A three-dimensional network structure magnesium-based composite shielding material and preparation method thereof

Abstract

The present invention discloses a magnesium-based composite shielding material with a three-dimensional network structure and a preparation method thereof, belonging to the technical field of magnesium-based composite shielding materials. The magnesium-based composite shielding material with a three-dimensional network structure comprises 30wt%-60wt% of tungsten, 30wt%-50wt% of boron carbide and 10wt%-40wt% of a magnesium matrix, wherein the average particle size of tungsten is ≤10μm, the average particle size of boron carbide is ≤40μm, the average particle size of the magnesium matrix is ≤80μm, and the ratio of the average particle size of tungsten or boron carbide to the average particle size of the magnesium matrix is between 1:16-1:2. The obtained shielding component particles are distributed in a three-dimensional network. The density of the composite shielding material is 2.9g / cm 3 ‑5.0g / cm 3 The present invention achieves a three-dimensional network distribution of shielding component particles by matching the particle size of powder particles, solving the previous problem of poor dispersion of shielding components and limited improvement in shielding performance caused by simply increasing the volume fraction of shielding components in composite shielding materials. The new shielding material has the characteristics of miniaturization, lightweight, and flexible adjustment of shielding performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnesium-based composite shielding materials, and in particular relates to a magnesium-based composite shielding material with a three-dimensional network structure and a preparation method thereof. Background Art

[0002] The statements in this section are merely intended to provide background information related to the technical solution of the present application to aid understanding, and they do not necessarily constitute prior art with respect to the technical solution of the present application.

[0003] With the gradual depletion of traditional fossil fuel reserves and growing energy demand, nuclear energy is gaining increasing attention in the power generation industry. However, the highly penetrating neutrons and gamma rays released by nuclear reactions can cause serious damage to personnel and equipment near the reactor, making radiation shielding materials essential for mitigating radiation damage. Commonly used radiation shielding materials in the nuclear power sector, such as heavy metals, concrete, hydrides, and polyethylene, generally suffer from deficiencies or limitations in high-temperature performance, efficiency, stability, lifespan, and environmental friendliness. In contrast, metal-based radiation shielding composites, such as magnesium-, aluminum-, iron-, and titanium-based materials, exhibit advantages such as radiation resistance, high-temperature resistance, and excellent mechanical and processability, making them attractive for use in the design of current and future advanced nuclear energy systems. Magnesium alloys, in particular, are increasingly becoming the matrix of choice for metal-based composite shielding materials due to their low density, high strength, high rigidity, excellent thermal conductivity, and excellent electromagnetic shielding capabilities.

[0004] Currently, traditional metal-based composite shielding materials are mostly composite materials with randomly and evenly distributed shielding components. To achieve a random and even distribution of shielding components, micron shielding component particles and micron metal matrix particles of comparable particle size are generally selected, or the micron shielding component particles are slightly larger than the micron metal matrix particles. The preparation of composite materials with uniformly distributed micron reinforcement particles and micron metal particles requires pre-treatment of the tungsten particles to prevent agglomeration, such as pre-dispersion in anhydrous ethanol, pre-dispersion by jet milling, or a combination of both. Furthermore, this uniform distribution reduces the continuity of the shielding components per unit volume in the composite shielding material, thereby reducing the probability of radiation interacting with the shielding components as it passes through the shielding material, weakening the shielding effect. This weakening of the shielding effect is particularly prominent when the thickness of traditional metal-based composite shielding materials is relatively thin. To avoid this problem, materials researchers often increase the volume fraction of shielding components in composite shielding materials or increase the overall thickness of the material. However, the addition of high volume fractions of shielding components can easily lead to new problems such as poor dispersion of the shielding components and limited improvement in shielding performance. Therefore, multiple pretreatment steps are usually required to achieve a random and uniform distribution of high volume fractions of shielding components. This leads to high production costs and a long production process, making it unsuitable for large-scale production. In addition, traditional shielding materials must be of sufficient thickness to ensure shielding effectiveness, which also limits the application scenarios of shielding materials.

