Compressible high-thermal-conductivity graphene thermal interface material and preparation method thereof

Abstract

The invention provides a compressible high-thermal-conductivity graphene thermal interface material and a preparation method thereof. The preparation method comprises the following steps: preparing a graphene oxide film with low structural unit thickness by adopting a centrifugal spin-coating film casting method, performing limited thermal expansion delamination, compounding with polysiloxane, and performing directional lamination to obtain a highly-oriented graphene / organic silicon composite material. And applying shear stress after pressurizing and densifying along the normal direction of the graphene sheet layer, so that the graphene structure unit forms a continuous buckling structure which is high in density and easy to compress. The densification process promotes the interaction among delamination structure units, broadens a phonon transmission channel, inhibits phonon-boundary scattering, enhances the comprehensive heat-conducting property, plays a role in promoting stress transmission among graphene, and ensures the formation of a continuous buckling structure under shear stress. A continuous buckling structure and a relatively low structure unit thickness (llt in the graphene structure unit; and the compression modulus of the densified vertical graphene array is jointly reduced by means of high density, high thermal conductivity and high compressibility of an existing thermal interface material, and the method can be applied to the fields of new energy automobiles, high-power chips, aerospace electronic equipment and the like, and the problem that high density, high thermal conductivity and high compressibility of the existing thermal interface material are difficult to consider at the same time is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management materials, and in particular relates to a compressible high thermal conductivity graphene thermal interface material with a multi-level structure and a preparation method thereof. Background Art

[0002] With the rapid development of 5G communications, artificial intelligence, and high-computing chips, the power density of electronic components is increasing exponentially. Thermal management has become a bottleneck restricting the performance, reliability, and lifespan of electronic devices. Traditional thermal interface materials, such as silicone greases and thermally conductive silicone pads, typically have thermal conductivities less than 5 W / m·K, making them incapable of meeting the efficient heat transfer requirements of applications such as high-power chips, IGBT modules, and lasers. Although vertically oriented graphene arrays (PGAs) fabricated through oriented alignment techniques can fully leverage graphene's high in-plane thermal conductivity when composited with polymers, surpassing the upper limit of thermal conductivity of existing interface materials, these materials suffer from high compression modulus, poor compression performance and interface compatibility, and high interface thermal resistance, significantly limiting their interfacial heat dissipation capabilities and practical applications. Striking a balance between high bulk thermal conductivity and high array density with low interface thermal resistance and low compression modulus for PGAs remains a significant challenge. Summary of the Invention

[0003] The present invention addresses the problem of high bulk thermal conductivity and low interface thermal resistance / low compression modulus in the existing vertically oriented graphene thermal interface materials, and provides a multi-level structured compressible high thermal conductivity graphene thermal interface material and its preparation method. Graphene structural units with a structural unit thickness of 80 to 500 nm are prepared by means of a continuous centrifugal casting process and confined heat treatment. The graphene structural units are processed by a bidirectional overlapping compression process: (1) by applying normal stress, the graphene array is densified, the phonon transmission channel is widened, the phonon-boundary scattering is suppressed, and the bulk thermal conductivity of the material is improved; (2) based on the densification process (1), the stress transfer between graphene sheets is enhanced, and by applying tangential stress, the graphene structural units are formed into a folded configuration along the orientation direction, thereby significantly reducing the compression modulus while maintaining a high array density. The graphene structural unit is normally cut, and the parallel oriented cortex formed by the plastic deformation of the graphene sheet during the cutting process further reduces the contact thermal resistance between it and the electronic components. The resulting thermal interface material has high density, high thermal conductivity, high compressibility and low thermal resistance.

