A method for modifying ceramic powder, a microwave dielectric ceramic slurry, a preparation method and application thereof

Abstract

The application belongs to the technical field of photocuring printing, and particularly relates to a modification method of ceramic powder, microwave dielectric ceramic slurry and a preparation method and application thereof. The siloxane group can be grafted on the surface of the ceramic powder by surface functionalization modification of the ceramic powder, and the acrylate group is exposed on the surface of the ceramic powder, so that the ceramic powder has photosensitive characteristics. The photosensitive group can be subjected to polymerization reaction with the acrylate group in the photosensitive resin used in the ceramic slurry, so as to improve the curing performance of the ceramic slurry, greatly reduce the refractive index of the ceramic powder, and improve the broadening curing depth D of the slurry under zero mis-curing width b Meanwhile, the curing layer thickness during photocuring printing is improved, the number of interlayer interfaces is reduced, the number of pore defects on the interlayer interfaces is reduced, and the density and quality factor are improved. The higher curing depth of the slurry is also helpful to improve the printing efficiency and promote the industrialized production of photocuring 3D printing radio frequency devices.

Description

Technical Field

[0001] This invention belongs to the field of photopolymerization printing technology, specifically relating to a method for modifying ceramic powder, a microwave dielectric ceramic slurry, its preparation method, and its application. Background Technology

[0002] Using photopolymer 3D printing to fabricate resonators, filters, ceramic capacitors, and antennas and other radio frequency devices demonstrates significant advantages in terms of printing accuracy, surface roughness, and molding quality.

[0003] However, due to the refractive index difference between the microwave dielectric ceramic powder and oligomers / monomers in the photocurable ceramic slurry, as well as the high light absorption characteristics of the powder in the ultraviolet / near-ultraviolet band, the curing depth of high-solid-content microwave dielectric ceramic photocurable slurries is very low. This leads to interlayer cracking during 3D printing, making direct printing extremely difficult. Furthermore, the refractive index difference results in a large amount of refracted light in the non-cured areas, causing edge mis-curing and reducing printing accuracy.

[0004] In addition, the high light absorption characteristics of ceramic powder indicate that more energy will be absorbed by the ceramic powder, so less energy will be used for the induced polymerization of photosensitive resin, resulting in a lower curing depth of the slurry and making it difficult to print. The usual solution is to increase the exposure energy to further increase the curing depth, but this will also increase the edge miscuring, leading to a decrease in printing accuracy.

[0005] Therefore, it is necessary to explore methods to reduce the ultraviolet light absorption rate of ceramic powder and narrow the refractive index difference between ceramic powder and oligomers and monomers, so as to further improve the curing depth of the slurry while ensuring printing accuracy. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing microwave dielectric ceramic photocurable slurry, such as the very low curing depth and the difficulty in balancing curing depth and printing accuracy, so as to provide a method for modifying ceramic powder, microwave dielectric ceramic slurry, its preparation method and application.

[0007] This invention proposes a method for modifying the surface of ceramic powder. When UV light irradiates the powder surface, most of the energy is absorbed by the functional groups on the powder surface to form free radicals, which facilitate polymerization with the photosensitive resin in the matrix, thereby increasing the absorption rate of UV light by the photosensitive groups and thus improving the polymerization efficiency and curing depth.

[0008] Therefore, the present invention provides the following technical solution:

[0009] This invention provides a method for modifying ceramic powder, comprising the following steps:

[0010] S1, the modifier is mixed with an organic solvent and hydrolyzed to obtain a hydrolyzed modifier; wherein the modifier has the composition shown in the following formula:

[0011] Among them, at least one of X1, X2, and X3 is an alkoxy group with 1-5 carbon atoms; Y represents an acrylate group, and R is C2-C. 20 carbon chain or C2-C 20 A heterochain containing heteroatoms; n is an integer between 1 and 5;

[0012] S2, add ceramic powder to hydrolysis modifier, stir, reflux, separate the product to obtain modified ceramic powder.

