Silicon carbide-diamond porous composite material as well as preparation method and application thereof

Abstract

The invention provides a silicon carbide-diamond porous composite material as well as a preparation method and application thereof. The silicon carbide-diamond porous composite material comprises diamond particles coated with silicon carbide layers, and the adjacent diamond particles coated with the silicon carbide layers are connected through silicon carbide or silicon carbide and silicon to form a three-dimensional continuous silicon carbide-diamond network and an interpenetrating porous pore network; the silicon carbide-diamond composite porous material comprises the following components in volume fraction: 50%-90% of diamond particles, 10%-50% of silicon carbide and 0%-20% of silicon. The material has high thermal conductivity (the highest thermal conductivity is 800W / m.K) and high strength (the bending strength reaches 200MPa), and is suitable for the fields of heat dissipation of electronic devices, high-end equipment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and in particular to a silicon carbide-diamond porous composite material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the electronics, military, aerospace, and other fields, the demand for high-power density and high-reliability power electronic devices is gradually increasing, posing greater challenges to high-thermal conductivity and low-expansion heat dissipation materials. Traditional metal heat dissipation materials can no longer meet the heat dissipation needs of high-power devices. Metal-based composite materials are gradually replacing traditional heat dissipation materials by fully leveraging the mechanical properties of metals and the high thermal conductivity of reinforcements. Common metal-based composite heat dissipation materials include aluminum silicon, silicon carbide aluminum, diamond aluminum, and diamond copper. Diamond aluminum has nearly three times the thermal conductivity of silicon carbide aluminum and lower density and cost than diamond copper. Therefore, diamond aluminum has extremely broad application prospects.

[0003] Diamond aluminum composites, also known as diamond particle-reinforced aluminum-matrix composites, are a particle-reinforced metal matrix composite formed by uniformly dispersing diamond particles throughout an aluminum alloy. These composites combine the advantages of both aluminum alloys and diamond materials. Diamond is one of the naturally occurring materials with excellent thermal conductivity and a low coefficient of thermal expansion. Aluminum alloys, as metal materials with excellent thermal conductivity, have low density and low manufacturing costs. Due to its excellent properties, diamond aluminum is expected to be widely used in the electronics industry, laser materials, power batteries, aerospace, and other fields.

[0004] However, due to the special crystal structure of diamond, the interface optimization mechanism and process between it and the metal matrix are very complex, which limits the transmission and transfer of the excellent properties of diamond to composite materials. Achieving optimal optimization of the two-phase interface through improvements and innovations in forming technology is the key to promoting the research and development and application of diamond aluminum composite materials. Traditional diamond aluminum composite materials are aluminum-based composite materials reinforced with diamond particles. The interface performance and thermal conductivity of the composite materials are improved by surface modification of diamond particles. However, the surface modification process is complex, costly, and inefficient. In addition, the modified layer has poor bonding with the diamond, and the surface modification layer is uneven. At the same time, the forming process adopts hot pressing sintering, spark plasma sintering, etc., which have long process flows, low efficiency, instability, and low yield, making it difficult to prepare composite materials with complex structures. Therefore, there is an urgent need to develop a new type of silicon carbide-bonded diamond porous material with low cost and high performance and its preparation process. A mature infiltration process can be used to achieve low-cost and short-process preparation of diamond aluminum composite materials.

[0005] In the traditional high-temperature sintering process, liquid silicon reacts chemically with diamond particles, causing the diamond surface to be eroded and even converted into a graphite phase with significantly reduced thermal conductivity (sp 2Hybridized carbon). This interfacial reaction can disrupt the integrity of the diamond lattice, thereby reducing the overall thermal conductivity and mechanical properties of the composite. Studies have shown that the reaction of diamond with silicon at high temperatures follows a carbon dissolution-precipitation mechanism, generating a SiC phase accompanied by a reorganization of the carbon structure. Furthermore, different sintering environments (such as vacuum, argon, or reactive atmospheres) significantly affect diamond stability, even accelerating graphitization under certain conditions. However, none of these methods address the erosion of diamond particles.

[0006] Overall, the current preparation technology for SiC-diamond porous composite materials still faces the following bottlenecks: how to effectively inhibit diamond graphitization and interfacial erosion, improve the material's thermal conductivity and mechanical stability, and how to simplify the process and improve cost-effectiveness while maintaining material performance.

[0007] Therefore, an innovative technical solution is urgently needed to optimize the stability of the SiC-diamond interface while achieving precise control of the pore structure to meet the needs of the next generation of high-heat flux electronic devices. It can also meet the needs of catalyst supports, filters, heat dissipation, electromagnetic shielding, wave absorption, and acoustic isolation. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a silicon carbide-diamond composite porous material and its preparation method and application.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] The present invention provides a silicon carbide-diamond composite porous material, which includes diamond particles coated with a silicon carbide layer, and adjacent diamond particles coated with the silicon carbide layer are connected by silicon carbide or silicon carbide and silicon to form a three-dimensional continuous silicon carbide-diamond network and an interconnected porous pore network. The silicon carbide-diamond composite porous material includes the following components by volume fraction: 50% to 90% diamond particle volume fraction, 10% to 50% silicon carbide, and 0% to 20% silicon.

