Glucose cracked carbon modified Al2O3-based microwave absorbing ceramic and preparation method thereof
By generating amorphous carbon-modified Al2O3-based microwave absorbing ceramics through glucose pyrolysis, the problems of low dielectric loss and high preparation cost are solved, achieving high-efficiency microwave absorption and lightweight design, suitable for scenarios such as 5G/6G communication base stations.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-31
AI Technical Summary
Existing Al2O3-based microwave absorbing materials have low dielectric loss and poor absorption performance. The introduction of traditional carbon materials leads to high preparation costs, which restricts their application.
Using glucose as a carbon source, amorphous carbon is generated through high-temperature pyrolysis to serve as a dielectric loss type microwave absorber. By combining Al2O3 and TiO2 and controlling the composition and sintering process of the material, efficient microwave absorption in a specific frequency band can be achieved.
It significantly improves the electromagnetic wave absorption efficiency of the material, reduces manufacturing costs, has a lower material density, is suitable for the lightweight requirements of modern electronic devices, and has a simple process that is easy to scale up for production.
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Figure CN121758149A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a glucose-modified carbon Al2O3-based microwave absorbing ceramic and its preparation method. This material is suitable for applications requiring lightweight and high stability, such as 5G / 6G communication base stations, anti-radar reconnaissance facilities, and microwave absorbing devices. Background Technology
[0002] With the rapid development of 5G communication, smart electronic devices and aerospace technology, electromagnetic radiation and electromagnetic interference problems have become increasingly prominent, not only affecting the normal operation of electronic devices, but also posing a potential threat to human health. Therefore, the research and development of high-performance microwave absorbing materials has become a research hotspot in the field of materials.
[0003] Ceramic matrix composites have become an important research direction for next-generation microwave absorbing materials due to their excellent high-temperature resistance, corrosion resistance, and mechanical properties. Among them, Al2O3 ceramics have advantages such as strong insulation, low dielectric constant, and stable chemical properties, making them an ideal matrix material. However, pure Al2O3 ceramics have weak dielectric loss, making it difficult to achieve efficient absorption of electromagnetic waves; at the same time, pure Al2O3 ceramics have extremely low dielectric loss and a permeability close to 1, resulting in almost no microwave absorption capability. Therefore, it is necessary to introduce functional phases to improve its microwave absorption performance. To enhance its microwave absorption performance, current technologies typically introduce carbon materials (such as carbon nanotubes and graphene) as loss media into the ceramic matrix. However, these carbon materials are expensive and difficult to disperse uniformly in the matrix, limiting their application.
[0004] Glucose, as an inexpensive and readily available precursor, can be pyrolyzed at high temperatures to generate amorphous carbon with good conductivity. Its conductivity is tunable and its microstructure easily controllable, providing a new approach for constructing a uniformly distributed microwave-absorbing phase in an Al2O3 matrix. By controlling the amount of glucose added and the pyrolysis process, the dielectric properties and microstructure of the composite material can be precisely controlled, thereby obtaining lightweight, stable ceramic materials with tunable microwave absorption properties.
[0005] Therefore, developing an Al2O3-based microwave absorbing ceramic based on glucose pyrolysis carbon modification is of great significance for overcoming the defects of existing materials and promoting the engineering application of microwave absorbing materials. Summary of the Invention
[0006] In view of this, in order to solve the problems of low dielectric loss and poor microwave absorption performance of existing Al2O3-based microwave absorbing materials, and the high preparation cost caused by the introduction of traditional carbon materials, which restricts their application, this invention provides a glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic and its preparation method. By controlling the content and distribution of glucose pyrolysis carbon, the material achieves efficient microwave absorption in a specific frequency band, while ensuring the material's lightweight and structural stability.
[0007] To achieve the above objectives, the present invention provides the following technical solution:
[0008] A glucose-modified carbon-based Al2O3 microwave absorbing ceramic is prepared from the following raw materials in the indicated mass percentages: glucose wt.% Al2O3 wt.%, TiO2 wt.%; Glucose is used as a carbon source and is decomposed at high temperature to generate amorphous carbon, which is used as a dielectric loss type microwave absorber.
