CN112430450B - Modified graphene nanosheet composite powder and preparation method thereof - Google Patents

Abstract

The invention relates to a modified graphene (ene) nanosheet composite powder and a preparation method. A certain amount of graphene (ene) nanosheets are soaked in nitric acid solution and mechanically stirred, and then the graphene (ene) nanosheets are washed and taken out, mixed with organic ligands, cobalt salts and deionized water, and mixed with ultrasonic vibration and mechanical stirring. Under the action, the graphene (ene) nanosheets are uniformly dispersed in the solution to form a slurry, and the obtained slurry is poured into the reaction kettle, and the reaction is carried out under certain conditions. Attached to the surface of graphene (ene) nanosheets. After the reaction is completed, take out the reactor, take out the reacted Co-MOFs-modified graphite (ene) composite powder after the reactor is naturally cooled to room temperature, and dry it in a vacuum drying oven to obtain the surface of the graphene (ene) nanosheets Composite powder containing Co-MOFs particles.

Description

A kind of modified graphene (ene) nanosheet composite powder and preparation method thereof

technical field

The invention relates to a surface modification process of graphene (ene) nanosheets, in particular to a modified graphene (ene) nanosheet composite powder and a preparation method thereof.

Background technique

Since its discovery, graphene has been widely used in various fields, such as batteries, electrical components, microwave absorption, and biological materials, due to its unique mechanical properties, electrical properties, and chemical stability. However, in many fields, it is difficult for a single graphene to meet its required performance requirements. Therefore, surface modification of graphene and exploration of methods that can update and improve its performance have gradually become the focus of research. Compared with the single-layer or double-layer graphene sheet structure, the graphite nanosheet prepared by physical vapor exfoliation method is a sheet-layer nanomaterial with a thickness of about 3 nanometers and a graphite structure with about 10 layers. The cost of this material is much lower than that of single-layer or double-layer graphene materials. On the other hand, MOF (metal organic framework) materials have received extensive attention and application in recent years due to their unique high porosity structure and controllable morphology. Especially in the field of wave absorption, using MOF to modify the surface of graphene dominated by dielectric loss can effectively improve the wave absorption performance, which is a good modification method.

The present invention aims to propose a novel preparation method for the modification of the surface of a graphene (ene) nanosheet by a cobalt metal organic framework complex, which is used to improve the wave absorption properties of the graphite (ene) powder.

SUMMARY OF THE INVENTION

The present invention aims to propose a new preparation method of modified graphite nano-sheet wave-absorbing composite powder and modified graphene (ene) nano-sheet composite powder, which are used to improve the wave-absorbing properties of the graphite (ene) powder.

The technical effect of the present invention can be obtained through the following technical solutions:

A preparation method of modified graphene (ene) nanosheet wave-absorbing composite powder and modified graphene (ene) nanosheet composite powder, the steps are as follows:

Step 1. Activation pretreatment: After soaking the graphene (ene) nanosheets in a nitric acid solution and stirring mechanically for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etch-activated graphene (ene) nanosheets. sheet A;

Step 2: The graphite (ene) nanosheets A described in the above step 1 are placed in the organic ligand, cobalt salt and deionized water at a ratio of 2g/L and fully stirred and mixed, so that the graphite (ene) nanosheets A, organic The ligand and cobalt salt are uniformly dispersed in deionized water to form slurry A,

Step 3: Pour the slurry A obtained in the above step 2 into the reactor, and react the slurry A and the reactor together at 120 to 200 ° C for 48 to 72 hours, during which Co-MOFs (cobalt metal) are generated. organic framework complex), and the Co-MOFs will be attached to the surface of the graphene (ene) nanosheet A at the same time to obtain a modified graphite (ene) composite powder B;

Step 4: Take out the reaction kettle in the above step 3, after the reaction kettle is naturally cooled to room temperature, take out the modified graphite (ene) composite powder B obtained in step 3 by suction filtration, and the modified graphite (ene) composite powder B B was dried in a vacuum drying oven at 65° C. for 12 hours to obtain modified graphite (ene) composite powder C.

Further, the graphene nanosheets A described in step 1 are taken out and rinsed, and need to be rinsed with deionized water for multiple measurements until the nitric acid solution soaked in the graphite (ene) nanosheets is diluted to pH>5.

