A lead-bismuth corrosion resistant max phase ceramic material and a preparation method and application thereof

Abstract

This invention belongs to the technical field of MAX phase ceramic materials, and relates to a lead-bismuth-resistant MAX phase ceramic material, its preparation method, and its application. This invention discloses a lead-bismuth-resistant MAX phase ceramic material by introducing a high oxygen affinity element Hf at the M-site, significantly enhancing the migration barrier of oxygen atoms between material layers. This allows the MAX phase ceramic material to effectively inhibit the migration and dissolution of A-site elements in a lead-bismuth environment, intrinsically improving the stability of the MAX phase crystal structure, thereby exhibiting excellent resistance to lead-bismuth corrosion.

Description

Technical Field

[0001] This invention belongs to the field of MAX phase ceramic materials technology, and relates to a MAX phase ceramic material resistant to lead-bismuth corrosion, its preparation method and application. Background Technology

[0002] Lead-cooled fast reactors (LFRs) belong to the fourth-generation advanced nuclear energy system reactor type, using liquid lead and lead-bismuth alloy (LBE) as the reactor coolant. This reactor type possesses excellent neutron performance, good chemical stability, and ease of miniaturization, making it one of the important research directions for future reactor development. Existing candidate materials suffer severe corrosion in high-temperature and liquid metal environments. For example, Cr and other major strengthening elements in 316L steel are prone to selective leaching, while T91 ferritic / martensitic steel faces severe grain boundary erosion and is more susceptible to failure under high-speed fluid erosion. Therefore, the development of novel structural materials with high compatibility with LBE is urgently needed.

[0003] Compared to traditional alloys, developing ceramic materials that combine high temperature resistance, radiation resistance, high toughness, and good Pb / LBE compatibility is of great significance for advancing LFR technology. MAX phase (general formula M...) n+1 AX n As a type of ternary layered compound, MAX phase has become a candidate material for future LFR structural components due to its excellent radiation resistance and corrosion resistance. The MAX phase crystal structure typically consists of covalent [M... n+1 X n The alternating stacking of structural sublayers and metallic A-layers endows it with unique potential as a core-based structural material: the nanolayered structure can accommodate irradiation defects, while the low MA-AM antisite defect formation energy helps dissipate energy and promote structural recovery, and the irradiation-induced phase transition is reversible at high temperatures. Regarding corrosion, the dense oxide layer formed by A / M site elements can inhibit degradation and even achieve high-temperature self-healing through oxides of A-site elements (such as Al). Furthermore, its compositional flexibility and nanocrystallization potential, combined with advanced synthesis techniques such as "chemical scissors," make customized design possible.

[0004] The compatibility of MAX phases in oxygen-controlled LBE environments is crucial for their application, primarily relying on the formation of continuous, dense oxide layers. These oxide layers typically originate from A-site (e.g., Al, Si) or M-site composite oxides with oxygen species. Current research focuses on the performance of such oxide layers and A-site elemental modulation strategies. Numerous examples have demonstrated their effectiveness, such as Cr2AlC and Ti3SiC2 forming effective protective layers in Pb and LBE after long-term exposure, respectively. A-site multi-element designs (e.g., Si replacing Al in Ti3AlC2) have also been shown to synergistically improve the continuity of Al2O3 protective layers. However, Zr2AlC still rapidly degrades in extremely low-oxygen LBE, revealing the limitations of this strategy. Notably, although the film-forming role of M-site elements is understood, their intrinsic interaction mechanism with LBE remains unknown, representing a weak link in current research. Summary of the Invention

[0005] The purpose of this invention is to address the problem of easy migration and instability of A-site elements in existing MAX phase materials in LBE environments. This invention proposes a MAX phase ceramic material resistant to lead-bismuth corrosion. By introducing the oxygen-affinity element Hf at the M site, the migration barrier of oxygen atoms between material layers is significantly enhanced. This allows the MAX phase ceramic material to effectively suppress the migration and dissolution of A-site elements in lead-bismuth environments, thereby intrinsically improving the stability of the MAX phase crystal structure and exhibiting excellent resistance to lead-bismuth corrosion.

