An insulating, heat-conducting and wave-absorbing composite powder, its preparation method and application

Abstract

The present invention discloses an insulating, heat-conducting and wave-absorbing composite powder and its preparation method and application. The preparation method of the insulating, heat-conducting and wave-absorbing composite powder of the present invention comprises the following steps: 1) Mixing soft magnetic metal powder and mercapto silane coupling agent and carrying out plasma ball milling to obtain soft magnetic metal sheets modified by the silane coupling agent; 2) Mixing the soft magnetic metal sheets modified by the silane coupling agent and hexagonal boron nitride and carrying out plasma ball milling to obtain the insulating, heat-conducting and wave-absorbing composite powder. The insulating, heat-conducting and wave-absorbing composite powder of the present invention has excellent wave-absorbing performance, good heat conductivity, and excellent oxidation resistance, corrosion resistance and electrical insulation. The silicone rubber composite material prepared by adding it into liquid silicone rubber has excellent wave-absorbing, heat-conducting, insulating, anti-aging and other properties, and is suitable for fields such as 5G communication, new energy vehicles, and electromagnetic protection.

Description

Technical Field

[0001] The invention relates to the technical field of heat-conducting and wave-absorbing materials, and in particular to an insulating heat-conducting and wave-absorbing composite powder and a preparation method and application thereof. Background Art

[0002] In recent years, with the rapid development of the electronics and communications industries, electromagnetic radiation pollution in the environment has become increasingly serious. In order to reduce the impact of electromagnetic radiation on the normal operation of electronic communication equipment and human health, researchers have conducted in-depth research on various absorbing materials, and absorbing materials based on soft magnetic metal materials have received widespread attention. Soft magnetic metal materials have the characteristics of high saturation magnetization and near-zero magnetostriction, and can achieve microwave absorption through magnetic loss. However, soft magnetic metal materials such as iron (Fe), cobalt (Co), nickel (Ni) and their alloys are relatively active at room temperature and are easily oxidized, especially in high temperature processes. The degree of oxidation will be further aggravated. Moreover, soft magnetic metal materials are easily corroded and lose their magnetism by the action of media such as salt spray, acid and alkali. In addition, soft magnetic metal materials usually have high conductivity, so they have poor insulation and are prone to impedance mismatch, which greatly limits their application in electronic and electrical appliances.

[0003] Therefore, it is of great significance to develop a thermally conductive and absorbing material with excellent absorbing performance, good thermal conductivity, oxidation resistance, corrosion resistance, and high insulation. Summary of the invention

[0004] The object of the present invention is to provide an insulating heat-conducting wave-absorbing composite powder and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A method for preparing an insulating, heat-conducting, and wave-absorbing composite powder comprises the following steps:

[0007] 1) mixing soft magnetic metal powder and mercaptosilane coupling agent and performing plasma ball milling to obtain a soft magnetic metal sheet modified by silane coupling agent;

[0008] 2) The soft magnetic metal sheet modified by the silane coupling agent and the hexagonal boron nitride are mixed and subjected to plasma ball milling to obtain an insulating, heat-conducting and wave-absorbing composite powder.

[0009] Preferably, a method for preparing an insulating, heat-conducting, and wave-absorbing composite powder comprises the following steps:

[0010] 1) adding soft magnetic metal powder, mercaptosilane coupling agent and ethanol into a ball mill, adding zirconium oxide balls, performing plasma ball milling, and drying to obtain a soft magnetic metal sheet modified by a silane coupling agent;

[0011] 2) Add the soft magnetic metal sheet modified by silane coupling agent, hexagonal boron nitride and ethanol into the ball mill, and then add zirconium oxide balls.

[0012] Then plasma ball milling and drying are performed to obtain insulating, heat-conducting and wave-absorbing composite powder.

[0013] Preferably, the insulating heat-conducting and wave-absorbing composite powder comprises the following raw materials in percentage by mass:

[0014] Soft magnetic metal powder: 16% to 95%;

[0015] Hexagonal boron nitride: 4.9% to 80%;

[0016] Mercaptosilane coupling agent: 0.1%~4%.

[0017] Preferably, the soft magnetic metal powder is at least one of carbonyl iron powder, sendustine powder, iron silicon chromium powder and iron nickel powder.

[0018] Preferably, the average particle size of the soft magnetic metal powder is 1 μm to 80 μm.

[0019] Preferably, the average particle size of the hexagonal boron nitride is 1 μm to 40 μm.

[0020] Preferably, the mercaptosilane coupling agent is at least one of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltriethoxysilane.

[0021] Preferably, the mass ratio of the zirconia balls to the material (ie, the soft magnetic metal powder and the mercaptosilane coupling agent, or the soft magnetic metal sheet modified by the silane coupling agent and hexagonal boron nitride) is 10 to 150:1.

[0022] Preferably, the filling rate of the ball mill (the ratio of the total volume of the zirconium oxide balls and the material to the volume of the ball mill) is 30% to 80%.

