Low-frequency wave-absorbing / heat-conducting composite material and preparation method thereof

Abstract

The application belongs to the field of polymer composite materials, and provides a low-frequency wave-absorbing / heat-conducting composite material and a preparation method thereof.The low-frequency wave-absorbing / heat-conducting composite material is prepared from CoNi fillers and polydimethylsiloxane; the CoNi fillers are prepared from cobalt salt and nickel salt under the conditions of a directing agent and a reducing agent; and the directing agent includes one or more of polyvinylpyrrolidone, cetyltrimethylammonium bromide and diethylenetriamine. The CoNi fillers are prepared by using one or more of polyvinylpyrrolidone, cetyltrimethylammoniun bromide and diethylenetriamine as a shape directing agent, so that the composite material has excellent heat conductivity and wave-absorbing performance; meanwhile, the composite material has high saturation magnetization, low coercivity and low-frequency wave-absorbing performance.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a low-frequency microwave absorbing / thermal conductive composite material and its preparation method. Background Technology

[0002] With the rapid development of 5G communication technology and flexible electronic devices, the resulting low-frequency electromagnetic interference and radiation pollution are becoming increasingly prominent. This not only causes electronic devices to malfunction but also poses a serious threat to human health. Microwave absorbing materials can absorb incident electromagnetic waves and convert them into heat or other energy through mechanisms such as dielectric loss or magnetic loss, effectively solving the problems of electromagnetic interference and radiation pollution. Furthermore, electronic devices generate a large amount of waste heat during operation, leading to temperature increases, decreased performance, and even burnout. High thermal conductivity materials are urgently needed to dissipate excess heat to the external environment in a timely and efficient manner, ensuring the operational stability of electronic devices.

[0003] Polydimethylsiloxane (PDMS) possesses advantages such as flexibility, ease of processing, and good chemical stability, making it widely used as a matrix for functional materials in flexible electronic devices. However, its bulk microwave absorption performance is poor (minimum reflection loss is almost 0 dB) and its thermal conductivity (λ) is low (0.2 W / (m·K)), making it difficult to meet the thermal conductivity and microwave absorption requirements of electronic devices. Therefore, designing and fabricating low-frequency microwave-absorbing PDMS thermally conductive composite materials suitable for the 5G frequency band is crucial for solving the problems of low-frequency electromagnetic pollution and heat accumulation.

[0004] Chinese patent CN114525036A discloses a method for preparing a microwave-absorbing thermally conductive pad, which chemically bonds a thermally conductive boron nitride substrate and a microwave-absorbing graphene substrate, exhibiting excellent thermal conductivity and microwave absorption properties in the direction perpendicular to the pad. Chinese patent CN114105529A discloses a method for preparing a microwave-absorbing thermally conductive pad by coating a thermally conductive filler with liquid metal and blending it with a microwave-absorbing filler. However, the above-mentioned microwave-absorbing thermally conductive polymer composite materials all use a blend of microwave-absorbing and thermally conductive fillers to improve the microwave absorption and thermal conductivity of the polymer composite material, which presents a problem where it is difficult to synergistically improve the thermal conductivity and microwave absorption properties. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a low-frequency microwave absorbing / thermal conductive composite material and its preparation method. The low-frequency microwave absorbing / thermal conductive composite material provided by this invention possesses both excellent thermal conductivity and microwave absorption properties.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a low-frequency microwave absorption / thermal conduction composite material, the raw materials for which include CoNi filler and polydimethylsiloxane;

[0008] The CoNi filler is prepared from cobalt salt and nickel salt as raw materials under the conditions of a directing agent and a reducing agent;

[0009] The directing agent includes one or more of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, and diethylenetriamine.

[0010] Preferably, the preparation method of the CoNi filler includes the following steps:

[0011] Cobalt salt, nickel salt, directing agent, reducing agent and solvent are mixed and a reduction reaction is carried out to obtain the CoNi filler.

[0012] Preferably, the reducing agent includes hydrazine hydrate and / or sodium borohydride.

[0013] Preferably, the weight ratio of the cobalt salt, nickel salt, directing agent, and reducing agent is 20–100:20–100:40–90:120–500.

