Silicon carbide composite powder, preparation method and silicon carbide ceramic material

Abstract

The invention relates to the technical field of ceramic materials, in particular to silicon carbide composite powder, a preparation method and a silicon carbide ceramic material. The invention provides a preparation method of silicon carbide composite powder. The preparation method comprises the following steps: S1, mixing silicon carbide powder and silicon powder according to a specific mass ratio; s2, the composite powder is subjected to atmospheric plasma spraying, and liquid composite powder is obtained; s3, quenching treatment is conducted on the liquid composite powder, and the silicon carbide composite powder is obtained in the quenching medium; spherical silicon carbide composite powder is prepared by adopting an atmospheric plasma spraying technology, and silicon-coated silicon / silicon carbide spherical composite powder is prepared by utilizing a silicon solid-liquid-solid phase conversion process, so that the problem of low stacking density caused by irregular shape attributes such as a lath shape and a corner angle shape of silicon carbide is effectively solved; the performance of the silicon carbide ceramic material prepared from the BJP can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a method for preparing a silicon carbide composite powder, the silicon carbide composite powder and a silicon carbide ceramic material. Background Art

[0002] Silicon carbide ceramics have properties such as high strength, high modulus, and high thermal conductivity, making them widely used in aerospace, energy, and chemical industries. At present, defense and industrial applications require silicon carbide ceramics to have more complex structures, such as lattice structures and topological structures, which poses a great challenge to the preparation technology of silicon carbide ceramics. Traditional preparation methods of silicon carbide ceramics, such as isostatic pressing and slip injection molding, cannot produce silicon carbide with highly complex structures. It is urgent to explore new molding processes to meet the development needs of defense and industry.

[0003] Additive manufacturing technology is a stacking manufacturing process based on the discrete-stacking principle, which involves two-dimensional slicing of three-dimensional models. This allows the preparation of silicon carbide ceramics with arbitrary structures and is considered to be the driving engine of the next industrial revolution.

[0004] Additive manufacturing technologies based on powder bed process include laser selective sintering, binder jet molding, etc. Taking binder jet molding (BJP) as an example, it is a room temperature additive manufacturing technology using powder as raw material. This technology selectively sprays binder on the raw material powder bed to bond the powder to form a two-dimensional thin layer. Repeating the above process in three-dimensional space can obtain a three-dimensional solid ceramic preform with a specific structure.

[0005] Unlike the slurry-based additive manufacturing technology, which adds a large amount of organic matter, the organic content in the powder bed additive manufacturing molding process is extremely low, and no degreasing and debinding process is required, which greatly shortens the preparation cycle. In the powder bed additive manufacturing molding process, such as laser selective sintering additive manufacturing technology and BJP, both face the challenge of low powder packing density leading to poor ceramic performance after reaction sintering. At present, spray granulation is a method commonly used to increase the packing density of silicon carbide powder. This method prepares a silicon carbide suspension solution, atomizes the solution in the form of droplets in a drying tower, and obtains spherical silicon carbide particles after high-temperature evaporation of the water in the droplets. However, in this process, pores are formed in situ with the evaporation of water, resulting in a large number of capillaries in the spherical silicon carbide particles. In the BJP process, in order to prevent the excessive overflow of the binder from affecting the molding accuracy, the content of the sprayed binder is usually only tens of picoliters. The large number of capillaries in the spray granulation powder will absorb most of the binder, resulting in a significant reduction in the molding effect, which is not conducive to the BJP additive manufacturing molding process. Therefore, under the premise of ensuring the BJP molding accuracy, exploring new methods to improve the powder stacking density can realize the development of high-performance silicon carbide ceramics with complex structures, which is crucial to meet the development of national defense and industry.

[0006] The existing spherical powder preparation method generally adopts the spray drying method. The binder of the powder is organic matter, and the solvent of the binder is water. The water solvent evaporates completely during the drying process, resulting in many pores on the surface of the spherical powder, which is not suitable for powder bed additive manufacturing technology. Plasma spraying technology is generally used for coating preparation and is less used in powder granulation. In particular, there is no report on the preparation of spherical silicon carbide powder by plasma spraying technology. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a silicon carbide composite powder with high sphericity and high density prepared by atmospheric plasma spraying technology, a method for preparing a corresponding high stacking density silicon carbide powder material, and a silicon carbide ceramic material prepared by the silicon carbide composite powder powder bed additive manufacturing combined with reaction sintering of the present invention.

