A photocured dark silicon carbide ceramic and its preparation process

Abstract

The present invention discloses a dark-colored silicon carbide ceramic capable of photocuring and its preparation process. By configuring a high-refractive-index photosensitive resin solution, and through the combined action of a structure-directing agent, a polymer wetting dispersant, a silane coupling agent, and a leveling agent, the resin improves the wetting of the silicon carbide powder by the resin, resulting in a silicon carbide slurry with high fluidity and stability. This increases the depth of photocuring and allows for the printing of silicon carbide green bodies using SLA or DLP technology, thus resolving the issues of photocuring in silicon carbide. By optimizing the particle size distribution of the silicon carbide ceramic and the carbon source for reaction sintering, the present invention achieves high-dimensional precision silicon carbide ceramics through degreasing and reaction sintering, effectively improving the bulk density, mechanical strength, and thermal conductivity of the reaction-sintered silicon carbide ceramics.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide ceramics, and in particular to a light-cured dark silicon carbide ceramic and a preparation process thereof. Background Art

[0002] Dark silicon carbide ceramics have been widely used in fields such as energy and chemical engineering, semiconductors, and aerospace due to their high hardness, good thermal conductivity, thermal shock resistance, high temperature resistance, and chemical stability. Traditional molding processes such as grouting, dry pressing, injection molding, and tape casting are costly and time-consuming, and the preparation and processing of some complex ceramic structures is difficult, which undoubtedly limits their widespread application. Ceramic photocuring 3D printing technology offers the advantages of rapid prototyping and moldless forming. Based on intelligently processed 3D digital model files, it constructs arbitrarily complex 3D solid shapes by adding material layer by layer. This 3D printing technology for silicon carbide ceramics has emerged as a result.

[0003] Traditional oxide ceramics such as aluminum nitride, aluminum oxide, and zirconium oxide are suitable for free-radical stereolithography. However, dark-colored silicon carbide (SiC) non-oxide ceramics, due to their high refractive index, are susceptible to interface scattering, which limits the penetration depth of ultraviolet light. A material's band gap (Eg) determines the wavelength range of light it absorbs. The relationship between the band gap and the absorption edge shows that the absorption edge wavelength λC (nm) = 1240 / Eg (eV). When the incident light wavelength is less than λC (photon energy > Eg), the material undergoes intrinsic absorption; when the incident light wavelength is greater than λC (photon energy < Eg), the material becomes transparent (ignoring impurities or defect absorption). The SiC band gap (eV) is approximately 2.3 to 3.3, resulting in an absorption edge in the 375-540nm range. This limits the applicability of SiC stereolithography (SLA) and DLP (digital light processing)-based SiC stereolithography technologies. First, silicon carbide's high absorption of ultraviolet light in the 355-405nm wavelength range limits its curing depth. Second, the significant difference in refractive index between the photosensitive resin and silicon carbide ceramics causes light scattering at the interface, reducing the penetration depth of the UV light. The cured thickness of silicon carbide ceramic slurry is typically only one-quarter to one-third that of alumina and zirconia ceramic slurries, affecting the interlayer bonding during printing. Furthermore, silicon carbide's light absorption is related to its particle size and specific surface area. Submicron silicon carbide often fails to print due to low curing depth. These factors lead to uneven curing, poor interlayer bonding, deformation, warping, and cracking during the silicon carbide molding process. Regarding silicon carbide sintering, silicon carbide ceramics are prone to significant shrinkage in the X, Y, and Z directions during sintering, resulting in dimensional deviations in precision ceramic parts and making it difficult to fabricate complex and fine-scale structures. Furthermore, with the increasing demand for large ceramic components, the ceramic slurry must remain stable throughout the curing process to prevent agglomeration, sedimentation, and phase separation. Ceramic slurry dispersion, solid content, rheological properties, and stability need to be optimized. Domestic micron-sized silicon carbide powders have irregular morphologies and contain impurities such as free Si, C, SiO2, Cl, and Fe. This affects the bulk density, mechanical strength, and thermal conductivity of the sintered silicon carbide ceramics. Consequently, achieving high-precision, high-performance silicon carbide ceramics is difficult.

[0004] Therefore, how to control the structure of silicon carbide from the two aspects of photocuring molding and sintering to obtain silicon carbide ceramics with complex and high-precision dimensions and high performance has always been a technical difficulty in this field. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned background technology, the present invention provides a dark silicon carbide ceramic formed by photocuring and a preparation process thereof, which improves the wetting of the resin on the silicon carbide powder, obtains a silicon carbide slurry with high fluidity and stability, increases the photocuring depth, prints the silicon carbide green body through SLA or DLP technology, solves the photocuring molding problem of silicon carbide, and obtains silicon carbide ceramics with high dimensional accuracy through degreasing and reaction sintering.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a dark silicon carbide ceramic formed by photocuring, comprising the following raw material components in parts by weight:

[0008] 70-80 parts of pretreated silicon carbide powder,

[0009] 20-30 parts of high refractive index photosensitive resin solution,

[0010] Second phase additive 0-8 parts,

[0011] 2 to 5 parts of dispersant,

[0012] 0-12 parts of optical channel building agent,

[0013] 0-5 parts surfactant,

[0014] 0-8 parts of structure directing agent,

[0015] Oily thickener 0.05-1 part,

[0016] Leveling agent 0-2 parts,

[0017] 0.2-1 part of photoinitiator;

[0018] The high refractive index photosensitive resin solution is mainly composed of high refractive index monofunctional monomers, difunctional monomers, multifunctional monomers and oligomers, and is also added with plasticizers and inert filler adhesives.

[0019] The monofunctional monomer accounts for 0 to 15% of the total mass of the photosensitive resin solution, the difunctional monomer accounts for 10 to 45% of the total mass of the photosensitive resin solution, the multifunctional monomer accounts for 0 to 25% of the total mass of the photosensitive resin solution, the oligomer accounts for 0 to 40% of the total mass of the photosensitive resin solution, the plasticizer accounts for 0 to 30% of the total mass of the photosensitive resin solution, and the inert filling adhesive accounts for 0 to 10% of the total mass of the photosensitive resin solution.

[0020] Dispersants include KD-1, BYK111, KOS110, BYK9076, fish oil, lecithin, oleamide, etc.

