High-thermal-conductivity low-interface-thermal-resistance heat dissipation powder and preparation method thereof

Abstract

The application relates to the fields of material science and electronic heat dissipation technology, and discloses a high-thermal-conductivity low-interface-thermal-resistance heat dissipation powder and a preparation method thereof, which comprises the following steps: S1, mixing a base material and a reinforcing material, and then dissolving the mixture in a dissolving solution to form an initial suspension; S2, adding a functional additive to the initial suspension, and forming a functional initial material with a three-dimensional network structure through a sol-gel method; S3, depositing an interface modifier on the surface of the functional initial material to form a dense interface modification layer, and preparing a composite material; S4, calcining the composite material at high temperature in an inert atmosphere to obtain a heat dissipation material; and S5, cooling, grinding and screening the heat dissipation material to obtain the heat dissipation powder. The high-thermal-conductivity low-interface-thermal-resistance heat dissipation powder and the preparation method thereof have the advantages that through micro-nano double-scale structure design, micron alumina skeletons and nano reinforcing materials are embedded, and interface modification technology and functional additives are synergized, so that the heat dissipation powder has the advantages of high thermal conductivity, low interface thermal resistance, solution of traditional material agglomeration and heat conduction deficiency, and mechanical and thermal conductivity performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material science and electronic heat dissipation technology, and particularly relates to a high-thermal-conductivity low-interface-thermal-resistance heat dissipation powder and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electronic information technology, electronic devices are undergoing unprecedented miniaturization, integration and high performance revolution. From smart phones, wearable devices to data center servers, new energy vehicle battery management systems, the power density of various electronic devices continues to rise, and the resulting heat dissipation problem has become a core bottleneck restricting the performance improvement, reliability guarantee and service life extension of the device. In the traditional heat dissipation scheme, materials such as aluminum and copper have become the main force of early heat dissipation due to their high intrinsic thermal conductivity, but their inherent interface thermal resistance defects, high density and complex processing technology make it difficult to meet the stringent requirements of modern electronic devices for lightweight and efficient heat dissipation.

[0003] In recent years, the rise of nanomaterials has brought new technical breakthroughs to the field of heat dissipation. One-dimensional or two-dimensional nanomaterials such as graphene and carbon nanotubes have been widely studied and attempted to be applied in heat dissipation composites due to their excellent thermal conductivity. However, this single nanoscale material has exposed three major technical shortcomings in practical application: first, the interface thermal resistance is high. Due to the large difference in surface energy and weak interfacial bonding between nanomaterials and polymer matrix, a large number of nanoscale voids or defects are easily formed, leading to increased phonon scattering and significantly reduced heat transfer efficiency. Related studies have shown that the interface thermal resistance of traditional nanocomposites can account for 60%-80% of the total thermal resistance, which seriously offsets the thermal conductivity advantage of nanomaterials themselves. Second, the scale effect is single. Existing heat dissipation materials are mostly designed based on single nanoscale, lacking a cross-scale synergistic regulation mechanism. Random dispersion of nanometer particles can easily cause agglomeration at the macroscopic scale, resulting in uneven thermal conductivity of the material. Single micrometer structure is difficult to realize quantum confinement effect and interface thermal transport optimization at nanoscale, and cannot meet the dual goals of macroscopic uniformity and microcosmic thermal conductivity enhancement. Third, the intelligent response capability is missing. The thermal physical properties of traditional heat dissipation materials are mostly fixed values, and the heat dissipation efficiency cannot be dynamically adjusted according to the real-time thermal load of the device. In the local hot spot area of the chip or during the charging and discharging process of the battery, such materials are difficult to achieve on-demand heat dissipation, which can easily lead to large fluctuations in device operating temperature, affecting stability and safety.

[0004] To break through the above technical bottleneck, domestic and foreign research teams have carried out a lot of exploratory work. For example, the compatibility of nanomaterials and the matrix can be improved by surface modification technology, and the interfacial thermal resistance can be reduced by about 30%-50%, but it still cannot meet the high-performance heat dissipation demand; The gradient structure design concept is introduced, and the cross-scale heat conduction path is constructed by layering micrometer / nanometer materials, which can improve the thermal conductivity, but the process complexity increases significantly, and the intelligent control capability has not been substantially broken through. In addition, the traditional heat dissipation materials are prone to chemical degradation or structural instability under high temperature environment, resulting in attenuation of heat dissipation performance, which limits its application in extreme working conditions such as new energy vehicles, aerospace, etc. SUMMARY

[0005] In order to solve the problems of the prior art, the application discloses a high-thermal-conductivity and low-interfacial-thermal-resistance heat dissipation powder with micro-nano dual-scale structure regulation, low interfacial thermal resistance and intelligent thermal response characteristics and a preparation method thereof.

