CN113149629A - High-temperature-resistant transition metal high-entropy oxide wave-absorbing filler and preparation method thereof - Google Patents
High-temperature-resistant transition metal high-entropy oxide wave-absorbing filler and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler and a preparation method thereof. The high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler comprises the following components: (1) spinel structure (Fe)a/(4+a)Co1/(4+a)Ni1/(4+a)Cr1/(4+a)Mn1/(4+a))3O4Wherein a is more than or equal to 1 and less than or equal to 3.5; or (2) corundum-type structure (Fe)b/(4+b)Co1/(4+b)Ni1/(4+b)Cr1/(4+b)Mn1/(4+b))2O3Wherein b is more than or equal to 5 and less than or equal to 6; or a combination of (1) + (2).
Description
Technical Field
The invention relates to a high-temperature-resistant high-entropy oxide and a preparation method thereof, in particular to a method for improving the absorption capacity of electromagnetic waves by forming single-phase or two-phase coexisting high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler by adjusting the content of component Fe, belonging to the field of high-temperature-resistant wave-absorbing materials.
Background
With the acceleration of the attack and defense conversion speed of modern war, the omnibearing stealth has become an important research target. The engine and the rear body structure are used as the most main radar scattering sources, on one hand, the radar is restricted by power conditions, and the invisible appearance has limited design scope; on the other hand, the normal temperature wave-absorbing material represented by the magnetic loss wave-absorbing material cannot be applied due to the constraint of high temperature conditions. The high-entropy oxide has excellent performances of oxidation resistance, high temperature resistance, corrosion resistance and the like, and provides a new solution for the high-temperature wave-absorbing material.
Since professor ist 2015 proved that entropy-stabilized ceramics, high-entropy ceramics became the hot direction of research. The performance of the entropy-stable material formed by multiple components can be synergistically enhanced by the multiple components, and the entropy-stable material has a wide application prospect. However, the existing high-entropy oxide is generally in a single-phase structure, so that the problems of insufficient microwave loss capacity, single loss mode and the like exist.
Disclosure of Invention
In order to solve the problems, the invention selects multiple elements of Fe, Co, Ni, Cr and Mn to form a high-temperature resistant phase with stable entropy, and forms single-phase or two-phase coexisting high-temperature resistant high-entropy oxide by adjusting the content of the element Fe, aiming at improving the dielectric loss and the wave absorbing performance of the oxide.
In a first aspect, the invention provides a high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler (or called high-temperature-resistant high-entropy oxide), which comprises the following components:
(1) spinel structure (Fe)a/(4+a)Co1/(4+a)Ni1/(4+a)Cr1/(4+a)Mn1/(4+a))3O4Wherein a is more than or equal to 1 and less than or equal to 3.5;
or (2) corundum-type structure (Fe)b/(4+b)Co1/(4+b)Ni1/(4+b)Cr1/(4+b)Mn1/(4+b))2O3Wherein b is more than or equal to 5 and less than or equal to 6;
or a combination of (1) + (2).
The two structures are very distinct in XRD pattern. In the SEM spectra, the spinel structure exhibits a pyramid-like shape, whereas the corundum-type structure exhibits a sphere-like shape.
High entropy oxides are single structures that form multiple constituents into a stable structure by means of entropy stabilization. This also makes it necessary to use formulations in which the various constituents are in equimolar proportions, thus ensuring the maximization of their configurational entropy; with the increase of Fe content, the configuration entropy thereof is gradually reduced and is not enough to stabilize the material in a single structure, so that phase separation occurs; with the further increase of the Fe content, the phase structure of the original high-entropy material is completely transformed.
Preferably, when the composition of the high-temperature-resistant high-entropy oxide is the combination of (1) + (2), the spinel structure (Fe)a/(4+a)Co1/(4+a)Ni1/(4+a)Cr1/(4+a)Mn1/(4+a))3O4: corundum type structure (Fe)b/(4+b)Co1/(4+b)Ni1/(4+b)Cr1/(4+b)Mn1/(4+b))2O3In a molar ratio of 1: (0.1 to 4), preferably 3:1 to 1: 4.
