High-entropy tetraboride / hexaboride material and method of making same

Abstract

This invention relates to a high-entropy tetraboron / hexaboride material and its preparation method, belonging to the field of ultra-high temperature ceramic materials technology. The nominal molecular formula of the material is (Y0). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6, and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 38.91–49.50:61.09–50.05. The raw material powder is wet-mixed using an acoustic resonance mixer until homogeneous, then dried; subsequently dry-pressed and calcined under vacuum at a constant temperature. When powder production is required, the agglomerates are broken up using the acoustic resonance mixer. This invention, by adjusting the elemental ratio, synthesizes La-based high-entropy boride powder for the first time. The resulting material has clear crystal morphology, controllable proportions, and uniform elemental distribution, retaining both high-entropy solid solution components and good thermal stability. Compared to single-component materials, this material exhibits superior oxidation resistance due to selective oxidation during the high-entropy effect. The preparation method can uniformly disperse the raw material powder, is simple, and easily scales up production.

Description

Technical Field

[0001] This invention relates to a high-entropy tetraboron / hexaboride material and its preparation method, belonging to the field of ultra-high temperature ceramic materials technology. Background Technology

[0002] Ultra-high temperature boride ceramics possess high specific strength, thermal shock resistance, corrosion resistance, and high-temperature creep resistance, making them a popular choice for high-temperature thermal protection structural materials. For example, they are used as antioxidant coatings for carbon / carbon (C / C) composites to improve their oxidation resistance in high-temperature, oxygen-containing environments. R. Wang et al. prepared a LaB6 antioxidant coating on the surface of C / C composites, achieving an effective antioxidant effect of 17 minutes at 2000℃. The antioxidant mechanism involves LaB6 completely transforming into oxides at 1300℃. These oxides diffuse on the material surface to form an oxide layer, enhancing the regularity of the graphitization structure and reducing the activated oxidation reaction zone on the material surface, thus achieving antioxidant properties. While LaB6 is considered to have significant application potential, the oxide layer formed by its oxides is susceptible to cracking and peeling under high-temperature, high-speed airflow and frequent temperature fluctuations during service, which is detrimental to the long-term stable operation of the coating.

[0003] To date, numerous studies have demonstrated that high-entropy boride ceramics and their extended materials (composite compounds), based on the high-entropy effect, slow diffusion effect, lattice distortion effect, and cocktail effect, possess advantages such as phase stability, high thermal conductivity, and low electrical conductivity, exhibiting physicochemical properties significantly superior to traditional ceramics. Among high-entropy borides, tetraborides (REB4) and hexaborides (REB6) exhibit different thermal stability. Studies have shown that the presence and relative thermal stability of rare-earth borides are related to the saturated vapor pressure of the metal cation and the strength of the boron-boron (BB) bond; increasing the saturated vapor pressure of the metal atoms leads to increased dissociation, which is undesirable for the thermal stability of rare-earth borides. For REB6, the decrease in cation radius is related to the weakening of the BB bond, thus the thermal stability of REB6 tends to decrease. Conversely, REB4, with its smaller cation radius, exhibits higher thermal stability, and REB6 with a larger cation radius often decomposes into REB4. No high-entropy antioxidant coating materials based on La have been reported.

[0004] Rare earth oxides are mostly susceptible to moisture in air and have a wide particle size distribution. The technical challenge of preventing raw material powder agglomeration while simultaneously addressing the de-agglomeration of fine powders during mixing is urgent. Resonant Acoustic Mixing (RAM) is a novel technology that has emerged in recent years, based on the coupling effect of macroscopic vibration mixing and microscopic acoustic field mixing. Initially applied to the direct mixing of powders and liquids, it utilizes the resonance of a mechanical vibration system to generate high-intensity vibration excitation, thereby exciting low-frequency, high-acceleration sound waves in a multiphase flow, achieving uniform mixing of materials through acoustic excitation. RAM creates uniform microscale mixing units throughout the mixing field, eliminating mixing dead zones. However, since high-entropy materials have multiple raw material components, the uniformity of multi-raw material mixing becomes a critical issue in their preparation. As the types and quantities of raw materials increase, simple direct mixing cannot meet the mixing requirements.

