Monene copper powder and preparation method thereof

Abstract

The invention discloses monene copper powder and a preparation method thereof. The preparation method of the graphene copper powder comprises the following steps that graphene is deposited and grown on the surface of micron-sized copper powder through chemical vapor deposition, and the graphene copper powder coated with the copper powder is obtained; wherein in the process of depositing and growing the graphene, mixed gas containing hydrogen and carbon source gas is introduced in a pulse pressure manner, so that the pressure in the reaction chamber is alternately changed between high pressure and low pressure. According to the method, a pulse pressure chemical vapor deposition method is adopted, carbon source gas is blown into the powder through the air pressure difference between the interior and the exterior of the powder, the mass transfer efficiency of the carbon source gas in the powder is improved, reaction by-products are blown to the exterior of the powder, and the quality of graphene is improved. According to the method, the large-scale controllable preparation of the monene copper powder with different graphene layer numbers and different graphene coating rates can be realized by regulating and controlling the combination of process parameters such as the pressure intensity of the carbon source and the growth time.

Description

Technical Field

[0001] The present invention relates to a graphene-coated copper powder and a preparation method thereof, belonging to the field of materials. Background Art

[0002] Graphene is a two-dimensional crystal material with a single layer or a few layers formed by sp2 hybridization of carbon atoms, and has excellent electrical properties (carrier mobility ), thermal conductivity (thermal conductivity of 5300 W / mK), and mechanical properties (intrinsic strength of 130 GPa). The combination of graphene and copper will produce a synergistic effect (such as the synergy between the high carrier mobility of graphene and the high carrier density of copper), which is expected to achieve simultaneous breakthroughs in the electrical conductivity, thermal conductivity, and mechanical properties of copper, making it an ideal candidate for a new generation of high-performance composite materials and expected to have an important impact in industrial fields such as electronics, electric power, energy, thermal management, and aerospace. High-temperature chemical vapor deposition on a copper substrate is the most mature method for preparing high-quality graphene and also the most promising method for preparing graphene-copper composites. However, the key problem is how to increase the proportion of graphene in the graphene-copper composite and fully utilize the synergistic effect between graphene and copper. Among the materials in the forms of bulk, foil, wire, and powder, the graphene-coated copper powder material has the highest proportion of graphene and can best exert the synergistic effect between graphene and copper.

[0003] However, copper powder is extremely easy to sinter into a copper block during high-temperature CVD, and it is also difficult for the carbon source to effectively transport inside the powder, resulting in great difficulties in the preparation of graphene-coated copper powder, especially in large-scale preparation. At present, there are the following several methods for preparing graphene-coated copper powder composites: First, a solid or liquid carbon source is coated on the surface of copper powder and then graphene is grown at high temperature to prepare graphene / copper powder composites (CN 105081312 A, CN 104874803 A, CN 111139453 B). However, the graphene-coated copper powder prepared by this method is easy to sinter, the quality of graphene is poor, and there is a lot of carbon deposition; Second, a fluidized bed is used as the reaction device, and a gaseous carbon source is used as the reaction gas to coat graphene on copper powder in a fluidized state to prepare graphene-coated copper powder composites (CN 110385432 A, CN110777354 A). This method requires a very large amount of gas and a very high cost to fluidize the copper powder, and the copper powder is also prone to adhesion during the fluidization process, making it difficult to scale up the production. Therefore, the large-scale preparation of graphene-coated copper powder with a high graphene coating rate and good quality is still difficult to achieve.

[0004] In summary, there are still problems in the preparation of graphene-coated copper powder, such as the low quality of graphene, the difficulty in ensuring the graphene coating rate, the small output, and the inability to achieve large-scale preparation. Therefore, it is of great significance to further explore a technical method that can achieve the large-scale preparation of high-quality graphene-coated copper powder. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of micron-scale copper monene powder and the copper monene powder prepared by this method; the present invention uses weakly polar or non-polar substance powder as the isolation powder, which not only separates copper powder particles but also avoids the adhesion of copper powder and isolation powder at high temperature, thus simplifying the separation step and improving the purity of copper monene powder; by using the pulsed pressure chemical vapor deposition technology, the problem of mass transfer efficiency inside the powder is improved, and thus the problem that the static chemical vapor deposition of stacked powder cannot be scaled up is overcome; by controlling factors such as the carbon source partial pressure, the pressure difference of pulsed pressure, the growth cycle, and the growth time, the control of the graphene coating rate and the number of layers of copper monene powder can be realized, and the controllable large-scale preparation of copper monene powder can be achieved.

