Insulating heat-conducting silicone grease, preparation method and application

Abstract

The invention provides insulating heat-conducting silicone grease and a preparation method and application thereof.The preparation method comprises the steps that spherical aluminum oxide is modified through a silane coupling agent, and modified aluminum oxide is obtained; mixing the modified aluminum oxide and the hydroxylated hexagonal boron nitride nanosheet, adding deionized water and a pH value regulator, mechanically shearing, collecting supernate, and drying to obtain KA-coated BN powder; and stirring the KA-coated BN powder, simethicone, a catalyst and an auxiliary agent, reacting, grinding, and removing bubbles to obtain the insulating heat-conducting silicone grease. According to the preparation method, the insulating heat-conducting silicone grease which is extremely high in inertness and not easy to prepare on a large scale can be prepared on a large scale, and the insulating heat-conducting silicone grease has high heat conductivity, corrosion resistance and insulativity and can be applied to the field of electronics and electromagnetism.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of infrastructure and IT support, and particularly relates to an insulating and heat-conducting silicone grease, a preparation method and application. BACKGROUND

[0002] Heat management and dissipation are common problems in many high-power heat exchange systems. In addition, with the rapid development of the fifth generation wireless system technology (5G), the heat density of the chip processor, the number of antennas, the strength of the electromagnetic signal and the screen ratio of the device have significantly increased. The fifth generation wireless system technology (5G) has put forward higher performance requirements and future growing needs for heat-conducting materials, especially with the emergence of 5G high-frequency signals, non-metallic materials such as glass, ceramics and polymers will gradually replace metal matrix materials.

[0003] At present, polymer-based materials have become one of the best heat transfer / dissipation candidate materials in future 5G applications due to their insulation, low cost, light weight and easy processing characteristics. However, the thermal conductivity of polymer-based materials is very poor, which greatly hinders their practical application. Therefore, the development of heat-conducting silicone grease with excellent electrical insulation performance, high thermal conductivity, low density, excellent oxidation resistance and significant mechanical strength has become a current research hotspot. SUMMARY

[0004] In order to solve the problems existing in the above-mentioned technologies, the present application proposes an insulating and heat-conducting silicone grease, a preparation method and application.

[0005] The first aspect embodiment of the present application proposes a preparation method of an insulating and heat-conducting silicone grease, comprising the following steps: modifying spherical alumina by using a silane coupling agent to obtain modified alumina; mixing the modified alumina and hydroxylated hexagonal boron nitride nanosheets, then adding deionized water and a pH adjuster, mechanically shearing and collecting supernatant to dry to obtain KA@BN powder; stirring, reacting, grinding and degassing the KA@BN powder, dimethyl silicone oil, catalyst and adjuvant to obtain the insulating and heat-conducting silicone grease.

[0006] In some embodiments of the present application, the preparation process of the modified alumina comprises: the spherical alumina is sequentially subjected to rinsing, ultrasonic treatment and drying, and then modified by using the silane coupling agent; and / or, the drying condition before the modification of the spherical alumina by using the silane coupling agent is 60-100℃ drying for 5-48h.

[0007] In some embodiments of the present application, in step (1), the spherical alumina after rinsing, ultrasonic, and drying is mixed with the silane coupling agent in a volume ratio of 1:2-3, then heated at 60-100°C for 1-10 h, and finally washed with a cleaning solution and dried to obtain the modified alumina And / or, the cleaning solution comprises ethanol and deionized water in a volume ratio of 3:7, and the washing is performed 2-6 times.

[0008] In some embodiments of the present application, in the preparation of the KA@BN powder, the mass ratio of the modified alumina to the hexagonal boron nitride nanosheet is 1:2-5. And / or, the pH adjuster is acetic acid, and the pH of the mixed solution is adjusted to 4.3-4.7. And / or, the mixed solution is subjected to mechanical shearing at 20-80°C for 6-20 h. And / or, the supernatant is obtained by centrifugation at 1000-2000 rpm / min for 10-30 min. And / or, the supernatant is washed with ethanol and deionized water for 2-6 times, respectively, and then dried.

[0009] In some embodiments of the present application, in the preparation of the insulating and heat-conducting silicone grease, the addition amount of the KA@BN powder is 1-5 wt% based on the dimethyl silicone oil. And / or, the catalyst is a platinum catalyst. And / or, the auxiliary agent comprises a silicone oil pre-dispersion and 3,7,11-trimethyldodecane-3-alcohol. And / or, the total addition amount of the auxiliary agent and the catalyst does not exceed 1% of the reaction system in terms of mass percentage. And / or, the stirring time of the KA@BN powder, the dimethyl silicone oil, the catalyst, and the auxiliary agent is 0-4 h. And / or, the reaction time is 10-48 h. And / or, the grinding is performed at least 3 times, and the mixture is uniformly stirred for 1 h before vacuuming to remove bubbles.