[0005] Chinese patent application CN115815607A discloses a highly efficient acoustic resonance mixing method using a composite high-energy ball mill. By adding spherical media materials of 0.1mm to 10mm to the raw materials, the spherical media vibrates violently along with the powder during mixing. This vibration causes collisions with agglomerated powder, effectively breaking down, deagglomerating, and refining the powder, thus achieving effective dispersion. Simultaneously, vacuuming before mixing further assists in deagglomerating the powder, resulting in a uniformly mixed raw material that meets the high mixing uniformity requirements of ultra-high performance and superhard material products. Ultrafine powder materials mixed using this method, such as ultra-fine oilstone powder and wafer thinning grinding wheel powder, can achieve uniform distribution of ultrafine raw materials, meeting the need for uniform product mixing and further improving product performance. However, due to the presence of spherical media, excessively fine powder will stick to the spherical media and the inner wall of the ball mill jar. As the vibration time increases, the sticking becomes more severe, which in turn hinders the mixing process. At the same time, for the mixing of more than three types of powders, the more types of powders there are, the greater the differences in their intrinsic properties. Even with the addition of spherical media, it is difficult to achieve uniform dispersion of the powders. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, one of the objectives of this invention is to provide a high-entropy tetraboron / hexaboride material; the material is a two-phase controllable high-entropy tetraboron / hexaboride material, with the main elemental components being yttrium (Y), lanthanum (La), holmium (Ho), erbium (Er) and ytterbium (Yb); the ratio of high-entropy tetraboride to hexaboride in the material is controllable, the composition is uniform, and it exhibits excellent thermal stability and oxidation resistance.

[0007] The second objective of this invention is to provide a method for preparing the high-entropy tetraboron / hexaboride material described in this invention, wherein the preparation method can uniformly disperse the raw material powder.

[0008] To achieve the objectives of this invention, the following technical solutions are provided.

[0009] A high-entropy tetraboron / hexaboride material, wherein the nominal molecular formula of the material is (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6, where (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 38.91–49.50:61.09–50.05.

[0010] When the material is used as a coating material, it is preferably a powder with a particle size of 0.8 μm to 2 μm.

[0011] A method for preparing the high-entropy tetraboron / hexaboride material of the present invention, wherein the preparation method comprises the following steps:

[0012] (1) Weigh each raw material powder according to the nominal molecular formula of the material, use an acoustic resonance mixer to wet mix the raw material powder evenly to obtain a slurry, dry it to obtain a mixed powder;

[0013] In step (1):

[0014] The raw material powders are yttrium oxide (Y2O3) powder, lanthanum oxide (La2O3) powder, holmium oxide (Ho2O3) powder, erbium oxide (Er2O3) powder, ytterbium oxide (Yb2O3) powder, and boron carbide (B4C) powder.

[0015] The wet mixing process parameters of the acoustic resonance instrument are as follows: the mixing medium is anhydrous ethanol and zirconium oxide balls, the programmable mode is automatic, the acceleration is 30g to 60g, the vibration frequency is 60Hz to 65Hz, and the vibration time is 3min to 6min.

[0016] Preferably, the diameter of the zirconia spheres is 3 mm to 10 mm, and the mass ratio of zirconia spheres to anhydrous ethanol is 2 to 3:1.

[0017] Acrylic mixing tanks are typically used as containers for holding raw material powders, and wet mixing is performed using an acoustic resonance mixer.

[0018] The preferred drying method is rotary drying; the preferred rotary drying temperature is 45℃~55℃, and the rotary drying time is 3h~8h.

[0019] (2) The mixed powder obtained in step (1) is dry-pressed under a pressure of 5MPa to 10MPa, held under pressure for 3s to 10s, and then vacuum-calcined at 1600℃ to 1800℃ for 60min to 120min to obtain an agglomerate, which is a high-entropy tetraboron / hexaboride material with the nominal molecular formula (Y). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6;

[0020] When the material is used as a coating material, it is preferable to use an acoustic resonance mixer to break the agglomerates into powder to obtain a high-entropy tetraboron / hexaboride material, wherein the particle size of the powder is 0.8μm to 2μm.

