A non-stoichiometric carbide and non-stoichiometric boride synergistically reinforced and toughened high-entropy carbon-boron multiphase ceramic and a preparation method thereof

Abstract

The application discloses a non-stoichiometric carbide and non-stoichiometric boride synergistically reinforced and toughened high-entropy carbon-boron composite ceramic and a preparation method thereof. y The chemical formula of the non-stoichiometric carbide is MC, wherein M is selected from V, W, Ti and Hf metals, and y is the value of the stoichiometric ratio, and the value range of y is 0.3-1.3; and the chemical formula of the stoichiometric boride is M'B2, wherein M' is selected from Ta, Nb, V, Zr and Ti metals. The application introduces vacancies into the carbon-boron dual-phase high-entropy ceramic to build a vacancy defect engineering. On one hand, the application realizes rapid densification of the material at a lower sintering temperature, and effectively reduces energy consumption and production cost in the preparation process; on the other hand, the application effectively improves the fracture toughness of the material and improves the comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a high-entropy carbon-boron multiphase ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides, and its preparation method. Background Technology

[0002] High-entropy boride ceramics possess ultra-high melting points, high hardness, excellent high-temperature stability, and oxidation resistance. Their properties can be flexibly controlled through compositional design, making them promising for applications in extreme environments such as aerospace thermal protection, nuclear energy structural components, and high-speed cutting tools. However, their intrinsic brittleness leads to low fracture toughness, posing a risk of sudden brittle fracture. Furthermore, due to strong covalent bonds and low diffusion coefficients, sintering densification is difficult, typically requiring temperatures above 2000 °C. Existing low-temperature preparation processes often sacrifice density, sample size, or process stability. In addition, the lack of theoretical prediction models for compositional design and the scarcity of high-temperature service performance data further restrict their engineering applications.

[0003] To address this issue, one approach is to toughen the material by altering the raw material formulation. Zou Qin et al. used Ti powder (purity >99.5%, particle size <10 μm) and TiB2 powder as raw materials, mixed them in a molar ratio of 1:1 to 1:9, and prepared non-stoichiometric TiB2 using mechanical alloying (ball-to-material ratio 10:1 to 20:1, ball milling for 20 to 60 h). X (X=1~1.8) powder; then add TiB X The mixture was combined with equimolar amounts of diborides such as TaB2, NbB2, and VB2, and after secondary ball milling, sintered in a hot-pressing furnace (1500–1900 °C, 30–50 MPa, vacuum or argon atmosphere) for 10–30 min to obtain high-entropy boride ceramics. The resulting TiB... X The bulk hardness reaches up to 26.5 GPa, and the fracture toughness reaches 6.4 MPa·m. 1 / 2 The high-entropy ceramic has a hardness of 24.6~26.8 GPa and a toughness of 5.7~6.4 MPa·m. 1 / 2The sintering temperature is 300-500 ℃ lower than that of traditional borides. By mechanical alloying, B vacancies are introduced into the TiB2 lattice and the proportion of Ti-Ti metal bonds is increased, achieving intrinsic toughening and sintering activation at the atomic bonding level, effectively coordinating the inherent contradiction between hardness and toughness. However, this patent still has the following problems: the risk of brittle fracture is still relatively high when used as a structural component; long-term high-energy ball milling (total 40-120 h) has high energy consumption and low efficiency, and is prone to introducing impurities from the grinding balls, posing challenges to the composition consistency and stability of mass production [Wang Mingzhi, Zou Qin, Zhao Yucheng, Liang Pengjie, Zhai Xinxuan, Ning Yangjin, Liu Shutong. A non-stoichiometric titanium boride and high-entropy boride ceramics prepared using the non-stoichiometric titanium boride: CN113416078B[P]. Yanshan University, published in 2022].

[0004] Lin Huatai et al. used Zr powder (4.87 g), Ta powder (9.662 g), Nb powder (4.96 g), W powder (9.81 g), Cr powder (2.776 g), B4C powder (2.95 g), and SiB6 powder (4.962 g) as raw materials (all with a particle size of 1-3 μm). They added anhydrous ethanol and Si3N4 or WC ball milling media, mixed the materials by ball milling, dried, and passed through an 80-1000 mesh sieve to obtain a mixed powder. The mixed powder was then placed into a graphite mold with a BN layer coated on the inner surface. Under a vacuum of 10 Pa, spark plasma sintering (SPS) was performed at a rate of 50-150 ℃ / min to 1850-2050 ℃, followed by a holding time of 20-35 MPa for 5-20 min. This in-situ reaction yielded a high-entropy boride composite silicon carbide ceramic with controllable microstructure, with the molecular formula (Zr0...). 0.2 Ta 0.2 Nb 0.2 W 0.2 Cr 0.2 B2-SiC. The resulting ceramics have a room temperature Vickers hardness of 27–32 GPa and a fracture toughness of 4.5–6.5 MPa·m. 1 / 2The flexural strength is 450~600 MPa, and the micromorphology of the SiC phase can be controlled by adjusting the sintering temperature, from equiaxed (1850 ℃) to a coexistence of equiaxed and long rod-shaped phases (1950 ℃) and then to long rod-shaped phases (2050 ℃). The formation of long rod-shaped SiC helps to improve fracture toughness. This patent utilizes in-situ reaction during spark plasma sintering to synthesize multiphase ceramics in one step, avoiding the complexity of traditional external SiC processes. Furthermore, the exothermic reaction promotes the formation of a high-entropy boride single phase, solving the problem of easy precipitation of impurity phases in W-containing systems. However, the patent still has the following problems: the hardness, toughness and strength data fluctuate greatly in different embodiments; the reaction sintering using metallic elements, B4C and SiB6 as raw materials is very complex and may generate other by-products [Lin Huatai, Tian Yu, Guo Weiming. A high-entropy boride composite silicon carbide ceramic with controllable microstructure and its preparation method and application: CN120717793A[P]. Guangdong University of Technology, published in 2025].

