A method for preparing graphene by plasma-assisted ball milling

Abstract

The application belongs to the technical field of graphene preparation, and particularly relates to a method for preparing graphene by using plasma-assisted ball milling. Nitrogen-water vapor mixed gas is used to form an expanded spacing between graphite layers, increase the interlayer distance, etch nano pits on the surface of the graphite, increase the roughness and active sites of the graphite surface, and help the subsequent ball milling medium to fully contact with the graphite, thereby improving the ball milling efficiency. The ball milling medium is prepared by using electronic waste and rice husk as raw materials, which not only realizes the recycling of resources, but also has good wear resistance and chemical stability, and provides suitable friction and shear force in the ball milling process, cooperates with the weakened interlayer force after the plasma treatment, and realizes efficient peeling. The peeling agent is modified cellulose nanocrystal, citric acid ester surfactant and glucose-derived carbon quantum dots, which are used to promote the preparation of high-purity and high-quality graphene products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of graphene preparation, and particularly relates to a method for preparing graphene by using plasma-assisted ball milling. BACKGROUND

[0002] Due to the two-dimensional planar structure of single-atom thickness, graphene exhibits unique physical and chemical properties, so that graphene-based materials exhibit great application potential in many fields, such as energy storage, transparent electrodes, lithium ion batteries, solar cells, fuel cells, building materials and the like. Therefore, it is of great significance to study the preparation process of high-quality and large-scale graphene. So far, people have developed many methods for preparing graphene. For example, the initial micromechanical exfoliation of graphite, epitaxial growth, chemical vapor deposition (CVD), electrochemical method, oxidation-reduction method and the like.

[0003] Although the previous research has improved the preparation process of graphene to some extent, the preparation process is often either relatively harsh or high in energy consumption, and the process is not continuous, the product yield is often low, and the product is unstable. Therefore, exploring a more suitable new preparation process of graphene is an important content for realizing the industrial application of graphene. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing graphene by using plasma-assisted ball milling in view of the existing problems.

[0005] The present application is realized by the following technical solutions:

[0006] A method for preparing graphene by using plasma-assisted ball milling, comprising the following steps:

[0007] S1, crushing flake graphite and placing it in a plasma reaction cavity, introducing nitrogen-hydrogen mixed gas, and performing plasma treatment;

[0008] S2, adding the graphene raw material treated by plasma, ball milling medium and exfoliating agent into a ball milling tank for ball milling treatment;

[0009] S3, removing the ball milling medium by centrifugal treatment, removing the exfoliating agent by dialysis treatment, and then performing freeze-drying treatment.

[0010] Further, the volume ratio of nitrogen to water vapor in the nitrogen-hydrogen mixed gas in step S1 is 8:2, and the plasma treatment is as follows: first, turn on the pulse plasma power supply, adjust the power supply frequency to 10 kHz and the voltage to 100 V, and treat for 10-12 min, then adjust the power supply frequency to 50 kHz and the voltage to 300 V, and treat for 5-6 min.

[0011] Further, the ball-to-material ratio in the ball milling process in step S2 is 15-25:1.

[0012] Further, the preparation of the ball milling medium in step S2 comprises the following steps:

[0013] (1) After the collected waste electronic components zirconia ceramic parts are crushed to a particle size of <5 mm, they are added to a mixed solution of 10% hydrochloric acid solution and 20% sodium hydroxide solution with a volume ratio of 1:1. After stirring at room temperature for 3-4 h, they are washed with ionized water until neutral, and then dried to obtain zirconia particles;

[0014] (2) To the above zirconia particles, 3% Y2O3 stabilizer and 5% carboxymethyl cellulose sodium aqueous solution are added, and then stirred and mixed uniformly. After cold isostatic pressing, a green body is obtained. The green body is placed in a high-temperature sintering furnace, heated to 1600°C at a rate of 8-10°C / min, and held for 3-4 h to obtain a zirconia ceramic core;

[0015] (3) The slurry is sprayed onto the surface of the zirconia ceramic core using a spraying method, and the thickness is controlled to be 15-25 μm. Then, sintering is carried out at 1300°C in an argon atmosphere for 1-2 h.