[0005] The emerging composite materials with a network distribution of reinforcements provide a new approach to solving this problem. This type of network distribution of reinforcements means that the reinforcement particles are continuously distributed between the matrix particles (or can be understood as "distributed around the matrix particles"). The reinforcement particles form a continuous "network", so it is called a network structure. Since the reinforcement particles and the matrix particles have a certain three-dimensional shape, the reinforcements are actually distributed in a network in three-dimensional space, so this structure is also called a three-dimensional network structure (3D network structure). This type of network structure composite material does not pursue a uniform distribution of reinforcements but rather makes the reinforcements distributed in a network in the matrix. If the shielding components are distributed in a network in the matrix, compared with the traditional random and uniform distribution of shielding components, it will be beneficial to improve the continuity of the distribution of shielding components in the composite shielding material, thereby increasing the probability of radiation interacting with the shielding components when passing through the shielding material and improving the shielding effect. However, current composite materials with a network distribution of shielding components (or reinforcements) typically require high-energy ball milling to disperse nano-reinforcement particles on the surface of micron-sized metal matrix particles. For example, Chinese patent CN116987921A uses this method to prepare a high-strength, fully lamellar network-structured TiAl-based composite material. However, high-energy ball milling is inefficient for preparing powders and introduces a large amount of fresh surface, which can easily cause safety issues such as combustion and explosion. Therefore, it is not suitable for large-scale production of large products. Summary of the Invention

[0006] In order to solve the problems in the prior art, the present invention proposes a magnesium-based composite shielding material with a three-dimensional mesh structure and a preparation method thereof. The preparation process of the shielding material is simple, the density and the macroscopic uniformity of the shielding effect are good, the continuity of the shielding components within the unit volume is good, and the shielding effect of the material is good.

[0007] The present invention discloses a magnesium-based composite shielding material with a three-dimensional network structure, comprising shielding component particles and magnesium matrix particles, wherein the shielding component particles are tungsten and boron carbide, the magnesium matrix particles are magnesium and / or magnesium alloy, and the shielding component particles are tungsten and boron carbide. continuousThe magnesium matrix is distributed around the magnesium matrix particles; wherein the mass percentage of tungsten is 30wt%-60wt%, the mass percentage of boron carbide is 30wt%-50wt%, and the mass percentage of magnesium matrix is 10wt%-40wt%, and the total weight percentage of the tungsten particles, boron carbide particles and magnesium matrix particles in the magnesium matrix composite material is ≤100%; the average particle size of the tungsten is ≤10μm, the average particle size of the boron carbide is ≤40μm, and the average particle size of the magnesium matrix is ≤80μm, preferably the average particle size of the tungsten is 1μm-10μm, the average particle size of the boron carbide is 1μm-40μm, and the average particle size of the magnesium matrix is 2μm-80μm; and the ratio of the average particle size of the tungsten to the magnesium matrix is between 1:16 and 1:2, and the ratio of the average particle size of the boron carbide to the magnesium matrix is between 1:16 and 1:2, preferably both are between 1:4 and 1:10. Furthermore, the density of the magnesium-based composite shielding material is 2.9 g / cm 3 -5.0g / cm 3 The purity of the tungsten is ≥99wt%, and the total boron-carbon content of the boron carbide is ≥98wt%. The tungsten element as a shielding component can achieve the effects of gamma-ray absorption and fast neutron moderation, and the boron element as a shielding component can achieve the effect of thermal neutron absorption. The shielding component is distributed in a continuous, three-dimensional network around the magnesium matrix (i.e., between the magnesium matrix) in the form of a particle reinforcement. Preferably, the magnesium or magnesium alloy powder is selected from one or more mixed powders of commercial magnesium alloys of ZK, AZ, WE, VW, and VK, or self-matched non-brand magnesium alloys.

