Light-cured dark silicon carbide ceramic and preparation process thereof

Abstract

According to the photocuring molded dark-color silicon carbide ceramic and the preparation process thereof, a photosensitive resin solution with a high refractive index is prepared, and under the combined action of a structure-directing agent, a macromolecular wetting type dispersing agent, a silane coupling agent, a flatting agent and the like, the wetting effect of resin on silicon carbide powder is improved; the silicon carbide slurry with high fluidity and stability is obtained, the photocuring depth is improved, a silicon carbide green body is printed through the SLA or DLP technology, and the photocuring forming problem of silicon carbide is solved. By optimizing the grain composition of the silicon carbide ceramic and optimizing the carbon source for reactive sintering, the silicon carbide ceramic with high dimensional precision is obtained through degreasing and reactive sintering, and the volume density, mechanical strength and heat-conducting property of the reactive sintering silicon carbide ceramic are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide ceramics technology, specifically to a photocurable dark-colored silicon carbide ceramic and its preparation process. Background Technology

[0002] Dark-colored silicon carbide ceramics, due to their high hardness, good thermal conductivity, thermal shock resistance, high-temperature resistance, and chemical stability, have been widely used in energy, chemical, semiconductor, and aerospace fields. Traditional molding processes such as slip casting, dry pressing, injection molding, and tape casting are costly and time-consuming, making the fabrication and processing of complex ceramic structural parts difficult, which undoubtedly limits their widespread application. Ceramic photopolymerization 3D printing technology offers advantages such as 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, giving rise to 3D printing technology for silicon carbide ceramics.

[0003] Traditional oxide ceramics such as aluminum nitride, alumina, and zirconium oxide are all suitable for free radical photopolymerization. However, dark-colored silicon carbide non-oxide ceramics are prone to scattering at interfaces due to their high refractive index, affecting the penetration depth of ultraviolet light. The band gap Eg of a material determines the wavelength range of its absorbed light. From the relationship between the band gap and the absorption edge, we know that the absorption edge wavelength λC (nm) = 1240 / Eg (ev). When the incident light wavelength < λC (photon energy > Eg), the material undergoes intrinsic absorption; when the incident light wavelength > λC (photon energy < Eg), the material is transparent to light (ignoring impurity or defect absorption). The band gap (ev) of silicon carbide is around 2.3–3.3, so the absorption edge is in the range of 375–540 nm, which limits SLA (stereolithography) and DLP (digital light processing) silicon carbide photopolymerization technologies. Firstly, silicon carbide's high absorption of ultraviolet light in the 355–405 nm wavelength range limits its curing depth. Secondly, the significant difference in refractive index between photosensitive resin and silicon carbide ceramics causes light scattering at the interface, reducing the penetration depth of ultraviolet light. The cured thickness of silicon carbide ceramic slurry is typically only 1 / 4 to 1 / 3 that of alumina and zirconia ceramic slurries, affecting interlayer adhesion during printing. Furthermore, the light absorption of silicon carbide is also related to its particle size and specific surface area; submicron-sized silicon carbide often fails to print due to its low curing depth. These factors lead to uneven curing, poor interlayer adhesion, 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 impossible to fabricate silicon carbide ceramics with complex and fine-sized structures. In addition, 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. The dispersion, solid content enhancement, rheological properties, and stability of ceramic slurries need further optimization. Domestically produced micron-sized silicon carbide powders have irregular morphologies and contain impurities such as free Si, C, SiO2, Cl, and Fe, which affect the bulk density, mechanical strength, and thermal conductivity of sintered silicon carbide ceramics. Therefore, obtaining silicon carbide ceramics with high-precision dimensions and high performance is quite difficult.

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

[0005] To address the problems existing in the background art, the present invention provides a photocurable dark silicon carbide ceramic and its preparation process, which improves the wetting of silicon carbide powder by the resin, obtains silicon carbide slurry with high fluidity and stability, enhances the photocuring depth, and prints silicon carbide green bodies using SLA or DLP technology, thus solving the photocurable molding problem of silicon carbide. High-dimensional precision silicon carbide ceramics are obtained through debinding and reaction sintering.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a photocurable dark-colored silicon carbide ceramic, comprising the following raw material components in parts by weight: 70-80 parts of pretreated silicon carbide powder 20-30 parts of high refractive index photosensitive resin solution Second phase additive 0-8 parts, 2-5 parts of dispersant 0-12 parts of optical channel building agent Surfactant 0-5 parts 0-8 parts of structure guiding agent Oily thickener 0.05-1 part 0-2 parts of leveling agent Photoinitiator 0.2–1 part; Among them, the high-refractive-index photosensitive resin solution is mainly composed of high-refractive-index monofunctional monomers, difunctional monomers, multifunctional monomers and oligomers, and also contains plasticizers and inert filler binders. Monofunctional monomers account for 0–15% of the total mass of the photosensitive resin solution, difunctional monomers account for 10–45% of the total mass of the photosensitive resin solution, polyfunctional monomers account for 0–25% of the total mass of the photosensitive resin solution, oligomers account for 0–40% of the total mass of the photosensitive resin solution, plasticizers account for 0–30% of the total mass of the photosensitive resin solution, and inert fillers and binders account for 0–10% of the total mass of the photosensitive resin solution.

[0007] Dispersants include KD-1, BYK111, KOS110, BYK9076, fish oil, lecithin, oleamide, etc.