[0011] Furthermore, in the silicon carbide-diamond composite porous material, the thickness of the silicon carbide layer on the diamond particles coated with the silicon carbide layer is 10 nm to 6 μm, and the coverage rate of the silicon carbide layer on the surface of the diamond particles is greater than or equal to 95%; the volume fraction of the porous pore network is 20% to 80%.

[0012] Furthermore, the thermal conductivity of the silicon carbide-diamond composite porous material is 50 to 800 W / m·K, and the bending strength is 5 to 200 MPa.

[0013] The present invention also provides a method for preparing the silicon carbide-diamond composite porous material according to the above-mentioned method, which comprises the following steps: step (1) preparing a carbon protective layer on the surface of diamond particles by a thermal cracking method to obtain diamond particles coated with a carbon layer; wherein commonly used thermal cracking methods include chemical vapor deposition, organic coating thermal cracking, etc. step (2) mixing ceramic powder, a binder and a solvent to obtain a slurry; using a dispersion method to fully mix the diamond particles coated with the carbon layer and the slurry in a mass ratio of 1:1 to form a uniform suspension; step (3) drying and crushing the suspension and then pressing it into a preform; wherein commonly used pressing methods include cold pressing, hot pressing, slip casting, freeze drying, cold isostatic pressing, hot isostatic pressing, extrusion molding or 3D printing. The preform is pyrolyzed in a controlled atmosphere at a temperature of 600 to 1200° C., with a heating rate of 1 to 10° C. / min and a holding time of 10 to 300 min to obtain a heat-treated preform; and in step (4), the heat-treated preform is sintered at 1400 to 1800° C. in high-purity argon, high-purity nitrogen or vacuum conditions and held for 1 min to 6 h to obtain the silicon carbide-diamond composite porous material.

[0014] Furthermore, in step (1), the size of the diamond particles is 100 nm to 1000 μm.

[0015] Furthermore, in step (2), the ceramic powder includes metallic silicon and / or silicon dioxide, and has a size of 50 nm to 200 μm; the binder includes one or more of phenolic resin, epoxy resin, polyvinyl alcohol, polyvinyl butyral, furan resin and polyurethane; the solvent is a polar or non-polar solvent; in the slurry, the amounts of the following raw materials are calculated by mass: 5 to 100 parts of the ceramic powder, 5 to 100 parts of the binder, and 5 to 100 parts of the solvent.

[0016] Furthermore, the size of the ceramic powder is 50 nm to 200 μm.

[0017] Furthermore, the raw materials of the slurry also include a curing agent, and the amount of the curing agent is less than or equal to 0.2 times the amount of the binder; wherein the curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, a phenolic curing agent, an imidazole curing agent, an isocyanate curing agent, an acid curing agent, and a cross-linking agent.

[0018] Furthermore, the raw materials of the slurry also include 10 to 150 parts of a pore-forming agent; wherein the pore-forming agent is selected from at least one of a low-temperature type, a medium-temperature type or a high-temperature type.

[0019] The present invention also provides an application of the above-mentioned silicon carbide-diamond composite porous material in high-performance composite material reinforcement, electronic device heat dissipation material, high-frequency electromagnetic shielding and absorbing material, high-temperature filter material, biomaterial, electrochemical catalytic carrier material, and sound absorption / noise reduction structural material. It should be noted that the electronic device heat dissipation material is suitable for high-power density chip packaging and thermal management; high-frequency electromagnetic shielding and absorbing material is used in 5G, satellite communications and radar systems; high-temperature filter material is suitable for molten metal filtration and gas-solid separation; biomaterials, such as tissue engineering scaffolds and bone replacement materials; electrochemical catalytic carrier materials, such as fuel cell electrode materials; sound absorption / noise reduction structural materials are used in aviation, aerospace and high-end equipment.

[0020] The present invention provides a silicon carbide-diamond composite porous material, its preparation method, and its application. Using an optimized precursor slurry preparation and high-temperature sintering process, the material possesses a controllable pore structure, improving stability and application adaptability. Compared to existing technologies, the technical solution provided by the present invention has at least the following advantages:

[0021] 1. The silicon carbide-diamond composite porous material described in the present invention comprises a silicon carbide-diamond network connected by diamond-silicon carbide-diamond phase boundaries to ensure high thermal conductivity of the silicon carbide-diamond composite porous material. At the same time, a silicon carbide layer is formed on more than 90% of the surface of the diamond particles to play a surface modification role.

[0022] 2. By uniformly coating the surface of diamond particles with a carbon layer, the erosion of silicon on the diamond particles during the reaction sintering process is hindered, thereby enhancing the mechanical properties and thermal conductivity of the material. This material has both high thermal conductivity (up to 800W / m·K) and high strength (flexural strength of 200MPa), making it suitable for heat dissipation in electronic devices, high-end equipment and other fields.

