Insulation shielding material based on FLG (at) Ag-QDs core-shell structure quantum filler and preparation method thereof

Abstract

The invention relates to the technical field of electromagnetic shielding materials, and provides an insulation shielding material based on FLG (at) Ag-QDs core-shell structure quantum filler and a preparation method thereof.The preparation method comprises the steps that few-layer graphene is prepared through pulse plasma discharge, modification sites are constructed on the edge of the few-layer graphene through plasma modification, and the graphene is prepared; and inducing in-situ growth of metal quantum dots at the modification sites through laser irradiation, coating the metal quantum dots through atomic layer deposition, and blending and molding the formed FLG (at) Ag-QDs core-shell structure quantum filler and a polymer matrix. According to the insulation shielding material based on the FLG (at) Ag-QDs core-shell structure quantum filler and the preparation method of the insulation shielding material, the high-frequency electromagnetic shielding performance can be improved, the insulation performance and the conductivity can be synergistically optimized, the dispersity and the interface bonding strength of the filler can be enhanced, excellent mechanical performance and flexibility can be kept, and the performance stability and reliability can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding materials, and in particular to an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler and a preparation method thereof. Background Art

[0002] With the rapid development of 5G communication technology, high-voltage direct current transmission systems, aerospace and other fields, higher technical requirements are placed on the electromagnetic shielding performance of power cables.

[0003] Currently widely used cable shielding materials suffer from the following major technical limitations: First, they suffer from significant deficiencies in shielding performance. Traditional metal braided shielding layers experience a significant attenuation of shielding effectiveness by over 30% when operating in high-frequency bands (above 10 GHz) due to the skin effect. While conductive carbon black-filled polymer composites can achieve a certain shielding effect, they require a high filler content of over 20% to achieve a shielding effectiveness of 30 dB, which significantly impacts the material's mechanical properties. Second, they face significant challenges in balancing material properties. High levels of conductive fillers can cause the elongation at break of the cross-linked polyethylene matrix to drop by over 50%, severely impacting the cable's flexibility and service life. Furthermore, uneven filler dispersion can cause localized abrupt changes in the material's dielectric properties, resulting in uneven electric field distribution within the insulation layer (with an inhomogeneity coefficient η > 1.8), significantly increasing the risk of electrical treeing.

[0004] The use of graphene to modify cross-linked polyethylene is a hot topic in the field. The current technical solution of using graphene to enhance cross-linked polyethylene faces four key technical challenges: The first is the dispersion problem. Due to the strong van der Waals force (about 2eV / nm) between graphene sheets, 2 ), which is prone to agglomeration in conventional melt blending processes. Even with strong shearing processes such as twin-screw extrusion, only a dispersion level of 500nm can be achieved, making it difficult to form an effective continuous conductive network.

[0005] The second is the interface compatibility problem. The inert sp 2 The interfacial binding energy between the carbon structure and the non-polar molecular chains of cross-linked polyethylene is low (less than 0.05 J / m 2 ), this weak interfacial interaction can cause the tensile strength of the composite material to drop by more than 15%. At the same time, graphene can also quench free radicals during the cross-linking process, reducing the gel content of the material by 20%.

[0006] The third problem is the performance synergy. Graphene needs to meet three mutually restrictive performance requirements at the same time: as a conductive medium, the conductivity must be more than 10 -3S / cm; as a dielectric regulating material, the dielectric constant needs to be maintained between 4-6; at the same time, the insulation performance of the matrix must be guaranteed, and the volume resistivity must be greater than 10 12 Ω·cm. It is difficult to achieve balanced optimization of these properties through traditional composite processes.

[0007] Fourth, there's the issue of process feasibility. Existing solution blending methods require the use of toxic solvents like xylene, while in-situ polymerization methods require temperatures exceeding 200°C. These requirements clearly conflict with the actual conditions of industrial cable production lines (processing temperatures of 150-180°C and residence times of less than 3 minutes).

[0008] A Chinese patent with publication number CN118165392B discloses an insulating material, its preparation method, and application. The technical approach of this solution is to reduce conductivity, inhibit space charge accumulation, and improve insulation through the band confinement effect of core-shell quantum dots. It cannot balance the conductive and insulating properties, which is contrary to the performance design of semi-conductive insulating materials.

[0009] Therefore, how to overcome the shortcomings of existing technologies and optimize the performance of semi-conductive shielding materials through graphene has become a technical problem that needs to be solved urgently. Summary of the Invention

[0010] In view of this, in order to overcome the deficiencies of the prior art, the present invention aims to provide an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler and a preparation method thereof.

