CN108314017B - Graphene and low-cost preparation method thereof - Google Patents
Graphene and low-cost preparation method thereof Download PDFInfo
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Abstract
The invention relates to graphene and a low-cost preparation method thereof, which comprises the steps of ultrasonically cleaning a plastic product, and then crushing and ball-milling the plastic product to obtain micro fragments of the plastic product; then carbonizing, ball-milling to obtain fine-grained carbonized powder, then carrying out secondary calcination on the carbonized powder, and finally obtaining graphene after washing, purification and drying; according to the invention, the graphene is prepared by using plastic products or daily waste plastic products, especially polyethylene plastics, polystyrene plastics and the like as raw materials through a specific process method, and the prepared graphene not only has the advantages of low cost, controllable layer number, large specific surface area and high conductivity, but also greatly reduces the environmental protection pressure by using the waste plastics as the raw materials; the method is suitable for preparation and production of low-cost graphene, and achievements can be applied to development of conductive materials, environmental protection, coatings, heat dissipation structures and solid propellants.
Description
Technical Field
The invention relates to graphene and a low-cost preparation method thereof, and belongs to the technical field of graphene preparation.
Background
Graphene is a polymer made of carbon atoms in sp2The hybrid tracks form a hexagonal planar film in a honeycomb lattice, and the two-dimensional material is only one carbon atom thick. The method is characterized in that different shapes of sheet layers are cut from graphene, zero-dimensional fullerene can be obtained by warping, one-dimensional barrel-shaped carbon nanotubes can be obtained by curling, and three-dimensional graphite can be obtained by stacking, so that the graphene is considered as a basic unit for forming other carbon materials and is the most ideal carbon material at present. The successful preparation of two-dimensional crystal materials represented by graphene opens up a new era of development of novel nano materials and functional materials/devices.
Due to the unique crystal structure of graphene, the graphene has a plurality of unique properties, such as an ultra-large specific surface area, excellent optical properties, good electrical and thermal conductivity, high mechanical strength, high carrier concentration mobility and the like. The theoretical specific surface area of the graphene reaches 2630m2Per g, about 3g of graphene can cover a standard football field; the optical transmittance of the graphene is as high as 97.3%, and the graphene is almost transparent; the migration rate of the graphene at room temperature to the carrier is up to 200000cm2V · s, 140 times that of silicon; theoretical conductivity of graphene is 104S/m is the material with the best conductivity at room temperature, the resistivity of the material even approaches zero at low temperature, the thermal conductivity reaches 5000W/(m.K), is higher than that of carbon nano-tube and diamond, is more than 10 times of that of copper at room temperature, and is also more than that of copper at room temperatureThe materials with the highest thermal conductivity at present; the Young's modulus of graphene is up to 1TPa, which is 10 times that of steel, which is the hardest material. Due to the excellent comprehensive performance of the graphene, the graphene can be widely applied to more than ten civil fields such as silicon electronic products, photoelectron sensors, nano electronic devices, super capacitors, solar cells, fuel cells, lithium ion batteries, transparent conductive touch panels, flexible display screens, biological/molecular sensors, optical modulators, medical materials, catalysts, antibacterial/anticorrosive materials and the like.
At present, the preparation methods of graphene are more, and common preparation methods comprise a micro-mechanical stripping method, a SiC epitaxial growth method, a redox method and a Chemical Vapor Deposition (CVD) method. The micro-mechanical stripping method can prepare micron-sized graphene, but the controllability is poor, the yield is low, and large-scale production is difficult to carry out; by adopting an epitaxial growth method, large-area single-layer graphene can be obtained by heating and carrying out epitaxial growth on the surface of the SiC (0001) crystal face, but the growth efficiency is low, the controllability is poor and the transfer is difficult; the redox method is a mainstream method for industrially preparing graphene at present, but the method has the defects of more obtained graphene, more layers, poorer quality and more difficulty in application in the electronic field; the CVD method is one of the approaches to obtain high-quality graphene, but has the biggest problem of difficulty in industrial production. Therefore, the existing main preparation technology has the problems of high cost, low yield, long time consumption, harsh experimental conditions and the like.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides graphene and a low-cost preparation method thereof, the method takes plastic products or daily waste plastic products, particularly polyethylene plastics, polystyrene plastics and the like as raw materials, the graphene is prepared by a specific process method, and the prepared graphene not only has the advantages of low cost, controllable layer number, large specific surface area and high conductivity, but also greatly reduces the environmental protection pressure by taking the waste plastics as the raw materials; the method is suitable for preparation and production of low-cost graphene, and achievements can be applied to development of conductive materials, environmental protection, coatings, heat dissipation structures and solid propellants.