[0009] Furthermore, Al2O3, as a low dielectric constant matrix, has a particle size of [missing information]. Al2O3 is used to provide stable structural support, ensuring the mechanical strength and chemical stability of the material.
[0010] Furthermore, TiO2, as a sintering aid, has a particle size of [missing information]. TiO2 is used to lower the sintering temperature of Al2O3 and promote ceramic densification.
[0011] A method for preparing glucose-modified Al2O3-based microwave absorbing ceramics includes the following steps:
[0012] S1. Raw material mixing and ball milling: Weigh according to mass percentage wt.% glucose, wt.% Al2O3, wt.% TiO2, using anhydrous ethanol as solvent (solvent amount is equal to the total mass of raw materials) (to ensure sufficient dispersion of raw materials), place the mixture in a planetary ball mill and mix according to preset parameters to obtain a uniform slurry;
[0013] S2. Drying and Granulation: The slurry obtained in step S1 is placed into a ceramic tray, dried at a preset temperature, and then granulated with a mass fraction of [missing information]. A % PVA solution was ground to a particle size of [missing value]. After granulation, a composite powder is obtained;
[0014] S3. Dry pressing: The composite powder obtained in step S2 is loaded into a square mold (the mold size is 22.86 mm × 10.16 mm × 2.5 mm), and dry pressed under a preset pressure by a tablet press to obtain a ceramic green body;
[0015] S4. Programmed Temperature Sintering: The ceramic green body obtained in step S3 is placed in a tube furnace for three-stage sintering. During the sintering process, flowing argon gas is introduced into the tube furnace as a protective atmosphere. In the heating step, the first stage heats up to 450℃ and holds for 1 h to remove moisture from the PVA binder and glucose; the second stage continues to heat up to 600℃ and holds for 0.5 h to promote the initial decomposition of glucose; the third stage continues to heat up to... Insulation To achieve complete glucose cleavage, the heating rate in all three stages was [missing information]. ℃ / min; After three-stage sintering, the ceramic green body was naturally cooled to room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0016] Furthermore, the rotational speed of the planetary ball mill in step S1 is... r / min, ball milling time is h, the ball-to-material ratio is .
[0017] Furthermore, after the slurry is loaded into the ceramic tray in step S2, it is placed... Dry in a forced-air drying oven at ℃ h, remove solvent.
[0018] Furthermore, in step S2, the PVA solution acts as a binder, and its addition amount is [amount missing]% of the total mass of the dried powder. %.
[0019] Furthermore, the dry pressing pressure in step S3 is... MPa, holding time is min, and a ceramic green body with a complete structure and no cracks is obtained.
[0020] Further, in step S4, the ceramic green body obtained in step S3 is placed in a tube furnace for four-stage sintering. During the sintering process, flowing argon gas is introduced into the tube furnace as a protective atmosphere. In the heating step, the first stage heats up to 450℃ and holds for 1 h; the second stage continues to heat up to 600℃ and holds for 0.5 h; the third stage continues to heat up to... ℃, heat preservation h; In the fourth stage, the temperature is raised again to 1650℃ and kept warm. h; the heating rate in all four stages is... ℃ / min; After four stages of sintering, the ceramic green body was naturally cooled to room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0021] The glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramics prepared by the above-mentioned method are particularly suitable for applications in 5G / 6G communication base stations, anti-radar reconnaissance facilities, or microwave absorbing devices, especially in scenarios where high temperature resistance, corrosion resistance, and lightweight materials are required.
[0022] The beneficial effects of this invention are as follows:
[0023] 1. The preparation method of glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic disclosed in this invention involves precisely controlling the amount of glucose added ( By controlling the content, distribution, and microstructure of pyrolysis carbon (wt.%) and sintering process, this method not only utilizes the conductivity loss inherent in the pyrolysis carbon itself but also significantly enhances interfacial polarization relaxation loss by constructing numerous heterogeneous interfaces within the Al2O3 matrix. The synergistic effect of these two loss mechanisms, combined with the optimized impedance matching characteristics achieved by controlling the conductivity / dielectric constant of the composite material, greatly improves the absorption efficiency of electromagnetic waves. Experiments show that the prepared ceramic, with a thickness of 2.5 mm, achieves a minimum reflection loss of up to [value missing] in the X-band (10.90 GHz). dB, exhibiting strong absorption characteristics in a specific frequency band.