[0023] Preferably, the plasma ball milling is performed at a ball milling speed of 500 rpm to 2000 rpm.

[0024] Preferably, the plasma ball milling is performed under the condition that the plasma discharge frequency is 5kHz to 12kHz.

[0025] Preferably, the plasma ball milling is carried out in an argon atmosphere, a nitrogen atmosphere, an oxygen atmosphere or an air atmosphere.

[0026] Preferably, the plasma ball milling is performed under the condition of an atmosphere pressure of 0.05 MPa to 0.20 MPa.

[0027] Preferably, the plasma ball milling is performed in a cyclic ball milling manner, wherein each cyclic process includes ball milling for 10 to 40 minutes and a pause for 20 to 40 minutes, and the total ball milling time is 2 to 10 hours.

[0028] Preferably, the drying is carried out at 80°C to 120°C, and the drying time is 2h to 6h.

[0029] An insulating, heat-conducting, and wave-absorbing composite powder is prepared by the above-mentioned preparation method.

[0030] Preferably, the particle size of the insulating, heat-conducting, and wave-absorbing composite powder is 2 μm to 150 μm.

[0031] A silicone rubber composite material, comprising the following components in parts by weight:

[0032] Vinyl silicone oil: 100 parts;

[0033] Hydrogenated silicone oil: 1 to 6 parts;

[0034] The above-mentioned insulating, heat-conducting and wave-absorbing composite powder: 50 to 400 parts;

[0035] Fumed silica: 1 to 10 parts;

[0036] Platinum catalyst: 0.1 to 0.8 parts;

[0037] Inhibitor: 0.01 to 0.2 parts.

[0038] Preferably, the platinum catalyst is at least one of methylvinylsiloxane-platinum complex, platinum-tetrahydrofuran complex, and chloroplatinic acid.

[0039] Preferably, the inhibitor is at least one of ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 3,6-dimethyl-1-heptyn-3-ol.

[0040] The principle of the invention is as follows: the invention utilizes the mechanical ball milling of plasma ball milling and the combined effect of the plasma self-heating field and the electric field to quickly flake the soft magnetic metal particles to obtain a larger magnetic permeability and dielectric constant, and enhance the electromagnetic wave loss capacity of the soft magnetic metal material; at the same time, the mercapto group of the mercaptosilane coupling agent forms a coordination bond with the metal ions on the soft magnetic metal sheet, and the mercaptosilane coupling agent can be connected to the surface of the metal sheet; in addition, plasma bombardment is utilized to destroy the bonding force between the hexagonal boron nitride sheets, and then the boron nitride is sheared and peeled off under the action of ball milling to prepare boron nitride nanosheets; a strong interface bond is formed between the boron nitride nanosheets and the metal sheet modified by the silane coupling agent, and a composite structure of nano boron nitride coated with the soft magnetic metal sheet is obtained; the boron nitride with high insulation reduces the conductivity of the soft magnetic metal sheet, adjusts the impedance matching, and at the same time, the multi-interface bond enhances the interface polarization loss, thereby obtaining a more excellent wave absorbing performance. In addition, boron nitride has excellent high temperature resistance and corrosion resistance, which can effectively block the corrosion of external oxygen, water, acid, alkali, salt spray, etc., protect the internal soft magnetic metal, and effectively extend the service life of the composite powder. Boron nitride has excellent thermal conductivity, which can improve the thermal conductivity of soft magnetic metal sheets to a certain extent, thereby improving the thermal conductivity of composite powders.

[0041] The beneficial effects of the present invention are as follows: the insulating, thermally conductive, and wave-absorbing composite powder of the present invention has excellent wave-absorbing performance, good thermal conductivity, and excellent oxidation resistance, corrosion resistance, and electrical insulation. The silicone rubber composite material prepared by adding the powder to liquid silicone rubber has excellent wave-absorbing, thermally conductive, insulating, and anti-aging properties, and is suitable for use in 5G communications, new energy vehicles, electromagnetic protection, and other fields.

[0042] Specifically:

[0043] 1) The present invention adopts plasma ball milling to replace traditional mechanical ball milling and ion deposition (the traditional mechanical ball milling has the problems of low ball milling efficiency and poor inorganic layer coating effect, while the traditional chemical methods such as ion deposition to realize the composite of soft magnetic metal materials and inorganic materials have the problems of complex preparation process, loose coating layer, difficult to control coating layer thickness, and difficult to achieve industrialization), which can more efficiently refine, activate and lamellarize soft magnetic metal powder, significantly shorten the ball milling time, improve the ball milling efficiency, increase the specific surface area and magnetic permeability of the material, and the preparation process is green, environmentally friendly, non-toxic and pollution-free;

[0044] 2) Under the combined action of plasma and mechanical ball milling, the binding force between the hexagonal boron nitride sheets in the present invention is weakened, and the sheets can be more efficiently peeled off to form nanosheets. Under the combined action of plasma thermal effect and mechanical force, the mercaptosilane coupling agent and the metal ions are combined on the surface of the soft magnetic metal through coordination, thereby modifying the soft magnetic metal sheets and the boron nitride nanosheets to produce covalent bonding, and promoting the boron nitride nanosheets to form a tight coating structure on the soft magnetic metal;

