A method for preparing SnBi / B4C radiation shielding composite material

Abstract

The application discloses a preparation method of SnBi / B4C radiation shielding composite material. The material selects SnBi alloy with high atomic number, large density, strong processability and corrosion resistance as a matrix, B4C particles with light weight, high strength, good stability and large neutron reaction cross section as reinforcing fillers, and is formed through a powder metallurgy process, so that the composite material with high strength and the ability of shielding thermal neutrons, gamma rays, X rays and alpha particles is obtained. Compared with traditional lead gamma ray shielding materials with single function, the SnBi / B4C radiation shielding composite material solves the problem that neutrons cannot be shielded, and the selected raw materials are non-toxic, so that the composite material is expected to replace lead and be used for radiation shielding in the medical field.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation technology, specifically relating to a method for preparing SnBi / B4C radiation shielding composite material. Background Technology

[0002] Radiation is widely used in medicine, including imaging techniques such as X-rays, computed tomography (CT), and magnetic resonance imaging (NMR) for non-invasive image acquisition of internal human structures, enabling accurate diagnosis of fractures, tumors, heart disease, and other conditions. Radiotherapy utilizes high-energy radiation, such as X-rays or heavy ion beams, to precisely locate and destroy cancer cells, improving treatment efficacy. Neutron therapy is even more effective under certain conditions due to its physical properties. Through the Bragg peak and neutron capture reaction, it achieves a stronger killing effect on cancer cells. In recent years, research on neutron therapy has yielded some results and has been applied in clinical treatment.

[0003] With the development of radiation medicine, the requirements for the performance of radiation protection materials have increased. When selecting protective materials, the comprehensive shielding performance of various types of radiation must be considered, including neutrons, gamma rays, X-rays, and other charged particles of different energies. Heavy elements (such as W, Pb, Bi, Sn, Fe, Cu, etc.) have good attenuation effects on gamma rays and X-rays, but they also need to be combined with protective materials that have a large neutron absorption cross-section, good physicochemical properties, and excellent radiation resistance stability to achieve a relatively comprehensive shielding capability.

[0004] Lead is widely used as a radiation shielding material in the medical field, but its high density, heavy weight, and toxicity limit its practical applications. SnBi alloys have good machinability and corrosion resistance, and offer good shielding effects against gamma rays and X-rays. B4C particles, due to their high strength, good stability, and large neutron reaction cross-section, can not only serve as reinforcing fillers to improve the mechanical properties of materials, but also act as neutron absorbers, endowing materials with neutron shielding capabilities. However, the individual use of these materials also has certain limitations. Therefore, this invention combines the advantages of each material component to successfully prepare a non-toxic, moderately dense SnBi / B4C radiation shielding composite material capable of simultaneously shielding against gamma rays and neutrons. Summary of the Invention

[0005] This invention proposes a method for preparing a non-toxic, moderately dense SnBi / B4C radiation shielding composite material that can simultaneously shield gamma rays and neutrons. The material is prepared using a molding process of ball milling, cold pressing, and vacuum hot pressing sintering, which fully utilizes the different excellent properties of the single material to obtain a high-performance SnBi / B4C radiation shielding composite material. This solves the problems of traditional lead shielding materials, such as toxicity, excessive mass, and inability to simultaneously shield gamma rays and neutron radiation.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for preparing a SnBi / B4C radiation shielding composite material, specifically including the following steps:

[0008] Step 1: Under inert gas protection, Sn powder, Bi powder, B4C powder, anhydrous ethanol and n-butanol are initially mixed by magnetic stirring to obtain a mixture;

[0009] Step 2: Pour the mixture obtained in Step 1 into a ball mill jar and ball mill it under inert gas protection to obtain a composite powder solution with fine particle size and uniform mixing.

[0010] Step 3: Under the protection of inert gas, the composite powder solution obtained in Step 2 is heated while being magnetically stirred until the liquid evaporates completely, resulting in a uniformly mixed composite powder.

