Co ion crosslinking edge graphene oxide / PVA heat conduction composite material and preparation method thereof

Abstract

The invention discloses a preparation method of a Co ion cross-linked edge graphene oxide / PVA (Polyvinyl Alcohol) heat-conducting composite material, which comprises the following steps of: ultrasonically and uniformly mixing an edge graphene oxide nanosheet EGON and CoCl2 in deionized water, and carrying out coordination reaction on cobalt ions Co < 2 + > and an oxygen-containing functional group at the edge of the EGON by stirring, so as to obtain the Co ion cross-linked edge graphene oxide / PVA heat-conducting composite material. Thus, coordination bonds are formed between the edge graphene oxide nanosheets through Co < 2 + >, and a stable Co < 2 + >-EOGN hybrid filler dispersion liquid is obtained; then, adding a PVA aqueous solution into the obtained Co < 2 + >-EOGN hybrid filler dispersion liquid, carrying out ultrasonic treatment and stirring to obtain a stable mixed system, then forming a film by adopting a vacuum suction filtration method, and carrying out hot pressing to finally obtain the Co ion cross-linked edge graphene oxide / PVA heat-conducting composite material film. In the method provided by the invention, the Co < 2 + > coordination optimizes a heat conduction path through interface bonding, so that the heat conduction performance of the polymer composite material is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer-based thermally conductive composite materials, and in particular to a Co ion-crosslinked edge graphene oxide / PVA thermally conductive composite material and a preparation method thereof. Background Art

[0002] With the rapid increase in the integration level and power density of electronic devices, local overheating has seriously affected the stability and life of the equipment. Thermally conductive polymer composites have become a research hotspot for thermal management materials due to their light weight, insulation and easy processing. However, the thermal conductivity of traditional polymers is low (0.1-0.3 W·m -1 ·K -1 ), it is necessary to add thermal conductive fillers to build a thermal conductive path to improve its thermal conductivity. Graphene has a very high thermal conductivity (3000-5000W·m -1 ·K -1 ) is considered an ideal filler, but existing graphene / polymer composites have shown limited improvement in thermal conductivity, primarily due to the interfacial thermal resistance between the filler and the matrix, which limits heat transfer efficiency. Therefore, reducing interfacial thermal resistance through microstructural design is key to improving the thermal conductivity of composites. Summary of the Invention

[0003] Based on the above-mentioned shortcomings of the prior art, the present invention provides a Co ion-crosslinked edge graphene oxide / PVA thermal conductive composite material and a preparation method thereof, aiming to 2+ The coordination with edge graphene oxide (EOG) constructs a cross-linked network, reduces the contact thermal resistance between fillers, and is combined with the PVA matrix to prepare a layered structure composite material, which significantly improves the thermal conductivity.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a Co ion cross-linked edge graphene oxide / PVA thermal conductive composite material, which is characterized by: ultrasonically mixing edge graphene oxide nanosheets (EGON) and CoCl2 in deionized water, and stirring to make the cobalt ions Co 2+ Coordinate with oxygen-containing functional groups (such as carboxyl, hydroxyl, etc.) on the edge of EGON, so that the edge graphene oxide nanosheets are connected by Co 2+ Form a coordination bond to obtain a stable Co 2+ -EOGN hybrid filler dispersion; then, in the obtained Co 2+ The PVA aqueous solution was added to the dispersion of the -EOGN hybrid filler, and a stable mixed system was obtained by ultrasonication and stirring. The film was then formed by vacuum filtration and hot pressing, and finally a Co ion-crosslinked edge graphene oxide / PVA thermal conductive composite film with a dense structure and excellent thermal conductivity was obtained, which was recorded as Co2+ -EOGN / PVA. The specific steps include:

[0006] Step 1, Co 2+ Preparation of -EOGN hybrid fillers

[0007] 80 mg of EGON was added to 100-250 mL of deionized water, and then 535-715 μL of 0.1 mol / L CoCl2 solution was added. Ultrasonication was performed for 2-4 hours, and stirring was performed for 12-24 hours to obtain Co 2+ -EOGN hybrid filler dispersion.

[0008] Step 2, Co 2+ -Preparation of EOGN / PVA thermal conductive composite materials

[0009] PVA particles were added to deionized water at a concentration of 4-5 mg / mL, and heated in an oil bath at 90-100°C with stirring until dissolved to obtain a PVA aqueous solution;

[0010] Take 1-5 mL of PVA aqueous solution and add it to the Co 2+ -EOGN hybrid filler dispersion, ultrasonic for 30 to 60 minutes, and stir for 1 to 2 hours to obtain Co 2+ -EGON / PVA aqueous suspension; Co 2+ -EGON / PVA aqueous suspension was vacuum filtered, and the obtained film was hot pressed to obtain Co 2+ -EOGN / PVA thermal conductive composite film.

