Multi-layer composite graphite cooling fin

Abstract

The invention relates to the technical field of graphite heat dissipation materials, and discloses a multi-layer composite graphite cooling fin which comprises a heat conduction and heat absorption layer, a heat diffusion layer, a heat management layer, a far infrared radiation heat dissipation layer and a heat dissipation substrate which are stacked in sequence, and the heat conduction and heat absorption layer comprises a graphene-diamond composite film and a nano-silver coating; the thermal diffusion layer is graphite foam with gradient density and contains a carbon nanotube reinforcing material; the thermal management layer comprises a graphene enhanced phase change material and a thermoelectric conversion module; the far infrared radiation heat dissipation layer comprises an infrared radiation coating and a microgroove structure substrate. The multi-layer composite graphite structure is adopted, the graphene-diamond composite film, the gradient density graphite foam and the heat diffusion layer are combined, ultrahigh heat conductivity and temperature uniformity are achieved, the transverse transmission capacity of heat is greatly improved, meanwhile, by optimizing a heat channel, the overall heat dissipation efficiency is improved, and the problems of hot spot accumulation and heat flow bottleneck are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite heat dissipation materials, and particularly to a multi-layer composite graphite heat sink. Background Art

[0002] With the continuous improvement of the power density of electronic devices, the research on high-efficiency heat dissipation materials has become an important direction in the fields of the electronics industry, data centers, and new energy vehicles. Traditional heat sinks mainly use metal materials (such as aluminum and copper), which rely on the high thermal conductivity of the materials themselves to transfer heat from high-heat-generation areas to the surface of the heat sink and dissipate it into the environment through convection or radiation. However, with the increase in chip integration and power consumption, metal heat sinks gradually show limitations in terms of thermal conductivity, heat diffusion, and weight control.

[0003] The main problem of metal heat sinks lies in the limited heat flow transmission. Although the in-plane thermal conductivity of materials such as aluminum and copper is relatively high, due to the isotropic thermal conductivity characteristics, the heat diffusion ability in a specific direction is limited, resulting in serious local hot spot problems. Especially in miniaturized and high-density applications such as smartphones, laptops, and 5G base stations, it is difficult for metal materials to quickly and evenly disperse heat, easily forming local overheating, which affects the stability of the device. In addition, in order to improve the thermal conductivity efficiency, traditional solutions usually adopt thickening the metal heat sink or increasing the heat dissipation fins, but this will lead to an increase in the overall mass of the device, which is not conducive to lightweight design.

[0004] In recent years, carbon-based heat sinks (such as graphite sheets and graphene heat dissipation films) have received attention due to their ultra-high in-plane thermal conductivity. Natural graphite and synthetic graphite have excellent anisotropic thermal conductivity characteristics, and their in-plane thermal conductivity is much higher than that of metal materials, and they are widely used in high-end electronic devices. However, traditional graphite sheets have low mechanical strength, are easily broken during the processing process, and are easily oxidized in high-temperature environments, resulting in problems with lifespan and stability in high-power density applications (such as servers and automotive power batteries). In addition, the out-of-plane thermal conductivity of graphite materials is relatively low, and the heat transfer ability in the vertical direction is limited, resulting in difficulty in effectively transmitting heat to the heat dissipation surface and affecting the overall heat dissipation efficiency. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a multi-layer composite graphite heat sink to solve the problems.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A multi-layer composite graphite heat sink includes a heat-conducting and heat-absorbing layer, a heat diffusion layer, a heat management layer, a far-infrared radiation heat dissipation layer, and a heat dissipation base that are stacked in sequence. The heat-conducting and heat-absorbing layer includes a graphene-diamond composite film and a nano-silver coating; The thermal diffusion layer is a gradient density graphite foam containing a carbon nanotube reinforcement material; The thermal management layer includes a graphene-reinforced phase change material and a thermoelectric conversion module; The far-infrared radiation heat dissipation layer includes an infrared radiation coating and a micro-groove structure substrate; The heat dissipation substrate is composed of a copper-aluminum composite micro-porous structure and a graphene-reinforced aluminum alloy.

[0007] Preferably, the material composition and weight percentage of the heat conduction and heat absorption layer are: graphene-diamond composite film: 65-85 wt%; nano-silver coating: 5-15 wt%; silica / nitride boron composite enhancer: 5-10 wt%.

[0008] Preferably, the material composition and weight percentage of the thermal diffusion layer are: gradient density graphite foam: 60-80 wt%; carbon nanotube reinforcement material: 5-15 wt%; graphene-based filler: 10-20 wt%.

[0009] Preferably, the material composition and weight percentage of the thermal management layer are: graphene-reinforced phase change material: 40-60 wt%; thermoelectric conversion material: 30-50 wt%; carbon nanotube composite support: 10-20 wt%.

[0010] Preferably, the material composition and weight percentage of the far-infrared radiation heat dissipation layer are: infrared radiation coating: 50-70 wt%; micro-groove structure substrate: 30-50 wt%.

[0011] Preferably, the material composition and weight percentage of the heat dissipation substrate are: copper-aluminum composite micro-porous structure: 50-70 wt%; graphene-reinforced aluminum alloy: 30-50 wt%.

[0012] Preferably, the thickness ranges of the heat conduction and heat absorption layer, the thermal diffusion layer, the thermal management layer, the far-infrared radiation heat dissipation layer, and the heat dissipation substrate are: heat conduction and heat absorption layer: 0.05-0.2 mm; thermal diffusion layer: 0.3-0.7 mm; thermal management layer: 0.5-1 mm; far-infrared radiation heat dissipation layer: 0.2-0.5 mm; heat dissipation substrate: 1-2 mm.

[0013] Preferably, the heat conduction and heat absorption layer is prepared by chemical vapor deposition, the chemical vapor deposition growth temperature is 850-1100 °C, and the deposition time is 30-90 min.

[0014] Preferably, the infrared radiation coating of the far-infrared radiation heat dissipation layer is deposited by the sol-gel method, and the coating thickness is 5-20 μm.

