Aluminum-based boron carbide composite material for shielding neutrons and method for manufacturing the same

Abstract

The application discloses an aluminum-based boron carbide composite material for shielding neutrons and a preparation method thereof. The aluminum-based boron carbide composite material is composed of boron carbide particles, carbon nanotubes and an aluminum matrix. The carbon nanotubes are distributed in the near-interface microzone within about 0-6 microns of the periphery of the boron carbide particles, and the size of the carbon nanotube layer wrapped in the near-interface microzone of the boron carbide is controlled by adjusting and controlling the mass fraction of the doped carbon nanotubes, so as to finally form a spherical composite reinforcing body in which the carbon nanotubes are wrapped around the boron carbide particles in the aluminum matrix. The boron carbide particles absorb neutrons, the carbon nanotubes block and absorb the by-product helium of the neutron reaction into the aluminum matrix, so as to avoid the formation of accumulated helium bubbles in the aluminum matrix and affect the material performance. The carbon nanotube-boron carbide spherical composite body enables the material to still have good structural performance after receiving irradiation, the helium bubble size is reduced by one order of magnitude, and the anti-irradiation damage capacity of the material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of neutron absorbing materials and aluminum-based composite materials, and provides an aluminum-based boron carbide composite material for shielding neutrons and a preparation method thereof. Background Art

[0002] Boron carbide (B4C) is widely used in nuclear fuel storage containers due to its excellent neutron absorption capacity. Furthermore, due to its low density and high specific strength, boron carbide is often used as a reinforcement in aluminum-based composites. As a result, the resulting boron carbide-reinforced aluminum-based composites exhibit both excellent neutron absorption and mechanical properties, and have found widespread application worldwide.

[0003] The neutron absorption ability of B4C is mainly due to the isotope 10 B has an ultra-high neutron absorption cross section (3837 Barn), and has the characteristics of wide neutron capture energy spectrum, no radioactive isotope production after decay, low secondary radiation energy, and high temperature resistance. 10 B captures a neutron and the following reaction occurs:

[0004] 10 B+n= 7 Li+ 4 He(500KeV)+2.78Mev

[0005] After the transmutation reaction occurs, 10 B will release 4 He ions are released, and the released He ions will nucleate, agglomerate, and grow inside the material as He bubbles. The size of the bubbles will increase with the increase of irradiation dose, eventually forming huge hole defects, affecting the neutron shielding effect and mechanical properties of the device, and shortening its service life.

[0006] Patent document CN 116516200 A discloses a boron carbide aluminum-based composite neutron shielding material and its preparation method. The boron carbide aluminum-based composite material uses micron-sized powder and nano-sized carbide, and adopts processes such as mixed sintering and deformation processing to achieve good neutron shielding effect. The nano-carbide can attract and preferentially aggregate the helium atoms produced by B4C after neutron absorption. However, despite the nano-carbide's ability to attract and adsorb helium bubbles, the helium bubbles dispersed in the composite matrix will still aggregate and grow at the grain boundaries and phase boundaries of the aluminum matrix, forming large bubbles and defects, which greatly damage the material properties. Summary of the Invention

[0007] To address the above issues, the present invention provides a neutron-shielding aluminum-based boron carbide composite material and its preparation method. The aluminum-based boron carbide composite material comprises boron carbide particles, carbon nanotubes, and an aluminum matrix. The carbon nanotubes are coated with aluminum powder and distributed in a near-interface microregion surrounding the boron carbide particles, within a sphere approximately 1 to 4 microns in diameter.

[0008] The technical solutions of the present invention are as follows:

[0009] A method for preparing a neutron shielding aluminum-based boron carbide composite material comprises the following steps:

[0010] 1) mixing carbon nanotubes with aluminum-based powder A, so that the carbon nanotubes are wrapped on the aluminum-based powder A to obtain carbon nanotube-aluminum powder;

[0011] 2) low-speed ball milling of carbon nanotubes and aluminum powder to obtain carbon nanotube / aluminum composite powder;

[0012] 3) high-speed ball milling of the carbon nanotube / aluminum composite powder and the boron carbide particles to obtain the carbon nanotube / aluminum-coated boron carbide composite powder;

[0013] 4) dispersing and compounding the carbon nanotube / aluminum-coated boron carbide composite powder with the aluminum-based powder B to obtain a boron carbide-carbon nanotube / aluminum mixed powder;

[0014] 5) The boron carbide-carbon nanotube / aluminum mixed powder is pressed, sintered, and deformed to obtain the neutron shielding aluminum-based boron carbide composite material; the aluminum-based powder A and the aluminum-based powder B have different particle sizes.

