A passive radiative cooling multi-principal-element rare earth cerate ceramic material

Abstract

The present application relates to a kind of passive radiation cooling multi-host element rare earth cerate ceramic material based on, the chemical formula of this multi-host element rare earth cerate ceramic material is A2Ce2O7, wherein A site is at least 2 kinds of elements in La, Pr, Gd, Lu, and the content of each element is between 25~50%;And have defect fluorite or pyrochlore structure, belong to the system of vertical crystal, Fm-3m space group or Fd-3m space group.The present application combines high infrared radiation performance and heat protection performance, obtains the rare earth cerate ceramic with passive radiation cooling heat dissipation performance, and by improving the infrared radiation performance of material surface, the infrared emissivity of 0.78~2.5 μm band is >0.90, the infrared emissivity of 2.5~16 μm band is >0.90, to maximize the heat radiation heat dissipation effect.The obtained multi-host element rare earth cerate ceramic material has potential application in the field of radiation heat management such as large energy equipment, aero-engine, gas turbine, electronic device, power station boiler.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radiant heat management materials, in particular to a passive radiation cooling multi-principal element rare earth cerate ceramic material. BACKGROUND

[0002] With the continuous increase of the thrust-to-weight ratio and service temperature of the core components of the aero-engine and gas turbine, the inlet temperature before the engine turbine is continuously rising, and the proportion of thermal radiation is becoming more and more important. The large amount of energy radiated at high temperature will accelerate the damage of the substrate material and reduce the service life of the hot end component. In addition, new infrastructure construction, mainly including 5G base station construction, high-speed rail traction system, solar cells, and small-sized and integrated electronic devices, the temperature rise caused by poor heat dissipation seriously limits the reliability and durability of these technologies.

[0003] Passive radiation cooling technology refers to the outward dispersion of heat through the infrared radiation performance of the material surface, especially the heat in the 8-13 μm band, which can be dissipated to the cold outer space through the atmospheric transparent window, so as to maximize the heat dissipation effect of thermal radiation. As a heat dissipation method without energy and resource driving, passive radiation cooling has the advantages of no energy consumption, no pollution, no medium, convenient operation and economy, and can be used as a strengthening of natural cooling.

[0004] Infrared radiation is a technology that improves the infrared emissivity of the surface of a heat source to enhance the heat exchange capacity. It is widely used in high-temperature heat dissipation due to its versatility and adjustability. Under the condition that convection and heat conduction are limited, it is the most effective way of heating and cooling. According to the Stefan-Boltzmann law E=σεT 4 , the size of thermal radiation E is proportional to the fourth power of temperature T. With the continuous increase of the inlet temperature, the temperature of the surface due to heating is also higher, and the effect of thermal radiation is more obvious. When the temperature is higher than 1000 ℃, the radiation heat transfer accounts for 80% of the three heat transfer modes.

[0005] In the rare earth cerate RE2Ce2O7, the Ce 4+ ion has a large radius, and the ratio of the radii of the A-site and B-site ions is usually <1.46. At the same time, the rare earth cerate generally has a 1 / 8 oxygen vacancy defect fluorite structure, which has a high thermal expansion coefficient, mainly due to the reduction of Ce 4+ to Ce 3+This leads to a decrease in the lattice energy of the system, and no phase transformation occurs even under long-term annealing at 1400 °C, exhibiting good high-temperature phase stability. Xue Liyan et al. prepared a cerate high-entropy ceramic material (patent number CN114751744A). This cerate rare earth salt possesses characteristics such as high melting point, low thermal conductivity, high coefficient of thermal expansion, low heat ratio, and high-temperature thermal stability. By combining multiple rare earth ions, high-entropy cerate rare earth ceramics are obtained, further improving the material's heat resistance. However, this technology does not consider the importance of infrared radiation performance for thermal protective coatings under high-temperature conditions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-performance passive radiation-cooled multi-principal rare earth cerate ceramic material.