[0013] Optionally, Y in the modifier has the following structure:

[0014] Wherein, R1 is an -H or C1-C5 alkyl group; for example, the alkyl group may be methyl or ethyl, etc.

[0015] And / or, the alkoxy group is ethoxy or methoxy;

[0016] And / or, the heteroatom is at least one of S, N or O.

[0017] Optionally, the modifier has any of the following compositions:

[0018]

[0019] Optionally, in step S1, the hydrolysis is carried out at room temperature for 1-2 hours;

[0020] And / or, in step S2, the stirring time is 1-2 hours;

[0021] And / or, the reflux temperature is 70-90℃, and the reflux time is 4-8h.

[0022] Optionally, the method for modifying ceramic powder satisfies at least one of the following (1)-(5):

[0023] (1) The amount of the modifier is 20-90% of the mass of the ceramic powder;

[0024] (2) The amount of organic solvent used is 1-100 times the mass of ceramic powder;

[0025] (3) The pH of the organic solvent is 4-5; In this invention, acetic acid is used to control the pH of the solution to 4-5, which reduces the homocondensation tendency of siloxane groups and increases the condensation of siloxanes with inorganic nanoparticles.

[0026] (4) The organic solvent is an ethanol solution with a concentration of 70 wt% or higher;

[0027] (5) In step S2, the ceramic powder is first mixed with a portion of the organic solvent and then added to the hydrolysis modifier.

[0028] The present invention also provides a modified ceramic powder obtained by the above-described modification method.

[0029] The present invention also provides a microwave dielectric ceramic slurry, comprising the modified ceramic powder described above.

[0030] Optionally, the microwave dielectric ceramic slurry includes the following components by mass percentage, based on the total mass of the slurry:

[0031] UV-curable oligomer 2.8-15%; diluent 3-15%; modified ceramic powder 70-90%; leveling agent 0.4-1.5%; defoamer 0.4-1.5%;

[0032] It also includes a photoinitiator comprising 0.15-0.9% of the total mass of the UV-curable oligomer and diluent; and a polymerization inhibitor comprising 0.03-0.3% of the total mass of the UV-curable oligomer and diluent.

[0033] Dispersant comprising 3-6% of the mass of modified ceramic powder.

[0034] The present invention also provides a method for preparing the above-mentioned microwave dielectric ceramic slurry, comprising the following steps:

[0035] S11, UV-curable oligomer, diluent, photoinitiator and polymerization inhibitor are mixed to obtain resin premix;

[0036] S12, add dispersant, modified ceramic powder, leveling agent and defoamer to the obtained resin premix, grind and defoam, and obtain microwave dielectric ceramic slurry.

[0037] The present invention also provides an application of the microwave dielectric ceramic slurry described above or prepared by the above method in photopolymerization 3D printing.

[0038] The modification principle of this invention is as follows: It primarily employs organic coating to functionalize the surface of ceramic powder, specifically using a multifunctional acrylate monomer containing siloxane alkyl groups, with the general structural formula: Functional modifiers such as 3-(acryloyloxy)propyltrimethoxysilane (TMSPA) and γ-methacryloyloxypropyltrimethoxysilane (TMSPM) are grafted onto the powder surface. TMSPM, TMSPA, and other functional modifiers have the following characteristics: one end contains an acrylate group that can participate in photopolymerization. The other end contains siloxane groups. These siloxane groups can be grafted onto the surface of ceramic powder after hydrolysis, exposing acrylate groups on the ceramic powder surface. This gives the ceramic powder photosensitive properties. These photosensitive groups can then polymerize with the acrylate groups in the photosensitive resin used in the ceramic slurry, thereby improving the curing performance of the ceramic slurry.

[0039] In this invention, the type of ceramic powder is not limited. Typically, but not limited to, commonly available powders on the market, such as 0.95MgTiO3-0.05CaTiO3 (abbreviated as 95MCT) powder and 0.9MgTiO3-0.1CaTiO3 (abbreviated as 90MCT) powder, can be used.

