Preparation method of multi-component photocured composite ceramic

Abstract

The application discloses a kind of preparation methods of multi-component photocuring composite ceramic, by adding tetraethyl orthosilicate in multi-component ceramic powder, obtain modified ceramic powder, then it is mixed with photosensitive resin prepolymer, dispersing agent, diluent, photo initiator uniformly, subsequently sequentially through DLP photocuring 3D printing, debinding, sintering after obtaining composite ceramic.The application utilizes the hydrolysis condensation characteristics of tetraethyl orthosilicate, makes it react on the surface of different ceramic powder, uniformly coats silica layer, can improve the phenomenon of curing uneven caused by the difference of refractive index, absorbance and reaction sensitivity of powder;The layer has low refractive index, can also solve the problem of insufficient curing depth of non-oxide ceramic.In addition, during sintering, the silica layer forms Y-Ce-Si-O ternary eutectic system with CeO2 and Y2O3, reduces the initial temperature of liquid phase, further promotes sintering densification, provides a feasible scheme for composite ceramic, high-entropy ceramic 3D printing.

Description

Technical Field

[0001] This invention belongs to the field of ceramic additive manufacturing technology and relates to a method for preparing multi-component photocurable composite ceramics. Background Technology

[0002] Photopolymer 3D printing technology is an efficient, convenient, and high-precision ceramic forming process. It can produce ceramic parts with regular internal structures and high degree of complexity and fineness without the need for molds, which is of great significance to the development of high-performance ceramic materials.

[0003] SiAlON (silicon-aluminum-oxynitride) ceramics, also known as silon ceramics, possess high strength, high toughness, excellent high-temperature stability, good oxidation resistance, and wear resistance, making them widely used in extreme environments such as high-temperature, heavy-load, and corrosive conditions. This material can be synthesized from Si3N4, AlN, and Al2O3 in a specific ratio. Depending on the silicon-to-aluminum ratio, different crystal structures can be prepared, primarily including α-SiAlON and β-SiAlON. As a high-performance ceramic material, silon ceramics have wide applications in aerospace, machinery, automotive, and electronics industries.

[0004] However, most current photocurable ceramic slurries are single-component, and the preparation of multi-component photocurable ceramic slurries is quite difficult. When preparing high-performance composite ceramics, different ceramic powders need to be added. Due to differences in refractive index, absorbance, and reactivity, photosensitive ceramic slurries prepared with different powder components are prone to uneven curing during exposure, resulting in excess serrated residues and affecting printing accuracy. Furthermore, Si3N4 and AlN, as non-oxide ceramics, have high surface free energy, leading to poor compatibility with resins. During the preparation of photosensitive ceramic slurries, particle agglomeration easily occurs, and the curing depth is low, resulting in weak interlayer bonding during photocuring printing.

[0005] Chinese patent CN113548899A discloses a silicon nitride ceramic slurry, silicon nitride ceramic, and preparation method based on powder modification. By oxidizing silicon nitride and adding a silane coupling agent for modification, the curing depth and stability of the Si3N4 ceramic slurry can be effectively improved. However, this method requires the oxidation of non-oxides. Even with maximum powder spreading during the oxidation process, the accumulated powder cannot guarantee the uniformity of the oxide layer thickness. Furthermore, the oxidation treatment alters the atomic structure and bonding mode of the material, leading to changes in its chemical composition, structure, and properties, thus affecting the original excellent properties of the powder.

[0006] Based on this, the present invention aims to modify multi-component ceramic powder to obtain photocurable ceramic slurry, and then prepare SiAlON composite ceramics with excellent performance. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention aims to provide a method for preparing multi-component photocurable composite ceramics. The method involves adding tetraethyl orthosilicate (TEOS) to multi-component ceramic powder to obtain modified ceramic powder, which is then uniformly mixed with photosensitive resin prepolymer, dispersant, diluent, and photoinitiator. The mixture is subsequently subjected to DLP photocuring 3D printing, debinding, and sintering to obtain the composite ceramic. This invention utilizes the hydrolytic condensation properties of TEOS to cause a reaction on the surfaces of different ceramic powders, thereby uniformly coating the powder surfaces with a layer of silica. This improves the uneven curing phenomenon caused by differences in powder refractive index, absorbance, and reaction sensitivity. Simultaneously, the coated silica layer possesses low refractive index characteristics, effectively solving the problem of insufficient curing depth in non-oxide ceramics. Furthermore, during the sintering process, the coated silica layer forms a ternary eutectic system (Y-Ce-Si-O) with CeO2 and Y2O3, which lowers the liquid phase initiation temperature and further promotes sintering densification, providing a feasible solution for 3D printing of composite ceramics, high-entropy ceramics, etc.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a multi-component photocurable composite ceramic comprises the following steps in sequence:

[0010] S1. Preparation of modified ceramic powder;

[0011] S11. After mixing Si3N4, AlN and Al2O3 evenly, a mixed ceramic powder is obtained. The mixed ceramic powder and sintering aid are added together to anhydrous ethanol. The solid-liquid ratio of the mixed ceramic powder to anhydrous ethanol is 0.3~0.5 g / mL, and a solid-liquid mixture is obtained.

[0012] S12. Place the zirconia grinding beads and the solid-liquid mixture in a ball mill. The mass ratio of the zirconia grinding beads to the ceramic powder mixed in the solid-liquid mixture is 3:1. Ball mill at 200~250 r / min for 2 h. Then add tetraethyl orthosilicate solution to obtain the modified precursor mixture.

[0013] S13. Place the modified precursor mixture in a container and heat it in a water bath at 50~80℃ while stirring for 3~6 h. Wash it with ethanol by centrifugation until the supernatant in the centrifuge tube is completely transparent and free of turbidity to obtain the modified ceramic powder precursor. Place the modified ceramic powder precursor in an oven and dry it at 70~90℃ for 10~12 h. Grind the dried material to 100 mesh to obtain the modified ceramic powder.

