CN116199213A - Method for dispersing graphene in liquid system - Google Patents
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- CN116199213A CN116199213A CN202310166134.XA CN202310166134A CN116199213A CN 116199213 A CN116199213 A CN 116199213A CN 202310166134 A CN202310166134 A CN 202310166134A CN 116199213 A CN116199213 A CN 116199213A
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- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 185
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 183
- 239000007788 liquid Substances 0.000 title claims abstract description 109
- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000006185 dispersion Substances 0.000 claims abstract description 132
- 238000000498 ball milling Methods 0.000 claims abstract description 60
- 238000000227 grinding Methods 0.000 claims abstract description 60
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 59
- 239000011259 mixed solution Substances 0.000 claims abstract description 47
- 238000011282 treatment Methods 0.000 claims abstract description 40
- 239000000843 powder Substances 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 239000000243 solution Substances 0.000 claims abstract description 5
- 239000010687 lubricating oil Substances 0.000 claims description 43
- 238000003756 stirring Methods 0.000 claims description 17
- 238000009775 high-speed stirring Methods 0.000 claims description 11
- 238000003801 milling Methods 0.000 claims description 5
- 238000005119 centrifugation Methods 0.000 claims description 2
- 239000000126 substance Substances 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 25
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 16
- 229910000831 Steel Inorganic materials 0.000 description 15
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- 238000001132 ultrasonic dispersion Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
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- 230000008859 change Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
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- 235000019198 oils Nutrition 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 241000193879 Corbicula fluminea Species 0.000 description 1
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- 238000005461 lubrication Methods 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
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- 238000010907 mechanical stirring Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
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- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/194—After-treatment
Abstract
The invention relates to a dispersion method of graphene in a liquid system. The dispersion method of graphene in a liquid system comprises the following steps: s1: placing graphene powder into a liquid for mixing to obtain a first mixed liquid; s2: performing ball milling ultrasonic treatment on the first mixed solution for more than three times to obtain a second mixed solution; s3: settling and layering the second mixed solution, and taking at least part of the upper layer solution as a third mixed solution; s4: and performing ball milling ultrasonic treatment on the third mixed solution for more than one time to obtain graphene dispersion liquid, wherein the ball milling ultrasonic treatment comprises ball milling treatment of adding grinding balls into the mixed solution for grinding and ultrasonic treatment of performing ultrasonic treatment on the mixed solution. The dispersion method provided by the invention has the advantage that the dispersibility of graphene in a liquid system can be improved without introducing other chemical substances.
Description
Technical Field
The invention relates to the field of graphene, in particular to a method for dispersing graphene in a liquid system.
Background
Graphene is used in various industries due to its excellent properties. However, graphene is not easy to disperse uniformly and agglomerate in lubricating oil or water and other liquids, which affects the application of the graphene in a liquid system, and particle size control and dispersion technology are key to preparing graphene-containing dispersion liquid. Nowadays, the dispersion problem of graphene is mainly solved by a chemical dispersion method, namely, the graphene is uniformly and stably dispersed in lubricating oil or water by utilizing the dispersion effect of a dispersing agent, but the method has the defect that the additionally added dispersing agent can influence the properties of graphene or a liquid system, so that the performance of a graphene dispersion liquid is influenced.
Disclosure of Invention
Based on this, an object of the present invention is to provide a method for dispersing graphene in a liquid system, which can improve the dispersibility of graphene in a liquid system without introducing other chemicals.
The invention relates to a dispersion method of graphene in a liquid system, which comprises the following steps:
s1: placing graphene powder into a liquid for mixing to obtain a first mixed liquid;
s2: performing ball milling ultrasonic treatment on the first mixed solution for more than three times to obtain a second mixed solution;
s3: settling and layering the second mixed solution, and taking at least part of upper layer solution as third mixed solution;
s4: performing ball milling ultrasonic treatment on the third mixed solution for more than one time to obtain graphene dispersion liquid;
the above-mentioned ball-milling ultrasonic treatment includes ball-milling treatment in which a grinding ball is added to the mixed liquid for grinding and ultrasonic treatment in which the mixed liquid is subjected to ultrasonic treatment.