[0007] To address the aforementioned problems, the present invention provides a multi-principal rare-earth cerate ceramic material based on passive radiation cooling, characterized in that: the chemical formula of the multi-principal rare-earth cerate ceramic material is A2Ce2O7, wherein the A site is at least two elements selected from La, Pr, Gd, and Lu, and the content of each element is between 25% and 50%; and it has a defective fluorite or pyrochlore structure, belonging to a cubic facet crystal system, with space group Fm-3m or Fd-3m.

[0008] The multi-principal rare earth cerate ceramic material has an infrared emissivity of >0.90 in the 0.78~2.5μm band and an infrared emissivity of >0.90 in the 2.5~16μm band.

[0009] The preparation method of the passively radiatively cooled multi-principal rare-earth cerate ceramic material as described above includes the following steps:

[0010] (1) AO with a metal element molar ratio of 1:1 x The powder and CeO2 powder were ball-milled and mixed as raw materials, and AO x La2O3, Pr6O 11 The precursor powder is obtained by drying, grinding, and passing it through a 400-mesh sieve, with at least two of the following elements in the powder: Gd2O3 and Lu2O3, and the content of each element at site A is between 25% and 50%.

[0011] (2) The precursor powder is calcined at high temperature in air, and then cooled and ground to obtain rare earth cerate powder material;

[0012] (3) The rare earth cerate powder material is first pressed into sheets after passing through a 400-mesh sieve, and then calcined and cooled at high temperature to obtain defect fluorite-type high-entropy cerate ceramic material.

[0013] The conditions for ball milling in step (1) are as follows: a planetary ball mill is used, the ball milling media is zirconia balls, the ball milling speed is 200~400 r / min, the ball milling time is 12~24 hours, and the mass ratio of ball to material to water is 3:1:2.

[0014] The drying conditions in step (1) refer to a temperature of 80~100℃ and a time of 12~24 hours.

[0015] The conditions for high-temperature calcination in step (2) are: calcination temperature of 1200~1600℃, heating rate of 2~5℃ / min, and calcination time of 6~8 hours.

[0016] The tableting conditions in step (3) refer to using a powder tablet press, with a pressure of 20~31 MPa and a tableting time of 10~20 min.

[0017] The conditions for high-temperature calcination in step (3) are: calcination temperature of 1200~1600℃, heating rate of 5℃ / min, and calcination time of 6~8 hours.

[0018] The cooling method in steps (2) and (3) is one of furnace cooling, air quenching cooling, and liquid nitrogen quenching cooling.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. In this invention, rare earth ions have high activity and large radius. When they are doped into the material, they will change the original crystal structure, increase internal defects, and cause lattice distortion, which will reduce the frequency of simple harmonic vibration of the material, thereby playing a positive role in improving infrared radiation performance.

[0021] 2. The multi-principal rare earth cerate ceramics prepared by this invention, due to the co-doping of multiple rare earth elements and the difference in the electron arrangement of the multiple elements in the 4f orbital, can generate an intermediate band at the Fermi level, thus broadening the infrared emission band range of the material.

[0022] 3. All doping elements in this invention belong to the lanthanide series. By utilizing the high temperature resistance of rare earth elements, multi-principal rare earth cerate ceramics have excellent high temperature resistance and thermal stability. After heat treatment at 1300℃, the infrared attenuation rate is only 1%.

[0023] 4. Within a given heat flux density range, the higher the emissivity of a material, the more heat is dissipated through surface radiation, resulting in superior heat dissipation performance of the thermal protection structure. This reduces energy damage to the substrate material and extends the service life of hot-end components. Therefore, this invention combines high infrared radiation performance with thermal protection performance to obtain rare-earth cerate ceramics with passive radiative cooling properties. By improving the infrared radiation performance of the material surface, achieving infrared emissivity >0.90 in the 0.78~2.5μm band and >0.90 in the 2.5~16μm band, the thermal radiation heat dissipation effect is maximized.

[0024] 5. This invention employs a combination of mechanical wet milling and high-temperature calcination to prepare multi-principal rare-earth cerate ceramics. This method offers advantages such as simple preparation techniques, high repeatability, high production efficiency, and suitability for automated operation. The resulting multi-principal rare-earth cerate ceramics exhibit a single phase, high purity, and uniform elemental distribution, demonstrating potential applications in radiant heat management for large-scale energy equipment, aero-engines, gas turbines, electronic devices, and power plant boilers. Attached Figure Description

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0026] Figure 1 This is Embodiment 1 of the present invention (La) 0.5 Pr 0.5 XRD pattern of 2Ce2O7.

