Anti-radiation high-entropy max phase ceramic and preparation method thereof

Abstract

The application relates to an anti-radiation high-entropy MAX phase ceramic and a preparation method thereof, and belongs to the technical field of nuclear reactor materials. a Zr b V c Nb d Ta e )2AlC; wherein a+b+c+d+e=1. The high-entropy MAX phase ceramic provided by the application has radiation resistance and high-temperature resistance, has a small neutron absorption cross section, can inhibit the growth of radiation defects and helium bubbles, and improves the safety of nuclear materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nuclear reactor materials, and particularly relates to an anti-irradiation high-entropy MAX phase ceramic and a preparation method thereof. BACKGROUND

[0002] High-performance nuclear materials are important guarantees for the safety of nuclear energy systems. At present, the main nuclear cladding material is zirconium alloy. However, under extreme conditions such as loss of coolant, the zirconium alloy cladding often reacts with water vapor at high temperatures to produce a large amount of hydrogen, which eventually leads to explosion, causing irreparable losses to the society and human life. Moreover, metal materials are prone to generate hydrides during service, leading to embrittlement of metal materials, reducing material performance, and affecting the safety of nuclear power systems.

[0003] Nuclear cladding materials often face harsh working environments such as high temperature, strong radiation, strong corrosion, and high wear during service. The cladding materials of the fourth generation nuclear reactor, which is currently in the research and development stage, are subjected to much higher radiation doses than the third generation nuclear reactor. Therefore, in order to meet the application requirements of the fourth generation nuclear reactor, it is crucial to improve the anti-radiation, anti-corrosion, anti-wear, and high-temperature resistance of the cladding materials through material design and development, which is of great importance to the safe development of nuclear energy. SUMMARY

[0004] Therefore, in order to solve the problem of poor radiation resistance and high-temperature resistance of current nuclear reactor cladding materials, the present application combines the advantages of high-entropy and MAX phase ceramic materials to provide a high-entropy MAX phase ceramic with good anti-radiation performance and a preparation method thereof.

[0005] Specifically, in a first aspect, the present application provides an anti-irradiation high-entropy MAX phase ceramic, the chemical composition of the anti-irradiation high-entropy MAX phase ceramic is represented by the general formula (Ti a Zr b V c Nb d Ta e )2AlC; wherein a+b+c+d+e=1.

[0006] Preferably, a=0.05-0.2, b=0.2-0.65, c=0.05-0.2, d=0.2-0.35, and e=0.05-0.2.

[0007] Preferably, the density of the anti-irradiation high-entropy MAX phase ceramic is 98.0-99.5%.

[0008] In a second aspect, the present application provides a preparation method of the above-mentioned anti-irradiation high-entropy MAX phase ceramic, comprising the following steps:

[0009] (1) selecting single element powders of Ti, Zr, V, Nb, Ta, Al and C as raw materials, weighing and mixing according to the molar ratio of general formula (Ti a Zr b V c Nb d Ta e )2AlC to obtain powder raw materials;

[0010] (2) pre-pressing the powder raw materials, then placing them in a protective atmosphere, and performing hot-press sintering at 1400-1600℃ for 0.5-2.5 hours to obtain the anti-irradiation high-entropy MAX phase ceramic.

[0011] Preferably, the purity of the single element powders is greater than 99.5wt%.

[0012] Preferably, the mixing method is ball milling, and the ball milling parameters include: solvent is ethanol, grinding medium is WC ball, ball-to-material mass ratio is 4-6:1, and ball milling speed is 300-600r / min.

[0013] In addition, preferably, the slurry obtained by ball milling is dried, and the drying method is vacuum rotary evaporation, with the rotary evaporation temperature controlled at 65℃.

[0014] Preferably, the protective atmosphere is an inert atmosphere, preferably argon atmosphere.

[0015] Preferably, the heating rate of the hot-press sintering is 15-30℃ / min, and the hot-press pressure during the heating process is 6-12MPa; the hot-press pressure during the holding process at the sintering temperature is 20-30MPa.

[0016] Preferably, after the hot-press sintering is completed, cooling is performed, and the cooling method is natural cooling to room temperature.