According to the invention, the agglomerated graphene in the liquid system is efficiently dispersed through repeated ball milling ultrasonic treatment, and further through sedimentation layering treatment and secondary ball milling ultrasonic treatment, the graphene is ensured to be completely and uniformly dispersed in the liquid system. Based on this specific combination of physical methods, the dispersibility of graphene in liquid systems can be improved without the need to introduce other chemicals.
Further, in the ball-milling ultrasonic treatment of the above step S2, the milling time of the ball-milling treatment is 30 minutes or more.
Further, in the ball-milling ultrasonic treatment of the above step S2, the milling time of the ball-milling treatment is 30 to 120 minutes.
Further, the grinding balls comprise 5% -10% of grinding balls with the diameter of 5mm, 20% -30% of grinding balls with the diameter of 3mm, 30% -50% of grinding balls with the diameter of 1mm and 20% -30% of grinding balls with the diameter of 0.5 mm.
Further, in the ball milling ultrasonic treatment of the above step S2, the time of the ultrasonic treatment is 30 to 120 minutes.
Further, in the step S1, the graphene powder and the liquid are mixed by a high-speed stirring treatment in which the stirring speed is 2000r/min or more and the stirring time is 30 minutes or more.
Further, in the ball-milling ultrasonic treatment of the above step S4, the milling time of the ball-milling treatment is 60 minutes or more, and the ultrasonic treatment time is 60 minutes or more.
Further, in the step S3, the second mixed solution is sedimented and layered by centrifugation or standing.
Further, the liquid is a lubricating oil.
On the other hand, the invention also provides a graphene dispersion liquid, which is obtained by any one of the dispersing methods.
For a better understanding and implementation, the present invention is described in detail below with reference to the drawings.
Drawings
Fig. 1 is a scanning electron microscope image of graphene used in examples and comparative examples according to the present invention.
Fig. 2 is an enlarged view of graphene dispersions 1 to 9 obtained in comparative examples 1 to 9. Wherein, (a-1) is a graph of graphene dispersion 1 at 50-fold magnification; (a-2) is a 50-fold enlarged view of graphene dispersion 2; (a-3) is a 50-fold enlarged view of graphene dispersion 3; (b-1) a graph of graphene dispersion 4 at 50-fold magnification; (b-2) a graph of graphene dispersion 5 at 50-fold magnification; (b-3) a 50-fold enlarged view of the graphene dispersion 6; (c-1) a graph of graphene dispersion 7 at 200-fold magnification; (c-2) a graph of graphene dispersion 8 at 200-fold magnification; (c-3) A drawing in which the graphene dispersion 9 was enlarged 200 times.
Fig. 3 is a 200-fold enlarged view of the graphene dispersion 10 obtained in example 1.
Fig. 4 is an infrared spectrum of the graphene dispersion liquid 10 obtained in example 1.
Fig. 5 is a graph of steel ball mill marks after four-ball friction test of graphene dispersion liquid and pure lubricating oil obtained in comparative example.
Wherein (a) is a steel ball mill pattern of graphene dispersion liquid 3; (b) a steel ball mill pattern of graphene dispersion 6; (c) a steel ball mill pattern of graphene dispersion 9; (d) is a steel ball mill mark diagram of pure lubricating oil.
Fig. 6 is a steel ball mill-spotting chart after four-ball friction test on the graphene dispersion 10 obtained in example 1.
Detailed Description
In order to solve the problems, the invention improves the dispersibility of graphene in lubricating oil by a pure physical method. Specific physical methods and combinations thereof are utilized to improve the aggregation of graphene in a liquid system.
The invention relates to a dispersion method of graphene in a liquid system, which comprises the following steps:
s1: placing graphene powder into a liquid for mixing to obtain a first mixed liquid;
s2: performing ball milling ultrasonic treatment on the first mixed solution for more than three times to obtain a second mixed solution;
s3: settling and layering the second mixed solution, and taking at least part of upper layer solution as third mixed solution;
s4: performing ball milling ultrasonic treatment on the third mixed solution for more than one time to obtain graphene dispersion liquid;
the ball milling ultrasonic treatment comprises ball milling treatment of adding a grinding ball into the mixed liquid for grinding and ultrasonic treatment of the mixed liquid.
Hereinafter, preferred embodiments of the above steps will be described in detail.
