Calcium titanate composite wave-absorbing material and preparation method thereof

Abstract

The invention belongs to the technical field of electronic materials, and particularly relates to a calcium titanate composite wave-absorbing material and a preparation method thereof. The material comprises the following components: a carbon material, metal powder, calcium titanate and organic silicon resin. The preparation method comprises the steps of blending, ball milling, polymerization molding and the like. The material has a three-layer structure, namely a calcium titanate resin layer, a calcium titanate low-carbon resin layer and a calcium titanate high-carbon resin layer. The effective bandwidth with the wave absorbing efficiency smaller than or equal to-10 dB covers the whole S wave band, the lowest wave absorbing efficiency is-31.5 dB, the preparation process is simple, raw materials are easy to obtain, and the material has application potential in the fields of 5G technology electromagnetic compatibility and equipment electromagnetic stealth.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials, specifically relating to a calcium titanate composite microwave absorbing material and its preparation method. Background Technology

[0002] Electromagnetic wave absorbing materials include magnetic loss type, resistive loss type and dielectric loss type. Among them, magnetic loss type includes ferrite and metallic magnetic micro powder, resistive loss type includes carbon black, carbon nanotubes, graphite and conductive polymers, and dielectric loss type includes barium titanate, silicon carbide and silicon nitride.

[0003] The research and engineering applications of microwave absorbing materials are very extensive. At present, the difficulty lies in how to develop new materials to achieve microwave absorption efficiency of ≤-10dB across the entire S-band (2-4GHz).

[0004] Calcium titanate (CaTiO3) is an inorganic compound belonging to the cubic crystal system. It is a fundamental inorganic dielectric material with excellent dielectric, temperature, mechanical, and optical properties, and is widely used in ceramic capacitors, PTC thermistors, microwave antennas, filters, and stainless steel welding rods, but rarely in electromagnetic wave absorption. Baoji University of Arts and Sciences investigated the absorption performance of bilayer absorbers with different thicknesses and orientations. Improvement in absorption depends entirely on various parameters, such as interface polarization, interlayer multiple reflections, conduction loss, phase cancellation, and shape anisotropy. Microcubic CaTiO3 (CTO) and polypyrrole nanotube (PPy) nanocomposites were prepared, and single-layer coaxial samples with M1 = CaTiO3 + 15 wt% polymer and M2 = CaTiO3 + 30 wt% polymer were measured. Different layer orientations and thicknesses of the bilayer absorber samples were optimized using CST software. For a 2.5 mm thick sample, the lowest reflection loss (RL) of M1 and M2 was determined. min The RL values ​​are -24 dB and -32 dB, respectively. When the thickness is reduced to 2 mm, the RL values ​​are -19 dB and -11 dB, respectively. This material has electromagnetic wave absorption properties only in the Ku and X bands. In the low-frequency S band, the effective bandwidth of absorption efficiency (reflection loss (RL)) ≤ -10 dB is 0 GHz, and it cannot be used for S-band absorption (Ceramics International, 2022, 48: 11953–11961).

