A photocurable silicon nitride ceramic slurry and its preparation method

Abstract

This invention discloses a photocurable silicon nitride ceramic slurry and its preparation method, relating to the field of photocurable printing technology. The preparation method includes the following steps: S1, preparing modified silicon nitride powder: coating the surface of silicon nitride powder with salt using a recrystallization method to obtain modified silicon nitride powder; S2, ball milling and mixing the modified silicon nitride powder and sintering aid, drying and sieving, and adding it to a resin premix to obtain the photocurable silicon nitride ceramic slurry. This invention utilizes the characteristic of saturated salt solutions precipitating upon cooling to coat the surface of silicon nitride powder with a layer of salt crystals. Because the refractive index of the salt crystal layer is lower and its light absorption is less, coating the surface of the silicon nitride powder with salt crystals can effectively reduce the refractive index and absorbance of the silicon nitride powder, improving the curing depth and printing accuracy of the slurry.

Description

Technical Field

[0001] This invention relates to the field of photopolymerization printing technology, and in particular to a photopolymerization silicon nitride ceramic slurry and its preparation method. Background Technology

[0002] Silicon nitride ceramics are widely used in various fields such as automotive, energy, and aerospace due to their excellent comprehensive properties. As engineering applications become increasingly sophisticated and complex, the demand for high-precision, complex-structure silicon nitride is constantly increasing. However, current high-precision, complex-structure silicon nitride is mainly processed using traditional methods such as turning, milling, and grinding, which are costly and time-consuming. Therefore, research and exploration of silicon nitride additive manufacturing, a new technology, is essential.

[0003] Currently, additive manufacturing, due to its ability to rapidly produce high-precision and complex shapes, has given rise to numerous printing processes, such as Selective Laser Sintering (SLS), Selective Laser Melting (SLM), Binder Jetting (3DP), Direct Writing (DIW), Digital Light Processing (DLP), and Stereolithography (SLA). Among these, because ceramics have high melting and boiling points, SLS and SLM are mainly used in metal additive manufacturing; while 3DP and DIW have lower precision and are only suitable for scenarios with lower precision and mechanical performance requirements; SLA uses point light source exposure, which is relatively slow. Therefore, DLP printing is currently the printing process that can balance high precision and high speed.

[0004] However, gray silicon nitride powder has high absorbance and refractive index, making it more difficult to achieve high curing depth and high printing accuracy compared to ceramics such as alumina, zirconium oxide, and aluminum nitride. To address this issue, researchers have proposed methods such as high-temperature oxidation of the silicon nitride powder surface and co-precipitation coating with white additives. However, high-temperature oxidation is energy-intensive and time-consuming, and its control over the oxygen content in the matrix is ​​poor, affecting thermal conductivity and high-temperature performance. Co-precipitation methods, in order to obtain a uniform white coating layer, require a limited amount of powder to be modified each time, and the formulation of the white additives is also limited, restricting the application of photocurable silicon nitride ceramics. Summary of the Invention

[0005] The technical problem to be solved by this invention is that silicon nitride ceramic slurry has a low curing depth and poor printing accuracy, which limits the application of photocurable silicon nitride ceramics.

[0006] To address the above problems, the present invention proposes the following technical solution:

[0007] On one hand, the present invention provides a method for preparing photocurable silicon nitride ceramic slurry, comprising the following steps:

[0008] S1. Preparation of modified silicon nitride powder: Salt is coated on the surface of silicon nitride powder by recrystallization to obtain modified silicon nitride powder;

[0009] S2. The modified silicon nitride powder and sintering aid are ball-milled and mixed, dried and sieved, and then added to the resin premix to obtain a photocurable silicon nitride ceramic slurry.

[0010] This invention utilizes the characteristic of saturated salt solutions precipitating upon cooling to coat the surface of silicon nitride powder with a layer of salt crystals. Since the refractive index of the salt crystal layer is lower (e.g., the refractive index of KCL crystal is about 1.37), it absorbs less light. Therefore, coating the surface of silicon nitride powder with salt crystals can reduce the refractive index and light absorption of silicon nitride powder to a certain extent, thus making it easier to obtain silicon nitride DLP printed products with high curing depth and high precision.

[0011] Further, step S1 specifically includes:

[0012] S11. Salt and silicon nitride powder are mixed with deionized water at a temperature of 40-60℃ to obtain a suspension.

