CN110227396B - Preparation method of graphene/polyolefin elastomer microspheres with near-zero dielectric constant - Google Patents
Preparation method of graphene/polyolefin elastomer microspheres with near-zero dielectric constant Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 123
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- 239000004317 sodium nitrate Substances 0.000 claims abstract description 9
- 235000010344 sodium nitrate Nutrition 0.000 claims abstract description 9
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- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical group Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 8
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- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 claims description 6
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Abstract
本发明涉及具有近零介电常数的石墨烯/聚烯烃弹性体微球制备方法，将浓硫酸、石墨、硝酸钠低温混合均匀后加入高锰酸钾，然后滴加双氧水并过滤，清洗至中性后进行分散，将得到的粉末加入到水中进行二次分散，得到分散液，加入酸性溶液后加热处理得到石墨烯泡沫，冷冻干燥后研磨成石墨烯粉末；滴加甲苯至聚烯烃弹性体颗粒溶胀后搅拌，加入石墨烯粉末混合均匀，静置并干燥处理得到石墨烯/聚烯烃弹性体微球。与现有技术相比，本发明制备的石墨烯/聚烯烃弹性体微球复合材料的介电常数在特定频段下接近零值，拓宽了目前超材料体验的研究范畴，其特殊于天然材料体系的介电常数能够进一步推进化学可控制备电磁性能材料的研制。
The invention relates to a method for preparing graphene/polyolefin elastomer microspheres with near-zero dielectric constant. Concentrated sulfuric acid, graphite and sodium nitrate are mixed uniformly at low temperature, potassium permanganate is added, hydrogen peroxide is added dropwise, filtered, and washed to medium The obtained powder is added to water for secondary dispersion to obtain a dispersion liquid, and after adding an acid solution, heat treatment is performed to obtain graphene foam, which is ground into graphene powder after freeze-drying; toluene is added dropwise to the polyolefin elastomer particles. Stirring after swelling, adding graphene powder and mixing evenly, standing and drying to obtain graphene/polyolefin elastomer microspheres. Compared with the prior art, the dielectric constant of the graphene/polyolefin elastomer microsphere composite material prepared by the present invention is close to zero value in a specific frequency band, which broadens the research scope of the current metamaterial experience, which is special to the natural material system. The dielectric constant can further advance the development of chemically controllable preparation of materials with electromagnetic properties.
Description
Technical Field
The invention relates to a preparation method of a material with a near-zero dielectric constant, in particular to a preparation method of a graphene/polyolefin elastomer microsphere with a near-zero dielectric constant.
Background
The dielectric constant near-zero material is an artificial special electromagnetic material which is researched more enthusiastically at present. In 1998, Pendry et al proposed that a lower equivalent plasma frequency can be achieved by using a periodically arranged wire array, and based on this, in 2002, researchers in French Fresnel Institute obtained an equivalent dielectric constant close to 0 from a metal copper sheet structure by selectively changing the structure size and the working frequency, so that electromagnetic waves can generate beam convergence through the structure, and high directivity of dipoles is achieved. Few researchers have studied synthetic materials with dielectric constants near zero. The graphene has the characteristics of excellent electron transmission performance, large specific surface area, excellent conductivity, good mechanical properties and the like, particularly has good light transmission and unique quantum Hall effect, and can provide an electron transmission path for a polyolefin elastomer matrix. Research shows that the equivalent dielectric constant can be close to zero through proper positive dielectric constant and negative dielectric constant, and therefore, the zero-refractive-index material is obtained. However, it is currently difficult to achieve near zero dielectric constant materials by synthetic means.
