A high-entropy rare earth-based hexaboride ceramic material, a preparation method and application thereof

Abstract

The application discloses a high-entropy rare-earth-based hexaboride ceramic material and a preparation method and application thereof, and has the following general chemical formula: RE(AE) x B6, wherein RE is selected from at least three of rare earth elements La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y, AE is selected from one of alkaline earth elements Be, Mg, Ca, Sr, Ba and Ra, and x is 0.2-0.5. The high-entropy rare-earth-based hexaboride ceramic powder has small grains and uniform distribution, and has good optical performance, namely high solar absorption and high infrared emissivity and good high-temperature thermal stability. Meanwhile, the preparation process of the high-entropy rare-earth-based hexaboride ceramic material is simple, the operation condition is controllable, and the high-entropy rare-earth-based hexaboride ceramic material is easy to be popularized and applied.

Description

Technical Field

[0001] The present invention relates to the field of solar energy absorption materials and infrared radiation materials, and relates to a high-entropy rare earth-based hexaboride ceramic material, a preparation method and applications thereof, and in particular to a high-entropy rare earth-based hexaboride with high solar energy absorption rate and high infrared emissivity, a preparation method and applications thereof. Background Art

[0002] In recent years, renewable energy has garnered widespread attention due to the depletion of fossil fuels, the increasing greenhouse effect, climate change, and energy security concerns in countries with limited fossil energy reserves. Solar power generation is becoming increasingly dominant, and the global power system is gradually transitioning toward a low-carbon future. Concentrated solar power (CPS) systems are a power generation method that collects solar energy and uses it directly as a heat source for power generation. However, the alternation of day and night and weather fluctuations significantly limit the application of solar thermal power generation technology. Combining CPS technology with thermal energy storage (TES) technology offers an attractive solution. Direct solar absorption and heat storage based on solid particles is also gaining increasing attention in high-temperature concentrated solar power generation. Solid particles in CPS systems must possess not only excellent optical and thermophysical properties, but also high solar absorptivity, high infrared emissivity, high specific heat, and good stability. Currently, the most studied CPS solid particles, such as alumina, cordierite, mullite, black silicon carbide, quartz, and ceramic sintered bauxite particles, are used as heat transfer fluids (HFTs) and TES materials. Rare earth lanthanum hexaboride was once found to be a potential material for use as a concentrated solar absorber, but its solar absorptivity and infrared emissivity are insufficient. Summary of the Invention

[0003] In order to improve the above technical problems, the present invention provides a high-entropy rare earth hexaboride with high solar absorptivity and high infrared emissivity, as well as a preparation method and application thereof. The present invention introduces the concept of high entropy through a solid-phase reaction method to obtain a high-entropy rare earth hexaboride material that can be used for solar absorption and infrared radiation.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a high entropy boride material having the following chemical formula: RE(AE) x B6, wherein: RE is selected from at least three of the rare earth elements La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Tm, Lu, Sc and Y, AE is selected from one of the alkaline earth elements Be, Mg, Ca, Sr, Ba and Ra, and x is 0.2 to 0.5, illustratively, x = 0.2, 0.25, 0.3, 0.4 or x = 0.5.

[0006] According to an embodiment of the present invention, the high entropy boride material is a high entropy rare earth-based hexaboride ceramic material, which has high solar energy absorptivity and high infrared emissivity.

[0007] Preferably, the average solar energy absorption rate of the high entropy boride material is 82-88%, exemplified by 82.68%, 85.61%, and 87.75%.

[0008] Preferably, the near-infrared emissivity of the high-entropy boride material is 80-90%, exemplified by 83.63%, 85.23%, and 88.76%.

[0009] Preferably, the mid- and far-infrared emissivity of the high-entropy boride material is 90-95%, exemplified by 91.12%, 93.01%, and 94.36%.

[0010] According to an embodiment of the present invention, the particle size of the high entropy boride material is D 90 ≤2.5μm.

[0011] According to an embodiment of the present invention, the high entropy boride material is La 0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6, La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6 and La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 At least one of B6.

[0012] Preferably, the high-entropy rare earth-based hexaboride ceramic material has a typical CsCl-type cubic structure.

