Photocuring 3D printing silicon carbide ceramic slurry based on coupling agent modified sol and preparation method thereof

Abstract

The invention discloses coupling agent modified silicon carbide-based photocuring 3D printing ceramic slurry and a preparation method thereof.The preparation method comprises the following steps: uniformly mixing a silane coupling agent, silicon carbide powder and Al (OH) 3 sol according to a certain proportion, heating, drying, grinding and sintering the mixture to obtain the coupling agent modified silicon carbide-based photocuring 3D printing ceramic slurry, the addition amount of the silane coupling agent is 1-8 wt% of the mass of the silicon carbide powder, and the preparation method of the coupling agent modified silicon carbide-based photocuring 3D printing ceramic slurry comprises the following steps: preparing the coupling agent modified silicon carbide-based photocuring 3D printing ceramic slurry; the SiC coated Al2O3 composite powder is obtained; and mixing with photosensitive resin, a dispersing agent and a photoinitiator to obtain the photocuring 3D printing ceramic slurry, and printing the ceramic slurry. The SiC-coated Al2O3 composite powder coated in the sol in which the silane coupling agent is added is compact in shell layer and uniform in dispersion, the coating effect of coating the silicon carbide ceramic powder by a sol-gel method can be improved by adding the silane coupling agent, the viscosity of the photocuring 3D printing silicon carbide ceramic slurry can be effectively reduced, and finally the mechanical property of a printed piece is improved.

Description

Technical Field

[0001] This invention belongs to the field of ceramic photopolymerization 3D printing technology, specifically relating to a photopolymerization 3D printing silicon carbide ceramic slurry based on coupling agent modified sol and its preparation method. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Silicon carbide (SiC) ceramic materials have a wide range of applications in aerospace (such as turbine engine combustion chamber liners, thermal protection system panels, and satellite antenna reflectors), biomedicine (such as artificial joint coatings or dental implant abutments after surface modification with hydroxyapatite), and electronic information (such as heat dissipation substrates for high-frequency devices in 5G base stations) due to their excellent high-temperature strength, wear resistance, corrosion resistance, and good thermal insulation properties.

[0004] Photopolymer 3D printing technology requires ceramic slurries to meet the following criteria: high solid content, low viscosity (to ensure uniform interlayer spreading), and large curing depth (to guarantee interlayer bonding strength). However, SiC powder has a dark color and a high absorption rate of ultraviolet light, resulting in a shallow light penetration depth and poor photopolymerization effect. In addition, SiC powder has a high surface energy, making it prone to agglomeration by van der Waals forces. Agglomeration leads to excessively high slurry viscosity, making it difficult to meet the printing flow requirements. Summary of the Invention

[0005] To address the above technical problems, this invention proposes a method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a method for preparing a photocurable silicon carbide ceramic slurry for 3D printing based on a coupling agent-modified sol, comprising the following steps: In a pre-prepared Al(OH)3 sol system, a specific proportion of silane coupling agent was introduced to modify silicon carbide (SiC) powder. The amount of silane coupling agent added was 1-8 wt% of the mass of silicon carbide powder. After heat treatment, drying, fine grinding and controlled sintering, SiC@Al2O3 composite powder with core-shell structure was successfully prepared.

[0007] SiC@Al2O3 composite powder was mixed with photosensitive resin, dispersant and photoinitiator to obtain photocurable 3D printing ceramic slurry.

[0008] Secondly, the present invention provides a photocurable silicon carbide ceramic slurry for 3D printing based on a coupling agent-modified sol, which is prepared by the aforementioned preparation method.

[0009] Thirdly, the present invention provides the application of the photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent modified sol in the fields of aerospace, biomedicine and electronic information.

[0010] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: Improving interfacial compatibility: Adding a certain amount of silane coupling agent to the sol can make the coated SiC powder disperse more evenly in the sol. Silanes with long alkyl chains (such as KH570) can coat hydrophobic particles (such as SiC) to build "molecular bridges" between the inorganic coating Al2O3 and the organic SiC, thereby improving the interfacial compatibility between the two, reducing the coating porosity, and obtaining a uniform and dense Al2O3 coating layer, thus improving the coating effect.