[0010] In the above embodiments, the application utilizes a silane coupling agent to achieve in-situ exfoliation and functionalization of BNNSs, and combines spherical alumina particles to form a stable and effective heat conduction path, wherein the presence of the silane coupling agent can well improve the dispersibility of the BNNSs in silicone oil, and the spherical alumina can enable the modified BNNS nanosheets to be stably spliced without destroying the structure of the BNNS nanosheets, thereby forming a good heat conduction path, so that the insulating and heat-conducting silicone grease is successfully synthesized, and the insulating and heat-conducting silicone grease which is inert and difficult to be mass-produced can be prepared in large quantities. Therefore, the silane coupling agent effectively solves the two key problems of high chemical stability of BNNSs which leads to difficulty in mass production and poor dispersibility due to nanosheets, particles and easy agglomeration.

[0011] The second aspect of the application provides an insulating and heat-conducting silicone grease obtained by the preparation method of any one of the first aspect.

[0012] In some embodiments of the application, the insulating and heat-conducting silicone grease is of a core-shell structure, comprising a shell composed of hexagonal boron nitride nanosheets and spherical alumina wrapped in the shell, and the shape of the hexagonal boron nitride nanosheets in the insulating and heat-conducting silicone grease remains complete.

[0013] In some embodiments of the application, the mass percentage of the KA@BN powder in the insulating and heat-conducting silicone grease is 10%-60%.

[0014] In some embodiments of the application, the thermal conductivity of the insulating and heat-conducting silicone grease is at most 6.42 W / (m·K), and the volume resistivity is more than 1.50*10 13 Ω·cm.

[0015] In the above embodiments, the insulating and heat-conducting silicone grease of the application is of a core-shell structure, the spherical alumina is first wrapped with BNNS, and then a heat conduction network is built in a ball-sheet integrated manner, and a quasi-isotropic heat conduction composite material is prepared by connecting the spherical alumina and the two-dimensional boron nitride sheet. The structure design allows effective heat transfer while maintaining the integrity of the nanosheet, and has high thermal conductivity.

[0016] In addition, the insulating and heat-conducting silicone grease of the application has excellent ductility, can achieve uniform distribution even in a small amount, and has good insulation and high corrosion resistance, and can be used for efficient heat dissipation of metal electronic devices in high humidity environment, overcoming the shortcomings of high cost, poor electromagnetic shielding ability and poor corrosion resistance of existing heat-conducting silicone grease.

[0017] The third aspect of the application provides the application of the insulating and heat-conducting silicone grease of any one of the second aspect in the field of electronics and electromagnetism.

[0018] In the above embodiment, the insulating heat-conducting silicone grease of the present application can be used on the surface of high-performance graphics processing units (GPUs) and general-purpose central processing units (CPUs). Due to its high thermal conductivity and low thermal resistance, the insulating heat-conducting silicone grease can significantly reduce the surface temperature of high heat flux chips and improve the performance of the chips, overcoming the shortcomings of high cost, poor thermal conductivity and poor corrosion resistance of existing heat-conducting silicone grease.

[0019] In summary, according to the insulating heat-conducting silicone grease, the preparation method and the application of the present application, the preparation method of the present application can mass-produce the insulating heat-conducting silicone grease which is extremely inert and not easy to mass-produce. The insulating heat-conducting silicone grease of the present application has high thermal conductivity, corrosion resistance and insulation, and can be used in electronic and electromagnetic equipment under high humidity, overcoming the shortcomings of high cost, poor thermal conductivity and poor corrosion resistance of existing heat-conducting silicone grease.

[0020] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings herein are incorporated into the specification and form part of the specification, showing embodiments consistent with the present application, and together with the specification, serve to explain the principles of the present application, and do not constitute undue limitations on the present application.

[0022] Figure 1 Preparation method flow chart of the insulating heat-conducting silicone grease according to the embodiments of the present application; Figure 2 Schematic diagram of the construction of the heat-conducting network in the insulating heat-conducting silicone grease according to the embodiments of the present application; Figure 3 Schematic diagram of the extension flow of the insulating heat-conducting silicone grease according to the embodiments of the present application.

[0023] Figure 4 Resistivity diagram of the insulating heat-conducting silicone grease according to the embodiments of the present application; Figure 5 Thermal conductivity diagram of the insulating heat-conducting silicone grease according to the embodiments of the present application; Figure 6 Schematic diagram of the corrosion resistance of the insulating heat-conducting silicone grease according to the embodiments of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments are described below by referring to the drawings.

[0025] Heat management and dissipation are common problems in many high-power heat exchange systems. In addition, with the rapid development of the fifth generation wireless system technology (5G), the heat density of the chip, the number of antennas, the strength of electromagnetic signals and the screen ratio of the device have increased significantly. The fifth generation wireless system technology (5G) has higher performance requirements and future growing needs for thermally conductive materials, especially with the emergence of 5G high-frequency signals, non-metallic materials such as glass, ceramics, polymers will gradually replace metal matrix materials.