For step S1: and (3) placing the graphene powder into the liquid for mixing to obtain a first mixed liquid.
Specifically, a proper amount of graphene powder can be weighed and put into a container filled with liquid, and graphene is uniformly mixed into the liquid by hand or a machine to obtain a first mixed liquid. Preferably, the mixing is performed by: after preliminary mixing of graphene powder and liquid by machine or manual stirring at a low speed of 500r/min or less, stirring at a high speed of 2000r/min or more for 30min or more.
In this step, the graphene powder means a single-layer or small-layer graphene, and the liquid may be a liquid system of oils such as lubricating oil, water, and oil-water mixture. The high-speed stirring treatment may be mechanical stirring or magnetic stirring by a high-speed stirrer, and the stirring speed may be set to not less than 2000r/min for achieving a good dispersing effect. When the stirring speed is too high, if the stirring speed is limited by the size of the container, hollow vortex is easy to form in the stirring container, so that the dispersion of graphene is influenced; the maximum stirring speed can be controlled according to the size of the container, and in general, the stirring speed can be set to 2000-3000 r/min. In the high-speed stirring treatment, the stirring time is more than 30min, so that uniformly mixed graphene mixed solution is easy to obtain, and the subsequent dispersion treatment is facilitated; when the stirring time exceeds 120 minutes, the dispersion degree of the graphene powder is not easily further improved, and the stirring time is preferably 30 to 120 minutes in consideration of both the dispersion effect and the dispersion efficiency.
For step S2: and performing ball milling ultrasonic treatment on the first mixed solution for more than three times to obtain a second mixed solution.
Specifically, the ball-milling ultrasonic treatment includes ball-milling treatment and ultrasonic treatment, and can be to perform the ball-milling treatment on the mixed solution and then perform the ultrasonic treatment on the mixed solution, or to perform the ultrasonic treatment on the mixed solution and then perform the ball-milling treatment on the mixed solution. For example, the first mixed solution in the step S1 can be poured into a clean and dry ball milling tank, and grinding balls with proper grading are added, so that the grinding time is not less than 30 minutes; then, carrying out ultrasonic (wave) treatment for not less than 30min on the ground mixed solution; and (3) repeatedly performing ball milling and ultrasonic treatment on the obtained mixed solution after ultrasonic treatment for more than two times to obtain a second mixed solution.
In the ball-milling ultrasonic treatment of the step, the grinding time of the ball-milling treatment is not less than 30min, the ultrasonic treatment time is not less than 30min, and when the ball-milling ultrasonic treatment is repeatedly performed for at least 3 times, the agglomerated graphene can be repeatedly ground and timely scattered, so that the graphene in a liquid system is efficiently and fully dispersed. When each treatment time is too long, the improvement of the dispersion degree of the graphene is extremely limited, and the graphene is highly likely to have serious curling, folding deformation and other performance changes, so that the grinding time of ball milling treatment in each ball milling ultrasonic treatment is preferably 30-120 min, and the ultrasonic time of ultrasonic treatment is preferably 30-120 min. In addition, when the ball-milling ultrasonic treatment is repeated 5 times or more, the dispersion effect is not greatly improved, and in consideration of both the dispersion effect and the dispersion efficiency, it is preferable to repeat the ball-milling ultrasonic treatment 3 to 5 times.
In the ball milling process, the grinding balls with proper grading are preferably: 5-10% of grinding balls with the diameter of 5mm, 20-30% of grinding balls with the diameter of 3mm, 30-50% of grinding balls with the diameter of 1mm and 20-30% of grinding balls with the diameter of 0.5 mm. The grinding balls with the specification have similar particle sizes with the graphene powder, so that the grinding degree is finer, and the dispersion efficiency of the graphene in the liquid can be improved. For example, a ball grading of 3mm diameter balls, 1mm diameter balls, 0.5mm diameter balls at a ratio of 1:2:3 or 2:3:5 may be used.