[0005] Another approach involves changing the sintering method. Chu Yanhui et al. used at least four metal diboride powders (particle size 1-3 μm, purity ≥99.5%) selected from TaB2, NbB2, TiB2, ZrB2, HfB2, CrB2, MoB2, VB2, and WB2 as raw materials, formulated according to the equimolar ratio of metal elements, and manually ground them for 20-40 min under an argon protective atmosphere to obtain mixed powders. The mixed powders were then pressed at 6-10 MPa for 3-5 min to form circular green blanks. The green blanks were placed in boxes made of graphite paper coated with hexagonal boron nitride, and then embedded in the through holes of graphite felt. The boxes were placed in an argon atmosphere, and alternating current was connected to both ends of the graphite felt. The Joule heat generated by the current through the graphite felt was used to sinter the green blanks to obtain high-entropy boride ceramic materials. The resulting ceramic material is a single-phase solid solution with uniform distribution of metallic elements and no agglomeration. Its density ranges from 91.5% to 92.5%, and its Vickers hardness under a 0.49 N load is adjustable from 23.2 GPa for the quaternary system to 36.4 GPa for the nonamenable system. This patent utilizes electric field sintering technology, employing graphite felt as a heating element to directly and rapidly heat the green body, reducing the sintering time to less than 2 minutes. This avoids the need for complex molds and high-pressure equipment required by traditional spark plasma sintering (SPS), achieving rapid and low-cost preparation of high-entropy boride ceramics with a large compositional space (quaternary to nonamenable) and uniform elemental distribution. However, the following problems still exist: the density of the obtained ceramic (91.5~92.5%) has not reached complete compaction (>99%), and there are many pores, which may affect its high-temperature mechanical properties and oxidation resistance; the manual grinding and manual sample loading processes are not conducive to industrial mass production, etc. [Chu Yanhui, Tang Haifeng, Tang Zhongyu, Qin Yexia. A high-entropy boride ceramic material and its preparation method and application: CN117105671A[P]. South China University of Technology, published in 2023]. Although the electric field sintering technology has achieved rapid and low-cost preparation, the sample density is insufficient, the size is small, and it depends on manual operation, which makes it difficult to meet the requirements of consistency and large-scale production for industrial applications. While current methods for sintering high-entropy boride ceramics have mitigated sintering temperatures to some extent by altering raw material formulations or sintering methods, making the process easier, several key issues remain. For example, prolonged high-energy ball milling is energy-intensive, easily introduces impurities, and the absolute toughness is insufficient to completely eliminate the risk of brittle fracture. In-situ reaction sintering with elemental metals and boride sources simplifies the process and solves the problem of impurity phase precipitation, but data fluctuations are significant, the reaction system is complex and prone to generating byproducts, and there is a lack of high-temperature performance support. Performance issues also exist: for instance, electric field sintering results in lower ceramic density, leading to internal porosity and deterioration of oxidation resistance. Byproducts generated during preparation cause significant fluctuations in the ceramic's hardness, toughness, and other mechanical properties. Summary of the Invention

[0006] The technical problem to be solved: Currently, the intrinsic brittleness of high-entropy boride ceramics leads to low fracture toughness, posing a risk of sudden brittle fracture. Simultaneously, due to strong covalent bonds and low diffusion coefficients, achieving both hardness and toughness is difficult, requiring sintering densification at temperatures above 2000 °C. However, existing low-temperature preparation processes often sacrifice density, sample size, or process stability. Furthermore, the lack of theoretical prediction models for composition design and the scarcity of high-temperature service performance data restrict their engineering applications. The lower density also degrades the ceramic's oxidation resistance, while the instability of sample size and processing results in significant fluctuations in mechanical properties such as hardness and toughness.

[0007] To address the aforementioned technical problems, this invention provides a high-entropy carbon-boron multiphase ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides, and its preparation method.

[0008] 2. Technical Solution: A high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides is prepared from raw materials including non-stoichiometric carbides and stoichiometric borides. The chemical formula of the non-stoichiometric carbide is MC. y , where M is selected from metals V, W, Ti, and Hf, and y is its stoichiometric ratio, which ranges from 0.3 to 1.3; The chemical formula of the stoichiometric boride is M'B2, where M' is selected from Ta, Nb, V, Zr, and Ti metals; The raw materials contain 8.5 to 24.9 wt.% non-stoichiometric carbides, with the balance being stoichiometric borates.

