Liquid metal / diamond composite material and preparation method thereof

Abstract

The invention provides a liquid metal / diamond composite material and a preparation method thereof. The preparation method comprises the steps that liquid metal and diamond are mixed in a gradient mode according to the mass ratio of 0.1: 1-0.5: 1, and the liquid metal / diamond composite material is obtained; the gradient mixing process comprises the following steps: mixing for 20-60 seconds at the speed of 500-800 r / min, then mixing for 10-20 seconds at the speed of 1000-1200 r / min, and finally mixing for 5-10 seconds at the speed of 1500-2000 r / min. The liquid metal / diamond composite material prepared by the preparation method has high heat-conducting property and wave-absorbing property.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorption-thermal conduction multifunctional materials technology, specifically relating to a liquid metal / diamond composite material and its preparation method. Background Technology

[0002] As modern electronic devices continue to evolve towards miniaturization, high integration, and high power, especially in 5G communication equipment, radar systems, and high-power power transmission systems, thermal management and electromagnetic wave absorption issues are becoming increasingly prominent. However, existing materials often struggle to achieve an effective balance between thermal conductivity and electromagnetic wave absorption performance. For example, while metals and conductive polymers possess excellent thermal conductivity, their electromagnetic wave absorption capabilities are relatively weak; and although ferromagnetic absorbing materials exhibit excellent electromagnetic loss characteristics, their low thermal conductivity makes them unsuitable for the heat dissipation requirements of high-power devices. Therefore, developing multifunctional composite materials that combine high thermal conductivity with excellent electromagnetic wave absorption performance has become a research hotspot and one of the technological bottlenecks in materials science.

[0003] Diamond, due to its extremely high thermal conductivity and good chemical stability, has been considered an ideal thermal management material. However, because diamond has extremely low electrical conductivity, it is almost an insulator, which limits its ability to absorb electromagnetic waves. Therefore, combining diamond with materials with good electromagnetic response characteristics (such as liquid metals) has become an effective strategy to improve its overall performance. Liquid metals not only have high thermal conductivity and good fluidity, but also possess a certain degree of dielectric modulation capability, and are therefore widely used in the construction of matrices for novel composite microwave absorbing and thermally conductive materials.

[0004] The paper titled "Surface-metallized diamond / liquid metal composites through diamond size engineering as high-performance thermal interface materials," published in Surfaces and Interfaces, Volume 60, page 105989, discloses the preparation of thermally conductive composite materials by mechanically mixing liquid metal (GaInSn) with surface-metallized diamond microparticles (using a Cr / Cu double-layer coating) at a 1:1 volume ratio. The thermal conductivity ranges from 100.8 to 117.8 W / m·K. This successfully constructed a liquid metal / diamond sandwich thermal interface material with extremely low interfacial thermal resistance, excellent insulation properties, and high thermal conductivity. The paper also systematically analyzes the influence of diamond particle size on thermal conductivity, demonstrating that particle size control can effectively optimize the interfacial structure and heat transfer path. While the liquid metal and diamond hybrid material disclosed in this paper exhibits high thermal conductivity, its microwave absorption properties require further improvement.

[0005] The invention patent application with publication number CN119432332A produces a composite material with a thermal conductivity of 80-133 W / m·K by mixing liquid metal with diamond particles and using flake graphite to form bridging channels between the diamond particles. Although the composite material disclosed in this application significantly enhances the thermal conductivity, it does not address improvements in microwave absorption performance.

[0006] Therefore, achieving functional synergy between liquid metal and diamond, while balancing efficient heat conduction and excellent electromagnetic wave absorption, remains one of the core challenges in the current research of this type of composite material, and is also an important direction for future materials engineering design. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the first aspect of this invention provides a method for preparing a liquid metal / diamond composite material, which yields a liquid metal / diamond composite material with both high thermal conductivity and microwave absorption properties.