The above object of the present invention is mainly achieved by the following technical solutions:
a low-cost preparation method of graphene comprises the following steps:
(1) crushing or cutting the plastic product and then performing ball milling to obtain plastic fragments;
(2) carbonizing the plastic fragments at high temperature under a vacuum condition, and performing ball milling on powder blocks obtained after carbonization to obtain carbonized powder;
(3) calcining the carbonized powder under the vacuum condition and under the condition of introducing reducing gas and protective gas;
(4) and washing, purifying and drying the calcined powder to obtain the graphene.
In the low-cost preparation method of the graphene, the plastic product is a polyethylene plastic product, a polystyrene plastic product or a polypropylene plastic product.
In the low-cost preparation method of the graphene, the plastic product is a plastic bag, a plastic bottle, a plastic skin or a plastic film.
In the low-cost preparation method of graphene, the plastic product is cleaned before being cut and ball-milled in the step (1), and the specific cleaning step includes:
(1.1) cutting the plastic product, putting the cut plastic product into a solvent, putting the solvent into an ultrasonic cleaning machine, and cleaning to remove pollutants on the surface of the plastic product;
(1.2) crushing or cutting the cleaned plastic product, and then cleaning again by using a solvent according to the method in the step (1.1).
In the low-cost preparation method of the graphene, in the step (1.1), the ultrasonic frequency is 100-1000W, and the ultrasonic time is 5-60 min.
In the low-cost preparation method of graphene, the solvent in the step (1.1) is absolute ethyl alcohol, acetone, tetrahydrofuran, ethyl acetate, diethyl ether or dimethylformamide.
In the low-cost preparation method of graphene, the ball-material mass ratio of ball-milling in the step (1) is 10: 1-100: 1.
in the low-cost preparation method of the graphene, the ball milling speed in the step (1) is 2000-10000 rpm, and the ball milling time is 30-200 min.
In the low-cost preparation method of graphene, the sheet diameter of the plastic chips in the step (1) is several micrometers to several hundred micrometers.
In the low-cost preparation method of the graphene, the high-temperature carbonization temperature in the step (2) is 800-1500 ℃, and the carbonization time is 5-80 min.
In the low-cost preparation method of the graphene, the vacuum degree in the steps (2) and (3) is less than 10-3MPa; the grain size of the carbonized powder obtained in the step (2) is 10 nm-200 nm.
In the low-cost preparation method of the graphene, the ball milling speed in the step (2) is 1000-8000 rpm, and the ball milling time is 10-150 min.
In the low-cost preparation method of graphene, the reducing gas in the step (3) is hydrogen or carbon monoxide, and the mass flow rate of the reducing gas is 10-200 sccm.
In the low-cost preparation method of the graphene, the protective gas in the step (3) is nitrogen, helium, argon or neon, and the mass flow of the protective gas is 100-800 sccm.
In the low-cost preparation method of the graphene, the calcination temperature in the step (3) is 1000-1500 ℃, and the calcination time is 10-80 min.
In the low-cost preparation method of the graphene, the step (4) is carried out with washing, purification and drying for multiple times; the washing times are 2-6 times; the washing solvent is deionized water, absolute ethyl alcohol, acetone or ethyl acetate.
In the low-cost preparation method of graphene, the purification process in the step (4) is one or a combination of two of centrifugal separation, electrodialysis, suction filtration, dialysis and molecular membrane filtration; in the step (4), the drying temperature is 20-80 ℃, and the drying time is 2-12 h.