[0016] Further, the preparation of the slurry in step (3) comprises the following steps:

[0017] A. After the dried rice husk is crushed to a particle size of <1 mm, it is placed in a muffle furnace and carbonized at 700°C for 5-6 h to obtain carbon powder. The carbon powder, sodium carbonate, and magnesium powder are thoroughly mixed in a mass ratio of 1:3:2, and then placed in a vacuum tube furnace and heated to 850°C under argon protection at a rate of 6-7°C / min. After holding for 3-4 h, the product is cooled and immersed in a mixed solution of hydrochloric acid (15%) and HF acid (hydrofluoric acid, 0.3%) with a volume ratio of 10:1 for 10-12 h. After washing with water until neutral, the product is dried to obtain bio-silicon carbide powder;

[0018] B. The bio-silicon carbide powder is mixed with water in a mass ratio of 1:5, and then 3% sodium alginate is added and stirred uniformly.

[0019] Further, the preparation of the stripping agent in step S2 comprises the following steps:

[0020] 1) The microcrystalline cellulose is crushed and then passed through a 100-mesh sieve. Then, it is mixed with a 60% sulfuric acid solution in a solid-to-liquid ratio of 1:10 in a constant-temperature water bath at 40-50°C for 80-100 min. Then, the sulfuric acid solution is diluted with deionized water until it is close to neutral. After centrifugation, the precipitate is washed with deionized water until the conductivity of the washing liquid is <10 μS / cm to obtain cellulose nanocrystals.

[0021] 2) ultrasonic dispersion of cellulose nanocrystals in an aqueous ethanol solution (ethanol: water = 1:1, v / v), after uniform dispersion, 3-aminopropyltriethoxysilane (APTES) is added in an amount of 0.1 times the mass of the cellulose nanocrystals, stirring at 40~50℃ for 3~4h, then removing the unreacted APTES by dialysis (dialysis bag molecular weight cut-off is 3500Da), acetylating with acetic anhydride, controlling the degree of substitution to be 0.2, to obtain modified cellulose nanocrystals;

[0022] 3) adding modified cellulose nanocrystals, citric acid ester surfactant and glucose-derived carbon quantum dots to deionized water in a mass ratio of 16:3:1, stirring at 8000~10000rpm at room temperature for 30~40min.

[0023] Further, the preparation method of the citric acid ester surfactant in step 3) is as follows: citric acid and polyethylene glycol 400 are added to a reaction kettle in a molar ratio of 1:3, then p-toluenesulfonic acid is added as a catalyst in an amount of 1% of the mass of citric acid, and esterification is carried out at 120~130℃ for 6~7h, after the reaction is completed, the catalyst is neutralized by adding saturated sodium carbonate solution, the pH is adjusted to 7~8, then the organic phase is separated with a separatory funnel, washed with deionized water for 3~4 times, and then distilled under reduced pressure.

[0024] Further, the preparation method of the glucose-derived carbon quantum dots in step 3) is as follows: glucose and deionized water are mixed in a mass ratio of 1:10, 0.1M citric acid is added, and hydrothermal reaction is carried out at 180~190℃ for 3~4h, after the reaction is completed, the reaction solution is filtered through a 0.22μm filter membrane, then the purified carbon quantum dot solution is obtained by dialysis (dialysis bag molecular weight cut-off is 1000Da), polyethyleneimine is added to the purified carbon quantum dot solution in an amount of 5% of the mass of the carbon quantum dots, and stirring is carried out at room temperature for 2~3h, then the dialysis (dialysis bag molecular weight cut-off is 3500Da) treatment is carried out again to obtain the glucose-derived carbon quantum dots.

[0025] Further, the ball milling speed in step S2 is controlled to be 400~600rpm, and the ball milling time is 3~5h.

[0026] Further, the centrifugal speed in step S3 is 8000~10000rpm, the centrifugal time is 10~15min, the molecular weight cut-off of the dialysis bag in the dialysis treatment is 3500~5000Da, and the dialysis time is 20~30h.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1. This invention employs a nitrogen-water vapor mixed gas and pulsed plasma dual-mode processing. First, it is processed at 10kHz and 100V, where nitrogen excitation generates high-energy nitrogen free radicals, which react with carbon atoms in the graphite interlayer to form nitrogen-containing functional groups. The insertion of these functional groups weakens the van der Waals forces between graphite layers. At the same time, the ·OH free radicals generated by the dissociation of water vapor react with impurities on the graphite surface to oxidize them, converting them into volatile or soluble substances, thereby cleaning the graphite surface. Next, the frequency and voltage are adjusted. Higher frequencies and voltages generate stronger energy, forming an expansion gap between graphite layers, increasing the interlayer distance, and etching nano-pits on the graphite surface to increase the surface roughness and active sites. This facilitates full contact between the subsequent ball milling media and the graphite, thereby enhancing the ball milling efficiency.