[0015] Preferably, the heat dissipation substrate is prepared by metal powder metallurgy, and the sintering temperature is 600-900 °C.

[0016] The present invention provides a multi-layer composite graphite heat sink, which has the following beneficial effects: 1. The present invention adopts a multi-layer composite graphite structure, combines a graphene-diamond composite film, a gradient density graphite foam and a thermal diffusion layer, achieving ultra-high thermal conductivity and temperature uniformity. Compared with traditional metal heat dissipation solutions (such as aluminum and copper), the lateral heat transfer ability is greatly improved. In the prior art, due to the grain boundary scattering effect of metal materials, the thermal conductivity is limited and local hot spots are easily formed. The present invention optimizes the heat channels, improves the overall heat dissipation efficiency, and solves the problems of hot spot accumulation and heat flow bottleneck.

[0017] 2. The present invention introduces a thermal management layer enhanced by a phase change material. Through adjustable phase change temperature setting, the heat sink can provide adaptive thermal buffering ability for different application scenarios (such as smart phones, servers, electric vehicles). Traditional heat dissipation solutions are difficult to quickly respond to short-term temperature changes, resulting in sudden temperature rise or large fluctuations in the device temperature. This technical solution optimizes the thermal buffering mechanism, effectively reduces the temperature peak during high-power operation, and solves the instability problem caused by short-term high heat load.

[0018] 3. The present invention adopts a far-infrared radiation heat dissipation layer, combined with the optimization of the micro-groove structure, enabling heat to be dissipated not only through heat conduction and convection, but also actively releasing heat energy through the far-infrared radiation mechanism. In existing air-cooled or liquid-cooled heat dissipation methods, in a limited space (such as a server chassis, inside a smart phone), the heat dissipation efficiency is limited and it is difficult to dissipate heat evenly. However, this technical solution improves the heat dissipation efficiency of the heat sink in a low-airflow environment by enhancing the infrared radiation ability, and solves the problem of heat accumulation in a closed environment.

[0019] 4. The thermoelectric conversion module of the present invention is integrated inside the heat sink. While discharging heat, it can convert part of the waste heat into electrical energy, realizing energy recovery and reuse. Compared with the traditional heat sink that simply discharges heat energy, this solution can achieve an energy conversion efficiency of nearly 8.5% at a large temperature difference through the optimization of thermoelectric materials, providing auxiliary power supply for low-power devices (such as fans, sensors), solving the problem of energy waste in existing heat dissipation technologies, and expanding the application potential of the heat sink in intelligent devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a perspective view of the present invention.

[0021] Among them, 1. Heat conduction and heat absorption layer; 2. Thermal diffusion layer; 3. Thermal management layer; 4. Far-infrared radiation heat dissipation layer; 5. Heat dissipation base. DETAILED DESCRIPTION OF THE INVENTION

[0022] Next, in combination with the drawings in the specification of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] Embodiment: Referring to the drawings, an embodiment of the present invention provides a multi-layer composite graphite heat sink, which includes a heat-conducting and heat-absorbing layer 1, a heat-diffusion layer 2, a heat-management layer 3, a far-infrared radiation heat-dissipation layer 4, and a heat-dissipation substrate 5 stacked in sequence, and the material components of each layer are as follows.

[0024] The heat-conducting and heat-absorbing layer 1 includes a graphene-diamond composite film (65 - 85 wt%); a nano-silver coating (5 - 15 wt%); a silicon oxide / boron nitride composite enhancer (5 - 10 wt%).

[0025] This layer is mainly responsible for efficiently absorbing heat and quickly conducting it to the lower layer. The graphene-diamond composite film has an extremely high thermal conductivity, reaching more than 2000 W / m·K, far exceeding that of traditional metals. The introduction of diamond micropowders further enhances the interlayer heat conduction effect and improves the mechanical strength at the same time. The nano-silver coating reduces the interfacial thermal resistance and optimizes the heat coupling efficiency. The silicon oxide and boron nitride composite enhancer improves the thermal stability and prevents local overheating.

[0026] Preparation process: The graphene-diamond composite film is grown by chemical vapor deposition (CVD) method at 850 - 1100 °C; the nano-silver coating is deposited by magnetron sputtering, and the film thickness is controlled between 200 - 500 nm; finally, the silicon oxide / boron nitride composite enhancer is uniformly coated by plasma-enhanced deposition.

[0027] The heat-diffusion layer 2 includes a gradient-density graphite foam (60 - 80 wt%); a carbon nanotube reinforcing material (5 - 15 wt%); a graphene-based filler (10 - 20 wt%).

[0028] This layer is mainly used for the lateral diffusion of heat, so that local hot spots are quickly dispersed to avoid heat accumulation. The gradient-density graphite foam has a layered pore structure, where the pores on the side close to the heat-absorbing layer are larger (20 - 50 μm), and the pores on the side close to the lower layer are smaller (5 - 15 μm), forming a thermal conductivity gradient. The addition of carbon nanotubes improves the interfacial bonding force and enhances the overall mechanical strength at the same time. The graphene-based filler optimizes the interlayer heat conduction path and improves the overall temperature uniformity ability.

[0029] Preparation process: The gradient density foam is prepared by graphitization at a high temperature (>1000 °C) using the self-assembly template method; the carbon nanotube reinforcing material is evenly distributed by the spraying method, and the concentration of the spraying solution is controlled at 0.05-0.2 wt%; finally, the graphene-based filler is filled using the supercritical fluid penetration technology to optimize the pore structure.

[0030] The thermal management layer 3 includes a graphene-reinforced phase change material (40-60 wt%); a thermoelectric conversion material (Bi2Te3, 30-50 wt%); and a carbon nanotube composite support (10-20 wt%).

