A multi-principal element doped low thermal conductivity high-entropy infrared radiation material

Abstract

The application relates to a multi-principal element doped low-thermal-conductivity high-entropy infrared radiation material, the thermal conductivity of the high-entropy infrared radiation material is <1 W·(m·k) ‑1 , the infrared emissivity in the 1-16 mu m wave band is >0.90; the chemical formula is A2B2O7, wherein A is at least three elements in La, Sm, Eu, Ni and Co, and the content of each element is between 20-34%; B is at least two elements in Ce, Zr, Cr and Mn, and the content of each element is between 25-50%. The high-entropy infrared radiation material has a defect fluorite or pyrochlore structure, belongs to a cubic crystal system, has high infrared emissivity, and has potential application value in the thermal protection field of aerospace vehicles, large energy equipment, industrial kilns, power station boilers and the like as a heat insulation material.

Description

Technical Field

[0001] This invention relates to the field of infrared radiation materials, and more particularly to a low thermal conductivity, high entropy infrared radiation material with multiple principal element doping. Background Technology

[0002] Heat transfer occurs in three main forms: convection, conduction, and radiation. According to Wien's displacement law and Planck's law, at 1000℃, 90% of the energy of a blackbody is transferred through thermal radiation, with most of the radiated heat wavelengths in the infrared band. Therefore, further heat dissipation through thermal radiation can be considered, especially in high-temperature vacuum environments where thermal radiation dissipation is dominant, and most of the radiation wavelengths are in the infrared band. Besides its promising applications in hypersonic vehicles, advanced aero-engines, and spacecraft, infrared radiation can also be applied to the interiors of industrial boilers to improve fuel efficiency and contribute to energy conservation and environmental protection. Therefore, researching comprehensive heat-resistant coating materials with low thermal conductivity and high infrared emissivity is of great significance.

[0003] Currently, research on thermal protective coatings mainly focuses on thermal barrier coatings. Thermal barrier coatings typically use materials with low thermal conductivity for insulation and provide erosion and corrosion resistance. They are used in hot-section components of aero-engines and land-based gas turbines to improve their thermal efficiency and durability. However, due to the rapid development of hypersonic aircraft and advanced aero-engines, a single low thermal conductivity thermal barrier coating is insufficient for practical applications at high temperatures.

[0004] Driven by the background of "energy conservation and carbon reduction" and the "dual carbon" goal, novel infrared radiation energy-saving materials have emerged, aiming to improve surface radiation characteristics and enhance radiative heat transfer. Currently, most infrared radiation materials are based on oxide systems, including rare earth oxides, cordierite, spinel, hexaaluminates, defective fluorite, perovskites, etc. They improve the infrared emissivity of mixed materials through multiphase mixing or doping. However, this affects the structural thermal stability of the material at high temperatures, and the material itself is prone to further reactions at high temperatures, thereby reducing the infrared radiation performance of the material.

[0005] A₂B₂O₇ oxides are a class of structural ceramic materials with large tunable composition and strong structural inclusiveness. They possess excellent thermal, electrical, magnetic, dielectric, optical, and catalytic properties, and have important applications in many fields. The crystal structure of A₂B₂O₇ oxides is mainly determined by the radius ratio (R₁, R₂, R₃) of the A and B site cations. A / R BThe influence of similar ionic radii and valence states allows for various chemical substitutions at the A and B sites of A₂B₂O₇, leading to the formation of many new compounds. Furthermore, the presence of 1 / 8 oxygen vacancies facilitates cation migration within the crystal. Due to its unique crystal structure and the ability to simultaneously dope multiple rare earth or transition metal elements at the A and B sites, this multi-principal structure results in microstructural changes such as impurity energy levels, lattice distortion, oxygen vacancies, and dipole moments, all of which contribute to improved infrared emissivity. However, research on the use of A₂B₂O₇ high-entropy oxides as infrared radiation materials is rarely reported. Developing an A₂B₂O₇ high-entropy oxide with low thermal conductivity and high infrared emissivity would have potential applications in thermal protection. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-performance multi-principal-doped low thermal conductivity high entropy infrared radiation material.

[0007] To address the aforementioned problems, the present invention provides a low thermal conductivity, high entropy infrared radiation material with multiple principal element doping, characterized in that: the thermal conductivity of the high entropy infrared radiation material is <1 W·(m·K). -1 It has an infrared emissivity of >0.90 in the 1~16μm band; its chemical formula is A2B2O7, wherein the A site is composed of at least three elements selected from La, Sm, Eu, Ni and Co, and the content of each element is between 20 and 34%; the B site is composed of at least two elements selected from Ce, Zr, Cr and Mn, and the content of each element is between 25 and 50%.