[0014] Preferably, the mixing of the cobalt salt, nickel salt, directing agent, reducing agent, and solvent includes the following steps: ultrasonically mixing the cobalt salt, nickel salt, directing agent, and solvent, and then adding the reducing agent and stirring to mix.

[0015] Preferably, the reduction reaction is carried out at a pressure of 1–10 MPa, a temperature of 50–300 °C, and a time of 1.5–30 h.

[0016] Preferably, the weight ratio of the CoNi filler to polydimethylsiloxane is 500-2000:50-1000.

[0017] This invention also provides a method for preparing the low-frequency microwave absorbing / thermal conductive composite material described in the above technical solution, comprising the following steps:

[0018] CoNi filler was added to polydimethylsiloxane in several batches and then hot-pressed and cured to obtain the low-frequency microwave absorbing / thermal conductive composite material.

[0019] Preferably, the CoNi filler is added to the polydimethylsiloxane in three batches, namely the first batch, the second batch, and the third batch; the weight ratio of the CoNi filler in the first batch, the second batch, and the third batch is 5:3:2.

[0020] Preferably, the hot-press curing pressure is 0.1-1.0 MPa, the temperature is 25-300°C, and the heat and pressure holding time is 3-10 hours.

[0021] This invention provides a low-frequency microwave absorbing / thermal conductive composite material, the raw materials of which include CoNi filler and polydimethylsiloxane; the CoNi filler is prepared from cobalt salt and nickel salt as raw materials under the conditions of a directing agent and a reducing agent; the directing agent includes one or more of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide and diethylenetriamine.

[0022] This invention uses one or more of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, and diethylenetriamine as shape guiding agents to prepare chain-like CoNi (c-CoNi) fillers, which endow the composite material with excellent thermal conductivity and microwave absorption properties. At the same time, the composite material of this invention has high saturation magnetization, low coercivity, and low-frequency microwave absorption properties. Attached Figure Description

[0023] Figure 1 SEM image of irregular chain-like CoNi prepared in Example 1;

[0024] Figure 2 SEM image of the regular chain-like CoNi prepared in Example 2;

[0025] Figure 3 SEM image of the aggregated CoNi prepared in Example 3;

[0026] Figure 4 The image shows the microwave absorption properties of the c-CoNi / PDMS composite material prepared in Example 4.

[0027] Figure 5 The image shows the microwave absorption properties of the c-CoNi / PDMS composite material prepared in Example 5.

[0028] Figure 6 The image shows the microwave absorption performance of the c-CoNi / PDMS composite material prepared in Example 6. Detailed Implementation

[0029] This invention provides a low-frequency microwave absorption / thermal conduction composite material, the raw materials for which include CoNi filler and polydimethylsiloxane;

[0030] The CoNi filler is prepared from cobalt salt and nickel salt as raw materials under the conditions of a directing agent and a reducing agent;

[0031] The directing agent includes one or more of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, and diethylenetriamine.

[0032] Unless otherwise specified, all raw materials used in this invention are preferably commercially available products.

[0033] The raw materials for preparing the low-frequency microwave absorbing / thermal conductive composite material provided by this invention include polydimethylsiloxane.

[0034] The raw materials for preparing the low-frequency microwave absorbing / thermal conductive composite material provided by the present invention include CoNi filler. In the present invention, the morphology of the CoNi filler preferably includes irregular chain, regular chain, and agglomerated forms, and more preferably regular chain.

[0035] In this invention, the weight ratio of the CoNi filler to polydimethylsiloxane is preferably 500-2000:50-1000, and more preferably 500-1000:250-800.

[0036] In this invention, the CoNi filler is prepared from cobalt salt and nickel salt as raw materials under the conditions of a directing agent and a reducing agent. Preferably, the preparation method of the CoNi filler in this invention includes the following steps:

[0037] Cobalt salt, nickel salt, directing agent, reducing agent and solvent are mixed and a reduction reaction is carried out to obtain the CoNi filler.

[0038] In this invention, the cobalt salt preferably includes one or more of cobalt nitrate, cobalt chloride, and cobalt acetate, and more preferably cobalt chloride. In this invention, the cobalt nitrate is preferably nickel nitrate hexahydrate (Co(NO3)2·6H2O); the cobalt chloride is preferably cobalt chloride hexahydrate (CoCl2·6H2O); and the cobalt acetate is preferably cobalt acetate tetrahydrate ((CH3COO)2Co·4H2O).

