CN113479869B - Method for grading and screening particle size of graphene - Google Patents
Method for grading and screening particle size of graphene Download PDFInfo
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- CN113479869B CN113479869B CN202110743240.0A CN202110743240A CN113479869B CN 113479869 B CN113479869 B CN 113479869B CN 202110743240 A CN202110743240 A CN 202110743240A CN 113479869 B CN113479869 B CN 113479869B
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The invention provides a method for grading and screening particle sizes of graphene, which is characterized in that a surfactant is attached to the surface of graphene, so that the surface energy and the agglomeration of the graphene are reduced, the improvement of the dispersibility of the graphene in a hydrophilic matrix is facilitated, the grading application effect can be achieved after screening, the graphene is prepared into 100mL of ethanol-graphene dispersion liquid, 0.1-0.5% of the surfactant is added, the mixture is stirred until the dispersion is uniform, and the grading effect is achieved by standing, centrifuging and other methods. The invention aims to provide a method for classifying and screening modified graphene, which solves the problem of large particle size of graphene and improves the classification effect by modifying and separating graphene.
Description
Technical Field
The invention relates to a particle size grading and screening method, in particular to a graphene particle size grading and screening method which achieves grading effect by reducing surface tension through surface modification and enabling graphene in uniform dispersion liquid to achieve self gravity and repulsion between layers.
Background
Since the discovery of graphene, graphene has been widely studied in many fields such as functional coatings, polymer composites, transparent electrodes, lithium ion batteries, supercapacitors, semiconductors, and the like because of its excellent properties such as electrical conductivity, thermal conductivity, and mechanical strength. However, due to the fact that graphene has a large specific surface area, the graphene has large surface activation energy, is easy to agglomerate in a microscopic mode and is difficult to disperse, and further application of the graphene is greatly limited. Therefore, how to uniformly disperse graphene in liquid or solid to form a film-based or connected network structure makes use of the excellent functions of graphene, such as electrical conductivity, thermal conductivity, barrier property, mechanical strength, etc., to save cost and improve product performance is a major difficulty and key point in current graphene research.
Graphene has strong hydrophobicity and poor hydrophilicity, so that in a system taking water as a dispersion medium, graphene is difficult to disperse, is easy to agglomerate and delaminate, has a short storage period, and greatly limits the application of graphene in an aqueous system.
When graphene is researched, the particle size distribution of graphene can influence the exertion of the effect of graphene, certain difficulty can be caused to scientific analysis due to the uncontrollable particle size, if graphene with larger particle size is doped, the exertion of the function of graphene can be reduced, and the stability of the function of the doped material is not facilitated due to the unconcentrated particle size distribution, so that different graphene derivatives are often required to be separated for separate research to obtain the graphene with specific structural parameters, and the graphene is preferably obtained according to the particle size range of the graphene and is suitably applied.
Disclosure of Invention
The invention aims to overcome the defect of lacking a graphene particle size screening method and provide a graphene particle size grading screening method which reduces surface tension through surface modification so that graphene in a uniform dispersion liquid can achieve a grading effect through self gravity and repulsion between grades.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for grading and screening graphene particle size comprises the following steps:
1) Preparing ethanol-graphene dispersion liquid, adding a surfactant, magnetically stirring or ultrasonically dispersing, standing for layering after a period of time to obtain a supernatant part and a lower-layer sedimentation part;
2) Centrifuging the supernatant part after layering in the step 1), and centrifuging the lower-layer sedimentation part; respectively dissolving the two groups of graphene obtained by centrifugal treatment with ethanol to obtain an upper graphene dispersion liquid and a lower graphene dispersion liquid;
3) Respectively centrifuging the upper graphene dispersion liquid and the lower graphene dispersion liquid obtained in the step 2), and dissolving the obtained upper graphene and lower graphene in ethanol;
4) Repeating the step 3) for a plurality of times to obtain upper graphene and lower graphene with tested particle sizes;
5) Dissolving the upper graphene and the lower graphene in the step 4) in a colloid separation medium for centrifugal treatment, and respectively performing centrifugal treatment from 1000r/min to 5000r/min to obtain the graded graphene.