[0015] In step 1), the particle size of the aluminum-based powder A is 5-10 μm.

[0016] In step 4), the particle size of the aluminum-based powder B is 20-50 μm.

[0017] In step 1), the inner diameter of the carbon nanotube is 10-30 nm, and the outer diameter of the carbon nanotube is 30-70 nm.

[0018] In step 3), the boron carbide particles have a particle size range of 1 to 500 μm, preferably 5 to 40 μm, and more preferably 20 to 30 μm.

[0019] In step 1), the mass ratio of carbon nanotubes to aluminum-based powder A is 1:4-1:8.

[0020] In step 3), the mass ratio of carbon nanotube / aluminum composite powder to boron carbide particles is 1:1-1:3.

[0021] In step 4), the mass ratio of the carbon nanotube / aluminum-wrapped boron carbide composite powder to the aluminum-based powder B is 1:3-1:7.

[0022] In step 1), the powder mixing conditions are: 1600-2000 rpm, and the mixing time is 15-20 minutes.

[0023] In step 2), the low-speed ball milling conditions are: ball-to-material ratio of 15-25:1; 80-120 rpm.

[0024] In step 2), the abrasive balls used in ball milling are zirconia balls with a diameter of 6-10 mm.

[0025] In step 3), the high-speed ball milling conditions are: ball-to-material ratio of 10-20:1, 300-500 rpm, ball milling time of 1-3 hours, and the grinding balls are zirconia balls with a diameter of 6-10 mm.

[0026] In step 4), the carbon nanotube / aluminum-boron carbide composite powder and the aluminum-based powder B are dispersed and composited by one or more of mechanical mixing, variable speed ball milling, high-speed stirring mixing or air flow mixing.

[0027] Preferably, in step 4), the carbon nanotube / aluminum-boron carbide composite powder and the aluminum-based powder B are dispersed and composited by variable speed ball milling; the variable speed ball milling conditions are: first, low speed 100 rpm ball milling for 3-4 hours, and then high speed 200 rpm ball milling for 2-3 hours.

[0028] In step 5), the carbon nanotube / aluminum-boron carbide composite powder is compacted by molding, cold isostatic pressing of powder or encapsulation.

[0029] In step 5), the sintering is performed by one or more of vacuum sintering, atmosphere protection sintering, hot pressing sintering, and hot isostatic pressing sintering.

[0030] In step 5), the sintering temperature is 500-650° C. and the sintering time is 0.1-10 h.

[0031] The aluminum matrix includes one or more of pure aluminum, 1 series aluminum alloy, 2 series aluminum alloy, 5 series aluminum alloy, 6 series aluminum alloy, and 7 series aluminum alloy.

[0032] In step 3), the deformation process adopts extrusion, rolling, forging, ring forging or spinning method.

[0033] The neutron shielding aluminum-based boron carbide composite material prepared by the above method also falls within the protection scope of the present invention.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) In the present invention, the function of the boron carbide particles is to absorb neutrons, and the function of the carbon nanotubes is to block the high-energy helium ions emitted from the boron carbide particles. The carbon nanotubes have excellent specific strength and specific modulus, and their own structural stability, making them an effective barrier material for high-energy helium ions. The energy of the high-energy helium ions emitted in the neutron absorption reaction of boron carbide is about 500 KeV. According to the SRIM (Stopping and Range of Ions in Matter) program, the stopping distance of 500 KeV incident helium ions in the aluminum-based boron carbide composite material is 0 to 3 μm. Using aluminum sheets to coat carbon nanotubes in the near-interface microregion of 0 to 6 μm of the boron carbide particles can effectively prevent high-energy helium ions from entering the composite matrix and causing structural damage.

[0036] (2) As a one-dimensional nanostructure, carbon nanotubes have a high specific surface area and high surface adsorption, and can absorb irradiated high-energy helium ions. Helium ions stagnant in the microregion of the boron carbide interface tend to aggregate into helium bubbles and enter the carbon nanotube core through the carbon nanotube / aluminum interface. At this time, the carbon nanotubes wrapped around the outer interface of the boron carbide can serve as an effective storage space for helium bubbles, preventing them from entering the interior of the aluminum matrix, thereby reducing the helium density inside the aluminum matrix, reducing internal damage to the aluminum matrix, and ensuring material performance.