[0011] Step 4: Place the composite powder obtained in Step 3 into a mold and cold press it to form a composite material preform;

[0012] Step 5: Place the composite preform obtained in Step 4 into a vacuum hot press furnace, and perform hot pressing sintering under inert gas protection. After cooling, SnBi / B4C radiation shielding composite material is obtained.

[0013] In step one, the average particle size of Sn powder is 18 μm, the average particle size of Bi powder is 20 μm, the mass ratio of Sn powder to Bi powder is 88:12, and Sn powder and Bi powder account for 85% to 97% of the total mass of Sn powder, Bi powder and B4C powder; B4C powder has a cubic crystal structure and an average particle size of 0.5 μm.

[0014] In step one, the total amount of anhydrous ethanol and n-butanol added is 1 to 1.5 times the total mass of Sn powder, Bi powder and B4C powder, and the mass ratio of anhydrous ethanol to n-butanol is 1:1.

[0015] In step two, zirconia balls are used as the milling media, with a ball-to-material ratio of 10:1 to 15:1.

[0016] In step two, the ball mill rotation speed is 400-600 r / min, the reversal time is 10 min, and the ball milling time is 8-12 h.

[0017] In step three, the composite powder solution is heated while being magnetically stirred until most of the anhydrous ethanol and n-butanol evaporate, and the mixed solution becomes semi-solid. Stirring is then stopped, and heating continues until the anhydrous ethanol and n-butanol completely evaporate, resulting in a uniformly mixed composite powder. This method can prevent the powder from stratifying and precipitating due to gravity in the solution because of large density differences. The powder moves vigorously in the solution under the action of magnetic stirring, which is beneficial to the dispersion of the powder. The magnetic stirring speed is 300-500 r / min, and the heating temperature is 40-60℃.

[0018] In step four, during the cold pressing process, the pressure is 25-35 MPa, and the holding time is 1-3 minutes.

[0019] In step five, the parameters for hot pressing sintering are: apply a pressure of 10 MPa to the composite green body, maintain for 90 to 150 minutes, and heat at a temperature of 210 to 250°C.

[0020] This invention first utilizes the pressure and shear force of ball milling, along with the dispersion effect of the solution, to effectively mix Sn powder, Bi powder, and B4C powder uniformly, avoiding powder agglomeration. The uniformly mixed powder is then cold-pressed into shape and placed in a vacuum hot press furnace for hot pressing sintering, resulting in a SnBi / B4C radiation shielding composite material with uniform composition. This fully leverages the γ-ray shielding effect of the SnBi matrix and the strengthening effect of B4C particles on the matrix, as well as their own neutron shielding effect, to obtain a high-performance B4C-reinforced SnBi-based composite material capable of simultaneously shielding neutron and γ-ray radiation. This solves the problem that existing shielding materials cannot simultaneously shield γ-ray and neutron radiation.

[0021] This invention involves heating the powder solution after ball milling while magnetically stirring it. The powder moves violently in the solution under the action of magnetic stirring, causing the liquid to evaporate, which is beneficial to the dispersion of the powder. This invention successfully solves the problem that Sn powder, Bi powder, and B4C powder will form stratified sediments in the solution due to the large density difference after wet milling and the effect of gravity.

[0022] This invention adds B4C particles to the SnBi alloy matrix. B4C can absorb a large number of neutrons without forming any radioactive isotopes, making it an ideal neutron absorber that provides excellent neutron radiation shielding capabilities. In addition, due to its low price, low density, high strength, good high-temperature stability, and good chemical stability, it is widely used in wear-resistant materials, ceramic reinforcing phases, and reinforcing fillers. Therefore, adding B4C particles to the SnBi alloy matrix can enhance the strength of the metal, reduce the weight of the material, and increase the hardness of the material.