[0021] Using the above technical solution:

[0022] This invention improves the wetting of silicon carbide powder by the resin through the combined action of a high-refractive-index photosensitive resin solution, a structure-directing agent, a polymer wetting dispersant, a silane coupling agent, and a leveling agent. This results in a highly fluid and stable silicon carbide slurry, increases the depth of photocuring, and enables the printing of silicon carbide green bodies using SLA or DLP technology, thus resolving the issues of photocuring silicon carbide. This invention also optimizes the particle size distribution of the silicon carbide ceramic and the carbon source for reactive sintering, achieving high-dimensional precision silicon carbide ceramics through degreasing and reactive sintering.

[0023] Specifically, the pre-dispersion and surface modification of the powder enhance the compatibility of the inorganic powder in the organic photocurable resin. The use of surfactants to regulate the slurry increases the fluidity of the slurry, facilitates spreading on the printing platform and makes the density of each layer more uniform. The regulation of the slurry by surfactants also effectively increases the storage stability of the slurry, and the slurry has a good leveling effect and is not easy to settle. The high-refractive-index photosensitive resin solution and the inorganic optical channel builder improve the depth of UV curing, ensure the quality of photocuring molding, and solve the problems of uneven curing, poor interlayer bonding, deformation, warping and cracking caused by low curing depth and cross-linking density. The second phase additive in the system acts as a sintering aid and reacts with impurities such as SiO2 in the low eutectic point and silicon carbide powder to purify its lattice oxygen, reduce phonon scattering and thus improve its thermal conductivity. The structure-directing agent polyethylene glycol exists in the cross-linked network of the green body. As a non-reactive diluent, it forms a dispersed phase in the resin and produces a uniformly distributed microporous structure when degraded. These micropores serve as gas escape channels during debinding and sintering, reducing local pressure accumulation and inhibiting crack formation.

[0024] By optimizing the proportion of multifunctional monomers in the high-refractive index photosensitive resin solution, the double bonds between molecules are reduced during the photocuring process due to addition reactions, which shortens the distance between molecules and ultimately causes volume shrinkage that affects the molding of the green body. At the same time, the proportion of monofunctional monomers is adjusted to give it a certain dilutability to ensure the fluidity and appropriate rheology of the organic adhesive. Both monofunctional monomers and oligomers can reduce the curing shrinkage of acrylic monomers, and oligomers can also increase the density of the green body during curing. By adjusting the proportion of each component in the photosensitive resin solution, the cracking phenomenon caused by stress concentration after debinding can be effectively reduced. The amount of high-refractive index photosensitive resin solution added is 20 to 30 parts by weight, and the preferred proportion of photosensitive resin is 25 parts by weight.

[0025] Furthermore, the monofunctional monomer is one or a mixture of acryloylmorpholine, o-phenylphenoxyethyl acrylate, hydroxyethyl acrylamide, phenoxy acrylate, and tert-butoxy acrylamide;

[0026] The bifunctional monomer is one or a mixture of 1,6-ethylene glycol diacrylate, dipropylene glycol diacrylate, and ethoxylated bisphenol A diacrylate;

[0027] The multifunctional monomer is one or a mixture of pentaerythritol triacrylate, trihydroxyethyl propane triacrylate, ethoxylated pentaerythritol tetraacrylate, bis-pentaerythritol hexaacrylate, and bisether fluorene acrylate.

[0028] Preferably, the monomers are acryloylmorpholine, o-phenylphenoxyethyl acrylate, 1,6-ethylene glycol diacrylate, ethoxylated bisphenol A diacrylate, and bis-pentaerythritol hexaacrylate.

[0029] The oligomer is one or a mixture of bisphenol A epoxy acrylate, bisphenol F epoxy acrylate resin, polyester acrylate resin, and polyurethane acrylate resin with a molecular weight between 1000 and 25000. Preferably, the oligomer is bisphenol A epoxy acrylate.

[0030] The plasticizer is one or a mixture of dibutyl phthalate, dioctyl phthalate, polyethylene glycol, etc. Considering the migration of DBP, polyethylene glycol is preferably used as the plasticizer.

[0031] The inert filling adhesive is one or a mixture of polyvinyl butyral, small molecule adhesive B002S, polyethersulfone, polyvinyl alcohol, and polymethyl methacrylate.

[0032] Furthermore, the optical channel building agent is high-purity fluorite powder with a purity greater than 99.9%.

[0033] Furthermore, the pretreated silicon carbide powder is obtained by ball milling green silicon carbide and / or gray silicon carbide, drying and sieving, and surface modification of the silicon carbide is performed using a silane coupling agent and a polymer wetting and dispersing agent during the ball milling process.

[0034] Specifically, the surface of the particle-graded silicon carbide powder is pretreated by adding a silane coupling agent, the main material silicon carbide powder is dispersed by a polymer wetting dispersant, and the powder is passed through a 100-mesh sieve after rotary evaporation drying or vacuum drying to complete the surface modification of the powder. The powder is pre-dispersed and surface-modified, thereby enhancing the compatibility of the inorganic powder in the organic photocurable resin.

[0035] Furthermore, the structure directing agent is polyethylene glycol 200.

[0036] The structure-directing agent polyethylene glycol exists in the cross-linked network of the green body. As a non-reactive diluent, it forms a dispersed phase in the resin and produces a uniformly distributed microporous structure when degraded. These micropores serve as gas escape channels during debinding and sintering, reducing local pressure accumulation and inhibiting crack formation.

[0037] Furthermore, the second-phase additive is one or a mixture of spherical nanoparticles of Y2O3, spherical nanoparticles of La2O3, spherical nanoparticles of Al2O3, spherical nanoparticles of MgO, and nanoparticles of CaO. Preferably, the second-phase additive is one or a mixture of spherical nanoparticles of Y2O3, spherical nanoparticles of La2O3, and spherical nanoparticles of Al2O3. More preferably, the second-phase additive is a mixture of Y2O3 and La2O3, or a mixture of Y2O3, La2O3, and Al2O3.

[0038] The second-phase additives in the system act as sintering aids, reacting at the eutectic point with impurities such as SiO2 in the SiC powder, purifying its lattice oxygen, reducing phonon scattering, and thus improving its thermal conductivity. The Y2O3, Al2O3, and La2O3 components of the sintered ceramic are distributed at grain boundaries and triple junctions, where the formation of low-melting-point eutectics facilitates silicon penetration. Furthermore, the preferred amorphous resin carbon source and graphite-based composite carbon source effectively reduce the volume fraction of silicon. Experimental results show that with increasing volume fractions of the second-phase additives Al2O3 and Y2O3 in the material, the density of the reaction-sintered SiC initially increases and then decreases. This is likely due to the high volume fraction of the eutectic phase, which makes the liquid phase too viscous, inhibiting diffusion and reaction processes. Furthermore, Y2O3 and Al2O3 can react with the carbon source during reaction sintering, resulting in excessive silicon residues, necessitating controlled addition levels.

