Ceramic core slurry and preparation method thereof

Abstract

The invention provides ceramic core slurry, and relates to the technical field of photocuring 3D printing additive manufacturing, the ceramic core slurry comprises ceramic powder, a modifier and a photocuring resin mixture; wherein the modifier is a polymeric dispersant. The modifier provided by the invention adopts a polymeric dispersant, and can react with-OH on the surface of the powder to form an organic layer (-Si-O-Al-) and reduce the surface energy, so that the dispersibility of the powder in a light-cured resin mixture is improved, that is, the compatibility of the modified powder and resin is improved, the friction among ceramic particles is reduced, and the particles can smoothly and relatively slide; therefore, the solid content of the ceramic core slurry is improved, and the viscosity is reduced.

Description

Technical Field

[0001] This invention belongs to the field of photopolymerization 3D printing additive manufacturing technology, specifically relating to a ceramic core slurry and its preparation method. Background Technology

[0002] Heavy-duty gas turbines possess advantages such as high power, high efficiency, and high reliability, and are widely used in aerospace, power, and marine industries. The core component of a heavy-duty gas turbine is the turbine itself, which consists of multiple blades. The shape and structure of these blades are crucial to the turbine's performance. As a key transitional component forming the internal cooling structure of the turbine blades, the ceramic core's shape and structure become increasingly complex, and its performance requirements become increasingly stringent.

[0003] Traditional molding processes suffer from drawbacks in fabricating complex ceramic cores, including complex processes, long cycles, high processing difficulty, low yield, and high production costs. Unlike traditional molding processes, photopolymer additive manufacturing (SEM) technology is based on a three-dimensional digital model. Through support setup and slicing, it generates computer-executable pixel units. Laser scanning layer by layer allows for the stacking of these units to fabricate devices of arbitrary shapes. Therefore, SEM eliminates the need for molds, shortening manufacturing time and significantly improving the complexity, dimensional accuracy, and surface finish of ceramic core structures. It also allows for more precise control of various parameters during production, overcoming the shortcomings of traditional ceramic core manufacturing processes. In practical applications, the rapid fabrication of ceramic cores using SEM can accelerate the upgrading of ceramic cores, improve production efficiency and product quality, reduce production costs, and promote the development of turbine blades, thereby further accelerating the development of heavy-duty gas turbines.

[0004] The low-viscosity, high-solids-content photopolymer ceramic slurry and its preparation method are key challenges in the photopolymer additive manufacturing of ceramic cores. The applicant has discovered that low-viscosity ceramic slurries ensure leveling and reduce interlayer defects during printing; the powder dispersion in low-viscosity slurries is more uniform, reducing light scattering and resulting in higher curing efficiency; and higher solids content reduces defects such as green body cracking caused by excessive resin content during printing, yielding high-precision ceramic core blanks with intact and defect-free surfaces. However, in existing additive manufacturing ceramic slurries, high solids content typically leads to high viscosity. Summary of the Invention

[0005] Therefore, the present invention provides a ceramic core slurry and its preparation method, which can solve the problem that ceramic slurries in the prior art are difficult to have both low viscosity and high solid content.

[0006] To address the above problems, the present invention provides a ceramic core slurry, which comprises a mixture of ceramic powder, a modifier, and a photocurable resin; The modifier is a polymeric dispersant.

[0007] Furthermore, the polymeric dispersant is a group carrying acidic or basic groups, or a group that can combine with hydroxyl groups on the surface of the ceramic powder.

[0008] Furthermore, the ceramic powder is SiO2 ceramic powder and / or Al2O3 ceramic powder; Preferably, the particle size of the SiO2 ceramic powder is 5-15 μm; Preferably, the Al2O3 ceramic powder has a particle size of 10-20 μm.

[0009] Furthermore, the cured resin mixture includes a photocurable resin, a monomer, and a photoinitiator; The photocurable resin includes cationic photocurable resin and free radical photocurable resin; the monomer includes cationic monomer and free radical monomer; the photoinitiator includes cationic photoinitiator and free radical photoinitiator.