[0006] Specifically, the preparation method of copper monene powder provided by the present invention includes the following steps: depositing and growing graphene on the surface of copper powder by chemical vapor deposition to obtain copper monene powder with graphene-coated copper powder; wherein, during the deposition and growth of graphene, a mixed gas containing hydrogen and a carbon source gas is introduced in a pulsed pressure manner, so that the pressure in the reaction chamber shows an alternating change between high pressure and low pressure.

[0007] In the preparation method of the present invention, the high pressure range is 100 Pa - 100 kPa, and the low pressure is not higher than 50% of the high pressure value; Preferably, the pulsed pressure is specifically: the pressure shows a periodic change of maintaining high pressure for 1 - 5 min and maintaining low pressure for 1 - 5 min.

[0008] In the preparation method of the present invention, the mixed gas further includes argon, and the pressure difference between the high pressure and the low pressure is increased by the introduction amount of argon.

[0009] In the preparation method of the present invention, the temperature of the chemical vapor deposition is 850 - 1200 °C, preferably 1030 - 1050 °C, and the time is 2 - 30 minutes.

[0010] In the preparation method of the present invention, the carbon source gas is a hydrocarbon gas such as methane, acetylene, ethylene, propylene, etc., and the carbon-hydrogen partial pressure ratio in the mixed gas is: methane partial pressure: hydrogen partial pressure = 0.3 - 50:200, or acetylene partial pressure: hydrogen partial pressure = 0.5 - 50:20000; Preferably, the carbon-hydrogen partial pressure ratio is: methane partial pressure: hydrogen partial pressure = 1:200, or acetylene partial pressure: hydrogen partial pressure = 1:20000.

[0011] In the preparation method of the present invention, when the partial pressure of methane < 5 Pa or the partial pressure of acetylene < 0.2 Pa, few-layer graphene with 1 - 3 layers is obtained; When the partial pressure of methane is 10 - 1000 Pa or the partial pressure of acetylene is 0.5 - 50 Pa, multi-layer graphene with 4 - 10 layers is obtained.

[0012] The preparation method of the present invention further includes a powder mixing step: mixing copper powder with isolation powder to obtain a mixed powder; Placing the mixed powder in a reaction chamber, and growing graphene by chemical vapor deposition on the surface of the copper powder; The copper powder is gas atomized copper powder, ultrasonic atomized copper powder, plasma atomized or electrolytic copper powder; And / or, the isolation powder is a strongly covalent bond powder with weak polarity or non-polarity; Preferably, the particle size of the isolation powder < the particle size of the copper powder, and the particle number ratio is: isolation powder: copper powder > 12:1; The isolation powder is selected from at least one of graphite powder, diamond powder, aluminum nitride powder, and boron nitride powder.

[0013] The preparation method of the present invention specifically includes the following steps: S1. Mixing micron-sized copper powder with isolation powder to obtain a mixed powder; S2. Placing the mixed powder in a reaction chamber and annealing it in a hydrogen atmosphere; S3. After the annealing is completed, introducing a mixed gas of hydrogen and a carbon source gas into the reaction chamber, and performing pulsed pressure chemical vapor deposition by adjusting the pressure in the reaction chamber to obtain copper powder with graphene.

[0014] In step S2, the hydrogen partial pressure range in the reaction chamber is 0.5 - 3 atm, the annealing temperature is 900 - 1000 °C, and the time is greater than 20 minutes.

[0015] Preferably, it further includes step S4: screening and cleaning to remove the isolation powder to obtain copper powder with graphene; Preferably, the screening includes ultrasonic vibration screening and air classification; and / or, alcohol is used for the cleaning.

