CN111058017B

CN111058017B - Graphene metal composite wire and low-temperature continuous preparation method thereof

Info

Publication number: CN111058017B
Application number: CN201911157000.1A
Authority: CN
Inventors: 刘悦; 杨昆明; 姚松松; 陈乃齐; 范同祥
Original assignee: Shanghai Jiaotong University
Current assignee: Chuanlan Technology (Shanghai) Co.,Ltd.
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2021-03-30
Anticipated expiration: 2039-11-22
Also published as: CN111058017A

Abstract

A graphene metal composite wire and a low-temperature continuous preparation method thereof are disclosed, wherein the preparation method comprises the following steps: providing a metal wire; transmitting a metal wire between a roll-to-roll input end and a roll-to-roll output end by using a roll-to-roll deposition mode, and depositing a graphene layer on the surface of the metal wire by using a plasma enhanced chemical vapor deposition process in the transmission process of the metal wire, wherein the deposition temperature of the plasma enhanced chemical vapor deposition process is 700-850 ℃. The preparation method improves the performance of the formed graphene metal composite wire.

Description

Graphene metal composite wire and low-temperature continuous preparation method thereof

Technical Field

The invention relates to the field of composite material preparation, in particular to a graphene metal composite wire and a low-temperature continuous preparation method thereof.

Background

The metal has the characteristics of high ductility, high electrical conductivity, high thermal conductivity and the like, is widely applied to the fields of electric power, communication and the like, but still cannot meet the urgent requirements of the industry, such as motors, transformers, wind driven generators, transmission lines and the like, on high-strength and high-conductivity wires, and the development of novel high-performance wires is imperative.

Graphene (Gr) is an ideal reinforcing phase for metal composites as a two-dimensional material with ultrahigh mechanical and electrical conductivity properties. The existing preparation technology for compounding Cr and metal mainly focuses on the following aspects: (1) powder metallurgy method; (2) friction stir welding; (3) a pressure infiltration method; (4) chemical Vapor Deposition (CVD), and the like.

The technology has the problems of high preparation cost, complex process, poor quality, limited thickness or incapability of large-scale industrial production and the like to different degrees.

Cu is a more common metal. At present, the preparation method of the Gr/Cu composite wire mainly focuses on the process of cold drawing at the later stage of powder metallurgy combination. The disadvantages of this method are mainly the inability to ensure high quality of Gr itself, strong interfacial bonding of Gr and Cu matrix, and the difficulty in achieving structural continuity of Gr in composite wires. Secondly, the large-scale and continuous preparation of the Gr/Cu composite wire is difficult to realize by the existing powder metallurgy preparation technology. Numerous studies have shown that Gr has high carrier mobility and self-supporting high quality, and defects, strain, wrinkles and the presence of functional groups in Gr all cause the thermal conductivity of Gr itself to decrease. Therefore, ensuring high quality of Gr is a prerequisite for achieving highly conductive composites. Meanwhile, Gr currently on the market exists mostly in the form of its derivatives, including Reduced Graphene Oxide (RGO), Graphene Nanoplatelets (GNPs), and Graphene Paper (GP). Therefore, the conductivity of the derivatives is greatly reduced in comparison with the Gr with high quality, and high conductivity strengthening efficiency cannot be ensured. At the same time, Gr is highly prone to agglomeration in the Cu matrix due to its large aspect ratio, strong van der waals forces between layers, large surface energy, and large differences in density with the metal matrix. In this case, while Gr is subjected to surface modification treatment on one hand, and Gr is pre-dispersed in the Cu matrix powder by a high-energy ball milling method on the other hand, both of them inevitably cause destruction of the high crystallinity of Gr, thereby lowering the electrical conductivity of the composite wire rod. In addition, the existing composite methods are all characterized in that a reinforcing phase is added to a metal matrix, so that the interface bonding between the Gr and the Cu matrix is generally weak, and the electronic coupling effect at the Gr/Cu interface is greatly reduced. Although some researchers adopt solid carbon sources to generate Gr in situ on the surface of the flaky Cu powder through flaky powder metallurgy so as to improve the quality of the Gr and the interface bonding between the Gr and a Cu matrix, the uniformity of the obtained Gr is poor, and uncontrollable conductivity is often caused.

