Modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material and preparation method thereof

Abstract

The application discloses a modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material and a preparation method thereof. The preparation method comprises the following steps: mixing and stirring modified rare earth ferrite, pyrrole, ferric chloride and an aramid fiber water solution to obtain an aramid fiber solution reinforced by the modified rare earth ferrite; freeze-drying the aramid fiber solution reinforced by the modified rare earth ferrite to obtain modified rare earth ferrite reinforced aerogel; pouring heat-conducting fillers / polydimethylsiloxane elastomers onto the modified rare earth ferrite reinforced aerogel, and curing after vacuum packaging to obtain the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material with a reticular structure. The material prepared by the application can realize the integration of shielding, heat conduction and corrosion resistance, has important application value in communication, vehicle-mounted radar and the field of national defense, and has important practical significance in the application of electromagnetic shielding materials in the future.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding materials technology, specifically relating to a modified rare earth ferrite aerogel-based multifunctional composite material with a mesh structure that provides shielding, thermal conductivity, and corrosion resistance, and its preparation method. Background Technology

[0002] While electronic and electrical equipment brings great convenience to people's lives, it also causes increasingly serious electromagnetic pollution. Electromagnetic waves not only interfere with the normal use of other components, rendering electronic devices malfunction, but also harm human health. Studies have shown that exposure to electromagnetic radiation increases the risk of mild or acute illnesses such as cancer, heart disease, and skin diseases. Therefore, the development of high-performance electromagnetic shielding materials has become a research hotspot. However, at the same time, electromagnetic shielding causes reflected electromagnetic waves to convert electromagnetic energy into heat energy. The heat accumulated inside instruments and composite materials can affect the normal operation and lifespan of instruments. In addition, electromagnetic shielding materials on instrument surfaces are often subjected to harsh environments, and improving corrosion resistance plays a crucial role in extending the lifespan of composite materials. Therefore, designing composite materials with strong electromagnetic shielding effects, excellent thermal conductivity, and corrosion resistance has broad application prospects in communication equipment and consumer electronics.

[0003] Traditional electromagnetic shielding and thermally conductive materials often involve adding a large amount of metal filler with both electrical and thermal conductivity to the material matrix. However, with the increasing demands for miniaturized and lightweight electronic devices, the high density and cost of metal fillers are increasingly limiting their further application. Furthermore, surface metal fillers are susceptible to corrosion, which is detrimental to long-term use. Therefore, developing composite materials that simultaneously achieve strong electromagnetic shielding with low filler content, high thermal conductivity, and corrosion resistance through structural design has become a critical issue that urgently needs to be addressed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a modified rare-earth ferrite aerogel-based multifunctional composite material with a mesh structure that provides shielding, thermal conductivity, and corrosion resistance, as well as its preparation method.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0006] (I) This invention provides a method for preparing a modified rare-earth ferrite aerogel-based shielding-thermal-conducting-corrosion-resistant multifunctional composite material, comprising the following steps:

[0007] Step 1: Mix and stir the modified rare earth ferrite, pyrrole, ferric chloride and aramid fiber aqueous solution to obtain a modified rare earth ferrite reinforced aramid fiber solution.

[0008] Step 2: Freeze the modified rare earth ferrite-reinforced aramid fiber solution, and dry the frozen sample to obtain modified rare earth ferrite-reinforced aerogel.

[0009] Step 3: Cast the thermally conductive filler / polydimethylsiloxane elastomer onto the modified rare earth ferrite-reinforced aerogel, vacuum encapsulate it, and then cure it to obtain a multifunctional composite material with a network structure based on the modified rare earth ferrite aerogel, which provides shielding, thermal conductivity, and corrosion protection.

[0010] Furthermore, in step one, the weight ratio of the modified rare earth ferrite, pyrrole, ferric chloride and aramid fiber aqueous solution is (4-8):(2-5):(2-5):(72-92), and more preferably (5-8):(4-5):(4-5):(72-92).

[0011] Furthermore, in step one, the modified rare earth ferrite is a neodymium-doped W-type barium ferrite with the molecular formula Ba. 1-x Nd x Co2Fe 16 O 27 x is 0.10, 0.15, or 0.20; the preparation method is as follows: Ba 2+ 、Nd 3+ Co 2+ and Fe 3+ The salt was mixed with deionized water, citric acid was added and stirred to dissolve, the solution was adjusted to neutral, and then heated and stirred until a viscous gel was formed. The gel was heated to remove excess water, and then heated to 190-220℃ to obtain a precursor. The precursor was then ground. The ground precursor powder was calcined and ground to obtain neodymium-doped W-type barium ferrite.