[0039] Furthermore, polymer wetting and dispersing agents include KD-1, BYK111, KOS110, BYK9076, fish oil, lecithin, oleic acid amide, etc. Surfactants include silane coupling agents, BYK thixotropic agents, Yoshida oil thickeners, etc. The photoinitiator is TPO or 819.

[0040] Furthermore, the dark silicon carbide ceramic also includes 5 to 18 parts of a carbon source, which is an organic resin carbon source and / or a graphite powder carbon source. The organic resin carbon source is amorphous carbon produced by high-temperature cracking of an organic resin such as a phenolic acrylic resin, or an inorganic substance such as graphite powder as a carbon source (the XRD of the graphite powder is crystalline).

[0041] Preferably, phenolic acrylic resin is added to the product formula system, which can participate in free radical photocuring and can also be cracked at high temperature to provide a rich carbon source.

[0042] Particle grading of silicon carbide powder and optimization of carbon source types have effectively improved the bulk density, mechanical strength and thermal conductivity of reaction-sintered silicon carbide ceramics. Horsfield's closest packing theory is one of the core theories for studying the close packing of granular materials. It is mainly used to guide the grading optimization of multi-level particle systems to achieve minimum porosity and maximum density. Horsfield's closest packing theory points out that by mixing particles of different particle sizes, tighter space filling can be achieved. The Dinger particle grading optimization model guides particle grading through numerical simulation and is suitable for multi-grading systems (such as three-level particle grading). The density, porosity and pore size of the green body are optimized through particle grading to adapt to the siliconization process of reaction-sintered silicon carbide, effectively reducing the volume fraction and size of silicon, thereby improving the overall performance of reaction-sintered silicon carbide.

[0043] A second aspect of the present invention provides a process for preparing the above-mentioned dark silicon carbide ceramic formed by photocuring, comprising the following steps:

[0044] S1. Silicon carbide powder pretreatment:

[0045] Based on the principle of closest packing, silicon carbide powder is graded into three particle sizes: large, medium, and small. 100 parts by weight of this graded silicon carbide powder and 3 parts by weight of the silane coupling agent KH-570 are added to a planetary ball mill for dispersion. The preferred silicon carbide ball milling beads are Nikkato 5mm:10mm in a ratio of 1:2. The milling is performed for 3 hours at a speed of 300 RPM, with a grinding media to material volume ratio of 3:1. 4 parts by weight of the polymer wetting and dispersing agent BYK-9076 are then added to the mill. After evacuation, the milling is continued for another 3 hours. After completion of the milling, the slurry is dried by rotary evaporation or vacuum drying, then passed through a 100-mesh sieve. The powder size is measured using a laser particle size analyzer to ensure that the powder size distribution does not shift significantly.

[0046] Silicon carbide powder, α-SiC, with a purity of ≥99%. Available green silicon carbide grades are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide grades are XF08, XF13, and BET9. After pre-dispersion and screening, all silicon carbides have a particle size span of ≤2.5, a D10 / D90 ratio of 1:2 to 1:3, and F·C <0.1, Si+SiO2 <0.1, Fe2O3 <0.08, and Cl, Na, and K <1000ppm.

[0047] S2. Configuration of high refractive index photosensitive resin solution:

[0048] First, add high-refractive-index monofunctional monomers, difunctional monomers, multifunctional monomers and oligomers, then add plasticizers and inert filler adhesives, set the temperature to 35°C, and stir at 600 rpm for 30 to 50 minutes to obtain a high-refractive-index photosensitive resin solution.

[0049] S3, Mixed:

[0050] The pretreated silicon carbide powder, carbon source, second phase additive, high refractive index photosensitive resin solution, dispersant, optical channel builder, surfactant, structure directing agent, photoinitiator, oily thickener and leveling agent are added in sequence according to the proportion and stirred for 5 to 12 hours to obtain silicon carbide photocuring slurry.

[0051] S4, light-curing molding and binder removal sintering:

[0052] Silicon carbide photocurable slurry is filled at a rate of 0.01 to 0.05. After filling, the printed part is printed and cured under a 405nm wavelength light source at a laser power of 70% to 100% and a laser scanning speed of 2500mm / s. The printed part is cleaned of the slurry and stored in a UV drying oven for a period of time before entering the debinding and degreasing stage.

[0053] The printed blank was placed in a binder removal furnace using graphite support pillars. After vacuuming, argon was introduced to expel residual oxygen from the furnace. The temperature was then raised from room temperature to 100°C at 0.5°C / min and held for 120 minutes. The temperature was then raised to 220°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 300°C, 400°C, and 500°C at 0.1°C / min, each held for 180 minutes. Finally, the temperature was raised to 600°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 1200°C at 0.5°C / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder, which had been pre-mixed with 1-4wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0054] The non-siliconized surface is wrapped with high-purity carbon paper, heated to 1600-1700℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and then kept warm for 2h. After gas phase and liquid phase siliconization reactions are carried out in a reaction sintering furnace, dark nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0055] Furthermore, in step S1, the silicon carbide powder is composed of three types of silicon carbide powder divided into large-particle silicon carbide powder, medium-particle silicon carbide powder and small-particle silicon carbide powder according to particle size. The particle size of the large-particle silicon carbide powder is 20-50 μm, the particle size of the medium-particle silicon carbide powder is 5-15 μm, and the particle size of the small-particle silicon carbide powder is 0.5-3 μm. The weight ratio of the large-particle silicon carbide powder, the medium-particle silicon carbide powder and the small-particle silicon carbide powder is (10-14): (4-8): (1-6).

