Shielding composite material and method for manufacturing the same

Abstract

The application discloses a shielding composite material and a preparation method thereof. The preparation method comprises the following steps: S1, preparing high-entropy oxide powder by using a wet chemical method; S2, uniformly mixing the high-entropy oxide powder and tungsten carbide powder to obtain a mixture; in the mixture, the mass fraction of the high-entropy oxide powder is 10-30 parts, and the mass fraction of the tungsten carbide powder is 70-90 parts; S3, performing discharge plasma sintering on the mixture to obtain the shielding composite material; the tungsten carbide grain size of the shielding composite material is less than or equal to 0.8 microns. The high-entropy oxide is prepared by using the wet chemical method, and the mixture formed by the high-entropy oxide powder and the tungsten carbide powder is sintered by using a discharge plasma sintering process; the prepared shielding composite material has the advantages of small grain size, high mechanical strength and excellent high-temperature oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of ceramic matrix composites, and in particular to a shielding composite material and its preparation method. Background Technology

[0002] Tungsten carbide ceramics are widely used in nuclear power and other fields due to their high hardness, excellent wear resistance, corrosion resistance, radiation resistance, good high-temperature stability, and excellent shielding performance. However, some inherent characteristics of tungsten carbide limit its applications: 1) High melting point: Tungsten carbide has a melting point of approximately 2870℃, classifying it as an ultra-high-temperature material; 2) Low diffusion rate: Tungsten carbide has a low atomic self-diffusion coefficient, resulting in insufficient material migration between particles at conventional sintering temperatures; 3) Strong covalent bonds: The WC covalent bonds in tungsten carbide are strong, with high atomic bonding forces, making it difficult to achieve effective bonding between particles through diffusion mechanisms, thus hindering sintering. Therefore, tungsten carbide ceramics are typically prepared by adding sintering aids and calcining at high temperatures. However, this process easily leads to abnormal grain growth in tungsten carbide, severely affecting the mechanical properties of the material, and tungsten carbide is also prone to oxidation at high temperatures. Therefore, how to achieve grain refinement and prepare high-density tungsten carbide ceramics has become an urgent problem to be solved.

[0003] CN109252081A discloses a high-entropy alloy binder phase ultrafine tungsten carbide cemented carbide and its preparation method, wherein a high-entropy alloy with components such as Al, Co, Cr, Cu, Fe and N is used as the binder phase to prepare the tungsten carbide cemented carbide. This method reduces the sintering temperature of tungsten carbide ceramic materials to a certain extent. However, it has the following problems: (1) The high-entropy alloy generates a liquid phase at high temperature, which easily promotes grain growth, making it difficult to effectively control the grain size of tungsten carbide in the material; (2) The presence of Co element in the binder phase seriously affects the high-temperature performance of tungsten carbide materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an improved method for preparing a shielding composite material and the obtained shielding composite material.

[0005] The technical solution adopted by this invention to solve its technical problem is: to provide a shielding composite material, comprising the following steps:

[0006] S1. High-entropy oxide powder was prepared using a wet chemical method;

[0007] S2. Mix the high-entropy oxide powder and tungsten carbide powder evenly to obtain a mixture;

[0008] In the mixture, the mass fraction of high-entropy oxide powder is 10-30 parts, and the mass fraction of tungsten carbide powder is 70-90 parts;

[0009] S3. The mixture is subjected to discharge plasma sintering to obtain a shielding composite material, which is a tungsten carbide-high entropy oxide composite material.

[0010] In one embodiment, the tungsten carbide grain size of the shielding composite material is ≤0.8μm.

[0011] In one embodiment, the flexural strength of the shielding composite material is ≥1000MPa.

[0012] In one embodiment, the high-entropy oxide powder contains at least five of the following metal elements: Co, Ni, Mg, Zn, Cu, Al, Fe, Cr, V, Ti, and Nb.

[0013] In one embodiment, the high-entropy oxide powder contains the metal elements Co, Ni, Mg, Zn, and Cu.

[0014] In one embodiment, step S1 includes:

[0015] S1.1 Add CoSO4·7H2O, NiSO4·6H2O, MgSO4, ZnSO4·7H2O, and CuSO4·5H2O to deionized water in a set ratio and stir until completely dissolved to obtain a mixed solution of metal sulfates.

[0016] S1.2 Add NaOH solution to the mixed solution of metal sulfates and heat at 50℃~80℃ for 3~6 hours.