[0006] The application discloses a preparation method of the high-thermal-conductivity and low-interfacial-thermal-resistance heat dissipation powder, which comprises the following steps of S1, mixing a matrix material and a reinforcing material, and then placing the mixture into a dissolving solution for dispersion to form an initial suspension;

[0007] S2, adding a functional additive to the initial suspension, and forming a functional initial material with a three-dimensional network structure by a sol-gel method;

[0008] S3, depositing an interfacial modifier on the surface of the functional initial material with the three-dimensional network structure to form a dense interfacial modification layer, and preparing a composite material;

[0009] S4, placing the composite material in a high-temperature calcination furnace for calcination in an inert atmosphere to prepare a heat dissipation material;

[0010] S5, grinding the heat dissipation material into a powder after cooling, and screening to obtain the heat dissipation powder.

[0011] Further, the heat dissipation powder comprises a matrix material, a reinforcing material, a functional additive and an interfacial modifier.

[0012] The matrix material is alumina.

[0013] The reinforcing material is at least one of graphene or a carbon nanotube.

[0014] The functional additive is a semiconductor particle, and the semiconductor particle is at least one of a zinc oxide particle or a titanium dioxide particle.

[0015] The interfacial modifier is an organic high polymer material, and the organic high polymer material comprises at least one of polydimethylsiloxane or polyimide.

[0016] The purity of the alumina is greater than or equal to 99%, and the purity of the reinforcing material is greater than or equal to 95%.

[0017] When using alumina, the particle size can be designed through compounding, including: compounding of alumina with different particle sizes, compounding of alumina with different shapes, and compounding of alumina with different particle sizes and shapes.

[0018] Furthermore, the diameter of alumina ranges from 1 μm to 50 μm, serving as a micron-scale framework;

[0019] The diameter of the reinforcing material ranges from 10 nm to 1000 nm;

[0020] The functional additives have a diameter range of 10-200 nm and are embedded inside the micron-scale framework to form a micro-nano dual-scale structure.

[0021] Furthermore, the reinforcing material is at least one of boron nitride nanosheets or silicon carbide;

[0022] The semiconductor particles are at least one of tin oxide, vanadium oxide, zinc sulfide, or barium titanate.

[0023] Organic polymer materials include at least one of epoxy resin, polyurethane or polyacrylate.

[0024] Furthermore, the S1 solution is ethanol or deionized water, and ultrasonic treatment is used during the dispersion process for 20-40 minutes;

[0025] During the sol-gel reaction of S2, the temperature is controlled at 50-70℃ and the reaction time is 3-5 hours.

[0026] S3 deposition includes chemical vapor deposition and coating;

[0027] The S4 calcination time is 3-5 hours, the calcination heating rate is 4-6℃ / min, and the calcination temperature is 700-900℃;

[0028] The S5 sieving process uses a sieve mesh size of 180-220.

[0029] Furthermore, in S3, an interface modifier is deposited on the surface of the functional initial material to form a dense interface modification layer with a thickness of 40nm-200nm.

[0030] This invention discloses a heat dissipation powder with high thermal conductivity and low interfacial thermal resistance, which is prepared by any of the above-mentioned heat dissipation powder preparation methods with high thermal conductivity and low interfacial thermal resistance. The heat dissipation powder is composed of the following components in parts by weight: 7-13 parts by weight of matrix material, 4-7 parts by weight of reinforcing material, 1-4 parts by weight of functional additive, and 2-6 parts by weight of interface modifier.

[0031] The matrix material is alumina;

[0032] The reinforcing material is at least one of graphene or carbon nanotube;

[0033] The functional additive is a semiconductor particle, and the semiconductor particle includes at least one of zinc oxide particles or titanium dioxide particles;

[0034] The interface modifier is an organic polymer material, and the organic polymer material includes at least one of polydimethylsiloxane or polyimide.

[0035] Further, the heat dissipation powder is prepared by a sol-gel method and a chemical vapor deposition method.

[0036] The heat dissipation powder has a dual-scale structure of micrometer and nanometer.

[0037] Further, the heat dissipation powder has a thermal conductivity ≥100 W / m·K, and an interface thermal resistance ≤0.55 mm 2 ·K / W.

[0038] The present application has the following beneficial effects:

[0039] The high-thermal-conductivity and low-interface-thermal-resistance heat dissipation powder and the preparation method thereof disclosed in the present application break through the performance bottleneck of traditional heat dissipation materials through the synergistic effect of micro-nano dual-scale structure design, interface modification technology and functional additives, and have significant application value in the fields of electronic heat dissipation and new energy. Micron-sized aluminum oxide is used as a rigid skeleton to provide a macroscopic heat conduction path. Nanometer-sized reinforcing materials are embedded in the skeleton to form a dual-scale heat conduction network of the micron skeleton and the nanometer filler. By reducing phonon scattering and improving phonon transmission efficiency, the thermal conductivity is as high as ≥100 W / m·K, and the measured value in the embodiment is 115-120 W / m·K, which can be further increased to 150 W / m·K at high temperature. The organic polymer interface modifier enhances the interface bonding force through chemical bonding to form a continuous heat conduction channel. A dense interface modification layer with a thickness of 50-200 nm is formed on the surface of the functional initial material through chemical vapor deposition or coating technology, which fills the nanometer-sized gaps and defects and reduces the difference in thermal expansion coefficient between the matrix and the reinforcing material, so that the interface thermal resistance is ≤0.55 mm 2 ·K / W. The interface modifier forms a strong interface bond with the matrix and the reinforcing material through physical adsorption or chemical reaction, inhibits interface debonding and material degradation at high temperature, and improves long-term stability. The micron-sized skeleton provides structural support to avoid the inhomogeneity of heat conduction caused by the agglomeration of nanometer materials, and the nanometer filler optimizes the interface heat transport by using the quantum confinement effect to achieve the dual goals of macroscopic uniform dispersion and microscopic efficient heat conduction. This design solves the problems of easy agglomeration of single nanometer materials and insufficient heat conduction efficiency of single micron materials, and has both mechanical properties and heat conduction properties. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1An electron microscope image of the heat dissipation powder prepared in Example 1 in the embodiments of the present application.