[0005] Ca and Ba belong to the same group of elements. BaTiO3 is a strong dielectric compound material with high dielectric constant and low dielectric loss, and is one of the most widely used materials in electronic ceramics. BaTiO3 has been extensively studied in the field of microwave absorption. Fuzhou University proposed a barium titanate-based multilayer composite microwave absorbing material and its preparation method (CN 117939867 A). Using BaCl2·2H2O as the barium source, TiCl4 as the titanium source, and NaOH as the mineralizing agent, barium titanate (BaTiO3) nanoparticles were prepared by hydrothermal method. Then, the BaTiO3 nanoparticles were mixed with FeCl3·6H2O and anhydrous sodium acetate to prepare the barium titanate-based multilayer composite microwave absorbing material by hydrothermal method. The magnetoelectric properties of the composite material were controlled by changing the ratio of BaTiO3 to Fe3O4. The composite microwave absorbing material with a ratio of 1:1 showed a high RL at a thickness of 2.05 mm and a frequency of 13.2 GHz. min The absorption efficiency can reach -48.1 dB; with a thickness of 1.90 mm, the effective absorption bandwidth can reach 6.3 GHz. The patent text indicates that in the low-frequency S-band, the material's absorption efficiency (reflection loss (RL)) ≤ -10 dB has an effective bandwidth of 0 GHz, making it unsuitable for S-band absorption. Central South University disclosed a ferrous sulfide-barium titanate absorbing material and its preparation method (CN 120272164 A). It is prepared via a two-step hydrothermal method. First, ferrous sulfide is prepared by mixing thiourea and ferrocene using a hydrothermal method. Then, barium chloride, tetrabutyl titanate, and the prepared ferrous sulfide are reacted using a hydrothermal method to obtain a ferrous sulfide-barium titanate composite material. The absorption performance of the composite material is adjusted by regulating the barium titanate content. The patent text indicates that the prepared composite material has an absorption efficiency (reflection loss (RL)) ≤ -10 dB in the low-frequency S-band, resulting in an effective bandwidth of 0 GHz, making it unsuitable for S-band absorption. North University of China prepared nano-barium titanate and carbonyl iron / barium titanate composite materials using the sol-gel method and physical blending method (Jing Hongxia, Li Qiaoling, Ye Yun, et al. Preparation and microwave absorption properties of carbonyl iron / barium titanate composite materials. Materials Engineering. 2015, 43(7): 38-42.). The phase, morphology and properties of the materials were characterized and analyzed by X-ray diffraction, transmission electron microscopy and vector network analysis. The results showed that the prepared samples were tetragonal barium titanate with a particle size of about 60 nm and uniformly dispersed carbonyl iron / barium titanate composite materials; in the range of 0-6 GHz, the microwave absorption performance of carbonyl iron / barium titanate composite materials was greatly improved compared with pure carbonyl iron. When the weight percentage of barium titanate was 4%, its microwave absorption performance was the best, RL min It can reach -22.9dB, and the effective bandwidth with absorption efficiency (reflection loss (RL)) ≤ -10dB is 2.196GHz, but the effective bandwidth in the S-band is 0GHz.

[0006] In summary, there are relatively few types of composite absorbing materials with calcium titanate and barium titanate as the main components. Existing materials have poor absorption performance in the S-band, with an effective bandwidth of 0 GHz and an absorption efficiency (reflection loss (RL) ≤ -10 dB. This invention aims to overcome the bottleneck of existing calcium titanate and barium titanate composite materials by developing a calcium titanate composite absorbing material with an effective bandwidth covering the entire S-band through material and structural design. Summary of the Invention

[0007] The purpose of this invention is to propose a calcium titanate composite absorbing material and its preparation method, with an absorption efficiency (reflection loss (RL)) ≤ -10dB and an effective bandwidth covering the entire S-band.

[0008] This invention proposes a calcium titanate composite microwave absorbing material, characterized by a three-layer structure: a calcium titanate resin layer, a low-carbon calcium titanate resin layer, and a high-carbon calcium titanate resin layer. The components and their weight percentages in the calcium titanate resin layer are as follows: calcium titanate 45%~55%, with the remainder being silicone resin. The components and their weight percentages in the low-carbon calcium titanate resin layer are as follows: low-carbon calcium titanate filler 70%~75%, with the remainder being silicone resin. The components and their weight percentages in the high-carbon calcium titanate resin layer are as follows: high-carbon calcium titanate filler 60%~65%, with the remainder being silicone resin. The thickness of the calcium titanate resin layer is 0.8~0.9 cm, the thickness of the low-carbon calcium titanate resin layer is 0.4~0.5 cm, and the thickness of the high-carbon calcium titanate resin layer is 1.7~1.8 cm.

[0009] The components and their weight percentages in the calcium titanate low-carbon filler are as follows: carbon material 15%~18%, iron powder 6%~7%, chromium powder 4%~5%, nickel powder 2%~3%, aluminum powder 1%~2%, and the remainder is calcium titanate; the carbon material can be any one of multi-walled carbon nanotubes, graphene, graphite nanosheets, or biochar.

[0010] The components and their weight percentages in the high-carbon calcium titanate filler are as follows: carbon material 25%~28%, iron powder 8%~9%, chromium powder 2%~3%, nickel powder 0.8%~1.0%, aluminum powder 0.1%~0.3%, and the remainder is calcium titanate; the carbon material can be any one of multi-walled carbon nanotubes, graphene, graphite nanosheets, or biochar.

