High-entropy oxide-boron nitride composite radiation refrigeration pigment and preparation method thereof

Abstract

The invention relates to a high-entropy oxide-boron nitride composite radiation refrigeration pigment and a preparation method thereof, the pigment is powder, the general formula of the high-entropy oxide is (A1xA2yA3zA4uA5v) O2, A1, A2, A3, A4 and A5 are any five elements of Ce, Zr, Hf, Ti, Sn and Ge, x, y, z, u and v are equal or approximately equal, and x + y + z + u + v = 1; the mass fraction ratio of the high-entropy oxide to the boron nitride is (60-90 wt%): (40-10 wt%). Meanwhile, the invention also discloses a preparation method of the pigment. The pigment disclosed by the invention has high thermal conductivity, and can be widely applied to the fields of thermal management, photovoltaic cooling, aerospace radiation heat dissipation 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 oxide-boron nitride composite radiation cooling pigment and its preparation method. Background Technology

[0002] High-entropy oxides have become rising stars in the ceramics field due to their unique crystal structure and rich physical properties. The unique high-entropy effect, similar to that of high-entropy alloys, has attracted widespread attention from domestic researchers. The design concept of high entropy originates from high-entropy alloys, which utilizes the solid solution of multi-component components to increase the configurational entropy of the system, thereby reducing the Gibbs free energy and ultimately improving the stability of the phase structure. In 2023, Gao Xianghu et al. prepared a high-entropy oxide [(MnCrFeCoCu)3O4], which exhibited excellent emissivity in a wide infrared band (Adv. Funct. Mater. 2023, 2303197). Currently, extensive research has been conducted on high-entropy materials. Utilizing their high entropy value, low Gibbs free energy, and large amount of lattice distortion, these materials exhibit excellent performance in electrical, optical, and magnetic fields, and their applications can cover almost the entire industrial field, including high-temperature and high-heat applications, energy and batteries, catalysis, and mechanical and microwave absorption.

[0003] Boron nitride possesses electrical insulation, light weight, and high thermal conductivity, with a theoretical thermal conductivity of 1700–2000 W·m. –1 ·K –1 Boron nitride is often used as a thermally conductive filler to improve the thermal conductivity of composite materials. In 2025, Wang Jikui et al. applied for a Chinese invention patent (application publication number CN119307073A) entitled "A method for preparing a high thermal conductivity polymer with modified boron nitride as a filler," which greatly improved the thermal conductivity of the material by using modified boron nitride as a filler. Due to its wide bandgap, hexagonal boron nitride also has high reflectivity and absorptivity and is often used as a radiative cooling material.

[0004] However, there are currently no reports on the preparation of high-entropy oxide / boron nitride high thermal conductivity composite radiation-cooling pigment materials by solid-state synthesis. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high thermal conductivity, high entropy oxide-boron nitride composite radiation-cooling pigment.

[0006] Another technical problem to be solved by the present invention is to provide a method for preparing the high-entropy oxide-boron nitride composite radiocooling pigment.

[0007] To address the aforementioned problems, the present invention provides a high-entropy oxide-boron nitride composite radiation-cooling pigment, characterized in that: the pigment is a powder, and the high-entropy oxide (HEO) has the general formula (A... 1x A2y A 3z A 4u A 5v O2, wherein A1, A2, A3, A4, and A5 are any five elements from Ce, Zr, Hf, Ti, Sn, and Ge, and x, y, z, u, and v are equal or approximately equal, and x + y + z + u + v = 1; the mass fraction ratio of high entropy oxide (HEO) to boron nitride (BN) is 60~90 wt%: 40~10 wt%.

[0008] The pigment has a total reflectance ≥0.92 in the 0.3–2.5 μm wavelength range, an emissivity ≥0.92 in the 8–13 μm wavelength range, and a normal thermal conductivity ≥30 W·m. -1 ·K -1 .

[0009] The average particle size of the pigment is in the range of 100 to 1000 nm.

[0010] The high-entropy oxide (HEO) has a single-phase fluorite structure, belongs to the cubic crystal system, and has a space group of [space group number missing]. Fm3m .

[0011] The boron nitride (BN) is a hexagonal nanosheet with a total reflectivity ≥0.90 in the 0.3–2.5 μm wavelength range and an emissivity ≥0.82 in the 8–13 μm wavelength range; its normal thermal conductivity is ≥45 W·m. -1 ·K -1 .