[0011] Enhanced interfacial adhesion: The hydrolysis of silane coupling agents forms silanol groups (Si-OH). These silanol groups can undergo co-condensation reactions with silanol groups in the sol-gel network to form strong Si-O-Si chemical bonds, or they can form chemical bonds with hydroxyl groups on the surface of inorganic substrates (such as metals, glass, and ceramics). Simultaneously, they are anchored to the organic coating material through chemical bonds or strong interactions (such as ionic bonds, hydrogen bonds, and van der Waals forces). The strength of this chemical bonding is much higher than that of physical adsorption, greatly improving the adhesion and stability of the coating layer.

[0012] Participation in Gel Network Formation: Silane coupling agents are themselves a silicon source. Their hydrolyzed silanol groups can directly participate in the sol-gel condensation reaction. By controlling the amount of silane coupling agent added, a small portion can be combined with the Al2O3 coating to form the final network structure. This makes the coupling agent molecule no longer a simple surface modifier, but part of the structure, thus more firmly binding the two materials with vastly different properties, SiC and Al2O3. Adding too much silane coupling agent will result in an excessive number of silanol groups, competing with the formation of the Al2O3 coating layer, leading to an incomplete Al2O3 coating. This will cause an increase in the viscosity of the ceramic slurry, affecting the printing effect. Excessive SiO2, the product of silanol groups, will also reduce the mechanical properties of the printed parts. Therefore, strictly controlling the amount of silane coupling agent added is crucial for coating.

[0013] Reducing surface cracking: The hydrophilic groups (Al(OH)3) in the gel network are a major cause of high drying stress. These hydroxyl groups adsorb a large amount of water, causing the water to evaporate in large quantities only when the pressure drops, resulting in severe shrinkage of the gel network. Adding a certain amount of silane coupling agent to the sol allows organic groups to be grafted onto the surface of the gel network, changing the surface of the gel pores from hydrophilic to hydrophobic. This reduces the amount of physically adsorbed water. More importantly, the hydrophobic surface itself repels water, allowing the solvent to be discharged under relatively high pressure, reducing the time and pressure required for the drying stage. This helps to reduce surface cracks in the gel and makes the coating layer more intact.

[0014] Improving the mechanical properties of printed parts: The SiC@Al2O3 powder prepared using this method can effectively increase the printing thickness, reduce the viscosity of the ceramic slurry, and ultimately improve the mechanical properties of the printed parts. This invention features a simple process, short preparation time, low production cost, and significant improvement effects. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 This is a process flow diagram of the preparation process of silicon carbide powder photocurable 3D printing ceramic slurry for coupling agent modified sol according to an embodiment of the present invention; Figure 2 This is a SEM image of the silicon carbide ceramic powder in the coupling agent modified sol before coating in this invention; Figure 3 This is a SEM image of the SiC@Al2O3 powder in Example 1 (heating temperature was 60°C). Figure 4 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 1 (heating temperature is 30℃). Figure 5 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 2 (heating temperature is 90℃). Figure 6 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 3; Figure 7 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 4; Figure 8 This is a comparison chart of the rheological properties of silicon carbide ceramic slurry in the embodiments and comparative examples of the present invention; Figure 9 This is a comparison chart of the mechanical properties of silicon carbide ceramic slurry in the embodiments and comparative examples of the present invention. Detailed Implementation

[0017] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] In a first aspect, the present invention provides a method for preparing a photocurable silicon carbide ceramic slurry for 3D printing based on a coupling agent-modified sol, comprising the following steps: In a pre-prepared Al(OH)3 sol system, a specific proportion of silane coupling agent was introduced to modify silicon carbide (SiC) powder. The amount of silane coupling agent added was 1-8 wt% of the mass of silicon carbide powder. After heat treatment, drying, fine grinding and controlled sintering, SiC@Al2O3 composite powder with core-shell structure was successfully prepared.

[0019] SiC@Al2O3 composite powder was mixed with photosensitive resin, dispersant and photoinitiator to obtain photocurable 3D printing ceramic slurry.

[0020] As shown above, SiC powder has a darker color and a higher absorption rate of ultraviolet light, resulting in a smaller light penetration depth and thus a poorer photocuring effect for SiC-based photocurable 3D printing ceramic slurry.