[0006] One objective of this invention is achieved through the following technical solution: A MAX phase ceramic material resistant to lead-bismuth corrosion, with the molecular formula (Hf) x M 1-x )2AX, where M is selected from one or more refractory transition metals from Nb, Ta, Mo, and W, A is a main group element Al and / or Si, X is element C, and 0 < x ≤ 0.5; After being corroded in a liquid lead-bismuth environment, the lead-bismuth resistant MAX phase ceramic material forms, from the inside to the outside, a matrix MAX phase corrosion layer, an oxygen-containing MAX phase layer, an amorphous corrosion product layer, and a lead-rich corrosion product layer in sequence; wherein, the oxygen-containing MAX phase layer, the amorphous corrosion product layer, and the lead-rich corrosion product layer are oxygen-containing corrosion layers, and the thickness of the oxygen-containing corrosion layer is <0.8μm.

[0007] Preferably, the lead-bismuth-resistant MAX phase ceramic material is resistant to lead-bismuth corrosion at 500°C and 10 °C. -7 After 1000 h of corrosion in liquid lead-bismuth with wt.% oxygen content, the thickness of the oxygen-containing corrosion layer is ≤0.65μm.

[0008] Further preferably, the lead-bismuth-resistant MAX phase ceramic material is resistant to lead-bismuth corrosion at 500°C and 10... -7After 1000 h of corrosion in liquid lead-bismuth with wt.% oxygen content, the thickness of the oxygen-containing corrosion layer is ≤0.48μm.

[0009] More preferably, the lead-bismuth-resistant MAX phase ceramic material is resistant to lead-bismuth corrosion at 500°C and 10... -7 Corrosion in liquid lead-bismuth with wt.% oxygen content for 1000 h resulted in an oxygen-containing corrosion layer thickness ≤0.35μm.

[0010] Preferably, the molecular formula of the lead-bismuth corrosion-resistant MAX phase ceramic material is (Hf x M 1-x )2AX, where M is selected from at least one of Nb, Ta, Mo, W, A is a main group element Al or Si, X is element C, and 0.1≤x≤0.5.

[0011] Preferably, the molecular formula of the lead-bismuth corrosion-resistant MAX phase ceramic material is (Hf x M 1-x )2AX, where M is selected from at least two of Nb, Ta, Mo, and W, A is a main group element Al or Si, and X is element C, 0.2≤x≤0.5.

[0012] Further preferably, the molecular formula of the lead-bismuth-resistant MAX phase ceramic material is (Hf x M 1-x )2AX, where M is selected from at least two of Nb, Ta, Mo, and W, A is a main group element Al or Si, and X is element C, 0.4≤x≤0.5.

[0013] Preferably, the hardness of the lead-bismuth corrosion-resistant MAX phase ceramic material is >6.0 GPa.

[0014] Preferably, the lead-bismuth corrosion-resistant MAX phase ceramic material has a space group of P63 / mmc, belongs to the hexagonal crystal system, and has a grain size of 10~50 μm.

[0015] Preferably, the unit cell of the lead-bismuth corrosion-resistant MAX phase ceramic material is composed of alternating MX and A layers.

[0016] The second objective of this invention is achieved through the following technical solution: A method for preparing a lead-bismuth corrosion-resistant MAX phase ceramic material includes: uniformly mixing Hf and / or Hf-containing materials, M and / or M-containing materials, A and / or A-containing materials, and X and / or X-containing materials in a molar ratio of 2:1:1, and placing the resulting mixture in an inert atmosphere to react at a high temperature of 800~1700℃ for 0.1~10h to obtain a lead-bismuth corrosion-resistant MAX phase ceramic material.

[0017] Preferably, the Hf and / or Hf-containing materials include at least one of hafnium powder, hafnium blocks, hafnium carbide, and hafnium hydride; The M and / or M-containing materials include at least one of elemental M, M-containing alloys, and M-containing carbides; The A and / or A-containing materials include at least one of elemental A and A-containing alloys; The X and / or X-containing materials include at least one of toner and M-containing carbides.

[0018] The third objective of this invention is achieved through the following technical solution: Application of a lead-bismuth corrosion-resistant MAX phase ceramic material in lead-cooled fast neutron reactors.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention successfully prepared MAX phase ceramic materials with Hf and at least one of Nb, Ta, Mo, and W in solid solution at the M site using powder metallurgy. This method is simple, low-cost, and widely applicable, and can be easily extended to other solid solution systems. 2. Compared with the traditional method that relies on the oxide protective film formed after corrosion, this invention enhances the bonding ability of O atoms in the MAX phase material by solid solution of Hf at the M site, which hinders the destruction of the MAX phase structure caused by the migration and loss of A-site atoms during lead-bismuth corrosion. This improves the intrinsic resistance of the MAX phase material to lead-bismuth corrosion. After corrosion in a liquid lead-bismuth environment for 1000 h, only a thin oxide layer is formed on the surface, which has good corrosion resistance. 3. The MAX phase ceramic material resistant to lead-bismuth corrosion of the present invention can be used as fuel cladding, core structural components or corrosion-resistant coatings in lead-cooled fast reactors using liquid lead-bismuth alloy (LBE) as coolant. Thanks to the solid solution strengthening and stabilizing effect of Hf element, this material can effectively resist the oxidation and dissolution corrosion of LBE, meeting the requirements of lead-cooled fast reactors for long-life and high-reliability structural materials. Attached Figure Description

