CN113428852A - Method for preparing graphene by grinding and stripping composite molten salt - Google Patents
Method for preparing graphene by grinding and stripping composite molten salt Download PDFInfo
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Abstract
The invention relates to the field of graphene preparation, and discloses a method for preparing graphene by grinding and stripping composite molten salt. The preparation method comprises the following preparation processes: (1) heating and melting sodium chloride and calcium chloride to form composite molten salt, then uniformly stirring and dispersing the composite molten salt and expanded graphite, and then cooling and crushing to obtain graphite and salt embedded large particles; (2) mixing and grinding graphite, large particles inlaid with salt, a dispersing agent, ethanol and a grinding medium, and stripping the inlaid graphite to form graphene while continuously grinding the large particles; (3) and filtering the ground material by using a coarse screen, removing the grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder. The preparation method provided by the invention not only improves the grinding efficiency, but also ensures that the obtained graphene has high quality.
Description
Technical Field
The invention relates to the field of graphene preparation, and discloses a method for preparing graphene by grinding and stripping composite molten salt.
Background
Graphene is a two-dimensional crystal composed of carbon atoms with a monoatomic layer thickness, the carbon atoms are bonded with each other in an sp2 hybridization manner to form a honeycomb crystal grid network, the basic structural unit of the graphene is a benzene six-membered ring, and the graphene can be regarded as a single-layer peeled graphite sheet with the thickness of only 0.35 nm. Like other two-dimensional materials such as mica, molybdenum disulfide, talcum powder, montmorillonite and boride, the graphite layers are connected by hydrogen bonds with high bond energy. Therefore, in order to exfoliate graphite into single-layer or multi-layer graphene, it is a key issue to overcome the hydrogen bonding energy between graphite layers.
At present, the traditional chemical oxidation method for preparing graphene is essentially to use a strong oxidant (concentrated sulfuric acid) to destroy hydrogen bonds between graphite layers, so that graphite is easily peeled to be graphene, and the method is suitable for large-scale preparation. However, the use of a large amount of strong oxidant easily causes environmental pollution and high cost. In addition, the lattice of graphene is damaged by using a strong oxidant, and the reinforcing property and the electrical property of graphene are greatly reduced. At present, most of graphene oxide is available on the market, and the application of the graphene oxide has great limitation.
Theoretically, the preparation of graphene becomes possible as long as the hydrogen bonds between the graphite layers are effectively destroyed. Therefore, the preparation of the graphene by adopting a physical method represented by mechanical force and overcoming the hydrogen bond stripping among graphite layers through mechanical force energy, electric energy, magnetic energy, optical energy, sound energy and the like becomes the best choice for preparing the high-quality graphene in a pollution-free, large-scale and low-cost manner. Particularly, the preparation of graphene by mechanical stripping is a mainstream technology for producing graphene gradually due to simple equipment, large output scale and environment-friendly production. According to the related art disclosed so far, there is a technology for preparing graphene by peeling with a grinding and shearing device such as a ball mill, a sand mill, a three-roll mill, a screw extruder, and the like.
In the production practice, graphite is gradually refined and stripped, the shearing force generated by shearing on the graphite is smaller and smaller along with the reduction of the particle size, so that the stripping efficiency is low, and the obtained graphene is a compound of graphite, graphene nanoplatelets, multi-layer graphene and single-layer graphene, and the quality of the graphene is low. With the application requirements of mechanically stripped graphene in high-end products such as lithium batteries, heat dissipation coatings, printing conductive paste and the like, the quality requirement of mechanically stripped graphene is higher and higher, and therefore, the quality and the production efficiency of mechanically stripped graphene preparation need to be further improved.
The Chinese patent application No. 201010179119.1 discloses a method for preparing graphene or graphene oxide by high-efficiency low-cost mechanical stripping, which utilizes solid particles and a liquid working medium (or a gas working medium) to separate after mechanically stripping a carbon material; obtaining graphene or graphene oxide; the carbon material is graphite powder, expanded graphite, expandable graphite or graphite oxide powder.