[0012] Furthermore, the molar ratio of citric acid to metal ions is 1:1; the calcination process is as follows: the ground precursor powder is placed in a muffle furnace, pre-calcined at 450°C for 3 hours at a heating rate of 5°C / min, and then heated to 1300°C and held for 3 hours at a heating rate of 5°C / min.

[0013] Furthermore, in step one, the preparation method of the aramid fiber aqueous solution is as follows: calcium chloride, p-phenylenediamine, and terephthaloyl chloride are completely dissolved in N-methylpyrrolidone, and stirred at 150-400 rpm for 3-6 hours to carry out the reaction; water is added to the solution after the reaction and stirred while stirring with a glass rod. After stirring is completed, the solution is allowed to stand and filtered. The viscous solution is wrapped with a filter screen to obtain the synthesized aramid fiber aqueous solution; the addition ratio of calcium chloride, p-phenylenediamine, terephthaloyl chloride, N-methylpyrrolidone, and water is 20g:3g:12g:70g:1000ml.

[0014] Furthermore, in step two, the freezing temperature is -20℃ and the drying temperature is 60-100℃.

[0015] Furthermore, in step three, the curing method is as follows: after vacuum sealing, the material is placed in a forced-air drying oven at a temperature of 80-100℃ to obtain a cured modified rare-earth ferrite aerogel-based shielding-thermal-conducting-corrosion-resistant multifunctional composite material.

[0016] Furthermore, in step three, the preparation method of the thermally conductive filler / polydimethylsiloxane elastomer is as follows: the thermally conductive filler and component A of the polydimethylsiloxane elastomer are blended and stirred once, then component B of the polydimethylsiloxane elastomer is added, the mixture is stirred a second time, and then placed in a vacuum oven to remove bubbles, thereby obtaining the thermally conductive filler / polydimethylsiloxane elastomer.

[0017] Furthermore, the mass ratio of the thermally conductive filler, component A of the polydimethylsiloxane elastomer, and component B of the polydimethylsiloxane elastomer is (20-30):(35-40):(35-40); the first stirring time is 20 minutes, and the second stirring time is 20 minutes.

[0018] Furthermore, the thermally conductive filler has a density of 2.3 g / cm³. 3 Boron nitride, 3.3 g / cm 3 Aluminum nitride, 3.2 g / cm³ 3 Silicon carbide and 4.0 g / cm 3 At least one of the following: aluminum oxide.

[0019] (ii) The present invention also provides a modified rare earth ferrite aerogel-based shielding-thermal-conducting-corrosion-resistant multifunctional composite material with a mesh structure, which is prepared by the preparation method described above.

[0020] Beneficial effects:

[0021] This invention provides a modified rare-earth ferrite aerogel-based multifunctional composite material with a mesh structure, integrating shielding, thermal conductivity, and corrosion protection, and its preparation method. By modifying the rare-earth-reinforced aerogel to create conductive pathways, excellent shielding performance is achieved under corrosive conditions. Furthermore, through structural design, a polydimethylsiloxane elastomer with excellent thermal conductivity is cast to further improve the thermal conductivity, thus achieving integrated shielding, thermal conductivity, and corrosion protection. This material has significant application value in communications, automotive radar, and defense fields, and holds important practical significance for the future application of electromagnetic shielding materials. Attached Figure Description

[0022] Figure 1 This is a comparison diagram of the electromagnetic shielding performance of the embodiments of the present invention and the comparative sample;

[0023] Figure 2This is a comparison diagram of the corrosion resistance performance of the embodiments of the present invention and the comparative sample;

[0024] Figure 3 This is a scanning electron microscope image of the sample from Embodiment 1 of the present invention. Detailed Implementation

[0025] 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 only some, not all, of the embodiments of the present invention. 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.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0027] Example 1

[0028] This embodiment provides a modified rare-earth ferrite aerogel-based multifunctional composite material for shielding, thermal conductivity, and corrosion protection, the preparation method of which includes the following steps:

[0029] Step 1: Prepare a solution of aramid fiber reinforced with modified rare earth ferrite.

[0030] By weight, 20 parts calcium chloride, 3 parts p-phenylenediamine and 12 parts terephthaloyl chloride were completely dissolved in 70 parts N-methylpyrrolidone. The stirrer speed was adjusted to 300 rpm and the reaction was carried out for 4 hours. 1000 ml of deionized water was added to the solution after the reaction while stirring with a glass rod. After the product was allowed to stand for a period of time to precipitate, it was filtered. The viscous solution was wrapped with a filter screen to obtain the synthesized aramid fiber aqueous solution.