The graphene prepared by the preparation method is adopted.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the graphene is prepared by using plastic products or daily waste plastic products, especially polyethylene plastics, polystyrene plastics and the like as raw materials through a specific process method, so that the prepared graphene not only greatly reduces the cost of the raw materials and has the advantages of low cost, controllable layer number, large specific surface area and high conductivity, but also greatly reduces the environmental protection pressure by using the waste plastics as the raw materials.
(2) The preparation method is different from the conventional oxidation-reduction method, and needs to use graphene as a raw material, strong acid, strong base and a large amount of solvent, so that the quality of the graphene is improved, and the harm to the environment is reduced.
(3) The preparation method is different from the conventional CVD method in that the graphene is obtained by depositing the carbon-containing compound on the surface of the metal after the carbon-containing compound is subjected to vacuum high-temperature cracking, and has the capacity of large-scale preparation.
(4) The multiple purification technology adopted by the preparation method can obviously improve the purity of the graphene to over 99.4 percent, so that the graphene has larger specific surface area and higher room-temperature electrical conductivity and thermal conductivity.
(5) The preparation method is suitable for preparation and production of low-cost graphene, and achievements can be applied to development of conductive materials, environmental protection, coatings, heat dissipation structures and solid propellants, and have important significance.
Drawings
Fig. 1 is a raman spectrum of graphene prepared in example 3 of the present invention.
Fig. 2 is an X-ray photoelectron spectrum of graphene prepared in example 3 of the present invention.
Fig. 3 is a transmission electron micrograph of graphene prepared in example 3 of the present invention.
Fig. 4 is a raman spectrum of graphene prepared in example 9 of the present invention.
Fig. 5 is an X-ray photoelectron spectrum of graphene prepared in example 9 of the present invention.
Fig. 6 is a transmission electron micrograph of graphene prepared in example 9 of the present invention.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific examples:
the method comprises the steps of ultrasonically cleaning a plastic product, crushing and ball-milling the plastic product to obtain micro fragments of the plastic product; and then carbonizing, ball-milling to obtain fine-grained carbonized powder, then carrying out secondary calcination on the carbonized powder, and finally obtaining the graphene after washing, purification and drying.
The invention relates to a low-cost preparation method of graphene, which specifically comprises the following steps:
(1) cutting the plastic product, putting the cut plastic product into a solvent, putting the cut plastic product into an ultrasonic cleaner, and cleaning the plastic product for a period of time to remove printing ink and attached pollutants on the surface of the plastic bag. The plastic product can be a waste plastic product, such as a plastic bag, a plastic film or a plastic skin of a plastic bottle, and can be a polyethylene plastic product, a polystyrene plastic product or a polypropylene plastic product.
In the step, the ultrasonic frequency is 100-1000W, and the ultrasonic time is 5-60 min. The selected cleaning solvent is absolute ethyl alcohol, acetone, tetrahydrofuran, ethyl acetate, diethyl ether or dimethylformamide.
(2) Crushing the cleaned plastic product into small pieces by using a precision cutter, and then cleaning the small pieces by using a solvent again; the selected solvent is the same as the step (1).
(3) And placing the small plastic product pieces in a ball-milling tank according to a certain ball-material ratio, and carrying out high-speed ball milling for a period of time to obtain curled plastic product micro-fragments. Wherein the ball mass ratio of ball materials of ball milling is 10: 1-100: 1. the ball milling speed is 2000-10000 rpm, and the ball milling time is 30-200 min. The sheet diameter of the obtained micro-chips of the plastic products is from several micrometers to hundreds of micrometers.
(4) And (3) placing the micro fragments of the plastic product in a vacuum furnace for high-temperature carbonization, and carrying out ball milling on the carbonized powder block for a period of time to obtain carbonized powder. Wherein the high-temperature carbonization temperature is 800-1500 ℃, and the carbonization time is 5-80 min; vacuum degree in vacuum furnace is less than 10-3MPa; the ball milling speed is 1000-8000 rpm, and the ball milling time is 10-150 min.
The grain diameter of the carbonized powder obtained in the step is 10 nm-200 nm.
(5) And placing the carbonized powder subjected to ball milling in a vacuum furnace for secondary calcination under reducing gas and protective gas. Wherein the calcination temperature is 1000-1500 ℃, and the calcination time is 10-80 min.