[0008] The above technical solution is adopted: This invention improves the wetting of silicon carbide powder by configuring a high-refractive-index photosensitive resin solution and utilizing the combined effects of structure-directing agents, polymeric wetting dispersants, silane coupling agents, and leveling agents. This results in a silicon carbide slurry with high fluidity and stability, enhancing the photocuring depth. Silicon carbide green bodies can then be printed using SLA or DLP technology, solving the photocuring molding problem of silicon carbide. Furthermore, this invention optimizes the particle size distribution of silicon carbide ceramics and the carbon source for reaction sintering, achieving high-dimensional precision silicon carbide ceramics through debinding and reaction sintering.

[0009] Specifically, pre-dispersion and surface modification of the powder enhance the compatibility of inorganic powders with organic photocurable resins. The use of surfactants to regulate the slurry increases its fluidity, facilitating spreading on the printing platform and ensuring more uniform density per layer. Surfactant regulation also effectively increases the slurry's storage stability, resulting in good leveling and reduced sedimentation. High-refractive-index photosensitive resin solutions and inorganic light channel builders improve the UV curing depth, ensuring high-quality photocuring and resolving issues such as uneven curing, poor interlayer bonding, deformation, warping, and cracking caused by low curing depth and crosslinking density. The second-phase additive in the system acts as a sintering aid, reacting with impurities such as SiO2 in the low-melting-point silicon carbide powder, purifying its lattice oxygen, reducing phonon scattering, and thus improving its thermal conductivity. The structure-directing agent polyethylene glycol exists in the cross-linked network of the preform. As a non-reactive diluent, it forms a dispersed phase in the resin. During degradation, it produces a uniformly distributed microporous structure. These micropores serve as channels for gas escape during the debinding and sintering process, reducing local pressure accumulation and inhibiting crack formation.

[0010] By optimizing the proportion of multifunctional monomers in the high-refractive-index photosensitive resin solution, the impact of volume shrinkage caused by the shortening of intermolecular distance due to the addition reaction of double bonds during photocuring on the preform molding is reduced. Simultaneously, the proportion of monofunctional monomers is adjusted to provide a certain degree of dilution, ensuring the flowability and suitable rheological properties of the organic binder. Both monofunctional monomers and oligomers can reduce the curing shrinkage of acrylic monomers, while oligomers can also increase the density of the preform during curing. By adjusting the proportions of each component in the photosensitive resin solution, cracking caused by stress concentration after adhesive removal can be effectively reduced. The amount of high-refractive-index photosensitive resin solution added is 20–30 parts by weight, with an optimal proportion of 25 parts by weight.

[0011] Furthermore, the monofunctional monomer is one or a mixture of several of the following: acrylamide, o-phenylphenoxyethyl acrylate, hydroxyethyl acrylamide, phenoxy acrylate, and tert-butoxy acrylamide. The bifunctional monomer is one or a mixture of several of 1,6-ethylene glycol diacrylate, dipropylene glycol diacrylate, and bisphenol A diacrylate. The multifunctional monomer is one or a mixture of several of pentaerythritol triacrylate, trihydroxyethylpropane triacrylate, pentaerythritol tetraacrylate ethoxylate, bis-pentaerythritol hexaacrylate, and dietherfluorene acrylate.

[0012] Preferably, the monomers are acrylamide, o-phenylphenoxyethyl acrylate, 1,6-ethylene glycol diacrylate, bisphenol A diacrylate, and bis-pentaerythritol hexaacrylate.

[0013] The oligomer is one or a mixture of several of the following: bisphenol A epoxy acrylate, bisphenol F epoxy acrylate, polyester acrylate, and polyurethane acrylate, with a molecular weight between 1000 and 25000. Preferably, the oligomer is bisphenol A epoxy acrylate.

[0014] The plasticizer is one or a mixture of several of dibutyl phthalate, dioctyl phthalate, and polyethylene glycol. Considering the migration of DBP, polyethylene glycol is preferred as the plasticizer.

[0015] The inert filler adhesive is one or a mixture of several of the following: polyvinyl butyral, small molecule adhesive B002S, polyethersulfone, polyvinyl alcohol, and polymethyl methacrylate.

[0016] Furthermore, the optical channel builder is high-purity fluorite powder with a purity greater than 99.9%.

[0017] Furthermore, the pretreated silicon carbide powder is made by ball milling green silicon carbide and / or gray silicon carbide, followed by drying and sieving. During the ball milling process, silane coupling agents and polymeric wetting and dispersing agents are used to modify the surface of the silicon carbide.

[0018] Specifically, the surface of silicon carbide powder with particle size distribution is pretreated by adding silane coupling agent, the main material silicon carbide powder is dispersed by polymer wetting and dispersing agent, and the powder is dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve to complete the surface modification of the powder. The pre-dispersion and surface modification of the powder enhance the compatibility of inorganic powder in organic photocurable resin.

[0019] Furthermore, the structure directing agent is polyethylene glycol 200.

[0020] The structure-directing agent polyethylene glycol exists in the cross-linked network of the preform. As a non-reactive diluent, it forms a dispersed phase in the resin. During degradation, it produces a uniformly distributed microporous structure. These micropores serve as channels for gas escape during the debinding and sintering process, reducing local pressure accumulation and inhibiting crack formation.

[0021] Further, the second phase additive is one or a mixture of several selected from spherical nanoparticles Y₂O₃, spherical nanoparticles La₂O₃, spherical nanoparticles Al₂O₃, spherical nanoparticles MgO, and nanoparticles CaO. Preferably, the second phase additive is one or a mixture of several selected from spherical nanoparticles Y₂O₃, spherical nanoparticles La₂O₃, and spherical nanoparticles Al₂O₃. More preferably, the second phase additive is a mixture of Y₂O₃ and La₂O₃, or a mixture of Y₂O₃, La₂O₃, and Al₂O₃.