[0011] According to a first aspect of the present invention, a method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler is provided, the method comprising: preparing few-layer graphene by pulsed plasma discharge, constructing modified sites at the edges of the few-layer graphene by plasma modification, inducing in situ growth of metal quantum dots at the modified sites by laser irradiation, coating the metal quantum dots by atomic layer deposition, and blending the formed FLG@Ag-QDs core-shell structure quantum filler with a polymer matrix.

[0012] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, the few-layer graphene is prepared in the following manner: using a microwave plasma enhanced chemical vapor deposition system, with a CH4 / H2 mixed gas with a volume ratio of 1:9 as a precursor, by pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30%, to prepare 3-5 layers of few-layer graphene, wherein the reaction temperature is 650°C, the microwave power is 800W, and the reaction pressure is 20Pa.

[0013] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, modified sites are constructed at the edge of the few-layer graphene by plasma modification, including: using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, plasma treating the few-layer graphene at a power of 300W for 5 minutes, and constructing modified sites by introducing carboxyl groups and epoxy groups at the edge of the graphene lattice.

[0014] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, metal quantum dots are induced to grow in situ at the modified sites by laser irradiation, including: preparing an induction solution using silver nitrate and sodium citrate, wherein the concentration of silver nitrate in the induction solution is 0.1 mol / L and the concentration of sodium citrate is 0.05 mol / L, dispersing 0.5-1.2 parts by weight of few-layer graphene with modified sites in 800 parts by weight of the induction solution, and growing silver quantum dots on the modified sites by dual-beam laser irradiation.

[0015] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, the wavelengths of the dual-beam laser are 532nm and 1064nm respectively, the power ratio of the 532nm laser to the 1064nm laser is 1:2, and the irradiation power density is 50W / cm 2 , the irradiation time is 30min.

[0016] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, the metal quantum dots are coated by atomic layer deposition, including: using trimethylaluminum and deionized water as precursors, performing 10-25 deposition cycles at a temperature of 155°C, and coating the metal quantum dots with multiple layers of alumina to obtain the FLG@Ag-QDs core-shell structure quantum filler.

[0017] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, each deposition cycle includes a trimethylaluminum precursor pulse with a flow rate of 80 sccm and a time of 0.1 s, a first nitrogen purge with a flow rate of 220 sccm and a time of 10 s, a water vapor pulse with a flow rate of 50 sccm and a time of 0.1 s, and a second nitrogen purge with a flow rate of 250 sccm and a time of 15 s.

[0018] Optionally, in the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, the formed FLG@Ag-QDs core-shell structure quantum filler is blended with a polymer matrix, comprising: Premix 0.35-1.98 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2 g / 10 min, and 2 parts by weight of dicumyl peroxide; Under nitrogen protection, the premixed material was melt-extruded using a co-rotating twin-screw extruder, and the extruded material was cross-linked by electron beam irradiation to produce an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

[0019] Optionally, in the preparation method of the insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler of the present invention, the aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5°C, the temperature of the extrusion melting zone is 175±5°C, the temperature of the extrusion homogenization zone is 185±5°C, the temperature of the extrusion head zone is 170±5°C, and the irradiation energy of the electron beam irradiation is 9±0.5MeV.

[0020] According to a second aspect of the present invention, an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler is provided. The insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler is prepared according to the above method.

[0021] The present invention provides an insulating shielding material based on a FLG@Ag-QDs core-shell structure quantum filler and a preparation method thereof, which has the following beneficial technical effects: 1. Improve high-frequency electromagnetic shielding performance. A local conductive network is constructed through the FLG@Ag-QDs core-shell structure. The average shielding effectiveness (SE) reaches over 33 dB in the 1-18 GHz frequency band, and the skin depth is as low as 1.8 μm (@10 GHz), effectively suppressing the high-frequency skin effect attenuation of traditional metal shielding layers.

[0022] 2. Synergistically optimize insulation performance and conductivity. The Al2O3 shell isolates Ag-QDs, blocking the macroscopic conductive path, so that the volume resistivity of the material at 20°C is maintained within 100Ω·cm. At the same time, a balance between dielectric constant and low dielectric loss is achieved through edge quantum dots.

[0023] 3. Enhance the filler dispersion and interface bonding strength. Through plasma edge modification and laser-induced in situ growth technology, Ag-QDs are evenly anchored on the edge of few-layer graphene. Combined with deposition cycle coating to inhibit agglomeration, nano-scale dispersion is achieved and the amount of filler added is reduced.

[0024] 4. Maintain excellent mechanical properties and flexibility. The low filling ratio and core-shell structure reduce damage to the matrix molecular chain. The composite material has an elongation at break greater than 400% and a tensile strength greater than 13 MPa.

