Method for wrapping high-refractive-index ceramic powder with low-refractive-index product layer and ceramic material

Abstract

The invention discloses a method for wrapping high-refractive-index ceramic powder with a low-refractive-index product layer and a ceramic material, and relates to the technical field of ceramic additive manufacturing. The method comprises the following steps: forming a low-refractive-index product layer on the surface of ceramic powder through a physical vapor deposition method, a chemical vapor deposition method or a hydrothermal method; the material of the low-refractive-index product layer comprises at least one of silicon dioxide, aluminum oxide, yttrium oxide or yttrium aluminum garnet; the ceramic powder is high-refractive-index ceramic powder and comprises at least one of silicon carbide, silicon nitride or aluminum nitride. According to the method, on the premise that the powder body is prevented from being damaged and impurities are prevented from being introduced, a coating layer which is uniform, compact and good in refractive index matching is formed, and therefore the curing depth and printing reliability of the high-refractive-index ceramic powder in photocuring forming are effectively improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ceramic additive manufacturing, and in particular to a method for wrapping high-refractive-index ceramic powder with a low-refractive-index product layer and a ceramic material. BACKGROUND

[0002] In recent years, advanced ceramics have been increasingly widely applied in aerospace, energy, electronics and chemical industry and other extreme environments due to their excellent high-temperature mechanical strength, high thermal conductivity, low thermal expansion coefficient and excellent corrosion resistance. However, the high hardness and high brittleness characteristics of the materials also bring great challenges to the forming and processing. Emerging additive manufacturing technology, especially light-cured three-dimensional printing, provides a new possibility for the preparation of complex structure ceramic parts, not only breaks through the limitations of traditional processes, but also realizes high-precision and high-surface-quality manufacturing, and further expands the application range of advanced ceramics.

[0003] Among the many light-cured ceramic additive manufacturing technologies, stereolithography (SLA) is of great concern due to its high printing speed, excellent forming precision and good surface quality. The process usually uses a photosensitive resin-based ceramic slurry, and a three-dimensional structure is prepared by layer-by-layer ultraviolet curing. In this process, the layer thickness of the slurry and the curing depth of the ultraviolet light are particularly critical, and the latter must be greater than the minimum layer thickness set by the equipment, otherwise it will lead to printing failure or poor interlayer bonding.

[0004] However, ceramic particles in the slurry will cause significant ultraviolet light scattering, which seriously weakens the penetration ability of light on the slurry, resulting in insufficient curing depth. Taking silicon carbide (SiC) as an example, although it has a lower ultraviolet absorption and a higher refractive index (about 2.76) near 405 nm, it is still much higher than that of photosensitive resin (about 1.5), causing obvious refractive index mismatch, causing strong scattering and restricting the improvement of curing depth. Experiments show that even under the ultraviolet light energy of 675 mJ / cm 2 To improve the curing effect, the methods of increasing the ceramic particle size or reducing the ceramic volume fraction can be used, but the former will lead to the decrease of sintering activity, and the latter will easily cause the problems of low green density, difficult debinding and deterioration of the final mechanical properties.

[0005] To solve the above problems, the prior art proposes to improve the optical compatibility by coating a low refractive index shell layer on the surface of SiC particles. For example, Chen Zhangwei et al. of Shenzhen University (CN202110176975.X) prepared a SiO2 coating layer on the surface of SiC by high-temperature oxidation method. Although this method can achieve coating to some extent, it still has problems such as easy over-oxidation of SiC core, poor uniformity of coating layer, high energy consumption, long process cycle, and easy damage to coating layer during post-processing, which limits its actual application effect and large-scale production potential.

[0006] Another solution comes from Ningbo Vulcan Technology Co., Ltd. (CN202411047047.3), which proposes to construct a Y2O3-Al2O3 composite coating layer on the surface of SiC particles by sol-gel method, in order to improve the photocuring performance and promote sintering at the same time. However, there is still a refractive index difference between Y2O3 (refractive index about 1.8) and Al2O3 (refractive index about 1.76) and the resin matrix, and the curing efficiency is limited (single-layer curing efficiency not more than 1.0 μm / s). In addition, this method is prone to impurities and structural defects in the coating layer due to the presence of precursor residues and gel shrinkage, which in turn causes light scattering; on the other hand, if the coating is not uniform, it will also affect the consistency of the sintering aid, causing deformation or cracking of the ceramic during densification.