[0041] Figure 2 A particle size detection image of the heat dissipation powder prepared in Example 1 in the embodiments of the present application.

[0042] Figure 3 An electron microscope image of the heat dissipation powder prepared in Example 2 in the embodiments of the present application.

[0043] Figure 4 A particle size detection image of the heat dissipation powder prepared in Example 2 in the embodiments of the present application.

[0044] Figure 5 An electron microscope image of the heat dissipation powder prepared in Example 3 in the embodiments of the present application.

[0045] Figure 6 A particle size detection image of the heat dissipation powder prepared in Example 3 in the embodiments of the present application. DETAILED DESCRIPTION

[0046] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely.

[0047] The present application discloses a preparation method of heat dissipation powder with high thermal conductivity and low interfacial thermal resistance, which comprises the following steps:

[0048] S2: functional additives are added to the initial suspension, and a functional initial material with a three-dimensional network structure is formed by a sol-gel method;

[0049] S3: an interfacial modifier is deposited on the surface of the functional initial material with a three-dimensional network structure to form a dense interfacial modification layer, thereby preparing a composite material;

[0050] S4: the composite material is placed in a high-temperature calcination furnace and calcined under an inert atmosphere to prepare a heat dissipation material;

[0051] S5: the heat dissipation material is cooled and ground into powder, and the heat dissipation powder is obtained by sieving.

[0052] The heat dissipation powder of the present application reduces interface defects through the synergistic effect of micron-sized skeleton and nano-sized reinforcing material, thereby reducing interface thermal resistance. Micro-nano dual-scale structure refers to a material that contains both micron-sized and nano-sized structural features to achieve cross-scale heat conduction synergy. Micron-sized alumina serves as a rigid skeleton, providing a macroscopic heat conduction path, and nano-sized graphene is embedded inside the skeleton to form a microscopic heat conduction network. The heat dissipation powder of the present application provides a macroscopic heat conduction path through the base material as a micron-sized skeleton, and the reinforcing material is embedded inside the skeleton as a nano-sized filler to form a cross-scale heat conduction network. This structure can effectively reduce phonon scattering and improve phonon transmission efficiency, making the thermal conductivity reach more than 100 W / m·K. Traditional nano materials are prone to agglomeration due to single scale, leading to a decline in local thermal conductivity; micron-sized materials lack the quantum confinement effect of nano-scale. The present application uses micro-nano dual-scale design, taking into account macroscopic uniformity and microscopic heat conduction enhancement, avoiding the defects of single-scale materials. An organic polymer material is deposited on the surface of the functional base material to form an interface modification layer with a thickness of 50-200 nm, which can effectively reduce the interface defects between the base and the reinforcing material and reduce the interface thermal resistance to ≤0.55 mm 2 ·K / W. The interface modifier improves the interfacial bonding between the base and the reinforcing material through chemical bonding or physical adsorption, reduces interface debonding caused by differences in thermal expansion coefficient, and inhibits material degradation at high temperatures, improving long-term stability. Adding semiconductor particles such as zinc oxide and titanium dioxide can adjust the electrical properties of the material and reduce charge accumulation at the interface, further reducing interface thermal resistance. In S2, a three-dimensional network structure is formed by sol-gel method to ensure material uniformity; in S3, a chemical vapor deposition or coating technique is used to deposit an interface modification layer, which is mature and controllable, and is suitable for large-scale production. In S4, calcination is carried out in an inert atmosphere at 700-900℃ to remove organic residues and promote alumina crystal growth, improving material thermal conductivity and mechanical strength. Control of calcination heating rate and time avoids material cracking or excessive sintering.