In a second aspect, the invention provides a preparation method of the high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler, which comprises the following steps: mixing water-soluble Fe salt, Co salt, Ni salt, Cr salt and Mn salt to prepare a reactant solution, wherein the molar concentration ratio of cations in the water-soluble Fe salt, the Co salt, the Ni salt, the Cr salt and the Mn salt is x:1:1:1 (x is more than or equal to 1 and less than or equal to 6); dropwise adding the reactant solution into a precipitant solution to obtain a high-entropy oxide precursor; and drying, grinding and removing moisture from the obtained high-entropy oxide precursor, sintering in air, and quenching in air to obtain the high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler.
The invention uses a wet chemical method to prepare the high-temperature-resistant high-entropy oxide, and has the advantages of simplicity, easy synthesis, stability, controllable crystal grain appearance and the like. With the increase of the content of the component Fe, the structure of the high-temperature-resistant high-entropy oxide is changed from a spinel structure to a corundum structure, and the ratio of Fe: co: ni: cr: mn ═ x:1:1:1: when the material is 1 hour (x is more than 3.5 and less than 5), obvious two-phase coexistence occurs, and the dielectric relaxation polarization and loss enhancement of the material in a microwave frequency band are generated, so that the corresponding dielectric constant is obviously improved, and the wave absorbing performance of the material is obviously improved. Wherein, when x is 4, the molar ratio of the spinel structure to the corundum structure is 1: 0.35, when x is 4.5, the molar ratio of spinel structure to corundum-type structure is 1: 3.18. by adjusting the process conditions such as the proportion of reactants, the dropping rate, the treatment temperature, the treatment time, whether tabletting or not and the like, the block or powder high-temperature-resistant high-entropy oxide can be synthesized.
Preferably, the high-temperature-resistant high-entropy oxide has good wave absorbing performance when x is 4, and can realize more than 90% of electromagnetic wave absorption within a frequency band of 15.3-17.3 GHz under the thickness of 10 mm.
Preferably, the water-soluble Fe salt is Fe (NO)3)3·9H2O、FeSO4·7H2O、Fe2(SO4)3At least one of; the Co salt is Co (NO)3)3·6H2O、CoSO4·7H2At least one of O; the Ni salt is Ni (NO)3)2·6H2O、NiSO4·6H2O、NiCl2·6H2At least one of O; the Cr salt is Cr (NO)3)3·9H2O,; the Mn salt is Mn (NO)3)2·4H2O、MnSO4·H2At least one of O.
Preferably, the total cation concentration of the reactant solution is 0.1-0.2 mol/L.
Preferably, the ratio of Fe: co: ni: cr: the molar concentration ratio of Mn cations is (3.5-4.5) 1:1:1: 1; preferably, the reactant solution has a Fe: co: ni: cr: when the molar concentration ratio of Mn cations is 4:1:1:1:1, the obtained high-temperature-resistant high-entropy oxide has a spinel structure and coexists in two phases in a corundum structure, and has higher dielectric constant and stronger wave-absorbing performance.
Preferably, theThe precipitant solution is carbonate solution, and the carbonate is K2CO3·1.5H2O、Na2CO3The molar concentration of carbonate ions in the carbonate solution is 0.15-0.3 mol/L.
Preferably, the molar concentration ratio of the cations in the reactant solution to the carbonate ions in the precipitant solution is 1 (1.5-2). If the concentration of carbonate ions is too low, excessive cations cannot be deposited, and if the concentration of carbonate ions is too high, excessive carbonate ions are wasted.
Preferably, the dropping rate of the reactant solution into the precipitant solution is 10 to 40 ml/min. Too rapid addition is detrimental to complete precipitation of the cations, especially when the subsequent addition is carried out at a point where the concentration of the corresponding carbonate ion is relatively dilute and too great an acceleration rate results in the failure to deposit a large number of cations. Too slow of dropping requires too long a time and cost.