[0011] The preparation method of calcium titanate composite microwave absorbing material includes the following steps: (1) Preparation of low-carbon calcium titanate filler: First, mix 15-18g of carbon material and 6-7g of iron powder, place them in a ball mill, and ball mill at 600-700rpm for 10-12 hours to obtain carbon / iron composite powder; then place 4-5g of chromium powder, 2-3g of nickel powder, 1-2g of aluminum powder and 65-72g of calcium titanate in a ball mill, and ball mill at 600-700rpm for 20-24 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder; then mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 600-700rpm for 6-8 hours to obtain low-carbon calcium titanate filler; (2) Preparation of high carbon calcium titanate filler: First, mix 25~28g of carbon material, 8~9g of iron powder and 0.1~0.3g of aluminum powder, place them in a ball mill, and ball mill at 800~900rpm for 6~8 hours to obtain carbon / iron / aluminum composite powder; then place 2~3g of chromium powder, 0.8~1.0g of nickel powder and 58.7~64.1g of calcium titanate in a ball mill, and ball mill at 800~900rpm for 12~14 hours to obtain chromium / nickel / calcium titanate composite powder; then mix the above carbon / iron / aluminum composite powder with chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 800~900rpm for 10~12 hours to obtain high carbon calcium titanate filler; (3) Preparation of calcium titanate composite microwave absorbing material: Mix 450-550g of calcium titanate with silicone water, with a total weight of 1000g, disperse evenly in a high-speed disperser, pour into a mold, and cure at room temperature to form a film with a thickness of 0.8-0.9cm to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 700~750g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 0.4~0.5cm to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 600~650g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 1.7~1.8cm to obtain calcium titanate composite microwave absorbing material.

[0012] The calcium titanate composite absorbing material was cut into 20cm×20cm samples. The absorption efficiency of the calcium titanate composite absorbing material was measured by using the bow method according to the standard "GJB 2038A-2011 Test Method for Emissivity of Radar Absorbing Materials".

[0013] The present invention has the following advantages: (1) It has a three-layer structure, namely a calcium titanate resin layer, a calcium titanate low-carbon resin layer and a calcium titanate high-carbon resin layer. This structure is the first of its kind.

[0014] (2) The effective bandwidth of the calcium titanate composite absorbing material with absorption efficiency (reflection loss (RL)) ≤ -10dB can cover the entire S-band, which is not available in other calcium titanate and barium titanate composite absorbing materials.

[0015] (3) The raw materials are readily available, the cost is low, the preparation process is simple, the technology is mature, and it is suitable for large-scale production and application.

[0016] Beihang University has studied hollow multi-shell high-entropy carbides (FeCoNiZnMg)Fe2O4@C, constructing microspheres with controllable carbon-coated three-layer shells and entropy-stable ferrite composition (Xiangyu Wang, Boyuan Cao, HengboYin, Pengfei Yan, and Tong Liu. Obtaining Low-Frequency and BroadbandAbsorbing Ferrite@C Microspheres through the High Entropy Engineering and Construction of Opened-Hollow Multi-Shell Architecture. Advanced Functional Materials, 2025, 35: 2504653.). The designed hollow three-shell structure enhances the magnetic interaction between the shells and modulates the magnetic domain structure and effective field. (FeCoNiZnMg)Fe2O4@C microspheres RL min It achieves a bandwidth of -60.5 dB and an effective bandwidth of 9.3 GHz. Simultaneously, the high-entropy effect effectively modulates the magnitude of the anisotropic magnetic field, significantly improving low-frequency absorption in the 4-8 GHz band, far exceeding materials where ferrite@C does not form a high-entropy phase. This material has an effective bandwidth of 2.8-4.0 GHz in the S-band, which cannot cover the entire S-band. Compared to (FeCoNiZnMg)Fe2O4@C microspheres, this invention has a different material system and structure, resulting in a wider effective bandwidth in the S-band.

[0017] The China Building Materials Academy Co., Ltd. designed and prepared layered gypsum-based composites for S-band electromagnetic wave absorption by introducing carbon black (CB) coated glass fiber meshes, and measured the electromagnetic wave absorption performance using the bow method (Shuai Xie, Zhijiang Ji, Yang Yang, Guoyan Hou, Jing Wang. Layeredgypsum-based composites with grid structures for S-band electromagnetic wave absorption. Composite Structures, 2017, 180: 513–520). The results show that the glass fiber grid can significantly improve electromagnetic wave absorption, and the absorption performance is affected by the period size, sample thickness, and CB content. Due to the formation of gradient impedance, the composite with a double-layer glass fiber mesh exhibits a wider bandwidth and lower reflection loss. Furthermore, the design of the double-layer matrix can shift the absorption peak to lower frequencies, which can be attributed to multiple scattering and reflection of the incident wave caused by expanded perlite. The reflection loss of the prepared composite can be less than -10 dB in the 2.2–3.63 GHz range. The effective bandwidth of this material does not cover the entire S-band. Although this invention also introduces carbon materials to adjust electromagnetic parameters and has a multi-layer structure, it does not require the design of period size. The material systems, structures, and absorption mechanisms of each are different. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the calcium titanate high-carbon filler prepared in Example 1.