[0008] The method for preparing liquid metal / diamond composite material provided by the present invention includes: Liquid metal and diamond are gradient-mixed at a mass ratio of 0.1:1 to 0.5:1 to obtain a liquid metal / diamond composite material; The gradient mixing process is as follows: first, mix at 500-800 r / min for 20-60 s, then mix at 1000-1200 r / min for 10-20 s, and finally mix at 1500-2000 r / min for 5-10 s.

[0009] The synergistic effect between the liquid metal and diamond microparticles provided by this invention is a key factor affecting the thermal conductivity and electromagnetic wave absorption capability of the composite material. When the liquid metal content is low, the heat conduction paths between the diamond microparticles are not dense enough, failing to significantly enhance the thermal conductivity of the composite material. Simultaneously, the low electromagnetic loss of the diamond microparticles, being the main component of the composite material, limits the wave absorption effect. When the liquid metal content is high, the liquid metal can form a tighter connection or fill gaps between the diamond microparticles, thereby promoting heat conduction and improving the overall thermal conductivity. However, when the liquid metal content is too high, the overall electrical conductivity of the composite material increases significantly, leading to more electromagnetic waves being reflected, thus reducing the material's wave absorption capability. Therefore, rationally controlling the liquid metal content is crucial for maintaining the high thermal conductivity of the composite material while optimizing impedance matching, which helps to maximize the incidence and absorption of electromagnetic waves.

[0010] In the mixing process of liquid metal and diamond microparticles, the main purpose of gradient mixing is to optimize the dispersibility of diamond microparticles, improve mixing uniformity, form a more continuous and uniform three-dimensional heat conduction network, and effectively control temperature and shear force during stirring, thereby improving the performance and stability of the composite material. During this process, excessively high stirring speeds may cause diamond microparticles to agglomerate due to excessive centrifugal force, thus affecting the mixing effect. By reasonably adjusting the speed gradient, using a lower speed in the initial stage of mixing can promote the gradual dispersion of diamond microparticles in the liquid metal; subsequently, gradually increasing the speed during mixing not only improves mixing efficiency but also effectively avoids excessive agglomeration of diamond microparticles.

[0011] Diamond possesses extremely high thermal conductivity and good chemical stability, making it an ideal material for thermal management. However, its low dielectric constant leads to impedance mismatch, limiting its electromagnetic wave absorption performance. Liquid metals, on the other hand, are ideal diamond matrices for constructing the aforementioned composite materials due to their good fluidity, excellent thermal conductivity, and tunable dielectric properties.

[0012] Preferably, the diamond microparticles have a particle size of 50-150 μm. In this liquid metal / diamond composite material, the liquid metal helps to form a more continuous and uniform three-dimensional heat conduction network between the diamond microparticles, ensuring continuous heat conduction and reducing interfacial thermal resistance. This invention effectively optimizes the interfacial structure and heat transfer path through particle size control, preventing the agglomeration of diamond microparticles from hindering uniform coating of the liquid metal and reducing network continuity. It also avoids insufficient contact points between diamond microparticles, which would lead to poor connectivity of the heat conduction path. Therefore, by controlling the diamond particle size, this invention enables the diamond microparticles to be uniformly dispersed and in full contact with the liquid metal, resulting in a more uniform distribution of the three-dimensional heat conduction network, promoting rapid heat diffusion in the composite material, and thus significantly improving the thermal conductivity of the composite material.

[0013] This invention achieves a continuous and uniform three-dimensional heat conduction network between the liquid metal and diamond particles by synergistically and precisely controlling the appropriate diamond particle size, the ratio of liquid metal to diamond microparticles, and a gradient mixing stirring method. This not only improves the thermal conductivity of the composite material but also enhances its electromagnetic wave absorption capability.

