Alumina ceramic-based wave-absorbing material and preparation method thereof

Abstract

The invention provides an aluminum oxide ceramic-based wave-absorbing material and a preparation method thereof, and belongs to the field of ceramic-based composite materials. The method comprises the following steps: mixing a resin monomer, a light curing agent, aluminum oxide powder, a dispersing agent, a rheological additive and a sintering additive to obtain aluminum oxide ceramic slurry; according to preset ceramic structure model data, the aluminum oxide ceramic slurry is subjected to photocuring 3D printing, and an aluminum oxide ceramic biscuit is obtained; degreasing and sintering the alumina ceramic biscuit to obtain an alumina ceramic matrix; and loading the wave-absorbing agent on an aluminum oxide ceramic matrix to obtain the aluminum oxide ceramic-based wave-absorbing material. The alumina ceramic-based wave-absorbing material has the characteristics of complex and adjustable structure, light weight, high precision, high mechanical strength, high melting point, broadband absorption and the like. The working temperature of a part made of the composite material can reach 900 DEG C or above, and the composite material can resist severe environments such as high-speed airflow scouring, oxidation and gas corrosion and can be used as a light-weight bearing part to be applied to invisible equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic matrix composite materials, and particularly relates to an alumina ceramic matrix wave-absorbing material and a preparation method thereof. BACKGROUND

[0002] Alumina ceramics have many excellent properties such as chemical corrosion resistance, high temperature resistance, high mechanical strength, high hardness, good wear resistance, and the like, and have become the most widely used, largest production and sales, and widest application field material among similar ceramic materials. However, alumina ceramics are brittle, and it is difficult to process alumina ceramic structural parts with complex structures, the customized mold has a long production cycle and high cost. Therefore, the use of light-cured 3D printing has great advantages, can improve the research and development efficiency, reduce material waste, and reduce the cost in large-scale application. It is one of the most studied directions in the current ceramic field. With the development of today's science and technology, additive manufacturing technology (3D printing) breaks through the limitation of traditional processing methods on the preparation precision of multi-layer and complex structures. Through special structural design, such as honeycomb structure, hollow structure, porous structure and the like, the performance of the material can be greatly expanded, so that the 3D printing technology has great potential in the future ceramic preparation process. At present, light-cured 3D printing technology is one of the more mature ceramic 3D printing methods, and has the advantages of fast solidification forming speed and high printing precision, and has become the main research direction of current ceramic additive manufacturing.

[0003] Combining alumina, 3D printing and wave-absorbing technology can prepare a multifunctional alumina ceramic matrix composite wave-absorbing material with high complexity, high accuracy, high mechanical strength, high melting point and wide-band absorption. At present, the research on wave-absorbing materials for low-temperature components such as wings in the lateral and forward directions is relatively extensive. However, the development of wave-absorbing materials for high-temperature components such as engine nozzles in the tail direction is slow. The high-temperature working environment puts strict requirements on the engine nozzle and other parts. The working temperature of these parts can reach 900 DEG C or above, and the harsh environment such as scouring of high-speed airflow, oxidation and gas corrosion poses great challenges to the research and development of high-temperature-resistant wave-absorbing materials. In order to meet the requirements of weapons and equipment on thrust, mass, reliability and the like, the structural and functional integration of high-temperature-resistant structural wave-absorbing composite materials has more advanced advantages, and is attracting more and more attention and research. SUMMARY

[0004] The present application provides an alumina ceramic matrix wave-absorbing material and a preparation method thereof, to solve the technical problem of how to improve the high-temperature resistance of the alumina ceramic matrix wave-absorbing material, so that the working temperature of the wave-absorbing component is 900 DEG C or above.

[0005] In a first aspect, an embodiment of the present application provides a preparation method of an alumina ceramic matrix wave-absorbing material, and the method comprises the following steps: The resin monomer, photocuring agent, alumina powder, dispersant, rheological aid and sintering aid are mixed to obtain an alumina ceramic slurry; According to the preset ceramic structure model data, the alumina ceramic slurry is subjected to photocuring 3D printing to obtain an alumina ceramic green body; The alumina ceramic green body is subjected to debinding and sintering to obtain an alumina ceramic matrix; and The wave-absorbing agent is loaded on the alumina ceramic matrix to obtain an alumina ceramic wave-absorbing material. The loading temperature is 100-1000℃, and the loading time is 2-72h.

[0006] Optionally, in the alumina ceramic slurry, the resin monomer is 15-25 parts by mass, the photocuring agent is 0.1-1 part by mass, the alumina powder is 70-90 parts by mass, the dispersant is 0.5-5 parts by mass, the rheological aid is 0.5-5 parts by mass, and the sintering aid is 0-5 parts by mass.

[0007] Optionally, the alumina powder is single-particle-size alumina powder or a mixed powder composed of two or more alumina powders with different particle sizes; and / or, The resin monomer includes one or a mixture of several of polyurethane acrylate, bisphenol A epoxy acrylate, ethylene glycol diacrylate, propoxylated neopentyl glycol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, hydroxyethyl acrylate and isooctyl acrylate; and / or, The photocuring agent includes one or a mixture of several of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, isopropyl thioxanthone and phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide; and / or, The dispersant includes one or a mixture of several of KOS110, KH550, KH560, polyethylene glycol 200 and polyethylene glycol 400; and / or, The rheological aid includes one or several of nano-silicon dioxide, nano-alumina, alumina with a particle size >5μm, talc powder, BYK anti-settling agent, polyvinyl alcohol, polyvinyl butyral and polyvinyl pyrrolidone; and / or, The sintering aid includes one or several of silicon dioxide, yttrium oxide, magnesium oxide, lithium fluoride and aluminum fluoride.

[0008] Optionally, the particle size D 50 of the alumina powder is 0.1-10μm, and the particle size D 99 is <20μm.