Therefore, the method for realizing the near-zero dielectric constant of the graphene/polyolefin elastomer microspheres by adopting the effective method has important significance for the application of the graphene/polyolefin elastomer microspheres in the field of artificial electromagnetic materials. Chinese patent CN105504453A discloses a polyolefin composite insulating material with high thermal oxidation stability and a preparation method thereof. The polyolefin composite insulating material comprises, by mass, 100% of a polyolefin polymer matrix and 0.5-2% of a modified graphene oxide filler, wherein the polyolefin polymer matrix accounts for 98-99.5%. The modified graphene oxide is the antioxidant-functionalized graphene oxide coated with polydopamine, the thermal oxidation stability of the composite material can be improved through the grafted antioxidant, and the graphene oxide can play a role in inhibiting the migration of the antioxidant. The adopted modified graphene oxide can enhance the interface bonding force between the polymer matrix and the filler, and can prevent the graphene oxide from being deeply reduced in the preparation process of the composite insulating material, so that the composite material keeps good insulating property.
In the patent, polydopamine is coated on the surface of two-dimensional graphene oxide with the surface grafted with an antioxidant, and then the functionalized two-dimensional graphene oxide nanosheet is used as a filler and is subjected to hot press forming with a polyolefin matrix, wherein the mass difference between the graphene oxide and the matrix is large, the dispersibility of the filler in the matrix is difficult to ensure uniform, and the functionalized two-dimensional lamellar layer is easy to bend and fold, so that the filling structure is easy to agglomerate, and the accumulation form is difficult to be the same. The dielectric constants of the above patents are all positive at low frequencies.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a preparation method of graphene/polyolefin elastomer microspheres with near-zero dielectric constants.
The purpose of the invention can be realized by the following technical scheme:
a preparation method of graphene/polyolefin elastomer microspheres with near-zero dielectric constants comprises the following specific steps:
(1) preparation of dispersion a: 10-150ml of concentrated sulfuric acid, 0.5-1.5g of graphite and 0.2-0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the graphite is uniformly dispersed, and then 1.0-4.5g of potassium permanganate is slowly added. Then continuously keeping the mixture in a water bath at 25-55 ℃ under magnetic stirring, and slowly adding 1.0-4.5g of potassium permanganate, wherein the reaction temperature is controlled at 25-35 ℃; pouring the reaction mixture into a beaker filled with 20-200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, sequentially cleaning with a dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10-50min, and ultrasonically dispersing at a frequency of 10-70KHz for 10-30 min; weighing 0.1-1g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100 plus 500ml of deionized water, carrying out secondary ultrasonic treatment for 0.5-2h at the frequency of 10-70KHz, centrifuging at the rotating speed of 3000 plus 8000r/min for half an hour, and taking the supernatant;
(2) preparing graphene powder: 10-100ml of prepared dispersion liquid A is measured and subjected to ultrasonic treatment for 1-8h at the frequency of 10-70KHz, the acid solution is slowly added while stirring, the mixed solution is poured into a reaction kettle and then placed in an oven for reaction for 8-16h at the temperature of 100 ℃ and 180 ℃ to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24-36h, and grinding into powder;
(3) weighing 1-5g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5-2.5 h; adding graphene powder, grinding until the graphene powder is uniformly mixed, and standing for 24-36 h.
(4) And (3) drying: and (3) drying the material after standing in a forced air drying oven at 50-100 ℃ for 5-24 hours to obtain the graphene/polyolefin elastomer microspheres.
In the step (2), the acidic solution is any one of ascorbic acid or hydroiodic acid, and the molar ratio of the dispersion liquid A to the acidic solution is 1:1 to 5: 1.
In the step (3), the addition amount of the graphene is 10-80% of the mass of the composite material.
The dielectric constant of the graphene/polyolefin elastomer microsphere composite material prepared by the invention is close to zero value under a specific frequency band, the research scope of the current metamaterial experience is widened, and the dielectric constant special for a natural material system can further promote the development of a chemically controllable material with electromagnetic performance. The preparation process of the invention is different from the current mainstream method of passing through the periodically arranged open resonant ring array, and the near-zero material is prepared by a material synthesis method, has the characteristics of zero phase change, super-coupling effect, electromagnetic tunneling and the like, and is widely applied to the aspects of constructing a waveguide coupler, enhancing the radiation directivity of an antenna, wave front shaping and the like. The graphene/polyolefin elastomer microspheres prepared by the method are powdery and have uniform particle size. The invention can be used for preparing the zero-refractive index meta-dielectric material.