[0004] The present invention adopts the following technical solution: a compressible high-thermal-conductivity graphene thermal interface material, which has a skin-core structure as a whole, wherein the skin layer is composed of planar stacked graphene sheets, and the core layer is composed of a graphene thermal conductive unit with a continuous buckling structure and an elastic polymer material, wherein the elastic polymer material wraps around the outside of the graphene thermal conductive unit and integrates it into one, and both sides of the graphene thermal conductive unit are connected to the graphene sheets in the skin layer as one; the graphene thermal conductive unit is composed of graphene structural units with a continuous buckling structure, and the graphene structural units are formed by stacking graphene sheets with a thickness of 80 to 500 nm. The structural units are bonded by van der Waals forces and are oriented in a direction perpendicular to the surface of the thermal interface material; and the overall thickness of the thermal interface material is 0.1 to 10 mm. The characteristics of this structure are: (1) the thickness of the graphene stack in the structural unit is 80~500 nm, which not only provides an effective heat conduction channel but also avoids the problem of difficulty in compression caused by high stacking; (2) a geometric folding configuration is introduced along the vertical direction, and its compression modulus is further reduced by using the geometric effect; (3) based on the synergistic effect of the multi-level structure, the technical bottleneck of the high density, high thermal conductivity and high compressibility of the vertically oriented graphene thermal interface material is broken through, and the overall density is increased by 50~100% under the same compression modulus compared with the conventional vertically oriented graphene thermal interface material; (4) the parallel oriented graphene cortex exhibits excellent interface bonding and deformation filling ability, which reduces the interface thermal resistance and comprehensively improves the thermal conductivity effect.

[0005] Furthermore, the skin layer accounts for 0.5-5% of the total material thickness. If the skin layer is too thick, heat cannot be quickly transferred vertically, resulting in a decrease in vertical thermal conductivity; if the skin layer is too thin, effective interface bonding and gap filling cannot be achieved, resulting in an increase in interfacial thermal resistance.

[0006] Furthermore, the continuous buckling structure is wavy or sawtooth-shaped, with a wave height of 30 to 80 μm and a wave height to wavelength ratio of 0.2 to 1. The wave height and wavelength reflect the degree of buckling of the entire graphene structural unit. The larger the wave height and the larger the wave height to wavelength ratio, the closer the overall material is to a horizontal heat dissipation material. If the wave height is too small and the wave height to wavelength ratio is smaller, the spring-like deformation effect cannot be provided, resulting in a decrease in the compression rate.

[0007] Furthermore, the graphene thermal conductive unit contains 10 to 300 layers of graphene structural units. The number of structural units significantly affects the processing difficulty. Too few structural units will require more thermal conductive units to assemble the thermal conductive units layer by layer, increasing the processing difficulty. Too many structural units will increase the difficulty of preparing the GO / PVA composite film and make it difficult to achieve stable production.

[0008] Furthermore, the overall density of the thermal interface material is between 0.62 and 1.21 g / cm 3 .

[0009] Furthermore, the elastic polymer material is formed by in-situ polymerization of vinyl silicone oil and hydrogen-containing silicone oil, and has a Shore hardness of 5 to 30 degrees.

[0010] The graphene mass fraction in the obtained compressible high thermal conductivity graphene thermal interface material is greater than 75%, and the longitudinal intrinsic thermal conductivity is 49.1~99.1 W m -1 K -1 ; The longitudinal equivalent thermal conductivity at 50 psi is 19.6~63.3 W m -1 K -1 , compression rate is 25.7~55.3%, tensile strength>1 MPa, and Shore hardness range is 30~60 degrees.

[0011] A method for preparing a compressible high thermal conductivity graphene thermal interface material, characterized by comprising the following steps: (1) Preparation of GO / PVA composite film by roller centrifugal spin coating: Graphene oxide (GO) solution with a concentration of 5-10 mg / mL and polyvinyl alcohol (PVA) solution with a concentration of 1-5 mg / mL were alternately dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of 0.15-1 μm and a PVA layer with a thickness of 5-10 nm were continuously spin-coated on the inner wall of the roller. This was repeated many times to obtain a GO / PVA composite film with a thickness of 10-100 μm. (2) Preparation of graphene thermal conductive unit by confined heat treatment: The film obtained in step (1) is placed between graphite plates with a slit height of 50-500 μm for confined thermal reduction to ensure that GO maintains a high degree of orientation when it is heated to expand and delaminate; high-purity argon is used as a protective gas for thermal reduction, and the temperature is set at 5-20 °C from room temperature. o C / min to 1000 o C, maintain for 10~120 min, then o C / min and the temperature was raised to 2800~3050 o C, maintain for 1 to 3 hours; (3) Assembling the graphene thermal conductive unit layer by layer: immerse the graphene thermal conductive unit obtained in step (2) into a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, with the mass ratio of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor being 1:3~5:0.0001~0.001:0.0001~0.0005. Vacuum immersion is performed for 0.5~2 h and then taken out. The graphene thermal conductive unit is then stacked layer by layer while applying pressure along the stacking direction and maintaining it for 0.5~4 h to obtain a density of 0.39~0.84 g / cm 3 Graphene composite block; (4) forming a continuous buckling structure: placing the block obtained in step (3) in a limiting mold, and while maintaining the stacking thickness of the heat conducting unit unchanged, applying pressure in a direction parallel to the heat conducting unit and compressing it by 20-50%, thereby forming a continuous buckling structure of the graphene structural unit; (5) Preparation of compressible high thermal conductivity graphene thermal interface material: The block obtained in step (4) is cut in a direction perpendicular to the orientation direction of the graphene structural unit, the cutting rate is 0.1~5 mm / min, and the cutting spacing is 100 μm~10 mm to obtain a compressible high thermal conductivity graphene thermal interface material.