[0008] The present invention provides a method for preparing a silicon carbide composite powder, the method for preparing the silicon carbide composite powder comprising the steps of: S1. The silicon carbide powder and the silicon powder are mixed in a mass ratio of (40~80): (60~20) to obtain a composite powder; S2. The composite powder is subjected to atmospheric plasma spraying to obtain a liquid composite powder; the liquid composite powder comprises silicon in a liquid melt state and silicon carbide in a powder state; the silicon in the liquid melt state encapsulates the silicon carbide in a powder state; S3. The liquid composite powder is quenched by a quenching medium to obtain the silicon carbide composite powder in the quenching medium.

[0009] Furthermore, the particle size of the silicon carbide powder ranges from 100 mesh to 2000 mesh, and the particle size of the silicon powder ranges from 1000 mesh to 2000 mesh; preferably, the particle size of the silicon powder is 2000 mesh.

[0010] Further, the atmospheric plasma spraying includes: conveying the composite powder to a plasma spray gun via a carrier gas; The carrier gas includes argon and hydrogen in a volume ratio range of (90-10):(10-90), the argon is used to stabilize the arc, and the hydrogen is used as a heat conducting medium; The power range of the plasma spray gun is 20 KW ~ 50 KW, the spraying distance of the atmospheric plasma spraying is 20 mm ~ 200 mm, and the spraying distance is the distance between the plasma spray gun and the quenching medium.

[0011] Furthermore, the mixing includes: fully mixing the silicon carbide powder and the silicon powder by wet ball milling in a ball mill; the ball milling medium of the wet ball milling is anhydrous ethanol, the grinding balls are silicon carbide balls, the ball-to-material ratio is 1-4.2, and the ball milling time is 5h-24h.

[0012] Furthermore, the quenching medium is water, oil, liquid nitrogen, carbon dioxide or argon.

[0013] The present invention also provides a silicon carbide composite powder, which is prepared by the method for preparing the silicon carbide composite powder of the present invention.

[0014] The present invention also provides a silicon carbide ceramic material, which is prepared by performing binder injection molding or laser selective sintering molding on silicon carbide composite powder to form a silicon carbide preform, and then performing reaction sintering; the silicon carbide composite powder is the silicon carbide composite powder mentioned above in the present invention.

[0015] Furthermore, in the process of preparing the silicon carbide preform by the binder spray molding, the binder used includes a solute and a solvent, the solute is selected from at least one of vinyl pyrrolidone, phenolic resin, furan resin or polyacrylic resin, and the solvent is selected from at least one of deionized water, anhydrous ethanol or ethylene glycol; During the process of preparing the silicon carbide preform by the binder spray molding, the molding thickness is set to 10 μm-100 μm, and the scanning spacing is set to 0.01 mm-1 mm.

[0016] Furthermore, the density of the silicon carbide preform is 1.2 g / cm 3 ~2.2g / cm 3 The bending strength of the silicon carbide preform is 2MPa~14MPa.

[0017] Furthermore, the flexural strength of the silicon carbide ceramic material is 220 MPa to 450 MPa, the elastic modulus of the silicon carbide ceramic material is 270 GPa to 420 GPa, and the fracture toughness of the silicon carbide ceramic material is 1.63 MPa·m 1 / 2 ~3.28MPa·m 1 / 2 The thermal conductivity of the silicon carbide ceramic material is 140W / mk~200W / mk, and the density of the silicon carbide ceramic material is 2.85g / cm 3 ~3.09g / cm 3 .

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects: The present invention prepares spherical silicon carbide composite powder by adopting atmospheric plasma spraying technology combined with quenching treatment, and creatively utilizes the silicon solid-liquid-solid phase transition process to prepare silicon-coated silicon / silicon carbide spherical composite powder, which not only overcomes the problem of pores on the surface of spherical powder caused by water evaporation in the composite powder during the existing spray granulation technology, but also overcomes the splashing problem caused by the incident flame flow impacting the quenching medium in the existing atmospheric plasma spraying technology by designing a quenching device; effectively solves the problem of low packing density caused by irregular shapes of silicon carbide such as laths and corners; and the preparation method of silicon carbide composite powder provided by the present invention is different from spray When granulating, water droplets are used as the granulating medium. The evaporation of water during the drying process of the spherical droplets causes a large number of capillaries on the surface and inside of the spherical powder, which can easily lead to the problem of low BJP molding quality. The present invention uses liquid silicon droplets as the granulating medium. The evaporation of silicon during the quenching process is extremely small. There are no or very few capillaries in the spherical composite powder, and the composite powder will not cause any interference to the BJP molding accuracy. Overall, the method for preparing a silicon carbide composite material provided by the present invention can effectively improve the performance of silicon carbide ceramics prepared by BJP, fully utilize BJP and reaction sintering processes to prepare complex structure ceramics, and at the same time give the ceramics excellent comprehensive properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the quenching process according to an embodiment of the present invention.