The ball milling treatment is preferably realized by a planetary high-energy ball mill, and the grinding balls and the grinding tanks can adopt nonferrous series grinding balls such as zirconia, tungsten carbide and the like so as to reduce the generation of impurities in the grinding tanks and the grinding balls in the ball milling process and enter a liquid system. Particularly, in the case of a liquid system of lubricating oil, iron-based grinding tends to cause mixing of iron filings into the liquid system, which reduces the lubricating property of the lubricating oil, and non-iron-based grinding can avoid this problem. The ultrasonic treatment can be realized by an ultrasonic disperser such as a plunge ultrasonic disperser. Optionally, the grinding speed is 600-1000 r/min, and the ultrasonic power is 600-1200W.
For step S3: and settling and layering the second mixed liquid, and taking at least part of the upper layer liquid as a third mixed liquid.
Specifically, the second mixed solution in the step S2 is subjected to centrifugal treatment or standing for 3-5 days to settle and layer, and then at least part of the upper mixed solution is taken as a third mixed solution. Preferably, the upper layer portion of the upper layer liquid is taken as the third mixed liquid, for example, three quarters of the upper layer liquid, one half of the upper layer liquid, and the like are taken as the third mixed liquid.
For step S4: and performing ball milling ultrasonic treatment on the third mixed solution for more than one time to obtain graphene dispersion liquid.
Specifically, the third mixed solution in step S3 may be subjected to a ball milling treatment for not less than 60 minutes and then to an ultrasonic treatment for 60 minutes or more, which is performed more than once in total. Also, based on the dispersion efficiency, effect and reason of avoiding the change of the properties of graphene, the ball milling time and the ultrasonic dispersion time are preferably 60 to 120 minutes, and the number of times of ball milling ultrasonic treatment is preferably 1 to 3.
In each of the treatments of the above steps, the temperature in each treatment may be controlled between the freezing point and the boiling point of the liquid system. When the treatment temperature is 15-100 ℃, the dispersion efficiency can be further improved, and the original property of the liquid system is ensured. Each process may be controlled to have a process temperature in a desired range by a batch process, and the process time of each process is an effective process time for actually performing the process.
According to the dispersion method of graphene in the liquid system, agglomerated graphene in the liquid system can be efficiently dispersed through repeated ball milling ultrasonic treatment, and further, through sedimentation layering treatment and subsequent ball milling ultrasonic treatment, graphene dispersion liquid in which graphene is completely and uniformly dispersed in the liquid system can be ensured to be obtained. According to the graphene dispersing method provided by the invention, other chemical reagents are not required to be added, so that the graphene can be fully and uniformly dispersed in a liquid system while the property of the graphene dispersing liquid is ensured not to be changed.
Hereinafter, the implementation of the method according to the present invention and the effects thereof will be further described with reference to examples and comparative examples. The following examples are merely illustrative of the present invention and do not limit the scope of the present invention.
Comparative examples 1 to 3 (high speed stirring)
Comparative examples 1 to 3 used only high-speed stirring treatment to disperse graphene, specifically: 100mL of lubricating oil (Shell HX75W-40 lubricating oil, manufactured by Shanghai Corbicula fluminea L., inc., hereinafter the same) is measured and placed in a container, and a high-speed dispersing machine (GFJ-0.4, manufactured by Shanghai modern environmental engineering technology Co., ltd., hereinafter the same) is adopted to stir and mix the lubricating oil in the container at a rotating speed of 150r/min, and meanwhile 10mg of graphene (manufactured by Nanjing Jicang nanotechnology Co., ltd., shown in FIG. 1, hereinafter the same) is added into the lubricating oil. After all graphene is added, the rotating speed is slowly increased to 2000r/min, and the mixture is stirred at a high speed for a certain time at room temperature (about 18 ℃) to obtain graphene dispersion liquid. Wherein, the time of high-speed stirring in comparative example 1 is 30min; the time of high-speed stirring in comparative example 2 was 60min; the time for high speed stirring in comparative example 3 was 120min. Graphene dispersions 1 to 3 were obtained in comparative examples 1 to 3, respectively.