[0021] The inventors attempted to coat the surface of SiC powder with an Al2O3 modified layer using a sol-gel method to reduce the absorbance of SiC powder. The principle is that the aluminum source precursor is hydrolyzed to generate Al(OH)3 sol (the specific preparation method is as follows: aluminum isopropoxide, nitric acid and deionized water are mixed in a molar ratio of 1:(0.01~0.5):(30~100), heated to 60~85℃ and magnetically stirred at a stirring speed of 300~500 r / min until the aluminum isopropoxide is completely dissolved and the Tyndall effect appears in the solution. Then, heating and stirring are continued for 1~3 h to obtain a uniform and stable Al(OH)3 sol system. Subsequently, it condenses on the SiC surface to form a gel layer, and then forms an Al2O3 layer during the subsequent drying and sintering process.

[0022] However, due to the high surface energy of SiC powder, it is easy to agglomerate in Al(OH)3 sol. The particles inside the agglomerate are tightly packed, making it difficult for the sol to penetrate into the agglomerate. Instead, the sol can only deposit on the outer surface of the agglomerate, resulting in a thick Al2O3 layer on the outside of the agglomerate, while the coating layer on the surface of the internal particles is very thin or even uncoated.

[0023] Insufficiently coated or excessively thin coated SiC particles retain high light absorption characteristics (SiC has a high absorption rate for ultraviolet light). When ultraviolet light irradiates the slurry, these areas preferentially absorb more light energy, resulting in a shallower light penetration depth than in the case of ideal uniform coating. Insufficient light penetration depth directly limits the thickness of a single-layer curing process, potentially leading to reduced interlayer bonding strength (incomplete interlayer fusion), and ultimately affecting the mechanical properties of the printed part (such as flexural strength and density).

[0024] Because the thickness of the particle coating layer varies greatly at different locations in the composite powder, the overall light absorption characteristics of the slurry are inconsistent. This results in areas with a thicker Al2O3 layer having weaker absorption of ultraviolet light and slower curing speeds, while areas without or with a thinner Al2O3 layer have stronger absorption of ultraviolet light and faster curing speeds. This difference in curing speed can lead to uneven curing levels in different areas of the same layer, potentially causing localized shrinkage stress concentration and reducing the dimensional accuracy and structural stability of the printed parts.

[0025] Agglomerates of SiC particles can lead to uneven particle distribution in the slurry. During the layup process of photopolymer printing, these agglomerates may clog the doctor blade or cause inconsistent coating thickness (localized over-dense or under-dense particle buildup). Uneven coating further amplifies the unevenness of photopolymerization, ultimately affecting the surface quality of the printed part (e.g., excessively high roughness) and the uniformity of its internal structure (e.g., uneven porosity distribution).

[0026] Silane coupling agents (such as alkoxy-containing silanes) hydrolyze to generate silanol groups (-Si-OH), which can undergo condensation reactions with hydroxyl groups on the SiC surface to form covalent bonds (-Si-O-SiC), thereby grafting organic groups (such as alkyl and vinyl groups) onto the SiC surface. These organic groups reduce the surface energy of SiC through steric hindrance or hydrophobic interactions, reducing interparticle attraction, significantly inhibiting agglomeration, and improving the dispersion uniformity of the powder in the Al(OH)3 sol mixture. Improved SiC dispersibility means individual particles are adequately isolated, allowing the sol to uniformly contact each particle surface, promoting uniform condensation of Al(OH)3 gel on the SiC surface. This indirectly improves the final coating quality of the SiC@Al2O3 composite powder, reducing problems such as poor photocuring effects (e.g., insufficient light penetration depth, uneven curing) caused by uneven coating.

[0027] The effectiveness of silane coupling agents is directly related to the dosage and heating temperature. Insufficient dosage results in incomplete and uneven dispersion of the powder, leading to minimal improvement in sol coating. Excessive dosage, on the other hand, causes condensation of the coupling agent itself, hindering the formation of the coating layer after solvent removal from the sol. Furthermore, heating temperature directly affects the effectiveness of silane coupling agents. Too low a temperature leads to excessively long hydrolysis times, increasing experimental time and negatively impacting sol coating; too high a temperature directly causes the silane coupling agent to fail.

[0028] Furthermore, the core of photopolymer 3D printing slurry is the composite system of SiC powder and photosensitive resin. SiC@Al2O3 composite powder without silane coupling agent-modified sol has a highly polar surface, resulting in poor compatibility and weak interfacial bonding with non-polar or weakly polar photosensitive resins (such as acrylates). The other end of the silane coupling agent (such as vinyl or epoxy groups) can chemically bond or physically entangle with active groups (such as double bonds) in the resin, forming an "inorganic-coupling agent-organic" structure. This interface optimization effectively improves the bonding strength between SiC and the resin, preventing a decrease in mechanical properties of the printed parts due to interfacial debonding after curing.