Further, the volume ratio of the graphite (ene) nanosheets and the nitric acid solution described in the step 1 is 1:1,

Further, in the second step, the full stirring is achieved by performing ultrasonic vibration and mechanical stirring at the same time, the ultrasonic power of the ultrasonic vibration is 300W, and the mechanical stirring rate is 2000r/min.

Further, the organic ligand in the second step is bipyridine, triphenylamine triformate, terephthalic acid, pyrazine or one or more organic ligands with the same properties as the aforementioned materials.

Further, the cobalt salts described in step 2 are commonly used cobalt compounds such as cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt nitrate.

Further, the graphite (ene) nanosheets described in step 1 can be graphite nanosheets obtained by physical gas phase exfoliation or reduced graphene oxide prepared by chemical redox method.

Further, in step 2, the ratio between the organic ligand, cobalt salt, and deionized water is 1:1:227 (unit: mol).

According to the modified graphene (ene) nanosheet composite powder obtained by the above-mentioned preparation method, the surface of the modified graphene (ene) composite powder C is uniformly loaded with Co-MOFs particles.

Beneficial effects:

The invention discloses a preparation method of a modified graphite nanosheet wave-absorbing composite powder and a modified graphite (ene) nanosheet composite powder. The acidified and sonicated graphite (ene) nanosheets, cobalt salts and organic ligands are stirred and fused in water, and then the resulting slurry is placed in a reactor, and the graphite (ene) nanosheets are combined with the reaction process by a hydrothermal method. The Co-MOFs (cobalt metal-organic framework complexes) generated in the composite powder are attached and bonded to obtain a composite powder of graphene (ene) nanosheets and Co-MOFs. In the present invention, the hydrothermal method is adopted to make the graphite (ene) nanosheets and Co-MOFs recombined, which saves the tedious steps of preparing MOF precursors and recombining them. The compounding of graphene (ene) nanosheets simplifies the process flow; in the process of ultrasonic and stirring the slurry, the dispersion degree of graphene (ene) nanosheets in the slurry can be effectively improved, and the ratio of graphene (ene) nanosheets can be increased. The surface area of Co-MOFs can be more uniformly supported on the surface of graphene nanosheets. The preparation process is simple, easy to operate, and can be put into industrial production.

Compared with the existing preparation process, the product structure of the graphene (ene) surface-modified composite wave absorbing material is single; in the prior art, the raw material used is the chemically prepared graphene oxide (ene) GO or the reduced graphite oxide (ene). The product rGO, and the preparation steps of the modification of Co-MOFs particles attached to the surface of the graphene (ene) nanosheets are complicated; and the graphene (ene) nanosheets are too small to be dispersed in the solution, and the process operation is difficult. Therefore, the present invention provides a preparation method with simple preparation, low equipment requirements and wide preparation conditions. Using the hydrothermal temperature difference as the driving force, organometallic ligands were synthesized in a single reaction and attached to the surface of graphene (ene) to complete the modification of cobalt metal-organic framework complexes on the surface of graphene (ene), thereby obtaining high porosity. The three-dimensional structure composite absorbing material, its complex morphology is conducive to the refraction and absorption of electromagnetic waves, can effectively overcome the natural disadvantage of single graphene (ene) nanosheets with only dielectric microwave loss, and retain the excellent mechanical properties of graphene (ene) materials. Under the premise, a variety of absorption mechanisms are introduced to improve the comprehensive absorbing properties of graphene (ene) materials. The obtained cobalt metal-organic framework complex-modified graphite (ene) powder has composite absorbing effects such as electrical loss and magnetic loss, which is obviously better than the absorbing powder using graphite nanosheets or cobalt alone.

Detailed ways

Hereinafter, the present invention will be further described based on preferred embodiments.

The vocabulary in this specification is used to describe embodiments of the invention, but not intended to limit the invention.

The invention takes graphene (ene) nanosheets as a matrix, is activated, dispersed in metal cobalt salts, organic ligands and deionized water for hydrothermal synthesis, and then obtains Co-MOFs composite graphite (ene) nanosheets composite adsorbent The preparation method of wave powder.

A preparation method of modified graphene (ene) nanosheet wave-absorbing composite powder and modified graphene (ene) nanosheet composite powder, the steps are as follows:

Step 1: after immersing the graphene (ene) nanosheets in a nitric acid solution and mechanically stirring for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etching-activated graphene (ene) nanosheets A;

Preferably, the volume ratio of the graphene (ene) nanosheets to the nitric acid solution is 1:1;

Preferably, the graphene nanosheets can be graphite nanosheets obtained by physical vapor phase exfoliation or reduced graphene oxide obtained by chemical redox method.

