An electromagnetic shielded cable for radio altimeters and its manufacturing method

Abstract

This invention discloses an electromagnetic shielding cable for radio altimeters and its preparation method, relating to the field of cable technology. The preparation method involves treating ethylene-tetrafluoroethylene copolymer particles with a mixed gas containing acrylic acid at low-temperature plasma. After mixing with a compatibilizer, chemical foaming agent, and nano-nucleating agent, the mixture is melt-blended using a twin-screw extruder and injected with supercritical carbon dioxide, followed by slow and rapid cooling to obtain a three-dimensional porous matrix containing micro- and nano-pores. Ferric oxide microparticles are synthesized using a solvothermal method, coated with a silicon dioxide dielectric layer, and then chemically plated with silver to prepare ternary core-shell composite particles. These particles are modified with aminopropyltriethoxysilane and block copolymers to obtain modified composite particles. The porous matrix and modified composite particles are melt-blended and granulated to obtain an electromagnetic shielding composite material. This material is then extruded onto a conductor to form an insulating shielding layer, thus producing the cable. The cable of this invention exhibits excellent electromagnetic shielding performance.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to an electromagnetic shielded cable for radio altimeters and its manufacturing method. Background Technology

[0002] Electromagnetic shielded cables play a crucial role in modern electronic equipment and communication systems, especially in devices such as radio altimeters that have extremely high requirements for the electromagnetic environment. The main function of electromagnetic shielded cables is to effectively shield against external electromagnetic interference, ensuring stable and accurate signal transmission and preventing signal distortion or bit errors caused by external electromagnetic fields.

[0003] Currently, most electromagnetically shielded cables on the market have a multi-layered structure. Generally, from the inside out, they consist of a conductor, an insulation layer, a shielding layer, and a sheath layer. The shielding layer may be composed of various materials such as metal foil (e.g., aluminum foil, copper foil) or metal braided mesh (e.g., tin-plated copper wire braided mesh, aluminum-magnesium alloy wire braided mesh). While this multi-layered structure can achieve good electromagnetic shielding to a certain extent, it also has many drawbacks. For example, the multi-layered structure makes the cable's structural design extremely complex. During manufacturing, it requires the selection of various materials and processing techniques, such as the wrapping of metal foil and the braiding of metal wires, which greatly increases the difficulty and cost of production. At the same time, the multi-layered structure increases the cable's weight and reduces its flexibility. In practical applications, especially in situations with high requirements for cable installation space and flexibility, such as wiring inside aerospace equipment, this can be very restrictive, increasing the difficulty of installation and maintenance. Summary of the Invention

[0004] The purpose of this invention is to provide an electromagnetically shielded cable for radio altimeters and its manufacturing method, thereby solving the technical problem of complex multi-layer cable structures mentioned in the background art. The single-layer electromagnetically shielded cable prepared by this invention has excellent electromagnetic shielding performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for manufacturing an electromagnetically shielded cable for a radio altimeter includes the following steps:

[0007] S1. Ethylene-tetrafluoroethylene copolymer particles are treated with low-temperature plasma. The treatment gas is a mixed gas containing acrylic acid. Then, the treated particles are mixed with compatibilizer, chemical foaming agent and nano nucleating agent, melt-blended by twin-screw extruder, and supercritical carbon dioxide is injected during the extrusion process. After slow cooling and rapid cooling treatment, a three-dimensional porous network structure matrix material containing micro and nano bubbles is obtained.

[0008] S2. Magnetite tetroxide magnetic microparticles were synthesized using a solvothermal method as the core. The core surface was coated with a silicon dioxide dielectric layer. Then, a metallic silver conductive layer was deposited on the dielectric layer surface using a chemical plating method to obtain ternary core-shell composite particles.

[0009] S3. The ternary core-shell composite particles are reacted sequentially with aminopropyltriethoxysilane and block copolymer to modify the particle surface, thereby obtaining modified composite particles with a flexible polymer interface layer grafted on the surface.

[0010] S4. The three-dimensional porous network structure matrix material and modified composite particles are melt-blended and granulated to obtain an electromagnetic shielding composite material.

[0011] S5. The electromagnetic shielding composite material is directly extruded onto the conductor using an extruder to form an insulating shielding layer, thereby obtaining the electromagnetic shielding cable.

[0012] In the technical solution of this invention, a large number of micro- and nano-scale pores are first introduced into the ethylene-tetrafluoroethylene copolymer insulation layer. These pores create an air-ETFE interface. When electromagnetic waves are incident on this structure, repeated reflection, refraction and scattering effects will occur at these heterogeneous interfaces, which greatly prolongs the propagation path of electromagnetic waves inside the material, thereby attenuating and dissipating the electromagnetic wave energy and initially improving the shielding performance of the cable against electromagnetic waves. Then, the ternary core-shell composite particles of Fe3O4@SiO2@Ag are utilized to further dissipate electromagnetic waves by utilizing their magnetic, dielectric, and conductive losses. Specifically, the core Fe3O4 acts as a magnetic component, efficiently dissipating the magnetic field component of the electromagnetic wave through mechanisms such as natural resonance and domain wall resonance, thus providing magnetic loss. The middle SiO2 dielectric layer not only isolates the magnetic core from the conductive silver shell, preventing eddy current effects from causing magnetic loss failure, but also introduces strong interfacial polarization relaxation, as well as the heterogeneous interface formed with the inner and outer layers, thus consuming electromagnetic energy. The outermost continuous silver shell forms a highly conductive network, converting electromagnetic energy into heat energy through ohmic loss. Finally, the core-shell particles were surface-modified with aminopropyltriethoxysilane and a block copolymer (PFP-b-PA6), which solved the problems of easy agglomeration of nanoparticles and weak interfacial bonding with the matrix. The aminopropyltriethoxysilane was anchored to the particle surface through chemical bonding, grafting active amino groups onto it. Subsequently, the PFP-b-PA6 block copolymer utilized its PA6 segment to form strong hydrogen bonds with the amino groups of KH-550, while its PFP segment exhibited excellent compatibility with the ETFE matrix. This "molecular bridge" design ensured the uniform and stable dispersion of functional particles in the matrix, forming a complete and efficient network. Simultaneously, it greatly enhanced the bonding force at the filler-matrix interface, avoiding abrupt changes in wave impedance and performance degradation caused by interfacial defects. This improved the electromagnetic shielding effect of the ternary core-shell composite particles while ensuring the excellent mechanical properties and long-term reliability of the composite material.Figure 1 The image shows a SEM image of the surface of the modified composite particles prepared in this invention. The image shows that the surface of the modified composite particles exhibits a rough morphology.

