High-entropy multi-principal-element corundum structure wide-spectrum radiation refrigeration pigment and preparation method thereof

Abstract

The invention relates to a high-entropy multi-principal-element corundum structure wide-spectrum radiation refrigeration pigment which is powder, the general formula of the pigment is (A1xA2yA3zA4uA5v) 2O3, A1, A2, A3, A4 and A5 are any five elements of Al, Ga, Sc, Y, In and La, x, y, z, u and v are equal or approximately equal, and x + y + z + u + v = 1; the crystal structure of the pigment belongs to a trigonal corundum phase crystal structure and is arranged in a hexagonal close packing manner, and the space group of the pigment is R-3c. Meanwhile, the invention also discloses a preparation method of the pigment. The obtained pigment has high reflectivity and emissivity, and can be widely applied to the fields of building cooling, photovoltaic device cooling, aerospace radiation heat dissipation, human body heat management and the like as a radiation refrigeration material.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling technology, and in particular to a high-entropy multi-principal-element corundum structure broadband radiation cooling pigment and its preparation method. Background Technology

[0002] In recent years, with the rapid growth of the global population and the rapid development of the economy, energy consumption and carbon emissions have become increasingly prominent issues. Under the "dual carbon" goal, reducing energy consumption in cooling is of significant practical importance for achieving this goal. Radiative cooling technology, due to its advantages of zero energy consumption and zero emissions, shows significant application potential in many fields, including building energy conservation, improving solar cell efficiency, textile material innovation, automotive thermal management, and chip heat dissipation. However, the reliability and durability of most materials are limited by their inherent properties or excessively high ambient temperatures. Radiative cooling is a strategy that lowers the temperature by radiating excess heat into the cold universe through an atmospheric transparent window (8-13 μm) without any energy consumption. In recent years, passive radiative cooling materials have shown great application prospects in energy-efficient buildings, personal thermal management, refrigeration systems, photovoltaic cooling, and thermo-photovoltaic systems.

[0003] Traditional radiation-cooling pigments are mostly made of materials such as silicon dioxide, barium sulfate, and polyvinylidene fluoride. They have high absorption of solar radiation in the 0.3~2.5μm band and limited emissivity in the infrared emission band (8~13 μm). They are prone to aging and performance degradation in long-term outdoor environments. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-performance, high-entropy, multi-principal-element corundum structure broadband radiation-cooled pigment.

[0005] Another technical problem to be solved by the present invention is to provide a method for preparing the high-entropy multi-principal-element corundum structure broadband radio-cooled pigment.

[0006] To address the aforementioned problems, the present invention provides a high-entropy multi-principal-element corundum structure broadband radiation-cooled pigment, characterized in that: the pigment is a powder with the general formula (A... 1x A 2y A 3z A 4u A 5v The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement and a space group of R-3c. The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement. The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement and a space group of R-3c.

[0007] The pigment has a refractive index greater than 1.5, an extinction coefficient close to 0, and a band gap greater than the energy of solar photons. It has a reflectivity ≥93% in the 0.3~2.5 μm band and an emissivity ≥0.93 in the 8~13 μm atmospheric window region.

[0008] The pigment has a non-uniform particle size distribution, with an average particle size in the range of 50 to 1000 nm.

[0009] The preparation method of a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment, as described above, includes the following steps: Step 1: Using any five oxides from Al2O3, Ga2O3, Sc2O3, Y2O3, In2O3, and La2O3 powders as raw materials, mix them according to the molar ratio of metal elements x:y:z:u:v, where x + y + z + u + v = 1, and x, y, z, u, and v are equal or approximately equal; the raw materials are ball-milled, dried, and ground to obtain the precursor powder; Step 2: The precursor powder is rapidly heated in a Joule heating device and calcined in an air atmosphere. After holding at the temperature, it is rapidly cooled and ground to obtain a high-entropy multi-principal corundum structure broadband radiation-cooled pigment.

[0010] The conditions for ball milling in step 1 refer to wet ball milling using a planetary ball mill, with ultrapure water as the ball milling solvent, a ball milling speed of 300-500 r / min, a ball milling time of 5-10 hours, and a ball-to-water mass ratio of 2-5:1:3.

[0011] The drying conditions in step 1 refer to a temperature of 80-100°C and a drying time of 12-24 hours.

[0012] The operating conditions of the Joule heating device in step 2 refer to rapidly heating to 500-1200℃ within 10-50 ms and holding at that temperature for calcination for 30-60 minutes.

[0013] In step 2, the cooling method is to rapidly cool down the Joule heating device, and the cooling time is 1 to 3 minutes.