The chinese patent application No. 201910254520.8 discloses a method for preparing graphene by mechanical exfoliation and the graphene prepared by the same, the raw materials of the graphene comprise, by mass: 4-25% of graphite powder, 70-95% of solvent and 0.1-5% of surfactant. The invention also provides a method for preparing graphene through mechanical stripping, which comprises the following steps: step (1), weighing raw materials in proportion; step (2), carrying out puffing treatment on graphite powder; step (3), mixing the expanded graphite with a solvent and a dispersant, and performing dispersion treatment; step (4), mechanically stripping the dispersion; step (5), homogenizing the treatment liquid; and 6, carrying out spray drying on the treatment solution to obtain graphene powder.
In the production practice, graphite is gradually refined and stripped, the shearing force generated by shearing on the graphite is smaller and smaller along with the reduction of the particle size, so that the stripping efficiency is low, and the obtained graphene is a compound of graphite, graphene nanoplatelets, multi-layer graphene and single-layer graphene, and the quality of the graphene is low. With the application requirements of mechanically stripped graphene in high-end products such as lithium batteries, heat dissipation coatings, printing conductive paste and the like, the quality requirement of mechanically stripped graphene is higher and higher, and therefore, the quality and the production efficiency of mechanically stripped graphene preparation need to be further improved.
Disclosure of Invention
According to the method, the existing method for preparing the graphene by mechanical stripping has the defects of low stripping efficiency and poor graphene quality.
The invention solves the problems through the following technical scheme:
a method for preparing graphene by grinding and stripping composite molten salt comprises the following specific steps:
(1) firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt;
(2) grinding the graphite obtained in the step (1), large particles inlaid with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 3-5 hours, and stripping the inlaid graphite to form graphene while continuously grinding the large particles;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
It is known that graphene can be obtained by mechanically grinding to break hydrogen bonds between graphene layers and thereby peel graphite layers apart. However, in the mechanical grinding process, as the granular materials are gradually refined, the grinding is more difficult and the efficiency is lower. Especially for nano-scale particles, the gaps between the grinding media balls are large, and it is difficult to form good grinding shear force. To achieve good shear milling at the nanometer scale, the particle size of the milling media needs to be sufficiently small. Currently grinding media used in sand mills reach a minimum of 0.1mm, but grinding media of sufficiently small particle size are difficult to separate, while grinding shear is limited. According to the method, the salt is heated and melted to form the molten salt, the molten salt is inlaid on the surface and the interlayer of the expanded graphite, the molten salt is equivalent to the support body, the graphite is in a larger particle, so that the graphite is fully contacted with a grinding medium, the shearing force is strong, the problem that grinding and stripping efficiency is influenced by gradual grinding and refining of pure graphite is solved, and the quality of graphene is improved.
The sodium chloride and the calcium chloride are both salts which are easy to dissolve in water, and the sodium chloride and the calcium chloride are adopted to form composite salt, so that the melting temperature can be reduced, and complete melting and uniform mixing are facilitated.
In the present invention, the temperature for melting by heating in step (1) is preferably 810 ℃.
The expanded graphite is a novel functional carbon material, and is a loose and porous vermicular substance obtained by intercalating, washing, drying and high-temperature bulking natural graphite flakes. The expanded graphite has excellent cold and heat resistance, corrosion resistance, self-lubrication and other excellent performances of natural graphite, and has the characteristics of softness, compression resilience, adsorbability, ecological environment harmony, biocompatibility, radiation resistance and the like which are not possessed by natural graphite. The expanded graphite is graphite that expands in the direction of the C axis between graphite layers, and the interlayer bonding force of graphite particles is weakened by expansion as compared with natural graphite, and thus the graphite particles are more easily exfoliated to form graphene.
In the present invention, the expanded graphite in the step (1) preferably has a particle size of 50 to 100 μm.
Furthermore, ethanol is added into the mechanical grinding system, calcium chloride in the composite molten salt is dissolved in the ethanol, so that the strength of large particles embedded by graphite and salt is reduced, the large particles are ground and refined, and sodium chloride is insoluble in the ethanol and can be used as a support framework of the graphite, so that a larger particle state is maintained, and stable and good shearing is realized.