[0013] According to an embodiment of the present invention, the high entropy boride material is prepared from raw materials including B4C, RE2O3 and AECO3 by a solid phase reaction method, wherein RE and AE have the definitions and selections as described above.

[0014] The present invention also provides a method for preparing the high-entropy boride material, comprising: mixing B4C with RE2O3 and AECO3, and then subjecting the mixture to a solid-phase reaction to obtain the high-entropy boride material. In the present invention, the chemical reaction process for obtaining the high-entropy boride material by reacting B4C with RE2O3 and AECO3 is as follows:

[0015] 4RE2O3+7B4C=4REBO3+REB6+7C (1)

[0016] 4REBO3+7C+5B4C=4REB6+12CO (2)

[0017] (1)+(2):4RE2O3+12B4C=5REB6+12CO

[0018] According to an embodiment of the present invention, the mixed raw materials may be ground before the solid phase reaction. For example, the grinding time may be more than 0.5 h.

[0019] According to an embodiment of the present invention, the preparation method further includes pressing the ground mixed raw materials. For example, the pressing pressure is 3-5 MPa, exemplified by 3 MPa, 4 MPa, 4.5 MPa, and 5 MPa; the pressing time is 10-60 seconds, exemplified by 20 seconds, 30 seconds, and 40 seconds; and the pressing method can be dry pressing.

[0020] According to an embodiment of the present invention, the sintering temperature of the solid-phase reaction is 1500-1700°C, exemplified by 1500°C, 1600°C, and 1700°C; the sintering time of the solid-phase reaction is 1-4h, exemplified by 2h, 2.5h, and 3h; the heating rate of the solid-phase reaction is 1-10°C / min, exemplified by 5°C / min.

[0021] According to an embodiment of the present invention, the preparation method further comprises crushing, grinding, and screening the product after the solid-phase reaction to obtain a high-entropy ceramic powder. Preferably, the screening is performed using a standard sieve of 200-400 mesh.

[0022] According to an embodiment of the present invention, the molar ratio of the total molar amount of RE (rare earth element) and AE (alkaline earth element) to boron carbide is 2:(3-3.45), and exemplarily is 2:3.3.

[0023] The present invention also provides for the use of the high-entropy boride material in solar energy absorption and storage, preferably in a concentrated solar power system, for example, for converting solar energy into thermal energy and then into electrical energy.

[0024] The present invention also provides a concentrated solar power (CPS) system containing the high entropy boride material.

[0025] Beneficial effects of the present invention:

[0026] To achieve integrated heat absorption and energy storage, as well as higher temperature service, a high-entropy method was used to prepare high-entropy hexaboride ceramics to improve their solar absorptivity and infrared emissivity. High-entropy ceramics exhibit high-entropy effects, including a delayed diffusion effect, a lattice distortion effect, and a "cocktail" effect. These effects result in slower grain growth, better high-temperature stability, and improved infrared emission performance.

[0027] Applying high entropy ceramics to concentrated solar power systems can achieve high solar absorption rates in the range of 0.28 to 2.5 μm and high infrared emissivity in the range of 2.5 to 25 μm, creating new materials that combine heat absorption and energy storage, thereby reducing the complexity of solar power generation systems, achieving high-efficiency power cycles, and improving the commercial competitiveness of CPS systems.

[0028] (1) The preparation process of the high entropy rare earth hexaboride of the present invention is simple, and the synthesized high entropy ceramic powder has small grains (D 90 ≤2.5μm) and evenly distributed.

[0029] (2) The high entropy rare earth hexaboride of the present invention has good optical properties, namely high solar absorptivity and high infrared emissivity, as well as good high-temperature thermal stability due to lattice distortion and hysteresis diffusion effects.

[0030] (3) The present invention adopts a high-temperature solid-phase method to prepare high-entropy rare earth-based hexaboride ceramic materials. The preparation process is simple and the operating conditions are controllable, which is easy to promote and apply industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a flow chart of the preparation process of high-entropy rare earth-based hexaboride ceramic powder with high solar water absorption and high infrared emissivity.

[0032] Figure 2 (La 0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6), (La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6), and (La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 B6) XRD pattern of high-entropy rare earth hexaboride ceramic powder.

[0033] Figure 3 Where a, b, and c are respectively (La0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6), (La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6) and (La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 B6) EDS element distribution diagram of high entropy ceramics.

