Defective fluorite-type high-entropy cerate ceramic with infrared radiation performance

Abstract

The present application relates to a kind of high-entropy cerate ceramics with infrared radiation performance of defective fluorite type, the crystal structure of the high-entropy cerate ceramic is defective fluorite type, its chemical formula is A2Ce2O7, wherein A site is at least five kinds of elements in La, Pr, Gd, Sr, Ca, Cu, Ni, Co, Mn, and the content of each element is between 14~20%;And the infrared emissivity of high-entropy cerate ceramic in 0.78~2.5 μm wave band is >0.90, and the infrared emissivity in 2.5~16 μm wave band is >0.92.The present application has excellent infrared radiation performance and high-temperature thermal stability, and has potential application prospect in high-temperature thermal radiation field, including aerospace vehicle, large energy equipment, industrial kiln, power station boiler and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-entropy ceramic materials, and particularly relates to a defect-fluorite high-entropy cerate ceramic with infrared radiation performance. BACKGROUND

[0002] The rapid growth of energy consumption makes the energy-saving situation in China very severe, and the infrared radiation technology has been rapidly developed in the heat dissipation of supersonic weapons and the energy saving of civil industries. The energy-saving potential in the field of infrared radiation materials is huge. According to the Wien displacement law and the Planck law, when the temperature is higher than 1000 DEG C, the radiation heat accounts for 80% of the three heat transfer modes, and the radiation energy corresponds to the wave band mainly concentrated in the range of 1-5 microns, which shows that the radiation heat is the key factor to determine the thermal efficiency. The index for measuring the radiation heat is the emissivity of the material, that is, the higher the emissivity, the better the radiation effect.

[0003] Lanthanum cerate (La2Ce2O7) has a disordered defect-fluorite structure, has low thermal conductivity, good thermal stability, can be stable without phase change after long-term annealing at 1400 DEG C, and has a strong competitive advantage in new type of thermal protection coating ceramic materials. However, the intrinsic emissivity of La2Ce2O7 material is low, the emissivity in the 0.78-2.5 micron wave band is less than 0.1, and the high-temperature thermal radiation performance is poor. At the same time, lanthanum cerate can be regulated by high-entropy components in the A position, and low-valence transition metal ions are selected, so that there is serious lattice distortion in the unit cell, which shows high mass disorder degree, ion size disorder degree and charge disorder degree, can significantly improve the comprehensive performance of the material, and exhibits excellent molten salt corrosion resistance, high-temperature phase stability and mechanical properties.

[0004] CN112062566A discloses a cerate composite material and a preparation method and application thereof. The cerate composite material has good phase stability, extremely low thermal conductivity, extremely strong anti-sintering property, and extremely high thermal expansion coefficient, and is suitable for use and popularization as a new generation of thermal barrier coating. However, the infrared emissivity of the material is low, and it is difficult to block the transfer of thermal radiation. SUMMARY

[0005] The present application relates to the technical field of high-entropy ceramic materials, and particularly relates to a defect-fluorite high-entropy cerate ceramic with infrared radiation performance.

[0006] In order to solve the above problems, the application discloses a defective fluorite-type high-entropy cerate ceramic with infrared radiation performance, characterized in that the crystal structure of the high-entropy cerate ceramic is a defective fluorite type, and the chemical formula is A2Ce2O7, wherein A is at least five elements selected from La, Pr, Gd, Sr, Ca, Cu, Ni, Co and Mn, and the content of each element is between 14% and 20%; and the infrared emissivity of the high-entropy cerate ceramic is greater than 0.90 in the 0.78-2.5 mu m wave band and greater than 0.92 in the 2.5-16 mu m wave band.

[0007] The application further discloses a preparation method of the defective fluorite-type high-entropy cerate ceramic with infrared radiation performance.

[0008] 1. The AO x powder and the CeO2 powder are ball-milled and mixed to obtain a precursor powder. x The A is at least five kinds of La2O3, Pr6O 11 , Gd2O3, SrO, CaO, CuO, NiO, CoO and MnO2 powders, and the content of each element at the A position is between 14% and 20%; the precursor powder is obtained by drying, grinding and passing through a 400-mesh screen.

[0009] 2. The precursor powder is high-temperature calcined in an air atmosphere, and after the calcination is completed, the high-entropy cerate powder material is obtained by cooling in the furnace and grinding.