[0023] The materials used in this invention are all non-toxic, more environmentally friendly and lighter than traditional lead shielding materials, and have neutron radiation shielding capabilities that lead does not possess. They can shield various types of radiation and have a wider range of applications. Attached Figure Description

[0024] Figure 1 Physical products of the SnBi / B4C radiation shielding composite material prepared in Example 1 of the present invention (a cold-pressed blank and a sintered finished product, respectively);

[0025] Figure 2 The image shows a SEM image of the SnBi / B4C radiation shielding composite material prepared in Example 1 of this invention.

[0026] Figure 3 The energy spectrum of the SnBi / B4C radiation shielding composite material prepared in Example 1 of this invention ( Figure 3 a) Element distribution ( Figure 3 b);

[0027] Figure 4 The image shows the gamma-ray shielding efficiency of the SnBi / B4C radiation shielding composite material prepared in Example 1 of this invention.

[0028] Figure 5 The thermal neutron shielding efficiency diagram is shown for the SnBi / B4C radiation shielding composite material prepared in Example 1 of this invention. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] The Sn powder used in the embodiments of the present invention has an average particle size of 18 μm, the Bi powder has an average particle size of 20 μm, and the B4C powder has a cubic crystal structure with an average particle size of 0.5 μm; all materials used in the embodiments are conventional commercially available products.

[0031] Example 1

[0032] A method for preparing a SnBi / B4C radiation shielding composite material, specifically including the following steps:

[0033] Step 1: Fill the vacuum glove box with argon gas to protect the raw materials. Add 20g of mixed powder, 12.5g of anhydrous ethanol and 12.5g of n-butanol to a beaker. The mixed powder contains 80.08% Sn powder, 10.92% Bi powder and 9% B4C powder by mass. Stir magnetically for 10 minutes to mix all the raw materials into a mixture.

[0034] Step 2: Pour the mixture obtained in Step 1 into a ball mill jar, fill the jar with argon gas, use zirconia balls as the ball milling medium, the ball-to-material ratio is 10:1, and wet mill for 8 hours at 600 r / min, changing the direction every 10 min to obtain a composite powder solution with fine particle size and uniform mixing.

[0035] Step 3: Under argon protection, the composite powder solution obtained in Step 2 is heated at 40°C and magnetically stirred at 500 r / min. The mixture is stirred and heated until most of the anhydrous ethanol and n-butanol evaporate and the mixed solution becomes semi-solid. Stirring is stopped, and the temperature is maintained until the anhydrous ethanol and n-butanol completely evaporate, resulting in a uniformly mixed composite powder.

[0036] Step 4: Place the composite powder obtained in Step 3 into a graphite mold and cold press it under a pressure of 25 MPa for 3 minutes to obtain a composite material preform.

[0037] Step 5: Place the composite preform obtained in Step 4 into a vacuum hot press furnace. Under argon protection, apply a pressure of 10 MPa to the composite preform and maintain it for 90 minutes. Heat the preform at 250°C and perform hot pressing sintering. After cooling, obtain the SnBi / B4C radiation shielding composite material.

[0038] SnBi / B4C radiation shielding composite materials with thicknesses ranging from 0.2 cm to 20 cm were prepared according to the above method.

[0039] Figure 1 The figures show the cold-pressed blank and the sintered finished product. As can be seen from the figures, the powder is formed under pressure, the surface of the blank is smooth, and after sintering, the powder particles bond and stick together, and the pores are discharged to obtain the sintered finished product.

[0040] Figure 2 The image shows a SEM image of the SnBi / B4C radiation shielding composite material. As can be seen from the image, the silvery-white Bi and gray Sn form an alloy, and the black B4C particles are evenly distributed on the SnBi alloy matrix. The fine and dispersed B4C particles can effectively hinder the movement of dislocations in the matrix, thereby improving the strength of the composite material.

