A method for preparing porous ceramics by sol-modified SiC particles photocuring

Abstract

The application provides a method for preparing porous ceramics by sol modification of SiC particles and photocuring, which comprises the following steps: forming a uniform SiO2 coating on the surface of SiC particles by sol treatment; then, configuring the modified SiC particles into a photocuring printing slurry for manufacturing a SiC blank with a complex shape; and finally, preparing porous SiC ceramics through a debinding and sintering process. The SiO2 coating can not only improve the photocuring printing performance of the SiC particles, but also effectively avoid the direct reaction between Al and SiC to generate harmful phase Al4C3 in the subsequent metal infiltration process. The method is simple in process, controllable and stable and reliable in parameters, and the obtained porous SiC ceramics have a continuous three-dimensional pore structure, and the pore structure and size are suitable for the flow and complete filling of aluminum melt, so that the porous SiC ceramics can be used for preparing high specific SiC / Al composite materials with a complex structure, and the photocuring printing technology can be expected to be applied to the fields of deep color ceramic printing and the manufacturing of SiC / metal composite materials with a complex structure.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing and ceramic material preparation technology, specifically relating to a method for manufacturing porous SiC ceramics by combining sol-modified SiC particles with photocuring additive manufacturing. Background Technology

[0002] Porous materials, due to their unique pore structure, can achieve a variety of functional properties and are known as porous functional materials. They possess excellent chemical and thermal stability, showing broad application potential in fields such as filtration materials, catalyst supports, thermal insulation materials, and biofunctional materials, especially in high-tech fields like aerospace, biomedicine, and environmental protection. Among them, porous SiC ceramics, with their low density, low coefficient of thermal expansion, high hardness, and excellent oxidation resistance, have demonstrated wide application value in aerospace, nuclear power, and transportation, becoming a research hotspot in materials science. In particular, metal infiltration technology based on porous SiC ceramic materials has been used to manufacture high-performance SiC / metal composites, with SiC / Al composites exhibiting excellent performance in lightweight, high-rigidity, and vibration-damping components. However, with the upgrading of application requirements for SiC / Al composites, the preparation technology of porous SiC is also beginning to develop towards more complex shapes and structures and lower economic costs.

[0003] Photopolymer additive manufacturing technology offers excellent technical support for the fabrication of complex SiC frameworks due to its high precision, efficiency, and low cost. However, currently available mature ceramic materials for photopolymer 3D printing mainly consist of white ceramic particles, including alumina, silicon dioxide, zirconium dioxide, and silicon nitride. SiC, on the other hand, is a dark-colored ceramic. The strong ultraviolet light absorption and refractive index mismatch with resins make it difficult to achieve uniform curing and sufficient thickness in the printing of dark-colored ceramics, thus limiting the development of photopolymer 3D printing of dark-colored ceramics. Therefore, there is an urgent need to develop photopolymer printing technology for dark-colored ceramic particles like SiC to meet the requirements for fabricating complex SiC ceramic frameworks, thereby serving the fabrication of porous SiC ceramics and subsequent metal infiltration needs. Summary of the Invention

[0004] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method for preparing porous SiC ceramics through sol-gel modification combined with photocuring. This method is simple, rationally designed, and easy to operate. By sol-gel treatment of SiC particles, SiC particles coated with a SiO2 film are prepared. The modified SiC particles are then used to prepare a photocurable ceramic slurry, which is used to print a SiC ceramic preform. Furthermore, a rationally designed debinding and sintering process is employed to prepare a complex porous SiC ceramic with suitable porosity and pore size, facilitating the infiltration of metals such as Al. This accelerates the photocurable printing of dark-colored ceramics and the development of high-ratio SiC / Al composite materials with complex structures.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing porous ceramics by photocuring sol-modified SiC particles, comprising the following steps:

[0006] Sol-gel modification of S1 and SiC particles

[0007] SiC particles were ultrasonically cleaned with anhydrous ethanol to remove surface impurities and then dried. They were then added to premixed solution B, followed by premixed solution A to obtain a reaction mixture. The reaction mixture was stirred at 25°C under sealed conditions for 9–16 h to perform sol modification on the surface of the SiC particles. After centrifugation, washing and drying, the modified SiC particles were obtained.