[0023] 3. The silicon carbide-diamond composite porous material described in the present invention has the characteristics of integrity, adjustable volume fraction and open porosity, high mechanical properties, high temperature resistance, corrosion resistance, high thermal conductivity, etc., and is isotropic, suitable for different application environments, and is conducive to the preparation of new functional materials and composite materials.

[0024] 4. The silicon carbide-diamond composite porous material described in the present invention is a new type of porous material with a simple preparation process and high efficiency. It has broad application prospects and can be applied to the following fields: composite material reinforcement, heat dissipation materials, electromagnetic shielding materials, absorbing materials, filters, biomaterials, catalytic carrier materials, electrode materials, and sound absorption / noise reduction materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] One or more embodiments are exemplarily described by the pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

[0026] Figure 1 A three-dimensional interconnected macroscopic pore morphology of the silicon carbide-diamond composite porous material (porosity 30%) provided in Example 2 of the present invention;

[0027] Figure 2 A microscopic morphology of a three-dimensionally interconnected micrometer-scale and / or nanometer-scale porous silicon carbide ceramic network of the silicon carbide-diamond composite porous material provided in Example 3 of the present invention;

[0028] Figure 3 The SiC-diamond bonding interface of the silicon carbide-diamond composite porous material (porosity 22%) provided in Example 6 of the present invention;

[0029] Figure 4 Schematic diagram of the microscopic morphology of the silicon carbide protective layer generated on the diamond surface of the silicon carbide-diamond composite porous material provided in Example 11 of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to specific embodiments.

[0031] The present invention provides a silicon carbide-diamond composite porous material, its preparation method, and application. This composite material is constructed by coating diamond particles with carbon, which reduces or even prevents erosion of the diamond particles by liquid silicon, ensuring the integrity of the diamond particles during the reaction sintering process. This creates a three-dimensional continuous silicon carbide-diamond network and a porous pore network, achieving both high thermal conductivity and high strength. Specifically, the present invention utilizes the following technical means:

[0032] (1) Material composition and structure

[0033] The porous material is composed of a porous skeleton with a three-dimensional interconnected pore structure, and the porosity is controlled within the range of 20% to 80% to meet the performance requirements of applications in multiple fields such as heat dissipation and catalysis.

[0034] Diamond particles form a three-dimensional continuous silicon carbide-diamond network through silicon carbide-diamond-silicon carbide phase boundaries, and diamond accounts for 50% to 90% of the volume fraction of the three-dimensional continuous silicon carbide-diamond network, giving full play to the high thermal conductivity of diamond.

[0035] A carbon layer is coated on the surface of diamond through thermal cracking (chemical vapor deposition, organic coating thermal cracking, etc.) process. The thickness of the surface carbon layer is controlled at 5nm~6μm, which avoids the erosion of silicon on diamond particles during the reaction sintering process and forms a stable bonding phase, significantly improving the interface thermal conductivity and mechanical properties.

[0036] The diamond particle size is controlled at 100nm~1000μm,

[0037] (2) Material preparation method:

[0038] First, a carbon layer with a thickness of 5nm to 6μm is coated on the surface of diamond particles using thermal cracking technology.

[0039] Then, a silicon carbide precursor slurry is prepared, and diamond particles coated with a carbon layer are evenly dispersed in the slurry to ensure the uniformity of the composite material.

[0040] The slurry is formed into an initial green body with a three-dimensional interconnected pore structure by cold pressing, hot pressing, slip casting, freeze drying, cold isostatic pressing, hot isostatic pressing, extrusion molding or 3D printing.

[0041] In an argon or vacuum atmosphere, reaction sintering is carried out at a temperature of 1400-1800°C to control the formation of silicon carbide, so that a high bonding strength interface is formed between diamond and silicon carbide.

[0042] By controlling the sintering atmosphere, time and heating rate, and regulating the integrity of diamond and the interface bonding state with silicon carbide, the thermal conductivity of the final material can reach 50 to 800 W / m·K and the bending strength range is 5 to 200 MPa.

[0043] Example 1:

[0044] In step (1), the diamond particles have a size of 100 μm and are coated with a carbon layer of 800 nm thick uniformly on the surface by cellulose coating and thermal cracking to obtain diamond particles coated with the carbon layer.

[0045] In step (2), 80 parts of polyurethane resin as a binder and 100 parts of acetone as a solvent are selected and stirred at a rate of 300 rpm for 5 minutes by a magnetic stirrer, and then 90 parts of silicon powder with a size of 20 μm are selected as ceramic powder and 1 part of a curing agent, an isocyanate curing agent, toluene diisocyanate, is selected and stirred at a rate of 500 rpm for 5 minutes by a non-contact stirrer to finally obtain a uniform slurry.

[0046] Step (3) The slurry and the diamond particles coated with the carbon layer are placed in a ball mill and uniformly mixed for 2 hours, dried at room temperature, ground into powder using a crusher, and cold-pressed at 300 MPa to obtain a preform.

[0047] The preform was pyrolyzed at 1000° C. in a nitrogen atmosphere with a heating rate of 5° C. / min and a holding time of 150 min.