[0013] Preferably, in step S1, the nanonucleating agent is nano-SiO2 pretreated with KH-550.

[0014] Preferably, the amount of the nanonucleating agent added is 0.5 to 1.5 wt% of the ethylene-tetrafluoroethylene copolymer particles.

[0015] Preferably, in step S3, the mass ratio of the ternary core-shell composite particles to aminopropyltriethoxysilane is 10:0.3-0.8.

[0016] Preferably, in step S3, the ternary core-shell composite particles, after being modified with aminopropyltriethoxysilane, undergo the following reaction:

[0017] The ternary core-shell composite particles modified with aminopropyltriethoxysilane were dispersed in Tris-HCl buffer solution, and then dopamine hydrochloride was added. The reaction was stirred continuously at room temperature. After the reaction was completed, the product was collected by centrifugation and washed with deionized water to obtain the final product.

[0018] In this invention, the research team discovered through in-depth study that the macroscopic impedance gradient characteristics introduced by the porous matrix and the microscopic interface polarization characteristics of the ternary core-shell particles exhibit a mismatch in electromagnetic wave frequency response. Specifically, when electromagnetic waves enter the outermost silver shell of the ternary core-shell particles from the polymer matrix, a significant abrupt change in microscopic interface impedance occurs. This abrupt change causes some electromagnetic waves that have already entered the material to be strongly reflected back at the particle surface, thus affecting the electromagnetic wave consumption effect of the ternary core-shell particles. To further address this problem, this invention further modifies the ternary core-shell composite particles modified with aminopropyltriethoxysilane, constructing a polydopamine dielectric buffer layer on the particle surface. The wave impedance of this layer is intermediate between that of the polymer matrix and the silver shell, thereby achieving a particle-level gradual transition in wave impedance and ensuring that electromagnetic waves can be efficiently and reflectively coupled into the core-shell particles for consumption. In the subsequent reaction, the PA6 segment in PFP-b-PA6 binds to the abundant functional groups of the outermost polydopamine layer through hydrogen bonds, while the PFP segment is perfectly compatible with the ethylene-tetrafluoroethylene copolymer matrix. The presence of the polydopamine layer does not weaken the interfacial bonding; on the contrary, due to its abundant functional groups, it enhances the interaction with the polymer.

[0019] Preferably, the mass ratio of the ternary core-shell composite particles modified with aminopropyltriethoxysilane to dopamine hydrochloride is 10:0.2-0.6.

[0020] Preferably, in step S3, the block copolymer is a PFP-b-PA6 block copolymer.

[0021] Preferably, the method for preparing the PFP-b-PA6 block copolymer includes the following steps:

[0022] S31. Under nitrogen protection, sodium hydride reacts with ε-caprolactam to generate sodium caprolactam, which initiates the polymerization reaction. After cooling, 6-azidohexanoyl chloride is added as a capping agent for end-capping. After the reaction, the product is dissolved in hexafluoroisopropanol, precipitated in cold methanol, washed and dried to obtain the azido-terminated polycaprolactam prepolymer.

[0023] S32. Perfluorononenoxybenzenesulfonyl fluoride was reacted with propyneamine in acetonitrile, N,N-diisopropylethylamine was added, the reaction was concentrated, and the precipitate was precipitated in methanol / water. After washing and drying, a fluorinated alkyne compound was obtained.

[0024] S33. The azido-terminated polycaprolactam prepolymer and the fluorinated alkyne compound were dissolved in DMF, and cuprous bromide and PMDETA were added to carry out the azido-alkyne cycloaddition reaction. The reaction solution was purified by a neutral alumina column, then treated with EDTA aqueous solution or copper removal resin, and finally precipitated in methanol / water and dried to obtain the PFP-b-PA6 block copolymer.

[0025] Preferably, in step S4, the mass ratio of the three-dimensional porous network structure matrix material to the modified composite particles is 80:18-22.

[0026] An electromagnetic shielded cable for a radio altimeter is prepared by the method described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. The single-layer insulation shielding design is simpler than traditional multi-layer cable structures. Furthermore, through the multiple reflection and scattering effects of the three-dimensional porous network matrix, combined with the synergistic effect of the magnetic, dielectric, and conductive losses of the Fe3O4@SiO2@Ag ternary core-shell composite particles, the attenuation and dissipation capability of electromagnetic waves is significantly improved, enhancing the electromagnetic shielding effect.

[0029] 2. By using a polydopamine dielectric buffer layer to achieve a gradual transition in wave impedance, electromagnetic waves are efficiently coupled into the particle interior and consumed, further enhancing electromagnetic shielding performance. Attached Figure Description

[0030] Figure 1 This is a SEM image of the surface of the modified composite particles prepared in this invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] Preparation of PFP-b-PA6 block copolymer:

[0034] Under nitrogen protection, 50 mL of anhydrous THF and 2.0 g of sodium hydride were added to a dry Schlenk flask. The system was cooled in an ice-water bath, and 30 mL of anhydrous THF solution containing 11.3 g of ε-caprolactam was slowly added dropwise. After the addition was complete, the ice bath was removed, the reaction mixture was heated to room temperature and stirred for 2 h until no bubbles were generated, yielding a sodium caprolactam salt suspension. The reaction system was then heated to 80 °C and refluxed for 12 h to carry out anionic ring-opening polymerization. After the reaction was completed, the system was cooled to 0 °C, and 15 mL of anhydrous THF solution containing 1.88 g of 6-chlorohexanoyl chloride was slowly added dropwise through a constant-pressure dropping funnel. After the addition was complete, the reaction mixture was allowed to warm naturally to room temperature and stirred for another 6 h to seal the reaction. Subsequently, an excess of saturated ammonium chloride solution was added to the reaction solution to quench the reaction, the combined organic phases were extracted with dichloromethane, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was redissolved in 30 mL of hexafluoroisopropanol, and then added dropwise to 600 mL of ice-cold methanol under vigorous stirring to induce precipitation. The white precipitate was collected by filtration, washed three times with cold methanol, and dried under vacuum at 40 °C for 24 h to obtain terminal acyl chloride-terminated polycaprolactam. This precipitate was dissolved in 50 mL of DMF, and 1.5 g of sodium azide was added. The mixture was stirred at 50 °C for 12 h. After the reaction was complete, the reaction solution was poured into 600 mL of ice water, and a white solid precipitated. This solid was filtered, washed thoroughly with water, and dried under vacuum at 40 °C to obtain the terminal azido-terminated polycaprolactam prepolymer.