[0025] 5. Improve performance stability and reliability. The electromagnetic shielding effectiveness fluctuates by <±2 dB across the entire frequency band. The Al2O3 shell protects Ag-QDs from oxidation, and the material maintains stable conductive and insulating properties during long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is an example flow chart of the steps of the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention; Figure 2 TEM electron diffraction pattern of the few-layer graphene prepared according to Example 1 of the present invention; Figure 3 This is a graph showing the average SE test data of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention; Figure 4 Graph showing the peak SE and frequency test results of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention; Figure 5 Graph showing the SE stability test results of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention; Figure 6 Graph showing skin depth test results at 10 GHz for the insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments may be combined with each other; and, based on the embodiments in this disclosure, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of this disclosure.

[0030] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0031] Figure 1 The following is an example of the steps of the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention, as shown in FIG. Figure 1 As shown, the preparation method of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler of the present invention comprises the following steps: Step S1: preparing few-layer graphene by pulsed plasma discharge.

[0032] Using a microwave plasma-enhanced chemical vapor deposition (MPECVD) system, using CH4 / H2 (1:9) as precursors, pulsed plasma discharge (10 kHz frequency, 30% duty cycle) was used at 650°C, 800W microwave power, and a reaction pressure of 20 Pa to deposit 3-5 layers of few-layer graphene. High-energy electron bombardment of CH4 molecules promotes the dissociation of the carbon source, while H2 simultaneously etches the amorphous carbon, ensuring a controlled number of graphene layers. The microwave plasma provides a highly active carbon source, reducing the high temperatures required for traditional CVD (<1000°C) and preventing disordered stacking of multilayer graphene.

[0033] Step S2: constructing modified sites on the edges of the few-layer graphene by plasma modification.

[0034] Using O2 / Ar (1:4) mixed gas as the precursor, the few-layer graphene was plasma treated at 300W power for 5 minutes. O2 generates active oxygen free radicals under the action of high-energy electrons, which attack the sp 2 Carbon forms carboxyl and epoxy groups, introducing carboxyl (-COOH) and epoxy (CO) groups at the edge. The negative charge of the carboxyl group can adsorb Ag. + , providing anchoring points for subsequent in-situ growth of quantum dots.

[0035] Step S3: Inducing in-situ growth of metal quantum dots at the modified sites by laser irradiation.

[0036] The modified FLG (few-layer graphene with modified sites) was dispersed in silver nitrate and sodium citrate solution and irradiated with double-beam laser to induce Ag + The modified sites are reduced to silver nanoparticles. 532nm laser excites sodium citrate to generate electrons, and 1064nm laser provides thermal effect, synergistically promoting Ag + Directed reduction. The carboxyl groups at the modified sites adsorb Ag through electrostatic interaction. + The laser energy is localized to ensure that quantum dots grow only at the edges, avoiding agglomeration and obtaining in-situ growth of Ag. + of few-layer graphene (Ag-QDs).

[0037] Step S4: coating the metal quantum dots by atomic layer deposition.

[0038] Using trimethylaluminum and H2O as precursors, 10-25 deposition cycles were carried out at 155°C. Each cycle included a trimethylaluminum pulse, N2 purge, H2O pulse and N2 purge. Trimethylaluminum and H2O were alternately adsorbed, and dense Al2O3 grew layer by layer on the surface of Ag-QDs to obtain FLG@Ag-QDs core-shell structure quantum filler. The Al2O3 shell can coat the Ag-QDs, preventing direct connection of the conductive network and ensuring the semi-conductivity of the material.

[0039] Step S5: blending the formed FLG@Ag-QDs core-shell structure quantum filler with a polymer matrix.

[0040] FLG@Ag-QDs are premixed with low-density polyethylene and a crosslinking agent, melt-blended via twin-screw extrusion, and then cross-linked and cured by electron beam irradiation. The core-shell structure of FLG@Ag-QDs reduces the van der Waals forces between fillers, combined with the shear force of the screw to achieve nanoscale dispersion. The edge distribution of the Ag-QDs forms a localized microscopic conductive network, enhancing shielding effectiveness. The Al2O3 shell blocks the macroscopic conductive pathway, maintaining volume resistivity. The low filler ratio prevents restricted matrix molecular chain motion, achieving a balance between shielding, semiconducting, and mechanical properties.

[0041] Example 1 1. Preparation of few-layer graphene: Using a microwave plasma-enhanced chemical vapor deposition system, a CH4 / H2 mixed gas with a volume ratio of 1:9 was used as the precursor. Pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30% was used to prepare 3-5 layers of few-layer graphene. The reaction temperature was 650°C, the microwave power was 800 W, and the reaction pressure was 20 Pa.

[0042] 2. Constructing modification sites: Using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, the few-layer graphene was plasma treated at a power of 300W for 5 minutes. By introducing carboxyl and epoxy groups at the edge of the graphene lattice, modification sites were constructed at the edge of the few-layer graphene.