[0039] In this invention, the nickel salt preferably includes one or more of nickel chloride, nickel nitrate, and nickel acetate, and more preferably nickel chloride. In this invention, the nickel chloride is preferably nickel chloride hexahydrate (NiCl2·6H2O), the nickel nitrate is preferably nickel nitrate hexahydrate (Ni(NO3)2·6H2O), and the nickel acetate is preferably nickel acetate tetrahydrate ((CH3COO)2Ni·4H2O).

[0040] In this invention, the directing agent includes one or more of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide and diethylenetriamine, more preferably polyvinylpyrrolidone (PVP).

[0041] In this invention, the reducing agent preferably includes hydrazine hydrate and / or sodium borohydride, and more preferably hydrazine hydrate (N2H4·H2O).

[0042] In this invention, the solvent is preferably an alcohol solvent, and the alcohol solvent preferably includes ethanol.

[0043] In this invention, the weight ratio of the cobalt salt, nickel salt, directing agent and reducing agent is preferably 20-100:20-100:40-90:120-500, and more preferably 30-60:30-60:50-80:200-400.

[0044] In this invention, the weight ratio of the cobalt salt to the solvent is preferably 20-100:3000-8000, and more preferably 30-60:3000-5000.

[0045] In this invention, the mixing of the cobalt salt, nickel salt, directing agent, reducing agent, and solvent preferably includes the following steps: ultrasonically mixing the cobalt salt, nickel salt, directing agent, and solvent, and then adding the reducing agent and stirring. In this invention, the reducing agent is preferably added dropwise. In this invention, the ultrasonic mixing power is preferably 120–250 W, more preferably 150–200 W; the time is preferably 15–80 min, more preferably 20–60 min. In this invention, the stirring time is preferably 1–10 min.

[0046] In this invention, the pressure of the reduction reaction is preferably 1-10 MPa, more preferably 2-6 MPa; the temperature is preferably 50-300°C, more preferably 170-185°C; and the time is preferably 1.5-30 h, more preferably 5-20 h.

[0047] In this invention, the reduction reaction is preferably carried out by mixing cobalt salt, nickel salt, directing agent, reducing agent and solvent in a reaction vessel, and then sealing the reaction vessel; the reaction vessel is placed in a drying oven to carry out the reduction reaction.

[0048] Following the reduction reaction, the present invention preferably further includes: naturally cooling the resulting reduction reaction system to room temperature, collecting the precipitate using a magnet, and washing and drying the precipitate. In this invention, the washing includes alternating water washing and alcohol washing; the water washing reagent is preferably distilled water; the alcohol washing reagent is preferably anhydrous ethanol. In this invention, the drying temperature is preferably 10–150°C, more preferably 40–120°C; the drying time is preferably 2–24 hours, more preferably 2–18 hours; the drying is preferably carried out in a vacuum drying oven.

[0049] In this invention, hydrazine hydrate is used as a reducing agent during the preparation of CoNi filler, and the specific reactions between the raw materials are as follows:

[0050] Co 2+ +Ni 2+ +6N2H4→[Co(N2H4)3] 2+ +[Ni(N2H4)3] 2+

[0051] [Co(N2H4)3] 2+ +[Ni(N2H4)3] 2+ +2N2H4→Co↓+Ni↓+8NH3↑+4N2↑+2H2↑+4H +

[0052] Co + Ni → CoNi

[0053] This invention also provides a method for preparing the low-frequency microwave absorbing / thermal conductive composite material described in the above technical solution, comprising the following steps:

[0054] CoNi filler was added to polydimethylsiloxane in several batches and then hot-pressed and cured to obtain the low-frequency microwave absorbing / thermal conductive composite material.

[0055] In this invention, the CoNi filler is preferably added to polydimethylsiloxane in three batches, namely the first batch, the second batch, and the third batch; the weight ratio of the CoNi filler in the first batch, the second batch, and the third batch is preferably 5:3:2.

