A silicon carbide optical mirror and additive manufacturing method thereof

Abstract

This invention discloses a silicon carbide optical mirror and its additive manufacturing method. The method includes the following steps: mixing carbon black powder, silicon carbide powder, and a binder to obtain a composite powder; forming the composite powder into a mirror green body using selective laser sintering (SLS) technology; subjecting the mirror green body to cyclic impregnation-carbonization treatment using a phenolic resin solution to obtain a mirror preform; performing silicon infiltration sintering on the mirror preform to obtain a silicon carbide ceramic body; and depositing a silicon carbide coating on the mirror surface of the silicon carbide ceramic body using halide chemical vapor deposition (CVD) technology. This invention combines additive manufacturing technology with halide CVD coating preparation technology, enabling the integral forming of large-size, complex, lightweight silicon carbide mirrors and rapid, non-destructive homogenization of the mirror surface. The resulting silicon carbide mirror surface coating exhibits uniform thickness, high bonding strength, good consistency, and excellent thermal stability, meeting the application requirements of space optical systems for high-resolution, large-field-of-view silicon carbide mirrors.

Description

Technical Field

[0001] This invention belongs to the field of mirror manufacturing technology, and particularly relates to a silicon carbide optical mirror and its additive manufacturing method. Background Technology

[0002] Optical remote sensors have wide applications in defense, energy, maritime affairs, disaster relief, and infrastructure construction, characterized by high efficiency and real-time performance, thus attracting widespread attention from countries worldwide. The reflector is a core component of a space optical system. To improve the resolution of optical remote sensors, the reflector aperture must be increased, but this increases the sensor's weight, leading to higher launch costs, greater difficulty in satellite deployment, and even exceeding rocket payload capacity. Therefore, ultra-lightweight reflectors have become an inevitable trend. Lightweight structures can maintain structural rigidity with lower mass, but this also leads to increased complexity in the mirror structure. Silicon carbide has advantages such as high specific stiffness and good thermal stability, making it a preferred material for optical reflectors. However, its high hardness and brittleness make it difficult to form highly complex components using traditional methods, limiting the ultra-lightweight design of silicon carbide mirrors. Furthermore, most large-diameter silicon carbide mirror blanks currently require splicing, resulting in long lead times and large surface shape errors.

[0003] Powder bed selective laser sintering additive manufacturing (PLS) can progressively build up arbitrarily complex structures using a 3D model, offering advantages such as large forming size, high powder production efficiency, and no need for support. This makes it a crucial approach for achieving ultra-lightweight manufacturing of highly complex silicon carbide mirrors. Combining PLS with liquid-phase silicon infiltration has become a key method for forming large-size, complex silicon carbide ceramic components. However, additive / silicon infiltration of silicon carbide ceramic components presents challenges such as residual silicon within the silicon carbide, differences in hardness between different phases on the surface, and "additive roughness marks," increasing the difficulty of optical processing. Currently, both domestically and internationally, chemical vapor deposition (CVD) and physical vapor deposition (PVD) are mainly used to prepare modification layers on the mirror blank surface to achieve homogenization of the silicon carbide mirror surface. However, these methods suffer from slow homogenization rates, high thermal mismatch rates between the modification layer and the silicon carbide substrate, low interfacial bonding strength, and susceptibility to cracking and detachment under varying temperatures. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, the present invention aims to provide a silicon carbide optical mirror and its additive manufacturing method, thereby solving the problems of slow homogenization rate, high thermal mismatch rate between the modified layer and the silicon carbide substrate, low interfacial bonding strength, and easy cracking and detachment due to temperature changes in the homogenization treatment of silicon carbide mirror surfaces.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for additive manufacturing a silicon carbide optical mirror includes the following steps:

[0007] S1. Mix carbon black powder, silicon carbide powder and binder evenly to obtain composite powder;

[0008] S2. Composite powder is printed into a green mirror blank using laser selective sintering technology;

[0009] S3. The green mirror blank is subjected to cyclic impregnation-carbonization treatment with phenolic resin solution to obtain the mirror preform;

[0010] S4. Vapor phase silicon infiltration sintering is performed on the preform of the reflector to obtain a dense silicon carbide ceramic reflector body;

[0011] S5. A silicon carbide coating is deposited on the mirror surface of a silicon carbide reflector ceramic body using halide chemical vapor deposition technology.