[0011] Preferably, in step 2, the pore size of the mixed fiber microporous filter membrane is 0.22 μm.

[0012] Preferably, in step 2, the hot pressing temperature is 50-60° C., the pressure is 10-12 MPa, and the time is 5-10 minutes.

[0013] Preferably, the edge-on graphene oxide nanosheets can be prepared by the following method: first, natural graphite is oxidized by a modified Hummers method, and the resulting graphite oxide is then exfoliated to obtain edge-on graphite oxide (EOG); further, the EOG is ultrasonically exfoliated under alkaline conditions to obtain edge-on graphene oxide nanosheets (EGON). Specifically, the method comprises the following steps:

[0014] Disperse 2.8-3.0g of graphite in 138-140mL of concentrated H2SO4 precooled to 0°C. Slowly add 18.0-18.5g of KMnO4, maintaining the temperature between 0-10°C. After addition, react at 70-80°C for 24 hours. Terminate the reaction by adding 10-20mL of a 30% H2O2 solution. The resulting product is centrifuged and washed with 3.4% HCl solution, then washed with ethanol and deionized water until neutral, filtered, and vacuum-dried to obtain EGO.

[0015] EGO was dispersed in deionized water at a concentration of 4-5 mg / mL, and 0.1 mol / L NaOH solution was slowly added dropwise until the pH value was 11-12. The solution was ultrasonicated for 6-12 hours, centrifuged, and the supernatant was collected. The solution was repeated 3-5 times and then dialyzed to neutrality. The edge-shaped graphene oxide nanosheets (EGON) were freeze-dried to obtain the result.

[0016] The Co prepared by the above preparation method of the present invention 2+ -EOGN / PVA thermal conductive composite film, Co 2+ The mass percentage of the -EOGN hybrid filler is 80 to 95 wt%.

[0017] The beneficial effects of the present invention are embodied in:

[0018] The present invention is through Co 2+ It reacts with the functional groups on the surface of edge graphene oxide nanosheets (EGON) to form a cross-linked network structure, which effectively reduces the contact thermal resistance between fillers. It further constructs a regular layered structure through vacuum filtration process, which significantly improves the continuity of the heat conduction path, thereby significantly improving the thermal conductivity of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a SEM image of EGO in Example 1 of the present invention;

[0020] Figure 2 is a SEM image of EGON in Example 1 of the present invention;

[0021] Figure 3 Co obtained in Example 1 of the present invention 2+ -SEM image of EGON;

[0022] Figure 4 Co obtained in Example 1 of the present invention 2+ -XPS pattern of EGON;

[0023] Figure 5 Co obtained in Example 1 of the present invention 2+ - XRD pattern of EGON;

[0024] Figure 6 Co obtained in Example 1 of the present invention 2+ -Surface SEM image of EGON / PVA film

[0025] Figure 7 Co obtained in Example 1 of the present invention 2+ - Cross-sectional SEM image of EGON / PVA film;

[0026] Figure 8 This is a comparison chart of the thermal diffusion coefficients of the samples obtained in Examples 1, 2, 3, and 4 of the present invention and Comparative Examples 1, 2, 3, and 4. DETAILED DESCRIPTION

[0027] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0028] Example 1

[0029] In this example, Co was prepared according to the following steps 2+ -EOGN / PVA thermal conductive composite film:

[0030] Step 1. Preparation of EGON

[0031] 3.0 g of graphite was dispersed in 138 mL of concentrated H₂SO₄ precooled to 0°C. 18.0 g of KMnO₄ was slowly added, maintaining the temperature at 0°C. After the addition, the reaction was allowed to proceed at 70°C for 24 hours. The reaction was terminated by adding 10 mL of a 30% H₂O₂ solution. The resulting product was washed by centrifugation with a 3.4% HCl solution, then washed with ethanol and deionized water until neutral, filtered, and vacuum-dried to obtain EGO.

[0032] EGO was dispersed in deionized water at a concentration of 5 mg / mL, and 0.1 mol / L NaOH solution was slowly added dropwise until the pH value reached 12, and then the solution was ultrasonicated for 12 hours. The supernatant was centrifuged and the solution was collected. The solution was dialyzed to neutrality after repeated three times and freeze-dried to obtain EGON.