[0012] Furthermore, the molecular weight of the polyvinyl alcohol in step (1) is between 8000 and 12000. If the molecular weight of the polyvinyl alcohol is too large, a carbon structure will be generated during thermal reduction, resulting in a decrease in the pores between the graphene structural units, making it difficult to form a continuous buckling structure during subsequent compression, and reducing the overall thermal conductivity.

[0013] Furthermore, the inhibitor in step (3) is one of the benzoquinone and hydroquinone free radical inhibitors.

[0014] Furthermore, the slitting method in step (5) is one of ultrasonic knife cutting, laser cutting, and wire cutting. During the cutting process, the graphene sheets on the surface undergo plastic deformation under the action of shear force and are arranged in a direction parallel to the material surface, forming a cortical structure.

[0015] The obtained compressible high thermal conductivity graphene thermal interface material has a density range of 0.62~1.21 g / cm 3 , the thickness range is 0.1~10 mm, and the longitudinal intrinsic thermal conductivity is 49.1~99.1 W m -1 K -1 , applicable temperature range -45~250 o C; the compression ratio ranges from 10.3% to 36.5% at a pressure of 10 psi, and the longitudinal equivalent thermal conductivity ranges from 9.7 to 40.3 W m -1 K -1 The compression ratio at 50 psi is in the range of 25.7% to 58.7%, and the longitudinal equivalent thermal conductivity is in the range of 19.6 to 63.3 W m -1 K -1 , thermal impedance range is 0.026 K cm 2 / W~0.93 K cm 2 W -1 .

[0016] The longitudinal intrinsic thermal conductivity is measured using the laser flash method and reflects the thermal conductivity of the material itself, ignoring the contact thermal resistance in actual applications. The longitudinal equivalent thermal conductivity is measured using the steady-state method, referring to ASTM D5470 and using the Ruiling LW 9389 tester. This examines the overall thermal resistance and thermal conductivity of the material at various pressures, taking into account the contact thermal resistance.

[0017] The beneficial effects of the present invention are: (1) Through continuous centrifugal casting and confined heat treatment, the structural unit thickness, thermal expansion ratio, and lamellae orientation of the graphene foam film are precisely controlled. Compared with the graphene foam film obtained by conventional GO solution coating and thermal expansion under non-confined conditions, the graphene foam film prepared by the method of the present invention has a higher lamellae orientation and a thinner structural unit thickness (80-500 nm), thereby giving it higher thermal conductivity and better flexibility along the orientation direction. During the confined heat treatment process, the gas generated by graphene oxide and polyvinyl alcohol between the structural unit layers is discharged through the confined channel, and the graphene still has a high orientation and packing density.

[0018] (2) Through the bidirectional overlapping compression process, while increasing the stacking density of the structural units, "widening" the phonon transmission channel, and improving the thermal conductivity of the material itself, a folding configuration is introduced along the graphene orientation direction, so that the compression mode of the graphene array is transformed from the "collapse" of the body to "geometric folding", obtaining an effect similar to spring compression, thereby achieving the purpose of releasing stress and reducing the modulus, overcoming the problem of the difficulty in balancing the high density / high body thermal conductivity and high strain / low contact thermal resistance of traditional vertically oriented graphene thermal interface materials.

[0019] (3) Introducing a horizontally oriented structure on the surface of the graphene thermal interface material to reduce the interfacial thermal resistance. The parallel oriented cortex formed by the plastic deformation of the graphene sheets during the slitting process has excellent interfacial bonding and deformation filling capabilities, further reducing the contact thermal resistance between it and electronic components and improving the overall thermal conductivity.