[0020] Reference numerals: 1. Plasma spray gun 2. Si / SiC molten droplet flame flow 3. baffle 4. hole 5. quenching medium. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0023] A specific embodiment of the present invention provides a method for preparing a silicon carbide composite powder, and the method for preparing the silicon carbide composite powder comprises the following steps: S1. Silicon carbide powder and silicon powder are mixed in a mass ratio of (40-80): (60-20) to obtain a composite powder; wherein, when the content of silicon powder as a binder of the silicon carbide composite powder is greater than 20%, it can play a better bonding effect on the silicon carbide powder. At the same time, in the reaction-sintered silicon carbide component prepared from the silicon carbide composite powder, the silicon content in the powder is controlled to be no more than 60%, which can better improve the performance of the silicon carbide component; the particle size range of the silicon carbide powder is 100 mesh to 2000 mesh, and in a further preferred embodiment, the particle size range of the silicon carbide powder is 800 mesh to 1500 mesh; the particle size range of the silicon powder is 1000 mesh to 20 00 mesh, further preferably, the particle size of the silicon powder is 2000 mesh; the difficulty and screening time of powder screening can be minimized, and at the same time, it can better ensure that the particle size of the composite powder after atmospheric plasma spraying granulation is more appropriate; the specific powder mixing process includes: the silicon carbide powder and the silicon powder in a specific mass ratio are fully mixed in a ball mill by wet ball milling; the ball milling medium of the wet ball milling is anhydrous ethanol, the grinding balls are silicon carbide balls, the ball-to-material ratio is 1~4.2, and the ball milling time is 5h~24h; after being fully mixed by wet ball milling, it is placed in a drying oven for drying, the drying time range can be 10h~18h, and the drying temperature range is 120℃~160℃.

[0024] S2. The dried composite powder is subjected to atmospheric plasma spraying to obtain a liquid composite powder; the liquid composite powder comprises silicon in a liquid melt state and silicon carbide in a powder state; the silicon in a liquid melt state encapsulates the silicon carbide in a powder state.

[0025] In a specific embodiment, the present invention creatively proposes a method of replacing water-based spray granulation with silicon, and at the same time carries out atmospheric plasma spraying technology research, designs and regulates carrier gas components, and adjusts the content of heat-conducting gas. The final solution can promote better melting of silicon and easily form molten droplets, effectively overcoming the problem of pores on the surface of spherical powder caused by evaporation of binder in composite powder in existing atmospheric plasma spraying technology; specifically, the atmospheric plasma spraying of the present invention includes: transporting the composite powder to a plasma spray gun through a carrier gas; the carrier gas includes argon and hydrogen in a volume ratio range of (90~10):(10~90), the argon is used to stabilize the arc, and the hydrogen is used as a heat-conducting medium; the power range of the plasma spray gun is 20 KW~50KW, and the spraying distance of the atmospheric plasma spraying is 20mm~200mm, and the spraying distance is the distance between the plasma spray gun and the quenching medium. By coupling the spraying power and the spraying distance, the melting state of the powder is regulated to achieve a liquid composite powder in which the silicon is in liquid state and the morphology of the silicon carbide particles remains stable, that is, the silicon in the liquid melt state envelops the molten droplets of the silicon carbide particles in the powder state; specifically, the molten droplets cool in the air, and the cooling time is proportional to the spraying distance. The longer the cooling time, the greater the hardness of the molten droplets, and the smaller the deformation when impacting the bottom of the spraying medium container, making it easier to obtain powder with high sphericity. Adjusting the spraying distance can also effectively improve the powder yield.