[0024] 2. The method for preparing Al2O3-based microwave absorbing ceramics modified with glucose pyrolysis disclosed in this invention uses glucose, which is widely available and inexpensive, as the carbon source, avoiding the use of expensive materials such as carbon nanotubes and graphene. The ball milling, dry pressing, and atmosphere sintering processes employed are all mature ceramic preparation technologies with simple procedures, easily controllable parameters, and good repeatability, providing a reliable and economical technical path for the large-scale preparation and engineering application of high-performance microwave absorbing ceramics. Furthermore, compared with traditional ferrite, metal powder, and other microwave absorbing materials, the ceramic material prepared by this invention has a lower density, meeting the requirements of modern electronic devices for lightweight microwave absorbing materials.
[0025] 3. The method for preparing glucose-modified Al2O3-based microwave absorbing ceramics disclosed in this invention achieves a significant improvement in microwave absorption performance by uniformly dispersing amorphous carbon generated from the pyrolysis of glucose at high temperature within an alumina matrix. This composite material not only inherits the excellent mechanical strength and thermal stability of alumina but also effectively enhances the dielectric loss capacity and impedance matching performance of the material due to the unique structural characteristics of glucose-modified carbon (such as high conductivity and large specific surface area). Thus, it exhibits excellent electromagnetic wave absorption capabilities over a wide frequency range. Furthermore, this composite material employs a simple mixing, molding, and sintering process, making it easy to mass-produce. It also utilizes low-cost glucose as a precursor, reducing manufacturing costs and minimizing environmental impact.
[0026] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description
[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:
[0028] Figure 1 This is a flowchart of a method for preparing glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramics according to the present invention;
[0029] Figure 2 The dielectric constant, dielectric loss, and frequency curves of samples prepared in different embodiments of the present invention are shown; wherein Figure 2 (a1)~2(a3) are respectively the real part of the dielectric constant, the imaginary part of the dielectric constant, and the dielectric loss tangent value versus frequency curves in Example 1; Figure 2 (b1)~2(b3) are respectively the real part of the dielectric constant, the imaginary part of the dielectric constant, and the dielectric loss tangent value versus frequency curves in Example 2; Figure 2 (c1)~2(c3) are the real part of the dielectric constant, the imaginary part of the dielectric constant, and the dielectric loss tangent value versus frequency, respectively, in Example 3. Figure 2 (d1)~2(d3) are the real part of the dielectric constant, the imaginary part of the dielectric constant, and the dielectric loss tangent value versus frequency, respectively, in Example 4. Figure 2 (e1)~2(e3) are the real part of the dielectric constant, the imaginary part of the dielectric constant, and the dielectric loss tangent of Example 5, respectively, versus frequency curves; the dielectric constant reflects the material's ability to store electric field energy at different frequencies; the dielectric loss reflects the material's dielectric loss capacity;
[0030] Figure 3 Samples prepared for different embodiments of the present invention at different thicknesses ( The reflection loss was measured in mm, and the sample thicknesses from top to bottom were 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, and 2.9 mm. Figure 3 (a) to 3 (e) correspond to the reflection loss diagrams of Examples 1 to 5, respectively.
[0031] Figure 4 The images show SEM images of the glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramics prepared in Examples 1, 2, 3, 4 and 5 of this invention. Detailed Implementation
[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0033] This glucose-modified carbon Al2O3-based microwave absorbing ceramic is prepared from the following raw materials by mass percentage: glucose wt.% Al2O3 wt.%, TiO2 wt.%.
[0034] Al2O3 is a low dielectric constant matrix with a particle size of [missing information]. TiO2 is used to provide stable structural support, ensuring the mechanical strength and chemical stability of the material. TiO2 is a sintering aid with a particle size of [missing information]. It is used to lower the sintering temperature of Al2O3 and promote ceramic densification. Glucose is used as a carbon source, which is decomposed at high temperature to generate amorphous carbon, which is used as a dielectric loss type microwave absorber to enhance the electrical conductivity loss and interfacial polarization relaxation loss of the material and improve microwave absorption performance.