[0037] (3) Nano-sized carbon nanotubes also have the function of absorbing internal defects in materials. In aluminum-based boron carbide composites, defects formed in the material will preferentially migrate and recombine near the carbon nanotubes, and eventually be absorbed by the carbon nanotubes. Carbon nanotubes uniformly dispersed near the boron carbide particles help reduce the defect density at the interface between the boron carbide and the aluminum matrix, thereby improving the plasticity of the composite material.

[0038] (4) The dispersion of carbon nanotubes in the near-interface microregion of boron carbide aluminum-based composite materials enhances the material's dispersion strengthening ability, improves the material's mechanical properties, and is conducive to the lightweight design of the material.

[0039] (5) The preparation method adopts powder metallurgy technology, which is suitable for the forming and processing of aluminum-based composite materials with different reinforcement mass fractions (5 to 40 wt.%) and large-scale component products, and can be used in neutron shielding application scenarios such as ground spent fuel storage and transportation, spacecraft and nuclear-powered aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0041] Figure 1 This is a schematic structural diagram of the aluminum-based boron carbide composite material for neutron shielding according to the present invention;

[0042] Figure 2The microstructural morphology of boron carbide, carbon nanotubes and aluminum matrix of the sample of Example 1 under a transmission electron microscope, where (a) is the distribution microstructure of boron carbide in the aluminum matrix; the enlarged blue box in (b) is a microscopic picture of the distribution morphology of carbon nanotubes inside the aluminum matrix, and the labeled CNT is carbon nanotubes (Carbon Nano-tubes). DETAILED DESCRIPTION

[0043] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0044] Figure 1 This is a schematic structural diagram of a neutron shielding aluminum-based boron carbide composite material according to the present invention.

[0045] Example 1

[0046] This embodiment provides a neutron shielding aluminum-based boron carbide composite material, which is composed of 10 wt.% boron carbide particles, 1 wt.% carbon nanotubes and a pure aluminum matrix.

[0047] The boron carbide particle size is 20 μm;

[0048] The carbon nanotubes have an inner diameter of 10 nm (diameter range 10-30 nm), an outer diameter of 50 nm (diameter range 30-70 nm), and an average length of 2 μm (length range 1-5 μm);

[0049] The pure aluminum matrix is ​​5μm pure aluminum powder and 30μm pure aluminum powder with a purity of 99.9%.

[0050] The method for preparing the neutron shielding aluminum-based boron carbide composite material comprises the following steps:

[0051] Step 1) 10 g of carbon nanotubes and 40 g of aluminum powder with a particle size of 5 μm were mixed using a mechanical fusion modification machine, model NOB-130. The centrifugal force generated by the high-speed rotating rotor in the equipment and the gravity of the material itself were used to wrap the small-sized material (carbon nanotubes) onto the large-sized material (micron aluminum powder). The rated speed was 1600 rpm and the time was 15 minutes to prepare carbon nanotube-aluminum powder.

[0052] Step 2) The carbon nanotube-aluminum powder prepared in step 1) is subjected to low-speed ball milling using a planetary ball mill at a rated speed of 100 rpm for 3 hours to prepare a carbon nanotube / aluminum composite powder; wherein the ball-to-material ratio is 20:1; the grinding balls are zirconia balls with a diameter of approximately 8 mm; at this point, the micronized aluminum powder has been flaked, and the carbon nanotubes are attached to the flaky aluminum powder.

[0053] Step 3) Add 100 g of boron carbide particles to 50 g of the carbon nanotube / aluminum composite powder prepared in step 2) and high-speed ball mill at 200 rpm for 2 hours to prepare a carbon nanotube / aluminum-coated boron carbide composite powder; wherein the ball-to-material ratio is 15:1; the abrasive balls are zirconia balls with a diameter of approximately 8 mm; at this point, the carbon nanotube / aluminum mixed powder prepared in step 2) adheres to the boron carbide particles to form a coating layer.

[0054] Step 4) Adding 850 g of aluminum powder with a particle size of 30 μm to 150 g of the carbon nanotube / aluminum-coated boron carbide composite powder prepared in step 3) and continuing ball milling, first at a low speed of 100 rpm for 3 hours and then at a high speed of 200 rpm for 2 hours, to prepare a boron carbide-carbon nanotube / aluminum mixed powder;

[0055] Step 5) 1 kg of the boron carbide-carbon nanotube / aluminum mixed powder was pressed into an ingot with a diameter of 80 mm under a pressure of 180 tons, sintered at 520° C. for 3 hours for densification, and extruded into a 50 mm×10 mm plate to obtain a dense neutron-shielding aluminum-based boron carbide composite material.