[0020] Figure 1 This is an XRD fitting diagram of the lead-bismuth corrosion-resistant MAX phase ceramic powder of Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the lead-bismuth corrosion-resistant MAX phase ceramic bulk material of Example 1 of the present invention; Figure 3 Here are the aberration-corrected high-resolution transmission electron microscope images and elemental distribution diagrams of the lead-bismuth corrosion-resistant MAX phase ceramic bulk material of Example 2 of this invention. Figure 4 The images show a comparison of the surfaces of the lead-bismuth-resistant MAX phase ceramic block of Example 1 and the MAX phase ceramic block of Comparative Example 1 after lead-bismuth corrosion by scanning electron microscope. Figure 5 The images show a comparison of the cross-sections of the lead-bismuth-resistant MAX phase ceramic block of Example 1 and the MAX phase ceramic block of Comparative Example 1 after lead-bismuth corrosion by scanning electron microscopy. Figure 6 The left image shows the elemental composition of the lead-bismuth-resistant MAX phase ceramic block of Example 1 and the right image of the MAX phase ceramic block of Comparative Example 1 after lead-bismuth corrosion. Figure 7 These are high-resolution TEM images and selected area electron diffraction patterns of each corrosion layer of the MAX phase ceramic bulk body resistant to lead-bismuth corrosion in Example 1 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described and illustrated below through specific embodiments. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the present invention.

[0022] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0023] In this article, the raw materials include: Hafnium powder, particle size 325 mesh; Niobium powder, 325 mesh; Tantalum powder, 325 mesh; Aluminum powder, particle size 37~74 μm; Carbon powder, with a particle size of 30~45 nm.

[0024] In this paper, the present invention demonstrates that different experimental synthetic routes can be used to synthesize the same target product, and the raw materials and reaction process parameters can be adjusted accordingly.

[0025] In this paper, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf x M 1-x )2AX, where M is selected from one or more refractory transition metals from Nb, Ta, Mo, and W, A is a main group element Al and / or Si, and X is element C, 0 < x ≤ 0.5; when x > 0.5, it is difficult to synthesize experimentally, and the corrosion test process may be severely affected by secondary phases, making it impossible to obtain corrosion resistance data of the intrinsic phase.

[0026] In this paper, the characterization includes: 1. Phase characterization of the original material and the material after corrosion: The original material was characterized by phase analysis using a Brucker D8 venture X-ray diffractometer, and the Ritveld method was used to fit the XRD results of the original sample. Since the corrosion layer of the liquid lead-bismuth alloy sample was relatively thin after etching, small-angle X-ray diffraction was performed using GIXRD to determine the phases contained in the corrosion layer. The instrument used was a Brucker D8 ADVANCEDAVINCI.

[0027] 2. Morphological characterization of raw and corroded materials: The surface morphology information of the polished and etched samples was obtained using a Hitachi Regulus 8230 scanning electron microscope.

[0028] 3. Characterization of the corrosion layer on the material after corrosion: The corrosion interface layer was obtained by cutting the etched sample using a Helios 5CX microscope. The microstructure of the sample corroded with high-temperature liquid lead-bismuth alloy for 1000 h was observed using a Talos F200X transmission electron microscope to obtain the structure and morphological characteristics of the corrosion layer and to further compare the differences in corrosion resistance of different materials to liquid lead-bismuth alloy.

[0029] 4. Material density test: The density of the material sample was tested using the Archimedes displacement method, with the equipment being the Sartorius Cubis II and the test medium being anhydrous ethanol.