[0021] In step (2):

[0022] The preferred roasting process is as follows:

[0023] The dry-pressed mixed powder is placed in a vacuum furnace. When the constant temperature calcination temperature is 1600℃, it is heated to 1600℃ at a heating rate of 10℃ / min. When the constant temperature calcination temperature is 1600℃~1800℃, it is heated to 1600℃ at a heating rate of 10℃ / min, and then heated to a temperature greater than 1600℃ and less than or equal to 1800℃ at a heating rate of 5℃ / min.

[0024] The crushing process parameters of the acoustic resonance mixer are as follows:

[0025] The milling media used are agate balls, with an acceleration of 55g to 60g, a vibration frequency of 62.5Hz to 63.5Hz, and a vibration time of 3min to 5min.

[0026] Preferably, the diameter of the agate ball is 5mm to 10mm, and the mass ratio of the agate ball to the agglomerate is 2 to 2.5:1.

[0027] Acrylic mixing tanks are typically used as containers for the acoustic resonance mixer to crush materials.

[0028] A high-entropy tetraboron / hexaboride coating is prepared on an alloy substrate using a high-entropy tetraboron / hexaboride material as described in this invention; preferably, the material is a powder with a particle size of 0.8 μm to 2 μm.

[0029] Beneficial effects

[0030] (1) This invention provides a high-entropy tetraboron / hexaboride material, the nominal molecular formula of which is (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 By adjusting the element ratio, La-based high-entropy boride powder was synthesized for the first time. Compared with single-component materials, this solid solution material exhibits superior oxidation resistance due to the high-entropy effect and selective oxidation during the oxidation process.

[0031] (2) This invention provides a high-entropy tetraboron / hexaboride material, wherein the material is a dual-phase material with adjustable tetraboride and hexaboride content, (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 38.91–49.50:61.09–50.05. By adjusting the proportion of La, the material obtained by the reaction has a clear crystal morphology, controllable proportion, and uniform element distribution. Within the above mass ratio range, the material retains the high-entropy solid solution composition and has good thermal stability.

[0032] (3) This invention provides a method for preparing high-entropy tetraboron / hexaboride materials. The preparation method uses five rare earth metal oxides and carbon boride as raw materials. First, the materials are wet-mixed using an acoustic resonance mixer. Then, high-entropy tetraboron / hexaboride agglomerates are successfully prepared by vacuum sintering using a boron / carbon thermal reduction method. The preparation method is simple and easy to scale up for production. When the material is to be used as a coating material, the agglomerates are crushed using an acoustic resonance mixer to obtain powder material.

[0033] (4) This invention provides a method for preparing high-entropy tetraboron / hexaboron compound materials. In step (1) of the preparation method, an acoustic resonance mixer is used for wet mixing. By adding liquid anhydrous ethanol and spherical mixing medium zirconia balls, the instrument acceleration, vibration frequency, vibration time, etc. are adjusted to achieve a specific resonance state. The spherical material in the container forms a macroscopic vibration mixing flow and a microscopic acoustic flow strong mixing flow coupling effect, realizing uniform and rapid mixing without dead angles. This greatly promotes the effective deagglomeration of various raw material powders. The presence of liquid forms a dual resonance between the spherical medium and the liquid, which not only avoids the sticking of fine powders to the wall, but also achieves effective dispersion of powders by means of the fluidity of the liquid. The liquid environment greatly promotes the mixing efficiency and mixing uniformity of the raw materials.

[0034] (5) The present invention provides a method for preparing high-entropy tetraboron / hexaboron compound materials. In step (1) of the preparation method, rotary evaporation drying is used, which not only greatly improves the drying efficiency and saves time, but also the vacuum environment during rotary evaporation drying can prevent the raw materials from being moistened again.