[0035] In a dry round-bottom flask, 5.0 g of perfluorononenoxybenzenesulfonyl fluoride and 100 mL of anhydrous acetonitrile were added and stirred until dissolved. Under nitrogen protection, 1.0 mL of propyneamine and 2.5 mL of N,N-diisopropylethylamine were added sequentially to the system. The reaction mixture was stirred at room temperature in the dark for 24 h. After the reaction was complete, most of the acetonitrile solvent was removed by rotary evaporation. The resulting viscous residue was dissolved in 50 mL of dichloromethane and washed with water and saturated brine. The organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The concentrate was added dropwise to 500 mL of a mixed solution of methanol and water (volume ratio 4:1) under vigorous stirring, resulting in the precipitation of a white solid. The solid was collected by filtration, washed with a cold methanol / water mixture, and dried under vacuum at 40 °C for 24 h to obtain a white solid fluorinated alkyne compound.

[0036] In a nitrogen-filled glove box, 2.0 g of terminal azido-based polycaprolactam prepolymer, 3.15 g of fluorinated alkyne compound, and 40 mL of anhydrous DMF were added sequentially to a dry Schlenk tube. After sealing the tube, it was removed from the glove box and connected to a vacuum line system. The tube was then evacuated and purged with nitrogen three times. Under nitrogen protection, the catalyst system was added sequentially using a syringe: 2 mL of DMF solution containing CuBr (28.7 mg, 0.2 mmol) and 2 mL of DMF solution containing PMDETA (41.8 μL, 0.2 mmol). The reaction system was placed in a 50°C oil bath and stirred vigorously in the dark for 24 h. After the reaction was complete, the reaction solution was passed through a short column containing neutral alumina to remove the copper catalyst and rinsed with DMF. The effluent was collected and poured into 400 mL of ice water containing 0.1 g of disodium EDTA, and stirred for 1 h to further complex residual copper ions. The precipitated polymer was filtered and redissolved in 30 mL of HFIP. This solution was then added dropwise to 600 mL of a vigorously stirred methanol / water (1:1, v / v) mixture to induce precipitation. The white fibrous solid was collected by filtration, washed with methanol, and dried under vacuum at 40 °C to constant weight to obtain the final product, PFP-b-PA6 block copolymer.

[0037] Preparation of nano-SiO2 nucleating agent pretreated with KH-550:

[0038] 100g of nano-SiO2 powder (particle size 20nm) was weighed and dispersed in a mixed solvent of 400mL anhydrous ethanol and 100mL deionized water. The mixture was ultrasonically treated with a power of 600W for 30min to ensure thorough dispersion. Subsequently, 1.5mL of silane coupling agent KH-550 was added to the system, and the mixture was refluxed and condensed at 80℃ with mechanical stirring at 300rpm for 8 hours. After the reaction was completed, the product was collected by centrifugation and washed three times with anhydrous ethanol. Finally, the product was dried in a vacuum drying oven at 80℃ for 12h to obtain the final product.

[0039] Preparation of an electromagnetic shielded cable for a radio altimeter:

[0040] Step 1: Take 500g of ETFE particles and spread them evenly in the sample chamber of the low-temperature plasma processor. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid in a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the pressure inside the chamber at 80 Pa. Treat for 10 minutes at a radio frequency power of 400 W. After completion, remove and set aside. Place the treated ETFE particles with 2% ETFE-g-MAH compatibilizer, 1.5% chemical foaming agent OBSH, and 1.3% KH-550 pretreated nano-SiO2 nucleating agent in a high-speed mixer and mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premixed material is fed into the main feed port of a twin-screw extruder. The temperatures of each zone of the extruder are set to 270℃, 285℃, 295℃, 290℃, and 280℃, and the screw speed is 200 rpm. Simultaneously, supercritical carbon dioxide is injected into the fourth zone of the barrel using a supercritical fluid injection pump, with the injection rate controlled at 0.5 kg / h. After the molten blend is extruded through the die, it is immediately subjected to slow cooling through a 120℃ insulated channel, followed by rapid cooling and shaping in a 20℃ cold water bath. Finally, it is pelletized by a pelletizer to obtain porous ETFE matrix material particles containing micro- and nano-scale pore structures.

[0041] Step 2: Weigh 2.70g of FeCl3·6H2O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20g of anhydrous sodium acetate and 2.00g of polyvinylpyrrolidone sequentially, and continue stirring for 30 min to form a homogeneous yellow solution. Transfer the mixed solution to a hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in a 200℃ drying oven for 10 h. After naturally cooling to room temperature, collect the generated black product using an external magnetic field. Wash it three times alternately with anhydrous ethanol and deionized water, and finally dry it in a 60℃ vacuum drying oven for 12 h to obtain spherical Fe3O4 particles. Take 0.5g of the dried Fe3O4 particles and disperse them in a mixed solution of 200 mL of ethanol and 50 mL of deionized water, and sonicate for 30 min. Subsequently, 5 mL of concentrated ammonia (28 wt%) was added to the solution, and after mechanical stirring for 15 min, 2 mL of tetraethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30 °C for 6 h. After the reaction was completed, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60 °C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 min to obtain a dispersion. Silver ammonia solution was prepared: 2.0 g of silver nitrate was dissolved in 50 mL of water, and concentrated ammonia was added dropwise with stirring until the initially formed brown precipitate just dissolved, resulting in a clear silver ammonia solution. The silver ammonia solution was mixed with the Fe3O4@SiO2 dispersion, heated to 60 °C in a water bath with continuous stirring, and then the pH of the system was adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-sodium potassium tartrate mixed solution was quickly added, and the reaction was carried out at 60 °C for 40 min. After observing that the solution turned grayish-black, heating was stopped, the product was magnetically separated, thoroughly washed with deionized water and ethanol, and vacuum dried at 60℃ to finally obtain Fe3O4@SiO2@Ag composite powder.

