Zero-defect loaded wave-absorbing material and preparation method thereof

Abstract

This invention discloses a zero-defect loaded microwave absorbing material and its preparation method, belonging to the field of electromagnetic wave absorbing materials. The invention involves mixing an absorbing agent and an adhesive, stirring thoroughly to obtain a high-viscosity electromagnetic slurry; filling the high-viscosity electromagnetic slurry into a molding die; eliminating internal defects in the slurry using a three-dimensional vibration table; then placing it in a vacuum oven for secondary defect elimination; finally, curing the treated slurry in the mold to obtain the zero-defect loaded microwave absorbing material. This invention uses vibration and vacuum to eliminate defects in the slurry, thus preparing the zero-defect loaded microwave absorbing material.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials, and specifically relates to a zero-defect load absorbing material and its preparation method. Background Technology

[0002] Rigid microwave absorbing materials are mainly composed of absorbers, binders, and various processing aids. They are multifunctional polymer composite materials with absorption properties such as electromagnetic interference resistance, microwave directional enhancement, and clutter suppression. Based on their loss mechanism, they can be divided into three main categories: resistive, dielectric, and magnetic dielectric. Their loss capacity is primarily affected by the absorber content within the material; the higher the absorber content, the stronger the microwave absorption loss capacity.

[0003] However, the absorbent content cannot be added indefinitely; it is limited by the molding process. When the absorbent is added to a certain level, it can no longer be bonded together by the adhesive, reaching the upper limit of absorbent addition. Before reaching this limit, the higher the absorbent content, the greater the viscosity of the slurry after mixing and homogenizing with the adhesive. This makes it more difficult to remove air trapped inside the slurry during mixing, resulting in numerous voids and defects within the material after curing, which is insufficient to meet the requirements of various aerospace products. Currently, the conventional vacuum degassing process for low-viscosity slurries is not suitable for high-viscosity slurries, making the zero-defect molding of high-filling-volume microwave absorbing materials a pressing issue.

[0004] Therefore, to address the above-mentioned material preparation issues, it is necessary to provide a high-filling-volume load-absorbing material and a zero-defect molding preparation method to meet the application requirements of various aerospace products for load-absorbing materials. Summary of the Invention

[0005] The purpose of this invention is to provide a zero-defect load absorbing material and its preparation method, which uses vibration and vacuum to eliminate defects in the slurry to prepare the zero-defect load absorbing material.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] A method for preparing a zero-defect loaded microwave absorbing material includes the following steps:

[0008] (1) Mix the microwave absorbing agent and adhesive, and stir thoroughly to obtain a high-viscosity electromagnetic slurry;

[0009] (2) The high-viscosity electromagnetic slurry is filled into the molding mold, and the internal defects of the slurry are eliminated by a three-dimensional vibration table. Then, it is placed in a vacuum oven for secondary defect elimination. Finally, the treated slurry is solidified in the mold to obtain a zero-defect load absorbing material.

[0010] Preferably, the mass ratio of the absorbent to the adhesive is 90:(9-10).

[0011] Preferably, the microwave absorbing agent is carbonyl iron powder or alloy powder.

[0012] Preferably, the particle size of the absorbing agent is 1-10 μm.

[0013] Preferably, the adhesive is epoxy resin, bismaleimide resin, or phenolic resin.

[0014] Preferably, the viscosity of the high-viscosity electromagnetic paste is 10 P·s ≤ μ ≤ 50 P·s.

[0015] Preferably, the vibration frequency of the three-dimensional vibration table is 20-40Hz.

[0016] Preferably, the vibration time of the three-dimensional vibration table is 5-15 minutes.

[0017] Preferably, the temperature of the vacuum oven is 80-100℃.

[0018] Preferably, the time in the vacuum oven is 30-60 minutes.

[0019] Preferably, the vacuum degree of the vacuum oven is ≤-0.09MPa.