[0020] (4) The graphene thermal interface material prepared based on the multi-level structure design has the advantages of high bulk thermal conductivity, high compressibility and low contact thermal resistance. While maintaining the same compression modulus as the traditional vertically oriented graphene thermal interface material, the density of the graphene array can be greatly increased, thereby significantly improving the material's comprehensive thermal conductivity without increasing the contact thermal resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the cross-sectional structure of the compressible high thermal conductivity graphene thermal interface material, where 1 is the skin layer, 2 is the core layer, and 3 is the graphene thermal conductive unit.

[0022] Figure 2Schematic diagram of a graphene thermal conductive unit, where 4 is a graphene structural unit and 5 is a graphene sheet.

[0023] Figure 3 This is a scanning electron microscope photograph of the graphene thermal interface material of Example 1.

[0024] Figure 4 This is a high-resolution transmission electron microscope photograph of the graphene thermal interface material structural unit of Example 1.

[0025] Figure 5 This is the stress-strain curve of the graphene thermal interface material of Example 1.

[0026] Figure 6 This is a high-resolution transmission electron microscope photograph of the graphene thermal interface material structural unit of Example 2.

[0027] Figure 7 This is the stress-strain curve of the graphene thermal interface material of Example 2.

[0028] Figure 8 This is a scanning electron microscope photograph of the graphene thermal interface material of Comparative Example 1.

[0029] Figure 9 This is the stress-strain curve of the graphene thermal interface material of Comparative Example 1. DETAILED DESCRIPTION

[0030] The present invention is described in detail below through examples. These examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential changes and adjustments based on the contents of the above invention, which all fall within the scope of protection of the present invention.

[0031] Example 1: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0032] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2o C / min to 3050 o C, and maintained for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit was obtained.

[0033] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 hour to obtain a density of 0.52 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0034] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0035] (5) The block obtained in step (4) was cut by ultrasonic knife, with the cutting direction perpendicular to the orientation direction of the graphene structural unit, the cutting rate was 0.1 mm / min, and the cutting spacing was 300 μm.

[0036] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.02 g cm -3 Its microstructure is as follows Figure 3 As shown, the core graphene thermal conductive units are vertically oriented over a long range and alternately folded along the thickness direction, forming a continuous buckling structure (left image). The continuous buckling structure is wavy, with a wave height of 80 μm and a wave height to wavelength ratio of 1; while the cortical graphene structural units are parallel oriented (right image), and the cortex accounts for 0.5% of the total thickness of the material. Using high-resolution transmission electron microscopy, it can be seen that the internal sheets of the graphene structural units are highly oriented and about 80 nm thick ( Figure 4 The vertical intrinsic thermal conductivity was measured by transient laser flash method to be 79.2 W m -1 K -1 The steady-state method was used to measure the compressibility at 10 psi to be 30.8%, and the equivalent thermal conductivity to be 29.4 W m -1 K -1 , the compression rate is 53.9% at 50 psi, and the equivalent thermal conductivity is 46.2 W m -1 K -1 , thermal impedance is 0.032 Kcm 2 W -1 The stress-strain curve of the thermal interface material was characterized by a universal material testing machine. Figure 5shown.

[0037] Example 2: (1) Using the roller centrifugal spin coating method, a 10 mg / mL graphene oxide (GO) solution and a 5 mg / mL polyvinyl alcohol (PVA) solution were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a 300 nm thick GO layer and a 10 nm thick PVA layer were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 100 μm.

[0038] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 500 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0039] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 2 hours. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 hour to obtain a density of 0.53 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0040] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0041] (5) The block obtained in step (4) was cut by ultrasonic knife, with the cutting direction perpendicular to the orientation direction of the graphene structural unit, the cutting rate was 0.1 mm / min, and the cutting spacing was 300 μm.