[0008] The premix A is prepared by mixing tetraethyl orthosilicate and anhydrous ethanol a; the premix B is prepared by mixing deionized water, ammonia water and anhydrous ethanol b.

[0009] The mass ratio of the raw materials in the reaction mixture is as follows: 0.5-1.0 parts SiC particles, 3-5 parts tetraethyl orthosilicate, 6-12 parts anhydrous ethanol a, 4-6 parts deionized water, 0.5-4 parts ammonia, and 4-20 parts anhydrous ethanol b; the concentration of the ammonia is 0.5-1.75 mol / L.

[0010] S2. Preparation of photocurable SiC slurry

[0011] The modified SiC particles obtained in S1 are mixed with a photocurable resin premix to prepare a photocurable SiC slurry. The photocurable SiC slurry also contains a dispersant, a photoinitiator, and an ultraviolet light absorber.

[0012] The mass ratio of the modified SiC particles to the photocurable resin premix is ​​11:(5.5-6.5);

[0013] S3, photocurable SiC preform

[0014] The photocurable SiC slurry obtained in S2 was photocured and 3D printed, and after drying, a photocurable SiC preform was obtained.

[0015] S4. Degreasing and oxidation sintering of photocured SiC preforms

[0016] The photocured SiC preform obtained in S3 was degreased and oxidized and sintered. After the process, it was cooled to room temperature, ultrasonically cleaned and dried to obtain porous SiC ceramic.

[0017] Preferably, the SiC particles in S1 are spherical particles with a particle size of 10-165 μm and a purity of ≥99.5%.

[0018] Preferably, the drying conditions for the SiC particles in S1 after sol modification are: drying at a temperature of 80–120°C for 2–8 hours.

[0019] Preferably, in S1, a SiO2 film is attached to the surface of the SiC particles after sol-gel modification. The thickness of the SiO2 film is 500-1000 nm, and the coverage of the SiC surface is >97%.

[0020] Preferably, in S2, the amount of dispersant added is 1% to 5% of the mass of the photocurable resin premix; the amount of photoinitiator added is 5% to 10% of the mass of the photocurable resin premix; and the amount of ultraviolet light absorber added is 0.5% to 1% of the mass of the photocurable resin premix.

[0021] Preferably, the preparation method of the photocurable SiC slurry in S2 is as follows: a photoinitiator and an ultraviolet absorber are added to a photocurable resin premix, and stirred at 25°C for 30-60 min to obtain slurry 1; half the mass of modified SiC particles and half the mass of dispersant are added to slurry 1, and stirred at 25°C for 30-60 min, followed by ball milling for 6-8 h to obtain slurry 2; the other half the mass of modified SiC particles and the other half the mass of dispersant are added to slurry 2, and stirred at 25°C for 30-60 min, followed by ball milling for 6-8 h, and after vacuum degassing, a photocurable dark-colored SiC slurry is obtained.

[0022] Preferably, the photocuring conditions in S3 are: photocuring 3D printing under ultraviolet light with a wavelength of 405nm, with each layer having a cured thickness of 50-200μm; the drying conditions are: heating to 120-150℃ at a heating rate of 0.2-0.6℃ / min and drying for 1-2 hours.

[0023] Preferably, in S4, an integrated degreasing and sintering process is adopted, in which degreasing and oxidation sintering are achieved in one furnace under atmospheric conditions. The method is as follows: under dry conditions, the photocured SiC preform is placed in a muffle furnace and heated to 650-700°C at a rate of 0.1-0.5°C / min, and held for 0.5-2 hours. The oxidation sintering conditions are as follows: the degreased SiC preform is heated to 1300-1400°C in a muffle furnace at a rate of 10-40°C / min, and held for 0.2-3 hours.