Comparative examples 4 to 6 (ultrasonic treatment)
Comparative examples 4 to 6 use only ultrasonic treatment to disperse graphene, specifically: firstly, 100mL of lubricating oil is weighed and placed in a container, and then 10mg of graphene is weighed and added into the lubricating oil for mixing at a rotating speed of 150 r/min. An ultrasonic dispersion apparatus (SCIENTZ-1500F ultrasonic dispersion apparatus, manufactured by ningbo new biosciences, inc.) was set in an intermittent operation mode of 15s to 20s to control the treatment temperature to 80 ℃ or lower, and effective dispersion was performed for a certain period of time under the condition of 600W power to obtain a graphene dispersion. Wherein, in comparative example 4, the ultrasonic time was 30min; the ultrasonic time in comparative example 5 was 60min; the sonication time was 120min in comparative example 6. Graphene dispersions 4 to 6 were obtained in comparative examples 4 to 6, respectively.
Comparative examples 7 to 9 (ball milling treatment)
Comparative examples 7 to 9 use only ball milling treatment to disperse graphene, specifically: firstly, 100mL of lubricating oil is weighed and placed in a container, and then 10mg of graphene is weighed and added into the lubricating oil for mixing at a rotating speed of 150 r/min. Adding grinding balls (the diameter of the zirconia grinding balls is 5mm, the diameter of the zirconia grinding balls is 3mm, the diameter of the zirconia grinding balls is 20 mm, the diameter of the zirconia grinding balls is 1mm, the diameter of the zirconia grinding balls is 45 mm, the diameter of the zirconia grinding balls is 0.5mm, the diameter of the zirconia grinding balls is 30% and the same applies below), pouring the mixed solution of graphene and lubricating oil into the grinding tank, covering the grinding tank, putting the grinding tank into a high-energy ball mill (Pulverisette 7 type miniature high-energy ball mill, manufactured by the company of Fritsch, germany, the same applies below), setting the rotating speed to be 600r/min, stopping working for 5min for 3min, and effectively dispersing for a certain time to obtain the graphene dispersion. Wherein, the grinding time is 30min in comparative example 7; the grinding time was 60min in comparative example 8; the grinding time was 120min in comparative example 9. Graphene dispersions 7 to 9 were obtained in comparative examples 7 to 9, respectively.
Example 1
Example 1 graphene was dispersed by the method according to the present invention, specifically: firstly, 100mL of lubricating oil is measured and placed in a container, the lubricating oil in the container is stirred at the rotating speed of 150r/min by adopting a high-speed dispersing machine, 10mg of graphene is added into the lubricating oil, after all graphene is added, the rotating speed is slowly increased to 2000r/min, and the stirring is carried out at the high speed for 30min at room temperature (about 18 ℃) to obtain a first mixed solution. Adding grinding balls prepared in a grinding tank, pouring the first mixed solution into the grinding tank, covering the grinding tank tightly, putting into a high-energy ball mill, setting the rotating speed to 600r/min, working for 5min, stopping for 3min, and effectively dispersing for 30min; then, setting an intermittent working mode of the ultrasonic dispersing equipment for 15s and 20s so as to control the temperature below 80 ℃, effectively dispersing for 30min under the condition of 600W of power, and repeatedly performing ball milling ultrasonic treatment for 3 times to obtain a second mixed solution; then, using a centrifuge to centrifuge the second mixed solution for 20min under the condition of 3000r/min, and taking three fourths of the upper layer solution as a third mixed solution; and (3) grinding the third mixed solution in a high-energy ball mill for 60min, and performing ultrasonic treatment for 60min to obtain the graphene dispersion liquid 10.
Since there is currently no parameter or standard suitable for measuring the dispersion degree of graphene-based materials, the present invention evaluates the dispersion methods of each of the examples and comparative examples by directly observing the dispersion degree of graphene dispersion liquid and determining the properties of the graphene dispersion liquid.
[ observation of degree of Dispersion ]
The graphene dispersions 1 to 6 obtained in comparative examples 1 to 6 were observed under a condition of 50-fold magnification, and the graphene dispersions 7 to 10 obtained in comparative examples 7 to 9 and example 1 were observed under a condition of 200-fold magnification, using a metallographic fluorescence microscope (model DM 6M, manufactured by Leica, germany, hereinafter the same). The enlarged images of the graphene dispersions 1 to 9 are shown in FIG. 2, wherein FIGS. 2 (a-1) to (a-3) correspond to the graphene dispersions 1 to 3, FIGS. 2 (b-1) to (b-3) correspond to the graphene dispersions 4 to 6, and FIGS. 2 (c-1) to (c-3) correspond to the graphene dispersions 7 to 9, respectively. An enlarged image of graphene dispersion 10 is shown in fig. 3.