[0031] Neodymium-doped W-type barium ferrite was prepared by sol-gel method. The molecular formula of neodymium-doped W-type barium ferrite is Ba. 1- x Nd x Co2Fe 16 O 27 x is taken as 0.10; the preparation method is as follows: first, according to the molar ratio of the molecular formula (Ba 2+ :Nd 3+ :Co 2+ :Fe 3+=1-x:x:2:16) Weigh out several metal ion nitrates, dissolve them in a small amount of deionized water, add citric acid monohydrate and stir to dissolve (the molar ratio of metal ions to citric acid is 1:1), then add ammonia to adjust the pH to about 7, place in an oil bath, adjust the temperature to 80℃ and keep it warm, stirring constantly until a viscous gel is formed. Cover the surface of the gel with tin foil and heat it to 120℃ at a rate of 5℃ / min, then keep it at that temperature for 10 hours to remove excess moisture. Then heat it to 200℃ at a rate of 5℃ / min and treat it at 200℃ for 2 hours to obtain the precursor. After thorough grinding, transfer it to a corundum crucible and place it in a muffle furnace. Pre-calcine it at 450℃ for 3 hours at a rate of 5℃ / min, then heat it to 1300℃ at the same rate and keep it at that temperature for 3 hours. After cooling, take out the sample, grind it to obtain neodymium-doped W-type barium ferrite.

[0032] Neodymium-doped W-type barium ferrite, pyrrole, and ferric chloride were added to an aqueous solution of aramid fiber while stirring with a glass rod to obtain a modified rare earth ferrite-reinforced aramid fiber solution. The weight ratio of the modified rare earth ferrite, pyrrole, ferric chloride, and the aqueous solution of aramid fiber was 8:5:5:72.

[0033] Step 2: Preparation of modified rare earth ferrite-reinforced aerogel.

[0034] The modified rare earth ferrite-reinforced aramid fiber solution was placed in a silicone soft mold and frozen in a refrigerator at -20℃. The frozen sample was then dried in a forced-air drying oven at 100℃ to obtain the modified rare earth ferrite-reinforced aerogel.

[0035] Step 3: Preparation of modified rare earth ferrite aerogel-based shielding-thermal-conducting-corrosion-resistant multifunctional composite material.

[0036] The thermally conductive filler was blended with component A of the polydimethylsiloxane elastomer (component A is polydimethylsiloxane) and stirred for 20 min. Then, component B of the polydimethylsiloxane elastomer (component B is a curing agent) was added, and the mixture was stirred for another 20 min. The mixture was then placed in a vacuum oven for degassing to obtain the thermally conductive filler / polydimethylsiloxane elastomer. The thermally conductive filler has a density of 2.3 g / cm³. 3 Boron nitride and 3.3 g / cm 3 Aluminum nitride. The mass ratio of thermally conductive filler, component A of polydimethylsiloxane elastomer, and component B of polydimethylsiloxane elastomer is 30:35:35.

[0037] Thermally conductive filler / polydimethylsiloxane elastomer was cast into a mold containing modified rare-earth ferrite-reinforced aerogel. Vacuum-assisted encapsulation was then performed, followed by curing in a forced-air drying oven at 100℃ to obtain a modified rare-earth ferrite aerogel-based multifunctional composite material with a network structure, providing shielding, thermal conductivity, and corrosion resistance. The network structure of the sample is shown below. Figure 3 As shown.

[0038] Example 2

[0039] This embodiment provides a modified rare-earth ferrite aerogel-based multifunctional composite material for shielding, thermal conductivity, and corrosion protection, the preparation method of which includes the following steps:

[0040] Step 1: Prepare a solution of aramid fiber reinforced with modified rare earth ferrite.

[0041] By weight, 20 parts calcium chloride, 3 parts p-phenylenediamine and 12 parts terephthaloyl chloride were completely dissolved in 70 parts N-methylpyrrolidone. The stirrer speed was adjusted to 400 rpm and the reaction was carried out for 3 hours. 1000 ml of deionized water was added to the solution after the reaction while stirring with a glass rod. After the product was allowed to stand for a period of time to precipitate, it was filtered. The viscous solution was wrapped with a filter screen to obtain the synthesized aramid fiber aqueous solution.

[0042] Neodymium-doped W-type barium ferrite was prepared by sol-gel method. The molecular formula of neodymium-doped W-type barium ferrite is Ba. 1- x Nd x Co2Fe 16 O 27 x is 0.15, and the preparation method is the same as in Example 1.

