CN114436656A - High-entropy silicate ceramic with low thermal conductivity and high thermal stability and preparation method and application thereof - Google Patents

High-entropy silicate ceramic with low thermal conductivity and high thermal stability and preparation method and application thereof Download PDF

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CN114436656A
CN114436656A CN202210112836.5A CN202210112836A CN114436656A CN 114436656 A CN114436656 A CN 114436656A CN 202210112836 A CN202210112836 A CN 202210112836A CN 114436656 A CN114436656 A CN 114436656A
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贺定勇
欧克
郭星晔
崔丽
周正
谈震
吴旭
邵蔚
王国红
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Beijing University of Technology
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Abstract

The invention relates to a high-entropy silicate ceramic with low thermal conductivity and high thermal stability, and a preparation method and application thereof. The chemical formula of the high-entropy ceramic material is RE2Si2O7Wherein RE can be any four rare earth elements of Er, Sc, Lu, Yb or Tm. The preparation method comprises the following steps: with four REs2O3Powder and pure SiO2The method comprises the following steps of mixing powder serving as a raw material and acetone or absolute ethyl alcohol serving as a mixing medium by using a high-energy ball mill, drying, grinding and screening the fully mixed powder, selecting screened fine powder, calcining at 1500-1600 ℃ to synthesize a high-entropy ceramic material, and preparing compact bulk ceramic by adopting a discharge plasma sintering method. The density of the prepared ceramic block can reach more than 98 percent, and the material is measuredHas very low thermal conductivity, and the thermal conductivity is less than 1.1W/m.K in the range of room temperature to 1000 ℃, and can be used as heat-proof and heat-insulating material.