According to the preparation method, graphene oxide aqueous solutions with different concentrations are prepared by a modified hummer method, and then are integrally formed into three-dimensional foam in a hydrothermal mode, the sheets are uniformly interwoven, the reduced graphene oxide three-dimensional structure after freeze drying and grinding is not easy to agglomerate, and the outer layer of a swollen polyolefin elastomer is coated, so that the internal matrix is protected, and the impact resistance and the heat resistance are improved; on the other hand, due to the excellent conductivity of the hydrothermal-reduced graphene, the positive and negative transformation of the dielectric constant within the frequency range of 1M-1GHz is further promoted, so that the graphene has the characteristics of a near-zero material, and the frequency range of the dielectric constant near zero is further expanded.
Compared with the prior art, the invention has the following advantages:
the method adopts an improved Hummers method to prepare the graphene oxide solution, the process is relatively simple, convenient, green and efficient, and natural graphite is fully stripped by controlling the reaction temperature and adding oxidants such as concentrated sulfuric acid, potassium permanganate and hydrogen peroxide; ultrasonic dispersion is adopted in the reaction process, so that the uniformity of a reaction system and the dispersibility of graphene are ensured.
Secondly, the dielectric constant of the prepared graphene/polyolefin elastomer microsphere at the frequency of 491MHz in 365-491MHz is between 2 and-2, and compared with the dielectric constant of the graphene/polyolefin elastomer synthesized by the existing method, the dielectric constant of the prepared graphene/polyolefin elastomer microsphere has the characteristic of being obviously close to 0. The polyolefin elastomer has insufficient conductivity, the dielectric constant of the polyolefin elastomer is positive in the frequency range of 1M-1GHz, the three-dimensional graphene foam sheet is coated to form a conductive network and present a certain metallicity, and plasma resonance is excited at 365-491MHz to enable the dielectric constant to be converted from 2 to-2. The composite product prepared by the method can effectively control the range of dielectric constant according to the added filler and the matrix, so that the composite product has the near-zero material characteristic of positive-negative conversion; and the preparation method is soft, controllable and efficient, so that the dielectric constant shows a stable change trend in a higher frequency range.
And thirdly, the graphene polyolefin elastomer composite material prepared by the invention can be used for preparing a zero-refractive-index metamaterial.
Drawings
Fig. 1 is a dielectric property diagram of the graphene/polyolefin elastomer microspheres prepared in examples 6 and 7.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
A preparation method of graphene/polyolefin elastomer microspheres with near-zero dielectric constants comprises the following specific steps:
(1) preparation of dispersion a: 10-150ml of concentrated sulfuric acid, 0.5-1.5g of graphite and 0.2-0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the graphite is uniformly dispersed, and then 1.0-4.5g of potassium permanganate is slowly added. Then continuously keeping the mixture in a water bath at 25-55 ℃ under magnetic stirring, and slowly adding 1.0-4.5g of potassium permanganate, wherein the reaction temperature is controlled at 25-35 ℃; pouring the reaction mixture into a beaker filled with 20-200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, sequentially cleaning with a dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10-50min, and ultrasonically dispersing at a frequency of 10-70KHz for 10-30 min; weighing 0.1-1g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100 plus 500ml of deionized water, carrying out secondary ultrasonic treatment for 0.5-2h at the frequency of 10-70KHz, centrifuging at the rotating speed of 3000 plus 8000r/min for half an hour, and taking the supernatant;
(2) preparing graphene powder: measuring 10-100ml of prepared dispersion A, carrying out ultrasonic treatment for 1-8h at the frequency of 10-70KHz, slowly adding an acidic solution (either ascorbic acid or hydroiodic acid) while stirring, wherein the molar ratio of the dispersion A to the acidic solution is 1: 1-5: 1; and pouring the mixed solution into a reaction kettle, and then placing the reaction kettle in an oven at the temperature of 100 ℃ and 180 ℃ for reaction for 8-16h to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24-36h, and grinding into powder;
(3) weighing 1-5g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5-2.5 h; adding graphene powder to enable the mass fraction of graphene in the composite material to be 10-80%, grinding until the graphene is uniformly mixed, and standing for 24-36 h.