[0029] 2. The ball milling media of this invention is prepared using electronic waste and rice husks as raw materials, realizing the recycling of resources. Y2O3 stabilizer is added and the sintering process is optimized in the preparation of zirconia ceramic core to improve the structural stability and wear resistance of the core. Using rice husks as raw material and adopting a unique preparation process, the coating layer is tightly bonded to the core, while having good wear resistance and chemical stability. It provides suitable friction and shear force during ball milling, and combined with the interlayer force weakened after plasma treatment, it achieves efficient peeling.

[0030] 3. In the preparation of the exfoliating agent of the present invention, functional groups such as amino and acetyl groups are introduced through acid hydrolysis, APTES modification, and acetylation treatment with acetic anhydride to improve the dispersibility of cellulose nanocrystals. The modified cellulose nanocrystals adsorb onto the graphene surface to form a hydration layer, generating a steric hindrance effect that hinders the aggregation of graphene sheets. The citrate surfactant reduces the interfacial energy between graphite and the medium and exfoliating agent, making graphene easier to exfoliate during ball milling. Carbon quantum dots are embedded between graphite layers to expand the interlayer spacing and synergistically promote graphene exfoliation and dispersion, thereby helping to obtain high-purity, high-quality graphene products. Detailed Implementation

[0031] To further explain the present invention, the following specific embodiments are described.

[0032] Example 1

[0033] A method for preparing graphene using plasma-assisted ball milling includes the following steps:

[0034] S1. After crushing the flake graphite, place it in the plasma reaction chamber and introduce a nitrogen-water vapor mixture (the volume ratio of nitrogen to water vapor is 8:2). First, turn on the pulsed plasma power supply, adjust the power supply frequency to 10kHz and the voltage to 100V, and process for 10 minutes. Then, adjust the power supply frequency to 50kHz and the voltage to 300V, and process for 5 minutes.

[0035] S2, the graphite raw material after plasma treatment and the ball milling medium, the stripping agent are added into the ball milling tank, the ball material ratio is 15:1, 400 rpm, ball milling 3h;

[0036] The preparation of the ball milling medium comprises the following steps:

[0037] (1) After the collected waste electronic components zirconia ceramic parts are crushed to a particle size of <5mm, they are added to a mixed solution of 10% hydrochloric acid solution and 20% sodium hydroxide solution with a volume ratio of 1:1, stirred at room temperature for 3-4h, then washed with ionized water until neutral, and dried to obtain zirconia particles;

[0038] (2) 3% Y2O3 stabilizer and 5% carboxymethyl cellulose sodium aqueous solution are added to the above zirconia particles, stirred and mixed uniformly, and then cold isostatic pressing is performed to obtain a green body, which is placed in a high-temperature sintering furnace and heated to 1600℃ at a rate of 8℃ / min, and held for 3h to obtain a zirconia ceramic core;

[0039] (3) After the dried rice husk is crushed to a particle size of <1mm, it is placed in a muffle furnace and carbonized at 700℃ for 5h to obtain carbon powder. The carbon powder, sodium carbonate and magnesium powder are thoroughly mixed in a mass ratio of 1:3:2, then placed in a vacuum tube furnace, heated to 850℃ under argon protection, and held for 3h before cooling. The product is immersed in a mixed solution of hydrochloric acid (15%) and HF acid (0.3%) with a volume ratio of 10:1 for 10h, washed with water until neutral, and dried to obtain biogenic silicon carbide powder;

[0040] (4) The biogenic silicon carbide powder is mixed with water in a mass ratio of 1:5, then 3% sodium alginate is added, and the slurry is stirred and mixed uniformly. The slurry is sprayed onto the surface of the zirconia ceramic core using a spraying method, and the thickness is controlled at 15μm. Then sintering is carried out at 1300℃ in an argon atmosphere for 1h;

[0041] The preparation of the stripping agent comprises the following steps:

[0042] 1) After the microcrystalline cellulose is crushed and passed through a 100 mesh sieve, it is mixed with a 60% sulfuric acid solution in a solid-liquid ratio of 1:10 in a constant temperature water bath at 40℃ for 80min. Then, the sulfuric acid solution is diluted to near neutral with deionized water, centrifuged, and the precipitate is washed with deionized water until the conductivity of the washing liquid is <10μS / cm to obtain cellulose nanocrystals;