[0048] Step (4) the preform is sintered at 1550° C. for 60 min under vacuum conditions;

[0049] The obtained silicon carbide-diamond porous composite material has a thermal conductivity of 162W / m·K, a flexural strength of 25MPa, a porosity of 45%, a silicon carbide protective layer thickness of 3μm, and a silicon carbide-diamond network with a diamond volume fraction of 72%, a silicon carbide volume fraction of 13%, and a silicon volume fraction of 15%.

[0050] Example 2:

[0051] Step (1) The diamond particles have a size of 100 μm and are impregnated with resin followed by drying, pyrolysis, and crushing. A three-impregnation process is performed to uniformly coat the diamond surface with a 500 nm thick carbon layer.

[0052] Step (2) 100 parts of silicon powder with a size of 20 μm are selected as ceramic powder, and then 25 parts of polyurethane resin are selected as a binder and 30 parts of anhydrous ethanol are selected as a solvent. The mixture is added into a magnetic stirrer and stirred at a rate of 500 rpm for 30 minutes. Then, 3 parts of curing agent isocyanate curing agent toluene diisocyanate are added and stirred at a rate of 900 rpm for another 3 minutes to prepare a uniform slurry.

[0053] Step (3) The diamond and slurry are mixed and ball-milled for 1 hour, then dried at 60° C., ground and crushed, and hot-pressed at a pressure of 100 MPa (the hot-pressing temperature is 110° C., and the temperature is kept at 110° C. for 5 minutes).

[0054] Step (4) the preform is sintered at 1550° C. for 10 min under vacuum conditions;

[0055] The thermal conductivity of the obtained silicon carbide-diamond porous composite material is 200W / m·K, the flexural strength is 28MPa, the porosity is 30%, the thickness of the silicon carbide protective layer is 6μm, and the volume fraction of diamond in the silicon carbide-diamond network is 80%, the volume fraction of silicon carbide is 11%, and the volume fraction of silicon is 9%. The micromorphology of the composite material is as follows: Figure 1 shown.

[0056] Example 3:

[0057] Step (1) The diamond particle size is 50 μm, and a 120 nm thick carbon layer is deposited on the diamond surface by chemical vapor deposition to ensure that the surface coating is uniform and dense.

[0058] Step (2) The ceramic powder selected was silicon powder with a size of 10 μm, a binder of phenolic resin, a curing agent of p-toluene disulfonic acid, and a solvent of anhydrous ethanol, with a slurry ratio of 70:30:1:15. The phenolic resin and anhydrous ethanol were then mixed in a magnetic stirrer at a speed of 300 rpm for 30 minutes, and then the silicon powder and curing agent were added and stirred at 600 rpm for 40 minutes at 40°C to prepare a uniform slurry.

[0059] Step (3) The diamond and slurry are stirred at a rate of 900 rpm for 2 minutes using a non-contact mixer, and then injected into a gypsum mold, left to stand, and dried to form.

[0060] Step (4) sintering the preform at 1450°C with a heating rate of 3°C / min and holding for 1 hour in a high-purity nitrogen environment;

[0061] The resulting silicon carbide-diamond porous composite material has a thermal conductivity of 140 W / m·K, a flexural strength of 50 MPa, a porosity of 35%, and a silicon carbide protective layer thickness of 2.1 μm. The volume fraction of diamond in the composite material is 75%, the volume fraction of silicon carbide is 17%, and the volume fraction of silicon is 8%. Its micromorphology is as follows Figure 2 shown.

[0062] Example 4:

[0063] Step (1) The diamond particles have a size of 100 μm and are evenly coated with a 200 nm thick carbon layer on the surface of the diamond particles by resin impregnation followed by drying, pyrolysis, and crushing.

[0064] Step (2) 30 parts of a water-soluble binder, PVA, and 80 parts of silicon powder with a particle size of 5 μm were selected as ceramic powders and mixed in 25 parts of deionized water. The mixture was stirred at 85° C. for 30 minutes at 500 rpm using a magnetic stirrer. After cooling, 5 parts of glycerin was added as a freezing control agent, and the mixture was stirred at 600 rpm for 15 minutes to prepare a uniform slurry. Step (3) The diamond and slurry were uniformly mixed in a non-contact stirrer at 900 rpm for 2 minutes, and then injected into a pre-cooled mold, which was then transferred to a freeze dryer for molding.

[0065] Step (4) sintering the preform at 1500°C with a heating rate of 5°C / min and holding for 30 minutes in a high-purity argon atmosphere;

[0066] The resulting porous silicon carbide-diamond composite material has a porosity of 50%, a flexural strength of 15 MPa, a thermal conductivity of 45 W / m·K, and a silicon carbide protective layer thickness of 3.4 μm. The composite material's volume fraction is 50% diamond, 27% silicon carbide, and 13% silicon.

[0067] Example 5:

[0068] Step (1) The diamond particles have a size of 50 μm and are coated with a 500 nm thick carbon layer uniformly on the diamond surface by cellulose coating and thermal cracking.