[0029] In summary, by adding silane coupling agents and silicon carbide powder to the sol, the agglomeration problem caused by the high surface energy of silicon carbide was solved, the surface tension of the gel network was reduced, the drying stress was reduced, which helped to form a complete, crack-free coating layer and optimize its interfacial compatibility with organic resin and subsequent coating layers, ultimately improving the performance and forming quality of photocurable 3D printing slurry.

[0030] In some embodiments, the silane coupling agent accounts for 1 to 5 wt% of the silicon carbide powder by mass. For example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0031] Preferably, the silane coupling agent accounts for 1 to 3 wt% of the silicon carbide powder.

[0032] In some embodiments, the particle size of the silicon carbide powder is 0.1-40 μm.

[0033] In some embodiments, the silane coupling agent is selected from at least one of KH560 (γ-(2,3-epoxypropoxy)propyltrimethoxysilane), KH550 (γ-aminopropyltriethoxysilane), or KH570 (γ-(methacryloyloxy)propyltrimethoxysilane).

[0034] In some embodiments, the heating temperature is 50-60°C and the heating time is 10-40 h.

[0035] During the low-temperature heating stage at 50-60℃, the core objective is to gently dry the sol and form a uniform Al(OH)3 gel coating layer under the action of the silane coupling agent, laying the foundation for the subsequent high-temperature sintering to prepare high-quality SiC@Al2O3 composite powder. The key to this step lies in temperature control, requiring a balance between the dissolution rate of the silane coupling agent, the solvent evaporation rate, and the integrity of the coating structure.

[0036] When the heating temperature is too low, the dissolution rate of the silane coupling agent and the evaporation rate of the solvent are slow, which may lead to solvent residue and a longer reaction time. This can generate bubbles or pores during subsequent high-temperature sintering, reducing the density of the composite powder. It also prevents the aluminum hydroxide sol from fully gelling, resulting in an uneven coating layer and a loose structure. During subsequent sintering, it is difficult to form a dense Al2O3 shell, thus affecting the interfacial bonding strength of the SiC@Al2O3 composite powder. When the heating temperature is too high, the silane coupling agent loses its effectiveness due to self-condensation at high temperatures, and the solvent evaporates too quickly. This may cause the aluminum hydroxide sol to shrink too rapidly, generating microcracks and disrupting the continuity of the coating layer, leading to defects in the Al2O3 shell during subsequent sintering. Therefore, a suitable heating temperature is crucial for controlling the hydrolysis of the silane coupling agent and ensuring its effective function in the sol.

[0037] In some embodiments, the drying is vacuum drying, with a drying temperature of 80-120°C and a drying time of more than 5 hours. A suitable drying temperature and sufficient drying time ensure that the powder is sufficiently dry, reducing powder agglomeration and facilitating sieving.

[0038] Preferably, the dried solid product is ground, sieved through a 100-mesh sieve, and then sintered.

[0039] In some embodiments, the sintering is carried out in an inert atmosphere, and the sintering procedure is to heat the temperature by 2~5°C to 1000-1200°C, hold it for 100-150 min, and then cool it with the furnace.

[0040] Preferably, the sintering temperature is 1100℃ and the sintering time is 120 min.

[0041] In some embodiments, the mass fraction of SiC powder in the photocurable 3D printing ceramic slurry is 40-70 wt%, the mass fraction of photosensitive resin is 20-36 wt%, and the mass fraction of dispersant is 1-6 wt%.

[0042] Preferably, the photosensitive resin is selected from at least one of 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), and acrylamide morpholine (ACMO).

[0043] Preferably, the dispersant is selected from at least one of KOS110, BYK103, OA, or BYK110.

[0044] Preferably, the photoinitiator is selected from at least one of TPO, 1173, or BAPO.

[0045] Secondly, this invention provides a photocurable silicon carbide ceramic slurry for 3D printing based on a coupling agent-modified sol, which is prepared by the aforementioned preparation method.

[0046] Thirdly, the present invention provides the application of the photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent modified sol in the fields of aerospace, biomedicine and electronic information.

[0047] The present invention will be further described below with reference to the embodiments.