[0031] This layer has dynamic thermal management capabilities and actively regulates the heat flow when the temperature changes. The graphene-reinforced phase change material (PCM) can melt or solidify within a specific temperature range, thereby storing or releasing heat to achieve thermal buffering. The Bi2Te3 thermoelectric conversion module can convert part of the thermal energy into electrical energy to improve the energy utilization rate. The carbon nanotube composite support provides high mechanical strength to prevent interlayer peeling caused by the expansion and contraction of the material.

[0032] Preparation process: The PCM is prepared using the microcapsule encapsulation technology, and the phase change temperature can be regulated at 40-80 °C; the Bi2Te3 thin film is prepared by physical vapor deposition (PVD) to optimize the thermoelectric conversion efficiency; the carbon nanotube composite support is constructed using the electrospinning technology to improve the overall stability.

[0033] The far-infrared radiation heat dissipation layer 4 includes an infrared radiation coating (50-70 wt%); a microgroove structure substrate (30-50 wt%).

[0034] This layer dissipates heat through far-infrared radiation to accelerate the release of heat. The Al2O3 / magnesium oxide composite coating can absorb the heat inside the device and radiate it outward at a wavelength of 8-14 μm. The microgroove structure substrate enhances the convective heat transfer effect, making the air flow more sufficient and improving the overall heat dissipation capacity.

[0035] Preparation process: The infrared radiation coating is deposited using the sol-gel method, and the coating thickness is 5-20 μm; the microgrooves are etched by precision CNC micro-machining, and the groove depth is 0.2-0.5 mm to optimize the heat dissipation area.

[0036] The heat dissipation substrate 5 includes a copper-aluminum composite microporous structure (50-70 wt%); a graphene-reinforced aluminum alloy (30-50 wt%).

[0037] This layer provides mechanical support and additional heat dissipation. The copper-aluminum composite microporous structure can further enhance the convective heat transfer ability and reduce the overall weight. The graphene-reinforced aluminum alloy has a high thermal conductivity and can effectively reduce the temperature gradient of the bottom layer.

[0038] Preparation process: Sintering is carried out by the metal powder metallurgy method, and the sintering temperature is 600 - 900 °C; Graphene is introduced into the aluminum alloy through electrodeposition technology to improve the heat conduction ability.

[0039] Example 1, Application of the multi-layer composite graphite heat sink in 5G base station equipment, the materials include the following components and proportions: Thermal conductive and heat absorbing layer 1: Graphene-diamond composite film: 75 wt%; Nano silver coating: 10 wt%; Silicon oxide / boron nitride composite enhancer: 15 wt%.

[0040] Thermal diffusion layer 2: Gradient density graphite foam: 70 wt%; Carbon nanotube reinforcing material: 10 wt%; Graphene-based filler: 20 wt%.

[0041] Thermal management layer 3: Graphene enhanced phase change material: 50 wt%; Thermoelectric conversion material (Bi2Te3): 40 wt%; Carbon nanotube composite support: 10 wt%.

[0042] Far-infrared radiation heat dissipation layer 4: Infrared radiation coating: 60 wt%; Micro-groove structure substrate: 40 wt%.

[0043] Heat dissipation substrate 5: Copper-aluminum composite micro-porous structure: 60 wt%; Graphene enhanced aluminum alloy: 40 wt%.

[0044] In order to verify the performance of the multi-layer composite graphite heat sink under this example, the sample preparation was completed according to the following preparation method, and a series of experimental tests were carried out, including the determination of thermal conductivity, temperature uniformity, far-infrared radiation ability and thermoelectric conversion efficiency.

[0045] Preparation of thermal conductive and heat absorbing layer 1: In a CVD system at 950 °C, using methane as the carbon source, the hydrogen flow rate is set to 100 sccm, and the graphene-diamond composite film is deposited on the quartz substrate for 60 min.

[0046] The magnetron sputtering method is used, the target material is silver with a purity of 99.9%, the sputtering power is 100 W, and the sputtering time is 25 min to form a nano silver coating.

[0047] The plasma enhanced deposition technology is used to coat the silicon oxide / boron nitride composite enhancer on the surface, and the deposition thickness is controlled at 200 - 400 nm.

[0048] Preparation of thermal diffusion layer 2: The gradient density graphite foam is prepared by the foam template method. The organic foam is impregnated in the graphite precursor solution, dried and then calcined in an argon atmosphere at 1050 °C for 2 h to obtain porous graphite foam.

[0049] The carbon nanotube reinforcing material is deposited by the spraying method, the concentration of the CNT dispersion liquid is 0.1 wt%, and the spraying pressure is set to 0.6 MPa.

[0050] The graphene-based filler is filled by the supercritical CO2 penetration method to optimize the microscopic heat conduction path.

[0051] Preparation of the thermal management layer 3: The phase change material is coated by microcapsules, the phase change temperature is set at 55 °C, the shell material is a polymer composite material, the emulsification rotation speed is 800 rpm, the reaction temperature is 75 °C, and the time is 3 h.

[0052] Deposit the Bi2Te3 thermoelectric thin film by the PVD method, the distance between the target and the substrate is 8 cm, the deposition temperature is 450 °C, and the film thickness is 20 μm.

[0053] Prepare the carbon nanotube composite scaffold by the electrospinning technique, the spinning voltage is 15 kV, the solution concentration is 2 wt%, and the spinning distance is 10 cm.

[0054] Preparation of the far-infrared radiation heat dissipation layer 4: Deposit the Al2O3 / magnesium oxide infrared coating by the sol-gel method, control the pH value of the sol at 3.5, the spin coating rotation speed is 2000 rpm, and the coating thickness is 15 μm.

[0055] Use CNC microfabrication to etch the microgroove structure, the groove spacing is 1 mm, the groove depth is 0.3 mm, and the heat dissipation surface area is increased.

[0056] Preparation of the heat dissipation substrate 5: Use the metal powder metallurgy method, mix the copper-aluminum powder in a ratio of 6:4, the sintering temperature is 750 °C, the heat preservation time is 2 h, and the cooling rate is 10 °C / min.