[0017] S1.3. The heated metal sulfate mixture solution is centrifuged and washed to obtain the precipitate;

[0018] S1.4. The precipitate is baked at 110℃~130℃ for 24~48 hours. The dried powder is then kept at 800℃~1000℃ for 1~3 hours and then quenched by air cooling to obtain high entropy oxide powder.

[0019] In one embodiment, in step S2, the median particle size of the tungsten carbide powder is 0.5 μm.

[0020] In one embodiment, in step S2, the high-entropy oxide powder and tungsten carbide powder are wet-mixed in a high-energy ball mill to ensure uniform dispersion and formation of mixed powder. The mixed powder is then dried and sieved to obtain a uniform mixture.

[0021] In one embodiment, in step S3, the mixture is placed in a discharge plasma sintering furnace, and under vacuum conditions, a pressure of 20 MPa to 30 MPa is applied. The power supply is turned on, the discharge plasma sintering furnace is heated and discharge plasma sintering is performed. After the temperature is raised to 1300°C to 1600°C, it is held for 5 to 20 minutes.

[0022] The present invention also provides a shielding composite material, which is prepared by any of the preparation methods described above.

[0023] The beneficial effects of this invention are as follows: High-entropy oxides prepared by wet chemical method have the characteristics of small particle size and high particle sphericity, and can be uniformly distributed in tungsten carbide matrix; the mixture formed by high-entropy oxide powder and tungsten carbide powder is sintered by spark plasma sintering (SPS) process, which has the advantages of fast heating rate, short sintering time, low sintering temperature and fast cooling rate. High-entropy oxides effectively inhibit abnormal growth of tungsten carbide grains, while promoting matrix sintering, thereby improving the mechanical strength and high temperature stability of the material.

[0024] The prepared shielding composite material has advantages such as small grain size, high mechanical strength and excellent high-temperature oxidation resistance. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0026] Figure 1 This is a microscopic morphology image of the shielding composite material prepared in Example 1 of this invention, with elemental EDS spectra of the elemental components.

[0027] Figure 2 This is a microscopic morphology image of the shielding composite material prepared in Example 2 of this invention, with elemental EDS spectra of the elemental components. Detailed Implementation

[0028] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] The shielding composite material of the present invention includes the following steps:

[0030] S1. High-entropy oxide powder was prepared using a wet chemical method.

[0031] The metal elements in high-entropy oxide powders include at least five of the following: Co, Ni, Mg, Zn, Cu, Al, Fe, Cr, V, Ti, and Nb. Therefore, high-entropy oxide powders include metal oxide powders corresponding to the above five or more metal elements.

[0032] In one embodiment, the metal elements of the high-entropy oxide powder include Co, Ni, Mg, Zn, and Cu.

[0033] Correspondingly, step S1 may specifically include:

[0034] S1.1 Add CoSO4·7H2O, NiSO4·6H2O, MgSO4, ZnSO4·7H2O, and CuSO4·5H2O to deionized water in a set ratio and stir until completely dissolved to obtain a mixed solution of metal sulfates.

[0035] S1.2 Add NaOH solution to the mixed solution of metal sulfates and heat at 50℃~80℃ for 3~6 hours.

[0036] S1.3. The heated metal sulfate mixture solution is centrifuged and washed to obtain the precipitate.

[0037] S1.4. The precipitate is baked at 110℃~130℃ for 24~48 hours. The dried powder is then held at 800℃~1000℃ for 1~3 hours, followed by air-cooling quenching to obtain high-entropy oxide powder. This high-entropy oxide powder includes oxide powders corresponding to Co, Ni, Mg, Zn and Cu.

[0038] Understandably, when the high-entropy oxide powder contains at least five of the following metal elements: Al, Fe, Cr, V, Ti, and Nb, or includes at least one of Al, Fe, Cr, V, Ti, and Nb in addition to Co, Ni, Mg, Zn, and Cu, or includes at least one of Co, Ni, Mg, Zn, and Cu and at least four of Al, Fe, Cr, V, Ti, and Nb, the specific steps for preparing the high-entropy oxide powder are the same as those in steps S1.1-S1.4 above.

[0039] In step S1, high-entropy oxide powder is prepared by wet chemical method, which has the characteristics of small particle size and high particle sphericity. The high-entropy oxide powder can be uniformly distributed in tungsten carbide matrix.

[0040] S2. Mix the high-entropy oxide powder and tungsten carbide powder evenly to obtain a mixture (i.e., mixed powder).