[0056] In this invention, after the CoNi filler is added to the polydimethylsiloxane in portions, it is preferable to further perform stirring and mixing and degassing treatment. In this invention, the stirring and mixing time is preferably 10–60 min, more preferably 20–40 min; the degassing treatment is preferably performed in a vacuum oven.

[0057] In this invention, the pressure of hot pressing and curing is preferably 0.1 to 1.0 MPa, the temperature is preferably 25 to 300°C, and more preferably 80 to 180°C; the heat preservation and pressure holding time is preferably 3 to 10 hours, and more preferably 3 to 8 hours.

[0058] The following detailed description of the low-frequency microwave absorbing / thermal conductive composite material and its preparation method provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] 48 parts by weight of CoCl2·6H2O, 48 parts by weight of NiCl2·6H2O, and 60 parts by weight of PVP were added to 3900 parts by weight of EG and sonicated for 30 min (power 150W). After mixing evenly, 300 parts by weight of hydrazine hydrate (N2H4·H2O) were added dropwise to the above mixed solution. After mechanical stirring for 5 min, the mixture was sealed in a reaction vessel and placed in a high-temperature forced-air drying oven at 3 MPa and 150℃ for 12 hours. After the reaction was completed and naturally cooled to room temperature, the precipitate at the bottom of the vessel was collected using a magnet and washed alternately with distilled water and anhydrous ethanol. Then, it was placed in a vacuum drying oven at 90℃ for 12 hours to obtain irregular chain-like CoNi.

[0061] Scanning electron microscope (SEM) images of the obtained irregular chain-like CoNi are shown below. Figure 1 As shown. Figure 1 This is a SEM image of the irregularly chained CoNi prepared in Example 1, from... Figure 1 It can be seen that the irregular chain-like CoNi is formed by the disordered assembly of spherical CoNi particles.

[0062] The saturation magnetization and coercivity of the irregularly chain-like CoNi were measured using a vibrating sample magnetometer. Electromagnetic parameters were measured using the ASTM D7449M-2014 / coaxial method. The minimum reflection loss and effective low-frequency absorption bandwidth of the irregularly chain-like CoNi were calculated. The results showed that the saturation magnetization of the obtained irregularly chain-like CoNi was 113.0 emu / g, and the coercivity was 75.3 Oe. When its thickness was 3.2 mm, the minimum reflection loss (RL) was... min The effective absorption bandwidth (EAB) is -44.2dB and the effective absorption bandwidth (EAB) is 3.04GHz (3.84~6.88GHz).

[0063] Example 2

[0064] 48 parts by weight of CoCl2·6H2O, 48 parts by weight of NiCl2·6H2O, and 60 parts by weight of PVP were added to 3900 parts by weight of EG and sonicated for 30 min (power 150W). After mixing evenly, 300 parts by weight of hydrazine hydrate (N2H4·H2O) were added dropwise to the above mixed solution. After mechanical stirring for 5 min, the mixture was sealed in a reaction vessel and placed in a high-temperature forced-air drying oven at 4 MPa and 180℃ for 12 hours. After the reaction was completed and the mixture was naturally cooled to room temperature, the precipitate at the bottom of the vessel was collected using a magnet and washed alternately with distilled water and anhydrous ethanol. Then, the mixture was placed in a vacuum drying oven at 90℃ for 12 hours to obtain regular chain-like CoNi (c-CoNi).

[0065] Scanning electron microscope (SEM) images of the obtained regular chain-like CoNi are shown below. Figure 2 As shown, Figure 2SEM images of the regularly chain-like CoNi prepared in Example 2, from... Figure 2 It can be seen that the CoNi particles are regularly arranged to form straight chain-like CoNi with a length of about 24 μm.

[0066] The saturation magnetization, coercivity, minimum reflection loss, and low-frequency effective absorption bandwidth of the obtained regular chain-like CoNi were tested using the method in Example 1. The results showed that the saturation magnetization was 120.5 emu / g and the coercivity was 100.9 Oe. When its thickness was 3.9 mm, RL... min The low-frequency EAB is -50.5dB, and the low-frequency EAB is 1.04GHz (2.64~3.68GHz).