[0010] Furthermore, by weight percentage, the cured resin mixture comprises the following components: 28-32 wt% cationic photocurable resin, 23-34 wt% free radical photocurable resin, 17-19 wt% cationic monomer, 20-24 wt% free radical monomer, 1-3 wt% cationic photoinitiator, and 3-6 wt% free radical photoinitiator.

[0011] Furthermore, the cationic photocurable resin is one or more alicyclic epoxy acrylates selected from alkyl epoxy-triacrylate, cyclohexyl epoxy-pentaacrylate, and carboxyl-terminated pentaerythritol triacrylate; and / or The free radical type photocurable resin is one or more of bisphenol A epoxy acrylate, phenolic epoxy acrylate, and fatty acid modified epoxy acrylate compounds.

[0012] Furthermore, the cationic monomer is a mixed monomer containing epoxy and enol ether groups; and / or The free radical monomers include one or more of the following: monofunctional monomer lauryl acrylate, difunctional monomer tripropylene glycol diacrylate, and polyfunctional monomer trimethylolpropane triacrylate.

[0013] Furthermore, the cationic photoinitiator includes one of the following: aryl diazonium salt, diaryl iodonium salt, triaryl thiodonium salt, and ferrocene aryl salt; and / or The free radical photoinitiator includes one of hydroxy ketone derivatives and acylphosphine oxides.

[0014] On the other hand, the present invention provides a method for preparing the ceramic core slurry according to any one of the above claims, comprising the following steps: Powder modification: The ceramic powder is surface modified in a solvent to obtain modified powder; Slurry preparation: The modified powder is mixed with a photocurable resin mixture to obtain the ceramic core slurry.

[0015] Furthermore, the powder modification step specifically includes: mixing and stirring the ceramic powder, modifier, and solvent for 4-10 hours, ultrasonically dispersing for 1-2 hours, and drying in a 50°C oven for 8-10 hours; and / or The steps for preparing the slurry include: mixing the modified powder and the photocurable resin mixture in a ball mill; preferably, the ball mill speed is 300-700 rpm; and the mixing time is 10-20 h.

[0016] The ceramic core slurry and its preparation method provided by this invention have the following beneficial effects: 1. In one aspect, the present invention provides a ceramic core slurry, the ceramic core slurry comprising a mixture of ceramic powder, a modifier, and a photocurable resin; wherein the modifier is a polymeric dispersant. It should be noted that the polymeric dispersant can react with the -OH groups on the surface of the powder to form an organic layer (-Si-O-Al-), reducing surface energy and improving the dispersibility of the powder in the photocurable resin mixture. That is, the compatibility between the modified powder and the resin is improved, reducing friction between ceramic particles, allowing the particles to slide smoothly relative to each other, thereby increasing the solid content of the ceramic core slurry and reducing its viscosity.

[0017] 2. Furthermore, this invention further reduces the viscosity of the slurry system by adding monofunctional monomers with short molecular chains and low viscosity (<10 mPa·s). Additionally, this invention employs a free radical-cationic composite photosensitive resin system. The free radical resin facilitates rapid curing of the slurry (within seconds), ensuring efficient subsequent additive manufacturing printing; the cationic resin exhibits low curing shrinkage (<2%), which enhances the dimensional stability of the subsequent preform.