[0043] 3. Growth of silver quantum dots on the modified sites: silver nitrate and sodium citrate were used to prepare an induction solution, in which the concentration of silver nitrate was 0.1 mol / L and the concentration of sodium citrate was 0.05 mol / L. 0.5 parts by weight of few-layer graphene with modified sites was dispersed in 800 parts by weight of the induction solution. A dual-beam laser with wavelengths of 532 nm and 1064 nm and a power ratio of 1:2 was used at a power of 50 W / cm 2 The modified sites were irradiated with an irradiation power density of 100 nm for 30 min to induce in situ growth of silver quantum dots.

[0044] 4. Metal quantum dot coating: Metal quantum dots were coated by atomic layer deposition, including 10 deposition cycles at 155°C using trimethylaluminum and deionized water as precursors. Each deposition cycle included a trimethylaluminum precursor pulse with a flow rate of 80 sccm and a time of 0.1 s, a first nitrogen purge with a flow rate of 220 sccm and a time of 10 s, a water vapor pulse with a flow rate of 50 sccm and a time of 0.1 s, and a second nitrogen purge with a flow rate of 250 sccm and a time of 15 s. The metal quantum dots were coated with multiple layers of alumina to obtain FLG@Ag-QDs core-shell structure quantum fillers.

[0045] 5. Blending molding: 1.98 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2 g / 10 min, and 2 parts by weight of diisopropylbenzene peroxide are premixed according to the ratio of parts by weight; the premixed material is melt-extruded using a co-rotating twin-screw extruder under nitrogen protection, the aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5℃, the temperature of the extrusion melting zone is 175±5℃, the temperature of the extrusion homogenization zone is 185±5℃, and the temperature of the extruder head zone is 170±5℃. The extruded material is electron beam irradiated and cross-linked, and the irradiation energy of the electron beam irradiation is 9±0.5MeV to obtain an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

[0046] Example 2 1. Preparation of few-layer graphene: Using a microwave plasma-enhanced chemical vapor deposition system, a CH4 / H2 mixed gas with a volume ratio of 1:9 was used as the precursor. Pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30% was used to prepare 3-5 layers of few-layer graphene. The reaction temperature was 650°C, the microwave power was 800 W, and the reaction pressure was 20 Pa.

[0047] 2. Constructing modification sites: Using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, the few-layer graphene was plasma treated at a power of 300W for 5 minutes. By introducing carboxyl and epoxy groups at the edge of the graphene lattice, modification sites were constructed at the edge of the few-layer graphene.

[0048] 3. Growth of silver quantum dots on the modified sites: silver nitrate and sodium citrate were used to prepare an induction solution, in which the concentration of silver nitrate was 0.1 mol / L and the concentration of sodium citrate was 0.05 mol / L. 0.68 parts by weight of few-layer graphene with modified sites was dispersed in 800 parts by weight of the induction solution. A dual-beam laser with wavelengths of 532 nm and 1064 nm and a power ratio of 1:2 was used at a power of 50 W / cm 2 The modified sites were irradiated with an irradiation power density of 100 nm for 30 min to induce in situ growth of silver quantum dots.

[0049] 4. Metal quantum dot coating: Metal quantum dots were coated by atomic layer deposition, including 14 deposition cycles at 155°C using trimethylaluminum and deionized water as precursors. Each deposition cycle included a trimethylaluminum precursor pulse with a flow rate of 80 sccm and a time of 0.1 s, a first nitrogen purge with a flow rate of 220 sccm and a time of 10 s, a water vapor pulse with a flow rate of 50 sccm and a time of 0.1 s, and a second nitrogen purge with a flow rate of 250 sccm and a time of 15 s. The metal quantum dots were coated with multiple layers of alumina to obtain FLG@Ag-QDs core-shell structure quantum fillers.

[0050] 5. Blending molding: 1.56 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2 g / 10 min, and 2 parts by weight of diisopropylbenzene peroxide are premixed according to the ratio of parts by weight; the premixed material is melt-extruded using a co-rotating twin-screw extruder under nitrogen protection, the aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5℃, the temperature of the extrusion melting zone is 175±5℃, the temperature of the extrusion homogenization zone is 185±5℃, and the temperature of the extruder head zone is 170±5℃. The extruded material is electron beam irradiated and cross-linked, and the irradiation energy of the electron beam irradiation is 9±0.5MeV to obtain an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

[0051] Example 3 1. Preparation of few-layer graphene: Using a microwave plasma-enhanced chemical vapor deposition system, a CH4 / H2 mixed gas with a volume ratio of 1:9 was used as the precursor. Pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30% was used to prepare 3-5 layers of few-layer graphene. The reaction temperature was 650°C, the microwave power was 800 W, and the reaction pressure was 20 Pa.