[0045] 3) The present invention utilizes boron nitride to effectively reduce the conductivity of the soft magnetic metal and adjust the impedance matching. In addition, the multiple heterogeneous interfaces formed between the boron nitride and the soft magnetic metal promote the interface polarization, greatly improving the wave absorption performance of the composite powder;

[0046] 4) The boron nitride coated on the surface of the soft magnetic metal powder in the present invention has excellent high temperature resistance, oxidation resistance, corrosion resistance, insulation and thermal conductivity, thereby correspondingly improving the oxidation resistance, corrosion resistance, insulation and thermal conductivity of the composite powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the SEM image of the insulating, thermally conductive, and wave-absorbing composite powder of Example 2.

[0048] Figure 2 The minimum reflection loss of the silicone rubber composite materials of Examples 1 to 5 and Comparative Examples 1 to 2 varies with frequency.

[0049] Figure 3 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Example 1 varies with frequency and thickness.

[0050] Figure 4 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Example 2 varies with frequency and thickness.

[0051] Figure 5 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Example 3 varies with frequency and thickness.

[0052] Figure 6 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Example 4 varies with frequency and thickness.

[0053] Figure 7 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Example 5 varies with frequency and thickness.

[0054] Figure 8 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Comparative Example 1 varies with frequency and thickness.

[0055] Fig. 9 This is a three-dimensional graph showing how the reflection loss of the silicone rubber composite material of Comparative Example 2 varies with frequency and thickness.

[0056] Fig.10 The Tafel curves of the silicone rubber composite materials of Examples 1-2 and Comparative Example 2 are shown.

[0057] Fig.11 The electrochemical impedance diagrams of the silicone rubber composite materials of Examples 1-2 and Comparative Example 2 are shown. DETAILED DESCRIPTION

[0058] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0059] Embodiment 1:

[0060] An insulating, heat-conducting, and wave-absorbing composite powder, comprising the following raw materials in percentage by mass:

[0061] Sendust powder (average particle size 30 μm to 40 μm): 89%;

[0062] Hexagonal boron nitride (average particle size 20 μm): 10%;

[0063] 3-Mercaptopropyltriethoxysilane: 1%.

[0064] The method for preparing the above-mentioned insulating heat-conducting and wave-absorbing composite powder comprises the following steps:

[0065] 1) 44.5 g of sendust powder, 0.5 g of 3-mercaptopropyltriethoxysilane and 2 g of anhydrous ethanol were added to a ball mill, and then 3600 g of zirconia balls were added according to a ball-to-material mass ratio of 80:1. The ball mill was sealed and installed on a plasma ball mill, and then the air pressure in the ball mill was evacuated to 0.05 MPa. The vibration control power supply and the plasma discharge control power supply were started, and the running time was set to 20 min, the stop time was set to 20 min, the number of cycles was set to 6 times, the total ball milling time was 2 h, the ball milling speed was 1500 rpm, the discharge frequency was 11 kHz, and the plasma ball mill was started for plasma ball milling. The material was taken out and placed under vacuum drying at 80 ° C for 3 h to obtain a silane coupling agent-modified soft magnetic metal sheet (average particle size less than 50 μm);

[0066] 2) Add 45g of silane coupling agent modified soft magnetic metal sheet, 5g of hexagonal boron nitride and 2g of ethanol to the ball mill, and then add 1000g of zirconia balls according to the ball-to-material mass ratio of 20:1, and then seal the ball mill and install it on a plasma ball mill, and then evacuate and introduce nitrogen until the air pressure in the ball mill is 0.05MPa, and then start the vibration control power supply and the plasma discharge control power supply, set the running time to 20min, the stop time to 20min, the number of cycles to 3 times, the total ball milling time to 1h, the ball milling speed to 1400rpm, the discharge frequency to 8kHz, and then start the plasma ball mill for plasma ball milling, and then take out the material and place it at 90°C for vacuum drying for 5h to obtain an insulating, thermally conductive and wave-absorbing composite powder.

[0067] A silicone rubber composite material, comprising the following components in parts by weight:

[0068] Vinyl silicone oil (viscosity 1000mPa·s): 100 parts;

[0069] Hydrogenated silicone oil (hydrogen content 0.8%): 4 parts;

[0070] The above-mentioned insulating, heat-conducting and wave-absorbing composite powder: 150 parts;

[0071] Fumed silica: 5 parts;

[0072] Methylvinylsiloxane-platinum complex: 0.3 parts;

[0073] Ethynyl cyclohexanol: 0.03 parts.