[0030] 5. Corrosion of high-temperature liquid lead-bismuth alloy materials: The equipment used in the corrosion test of liquid lead-bismuth alloy was a static lead-bismuth alloy corrosion furnace. The equipment consisted of an alumina crucible containing the lead-bismuth alloy, a heating resistor, a thermocouple, an oxygen sensor, and a gas passage. The corrosion parameters were set as follows: temperature 500℃, oxygen content 10%. -7 The corrosion time was 1000 h. The temperature was controlled by a heating resistor and a thermocouple; the oxygen content was controlled by a gas passage (the introduced gases included argon, an argon-hydrogen mixture, and an argon-oxygen mixture) and an oxygen sensor. Samples were machined into rectangular specimens of 9×4×1 mm using wire cutting, with a hole drilled in the center. A molybdenum wire was threaded through the hole and suspended from the sample rod, which was then placed inside the furnace. To prevent the sample from floating on the surface of the liquid lead-bismuth, the length of the molybdenum wire was controlled to be less than the distance from the suspension point to the liquid surface, ensuring that the sample was always immersed in the liquid lead-bismuth alloy for corrosion. After 1000 h of continuous corrosion, the sample was removed and cooled to room temperature. Excess lead-bismuth alloy was removed by cleaning with a washing solution prepared in a 1:1:1 volume ratio of anhydrous ethanol:acetic acid:saturated hydrogen peroxide. The corrosion cross-section of the sample was prepared by focused ion beam cutting to further determine the material's resistance to high-temperature liquid lead-bismuth alloy corrosion.

[0031] Example 1 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.29 Nb 0.36 Ta 0.35 )2AlC, the preparation method of which includes the following steps: (1) Weigh 4.19 g of hafnium powder, 2.18 g of niobium powder, 4.22 g of tantalum powder, 0.95 g of aluminum powder, and 0.42 g of nano carbon powder. Place the above materials in a ball mill jar. The grinding material is zirconia grinding beads with a diameter of 3 mm and a material-to-ball mass ratio of 1:3. Add anhydrous ethanol to purge the air from the ball mill jar. The ball milling time is 12 h. After completion, vacuum dry to obtain a mixture.

[0032] (2) After pressing the mixture into tablets using a mold, it was placed into an alumina crucible and heated in a vacuum tube furnace. The reaction conditions were: reaction temperature 1600℃, holding time 480 min, and protection with an inert argon atmosphere. After the furnace temperature cooled to room temperature, the reaction product was removed from the crucible.

[0033] (3) The reaction product was placed in a mortar, ground and crushed, and then sieved with a 325-mesh stainless steel mesh to obtain MAX phase ceramic powder resistant to lead and bismuth corrosion.

[0034] (4) The lead-bismuth-resistant MAX phase ceramic powder was placed in a 20 mm graphite mold and heated in a hot press furnace to a temperature of 1600 °C and held at that temperature for 20 min, during which a pressure of 50 MPa was applied. After the hot pressing step was completed, the powder was cooled to room temperature and the surface graphite layer was removed to obtain the lead-bismuth-resistant MAX phase ceramic bulk material.

[0035] XRD tests were performed on the lead-bismuth corrosion-resistant MAX phase ceramic powder of this embodiment. Further full-spectrum analysis using the Reitveld method yielded a data fitting error Rwp = 12.02%, and the phase peak data corresponded to the MAX phase material peaks with n = 1. Figure 1 This demonstrates the successful preparation of a 211 MAX phase material with Hf, Nb, and Ta solid solutions at the M site, with calculated lattice constants of a = 0.3074 nm and c = 1.3952 nm. The final powder sample contained trace amounts of hafnium oxide and carbide impurities; the former originated from the oxidation of hafnium powder in the raw materials, while the latter came from byproducts obtained during the reaction.

[0036] pass Figure 2 Scanning electron microscopy combined with energy dispersive spectroscopy was used to analyze the MAX phase ceramic bulk resistant to lead-bismuth corrosion. The composition of each element in the sample was analyzed, and the data results are shown in Table 1 below. It can be seen that the M site includes three elements: Hf, Nb and Ta. The sum of the atomic percentages of the three elements and the percentage of Al content is 1.99, which is approximately 2, corresponding to the 211 MAX phase peak obtained from the XRD data.

[0037] Table 1. Energy dispersive spectroscopy (EDS) analysis results of MAX phase ceramic bulk materials resistant to lead-bismuth corrosion. The density of the lead-bismuth-resistant MAX phase ceramic bulk in this embodiment was determined to be 9.54 g / cm³ using the Archimedes' displacement method. 3 .