Description

High-entropy silicate ceramic with low thermal conductivity and high thermal stability, and preparation method and application thereof
Technical Field
The invention relates to the technical field of high-entropy ceramic materials, in particular to a high-entropy silicate ceramic with extremely low thermal conductivity and high thermal stability, and a preparation method and application thereof.
Background
The material design concept of the multi-principal-element high-entropy alloy is that by introducing multiple (usually five or more) elements with the same components, the atomic percentage of each element is 5-35%, so that the alloy has the thermodynamic high-entropy effect, the retarded diffusion effect, the lattice distortion effect, the cocktail effect and the like, and excellent performance is obtained. By taking the design concept of the high-entropy regulation and control into account, the high-entropy ceramic material comes from the birth, and the stable single phase (Mg) is successfully synthesized for the first time in 2015 by the Rost and the like0.2Zn0.2Cu0.2Co0.2Ni0.2) O high-entropy ceramics. Since then, high-entropy ceramic materials of different compositions and structures have begun to be widely noticed by the academic world, high-entropy ceramics such as borides, carbides, fluorites, spinels, perovskites, monosilicates, magnetoplumbites, pyrochlores and the like have been successfully prepared, and the obtained high-entropy ceramics tend to show unique properties such as a lower thermal expansion coefficient, a lower thermal conductivity, a higher elastic modulus, a higher dielectric constant and the like.
Common rare earth silicates are rare earth monosilicates (RE)2SiO5) And pyrosilicates (RE)2Si2O7) Structures of respectively rare earth oxides (RE)2O3) And silicon dioxide (SiO)2) Is prepared according to the proportion of 1: 1 and 1: 2. Since the 4f orbital electron of the rare earth element has a special filling state, when the electron transits between different energy levels, the rare earth silicate shows a plurality of unique physicochemical properties, so that the rare earth silicate is widely applied to the fields of optics, magnetics and electrics. In addition, the rare earth pyrosilicate has high melting point, lower thermal conductivity, good high-temperature water corrosion resistance, thermal expansion coefficient and ceramic matrix compoundingThe material (CMC) is relatively close and the like, and has good application prospect in the aerospace field as the environmental barrier coating of the CMC.
The phase structure composition and evolution of the high-entropy rare earth pyrosilicate are very complex, and the rare earth comprises 17 elements such as Sc, Y, La-Lu and the like, so that various pyrosilicate crystal structures can be formed. Wherein, Sc, Lu, Yb and Tm only have a single beta phase, have stable structure and belong to a monoclinic system; the pyrosilicate formed by La-Nd and other elements has two different phase structures of A and G, wherein the A phase is a tetragonal system, and the G phase is a monoclinic system; sm2Si2O7There are A, G and F three phase structures, where the F phase is triclinic; eu (Eu)2Si2O7F, A, alpha and delta structures exist, wherein alpha phase is a triclinic system, and delta phase is an orthorhombic system; gd. Pyrosilicates of Tb and Dy only have alpha and delta phase structures; y is2Si2O7And Ho2Si2O7There are four phases, α, β, γ and δ, where γ is monoclinic; er2Si2O7There are three structures, α, β and γ. There are studies showing YxYb(2-x)Si2O7、YxLu(2-x)Si2O7、YxSc(2-x)Si2O7Can form stable crystal structure, when the value of x is less than 1.1, 1.1 and 1.7, the crystal can maintain single beta phase structure from room temperature to 1700 ℃, and conversely, the crystal undergoes the phase transition process of beta → gamma → delta along with the increase of temperature. Furthermore, there are studies showing Sc2Si2O7And Lu2Si2O7Can be completely mutually dissolved and can form a single beta phase structure. Pyrosilicates composed of more than two rare earth elements are rarely reported at present.
Disclosure of Invention
The object of the present invention is to provide a high-entropy silicate ceramic having extremely low thermal conductivity and high thermal stability.
In a first aspect, the invention provides a multi-element high-entropy ceramic, wherein the chemical formula of the multi-element high-entropy ceramic is
Figure BDA0003495357960000021
RE may be any four rare earth elements of Er, Sc, Lu, Yb or Tm, where w + x + y + z is 1.
In the multi-element high-entropy ceramic provided by the invention, the rare earth element is rare earth oxide Sc2O3、 Yb2O3、Lu2O3、Tm2O3Or Er2O3In any four combinations, the four rare earth oxides each comprise the rare earth oxide RE in molar ratio2O320-30% of the total amount; preferably, the four rare earth oxides each comprise the rare earth oxide RE in terms of mole ratios2O325% of the total amount.
In a second aspect, the invention provides a preparation method of a low-thermal-conductivity high-entropy rare earth silicate ceramic, which comprises the following steps:
(1) with RE2O3Powder and SiO2The powder is taken as a raw material, RE is any four elements of Er, Sc, Lu, Yb or Tm, in terms of molar ratio,
Figure BDA0003495357960000034
Figure BDA0003495357960000035
(2) fully mixing and crushing the ceramic powder by using acetone or absolute ethyl alcohol as a mixing medium by using a high-energy ball mill for 24-48 hours;
(3) drying, grinding and screening the fully mixed powder, selecting fine powder with the particle size of below 500-800 meshes, calcining the fine powder at the temperature of 1500-1600 ℃ without pressure, cooling, crushing and grinding the calcined ceramic to obtain the ceramic
Figure BDA0003495357960000032
A high entropy ceramic powder material;
(4)
Figure BDA0003495357960000033
the block material of high-entropy ceramic adopts discharge plasma sintering methodThe preparation method comprises the steps of sintering at 1250-1400 ℃, heating at 100 ℃/min, vacuum at 5-10 Pa, pressure at 50-100 MPa, and heat preservation for 5-10 minutes, so that the compact block high-entropy ceramic can be obtained.
In the preparation method of the low-thermal-conductivity high-entropy rare earth silicate ceramic provided by the invention, SiO2And rare earth oxide RE2O3The purity of the powder is more than or equal to 99.99 wt.%, and the granularity of the original powder is less than 10 μm.