[0043] 2) Cellulose nanocrystals were ultrasonically dispersed in an ethanol aqueous solution (ethanol: water = 1:1, v / v), and after uniform dispersion, 0.1 times the mass of the cellulose nanocrystals of APTES was added, and stirred at 40℃ for 3h, then unreacted APTES was removed by dialysis (dialysis bag molecular weight cut-off 3500Da), and acetylation treatment with acetic anhydride was performed to control the degree of substitution to 0.2, to obtain modified cellulose nanocrystals;

[0044] 3) Citric acid and polyethylene glycol 400 were added to a reaction kettle in a molar ratio of 1:3, then 1% of the mass of the citric acid of p-toluenesulfonic acid was added as a catalyst, and esterification was carried out at 120℃ for 6h, after the reaction was completed, the catalyst was neutralized with saturated sodium carbonate solution, and the pH was adjusted to 7, then the organic phase was separated with a separatory funnel, and after washing with deionized water 3-4 times, the citric acid ester surfactant was obtained by distillation under reduced pressure;

[0045] 4) Glucose and deionized water were mixed in a mass ratio of 1:10, 0.1M citric acid was added, and hydrothermal reaction was carried out at 180℃ for 3h, after the reaction was completed, filtration was performed through a 0.22μm filter, then dialysis (dialysis bag molecular weight cut-off 1000Da) was performed to obtain a purified carbon quantum dot solution, 5% of the mass of the carbon quantum dots of polyethyleneimine was added to the purified carbon quantum dot solution, and after stirring at room temperature for 2h, dialysis (dialysis bag molecular weight cut-off 3500Da) was performed again to obtain glucose-derived carbon quantum dots;

[0046] 5) Modified cellulose nanocrystals, citric acid ester surfactant, and glucose-derived carbon quantum dots were added to deionized water in a mass ratio of 16:3:1, and stirring treatment was performed at room temperature at 8000rpm for 30min;

[0047] S3, centrifugation at 8000rpm for 10min to remove the ball milling medium, dialysis (dialysis bag molecular weight cut-off 3500Da) treatment for 20h to remove the exfoliating agent, and then freeze-drying treatment.

[0048] Example 2

[0049] A method for preparing graphene by plasma-assisted ball milling, comprising the following steps:

[0050] S1, after crushing flake graphite, it was placed in a plasma reaction chamber, and nitrogen-water vapor mixed gas (volume ratio of nitrogen to water vapor was 8:2) was introduced, first the pulse plasma power was turned on, the power frequency was adjusted to 10kHz, and the voltage was 100V, and the treatment was 11min, then the power frequency was adjusted to 50kHz, and the voltage was 300V, and the treatment was 5min;

[0051] S2, the graphite raw material after plasma treatment and ball milling medium, stripping agent are added into the ball milling tank, the ball material ratio is 20:1, 500rpm, ball milling 4h;

[0052] The preparation of the ball milling medium comprises the following steps:

[0053] (1) After the collected waste electronic components zirconia ceramic parts are crushed to a particle size of <5mm, they are added to a mixed solution of 10% hydrochloric acid solution and 20% sodium hydroxide solution in a volume ratio of 1:1, stirred at room temperature for 3.5h, then washed with ionized water until neutral, and dried to obtain zirconia particles;

[0054] (2) A mass fraction of 3% Y2O3 stabilizer and a mass fraction of 5% carboxymethyl cellulose sodium aqueous solution are added to the above zirconia particles, stirred and uniformly mixed, and then cold isostatic pressing is performed to obtain a green body. The green body is placed in a high-temperature sintering furnace, heated to 1600℃ at a rate of 9℃ / min, and held for 3.5h to obtain a zirconia ceramic core;

[0055] (3) After the dried rice husk is crushed to a particle size of <1mm, it is placed in a muffle furnace and carbonized at 700℃ for 5.5h to obtain carbon powder. The carbon powder, sodium carbonate and magnesium powder are thoroughly mixed in a mass ratio of 1:3:2, then placed in a vacuum tube furnace, heated to 850℃ under argon protection at a rate of 6.5℃ / min, and held for 3.5h. After cooling, the product is immersed in a mixed solution of hydrochloric acid (15%) and HF acid (0.3%) in a volume ratio of 10:1 for 11h, washed with water until neutral, and dried to obtain bio-silicon carbide powder;

