Composite material based on liquid metal / diamond hybrid particles, preparation method and application

Abstract

The invention discloses a composite material based on liquid metal / diamond hybrid particles, a preparation method and application, and the preparation method comprises the following steps: step 1, mixing liquid metal and diamond particles, and fully grinding to obtain the liquid metal / diamond hybrid particles; step 2, adding an additive into the base silicone oil, and fully mixing to obtain a silica gel precursor; and 3, stirring and mixing the liquid metal / diamond hybrid particles obtained in the step 1 and the silica gel precursor obtained in the step 2, and curing and forming to obtain the required composite material. The composite material obtained by the invention has high heat-conducting property, high processability and reliable and stable insulating property.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and in particular to a composite material based on liquid metal / diamond hybrid particles, a preparation method and application thereof. Background Art

[0002] In today's electronic equipment field, the trend of high power density and integration is becoming more and more prominent, and the heat dissipation problem has become the core bottleneck restricting the improvement of equipment performance. In key fields such as communications, integrated circuits, and transportation, the heat dissipation demand for electronic devices and industrial equipment is increasing day by day. Electronic devices will generate a lot of heat when they are running for a long time. If the heat dissipation is not timely and sufficient, it will not only lead to performance degradation and shortened life, but may even cause serious safety accidents. Therefore, the research and development of high-performance thermal conductive materials is not only an inevitable trend of technological development, but also a key link to ensure the stable operation of electronic equipment and promote the continuous progress of the electronics industry.

[0003] As a critical thermal interface material in electronic devices, thermal conductive gaskets are mainly used to fill the tiny gap between heating elements and heat dissipation devices, thereby significantly improving the efficiency of heat transfer. At present, the common thermal conductive gaskets on the market are mostly made of polymer composite materials, that is, high thermal conductivity fillers are added to polymer matrices such as silicone rubber and polyurethane, hoping to obtain the characteristics of both polymer softness and high thermal conductivity of fillers.

[0004] Diamond is well-known for its excellent thermal conductivity, which can reach 2000W / m·K at room temperature. It also has a low thermal expansion coefficient and good insulation properties, showing great application potential in the field of heat dissipation. However, the application of diamond in the field of thermal conductive gaskets is relatively rare, mainly because of the many technical difficulties faced in practical applications:

[0005] For example, the preparation process is complicated, and the construction of the thermal conductivity path of the composite material requires the fillers to contact each other. In order to achieve a higher thermal conductivity, a high content of diamond (>50vol%) is usually required. This will lead to excessive viscosity of the system, and the preparation process is difficult, and the molding of the thermal conductive gasket faces great challenges.

[0006] Thermal conductivity is limited, it is difficult for diamond particles to fully contact in the polymer, and there are pores between the particles. Moreover, the surface of diamond is inert and has almost no functional groups, and its interfacial compatibility with the polymer is poor, resulting in pores at the contact between the two. Even if the diamond content is high, it is difficult to achieve the ideal thermal conductivity effect, and the problems of interface thermal resistance and contact thermal resistance are prominent. For example, phonon scattering at the interface between diamond and substrate limits the effective improvement of thermal conductivity, and it is difficult for dispersed diamond particles to form an effective heat transport channel, causing the thermal conductivity of the composite material to be much lower than expected.

[0007] Inconvenient to process and use. Diamond is the hardest substance in nature and is extremely difficult to process. It is easy to scratch electronic devices during use. In addition, after the thermal pad is made, its hardness is relatively high, so there are still a large number of tiny pores between the thermal pad and the heat source and heat dissipation device. The air in the pores is a poor conductor of heat, with a thermal conductivity of only 0.02W / (m·K), which seriously limits its practical application.