[0008] In addition, the present invention also discloses a method for preparing the above-mentioned magnesium-based composite shielding material with a three-dimensional network structure, comprising the following steps:

[0009] (1) Mixing and dispersion: Powders of tungsten with an average particle size of ≤10 μm, boron carbide with an average particle size of ≤40 μm, and a magnesium matrix with an average particle size of ≤80 μm are mechanically mixed, and the average particle size ratio of the tungsten to the magnesium matrix is between 1:16 and 1:2, and the average particle size ratio of the boron carbide to the magnesium matrix is between 1:16 and 1:2. The mechanical mixing is carried out under the protection of an atmosphere of argon, nitrogen, carbon dioxide, or a mixture thereof. Grinding balls are used during the mechanical mixing process, and the diameter of the grinding balls is Φ5 mm to Φ20 mm. The weight ratio of the grinding balls to the powder to be mixed is 0.5:1 to 2:1. The mixing time is 8 h to 16 h, and a mixed powder blank is obtained after mixing. Preferably, the mixing is carried out in a mixer.

[0010] (2) Vacuum degassing: The mixed powder blank is placed in a metal bag, and the mixed powder blank is heated and kept warm while being degassed. Then, the mixed powder blank is heated at a temperature of 400-500°C and a vacuum degree of 10 -2 Pa-10-5 The metal sheath is welded and sealed under the condition of Pa;

[0011] (3) Hot isostatic pressing: The metal sheath containing the mixed powder blank is then subjected to hot isostatic pressing. The specific conditions of the hot isostatic pressing treatment are: heating rate of 2°C / min-10°C / min, sintering temperature of 400°C-550°C, pressure of 100MPa-200MPa, heat preservation and pressure holding time of 1h-4h, followed by furnace cooling, and finally the metal sheath is removed by lathing to obtain a magnesium-based composite shielding material.

[0012] In addition, the vacuum hot pressing method can also be used to replace the above-mentioned step (2) vacuum degassing and step (3) hot isostatic pressing. The specific process is: the mixed powder blank is placed in the mold cavity of the vacuum hot pressing machine and vacuum hot pressed to obtain the magnesium-based composite shielding material. The reaction conditions of the vacuum hot pressing method are: sintering temperature of 400℃-550℃, pressure of 10t-50t, vacuum degree of 10 -2 Pa-10 - 5 Pa, the heat preservation and pressure holding time is 2h-6h, and then it is cooled with the furnace.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are:

[0014] (1) Compared with the process technology of dispersing nano-reinforcement particles on the surface of micron metal particles by high-energy ball milling, the present invention creatively proposes to use the particle size ratio of two types of powders, namely shielding component (reinforcement) and metal matrix: the particle size of the metal matrix particles in the shielding material is significantly larger than the particle size of the shielding component particles, thereby realizing a three-dimensional network distribution of micron shielding component (boron carbide, tungsten) particles around the micron metal matrix particles. The use of micron particles is lower in cost, less prone to agglomeration and oxidation, and does not require various pretreatments of nanopowders. The preparation process is simple, the process flow is short, the cost is low, and it is easy to implement.

[0015] (2) Compared with traditional composite shielding materials that require multiple pre-treatment steps to achieve random and uniform distribution of shielding components with high volume fractions, the present invention takes the opposite approach and does not pursue uniform distribution between shielding component particles at the microscopic level. Instead, it achieves a three-dimensional network distribution of shielding components through a reasonable ratio of particle size to achieve macroscopic uniformity of measurable density and shielding effect, thus avoiding the current problem of shielding components being difficult to disperse uniformly in high volume fraction shielding materials. Therefore, there is no need to pre-treat tungsten particles to prevent agglomeration. This material utilizes particle size ratio to relatively "concentrate" the shielding components around the magnesium matrix particles. Compared with the traditional random and uniform distribution of shielding components, this distribution method of shielding components can improve the continuity of the distribution of shielding components in the composite shielding material, increase the probability of radiation interacting with the shielding components when passing through the shielding material, and improve the shielding effect. It solves the problems of poor dispersion of shielding components, limited improvement in shielding performance, and the need for sufficient thickness to ensure shielding reliability caused by simply increasing the volume fraction of shielding components in composite shielding materials. This new shielding material features miniaturization, lightweight construction, and flexible adjustment of shielding performance, making it particularly suitable for applications in new nuclear reactors where the thickness of shielding components is limited. The invention has low production costs and a short production process, making it suitable for large-scale production and potentially applicable to other aluminum-, iron-, and titanium-based composite shielding materials.