[0010] 3. The high-entropy cerate powder material is passed through a 400-mesh screen, and then the defective fluorite-type high-entropy cerate ceramic is obtained by tabletting and high-temperature calcination, and after the calcination is completed, the defective fluorite-type high-entropy cerate ceramic is obtained by cooling in the furnace.

[0011] In the step 1, the ball-milling condition is that a planetary ball mill is used, 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 the ball, the material and the water is 3:1:2.

[0012] In the step 1, the drying condition is that the temperature is 80-100 DEG C, and the time is 12-24 hours.

[0013] In the step 2, the high-temperature calcination condition is that the calcination temperature is 1200-1500 DEG C, the heating rate is 3-5 DEG C / min, and the calcination time is 6-8 hours.

[0014] In the step 3, the tabletting condition is that a powder tabletting machine is used, the pressure is 20-31 MPa, and the tabletting time is 10-20 min.

[0015] The conditions of high-temperature calcination in the step ⑶ refer to a calcination temperature of 1200-1500 DEG C, a temperature rising rate of 5 DEG C / min, and a calcination time of 6-8 hours.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] 1. The defect fluorite-type high-entropy cerate ceramic prepared by the present application has an octahedral crystal structure and belongs to an orthorhombic crystal system and an Fm-3m space group, as shown in the figure. Figure 1 The chemical formula is A2Ce2O7, wherein there are more than five elements at the A site, including La, Pr, Gd, Sr, and Ca, Cu, Ni, Co, and Mn elements, and each atom is randomly distributed in the crystal lattice. A The ratio of the cation radius of the A site to the Ce cation radius (R

[0018] 2. Due to the coexistence of rare earth elements and transition metal elements at the A site, and the electronic arrangement characteristics of the 3d orbit of the transition metal element and the 4f orbit of the rare earth element, the high-entropy cerate forms an impurity energy level near the Fermi energy level, effectively reducing the intrinsic band gap of the cerate material (the band gap of lanthanum cerate E g = 3.06 eV, and the band gap of the high-entropy cerate is less than 1.26 eV), and the enhanced interband transition (d-d) and band transition (d-f) can increase the electron transition probability, thereby improving the infrared emissivity.

[0019] 3. Due to the high-entropy design strategy at the A site, the configurational entropy will increase with the introduction of the main components, thereby reducing the Gibbs free energy. Especially at high temperatures, the contribution of configurational entropy to the reduction of Gibbs free energy is more prominent, which is conducive to improving the stability of the high-entropy phase. In addition, the increase of the mixing entropy can significantly improve the solid solution content of the solid solution, breaking through the solid solution limit in the Hume-Rothery law, which makes the high-entropy cerate ceramic still maintain the defect fluorite crystal structure and excellent infrared emissivity in the 1500 DEG C long-time thermal stability experiment.

[0020] 4. The high-entropy cerate is prepared by the mechanical wet grinding method and high-temperature calcination method, which has the advantages of simple preparation technology, strong repeatability, high production efficiency, and can be suitable for automatic operation. The prepared high-entropy cerate has single phase, high purity, and uniform element distribution, and has potential application prospects in the field of high-temperature thermal radiation, including aerospace vehicles, large energy equipment, industrial kilns, power station boilers, etc. BRIEF DESCRIPTION OF DRAWINGS

[0021] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0022] Figure 1 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application.

[0023] Figure 2 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application. 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application.

[0024] Figure 3 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application. 0.2 Pr 0.2 Gd 0.2 Ca 0.2 Cu 0.2 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application.

[0025] Figure 4 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application. 0.2 Pr 0.2 Cu 0.15 Co 0.15 Ni 0.15 Ca 0.15 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application.

[0026] Figure 5 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application. 0.15 Pr 0.14 Gd 0.14 Sr 0.14 Mn 0.14 Cu 0.14 Co 0.14 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application.

[0027] Figure 6 Infrared radiation spectrum of the defective fluorite-type high-entropy cerate ceramic prepared in Example 1 of the present application in the 0.78-2.5 μm wave band.

[0028] Figure 7 Infrared radiation spectrum of the defective fluorite-type high-entropy cerate ceramic prepared in Example 1 of the present application in the 2.5-16 μm wave band.