[0016] The copper powder with graphene prepared by the present invention includes copper powder and graphene coated on the surface of the copper powder. The copper powder with graphene is micron-sized, and the particle size range is 10 μm - 500 μm, preferably 10 μm - 80 μm.

[0017] The growth method provided by the present invention uses isolation powder to completely separate copper powder particles, thereby avoiding contact between copper powder particles and further avoiding sintering of copper powder at high temperatures. Moreover, powder particles of weakly polar or non-polar, strongly covalent bond substances are used to avoid adhesion between the isolation powder and copper powder at high temperatures, thus contaminating the graphene-coated copper powder. The method of pulsed pressure chemical vapor deposition is adopted. By using the pressure difference between the inside and outside of the powder, the carbon source gas is blown into the inside of the powder, improving the mass transfer efficiency of the carbon source gas inside the powder and blowing the reaction by-products to the outside of the powder, thereby improving the quality of graphene. Pulsed pressure chemical vapor deposition overcomes the problem of difficult mass transfer inside the mixed powder in a stacked state and breaks through the problem of limited production in static chemical vapor deposition of stacked powders, enabling large-scale preparation. By regulating process parameter combinations such as carbon source pressure and growth time, large-scale controllable preparation of graphene-coated copper powder with different numbers of graphene layers and different graphene coating rates can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flowchart for the preparation of graphene-coated copper powder of the present invention.

[0019] Figure 2 It is an X-ray scanning cross-sectional view of the distribution of copper powder particles in the mixed powder in Example 1 of the present invention.

[0020] Figure 3 It is a process diagram of pulsed pressure chemical vapor deposition in Example 1 of the present invention.

[0021] Figure 4 It is a Raman spectrum of the graphene-coated copper powder prepared in Example 1 of the present invention.

[0022] Figure 5 It is a comparison of the graphene-coated copper powder prepared by constant pressure static chemical vapor deposition in Comparative Example 1 and pulsed pressure chemical vapor deposition in Example 1 of the present invention.

[0023] Figure 6 It is a physical diagram of the pure copper powder used in Example of the present invention and the prepared graphene-coated copper powder.

[0024] Figure 7 It is an SEM photograph of graphene-coated copper powder with different graphene coating rates.

[0025] Figure 8 It is an SEM photograph of the graphene-coated copper powder prepared in Example 6 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. The methods are conventional methods unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified.

[0027] The preparation method of the copper-monthenicene powder provided by the present invention comprises the following steps: 1): Mix the copper powder with the isolation powder.

[0028] Weigh the copper powder and the isolation powder according to a given ratio, and put them into a V-type powder mixer to mix for 30 min. The rotation speed of the V-type powder mixer is 120 revolutions per minute.

[0029] Among them, the copper powder is commercially purchased gas atomized copper powder or ultrasonic atomized copper powder or electrolytic copper powder. The size of the copper powder is micron-level, and the particle size range is 10μm - 500μm.

[0030] The isolation powder is a strongly covalent bond powder with weak polarity or non-polarity, preferably at least one of graphite powder, diamond powder, aluminum nitride powder, and boron nitride powder.

[0031] The particle size of the isolation powder < the particle size of the copper powder, and the particle number ratio is: isolation powder: copper powder > 12:1.

[0032] 2): High-temperature annealing of the mixed powder.

[0033] Put the mixed powder of the copper powder and the isolation powder into the reaction chamber of a tube furnace, close the tube furnace, evacuate and maintain for 10 min to remove the gas in the mixed powder. Subsequently, introduce hydrogen, maintain the hydrogen pressure at 0.5 - 3 atm, heat up to 900 - 1000°C, and perform high-temperature annealing for a time greater than 20 min.

[0034] 3): Pulse pressure type high-temperature chemical vapor deposition.

[0035] Raise the temperature of the reaction chamber of the tube furnace to 850 - 1200°C, and reduce the pressure in the reaction chamber to 100 - 500 Pa. Introduce a mixed gas of a carbon source gas and hydrogen, adjust the pressure in the reaction chamber to make the pressure in the reaction chamber show an alternating change of high pressure and low pressure, and perform chemical vapor deposition growth for 2 - 30 minutes.