[0056] Figure 2 The microstructural morphology of boron carbide, carbon nanotubes and aluminum matrix of the sample of this embodiment under transmission electron microscopy, where (a) is the distribution microstructure of boron carbide in the aluminum matrix; the enlarged blue box in (b) is a microscopic picture of the distribution morphology of carbon nanotubes inside the aluminum matrix, and the labeled CNT is carbon nanotubes (Carbon Nano-tubes).

[0057] After being wrapped by aluminum powder, the carbon nanotubes are distributed in the near-interface micro-region around the boron carbide particles, and the distribution range is within a space sphere of about 0 to 6 microns outside the boron carbide particles.

[0058] Example 2

[0059] The material specifications are the same as those in Example 1, and the preparation method is as follows:

[0060] Step 1) 8 g of carbon nanotubes and 37 g of aluminum powder with a particle size of 8 μm were mixed using a mechanical fusion modification machine, model NOB-130. The centrifugal force generated by the high-speed rotating rotor in the equipment and the gravity of the material itself were used to wrap the small-sized material (carbon nanotubes) onto the large-sized material (micron aluminum powder). The rated speed was 1800 rpm and the time was 18 minutes to prepare carbon nanotube-aluminum powder.

[0061] Step 2) The carbon nanotube-aluminum powder prepared in step 1) was subjected to low-speed ball milling using a planetary ball mill at a rated speed of 110 rpm for 2.5 hours to prepare a carbon nanotube / aluminum composite powder; wherein the ball-to-material ratio was 22:1; the grinding balls were zirconia balls with a diameter of approximately 9 mm; at this point, the micronized aluminum powder had been flaked, and the carbon nanotubes were attached to the flaky aluminum powder.

[0062] Step 3) Add 90 g of boron carbide particles to 45 g of the carbon nanotube / aluminum composite powder prepared in step 2) and high-speed ball mill at 400 rpm for 2 hours to prepare a carbon nanotube / aluminum-coated boron carbide composite powder; wherein the ball-to-material ratio is 18:1; the abrasive balls are zirconia balls with a diameter of approximately 9 mm; at this point, the carbon nanotube / aluminum mixed powder prepared in step 2) adheres to the boron carbide particles to form a coating layer.

[0063] Step 4) 865 g of aluminum powder with a particle size of 35 μm was added to 135 g of the carbon nanotube / aluminum-coated boron carbide composite powder prepared in step 3), and the mixture was ball milled at a low speed of 100 rpm for 3.5 hours and then at a high speed of 200 rpm for 2.5 hours to prepare a boron carbide-carbon nanotube / aluminum mixed powder.

[0064] Step 5) 1 kg of the boron carbide-carbon nanotube / aluminum mixed powder was pressed into an ingot with a diameter of 85 mm under a pressure of 190 tons, sintered at 580° C. for 2 hours for densification, and extruded into a 45 mm × 12 mm plate to obtain a dense neutron-shielding aluminum-based boron carbide composite material.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is:

[0067] The materials used are consistent: a composite material consisting of 10 wt.% boron carbide particles, 1 wt.% carbon nanotubes, and a pure aluminum matrix. The boron carbide particles are 20 μm in size; the carbon nanotubes have an inner diameter of 10 nm (diameter range 10-30 nm), an outer diameter of 50 nm (diameter range 30-70 nm), and an average length of 2 μm (length range 1-5 μm). The matrix is ​​99.9% pure aluminum powders of 5 μm and 30 μm in size.

[0068] The preparation steps are different from those in Example 1; in this comparative example, the specific preparation steps are as follows:

[0069] Step 1) According to the above ratio, 10g of carbon nanotubes and 890g of aluminum powder were ball-milled together, wherein the 890g of aluminum powder contained 40g of 5μm aluminum powder and 850g of 30μm aluminum powder, at 100 rpm for 4 hours to prepare a graphitized carbon nanotube / aluminum composite powder;

[0070] Step 2) adding 100 g of boron carbide particles to the carbon nanotube / aluminum composite powder, blending at a low speed of 100 rpm for 3 hours, and then ball milling at a high speed of 200 rpm for 2 hours to prepare a boron carbide-carbon nanotube / aluminum mixed powder;