[0017] Advantages

[0018] The present application increases the solid solution of transition metal elements to increase the entropy to obtain a uniform high-entropy MAX phase ceramic. The high-entropy MAX phase ceramic has a large atomic dispersion and lattice stress, and vacancies exist due to valence state compensation and delayed diffusion effect. The large atomic dispersion and lattice stress can inhibit defect diffusion aggregation, and the vacancies provide defect residence space to block defect growth, thereby helping to improve the anti-irradiation damage performance of the MAX phase ceramic.

[0019] By regulating the proportion of transition metal elements (the composition of Zr and Nb is higher), the MAX phase ceramic with lower neutron absorption cross section can be obtained while the entropy is increased. The high-entropy MAX phase ceramic provided by the application has good radiation resistance and high-temperature resistance, small neutron absorption cross section, can well inhibit the growth of radiation defects and helium bubbles, and greatly improves the safety of nuclear materials. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The element distribution map of the anti-radiation high-entropy MAX phase ceramic prepared in Example 1 of the application, and the HAADF white point represents the atomic position;

[0021] Figure 2 The atomic phase diagram of the anti-radiation high-entropy MAX phase ceramic prepared in Example 1 of the application at a radiation dose of 2.5dpa;

[0022] Figure 3 The selected area electron diffraction contrast diagram of the anti-radiation high-entropy MAX phase ceramic prepared in Example 1 of the application and the unary low-entropy MAX phase ceramic after 540keV helium ion irradiation;

[0023] Figure 4 The helium bubble distribution map of the anti-radiation high-entropy MAX phase ceramic prepared in Example 1 of the application after 540keV helium ion irradiation and then 800℃ annealing. DETAILED DESCRIPTION

[0024] The application will be further described by the following embodiments, and it should be understood that the following embodiments are only used to illustrate the application, but not to limit the application.

[0025] The application combines the advantages of high-entropy and MAX phase ceramic materials, and provides a high-entropy MAX phase ceramic with good radiation resistance. The anti-radiation high-entropy MAX phase ceramic is composed of Ti, Zr, V, Nb, Ta, Al and C seven elements, and the chemical composition general formula is (Ti a Zr b V c Nb d Ta e )2AlC, wherein a+b+c+d+e=1.

[0026] In some preferred embodiments, a can be controlled to be 0.05-0.2, b can be controlled to be 0.2-0.65, c can be controlled to be 0.05-0.2, d can be controlled to be 0.2-0.35, and e can be controlled to be 0.05-0.2. The density of the anti-radiation high-entropy MAX phase ceramic is 98.0-99.5%.

[0027] High-entropy MAX phase ceramic material combines high temperature stability, high strength of ceramic and good electrical conductivity, thermal conductivity, fracture toughness, thermal shock resistance and machinability of metal material. The material in this form generally does not react with water vapor and does not cause hydrogen embrittlement, and can maintain good stability in a wide temperature range. At the same time, the characteristics of high-entropy also make the material have high-entropy, lattice distortion, delayed diffusion and "cocktail" effects, which help MAX phase ceramic material to inhibit the clustering behavior of irradiation defects and improve the anti-irradiation performance of the material.

[0028] The following exemplary illustrates the preparation method of the anti-irradiation high-entropy MAX phase ceramic provided by the application, mainly including the following steps.

[0029] Mixing. Selecting the single element powders of Ti, Zr, V, Nb, Ta, Al and C (graphite, etc.) with a purity of more than 99.5wt%, weighing and uniformly mixing according to the molar ratio of general formula (Ti a Zr b V c Nb d Ta e )2AlC to obtain the powder raw material.

[0030] In some embodiments, according to the provisions of the element content in the high-entropy concept, the contents of a, b, c, d and e in the general formula (Ti a Zr b V c Nb d Ta e )2AlC can be controlled as a=0.05-0.2, b=0.2-0.65, c=0.05-0.2, d=0.2-0.35, e=0.05-0.2, and a+b+c+d+e=1.

[0031] Compared with unary MAX phase ceramic, the high-entropy MAX phase ceramic provided by the application has better irradiation resistance and high temperature resistance. The transition metal single elements selected by the preparation method disclosed by the application have low melting points and are close to each other, and have low neutron absorption cross section, so that a solid solution can be formed at a lower temperature, thereby being easy to form a high-entropy MAX phase.