[0024] Preferably, the drying temperature in step S4 is 80–120°C, and the drying time is 2–6 hours.

[0025] Preferably, the porous SiC ceramic in S4 has isotropic, uniform and interconnected pores with a porosity of 45-55%.

[0026] The present invention has the following significant technical effects:

[0027] 1. This invention provides a method for photocuring porous ceramics using sol-modified SiC particles. The sol-modification improves the photocurability and printability of SiC ceramic particles, allowing for the design of macroscopic shape, micropore size, and SiO2 film thickness for complex porous SiC ceramics as needed. This method can effectively meet the requirements of aluminizing and is expected to be applied and promoted in the fields of photocuring and printing of dark SiC ceramics and manufacturing of complex high-ratio SiC / Al composite materials.

[0028] 2. This invention improves the surface state of SiC ceramic particles by forming a SiO2 film on the surface of SiC particles through sol modification, making them more compatible with photocuring forming processes. This results in more uniform and stable SiC porous ceramics. When SiC porous ceramics are used to prepare high-ratio SiC / Al composite materials, the direct contact between Al and SiC during subsequent impregnation processes avoids the formation of harmful Al4C3 phase. The process is simple, the parameters are controllable, and it is stable and reliable.

[0029] 3. This application is the first to propose a process for simultaneous photopolymerization molding of SiC preforms and degreasing, oxidation and sintering, which can not only shorten the sample preparation cycle and reduce sample damage during handling, but also significantly improve the quality and surface structure of porous SiC ceramics. The prepared porous SiC ceramics have good permeability, a continuous three-dimensional pore structure, and pore structure and size that are suitable for the flow and complete filling of molten aluminum and other materials.

[0030] 4. The process described in this application is simple, reliable, and easy to implement. The raw materials used are inexpensive. Its technical principles and methods can be extended to the preparation of ceramic-metal composite materials with any high ratio, and even the preparation of high-melting-point metal-low-melting-point composite metal materials, which has broad guiding significance. The preparation of photocurable SiC slurry can be used to guide the slurry design for photocurable 3D printing of dark ceramic particles. The debinding and sintering process does not require special gas protection and can be used to guide the design of debinding and sintering process for photocurable additive manufacturing blanks.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] Figure 1 The figures show the morphology of SiC particles with an average particle size of 10 μm in Example 1 before and after modification. In the figure, (a) is before modification and (b) is after modification.

[0033] Figure 2 The figures show the morphology of SiC particles with an average particle size of 90 μm in Example 1 before and after modification. (a) shows the morphology before modification, (b) shows the morphology after modification, and (c) shows the morphology after modification. Figure 2 (b) A magnified view of the area within the red box;

[0034] Figure 3 This is a schematic diagram of the degreasing and oxidation sintering process in Example 1;

[0035] Figure 4 It is the SiC preform printed by photopolymerization in Example 1;

[0036] Figure 5 It is the porous SiC ceramic of Example 1;

[0037] Figure 6 This is a microscopic morphology diagram of the porous SiC ceramic aluminized composite material in Example 1;

[0038] Figure 7 This is the X-ray diffraction (XRD) pattern of the porous SiC ceramic aluminized composite material in Example 1. Detailed Implementation

[0039] Example 1

[0040] This embodiment describes a method for preparing porous ceramics by photocuring sol-modified SiC particles, including the following steps:

[0041] Sol-gel modification of S1 and SiC particles

[0042] SiC particles were ultrasonically cleaned with anhydrous ethanol at 180W for 30 min to remove surface impurities, and then dried at 120℃ for 2 h. The dried SiC particles were added to premixed solution B, and then premixed solution A was added to obtain a reaction mixture. The reaction mixture was stirred at 25℃ under closed conditions for 9 h to perform sol modification on the surface of SiC particles. After completion, the particles were centrifuged at 2000 r / min, washed 4 times with deionized water, and dried at 120℃ for 2 h to obtain modified SiC particles. The surface of the modified SiC may still contain a small amount of unattached SiO2 particles.