[0026] Polymer-based materials are one of the best heat transfer / dissipation candidates for future 5G applications due to their insulating, low-cost, lightweight, and easy-to-process properties. However, the thermal conductivity of polymer-based materials is very poor, which greatly hinders their practical application. In order to ensure the efficiency and reliability of 5G devices, it is very important to improve the thermal conductivity of polymer-based materials. Silicone oil is one of the best choices for electronic packaging thermal interface materials due to its low price, insulation, oil resistance, solvent resistance, excellent gas barrier performance, and biodegradable performance. In addition, silicone oil has excellent mechanical properties, good weather resistance, long service life, and other characteristics.

[0027] In the current research field, in addition to traditional thermally conductive particles such as alumina nanoparticles and aluminum nitride fibers, graphene in two-dimensional materials is the most popular. Related technologies show that graphene has extremely high thermal conductivity, exceeding 4000 W / (m·K), which is much higher than the thermal conductivity of copper (400 W / (m·K). Therefore, graphene as a thermally conductive filler can well improve the thermal conductivity of polymers. However, graphene is an excellent conductive material, which makes it unsuitable for environments that require good electrical insulation performance. In addition, when defects occur in graphene or graphene forms a three-dimensional network structure in polymer-based materials, the composite material will be converted into a good electromagnetic absorption / shielding material, and as a metal it will also interfere with 5G high-frequency signals. Therefore, the development of thermally conductive silicone grease with excellent electrical insulation performance, high thermal conductivity, low density, excellent oxidation resistance, and significant mechanical strength has become a current research hotspot.

[0028] Hexagonal boron nitride (h-BN), also known as "white graphene", is a two-dimensional layered material composed of the same number of boron and nitrogen atoms alternately at the six corners of a planar hexagon. Hexagonal boron nitride nanosheet (BNNS) has a similar lattice constant to graphene, with a lattice mismatch of less than 1.7%, so it has similar properties to graphene, such as excellent mechanical properties, chemical stability, good lubricity, and unique optical properties. Most importantly, h-BN also has high thermal conductivity, with a theoretical thermal conductivity of 1700-2000 W / m·K. However, due to the difference in ionicity between boron and nitrogen atoms, h-BN exhibits excellent insulating properties (the band gap of multi-layer BNNS is 5.2-5.4 eV, and that of single-layer is about 5.97 eV), which makes h-BN a good thermal conduction and heat dissipation material in cases where electrical conduction is not allowed.

[0029] Related art provides a scheme for preparing a heat-conducting silicone grease using aluminum oxide, zinc oxide heat-conducting powder, grinding and dispersing in a ball mill, and incorporating silicone oil. However, the heat-conducting silicone grease includes 10-30 parts by weight of silicone oil and 170-5700 parts by weight of heat-conducting powder, which uses too much heat-conducting powder and makes the flowability of the heat-conducting silicone grease poor. Related art also provides a scheme for preparing a composite heat-conducting silicone grease using aluminum oxide, aluminum nitride, boron nitride, silicon nitride, and silicon carbide composite powder, and then using an organic treatment agent for modification. However, this scheme has the disadvantage of relying on too many types of heat-conducting powder, which can damage the flowability when incorporated in too much.

[0030] Related art provides a scheme for preparing a heat-conducting silicone grease by incorporating liquid metal. However, this scheme has the disadvantage that the liquid metal itself can conduct electricity, which can reduce the insulating properties of the heat-conducting silicone grease. Related art also provides a scheme for preparing a heat-conducting silicone grease using spherical boron nitride, flaky boron nitride, spherical aluminum oxide, and a silane coupling agent. However, the treatment ratio and process of the pre-treated heat-conducting powder to hexagonal boron nitride nanosheet (BNNS) in this scheme are not reasonably adjusted, and the contact between the filler particles does not form a high-efficiency heat-conducting network, so the heat-conducting coefficient of the heat-conducting silicone grease does not perform optimally.

[0031] In some related art, a quasi-isotropic thermal conductive composite material is prepared by connecting spherical aluminum oxide and two-dimensional boron nitride sheets. However, the heat transport network in the thermal conductive composite material is fragmented between spherical aluminum oxide and two-dimensional boron nitride sheets (BNNS), and the heat transfer between them needs to overcome a large interfacial thermal resistance. At the same time, BNNS tends to agglomerate itself, making it difficult to build a continuous and effective two-dimensional heat-conducting path in space, and the heat-conducting path formed by spherical aluminum oxide is also easily broken by BNNS agglomerates, causing the heat-conducting path to be discontinuous and the heat-conducting performance to be poor, which is suitable for ordinary occasions with low requirements for heat-conducting performance. Therefore, the main bottlenecks currently plaguing the synthesis of high-thermal-conductivity silicone grease from hexagonal boron nitride nanosheet (BNNS) include: ①BNNSs has excellent chemical stability and strong inertness, which makes it difficult to be prepared on a large scale, resulting in great obstacles in industrial applications, so it is necessary to ensure high yield while preparing BNNSs; ②BNNSs has poor dispersibility, which determines the effect of heat conduction path of BNNSs, and is the key to successful synthesis of high-thermal-conductivity silicone grease; ③At present, the use of thermal conductive silicone grease may be used in a high humidity environment, so its insulation and corrosion resistance is also crucial.