[0035] (6) This invention provides a method for preparing high-entropy tetraboron / hexaboron compound materials. In step (2) of the preparation method, the mixed powder is pre-pressed to increase the contact area of ​​the powder and provide a pre-pressure to promote the solid solution of elements. The vacuum calcination adopts a two-stage heating program. The first stage rapidly heats up to near the reaction temperature, and the second stage slowly heats up to ensure sufficient carbon / boron thermal reduction reaction time. By controlling the sintering temperature, holding time and other processes, a better high-entropy solid solution can be formed.

[0036] (7) The present invention provides a method for preparing a high-entropy tetraboron / hexaboron compound material. When the material is used as a coating material, the agglomerates are broken down by an acoustic resonance mixer to obtain powder with a particle size of 0.8μm to 2μm. The agate medium has high hardness and good crushing effect, which prevents the introduction of impurities, thereby obtaining powder with uniform and regular particle size distribution for subsequent use as a coating material. Attached Figure Description

[0037] Figure 1 The image shows the XRD pattern of a high-entropy tetraboron / hexaboride material prepared in Example 1.

[0038] Figure 2 The images shown are SEM images of the agglomerates prepared in Example 1 before and after crushing; where Figure (a) is before crushing and Figure (b) is after crushing.

[0039] Figure 3 The graph shows the thermogravimetric differential thermal analysis (TG-DSC) results of the high-entropy tetraboron / hexaboride material prepared in Example 1. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are available from publicly available commercial sources.

[0041] The following comparative examples and embodiments:

[0042] The acoustic resonance mixer is: MixBox-G1 Acoustic Resonance Mixer, Zhengzhou Abrasives & Grinding Research Institute Co., Ltd.

[0043] The following tests are involved:

[0044] (1) X-ray diffraction test

[0045] X-ray diffractometer (XRD): Empyream, Malvern Panalytical Ltd;

[0046] (2) Oxygen, nitrogen and hydrogen analysis test

[0047] Oxygen, nitrogen, and hydrogen analyzer: ONH836, LECO Corporation, USA;

[0048] (3) Scanning electron microscopy and energy dispersive spectroscopy (EDS) analysis

[0049] Scanning electron microscope (SEM): Sigma 300+ Oxford Energy Dispersive X-ray Spectrometer, Zeiss;

[0050] (4) Thermogravimetric differential thermal analysis (TG-DSC)

[0051] Synchronous thermal analyzer: STA 449F5, Netzsch, Germany.

[0052] (5) Static oxidation test

[0053] Box-type resistance furnace: ZKKSL-1600-X, Zhengzhou Kejing Electric Furnace Co., Ltd.;

[0054] Test method: The antioxidant performance was tested according to the industry standard JC / T 2530-2019. The standard sample was placed in a box-type resistance furnace and heated from room temperature to 1200℃ at a rate of 10℃ / min, held for 60min, and then cooled to room temperature with the furnace. The mass of the sample before and after oxidation was accurately weighed.

[0055] Example 1

[0056] (1) According to the molar ratio of Y2O3:La2O3:Ho2O3:Er2O3:Yb2O3:B4C = 1:1:1:1:15, weigh 2.2578g of Y2O3 powder, 3.2586g of La2O3 powder, 3.7792g of Ho2O3 powder, 3.8242g of Er2O3 powder, 3.9410g of Yb2O3 powder and 8.2911g of B4C powder respectively, and use an acoustic resonance mixer to wet mix the powders to obtain a slurry. After drying at 55℃ for 3h, a mixed powder is obtained.

[0057] The acoustic resonance apparatus uses an acrylic mixing tank for wet mixing. The specific process parameters are as follows: the mixing medium is anhydrous ethanol and zirconia balls. The zirconia balls are composed of zirconia balls with diameters of 3mm, 5mm and 10mm mixed in a mass ratio of 1:2:1. The mass ratio of zirconia balls to anhydrous ethanol is 2:1. The programmable mode is automatic, the mixing acceleration is 50g, the vibration frequency is 63.1Hz and the vibration time is 3min.

