A high-entropy perovskite-type electromagnetic wave absorbing material and preparation method thereof

Abstract

The present invention belongs to the technical field of electromagnetic wave absorbing materials and discloses a high-entropy perovskite-type electromagnetic wave absorbing material and a preparation method thereof. The present invention provides a high-entropy perovskite-type electromagnetic wave absorbing material. Compared with traditional microwave absorbers, the high-entropy perovskite-type electromagnetic wave absorbing material obtained by the present invention has the characteristics of a wide effective absorption bandwidth and high absorption intensity at a low thickness. The present invention also provides a preparation method of the high-entropy perovskite-type electromagnetic wave absorbing material. The preparation method adopts a sol-gel method combined with a calcination process, omitting the grinding and compression steps; uses water as a solvent, does not require the use of highly toxic chemical reagents, and is environmentally friendly and pollution-free; and the preparation process is simple, low-cost, and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and in particular to a high-entropy perovskite-type electromagnetic wave absorbing material and a preparation method thereof. Background Art

[0002] The rapid development of communications technology has greatly promoted scientific and technological progress and improved our lives. However, this has also led to the continuous radiation of electromagnetic signals from system hardware into the transmission medium, leading to increasingly prominent electromagnetic leakage and interference issues, which adversely affect the normal operation of electronic equipment and human health. To address the increasingly serious electromagnetic pollution and electromagnetic compatibility issues, research on electromagnetic wave absorbing materials has attracted increasing attention. Ideal and efficient electromagnetic wave absorbing materials should possess strong absorption characteristics, a wide absorption frequency range, a thin matching thickness, and a low density.

[0003] As a strong dielectric loss-type absorbing material, perovskite material has good thermal stability and has become a highly regarded electromagnetic wave absorbing material. Cai Jia et al. from Guilin University of Electronic Technology found that some Co 3+ Transformed into Co 4+ , resulting in adjacent cobalt ions with different valence states, unable to form paired electrons, and increasing the material's conductivity. At a 10% dopant concentration, the maximum absorption peak at 11.4 GHz at a thickness of 1.8 mm, with an effective absorption bandwidth less than 2 GHz, is observed. Doping with sodium ions reduces the thickness, but the effective absorption bandwidth remains narrow. Current development of perovskite absorbers focuses primarily on doping and the preparation of composite magnetic loss-type materials. However, existing efforts struggle to simultaneously meet the requirements for strong electromagnetic wave absorption properties, a wide absorption frequency range, thin thickness, and low density. Summary of the Invention

[0004] In view of this, the present invention provides a high-entropy perovskite electromagnetic wave absorption material and a preparation method thereof to solve the problem that electromagnetic wave absorption materials in the prior art are difficult to simultaneously meet the requirements of strong absorption characteristics, wide absorption frequency range, thin matching thickness and light density.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for preparing a high-entropy perovskite-type electromagnetic wave absorbing material, comprising the following steps:

[0007] Cobalt salt, iron salt, nickel salt, lanthanum salt, manganese salt, chromium salt, polymerizing agent, dispersant and solvent are mixed to obtain a mixed solution; the mixed solution is evaporated and dried in sequence to obtain a precursor; and the precursor is calcined to obtain a high entropy perovskite type electromagnetic wave absorbing material.

[0008] Preferably, the cobalt salt is cobalt nitrate, cobalt sulfate or cobalt chloride; the iron salt is iron nitrate, iron sulfate or iron chloride; the nickel salt is nickel nitrate, nickel sulfate or nickel chloride; the lanthanum salt is lanthanum nitrate, lanthanum sulfate or lanthanum chloride; the manganese salt is manganese nitrate, manganese sulfate or manganese chloride; and the chromium salt is chromium nitrate, chromium sulfate or chromium chloride.

[0009] Preferably, the polymerization agent is citric acid; the dispersant is ethylene glycol; and the solvent is water.

[0010] Preferably, in the mixed solution, the molar ratio of lanthanum ion, cobalt ion, chromium ion, iron ion, manganese ion, nickel ion and polymerizer is 4.8-5.2:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2:8-12.

[0011] Preferably, the mass volume ratio of the polymerizer to the dispersant is 4-5 g:4-7 mL; the volume ratio of the dispersant to the solvent is 1-1.2:10.

[0012] Preferably, the evaporation temperature is 70-90° C., and the evaporation time is 6-10 hours.

[0013] Preferably, the drying temperature is 70-100° C., and the drying time is 5-8 hours.