[0057] Introduce a graphene layer on the substrate surface by the electrodeposition method to improve the thermal conductivity, the current density is 20 mA / cm 2 , and the deposition time is 30 min.

[0058] Experimental tests and data: After the tests are completed, measure the thermal conductivity, thermal uniformity, far-infrared radiation ability and thermoelectric conversion efficiency of the heat sink under different temperature conditions, and record the data.

[0059] Table 1: Experimental data of the multi-layer composite graphite heat sink The performance of the thermal conduction layer is quite outstanding. Especially, the in-plane thermal conductivity breaks through 1000 W / m·K, which is more than three times higher than that of traditional metal heat dissipation materials (such as aluminum at 300 W / m·K). This phenomenon can be attributed to the high order of the graphene-diamond composite structure, which reduces the grain boundary scattering, thus ensuring the rapid diffusion of heat along the plane direction. The gradient pore structure of the thermal diffusion layer 2 effectively enhances the overall mechanical strength while improving the thermal conductivity, avoiding the formation of local overheating areas.

[0060] On the other hand, the thermal management layer 3 performs stably during drastic temperature fluctuations. In the experiment, the heat absorption capacity of the phase change material reduces the temperature peak by approximately 10 - 15 °C. Especially in the case of simulating the continuous high-power operation of a 5G base station, it can effectively slow down the temperature rising rate. The test of the thermoelectric conversion module shows that at a temperature difference of 50 °C, the conversion efficiency can reach 7.9%, indicating that the heat is not only simply discharged but also partially recovered as electrical energy, endowing the system with additional energy recovery value.

[0061] Finally, the test data of the far-infrared radiation layer are relatively ideal, with an infrared radiation rate as high as 87.6%. This indicates that in terms of heat release, this layer can effectively transfer energy through far-infrared radiation. Especially in an environment where convective heat transfer is limited, this active radiation mechanism greatly enhances the heat dissipation capacity. At the same time, the design of the micro-groove structure not only enhances air convection heat dissipation but also optimizes the heat distribution across the entire heat sink, keeping the temperature gradient within ±3 °C. Example 2: Application of the multi-layer composite graphite heat sink in a high-performance laptop. Different from the above example, the materials in this example include the following components and proportions: Thermal conductive and heat absorption layer 1: Graphene-diamond composite film: 80 wt%; Nano-silver coating: 10 wt%; Silicon oxide / boron nitride composite reinforcing agent: 10 wt%.

[0062] Thermal diffusion layer 2: Gradient density graphite foam: 65 wt%; Carbon nanotube reinforcing material: 15 wt%; Graphene-based filler: 20 wt%.

[0063] Thermal management layer 3: Graphene-enhanced phase change material: 45 wt%; Thermoelectric conversion material (Bi2Te3): 45 wt%; Carbon nanotube composite support: 10 wt%.

[0064] Far-infrared radiation heat dissipation layer 4: Infrared radiation coating (magnesium oxide / titanium oxide): 63 wt%; Micro-groove structure substrate: 37 wt%.

[0065] Heat dissipation substrate 5: Copper-aluminum composite micro-porous structure: 55 wt%; Graphene-enhanced aluminum alloy: 45 wt%.

[0066] To verify the performance of the multi-layer composite graphite heat sink under this example, sample preparation was completed according to the following preparation method, and a series of experimental tests were carried out, including the determination of thermal conductivity, temperature uniformity, far-infrared radiation ability, and thermoelectric conversion efficiency.

[0067] Preparation of thermal conductive and heat absorption layer 1: Grow the graphene-diamond composite film by CVD method, with a methane concentration of 3%, a CVD temperature of 1000 °C, and a deposition time of 70 min.

[0068] Using magnetron sputtering technology, deposit a nano-silver coating on the surface of the thin film, with a sputtering power of 120 W and a deposition thickness of 250 nm.

[0069] Plasma-enhanced deposition of silicon oxide / boron nitride composite enhancer, with a deposition time of 30 min to enhance the stability of the film layer.

[0070] Preparation of the thermal diffusion layer 2: Prepare gradient density graphite foam by the cold pressing-thermal treatment method, with a forming pressure of 15 MPa and a subsequent graphitization temperature of 1100 °C.

[0071] Spray carbon nanotube reinforcement material, with a CNT dispersion concentration of 0.2 wt% and a spraying pressure of 0.4 MPa.

[0072] Fill the graphene-based filler by the solvent evaporation method to form an efficient heat channel inside the material.

[0073] Preparation of the thermal management layer 3: Prepare the phase change material by the microcapsule coating method, set the phase change temperature at 60 °C, the stirring rate at 900 rpm, and the reaction time at 2.5 h.

[0074] Deposit Bi2Te3 thermoelectric thin film by physical vapor deposition (PVD), with a substrate temperature of 480 °C and a film thickness of 18 μm.

[0075] Construct a carbon nanotube composite scaffold by electrospinning, with a spinning voltage of 12 kV and a spinning distance of 8 cm.

[0076] Preparation of the far-infrared radiation heat dissipation layer 4: Coat the infrared radiation coating by the sol-gel method, with a spin coating speed of 1800 rpm, control the pH value of the sol at 3.8, and finally form a 14-μm coating.

[0077] Use CNC microfabrication to etch the microgroove structure, with a groove depth of 0.25 mm to optimize the heat dissipation effect.

[0078] Preparation of the heat dissipation substrate 5: Mix copper-aluminum powder in a ratio of 7:3 and sinter by powder metallurgy method at a temperature of 720 °C for a holding time of 1.5 h.

[0079] Enhance the graphene layer by electrodeposition method, with a current density of 15 mA / cm 2 and a deposition time of 40 min.

[0080] Experimental tests and data: After the tests are completed, measure the thermal conduction characteristics, thermal uniformity, thermal response time, and far-infrared radiation efficiency of the heat sink under different power consumptions and environmental conditions, and record the experimental data.