In the technical scheme, the polarity of graphene is changed by introducing other molecular structures through non-covalent bond modification, then the graphene sheet layers can be effectively stripped through mechanical stirring or ultrasonic and other external mechanical methods, the agglomerated graphene sheet layers are separated again, and then the particle size of graphene is graded and screened through physical methods such as centrifugation.
The surfactant is attached to the surface of the graphene, so that the surface energy of the graphene is reduced, and the agglomeration of the graphene is reduced; meanwhile, the purpose of reducing the particle size is achieved under the action of a homovalent bond repulsive force after the organic molecules are modified, so that the effect of grading application can be achieved after screening.
And (4) performing ultra-high speed centrifugation at 1000r/min, 2000r/min, 3000r/min, 4000r/min and 5000r/min to obtain the graphene which is classified under different particle sizes.
As a preferable scheme of the invention, in the step 1), the stirring is magnetic stirring at the rotating speed of 500r/min-600r/min, and the stirring time is 30min-40min.
In the technical scheme, the rotating speed of mechanical stirring cannot be too high, so that the structure of graphene is prevented from being broken by mechanical destructive force, the improvement effect of the surfactant is influenced, the selection of stirring time cannot be too short, and organic non-covalent bond molecules cannot be bonded due to too short time; nor too long, which would result in foaming and deactivation.
As a preferable scheme of the invention, in the step 1), the standing time is 16-24 h.
As a preferable embodiment of the present invention, in the step 1), in the ethanol-graphene dispersion liquid, a mass ratio of graphene to ethanol is 1 to 2g:100-150g.
As a preferable scheme of the present invention, in the step 1), the surfactant is added in an amount of 0.1% to 0.5% by mass of the graphene, and the surfactant includes an alkanone, an N-methyl-pyrrole compound, sodium dodecyl benzene sulfonate or sodium cholate.
In a preferable scheme of the invention, in the step 3), the rotation speed of the centrifugal treatment is 6000r/min-8000r/min.
In a preferable embodiment of the present invention, in the step 4), the number of times of repeating the step 3) is 3 to 5.
In the technical scheme, the repeated centrifugation-ethanol washing is used for thoroughly washing and tightening the ungrafted surfactants and preventing the surfactants from forming false packages to influence the grading screening result.
In a preferred embodiment of the present invention, in the step 5), the colloid separation medium includes a sucrose solution, a fructose solution, a maltose solution, or a sodium chloride solution.
In the technical scheme, the colloid separation medium can be one of saturated saline solution with the mass concentration of 25% or saturated solution of fructose and maltose, and can also be sucrose solution with the mass concentration of 60%.
In a preferred embodiment of the present invention, the colloid separation medium is a sucrose solution with a mass concentration of 60%.
In the technical scheme, the sucrose belongs to a solution with large dispersity and stable thermodynamics, and the colloid separation medium has better carrying property and dispersity on graphene under the concentration of 60%, so that the mass concentration of the sucrose solution is 60% in the colloid separation medium.
As a preferable scheme of the invention, the method further comprises the following step 6): and (3) taking the graphene screened and classified in the step 5), carrying out centrifugal treatment, selecting deionized water as a solvent, removing supernatant after centrifugation is finished, continuing to centrifuge and adding deionized water into lower-layer precipitates until the separated graphene is washed clean, drying the washed graphene in an oven, dissolving the dried graphene in ethanol, and dispersing under ultrasound to prepare the graphene dispersion liquid for testing performance.
Compared with the prior art, the invention has the following beneficial effects:
according to the method, the surface tension of the graphene particle size is reduced through organic molecule modification, so that the purpose of particle size reduction of graphene is achieved under the repulsion effect of homovalent bonds, and meanwhile, layering is utilized to further screen the graphene, so that the particle size of a batch of graphene is effectively reduced, and the graphene has wider application.