[0014] Preferably, the liquid metal is a gallium-indium alloy (GaIn). GaIn is a preferred material for mixing liquid metal with diamond particles primarily due to its low melting point (15-30°C), allowing it to remain liquid at room temperature or with slight heating, facilitating mixing with diamond particles. Furthermore, GaIn exhibits excellent wettability, effectively penetrating and uniformly coating diamond particles, ensuring good contact and bonding. Other liquid metals, due to their poor wettability, may result in uneven mixing. GaIn also possesses high thermal conductivity, effectively improving the material's thermal management performance, making it particularly suitable for applications with high heat dissipation requirements, such as heat conduction in electronic components. Simultaneously, its relatively low cost provides a higher cost-performance ratio, making it suitable for large-scale applications.

[0015] More preferably, when the mass ratio of liquid metal to diamond microparticles is 0.2:1-0.4:1, this ratio can further ensure that the composite material obtains high thermal conductivity while optimizing the electromagnetic wave impedance of the composite material by adjusting the liquid metal content, thereby achieving effective matching with the impedance of the surrounding environment, promoting the maximum incidence and absorption of electromagnetic waves, and thus exhibiting excellent wave absorption performance. This effectively solves the problem of the difficulty in balancing thermal conductivity and electromagnetic wave absorption performance.

[0016] Preferably, the diamond surface is treated to remove impurities before the liquid metal and diamond are gradient-mixed.

[0017] More preferably, the impurity removal treatment method is to treat the surface with concentrated hydrochloric acid for 1-6 hours, wherein the concentration of the concentrated hydrochloric acid is 36%-38%, in order to remove surface impurities.

[0018] The second aspect of the present invention provides a liquid metal / diamond composite material prepared by the above preparation method. This liquid metal / diamond composite material has both high thermal conductivity and wave absorption functions, good operational performance, and has broad application prospects in the field of composite materials.

[0019] The liquid metal / diamond composite material has a uniform and continuous three-dimensional network structure, giving it an electrical conductivity range of 0.24-2.56 S / m in the 2-18 GHz frequency band.

[0020] This structure not only promotes rapid heat diffusion and improves the thermal conductivity of the material, but also allows the liquid metal and diamond particles to form multiple heterogeneous interfaces, inducing the synergistic effect of various loss mechanisms such as dipole polarization, interface polarization and conduction loss, thereby further enhancing the electromagnetic wave absorption capability of the material.

[0021] Preferably, the thermal conductivity of the liquid metal / diamond composite material can reach 114 W / m·K, the minimum reflection loss can reach -35.87 dB in the 2-18 GHz frequency band, and the maximum effective absorption bandwidth can reach 3.19 GHz (EAB: the frequency bandwidth corresponding to RL < -10 dB). Its thermal conductivity and electromagnetic wave absorption capacity data indicate that the liquid metal / diamond composite material has excellent performance and is a good multifunctional composite material.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention controls the content of liquid metal and diamond, and uses gradient mixing to ensure that the liquid metal is evenly distributed among the diamonds. This minimizes the reflection of electromagnetic waves caused by the increased overall conductivity due to the aggregation of liquid metal, thereby reducing the material's wave absorption capacity. At the same time, it allows the diamonds to overlap directly or indirectly, working synergistically with a small amount of liquid metal to ensure that even with a small amount of liquid metal, a suitable thermal conductivity can be achieved. Thus, the liquid metal / diamond composite material provided by this invention has good thermal conductivity and wave absorption performance. Attached Figure Description