Preferably, the temperature for removing water is 400-500 ℃ and the time is 1-5 hours. Preferably, the sintering temperature is 400-1400 ℃, and the time is 2-10 hours; preferably, the sintering process in the air is to firstly preserve heat for 1-5 hours at 400-500 ℃ and then preserve heat for 1-5 hours at 1000-1400 ℃. The sintering temperature is too low, entropy stable ceramics cannot be formed, the temperature is too high, and the crucible cannot bear rapid quenching in air, so that impurities are generated. The sintering time is too short, which is not beneficial to the full diffusion of the components and promotes the formation of the entropy stable structure. The sintering time is too long, and the time cost is high.
Preferably, the temperature rise rate of the sintering is 3-20 ℃/min. The heating rate is too low, the efficiency is low, and the time cost is too high; the temperature rise speed is too high, the requirement on a temperature rise instrument is too high, and the sintering furnace cannot bear the temperature rise speed.
Has the advantages that:
(1) the process for preparing the high-temperature-resistant high-entropy oxide with single phase or two phases coexisting by using a wet chemical method is simple and easy to implement, the manufacturing period is shortened, the used raw materials are cheap, and the production cost is greatly reduced; the prepared high-entropy oxide powder has high purity and can be directly sintered and molded.
(2) The high-entropy oxide has excellent high-temperature resistance and oxidation resistance, and the structure and the wave-absorbing performance of the high-entropy oxide are kept unchanged after the high-entropy oxide is used for 4 hours in a high-temperature environment at 1400 ℃; when the high-temperature-resistant high-entropy oxide has a structure with two phases (a spinel structure is changed into a corundum structure) coexisting, the loss capacity is increased, the dielectric constant is increased, and the wave absorption performance is improved.
Drawings
Fig. 1 is an XRD spectrum of the high-temperature-resistant high-entropy oxide powder prepared in example 1 provided by the present invention (x is 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, and 6, respectively).
FIG. 2 is an SEM spectrum of the high temperature-resistant high entropy oxide powder prepared in example 1 provided by the present invention; fig. 2 is an SEM picture of (a) a high-entropy oxide powder with x ═ 2 without high-temperature air annealing treatment; fig. 2 (b) is an SEM picture after being served for 4h in a high temperature environment of 1400 ℃ with x ═ 2; fig. 2 (c) is an SEM picture of the high-entropy oxide powder with x ═ 4 without high-temperature air annealing treatment; fig. 2 (d) is an SEM picture after being served for 4h in a high temperature environment of 1400 ℃; fig. 2 shows SEM pictures of (e) high-entropy oxide powder with x ═ 4 without high-temperature air annealing treatment; (f) is SEM picture after x is 4 and is used for 4h under 1400 deg.C high temperature environment.
FIG. 3 is an electromagnetic parameter spectrum of the high temperature-resistant high entropy oxide powder prepared in example 1 provided by the present invention; FIG. 3 (a) shows the real parts of the dielectric constants of the high-entropy oxide powders with different values of x; FIG. 3 (b) shows the imaginary dielectric constants of the high-entropy oxide powders with different x values; FIG. 3 (c) shows the real parts of the magnetic permeability of the high-entropy oxide powders with different values of x; in FIG. 3, (d) is the imaginary part of the permeability of the high-entropy oxide powder with different x values.
FIG. 4 is a wave-absorbing property spectrum of the high-temperature-resistant high-entropy oxide powder prepared in example 1.
FIG. 5 is a magnetization curve map of the high-temperature-resistant high-entropy oxide powder prepared in example 1 according to the present invention.
FIG. 6 is an XRD pattern of the high temperature-resistant high entropy oxide powder prepared under different sintering temperatures in example 2.
FIG. 7 is an XRD spectrum of the two-phase coexisting high temperature-resistant high entropy oxide powder prepared in example 3 after being processed at different high temperatures.
FIG. 8 is a spectrum of the wave-absorbing properties of the high-temperature-resistant high-entropy oxide powder with two coexisting phases prepared in example 3.
Detailed Description
The present invention is further described below in conjunction with the following embodiments, which are intended to illustrate and not to limit the present invention.
