Ceramic photocuring slurry based on photoluminescent particles, preparation method and application

Abstract

The invention relates to the technical field of additive manufacturing, and particularly discloses ceramic photocuring slurry based on photoluminescent particles as well as a preparation method and application of the ceramic photocuring slurry. The ceramic photocuring slurry provided by the invention is prepared from the following raw materials: photoluminescence particle coated ceramic powder, acrylic photosensitive resin and a photoinitiator. Through the collaborative design of the photoluminescence effect and the multi-wavelength photo-initiation system, the improvement of the photocuring depth of the high-refractive-index ceramic is realized, and the defects of cracking, warping and the like between layers during additive manufacturing are effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic additive manufacturing, and in particular to a ceramic light-curing slurry based on photoluminescent particles, as well as a preparation method and application thereof. Background Art

[0002] Ceramic photocuring additive manufacturing (APM) uses ultraviolet laser light or UV-LED light of a specific wavelength and intensity as an energy source, selectively irradiating the surface of a ceramic slurry containing a photosensitive resin to cure it. The slurry then accumulates layer by layer to form a green body, which is then densified to form ceramic parts. The curing of the ceramic slurry relies on a cross-linking polymerization reaction initiated by the photosensitive resin in the slurry under UV light. However, the ceramic particles in the slurry scatter, attenuate, and absorb the incident light, significantly reducing the rate of the photopolymerization reaction. The extent of this effect depends primarily on the type, size, and content of the ceramic particles, as well as the refractive index matching between the particles and the dispersion medium.

[0003] Research has found that at high solids contents, the photocuring reaction of low-refractive-index ceramics (such as silicon dioxide with n=1.56) and medium-refractive-index ceramics (such as aluminum oxide with n=1.70) generally proceeds fully. However, high-refractive-index ceramics, particularly those with darker colors (such as silicon nitride with n=2.1 and silicon carbide with n=2.5), are more difficult to cure, with a single-layer cure depth typically only 30-60μm. In practical applications (e.g., in the paper "A perspective on 3D printing of silicon carbide," Journal of the European Ceramic Society), the print layer thickness is typically set at half the cure depth. This means that the print layer thickness of high-refractive-index ceramics is only 15-30μm, far less than the 70-100μm typically used for materials like aluminum oxide and silicon oxide. This reduced layer thickness severely limits forming efficiency and can easily lead to defects such as cracking and warping between layers.

[0004] At present, the main way to improve the photocuring depth of high-refractive-index ceramics is to construct a low-refractive-index interface layer. This low-refractive-index interface layer is usually composed of oxide ceramics. For example, the authorized patent CN202210088639.4 and the invention patent CN202311055330.6 provide a surface interface layer modification method for silicon nitride and silicon carbide materials, respectively. This type of modification method will change the surface properties of the powder, have an adverse effect on the sintering process, and may also introduce negative impurity phases into the slurry, thereby leading to a decrease in the mechanical, electromagnetic and other properties of the component after sintering. These problems seriously restrict the application effect of high-refractive-index ceramic materials in photocuring additive manufacturing. Summary of the Invention

[0005] The present invention provides a ceramic photocuring slurry based on photoluminescent particles, as well as a preparation method and application thereof. By adding photoluminescent particles to the ceramic slurry, the curing depth of high-refractive-index, dark-colored ceramic powder materials is increased, the wall forming efficiency is improved, and defects such as cracking and warping between layers are avoided.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a ceramic slurry based on photoluminescent particles, comprising raw materials: photoluminescent particle-coated ceramic powder, acrylic photosensitive resin, and photoinitiator; wherein the photoluminescent particles are metal ion-doped inorganic matter and / or organic fluorescent material; the ceramic powder is a high-refractive index ceramic material; the photoinitiator comprises a first photoinitiator and a second photoinitiator, the main absorption wavelength of the first photoinitiator matches the emission wavelength of the ultraviolet light source, and the main absorption wavelength of the second photoinitiator matches the emission wavelength of the photoluminescent particles.