[0013] S12. Reduce the temperature of the suspension until the salt content in the suspension is supersaturated, so that the salt precipitates out of the suspension and coats the silicon nitride powder;

[0014] S13. Filter to obtain modified silicon nitride powder.

[0015] In this invention, sieved silicon nitride powder is added to a high-concentration salt solution. As the temperature decreases, the salt solution becomes supersaturated and solid salt crystals precipitate. The precipitated solid salt crystals grow using silicon nitride grains as templates, thereby uniformly coating the surface of the silicon nitride powder with a layer of salt crystals.

[0016] Specifically, in step S13, filtration is performed by suction filtration, and the filtered solid is dried in an oven at 50-60°C to obtain modified silicon nitride powder.

[0017] Furthermore, in step S12, the content of the precipitated salt is 0.1-10% of the mass of the silicon nitride powder.

[0018] Furthermore, the D50 particle size of the silicon nitride powder is 0.5–3 μm.

[0019] Specifically, in step S2, the process further includes adding silicon nitride balls with a diameter of 3 mm in the presence of a solvent and ball milling them using a planetary ball mill at a speed of 200-300 r / min for 1-3 h. The amount of silicon nitride balls used is 1.5-3 times the mass of the powder. The solvent is at least one of ethanol, isopropanol, n-butanol, ethyl acetate, butyl acetate, butanone, and cyclohexanone, preferably ethanol or n-butanol, and the amount is 2-3 times the mass of the powder.

[0020] After ball milling, the powder is dried in an oven at 50-60℃ and sieved through a 100-200 mesh.

[0021] Furthermore, the solid content of the photocurable silicon nitride ceramic slurry is 40-50 vol%.

[0022] Furthermore, the salt is at least one of KCl, NaCl, or KNO3.

[0023] Further, the resin premix comprises resin, dispersant, and photoinitiator; the resin is selected from at least one of BPA1OEODMA, TMPTA, HDDA, PPTTA, DOP, and n-octanol; the dispersant is at least one of KOS-110, BYK-110, and BYK-111, and is used in an amount of 0.5 to 2 wt% of the solid content; the photoinitiator is at least one of 819, 1000, 1156, TPO, and TPO-L, and is used in an amount of 1 to 1.5 wt% of the resin.

[0024] More preferably, the dispersant is at least one of KOS-110 and BYK-110, and the amount used is 0.5 to 2 wt% of the solid content; the photoinitiator is one of 819 and TPO, and the amount used is 1 wt% of the resin.

[0025] It should be noted that when preparing the slurry, the resin premix should first be ultrasonically mixed evenly for 2–5 minutes. After the slurry is prepared, it should be homogenized using a homogenizer at a speed of 1500–2000 r / min for 30–120 s.

[0026] Furthermore, the sintering aid includes alkali metal compounds and rare earth compounds, wherein the alkali metal compound is at least one of MgO, MgF2, Al2O3 and CaO, and the rare earth compound is at least one of Y2O3, Yb2O3, CeO, Dy2O3, YF3 and YbF3.

[0027] On the other hand, the present invention provides a photocurable silicon nitride ceramic slurry, which is prepared by the preparation method described above.

[0028] In another aspect, the present invention provides a photocurable silicon nitride ceramic, which is prepared by the above-described preparation method using a photocurable silicon nitride ceramic slurry, or obtained by DLP printing, debinding, and sintering of the photocurable silicon nitride ceramic slurry.

[0029] Furthermore, the process parameters for photopolymerization printing are: exposure time 3-12s.

[0030] Compared with the prior art, the technical effects achieved by the present invention include:

[0031] The present invention provides a method for preparing photocurable silicon nitride ceramic slurry, comprising the following steps: S1, preparing modified silicon nitride powder: coating the surface of silicon nitride powder with salt by recrystallization to obtain modified silicon nitride powder; S2, ball milling and mixing the modified silicon nitride powder and sintering aid, drying and sieving, and adding it to a resin premix to obtain photocurable silicon nitride ceramic slurry. The present invention utilizes the characteristic of saturated salt solution precipitation upon cooling to coat the surface of silicon nitride powder with a layer of salt crystals. Since the refractive index of the salt crystal layer is lower (e.g., the refractive index of KCL crystal is approximately 1.37), it absorbs less light. Therefore, coating the surface of the silicon nitride powder with salt crystals can effectively reduce the refractive index and absorbance of the silicon nitride powder, thereby improving the curing depth and printing accuracy of the slurry. Experiments show that by modifying silicon nitride powder with salt coating, the curing depth of silicon nitride slurry is increased by 14%–23% and 21%–31% compared to unmodified powder and powder modified with conventional modifier (KH570), respectively. This invention significantly improves the problem of low curing depth and poor accuracy caused by the large refractive index and light absorption of silicon nitride slurry during photopolymerization printing. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is the solubility curve of KCl crystals. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0036] It should also be understood that the terminology used in this specification of embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used in this specification of embodiments of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0037] Example 1

