Preparation method of high-thermal-conductivity 3-3 type graphene / epoxy resin composite material

Abstract

This invention belongs to the field of composite material technology and relates to a method for preparing a graphene / epoxy resin composite material with high thermal conductivity. Graphene aerogel is prepared by vacuum freeze-drying. The aerogel is then subjected to two reduction treatments at 600–1000℃ and 2300–3300℃, respectively. The aerogel is then immersed in a mixed solution of epoxy resin and curing agent, vacuumed at 70–90℃ for 0.5–1.5 h, pre-cured at 110–130℃ for 1.5–2.5 h, and cured at 140–160℃ for 14–16 h. After cooling to room temperature, a type 3–3 graphene / epoxy resin composite material is obtained. This method effectively improves the thermal conductivity of the graphene / epoxy resin composite material. This invention also relates to the graphene / epoxy resin composite material prepared by this method and its applications.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and specifically relates to a method for preparing a high thermal conductivity 3-3 type graphene / epoxy resin composite material. Background Technology

[0002] Electronic packaging materials are a crucial component of electronic devices, not only supporting and protecting them but also dissipating the heat generated during operation. Epoxy resins are widely used in electronic packaging due to their high heat resistance, good adhesion, and low curing shrinkage. However, with the rapid development of high-power electronic devices, the inherently low thermal conductivity of epoxy resins (approximately 0.2 W / mK at room temperature) is insufficient to handle the heat buildup in electronic devices, necessitating the use of composite phases with high thermal conductivity to improve thermal performance.

[0003] To improve the thermal conductivity of epoxy resin-based composites, high thermal conductivity phases (such as boron nitride, aluminum nitride, silicon nitride, and graphene) are typically added to the epoxy resin to prepare the composites. However, due to the small size of thermally conductive phases like graphene, if these phases are uniformly dispersed in the epoxy resin matrix, the numerous thermally conductive phase / epoxy resin interfaces will introduce significant interfacial thermal resistance, thereby reducing the thermal conductivity of the epoxy resin-based composite. Studies have found that surface modification can improve the interfacial bonding between the high thermal conductivity phase and the epoxy resin matrix and reduce interfacial thermal resistance; however, due to the excessive number of interfaces, it is difficult to significantly improve the thermal conductivity of the composite. To improve the thermal conductivity of epoxy resin-based composites, the thermally conductive phases can be arranged to construct effective thermal conduction pathways while reducing the adverse effects of interfacial thermal resistance. However, it is difficult to construct effective thermal conduction pathways using simple blending processes. While high filler content helps form thermal conduction pathways, it is detrimental to the mechanical strength and structural thermal stability of the composite. In conclusion, the currently used surface modification and simple blending techniques cannot fundamentally improve the thermal conductivity of epoxy resin-based composites. Constructing effective thermal conductivity pathways with low thermally conductive phase filler content is a key technology for improving the thermal conductivity of epoxy resin-based composites.

[0004] Among many high thermal conductivity nanofillers, monolayer graphene has a thermal conductivity as high as 5300 W / mK, and its excellent thermal conductivity makes it have great development potential in the field of thermal management. In order to construct an efficient thermal conduction pathway, researchers prefabricate graphene into a three-dimensional structure and then fill epoxy resin into the three-dimensional graphene structure to prepare a composite material. The literature Liu Z, et al., Exceptionally high thermal and electrical conductivity of three-dimensional graphene-foam-based polymer composites, RSC Advances, 2016, 6(27): 22364-22369 discloses that polyurethane foam is used as a template, first impregnated with graphene ethanol solution, then calcined to obtain a three-dimensional graphene skeleton, and then impregnated with epoxy resin to finally obtain a graphene / epoxy resin composite material; when the graphene content is 5wt%, the thermal conductivity of the composite material is 1.52 W / mK. The literature Liu Y, et al., "Improved thermal conductivity of epoxyresin by graphene–nickel three-dimensional filler," Carbon Resources Conversion, 2020, 3:29-35, discloses the growth of graphene on nickel foam using chemical vapor deposition, followed by embedding the graphene-coated nickel foam into epoxy resin. The graphene and nickel foam form a three-dimensional thermally conductive network within the epoxy resin. When the graphene content is 10.1 wt%, the thermal conductivity of the graphene-nickel / epoxy resin composite reaches 2.65 W / mK. It is noteworthy that for composites containing only graphene and epoxy resin, the reported thermal conductivity still falls short of 2 W / mK. This is because the graphene structure is disrupted during the preparation of the three-dimensional interconnected structure, resulting in a significant decrease in thermal conductivity. The performance improvement of the graphene-reinforced epoxy resin composite falls far short of expectations, failing to fully reflect the high thermal conductivity of graphene.