[0043] Premix A is prepared by mixing tetraethyl orthosilicate and anhydrous ethanol a; premix B is prepared by mixing deionized water, ammonia water and anhydrous ethanol b.

[0044] The mass ratio of the raw materials in the reaction mixture is as follows: 0.7 parts SiC particles, 3.2 parts tetraethyl orthosilicate, 9.2 parts anhydrous ethanol a, 4.8 parts deionized water, 3 parts ammonia, and 7.6 parts anhydrous ethanol b; wherein the SiC particles include two types with an average particle size of 10 μm and 90 μm, the ratio of the average particle size of 10 μm to that of 90 μm is 3:7, the purity is ≥99.5%, and the concentration of the ammonia is 1.5 mol / L.

[0045] S2. Preparation of photocurable SiC slurry

[0046] The composition of the photocurable SiC slurry is as follows: the mass ratio of modified SiC particles obtained in S1 to the photocurable resin premix is ​​11:6; the dispersant is 1.5% of the mass of the photocurable resin premix; the photoinitiator is 5.5% of the mass of the photocurable resin premix; and the UV absorber is 0.5% of the mass of the photocurable resin premix. The photocurable resin premix is ​​purchased Versace rigid resin (101S1); the UV absorber is UV-770; the photoinitiator is (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide; and the dispersant is an oily thickener (J0602).

[0047] The preparation method is as follows: Photoinitiator and ultraviolet absorber are added to photocurable resin premix and stirred at 25°C for 30 min to obtain slurry 1; half the mass of modified SiC particles and half the mass of dispersant are added to slurry 1, stirred at 25°C for 30 min and then ball-milled for 6 h to obtain slurry 2; the other half the mass of modified SiC particles and the other half the mass of dispersant are added to slurry 2, stirred at 25°C for 30 min and then ball-milled for 6 h, and after vacuum degassing, photocurable dark SiC slurry is obtained.

[0048] S3, photocurable SiC preform

[0049] The photocurable dark SiC slurry obtained in S2 was applied to a glass slide of a photocurable 3D printer and cured under a 405nm ultraviolet light source for 10 seconds. The uncured slurry was then removed, and the thickness of a single layer was measured to be 160μm using a micrometer. Then, the printing was performed layer by layer to obtain a shaped SiC preform with dimensions of 5mm×5mm×50mm. The obtained SiC preform was then placed in a forced-air drying oven and heated to 120℃ at a heating rate of 0.4℃ / min for 2 hours to obtain a photocurable SiC preform.

[0050] S4. Degreasing and oxidation sintering of photocured SiC preforms

[0051] Under dry conditions, the photocured SiC preform obtained by S3 was placed in a muffle furnace and heated from room temperature to 650℃ at a rate of 0.5℃ / min and held for 1 hour; then heated to 1350℃ at a rate of 20℃ / min and held for 1 hour; after the end, it was cooled to room temperature, ultrasonically cleaned with deionized water for 30 minutes, and then dried at 120℃ for 2 hours to obtain porous SiC ceramic.

[0052] Figure 1 The images show the surface morphology of the original SiC particles with an average particle size of 10 μm and the SiC particles after sol-gel treatment. It can be seen that the SiO2 layer was successfully grown on the surface of the SiC particles after sol-gel treatment, and the originally sharp SiC particle surface became blunt. Figure 2 The images show the surface morphology of pristine SiC particles with an average particle size of 90 μm and the SiC surface after sol-gel treatment, demonstrating that a SiO2 layer was successfully formed on the surface of the SiC particles after sol-gel modification. In this embodiment, the average thickness of the SiO2 layer formed on the surface of the SiC particles after sol-gel modification is ~830 nm, with a coverage rate of 99% on the SiC surface.