[0041] Figure 3 a is the energy spectrum of the SnBi / B4C radiation shielding composite material, which shows the approximate composition distribution of the composite material. The components other than Sn, Bi and B4C have basically volatilized during the sintering process. Figure 3 b represents the elemental distribution of the SnBi / B4C radiation shielding composite material. As can be seen from the figure, the elements are evenly distributed, proving the feasibility of the powder mixing method using wet grinding in a ball mill with simultaneous heating and stirring. The uniform distribution of elements in this material is beneficial for reducing radiation transmittance and improving the mechanical properties of the material.

[0042] Figure 4 The graph shows the gamma-ray shielding efficiency of SnBi / B4C radiation shielding composite material. It illustrates the shielding capability of SnBi / B4C radiation shielding composite material against gamma rays at different energies and thicknesses. The closer the shielding efficiency is to 1, the better the protection. At the same energy, the thicker the material, the higher the shielding efficiency. A shielding material of about 3 cm thickness can shield more than 80% of gamma-ray radiation below 1 MeV.

[0043] Figure 5 The graph shows the thermal neutron shielding efficiency of the SnBi / B4C radiation shielding composite material. The energy of the thermal neutron is 0.0253 eV. As can be seen from the graph, the shielding efficiency gradually approaches 1 as the material thickness increases. Approximately 0.8 cm of SnBi / B4C radiation shielding composite material can shield 80% of thermal neutrons. With the increase of B4C content and material thickness, its thermal neutron protection performance will gradually improve.

[0044] Example 2

[0045] A method for preparing a SnBi / B4C radiation shielding composite material, specifically including the following steps:

[0046] Step 1: Fill the vacuum glove box with argon gas to protect the raw materials. Add 20g of mixed powder, 10g of anhydrous ethanol and 10g of n-butanol to a beaker. The mixed powder contains 85.36% Sn powder, 11.64% Bi powder and 3% B4C powder by mass. Stir magnetically for 10 minutes to mix all the raw materials into a mixture.

[0047] Step 2: Pour the mixture obtained in Step 1 into a ball mill jar, fill the jar with argon gas, use zirconia balls as the ball milling medium, the ball-to-material ratio is 13:1, wet mill for 10 hours at 500 r / min, changing the direction every 10 minutes, to obtain a composite powder solution with fine particle size and uniform mixing.

[0048] Step 3: Under argon protection, the composite powder solution obtained in Step 2 is heated at 50°C and magnetically stirred at 400 r / min. The mixture is stirred and heated until most of the anhydrous ethanol and n-butanol evaporate and the mixed solution becomes semi-solid. Stirring is stopped, and the temperature is maintained until the anhydrous ethanol and n-butanol completely evaporate, resulting in a uniformly mixed composite powder.

[0049] Step 4: Place the composite powder obtained in Step 3 into a graphite mold and cold press it under a pressure of 30 MPa for 2 minutes to obtain a composite material preform;

[0050] Step 5: Place the composite preform obtained in Step 4 into a vacuum hot press furnace. Under argon protection, apply a pressure of 10 MPa to the composite preform and maintain it for 120 min. Heat the preform at 230℃ and perform hot pressing sintering. After cooling, obtain the SnBi / B4C radiation shielding composite material.

[0051] Example 3

[0052] A method for preparing a SnBi / B4C radiation shielding composite material, specifically including the following steps:

[0053] Step 1: Fill the vacuum glove box with argon gas to protect the raw materials. Add 20g of mixed powder, 15g of anhydrous ethanol and 15g of n-butanol to a beaker. The mixed powder includes 74.8% Sn powder, 10.2% Bi powder and 15% B4C powder by mass. Stir magnetically for 10 minutes to mix all the raw materials into a mixture.

[0054] Step 2: Pour the mixture obtained in Step 1 into a ball mill jar, fill the jar with argon gas, use zirconia balls as the ball milling medium, the ball-to-material ratio is 15:1, wet mill for 12 hours at 400 r / min, changing the direction every 10 min, to obtain a composite powder solution with fine particle size and uniform mixing.