[0016] (3) The present invention uses a mixer for mechanical mixing, which can carry out large-scale mixing and dispersion processing, so the number of mixing times is small, the preparation process is simple, and the process flow is short; at the same time, the mixer does not introduce too much energy during the mixing process, and the powder is not easy to be crushed and refined, which can effectively avoid the oxidation heat release combustion or explosion caused by powder refinement, and is therefore safer than the high-energy ball milling method. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the conventional uniform distribution of shielding components and the mesh distribution of shielding components of the present invention when rays are incident;

[0018] Figure 2 is an example SEM photograph of magnesium alloy particles in Example 1;

[0019] Figure 3 This is an example SEM photo of tungsten particles in Example 1;

[0020] Figure 4 This is an example SEM photo of the boron carbide particles in Example 1;

[0021] Figure 5 This is an SEM example photo of the microstructure morphology of the magnesium-based composite shielding material in Example 1 (low magnification);

[0022] Figure 6This is an SEM example photo of the microstructure morphology of the magnesium-based composite shielding material in Example 1 (high magnification);

[0023] Figure 7 This is an example SEM photo of the microstructure of the magnesium-based composite shielding material in Example 6 (low magnification);

[0024] Figure 8 This is an SEM example photo of the microstructure morphology of the magnesium-based composite shielding material in Comparative Example 1 (low magnification). DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the following describes in detail the magnesium-based composite shielding material with a three-dimensional mesh structure and its preparation method in conjunction with the examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] Example 1

[0027] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 30wt% boron carbide particles and 40wt% WE43 magnesium alloy particles, with average particle sizes of 10μm, 20μm and 80μm respectively (see attached). Figure 2 -Attached Figure 4 The preparation method is as follows:

[0028] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles are mixed for 12 hours. Grinding balls are used during the mechanical mixing process. The diameter of the grinding balls is Φ20 mm. The weight ratio of the grinding balls to the mixed powders is 1:1. After mixing, a mixed powder blank is obtained;

[0029] (2) The mixed powder blank was placed in a pre-made aluminum package, and the mixed powder blank was heated, kept warm, and degassed. After keeping warm for 10 hours, the mixed powder blank was heated at 400 ° C and the vacuum degree was less than 1×10 -3 Welding seal under the condition of Pa;

[0030] (3) The temperature was raised to 420°C at a rate of 5°C / min, and the hot isostatic pressing conditions were 160 MPa and 4 hours of heat preservation and pressure maintenance. The magnesium-based composite shielding material was formed by cooling to room temperature with the furnace, and the surface aluminum skin was removed to obtain the blank of the magnesium-based composite shielding material (its microstructure is shown in the attached figure). Figure 5 , Attachment Figure 6 As shown). Figure 4 and Figure 5 It can be seen that the gray matrix is a magnesium alloy matrix, the white particles are tungsten particles, and the black particles are boron carbide particles. It can be seen that the shielding component particles are distributed in a network around the matrix.

[0031] Example 2

[0032] The magnesium-based composite shielding material is prepared by mixing 40 wt% tungsten particles, 40 wt% boron carbide particles, and 20 wt% AZ31 magnesium alloy particles, with average particle sizes of 10 μm, 20 μm, and 80 μm, respectively. The preparation method is as follows:

[0033] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles were mixed for 8 hours. Grinding balls were used during the mechanical mixing process. The diameter of the grinding balls was Φ10 mm. The weight ratio of the grinding balls to the mixed powders was 2:1. After mixing, a mixed powder blank was obtained.

[0034] (2) The mixed powder blank was placed in a pre-made magnesium bag, and the mixed powder blank was heated, kept warm and degassed. After keeping warm for 10 hours, the mixed powder blank was heated at 400 ° C and the vacuum degree was less than 1×10 -3 Welding seal under the condition of Pa;

[0035] (3) The temperature is raised to 430°C at a rate of 5°C / min, and the hot isostatic pressing conditions are a pressure of 120 MPa and heat preservation and pressure maintenance for 4 hours. The magnesium-based composite shielding material is formed by cooling to room temperature with the furnace, and the surface magnesium skin is removed to obtain the initial blank of the magnesium-based composite shielding material.