[0052] 2. Constructing modification sites: Using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, the few-layer graphene was plasma treated at a power of 300W for 5 minutes. By introducing carboxyl and epoxy groups at the edge of the graphene lattice, modification sites were constructed at the edge of the few-layer graphene.

[0053] 3. Growth of silver quantum dots on the modified sites: silver nitrate and sodium citrate were used to prepare an induction solution, in which the concentration of silver nitrate was 0.1 mol / L and the concentration of sodium citrate was 0.05 mol / L. 0.85 parts by weight of few-layer graphene with modified sites was dispersed in 800 parts by weight of the induction solution. A dual-beam laser with wavelengths of 532 nm and 1064 nm and a power ratio of 1:2 was used at a power of 50 W / cm 2 The modified sites were irradiated with an irradiation power density of 100 nm for 30 min to induce in situ growth of silver quantum dots.

[0054] 4. Metal quantum dot coating: Metal quantum dots were coated by atomic layer deposition, including 17 deposition cycles at 155°C using trimethylaluminum and deionized water as precursors. Each deposition cycle included a trimethylaluminum precursor pulse with a flow rate of 80 sccm and a time of 0.1 s, a first nitrogen purge with a flow rate of 220 sccm and a time of 10 s, a water vapor pulse with a flow rate of 50 sccm and a time of 0.1 s, and a second nitrogen purge with a flow rate of 250 sccm and a time of 15 s. The metal quantum dots were coated with multiple layers of alumina to obtain FLG@Ag-QDs core-shell structure quantum fillers.

[0055] 5. Blending molding: 1.15 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2 g / 10 min, and 2 parts by weight of diisopropylbenzene peroxide are premixed according to the ratio of parts by weight; the premixed material is melt-extruded using a co-rotating twin-screw extruder under nitrogen protection, the aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5℃, the temperature of the extrusion melting zone is 175±5℃, the temperature of the extrusion homogenization zone is 185±5℃, and the temperature of the extruder head zone is 170±5℃. The extruded material is electron beam irradiated and cross-linked, and the irradiation energy of the electron beam irradiation is 9±0.5MeV to obtain an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

[0056] Example 4 1. Preparation of few-layer graphene: Using a microwave plasma-enhanced chemical vapor deposition system, a CH4 / H2 mixed gas with a volume ratio of 1:9 was used as the precursor. Pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30% was used to prepare 3-5 layers of few-layer graphene. The reaction temperature was 650°C, the microwave power was 800 W, and the reaction pressure was 20 Pa.

[0057] 2. Constructing modification sites: Using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, the few-layer graphene was plasma treated at a power of 300W for 5 minutes. By introducing carboxyl and epoxy groups at the edge of the graphene lattice, modification sites were constructed at the edge of the few-layer graphene.

[0058] 3. Growth of silver quantum dots on the modified sites: silver nitrate and sodium citrate were used to prepare an induction solution, in which the concentration of silver nitrate was 0.1 mol / L and the concentration of sodium citrate was 0.05 mol / L. 1.05 parts by weight of few-layer graphene with modified sites was dispersed in 800 parts by weight of the induction solution. A dual-beam laser with wavelengths of 532 nm and 1064 nm and a power ratio of 1:2 was used at a power of 50 W / cm 2 The modified sites were irradiated with an irradiation power density of 100 nm for 30 min to induce in situ growth of silver quantum dots.

[0059] 4. Metal quantum dot coating: Metal quantum dots were coated by atomic layer deposition, including 21 deposition cycles at 155°C using trimethylaluminum and deionized water as precursors. Each deposition cycle included a trimethylaluminum precursor pulse with a flow rate of 80 sccm and a time of 0.1 s, a first nitrogen purge with a flow rate of 220 sccm and a time of 10 s, a water vapor pulse with a flow rate of 50 sccm and a time of 0.1 s, and a second nitrogen purge with a flow rate of 250 sccm and a time of 15 s. The metal quantum dots were coated with multiple layers of alumina to obtain FLG@Ag-QDs core-shell structure quantum fillers.

[0060] 5. Blending molding: 0.76 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2g / 10min, and 2 parts by weight of diisopropylbenzene peroxide are premixed according to the ratio of parts by weight; the premixed material is melt-extruded using a co-rotating twin-screw extruder under nitrogen protection, the aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5℃, the temperature of the extrusion melting zone is 175±5℃, the temperature of the extrusion homogenization zone is 185±5℃, and the temperature of the extruder head zone is 170±5℃. The extruded material is electron beam irradiated and cross-linked, and the irradiation energy of the electron beam irradiation is 9±0.5MeV to obtain an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

[0061] Example 5 1. Preparation of few-layer graphene: Using a microwave plasma-enhanced chemical vapor deposition system, a CH4 / H2 mixed gas with a volume ratio of 1:9 was used as the precursor. Pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30% was used to prepare 3-5 layers of few-layer graphene. The reaction temperature was 650°C, the microwave power was 800 W, and the reaction pressure was 20 Pa.