[0018] 3. On the other hand, the present invention provides a method for preparing the ceramic core slurry according to any one of the above claims, comprising the following steps: powder modification: surface modification of the ceramic powder in a solvent to obtain modified powder; slurry preparation: mixing the modified powder with a photocurable resin mixture to obtain the ceramic core slurry. Detailed Implementation

[0019] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with preferred embodiments, provides a detailed explanation of the specific implementation methods, structures, features, and effects according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0020] This invention provides a ceramic core slurry, which comprises a mixture of ceramic powder, a modifier, and a photocurable resin; The modifier is a polymeric dispersant, which may contain acidic groups (such as carboxyl-COOH, phosphate-PO3H2), basic groups (such as amino-NH2), amides, urea groups, or functional groups that can bind to the powder surface through hydrogen bonds or ionic bonds, and be firmly adsorbed onto the surface of ceramic powder particles through chemical reactions. In addition, it may contain non-polar long-chain alkyl groups, moderately polar polyester chains, or highly polar polyether chains. These chain segments extend into the surrounding resin system, forming a coating layer and generating a steric hindrance effect, preventing ceramic powder particles from approaching each other and flocculating or settling.

[0021] Based on the above method, the polymeric dispersant can react with -OH on the surface of the powder to form an organic layer (-Si-O-Al-), reducing the surface energy and improving the dispersibility of the powder in the photocurable resin mixture. That is, the compatibility between the modified powder and the resin is improved, reducing the friction between ceramic particles, and the particles can slide smoothly relative to each other, thereby increasing the solid content of the ceramic core slurry and reducing its viscosity.

[0022] Furthermore, the ceramic powder is SiO2 ceramic powder and / or Al2O3 ceramic powder; Preferably, the particle size of the SiO2 ceramic powder is 5-15 μm; Preferably, the particle size of the Al2O3 ceramic powder is 10-20 μm.

[0023] Furthermore, the cured resin mixture includes a photocurable resin, a monomer, and a photoinitiator; Among them, the photocurable resin includes cationic photocurable resin and free radical photocurable resin; the monomer includes cationic monomer and free radical monomer; the photoinitiator includes cationic photoinitiator and free radical photoinitiator.

[0024] By adding monofunctional monomers with short molecular chains and low viscosity (<10 mPa·s), the viscosity of the slurry system is further reduced. Furthermore, this invention employs a free radical-cationic composite photosensitive resin system. The free radical resin facilitates rapid curing of the slurry (within seconds), ensuring efficient subsequent additive manufacturing printing; the cationic resin exhibits low curing shrinkage (<2%), which enhances the dimensional stability of the subsequent preform.

[0025] Furthermore, by weight percentage, the cured resin mixture comprises the following components: 28-32 wt% cationic photocurable resin, 23-34 wt% free radical photocurable resin, 17-19 wt% cationic monomer, 20-24 wt% free radical monomer, 1-3 wt% cationic photoinitiator, and 3-6 wt% free radical photoinitiator.

[0026] Furthermore, the cationic photocurable resin is one or more alicyclic epoxy acrylates such as alkyl epoxy-triacrylate, cyclohexyl epoxy-pentaacrylate, and carboxyl-terminated pentaerythritol triacrylate; and / or The free radical type photocurable resin is one or more of bisphenol A epoxy acrylate, phenolic epoxy acrylate, and fatty acid modified epoxy acrylate compounds.

[0027] Furthermore, the cationic monomer is a mixed monomer containing epoxy and enol ether groups; and / or Free radical monomers include one or more of the following: monofunctional monomer lauryl acrylate, difunctional monomer tripropylene glycol diacrylate, and polyfunctional monomer trimethylolpropane triacrylate.

[0028] Furthermore, cationic photoinitiators include one of the following: aryl diazonium salts, diaryliodonium salts, triaryl thiodonium salts, and ferrocene aryl salts; and / or Free radical photoinitiators include one of hydroxy ketone derivatives and acylphosphine oxides.

[0029] The polymer chain modifier contains acidic groups (such as carboxyl-COOH, phosphate-PO3H2), basic groups (such as amino-NH2), amides, urea groups, or functional groups that can bind to the powder surface through hydrogen bonds or ionic bonds. It is firmly adsorbed onto the surface of ceramic powder particles through chemical reactions. In addition, it contains non-polar long-chain alkyl groups, moderately polar polyester chains, or highly polar polyether chains. These chain segments extend into the surrounding resin system, forming a coating layer and creating a steric hindrance effect, preventing ceramic powder particles from approaching each other and flocculating and settling. The comparison of sedimentation effects before and after modification is as follows: after 24 hours in a 10ml graduated cylinder, the volume of the supernatant of the modified slurry is ≤1.5ml; the volume of the supernatant of the unmodified slurry is ≤3ml.