In the step, the reducing gas is hydrogen or carbon monoxide, and the mass flow of the reducing gas is 10-200 sccm. The protective gas is nitrogen, helium, argon or neon, and the mass flow of the protective gas is 100-800 sccm.
(6) And washing, purifying and drying the powder subjected to secondary calcination for multiple times to obtain the graphene. Wherein the washing times are 2-6 times, and the washing solvent is deionized water, absolute ethyl alcohol, acetone or ethyl acetate.
The purification process in the step is one or the combination of two of centrifugal separation, electrodialysis, suction filtration, dialysis and molecular membrane filtration.
The drying temperature is 20-80 ℃, and the drying time is 2-12 h.
The invention also provides the graphene prepared by the method.
Example 1:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into tetrahydrofuran, putting the polyethylene plastic bag into an ultrasonic cleaning machine, and cleaning for 40min at 300W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces again by using tetrahydrofuran, wherein the method is the same as the step 1;
and step 3: and (3) mixing the small polyethylene plastic bags according to a ball-material ratio of 50: 1, placing the mixture in a ball milling tank to ball mill for 70min at 6000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 40-70 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag in a vacuum furnace for carbonization at 1200 ℃ for 20min, and ball-milling the carbonized powder blocks for 60min at 4000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder was 200 nm.
And 5: placing the carbonized powder after ball milling in a vacuum furnace, and carrying out secondary calcination for 40min at 1300 ℃ under the atmosphere of CO (mass flow of 50sccm) and He (mass flow of 300 sccm);
step 6: washing the twice calcined powder with acetone for 2 times, performing suction filtration and centrifugal separation, and drying at 35 ℃ for 6 hours to obtain the graphene.
Graphene performance: purity: 99.4%, specific surface area: 536m2,/g, powder conductivity: 1850S/m, thermal conductivity: 1125W/(m.K).
Example 2:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into acetone, putting the polyethylene plastic bag into an ultrasonic cleaning machine, and cleaning the polyethylene plastic bag for 30min at 400W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and cleaning the small pieces by using acetone again; the method is the same as the step 1;
and step 3: and (3) mixing the small polyethylene plastic bags according to a ball-material ratio of 70: 1, placing the mixture in a ball milling tank to perform ball milling for 50min at 9000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 10-30 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag in a vacuum furnace for carbonization at 1300 ℃ for 20min, and ball-milling the carbonized powder blocks for 80min at 5000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 25 nm;
and 5: putting the carbonized powder after ball milling into a vacuum furnace in H2Performing secondary calcination at 1400 ℃ for 45min under the atmosphere of (the mass flow is 120sccm) and Ar (the mass flow is 500 sccm);
step 6: and washing the twice calcined powder with acetone for 4 times, filtering with a molecular membrane, and drying at 30 ℃ for 5 hours to obtain the graphene.
Graphene performance: purity: 99.6%, specific surface area: 765m2,/g, powder conductivity: 2460S/m, thermal conductivity: 1314W/(m.K).
Example 3:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into ether, putting the polyethylene plastic bag into an ultrasonic cleaner, and cleaning for 50min at 250W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces by using ether again; the method is the same as the step 1;
and step 3: and (3) mixing the polyethylene plastic bag chips according to a ball-material ratio of 100: 1, placing the mixture in a ball milling tank to ball mill for 150min at 4500rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 5-20 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag in a vacuum furnace for carbonization at 900 ℃ for 70min, and ball-milling the carbonized powder blocks for 50min at 7000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the particle size of the obtained carbonized powder was 10 nm.
And 5: placing the carbonized powder after ball milling in a vacuum furnace, and calcining for 55min at 1150 ℃ under the atmosphere of CO (the mass flow is 30sccm) and Ne (the mass flow is 300 sccm);
step 6: washing the twice calcined powder with absolute ethyl alcohol for 5 times, then carrying out centrifugal separation and dialysis, and then drying at 20 ℃ for 8h to obtain the graphene.
Graphene performance: purity: 99.7%, specific surface area: 1086m2,/g, powder conductivity: 3279S/m, thermal conductivity: 1725W/(m.K).