[0008] At present, the methods to solve these problems include chemical modification of diamond, such as depositing a layer of polymer on the surface of diamond to improve its compatibility with the substrate, thereby reducing the contact thermal resistance. The advantage of this method is that the operation is relatively simple and can effectively improve the interfacial bonding strength. However, its disadvantage is that the thermal conductivity of the polymer layer used for modification is only 0.2W / (m·K), which is negligible compared to the high thermal conductivity of diamond itself, greatly limiting the improvement of the overall thermal conductivity of the composite material. To solve the problem of hardness, other metals are plated, such as preparing a metal film with high adhesion on the surface of diamond through vacuum coating technology, thereby improving the surface properties of diamond and reducing its scratches on the device. However, this method has the disadvantages of high equipment cost and low production efficiency. Another solution is high temperature treatment, which causes a certain degree of graphitization of the diamond surface through high temperature, thereby reducing its hardness and reducing the risk of scratches. However, this process is complicated, and high temperature treatment may introduce other problems, such as the graphitization of diamond may cause its thermal conductivity to decrease. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a composite material based on liquid metal / diamond hybrid particles, a preparation method and application thereof.

[0010] The technical solution adopted by the present invention is:

[0011] A method for preparing a composite material based on liquid metal / diamond hybrid particles comprises the following steps:

[0012] Step 1: Mix liquid metal and diamond particles, and grind them thoroughly to obtain liquid metal / diamond hybrid particles;

[0013] Step 2: Add additives to the base silicone oil and mix thoroughly to obtain a silicone gel prepolymer;

[0014] Step 3: The liquid metal / diamond hybrid particles obtained in step 1 and the silicone gel precursor obtained in step 2 are stirred and mixed, and then cured and molded to obtain the desired composite material.

[0015] Furthermore, the liquid metal in step 1 is a metal gallium alloy, and the volume ratio of the liquid metal to the diamond particles is 0.02-0.12:1.

[0016] Furthermore, in step 1, the particle size of the diamond particles is in the range of 7 to 200 μm, the grinding pressure is in the range of 0.5 to 2 MPa, and the grinding time is in the range of 10 to 20 min.

[0017] Furthermore, the additives in step 2 include chain extenders, cross-linking agents, inhibitors and catalysts.

[0018] Furthermore, the base silicone oil is a double-terminal ethylene silicone oil with a viscosity of 20-1000 cps; the chain extender is a double-terminal hydrogen-containing silicone oil, and the cross-linking agent is a side-terminal hydrogen-containing silicone oil; the catalyst is a Karstedt catalyst, and the inhibitor is diallyl maleate.

[0019] Further, the mixing process in step 2 is as follows:

[0020] Place the base silicone oil, chain extender, crosslinker and inhibitor in a stirrer; the stirring system is as follows:

[0021] Stir at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, at 60 rpm / min for 60 s, and at 80 rpm / min for 600 s;

[0022] After adding the catalyst and inhibitor dropwise, the mixture was stirred at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, and at 60 rpm / min for 60 s;

[0023] Vacuum to remove air bubbles.

[0024] Furthermore, in step 3, the volume ratio of the liquid metal / diamond hybrid particles to the silica gel is 3:7 to 7:3.

[0025] Furthermore, the stirring system of the liquid metal / diamond hybrid particles and the silica gel in step 3 is as follows:

[0026] Stir at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, at 60 rpm / min for 60 s, and at 80 rpm / min for 600 s;

[0027] Curing is performed at room temperature and under pressure.

[0028] A composite material based on liquid metal / diamond hybrid particles. The composite material uses silica gel as a matrix and the liquid metal / diamond hybrid particles as a dispersant.

[0029] Furthermore, the composite material is used to prepare heat dissipation components of electronic equipment.

[0030] The beneficial effects of the present invention are:

[0031] (1) The present invention uses liquid metal to physically modify diamond, forming a solid-liquid-solid interface on the diamond surface; and can fill tiny defects and pores on the diamond surface; the high thermal conductivity of the liquid metal enables heat to be quickly transferred between the liquid metal and the diamond; the ultra-soft silicone gel tightly wraps the hybrid particles to form a continuous thermal conductive network; so that the obtained composite material has high thermal conductivity;

[0032] (2) The liquid metal used in the present invention plays a lubricating role between diamond particles, reducing the mixed viscosity of the composite system; and the liquid metal is evenly distributed on the diamond surface, and each component is evenly dispersed in the silicone gel, improving the processing performance of the composite material;