[0009] Furthermore, the raw materials also include non-stoichiometric borates, the chemical formula of which is M. ’’ B x M ’’ Selected from V, W, Ti, and Hf metals, x is its stoichiometric ratio, ranging from 0.6 to 2.6, and the mass fraction of non-stoichiometric borate is 8.5 to 10.4 wt.%.

[0010] Furthermore, the non-stoichiometric carbide or non-stoichiometric boride is composed of the corresponding elemental metal M or M ’’ The corresponding stoichiometric carbides or borides are prepared by mechanical alloying in a certain proportion.

[0011] Preferably, the metallic element M or M ’’The corresponding stoichiometric carbide or boride particles are all 1~3 μm in size and have a purity of not less than 99.5%.

[0012] Preferably, the chemical formula of the non-stoichiometric carbide is TiC. 0.4 VC 0.4 WC 0.4 or HfC 0.4 The chemical formula of the non-stoichiometric boride is TiB. 1.5 .

[0013] Preferably, the stoichiometric boride is a mixture of four borides: TaB2, NbB2, VB2, and ZrB2.

[0014] The preparation method of the above-mentioned high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1, non-stoichiometric carbides MC y Or non-stoichiometric borate M ’’ B x Powder preparation: according to MC y Or M ’’ B x The metal element powder and the corresponding carbide or boride powder are weighed according to the stoichiometric ratio, and the materials are loaded into the air and prepared by mechanical alloying. S2. Preparation of mixed powder: The non-stoichiometric carbide MC obtained in step S1 is mixed with... y The powder is mixed with the selected stoichiometric boride powder in a certain proportion using ball milling. If the raw materials also include a non-stoichiometric boride M... ’’ B x For powdered materials, add them to the ball mill mixture at this step; S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and then cold pressed. S4. Spark plasma sintering (SPS): The cold-pressed sample is subjected to SPS sintering; the sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1500~1900 ℃, the holding time is 2~60 min, and then the temperature is reduced and the pressure is released to obtain a high-entropy carbon-boron multiphase ceramic blank with synergistic reinforcement and toughening of non-stoichiometric carbide and non-stoichiometric boride. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0015] Furthermore, in S1, the ball-to-material mass ratio during mechanical alloying is 2:1 to 20:1, the rotation speed is 300 to 600 r / min, the ball milling time is 2 to 60 h, and the machine is stopped for 30 min every 2 h.

[0016] Furthermore, in S2, the ball-to-material mass ratio is 2:1 to 20:1, the rotation speed is 300 to 600 r / min, and the ball milling time is 2 to 60 h. Materials are loaded and unloaded in air.

[0017] Furthermore, in S2, the cold pressing pressure is set to 30 MPa, and the holding time is 10 s.

[0018] Furthermore, the SPS sintering process and parameters in S3 are as follows: After placing the graphite mold with graphite felt, it is placed in the SPS sintering system and slowly pressurized to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism, which is as follows: heating from room temperature to 600 ℃ in 5 min, holding at 600 ℃ for 5 min, stopping the evacuation after the holding period, and filling with argon gas to -0.05 Pa; then heating at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintering at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; holding at the final sintering temperature for 2~60 min, and then removing the blank after furnace cooling.

[0019] 3. Beneficial effects: The high-entropy carbon-boron multiphase ceramics prepared by this invention have a bulk density of 6.63~7.98 g / cm³. 3 It has a density of 90.1%–99.7%, a Vickers hardness of 12.2–23.2 GPa, and a fracture toughness of 5.3–8.1 MPa·m. 1 / 2 The compressive strength is 1017.4~1351.7 MPa, and the flexural strength is 467~675 MPa. The initial oxidation temperature is 480~623 ℃, the final oxidation temperature is 1113~1304 ℃, and the oxidation weight gain is 6.55~26.89%.

[0020] The core innovation of this invention lies in the simultaneous introduction of vacancies into carbon-boron dual-phase high-entropy ceramics, constructing a vacancy defect engineering. On the one hand, the presence of vacancies can significantly reduce the diffusion activation energy of atoms or ions in the crystal lattice, accelerating the diffusion process, thereby achieving rapid densification of the material at a lower sintering temperature and effectively reducing energy consumption and production costs during the preparation process. On the other hand, vacancies, as point defects in the crystal lattice, induce crack deflection, branching, or bypassing during crack propagation, absorbing more fracture energy by extending the crack propagation path and increasing the fracture surface area, thus effectively improving the fracture toughness of the material. Simultaneously, vacancies promote diffusion and solid solution of various phases, improving overall performance. Furthermore, this invention also introduces carbides as a reinforcing phase. Due to the difference in elastic modulus and thermal expansion coefficient between carbides and the matrix, when cracks propagate to the interface region, carbides can induce various toughening mechanisms such as crack deflection, bypassing, or second-phase bridging, further consuming crack propagation energy. Working synergistically with vacancies, they jointly achieve a significant improvement in the fracture toughness of carbon-boron dual-phase high-entropy ceramics. This makes the resulting carbon-boron dual-phase high-entropy ceramics have broad application prospects in extreme environment fields such as aerospace thermal protection, nuclear energy structural components, and high-speed cutting tools. Attached Figure Description

[0021] Figure 1 The images show the XRD patterns of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 1, 2, and 3.