[0022] The second-phase additive in the system acts as a sintering aid, reacting with impurities such as SiO2 in the eutectic and silicon carbide powders to purify the lattice oxygen, reduce phonon scattering, and thus improve its thermal conductivity. The Y2O3, Al2O3, and La2O3 in the sintered ceramics are distributed at grain boundaries and tri-point junctions. The formation of their low-melting-point eutectic compounds facilitates silicon penetration. Furthermore, the preferred amorphous resin carbon source and graphite-type composite carbon source effectively reduce the volume fraction of silicon. Experiments have shown that as the volume fraction of the second-phase additives Al2O3 and Y2O3 in the material increases, the density of the reaction-sintered silicon carbide first increases and then decreases. This may be because a higher volume fraction of the eutectic phase makes the liquid phase too viscous, inhibiting diffusion and the reaction process. Additionally, Y2O3 and Al2O3 can react with the reaction-sintered carbon source, resulting in excessive silicon residue, necessitating control of their addition amount.

[0023] Furthermore, the polymeric wetting and dispersing agents include KD-1, BYK111, KOS110, BYK9076, fish oil, lecithin, oleamide, etc. Surfactants include silane coupling agents, BYK thixotropic agents, Yoshida oily thickeners, etc. The photoinitiator is TPO or 819.

[0024] Furthermore, the dark silicon carbide ceramic also includes 5 to 18 parts of 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 pyrolysis of organic resins such as phenolic acrylic resin, or inorganic substances such as graphite powder as carbon source (the XRD of graphite powder is crystalline).

[0025] Preferably, phenolic acrylic resin is added to the product formulation system, which can participate in free radical photocuring and provide a rich carbon source through high-temperature pyrolysis.

[0026] Optimizing the particle size distribution and carbon source of silicon carbide powder effectively improves 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, primarily used to guide the optimization of the particle size distribution in multi-level particle systems to achieve minimum porosity and maximum density. Horsfield's closest packing theory states that a denser space filling can be achieved by mixing particles of different sizes. The Dinger particle size distribution optimization model guides particle size distribution through numerical simulation and is applicable to multi-level systems (such as tertiary particle sizes). By optimizing the density, open porosity, and pore size of the green body through particle size distribution optimization to adapt to the silicon infiltration process of reaction-sintered silicon carbide, the volume fraction and size of silicon are effectively reduced, thereby improving the overall performance of reaction-sintered silicon carbide.

[0027] A second aspect of the present invention provides a process for preparing the above-mentioned photocurable dark silicon carbide ceramic, comprising the following steps: S1. Pretreatment of silicon carbide powder: Based on the principle of closest packing, silicon carbide powder was selected with three particle sizes: large, medium, and small. 100 parts by weight of the particle-graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were added to a planetary ball mill for dispersion. The preferred silicon carbide ball milling beads were Nikkato 5mm:10mm = 1:2. The milling process was first carried out for 3 hours at a speed of 300 RPM, with a grinding media to material volume ratio of 3:1. Then, 4 parts by weight of polymeric wetting and dispersing agent BYK-9076 were added to the mill jar, and after vacuuming, milling continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve. The particle size was measured using a laser particle size analyzer to ensure that the particle size distribution did not deviate significantly.

[0028] Silicon carbide powder, α-SiC, with a purity greater than or equal to 99%. Optional green silicon carbide grades are F240, F280, F360, F400, F500, F600, F800, and F1200; optional gray silicon carbide grades are XF08, XF13, and BET9. All silicon carbide, after pre-dispersion and sieving, has a particle size span ≤2.5, a D10 to D90 ratio of 1:2 to 1:3, F·C < 0.1, Si+SiO2 < 0.1, Fe2O3 < 0.08, and Cl, Na, and K < 1000 ppm.

[0029] S2. Preparation of high refractive index photosensitive resin solution: First, add high-refractive-index monofunctional monomers, difunctional monomers, polyfunctional monomers, and oligomers, then add plasticizers and inert filler binders. Set the temperature to 35℃ and stir at 600 rpm for 30–50 min to obtain a high-refractive-index photosensitive resin solution.

[0030] S3, Mixing: Pretreated silicon carbide powder, carbon source, second-phase additive, high-refractive-index photosensitive resin solution, dispersant, light channel builder, surfactant, structure guide agent, photoinitiator, oily thickener, and leveling agent are added in sequence according to the specified proportions and stirred for 5 to 12 hours to obtain silicon carbide photocurable slurry.

[0031] S4. Photopolymerization molding and debinding sintering: Silicon carbide photocurable slurry is filled at a rate of 0.01–0.05. After filling, the slurry is printed and cured using a laser with a power of 70%–100% and a scanning speed of 2500 mm / s under a 405 nm wavelength light source. The slurry on the printed preform is then cleaned off and stored in an ultraviolet drying oven for a period of time before proceeding to the degreasing stage.

[0032] The printed preform was placed in a debinding furnace using a graphite support pillar. After evacuation, argon gas was introduced to remove residual oxygen. The temperature was increased from room temperature to 100℃ at a rate of 0.5℃ / min and held for 120 min; then increased to 220℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 300℃, 400℃, and 500℃ at a rate of 0.1℃ / min and held for 180 min each; finally, increased to 600℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 1200℃ at a rate of 0.5℃ / min to obtain the preform. The preform was then placed in a graphite mold and filled with Si powder. The Si powder was pre-mixed with 1-4 wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0033] High-purity carbon paper is wrapped around the un-siliconized surface, heated to 1600-1700℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and held for 2 hours. After gas-phase and liquid-phase siliconization reactions are carried out in a reaction sintering furnace, dark-colored nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0034] Further, in step S1, the silicon carbide powder is composed of three types of particles: 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, medium-particle silicon carbide powder, and small-particle silicon carbide powder is (10-14):(4-8):(1-6).