[0033] (3) The ultra-soft silicone gel generated by the chain extension-crosslinking reaction of the present invention wraps the diamond with the liquid metal, thereby avoiding the contact between the diamond and the electronic device and reducing the hardness of the composite material;

[0034] (4) The amount of liquid metal added to the composite material of the present invention is small, the ultra-soft silicone gel has good insulation properties, and its structure can isolate the liquid metal, so the composite material has reliable and stable insulation properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic flow chart of the preparation method of the present invention.

[0036] Figure 2 1 is a SEM image of the material obtained in Example 1 of the present invention, a is a SEM image of the diamond used in step 1, and b is a SEM image of the liquid metal / diamond hybrid particles obtained in step 1.

[0037] Figure 3 1 and 2 are SEM images of the composite materials obtained in Example 1 and Comparative Example 1 of the present invention, a is a cross-sectional SEM image of the composite material obtained in Comparative Example 1, and b is a SEM image of the composite material obtained in Example 1. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, a method for preparing a composite material based on liquid metal / diamond hybrid particles comprises the following steps:

[0040] Step 1: Mix the liquid metal and diamond particles, and grind them thoroughly to obtain liquid metal / diamond hybrid particles LM / Dia hybrid particles; the liquid metal is a metal gallium alloy, and the volume ratio of liquid metal to diamond particles is 0.02-0.12:1. Too much liquid metal will increase the conductivity of the thermal pad and weaken the insulation performance of the thermal pad. At the same time, liquid metal leakage is prone to occur during service, posing a potential risk to electronic packaging applications that originally rely on insulation. In addition, since the thermal conductivity of liquid metal is much lower than that of diamond, when the total amount of filler is constant, the higher the liquid metal content, the lower the diamond content, resulting in a lower degree of development of the high thermal conductivity thermal network, and the thermal conductivity of the thermal pad decreases instead. When the liquid metal content is too low, the optimization effect is not obvious.

[0041] The particle size of diamond particles ranges from 7 to 200 μm, the grinding pressure is 0.5 to 2 MPa, and the grinding time is 10 to 20 minutes. The liquid metal is an alloy of metal gallium, including gallium-indium alloy and gallium-indium-tin alloy. The liquid metal and diamond are mixed by grinding, and the grinding is continued for 5-10 minutes after the metallic luster is achieved to ensure that the liquid metal evenly covers the diamond surface. Compared with other methods of dispersing liquid metal, the oxide layer produced during grinding is less, which can just ensure that the liquid metal adheres to the diamond surface without producing too much oxide layer to affect the thermal conductivity.

[0042] Liquid metal is mixed with diamond particles to obtain a "core-shell" structure in which the liquid metal partially covers the diamond surface. This structure can effectively form a solid-liquid-solid connection, improve the interface compatibility between diamonds and between diamonds and polymer matrix, and reduce contact thermal resistance.

[0043] Step 2: Add additives to the base silicone oil and mix them thoroughly to obtain a silicone gel prepolymer; the base silicone oil is a double-terminal ethylene silicone oil with a viscosity of 20-1000cps; the additives include a chain extender, a cross-linker, an inhibitor and a catalyst. The chain extender is a double-terminal hydrogen-containing silicone oil with a viscosity of 10-100cps, and the cross-linker is a side-terminal hydrogen-containing silicone oil with a viscosity of 10-100cps and a hydrogen content of 0.1-5mmol / g; the catalyst is a Karstedt catalyst, which is compatible with liquid silicone rubber, has high catalytic activity, good selectivity and excellent storage stability. The inhibitor is diallyl maleate, which has a significant inhibitory effect and better storage stability than other inhibitors. The molar ratio of vinyl in the base silicone oil to the silicon hydrogen group in the chain extender and cross-linker is 0.8-1.2, the molar ratio of silicon hydrogen group in the chain extender and cross-linker is 1-30, and the amount of the inhibitor is 1-10ppm of the base silicone oil. The dosage of Karstedt catalyst is 5-20ppm of the base silicone oil. It has a good catalytic effect and does not cause yellowing due to excessive catalyst.