[0048] Example 1 A method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol, such as... Figure 1 As shown, it includes the following steps: 8 g of aluminum isopropoxide and nitric acid (1 mol / L) were slowly added dropwise to 150 g of deionized water and mixed thoroughly. The mixture was heated (65°C) and stirred with a magnetic stirrer at 300 r / min for 3 h until an alumina sol was formed. 4 g of SiC powder with a particle size of 20 μm and 2 wt% of silane coupling agent KH570 (relative to SiC powder) were added to Al(OH)3 gel. The temperature was lowered to 60 °C and the mixture was stirred for 2.5 h with magnetic stirring at a speed of 500 r / min to obtain SiC@Al2O3 composite powder mixture.

[0049] The SiC@Al2O3 composite powder mixture was placed in a drying oven and heated to 100℃ for more than 10 hours. The dried SiC@Al2O3 composite powder was then transferred to a mortar and crushed at room temperature through a 100-mesh sieve to obtain a uniform powder.

[0050] The uniform powder was sintered in a tube furnace with N2 as the protective gas. The specific sintering procedure was as follows: In the first stage, the temperature was increased to 1100℃ at a first heating rate of 5℃ under room temperature conditions, and then held for 2 hours. After the holding time, the sintered body was allowed to cool naturally in the tube furnace for 10 hours. SEM images of the SiC@Al2O3 powder were obtained. Figure 3 .

[0051] Figure 2 This is a powder SEM image (raw SiC) of the coupling agent modified sol before photopolymerization 3D printing of silicon carbide coating in this invention.

[0052] SiC@Al2O3 composite powder (70%), photosensitive resins TMPTA (6%), HDDA (14%), and ACMO (7%), dispersant BYK110 (3%), and photoinitiator TPO (6% - relative to resin mass) were mixed. The percentages (%) represent mass percentages. The mixture was then stirred using a magnetic stirrer at 350 rpm for 30 min. The rheological properties of the ceramic slurry were tested. (See attached table). Figure 8 .

[0053] The ceramic slurry from Example 1 was poured into the feed tank of a digital light processing SLA molding equipment. A 3D model of the ceramic part was designed using 3D modeling software and imported into the photopolymerization molding equipment. Photopolymerization printing was performed at a scanning speed of 4000 mm / s, a laser power of 870 MW, and a layer thickness of 40 μm to obtain a SiC@Al2O3 ceramic green body. The SiC@Al2O3 ceramic green body was then subjected to programmed temperature rise under the following conditions: heating to 150℃ at a rate of 1℃ / min and holding for 1.5 h; heating to 200℃ at a rate of 0.1℃ / min and holding for 2 h; heating to 350℃ at a rate of 0.1℃ / min and holding for 2 h; heating to 520℃ at a rate of 0.2℃ / min and holding for 3 h; and heating to 800℃ at a rate of 1℃ / min and holding for 0.5 h. h, a SiC@Al2O3 ceramic preform was obtained; further heating initiated a carbothermic reduction reaction. The heating process was as follows: the temperature was increased from 800℃ to 1500℃ at a rate of 1℃ / min, and held for 2 hours to obtain the silicon carbide ceramic printed part. The mechanical properties of the ceramic printed part were tested, see [link to relevant documentation]. Figure 9 .

[0054] Mechanical property testing primarily focuses on the bending strength of the printed parts. A three-point bending tester is used to test the mechanical properties of silicon carbide ceramic printed parts (GB / T 6569-1986). The three-point bending tester mainly consists of a loading system, a support system, and a measuring system. During testing, the test piece is placed on two support points, and then a force is applied to the middle of the specimen through the loading system. The testing system records the amount of deformation and the magnitude of the force exerted on the specimen during the stress process.

[0055] The silicon carbide ceramic slurry prepared in Example 1 has a curing depth of 170 μm.

[0056] Example 2 The difference from Example 1 is that KH570 accounts for 1% of the mass fraction of SiC powder.

[0057] The rest is the same as in Example 1. The rheological and mechanical properties of the silicon carbide ceramic slurry were tested; the rheological property tests are shown in [link to example]. Figure 8 Mechanical performance tests are available in [link / reference]. Figure 9 .

[0058] The silicon carbide ceramic slurry prepared in Example 2 has a curing depth of 135 μm.

[0059] Example 3 The difference from Example 1 is that KH570 accounts for 5% of the mass fraction of SiC powder.

[0060] The rest is the same as in Example 1. The rheological and mechanical properties of the silicon carbide ceramic slurry were tested; the rheological property tests are shown in [link to example]. Figure 8 Mechanical performance tests are available in [link / reference]. Figure 9 .