[0007] Compared with the existing technology, the ceramic slurry provided by the present invention adds nanoparticles with photoluminescence effect (PL). When ultraviolet light irradiates the slurry, the photoluminescent particles can absorb part of the ultraviolet light and produce light of another wavelength but weaker intensity (hereinafter referred to as the secondary light source), forming a supplementary light field inside the slurry, greatly improving the curing depth; at the same time, the present invention introduces a composite photoinitiator to form a dual-wavelength initiation system, which can respond to ultraviolet light to trigger the polymerization of surface resin, and can also respond to visible light emitted by the photoluminescent particles to trigger the polymerization of deep resin, realizing gradient curing from the surface to the inside, avoiding the problems of shallow over-curing and deep under-curing, and the gradient cross-linked network formed by deep curing effectively reduces the interlayer stress, avoiding defects such as cracking and warping between layers.

[0008] Furthermore, the mass ratio of the photoluminescent particle-coated ceramic powder and the acrylic photosensitive resin is 1:1; the added amount of the photoinitiator is 8-12wt% of the mass of the photoluminescent particle-coated ceramic powder; and the mass ratio of the first photoinitiator to the second photoinitiator is (1-3):1.

[0009] Furthermore, the photoluminescent particles include at least one of doped silicon nitride nanowires, nano zinc oxide, polystyrene fluorescent microspheres, coumarin or rhodamine.

[0010] Furthermore, the doping element of the doped silicon nitride nanowire includes at least one of Y, Ce, or Nb, with a doping amount of 3-7 at%. "At%" refers to the atomic percentage, which refers to the content at the microscopic level. If the atomic number of the entire doped silicon nitride nanowire is 100%, the content of the doping element is 3-7 at%.

[0011] Furthermore, the ceramic powder is silicon nitride or silicon carbide.

[0012] Furthermore, the photosensitive resin includes at least one of trimethylolpropane triacrylate, bisphenol A dimethacrylate, 1,6-hexanediol diacrylate, and polyethylene glycol diacrylate.

[0013] Furthermore, the first photoinitiator is photoinitiator TPO, and the second photoinitiator includes at least one of photoinitiator 784, photoinitiator 819 or Eosin Y.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned ceramic slurry based on photoluminescent particles, comprising the following steps: Take a portion of the acrylic photosensitive resin, add the photoluminescent particle-coated ceramic powder and the photoinitiator thereto, then add the remaining acrylic photosensitive resin, and mix them evenly using a vacuum non-intrusive homogenizer to obtain the ceramic photocurable slurry; wherein the vacuum non-intrusive homogenizer has a homogenizing speed of 1500-3000 rpm, a mixing time of 120-300 s, and a vacuum delay time of ≥90 s.

[0015] During the ball milling process, photoluminescent particles preferentially attach to defect sites on the surface of ceramic particles, forming evenly distributed fluorescent activation points. During photocuring, a gradient cross-linking structure (dense surface and moderate cross-linking in the deep layer) is generated, effectively reducing internal stress. During sintering, some particles are converted into sintering aids, promoting densification and optimizing grain boundary structure. This multi-scale structural regulation enables the material to have both excellent forming and sintering properties.

[0016] In a third aspect, the present invention provides an application of the above-mentioned ceramic slurry based on photoluminescent particles in ceramic photocuring additive manufacturing.

[0017] Furthermore, the additive manufacturing includes the steps of: curing the ceramic photocurable slurry layer by layer under ultraviolet light, and sintering to obtain a finished ceramic product.