[0042] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.07 g cm -3The core graphene structural unit has a continuous buckling structure, which is wavy with a wave height of 50 μm and a ratio of wave height to wavelength of 1. Using high-resolution transmission electron microscopy, it can be seen that the internal sheets of the graphene structural unit are highly oriented and have a thickness of about 150 nm ( Figure 6 ), the skin accounts for 5% of the total thickness of the material; the out-of-plane thermal conductivity measured by transient laser flash method is 88.3 W m -1 K -1 The steady-state method was used to measure the compressibility at 10 psi to be 18.2%, and the equivalent thermal conductivity to be 24.3 W m -1 K -1 , the compression rate is 43.4% at 50 psi, and the equivalent thermal conductivity is 37.6 W m -1 K -1 , thermal impedance is 0.043 K cm 2 W -1 The stress-strain curve of the thermal interface material was characterized by a universal material testing machine. Figure 7 shown.

[0043] Example 3: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 7.5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 2.5 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of 300 nm and a PVA layer with a thickness of 7.5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 50 μm.

[0044] (2) The GO / PVA composite film obtained in step (1) was placed between graphite plates with a slit height of 500 μm for confined thermal reduction. The thermal reduction process was as follows: high-purity argon was used as the protective gas, and the temperature was set at 20 o C / min to 1000 o C, maintained for 120 min, then at 5 o C / min to 3050 o C, and kept for 1 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0045] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 0.5 h. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 h to obtain a density of 0.51 g / cm 3The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:5:0.0001:0.0001, and the inhibitor is hydroquinone.

[0046] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0047] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 5 mm / min, and the cutting spacing being 300 μm.

[0048] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.05 g cm -3 The core graphene structural unit has a continuous buckling structure, which is wavy, with a wave height of 80 μm, a wave height to wavelength ratio of 1, and a thickness of about 150 nm. The skin layer is composed of planar stacked graphene sheets, accounting for 1% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 76.1 W m -1 K -1 The compressibility was 22.8% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 19.2 W m -1 K -1 , the compression rate is 46.1% at 50 psi, and the equivalent thermal conductivity is 33.5 W m -1 K -1 , thermal impedance is 0.048 K cm 2 W -1 .

[0049] Example 4: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of 1 μm and a PVA layer with a thickness of 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 10,000 and 12,000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 25 μm.

[0050] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 500 μm for restricted thermal reduction to ensure that the GO maintains a high degree of orientation when it is thermally expanded and delaminated. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 10 oC / min to 1000 o C, maintained for 10 min, then at 2.5 o C / min to 2800 o C, and kept for 1.5 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0051] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1.5 h. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 0.8 h to obtain a density of 0.5 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is in the range of 1:3-5:0.0001:0.0005, and the inhibitor is p-benzoquinone.

[0052] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0053] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction perpendicular to the orientation direction of the graphene structural unit, the cutting rate was 2 mm / min, and the cutting spacing was 300 μm.

[0054] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.04 g cm -3 The core graphene structural unit has a continuous buckling structure with a thickness of about 500 nm. The continuous buckling structure is wavy with a wave height of 80 μm and a ratio of wave height to wavelength of 1. The skin layer is composed of planar stacked graphene sheets, accounting for 1% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 68.7 W m -1 K -1 The compressibility was 12.2% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 12.2 W m -1 K -1 , the compression rate is 28.2% at 50 psi, and the equivalent thermal conductivity is 23.8 W m -1 K -1 , thermal impedance is 0.093 K cm 2 W -1 .

[0055] Example 5: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 10,000 and 12,000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0056] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0057] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure in the stacking direction and maintaining it for 4 hours to obtain a density of 0.84 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0058] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 20%, so that the graphene structural unit forms a continuous buckling structure.

[0059] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.2 mm / min, and the cutting spacing being 300 μm.

[0060] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.01 g cm -3The core graphene structural unit has a continuous buckling structure with a thickness of about 80 nm. The continuous buckling structure is wavy with a wave height of 0.2 μm and a ratio of wave height to wavelength of 1. The skin layer is composed of planar stacked graphene sheets, accounting for 2% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 99.1 W m -1 K -1 The compressibility was 10.3% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 13.9 W m -1 K -1 , the compression rate is 25.7% at 50 psi, and the equivalent thermal conductivity is 27.7 W m -1 K -1 , thermal impedance is 0.081 K cm 2 W -1 .

[0061] Example 6: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0062] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0063] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 4 hours to obtain a density of 0.83 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0064] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 30%, so that the graphene structural unit forms a continuous buckling structure.

[0065] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.1 mm / min, and the cutting spacing being 300 μm.