[0022] Figure 2 The images show the XRD patterns of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 4, 5, and 6.

[0023] Figure 3 The XRD patterns of high-entropy carbon-boron multiphase ceramics at different sintering temperatures are shown for Examples 7 and 8.

[0024] Figure 4 The images show the XRD patterns of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 11, 12, and 13.

[0025] Figure 5 The diagram shows the bulk density and compaction of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 1, 2, and 3.

[0026] Figure 6 The diagram shows the bulk density and compaction of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 4, 5, and 6.

[0027] Figure 7 The diagram shows the bulk density and compaction of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 7 and 8.

[0028] Figure 8The diagram shows the bulk density and compaction of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 11, 12, and 13.

[0029] Figure 9 The graph shows the mechanical properties of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 1, 2, and 3.

[0030] Figure 10 The graphs show the mechanical properties of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 4, 5, and 6.

[0031] Figure 11 The mechanical properties of high-entropy carbon-boron multiphase ceramics at different sintering temperatures are shown in Examples 7 and 8.

[0032] Figure 12 The mechanical properties of high-entropy carbon-boron multiphase ceramics at different sintering temperatures are shown in Examples 11, 12, and 13.

[0033] Figure 13 The DSC-TG curves are for the high-entropy carbon-boron composite ceramics corresponding to Example 1.

[0034] Figure 14 The DSC-TG curves are for the high-entropy carbon-boron composite ceramics corresponding to Example 5.

[0035] Figure 15 The DSC-TG curves are for the high-entropy carbon-boron composite ceramics corresponding to Example 7.

[0036] Figure 16 The images show SEM images of high-entropy carbon-boron multiphase ceramics at different sintering temperatures corresponding to Examples 1 and 2.

[0037] Figure 17 The image shown is a SEM image of the high-entropy carbon-boron composite ceramic corresponding to Example 5.

[0038] Figure 18 The image shown is a SEM image of the high-entropy carbon-boron composite ceramic corresponding to Example 7.

[0039] Figure 19 The image shows the SEM image of the high-entropy carbon-boron composite ceramic corresponding to Example 12.

[0040] Figure 20 SEM image of the high-entropy carbon-boron composite ceramic corresponding to Example 13. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings.

[0042] The testing equipment described in this invention are all instruments used in conventional testing methods, such as X-ray diffractometer (XRD), Vickers hardness tester, apparent porosity and bulk density tester, scanning electron microscope (SEM), universal testing machine, assembled material surface and interface performance tester, and synchronous thermal analyzer, etc. Example 1

[0043] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 7.32 g of Ti powder, 4.46 g of TiC powder, and 8.14 g of TiB2 powder were weighed in air and placed into a grinding jar. Mechanical alloying was used, with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a grinding time of 60 h. To prevent cold welding of the raw materials on the inner wall of the grinding jar during ball milling, the mill was stopped for 30 min every 2 h. This yielded a non-stoichiometric compound powder, containing TiC... 0.4 and TiB 1.5 The molar ratio is 1:1.

[0044] S2. Preparation of mixed powder: Weigh TiC in air. 0.4 0.85 g powder, TiB 1.5 1.04 g of powder, 3.27 g of TaB2 powder, 1.85 g of NbB2 powder, 1.17 g of VB2 powder, and 1.82 g of ZrB2 powder were prepared. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0045] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0046] S4. The cold-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1600 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0047] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering system and slowly pressurized to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after furnace cooling.

[0048] S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0049] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 1 As shown, the volume density and packing density diagrams are as follows: Figure 5 As shown in the figure, the mechanical properties are as follows: Figure 9 As shown, the DSC / TG chart is as follows: Figure 13 As shown, the SEM image is as follows: Figure 16 As shown, the results indicate that the sintered product of this embodiment mainly exhibits two phases: one is a cubic carbide phase, and the other is a hexagonal close-packed boride phase. The bulk density of the high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides in this embodiment is 6.6 g / cm³. 3 It has a density of 99.2%, a hardness of 22.8 GPa, and a toughness of 8.1 MPa·m. 1 / 2 The compressive strength is 1351.7 MPa, and the flexural strength is 675 MPa. The initial oxidation temperature is 612 ℃, the final oxidation temperature is 1113 ℃, and the weight gain due to oxidation is 18.05%. Example 2