[0035] Compared with the prior art, the present invention has the following beneficial effects: This invention successfully prepared high-precision dark nano-silicon carbide ceramics through photopolymerization molding and reaction sintering. (1) Pre-dispersion and surface modification of the powder enhance the compatibility of inorganic powder in organic photopolymerization resin. The surfactant controls the slurry, increasing its fluidity and facilitating its spread on the printing platform and ensuring more uniform density of each layer. The surfactant effectively increases the storage stability of the slurry, resulting in good slurry leveling and less sedimentation. The high-refractive-index photosensitive resin solution and inorganic light channel building agent enhance the UV curing depth, ensuring the quality of photopolymerization molding and solving the problems of uneven curing, poor interlayer bonding, deformation, warping, and cracking caused by low curing depth and crosslinking density. (2) The structure-directing agent polyethylene glycol exists in the crosslinking 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 during degradation. These micropores serve as gas escape channels during the debinding and sintering process, reducing local pressure accumulation and inhibiting crack formation. (3) The particle size distribution of silicon carbide powder and the type of carbon source were optimized, which effectively improved the bulk density, mechanical strength and thermal conductivity of reaction sintered silicon carbide ceramics. Attached Figure Description

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1 The state of the silicon carbide photocurable slurry prepared in Examples 1, 2 and Comparative Example 1; Figure 2 The state of the silicon carbide photocurable slurry prepared in Examples 1, 2 and Comparative Example 1 after one week; Figure 3 The images show the state of the silicon carbide photocurable paste printing samples after adhesive removal in Examples 1, 2 and Comparative Example 1. Detailed Implementation

[0038] 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.

[0039] Example 1 The fabrication process of photocured dark-colored silicon carbide ceramics includes the following steps: S1. Pretreatment of silicon carbide powder: 100 parts by weight of particle-graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were added to a planetary ball mill for dispersion. Nikkato 5mm:10mm grinding beads were preferred (1:2 ratio). The milling process was first carried out for 3 hours at 300 RPM with a grinding media to material volume ratio of 3:1. Then, 4 parts by weight of the polymeric wetting and dispersing agent BYK-9076 were added to the mill jar. After vacuuming, milling continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve. The particle size was measured using a laser particle size analyzer to ensure that the particle size distribution did not deviate significantly.

[0040] Silicon carbide powder, α-SiC, with a purity of ≥99%. Optional green silicon carbide models are F240, F280, F360, F400, F500, F600, F800, and F1200, while optional gray silicon carbide models are XF08, XF13, and BET9.

[0041] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powder: 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 powder is 6:3:1.

[0042] After pre-dispersion and sieving, all silicon carbide particles have a particle size span ≤2.5, a D10 to D90 ratio of 1:2 to 1:3, F·C <0.1, Si+SiO2 <0.1, Fe2O3 <0.08, and Cl, Na, K <1000ppm.

[0043] S2. Preparation of high refractive index photosensitive resin solution: First, add 10wt% of a high-refractive-index monofunctional monomer, 30wt% of a difunctional monomer, 15wt% of a polyfunctional monomer, and 20wt% of an oligomer. Then add 20wt% of a plasticizer and 5wt% of an inert filler binder. Set the temperature to 35℃ and stir at 600rpm for 30min to obtain a high-refractive-index photosensitive resin solution.

[0044] The monomers are: a mixture of monofunctional acrylomorpholine and o-phenylphenoxyethyl acrylate; a mixture of difunctional 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate; a polyfunctional bis-pentaerythritol hexaacrylate; an oligomer with a molecular weight between 1,000 and 25,000 bisphenol A epoxy acrylate; a plasticizer of polyethylene glycol; and an inert filler binder of polyvinyl butyral.

[0045] S3, Mixing: 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 light channel building agent, 3 parts of surfactant, 5 parts of structure guiding 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 specified proportions and stirred for 8 hours to obtain silicon carbide photocurable slurry.

[0046] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles 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 oily thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0047] S4. Photopolymerization molding and debinding sintering: Silicon carbide photocurable slurry was applied at a filling speed of 0.05 mm / s and a laser scanning speed of 2500 mm / s. After application, the slurry was printed and cured using a 405 nm wavelength light source at 100% laser power. The printed preform was then cleaned of the slurry and stored in an ultraviolet drying oven for a period of time before entering the degreasing stage.

[0048] The printed preform was placed in a debinding furnace using a graphite support pillar. After evacuation, argon gas was introduced to remove residual oxygen from the furnace. The temperature was increased from room temperature to 100℃ at a rate of 0.5℃ / min and held for 120 min; then increased to 220℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 300℃, 400℃, and 500℃ at a rate of 0.1℃ / min and held for 180 min each; finally, increased to 600℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 1200℃ at a rate of 0.5℃ / min to obtain the preform. Finally, the preform was placed in a graphite mold and filled with Si powder. The Si powder was pre-mixed with 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0049] High-purity carbon paper is wrapped around the un-siliconized surface, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and held at that temperature for 2 hours. After gas-phase and liquid-phase siliconization reactions are carried out in a reaction sintering furnace, dark-colored nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0050] Example 2 The fabrication process of photocured dark-colored silicon carbide ceramics includes the following steps: S1. Pretreatment of silicon carbide powder: 100 parts by weight of particle-graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were added to a planetary ball mill for dispersion. Nikkato 5mm:10mm grinding beads were preferred (1:2 ratio). The milling process was first carried out for 3 hours at 300 RPM with a grinding media to material volume ratio of 3:1. Then, 4 parts by weight of the polymeric wetting and dispersing agent BYK-9076 were added to the mill jar. After vacuuming, milling continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve. The particle size was measured using a laser particle size analyzer to ensure that the particle size distribution did not deviate significantly.