The method disclosed by the invention is simple, the surface tension is reduced through surface modification, the graphene in the uniform dispersion liquid achieves the grading effect through self gravity and repulsion between grades, the method has a good reference significance for grading application of the graphene, the extraction is convenient, and the effect is obvious.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Example 1
1g of graphene powder is weighed and dissolved in 100mL of ethanol, and the mixture is magnetically stirred for 10min or ultrasonically dispersed for 5min to obtain a uniform solution. The dispersion was prepared into 100mL of an ethanol-graphene dispersion, and the particle size distribution range was measured by a particle size analysis method, and the measurement results are shown in table 1.
TABLE 1
| Particle size distribution | x 10，3 | x 50，3 | SMD | VMD |
| Test results | 11.60μm | 22.71μm | 19.33μm | 24.24μm |
Example 2
Firstly, 1g of graphene powder is selected to be dissolved in 100mL of ethanol, and the graphene powder is uniformly dispersed by magnetic stirring for 10min or ultrasonic dispersion for 5 min. And then adding 0.1% sodium cholate into the dispersed graphene dispersion liquid for modification treatment, stirring for more than 30min through mechanical stirring at 500r/min, recording the sedimentation change of the graphene which is kept for 16h for a long time, centrifuging the supernatant and the lower sedimentation part, dissolving the two groups of graphene obtained through centrifugation by using ethanol (by virtue of ultrasonic waves), then centrifuging again, wherein the centrifugation speed is 6000r/min-8000r/min, circulating for three times in the way, washing for three times by using ethanol, analyzing the particle size of the graphene obtained through twice modification, and the test result is shown in table 2.
TABLE 2
| Particle size distribution | x 10，3 | x 50，3 | SMD | VMD |
| Upper layer particle size | 3.81μm | 8.77μm | 6.42μm | 9.79μm |
| Lower layer particle size | 4.21μm | 10.25μm | 7.37μm | 11.79μm |
Example 3
Firstly, 1g of graphene powder is dissolved in 100mL of ethanol, and the graphene powder is uniformly dispersed by magnetic stirring for 10min or ultrasonic dispersion for 5 min. And then adding 0.1% of alkanone into the dispersed graphene dispersion liquid for modification treatment, stirring for more than 30min by mechanical stirring at 500r/min, recording the sedimentation change of the graphene which is kept for 16h for a long time, washing the settled graphene with ethanol for three times, drying, dissolving the modified graphene in a sucrose solution, centrifuging at 1000r/min-5000r/min, wherein no precipitation and no delamination occur at 1000r/min-3000r/min, delamination occurs at 4000r/min, more upper-layer graphene is suspended at 5000r/min, washing the upper-layer and lower-layer modified graphene obtained at 5000r/min with ethanol for three times, centrifuging at a rotating speed of 8000r/min in the middle, and measuring the particle size after the completion respectively, wherein the results are shown in table 3.
TABLE 3
| Particle size distribution | x 10，3 | x 50，3 | SMD | VMD |
| Upper layer particle size | 3.89μm | 9.86μm | 6.93μm | 11.44μm |
| Lower layer particle size | 4.55μm | 10.38μm | 7.77μm | 11.63μm |
As can be seen from tables 1 and 2: the particle size of the graphene before unmodified, which is measured in example 1, the proportion of 10% of the smaller particle size is 11.60 μm, wherein the particle size range of more than 50% is more than 22.71 μm, the surface area average particle Size (SMD) is 19.33 μm, and the volume average particle size (VMD) is 24.24 μm, after the graphene is modified by 0.1% sodium cholate, the particle sizes of the upper layer and the lower layer of the graphene are respectively measured, and the comparison shows that the surface energy of the graphene and the agglomeration of the graphene are reduced by the surfactant attached to the surface of the graphene; the method is beneficial to improving the dispersibility of graphene in a hydrophilic matrix, effectively screening the particle size range of the graphene while reducing the particle size of the graphene, and after modification and screening, the particle sizes of the upper layer and the lower layer are respectively found to be 50% smaller than 8.77 mu m and 10.25 mu m, the surface area average particle Size (SMD) is reduced by about 2/3, the volume average particle size (VMD) is reduced by 1/2, and the ratio of the upper layer to the lower layer is larger. Therefore, the particle size of the graphene is effectively reduced by modifying the sodium cholate, and the particle size of the graphene is screened to a certain extent.