[0038] Figure 3 The image shows the phase morphology of the lead-bismuth corrosion-resistant MAX phase ceramic bulk under an aberration-corrected transmission electron microscope in this embodiment. The uniform layered arrangement reveals an atomic arrangement along the [11-20] direction, exhibiting the characteristic alternating arrangement of MX and A layers typical of MAX phase materials. Specifically, it consists of two alternating brighter atomic layers (MX layers) and one darker atomic layer (A layer), with the ratio of M-site atoms to A-site atoms being 2:1.

[0039] Example 2 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.5 Nb 0.2 Ta 0.3 )2AlC, the preparation method of which includes the following steps: (1) Weigh 6.28 g of hafnium powder, 0.82 g of niobium powder, 2.38 g of tantalum powder, 0.59 g of aluminum powder, and 0.26 g of nano-carbon powder. Place the above materials in a ball mill jar. The grinding material is zirconia grinding beads with a diameter of 3 mm and a material-to-ball mass ratio of 1:3. Add anhydrous ethanol to purge the air from the ball mill jar. The ball milling time is 12 h. After completion, vacuum dry to obtain a mixed powder.

[0040] (2) A 20 mm diameter graphite mold was used to hold the mixed powder, with graphite paper separating the powder from the mold. The powder was pre-pressed in the mold using a liquid press at a pressure of 5 MPa for 10 min. The sample was then sintered in a spark plasma sintering furnace at a target temperature of 1600 ℃ for 20 min, with a pressure of 50 MPa applied during the holding period. The temperature program was set as follows: below 1000 ℃, the heating / cooling rate was 50 ℃ / min; above 1000 ℃, the heating / cooling rate was 25 ℃ / min. After sintering, residual graphite was initially scraped off with a scraper to obtain a MAX phase ceramic material resistant to lead-bismuth corrosion.

[0041] Example 3 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.29 Nb 0.36 Ta 0.35 )2SiC, the preparation method of which includes the following steps: (1) Weigh the (Hf) obtained in Example 1 0.29 Nb 0.36 Ta 0.35 2.27 g of AlC powder and 0.85 g of liquid SiCl4 were used. Based on the density of 1.483 g / ml, the corresponding volume was 0.573 ml. An excess of 10% was used to ensure the complete reaction of the experiment.

[0042] (2) Place the above reaction raw materials together in a glass tube frozen by liquid nitrogen, use a vacuum tube sealing machine to extract the air in the tube and vacuum seal the glass tube.

[0043] (3) The sample tube was heated to 800 °C using a muffle furnace and held at that temperature for 8 h. After the high-temperature reaction was completed, the sample tube was removed and cooled to room temperature. The sample tube was then broken open to remove the mixed powder after the reaction. The mixed sample powder was washed with deionized water by vacuum filtration, and dried after filtration to obtain (Hf) 0.29 Nb 0.36 Ta 0.35 )2SiC powder.

[0044] (4) After drying (Hf) 0.29 Nb 0.36 Ta 0.35 2SiC powder was placed in a 20 mm graphite mold, and the mold was heated to 1300 °C using a hot press furnace and held at that temperature for 20 min, during which a pressure of 40 MPa was applied. After the hot pressing step was completed, the sample was cooled to room temperature, and the graphite layer on the sample surface was removed to obtain a MAX phase ceramic bulk material resistant to lead-bismuth corrosion.

[0045] Example 4 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.2 Nb 0.8 )2AlC, the preparation method of which includes the following steps: (1) Weigh 0.83 g of hafnium powder, 1.72 g of niobium powder, 0.31 g of aluminum powder, 0.14 g of nano carbon powder and 9 g of sodium chloride. Mix the above powders in a mortar for 30 min until they are evenly mixed to obtain a mixed powder.

[0046] (2) The above mixed powder was placed in an alumina crucible and subjected to a high-temperature reaction in a vacuum tube furnace. The reaction conditions were: reaction temperature 1450 °C, holding time 6 h, and protection with an inert argon atmosphere. After the furnace temperature cooled to room temperature, the reaction product was removed from the crucible.

[0047] (3) Grind the above reaction products with a mortar and pestle, put the ground powder into a beaker, add deionized water, stir and sonicate for 30 min, let the beaker stand for 1 h, pour off the supernatant in the beaker, repeat 3 times, wash once more with anhydrous ethanol, and then dry in a 50 ℃ oven for 12 h to obtain MAX phase ceramic powder resistant to lead bismuth corrosion.