[0009] Optionally, the viscosity of the alumina ceramic slurry is 0.5 Pa.s to 50 Pa.s.

[0010] Optionally, the light-cured 3D printing comprises the following parameters: light wavelength is 405 nm, exposure intensity is 5 mW / cm 2 ~ 50 mW / cm 2 , exposure time is 1 s to 10 s, and single-layer printing thickness is 20 μm to 300 μm.

[0011] Optionally, the heating rate of the debinding is 0.1 ℃ / min to 2 ℃ / min, the maximum temperature of the debinding is 500 ℃ to 1000 ℃, and the holding time of the debinding at the maximum temperature is 1 h to 10 h.

[0012] Optionally, the heating rate of the sintering is 1 ℃ / min to 10 ℃ / min, the maximum temperature of the sintering is 1200 ℃ to 1800 ℃, and the holding time of the sintering at the maximum temperature is 1 h to 10 h.

[0013] Optionally, the wave-absorbing agent comprises one or a mixture of several of carbon black, graphite, graphene, carbon nanotube, ferrite, carbonyl iron powder, polyvinylidene fluoride, and dopamine hydrochloride.

[0014] In a second aspect, the alumina ceramic wave-absorbing material prepared by the method of any one of the first aspect is provided, and the alumina ceramic wave-absorbing material satisfies the following performances: working temperature ≥ 900 ℃, bending strength is 220 MPa to 295 MPa, density is 3.66 g / cm 3 ~ 3.83 g / cm 3 , and the reflection loss between 5 GHz and 40 GHz is 35 dB.

[0015] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages: The embodiments of the present application provide a preparation method of an alumina ceramic wave-absorbing material, which comprises: mixing resin monomers, a light-curing agent, alumina powder, a dispersing agent, a rheological aid, and a sintering aid to obtain an alumina ceramic slurry; performing light-cured 3D printing on the alumina ceramic slurry according to preset ceramic structure model data to obtain an alumina ceramic green body; performing debinding and sintering on the alumina ceramic green body to obtain an alumina ceramic matrix; and loading a wave-absorbing agent on the alumina ceramic matrix to obtain the alumina ceramic wave-absorbing material; wherein the loading temperature is 100 ℃ to 1000 ℃, and the loading time is 2 h to 72 h.

[0016] Firstly, by reasonably designing the composition of the alumina ceramic slurry, alumina itself has extremely high melting point and excellent high-temperature chemical stability, and is not prone to crystal transformation or decomposition in an environment above 900 DEG C, thereby providing a basic high-temperature resistant framework for the material; the sintering aid promotes the densification sintering of alumina at a lower temperature, avoids excessive grain growth or phase transformation caused by high-temperature sintering, and ensures the high-temperature strength of the substrate after sintering; the dispersant and rheological aid ensure the uniform dispersion of alumina powder in the slurry, avoid particle agglomeration or delamination during printing, and the uniform microstructure can reduce cracking caused by stress concentration at high temperature, thereby improving the high-temperature mechanical properties of the material.

[0017] Secondly, by using the light-cured additive manufacturing technology (3D printing), the density and structural consistency of the green body are ensured, thereby laying a foundation for forming a uniform and dense ceramic matrix in the subsequent sintering.

[0018] Thirdly, by excluding organic components such as resin monomers in the debinding stage, the purity of the ceramic matrix is ensured by avoiding the reaction of residual carbides with alumina at high temperature. In the sintering stage, the alumina particles are fully bonded to form a dense ceramic matrix, thereby improving the high-temperature strength and thermal shock resistance.

[0019] Finally, when the organic carbon source is loaded at 100 DEG C to 1000 DEG C, the carbon source is carbonized at high temperature to form a graphitized or amorphous carbon structure, and a "ceramic-carbon" composite interface is formed with the alumina matrix. The carbon phase after carbonization has good thermal conductivity, which can assist the alumina matrix in heat dissipation and reduce the risk of local overheating; at the same time, the flexibility of the carbon phase can buffer the thermal strain at high temperature and reduce the cracking of the matrix.

[0020] Thus, the high-temperature resistance of the alumina ceramic-based wave-absorbing material is improved, so that the working temperature of the wave-absorbing component is above 900 DEG C. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor.

[0023] Figure 1 A flowchart of a preparation method of an alumina ceramic-based wave-absorbing material provided in the embodiments of the present application is shown in the figure. Figure 2 Different types of alumina ceramic structures drawn by design software provided in the embodiments of the present application are shown in the figures. Figure 3 A practical structure schematic diagram of the alumina ceramic base provided for Embodiment 1 of the present application; Figure 4 A microstructure schematic diagram of the alumina ceramic base provided for Embodiment 1 of the present application; Figure 5 A wave-absorbing performance test result diagram of the alumina ceramic base wave-absorbing composite material provided for Embodiment 1 of the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] The range descriptions described herein, such as numerical range, ratio range, etc., all include all possible sub-ranges within the range and single values, for example, the range description of “1 to 6” or “1-6” covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms “include”, “contain” and the like used herein mean “include but not limited to”; the relationship terms “first”, “second” and the like are only used to distinguish different entities or operations, and do not imply actual sequence or relationship; “and / or” means that multiple cases can exist independently or simultaneously; “at least one”, “multiple”, “at least one” and the like refer to any combination of the corresponding objects, including single or multiple combinations of objects. The proportional relationship involved herein, such as mass ratio, molar ratio, etc., should be understood as the corresponding relationship between the front and the rear in the proportional form according to the description order. The raw materials, reagents, instruments and equipment used herein can be purchased or prepared by existing methods.

[0026] Figure 1 A flowchart schematic diagram of a preparation method of an alumina ceramic base wave-absorbing material provided by the embodiments of the present application.