[0036] Example 3

[0037] The magnesium-based composite shielding material is prepared by mixing 30 wt% tungsten particles, 30 wt% boron carbide particles, and 40 wt% self-blended magnesium-gadolinium-zirconium (Mg-Gd-Zr, containing about 10 wt% gadolinium and about 1 wt% zirconium) magnesium alloy particles, with average particle sizes of 5 μm, 10 μm, and 50 μm, respectively. The preparation method is as follows:

[0038] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles were mixed for 12 hours. Grinding balls were used during the mechanical mixing process. The diameter of the grinding balls was Φ5 mm. The weight ratio of the grinding balls to the mixed powders was 0.5:1. After mixing, a mixed powder blank was obtained;

[0039] (2) The mixed powder blank is placed in a prefabricated steel ladle, and the mixed powder blank is heated, kept warm, and degassed. After keeping warm for 10 hours, the mixed powder blank is heated at 400°C and the vacuum degree is less than 1×10 -3 Welding seal under the condition of Pa;

[0040] (3) The temperature is raised to 530°C at a rate of 5°C / min, and the hot isostatic pressing conditions are a pressure of 125 MPa and heat preservation and pressure maintenance for 4 hours. The magnesium-based composite shielding material is formed by cooling to room temperature with the furnace, and the surface steel skin is turned off to obtain the initial blank of the magnesium-based composite shielding material.

[0041] Example 4

[0042] The magnesium-based composite shielding material is prepared by mixing 30 wt% tungsten particles, 30 wt% boron carbide particles, and 40 wt% self-blended magnesium-gadolinium-zirconium (Mg-Gd-Zr, containing about 10 wt% gadolinium and about 1 wt% zirconium) magnesium alloy particles, with average particle sizes of 10 μm, 40 μm, and 80 μm, respectively. The preparation method is as follows:

[0043] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles were mixed for 12 hours. Grinding balls were used during the mechanical mixing process. The diameter of the grinding balls was Φ20 mm. The weight ratio of the grinding balls to the mixed powders was 1.5:1. After mixing, a mixed powder blank was obtained;

[0044] (2) The mixed powder blank is placed in a prefabricated steel ladle, and the mixed powder blank is heated, kept warm, and degassed. After keeping warm for 10 hours, the mixed powder blank is heated at 400°C and the vacuum degree is less than 1×10 -3 Welding seal under the condition of Pa;

[0045] (3) The temperature is raised to 530°C at a rate of 5°C / min, and the hot isostatic pressing conditions are a pressure of 130 MPa and heat preservation and pressure maintenance for 4 hours. The magnesium-based composite shielding material is formed by cooling to room temperature with the furnace, and the surface steel skin is turned off to obtain the initial blank of the magnesium-based composite shielding material.

[0046] Example 5

[0047] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 50wt% boron carbide particles, and 20wt% WE43 magnesium alloy particles, with average particle sizes of 10μm, 20μm, and 80μm, respectively. The preparation method is as follows:

[0048] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles are mixed for 12 hours. Grinding balls are used during the mechanical mixing process. The diameter of the grinding balls is Φ20 mm. The weight ratio of the grinding balls to the mixed powders is 1:1. After mixing, a mixed powder blank is obtained;

[0049] (2) The mixed powder blank is placed in a prefabricated steel ladle, and the mixed powder blank is heated, kept warm, and degassed. After keeping warm for 10 hours, the mixed powder blank is heated at 400°C and the vacuum degree is less than 1×10 -3 Welding seal under the condition of Pa;

[0050] (3) The temperature is raised to 520°C at a rate of 5°C / min, and the hot isostatic pressing conditions are a pressure of 150 MPa and heat preservation and pressure maintenance for 4 hours. The magnesium-based composite shielding material is formed by cooling to room temperature with the furnace, and the surface steel skin is turned off to obtain the initial blank of the magnesium-based composite shielding material.

