Neutron-gamma ray shielding carbon fiber material and preparation method thereof

Abstract

The invention discloses a neutron-gamma ray shielding carbon fiber material and a preparation method thereof, and belongs to the technical field of high-performance composite materials. The material is of a core-shell composite structure from inside to outside, and specifically comprises a modified carbon fiber matrix in which a neutron absorption phase and a gamma ray shielding phase are uniformly dispersed; the surface of the modified carbon fiber matrix is coated with the metal aluminum layer; and the nano-scale copper layer is deposited on the surface of the metal aluminum layer. The neutron absorption phase is boron carbide, and the gamma ray shielding phase is a high-entropy alloy phase containing at least three of lead (Pb), tungsten (W), tantalum (Ta), bismuth (Bi), vanadium (V), molybdenum (Mo) and niobium (Nb). Through the design of in-situ conversion of boron carbide from boron oxide and multi-element cooperation of the high-entropy alloy, an efficient neutron absorption phase and a gamma ray attenuation phase are constructed in the body fiber at the same time, and cooperative shielding of a mixed radiation field is achieved.

Description

Technical Field

[0001] This invention relates to the field of high-performance composite materials technology, specifically to a multifunctional carbon fiber material and its preparation method that combines highly efficient neutron and gamma-ray shielding performance with high thermal conductivity and high electrical conductivity. Background Technology

[0002] Carbon fiber, due to its excellent properties of being lightweight, high-strength, and high-modulus, plays an irreplaceable role in aerospace, defense, and high-end equipment. With the increasing complexity of applications (such as nuclear power plants, space radiation environments, and medical radiation equipment), there is an urgent need for multifunctional integrated structural materials. These materials must maintain their mechanical properties while also possessing effective shielding capabilities against ionizing radiation such as neutrons and gamma rays, as well as excellent thermal and electrical conductivity to meet thermal management and electromagnetic compatibility requirements.

[0003] Currently, radiation shielding mainly relies on heavy materials such as lead plates and concrete, which are insufficient to meet the requirements for lightweight and flexible materials. Existing technologies attempt to prepare composite materials by blending shielding fillers (such as boron carbide, tungsten, and lead) with polymer matrices (such as polyethylene and epoxy resin). However, this method often leads to a significant decrease in the mechanical properties of the material, and the poor heat resistance of the polymer matrix limits its application in high-temperature environments. Another approach is to coat the surface of carbon fiber fabric with a shielding coating, but the coating is prone to peeling, has weak interfacial bonding, and severely affects the flexibility and weaving processability of the fibers. Therefore, developing an integrated carbon fiber material that possesses both radiation shielding functionality and excellent mechanical and thermal / electrical transport properties has become a pressing technical challenge in this field. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide a neutron-gamma-ray shielding carbon fiber material and its preparation method. This material achieves a balance between synergistic shielding of neutrons and gamma rays, high thermal and electrical conductivity, and high strength, and the process is stable and suitable for continuous production.

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

[0006] A neutron-gamma ray shielding carbon fiber material, wherein the material has a core-shell composite structure from the inside out, specifically comprising: a modified carbon fiber matrix, wherein a neutron absorbing phase and a gamma ray shielding phase are uniformly dispersed inside; a metallic aluminum layer covering the surface of the modified carbon fiber matrix; and a nanoscale copper layer deposited on the surface of the metallic aluminum layer.

[0007] Furthermore, the neutron absorbing phase is boron carbide (B4C), and the gamma-ray shielding phase is a high-entropy alloy phase containing at least three of the elements lead (Pb), tungsten (W), tantalum (Ta), bismuth (Bi), vanadium (V), molybdenum (Mo), and niobium (Nb).

[0008] Furthermore, the modified carbon fiber matrix is ​​prepared by high-temperature sintering of a polyacrylonitrile precursor and filler. The filler includes a boron oxide (B2O3) precursor for in-situ generation of boron carbide and a high-entropy alloy powder for forming a high-entropy alloy phase. The key role of boron oxide is that during the high-temperature carbonization of PAN, it can react with carbon in situ to generate boron carbide (B4C), a recognized highly efficient thermal neutron absorber. 10 B has a high neutron absorption cross section. The role of high-entropy alloy fillers is that they contain a variety of high atomic number (high Z) elements, which can achieve more efficient attenuation of wide-spectrum gamma rays through the "synergistic shielding effect". Moreover, high-entropy alloys usually have better high-temperature structural stability and resistance to radiation swelling compared to pure metals.