[0053] Figure 3 This is a schematic diagram of the degreasing and oxidation sintering process. The degreasing and oxidation sintering process is divided into two stages: the degreasing stage and the oxidation sintering stage. The degreasing stage involves raising the temperature from room temperature to T1 = 550~700℃ at a rate of V1 = 0.1~0.5℃ / min, which should not exceed 0.5℃ / min, as exceeding this rate will cause the SiC green body to separate or crack. The temperature is held at T1 for t1 = 0.5~2h to ensure that the resin is completely removed. The oxidation sintering temperature is T2 = 1300~1400℃, and the heating rate from T1 to T2 is V2 = 10~40℃ / min. The temperature is held at T2 for t2 = 0.2~3h.

[0054] Figure 4 It is a SiC preform printed by photopolymerization.

[0055] Figure 5This is a diagram of porous SiC ceramic and its structure. Its porosity is 47.3%, the average pore size is 12.8 μm, and the bending strength of the standard sample is 1.7 MPa.

[0056] The porous SiC ceramic framework prepared in this embodiment was subjected to aluminizing treatment. The aluminizing process was vacuum pressure aluminizing, the aluminizing alloy was ZL102 alloy, the aluminizing pressure was 8 MPa, and the aluminizing temperature was 800℃. The microstructure of the SiC / composite material obtained after aluminizing treatment is shown in the figure below. Figure 6 As shown, no obvious impermeability was observed, and the X-ray diffraction (XRD) results showed that no diffraction peaks of Al4C3 were observed. Figure 7 The flexural strength of the standard-sized SiC / composite sample after aluminizing is ~423MPa and the elastic modulus is ~176GPa, indicating good comprehensive mechanical properties.

[0057] Example 2

[0058] This embodiment describes a method for preparing porous ceramics by photocuring sol-modified SiC particles, including the following steps:

[0059] Sol-gel modification of S1 and SiC particles

[0060] SiC particles were ultrasonically cleaned with anhydrous ethanol at 180W for 30 minutes to remove surface impurities. They were then dried at 120℃ for 2 hours. The dried SiC particles were slowly added to premixed solution B, followed by rapid addition of premixed solution A to obtain a reaction mixture. The reaction mixture was stirred at 25℃ under sealed conditions for 16 hours to perform sol modification on the surface of the SiC particles. After completion, the particles were centrifuged at 2000r / min, washed three times with anhydrous ethanol, and dried at 80℃ for 8 hours. The particles were then sieved to remove unattached SiO2 particles to obtain SiC particles with a SiO2 layer on the surface, which are the modified SiC particles.

[0061] Premix A is prepared by mixing tetraethyl orthosilicate and anhydrous ethanol a; premix B is prepared by mixing deionized water, ammonia, and anhydrous ethanol b.

[0062] The mass ratio of the raw materials in the reaction mixture is as follows: 0.7 parts SiC particles, 3.2 parts tetraethyl orthosilicate, 0.46 parts anhydrous ethanol a1, 4.8 parts deionized water, 3 parts ammonia, and 18 parts anhydrous ethanol b; wherein the SiC particles include two types with an average particle size of 10 μm and 90 μm, the ratio of the average particle size of 10 μm to that of 90 μm is 4:6, the purity is ≥99.5%, and the concentration of the ammonia is 1 mol / L.

[0063] S2. Preparation of photocurable SiC slurry

[0064] The composition of the photocurable SiC slurry is as follows: the mass ratio of modified SiC particles obtained in S1 to the photocurable resin premix is ​​11:6.5; the dispersant is 3% of the mass of the photocurable resin premix; the photoinitiator is 8% of the mass of the photocurable resin premix; and the ultraviolet absorber is 1% of the mass of the photocurable resin premix. The photocurable resin premix is ​​purchased Versace rigid resin (101S1); the ultraviolet absorber is UV-770; the photoinitiator is (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide; and the dispersant is an oily thickener (J0602).