[0026] S3. The liquid composite powder is quenched by a quenching medium to obtain the silicon carbide composite powder in the quenching medium. Specifically, the quenching medium is water, oil, liquid nitrogen or other gases such as carbon dioxide and argon; while the present invention adopts atmospheric plasma spraying technology to prepare spherical silicon carbide composite powder, it also creatively proposes a new design concept of quenching test device in the quenching process, adding a perforated baffle design to ensure that the molten droplets in the spray gun are incident on the quenching medium while preventing the droplets from splashing back, effectively overcoming the splashing problem caused by the incident flame flow impacting the quenching medium in the prior art.

[0027] A specific embodiment of the present invention further provides a silicon carbide composite powder, which is prepared by the method for preparing the silicon carbide composite powder of the present invention.

[0028] A specific embodiment of the present invention further provides a silicon carbide ceramic material, which is prepared by performing binder injection molding on silicon carbide composite powder to form a silicon carbide preform, and then performing reaction sintering; the silicon carbide composite powder is the silicon carbide composite powder mentioned above in the present invention.

[0029] In a specific embodiment, in the process of preparing the silicon carbide preform by the binder spray molding, the binder used includes a solute and a solvent, the solute is selected from at least one of vinyl pyrrolidone, phenolic resin, furan resin or polyacrylic resin, and the solvent is selected from at least one of deionized water, anhydrous ethanol or ethylene glycol; in the process of preparing the silicon carbide preform by the binder spray molding, the molding thickness is set to 10μm~100μm, and the scanning spacing is set to 0.01mm~1mm. The density of the silicon carbide preform is 1.2g / cm 3 ~2.2g / cm 3 The bending strength of the silicon carbide preform is 2MPa~14MPa. Through the silicon carbide composite material and preparation method of the present invention, the bending strength of the silicon carbide ceramic material finally obtained is 220MPa~450MPa, the elastic modulus of the silicon carbide ceramic material is 270GPa~420GPa, and the fracture toughness of the silicon carbide ceramic material is 1.63MPa·m 1 / 2 ~3.28MPa·m 1 / 2 The thermal conductivity of the silicon carbide ceramic material is 140W / mk~200W / mk, and the density of the silicon carbide ceramic material is 2.85g / cm 3 ~3.09g / cm 3 .

[0030] The following is an exemplary description of the method for preparing the high sphericity and high density silicon carbide composite powder and the silicon carbide ceramic material prepared by BJP combined with reaction sintering of the present invention. The preparation method mainly comprises the following steps: (1) Preparation of raw powder. The silicon carbide raw powder is screened by a vibrating screen. If the powder particle size is too small, the screening is difficult and the screening time is increased. If the powder particle size is too large, the composite powder particle size after atmospheric plasma spraying granulation may be larger. The increase in the powder gap after spreading is not conducive to increasing the packing density. The present invention preferably screens 800-1500 mesh silicon carbide powder and 1000-2000 mesh silicon powder as raw powder; the raw powder is mixed according to the mass ratio of (40-80): (60-20), and is wet-milled in a ball mill to be fully mixed. The ball milling medium is anhydrous ethanol, the grinding ball is a silicon carbide ball, the ball-to-material ratio is 1-4.2, and the ball milling time is 5h-24h. The ball-milled mixture is dried to obtain a composite powder.

[0031] (2) Preparation of spherical dense powder. The composite powder is transported to the plasma spray gun by a carrier gas. The main components of the carrier gas are argon and hydrogen, where argon is used to stabilize the arc and hydrogen is used as a heat-conducting medium. The volume ratio is (90~10):(10~90). The power of the plasma spray gun is 20KW~50KW, and the spraying distance is 20mm~200mm. After the composite powder is instantly heated by the plasma spray gun, silicon wraps the silicon carbide particles in the form of a melt to form a molten droplet. The molten droplet has better fluidity than the angular silicon carbide particles. The molten droplet is then quenched to make the molten droplet instantly condense and retain the spherical or nearly spherical state of the molten droplet. The liquid molten droplet is transformed into a solid spherical composite powder in the quenching medium, wherein the quenching medium is water, oil, liquid nitrogen or other gases such as carbon dioxide and argon. The volume ratio of the prepared silicon carbide composite powder to the volume of a perfect sphere with the same surface area is between 0.8 and 1, indicating that it has high sphericity; the porosity of the prepared silicon carbide composite powder is less than 10%, indicating that it also has high density.