[0048] (4) The dried lead-bismuth-resistant MAX phase ceramic powder was placed in a graphite mold with a diameter of 20 mm and heated using a hot press furnace. The sample temperature was heated to 1550 °C and held at this temperature for 20 min, during which a pressure of 50 MPa was applied. After the hot pressing step was completed, the sample was cooled to room temperature and the graphite layer on the sample surface was removed to obtain the lead-bismuth-resistant MAX phase ceramic bulk material.

[0049] Example 5 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.2 Ta 0.8 )2AlC, the preparation method of which includes the following steps: (1) Weigh 0.54 g of hafnium powder, 2.17 g of tantalum powder, 0.20 g of aluminum powder, 0.09 g of nano carbon powder and 9 g of sodium chloride. Mix the above powders in a mortar for 30 min until they are evenly mixed to obtain a mixed powder.

[0050] (2) The above mixed powder was placed in an alumina crucible and subjected to a high-temperature reaction in a vacuum tube furnace. The reaction conditions were: reaction temperature 1400 °C, holding time 6 h, and protection with an inert argon atmosphere. After the furnace temperature cooled to room temperature, the reaction product was removed from the crucible.

[0051] (3) Grind the above reaction products with a mortar and pestle, put the ground powder into a beaker, add deionized water, stir and sonicate for 30 min, let the beaker stand for 1 h, pour off the supernatant in the beaker, repeat 3 times, wash once more with anhydrous ethanol, and then dry in a 50 ℃ oven for 12 h to obtain MAX phase ceramic powder resistant to lead bismuth corrosion.

[0052] (4) The dried lead-bismuth-resistant MAX phase ceramic powder was placed in a 20 mm diameter graphite mold and heated using a hot press furnace. The sample temperature was raised to 1500 °C and held at this temperature for 20 min, during which a pressure of 50 MPa was applied. After completing the hot pressing step, the sample was cooled to room temperature, and the graphite layer on the sample surface was removed to obtain the lead-bismuth-resistant MAX phase ceramic bulk material. Example 6 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.2 Nb 0.4 Ta0.4 )2AlC, the preparation method of which includes the following steps: (1) Weigh 1.29 g of hafnium powder, 1.34 g of niobium powder, 2.60 g of tantalum powder, 0.49 g of aluminum powder, and 0.22 g of nano-carbon powder. Place the above materials in a ball mill jar. The grinding material is zirconia grinding beads with a diameter of 3 mm and a material-to-ball mass ratio of 1:3. Add anhydrous ethanol to remove air from the ball mill jar. The ball milling time is 12 h. After completion, vacuum dry to obtain a mixed powder.

[0053] (2) Follow the steps (2~4) of Example 1 to obtain a MAX phase ceramic bulk material resistant to lead-bismuth corrosion.

[0054] Example 7 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.4 Nb 0.3 Ta 0.3 )2AlC, the preparation method of which includes the following steps: (1) Weigh 2.43 g of hafnium powder, 0.95 g of niobium powder, 1.85 g of tantalum powder, 0.46 g of aluminum powder, and 0.20 g of nano-carbon powder. Place the above materials in a ball mill jar. The grinding material is zirconia grinding beads with a diameter of 3 mm and a material-to-ball mass ratio of 1:3. Add anhydrous ethanol to purge the air from the ball mill jar. The ball milling time is 12 h. After completion, vacuum dry to obtain a mixed powder.

[0055] (2) Follow the steps (2~4) of Example 1 to obtain a MAX phase ceramic bulk material resistant to lead-bismuth corrosion.

[0056] Example 8 In this embodiment, the molecular formula of the MAX phase ceramic material resistant to lead-bismuth corrosion is (Hf 0.5 Nb 0.25 Ta 0.25 )2AlC, the preparation method of which includes the following steps: (1) Weigh 3.02 g of hafnium powder, 0.79 g of niobium powder, 1.53 g of tantalum powder, 0.46 g of aluminum powder, and 0.20 g of nano carbon powder. Place the above materials in a ball mill jar. The grinding material is zirconia grinding beads with a diameter of 3 mm and a material-to-ball mass ratio of 1:3. Add anhydrous ethanol to remove air from the ball mill jar. The ball milling time is 12 h. After completion, vacuum dry to obtain a mixed powder.

[0057] (2~4) Follow the steps (2~4) of Example 1 to obtain a MAX phase ceramic bulk material resistant to lead-bismuth corrosion.