[0014] Preferably, the calcination temperature is 1050-1250° C., the calcination time is 3-5 hours, and the calcination heating rate is 4-6° C. / min.

[0015] The present invention also provides a high-entropy perovskite type electromagnetic wave absorbing material prepared by the preparation method of the high-entropy perovskite type electromagnetic wave absorbing material.

[0016] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The high entropy perovskite electromagnetic wave absorbing material has both dielectric loss and magnetic loss properties, can be compounded with paraffin wax in a ratio of 4:1, has a thickness of 1.4 mm, an effective absorption bandwidth of 2.87 GHz, and a minimum reflectivity of -52.042 dB; Therefore, the high entropy perovskite electromagnetic wave absorbing material (La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O3) has the characteristics of wide effective absorption bandwidth and high absorption intensity at low thickness;

[0018] (2) The present invention uses water as a solvent, does not require the use of highly toxic chemical reagents, and is environmentally friendly and pollution-free; and the preparation process is simple and low-cost, making it suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0020] Figure 1 XRD patterns of the high entropy perovskite-type electromagnetic wave absorbing materials obtained in Examples 1 to 2 and Comparative Examples 1 to 3 of the present invention;

[0021] Figure 2 This is a SEM image of the high-entropy perovskite electromagnetic wave absorbing material obtained in Example 1 of the present invention;

[0022] Figure 3 This is a SEM image of the high-entropy perovskite electromagnetic wave absorbing material obtained in Example 2 of the present invention;

[0023] Figure 4 This is a SEM image of the high-entropy perovskite electromagnetic wave absorbing material obtained in Comparative Example 1 of the present invention;

[0024] Figure 5 This is a SEM image of the high-entropy perovskite electromagnetic wave absorbing material obtained in Comparative Example 2 of the present invention;

[0025] Figure 6 This is a SEM image of the high-entropy perovskite electromagnetic wave absorbing material obtained in Comparative Example 3 of the present invention;

[0026] Figure 7 Graph showing reflection loss of the high entropy perovskite-type electromagnetic wave absorbing materials obtained in Examples 1 to 2 of the present invention and Comparative Examples 1 to 3 at a thickness of 1.4 mm;

[0027] Figure 8 Impedance matching diagrams of the high-entropy perovskite electromagnetic wave absorbing materials obtained in Examples 1 to 2 and Comparative Examples 1 to 3 of the present invention at a thickness of 1.4 mm;

[0028] Figure 9 This is a reflection loss diagram of the high-entropy perovskite electromagnetic wave absorption material obtained in Example 2 of the present invention at different thicknesses. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a high-entropy perovskite-type electromagnetic wave absorbing material, comprising the following steps:

[0030] Cobalt salt, iron salt, nickel salt, lanthanum salt, manganese salt, chromium salt, polymerizing agent, dispersant and solvent are mixed to obtain a mixed solution; the mixed solution is evaporated and dried in sequence to obtain a precursor; and the precursor is calcined to obtain a high entropy perovskite type electromagnetic wave absorbing material.

[0031] In the present invention, the cobalt salt is preferably cobalt nitrate, cobalt sulfate or cobalt chloride, more preferably cobalt nitrate or cobalt chloride; the iron salt is preferably ferric nitrate, ferric sulfate or ferric chloride, more preferably ferric nitrate or ferric chloride; the nickel salt is preferably nickel nitrate, nickel sulfate or nickel chloride, more preferably nickel nitrate or nickel chloride; the lanthanum salt is preferably lanthanum nitrate, lanthanum sulfate or lanthanum chloride, more preferably lanthanum nitrate or lanthanum chloride; the manganese salt is preferably manganese nitrate, manganese sulfate or manganese chloride, more preferably manganese sulfate or manganese chloride; the chromium salt is preferably chromium nitrate, chromium sulfate or chromium chloride, more preferably chromium nitrate or chromium chloride.

[0032] In the present invention, the polymerization agent is preferably citric acid; the dispersant is preferably ethylene glycol; and the solvent is preferably water.

[0033] In the present invention, in the mixed solution, the molar ratio of lanthanum ion, cobalt ion, chromium ion, iron ion, manganese ion, nickel ion and polymerizer is preferably 4.8-5.2:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2:8-12, and more preferably 4.9-5.1:0.9-1.1:0.9-1.1:1-1.1:0.9-1.1:0.9-1.1:9-11.