[0043] Neodymium-doped W-type barium ferrite, pyrrole, and ferric chloride were added to an aqueous solution of aramid fiber while stirring with a glass rod to obtain a modified rare earth ferrite-reinforced aramid fiber solution. The weight ratio of the modified rare earth ferrite, pyrrole, ferric chloride, and the aqueous solution of aramid fiber was 5:4:4:92.

[0044] Step 2: Preparation of modified rare earth ferrite-reinforced aerogel.

[0045] The modified rare earth ferrite-reinforced aramid fiber solution was placed in a silicone soft mold and frozen in a refrigerator at -20℃. The frozen sample was then dried in a forced-air drying oven at 80℃ to obtain the modified rare earth ferrite-reinforced aerogel.

[0046] Step 3: Preparation of modified rare earth ferrite aerogel-based shielding-thermal-conducting-corrosion-resistant multifunctional composite material.

[0047] The thermally conductive filler was blended with component A of the polydimethylsiloxane elastomer and stirred for 20 minutes. Then, component B of the polydimethylsiloxane elastomer was added, and the mixture was stirred for another 20 minutes. The mixture was then placed in a vacuum oven for degassing to obtain the thermally conductive filler / polydimethylsiloxane elastomer. The thermally conductive filler has a density of 4.0 g / cm³. 3 The alumina. The mass ratio of thermally conductive filler, component A of polydimethylsiloxane elastomer, and component B of polydimethylsiloxane elastomer is 30:35:35.

[0048] Thermally conductive filler / polydimethylsiloxane elastomer was cast into a mold containing modified rare earth ferrite-reinforced aerogel. Vacuum-assisted encapsulation was then performed, followed by curing in a forced-air drying oven at 80°C to obtain a multifunctional composite material with a network structure based on modified rare earth ferrite aerogel for shielding, thermal conductivity, and corrosion protection.

[0049] Comparative Example 1

[0050] This comparative example provides a modified rare-earth ferrite-reinforced aerogel, including steps one and two of Example 1.

[0051] Comparative Example 2

[0052] This comparative example provides a polydimethylsiloxane elastomer reinforced with modified rare earth ferrite and thermally conductive filler. The preparation method is as follows: neodymium-doped W-type barium ferrite powder (preparation method is the same as in Example 1) is directly blended with thermally conductive filler / polydimethylsiloxane elastomer (preparation method is the same as in Example 1) and then cured to obtain an aerogel without a network structure.

[0053] Performance testing:

[0054] The samples prepared in Examples 1-2 and Comparative Examples 1-2 were stamped into cuboids of 22.84mm × 10.12mm × 2mm using a special mold, and their shielding performance, thermal conductivity, and corrosion resistance were tested.

[0055] 1) Shielding effectiveness test: The shielding effectiveness of the samples in the 8-12.4 GHz range was tested using a vector network analyzer. Test results are shown below. Figure 1 .like Figure 1 As shown, compared with Comparative Examples 1 and 2, the electromagnetic shielding performance of Examples 1 and 2 is significantly enhanced.

[0056] 2) Corrosion Resistance Test: The sample was placed in a salt spray chamber at 35°C and 5% wt NaCl for 7 days, and the shielding effectiveness was retested. The electromagnetic shielding effectiveness test results after corrosion are shown in [link to relevant documentation]. Figure 2 .like Figure 2As shown, the electromagnetic shielding performance of the samples in Examples 1 and 2 did not decrease significantly before and after corrosion, and could meet the electromagnetic shielding requirements, demonstrating good corrosion resistance.

[0057] 3) Thermal conductivity test: The thermal conductivity of the samples was tested using a Hot Disk thermal conductivity meter. The test results are shown in Table 1. As can be seen from Table 1, samples 1 and 2 in this example have good thermal conductivity.

[0058] Table 1 - Thermal conductivity test results

[0059]

[0060] This invention provides a modified rare-earth ferrite aerogel-based multifunctional composite material with a mesh structure, integrating shielding, thermal conductivity, and corrosion protection, and its preparation method. By modifying the rare-earth-reinforced aerogel to build conductive pathways, excellent shielding performance is achieved under corrosive conditions. Furthermore, through structural design, a polydimethylsiloxane elastomer with excellent thermal conductivity is cast to improve the thermal conductivity, achieving integrated shielding, thermal conductivity, and corrosion protection. The preparation method described in this invention produces a flexible, lightweight, and highly thermally conductive structural electromagnetic shielding composite material. Tests using a vector network analyzer and a thermal conductivity meter show that compared to ordinary flexible electromagnetic shielding thermally conductive materials, the highly thermally conductive structural electromagnetic shielding composite material exhibits significantly improved shielding effectiveness and thermal conductivity, demonstrating the effectiveness of the structural design. In addition, it maintains excellent shielding effectiveness even under prolonged corrosive conditions, meeting the requirement for durable use and possessing significant practical implications for future applications of electromagnetic shielding materials.