(4) And (3) drying: and (3) drying the material after standing in a forced air drying oven at 50-100 ℃ for 5-24 hours to obtain the graphene/polyolefin elastomer microspheres.
The following are more detailed embodiments, and the technical solutions and the technical effects obtained by the present invention will be further described by the following embodiments.
Example 1:
the embodiment is a preparation method of a graphene/polyolefin elastomer microsphere with a near-zero dielectric constant, and the preparation method is carried out according to the following steps.
(1) Preparation of dispersion a: 138ml of concentrated sulfuric acid, 1.5g of graphite and 0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the components are uniformly dispersed, and then 4.5g of potassium permanganate is slowly added. Then, continuously keeping the mixture in a water bath at 35 ℃ under magnetic stirring, and meanwhile, slowly adding 4.5g of potassium permanganate, and controlling the reaction temperature to be 35 ℃; pouring the reaction mixture into a beaker filled with 200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, cleaning with dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10min, and performing ultrasonic treatment at a frequency of 10KHz for 30 min; weighing 0.2g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100ml of deionized water, carrying out ultrasonic treatment for 2h at the frequency of 10KHz, centrifuging for half an hour at the rotating speed of 8000r/min, and taking supernatant;
(2) preparing graphene powder: 100ml of prepared dispersion liquid A is weighed and subjected to ultrasonic treatment for 8 hours at the frequency of 10KHz, and ascorbic acid is slowly added while stirring, wherein the molar ratio of the dispersion liquid A to the acid liquid is 1: 1; and pouring the mixed solution into a reaction kettle, placing the reaction kettle in an oven, and reacting for 16 hours at 180 ℃ to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24h, and grinding into powder;
(3) weighing 1g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5 h; adding graphene powder to enable the mass fraction of graphene in the composite material to be 40%, grinding until the graphene is uniformly mixed, and standing for 24 hours.
(4) And (3) drying: and (3) drying the material after standing in a forced air drying oven at 50 ℃ for 12 hours to obtain the graphene/polyolefin elastomer microspheres.
Example 2:
the embodiment is a preparation method of a graphene/polyolefin elastomer microsphere with a near-zero dielectric constant, and the preparation method is carried out according to the following steps.
(1) Preparation of dispersion a: 138ml of concentrated sulfuric acid, 1.5g of graphite and 0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the components are uniformly dispersed, and then 4.5g of potassium permanganate is slowly added. Then, continuously keeping the mixture in a water bath at 35 ℃ under magnetic stirring, and meanwhile, slowly adding 4.5g of potassium permanganate, and controlling the reaction temperature to be 35 ℃; pouring the reaction mixture into a beaker filled with 200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, cleaning with dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10min, and performing ultrasonic treatment at a frequency of 20KHz for 30 min; weighing 0.2g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100ml of deionized water, carrying out ultrasonic treatment for 2h at the frequency of 20KHz, centrifuging for half an hour at the rotating speed of 8000r/min, and taking supernatant;
(2) preparing graphene powder: 100ml of prepared dispersion liquid A is weighed and subjected to ultrasonic treatment for 8 hours at the frequency of 20KHz, and ascorbic acid is slowly added while stirring, wherein the molar ratio of the dispersion liquid A to the acid liquid is 1: 2; and pouring the mixed solution into a reaction kettle, placing the reaction kettle in an oven, and reacting for 16 hours at 180 ℃ to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24h, and grinding into powder;
(3) weighing 1g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5 h; adding graphene powder to enable the mass fraction of graphene in the composite material to be 50%, grinding until the graphene is uniformly mixed, and standing for 24 hours.