[0034] In the present invention, the mass volume ratio of the polymerizer and the dispersant is preferably 4-5 g:4-7 mL, more preferably 4.2-4.8 g:5-6 mL; the volume ratio of the dispersant and the solvent is preferably 1-1.2:10, more preferably 1.1-1.15:10.

[0035] In the present invention, before evaporation, aqueous ammonia is added to the mixture of cobalt salt, iron salt, nickel salt, lanthanum salt, manganese salt, chromium salt, polymerizing agent, dispersant and solvent so that the pH of the mixture is preferably 7 to 7.5, more preferably 7.2 to 7.3.

[0036] In the present invention, the evaporation is carried out under stirring conditions, the evaporation temperature is preferably 70-90°C, more preferably 75-85°C; the evaporation time is preferably 6-10h, more preferably 8h; the stirring speed is 5-20r / min, more preferably 10r / min.

[0037] In the present invention, the drying temperature is preferably 70 to 100° C., more preferably 75 to 90° C.; the drying time is preferably 5 to 8 hours, more preferably 6 to 7 hours.

[0038] In the present invention, the calcination is carried out in an air atmosphere, and the calcination temperature is preferably 1050-1250°C, more preferably 1080-1220°C; the calcination time is preferably 3-5h, more preferably 3.5-4.5h; the calcination heating rate is preferably 4-6°C / min, more preferably 4.5-5°C / min.

[0039] The present invention also provides a high-entropy perovskite type electromagnetic wave absorbing material prepared by the preparation method of the high-entropy perovskite type electromagnetic wave absorbing material.

[0040] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] The method for preparing the high entropy perovskite electromagnetic wave absorbing material of this embodiment includes the following steps:

[0043] (1) Preparation of precursor by sol-gel method: 4.33g of lanthanum nitrate hexahydrate, 0.5821g of cobalt nitrate hexahydrate, 0.808g of iron nitrate nonahydrate, 0.5816g of nickel nitrate hexahydrate, 0.3958g of manganese chloride tetrahydrate and 0.5329g of chromium chloride hexahydrate were weighed and dissolved in 50mL of distilled water. Then 4.2028g of citric acid monohydrate and 5.5mL of ethylene glycol were weighed and stirred until completely dissolved. Ammonia water was used to adjust the pH of the solution to 7, and the above solution was heated at a constant temperature of 80℃ and stirred at a stirring speed of 10r / min for 8h to form a sol. The solution was placed in a blast drying oven and dried at 100℃ for 8h. After naturally cooling to room temperature, the obtained dry gel was taken out to obtain the precursor.

[0044] (2) Sintering to prepare high entropy perovskite electromagnetic wave absorbing material: The precursor obtained in step (1) was placed in a muffle furnace and calcined in an air atmosphere, heated to 1100°C and calcined for 4 hours at a heating rate of 5°C / min, and naturally cooled to obtain the product La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O3.

[0045] Example 2

[0046] The method for preparing the high entropy perovskite electromagnetic wave absorbing material of this embodiment includes the following steps:

[0047] (1) Preparation of precursor by sol-gel method: 4.33g of lanthanum nitrate hexahydrate, 0.5821g of cobalt nitrate hexahydrate, 0.808g of iron nitrate nonahydrate, 0.5816g of nickel nitrate hexahydrate, 0.3958g of manganese chloride tetrahydrate and 0.5329g of chromium chloride hexahydrate were weighed and dissolved in 50mL of distilled water. Then 4.2028g of citric acid monohydrate and 5.5mL of ethylene glycol were weighed and stirred until completely dissolved. Ammonia water was used to adjust the pH of the solution to 7, and the above solution was heated at a constant temperature of 80℃ and stirred at a stirring speed of 10r / min for 8h to form a sol. The solution was placed in a blast drying oven and dried at 100℃ for 8h. After naturally cooling to room temperature, the obtained dry gel was taken out to obtain the precursor.

[0048] (2) Sintering to prepare high entropy perovskite type electromagnetic wave absorbing material: The precursor obtained in step (1) is placed in a muffle furnace and calcined in an air atmosphere, heated to 1200 ° C. and calcined for 4 hours at a heating rate of 5 ° C. / min. After natural cooling, the product La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O3.