[0007] At present, there is still a lack of a low-refractive-index coating method that can achieve high efficiency, uniformity and structural integrity, which can significantly improve the photocuring depth and printing reliability of SiC slurry, without compromising the sintering activity and final mechanical properties, so as to meet the industrialization needs of high-quality, complex-structure SiC ceramic parts photocuring additive manufacturing. SUMMARY

[0008] In view of the shortcomings of the prior art, the present application provides a method for coating high-refractive-index ceramic powder with a low-refractive-index product layer and a ceramic material, aiming to solve the following problems:

[0009] Overcome the problems of over-oxidation of SiC core, uneven SiO2 shell, high energy consumption and damage to shell layer caused by high-temperature oxidation method;

[0010] Overcome the problems of poor refractive index matching between Y2O3-Al2O3 and resin, impurities in the coating layer, and uneven distribution of sintering aid;

[0011] By optimizing the coating layer material and preparation process, the photocuring depth and efficiency of the ceramic slurry are improved, and the stereolithography performance of high-refractive-index ceramic powder is improved.

[0012] To solve the above problems, the present application provides the following technical solutions:

[0013] In a first aspect, the present application provides a method for coating high-refractive ceramic powder with a low-refractive product layer, comprising: forming a low-refractive product layer on the surface of the ceramic powder by physical vapor deposition, chemical vapor deposition or hydrothermal method; the material of the low-refractive product layer comprises at least one of silicon dioxide, aluminum oxide, yttrium oxide or yttrium aluminum garnet. The ceramic powder is high-refractive ceramic powder, comprising at least one of silicon carbide, silicon nitride or aluminum nitride.

[0014] In a further aspect, the ceramic powder is obtained by granulating powder with a particle size of 0.01-1.5 μm to obtain a particle size of 10-150 μm; and the thickness of the low-refractive product layer is 1 nm-10 μm. The ceramic powder after granulation has a particle size of 10-150 μm, has a spherical or near-spherical morphology and good flowability.

[0015] The ceramic powder is obtained by granulating powder with a particle size of 0.01-1.5 μm to obtain a particle size of 10-150 μm. The ceramic powder in this range helps to achieve a high solid content and good rheological properties in the slurry, while avoiding the problem of intensified sedimentation or light scattering caused by excessively large particles. Smaller particle size helps to increase the specific surface area and improve sintering activity. The thickness of the low-refractive product layer is set to 1 nm-10 μm, which can effectively modulate the refractive index and will not excessively increase the volume of the coating layer to affect the subsequent sintering densification. This thickness range is sufficient to form a continuous and complete coating layer, ensuring that the light can still maintain a low energy loss when passing through numerous powder-resin interfaces, thereby significantly improving the solidification depth and printing success rate. In addition, this parameter range takes into account the process feasibility and the mechanical properties of the final ceramic part. A too thin layer may not effectively suppress scattering, and a too thick layer may introduce defects or hinder sintering.

[0016] In a further aspect, the physical vapor deposition method comprises the following steps:

[0017] S11, vacuuming the plating chamber to 10 Pa;

[0018] S12, heating the plating chamber to 900-1000℃ and maintaining the temperature;

[0019] S13, introducing argon gas and applying a direct current voltage of 500-1000 V to make argon ions bombard the target material and make target atoms escape;

[0020] S14, starting the high-frequency vibration device to suspend the ceramic powder and deposit the low-refractive product layer on the surface thereof.

[0021] Further, in step S12, the holding time is 30-180 min; in step S13, the argon flow rate is 20-50 sccm; in step S14, the vibration frequency of the high-frequency vibration device is 50-100 Hz, and the reaction time is 30-120 min.