[0055] Step 3: Under argon protection, the composite powder solution obtained in Step 2 is heated at 60°C and magnetically stirred at 300 r / min. The mixture is stirred and heated until most of the anhydrous ethanol and n-butanol evaporate and the mixed solution becomes semi-solid. Stirring is stopped, and the temperature is maintained until the anhydrous ethanol and n-butanol completely evaporate, resulting in a uniformly mixed composite powder.

[0056] Step 4: Place the composite powder obtained in Step 3 into a graphite mold and cold press it under a pressure of 35 MPa for 1 minute to obtain a composite material preform.

[0057] Step 5: Place the composite preform obtained in Step 4 into a vacuum hot press furnace. Under argon protection, apply a pressure of 10 MPa to the composite preform and maintain it for 150 min. Heat the preform at 210℃ and perform hot pressing sintering. Then, after cooling treatment, obtain the SnBi / B4C radiation shielding composite material.

[0058] This invention utilizes ball milling and powder metallurgy forming methods to fully leverage the γ-ray shielding capability of SnBi alloy and the reinforcing and neutron radiation shielding effects of B4C particles to prepare a SnBi / B4C radiation shielding composite material.

[0059] The above description is merely a preferred embodiment of the present invention and does not impose any limitation on the present invention. All simple modifications, alterations, and equivalent changes made according to the technical essence of the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing a SnBi / B4C radiation shielding composite material, characterized in that, Includes the following steps: Step 1: Under inert gas protection, Sn powder, Bi powder, B4C powder, anhydrous ethanol and n-butanol are stirred and mixed to obtain a mixture; Step 2: The mixture obtained in Step 1 is ball-milled under inert gas protection to obtain a composite powder solution; Step 3: Under the protection of an inert gas, the composite powder solution obtained in Step 2 is heated while stirring until the liquid evaporates completely, thus obtaining the composite powder. Step 4: Place the composite powder obtained in Step 3 into a mold and cold press it to form a composite material preform; Step 5: The composite preform obtained in Step 4 is hot-pressed and sintered in a vacuum hot press furnace under inert gas protection. After cooling, SnBi / B4C radiation shielding composite material is obtained. In step one, the average particle size of Sn powder is 18 μm, the average particle size of Bi powder is 20 μm, the mass ratio of Sn powder to Bi powder is 88:12, and Sn powder and Bi powder account for 85%~97% of the total mass of Sn powder, Bi powder and B4C powder; B4C powder has a cubic crystal structure and an average particle size of 0.5 μm; the total amount of anhydrous ethanol and n-butanol added is 1~1.5 times the total mass of Sn powder, Bi powder and B4C powder, and the mass ratio of anhydrous ethanol to n-butanol is 1:

1.

2. The method for preparing the SnBi / B4C radiation shielding composite material according to claim 1, characterized in that, In step two, zirconia balls are used as the milling media, with a ball-to-material ratio of 10:1 to 15:

1.

3. The method for preparing the SnBi / B4C radiation shielding composite material according to claim 1, characterized in that, In step two, the ball milling speed is 400~600 r / min, the reversal time is 10 min, and the ball milling time is 8~12 h.

4. The method for preparing the SnBi / B4C radiation shielding composite material according to claim 1, characterized in that, In step three, the magnetic stirring speed is 300~500 r / min, and the heating temperature is 40~60℃.

5. The method for preparing the SnBi / B4C radiation shielding composite material according to claim 1, characterized in that, In step four, the cold pressing pressure is 25~35MPa, and the holding time is 1~3min.

6. The method for preparing the SnBi / B4C radiation shielding composite material according to claim 1, characterized in that, In step five, the hot pressing sintering pressure is 10 MPa, the holding time is 90~150 min, and the temperature is 210~250℃.

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