[0012] Preferably, in step S1, the carbon black powder has a particle size of 20-30 μm; the silicon carbide powder is a graded powder, including silicon carbide powder with particle sizes of 5 μm, 20 μm and 50 μm, and the mass ratio of the three different particle sizes of silicon carbide powder is 10:20:70; the binder is one or more of phenolic resin, epoxy resin and dextrin.

[0013] Preferably, in step S1, the composite powder comprises, by weight percentage, 60%-70% silicon carbide powder, 15%-20% carbon black powder, and 10%-25% binder.

[0014] Preferably, in step S2, the process parameters of the laser selective sintering forming technology are: preheating temperature 50-60℃, laser power 6-12W, printing layer thickness 0.1-0.2mm, laser scanning speed 1000-2000mm / s, and laser scanning spacing 0.1-0.2mm.

[0015] Preferably, step S2 further includes laser homogenization treatment of the printed mirror blank to fully melt the binder and reduce the surface roughness of the blank; the laser power of the laser homogenization treatment is 6-9W, the laser scanning speed is 1500-2000mm / s, and the laser scanning spacing is 0.1-0.2mm.

[0016] Preferably, step S3, the cyclic impregnation-carbonization treatment method, includes: carbonizing the green mirror blank under an inert atmosphere; placing the carbonized green mirror blank in a phenolic resin solution with a concentration of 50-70% for vacuum impregnation; curing the vacuum-impregnated green mirror blank at 180-200°C; and repeating the carbonization treatment and vacuum impregnation on the cured green mirror blank.

[0017] Preferably, in step S4, the preform of the reflector is subjected to vapor phase silicon infiltration sintering, which includes: suspending the preform of the reflector in a sintering furnace using a graphite shield and laying silicon particles below it; heating it to 1300-1400°C under vacuum at a heating rate of 10-20°C / min; then heating it to 1700-1800°C at a heating rate of 5-10°C / min; holding it at this temperature for 1-2 hours; and then cooling it to room temperature at a cooling rate of 5-10°C / min.

[0018] Preferably, in step S5, the process parameters for halide chemical vapor deposition are as follows: SiCl4 is used as the silicon source, CH4 as the carbon source, H2 as the carrier gas, the deposition temperature is 1000-1300℃, the deposition pressure is 5-10kPa, and the deposition time is 20-60min; the flow rate of the silicon source gas is 200-300sccm, the flow rate of hydrogen is 300-420sccm, and the carbon-silicon molar ratio of the reaction gas is 0.71-1.14.

[0019] Preferably, in step S5, the thickness of the silicon carbide coating is 100–300 μm.

[0020] The present invention also provides a silicon carbide optical mirror prepared by the above method.

[0021] The beneficial effects of this invention are:

[0022] This invention combines additive manufacturing technology with halide CVD coating technology to achieve the integral molding of large-size, complex, and lightweight silicon carbide mirrors and rapid, non-destructive homogenization of the mirror surface. The preparation method is simple to operate and easy to promote and use. The silicon carbide mirror surface coating after surface homogenization treatment has uniform thickness, high bonding strength, good consistency, and excellent thermal stability. It can be directly polished without secondary processing. The surface accuracy of the polished mirror can reach below 1nm, which meets the application requirements of space optical systems for high-resolution, large-field-of-view silicon carbide mirrors.

[0023] This invention improves the bulk density of additive powder by combining powder particle size distribution with external carbon source, thereby reducing the residual silicon content of sintered body; it uses laser secondary homogenization to treat the surface of mirror green blank, and combines it with vapor phase silicon infiltration densification process to reduce the surface roughness of mirror blank, thereby improving the degree of silicon infiltration reaction sintering densification and reducing the difficulty of subsequent processing. Detailed Implementation

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

[0025] This invention provides a method for additive manufacturing a silicon carbide optical mirror, comprising the following steps:

[0026] S1. By weight percentage, 15%-20% carbon black powder, 60%-70% silicon carbide powder, and 10%-25% binder are uniformly mixed to obtain a composite powder. The carbon black powder has a particle size of 20-30 μm; the silicon carbide powder is a graded powder, including silicon carbide powders with particle sizes of 5 μm, 20 μm, and 50 μm, with a mass ratio of the three different particle sizes of silicon carbide powders of 10:20:70; the binder is one or more of phenolic resin, epoxy resin, and dextrin.

[0027] S2. Composite powder is printed using selective laser sintering (SLS) technology to obtain a green mirror blank, and the green mirror blank is then homogenized. The preheating temperature for SLS is 50–60℃, the laser power is 6–12W, the printing layer thickness is 0.1–0.2mm, and the laser scanning speed is 1000–2000mm / s. The laser power for homogenization is 6–9W, the laser scanning speed is 1500–2000mm / s, and the laser scanning spacing is 0.1–0.2mm.