[0027] As shown in Figure 1 The embodiments of the present application provide a preparation method of an alumina ceramic base wave-absorbing material, which comprises: S1, mixing resin monomers, photocuring agents, alumina powders, dispersants, rheological aids and sintering aids to obtain an alumina ceramic slurry; In some embodiments, in the alumina ceramic slurry, the resin monomer is 15-25 parts by mass, the photocuring agent is 0.1-1 part by mass, the alumina powder is 70-90 parts by mass, the dispersant is 0.5-5 parts by mass, the rheological aid is 0.5-5 parts by mass, and the sintering aid is 0-5 parts by mass.

[0028] In some embodiments, the alumina powder is a single-particle-size alumina powder or a mixed powder composed of two or more alumina powders with different particle sizes; and / or, The resin monomer includes one or a mixture of several of polyurethane acrylate, bisphenol A epoxy acrylate, ethylene glycol diacrylate, propoxylated neopentyl glycol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, hydroxyethyl acrylate, and isooctyl acrylate; and / or, The photocuring agent includes one or a mixture of several of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, isopropyl thioxanthone, and phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide; and / or, The dispersant includes one or a mixture of several of KOS110, KH550, KH560, polyethylene glycol 200, and polyethylene glycol 400; and / or, The rheological aid includes one or several of nano-silicon dioxide, nano-alumina, alumina with a particle size >5 μm, talc powder, BYK anti-settling agent, polyvinyl alcohol, polyvinyl butyral, and polyvinyl pyrrolidone; and / or, The sintering aid includes one or several of silicon dioxide, yttrium oxide, magnesium oxide, lithium fluoride, and aluminum fluoride.

[0029] The resin monomer (15-25 parts by mass) as the matrix of the photocuring resin, such as polyurethane acrylate, etc., is rapidly cured by high molecular crosslinking reaction under 405 nm light irradiation, providing structural support for 3D printing. The amount directly affects the flowability and curing rate of the slurry. When it is less than 15 parts, the curing strength is insufficient; when it is more than 25 parts, the viscosity of the slurry increases, which is not conducive to printing.

[0030] The photocuring agent (0.1-1 part by mass) absorbs light energy (such as 405 nm wavelength) and decomposes to generate free radicals, initiating the crosslinking of the resin monomer and acting as a “trigger” for the curing reaction. Too little amount will result in insufficient curing, and the formed piece is prone to deformation; too much amount may cause over-curing, affecting the toughness of the material and the printing accuracy.

[0031] Alumina powder (70-90 parts by mass) constitutes the main component of the ceramic matrix, determining the high-temperature resistance (working temperature ≥ 900℃), bending strength (220-295 MPa) and density (3.66-3.83 g / cm 3 ) of the material. High solid content (more than 70%) can reduce sintering shrinkage and improve mechanical properties.

[0032] Dispersants (0.5-5 parts by mass) such as KOS110, KH550, etc., prevent alumina powder from agglomerating in the resin through electrostatic repulsion or steric hindrance effects, ensuring slurry uniformity. Insufficient dosage can lead to powder settling, affecting layer-to-layer bonding during printing; excessive dosage may increase slurry viscosity and reduce flowability.

[0033] Rheological aids (0.5-5 parts by mass) including nano-silica, BYK anti-settling agents, etc., adjust the thixotropy and suspension stability of the slurry, preventing powder settling or slurry flow during printing. They play a key role in maintaining slurry viscosity within the range of 0.5-50 Pa•s, ensuring smooth extrusion and good shape retention during printing.

[0034] Sintering aids (0-5 parts by mass) such as silica, yttria, etc., form a low-melting-point liquid phase during sintering, promoting alumina particle rearrangement and densification, reducing sintering temperature (1200-1800℃) and improving ceramic density. Excessive dosage can introduce impurity phases, affecting high-temperature resistance.

[0035] For example, the mass parts of the resin monomer can be 15, 17, 19, 20, 22, 24, 25, etc., the mass parts of the photocuring agent can be 0.1, 0.2, 0.4, 0.6, 0.8, 1, etc., the mass parts of the alumina powder can be 70, 75, 80, 85, 90, etc., the mass parts of the dispersant can be 0.5, 1, 2, 3, 4, 5, etc., the mass parts of the rheological aid can be 0.5, 1, 2, 3, 4, 5, etc., and the mass parts of the sintering aid can be 0, 0.5, 1, 2, 3, 4, 5, etc.

[0036] In some embodiments, the particle size D 50 of the alumina powder is 0.1-10 μm, and the particle size D 99 is less than 20 μm.

[0037] The particle size of the alumina powder is D50=0.1-10 μm, D99<20 μm, and the particle size <0.1 μm is easy to agglomerate, increasing the viscosity of the slurry; the particle size >10 μm causes uneven layer thickness and precision reduction in printing. Meanwhile, the >20 μm large particles are removed to avoid clogging of the 3D printer nozzle and ensure the continuity of the printing process. The mixed multi-particle size powder can optimize the bulk density, reduce the sintering porosity, and reduce the shrinkage. For example, the particle size D 50 may be 0.1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, etc. 99 may be 19.9 μm, 19 μm, 18 μm, 17 μm, 16 μm, 15 μm, etc.

[0038] In some embodiments, the viscosity of the alumina ceramic slurry is 0.5 Pa.s-50 Pa.s.

[0039] The viscosity of the slurry is limited to 0.5-50 Pa.s, and below 0.5 Pa.s, the slurry is too thin, and it is easy to flow during printing, and the complex structure shape cannot be maintained, and the precision is lost; and above 50 Pa.s, the flowability is very poor, the extrusion resistance of the nozzle is large, which may cause material breakage or poor interlayer adhesion, and the strength of the formed part is reduced. For example, the viscosity of the alumina ceramic slurry can be 0.5 Pa.s, 1 Pa.s, 5 Pa.s, 10 Pa.s, 20 Pa.s, 30 Pa.s, 40 Pa.s, 50 Pa.s, etc.