[0032] (3) BJP molding of silicon carbide preforms. Select one or more mixtures of polyvinyl pyrrolidone, phenolic resin, furan resin, and polyacrylic resin as the solute in the BJP binder, and select one or more mixtures of deionized water, anhydrous ethanol, and ethylene glycol as the solvent in the BJP binder; molding parameter settings: To complete the preparation of high-precision structural parts, the molding thickness is 10μm~100μm, the scanning spacing is 0.01mm~1mm, and BJP molding is performed according to the pre-set geometric structure. The density of the prepared silicon carbide preform is 1.2g / cm 3 ~2.2g / cm 3 , the bending strength is 2MPa~14MPa.

[0033] (4) Preparation of silicon carbide ceramics by reaction sintering. The above-mentioned shaped silicon carbide preform is embedded in silicon powder and placed in a vacuum sintering furnace. In this process, the particle size range of silicon powder is 5nm~73μm, the sintering temperature is 1400℃~1670℃, the insulation time is 4h~21h, and the silicon carbide ceramic composite material is obtained after cooling to room temperature.

[0034] The silicon carbide ceramic composite material prepared by the present invention has excellent comprehensive properties, with a bending strength of 220MPa~450MPa, an elastic modulus of 270GPa~420GPa, and a fracture toughness of 1.63MPa·m 1 / 2 ~3.28MPa·m 1 / 2 , thermal conductivity is 140W / m·k~200W / m·k, density is 2.75g / cm 3 ~3.09g / cm 3 .

[0035] The present invention adopts atmospheric plasma spraying technology combined with quenching treatment to prepare spherical silicon carbide composite powder, and creatively utilizes the silicon solid-liquid-solid phase transition process to prepare silicon-coated silicon / silicon carbide spherical composite powder, which not only overcomes the problem of pores on the surface of spherical powder caused by evaporation of water solvent in the existing spray granulation technology, but also overcomes the splashing problem caused by the impact of incident flame flow on quenching medium in the existing technology; effectively solves the problem of low packing density caused by irregular shape properties of silicon carbide such as lath and angular shape; moreover, the preparation method of silicon carbide composite powder provided by the present invention is different from spray granulation using water droplets as As a granulation medium, the evaporation of water during the drying process of the spherical droplets causes a large number of capillaries on the surface and inside of the spherical powder, which can easily lead to the problem of low BJP molding quality; the present invention uses liquid silicon droplets as the granulation medium, the evaporation of silicon during the quenching process is extremely small, and there are no or very few capillaries in the spherical composite powder, and the composite powder will not cause any interference to the BJP molding accuracy; on the whole, the method for preparing a silicon carbide composite material provided by the present invention can effectively improve the performance of silicon carbide ceramics prepared by BJP, and while making full use of BJP and reaction sintering technology to prepare complex structure ceramics, the ceramics are endowed with excellent comprehensive properties.

[0036] Next, the present invention will be specifically described in conjunction with embodiments. It should be understood that the following embodiments are only used to understand the present invention, but not to limit the present invention.

[0037] Example 1 (1) Preparation of raw material powder. Take 1200 mesh silicon carbide powder and 2000 mesh silicon powder, mix them in a mass ratio of 59:41, use a planetary ball mill, and mill for 16 hours. The ball milling medium is anhydrous ethanol, the grinding ball material is silicon carbide, and the ball-to-material ratio is 3:1. The milled powder slurry is placed in a drying oven and dried at 140°C for 10 hours to obtain a uniformly mixed composite powder.

[0038] (2) Preparation of spherical dense powder. Argon and hydrogen were used as carrier gases with a volume ratio of 9:1 for atmospheric plasma spraying. The spraying power was 45KW, the spraying distance was 150mm, and quenching oil was used for quenching treatment to obtain spherical dense composite powder.

[0039] (3) BJP molding of silicon carbide preforms. Phenolic resin, anhydrous ethanol, and ethylene glycol were used to prepare a binder solution in a mass ratio of 4:4:2, and the printing layer thickness was adjusted to 70 μm for BJP molding to prepare silicon carbide preforms.

[0040] (4) Preparation of silicon carbide ceramics by reaction sintering. The preform was subjected to reaction sintering densification treatment at a temperature of 1650°C for 4 hours and cooled to room temperature to obtain a density of 2.76 g / cm 3 Dense silicon carbide ceramics.