[0032] Therefore, the present application provides an insulating thermal conductive silicone grease, a preparation method and application, which has high thermal conductivity and low thermal resistance characteristics, and has high corrosion resistance, to solve the technical problems of high cost and poor electromagnetic shielding ability of the current thermal conductive silicone grease.

[0033] The insulating thermal conductive silicone grease provided by the present application and its preparation method and application will be described in detail below in combination with the drawings.

[0034] Figure 1 The preparation method of the insulating thermal conductive silicone grease provided by the present application is shown in the flow chart. As shown in Figure 1 The first aspect of the present application provides a preparation method of an insulating thermal conductive silicone grease, comprising the following steps: (1) The spherical alumina is modified by using a silane coupling agent to obtain modified alumina; (2) The modified alumina and hydroxylated hexagonal boron nitride nanosheets are mixed, then deionized water and a pH adjuster are added, and the mixture is mechanically sheared and the supernatant is collected and dried to obtain KA@BN powder; (3) The KA@BN powder, dimethyl silicone oil, catalyst and additive are stirred, reacted, ground and degassed to obtain the insulating thermal conductive silicone grease.

[0035] In some embodiments of the present application, in step (1), the spherical alumina is modified by silane coupling agent after being sequentially rinsed, ultrasonicated and dried. In other words, the alumina particles are first rinsed and then ultrasonicated. The rinsing can remove the industrial dust and soluble impurities physically adsorbed on the surface of the alumina particles, and the ultrasonic cleaning can use micro-jet impact to deeply remove stubborn pollutants attached to the surface of the particles and pores. Then, the cleaned alumina particles are placed in an oven, dried at 60-100°C for 5-48h to remove the adsorbed water. The dried spherical alumina is added with silane coupling agent such as KH550 (40-120mL). The addition ratio of the dried spherical alumina to KH550 can be 1:3, which can effectively modify Al2O3 to form an intermediate (Al2O3 / KH550). The chemical formula of KH550 is NH2-(CH2)3-Si(OC2H5)3. The main purpose of adding KH550 is to make the modified Al2O3 have an amino end (-NH2) which can react with the -OH groups of the hydroxylated BNNSs in the subsequent step to form a polymer structure. Alumina is used to form a heat conduction path. The reaction after modifying the alumina can increase the surface reactivity of Al2O3 and reduce the difficulty of the reaction). The spherical alumina and KH550 are heated in a water bath at 60-100°C for 1-10h, and then cleaned with a cleaning solution composed of ethanol and deionized water in a volume ratio of 3:7 for 2-6 times, and then dried to obtain modified alumina (Al2O3 / KH550) for use.

[0036] In some embodiments of the present application, in step (2), the Al2O3 / KH550 obtained in step (1) and the hydroxylated hexagonal boron nitride nanosheet (purchased as a finished product) are first mixed in a mass ratio of 1:2-5. For example, in some embodiments, the mass ratio of Al2O3 / KH550 and the hydroxylated hexagonal boron nitride nanosheet is 1:(2, 3, 4 or 5). In some embodiments, if the mass ratio of Al2O3 / KH550 and the hydroxylated hexagonal boron nitride nanosheet is too high, such as higher than 1:2, the NNSs coating layer is too thin, and there is a bare alumina area, which is easily eroded by water in a high humidity environment. In some embodiments, if the mass ratio of Al2O3 / KH550 and the hydroxylated hexagonal boron nitride nanosheet is too low, such as lower than 1:5, the un-polymerized free nanosheet is easy to agglomerate, which reduces the fluidity of the system.

[0037] When Al2O3 / KH550 and hydroxylated hexagonal boron nitride nanosheets are mixed according to the mass ratio, deionized water and a pH adjuster such as acetic acid are added to adjust the pH value of the solution to 4.3-4.7, and the mixture is placed in a high-energy ball mill for mechanical shearing at 20-80°C for 6-20h, and then the mixture is collected and treated by a centrifuge to separate the insufficiently coated BNNSs and the free KA@BN particles. The separation effect is better when the mixture is centrifuged at a speed of 1000-2000 rpm / min for 10-30 min. This step can significantly improve the uniformity of the KA@BN powder and ensure the batch stability of the subsequent silicone grease. The supernatant obtained by this step is washed with ethanol and deionized water for 2-6 times, for example, the supernatant is washed with ethanol and deionized water for 3 times, and then dried. Finally, the KA@BN (silane coupling agent modified BNNS) powder with good dispersibility is obtained by drying.