[0044] The mixing reaction process is as follows:

[0045] The base silicone oil, chain extender, crosslinker and inhibitor are placed in a double planetary mixer; the stirring system is as follows:

[0046] Stir at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, at 60 rpm / min for 60 s, and at 80 rpm / min for 600 s;

[0047] After adding the catalyst and inhibitor dropwise, the mixture was stirred at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, and at 60 rpm / min for 60 s;

[0048] Vacuum to remove air bubbles.

[0049] Step 3: Stir the liquid metal / diamond hybrid particles obtained in step 1 and the silicone gel prepolymer obtained in step 2 (using a double planetary stirrer for gradient stirring), and then solidify and shape to obtain the desired composite material (LM / Dia / silicone gel composite material). The volume ratio of liquid metal / diamond hybrid particles to silicone gel is 3:7 to 7:3. The stirring system of liquid metal / diamond hybrid particles and silicone gel is as follows:

[0050] Stir at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, at 60 rpm / min for 60 s, and at 80 rpm / min for 600 s;

[0051] Curing is performed at room temperature and under pressure.

[0052] The composite material uses silicone gel as a matrix and liquid metal / diamond hybrid particles as a dispersant. The composite material is used to prepare heat dissipation components of electronic devices, such as thermal conductive pads.

[0053] From a microscopic perspective, the present invention forms a solid-liquid-solid interface on the surface of the diamond after the liquid metal physically modifies the diamond. The liquid metal can fill tiny defects and pores on the surface of the diamond, reducing phonon scattering. As the main carrier of heat conduction, the reduction in phonon scattering means that heat can be conducted more efficiently through diamond particles. At the same time, the high thermal conductivity of the liquid metal enables heat to be quickly transferred between the liquid metal and the diamond, reducing the contact thermal resistance and the interface thermal resistance. When the ultra-soft silicone gel is compounded with the hybrid particles, the silicone gel molecules can tightly wrap the hybrid particles to form a continuous thermal conductive network, thereby fully meeting the heat dissipation needs of electronic equipment and ensuring stable heat dissipation of electronic equipment during high-power operation.

[0054] Liquid metal has the characteristics of low viscosity and high fluidity, which is due to the relatively weak interaction between its atoms, and the atoms can move relatively freely. When liquid metal is mixed with diamond, its molecules or atoms can act as a lubricant between diamond particles, reducing the friction between particles, thereby effectively reducing the mixed viscosity of the composite system. During the stirring process of the double planetary agitator, this low viscosity characteristic reduces the resistance inside the material and the torque required for stirring, so the stirring time is greatly shortened and the energy consumption is significantly reduced. Precise control of preparation process parameters, such as grinding pressure, stirring speed and time, can ensure the uniform distribution of liquid metal on the diamond surface and the uniform dispersion of each component in the silicone gel. This uniform distribution at the microscopic level ensures the stability and consistency of the material's performance at the macroscopic level, providing a reliable guarantee for large-scale industrial production.

[0055] The ultra-soft silicone gel designed by a specific chain extension-cross-linking reaction has a unique molecular structure. During the chain extension-cross-linking reaction, the molecular chains continue to grow and connect to each other, forming a three-dimensional network structure with high flexibility and elasticity. This structure gives silicone gel an extremely low compression modulus, and the liquid metal can undergo a large deformation without breaking when subjected to external force, thereby giving the thermal pad good softness. At the same time, some functional groups in the silicone gel molecular structure, such as hydroxyl and methyl, can undergo physical adsorption or weak chemical reaction with the surface of the heating element and the heat dissipation device, producing a certain adhesion strength, so that the thermal pad can fit tightly on the device surface. This close fit reduces the tiny pores formed by air filling. The thermal conductivity of air is extremely low, and reducing pores means reducing the obstacles to heat transfer, thereby improving heat dissipation efficiency. In addition, due to the wrapping of diamonds by ultra-soft silicone gel and liquid metal, direct contact between diamonds and electronic devices is avoided, effectively preventing the risk of scratching electronic devices due to the high hardness of diamonds, extending the service life of the equipment, and reducing maintenance costs.