[0050] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 7.32 g of Ti powder, 4.46 g of TiC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a grinding jar. Mechanical alloying was used, with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a grinding time of 60 h. To prevent cold welding of the raw materials on the inner wall of the grinding jar during ball milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0051] S2. Preparation of mixed powder: Weigh TiC in air. 0.4 0.85 g powder, TiB 1.5 1.04 g of powder, 3.27 g of TaB2 powder, 1.85 g of NbB2 powder, 1.17 g of VB2 powder, and 1.82 g of ZrB2 powder were prepared. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0052] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed at a pressure of 30 MPa for a holding time of 10 s. S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1700 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0053] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0054] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 1 As shown, the volume density and packing density diagrams are as follows: Figure 5 As shown in the figure, the mechanical properties are as follows: Figure 9 As shown, the SEM image is as follows: Figure 16 As shown, the results indicate that the sintered product of this embodiment mainly exhibits two phases: one is a cubic carbide phase, and the other is a hexagonal close-packed boride phase. The bulk density of the high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides in this embodiment is 6.6 g / cm³. 3It has a density of 99.7%, a hardness of 21.7 GPa, and a toughness of 7.3 MPa·m. 1 / 2 . Example 3

[0055] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 7.32 g of Ti powder, 4.46 g of TiC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a grinding jar. Mechanical alloying was used, with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a grinding time of 60 h. To prevent cold welding of the raw materials on the inner wall of the grinding jar during ball milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0056] S2. Preparation of mixed powder: Weigh TiC in air. 0.4 0.85 g powder, TiB 1.5 1.04 g of powder, 3.27 g of TaB2 powder, 1.85 g of NbB2 powder, 1.17 g of VB2 powder, and 1.82 g of ZrB2 powder were prepared. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0057] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0058] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1800 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0059] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0060] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 1 As shown, the volume density and packing density diagrams are as follows: Figure 5 As shown in the figure, the mechanical properties are as follows: Figure 9 As shown, the results indicate that the sintered product of Example 1 mainly exhibits two phases: one is a cubic carbide phase, and the other is a hexagonal close-packed boride phase. The bulk density of the non-stoichiometric high-entropy ceramic of this example is 6.6 g / cm³. 3 It has a density of 98.9%, a hardness of 20.4 GPa, and a toughness of 7.2 MPa·m. 1 / 2 . Example 4

[0061] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 5.483 g of V powder, 4.517 g of VC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0062] S2. Preparation of mixed powder: Weigh VC in air. 0.4 0.89 g of powder, TiB 1.51.04 g of powder, 3.25 g of TaB2 powder, 1.81 g of NbB2 powder, 1.21 g of VB2 powder, and 1.8 g of ZrB2 powder were prepared. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0063] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0064] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1500 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0065] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt furnace, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0066] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 2 As shown, the volume density and packing density diagrams are as follows: Figure 6 As shown in the figure, the mechanical properties are as follows: Figure 10 As shown in the figure, the main phases formed are still two phases: the cubic HEC phase and the hexagonal HEB phase, accompanied by a small amount of ZrO2. The bulk density of the non-stoichiometric high-entropy ceramic in Example 4 is 6.7 g / cm³. 3 It has a density of 99.4%, a hardness of 21.1 GPa, and a toughness of 5.8 MPa·m. 1 / 2 . Example 5

[0067] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 5.483 g of V powder, 4.517 g of VC powder, and 8.14 g of TiB2 powder were weighed in air and placed into a ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0068] S2. Preparation of mixed powder: Weigh VC in air. 0.4 0.89 g of powder, TiB 1.5 1.04 g of powder, 3.25 g of TaB2 powder, 1.81 g of NbB2 powder, 1.21 g of VB2 powder, and 1.8 g of ZrB2 powder were prepared. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0069] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0070] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1600 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0071] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0072] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 2 As shown, the volume density and packing density diagrams are as follows: Figure 6 As shown in the figure, the mechanical properties are as follows: Figure 10 As shown, the DSC / TG chart is as follows: Figure 15 As shown, the SEM image is as follows: Figure 17 As shown in the figure, the main phases formed are still two phases: the cubic HEC phase and the hexagonal HEB phase, accompanied by a small amount of ZrO2. The bulk density of the non-stoichiometric high-entropy ceramic in this embodiment is 6.8 g / cm³. 3 It has a density of 99.8%, a hardness of 21.7 GPa, and a toughness of 7.9 MPa·m. 1 / 2 The compressive strength is 1297.6 MPa, and the flexural strength is 522 MPa. The initial oxidation temperature is 597 ℃, the final oxidation temperature is 1241 ℃, and the weight gain due to oxidation is 26.89%. Example 6

[0073] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 5.483 g of V powder, 4.517 g of VC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0074] S2. Preparation of mixed powder: Weigh VC in air. 0.4 0.89 g of powder, TiB 1.5 1.04 g of powder, 3.25 g of TaB2 powder, 1.81 g of NbB2 powder, 1.21 g of VB2 powder, and 1.8 g of ZrB2 powder were prepared. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0075] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0076] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1700 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0077] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0078] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 2 As shown, the volume density and packing density diagrams are as follows: Figure 6 As shown in the figure, the mechanical properties are as follows: Figure 10 As shown in the figure, the main phases formed are still two phases: the cubic HEC phase and the hexagonal HEB phase, accompanied by a small amount of ZrO2. The bulk density of the non-stoichiometric high-entropy ceramic in this embodiment is 6.8 g / cm³. 3 It has a density of 99.7%, a hardness of 21.3 GPa, and a toughness of 6.8 MPa·m. 1 / 2 Example 7