[0035] Example 1
[0036] This glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic uses Al2O3 as the matrix, amorphous carbon generated by high-temperature pyrolysis of glucose as the microwave absorber, and TiO2 as the sintering aid. The mass percentage of each component is: 4 wt.% glucose, 92 wt.% Al2O3, and 4 wt.% TiO2.
[0037] The particle size of Al2O3 is in the range of 1 μm, and the particle size of sintering aid TiO2 is in the range of 1 μm.
[0038] like Figure 1 The method for preparing glucose-modified carbon-based Al2O3 microwave absorbing ceramics includes the following steps:
[0039] S1. Weigh 4 wt.% glucose, 92 wt.% Al2O3, and 4 wt.% TiO2. Use anhydrous ethanol as a solvent, mix them, and then mill them in a planetary ball mill at a speed of 300 r / min for 8 h to obtain a uniform slurry.
[0040] S2. After drying the slurry from step S1 in air at 80°C for 24 hours, add PVA solution and grind and granulate. The mass fraction of PVA particles in the PVA solution is 5%.
[0041] S3. The powder from step S2 is loaded into a square mold and dry-pressed by a tablet press at a pressure of 10 MPa to obtain a ceramic green body.
[0042] S4. Place the ceramic blank from step S3 into a tube furnace and introduce flowing argon gas as a protective atmosphere. The predetermined temperatures and holding times for the three stages of the heating process are 450℃ and 1 h (first stage, 3℃ / min), 600℃ and 0.5 h (second stage, 3℃ / min), and 1600℃ and 2 h (third stage, 5℃ / min). Finally, remove the ceramic blank at room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0043] The sample was fabricated to dimensions of 22.86 mm × 10.16 mm × 2.5 mm. A rectangular waveguide transmission line was used as the test fixture, and a vector network analyzer was used to measure its performance in the X-band. The dielectric constant is measured in the range of GHz, and the reflection loss of the sample is further calculated using the measured dielectric constant, thereby obtaining the real part of its dielectric constant in the X-band. Figure 2 (a1) ), Imaginary part ( Figure 2 (a2)) and dielectric loss ( Figure 2 (a3)), the range of the real part of the dielectric constant is The imaginary part range is The dielectric loss is between Between these, the reflection loss characteristics of the sample at different thicknesses are as follows: Figure 3 As shown in (a), the minimum reflection loss at 1.5 mm and 2.5 mm is both dB (10.55 GHz).
[0044] Example 2
[0045] This glucose-pyrolyzed carbon-modified Al2O3-based microwave absorbing ceramic uses Al2O3 as the matrix, amorphous carbon generated from the high-temperature pyrolysis of glucose as the microwave absorber, and TiO2 as the sintering aid. The mass percentage of each component is as follows: 6 wt.% glucose, 90 wt.% Al2O3, and 4 wt.% TiO2.
[0046] The particle size of Al2O3 is in the range of 1 μm, and the particle size of sintering aid TiO2 is in the range of 1 μm.
[0047] The preparation method of this glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic includes the following steps:
[0048] S1. Weigh 6 wt.% glucose, 90 wt.% Al2O3, and 4 wt.% TiO2, use anhydrous ethanol as solvent, mix them, and then ball mill them in a planetary ball mill at a speed of 300 r / min for 8 h to obtain a uniform slurry.
[0049] S2. After drying the slurry from step S1 in air at 80°C for 24 hours, add PVA solution and grind and granulate. The mass fraction of PVA particles in the PVA solution is 5%.
[0050] S3. The powder from step S2 is loaded into a square mold and dry-pressed by a tablet press at a pressure of 10 MPa to obtain a ceramic green body.