[0029] Figure 8 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application. 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 XRD pattern of the defective fluorite-type high-entropy cerate ceramic of the present application. DETAILED DESCRIPTION

[0030] A defect-fluorite type high-entropy cerate ceramic with infrared radiation performance, the crystal structure of the high-entropy cerate ceramic is defect-fluorite type, the chemical formula is A2Ce2O7, wherein A is at least five elements selected from La, Pr, Gd, Sr, Ca, Cu, Ni, Co and Mn, and the content of each element is between 14 and 20%; and the infrared emissivity of the high-entropy cerate ceramic is >0.90 in the 0.78-2.5 μm wave band, and >0.92 in the 2.5-16 μm wave band.

[0031] The preparation method of the defect-fluorite type high-entropy cerate ceramic with infrared radiation performance comprises the following steps:

[0032] (1) AO x powder and CeO2 powder are used as raw materials, AO x is at least five kinds of La2O3, Pr6O 11 , Gd2O3, SrO, CaO, CuO, NiO, CoO and MnO2 powder, and the content of each element at A site is between 14 and 20%. Each raw material is ball milled by a planetary ball mill, the ball milling medium is 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, it is dried at 80-100℃ for 12-24 hours, ground and sieved through a 400 mesh sieve to obtain a precursor powder.

[0033] (2) The precursor powder is calcined at a high temperature in an air atmosphere, the calcination temperature is 1200-1500℃, the heating rate is 3-5℃ / min, and the calcination time is 6-8 hours. After calcination, the defect-fluorite type high-entropy cerate powder material is obtained by cooling in the furnace and grinding.

[0034] (3) After the defect-fluorite type high-entropy cerate powder material is sieved through a 400 mesh sieve, it is first pressed into a tablet by a powder tablet press, the pressure is 20-31 MPa, and the tablet pressing time is 10-20 min. Then, it is calcined at a high temperature of 1200-1500℃ for 6-8 hours, and the heating rate is 5℃ / min. After calcination, the defect-fluorite type high-entropy cerate ceramic is obtained by cooling in the furnace. The crystal structure of the defect-fluorite type high-entropy cerate ceramic is shown in Figure 1 .

[0035] Example 1

[0036] A preparation method of a defect-fluorite type high-entropy cerate ceramic with infrared radiation performance comprises the following steps:

[0037] (1) Weigh out 1.6292g La2O3 and 1.7024g Pr6O 11 0.7955g CuO, 0.7436g NiO, 0.7493g CoO, and 8.6057g CeO2 were mixed to obtain a powdered raw material. The mixture was then ball-milled using a planetary ball mill with zirconia balls as the milling media at a speed of 200 r / min for 12 hours. The ball-to-material-to-water mass ratio (g / g) was 3:1:2. The mixture was then dried at 80℃ for 24 hours, ground, and sieved through a 400-mesh sieve to obtain the precursor powder.

[0038] (2) The precursor powder was calcined at high temperature in air, with the temperature increased to 1200℃ at a rate of 3℃ / min, and calcined for 6 hours. After calcination, the powder was cooled in the furnace and ground to obtain the defective fluorite-type high-entropy cerate powder material.

[0039] (3) After the defective fluorite-type high-entropy cerate powder material is passed through a 400-mesh sieve, it is first pressed into tablets using a powder press at a pressure of 20 MPa for 20 min. Then, it is calcined at high temperature in air, with the temperature increased to 1200℃ at a rate of 5℃ / min, and calcined for 6 hours. After calcination, it is cooled in the furnace to obtain the defective fluorite-type high-entropy cerate ceramic (La). 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 )2Ce2O7.

[0040] Regarding the obtained (La) 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 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.

[0041] Regarding the obtained (La) 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 The infrared radiation properties and thermal stability of 2Ce2O7 were evaluated:

[0042] The infrared radiation performance of the defective fluorite-type high-entropy cerate ceramic was evaluated by using a Lambda 950 type ultraviolet / visible / near-infrared spectrophotometer (with a 150 mm integrating sphere) manufactured by PerkinElmer Company of the United States, and the infrared emissivity of the defective fluorite-type high-entropy cerate ceramic in the 0.78-2.5 μm and 2.5-16 μm wave bands was measured, and the results are shown in Figures 6~7 Then, the infrared emissivity in the corresponding wave band was calculated according to formulas (1) and (2).