[0038] This embodiment provides a photocurable silicon nitride ceramic slurry, its preparation method, and the silicon nitride ceramic obtained from the slurry. Details are as follows:

[0039] Step S1: Weigh 37.92g of KCl crystals and 30g of Si3N4 powder with a D50 of 0.7um, add 100ml of deionized water and mix well. Heat the solution to 40℃ to obtain a suspension.

[0040] Step S2: Reduce the temperature of the suspension to 30°C to allow KCl to precipitate from the suspension and coat the Si3N4 powder.

[0041] Step S3: Remove deionized water from the suspension by vacuum filtration, and dry the solid in an oven at 60°C to obtain 29.99g of modified silicon nitride powder. This is due to the loss caused during vacuum filtration (e.g., some powder adheres to the vacuum funnel and filter paper), and the final amount obtained is less than the amount of the original silicon nitride powder.

[0042] Step S4: Weigh the modified silicon nitride powder according to the ratio Y2O3:MgO = 93:2:5 (wt%), mix them, and the total amount is 30g. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve it through a 100-mesh screen to obtain the mixed powder.

[0043] Step S5: Weigh 6g of resin according to the ratio of PPTTA:HDDA:DOP = 5:2:3; weigh 0.13g of dispersant BYK-110 (1 wt% of the powder); weigh 0.06g of photoinitiator TPO (1 wt% of the resin). After mixing, sonicate for 3 minutes to obtain the resin premix.

[0044] Step S6: Add 13g of the mixed powder from step S4 to the resin premix from step S5, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0045] Step S7: The obtained silicon nitride ceramic slurry is printed into a shape using a photopolymerization printer, and after degreasing and sintering, silicon nitride ceramic devices are obtained.

[0046] Example 2

[0047] This embodiment provides a photocurable silicon nitride ceramic slurry, its preparation method, and the silicon nitride ceramic obtained from the slurry. Details are as follows:

[0048] Step S1: Weigh 38.52g of KCl crystals and 30g of Si3N4 powder with a D50 of 0.7um, add 100ml of deionized water and mix well. Heat the solution to 40℃ to obtain a suspension.

[0049] Step S2: Reduce the temperature of the suspension to 30°C to allow KCl to precipitate from the suspension and coat the Si3N4 powder.

[0050] Step S3: Remove deionized water from the suspension by vacuum filtration, and dry the solid in an oven at 60°C to obtain 30.58g of modified silicon nitride powder.

[0051] Step S4: Weigh the modified silicon nitride powder according to the ratio Y2O3:MgO = 93:2:5 (wt%), mix them, and the total amount is 30g. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve it through a 100-mesh screen to obtain the mixed powder.

[0052] Step S5: Weigh 6g of resin according to the ratio of PPTTA:HDDA:DOP = 5:2:3; weigh 0.13g of dispersant BYK-110 (1 wt% of the powder); weigh 0.06g of photoinitiator TPO (1 wt% of the resin). After mixing, sonicate for 3 minutes to obtain the resin premix.

[0053] Step S6: Add 13g of the mixed powder from step S4 to the resin premix from step S5, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0054] Step S7: Print the obtained silicon nitride ceramic slurry into a shape using a photopolymerization printer to obtain a silicon nitride ceramic device.

[0055] Example 3

[0056] This embodiment provides a photocurable silicon nitride ceramic slurry, its preparation method, and the silicon nitride ceramic obtained from the slurry. Details are as follows:

[0057] Step S1: Weigh 39.12g of KCl crystals and 30g of Si3N4 powder with a D50 of 0.7um, add 100ml of deionized water and mix well. Heat the solution to 40℃ to obtain a suspension.

[0058] Step S2: Reduce the temperature of the suspension to 30°C to allow KCl to precipitate from the suspension and coat the Si3N4 powder.

[0059] Step S3: Remove deionized water from the suspension by vacuum filtration, and dry the solid in an oven at 60°C to obtain 31.16g of modified silicon nitride powder.

