CN114853458B - High-entropy ceramic, preparation method thereof and application of high-entropy ceramic as electromagnetic wave absorbing material - Google Patents
High-entropy ceramic, preparation method thereof and application of high-entropy ceramic as electromagnetic wave absorbing material Download PDFInfo
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- 239000000919 ceramic Substances 0.000 title claims abstract description 61
- 239000011358 absorbing material Substances 0.000 title claims abstract description 8
- 238000002360 preparation method Methods 0.000 title abstract description 12
- 238000010521 absorption reaction Methods 0.000 claims abstract description 20
- 239000002994 raw material Substances 0.000 claims abstract description 13
- 239000011812 mixed powder Substances 0.000 claims abstract description 11
- 238000001354 calcination Methods 0.000 claims abstract description 10
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 10
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 10
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- 238000003825 pressing Methods 0.000 claims abstract description 5
- 239000000126 substance Substances 0.000 claims abstract description 4
- 238000002156 mixing Methods 0.000 claims abstract description 3
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- 238000000034 method Methods 0.000 claims description 16
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- 239000011029 spinel Substances 0.000 claims description 3
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- 230000000052 comparative effect Effects 0.000 description 6
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- 238000002441 X-ray diffraction Methods 0.000 description 2
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention belongs to the technical field of electromagnetic wave absorbing materials, and discloses high-entropy ceramic, a preparation method thereof and application of the high-entropy ceramic as an electromagnetic wave absorbing material. The chemical formula is (Fe) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 The microscopic morphology is planar and has two crystal forms: spinel-type and perovskite-type; the preparation steps are as follows: (1) Cr is the sum of the mole numbers of FeO, coO, niO, cuO and ZnO 2 O 3 Weighing the equivalent molar weight of FeO, coO, niO, cuO and ZnO in the ratio of =1 to (1-3), and weighing the powdery metal oxide raw materials FeO, coO, niO, cuO, znO and Cr in corresponding mass 2 O 3 And mixing uniformly; (2) Pressing the mixed powder prepared in the step (1) into blocks, controlling the temperature to be 1000-1400 ℃ and calcining for 6-12h, and taking out the calcined product to obtain the high-entropy ceramic. The invention prepares the high-entropy ceramics with electromagnetic wave absorption performance, and provides conditions for the practical application of the electromagnetic absorption and shielding of the high-entropy ceramics.
Description
Technical Field
The invention belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to high-entropy ceramic, a preparation method thereof and application of the high-entropy ceramic as an electromagnetic wave absorbing material.
Background
High entropy ceramics are solid solutions of inorganic compounds having one or more Wyckoff sites in which the atomic ratios of the various principal elements are equal or nearly equal. The emergence of this new family of materials presents new opportunities for material design and tailoring of properties. Unlike metallic materials, the diversity of ceramic crystal structures and electronic structures provides a huge performance tuning space for band structure engineering and phonon engineering. In addition to the strengthening, hardening and low thermal conductivity that have been found in high-entropy alloys, new characteristics such as a large dielectric constant, super ionic conductivity, excellent anisotropic thermal expansion coefficient, strong electromagnetic wave absorption, and the like have been found in high-entropy ceramics. The disordered multicomponent system in the structure occupies most of the unknown center of the phase diagram. High entropy ceramic systems soon proved useful in a wide range of technical fields, including thermal barrier coatings, thermoelectric materials, catalysts, batteries and wear and corrosion resistant coatings, lithium ion batteries, thermoelectrics, catalysts, electromagnetic wave absorption and stealth. By definition of entropy, a high entropy alloy is defined as an alloy having a configurational entropy greater than 1.5R (where R is the gas constant) when forming a random solid solution; the high entropy concept extends to high entropy ceramics, which are structurally ordered but compositionally disordered. The advent of high entropy ceramics provides more opportunities to tailor the performance of material applications and overcome bottlenecks. In addition, the grain size and morphology, the surface state and the microstructure of the high-entropy ceramic directly influence the properties and the purposes of the high-entropy ceramic. By selecting a certain preparation method, the oxide powder with a high-entropy ceramic structure and controllable chemical components can be obtained, and then the magnetism, the catalytic performance and the electromagnetic wave absorption characteristic of the high-entropy powder are adjusted and designed, so that the preparation method has very important significance for the application and development of the high-entropy ceramic in the fields of wear-resistant and corrosion-resistant materials, electromagnetic wave absorption materials and the like.