[0027] Figure 2 This is Embodiment 2 of the present invention (La) 0.34 Pr 0.33 Gd 0.33 XRD pattern of 2Ce2O7.

[0028] Figure 3 This is embodiment 4 of the present invention (La) 0.25 Pr 0.25 Gd 0.25 Lu 0.25 XRD pattern of 2Ce2O7.

[0029] Figure 4 The infrared radiation spectrum of the multi-principal rare earth cerate ceramic prepared in Example 2 of this invention is shown in the 0.78~2.5μm band.

[0030] Figure 5 The infrared radiation spectrum of the multi-principal rare earth cerate ceramic prepared in Example 2 of this invention is shown in the 2.5~16μm band.

[0031] Figure 6 This is embodiment 4 of the present invention (La) 0.25 Pr 0.25 Gd0.25 Lu 0.25 XRD pattern of the A2Ce2O7 after heat stability experiment at 1500℃. DETAILED DESCRIPTION

[0032] A passive radiative cooling multi-principal element rare earth cerate ceramic material, the chemical formula of which is A2Ce2O7, wherein A is at least two elements selected from La, Pr, Gd and Lu, and the content of each element is between 25% and 50%; and the material has a defect fluorite or pyrochlore structure, belongs to a cubic crystal system, and has a Fm-3m space group or a Fd-3m space group.

[0033] The multi-principal element rare earth cerate ceramic material has an infrared emissivity of >0.90 in a 0.78-2.5 μm wave band and an infrared emissivity of >0.90 in a 2.5-16 μm wave band.

[0034] The preparation method of the passive radiative cooling multi-principal element rare earth cerate ceramic material comprises the following steps:

[0035] 1. AO x powder and CeO2 powder are used as raw materials, AO x is at least two kinds of La2O3, Pr6O 11 , Gd2O3 and Lu2O3 powder, and the content of each element at A is between 25% and 50%. Each raw material is ball-mixed by using a planetary ball mill, the ball-milling medium is a zirconia ball, the ball-milling speed is 200-400 r / min, the ball-milling time is 12-24 hours, and the mass ratio (g / g) of ball-milling medium to ball-milling material to water is 3:1:2. Then, the mixture is dried at 80-100℃ for 12-24 hours, ground, and sieved through a 400-mesh sieve to obtain a precursor powder.

[0036] 2. The precursor powder is high-temperature calcined in an air atmosphere, the calcination temperature is 1200-1600℃, the temperature rising rate is 2-5℃ / min, and the calcination time is 6-8 hours. After the calcination is completed, one of furnace cooling, air quenching and liquid nitrogen quenching is used for cooling, and the rare earth cerate powder material is obtained after being ground.

[0037] 3. After the rare earth cerate powder material is sieved through a 400-mesh sieve, tablet pressing is first performed by using a powder tablet press, the pressure is 20-31 MPa, and the tablet pressing time is 10-20 min. Then, high-temperature calcination is performed at 1200-1600℃ for 6-8 hours, and the temperature rising rate is 5℃ / min. After the calcination is completed, one of furnace cooling, air quenching and liquid nitrogen quenching is used for cooling, and the defect fluorite high-entropy cerate ceramic material is obtained.

[0038] Example 1

[0039] A preparation method of a passive radiative cooling multi-principal-element rare earth cerate ceramic material, comprising the following steps:

[0040] 1. Take 8.1451g La2O3, 25.536g Pr6O 11 , 8.6057g CeO2, to obtain a mixed raw material powder. A planetary ball mill is used for ball milling mixing, the ball milling medium is zirconia ball, the ball milling speed is 200 r / min, the ball milling time is 18 hours, and the mass ratio (g / g) of ball to water is 3:1:2. Then, drying at 80℃ for 18 hours, grinding and passing through a 400 mesh sieve to obtain a precursor powder.