[0008] The high-entropy infrared radiation material has a defective fluorite or pyrochlore structure, belongs to a cubic facet crystal system, and has the space group Fm-3m or Fd-3m.

[0009] The preparation method of the multi-principal-doped low thermal conductivity high entropy infrared radiation material as described above includes the following steps:

[0010] Step 1: Using AO with a metal element molar ratio of 1:1 x Powder and BO y Powder as raw material, AO x It consists of at least three of the following: La2O3, Sm2O3, Eu2O3, NiO, and CoO powders, with each element comprising between 20% and 34% of the total content. BO y The precursor powder consists of at least two of CeO2, ZrO2, Cr2O3, and MnO2 powders, with each element having a content between 25% and 50%. The raw materials are ball-milled, mixed, dried, ground, and passed through a 400-mesh sieve to obtain the precursor powder.

[0011] Step 2: The precursor powder is calcined at high temperature in air, and after cooling and grinding, A2B2O7 high-entropy oxide powder material is obtained.

[0012] Step 3: The A2B2O7 high-entropy oxide powder material is passed through a 400-mesh sieve, pressed into tablets, calcined at high temperature, and cooled to obtain the high-entropy infrared radiation material.

[0013] The conditions for ball milling in step 1 refer to using a planetary ball mill, using zirconia balls as the milling medium, a milling speed of 200~400 r / min, a milling time of 12~24 hours, and a ball-to-material-to-water mass ratio of 3:1:2.

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

[0015] The conditions for high-temperature calcination in step 2 are: calcination temperature of 1000~1500℃, heating rate of 3~5℃ / 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 20~31MPa and a tableting time of 10~20min.

[0017] The conditions for high-temperature calcination in step 3 are: calcination temperature of 1000~1500℃, 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. The high-entropy infrared radiation material prepared by this invention has the chemical formula A₂B₂O₇, possesses a defective fluorite or pyrochlore structure, and belongs to a cubic facet crystal system. The A and B site ions and oxygen vacancies are randomly distributed, exhibiting a disordered state. The ratio of the radii of the A and B site cations (R₁, R₂, R₃) is... A / R B ) are the main factors affecting phase structure, such as Figure 1 As shown. When R A / R B When R < 1.46, it tends to form defective fluorite structures, Fm-3m space group; when 1.46 ≤ R A / R B When ≤1.78, it tends to form an ordered pyrochlore structure, Fd-3m space group, and cation A. 3+ and B 4+ They are located at positions 16c and 16d respectively and form an ordered cubic close-packed arrangement.

[0021] 2. Because multiple principal elements exist simultaneously at sites A and B, the material has a higher doping tolerance. Impurity energy levels are introduced into the band gap, which broadens the range of carrier transitions, promotes the transition frequency of free carriers, and increases the concentration of carriers in the valence band, thereby improving the infrared emissivity of the material.

[0022] 3. In this invention, due to the differences in mass and radius of various principal elements, the lattice expands or contracts, resulting in lattice distortion. At the same time, the decrease in crystal symmetry increases the dipole moment, thereby promoting the absorption of rotational vibration energy levels and thus improving the infrared emissivity of the material.

[0023] 4. In this invention, the A and B site elements include rare earth elements and transition metal elements. The change in the valence of multi-valence elements can generate small polarons, thereby promoting electronic transitions and increasing the mid-infrared emissivity, so that the infrared emissivity of the low thermal conductivity and high entropy A2B2O7 infrared radiation material is >0.90 in the 1~16μm band.

[0024] 5. In this invention, due to the presence of high-concentration oxygen vacancies and the highly disordered arrangement of multi-component cations in a unique high-entropy configuration, this highly disordered high-entropy structure can significantly enhance lattice anharmonic vibrations and phonon scattering, resulting in a substantial reduction in thermal conductivity, with a minimum thermal conductivity of 0.58 W·(m·k) at 800℃. -1 .

[0025] 6. The material described in this invention is prepared using a combination of mechanical wet milling and high-temperature calcination, which offers advantages such as simple preparation technology, high repeatability, high production efficiency, and suitability for automated operation. The resulting high-entropy infrared radiation material is characterized by its single phase, high purity, and uniform elemental distribution, making it a potential application as a thermal insulation material in thermal protection fields such as aerospace vehicles, large-scale energy equipment, industrial kilns, and power plant boilers. Attached Figure Description

[0026] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0027] Figure 1 The image shows the crystal structure of the high-entropy infrared radiation material of this invention. The left image shows a defective fluorite, and the right image shows a pyrochlore structure.