[0041] Tungsten carbide powder, as the matrix of the composite material, accounts for 70–90 parts by mass in the mixture; high-entropy oxide powder accounts for 10–30 parts by mass in the mixture.

[0042] In one embodiment, high-entropy oxide powder and tungsten carbide powder are wet-mixed in a high-energy ball mill to ensure uniform dispersion and form a mixed powder. The mixed powder is then dried and sieved to obtain a homogeneous mixture.

[0043] Preferably, in order to make the final composite material have low porosity, the median particle size of tungsten carbide powder is 0.5 μm.

[0044] S3. The mixture is subjected to discharge plasma sintering to obtain tungsten carbide-high entropy oxide composite material, i.e. shielding composite material.

[0045] Specifically, the mixture is placed in a discharge plasma sintering furnace, and the furnace is evacuated to create a vacuum. Under vacuum conditions, a pressure of 20 MPa to 30 MPa is applied, the power supply is turned on, the discharge plasma sintering furnace is heated, and discharge plasma sintering is performed. After the temperature reaches 1300℃ to 1600℃, it is held for 5 to 20 minutes.

[0046] In this invention, a discharge plasma sintering (SPS) process is used to sinter a mixture to obtain a shielding composite material. This process has the advantages of fast heating rate, short sintering time, low sintering temperature, and fast cooling rate, which further improves the densification of the composite matrix and significantly improves the overall performance of the material.

[0047] During the sintering process, high-entropy oxides effectively inhibit abnormal growth of tungsten carbide grains while promoting the sintering of the tungsten carbide matrix, thereby improving the mechanical strength and high-temperature stability of the material.

[0048] The tungsten carbide grain size of the shielding composite material prepared by the above method is ≤0.8μm. The flexural strength of the shielding composite material is ≥1000MPa.

[0049] The present invention will be further illustrated by specific embodiments below.

[0050] Example 1:

[0051] Using 20 parts by mass of high-entropy oxide powder and 80 parts by mass of tungsten carbide powder as raw materials, the mixture is homogenized by high-energy ball milling and then sintered by discharge plasma to obtain the shielding composite material.

[0052] The specific preparation method includes the following steps:

[0053] S1. Five metal sulfates, CoSO4·7H2O, NiSO4·6H2O, MgSO4, ZnSO4·7H2O, and CuSO4·5H2O, were added to 400 mL of deionized water in a specific ratio and stirred until completely dissolved. A 1 mol / L NaOH solution was then added to the metal sulfate mixture. The resulting solution was heated in a water bath at 50℃–80℃ for 3–6 hours. The solution was then transferred to centrifuge tubes and centrifuged and washed repeatedly. The precipitate was baked at 110℃–130℃ for 24–36 hours. The dried powder was then placed in a muffle furnace and held at 900℃–1000℃ for 1–2 hours, followed by air-cooling quenching to obtain high-entropy oxide powder.

[0054] S2. The prepared high-entropy oxide powder and tungsten carbide powder are wet-mixed in a high-energy ball mill to ensure uniform dispersion. The mixed powder is then dried and sieved to obtain a homogeneous mixture. Next, the powder is placed in a discharge plasma sintering furnace, and under vacuum conditions, a pressure of 20-25 MPa is applied. The power supply is started to heat up and discharge plasma sintering is performed, reaching a temperature of 1300℃-1400℃ and holding for 15-20 minutes.

[0055] The microstructure of the shielding composite material prepared in Example 1 is shown in the figure below. Figure 1 As shown in the figure (the right side of the figure shows the EDS elemental analysis spectrum of each element), it can be seen from the figure that the high-entropy oxide and tungsten carbide are evenly distributed, forming a micro-uniform composite material; the tungsten carbide grain size of this shielding composite material is ≤0.7μm, and the flexural strength is ≥1000MPa.

[0056] Example 2:

[0057] Using 30 parts by mass of high-entropy oxide powder and 70 parts by mass of tungsten carbide powder as raw materials, the mixture is homogenized by high-energy ball milling and then sintered by discharge plasma to obtain the shielding composite material.