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The present invention successfully prepares high-precision dark nano-silicon carbide ceramics by photocuring molding and reaction sintering. (1) The powder is pre-dispersed and surface modified to enhance the compatibility of inorganic powder in organic photocuring resin. The surfactant regulates the slurry to increase the fluidity of the slurry, making it easier to spread on the printing platform and more uniform in density per layer. The surfactant regulates the slurry to effectively increase the storage stability of the slurry, and the slurry has a good leveling effect and is not easy to settle. The high-refractive photosensitive resin solution and inorganic light channel builder improve the UV curing depth, ensure the quality of photocuring molding, and solve the problems of uneven curing, poor interlayer bonding, deformation, warping and cracking caused by low curing depth and cross-linking density. (2) The structural directing agent polyethylene glycol exists in the cross-linking network of the green body and, as a non-reactive diluent, forms a dispersed phase in the resin. When degraded, it produces a uniformly distributed microporous structure. These micropores serve as gas escape channels during the debinding sintering process, reducing local pressure accumulation and inhibiting crack formation. (3) The particle grading of silicon carbide powder and the optimization of carbon source types effectively improved the volume density, mechanical strength and thermal conductivity of reaction-sintered silicon carbide ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] Figure 1 The state of the silicon carbide photocurable slurry just prepared in Examples 1, 2 and Comparative Example 1;

[0060] Figure 2 The silicon carbide photocurable slurry prepared in Examples 1, 2 and Comparative Example 1 is in a state after being left for one week;

[0061] Figure 3 This is the state of the silicon carbide photocuring slurry printing samples of Examples 1, 2 and Comparative Example 1 after debinding. DETAILED DESCRIPTION

[0062] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0063] Example 1

[0064] The preparation process of dark silicon carbide ceramics formed by photocuring includes the following steps:

[0065] S1. Silicon carbide powder pretreatment:

[0066] 100 parts by weight of graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were dispersed in a planetary ball mill. The preferred silicon carbide ball milling beads were Nikkato 5mm:10mm beads in a ratio of 1:2. Milling was performed for 3 hours at 300 RPM, with a grinding media to material volume ratio of 3:1. 4 parts by weight of polymer wetting and dispersing agent BYK-9076 were then added to the mill. After evacuation, the milling was continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying, then passed through a 100-mesh sieve. The powder size was measured using a laser particle size analyzer to ensure that the particle size distribution did not shift significantly.

[0067] Silicon carbide powder, α-SiC, with a purity of ≥99%. Available green silicon carbide grades are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide grades are XF08, XF13, and BET9.

[0068] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powders: F240 with a particle size of 5 mm, F500 with a particle size of 10 mm, and F1200 with a particle size of 20 mm. The weight ratio of the three types of silicon carbide powders is 6:3:1.

[0069] After pre-dispersion and screening, all silicon carbide has a particle size span of ≤2.5, a ratio of D10 to D90 of 1:2 to 1:3, F·C < 0.1, Si+SiO2 < 0.1, Fe2O3 < 0.08, and Cl, Na, K < 1000ppm.

[0070] S2. Configuration of high refractive index photosensitive resin solution:

[0071] First, add 10wt% of a high-refractive-index monofunctional monomer, 30wt% of a difunctional monomer, 15wt% of a multifunctional monomer, and 20wt% of an oligomer, then add 20wt% of a plasticizer and 5wt% of an inert filler adhesive. Set the temperature to 35°C and stir at 600rpm for 30min to obtain a high-refractive-index photosensitive resin solution.

[0072] The monofunctional monomer is a mixture of acryloylmorpholine and o-phenylphenoxyethyl acrylate. The difunctional monomer is a mixture of 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate. The multifunctional monomer is dipentaerythritol hexaacrylate. The oligomer is bisphenol A epoxy acrylate with a molecular weight between 1,000 and 25,000. The plasticizer is polyethylene glycol. The inert filler binder is polyvinyl butyral.

[0073] S3, Mixed:

[0074] 75 parts of pretreated silicon carbide powder, 12 parts of carbon source, 3 parts of second phase additive, 20 parts of high refractive index photosensitive resin solution, 3 parts of dispersant, 5 parts of optical channel builder, 3 parts of surfactant, 5 parts of structure directing agent, 0.5 parts of photoinitiator, 0.5 parts of oily thickener and 1 part of leveling agent were added in sequence according to the proportion and stirred for 8 hours to obtain silicon carbide photocuring slurry.

[0075] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles of Y2O3, La2O3, and Al2O3. The dispersant is BYK-9076. The optical channel builder is high-purity fluorite powder. The surfactant is a silane coupling agent. The structure-directing agent is polyethylene glycol 200. The photoinitiator is TPO. The oil-based thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0076] S4, light-curing molding and binder removal sintering:

[0077] Silicon carbide photocurable slurry was filled at a filling speed of 0.05 and a laser scanning speed of 2500 mm / s. After filling, the printed blank was printed and cured under a 405 nm light source at a laser power of 100%. The slurry on the printed blank was cleaned and stored in a UV drying oven for a period of time before entering the debinding and degreasing stage.

[0078] The printed blank was placed in a debinding furnace using graphite support pillars. After vacuuming, argon was introduced to expel residual oxygen from the furnace. The temperature was then raised from room temperature to 100°C at 0.5°C / min and held for 120 minutes. The temperature was then raised to 220°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 300°C, 400°C, and 500°C at 0.1°C / min, each held for 180 minutes. The temperature was finally raised to 600°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 1200°C at 0.5°C / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder, which had been pre-mixed with a 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0079] The non-siliconized surface is wrapped with high-purity carbon paper, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and then kept warm for 2h. After gas phase and liquid phase siliconization reactions are carried out in a reaction sintering furnace, dark nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0080] Example 2

[0081] The preparation process of dark silicon carbide ceramics formed by photocuring includes the following steps:

[0082] S1. Pretreatment of silicon carbide powder:

[0083] 100 parts by weight of graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were dispersed in a planetary ball mill. The preferred silicon carbide ball milling beads were Nikkato 5mm:10mm beads in a ratio of 1:2. Milling was performed for 3 hours at 300 RPM, with a grinding media to material volume ratio of 3:1. 4 parts by weight of polymer wetting and dispersing agent BYK-9076 were then added to the mill. After evacuation, the milling was continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying, then passed through a 100-mesh sieve. The powder size was measured using a laser particle size analyzer to ensure that the particle size distribution did not shift significantly.

[0084] Silicon carbide powder, α-SiC, with a purity of ≥99%. Available green silicon carbide grades are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide grades are XF08, XF13, and BET9.

[0085] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powders: F240 with a particle size of 50 μm, F500 with a particle size of 10 μm, and F1200 with a particle size of 3 μm. The weight ratio of the three types of silicon carbide powders is 5:3:2.

[0086] After pre-dispersion and screening, all silicon carbide has a particle size span of ≤2.5, a ratio of D10 to D90 of 1:2 to 1:3, F·C < 0.1, Si+SiO2 < 0.1, Fe2O3 < 0.08, and Cl, Na, K < 1000ppm.

[0087] S2. Configuration of high refractive index photosensitive resin solution:

[0088] First, add 10wt% of a high-refractive-index monofunctional monomer, 30wt% of a difunctional monomer, 15wt% of a multifunctional monomer, and 20wt% of an oligomer, then add 20wt% of a plasticizer and 5wt% of an inert filler adhesive. Set the temperature to 35°C and stir at 600rpm for 30min to obtain a high-refractive-index photosensitive resin solution.