[0056] The guarantee of its insulation performance comes from the unique liquid metal wrapped diamond structure design. This design can achieve a significant improvement in thermal conductivity at a very low liquid metal dosage, thereby greatly reducing the amount of conductive liquid metal added, thereby ensuring the overall insulation performance of the material. The ultra-soft silicone gel itself has excellent insulation properties, and its molecular structure can effectively isolate the liquid metal from the electrical contact with the outside world, further enhancing the insulation effect of the material. In addition, by precisely controlling the distribution and content of liquid metal and optimizing the formula of silicone gel, the material can maintain reliable insulation performance while having excellent thermal conductivity, meeting the strict requirements of electronic equipment for insulation performance.

[0057] The diamond thermal conductive silicone gel of the present invention has a wide range of applicability in the field of heat dissipation of various electronic devices due to its unique microstructure and performance advantages. In communication equipment, its good thermal conductivity can quickly dissipate the heat generated by the chip to ensure the stable transmission of communication signals; in integrated circuit chips, low hardness and high adhesion can adapt to the tiny and complex structure of the chip to ensure the heat dissipation effect; in electric vehicle battery management systems, the material has good stability and chemical compatibility, and can work stably for a long time in the complex chemical environment generated by battery charging and discharging, and will not cause performance degradation due to chemical reactions. This adaptability in different complex working environments gives the material a broad market application prospect.

[0058] Example 1

[0059] Liquid metal / diamond hybrid particle based composites were prepared as follows:

[0060] Step 1: Mix liquid metal and diamond particles, and grind them thoroughly to obtain liquid metal / diamond hybrid particles;

[0061] Select diamond with a particle size of 100 microns and a density of 3.5 g / cm 3 The liquid metal is eutectic gallium indium, with a melting point of 15.7°C and a density of 6.25 g / cm 3 , it is liquid at room temperature, which can ensure good thermal conductivity and fluidity; the volume ratio of liquid metal to diamond is 0.11.

[0062] The liquid metal and diamond are placed in a grinding device for grinding; the grinding time is 15 minutes, and the pressure during the grinding process is 1.5 MPa. After grinding, the liquid metal is evenly covered on the surface of the diamond, and the mixture is light gray with a metallic luster.

[0063] Step 2: Add additives to the base silicone oil and mix thoroughly to obtain a silicone gel prepolymer;

[0064] The double-terminal ethylene silicone oil with a viscosity of 100cps was selected as the base silicone oil; the additives were chain extender, cross-linker, catalyst and inhibitor. The chain extender was double-terminal hydrogen-containing silicone oil with a viscosity of 14cps; the cross-linker was side-terminal hydrogen-containing silicone oil with a viscosity of 13cps and a hydrogen content of 1.95mmol / g. The catalyst was a Karstedt catalyst, and the inhibitor was diallyl maleate.

[0065] The molar ratio of vinyl in the base silicone oil to silyl hydrogen in the chain extender and crosslinker is 1, the molar ratio of silyl hydrogen in the chain extender and crosslinker is 5, and the dosage of the inhibitor is 2 ppm of the base silicone oil.

[0066] Put the base silicone oil, chain extender, crosslinking agent and inhibitor in a double planetary agitator, start the agitator, and stir them according to the gradient stirring process of 20 rpm / min for 60 s, 40 rpm / min for 60 s, 60 rpm / min for 60 s, and 80 rpm / min for 600 s to make them uniformly mixed.

[0067] Then, 10 ppm of Karstedt catalyst was added to the base silicone oil, and the double planetary stirrer was used again to stir evenly at a speed of 20 rpm / min for 60 s, 40 rpm / min for 60 s, and 60 rpm / min for 60 s to obtain a silicone gel prepolymer.