[0074] The preparation method of the above silicone rubber composite material comprises the following steps:

[0075] 1) Vinyl silicone oil, hydrogenated silicone oil, insulating thermal conductive wave absorbing composite powder, fumed silica and ethynyl cyclohexanol were sequentially added into a polyethylene cup, and then mixed with a homogenizer at 2000 rpm for 3 min, and then methyl vinyl siloxane-platinum complex was added and mixed at 1800 rpm for 3 min to obtain a silicone rubber mixture;

[0076] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0077] Embodiment 2:

[0078] An insulating, heat-conducting, and wave-absorbing composite powder, comprising the following raw materials in percentage by mass:

[0079] Sendust powder (average particle size 30 μm to 40 μm): 78%;

[0080] Hexagonal boron nitride (average particle size 20 μm): 20%;

[0081] 3-Mercaptopropyltriethoxysilane: 2%.

[0082] The method for preparing the above-mentioned insulating heat-conducting and wave-absorbing composite powder comprises the following steps:

[0083] 1) 39 g of sendust powder, 1 g of 3-mercaptopropyltriethoxysilane and 2 g of anhydrous ethanol were added to a ball mill, and then 4000 g of zirconia balls were added according to a ball-to-material mass ratio of 100:1. The ball mill was sealed and installed on a plasma ball mill, and then evacuated and nitrogen was introduced until the air pressure in the ball mill was 0.1 MPa. The vibration control power supply and the plasma discharge control power supply were started again, and the running time was set to 30 min, the stop time was set to 20 min, the number of cycles was set to 6 times, the total ball milling time was 3 h, the ball milling speed was 1200 rpm, the discharge frequency was 10 kHz, and the plasma ball mill was started again for plasma ball milling. The material was taken out and placed under vacuum drying at 80 ° C for 3 h to obtain a silane coupling agent-modified soft magnetic metal sheet (average particle size less than 40 μm);

[0084] 2) Add 40g of silane coupling agent modified soft magnetic metal sheet, 10g of hexagonal boron nitride and 4g of ethanol to the ball mill, and then add 1000g of zirconia balls according to the ball-to-material mass ratio of 20:1, and then seal the ball mill and install it on a plasma ball mill, and then evacuate and introduce nitrogen until the air pressure in the ball mill is 0.05MPa, and then start the vibration control power supply and the plasma discharge control power supply, set the running time to 20min, the stop time to 20min, the number of cycles to 3 times, the total ball milling time to 1h, the ball milling speed to 1400rpm, the discharge frequency to 8kHz, and then start the plasma ball mill for plasma ball milling, and then take out the material and place it at 90°C for vacuum drying for 5h to obtain an insulating, thermally conductive and wave-absorbing composite powder.

[0085] A silicone rubber composite material, comprising the following components in parts by weight:

[0086] Vinyl silicone oil (viscosity 2000mPa·s): 100 parts;

[0087] Hydrogenated silicone oil (hydrogen content 0.8%): 4 parts;

[0088] The above-mentioned insulating, heat-conducting and wave-absorbing composite powder: 150 parts;

[0089] Fumed silica: 5 parts;

[0090] Platinum-tetrahydrofuran complex: 0.3 parts;

[0091] 3,5-Dimethyl-1-hexyn-3-ol: 0.03 parts.

[0092] The preparation method of the above silicone rubber composite material comprises the following steps:

[0093] 1) Vinyl silicone oil, hydrogen-containing silicone oil, insulating thermal conductive wave absorbing composite powder, fumed silica and 3,5-dimethyl-1-hexyn-3-ol were added to a polyethylene cup in sequence, and then mixed with a homogenizer at 1000 rpm for 6 minutes, and then platinum-tetrahydrofuran complex was added and mixed at 1500 rpm for 3 minutes to obtain a silicone rubber mixture;

[0094] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0095] Embodiment 3:

[0096] An insulating, heat-conducting, and wave-absorbing composite powder, comprising the following raw materials in percentage by mass:

[0097] Carbonyl iron powder (average particle size 3 μm to 4 μm): 57%;

[0098] Hexagonal boron nitride (average particle size 2 μm): 40%;

[0099] γ-Mercaptopropyltrimethoxysilane: 3%.

[0100] The method for preparing the above-mentioned insulating heat-conducting and wave-absorbing composite powder comprises the following steps:

[0101] 1) Add 57g of carbonyl iron powder, 3g of γ-mercaptopropyltrimethoxysilane and 8g of anhydrous ethanol to a ball mill, then add 4200g of zirconia balls according to a ball-to-material mass ratio of 70:1, seal the ball mill and install it on a plasma ball mill, evacuate and introduce argon until the air pressure in the ball mill is 0.05MPa, start the vibration control power supply and the plasma discharge control power supply, set the running time to 30min, the stop time to 20min, the number of cycles to 3 times, the total ball milling time to 1.5h, the ball milling speed to 1500rpm, the discharge frequency to 11kHz, and then start the plasma ball mill for plasma ball milling, then take out the material and place it at 80°C for vacuum drying for 3h to obtain a silane coupling agent-modified soft magnetic metal sheet (average particle size less than 10μm);