[0089] The monofunctional monomer is a mixture of acryloylmorpholine and o-phenylphenoxyethyl acrylate. The difunctional monomer is a mixture of 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate. The multifunctional monomer is dipentaerythritol hexaacrylate. The oligomer is bisphenol A epoxy acrylate with a molecular weight between 1,000 and 25,000. The plasticizer is polyethylene glycol. The inert filler binder is polyvinyl butyral.

[0090] S3, Mixed:

[0091] 70 parts of pretreated silicon carbide powder, 5 parts of carbon source, 8 parts of second phase additive, 25 parts of high refractive index photosensitive resin solution, 2 parts of dispersant, 8 parts of optical channel builder, 3 parts of surfactant, 8 parts of structure directing agent, 0.2 parts of photoinitiator, 0.5 parts of oily thickener and 1 part of leveling agent were added in sequence according to the proportion and stirred for 8 hours to obtain silicon carbide photocuring slurry.

[0092] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles of Y2O3, La2O3, and Al2O3. The dispersant is KD-1. The optical channel builder is high-purity fluorite powder. The surfactant is a silane coupling agent. The structure-directing agent is polyethylene glycol 200. The photoinitiator is TPO. The oil-based thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0093] S4, light-curing molding and binder removal sintering:

[0094] Silicon carbide photocurable slurry was filled at a filling speed of 0.05 and a laser scanning speed of 2500 mm / s. After filling, the printed blank was printed and cured under a 405 nm light source at a laser power of 100%. The slurry on the printed blank was cleaned and stored in a UV drying oven for a period of time before entering the debinding and degreasing stage.

[0095] The printed blank was placed in a debinding furnace using graphite support pillars. After vacuuming, argon was introduced to expel residual oxygen from the furnace. The temperature was then raised from room temperature to 100°C at 0.5°C / min and held for 120 minutes. The temperature was then raised to 220°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 300°C, 400°C, and 500°C at 0.1°C / min, each held for 180 minutes. The temperature was finally raised to 600°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 1200°C at 0.5°C / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder, which had been pre-mixed with a 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0096] The non-siliconized surface is wrapped with high-purity carbon paper, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and then kept warm for 2h. After gas phase and liquid phase siliconization reactions are carried out in a reaction sintering furnace, dark nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0097] Example 3

[0098] The preparation process of dark silicon carbide ceramics formed by photocuring includes the following steps:

[0099] S1. Silicon carbide powder pretreatment:

[0100] 100 parts by weight of graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were dispersed in a planetary ball mill. The preferred silicon carbide ball milling beads were Nikkato 5mm:10mm beads in a ratio of 1:2. Milling was performed for 3 hours at 300 RPM, with a grinding media to material volume ratio of 3:1. 4 parts by weight of polymer wetting and dispersing agent BYK-9076 were then added to the mill. After evacuation, the milling was continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying, then passed through a 100-mesh sieve. The powder size was measured using a laser particle size analyzer to ensure that the particle size distribution did not shift significantly.

[0101] Silicon carbide powder, α-SiC, purity greater than or equal to 99%. Available green silicon carbide models are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide models are XF08, XF13, and BET9.

[0102] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powders: F320 with a particle size of 30 μm, F500 with a particle size of 10 μm, and F1200 with a particle size of 3 μm. The weight ratio of the three types of silicon carbide powders is 6:3:1.

[0103] After pre-dispersion and screening, all silicon carbide has a particle size span of ≤2.5, a ratio of D10 to D90 of 1:2 to 1:3, F·C < 0.1, Si+SiO2 < 0.1, Fe2O3 < 0.08, and Cl, Na, K < 1000ppm.

[0104] S2. Configuration of high refractive index photosensitive resin solution:

[0105] First, add 5wt% of a high-refractive-index monofunctional monomer, 10wt% of a difunctional monomer, 25wt% of a multifunctional monomer, and 30wt% of an oligomer, then add 20wt% of a plasticizer and 10wt% of an inert filler adhesive. Set the temperature to 35°C and stir at 600 rpm for 30 minutes to obtain a high-refractive-index photosensitive resin solution.

[0106] The monofunctional monomer is a mixture of acryloylmorpholine and o-phenylphenoxyethyl acrylate. The difunctional monomer is a mixture of 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate. The multifunctional monomer is dipentaerythritol hexaacrylate. The oligomer is bisphenol A epoxy acrylate with a molecular weight between 1,000 and 25,000. The plasticizer is polyethylene glycol. The inert filler binder is polyvinyl butyral.

[0107] S3, Mixed:

[0108] 80 parts of pretreated silicon carbide powder, 18 parts of carbon source, 5 parts of second phase additive, 30 parts of high refractive index photosensitive resin solution, 5 parts of dispersant, 12 parts of optical channel building agent, 3 parts of surfactant, 5 parts of structure directing agent, 1 part of photoinitiator, 0.5 parts of oily thickener and 1 part of leveling agent were added in sequence according to the proportion and stirred for 9 hours to obtain silicon carbide photocuring slurry.

[0109] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles of Y2O3, La2O3, and Al2O3. The dispersant is BYK111. The optical channel builder is high-purity fluorite powder. The surfactant is a silane coupling agent. The structure-directing agent is polyethylene glycol 200. The photoinitiator is TPO. The oil-based thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0110] S4, light-curing molding and binder removal sintering:

[0111] Silicon carbide photocurable slurry was filled at a filling speed of 0.05 and a laser scanning speed of 2500 mm / s. After filling, the printed blank was printed and cured under a 405 nm light source at a laser power of 100%. The slurry on the printed blank was cleaned and stored in a UV drying oven for a period of time before entering the debinding and degreasing stage.

[0112] The printed blank was placed in a debinding furnace using graphite support pillars. After vacuuming, argon was introduced to expel residual oxygen from the furnace. The temperature was then raised from room temperature to 100°C at 0.5°C / min and held for 120 minutes. The temperature was then raised to 220°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 300°C, 400°C, and 500°C at 0.1°C / min, each held for 180 minutes. The temperature was finally raised to 600°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 1200°C at 0.5°C / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder, which had been pre-mixed with a 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0113] The non-siliconized surface is wrapped with high-purity carbon paper, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and then kept warm for 2h. After gas phase and liquid phase siliconization reactions are carried out in a reaction sintering furnace, dark nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0114] Example 4

[0115] The preparation process of dark silicon carbide ceramics formed by photocuring includes the following steps:

[0116] S1. Pretreatment of silicon carbide powder:

[0117] 100 parts by weight of graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were dispersed in a planetary ball mill. The preferred silicon carbide ball milling beads were Nikkato 5mm:10mm beads in a ratio of 1:2. Milling was performed for 3 hours at 300 RPM, with a grinding media to material volume ratio of 3:1. 4 parts by weight of polymer wetting and dispersing agent BYK-9076 were then added to the mill. After evacuation, the milling was continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying, then passed through a 100-mesh sieve. The powder size was measured using a laser particle size analyzer to ensure that the particle size distribution did not shift significantly.