[0014] Compared with the prior art, the present invention has the following advantages: 1. The pigment described in this invention has a trigonal corundum phase crystal structure, with the corundum phase being the R-3c space group. The corundum oxide is arranged in a hexagonal close-packed configuration, with metal ions and 6 oxygen atoms forming a coordination structure and filling the octahedral voids. It has the characteristics of high purity, stable crystal structure, and uniform element distribution.

[0015] 2. The pigment described in this invention, due to multi-principal element doping, forms a high-entropy material with a corundum structure. The pigment has a refractive index greater than 1.5, an extinction coefficient close to 0, and a band gap greater than the energy of solar photons (0.49~4.13 eV). It exhibits a reflectivity ≥93% in the 0.3~2.5 μm wavelength range and an emissivity ≥0.93 in the 8~13 μm atmospheric window region. Compared to traditional corundum structure pigments, the high-entropy corundum structure pigment possesses higher reflectivity and emissivity primarily due to the following reasons: (1) The multi-principal high-entropy corundum material prepared by the present invention has particles in the range of 50 ~ 1000 nm, including nano-sized particles and micro-sized particles. The particle size varies, and light will be scattered multiple times on the surface of various particles, thereby improving the reflectivity and effectively avoiding the reduction of reflectivity due to local agglomeration. In addition, when the particle size is comparable to or close to the wavelength of the incident light, efficient Mie scattering will be achieved, which is beneficial to the high reflectivity of the solar spectrum (0.3~2.5 μm).

[0016] (2) The oxide materials used in this invention are all wide optical bandgap materials. The high-entropy corundum pigment prepared has a bandgap greater than the solar photon energy (0.49~4.13 eV). The wider bandgap will enhance the scattering of light inside the material, thereby increasing the reflectivity of the solar spectrum (0.3~2.5 μm).

[0017] (3) In this invention, rare earth ions are doped in the multi-component composition. Due to their high activity and large radius, the doping into the material will cause changes in the original crystal structure, increase internal defects, and cause lattice distortion, which reduces the frequency of simple harmonic vibration of the material, thereby playing a positive role in improving the radiation emissivity (8~13 μm).

[0018] 3. The pigment described in this invention is prepared using a combination of mechanical wet milling and rapid Joule heating technology. Joule heating technology utilizes an electric current applied to a conductor to increase its internal energy, generating a thermal effect. By controlling the current, transient high or ultra-high temperatures can be achieved in the reactants. Compared to traditional solid-state synthesis, sol-gel methods, and hydrothermal methods for preparing high-entropy materials, this method offers significant advantages such as faster synthesis speed, more precise temperature control, higher thermal energy utilization efficiency, shorter production cycle, and suitability for automated operation.

[0019] 4. The pigment described in this invention can be widely used as a radiation cooling material in fields such as building cooling, photovoltaic device cooling, aerospace radiation heat dissipation, and human body thermal management. Attached Figure Description

[0020] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0021] Figure 1The image shows the XRD pattern of the high-entropy multi-principal-element corundum structure broadband radio-cooled pigment obtained in Example 1 of this invention.

[0022] Figure 2 This is a SEM image of the high-entropy multi-principal-element corundum structure (AlGaScYIn)2O3 broadband radiocooled pigment obtained in Example 1 of the present invention.

[0023] Figure 3 This is a particle size distribution diagram of the high-entropy multi-principal-element corundum structure (AlGaScYIn)2O3 broadband radiation-cooled pigment obtained in Example 1 of the present invention.

[0024] Figure 4 The solar reflectance spectrum of the high-entropy multi-principal-element corundum structure (AlGaScYIn)2O3 broadband radio-cooled pigment obtained in Example 1 of this invention is shown in the 0.3~2.5 μm wavelength range.

[0025] Figure 5 The infrared emission spectrum of the high-entropy multi-principal-element corundum structure (AlGaScYIn)2O3 broadband radiocooled pigment obtained in Example 1 of this invention is shown in the 8~13 μm band. Detailed Implementation

[0026] A high-entropy multi-principal-element corundum structure broadband radiocooling pigment, which is a powder, has the general formula (A... 1x A 2y A 3z A 4u A 5v The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement and a space group of R-3c. The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement. The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement and a space group of R-3c.

[0027] The pigment has a refractive index greater than 1.5, an extinction coefficient close to 0, and a band gap greater than the energy of solar photons (0.49~4.13 eV). It exhibits a reflectivity ≥93% in the 0.3~2.5 μm wavelength range and a radiative emissivity ≥0.93 in the 8~13 μm atmospheric window region. Its particle size distribution is non-uniform, with an average particle size ranging from 50 to 1000 nm.