[0102] 2) Add 30g of silane coupling agent modified soft magnetic metal sheet, 20g of hexagonal boron nitride and 2g of ethanol to the ball mill, and then add 1500g of zirconia balls according to the ball-to-material mass ratio of 30:1, and then seal the ball mill and install it on a plasma ball mill, and then evacuate and introduce argon gas until the air pressure in the ball mill is 0.05MPa, and then start the vibration control power supply and the plasma discharge control power supply, set the running time to 20min, the stop time to 20min, the number of cycles to 3 times, the total ball milling time to 1h, the ball milling speed to 1400rpm, the discharge frequency to 8kHz, and then start the plasma ball mill for plasma ball milling, and then take out the material and place it at 80°C for vacuum drying for 5h to obtain an insulating, thermally conductive and wave-absorbing composite powder.

[0103] A silicone rubber composite material, comprising the following components in parts by weight:

[0104] Vinyl silicone oil (viscosity 1000mPa·s): 100 parts;

[0105] Hydrogenated silicone oil (hydrogen content 1.8%): 2 parts;

[0106] The above-mentioned insulating, heat-conducting and wave-absorbing composite powder: 150 parts;

[0107] Fumed silica: 5 parts;

[0108] Platinum-tetrahydrofuran complex: 0.3 parts;

[0109] Ethynyl cyclohexanol: 0.03 parts.

[0110] The preparation method of the above silicone rubber composite material comprises the following steps:

[0111] 1) Vinyl silicone oil, hydrogen-containing silicone oil, insulating thermal conductive wave absorbing composite powder, fumed silica and ethynyl cyclohexanol were added to a polyethylene cup in sequence, and then mixed with a homogenizer at 2500 rpm for 2 minutes, and then platinum-tetrahydrofuran complex was added and mixed at 1800 rpm for 4 minutes to obtain a silicone rubber mixture;

[0112] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0113] Embodiment 4:

[0114] An insulating, heat-conducting, and wave-absorbing composite powder, comprising the following raw materials in percentage by mass:

[0115] Iron-nickel powder (average particle size 10 μm to 20 μm): 68%;

[0116] Hexagonal boron nitride (average particle size 4 μm): 30%;

[0117] γ-Mercaptopropyltrimethoxysilane: 2%.

[0118] The method for preparing the above-mentioned insulating heat-conducting and wave-absorbing composite powder comprises the following steps:

[0119] 1) 68 g of iron-nickel powder, 2 g of γ-mercaptopropyltrimethoxysilane and 4 g of anhydrous ethanol were added to a ball mill, and then 3500 g of zirconia balls were added according to a ball-to-material mass ratio of 50:1. The ball mill was sealed and installed on a plasma ball mill, and then vacuumed to a pressure of 0.05 MPa in the ball mill, and then the vibration control power supply and the plasma discharge control power supply were started, and the running time was set to 20 min, the stop time was set to 20 min, the number of cycles was set to 6 times, the total ball milling time was 2 h, the ball milling speed was 1300 rpm, the discharge frequency was 11 kHz, and then the plasma ball mill was started for plasma ball milling, and then the material was taken out and placed at 80 ° C for vacuum drying for 4 h to obtain a silane coupling agent-modified soft magnetic metal sheet (average particle size less than 30 μm);

[0120] 2) Add 35g of silane coupling agent modified soft magnetic metal sheet, 15g of hexagonal boron nitride and 2g of ethanol to the ball mill, and then add 2000g of zirconia balls according to the ball-to-material mass ratio of 40:1, and then seal the ball mill and install it on a plasma ball mill, and then evacuate and introduce nitrogen until the air pressure in the ball mill is 0.07MPa, and then start the vibration control power supply and the plasma discharge control power supply, set the running time to 20min, the stop time to 20min, the number of cycles to 6 times, the total ball milling time to 2h, the ball milling speed to 1300rpm, the discharge frequency to 9kHz, and then start the plasma ball mill for plasma ball milling, and then take out the material and place it at 80°C for vacuum drying for 5h to obtain an insulating, thermally conductive and wave-absorbing composite powder.

[0121] A silicone rubber composite material, comprising the following components in parts by weight:

[0122] Vinyl silicone oil (viscosity 500mPa·s): 100 parts;

[0123] Hydrogenated silicone oil (hydrogen content 1.0%): 2 parts;

[0124] The above-mentioned insulating, heat-conducting and wave-absorbing composite powder: 150 parts;

[0125] Fumed silica: 3 parts;

[0126] Methylvinylsiloxane-platinum complex: 0.3 parts;

[0127] 3,6-Dimethyl-1-heptyn-3-ol: 0.03 parts.