[0009] Furthermore, based on the mass of the polyacrylonitrile precursor, the added mass of the boron oxide precursor is 5% to 25%, and the added mass of the high-entropy alloy powder is 10% to 40%.

[0010] Further, the thickness of the aluminum layer is 0.1~2.0 micrometers; the thickness of the nano-flake copper layer is 1~15 micrometers, and the diameter of the nano-flake copper flakes is 50 nanometers~3 micrometers. Aluminum (Al) transition layer: This layer, as a functionally graded layer, plays multiple roles: ① protecting internal fibers and fillers, preventing oxidation; ② serving as an excellent thermally and electrically conductive intermediate layer, improving interfacial heat / electrical transport; ③ providing an ideal metal substrate for subsequent copper layer deposition, enhancing interlayer bonding. Nano-flake copper (Cu) functional surface layer: This layer is composed of a large number of nanoscale flake copper layers stacked together, forming a microscopically rough surface. Its functions are: ① copper itself (high Z element) supplements gamma shielding capability; ② the nano-flake structure greatly increases the specific surface area, significantly improving lateral thermal and electrical conductivity; ③ imparting a metallic luster and electromagnetic shielding (EMI) performance to the material surface.

[0011] A method for preparing the above-mentioned neutron-gamma ray shielding carbon fiber material, the method comprising:

[0012] S1: Polyacrylonitrile, boron oxide powder, and high-entropy alloy powder are uniformly dispersed in an organic solvent to prepare a spinning solution with a concentration of 10-20 wt%. Precursor fibers are then obtained through spinning and pre-oxidation. The spinning and pre-oxidation processes are as follows: Spinning is performed using a dry-jet wet-spinning process. After extrusion from the spinneret, the fibers pass through an air layer of several centimeters before solidifying in a coagulation bath at a temperature below 10°C to obtain nascent fibers. Subsequently, the fibers enter the pre-oxidation process, where they are heated from room temperature (20-30°C) to 200-300°C at an extremely slow heating rate of 0.5-3°C / min in a multi-temperature zone pyrolysis furnace, and then kept at this temperature in air for 0.5-2 hours.

[0013] S2: The precursor fiber is sintered under a protective atmosphere to carbonize polyacrylonitrile to form a carbon fiber matrix, while boron oxide reacts with carbon in situ to generate boron carbide, thus obtaining a modified carbon fiber matrix.

[0014] S3: The modified carbon fiber matrix is ​​surface activated, and then a metallic aluminum layer is deposited on its surface by chemical plating;

[0015] S4: Using a fiber with a metal aluminum layer deposited on its surface as the working electrode, a nanoscale copper layer is deposited on its surface by electrophoretic deposition.

[0016] Further, in step S1, the high-entropy alloy powder is a PbWTa-based, PbWTaMo-based, or PbWTaNb-based alloy powder with an equiatomic ratio or near-equiatomic ratio.

[0017] Further, in step S2, the protective atmosphere is nitrogen or argon; the sintering includes low-temperature carbonization at 400~800℃ and high-temperature carbonization at 800~1500℃, with a sintering time of 60~180 minutes for each.

[0018] Further, in step S3, the surface activation treatment is a sensitization-activation method or plasma surface activation treatment; the plasma surface activation treatment specifically involves: in an activation gas (such as oxygen, nitrogen, or air), the flow rate is controlled within the range of 20~50 sccm, the radio frequency power is 100~300 W, and the treatment time is 5~15 minutes; the electroless plating uses an organoaluminum compound as the main salt in the plating solution, carried out in a non-aqueous solvent system, with a concentration of 0.05~0.15 mol / L, a deposition temperature of 80℃~180℃, and a deposition time of 1~900s, for example, 120s. The organoaluminum compound is an alkylaluminum derivative such as triisobutylaluminum or triethylaluminum. The non-aqueous solvent system often uses inert organic solvents, such as aromatic hydrocarbons like toluene and xylene, or aliphatic hydrocarbons like hexane and heptane, to ensure the stable dissolution of the organoaluminum salt and avoid reaction with water.