[0023] Figure 1 The surface morphology of the liquid metal / diamond composite material prepared in Examples 1-3 of this invention; Figure 2 The conductivity of the liquid metal / diamond composite material prepared in Examples 1-3 of this invention in the 2-18 GHz frequency band is given. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In liquid metal / diamond composites, the liquid metal content has a decisive impact on conductivity and wave absorption mechanisms. When the liquid metal content is too high, the overall conductivity of the material increases, leading to strong reflection of electromagnetic waves and preventing wave energy from penetrating the material for effective absorption. Conversely, when the liquid metal content is too low, the overall conductive path of the material is discontinuous, weakening the propagation ability of electromagnetic waves and limiting the absorption effect. Therefore, the liquid metal content needs to be precisely controlled between wave transmission and absorption to achieve optimal synergistic control of impedance matching and electromagnetic loss mechanisms. It is worth noting that the electromagnetic wave absorption capacity of composite materials mainly depends on their dielectric constant, permeability, and conductivity, while thermal conductivity is influenced by both lattice vibrations and electronic conduction mechanisms. Therefore, achieving functional synergy between liquid metal and diamond, balancing efficient thermal conduction and excellent electromagnetic wave absorption, remains one of the core challenges in current research on this type of composite material and an important direction for future materials engineering design.

[0026] This invention selects liquid metal as an additive and diamond microparticles as the main component. By optimizing the ratio between the additive and the main component, a liquid metal / diamond composite material with both high thermal conductivity and microwave absorption functions is prepared through gradient mixing. This material not only has good operability but is also suitable for heat dissipation and electromagnetic protection of high-power electronic devices, showing broad application prospects.

[0027] The liquid metal / diamond composite material provided by this invention has significantly improved thermal conductivity: the liquid metal / diamond composite material of this invention has excellent thermal conductivity, with a thermal conductivity as high as 114 W / m·K, which far exceeds the thermal conductivity of existing common thermal conductive and microwave absorbing materials, and can effectively improve the heat dissipation effect of high-power electronic devices.

[0028] The electromagnetic wave absorption performance of the liquid metal / diamond composite material provided by this invention is optimized: by precisely controlling the liquid metal content, the liquid metal / diamond composite material of this invention can achieve effective impedance matching with the surrounding environment, significantly improving the absorption capacity of electromagnetic waves. In the 2-18 GHz frequency band, the material's minimum reflection loss can reach -35.87 dB, and the maximum effective absorption bandwidth is 3.19 GHz, exhibiting excellent electromagnetic wave absorption performance.

[0029] The present invention provides a liquid metal diamond composite material with balanced thermal conductivity and electromagnetic wave absorption: The present invention solves the problem of balancing thermal conductivity and electromagnetic wave absorption in existing materials, so that the composite material can achieve the best balance between the two properties, which meets the dual requirements of high-power electronic devices that require both good thermal management and electromagnetic protection.

[0030] The liquid metal diamond composite material provided by this invention has good operability and has broad application prospects in heat dissipation and electromagnetic protection of high-power electronic devices, providing an efficient solution for related fields.

[0031] Example 1 GaN liquid metal and diamond microparticles with a particle size of 50 μm were mixed. The diamond microparticles were treated with concentrated hydrochloric acid (36%-38%) for 1 hour to remove surface impurities. Subsequently, the liquid metal and diamond microparticles were weighed according to a mass ratio of 0.1:1, and the mixture was put into a high-speed mixer. First, the mixture was mixed at a speed of 500 r / min for 60 s, then at a speed of 1000 r / min for 20 s, and finally at a speed of 1500 r / min for 10 s to obtain a liquid metal / diamond composite material (LM0.1 / D).

[0032] The thermal conductivity and absorption performance of the obtained LM0.1 / D are shown in Tables 1 and 2, respectively. Its thermal conductivity is 68 W / m·K, the minimum reflection loss is -10.48 dB, and the maximum effective absorption bandwidth is 0.59 GHz.

[0033] Example 2 GaN liquid metal and diamond microparticles with a particle size of 100 μm were mixed. The diamond microparticles were treated with concentrated hydrochloric acid (36%-38%) for 3 hours to remove surface impurities. Subsequently, the liquid metal and diamond microparticles were weighed according to a mass ratio of 0.3:1, and the mixture was put into a high-speed mixer. First, the mixture was mixed at a speed of 800 r / min for 20 s, then at a speed of 1200 r / min for 10 s, and finally at a speed of 2000 r / min for 5 s to obtain a liquid metal / diamond composite material (LM0.3 / D).