[0019] Figure 2 The image shows the energy dispersive spectroscopy elemental analysis of the calcium titanate high-carbon filler prepared in Example 1.

[0020] Figure 3 The image shows the Cole-Cole diagram of the calcium titanate high-carbon filler prepared in Example 1.

[0021] Figure 4 The image shows the Cole-Cole diagram of the calcium titanate low-carbon filler prepared in Example 1.

[0022] Figure 5 The image shows the absorption efficiency of the calcium titanate composite absorbing material prepared in Example 1 in the S-band. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Example 1

[0024] (1) Preparation of calcium titanate low-carbon filler: First, mix 15g of multi-walled carbon nanotubes and 6g of iron powder, place them in a ball mill, and ball mill at 600 rpm for 10 hours to obtain carbon / iron composite powder; then, place 4g of chromium powder, 2g of nickel powder, 1g of aluminum powder, and 65g of calcium titanate in a ball mill, and ball mill at 600 rpm for 20 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder; then, mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 600 rpm for 6 hours to obtain calcium titanate low-carbon filler; (2) Preparation of calcium titanate high-carbon filler: First, mix 25g of multi-walled carbon nanotubes, 8g of iron powder, and 0.1g of aluminum powder, place them in a ball mill, and ball mill at 800 rpm for 6 hours to obtain carbon / iron / aluminum composite powder; then, place 2g of chromium powder, 0.8g of nickel powder, and 58.7g of calcium titanate in a ball mill, and ball mill at 800 rpm for 12 hours to obtain chromium / nickel / calcium titanate composite powder; then, mix the above carbon / iron / aluminum composite powder with the chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 800 rpm for 10 hours to obtain calcium titanate high-carbon filler; (3) Preparation of calcium titanate composite microwave absorbing material: Mix 450g of calcium titanate with silicone water, the total weight is 1000g, disperse evenly in a high-speed disperser, pour into a mold, and cure at room temperature to form a 0.9cm thick film to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 700g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 0.4cm to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 600g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a 1.7cm thick film to obtain calcium titanate composite microwave absorbing material.

[0025] The calcium titanate composite absorbing material was cut into 20cm×20cm samples. Following the standard "GJB 2038A-2011 Radar Absorbing Material Emissivity Test Method", the bow-shaped method was used for testing. The absorption efficiency of the calcium titanate composite absorbing material was measured as follows: the effective bandwidth of absorption efficiency ≤ -10dB covers the entire S-band, and the minimum absorption efficiency (RL) is... min The absorption efficiency is -31.5dB, and the average absorption efficiency is -16.8dB.

[0026] Figure 1 This is a scanning electron microscope (SEM) image of calcium titanate high-carbon filler, from... Figure 1 As can be seen, the spear-shaped carbon nanotubes are uniformly dispersed on the surface of the calcium titanate particles, and some carbon nanotubes are embedded inside the calcium titanate particles.

[0027] Figure 2 This is the energy dispersive spectroscopy elemental analysis chart of calcium carbonate high-carbon filler, from... Figure 2 It can be seen that the weight percentages of elements C, O, Ti, Ca, Fe, Cr, Ni, and Al are 26.3%, 24.9%, 20.3%, 16.8%, 8.5%, 2.2%, 0.9%, and 0.2%, respectively, which are roughly equivalent to the proportions of elements in the raw materials.

[0028] Figure 3 This is the Cole-Cole diagram of calcium titanate high-carbon filler, by... Figure 3 It can be seen that electromagnetic wave loss includes dielectric loss, resistive loss and magnetic loss. Dielectric loss includes dipole polarization and interface polarization, etc.

[0029] Figure 4 This is the Cole-Cole diagram of calcium titanate low-carbon filler, by... Figure 4 It can be seen that electromagnetic wave loss and Figure 3 The differences are that resistive loss is reduced, dielectric loss is increased, and magnetic loss is roughly the same.