[0061] The silicon carbide ceramic slurry prepared in Example 3 has a curing depth of 130 μm.

[0062] Comparative Example 1 The difference from Example 1 is that: after adding 4 g of SiC powder with a particle size of 20 μm and 2% KH570 (accounting for 2% of the mass fraction of SiC powder) to the alumina sol, the stirring temperature was adjusted to 30°C, and the stirring was continued for 2.5 h using magnetic stirring at a speed of 500 r / min to obtain a SiC@Al2O3 composite powder mixture.

[0063] Everything else is the same as in Example 1. SEM was used to test the silicon carbide ceramic powder and observe its coating condition, such as... Figure 4 As shown. The rheological and mechanical properties of the silicon carbide ceramic slurry were tested. The rheological property tests are shown in [reference needed]. Figure 8 Mechanical performance tests are available in [link / reference]. Figure 9 .

[0064] The silicon carbide ceramic slurry prepared in Comparative Example 4 had a curing depth of 109 μm.

[0065] Comparative Example 2 The difference from Example 1 is that: 4 g of SiC powder with a particle size of 20 μm and 2% KH570 (accounting for 2% of the mass fraction of SiC powder) were added to the alumina sol, the temperature was raised to 90°C, and the mixture was stirred for 2.5 h with magnetic stirring at a speed of 500 r / min to obtain a SiC@Al2O3 composite powder mixture.

[0066] Everything else is the same as in Example 1. SEM was used to test the silicon carbide ceramic powder and observe its coating condition, such as... Figure 5 As shown. The rheological and mechanical properties of the silicon carbide ceramic slurry were tested. The rheological property tests are shown in [reference needed]. Figure 8 Mechanical performance tests are available in [link / reference]. Figure 9 .

[0067] The silicon carbide ceramic slurry prepared in Comparative Example 2 had a curing depth of 106 μm.

[0068] Comparative Example 3 The difference between this comparative example and Example 1 is that 2 wt% KH570 was added when the Al2O3 layer was coated by sol-gel method in Example 1, while no silane coupling agent was added when the Al2O3 layer was coated by sol-gel method in Comparative Example 3, and SiC@Al2O3 composite powder was obtained after the coating was completed.

[0069] Everything else is the same as in Example 1. SEM was used to test the silicon carbide ceramic powder and observe its coating condition, such as... Figure 6 As shown. The rheological and mechanical properties of the silicon carbide ceramic slurry were tested. The rheological property tests are shown in [reference needed]. Figure 8 Mechanical performance tests are available in [link / reference]. Figure 9 .

[0070] The silicon carbide ceramic slurry prepared in Comparative Example 3 had a curing depth of 98 μm.

[0071] Comparative Example 4 The difference from Example 1 is that: SiC powder, KH570, and anhydrous ethanol were mixed and ball-milled in a specific ratio, with KH570 accounting for 2% of the SiC powder by mass, the mass ratio of anhydrous ethanol to SiC powder being 2:1, the ball-to-powder ratio being 5:1, the ball mill speed being 3000 r / min, and the ball milling time being 8 h. After ball milling, the modified powder solution was washed three times with anhydrous ethanol, then dried and ground to obtain modified SiC powder. Subsequently, the modified SiC powder was added to alumina sol.

[0072] Everything else is the same as in Example 1. SEM was used to test the silicon carbide ceramic powder and observe its coating condition, such as... Figure 7 As shown. The rheological and mechanical properties of the silicon carbide ceramic slurry were tested. The rheological property tests are shown in [reference needed]. Figure 8 Mechanical performance tests are available in [link / reference]. Figure 9 .

[0073] The silicon carbide ceramic slurry prepared in Comparative Example 4 had a curing depth of 118 μm.

[0074] Figure 3 This is a SEM image of the SiC@Al2O3 powder in Example 1 (heating temperature was 60°C). Figure 4 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 1 (heating temperature is 30℃). Figure 5 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 2 (heating temperature: 90℃). (From...) Figure 3 , Figure 4 and Figure 5It is known that when using the sol-gel method to coat materials, a heating temperature of 60℃ can result in a relatively uniform Al2O3 coating thickness on the surface of SiC powder, a high coating rate, and the absence of defects such as cracks and pores. Figure 3 As shown. At a heating temperature of 30℃, due to the low temperature, the coupling agent hydrolysis time is too long, limiting its effectiveness and leading to an excessively long gel formation time. This results in an uneven Al2O3 coating on the SiC powder surface, with some SiC powder surfaces not being fully coated, such as... Figure 4 As shown. The heating temperature was 90℃. Due to the excessively high heating temperature, the silane coupling agent lost its effectiveness, resulting in poor Al2O3 coating and excessively rapid formation, leading to cracks, as shown. Figure 5 As shown.