[0034] Figure 4 (La 0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6), (La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6) and (La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 B6) UV-visible-near-infrared reflectance spectrum of high-entropy ceramics.

[0035] Figure 5 ((La 0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6), (La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6) and (La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 B6) Histogram of the average solar absorptivity in the near-infrared band and the mid- and far-infrared emissivity of high-entropy ceramics. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above-mentioned invention are encompassed within the scope of protection that the present invention is intended to protect.

[0037] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0038] Example 1

[0039] like Figure 1 As shown, a high-entropy rare earth-based hexaboride ceramic material with high solar absorptivity and high infrared emissivity is prepared as follows:

[0040] (1) Weigh 0.025 mol of La2O3 (lanthanum oxide), 0.025 mol of Sm2O3 (samarium oxide), 0.025 mol of Eu2O3 (europium oxide) powder, 0.05 mol of CeO2 (cerium oxide), and 0.33 mol of B4C powder respectively, transfer all the raw materials into an agate mortar, and grind for more than 40 min until they are completely mixed;

[0041] (2) The mixture powder ground uniformly in step (1) was tableted using a tableting die with a diameter of 15 mm, a tablet press pressure of 4 MPa, and a pressing time of 40 s to obtain embryo A;

[0042] (3) The embryo A obtained in step (2) was synthesized in an argon atmosphere under normal pressure, with a synthesis temperature of 1600°C, a heating rate of 5°C / min, and a holding time of 2h to obtain a high entropy ceramic La 0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6;

[0043] (4) The high entropy ceramic synthesized in step (3) is crushed, ground, and sieved (400 mesh) to obtain a high entropy ceramic powder.

[0044] like Figure 2 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Eu 0.25 The XRD pattern of B6 is basically consistent with the standard card of a single phase in the ICDD database, and there are no impurity peaks, which shows that the high-entropy rare earth hexaboride prepared in this example is a single-phase solid solution with a CsCl-type body-centered cubic structure.

[0045] like Figure 3 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Eu 0.25EDS element distribution diagram of B6. It can be seen from the figure that the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Eu 0.25 The rare earth elements in B6 are evenly distributed without segregation.

[0046] like Figure 4 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Eu 0.25 The reflectivity spectrum of B6 at 0.28-2.5 μm is plotted, and its solar absorptivity is calculated using the following formula:

[0047]

[0048] Where: S(λ) is the solar emission spectrum, integrated between λ = 0.28 μm and λ = 2.5 μm. It is found that its average solar absorptivity is as high as 82.68%, which is nearly half of that of single-phase LaB6 (54.05%).

[0049] like Figure 5 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Eu 0.25 The average infrared emissivity of B6 in the near-infrared and far-infrared regions is significantly enhanced compared with that of single-phase LaB6, and the mid-infrared and far-infrared emissivity is also slightly enhanced, reaching 83.63% and 91.12% respectively.

[0050] Example 2

[0051] like Figure 1 As shown, a high-entropy rare earth-based hexaboride ceramic material with high solar absorptivity and high infrared emissivity is prepared as follows:

[0052] (1) Weigh 0.025 mol of La2O3 (lanthanum oxide), 0.025 mol of Sm2O3 (samarium oxide), 0.05 mol of CeO2 (cerium oxide), and 0.05 mol of BaCO3 (barium carbonate), respectively, and add 0.33 mol of B4C powder. Transfer all the raw materials into an agate mortar and grind for more than 45 minutes until they are completely mixed.

[0053] (2) The mixture powder ground uniformly in step (1) was tableted using a tableting die with a diameter of 15 mm, a tablet press pressure of 4.5 MPa, and a pressing time of 30 s to obtain embryo B;

[0054] (3) The embryo B obtained in step (2) was synthesized in an argon atmosphere under normal pressure, with a synthesis temperature of 1600°C, a heating rate of 5°C / min, and a holding time of 2.5h to obtain a high entropy ceramic La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6;

[0055] (4) The high entropy ceramic synthesized in step (3) is crushed, ground, and sieved (400 mesh) to obtain a high entropy ceramic powder.

[0056] like Figure 2 As shown, the high entropy rare earth-alkaline earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Ba 0.25 The XRD pattern of B6 is basically consistent with the standard card of a single phase in the ICDD database, and there are no impurity peaks, which shows that the high-entropy rare earth hexaboride prepared in this example is a single-phase solid solution with a CsCl-type body-centered cubic structure.