[0038] In some embodiments of the present application, in step (3), the KA@BN powder prepared in step (2) is added to dimethyl silicone oil, and the addition amount of the KA@BN powder is 1-5 wt% based on the dimethyl silicone oil; a certain amount of catalyst and additive are then added; the catalyst is platinum catalyst, and the additive includes silicone oil pre-dispersion and 3,7,11-trimethyldodecane-3-ol (TMDO); the silicone oil pre-dispersion can be a black paste well known to those skilled in the art. Based on the reaction system of the KA@BN powder, dimethyl silicone oil, catalyst and additive, the addition amount of the catalyst and additive does not exceed 1% in mass percentage. The KA@BN powder, dimethyl silicone oil, catalyst and additive are stirred in a double planetary mixer to uniformly mix them for 0-4 h, and then left still for 10-48 h to allow the internal components to fully compatibilize and crosslink. Finally, the sample is ground at least 3 times and uniformly stirred for 1 h, and then vacuumized to remove air bubbles, so as to avoid air bubbles from causing the thermal conductivity to decrease. Finally, the insulating and heat-conducting silicone grease (KA@BN heat-conducting silicone grease) is obtained.

[0039] In the above embodiments, the present application uses a silane coupling agent to achieve in-situ exfoliation and functionalization of BNNSs, that is, to efficiently exfoliate and disperse inert BNNSs under mild conditions, to simultaneously obtain reactivity, and to combine spherical alumina particles to form stable and effective heat conduction channels. The presence of the silane coupling agent can well improve the dispersibility of the BNNSs in the silicone oil, and the spherical alumina can make the modified BNNS nanosheets stably lap and form a good heat conduction channel without destroying the structure of the BNNS nanosheets, thereby successfully synthesizing the insulating and heat-conducting silicone grease.

[0040] The second aspect embodiment of the present application proposes an insulating and heat-conducting silicone grease obtained by the preparation method of any one of the first aspect.

[0041] In some embodiments of the present application, the insulating heat-conducting silicone grease is in a core-shell structure, including a shell composed of hexagonal boron nitride nanosheets and a spherical alumina wrapped in the shell; and the shape of the hexagonal boron nitride nanosheets in the insulating heat-conducting silicone grease remains complete.

[0042] In other words, the insulating heat-conducting silicone grease is in a core-shell structure, including a shell composed of hexagonal boron nitride nanosheets and an inner core wrapped in the shell, wherein the inner core is spherical alumina, forming a stable and effective heat-conducting network. In the present embodiment, the insulating heat-conducting silicone grease is a quasi-isotropic thermal conductive composite prepared by connecting spherical alumina and two-dimensional hexagonal boron nitride nanosheets, which is a spherical-plate integrated heat-conducting network composed of spherical alumina particles and hexagonal boron nitride nanosheets, as shown in Figure 2 The structure design allows the insulating heat-conducting silicone grease to realize effective heat transfer while maintaining the integrity of the two-dimensional hexagonal boron nitride nanosheets, and the present insulating heat-conducting silicone grease also maintains the electrical insulation of the material, meeting the strict requirements of data centers for high-performance heat dissipation materials.

[0043] In some embodiments of the present application, the mass percentage content of the KA@BN powder in the insulating heat-conducting silicone grease is 10%-60%.

[0044] The insulating heat-conducting silicone grease in the present embodiment has excellent ductility, and can realize uniform distribution even in the case of a small amount of addition. The obtained KA@BN composite heat-conducting silicone grease was subjected to ductility flowability test, and the ductility flowability test results of the KA@BN composite heat-conducting silicone grease with a concentration of 20% are shown in Figure 3 As shown in Figure 3 It can be seen intuitively that the prepared composite heat-conducting silicone grease has high ductility flowability.

[0045] In some embodiments of the present application, the mass percentage content of the KA@BN powder in the insulating heat-conducting silicone grease is 10%-60%. For example, the mass percentage content of the KA@BN powder in the insulating heat-conducting silicone grease is 10%, 20%, 30%, 40%, 50% or 60%, etc. In some schemes, the mass percentage content of the KA@BN powder in the insulating heat-conducting silicone grease is 5%, 10%, 15% and 20%. As shown in Figure 4 It can be seen that as the content of the KA@BN powder increases, the volume resistance of the insulating heat-conducting silicone grease still remains above 1.50x10 13 Ω·cm, and has good electrical insulation performance.

[0046] In some schemes, the mass percentage content of the KA@BN powder in the insulating heat-conducting silicone grease is 0%, 10%, 15% and 20%, and the thermal conductivity thereof was compared with that of an alumina heat-conducting silicone grease with a mass percentage content of the KA@BN powder of 0%, 10%, 15% and 20%, as shown in Figure 5As shown, the thermal conductivity of the KA@BN composite heat-conducting silicone grease obtained by the present application can reach 6.42 W / (m·K), and the thermal conductivity is better than that of the aluminum oxide heat-conducting silicone grease.