[0060] Step S4: Weigh the modified silicon nitride powder according to the ratio Y2O3:MgO = 93:2:5 (wt%), mix them, and the total amount is 30g. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve it through a 100-mesh screen to obtain the mixed powder.

[0061] Step S5: Weigh 6g of resin according to the ratio of PPTTA:HDDA:DOP = 5:2:3; weigh 0.13g of dispersant BYK-110 (1 wt% of the powder); weigh 0.06g of photoinitiator TPO (1 wt% of the resin). After mixing, sonicate for 3 minutes to obtain the resin premix.

[0062] Step S6: Add 13g of the mixed powder from step S4 to the resin premix from step S5, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0063] Step S7: Print the obtained silicon nitride ceramic slurry into a shape using a photopolymerization printer to obtain a silicon nitride ceramic device.

[0064] Example 4

[0065] This embodiment provides a photocurable silicon nitride ceramic slurry, its preparation method, and the silicon nitride ceramic obtained from the slurry. Details are as follows:

[0066] Step S1: Weigh 39.72g of KCl crystals and 30g of Si3N4 powder with a D50 of 0.7um, add 100ml of deionized water and mix well. Heat the solution to 40℃ to obtain a suspension.

[0067] Step S2: Reduce the temperature of the suspension to 30°C to allow KCl to precipitate from the suspension and coat the Si3N4 powder.

[0068] Step S3: Remove deionized water from the suspension by vacuum filtration, and dry the solid in an oven at 60°C to obtain 31.75g ​​of modified silicon nitride powder.

[0069] Step S4: Weigh the modified silicon nitride powder according to the ratio Y2O3:MgO = 93:2:5 (wt%), mix them, and the total amount is 30g. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve it through a 100-mesh screen to obtain the mixed powder.

[0070] Step S5: Weigh 6g of resin according to the ratio of PPTTA:HDDA:DOP = 5:2:3; weigh 0.13g of dispersant BYK-110 (1 wt% of the powder); weigh 0.06g of photoinitiator TPO (1 wt% of the resin). After mixing, sonicate for 3 minutes to obtain the resin premix.

[0071] Step S6: Add 13g of the mixed powder from step S4 to the resin premix from step S5, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0072] Step S7: Print the obtained silicon nitride ceramic slurry into a shape using a photopolymerization printer to obtain a silicon nitride ceramic device.

[0073] Example 5

[0074] This embodiment provides a photocurable silicon nitride ceramic slurry, its preparation method, and the silicon nitride ceramic obtained from the slurry. Details are as follows:

[0075] Step S1: Weigh 40.32g of KCl crystals and 30g of Si3N4 powder with a D50 of 0.7um, add 100ml of deionized water and mix well. Heat the solution to 50℃ to obtain a suspension.

[0076] Step S2: Reduce the temperature of the suspension to 30°C to allow KCl to precipitate from the suspension and coat the Si3N4 powder.

[0077] Step S3: Remove deionized water from the suspension by vacuum filtration, and dry the solid in an oven at 60°C to obtain 32.34g of modified silicon nitride powder.

[0078] Step S4: Weigh the modified silicon nitride powder according to the ratio Y2O3:MgO = 93:2:5 (wt%), mix them, and the total amount is 30g. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve it through a 100-mesh screen to obtain the mixed powder.

[0079] Step S5: Weigh 6g of resin according to the ratio of PPTTA:HDDA:DOP = 5:2:3; weigh 0.13g of dispersant BYK-110 (1 wt% of the powder); weigh 0.06g of photoinitiator TPO (1 wt% of the resin). After mixing, sonicate for 3 minutes to obtain the resin premix.

[0080] Step S6: Add 13g of the mixed powder from step S4 to the resin premix from step S5, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0081] Step S7: Print the obtained silicon nitride ceramic slurry into a shape using a photopolymerization printer to obtain a silicon nitride ceramic device.

[0082] Example 6

[0083] This embodiment provides a photocurable silicon nitride ceramic slurry, its preparation method, and the silicon nitride ceramic obtained from the slurry. Details are as follows:

[0084] Step S1: Weigh 37.92g of KCl crystals and 30g of Si3N4 powder with a D50 of 0.7um, add 100ml of deionized water and mix well. Heat the solution to 40℃ to obtain a suspension.

[0085] Step S2: Reduce the temperature of the suspension to 30°C to allow KCl to precipitate from the suspension and coat the Si3N4 powder.

