High-entropy oxide ceramic with wave-absorbing and heat-insulating properties and preparation method thereof

Abstract

The application provides a high-entropy oxide ceramic with wave-absorbing and heat-insulating performance and a preparation method thereof.The chemical formula of the ceramic is ABO3, wherein A positions contain two elements of Bi and Na, and simultaneously contain any two of Ca, Sr and Ba; B positions contain any two of Sn, Ti, Zr and Ce; and all the elements are in equal molar ratio at respective positions.The preparation method comprises the steps of ball milling, drying, calcining, tabletting and microwave sintering.Compared with the prior art, the high-entropy oxide ceramic provided by the application has excellent wave-absorbing and heat-insulating performance and has the advantage of low preparation cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-entropy ceramic materials, and specifically discloses a high-entropy oxide ceramic with wave-absorbing and heat-insulating properties and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the aerospace field, the application environment of wave-absorbing materials in aerospace, cruise missiles and hypersonic aircraft equipment is becoming more and more demanding, so new wave-absorbing materials with both wave-absorbing and high-temperature heat-insulating functions have emerged as the times require. At present, few new materials with integrated wave-absorbing and heat-insulating functions have been reported, and how to effectively integrate these functions through a simple and efficient method is still a great challenge. It is crucial to develop materials with excellent high-temperature heat-insulating properties and wave-absorbing properties.

[0003] C / SiC nanofibers have good wave-absorbing and heat-insulating properties, but they do not have excellent wave-absorbing properties in the X-band and are easily oxidized at high temperatures of 1200 DEG C, thereby affecting their stability. Carbon / SiO2@CNTs composite aerogels obtained by freeze-drying have excellent wave-absorbing and heat-insulating properties, but their cost is very high and they are not suitable for use in high-temperature extreme conditions.

[0004] High-entropy oxide ceramics have excellent properties such as a huge component adjustment space, oxidation resistance and high-temperature stability. High-entropy perovskite structure oxides often have extremely low thermal conductivity and excellent high-temperature stability, and are expected to be used as wave-absorbing materials in high-temperature extreme environments. At present, some technologies can be used to prepare high-entropy oxide ceramics with both wave-absorbing and heat-insulating properties. For example, patent CN114853458A discloses a high-entropy ceramic and a preparation method and application thereof as an electromagnetic wave absorbing material, and the molecular formula of the spinel and perovskite type high-entropy ceramic is (Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr2O4; patent CN115504778A discloses a cobalt-based high-entropy ceramic and a preparation method and application thereof, and the chemical formula of the spinel type and rock salt type crystal structure high-entropy ceramic is (Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O / Co2O4. However, the wave-absorbing performance of the high-entropy oxide ceramic materials prepared by these methods needs to be further improved, and the sintering cost is high.

[0005] Therefore, how to prepare high-entropy oxide ceramics with high wave-absorbing and heat-insulating properties and reduce the preparation cost is a technical problem that needs to be solved in the industry at present. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a high-entropy oxide ceramic with wave-absorbing and heat-insulating properties and a preparation method, which can obtain a high-entropy oxide ceramic with high wave-absorbing and heat-insulating properties and low preparation cost.

[0007] In order to achieve the above technical purpose, the present application adopts the following technical solutions:

[0008] A high-entropy oxide ceramic with wave-absorbing and heat-insulating properties, the chemical formula of which is ABO3, and the crystal structure of which is perovskite type; the A site of the chemical formula contains two elements of Bi and Na, and simultaneously contains any two of Ca, Sr and Ba; the B site of the chemical formula contains any two of Sn, Ti, Zr and Ce; and the elements at the A site are in equal molar ratio.

[0009] Further, the elements at the B site of the chemical formula of the high-entropy oxide ceramic are in equal molar ratio.

[0010] A preparation method of a high-entropy oxide ceramic with wave-absorbing and heat-insulating properties, characterized in that it comprises the following steps:

[0011] S1. Weigh Bi2O3 and Na2O3 powders, weigh any two of CaCO3, SrCO3 and BaCO3 powders, and weigh any two of SnO2, TiO2, ZrO2 and CeO2 powders to obtain powder raw materials;

[0012] S2. Add anhydrous ethanol and ball milling beads to the powder raw materials of step S1, and obtain a mixed powder after ball milling, drying and sieving;

[0013] S3. Calcine and tabletize the mixed powder of step S2 to obtain a cold-pressed blank;

[0014] S4. Microwave sinter the cold-pressed blank of step S3 to obtain a high-entropy oxide ceramic.