[0058] Comparative Example 1 The molecular formula of the Hf solid solution MAX phase ceramic material in this comparative example is (Nb) 0.5 Ta0.5 )2AlC, the preparation method of which includes the following steps: (1) Weigh 1.77 g of niobium powder, 3.44 g of tantalum powder, 0.52 g of aluminum powder, and 0.30 g of nano carbon powder. Place the above materials in a ball mill jar. The grinding material is zirconia grinding beads with a diameter of 3 mm and a material-to-ball mass ratio of 1:3. Add anhydrous ethanol to remove air from the ball mill jar. The ball milling time is 12 h. After completion, vacuum dry to obtain a mixed powder.

[0059] (2~4) Follow the steps (2~4) of Example 1 to obtain MAX phase ceramic bulk material.

[0060] The lead-bismuth corrosion-resistant MAX phase ceramic bulk material (Hf) from Example 1 was used. 0.29 Nb 0.36 Ta 0.35 )2AlC and Comparative Example 1 MAX phase ceramic bulk (Nb) 0.5 Ta 0.5 )2AlC was used for lead-bismuth corrosion testing. The cross-section of the corroded sample was obtained by FIB cutting, such as Figure 4 As shown, the Hf-containing solid solution MAX phase material in Example 1 has a smooth and clean surface, with no corrosion products of significant thickness on the main surface area. The Hf-free solid solution MAX phase material has a covering oxide layer on its surface, and unevenly sized pores are distributed on the surface, with cracks connecting the pores. The latter exhibits more severe interaction with liquid lead bismuth under corrosive conditions, and the surface corrosion products cannot form a dense protective layer to prevent further corrosion.

[0061] Further in-depth analysis of the corrosion cross-sections of the two samples was conducted, based on... Figure 5 It can be seen that both form a multilayer corrosion product structure, which, from the inside out, consists of: #1 matrix MAX phase corrosion layer, #2 oxygen-containing MAX phase layer, #3 amorphous corrosion product layer, and #4 lead-rich corrosion product layer. Regarding the thickness of the oxygen-containing corrosion layer, the corrosion influence depth of the Hf-containing MAX phase in Example 1 is only ~0.5 μm, significantly lower than the 0.99 μm corrosion influence depth of the Hf-free MAX phase in Comparative Example 1. This indicates that the presence of Hf effectively weakens the interaction between the MAX phase material and the corrosive medium.

[0062] Figure 6Elemental distribution analysis was performed on each corrosion layer of both samples. The outermost layer contained Pb, a corrosive medium, with a content greater than 1%, indicating that Pb participates in the outermost corrosion product reaction. Furthermore, the Hf-free MAX phase ceramic block showed significant Al loss in both the oxygen-containing corrosion layer and the substrate layer; while the Hf-containing MAX phase ceramic block in Example 1 showed higher Al content in each corrosion layer than the Hf-free MAX phase ceramic block in Comparative Example 1, with the Al to M-site element content ratio remaining approximately 1:2. This phenomenon indicates that in the liquid lead-bismuth corrosion environment, Hf solid solution provides excellent protection for the MAX phase crystal structure, effectively suppressing selective Al loss, thus explaining the excellent corrosion resistance of the Hf-containing material.

[0063] Figure 7 The four-layer corrosion structure of the Hf-containing MAX phase ceramic bulk in Example 1 was characterized by high-resolution TEM images and corresponding selected area electron diffraction (SED) patterns. The high-resolution image of #1 shows a near-matrix MAX phase atomic layer distribution structure, with SED spots corresponding to [11-20] axis diffraction spots. The high-resolution image of #2 also shows a MAX phase atomic layer distribution, but due to the influence of oxygen, the internal distortion is obvious, and the corresponding [11-20] axis diffraction spots are blurred. The high-resolution image of #3 shows no periodic atomic arrangement, and the SED shows an amorphous halo, proving that this region is amorphous. The high-resolution image of #4 shows both amorphous and nano-crystalline regions, and the SED shows irregular polycrystalline diffraction spots and an amorphous halo, indicating that the outermost corrosion product is a state of coexistence of amorphous and nanocrystalline.

[0064] The lead-bismuth corrosion-resistant MAX phase ceramic bulk materials in Examples 2-5 also have a relatively thin corrosion layer.