[0019] Further, in step S4, the electrophoretic deposition is carried out in a suspension of nano-scale copper, wherein the concentration of nano-scale copper in the suspension is 5~50 g / L, the applied DC voltage is 20~80 V, and the deposition time is 2~20 minutes.

[0020] The advantages of this invention over the prior art are as follows:

[0021] (1) Excellent and comprehensive shielding performance: Through the design of "in-situ conversion of boron oxide to boron carbide" and "multi-element synergy of high-entropy alloy", a highly efficient neutron absorption phase and a gamma ray attenuation phase are constructed in the bulk fiber, realizing synergistic shielding of mixed radiation fields.

[0022] (2) Multifunctional integration: It integrates multiple functions such as radiation shielding, structural bearing, high-efficiency heat conduction (the aluminum layer and the scale copper layer form a fast heat channel) and excellent electrical conductivity in a single fiber, breaking through the limitation of the single function of traditional materials.

[0023] (3) Stable and reliable structure: The gradient structure design of "carbon matrix-aluminum-copper" from the inside to the outside, combined with chemical plating and electrophoretic deposition process, ensures that the functional layers are firmly bonded and not easy to peel off, and the overall reliability of the material is high.

[0024] (4) High feasibility of the process: Each step is based on mature material processing technology (spinning, sintering, chemical plating, electrophoresis) and is innovatively integrated. The process is clear and the parameters are controllable, which is conducive to realizing continuous and large-scale production.

[0025] (5) Broad application prospects: It is particularly suitable for occasions with extreme requirements for lightweight, high strength and high shielding efficiency, such as: lightweight mobile shielding for new generation nuclear facilities, radiation protection layer of spacecraft cabin and spacesuit, mobile protective equipment for nuclear medicine, heat dissipation and shielding shell of high power electronic equipment, etc. Attached Figure Description

[0026] Figure 1 This is a morphological diagram of the internal structure of the carbon fiber in the neutron-gamma ray shielding carbon fiber material of this invention.

[0027] Figure 2 Photograph of the carbon fiber after copper plating on the neutron-gamma ray shielding carbon fiber material of this invention;

[0028] Figure 3 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0030] The specific preparation method of the neutron-gamma ray shielding carbon fiber material of the present invention is as follows:

[0031] S1. Preparation of spinning solution and spinning:

[0032] Polyacrylonitrile (PAN) powder is dissolved in an organic solvent (such as dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF)) to form a homogeneous spinning solution. Neutron-absorbing filler (boron oxide powder) and gamma-shielding filler (such as Pb-W-Ta high-entropy alloy powder) are thoroughly dispersed in this spinning solution. The filler needs to be pretreated (e.g., modified with a silane coupling agent) to improve its dispersion stability in the PAN solution and its interfacial bonding with the carbon matrix. Using wet or dry-jet wet spinning techniques, the above mixed spinning solution is extruded into a coagulation bath to form fibers, followed by washing, drawing, and drying to obtain nascent PAN fibers containing the filler. Subsequently, a pre-oxidation treatment (stepwise heating at 200–300°C in air) is performed to transform it into non-melting and non-flammable pre-oxidized fibers (precursor fibers).

[0033] S2. High-temperature sintering and carbonization:

[0034] Pre-oxidized fibers are placed in a high-temperature tube furnace and sintered at high temperatures under the protection of an inert gas (such as high-purity nitrogen or argon). The sintering process includes low-temperature carbonization (400~800℃) and high-temperature carbonization (800~1500℃). During this process, PAN macromolecules undergo cross-linking, cyclization, and dehydrogenation reactions, transforming into a carbon fiber matrix with a disordered layered graphite structure. A key reaction occurs simultaneously: boron oxide (B2O3) dispersed inside the fiber reacts with the decomposed carbon (C) at high temperature, generating boron carbide (B4C) particles in situ. Simultaneously, high-entropy alloy fillers are firmly embedded in the formed carbon skeleton. This step ultimately yields a modified carbon fiber matrix with neutron and gamma shielding capabilities.