[0057] like Figure 3 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Ba 0.25 EDS element distribution diagram of B6. It can be seen from the figure that the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Ba 0.25 The rare earth elements in B6 are evenly distributed without segregation.

[0058] like Figure 4 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Ba 0.25 The reflectivity spectrum of B6 at 0.28-2.5 μm was obtained, and its solar absorptivity was calculated in the same manner as in Example 1. It was found that its average solar absorptivity was as high as 85.61%.

[0059] like Figure 5 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.25 Sm 0.25 Ce 0.25 Ba 0.25The average infrared emissivity of B6 in the near-infrared and far-infrared regions is significantly enhanced compared with that of single-phase LaB6, that is, the solar energy absorption rate, and the mid-infrared and far-infrared emissivity are also slightly enhanced, reaching 85.23% and 94.36% respectively.

[0060] Example 3

[0061] like Figure 1 As shown, a high-entropy rare earth-based hexaboride ceramic material with high solar absorptivity and high infrared emissivity is prepared as follows:

[0062] (1) Weigh 0.02 mol of La2O3 (lanthanum oxide), 0.02 mol of Sm2O3 (samarium oxide), 0.02 mol of Eu2O3 (europium oxide) powder, 0.04 mol of CeO2 (cerium oxide), 0.04 mol of BaCO3, and 0.33 mol of B4C powder respectively, transfer all the raw materials into an agate mortar, and grind for more than 50 min until they are completely mixed;

[0063] (2) The mixture powder ground evenly in step (1) was tableted, the diameter of the edible tableting mold was 15 mm, the tableting machine pressure was set to 5 MPa, and the pressing time was 20 s to obtain embryo C;

[0064] (3) The embryo C obtained in step (2) was synthesized in an argon atmosphere under normal pressure, with a synthesis temperature of 1600°C, a heating rate of 5°C / min, and a holding time of 3h to obtain a high entropy ceramic La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 B6;

[0065] (4) The high entropy ceramic synthesized in step (3) is crushed, ground, and sieved (400 mesh) to obtain a high entropy ceramic powder.

[0066] like Figure 2 As shown, the rare earth-based high entropy hexaboride ceramic material La prepared in this embodiment 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 The XRD pattern of B6 is basically consistent with the standard card of a single phase in the ICDD database, and there are no impurity peaks, which shows that the high-entropy rare earth hexaboride prepared in this example is a single-phase solid solution with a CsCl-type body-centered cubic structure.

[0067] like Figure 3 As shown, the rare earth-based high entropy hexaboride ceramic material La prepared in this embodiment 0.2 Sm0.2 Ce 0.2 Eu 0.2 Ba 0.2 EDS element distribution diagram of B6. It can be seen from the figure that the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 The rare earth elements in B6 are evenly distributed without segregation.

[0068] like Figure 4 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 The reflectivity spectrum of B6 at 0.28-2.5 μm was obtained, and its solar absorptivity was calculated in the same manner as in Example 1. It was found that its average solar absorptivity was as high as 87.75%.

[0069] like Figure 5 As shown, the high entropy rare earth hexaboride ceramic material La prepared in this embodiment 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 The average infrared emissivity of B6 in the near-infrared and far-infrared regions is significantly enhanced compared with that of single-phase LaB6, that is, the solar energy absorption rate, and the mid-infrared and far-infrared emissivity are also slightly enhanced, reaching 88.76% and 93.01% respectively.

[0070] The above examples illustrate the embodiments of the present invention. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A high entropy boride material, characterized in that: The high entropy boride material is La 0.25 Sm 0.25 Ce 0.25 Eu 0.25 B6, La 0.25 Sm 0.25 Ce 0.25 Ba 0.25 B6 or La 0.2 Sm 0.2 Ce 0.2 Eu 0.2 Ba 0.2 B6.

2. Use of the high entropy boride material according to claim 1 in solar energy absorption and storage.

3. The use according to claim 2, characterized in that Application of the high entropy boride material in a concentrated solar energy system.

4. A concentrated solar power system, characterized in that: It contains the high entropy boride material according to claim 1.

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