[0065] The lead-bismuth-resistant MAX phase ceramic bulk materials from Examples 6-8 were subjected to lead-bismuth corrosion tests. Corrosion samples were obtained by FIB cutting. All sample sections exhibited a four-layer corrosion structure. Furthermore, with increasing Hf solid solution content at the M-site, the oxygen penetration layer gradually thinned after corrosion, reaching 0.65 μm (0.2 Hf), 0.35 μm (0.4 Hf), and 0.30 μm (0.5 Hf), respectively. This indicates that increasing Hf solid solution weakens the corrosion interaction between the sample and liquid lead-bismuth. Elemental scanning electron microscopy (TEM) was performed on the corrosion layer region near the original substrate. Comparing the O and Al content, the O content in the near-substrate layer of the sample with high Hf solid solution was significantly higher than the other two samples. The ratio of Al to total M-site elements was also closer to 1:2. This suggests that high Hf solid solution promotes the bonding ability between the MAX phase and O atoms within the interlayer, hindering the migration and loss of Al atoms, thereby protecting the MAX phase from structural damage caused by corrosion.

[0066] In summary, by introducing the oxygen-affinity element Hf at the M site, this invention significantly enhances the migration barrier of oxygen atoms between material layers, enabling MAX phase ceramic materials to effectively suppress the migration and dissolution of A-site elements in a lead-bismuth environment. This intrinsically improves the stability of the MAX phase crystal structure, thereby exhibiting excellent resistance to lead-bismuth corrosion.

[0067] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0068] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0069] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A lead bismuth corrosion resistant MAX phase ceramic material, characterized in that, The molecular formula is (Hf x M 1-x )2AX, wherein M is selected from one or more refractory transition metals of Nb, Ta, Mo, W, A is a main group element of Al and / or Si, and X is an element C, 0 After being corroded in a liquid lead-bismuth environment, the lead-bismuth resistant MAX phase ceramic material forms, from the inside to the outside, a matrix MAX phase corrosion layer, an oxygen-containing MAX phase layer, an amorphous corrosion product layer, and a lead-rich corrosion product layer in sequence; wherein, the oxygen-containing MAX phase layer, the amorphous corrosion product layer, and the lead-rich corrosion product layer are oxygen-containing corrosion layers, and the thickness of the oxygen-containing corrosion layer is <0.8μm.

2. The MAX phase ceramic material resistant to lead-bismuth corrosion according to claim 1, characterized in that, The lead-bismuth corrosion-resistant MAX phase ceramic material is subjected to corrosion at 500℃ and 10℃. -7 After 1000 h of corrosion in liquid lead-bismuth with wt.% oxygen content, the thickness of the oxygen-containing corrosion layer is ≤0.65μm.

3. The MAX phase ceramic material resistant to lead-bismuth corrosion according to claim 1, characterized in that, The molecular formula of the lead-bismuth corrosion-resistant MAX phase ceramic material is (Hf x M 1-x )2AX, where M is selected from at least one of Nb, Ta, Mo, W, A is a main group element Al or Si, X is element C, and 0.1≤x≤0.

5.

4. The MAX phase ceramic material resistant to lead-bismuth corrosion according to claim 1, characterized in that, The molecular formula of the lead-bismuth corrosion-resistant MAX phase ceramic material is (Hf x M 1-x )2AX, where M is selected from at least two of Nb, Ta, Mo, and W, A is a main group element Al or Si, and X is element C, 0.2≤x≤0.

5.

5. A method for preparing a MAX phase ceramic material resistant to lead-bismuth corrosion as described in claim 1, characterized in that, The preparation method includes: uniformly mixing Hf and / or Hf-containing materials, M and / or M-containing materials, A and / or A-containing materials, and X and / or X-containing materials in a molar ratio of 2:1:1, and placing the resulting mixture in an inert atmosphere to react at a high temperature of 800~1700℃ for 0.1~10h to obtain a MAX phase ceramic material resistant to lead-bismuth corrosion.

6. The method of claim 5, wherein the method further comprises the step of: The Hf and / or Hf-containing materials include at least one of hafnium powder, hafnium blocks, hafnium carbide, and hafnium hydride.

7. The method of claim 5, wherein the method further comprises the step of: The M and / or M-containing materials include at least one of elemental M, M-containing alloys, and M-containing carbides.

8. The method for preparing the lead-bismuth corrosion-resistant MAX phase ceramic material according to claim 5, characterized in that, The A and / or A-containing materials include at least one of elemental A and A-containing alloys.

9. The method for preparing the lead-bismuth corrosion-resistant MAX phase ceramic material according to claim 5, characterized in that, The X and / or X-containing materials include at least one of toner and M-containing carbides.

10. The application of a lead-bismuth corrosion-resistant MAX phase ceramic material as described in claim 1 in the field of lead-cooled fast neutron reactors.

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