[ component analysis ]
The components of the pure lubricating oil and graphene dispersion 10 were analyzed by a fourier transform infrared spectrometer (IS 50 fourier transform infrared spectrometer, samer, usa) and the results are shown in fig. 4.
[ Performance test ]
The friction coefficients of the pure lubricating oil and the graphene dispersions 3, 6, 9, 10 to which no graphene was added were measured 5 times each using a four-ball friction tester (model MRS-10H, manufactured by Jinan Chen da tester Co., ltd.) under conditions of an oil box temperature of 75 ℃ + -2, a servo motor rotation speed of 1200+ -60 r/min, a test duration of 3600+ -60 s, and a pressure of 392+ -2N, and the average value and standard deviation thereof were calculated, and the friction coefficient values, average values, and standard deviations obtained by the measurement are shown in Table 1.
The steel balls after the completion of the test in Table 1 were subjected to the measurement of the spot diameter, and the spot diameter values (in mm) as the measurement results, and the average value and standard deviation thereof are shown in Table 2. The morphology of the spots of each steel ball was also observed by a metallographic fluorescence microscope, and the results are shown in fig. 5 and 6. Fig. 5 (a) to (d) are graphs of steel ball mill marks after four-ball friction test of graphene dispersion 3, graphene dispersion 6, graphene dispersion 9, and pure lubricating oil, respectively. Fig. 6 is a graph of steel ball spotting after a four-ball friction test of graphene dispersion 10.
[ Table 1 ]
| Number of |
1 | 2 | 3 | 4 | 5 | Average value of | Standard deviation of |
| |
0.106 | 0.104 | — | — | 0.108 | 0.106 | — |
| Graphene dispersion 6 | 0.104 | 0.103 | 0.107 | 0.105 | — | 0.105 | — |
| |
0.106 | 0.102 | 0.107 | 0.106 | 0.103 | 0.105 | 0.0022 |
| Graphene dispersion 10 | 0.105 | 0.103 | 0.103 | 0.104 | 0.105 | 0.104 | 0.0010 |
| Pure lubricating oil | 0.106 | 0.105 | 0.106 | 0.104 | 0.105 | 0.105 | 0.0008 |
* "-" indicates that the complete test has not been completed due to a protective shutdown of the equipment caused by a sudden increase in friction.
[ Table 2 ]
| Number of |
1 | 2 | 3 | 4 | 5 | Average value of | Standard deviation of |
| |
0.630 | 0.643 | — | — | 0.672 | 0.648 | 0.0215 |
| Graphene dispersion 6 | 0.618 | 0.641 | 0.651 | 0.631 | — | 0.635 | 0.0141 |
| |
0.607 | 0.646 | 0.631 | 0.629 | 0.618 | 0.626 | 0.0147 |
| Graphene dispersion 10 | 0.626 | 0.621 | 0.635 | 0.614 | 0.604 | 0.620 | 0.0118 |
| Pure lubricating oil | 0.643 | 0.616 | 0.633 | 0.638 | 0.620 | 0.630 | 0.0116 |
As shown in fig. 2, the results of observation of each graphene dispersion liquid by a metallographic fluorescence microscope show that the dispersion degree of the graphene in fig. 2 (c-1) to (c-3) is higher than that in fig. 2 (b-1) to (b-3) and higher than that in fig. 2 (a-1) to (a-3) under the same treatment time, that is, the dispersion effect of the ultrasonic treatment on the graphene is better than that of the high-speed stirring treatment, and the ball milling treatment is better than that of the ultrasonic treatment. Longitudinal comparison shows that the increase of time in each treatment is beneficial to the dispersion of graphene, but the dispersion effect on graphene is limited as time increases. On the other hand, as is clear from comparison of FIGS. 2 (c-1) to (c-3) and FIG. 3, the degree of dispersion of the graphene dispersion liquid 10 obtained in example 1 was further superior to those of the graphene dispersion liquids 6 to 9 subjected to only the ball milling treatment.