[0071] Step 3) The boron carbide-graphitized carbon nanotube / aluminum mixed powder was pressed into an ingot with a diameter of 80 mm under a pressure of 180 tons, sintered at 550° C. for 3 hours for densification, and extruded into a 50 mm×10 mm plate to obtain a boron carbide-graphitized carbon nanotube / aluminum composite material.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that the carbon nanotube content is different. The mass fraction of carbon nanotubes used is 2 wt.%, that is, in this comparative example, 20 g of carbon nanotubes and 30 g of aluminum powder with a diameter of 5 μm are added and mixed, and the subsequent steps remain unchanged.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is:

[0076] The materials used are consistent: a composite material consisting of 10 wt.% boron carbide particles, 1 wt.% carbon nanotubes, and a pure aluminum matrix. The boron carbide particles are 20 μm in size; the carbon nanotubes have an inner diameter of 10 nm (diameter range 10-30 nm), an outer diameter of 50 nm (diameter range 30-70 nm), and an average length of 2 μm (length range 1-5 μm); and the pure aluminum matrix is ​​composed of 5 μm and 30 μm pure aluminum powders with a purity of 99.9%.

[0077] The preparation steps are different from those in Example 1; in this comparative example, the specific preparation steps are as follows:

[0078] Step 1) 10 g of carbon nanotubes, 100 g of boron carbide, and 890 g of aluminum powder (including 40 g of 5 μm aluminum powder and 850 g of 30 μm aluminum powder) were mixed in the above proportions using a high-speed mechanical mixer at a rated speed of 1600 rpm for 20 minutes.

[0079] Step 2) The mixed powder in step 1) was placed in a planetary ball mill for ball milling. The ball mill speed was 200 rpm, the ball milling time was 3 hours, the ball-to-material ratio was 20:1, and 8 mm zirconia balls were used.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that in step 1), the 5 μm aluminum powder is replaced with 30 μm aluminum powder.

[0082] Comparative Example 5

[0083] The difference between this comparative example and Example 1 is that no carbon nanotubes are added. The aluminum-based boron carbide composite material of this comparative example is a composite material consisting of 10 wt.% boron carbide particles and a pure aluminum matrix.

[0084] Performance Testing

[0085] 1. Mechanical properties test

[0086] A universal materials testing machine (Instron Model 3344) equipped with a static axial clamp-on extensometer (Instron Model 2630-101) was used to test the -4 s -1 Uniaxial tensile testing of the composite material was performed at room temperature under a constant loading rate of . The specimen dimensions, shape, and test methods were in accordance with GB / T 228.1-2010, "Metallic Materials - Tensile Tests at Room Temperature," using circular tensile specimens with a gauge length of 25 mm and a diameter of 5 mm. Tensile specimens were first cut from the extruded sheet using wire cutting, with the tensile axis parallel to the extrusion direction. The parallel surface of the specimen was then polished with fine sandpaper (1200 grit) to remove surface oil and other contaminants, resulting in a smooth specimen surface.

[0087] Ion irradiation: ion implantation machine was used to carry out ion irradiation with a dose of 3×10 17 ions / cm -2 In the helium ion implantation experiment, before the ion implantation, the sample was sampled from the extruded sheet of aluminum-based composite material by wire cutting along the plane perpendicular to the extrusion direction. After sampling, it was first ground and polished, and then annealed to ensure a smooth surface and eliminate processing defects.

[0088] Table 1

[0089]

[0090] Microscopic characterization: Field emission transmission electron microscopy (TEM) was used to capture the material morphology, high-resolution images (HRTEM) and high-angle annular dark field (HAADF) images to characterize and analyze the boron carbide particles and carbon nanotubes in the interface microregion of the composite material. The model was FEI Talos F200X G2, and the accelerating voltage was 200 kV.

[0091] Table 2

[0092]

[0093]

[0094] Figure 2 The microstructural morphology of boron carbide, carbon nanotubes and aluminum matrix of the product of Example 2 under a transmission electron microscope, wherein a) is the distribution microstructure of boron carbide in the aluminum matrix; b) is an enlargement of the blue box in a), which is a microscopic picture of the distribution morphology of carbon nanotubes inside the aluminum matrix, and the labeled CNT is carbon nanotubes (Carbon Nano-tubes).