[0058] (2) The mixed powder obtained in step (1) was dry-pressed under a pressure of 10 MPa and held for 10 s. The pressed blank was then placed in a vacuum furnace and heated to 1600 ℃ at a heating rate of 10 ℃ / min. It was then calcined at 1600 ℃ for 120 min. Heating was then stopped and the blank was allowed to cool naturally to room temperature to obtain an agglomerate. The agglomerate was broken up using an acoustic resonance mixer to obtain a powder, which is a high-entropy tetraboron / hexaboride material.

[0059] The acoustic resonance crushing uses an acrylic mixing tank as the container. The specific crushing process parameters are as follows: the ball milling media are agate balls with diameters of 5mm, 8mm, and 10mm mixed in a mass ratio of 1:1:1; the crushing acceleration is 60g; the vibration frequency is 63Hz; the vibration time is 3min; and the mass ratio of agate balls to high-entropy tetraboron / hexaboride agglomerates is 2:1.

[0060] The high-entropy tetraboron / hexaboride material prepared in this embodiment was subjected to the following performance tests:

[0061] (1) X-ray diffraction test

[0062] The material was characterized by X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown, the XRD pattern reveals characteristic peaks corresponding to the tetraboride and hexaboride peaks, with no other impurity peaks, indicating that the material consists of only two phases. Fine-tuning and fitting the XRD pattern reveals a pentagonal high-entropy tetraboride / hexaboride two-phase composite.

[0063] (2) Oxygen and nitrogen analysis test

[0064] The oxygen content of the material was measured to be only 0.2 wt.% using an oxygen, nitrogen, and hydrogen analyzer, indicating that the reaction was complete, there were no oxide residues, and the purity was high.

[0065] (3) Scanning electron microscopy observation + energy dispersive spectroscopy analysis

[0066] The morphology of the agglomerates prepared in step (2) of this embodiment and the powder obtained after crushing were observed using a scanning electron microscope (SEM). The results are as follows: Figure 2 As shown, the aggregates before breakage have a loose aggregate structure, and the particles are nearly spherical; as Figure 2 As shown in (a), the powder obtained after crushing by the acoustic vibration mixer consists of regular polyhedral particles with a significantly reduced particle size of 0.8 μm to 1.5 μm. The particles are fine and uniform. Figure 2 As shown in (b).

[0067] The energy dispersive spectroscopy (EDS) analysis results are shown in Table 1 below, indicating that the composition of the material conforms to the nominal molecular formula (γ). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6, after refinement using Rietveld X-ray polycrystalline diffraction data, showed that the composition results were consistent with the energy dispersive spectroscopy results. The refinement results showed that (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 49.50:50.5.

[0068] (4) Thermogravimetric differential thermal analysis (TG-DSC)

[0069] The material was subjected to TG-DSC thermal stability analysis under air conditions, and the results are as follows: Figure 3 As shown, the entire change process is accompanied by a significant endothermic reaction, with high entropy (Y). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2Er 0.2 Yb 0.2 LaB6 slowly increases in weight over a wide temperature range, and three DTG peaks appear at 832.21℃, 1006.5℃, and 1224.6℃, respectively. Unlike the single peak of the oxidation of the single component LaB6, this indicates that the high-entropy oxidation is stepwise and occurs at relatively high temperatures, indicating that the material is a high-entropy material with excellent thermal stability.

[0070] (5) Static oxidation test

[0071] Static oxidation tests were performed on the material, and the results showed that its oxidative weight gain was only 15 mg / cm³. 2 This indicates good antioxidant properties.

[0072] Table 1 EDS Analysis Results

[0073]

[0074]

[0075] Example 2

[0076] (1) According to the molar ratio of Y2O3:La2O3:Ho2O3:Er2O3:Yb2O3:B4C = 1:1.1:1:1:1:15.3, weigh 2.2578g of Y2O3 powder, 3.5839g of La2O3 powder, 3.7792g of Ho2O3 powder, 3.8242g of Er2O3 powder, 3.9410g of Yb2O3 powder and 8.4540g of B4C powder respectively, and use an acoustic resonance mixer to wet mix the powders to obtain a slurry. After drying at 45℃ for 8 hours, a mixed powder is obtained.