As shown in fig. 1, a raman spectrum of the graphene prepared in example 3 of the present invention is shown, fig. 2 is an X-ray photoelectron spectrum of the graphene prepared in example 3 of the present invention, fig. 3 is a transmission electron micrograph of the graphene prepared in example 3 of the present invention, and it can be seen from the graphs that the number of graphene layers prepared in example 3 is 2, the main element is carbon, and defects and impurities are very few, which proves that the prepared graphene has good quality.
Example 4:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into absolute ethyl alcohol, putting the polyethylene plastic bag into an ultrasonic cleaning machine, and cleaning for 40min at 650W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces again by using absolute ethyl alcohol; the method is the same as the step 1;
and step 3: and (3) mixing the small polyethylene plastic bags according to a ball-material ratio of 80: 1, placing the mixture in a ball milling tank, and ball milling the mixture for 70min at 8000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 80-120 microns;
and 4, step 4: placing the polyethylene plastic bag micro-fragments in a vacuum furnace for carbonization at 1100 ℃ for 50min, and ball-milling the carbonized powder blocks for 50min at 4000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder was 20 nm.
And 5: putting the carbonized powder after ball milling into a vacuum furnace in H2(Mass flow 100sccm) and N2Performing secondary calcination at 1300 ℃ for 36min under the atmosphere of 400sccm of mass flow;
step 6: and washing the twice calcined powder for 6 times by using deionized water, performing electrodialysis, and drying at 80 ℃ for 12 hours to obtain the graphene.
Graphene performance: purity: 99.5%, specific surface area: 784m2,/g, powder conductivity: 2550S/m, thermal conductivity: 1328W/(m.K).
Example 5:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into dimethylformamide, putting the polyethylene plastic bag into an ultrasonic cleaner, and cleaning the polyethylene plastic bag for 60min at 100W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces again by using dimethylformamide; the method is the same as the step 1;
and step 3: and (3) mixing the polyethylene plastic bag chips according to a ball-material ratio of 10: 1, placing the mixture in a ball milling tank to perform ball milling for 30min at 10000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 6-15 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag in a vacuum furnace for carbonization at 1000 ℃ for 65min, and ball-milling carbonized powder blocks for 10min at 8000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder was 30 nm.
And 5: ball for gamePutting the ground carbonized powder in a vacuum furnace in H2Performing secondary calcination at 1200 ℃ for 45min under the atmosphere of (mass flow rate of 200sccm) and He (mass flow rate of 800 sccm);
step 6: washing the twice calcined powder with ethyl acetate for 4 times, then carrying out suction filtration and centrifugal separation, and then drying at 35 ℃ for 2h to obtain the graphene.
Graphene performance: purity: 99.5%, specific surface area: 656m2,/g, powder conductivity: 2105S/m, thermal conductivity: 1212W/(m.K).
Example 6:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into ethyl acetate, putting the polyethylene plastic bag into an ultrasonic cleaner, and cleaning the polyethylene plastic bag for 5min at 1000W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces again by using ethyl acetate; the method is the same as the step 1;
and step 3: and (3) mixing the polyethylene plastic bag chips according to a ball-material ratio of 60: 1, placing the mixture in a ball milling tank to perform ball milling for 120min at 5000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 60-90 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag in a vacuum furnace for carbonization at 800 ℃ for 80min, and ball-milling the carbonized powder blocks for 80min at 6500rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder was 50 nm.
And 5: placing the carbonized powder after ball milling in a vacuum furnace, and calcining for 80min at 1000 ℃ under the atmosphere of CO (mass flow of 10sccm) and Ne (mass flow of 100 sccm);
step 6: and washing the twice calcined powder for 3 times by ethyl acetate, dialyzing, and drying at 35 ℃ for 6 hours to obtain the graphene.
Graphene performance: purity: 99.6%, specific surface area: 755m2,/g, powder conductivity: 2468S/m, thermal conductivity: 1305W/(m.K).