[0034] The thermal conductivity and absorption performance of the obtained LM0.3 / D are shown in Tables 1 and 2, respectively. Its thermal conductivity is 114 W / m·K, the minimum reflection loss is -35.87 dB, and the maximum effective absorption bandwidth is 3.19 GHz.

[0035] Example 3 GaN liquid metal and diamond microparticles with a particle size of 150 μm were mixed. The diamond microparticles were treated with concentrated hydrochloric acid (36%-38%) for 6 hours to remove surface impurities. Subsequently, the liquid metal and diamond microparticles were weighed according to a mass ratio of 0.5:1, and the mixture was put into a high-speed mixer. First, the mixture was mixed at a speed of 600 r / min for 40 s, then at a speed of 1100 r / min for 15 s, and finally at a speed of 1800 r / min for 6 s to obtain a liquid metal / diamond composite material (LM0.5 / D).

[0036] The thermal conductivity and absorption performance of the obtained LM0.5 / D are shown in Tables 1 and 2, respectively. Its thermal conductivity is 128 W / m·K, the minimum reflection loss is -16.40 dB, and the maximum effective absorption bandwidth is 2.46 GHz.

[0037] Comparative Example 1 The only difference from Example 2 is that the mass ratio of liquid metal to diamond microparticles in Comparative Example 1 is 1:1. Everything else is the same as in Example 2, resulting in a liquid metal / diamond composite material (LM1 / D).

[0038] The thermal conductivity and absorption performance of the obtained LM1 / D are shown in Tables 1 and 2, respectively. Its thermal conductivity is 106.36 W / m·K, the minimum reflection loss is -6.30 dB, and the maximum effective absorption bandwidth is 0 GHz.

[0039] Comparative Example 2 Compared with Example 2 above, the difference of Comparative Example 2 is that this sample is composed only of diamond microparticles and no liquid metal is added, resulting in sample D.

[0040] The absorption performance of the obtained sample D is shown in Table 2. Its minimum reflection loss is -2.82dB and its maximum effective absorption bandwidth is 0GHz.

[0041] Comparative Example 3 Compared with Example 2 above, the difference of Comparative Example 3 is that this sample is composed only of liquid metal and no diamond microparticles are added, resulting in sample LM.

[0042] The thermal conductivity of the obtained sample LM is shown in Table 1, which is 39 W / m·K.

[0043] Comparative Example 4 The only difference from Example 2 is that the liquid metal / diamond composite material (S1-LM1 / D) in Comparative Example 4 was prepared by a non-gradient mixing process (2000 r / min; 5 s).

[0044] The thermal conductivity and microwave absorption performance of the obtained sample S1-LM1 / D are shown in Tables 1 and 2, respectively. Its thermal conductivity is 85.8 W / m·K, the minimum reflection loss is -9.98 dB, and the maximum effective absorption bandwidth is 0.52 GHz.

[0045] Comparative Example 5 The only difference from Example 2 is that the liquid metal / diamond composite material (S2-LM1 / D) of Comparative Example 5 is first mixed at 900 r / min for 90 s, then at 1400 r / min for 30 s, and finally at 2500 r / min for 5 s.

[0046] The thermal conductivity and absorption performance of the obtained sample S2-LM1 / D are shown in Tables 1 and 2, respectively. Its thermal conductivity is 92.4 W / m·K, the minimum reflection loss is -10.45 dB, and the maximum effective absorption bandwidth is 0.54 GHz.

[0047] Comparative Example 6 The thermally conductive material reported in the literature "Excellent Low-Frequency Microwave Absorption and High Thermal Conductivity in Polydimethylsiloxane Composites Endowed by Hydrangea-Like CoNi@BN Heterostructure Fillers, Advanced Materials (IF26.8) Pub Date: 2024-10-09, DOI:10.1002 / adma.202410186" is (CoNi / BN) / PDMS. The thermal conductivity of this material is shown in Table 1, and its thermal conductivity is 7.31 W / m·K.