[0077] The acoustic resonance wet mixing process uses an acrylic mixing tank, and the specific process parameters are as follows:

[0078] The mixing medium is anhydrous ethanol and zirconia balls. The zirconia balls are 3mm, 5mm and 10mm in diameter and are mixed in a mass ratio of 1:2:1. The mass ratio of zirconia balls to anhydrous ethanol is 3:1. The program control mode is automatic mode, the mixing acceleration is 30g, the vibration frequency is 65Hz and the vibration time is 6min.

[0079] (2) The mixed powder obtained in step (1) was dry-pressed under a pressure of 10 MPa and held for 3 seconds. The dry-pressed blank was then placed in a vacuum furnace and heated to 1600°C at a heating rate of 10°C / min, and then heated to 1800°C at a heating rate of 5°C / min. The blank was then calcined at 1800°C for 60 minutes. The heating was then stopped and the blank was allowed to cool naturally to room temperature to obtain an agglomerate. The agglomerate was broken up using an acoustic resonance mixer to obtain a powder, which is a high-entropy tetraboron / hexaboride material.

[0080] The acoustic resonance crushing uses an acrylic mixing tank as the container. The specific crushing process parameters are as follows: the ball milling media is agate balls, which are composed of agate balls with diameters of 5mm, 8mm and 10mm mixed in a mass ratio of 1:1:1; the crushing acceleration is 55g; the vibration frequency is 62.5Hz; the vibration time is 5min; and the mass ratio of agate balls to high-entropy tetraboron / hexaboronide agglomerates is 2.5:1.

[0081] The high-entropy tetraboron / hexaboride material prepared in this embodiment was subjected to the following performance tests:

[0082] (1) X-ray diffraction test

[0083] The material was characterized by X-ray diffraction (XRD). The XRD pattern showed characteristic peaks corresponding to the tetraboride and hexaboride peaks, with no other impurity peaks, indicating that the material consists of only two phases. Fine-tuning and fitting of the XRD pattern revealed a pentagonal high-entropy tetraboride / hexaboride two-phase composite.

[0084] (2) Oxygen and nitrogen analysis test

[0085] The oxygen content of the material was measured to be only 0.2 wt.% using an oxygen, nitrogen, and hydrogen analyzer, indicating that the reaction was complete, there were no oxide residues, and the purity was high.

[0086] (3) Scanning electron microscopy and energy dispersive spectroscopy analysis

[0087] The morphology of the agglomerates prepared in step (2) of this embodiment and the powder after crushing were observed by scanning electron microscopy (SEM). The results showed that the agglomerates before crushing were loose agglomerate structures with nearly spherical particles. The powder obtained after crushing by the acoustic vibration mixer was a regular polyhedral particle with a significantly reduced particle size of 1 μm to 2 μm. The particles were small and uniform.

[0088] Energy dispersive spectroscopy (EDS) analysis results show that the composition of the material conforms to the nominal molecular formula (γ). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6, after refinement using Rietveld X-ray polycrystalline diffraction data, showed that the composition results were consistent with the energy dispersive spectroscopy results. The refinement results showed that (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 40.04:59.96.

[0089] (4) Thermogravimetric differential thermal analysis (TG-DSC)

[0090] The material was subjected to TG-DSC thermal stability analysis under air conditions. The results showed that the entire change process was accompanied by a significant endothermic reaction and high entropy (γ). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 LaB6 slowly increases in weight over a wide temperature range, and three DTG peaks appear at 832.21℃, 1006.5℃, and 1224.6℃, respectively. Unlike the single peak of the oxidation of the single component LaB6, this indicates that the high-entropy oxidation is stepwise and occurs at relatively high temperatures, indicating that the material is a high-entropy material with excellent thermal stability.

[0091] (5) Static oxidation test

[0092] Static oxidation tests were performed on the material, and the results showed that its weight gain due to oxidation was only 11.7 mg / cm³. 2 This indicates good antioxidant properties.