[0081] Table 2 Experimental data of the multi-layer composite graphite heat sink Analysis and summary of experimental results: The in-plane thermal conductivity of the heat sink still remains at a relatively high level, but compared with Example 1, it has slightly decreased. This can be attributed to the more lightweight structural adjustment, especially the reduction of the graphite content in the gradient density graphite foam to meet the overall thin and light requirements of the laptop. However, this adjustment does not significantly affect the temperature uniformity ability. The experimental data shows that even under a high power consumption of 50W, the thermal diffusion layer 2 can still maintain the temperature difference within ±4°C. This indicates that the synergistic effect of the carbon nanotube enhanced structure and the graphene-based filler enables the heat to flow more uniformly within the material, avoiding the accumulation of local hot spots.

[0082] On the other hand, the response time of the thermal management layer 3 is relatively fast. Especially when ΔT = 80°C, the thermal diffusion time is shortened to 65.8 ms, indicating that the heat absorption and release rates of the phase change material have been optimized. Compared with the traditional metal heat dissipation solution (such as an aluminum heat sink, the thermal diffusion time is usually >150 ms), the thermal buffering ability of this solution is superior. The test of the thermoelectric conversion module shows that at a large temperature difference, the energy conversion efficiency reaches 8.1%, which means that part of the thermal energy can be recovered for fan power supply or other low-power components, improving the energy utilization rate of the system.

[0083] In addition, the test results of the far-infrared radiation layer show that its emissivity remains at about 86.2%, approaching the theoretical limit. The introduction of the microgroove structure not only enhances the convective heat transfer effect but also makes the radiation heat dissipation more uniform, reducing the thermal accumulation in local areas. Considering these data, the heat sink in this embodiment performs excellently in the high-power consumption scenario of the laptop, which can not only improve the overall heat dissipation efficiency but also bring additional benefits in energy recovery.

[0084] Example 3, Application of the multi-layer composite graphite heat sink in smartphone heat dissipation. Different from the above examples, the materials in this example include the following components and proportions: Thermal conductive and heat absorbing layer 1: Graphene-diamond composite film: 70wt%; Nano silver coating: 15wt%; Silicon oxide / boron nitride composite enhancer: 15wt%.

[0085] Thermal diffusion layer 2: Gradient density graphite foam: 75wt%; Carbon nanotube enhanced material: 10wt%; Graphene-based filler: 15wt%.

[0086] Thermal management layer 3: Graphene enhanced phase change material: 55wt%; Thermoelectric conversion material (Bi2Te3): 35wt%; Carbon nanotube composite support: 10wt%.

[0087] Far-infrared radiation heat dissipation layer 4: Infrared radiation coating (magnesium oxide / titanium oxide): 66wt%; Microgroove structure substrate: 34wt%.

[0088] Heat dissipation substrate 5: Copper-aluminum composite microporous structure: 50 wt%; Graphene-reinforced aluminum alloy: 50 wt%.

[0089] To verify the performance of the multi-layer composite graphite heat sink under this embodiment, sample preparation was completed according to the following preparation method, and a series of experimental tests were carried out, including the determination of thermal conductivity, temperature uniformity, far-infrared radiation ability, and thermoelectric conversion efficiency.

[0090] Preparation of the thermal conduction and heat absorption layer 1: Grow a graphene-diamond composite film by CVD method, with a methane concentration of 2.5%, a CVD temperature of 900 °C, and a deposition time of 50 min to form a film layer with a thickness of about 150 nm.

[0091] Deposit a nano-silver coating by magnetron sputtering, with a target purity of 99.95%, a sputtering power of 110 W, a sputtering time of 20 min, and the coating thickness controlled at about 200 nm.

[0092] Adopt plasma-assisted deposition to uniformly coat the silica / boron nitride composite enhancer on the film surface, and control the deposition thickness in the range of 250 - 300 nm.

[0093] Preparation of the thermal diffusion layer 2: Prepare gradient density graphite foam by freeze-drying-graphitization method. The precursor solution is frozen for 12 h and then graphitized at 1000 °C for 1.5 h to form a uniform porous structure.

[0094] Deposit carbon nanotube reinforcement by electrostatic spraying method, with a CNT dispersion concentration of 0.15 wt%, a spraying distance of 10 cm, and a pressure set at 0.55 MPa.

[0095] Fill the graphene-based filler through high-temperature melt infiltration technology to optimize the thermal diffusion path and improve the overall thermal uniformity.

[0096] Preparation of the thermal management layer 3: Prepare graphene-reinforced phase change material by microencapsulation phase change technology, with the phase change temperature set at 45 °C, an emulsifier concentration of 0.3 wt%, a stirring rate of 850 rpm, and a coating time of 2 h.

[0097] Deposit Bi2Te3 thermoelectric thin film by PVD, with a deposition temperature of 450 °C, a distance between the target and the substrate of 9 cm, and a final film thickness of 15 μm.

[0098] Prepare a carbon nanotube composite scaffold by electrospinning technology, with a spinning voltage of 14 kV and a spinning distance of 9 cm to form a uniform fiber network structure.

[0099] Preparation of the far-infrared radiation heat dissipation layer 4: Coat the magnesium oxide / titanium oxide far-infrared radiation coating by sol-gel method, adjust the pH value of the sol to 3.7, and the spin coating speed to 1900 rpm to form a 12-μm-thick coating.

[0100] CNC precision machining and etching of micro-groove structure, groove width 0.15mm, groove depth 0.2mm, optimize surface heat dissipation performance.

[0101] Preparation of heat dissipation substrate 5: A copper-aluminum composite microporous substrate was prepared by powder metallurgy, with a metal powder ratio of 5:5, a sintering temperature of 700°C, and a cooling rate of 12°C / min to ensure uniform distribution of micropores.

[0102] Graphene layer enhanced by electrodeposition technique with a current density of 18 mA / cm 2 , deposition time 35min, improve thermal conductivity.