[0020] A zero-defect load absorbing material is prepared using the above-described preparation method.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) This invention removes bubbles from high-viscosity slurry by combining two processes: three-dimensional vibration table degassing and vacuum oven degassing. This enables zero-defect molding of high-fill-content load-absorbing materials, which greatly promotes the further improvement of the performance of load-absorbing materials.

[0023] (2) A necessary condition for bubble removal using a three-dimensional vibration table in this invention is that the viscosity of the slurry is moderate. Because in low-viscosity slurries (μ < 10 P·s), the high-density metal absorber in the slurry will settle during vibration degassing, leading to phase separation and affecting the overall uniformity of the material. High-viscosity slurries (10 P·s ≤ μ ≤ 50 P·s) have a high overall viscosity and are less prone to settling, making them suitable for vibration table degassing. However, it is necessary to study the vibration time and frequency to avoid excessively long vibration times or high frequencies that could significantly affect the overall uniformity of the material. Even higher viscosity slurries (μ > 50 P·s) have an excessively high absorbent content, making it difficult for the absorbent and binder to effectively disperse, mix, and bond together, thus losing their vibration plasticity and making them unsuitable for three-dimensional vibration table degassing. Therefore, by limiting the slurry to a suitable viscosity and then using a three-dimensional vibration table, this invention can significantly reduce the difficulty of eliminating internal defects in the slurry and lower production costs.

[0024] (3) The zero-defect load absorbing material obtained in this application can meet the needs of aviation and aerospace products for high-performance load absorbing materials. Attached Figure Description

[0025] Figure 1 This is a CT scan of the zero-defect load absorbing material in Example 1;

[0026] Figure 2 This is a schematic diagram of the overall electromagnetic uniformity test sampling of the load-absorbing material.

[0027] Figure 3 This is a photograph of the zero-defect load absorbing material in Comparative Example 1.

[0028] Figure 4 This is a CT scan of the defective load absorbing material in Comparative Example 3.

[0029] Figure 5 This is a CT scan of the defective load absorbing material in Comparative Example 4.

[0030] Figure 6 This is a CT scan of the defective load absorbing material in Comparative Example 5. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a high-fill-content microwave absorbing material and a zero-defect molding method for its preparation. The preparation method includes the following steps:

[0033] (1) Mix the microwave absorber and adhesive in a certain proportion and stir thoroughly to obtain a high-viscosity electromagnetic slurry;

[0034] (2) The mixed and homogenized slurry is filled into the molding mold. A three-dimensional vibration table is used to eliminate internal defects of the slurry at a certain vibration frequency and time. Then, it is placed in a vacuum oven for secondary defect elimination at a certain temperature, vacuum degree and time. Finally, the treated slurry is solidified in the mold to obtain a zero-defect load absorbing material. The material is non-destructive tested and its uniformity is verified by industrial CT and electromagnetic parameter testing system.

[0035] In a preferred embodiment, the mass ratio of the absorbent to the adhesive is 90:(9-10) (for example, it can be 90:9, 90:9.5 or 90:10).

[0036] According to some preferred embodiments, the particle size of the absorbent is 1-10 μm (e.g., it can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm).

[0037] According to some preferred embodiments, the microwave absorbing agent is carbonyl iron powder or alloy powder.

[0038] According to some preferred embodiments, the resin is an epoxy resin, a bismaleimide resin, or a phenolic resin.

[0039] According to some preferred embodiments, the viscosity of the high-viscosity electromagnetic paste is 10 P·s ≤ μ ≤ 50 P·s (for example, it can be 10 P·s, 20 P·s, 30 P·s, 40 P·s or 50 P·s).

[0040] According to some preferred embodiments, the vibration frequency of the three-dimensional vibration table is 20-40Hz (for example, it can be 20Hz, 30Hz or 40Hz).

[0041] According to some preferred embodiments, the vibration time of the three-dimensional vibration table is 5-15 minutes (for example, it can be 5 minutes, 10 minutes or 15 minutes).