[0051] Silicon carbide powder, α-SiC, with a purity of ≥99%. Optional green silicon carbide models are F240, F280, F360, F400, F500, F600, F800, and F1200, while optional gray silicon carbide models are XF08, XF13, and BET9.

[0052] In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powder: 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 powder is 5:3:2.

[0053] After pre-dispersion and sieving, all silicon carbide particles have a particle size span ≤2.5, a D10 to D90 ratio of 1:2 to 1:3, F·C <0.1, Si+SiO2 <0.1, Fe2O3 <0.08, and Cl, Na, K <1000ppm.

[0054] S2. Preparation of high refractive index photosensitive resin solution: First, add 10wt% of a high-refractive-index monofunctional monomer, 30wt% of a difunctional monomer, 15wt% of a polyfunctional monomer, and 20wt% of an oligomer. Then add 20wt% of a plasticizer and 5wt% of an inert filler binder. Set the temperature to 35℃ and stir at 600rpm for 30min to obtain a high-refractive-index photosensitive resin solution.

[0055] The monomers are: a mixture of monofunctional acrylomorpholine and o-phenylphenoxyethyl acrylate; a mixture of difunctional 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate; a polyfunctional bis-pentaerythritol hexaacrylate; an oligomer with a molecular weight between 1,000 and 25,000 bisphenol A epoxy acrylate; a plasticizer of polyethylene glycol; and an inert filler binder of polyvinyl butyral.

[0056] S3, Mixing: 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 light channel builder, 3 parts of surfactant, 8 parts of structure guide 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 specified proportions and stirred for 8 hours to obtain silicon carbide photocurable slurry.

[0057] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles 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 oily thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0058] S4. Photopolymerization molding and debinding sintering: Silicon carbide photocurable slurry was applied at a filling speed of 0.05 mm / s and a laser scanning speed of 2500 mm / s. After application, the slurry was printed and cured using a 405 nm wavelength light source at 100% laser power. The printed preform was then cleaned of the slurry and stored in an ultraviolet drying oven for a period of time before entering the degreasing stage.

[0059] The printed preform was placed in a debinding furnace using a graphite support pillar. After evacuation, argon gas was introduced to remove residual oxygen from the furnace. The temperature was increased from room temperature to 100℃ at a rate of 0.5℃ / min and held for 120 min; then increased to 220℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 300℃, 400℃, and 500℃ at a rate of 0.1℃ / min and held for 180 min each; finally, increased to 600℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 1200℃ at a rate of 0.5℃ / min to obtain the preform. Finally, the preform was placed in a graphite mold and filled with Si powder. The Si powder was pre-mixed with 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0060] High-purity carbon paper is wrapped around the un-siliconized surface, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and held at that temperature for 2 hours. After gas-phase and liquid-phase siliconization reactions are carried out in a reaction sintering furnace, dark-colored nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0061] Example 3 The fabrication process of photocured dark-colored silicon carbide ceramics includes the following steps: S1. Pretreatment of silicon carbide powder: 100 parts by weight of particle-graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were added to a planetary ball mill for dispersion. Nikkato 5mm:10mm grinding beads were preferred (1:2 ratio). The milling process was first carried out for 3 hours at 300 RPM with a grinding media to material volume ratio of 3:1. Then, 4 parts by weight of the polymeric wetting and dispersing agent BYK-9076 were added to the mill jar. After vacuuming, milling continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve. The particle size was measured using a laser particle size analyzer to ensure that the particle size distribution did not deviate significantly.

[0062] 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; available gray silicon carbide grades are XF08, XF13, and BET9. In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powder: 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 powder is 6:3:1.

[0063] After pre-dispersion and sieving, all silicon carbide particles have a particle size span ≤2.5, a D10 to D90 ratio of 1:2 to 1:3, F·C <0.1, Si+SiO2 <0.1, Fe2O3 <0.08, and Cl, Na, K <1000ppm.

[0064] S2. Preparation of high refractive index photosensitive resin solution: First, add 5 wt% of a high-refractive-index monofunctional monomer, 10 wt% of a difunctional monomer, 25 wt% of a polyfunctional monomer, and 30 wt% of an oligomer. Then add 20 wt% of a plasticizer and 10 wt% of an inert filler binder. Set the temperature to 35°C and stir at 600 rpm for 30 minutes to obtain a high-refractive-index photosensitive resin solution.

[0065] The monomers are: a mixture of monofunctional acrylomorpholine and o-phenylphenoxyethyl acrylate; a mixture of difunctional 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate; a polyfunctional bis-pentaerythritol hexaacrylate; an oligomer with a molecular weight between 1,000 and 25,000 bisphenol A epoxy acrylate; a plasticizer of polyethylene glycol; and an inert filler binder of polyvinyl butyral.

[0066] S3, Mixing: 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 light channel builder, 3 parts of surfactant, 5 parts of structure guide agent, 1 part of photoinitiator, 0.5 parts of oily thickener, and 1 part of leveling agent were added in sequence according to the specified proportions and stirred for 9 hours to obtain silicon carbide photocurable slurry.