[0051] S4. Place the ceramic blank from step S3 into a tube furnace and introduce flowing argon gas as a protective atmosphere. The predetermined temperatures and holding times for the three stages of the heating process are 450℃ and 1 h (first stage, 3 ℃ / min), 600℃ and 0.5 h (second stage, 3℃ / min), and 1600℃ and 2 h (third stage, 5 ℃ / min). Finally, remove the ceramic blank at room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0052] The sample was fabricated to dimensions of 22.86 mm × 10.16 mm × 2.5 mm. A rectangular waveguide transmission line was used as the test fixture, and a vector network analyzer was used to measure its performance in the X-band. The dielectric constant is measured in the range of GHz, and the reflection loss of the sample is further calculated using the measured dielectric constant, thereby obtaining the real part of its dielectric constant in the X-band. Figure 2 (b1) ), Imaginary part ( Figure 2 (b2)) and dielectric loss ( Figure 2 (b3)), the range of the real part of the dielectric constant is The imaginary part range is The dielectric loss is between Between these, the reflection loss characteristics of the sample at different thicknesses are as follows: Figure 3 As shown in (b), the minimum reflection loss at 2.5 mm is dB (10.90 GHz).
[0053] Example 3
[0054] This glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic uses Al2O3 as the matrix, amorphous carbon generated from the high-temperature pyrolysis of glucose as the microwave absorber, and TiO2 as the sintering aid. The mass percentage of each component is as follows: 8 wt.% glucose, 88 wt.% Al2O3, and 4 wt.% TiO2.
[0055] The particle size of Al2O3 is in the range of 1 μm, and the particle size of sintering aid TiO2 is in the range of 1 μm.
[0056] The preparation method of this glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic includes the following steps:
[0057] S1. Weigh 8 wt.% glucose, 88 wt.% Al2O3, and 4 wt.% TiO2, use anhydrous ethanol as solvent, mix them, and then mill them in a planetary ball mill at a speed of 300 r / min for 8 h to obtain a uniform slurry.
[0058] S2. After drying the slurry from step S1 in air at 80°C for 24 hours, add PVA solution and grind and granulate. The mass fraction of PVA particles in the PVA solution is 5%.
[0059] S3. The powder from step S2 is loaded into a square mold and dry-pressed by a tablet press at a pressure of 10 MPa to obtain a ceramic green body.
[0060] S4. Place the ceramic blank from step S3 into a tube furnace and introduce flowing argon gas as a protective atmosphere. The predetermined temperatures and holding times for the three stages of the heating process are 450℃ and 1 h (first stage, 3℃ / min), 600℃ and 0.5 h (second stage, 3℃ / min), and 1600℃ and 2 h (third stage, 5℃ / min). Finally, remove the ceramic blank at room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0061] The sample was fabricated to dimensions of 22.86 mm × 10.16 mm × 2.5 mm. A rectangular waveguide transmission line was used as the test fixture, and a vector network analyzer was used to measure its performance in the X-band. The dielectric constant is measured in the range of GHz, and the reflection loss of the sample is further calculated using the measured dielectric constant, thereby obtaining the real part of its dielectric constant in the X-band. Figure 2 (c1)), Imaginary part ( Figure 2 (c2)) and dielectric loss ( Figure 2 (c3)), the range of the real part of the dielectric constant is The imaginary part range is The dielectric loss is between Between these, the reflection loss characteristics of the sample at different thicknesses are as follows: Figure 3 As shown in (c), the minimum reflection loss at 1.5 mm and 2.5 mm is both dB (10.36 GHz).
[0062] Example 4
[0063] This glucose-pyrolyzed carbon-modified Al2O3-based microwave absorbing ceramic uses Al2O3 as the matrix, amorphous carbon generated from the high-temperature pyrolysis of glucose as the microwave absorber, and TiO2 as the sintering aid. The mass percentage of each component is as follows: 10 wt.% glucose, 86 wt.% Al2O3, and 4 wt.% TiO2.
[0064] The particle size of Al2O3 is in the range of 1 μm, and the particle size of sintering aid TiO2 is in the range of 1 μm.
[0065] The preparation method of this glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic includes the following steps:
[0066] S1. Weigh 10 wt.% glucose, 86 wt.% Al2O3, and 4 wt.% TiO2. Use anhydrous ethanol as a solvent, mix them, and then mill them in a planetary ball mill at a speed of 300 r / min for 8 h to obtain a uniform slurry.