(4) And (3) drying: and (3) drying the material after standing in a forced air drying oven at 50 ℃ for 12 hours to obtain the graphene/polyolefin elastomer microspheres.
The dielectric constant of the graphene/polyolefin elastomer microsphere prepared by the method is 0.05 at 970MHz, and compared with the dielectric constant of the graphene/polyolefin elastomer synthesized by the existing method, the graphene/polyolefin elastomer microsphere has the characteristic of obviously approaching 0.
Example 3:
the embodiment is a preparation method of a graphene/polyolefin elastomer microsphere with a near-zero dielectric constant, and the preparation method is carried out according to the following steps.
(1) Preparation of dispersion a: 138ml of concentrated sulfuric acid, 1.5g of graphite and 0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the components are uniformly dispersed, and then 4.5g of potassium permanganate is slowly added. Then, continuously keeping the mixture in a water bath at 35 ℃ under magnetic stirring, and meanwhile, slowly adding 4.5g of potassium permanganate, and controlling the reaction temperature to be 35 ℃; pouring the reaction mixture into a beaker filled with 200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, cleaning with dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10min, and performing ultrasonic treatment at a frequency of 50KHz for 30 min; weighing 0.2g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100ml of deionized water, carrying out ultrasonic treatment for 2h at the frequency of 50KHz, centrifuging for half an hour at the rotating speed of 8000r/min, and taking supernatant;
(2) preparing graphene powder: 100ml of prepared dispersion liquid A is weighed and subjected to ultrasonic treatment for 8 hours at the frequency of 50KHz, and hydroiodic acid is slowly added while stirring, wherein the molar ratio of the dispersion liquid A to the acid liquid is 1: 1; and pouring the mixed solution into a reaction kettle, placing the reaction kettle in an oven, and reacting for 16 hours at 180 ℃ to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24h, and grinding into powder;
(3) weighing 1g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5 h; adding graphene powder to enable the mass fraction of graphene in the composite material to be 40%, grinding until the graphene is uniformly mixed, and standing for 24 hours.
(4) And (3) drying: and (3) drying the material after standing in a forced air drying oven at 50 ℃ for 12 hours to obtain the graphene/polyolefin elastomer microspheres.
The dielectric constant of the graphene/polyolefin elastomer microspheres prepared by the method is 0.42 at 369MHz, and compared with the dielectric constant of the graphene/polyolefin elastomer synthesized by the existing method, the dielectric constant of the graphene/polyolefin elastomer microspheres has the characteristic of obviously approaching 0.
Example 4:
the embodiment is a preparation method of a graphene polyolefin elastomer composite material with a near-zero dielectric constant, and is different from embodiment 2 in that: in the step (2), the acid solution is hydroiodic acid, and other steps are the same.
Example 5:
the present embodiment is a method for preparing a graphene/polypyrrole nanoparticle with a negative dielectric constant, and is different from embodiment 3 in that: the addition amount of the graphene in the step (3) is 60%, and other steps are the same.
Example 6:
firstly, preparing a dispersion liquid A: 138ml of concentrated sulfuric acid, 1.5g of graphite and 0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the components are uniformly dispersed, and then 4.5g of potassium permanganate is slowly added. Then, continuously keeping the mixture in a water bath at 35 ℃ under magnetic stirring, and meanwhile, slowly adding 4.5g of potassium permanganate, and controlling the reaction temperature to be 35 ℃; pouring the reaction mixture into a beaker filled with 200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, cleaning with dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10min, and performing ultrasonic treatment at a frequency of 70KHz for 30 min; weighing 0.2g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100ml of deionized water, carrying out ultrasonic treatment for 2h at the frequency of 70KHz, centrifuging for half an hour at the rotating speed of 8000r/min, and taking supernatant;
secondly, preparing graphene powder: 100ml of prepared dispersion liquid A is weighed and subjected to ultrasonic treatment for 8 hours at the frequency of 70KHz, and ascorbic acid is slowly added while stirring, wherein the molar ratio of the dispersion liquid A to the acid liquid is 1: 1; and pouring the mixed solution into a reaction kettle, placing the reaction kettle in an oven, and reacting for 16 hours at 180 ℃ to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24h, and grinding into powder;
weighing 1g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5 h; adding graphene powder to enable the mass fraction of graphene in the composite material to be 40%, grinding until the graphene is uniformly mixed, and standing for 24 hours.