The invention adopts water-soluble Fe salt, Co salt, Ni salt, Cr salt, Mn salt and carbonate as raw material powder, and prepares the high-temperature-resistant high-entropy oxide by a wet chemical deposition method. The method for preparing the high-temperature-resistant high-entropy oxide by adjusting the content of the component Fe by using a wet chemical method provided by the invention is exemplarily illustrated as follows.
Obtaining the high-entropy oxide precursor. Dissolving water-soluble Fe salt, Co salt, Ni salt, Cr salt and Mn salt as reactants and carbonate as a precipitator in different beakers respectively, stirring uniformly, and dripping the reactant solution into the precipitator solution to obtain a primary product (namely a high-entropy oxide precursor which is a Co-precipitate of metal cations and carbonate ions). Wherein the water soluble Fe salt is selected from Fe (NO)3)3·9H2O particles, FeSO4·7H2O powder, Fe2(SO4)3And (3) powder. Co (NO) can be selected as raw material of Co salt3)3·6H2Particles of O, CoSO4·7H2And (4) O powder. The raw material of Ni salt can be selected from Ni (NO)3)2·6H2O powder, NiSO4·6H2O powder, NiCl2·6H2And (4) O powder. Cr (NO) can be selected as raw material of Cr salt3)3·9H2And (4) O particles. Mn (NO) can be selected as raw material of Mn salt3)2·4H2O particles, MnSO4·H2And (4) O powder. The raw material of carbonate can be K2CO3·1.5H2O powder, Na2CO3And (3) powder. As an example, reactants (water-soluble Fe salt, Co salt, Ni salt, Cr salt, Mn salt) are mixed in a certain molar ratio (Fe ion)Co ions, Ni ions, Cr ions, Mn ions, x:1:1:1, x is not less than 1 and not more than 6), dissolving the Co ions and the Ni ions in the same beaker, dissolving a precipitator (carbonate) in another beaker, wherein the solvent can be deionized water to obtain a reactant solution and a precipitator solution, slowly dripping the reactant solution into the precipitator solution, stirring, standing, centrifuging and filtering to obtain the high-entropy oxide precursor. When x is more than 3.5 and less than 5, the high-temperature-resistant high-entropy oxide with a spinel structure and a corundum structure coexisting can be prepared. When x is more than or equal to 1 and less than or equal to 3.5, the high-temperature-resistant high-entropy oxide with a spinel structure can be prepared. When x is more than or equal to 5 and less than or equal to 6, the high-temperature-resistant high-entropy oxide with the corundum structure can be prepared. The concentration of cations in the obtained reactant solution can be 0.1-0.2 mol/L. Precipitant (K)2CO3·1.5H2O) can be 0.15-0.3 mol/L, and the dropping speed can be 10-40 ml/min. The stirring parameters are as follows: the speed is 100-300 rpm, and the time is 1-3 h. Too slow a stirring rate, too short a stirring time, is not conducive to complete precipitation, and too fast a stirring time is likely to splash the solution. The standing time is 12 h. The parameters of filtration (centrifugation) were: the centrifugal speed is 3000-7000 r/min, and the separation time is 5-20 min. The rotating speed is too slow, the separation is difficult to be realized if the time is too short, the rotating speed is too fast, the requirement on the machine is too high if the time is too long, and the time cost is too high.
And drying, crushing and removing moisture at high temperature from the obtained high-entropy oxide precursor. As an example, the drying process may be to place the precursor in an oven at 80-100 ℃ for 8-12 hours. The pulverization can be grinding the dried sample into powder, and the average particle size of the powder can be 100-300 meshes. The high temperature water removal process may be: placing the powder in Al2O3And putting the crucible into a tube furnace, heating to 400-500 ℃ at the heating rate of 3-20 ℃/min, and preserving the heat in the air for 1-5 hours to remove water.