[0036] Among them, the high-pressure range is 100 Pa - 100 kPa, and the low pressure is not higher than 50% of the high-pressure value. Preferably, the pulse pressure is specifically: making the pressure show a periodic change of maintaining high pressure for 1 - 5 min and maintaining low pressure for 1 - 5 min.

[0037] The mixed gas also includes argon, and the differential pressure between the high pressure and the low pressure is increased by the introduction amount of argon.

[0038] The carbon source gas is a hydrocarbon gas such as methane, acetylene, ethylene, or propylene. The carbon-hydrogen partial pressure ratio in the mixed gas is: methane partial pressure: hydrogen partial pressure = 0.3 - 50:200, or acetylene partial pressure: hydrogen partial pressure = 0.5 - 50:20000; preferably, the carbon-hydrogen partial pressure ratio is: methane partial pressure: hydrogen partial pressure = 1:200, or acetylene partial pressure: hydrogen partial pressure = 1:20000.

[0039] When the partial pressure of methane < 5 Pa or the partial pressure of acetylene < 0.2 Pa, few-layer graphene with 1 - 3 layers is obtained; when the partial pressure of methane is 10 - 1000 Pa or the partial pressure of acetylene is 0.5 - 50 Pa, multi-layer graphene with 4 - 10 layers is obtained.

[0040] 4): Separate the copper-monthenide powder.

[0041] Take out the mixed powder from the tube furnace, and screen the copper-monthenide powder and the isolation powder by ultrasonic vibration screening or air classification to obtain the preliminarily screened copper-monthenide powder. Then put the copper-monthenide powder into pure alcohol and ultrasonically clean it with an ultrasonic cleaner to further remove the isolation powder in the copper-monthenide powder. Place the cleaned copper-monthenide powder in a vacuum drying oven to dry and remove the alcohol to obtain pure copper-monthenide powder.

[0042] The copper-monthenide powder and its preparation method according to an embodiment of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Among them, the raw materials can be obtained from public commercial channels without special instructions.

[0043] According to Figure 1 the shown process to prepare the copper-monthenide powder.

[0044] Example 1, 1). Ultrasonically vibrate and screen the commercially purchased copper powder, select two kinds of sieve meshes of 20 μm and 60 μm, and obtain copper powder with a particle size between 20 μm - 60 μm. Ultrasonically vibrate and screen the commercially purchased spherical graphite powder, select two kinds of sieve meshes of 20 μm and 15 μm, and obtain spherical graphite powder with a particle size between 15 μm - 20 μm. Weigh 200 g of copper powder and 300 g of spherical graphite powder (the particle number ratio of the two is about 1:65), put them into a V-type powder mixer and mix for 30 min at a rotation speed of 120 revolutions per minute. The distribution state of the copper powder in the mixed powder is as Figure 2 shown, and it can be seen that the copper powder can be well separated by the graphite powder.

[0045] 2). Place the mixed powder into the tube furnace, evacuate to below 10 Pa and maintain for 10 min. Then introduce 1000 sccm of hydrogen, maintain the pressure at 5000 Pa, and heat up to 950 °C in 40 min. Anneal at 950 °C for 30 min.

[0046] 3), Subsequently, the temperature is raised to 1040 °C in 8 minutes, and the air pressure is pumped to 100 Pa. Then, the temperature is raised to 1050 °C in 2 minutes, and 1000 sccm of hydrogen and 5 sccm of methane are introduced. The total air pressure is maintained at 1005 Pa for 1 minute, and then the total air pressure is reduced to 500 Pa and maintained for 1 minute. This cycle is repeated 4 times. Finally, furnace cooling is carried out under a carbon source atmosphere of 1005 Pa. The pulsed pressure chemical vapor deposition process is as Figure 3 shown.

[0047] 4), Take out the mixed powder, separate the mengene copper powder from the graphite powder by ultrasonic vibration screening, and select a 20 μm sieve mesh. Put the preliminarily screened mengene copper powder into a large beaker, pour in pure alcohol, and carry out ultrasonic cleaning for 20 minutes. Utilize the different densities of the copper powder and the graphite powder to further remove the graphite powder. Place the mengene copper powder in a vacuum drying oven for drying to obtain the mengene copper powder.