[0066] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.21 g cm -3 The core graphene structural unit has a continuous buckling structure with a thickness of about 80 nm. The continuous buckling structure is wavy with a wave height of 60 μm and a wave height to wavelength ratio of 0.5. The skin layer is composed of planar stacked graphene sheets, accounting for 1% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 91.9 W m -1 K -1 The compressibility was 12.7% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 12.8 W m -1 K -1 , the compression rate is 30.1% at 50 psi, and the equivalent thermal conductivity is 27.2 W m -1 K -1 , thermal impedance is 0.078 K cm 2 W -1 .

[0067] Example 7: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 500 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 20 μm.

[0068] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 100 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 oC, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0069] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 0.5 hours to obtain a density of 0.39 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0070] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 30%, so that the graphene structural unit forms a continuous buckling structure.

[0071] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.1 mm / min, and the cutting spacing being 300 μm.

[0072] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 0.62 g cm -3 The core graphene structural unit has a continuous buckling structure with a thickness of about 250 nm. The continuous buckling structure is wavy with a wave height of 60 μm and a wave height to wavelength ratio of 0.5. The skin layer is composed of planar stacked graphene sheets, accounting for 1% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 49.1 W m -1 K -1 The steady-state method was used to measure the compressibility at 10 psi to be 36.5%, and the equivalent thermal conductivity to be 11.7 W m -1 K -1 , the compression rate is 55.3% at 50 psi, and the equivalent thermal conductivity is 26.1 W m -1 K -1 , thermal impedance is 0.053 K cm 2 W -1 .

[0073] Example 8: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0074] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0075] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 0.5 h. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure in the stacking direction and maintaining it for 1.5 h to obtain a density of 0.49 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0076] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0077] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.1 mm / min, and the cutting spacing being 100 μm.

[0078] The obtained graphene thermal interface material has a thickness of 100 μm and a density of 0.98 g cm -3The core graphene structural unit has a continuous buckling structure with a thickness of about 80 nm. The continuous buckling structure is wavy with a wave height of 80 μm and a ratio of wave height to wavelength of 1. The skin layer is composed of planar stacked graphene sheets, accounting for 1% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 80.3 W m -1 K -1 The compressibility was 34.5% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 9.7 W m -1 K -1 , the compression rate is 58.7% at 50 psi, and the equivalent thermal conductivity is 19.6 W m -1 K -1 , thermal impedance is 0.026 K cm 2 W -1 .

[0079] Example 9: (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0080] (2) The GO / PVA composite film obtained in step (1) is placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0081] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 hour to obtain a density of 0.47 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0082] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0083] (5) The block obtained in step (4) was cut by ultrasonic knife, with the cutting direction perpendicular to the orientation direction of the graphene structural unit, the cutting rate was 0.1 mm / min, and the cutting spacing was 10 mm.

[0084] The obtained graphene thermal interface material has a thickness of 10 mm and a density of 1.03 g cm -3 The core graphene structural unit has a continuous buckling structure with a thickness of about 80 nm. The continuous buckling structure is wavy with a wave height of 80 μm and a ratio of wave height to wavelength of 1. The skin layer is composed of planar stacked graphene sheets, accounting for 3% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 74.2 W m -1 K -1 The compressibility was 23.7% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 40.3 W m -1 K -1 , the compression rate is 36.8% at 50 psi, and the equivalent thermal conductivity is 63.3 W m -1 K -1 , thermal impedance is 0.93 K cm 2 W -1 .

[0085] Comparative Example 1: No pressure is applied parallel to the direction of the heat transfer unit, and no continuous buckling structure is generated (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0086] (2) The GO / PVA composite film was placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process was as follows: high-purity argon was used as the protective gas, and the temperature was set at 5 o C / min to 1000 o C, maintain for 60 min, then o C / min to 3050 oC, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0087] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 hour to obtain a density of 1.03 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0088] (4) The graphene block obtained in step (3) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.1 mm / min, and the cutting spacing being 300 μm.

[0089] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.03 g cm -3 , the core graphene structural unit does not have a continuous buckling structure ( Figure 8 The out-of-plane thermal conductivity of the material was 114.8 W m-2, which was measured by transient laser flash method. -1 K -1 The compressibility was 5.6% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 9.9 W m -1 K -1 , the compression rate is 9.8% at 50 psi, and the equivalent thermal conductivity is 15.6 W m -1 K -1 , thermal impedance is 0.18 K cm 2 W -1 The stress-strain curve of the thermal interface material was characterized by a universal material testing machine. Figure 9 shown.