[0065] The preparation method is as follows: Photoinitiator and ultraviolet absorber are added to photocurable resin premix and stirred at 25°C for 60 min to obtain slurry 1; half the mass of modified SiC particles and half the mass of dispersant are added to slurry 1, stirred at 25°C for 60 min and then ball-milled for 7 h to obtain slurry 2; the other half the mass of modified SiC particles and the other half the mass of dispersant are added to slurry 2, stirred at 25°C for 60 min and then ball-milled for 7 h, and after vacuum degassing, photocurable dark SiC slurry is obtained.

[0066] S3, photocurable SiC preform

[0067] The photocurable dark SiC slurry obtained in S2 was applied to a glass slide of a photocurable 3D printer and cured for 8 seconds under a 405nm ultraviolet light source. The uncured slurry was then removed, and the thickness of a single layer was measured to be 140μm using a micrometer. Then, the printing was performed layer by layer to obtain a shaped SiC preform with dimensions of 5mm×5mm×50mm. The obtained SiC preform was then placed in a forced-air drying oven and heated to 150℃ at a heating rate of 0.6℃ / min for 1 hour to obtain a photocurable SiC preform.

[0068] S4. Degreasing and oxidation sintering of photocured SiC preforms

[0069] Under dry conditions, the photocured SiC preform obtained in S3 was placed in a muffle furnace and heated from room temperature to 650℃ at a rate of 0.3℃ / min and held for 2 hours; then heated to 1400℃ at a rate of 40℃ / min and held for 1 hour; after the end, it was cooled to room temperature, ultrasonically cleaned with anhydrous ethanol for 20 minutes, and then dried at 100℃ for 4 hours to obtain porous SiC ceramic.

[0070] In this embodiment, the average thickness of the SiO2 layer formed on the surface of SiC particles after sol-gel modification is ~660nm, and the coverage rate on the SiC surface is 99%.

[0071] The porous SiC ceramic prepared in this embodiment has a porosity of 52.4%, an average pore size of 14.1 μm, and a standard sample bending strength of 1.85 MPa.

[0072] Using the aluminizing process in Example 1, the standard-sized SiC / composite sample had a flexural strength of ~412 MPa and an elastic modulus of ~171 GPa.

[0073] Example 3

[0074] This embodiment describes a method for preparing porous ceramics by photocuring sol-modified SiC particles, including the following steps:

[0075] Sol-gel modification of S1 and SiC particles

[0076] SiC particles were ultrasonically cleaned with anhydrous ethanol at 180W for 30 min to remove surface impurities, and then dried at 120℃ for 2 h. The dried SiC particles were slowly added to premixed solution B, and then premixed solution A was quickly added to obtain a reaction mixture. The reaction mixture was stirred at 25℃ under sealed conditions for 12 h to perform sol modification on the surface of SiC particles. After completion, the particles were centrifuged at 2000 r / min, washed three times with anhydrous ethanol, and dried at 100℃ for 5 h to obtain modified SiC particles.

[0077] Premix A is prepared by mixing tetraethyl orthosilicate and anhydrous ethanol a; premix B is prepared by mixing deionized water, ammonia, and anhydrous ethanol b.

[0078] The mass ratio of the raw materials in the reaction mixture is as follows: 1 part SiC particles, 5 parts tetraethyl orthosilicate, 8 parts anhydrous ethanol a, 4 parts deionized water, 2 parts ammonia, and 5.5 parts anhydrous ethanol b; wherein the SiC particles include three types with average particle sizes of 10μm, 90μm and 165μm, in a ratio of 3:7:1, with a purity ≥99.5%, and the concentration of the ammonia is 1.75mol / L.