[0028] S3. The homogenized green mirror blank is carbonized under an inert atmosphere; the carbonized green mirror blank is then vacuum impregnated in a 50-70% phenolic resin solution, and the vacuum-impregnated green mirror blank is cured at 180-200℃. Subsequently, the cured blank is subjected to a cyclic impregnation-carbonization process to obtain the preformed green mirror.

[0029] S4. Performing vapor-phase silicon infiltration sintering on the mirror preform, including: suspending the mirror preform in a sintering furnace using a graphite shield, laying silicon particles below it, heating to 1300-1400℃ under vacuum at a heating rate of 10-20℃ / min, then heating to 1700-1800℃ at a heating rate of 5-10℃ / min, holding at that temperature for 1-2 hours, and then cooling to room temperature at a cooling rate of 5-10℃ / min to obtain a dense silicon carbide mirror ceramic body.

[0030] S5. A silicon carbide coating with a thickness of 100–300 μm was deposited on the surface of a silicon carbide ceramic mirror using halide chemical vapor deposition (CVD). The CVD process parameters were as follows: SiCl4 as the silicon source, CH4 as the carbon source, and H2 as the carrier gas; deposition temperature of 1000–1300 °C; deposition pressure of 5–10 kPa; deposition time of 20–60 min; silicon source gas flow rate of 200–300 sccm; hydrogen flow rate of 300–420 sccm; and carbon-silicon molar ratio of the reaction gas of 0.71–1.14.

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in further detail below. The carbon black powder used in the following examples has a particle size of 20–30 μm.

[0032] Example 1

[0033] A method for additive manufacturing of a silicon carbide optical mirror specifically includes the following steps:

[0034] 1) Three types of silicon carbide powder with particle sizes of 5μm, 20μm and 50μm were mixed in a mass ratio of 10:20:70, and then mixed with carbon black powder and epoxy resin powder in a mass percentage of 70%, 20% and 10%, respectively. The mixture was then ball-milled at a speed of 100r / s for 2h to obtain a mixed powder.

[0035] 2) The mixed powder was placed in the forming chamber of a laser selective sintering device and preheated at 60°C for 10 minutes. Then, sintering was performed using a 12W laser power, a scanning speed of 2000mm / s, and a layer thickness of 0.1mm to obtain a mirror blank. The printing parameters of the laser printing device were then adjusted to: laser power 6W, laser scanning speed 1500mm / s, and laser scanning spacing 0.1mm. The upper surface of the mirror blank was then laser-scanned to obtain a homogenized mirror blank.

[0036] 3) Place the homogenized mirror blank into a vacuum carbonization furnace, heat it to 850°C at a heating rate of 2°C / min under argon protection, then hold it at that temperature for 2 hours for carbonization, and then cool it down to room temperature at a cooling rate of 5°C / min.

[0037] 4) Weigh 200g of modified phenolic resin and 200g of formaldehyde, and stir the mixture of the two in a water bath at 45℃ for 2 hours to prepare a 50% concentration impregnation solution. Then, place the carbonized preform in the impregnation solution and impregnate it under a vacuum of -0.1MPa for 60 minutes. Take out the preform and cure it at 180℃ for 1 hour. Place the cured preform in the carbonization furnace again for a second carbonization treatment. Repeat the above steps twice to obtain the preform.

[0038] 5) The preform is suspended in the sintering furnace using a graphite protective plate, and silicon particles are laid below it. The vacuum degree of the furnace is maintained at -0.1MPa. Then the temperature is increased to 1400℃ at a rate of 10℃ / min, and then increased to 1700℃ at a rate of 5℃ / min. The temperature is held for 2 hours, and then cooled to room temperature at a cooling rate of 5℃ / min. The preform is then removed to obtain a dense silicon carbide reflector ceramic body.

[0039] 6) Place the silicon carbide ceramic mirror into the chamber of the chemical vapor deposition equipment, evacuate to a vacuum level of 2 kPa, introduce SiCl4 and CH4 into the deposition chamber using H2 as the carrier gas, control the chamber pressure to 5 kPa, the silicon source gas flow rate to 300 sccm, the hydrogen flow rate to 420 sccm, and the carbon-silicon molar ratio of the reaction gas to 1.14. Control the power of the external heat source to heat the entire component to 1300℃, and begin depositing a silicon carbide coating on the mirror surface of the silicon carbide ceramic mirror. After 30 minutes of deposition, remove the component to obtain the silicon carbide optical mirror.