[0022] Further, the chemical vapor deposition method comprises the following steps:

[0023] S21, placing the ceramic powder into a reaction chamber and vacuumizing;

[0024] S22, introducing inert gas as carrier gas and introducing precursor vapor;

[0025] S23, decomposing the precursor at 500-700 ℃ and forming a continuous coating layer on the surface of the powder;

[0026] S24, cooling and slightly grinding the powder after the reaction.

[0027] Further, in step S22, the inert gas is argon, and the argon flow rate is 20-50 sccm; in step S23, the vaporization temperature of the precursor is 120-150 ℃; the rotation rate of the rotation device or stirring device of the reaction chamber is 20-40 r / min, and the reaction time of step S23 is 30-120 min.

[0028] Further, the hydrothermal method comprises the following steps:

[0029] S31, dispersing the ceramic powder in a dispersion medium to form a suspension;

[0030] S32, adding a low-refractive product precursor and mixing uniformly;

[0031] S33, hydrothermal reaction at 120-250 ℃ to coat the product layer on the surface of the powder;

[0032] S34, separating, washing and drying the obtained powder after the reaction.

[0033] Further, in step S31, magnetic stirring is adopted, and the time of the magnetic stirring is 10-180 min; in step S33, the hydrothermal reaction time is 30 min-360 min; in step S34, the drying temperature is 50-100 ℃.

[0034] In a second aspect, the embodiments of the present application further provide a ceramic material prepared by the method of coating high-refractive ceramic powder with a low-refractive product layer according to the first aspect.

[0035] The method of the present application can improve the stereolithography performance of the ceramic material. The stereolithography is any one of DLP (Digital Light Processing), VPP (Vat Photopolymerization) and SL (Stereolithography).

[0036] The present application provides a method for wrapping high refractive index ceramic powder with low refractive index product layer and ceramic material. The present application constructs a low refractive index product layer on the surface of high refractive index ceramic powder by physical vapor deposition, chemical vapor deposition or hydrothermal method. The selected coating materials include at least one of glass, silicon dioxide, aluminum oxide, yttrium oxide or yttrium aluminum garnet. These materials have a relatively close refractive index with the photocurable resin, which can significantly improve the optical compatibility of the ceramic powder in the photocuring forming process. Due to the large refractive index difference between the high refractive index ceramic powder and the photosensitive resin, the ultraviolet light will be severely scattered in the slurry, thereby reducing the penetration ability of the light and limiting the curing depth. The present application forms a low refractive index product layer on the surface of the powder, which can effectively reduce the refractive index mismatch between the powder and the surrounding resin, reduce the reflection and scattering effect of the ultraviolet light on the particle surface, and enable the ultraviolet light to penetrate the slurry more deeply, thereby increasing the single layer curing thickness and enhancing the interlayer bonding force, and ultimately significantly improving the printing success rate and the structural integrity of the formed parts.

[0037] In addition, the physical vapor deposition method used in the present application can uniformly deposit the escaped atomic vapor on the surface of the powder by ion bombardment of the target material under high vacuum and medium temperature conditions, forming a dense and continuous coating layer, avoiding damage and oxidation problems of the powder body caused by high temperature treatment. The chemical vapor deposition method forms a uniform coating layer on the surface of the powder by the decomposition reaction of the gas phase precursor, and the process parameters can accurately control the thickness and composition of the coating layer, avoid the introduction of impurities and maintain good powder dispersibility. The hydrothermal method utilizes the dissolution-precipitation mechanism in the liquid phase environment to realize the uniform growth of the coating layer at a lower temperature, and is particularly suitable for surface modification of heat-sensitive ceramic materials. These three methods can avoid damage to the original structure of the powder to different extents, while ensuring that the coating layer has good bonding strength and optical uniformity.