[0014] S2. Preparation of photocurable ceramic slurry;

[0015] S21. Mix the photosensitive resin prepolymer, dispersant, diluent and photoinitiator evenly to obtain a mixture;

[0016] S22. Add the above modified ceramic powder to the mixture in batches, stir evenly, ball mill at 200~250 r / min for 3~6 h, and after vacuum degassing, obtain a light-cured ceramic slurry with a solid content of 40~45 vol.%;

[0017] S3. Preparation of composite ceramic green bodies;

[0018] Using the above-mentioned photocurable ceramic slurry as raw material, a composite ceramic green body was obtained by 3D printing using a DLP photocurable printer;

[0019] S4. Preparation of composite ceramics;

[0020] The composite ceramic green body was degreased and sintered under a nitrogen atmosphere to obtain the composite ceramic.

[0021] As a limitation of the preparation method of the present invention, in step S11, the molar ratio of Si3N4, AlN and Al2O3 is 5:1:1; the sintering aid is a compound of CeO2 and Y2O3 with a molar ratio of 2.2:1, and the amount of sintering aid added is 8 wt.% of the mass of the mixed ceramic powder.

[0022] As another limitation of the preparation method of the present invention, in step S12, the preparation process of the tetraethyl orthosilicate solution is as follows: after mixing anhydrous ethanol and deionized water evenly, the pH of the solution is adjusted to 3 using HCl, tetraethyl orthosilicate is slowly poured into it, and the mixture is stirred at 10~30 rpm for 0.5 h; the volume ratio of anhydrous ethanol to deionized water and tetraethyl orthosilicate is 5:10:1.

[0023] As a third limitation of the preparation method of the present invention, in step S12, the solid-liquid ratio of the mixed ceramic powder to the tetraethyl orthosilicate solution is 2~5 g / mL.

[0024] In this invention, the solid-liquid ratio of the mixed ceramic powder to the tetraethyl orthosilicate solution affects the curing depth and rheological properties of the photosensitive ceramic slurry. At this ratio, it helps reduce the scattering loss of ultraviolet light in the slurry, thereby increasing the curing depth. If the ratio is greater than this, the increased SiO2 coating thickness further expands the specific surface area of ​​the powder, reducing the amount of freely flowing liquid in the system and leading to increased slurry viscosity. If the ratio is less than this, the SiO2 produced by the hydrolysis and condensation of tetraethyl orthosilicate cannot completely coat all the powder surfaces, resulting in uneven curing and excessive serrated residue, affecting printing accuracy.

[0025] As a fourth limitation of the preparation method of the present invention, in step S21, the preparation process of the photosensitive resin prepolymer is as follows: after mixing the multifunctional resin monomer and the monofunctional resin monomer at a mass percentage of 7:3, the mixture is ball-milled at 230 r / min for 0.5~1 h to obtain the photosensitive resin prepolymer.

[0026] The multifunctional resin monomer is at least two of trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA), and 1,6-hexanediol diacrylate (HDDA); the monofunctional resin monomer is at least one of N-vinylpyrrolidone (NVP), isobornyl acrylate (IBOA), 4-acryloylmorpholine (ACMO), and N,N-dimethylacrylamide (DMAA).

[0027] As a fifth limitation of the preparation method of the present invention, in step S21, the dispersant is BYK-111 or JH-21, and the amount of dispersant added is 1-3 wt.% of the mass of the modified ceramic powder; the diluent is methyl methacrylate (MMA) or γ-glycidyl etheroxypropyltrimethoxysilane (KH-560), and the amount of diluent added is 1-5 wt.% of the mass of the modified ceramic powder; the photoinitiator is phenylphosphine dioxide 819 or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and the amount of photoinitiator added is 1-3 wt.% of the mass of the photosensitive resin prepolymer.

[0028] As a sixth limitation of the preparation method of the present invention, in step S3, the wavelength of the light source of the DLP photopolymerization printer is 405 nm and the light intensity is 60 mW / cm². 2 The single-layer exposure time is 2000 ms, and the blade layer thickness is 50 μm.

[0029] As a seventh limitation of the preparation method of the present invention, in step S4, the degreasing process is carried out in the following order:

[0030] (a) In the first heating stage, the temperature is increased from room temperature to 110-120℃ at a heating rate of 1-2℃ / min, and held for 0.5-1h;

[0031] (b) In the second heating stage, the temperature is increased from 110~120℃ to 580~600℃ at a heating rate of 0.2~0.5℃ / min, and held for 0.5~1 h;

[0032] (c) Cooling stage: The furnace is cooled to room temperature.

[0033] In this invention, the degreasing process affects the density and mechanical properties of subsequent structural components. During the first heating stage, as the temperature rises from room temperature to 110-120°C at a rate of 1-2°C / min, the moisture adsorbed in the green body, along with incompletely polymerized or free resin molecules, evaporates, thus initially dehydrating the green body and removing uncured resin. If the heating rate is less than 1°C / min during this stage, the evaporation time of moisture and free resin is prolonged, causing moisture and free resin molecules to locally accumulate in the green body before reaching the boiling point, thereby preventing the green body from reaching its boiling point. Rapid evaporation generates internal stress, causing cracks in the green body. If the heating rate exceeds 2℃ / min, moisture and free resin will rapidly vaporize, leading to delamination or even cracking of the green body. If the temperature exceeds 120℃ during this stage, the evaporation rate of free resin will accelerate, resulting in excessive internal stress and cracking of the green body. If the temperature is below 110℃, moisture and free resin molecules will not evaporate completely, leaving residues inside the green body. These residues will then decompose simultaneously with the organic matter in the subsequent high-temperature degreasing stage, generating a large amount of gas and causing structural damage to the green body. Holding the temperature for 0.5~1 h ensures that the moisture and free resin inside the green body evaporate fully and evenly, avoiding residues, and also ensures that the overall temperature of the green body is uniform, reducing thermal stress.