[0040] The silicon carbide optical mirror material prepared in this embodiment contains 15 vol.% silicon and 85 vol.% silicon carbide, with a material density of 2.97 g / cm³. 3 The flexural strength is 301.75 MPa, and the elastic modulus is 343.17 GPa. After mirror homogenization treatment, the material is 99.9999% pure highly oriented cubic silicon carbide, with a thickness of 200 μm and a density of 3.1 g / cm³. 3 The coefficient of thermal expansion is 2.51 × 10⁻⁶. -6 / K, thermal conductivity is 187.3 W·m -1 ·K -1 The surface roughness is 31 μm.

[0041] Example 2

[0042] A method for additive manufacturing of a silicon carbide optical mirror specifically includes the following steps:

[0043] 1) Three types of silicon carbide powder with particle sizes of 5μm, 20μm and 50μm were mixed in a mass ratio of 10:20:70, and then mixed with carbon black powder and cyclodextrin at a mass percentage of 60%, 15% and 25%, respectively. The mixture was then ball-milled at a speed of 100r / s for 2h to obtain a mixed powder.

[0044] 2) The mixed powder was placed in the forming chamber of the laser selective sintering equipment and preheated at 50°C for 5 minutes. Then, sintering was performed using a laser power of 6W, a scanning speed of 1000mm / s, and a layer thickness of 0.2mm to obtain a mirror blank. The printing parameters of the laser printing equipment were then adjusted to: laser power of 6W, laser scanning speed of 1500mm / s, and laser scanning spacing of 0.1mm. The upper surface of the mirror blank was then laser-scanned to obtain a homogenized mirror blank.

[0045] 3) Place the homogenized mirror blank into a vacuum carbonization furnace, heat it to 850°C at a heating rate of 2°C / min under argon protection, then hold it at that temperature for 2 hours for carbonization, and then cool it down to room temperature at a cooling rate of 5°C / min.

[0046] 4) Weigh 140g of modified phenolic resin and 60g of formaldehyde, and stir the mixture of the two in a water bath at 45℃ for 2h to prepare a 70% concentration impregnation solution. Then place the carbonized preform in the impregnation solution and impregnate it under a vacuum of -0.1MPa for 60min. Take out the preform and cure it at 180℃ for 1h. Place the cured preform in the carbonization furnace again for a second carbonization treatment. Repeat the above steps twice to obtain the preform.

[0047] 5) The preform is suspended in the sintering furnace using a graphite protective plate, and silicon particles are laid below it. The vacuum degree of the furnace is maintained at -0.1MPa. Then the temperature is increased to 1400℃ at a rate of 10℃ / min, and then increased to 1700℃ at a rate of 5℃ / min. The temperature is held for 2 hours, and then cooled to room temperature at a cooling rate of 5℃ / min. The preform is then removed to obtain a dense silicon carbide reflector ceramic body.

[0048] 6) Place the silicon carbide ceramic mirror into the chamber of the chemical vapor deposition equipment, evacuate to a vacuum level of 2 kPa, introduce SiCl4 and CH4 into the deposition chamber using H2 as the carrier gas, control the chamber pressure to 10 kPa, the silicon source gas flow rate to 300 sccm, the hydrogen flow rate to 420 sccm, and the carbon-silicon molar ratio of the reaction gas to 0.71. Control the power of the external heat source to heat the entire component to 1200℃, and begin depositing a silicon carbide coating on the mirror surface of the silicon carbide ceramic mirror. After 60 minutes of deposition, remove the component to obtain the silicon carbide optical mirror.

[0049] The silicon carbide mirror body material prepared in this embodiment contains 20 vol.% silicon and 80 vol.% silicon carbide, and has a material density of 2.78 g / cm³. 3 The flexural strength is 278.10 MPa, and the elastic modulus is 291.51 GPa. After mirror homogenization treatment, the material is 99.9999% pure highly oriented cubic silicon carbide, with a thickness of 300 μm and a density of 3.0 g / cm³. 3The coefficient of thermal expansion is 3.85 × 10⁻⁶. -6 / K, thermal conductivity is 171.4 W·m -1 ·K -1 The surface roughness is 73 μm.