[0103] Experimental tests and data: Test the in-plane thermal conductivity, thermal response speed, far-infrared emissivity and thermoelectric conversion efficiency of the samples, and record the experimental data.

[0104] Table 3 Experimental data of multi-layer composite graphite heat sink for smartphone heat dissipation: Analysis and summary of experimental results: The thermal conductivity data is slightly lower than that of high-performance notebooks and 5G base station applications, but this does not mean that the performance has been reduced, but rather it is the result of optimization for the heat dissipation environment of smartphones. The ultra-thin design of the graphene-diamond composite film enables the material to adapt more quickly to temperature fluctuations in a short period of time. At the same time, the gradient density graphite foam maintains good thermal diffusion capabilities while being thinned. Test results show that even under a test environment of 50°C, the in-plane thermal conductivity remains at 845.1W / m·K, which is much higher than the traditional aluminum alloy (about 200W / m·K) heat dissipation material, ensuring the stability of the mobile phone when running at high loads.

[0105] Phase change materials start to work at around 45°C, significantly reducing transient temperature peaks and shortening heat diffusion time. Under the test condition of ΔT = 30°C, the heat diffusion time is 81.5ms, which is a great improvement compared to the average 150-200ms of traditional graphene heat dissipation films. This means that when the device is running at high power consumption for a short period of time (such as gaming, video shooting), the temperature will not suddenly soar, but will change at a relatively gentle rate, improving the user experience. The experimental data of the thermoelectric conversion module shows that at ΔT = 45°C, the thermoelectric efficiency can reach 7.4%. Although it is slightly lower than the notebook solution, it is already a very impressive data in miniaturized devices such as smartphones, and can even support the operation of some low-power components, such as micro fans or OLED display standby mode.

[0106] The performance of the far-infrared radiation layer is particularly prominent, with a radiation rate reaching 88.4%, which is higher than that of laptop and 5G base station applications. This is closely related to the optimization of the microgroove structure. In the small space of a smartphone, the effect of active convective heat dissipation is limited, while far-infrared radiation can effectively increase the heat transfer efficiency and reduce the heat accumulation in the device. The additional flow-guiding effect of the microgroove structure also enables the heat not to be confined to a certain area but to spread evenly outward and finally be dissipated into the air through the mobile phone housing. Generally speaking, this multi-layer composite heat dissipation structure performs excellently in the application scenario of smartphones. It can not only quickly respond to short-term high-temperature fluctuations but also efficiently dissipate heat, avoid local overheating, and improve the stability of the overall system. Example 4: The multi-layer composite graphite heat sink is applied in a data center server. Different from the above examples, the materials of this example include the following components and proportions: Thermal conductive and heat-absorbing layer 1: Graphene-diamond composite film: 70wt%; Nano silver coating: 12wt%; Silicon oxide / boron nitride composite reinforcing agent: 18wt%.

[0107] Thermal diffusion layer 2: Gradient density graphite foam: 68wt%; Carbon nanotube reinforcing material: 15wt%; Graphene-based filler: 17wt%.

[0108] Thermal management layer 3: Graphene-enhanced phase change material: 55wt%; Thermoelectric conversion material (Bi2Te3): 35wt%; Carbon nanotube composite support: 10wt%.

[0109] Far-infrared radiation heat dissipation layer 4: Infrared radiation coating (aluminum oxide / magnesium oxide): 65wt%; Microgroove structure substrate: 35wt%.

[0110] Heat dissipation substrate 5: Copper-aluminum composite microporous structure: 58wt%; Graphene-reinforced aluminum alloy: 42wt%.

[0111] To verify the performance of the multi-layer composite graphite heat sink under this example, sample preparation was completed according to the following preparation method, and a series of experimental tests were carried out, including the determination of thermal conductivity, temperature uniformity, far-infrared radiation ability, and thermoelectric conversion efficiency.

[0112] Preparation of thermal conductive and heat-absorbing layer 1: Grow the graphene-diamond composite film by CVD method, with a methane concentration of 3.5%, a CVD temperature of 1050°C, and a deposition time of 75 minutes to form a 200-nm-thick film.

[0113] Deposit the nano silver coating by magnetron sputtering method, with a sputtering power of 130W and a deposition thickness of 280nm.

[0114] Use plasma-enhanced deposition technology to uniformly coat the silicon oxide / boron nitride composite reinforcing agent on the film surface, and control the deposition thickness within 300 - 400nm.

[0115] Preparation of the thermal diffusion layer 2: Gradient-density graphite foam was prepared by the sol-gel method. The precursor solution was stirred for 6 h, followed by freeze-drying for 18 h. The graphitization temperature was 1150 °C and the time was 2 h.

[0116] Carbon nanotube reinforcement materials were deposited by the high-voltage electrostatic spraying method. The spraying pressure was 0.7 MPa and the CNT concentration was 0.25 wt%.

[0117] Graphene-based fillers were filled by the supercritical fluid penetration technology to optimize the thermal diffusion channels.

[0118] Preparation of the thermal management layer 3: Phase change materials were coated with microcapsules. The phase change temperature was set at 65 °C, the emulsifier concentration was 0.35 wt%, the stirring rate was 950 rpm, and the coating time was 2.5 h.

[0119] Bi2Te3 thermoelectric thin films were deposited by PVD. The deposition temperature was 500 °C and the film thickness was 22 μm.

[0120] Carbon nanotube composite scaffolds were prepared by the electrospinning technique. The spinning voltage was 16 kV and the spinning distance was 9.5 cm.

[0121] Preparation of the far-infrared radiation heat dissipation layer 4: Alumina / magnesia far-infrared radiation coatings were coated by the sol-gel method. The spin coating speed was 2000 rpm and the coating thickness was 15 μm.

[0122] CNC precision machining was used to etch microgroove structures. The groove width was 0.3 mm and the groove depth was 0.35 mm.

[0123] Preparation of the heat dissipation substrate 5: Copper-aluminum composite microporous substrates were prepared by powder metallurgy. The metal powder ratio was 6:4, the sintering temperature was 750 °C, and the cooling rate was 10 °C / min.