[0034] In the second heating stage, when the temperature is increased from 110~120℃ to 580~600℃ at a rate of 0.2~0.5℃ / min, the main resin organic matter in the green body undergoes thermal decomposition, causing the resin molecules to decompose into smaller molecules and volatilize. If the heating rate is less than 0.2℃ / min in this stage, the decomposition time of the resin organic matter will be prolonged, leading to local accumulation of the decomposed small molecules. This accumulation will block the pores and affect subsequent glue removal. If the heating rate is greater than 0.5℃ / min, the resin organic matter will decompose too quickly, and the rate of gas production will exceed the diffusion rate, resulting in cracking and disintegration of the green body. If the temperature is greater than 600℃ in this stage, the decomposition rate of the resin organic matter will be too fast, resulting in cracking of the green body. If the temperature is less than 580℃, the main resin molecules will not decompose sufficiently, resulting in a large amount of resin residue inside the green body. This residue will volatilize simultaneously with the subsequent high-temperature sintering stage, generating a large amount of gas that will damage the green body structure. The purpose of heat preservation for 0.5 to 1 hour is to allow the organic matter in the resin to decompose fully, while ensuring uniform internal temperature of the green body and reducing the damage of internal stress to the structure.

[0035] As an eighth limitation of the preparation method of the present invention, in step S4, the sintering process is carried out in the following order:

[0036] (d) In the first heating stage, the temperature is increased from room temperature to 800-1000℃ at a heating rate of 10-15℃ / min, and held for 0.5-1 h;

[0037] (e) In the second heating stage, the temperature is increased from 800-1000℃ to 1300-1400℃ at a heating rate of 5-10℃ / min, and held for 0.5-1 h;

[0038] (f) In the third heating stage, the temperature is increased from 1300~1400℃ to 1600~1850℃ at a heating rate of 2~5℃ / min, and held for 3~5 h;

[0039] (g) Cooling stage: The furnace is cooled to room temperature.

[0040] In this invention, the sintering process affects the density and grain size of the material, thereby influencing its mechanical properties. Specifically: In the first stage, residual organic impurities in the green body undergo pyrolysis and volatilization, removing organic matter remaining from the degreasing stage. Simultaneously, sintering aids CeO2 and Y2O3, as well as the SiO2 coating layer on the powder surface which also acts as a sintering aid, undergo lattice activation, laying the foundation for subsequent grain growth. If the heating rate is less than 10℃ / min in this stage, the pyrolysis and volatilization time of organic impurities will be too long, resulting in the green body remaining in the low-temperature region for too long. Impurities are prone to re-adsorption and aggregation on the particle surface, and the sintering aids also... Insufficient activation can occur if the heating rate exceeds 15℃ / min during this stage, causing impurities to volatilize too quickly and resulting in an excessively large temperature gradient within the green body, leading to cracking. If the temperature is below 800℃, the residual organic matter will not pyrolyze completely, and the sintering aid lattice activation will be insufficient, making the residual areas prone to carbonization and forming defects during subsequent sintering, and the sintering aid will not be able to function effectively. If the temperature is above 1000℃, the sintering aid will form a liquid phase prematurely, causing the ceramic particles to sinter prematurely, resulting in uneven distribution of the aid, making it impossible to control uniform particle growth, and affecting the overall density and uniformity. Holding the temperature for 0.5~1 h is to ensure that the residual organic matter volatilizes completely, the sintering aid is fully activated and evenly distributed, and the internal heating temperature of the green body is kept uniform.

[0041] In the second stage, ceramic particles grow, and sintering necks gradually form at the particle contact points. The green body volume slowly shrinks, and the porosity decreases. Sintering aids CeO2 and Y2O3, as well as the SiO2 coating layer on the powder surface, begin to form a liquid phase, filling the micropores between particles and promoting interparticle bonding, thus inhibiting abnormal particle growth. If the heating rate is less than 5℃ / min in this stage, the sintering neck growth will be too slow, the liquid phase formation rate will be slow, and the distribution will be uneven, leading to localized abnormal particle growth. If the heating rate is greater than 10℃ / min in this stage, ... Excessive growth of the sintering neck can lead to an insufficient amount of liquid phase to be evenly distributed, resulting in uneven particle growth and localized stress concentration in the green body, causing cracks or warping. If the temperature is below 1300℃ during this stage, the sintering neck will not grow effectively, and the formation of CeO2, Y2O3, and SiO2 liquid phases will be insufficient, leading to poor interparticle bonding and decreased density. If the temperature is above 1400℃ during this stage, there will be too much liquid phase, causing abnormal grain growth due to excessive liquid phase promotion, resulting in deformation or cracking of the green body. Holding at this temperature for 0.5~1 h is to promote uniform growth of the sintering neck, allowing the sintering aids to fully generate and evenly distribute the liquid phase, thus promoting uniform grain growth.

[0042] The third stage involves densification of the ceramic green body and uniform grain growth. The sintering neck continues to grow and connect to form a continuous ceramic matrix, eliminating a large number of pores and significantly increasing density. If the heating rate is less than 2℃ / min in this stage, the densification process will be too slow, leading to excessive grain growth, abnormal grain growth, and a decrease in mechanical properties. If the heating rate is greater than 5℃ / min, the internal thermal stress of the green body will be too high, resulting in uneven densification and failure to eliminate closed pores to the maximum extent, thus reducing mechanical properties. If the temperature is less than 1600℃ in this stage, the growth of the sintering neck will be slow, preventing further grain growth and resulting in low material density and a decrease in mechanical properties. If the temperature is greater than 1850℃ in this stage, the ceramic matrix will be over-sintered, leading to abnormal grain growth and a sharp decrease in material strength. Holding for 3-5 hours is to ensure sufficient densification of the green body, uniform grain growth, and elimination of internal residual stress.

[0043] The technical solution described above in this invention is a whole, with each step closely related and mutually influencing the others, collectively determining the morphology and properties of the product. This invention modifies ceramic powder using tetraethyl orthosilicate, utilizing the hydrolytic condensation properties of tetraethyl orthosilicate to react on the surfaces of different ceramic powders, thereby uniformly coating the powder surface with a layer of silica. This modification effectively improves the uneven curing phenomenon caused by differences in refractive index, absorbance, and reaction sensitivity among different powders. Simultaneously, the coated silica layer has a low refractive index, further solving the problem of low curing depth in non-oxide ceramics. During sintering, the silica layer coated on the ceramic powder can also form a ternary eutectic system (Y-Ce-Si-O) with the sintering aids CeO2 and Y2O3, lowering the liquidus initiation temperature and further promoting sintering densification. Furthermore, this ceramic powder modification method does not alter the powder's own chemical structure, overcoming the problem in existing technologies where oxidizing the powder can increase the curing depth but sacrifices the powder's inherent properties.