[0050] Example 3

[0051] A method for additive manufacturing of a silicon carbide optical mirror specifically includes the following steps:

[0052] 1) Three silicon carbide powders with particle sizes of 5μm, 20μm and 50μm were mixed in a mass ratio of 10:20:70, and then mixed with carbon black powder and phenolic resin at a mass percentage of 67%, 15% and 18%, respectively. The mixture was then ball-milled at 100r / s for 2h to obtain a mixed powder.

[0053] 2) The mixed powder was placed in the forming chamber of a laser selective sintering device and preheated at 60°C for 10 minutes. Then, sintering was performed using an 8W laser power, a scanning speed of 2000mm / s, and a layer thickness of 0.15mm to obtain a green mirror blank. The printing parameters of the laser printing device were then adjusted to: laser power 6W, laser scanning speed 1500mm / s, and laser scanning spacing 0.1mm. The upper surface of the green mirror blank was then laser-scanned to obtain a homogenized mirror blank.

[0054] 3) Place the homogenized mirror blank into a vacuum carbonization furnace, heat it to 850°C at a heating rate of 2°C / min under argon protection, then hold it at that temperature for 2 hours for carbonization, and then cool it down to room temperature at a cooling rate of 5°C / min.

[0055] 4) Weigh 120g of modified phenolic resin and 80g of formaldehyde, and stir the mixture of the two in a water bath at 45℃ for 2h to prepare a 60% concentration impregnation solution. Then place the carbonized preform in the impregnation solution and impregnate it under a vacuum of -0.1MPa for 60min. Take out the preform and cure it at 180℃ for 1h. Place the cured preform in the carbonization furnace again for a second carbonization treatment. Repeat the above steps twice to obtain the preform.

[0056] 5) The preform is suspended in the sintering furnace using a graphite protective plate, and silicon particles are laid below it. The vacuum degree of the furnace is maintained at -0.1MPa. Then the temperature is increased to 1400℃ at a rate of 10℃ / min, and then increased to 1700℃ at a rate of 5℃ / min. The temperature is held for 1 hour, and then cooled to room temperature at a cooling rate of 5℃ / min before being removed to obtain a dense silicon carbide reflector ceramic body.

[0057] 6) Place the silicon carbide ceramic mirror into the chemical vapor deposition equipment chamber, evacuate to a vacuum level of 2 kPa, introduce SiCl4 and CH4 into the deposition chamber using H2 as the carrier gas, control the chamber pressure to 7 kPa, the silicon source gas flow rate to 300 sccm, the hydrogen flow rate to 420 sccm, and the carbon-silicon molar ratio of the reaction gas to 0.86. Control the power of the external heat source to heat the entire component to 1000℃, and begin depositing a silicon carbide coating on the mirror surface of the silicon carbide ceramic mirror. After 20 minutes of deposition, remove the component to obtain the silicon carbide optical mirror.

[0058] The silicon carbide mirror body material prepared in this embodiment contains 17 vol.% silicon and 83 vol.% silicon carbide, and has a material density of 2.83 g / cm³. 3 The flexural strength is 288.14 MPa, and the elastic modulus is 305.08 GPa. After mirror-surface homogenization treatment, the material is 99.9999% pure highly oriented cubic silicon carbide, with a thickness of 100 μm and a density of 3.03 g / cm³. 3 The coefficient of thermal expansion is 3.07 × 10⁻⁶. -6 / K, thermal conductivity is 178.20 W·m -1 ·K -1 The surface roughness is 56 μm.

[0059] Example 4

[0060] A silicon carbide optical mirror was prepared using a method essentially the same as in Example 3, except that in step 1), silicon carbide powder with a particle size of 50 μm was mixed with carbon black powder and phenolic resin at a mass percentage of 67%, 15%, and 18%, respectively, and then ball-milled at a speed of 100 r / s for 2 h to obtain a mixed powder.

[0061] Comparative Example 1

[0062] A silicon carbide optical mirror was prepared using a method essentially the same as in Example 3, except that in step 1), three types of silicon carbide powder with particle sizes of 5 μm, 20 μm, and 50 μm were mixed in a mass ratio of 10:20:70, and then mixed with phenolic resin at mass percentages of 82% and 18%, respectively. The mixture was then ball-milled at 100 r / s for 2 h to obtain a mixed powder.

[0063] Comparative Example 2

[0064] The silicon carbide optical mirror was prepared using a method that was basically the same as in Example 3. The difference was that the surface of the silicon carbide optical mirror was not homogenized, that is, the silicon carbide coating was not deposited on the mirror surface of the silicon carbide mirror ceramic body by the halide chemical vapor deposition technique in step 6).