Therefore, how to realize high-quality continuous preparation of the graphene metal composite wire material is a problem to be solved urgently at present.

Disclosure of Invention

The invention aims to solve the technical problem of providing a graphene metal composite wire and a low-temperature continuous preparation method thereof.

In order to solve the problems, the invention provides a low-temperature continuous preparation method of a graphene metal composite wire, which comprises the following steps: providing a metal wire; transmitting a metal wire between a roll-to-roll input end and a roll-to-roll output end by using a roll-to-roll deposition mode, and depositing a graphene layer on the surface of the metal wire by using a plasma enhanced chemical vapor deposition process in the transmission process of the metal wire, wherein the deposition temperature of the plasma enhanced chemical vapor deposition process is 700-850 ℃.

Optionally, the diameter of the metal wire is 10 μm to 500 μm.

Optionally, the material of the wire comprises at least one of copper, silver or aluminum.

Optionally, the radio frequency power of the plasma enhanced chemical vapor deposition process is 5W to 200W, the adopted deposition gas is a gas containing C, H elements, and the growth time of the graphene is 30min to 60 min.

Optionally, the deposition gas comprises CH₄、C₂H₂、C₂H₄、C₂H₆、C₃H₈The flow rate of the deposition gas is 1sccm to 50 sccm.

Optionally, the transmission speed of the metal wire is 1 mm/min-500 mm/min.

Optionally, the number of layers of the graphene is adjusted by adjusting the radio frequency power.

Optionally, the number of the growth layers of the graphene is 1-10.

Optionally, before depositing the graphene layer, the metal wire is annealed.

The technical scheme of the invention also provides a graphene metal composite wire material, which comprises a metal wire, a metal wire and a metal wire core, wherein the length of the metal wire is more than 1 m; and the graphene layer completely covers the surface of the metal wire and is uniform in thickness, and is formed by adopting a plasma enhanced chemical vapor deposition process at 700-850 ℃.

Optionally, the diameter of the metal wire is 10 μm to 500 μm.

Optionally, the graphene layer includes 1-10 layers of graphene.

Optionally, the interfacial work of separation between the graphene layer and the metal wire is at least 0.72J/m²。

The continuous preparation method of the graphene metal composite wire material adopts PECVD enhanced R2R CVD, not only can realize continuous controllable preparation of high-quality Gr, but also has low synthesis temperature and larger selection range of substrate wire materials.

Drawings

FIG. 1 is a schematic structural diagram of a roll-to-roll deposition apparatus used in a roll-to-roll deposition method according to an embodiment of the present invention;

FIG. 2 shows deposition gases at specific Ar and CH₄A density test result graph of each group when the flow rate and the radio frequency power are 100W;

FIG. 3 is a graph showing the variation of the density of three groups under different RF power conditions;

FIG. 4 is a Raman spectrum of Gr formed at 830 ℃ under different RF power according to an embodiment of the present invention;

FIG. 5 is a Raman spectrum of Gr at different deposition temperatures at specific powers in accordance with an embodiment of the present invention;

FIG. 6 is a diagram of the interface between Cu and Gr according to an embodiment of the present invention;

FIG. 7 is a Raman characterization plot of the different numbers of layers Gr in an embodiment of the present invention;

fig. 8 is an electron microscope photograph of graphene grown on an Al surface by a PECVD enhanced R2R CVD process at 800 ℃.

Detailed Description

The following describes in detail specific embodiments of the graphene metal composite wire and the continuous preparation method thereof provided by the invention with reference to the accompanying drawings.

In a specific embodiment of the present invention, a metal wire is transported between a roll-to-roll input end and a roll-to-roll output end by using a roll-to-roll deposition method, and a graphene layer is deposited on the surface of the metal wire during the transportation of the metal wire.

Fig. 1 is a schematic structural diagram of a roll-to-roll deposition apparatus used in a roll-to-roll deposition method according to an embodiment of the present invention.