[0033] Step 2, Co 2+ Preparation of -EOGN hybrid fillers

[0034] 80 mg of EGON was added to 250 mL of deionized water, and then 715 μL of 0.1 mol / L CoCl2 solution was added. Ultrasonication was performed for 2 hours and stirring was performed for 12 hours to obtain Co 2+ -EOGN hybrid filler dispersion.

[0035] Step 3, Co 2+-Preparation of EOGN / PVA thermal conductive composite materials

[0036] PVA particles were added to deionized water at a concentration of 4 mg / mL, and heated and stirred in an oil bath at 100° C. (stirring speed 500 rpm, stirring time 24 hours) until dissolved to obtain a PVA aqueous solution.

[0037] Take 5mL PVA aqueous solution and add it to the Co 2+ -EOGN hybrid filler dispersion, ultrasonic for 30 minutes, and stirred for 1 hour to obtain Co 2+ -EGON / PVA aqueous suspension; Co 2+ -EGON / PVA aqueous suspension was vacuum filtered, and the obtained film was hot pressed (the hot pressing temperature was 60°C, the pressure was 10 MPa, and the time was 5 minutes) to obtain Co 2+ -EOGN / PVA thermal conductive composite film, in which Co 2+ -The mass fraction of EGON filler in the composite material is 80%.

[0038] Figure 1 is the SEM image of EGO prepared in this embodiment, Figure 2 This is the SEM image of the EGON prepared in this example, from which it can be seen that the graphene sheet is thinning. Figure 3 Co obtained in this example 2+ -EOGN hybrid filler SEM image, it can be seen that the edge graphene oxide is connected together by cobalt ion coordination.

[0039] Figure 4 Co obtained in this example 2+ -EOGN hybrid filler XPS graph shows that there are obvious C1s, O 1s and Co 2p signals in the material, confirming that the material mainly contains three elements: carbon, oxygen and cobalt. Further Co 2p high-resolution energy spectrum analysis shows that the cobalt element mainly exists in the form of Co–O coordination, accompanied by obvious satellite peaks, indicating that the cobalt ion is in a higher oxidation state (such as Co 2+ or Co 3+ This result indicates that the cobalt ions have successfully coordinated with the oxygen-containing functional groups (such as carboxyl and hydroxyl groups) on the edge of graphene oxide, forming a stable metal-organic coordination structure.

[0040] Figure 5 Co obtained in this example 2+-EOGN hybrid filler XRD pattern, as can be seen from the figure, the material has an obvious diffraction peak at 11.5°, corresponding to the (001) crystal plane of graphene oxide (GO), indicating that there is a layered graphene oxide structure in the material. The strong diffraction peak at 26.2° is the diffraction peak of the (002) crystal plane of graphene or reduced graphene oxide (rGO), indicating that some areas have undergone reduction or restacking, and a certain graphite crystal structure has been restored. At the same time, the diffraction peak of the G (004) crystal plane can be observed at 54.6°, further indicating that there is a certain degree of ordered stacking graphite structure in the material. The above results show that the material, while retaining the layered structure of graphene oxide, has achieved the ordering and stabilization of part of the structure by coordinating with cobalt ions.

[0041] Figure 6 Co obtained in this example 2+ -Surface SEM image of EGON / PVA film shows that the surface of the composite material is very smooth. Figure 7 Co obtained in this example 2+ -The cross-sectional SEM image of the EGON / PVA film shows that the composite material has a good layered structure and the edge graphene oxide is evenly dispersed in the PVA matrix, which inhibits filler agglomeration and improves the performance of the composite material.

[0042] Example 2

[0043] In this example, Co was prepared in the same manner as in Example 1. 2+ -EOGN / PVA thermal conductive composite material, the only difference is that the amount of PVA aqueous solution in step 3 is 3.5mL, and the Co 2+ -The mass fraction of EOGN filler is 85%.

[0044] Example 3

[0045] In this example, Co was prepared in the same manner as in Example 1. 2+ -EOGN / PVA thermal conductive composite material, the only difference is that in step 4: the amount of PVA aqueous solution is 2.2mL, and the Co 2+ -The mass fraction of EOGN filler is 90%.

[0046] Example 4

[0047] In this example, Co was prepared in the same manner as in Example 1. 2+ -EOGN / PVA thermal conductive composite material, the only difference is that in step 4: the amount of PVA aqueous solution is 1.05mL, and the Co 2+ -The mass fraction of EOGN filler is 95%.

[0048] Comparative Example 1

[0049] In this comparative example, a thermally conductive composite material was prepared in the same manner as in Example 1, except that the amount of CoCl2 solution added in step 2 was 0. The resulting film was designated as EGON / PVA, wherein Co 2+ -The mass fraction of EGON filler in the composite material is 80%.