[0040] In some embodiments, the drying temperature of the alumina is 100-150 ℃, and the drying time is 2-8 h.

[0041] The alumina powder is dried at 100-150 ℃ for 2-8 h, and the purpose is to remove the moisture in the powder. The presence of moisture will affect the performance of the slurry, causing agglomeration or adverse reactions with other ingredients, and after drying, the stability and uniformity of the subsequent slurry preparation can be ensured.

[0042] S2, according to the preset ceramic structure model data, the alumina ceramic slurry is subjected to light curing 3D printing to obtain an alumina ceramic green body; The model data suitable for 3D printing is obtained by drawing the model through a three-dimensional drawing software, which is a key step for determining the shape and size of the wave-absorbing material, and various complex structures can be designed according to the actual application requirements, providing accurate guidance for subsequent 3D printing.

[0043] In some embodiments, the light curing 3D printing includes the following parameters: the light wavelength is 405 nm, the exposure intensity is 5 mW / cm 2 -50 mW / cm 2 , the exposure time is 1 s-10 s, and the single-layer printing thickness is 20 μm-300 μm.

[0044] The light wavelength of 405 nm is selected for 3D printing forming because the light of this wavelength can be effectively absorbed by the light-cured resin, triggering a light-curing reaction to make the slurry solidify and form layer by layer. The exposure intensity is limited to 5-50 mW / cm 2 , and the exposure time is 1-10 s, which can ensure that the slurry is moderately cured. If the intensity is lower than 5 mW / cm 2 or the time is shorter than 1 s, the slurry will not be fully cured, affecting the forming quality; if the intensity is higher than 50 mW / cm 2 or the time exceeds 10 s, it is easy to cause over-curing, affecting the printing precision and material performance. The single-layer printing thickness is set to 20-300 μm, and the control of the single-layer thickness can affect the forming precision and printing efficiency. When the single-layer thickness is less than 20 microns, the forming precision is improved, but the printing efficiency is reduced; when the single-layer thickness is greater than 300 microns, the printing efficiency is improved, but the forming precision is reduced. Exemplarily, the exposure intensity can be 5 mW / cm 2 , 10 mW / cm 2 , 20 mW / cm 2 , 30 mW / cm 2 , 40 mW / cm 2 , 50 mW / cm 2 , etc., the exposure time can be 1 s, 3 s, 4 s, 6 s, 8 s, 10 s, etc., and the single-layer printing thickness can be 20 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc.

[0045] S3, debinding and sintering the alumina ceramic body to obtain an alumina ceramic substrate; In some embodiments, the debinding has a heating rate of 0.1-2 ℃ / min, a maximum temperature of 500-1000 ℃, and a holding time at the maximum temperature of 1-10 h.

[0046] The defatting temperature increasing rate is 0.1-2℃ / min, and slow temperature increasing can make the organic additives (such as resin monomer, dispersant, etc.) in the ceramic body gradually decompose and volatilize, preventing the ceramic from cracking due to rapid temperature increasing. The defatting maximum temperature is 500-1000℃, and the defatting is kept at the maximum temperature for 1-10h, ensuring that all the organic additives are completely removed, creating good conditions for subsequent sintering, otherwise the residual organic matter will affect the performance and quality of the ceramic. For example, the defatting temperature increasing rate can be 0.1℃ / min, 0.3℃ / min, 0.5℃ / min, 0.8℃ / min, 1℃ / min, 1.2℃ / min, 1.5℃ / min, 1.8℃ / min, 2℃ / min, etc., the defatting maximum temperature can be 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, etc., and the defatting keeping time at the maximum temperature can be 1h, 3h, 5h, 7h, 9h, 10h, etc.

[0047] In some embodiments, the sintering temperature increasing rate is 1-10℃ / min, the sintering maximum temperature is 1200-1800℃, and the sintering keeping time at the maximum temperature is 1-10h.

[0048] Defining the sintering temperature increasing rate as 1-10℃ / min, the sintering maximum temperature as 1200-1800℃, and the sintering keeping time at the maximum temperature as 1-10h can make the alumina ceramic undergo phase transition, the crystal grains gradually grow and densify, and a ceramic matrix with good mechanical properties and other properties is formed. If the temperature is lower than 1200℃ or the time is shorter than 1h, the ceramic cannot be fully sintered, resulting in low density and poor performance such as strength. If the temperature is higher than 1800℃ or the time is longer than 10h, the crystal grains grow excessively, which in turn reduces the performance of the ceramic. For example, the sintering temperature increasing rate can be 1℃ / min, 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min, 10℃ / min, etc., the sintering maximum temperature can be 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃, etc., and the sintering keeping time at the maximum temperature can be 1h, 3h, 5h, 7h, 9h, 10h, etc.

[0049] S4, loading the wave-absorbing agent on the alumina ceramic matrix to obtain an alumina ceramic wave-absorbing material; In some embodiments, the loading temperature is 100-1000℃, and the loading time is 2-72h.

[0050] In some embodiments, the wave-absorbing agent includes one or a mixture of several of carbon black, graphite, graphene, carbon nanotube, ferrite, carbonyl iron powder, polyvinylidene fluoride, and dopamine hydrochloride.

[0051] Wave-absorbing agents such as carbon black, graphene, etc., mainly serve to absorb electromagnetic waves, convert electromagnetic wave energy into heat energy or other forms of consumption, prevent electromagnetic waves from penetrating or reflecting, so as to make the alumina ceramic matrix material have wave-absorbing performance.