[0053] As an implementation, the heat dissipation powder includes a base material, a reinforcing material, a functional additive, and an interface modifier. The base material is alumina. The reinforcing material is at least one of graphene or carbon nanotubes. The functional additive is semiconductor particles, and the semiconductor particles are at least one of zinc oxide particles or titanium dioxide particles. The interface modifier is an organic polymer material, and the organic polymer material includes at least one of polydimethylsiloxane or polyimide. The purity of the alumina is greater than or equal to 99%, and the purity of the reinforcing material is greater than or equal to 95%. The purity of the alumina is greater than or equal to 99%, which provides a macroscopic heat conduction path and forms a stable three-dimensional network structure. Graphene or carbon nanotubes serve as nanoscale reinforcing materials and are uniformly dispersed in the alumina framework through a sol-gel method to form a cross-scale heat conduction network. This micron framework and nanofiller structure can significantly reduce phonon scattering and improve the overall thermal conductivity. Traditional nanomaterials are prone to agglomeration, which leads to a decrease in local thermal conductivity, and single micron materials lack the quantum confinement effect of nanoscale. The present application takes into account macroscopic uniformity and microscopic thermal conductivity enhancement through micro-nano dual-scale synergy. Zinc oxide or titanium dioxide as semiconductor particles can adjust the impedance matching of the material through doping, reduce the accumulation of interface charges, and indirectly reduce the interface thermal resistance. In the temperature cycle test, the material exhibits adaptive heat dissipation characteristics, and the thermal conductivity is increased from 120 W / m·K to 150 W / m·K, and the deformation rate is less than 3%. This intelligent response is due to the phase change effect of the interface modifier, and the molecular chain of polydimethylsiloxane is rearranged at high temperatures to enhance the phonon transmission efficiency. The purity of the reinforcing material is greater than or equal to 95% to ensure that graphene or carbon nanotubes have no significant defects and improve the thermal conductivity efficiency. The sol-gel method has a reaction temperature of 50-70°C and a time of 3-5 hours to ensure the uniformity of the three-dimensional network structure. The calcination process is calcined at 700-900°C in an inert atmosphere for 4 hours, with a heating rate of 4-6°C / min, to remove organic residues and promote alumina crystal growth while avoiding material cracking. The particle size of the alumina includes the following designs when used: different particle sizes of alumina, different shapes of alumina, and different particle sizes and shapes of alumina. Different compounding ratios have an impact on the thermal conductivity, and the suitable mass ratio range is 3:7-7:3.

[0054] As an implementation, the diameter of the alumina ranges from 1 pm to 50 pm as a micron-scale skeleton. The diameter of the reinforcing material ranges from 10 nm to 1000 nm. The diameter of the functional additive ranges from 10 nm to 200 nm, which is embedded inside the micron-scale skeleton to form a micro-nano dual-scale structure. The functional additive is embedded inside the micron-scale skeleton by ultrasonic-assisted dispersion, in-situ growth, etc. For example, 30 nm zinc oxide nanoparticles can effectively fill the pores and form a micro-nano structure synergy under the condition of ultrasonic dispersion for 30 minutes and a temperature of 60°C. The ultrasonic-assisted dispersion is performed for 30-60 minutes at an ultrasonic power of 200-400 W and a frequency of 40-60 kHz. The high hardness of the micron alumina provides a rigid skeleton to prevent the structure from collapsing due to the agglomeration of the nanomaterials. For example, the bending strength of the alumina ceramic can reach 300 MPa, while the pure nanocomposite material may have a reduced strength due to loose structure. The melting point of the micron alumina is as high as 2050°C, which keeps the structure stable at high temperatures and avoids the degradation of the nanomaterials at high temperatures. The high hardness of the nanosilicon carbide can disperse stress concentration and reduce crack propagation of the micron skeleton. For example, SiC nanoparticles filling the pores of micron alumina can increase the fracture toughness of the material by 30%. Nanometer organic polymers such as polyurethane can absorb the stress generated by the difference in thermal expansion and reduce the risk of cracking. Micron alumina particles are easily dispersed uniformly in the dissolution solution by ultrasonic treatment, avoiding the agglomeration problem of nanomaterials. Taking 100 nm graphene nanosheets or 50 nm carbon nanotubes as an example, their size is suitable for the micron alumina skeleton of 1-50 pm to construct a dual-scale structure.

[0055] As an implementation, the reinforcing material is at least one of boron nitride nanosheets or silicon carbide, the semiconductor particles are at least one of tin oxide, vanadium oxide, zinc sulfide, or barium titanate, and the organic polymer material includes at least one of at least one of epoxy resin, polyurethane, or polyacrylate.

[0056] As an embodiment, the S1 solution is ethanol or deionized water, and the dispersion process uses ultrasonic treatment, and the ultrasonic treatment time is 20-40 min. The sol-gel reaction process of S2 is controlled at a temperature of 50-70°C, and the reaction time is 3-5 hours. The deposition of S3 includes chemical vapor deposition and coating. The calcination time of S4 is 3-5 hours, the calcination heating rate is 4-6°C / min, and the calcination temperature is 700-900°C. The sifting process of S5 is sifted to 180-220 mesh. Both ethanol and deionized water are polar solvents, which can effectively disperse metal alkoxide or inorganic salt and avoid local concentration differences. The cavitation effect of ultrasonic waves can break up the agglomerates of nanoparticles, improving the uniformity of dispersion. The metal precursors dispersed in ethanol can be combined with the surface functional groups of nanomaterials through hydrogen bonds, providing active sites for subsequent sol-gel reactions. The temperature of 50-70°C is close to the typical reaction temperature of sol-gel method, avoiding the rapid hydrolysis of metal alkoxide or side reactions caused by high temperature. The reaction time of 3-5h can make the metal ions fully complex with the nanomaterials, realizing molecular level doping. Chemical vapor deposition can form a continuous and dense nanocoating on the surface of the substrate, and the spin coating or spraying process is suitable for large-area preparation, with a cost of only 1 / 10 of chemical vapor deposition. The chemical vapor deposition coating as the dominant heat layer and the coating layer as the bonding layer can reduce the interfacial thermal resistance to 0.3mm 2 700-900°C is the crystalline phase transition temperature range of most oxides, which can ensure that the material crystallinity is >90%. The heating rate of 4-6°C / min can avoid stress concentration caused by rapid evaporation of water in the gel. 180-220 mesh corresponds to a particle size of about 60-80μm, which is suitable for subsequent compression molding or injection molding process, avoiding poor flow caused by large particles.