[0018] In summary, the present invention has the following beneficial effects: This invention achieves enhanced photocuring depth in high-refractive-index ceramics through the synergistic effect of photoluminescence and a multi-wavelength photoinitiator system. After absorbing ultraviolet light, the photoluminescent particles emit visible light, forming a secondary light source within the ceramic slurry. This triggers deep resin polymerization, achieving gradient curing from the surface to the inside. This method increases the single-layer curing depth of ceramic materials such as silicon nitride to 101–122 μm, and the corresponding layer thickness increases from 15–30 μm to 50–61 μm. Compared with traditional interface layer modification methods, this method eliminates the need for the introduction of foreign oxides, preventing the formation of impurity phases during sintering and ensuring the mechanical properties of the final part. The technical solution provided by this invention is suitable for photocuring additive manufacturing of high-refractive-index (such as Si3N4, SiC, ZrO2) and dark-colored (such as black SiC) ceramic materials, providing a new approach for the efficient, high-quality formation of complex ceramic parts. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the specific implementation methods will be briefly introduced below. Obviously, the embodiments described below are some implementation methods of the present invention. For ordinary technicians in this field, other implementation methods can be obtained based on these embodiments without paying creative work.

[0020] If specific experimental steps or conditions are not specified in the examples, the procedures or conditions of conventional experimental steps described in the literature in the field can be followed. All raw materials and instruments used are commercially available, including but not limited to those used in the examples of this application.

[0021] Example 1 This embodiment provides a ceramic photocurable slurry based on photoluminescent particles. The raw materials are: photoluminescent particle-coated ceramic powder, trimethylolpropane triacrylate (TMPTA), photoinitiator TPO, and photoinitiator 784. The mass of the photoluminescent particle-coated ceramic powder is 45 g, the mass of TMPTA is 45 g, the mass of the photoinitiator TPO is 3.5 g, and the mass of the photoinitiator 784 is 1.5 g.

[0022] The raw materials for preparing the photoluminescent particle-coated ceramic powder are silicon nitride ceramic powder and 5at% Y-doped silicon nitride nanowires, and the preparation process is as follows: (1) Add 50 parts by volume of silicon nitride ceramic powder, 2 parts by volume of 5 at% Y-doped silicon nitride nanowires, and 48 parts by volume of anhydrous ethanol into a ball mill jar, seal the jar, and flush with nitrogen; (2) Silicon nitride ceramic powder and Y-doped silicon nitride nanowires were mixed in a planetary ball mill using a low-speed wet ball milling mode at a mixing speed of 60 rpm for 1.5 h. (3) The ball-milled material is taken out and placed in an oven for drying, and then sieved in a vibrating screening machine to obtain a photoluminescent particle-coated ceramic powder.

[0023] This embodiment also provides a method for preparing the above-mentioned ceramic photocurable slurry, comprising the following steps: Take part of the TMPTA, add the photoinitiator and photoluminescent particle-coated ceramic powder into it, then pour in the remaining TMPTA and mix evenly on a vacuum non-invasive homogenizer with a homogenization speed of 2500 rpm, a time of 120 s, and a vacuum delay time of 90 s to obtain a ceramic photocuring slurry.

[0024] Additive manufacturing was carried out using the ceramic photocuring slurry prepared above. Under the excitation of a 355nm ultraviolet laser, the ceramic photocuring slurry produced secondary luminescence in the 530-580nm band, was cured layer by layer, and then sintered to obtain a finished ceramic.

[0025] Example 2 This embodiment provides a ceramic photocurable slurry based on photoluminescent particles. The raw materials are: photoluminescent particle-coated ceramic powder, trimethylolpropane triacrylate (TMPTA), photoinitiator TPO, and photoinitiator 819. The mass of the photoluminescent particle-coated ceramic powder is 45 g, the mass of TMPTA is 45 g, the mass of the photoinitiator TPO is 3.15 g, and the mass of the photoinitiator 819 is 1.35 g.