[0048] Performance Analysis This invention discloses a method for preparing a liquid metal / diamond composite material and the composite material itself, achieving a composite material with both high thermal conductivity and strong microwave absorption. The performance testing methods for the samples prepared in this invention and the comparative sample are as follows: the microwave absorption performance was tested using the coaxial method of a vector network analyzer (test standard GJB5239-2004); the thermal conductivity was tested using a laser thermal conductivity meter (LFA467, NETZSCH, Germany) via the flash method to determine the thermal diffusivity or thermal conductivity (GB / T 22588-2008); the specific heat capacity was determined using a differential scanning calorimeter (DSC 2500, TA, USA); the density was determined using the Archimedes displacement method, and the thermal conductivity (λ) was calculated using the formula λ = α·ρ·cp.

[0049] By comparing the examples and comparative examples, it can be seen that the reasonable control of the parameters and component ratios in each step of the preparation method of the present invention has a key impact on the performance of the final liquid metal / diamond composite material.

[0050] Figure 1The figures show the surface morphology of the liquid metal / diamond composite materials prepared in Examples 1-3 of this invention. As can be seen from the figures, the liquid metal / diamond composite materials prepared by this invention enable uniform dispersion of diamond particles and sufficient contact with the liquid metal, while simultaneously promoting direct or indirect overlap of the diamond particles, thereby forming a synergistic effect. In this way, a small amount of liquid metal can construct a uniform three-dimensional thermal conductivity network, ensuring that the composite material maintains ideal thermal conductivity even with a small amount of liquid metal.

[0051] Figure 2 The figure shows the electrical conductivity of the liquid metal / diamond composite materials prepared in Examples 1-3 of this invention in the 2-18 GHz frequency band. As can be seen from the figure, the electrical conductivity of the composite material increases with the increase of liquid metal content. This result indicates that the connection or filling effect of liquid metal between diamond particles significantly affects the electrical conductivity of the composite material, thereby influencing the incident and absorption efficiency of electromagnetic waves.

[0052] The thermal conductivity of the liquid metal / diamond composite materials obtained in Examples 1-3 of this invention, Comparative Examples 1, 3-5, and other thermally conductive and microwave-absorbing materials is shown in Table 1. It can be seen that the change in liquid metal content in the liquid metal / diamond composite material directly affects the thermal conductivity of the composite material. When the liquid metal content is low, the arrangement between diamond particles may be relatively loose, resulting in limited thermal conductivity. However, as the liquid metal content increases, the filling effect of the liquid metal helps the diamond particles to be arranged more compactly, thereby reducing the gaps between particles. The increase in liquid metal helps to form a more continuous and uniform three-dimensional heat conduction network between diamond particles. This three-dimensional heat conduction network promotes the rapid diffusion of heat in the composite material, significantly improving the thermal conductivity of the material. The liquid metal / diamond composite material obtained in Example 3 has a high thermal conductivity (128 W / m·K), which is much higher than the thermal conductivity of the liquid metal itself and the thermal conductivity of other thermally conductive and microwave-absorbing materials. Furthermore, Comparative Examples 4 and 5 demonstrate that the gradient mixing process can optimize the dispersion of diamond microparticles, improve mixing uniformity, form a continuous and uniform three-dimensional heat conduction network, and effectively control the temperature and shear force during the stirring process, thereby improving the performance and stability of the composite material. Moreover, within the stated speed range, the mixing uniformity can be further improved by reasonably adjusting the rotation speed gradient, avoiding excessive aggregation and dispersion of diamond microparticles, thereby forming a more continuous and uniform three-dimensional heat conduction network and further improving the thermal conductivity of the material.