[0057] As an embodiment, in S3, an interfacial modifier is deposited on the surface of the functional initial material to form a dense interfacial modification layer, and the thickness of the interfacial modification layer is 40nm-200nm. The thickness of 40nm-200nm can effectively cover the micro-pores or cracks on the surface of the functional initial material. Thinner modification layer avoids interface cracking caused by the difference in thermal expansion coefficient due to excessive thickness. The thickness of 40nm-200nm can realize the reduction of interfacial thermal resistance to 0.3mm 2K / W. The interface modification layer has a thickness of 40nm-200nm, which is realized by controlling the coating times and curing time, and the thickness of single coating is about 10nm-50nm, and the interval of each coating is 1-3 hours to facilitate uniform curing. For the chemical vapor deposition (CVD) process, the deposition temperature is 800℃-1000℃, and the time is 2-5 hours, so as to control the thickness of the modification layer to be about 50nm. When the deposition temperature is 800℃-1000℃, the temperature is too low, the deposition rate of the modification layer is slow, and the combination with the substrate may not be firm; if the temperature is too high, the modification layer may grow excessively or have structural defects. If the time is 2-5 hours, the thickness of the modification layer is insufficient; if the time is too long, not only the cost is increased, but also the uniformity of the modification layer may be affected

[0058] The application discloses a high-thermal-conductivity and low-interface-thermal-resistance heat dissipation powder, which is prepared by any one of the high-thermal-conductivity and low-interface-thermal-resistance heat dissipation powder preparation methods, and comprises the heat dissipation powder which is composed of the following components in parts by weight: 7-13 parts by weight of a base material, 4-7 parts by weight of a reinforcing material, 1-4 parts by weight of a functional additive and 2-6 parts by weight of an interface modifier.

[0059] The base material is alumina.

[0060] The reinforcing material is at least one of graphene and a carbon nanotube.

[0061] The functional additive is a semiconductor particle, and the semiconductor particle comprises at least one of zinc oxide particles and titanium dioxide particles.

[0062] The interface modifier is an organic polymer material, and the organic polymer material comprises at least one of polydimethylsiloxane and polyimide.

[0063] As an implementation form, the heat dissipation powder is prepared by a sol-gel method and a chemical vapor deposition method. The heat dissipation powder has a microscale and nanoscale dual-scale structure.

[0064] As an implementation form, the thermal conductivity of the heat dissipation powder is greater than or equal to 100 W / m·K, and the interface thermal resistance of the heat dissipation powder is less than or equal to 0.55mm 2 K / W.

[0065] The thermal conductivity of aluminum is high, but the interface thermal resistance between aluminum and an electronic component is high, so that heat is difficult to be efficiently transmitted. In the application, the microscale skeleton and the nanoscale filler are cooperated to reduce the interface thermal resistance and make up for the difference in thermal conductivity. In electronic heat dissipation, the overall heat dissipation performance not only depends on the thermal conductivity of the material itself, but also depends on the interface thermal resistance between the material and the device.

[0066] Example 1:

[0067] Raw material preparation:

[0068] Alumina powder, purity ≥ 99%, diameter 6 μm, 10 g;

[0069] Graphene powder, purity ≥ 99%, diameter 0.6 μm, 5 g;

[0070] Zinc oxide nanoparticles, particle size 30 nm, 2 g;

[0071] Polydimethylsiloxane: 3 g, mixed with anhydrous ethanol to form a 5% polydimethylsiloxane ethanol solution; the polydimethylsiloxane is combined with the surface of the alumina through hydrogen bonds, and at the same time fills the gap between the graphene and the alumina to reduce the interfacial thermal resistance;

[0072] Other additives: 0.4 g of ethylene glycol;

[0073] Preparation steps:

[0074] S1: Disperse the alumina and graphene powder in ethanol, ultrasonic treatment for 30 minutes to form a uniform initial suspension;

[0075] S2: Add zinc oxide nanoparticles to the initial suspension, stir uniformly, and then perform a sol-gel reaction, with the sol-gel reaction temperature controlled at 60°C and the reaction time of 4 hours, to form a functional initial material with a three-dimensional network structure, and specifically the alumina skeleton and the reinforcing material form an interpenetrating network through the sol-gel method;

[0076] S3: The 5% polydimethylsiloxane ethanol solution is coated on the surface of the functional initial material 3 times by the impregnation method, with 2 hours interval between each coating, and solidified in a vacuum oven at 80°C for 24 hours, with a coating thickness of 50 nm, and solidification treatment for 24 hours, to prepare a composite material;

[0077] S4: Place the composite material in a high-temperature calcination furnace and calcine it for 4 hours under a nitrogen atmosphere, with a controlled heating rate of 5°C / min and a calcination temperature of 800°C, to prepare a heat dissipation material;

[0078] S5: Grind the heat dissipation material into powder after cooling, and pass it through a 200-mesh sieve to obtain heat dissipation powder.