The roll-to-roll (R2R) deposition mode can continuously prepare the composite metal wire. The R2R deposition apparatus mainly comprises a gas supply system, a vacuum system, a high temperature system, a roll-to-roll system, a radio frequency system and a cooling system. Wherein, the gas supply system mainly provides deposition gas, catalytic gas or carrier gas and the like; the vacuum system is vacuumized by a vacuum pump; the high-temperature system is controlled by a programmed heating and cooling system; controlling the moving speed of the metal wire of the coiling system; the radio frequency system is used for providing radio frequency power in the deposition process to enable deposition gas to be in a plasma state, and the cooling system is mainly used for rapidly cooling the composite metal wire after the two-dimensional material is grown.

Fig. 1 is a schematic partial structure diagram of a roll-to-roll deposition apparatus according to an embodiment of the present invention.

The roll-to-roll vapor deposition apparatus includes a tube furnace 101, a roll input end 102 and a roll output end 103 respectively located at both sides of the tube furnace 101. The opposite-winding input end 102 and the opposite-winding output end 103 respectively comprise cylindrical rollers, a continuous metal wire 105 is wound on the rollers of the opposite-winding input end 102, the metal wire 105 is conveyed into the tubular furnace 101 through conveying of a conveying belt and rotation of the rollers, graphene deposition is carried out, a graphene metal composite wire material is formed and output from the other end of the tubular furnace 101, and the roller of the opposite-winding output end 103 is wound, so that continuous preparation can be realized.

The roll-to-roll vapor deposition equipment further comprises a radio frequency system 104, which is used for converting the deposition gas introduced into the tube furnace 101 into plasma so as to perform a plasma chemical vapor deposition process on the surface of the metal wire entering the tube furnace 101 to deposit graphene.

The roll-to-roll deposition apparatus is only one example of one embodiment of the present invention, and those skilled in the art may adopt deposition apparatuses with other structures to transport the metal wire in a roll-to-roll transport manner, and the metal wire passes through the plasma enhanced chemical vapor deposition chamber during the transport process, and graphene is deposited on the surface of the metal wire by using a PECVD process.

The common CVD process is used for depositing graphene, the temperature is required to be higher, generally above 1000 ℃, and if the graphene is deposited on the surface of a metal wire, the diameter of the metal wire is strictly required, generally below 50 μm, otherwise, a graphene layer with higher quality is difficult to grow on the surface of the metal wire; the higher temperature has higher requirements on the melting point of the metal material, for example, the melting point of Cu and the alloy thereof is already exceeded at 1000 ℃, so that the problems of Cu wire breakage and the like in the deposition process are easily caused, and the selection range of the metal wire substrate of the metal wire material is greatly limited.

In addition, in a common deposition process, the growth time or the gas ratio of graphene is generally adjusted to adjust the number of graphene layers. However, in the embodiment of the present invention, since the wire is easily broken during the conveying process, and the deposition time of the graphene needs to be controlled by the conveying rate, in order to avoid adjusting the rotating speed of the coil, the reliable stability of the wire conveying process is affected. If the number of layers to be produced is adjusted by adjusting the gas proportion, the problem of inaccurate regulation and control is also easily caused, so a new mode for adjusting the number of layers to be grown of the graphene needs to be found.

In the specific implementation mode of the invention, the graphene layer is deposited on the surface of the metal wire by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) process, so that the deposition temperature can be reduced, the problems of softening, breaking and the like of the metal wire in the deposition process can be avoided, and the power consumption can be reduced. Before graphene deposition, annealing treatment can be performed on the metal wire to eliminate the defects on the surface of the metal wire and remove impurities attached to the surface.

In one embodiment of the present invention, Cu wire is used as a substrate for the composite metal wire, and in other embodiments, metal wires such as Ag and its alloy, Al and its alloy, etc. can be used as the substrate.