[0069] Step (2) The ceramic powder is silicon powder with a particle size of 2 μm, the binder is polyurethane resin, the curing agent is isocyanate curing agent toluene diisocyanate, and the solvent is anhydrous ethanol, with a slurry ratio of 70:5:2:40. The raw materials are mixed according to the proportion and added to a mixing tank. The mixture is mixed with a non-contact mixer at a speed of 300 rpm for 30 seconds, then at a speed of 600 rpm for 60 seconds, and then at a speed of 1200 rpm for 90 seconds to prepare a uniform slurry.

[0070] Step (3) The diamond particles and the slurry are uniformly mixed by ball milling for 4 hours, and then injected into a silicone mold and naturally cooled and solidified to form a shape.

[0071] In step (4), the preform is sintered at 1550°C, with a heating rate of 3°C / min from room temperature to 1000°C and a heating rate of 8°C / min from 1000°C to 1550°C. The entire sintering process is completed in a high-purity argon atmosphere.

[0072] The obtained silicon carbide-diamond porous composite material has a thermal conductivity of 150W / m·K, a porosity of 30%, and a flexural strength of 100MPa. The volume fraction of diamond in the composite material is 75%, the volume fraction of silicon carbide is 15%, and the volume fraction of silicon is 10%.

[0073] Example 6:

[0074] Step (1) The diamond particles have sizes of 400 μm and 50 μm, and the ratio of 400 μm to 50 μm diamond particles is 4:1. A 200 nm thick carbon layer is uniformly deposited on the surface using a chemical vapor deposition process.

[0075] In step (2), silicon powder with a particle size of 10 μm is selected as the ceramic powder, phenolic resin is used as the binder in the slurry system, acidic curing agent benzenesulfonic acid is used as the curing agent, and anhydrous ethanol is used as the slurry solvent. The mixture is mixed in a ratio of 70:30:2:20 and stirred at a rate of 800 rpm for 5 minutes at room temperature using a non-contact mixer to prepare a uniform slurry.

[0076] Step (3) The diamond particles and the slurry were mixed in a non-contact mixer at a rate of 900 rpm for 3 min, then dried in a drying blower at 85° C. for 4 h, and then ground and crushed and hot isostatically pressed at a pressure of 200 MPa.

[0077] The preform was pyrolyzed at 600°C in an argon atmosphere with a heating rate of 2°C / min and a holding time of 10 min.

[0078] Step (4) The preform is sintered in stages at 1600°C, with a heating rate of 3°C / min from room temperature to 1000°C, a heating rate of 8°C / min from 1000°C to 1350°C, and a heating rate of 10°C / min from 1350°C to 1600°C. Finally, the preform is kept at 1600°C for 5 minutes. The sintering process is completed under high-purity argon conditions.

[0079] The obtained silicon carbide-diamond porous composite material has a porosity of 22%, a thickness of the silicon carbide protective layer of 100nm, a diamond volume fraction of 87%, a silicon carbide volume fraction of 13%, a silicon volume fraction of 0, a thermal conductivity of 752W / m·K, and a flexural strength of 159MPa. The interface of the composite material is as follows Figure 3 shown.

[0080] Example 7:

[0081] In step (1), the diamond particles have a size of 100 μm and are evenly coated with an 800 nm thick carbon layer on the surface by a polymer coating and thermal cracking method.

[0082] Step (2) Select silicon powder with a particle size of 20 μm as ceramic powder, acetone as solvent, select 30 parts of silicon powder and 10 parts of acetone in a ratio of 3:1, stir at a rate of 300 rpm in a magnetic stirrer for 30 minutes to obtain a uniform suspension, then select 10 parts of epoxy resin as a binder and dissolve it in the suspension, and finally add 1 part of isocyanate curing agent toluene diisocyanate as a curing agent, stir at a rate of 800 rpm in a non-contact stirrer for 3 minutes to obtain a uniform slurry.

[0083] Step (3) The diamond particles and the slurry were uniformly mixed in a ball mill at 300 rpm for 8 h and then formed by 3D printing.

[0084] The preform was pyrolyzed at 1000°C in a nitrogen atmosphere with a heating rate of 8°C / min and a holding time of 90 min.

[0085] Step (4) the preform is sintered at 1650°C at a heating rate of 8°C / min and kept at 1650°C for 60 minutes under vacuum conditions;

[0086] The obtained silicon carbide-diamond porous composite material has a thermal conductivity of 385W / m·K, a flexural strength of 47MPa, a porosity of 35%, a silicon carbide protective layer thickness of 1.5μm, and a silicon carbide-diamond network with a diamond volume fraction of 79%, a silicon carbide volume fraction of 19%, and a silicon volume fraction of 2%.

[0087] Example 8:

[0088] Step (1) The diamond particles have a size of 200 nm, and a 20 nm thick carbon layer is uniformly deposited on the surface using a chemical vapor deposition process.