[0005] Therefore, there is still a need to develop a graphene / epoxy resin composite material with high thermal conductivity and its preparation method. Summary of the Invention

[0006] In view of this, the purpose of this invention is to overcome the problem of low thermal conductivity due to excessive graphene / epoxy resin interfaces, to construct a three-dimensional thermally conductive graphene pathway in an epoxy resin matrix, and to restore the structure and thermal conductivity of graphene through high-temperature reduction treatment, thereby providing a method for preparing a high thermal conductivity type 3-3 graphene / epoxy resin composite material.

[0007] Another objective of this invention is to provide a high thermal conductivity 3-3 type graphene / epoxy resin composite material.

[0008] Another objective of this invention is to provide the application of the above-mentioned composite material as an electronic packaging material.

[0009] The present invention discloses a method for preparing a high thermal conductivity type 3-3 graphene / epoxy resin composite material, comprising the following steps:

[0010] 1) Graphene hydrogel was prepared by chemical reduction method. 2-5 mg / mL of graphene oxide aqueous solution was mixed with ascorbic acid and reduced at a certain temperature for a period of time to obtain the graphene hydrogel.

[0011] 2) Soak the graphene hydrogel described in step 1) in deionized water to remove the original solvent and other impurities;

[0012] 3) Freeze-solidify the graphene hydrogel after soaking in step 2) at a set temperature;

[0013] 4) The graphene hydrogel solidified in step 3) is freeze-dried under vacuum for 24-72 hours to obtain graphene aerogel.

[0014] 5) The graphene aerogel obtained in step 4) is pre-reduced at 600-1000℃ for 0.5-1.5h under argon protection, and then the graphene aerogel is further reduced at 2300-3300℃ for 0.5-1.5h.

[0015] 6) Cut off the top and bottom surfaces of the further reduced graphene aerogel described in step 5) to expose the internal pore structure, and then immerse the graphene aerogel in a mixed solution of epoxy resin and curing agent, and vacuum it at 70-90°C for 0.5-1.5 hours.

[0016] 7) Pre-cur the graphene aerogel fully impregnated with epoxy resin described in step 6) at 110-130°C for 1.5-2.5 hours, and then cure it at 140-160°C for 14-16 hours.

[0017] 8) Cool to room temperature to obtain type 3-3 graphene / epoxy resin composite material.

[0018] Further, the aqueous solution of graphene oxide in step 1) is mixed with ascorbic acid at a mass ratio of 1:2 to 6, preferably 1:4.

[0019] Furthermore, the reduction temperature of the graphene oxide in step 1) is 55–70°C; the reduction time of the graphene oxide is 2–3 h.

[0020] Furthermore, in step 2), each soaking lasts 3 hours, for a total of three soaks.

[0021] Furthermore, the freezing temperature described in step 3) is -10 to -196°C.

[0022] Further, in step 5), the graphene aerogel is pre-reduced at 800–1000°C for 0.5–1.5 h under argon protection, and then further reduced at 2500–3000°C or 2600–3000°C for 0.5–1.5 h.

[0023] Further, in step 6), the volume ratio of epoxy resin to curing agent is 10:8 to 9, preferably 10:9.

[0024] The curing agent is methylhexahydrophthalic anhydride, but is not limited to this.

[0025] Compared with other technologies, the significant advantages of this invention are:

[0026] 1) Assemble nanoscale graphene into macroscale graphene aerogel. Combining the high thermal conductivity of graphene with the three-dimensional connectivity of aerogel, construct a three-dimensional thermal conductivity pathway in the epoxy resin matrix. This effectively improves the thermal conductivity of the composite material with a low graphene filling amount, overcoming the problem of low thermal conductivity due to excessive graphene / epoxy resin interfaces.

[0027] 2) High-temperature reduction of graphene aerogel at 2300–3300℃ effectively restores the structure and thermal conductivity of graphene, which is key to obtaining high thermal conductivity graphene / epoxy resin composites. The thermal conductivity of the graphene / epoxy resin composite prepared after high-temperature reduction treatment of graphene aerogel can reach as high as 68 W / mK. In contrast, if the graphene aerogel is not subjected to high-temperature reduction treatment, the thermal conductivity of the prepared graphene / epoxy resin composite is only 0.18 W / mK.