Example 7:
step 1: cutting a polypropylene plastic bag, putting the cut polypropylene plastic bag into acetone, putting the cut polypropylene plastic bag into an ultrasonic cleaner, and cleaning the polypropylene plastic bag for 25min at 650W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polypropylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces by using acetone again; the method is the same as the step 1;
and step 3: and (3) mixing the small polypropylene plastic bags according to a ball-to-feed ratio of 50: 1, placing the mixture in a ball milling tank to perform ball milling for 200min at 2000rmp to obtain curled polypropylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 320-380 microns.
And 4, step 4: placing the polypropylene plastic bag micro-fragments in a vacuum furnace for carbonization at 1500 ℃ for 5min, and ball-milling the carbonized powder blocks for 15min at 1000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 100 nm;
and 5: placing the carbonized powder after ball milling in a vacuum furnace, and calcining for 10min at 1500 ℃ in the atmosphere of CO (mass flow of 40sccm) and Ar (mass flow of 300 sccm);
step 6: and washing the twice calcined powder with acetone for 3 times, performing electrodialysis, and drying at 30 ℃ for 4 hours to obtain the graphene.
Graphene performance: purity: 99.4%, specific surface area: 688m2,/g, powder conductivity: 2385S/m, thermal conductivity: 1290W/(m.K).
Example 8:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into absolute ethyl alcohol, putting the polyethylene plastic bag into an ultrasonic cleaning machine, cleaning the polyethylene plastic bag for 30min at 400W, and removing printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces again by using absolute ethyl alcohol, wherein the method is the same as the step 1;
and step 3: and (3) mixing the polyethylene plastic bag chips according to a ball-material ratio of 90: 1, placing the mixture in a ball milling tank to ball mill for 60min at 6000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 180-220 microns;
and 4, step 4: placing the micro-fragments of polyethylene plastic bag in a vacuum furnace, carbonizing at 1200 deg.C for 35min, and making the carbonized powder blockBall milling for 40min at 5000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 20 nm;
and 5: putting the carbonized powder after ball milling into a vacuum furnace in H2Performing secondary calcination at 1100 deg.C for 60min under the atmosphere of (mass flow rate of 150sccm) and He (mass flow rate of 700 sccm);
step 6: washing the powder after the secondary calcination for 4 times by using absolute ethyl alcohol, filtering by using a molecular membrane, and drying at 30 ℃ for 7 hours to obtain the graphene.
Graphene performance: purity: 99.8%, specific surface area: 905m2,/g, powder conductivity: 3038S/m, thermal conductivity: 1672W/(m.K).
Example 9:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into ether, putting the polyethylene plastic bag into an ultrasonic cleaner, and cleaning for 20min at 650W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and cleaning the small pieces by using ether again, wherein the method is the same as the step 1;
and step 3: and (3) mixing the polyethylene plastic bag chips according to a ball-material ratio of 60: 1, placing the mixture in a ball milling tank, and ball milling the mixture for 50min at 8000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 90-120 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag in a vacuum furnace for carbonization at 1000 ℃ for 60min, and ball-milling the carbonized powder blocks for 100min at 3000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 40 nm;
and 5: putting the carbonized powder after ball milling into a vacuum furnace in a vacuum furnace at the mass flow of CO (100 sccm) and N2Performing secondary calcination for 50min at 1200 ℃ under the atmosphere of the mass flow of 600 sccm;
step 6: and washing the twice calcined powder for 5 times by using deionized water, performing centrifugal separation and dialysis, and drying at 70 ℃ for 10 hours to obtain the graphene.
Graphene performance: purity: 99.6%, specific surface area: 822m2,/g, powder conductivity:2985S/m, thermal conductivity: 1655W/(m.K).
As shown in fig. 4, a raman spectrum of the graphene prepared in example 9 of the present invention, fig. 5 is an X-ray photoelectron spectrum of the graphene prepared in example 9 of the present invention, and fig. 6 is a transmission electron micrograph of the graphene prepared in example 9 of the present invention, which shows that: the number of graphene layers prepared in example 3 is about 3-4, the main element is carbon, and defects and impurities are very few, so that the prepared graphene has good quality.