[0093] Example 3

[0094] (1) According to the molar ratio of Y2O3:La2O3:Ho2O3:Er2O3:Yb2O3:B4C = 1:1.2:1:1:1:15.6, weigh 2.2578g of Y2O3 powder, 3.9097g of La2O3 powder, 3.7792g of Ho2O3 powder, 3.8242g of Er2O3 powder, 3.9410g of Yb2O3 powder and 8.6197g of B4C powder respectively, and use an acoustic resonance mixer to wet mix the powders to obtain a slurry. After drying at 50℃ for 6h, a mixed powder is obtained.

[0095] The acoustic resonance wet mixing process uses an acrylic mixing tank, and the specific process parameters are as follows:

[0096] The mixing medium is anhydrous ethanol and zirconia balls. The zirconia balls are made by mixing zirconia balls with diameters of 3 mm, 5 mm and 10 mm in a mass ratio of 1:2:1. The mass ratio of zirconia balls to anhydrous ethanol is 3:1. The programmable control mode is automatic mode, the mixing acceleration is 50g, the vibration frequency is 60Hz and the vibration time is 3min.

[0097] (2) The mixed powder obtained in step (1) was dry-pressed under a pressure of 5 MPa and held for 10 s. The dry-pressed blank was then placed in a vacuum furnace and heated to 1600°C at a heating rate of 10°C / min, and then heated to 1700°C at a heating rate of 5°C / min. The blank was then calcined at 1700°C for 90 min. The heating was then stopped and the blank was allowed to cool naturally to room temperature to obtain an agglomerate. The agglomerate was broken up using an acoustic resonance mixer to obtain a powder, which is a high-entropy tetraboron / hexaboride material.

[0098] The acoustic resonance crushing uses an acrylic mixing tank as the container. The specific crushing process parameters are as follows: the ball milling media is agate balls, which are made of agate balls with diameters of 5mm, 8mm and 10mm mixed in a mass ratio of 1:1:1; the crushing acceleration is 60g; the vibration frequency is 63.5Hz; the vibration time is 5min; and the mass ratio of agate balls to high-entropy tetraboron / hexaboride agglomerates is 2.5:1.

[0099] The high-entropy tetraboron / hexaboride material prepared in this embodiment was subjected to the following performance tests:

[0100] (1) X-ray diffraction test

[0101] The material was characterized by X-ray diffraction (XRD). The XRD pattern showed characteristic peaks corresponding to the tetraboride and hexaboride peaks, with no other impurity peaks, indicating that the material consists of only two phases. Fine-tuning and fitting of the XRD pattern revealed a pentagonal high-entropy tetraboride / hexaboride two-phase composite.

[0102] (2) Oxygen and nitrogen analysis test

[0103] The oxygen content of the material was measured to be only 0.2 wt.% using an oxygen, nitrogen, and hydrogen analyzer, indicating that the reaction was complete, there were no oxide residues, and the purity was high.

[0104] (3) Scanning electron microscopy and energy dispersive spectroscopy analysis

[0105] The morphology of the agglomerates prepared in step (2) of this embodiment and the powder after crushing were observed by scanning electron microscopy (SEM). The results showed that the agglomerates before crushing were loose agglomerate structures with nearly spherical particles. The powder obtained after crushing by the acoustic vibration mixer was a regular polyhedral particle with a significantly reduced particle size of 0.8 μm to 1.2 μm. The particles were small and uniform.

[0106] Energy dispersive spectroscopy (EDS) analysis results show that the composition of the material conforms to the nominal molecular formula (γ). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6, after refinement using Rietveld X-ray polycrystalline diffraction data, showed that the composition results were consistent with the energy dispersive spectroscopy results. The refinement results showed that (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 38.91:61.09.

[0107] (4) Thermogravimetric differential thermal analysis (TG-DSC)

[0108] The material was subjected to TG-DSC thermal stability analysis under air conditions. The results showed that the entire change process was accompanied by a significant endothermic reaction and high entropy (γ). 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2LaB6 slowly increases in weight over a wide temperature range, and three DTG peaks appear at 832.21℃, 1006.5℃, and 1224.6℃, respectively. Unlike the single peak of the oxidation of the single component LaB6, this indicates that the high-entropy oxidation is stepwise and occurs at relatively high temperatures, indicating that the material is a high-entropy material with excellent thermal stability.