Different from the method for depositing graphene on a planar substrate by adopting PECVD, the method for depositing graphene on a metal wire by adopting PECVD needs to fully consider the influence of the diameter of the metal wire on the deposition effect. Since deposition on the surface of a metal wire belongs to three-dimensional deposition, in order to form a graphene layer with higher deposition quality, the deposition process is required to have higher coverage rate. Generally, the smaller the diameter of the wire, the easier it is to form a higher quality graphene layer. However, due to the roll-to-roll transmission, the thin metal wires are easy to break during the transmission process, and the continuous preparation cannot be completed.

In order to solve the above problems, the inventors carefully studied the deposition process of PECVD, and adjusted the deposition parameters of PECVD for the specific deposition substrate of wire, so that it has high coverage efficiency without the diameter of wire being too small. And the stress condition of the metal wire in the roll-to-roll transmission process is comprehensively considered, and the metal wire with the diameter of 10-500 mu m is selected as a deposition substrate. Preferably, the diameter of the metal wire is 100-300 μm, the roll-to-roll transmission speed is 1-500 mm/min, and the growth time of the graphene in the furnace tube constant-temperature area is 30-60 min.

The deposition temperature of the PECVD can be set to 700-850 ℃, and preferably 800-830 ℃. The deposition gas used in the deposition process includes C and H gases, e.g. CH₄、C₂H₂、C₂H₄、C₂H₆、C₃H₈The flow rate of the deposition gas may be 1sccm to 200sccm, preferably 1sccm to 50 sccm. The deposition process also requires the introduction of a protective gas, such as Ar or N₂The flow rate of the protective gas may be 1to 500sccm, preferably 40 to 200sccm, and the pressure in the reaction chamber is pumped up to 0.05to 1000Torr, preferably 1to 400Torr by a vacuum pump.

Generally, graphene (Gr) is prepared using a general CVD process, except that CH is required₄、C₂H₂When the carbon source is gaseous, H is also required to be introduced₂Exert H₂Etching amorphous carbon during deposition.In the embodiment of the invention, the direct decomposition of the gaseous carbon source into H, H can be realized by utilizing the radio frequency effect generated under the specific power condition₂、CH₂And CH₃Etc. to achieve large area deposition of Gr, therefore, in the present invention, the introduced deposition gas includes C, H elements, please refer to fig. 2, where fig. 2 shows specific Ar and CH₄The density of each group is measured at a flow rate and a radio frequency power of 100W, and mass spectrograms of different groups are obtained by a Residual Gas Analyzer (RGA). It can be seen that under the action of plasma radio frequency, a plurality of groups exist simultaneously. Moreover, by changing the radio frequency power, the regulation and control of the density of the H groups can be realized. FIG. 3 is a graph showing the density variation trend of three groups under different RF powers, which shows H, H W within the RF range of 10W-300W₂And CH₄The density of (a). It can be seen that when the RF power is less than 100W, H and H₂The density of radicals tends to decrease with increasing power, while CH₄The density shows the opposite change. When the radio frequency power is higher than 100W, the density of the three groups almost tends to be stable. In order to improve the etching effect of the H group on the amorphous carbon in the PECVD process, the radio frequency power of the PECVD can be set to be 10-200W.

Based on the above studies, in the embodiment of the present invention, the number of layers of the Gr layer can be controllably grown from 1to 10 layers by changing the rf power from 10W to 200W and gradually increasing the pressure in the tube furnace 101 from 1Torr to 400Torr through the manual pressure valve, and the number of layers of the deposited graphene can be adjusted without adjusting the transmission speed of the wire.

In one embodiment of the present invention, an industrial cold-drawn Cu wire with a length of 400m and a diameter of 100 μm was used as the graphene growth substrate. Before depositing graphene, the Cu wire can be conveyed by a roll to roll way at 650-830 ℃ and H₂Annealing for 30-60 min under the protective atmosphere, and collecting the annealed Cu wires at the output end of the coil. The roughness of the surface of the Cu wire can be reduced and the Cu wire can be removed by the annealing treatmentImpurities on the surface improve the quality of subsequent graphene deposition.