[0058] The specific preparation method includes the following steps:

[0059] S1. Five metal sulfates, CoSO4·7H2O, NiSO4·6H2O, MgSO4, ZnSO4·7H2O, and CuSO4·5H2O, were added to 400 mL of deionized water in a specific ratio and stirred until completely dissolved. A 1 mol / L NaOH solution was then added to the metal sulfate mixture. The resulting solution was heated in a water bath at 50℃–80℃ for 3–6 hours. The solution was then transferred to centrifuge tubes and centrifuged and washed multiple times. The precipitate was then baked at 110℃–130℃ for 36–48 hours. The dried powder was then placed in a muffle furnace and held at 800℃–900℃ for 2–3 hours, followed by air-cooling quenching to obtain high-entropy oxide powder.

[0060] S2. The prepared high-entropy oxide powder and tungsten carbide powder are wet-mixed in a high-energy ball mill to ensure uniform dispersion. The mixed powder is then dried and sieved to obtain a homogeneous mixture. Next, the powder is placed in a discharge plasma sintering furnace, and under vacuum conditions, a pressure of 25-30 MPa is applied. The power supply is started to heat up and discharge plasma sintering is performed, with the temperature raised to 1400℃-1600℃ and held for 5-15 minutes.

[0061] The microstructure of the shielding composite material prepared in Example 2 is shown in the figure below. Figure 2 As shown in the figure (the right side of the figure shows the EDS elemental analysis spectra of each element), it can be seen from the figure that the high-entropy oxide and tungsten carbide are evenly distributed, forming a microscopically homogeneous composite material. The tungsten carbide grain size of this shielding composite material is ≤0.8μm, and the flexural strength is ≥1100MPa.

[0062] When the shielding composite material of this invention is used in nuclear power plants, it can be installed as a shielding wall on the side of equipment with radiation risks, or as a shielding cover around the equipment, or it can be installed between two plant buildings or other situations requiring shielding. This shielding composite material is a tungsten carbide-high entropy oxide composite material, which, compared with shielding materials formed from pure lead or pure tungsten, achieves the same shielding performance while having advantages such as lighter weight and smaller space occupation.

[0063] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a shielding composite material, characterized in that, Includes the following steps: S1. High-entropy oxide powder was prepared using a wet chemical method; S2. Mix the high-entropy oxide powder and tungsten carbide powder evenly to obtain a mixture; In the mixture, the mass fraction of high-entropy oxide powder is 10-30 parts, and the mass fraction of tungsten carbide powder is 70-90 parts; the metal elements in the high-entropy oxide powder include at least five of the following: Co, Ni, Mg, Zn, Cu, Al, Fe, Cr, V, Ti, and Nb. S3. The mixture is subjected to discharge plasma sintering to obtain a shielding composite material, which is a tungsten carbide-high entropy oxide composite material; the tungsten carbide grain size of the shielding composite material is ≤0.8μm, and the flexural strength of the shielding composite material is ≥1000MPa.

2. The method for preparing the shielding composite material according to claim 1, characterized in that, The high-entropy oxide powder contains the following metallic elements: Co, Ni, Mg, Zn, and Cu.

3. The method for preparing the shielding composite material according to claim 2, characterized in that, Step S1 includes: S1.1 Add CoSO4•7H2O, NiSO4•6H2O, MgSO4, ZnSO4•7H2O, and CuSO4•5H2O to deionized water in a set ratio and stir until completely dissolved to obtain a mixed solution of metal sulfates. S1.2 Add NaOH solution to the mixed solution of metal sulfates and heat at 50℃~80℃ for 3~6 hours. S1.

3. The heated metal sulfate mixture solution is centrifuged and washed to obtain the precipitate; S1.

4. The precipitate is baked at 110℃~130℃ for 24~48 hours. The dried powder is then kept at 800℃~1000℃ for 1~3 hours and then quenched by air cooling to obtain high entropy oxide powder.

4. The method for preparing the shielding composite material according to claim 1, characterized in that, In step S2, the median particle size of the tungsten carbide powder is 0.5 μm.

5. The method for preparing the shielding composite material according to claim 1, characterized in that, In step S2, the high-entropy oxide powder and tungsten carbide powder are wet-mixed in a high-energy ball mill to ensure uniform dispersion and formation of mixed powder. The mixed powder is then dried and sieved to obtain a uniform mixture.

6. The method for preparing the shielding composite material according to claim 1, characterized in that, In step S3, the mixture is placed in a discharge plasma sintering furnace. Under vacuum conditions, a pressure of 20MPa to 30MPa is applied, the power supply is turned on, the discharge plasma sintering furnace is heated and discharge plasma sintering is performed. After the temperature is raised to 1300℃ to 1600℃, it is held for 5 to 20 minutes.

7. A shielding composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

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