[0040] In this invention, the specific raw material selection in the microwave dielectric ceramic slurry is not limited, and the influence of raw material selection and content on the slurry is not reflected. Typically, without limitation, the UV-curable oligomer includes at least one of epoxy acrylate, polyurethane acrylate, and polyester acrylate; the diluent includes at least one of tripropylene glycol diacrylate, trimethylolpropane triacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, bis(trimethylolpropane)tetraacrylate, polyethylene glycol diacrylate, hydroxyethyl methacrylate, ethoxylated pentaerythritol tetraacrylate, and isobornyl acrylate; the photoinitiator includes α-diketone compounds camphorquinone, fluorodiphenyltitanium oxycarbonate VL-3084, and bis(2,6-difluoro-3-pyrrolephenyltitanium oxycarbonate), (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide. The polymer comprises at least one of 4,4'-dimethyldiphenyliodonium hexafluorophosphate and methyldiphenylthionium tetrafluoroborate; the polymerization inhibitor comprises at least one of hydroquinone, 2,6-di-tert-butyl-4-methylphenol, and p-hydroxyanisole; the dispersant comprises at least one of Disperbyk 110, titanium dioxide dispersant Disperbyk 180, titanium dioxide dispersant Disperbyk 163, polyethylene glycol 200, trioctylphosphine oxide, ethylene-vinyl acetate copolymer, and ammonium polyacrylate; the leveling agent comprises at least one of BYK-333, BYK-380N, Rad2100, Deqian 457 leveling agent, and EFKA-3785 leveling agent; and the defoamer comprises at least one of BYK-053, Deqian 2700, Deqian 3100, and dimethylsiloxane Foamex N.

[0041] The following is an explanation of curing depth, curing width, and increasing curing depth:

[0042] Based on Jacob's equation, Beer-Lambert's law, and other relevant formulas and studies, Halloran et al. gave the curing depth C. d and curing width W ex Relationship with energy:

[0043] C d Where E is the curing depth, S is the UV incident energy, and E is the UV curing depth. d It is depth sensitivity, E d It is a deep critical energy.

[0044] W cure =W beam +2W ex W ex Excess curing width, i.e., the curing width exceeding the incident ultraviolet light width, was also found to increase with the logarithm of the exposure energy. Furthermore, the quasi-Beer-Lambert formula was proposed: S w It is the width sensitivity (resin sensitivity in the horizontal direction), E w This is the width critical energy (the critical energy for horizontal polymerization). This behavior occurs because some of the incident light is scattered to the sides. The suspension remains a Beer-Lambert absorber, therefore the solidification width W... ex It also has a semi-logarithmic relationship with the exposure energy.

[0045] Ideally, a ceramic slurry should have the largest possible curing depth without creating a curing width. This can be achieved by widening the curing depth (D). b It can be described as the curing depth at the start of widening (E = E). w At this point, the curing width W ex It is zero.

[0046] formula That is, become

[0047] Through C d S was calculated by linear fitting of the relationship with E. d With E d Through W ex S was calculated by linear fitting of the relationship with E. w With E w S calculated d With E d and E w D can be further calculated b This refers to the cured depth at which broadening begins. Using D... b Values ​​enable near-net-size printing, transforming the evaluation of paste curing performance into the use of D... bThis is measured by the curing depth at zero curing width. By increasing the curing depth, the accuracy of photopolymer 3D printing can be improved, which can increase the operating frequency of photopolymer 3D printed radio frequency microwave devices.

