example 3 were confirmed and shown in FIG.

The XRD peak of the graphene-copper composite sample shows the same peak as the raw copper powder, while the graphite-copper composite shows graphite, copper and several unidentified small peaks.

< Experimental Example  7>

3 DGR - Cu  The composite Raman ( Raman ) analysis

Raman analysis of 3DGR-Cu composites was performed as follows based on Nacken et al. (2015).

Raman spectra were recorded on a spectrometer (Horiba Jobin-Yvon LabRam Aramis spectrometer) and an 514 nm line of an Ar-ion laser was used as an excitation source.

Samples for analysis were prepared using the same method as in FIG. 7, except that a thin copper disk with graphene removed from the surface was fixed to the mounting resin and then copper was etched. After the copper was completely etched from the sample to leave only the three-dimensional graphene, the sample was washed three times for a long time using ethanol and ultrapure water so as not to wash the three-dimensional graphene. Raman spectra were obtained at five or more different locations of possible positions on a flat surface. The background signal was removed from the mounting resin and analyzed. However, due to the collapse of three - dimensional graphene, Raman analysis could obtain three - dimensional graphene with only ~ two layers. Therefore, transmission electron microscopy (TEM) analysis seems to be necessary to show the three-dimensional graphene in detail and to show the atomic structure of the surface at grain boundaries for graphene-copper composites.

The Raman spectrum as described above is shown in FIG. The drawing shows three-dimensional graphene on the mounting resin.

< Experimental Example  8>

3 DGR - Cu  Thermal conductivity analysis of composites

The thermal conductivity of graphene-reinforced copper composite of the present invention and ordinary copper not reinforced with graphene were confirmed according to the temperature, and the results are shown in Fig.

As can be seen from FIG. 12, the graphene-reinforced copper composite material of the present invention had a thermal conductivity two times higher than that of general copper.

Claims (10)

Preparing a copper powder having a purity of 99% or more as a sample of a green compact having a constant volume;
Charging the copper sample into a chemical vacuum deposition system;
Making the inside of the system into a hydrogen gas atmosphere;
Setting a pressure inside the system to a first pressure (P1) within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr) and introducing hydrogen gas at a flow rate of 5 to 15 sccm;
Heating the furnace in the system to a set temperature within the range of 400 to 1000 占 폚;
Performing a annealing heat treatment for 20 to 40 minutes after the set temperature is reached;
The inside pressure of the system is set to a second pressure (P2) within a range of 2 atm to a low vacuum (~ 1 x ^10-3 Torr), and a source gas for supplying carbon is supplied at a flow rate of 4 to 10 sccm, Growing a graphene network structure; And
And cooling the mixture to a room temperature. 2. A method of producing a copper composite material according to claim 1, The method according to claim 1,
Wherein the first pressure (P1) is set to 200 to 400 mTorr. The method according to claim 1,
And the second pressure (P2) is set to 350 to 550 mTorr. The method according to claim 1,
Wherein the time required for the furnace to reach the set temperature is 40 to 70 minutes. The method according to claim 1,
Wherein the source gas for supplying carbon is methane or ethane. The method according to claim 1,
Wherein the growth time of the network structure is 30 to 60 minutes. The method according to claim 1,
Wherein the cooling is performed at a rate of 25 to 45 占 폚 / min to room temperature. The method according to claim 1,
Wherein the cooling is carried out at a cooling rate of 150 to 250 DEG C / min to room temperature. Characterized in that graphite or graphene forms a three-dimensional network structure between the compacted copper particles and the graphite or graphene is reinforced with a three-dimensional graphite or graphene network structure. 10. The method of claim 9,
9. A copper composite material reinforced with a three-dimensional graphite or graphene network structure, wherein the composite material is made by the method of any one of claims 1 to 8.

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