Method for preparing nano graphene and composite material thereof at low temperature

Abstract

The invention relates to a method for preparing nano graphene and a composite material thereof at low temperature. The method is mainly realized by taking metal oxide or metal salt powder as a precursor and carbon-containing gas as a carbon source and combining means such as a plasma enhancement technology. Firstly, a precursor is placed in a vacuum furnace; then vacuumizing to a background; introducing a certain proportion of carbon source gas and auxiliary gas, and keeping the gas pressure at 10-5000 Pa; performing plasma treatment on the gas in the furnace in a certain manner; raising the temperature to 150-500 DEG C at a certain heating rate, and keeping the temperature for a period of time; and then closing the carbon source gas, stopping plasmatization, and cooling to room temperature to prepare the nano graphene and the composite material thereof. The method has the advantages that the growth temperature of the graphene is low (can be as low as 150 DEG C), and the nano graphene with the superfine particle level (1-10 nm) and the graphene / metal particle composite material perfectly coated with the graphene can be prepared.

Description

Technical Field

[0001] The invention provides a method for preparing nano graphene and a composite material thereof at low temperature, belonging to the field of graphene material preparation. Background Art

[0002] Graphene is a new material that combines ultra-high strength, ultra-high electron mobility, and ultra-high thermal conductivity. It has important application prospects in materials, energy, biomedicine, and drug delivery, and is considered a revolutionary material for the future.

[0003] Chemical vapor deposition is one of the three most important graphene preparation technologies along with mechanical exfoliation and chemical exfoliation. In chemical vapor deposition, the growth of high-quality graphene usually requires metal blocks, foils and powders as substrates. However, this method currently still has problems such as high process temperature (generally greater than 700°C) and difficulty in obtaining nanographene in large quantities. The reason is that the surface energy of metal blocks, foils and metal powders with a diameter greater than 100nm is not high enough, and it is impossible to efficiently catalyze the self-assembly of free carbon atoms on their surfaces into graphene films at temperatures below 700°C. Moreover, even if nanometal powders with a diameter of less than 100nm are used as substrates, the purpose cannot be achieved. Because the surface energy of nanometal powders is relatively high, they will fuse and grow together when the temperature is higher than 200°C, and the nanometal powders will "disappear". Even if a complex medium addition method is used, such as adding a large amount of high melting point and highly inert magnesium oxide powder, the purpose cannot be achieved. This is because it not only fails to completely separate the agglomerated nanopowders one by one, but also reduces the permeability of carbon-containing gases in the powders, and adds many process links for the later purification of the product.

[0004] Therefore, it is particularly meaningful to invent a method for fundamentally realizing low-temperature preparation of nanographene, which also lays a solid foundation for the preparation of ultrafine particle (1-10nm) graphene composite materials. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a method for preparing nanographene and its composite material at low temperature. The idea is: while metal oxides or metal salts are converted into ultrafine metal nanoparticles through thermal decomposition reaction or reduction reaction, carbon atoms cracked by carbon source gas in plasma state are immediately deposited in situ on the surface of metal nanoparticles to obtain ultrafine metal nanoparticles (1-10nm) wrapped by amorphous carbon, and the fusion growth of ultrafine metal nanoparticles is prevented; then, as the temperature rises or the temperature is kept warm, the wrapped amorphous carbon is in situ catalytically converted into high-quality graphene film by utilizing the high catalytic effect of ultrafine metal nanoparticles; finally, ultrafine nanographene and composite materials composed of nanographene and metal nanoparticles are obtained.

[0006] The present invention is achieved through the following technical solutions.

[0007] A method for preparing nanographene and its composite materials at low temperature, the specific steps of which are as follows:

[0008] It mainly uses metal oxide or metal salt powder as precursor and carbon-containing gas as carbon source, and is realized by combining plasma enhancement technology and other means; first, the precursor is placed in a vacuum furnace; then, the vacuum is evacuated to the background; then a certain proportion of carbon source gas and auxiliary gas are introduced to keep the gas pressure at 10-5000Pa; then the gas in the furnace is plasmatized in a certain way; then, the temperature is increased to 150-500°C at a certain heating rate and kept warm for a period of time; then, the carbon source gas is turned off, the plasmatization is stopped, and the furnace is cooled to room temperature, so that nanographene and its composite materials can be prepared.