And quenching after sintering to obtain the high-temperature-resistant high-entropy oxide. As an example, the high-temperature-resistant high-entropy oxide can be obtained by sintering at 1000-1400 ℃ for 1-5 hours and then quenching in air. The temperature rise rate of the sintering can be 3-20 ℃/min, and the sintering is carried outThe cooling rate can be 3-20 ℃/min. Specifically, the primary product is subjected to pressureless sintering by using a tube furnace, and is subjected to heat preservation for 1-5 hours at different sintering temperatures in the air atmosphere, so that the high-temperature-resistant high-entropy oxide is prepared by sintering. As a detailed example, the reactant solution is slowly added dropwise to the precipitant solution, and after stirring, standing, filtering (centrifugal separation), drying and grinding, the obtained product is put in Al2O3And putting the crucible into a tube furnace, heating to 400-500 ℃ at a heating rate of 3-20 ℃/min, preserving heat for 1-5 hours, heating to 1000-1400 ℃ at the same rate, preserving heat for 1-5 hours, taking out a sample, and quenching in air to obtain the high-temperature-resistant high-entropy oxide. The first stage sintering is to remove moisture, and then after the first stage sintering, the powder can be pressed into a ceramic block after cooling, and then the second stage sintering is carried out, so as to directly obtain the high-entropy oxide block or powder.
The method of the invention has the advantages that: the process for preparing the high-temperature-resistant high-entropy oxide by using the wet chemical method is simple and easy to implement, the preparation period is shortened, the used raw materials are cheap, and the production cost is greatly reduced; the prepared high-entropy oxide powder has high purity and can be directly sintered and molded. The high-entropy oxide has excellent high-temperature resistance and oxidation resistance, and can be used for 4 hours in a high-temperature environment of 1400 ℃, and an XRD (X-ray diffraction) spectrum still keeps the original structure; when the molar concentration ratio of the cations in the reactants (water-soluble Fe salt, Co salt, Ni salt, Cr salt and Mn salt) is (3.5-5): 1:1:1:1, the high-temperature-resistant high-entropy oxide has two phases (spinel structure and corundum structure) coexisting, and the optimal wave-absorbing performance is obtained.
And (3) testing: the phase composition of the powder is detected by adopting an X-ray powder diffractometer, the morphological characteristics of the powder are observed by adopting a scanning electron microscope, and the electromagnetic wave parameters of the sample are tested by adopting a network vector analyzer.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art in light of the foregoing description are intended to be included within the scope of the invention.
Example 1
With Fe (NO)3)3·9H2O particles, Co (NO)3)2·6H2O particles, NiSO4·6H2O particles, Cr (NO)3)2·9H2O particles, MnSO4·H2O powder as reactant, K2CO3·1.5H2O powder is used as a precipitator and is respectively dissolved in deionized water, and the mixture is stirred until the O powder is completely dissolved, wherein the molar concentration ratio of cations (Fe ions: Co ions: Ni ions: Cr ions: Mn ions) in a reactant is x:1:1:1 (x is more than or equal to 1 and less than or equal to 6), the gradient interval of the Fe content of the components is 0.5, the total cation concentration in the reactant solution is 0.1mol/L, and the concentration of the precipitator solution is 0.15 mol/L. Dropwise adding the reactant solution into the precipitant solution at a dropwise adding rate of 40ml/min, keeping stirring for 4 hours, standing for 24 hours, pouring out supernatant, and centrifuging the precipitate (at a speed of 7000rpm) to obtain a high-entropy oxide precursor; drying the precursor in an oven (air atmosphere) at 80 deg.C for 12 hr, grinding the dried sample into powder, and placing in Al2O3And putting the crucible into a tubular furnace, heating to 450 ℃ at the heating rate of 5 ℃/min, preserving heat in the air for 2 hours, removing water, heating to 1050 ℃ at the heating rate of 5 ℃/min, preserving heat in the air for 2 hours, taking out a sample, quenching in the air, and cooling to obtain the high-temperature-resistant high-entropy oxide powder.
The XRD pattern of the prepared high-temperature-resistant high-entropy oxide powder is shown in figure 1, and it can be seen from the figure that when x is more than or equal to 1 and less than or equal to 3.5, the XRD pattern shows that the high-entropy oxide is mainly in a spinel structure; when x is more than 3.5 and less than 5, the XRD pattern shows that the high-entropy oxide is in the coexistence of two phases of a spinel structure and a corundum structure; when x is more than or equal to 5 and less than or equal to 6, an XRD (X-ray diffraction) diagram shows that the high-entropy oxide is mainly of a corundum structure.