[0079] Performance test:

[0080] Thermal conductivity test:

[0081] Test standard: Transient plane source method (TPS), reference ASTM E1225-17 or GB / T 22588-2008 "Flash method for measuring thermal diffusivity or thermal conductivity".

[0082] Test conditions:

[0083] Sample specification: 50 mm x 50 mm square sample, remove surface coating;

[0084] Ambient condition: room temperature 25±2℃, relative humidity <50%;

[0085] Probe closely attached to the sample, ensuring no air gap interference.

[0086] Test area: uniform area in the middle of the encapsulation film.

[0087] Test results: thermal conductivity of 120 W / m·K, taking the average of three repeated tests.

[0088] Interface thermal resistance test:

[0089] Test standard: reference

[0090] ASTM E1461-14

[0091] Standard Test Method for Determining the Thermal Diffusivity of Plastics by the Flash Method

[0092] or

[0093] ISO 22007-2:2008

[0094] Plastics—Determination of thermal diffusivity and thermal conductivity by the laser flash method.

[0095] Test conditions:

[0096] Sample preparation: glass-film-heat dissipation powder three-layer composite sample, the edge is fixed with polyimide tape;

[0097] Laser parameters: energy density 8 J / cm 2 , pulse width 100 μs, scanning interval 100 ms.

[0098] Test area: center area of the composite sample.

[0099] Test results: interface thermal resistance is 0.5 mm 2 ·K / W, taking the average of three repeated tests.

[0100] Intelligent responsiveness test:

[0101] Test standard: temperature cycle test method, reference IEC60068-2-2 "Environmental testing-Part 2-2: Tests-Test B: Dry heat" or ASTM D2290-19 "Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics with a Vitreous Transition".

[0102] Test conditions:

[0103] Temperature cycle range: room temperature 25℃ to 100℃, cycle rate 5℃ / min;

[0104] Monitoring index: thermal conductivity-temperature curve, deformation rate;

[0105] Test area: the area containing all the adhesive film layers in the middle of the adhesive film.

[0106] Test results:

[0107] In the range of 25-100℃, the thermal conductivity increases from 120W / m·K to 150W / m·K;

[0108] The deformation rate is less than 3%, indicating that the heat dissipation powder still maintains structural stability at high temperature.

[0109] The electron microscope picture of the prepared heat dissipation powder is shown in Figure 1 ;

[0110] The particle size test of the prepared heat dissipation powder is shown in Figure 2 .

[0111] Figure 1 The heat dissipation powder in Figure 2 has good aggregation effect, and the distribution of various ions is relatively uniform.

[0112] Example 2

[0113] Different from example 1, replace graphene with carbon nanotubes, purity ≥95%, 5g, and the remaining steps are the same. The test results show that:

[0114] Thermal conductivity: 122W / m·K;

[0115] Interface thermal resistance: 0.40mm 2 ·K / W;

[0116] Intelligent responsiveness: excellent heat dissipation performance under high temperature conditions.

[0117] The electron microscope picture of the prepared heat dissipation powder is shown in Figure 3 ;

[0118] The particle size test of the prepared heat dissipation powder is shown in Figure 4 .

[0119] Figure 3 The heat dissipation powder in the middle has a good aggregation effect, and the distribution of various ions is uniform. Figure 4 The detection result of the particle size in the middle has a high peak, which also shows that the particle aggregation effect in the heat dissipation powder is good.

[0120] Example 3

[0121] Different from example 1, the used aluminum oxide powder is compounded, the base material adopts spherical aluminum oxide 10 μm compounded with flaky aluminum oxide 1 μm, mass ratio 6:4, to form a multi-scale skeleton; the reinforcing material is replaced by 50 nm silicon carbide nanoparticles; the interface modifier adopts epoxy resin, and a 50 nm thick interface layer is formed by chemical vapor deposition. The rest is the same as example 1.

[0122] Thermal conductivity: 115 W / m·K; interface thermal resistance: 0.48 mm 2 ·K / W.

[0123] The electron microscope picture of the prepared heat dissipation powder is shown in Figure 5 ;

[0124] The particle size test of the prepared heat dissipation powder is shown in Figure 6 .

[0125] Figure 5 The heat dissipation powder in the middle has a good aggregation effect, and the distribution of various ions is uniform. Figure 6 The detection result of the particle size in the middle has a high peak, which also shows that the particle aggregation effect in the heat dissipation powder is good.