[0056] (4) The bio-based silicon carbide powder is mixed with water in a mass ratio of 1:5, then 3% sodium alginate is added, and the slurry is stirred and uniformly mixed. The slurry is sprayed onto the surface of the zirconia ceramic core using a spraying method, and the thickness is controlled to be 20μm. Then sintering is carried out at 1300℃ in an argon atmosphere for 1.5h;

[0057] The preparation of the stripping agent comprises the following steps:

[0058] 1) After the microcrystalline cellulose is crushed and passed through a 100 mesh sieve, it is mixed with a mass fraction of 60% sulfuric acid solution in a solid-liquid ratio of 1:10 in a constant temperature water bath at 45℃ for 90min. Then, after diluting the sulfuric acid solution to near neutral with deionized water, centrifuging, collecting the precipitate, and washing the precipitate with deionized water until the conductivity of the washing liquid is <10μS / cm, cellulose nanocrystals are obtained;

[0059] 2) Cellulose nanocrystals were ultrasonically dispersed in an ethanol aqueous solution (ethanol: water = 1:1, v / v), and after uniform dispersion, 0.1 times the mass of APTES was added, and stirring was performed at 45℃ for 3.5h, then unreacted APTES was removed by dialysis (dialysis bag molecular weight cut-off 3500Da), and acetic anhydride acetylation treatment was performed to control the degree of substitution to 0.2, to obtain modified cellulose nanocrystals;

[0060] 3) Citric acid and polyethylene glycol 400 were added to a reaction kettle in a molar ratio of 1:3, then 1% of the mass of the citric acid was added as a catalyst, and esterification was performed at 125℃ for 6.5h, after the reaction was completed, the catalyst was neutralized with saturated sodium carbonate solution, the pH was adjusted to 7.5, then the organic phase was separated with a separatory funnel, and after being washed with deionized water 3 times, the citric acid ester surfactant was obtained by distillation under reduced pressure;

[0061] 4) Glucose and deionized water were mixed in a mass ratio of 1:10, 0.1M citric acid was added, and hydrothermal reaction was performed at 185℃ for 3.5h, after the reaction was completed, filtration was performed through a 0.22μm filter, then dialysis (dialysis bag molecular weight cut-off 1000Da) was performed to obtain a purified carbon quantum dot solution, 5% of the mass of the carbon quantum dots was added as polyethyleneimine, and stirring was performed at room temperature for 2.5h, then dialysis (dialysis bag molecular weight cut-off 3500Da) was performed again to obtain glucose-derived carbon quantum dots;

[0062] 5) Modified cellulose nanocrystals, citric acid ester surfactant, and glucose-derived carbon quantum dots were added to deionized water in a mass ratio of 16:3:1, and stirring was performed at room temperature at 9000rpm for 35min;

[0063] S3, centrifugation was performed at 9000rpm for 12min to remove the ball milling medium, dialysis (dialysis bag molecular weight cut-off 4000Da) was performed for 25h to remove the exfoliating agent, and then freeze-drying was performed.

[0064] Example 3

[0065] A method for preparing graphene by plasma-assisted ball milling, comprising the following steps:

[0066] S1, after the flake graphite was crushed, it was placed in a plasma reaction chamber, nitrogen-water vapor mixed gas (volume ratio of nitrogen to water vapor was 8:2) was introduced, the pulse plasma power was first turned on, the power frequency was adjusted to 10kHz, the voltage was 100V, and the treatment was performed for 12min, then the power frequency was adjusted to 50kHz, the voltage was 300V, and the treatment was performed for 6min;

[0067] S2, the graphite raw material after plasma treatment, ball milling medium and stripping agent are added into the ball milling tank, the ball to material ratio is 25:1, 600 rpm, ball milling for 5h;

[0068] The preparation of the ball milling medium comprises the following steps:

[0069] (1) After the collected waste electronic components zirconia ceramic parts are crushed to a particle size of <5mm, they are added to a mixed solution of 10% hydrochloric acid solution and 20% sodium hydroxide solution with a volume ratio of 1:1, stirred at room temperature for 3-4h, then washed with ionized water until neutral, and dried to obtain zirconia particles;

[0070] (2) 3% Y2O3 stabilizer and 5% carboxymethyl cellulose sodium aqueous solution are added to the above zirconia particles, stirred and uniformly mixed, and then cold isostatic pressing is performed to obtain a green body. The green body is placed in a high-temperature sintering furnace, heated to 1600℃ at a rate of 10℃ / min, and held for 4h to obtain a zirconia ceramic core;