[0068] The prepolymer was placed in a vacuum environment for 3 minutes to completely remove bubbles.

[0069] Step 3: Mix the liquid metal / diamond hybrid particles obtained in step 1 and the silicone gel precursor obtained in step 2 in a volume ratio of 7:3. Use a double planetary stirrer to stir and mix, and stir at a speed of 20 rpm / min for 60 seconds, 40 rpm / min for 60 seconds, 60 rpm / min for 60 seconds, and 80 rpm / min for 600 seconds to make the mixture uniform.

[0070] The stirred mixture was spread in a U-shaped mold with a thickness of 1 mm and pressurized and cured at room temperature for 12 hours to finally obtain the desired composite material of diamond / liquid metal / ultra-soft silicone gel.

[0071] Figure 2 Figure a is a SEM image of a diamond particle with a particle size of 50 μm. As can be seen from the figure, the fine morphology of the diamond particles is a typical truncated octahedral geometry, with a smooth surface, regular shape, and uniform size. However, the smooth surface of the particles suggests that their surface is chemically inert: the carbon atoms sp 3 The saturation of the hybrid structure results in a lack of active functional groups such as hydroxyl and carboxyl groups on the surface, and no microscopic mechanical interlocking structures (such as nano-grooves or protrusions). Although this low surface energy characteristic is beneficial to improving the intrinsic hardness and thermal stability of the material, when it is composited with a polymer matrix, it will reduce the thermal conductivity and mechanical properties of the composite material due to weak interfacial chemical bonding and insufficient physical anchoring effect.

[0072] Figure 2Figure b is a SEM image of the hybrid particles of diamond particles and liquid metal, where the volume ratio of liquid metal to diamond is 0.11:1. As can be seen from the figure, the liquid metal is tightly attached to the diamond surface, and its flow characteristics make the encapsulation layer present a smooth curved surface transition. This encapsulation behavior reflects that the liquid metal has excellent wettability and adsorption ability on the diamond surface, which may be due to the surface oxide layer (gallium oxide) of the liquid metal and the diamond sp 3 The charge distribution of the carbon structure forms a stable physical interaction. This hybrid structure provides a new idea for the functional modification of thermal conductive gaskets: the liquid metal layer can act as a flexible interface layer between diamond and polymer matrix, and can also use its intrinsic high thermal conductivity (~15W / m·K) and diamond (>2000W / m·K) to build a multi-level thermal conductive path, thereby synergistically improving the interface heat conduction efficiency of the composite gasket.

[0073] Figure 3 Figure a is a scanning electron microscope image of the diamond-silicon gel thermal conductive composite material. Figure 3 Figure b is a scanning electron microscope image of the diamond / liquid metal hybrid particle-silicone gel thermal conductive composite material. Comparing these two images, it can be clearly seen that the addition of liquid metal has a significant impact on the microstructure of the composite material, thereby improving the thermal conductivity of the composite material. Figure 2 As can be seen in Figure a, the diamond surface only forms a weak van der Waals force bond with the silicone gel due to its chemical inertness. The silicone gel loosely wraps the diamond, and exposed diamond edges and micron-sized pits on the surface can be seen in some areas. The heat conduction path is interrupted and the heat transfer efficiency is low. Figure 2 It can be seen from Figure b that after adding liquid metal to physically modify the diamond, the liquid metal forms a uniform metal coating layer on the surface of the diamond, forming a diamond (solid)-liquid metal (liquid)-silicone gel / diamond (solid) interface. This layer of metal not only fills the tiny defects and gaps on the surface of the diamond particles, but also enhances the bonding force between the particles and the matrix.

[0074] Example 2

[0075] The other steps of this embodiment are the same as those of Embodiment 1, except that in step 3, the volume ratio of the liquid metal / diamond hybrid particles to the silicone gel is 5:5.

[0076] Example 3

[0077] The other steps of this embodiment are the same as those of Embodiment 1, except that in step 3, the volume ratio of the liquid metal / diamond hybrid particles to the silicone gel is 3:7.