[0042] Step 3: Take 20g of Fe3O4@SiO2@Ag composite powder and disperse it in 400 mL of a mixed solvent of ethanol / water (volume ratio 4:1). Sonicate the mixture for 1 h to ensure complete dispersion. Add 1.4g of KH-550 silane coupling agent to the system and reflux and stir at 80℃ for 8 h. After the reaction is complete, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry under vacuum at 60℃.

[0043] 50g of KH-550-modified particles were dispersed in 500mL of Tris-HCl buffer solution at pH 8.5, and then 2.5g of dopamine hydrochloride was added. The mixture was stirred continuously at room temperature for 10h. After the reaction was completed, the product was collected by centrifugation and washed repeatedly with deionized water until the supernatant was colorless. The supernatant was then dried under vacuum at 60℃.

[0044] The polydopamine-modified particles were co-dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 min. The mixture was then mechanically stirred at 80 °C for 6 h, followed by heating to 100 °C and using a rotary evaporator to slowly remove the DMF solvent under reduced pressure. The resulting solid product was further dried in a vacuum oven at 80 °C for 12 h to completely remove residual solvent, ultimately yielding modified composite particles coated with a flexible polymer interface layer.

[0045] Step 4: Mix porous ETFE matrix particles and modified composite particles at a mass ratio of 80:21, place in an internal mixer, and perform solid-state shear mixing at 265℃ and 30 rpm for 5 minutes. Feed the premix into a twin-screw extruder for melt blending and granulation, setting the temperature to 285℃ and the screw speed to 150 rpm, to obtain electromagnetic shielding composite material particles.

[0046] Step 5: The electromagnetic shielding composite material particles are directly extruded onto silver-plated copper core wire (conductor diameter 0.5mm) using a single-screw extruder to form an insulating shielding layer. The extruder temperature is set to 285℃, and the extrusion speed is 2m / min, ensuring that the layer thickness is uniformly controlled at 0.3mm. The extruded cable is then cooled in a water-cooling bath and annealed at 100℃ for 2 hours to eliminate internal stress, thus obtaining the final product.

[0047] Example 2

[0048] The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as in Example 1.

[0049] Preparation of an electromagnetic shielded cable for a radio altimeter:

[0050] Step 1: Take 500g of ETFE particles and spread them evenly in the sample chamber of the low-temperature plasma processor. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid in a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the pressure inside the chamber at 80 Pa. Treat for 10 minutes at a radio frequency power of 400 W. After completion, remove and set aside. Place the treated ETFE particles with 2% ETFE-g-MAH compatibilizer, 1.5% chemical foaming agent OBSH, and 0.8% nano-SiO2 nucleating agent pretreated with KH-550 in a high-speed mixer and mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premixed material is fed into the main feed port of a twin-screw extruder. The temperatures of each zone of the extruder are set to 270℃, 285℃, 295℃, 290℃, and 280℃, and the screw speed is 200 rpm. Simultaneously, supercritical carbon dioxide is injected into the fourth zone of the barrel using a supercritical fluid injection pump, with the injection rate controlled at 0.5 kg / h. After the molten blend is extruded through the die, it is immediately subjected to slow cooling through a 120℃ insulated channel, followed by rapid cooling and shaping in a 20℃ cold water bath. Finally, it is pelletized by a pelletizer to obtain porous ETFE matrix material particles containing micro- and nano-scale pore structures.

[0051] Step 2: Weigh 2.70g of FeCl3·6H2O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20g of anhydrous sodium acetate and 2.00g of polyvinylpyrrolidone sequentially, and continue stirring for 30 min to form a homogeneous yellow solution. Transfer the mixed solution to a hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in a 200℃ drying oven for 10 h. After naturally cooling to room temperature, collect the generated black product using an external magnetic field. Wash it three times alternately with anhydrous ethanol and deionized water, and finally dry it in a 60℃ vacuum drying oven for 12 h to obtain spherical Fe3O4 particles. Take 0.5g of the dried Fe3O4 particles and disperse them in a mixed solution of 200 mL of ethanol and 50 mL of deionized water, and sonicate for 30 min. Subsequently, 5 mL of concentrated ammonia (28 wt%) was added to the solution, and after mechanical stirring for 15 min, 2 mL of tetraethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30 °C for 6 h. After the reaction was completed, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60 °C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 min to obtain a dispersion. Silver ammonia solution was prepared: 2.0 g of silver nitrate was dissolved in 50 mL of water, and concentrated ammonia was added dropwise with stirring until the initially formed brown precipitate just dissolved, resulting in a clear silver ammonia solution. The silver ammonia solution was mixed with the Fe3O4@SiO2 dispersion, heated to 60 °C in a water bath with continuous stirring, and then the pH of the system was adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-sodium potassium tartrate mixed solution was quickly added, and the reaction was carried out at 60 °C for 40 min. After observing that the solution turned grayish-black, heating was stopped, the product was magnetically separated, thoroughly washed with deionized water and ethanol, and vacuum dried at 60℃ to finally obtain Fe3O4@SiO2@Ag composite powder.

[0052] Step 3: Take 20g of Fe3O4@SiO2@Ag composite powder and disperse it in 400 mL of a mixed solvent of ethanol / water (volume ratio 4:1). Sonicate the mixture for 1 h to ensure complete dispersion. Add 0.8g of KH-550 silane coupling agent to the system and reflux and stir at 80℃ for 8 h. After the reaction is complete, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry under vacuum at 60℃.