[0089] In step (2), silicon powder with a particle size of 50 nm is selected as the ceramic powder, phenolic resin and polyvinyl alcohol are mixed in a ratio of 2:1 as a binder, isocyanate curing agent toluene diisocyanate is selected as a curing agent, acetone is used as a solvent, the slurry ratio is 60:10:1:20, and the raw materials are stirred at a rate of 1000 rpm for 90 seconds by a non-contact mixer according to the ratio to prepare a uniform slurry.

[0090] Step (3) The diamond particles and the slurry were uniformly mixed in a ball mill at a rate of 500 rpm for 5 h, then dried at 60° C. for 6 h, and then ground and crushed and pressed into shape at a pressure of 300 MPa.

[0091] The preform was pyrolyzed in a nitrogen atmosphere at a temperature of 1000°C, a heating rate of 5°C / min, and a holding time of 150 min.

[0092] Step (4) the preform is sintered at 1500° C. for 120 min under vacuum conditions;

[0093] The obtained silicon carbide-diamond porous composite material has a thermal conductivity of 63W / m·K, a flexural strength of 128MPa, a porosity of 45%, a silicon carbide protective layer thickness of 59nm, and a silicon carbide-diamond network with a diamond volume fraction of 52%, a silicon carbide volume fraction of 25%, and a silicon volume fraction of 23%.

[0094] Example 9:

[0095] Step (1) Preparation of carbon-coated diamond particles:

[0096] Diamond particles with a particle size of 300 μm were selected, and a 500 nm thick carbon layer was deposited on the surface by chemical vapor deposition (CVD) to ensure uniform and dense coating.

[0097] Step (2) Preparation and uniform mixing of silicon carbide precursor slurry:

[0098] Metallic silicon powder with an average particle size of 30 μm was selected as the ceramic powder. The binder was a mixture of epoxy resin and polyvinyl alcohol in a 2:1 ratio. The curing agent was an acid anhydride, and the solvent was anhydrous ethanol, a polar solvent. The slurry was prepared using a mass ratio of 40:15:1.5:15. The raw materials were mixed in a magnetic stirrer at 500 rpm for 30 minutes to ensure uniform dispersion.

[0099] The carbon-coated diamond particles were mixed with the slurry in a ratio of 1:1 and dispersed by high-efficiency ball milling for 2 hours to make the slurry uniform.

[0100] Step (3) The diamond particles and the slurry are evenly mixed and then dried at 60° C. for 4 h. The mixture is then crushed by a crusher and the powder is formed by cold isostatic pressing (uniaxial pressure of 100 MPa and pressure increase rate of 10 MPa / min).

[0101] The preform was pyrolyzed at 800 °C in a high-purity nitrogen atmosphere with a heating rate of 3 °C / min and a holding time of 120 min to remove organic components and form a preliminary skeleton.

[0102] Step (4) high temperature sintering:

[0103] The pyrolyzed preform was placed in a vacuum environment and sintered in stages at 1700°C (the heating rate was 3°C / min from room temperature to 1000°C, the heating rate was 8°C / min from 1000°C to 1400°C, and the heating rate was 10°C / min from 1400°C to 1700°C), and then kept at 1700°C for 90 minutes to promote the formation of silicon carbide and enhance the structural stability of the material.

[0104] The resulting porous silicon carbide-diamond composite material has a thermal conductivity of 512 W / m·K, a flexural strength of 78 MPa, a porosity of 38%, and a 2.1 μm thick silicon carbide protective layer on the diamond surface. The composite material has a volume fraction of 82% diamond, 14% silicon carbide, and 4% silicon.

[0105] Example 10:

[0106] Step (1) Preparation of carbon-coated diamond particles:

[0107] Diamond particles with particle sizes of 50nm and 500nm were selected and mixed in a ratio of 3:1. A 200nm thick carbon layer was formed on their surface using a thermal cracking method to improve the interface bonding strength.

[0108] Step (2) Preparation and uniform mixing of silicon carbide precursor slurry:

[0109] 25 parts of silica powder with an average particle size of 100nm, 8 parts of polyurethane resin as a binder, 1 part of a polyamine curing agent, and 12 parts of acetone solvent were measured separately. The nano-SiO2 powder was added to a stirrer containing acetone solvent three times, with an interval of 5 minutes between each addition. A high-speed disperser (2000rpm) was simultaneously turned on for primary dispersion. Subsequently, the polyurethane resin was added, the temperature was raised to 60°C, and planetary stirring was switched to (revolution 30rpm / rotation 800rpm) for 1 hour. Finally, the amine curing agent was slowly added dropwise at a rate of 0.5mL / min. After mixing, the mixture was passed through a 200-mesh stainless steel sieve to obtain a uniform slurry.

[0110] Diamond particles and slurry were mixed at a ratio of 1:1 and dispersed using ultrasonic dispersion technology for 60 min to ensure uniformity.

[0111] Step (3) molding and preheating:

[0112] The mixed slurry was dried at 60° C. for 6 h, crushed by a crusher, and formed by cold isostatic pressing (uniaxial pressure of 150 MPa and press rate of 15 MPa / min).