[0035] S3. Chemical aluminum plating:

[0036] First, the modified carbon fiber matrix obtained in step S2 undergoes surface activation treatment (typically using a sensitization-activation method, such as using SnCl2 and PdCl2 solutions, or direct activation in a palladium-containing solution at a concentration of 1-20 wt% for 10 min-4 h), depositing catalytically active palladium (Pd) nanoparticles on its surface. Then, the activated fibers are immersed in an electroless electroless aluminum plating solution (typically formulated as triisobutylaluminum Al(i-C4H9)3 or other organoaluminum compounds as the main salt, undergoing reduction deposition under specific solvent and temperature). By controlling the plating solution temperature and immersion time, a continuous, dense, and strongly bonded metallic aluminum layer is formed on the fiber surface.

[0037] S4. Electrophoretic deposition of copper nanoflakes:

[0038] Carbon fibers coated with an aluminum layer are used as the cathode, and inert electrodes (such as platinum sheets or stainless steel) are used as the anode, both placed in an electrophoretic deposition solution. The electrophoretic solution is a suspension of uniformly dispersed nanoscale flake copper powder (flake copper), and the solvent can be ethanol, isopropanol, or deionized water, with the addition of dispersants (such as polyvinylpyrrolidone, PVP) and charge regulators (such as magnesium nitrate). Under the action of a DC electric field (such as 10~100V), the positively charged nanoscale flake copper migrates towards the anode and is uniformly deposited on the cathode (fiber) surface. By controlling the voltage, deposition time, and suspension concentration, a nanoscale flake copper functional surface layer of a predetermined thickness is obtained.

[0039] Example 1: Balanced Performance Type

[0040] A general-purpose shielding material that combines good mechanical properties and shielding effectiveness, wherein the method is as follows:

[0041] Composition: Precursor: polyacrylonitrile; Filler: boron oxide precursor (added at 15% of the mass of polyacrylonitrile), equiatomic ratio Pb-W-Ta ternary high entropy alloy powder (added at 20%).

[0042] S1: Polyacrylonitrile, boron oxide powder, and high-entropy alloy powder are uniformly dispersed in an organic solvent to prepare a spinning solution with a concentration of 10-20 wt%. Precursor fibers are then obtained through spinning and pre-oxidation. The spinning and pre-oxidation processes are as follows: Spinning is performed using a dry-jet wet-spinning process. Generally, after extrusion from the spinneret, the fibers pass through an air layer of several centimeters before entering a coagulation bath at a temperature below 10°C to solidify and form nascent fibers. Subsequently, the fibers enter the pre-oxidation process, where they are heated from room temperature (20-30°C) to 260°C at an extremely slow heating rate of 0.5-3°C / min in a multi-temperature zone pyrolysis furnace, and then kept at this temperature in air for 1 hour.

[0043] S2: The precursor fiber is sintered under a protective atmosphere to carbonize polyacrylonitrile to form a carbon fiber matrix, while boron oxide reacts with carbon in situ to generate boron carbide, thus obtaining a modified carbon fiber matrix; the protective atmosphere is nitrogen or argon; the sintering includes low-temperature carbonization at 600℃ and high-temperature carbonization at 1000℃, with a sintering time of 100 minutes for each.

[0044] S3: The modified carbon fiber matrix is ​​subjected to plasma surface activation treatment, and then a metallic aluminum layer is deposited on its surface by chemical plating. The plasma surface activation treatment is specifically carried out in oxygen at a flow rate controlled within 30 sccm, a vacuum degree of 5 Pa, a radio frequency power of 200 W, and a treatment time of 10 minutes. The chemical plating is specifically carried out by immersing the activated fiber in an electroless chemical aluminum plating solution (with triisobutylaluminum [Al(i-C4H9)3] as the main salt, a concentration of 0.1 mol / L, and anhydrous toluene as the solvent). Under argon protection and constant temperature conditions of 90°C, the fiber is immersed for 15 minutes, and after cleaning, a continuous and dense aluminum coating is obtained on the surface, with an aluminum layer thickness of approximately 0.8 micrometers.