[0048] The technical solution of this invention has the following advantages:

[0049] The method for modifying ceramic powder provided by this invention includes the following steps: S1, mixing a modifier with an organic solvent and hydrolyzing it to obtain a hydrolyzed modifier; wherein the modifier is a compound with a specific composition having siloxane groups and acrylate groups; S2, adding ceramic powder to the hydrolyzed modifier, stirring, refluxing, separating the product, and obtaining modified ceramic powder. By using a modifier with a specific composition containing siloxane groups and acrylate groups to organically coat the ceramic powder, surface functionalization modification is achieved. After hydrolysis, the siloxane groups can be grafted onto the surface of the ceramic powder, exposing the acrylate groups on the surface, giving the ceramic powder photosensitive properties. These photosensitive groups can undergo polymerization reactions with the acrylate groups in the photosensitive resin used in the ceramic slurry to improve the curing performance of the ceramic slurry, significantly reducing the refractive index of the ceramic powder, increasing the width critical energy Ew, reducing the phenomenon of mis-curing towards the edges, and improving printing accuracy. By increasing the curing depth (Db) of the slurry while achieving zero curing error width, and simultaneously increasing the cured layer thickness during photopolymerization printing, the number of interlayer interfaces and pore defects at these interfaces is reduced, leading to increased density and a higher quality factor for microwave dielectric ceramics. This achieves high-depth, high-precision printing of microwave dielectric ceramic materials, with improved density and quality factor. The higher curing depth of the slurry contributes to improved printing efficiency and promotes the industrial production of photopolymerization 3D printed radio frequency devices.

[0050] The microwave dielectric ceramic slurry provided by this invention has a resin film covering the surface of the ceramic powder after grafting with a functional modifier. The refractive index of the resin film is much lower than that of the ceramic powder, which can greatly reduce the refractive index of the ceramic powder and thus shorten the refractive index difference between the ceramic powder and the resin premix. This reduces scattering caused by the difference in refractive index during photocuring and also reduces the curing width caused by scattering, which can further improve printing accuracy.

[0051] The application of the microwave dielectric ceramic slurry provided by this invention in photopolymerization 3D printing can be referenced to the slurry's increased curing depth D. b The value is used to set the printing layer thickness. The definition of the increased curing depth is the curing depth at zero curing width, using D. bThis method can achieve near-net-size printing with high printing accuracy. Specifically, the curing layer thickness setting during photopolymerization printing can be increased from 33μm to 80μm, which reduces the number of interlayer interfaces by more than half. This significantly reduces the number of pores and defects at the interlayer interfaces, improving the transmission effect of electromagnetic waves on the surface of radio frequency devices and greatly reducing the "absorption" and "weakening" effects of surface molding quality on signal transmission. Attached Figure Description

[0052] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0053] Figure 1 This is a curve showing the change in curing depth of the microwave dielectric ceramic slurry obtained in Example 1 of the present invention as a function of exposure energy;

[0054] Figure 2 This is a curve showing the change in curing width of the microwave dielectric ceramic slurry obtained in Example 1 of the present invention as a function of exposure energy. Detailed Implementation

[0055] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0056] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0057] In the following examples and comparative examples, 1 part = 10g.

[0058] Example 1

[0059] This embodiment provides a microwave dielectric ceramic slurry, the composition of which and its preparation method are as follows:

[0060] Step 1: Modification of ceramic powder: First, prepare 300 parts of an ethanol-water solution containing 30 wt% water, adjust the pH to 4.5 with acetic acid, and ultrasonically disperse for 60 min to obtain a mixed solution; take 200 parts of the above mixture and add 20% of 3-(acryloyloxy)propyltrimethoxysilane (TMSPA) monomer (relative to the mass of the added dried ceramic powder), and hydrolyze magnetically for 1 h at room temperature to obtain the hydrolyzed functional monomer; take the remaining mixture in a three-necked flask and add 50 parts of dried ceramic powder (95 MCT), and stir to form a particle suspension; add the hydrolyzed functional monomer to the powder particle suspension, stir continuously at room temperature for 1 h, and then reflux at 70 °C for 4 h. At the end of the reaction, cool the mixture and dilute it with water, centrifuge for 5 minutes, and finally collect the precipitate, dry it at 110 °C for 12 h to obtain the functionalized modified ceramic powder, and then store it in a desiccator for later use.