[0038] The low refractive index product layer provided by the present application not only improves the photocuring performance, but also helps to maintain the sintering activity and mechanical properties of the ceramic powder itself. The uniform and complete coating layer has no porosity defects, which can effectively prevent energy loss of the light during propagation, thereby improving the utilization rate and curing efficiency of the ultraviolet light. In addition, this method has good process compatibility and scalability, and is suitable for a variety of high refractive index ceramic systems, providing a reliable material basis for photocuring additive manufacturing of complex structure ceramic parts, and has important industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings described in the following are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0040] Figure 1 Electronic images and C, Si, O element distribution maps of SiC@SiO2 powder prepared for Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the present application.

[0042] It should be understood that, when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0043] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and the appended claims of the present application, the singular forms "a", "an" and "the" are intended to include the plural forms, unless the context clearly indicates otherwise.

[0044] It should be further understood that the term "and / or" used in the specification and the appended claims of the present application means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0045] The present application provides a method for wrapping high-refractive-index ceramic powder with a low-refractive-index product layer, which comprises: forming a low-refractive-index product layer on the surface of the ceramic powder by physical vapor deposition (PVD), chemical vapor deposition (CVD) or hydrothermal method; the material of the low-refractive-index product layer comprises at least one of glass, silicon dioxide, aluminum oxide, yttrium oxide or yttrium aluminum garnet; the ceramic powder is high-refractive-index ceramic powder, which comprises at least one of silicon carbide, silicon nitride or aluminum nitride.

[0046] It is emphasized that PVD is deposited by ion bombardment of the target in a vacuum environment, with a temperature of only 900-1000℃ (lower than the upper limit of high-temperature oxidation of 1200℃), and a short deposition time (20-120 min); the hydrothermal method is carried out in a sealed reaction kettle at 120-250℃, completely avoiding the excessive oxidation of the SiC core body by high temperature, and the structure is complete.

[0047] CVD can form a continuous and uniform SiO2 layer on the SiC surface by controlling the precursor (such as ethyl silicate) concentration, reaction temperature and gas flow; PVD can accurately control the SiO2 shell thickness by adjusting the target power and deposition time, avoiding local over-thickness or absence, with a deviation of ≤5%, and the uniformity is much higher than that of high-temperature oxidation method.

[0048] The reaction time of PVD and CVD is only 30-120 min, and the reaction time of the hydrothermal method is 30-360 min, which is much lower than the 1-20 h of high-temperature oxidation, and the energy consumption is reduced by more than 50%, which is suitable for mass production; only light grinding (break the soft agglomeration) is required, avoiding the mechanical damage of the shell layer by breaking in the high-temperature oxidation method, and the shell layer integrity is more than 95%, which can ensure the continuity and effectiveness of the coating layer.

[0049] Regarding the material of the low-refractive-index product layer, the refractive index is preferably similar to that of the photocurable resin used in stereolithography.

[0050] Example 1:

[0051] S21, after granulation treatment of SiC powder with a particle size of 0.01-1.5 μm, SiC ceramic powder with a particle size D50 = 45 μm is obtained, which is uniformly placed in a chemical vapor deposition reaction chamber, and the reaction chamber is evacuated to 10 Pa to exclude air interference.

[0052] S22, using ethyl silicate as the precursor, argon gas is introduced as the carrier gas and protective gas, and the gas flow is controlled at 30 sccm to make the precursor vapor uniformly diffuse to the surface of the powder.

[0053] S23, set the reaction chamber temperature to 550℃, the precursor vaporization temperature to 120℃, start the stirring device to stir the powder at a rate of 40 r / min for 40 minutes, so that the precursor is uniformly deposited on the surface of the SiC powder by gas phase chemical reaction and forms a continuous low-refractive-index coating layer.

[0054] S24, after the reaction is completed, stop the gas supply and rotation, and wait for the reaction chamber to cool to room temperature, then take out the powder and perform 10 minutes of light grinding to eliminate soft agglomeration, and finally obtain SiO2-coated SiC powder (denoted as SiC@SiO2 powder). The electronic image and C, Si, O element distribution diagram of the SiC@SiO2 powder obtained in this example are shown in (b) of FIG. 1. Figure 1 ​

[0055] The SiC@SiO2 powder and photosensitive resin were prepared into a slurry, and then cured in a DLP printer. The single-layer curing depth was about 36 pm.