Fourthly, drying: and (3) drying the material after standing in a forced air drying oven at 50 ℃ for 12 hours to obtain the graphene/polyolefin elastomer microspheres.
The graphene polyolefin elastomer composite material with the near-zero dielectric constant prepared by the experiment is named as 40% graphene/polyolefin elastomer microsphere composite material.
The dielectric properties of the graphene/polyolefin elastomer microspheres (40% by weight of graphene/polyolefin elastomer) with near-zero dielectric constant prepared in the experiment are tested by using Agilent E4991A, and the dielectric constant is 0.05 at 970MHz frequency as can be seen from FIG. 1.
Example 7:
firstly, preparing a dispersion liquid A: 138ml of concentrated sulfuric acid, 1.5g of graphite and 0.75g of sodium nitrate are measured, placed in an ice bath environment, magnetically stirred until the components are uniformly dispersed, and then 4.5g of potassium permanganate is slowly added. Then, continuously keeping the mixture in a water bath at 35 ℃ under magnetic stirring, and meanwhile, slowly adding 4.5g of potassium permanganate, and controlling the reaction temperature to be 35 ℃; pouring the reaction mixture into a beaker filled with 200 ml of ice water, dropwise adding 30% hydrogen peroxide while stirring, filtering while hot, cleaning with dilute hydrochloric acid solution and deionized water to neutrality, centrifuging at a rotating speed of 8000r/min for 10min, and performing ultrasonic treatment at a frequency of 40KHz for 30 min; weighing 0.2g of the powder obtained by drying and grinding the solution, adding the powder into a beaker, adding 100ml of deionized water, carrying out ultrasonic treatment for 2h at the frequency of 40KHz, centrifuging for half an hour at the rotating speed of 8000r/min, and taking supernatant;
secondly, preparing graphene powder: 100ml of prepared dispersion liquid A is weighed and subjected to ultrasonic treatment for 8 hours at the frequency of 40KHz, and hydroiodic acid is slowly added while stirring, wherein the molar ratio of the dispersion liquid A to the acid liquid is 1: 2; and pouring the mixed solution into a reaction kettle, placing the reaction kettle in an oven, and reacting for 16 hours at 180 ℃ to obtain the three-dimensional columnar graphene foam. Freeze-drying the foam for 24h, and grinding into powder;
weighing 1g of polyolefin elastic particles, placing the polyolefin elastic particles in a watch glass, dropwise adding toluene until the polyolefin elastic particles swell, and magnetically stirring for 0.5 h; adding graphene powder to enable the mass fraction of graphene in the composite material to be 50%, grinding until the graphene is uniformly mixed, and standing for 24 hours.
Fourthly, drying: and (3) drying the material after standing in a forced air drying oven at 50 ℃ for 12 hours to obtain the graphene/polyolefin elastomer microspheres.
The graphene polyolefin elastomer composite material with the near-zero dielectric constant prepared by the experiment is named as a 50% graphene/polyolefin elastomer microsphere composite material.
The dielectric properties of the graphene/polyolefin elastomer microspheres (40% graphene/polyolefin elastomer) with the near-zero dielectric constant prepared by the experiment are tested by using Agilent E4991A, and the dielectric constant is-1.13 and near-zero at 985MHz as shown in figure 1.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (5)
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