[0041] Example 2 (1) Preparation of raw material powder. Take 1500 mesh silicon carbide powder and 2000 mesh silicon powder, mix them in a mass ratio of 80:20, use a planetary ball mill, and mill for 20 hours. The ball milling medium is anhydrous ethanol, the grinding ball material is silicon carbide, and the ball-to-material ratio is 3:1. The milled powder slurry is placed in a drying oven and dried at 140°C for 10 hours to obtain a uniformly mixed composite powder.

[0042] (2) Preparation of spherical dense powder. Argon and hydrogen were used as carrier gases with a volume ratio of 9:1 for atmospheric plasma spraying. The spraying power was 45KW, the spraying distance was 100mm, and water was used for quenching. To prevent the high-speed flame flow from causing violent fluctuations or splashing on the water surface during the spraying process, the design diagram of atmospheric plasma spraying is shown in the figure below. Figure 1 As shown, the Si / SiC molten droplet flame flow 2 is in the shape of spherical droplets. After being sprayed out by the plasma spray gun 1, it contacts the quenching medium 5 from the hole 4, and the spherical droplets are suddenly cooled to become solid spherical powder. In this process, the spherical droplets are sprayed in the quenching medium 5, and the quenching medium 5 is easy to splash after being impacted. In order to prevent the quenching medium 5 from splashing and causing pollution or damage, the hole 4 is a high-speed incident flame flow, and the splashing quenching medium 5 cannot escape from the hole 4 in the opposite direction of the flame flow. Therefore, by designing the baffle 3, the quenching medium 5 can be effectively blocked from splashing out of the container, thereby ensuring the safety and environmental protection of the entire preparation process; by designing the hole 4 to weaken the jet impact, after the spraying process is completed, a better spherical dense silicon carbide composite powder can be obtained.

[0043] (3) BJP molding of silicon carbide preforms. Phenolic resin, anhydrous ethanol, and ethylene glycol were used to prepare a binder solution in a mass ratio of 6:2:2, and the printing layer thickness was adjusted to 50 μm for BJP molding to prepare silicon carbide preforms.

[0044] (4) Preparation of silicon carbide ceramics by reaction sintering. The preform was subjected to reaction sintering densification treatment at a temperature of 1650°C for 4 hours and cooled to room temperature to obtain a density of 3.02 g / cm 3 Dense silicon carbide ceramics.

[0045] Example 3 Step (1) is the same as in Example 2.

[0046] (2) Preparation of spherical dense powder. Argon and hydrogen were used as carrier gases with a volume ratio of 8:2 for atmospheric plasma spraying. To prevent the evaporation of liquid silicon during the spraying process, the spraying power was reduced from 45KW to 35KW, and the spraying distance was increased to 200mm. On the one hand, the cooling time of the molten droplets in the air was increased, and on the other hand, the jet velocity was slowed down to reduce the splashing during the quenching process and improve the powder yield. After the spraying process, spherical dense silicon carbide composite powder was obtained.

[0047] (3) BJP molding of silicon carbide preforms. Phenolic resin, anhydrous ethanol, and ethylene glycol were used to prepare a binder solution in a mass ratio of 6:2:2. The printing layer thickness was adjusted to 50 μm for BJP molding to prepare a silicon carbide preform. The preform was impregnated with a binder to further increase the carbon content of the preform.

[0048] (4) Preparation of silicon carbide ceramics by reaction sintering. After the preform was degreased and debinded, it was subjected to reaction sintering densification treatment. The sintering temperature was 1670°C, kept at this temperature for 2 hours, and cooled to room temperature to obtain a density of 3.07 g / cm 3 Dense silicon carbide ceramics with a flexural strength of 350MPa.

[0049] Example 4 (1) Preparation of raw material powder. Take 1300 mesh silicon carbide powder and 1800 mesh silicon powder, mix them in a mass ratio of 50:50, use a planetary ball mill, and mill for 16 hours. The ball milling medium is anhydrous ethanol, the grinding ball material is silicon carbide, and the ball-to-material ratio is 3:1. The milled powder slurry is placed in a drying oven and dried at 140°C for 10 hours to obtain a uniformly mixed composite powder.

[0050] (2) Preparation of spherical dense powder. Argon and hydrogen were used as carrier gases with a volume ratio of 9:1 for atmospheric plasma spraying. The spraying power was 35KW and the spraying distance was 200mm. Solid carbon dioxide was used for quenching to obtain spherical dense silicon carbide composite powder.