In a preferred embodiment of the present invention, in the step (1), the raw materials include, by weight, 5 parts of sodium chloride, 1 part of calcium chloride, and 2 parts of expanded graphite.
Preferably, the dispersant in step (2) is polyvinylpyrrolidone. More preferably, the polyvinylpyrrolidone has a number average molecular weight of 30 ten thousand.
Preferably, the purity of the ethanol in the step (2) is 99%.
The grinding medium is an energy carrier during grinding, and the material particles are dispersed or crushed through mutual friction, shearing and collision of the grinding medium. The zirconia ceramic ball has high strength and high toughness, good wear resistance, high temperature resistance, corrosion resistance, high rigidity, no magnetic conduction and good electrical insulation at normal temperature, and is an ideal grinding medium because the zirconia ceramic ball has good roundness and smooth surface and has little abrasion to equipment and good toughness, and the zirconia ceramic ball does not crack or peel during high-speed grinding.
Preferably, the grinding medium in step (2) is zirconia ceramic balls. In a further preferred embodiment of the present invention, the zirconia ceramic balls have a particle size of 0.3 mm.
More preferably, the raw materials in the step (2) comprise, by weight, 10-20 parts of graphite and salt-intercalated large particles, 0.5-0.8 part of a dispersing agent, 70-80 parts of ethanol, and 60-100 parts of a grinding medium.
The invention provides a method for preparing graphene by grinding and stripping composite molten salt, which comprises the steps of uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; grinding large particles, a dispersing agent, ethanol and a grinding medium, which are inlaid with graphite and salt, in a ball mill for 3-5 hours, and stripping the inlaid graphite to form graphene while continuously grinding the large particles; filtering the ground material with a coarse mesh to remove the grinding medium, then filtering with a fine mesh to remove ethanol, further desalting by repeated water washing, and drying.
The invention provides a method for preparing graphene by grinding and stripping composite molten salt, which has the outstanding characteristics and excellent effects compared with the prior art:
1. the method for preparing the graphene by inlaying the expanded graphite with the composite molten salt and then carrying out ball milling and stripping is provided.
2. By inlaying the composite molten salt, the molten salt is equivalent to a support body, so that the graphite is in a larger particle, the graphite is fully contacted with a grinding medium, the shearing force is strong, and the problem that the grinding stripping efficiency is influenced by gradual grinding and refining of pure graphite is solved.
3. The ground composite salt is easy to dissolve in water and can be removed by simple water washing, the process is simple and the cost is low.
4. By selecting the composite salt consisting of sodium chloride and calcium chloride, the calcium chloride is dissolved in ethanol, so that the strength of large particles is reduced, the large particles are favorably ground and refined, the sodium chloride is insoluble in ethanol and can be used as a supporting framework of graphite to keep the graphite to be sheared and peeled from a grinding medium under the condition of larger particles, therefore, the grinding efficiency is improved, and the obtained graphene has high quality.