Step 2: In the above step 1, the graphite (ene) nanosheet A is fully stirred and mixed with the organic ligand, cobalt salt and deionized water, so that the graphene (ene) nanosheet A, organic ligand, cobalt Salt, disperse uniformly in deionized water to form slurry A;

Preferably, the sufficient stirring is achieved by performing ultrasonic vibration and mechanical stirring at the same time. Through ultrasonic vibration and mechanical stirring, the graphene nanosheets A can be dispersed as uniformly as possible in the slurry A, which is more conducive to the subsequent full contact and recombination of Co-MOFs.

Preferably, the graphene (ene) nanosheets A are taken out and rinsed, and need to be rinsed with deionized water for several times until the nitric acid solution soaking the graphene (ene) nanosheets is diluted to pH>5.

Preferably, the organic ligand is bipyridine, triphenylamine triformate, terephthalic acid, pyrazine or an organic ligand having the same properties as the aforementioned materials.

Preferably, the cobalt salt is a commonly used cobalt compound such as cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt nitrate.

In this process, the cobalt metal-organic complex is formed in an aqueous solution, and is attached to the surface of the graphene nanosheet at the same time, thereby eliminating the tedious processing steps of first forming the complex and then recombining it.

Step 3: Pour the slurry A obtained in the above step 2 into the reactor, and react the slurry A and the reactor together at 120 to 200 ° C for 48 to 72 hours, during which Co-MOFs (cobalt metal) are generated. organic framework complex), and the Co-MOFs will be attached to the surface of the graphene (ene) nanosheet A at the same time to obtain a modified graphite (ene) composite powder B;

The above reaction produces a binuclear cobalt metal-organic framework complex with a unique three-dimensional porous structure, and the reaction is simultaneously attached to the surface of graphene (ene) nanosheets.

Step 4: Take out the reaction kettle in the above step 3, after the reaction kettle is naturally cooled to room temperature, take out the modified graphite (ene) composite powder B obtained in step 3, and put the modified graphite (ene) composite powder B in the Dry in a vacuum drying oven at 65°C to obtain modified graphite (ene) composite powder C.

Listed below are several methods for preparing a modified graphite (ene) nanosheet wave-absorbing composite powder using the above method and the modified graphene (ene) nanosheet composite powder.

Example 1

Step 1: after immersing the graphene (ene) nanosheets in a nitric acid solution and mechanically stirring for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etching-activated graphene (ene) nanosheets A;

Step 2: Place the graphite (ene) nanosheet A in deionized water, 3.5g/L cobalt acetate, 1.5g/L bipyridine, 4,4',4" in the ratio of 2g/L in the above step 1. -In the solution of triphenylamine triformate 3.8g/L, ultrasonic vibration and mechanical stirring are fully stirred and mixed simultaneously, ultrasonic power 300W, mechanical stirring rate 2000r/min.The graphite (ene) nanosheets A, 4, 4', 4 are made "-Triphenylamine tricarboxylate, bipyridine, cobalt acetate, uniformly dispersed in deionized water to form slurry A;

Step 3: Pour the slurry A obtained in the above step 2 into the reaction kettle, put the reaction kettle into a 120°C oven for 72 hours, and then take it out.

Step 4: Take out the reaction kettle in the above step 3, and after the reaction kettle is naturally cooled to room temperature, carry out suction filtration to take out the modified graphite (ene) composite powder B obtained in step 3, and remove the modified graphite (ene) composite powder B. After the body B was dried in a vacuum drying oven at 65°C for 12 hours, the modified graphite (ene) composite powder C was obtained.

The modified graphite (ene) composite powder obtained in this implementation has high performance, which shows that the minimum reflection loss value is -48.3dB and the absorption bandwidth is 7.44GHz when the thickness is 5.7mm and 5.04GHz.

Embodiment 2

Step 1: after immersing the graphene (ene) nanosheets in a nitric acid solution and mechanically stirring for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etching-activated graphene (ene) nanosheets A;

Step 2: Place the graphite (ene) nanosheet A in deionized water, cobalt nitrate 19.4g/L, bipyridine 1.5g/L, 1,4-terephthalene at a ratio of 2g/L in the above step 1 In the solution of formic acid 11g/L, ultrasonic vibration and mechanical stirring were fully stirred and mixed at the same time, the ultrasonic power was 300W, and the mechanical stirring rate was 2000r/min. Dispersing the graphene nanosheets A, 4-terephthalic acid, bipyridine, and cobalt nitrate in deionized water uniformly forms slurry A;

Step 3: Pour the slurry A obtained in the above step 2 into the reaction kettle, put the reaction kettle into a 120°C oven for 72 hours, and then take it out.