[0048] The Raman spectrum of the mengene copper powder prepared in Example 1 of the present invention is as Figure 4 shown. It can be seen that the graphene is deposited on the surface of the copper powder, rather than amorphous carbon.

[0049] Comparative Example 1, In this comparative example, in step 3), constant pressure high-temperature chemical vapor deposition is adopted. At 1050 °C, 1000 sccm of hydrogen and 5 sccm of methane are introduced, and the total air pressure is maintained at 1005 Pa for 8 minutes. Subsequently, furnace cooling is carried out under a carbon source atmosphere of 1005 Pa. Other conditions are the same as those in Example 1.

[0050] Figure 5 is the SEM image of the mengene copper powder prepared by constant pressure static high-temperature chemical vapor deposition in Comparative Example 1 and pulsed pressure high-temperature vapor deposition in Example 1. The sampling depth is 5 cm deep from the powder surface. From Figure 5 it can be seen that due to the problem of difficult mass transfer during ordinary constant pressure static growth, the graphene coating rate on the surface of the copper powder is low, only about 4%. However, the surface of the mengene copper powder prepared by pulsed pressure high-temperature vapor deposition is almost fully coated with graphene, and the coating rate can reach 98%, which proves the effectiveness of the method of the present invention.

[0051] Example 2, In this example, copper powder with a particle size of 10 μm - 20 μm and graphite powder slightly less than 10 μm are obtained by ultrasonic vibration screening and mixed. The mixing ratio is copper powder mass: graphite powder mass = 2:3 (the particle number ratio of the two is about 1:30). The sieve mesh used for separation is a 10 μm sieve mesh. Other conditions are the same as those in Example 1, and mengene copper powder with a particle size in the range of 10 μm - 20 μm can be prepared.

[0052] Example 3, In this embodiment, copper powder with a particle size of 60 μm - 80 μm and graphite powder with a particle size of 20 μm - 25 μm are obtained by ultrasonic vibration screening and then mixed. The mixing ratio is copper powder mass : graphite powder mass = 2:3 (the particle number ratio of the two is 1:168). The sieve mesh used for separation is a 60 μm sieve mesh. Other conditions are the same as those in Example 1, and monene copper powder with a particle size in the range of 60 μm - 80 μm can be prepared.

[0053] The physical pictures of monene copper powder with different particle sizes prepared in Example 2 (10 μm - 20 μm), Example 1 (20 μm - 60 μm), and Example 3 (60 μm - 80 μm) are as Figure 6 shown. It can be seen that the method of the present invention is suitable for preparing micron-sized monene copper powder with a particle size ≥ 10 μm.

[0054] Example 4, In this embodiment, during the pulsed pressure type high-temperature chemical vapor deposition in step 3), 1 sccm of methane and 200 sccm of hydrogen are introduced. The pulsed gas pressure is set to a high pressure of 201 Pa for 1 min and a low pressure of 100 Pa for 1 min, and the cycle is repeated 4 times. Other conditions are the same as those in Example 1.

[0055] Example 5, In this embodiment, during the pulsed pressure type high-temperature chemical vapor deposition in step 3), 3 sccm of methane and 600 sccm of hydrogen are introduced. The pulsed gas pressure is set to a high pressure of 603 Pa for 1 min and a low pressure of 300 Pa for 1 min, and the cycle is repeated 4 times. Other conditions are the same as those in Example 1.

[0056] The SEM photos of monene copper powder with different graphene coating rates prepared by the methods of Example 4, Example 5, and Example 1 are as Figure 7 shown. The graphene coating rates are 43%, 56%, and 98% respectively, indicating that by adjusting the methane flow rate and partial pressure, the graphene coating rate can be effectively controlled.

[0057] Example 6, In this embodiment, during the pulsed pressure type high-temperature chemical vapor deposition in step 3), 5 sccm of methane and 1000 sccm of hydrogen are introduced. The pulsed gas pressure is set to a high pressure of 1005 Pa for 1 min and a low pressure of 800 Pa for 1 min, and the cycle is repeated 4 times. Other conditions are the same as those in Example 1.