[0030] Figure 5 This is a waveform absorption performance diagram of calcium titanate composite absorbing material in the S-band, composed of... Figure 5 It can be seen that the calcium titanate composite absorbing material has two absorption peaks in the S-band, which are near 2.25 GHz and 3.4 GHz, respectively, with peak values ​​of -18.1 dB and -31.5 dB. The effective bandwidth with an absorption efficiency of ≤-10 dB covers the entire S-band. Example 2

[0031] (1) Preparation of calcium titanate low-carbon filler: First, mix 18g of graphene and 7g of iron powder, place them in a ball mill, and ball mill at 700 rpm for 12 hours to obtain carbon / iron composite powder. Then, place 5g of chromium powder, 3g of nickel powder, 2g of aluminum powder, and 70g of calcium titanate in a ball mill, and ball mill at 700 rpm for 24 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder. Then, mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 700 rpm for 8 hours to obtain calcium titanate low-carbon filler. (2) Preparation of calcium titanate high-carbon filler: First, mix 28g of graphene, 9g of iron powder, and 0.3g of aluminum powder, place them in a ball mill, and ball mill at 900 rpm for 8 hours to obtain carbon / iron / aluminum composite powder; then, place 3g of chromium powder, 1.0g of nickel powder, and 58.7g of calcium titanate in a ball mill, and ball mill at 900 rpm for 14 hours to obtain chromium / nickel / calcium titanate composite powder; then, mix the above carbon / iron / aluminum composite powder with the chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 900 rpm for 12 hours to obtain calcium titanate high-carbon filler; (3) Preparation of calcium titanate composite microwave absorbing material: Mix 550g of calcium titanate with silicone water, the total weight is 1000g, disperse evenly in a high-speed disperser, pour into a mold, and cure at room temperature to form a film with a thickness of 0.8cm to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 750g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a 0.5cm thick film to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 650g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a 1.7cm thick film to obtain calcium titanate composite microwave absorbing material.

[0032] The calcium titanate composite absorbing material was cut into 20cm×20cm samples. Following the standard "GJB 2038A-2011 Radar Absorbing Material Emissivity Test Method", the bow-shaped method was used for testing. The absorption efficiency of the calcium titanate composite absorbing material was measured as follows: the effective bandwidth of absorption efficiency ≤ -10dB covers the entire S-band, and the minimum absorption efficiency (RL) is... min The absorption efficiency is -30.7dB, and the average absorption efficiency is -17.8dB. Example 3

[0033] (1) Preparation of calcium titanate low-carbon filler: First, mix 16g of graphite nanosheets and 6g of iron powder, place them in a ball mill, and ball mill at 650 rpm for 11 hours to obtain carbon / iron composite powder. Then, place 4.5g of chromium powder, 2.5g of nickel powder, 1.5g of aluminum powder, and 67g of calcium titanate in a ball mill, and ball mill at 700 rpm for 22 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder. Finally, mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 600 rpm for 7 hours to obtain calcium titanate low-carbon filler. (2) Preparation of calcium titanate high-carbon filler: First, mix 26g of graphene, 8.5g of iron powder, and 0.2g of aluminum powder, place them in a ball mill, and ball mill at 850 rpm for 7 hours to obtain carbon / iron / aluminum composite powder; then, place 2.5g of chromium powder, 0.9g of nickel powder, and 60g of calcium titanate in a ball mill, and ball mill at 850 rpm for 13 hours to obtain chromium / nickel / calcium titanate composite powder; then, mix the above carbon / iron / aluminum composite powder with the chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 900 rpm for 11 hours to obtain calcium titanate high-carbon filler; (3) Preparation of calcium titanate composite microwave absorbing material: Mix 500g of calcium titanate with silicone water to make a total weight of 1000g. Disperse the mixture evenly in a high-speed disperser, then pour it into a mold and cure it at room temperature to form a 0.8cm thick film to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 700g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a 0.5cm thick film to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 630g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a 1.7cm thick film to obtain the calcium titanate composite microwave absorbing material.