[0053] 50g of KH-550-modified particles were dispersed in 500mL of Tris-HCl buffer solution at pH 8.5, and then 1.5g of dopamine hydrochloride was added. The mixture was stirred continuously at room temperature for 10h. After the reaction was complete, the product was collected by centrifugation and washed repeatedly with deionized water until the supernatant was colorless. The supernatant was then dried under vacuum at 60℃.

[0054] The polydopamine-modified particles were co-dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 min. The mixture was then mechanically stirred at 80 °C for 6 h, followed by heating to 100 °C and using a rotary evaporator to slowly remove the DMF solvent under reduced pressure. The resulting solid product was further dried in a vacuum oven at 80 °C for 12 h to completely remove residual solvent, ultimately yielding modified composite particles coated with a flexible polymer interface layer.

[0055] Step 4: Mix porous ETFE matrix particles and modified composite particles at a mass ratio of 80:19, place in an internal mixer, and perform solid-state shear mixing at 265℃ and 30 rpm for 5 minutes. Feed the premix into a twin-screw extruder for melt blending and granulation, setting the temperature to 285℃ and the screw speed to 150 rpm, to obtain electromagnetic shielding composite material particles.

[0056] Step 5: The electromagnetic shielding composite material particles are directly extruded onto silver-plated copper core wire (conductor diameter 0.5mm) using a single-screw extruder to form an insulating shielding layer. The extruder temperature is set to 285℃, and the extrusion speed is 2m / min, ensuring that the layer thickness is uniformly controlled at 0.3mm. The extruded cable is then cooled in a water-cooling bath and annealed at 100℃ for 2 hours to eliminate internal stress, thus obtaining the final product.

[0057] Example 3

[0058] The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as in Example 1.

[0059] Preparation of an electromagnetic shielded cable for a radio altimeter:

[0060] Step 1: Take 500g of ETFE particles and spread them evenly in the sample chamber of the low-temperature plasma processor. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid in a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the pressure inside the chamber at 80 Pa. Treat for 10 minutes at a radio frequency power of 400 W. After completion, remove and set aside. Place the treated ETFE particles with 2% ETFE-g-MAH compatibilizer, 1.5% chemical foaming agent OBSH, and 1.0% nano-SiO2 nucleating agent pretreated with KH-550 in a high-speed mixer and mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premixed material is fed into the main feed port of a twin-screw extruder. The temperatures of each zone of the extruder are set to 270℃, 285℃, 295℃, 290℃, and 280℃, and the screw speed is 200 rpm. Simultaneously, supercritical carbon dioxide is injected into the fourth zone of the barrel using a supercritical fluid injection pump, with the injection rate controlled at 0.5 kg / h. After the molten blend is extruded through the die, it is immediately subjected to slow cooling through a 120℃ insulated channel, followed by rapid cooling and shaping in a 20℃ cold water bath. Finally, it is pelletized by a pelletizer to obtain porous ETFE matrix material particles containing micro- and nano-scale pore structures.

[0061] Step 2: Weigh 2.70g of FeCl3·6H2O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20g of anhydrous sodium acetate and 2.00g of polyvinylpyrrolidone sequentially, and continue stirring for 30 min to form a homogeneous yellow solution. Transfer the mixed solution to a hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in a 200℃ drying oven for 10 h. After naturally cooling to room temperature, collect the generated black product using an external magnetic field. Wash it three times alternately with anhydrous ethanol and deionized water, and finally dry it in a 60℃ vacuum drying oven for 12 h to obtain spherical Fe3O4 particles. Take 0.5g of the dried Fe3O4 particles and disperse them in a mixed solution of 200 mL of ethanol and 50 mL of deionized water, and sonicate for 30 min. Subsequently, 5 mL of concentrated ammonia (28 wt%) was added to the solution, and after mechanical stirring for 15 min, 2 mL of tetraethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30 °C for 6 h. After the reaction was completed, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60 °C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 min to obtain a dispersion. Silver ammonia solution was prepared: 2.0 g of silver nitrate was dissolved in 50 mL of water, and concentrated ammonia was added dropwise with stirring until the initially formed brown precipitate just dissolved, resulting in a clear silver ammonia solution. The silver ammonia solution was mixed with the Fe3O4@SiO2 dispersion, heated to 60 °C in a water bath with continuous stirring, and then the pH of the system was adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-sodium potassium tartrate mixed solution was quickly added, and the reaction was carried out at 60 °C for 40 min. After observing that the solution turned grayish-black, heating was stopped, the product was magnetically separated, thoroughly washed with deionized water and ethanol, and vacuum dried at 60℃ to finally obtain Fe3O4@SiO2@Ag composite powder.

[0062] Step 3: Take 20g of Fe3O4@SiO2@Ag composite powder and disperse it in 400 mL of a mixed solvent of ethanol / water (volume ratio 4:1). Sonicate the mixture for 1 h to ensure complete dispersion. Add 1.0g of KH-550 silane coupling agent to the system and reflux and stir at 80℃ for 8 h. After the reaction is complete, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry under vacuum at 60℃.

[0063] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer solution at pH 8.5, and then 2.0 g of dopamine hydrochloride was added. The mixture was stirred continuously at room temperature for 10 h. After the reaction was complete, the product was collected by centrifugation and washed repeatedly with deionized water until the supernatant was colorless. The supernatant was then dried under vacuum at 60 °C.

[0064] The polydopamine-modified particles were co-dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 min. The mixture was then mechanically stirred at 80 °C for 6 h, followed by heating to 100 °C and using a rotary evaporator to slowly remove the DMF solvent under reduced pressure. The resulting solid product was further dried in a vacuum oven at 80 °C for 12 h to completely remove residual solvent, ultimately yielding modified composite particles coated with a flexible polymer interface layer.

[0065] Step 4: Mix porous ETFE matrix particles and modified composite particles at a mass ratio of 80:20, place in an internal mixer, and perform solid-state shear mixing at 265℃ and 30 rpm for 5 minutes. Feed the premix into a twin-screw extruder for melt blending and granulation, setting the temperature to 285℃ and the screw speed to 150 rpm, to obtain electromagnetic shielding composite material particles.