[0051] Example 6

[0052] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 30wt% boron carbide particles, and 40wt% WE43 magnesium alloy particles, with average particle sizes of 10μm, 20μm, and 80μm, respectively. The preparation method is as follows:

[0053] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles are mixed for 12 hours. Grinding balls are used during the mechanical mixing process. The diameter of the grinding balls is Φ20 mm. The weight ratio of the grinding balls to the mixed powders is 1:1. After mixing, a mixed powder blank is obtained;

[0054] (2) The mixed powder blank was placed in the mold cavity of the vacuum hot press and vacuum hot pressed. The sintering temperature was 430℃, the pressure was 40t, and the vacuum degree was 0.5×10 -3 Pa, the heat preservation and pressure holding time is 4 hours, and then the furnace is cooled to obtain a magnesium-based composite shielding material.

[0055] Example 7

[0056] The magnesium-based composite shielding material is prepared by mixing 60wt% tungsten particles, 30wt% boron carbide particles, and 10wt% WE43 magnesium alloy particles, with average particle sizes of 2μm, 5μm, and 30μm, respectively. The preparation method is as follows:

[0057] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles were mixed for 12 hours. Grinding balls were used during the mechanical mixing process. The diameter of the grinding balls was Φ5 mm. The weight ratio of the grinding balls to the mixed powders was 0.5:1. After mixing, a mixed powder blank was obtained;

[0058] (2) The mixed powder blank was placed in a pre-made aluminum package, and the mixed powder blank was heated, kept warm, and degassed. After keeping warm for 8 hours, the mixed powder blank was heated at 500 ° C and the vacuum degree was less than 1×10 -2 Welding seal under the condition of Pa;

[0059] (3) The temperature is raised to 400°C at a rate of 2°C / min, and the hot isostatic pressing conditions are a pressure of 200 MPa and heat preservation and pressure maintenance for 2 hours. The magnesium-based composite shielding material is formed by cooling to room temperature with the furnace, and the surface aluminum skin is removed to obtain the initial blank of the magnesium-based composite shielding material.

[0060] Example 8

[0061] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 30wt% boron carbide particles, and 40wt% WE43 magnesium alloy particles, with average particle sizes of 10μm, 40μm, and 80μm, respectively. The preparation method is as follows:

[0062] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles are mixed for 12 hours. Grinding balls are used during the mechanical mixing process. The diameter of the grinding balls is Φ20 mm. The weight ratio of the grinding balls to the mixed powders is 1:1. After mixing, a mixed powder blank is obtained;

[0063] (2) The mixed powder blank was placed in a pre-made aluminum package, and the mixed powder blank was heated, kept warm, and degassed. After keeping warm for 10 hours, the mixed powder blank was heated at 400 ° C and the vacuum degree was less than 1×10 -5 Welding seal under the condition of Pa;

[0064] (3) The temperature is raised to 550°C at a rate of 10°C / min, and the hot isostatic pressing conditions are a pressure of 100 MPa and heat preservation and pressure maintenance for 2 hours. The magnesium-based composite shielding material is formed by cooling to room temperature with the furnace, and the surface aluminum skin is removed to obtain the initial blank of the magnesium-based composite shielding material.

[0065] Example 9

[0066] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 30wt% boron carbide particles, and 40wt% WE43 magnesium alloy particles, with average particle sizes of 10μm, 20μm, and 80μm, respectively. The preparation method is as follows:

[0067] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles are mixed for 12 hours. During the mechanical mixing process, grinding balls are used. The diameter of the grinding balls is Φ10 mm. The weight ratio of the grinding balls to the mixed powder is 1:1. After mixing, a mixed powder blank is obtained;

[0068] (2) The mixed powder blank was placed in the mold cavity of the vacuum hot press and vacuum hot pressed. The sintering temperature was 550℃, the pressure was 10t, and the vacuum degree was 1×10 -5 Pa, the heat preservation and pressure holding time is 2h, and then the furnace is cooled to obtain a magnesium-based composite shielding material.