[0028] 3) Graphene aerogel was used as a thermally conductive reinforcing phase to prepare type 3 graphene / epoxy resin composites. The thermal conductivity can reach up to 68 W / mK, which is much higher than that of graphene / epoxy resin composites prepared by existing technologies, thus meeting the requirements for electronic packaging materials. Attached Figure Description

[0029] Figure 1 This is a cross-sectional scanning electron microscope image of the graphene / epoxy resin composite material prepared in Example 1;

[0030] Figure 2 The images show the Raman spectra of graphene aerogel (GA) obtained directly after vacuum freeze-drying (without any heat treatment) and graphene aerogel treated with high temperature reduction (GA-3000℃) in Example 1. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are some preferred embodiments of the present invention and are not intended to limit the scope of the present invention.

[0032] Graphene's excellent thermal conductivity is evident at the nanoscale, making it difficult to directly apply to the macroscale. To develop high thermal conductivity graphene / epoxy resin composites, this invention proposes assembling nanoscale graphene into macroscale graphene aerogels, restoring the graphene's structure and thermal conductivity through high-temperature reduction treatment, and then filling the three-dimensionally interconnected graphene aerogels with epoxy resin. This creates three-dimensional thermally conductive pathways within the epoxy resin matrix, significantly improving the thermal conductivity of the graphene / epoxy resin composite with a relatively low graphene content.

[0033] The term "3-3 type" means that both graphene and epoxy resin are 3-dimensionally connected.

[0034] This invention provides a method for preparing a high thermal conductivity type 3-3 graphene / epoxy resin composite material, specifically comprising the following steps:

[0035] 1) Graphene hydrogels were prepared by chemical reduction method. 2-5 mg / mL of graphene oxide aqueous solution was mixed with ascorbic acid at a preferred mass ratio of 1:4 and reduced at a certain temperature for a period of time.

[0036] 2) Soak the graphene hydrogel described in step 1) in deionized water to replace the original solvent and other impurities in the hydrogel. Preferably, soak for 3 hours each time, for a total of three soaks.

[0037] 3) Freeze-solidify the graphene hydrogel after soaking in step 2) at a set temperature;

[0038] 4) The graphene hydrogel solidified in step 3) is freeze-dried under vacuum for 24-72 hours to obtain graphene aerogel.

[0039] 5) The graphene aerogel described in step 4) is pre-reduced at 600-1000℃ for 0.5-1.5h under argon protection, preferably at 1000℃ for 1h, and then the graphene aerogel is further reduced at 2300-3300℃ for 0.5-1.5h.

[0040] 6) Cut off the top and bottom surfaces of the further reduced graphene aerogel described in step 5) to expose the internal pore structure, and then immerse the aerogel in a mixed solution of epoxy resin and curing agent, and vacuum it at 70-90°C for 0.5-1.5 hours.

[0041] 7) Pre-cur the graphene aerogel fully impregnated with epoxy resin described in step 6) at 110-130°C for 1.5-2.5 hours, and then cure it at 140-160°C for 14-16 hours.

[0042] 8) Cool to room temperature to obtain type 3-3 graphene / epoxy resin composite material.

[0043] In one embodiment, the reduction temperature of the graphene oxide in step 1) is 55 to 70°C; for example, but not limited to, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, and 70°C.

[0044] In one embodiment, the reduction time of the graphene oxide in step 1) is 2 to 3 hours.

[0045] Further, the freezing temperature in step 3) is -10 to -196℃, and may be, but is not limited to, -10℃, -15℃, -20℃, -25℃, -30℃, -35℃, -40℃, -45℃, -50℃, -55℃, -60℃, -65℃, -70℃, -75℃, -80℃, -85℃, -90℃, -95℃, -100℃, -105℃, -110℃, -120℃, -130℃, -140℃, -150℃, -160℃, -170℃, -180℃, -190℃, and -196℃.

[0046] Further, the graphene aerogel described in step 5) is pre-reduced at 600–1000°C under argon protection. This pre-reduction temperature can be, but is not limited to, 600°C, 700°C, 800°C, 900°C, 950°C, or 1000°C. The graphene aerogel is then further reduced at 2300°C, 2400°C, 2500°C, 2600°C, 2700°C, 2800°C, 2900°C, 3000°C, 3100°C, 3200°C, or 3300°C for 0.5–1.5 hours.

[0047] Further, in step 6), the volume ratio of the epoxy resin to the curing agent is 10:8 to 9, preferably 10:9.

[0048] The present invention also relates to a high thermal conductivity type 3-3 graphene / epoxy resin composite material prepared by the same method.

[0049] To better understand the present invention, specific embodiments will be described in detail below.

[0050] Example 1

[0051] 1) Graphene hydrogel was prepared by chemical reduction method by mixing 3 mg / mL of graphene oxide aqueous solution with ascorbic acid at a mass ratio of 1:4 and keeping it at 55℃ for 2 h.