[0043]

[0044] Wherein, α(θ, λ) is the absorptivity of the material at the solar incident angle θ and the wavelength λ; R(θ, λ) is the reflectivity of the material at the solar incident angle θ and the 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 the wavelength λ and the temperature T; I b (λ, T) is the thermal radiation intensity of the blackbody material at the temperature T.

[0045] It is calculated that the infrared emissivity of (La 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 )2Ce2O7 in the 0.78-2.5 μm wave band is 0.928, and the infrared emissivity in the 2.5-16 μm wave band is 0.933.

[0046] (La 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 )2Ce2O7 was placed in a box furnace and subjected to long-time thermal stability experiment under the condition of air atmosphere and 1500°C, and the results are shown in Figure 8 The figure shows that the (La 0.2 Pr 0.2 Cu 0.2 Ni 0.2 Co 0.2 )2Ce2O7 crystal structure is stable, and the infrared emissivity in the 0.78-2.5 μm wave band after the thermal stability experiment is 0.916, and the infrared emissivity in the 2.5-16 μm wave band is 0.921.

[0047] The above data show that the defective fluorite-type high-entropy cerate ceramic prepared in the application has excellent infrared radiation performance and high-temperature thermal stability, and therefore can be applied to the field of high-temperature thermal radiation technology.

[0048] Example 2

[0049] A preparation method of a defective fluorite-type high-entropy cerate ceramic with infrared radiation performance, comprising the following steps:

[0050] (1) 1.6292g of La2O3, 1.7024g of Pr6O 11 , 1.8124g of Gd2O3, 0.5608g of CaO, 0.7955g of CuO, and 8.6057g of CeO2 are weighed to obtain mixed raw material powder.

[0051] (2) The precursor powder is high-temperature calcined in an air atmosphere, and heated to 1200℃ at a rate of 5℃ / min, and calcined for 8 hours.

[0052] (3) After the defective fluorite-type high-entropy cerate powder material is sieved through a 400-mesh sieve, tabletting is first performed using a powder tablet machine, and the pressure is 25 MPa and the tabletting time is 15 min. 0.2 Pr 0.2 Gd 0.2 Ca 0.2 Cu 0.2 )2Ce2O7.

[0053] The obtained (La 0.2 Pr 0.2 Gd 0.2 Ca 0.2 Cu 0.2 )2Ce2O7 is subjected to XRD testing, and the results are shown in Figure 3 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.

[0054] Example 3

[0055] A preparation method of a defective fluorite-type high-entropy cerate ceramic with infrared radiation performance, comprising the following steps:

[0056] (1) 1.6292g of La2O3, 1.7024g of Pr6O 110.6119g CuO, 0.5619g CoO, 0.5601g NiO, 0.4313g CaO, and 8.6057g CeO2 were mixed to obtain a powdered raw material. The mixture was then ball-milled using a planetary ball mill with zirconia balls as the milling media at 300 r / min for 24 hours. The ball-to-material-to-water mass ratio (g / g) was 3:1:2. The mixture was then dried at 90℃ for 24 hours, ground, and sieved through a 400-mesh sieve to obtain the precursor powder.

[0057] (2) The precursor powder was calcined at high temperature in air, with the temperature increased to 1500℃ at a rate of 3℃ / min, and calcined for 7 hours. After calcination, the powder was cooled in the furnace and ground to obtain the defective fluorite-type high-entropy cerate powder material.

[0058] (3) After the defective fluorite-type high-entropy cerate powder material is passed through a 400-mesh sieve, it is first pressed into tablets using a powder press at a pressure of 31 MPa for 10 min. Then, it is calcined at high temperature in air, with the temperature increased to 1500℃ at a rate of 5℃ / min, and calcined for 7 hours. After calcination, it is cooled in the furnace to obtain the defective fluorite-type high-entropy cerate ceramic (La). 0.2 Pr 0.2 Cu 0.15 Co 0.1 5Ni 0.15 Ca 0.15 )2Ce2O7.

[0059] Regarding the obtained (La) 0.2 Pr 0.2 Cu 0.15 Co 0.15 Ni 0.15 Ca 0.15 XRD tests were performed on 2Ce2O7, 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.