[0050] Comparative Example 2

[0051] In this comparative example, a thermally conductive composite material was prepared in the same manner as in Example 2, except that the amount of CoCl2 solution added in step 2 was 0. The resulting film was denoted as EGON / PVA, wherein the mass fraction of the EGON filler in the composite material was 85%.

[0052] Comparative Example 3

[0053] In this comparative example, a thermally conductive composite material was prepared in the same manner as in Example 3, except that the amount of CoCl2 solution added in step 2 was 0. The resulting film was denoted as EGON / PVA, wherein the mass fraction of the EGON filler in the composite material was 90%.

[0054] Comparative Example 4

[0055] In this comparative example, a thermally conductive composite material was prepared in the same manner as in Example 4, except that the amount of CoCl2 solution added in step 2 was 0. The resulting film was denoted as EGON / PVA, wherein the mass fraction of the EGON filler in the composite material was 95%.

[0056] The thermal conductivity of the samples obtained in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4 is shown in Table 1 and Figure 8 shown.

[0057] Table 1. Thermal diffusivity of samples obtained in various embodiments and comparative examples

[0058]

[0059] From Table 1 and Figure 6 It can be seen that the thermal diffusion coefficients of the samples obtained in Examples 1 to 4 are significantly improved compared with Comparative Examples 1 to 4. 2+ Compared with pure edge graphene oxide, the thermal diffusion coefficient of ion-coordinated edge graphene oxide is significantly improved at the same filler content, and when the loading reaches 90%, the thermal diffusion coefficient of the composite material reaches its highest value. This is mainly because the cobalt ion coordination reduces the phonon scattering between fillers, which can effectively reduce the contact thermal resistance between fillers, thereby improving thermal conductivity.

[0060] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a Co ion-crosslinked edge graphene oxide / PVA thermally conductive composite material, characterized in that: After the edge graphene oxide nanosheets EGON and CoCl2 were ultrasonically mixed in deionized water, the cobalt ions Co 2+ Coordinate reaction with oxygen-containing functional groups at the edge of EGON, so that the edge graphene oxide nanosheets are connected by Co 2+ Form a coordination bond to obtain a stable Co 2+ -EOGN hybrid filler dispersion; then, in the obtained Co 2+ The PVA aqueous solution was added to the dispersion of the -EOGN hybrid filler, and a stable mixed system was obtained by ultrasonication and stirring. Then, a film was formed by vacuum filtration and hot pressing, and finally a Co ion-crosslinked edge graphene oxide / PVA thermal conductive composite film was obtained, which was recorded as Co 2+ -EOGN / PVA.

2. The preparation method according to claim 1, characterized in that The specific steps include: Step 1, Co 2+ Preparation of -EOGN hybrid fillers 80 mg of EGON was added to 100-250 mL of deionized water, and then 535-715 μL of 0.1 mol / L CoCl2 solution was added. Ultrasonication was performed for 2-4 hours, and stirring was performed for 12-24 hours to obtain Co 2+ -EOGN hybrid filler dispersion; Step 2, Co 2+ -Preparation of EOGN / PVA thermal conductive composite materials PVA particles were added to deionized water at a concentration of 4-5 mg / mL, and heated in an oil bath at 90-100°C with stirring until dissolved to obtain a PVA aqueous solution; Take 1-5 mL of PVA aqueous solution and add it to the Co 2+ -EOGN hybrid filler dispersion, ultrasonic for 30 to 60 minutes, and stir for 1 to 2 hours to obtain Co 2+ -EGON / PVA aqueous suspension; Co 2+ -EGON / PVA aqueous suspension was vacuum filtered, and the obtained film was hot pressed to obtain Co 2+ -EOGN / PVA thermal conductive composite film.

3. The preparation method according to claim 2, wherein: In step 2, the pore size of the mixed fiber microporous filter membrane is 0.22 μm.

4. The preparation method according to claim 2, wherein: In step 2, the hot pressing temperature is 50-60° C., the pressure is 10-12 MPa, and the time is 5-10 minutes.

5. A Co ion-crosslinked edge graphene oxide / PVA thermal conductive composite material prepared by the preparation method according to any one of claims 1 to 4.

6. The Co ion-crosslinked edge graphene oxide / PVA thermal conductive composite material according to claim 5, characterized in that: The obtained Co 2+ -EOGN / PVA thermal conductive composite film Co 2+ The mass percentage of the -EOGN hybrid filler is 80 to 95 wt%.

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