[0061] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material, characterized in that, The method comprises the following steps: Step one, mix and stir the modified rare earth ferrite, pyrrole, ferric chloride and aramid fiber aqueous solution to obtain a modified rare earth ferrite reinforced aramid fiber solution; in the step one, the modified rare earth ferrite is neodymium doped W type barium ferrite, and the molecular formula is Ba 1-x Nd x Co2Fe 16 O 27 , x is 0.10, 0.15 or 0.20; the preparation method is: mixing the salts of Ba 2+ , Nd 3+ , Co 2+ and Fe 3+ with deionized water, adding citric acid and stirring to dissolve, adjusting the solution to be neutral, then heating and stirring until a thick gel is produced; continue to heat the gel to remove excess water, then heat to 190~220℃ for treatment to obtain a precursor, grind the precursor; calcine the ground precursor powder to obtain a neodymium doped W type barium ferrite; Step two, freeze the modified rare earth ferrite reinforced aramid fiber solution, and dry the frozen sample to obtain a modified rare earth ferrite reinforced aerogel; Step three, pour the heat-conducting filler / polydimethylsiloxane elastomer onto the modified rare earth ferrite reinforced aerogel, and then perform curing after vacuum packaging to obtain a modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material with a network structure.

2. The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 1, characterized in that: In step one, the weight ratio of the modified rare earth ferrite, pyrrole, ferric chloride and aramid fiber aqueous solution is (4-8):(2-5):(2-5):(72-92).

3. The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 1, characterized in that: The molar ratio of citric acid to metal ions is 1:1; The calcination process is as follows: the ground precursor powder is placed in a muffle furnace, the temperature is raised at a rate of 5 ℃ / min, precalcination is performed at 450 ℃ for 3 h, and then the temperature is raised at a rate of 5 ℃ / min to 1300 ℃ for 3 h.

4. The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 1, characterized in that: In step one, the method for preparing the aramid fiber aqueous solution is as follows: The calcium chloride, p-phenylenediamine and terephthaloyl chloride are completely dissolved in the nitrogen methyl pyrrolidone, and the reaction is performed under stirring at 150-400 rpm for 3-6 h; water is added to the solution after the reaction and stirred, and then the solution is left to stand and filtered after the stirring is completed; the synthesized aramid fiber aqueous solution is obtained by wrapping the viscous solution with a filter screen. The addition ratio of the calcium chloride, p-phenylenediamine, terephthaloyl chloride, nitrogen methyl pyrrolidone and water is 20 g:3 g:12 g:70 g:1000 ml.

5. The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 1, characterized in that: In step two, the freezing temperature is -20 ℃, and the drying temperature is 60-100 ℃; In step three, the curing method is as follows: after the vacuum packaging is completed, the material is placed in a forced air drying oven, the temperature is set to 80-100 ℃, and the cured modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material is obtained.

6. The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 1, characterized in that: In step three, the method for preparing the heat-conducting filler / polydimethylsiloxane elastomer is as follows: The heat-conducting filler and the A component of the polydimethylsiloxane elastomer are blended, and then the B component of the polydimethylsiloxane elastomer is added, the mixture is stirred twice, and then the heat-conducting filler / polydimethylsiloxane elastomer is obtained by placing the mixture in a vacuum oven for debubbling. 7.The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 6, characterized in that, The mass ratio of the heat-conducting filler, the A component of the polydimethylsiloxane elastomer and the B component of the polydimethylsiloxane elastomer is (20-30) : (35-40) : (35-40). The first stirring time is 20 min and the second stirring time is 20 min. 8.The method for preparing the modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion-resistant multifunctional composite material according to claim 6, characterized in that, The thermally conductive filler is at least one of boron nitride having a density of 2.3 g / cm 3 , aluminum nitride having a density of 3.3 g / cm 3 , silicon carbide having a density of 3.2 g / cm 3 , and aluminum oxide having a density of 4.0 g / cm 3 .

9. A modified rare earth ferrite aerogel-based shielding-heat-conducting-corrosion- resistant multifunctional composite material, characterized in that, Prepared by the method according to any one of claims 1-8.

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