[0015] Further, the mass ratio of the powder raw materials, anhydrous ethanol and ball milling beads in step S2 is 1:(0.5-1.5):(1-2), the ball milling beads are zirconium oxide, the ball milling speed is 200-300 r / min, and the ball milling time is 6-12 h.

[0016] Further, the calcination temperature in step S3 is 600-800℃, and the calcination time is 2-6 h.

[0017] Further, the tabletizing pressure in step S3 is 10-20 MPa, and the tabletizing duration is 60-300 s.

[0018] Further, the microwave frequency in step S4 is 2.45 GHz, the sintering atmosphere is air, and the gas pressure in the sintering cavity is 0.1-0.3 MPa.

[0019] Further, the microwave sintering process in the step S4 is to first heat the microwave sintering furnace to 900 DEG C at a rate of 10 DEG C / min, and then heat to 1500-1600 DEG C at a rate of 5 DEG C / min, and after the heat preservation is over, cool to room temperature with the furnace.

[0020] The present application has the following beneficial effects: the present application proposes a high-entropy oxide ceramic with wave-absorbing and heat-insulating performance and a preparation method, and the high-entropy oxide ceramic with high wave-absorbing and heat-insulating performance is obtained by microwave sintering. Compared with the prior art, the present application greatly increases the complex structure of the crystal by simultaneously doping the A and B sites of the perovskite structure and using equimolar doping at the B site, hinders the scattering of phonons therein, and improves the heat-insulating performance at high temperatures. Secondly, the present application only dopes 4-site metal oxides at the A site of the perovskite structure, significantly improves the melting point, and strengthens the wave-absorbing performance. In addition, the traditional sintering method has the problem of uneven heating, the present application uses microwave for internal heating, the whole ceramic can be uniformly heated by controlling the heating rate, so that a high-entropy ceramic with better performance is obtained, and the sintering cost is greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0022] Figure 1 It is an XRD graph of the high-entropy perovskite material in Example 1 of the present application.

[0023] Figure 2 It is an EDS graph of the high-entropy perovskite material obtained in Example 1 of the present application.

[0024] Figure 3 It is a high-temperature thermal conductivity graph of the high-entropy perovskite material obtained in Example 1 of the present application from room temperature to 1000 DEG C.

[0025] Figure 4 It is a reflection loss graph of Example 1 of the present application under different thicknesses.

[0026] Figure 5 It is an impedance matching graph of the high-entropy perovskite material in Example 1 of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Apparently, the described embodiments are only some of the embodiments of the present application, instead of all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0028] Embodiment 1

[0029] S1. Bi2O3, Na2O3, CaCO3, SrCO3, SnO2 and TiO2 powders were weighed according to a molar ratio of 0.5:0.5:1:1:2:2 to obtain powder raw materials;

[0030] S2. Anhydrous ethanol and ball milling beads were added to the powder raw materials in step S1, and after ball milling, drying and sieving, mixed powders were obtained, the mass ratio of the powder raw materials, anhydrous ethanol and ball milling beads was 1:0.5:1, the ball milling beads were zirconium oxide, the ball milling speed was 200 r / min, and the ball milling time was 6 h;

[0031] S3. The mixed powders in step S2 were calcined at 600℃ for 2 h, and then pressed at 10 MPa for 60 s to obtain a cold-pressed blank;

[0032] S4. The cold-pressed blank in step S3 was subjected to microwave sintering, the microwave frequency was 2.45 GHz, air was used as the sintering atmosphere, the gas pressure in the sintering cavity was 0.1 MPa, the temperature was first raised to 900℃ at a rate of 10℃ / min, and then raised to 1500℃ at a rate of 5℃ / min, the holding time was 3 h, and after the holding was completed, the furnace was cooled to room temperature, and a high-entropy oxide ceramic was obtained.