[0049] Comparative Example 1

[0050] The preparation method of the high entropy perovskite type electromagnetic wave absorbing material of this comparative example comprises the following steps:

[0051] (1) Preparation of precursor by sol-gel method: 4.33g of lanthanum nitrate hexahydrate, 0.5821g of cobalt nitrate hexahydrate, 0.808g of iron nitrate nonahydrate, 0.5816g of nickel nitrate hexahydrate, 0.3958g of manganese chloride tetrahydrate and 0.5329g of chromium chloride hexahydrate were weighed and dissolved in 50mL of distilled water. Then 4.2028g of citric acid monohydrate and 5.5mL of ethylene glycol were weighed and stirred until completely dissolved. Ammonia water was used to adjust the pH of the solution to 7, and the above solution was heated at a constant temperature of 80℃ and stirred at a stirring speed of 10r / min for 8h to form a sol. The solution was placed in a blast drying oven and dried at 100℃ for 8h. After naturally cooling to room temperature, the obtained dry gel was taken out to obtain the precursor.

[0052] (2) Sintering to prepare high entropy perovskite electromagnetic wave absorbing material: The precursor obtained in step (1) was placed in a muffle furnace and calcined in an air atmosphere, heated to 900 ° C for 4 hours at a heating rate of 5 ° C / min, and naturally cooled to obtain the product La (Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O3.

[0053] Comparative Example 2

[0054] The preparation method of the high entropy perovskite type electromagnetic wave absorbing material of this comparative example comprises the following steps:

[0055] (1) Preparation of precursor by sol-gel method: 4.33g of lanthanum nitrate hexahydrate, 0.5821g of cobalt nitrate hexahydrate, 0.808g of iron nitrate nonahydrate, 0.5816g of nickel nitrate hexahydrate, 0.3958g of manganese chloride tetrahydrate and 0.5329g of chromium chloride hexahydrate were weighed and dissolved in 50mL of distilled water. Then 4.2028g of citric acid monohydrate and 5.5mL of ethylene glycol were weighed and stirred until completely dissolved. Ammonia water was used to adjust the pH of the solution to 7, and the above solution was heated at a constant temperature of 80℃ and stirred at a stirring speed of 10r / min for 8h to form a sol. The solution was placed in a blast drying oven and dried at 100℃ for 8h. After naturally cooling to room temperature, the obtained dry gel was taken out to obtain the precursor.

[0056] (2) Sintering to prepare high entropy perovskite type electromagnetic wave absorbing material: The precursor obtained in step (1) is placed in a muffle furnace and calcined in an air atmosphere, heated to 1000°C and calcined for 4 hours at a heating rate of 5°C / min, and the product La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O3.

[0057] Comparative Example 3

[0058] The preparation method of the high entropy perovskite type electromagnetic wave absorbing material of this comparative example comprises the following steps:

[0059] (1) Preparation of precursor by sol-gel method: 4.33g of lanthanum nitrate hexahydrate, 0.5821g of cobalt nitrate hexahydrate, 0.808g of iron nitrate nonahydrate, 0.5816g of nickel nitrate hexahydrate, 0.3958g of manganese chloride tetrahydrate and 0.5329g of chromium chloride hexahydrate were weighed and dissolved in 50mL of distilled water. Then 4.2028g of citric acid monohydrate and 5.5mL of ethylene glycol were weighed and stirred until completely dissolved. Ammonia water was used to adjust the pH of the solution to 7, and the above solution was heated at a constant temperature of 80℃ and stirred at a stirring speed of 10r / min for 8h to form a sol. The solution was placed in a blast drying oven and dried at 100℃ for 8h. After naturally cooling to room temperature, the obtained dry gel was taken out to obtain the precursor.

[0060] (2) Sintering to prepare high entropy perovskite type electromagnetic wave absorbing material: The precursor obtained in step (1) is placed in a muffle furnace and calcined in an air atmosphere, heated to 1300 ° C. and calcined for 4 hours at a heating rate of 5 ° C. / min. After natural cooling, the product La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni0.2 )O3.

[0061] The surface morphology and performance of the high entropy perovskite type electromagnetic wave absorbing materials obtained in Examples 1 to 2 and Comparative Examples 1 to 3 were tested. The test results are as follows: Figures 1 to 9 shown.

[0062] Depend on Figure 1 As can be seen, at a treatment temperature of 900°C, Comparative Example 1 exhibits a non-perovskite second phase. At 1000°C, the number of second-phase diffraction peaks increases in Comparative Example 2. When the temperature rises to 1100°C, Example 1 forms a single-phase perovskite structure. At 1200°C, the material obtained in Example 2 maintains a relatively good single perovskite structure. As the temperature rises to 1300°C, Comparative Example 3 again produces a second phase. This indicates that the high-entropy perovskite electromagnetic wave absorption material obtained by the present invention possesses a relatively complete single-phase perovskite structure, with a complete crystal form and a single structure.