[0030] Free radical polymerization has an extremely fast rate, providing initial strength and curing speed; cationic polymerization has a slower rate but strong post-curing ability and can continue even after light exposure stops. This ensures thorough deep curing and avoids poor curing of the underlying layers due to insufficient light penetration. Cationic polymerization is a ring-opening polymerization, with very small volume shrinkage (typically <3%), far lower than the shrinkage rate of free radical chain polymerization (which can reach 5-10% or more). By combining a high proportion of cationic resin (28-32%) with cationic monomer (17-19%), the polymerization shrinkage of the entire system is significantly reduced. This is crucial for ceramic additive manufacturing, minimizing internal stress and deformation during printing and ensuring dimensional accuracy. The introduction of free radical resins (such as acrylates) can adjust the rigidity of the network, avoiding the brittleness that may result from pure epoxy systems, improving toughness, and thus improving green strength and reducing brittle fracture. This mixed system has good compatibility and wettability with different types of ceramic powders (such as silica, alumina, zircon, etc.), which helps to prepare stable and uniform high-solids content slurries.

[0031] The formulation contains up to 37-43 wt% monomers, which are low-viscosity liquids. Their main function is to dilute the high-viscosity prepolymer (resin), thereby significantly reducing the viscosity of the entire mixture. Combinations of different types of monomers (such as epoxy and acrylate monomers) have a better dilution effect on the resin mixture than single-type monomers, resulting in a lower overall viscosity. Because the viscosity of the resin mixture itself is effectively reduced by the monomers, it leaves ample room for the addition of high volume fractions (typically >50 vol%) of ceramic powder. The system's good dispersibility and compatibility help the ceramic powder to disperse uniformly in low-viscosity media, preventing the formation of flocculated structures that lead to a sharp increase in viscosity, thus supporting higher solids content.

[0032] On the other hand, the present invention provides a method for preparing the ceramic core slurry according to any one of the above claims, comprising the following steps: Powder modification: Surface modification of ceramic powder is performed in a solvent to obtain modified powder; Slurry preparation: The modified powder and the photocurable resin mixture are mixed to obtain the ceramic core slurry.

[0033] Furthermore, the specific steps of powder modification are as follows: mixing and stirring the ceramic powder, modifier, and solvent for 4-10 hours, ultrasonically dispersing for 1-2 hours, and drying in a 50℃ oven for 8-10 hours; and / or The steps for preparing the slurry include: mixing the modified powder and the photocurable resin in a ball mill; preferably, the ball mill speed is 300-700 rpm; and the mixing time is 10-20 h.

[0034] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0035] Example 1 This embodiment prepares a low-viscosity, high-solids-content photocurable additive manufacturing ceramic core slurry. The raw material formulation is as follows: 60 parts by volume of SiO2 powder with a particle size of 8 micrometers, 10 parts by volume of Al2O3 powder with a particle size of 15 micrometers, and 30 parts by volume of photocurable resin. The photocurable resin formulation is as follows: 28 wt% alkyl epoxy-triacrylate; 34 wt% fatty acid-modified epoxy acrylate; 19 wt% mixed monomer containing epoxy and enol ether groups; 14 wt% lauryl acrylate; 3 wt% aryl thioonium salt; and 2 wt% acylphosphine oxide.

[0036] This embodiment provides a method for preparing a low-viscosity, high-solids-content photocurable additive manufacturing ceramic core slurry, comprising the following steps: 1) Powder modification: Mix 240g of SiO2 powder with a particle size of 8 micrometers, 40g of Al2O3 powder with a particle size of 15 micrometers, 0.5g of polymer chain modifier and 500ml of solvent and stir for 5h, ultrasonically disperse for 1h, dry in an oven at 50℃ for 10h, grind and sieve for later use.