Drawings
Fig. 1 is a field diagram of a temperature change test of the surface of an aluminum plate, wherein a is a temperature test of the surface of a heat dissipation coating prepared from graphene of example 6 for 20min, b is a temperature test of the surface of a heat dissipation coating prepared from graphene of comparative example 1 for 20min, c is a temperature test of the surface of a heat dissipation coating prepared from graphene of comparative example 2 for 20min, and d is a temperature test of the surface of a blank coating for 20 min.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
(1) Firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; the temperature for heating and melting is 810 ℃; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite;
(2) grinding the graphite obtained in the step (1), large particles embedded with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 4 hours, and stripping the embedded graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, according to parts by weight, 15 parts by weight of graphite and salt-embedded large particles, 0.6 part by weight of a dispersing agent, 75 parts by weight of ethanol and 70 parts by weight of grinding media are added;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Example 2
(1) Firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; the temperature for heating and melting is 810 ℃; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite;
(2) grinding the graphite obtained in the step (1), large particles inlaid with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 4.5 hours, and stripping the inlaid graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, according to parts by weight, 15 parts by weight of graphite and salt-embedded large particles, 0.8 part by weight of a dispersing agent, 75 parts by weight of ethanol and 80 parts by weight of grinding media are added;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Example 3
(1) Firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; the temperature for heating and melting is 810 ℃; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite;
(2) grinding the graphite obtained in the step (1), large particles embedded with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 3.5 hours, and stripping the embedded graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, 13 parts by weight of graphite and salt-intercalated large particles, 0.7 part by weight of a dispersing agent, 72 parts by weight of ethanol and 70 parts by weight of grinding media are calculated;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Example 4
(1) Firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; the temperature for heating and melting is 810 ℃; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite;
(2) grinding the graphite obtained in the step (1), large particles embedded with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 4 hours, and stripping the embedded graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, 12 parts by weight of graphite and salt-intercalated large particles, 0.7 part by weight of a dispersing agent, 77 parts by weight of ethanol and 80 parts by weight of grinding media are calculated;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Example 5
(1) Firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; the temperature for heating and melting is 810 ℃; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite;
(2) grinding the graphite obtained in the step (1), large particles embedded with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 3 hours, and stripping the embedded graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, 20 parts by weight of graphite and salt-intercalated large particles, 0.8 part by weight of a dispersant, 70 parts by weight of ethanol and 100 parts by weight of grinding media are calculated;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Example 6
(1) Firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt; the temperature for heating and melting is 810 ℃; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite;
(2) grinding the graphite obtained in the step (1), large particles embedded with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 5 hours, and stripping the embedded graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, 20 parts by weight of graphite and salt-intercalated large particles, 0.5 part by weight of a dispersing agent, 80 parts by weight of ethanol and 60 parts by weight of grinding media are calculated;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Comparative example 1
(1) Grinding the expanded graphite, a dispersing agent, ethanol and a grinding medium in a ball mill for 5 hours; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm; the particle size of the expanded graphite is 50 mu m;
in the grinding system, 5 parts by weight of expanded graphite, 0.5 part by weight of dispersant, 80 parts by weight of ethanol and 60 parts by weight of grinding medium are calculated according to the parts by weight;
(2) filtering the material ground in the step (1) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, and drying to obtain graphene powder.
Comparative example 1 the expanded graphite was not intercrossed with the molten salt but directly ground with the expanded graphite, a dispersant, ethanol, and a grinding medium in a ball mill under the same preparation conditions as in example 6.
Comparative example 2
(1) Firstly, heating and melting sodium chloride to form molten salt, then adding the expanded graphite into the molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and the interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with graphite and salt embedded; the particle size of the expanded graphite is 50 mu m;
in the dispersion system, 5 parts by weight of sodium chloride and 2 parts by weight of expanded graphite are calculated according to the parts by weight;
(2) grinding the graphite obtained in the step (1), large particles embedded with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 5 hours, and stripping the embedded graphite to form graphene while continuously grinding the large particles; the dispersing agent is polyvinylpyrrolidone with the number-average molecular weight of 30 ten thousand; the purity of the ethanol is 99 percent; the grinding medium is zirconia ceramic balls with the grain diameter of 0.3 mm;
in the grinding system, 20 parts by weight of graphite and salt-intercalated large particles, 0.5 part by weight of a dispersing agent, 80 parts by weight of ethanol and 60 parts by weight of grinding media are calculated;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
Comparative example 2 calcium chloride was not added and other preparation conditions were the same as in example 6.
Graphene performance verification:
because graphite alkene is difficult audio-visual to judge the quality, this is through preparing into heat dissipation coating with graphite alkene, measures the quality of graphite alkene indirectly through the thermal diffusivity. 50g of graphene obtained in examples 1-6 and comparative examples 1-2 is added into 300mL of aqueous fluorocarbon emulsion to be dispersed into a heat dissipation coating, then the heat dissipation coating is self-leveled and naturally dried for 48 hours on an aluminum plate with the thickness of 1mm, the aluminum plate without the coating is a blank reference sample, then the aluminum plate is placed on a constant temperature plate with the temperature of 120 ℃, the coating faces upwards, and the change of the surface temperature of the coating is tested.