[0028] Figure 2 This is Embodiment 1 of the present invention (La) 0.33 Sm 0.34 Co 0.34 )2(Ce 0.5 Zr 0.5 XRD pattern of 2O7.

[0029] Figure 3 This is Embodiment 2 of the present invention (La) 0.2Sm 0.2 Eu 0.2 Ni 0.2 Co 0.2 )2(Ce 0.5 Cr 0.5 XRD pattern of 2O7.

[0030] Figure 4 This is embodiment 3 of the present invention (La) 0.25 Sm 0.25 Ni 0.25 Co 0.25 )2(Ce 0.5 Cr 0.25 Mn 0.25 XRD pattern of 2O7.

[0031] Figure 5 The infrared radiation spectrum of the low thermal conductivity, high entropy A2B2O7 infrared radiation material prepared in Example 3 of this invention is shown in the 1~16μm band.

[0032] Figure 6 This is Embodiment 1 of the present invention (La) 0.33 Sm 0.34 Co 0.34 )2(Ce 0.5 Zr 0.5 Thermal conductivity spectra of 2O7 at room temperature and 800℃.

[0033] Figure 7 This is embodiment 3 of the present invention (La) 0.25 Sm 0.25 Ni 0.25 Co 0.25 )2(Ce 0.5 Cr 0.25 Mn 0.25 Thermal conductivity spectra of 2O7 at room temperature and 800℃. Detailed Implementation

[0034] A low thermal conductivity, high entropy infrared radiation material with multiple principal element doping, wherein the thermal conductivity of the high entropy infrared radiation material is <1 W·(m·K). -1 The infrared emissivity in the 1–16 μm band is >0.90; its chemical formula is A₂B₂O₇, where the A-site contains at least three elements selected from La, Sm, Eu, Ni, and Co, with each element comprising 20–34% of the total content; and the B-site contains at least two elements selected from Ce, Zr, Cr, and Mn, with each element comprising 25–50% of the total content. This high-entropy infrared radiation material has a defective fluorite or pyrochlore structure, belongs to a cubic facet crystal system, and has the space group Fm-3m or Fd-3m.

[0035] A method for preparing a low thermal conductivity, high entropy infrared radiation material doped with multiple principal elements includes the following steps:

[0036] Step 1: Using AO with a metal element molar ratio of 1:1 x Powder and BO y Powder as raw material, AO x It consists of at least three of the following: La2O3, Sm2O3, Eu2O3, NiO, and CoO powders, with each element comprising between 20% and 34% of the total content. BO y The precursor powder consists of at least two of CeO2, ZrO2, Cr2O3, and MnO2, with each element comprising 25% to 50% of the total content. The raw materials are ball-milled using a planetary ball mill with zirconia balls as the milling media. The milling speed is 200–400 r / min, and the milling time is 12–24 hours. The mass ratio of ball-material to water (g / g) is 3:1:2. The mixture is then dried at 80–100℃ for 12–24 hours, ground, and sieved through a 400-mesh sieve to obtain the precursor powder.

[0037] Step 2: The precursor powder is calcined at high temperature in air atmosphere at a temperature of 1000~1500℃, a heating rate of 3~5℃ / min, and a calcination time of 6~8 hours. After calcination, it is cooled by one of the following methods: furnace cooling, air quenching, or liquid nitrogen quenching. After grinding, A2B2O7 high-entropy oxide powder material is obtained.

[0038] Step 3: The A2B2O7 high-entropy oxide powder material is passed through a 400-mesh sieve and first compressed into tablets using a powder tablet press at a pressure of 20-31 MPa for 10-20 minutes. Then, it is calcined at 1000-1500℃ for 6-8 hours at a heating rate of 5℃ / min, and cooled using one of the following methods: furnace cooling, air quenching, or liquid nitrogen quenching, to obtain the high-entropy infrared radiation material.

[0039] Example 1

[0040] A method for preparing a low thermal conductivity, high entropy infrared radiation material doped with multiple principal elements includes the following steps:

[0041] Step 1: Weigh 10.7517g La2O3, 11.8564g Sm2O3, 2.5476g CoO, 8.6057g CeO2, and 6.1611g ZrO2. Mix them using a planetary ball mill with zirconia balls as the milling media. The mass ratio of ball to material to water (g / g) is 3:1:2. The milling speed is 200 r / min, and the milling time is 24 hours. After drying at 80℃ for 24 hours, grind and pass through a 400-mesh sieve to obtain the precursor powder.