[0034] The calcium titanate composite absorbing material was cut into 20cm×20cm samples. Following the standard "GJB 2038A-2011 Radar Absorbing Material Emissivity Test Method", the bow-shaped method was used for testing. The absorption efficiency of the calcium titanate composite absorbing material was measured as follows: the effective bandwidth of absorption efficiency ≤ -10dB covers the entire S-band, and the minimum absorption efficiency (RL) is... min The absorption efficiency is -26.1dB, and the average absorption efficiency is -14.9dB. Example 4

[0035] (1) Preparation of calcium titanate low-carbon filler: First, mix 18g of biochar and 6g of iron powder, place them in a ball mill, and ball mill at 600 rpm for 12 hours to obtain carbon / iron composite powder; then, place 5g of chromium powder, 2g of nickel powder, 1g of aluminum powder, and 70g of calcium titanate in a ball mill, and ball mill at 700 rpm for 20 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder; then, mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 700 rpm for 6 hours to obtain calcium titanate low-carbon filler; (2) Preparation of calcium titanate high-carbon filler: First, mix 25g of multi-walled carbon nanotubes, 9g of iron powder, and 0.3g of aluminum powder, place them in a ball mill, and ball mill at 800 rpm for 6 hours to obtain carbon / iron / aluminum composite powder; then, place 2g of chromium powder, 1.0g of nickel powder, and 61g of calcium titanate in a ball mill, and ball mill at 900 rpm for 12 hours to obtain chromium / nickel / calcium titanate composite powder; then, mix the above carbon / iron / aluminum composite powder with the chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 850 rpm for 12 hours to obtain calcium titanate high-carbon filler; (3) Preparation of calcium titanate composite microwave absorbing material: Mix 550g of calcium titanate with silicone water, the total weight is 1000g, disperse evenly in a high-speed disperser, pour into a mold, and cure at room temperature to form a 0.9cm thick film to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 700g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 0.4cm to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 650g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a 1.7cm thick film to obtain calcium titanate composite microwave absorbing material.

[0036] The calcium titanate composite absorbing material was cut into 20cm×20cm samples. Following the standard "GJB 2038A-2011 Radar Absorbing Material Emissivity Test Method", the bow-shaped method was used for testing. The absorption efficiency of the calcium titanate composite absorbing material was measured as follows: the effective bandwidth of absorption efficiency ≤ -10dB covers the entire S-band, and the minimum absorption efficiency (RL) is... min The absorption efficiency is -24.9 dB, and the average absorption efficiency is -16.1 dB. Example 5

[0037] (1) Preparation of calcium titanate low-carbon filler: First, mix 16g of graphite nanosheets and 7g of iron powder, place them in a ball mill, and ball mill at 700 rpm for 10 hours to obtain carbon / iron composite powder. Then, place 5g of chromium powder, 2g of nickel powder, 1g of aluminum powder, and 68g of calcium titanate in a ball mill, and ball mill at 700 rpm for 20 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder. Then, mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 700 rpm for 8 hours to obtain calcium titanate low-carbon filler. (2) Preparation of calcium titanate high-carbon filler: First, mix 28g of biochar, 9g of iron powder, and 0.1g of aluminum powder, place them in a ball mill, and ball mill at 900 rpm for 8 hours to obtain carbon / iron / aluminum composite powder; then, place 3g of chromium powder, 0.8g of nickel powder, and 64.1g of calcium titanate in a ball mill, and ball mill at 900 rpm for 14 hours to obtain chromium / nickel / calcium titanate composite powder; then, mix the above carbon / iron / aluminum composite powder with the chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 900 rpm for 10 hours to obtain high-carbon calcium titanate filler; (3) Preparation of calcium titanate composite microwave absorbing material: Mix 550g of calcium titanate with silicone water, the total weight is 1000g, disperse evenly in a high-speed disperser, pour into a mold, and cure at room temperature to form a film with a thickness of 0.8cm to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 700g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 0.4cm to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 640g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 1.8cm to obtain calcium titanate composite microwave absorbing material.

[0038] The calcium titanate composite absorbing material was cut into 20cm×20cm samples. Following the standard "GJB 2038A-2011 Radar Absorbing Material Emissivity Test Method", the bow-shaped method was used for testing. The absorption efficiency of the calcium titanate composite absorbing material was measured as follows: the effective bandwidth of absorption efficiency ≤ -10dB covers the entire S-band, and the minimum absorption efficiency (RL) is... min The absorption efficiency is -28.2dB, and the average absorption efficiency is -15.3dB.