As shown in table 1, the test of the graphene dispersion liquid 3 is not completed twice, and the test of the graphene dispersion liquid 6 is not completed once, because undispersed agglomerated graphene exists in the graphene dispersion liquid, the agglomerated graphene particles suddenly enter between friction surfaces of the steel ball, the original balance is broken, the friction force is increased suddenly, and the equipment is stopped. This also illustrates that the agglomerated graphene is not well dispersed by the high-speed stirring treatment or ultrasonic treatment alone.
In table 1, it is clear from the standard deviation of the friction coefficient of each dispersion that the fluctuation of the friction coefficient of the graphene dispersion 10 is smaller than that of the graphene dispersion 9 and extremely close to that of the pure lubricating oil, indicating that the dispersion of graphene in the graphene dispersion 10 is extremely uniform. On the other hand, comparing the average value of the friction coefficients, the friction coefficients of the graphene dispersion liquid 3, 6 and 9 are higher than that of pure lubricating oil; the graphene dispersion 10 obtained in example 1 has a lower friction coefficient than that of the graphene dispersions 3, 6, 10, but also that of the pure lubricating oil; it can be seen that the graphene dispersion obtained by dispersing graphene in a lubricating oil according to the method of example 1 of the present invention can improve the lubricating effect of the lubricating oil.
In the mill spot measurements shown in table 2, it can be seen from the standard deviation that the mill spot diameter of the graphene dispersions 3, 6, 9 fluctuates greatly, which is related to the presence of small amounts of undispersed agglomerated graphene in the dispersion; the data fluctuation of the graphene dispersion liquid 10 is almost consistent with the data fluctuation degree of the pure lubricating oil, which shows that the graphene dispersion liquid 10 has almost no agglomerated graphene, and the graphene is fully and uniformly dispersed in the lubricating oil. On the other hand, comparison of average values of the abrasive spot diameters shows that the abrasive spot diameters of the graphene dispersion liquid 9 and the graphene dispersion liquid 10 are smaller than those of pure lubricating oil, and therefore the abrasive resistance of the lubricating oil can be improved by the graphene dispersion liquid 9 and the graphene dispersion liquid 10; and the smaller the diameter of the mill marks of the graphene dispersion 10, the better the abrasion resistance.
Fig. 5 and 6 show the respective graphene dispersions and the mottle diagrams of the pure lubricating oil. From the aspect of the form of the abrasive spots, the abrasive spots of the steel balls corresponding to the lubricating oil shown in the (d) of fig. 5 are relatively flat, no obvious scratches exist, and the form is round; the steel ball mill corresponding to the graphene dispersion 3 shown in fig. 5 (a) is uneven and has significantly deeper mill marks, and may cause abrasion by particles formed of undispersed graphene. The probability of occurrence of deep grinding marks for the steel balls corresponding to the graphene dispersion 6 shown in fig. 5 (b) and the steel balls corresponding to the graphene dispersion 9 shown in fig. 5 (c) gradually decreases. The graphene dispersion liquid 10 shown in fig. 6 has smaller probability of occurrence of obvious grinding marks than the graphene dispersion liquid 6 and the graphene dispersion liquid 9, and has similar grinding mark degree with the lubricating oil shown in fig. 5 (d); the graphene dispersion liquid 10 is described as having extremely uniform graphene dispersion.
As a result of the infrared spectroscopic analysis, as shown in fig. 4, the graphene dispersion 10 was substantially identical to the infrared spectrum of the pure lubricating oil, indicating that the dispersion method of example 1 did not cause the composition of the lubricating oil to change.
According to the test results, the results of direct observation, standard deviation in each test and the form of the abrasive spots show that the graphene dispersion liquid 10 has almost no agglomerated graphene, and the dispersion of the graphene is extremely uniform; further, the infrared results indicate that the composition of graphene and lubricating oil in the graphene dispersion 10 is not changed. Therefore, the graphene dispersing method can efficiently and fully disperse the agglomerated graphene in the liquid, so that the agglomerated graphene is uniformly dispersed in the liquid, and the property of the liquid is not changed.
Further, the results of the friction coefficient and the plaque diameter show that the graphene dispersion 10 obtained in example 1 also has excellent lubrication effect and antiwear performance. This demonstrates that when graphene is dispersed in a lubricating oil by the dispersion method of the present invention, a graphene dispersion excellent in lubricating effect and antiwear performance can be obtained.