[0079] S2. Preparation of photocurable SiC slurry

[0080] The composition of the photocurable SiC slurry is as follows: the mass ratio of modified SiC particles obtained in S1 to the photocurable resin premix is ​​11:5.5; the dispersant is 1% of the mass of the photocurable resin premix; the photoinitiator is 10% of the mass of the photocurable resin premix; and the UV absorber is 0.8% of the mass of the photocurable resin premix. The photocurable resin premix is ​​purchased Versace rigid resin (101S1); the UV absorber is UV-770; the photoinitiator is (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide; and the dispersant is an oily thickener (J0602).

[0081] The preparation method is as follows: Photoinitiator and ultraviolet absorber are added to photocurable resin premix and stirred at 25°C for 45 min to obtain slurry 1; half the mass of modified SiC particles and half the mass of dispersant are added to slurry 1, stirred at 25°C for 45 min and then ball-milled for 8 h to obtain slurry 2; the other half the mass of modified SiC particles and the other half the mass of dispersant are added to slurry 2, stirred at 25°C for 45 min and then ball-milled for 8 h, and after vacuum degassing, photocurable dark SiC slurry is obtained.

[0082] S3, photocurable SiC preform

[0083] The photocurable dark SiC slurry obtained in S2 was applied to a glass slide of a photocurable 3D printer and cured under a 405nm ultraviolet light source for 15 seconds. The uncured slurry was then removed, and the thickness of a single layer was measured to be 200μm using a micrometer. Then, the printing was performed layer by layer to obtain a shaped SiC preform with dimensions of 5mm×5mm×50mm. The obtained SiC preform was then placed in a forced-air drying oven and heated to 135℃ at a heating rate of 0.3℃ / min for 1.5h to obtain a photocurable SiC preform.

[0084] S4. Degreasing and oxidation sintering of photocured SiC preforms

[0085] Under dry conditions, the photocured SiC preform obtained by S3 was placed in a muffle furnace and heated from room temperature to 700℃ at a rate of 0.4℃ / min and held for 0.5h; then heated to 1300℃ at a rate of 30℃ / min and held for 3h; after the end, it was cooled to room temperature, ultrasonically cleaned with anhydrous ethanol for 20min, and then dried at 80℃ for 6h to obtain porous SiC ceramic.

[0086] In this embodiment, the average thickness of the SiO2 layer formed on the surface of SiC particles after sol-gel modification is ~910nm, and the coverage rate on the SiC surface is 98.3%.

[0087] The porous SiC ceramic prepared in this embodiment has a porosity of 51.8%, an average pore size of 15.8 μm, and a standard sample bending strength of 1.78 MPa.

[0088] Using the aluminizing process in Example 1, the standard-sized SiC / composite sample had a flexural strength of ~417 MPa and an elastic modulus of ~174 GPa.

[0089] Comparative Example 1

[0090] This comparative example uses the SiC particles and slurry formulation described in Example 1 to prepare the SiC particle slurry. The difference is that the SiC particles in this comparative example were not treated with a sol-gel. After exposing the slurry to a 405nm ultraviolet light source for 10 seconds, the uncured slurry was cleaned off, and the cured thickness was measured to be only 90μm using a micrometer. This indicates that the sol-gel treated SiC particles can significantly improve the single-layer cured thickness during photopolymerization printing.