[0047] In some schemes, the corrosion resistance of the KA@BN composite heat-conducting silicone grease in a marine environment is simulated, and the comparative changes of the control sample and the sample coated with the KA@BN composite heat-conducting silicone grease of the present application are observed on the first day, the third day and the seventh day by using the conventional test method in the art, and the schematic diagram is as shown in Figure 6 As shown in Figure 6 The KA@BN composite heat-conducting silicone grease has excellent corrosion resistance and can play a role of corrosion protection barrier, and all the performances ensure that the KA@BN composite heat-conducting silicone grease is expected to be used in electronic devices working in harsh marine environments.

[0048] The third aspect embodiment of the present application proposes the application of the insulating heat-conducting silicone grease of any one of the second aspect in the field of electronic and electromagnetic.

[0049] The thermal conductivity of the insulating heat-conducting silicone grease in the present application is at most 6.42 W / (m·K), and the volume resistivity is more than 1.50×10 13 Ω·cm, and the performance ensures that it can be applied to electronic and electromagnetic devices in high humidity, and can be used as a heat dissipation material for large data centers and computing power networks, for example, can be used on the surface of high-performance GPUs and general-purpose CPUs. Due to its high thermal conductivity and low thermal resistance characteristics, it can significantly reduce the surface temperature of high heat flux chips, improve chip performance, and overcome the shortcomings of high cost and poor thermal conductivity of existing heat-conducting silicone grease, providing an innovative solution to the heat dissipation problem in high-density computing environments. In commercial applications, the insulating heat-conducting silicone grease of the present application can significantly improve the thermal management efficiency of data centers, reduce energy consumption, and reduce equipment failures and maintenance costs caused by overheating.

[0050] Meanwhile, the hexagonal boron nitride nanosheet (BNNSs) is in-situ exfoliated and functionalized by using silane coupling agent KH550, and the spherical aluminum oxide particles form a stable and effective heat conduction path. This unique structural design not only optimizes the heat conduction efficiency, but also maintains the electrical insulation of the material, meeting the strict requirements of data centers for high-performance heat dissipation materials. In addition, its excellent corrosion resistance in high humidity environment makes it an ideal choice for data centers in marine climates or tropical regions. Finally, the durability and low maintenance cost of the material can bring significant economic savings to data center operators, and the environmental protection characteristics also meet the global trend of sustainable development. In addition, the corrosion resistance of the heat-conducting silicone grease in high humidity helps to improve the heat dissipation capacity and system reliability, and has corresponding practical value and market application potential.

[0051] In order to make the skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. It should be noted that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0052] The raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or can be obtained by existing known methods. In addition, the thermal conductivity testing method in some embodiments of the present application is as follows: the sample of the insulating thermal conductive silicone grease is uniformly applied on a copper block, ensuring that the diameter is 12.8 mm, and the thermal conductivity test is performed on each different sample for three times to ensure the reproducibility of the results. The thermal conductivity is measured by using LFA457 analyzer of Germany NETZSCH company, and the heat transfer behavior is evaluated.

[0053] Example 1 This embodiment proposes an insulating thermal conductive silicone grease, its preparation method and specific parameters are as follows: Al2O3 particles are placed in an oven, dried at 60℃ for 24h to remove adsorbed water, then 60mL of KH550 is added, heated at 60℃ water bath for 2h to obtain modified alumina (Al2O3 / KH550), finally washed with a cleaning solution composed of ethanol and deionized water in a volume ratio of 3:7 for 3 times and dried for standby.

[0054] Mix 1.0g of Al2O3 / KH550 and 2.0g of hydroxylated BNNSs, then add deionized water, adjust the pH value of the solution to 4.5±0.2 with acetic acid, and load into a sealed polytetrafluoroethylene ball mill tank with zirconia balls of 3mm and 5mm in diameter. The rotation speed of the planetary mill is set to 300rpm / min, and the mechanical shearing is carried out at 25℃ for 8h. Then the mixed solution is collected and treated by centrifuge at 1000rpm for 10min to remove oversized particles, and then the mixed solution is collected for further treatment. Next, the supernatant is collected after the above mixed solution is treated by centrifuge, and washed with ethanol and deionized water for 3 times respectively, and finally dried at 20-60℃ for 3h to obtain KA@BN powder with good dispersibility.

[0055] Add 1.0g of the prepared KA@BN powder to 80mL of dimethyl silicone oil, and then add 0.1g of platinum catalyst, 0.1g of black paste, and 0.04g of 3,7,11-trimethyldodecane-3-ol (TMDO) (the ratio of the three is 2:2:5) respectively. Stir in a double planetary mixer at 300rpm / min for 1h to mix uniformly. Then let it stand for 24h to allow the internal components to fully compatibilize and crosslink. Finally, grind the sample 3 times, uniformly stir for 1h, and then vacuum to remove bubbles to obtain KA@BN thermal conductive silicone grease.