[0026] The raw materials for preparing the photoluminescent particle-coated ceramic powder are silicon nitride ceramic powder and zinc oxide nanowires, and the preparation process is as follows: (1) Add 50 parts by volume of silicon nitride ceramic powder, 1.5 parts by volume of zinc oxide nanowires, and 48 parts by volume of anhydrous ethanol into a ball mill jar, seal the jar, and flush with nitrogen; (2) Silicon nitride ceramic powder and Y-doped silicon nitride nanowires were mixed in a planetary ball mill using a low-speed wet ball milling mode at a mixing speed of 80 rpm for 1 h. (3) The ball-milled material is taken out and placed in an oven for drying, and then sieved in a vibrating screening machine to obtain a photoluminescent particle-coated ceramic powder.

[0027] This embodiment also provides a method for preparing the above-mentioned ceramic photocurable slurry, comprising the following steps: Take part of the TMPTA, add the photoinitiator and the photoluminescent particle-coated ceramic powder into it, then pour in the remaining TMPTA and mix evenly on a vacuum non-invasive homogenizer with a homogenization speed of 3000 rpm, a time of 300 s, and a vacuum delay time of 90 s to obtain a ceramic photocuring slurry.

[0028] Additive manufacturing was carried out using the ceramic photocuring slurry prepared above. Under the excitation of a 355nm ultraviolet laser, the ceramic photocuring slurry produced secondary luminescence in the 480nm band, was cured layer by layer, and then sintered to obtain a finished ceramic.

[0029] Example 3 This embodiment provides a ceramic photocurable slurry based on photoluminescent particles. The raw materials are: photoluminescent particle-coated ceramic powder, 1,6-hexanediol diacrylate (HDDA), photoinitiator TPO, and Eosin Y. The mass of the photoluminescent particle-coated ceramic powder is 45 g, the mass of HDDA is 45 g, the mass of the photoinitiator TPO is 2.9 g, and the mass of Eosin Y is 2.9 g.

[0030] The raw materials for preparing the photoluminescent particle-coated ceramic powder are silicon nitride ceramic powder and polystyrene fluorescent microspheres, and the preparation process is as follows: (1) Add 50 parts by volume of silicon nitride ceramic powder, 5 parts by volume of polystyrene fluorescent microspheres, and 45 parts by volume of anhydrous ethanol into a ball mill jar, seal the jar, and flush with nitrogen; (2) Silicon nitride ceramic powder and Y-doped silicon nitride nanowires were mixed in a planetary ball mill using a low-speed wet ball milling mode at a mixing speed of 100 rpm for 2 h. (3) The ball-milled material is taken out and placed in an oven for drying, and then sieved in a vibrating screening machine to obtain a photoluminescent particle-coated ceramic powder.

[0031] This embodiment also provides a method for preparing the above-mentioned ceramic photocurable slurry, comprising the following steps: Take part of the HDDA, add the photoinitiator and photoluminescent particle-coated ceramic powder into it, then pour in the remaining HDDA and mix evenly on a vacuum non-invasive homogenizer with a homogenization speed of 1500 rpm, a time of 200 s, and a vacuum delay time of 90 s to obtain a ceramic photocurable slurry.

[0032] Additive manufacturing was carried out using the ceramic photocuring slurry prepared above. Under the excitation of a 405nm ultraviolet laser, the ceramic photocuring slurry produced secondary luminescence in the 610nm band, was cured layer by layer, and then sintered to obtain a finished ceramic.

[0033] Comparative Example 1 The only difference between this comparative example and Example 1 is that no photoluminescent particles are added to the ceramic slurry, and the composition of other raw materials and the preparation method are the same as those in Example 1.

[0034] Comparative Example 2 The only difference between this comparative example and Example 1 is that a single photoinitiator, TPO, is used; the composition of other raw materials and the preparation method are the same as those in Example 1.

[0035] Comparative Example 3 The only difference between this comparative example and Example 1 is that an equal amount of nano-SiO2 is used instead of the photoluminescent particles. The composition of other raw materials and the preparation method are the same as those in Example 1.