[0067] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles 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 oily thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0068] S4. Photopolymerization molding and debinding sintering: Silicon carbide photocurable slurry was applied at a filling speed of 0.05 mm / s and a laser scanning speed of 2500 mm / s. After application, the slurry was printed and cured using a 405 nm wavelength light source at 100% laser power. The printed preform was then cleaned of the slurry and stored in an ultraviolet drying oven for a period of time before entering the degreasing stage.

[0069] The printed preform was placed in a debinding furnace using a graphite support pillar. After evacuation, argon gas was introduced to remove residual oxygen from the furnace. The temperature was increased from room temperature to 100℃ at a rate of 0.5℃ / min and held for 120 min; then increased to 220℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 300℃, 400℃, and 500℃ at a rate of 0.1℃ / min and held for 180 min each; finally, increased to 600℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 1200℃ at a rate of 0.5℃ / min to obtain the preform. Finally, the preform was placed in a graphite mold and filled with Si powder. The Si powder was pre-mixed with 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0070] High-purity carbon paper is wrapped around the un-siliconized surface, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and held at that temperature for 2 hours. After gas-phase and liquid-phase siliconization reactions are carried out in a reaction sintering furnace, dark-colored nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0071] Example 4 The fabrication process of photocured dark-colored silicon carbide ceramics includes the following steps: S1. Pretreatment of silicon carbide powder: 100 parts by weight of particle-graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were added to a planetary ball mill for dispersion. Nikkato 5mm:10mm grinding beads were preferred (1:2 ratio). The milling process was first carried out for 3 hours at 300 RPM with a grinding media to material volume ratio of 3:1. Then, 4 parts by weight of the polymeric wetting and dispersing agent BYK-9076 were added to the mill jar. After vacuuming, milling continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve. The particle size was measured using a laser particle size analyzer to ensure that the particle size distribution did not deviate significantly.

[0072] 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; available gray silicon carbide grades are XF08, XF13, and BET9. In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powder: 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 powder is 5:3:2.

[0073] After pre-dispersion and sieving, all silicon carbide particles have a particle size span ≤2.5, a D10 to D90 ratio of 1:2 to 1:3, F·C <0.1, Si+SiO2 <0.1, Fe2O3 <0.08, and Cl, Na, K <1000ppm.

[0074] S2. Preparation of high refractive index photosensitive resin solution: First, add 5 wt% of a high-refractive-index monofunctional monomer, 45 wt% of a difunctional monomer, 5 wt% of a polyfunctional monomer, and 40 wt% of an oligomer. Then add 2 wt% of a plasticizer and 3 wt% of an inert filler binder. Set the temperature to 35°C and stir at 600 rpm for 50 minutes to obtain a high-refractive-index photosensitive resin solution.

[0075] The monomers are: a mixture of monofunctional acrylomorpholine and o-phenylphenoxyethyl acrylate; a mixture of difunctional 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate; a polyfunctional bis-pentaerythritol hexaacrylate; an oligomer with a molecular weight between 1,000 and 25,000 bisphenol A epoxy acrylate; a plasticizer of polyethylene glycol; and an inert filler binder of polyvinyl butyral.

[0076] S3, Mixing: 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 light channel building agent, 3 parts of surfactant, 2 parts of structure guiding 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 specified proportions and stirred for 9 hours to obtain silicon carbide photocurable slurry.

[0077] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles 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 oily thickener is polyurethane epoxy resin. The leveling agent is BYK333.

[0078] S4. Photopolymerization molding and debinding sintering: Silicon carbide photocurable slurry was applied at a filling speed of 0.05 mm / s and a laser scanning speed of 2500 mm / s. After application, the slurry was printed and cured using a 405 nm wavelength light source at 100% laser power. The printed preform was then cleaned of the slurry and stored in an ultraviolet drying oven for a period of time before entering the degreasing stage.

[0079] The printed preform was placed in a debinding furnace using a graphite support pillar. After evacuation, argon gas was introduced to remove residual oxygen from the furnace. The temperature was increased from room temperature to 100℃ at a rate of 0.5℃ / min and held for 120 min; then increased to 220℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 300℃, 400℃, and 500℃ at a rate of 0.1℃ / min and held for 180 min each; finally, increased to 600℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 1200℃ at a rate of 0.5℃ / min to obtain the preform. Finally, the preform was placed in a graphite mold and filled with Si powder. The Si powder was pre-mixed with 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0080] High-purity carbon paper is wrapped around the un-siliconized surface, heated to 1600℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and held at that temperature for 2 hours. After gas-phase and liquid-phase siliconization reactions are carried out in a reaction sintering furnace, dark-colored nano-silicon carbide ceramics with high-precision dimensions are obtained.

[0081] Example 5 The fabrication process of photocured dark-colored silicon carbide ceramics includes the following steps: S1. Pretreatment of silicon carbide powder: 100 parts by weight of particle-graded silicon carbide powder and 3 parts by weight of silane coupling agent KH-570 were added to a planetary ball mill for dispersion. Nikkato 5mm:10mm grinding beads were preferred (1:2 ratio). The milling process was first carried out for 3 hours at 300 RPM with a grinding media to material volume ratio of 3:1. Then, 4 parts by weight of the polymeric wetting and dispersing agent BYK-9076 were added to the mill jar. After vacuuming, milling continued for another 3 hours. After milling, the slurry was dried by rotary evaporation or vacuum drying and then passed through a 100-mesh sieve. The particle size was measured using a laser particle size analyzer to ensure that the particle size distribution did not deviate significantly.