[0086] Step S3: Remove deionized water from the suspension by vacuum filtration, and dry the solid in an oven at 60°C to obtain 29.99g of modified silicon nitride powder.

[0087] Step S4: Weigh the modified silicon nitride powder according to the ratio Y2O3:MgO = 93:2:5 (wt%), mix them, and the total amount is 30g. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve it through a 100-mesh screen to obtain the mixed powder.

[0088] Step S5: Weigh 5g of resin according to the ratio of PPTTA:HDDA:DOP = 5:2:3; weigh 2wt% (0.26g) of dispersant BYK-110 (powder); weigh 1wt% (0.06g) of photoinitiator TPO (photoinitiator). After mixing, sonicate for 3 minutes to obtain the resin premix.

[0089] Step S6: Add 16.25g of the mixed powder from step S4 to the resin premix from step S5, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 50vol%.

[0090] Step S7: The obtained silicon nitride ceramic slurry is printed into a shape using a photopolymerization printer, and after degreasing and sintering, silicon nitride ceramic devices are obtained.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that the silicon nitride powder in this comparative example is not salt-coated. The specific preparation process is as follows:

[0093] Step S1: Weigh 30g of a mixed powder of Si3N4 (D50 = 0.7):Y2O3:MgO = 93:2:5 (wt%) according to the ratio. Add 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls to a planetary ball mill and mix and mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls, and then place the mixture in an oven at 60℃ to dry. After drying, sieve through a 100-mesh screen to obtain the mixed powder.

[0094] Step S2: Weigh 6g of resin according to PPTTA:HDDA:DOP = 5:2:3; weigh 1wt% of dispersant BYK-110 (0.13g) and 1wt% of photoinitiator TPO (0.06g) of resin; mix and sonicate for 3 minutes to obtain resin premix.

[0095] Step S3: Add 13g of the mixed powder from step S1 to the resin premix from step S2, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0096] Step S4: Print the obtained silicon nitride ceramic slurry into a shape using a photopolymerization printer to obtain a silicon nitride ceramic device.

[0097] Comparative Example 2

[0098] The difference between this comparative example and Example 1 is that the silicon nitride powder in this comparative example is modified with KH570. The specific preparation process is as follows:

[0099] Step S1: Weigh 30g of a mixed powder of Si3N4 (D50 = 0.7):Y2O3:MgO = 93:2:5 (wt%) according to the ratio. Weigh 2wt% of KH570, i.e., 0.6g. Add the mixed powder and KH570 to 100g of anhydrous ethanol and 50g of 3mm silicon nitride balls. Mix and ball mill in a planetary ball mill at 300r / min for 1 hour. Filter to remove the silicon nitride balls. Place the mixture in an oven at 60℃ to dry. After drying, sieve through a 100-mesh screen to obtain the KH570 modified mixed powder.

[0100] Step S2: Weigh 6g of resin according to PPTTA:HDDA:DOP = 5:2:3; weigh 1wt% of dispersant BYK-110 (0.13g) and 1wt% of photoinitiator TPO (0.06g) of resin; mix and sonicate for 3 minutes to obtain resin premix.

[0101] Step S3: Add 13g of the mixed powder from step S1 to the resin premix from step S2, and mix with a homogenizer at 2000r / min for 60s to prepare a silicon nitride ceramic slurry with a solid content of 40vol%.

[0102] Step S4: Print the obtained silicon nitride ceramic slurry into a shape using a photopolymerization printer to obtain a silicon nitride ceramic device.

[0103] Table 1. At 12 mJ / cm 2 The curing depth (μm) of the silicon nitride slurries prepared in Example 1 and Comparative Examples 1-2 at different curing times under the given exposure energy.

[0104]

[0105] Table 2. At 120.1 mJ / cm 2 Curing depth of silicon nitride slurry prepared in different embodiments under total exposure energy

[0106]

[0107]

[0108] Note: Example of calculating KCl precipitation amount: See the solubility of KCl crystals at different temperatures. Figure 1 Using 30g of silicon nitride powder as the main component, the solubility of KCl is 45.8g at 60℃, and the theoretical solubility of KCl is 40.1g at 40℃. If 40.7g of KCl is added to 100ml of deionized water at 60℃, and the solution temperature is then lowered to 40℃, theoretically 0.6g of KCl will precipitate, which is 2wt% of the 30g silicon nitride powder. Therefore, the theoretical precipitation amount is 2wt%.