[0060] Example 4

[0061] A method for preparing defective fluorite-type high-entropy cerate ceramics with infrared radiation properties includes the following steps:

[0062] (1) Weigh out 1.6292g La2O3 and 1.7024g Pr6O 110.6119g CuO, 0.5619g CoO, 0.5601g NiO, 0.4313g CaO, and 8.6057g CeO2 were mixed to obtain a powdered raw material. The mixture was then ball-milled using a planetary ball mill with zirconia balls as the milling media at a speed of 400 r / min for 12 hours. The ball-to-material-to-water mass ratio (g / g) was 3:1:2. The mixture was then dried at 100℃ for 12 hours, ground, and sieved through a 400-mesh sieve to obtain the precursor powder.

[0063] (2) The precursor powder was calcined at high temperature in air, with the temperature increased to 1300℃ at a rate of 4℃ / min, and calcined for 8 hours. After calcination, the powder was cooled in the furnace and ground to obtain the defective fluorite-type high-entropy cerate powder material.

[0064] (3) After the defective fluorite-type high-entropy cerate powder material is passed through a 400-mesh sieve, it is first pressed into tablets using a powder press at a pressure of 31 MPa for 20 min. Then, it is calcined at high temperature in air, with the temperature increased to 1500℃ at a rate of 5℃ / min, and calcined for 8 hours. After calcination, it is cooled in the furnace to obtain the defective fluorite-type high-entropy cerate ceramic (La). 0.15 Pr 0.14 Gd 0.14 Sr 0.14 Mn 0.14 Cu 0.14 Co 0.14 )2Ce2O7.

[0065] Regarding the obtained (La) 0.15 Pr 0.14 Gd 0.14 Sr 0.14 Mn 0.14 Cu 0.14 Co 0.14 XRD tests were performed on 2Ce2O7, and the results are as follows: Figure 5 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.

[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 defective fluorite-type high-entropy cerate ceramic having infrared radiation properties, characterized by: The crystal structure of the high-entropy cerate ceramic is a defective fluorite type, and the chemical formula is A2Ce2O7, wherein A is at least five elements selected from La, Pr, Gd, Sr, Ca, Cu, Ni, Co and Mn, and rare earth elements and transition metal elements are simultaneously present, and the content of each element is between 14% and 20%; the infrared emissivity of the high-entropy cerate ceramic is greater than 0.90 in the 0.78-2.5 μm wave band, and greater than 0.92 in the 2.5-16 μm wave band; and the preparation method of the high-entropy cerate ceramic comprises 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 selecting at least five of the following: Gd2O3, SrO, CaO, CuO, NiO, CoO, and MnO2 powders, with the content of each element at site A ranging from 14% to 20%. The precursor powder is obtained by drying, grinding, and passing through a 400-mesh sieve. (2) the precursor powder is calcined at high temperature in an air atmosphere, and after the calcination is completed, the material is cooled in the furnace, and then ground to obtain a defective fluorite type high-entropy cerate powder material; (4) the defective fluorite type high-entropy cerate powder material is sieved through a 400 mesh sieve, then pressed into a sheet, and then calcined at high temperature, and after the calcination is completed, the material is cooled in the furnace to obtain a defective fluorite type high-entropy cerate ceramic.

2. The defective fluorite-type high-entropy cerate ceramic with infrared radiation performance of claim 1, wherein: In step (1), the ball milling conditions are as follows: a planetary ball mill is used, the ball milling medium is 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.

3. The defective fluorite-type high-entropy cerate ceramic with infrared radiation performance of claim 1, wherein: In step (1), the drying conditions are as follows: the temperature is 80-100℃, and the time is 12-24 hours.

4. The defective fluorite-type high-entropy cerate ceramic with infrared radiation performance of claim 1, wherein: In step (2), the high-temperature calcination conditions are as follows: the calcination temperature is 1200-1500℃, the heating rate is 3-5℃ / min, and the calcination time is 6-8 hours.

5. The defective fluorite-type high-entropy cerate ceramic with infrared radiation performance of claim 1, wherein: In step (3), the sheet pressing conditions are as follows: a powder sheet press is used, the pressure is 20-31 MPa, and the sheet pressing time is 10-20 min.

6. The defective fluorite-type high-entropy cerate ceramic with infrared radiation performance of claim 1, wherein: In step (4), the high-temperature calcination conditions are as follows: the calcination temperature is 1200-1500℃, the heating rate is 5℃ / min, and the calcination time is 6-8 hours.

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