[0044] The multi-component photocurable ceramic slurry of this invention achieves multiple technical effects by introducing a blend of multifunctional and monofunctional resin monomers: firstly, it ensures sufficient polymerizable functional groups in the system, resulting in a high crosslinking density in the printed ceramic preform; secondly, the low viscosity of the monofunctional resin ensures good slurry flowability. Specifically: multifunctional resin monomers have a large molecular weight and therefore the highest viscosity, making it difficult to prepare ceramic slurries with high solid content; while monofunctional resins have low viscosity, their small molecular weight results in low crosslinking density and a fragile network structure. By blending multifunctional and low-functional resins, the viscosity of the system is effectively reduced while maintaining certain curing performance, resulting in better slurry flowability; simultaneously, resin blending can balance the curing speed and enhance mechanical properties.

[0045] The above technical solution has the following advantages or beneficial effects:

[0046] 1. This invention modifies multi-component powders using tetraethyl orthosilicate. Tetraethyl orthosilicate hydrolyzes and condenses on the surface of different ceramic powders, resulting in a uniform coating of silica on the powder surface. This improves the uneven curing phenomenon caused by factors such as refractive index, absorbance, and reaction sensitivity of different powders. The coated silica layer has a low refractive index, which solves the problem of low curing depth of non-oxide ceramics. Furthermore, this ceramic powder modification method does not change the chemical structure of the powder itself, solving the problem that existing technologies, while increasing the curing depth by oxidizing the powder, sacrifice the excellent properties of the powder itself.

[0047] 2. During the sintering process, the SiO2 coating on the surface of the ceramic powder forms a ternary eutectic system (Y-Ce-Si-O) with the sintering aids CeO2 and Y2O3, which lowers the liquid phase initiation temperature to 1300~1400℃. This induces the formation of the liquid phase, promotes the densification of the green body, and helps to improve the mechanical properties of the ceramic material.

[0048] 3. The multi-component photocurable ceramic slurry prepared by the present invention can achieve multiple technical effects by introducing multifunctional resin monomers and monofunctional resin monomers for compounding: on the one hand, it can ensure that there are sufficient polymerizable functional groups in the system, so that the printed ceramic green body has a high crosslinking density; on the other hand, by taking advantage of the low viscosity characteristics of monofunctional resins, it ensures that the slurry has good fluidity.

[0049] 4. The multi-component photocurable ceramic slurry prepared by this invention has the advantages of low viscosity and high stability, as well as large curing depth and high printing accuracy. It can prepare high-performance composite ceramics with complex structures, providing a feasible solution for the application of photocurable 3D printing technology for multi-component composite ceramics, high-entropy ceramics and other materials.

[0050] 5. The SiAlON composite ceramic prepared by this invention has a ceramic density of 2.93 g / cm³. 3 ~3.24g / cm 3 The shrinkage rate is 25%~29%, and the flexural strength is 312.47 MPa~355.46 MPa.

[0051] This invention is applicable to the preparation of multi-component photocurable composite ceramics.

[0052] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0053] Figure 1 The images shown are transmission electron microscope (TEM) images of the modified ceramic powder obtained in step S1 of Example 1 of the present invention, wherein: (a) is a TEM image; (b) is a high-magnification TEM image of region B in image (a); (c) is a high-resolution transmission electron microscope (HRTEM) image of region C in image (a); (d) is an inverse fast Fourier transform (IFFT) image of region D in image (c); (e) is a fast Fourier transform (FFT) image of region D in image (c); (f) is an IFFT image of region E in image (c); and (g) is an FFT image of region E in image (c).

[0054] Figure 2 The image shows the actual composite ceramic green body obtained by steps S1, S2, and S3 in Embodiment 2 of the present invention.

[0055] Figure 3This is a photograph of the SiAlON composite ceramic prepared in Example 3 of the present invention.

[0056] Figure 4 The image shows a cross-sectional SEM image of the SiAlON composite ceramic prepared in Example 3 of this invention.

[0057] Figure 5 The images show the single-layer curing diagrams of the photocurable ceramic slurry obtained in Comparative Example 1 and Example 1 of the present invention, wherein: (a) is a single-layer curing diagram of the photocurable ceramic slurry prepared using unmodified ceramic powder (Comparative Example 1), and (b) is a single-layer curing diagram of the photocurable ceramic slurry prepared using modified ceramic powder (Example 1).

[0058] Figure 6 This is a single-layer curing diagram of the photocurable ceramic slurry obtained in step S2 of Comparative Example 2 of the present invention;

[0059] Figure 7 This is a TEM image of the SiO2 mixed ceramic powder obtained in step S1 of Comparative Example 2 of the present invention at 100 nm.

[0060] Figure 8 This is a TEM image of the SiO2 mixed ceramic powder obtained in step S1 of Comparative Example 2 of the present invention at 20 nm. Detailed Implementation

[0061] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0062] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified. Example 1

[0063] This embodiment prepares a SiAlON composite ceramic, and the preparation process and steps are as follows:

[0064] S1. Preparation of modified ceramic powder;

[0065] S11. Weigh Si3N4, AlN, and Al2O3 in a molar ratio of 5:1:1 and mix them evenly to obtain a mixed ceramic powder. Add the mixed ceramic powder and a sintering aid (the sintering aid is a compound of CeO2 and Y2O3 in a molar ratio of 2.2:1, and the amount of the sintering aid added is 8 wt.% of the mass of the mixed ceramic powder) to anhydrous ethanol. The solid-liquid ratio of the mixed ceramic powder to anhydrous ethanol is 0.3 g / mL to obtain a solid-liquid mixture.