Then, the collected annealed Cu wire is placed at the output end of the opposite roll again, the temperature is raised to the deposition temperature of 830 ℃, the gas flow in the tube furnace is adjusted to 40sccm Ar and 1sccm CH4, the vacuum is pumped to about 1Torr by a vacuum pump, the radio frequency power is 50W, and the growth of single-layer Gr is carried out under the condition. And adjusting the speed of the opposite rolling to ensure that the growth time of Gr in the constant-temperature area of the tube furnace is 30 min. And rapidly cooling the grown single-layer Gr/Cu composite wire material to room temperature from high temperature by using a circulating cooling water system, and collecting the single-layer Gr/Cu composite wire material at the output end of the paired rolls.

FIG. 4 shows the Raman spectrum of Gr at 830 ℃ and different RF powers. From the Raman results, when the radio frequency power is lower than 150W, the ratio of the 2D peak to the G peak of the Gr is larger than 2, and the half-width peak is-30 cm < -1 >, which shows that the growth of the high-quality single-layer Gr can be realized under the existing parameter conditions. When the RF power reaches 170W, the ratio of the D peak to the G peak increases, indicating that the defect content in Gr increases. From the raman spectrum of Gr in fig. 5 under the conditions of specific power and different deposition temperatures, although the number of layers of Gr is a single layer in the process of increasing the temperature from 700 ℃ to 830 ℃, the quality is significantly improved; and the interface bonding strength of Cu and Gr is improved, and the interface strain is reduced. Referring to fig. 6, which is an electron microscope image of the Cu filament according to an embodiment of the present invention after depositing a Gr layer on the surface thereof, it can be seen that there is almost no strain on the interface (interface) between the Gr layer and the Cu, and there are almost no defects in the Gr layer. Therefore, the embodiment of the invention prepares the high-quality single-layer Gr/Cu composite wire material at 830 ℃.

In another embodiment, the gas flow is maintained at 40sccm Ar and 1sccm CH during deposition₄The radio frequency power is changed from 10W to 200W, and the pressure in the tube furnace is gradually increased from 1Torr to 400Torr through a manual pressure valve, so that the controllable growth of Gr layers from a single layer to about ten layers is realized.

In the case where multiple layers of Gr are formed on the surface of the Cu wire, Raman characterization of different layers of Gr is shown in fig. 7, and due to an increase in growth pressure, the etching ability of the H group to the amorphous carbon is reduced, so that a defect peak (D peak) occurs at ten layers of Gr. Therefore, 1-10 graphene layers with high quality can be grown on the surface of the metal wire by adopting a PECVD deposition process on the surface of the metal wire through the specific embodiment of the invention.

In the specific embodiment, the PECVD-enhanced roll-to-roll CVD process is utilized to deposit Gr with different layers on the surface of the Cu wire at a low temperature, so that the difficulties that the existing Gr/Cu composite wire is long in preparation period, small in sample size, discontinuous in Gr structure, easy to break in a high-temperature Cu wire and the like are overcome, and the energy consumption is reduced by reducing the Gr deposition temperature. Besides, the deposition temperature of PECVD is low, the selection of the types of metal substrate wires can be expanded, and besides a Cu wire substrate, other high-conductivity metal wires, such as Cu alloy wires or Ag wires, can be prepared into high-quality Gr/metal composite wires under the low-temperature condition by a process of enhancing R2R CVD by PECVD.

The method can also be used for growing graphene on the surface of the low-melting-point metal, such as growing graphene on the surface of Al. Referring to fig. 8, an electron microscope photograph of graphene grown on the surface of an Al filament by a PECVD enhanced R2R CVD process at 800 ℃, wherein Platinum (Platinum) is used to protect the graphene structure from being damaged during the sample preparation process, and is expected to be simultaneously prepared into a light, high-strength, and highly conductive Al-based composite material.

Aiming at the problems of lower Gr quality and weaker combination with a Cu matrix interface in the prior art, the invention adopts a PECVD combined R2R CVD vapor deposition method, and firstly, Gr is deposited on the surface of a Cu wire material under the environment of ultrahigh vacuum degree and about 800 ℃, so that the regulation and control of Gr quality and the number of layers are realized, the interface combination strength between the Gr and the Cu is improved, the interface strain is reduced, and the improvement of the electronic coupling effect at the Gr and Cu interface is promoted.