[0078] Example 4

[0079] The other steps of this embodiment are the same as those of Embodiment 1, except that in step 3, the volume ratio of the liquid metal / diamond hybrid particles to the silicone gel is 9:1.

[0080] Example 5

[0081] The other steps of this embodiment are the same as those of Embodiment 1, except that in Step 1, the volume ratio of liquid metal to diamond is 0.02:1.

[0082] Example 6

[0083] The other steps of this embodiment are the same as those of Embodiment 1, except that in Step 1, the volume ratio of liquid metal to diamond is 0.077:1.

[0084] In order to illustrate the effect of the present invention, the following comparative example is set.

[0085] Comparative Example 1

[0086] The other steps of this comparative example are the same as those of Example 1, except that step 1 is not included, and in step 3, diamond and silicone gel are directly mixed in a volume ratio of 7:3.

[0087] Comparative Example 2

[0088] The other steps of this comparative example are the same as those of Example 1, except that the volume ratio of liquid metal to diamond in step 1 is 0.167:1.

[0089] Comparative Example 3

[0090] The other steps of this comparative example are the same as those of Example 1, except that step 2 is not included, and in step 3, Dow Corning 184 is used to replace the silicone gel prepared in step 2.

[0091] The resistivity, thermal conductivity and hardness of the composite materials obtained in the above examples and comparative examples were tested according to existing methods. The results are shown in Table 1.

[0092] Table 1. Performance parameters of examples and comparative examples

[0093]

[0094]

[0095] The experimental results show that the thermal conductivity of the thermally conductive gasket is closely related to the diamond / liquid metal content. As shown in Examples 1-4, as the diamond / liquid metal content increases, the thermal conductivity increases significantly, reaching 9.85W / (m·K) at a content of 70vol%, reaching a maximum value. However, when the content increases further, the thermal conductivity decreases due to factors such as filler agglomeration, increased interface and contact thermal resistance.

[0096] On the other hand, Examples 1, 5-6 and Comparative Examples 1-2 show that when the content of diamond / liquid metal hybrid particles is fixed, as the amount of liquid metal increases, the thermal conductivity of the thermally conductive gasket shows a trend of first rising and then falling. When the volume ratio of liquid metal to diamond is 0.117, the thermal conductivity reaches the maximum value, and the thermal conductivity is increased by 115% compared with Comparative Example 1 without adding liquid metal under the same filler content. Specifically, when the liquid metal content is low, a large amount of diamond builds a thermal conduction path, and the liquid metal forms a solid-liquid-solid interface on the diamond surface, filling the tiny defects and pores on the diamond surface. The high thermal conductivity characteristics of liquid metal enable heat to be quickly transferred between liquid metal and diamond. As the liquid metal content increases, the contact thermal resistance and the interface thermal resistance decrease, and the thermal conductivity increases. However, when the amount of liquid metal increases further, the amount of diamond decreases, the thermal conduction path decreases, and the thermal conductivity decreases accordingly.

[0097] Inevitably, the addition of liquid metal deteriorates the insulation performance of the thermally conductive gasket to a certain extent. However, due to the unique structure design of liquid metal wrapped in diamond, a significant improvement in thermal conductivity is achieved at a very low amount of liquid metal, thereby greatly reducing the amount of conductive liquid metal added. Example 1 In the end, the material can maintain reliable insulation performance while having excellent thermal conductivity, meeting the strict requirements of electronic equipment for insulation performance (>10^8Ω·cm).

[0098] In addition, Example 1 and Comparative Example 3 show that the Shore A hardness of the thermal conductive gasket prepared by using the homemade silicone gel is 57% lower than that of the thermal conductive gasket prepared by using Dow Corning 184.

[0099] The composite material prepared by the method of the present invention can be used as a thermally conductive gasket, which can be used in current electronic devices to solve the heat dissipation problem of current equipment. In addition, the problems existing in the current preparation process, such as the inertness of the diamond surface, poor compatibility with the polymer matrix interface, and numerous pores between particles and at the contact with the polymer, cause serious contact thermal resistance and interface thermal resistance problems, and greatly limit the thermal conductivity efficiency. In the processing and use links, the extremely high hardness of diamond is not only difficult to process, but also easy to scratch electronic devices during use. The manufactured thermally conductive gasket has a large number of tiny pores between the heat source and the heat dissipation device due to its high hardness, and the low thermal conductivity of air further weakens the heat dissipation effect.