[0128] The preparation method of the above silicone rubber composite material comprises the following steps:

[0129] 1) Vinyl silicone oil, hydrogenated silicone oil, insulating thermal conductive wave absorbing composite powder, fumed silica and 3,6-dimethyl-1-heptyne-3-ol were sequentially added into a polyethylene cup, and then mixed with a homogenizer at 2500 rpm for 1 min, and then methyl vinyl siloxane-platinum complex was added and mixed at 1200 rpm for 5 min to obtain a silicone rubber mixture;

[0130] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0131] Embodiment 5:

[0132] An insulating, heat-conducting, and wave-absorbing composite powder, comprising the following raw materials in percentage by mass:

[0133] Sendust powder (average particle size 30 μm to 40 μm): 46%;

[0134] Hexagonal boron nitride (average particle size 20 μm): 50%;

[0135] γ-Mercaptopropylmethyldimethoxysilane: 4%.

[0136] The method for preparing the above-mentioned insulating heat-conducting and wave-absorbing composite powder comprises the following steps:

[0137] 1) 46 g of sendust powder, 4 g of γ-mercaptopropylmethyldimethoxysilane and 1.5 g of anhydrous ethanol were added to a ball mill, and then 2500 g of zirconia balls were added according to a ball-to-material mass ratio of 50:1. The ball mill was sealed and installed on a plasma ball mill, and then vacuumed to a pressure of 0.05 MPa in the ball mill, and then the vibration control power supply and the plasma discharge control power supply were started, and the running time was set to 30 min, the stop time was set to 30 min, the number of cycles was set to 4 times, the total ball milling time was 2 h, the ball milling speed was 1500 rpm, the discharge frequency was 11 kHz, and then the plasma ball mill was started for plasma ball milling, and then the material was taken out and placed at 80 ° C for vacuum drying for 6 h to obtain a silane coupling agent-modified soft magnetic metal sheet (average particle size less than 30 μm);

[0138] 2) Add 25g of silane coupling agent modified soft magnetic metal sheet, 25g of hexagonal boron nitride and 1.5g of ethanol to the ball mill, and then add 1500g of zirconia balls according to the ball-to-material mass ratio of 30:1, and then seal the ball mill and install it on a plasma ball mill, and then evacuate and introduce nitrogen until the air pressure in the ball mill is 0.05MPa, and then start the vibration control power supply and the plasma discharge control power supply, set the running time to 20min, the stop time to 20min, the number of cycles to 6 times, the total ball milling time to 2h, the ball milling speed to 1300rpm, the discharge frequency to 9kHz, and then start the plasma ball mill for plasma ball milling, and then take out the material and place it at 80°C for vacuum drying for 5h to obtain an insulating, thermally conductive and wave-absorbing composite powder.

[0139] A silicone rubber composite material, comprising the following components in parts by weight:

[0140] Vinyl silicone oil (viscosity 2500mPa·s): 100 parts;

[0141] Hydrogenated silicone oil (hydrogen content 1.8%): 2 parts;

[0142] The above-mentioned insulating, heat-conducting and wave-absorbing composite powder: 150 parts;

[0143] Fumed silica: 2 parts;

[0144] Chloroplatinic acid: 0.3 parts;

[0145] 3,6-Dimethyl-1-heptyn-3-ol: 0.03 parts.

[0146] The preparation method of the above silicone rubber composite material comprises the following steps:

[0147] 1) Vinyl silicone oil, hydrogenated silicone oil, insulating thermal conductive wave absorbing composite powder, fumed silica and 3,6-dimethyl-1-heptyne-3-ol were sequentially added into a polyethylene cup, and then mixed with a homogenizer at 2000 rpm for 2 min, and then chloroplatinic acid was added and mixed at 2000 rpm for 3 min to obtain a silicone rubber mixture;

[0148] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0149] Comparative Example 1:

[0150] A silicone rubber composite material, comprising the following components in parts by weight:

[0151] Vinyl silicone oil (viscosity 1000mPa·s): 100 parts;

[0152] Hydrogenated silicone oil (hydrogen content 0.8%): 4 parts;

[0153] Sendust powder (average particle size 30 μm to 40 μm): 150 parts;

[0154] Fumed silica: 5 parts;

[0155] Methylvinylsiloxane-platinum complex: 0.3 parts;

[0156] Ethynyl cyclohexanol: 0.03 parts.

[0157] The preparation method of the above silicone rubber composite material comprises the following steps:

[0158] 1) Vinyl silicone oil, hydrogen-containing silicone oil, iron-silicon-aluminum powder, fumed silica and ethynyl cyclohexanol were added to a polyethylene cup in sequence, and then mixed with a homogenizer at 1800 rpm for 3 min, and then methyl vinyl siloxane-platinum complex was added and mixed at 1800 rpm for 3 min to obtain a silicone rubber mixture;

[0159] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0160] Comparative Example 2:

[0161] A sheet-like sendust, the preparation method of which comprises the following steps:

[0162] 50g of sendust powder (average particle size of 30μm to 40μm) and 2g of anhydrous ethanol were added to a ball mill, and then 4000g of carbide balls were added according to a ball-to-material mass ratio of 80:1. The ball mill was sealed and installed on a plasma ball mill, and then vacuumed to a pressure of 0.05MPa in the ball mill, and then the vibration control power supply and the plasma discharge control power supply were started, and the running time was set to 20min, the stop time was set to 20min, the number of cycles was set to 6 times, the total ball milling time was 2h, the ball milling speed was 1500rpm, the discharge frequency was 11kHz, and then the plasma ball mill was started for plasma ball milling, and then the material was taken out and placed at 80°C for vacuum drying for 3h to obtain flaky sendust (average particle size of less than 50μm);