[0052] By using impregnation loading, vacuum impregnation loading, bonding loading and the like, the wave-absorbing agent can be uniformly loaded on the alumina ceramic matrix at 100-1000℃ for 2-72h, to form a good interface bonding, so as to ensure that the wave-absorbing agent can fully play a role and improve the wave-absorbing performance of the material. The loading temperature and time will affect the penetration depth and distribution uniformity of the wave-absorbing agent in the matrix, and further affect the wave-absorbing effect. For example, the loading temperature can be 100℃, 200℃, 300℃, 500℃, 700℃, 900℃, 1000℃, etc., and the loading time can be 2h, 5h, 10h, 15h, 20h, 30h, 50h, 60h, 72h, etc.

[0053] Based on the overall inventive concept, the alumina ceramic matrix wave-absorbing material prepared by the method described in any one of the above embodiments satisfies the following performance: working temperature ≥ 900℃, bending strength 220MPa-295MPa, density 3.66g / cm 3 -3.83g / cm 3 , and the reflection loss between 5GHz and 40GHz is 35dB.

[0054] The alumina ceramic matrix wave-absorbing material prepared by the embodiments of the present application has the characteristics of complex and adjustable structure, lightweight, high precision, high mechanical strength, high melting point and wide frequency band wavelength absorption. The working temperature of these components can reach 900℃ or above, and they can withstand the erosion of high-speed airflow, oxidation and gas corrosion in harsh environments, and can be used as lightweight load-bearing components for stealth equipment.

[0055] Therefore, through the multi-dimensional design of "high-performance ceramic matrix + functionalized carbon source loading + 3D printing precise forming", the present application realizes the synergistic optimization of the mechanical properties, wave-absorbing performance, high temperature resistance and structural adaptability of the material.

[0056] I. Cause of high mechanical strength and high melting point (1) Intrinsic properties of alumina ceramic matrix: high-purity alumina skeleton, alumina (Al203) itself has extremely high melting point (about 2054℃) and mechanical strength (theoretical bending strength can reach more than 300MPa). In this application, the proportion of alumina powder is as high as 70-90 parts by mass, which constitutes the main skeleton of the material, directly giving the material the characteristics of high temperature resistance (working temperature ≥ 900℃) and high rigidity. The densification sintering process, through high temperature sintering of 1200-1800℃, cooperates with sintering aids (such as silicon dioxide, yttrium oxide, etc.) to form a low melting point liquid phase, promote the rearrangement of alumina particles and neck growth, reduce porosity, and improve the density (density 3.66-3.83g / cm 3 , close to the theoretical density). The dense ceramic matrix significantly enhances the bending strength (220-295MPa) and impact resistance.

[0057] (2) Microstructure optimization: particle size control and compound design, the particle size D50 of alumina powder is controlled in 0.1-10μm, D99<20μm, avoiding the problem of micron-sized particle agglomeration or large particle blocking the nozzle. Multi-particle size powder compound can optimize the bulk density, reduce sintering porosity, and further improve the mechanical properties. The grain size is controlled, and the sintering temperature and holding time are accurately controlled (such as heating rate 1-10℃ / min, holding time 1-10h) to avoid excessive grain growth. Uniform fine-grained structure (grain size moderate) can not only ensure the strength, but also prevent brittle fracture.

[0058] II. Mechanism of wave absorption performance (35dB of reflection loss at 5GHz-40GHz) (1) Wave absorption effect of wave absorber: synergistic effect of multiple wave absorbers, the loaded wave absorber (such as carbon black, graphene, carbon nanotube, etc.) has excellent electromagnetic wave absorption capacity, its mechanism includes: dielectric loss: the conjugated π bond, defect structure and surface functional group of carbon material can produce polarization relaxation, which converts electromagnetic wave energy into heat energy consumption. Conductive loss: carbon nanotubes, graphene and other materials with high electrical conductivity can form a conductive network to absorb electromagnetic waves through ohmic loss. Multiple scattering: the interface between nanoscale carbon materials and ceramic matrix can induce multiple reflection and scattering of electromagnetic waves, prolonging the energy dissipation path. The influence of loading process, 100-1000℃ loading for 2-72h, makes the carbon source uniformly distributed in the ceramic pores or surface, forming a "ceramic-carbon" composite interface, enhancing the interface polarization loss and broadening the wave absorption frequency band (5-40GHz).

[0059] (2) Structure design and wave absorption matching: The matching effect of porous ceramic matrix, the porous structure formed after resin curing during 3D printing (porosity controllable), can adjust the dielectric constant and magnetic permeability of the material, making the impedance matching of the material and air better, reducing electromagnetic wave reflection, and promoting the entry of incident waves into the material to be absorbed. The regulation of complex structure can further optimize the propagation path of electromagnetic waves in the material, enhance scattering and loss, and achieve wideband wave absorption.

[0060] Three, the advantages of lightweight and complex structure adjustment (1) 3D printing process empowerment: The accuracy of light curing molding, using 405 nm light curing 3D printing technology, single layer printing thickness 20-300 pm, can prepare green body with complex geometric shape (such as hollow, gradient porosity, bionic structure), which retains high precision structure after sintering. This process breaks through the limitations of traditional ceramic forming and realizes the integration of "structure design-performance regulation". Low sintering shrinkage, high solid content alumina slurry (more than 70%) combined with multi-particle size powder compounding, reduces the sintering shrinkage to below 5%, ensuring the dimensional accuracy of complex structures and avoiding deformation and cracking.

[0061] (2) Porous structure and low density: Controllable porosity design, uniform pores are formed during the debinding process, and the porosity can be adjusted by slurry formulation (such as resin content) and sintering process. Low density (3.66-3.83 g / cm 3 ) not only reduces weight, but also optimizes wave absorption performance through the synergistic effect of pores and carbon sources.