[0065] To more clearly demonstrate the beneficial effects of the method of the present invention, the test results of the above embodiments and comparative examples are listed in Table 1:

[0066] Table 1 Test results for each embodiment and comparative example

[0067]

[0068]

[0069] As can be seen from the table above, the residual silicon content inside the silicon carbide optical mirror prepared in this embodiment of the invention is significantly reduced, decreasing the phase difference between the silicon carbide and the silicon carbide deposited on the mirror surface. This improves the bonding strength between the coating and the substrate and reduces thermal cracking. Furthermore, this invention uses halide CVD to coat the surface of the additively manufactured mirror, achieving rapid and non-destructive homogenization of the silicon carbide mirror surface. Halide CVD can rapidly synthesize high-purity silicon carbide coatings in situ at high temperatures, with low requirements for substrate roughness. This effectively improves the mirror surface finish and material uniformity, optimizes its optical performance, and facilitates subsequent optical processing to obtain ultra-high precision mirror surfaces.

[0070] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0071] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for additive manufacturing a silicon carbide optical mirror, characterized in that, Includes the following steps: S1. Carbon black powder, silicon carbide powder, and binder are uniformly mixed to obtain a composite powder; the carbon black powder has a particle size of 20-30 μm; the silicon carbide powder is a graded powder, comprising silicon carbide powder with particle sizes of 5 μm, 20 μm, and 50 μm mixed in a mass ratio of 10:20:70; the binder is one or more of phenolic resin, epoxy resin, and dextrin; by weight percentage, the composite powder comprises 60%-70% silicon carbide powder, 15%-20% carbon black powder, and 10%-25% binder. S2. The composite powder is printed into a green mirror blank using laser selective sintering technology; S3. The green mirror blank is subjected to cyclic impregnation-carbonization treatment with phenolic resin solution to obtain a mirror preform; S4. The preform of the reflector is subjected to silicon infiltration sintering to obtain a dense silicon carbide ceramic reflector body; S5. A silicon carbide coating is deposited on the mirror surface of the silicon carbide ceramic mirror using halide chemical vapor deposition technology; The process parameters for halide chemical vapor deposition are as follows: SiCl4 is used as the silicon source, CH4 as the carbon source, H2 as the carrier gas, the deposition temperature is 1000~1200℃, the deposition pressure is 5~10kPa, and the deposition time is 20~60 min; the flow rate of the silicon source gas is 200~300sccm, the flow rate of hydrogen is 300~420sccm, and the carbon-silicon molar ratio of the reaction gas is 0.71~1.

14.

2. The method for additive manufacturing of a silicon carbide optical mirror according to claim 1, characterized in that, In step S2, the process parameters of the laser selective sintering forming technology are: preheating temperature 50~60℃, laser power 6~12 W, printing layer thickness 0.1~0.2 mm, laser scanning speed 1000~2000 mm / s, and laser scanning spacing 0.1~0.2 mm.

3. The method for additive manufacturing of a silicon carbide optical mirror according to claim 1, characterized in that, Step S2 further includes laser homogenization of the printed mirror blank; the laser power for laser homogenization is 6~9 W, the laser scanning speed is 1500~2000 mm / s, and the laser scanning spacing is 0.1~0.2 mm.

4. The method for additive manufacturing of a silicon carbide optical mirror according to claim 1, characterized in that, In step S3, the cyclic impregnation-carbonization treatment method includes: carbonizing the green mirror blank under an inert atmosphere; placing the carbonized green mirror blank in a phenolic resin solution with a concentration of 50-70% for vacuum impregnation; curing the vacuum-impregnated green mirror blank at 180-200°C; and repeating the carbonization treatment and vacuum impregnation on the cured green mirror blank.

5. The method for additive manufacturing of a silicon carbide optical mirror according to claim 1, characterized in that, In step S4, the preform of the reflector is subjected to vapor phase silicon infiltration sintering, which includes: suspending the preform of the reflector in a sintering furnace with a graphite shield and laying silicon particles below it; heating to 1300-1400°C under vacuum at a heating rate of 10-20°C / min; heating to 1700-1800°C at a heating rate of 5-10°C / min; holding at this temperature for 1-2 hours; and then cooling to room temperature at a cooling rate of 5-10°C / min.

6. The method for additive manufacturing of a silicon carbide optical mirror according to claim 1, characterized in that, In step S5, the thickness of the silicon carbide coating is 100~300 μm.

7. A silicon carbide optical mirror prepared by the method according to any one of claims 1 to 6.

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