[0012] The preparation method of the high-entropy oxide-boron nitride composite radiation-cooling pigment as described above includes the following steps: Step 1: Using any five oxides from CeO2, ZrO2, HfO2, TiO2, SnO2, and GeO2 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 calcined in stages in an air atmosphere, and after cooling and grinding, high entropy oxide (HEO) is obtained. Step 3: Mix and grind the high entropy oxide (HEO) and boron nitride (BN) at a mass fraction ratio of 60~90 wt%: 40~10 wt% to obtain the high entropy oxide-boron nitride (HEO-BN) composite radiation-cooling pigment.

[0013] The conditions for ball milling in step 1 refer to using a planetary ball mill, using 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.

[0014] The drying conditions in step 1 refer to a temperature of 80-100°C and a drying time of 12-24 hours.

[0015] The conditions for segmented calcination in step 2 are as follows: first, the temperature is increased to 500℃ at a rate of 5℃ / min, and then the temperature is increased at a rate of 2~5℃ / min, with a calcination temperature of 1000~1400℃ and a calcination time of 4~10 hours.

[0016] The cooling method in step 2 is one of furnace cooling, air quenching cooling, and liquid nitrogen quenching cooling.

[0017] Compared with the prior art, the present invention has the following advantages: 1. The high-entropy oxide-boron nitride composite radiation-cooling pigment prepared by the present invention has a particle size in the range of 100~1000 nm, with a large size difference. When sunlight shines on the material, light of different wavelengths will be scattered by particles of different sizes. The synergistic effect of multiple sizes can improve the material's high reflectivity to the solar spectrum (0.3~2.5 μm).

[0018] 2. In this invention, HEO is a high-entropy fluorite oxide containing transition metal ions and rare earth ions. The difference in ionic radius produces a large amount of lattice distortion. At the same time, the decrease in crystal symmetry increases the dipole moment, thereby promoting the absorption of rotational vibrational energy levels, thus playing a positive role in improving the radiation emissivity (8~13 μm).

[0019] 3. The boron nitride composite of this invention is a hexagonal crystal nanosheet with a high refractive index; the morphology of the nanosheet can achieve Mie scattering, which can effectively reflect sunlight (0.3~2.5 μm); boron nitride has a high emissivity in the atmospheric window range of 8~13 μm; at the same time, boron nitride has excellent thermal conductivity, which can effectively improve the low thermal conductivity of high-entropy materials.

[0020] 4. Due to the high thermal conductivity of boron nitride, the thermal conductivity of high-entropy oxides with low thermal conductivity is improved, which is beneficial to the application of the prepared high-entropy oxide-boron nitride composite radiation cooling pigment in radiation heat management, radiation cooling and large-scale radiation heat dissipation equipment.

[0021] 5. This invention employs mechanical wet grinding and solid-phase synthesis calcination, which ensures thorough mixing of metal elements. It has advantages such as simple operation, short production cycle, and industrial production capability. The prepared high-entropy oxide-boron nitride composite radiation cooling pigment can be widely used as a radiation cooling material in fields such as thermal management, photovoltaic cooling, and aerospace radiation heat dissipation. Attached Figure Description

[0022] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0023] Figure 1 The image shows the XRD pattern of the HEO-BN composite radiation-cooled pigment obtained in Example 1 of this invention.

[0024] Figure 2 The solar reflectance spectrum of the HEO-BN composite radiation-cooled pigment obtained in Example 1 of this invention is shown in the 0.3~2.5 μm wavelength range.

[0025] Figure 3 The infrared emission spectrum of the HEO-BN composite radiation-cooled pigment obtained in Example 1 of this invention is shown in the 8~13 μm band. Detailed Implementation

[0026] A high-entropy oxide-boron nitride composite radiation-cooling pigment, wherein the pigment is a powder, and the general formula of the high-entropy oxide (HEO) is (A 1x A 2y A 3z A 4u A 5v O2, wherein A1, A2, A3, A4, and A5 are any five elements from Ce, Zr, Hf, Ti, Sn, and Ge, and x, y, z, u, and v are equal or approximately equal, and x + y + z + u + v = 1; the mass fraction ratio (g / g) of high entropy oxide (HEO) to boron nitride (BN) is 60~90 wt%: 40~10 wt%.

[0027] The pigment has a total reflectance ≥0.92 in the 0.3–2.5 μm wavelength range, an emissivity ≥0.92 in the 8–13 μm wavelength range, and a normal thermal conductivity ≥30 W·m. -1 ·K -1 Its average particle size is in the range of 100 to 1000 nm.

[0028] Among them, the high-entropy oxide (HEO) has a single-phase fluorite structure, belongs to the cubic crystal system, and has a space group of . Fm3m .