[0045] S4: Using fibers with a surface-deposited aluminum layer as the working electrode, a nano-scale copper layer is deposited on its surface via electrophoretic deposition. Electrophoretic Copper Deposition: Using aluminum-plated fibers as the working electrode, a nano-scale copper layer is deposited on its surface via electrophoretic deposition. The electrophoretic solution is a suspension of nano-copper flakes (approximately 500 nm in diameter) dispersed in isopropanol (concentration 2 wt%), the deposition voltage is 50 V, and the deposition time is 8 minutes. Finally, a nano-scale copper coating with a thickness of approximately 5 micrometers is formed on the fiber surface, resulting in a composite shielding material.

[0046] Material properties: Fiber strength: Due to the relatively uniform dispersion of in-situ generated B4C particles and high-entropy alloy phase in the carbon matrix and the moderate sintering temperature, the fiber has achieved high structural integrity, with a single filament tensile strength of 3.8 GPa, demonstrating excellent load-bearing capacity. 60 Co gamma-ray shielding efficiency: The uniformly distributed high-entropy alloy phase (containing high atomic number elements such as Pb, W, and Ta) provides the main gamma-ray photoelectric effect and Compton scattering absorption. The dense nano-copper / aluminum composite coating on the surface further enhances the interaction between the gamma rays and electrons. For 1.25 MeV... 60 Co gamma rays have a linear attenuation coefficient of 0.28 cm⁻¹. -1 The shielding efficiency exceeds 94% at a thickness of 10mm.

[0047] Example 2: High-strength and lightweight

[0048] This embodiment focuses on improving the specific strength of the material and is suitable for structural-functional integrated applications where weight is a concern.

[0049] Composition: Precursor: polyacrylonitrile, filler: boron oxide precursor (added at 10% to reduce excessive second phase cutting of the matrix), near-equal atomic ratio Pb-W-Ta-Mo quaternary high entropy alloy powder (added at 15%, with Mo partially replaced to improve the interfacial bonding strength between the alloy phase and the carbon matrix).

[0050] The difference between this embodiment and Embodiment 1 is as follows: Sintering process: High-temperature carbonization is carried out at 1400°C in argon for 90 minutes to promote the graphitization of carbon fibers and improve intrinsic strength. Coating: The thickness of the chemically plated aluminum layer is reduced to 0.3 micrometers to reduce weight. Electrophoretic deposition of small-diameter (approximately 200 nm) nanoscale copper flakes takes 5 minutes to form a thin and dense coating with a thickness of approximately 2 micrometers.

[0051] Material properties: Fiber strength: By reducing the total filler content and optimizing the sintering process, defects in the carbon fiber matrix are reduced and the crystallinity is improved. The resulting fiber strength is significantly increased to 4.5 GPa, exhibiting excellent mechanical properties. 60 Co gamma-ray shielding efficiency: Although the high-Z filler content is reduced, the optimized alloy composition and more dense and uniform matrix structure ensure effective shielding capability. The nano-copper / aluminum coating, though thin, is uniform and complete. 60 The linear attenuation coefficient of Co gamma rays is 0.22 cm⁻¹. -1 With a thickness of 10mm, the shielding efficiency is approximately 89%, achieving a good balance between lightweight and effective shielding.

[0052] Example 3: High Shielding Efficiency Type

[0053] This embodiment aims to maximize the material's gamma-ray shielding capability, making it suitable for high-intensity radiation environments.

[0054] Composition: Precursor: polyacrylonitrile, filler: boron oxide precursor (added at 20%), equiatomic ratio Pb-W-Ta-Nb pentagonal high entropy alloy powder (added at 35%, close to the upper limit, to maximize the high Z element content).