[0062] Four, the guarantee of high temperature resistance and environmental adaptability (1) Thermal stability of ceramic matrix: Alumina ceramic maintains stable crystal structure (α-Al2O3) above 900℃, excellent oxidation resistance, can resist high-speed airflow erosion and gas corrosion. The grain boundary phase formed by sintering aids remains inert at high temperatures, avoiding material performance degradation.

[0063] (2) High temperature compatibility of carbon source: The loaded carbon source (such as graphene, carbon nanotube) can maintain structural stability in an inert atmosphere or under the protection of an oxidation-resistant coating at high temperatures, continuously playing a wave absorption role. Even if part of the carbon source is oxidized at high temperatures, the ceramic matrix can still maintain structural integrity, ensuring the reliability of the material in harsh environments.

[0064] The alumina ceramic wave-absorbing material is realized based on the preparation method of the alumina ceramic wave-absorbing material. The specific steps of the preparation method of the alumina ceramic wave-absorbing material can be referred to the above embodiments. Since the alumina ceramic wave-absorbing material adopts part or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0065] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application. The experimental methods not specified in the following examples are generally determined according to the industry standard. If there is no corresponding industry standard, it is carried out according to the general international standard, the conventional condition, or the condition suggested by the manufacturer.

[0066] Example 1 The present embodiment provides a preparation method of an alumina ceramic wave-absorbing material, which comprises the following steps: Step 1, slurry preparation: select alumina powder with a particle size of 1.2 microns as raw material, the drying temperature is 120℃, and the drying time is 3h. Take 10 parts of polyurethane acrylate resin monomer, 3 parts of bisphenol A epoxy acrylate, 7 parts of ethylene glycol diacrylate, add 0.3 parts of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator, mix uniformly, then add 80 parts of alumina powder, 1.6 parts of KH550 dispersant, and 2 parts of BYK410 stabilizer, stir until the solution is completely mixed and uniform, to obtain an alumina ceramic slurry, the slurry viscosity is 7.4Pa.s; Step 2, model design: build a periodic metamaterial model through three-dimensional design software to obtain a model suitable for 3D printing; the present embodiment adopts Figure 2 d pattern; Step 3, 3D printing forming: import the model into a photocuring 3D printer, set the exposure intensity to 30mW / cm 2 , the exposure time to 3s, and the single-layer printing thickness to 75 microns, after printing, use a cleaning agent to clean, to obtain an alumina ceramic green body; Step 4, debinding and sintering: the debinding temperature is raised at a rate of 0.2℃ / min to 600℃ and kept for 2h, then the temperature is raised to 1600℃ at a rate of 2℃ / min and kept for 2h. The ceramic material matrix is obtained; Step 5, wave-absorbing agent loading: Dopamine hydrochloride is dissolved in tris-hydroxymethyl aminomethane buffer as an organic carbon source, and stirred well to obtain an organic carbon source wave-absorbing material precursor. Then, the dopamine hydrochloride is impregnated into the alumina ceramic by vacuum impregnation method, the impregnation temperature is 60℃, and the impregnation time is 72h. The impregnated alumina ceramic block is taken out and placed in a tube furnace, heated to 1000℃ under Ar atmosphere, and the organic carbon is pyrolyzed to form a carbon adhesion layer, thereby obtaining an alumina ceramic-based wave-absorbing composite material, as shown in Figure 3 .

[0067] Example 2 The present embodiment provides an alumina ceramic-based wave-absorbing material and a preparation method thereof, comprising the following steps: Step 1, slurry preparation: alumina powder with a particle size of 0.6 microns is selected as raw material, the drying temperature is 120℃, and the drying time is 3h. 15 parts of polyurethane acrylate resin monomer, 5 parts of bisphenol A epoxy acrylate, 0.3 parts of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator, 80 parts of alumina powder, 2.0 parts of KOS110, 1 part of BYK420, and 5 parts of yttrium oxide are mixed uniformly, and then 2.0 parts of KOS110, 1 part of BYK420, and 5 parts of yttrium oxide are added and stirred until the solution is completely mixed and uniform, to obtain an alumina ceramic slurry, and the slurry viscosity is 15Pa.s; Step 2, model design: a periodic metamaterial model is constructed by a three-dimensional design software to obtain a model suitable for 3D printing; Step 3, 3D printing forming: the model is imported into a photocuring 3D printer, the exposure intensity is set to 30mW / cm 2 , the exposure time is 3s, and the single-layer printing thickness is 50 microns. After printing, the alumina ceramic green body is obtained after cleaning; Step 4, debinding and sintering: the debinding temperature is raised at a rate of 0.2℃ / min to 600℃ and kept for 2h, and then the temperature is raised at a rate of 2℃ / min to 1500℃ and kept for 2h, to obtain a ceramic material matrix; Step 5, wave-absorbing agent loading: 8mL of high-temperature inorganic glue B is weighed, and then equal mass ratio of carbonyl iron powder and polyvinylidene fluoride is added and mixed uniformly, and then added to a certain amount of A glue solution. The mixed solution is placed on a magnetic stirring table for sufficient mixing to obtain a wave-absorbing material precursor. Then, the wave-absorbing agent is impregnated into the alumina ceramic by impregnation method, the impregnation temperature is 200℃, and the impregnation time is 8h. An alumina ceramic-based wave-absorbing composite material is obtained.