[0069] Example 10

[0070] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 30wt% boron carbide particles, and 40wt% WE43 magnesium alloy particles, with average particle sizes of 10μm, 20μm, and 80μm, respectively. The preparation method is as follows:

[0071] (1) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles were mixed for 16 hours. Grinding balls were used during the mechanical mixing process. The diameter of the grinding balls was Φ20 mm. The weight ratio of the grinding balls to the mixed powders was 2:1. After mixing, a mixed powder blank was obtained.

[0072] (2) The mixed powder blank was placed in the mold cavity of the vacuum hot press and vacuum hot pressed. The sintering temperature was 400 °C, the pressure was 50t, and the vacuum degree was 1×10 -2 Pa, the heat preservation and pressure holding time is 6 hours, and then the furnace is cooled to obtain a magnesium-based composite shielding material.

[0073] The material properties of Examples 1-10 are shown in Table 1:

[0074] Table 1 Material properties of the above examples

[0075]

[0076] Comparative Example 1

[0077] The magnesium-based composite shielding material is prepared by mixing 30wt% tungsten particles, 30wt% boron carbide particles, and 40wt% WE43 magnesium alloy particles, with average particle sizes of 25μm, 60μm, and 50μm, respectively. The preparation method is as follows:

[0078] (1) Pre-grinding the boron carbide particles by jet milling to remove sharp edges and corners of the particles, and pre-dispersing the tungsten particles by anhydrous ethanol, jet milling, or a combination of the two;

[0079] (2) Using a double cone mixer under argon protection, the powders of tungsten particles, boron carbide particles and magnesium alloy particles are mixed for 12 hours. Grinding balls are used during the mechanical mixing process. The diameter of the grinding balls is Φ20 mm. The weight ratio of the grinding balls to the mixed powders is 1:1. After mixing, a mixed powder blank is obtained;

[0080] (3) The mixed powder blank was placed in a pre-made aluminum package, and the mixed powder blank was heated, kept warm, and degassed. After keeping warm for 10 hours, the mixed powder blank was heated at 400 ° C and the vacuum degree was less than 1×10 -3 Welding seal under the condition of Pa;

[0081] (4) The temperature was raised to 420°C at a rate of 5°C / min, and the hot isostatic pressing conditions were a pressure of 160 MPa and heat preservation and pressure maintenance for 4 hours. The furnace was cooled to room temperature to realize the molding of the magnesium-based composite shielding material. The surface aluminum skin was removed to obtain the blank of the magnesium-based composite shielding material (its microstructure is shown in the attached figure). Figure 8 shown). Figure 8 The medium gray matrix is a magnesium alloy matrix, the white particles are tungsten particles, and the black particles are boron carbide particles. The particle distribution is relatively uniform.

[0082] Table 2 compares the shielding performance of Example 1 and Comparative Example 1. A larger linear attenuation coefficient for the Cf fast neutron source indicates better radiation protection. Under the same shielding component dosage, density, and compactness, Example 1's shielding efficiency (Cf fast neutron source) is 3-8% higher than Comparative Example 1. The improvement in shielding efficiency is more pronounced with thinner materials tested.

[0083] Table 2 Shielding performance comparison of Example 1 and Comparative Example 1

[0084]

[0085] It should be understood that the above embodiments are only used to illustrate the preferred implementation details of the present invention, and are not used to limit the content and scope of the present invention. For general R&D and technical personnel in this field and profession, the present invention can have various adjustments and variations; therefore, any adjustments, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention, without the relevant personnel making any creative efforts, should be included in the scope of protection of the present invention.

Claims

1. A magnesium-based composite shielding material with a three-dimensional network structure, characterized in that: It comprises shielding component particles and magnesium matrix particles, wherein the shielding component particles are tungsten and boron carbide, the magnesium matrix is magnesium and / or magnesium alloy, and the shielding component particles are continuously distributed around the magnesium matrix particles; The mass percentage of tungsten is 30wt%-60wt%, the mass percentage of boron carbide is 30wt%-50wt%, and the mass percentage of the magnesium matrix is 10wt%-40wt%. The purity of the tungsten is ≥99wt%, and the total boron-carbon content of the boron carbide is ≥98wt%. The average particle size of the tungsten is ≤10μm, the average particle size of the boron carbide is ≤40μm, and the average particle size of the magnesium matrix is ≤80μm. The ratio of the average particle size of the tungsten to the magnesium matrix is between 1:16 and 1:2, and the ratio of the average particle size of the boron carbide to the magnesium matrix is between 1:16 and 1:

2.