[0118] Silicon carbide powder, α-SiC, purity greater than or equal to 99%. Available green silicon carbide models are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide models are XF08, XF13, and BET9.

[0119] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powders: F360 with a particle size of 30 μm, F500 with a particle size of 10 μm, and F1200 with a particle size of 3 μm. The weight ratio of the three types of silicon carbide powders is 5:3:2.

[0120] After pre-dispersion and screening, all silicon carbide has a particle size span of ≤2.5, a ratio of D10 to D90 of 1:2 to 1:3, F·C < 0.1, Si+SiO2 < 0.1, Fe2O3 < 0.08, and Cl, Na, K < 1000ppm.

[0121] S2. Configuration of high refractive index photosensitive resin solution:

[0122] First, add 5wt% of a high-refractive-index monofunctional monomer, 45wt% of a difunctional monomer, 5wt% of a multifunctional monomer, and 40wt% of an oligomer, then add 2wt% of a plasticizer and 3wt% of an inert filler adhesive. Set the temperature to 35°C and stir at 600 rpm for 50 minutes to obtain a high-refractive-index photosensitive resin solution.

[0123] The monofunctional monomer is a mixture of acryloylmorpholine and o-phenylphenoxyethyl acrylate. The difunctional monomer is a mixture of 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate. The multifunctional monomer is dipentaerythritol hexaacrylate. The oligomer is bisphenol A epoxy acrylate with a molecular weight between 1,000 and 25,000. The plasticizer is polyethylene glycol. The inert filler binder is polyvinyl butyral.

[0124] S3, Mixed:

[0125] 75 parts of pretreated silicon carbide powder, 10 parts of carbon source, 5 parts of second phase additive, 25 parts of high refractive index photosensitive resin solution, 4 parts of dispersant, 5 parts of optical channel building agent, 3 parts of surfactant, 2 parts of structure directing agent, 0.5 parts of photoinitiator, 0.5 parts of oily thickener and 1 part of leveling agent were added in sequence according to the proportion and stirred for 9 hours to obtain silicon carbide photocuring slurry.

[0126] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles of Y2O3, La2O3, and Al2O3. The dispersant is BYK111. The optical channel builder is high-purity fluorite powder. The surfactant is a silane coupling agent. The structure-directing agent is polyethylene glycol 200. The photoinitiator is TPO. The oil-based thickener is polyurethane epoxy resin. The leveling agent is BYK333.

[0127] S4, light-curing molding and binder removal sintering:

[0128] Silicon carbide photocurable slurry was filled at a filling speed of 0.05 and a laser scanning speed of 2500 mm / s. After filling, the printed blank was printed and cured under a 405 nm light source at a laser power of 100%. The slurry on the printed blank was cleaned and stored in a UV drying oven for a period of time before entering the debinding and degreasing stage.

[0129] The printed blank was placed in a debinding furnace using graphite support pillars. After vacuuming, argon was introduced to expel residual oxygen from the furnace. The temperature was then raised from room temperature to 100°C at 0.5°C / min and held for 120 minutes. The temperature was then raised to 220°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 300°C, 400°C, and 500°C at 0.1°C / min, each held for 180 minutes. The temperature was finally raised to 600°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 1200°C at 0.5°C / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder, which had been pre-mixed with a 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0130] The non-siliconized surface is wrapped with high-purity carbon paper, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and then kept warm for 2h. After gas phase and liquid phase siliconization reactions are carried out in a reaction sintering furnace, dark nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0131] Example 5

[0132] The preparation process of dark silicon carbide ceramics formed by photocuring includes the following steps:

[0133] S1. Silicon carbide powder pretreatment:

[0134] 100 parts by weight of graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were dispersed in a planetary ball mill. The preferred silicon carbide ball milling beads were Nikkato 5mm:10mm beads in a ratio of 1:2. Milling was performed for 3 hours at 300 RPM, with a grinding media to material volume ratio of 3:1. 4 parts by weight of polymer wetting and dispersing agent BYK-9076 were then added to the mill. After evacuation, the milling was continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying, then passed through a 100-mesh sieve. The powder size was measured using a laser particle size analyzer to ensure that the particle size distribution did not shift significantly.

[0135] Silicon carbide powder, α-SiC, purity greater than or equal to 99%. Available green silicon carbide models are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide models are XF08, XF13, and BET9.

[0136] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powders: F320 with a particle size of 30 μm, F500 with a particle size of 10 μm, and XF08 with a particle size of 1 μm. The weight ratio of the three types of silicon carbide powders is 5:3:2.

[0137] After pre-dispersion and screening, all silicon carbide has a particle size span of ≤2.5, a ratio of D10 to D90 of 1:2 to 1:3, F·C < 0.1, Si+SiO2 < 0.1, Fe2O3 < 0.08, and Cl, Na, K < 1000ppm.

[0138] S2. Configuration of high refractive index photosensitive resin solution:

[0139] First, add 15wt% of a high-refractive-index monofunctional monomer, 35wt% of a difunctional monomer, 20wt% of a multifunctional monomer, and 5wt% of an oligomer, then add 15wt% of a plasticizer and 10wt% of an inert filler adhesive. Set the temperature to 35°C and stir at 600rpm for 30min to obtain a high-refractive-index photosensitive resin solution.

[0140] The monofunctional monomer is a mixture of acryloylmorpholine and o-phenylphenoxyethyl acrylate. The difunctional monomer is a mixture of 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate. The multifunctional monomer is dipentaerythritol hexaacrylate. The oligomer is bisphenol A epoxy acrylate with a molecular weight between 1,000 and 25,000. The plasticizer is polyethylene glycol. The inert filler binder is polyvinyl butyral.

[0141] S3, Mixed:

[0142] 70 parts of pretreated silicon carbide powder, 5 parts of carbon source, 4 parts of second phase additive, 25 parts of high refractive index photosensitive resin solution, 3 parts of dispersant, 4 parts of optical channel builder, 3 parts of surfactant, 5 parts of structure directing agent, 0.3 parts of photoinitiator, 0.5 parts of oily thickener and 1 part of leveling agent were added in sequence according to the proportion and stirred for 9 hours to obtain silicon carbide photocuring slurry.