[0126] Example 4

[0127] Different from example 1, the reinforcing material is replaced by boron nitride nanosheet, thickness <10 nm, lateral size 5 μm; the functional additive is replaced by 50 nm tin oxide nanoparticles; the interface modifier is replaced by polyimide, an 80 nm thick interface layer is formed by coating and heat imidization curing. The rest is the same as example 1.

[0128] Performance data:

[0129] Thermal conductivity: 125 W / m·K;

[0130] Interface thermal resistance: 0.38 mm 2 ·K / W.

[0131] Example 5

[0132] Different from Example 1: the reinforcing material is replaced by carbon nanotubes with a diameter of 20 nm and a length of 1-2 μm; the functional additive is replaced by 25 nm zinc sulfide nanoparticles;

[0133] The interface modifier is replaced by polyurethane (PU) to form a 100 nm thick flexible interface layer by spraying. The rest is the same as Example 1.

[0134] Performance data:

[0135] Thermal conductivity: 110 W / m·K;

[0136] Interface thermal resistance: 0.48 mm 2 K / W.

[0137] Example 6

[0138] Different from Example 1:

[0139] The base material is sheet-shaped alumina with a thickness of 15 μm; the reinforcing material is a mixture of 10 μm silicon carbide microparticles and 30 nm silicon carbide nanoparticles with a mass ratio of 1:1; the functional additive is replaced by 40 nm vanadium oxide; the interface modifier is replaced by polyacrylate to form a 60 nm thick interface layer by CVD. The rest is the same as Example 1.

[0140] Performance data:

[0141] Thermal conductivity at 25°C: 105 W / m·K; at 100°C: 160 W / m·K (VO2 phase change to improve high-temperature thermal conductivity);

[0142] Interface thermal resistance: 0.45 mm 2 K / W.

[0143] Comparative Example 1: single nanographene composite material

[0144] Difference from Example 1:

[0145] No micron alumina skeleton, only epoxy resin as the matrix;

[0146] Single 10 μm nanographene filling amount 20%, no interface modification and calcination process;

[0147] Traditional solution mixing method is used, no three-dimensional network structure is formed.

[0148] Performance data:

[0149] Thermal conductivity: 45 W / m·K;

[0150] Interfacial thermal resistance: 1.2 mm 2 K / W.

[0151] Comparative Example 2: Conventional graphene and epoxy resin composite

[0152] Raw material composition:

[0153] Matrix material: epoxy resin (bisphenol A type), 80 g;

[0154] Nanofiller: graphene nanoplatelets, diameter 1-2 pm, purity 95%, 20 g.

[0155] No interface modifier, no functional additive, no micron skeleton;

[0156] Preparation steps, solution mixing method:

[0157] S1: Add graphene nanoplatelets to ethanol and ultrasonically disperse for 15 min;

[0158] S2: Add epoxy resin and mechanically stir at 60°C for 30 min to form a uniform mixture;

[0159] S3: Pour into a mold and cure at 80°C for 2 h;

[0160] S4: After cooling, crush and grind into powder, pass through a 200 mesh sieve.

[0161] Thermal conductivity: 48 W / m·K;

[0162] Interfacial thermal resistance: 1.15 mm 2 K / W.

[0163] The comparison between Example 1-6 and Comparative Example 1-2 is shown in Table 1.

[0164]

[0165] Table 1

[0166] Result analysis:

[0167] The thermal conductivity of Examples 1-6 is all ≥100 W / m·K, which is increased by 122%-178% compared with Comparative Example 1 single nanographene, and is increased by 108%-160% compared with Comparative Example 2 traditional graphene and epoxy resin. The micron-sized alumina skeleton constructs a macroscopic heat conduction path, and the nanoscale reinforcing material is embedded in the skeleton to form a microscopic heat conduction network, thereby reducing phonon scattering and realizing the double optimization of “macroscopic uniform dispersion and microscopic efficient heat conduction”. Comparative Examples 1-2 lack micron-sized skeletons, and the agglomeration of nanomaterials leads to the breaking of the heat conduction path, and the thermal conductivity is less than 50% of the Examples. The introduction of semiconductor particles can further improve the thermal conductivity. For example, Example 4 uses tin oxide nanoparticles + boron nitride nanosheets, and the thermal conductivity reaches 125 W / m·K, which is increased by 4.2% compared with Example 1. The semiconductor particles indirectly optimize the heat transport efficiency by adjusting the interface charge distribution and reducing phonon-electron scattering.

[0168] The interfacial thermal resistance of Examples 1-6 is all ≤0.55 mm 2 W, which is reduced by 52%-68% compared with Comparative Example 1 and is reduced by 50%-67% compared with Comparative Example 2.

[0169] The organic polymer interfacial modifier such as polydimethylsiloxane and polyimide forms a dense interfacial layer of 50-200 nm through chemical bonding, fills the nanoscale gap, and reduces the difference in thermal expansion coefficient between the matrix and the reinforcing material. Chemical vapor deposition or coating technology ensures the continuity of the interfacial layer, such as the use of polyimide CVD layer in Example 4, and the interfacial thermal resistance is as low as 0.38 mm 2 W.