[0079] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 5.847 g of W powder, 4.513 g of WC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0080] S2. Preparation of mixed powder: Weigh WC in air. 0.4 2.49 g of powder, TiB 1.5 The following powders were prepared: 0.85 g of TaB2 powder, 2.68 g of TaB2 powder, 1.52 g of NbB2 powder, 0.96 g of VB2 powder, and 1.49 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0081] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0082] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1800 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0083] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0084] The sample of this embodiment was characterized, and the XRD pattern of the sample is shown below. Figure 3 As shown, the volume density and packing density diagrams are as follows: Figure 7 As shown in the figure, the mechanical properties are as follows: Figure 11 As shown, the DSC / TG chart is as follows: Figure 15 As shown, the SEM image is as follows: Figure 18 As shown in the figure, the main phase formed is the hexagonal HEB phase, accompanied by the presence of ZrO2. The bulk density of the non-stoichiometric high-entropy ceramic in this embodiment is 7.2 g / cm³. 3 It has a density of 90.1%, a hardness of 15.3 GPa, and a toughness of 5.9 MPa·m. 1 / 2 The compressive strength is 1038.1 MPa, and the flexural strength is 467 MPa. The initial oxidation temperature is 480 ℃, the final oxidation temperature is 1209 ℃, and the weight gain due to oxidation is 6.55%. Example 8

[0085] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 5.847 g of W powder, 4.513 g of WC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0086] S2. Preparation of mixed powder: Weigh WC in air. 0.4 2.49 g of powder, TiB 1.5 The following powders were prepared: 0.85 g of TaB2 powder, 2.68 g of TaB2 powder, 1.52 g of NbB2 powder, 0.96 g of VB2 powder, and 1.49 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0087] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0088] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1900 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0089] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0090] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 3 As shown, the volume density and packing density diagrams are as follows: Figure 7 As shown, the mechanical property diagram is as follows: Figure 11 As shown in the figure, the main phase formed is the hexagonal HEB phase, accompanied by the presence of ZrO2. The bulk density of the non-stoichiometric high-entropy ceramic in this embodiment is 7.6 g / cm³. 3 It has a density of 94.8%, a hardness of 15.6 GPa, and a toughness of 5.4 MPa·m. 1 / 2 . Example 9

[0091] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 4.511 g of Hf powder, 5.489 g of HfC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a stainless steel ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0092] S2. Preparation of mixed powder: Weigh HfC in air. 0.4 2.44 g of powder, TiB 1.5 The following powders were prepared: 0.86 g of TaB2 powder, 2.7 g of TaB2 powder, 1.53 g of NbB2 powder, 0.97 g of VB2 powder, and 1.5 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0093] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0094] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1900 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0095] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0096] The bulk density of the non-stoichiometric high-entropy ceramic in this embodiment is 7.73 g / cm³. 3 The density is 98%, and the hardness and toughness are 16.2 GPa and 5.4 MPa·m, respectively. 1 / 2 . Example 10

[0097] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 1.865 g of Ti powder, 4.511 g of Hf powder, 5.489 g of HfC powder, and 8.14 g of TiB2 powder were weighed in air and placed in a stainless steel ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0098] S2. Preparation of mixed powder: S2. Preparation of mixed powder: Weigh HfC in air. 0.4 2.44 g of powder, TiB 1.5 The following powders were prepared: 0.86 g of TaB2 powder, 2.7 g of TaB2 powder, 1.53 g of NbB2 powder, 0.97 g of VB2 powder, and 1.5 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0099] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0100] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1900 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0101] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0102] The bulk density of the non-stoichiometric high-entropy ceramic in this embodiment is 7.98 g / cm³. 3 It has a density of 98%, a hardness of 17.5 GPa, and a toughness of 6.2 MPa·m. 1 / 2 . Example 11

[0103] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 5.454 g of Ti powder and 4.456 g of TiC powder were weighed in air and placed in a stainless steel ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0104] S2. Preparation of mixed powder: Weigh TiC in air. 0.4 The following powders were prepared: 0.95 g of TaB2 powder, 3.65 g of TaB2 powder, 2.06 g of NbB2 powder, 1.31 g of VB2 powder, and 2.03 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0105] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0106] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1600 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0107] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0108] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 4 As shown, the volume density and packing density diagrams are as follows: Figure 8 As shown, the mechanical property diagram is as follows: Figure 12 As shown, the results indicate that the sintered product of Example 1 mainly exhibits a close-packed hexagonal boride phase and a portion of the NbB2 phase. The bulk density of the non-stoichiometric high-entropy ceramic of this example is 6.2 g / cm³. 3 It has a density of 88.5%, and a hardness and toughness of 11.3 GPa and 5.7 MPa·m, respectively. 1 / 2 Example 12