[0067] Example 3

[0068] 48 parts by weight of CoCl2·6H2O, 48 parts by weight of NiCl2·6H2O, and 60 parts by weight of PVP were added to 3900 parts by weight of EG and sonicated for 30 min (power 150W). After mixing evenly, 300 parts by weight of hydrazine hydrate (N2H4·H2O) were added dropwise to the above mixed solution. After mechanical stirring for 5 min, the mixture was sealed in a reaction vessel and placed in a high-temperature forced-air drying oven at 5 MPa and 210℃ for 12 hours. After the reaction was completed and naturally cooled to room temperature, the precipitate at the bottom of the vessel was collected using a magnet and washed alternately with distilled water and anhydrous ethanol. Then, it was placed in a vacuum drying oven at 90℃ for 12 hours to obtain agglomerated CoNi.

[0069] Scanning electron microscope (SEM) images of the obtained aggregated CoNi are shown below. Figure 3 As shown. Figure 3 SEM images of the aggregated CoNi prepared in Example 3, from... Figure 3 It can be seen that CoNi particles agglomerate to form clusters of CoNi.

[0070] The saturation magnetization, coercivity, minimum reflection loss, and effective low-frequency absorption bandwidth of the obtained agglomerated CoNi were tested using the method in Example 1. The results showed that the saturation magnetization was 104.8 emu / g and the coercivity was 106.8 Oe. When its thickness was 4.2 mm, RL... min The low-frequency EAB is -17.5dB, and the low-frequency EAB is 0.48GHz (2.00~2.48GHz).

[0071] Example 4

[0072] The regular chain-like CoNi prepared in Example 2 was divided into three parts at a mass ratio of 5:3:2, with 600 parts by weight. The parts were added to 400 parts by weight of PDMS one by one. The mixture was mechanically stirred for 30 minutes, and after degassing, it was poured into a mold. Then, it was hot-pressed at 100°C and 0.8 MPa for 3 hours to prepare a low-frequency absorbing c-CoNi / PDMS thermally conductive composite material.

[0073] The microwave absorption properties of the obtained low-frequency absorbing c-CoNi / PDMS thermally conductive composite material are as follows: Figure 4 As shown. Figure 4 The image shows the microwave absorption performance of the low-frequency absorbing c-CoNi / PDMS thermally conductive composite material prepared in Example 4. Figure 4 It can be seen that when the composite material thickness is 2.4 mm, RL min The low-frequency EAB is -41.4dB, and the low-frequency EAB is 1.20GHz (6.80~8.00GHz).

[0074] The electromagnetic parameters of the low-frequency absorbing c-CoNi / PDMS thermally conductive composite material were tested using ASTM D7449M-2014, and its microwave absorption performance was calculated. The thermal conductivity of the low-frequency absorbing c-CoNi / PDMS thermally conductive composite material was tested using ISO 22007-2:2008. The tensile strength and elongation at break of the low-frequency absorbing c-CoNi / PDMS thermally conductive composite material were tested using ASTM D638. The hardness of the low-frequency absorbing c-CoNi / PDMS thermally conductive composite material was tested using GB 2411-1980. The results are as follows: λ ∥ The strength is 1.43 W / (m·K), the tensile strength is 4.7 MPa, the elongation at break is 125%, and the hardness is 50 HA.

[0075] Example 5

[0076] The regular chain-like CoNi prepared in Example 2 was divided into three parts at a mass ratio of 5:3:2, with 650 parts by weight. Each part was added to 350 parts of PDMS, and the mixture was mechanically stirred for 30 minutes. After degassing, the mixture was poured into a mold and then hot-pressed at 100°C and 0.8 MPa for 3 hours to prepare a low-frequency absorbing c-CoNi / PDMS thermally conductive composite material.

[0077] The microwave absorption properties of the obtained low-frequency absorbing c-CoNi / PDMS thermally conductive composite material are as follows: Figure 5 As shown. Figure 5 The image shows the microwave absorption performance of the low-frequency absorbing c-CoNi / PDMS thermally conductive composite material prepared in Example 5. Figure 5 It can be seen that when the composite material thickness is 4.1 mm, RLmin The low-frequency EAB is -56.7dB, and the low-frequency EAB is 1.04GHz (2.96~4.00GHz).