[0041] 2. The precursor powder is high-temperature calcined in an air atmosphere, heated to 1200℃ at a rate of 5℃ / min, and calcined for 8 hours. After calcination, the furnace is cooled, and the rare earth cerate powder material is obtained by grinding.

[0042] 3. After the rare earth cerate powder material is passed through a 400 mesh sieve, it is first pressed into a tablet using a powder tablet press, with a pressure of 20MPa and a tablet pressing time of 20 min. Then, high-temperature calcination is carried out in an air atmosphere, heated to 1200℃ at a rate of 5℃ / min, and calcined for 8 hours. After calcination, air quenching cooling is carried out, and a defective fluorite-type high-entropy cerate ceramic (La 0.5 Pr 0.5 )2Ce2O7 is obtained.

[0043] The obtained (La 0.5 Pr 0.5 )2Ce2O7 is subjected to XRD testing, and the results are shown in Figure 1 . As can be seen from the figure, the spectrum is very consistent with the La2Ce2O7 spectrum (PDF#04-012-6393) with a defective fluorite structure in the ICDD database, indicating that the high-entropy oxide prepared in this embodiment is a single-phase solid solution.

[0044] Example 2

[0045] A preparation method of a passive radiative cooling multi-principal-element rare earth cerate ceramic material, comprising the following steps:

[0046] 1. Take 1.6292g La2O3, 1.7024g Pr6O 11 , 1.8125g Gd2O3, 5.1634g CeO2, to obtain a mixed raw material powder. A planetary ball mill is used for ball milling mixing, the ball milling medium is zirconia ball, the ball milling speed is 300 r / min, the ball milling time is 12 hours, and the mass ratio (g / g) of ball to water is 3:1:2. Then, drying at 80℃ for 24 hours, grinding and passing through a 400 mesh sieve to obtain a precursor powder.

[0047] (2) The precursor powder was calcined at high temperature in air, with the temperature increased to 1600℃ at a rate of 5℃ / min, and calcined for 6 hours. After calcination, it was cooled by air quenching and then ground to obtain rare earth cerate powder material.

[0048] (3) After passing through a 400-mesh sieve, the rare earth cerate powder material is first compressed into tablets using a powder tablet press at a pressure of 20 MPa for 10 min. Then, it is calcined at high temperature in air, with the temperature increased at 5℃ / min to 1600℃ and calcined for 6 hours. After calcination, it is quenched and cooled with liquid nitrogen to obtain defect fluorite-type high-entropy cerate ceramic (La). 0.34 Pr 0.33 Gd 0.33 )2Ce2O7.

[0049] For the obtained (La) 0.34 Pr 0.33 Gd 0.33 XRD tests were performed on 2Ce2O7, and the results are as follows: Figure 2 As shown in the figure, the spectral line is in excellent agreement with the La2Ce2O7 spectral line (PDF#04-012-6393) with defective fluorite structure in the ICDD database, indicating that the high-entropy oxide prepared in this example is a single-phase solid solution.

[0050] The obtained (La) spectrophotometer was analyzed using a Lambda 950 UV / Vis / NIR spectrophotometer (equipped with a 150mm integrating sphere) manufactured by PerkinElmer, USA. 0.34 Pr 0.33 Gd 0.33 The optical properties of 2Ce₂O₇ were evaluated, and its infrared emissivity in the 0.78–2.5 μm and 2.5–16 μm wavelength bands was measured. Figures 4-5 As shown. Then, the infrared emissivity of this band is calculated according to the calculation formulas (1) to (2).

[0051]

[0052] Where: α(θ, λ) is the absorptivity of the material at the solar incidence angle θ and wavelength λ; R(θ,λ) is the reflectivity of the material at the solar incidence angle θ and wavelength λ; I S (λ) is the spectral radiation intensity of the sun when the atmospheric mass is AM 1.5; ε(λ,T) is the emissivity of the material at wavelength λ and temperature T; I b (λ,T) is the thermal radiation intensity of a blackbody material at temperature T.

[0053] According to calculations, (La) 0.34 Pr 0.33 Gd 0.33The infrared emissivity of the Ce2O7 is 0.931 in the 0.78-2.5-micron band and 0.952 in the 2.5-16-micron band. Therefore, the prepared main-element rare earth cerate ceramic has excellent radiation heat dissipation capacity.