The dispersion method is particularly suitable for dispersing graphene in a liquid system with the graphene concentration below 0.5mg/mL, and can fully, uniformly and efficiently disperse graphene in the liquid system without introducing other chemical substances.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention.
Claims (10)
1. A method for dispersing graphene in a liquid system, comprising the steps of:
s1: placing graphene powder into a liquid for mixing to obtain a first mixed liquid;
s2: performing ball milling ultrasonic treatment on the first mixed solution for more than three times to obtain a second mixed solution;
s3: settling and layering the second mixed solution, and taking at least part of upper layer solution as third mixed solution;
s4: performing ball milling ultrasonic treatment on the third mixed solution for more than one time to obtain graphene dispersion liquid;
the ball milling ultrasonic treatment comprises ball milling treatment of adding a grinding ball into the mixed liquid for grinding and ultrasonic treatment of the mixed liquid.
2. The method for dispersing graphene in a liquid system according to claim 1, wherein in the ball-milling ultrasonic treatment of step S2, the milling time of the ball-milling treatment is 30 minutes or more.
3. The method for dispersing graphene in a liquid system according to claim 2, wherein in the ball-milling ultrasonic treatment of step S2, the milling time of the ball-milling treatment is 30 to 120 minutes.
4. A method of dispersing graphene in a liquid system according to claim 3, wherein the grinding balls comprise 5 to 10% of grinding balls having a diameter of 5mm, 20 to 30% of grinding balls having a diameter of 3mm, 30 to 50% of grinding balls having a diameter of 1mm and 20 to 30% of grinding balls having a diameter of 0.5 mm.
5. The method for dispersing graphene in a liquid system according to claim 4, wherein in the ball-milling ultrasonic treatment of step S2, the ultrasonic treatment is performed for 30 to 120 minutes.
6. The method according to claim 5, wherein in step S1, the graphene powder and the liquid are mixed by a high-speed stirring treatment at a stirring speed of 2000r/min or more and a stirring time of 30 minutes or more.
7. The method for dispersing graphene in a liquid system according to claim 6, wherein in the ball-milling ultrasonic treatment of step S4, the grinding time of the ball-milling treatment is 60 minutes or more and the ultrasonic treatment time is 60 minutes or more.
8. The method according to claim 7, wherein in step S3, the second mixed solution is sedimented and layered by centrifugation or standing.
9. The method of claim 1, wherein the liquid is a lubricating oil.
10. A graphene dispersion liquid, characterized by being obtained by the dispersion method according to any one of claims 1 to 9.
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| CN101671015A (en) * | 2009-10-13 | 2010-03-17 | 南昌航空大学 | Method of producing graphene |
| CN103922323A (en) * | 2014-04-10 | 2014-07-16 | 华侨大学 | Method for preparing small-diameter graphene |
| CN106009787A (en) * | 2016-05-18 | 2016-10-12 | 中国科学院山西煤炭化学研究所 | Graded dispersion method and device for preparing graphene-based waterborne dispersion liquid |
| CN106430170A (en) * | 2016-10-18 | 2017-02-22 | 长沙理工大学 | Preparation method of graphene dispersion solution |
| JP2017114750A (en) * | 2015-12-25 | 2017-06-29 | 国立大学法人室蘭工業大学 | Method for acquiring graphene dispersion |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101671015A (en) * | 2009-10-13 | 2010-03-17 | 南昌航空大学 | Method of producing graphene |
| CN103922323A (en) * | 2014-04-10 | 2014-07-16 | 华侨大学 | Method for preparing small-diameter graphene |
| JP2017114750A (en) * | 2015-12-25 | 2017-06-29 | 国立大学法人室蘭工業大学 | Method for acquiring graphene dispersion |
| CN106009787A (en) * | 2016-05-18 | 2016-10-12 | 中国科学院山西煤炭化学研究所 | Graded dispersion method and device for preparing graphene-based waterborne dispersion liquid |
| CN106430170A (en) * | 2016-10-18 | 2017-02-22 | 长沙理工大学 | Preparation method of graphene dispersion solution |
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