[0071] (3) After the dried rice husk is crushed to a particle size of <1mm, it is placed in a muffle furnace and carbonized at 700℃ for 6h to obtain carbon powder. The carbon powder, sodium carbonate and magnesium powder are thoroughly mixed in a mass ratio of 1:3:2, then placed in a vacuum tube furnace, heated to 850℃ under argon protection, and held for 4h. After cooling, the product is immersed in a mixed solution of hydrochloric acid (15%) and HF acid (0.3%) with a volume ratio of 10:1 for 12h, washed with water until neutral, and dried to obtain bio-silicon carbide powder;

[0072] (4) The bio-based silicon carbide powder is mixed with water in a mass ratio of 1:5, then 3% sodium alginate is added, and the slurry is stirred and uniformly mixed. The slurry is sprayed onto the surface of the zirconia ceramic core using a spraying method, and the thickness is controlled at 25μm. Then sintering is carried out at 1300℃ in an argon atmosphere for 2h;

[0073] The preparation of the stripping agent comprises the following steps:

[0074] 1) After the microcrystalline cellulose is crushed and passed through a 100 mesh sieve, it is mixed with a 60% sulfuric acid solution in a solid-liquid ratio of 1:10 in a constant temperature water bath at 50℃ for 100min. Then, after diluting the sulfuric acid solution to near neutral with deionized water, centrifuging, collecting the precipitate, and washing the precipitate with deionized water until the conductivity of the washing liquid is <10μS / cm, cellulose nanocrystals are obtained;

[0075] 2) Cellulose nanocrystals were ultrasonically dispersed in an ethanol aqueous solution (ethanol: water = 1:1, v / v), and after uniform dispersion, 0.1 times the mass of APTES was added, and stirring was performed at 50°C for 4h, then unreacted APTES was removed by dialysis (dialysis bag molecular weight cut-off 3500Da), and acetic anhydride acetylation treatment was performed to control the degree of substitution to 0.2, to obtain modified cellulose nanocrystals;

[0076] 3) Citric acid and polyethylene glycol 400 were added to a reaction kettle in a molar ratio of 1:3, then 1% of the mass of citric acid was added as a catalyst, and esterification was performed at 130°C for 7h, after the reaction was completed, the catalyst was neutralized by adding saturated sodium carbonate solution, the pH was adjusted to 8, then the organic phase was separated with a separatory funnel, and after being washed with deionized water 4 times, the citric acid ester surfactant was obtained by distillation under reduced pressure;

[0077] 4) Glucose and deionized water were mixed in a mass ratio of 1:10, 0.1M citric acid was added, and hydrothermal reaction was performed at 190°C for 4h, after the reaction was completed, the solution was filtered through a 0.22μm filter membrane, then dialysis (dialysis bag molecular weight cut-off 1000Da) was performed to purify the solution to obtain a purified carbon quantum dot solution, 5% of the mass of the carbon quantum dots was added as polyethyleneimine, and stirring was performed at room temperature for 3h, then dialysis (dialysis bag molecular weight cut-off 3500Da) was performed again to obtain glucose-derived carbon quantum dots;

[0078] 5) Modified cellulose nanocrystals, citric acid ester surfactant, and glucose-derived carbon quantum dots were added to deionized water in a mass ratio of 16:3:1, and stirring was performed at room temperature at 10000rpm for 40min;

[0079] S3, 10000rpm centrifugation for 15min to remove the ball milling medium, dialysis (dialysis bag molecular weight cut-off 5000Da) for 30h to remove the peeling agent, and then freeze-drying treatment was performed.

[0080] Comparative Example 1

[0081] Comparative Example 1 and Example 2 were compared, and in Comparative Example 1, the nitrogen-hydrogen mixed gas in step S1 was replaced with nitrogen, and the other steps were the same as in Example 2.

[0082] Comparative Example 2

[0083] Comparative Example 2 is the same as Example 2 except that in Step S1, “first turn on the pulse plasma power supply, adjust the power supply frequency to 10 kHz, the voltage to 100 V, and process for 11 min, then adjust the power supply frequency to 50 kHz, the voltage to 300 V, and process for 5 min” is replaced by “turn on the pulse plasma power supply, adjust the power supply frequency to 10 kHz, the voltage to 100 V, and process for 16 min”, and other steps are the same as Example 2.