The graphene modified by the alkanone is put into a sucrose colloid separation medium with a certain density gradient, the alkanone can well reduce the agglomeration of the graphene and reduce the particle size of the graphene, the colloid dispersion medium has better bearing property on the classification of the graphene, and the test result shows that 50% of the particle sizes of the upper layer and the lower layer are respectively less than 9.86 μm and 10.38 μm, the surface area average particle Size (SMD) of the upper layer and the surface area average particle Size (SMD) of the lower layer are respectively 6.93 μm and 7.77 μm, and the volume average particle size (VMD) of the upper layer and the lower layer is respectively 11.44 μm and 11.63 μm.
While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that the foregoing and other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention. Those skilled in the art can make various changes, modifications and equivalents to the disclosed technology without departing from the spirit and scope of the present invention, and all such changes, modifications and equivalents are intended to be included therein as equivalents of the present invention; meanwhile, any equivalent changes, modifications and evolutions of the above embodiments according to the essential technology of the present invention are still within the scope of the technical solution of the present invention.
Claims (8)
1. A method for grading and screening particle sizes of graphene is characterized by comprising the following steps:
1) Preparing ethanol-graphene dispersion liquid, adding a surfactant, magnetically stirring or ultrasonically dispersing, standing for layering after a period of time to obtain a supernatant part and a lower-layer sedimentation part; the addition amount of the surfactant is 0.1-0.5% of the mass of the graphene, and the surfactant is alkanone or sodium cholate;
2) Centrifuging the supernatant part after layering in the step 1), and centrifuging the lower-layer sedimentation part; respectively dissolving the two groups of graphene obtained by centrifugal treatment with ethanol to obtain an upper graphene dispersion liquid and a lower graphene dispersion liquid;
3) Respectively centrifuging the upper graphene dispersion liquid and the lower graphene dispersion liquid obtained in the step 2), and dissolving the obtained upper graphene and lower graphene in ethanol;
4) Repeating the step 3) for a plurality of times to obtain upper graphene and lower graphene with tested particle sizes;
5) Dissolving the upper graphene and the lower graphene in the step 4) in a colloid separation medium for centrifugal treatment, and respectively performing centrifugal treatment from 1000r/min to 5000r/min to obtain graded graphene;
6): and (3) taking the graphene subjected to screening and grading in the step 5), performing centrifugal treatment, selecting deionized water as a solvent, removing the supernatant after centrifugation is finished, continuously centrifuging the lower-layer precipitate, adding deionized water until the separated graphene is washed cleanly, drying the washed graphene in an oven, dissolving the dried graphene in ethanol, and dispersing under ultrasound to prepare the graphene dispersion liquid for testing performance.
2. The method for classifying and screening the particle size of graphene according to claim 1, wherein in the step 1), the stirring is magnetic stirring at a rotation speed of 500r/min to 600r/min for 30min to 40min.
3. The method for classifying the particle size of graphene according to claim 1, wherein the standing time in step 1) is 16h to 24h.
4. The method for classifying the particle size of graphene according to claim 1, wherein in the step 1), the mass ratio of graphene to ethanol in the ethanol-graphene dispersion liquid is 1-2g:100-150g.
5. The method for classifying the particle size of graphene according to claim 1, wherein the rotation speed of the centrifugal treatment in step 3) is 6000r/min to 8000r/min.
6. The method for classifying the particle size of graphene according to claim 1, wherein in the step 4), the step 3) is repeated 3 to 5 times.
7. The method as claimed in claim 1, wherein in step 5), the colloid separation medium includes sucrose solution, fructose solution, maltose solution or sodium chloride solution.
8. The method as claimed in claim 7, wherein the colloid separation medium is sucrose solution with a mass concentration of 60%.
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