[0109] (5) Static oxidation test

[0110] Static oxidation tests were performed on the material, and the results showed that its oxidative weight gain was only 10.2 mg / cm³. 2 This indicates good antioxidant properties.

[0111] The above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-entropy tetraboron / hexaboride material, characterized in that: The nominal molecular formula of the material is (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 )B4 / (Y 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B6, where (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 B4 and (Y) 0.2 La 0.2 Ho 0.2 Er 0.2 Yb 0.2 The mass ratio of B6 is 38.91–49.50:61.09–50.

05.

2. The high-entropy tetraboron / hexaboride material according to claim 1, characterized in that: The material is a powder with a particle size of 0.8 μm to 2 μm.

3. A method for preparing a high-entropy tetraboron / hexaboride material as described in claim 1 or 2, characterized in that: The preparation method steps are as follows: (1) Weigh each raw material powder according to the nominal molecular formula of the material, use an acoustic resonance mixer to wet mix the raw material powder evenly to obtain a slurry, dry it to obtain a mixed powder; (2) The mixed powder was dry-pressed under a pressure of 5MPa to 10MPa, held for 3s to 10s, and then vacuum constant temperature calcined at 1600℃ to 1800℃ for 60min to 120min to obtain an agglomerate, which is a high-entropy tetraboron / hexaboron compound material. When it is necessary to prepare it into powder, the agglomerates are broken up using an acoustic resonance mixer to obtain a high-entropy tetraboron / hexaboride material.

4. The method for preparing a high-entropy tetraboron / hexaboride material according to claim 3, characterized in that: In step (1), the raw material powder is yttrium oxide powder, lanthanum oxide powder, holmium oxide powder, erbium oxide powder, ytterbium oxide powder and boron carbide powder; The wet mixing process parameters of the acoustic resonance instrument are as follows: the mixing medium is anhydrous ethanol and zirconium oxide balls, the programmable mode is automatic, the acceleration is 30g to 60g, the vibration frequency is 60Hz to 65Hz, and the vibration time is 3min to 6min.

5. The method for preparing a high-entropy tetraboron / hexaboride material according to claim 4, characterized in that: In step (2), the roasting process is as follows: The dry-pressed mixed powder is placed in a vacuum furnace. When the constant temperature calcination temperature is 1600℃, it is heated to 1600℃ at a heating rate of 10℃ / min. When the constant temperature calcination temperature is 1600℃~1800℃, it is heated to 1600℃ at a heating rate of 10℃ / min, and then heated to a temperature greater than 1600℃ and less than or equal to 1800℃ at a heating rate of 5℃ / min.

6. The method for preparing a high-entropy tetraboron / hexaboride material according to claim 4, characterized in that: In step (1), the diameter of the zirconia balls is 3 mm to 10 mm, and the mass ratio of the zirconia balls to anhydrous ethanol is 2 to 3:1; the drying method is rotary drying, the rotary drying temperature is 45℃ to 55℃, and the rotary drying time is 3h to 8h.

7. A method for preparing a high-entropy tetraboron / hexaboride material according to any one of claims 3 to 6, characterized in that: The crushing process parameters of the acoustic resonance mixer are as follows: The milling media used are agate balls, with an acceleration of 55g to 60g, a vibration frequency of 62.5Hz to 63.5Hz, and a vibration time of 3min to 5min.

8. The method for preparing a high-entropy tetraboron / hexaboride material according to claim 7, characterized in that: The agate spheres have a diameter of 5mm to 10mm, and the mass ratio of the agate spheres to the aggregates is 2 to 2.5:

1.

9. A high-entropy tetraboron / hexaboride coating, characterized in that: The coating is prepared on an alloy substrate using a high-entropy tetraboron / hexaboride material as described in claim 1 or 2.

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