[0109] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 5.454 g of Ti powder and 4.456 g of TiC powder were weighed in air and placed in a stainless steel ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0110] S2. Preparation of mixed powder: Weigh TiC in air. 0.4The following powders were prepared: 0.95 g of TaB2 powder, 3.65 g of TaB2 powder, 2.06 g of NbB2 powder, 1.31 g of VB2 powder, and 2.03 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0111] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0112] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1700 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0113] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0114] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 4 As shown, the volume density and packing density diagrams are as follows: Figure 8 As shown, the mechanical property diagram is as follows: Figure 12 As shown, the SEM image is as follows: Figure 19 The results show that the sintered product of this embodiment mainly exhibits two phases: one is a cubic carbide phase, and the other is a hexagonal close-packed boride phase. The bulk density of the non-stoichiometric high-entropy ceramic of this embodiment is 6.9 g / cm³. 3 It has a density of 97.9%, a hardness of 21.7 GPa, and a toughness of 6.3 MPa·m. 1 / 2 . Example 13

[0115] A method for preparing high-entropy carbon-boron multiphase ceramics that are synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides includes the following steps: S1. Preparation of Non-Stoichiometric Compound Powder: 5.454 g of Ti powder and 4.456 g of TiC powder were weighed in air and placed in a stainless steel ball mill jar. The powder was prepared using a mechanical alloying method with a ball-to-powder mass ratio of 10:1, a rotation speed of 450 r / min, and a milling time of 60 h. To prevent cold welding of the raw materials on the inner wall of the ball mill jar during milling, the mill was stopped for 30 min every 2 h, thus obtaining the non-stoichiometric compound powder.

[0116] S2. Preparation of mixed powder: Weigh TiC in air. 0.4 The following powders were prepared: 0.95 g of TaB2 powder, 3.65 g of TaB2 powder, 2.06 g of NbB2 powder, 1.31 g of VB2 powder, and 2.03 g of ZrB2 powder. The non-stoichiometric compound powder obtained in step S1 was mixed with the selected stoichiometric boride powder in a specific ratio using ball milling. The ball-to-powder mass ratio was 20:1, the milling speed was 300 r / min, and the milling time was 20 h.

[0117] S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and cold pressed. The pressure is set to 30 MPa and the holding time is 10 s.

[0118] S4. The pre-pressed sample is subjected to spark plasma sintering (SPS). The sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1800 ℃, and the holding time is 15 min. Then, the sample is cooled and depressurized to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0119] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the evacuation is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; the final sintering temperature is held for 15 min, and the blank is removed after cooling in the furnace. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

[0120] The sample in this embodiment was characterized, and its XRD pattern is shown below. Figure 4 As shown, the volume density and packing density diagrams are as follows: Figure 8 As shown, the mechanical property diagram is as follows: Figure 12 As shown, the SEM image is as follows: Figure 20 The results show that the sintered product of Example 1 mainly exhibits two phases: one is a cubic carbide phase, and the other is a hexagonal close-packed boride phase. The bulk density of the non-stoichiometric high-entropy ceramic of this example is 7.0 g / cm³. 3 It has a density of 99.6%, and a hardness and toughness of 22.8 GPa and 6.6 MPa·m, respectively. 1 / 2 .

[0121] Through a horizontal comparison of Examples 1, 2, and 3, it was found that TiC 0.4 Powder and TiB 1.5 Powder-reinforced and toughened duplex high-entropy ceramics achieve optimal performance when sintered at 1600℃. Subsequently, with increasing sintering temperature, both hardness and toughness decrease. This demonstrates that sintering temperature significantly impacts the performance of high-entropy ceramics. At the densification stage, the grain size of the ceramic reaches its minimum. As the sintering temperature increases, the content of byproducts rises, while the relative content of borides gradually decreases, leading to increased grain size and reduced performance.

[0122] By comparing Examples 1 and 13 longitudinally, it was found that when TiC was added... 0.4 In the case of powder, add additional TiB 1.5 The high-entropy ceramics obtained by sintering powder exhibit significantly improved toughness, while their sintering temperature is also reduced. This is because the transgranular fracture mode requires the cracks to overcome more atomic bond forces, thus enhancing the fracture toughness of the material.

[0123] By comparing Examples 5 and 2 longitudinally, it was found that their mechanical properties are very similar. This may be because the positions of V and Ti in the periodic table result in similar electronic structures and similar physical and chemical properties for these two elements.

[0124] A longitudinal comparison of Examples 7 with 5 and 1 revealed that the ceramic of Example 7 exhibits better oxidation resistance than the others. This is due to the unique physicochemical properties of W element, which enables the formation of a stable and dense oxide layer under high-temperature conditions.

[0125] Through a horizontal comparison of Examples 7 and 8, it was found that through WC 0.4 Powder and TiB 1.5Powder-reinforced and toughened duplex high-entropy ceramics exhibit optimal ceramic properties at a certain temperature. Subsequently, as the sintering temperature gradually increases, the changes in hardness and toughness of the material are relatively small. This indicates that the influence of temperature on its properties gradually decreases after basic densification is achieved.