The SEM spectrum of the prepared high-temperature-resistant high-entropy oxide powder is shown in figure 2. In fig. 2, (a) is an SEM picture of the high-entropy oxide powder with x ═ 2 without high-temperature air annealing treatment, and (b) in fig. 2 is an SEM picture of the high-entropy oxide powder with x ═ 2 after being used for 4 hours in a high-temperature environment of 1400 ℃, the SEM picture of the high-entropy oxide powder with x ═ 2 before and after high-temperature oxidation treatment has not undergone significant change, and mainly includes spinel-structured crystal grains. Wherein the grain shape and size are consistent, and after high temperature treatment, a large number of defects are eliminated, and the image is smoother and smoother. Fig. 2 (c) is an SEM picture of the high-entropy oxide powder with x ═ 4 without high-temperature air annealing treatment, fig. 2 (c) is an SEM picture of x ═ 4 after being used for 4 hours in a high-temperature environment of 1400 ℃, and the SEM picture of the high-entropy oxide powder with x ═ 4 does not undergo significant change before and after being subjected to high-temperature oxidation treatment, wherein both the spinel-structured grains and the corundum-structured grains are in a state of coexisting in a large amount. And the shape and the size of the crystal grains are basically consistent before and after high-temperature heat treatment, and a large number of defects are eliminated after the high-temperature heat treatment, so that the image is smoother and smoother. Fig. 2 shows SEM pictures of (e) high-entropy oxide powder with x ═ 6 without high-temperature air annealing treatment; in fig. 2, (f) is an SEM picture of x ═ 6 after being used for 4 hours in a high-temperature environment of 1400 ℃, and before and after the high-temperature oxidation treatment, the SEM picture of the high-entropy oxide having x ═ 6 does not undergo significant change, and the high-entropy oxide mainly contains corundum-type structural grains. And the shape and the size of the crystal grains are basically consistent before and after high-temperature heat treatment, and a large number of defects are eliminated after the high-temperature heat treatment, so that the image is smoother and smoother.
An electromagnetic parameter map of the prepared high-temperature-resistant high-entropy oxide powder is shown in fig. 3, when x is 4, the high-entropy oxide has the maximum real dielectric constant part and is stabilized at about 4.5 under the frequency of 2-18 GHz, and compared with other values of x shown in the figure, the dielectric constant of the material is obviously improved, which indicates that the material has the maximum dielectric polarization when x is 4.
The wave-absorbing performance spectrum of the prepared high-temperature-resistant high-entropy oxide powder is shown in figure 4, and the wave-absorbing performance of the high-temperature-resistant high-entropy oxide powder at the microwave frequency of 2-18 GHz is tested in figure 4. It can be seen that when the value of x is 2, 4, and 6, under the condition that the thickness of the material is 10mm, the improvement of the wave absorption performance is obvious when x is 4, and the electromagnetic wave absorption of more than 90% is realized under the frequency of 15.3 to 17.3 GHz.
The saturation magnetization spectrum of the prepared high-temperature-resistant high-entropy oxide powder is shown in fig. 5, and the maximum saturation magnetization is 40emu/g when x is 3.5.
In conclusion, when x is more than 3.5 and less than 5, the high-entropy oxide is in a two-phase coexisting structure and has larger dielectric polarization and magnetic polarization, so that larger wave-absorbing performance is obtained.