As can be seen from Table 1: the graphene obtained by the method has good thermal radiation performance, so that thermal radiation is radiated in time, and the temperature of the coating is kept at a relatively low level; the comparative example 1 directly grinds the expanded graphite, and the graphene prepared by grinding has low purity and quality, relatively weak heat radiation and poor heat dissipation effect within the same grinding time; in the comparative example 2, calcium chloride is not added, so that the particles which are independently molten and inlaid by sodium chloride are not easy to grind, the grinding energy consumption is high, and in the same grinding time, the purity and the quality of the graphene prepared by grinding are not high, the heat radiation is relatively weak, and the heat radiation effect is slightly poor.
Fig. 1 is a field diagram of a temperature change test of the surface of an aluminum plate, wherein a is a temperature test of the surface of a heat dissipation coating prepared from graphene of example 6 for 20min, b is a temperature test of the surface of a heat dissipation coating prepared from graphene of comparative example 1 for 20min, c is a temperature test of the surface of a heat dissipation coating prepared from graphene of comparative example 2 for 20min, and d is a temperature test of the surface of a blank coating for 20 min.
Table 1:
| performance index | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 | Comparative example 1 | Comparative example 2 | Blank sample |
| Temperature (deg.C) for 5min | 82.7 | 82.1 | 82.5 | 82.8 | 82.4 | 81.9 | 99.5 | 88.5 | 113.7 |
| Temperature (. degree.C.) for 10min | 97.6 | 97.1 | 97.4 | 97.7 | 97.3 | 96.8 | 112.1 | 103.5 | 115.5 |
| 15min temperature (. degree.C.) | 103.2 | 102.6 | 102.9 | 103.4 | 102.7 | 102.4 | 114.7 | 106.2 | 116.2 |
| Temperature (. degree.C.) for 20min | 104.2 | 104.1 | 104.3 | 104.7 | 103.9 | 104.6 | 116.4 | 108.4 | 118.3 |
Claims (10)
1. The method for preparing graphene by grinding and stripping composite molten salt is characterized by comprising the following specific steps:
(1) firstly, uniformly mixing sodium chloride and calcium chloride salt, heating and melting to form composite molten salt, then adding expanded graphite into the composite molten salt, stirring and dispersing uniformly to enable the molten salt and the surface and interlayer of the expanded graphite to be embedded into a whole, and then cooling and crushing to obtain large particles with embedded graphite and salt;
(2) grinding the graphite obtained in the step (1), large particles inlaid with salt, a dispersing agent, ethanol and a grinding medium in a ball mill for 3-5 hours, and stripping the inlaid graphite to form graphene while continuously grinding the large particles;
(3) filtering the material ground in the step (2) by using a coarse screen, removing a grinding medium, then filtering by using a fine screen, removing ethanol, further removing desalination by repeatedly washing, and drying to obtain graphene powder.
2. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: the temperature of the heating and melting in the step (1) is 810 ℃.
3. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: the particle size of the expanded graphite in the step (1) is 50-100 mu m.
4. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: the raw materials in the step (1) comprise, by weight, 5 parts of sodium chloride, 1 part of calcium chloride and 2 parts of expanded graphite.
5. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: and (3) the dispersing agent in the step (2) is polyvinylpyrrolidone.
6. The method for preparing graphene by grinding and stripping composite molten salt according to claim 5, characterized by comprising the following steps: the polyvinylpyrrolidone has a number average molecular weight of 30 ten thousand.
7. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: the purity of the ethanol obtained in the step (2) is 99%.
8. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: and (3) the grinding medium in the step (2) is zirconia ceramic balls.
9. The method for preparing graphene by grinding and stripping composite molten salt according to claim 8, characterized by comprising the following steps: the particle size of the zirconia ceramic ball is 0.3 mm.
10. The method for preparing graphene by grinding and stripping composite molten salt according to claim 1, characterized by comprising the following steps: the raw materials in the step (2) comprise, by weight, 10-20 parts of graphite and salt-embedded large particles, 0.5-0.8 part of a dispersing agent, 70-80 parts of ethanol and 60-100 parts of a grinding medium.
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