[0084] Comparative Example 3

[0085] Comparative Example 3 is the same as Example 2 except that in Step S2, the ball milling medium is replaced by commercially available ZrO2 spherical milling balls with a diameter of 10 mm (density 5.8 g / cm 3 ), and other steps are the same as Example 2.

[0086] Comparative Example 4

[0087] Comparative Example 4 is the same as Example 2 except that in Step S2, the exfoliating agent is replaced by a 1% sodium dodecyl sulfate (SDS) aqueous solution, and other steps are the same as Example 2.

[0088] Performance Test

[0089] 1. Graphene structure and electrical performance test

[0090] The atomic force microscope was used to observe the thickness and lateral size of the graphene sheet, and the single-layer rate was calculated. The graphene powder was pressed into a sheet, and the four-probe instrument was used to test the room temperature conductivity. The test results are shown in Table 1 below.

[0091] Table 1

[0092] Single layer rate (%) Conductivity (%) Example 1 76 1.3 x 10 5 ]]> Example 2 77 1.3 x 10 5 ]]> Example 3 77 1.3 x 10 5 ]]> Comparative Example 1 58 4.8 x 10 4 ]] Comparative Example 2 67 9.5 x 10 4 ]] Comparative Example 3 65 1.0 x 10 5 ]] Comparative Example 4 69 3.9 x 10 4 ]]

[0093] From Table 1 above, compared with the comparative examples, the single-layer rate and conductivity of the graphene prepared by the double-mode plasma treatment and optimization of the ball milling medium and exfoliating agent in the example are significantly improved.

[0094] 2. Ball milling medium performance test

[0095] According to the mass of the medium before and after grinding, the wear percentage was calculated, and the performance of the medium was evaluated by the amount of graphite exfoliated per unit time. The test results are shown in Table 2 below.

[0096] Wear rate (%) Peeling efficiency (%) Example 2 0.7 1.3 Comparative Example 3 5.2 0.7

[0097] From Table 2 above, the ball milling medium of the present application has a wear rate reduction of 86.5% and an exfoliation efficiency improvement of 85.7% compared with commercially available ZrO2 spherical milling balls with a diameter of 10 mm, and the ball milling medium of the present application has better ball milling performance and stability.

[0098] 3. Stripping agent recycling test

[0099] The stripping agent was recovered and reused. The change in graphene monolayer ratio after each use was monitored to determine the maximum number of cycles. The test results are shown in Table 3 below.

[0100] Table 3

[0101] Cycle number Example 2 single layer rate (%) Comparative Example 4 single layer rate (%) 1 77 69 5 75 63 10 70 55

[0102] As shown in Table 3 above, the release agent of the present invention still maintains a single-layer rate of 70% after 10 training cycles, which is a significant improvement in performance compared to Comparative Example 4.

[0103] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing graphene using plasma-assisted ball milling, characterized in that, Includes the following steps: S1. After crushing the flake graphite, place it in the plasma reaction chamber and introduce a nitrogen-water vapor mixture for plasma treatment. S2. Add the plasma-treated graphite raw material, grinding media, and stripping agent into the grinding jar for ball milling. The preparation of the ball milling media includes the following steps: (1) After the collected waste electronic components and zirconium ceramic parts are crushed to a particle size of <5mm, they are added to a mixture of 10% hydrochloric acid solution and 20% sodium hydroxide solution with a volume ratio of 1:

1. After stirring at room temperature for 3-4 hours, the mixture is rinsed with deionized water until neutral and dried to obtain zirconium oxide particles. (2) Add 3% Y2O3 stabilizer and 5% sodium carboxymethyl cellulose aqueous solution to the above zirconium oxide particles, stir and mix well, and then cold isostatically press to obtain a green body. Place the green body in a high-temperature sintering furnace and heat it to 1600℃ at 8~10℃ / min, and keep it at the temperature for 3~4h to obtain a zirconium oxide ceramic core. (3) The slurry is sprayed onto the surface of the zirconia ceramic core by spraying method, and the thickness is controlled to be 15~25μm. Then it is sintered in an argon atmosphere at 1300℃ for 1~2h. S3. Centrifugation removes the ball milling media, dialysis removes the stripping agent, and then freeze-drying is performed.

2. The method for preparing graphene using plasma-assisted ball milling according to claim 1, characterized in that, In step S1, the volume ratio of nitrogen to water vapor in the nitrogen-water vapor mixture is 8:

2. The plasma treatment is as follows: first, turn on the pulsed plasma power supply, adjust the power supply frequency to 10kHz and the voltage to 100V, and treat for 10~12 minutes. Then, adjust the power supply frequency to 50kHz and the voltage to 300V, and treat for 5~6 minutes.