Example 2
With Fe (NO)3)3·9H2O particles, Co (NO)3)2·6H2O particles, NiSO4·6H2O particles, Cr (NO)3)2·9H2O particles, MnSO4·H2O powder as reactant, K2CO3·1.5H2And O powder is used as a precipitator and is respectively dissolved in deionized water, and the mixture is stirred until the O powder is completely dissolved, wherein the molar concentration ratio of cations in the reactant is 1:1:1:1, the total concentration of the cations in the reactant solution is 0.1mol/L, and the concentration of the precipitator solution is 0.15 mol/L. Dropwise adding the reactant solution into the precipitant solution at a dropwise adding rate of 40ml/min, keeping stirring for 4 hours, standing for 24 hours, pouring out supernatant, and performing centrifugal filtration (at a speed of 7000rpm) on the precipitate to obtain a high-entropy oxide precursor; drying the precursor in an oven (air atmosphere) at 80 deg.C for 12 hr, grinding the dried sample into powder, and placing in Al2O3Putting the crucible into a tube furnace, heating to 450 ℃ at the heating rate of 5 ℃/min, and preserving the heat in the air for 2 hours to remove the moisture; dividing the sample into three parts, heating to 700 deg.C, 800 deg.C and 1050 deg.C at a heating rate of 5 deg.C/min, respectively, keeping the temperature in the air for 2 hr, taking out the sample, quenching in the air, cooling to obtain the final product (Fe)0.2Co0.2Ni0.2Cr0.2Mn0.2)3O4High entropy oxide powder.
Prepared (Fe)0.2Co0.2Ni0.2Cr0.2Mn0.2)3O4The XRD pattern of the high-entropy oxide powder is shown in FIG. 6, which shows that when x is 1, the second stage of the high-entropy oxide isThe sintering temperature can be at least 700 ℃ at the lowest.
Example 3
With Fe (NO)3)3·9H2O particles, Co (NO)3)2·6H2O particles, NiSO4·6H2O particles, Cr (NO)3)2·9H2O particles, MnSO4·H2O powder as reactant, K2CO3·1.5H2And O powder is used as a precipitator and is respectively dissolved in deionized water, and the mixture is stirred until the O powder is completely dissolved, wherein the molar concentration ratio of cations in the reactant is 4:1:1:1, the total cation concentration in the reactant solution is 0.1mol/L, and the concentration of the precipitator solution is 0.15 mol/L. Dropwise adding the reactant solution into the precipitant solution at a dropwise adding rate of 40ml/min, keeping stirring for 4 hours, standing for 24 hours, pouring out supernatant, and performing centrifugal separation (at a speed of 7000rpm) on the precipitate to obtain a high-entropy oxide precursor; drying the precursor in an oven (air atmosphere) at 80 deg.C for 12 hr, grinding the dried sample into powder, and placing in Al2O3And putting the crucible into a tubular furnace, heating to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat in the air for 2 hours, removing the water, heating to 1050 ℃ at the heating rate of 5 ℃/min, preserving the heat in the air for 2 hours, taking out a sample, quenching in the air, and cooling to obtain the high-temperature-resistant high-entropy oxide powder with two coexistent phases. Dividing the sample into two parts, respectively placing the two parts in a tube furnace at 700 ℃ and 1400 ℃ for high-temperature treatment in air for 4 hours, wherein the heating rate and the cooling rate are both 5 ℃/min, and after cooling, obtaining high-temperature-resistant high-entropy oxide powder with two coexisting phases after the high-temperature treatment.
The XRD spectrum of the two-phase coexisting high-temperature-resistant high-entropy oxide powder prepared in this example is shown in fig. 7, and it can be seen from the XRD spectrum that after the high-entropy oxide powder with x ═ 4 is oxidized at 700 ℃ and 1400 ℃ in air for 4 hours, the XRD crystal form of the high-entropy oxide powder does not change significantly, indicating that it has better high-temperature-resistant and oxidation-resistant properties.
The spectrum of the wave-absorbing property of the two-phase coexisting high-temperature-resistant high-entropy oxide powder prepared in the embodiment is shown in fig. 8, and the electromagnetic wave absorption properties of the powder after being subjected to high-temperature oxidation treatment for 4 hours in untreated air at 700 ℃ and after being subjected to high-temperature oxidation treatment for 4 hours in air at 1400 ℃ are respectively tested under the condition of the thickness of 10 mm. The microwave-absorbing material shows consistent microwave-absorbing performance, and shows that the microwave-absorbing material has very good application prospect in the field of high-temperature microwave absorption.