[0062] 2. Constructing modification sites: Using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, the few-layer graphene was plasma treated at a power of 300W for 5 minutes. By introducing carboxyl and epoxy groups at the edge of the graphene lattice, modification sites were constructed at the edge of the few-layer graphene.

[0063] 3. Growth of silver quantum dots on the modified sites: silver nitrate and sodium citrate were used to prepare an induction solution, in which the concentration of silver nitrate was 0.1 mol / L and the concentration of sodium citrate was 0.05 mol / L. 1.2 parts by weight of few-layer graphene with modified sites was dispersed in 800 parts by weight of the induction solution. A dual-beam laser with wavelengths of 532 nm and 1064 nm and a power ratio of 1:2 was used at a power of 50 W / cm 2The modified sites were irradiated with an irradiation power density of 100 nm for 30 min to induce in situ growth of silver quantum dots.

[0064] 4. Metal quantum dot coating: Metal quantum dots were coated by atomic layer deposition, including 25 deposition cycles at 155°C using trimethylaluminum and deionized water as precursors. Each deposition cycle included a trimethylaluminum precursor pulse with a flow rate of 80 sccm and a time of 0.1 s, a first nitrogen purge with a flow rate of 220 sccm and a time of 10 s, a water vapor pulse with a flow rate of 50 sccm and a time of 0.1 s, and a second nitrogen purge with a flow rate of 250 sccm and a time of 15 s. The metal quantum dots were coated with multiple layers of alumina to obtain FLG@Ag-QDs core-shell structure quantum fillers.

[0065] 5. Blending molding: 0.35 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2g / 10min, and 2 parts by weight of diisopropylbenzene peroxide are premixed according to the ratio of parts by weight; the premixed material is melt-extruded using a co-rotating twin-screw extruder under nitrogen protection, the aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5℃, the temperature of the extrusion melting zone is 175±5℃, the temperature of the extrusion homogenization zone is 185±5℃, and the temperature of the extruder head zone is 170±5℃. The extruded material is electron beam irradiated and cross-linked, and the irradiation energy of the electron beam irradiation is 9±0.5MeV to obtain an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

[0066] Example 6 The few-layer graphene prepared in Example 1 of the present invention was measured and characterized using a transmission electron microscope (TEM). 0.1 mg of the few-layer graphene was weighed and ultrasonically dispersed in 1 mL of anhydrous ethanol in an ice bath. Using a micropipette, 5 μL of the dispersion was slowly dripped onto the center of a 3 mm diameter ultrathin carbon support film copper mesh. After the solvent evaporated naturally for 80% for 5 minutes, the sample was transferred to a 60°C vacuum drying oven for 10 minutes. During testing, the accelerating voltage was 200 kV and the electron beam current was ≤10 μA. Figure 2 TEM electron diffraction pattern of the few-layer graphene prepared according to Example 1 of the present invention, as shown in FIG. Figure 2 As shown, the few-layer graphene prepared in Example 1 of the present invention has three parallel diffraction lattice fringes and a uniform interlayer spacing.

[0067] The chemical composition of the few-layer graphene with edge-modified sites was analyzed using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer equipped with a monochromatic Al Kα source (1486.6 eV). The scan range was 0-1200 eV for the full spectrum plus C 1s / O 1s high-resolution spectroscopy. The full spectrum was performed at a pass energy of 50 eV and the high-resolution spectrum was performed at 20 eV. The full X-ray photoelectron spectroscopy (XPS) analysis results of the few-layer graphene with edge-modified sites are shown in Table 1. The C 1s high-resolution spectrum was fitted using a Voigt function. The fitting results for the C 1s high-resolution spectrum are shown in Table 2. The O 1s high-resolution spectrum results are shown in Table 3.

[0068] Table 1

[0069] Table 2

[0070] Table 3

[0071] As shown in Table 1, the binding energies of carbon (C 1s) and oxygen (O 1s) in the sample are 284.5 eV and 531.0 eV, respectively, with atomic percentages of 82.7% and 17.3%, respectively. The oxygen-to-carbon atomic ratio (O / C) is 20.9%, indicating the successful introduction of oxygen-containing functional groups onto the graphene edges, providing active sites for the subsequent growth of metal quantum dots.

[0072] As shown in Table 2, the peak position of 284.5 eV corresponds to sp 2 The hybridized C=C bond (accounting for 65.4%) indicates that the main structure of graphene is intact; 286.5eV and 288.9eV correspond to the CO bond (18.7%) and carboxyl group (-COOH, 6.5%), respectively, confirming that plasma modification introduced carboxyl and epoxy groups (CO) at the edge, which is consistent with the O / C ratio in Table 1.