[0066] S12. Place the zirconia grinding beads and the solid-liquid mixture in a ball mill. The mass ratio of the zirconia grinding beads to the ceramic powder mixed in the solid-liquid mixture is 3:1. After ball milling at 200 r / min for 2 h, remove the mixture and add tetraethyl orthosilicate solution (preparation process of tetraethyl orthosilicate solution: after mixing anhydrous ethanol and deionized water evenly, adjust the pH value of the solution to 3 with HCl, slowly pour in tetraethyl orthosilicate, stir at 10 rpm for 0.5 h, the volume ratio of anhydrous ethanol to deionized water and tetraethyl orthosilicate is 5:10:1). The solid-liquid ratio of the mixed ceramic powder to the tetraethyl orthosilicate solution is 2 g / mL to obtain the modified precursor mixture.

[0067] S13. After heating and stirring the modified precursor mixture in a water bath at 70°C for 4 hours, centrifuge and wash with ethanol until the supernatant in the centrifuge tube is completely transparent and free of turbidity to obtain the modified ceramic powder precursor; place the modified ceramic powder precursor in an oven at 70°C for 12 hours to dry, and grind the dried material to 100 mesh to obtain the modified ceramic powder.

[0068] S2. Preparation of photocurable ceramic slurry;

[0069] S21. After uniformly mixing photosensitive resins TMPTA, HDDA, and NVP in a mass percentage ratio of 5:2:3, the mixture is ball-milled at 230 r / min for 0.5 h to obtain a photosensitive resin prepolymer. Then, BYK-111 dispersant is weighed at 1 wt.% of the modified ceramic powder mass, MMA diluent is weighed at 3 wt.% of the modified ceramic powder mass, and phenyl phosphorus dioxide 819 photoinitiator is weighed at 1 wt.% of the photosensitive resin prepolymer mass. 50 g of the photosensitive resin prepolymer is mixed uniformly with the weighed BYK-111 dispersant, MMA diluent, and phenyl phosphorus dioxide 819 photoinitiator to obtain a mixture.

[0070] S22. Add 120 g of the above modified ceramic powder to the mixture in batches, stir evenly, ball mill at 230 r / min for 3 h, and then place it in a vacuum degassing device. Degas at a vacuum degree of 0.08 MPa and a rotation speed of 50 r / min for 0.5 h to obtain a photocurable ceramic slurry with a solid content of 45 vol.%.

[0071] S3. Preparation of composite ceramic green bodies;

[0072] Using the aforementioned photocurable ceramic slurry as raw material, 3D printing was performed using a DLP photocurable printer. The light source wavelength during 3D printing was 405 nm, and the light intensity was 60 mW / cm². 2 The single-layer exposure time was 2000 ms, and the blade layer thickness was 50 μm, resulting in a composite ceramic green body.

[0073] S4. Preparation of SiAlON composite ceramics;

[0074] The obtained composite ceramic green body was placed in a degreasing furnace and heated from room temperature to 110°C at a heating rate of 1°C / min under a nitrogen atmosphere, and held for 0.5 h. Then, it was heated from 110°C to 580°C at a heating rate of 0.3°C / min, and held for 1 h. Finally, it was cooled to room temperature with the furnace and then removed.

[0075] The degreased composite ceramic green body was placed in a sintering furnace and heated from room temperature to 1000℃ at a rate of 15℃ / min under a nitrogen atmosphere, and held for 0.5 h. Then, the temperature was increased from 1000℃ to 1400℃ at a rate of 10℃ / min and held for 0.5 h. After that, the temperature was increased from 1400℃ to 1850℃ at a rate of 5℃ / min and held for 4 h. Finally, the furnace was cooled to room temperature to obtain SiAlON composite ceramic, which is β-SiAlON ceramic.

[0076] The SiAlON composite ceramic prepared in this embodiment was tested, and its density was 3.24 g / cm³. 3 The shrinkage rate is 29%, the flexural strength is 355.46 MPa, and the dielectric constant is 3.9.

[0077] like Figure 1 The images shown are TEM images of the modified ceramic powder obtained in step S1 of this embodiment. (a) shows that the TEOS sol-gel randomly coats different powder components together during the SiO2 formation process; (b) clearly shows a translucent SiO2 layer coating the powder surface, with the interface between the Si3N4 powder and the surface SiO2 coating layer clearly visible; (c) shows the interface between Al2O3 and Si3N4 powders, with clear Al2O3 and Si3N4 lattice fringes; (d) shows the lattice fringes spacing. By combining the diffraction spots in the FFT plot to identify the corresponding Al2O3 phase, each spot in the plot corresponds to a set of diffraction signals on parallel crystal planes in the crystal, with the crystal plane indices being as follows: , , The unit cell is an hcp hexagonal close-packed structure with the

[010] crystal orientation; (e) the lattice fringe spacing. By combining the diffraction spots in the FFT plot to identify the corresponding Si3N4 phase, each spot in the plot corresponds to a set of diffraction signals on parallel crystal planes in the crystal, with the crystal plane indices being respectively... , , The unit cell is an hcp close-packed hexagonal structure. Crystal orientation. This demonstrates that powders of different components can be coated together by generating SiO2 through TEOS sol-gel. Example 2

[0078] This embodiment prepares a SiAlON composite ceramic, and the preparation process and steps are as follows:

[0079] S1. Preparation of modified ceramic powder;

[0080] S11. Weigh Si3N4, AlN, and Al2O3 in a molar ratio of 5:1:1 and mix them evenly to obtain a mixed ceramic powder. Add the mixed ceramic powder and a sintering aid (the sintering aid is a compound of CeO2 and Y2O3 in a molar ratio of 2.2:1, and the amount of the sintering aid added is 8 wt.% of the mass of the mixed ceramic powder) to anhydrous ethanol. The solid-liquid ratio of the mixed ceramic powder to anhydrous ethanol is 0.5 g / mL to obtain a solid-liquid mixture.