[0090] Comparative Example 2: Structural unit is too thick (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 10 μm and a PVA layer with a thickness of about 500 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 100 μm.

[0091] (2) The GO / PVA composite film was placed between graphite plates with a slit height of 500 μm for confined thermal reduction. The thermal reduction process was as follows: high-purity argon was used as the protective gas, and the temperature was set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0092] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 hour to obtain a density of 0.48 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0093] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0094] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.1 mm / min, and the cutting spacing being 300 μm.

[0095] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 1.08 g cm -3 The core graphene structural unit has a continuous buckling structure, but the thickness of the structural unit is about 2.5 μm. The continuous buckling structure is wavy, with a wave height of 30 μm and a ratio of wave height to wavelength of 0.1. The skin layer is composed of planar stacked graphene sheets, which accounts for 1% of the total thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 83.5 W m -1 K -1 The compressibility was 6.8% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 11.1 W m -1 K -1 , the compression rate is 12.4% at 50 psi, and the equivalent thermal conductivity is 16.4 Wm -1 K -1 , thermal impedance is 0.15 K cm 2 W -1.

[0096] Comparative Example 3: The stacking density of graphene structural units is too low (1) Using the roller centrifugal spin coating method, a graphene oxide (GO) solution with a concentration of 5 mg / mL and a polyvinyl alcohol (PVA) solution with a concentration of 1 mg / mL were successively dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of about 150 nm and a PVA layer with a thickness of about 5 nm were continuously spin-coated on the inner wall of the roller. The molecular weight of the polyvinyl alcohol was between 8000 and 10000. The above steps were repeated many times to obtain a GO / PVA composite film with a thickness of 10 μm.

[0097] (2) The film is placed between graphite plates with a slit height of 50 μm for confined thermal reduction. The thermal reduction process is as follows: high-purity argon is used as the protective gas, and the temperature is set at 5 o C / min to 1000 o C, maintained for 60 min, then at 2 o C / min to 3050 o C, and kept for 3 h. During the thermal reduction process, PVA was thermally decomposed, and finally a graphene thermal conductive unit with controllable thickness and high orientation was obtained.

[0098] (3) The graphene thermal conductive unit obtained in step (2) was immersed in a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, and was taken out after vacuum immersion for 1 hour. Then, the graphene thermal conductive unit was stacked layer by layer while applying pressure along the stacking direction and maintaining it for 1 hour to obtain a density of 0.21 g / cm 3 The ratio of the vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor is 1:3:0.001:0.0001, and the inhibitor is p-benzoquinone.

[0099] (4) The block obtained in step (3) is placed in a limiting mold. On the basis of keeping the stacking thickness of the heat conducting unit unchanged, pressure is applied in a direction parallel to the heat conducting unit and the unit is compressed by 50%, so that the graphene structural unit forms a continuous buckling structure.

[0100] (5) The block obtained in step (4) was cut by wire cutting, with the cutting direction being perpendicular to the orientation direction of the graphene structural unit, the cutting rate being 0.1 mm / min, and the cutting spacing being 300 μm.

[0101] The obtained graphene thermal interface material has a thickness of 300 μm and a density of 0.43 g cm -3Since the density of the graphene composite block compressed in step (3) is too low, the force transmission cannot be effectively realized in the compression of step (4), resulting in the graphene structural unit not having a continuous buckling structure. The skin layer is composed of planar stacked graphene sheets, and the skin layer accounts for 1% of the overall thickness of the material. The out-of-plane thermal conductivity measured by the transient laser flash method is 50.6 W m -1 K -1 The compressibility was 8.8% at 10 psi using the steady-state method, and the equivalent thermal conductivity was 7.6 W m -1 K -1 , the compression rate is 17.2% at 50 psi, and the equivalent thermal conductivity is 12.6W m -1 K -1 , thermal impedance is 0.19 K cm 2 W -1 .