[0028] A method for preparing a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment includes the following steps: Step 1: Using any five oxides from Al2O3, Ga2O3, Sc2O3, Y2O3, In2O3, and La2O3 powders as raw materials, mix them according to the molar ratio of metal elements x:y:z:u:v, where x + y + z + u + v = 1, and x, y, z, u, and v are equal or approximately equal. Wet ball mill each raw material using a planetary ball mill with ultrapure water as the milling solvent. The milling speed is 300-500 r / min, and the milling time is 5-10 hours. The mass ratio of ball to material to water (g / g) is 2-5:1:3. After ball milling and mixing, dry at 80-100℃ for 12-24 hours, and then grind to obtain the precursor powder.

[0029] Step 2: The precursor powder is rapidly heated to 500-1200 °C within 10-50 ms in a Joule heating device and calcined in air. After holding at this temperature for 30-60 minutes, it is rapidly cooled using the Joule heating device for 1-3 minutes. Finally, grinding yields a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment.

[0030] Example 1 A method for preparing a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment includes the following steps: Step 1: Weigh out 1 mol each of Al₂O₃, Ga₂O₃, Sc₂O₃, Y₂O₃, and In₂O₃ powders according to a metal element molar ratio of 1:1:1:1:1. Perform wet ball milling on each raw material using a planetary ball mill. Use ultrapure water as the milling solvent. Mill at 300 r / min for 5 hours. The mass ratio of ball to material to water (g / g) is 2:1:3. After ball milling and mixing, dry at 80 °C for 12 hours. Grind the resulting powder to obtain the precursor powder.

[0031] Step 2: The precursor powder is rapidly heated to 500 °C within 10 ms in a Joule heating device and calcined in air. After holding at this temperature for 30 minutes, it is rapidly cooled down using the Joule heating device for 1 minute. Finally, after grinding, a high-entropy multi-principal-element corundum structure (AlGaScYIn)₂O₃ broadband radiocooled pigment is obtained.

[0032] X-ray diffraction analysis was performed on the obtained high-entropy multi-principal-element corundum structure (AlGaScYIn)₂O₃ broadband radiocooled pigment, such as... Figure 1 As shown in the figure, the XRD pattern reveals that the prepared powder material has a corundum structure. The spectral lines are in excellent agreement with Ca2O3 (PDF#06-0503) with a corundum structure in the ICDD database, indicating that the material prepared in this embodiment is a high-entropy multi-principal-element corundum structure oxide material.

[0033] Microscopic morphology analysis was performed on the obtained high-entropy multi-principal-element corundum (AlGaScYIn)₂O₃ broadband radiation-cooled pigment, such as... Figure 2 As shown in the SEM image, the prepared powder material has an octahedral structure, which matches the morphology of corundum, indicating that the material prepared in this embodiment is a high-entropy multi-principal-element corundum oxide material.

[0034] Particle size distribution analysis was performed on the obtained high-entropy multi-principal-element corundum structure (AlGaScYIn)₂O₃ broadband radiation-cooled pigment, such as... Figure 3 As shown in the figure, the particle size distribution diagram reveals that the prepared powder material has a particle size range of 50 to 1000 nm, with an average particle size of 390 ± 10 nm.

[0035] The radiation cooling performance of the obtained high-entropy multi-principal-element corundum structure (AlGaScYIn)2O3 broadband radiation-cooled pigment was evaluated: Test methods: The reflectance of this high-entropy multi-principal-element corundum structure broadband radiocooled pigment was evaluated using a PerkinElmer Lambda 950 UV / Vis / NIR spectrophotometer (equipped with a 150mm integrating sphere), measuring its reflectance in the 0.3–2.5 μm wavelength range. The emissivity of this high-entropy multi-principal-element corundum structure broadband radiocooled pigment was evaluated using a Senor TSS-5X-2 infrared emissivity analyzer, measuring its emissivity in the 28–13 μm wavelength range.

[0036] 0.2 g of the high-entropy multi-principal-element corundum structure (AlGaScYIn)₂O₃ broadband radiocooled pigment prepared in this example was tested. Its Eg was 5.2 eV, and its particle size was 50 ~ 200 nm (e.g., ...). Figure 2 As shown), the total reflectivity in the 0.3~2.5 μm band is 92% (as shown). Figure 4 As shown); the radiative emissivity of the atmospheric window region in the 8~13 μm band is 93% (e.g. Figure 5 (As shown); normal thermal conductivity is 32 W·m. –1 ·K –1 .

[0037] Example 2 A method for preparing a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment includes the following steps: Step 1: Weigh out 1 mol each of Al₂O₃, Ga₂O₃, Sc₂O₃, Y₂O₃, and La₂O₃ powders according to a metal element molar ratio of 1:1:1:1:1. Perform wet ball milling on each raw material using a planetary ball mill. Use ultrapure water as the milling solvent. Mill at 400 r / min for 8 hours. The mass ratio of ball to material to water (g / g) is 4:1:3. After ball milling and mixing, dry at 90 °C for 14 hours. Grind the resulting powder to obtain the precursor powder.