[0081] S12. Place the zirconia grinding beads and the solid-liquid mixture in a ball mill. The mass ratio of the zirconia grinding beads to the ceramic powder mixed in the solid-liquid mixture is 3:1. After ball milling at 230 r / min for 2 h, remove the mixture and add tetraethyl orthosilicate solution (preparation process of tetraethyl orthosilicate solution: after mixing anhydrous ethanol and deionized water evenly, adjust the pH value of the solution to 3 with HCl, slowly pour in tetraethyl orthosilicate, stir at 25 rpm for 0.5 h, the volume ratio of anhydrous ethanol to deionized water and tetraethyl orthosilicate is 5:10:1). The solid-liquid ratio of the mixed ceramic powder to the tetraethyl orthosilicate solution is 3 g / mL, to obtain the modified precursor mixture.

[0082] S13. After heating and stirring the modified precursor mixture in a water bath at 80°C for 6 hours, centrifuge and wash with ethanol until the supernatant in the centrifuge tube is completely transparent and free of turbidity to obtain the modified ceramic powder precursor; place the modified ceramic powder precursor in an oven and dry at 90°C for 10 hours, then grind the dried material to 100 mesh to obtain the modified ceramic powder.

[0083] S2. Preparation of photocurable ceramic slurry;

[0084] S21. The photosensitive resins TPGDA, HDDA, and ACMO are mixed evenly in a mass ratio of 5:2:3 and then ball-milled at 230 r / min for 1 h to obtain the photosensitive resin prepolymer. Then, BYK-111 dispersant is weighed at 3 wt.% of the modified ceramic powder mass, KH560 diluent is weighed at 5 wt.% of the modified ceramic powder mass, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide photoinitiator is weighed at 1.5 wt.% of the photosensitive resin prepolymer mass. 60 g of the photosensitive resin prepolymer is mixed evenly with the weighed BYK-111 dispersant, KH560 diluent, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide photoinitiator to obtain a mixture.

[0085] S22. Add 135 g of the above modified ceramic powder to the mixture in batches, stir evenly, and then ball mill at 200 r / min for 6 h. Then place it in a vacuum degassing device and degas at a vacuum degree of 0.08 MPa and a rotation speed of 50 r / min for 0.5 h to obtain a light-cured ceramic slurry with a solid content of 43 vol.%.

[0086] S3. Preparation of composite ceramic green bodies;

[0087] Using the aforementioned photocurable ceramic slurry as raw material, 3D printing was performed using a DLP photocurable printer. The light source wavelength during 3D printing was 405 nm, and the light intensity was 60 mW / cm². 2 The single-layer exposure time was 2000 ms, and the blade layer thickness was 50 μm, resulting in a composite ceramic green body.

[0088] S4. Preparation of SiAlON composite ceramics;

[0089] The obtained composite ceramic green body was placed in a degreasing furnace and heated from room temperature to 120°C at a heating rate of 2°C / min under a nitrogen atmosphere, and held for 1 h; then heated from 120°C to 590°C at a heating rate of 0.2°C / min, and held for 0.5 h; finally cooled to room temperature with the furnace and then removed.

[0090] The extracted composite ceramic green body was placed in a sintering furnace and heated from room temperature to 900℃ at a rate of 10℃ / min under a nitrogen atmosphere, and held for 1 h. Then, it was heated from 900℃ to 1300℃ at a rate of 5℃ / min and held for 0.75 h. After that, it was heated from 1300℃ to 1600℃ at a rate of 2℃ / min and held for 3 h. Finally, it was cooled to room temperature with the furnace to obtain SiAlON composite ceramic, which is β-SiAlON ceramic.

[0091] The SiAlON composite ceramic prepared in this embodiment was tested, and its density was 2.93 g / cm³. 3 The shrinkage rate is 25%, the flexural strength is 312.47 MPa, and the dielectric constant is 3.1.

[0092] like Figure 2 The figure shows the composite ceramic green body obtained by 3D printing in this embodiment. As can be seen from the figure, the multi-component photocurable slurry prepared by TEOS modified powder exhibits high printing accuracy during the curing process. The complex three-dimensional structure prepared is not only clear in outline but also free of obvious defects and has good structural integrity. Example 3

[0093] This embodiment prepares a SiAlON composite ceramic, and the preparation process and steps are as follows:

[0094] S1. Preparation of modified ceramic powder;

[0095] S11. Weigh Si3N4, AlN, and Al2O3 in a molar ratio of 5:1:1 and mix them evenly to obtain a mixed ceramic powder. Add the mixed ceramic powder and a sintering aid (the sintering aid is a compound of CeO2 and Y2O3 in a molar ratio of 2.2:1, and the amount of the sintering aid added is 8 wt.% of the mass of the mixed ceramic powder) to anhydrous ethanol. The solid-liquid ratio of the mixed ceramic powder to anhydrous ethanol is 0.4 g / mL to obtain a solid-liquid mixture.

[0096] S12. Zirconia grinding beads and solid-liquid mixture are placed in a ball mill. The mass ratio of zirconia grinding beads to ceramic powder mixed in the solid-liquid mixture is 3:1. After ball milling at 250 r / min for 2 h, tetraethyl orthosilicate solution is added (the preparation process of tetraethyl orthosilicate solution is as follows: after mixing anhydrous ethanol and deionized water evenly, the pH value of the solution is adjusted to 3 using HCl, and tetraethyl orthosilicate is slowly poured in. The mixture is stirred at 30 rpm for 0.5 h. The volume ratio of anhydrous ethanol to deionized water and tetraethyl orthosilicate is 5:10:1). The solid-liquid ratio of the mixed ceramic powder to the tetraethyl orthosilicate solution is 5 g / mL, and the modified precursor mixture is obtained.

[0097] S13. After heating and stirring the modified precursor mixture in a 50°C water bath for 3 hours, wash it with ethanol by centrifugation until the supernatant in the centrifuge tube is completely transparent and free of turbidity to obtain the modified ceramic powder precursor. Place the modified ceramic powder precursor in an oven at 80°C for 11 hours and grind the dried material to 100 mesh to obtain the modified ceramic powder.