[0067] S2. After drying the slurry from step S1 in air at 80°C for 24 hours, add PVA solution and grind and granulate. The mass fraction of PVA particles in the PVA solution is 5%.
[0068] S3. The powder from step S2 is loaded into a square mold and dry-pressed by a tablet press at a pressure of 10 MPa to obtain a ceramic green body.
[0069] S4. Place the ceramic blank from step S3 into a tube furnace and introduce flowing argon gas as a protective atmosphere. The predetermined temperatures and holding times for the four stages of the heating process are 450℃ and 1 h (first stage, 3℃ / min), 600℃ and 0.5 h (second stage, 3℃ / min), 1600℃ and 2 h (third stage, 5℃ / min), and 1650℃ and 0.5 h (fourth stage, 2℃ / min). Finally, remove the ceramic blank at room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0070] The sample was fabricated to dimensions of 22.86 mm × 10.16 mm × 2.5 mm. A rectangular waveguide transmission line was used as the test fixture, and a vector network analyzer was used to measure its performance in the X-band. The dielectric constant is measured in the range of GHz, and the reflection loss of the sample is further calculated using the measured dielectric constant, thereby obtaining the real part of its dielectric constant in the X-band. Figure 2 (d1)), Imaginary part ( Figure 2 (d2)) and dielectric loss ( Figure 2 (d3)), the range of the real part of the dielectric constant is The imaginary part range is The dielectric loss is between Between. The reflection loss characteristics of the sample at different thicknesses are as follows: Figure 3 As shown in (d), the minimum reflection loss reaches [value missing] when the thickness is 2.9 mm. dB (9.71 GHz).
[0071] Example 5
[0072] This glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic uses Al2O3 as the matrix, amorphous carbon generated from the high-temperature pyrolysis of glucose as the microwave absorber, and TiO2 as the sintering aid. The mass percentage of each component is as follows: 12 wt.% glucose, 84 wt.% Al2O3, and 4 wt.% TiO2.
[0073] Among them, the particle size of Al2O3 is in the range of 1 μm, and the particle size of the sintering aid TiO2 is in the range of 1 μm.
[0074] The preparation method of this glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramic includes the following steps:
[0075] S1. Weigh 12wt.% glucose, 84wt.% Al2O3, and 4wt.% TiO2, use anhydrous ethanol as solvent, mix them, and then mill them in a planetary ball mill at a speed of 300 r / min for 8 h to obtain a uniform slurry.
[0076] S2. After drying the slurry from step S1 in air at 80°C for 24 hours, add PVA solution and grind and granulate. The mass fraction of PVA particles in the PVA solution is 5%.
[0077] S3. The powder from step S2 is loaded into a square mold and dry-pressed by a tablet press at a pressure of 10 MPa to obtain a ceramic green body.
[0078] S4. Place the ceramic blank from step S3 into a tube furnace and introduce flowing argon gas as a protective atmosphere. The predetermined temperatures and holding times for the four stages of the heating process are 450℃ and 1 h (first stage, 3℃ / min), 600℃ and 0.5 h (second stage, 3℃ / min), 1600℃ and 2 h (third stage, 5℃ / min), and 1650℃ and 0.5 h (fourth stage, 2℃ / min). Finally, remove the ceramic blank at room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
[0079] The sample was fabricated to dimensions of 22.86 mm × 10.16 mm × 2.5 mm. A rectangular waveguide transmission line was used as the test fixture, and a vector network analyzer was used to measure its performance in the X-band. The dielectric constant is measured in the range of GHz, and the reflection loss of the sample is further calculated using the measured dielectric constant, thereby obtaining the real part of its dielectric constant in the X-band. Figure 2 (e1)), Imaginary part ( Figure 2 (e2)) and dielectric loss ( Figure 2 (e3)), the range of the real part of the dielectric constant is The imaginary part range is The dielectric loss is between Between. The reflection loss characteristics of the sample at different thicknesses are as follows: Figure 3 As shown in (e), the minimum reflection loss reaches [value missing] when the thickness is 2.6 mm. dB (9.77 GHz).