Step 4: Take out the reaction kettle in the above step 3, and after the reaction kettle is naturally cooled to room temperature, carry out suction filtration to take out the modified graphite (ene) composite powder B obtained in step 3, and remove the modified graphite (ene) composite powder B. After the body B was dried in a vacuum drying oven at 65°C for 12 hours, the modified graphite (ene) composite powder C was obtained.

The modified graphite (ene) composite powder obtained in this implementation has high performance, as shown in the fact that the minimum reflection loss value is -37.4dB and the absorption bandwidth is 8.56GHz when the thickness is 5.1mm and 5.44GHz.

Embodiment 3

Step 1: after immersing the graphene (ene) nanosheets in a nitric acid solution and mechanically stirring for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etching-activated graphene (ene) nanosheets A;

Step 2: Place the graphite (ene) nanosheets A in deionized water, cobalt sulfate 5.6g/L, pyrazine 1.6g/L, 1,4-terephthalene at a ratio of 2g/L in the above step 1 In the solution of formic acid 11g/L, ultrasonic vibration and mechanical stirring were fully stirred and mixed at the same time, the ultrasonic power was 300W, and the mechanical stirring rate was 2000r/min. Dispersing the graphene nanosheets A, 4-terephthalic acid, pyrazine, and cobalt sulfate in deionized water uniformly forms slurry A;

Step 3: Pour the slurry A obtained in the above step 2 into the reaction kettle, put the reaction kettle into a 120°C oven for 72 hours, and then take it out.

Step 4: Take out the reaction kettle in the above step 3, and after the reaction kettle is naturally cooled to room temperature, carry out suction filtration to take out the modified graphite (ene) composite powder B obtained in step 3, and remove the modified graphite (ene) composite powder B. After the body B was dried in a vacuum drying oven at 65°C for 12 hours, the modified graphite (ene) composite powder C was obtained.

The modified graphite (ene) composite powder obtained in this implementation has high performance, as shown in the fact that the minimum reflection loss value is -24.6dB and the absorption bandwidth is 6.67GHz when the thickness is 4.7mm and 6.08GHz.

Embodiment 4

Step 1: after immersing the graphene (ene) nanosheets in a nitric acid solution and mechanically stirring for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etching-activated graphene (ene) nanosheets A;

Step 2: Place the graphite (ene) nanosheets A in deionized water, cobalt chloride 4.7g/L, bipyridine 1.5g/L, 1,4-p-benzene at a ratio of 2g/L in the above step 1 In the solution of diformic acid 11g/L, ultrasonic vibration and mechanical stirring were fully stirred and mixed at the same time, the ultrasonic power was 300W, and the mechanical stirring rate was 2000r/min. Disperse the graphene nanosheet A, 4-terephthalic acid, bipyridine and cobalt chloride in deionized water uniformly to form slurry A;

Step 3: Pour the slurry A obtained in the above step 2 into the reaction kettle, put the reaction kettle into a 120°C oven for 72 hours, and then take it out.

Step 4: Take out the reaction kettle in the above step 3, and after the reaction kettle is naturally cooled to room temperature, carry out suction filtration to take out the modified graphite (ene) composite powder B obtained in step 3, and remove the modified graphite (ene) composite powder B. After the body B was dried in a vacuum drying oven at 65°C for 12 hours, the modified graphite (ene) composite powder C was obtained.

The modified graphite (ene) composite powder obtained in this implementation has high performance, which shows that the minimum reflection loss value is -39.5dB and the absorption bandwidth is 6.43GHz when the thickness is 5.1mm and 3.92GHz.