[0098] S2. Preparation of photocurable ceramic slurry;

[0099] S21. The photosensitive resins TPGDA, HDDA, and IBOA are mixed evenly in a mass ratio of 5:2:3, and then ball-milled at 230 r / min for 0.8 h to obtain a photosensitive resin prepolymer. Then, 2 wt.% of JH-21 dispersant, 1 wt.% of KH560 diluent, and 3 wt.% of phenyl phosphorus dioxide 819 photoinitiator are weighed according to the mass of the modified ceramic powder. 80 g of the photosensitive resin prepolymer is mixed evenly with the weighed JH-21 dispersant, KH560 diluent, and phenyl phosphorus dioxide 819 photoinitiator to obtain a mixture.

[0100] S22. Add 158 g of the above modified ceramic powder to the mixture in batches, stir evenly, ball mill at 250 r / min for 5 h, and then place it in a vacuum degassing device. Degas at a vacuum degree of 0.08 MPa and a rotation speed of 50 r / min for 0.5 h to obtain a photocurable ceramic slurry with a solid content of 40 vol.%.

[0101] S3. Preparation of composite ceramic green bodies;

[0102] Using photocurable ceramic slurry as raw material, 3D printing was performed using a DLP photocurable printer. The light source wavelength during 3D printing was 405 nm, and the light intensity was 60 mW / cm². 2 The single-layer exposure time was 2000 ms, and the blade layer thickness was 50 μm, resulting in a composite ceramic green body.

[0103] S4. Preparation of SiAlON composite ceramics;

[0104] The obtained composite ceramic green body was placed in a degreasing furnace and heated from room temperature to 115℃ at a heating rate of 1.5℃ / min under a nitrogen atmosphere, and held for 0.75 h. Then, it was heated from 115℃ to 600℃ at a heating rate of 0.5℃ / min and held for 0.75 h. Finally, it was cooled to room temperature with the furnace and then removed.

[0105] The extracted composite ceramic green body was placed in a sintering furnace and heated from room temperature to 800℃ at a rate of 12.5℃ / min under a nitrogen atmosphere, and held for 0.75 h. Then, the temperature was increased from 800℃ to 1350℃ at a rate of 7.5℃ / min and held for 1 h. After that, the temperature was increased from 1350℃ to 1700℃ at a rate of 4℃ / min and held for 5 h. Finally, the furnace was cooled to room temperature to obtain SiAlON composite ceramic, which is β-SiAlON ceramic.

[0106] The SiAlON composite ceramic prepared in this embodiment was tested, and its density was 3.12 g / cm³. 3The shrinkage rate is 27%, the flexural strength is 332.26 MPa, and the dielectric constant is 3.7.

[0107] like Figure 3 The image shows the physical specimen of the SiAlON composite ceramic prepared in this embodiment. As can be seen, the overall structure of the sintered ceramic remains relatively intact, without large-scale deformation or collapse. The ceramic structure exhibits some shrinkage, which is due to the grain growth filling the voids created after binder removal, thus densifying the interior.

[0108] like Figure 4 The image shows a cross-sectional SEM image of the SiAlON composite ceramic prepared in this embodiment. As can be seen from the image, the SiAlON composite ceramic mainly consists of rod-shaped grains with a relatively dense microstructure, relatively uniform grain distribution, and tight bonding between grains. Comparative Example

[0109] To investigate the influence of different raw materials on the properties of the product during the preparation process of this invention, the following comparative experiments were conducted. Different SiAlON ceramics were prepared according to the following comparative examples:

[0110] Comparative Example 1

[0111] This comparative example prepares a SiAlON ceramic. The preparation process is similar to that of Example 1, except that in step S1, tetraethyl orthosilicate solution is not added, that is, the powder is not modified. The rest of the process and steps are the same as those in Example 1.

[0112] like Figure 5 (a) and (b) are single-layer curing diagrams of multi-component photocurable slurries prepared from unmodified powder and modified powder, respectively. Figure 5 As shown in (a), the photocurable ceramic slurry prepared from unmodified powder exhibits burrs or serrated residues at the contour edges after single-layer curing. This phenomenon is due to the difference in refractive index between different powders. During ultraviolet irradiation, the refraction and scattering of light at the interfaces of different powders are inconsistent, resulting in uneven curing of the slurry and a decrease in printing accuracy. Uneven curing can also lead to more serious consequences. During photocurable printing, the slurry may be over-cured in some areas while remaining incompletely cured in others. This uneven curing directly affects the bonding effect between layers, making it impossible for adjacent printed layers to bond tightly, ultimately leading to printing failure.

[0113] In contrast, photocurable ceramic slurries prepared using TEOS-modified powder exhibit higher printing accuracy during the curing process. Figure 5 As shown in (b), the edges of the graphic are smooth and fluid, the single layer is uniformly cured, and there is no excess residue.

[0114] Comparative Example 2

[0115] This comparative example prepares a SiAlON ceramic. The preparation process is similar to that of Example 1, except that in step S1, the tetraethyl orthosilicate solution is replaced with SiO2 powder to obtain SiO2 mixed ceramic powder. The amount of SiO2 powder added is 5 wt.% of the mass of the mixed ceramic powder. The remaining processes and steps are the same as in Example 1.

[0116] After observing the single-layer curing effect of the ceramic slurry obtained in this comparative example, it was found that, as Figure 6 As shown, its curing effect is the same as that of the slurry prepared from unmodified ceramic powder, both exhibiting burrs or serrated residues at the contour edges. This uneven curing directly affects the interlayer bonding effect, causing adjacent printed layers to fail to bond tightly, ultimately resulting in printing failure. The SiO2 mixed ceramic powder obtained in this comparative example was observed under a TEM. Figure 7 , Figure 8 As shown, the added SiO2 powder cannot coat the surface of other powders, and does not produce the effect shown in the figure. Figure 1 The SiO2 coating shown cannot achieve the effect of modifying powder using TEOS.

[0117] Comparative Example 3

[0118] This comparative example prepares a SiAlON ceramic. The preparation process is similar to that of Example 1, except that in step S1, the tetraethyl orthosilicate solution is replaced with a tetramethoxysilane (TMOS) solution. The rest of the process and steps are the same as in Example 1.