Disclosure of Invention
The invention aims to provide high-entropy ceramic, a preparation method thereof and application of the high-entropy ceramic as an electromagnetic wave absorption material.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a high-entropy ceramic characterized by: the chemical formula is (Fe) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 The microscopic appearance is planar and has two crystal forms: spinel and perovskite type。
The preparation method of the high-entropy ceramic comprises the following preparation steps:
(1) Cr is the sum of the mole numbers of FeO, coO, niO, cuO and ZnO 2 O 3 Weighing the equivalent molar weight of FeO, coO, niO, cuO and ZnO in the ratio of =1 to (1-3), and weighing the powdery metal oxide raw materials FeO, coO, niO, cuO, znO and Cr in corresponding mass 2 O 3 And mixing uniformly;
(2) Pressing the mixed powder prepared in the step (1) into blocks, controlling the temperature to be 1000-1400 ℃ and calcining for 6-12h, and taking out the calcined product to obtain the high-entropy ceramic.
Preferably, in step (1), all the metal oxide raw materials are uniformly mixed by a ball milling process.
Preferably, the ball milling process is wet ball milling: putting all the metal oxide raw materials into a ball mill together, adding ball milling beads and absolute ethyl alcohol, uniformly ball milling, and drying to obtain mixed powder.
Preferably, the mass ratio of the ball milling beads to the total amount of all metal oxide raw materials and the absolute ethyl alcohol is (1-5) to 1 to (0.5-1.5).
Preferably, the drying temperature is 50-80 deg.C, and the drying time is 3-6 h.
Preferably, in step (2), the temperature is raised to the calcination temperature at a rate of 5-10 ℃/min.
Preferably, in the step (2), the pressure during pressing is 60-100MPa, and the duration is 60-120s.
Preferably, the use of the high-entropy ceramic as claimed in claim 1 as an electromagnetic wave absorbing material.
In the invention, five metal oxides of FeO, coO, niO, cuO and ZnO are used as the general formula AB 2 O 4 Phase A of (1), cr 2 O 3 As formula AB 2 O 4 In the phase B, absolute ethyl alcohol is used as a solvent, so that elements are fully and uniformly mixed during ball milling, and the mixed elements are convenient to dry.
Has the advantages that:
(1) The invention provides high-entropy ceramic with electromagnetic wave absorption performance, wherein the micro-morphology is planar and has two crystal forms: spinel type and perovskite type, have been reported;
(2) The invention prepares the high-entropy ceramics with electromagnetic wave absorption performance, and provides conditions for the practical application of electromagnetic absorption and shielding of the high-entropy ceramics.
Drawings
FIG. 1: high entropy ceramics (Fe) obtained in example 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 XRD pattern of (a).
FIG. 2: high entropy ceramics (Fe) obtained in example 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 SEM image of (d).
FIG. 3: high entropy ceramics (Fe) obtained in example 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 Wave-absorbing performance curve.
FIG. 4: high entropy ceramics (Fe) obtained in comparative example 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 Wave-absorbing performance curve.
FIG. 5: high entropy ceramic (Mg) obtained in comparative example 2 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 Wave-absorbing performance curve.
Detailed Description
In order to make the invention clearer and clearer, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
High-entropy ceramic (Fe) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 The preparation method comprises the following steps:
(1) 0.04mol of FeO (2.874 g), 0.04mol of CoO (2.9972 g), 0.04mol of NiO (2.9876 g), 0.04mol of CuO (3.182 g), 0.04mol of ZnO (3.2564 g), and 0.2mol of Cr 2 O 3 (30.398 g) which are put into a ball mill together, 137g of ball milling beads and 35mL of absolute ethyl alcohol are added, the mixture is stirred into paste, the paste is ball milled for 8 hours at room temperature by the ball mill, the ball milled mixture is put into a drying oven to be heated to 80 ℃, and the heat preservation and the drying are carried out for 3 hours, so as to obtain mixed powder;
(2) Weighing 10g of the mixed powder prepared in the step (1), putting the mixed powder into a circular die with the diameter of 30mm, and applying the pressure of 68MPa by using a tablet press for 90s to obtain a block;
(3) And (3) putting the block obtained in the step (2) into a muffle furnace, heating to the calcination temperature of 1300 ℃ at the speed of 10 ℃/min, calcining for 6h, and taking out the calcined product to obtain the high-entropy ceramic.