[0091] The method for preparing porous ceramics by photocuring sol-modified SiC particles according to the present invention allows for the design of the macroscopic shape, microscopic pores, and SiO2 film thickness of complex porous SiC ceramics as needed. This effectively meets the requirements for aluminizing and is expected to find application and widespread use in the photocuring printing of dark-colored SiC ceramics and the manufacturing of complex high-partial SiC / Al composite materials. The technical principles and methods of this invention can be extended to the preparation of arbitrary high-partial ceramic-metal composite materials, and even the preparation of high-melting-point metal-low-melting-point composite metal materials, providing broad guidance.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing porous ceramics for aluminizing processes by photocuring sol-modified SiC particles, characterized in that, Includes the following steps: Sol-gel modification of S1 and SiC particles SiC particles were ultrasonically cleaned with anhydrous ethanol to remove surface impurities and then dried. They were then added to premixed solution B, followed by premixed solution A to obtain a reaction mixture. The reaction mixture was stirred at 25°C under sealed conditions for 9-16 h to perform sol modification on the surface of the SiC particles. After centrifugation, washing and drying, the modified SiC particles were obtained. The premix A is prepared by mixing tetraethyl orthosilicate and anhydrous ethanol a; the premix B is prepared by mixing deionized water, ammonia water and anhydrous ethanol b. The mass ratio of the raw materials in the reaction mixture is as follows: 0.5-1.0 parts SiC particles, 3-5 parts tetraethyl orthosilicate, 6-12 parts anhydrous ethanol a, 4-6 parts deionized water, 0.5-4 parts ammonia, and 4-20 parts anhydrous ethanol b; the concentration of the ammonia is 0.5-1.75 mol / L. After sol-gel modification, a SiO2 film is attached to the surface of the SiC particles. The thickness of the SiO2 film is 500~1000 nm, and the coverage of the SiC surface is >97%. S2. Preparation of photocurable SiC slurry The modified SiC particles obtained in S1 are combined with Vanscore rigid resin to prepare a photocurable SiC slurry. The photocurable SiC slurry also contains a dispersant, a photoinitiator, and an ultraviolet light absorber. The mass ratio of the modified SiC particles to the rigid resin of Versace is 11:(5.5~6.5); the amount of dispersant added is 1%~5% of the mass of the rigid resin of Versace; the amount of photoinitiator added is 5%~10% of the mass of the rigid resin of Versace; and the amount of ultraviolet light absorber added is 0.5%~1% of the mass of the rigid resin of Versace. S3, photocurable SiC preform The photocurable SiC slurry obtained in S2 was photocured and 3D printed, and after drying, a photocurable SiC preform was obtained. S4. Degreasing and oxidation sintering of photocured SiC preforms The photocured SiC preform obtained from S3 was subjected to degreasing and oxidation sintering treatment using an integrated degreasing and sintering process, which was completed in one furnace under atmospheric conditions. The method was as follows: Under dry conditions, the photocured SiC preform was placed in a muffle furnace and heated to 650-700℃ at a rate of 0.1-0.5℃ / min, held for 0.5-2 h, and then heated to 1300-1400℃ at a rate of 10-40℃ / min, held for 0.2-3 h. After the process, it was cooled to room temperature, ultrasonically cleaned and dried to obtain porous SiC ceramic. The porous SiC ceramic has isotropic, uniform, and interconnected pores with a porosity of 45-55%.

2. The method according to claim 1, characterized in that, The SiC particles described in S1 are spherical particles with a particle size of 10~165 μm and a purity of ≥99.5%.

3. The method according to claim 1, characterized in that, The drying conditions for the SiC particles described in S1 after sol modification are: drying at 80~120℃ for 2~8 h.

4. The method according to claim 1, characterized in that, The preparation method of the photocurable SiC slurry described in S2 is as follows: a photoinitiator and an ultraviolet absorber are added to a Vansco rigid resin and stirred at 25°C for 30-60 min to obtain slurry 1; half the mass of modified SiC particles and half the mass of dispersant are added to slurry 1, stirred at 25°C for 30-60 min and then ball-milled for 6-8 h to obtain slurry 2; the other half the mass of modified SiC particles and the other half the mass of dispersant are added to slurry 2, stirred at 25°C for 30-60 min and then ball-milled for 6-8 h, and after vacuum degassing, a photocurable dark-colored SiC slurry is obtained.

5. The method according to claim 1, characterized in that, The photocuring conditions described in S3 are: photocuring 3D printing under ultraviolet light with a wavelength of 405 nm, with each layer having a curing thickness of 50~200 μm; the drying conditions are: heating to 120~150℃ at a heating rate of 0.2~0.6℃ / min and drying for 1~2 h.

6. The method according to claim 1, characterized in that, The drying temperature described in S4 is 80~120℃, and the time is 2~6h.

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