[0119] Observations on the modified ceramic powder obtained in this comparative example revealed that although the tetramethoxysilane solution and the tetraethyl orthosilicate solution are similar in that they can both form a -Si-O-Si- network through dehydration / condensation, the difference lies in that tetraethyl orthosilicate produces ethanol during de-alcoholization condensation, while tetramethoxysilane produces methanol during de-alcoholization condensation. In terms of reaction rate comparison, the reaction rate of tetraethyl orthosilicate is moderate, resulting in a good coating effect on the powder surface, while the reaction rate of tetramethoxysilane is faster, leading to rapid gel formation and inability to uniformly coat the powder surface.

[0120] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 claims of the present invention.

Claims

1. A method for preparing a multi-component photocurable composite ceramic, characterized in that, Follow these steps in sequence: S1. Preparation of modified ceramic powder; S11. After mixing Si3N4, AlN and Al2O3 evenly, a mixed ceramic powder is obtained. The mixed ceramic powder and sintering aid are added together to anhydrous ethanol. The solid-liquid ratio of the mixed ceramic powder to anhydrous ethanol is 0.3~0.5 g / mL, and a solid-liquid mixture is obtained. S12. Zirconia grinding beads and solid-liquid mixture are placed in a ball mill with a mass ratio of 3:1 between the zirconia grinding beads and the mixed ceramic powder in the solid-liquid mixture. The mixture is ball-milled at 200-250 r / min for 2 h. Then, tetraethyl orthosilicate solution is added to the mixture with a solid-liquid ratio of 2-5 g / mL between the mixed ceramic powder and the tetraethyl orthosilicate solution to obtain a modified precursor mixture. The preparation process of the tetraethyl orthosilicate solution is as follows: after mixing anhydrous ethanol and deionized water evenly, the pH of the solution is adjusted to 3 using HCl, and tetraethyl orthosilicate is slowly poured into it and stirred at 10~30 rpm for 0.5 h; the volume ratio of anhydrous ethanol to deionized water to tetraethyl orthosilicate is 5:10:

1. S13. Place the modified precursor mixture in a container and heat it in a water bath at 50~80℃ while stirring for 3~6 h. Wash it with ethanol by centrifugation until the supernatant in the centrifuge tube is completely transparent and free of turbidity to obtain the modified ceramic powder precursor. Place the modified ceramic powder precursor in an oven and dry it at 70~90℃ for 10~12 h. Grind the dried material to 100 mesh to obtain the modified ceramic powder. S2. Preparation of photocurable ceramic slurry; S21. Mix the photosensitive resin prepolymer, dispersant, diluent and photoinitiator evenly to obtain a mixture; The preparation process of the photosensitive resin prepolymer is as follows: after mixing the multifunctional resin monomer and the monofunctional resin monomer at a mass percentage of 7:3, the mixture is ball-milled at 230 r / min for 0.5~1 h to obtain the photosensitive resin prepolymer. The multifunctional resin monomer is at least two of trimethylolpropane triacrylate, tripropylene glycol diacrylate, and 1,6-hexanediol diacrylate; the monofunctional resin monomer is at least one of N-vinylpyrrolidone, isobornyl acrylate, 4-acryloylmorpholine, and N,N-dimethylacrylamide. S22. Add the above modified ceramic powder to the mixture in batches, stir evenly, ball mill at 200~250 r / min for 3~6 h, and after vacuum degassing, obtain a light-cured ceramic slurry with a solid content of 40~45 vol.%; S3. Preparation of composite ceramic green bodies; Using the above-mentioned photocurable ceramic slurry as raw material, a composite ceramic green body was obtained by 3D printing using a DLP photocurable printer; S4. Preparation of composite ceramics; The composite ceramic green body was degreased and sintered under a nitrogen atmosphere to obtain the composite ceramic. The sintering process is carried out in the following order: (a) In the first heating stage, the temperature is increased from room temperature to 800-1000℃ at a heating rate of 10-15℃ / min, and held for 0.5-1h; (b) In the second heating stage, the temperature is increased from 800-1000℃ to 1300-1400℃ at a heating rate of 5-10℃ / min, and held for 0.5-1 h; (c) In the third heating stage, the temperature is increased from 1300~1400℃ to 1600~1850℃ at a heating rate of 2~5℃ / min, and held for 3~5 h; (d) Cooling stage: The furnace is cooled to room temperature.

2. The method for preparing a multi-component photocurable composite ceramic according to claim 1, characterized in that, In step S11, the molar ratio of Si3N4, AlN and Al2O3 is 5:1:1; the sintering aid is a mixture of CeO2 and Y2O3 with a molar ratio of 2.2:1, and the amount of sintering aid added is 8 wt.% of the mass of the mixed ceramic powder.

3. The method for preparing a multi-component photocurable composite ceramic according to claim 1, characterized in that, In step S21, the dispersant is BYK-111 or JH-21, and the amount of dispersant added is 1-3 wt.% of the modified ceramic powder; the diluent is methyl methacrylate or γ-glycidyl etheroxypropyltrimethoxysilane, and the amount of diluent added is 1-5 wt.% of the modified ceramic powder; the photoinitiator is phenylphosphine dioxide 819 or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and the amount of photoinitiator added is 1-3 wt.% of the photosensitive resin prepolymer.

4. The method for preparing a multi-component photocurable composite ceramic according to claim 1, characterized in that, In step S3, the wavelength of the light source in the DLP photopolymerization printer is 405 nm, and the light intensity is 60 mW / cm². 2 The single-layer exposure time is 2000 ms, and the blade layer thickness is 50 μm.

5. The method for preparing a multi-component photocurable composite ceramic according to claim 1, characterized in that, In step S4, the degreasing process is performed sequentially according to the following steps: (e) In the first heating stage, the temperature is increased from room temperature to 110-120℃ at a heating rate of 1-2℃ / min, and held for 0.5-1 h; (f) In the second heating stage, the temperature is increased from 110~120℃ to 580~600℃ at a heating rate of 0.2~0.5℃ / min, and held for 0.5~1 h; (g) Cooling stage: The furnace is cooled to room temperature.

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