Claims

1. A calcium titanate composite microwave absorbing material, characterized in that, The material has a three-layer structure: a calcium titanate resin layer, a low-carbon calcium titanate resin layer, and a high-carbon calcium titanate resin layer. The components and their weight percentages in the calcium titanate resin layer are as follows: calcium titanate 45%–55%, with the remainder being silicone resin. The components and their weight percentages in the low-carbon calcium titanate resin layer are as follows: low-carbon calcium titanate filler 70%–75%, with the remainder being silicone resin. The components and their weight percentages in the high-carbon calcium titanate resin layer are as follows: high-carbon calcium titanate filler 60%–65%, with the remainder being silicone resin. The thickness of the calcium titanate resin layer is 0.8–0.9 cm, the thickness of the low-carbon calcium titanate resin layer is 0.4–0.5 cm, and the thickness of the high-carbon calcium titanate resin layer is 1.7–1.8 cm.

2. The calcium titanate composite microwave absorbing material according to claim 1, characterized in that, The components and their weight percentages in the calcium titanate low-carbon filler are as follows: carbon material 15%~18%, iron powder 6%~7%, chromium powder 4%~5%, nickel powder 2%~3%, aluminum powder 1%~2%, and the balance is calcium titanate; among which, the carbon material can be any one of multi-walled carbon nanotubes, graphene, graphite nanosheets, and biochar.

3. The calcium titanate composite microwave absorbing material according to claim 1, characterized in that, The components and their weight percentages in the high-carbon calcium titanate filler are as follows: carbon material 25%~28%, iron powder 8%~9%, chromium powder 2%~3%, nickel powder 0.8%~1.0%, aluminum powder 0.1%~0.3%, and the balance is calcium titanate; among which, the carbon material can be any one of multi-walled carbon nanotubes, graphene, graphite nanosheets, and biochar.

4. The method for preparing the calcium titanate composite microwave absorbing material according to claim 1, characterized in that, The steps are as follows: (1) Preparation of calcium titanate low-carbon filler: First, mix 15-18g of carbon material and 6-7g of iron powder, place them in a ball mill, and ball mill at 600-700 rpm for 10-12 hours to obtain carbon / iron composite powder. Then, place 4-5g of chromium powder, 2-3g of nickel powder, 1-2g of aluminum powder, and 65-72g of calcium titanate in a ball mill, and ball mill at 600-700 rpm for 20-24 hours to obtain chromium / nickel / aluminum / calcium titanate composite powder. Then, mix the above carbon / iron composite powder with the chromium / nickel / aluminum / calcium titanate composite powder, place them in a ball mill, and ball mill at 600-700 rpm for 6-8 hours to obtain calcium titanate low-carbon filler. The carbon material can be any one of multi-walled carbon nanotubes, graphene, graphite nanosheets, or biochar. (2) Preparation of calcium titanate high-carbon filler: First, mix 25-28g of carbon material, 8-9g of iron powder, and 0.1-0.3g of aluminum powder, place them in a ball mill, and ball mill at 800-900 rpm for 6-8 hours to obtain carbon / iron / aluminum composite powder. Then, place 2-3g of chromium powder, 0.8-1.0g of nickel powder, and 58.7-64.1g of calcium titanate in a ball mill and ball mill at 800-900 rpm for 12-14 hours to obtain chromium / nickel / calcium titanate composite powder. Then, mix the above carbon / iron / aluminum composite powder with the chromium / nickel / calcium titanate composite powder, place them in a ball mill, and ball mill at 800-900 rpm for 10-12 hours to obtain calcium titanate high-carbon filler. The carbon material can be any one of multi-walled carbon nanotubes, graphene, graphite nanosheets, or biochar. (3) Preparation of calcium titanate composite microwave absorbing material: Mix 450-550g of calcium titanate with silicone water, with a total weight of 1000g, disperse evenly in a high-speed disperser, pour into a mold, and cure at room temperature to form a film with a thickness of 0.8-0.9cm to obtain a calcium titanate resin layer. Place the mold on the calcium titanate resin layer, mix 700~750g of the calcium titanate low carbon filler prepared in step (1) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 0.4~0.5cm to obtain the calcium titanate low carbon resin layer. Place the mold on the calcium titanate low carbon resin layer, mix 600~650g of the calcium titanate high carbon filler prepared in step (2) with silicone water, the total weight is 1000g, place it in a high-speed disperser to disperse evenly, then pour it into the mold, and cure it at room temperature to form a film with a thickness of 1.7~1.8cm to obtain calcium titanate composite microwave absorbing material.

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