[0054] Example 3

[0055] A preparation method of a passive radiation cooling multi-main-element rare earth cerate ceramic material, comprising the following steps:

[0056] 1. 1.6292 g of La2O3, 1.7024 g of Pr6O 11 , 0.6630 g of Lu2O3 and 5.1634 g of CeO2 are weighed to obtain mixed raw material powder. The raw materials are ball-mixed by using a planetary ball mill, the ball-milling medium is zirconia ball, the ball-milling speed is 300 r / min, the ball-milling time is 24 hours, and the mass ratio (g / g) of ball, medium and water is 3:1:2. Then, the mixture is dried at 90 DEG C for 16 hours, ground and sieved through a 400-mesh sieve to obtain precursor powder.

[0057] 2. The precursor powder is high-temperature calcined in an air atmosphere, the temperature is raised to 1400 DEG C at a rate of 4 DEG C / min, and the calcination is performed for 7 hours. After the calcination is completed, the furnace is cooled, and the rare earth cerate powder material is obtained by grinding.

[0058] 3. After the rare earth cerate powder material is sieved through a 400-mesh sieve, tabletting is performed by using a powder tabletting machine, the pressure is 31 MPa, and the tabletting time is 20 min. Then, high-temperature calcination is performed in an air atmosphere, the temperature is raised to 1400 DEG C at a rate of 4 DEG C / min, and the calcination is performed for 7 hours. After the calcination is completed, the furnace is cooled to obtain the defect-fluorite-type high-entropy cerate ceramic (La 0.34 Pr 0.33 Lu 0.33 )2Ce2O7.

[0059] Example 4

[0060] A preparation method of a passive radiation cooling multi-main-element rare earth cerate ceramic material, comprising the following steps:

[0061] 1. 0.8146 g of La2O3, 0.4256 g of Pr6O 11 , 0.9062 g of Gd2O3, 0.9948 g of Lu2O3 and 3.4421 g of CeO2 are weighed to obtain mixed raw material powder. The raw materials are ball-mixed by using a planetary ball mill, the ball-milling medium is zirconia ball, the ball-milling speed is 400 r / min, the ball-milling time is 24 hours, and the mass ratio (g / g) of ball, medium and water is 3:1:2. Then, the mixture is dried at 100 DEG C for 12 hours, ground and sieved through a 400-mesh sieve to obtain precursor powder.

[0062] (2) The precursor powder was calcined at high temperature in air, with the temperature increased to 1600℃ at a rate of 3℃ / min, and calcined for 8 hours. After calcination, it was quenched and cooled with liquid nitrogen, and then ground to obtain rare earth cerate powder material.

[0063] (3) After the rare earth cerate powder material passes through a 400-mesh sieve, it is first compressed into tablets using a powder tablet press at a pressure of 25 MPa for 15 min. Then, it is calcined at high temperature in air, with the temperature increased at 3℃ / min to 1600℃ and calcined for 8 hours. After calcination, it is cooled in the furnace to obtain defect fluorite-type high-entropy cerate ceramic (La). 0.25 Pr 0.25 Gd 0.25 Lu 0.25 )2Ce2O7.

[0064] For the obtained (La) 0.25 Pr 0.25 Gd 0.25 Lu 0.25 XRD tests were performed on 2Ce2O7, and the results are as follows: Figure 3 As shown in the figure, the spectral line is in excellent agreement with the La2Ce2O7 spectral line (PDF#04-012-6393) with defective fluorite structure in the ICDD database, indicating that the high-entropy oxide prepared in this example is a single-phase solid solution.

[0065] The obtained (La) 0.25 Pr 0.25 Gd 0.25 Lu 0.25 )2Ce2O7 was placed in an air atmosphere in a box furnace and subjected to a long-term thermal stability test at 1300℃. The results are as follows: Figure 6 As shown, long-term thermal stability experiments at 1300℃ demonstrate that the crystal structure of the above-mentioned multi-principal rare-earth cerate ceramic is stable, with an infrared attenuation rate of only 1% in the 0.78~2.5 μm and 2.5~16 μm wavelength bands. Therefore, the principal rare-earth cerate ceramic prepared in this invention exhibits high-temperature thermal stability.