[0124] The graphene layer was enhanced by the electrodeposition technique with a current density of 22 mA / cm 2 , and the deposition time was 40 min.

[0125] Experimental tests and data: The thermal conductivity, temperature uniformity, far-infrared radiation ability, and long-term stability of the heat sink were tested in the server environment, and the experimental data were recorded.

[0126] Table 4 Experimental data of the multi-layer composite graphite heat sink for server heat dissipation: Analysis and summary of experimental results: The server has high heat dissipation requirements. The in-plane thermal conductivity of the heat sink exceeds 1045 W / m·K. Compared with traditional copper materials (about 400 W / m·K), the heat conduction ability is more than doubled. In the multi-layer composite structure, the gradient density graphite foam has remarkable temperature uniformity, which suppresses local hot spot problems, enables the CPU temperature to be evenly distributed, and avoids performance degradation caused by the accumulation of hot spots.

[0127] When the server runs at high load for a long time, the phase change material can effectively buffer the thermal shock and maintain a stable temperature. In the experiment, the thermal diffusion time is only 68.4 ms, which is three times faster than that of traditional aluminum heat sinks (>200 ms). In addition, the thermoelectric conversion module reaches an efficiency of 7.8% at a temperature difference of 50 °C, providing additional low-power energy supply for the system and supporting the operation of some sensing devices.

[0128] The performance of the far-infrared radiation layer is particularly prominent. The emissivity is as high as 89.3%. The optimized microgroove structure further improves the radiation heat transfer ability of the heat sink. Inside the server chassis, where air flow is restricted, this far-infrared heat dissipation method effectively reduces the heat accumulation inside the device and improves the long-term stability.

[0129] Example 5, the application of the multi-layer composite graphite heat sink in the heat dissipation of electric vehicle power batteries. Different from the above examples, the materials in this example include the following components and proportions: Thermal conduction and heat absorption layer 1: Graphene-diamond composite film: 72 wt%; Nano silver coating: 13 wt%; Silicon oxide / boron nitride composite reinforcing agent: 15 wt%.

[0130] Thermal diffusion layer 2: Gradient density graphite foam: 67 wt%; Carbon nanotube reinforcing material: 18 wt%; Graphene-based filler: 15 wt%.

[0131] Thermal management layer 3: Graphene-enhanced phase change material: 52 wt%; Thermoelectric conversion material (Bi2Te3): 38 wt%; Carbon nanotube composite support: 10 wt%.

[0132] Far-infrared radiation heat dissipation layer 4: Infrared radiation coating (aluminum oxide / magnesium oxide): 68 wt%; Microgroove structure substrate: 32 wt%.

[0133] Heat dissipation substrate 5: Copper-aluminum composite microporous structure: 60 wt%; Graphene-enhanced aluminum alloy: 40 wt%.

[0134] To verify the performance of the multi-layer composite graphite heat sink under this example, sample preparation was completed according to the following preparation method, and a series of experimental tests were carried out, including the determination of thermal conductivity, temperature uniformity, far-infrared radiation ability, and thermoelectric conversion efficiency.

[0135] Thermal Conductive and Heat Absorbing Layer 1: CVD-grown graphene-diamond composite film, CVD temperature 1100 °C, deposition time 80 min.

[0136] Magnetron sputtered nano-silver coating, sputtering power 140 W, deposition thickness 300 nm.

[0137] Thermal Diffusion Layer 2: Gradient density graphite foam prepared by sol-gel method, freeze-dried for 24 h, graphitization temperature 1200 °C.

[0138] Carbon nanotube reinforcement material deposited by electrostatic spraying method, spraying pressure 0.8 MPa.

[0139] Thermal Management Layer 3: Microcapsule-coated phase change material, phase change temperature set at 70 °C.

[0140] PVD deposition of Bi2Te3 thermoelectric thin film, film thickness 25 μm.

[0141] Far-infrared Radiation Heat Dissipation Layer 4: Alumina / magnesia far-infrared radiation coating applied by sol-gel method.

[0142] Heat Dissipation Substrate 5: Copper-aluminum composite microporous substrate prepared by metal powder metallurgy method, sintering temperature 780 °C.

[0143] Experimental Tests and Data: Test the thermal conductivity, temperature uniformity, far-infrared radiation ability and long-term stability of the heat sink in the environment of electric vehicle power batteries, and record the experimental data.

[0144] Table 5 Experimental Data of Multilayer Composite Graphite Heat Sink for Electric Vehicle Power Battery Cooling: Test item Equipment parameter Result data Error range In-plane thermal conductivity (W / m·K) LFA-1000 1120.5 ±3.1％ Thermal diffusion time (ms) FLIR 58.7 ±4.3％ Far-infrared emissivity (%) FTIR 91.2 ±1.5％ Thermoelectric conversion efficiency (%) Thermoelectric module test system 8.5 ±0.7％ Analysis and Summary of Experimental Results: The heat dissipation requirements of electric vehicles are extremely high. The heat sink in this embodiment still maintains excellent performance in high-temperature environments. The gradient density graphite foam ensures temperature uniformity, and the rapid response ability of the phase change material optimizes battery thermal management. The far-infrared radiation layer improves the overall heat dissipation efficiency, making the power battery more stable during long-term operation.

[0145] The multilayer composite graphite heat sink performs excellently in different application scenarios. From 5G base stations, laptops, smartphones, to servers and electric vehicles, the experimental data of each embodiment reflects its excellent performance in heat conduction, thermal uniformity, transient response and energy recovery. However, different scenarios have different emphases on heat dissipation requirements, so fine-tuning of the material structure is particularly crucial.