[0073] As shown in Table 3, 531.2 eV and 532.6 eV correspond to carboxyl / carbonyl (O=C, accounting for 42.1%) and epoxy / hydroxyl (OC, 57.9%), respectively, which further verifies the existence of carboxyl groups (echoing the -COOH peak in Table 2), and the epoxy group accounts for a higher proportion, indicating that the modification sites are mainly oxygen-containing functional groups, providing a chemical basis for the in situ growth of silver quantum dots.

[0074] The shielding effectiveness of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention was tested using a Keysight PNA-L N5234A vector network analyzer. The sample thickness was 2 mm, and the surface was polished to a roughness of less than 1 μm. The sample was clamped using a coaxial flange fixture with model APC-7 to test the electromagnetic shielding performance of the sample in the 1-18 GHz frequency band. The test temperature was 25±1°C, and the test humidity was 50±5% RH. Figure 3 This is a graph showing the average SE test data of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention; Figure 4 Graph showing the peak SE and frequency test results of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention; Figure 5 Graph showing the SE stability test results of the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention; Figure 6 Graph showing skin depth test results at 10 GHz for the insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler prepared according to Examples 1-5 of the present invention.

[0075] like Figures 3 to 6 As shown, the average shielding effectiveness of the insulating shielding materials based on the FLG@Ag-QDs core-shell structure quantum filler prepared in Examples 1 to 6 is not less than 33.4 dB, the skin depth is not greater than 3.2 μm (@10 GHz), and the SE stability is excellent in the entire frequency band (fluctuation <±2 dB), indicating that the FLG@Ag-QDs core-shell structure effectively suppresses the skin effect.

[0076] The volume resistivity of the insulating shielding materials based on the FLG@Ag-QDs core-shell structure quantum filler prepared in Examples 1-5 of the present invention was tested using an insulation resistance tester of model FLUKE 1507. The test method is based on GB / T3048.3-2007. The test results are shown in Table 4. The dielectric properties of the insulating shielding materials based on the FLG@Ag-QDs core-shell structure quantum filler prepared in Examples 1-5 of the present invention were tested using a dielectric spectrometer of model Novocontrol Alpha-A. The test standard is based on ASTM D150-18. The test results are shown in Table 5.

[0077] Table 4

[0078] Table 5

[0079] As shown in Table 5, the dielectric constant (εr) of the quantum filler based on the FLG@Ag-QDs core-shell structure prepared in the embodiment of the present invention is 4.2@1 kHz, the dielectric loss (tanδ) is only 0.0032, and the relaxation peak is located at 10 5 Hz, indicating that the material has excellent dielectric stability at high frequencies. With the increase of filler, εr and tanδ increase slightly, but both remain within a reasonable range, indicating that the core-shell structure avoids dielectric mutation.

[0080] The mechanical properties of the insulating shielding materials based on the FLG@Ag-QDs core-shell structure quantum fillers prepared in Examples 1-5 of the present invention were tested using an INSTRON 5985 universal material mechanical testing machine. Five groups of samples were tested for each example, and the average value was taken. The test results are shown in Table 6.

[0081] Table 6

[0082] As shown in Table 6, all examples exhibited elongation at break exceeding 400% and tensile strength of at least 13.2 MPa, demonstrating the material's excellent combination of flexibility and strength. Increasing the filler ratio slightly decreased the material's strength, but improved its ductility. This is attributed to the nanoscale effect and uniform dispersion of the quantum filler, which prevents the mechanical damage to the matrix often associated with traditional fillers.

[0083] The present invention is based on an insulating shielding material and a preparation method of FLG@Ag-QDs core-shell structure quantum filler. Through edge modification, in-situ growth, and deposition coating regulation, it achieves a synergistic breakthrough in electromagnetic shielding, insulation, and mechanical properties at a low filling amount, and has the following beneficial technical effects: 1. Improve high-frequency electromagnetic shielding performance. A local conductive network is constructed through the FLG@Ag-QDs core-shell structure. The average shielding effectiveness (SE) reaches over 33 dB in the 1-18 GHz frequency band, and the skin depth is as low as 1.8 μm (@10 GHz), effectively suppressing the high-frequency skin effect attenuation of traditional metal shielding layers.

[0084] 2. Synergistically optimize insulation performance and conductivity. The Al2O3 shell isolates Ag-QDs, blocking the macroscopic conductive path, so that the volume resistivity of the material at 20°C is maintained within 100Ω·cm. At the same time, a balance between dielectric constant and low dielectric loss is achieved through edge quantum dots.