[0066] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A passive radiative cooling multi-principal-element rare-earth cerate ceramic material, characterized in that: The multi-main element rare earth cerate ceramic material has a chemical formula of A2Ce2O7, wherein A is at least two elements selected from La, Pr, Gd and Lu, and the molar percentage content of each element is between 25 and 50%; and has a defect fluorite or pyrochlore structure, belongs to a cubic crystal system, and has a Fm-3m space group or a Fd-3m space group.

2. A passive radiative cooling multi-principal-element cerate ceramic material according to claim 1, wherein: The multi-main element rare earth cerate ceramic material has an infrared emissivity of >0.90 in a 0.78-2.5 μm wave band and an infrared emissivity of >0.90 in a 2.5-16 μm wave band.

3. A preparation method of a passive radiation-cooled multi-main element rare earth cerate ceramic material according to claim 1, comprising the following steps: (1) AO with a metal element molar ratio of 1:1 x The powder and CeO2 powder were ball-milled and mixed as raw materials, and AO x La2O3, Pr6O 11 The precursor powder is obtained by drying, grinding, and passing it through a 400-mesh sieve, with at least two of the following elements being selected: Gd2O3 and Lu2O3 powders, and the molar percentage content of each element at site A being between 25% and 50%. (2) the precursor powder is calcined at a high temperature in an air atmosphere, and after cooling and grinding, a rare earth cerate powder material is obtained; (3) the rare earth cerate powder material is sieved through a 400-mesh sieve, and then is pressed into a sheet, and after high-temperature calcination and cooling, a defect fluorite-type high-entropy cerate ceramic material is obtained.

4. The method of claim 3, wherein the passive radiative cooling multi-principal element rare earth cerate ceramic material is prepared by the steps of: preparing a precursor material comprising a mixture of a rare earth oxide, a cerium oxide, and a lanthanum oxide; and sintering the precursor material at a temperature of 1200 °C to 1400 °C for 1 to 10 hours in a reducing atmosphere. In the step (1), the ball milling is performed by using a planetary ball mill, the ball milling medium is a zirconia ball, the ball milling speed is 200-400 r / min, the ball milling time is 12-24 hours, and the mass ratio of ball, powder and water is 3:1:

2.

5. The method of claim 3, wherein the passive radiative cooling multi-principal element rare earth cerate ceramic material is prepared by the steps of: preparing a precursor material comprising a mixture of a rare earth oxide, a cerium oxide, and a lanthanum oxide; and sintering the precursor material at a temperature of 1200 °C to 1400 °C for 1 to 10 hours in a reducing atmosphere. In the step (1), the drying is performed at a temperature of 80-100℃ for 12-24 hours.

6. The method of claim 3, wherein the passive radiative cooling multi-principal element rare earth cerate ceramic material is prepared by the steps of: preparing a precursor material; and sintering the precursor material to form the passive radiative cooling multi-principal element rare earth cerate ceramic material. In the step (2), the high-temperature calcination is performed at a calcination temperature of 1200-1600℃, a temperature rising rate of 2-5℃ / min, and a calcination time of 6-8 hours.

7. The method for preparing a passively radiatively cooled multi-principal-element rare-earth cerate ceramic material as described in claim 3, characterized in that: In the step (3), the sheet pressing is performed by using a powder sheet press, a pressing pressure of 20-31 MPa, and a pressing time of 10-20 min.

8. The method of claim 3, wherein the passive radiative cooling multi-principal element rare earth cerate ceramic material is prepared by the steps of: In the step (3), the high-temperature calcination is performed at a calcination temperature of 1200-1600℃, a temperature rising rate of 5℃ / min, and a calcination time of 6-8 hours. ​ 9. The preparation method of a passively radiatively cooled multi-principal-element rare-earth cerate ceramic material as described in claim 3, characterized in that: In the step (2) and the step (3), the cooling mode is one of furnace cooling, air quenching cooling and liquid nitrogen quenching cooling.

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