[0036] Performance testing: The ceramic slurries provided in the examples of the present invention and the comparative examples were subjected to performance tests. The specific test methods are as follows: Single layer cure depth: Inject the slurry into a glass sandwich with a gap of 100-500μm and scrape the surface flat; irradiate with UV light at a fixed intensity for 10-30s; remove the cured sample and clean the uncured part with isopropyl alcohol; use a vernier caliper to measure the cured layer thickness.

[0037] Bending strength: Based on GB / T 4741-1999 Test method for flexural strength of ceramic materials, a universal testing machine was used to test the flexural strength of the material.

[0038] Table 1 As can be seen from the above table, the curing depths of Examples 1-3 (108-122 μm) are significantly higher than those of Comparative Examples 1-3 (50-89 μm), demonstrating that the photoluminescence effect can enhance energy penetration and achieve an increased curing depth without the need to introduce foreign oxides, thereby avoiding affecting the mechanical properties of the material.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A ceramic light-curing slurry based on photoluminescent particles, characterized in that: Including raw materials: photoluminescent particle coated ceramic powder, acrylic photosensitive resin, photoinitiator; The photoluminescent particles are metal ion-doped inorganic and / or organic fluorescent materials; the ceramic powder is a high-refractive-index ceramic material; the photoinitiator includes a first photoinitiator and a second photoinitiator, the main absorption wavelength of the first photoinitiator matches the emission wavelength of the ultraviolet light source, and the main absorption wavelength of the second photoinitiator matches the emission wavelength of the photoluminescent particles.

2. The photoluminescent particle-based ceramic photocurable slurry according to claim 1, wherein: The mass ratio of the photoluminescent particle-coated ceramic powder and the acrylic photosensitive resin is 1:1; the added amount of the photoinitiator is 8-12wt% of the mass of the photoluminescent particle-coated ceramic powder; and the mass ratio of the first photoinitiator to the second photoinitiator is (1-3):

1.

3. The photocurable ceramic slurry based on photoluminescent particles according to claim 1, wherein: The photoluminescent particles include at least one of doped silicon nitride nanowires, nano zinc oxide, polystyrene fluorescent microspheres, coumarin or rhodamine.

4. The photoluminescent particle-based ceramic photocurable slurry according to claim 3, wherein: The doping element of the doped silicon nitride nanowires includes at least one of Y, Ce or Nb, and the doping amount is 3-7at%.

5. The photocurable ceramic slurry based on photoluminescent particles according to claim 1, wherein: The ceramic powder is silicon nitride or silicon carbide.

6. The photocurable ceramic slurry based on photoluminescent particles according to claim 1, wherein: The acrylic photosensitive resin includes at least one of trimethylolpropane triacrylate, bisphenol A dimethacrylate, 1,6-hexanediol diacrylate, and polyethylene glycol diacrylate.

7. The photocurable ceramic slurry based on photoluminescent particles according to claim 1, wherein: The first photoinitiator is photoinitiator TPO, and the second photoinitiator includes at least one of photoinitiator 784, photoinitiator 819, or eosin Y.

8. A method for preparing a ceramic photocurable slurry based on photoluminescent particles according to any one of claims 1 to 7, characterized in that: The following steps are involved: Taking a portion of the acrylic photosensitive resin, adding the photoluminescent particle-coated ceramic powder and a photoinitiator thereto, and then adding the remaining acrylic photosensitive resin, and mixing them uniformly using a vacuum non-invasive homogenizer to obtain the ceramic light-curing slurry; The homogenizing speed of the vacuum non-invasive homogenizing equipment is 1500-3000 rpm, the mixing time is 120-300 s, and the vacuum delay time is ≥90 s.

9. Use of the ceramic photocurable slurry based on photoluminescent particles according to any one of claims 1 to 7 in ceramic photocurable additive manufacturing.

10. The use according to claim 9, characterized in that The additive manufacturing comprises the steps of: curing the ceramic photocurable slurry layer by layer under ultraviolet light, and then sintering and forming the slurry to obtain a finished ceramic product.

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