The XRD pattern and the SEM pattern of the prepared high-entropy ceramic are respectively shown in figures 1 and 2, and the obtained high-entropy ceramic has two crystal forms: spinel-type and perovskite-type; the obtained high-entropy ceramic crystal grows in a plane shape.
Example 2
The difference from example 1 is that: the raw materials used in the step (1) are as follows: 0.03mol FeO (2.1555 g), 0.03mol CoO (2.2479 g), 0.03mol NiO (2.2407 g), 0.03mol CuO (2.3865 g), 0.03mol ZnO (2.4423 g), 0.15mol Cr 2 O 3 (22.7985 g), ball milling beads 103g, and absolute ethyl alcohol 26mL; otherwise, the same procedure as in example 1 was repeated.
The XRD and SEM characterization results of the high-entropy ceramic block prepared by the embodiment are the same as those of the embodiment 1.
Example 3
The difference from example 1 is that: the raw materials used in the step (1) are as follows: 0.05mol FeO (3.5925 g), 0.05mol CoO (3.7465 g), 0.05mol NiO (3.7345 g), 0.05mol CuO (3.9775 g), 0.05mol ZnO (4.0705 g), 0.25mol Cr 2 O 3 (37.9975 g), ball milling beads 172g, absolute ethyl alcohol 44mL; otherwise, the same procedure as in example 1 was repeated.
The XRD and SEM characterization results of the high-entropy ceramic block prepared by the embodiment are the same as those of the embodiment 1.
Example 4
The difference from example 1 is that: the raw materials used in the step (1) are as follows: 0.06mol FeO (4.311 g), 0.06mol CoO (4.4958 g), 0.06molmol NiO（4.4814g）、0.06mol CuO（4.773g）、0.06mol ZnO（4.8846g）、0.3mol Cr 2 O 3 (45.597 g), ball milling beads 206g, and absolute ethyl alcohol 53mL; otherwise, the same procedure as in example 1 was repeated.
The XRD and SEM characterization results of the high-entropy ceramic block prepared by the embodiment are the same as those of the embodiment 1.
Example 5
The difference from example 1 is that: the raw materials used in the step (1) are as follows: 0.07mol FeO (5.0295 g), 0.07mol CoO (5.2451 g), 0.07mol NiO (5.2283 g), 0.07mol CuO (5.5685 g), 0.07mol ZnO (5.6987 g), 0.35mol Cr 2 O 3 (53.1965 g), 240g of ball-milled beads, and 61mL of absolute ethanol; the rest of the procedure was the same as in example 1.
The XRD and SEM characterization results of the high-entropy ceramic block prepared by the embodiment are the same as those of the embodiment 1.
Comparative example 1
The difference from example 1 is that: in the step (3), the calcining temperature is changed to 1200 ℃; otherwise, the same procedure as in example 1 was repeated.
Comparative example 2
High-entropy ceramic (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 The preparation method comprises the following steps:
(1) 0.04mol of MgO (1.612 g), 0.04mol of CoO (2.9972 g), 0.04mol of NiO (2.9876 g), 0.04mol of CuO (3.182 g), 0.04mol of ZnO (3.2564 g), and 0.2mol of Cr 2 O 3 (30.398 g) which are put into a ball mill together, 133g of ball milling beads and 34mL of absolute ethyl alcohol are added, the mixture is stirred into paste, the paste is ball milled for 8 hours at room temperature by the ball mill, the ball milled mixture is put into a drying oven to be heated to 80 ℃, and the heat preservation and the drying are carried out for 3 hours, so as to obtain mixed powder;
(2) Weighing 10g of the mixed powder prepared in the step (1), putting the mixed powder into a circular die with the diameter of 30mm, and applying the pressure of 68MPa by using a tablet press for 90s to obtain a block;
(3) And (3) putting the block obtained in the step (2) into a muffle furnace, heating to the calcination temperature of 1300 ℃ at the speed of 10 ℃/min, calcining for 6h, and taking out the calcined product to obtain the high-entropy ceramic.