[0042] According to some preferred embodiments, the temperature of the vacuum oven is 80-100°C.

[0043] According to some preferred embodiments, the time in the vacuum oven is 30-60 minutes.

[0044] According to some preferred embodiments, the vacuum degree of the vacuum oven is ≤-0.09MPa.

[0045] To more clearly illustrate the technical solution and advantages of the present invention, the following detailed description of a high-filling-volume microwave absorbing material and a zero-defect molding preparation method is provided through several embodiments.

[0046] Example 1

[0047] (1) 900g carbonyl iron powder (particle size 5μm) and 100g epoxy resin were placed in a planetary mixer and homogenized to obtain a high-viscosity electromagnetic slurry with a viscosity of 10P·s.

[0048] (2) The mixed and homogenized slurry is filled into the molding mold. A three-dimensional vibration table is used to vibrate at a vibration frequency of 20Hz for 10 minutes to eliminate internal defects in the slurry. Then, it is placed in a vacuum oven and treated at 100℃ and -0.095MPa for 30 minutes. Finally, the treated slurry is solidified in the mold to obtain a zero-defect load absorbing material.

[0049] Example 2

[0050] Example 2 is basically the same as Example 1, except that the mass ratio of absorbent to adhesive is 90:9. That is, 900g of carbonyl iron powder and 90g of epoxy resin, and the viscosity of the slurry is 50P·s.

[0051] Example 3

[0052] Example 3 is basically the same as Example 1, except that the particle size of carbonyl iron powder is 10 μm.

[0053] Example 4

[0054] Example 4 is basically the same as Example 1, except that the resin adhesive is bismaleimide resin and the slurry viscosity is 30 P·s.

[0055] Example 5

[0056] Example 5 is basically the same as Example 1, except that the vibration frequency of the three-dimensional vibration table is 40Hz.

[0057] Example 6

[0058] Example 6 is basically the same as Example 1, except that the vibration time of the three-dimensional vibration table is 15 minutes.

[0059] Example 7

[0060] Example 7 is basically the same as Example 1, except that the temperature of the vacuum oven is 80°C.

[0061] Example 8

[0062] Example 8 is basically the same as Example 1, except that the vacuum degree of the vacuum oven is -0.090MPa.

[0063] Example 9

[0064] Example 9 is basically the same as Example 1, except that the vacuum oven treatment time is 60 minutes.

[0065] Comparative Example 1

[0066] (1) 700g carbonyl iron powder (particle size 5μm) and 300g epoxy resin were placed in a planetary mixer and homogenized to obtain a high viscosity electromagnetic slurry.

[0067] (2) The mixed and homogenized slurry is filled into the molding mold. A three-dimensional vibration table is used to vibrate at a vibration frequency of 20Hz for 10 minutes to eliminate internal defects in the slurry. Then, it is placed in a vacuum oven and treated at 100℃ and -0.095MPa for 30 minutes. Finally, the treated slurry is solidified in the mold to obtain the load-bearing microwave absorbing material.

[0068] Comparative Example 2

[0069] (1) Place 900g carbonyl iron powder (particle size 20μm) and 100g epoxy resin in a planetary mixer to homogenize and mix, and obtain a high viscosity electromagnetic slurry.

[0070] (2) The mixed and homogenized slurry is filled into the molding mold. A three-dimensional vibration table is used to vibrate at a vibration frequency of 20Hz for 10 minutes to eliminate internal defects in the slurry. Then, it is placed in a vacuum oven and treated at 100℃ and -0.095MPa for 30 minutes. Finally, the treated slurry is solidified in the mold to obtain the load-bearing microwave absorbing material.

[0071] Comparative Example 3

[0072] (1) Place 900g carbonyl iron powder (particle size 5μm) and 100g epoxy resin in a planetary mixer to homogenize and mix, and obtain a high viscosity electromagnetic slurry.