[0163] A silicone rubber composite material, comprising the following components in parts by weight:

[0164] Vinyl silicone oil (viscosity 1000mPa·s): 100 parts;

[0165] Hydrogenated silicone oil (hydrogen content 0.8%): 4 parts;

[0166] The above-mentioned sheet-like sendust: 150 parts;

[0167] Fumed silica: 5 parts;

[0168] Methylvinylsiloxane-platinum complex: 0.3 parts;

[0169] Ethynyl cyclohexanol: 0.03 parts.

[0170] The preparation method of the above silicone rubber composite material comprises the following steps:

[0171] 1) Vinyl silicone oil, hydrogen-containing silicone oil, flake sendust, fumed silica and ethynyl cyclohexanol were added to a polyethylene cup in sequence, and then mixed with a homogenizer at 1500 rpm for 2 min, and then methyl vinyl siloxane-platinum complex was added and mixed at 1500 rpm for 3 min to obtain a silicone rubber mixture;

[0172] 2) The silicone rubber mixture is placed on a flat vulcanizer and vulcanized into a sheet. The vulcanization pressure is 15 MPa, the vulcanization temperature is 180° C., and the vulcanization time is 5 min to obtain a silicone rubber composite material.

[0173] Performance Test:

[0174] 1) The scanning electron microscope (SEM) image of the insulating heat-conducting and wave-absorbing composite powder of Example 2 is as follows: Figure 1 shown.

[0175] Depend on Figure 1 It can be seen that the surface of the insulating, heat-conducting, and wave-absorbing composite powder of Example 2 is rough, and boron nitride forms a tight coating structure on the surface of the flaky Sendust.

[0176] In addition, it was found through testing that the microscopic morphology of the insulating heat-conducting and wave-absorbing composite powders corresponding to Example 1 and Examples 3 to 5 was similar to that of the insulating heat-conducting and wave-absorbing composite powders corresponding to Example 2.

[0177] 2) Minimum reflection loss (RL) of the silicone rubber composite materials of Examples 1 to 5 and Comparative Examples 1 to 2 min ) changes with frequency as shown in the curve Figure 2 As shown, the three-dimensional graphs of reflection loss changing with frequency and thickness are shown in Figures 3 to 9 shown.

[0178] Depend on Figures 2 to 9 It can be seen that compared with the silicone rubber composite materials of comparative examples 1 to 2, the silicone rubber composite materials of embodiments 1 to 5 have greatly improved wave absorption performance, significantly reduced minimum reflection loss, and increased effective absorption bandwidth (reflection loss RL<-10dB).

[0179] 3) The Tafel curves of the silicone rubber composite materials of Examples 1 to 2 and Comparative Example 2 are as follows: Fig.10 The electrochemical impedance spectroscopy diagram is shown in Fig.11 shown.

[0180] Depend on Fig.10 and Fig.11 It can be seen that compared with the silicone rubber composite material of Comparative Example 2, the corrosion potential of the silicone rubber composite materials of Examples 1 to 2 is positively shifted, and the electrochemical impedance is significantly increased, indicating that the insulating, thermally conductive, and wave-absorbing composite powder of the present invention has good corrosion resistance.

[0181] 4) The microwave absorption performance, thermal conductivity, electrical conductivity and aging performance of the silicone rubber composite materials of Examples 1 to 5 and Comparative Examples 1 to 2 were tested. The test results are shown in the following table:

[0182] Table 1 Test results of microwave absorption, thermal conductivity, electrical conductivity and aging performance of silicone rubber composite materials

[0183]

[0184]

[0185] Note:

[0186] Absorption performance: The vector network analyzer was used to test the concentric ring samples with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm. The complex dielectric constant and complex magnetic permeability of the silicone rubber composite material were tested by the coaxial method. The test frequency range was 2 GHz to 18 GHz. According to the transmission line theory, the complex dielectric constant and complex magnetic permeability of the absorber at a given frequency and the thickness of the absorbing material were used to calculate the reflection loss (RL):

[0187] The reflection loss of a single-layer absorber is calculated by formula (1):

[0188]

[0189] Where Z0 is the free space impedance, which is approximately 377, and Z in is the standardized input impedance, and the calculation formula is shown in formula (2):

[0190] Z in =(μ r / ε r ) 1 / 2 tanh[j(2πfd / c)(μ r ε r ) 1 / 2 ] (2)

[0191] In the formula, μ r is the free space permeability and the relative permeability of the material, ε r is the free space dielectric constant and the relative dielectric constant of the material, j represents the imaginary part, f is the frequency, d is the sample thickness, and c is the speed of light (tanh is the hyperbolic tangent function).