Study of electromagnetic wave absorption properties:
the high-entropy ceramic blocks obtained in example 1 and comparative examples 1 to 2 were used as samples, and the dielectric properties and electromagnetic properties of the materials were analyzed by a vector network analyzer (VNA, agilent N5234A,8.2 to 12.4 GHz). The specific method comprises the following steps: firstly, cutting a round block into cuboid ceramics with the length of 22.86mm and the width of 10.16mm, and accurately polishing by using an automatic polishing machine. And (3) simulating and testing the wave absorbing performance of samples with different thicknesses by using a vector network analyzer.
The wave-absorbing performance curve of the high-entropy ceramic block prepared in example 1 is shown in fig. 3, and the number in the legend represents the thickness of a sample simulated by a network vector analyzer. As can be seen from fig. 3: the high-entropy ceramic block body shows excellent electromagnetic wave absorbing performance, wherein the maximum reflection loss reaches-34.59 dB when the thickness of the wave absorbing coating is only 2.1mm, and the effective wave absorbing frequency band (the reflection loss is less than-10 dB, and the 90% of electromagnetic wave absorption is represented) reaches 4.2 GHz (8.2-12.4 GHz).
Wave-absorbing property curves of the high-entropy ceramics prepared in the comparative examples 1-2 are respectively shown in fig. 4 and 5, and the obtained high-entropy ceramics do not have effective electromagnetic wave absorption properties.
Claims (8)
1. A high-entropy ceramic applied to electromagnetic wave absorption is characterized in that: the chemical formula is (Fe) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )Cr 2 O 4 -NiCrO 3 The microscopic appearance is planar and has two crystal forms: spinel type and perovskite type.
2. A method for preparing a high-entropy ceramic for electromagnetic wave absorption according to claim 1, comprising the steps of:
(1) Cr is the sum of the mole numbers of FeO, coO, niO, cuO and ZnO 2 O 3 The weight ratio of FeO, coO, niO, cuO and ZnO is 1 to 1-3, and the raw materials of the powdery metal oxides of FeO, coO, niO, cuO, znO and Cr with corresponding mass are weighed 2 O 3 And mixing well；
(2) Pressing the mixed powder prepared in the step (1) into blocks, controlling the temperature to be 1300 ℃ and calcining for 6-12h, and taking out the calcined product to obtain the high-entropy ceramic; the pressure during pressing is 60-100MPa, and the duration is 60-120s.
3. A method for preparing a high-entropy ceramic for electromagnetic wave absorption as claimed in claim 2, wherein: in the step (1), all the metal oxide raw materials are uniformly mixed by adopting a ball milling process.
4. The method for preparing high-entropy ceramic for electromagnetic wave absorption according to claim 3, wherein the ball milling process is wet ball milling: putting all metal oxide raw materials into a ball mill together, adding ball milling beads and absolute ethyl alcohol, uniformly ball milling, and drying to obtain mixed powder.
5. A method of preparing a high-entropy ceramic for electromagnetic wave absorption as claimed in claim 4, wherein: the mass ratio of the ball milling beads to the total amount of all the metal oxide raw materials and the absolute ethyl alcohol is (1-5) to 1 to (0.5-1.5).
6. A method of preparing a high-entropy ceramic for electromagnetic wave absorption as claimed in claim 4, wherein: the drying temperature is 50-80 ℃, and the drying time is 3-6 h.
7. The method of preparing a high-entropy ceramic for electromagnetic wave absorption as claimed in claim 2, wherein: in the step (2), the temperature is raised to the calcination temperature at the speed of 5-10 ℃/min.
8. Use of the high-entropy ceramic as claimed in claim 1 as an electromagnetic wave absorbing material.
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