Embodiment 5

Step 1: after immersing the graphene (ene) nanosheets in a nitric acid solution and mechanically stirring for not less than 12 hours, the graphene (ene) nanosheets are taken out for washing, and filtered for standby to obtain etching-activated graphene (ene) nanosheets A;

Step 2: Place the graphite (ene) nanosheet A in deionized water, 3.5g/L cobalt acetate, 1.5g/L bipyridine, 4,4',4" in the ratio of 2g/L in the above step 1. -In the solution of triphenylamine triformate 3.8g/L, ultrasonic vibration and mechanical stirring are fully stirred and mixed simultaneously, ultrasonic power 300W, mechanical stirring rate 2000r/min.The graphite (ene) nanosheets A, 4, 4', 4 are made "-Triphenylamine tricarboxylate, bipyridine, cobalt acetate, uniformly dispersed in deionized water to form slurry A;

Step 3: Pour the slurry A obtained in the above step 2 into the reaction kettle, put the reaction kettle into a 200°C oven for 48 hours, and then take it out.

Step 4: Take out the reaction kettle in the above step 3, and after the reaction kettle is naturally cooled to room temperature, carry out suction filtration to take out the modified graphite (ene) composite powder B obtained in step 3, and remove the modified graphite (ene) composite powder B. After the body B was dried in a vacuum drying oven at 65°C for 12 hours, the modified graphite (ene) composite powder C was obtained.

The modified graphite (ene) composite powder obtained in this implementation has high performance, which is manifested as a minimum reflection loss value of -33.4dB and an absorption bandwidth of 7.20GHz when the thickness is 4.8mm and 4.96GHz.

The specific embodiments of the present invention have been described in detail above. For those skilled in the art, on the premise of not departing from the principles of the present invention, the present invention can also be modified and improved several times, and these modifications and improvements also belong to the present invention. The scope of protection of the invention claims.

Claims (7)

1. a modified graphene nanosheet composite powder preparation method, is characterized in that: Step 1. Activation pretreatment: after soaking the graphene nanosheets in a nitric acid solution and mechanically stirring for no less than 12 hours, taking out the graphene nanosheets for washing, and filtering for later use to obtain the etched and activated graphene nanosheets A; Step 2: The graphene nanosheets A described in the above step 1 are placed in organic ligands, cobalt salts and deionized water at a ratio of 2 g/L and fully stirred and mixed, so that the graphene nanosheets A, organic ligands, cobalt Salt, disperse uniformly in deionized water to form slurry A; Step 3: Pour the slurry A obtained in the above step 2 into the reaction kettle, and react the slurry A and the reaction kettle together under the condition of 120~200 ° C for 48~72 hours, in the process, generate cobalt metal organic framework complexes , and the cobalt metal organic framework complex will be attached to the surface of the graphene nanosheet A at the same time to obtain a modified graphene composite powder B; Step 4: Take out the reaction kettle in the above step 3, after the reaction kettle is naturally cooled to room temperature, take out the modified graphene composite powder B obtained in step 3 by suction filtration, and set the modified graphene composite powder B at 65 ° C. Dry in a vacuum drying oven for 12 hours to obtain modified graphene composite powder C; The graphene nanosheet A described in step 1 is taken out and rinsed, and needs to be rinsed with deionized water for multiple measurements until the nitric acid solution soaked in the graphene nanosheet is diluted to pH>5; The volume ratio of the graphene nanosheets and the nitric acid solution described in the step 1 is 1:1. 2. a kind of modified graphene nanosheet composite powder preparation method according to claim 1, is characterized in that, The sufficient stirring in step 2 is achieved by performing ultrasonic vibration and mechanical stirring at the same time, the ultrasonic power of the ultrasonic vibration is 300W, and the mechanical stirring rate is 2000r/min. 3. a kind of modified graphene nanosheet composite powder preparation method according to claim 1, is characterized in that, The organic ligand described in the second step is one or more of bipyridine, triphenylamine triformate, terephthalic acid, and pyrazine. 4. a kind of modified graphene nanosheet composite powder preparation method according to claim 1, is characterized in that, The cobalt salt described in step 2 is one or more of cobalt acetate, cobalt sulfate, cobalt chloride, and cobalt nitrate. 5. a kind of modified graphene nanosheet composite powder preparation method according to claim 1, is characterized in that, The graphene nanosheets described in step 1 are graphene nanosheets obtained by physical vapor exfoliation method or reduced graphene oxide prepared by chemical redox method. 6. a kind of modified graphene nano-sheet composite powder preparation method according to claim 1, is characterized in that, In step 2, the molar ratio between the organic ligand, cobalt salt, and deionized water is 1:1:227. 7. The modified graphene nanosheet composite powder obtained by the preparation method according to any one of claims 1 to 6, wherein the surface of the modified graphene composite powder C is uniformly loaded with cobalt metal organic Frame complex particles.