[0056] The thermal conductivity and corrosion resistance test results of the KA@BN heat-conducting silicone grease prepared in this example show that the thermal conductivity of the KA@BN composite heat-conducting silicone grease obtained in this example can reach 6.42 W / (m·K), and the volume resistivity can exceed 1.50 x 10 13 Ω·cm. The advantage of this composite heat-conducting silicone grease over commercial products is its three-dimensional heat-conducting network, which not only provides excellent heat-conducting performance, but also has excellent corrosion resistance, and can act as a corrosion barrier. All the performances ensure that the KA@BN composite heat-conducting silicone grease is expected to be used in electronic devices working in harsh marine environments.

[0057] Example 2 This example proposes an insulating heat-conducting silicone grease, its preparation method and specific parameters are as follows: Al2O3 particles are placed in an oven, dried at 60°C for 24h to remove adsorbed water, then 60mL of KH550 is added, heated in a 60°C water bath for 2h to obtain modified alumina (Al2O3 / KH550), and finally washed with a cleaning solution composed of ethanol and deionized water in a volume ratio of 3:7 for 3 times and dried for standby.

[0058] First, 1.0g of Al2O3 / KH550 and 2.0g of hydroxylated BNNSs are mixed, then deionized water is added, and the solution pH value is adjusted to 4.5 with acetic acid, and then loaded into a sealed polytetrafluoroethylene ball mill tank with zirconia balls of 3mm and 5mm in diameter. The rotation speed of the planetary mill is set to 300rpm / min, and the mechanical shearing is carried out at 25°C for 8h. Then the mixed solution is collected and treated by centrifuge at 1000rpm for 10min to remove oversized particles, and then the mixed solution is collected for further treatment. Secondly, the supernatant is collected after the above mixed solution is treated by centrifuge, and washed with ethanol and deionized water for 3 times respectively, and finally dried at 70°C for 3h to obtain KA@BN powder with good dispersibility.

[0059] Take 2.0g of the above prepared KA@BN powder and add it to 80mL of dimethyl silicone oil, then add 0.1g of platinum catalyst, 0.1g of black paste, and 0.08g of 3,7,11-trimethyldodecane-3-alcohol (TMDO) (the ratio of the three is 2:2:10) respectively, and stir in a double planetary mixer at 300rpm / min for 1h to make them uniformly mixed. Then let it stand for 24h to allow the internal components to fully compatibilize and crosslink, and finally grind the sample 3 times, uniformly stir for 1h, and then vacuum to remove bubbles to obtain KA@BN heat-conducting silicone grease.

[0060] The thermal conductivity and corrosion resistance test results of the KA@BN heat-conducting silicone grease prepared in this example show that the thermal conductivity of the KA@BN composite heat-conducting silicone grease obtained in this example can reach 6.32 W / (m·K), and the volume resistivity can exceed 1.50 x 10 13Ω·cm. The composite thermal conductive silicone grease has a three-dimensional thermal conductive network, which not only provides excellent thermal conductivity, but also has excellent corrosion resistance and can act as a corrosion barrier. All the performances ensure that the KA@BN composite thermal conductive silicone grease can be used in electronic devices working in harsh marine environments.

[0061] Example 3 This example proposes an insulating thermal conductive silicone grease, the preparation method and specific parameters are as follows: Al2O3 particles are placed in an oven, dried at 60°C for 24h to remove adsorbed water, then 60mL of KH550 is added, heated in a 60°C water bath for 2h to obtain modified alumina (Al2O3 / KH550), and finally washed with a cleaning solution composed of ethanol and deionized water in a volume ratio of 3:7 for 3 times and dried for standby.

[0062] Mix 1.0g of Al2O3 / KH550 and 2.0g of hydroxylated BNNSs, then add deionized water, adjust the solution pH to 4.5 with acetic acid, and load into a sealed polytetrafluoroethylene ball mill tank with zirconia balls of 3mm and 5mm in diameter. The rotational speed of the planetary mill is set to 200rpm / min, and the mechanical shearing is carried out at 25°C for 8h. Then the mixed solution is collected and treated by centrifuge at 1000rpm for 10min to remove oversized particles, and then the mixed solution is collected for further treatment. The supernatant is collected after the above mixed solution is treated by centrifuge, and washed with ethanol and deionized water for 3 times respectively, and finally dried at 70°C for 3h to obtain KA@BN powder with good dispersibility.

[0063] Add 1.0g of the prepared KA@BN powder to 80mL of dimethyl silicone oil, and then add 0.1g of platinum catalyst, 0.1g of black paste, and 0.04g of 3,7,11-trimethyldodecane-3-ol (TMDO) (the ratio of the three is 2:5:5) respectively. Stir in a double planetary mixer at 300rpm / min for 1h to make them uniformly mixed. Then let it stand for 24h to allow the internal components to fully compatibilize and crosslink. Finally, grind the sample 3 times, uniformly stir for 1h, and then vacuum to remove bubbles to obtain KA@BN thermal conductive silicone grease.