[0033] After XRD, EDS, high-temperature thermal conductivity and reflection loss analysis, the results are shown in the following Figures 1-5 , a high-entropy oxide (Bi 0.25 Na 0.25 Ca 0.25 Sr 0.25 )(Ti 0.5 Sn 0.5 )O3 was successfully prepared. Under room temperature conditions, when the effective absorption was 3.12 GHz and the frequency was 9.2 GHz, the reflection loss of the high-entropy ceramic could reach 44.6 GB. The room temperature thermal conductivity was 1.19 Wm -1 K -1 , and the high-entropy ceramic had high wave absorption and heat insulation performance.

[0034] Embodiment 2

[0035] S1. Bi2O3, Na2O3, CaCO3, SrCO3, SnO2, TiO2 powders were weighed according to the molar ratio of 0.5:0.5:1:1:2:2 to obtain the powder raw material;

[0036] S2. Anhydrous ethanol and ball milling beads were added to the powder raw material of step S1, and after ball milling, drying and sieving, a mixed powder was obtained, the mass ratio of the powder raw material, anhydrous ethanol and ball milling beads was 1:1.5:2, the ball milling beads were zirconium oxide, the ball milling speed was 300 r / min, and the ball milling time was 12 h;

[0037] S3. The mixed powder of step S2 was calcined at 800℃ for 6h, and then pressed at 20MPa for 300s to obtain a cold-pressed blank;

[0038] S4. The cold-pressed blank of step S3 was subjected to microwave sintering, the microwave frequency was 2.45GHz, air was used as the sintering atmosphere, the gas pressure in the sintering cavity was 0.3MPa, the temperature was first raised to 900℃ at a rate of 10℃ / min, and then raised to 1600℃ at a rate of 5℃ / min, the holding time was 6h, and after the holding was completed, the furnace was cooled to room temperature, to obtain a high-entropy oxide ceramic.

[0039] After XRD, EDS, high-temperature thermal conductivity and reflection loss analysis, a high-entropy oxide (Bi 0.25 Na 0.25 Ca 0.25 Sr 0.25 )(Ti 0.5 Sn 0.5 )O3 was successfully prepared. -1 K -1 , with high wave absorption and heat insulation performance.

[0040] Example 3:

[0041] The steps were the same as in Example 2, except that in step S2, the mass ratio of the powder raw material, anhydrous ethanol and ball milling beads was 1:1:1.5, the ball milling speed was 250 r / min, and the ball milling time was 8h; in step S3, the calcination temperature was 700℃, the calcination time was 4h, and then pressed at 15MPa for 200s to obtain a cold-pressed blank, in step S4, the microwave sintering was first raised to 900℃ at a rate of 10℃ / min, and then raised to 1550℃ at a rate of 5℃ / min, the holding time was 4.5h. The other conditions were the same.

[0042] After XRD, EDS, high-temperature thermal conductivity and reflection loss analysis, a high-entropy oxide (Bi 0.25Na 0.25 Ca 0.25 Sr 0.25 )(Ti 0.5 Sn 0.5 )O3, under room temperature, when the thickness is 2.8mm, the effective absorption bandwidth is 3.15GHz, and the frequency is 9.1GHz, the high-entropy ceramic reflection loss can reach 40.21GB. The room temperature thermal conductivity is 1.54Wm -1 K -1 , which has high wave absorption and heat insulation performance.

[0043] Example 4:

[0044] The steps are the same as those in Example 2, except that in step S1, the oxide raw materials are bismuth oxide, sodium carbonate, strontium carbonate, barium carbonate, titanium oxide and tin oxide, and the molar ratio is 0.5:0.5:1:1:2:2.

[0045] After XRD, EDS, high-temperature thermal conductivity and reflection loss analysis, the high-entropy oxide (Bi 0.25 Na 0.25 Ba 0.25 Sr 0.25 )(Ti 0.5 Sn 0.5 )O3, under room temperature, when the thickness is 2.6mm, the effective absorption bandwidth is 3.07GHz, and the frequency is 8.78GHz, the high-entropy ceramic reflection loss can reach 39.74GB. The room temperature thermal conductivity is 2.01Wm -1 K -1 , which has high wave absorption and heat insulation performance.

[0046] Example 5:

[0047] The steps are the same as those in Example 2, except that in step S1, the oxide raw materials are bismuth oxide, sodium carbonate, strontium carbonate, barium carbonate, titanium oxide and tin oxide, and the molar ratio is 0.5:0.5:1:1:2:2.