[0042] Step 2: The precursor powder is calcined at high temperature in air, with the temperature increased to 1000℃ at a rate of 3℃ / min, and calcined for 6 hours. After calcination, it is cooled in the furnace and ground to obtain A2B2O7 high-entropy oxide powder material.

[0043] Step 3: The A2B2O7 high-entropy oxide powder material is passed through a 400-mesh sieve and first compressed into tablets using a powder tableting machine at a pressure of 20 MPa for 20 minutes. Then, the temperature is increased to 1000℃ at a rate of 5℃ / min, calcined for 6 hours, and finally air-quenched to obtain (La). 0.33 Sm 0.34 Co 0.34 )2(Ce 0.5 Zr 0.5 )2O7 high-entropy infrared radiation material.

[0044] Regarding the obtained (La) 0.33 Sm 0.34 Co 0.34 )2(Ce 0.5 Zr 0.5 Diffraction tests were performed on 2O7, 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.

[0045] The thermal conductivity of this material was evaluated using a high-temperature laser thermal conductivity analyzer (DLF 2800, TA, USA), and the results are as follows: Figure 6 As shown in the figure, the thermal conductivity of this material at room temperature and 800℃ is 0.92 W·(m·K). -1 And 0.68 W·(m·k) -1 .

[0046] Example 2

[0047] A method for preparing a low thermal conductivity, high entropy infrared radiation material doped with multiple principal elements includes the following steps:

[0048] Step 1: Weigh 1.6292g La2O3, 3.4872g Sm2O3, 3.5192g Eu2O3, 0.7436g NiO, 0.7493g CoO, 4.3028g CeO2, and 3.7997g Cr2O3. Mix them using a planetary ball mill with zirconia balls as the milling media. The ball-to-material-to-water mass ratio (g / g) is 3:1:2. The milling speed is 300 r / min, and the milling time is 16 hours. Then, dry the mixture at 90℃ for 12 hours, grind it, and pass it through a 400-mesh sieve to obtain the precursor powder.

[0049] Step 2: The precursor powder is calcined at high temperature in air, with the temperature increased to 1300℃ at a rate of 5℃ / min, and calcined for 8 hours. After calcination, it is air-quenched and cooled, and then ground to obtain A2B2O7 high-entropy oxide powder material.

[0050] Step 3: The A2B2O7 high-entropy oxide powder material is passed through a 400-mesh sieve and first compressed into tablets using a powder tableting machine at a pressure of 25 MPa for 18 minutes. Then, the temperature is increased to 1300℃ at a rate of 5℃ / min and calcined for 8 hours, followed by furnace cooling to obtain (La). 0.2 Sm 0.2 Eu 0.2 Ni 0.2 Co 0.2 )2(Ce 0.5 Cr 0.5 )2O7 high-entropy infrared radiation material.

[0051] Regarding the obtained (La) 0.2 Sm 0.2 Eu 0.2 Ni 0.2 Co 0.2 )2(Ce 0.5 Cr 0.5 Diffraction tests were performed on 2O7, 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.

[0052] Example 3

[0053] A method for preparing a low thermal conductivity, high entropy infrared radiation material doped with multiple principal elements includes the following steps:

[0054] Step 1: Weigh 4.0726g La2O3, 4.3591g Sm2O3, 0.9336g NiO, 0.9366g CoO, 4.3028g CeO2, 1.8998g Cr2O3, and 1.0867g MnO2. Mix these components using a planetary ball mill with zirconia balls as the milling media. The ball-to-material-to-water mass ratio (g / g) is 3:1:2. The milling speed is 400 r / min, and the milling time is 12 hours. After drying at 100℃ for 16 hours, grind the mixture and pass it through a 400-mesh sieve to obtain the precursor powder.

[0055] Step 2: The precursor powder is calcined at high temperature in air, with the temperature increased to 1500℃ at a rate of 4℃ / min, and calcined for 7 hours. After calcination, it is quenched and cooled with liquid nitrogen, and then ground to obtain A2B2O7 high-entropy oxide powder material.

[0056] Step 3: The A2B2O7 high-entropy oxide powder material is passed through a 400-mesh sieve and first compressed into tablets using a powder tableting machine at a pressure of 31 MPa for 10 minutes. Then, the temperature is increased to 1500℃ at a rate of 5℃ / min, calcined for 7 hours, and finally quenched with liquid nitrogen to obtain (La). 0.25 Sm 0.25 Ni 0.25 Co 0.25 )2(Ce 0.5 Cr 0.25 Mn 0.25 )2O7 high-entropy infrared radiation material.