[0063] Depend on Figures 2 to 6 It can be seen that the structure of the high-entropy perovskite-type electromagnetic wave absorbing material obtained in the present invention is relatively regular, presenting an octahedral structure.

[0064] Depend on Figure 7 The resulting material exhibits excellent electromagnetic wave absorption performance at a sintering temperature of 1200°C, with a minimum reflectivity of -52.04 dB and an effective absorption bandwidth of 3.02 GHz (11.95-14.97 GHz). Sintering temperatures that are too low (900°C) or too high (1300°C) are not conducive to improving the material's electromagnetic wave absorption performance. This indicates that the high-entropy perovskite-type electromagnetic wave absorption material obtained by the present invention has excellent electromagnetic wave absorption performance.

[0065] Depend on Figure 8 It can be seen that the high-entropy perovskite electromagnetic wave absorption material obtained in the present invention exhibits relatively excellent wave impedance matching characteristics, while the wave impedance matching characteristics of Comparative Examples 1 and 3 are poor.

[0066] Depend on Figure 9 It can be seen that the high-entropy perovskite electromagnetic wave absorption material obtained in Example 1 of the present invention exhibits effective electromagnetic wave absorption performance in the thickness range of 1 to 3 mm, and its effective absorption bandwidth can effectively cover 6 to 18 GHz.

[0067] The high-entropy perovskite electromagnetic wave absorbing material of the present invention is prepared by the sol-gel method. Its optimal absorption performance can be obtained by calcining the dried precursor gel at a high temperature of 1200°C in an air atmosphere, omitting the grinding and compression processes. The loss of the material is mainly attributed to dielectric loss. Compared with traditional microwave absorbers, the high-entropy perovskite electromagnetic wave absorbing material obtained by the present invention has the characteristics of wide effective absorption bandwidth and high absorption intensity at low thickness. At the same time, the present invention uses water as a solvent, does not require the use of highly toxic chemical reagents, and is environmentally friendly and pollution-free. In addition, the preparation process is simple and the cost is low, making it suitable for large-scale industrial production.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a high entropy perovskite type electromagnetic wave absorbing material, characterized in that: The steps include: Mixing cobalt salt, iron salt, nickel salt, lanthanum salt, manganese salt, chromium salt, polymerizing agent, dispersant and solvent to obtain a mixed solution; evaporating and drying the mixed solution in sequence to obtain a precursor; calcining the precursor to obtain a high entropy perovskite type electromagnetic wave absorbing material; The calcination temperature is 1050-1250°C, the calcination time is 3-5h, and the calcination heating rate is 4-6°C / min; In the mixed solution, the molar ratio of lanthanum ion, cobalt ion, chromium ion, iron ion, manganese ion, nickel ion and polymerizer is 4.8-5.2:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2:8-12.

2. The method for preparing the high entropy perovskite type electromagnetic wave absorbing material according to claim 1, characterized in that: The cobalt salt is cobalt nitrate, cobalt sulfate or cobalt chloride; the iron salt is iron nitrate, iron sulfate or iron chloride; the nickel salt is nickel nitrate, nickel sulfate or nickel chloride; the lanthanum salt is lanthanum nitrate, lanthanum sulfate or lanthanum chloride; the manganese salt is manganese nitrate, manganese sulfate or manganese chloride; the chromium salt is chromium nitrate, chromium sulfate or chromium chloride.

3. The method for preparing the high entropy perovskite type electromagnetic wave absorbing material according to claim 2, characterized in that: The polymerizing agent is citric acid; the dispersant is ethylene glycol; and the solvent is water.

4. The method for preparing the high entropy perovskite type electromagnetic wave absorbing material according to claim 3, characterized in that: The mass volume ratio of the polymerizer and the dispersant is 4-5 g:4-7 mL; the volume ratio of the dispersant and the solvent is 1-1.2:

10.

5. The method for preparing the high entropy perovskite type electromagnetic wave absorbing material according to claim 4, characterized in that: The evaporation temperature is 70-90° C., and the evaporation time is 6-10 hours.

6. The method for preparing the high entropy perovskite type electromagnetic wave absorbing material according to claim 1, characterized in that: The drying temperature is 70-100° C., and the drying time is 5-8 hours.

7. The high-entropy perovskite type electromagnetic wave absorbing material prepared by the method for preparing the high-entropy perovskite type electromagnetic wave absorbing material according to any one of claims 1 to 6.

Images