[0113] The preform was pyrolyzed at 1000°C in a high-purity nitrogen environment with a heating rate of 6°C / min and a holding time of 180 min to promote the formation of a silicon carbide network.

[0114] Step (4) high temperature sintering:

[0115] The preform was sintered in a high-purity argon environment at 1550°C with a heating rate of 8°C / min and kept at 1550°C for 60 minutes to improve the density and thermal conductivity of the material.

[0116] The resulting porous silicon carbide-diamond composite material has a thermal conductivity of 225 W / m·K, a flexural strength of 132 MPa, a porosity of 28%, and a silicon carbide protective layer thickness of 800 nm. The composite material has a volume fraction of 75% diamond, 18% silicon carbide, and 7% silicon.

[0117] Example 11:

[0118] Step (1) Preparation of carbon-coated diamond particles:

[0119] Diamond particles with a particle size of 1000 μm were selected and coated with a 1.5 μm thick carbon layer using a chemical vapor deposition (CVD) method.

[0120] Step (2) Preparation and uniform mixing of silicon carbide precursor slurry:

[0121] The ceramic powder used was metallic silicon powder with an average particle size of 200μm. The binder was phenolic resin, the curing agent was an imidazole-based curing agent, and the solvent was anhydrous ethanol. The slurry ratio (by mass) was 70:25:2:18. The phenolic resin and anhydrous ethanol were mixed according to the above ratio and then stirred in a magnetic stirrer at 300 rpm for 20 minutes to ensure uniform mixing. The silicon powder was then added evenly in three additions, with 5-minute intervals between each addition to ensure uniform dispersion. Finally, the imidazole-based curing agent was added and mixed at 800 rpm for 5 minutes to obtain a uniform slurry.

[0122] Diamond particles and slurry were mixed in a ratio of 1:1 and mixed in a high-speed mixer for 30 min to ensure that the diamonds were evenly distributed in the slurry.

[0123] Step (3) molding and preheating:

[0124] The slurry was dried at room temperature and then ground and pulverized, and then formed by a hot pressing process (pressure of 80 MPa, hot pressing temperature of 110° C., and keeping at 110° C. for 5 minutes).

[0125] The preform was pyrolyzed in a nitrogen atmosphere at a temperature of 600° C. with a heating rate of 4° C. / min and a holding time of 90 min to remove organic components.

[0126] Step (4) high temperature sintering:

[0127] The preform is sintered in a vacuum environment at 1900°C for 30 minutes to densify the material structure and improve the interface bonding performance.

[0128] The thermal conductivity of the resulting silicon carbide-diamond porous composite material is 498W / m·K, the flexural strength is 165MPa, the porosity is 20%, and the thickness of the silicon carbide protective layer is 3.5μm. The volume fraction of diamond in the composite material is 88%, the volume fraction of silicon carbide is 10%, and the volume fraction of silicon is 2%. Its micromorphology is as follows Figure 4 shown.

[0129] Comparative Example 1:

[0130] In step (1), 100 μm diamond particles were used directly without carbon coating.

[0131] Step (2) uses the same ceramic powder (silicon powder, size 20 μm) and binder system as in Example 1, and the slurry ratio remains consistent (30:10:1:10).

[0132] Step (3) After the diamond particles are evenly mixed with the slurry, they are dried, crushed and pressed into shape.

[0133] In step (4), the preform is pyrolyzed in a nitrogen atmosphere at 1000° C., with a heating rate of 5° C. / min and a holding time of 150 min.

[0134] Step (5) The preform is sintered at 1550° C. under vacuum conditions and kept warm for 60 minutes.

[0135] The resulting silicon carbide-diamond composite material has a thermal conductivity of 85 W / m·K, a flexural strength of 12 MPa, and a porosity of 50%. Because it lacks a carbon coating, diamond reacts violently with silicon, resulting in poor interfacial bonding and reduced thermal conductivity and mechanical properties.

[0136] Comparative Example 2:

[0137] In step (1), 400 μm and 50 μm diamond particles (ratio 4:1) were used to uniformly deposit a 200 nm thick carbon layer on the surface (CVD method).

[0138] Step (2) uses the same ceramic powder (silicon powder, size 10 μm) and binder system (phenolic resin) as in Example 2, and the slurry ratio remains consistent (50:20:2:20).

[0139] Step (3) After the diamond particles are evenly mixed with the slurry, they are dried, crushed and pressed into shape.

[0140] Step (4) The preform is pyrolyzed in an argon atmosphere at 600°C with a heating rate of 2°C / min and kept warm for 10 minutes.

[0141] In step (5), the performance test was directly performed without the 1300°C sintering step.

[0142] Results: The material has a porosity of up to 30%, a thermal conductivity of only 37 W / m·K, and a flexural strength of 2 MPa, indicating that high-temperature sintering is crucial for material densification and interface bonding.