[0143] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles of Y2O3, La2O3, and Al2O3. The dispersant is KD-1. The optical channel builder is high-purity fluorite powder. The surfactant is a silane coupling agent. The structure-directing agent is polyethylene glycol 200. The photoinitiator is TPO. The oil-based thickener is PMMA from Chi Mei (Taiwan, China). The leveling agent is LGH-7499.

[0144] S4, light-curing molding and binder removal sintering:

[0145] Silicon carbide photocurable slurry was filled at a filling speed of 0.05 and a laser scanning speed of 2500 mm / s. After filling, the printed blank was printed and cured under a 405 nm light source at a laser power of 100%. The slurry on the printed blank was cleaned and stored in a UV drying oven for a period of time before entering the debinding and degreasing stage.

[0146] The printed blank was placed in a debinding furnace using graphite support pillars. After vacuuming, argon was introduced to expel residual oxygen from the furnace. The temperature was then raised from room temperature to 100°C at 0.5°C / min and held for 120 minutes. The temperature was then raised to 220°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 300°C, 400°C, and 500°C at 0.1°C / min, each held for 180 minutes. The temperature was finally raised to 600°C at 0.2°C / min and held for 120 minutes. The temperature was then raised to 1200°C at 0.5°C / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder, which had been pre-mixed with a 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0147] The non-siliconized surface is wrapped with high-purity carbon paper, heated to 1700℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and then kept warm for 2h. After gas phase and liquid phase siliconization reactions are carried out in a reaction sintering furnace, dark nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0148] Comparative Example 1

[0149] Comparative Example 1 is a comparative test example of Example 2:

[0150] The preparation process of the dark silicon carbide ceramic formed by photocuring in Comparative Example 1 comprises the following steps:

[0151] S1. Silicon carbide powder with particle size distribution:

[0152] Silicon carbide powder, α-SiC, purity greater than or equal to 99%. Available green silicon carbide models are F240, F280, F360, F400, F500, F600, F800, and F1200, and available gray silicon carbide models are XF08, XF13, and BET9.

[0153] In this comparative example, the silicon carbide powder consists of three types of silicon carbide powders: F240 with a particle size of 50 μm, F500 with a particle size of 10 μm, and F1200 with a particle size of 3 μm. The weight ratio of the three types of silicon carbide powders is 5:3:2.

[0154] S2. Photosensitive resin solution configuration:

[0155] First, add 5wt% of monofunctional monomer, 40wt% of difunctional monomer, and 30wt% of trifunctional monomer, then add 20wt% of plasticizer and 5wt% of inert filler adhesive, set the temperature to 35°C, and stir at 600 rpm for 30 minutes to obtain a high refractive index photosensitive resin solution.

[0156] The monofunctional monomer is IBOMA (isobornyl methacrylate). The difunctional monomer is HDDA (1,6-hexanediol diacrylate). The trifunctional monomer is TMPTA (trimethylolpropane triacrylate). The plasticizer is polyethylene glycol. The inert filler binder is polyvinyl butyral.

[0157] S3, Mixed:

[0158] 70 parts of pretreated silicon carbide powder, 5 parts of carbon source, 8 parts of second phase additive, 20 parts of photosensitive resin solution, 2 parts of dispersant, 3 parts of surfactant, 0.2 parts of photoinitiator, 0.5 parts of oily thickener and 1 part of leveling agent were added in sequence according to the proportion and stirred for 8 hours to obtain silicon carbide photocuring slurry.

[0159] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles of Y2O3, La2O3, and Al2O3. The dispersant is KD-1. The optical channel builder is high-purity fluorite powder. The surfactant is a silane coupling agent. The structure-directing agent is polyethylene glycol 200. The photoinitiator is TPO. The oil-based thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0160] S4, Stereolithography:

[0161] The silicon carbide photocuring slurry was filled with a filling speed of 0.05 and a laser scanning speed of 2500 mm / s. After filling, the laser power was 100% and the printing and curing were performed under a 405 nm band light source.

[0162] During the photocuring process, the thickness of a single layer of photocuring was only 50 μm, and the curing depth was too low to be printed. Therefore, the subsequent debinding and sintering operations were not performed.

[0163] Experimental test:

[0164] 1. The single-layer curing depth and printing effect of the silicon carbide photocurable slurry in Examples 1-4 and Comparative Example 1 were tested, as shown in Table 1.

[0165] Table 1

[0166] sample Single layer cured thickness Single-chip effect Printing effect Example 1 180μm Good strength, no deformation The solid sample has high hardness and good flexibility Example 2 165μm Good strength, no deformation The solid sample has high hardness and good flexibility Example 3 140μm Good strength, no deformation The solid sample has high hardness and good flexibility Example 4 130μm Good strength, no deformation The solid sample has high hardness and good flexibility Example 5 120μm Good strength, no deformation The solid sample has high hardness and good flexibility Comparative Example 1 50μm The slurry settles and delaminates, the curing depth is low, and it warps and deforms. Printing failed

[0167] In Examples 1-5, the single-layer curing depth of the silicon carbide photocurable slurry was greater than 160 μm, and the overall printing effect was good. However, in Comparative Example 1, the silicon carbide powder was not dispersed and surface treated, and a high-refractive-index photosensitive resin solution was not used. The resulting silicon carbide photocurable slurry had a low single-layer curing depth of only 50 μm, and the printed single piece exhibited warping and deformation, resulting in printing failure.

[0168] The states of the silicon carbide photocurable slurries prepared in Examples 1, 2 and Comparative Example 1 at different stages were analyzed. Figure 1 The three types of silicon carbide photocuring pastes are just prepared. Figure 2 The state of three types of silicon carbide photocuring slurries after being placed for one week. Figure 3 The state of samples printed with three types of silicon carbide photocuring paste after debinding.

[0169] By comparison, the silicon carbide photocurable slurry of Comparative Example 1, which was not regulated by the present invention, had poor fluidity and stability. After one week, both large and small silicon carbide particles experienced varying degrees of sedimentation. In contrast, the silicon carbide photocurable slurries of Examples 1 and 2, regulated by the present invention, exhibited excellent fluidity and stability. The slurries exhibited shear-thinning characteristics, making them suitable for actual printing processes. Furthermore, the slurries showed no sedimentation after one week.

[0170] In addition, by Figure 3 It can be seen that after printing and debinding, the slurries of Examples 1 and 2 had good strength and no deformation. Light curing is a layer-by-layer accumulation. The cured sheet obtained after light curing of the printed slurry in Comparative Example 1 was only 50-60 μm. Comparative Example 1 could not be printed due to slurry sedimentation and low curing depth.