[0102] Table 1 Parameters and performance comparison of examples and comparative examples

Claims

1. A compressible high thermal conductivity graphene thermal interface material, characterized in that: The overall structure is a skin-core structure. The skin layer is composed of planar stacked graphene sheets, and the core layer is composed of a graphene thermal conductive unit with a continuous buckling structure and an elastic polymer material. The elastic polymer material wraps the outside of the graphene thermal conductive unit and combines it into one. The two sides of the graphene thermal conductive unit are connected to the graphene sheets in the skin layer as a whole; the graphene thermal conductive unit is composed of a graphene structural unit with a continuous buckling structure. The graphene structural unit is composed of stacked graphene sheets with a thickness of 80~500 nm. The structural units are bonded by van der Waals forces and oriented in a direction perpendicular to the surface of the thermal interface material; the overall thickness of the thermal interface material is 0.1~10 mm.

2. The thermal interface material according to claim 1, wherein The skin layer accounts for 0.5-5% of the overall thickness of the material.

3. The thermal interface material according to claim 1 or 2, characterized in that: The continuous buckling structure is wavy or sawtooth-shaped, with a wave height of 30 to 80 μm and a ratio of wave height to wavelength of 0.2 to 1.

4. The thermal interface material according to claim 1, wherein The graphene heat conducting unit comprises 10 to 300 layers of graphene structural units.

5. The thermal interface material according to claim 1, wherein: The overall density of the thermal interface material is 0.62~1.21 g / cm 3 .

6. The thermal interface material according to claim 1, wherein The elastic polymer material is formed by in-situ polymerization of vinyl silicone oil and hydrogen-containing silicone oil, and has a Shore hardness of 5 to 30 degrees.

7. A method for preparing a compressible high thermal conductivity graphene thermal interface material, characterized in that: The following steps are involved: (1) Preparation of GO / PVA composite film by roller centrifugal spin coating: Graphene oxide (GO) solution with a concentration of 5-10 mg / mL and polyvinyl alcohol (PVA) solution with a concentration of 1-5 mg / mL were alternately dripped into a horizontally arranged centrifugal roller, so that under the action of centrifugal force, a GO layer with a thickness of 0.15-1 μm and a PVA layer with a thickness of 5-10 nm were continuously spin-coated on the inner wall of the roller. This was repeated many times to obtain a GO / PVA composite film with a thickness of 10-100 μm. (2) Preparation of graphene thermal conductive unit by confined heat treatment: The film obtained in step (1) is placed between graphite plates with a slit height of 50-500 μm for confined thermal reduction to ensure that the GO maintains a high degree of orientation when it expands and delaminates due to heat; Thermal reduction uses high-purity argon as protective gas, and the temperature is adjusted from room temperature to 5~20 o C / min to 1000 o C, maintain for 10~120 min, then o C / min and the temperature was raised to 2800~3050 o C, maintain for 1 to 3 hours; (3) Assembling the graphene thermal conductive unit layer by layer: immerse the graphene thermal conductive unit obtained in step (2) into a mixed solution consisting of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor, with the mass ratio of vinyl silicone oil, hydrogenated silicone oil, platinum catalyst and inhibitor being 1:3~5:0.0001~0.001:0.0001~0.0005. Vacuum immersion is performed for 0.5~2 h and then taken out. The graphene thermal conductive unit is then stacked layer by layer while applying pressure along the stacking direction and maintaining it for 0.5~4 h to obtain a density of 0.39~0.84 g / cm 3 Graphene composite block; (4) forming a continuous buckling structure: placing the block obtained in step (3) in a limiting mold, and while maintaining the stacking thickness of the heat conducting unit unchanged, applying pressure in a direction parallel to the heat conducting unit and compressing it by 20-50%, thereby forming a continuous buckling structure of the graphene structural unit; (5) Preparation of compressible high thermal conductivity graphene thermal interface material: The block obtained in step (4) is cut in a direction perpendicular to the orientation direction of the graphene structural unit, the cutting rate is 0.1~5 mm / min, and the cutting spacing is 100 μm~10 mm to obtain a compressible high thermal conductivity graphene thermal interface material.

8. The preparation method according to claim 7, characterized in that The molecular weight of the polyvinyl alcohol described in step (1) is between 8000 and 12000.

9. The preparation method according to claim 7, characterized in that The inhibitor described in step (3) is one of the benzoquinone and hydroquinone free radical inhibitors.

10. The preparation method according to claim 7, characterized in that The cutting method described in step (5) is one of ultrasonic knife cutting, laser cutting and wire cutting.

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