Table 1 shows the raw materials and experimental conditions used for the high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler prepared in examples 1 to 3 of the present invention:
Claims (10)
1. the high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler is characterized by comprising the following components in percentage by weight:
(1) spinel structure (Fe)a/(4+a)Co1/(4+a)Ni1/(4+a)Cr1/(4+a)Mn1/(4+a))3O4Wherein a is more than or equal to 1 and less than or equal to 3.5;
or (2) corundum-type structure (Fe)b/(4+b)Co1/(4+b)Ni1/(4+b)Cr1/(4+b)Mn1/(4+b))2O3Wherein b is more than or equal to 5 and less than or equal to 6;
or a combination of (1) + (2).
2. The high temperature resistant transition metal high entropy oxide wave absorbing filler of claim 1, wherein when the high temperature resistant transition metal high entropy oxide wave absorbing filler is a combination of (1) + (2), the spinel structure (Fe)a/(4+a)Co1/(4+a)Ni1/(4+a)Cr1/(4+a)Mn1/(4+a))3O4: corundum type structure (Fe)b/(4+b)Co1/(4+b)Ni 1/(4+b)Cr1/(4+b)Mn1/(4+b))2O3In a molar ratio of 1: (0.1-4).
3. A method for preparing a high temperature resistant transition metal high entropy oxide wave absorbing filler as claimed in any of claims 1 or 2, comprising:
mixing water-soluble Fe salt, Co salt, Ni salt, Cr salt and Mn salt to prepare a reactant solution, wherein the molar concentration ratio of cations in the water-soluble Fe salt, the Co salt, the Ni salt, the Cr salt and the Mn salt is x:1:1:1, and x is more than or equal to 1 and less than or equal to 6;
dropwise adding the reactant solution into a precipitant solution to obtain a high-entropy oxide precursor;
and drying, grinding and removing moisture from the obtained high-entropy oxide precursor, sintering in air, and quenching in air to obtain the high-temperature-resistant transition metal high-entropy oxide wave-absorbing filler.
4. The method according to claim 3, wherein the water-soluble Fe salt is Fe (NO)3)3‧9H2O、 FeSO4‧7H2O、Fe2(SO4)3At least one of; the Co salt is Co (NO)3)3‧6H2O、CoSO4·7H2At least one of O; the Ni salt is Ni (NO)3)2‧6H2O、NiSO4‧6H2O、NiCl2‧6H2At least one of O; the Cr salt is Cr (NO)3)3‧9H2O; the Mn salt is Mn (NO)3)2‧4H2O、MnSO4‧H2At least one of O.
5. The preparation method according to claim 3 or 4, wherein the total cation concentration of the reactant solution is 0.1-0.2 mol/L; preferably, the molar concentration ratio of Fe, Co, Ni, Cr and Mn cations in the reactant solution is (3.5-4.5) to 1:1:1: 1; preferably, the reactant solution has a Fe: co: ni: cr: the molar concentration ratio of the Mn cations is 4:1:1:1: 1.
6. The method according to any one of claims 3 to 5, wherein the precipitant solution is a carbonate solution, and the carbonate is K2CO3‧1.5H2O、Na2CO3The molar concentration of carbonate ions in the carbonate solution is 0.15-0.3 mol/L.
7. The method according to any one of claims 3 to 6, wherein the molar concentration ratio of the cation in the reactant solution to the carbonate ion in the precipitant solution is 1 (1.5-2).
8. The method according to any one of claims 3 to 7, wherein the dropping rate of the reactant solution into the precipitant solution is 10 to 40 ml/min.
9. The method according to any one of claims 3 to 8, wherein the temperature for removing water is 400 to 500 ℃ for 1 to 5 hours.
10. The method according to any one of claims 3 to 9, wherein the sintering temperature is 400 to 1400 ℃ for 2 to 10 hours; preferably, the sintering is performed by firstly preserving heat at 400-500 ℃ for 1-5 hours and then preserving heat at 1000-1400 ℃ for 1-5 hours.
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