[0075] Therefore, heating temperature is closely related to the function of silane coupling agents. Temperature directly affects the speed and extent of key steps such as hydrolysis and condensation of silane coupling agents, thus directly impacting the coating effect. Too low a temperature results in a very slow hydrolysis rate of the silane coupling agent, and incomplete hydrolysis reduces coupling efficiency. A suitable heating temperature is beneficial for the silane coupling agent to function effectively, improving the uniformity and thickness of the Al2O3 coating layer and reducing coating defects such as core-shell cracking. Too high a temperature leads to excessively rapid hydrolysis of the silane coupling agent, resulting in self-condensation, where silane molecules link together to form oligomers or precipitates before they can function, significantly reducing the coupling effect.

[0076] Figure 6 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 3; Figure 7 This is a SEM image of the SiC@Al2O3 powder in Comparative Example 4. According to... Figure 6 , 7 It can be seen that, Figure 6 The lack of silane coupling agent during the coating process resulted in poor dispersibility of SiC@Al2O3 powder, with all the powder piling up together, leading to poor coating effect. Figure 7 Although 2% silane coupling agent was added, resulting in good powder dispersibility, the effect of the coupling agent in the formation of the Al2O3 layer was not significant because it first coated and modified the SiC powder. The coating effect was significantly worse than in the example where the silane coupling agent was directly added to the sol. Therefore, whether or not to add silane coupling agent, and the order of addition, greatly affects the coating effect. Adding an appropriate amount of silane coupling agent and choosing a suitable order of addition can effectively improve the coating effect.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol, characterized in that: Includes the following steps: In a pre-prepared Al(OH)3 sol system, a specific proportion of silane coupling agent was introduced to modify silicon carbide (SiC) powder. The amount of silane coupling agent added was 1-8 wt% of the mass of silicon carbide powder. After heat treatment, drying, fine grinding and controlled sintering, SiC@Al2O3 composite powder with core-shell structure was successfully prepared.

2. The method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol according to claim 1, characterized in that: The silane coupling agent accounts for 1-5 wt% of the silicon carbide powder by mass. Preferably, the silane coupling agent accounts for 1 to 3 wt% of the silicon carbide powder.

3. The method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol according to claim 1, characterized in that: The heating temperature is 50-60℃, and the heating time is 10-40 h.

4. The method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol according to claim 1, characterized in that: The drying process is vacuum drying, with a drying temperature of 80~120℃ and a drying time of more than 5 hours. Preferably, the dried solid product is ground, sieved through a 100-mesh sieve, and then sintered.

5. The method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol according to claim 1, characterized in that: The sintering is carried out in an inert atmosphere, and the sintering procedure is to raise the temperature by 2~5℃ to 1000~1200℃, hold for 100~150 min, and then cool with the furnace. Preferably, the sintering temperature is 1100 ℃ and the sintering time is 120 min.

6. The method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol according to claim 1, characterized in that: In the photopolymerizable 3D printing ceramic slurry, the mass fraction of SiC powder is 40~70 wt%, the mass fraction of photosensitive resin is 20~36 wt%, the mass fraction of dispersant is 1~6 wt%, and the mass fraction of photoinitiator is 3~8 wt%.

7. The method for preparing photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent-modified sol according to claim 6, characterized in that: The photosensitive resin is selected from at least one of 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), and acrylamide morpholine (ACMO).

8. The method for preparing photocurable 3D printing silicon carbide ceramic slurry based on coupling agent modified sol according to claim 6, characterized in that: The dispersant is selected from at least one of KOS110, BYK103, OA or BYK110; Preferably, the photoinitiator is selected from at least one of TPO, 1173, or BAPO.

9. A photocurable sol-gel based on a coupling agent-modified sol for 3D printing silicon carbide ceramics, characterized in that: It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the photocurable silicon carbide ceramic slurry for 3D printing based on coupling agent modified sol as described in claim 9 in the fields of aerospace, biomedicine and electronic information.

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