[0061] Step 2: Prepare the premix: Mix 15 parts of UV-curable oligomeric aromatic polyurethane acrylate (Shandong Jiaying Chemical Technology Co., Ltd., 6-functionality aromatic, content ≥99.9%), 3 parts of diluent polyethylene glycol diacrylate (Sinopharm Chemical Reagent Co., Ltd., average molecular weight 575), 0.15 parts of photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (Sinopharm Chemical Reagent Co., Ltd., content 97%), and 0.03 parts of polymerization inhibitor 2,6-di-tert-butyl-4-methylphenol (Sinopharm Chemical Reagent Co., Ltd., Acros-C21983) at 60°C on a heating table covered with a black light shield to obtain the UV-curable resin premix.

[0062] Step 3: Preparation of ceramic slurry: Add the photocurable resin premix from Step 2 to a mixing tank, add 3 parts of dispersant Disperbyk 110 (BYK Chemicals GmbH, Germany), mix evenly, then add 83 parts of functionalized modified ceramic powder from Step 1 in two batches, followed by 0.5 parts of leveling agent BYK-333 (Dongguan Heli Chemical Trading Co., Ltd.) and 0.5 parts of defoamer BYK-053 (Dongguan Heli Chemical Trading Co., Ltd.). Place the mixture in a vacuum mixer and degas it under vacuum. Then, use a three-roll mill to crush the agglomerated particles. Afterward, vacuum mix the mixture in the vacuum mixer until the slurry is uniform and free of bubbles to obtain a uniformly dispersed slurry. Store it at a low temperature and away from light for later use.

[0063] Step 4: Slurry Performance Testing: Transfer the layered model file for material testing to the printer, spread the slurry evenly on the printing platform, and set the exposure power to 5mW / cm². 2Single-layer curing was performed with exposure times of 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, and 10s. The curing depth and width of the slurry were measured using a micrometer-based high-precision thickness gauge and an optical microscope. The relationship between exposure energy and curing depth was obtained as follows: Figure 1 As shown, and the relationship between exposure energy and curing width is as follows: Figure 2 As shown, the increased curing depth D was calculated using linear fitting. b ;

[0064] Step 5: Printing Experiment: Initialize the printer and transfer the model, following the instructions in Step 4 regarding the increased curing depth D. b Based on experience, the printing layer thickness is between one-third and one-half of the curing depth. Setting the printing layer thickness to 39μm allows for near-net-size printing with zero curing width.

[0065] Step 6, Degreasing and Sintering: The printed blanks are processed under different degreasing and sintering parameters.

[0066] Debinding and sintering are standard parameters in the field. For example, the 3D printed preform is heated and dried at 50℃-120℃ for 6-12 hours, then heated to 200℃-250℃ at a rate of 1℃ / min-3℃ / min, and then held at 200℃-250℃ for 1-3 hours to remove the binder. The temperature is then increased to 275℃-350℃ at a rate of 0.5℃ / min-2℃ / min, and then held at 275℃-350℃ for 1-3 hours to remove the binder. This process is repeated with a heating rate of 0.5℃ / min-2℃ / min. Raise the temperature to 400℃-500℃, then maintain the temperature at 400℃-500℃ for 1-6 hours to remove the adhesive. Next, raise the temperature to 500℃-600℃ at a rate of 0.5℃ / min-2℃ / min, and maintain the temperature at 500℃-600℃ for 1-6 hours to remove the adhesive. Finally, raise the temperature to 1450℃-1550℃ at a rate of 2℃ / min-5℃ / min, and maintain the temperature at 1450℃-1550℃ for 1-3 hours. During the cooling phase, control the cooling rate at 0.5-2℃ / min, and remove the product when it reaches room temperature.