[0082] 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; available gray silicon carbide grades are XF08, XF13, and BET9. In this embodiment, the silicon carbide powder is composed of three types of silicon carbide powder: 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 powder is 5:3:2.

[0083] After pre-dispersion and sieving, all silicon carbide particles have a particle size span ≤2.5, a D10 to D90 ratio of 1:2 to 1:3, F·C <0.1, Si+SiO2 <0.1, Fe2O3 <0.08, and Cl, Na, K <1000ppm.

[0084] S2. Preparation of high refractive index photosensitive resin solution: First, add 15wt% of a high-refractive-index monofunctional monomer, 35wt% of a difunctional monomer, 20wt% of a polyfunctional monomer, and 5wt% of an oligomer. Then add 15wt% of a plasticizer and 10wt% of an inert filler binder. Set the temperature to 35℃ and stir at 600rpm for 30min to obtain a high-refractive-index photosensitive resin solution.

[0085] The monomers are: a mixture of monofunctional acrylomorpholine and o-phenylphenoxyethyl acrylate; a mixture of difunctional 1,6-ethylene glycol diacrylate and ethoxylated bisphenol A diacrylate; a polyfunctional bis-pentaerythritol hexaacrylate; an oligomer with a molecular weight between 1,000 and 25,000 bisphenol A epoxy acrylate; a plasticizer of polyethylene glycol; and an inert filler binder of polyvinyl butyral.

[0086] S3, Mixing: 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 light channel builder, 3 parts of surfactant, 5 parts of structure guide 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 specified proportions and stirred for 9 hours to obtain silicon carbide photocurable slurry.

[0087] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles 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 oily thickener is Chi Mei PMMA from Taiwan. The leveling agent is LGH-7499.

[0088] S4. Photopolymerization molding and debinding sintering: Silicon carbide photocurable slurry was applied at a filling speed of 0.05 mm / s and a laser scanning speed of 2500 mm / s. After application, the slurry was printed and cured using a 405 nm wavelength light source at 100% laser power. The printed preform was then cleaned of the slurry and stored in an ultraviolet drying oven for a period of time before entering the degreasing stage.

[0089] The printed preform was placed in a debinding furnace using a graphite support pillar. After evacuation, argon gas was introduced to remove residual oxygen from the furnace. The temperature was increased from room temperature to 100℃ at a rate of 0.5℃ / min and held for 120 min; then increased to 220℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 300℃, 400℃, and 500℃ at a rate of 0.1℃ / min and held for 180 min each; finally, increased to 600℃ at a rate of 0.2℃ / min and held for 120 min; then increased to 1200℃ at a rate of 0.5℃ / min to obtain the preform. Finally, the preform was placed in a graphite mold and filled with Si powder. The Si powder was pre-mixed with 3wt% boron nitride release agent to reduce silicon adhesion on the ceramic part.

[0090] High-purity carbon paper is wrapped around the un-siliconized surface, heated to 1700℃ at a heating rate of 0.5℃ / min under vacuum negative pressure or argon atmosphere, and held for 2 hours. After gas-phase and liquid-phase siliconization reactions are carried out in a reaction sintering furnace, dark-colored nano-silicon carbide ceramics with high precision dimensions are obtained.

[0091] Comparative Example 1 Comparative Example 1 is a comparative test example of Example 2: The preparation process of the photocured dark silicon carbide ceramic in Comparative Example 1 includes the following steps: S1, silicon carbide powder with particle size distribution: 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; available gray silicon carbide grades are XF08, XF13, and BET9. In this comparative example, the silicon carbide powder consists of three types of silicon carbide powder: 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 powder is 5:3:2.

[0092] S2. Preparation of photosensitive resin solution: First, add 5 wt% monofunctional monomer, 40 wt% difunctional monomer, and 30 wt% trifunctional monomer, then add 20 wt% plasticizer and 5 wt% inert filler binder. Set the temperature to 35℃ and stir at 600 rpm for 30 min to obtain a high refractive index photosensitive resin solution.

[0093] 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.

[0094] S3, Mixing: 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 specified proportions and stirred for 8 hours to obtain silicon carbide photocurable slurry.

[0095] The carbon source is phenolic acrylic resin. The second-phase additive is a mixture of spherical nanoparticles 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 oily thickener is polyurethane epoxy resin. The leveling agent is LGH-7499.

[0096] S4, UV curing: The silicon carbide photocurable slurry was filled at a filling speed of 0.05 mm / s and a laser scanning speed of 2500 mm / s. After filling, the laser power was 100% and the slurry was printed and cured under a 405 nm wavelength light source.

[0097] During the photopolymerization process, the thickness of a single layer is only 50μm, and the curing depth is too low to print. Therefore, no subsequent adhesive removal and sintering operation was performed.

[0098] Experimental test: 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.

[0099] Table 1 sample Single-layer curing 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 separates, has a low curing depth, and warps and deforms. Printing failed In Examples 1-5, the silicon carbide photocurable slurry achieved a single-layer curing depth greater than 160 μm, and the overall printing effect was good. However, in Comparative Example 1, the silicon carbide powder was not dispersed or surface-treated, and a high-refractive-index photosensitive resin solution was not used. The resulting silicon carbide photocurable slurry achieved a single-layer curing depth of only 50 μm, indicating a low curing depth. Furthermore, the printed wafers warped and deformed, leading to printing failure.