[0192] Thermal conductivity: tested by a thermal constant analyzer (Hot Disk).

[0193] Volume resistivity: Refer to "GB / T 1692-2008 Determination of insulation resistivity of vulcanized rubber" for testing, use PC40B high insulation resistance measuring instrument, ambient temperature is 25℃±5℃, humidity is 55%±5%, test voltage is 1000V, sample size is 100mm (length) × 100mm (width) × 1mm (thickness), take three samples for testing, and take the average value of the results. Calculate volume resistivity ρ according to formula (3): v :

[0194] ρ v =R v π(d1+g) 2 / 4t=21.24R v / t(Ω·cm) (3)

[0195] Where d1 is the diameter of the measuring electrode (5 cm), g is the gap between the measuring electrode and the guard electrode (0.2 cm), t is the thickness of the insulating material sample (unit: cm), R v is the measured volume resistance (unit: Ω).

[0196] From Table 1, we can see that:

[0197] a) The insulating heat-conducting wave-absorbing composite powders prepared by plasma ball milling of the silicone rubber composite materials of Examples 1 to 5 have more excellent wave-absorbing performance than the silicone rubber composite materials of Comparative Examples 1 to 2. Among them, the effective absorption bandwidth of Example 1 is 4.03 GHz, and the minimum reflection loss is -50.30 dB, and the minimum reflection loss of Example 2 is -62.82 dB, indicating that after being coated with boron nitride, the conductivity of the soft magnetic metal is reduced, and the impedance matching is improved, which is conducive to the entry of electromagnetic waves into the wave-absorbing material. At the same time, multiple heterogeneous interfaces also greatly increase the interface polarization loss, thereby significantly improving the wave-absorbing performance of the material. The electromagnetic wave absorption center frequency band of the silicone rubber composite materials of each embodiment can be adjusted by changing the ball milling atmosphere, the discharge frequency and the type of soft magnetic metal to achieve effective absorption within 2 GHz to 18 GHz;

[0198] b) After the silicone rubber composite materials of Examples 1 to 5 were aged in hot air at 200°C for 24h, the corresponding effective absorption bandwidths did not change significantly, indicating that the insulating, heat-conducting, and wave-absorbing composite powders of the present invention have excellent high-temperature oxidation resistance;

[0199] c) The thermal conductivity of the silicone rubber composite materials of Examples 1 to 5 can reach up to 1.53 W·m -1 ·K -1 , to a certain extent, it can meet the thermal conductivity and heat dissipation requirements of electronic appliances;

[0200] d) The volume resistivity of the silicone rubber composite materials of Examples 1 to 5 is greater than 10 10 Ω·cm, has good insulation performance and can be used in electronic and electrical products with high insulation requirements.

[0201] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A preparation method of an insulating, heat-conducting and wave-absorbing composite powder, characterized in that, It includes the following steps: 1) Mix the soft magnetic metal powder and the mercapto silane coupling agent and conduct plasma ball milling to obtain the soft magnetic metal sheets modified by the silane coupling agent; 2) Mix the soft magnetic metal sheets modified by the silane coupling agent and hexagonal boron nitride and conduct plasma ball milling to obtain the insulating, heat-conducting and wave-absorbing composite powder; The insulating, heat-conducting and wave-absorbing composite powder includes the following raw materials for preparation by mass percentage: soft magnetic metal powder: 16% - 95%; Hexagonal boron nitride: 4.9% - 80%; mercapto silane coupling agent: 0.1% - 4%; The average particle size of the soft magnetic metal powder is 1 μm - 80 μm.

2. The preparation method according to claim 1, characterized in that: The soft magnetic metal powder is at least one of carbonyl iron powder, iron silicon aluminum powder, iron silicon chromium powder, and iron nickel powder.

3. The preparation method according to claim 1, characterized in that: The average particle size of the hexagonal boron nitride is 1 μm - 40 μm.

4. The preparation method according to claim 1, characterized in that: The mercapto silane coupling agent is at least one of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane.

5. The preparation method according to claim 1, characterized in that: The plasma ball milling is carried out in an argon atmosphere, a nitrogen atmosphere, an oxygen atmosphere or an air atmosphere.

6. An insulating, heat-conducting and wave-absorbing composite powder, characterized in that, It is made by the preparation method described in any one of claims 1 - 5.

7. The insulating, heat-conducting and wave-absorbing composite powder according to claim 6, wherein: The particle size of the insulating, heat-conducting and wave-absorbing composite powder is 2 μm - 150 μm.

8. A silicone rubber composite material, characterized in that, It includes the following components by mass parts: Vinyl silicone oil: 100 parts; Hydrogen-containing silicone oil: 1 part - 6 parts; The insulating, heat-conducting and wave-absorbing composite powder described in claim 6 or 7: 50 parts - 400 parts; Fumed silica: 1 part - 10 parts; Platinum catalyst: 0.1 part - 0.8 part; Inhibitor: 0.01 part - 0.2 part.

Images