[0037] 2) Slurry preparation: 28g of alkyl epoxy-triacrylate; 34g of fatty acid modified epoxy acrylate; 19g of mixed monomers containing epoxy and enol ether groups; 14g of lauryl acrylate; 3g of aryl thioonium salt; and 2g of acylphosphine oxide.

[0038] Stir and mix for 3 hours, then add the pre-modified ceramic powder obtained in step 1) to the mixture and place it in a ball mill and stir at 400 rpm for 12 hours.

[0039] The test data of viscosity and solid content of the low viscosity, high solid content photocurable additive manufacturing ceramic core slurry prepared in this embodiment are shown in Table 1.

[0040] Example 2 This embodiment prepares a low-viscosity, high-solids-content photocurable additive manufacturing ceramic core slurry. The raw material formulation is as follows: 50 parts by volume of 5-micron SiO2 powder, 10 parts by volume of 10-micron Al2O3 powder, and 40 parts by volume of photocurable resin. The photocurable resin formulation is as follows: 32 wt% alkyl epoxy-triacrylate; 23 wt% fatty acid-modified epoxy acrylate; 17 wt% mixed monomer containing epoxy and enol ether groups; 24 wt% lauryl acrylate; 1 wt% aryl thioonium salt; and 3 wt% acylphosphine oxide.

[0041] This embodiment provides a method for preparing a low-viscosity, high-solids-content photocurable additive manufacturing ceramic core slurry, comprising the following steps: 1) Powder modification: Mix 200g of SiO2 powder with a particle size of 5 micrometers, 40g of Al2O3 powder with a particle size of 10 micrometers, 1g of polymer chain modifier and 600ml of solvent for 8 hours, ultrasonically disperse for 2 hours, dry in an oven at 50℃ for 10 hours, grind and sieve for later use.

[0042] 2) Slurry preparation: 32g of alkyl epoxy-triacrylate; 23g of fatty acid modified epoxy acrylate; 17g of mixed monomers containing epoxy and enol ether groups; 24g of lauryl acrylate; 1g of aryl thioonium salt; and 3g of acylphosphine oxide.

[0043] After stirring and mixing for 3 hours, the pre-modified ceramic powder obtained in step 1) is added to the mixture and stirred in a ball mill at 500 rpm for 16 hours.

[0044] The test data of viscosity and solid content of the low viscosity, high solid content photocurable additive manufacturing ceramic core slurry prepared in this embodiment are shown in Table 1.

[0045] Comparative Example 1 Comparative Example 1 prepared a photocurable additive manufacturing ceramic core slurry. The only difference between Comparative Example 1 and Example 1 is that the ceramic powder in this comparative example was not modified.

[0046] The other steps are the same.

[0047] The viscosity and solid content test data of the photocurable additive manufacturing ceramic core slurry prepared in this comparative example are shown in Table 1. Since the powder in Comparative Example 1 was not modified, the ceramic powder has an extremely high specific surface area and surface energy, and it will spontaneously agglomerate, causing the slurry viscosity to increase sharply.

[0048] Comparative Example 2 Comparative Example 2 prepared a photocurable additive manufacturing ceramic core slurry. The only difference between Comparative Example 2 and Example 1 is that no monofunctional monomer was added in this comparative example.

[0049] The other steps are the same.

[0050] The viscosity and solids content test data of the photocurable additive manufacturing ceramic core slurry prepared in this comparative example are shown in Table 1. Since Comparative Example 2 did not add a monofunctional monomer, it was not possible to significantly dilute the high-viscosity prepolymer (resin), thereby reducing the overall viscosity of the slurry.

[0051] Table 1 shows the test data of viscosity and solid content of the ceramic slurries prepared in Examples 1-2 and Comparative Examples 1-2.