[0055] The difference between this embodiment and Embodiment 1 is as follows: Sintering process: High-temperature carbonization is carried out at 1250°C in nitrogen for 150 minutes to ensure sufficient reaction and dispersion of the filler, while avoiding excessive volatilization or agglomeration of alloying elements due to excessively high temperatures. Coating: A chemically plated aluminum layer with a thickness of 1.5 micrometers serves as a good base layer and secondary shielding layer. Electrophoretic deposition of large-diameter (approximately 2 micrometers) nanoscale copper flakes takes 15 minutes to form a dense, overlapping surface layer with a thickness of approximately 12 micrometers, resembling "armor."

[0056] Material properties: Fiber strength: Due to the high content of second-phase filler, the continuity of the carbon fiber matrix is ​​disrupted to some extent, resulting in a sacrifice in fiber strength to 2.6 GPa, but it still remains at an usable level. 60 Co gamma-ray shielding efficiency: The extremely high high-entropy alloy content and the ultra-thick surface composite metal coating (Al+Cu) together constitute a powerful shield. 60 Co gamma rays have a linear attenuation coefficient as high as 0.35 cm⁻¹. -1With a thickness of 10mm, the shielding efficiency exceeds 97%, demonstrating excellent radiation protection performance.

[0057] Example 4: Process Optimization

[0058] This embodiment explores the performance of materials under mild processing conditions in order to balance cost and performance.

[0059] Composition: Precursor: polyacrylonitrile, filler: boron oxide precursor (8% added), equiatomic ratio Pb-W-Ta ternary high entropy alloy powder (12% added).

[0060] The difference between this embodiment and Embodiment 1 is as follows: Sintering process: High-temperature carbonization is carried out at 1100°C in nitrogen for 180 minutes, using a relatively mild temperature and a longer time to promote structural stability. Coating: Chemical aluminum plating is performed at 120°C to obtain an aluminum layer with a thickness of approximately 0.5 micrometers. Electrophoretic deposition is performed at a lower voltage (30V) to deposit a nanoscale copper layer (approximately 1 micrometer in diameter) for 10 minutes, forming a coating with a thickness of approximately 6 micrometers.

[0061] Material properties: Fiber strength: The lower sintering temperature results in a slightly lower degree of graphitization of the carbon fibers, but the mild conditions reduce defects caused by thermal stress, and the lower filler content ensures that the fiber strength remains good at 3.2 GPa. 60 C-ray gamma-ray shielding efficiency: Due to the relatively small total filler volume, the shielding capability mainly depends on the surface metal coating. The linear attenuation coefficient is 0.18 cm⁻¹. -1 The shielding efficiency at a thickness of 10 mm is approximately 83%. This example demonstrates that, with a moderate reduction in shielding requirements, a lower-cost and reliable shielding material can be obtained through a milder process.

[0062] Example 5: Interface Enhancement Type

[0063] This embodiment focuses on improving the interfacial bonding between the filler and the substrate, and between the coating and the fiber, in order to enhance overall performance.

[0064] Composition: Precursor: polyacrylonitrile; Filler: boron oxide precursor (18%), with a surface carbon coating pretreatment of Pb-W-Ta ternary high-entropy alloy powder (25%). This aims to improve the compatibility between the alloy particles and the carbon matrix.

[0065] The difference between this embodiment and Embodiment 1 is as follows: Sintering process: High-temperature carbonization is carried out at 1300℃ and sintered in argon for 120 minutes to ensure good bonding between the coated carbon layer and the substrate. Coating: The modified carbon fiber substrate undergoes a surface activation treatment to significantly enhance the adhesion of the chemically plated aluminum layer (1.0 micrometer thick). During electrophoretic deposition, a dispersant is added to the suspension to obtain a dense and highly adhesive nanoscale copper layer (approximately 800 nm in diameter) with a thickness of about 8 micrometers.

[0066] Material Properties: Fiber Strength: Thanks to the strengthened interfacial bonding, stress transfer is more efficient, reducing stress concentration at the interface. Although the filler content is not low, the fiber strength still reaches 3.5 GPa, exhibiting excellent strength and toughness. 60 Co gamma-ray shielding efficiency: Excellent interfacial bonding ensures the uniform distribution of the high-entropy alloy phase in the matrix, with no significant agglomeration, allowing its shielding effectiveness to be fully realized. The strongly adhered, dense metal coating is free of microcracks, providing complete surface shielding. The linear attenuation coefficient is 0.30 cm⁻¹. -1 The shielding efficiency exceeds 95% at a thickness of 10mm. This embodiment achieves both high strength and high shielding efficiency through interface engineering.