Example 10:
step 1: cutting a polyethylene plastic bottle, putting the polyethylene plastic bottle into ethyl acetate, putting the polyethylene plastic bottle into an ultrasonic cleaner, and cleaning for 15min at 800W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bottle into small pieces by using a precision cutter, and cleaning the small pieces by using ethyl acetate again, wherein the method is the same as the step 1;
and step 3: and (3) cutting the polyethylene plastic bottle into small pieces according to a ball-material ratio of 70: 1, placing the mixture in a ball milling tank, and ball milling the mixture for 80min at 5000rmp to obtain curled polyethylene plastic bottle micro fragments; the sheet diameter of the obtained micro-fragments is 230-260 microns;
and 4, step 4: placing micro fragments of a polyethylene plastic bottle in a vacuum furnace, carbonizing for 15min at 1400 ℃, and ball-milling the carbonized powder block for 40min at 6000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 80 nm;
and 5: putting the carbonized powder after ball milling into a vacuum furnace in H2Performing secondary calcination at 1250 ℃ for 50min under the atmosphere of (the mass flow is 120sccm) and Ar (the mass flow is 600 sccm);
step 6: and washing the twice calcined powder with ethyl acetate for 5 times, performing electrodialysis, and drying at 20 ℃ for 8 hours to obtain the graphene.
Graphene performance: purity: 99.5%, specific surface area: 715m2,/g, powder conductivity: 2402S/m, thermal conductivity: 1293W/(m.K).
Example 11:
step 1: cutting a polystyrene plastic bag, putting the cut polystyrene plastic bag into acetone, putting the polystyrene plastic bag into an ultrasonic cleaning machine, and cleaning for 35min at 400W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polystyrene plastic bag into small pieces by using a precision cutter, and cleaning the small pieces by using acetone again, wherein the method is the same as the step 1;
and step 3: and (3) mixing small pieces of the polystyrene plastic bag according to a ball-material ratio of 80: 1, placing the mixture in a ball milling tank to ball mill for 80min at 6000rmp to obtain curled polystyrene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 70-90 microns;
and 4, step 4: placing the micro fragments of the polystyrene plastic bag in a vacuum furnace for carbonization at 1250 ℃ for 30min, and ball-milling the carbonized powder blocks for 70min at 5000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 40 nm;
and 5: placing the carbonized powder after ball milling in a vacuum furnace, and performing secondary calcination for 50min at 1350 ℃ under the atmosphere of CO (the mass flow of 80sccm) and Ar (the mass flow of 500 sccm);
step 6: washing the twice calcined powder with acetone for 3 times, then carrying out centrifugal separation and electrodialysis, and then drying at 35 ℃ for 3 hours to obtain the graphene.
Graphene performance: purity: 99.5%, specific surface area: 820m2,/g, powder conductivity: 2916S/m, thermal conductivity: 1425W/(m.K).
Example 12:
step 1: cutting a polyethylene plastic bag, putting the polyethylene plastic bag into absolute ethyl alcohol, putting the polyethylene plastic bag into an ultrasonic cleaning machine, and cleaning for 50min at 250W to remove printing ink and attached pollutants on the surface of the plastic bag;
step 2: crushing the cleaned polyethylene plastic bag into small pieces by using a precision cutter, and then cleaning the small pieces again by using absolute ethyl alcohol, wherein the method is the same as the step 1;
and step 3: and (3) mixing the polyethylene plastic bag chips according to a ball-material ratio of 60: 1, placing the mixture in a ball milling tank to ball mill for 45min at 7000rmp to obtain curled polyethylene plastic bag micro fragments; the sheet diameter of the obtained micro-fragments is 40-70 microns;
and 4, step 4: placing the micro-fragments of the polyethylene plastic bag into a vacuum furnace for carbonization at 1100 ℃ for 60Performing ball milling on the carbonized powder block for 50min at 6000rmp to obtain carbonized powder; vacuum degree in vacuum furnace is less than 10-3MPa; the grain size of the obtained carbonized powder is 60 nm;
and 5: putting the carbonized powder after ball milling into a vacuum furnace in H2(Mass flow 100sccm) and N2Performing secondary calcination at 1200 ℃ for 45min under the atmosphere of 650sccm of mass flow;
step 6: and washing the powder subjected to the secondary calcination for 5 times by using absolute ethyl alcohol, filtering by using a molecular membrane, and drying at 35 ℃ for 5 hours to obtain the graphene.