[0058] The SEM photo of the monene copper powder prepared by the method in Example 6 is as Figure 8 shown. The graphene coating rate is only 24%, indicating that the greater the pressure difference between the high pressure and the low pressure of the pulsed pressure, the more conducive it is to the internal gas flow exchange and carbon source transmission of the powder, and thus more conducive to increasing the graphene coating rate.

Claims

1. A preparation method of mengene copper powder, comprising the following steps: Graphene-coated copper powder is obtained by depositing and growing graphene on the surface of micron-sized copper powder through chemical vapor deposition; among them, During the deposition of graphene, a mixed gas containing hydrogen and a carbon source gas is introduced in a pulsed pressure manner, so that the pressure in the reaction chamber shows an alternating change between high pressure and low pressure.

2. The preparation method according to claim 1, characterized in that, The high pressure range is 100 Pa - 100 kPa, and the low pressure is not higher than 50% of the high pressure value; Preferably, the pulsed pressure is specifically: the pressure shows a periodic change of maintaining high pressure for 1 - 5 min and maintaining low pressure for 1 - 5 min.

3. The preparation method according to claim 1 or 2, characterized in that, The mixed gas further includes argon, and the pressure difference between the high pressure and the low pressure is increased by the introduced amount of argon.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The temperature of the chemical vapor deposition is 850 - 1200 °C, and the time is 2 - 30 minutes; The carbon source gas is a hydrocarbon gas, including at least one of methane, acetylene, ethylene, and propylene; The carbon-hydrogen partial pressure ratio in the mixed gas is: methane partial pressure: hydrogen partial pressure = 0.3~50:200, or acetylene partial pressure: hydrogen partial pressure = 0.5~50:20000.

5. The preparation method according to claim 4, characterized in that, When the partial pressure of methane < 5 Pa or the partial pressure of acetylene < 0.2 Pa, 1 - 3 layers of few-layer graphene are obtained; When the partial pressure of methane is 10 - 1000 Pa or the partial pressure of acetylene is 0.5 - 50 Pa, 4 - 10 layers of multi-layer graphene are obtained.

6. The preparation method according to any one of claims 1-5, characterized in that, It further includes a powder mixing step: mixing copper powder with an isolation powder to obtain a mixed powder; Placing the mixed powder in a reaction chamber, and depositing and growing graphene on the surface of the copper powder by chemical vapor deposition.

7. The preparation method according to claim 6, characterized in that, The copper powder is gas atomized copper powder, ultrasonic atomized copper powder, plasma atomized or electrolytic copper powder; And / or, the isolation powder is a strongly covalent bond powder with weak polarity or non-polarity; And / or, the isolation powder is selected from at least one of graphite powder, diamond powder, aluminum nitride powder, and boron nitride powder; Preferably, the particle size of the isolation powder < the particle size of the copper powder, and the particle number ratio is: isolation powder: copper powder > 12:

1.

8. The preparation method according to any one of claims 1-7, characterized in that, The preparation method specifically includes the following steps: S1. Mix micron-sized copper powder with an isolation powder to obtain a mixed powder; S2. Place the mixed powder in a reaction chamber and anneal it in a hydrogen atmosphere; S3. After the annealing is completed, introduce a mixed gas of hydrogen and a carbon source gas into the reaction chamber, and perform pulsed pressure chemical vapor deposition by adjusting the pressure in the reaction chamber to obtain micron-sized mengene copper powder.

9. The preparation method according to claim 8, characterized in that, In step S2, the hydrogen partial pressure range in the reaction chamber is 0.5 - 3 atm, the annealing temperature is 900 - 1000 °C, and the time is greater than 20 minutes; It further includes step S4: screening and cleaning to remove the isolation powder to obtain mengene copper powder; Preferably, the screening includes ultrasonic vibration screening and air classification; and / or, alcohol is used for cleaning.

10. The mengene copper powder prepared by the method according to any one of claims 1 - 9, including copper powder and graphene coated on the surface of the copper powder, and the mengene copper powder is micron-sized, and the particle size range is 10 μm~500 μm.

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