Claims

1. A neutron-gamma ray shielding carbon fiber material, characterized in that: The material specifically includes: a modified carbon fiber matrix, in which a neutron absorbing phase and a gamma-ray shielding phase are uniformly dispersed; a metallic aluminum layer covering the surface of the modified carbon fiber matrix; and a nanoscale copper layer deposited on the surface of the metallic aluminum layer.

2. The neutron-gamma ray shielding carbon fiber material according to claim 1, characterized in that: The neutron absorbing phase is boron carbide (B4C), and the gamma-ray shielding phase is a high-entropy alloy phase containing at least three of the elements lead (Pb), tungsten (W), tantalum (Ta), bismuth (Bi), vanadium (V), molybdenum (Mo), and niobium (Nb).

3. The neutron-gamma ray shielding carbon fiber material according to claim 1 or 2, characterized in that: The modified carbon fiber matrix is ​​made by high-temperature sintering of polyacrylonitrile precursor and filler. The filler includes boron oxide (B2O3) precursor for in-situ generation of boron carbide and high-entropy alloy powder for forming a high-entropy alloy phase.

4. The neutron-gamma ray shielding carbon fiber material according to claim 3, characterized in that: Based on the mass of the polyacrylonitrile precursor, the added mass of the boron oxide precursor is 5% to 25%, and the added mass of the high-entropy alloy powder is 10% to 40%.

5. The neutron-gamma ray shielding carbon fiber material according to claim 1, characterized in that: The thickness of the aluminum layer is 0.1 to 2.0 micrometers; the thickness of the nano-scale copper layer is 1 to 15 micrometers, and the diameter of the nano-scale copper flakes is 50 nanometers to 3 micrometers.

6. A method for preparing the neutron-gamma ray shielding carbon fiber material according to any one of claims 1 to 5, characterized in that: The method is as follows: S1: Polyacrylonitrile, boron oxide powder and high entropy alloy powder are uniformly dispersed in an organic solvent to prepare a spinning solution with a concentration of 10~20wt%, and precursor fibers are obtained by spinning and pre-oxidation. S2: The precursor fibers are sintered under a protective atmosphere to obtain a modified carbon fiber matrix. S3: The modified carbon fiber matrix is ​​surface activated, and then a metallic aluminum layer is deposited on its surface by chemical plating; S4: Using a fiber with a metal aluminum layer deposited on its surface as the working electrode, a nanoscale copper layer is deposited on its surface by electrophoretic deposition.

7. The method according to claim 6, characterized in that: In step S1, the high-entropy alloy powder is a PbWTa, PbWTaMo, or PbWTaNb alloy powder with an equiatomic or near-equiatomic ratio.

8. The method according to claim 6, characterized in that: In step S2, the protective atmosphere is nitrogen or argon; the sintering includes low-temperature carbonization at 400~800℃ and high-temperature carbonization at 800~1500℃, with a sintering time of 60~180 minutes for each.

9. The method according to claim 6, characterized in that: In step S3, the surface activation treatment is either a sensitization-activation method or a plasma surface activation treatment; the plasma surface activation treatment specifically involves: in an activation gas (such as oxygen, nitrogen, or air), the flow rate is controlled within the range of 20~50 sccm, the radio frequency power is 100~300 W, and the treatment time is 5~15 minutes; the electroless plating uses an organic aluminum compound as the main salt in the plating solution, is carried out in a non-aqueous solvent system, the concentration is 0.05~0.15 mol / L, the deposition temperature is 80℃~180℃, and the deposition time is 1~900s.

10. The method according to claim 6, characterized in that: In step S4, the electrophoretic deposition is carried out in a suspension of nano-flake copper, the concentration of nano-flake copper in the suspension is 5~50 g / L, the applied DC voltage is 20~80 V, and the deposition time is 2~20 minutes.

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