[0032] In the M-site elements (Ti, Zr, V, Nb, Ta) selected by the preparation method of the application, the content of each element is controlled to be more than 5at% (0.05), so that the ceramic material can realize the high-entropy effect. Otherwise, if the content of each M-site transition metal is low, it is difficult to achieve a certain entropy increase effect.

[0033] In the solid solubility range allowed by the high-entropy effect, the content of Zr and Nb is relatively increased, the content of Ti, V and Ta is relatively reduced, and the content of Zr is controlled to be less than 65 at% (0.65), so that the high-entropy effect can be realized. In this way, the high-entropy effect can be exerted while maintaining the effect of relatively small neutron absorption cross section, thereby appropriately avoiding unnecessary consumption of neutrons by the nuclear reactor, and inhibiting the growth of irradiation defects and helium bubbles due to the lattice distortion and delayed diffusion effects of high-entropy, thereby greatly improving the safety of nuclear materials.

[0034] Ball milling. The above-obtained powder raw material is placed in a ball milling tank, ethanol or the like is used as a solvent, WC balls or the like are used as a grinding medium, the mass ratio of balls to material is 4-6:1, the ball milling speed is 300-600 r / min, and ball milling is performed to obtain a uniformly mixed slurry. In some embodiments, the mass ratio of balls to material can be controlled to be 6:1, and the ball milling speed is 400 r / min.

[0035] Drying. The above-obtained uniformly mixed slurry is subjected to vacuum rotary evaporation to be fully dried to obtain a sintering powder. The rotary evaporation temperature can be controlled to be 65°C.

[0036] Molding and sintering. The above-obtained sintering powder is placed in a graphite mold, pre-pressed into a shape, and then placed in a vacuum hot pressing furnace for hot pressing and sintering.

[0037] In some embodiments, the process of hot pressing and sintering can be: first vacuumizing, then introducing argon gas with a purity of 99.99 wt% for protection, and the protection atmosphere pressure is 1 atmosphere. At the same time, the heating rate can be controlled to be 15-30°C / min in combination with the performance of the hot pressing furnace. A slow heating rate can cause Al to settle, thereby reducing the purity of the synthesized MAX phase. The hot pressing pressure during heating can be controlled to be 6-12 MPa to avoid the metal being forcedly squeezed out of the mold due to melting. A high pressure can cause the metal in a semi-melted state to be squeezed out of the mold, thereby failing to obtain a complete material; and a low pressure can cause the sintered MAX phase ceramic to be not uniform and dense enough. The temperature is maintained at 1400°C-1600°C for 0.5-2.5 h, and the pressure during the maintaining process can be controlled to be 20-30 MPa.

[0038] After sintering, the furnace body is naturally cooled to room temperature to obtain the anti-irradiation high-entropy MAX phase ceramic.

[0039] The following further illustrates the embodiments to explain the present application in detail. It should also be understood that the following embodiments are only used to further illustrate the present application and cannot be understood as a limitation to the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters and the like described in the following examples are only one example in the appropriate range, that is, those skilled in the art can make appropriate selection within the range through the description herein, and are not limited to the specific values of the following examples.

[0040] Embodiment 1

[0041] Mixing. The elemental powders of Ti, Zr, V, Nb, Ta, Al and C with a purity greater than 99.5wt% were selected, and the elemental powders were weighed and uniformly mixed according to the molar ratio Ti:Zr:V:Nb:Ta:Al:C = 0.4:0.4:0.4:0.5:0.3:1:1 to obtain 10g of the powder raw material.

[0042] Ball milling. The powder raw material obtained above was placed in a ball milling tank, ethanol was used as a solvent, and WC balls were used as a grinding medium to perform ball milling to obtain a uniformly mixed slurry. The mass ratio of balls to material was 6:1, and the ball milling speed was 400r / min.

[0043] Drying. The uniformly mixed slurry obtained above was subjected to vacuum rotary evaporation to fully dry it to obtain a sintering-ready powder. The rotary evaporation temperature was controlled at 65℃.