[0095] The aluminum-based boron carbide composite material consists of boron carbide particles, carbon nanotubes, and an aluminum matrix. The carbon nanotubes are distributed in a near-interface microregion within about 0-6 microns around the boron carbide particles. The size of the carbon nanotube layer wrapped in the near-interface microregion of the boron carbide is controlled by regulating the mass fraction of the doped carbon nanotubes, ultimately forming a spherical composite reinforcement in which the carbon nanotubes wrap the boron carbide particles within the aluminum matrix. The boron carbide particles absorb neutrons, and the carbon nanotubes block and absorb helium, a byproduct of the neutron reaction, from entering the aluminum matrix, thereby preventing the formation of aggregated helium bubbles inside the aluminum matrix that affect material properties and improving comprehensive properties such as neutron shielding, radiation damage resistance, and mechanical strength.

[0096] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for preparing a neutron shielding aluminum-based boron carbide composite material, characterized in that: The steps include: 1) mixing carbon nanotubes with aluminum-based powder A, so that the carbon nanotubes are wrapped on the aluminum-based powder A to obtain carbon nanotube-aluminum powder; 2) low-speed ball milling of carbon nanotubes and aluminum powder to obtain carbon nanotube / aluminum composite powder; 3) high-speed ball milling of the carbon nanotube / aluminum composite powder and the boron carbide particles to obtain the carbon nanotube / aluminum-coated boron carbide composite powder; 4) dispersing and compounding the carbon nanotube / aluminum-coated boron carbide composite powder with the aluminum-based powder B to obtain a boron carbide-carbon nanotube / aluminum mixed powder; 5) compacting, sintering, and deforming the boron carbide-carbon nanotube / aluminum mixed powder to obtain the carbon nanotube / boron carbide aluminum-based composite material; The aluminum-based powder A and the aluminum-based powder B have different particle sizes; In step 1), the particle size of the aluminum-based powder A is 5-10 μm; The particle size of the aluminum-based powder B is 20-50 μm.

2. The preparation method according to claim 1, characterized in that In step 1), the inner diameter of the carbon nanotube is 10-30 nm, and the outer diameter of the carbon nanotube is 30-70 nm; And / or, in step 3), the particle size of the boron carbide particles ranges from 1 to 500 μm.

3. The preparation method according to claim 1, characterized in that In step 1), the mass ratio of carbon nanotubes to aluminum-based powder A is 1:4-1:8; And / or, in step 3), the mass ratio of carbon nanotube / aluminum composite powder to boron carbide particles is 1:1-1:3; And / or, in step 4), the mass ratio of the carbon nanotube / aluminum-coated boron carbide composite powder to the aluminum-based powder B is 1:3-1:

7.

4. The preparation method according to claim 1, characterized in that In step 1), the powder mixing conditions are: 1600-2000 rpm, time is 15-20 min; And / or, in step 2), the low-speed ball milling conditions are: ball-to-material ratio of 15-25:1; 80-120 rpm; And / or, in step 2), the abrasive balls used in ball milling are zirconia balls with a diameter of 6-10 mm; And / or, in step 3), the high-speed ball milling conditions are: ball-to-material ratio of 10-20:1, 300-500 rpm, ball milling time of 1-3 hours, and the grinding balls are zirconia balls with a diameter of 6-10 mm.

5. The preparation method according to claim 1, characterized in that In step 4), the carbon nanotube / aluminum-boron carbide composite powder and the aluminum-based powder B are dispersed and composited by one or more of mechanical mixing, variable speed ball milling, high-speed stirring mixing, and air flow mixing.

6. The preparation method according to claim 5, characterized in that The carbon nanotube / aluminum-boron carbide composite powder and the aluminum powder are dispersed and composited by variable speed ball milling; the variable speed ball milling conditions are: first, low speed 100-150 rpm ball milling for 3-4 hours, and then high speed 200-500 rpm ball milling for 2-3 hours.

7. The preparation method according to claim 1, characterized in that In step 5), the carbon nanotube / aluminum-boron carbide composite powder is pressed by molding, cold isostatic pressing of powder or encapsulation; And / or, in step 5), the sintering is performed by one or more of vacuum sintering, atmosphere protection sintering, hot pressing sintering, and hot isostatic pressing sintering; the sintering temperature is 500-650° C., and the time is 0.1-10 h.

8. The preparation method according to claim 1, characterized in that The aluminum-based powder A and the aluminum-based powder B are selected from one or more of pure aluminum, 1 series aluminum alloy, 2 series aluminum alloy, 5 series aluminum alloy, 6 series aluminum alloy, and 7 series aluminum alloy.

9. A neutron shielding aluminum-based boron carbide composite material prepared by the method according to any one of claims 1 to 8.

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