[0052]

[0053] As can be seen from Table 1, the embodiments of the present invention utilize a combination of free radical photocurable resin and cationic photocurable resin, combined with low-viscosity monofunctional monomers, to effectively reduce the viscosity of ceramic slurry; furthermore, the surface of ceramic powder is coated and modified to reduce interparticle van der Waals forces and improve the dispersibility of powder in the resin system, thereby increasing the solid content of ceramic slurry, and finally realizing the preparation of low-viscosity, high-solids-content photocurable additive manufacturing ceramic core slurry.

[0054] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A ceramic core slurry, characterized in that, The ceramic core slurry comprises a mixture of ceramic powder, modifier, and photocurable resin; The modifier is a polymeric dispersant.

2. The ceramic core slurry according to claim 1, characterized in that, The polymeric dispersant is a group carrying an acidic group, a basic group, or a group that can combine with hydroxyl groups on the surface of the ceramic powder.

3. The ceramic core slurry according to claim 1, characterized in that, The ceramic powder is SiO2 ceramic powder and / or Al2O3 ceramic powder; Preferably, the particle size of the SiO2 ceramic powder is 5-15 μm; Preferably, the Al2O3 ceramic powder has a particle size of 10-20 μm.

4. The ceramic core slurry according to claim 1, characterized in that, The cured resin mixture includes a photocurable resin, a monomer, and a photoinitiator; The photocurable resin includes cationic photocurable resin and free radical photocurable resin; the monomer includes cationic monomer and free radical monomer; the photoinitiator includes cationic photoinitiator and free radical photoinitiator.

5. The ceramic core slurry according to claim 4, characterized in that, The cured resin mixture comprises the following components by weight percentage: 28-32 wt% cationic UV-curable resin, 23-34 wt% free radical UV-curable resin, 17-19 wt% cationic monomer, 20-24 wt% free radical monomer, 1-3 wt% cationic photoinitiator, and 3-6 wt% free radical photoinitiator.

6. The ceramic core slurry according to claim 4, characterized in that, The cationic photocurable resin is one or more alicyclic epoxy acrylates such as alkyl epoxy-triacrylate, cyclohexyl epoxy-pentaacrylate, and carboxyl-terminated pentaerythritol triacrylate; and / or The free radical type photocurable resin is one or more of bisphenol A epoxy acrylate, phenolic epoxy acrylate, and fatty acid modified epoxy acrylate compounds.

7. The ceramic core slurry according to claim 4, characterized in that, The cationic monomer is a mixed monomer containing epoxy and enol ether groups; and / or The free radical monomers include one or more of the following: monofunctional monomer lauryl acrylate, difunctional monomer tripropylene glycol diacrylate, and polyfunctional monomer trimethylolpropane triacrylate.

8. The ceramic core slurry according to claim 4, characterized in that, The cationic photoinitiator includes one of aryl diazonium salt, diaryl iodonium salt, triaryl thiodonium salt, and aryl ferrocene salt; and / or The free radical photoinitiator includes one of hydroxy ketone derivatives and acylphosphine oxides.

9. A method for preparing the ceramic core slurry according to any one of claims 1-8, characterized in that, Includes the following steps: Powder modification: The ceramic powder is surface modified in a solvent to obtain modified powder; Slurry preparation: The modified powder is mixed with a photocurable resin mixture to obtain the ceramic core slurry.

10. The method for preparing the ceramic core slurry according to claim 9, characterized in that, The specific steps of the powder modification are as follows: mixing and stirring the ceramic powder, modifier, and solvent for 4-10 hours, ultrasonically dispersing for 1-2 hours, and drying in a 50℃ oven for 8-10 hours; and / or The steps for preparing the slurry include: mixing the modified powder and the photocurable resin mixture in a ball mill; preferably, the ball mill speed is 300-700 rpm; and the mixing time is 10-20 h.

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