[0009] The metal element in the metal salt is one or more of Ni, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, Ag, Cd, W, Au, Pt, and Cu.

[0010] The metal salt is one or more of carbonate, oxalate, acetate, nitrate and chlorate.

[0011] The carbon-containing gas is hydrocarbon or CO.

[0012] The certain ratio is the ratio of the carbon source gas to the auxiliary gas, and the ratio is 1:0-300.

[0013] The auxiliary gas is hydrogen or argon, and the ratio is 1:0.1-10.

[0014] The certain mode is one or more of radio frequency discharge, direct current glow discharge and microwave discharge.

[0015] The certain heating rate is 1-100°C / min.

[0016] The period of time is 0 to 20 hours.

[0017] The particle size of the powder is 5nm-100μm.

[0018] Beneficial effects of the present invention: The present invention has a low graphene growth temperature (can be as low as 150°C), and can prepare nanographene with ultrafine particle size (1 to 10 nm) and graphene / metal particle composite materials perfectly coated with graphene. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the XRD pattern of the needle-shaped basic copper nickel carbonate used as the raw material in Example 1.

[0020] Figure 2 This is the SEM image (50,000 times) of the needle-shaped basic copper nickel carbonate used as the raw material in Example 1.

[0021] Figure 3 This is the SEM image (50,000 times) of the composite material prepared in Example 1.

[0022] Figure 4 This is the SEM image (200,000 times) of the composite material prepared in Example 1.

[0023] Figure 5 This is a TEM image of the composite material prepared in Example 1 (graphene / metal particle composite material).

[0024] Figure 6 This is the TEM image of the ultrafine nanographene prepared in Example 1. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific implementation modes.

[0026] Example 1

[0027] The method for preparing nanographene and its composite material at low temperature comprises the following steps:

[0028] The precursor is mainly needle-shaped basic copper-nickel carbonate powder (copper-nickel ratio 1:1) with a diameter of about 70nm. Figure 1 , Figure 2 XRD and SEM, respectively, with C 2 H 2 The precursor is placed in a vacuum furnace, and then the vacuum is pumped down to the background. Then, a carbon source gas and an auxiliary gas (Ar:H) with a ratio of 1:80 are introduced. 2 =1:1), keep the gas pressure at 220Pa; then use radio frequency discharge to plasmatize the gas in the furnace; then heat it to 300℃ at a heating rate of 25℃ / min and keep it warm for 0.1h; then turn off the carbon source gas, stop plasmatization, and cool it to room temperature, and ultrafine nanographene with a diameter of about 3-7nm and Gr / NiCu composite materials perfectly wrapped by graphene are prepared ( Figure 3 / 4 and Figure 5 They are the SEM and TEM images of the composite material obtained after growing ultrafine nanographene; Figure 6 To treat the internal particles with HNO 3 TEM image of pure ultrafine nanographene obtained after etching).

[0029] Example 2

[0030] The method for preparing nanographene and its composite material at low temperature comprises the following steps:

[0031] It mainly uses iron oxalate powder with a particle size of about 100 μm as the precursor and CH 4 as the carbon source, and combined with plasma enhanced technology and other means to achieve; first, the precursor is placed in a vacuum furnace; then the vacuum is evacuated to the background; then a 1:0 carbon source gas and auxiliary gas are introduced to keep the gas pressure at 10Pa; the gas in the furnace is plasmatized by microwave discharge; then the temperature is increased to 410℃ at a heating rate of 1℃ / min and kept for 10min; then the carbon source gas is turned off, the plasmatization is stopped, and the furnace is cooled to room temperature, thereby preparing ultrafine nanographene with a diameter of about 2 to 5nm and Gr / Fe composite materials perfectly wrapped by graphene.

[0032] Example 3

[0033] The method for preparing nanographene and its composite material at low temperature comprises the following steps:

[0034] It mainly uses silver oxide powder with a particle size of about 5nm as a precursor and C 2 H 2 The precursor is placed in a vacuum furnace, and then the vacuum is pumped down to the background. Then, a carbon source gas and an auxiliary gas (Ar:H) with a ratio of 1:300 are introduced. 2 =1:10), keeping the gas pressure at 5000Pa; then plasmatizing the gas in the furnace by direct current glow discharge; then raising the temperature to 150°C at a heating rate of 100°C / min and keeping the temperature for 20h; then turning off the carbon source gas, stopping the plasmatization, and cooling to room temperature, ultrafine nanographene with a diameter of about 1 to 3nm and Gr / Ag composite materials perfectly wrapped by graphene were prepared.