[0100] Innovatively adopt liquid metal / diamond hybrid particles and compound with self-designed ultra-soft silicone gel; liquid metal has high thermal conductivity, good wettability, low viscosity and high fluidity due to its liquid properties at room temperature, forming a solid-liquid-solid interface on the diamond surface, which can not only repair diamond surface defects, but also enhance the interface compatibility with the polymer matrix, effectively overcome the contact thermal resistance and interface thermal resistance problems, and room temperature operation reduces production costs. At the same time, the ultra-soft silicone gel designed by specific chain extension-cross-linking reaction has extremely low compression modulus and certain adhesion strength. While improving thermal conductivity, it also takes into account the softness and fit of the thermal conductive gasket, fully meeting the stringent requirements of electronic equipment heat dissipation, and significantly improving the heat dissipation performance of electronic equipment and the comprehensive performance of materials.

Claims

1. A method for preparing a composite material based on liquid metal / diamond hybrid particles, characterized in that: The following steps are involved: Step 1: Mix liquid metal and diamond particles, and grind them thoroughly to obtain liquid metal / diamond hybrid particles; Step 2: Add additives to the base silicone oil and mix thoroughly to obtain a silicone gel prepolymer; Step 3: The liquid metal / diamond hybrid particles obtained in step 1 and the silicone gel precursor obtained in step 2 are stirred and mixed, and then cured and molded to obtain the desired composite material.

2. The method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 1, characterized in that: The liquid metal in step 1 is a metal gallium alloy, and the volume ratio of the liquid metal to the diamond particles is 0.02-0.12:

1.

3. The method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 1, characterized in that: In step 1, the particle size of the diamond particles is in the range of 7 to 200 μm, the grinding pressure is in the range of 0.5 to 2 MPa, and the grinding time is in the range of 10 to 20 min.

4. The method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 1, characterized in that: The additives in step 2 include chain extenders, cross-linking agents, inhibitors and catalysts.

5. The method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 4, characterized in that: The base silicone oil is double-terminal ethylene silicone oil with a viscosity of 20-1000 cps; the chain extender is double-terminal hydrogen-containing silicone oil, the cross-linking agent is side-terminal hydrogen-containing silicone oil; the catalyst is a Karstedt catalyst, and the inhibitor is diallyl maleate.

6. A method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 5, characterized in that: The mixing process in step 2 is as follows: Place the base silicone oil, chain extender, crosslinker and inhibitor in a stirrer; the stirring system is as follows: Stir at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, at 60 rpm / min for 60 s, and at 80 rpm / min for 600 s; After adding the catalyst and inhibitor dropwise, the mixture was stirred at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, and at 60 rpm / min for 60 s; Vacuum to remove air bubbles.

7. The method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 1, characterized in that: In step 3, the volume ratio of the liquid metal / diamond hybrid particles to the silica gel is 3:7 to 7:

3.

8. The method for preparing a composite material based on liquid metal / diamond hybrid particles according to claim 1, characterized in that: The stirring system of the liquid metal / diamond hybrid particles and the silica gel in step 3 is as follows: Stir at 20 rpm / min for 60 s, at 40 rpm / min for 60 s, at 60 rpm / min for 60 s, and at 80 rpm / min for 600 s; Curing is performed at room temperature and under pressure.

9. A composite material based on liquid metal / diamond hybrid particles obtained by any preparation method of claims 1 to 8, characterized in that: The composite material uses silica gel as a matrix and liquid metal / diamond hybrid particles as a dispersant.

10. The use of a composite material based on liquid metal / diamond hybrid particles as claimed in claim 9, characterized in that: The composite material is used for preparing heat dissipation components of electronic equipment.

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