[0029] Boron nitride (BN) is a hexagonal nanosheet, a commercially available product, such as that produced by Zhejiang Yamei Nanotechnology Co., Ltd. It exhibits a total reflectivity ≥0.90 in the 0.3–2.5 μm wavelength range and an emissivity ≥0.82 in the 8–13 μm wavelength range; its normal thermal conductivity is 45 W·m. -1 ·K -1 .

[0030] A method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment includes the following steps: Step 1: Using any five oxides from CeO2, ZrO2, HfO2, TiO2, SnO2, and GeO2 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. Each raw material is ball-milled 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.

[0031] Step 2: The precursor powder is calcined in stages in an air atmosphere. First, the temperature is increased to 500℃ at a rate of 5℃ / min, then increased further at a rate of 2~5℃ / min, with a calcination temperature of 1000~1400℃ and a calcination time of 4~10 hours. Then, it is cooled using one of the following methods: furnace cooling, air quenching, or liquid nitrogen quenching. After grinding, the high-entropy oxide (HEO) is obtained.

[0032] Step 3: Mix and grind high entropy oxide (HEO) and boron nitride (BN) at a mass fraction ratio (g / g) of 60~90 wt%: 40~10 wt% to obtain high entropy oxide-boron nitride (HEO-BN) composite radiation-cooling pigment. Example 1

[0033] A method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment includes the following steps: Step 1: Weigh out 1 mol of CeO2, 1 mol of ZrO2, 1 mol of HfO2, 1 mol of TiO2, and 1 mol of SnO2 according to the metal element molar ratio of 1:1:1:1:1. Mill each raw material using a planetary ball mill with ultrapure water as the milling solvent. The milling speed is 300 r / min, and the milling time is 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 ℃ for 12 hours, and then grind to obtain the precursor powder.

[0034] Step 2: The precursor powder was calcined in stages in air. First, the temperature was increased to 500 °C at a rate of 5 °C / min, and then increased further at a rate of 2 °C / min until the calcination temperature reached 1000 °C for 4 hours. The powder was then cooled using a furnace cooling method, and after grinding, HEO was obtained.

[0035] Step 3: Mix and grind 60 g HEO and 40 g BN to obtain HEO-BN composite radiation-cooling pigment.

[0036] X-ray diffraction analysis was performed on the obtained HEO-BN composite radiation-cooled pigment, such as... Figure 1 As shown in the figure. The XRD pattern reveals that the prepared powder material has both fluorite and BN structures. The spectrum is in excellent agreement with CeO2 (PDF#43-1002) and BN (PDF#34-0421) with fluorite structures in the ICDD database, indicating that the material prepared in this embodiment is a high-entropy oxide-boron nitride composite material.

[0037] The radiation cooling performance of the obtained HEO-BN composite radiation-cooled pigment was evaluated: Test methods: The reflectance of this high-entropy oxide-boron nitride was evaluated using a Lambda 950 UV / Vis / NIR spectrophotometer (equipped with a 150mm integrating sphere) manufactured by PerkinElmer, USA, measuring its reflectance in the 0.3–2.5 μm wavelength range. The emissivity of this high-entropy oxide-boron nitride was evaluated using a TSS-5X-2 infrared emissivity analyzer manufactured by Senor, Japan, measuring its emissivity in the 8–13 μm wavelength range.

[0038] 0.2 g of the (CeZrHfTiSn)O2-BN composite radiation-cooled pigment prepared in this embodiment was tested. The results showed that the total reflectance of this composite radiation-cooled pigment in the 0.3~2.5 μm wavelength range was 0.92 (e.g., ...). Figure 2 As shown); the emissivity in the 8~13 μm band is 0.93 (as shown). Figure 3 (As shown); normal thermal conductivity is 32 W·m. -1 ·K -1 . Example 2

[0039] A method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment includes the following steps: Step 1: Weigh out ZrO2 (1 mol), HfO2 (1 mol), TiO2 (1 mol), SnO2 (1 mol), and GeO2 (1 mol) powders according to a metal element molar ratio of 1:1:1:1:1. Mill each raw material using a planetary ball mill with ultrapure water as the milling solvent. The milling speed is 400 r / min, and the milling time is 8 hours. The mass ratio of ball to material to water (g / g) is 4:1:3. After ball milling and mixing, dry at 95 ℃ for 16 hours, and then grind to obtain the precursor powder.

[0040] Step 2: The precursor powder was calcined in stages in an air atmosphere. First, the temperature was increased to 500 °C at a rate of 5 °C / min, and then increased further at a rate of 4 °C / min until the calcination temperature reached 1200 °C for 8 hours. Then, it was cooled by air quenching, and after grinding, HEO was obtained.