[0056] Example 2:

[0057] S11, SiC powder with a particle size of 0.01-1.5 pm was granulated to obtain SiC ceramic powder with a particle size D50=45 pm, which was uniformly placed in a coating chamber. The coating chamber was pumped to a vacuum degree of 10 Pa by a vacuum pump to remove internal air, water vapor and other impurity gases to avoid interference with the subsequent ion bombardment and film deposition process.

[0058] S12, the external heating device was started, and the temperature was programmed to rise to 1000°C at a rate of 10°C / min, and kept at this temperature for 40 minutes to fully remove the residual water vapor in the coating chamber and evaporate the adsorbed substances on the surface of the SiC ceramic powder.

[0059] S13, argon gas was introduced into the coating chamber as working gas, and the gas flow was controlled at 30 sccm. A high-energy argon ion was generated by applying a direct current voltage of 800 V through an electric control system. The argon ion bombarded the silicon dioxide target material located in the cathode at high speed under the action of the electric field, and the atoms on the surface of the target material escaped to form silicon dioxide atom vapor.

[0060] S14, the high-frequency vibration device was started, and the SiC powder was in a suspended and dispersed state at a frequency of 50 Hz for 40 minutes to ensure that the powder particles were uniformly contacted with the atom vapor and deposited to form a continuous and dense silicon dioxide film, and finally obtain SiO2 coated SiC powder (denoted as SiC@SiO2 powder). The electronic image and C, Si, O element distribution diagram of the SiC@SiO2 powder obtained in this example are shown in (c) of FIG. 4. Figure 1

[0061] The obtained SiC@SiO2 powder and photosensitive resin were prepared into a slurry, and then cured in a DLP printer. The single-layer curing depth was about 33 pm.

[0062] Example 3:

[0063] S31, SiC powder with a particle size of 0.01-1.5 pm was granulated to obtain SiC ceramic powder with a particle size D50=45 pm. The SiC ceramic powder was added to water and magnetically stirred for 30 minutes to form a stable suspension.

[0064] S32, the silicon dioxide precursor capable of generating a low-refractive-index product layer was added, and the stirring was continued for 30 minutes to make the mixture uniform.

[0065] ​S33, the suspension is transferred to a hydrothermal reactor for reaction at 220℃ for 240 minutes to form a continuous and uniform SiO2 coating layer on the surface of the SiC powder through a hydrothermal dissolution-precipitation and in-situ reaction mechanism.

[0066] S34, after the reaction, the reactor is cooled, and the solid-liquid two-phase is separated by centrifugation, and impurities are removed by multiple ethanol washing, and finally dried at 90℃ for 4 hours to obtain the SiO2-coated SiC powder (denoted as SiC@SiO2 powder). The electronic image and C, Si, O element distribution diagram of the SiC@SiO2 powder obtained in the embodiment are shown in (d) of FIG. 1. Figure 1

[0067] The SiC@SiO2 powder is prepared into a slurry with a photosensitive resin, and the slurry is tested by DLP printing, and the single-layer curing depth is about 34μm.

[0068] Comparative Example 1:

[0069] The SiC powder with a particle size of 0.01-1.5μm is granulated to obtain SiC ceramic powder with a particle size D50=45μm. The SiC powder is prepared into a slurry with a photosensitive resin, and the slurry is cured without coating treatment under the same DLP printer conditions, and the single-layer curing depth is only 9μm. The electronic image and C, Si, O element distribution diagram of the SiC powder of Comparative Example 1 are shown in (a) of FIG. 1. Figure 1

[0070] In the embodiment of the application, SiO2 is used to coat SiC powder, and low-refractive-product layer SiO2 is introduced by PVD, CVD and hydrothermal method, respectively:

[0071] The refractive index of SiO2 (-1.47) is close to that of the light-curing resin (-1.5), which can significantly reduce light scattering, and the curing depth is increased to 34-35μm.