2. The magnesium-based composite shielding material with a three-dimensional network structure according to claim 1, characterized in that: The average particle size of the tungsten is 1 μm-10 μm, the average particle size of the boron carbide is 1 μm-40 μm, and the average particle size of the magnesium matrix is 2 μm-80 μm.

3. The magnesium-based composite shielding material with a three-dimensional network structure according to claim 1, characterized in that: The density of the magnesium-based composite shielding material is 2.9 g / cm 3 -5.0g / cm 3 .

4. A method for preparing a magnesium-based composite shielding material with a three-dimensional network structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Mixing and dispersing: mechanically mixing powders of tungsten with an average particle size of ≤10 μm, boron carbide with an average particle size of ≤40 μm, and a magnesium matrix with an average particle size of ≤80 μm, wherein the ratio of the average particle size of the tungsten to the magnesium matrix is between 1:16 and 1:2, and the ratio of the average particle size of the boron carbide to the magnesium matrix is between 1:16 and 1:

2. The mechanical mixing is carried out under the protection of an atmosphere of argon, nitrogen, carbon dioxide, or a mixture thereof. Grinding balls are used during the mechanical mixing process, wherein the diameter of the grinding balls is Φ5 mm to Φ20 mm, and the weight ratio of the grinding balls to the mixed powder is 0.5:1 to 2:

1. The mixing time is 8 h to 16 h, and a mixed powder blank is obtained after mixing. (2) Vacuum degassing: The mixed powder blank is placed in a metal sleeve, and the mixed powder blank is heated and kept warm while being degassed, and then the metal sleeve is welded and sealed; (3) Hot isostatic pressing: The metal sheath containing the mixed powder blank is then subjected to hot isostatic pressing, and the metal sheath is finally removed by lathing to obtain a magnesium-based composite shielding material.

5. The method for preparing a magnesium-based composite shielding material with a three-dimensional network structure according to claim 4, characterized in that: Step (2) During the vacuum degassing process, the temperature is 400-500°C and the vacuum degree is 10 -2 Pa-10 -5 The metal sheath is welded and sealed under the condition of Pa.

6. The method for preparing a magnesium-based composite shielding material with a three-dimensional network structure according to claim 4, characterized in that: The specific conditions of the hot isostatic pressing treatment in step (3) are: heating rate of 2°C / min-10°C / min, sintering temperature of 400°C-550°C, pressure of 100MPa-200MPa, heat preservation and pressure holding time of 1h-4h, and then cooling with the furnace.

7. A method for preparing a magnesium-based composite shielding material having a three-dimensional network structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Mixing and dispersing: mechanically mixing powders of tungsten with an average particle size of ≤10 μm, boron carbide with an average particle size of ≤40 μm, and a magnesium matrix with an average particle size of ≤80 μm, wherein the ratio of the average particle size of the tungsten to the magnesium matrix is between 1:16 and 1:2, and the ratio of the average particle size of the boron carbide to the magnesium matrix is between 1:16 and 1:2, to obtain a mixed powder blank; (2) Vacuum hot pressing: The mixed powder blank is placed into the mold cavity of a vacuum hot press and vacuum hot pressed to obtain a magnesium-based composite shielding material.

8. The method for preparing a magnesium-based composite shielding material with a three-dimensional network structure according to claim 7, characterized in that: The specific conditions of vacuum hot pressing in step (2) are: sintering temperature of 400℃-550℃, pressure of 10t-50t, vacuum degree of 10 -2 Pa-10 -5 Pa, the heat preservation and pressure holding time is 2h-6h, and then it is cooled with the furnace.

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