[0044] Molding and sintering. The sintering-ready powder above was placed in a graphite die, pre-pressed into a shape, and then placed in a vacuum hot pressing furnace for hot pressing and sintering. The hot pressing and sintering process was as follows: first, vacuum was drawn, then pure argon gas with a purity of 99.99wt% was introduced for protection, the pressure of the protective atmosphere was 1atm, the heating rate was 20℃ / min, the pressure during the heating process was 6MPa, the temperature was raised to 1400℃ and held for 1h, and the pressure during the holding process was 20MPa. After sintering, the furnace body was naturally cooled to room temperature to prepare the anti-irradiation high-entropy MAX phase ceramic.

[0045] Figure 1 The element distribution map of the anti-irradiation high-entropy MAX phase ceramic prepared in Embodiment 1 of the present application is shown, and the HAADF white dot represents the atomic position. As can be seen from the figure, each element in the anti-irradiation high-entropy MAX phase ceramic prepared in Embodiment 1 is uniformly solid-solved.

[0046] A room temperature anti-irradiation test was performed on the high-entropy MAX phase ceramic grains obtained by hot pressing and sintering using 540keV helium ions. Figure 2The atomic phase diagram of the anti-radiation high-entropy MAX phase ceramic prepared in Embodiment 1 at an irradiation dose of 2.5 dpa is shown in the figure. As can be seen from the figure, the layered structure of the prepared anti-radiation high-entropy MAX phase ceramic material remains relatively complete, which indicates that the material has good anti-radiation performance.

[0047] The anti-radiation test of the high-entropy MAX phase ceramic grains obtained by hot-pressing sintering was carried out at room temperature using 540 keV helium ions. Figure 3 The selected area electron diffraction comparison diagram of the anti-radiation high-entropy MAX phase ceramic prepared in Embodiment 1 and the unary low-entropy MAX phase ceramic after irradiation by 540 keV helium ions is shown in the figure. As can be seen from the figure, the high-entropy MAX phase ceramic still maintains a relatively complete hexagonal structure after irradiation, while the unary low-entropy MAX phase ceramic has undergone a phase transition from hexagonal to cubic. Compared with the unary MAX phase ceramic, the high-entropy MAX phase ceramic of the application has better radiation resistance.

[0048] The anti-radiation test of the anti-radiation high-entropy MAX phase ceramic grains obtained by hot-pressing sintering was carried out at room temperature using 540 keV helium ions, and annealing was carried out at 800 DEG C. The anti-radiation high-entropy MAX phase ceramic prepared after irradiation was annealed at 800 DEG C, which can simulate the temperature and irradiation conditions under accident conditions.

[0049] Figure 4 The helium bubble distribution diagram of the anti-radiation high-entropy MAX phase ceramic prepared in Embodiment 1 after 800 DEG C annealing after irradiation by 540 keV helium ions is shown in the figure. As can be seen from the figure, the anti-radiation high-entropy MAX phase ceramic prepared in the application does not generate dislocations after annealing, the helium bubble size is small (6-10 nm), and the material layered structure is restored relatively complete, which indicates that the material has good high-temperature anti-radiation performance.

[0050] Embodiment 2

[0051] The scheme is basically the same as that of Embodiment 1, and the main difference is that the molar ratio of each single element powder is Ti:Zr:V:Nb:Ta:Al:C = 0.2:0.7:0.2:0.7:0.2:1:1; and the sintering temperature is 1500 DEG C.

[0052] Embodiment 3

[0053] The scheme is basically the same as that of Embodiment 1, and the main difference is that the molar ratio of each single element powder is Ti:Zr:V:Nb:Ta:Al:C = 0.1:1.3:0.1:0.4:0.1:1:1; the hot-pressing pressure during the heating process is 12 MPa, and the sintering temperature is 1600 DEG C.

[0054] Embodiment 4

[0055] The scheme is basically the same as that of Example 1, with the main difference being that the ball milling rotation speed is 600 r / min; the holding time of sintering is 2 hours, and the sintering temperature is 1600℃.