[0067] In this embodiment, the parameters for degreasing and sintering are as follows: the 3D printed blank is heated and dried for 12 hours at a temperature of 120°C, then heated to 200°C at a heating rate of 1°C / min, and then held at 200°C for 3 hours to remove the binder. Next, the temperature is raised to 275°C at a heating rate of 0.5°C / min, and then held at 275°C for 3 hours to remove the binder. Then, the temperature is raised to 400°C at a heating rate of 0.5°C / min, and then held at 400°C for 6 hours to remove the binder. Next, the temperature is raised to 600°C at a heating rate of 1°C / min, and then held at 600°C for 6 hours to remove the binder. Finally, the temperature is raised to 1450°C at a heating rate of 2°C / min, and held at 1450°C for 3 hours. The cooling rate during the cooling stage is controlled at 1°C / min, and the blank is removed after cooling to room temperature.

[0068] Figure 1 , Figure 2 The curing depth and curing width of the obtained microwave dielectric ceramic slurry were obtained as curves of change with exposure energy. The curing depth was increased to 95 μm by linear fitting calculation, which is 18.75% higher than that of Comparative Example 1 without TMSPA graft modification.

[0069] Example 2

[0070] This embodiment provides a microwave dielectric ceramic slurry, which differs from Example 1 only in that the amount of 3-(acryloyloxy)propyltrimethoxysilane (TMSPA) added accounts for 35% of the mass of the dried ceramic powder.

[0071] Linear fitting calculations showed that the broadened curing depth was 101 μm, which was 26.25% higher than that of Comparative Example 1 without TMSPA grafting. The printing layer thickness was set to 42 μm.

[0072] Example 3

[0073] This embodiment provides a microwave dielectric ceramic slurry, which differs from Example 1 only in that the amount of 3-(acryloyloxy)propyltrimethoxysilane (TMSPA) added accounts for 50% of the mass of the dried ceramic powder.

[0074] Linear fitting calculations showed that the broadened curing depth was 152 μm, which is 90% higher than that of Comparative Example 1 without TMSPA grafting. The printing layer thickness was set to 63 μm.

[0075] Example 4

[0076] This embodiment provides a microwave dielectric ceramic slurry, which differs from Example 1 only in that the amount of 3-(acryloyloxy)propyltrimethoxysilane (TMSPA) added accounts for 75% of the mass of the dried ceramic powder.

[0077] Linear fitting calculations showed that the broadened curing depth was 194 μm, which was 142.5% higher than that of Comparative Example 1 without TMSPA grafting. The printing layer thickness was set to 80 μm.

[0078] Example 5

[0079] This embodiment provides a microwave dielectric ceramic slurry, which differs from Embodiment 1 only in that an equal mass of γ-methacryloyloxypropyltrimethoxysilane (TMSPM) is used instead of TMSPA.

[0080] Linear fitting calculations showed that the broadened curing depth was 91 μm, which was 13.75% higher than that of Comparative Example 1, which was grafted without functional modifiers. The printing layer thickness was set to 37 μm.

[0081] Example 6

[0082] This embodiment provides a microwave dielectric ceramic slurry, which differs from Embodiment 1 only in that an equal mass of a modifier having the following structure is used instead of TMSPA:

[0083] This modifier can be synthesized from pentaerythritol tetraacrylate (PETA) and 3-mercaptopropyltrimethoxysilane (MPTMS) via a thiol-Michael addition reaction in a 1:1 stoichiometric ratio.

[0084] Linear fitting calculations showed that the broadened curing depth was 151 μm, which was 88.75% higher than that of Comparative Example 1, which was grafted without functional modifiers. The printing layer thickness was set to 62 μm.

[0085] Example 7

[0086] This embodiment provides a microwave dielectric ceramic slurry, which differs from Embodiment 1 only in that an equal mass of a modifier having the following structure is used instead of TMSPA:

[0087] The modifier dipentaerythritol hexaacrylate (DPHA) was synthesized from 3-mercaptopropyltrimethoxysilane (MPTMS) via a thiol-Michael addition reaction in a stoichiometric ratio of 1:1.