[0064] The thermal conductivity and corrosion resistance test results of the KA@BN thermal conductive silicone grease prepared in this example show that the thermal conductivity of the obtained KA@BN composite thermal conductive silicone grease can reach 6.11W / (m·K), and the volume resistivity can exceed 1.50×10 13 Ω·cm. The composite thermal conductive silicone grease has a three-dimensional thermal conductive network, which not only provides excellent thermal conductivity, but also has excellent corrosion resistance and can act as a corrosion barrier. All the performances ensure that the KA@BN composite thermal conductive silicone grease can be used in electronic devices working in harsh marine environments.

[0065] Therefore, the insulating heat-conducting silicone grease of the present application has excellent heat conductivity and insulation, is especially suitable for high humidity environment, and meets the demand of data centers for high-performance heat dissipation materials. The insulating heat-conducting silicone grease is functionally treated on the BNNSs by the silane coupling agent KH550, and combines with spherical alumina to form an efficient heat conduction network, thereby improving the heat conduction efficiency and maintaining electrical insulation, and technically meeting the demand of development of thermal interface materials.

[0066] It should be understood that the various forms of flow shown above can be used to reorder, add or delete steps. For example, the steps described in the present disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, which is not limited herein.

[0067] The above detailed description does not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing an insulating and thermally conductive silicone grease, characterized in that, Includes the following steps: Spherical alumina was modified using a silane coupling agent to obtain modified alumina; The modified alumina and hydroxylated hexagonal boron nitride nanosheets were mixed, and then deionized water and a pH adjuster were added. The mixture was mechanically sheared, and the supernatant was collected and dried to obtain KA@BN powder. The KA@BN powder, dimethyl silicone oil, catalyst, and additives are stirred, reacted, ground, and degassed to obtain the insulating and thermally conductive silicone grease.

2. The preparation method according to claim 1, characterized in that, The preparation process of the modified alumina includes: The spherical alumina is sequentially rinsed, ultrasonicated, and dried, and then modified using the silane coupling agent. And / or, the drying conditions for the spherical alumina before modification with the silane coupling agent are: drying at 60-100℃ for 5-48 hours.

3. The preparation method according to claim 2, characterized in that, The spherical alumina, which has been successively rinsed, sonicated, and dried, is mixed with the silane coupling agent at a volume ratio of 1:2-3; then heated at 60℃-100℃ for 1-10 h; finally, it is washed with a cleaning solution and dried to obtain the modified alumina. And / or, the cleaning solution comprises ethanol and deionized water in a volume ratio of 3:7, and the cleaning is performed 2-6 times.

4. The preparation method according to claim 1, characterized in that, The preparation process of the KA@BN powder includes: the mass ratio of the modified alumina and the hexagonal boron nitride nanosheets is 1:2-5; And / or, the pH adjuster is acetic acid, which adjusts the pH of the mixture to 4.3-4.7; And / or, the mixture is mechanically sheared at 20-80°C for 6-20 h; And / or, the supernatant is obtained by centrifugation at 1000-2000 rpm / min for 10-30 min; And / or, the supernatant is washed 2-6 times with ethanol and deionized water respectively and then dried.

5. The preparation method according to any one of claims 1-4, characterized in that, The preparation process of the insulating and thermally conductive silicone grease includes: using the dimethyl silicone oil as a base, the amount of KA@BN powder added is 1-5 wt%; And / or, the catalyst is a platinum catalyst; And / or, the additives include silicone oil predispersant and 3,7,11-trimethyldodecyl-3-ol; And / or, by mass percentage, the total amount of the additive and the catalyst added does not exceed 1% of the reaction system; And / or, the stirring time for the KA@BN powder, the dimethyl silicone oil, the catalyst, and the additive is 0-4 h; And / or, the reaction time is 10-48 h; And / or, grind at least 3 times and stir for 1 hour, then vacuum to remove air bubbles.

6. An insulating and thermally conductive silicone grease, characterized in that, It is obtained by the preparation method according to any one of claims 1-5.

7. The insulating and thermally conductive silicone grease according to claim 6, characterized in that, It has a core-shell structure, comprising a shell composed of hexagonal boron nitride nanosheets and spherical alumina encased within the shell; and the shape of the hexagonal boron nitride nanosheets in the insulating thermal grease remains intact.

8. The insulating and thermally conductive silicone grease according to claim 6, characterized in that, Based on the insulating and thermally conductive silicone grease, the mass percentage of the KA@BN powder is 10%-60%.

9. The insulating and thermally conductive silicone grease according to claim 6, characterized in that, The insulating thermally conductive grease has a maximum thermal conductivity of 6.42 W / (m·K) and a volume resistivity exceeding 1.50 × 10⁻⁶. 13 Ω·cm.

10. The application of the insulating and thermally conductive silicone grease according to any one of claims 6-9 in the field of electronics and electromagnetics.

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