[0066] Step 5: The electromagnetic shielding composite material particles are directly extruded onto silver-plated copper core wire (conductor diameter 0.5mm) using a single-screw extruder to form an insulating shielding layer. The extruder temperature is set to 285℃, and the extrusion speed is 2m / min, ensuring that the layer thickness is uniformly controlled at 0.3mm. The extruded cable is then cooled in a water-cooling bath and annealed at 100℃ for 2 hours to eliminate internal stress, thus obtaining the final product.

[0067] Example 4

[0068] The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as in Example 1.

[0069] Preparation of an electromagnetic shielded cable for a radio altimeter:

[0070] Step 1: Take 500g of ETFE particles and spread them evenly in the sample chamber of the low-temperature plasma processor. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid in a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the pressure inside the chamber at 80 Pa. Treat for 10 minutes at a radio frequency power of 400 W. After completion, remove and set aside. Place the treated ETFE particles with 2% ETFE-g-MAH compatibilizer, 1.5% chemical foaming agent OBSH, and 1.5% nano-SiO2 nucleating agent pretreated with KH-550 in a high-speed mixer and mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premixed material is fed into the main feed port of a twin-screw extruder. The temperatures of each zone of the extruder are set to 270℃, 285℃, 295℃, 290℃, and 280℃, and the screw speed is 200 rpm. Simultaneously, supercritical carbon dioxide is injected into the fourth zone of the barrel using a supercritical fluid injection pump, with the injection rate controlled at 0.5 kg / h. After the molten blend is extruded through the die, it is immediately subjected to slow cooling through a 120℃ insulated channel, followed by rapid cooling and shaping in a 20℃ cold water bath. Finally, it is pelletized by a pelletizer to obtain porous ETFE matrix material particles containing micro- and nano-scale pore structures.

[0071] Step 2: Weigh 2.70g of FeCl3·6H2O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20g of anhydrous sodium acetate and 2.00g of polyvinylpyrrolidone sequentially, and continue stirring for 30 min to form a homogeneous yellow solution. Transfer the mixed solution to a hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in a 200℃ drying oven for 10 h. After naturally cooling to room temperature, collect the generated black product using an external magnetic field. Wash it three times alternately with anhydrous ethanol and deionized water, and finally dry it in a 60℃ vacuum drying oven for 12 h to obtain spherical Fe3O4 particles. Take 0.5g of the dried Fe3O4 particles and disperse them in a mixed solution of 200 mL of ethanol and 50 mL of deionized water, and sonicate for 30 min. Subsequently, 5 mL of concentrated ammonia (28 wt%) was added to the solution, and after mechanical stirring for 15 min, 2 mL of tetraethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30 °C for 6 h. After the reaction was completed, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60 °C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 min to obtain a dispersion. Silver ammonia solution was prepared: 2.0 g of silver nitrate was dissolved in 50 mL of water, and concentrated ammonia was added dropwise with stirring until the initially formed brown precipitate just dissolved, resulting in a clear silver ammonia solution. The silver ammonia solution was mixed with the Fe3O4@SiO2 dispersion, heated to 60 °C in a water bath with continuous stirring, and then the pH of the system was adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-sodium potassium tartrate mixed solution was quickly added, and the reaction was carried out at 60 °C for 40 min. After observing that the solution turned grayish-black, heating was stopped, the product was magnetically separated, thoroughly washed with deionized water and ethanol, and vacuum dried at 60℃ to finally obtain Fe3O4@SiO2@Ag composite powder.

[0072] Step 3: Take 20g of Fe3O4@SiO2@Ag composite powder and disperse it in 400 mL of a mixed solvent of ethanol / water (volume ratio 4:1). Sonicate the mixture for 1 h to ensure complete dispersion. Add 1.6g of KH-550 silane coupling agent to the system and reflux and stir at 80℃ for 8 h. After the reaction is complete, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry under vacuum at 60℃.

[0073] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer solution at pH 8.5, and then 3.0 g of dopamine hydrochloride was added. The mixture was stirred continuously at room temperature for 10 h. After the reaction was complete, the product was collected by centrifugation and washed repeatedly with deionized water until the supernatant was colorless. The supernatant was then dried under vacuum at 60 °C.

[0074] The polydopamine-modified particles were co-dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 min. The mixture was then mechanically stirred at 80 °C for 6 h, followed by heating to 100 °C and using a rotary evaporator to slowly remove the DMF solvent under reduced pressure. The resulting solid product was further dried in a vacuum oven at 80 °C for 12 h to completely remove residual solvent, ultimately yielding modified composite particles coated with a flexible polymer interface layer.

[0075] Step 4: Mix porous ETFE matrix particles and modified composite particles at a mass ratio of 80:22, place in an internal mixer, and perform solid-state shear mixing at 265℃ and 30 rpm for 5 minutes. Feed the premix into a twin-screw extruder for melt blending and granulation, setting the temperature to 285℃ and the screw speed to 150 rpm, to obtain electromagnetic shielding composite material particles.

[0076] Step 5: The electromagnetic shielding composite material particles are directly extruded onto silver-plated copper core wire (conductor diameter 0.5mm) using a single-screw extruder to form an insulating shielding layer. The extruder temperature is set to 285℃, and the extrusion speed is 2m / min, ensuring that the layer thickness is uniformly controlled at 0.3mm. The extruded cable is then cooled in a water-cooling bath and annealed at 100℃ for 2 hours to eliminate internal stress, thus obtaining the final product.

[0077] Example 5

[0078] The preparation method of PFP-b-PA6 block copolymer and KH-550 pretreated nano-SiO2 nucleating agent is the same as in Example 1.