[0171] The volume density, residual Si, flexural strength and thermal conductivity of the dark silicon carbide ceramics obtained by reaction sintering in Examples 1-5 and Comparative Example 1 were tested. The test results are shown in Table 2.

[0172] Table 2

[0173] sample Bulk density Residual Si (Vol%) Flexural strength (MPa) Thermal conductivity (W / (m·K)) Example 1 3.05 ＜20 260 82 Example 2 3.04 ＜20 280 106 Example 3 3.05 ＜20 280 110 Example 4 3.06 ＜20 295 120 Example 5 3.06 ＜20 250 100 Comparative Example 1 Print failed, not tested Print failed, not tested Print failed, not tested Print failed, not tested

[0174] It can be seen from the test results in Table 2 that the solution of the present invention improves the volume density, mechanical strength and thermal conductivity of the reaction-sintered silicon carbide ceramics, and the content of residual Si in the sample is low.

[0175] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A dark silicon carbide ceramic formed by photocuring, characterized in that: The raw material components include the following parts by weight: 70-80 parts of pretreated silicon carbide powder, 20-30 parts of high refractive index photosensitive resin solution, 3 to 8 parts of the second phase additive, 2 to 5 parts of dispersant, 4-12 parts of optical channel building agent, 0-5 parts surfactant, 2 to 8 parts of structure directing agent, Oily thickener 0.05-1 part, Leveling agent 0-2 parts, 0.2-1 part of photoinitiator; The high refractive index photosensitive resin solution is mainly composed of high refractive index monofunctional monomers, difunctional monomers, multifunctional monomers and oligomers, and is also added with plasticizers and inert filler adhesives. The monofunctional monomer accounts for 5-15% of the total mass of the photosensitive resin solution, the difunctional monomer accounts for 10-45% of the total mass of the photosensitive resin solution, the multifunctional monomer accounts for 5-25% of the total mass of the photosensitive resin solution, the oligomer accounts for 5-40% of the total mass of the photosensitive resin solution, the plasticizer accounts for 2-30% of the total mass of the photosensitive resin solution, and the inert filler binder accounts for 3-10% of the total mass of the photosensitive resin solution; The optical channel building agent is high-purity fluorite powder with a purity greater than 99.9%; The structure-directing agent is polyethylene glycol 200; The pretreated silicon carbide powder is obtained by ball milling green silicon carbide and / or gray silicon carbide, drying and sieving. During the ball milling process, a silane coupling agent and a polymer wetting and dispersing agent are used to perform surface modification on the silicon carbide. The silicon carbide powder is divided into three types according to particle size: large-particle silicon carbide powder, medium-particle silicon carbide powder and small-particle silicon carbide powder. The particle size of the large-particle silicon carbide powder is 20-50 μm, the particle size of the medium-particle silicon carbide powder is 5-15 μm, and the particle size of the small-particle silicon carbide powder is 0.5-3 μm. The weight ratio of the large-particle silicon carbide powder, the medium-particle silicon carbide powder and the small-particle silicon carbide powder is (10-14): (4-8): (1-6). The dark silicon carbide ceramic further comprises 5 to 18 parts of a carbon source, wherein the carbon source is a phenolic acrylic resin; The second phase additive is one or a mixture of spherical nanoparticles Y2O3, spherical nanoparticles La2O3, spherical nanoparticles Al2O3, spherical nanoparticles MgO and nanoparticles CaO.

2. The dark-colored silicon carbide ceramic formed by photocuring according to claim 1, characterized in that: The monofunctional monomer is one or a mixture of acryloylmorpholine, o-phenylphenoxyethyl acrylate, hydroxyethyl acrylamide, phenoxy acrylate, and tert-butoxy acrylamide; The bifunctional monomer is one or a mixture of 1,6-ethylene glycol diacrylate, dipropylene glycol diacrylate, and ethoxylated bisphenol A diacrylate; The multifunctional monomer is one or a mixture of pentaerythritol triacrylate, trihydroxyethyl propane triacrylate, ethoxylated pentaerythritol tetraacrylate, bis-pentaerythritol hexaacrylate, and bisether fluorene acrylate; The oligomer is one or a mixture of bisphenol A epoxy acrylate, bisphenol F epoxy acrylic resin, polyester acrylic resin, and polyurethane acrylic resin with a molecular weight between 1000 and 25000; The plasticizer is one or a mixture of dibutyl phthalate, dioctyl phthalate, and polyethylene glycol; The inert filling adhesive is one or a mixture of polyvinyl butyral, small molecule adhesive B002S, polyethersulfone, polyvinyl alcohol, and polymethyl methacrylate.

3. A process for preparing dark-colored silicon carbide ceramics formed by photocuring as claimed in claim 1 or 2, characterized in that: The steps include: S1. Silicon carbide powder pretreatment: According to the principle of closest packing, silicon carbide powder is graded into three particle sizes: large, medium and small. The graded silicon carbide powder and silane coupling agent are added to a ball mill for dispersion. A polymer wetting and dispersing agent is then added to the ball mill. After vacuuming, the ball milling is continued. After the ball milling is completed, the slurry is dried and sieved. S2. Configuration of high refractive index photosensitive resin solution: First, a monofunctional monomer, a difunctional monomer, a multifunctional monomer and an oligomer with a high refractive index are added, and then a plasticizer and an inert filler adhesive are added, and the mixture is stirred and mixed to obtain a photosensitive resin solution with a high refractive index; S3, Mixed: The pretreated silicon carbide powder, the second phase additive, the high refractive index photosensitive resin solution, the phenolic acrylic resin, the dispersant, the optical channel builder, the surfactant, the structure directing agent, the photoinitiator, the oily thickener, and the leveling agent are sequentially added and stirred and mixed according to the proportion to obtain a silicon carbide light-curing slurry; S4, light-curing molding and binder removal sintering: The silicon carbide photocuring slurry is filled and printed under a 405nm band light source, and then a preform is obtained after debinding and carbonization. Finally, a dark nano-silicon carbide ceramic with high-precision size is obtained through reaction sintering.

4. The process for preparing dark silicon carbide ceramics formed by photocuring according to claim 3, characterized in that: In step S4, during the debinding and carbonization process, an inert gas is introduced into the debinding furnace and the temperature is slowly increased. During the reaction sintering process, an inert gas is introduced into the reaction sintering furnace and the temperature is increased to 1600-1700° C. at a heating rate of 0.5° C. / min and then kept warm for 2 hours.

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