[0057] Regarding the obtained (La) 0.25 Sm 0.25 Ni 0.25 Co 0.25 )2(Ce 0.5 Cr 0.25 Mn 0.25 Diffraction tests were performed on 2O7, and the results are as follows: Figure 4 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.

[0058] The infrared radiation properties of this material were evaluated using a Lambda 950 UV / Vis / NIR spectrophotometer (equipped with a 150mm integrating sphere) manufactured by PerkinElmer, USA. Its reflectance in the 1–16 μm wavelength range was measured, and then the infrared emissivity in this wavelength range was calculated using the formula. The results are as follows: Figure 5 As shown in the figure, the infrared emissivity of this material in the 1~16μm band is 0.933.

[0059] The thermal conductivity of this material was evaluated using a high-temperature laser thermal conductivity analyzer (DLF 2800, TA, USA), and the results are as follows: Figure 7 As shown in the figure, the thermal conductivity of this material at room temperature and 800℃ is 0.90 W·(m·K). -1 And 0.58 W·(m·k) -1 .

[0060] 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 low thermal conductivity, high entropy infrared radiation material doped with multiple principal elements, characterized in that: The thermal conductivity of this high-entropy infrared radiation material is <1 W·(m·K). -1 It has an infrared emissivity >0.90 in the 1~16μm band; its chemical formula is A2B2O7, wherein when the A site is La, Sm, or Co, the B site is Ce or Zr; when the A site is La, Sm, Eu, Ni, or Co, the B site is Ce or Cr; when the A site is La, Sm, Ni, or Co, the B site is Ce, Cr, or Mn; and the content of each element at the A site is between 20 and 34%, and the content of each element at the B site is between 25 and 50%.

2. The multi-principal element doped low thermal conductivity high-entropy infrared radiative material of claim 1, wherein: The high-entropy infrared radiation material has a defective fluorite or pyrochlore structure, belongs to a cubic facet crystal system, and has the space group Fm-3m or Fd-3m.

3. The method for preparing a multi-principal-doped low thermal conductivity, high entropy infrared radiation material as described in claim 1, comprising the following steps: Step 1: Using AO with a metal element molar ratio of 1:1 x Powder and BO y Powder as raw material, AO x It consists of at least three of the following: La2O3, Sm2O3, Eu2O3, NiO, and CoO powders, with each element comprising between 20% and 34% of the total content. BO y The precursor powder consists of at least two of CeO2, ZrO2, Cr2O3, and MnO2 powders, with each element having a content between 25% and 50%. The raw materials are ball-milled, mixed, dried, ground, and passed through a 400-mesh sieve to obtain the precursor powder. Step 2: The precursor powder is calcined at high temperature in air, and after cooling and grinding, A2B2O7 high-entropy oxide powder material is obtained. Step 3: The A2B2O7 high-entropy oxide powder material is passed through a 400-mesh sieve, pressed into tablets, calcined at high temperature, and cooled to obtain the high-entropy infrared radiation material.

4. The method for preparing a multi-principal-doped, low thermal conductivity, high entropy infrared radiation material as described in claim 3, characterized in that: The conditions for ball milling in step 1 refer to using a planetary ball mill, using zirconia balls as the milling medium, a milling speed of 200~400 r / min, a milling time of 12~24 hours, and a ball-to-material-to-water mass ratio of 3:1:

2.

5. The method for preparing a multi-principal-doped, low thermal conductivity, high entropy infrared radiation material as described in claim 3, characterized in that: The drying conditions in step 1 refer to a temperature of 80~100℃ and a drying time of 12~24 hours.

6. The method for preparing a multi-principal-doped, low thermal conductivity, high entropy infrared radiation material as described in claim 3, characterized in that: The conditions for high-temperature calcination in step 2 are: calcination temperature of 1000~1500℃, heating rate of 3~5℃ / min, and calcination time of 6~8 hours.

7. The method for preparing a multi-principal-doped, low thermal conductivity, high entropy infrared radiation material as described in claim 3, characterized in that: The tableting conditions in step 3 refer to using a powder tablet press, with a pressure of 20~31MPa and a tableting time of 10~20min.

8. The method for preparing a multi-principal-doped, low thermal conductivity, high entropy infrared radiation material as described in claim 3, characterized in that: The conditions for high-temperature calcination in step 3 are: calcination temperature of 1000~1500℃, heating rate of 5℃ / min, and calcination time of 6~8 hours.

9. The method for preparing a multi-principal-doped, low thermal conductivity, high entropy infrared radiation material as described in claim 3, characterized in that: The cooling method in steps 2 and 3 is one of furnace cooling, air quenching cooling, and liquid nitrogen quenching cooling.

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