[0109] As shown in Tables 1 and 2, the KCl doping in the embodiments of the present invention is set with a theoretical KCl precipitation gradient of 2 wt%. In embodiments with a theoretical KCl precipitation of 2% to 10%, the curing depth of the slurry is increased by 14% to 23% compared to unmodified silicon nitride powder, and by 21% to 31% compared to 2 wt% KH570 modified silicon nitride powder. Because the modified silicon nitride powder of the present invention is coated with KCl crystals, its surface absorption and scattering effects on light are reduced compared to unmodified silicon nitride powder, thus increasing the curing depth at the same total exposure energy. Therefore, at the same curing depth, the total exposure energy required for KCl-modified silicon nitride slurry is reduced, and the overexposure width is correspondingly reduced, thereby improving printing accuracy.

[0110] In this embodiment of the invention, KCl crystals are used as an example to recrystallize and coat silicon nitride powder. In other embodiments, NaCl or KNO3 crystals can be used to recrystallize and coat silicon nitride powder.

[0111] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0112] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a photocurable silicon nitride ceramic slurry, characterized by, The method comprises the following steps: S1, preparing modified silicon nitride powder: using recrystallization method to coat salt on the surface of silicon nitride powder to obtain modified silicon nitride powder; the salt is at least one of KCl, NaCl or KNO3; S2, mixing the modified silicon nitride powder and sintering aid by ball milling, drying and sieving, and adding into resin premix to obtain photocured silicon nitride ceramic slurry; The step S1 specifically comprises: S11, mixing salt and silicon nitride powder in deionized water at 40-60℃ to obtain a suspension; S12, reducing the temperature of the suspension to make the salt content in the suspension supersaturated, so that the salt is precipitated from the suspension and coated on the silicon nitride powder; S13, filtering to obtain modified silicon nitride powder.

2. The method of claim 1, wherein the photo-curable silicon nitride ceramic slurry is prepared by the steps of: mixing a silicon nitride powder, a photo-curable resin, a photo-initiator, and a solvent to prepare a mixture; and adding a dispersant to the mixture to prepare the photo-curable silicon nitride ceramic slurry. In the step S12, the precipitated salt content is 0.1-10% of the mass of the silicon nitride powder.

3. The method of claim 1, wherein the photo-curable silicon nitride ceramic slurry is prepared by the steps of: mixing a silicon nitride powder, a photo-curable resin, a photo-initiator, and a solvent to prepare a mixture; and adding a dispersant to the mixture to prepare the photo-curable silicon nitride ceramic slurry. The D50 particle size of the silicon nitride powder is 0.5-3um.

4. The method for preparing photocurable silicon nitride ceramic slurry as described in claim 1, characterized in that, The solid content of the photocured silicon nitride ceramic slurry is 40-50vol%.

5. The method of claim 1, wherein the photo-curable silicon nitride ceramic slurry is prepared by the steps of: mixing a silicon nitride powder, a photo-curable resin, a photo-initiator, and a solvent to prepare a mixture; and adding a dispersant to the mixture to prepare the photo-curable silicon nitride ceramic slurry. The resin premix is composed of resin, dispersant and photoinitiator; the resin is at least one of BPA10EODMA, TMPTA, HDDA, PPTTA, DOP and n-octanol; the dispersant is at least one of KOS-110, BYK-110 and BYK-111, and the amount is 0.5-2wt% of the solid content; the photoinitiator is at least one of 819, 1000, 1156, TPO and TPO-L, and the amount is 1-1.5wt% of the resin.

6. The method of claim 1, wherein the photo-curable silicon nitride ceramic slurry is prepared by the steps of: mixing a silicon nitride powder, a photo-curable resin, a photo-initiator, and a solvent to prepare a mixture; and adding a dispersant to the mixture to prepare the photo-curable silicon nitride ceramic slurry. The sintering aid comprises at least one of MgO, MgF2, Al2O3 and CaO and rare earth compound, wherein the rare earth compound is at least one of Y2O3, Yb2O3, Dy2O3, YF3 and YbF3.

7. A photocurable silicon nitride ceramic slurry, characterized by, The photocured silicon nitride ceramic slurry prepared by the preparation method of any one of claims 1-6, or the photocured silicon nitride ceramic slurry prepared by the preparation method of any one of claims 1-6 is subjected to DLP printing, debinding and sintering to obtain a blank.

8. A photocured silicon nitride ceramic, characterized by, ​

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