[0073] (2) The mixed and homogenized slurry is filled into the molding mold. A three-dimensional vibration table is used to vibrate at a vibration frequency of 10Hz for 10 minutes to eliminate internal defects in the slurry. Then, it is placed in a vacuum oven and treated at 100℃ and -0.095MPa for 30 minutes. Finally, the treated slurry is solidified in the mold to obtain the load-bearing microwave absorbing material.

[0074] Comparative Example 4

[0075] (1) Place 900g carbonyl iron powder (particle size 5μm) and 100g epoxy resin in a planetary mixer to homogenize and mix, and obtain a high viscosity electromagnetic slurry.

[0076] (2) The mixed and homogenized slurry is filled into the molding mold. A three-dimensional vibration table is used to vibrate at a vibration frequency of 20Hz for 30 minutes to eliminate internal defects in the slurry. Then, it is placed in a vacuum oven and treated at 100℃ and -0.095MPa for 30 minutes. Finally, the treated slurry is solidified in the mold to obtain the load-bearing microwave absorbing material.

[0077] Comparative Example 5

[0078] (1) Place 900g carbonyl iron powder (particle size 5μm) and 100g epoxy resin in a planetary mixer to homogenize and mix, and obtain a high viscosity electromagnetic slurry.

[0079] (2) Fill the mold with the mixed and homogenized slurry, then place it in a vacuum oven and treat it at 100℃ and -0.095MPa for 30 minutes. Finally, solidify the treated slurry in the mold to obtain the load-bearing microwave absorbing material.

[0080] Comparative Example 6

[0081] (1) 900g carbonyl iron powder (particle size 5μm) and 60g epoxy resin were placed in a planetary mixer and mixed evenly. The carbonyl iron powder and epoxy resin could not be effectively dispersed, mixed and bonded into a whole.

[0082] (2) The above-obtained slurry is filled into the molding mold. Due to the high viscosity of the slurry, it loses its vibration plasticity and cannot be used to prepare zero-defect load absorbing material through this molding process.

[0083] The load-absorbing materials obtained in Examples 1 to 9 and Comparative Examples 1 to 5 were subjected to internal defect detection using industrial CT, and the defect-free products were further analyzed. Figure 1 Material homogeneity was tested according to a specific sampling method (dispersion coefficient ≤ 10% was considered small). The specific test was conducted according to... Figure 2 Single material samples were taken and machined into waveguide specimens according to standard methods. The complex permittivity ε', ε” and permeability μ', μ” at different frequencies were measured using a vector grid analyzer within the range of 2.6-3.95 GHz, and their dispersion coefficients were calculated. The specific results are shown in Table 1.

[0084] Table 1. Electromagnetic homogeneity sampling mechanical property test results

[0085]

[0086] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a zero-defect loaded microwave absorbing material, characterized in that, Includes the following steps: (1) Mix the microwave absorbing agent and the adhesive, wherein the mass ratio of the microwave absorbing agent to the adhesive is 90:(9-10), and the particle size of the microwave absorbing agent is 1-10μm. Stir thoroughly to obtain a high-viscosity electromagnetic slurry, wherein the viscosity of the high-viscosity electromagnetic slurry is 10P·s≤μ≤50P·s. (2) The high-viscosity electromagnetic slurry is filled into the molding mold, and the internal defects of the slurry are eliminated by a three-dimensional vibration table. The vibration frequency of the three-dimensional vibration table is 20-40Hz and the vibration time is 5-15min. Then, it is placed in a vacuum oven for secondary defect elimination. Finally, the treated slurry is solidified in the mold to obtain a zero-defect load absorbing material.

2. The preparation method according to claim 1, characterized in that, The microwave absorbing agent is carbonyl iron powder or alloy powder.

3. The preparation method according to claim 1, characterized in that, The adhesive is epoxy resin, bismaleimide resin, or phenolic resin.

4. The preparation method according to claim 1, characterized in that, The temperature of the vacuum oven is 80-100℃, and the time is 30-60 minutes.

5. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum oven is ≤-0.09MPa.

6. A zero-defect load absorbing material, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

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