[0035] Example 4

[0036] The method for preparing nanographene and its composite material at low temperature comprises the following steps:

[0037] The process is mainly based on zinc acetate powder with a particle size of about 300 nm as the precursor and CO as the carbon source, and is achieved by combining plasma enhancement technology and other means. First, the precursor is placed in a vacuum furnace; then the vacuum is pumped to the background; then a 1:130 carbon source gas and auxiliary gas (Ar:H 2 =1:0.1), keeping the gas pressure at 1050Pa; then plasmatizing the gas in the furnace by radio frequency discharge; then raising the temperature to 450°C at a heating rate of 45°C / min and keeping it warm for 0.5h; then turning off the carbon source gas, stopping the plasmatization, and cooling to room temperature, ultrafine nanographene with a diameter of about 6 to 10nm and Gr / Zn composite materials perfectly wrapped by graphene were prepared.

[0038] Example 5

[0039] The method for preparing nanographene and its composite material at low temperature comprises the following steps:

[0040] It mainly uses lead nitrate powder with a particle size of about 50μm as the precursor and C 2 H 4 The precursor is placed in a vacuum furnace, and then the vacuum is pumped down to the background. Then, a carbon source gas and an auxiliary gas (Ar:H) in a ratio of 1:0.5 are introduced. 2 =1:7), keeping the gas pressure at 35Pa; then plasmatizing the gas in the furnace by radio frequency discharge; then raising the temperature to 500°C at a heating rate of 75°C / min and keeping it warm for 3.5h; then turning off the carbon source gas, stopping the plasmatization, and cooling to room temperature, ultrafine nanographene with a diameter of about 5 to 9nm and Gr / Pb composite materials perfectly wrapped by graphene were prepared.

[0041] Example 6

[0042] The method for preparing nanographene and its composite material at low temperature comprises the following steps:

[0043] It is mainly composed of chloroauric acid (HAuCl 4 ) powder as precursor, CH 4 The precursor is placed in a vacuum furnace, and then the vacuum is pumped down to the background. Then, a carbon source gas and an auxiliary gas (Ar:H) with a ratio of 1:150 are introduced. 2 =1:2), keeping the gas pressure at 534Pa; then plasmatizing the gas in the furnace by radio frequency discharge; then raising the temperature to 380℃ at a heating rate of 20℃ / min and keeping it warm for 0.3h; then turning off the carbon source gas, stopping the plasmatization, and cooling to room temperature, ultrafine nanographene with a diameter of about 3 to 5nm and Gr / Au composite materials perfectly wrapped by graphene were prepared.

Claims

1. A method for preparing nanographene and its composite materials at low temperature, characterized in that: It mainly uses metal oxide or metal salt powder as precursor and carbon-containing gas as carbon source, and is realized by combining plasma enhancement technology and other means; first, the precursor is placed in a vacuum furnace; then, the vacuum is evacuated to the background; then a certain proportion of carbon source gas and auxiliary gas are introduced to keep the gas pressure at 10-5000Pa; then the gas in the furnace is plasmatized in a certain way; then, the temperature is increased to 150-500°C at a certain heating rate and kept warm for a period of time; then, the carbon source gas is turned off, the plasmatization is stopped, and the furnace is cooled to room temperature, so that nanographene and its composite materials can be prepared.

2. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The metal element in the metal salt is one or more of Ni, Ti, V, Cr, Mn, Fe, Co, Zn, Mo, Ag, Cd, W, Au, Pt, and Cu.

3. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The metal salt is one or more of carbonate, oxalate, acetate, nitrate and chlorate.

4. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The carbon-containing gas is hydrocarbon or CO.

5. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The certain ratio is the ratio of the carbon source gas to the auxiliary gas, and the ratio is 1:0-300.

6. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The auxiliary gas is hydrogen or argon, and the ratio is 1:0.1-10.

7. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The certain mode is one or more of radio frequency discharge, direct current glow discharge and microwave discharge.

8. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The certain heating rate is 1-100°C / min.

9. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The period of time is 0 to 20 hours.

10. The method for preparing nanographene and its composite material at low temperature according to claim 1, characterized in that: The particle size of the powder is 5nm-100μm.

Images