[0068] Example 3 The present embodiment provides an alumina ceramic-based wave-absorbing material and a preparation method thereof, comprising the following steps: Step 1, slurry preparation: select the particle size of 1.0 micron and 5.0 micron alumina powder as raw material, drying temperature is 120℃, drying time is 3h. Take 10 parts of polyurethane acrylate resin monomer, 3 parts of bisphenol A epoxy acrylate, 7 parts of ethylene glycol diacrylate, add 0.4 parts of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide photocuring agent, mix uniformly, then add 60 parts of 1.0 micron alumina powder, 20 parts of 5.0 micron alumina powder, 1.6 parts of KH550, 1 part of BYK430, stir until the solution is completely mixed, obtain alumina ceramic slurry, the viscosity of the slurry is 10.4Pa.s; Step 2, model design: build a periodic metamaterial model by three-dimensional design software, obtain a model suitable for 3D printing; Step 3, 3D printing forming: import the model into the photocuring 3D printer, set the exposure intensity to 30mW / cm 2 , the exposure time is 2s, the single layer printing thickness is 75 microns, use the sinking type printer to print layer by layer until the printing is completed, use cleaning agent to clean, obtain the alumina ceramic green body; Step 4, debinding and sintering: the heating rate is 0.2℃ / min during debinding, keep the temperature at 600℃ for 2h, then increase the temperature to 1650℃ at the rate of 2℃ / min, keep the temperature for 2h, obtain the ceramic material matrix.

[0069] Step 5, wave absorber loading: take 8mL of high temperature inorganic glue B, then add equal mass ratio of polyvinylidene fluoride, dopamine hydrochloride and multi-walled carbon nanotube carbon source respectively, mix uniformly, add to a certain amount of A glue solution, mix thoroughly after stirring, obtain the wave absorbing material precursor, then immerse the wave absorber into the alumina ceramic by immersion method, the immersion temperature is 200℃, the immersion time is 24h. Obtain the alumina ceramic based wave absorbing composite material.

[0070] Comparative example 1 This comparative example provides an alumina ceramic based wave absorbing material and a preparation method thereof, including the following steps: Step 1, slurry preparation: select the particle size of 1.2 micron alumina powder as raw material, drying temperature is 120℃, drying time is 3h. Take 10 parts of polyurethane acrylate resin monomer, 3 parts of bisphenol A epoxy acrylate, 7 parts of ethylene glycol diacrylate, add 0.3 parts of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide photocuring agent, mix uniformly, then add 80 parts of alumina powder, 2 parts of BYK410, the mixture after stirring is wet solid, which does not have fluidity and cannot be 3D printed.

[0071] Comparative example 2 This comparative example provides an alumina ceramic based wave absorbing material and a preparation method thereof, including the following steps: Step 1, slurry preparation: select the particle size of 1.2 micron alumina powder as raw material, drying temperature is 120℃, drying time is 3h. Take 10 parts of polyurethane acrylate resin monomer, 3 parts of bisphenol A epoxy acrylate, 7 parts of ethylene glycol diacrylate, add 0.3 parts of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide photo-curing agent, mix uniformly, then add 80 parts of alumina powder, 1.6 parts of KH550 dispersant, 2 parts of BYK410 stabilizer, stir until the solution is completely mixed and uniform, to obtain alumina ceramic slurry, the viscosity of the slurry is 7.4Pa.s; Step 2, model design: build a periodic metamaterial model by three-dimensional design software to obtain a model suitable for 3D printing; this comparative example adopts Figure 2 d pattern; Step 3, 3D printing forming: import the model into the light-curing 3D printer, set the exposure intensity to 30mW / cm 2 , the exposure time is 3s, the single layer printing thickness is 75 microns, after printing, use cleaning agent to clean, to obtain alumina ceramic green body; Step 4, debinding and sintering: heat at a rate of 2℃ / min to 1600℃, keep for 2h, to obtain ceramic material, the material has more cracks, the edge part drops slag, the density is lower than 3.0g / cm 3 , the bending strength cannot be tested, resulting in that the subsequent wave-absorbing agent loading step cannot be carried out.

[0072] Comparative Example 3 The comparative example provides an alumina ceramic-based wave-absorbing material and a preparation method thereof, including the following steps: Step 1, slurry preparation: select the particle size of 1.2 micron alumina powder as raw material, drying temperature is 120℃, drying time is 3h. Take 10 parts of polyurethane acrylate resin monomer, 3 parts of bisphenol A epoxy acrylate, 7 parts of ethylene glycol diacrylate, add 0.3 parts of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide photo-curing agent, mix uniformly, then add 80 parts of alumina powder, 1.6 parts of KH550 dispersant, 2 parts of BYK410 stabilizer, stir until the solution is completely mixed and uniform, to obtain alumina ceramic slurry, the viscosity of the slurry is 7.4Pa.s; Step 2, model design: build a periodic metamaterial model by three-dimensional design software to obtain a model suitable for 3D printing; this comparative example adopts Figure 2 d pattern; Step 3, 3D printing forming: import the model into the light-curing 3D printer, set the exposure intensity to 30mW / cm 2 , the exposure time is 3s, the single layer printing thickness is 75 microns, after printing, use cleaning agent to clean, to obtain alumina ceramic green body; Step 4, debinding and sintering: During debinding, the heating rate is 0.2℃ / min, and the temperature is held at 600℃ for 2 hours. Then, the temperature is increased to 1100℃ at a rate of 2℃ / min and held for 2 hours. A ceramic material matrix is ​​obtained. Step 5, Absorbing Agent Loading: Dopamine hydrochloride was used as an organic carbon source and dissolved in a tris(hydroxymethyl)aminomethane buffer solution. The solution was stirred thoroughly to obtain an organic carbon source microwave absorbing material precursor. Then, dopamine hydrochloride was impregnated into the alumina ceramic using a vacuum impregnation method at 60°C for 1 hour. The impregnated alumina ceramic block was removed and placed in a tube furnace. Under an Ar atmosphere, it was heated to 1000°C to pyrolyze the organic carbon, forming a carbon deposit layer, thus obtaining the alumina ceramic-based microwave absorbing composite material.

[0073] The mechanical properties, microwave absorption properties, and maximum operating temperature of the alumina ceramic-based microwave absorbing composite materials obtained in Examples 1-3 and Comparative Example 3 were analyzed, and the results are shown in Table 1.