[0088] Linear fitting calculations showed that the broadened curing depth was 189 μm, which was 136.25% higher than that of Comparative Example 1, which was grafted without functional modifiers. The printing layer thickness was set to 78 μm.

[0089] Example 8

[0090] This embodiment provides a microwave dielectric ceramic slurry, which differs from Embodiment 1 only in that: in step one, it is refluxed at 70°C for 8 hours.

[0091] The curing depth was calculated to be 97 μm based on linear fitting.

[0092] Example 9

[0093] This embodiment provides a microwave dielectric ceramic slurry, which differs from Embodiment 1 only in that: in step one, it is refluxed at 90°C for 4 hours.

[0094] Linear fitting calculations showed that the thickened curing depth was 96 μm.

[0095] Comparative Example 1

[0096] This comparative example provides a microwave dielectric ceramic slurry, which differs from Example 1 only in that the ceramic powder is not modified with TMSPA. Linear fitting calculations show that the broadened curing depth is 80 μm.

[0097] Comparative Example 2

[0098] This comparative example provides a microwave dielectric ceramic slurry, differing from Example 1 only in that an equal mass of silane coupling agent KH-560 without acrylate groups is used instead of TMSPA. Linear fitting calculations showed an increased curing depth of 79 μm. In this comparative example, the silane coupling agent KH-560 grafted onto the powder surface only serves as a surface modification and does not expose acrylate groups on the powder surface. During photopolymerization, the number of photosensitive groups per unit volume is only the same as the number of acrylate groups in the added resin matrix, and it does not improve its curing performance.

[0099] Comparative Example 3

[0100] This comparative example provides a microwave dielectric ceramic slurry, differing from Example 1 only in that an equal mass of siloxane-free n-propyl acrylate is used instead of TMSPA. Linear fitting calculations showed an increased curing depth of 80 μm. The siloxane-free n-propyl acrylate used in this comparative example, after undergoing the same grafting process, could not be grafted onto the powder surface. After extensive water washing and centrifugation, the n-propyl acrylate was washed away and therefore did not contribute to increasing curing performance during slurry preparation.

[0101] Test case

[0102] The pre-cut model files for material testing were transferred to the printer, and the slurries for each embodiment and comparative example were laid flat on the printing platform. The exposure power was set to 5mW / cm². 2Single-layer curing was performed with exposure times of 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, and 10s. The curing depth and width of the slurry were measured using a micrometer-based high-precision thickness gauge and an optical microscope. The relationships between exposure energy and curing depth, as well as between exposure energy and curing width, were obtained. Linear fitting was then used to calculate the critical energy E for curing width. w and widening the curing depth D b .

[0103] Printing accuracy: Based on the exposure energy and printing layer thickness obtained from the above fitting, a cylindrical model with a diameter of 10mm and a height of 10mm was 3D printed. The diameter of the printed cylindrical blank was measured using an optical microscope and compared with the diameter of the cylindrical model to find the difference.

[0104] Density: According to standard GB / T 25995-2010, density is calculated by dividing the bulk density by the theoretical density.

[0105] Quality factor: The quality factor of the sample was tested using a vector network analyzer and a resonant cavity fixture.

[0106] The specific results are shown in the table below:

[0107] Table 1

[0108]

[0109] Note: E in the table w That is, to achieve D b The required exposure energy.

[0110] Examples 1-4 involve changing the TMSPA content. A higher TMSPA content results in a greater curing depth and a thicker printed layer. A thicker printed layer reduces the number of interlayer interfaces, significantly decreasing the number of pores and defects at these interfaces, thus improving density. Examples 1, 6, and 7 involve changing the number of acrylate groups in the multifunctional acrylate monomer. A higher number of photosensitive resin groups in the multifunctional acrylate monomer results in a greater curing depth and a thicker printed layer. Example 1 uses a multifunctional acrylate monomer containing acrylate groups, and Example 5 uses a multifunctional acrylate monomer containing methacrylate groups. Changing the type of acrylate groups in the multifunctional acrylate monomer can also increase the curing depth. The higher reactivity of acrylate groups contributes to a greater curing depth.