3. The method for preparing graphene using plasma-assisted ball milling according to claim 1, characterized in that, The ball-to-material ratio during the ball milling process described in step S2 is 15~25:

1.

4. The method for preparing graphene using plasma-assisted ball milling according to claim 1, characterized in that, The preparation of the slurry described in step (3) includes the following steps: A. After crushing the dried rice husks to a particle size of <1mm, place them in a muffle furnace and carbonize them at 700℃ for 5-6h to obtain carbon powder. Mix the carbon powder, sodium carbonate, and magnesium powder thoroughly in a mass ratio of 1:3:2, and then place them in a vacuum tube furnace. Under argon protection, heat the furnace to 850℃ at 6-7℃, hold for 3-4h, and then cool. Soak the product in a mixture of hydrochloric acid and HF acid in a volume ratio of 10:1 for 10-12h, wash with water until neutral, and then dry to obtain bio-silicon carbide powder. B. Mix bio-based silicon carbide powder with water at a mass ratio of 1:5, then add 3% sodium alginate by mass and stir until well mixed.

5. The method for preparing graphene using plasma-assisted ball milling according to claim 1, characterized in that, The preparation of the stripping agent described in step S2 includes the following steps: 1) After pulverizing the microcrystalline cellulose, pass it through a 100-mesh sieve, then mix it with a 60% sulfuric acid solution at a solid-liquid ratio of 1:

10. Stir the mixture in a constant temperature water bath at 40-50℃ for 80-100 minutes. Then add deionized water to dilute the sulfuric acid solution to near neutrality, centrifuge, collect the precipitate, and wash the precipitate with deionized water until the conductivity of the washing solution is <10μS / cm to obtain cellulose nanocrystals. 2) The cellulose nanocrystals were ultrasonically dispersed in an ethanol aqueous solution. After uniform dispersion, 0.1 times the mass of APTES of the cellulose nanocrystals were added. The mixture was stirred at 40-50℃ for 3-4 hours. Unreacted APTES was then removed by dialysis. Acetic anhydride acetylation was performed, and the degree of substitution was controlled to be 0.2 to obtain modified cellulose nanocrystals. 3) Add the modified cellulose nanocrystals, citrate surfactant, and glucose-derived carbon quantum dots to deionized water at a mass ratio of 16:3:1, and stir at 8000~10000 rpm for 30~40 minutes at room temperature.

6. The method for preparing graphene using plasma-assisted ball milling according to claim 5, characterized in that, The preparation method of the citrate surfactant described in step 3) is as follows: citric acid and polyethylene glycol 400 are added to a reaction vessel at a molar ratio of 1:3, and then 1% by weight of p-benzenesulfonic acid is added as a catalyst. The esterification reaction is carried out at 120~130℃ for 6~7h. After the reaction is completed, saturated sodium carbonate solution is added to neutralize the catalyst, the pH is adjusted to 7~8, and then the organic phase is separated by a separatory funnel. After washing with deionized water 3~4 times, the product is obtained by vacuum distillation.

7. The method for preparing graphene using plasma-assisted ball milling according to claim 5, characterized in that, The preparation method of glucose-derived carbon quantum dots described in step 3) is as follows: glucose and deionized water are mixed at a mass ratio of 1:10, 0.1M citric acid is added, and a hydrothermal reaction is carried out at 180~190℃ for 3~4h. After the reaction is completed, the mixture is filtered through a 0.22μm filter membrane and then dialyzed to obtain a purified carbon quantum dot solution. Polyethyleneimine accounting for 5% of the mass of carbon quantum dots is added to the purified carbon quantum dot solution, and the mixture is stirred and reacted at room temperature for 2~3h. Then, the mixture is dialyzed again to obtain glucose-derived carbon quantum dots.

8. The method for preparing graphene using plasma-assisted ball milling according to claim 1, characterized in that, In step S2, the ball milling process is performed with a speed of 400-600 rpm and a milling time of 3-5 hours.

9. The method for preparing graphene using plasma-assisted ball milling according to claim 1, characterized in that, In step S3, the centrifugation speed is 8000~10000 rpm and the centrifugation time is 10~15 min. In the dialysis treatment, the molecular weight cutoff of the dialysis bag is 3500~5000 Da and the dialysis time is 20~30 h.