[0074] Table 1. Performance of alumina ceramic-based microwave absorbing composite materials in Examples 1-3 and Comparative Example 3

[0075] As shown in Table 1, the alumina ceramic-based microwave absorbing materials in Examples 1-3 have an operating temperature ≥900℃, a flexural strength of 220MPa~295MPa, and a density of 3.66g / cm³. 3 ~3.83g / cm 3 The reflection loss between 5GHz and 40GHz is 35dB. In Comparative Example 3, the immersion temperature was room temperature, and the immersion time was reduced to 1 hour, resulting in poor absorption performance.

[0076] Figure 4 This is a schematic diagram of the microstructure of the alumina ceramic substrate provided in Example 1 of this application.

[0077] Depend on Figure 4 It can be seen that the ceramic has good uniformity and density, indicating that it has high mechanical properties.

[0078] Figure 5 The graph shows the test results of the microwave absorption performance of the alumina ceramic-based microwave absorbing composite material provided in Example 1 of this application.

[0079] Depend on Figure 5 It is known that ceramic matrix composites can effectively absorb electromagnetic waves in the 5-40GHz range, with a reflection loss of up to 35dB.

[0080] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: In the embodiments of the present application, the light-cured additive manufacturing technology (3D printing) is adopted, the limitation of the preparation precision of the traditional processing means for the multi-layer and complex structure is broken, the performance of the material is greatly expanded, the forming speed is fast, the precision is high, the multifunctional alumina ceramic-based composite wave-absorbing material with high structural complexity, high precision, high mechanical strength, high melting point, wide-band absorption and adjustable wave-absorbing frequency band can be prepared.

[0081] In the embodiments of the present application, the working temperature of the component obtained from the alumina ceramic-based wave-absorbing material can reach 900 DEG C or above, and the component can resist the erosion, oxidation and gas corrosion of the harsh environment such as high-speed airflow, and can be used as a light-weight load-bearing component for stealth equipment, and can also be used for shielding the electromagnetic wave pollution caused by the high-power electronic industry.

[0082] The above only is the specific implementation manner of the present application, and enables the person skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an alumina ceramic wave-absorbing material, the method comprising: mixing a resin monomer, a photocuring agent, an alumina powder, a dispersing agent, a rheological aid, and a sintering aid to obtain an alumina ceramic slurry; photocuring the alumina ceramic slurry according to a preset ceramic structure model data to obtain an alumina ceramic green body; debinding and sintering the alumina ceramic green body to obtain an alumina ceramic matrix; and loading a wave-absorbing agent on the alumina ceramic matrix to obtain the alumina ceramic wave-absorbing material; wherein the wave-absorbing agent is an organic carbon source, the loading temperature is 100-1000°C, and the loading time is 2-72 hours. In the alumina ceramic slurry, the resin monomer is 15-25 parts by mass, the photocuring agent is 0.1-1 part by mass, the alumina powder is 70-90 parts by mass, the dispersing agent is 0.5-5 parts by mass, the rheological aid is 0.5-5 parts by mass, and the sintering aid is 0-5 parts by mass.

2. The method of claim 1, wherein, The alumina powder is a single-particle-size alumina powder or a mixed powder composed of two or more alumina powders with different particle sizes; and / or 3. The method of claim 2, wherein, The resin monomer comprises one or a mixture of several of polyurethane acrylate, bisphenol A epoxy acrylate, ethylene glycol diacrylate, propoxylated neopentyl glycol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, hydroxyethyl acrylate, and isooctyl acrylate; and / or The photocuring agent comprises one or a mixture of several of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, isopropyl thioxanthone, and phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide; and / or The dispersing agent comprises one or a mixture of several of KOS110, KH550, KH560, polyethylene glycol 200, and polyethylene glycol 400; and / or The rheological aid comprises one or several of nano-silicon dioxide, nano-alumina, alumina with a particle size >5 μm, talc powder, BYK anti-settling agent, polyvinyl alcohol, polyvinyl butyral, and polyvinyl pyrrolidone; and / or The sintering aid comprises one or several of silicon dioxide, yttrium oxide, magnesium oxide, lithium fluoride, and aluminum fluoride. The viscosity of the alumina ceramic slurry is 0.5-50 Pa.s.

4. The method of claim 3, wherein, The particle size D of the alumina powder is 0.1 μm to 10 μm 50 The particle size D of the alumina powder is 0.1 μm to 10 μm 99 <20 μm.

5. The method of claim 2, wherein, The debinding is performed at a heating rate of 0.1-2°C / min and a maximum temperature of 500-1000°C, and the debinding is maintained at the maximum temperature for 1-10 hours.

6. The method of claim 1, wherein, The light curing 3D printing includes the following parameters: light wavelength is 405nm, exposure intensity is 5mW / cm 2 ~50mW / cm 2 , exposure time is 1s~10s, and single layer printing thickness is 20μm~300μm.

7. The method of claim 1, wherein, The sintering is performed at a heating rate of 1-10°C / min and a maximum temperature of 1200-1800°C, and the sintering is maintained at the maximum temperature for 1-10 hours.

8. The method of claim 1, wherein, The wave-absorbing agent comprises one or a mixture of several of carbon black, graphite, graphene, carbon nanotubes, ferrite, carbonyl iron powder, polyvinylidene fluoride, and dopamine hydrochloride.

9. The method of claim 1, wherein, ​ 10. The alumina ceramic wave-absorbing material prepared by the method of any one of claims 1-9, wherein the alumina ceramic wave-absorbing material satisfies the following performances: a working temperature of 900 DEG C or more, a bending strength of 220 MPa to 295 MPa, a density of 3.66 g / cm3 to 3.83 g / cm3, and a reflection loss of 35 dB between 5 GHz and 40 GHz. 3 3 ​​

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