[0048] After XRD, EDS, high-temperature thermal conductivity and reflection loss analysis, the high-entropy oxide (Bi 0.25 Na 0.25 Ca 0.25 Sr 0.25 )(Ti 0.75 Zr 0.25)O3, the high-entropy ceramic reflection loss can reach 32.41 GB under room temperature condition, with the effective absorption bandwidth of 2.54 GHz and the frequency of 9.45 GHz. The room temperature thermal conductivity is 1.71 Wm -1 K -1 , with high wave absorption and heat insulation performance.

[0049] Example 6:

[0050] The steps are the same as those in Example 2, except that in step S1, the oxide raw materials are bismuth oxide, sodium carbonate, strontium carbonate, calcium carbonate, titanium oxide and cerium oxide, and the molar ratio is 0.5:0.5:1:1:1:3. In step S4, the microwave sintering is first heated to 900℃ at a rate of 10℃ / min, and then heated to 1550℃ at a rate of 5℃ / min, and the holding time is 6h.

[0051] After XRD, EDS, high-temperature thermal conductivity and reflection loss analysis, the high-entropy oxide (Bi 0.25 Na 0.25 Ca 0.25 Sr 0.25 )(Ti 0.25 Ce 0.75 )O3 is successfully prepared. Under room temperature condition, when the thickness is 2.6mm, the effective absorption bandwidth is 6.45GHz, and the frequency is 9.45GHz, the high-entropy ceramic reflection loss can reach 34.41 GB. The room temperature thermal conductivity is 3.24 Wm -1 K -1 , with high wave absorption and heat insulation performance.

Claims

1. A high-entropy oxide ceramic possessing both wave absorption and heat insulation properties, characterized in that, The high-entropy oxide ceramic has a chemical formula of ABO3 and a perovskite crystal structure; the A site in the chemical formula of the high-entropy oxide ceramic contains Bi and Na, and simultaneously contains any two of Ca, Sr and Ba; the B site in the chemical formula of the high-entropy oxide ceramic contains any two of Sn, Ti, Zr and Ce; the elements in the A site in the chemical formula of the high-entropy oxide ceramic are in an equimolar ratio; and the elements in the B site in the chemical formula of the high-entropy oxide ceramic are in an equimolar ratio. The high-entropy oxide ceramic is obtained by microwave sintering; the microwave frequency is 2.45 GHz, the sintering atmosphere is air, and the air pressure in the sintering cavity is 0.1-0.3 MPa; the microwave sintering process is as follows: first, the microwave sintering furnace is heated at a rate of 10 ℃ / min to 900 ℃, then heated at a rate of 5 ℃ / min to 1500-1600 ℃, then kept at this temperature for 3-6 h, and then cooled to room temperature with the furnace.

2. The method for preparing high-entropy oxide ceramic with wave-absorbing and heat-insulating properties according to claim 1, characterized in that, The method comprises the following steps: S1. weighing Bi2O3 and Na2O3 powders, weighing any two of CaCO3, SrCO3 and BaCO3 powders, and weighing any two of SnO2, TiO2, ZrO2 and CeO2 powders to obtain powder raw materials; S2. adding anhydrous ethanol and ball milling beads to the powder raw materials in step S1, and obtaining a mixed powder after ball milling, drying and sieving; S3. calcining and tabletting the mixed powder in step S2 to obtain a cold-pressed blank; S4. microwave sintering the cold-pressed blank in step S3 to obtain a high-entropy oxide ceramic.

3. The preparation method of the high-entropy oxide ceramic with wave-absorbing and heat-insulating properties according to claim 2, characterized in that, In step S2, the mass ratio of the powder raw materials, anhydrous ethanol and ball milling beads is 1:(0.25-1):(1-2), the ball milling beads are zirconium oxide, the ball milling speed is 200-300 r / min, and the ball milling time is 6-12 h.

4. The preparation method of the high-entropy oxide ceramic with wave-absorbing and heat-insulating properties according to claim 2, characterized in that, In step S3, the calcination temperature is 600-800 ℃, and the calcination time is 2-6 h.

5. The preparation method of the high-entropy oxide ceramic with wave-absorbing and heat-insulating properties according to claim 2, characterized in that, In step S3, the tabletting pressure is 10-20 MPa, and the tabletting duration is 60-300 s.

Images