In conclusion, the PECVD-enhanced R2R CVD adopted by the invention not only can realize the controllable preparation of high-quality Gr, but also has low synthesis temperature and larger selection range of the substrate wire. Finally, the conductivity of the single-layer Gr/Cu composite wire is 65 multiplied by 10⁶S/m is higher than the conductivity of international annealed Cu by 12 percent.

The specific embodiment of the invention also provides the graphene metal composite wire material formed by adopting the method.

The graphene metal composite wire comprises: a metal wire having a length of 1m or more; and the graphene layer completely covers the surface of the metal wire and is uniform in thickness, and is formed by adopting a plasma enhanced chemical vapor deposition process at 700-850 ℃.

The diameter of the metal wire is 10-500 mu m. The material of the wire comprises at least one of copper, silver or aluminum.

The graphene layer comprises 1-10 layers of graphene, and the bonding strength interface separation work of the graphene layer and the metal wire interface is at least 0.72J/m²The interface separation work is 0.45J/m higher than that of the existing transfer graphene and metal wire²Therefore, the interface bonding strength of the graphene layer and the metal wire is higher than that of the externally-added graphene and the metal wire, the critical stress required for resisting the interface peeling of the externally-added load is higher, and the reliability of the composite metal wire is higher.

The graphene metal composite wire realizes continuous preparation, has larger length and wider application scene. The graphene layer is formed by a plasma enhanced chemical vapor deposition process, so that the metal wire is wide in material selection range, the strength of the graphene layer and the metal wire interface is high, the interface strain is less, and the performance of the graphene metal composite wire can be remarkably improved.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A low-temperature continuous preparation method of a graphene metal composite wire is characterized by comprising the following steps:

providing a metal wire;

transmitting a metal wire between a roll-to-roll input end and a roll-to-roll output end by using a roll-to-roll deposition mode, and depositing a graphene layer on the surface of the metal wire by using a plasma enhanced chemical vapor deposition process in the metal wire transmission process, wherein the deposition temperature of the plasma enhanced chemical vapor deposition process is 700-850 ℃, the radio frequency power is changed from 10W-200W, and the controllable growth of the layer number of the graphene layer is realized by gradually increasing the pressure in a plasma enhanced chemical vapor deposition furnace from 1 Torr-400 Torr.

2. The continuous production method at low temperature according to claim 1, wherein the diameter of the wire is 10 to 500 μm.

3. The low-temperature continuous preparation method according to claim 1, wherein the material of the metal wire comprises at least one of copper and silver.

4. The low-temperature continuous preparation method according to claim 1, wherein the adopted deposition gas is a gas containing C, H elements, and the growth time of the graphene is 30-60 min.

5. The method according to claim 4, wherein the deposition gas comprises CH₄、C₂H₂、C₂H₄、C₂H₆、C₃H₈The flow rate of the deposition gas is 1sccm to 50 sccm.

6. The low-temperature continuous production method according to claim 1, wherein the wire is transported at a speed of 1mm/min to 500 mm/min.

7. The low-temperature continuous preparation method according to claim 1, wherein the number of graphene growth layers is 1-10.

8. The method according to claim 1, wherein the metal wire is annealed before the graphene layer is deposited.

9. The graphene metal composite wire prepared by the preparation method according to claim 1, comprising:

a metal wire having a length of 1m or more;

the graphene layer completely covers the surface of the metal wire and is uniform in thickness, the graphene layer is formed by adopting a plasma enhanced chemical vapor deposition process at the temperature of 700-850 ℃, the graphene layer comprises 1-10 layers of graphene, and the interface separation work of the graphene layer and the metal wire is at least 0.72J/m²。

10. The graphene-metal composite wire according to claim 9, wherein the diameter of the metal wire is 10 to 500 μm.

11. The graphene metal composite wire according to claim 9, wherein the material of the metal wire includes at least one of copper and silver.