[0080] The glucose pyrolysis carbon-modified Al2O3-based microwave absorbing ceramics prepared by this method can be applied in the fields of 5G / 6G communication base stations, anti-radar reconnaissance facilities, or microwave absorbing devices.
[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A glucose-split carbon-modified AI2O3-based microwave absorbing ceramic, characterized by, Prepared from the following raw materials by mass percentage: glucose wt.%, Al2O3 wt.%, TiO2 wt.%; the glucose is pyrolyzed to form amorphous carbon as a dielectric loss type wave-absorbing agent; the glucose serves as a carbon source for enhancing the electric conduction loss and interface polarization relaxation loss of the material and improving the microwave absorption performance.
2. The base microwave absorbing ceramic of claim 1, wherein, The Al2O3 as the low dielectric constant matrix has a particle size of .
3. The base microwave absorbing ceramic of claim 1, wherein, The TiO2acts as a sintering aid, and has a particle size of .
4. The method of producing a glucose-cleaving carbon-modified Al203-based microwave absorbing ceramic according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1, raw material mixing and ball milling: the raw materials were weighed according to the mass percentage wt.% of glucose, wt.% of Al2O3, wt.% of TiO2, with anhydrous ethanol as the solvent, the solvent amount being times the total mass of the raw materials, and the mixture was placed in a planetary ball mill and mixed according to the preset parameters to obtain a uniform slurry; S2, drying and granulation: the slurry obtained in step S1 is loaded into a ceramic tray, dried at a preset temperature, and then a PVA solution with a mass fraction of is added, ground to a particle size of , and granulated to obtain a composite powder; S3, dry pressing: the composite powder obtained in step S2 is loaded into a square mold, and dry pressing is performed under a preset pressure by a tablet press to obtain a ceramic green body; S4, temperature-programmed sintering: the ceramic green body obtained in step S3 is placed in a tube furnace for three-stage sintering, and flowing argon gas is introduced into the tube furnace as a protective atmosphere during the sintering process. In the heating step, the temperature is first raised to 450°C, and then held for 1 h; then the temperature is continuously raised to 600°C, and then held for 0.5 h; then the temperature is continuously raised to , and then held for . The three-stage heating rate is °C / min; the ceramic green body after three-stage sintering is naturally cooled to room temperature, and a glucose-cracked carbon-modified Al2O3-based microwave absorption ceramic is prepared.
5. The production method according to claim 4, wherein The rotation speed of the planetary ball mill in step S1 is r / min, the ball milling time is h, and the ball-to-material ratio is .
6. The production method according to claim 4, wherein In step S2, after the slurry is poured into the ceramic tray, it is placed... Dry in a forced-air drying oven at ℃ h, remove solvent.
7. The production method according to claim 4, wherein The PVA solution in step S2 is used as a binder, and the amount of addition is 0.5% of the total mass of the dried powder .
8. The production method according to claim 4, wherein The dry-pressing forming pressure in step S3 is MPa, and the pressure holding time is min, to obtain a ceramic green body with complete structure and no cracks.
9. The production method according to claim 4, wherein In step S4, the ceramic green body obtained in step S3 is placed in a tube furnace for four-stage sintering. During the sintering process, flowing argon gas is introduced into the tube furnace as a protective atmosphere. In the heating step, the first stage heats up to 450℃ and holds for 1 h; the second stage continues to heat up to 600℃ and holds for 0.5 h; the third stage continues to heat up to... ℃, heat preservation h; In the fourth stage, the temperature is raised again to 1650℃ and kept warm. h; the heating rate in all four stages is... ℃ / min; After four stages of sintering, the ceramic green body was naturally cooled to room temperature to obtain glucose pyrolysis carbon modified Al2O3-based microwave absorbing ceramic.
10. The application of the glucose-cracking carbon-modified Al2O3-based microwave absorption ceramic prepared by the preparation method of claim 4 or 9 in the field of 5G / 6G communication base stations, anti-radar reconnaissance facilities or microwave absorption devices, especially in scenarios requiring high-temperature resistance, corrosion resistance and lightweight of the material.