[0111] Compared to Comparative Example 1, Example 4 shows that the curing layer thickness during photopolymerization printing can be increased from 33 μm to 80 μm. This reduces the number of interlayer interfaces by more than half, resulting in a significant reduction in the number of pore defects at the interlayer interfaces. The density increases from 89.11% to 94.21%, and the quality factor of the microwave dielectric ceramic increases from 34600 to 39879. The increased curing depth also leads to a gradual improvement in surface quality perpendicular to the Z-axis of the printed sample with increasing layer thickness. The printing accuracy increases from 191 μm to 10 μm, further improving the transmission effect of electromagnetic waves on the surface of radio frequency devices and greatly reducing the "absorption" and "weakening" effects of surface molding quality on signal transmission.

[0112] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A microwave dielectric ceramic slurry, characterized in that, The microwave dielectric ceramic slurry comprises the following components by mass percentage, based on its total mass: UV-curable oligomer 3-15%; diluent 2.8-15%; modified ceramic powder 70-90%; leveling agent 0.4-1.5%; defoamer 0.4-1.5%; It also includes a photoinitiator comprising 0.15-0.9% of the total mass of UV-curable oligomers and diluents; and a polymerization inhibitor comprising 0.03-0.3% of the total mass of UV-curable oligomers and diluents. Dispersant comprising 3-6% of the modified ceramic powder by mass; The UV-curable oligomer includes at least one of epoxy acrylate, polyurethane acrylate, and polyester acrylate; The method for modifying the ceramic powder includes the following steps: S1, the modifier is mixed with an organic solvent and hydrolyzed to obtain a hydrolyzed modifier; wherein the pH of the organic solvent is 4-5, and the modifier has the composition shown in the following formula: Among them, at least one of X1, X2, and X3 is an alkoxy group with 1-5 carbon atoms; Y represents an acrylate group, and R is C2-C 20 carbon chain or C2-C 20 A heterochain containing heteroatoms; n is an integer between 1 and 5; S2, add ceramic powder to hydrolysis modifier, stir, reflux, separate the product to obtain modified ceramic powder; The amount of the modifier is 35-75% of the mass of the ceramic powder.

2. The microwave dielectric ceramic slurry according to claim 1, characterized in that, The modifier Y has the following structure: Wherein, R1 is a -H or C1-C5 alkyl group; And / or, the alkoxy group is ethoxy or methoxy; And / or, the heteroatom is at least one of S, N or O.

3. The microwave dielectric ceramic slurry according to claim 2, characterized in that, The modifier has any of the following compositions: ， ， ， 。 4. The microwave dielectric ceramic slurry according to any one of claims 1-3, characterized in that, In step S1, the hydrolysis is carried out at room temperature for 1-2 hours. And / or, in step S2, the stirring time is 1-2 hours; And / or, the reflux temperature is 70-90℃, and the reflux time is 4-8h.

5. The microwave dielectric ceramic slurry according to any one of claims 1-4, characterized in that, Satisfy at least one of the following (1)-(3): (1) The amount of organic solvent used is 1-100 times the mass of the ceramic powder; (2) The organic solvent is an ethanol solution with a concentration of 70 wt% or higher; (3) In step S2, the ceramic powder is first mixed with a portion of the organic solvent and then added to the hydrolysis modifier.

6. A method for preparing the microwave dielectric ceramic slurry according to any one of claims 1-5, characterized in that, Includes the following steps: S11, UV-curable oligomer, diluent, photoinitiator and polymerization inhibitor are mixed to obtain resin premix; S12, add dispersant, modified ceramic powder, leveling agent and defoamer to the obtained resin premix, grind and defoam, and obtain microwave dielectric ceramic slurry.

7. The application of the microwave dielectric ceramic slurry according to any one of claims 1-5 or the microwave dielectric ceramic slurry prepared by the preparation method according to claim 6 in photopolymerization 3D printing.

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