[0038] Step 2: The precursor powder was rapidly heated to 1000 °C within 130 ms in a Joule heating device and calcined in air. After holding at this temperature for 45 minutes, it was rapidly cooled down using the Joule heating device for 2 minutes. Finally, after grinding, a high-entropy multi-principal-element corundum structure (AlGaScYLa)₂O₃ broadband radiocooled pigment was obtained.

[0039] The radiation cooling performance of the obtained high-entropy multi-principal-element corundum structure (AlGaScYLa)2O3 broadband radiation-cooled pigment was evaluated, and the test method was the same as in Example 1.

[0040] The results showed that the pigment had a band gap (Eg) of 5.15 eV and a particle size of 70–800 nm. Its reflectivity was 95% in the 0.3–2.5 μm band, and its emissivity was 0.96 in the 8–13 μm atmospheric window region.

[0041] Example 3 A method for preparing a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment includes the following steps: Step 1: Weigh out 1 mol each of Al₂O₃, Ga₂O₃, Y₂O₃, In₂O₃, and La₂O₃ powders according to a metal element molar ratio of 1:1:1:1:1. Perform wet ball milling on each raw material using a planetary ball mill. Use ultrapure water as the milling solvent. Mill at 500 r / min for 10 hours. The mass ratio of ball to material to water (g / g) is 5:1:3. After ball milling and mixing, dry at 100 °C for 24 hours. Grind the resulting powder to obtain the precursor powder.

[0042] Step 2: The precursor powder was rapidly heated to 1200 °C within 50 ms in a Joule heating device and calcined in air. After holding at this temperature for 60 minutes, it was rapidly cooled down using the Joule heating device for 3 minutes. Finally, after grinding, a high-entropy multi-principal-element corundum structure (AlGaScInLa)₂O₃ broadband radiocooled pigment was obtained.

[0043] The radiation cooling performance of the obtained high-entropy multi-principal-element corundum structure (AlGaScInLa)2O3 broadband radiation-cooled pigment was evaluated, and the test method was the same as in Example 1.

[0044] The results showed that the pigment had a band gap (Eg) of 5.25 eV and a particle size of 80–500 nm. Its reflectivity was 96% in the 0.3–2.5 μm band, and its emissivity was 0.94 in the 8–13 μm atmospheric window region.

Claims

1. A high-entropy multi-principal-element corundum structure broadband radiocooling pigment, characterized in that: The pigment is a powder, and its general formula is (A 1x A 2y A 3z A 4u A 5v The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement and a space group of R-3c. The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement. The pigment is a trigonal corundum phase crystal structure with a hexagonal close-packed arrangement and a space group of R-3c.

2. The high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 1, characterized in that: The pigment has a refractive index greater than 1.5, an extinction coefficient close to 0, and a band gap greater than the energy of solar photons. It has a reflectivity ≥93% in the 0.3~2.5 μm band and an emissivity ≥0.93 in the 8~13 μm atmospheric window region.

3. The high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 1, characterized in that: The pigment has a non-uniform particle size distribution, with an average particle size in the range of 50 to 1000 nm.

4. The preparation method of a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 1, comprising the following steps: Step 1: Using any five oxides from Al2O3, Ga2O3, Sc2O3, Y2O3, In2O3, and La2O3 powders as raw materials, mix them according to the molar ratio of metal elements x:y:z:u:v, where x + y + z + u + v = 1, and x, y, z, u, and v are equal or approximately equal; the raw materials are ball-milled, dried, and ground to obtain the precursor powder; Step 2: The precursor powder is rapidly heated in a Joule heating device and calcined in an air atmosphere. After holding at the temperature, it is rapidly cooled and ground to obtain a high-entropy multi-principal corundum structure broadband radiation-cooled pigment.

5. The preparation method of a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 4, characterized in that: The conditions for ball milling in step 1 refer to wet ball milling using a planetary ball mill, with ultrapure water as the ball milling solvent, a ball milling speed of 300-500 r / min, a ball milling time of 5-10 hours, and a ball-to-water mass ratio of 2-5:1:

3.

6. The method for preparing a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 4, characterized in that: The drying conditions in step 1 refer to a temperature of 80-100°C and a drying time of 12-24 hours.

7. The preparation method of a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 4, characterized in that: The operating conditions of the Joule heating device in step 2 refer to rapidly heating to 500-1200℃ within 10-50 ms and holding at that temperature for calcination for 30-60 minutes.

8. The method for preparing a high-entropy multi-principal-element corundum structure broadband radio-cooled pigment as described in claim 4, characterized in that: In step 2, the cooling method is to rapidly cool down the Joule heating device, and the cooling time is 1 to 3 minutes.

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