[0056] Comparative Example 1

[0057] The scheme is basically the same as that of Example 1, with the main difference being that, in the sintering, the hot-pressing pressure during the heating process is 20 MPa, and the sintering temperature is 1500℃.

[0058] In this comparative example, because the hot-pressing pressure during the heating process is too large, the metal is extruded out of the mold after reaching the melting point, and the block body and the mold are bonded after the reaction is completed, so the high-entropy MAX phase ceramic cannot be obtained.

[0059] Comparative Example 2

[0060] The scheme is basically the same as that of Example 1, with the main difference being that, in the sintering, the hot-pressing pressure during the heating process is 3 MPa, and the sintering temperature is 1500℃.

[0061] In this comparative example, because the hot-pressing pressure during the heating process is too small, the high-entropy MAX phase ceramic block body after the reaction is completed has low density and has many pores.

[0062] Comparative Example 3

[0063] The scheme is basically the same as that of Example 1, with the main difference being that, in the sintering, the heating rate is 3℃ / min, and the sintering temperature is 1500℃.

[0064] In this comparative example, because the heating rate is too low, the Al stays near the melting point for a long time, resulting in the Al not being reacted in time and settling down, and finally leading to a decrease in the purity of the ceramic sample.

[0065] Comparative Example 4

[0066] The scheme is basically the same as that of Example 1, with the main difference being that the molar ratio of the elemental powders is Ti:Zr:V:Nb:Ta:Al:C = 0.5:0.05:0.5:0.05:0.9:1:1.

[0067] In this comparative example, because the contents of Zr and Nb are too low, the configurational entropy is relatively low, the high-entropy effect cannot be achieved, the formed MAX phase is relatively disordered, and TaC enrichment occurs.

[0068] Although the content of the present application has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as limiting the present application. After reading the above content, various modifications and alternatives of the present application will be apparent to those skilled in the art. Therefore, the protection scope of the present application should be defined by the appended claims.

Claims

1. A method for preparing an anti-radiation high-entropy MAX phase ceramic, characterized in that, The chemical composition of the anti-radiation high-entropy MAX phase ceramic is (Ti a Zr b V c Nb d Ta e )2AlC; wherein a+b+c+d+e=1, a=0.05-0.2, b=0.2-0.65, c=0.05-0.2, d=0.2-0.35, e=0.05-0.2, and a, b, c, d, and e are not simultaneously 0.2; the density of the anti-radiation high-entropy MAX phase ceramic is 98.0-99.5%. The preparation method of the anti-radiation high-entropy MAX phase ceramic comprises the following steps: (1) Selecting elemental powders of Ti, Zr, V, Nb, Ta, Al and C as raw materials, weighing and uniformly mixing according to the molar ratio of general formula (Ti a Zr b V c Nb d Ta e )2AlC to obtain a powder raw material; (2) After the powder raw material is pre-pressed and formed, it is placed in a protective atmosphere, and hot-pressing sintering is performed at 1400-1600 DEG C for 0.5-2.5 hours to obtain the anti-radiation high-entropy MAX phase ceramic. The heating rate of the hot-pressing sintering is 15-30 DEG C / min, the hot-pressing pressure during the heating process is 6-12 MPa, and the hot-pressing pressure during the heat preservation process at the hot-pressing sintering temperature is 20-30 MPa.

2. The production method according to claim 1, characterized by, The purity of the elemental powder is greater than 99.5wt%.

3. The production method according to claim 1, characterized by, The mixing method of the raw material is ball-milling mixing, and the ball-milling mixing parameters include: the solvent is ethanol, the grinding medium is WC ball, the ball-to-material mass ratio is 4-6:1, and the ball-milling rotation speed is 300-600 r / min.

4. The production method according to claim 3, characterized by, The slurry obtained by the ball-milling mixing is dried, and the drying method is vacuum rotary evaporation, and the rotary evaporation temperature is controlled to be 65 DEG C.

5. The preparation method according to claim 1, characterized in that, The protective atmosphere is an inert atmosphere.

6. The production method according to claim 5, wherein The inert atmosphere is an argon atmosphere.

7. The preparation method according to claim 1, characterized in that, After the hot-pressing sintering is completed, cooling is performed, and the cooling method is natural cooling to room temperature.

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