[0143] The silicon carbide-diamond composite porous material of the present invention is constructed by a three-dimensional interconnected silicon carbide-diamond network and a porous pore network through mutual penetration. Among them, the silicon carbide-diamond network is formed by diamond particles with a silicon carbide protective layer formed on the surface connected by diamond-silicon carbide-diamond phase boundaries. By preparing a carbon coating layer on the diamond surface, the erosion of silicon on diamond during the reaction sintering process can be avoided to ensure the integrity of the diamond particles and achieve high thermal conductivity and high strength of the silicon carbide-diamond composite porous material. By adopting the structural design and preparation method described in the present invention, a high thermal conductivity silicon carbide-diamond composite porous material with highly adjustable diamond volume, pore size and porosity can be obtained. Among them, the thermal conductivity range is 50 to 800 W / m·K, the bending strength range is 5 to 200 MPa, and it can effectively resist acid and alkali corrosion. Through the above design, the mechanical and thermal conductivity properties of silicon carbide-diamond composite porous materials are guaranteed, and the goals of lightness and multi-function are achieved, thereby meeting the application needs of multiple fields such as catalyst carriers, filters, heat dissipation, electromagnetic shielding, wave absorption and acoustic isolation, and composite material reinforcements.

[0144] Those skilled in the art will appreciate that the above-described embodiments are specific examples of the present invention, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present invention. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A silicon carbide-diamond porous composite material, characterized in that: The silicon carbide-diamond composite porous material comprises diamond particles coated with a silicon carbide layer, and adjacent diamond particles coated with a silicon carbide layer are connected by silicon carbide or silicon carbide and silicon to form a three-dimensional continuous silicon carbide-diamond network and an interconnected porous pore network; The silicon carbide-diamond composite porous material comprises the following components by volume fraction: 50% to 90% of diamond particles, 10% to 50% of silicon carbide, and 0% to 20% of silicon.

2. The silicon carbide-diamond composite porous material according to claim 1, characterized in that: In the silicon carbide-diamond composite porous material, the thickness of the silicon carbide layer on the diamond particles coated with the silicon carbide layer is 10 nm to 6 μm, and the coverage of the silicon carbide layer on the surface of the diamond particles is greater than or equal to 95%; The volume fraction of the porous pore network is 20% to 80%.

3. The silicon carbide-diamond composite porous material according to claim 1, characterized in that: The thermal conductivity of the silicon carbide-diamond composite porous material is 50 to 800 W / m·K, and the bending strength is 5 to 200 MPa.

4. A method for preparing a silicon carbide-diamond composite porous material according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Step (1) preparing a carbon protective layer on the surface of diamond particles by a thermal cracking method to obtain diamond particles coated with a carbon layer; Step (2) mixing ceramic powder, a binder and a solvent to obtain a slurry; and fully mixing the diamond particles coated with the carbon layer and the slurry in a mass ratio of 1:1 by a dispersion method to form a uniform suspension; Step (3) drying and crushing the suspension and then pressing it into a shape to obtain a preform; pyrolyzing the preform in a controlled atmosphere at a temperature of 600 to 1200° C., with a heating rate of 1 to 10° C. / min and a holding time of 10 to 300 min to obtain a heat-treated preform; Step (4) sintering the heat-treated preform at 1400-1800° C. in high-purity argon, high-purity nitrogen or vacuum conditions for 1 minute to 6 hours to obtain the silicon carbide-diamond composite porous material.

5. The method for preparing the silicon carbide-diamond composite porous material according to claim 4, characterized in that: In step (1), the size of the diamond particles is 100 nm to 1000 μm.

6. The method for preparing the silicon carbide-diamond composite porous material according to claim 4, characterized in that: In step (2), the ceramic powder includes metallic silicon and / or silicon dioxide, and has a size of 50 nm to 200 μm; The binder comprises one or more of phenolic resin, epoxy resin, polyvinyl alcohol, polyvinyl butyral, furan resin and polyurethane; The solvent is a polar or non-polar solvent; In the slurry, the following raw materials are used in amounts by mass: 5 to 100 parts of the ceramic powder, 5 to 100 parts of the binder, and 5 to 100 parts of the solvent.

7. The method for preparing the silicon carbide-diamond composite porous material according to claim 4, characterized in that: The size of the ceramic powder is 50 nm to 200 μm.

8. The method for preparing the silicon carbide-diamond composite porous material according to claim 6, characterized in that: The raw materials of the slurry also include a curing agent, and the amount of the curing agent is less than or equal to 0.2 times the amount of the binder; The curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, a phenolic curing agent, an imidazole curing agent, an isocyanate curing agent, an acid curing agent, and a cross-linking agent.

9. The method for preparing the silicon carbide-diamond composite porous material according to claim 8, characterized in that: The raw materials of the slurry also include 10 to 150 parts of a pore-forming agent; Wherein, the pore-forming agent is selected from at least one of low-temperature type, medium-temperature type or high-temperature type.

10. Use of the silicon carbide-diamond composite porous material according to any one of claims 1 to 3 in high-performance composite material reinforcements, electronic device heat dissipation materials, high-frequency electromagnetic shielding and absorbing materials, high-temperature filtration materials, biomaterials, electrochemical catalytic support materials, and sound absorption / noise reduction structural materials.

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