[0085] 3. Enhance the filler dispersion and interface bonding strength. Through plasma edge modification and laser-induced in situ growth technology, Ag-QDs are evenly anchored on the edge of few-layer graphene. Combined with deposition cycle coating to inhibit agglomeration, nano-scale dispersion is achieved and the amount of filler added is reduced.

[0086] 4. Maintain excellent mechanical properties and flexibility. The low filling ratio and core-shell structure reduce damage to the matrix molecular chain. The composite material has an elongation at break greater than 400% and a tensile strength greater than 13 MPa.

[0087] 5. Improve performance stability and reliability. The electromagnetic shielding effectiveness fluctuates by <±2 dB across the entire frequency band. The Al2O3 shell protects Ag-QDs from oxidation, and the material maintains stable conductive and insulating properties during long-term use.

[0088] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler, characterized in that: The method comprises: preparing few-layer graphene by pulsed plasma discharge, constructing modified sites at the edges of the few-layer graphene by plasma modification, inducing in-situ growth of metal quantum dots at the modified sites by laser irradiation, coating the metal quantum dots by atomic layer deposition, and blending the formed FLG@Ag-QDs core-shell structure quantum filler with a polymer matrix.

2. The method for preparing the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler according to claim 1, characterized in that: Few-layer graphene was prepared as follows: a microwave plasma-enhanced chemical vapor deposition system was used, with a CH4 / H2 mixed gas with a volume ratio of 1:9 as a precursor, and pulsed plasma discharge with a discharge frequency of 10 kHz and a discharge duty cycle of 30% was used to prepare 3-5 layers of few-layer graphene. The reaction temperature was 650°C, the microwave power was 800 W, and the reaction pressure was 20 Pa.

3. The method for preparing the insulating shielding material based on the FLG@Ag-QDs core-shell structure quantum filler according to claim 1, characterized in that: Modification sites are constructed at the edges of few-layer graphene through plasma modification, including: using an O2 / Ar mixed gas with a volume ratio of 1:4 as a precursor, plasma treating the few-layer graphene at a power of 300W for 5 minutes, and constructing modification sites by introducing carboxyl and epoxy groups at the edges of the graphene lattice.

4. The method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler according to claim 1, characterized in that: Inducing in-situ growth of metal quantum dots at modified sites by laser irradiation includes: preparing an induction solution using silver nitrate and sodium citrate, wherein the concentration of silver nitrate in the induction solution is 0.1 mol / L and the concentration of sodium citrate is 0.05 mol / L; dispersing 0.5-1.2 parts by weight of few-layer graphene with modified sites in 800 parts by weight of the induction solution; and growing silver quantum dots on the modified sites by dual-beam laser irradiation.

5. The method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler according to claim 4, characterized in that: The wavelengths of the dual-beam laser are 532nm and 1064nm respectively. The power ratio of the 532nm laser to the 1064nm laser is 1:2, and the irradiation power density is 50W / cm 2 , the irradiation time is 30min.

6. The method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler according to claim 1, characterized in that: The metal quantum dots are coated by atomic layer deposition, including: using trimethylaluminum and deionized water as precursors, performing 10-25 deposition cycles at a temperature of 155°C, and coating the metal quantum dots with multiple layers of aluminum oxide to produce FLG@Ag-QDs core-shell structure quantum fillers.

7. The method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler according to claim 6, characterized in that: Each deposition cycle consisted of a trimethylaluminum precursor pulse at 80 sccm for 0.1 s, a first nitrogen purge at 220 sccm for 10 s, a water vapor pulse at 50 sccm for 0.1 s, and a second nitrogen purge at 250 sccm for 15 s.

8. The method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler according to claim 1, characterized in that: The formed FLG@Ag-QDs core-shell structure quantum filler is blended with a polymer matrix to form a composite, including: Premix 0.35-1.98 parts by weight of FLG@Ag-QDs core-shell structure quantum filler, 100 parts by weight of low-density polyethylene with a melt index of 2 g / 10 min, and 2 parts by weight of dicumyl peroxide; Under nitrogen protection, the premixed material was melt-extruded using a co-rotating twin-screw extruder, and the extruded material was cross-linked by electron beam irradiation to produce an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler.

9. The method for preparing an insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler according to claim 1, characterized in that: The aspect ratio of the twin screw is 40, the screw speed is 100±10rpm, the temperature of the extrusion feeding zone is 120±5°C, the temperature of the extrusion melting zone is 175±5°C, the temperature of the extrusion homogenization zone is 185±5°C, the temperature of the extruder head zone is 170±5°C, and the irradiation energy of the electron beam irradiation is 9±0.5MeV.

10. An insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler, characterized in that: The insulating shielding material based on FLG@Ag-QDs core-shell structure quantum filler is prepared according to any one of the methods described in claims 1 to 9.

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