[0051] (3) BJP molding of silicon carbide preforms. Phenolic resin, anhydrous ethanol, and ethylene glycol were used to prepare a binder solution in a mass ratio of 4:4:2, and the printing layer thickness was adjusted to 70 μm for BJP molding to prepare silicon carbide preforms.

[0052] (4) Preparation of silicon carbide ceramics by reaction sintering. The preform was subjected to reaction sintering densification treatment at a temperature of 1680°C for 5 hours and then cooled to room temperature to obtain a density of 2.82 g / cm 3 Dense silicon carbide ceramics.

[0053] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0054] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing silicon carbide composite powder, characterized in that: The method for preparing the silicon carbide composite powder comprises the steps of: S1. The silicon carbide powder and the silicon powder are mixed in a mass ratio of (40~80): (60~20) to obtain a composite powder; S2. The composite powder is subjected to atmospheric plasma spraying to obtain a liquid composite powder; the liquid composite powder comprises silicon in a liquid melt state and silicon carbide in a powder state; the silicon in the liquid melt state encapsulates the silicon carbide in a powder state; S3. The liquid composite powder is quenched by a quenching medium to obtain the silicon carbide composite powder in the quenching medium.

2. The method for preparing silicon carbide composite powder according to claim 1, characterized in that: The particle size of the silicon carbide powder ranges from 100 mesh to 2000 mesh, and the particle size of the silicon powder ranges from 1000 mesh to 2000 mesh; preferably, the particle size of the silicon powder is 2000 mesh.

3. The method for preparing silicon carbide composite powder according to claim 1, characterized in that: The atmospheric plasma spraying comprises: conveying the composite powder to a plasma spray gun via a carrier gas; The carrier gas includes argon and hydrogen in a volume ratio range of (90-10):(10-90), the argon is used to stabilize the arc, and the hydrogen is used as a heat conducting medium; The power range of the plasma spray gun is 20 KW ~ 50 KW, the spraying distance of the atmospheric plasma spraying is 20 mm ~ 200 mm, and the spraying distance is the distance between the plasma spray gun and the quenching medium.

4. The method for preparing silicon carbide composite powder according to claim 1, characterized in that: The mixing comprises: fully mixing the silicon carbide powder and the silicon powder by wet ball milling in a ball mill; the ball milling medium of the wet ball milling is anhydrous ethanol, the grinding balls are silicon carbide balls, the ball-to-material ratio is 1-4.2, and the ball milling time is 5h-24h.

5. The method for preparing silicon carbide composite powder according to claim 1, characterized in that: The quenching medium is water, oil, liquid nitrogen, carbon dioxide or argon.

6. A silicon carbide composite powder, characterized in that: The silicon carbide composite powder is prepared by the method for preparing the silicon carbide composite powder according to any one of claims 1 to 5.

7. A silicon carbide ceramic material, characterized in that: The silicon carbide ceramic material is prepared by subjecting the silicon carbide composite powder to binder injection molding or laser selective sintering molding to form a silicon carbide preform, and then subjecting the silicon carbide composite powder to reaction sintering to obtain the silicon carbide ceramic material; the silicon carbide composite powder is the silicon carbide composite powder described in claim 6.

8. The silicon carbide ceramic material according to claim 7, characterized in that: In the process of preparing the silicon carbide preform by the binder spray molding, the binder used includes a solute and a solvent, the solute is selected from at least one of vinyl pyrrolidone, phenolic resin, furan resin or polyacrylic resin, and the solvent is selected from at least one of deionized water, anhydrous ethanol or ethylene glycol; During the process of preparing the silicon carbide preform by binder spray molding, the molding thickness is set to 10 μm-100 μm, and the scanning interval is set to 0.01 mm-1 mm.

9. The silicon carbide ceramic material according to claim 7, characterized in that: The density of the silicon carbide preform is 1.2 g / cm 3 ~2.2g / cm 3 The bending strength of the silicon carbide preform is 2MPa~14MPa.

10. The silicon carbide ceramic material according to claim 7, characterized in that: The flexural strength of the silicon carbide ceramic material is 220 MPa-450 MPa, the elastic modulus of the silicon carbide ceramic material is 270 GPa-420 GPa, and the fracture toughness of the silicon carbide ceramic material is 1.63 MPa·m 1 / 2 ~3.28MPa·m 1 / 2 The thermal conductivity of the silicon carbide ceramic material is 140W / mk~200W / mk, and the density of the silicon carbide ceramic material is 2.85g / cm 3 ~3.09g / cm 3 .

Images