[0053] The reflection loss (RL) and effective absorption bandwidth (EAB) of the liquid metal / diamond composite materials obtained in Examples 1-3 and Comparative Examples 1, 3-5 in the 2-18 GHz range are shown in Table 2. As can be seen from Examples 1-3, rationally controlling the liquid metal content can optimize the electromagnetic wave impedance of the composite material, thereby achieving effective matching with the impedance of the surrounding environment, promoting maximum incident and absorbed electromagnetic waves, and thus exhibiting excellent absorption performance. This is mainly attributed to the ability of liquid metal to adjust the dielectric properties of the composite material, including the dielectric constant and dielectric loss. Increasing the dielectric constant helps improve the composite material's response to electromagnetic waves, while increasing the dielectric loss helps improve energy conversion efficiency, i.e., the ability to convert electromagnetic energy into heat energy. This adjustment of dielectric properties enables the composite material to exhibit excellent absorption performance within a specific frequency range. Furthermore, the formation of multiple heterogeneous interfaces between the liquid metal and diamond particles induces the synergistic effect of various loss mechanisms such as dipole polarization, interfacial polarization, and conduction loss, further effectively enhancing the material's electromagnetic wave absorption capability. In particular, the liquid metal / diamond composite material prepared in Example 2 exhibited a thermal conductivity of 114 W / m·K, a minimum reflection loss of -35.87 dB, and a maximum effective absorption bandwidth of 3.19 GHz (EAB: the frequency bandwidth corresponding to RL < –10 dB) under the condition that the mass ratio of liquid metal to diamond particles was 0.3:1.

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0055] Table 1. Thermal conductivity of samples from the present invention and comparative examples

[0056] Table 2. Reflection loss and effective absorption bandwidth of the present invention's case and comparative case samples in the 2-18 GHz range.

[0057]

Claims

1. A method for preparing a liquid metal / diamond composite material, characterized in that, include: Liquid metal and diamond are gradient-mixed at a mass ratio of 0.1:1 to 0.5:1 to obtain a liquid metal / diamond composite material; The gradient mixing process is as follows: first, mix at 500-800 r / min for 20-60 s, then mix at 1000-1200 r / min for 10-20 s, and finally mix at 1500-2000 r / min for 5-10 s.

2. The method for preparing the liquid metal / diamond composite material according to claim 1, characterized in that, The diamond microparticles have a particle size of 50-150 μm.

3. The method for preparing the liquid metal / diamond composite material according to claim 1, characterized in that, The liquid metal is a gallium-indium alloy.

4. The method for preparing the liquid metal / diamond composite material according to claim 1, characterized in that, The mass ratio of the liquid metal to the diamond particles is 0.2:1 to 0.4:

1.

5. The method for preparing the liquid metal / diamond composite material according to claim 1, characterized in that, Before gradient mixing of liquid metal and diamond, the surface of diamond is cleaned to remove impurities.

6. The method for preparing the liquid metal / diamond composite material according to claim 5, characterized in that, The impurity removal treatment method is to treat the surface with concentrated hydrochloric acid for 1-6 hours, wherein the concentration of the concentrated hydrochloric acid is 36%-38%.

7. A liquid metal / diamond composite material prepared by the method of any one of claims 1-6.

8. The liquid metal / diamond composite material according to claim 7, characterized in that, The liquid metal / diamond composite material has a uniform and continuous three-dimensional network structure.

9. The liquid metal / diamond composite material according to claim 7 or 8, characterized in that, The electrical conductivity of the liquid metal / diamond composite material ranges from 0.24 to 2.56 S / m in the 2-18 GHz frequency band.

10. The liquid metal / diamond composite material according to claim 7, characterized in that, The liquid metal / diamond composite material has a thermal conductivity of 114 W / m·K, a minimum reflection loss of -35.87 dB in the 2-18 GHz frequency band, and a maximum effective absorption bandwidth of 3.19 GHz.

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