[0052] 2) Soak the graphene hydrogel described in step 1) in deionized water for 3 hours to replace the original solvent and other impurities in the hydrogel. Repeat this soaking process three times.

[0053] 3) Freeze and solidify the graphene hydrogel after soaking in step 2) at -20°C;

[0054] 4) The graphene hydrogel solidified in step 3) was freeze-dried under vacuum for 48 hours to obtain a cylindrical graphene aerogel with a diameter of 21.12 mm and a height of 17.35 mm.

[0055] 5) The graphene aerogel described in step 4) was reduced at 1000℃ and 3000℃ for 1 hour each under argon protection;

[0056] 6) Cut off the top and bottom surfaces of the graphene aerogel reduced at high temperature in step 5) to expose the internal pore structure, and then immerse the aerogel in a mixed solution of epoxy resin and curing agent, and vacuum at 80°C for 1 hour; wherein the curing agent is methyl hexahydrophthalic anhydride.

[0057] 7) Pre-cure the graphene aerogel fully impregnated with epoxy resin as described in step 6) at 120°C for 2 hours, and then cure it at 150°C for 15 hours.

[0058] 8) Cool to room temperature to obtain type 3-3 graphene / epoxy resin composite material.

[0059] The thermal diffusivity of the 3-3 type graphene / epoxy resin composite material obtained in this embodiment is 49.626 mm. 2 It has a specific heat of 1.167 J / gK, a graphene content of 4.26 wt%, and a density of 1.182 g / cm³. 3 The thermal conductivity is 68 W / mK. A cross-sectional scanning electron microscope image of this graphene / epoxy resin composite material is shown below. Figure 1 As shown. Figure 2 The images show the Raman spectra of graphene aerogel (GA) obtained directly after vacuum freeze-drying (without any heat treatment) and graphene aerogel treated with high temperature reduction (GA-3000℃) in Example 1.

[0060] Example 2

[0061] 1) Graphene hydrogel was prepared by chemical reduction method by mixing 3 mg / mL of graphene oxide aqueous solution with ascorbic acid at a mass ratio of 1:4 and keeping it at 55℃ for 2 h.

[0062] 2) Soak the graphene hydrogel described in step 1) in deionized water for 3 hours to replace the original solvent and other impurities in the hydrogel. Repeat this soaking process three times.

[0063] 3) Freeze-solidify the graphene hydrogel after soaking in step 2) at -40°C;

[0064] 4) The graphene hydrogel solidified in step 3) was freeze-dried under vacuum for 48 hours to obtain a cylindrical graphene aerogel with a diameter of 20.88 mm and a height of 17.21 mm.

[0065] 5) The graphene aerogel obtained in step 4) was reduced at 1000℃ and 3000℃ for 1 h each under argon protection.

[0066] 6) Cut off the top and bottom surfaces of the graphene aerogel reduced at high temperature in step 5) to expose the internal pore structure, and then immerse the aerogel in a mixed solution of epoxy resin and curing agent, and vacuum at 80°C for 1 hour.

[0067] 7) Pre-cure the graphene aerogel fully impregnated with epoxy resin as described in step 6) at 120°C for 2 hours, and then cure it at 150°C for 15 hours.

[0068] 8) Cool to room temperature to obtain type 3-3 graphene / epoxy resin composite material.

[0069] The thermal diffusivity of the 3-3 type graphene / epoxy resin composite material obtained in this embodiment is 42.407 mm. 2 Its specific heat is 1.167 J / gK, and its density is 1.114 g / cm³. 3 Its thermal conductivity is 55 W / mK.

[0070] Example 3

[0071] A 3 mg / mL aqueous solution of graphene oxide was mixed with ascorbic acid at a mass ratio of 1:4 and kept at 60 °C for 2 h to prepare a graphene hydrogel by chemical reduction.

[0072] 2) Soak the graphene hydrogel described in step 1) in deionized water for 3 hours to replace the original solvent and other impurities in the hydrogel. Repeat this soaking process three times.

[0073] 3) Freeze and solidify the graphene hydrogel after soaking in step 2) at -20°C;

[0074] 4) The graphene hydrogel solidified in step 3) was freeze-dried under vacuum for 72 hours to obtain a cylindrical graphene aerogel with a diameter of 19.57 mm and a height of 16.94 mm.

[0075] 5) The graphene aerogel described in step 4) was reduced at 1000℃ and 2500℃ for 1 hour each under argon protection;

[0076] 6) Cut off the top and bottom surfaces of the graphene aerogel reduced at high temperature in step 5) to expose the internal pore structure, then immerse the aerogel in a mixed solution of epoxy resin and curing agent, and vacuum at 90°C for 1 hour.