[0078] The microwave absorption properties, thermal conductivity, tensile strength, elongation at break, and hardness of the obtained low-frequency microwave absorbing c-CoNi / PDMS thermally conductive composite material were tested using the method in Example 4. The results are as follows: λ ∥ It has a strength of 2.05 W / (m·K), a tensile strength of 4.1 MPa, an elongation at break of 111%, and a hardness of 56 HA. The low-frequency EAB can fully cover the n78 band (3.3~3.8GHz) required for 5G communication.

[0079] Example 6

[0080] The regular chain-like CoNi prepared in Example 2 was divided into three parts at a mass ratio of 5:3:2 and added to 300 parts by weight of PDMS in turn. The mixture was mechanically stirred for 30 minutes, and after degassing, it was poured into a mold. Then, it was hot-pressed at 100°C and 0.8 MPa for 3 hours to prepare a low-frequency absorbing c-CoNi / PDMS thermally conductive composite material.

[0081] The microwave absorption properties of the obtained low-frequency absorbing c-CoNi / PDMS thermally conductive composite material are as follows: Figure 6 As shown. Figure 6 The image shows the microwave absorption properties of the c-CoNi / PDMS composite material prepared in Example 6. Figure 6 It can be seen that when the composite material thickness is 4.6 mm, RL min The low-frequency EAB is -17.7dB, and the low-frequency EAB is 0.48GHz (2.00~2.48GHz).

[0082] The microwave absorption properties, thermal conductivity, tensile strength, elongation at break, and hardness of the obtained low-frequency microwave absorbing c-CoNi / PDMS thermally conductive composite material were tested using the method in Example 4. The results are as follows: λ ∥ It has a strength of 2.44 W / (m·K), a tensile strength of 3.0 MPa, an elongation at break of 67%, and a hardness of 64 HA.

[0083] 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 principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-frequency microwave absorbing / thermal conductive composite material, characterized in that, The raw materials for preparation include CoNi filler and polydimethylsiloxane; The preparation method of the CoNi filler includes the following steps: 48 parts by weight of CoCl2·6H2O, 48 parts by weight of NiCl2·6H2O, and 60 parts by weight of polyvinylpyrrolidone were added to 3900 parts by weight of ethylene glycol and sonicated at 150W for 30 min. After mixing evenly, 300 parts by weight of hydrazine hydrate were added dropwise to the mixed solution. After mechanical stirring for 5 min, the mixture was sealed in a reaction vessel and placed in a high-temperature forced-air drying oven at 4 MPa and 180℃ for 12 hours. After the reaction was completed and the mixture was naturally cooled to room temperature, the precipitate at the bottom of the vessel was collected using a magnet and washed alternately with distilled water and anhydrous ethanol. Then, the mixture was placed in a vacuum drying oven at 90℃ for 12 hours to obtain the CoNi filler. The CoNi filler is a straight chain of CoNi arranged in a regular pattern with a length of 24 μm. The preparation method of the low-frequency microwave absorbing / thermal conductive composite material includes the following steps: CoNi filler was added to polydimethylsiloxane in several batches and then hot-pressed and cured to obtain the low-frequency microwave absorbing / thermal conductive composite material. The CoNi filler was added to polydimethylsiloxane in three batches, namely the first batch, the second batch, and the third batch; the weight ratio of the CoNi filler in the first batch, the second batch, and the third batch was 5:3:

2.

2. The low-frequency microwave absorbing / thermal conductive composite material according to claim 1, characterized in that, The weight ratio of the CoNi filler to polydimethylsiloxane is 500~2000:50~1000.

3. The method for preparing the low-frequency microwave absorbing / thermal conductive composite material according to any one of claims 1 to 2, characterized in that, Includes the following steps: CoNi filler was added to polydimethylsiloxane in several batches and then hot-pressed and cured to obtain the low-frequency microwave absorbing / thermal conductive composite material. The CoNi filler was added to polydimethylsiloxane in three batches, namely the first batch, the second batch, and the third batch; the weight ratio of the CoNi filler in the first batch, the second batch, and the third batch was 5:3:

2.

4. The preparation method according to claim 3, characterized in that, The hot-press curing pressure is 0.1~1.0MPa, the temperature is 25~300℃, and the heat and pressure holding time is 3~10 hours.

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