[0100] The states of the silicon carbide photocurable slurries prepared in Examples 1 and 2 and Comparative Example 1 at different stages were analyzed. Figure 1 These are the freshly prepared states of the three silicon carbide photocurable pastes. Figure 2 The images show the state of the three silicon carbide photocurable slurries after one week. Figure 3 The images show the state of three silicon carbide photocurable slurry printing samples after adhesive removal.

[0101] The comparison revealed that the silicon carbide photocurable slurry in Comparative Example 1, which was not regulated by the present invention, exhibited poor fluidity and stability, and after one week, both large and small silicon carbide particles settled to varying degrees. In contrast, the silicon carbide photocurable slurries in Examples 1 and 2, regulated by the present invention, displayed excellent fluidity and stability, exhibiting shear thinning characteristics suitable for actual printing processes, and no settling occurred after one week.

[0102] In addition, by Figure 3 It can be seen that the slurries of Examples 1 and 2, after printing and adhesive removal, showed good sample strength and no deformation. Photocuring involves layer-by-layer deposition. In Comparative Example 1, the cured sheet obtained after photocuring of the printed slurry was only 50-60µm. Comparative Example 1 could not be printed due to slurry settling and low curing depth.

[0103] The bulk density, residual Si, flexural strength, and thermal conductivity of the dark silicon carbide ceramics prepared by reaction sintering in Examples 1-5 and Comparative Example 1 were tested, and the test results are shown in Table 2.

[0104] Table 2 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 Printing failed, not tested. Printing failed, not tested. Printing failed, not tested. Printing failed, not tested. As can be seen from the test results in Table 2, the method of the present invention improves the bulk density, mechanical strength and thermal conductivity of reaction sintered silicon carbide ceramics, and the residual Si content in the sample is low.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dark-colored silicon carbide ceramic formed by photocuring, characterized in that: The invention comprises the following raw material components in parts by weight: 70-80 parts of pre-treated silicon carbide powder, 20-30 parts of high refractive index photosensitive resin solution, Second phase additive 0-8 parts, 2-5 parts of dispersant, 0-12 parts of optical channel building agent, Surfactant 0-5 parts, 0-8 parts of structure directing agent, Oily thickener 0.05-1 part, Leveling agent 0-2 parts, Photoinitiator 0.2-1 part; The high refractive index photosensitive resin solution mainly contains 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 0-15% 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 0-25% of the total mass of the photosensitive resin solution, the oligomer accounts for 0-40% of the total mass of the photosensitive resin solution, the plasticizer accounts for 0-30% of the total mass of the photosensitive resin solution, and the inert filling adhesive accounts for 0-10% of the total mass of the photosensitive resin solution.

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, triethylol propane triacrylate, ethoxylated pentaerythritol tetraacrylate, di-pentaerythritol hexaacrylate, and diether fluorene acrylate; The oligomer is one or a mixture of bisphenol A epoxy acrylate, bisphenol F epoxy acrylic resin, polyester acrylic resin, polyurethane acrylic resin with a molecular weight between 1000 and 25000; The plasticizer is one or a mixture of dibutyl phthalate, dioctyl phthalate, polyethylene glycol; The inert filling adhesive is one or a mixture of polyvinyl butyral, small molecule adhesive B002S, polyether sulfone, polyvinyl alcohol, polymethyl methacrylate.

3. The dark-colored silicon carbide ceramic formed by photocuring according to claim 1, characterized in that: The optical channel building agent is high-purity fluorite powder.

4. The dark-colored silicon carbide ceramic formed by photocuring according to claim 1, characterized in that: The pretreated silicon carbide powder is obtained by ball milling green silicon carbide and / or gray silicon carbide, and then 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.

5. The dark-colored silicon carbide ceramic formed by photocuring according to claim 1, characterized in that: The structure directing agent is polyethylene glycol 200.

6. The dark-colored silicon carbide ceramic formed by photocuring according to claim 1, characterized in that: 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.

7. The dark-colored silicon carbide ceramic formed by photocuring according to claim 1, characterized in that: The dark silicon carbide ceramic also includes 5 to 18 parts of a carbon source, and the carbon source is an organic resin carbon source and / or a graphite powder carbon source.

8. A process for preparing dark-colored silicon carbide ceramics formed by photocuring as claimed in any one of claims 1 to 7, characterized in that: The steps include: S1. Silicon carbide powder pretreatment: According to the principle of closest packing, the silicon carbide powder is selected into three particle sizes of large, medium and small for particle grading. The graded silicon carbide powder and silane coupling agent are added to the ball mill for dispersion. Then the polymer wetting dispersant is added to the ball milling tank. After vacuuming, the ball milling is continued. After the ball milling is completed, the slurry is dried and sieved. S2, high refractive index photosensitive resin solution configuration: Firstly, 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 building agent, the surfactant, the structure directing agent, the photoinitiator, the oily thickener, and the leveling agent are sequentially added in proportion and stirred and mixed to obtain a silicon carbide photocurable slurry; S4, light curing molding and debinding 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, and finally a dark nano silicon carbide ceramic with high-precision size is obtained through reaction sintering.

9. The process for preparing dark-colored silicon carbide ceramics formed by photocuring according to claim 8, characterized in that: In the 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 their particle sizes. 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).

10. The process for preparing dark-colored silicon carbide ceramics formed by photocuring according to claim 8, characterized in that: In step S4, during the debinding and carbonization process, an inert gas is introduced into the debinding furnace and the heating process is slow; during the reaction sintering process, an inert gas is introduced into the reaction sintering furnace, and the temperature is heated to 1600-1700° C. at a heating rate of 0.5° C. / min and then kept warm for 2 hours.

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