[0146] First, in terms of in-plane thermal conductivity, as the application scenarios change, the thermal conductivity floats between 870 W / m·K (smartphone) and 1120 W / m·K (electric vehicle). High power density applications (such as servers and electric vehicles) require higher thermal conductivity, so a gradient graphite foam structure with a higher graphitization temperature is adopted, and at the same time, the carbon nanotube filling strategy is optimized to ensure efficient transmission of the heat flow path. For thin and light devices such as laptops and smartphones, the density of the graphite foam is appropriately reduced to reduce weight while ensuring the heat dissipation capacity.

[0147] Secondly, the optimization of the thermal management layer 3 shows unique value in each embodiment. In scenarios such as servers and electric vehicles, due to the relatively high operating environment temperature, the working temperature of the phase change material is set at 65 - 70 °C, enabling it to provide additional thermal buffering under high-temperature loads. For smartphones and laptops, the phase change temperature of the material is set at 45 - 60 °C to adapt to temperature fluctuations in a short period and reduce local overheating. The test data of the thermal diffusion time shows that the thermal diffusion time in electric vehicle applications is the shortest, only 58.7 ms, indicating better thermal management capabilities under extreme working conditions.

[0148] Finally, the role of the far-infrared radiation heat dissipation layer 4 varies in different scenarios. In confined spaces (such as smartphones and servers), its contribution to the heat dissipation efficiency is particularly prominent, with the emissivity reaching 88.4% (smartphone) to 91.2% (electric vehicle). The optimization of the microgroove structure not only enhances the far-infrared radiation ability but also improves the convective heat transfer effect, enabling heat to be dispersed to the external environment more quickly. In server applications, this mechanism is particularly important because it is difficult for traditional air-cooling methods to effectively cover all high-heat-generation areas, and far-infrared radiation provides an additional heat dissipation path to alleviate the accumulation of local hotspots.

[0149] Generally speaking, the multi-layer composite graphite heat sink shows a high degree of customizability in different application scenarios. By optimizing the structures of the thermal conduction layer, diffusion layer, phase change layer, and radiation layer, it can accurately adapt to the needs of different devices, achieve efficient heat dissipation, rapid thermal response, and energy recovery in some applications. The data fluctuations in different embodiments precisely reflect the optimization directions in their respective application scenarios, rather than simply comparing performance advantages and disadvantages. In the future, further optimizing the material microstructure and combining new thermoelectric conversion technologies may further promote the intelligence and self-adaptive heat dissipation ability of the heat sink while improving the heat dissipation efficiency.

[0150] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-layer composite graphite heat sink, comprising a heat-conducting and heat-absorbing layer (1), a heat-diffusion layer (2), a heat-management layer (3), a far-infrared radiation heat-dissipation layer (4), and a heat-dissipation substrate (5) stacked in sequence, characterized in that: The heat-conducting and heat-absorbing layer (1) comprises a graphene-diamond composite film and a nano silver coating; The heat-diffusion layer (2) is a gradient-density graphite foam containing a carbon nanotube reinforcing material; The heat-management layer (3) contains a graphene-reinforced phase-change material and a thermoelectric conversion module; The far-infrared radiation heat-dissipation layer (4) comprises an infrared radiation coating and a micro-groove structure substrate; The heat-dissipation substrate (5) is composed of a copper-aluminum composite micro-porous structure and a graphene-reinforced aluminum alloy.

2. The multi-layer composite graphite heat sink according to claim 1, wherein The material composition and weight percentage of the heat-conducting and heat-absorbing layer (1) are: graphene-diamond composite film: 65 - 85 wt%; nano silver coating: 5 - 15 wt%; silica / nitride boron composite reinforcing agent: 5 - 20 wt%.

3. A multi-layer composite graphite heat sink according to claim 1, wherein, The material composition and weight percentage of the heat-diffusion layer (2) are: gradient-density graphite foam: 60 - 80 wt%; carbon nanotube reinforcing material: 5 - 15 wt%; graphene-based filler: 10 - 20 wt%.

4. The multi-layer composite graphite heat sink according to claim 1, wherein, The material composition and weight percentage of the heat-management layer (3) are: graphene-reinforced phase-change material: 40 - 60 wt%; thermoelectric conversion material: 30 - 50 wt%; carbon nanotube composite support: 10 - 20 wt%.

5. A multi-layer composite graphite heat sink according to claim 1, wherein, The material composition and weight percentage of the far-infrared radiation heat-dissipation layer (4) are: infrared radiation coating: 50 - 70 wt%; micro-groove structure substrate: 30 - 50 wt%.

6. The multi-layer composite graphite heat sink according to claim 1, wherein The material composition and weight percentage of the heat-dissipation substrate (5) are: copper-aluminum composite micro-porous structure: 50 - 70 wt%; graphene-reinforced aluminum alloy: 30 - 50 wt%.

7. The multi-layer composite graphite heat sink according to claim 1, characterized in that, The thickness ranges of the heat-conducting and heat-absorbing layer (1), the heat-diffusion layer (2), the heat-management layer (3), the far-infrared radiation heat-dissipation layer (4), and the heat-dissipation substrate (5) are: heat-conducting and heat-absorbing layer (1): 0.05 - 0.2 mm; heat-diffusion layer (2): 0.3 - 0.7 mm; heat-management layer (3): 0.5 - 1 mm; far-infrared radiation heat-dissipation layer (4): 0.2 - 0.5 mm; heat-dissipation substrate (5): 1 - 2 mm.

8. The multi-layer composite graphite heat sink according to claim 1, wherein, The heat-conducting and heat-absorbing layer (1) is prepared by chemical vapor deposition, and the chemical vapor deposition growth temperature is 850 - 1100 °C, and the deposition time is 30 - 90 min.

9. The multi-layer composite graphite heat sink according to claim 1, wherein, The infrared radiation coating of the far-infrared radiation heat-dissipation layer (4) is deposited by sol-gel method, and the coating thickness is 5 - 20 μm.

10. A multi-layer composite graphite heat sink according to claim 1, characterized in that, The heat-dissipation substrate (5) is prepared by metal powder metallurgy, and the sintering temperature is 600 - 900 °C.

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