[0079] Preparation of an electromagnetic shielded cable for a radio altimeter:

[0080] Step 1: Take 500g of ETFE particles and spread them evenly in the sample chamber of the low-temperature plasma processor. After sealing, evacuate the system to a pressure of 80 Pa. Use a mixture of argon and acrylic acid in a volume ratio of 9:1 as the treatment gas. Adjust the gas flow rate to stabilize the pressure inside the chamber at 80 Pa. Treat for 10 minutes at a radio frequency power of 400 W. After completion, remove and set aside. Place the treated ETFE particles with 2% ETFE-g-MAH compatibilizer, 1.5% chemical foaming agent OBSH, and 0.5% KH-550 pretreated nano-SiO2 nucleating agent in a high-speed mixer and mix at 800 rpm for 5 minutes at room temperature to obtain a premix. The premixed material is fed into the main feed port of a twin-screw extruder. The temperatures of each zone of the extruder are set to 270℃, 285℃, 295℃, 290℃, and 280℃, and the screw speed is 200 rpm. Simultaneously, supercritical carbon dioxide is injected into the fourth zone of the barrel using a supercritical fluid injection pump, with the injection rate controlled at 0.5 kg / h. After the molten blend is extruded through the die, it is immediately subjected to slow cooling through a 120℃ insulated channel, followed by rapid cooling and shaping in a 20℃ cold water bath. Finally, it is pelletized by a pelletizer to obtain porous ETFE matrix material particles containing micro- and nano-scale pore structures.

[0081] Step 2: Weigh 2.70g of FeCl3·6H2O and dissolve it in 80 mL of ethylene glycol. Stir magnetically until completely dissolved. Then, add 7.20g of anhydrous sodium acetate and 2.00g of polyvinylpyrrolidone sequentially, and continue stirring for 30 min to form a homogeneous yellow solution. Transfer the mixed solution to a hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in a 200℃ drying oven for 10 h. After naturally cooling to room temperature, collect the generated black product using an external magnetic field. Wash it three times alternately with anhydrous ethanol and deionized water, and finally dry it in a 60℃ vacuum drying oven for 12 h to obtain spherical Fe3O4 particles. Take 0.5g of the dried Fe3O4 particles and disperse them in a mixed solution of 200 mL of ethanol and 50 mL of deionized water, and sonicate for 30 min. Subsequently, 5 mL of concentrated ammonia (28 wt%) was added to the solution, and after mechanical stirring for 15 min, 2 mL of tetraethyl orthosilicate was slowly added dropwise using a constant pressure dropping funnel. The reaction was continued at 30 °C for 6 h. After the reaction was completed, the product was magnetically separated, washed three times with ethanol, and dried under vacuum at 60 °C to obtain Fe3O4@SiO2 powder. 0.5 g of Fe3O4@SiO2 powder was dispersed in 100 mL of deionized water and sonicated for 30 min to obtain a dispersion. Silver ammonia solution was prepared: 2.0 g of silver nitrate was dissolved in 50 mL of water, and concentrated ammonia was added dropwise with stirring until the initially formed brown precipitate just dissolved, resulting in a clear silver ammonia solution. The silver ammonia solution was mixed with the Fe3O4@SiO2 dispersion, heated to 60 °C in a water bath with continuous stirring, and then the pH of the system was adjusted to 11 with NaOH solution. 20 mL of a 0.4 mol / L glucose-sodium potassium tartrate mixed solution was quickly added, and the reaction was carried out at 60 °C for 40 min. After observing that the solution turned grayish-black, heating was stopped, the product was magnetically separated, thoroughly washed with deionized water and ethanol, and vacuum dried at 60℃ to finally obtain Fe3O4@SiO2@Ag composite powder.

[0082] Step 3: Take 20g of Fe3O4@SiO2@Ag composite powder and disperse it in 400 mL of a mixed solvent of ethanol / water (volume ratio 4:1). Sonicate the mixture for 1 h to ensure complete dispersion. Add 0.6g of KH-550 silane coupling agent to the system and reflux and stir at 80℃ for 8 h. After the reaction is complete, collect the product by centrifugation, wash three times with ethanol to remove physically adsorbed coupling agent, and dry under vacuum at 60℃.

[0083] 50 g of KH-550-modified particles were dispersed in 500 mL of Tris-HCl buffer solution at pH 8.5, and then 1.0 g of dopamine hydrochloride was added. The mixture was stirred continuously at room temperature for 10 h. After the reaction was complete, the product was collected by centrifugation and washed repeatedly with deionized water until the supernatant was colorless. The supernatant was then dried under vacuum at 60 °C.

[0084] The polydopamine-modified particles were co-dispersed with 4.0 g of PFP-b-PA6 block copolymer in 200 mL of DMF and sonicated for 30 min. The mixture was then mechanically stirred at 80 °C for 6 h, followed by heating to 100 °C and using a rotary evaporator to slowly remove the DMF solvent under reduced pressure. The resulting solid product was further dried in a vacuum oven at 80 °C for 12 h to completely remove residual solvent, ultimately yielding modified composite particles coated with a flexible polymer interface layer.

[0085] Step 4: Mix porous ETFE matrix particles and modified composite particles at a mass ratio of 80:18, place in an internal mixer, and perform solid-state shear mixing at 265℃ and 30 rpm for 5 minutes. Feed the premix into a twin-screw extruder for melt blending and granulation, setting the temperature to 285℃ and the screw speed to 150 rpm, to obtain electromagnetic shielding composite material particles.

[0086] Step 5: The electromagnetic shielding composite material particles are directly extruded onto silver-plated copper core wire (conductor diameter 0.5mm) using a single-screw extruder to form an insulating shielding layer. The extruder temperature is set to 285℃, and the extrusion speed is 2m / min, ensuring that the layer thickness is uniformly controlled at 0.3mm. The extruded cable is then cooled in a water-cooling bath and annealed at 100℃ for 2 hours to eliminate internal stress, thus obtaining the final product.

[0087] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 1 is omitted, that is, the porous ETFE matrix particles in step 4 are replaced with ordinary ETFE matrix particles.

[0088] Comparative Example 2: The difference between Comparative Example 1 and Example 1 is that steps 2 and 3 are omitted, that is, the modified composite particles in step 4 are removed.

[0089] Comparative Example 3: The difference between Comparative Example 1 and Example 1 is that step 3 is omitted, that is, the modified composite particles in step 4 are replaced with Fe3O4@SiO2@Ag composite powder.

[0090] Comparative Example 4: The difference between Comparative Example 1 and Example 1 is that in step 3, the particles modified with KH-550 do not react with dopamine hydrochloride, but react directly with PFP-b-PA6 block copolymer.