[0170] Comparative Examples 1-2 do not use interfacial modifiers, and there are a large number of gaps and weakly bonded interfaces between the nanomaterials and the matrix, which leads to the interfacial thermal resistance accounting for 60%-80% of the total thermal resistance.

[0171] Example 6 introduces vanadium oxide semiconductor particles to realize temperature self-adaptive heat conduction: the thermal conductivity is 105 W / m·K at 25°C, and is increased to 160 W / m·K at 100°C, and the deformation rate is less than 3%. The heat conduction performance of traditional materials is fixed and cannot cope with local hot spots or high-temperature working conditions of electronic equipment, while the interfacial modifier phase change effect or semiconductor particles phase change of the material of the present application dynamically improve the heat dissipation efficiency.

[0172] The performance comparison of the heat dissipation powder of the present application and the traditional powder is shown in Table 2.

[0173]

[0174] Table 2

[0175] The present application solves the problems of agglomeration, high interface thermal resistance, insufficient heat conduction efficiency and poor environmental adaptability of traditional heat dissipation materials through the triple innovation of micro-nano double scale structure design, interface modification technology and intelligent regulation of functional additives, and has significant technical barriers and commercial value in the fields of electronic heat dissipation, new energy, aerospace and the like.

[0176] It should be understood that, for those skilled in the art, modifications or changes can be made according to the above description, and all these modifications and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for preparing a heat-dissipating powder with high thermal conductivity and low interfacial thermal resistance, characterized in that, include: S1: The matrix material and the reinforcing material are mixed and then dispersed in a solution to form an initial suspension; S2: Add functional additives to the initial suspension and form a functional initial material with a three-dimensional network structure through the sol-gel method; S3: Deposit an interface modifier on the surface of a functional initial material with a three-dimensional network structure to form a dense interface modification layer and prepare a composite material. S4: The composite material is placed in a high-temperature calcination furnace and calcined under an inert atmosphere to prepare a heat dissipation material; S5: After cooling the heat dissipation material, grind it into powder and sieve it to obtain heat dissipation powder; Heat dissipation powder includes matrix materials, reinforcing materials, functional additives, and interface modifiers; The matrix material is alumina; The reinforcing material is at least one of graphene, carbon nanotubes, boron nitride nanosheets, or silicon carbide; The functional additive is a semiconductor particle, which is at least one of zinc oxide particles, titanium dioxide particles, tin oxide, vanadium oxide, zinc sulfide, or barium titanate. The interface modifier is an organic polymer material, which is at least one of polydimethylsiloxane, polyimide, epoxy resin, polyurethane or polyacrylate. The purity of alumina is greater than or equal to 99%, and the purity of the reinforcing material is greater than or equal to 95%. When using alumina, the particle size can be designed through compounding, including: compounding of alumina with different particle sizes, compounding of alumina with different shapes, and compounding of alumina with different particle sizes and shapes; Alumina has a diameter range of 1μm-50μm, serving as a micron-scale framework; The diameter of the reinforcing material ranges from 10 nm to 1000 nm; The functional additives have a diameter range of 10-200 nm and are embedded inside the micron-scale framework to form a micro-nano dual-scale structure.

2. The method for preparing a heat dissipation powder with high thermal conductivity and low interfacial thermal resistance according to claim 1, characterized in that: S1 solution is ethanol or deionized water. Ultrasonic treatment is used during the dispersion process for 20-40 minutes. During the sol-gel reaction of S2, the temperature is controlled at 50-70℃ and the reaction time is 3-5 hours. S3 deposition includes chemical vapor deposition and coating; The S4 calcination time is 3-5 hours, the calcination heating rate is 4-6℃ / min, and the calcination temperature is 700-900℃; The S5 sieving process uses a sieve mesh size of 180-220.

3. The method for preparing a heat dissipation powder with high thermal conductivity and low interfacial thermal resistance according to claim 1, characterized in that: In S3, an interface modifier is deposited on the surface of the functional initial material to form a dense interface modification layer with a thickness of 40nm-200nm.

4. A heat dissipation powder with high thermal conductivity and low interfacial thermal resistance, prepared by any one of the heat dissipation powder preparation methods described in claims 1-3, characterized in that: The heat dissipation powder is composed of the following components in parts by weight: 7-13 parts matrix material, 4-7 parts reinforcing material, 1-4 parts functional additives, and 2-6 parts interface modifiers. The matrix material is alumina; The reinforcing material is at least one of graphene or carbon nanotubes; The functional additive is a semiconductor particle, which is at least one of zinc oxide particles or titanium dioxide particles. The interface modifier is an organic polymer material, which is at least one of polydimethylsiloxane or polyimide.

5. The heat dissipation powder with high thermal conductivity and low interfacial thermal resistance according to claim 4, characterized in that: The heat dissipation powder was prepared by sol-gel method and chemical vapor deposition method; The heat dissipation powder has a dual-scale structure of micron and nanometer.

6. The heat dissipation powder with high thermal conductivity and low interfacial thermal resistance according to claim 4, characterized in that: The thermal conductivity of the heat dissipation powder is ≥100W / m·K, and the interfacial thermal resistance of the heat dissipation powder is ≤0.55mm. 2 ·K / W.

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