[0072] PVD uses silicon dioxide as a precursor to form a dense SiO2 layer by ion bombardment, CVD uses ethyl silicate as a precursor to form a dense SiO2 layer by vapor deposition, or hydrothermal method uses silicon dioxide as a precursor to form a continuous SiO2 coating layer by dissolution-precipitation reaction, which can avoid the residual of chloride ions, the SiO2 layer has no porosity defects, the light transmittance is increased by 20%, the printing precision is directly improved, the curing depth is 34-35μm under 10s exposure time, and the unit time efficiency is 3.4-3.5μm / s. Subsequent sintering only needs conventional process, and does not need to rely on Y2O3-Al2O3 as a sintering aid, which avoids performance fluctuations caused by uneven distribution of the aid, and the ceramic density is more than 99%.

[0073] ​​In the above embodiments, the description of each embodiment is focused on, and the part not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0074] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, these modifications and variations of the present application are also intended to be within the scope of the present application claims and their equivalents. Therefore, the present application is also intended to include these modifications and variations.

[0075] The above description is merely a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of coating high refractive index ceramic powders with a low refractive index product layer, characterized in that The application relates to a ceramic material and a preparation method thereof. A low-refractive product layer is formed on the surface of ceramic powder by a physical vapor deposition method, a chemical vapor deposition method or a hydrothermal method; the material of the low-refractive product layer comprises at least one of glass, silicon dioxide, aluminum oxide, yttrium oxide or yttrium aluminum garnet; and the ceramic powder is high-refractive ceramic powder comprising at least one of silicon carbide, silicon nitride or aluminum nitride.

2. The method of claim 1, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. The thickness of the low-refractive product layer is 1nm-10mu.

3. The method of claim 1, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. The ceramic powder is obtained by granulating powder with a particle size of 0.01-1.5mu, and the particle size is 10-150mu.

4. The method of claim 1, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. The physical vapor deposition method comprises the following steps: S11, vacuumizing the plating chamber to below 13Pa; S12, heating the plating chamber to 900-1000C and keeping the temperature; S13, introducing argon and applying a 500-1000V direct current to make argon ions bombard the target material and make target atoms escape; S14, starting a high-frequency vibration device to make the ceramic powder suspend, and the target atoms deposit on the surface of the ceramic powder to form the low-refractive product layer.

5. The method of claim 4, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. In step S12, the keeping time is 30-180min; in step S13, the gas flow of argon is 20-50sccm; and in step S14, the vibration frequency of the high-frequency vibration device is 50-100Hz, and the reaction time is 30-120min.

6. The method of claim 1, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. The chemical vapor deposition method comprises the following steps: S21, placing the ceramic powder in a reaction chamber and vacuumizing; S22, introducing inert gas as carrier gas and introducing precursor vapor; S23, decomposing the precursor at 500-700C to deposit a coating layer on the surface of the powder; S24, cooling and grinding the powder after the reaction.

7. The method of claim 6, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. In step S22, the inert gas is argon, and the gas flow of argon is 20-50sccm; in step S23, the vaporization temperature of the precursor is 120-150C; the rotation speed of the rotation device or stirring device of the reaction chamber is 20-40r / min, and the reaction time of step S23 is 30-120min.

8. The method of claim 1, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. The hydrothermal method comprises the following steps: S31, dispersing the ceramic powder in a dispersion medium to form a suspension; S32, adding a low-refractive product precursor and mixing uniformly; S33, hydrothermal reaction at 120-250C to make the product layer coat the surface of the powder; S34, separating, washing and drying the obtained powder after the reaction.

9. The method of claim 8, wherein the low refractive index product layer is wrapped around the high refractive index ceramic powder. In step S31, magnetic stirring is adopted, and the time of the magnetic stirring is 10-180min; in step S33, the time of the hydrothermal reaction is 30min-360min; and in step S34, the drying temperature is 50-100C.

10. A ceramic material, characterized by, The ceramic material is prepared by wrapping the high-refractive ceramic powder with the low-refractive product layer according to the method in any one of claims 1-9.

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