Graphene performance: purity: 99.6%, specific surface area: 745m2,/g, powder conductivity: 2456S/m, thermal conductivity: 1327W/(m.K).
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
Claims (14)
1. A low-cost preparation method of graphene is characterized by comprising the following steps: the method comprises the following steps:
(1) crushing or cutting the plastic product and then performing ball milling to obtain plastic fragments;
(2) carbonizing the plastic fragments at high temperature under a vacuum condition, and performing ball milling on powder blocks obtained after carbonization to obtain carbonized powder;
(3) calcining the carbonized powder under the vacuum condition and under the condition of introducing reducing gas and protective gas;
(4) washing, purifying and drying the calcined powder to obtain graphene;
the plastic product is a polyethylene plastic product, a polystyrene plastic product or a polypropylene plastic product;
the sheet diameter of the plastic fragments in the step (1) is several micrometers to several hundred micrometers;
the temperature of high-temperature carbonization in the step (2) is 800-1500 ℃, and the carbonization time is 5-80 min;
in the step (3), the calcination temperature is 1000-1500 ℃, and the calcination time is 10-80 min.
2. The low-cost preparation method of graphene according to claim 1, characterized in that: the plastic product is a plastic bag, a plastic bottle, a plastic skin or a plastic film.
3. The low-cost preparation method of graphene according to claim 1, characterized in that: the step (1) of cleaning the plastic product before cutting the plastic product and performing ball milling comprises the following specific cleaning steps:
(1.1) cutting the plastic product, putting the cut plastic product into a solvent, putting the solvent into an ultrasonic cleaning machine, and cleaning to remove pollutants on the surface of the plastic product;
(1.2) crushing or cutting the cleaned plastic product, and then cleaning again by using a solvent according to the method in the step (1.1).
4. The low-cost preparation method of graphene according to claim 3, characterized in that: in the step (1.1), the ultrasonic frequency is 100-1000W, and the ultrasonic time is 5-60 min.
5. The low-cost preparation method of graphene according to claim 3, characterized in that: in the step (1.1), the solvent is absolute ethyl alcohol, acetone, tetrahydrofuran, ethyl acetate, diethyl ether or dimethylformamide.
6. The low-cost preparation method of graphene according to claim 1, characterized in that: the ball-milling in the step (1) is carried out with the ball-milling material mass ratio of 10: 1-100: 1.
7. the low-cost preparation method of graphene according to claim 1, characterized in that: in the step (1), the ball milling speed is 2000-10000 rpm, and the ball milling time is 30-200 min.
8. The low-cost preparation method of graphene according to claim 1, characterized in that: the vacuum degree in the steps (2) and (3) is less than 10-3MPa; the grain size of the carbonized powder obtained in the step (2) is 10 nm-200 nm.
9. The low-cost preparation method of graphene according to claim 1, characterized in that: in the step (2), the ball milling speed is 1000-8000 rpm, and the ball milling time is 10-150 min.
10. The low-cost preparation method of graphene according to claim 1, characterized in that: the reducing gas in the step (3) is hydrogen or carbon monoxide, and the mass flow of the reducing gas is 10-200 sccm.
11. The low-cost preparation method of graphene according to claim 1, characterized in that: and (4) in the step (3), the protective gas is nitrogen, helium, argon or neon, and the mass flow of the protective gas is 100-800 sccm.
12. The low-cost preparation method of graphene according to claim 1, characterized in that: washing, purifying and drying for multiple times in the step (4); the washing times are 2-6 times; the washing solvent is deionized water, absolute ethyl alcohol, acetone or ethyl acetate.
13. The low-cost preparation method of graphene according to claim 1, characterized in that: the purification process in the step (4) is one or a combination of two of centrifugal separation, electrodialysis, suction filtration, dialysis and molecular membrane filtration; in the step (4), the drying temperature is 20-80 ℃, and the drying time is 2-12 h.
14. Graphene prepared by the preparation method of any one of claims 1 to 13.
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