[0091] Performance testing:

[0092] 1. Electromagnetic Shielding Performance Test: Based on the electromagnetic shielding effectiveness test standard in QB / T 18313-2022 "Copper Tape for Cable Shielding," and considering the actual operating frequency band of the radio altimeter (1.2GHz~1.6GHz, L-band), the "coaxial transmission line method" was used for testing. Cable samples prepared in each embodiment and comparative example were cut into 100mm long standard specimens, with coaxial connectors at both ends, and fixed in the shielding effectiveness test system (including a signal generator, spectrum analyzer, and coaxial test fixture). The signal generator output power was set to 10dBm, and the "incident signal strength (E0) without shielding" and the "transmitted signal strength (E0) after cable shielding" were measured at three characteristic frequency points: 1.2GHz, 1.4GHz, and 1.6GHz. i According to the formula SE=20lg(E0 / E), i The shielding effectiveness was calculated, and the average value at three frequency points was taken as the final result, expressed in dB (decibels). A higher value indicates a better shielding effect. The test results are shown in Table 1.

[0093] 2. Bending Performance Test: Referring to the bending performance test method in GB / T 14049-2008 "Overhead Insulated Cables with Rated Voltage of 10kV and Below", and considering the actual installation scenario of radio altimeter cables, complete cable samples were tested. A 1m long cable sample was cut, and a bending tester was used. The bending radius was set to 5 times the cable's outer diameter, and "reciprocating bending" was performed at a rate of 10 times / min (bending 90° to one side from the initial position, then returning to the initial position, and bending 90° to the other side is considered one complete bend). After a total of 100 bends, the insulation shielding layer was observed for cracks, peeling, or other damage. Simultaneously, the electromagnetic shielding effectiveness of the bent cable at a frequency of 1.4GHz was tested, and the rate of change of shielding effectiveness before and after bending was calculated: ΔSE = (SE after bending - SE before bending) / SE before bending × 100%. The smaller the rate of change, the better the cable's bending reliability. The test results are shown in Table 1.

[0094] Table 1:

[0095]

[0096] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing an electromagnetically shielded cable for a radio altimeter, characterized in that, Includes the following steps: S1. Ethylene-tetrafluoroethylene copolymer particles are treated with low-temperature plasma in a mixture of argon and acrylic acid. The treated particles are then mixed with compatibilizer, chemical foaming agent and nano nucleating agent, melt-blended by twin-screw extruder, and supercritical carbon dioxide is injected during the extrusion process. After slow cooling and rapid cooling, a three-dimensional porous network structure matrix material containing micro and nano bubbles is obtained. S2. Magnetite tetroxide magnetic microparticles were synthesized using a solvothermal method as the core. The core surface was coated with a silicon dioxide dielectric layer. Then, a metallic silver conductive layer was deposited on the dielectric layer surface using a chemical plating method to obtain ternary core-shell composite particles. S3. The ternary core-shell composite particles are reacted sequentially with aminopropyltriethoxysilane and block copolymer to modify the particle surface, thereby obtaining modified composite particles with a flexible polymer interface layer grafted on the surface. The block copolymer is a PFP-b-PA6 block copolymer, and its preparation method is as follows: S31. Under nitrogen protection, sodium hydride reacts with ε-caprolactam to generate sodium caprolactam, which initiates the polymerization reaction. After cooling, 6-azidohexanoyl chloride is added as a capping agent for end-capping. After the reaction, the product is dissolved in hexafluoroisopropanol, precipitated in cold methanol, washed and dried to obtain the azido-terminated polycaprolactam prepolymer. S32. Perfluorononenoxybenzenesulfonyl fluoride was reacted with propyneamine in acetonitrile, N,N-diisopropylethylamine was added, the reaction was concentrated, and the precipitate was obtained in a mixed solution of methanol and water. After washing and drying, a fluorinated alkyne compound was obtained. S33. The azido-terminated polycaprolactam prepolymer and the fluorinated alkyne compound were dissolved in DMF, and cuprous bromide and PMDETA were added to carry out the azido-alkyne cycloaddition reaction. The reaction solution was purified by a neutral alumina column, then treated with EDTA aqueous solution or copper removal resin, and finally precipitated in a mixed solution of methanol and water. After drying, PFP-b-PA6 block copolymer was obtained. S4. The three-dimensional porous network structure matrix material and modified composite particles are melt-blended and granulated to obtain an electromagnetic shielding composite material. S5. The electromagnetic shielding composite material is directly extruded onto the conductor using an extruder to form an insulating shielding layer, thereby obtaining the electromagnetic shielding cable.

2. The method for preparing an electromagnetic shielded cable for a radio altimeter according to claim 1, characterized in that, In step S1, the nanonucleating agent is nano-SiO2 pretreated with KH-550.

3. The method for preparing an electromagnetic shielded cable for a radio altimeter according to claim 2, characterized in that, The amount of the nanonucleating agent added is (0.5~1.5) wt% of the ethylene-tetrafluoroethylene copolymer particles.

4. The method for preparing an electromagnetic shielded cable for a radio altimeter according to claim 1, characterized in that, In step S3, the mass ratio of the ternary core-shell composite particles to aminopropyltriethoxysilane is 10:(0.3-0.8).

5. The method for preparing an electromagnetic shielded cable for a radio altimeter according to claim 1, characterized in that, In step S3, the ternary core-shell composite particles, after being modified with aminopropyltriethoxysilane, undergo the following reaction: The ternary core-shell composite particles modified with aminopropyltriethoxysilane were dispersed in Tris-HCl buffer solution, and then dopamine hydrochloride was added. The reaction was stirred continuously at room temperature. After the reaction was completed, the product was collected by centrifugation and washed with deionized water to obtain the final product.

6. The method for preparing an electromagnetic shielded cable for a radio altimeter according to claim 5, characterized in that, The mass ratio of the ternary core-shell composite particles modified with aminopropyltriethoxysilane to dopamine hydrochloride is 10:(0.2-0.6).

7. The method for preparing an electromagnetic shielded cable for a radio altimeter according to claim 1, characterized in that, In step S4, the mass ratio of the three-dimensional porous network structure matrix material to the modified composite particles is 80:(18-22).

8. An electromagnetically shielded cable for a radio altimeter, characterized in that, It is prepared by the method described in any one of claims 1-7.

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