[0041] Step 3: Mix and grind 80 g HEO and 20 g BN to obtain HEO-BN composite radiation-cooling pigment.

[0042] The obtained HEO-BN composite radiation-cooling pigment was evaluated for its radiation-cooling performance using the same testing method as in Example 1.

[0043] The results showed that the total reflectance of the HEO-BN composite radiation-cooled pigment was 0.93 in the 0.3–2.5 μm band; the emissivity was 0.92 in the 8–13 μm band; and the normal thermal conductivity was 33 W·m. -1 ·K -1 . Example 3

[0044] A method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment includes the following steps: Step 1: Weigh out 1 mol of CeO2, 1 mol of ZrO2, 1 mol of HfO2, 1 mol of TiO2, and 1 mol of GeO2 according to the molar ratio of metal elements 1:1:1:1:1. Mill each raw material using a planetary ball mill with ultrapure water as the milling solvent. The milling speed is 500 r / min, and the milling time is 10 hours. The mass ratio of ball to material to water (g / g) is 5:1:3. After ball milling and mixing, dry the mixture at 100 °C for 24 hours. Then grind the mixture to obtain the precursor powder.

[0045] Step 2: The precursor powder was calcined in stages in an air atmosphere. First, the temperature was increased to 500 °C at a rate of 5 °C / min, and then increased at a rate of 5 °C / min until the calcination temperature reached 1400 °C for 10 hours. Then, it was cooled by liquid nitrogen quenching, and after grinding, HEO was obtained.

[0046] Step 3: Mix and grind 90 g HEO and 10 g BN to obtain HEO-BN composite radiation-cooling pigment.

[0047] The obtained HEO-BN composite radiation-cooling pigment was evaluated for its radiation-cooling performance using the same testing method as in Example 1.

[0048] The results showed that the total reflectance of the HEO-BN composite radiation-cooled pigment was 0.94 in the 0.3–2.5 μm band; the emissivity was 0.92 in the 8–13 μm band; and the normal thermal conductivity was 40 W·m. -1 ·K -1 .

Claims

1. A high-entropy oxide-boron nitride composite radiation-cooling pigment, characterized in that: The pigment is a powder, and its general formula for high-entropy oxides is (A... 1x A 2y A 3z A 4u A 5v O2, wherein A1, A2, A3, A4, and A5 are any five elements from Ce, Zr, Hf, Ti, Sn, and Ge, and x, y, z, u, and v are equal or approximately equal, and x + y + z + u + v = 1; the mass fraction ratio of high-entropy oxide to boron nitride is 60~90 wt%: 40~10 wt%.

2. The high-entropy oxide-boron nitride composite radiocooling pigment as described in claim 1, characterized in that: The pigment has a total reflectance of 0.92–0.94 in the 0.3–2.5 μm wavelength range, an emissivity of 0.92–0.93 in the 8–13 μm wavelength range, and a normal thermal conductivity of 30–40 W·m. -1 ·K -1 .

3. The high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 1, characterized in that: The average particle size of the pigment is in the range of 100 to 1000 nm.

4. The high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 1, characterized in that: The high-entropy oxide has a single-phase fluorite structure, belongs to the cubic crystal system, and has a space group of [space group number missing]. Fm3m .

5. The high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 1, characterized in that: The boron nitride is a hexagonal nanosheet.

6. The preparation method of a high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 1, comprising the following steps: Step 1: Using any five oxides from CeO2, ZrO2, HfO2, TiO2, SnO2, and GeO2 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 calcined in stages in an air atmosphere, and after cooling and grinding, high-entropy oxide is obtained; Step 3: Mix and grind the high-entropy oxide and boron nitride at a mass fraction ratio of 60~90 wt%: 40~10 wt% to obtain the high-entropy oxide-boron nitride composite radiation-cooling pigment.

7. The preparation method of a high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 6, characterized in that: The conditions for ball milling in step 1 refer to using a planetary ball mill, using 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.

8. The method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 6, 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.

9. The method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 6, characterized in that: The conditions for segmented calcination in step 2 are as follows: first, the temperature is increased to 500℃ at a rate of 5℃ / min, and then the temperature is increased at a rate of 2~5℃ / min, with a calcination temperature of 1000~1400℃ and a calcination time of 4~10 hours.

10. The method for preparing a high-entropy oxide-boron nitride composite radiation-cooling pigment as described in claim 6, characterized in that: The cooling method in step 2 is one of furnace cooling, air quenching cooling, and liquid nitrogen quenching cooling.

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