[0126] A longitudinal comparison of Example 7 with Examples 13 and 1 revealed that Example 7 exhibited lower hardness and toughness compared to the others. This was primarily due to the WC content. 0.4 It has a hexagonal structure, and hexagonal transition metal compounds are characterized by being difficult to sinter and form dense structures.

[0127] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides, characterized in that, The raw materials used to prepare it include non-stoichiometric carbides and stoichiometric borides; The chemical formula of the non-stoichiometric carbide is MC. y M is selected from metals such as V, W, Ti, and Hf, and y is its stoichiometric ratio, which ranges from 0.3 to 1.

3. The chemical formula of the stoichiometric boride is M'B2, where M' is selected from Ta, Nb, V, Zr, and Ti metals; The raw materials contain 8.5 to 24.9 wt.% non-stoichiometric carbides, with the balance being stoichiometric borates.

2. The high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides according to claim 1, characterized in that, The raw materials also include non-stoichiometric borates, the chemical formula of which is M. ’’ B x M ’’ Selected from V, W, Ti, and Hf metals, x is the stoichiometric value, ranging from 0.6 to 2.6, and the mass fraction of non-stoichiometric borate is 8.5 to 10.4 wt.%.

3. The high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides according to claim 2, characterized in that, The non-stoichiometric carbides or non-stoichiometric borides are composed of the corresponding elemental metal M or M. ’’ The corresponding stoichiometric carbides or borides are prepared by mechanical alloying in a certain proportion.

4. The high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides according to claim 2, characterized in that, The chemical formula of the non-stoichiometric carbide is TiC. 0.4 VC 0.4 WC 0.4 or HfC 0.4 The chemical formula of the non-stoichiometric boride is TiB. 1.5 .

5. The high-entropy carbon-boron multiphase ceramic synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides according to claim 2, characterized in that, The stoichiometric borides are a mixture of four borides: TaB2, NbB2, VB2, and ZrB2.

6. The method for preparing high-entropy carbon-boron multiphase ceramics synergistically reinforced and toughened by non-stoichiometric carbides and non-stoichiometric borides as described in any one of claims 1-5, characterized in that, Includes the following steps: S1, non-stoichiometric carbides MC y Or non-stoichiometric borate M ’’ B x Powder preparation: according to MC y Or M ’’ B x The metal element powder and the corresponding carbide or boride powder are weighed according to the stoichiometric ratio, and the materials are loaded into the air and prepared by mechanical alloying. S2. Preparation of mixed powder: The non-stoichiometric carbide MC obtained in step S1 is mixed with... y The powder is mixed with the selected stoichiometric boride powder in a certain proportion using ball milling. If the raw materials also include a non-stoichiometric boride M... ’’ B x For powdered materials, add them to the ball mill mixture at this step; S3. Cold pressing: The mixed powder is evenly loaded into a graphite mold and then cold pressed. S4. Spark plasma sintering (SPS): The cold-pressed sample is subjected to SPS sintering; the sintering pressure is 40 MPa, the vacuum degree is 60 Pa, the sintering temperature is 1500~1900 ℃, the holding time is 2~60 min, and then the temperature is reduced and the pressure is released to obtain a high-entropy carbon-boron multiphase ceramic blank with synergistic reinforcement and toughening of non-stoichiometric carbide and non-stoichiometric boride. S5. The prepared blank is subjected to surface grinding and deburring to obtain a high-entropy carbon-boron composite ceramic with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides.

7. The method for preparing high-entropy carbon-boron multiphase ceramics with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides according to claim 6, characterized in that, In S1, the ball-to-material mass ratio is 2:1 to 20:1, the rotation speed is 300 to 600 r / min, the ball milling time is 2 to 60 h, and the machine is stopped for 30 min every 2 h.

8. The method for preparing high-entropy carbon-boron multiphase ceramics with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides according to claim 6, characterized in that, In S2, the ball-to-material mass ratio is 2:1 to 20:1, the rotation speed is 300 to 600 r / min, and the ball milling time is 2 to 60 h. Materials are loaded and unloaded in air.

9. The method for preparing high-entropy carbon-boron multiphase ceramics with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides according to claim 6, characterized in that, In S2, the cold pressing pressure is set to 30 MPa, and the holding time is 10s.

10. The method for preparing high-entropy carbon-boron multiphase ceramics with synergistic reinforcement and toughening by non-stoichiometric carbides and non-stoichiometric borides according to claim 6, characterized in that, The SPS sintering process and parameters in S3 are as follows: After placing the graphite mold in the SPS sintering system with graphite felt, the pressure is slowly increased to 40 MPa. After evacuating to 60 Pa, sintering is carried out according to the set heating mechanism, which is as follows: heating from room temperature to 600 ℃ in 5 min, holding at 600 ℃ for 5 min, stopping the evacuation after the holding period, and filling with argon gas to -0.05 Pa; then heating at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sintering at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; holding at the final sintering temperature for 2~60 min, and then removing the blank after furnace cooling.

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