[0077] 7) Pre-cure the graphene aerogel fully impregnated with epoxy resin as described in step 6) at 130°C for 2 hours, and then cure it at 160°C for 15 hours.

[0078] 8) Cool to room temperature to obtain type 3-3 graphene / epoxy resin composite material.

[0079] The thermal diffusivity of the 3-3 type graphene / epoxy resin composite material obtained in this embodiment is 5.140 mm. 2 Its specific heat is 1.167 J / gK, and its density is 1.189 g / cm³. 3 The thermal conductivity is 7 W / mK. In this Example 3, the reduction temperature in step 5) is 2500℃, lower than the reduction temperature of 3000℃ in Examples 1 and 2. Therefore, the graphene structure was not fully restored as in Examples 1 and 2, resulting in a lower thermal diffusivity and consequently a lower thermal conductivity. However, the thermal conductivity in this Example 3 is still much higher than that of graphene / epoxy resin composites prepared by existing technologies.

[0080] Comparative Example 1

[0081] 1) Graphene hydrogel was prepared by chemical reduction method by mixing 3 mg / mL of graphene oxide aqueous solution with ascorbic acid at a mass ratio of 1:4 and keeping it at 55℃ for 2 h.

[0082] 2) Soak the graphene hydrogel described in step 1) in deionized water for 3 hours to replace the original solvent and other impurities in the hydrogel. Repeat this soaking process three times.

[0083] 3) Freeze and solidify the graphene hydrogel after soaking in step 2) at -20°C;

[0084] 4) The graphene hydrogel solidified in step 3) was freeze-dried under vacuum for 48 hours to obtain a cylindrical graphene aerogel with a diameter of 21.25 mm and a height of 17.29 mm.

[0085] 5) Cut off the top and bottom surfaces of the cylindrical graphene aerogel described in step 4) to expose the internal pore structure, then immerse the aerogel in a mixed solution of epoxy resin and curing agent, and vacuum it at 80°C for 1 hour.

[0086] 6) Pre-cure the graphene aerogel fully impregnated with epoxy resin as described in step 5) at 120°C for 2 hours, and then cure it at 150°C for 15 hours.

[0087] 7) Cool to room temperature to obtain type 3-3 graphene / epoxy resin composite material.

[0088] The thermal diffusivity of the 3-3 type graphene / epoxy resin composite material obtained in this embodiment is 0.126 mm. 2 Its specific heat is 1.167 J / gK, and its density is 1.206 g / cm³. 3 Its thermal conductivity is 0.18 W / mK.

[0089] While embodiments of the present invention have been provided herein, those skilled in the art should understand that modifications can be made to the embodiments without departing from the spirit of the invention. The above embodiments are merely exemplary and should not be construed as limiting the scope of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a high thermal conductivity type 3-3 graphene / epoxy resin composite material, comprising the following steps: 1) Graphene hydrogel was prepared by chemical reduction method by mixing 3 mg / mL of graphene oxide aqueous solution with ascorbic acid at a mass ratio of 1:4 and keeping it at 55℃ for 2 h. 2) Soak the graphene hydrogel described in step 1) in deionized water for 3 hours to replace the original solvent and other impurities in the hydrogel. Repeat this soaking process three times. 3) Freeze-solidify the graphene hydrogel obtained from soaking in step 2) at -20°C; 4) The graphene hydrogel solidified in step 3) was freeze-dried under vacuum for 48 h to obtain a cylindrical graphene aerogel with a diameter of 21.12 mm and a height of 17.35 mm. 5) The graphene aerogel obtained in step 4) was reduced at 1000℃ and 3000℃ for 1 h each under argon protection; 6) Cut off the top and bottom surfaces of the graphene aerogel reduced at high temperature in step 5) to expose the internal pore structure, and then immerse the aerogel in a mixed solution of epoxy resin and curing agent, and vacuum at 80°C for 1 h; wherein the curing agent is methyl hexahydrophthalic anhydride. 7) Pre-cur the graphene aerogel fully impregnated with epoxy resin described in step 6) at 120°C for 2 h, and then cure it at 150°C for 15 h. 8) Cool to room temperature to obtain a type 3-3 graphene / epoxy resin composite material, wherein the graphene content is 4.26 wt% and the thermal conductivity is 68 W / mK.

2. The high thermal conductivity 3-3 type graphene / epoxy resin composite material prepared by the preparation method according to claim 1.

3. The application of the 3-3 type graphene / epoxy resin composite material as an electronic packaging material according to claim 2.

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