In the preparation method of the low-thermal-conductivity high-entropy rare earth silicate ceramic, in the step (3), after high-temperature pressureless calcination and furnace cooling to 1100-1300 ℃, the high-thermal-conductivity high-entropy rare earth silicate ceramic and a crucible are taken out and placed in an air environment for air cooling, or compressed air is used for forced air cooling, and the cooling speed is accelerated to reduce diffusion and segregation of rare earth elements in silicate.
In the preparation method of the low-thermal-conductivity high-entropy rare earth silicate ceramic, the pressureless calcination process is carried out in the atmosphere of normal pressure air, and the spark plasma sintering is carried out in the atmosphere of low pressure of 5-10 Pa.
As a specific embodiment mode of the invention, the preparation method of the low-thermal-conductivity high-entropy rare earth silicate ceramic provided by the invention comprises the following steps:
(1) the selection and the proportion of the raw materials are as follows: with rare earth oxide RE2O3Powder and SiO2The powder is taken as a raw material, RE is any four elements of Er, Sc, Lu, Yb or Tm, wherein four RE elements are2O3Powder and pure SiO2The molar ratio of the powder is (0.8-1.2): (6.4-9.6) configuration
Figure BDA0003495357960000041
Figure BDA0003495357960000042
Approximately 1: 8). Selected rare earth oxides RE2O3And SiO2The purity of the powder is more than or equal to 99.99 wt.%, and the granularity of the original powder is less than 10 μm.
(2) Mixing and crushing of powder: and (2) taking absolute ethyl alcohol or acetone as a mixed medium, taking agate grinding balls as a ball milling medium, putting the mixture into a ball milling tank according to the ball-material ratio of 3: 1, fully mixing and crushing the ceramic powder by using a high-energy ball mill, wherein the rotating speed of the ball mill is 400-600 r/min, and the mixing time is 24-48 hours.
(3) Drying and crushing powder: and (3) putting the fully mixed powder into an oven for drying, removing absolute ethyl alcohol, drying at 160-180 ℃, grinding and screening the dried powder, selecting fine powder with the particle size of below 800 meshes, and performing high-temperature calcination in the next step.
(4) High-temperature solid-phase reaction synthesis of high-entropy powder: placing the mixed powder into a crucible, calcining the mixed powder under the normal pressure air environment and the temperature of 1500-1600 ℃ under no pressure, preserving the heat for 4-6 hours, cooling the mixed powder to 1100 ℃ along with a furnace, crushing and grinding the calcined blocks after cooling to obtain the high-purity calcium oxide powder
Figure BDA0003495357960000044
High entropy ceramic powder material.
(5) Preparing high-entropy block ceramic: preparation of high-entropy ceramics by spark plasma sintering method
Figure BDA0003495357960000043
The sintering temperature of the block material is 1250-1400 ℃, the heating rate is 100 ℃/min, the vacuum degree is 5-10 Pa, the pressure is 50-100 MPa, and the heat preservation time is 5-10 minutes, so that the compact block high-entropy ceramic can be obtained.
And measuring the density of the high-entropy rare earth silicate ceramic block material by adopting a drainage method or a microstructure photo image analysis method, wherein the measured density of the block material is more than 98%.
The thermal diffusion coefficient of the block ceramic at different temperatures is measured by adopting a laser flash method, and the specific heat capacity of the block ceramic at different temperatures is measured by adopting a differential scanning calorimetry analyzer. And multiplying the measured thermal diffusion coefficient, specific heat capacity and density of the high-entropy ceramic to obtain the thermal conductivity of the prepared high-entropy block material, wherein the thermal conductivity is lower than 1.1W/m/K within the range from room temperature to 1000 ℃.
According to the understanding of the technical personnel in the field, the invention requests to protect the application of the multi-element high-entropy ceramics in the preparation of heat insulation materials or high-density ceramic blocks.
According to the high-entropy rare earth silicate provided by the invention, a plurality of rare earth elements are added according to equal atomic ratio, so that great lattice distortion and structural disorder degree can be introduced, and chemical bonds of the high-entropy rare earth silicate are highly non-uniform, so that a silicate material with lower thermal conductivity is expected to be obtained, and the high-entropy rare earth silicate can be used as a thermal protection material in the fields of aerospace and the like.
The high-entropy rare earth disilicate ceramic material with a beta-phase stable structure is prepared, a block material with higher density is prepared by adopting a spark plasma sintering method, and researches show that the obtained block material has the characteristic of low thermal conductivity and can be used as a thermal protection material.
The invention has the beneficial effects that:
(1) rare earth oxide Sc selected by the invention2O3、Yb2O3、Lu2O3、Tm2O3With SiO2Can synthesize beta-phase (monoclinic system) pyrosilicate Sc2Si2O7、Yb2Si2O7、 Lu2Si2O7Or Tm2Si2O7The material keeps a stable single-phase state from room temperature to the melting point (about 1800-2000 ℃), and Er2O3Can form stable beta-phase pyrosilicate within the temperature range of 1050-1300 ℃.
(2) The high-entropy rare earth silicate powder prepared by the invention is cooled to 1050-1300 ℃ in the pressureless calcination process, and then is rapidly cooled to room temperature from the temperature range, so that the diffusion and segregation of rare earth elements in silicate are reduced, and the material can be ensured to keep a beta-phase crystal structure.
(3) The high-entropy ceramic prepared by the invention has few raw material types, and only needs 5 oxide materials, wherein the oxide materials contain four rare earth oxides and silicon dioxide. The basic design principle of the high-entropy ceramic material (namely, five or more main elements) can be met, and the complexity of the material is reduced as much as possible, so that the uncertainty of the material synthesis process is greatly reduced, and the risk of generating byproducts is reduced.
(4) The high-entropy ceramic material prepared by the invention can be prepared into a ceramic block material with higher density, and the block ceramic has lower thermal conductivity and can be used as a thermal protection material.
Drawings
FIG. 1 shows (Er) synthesized in the examples of the present invention0.25Sc0.25Lu0.25Yb0.25)2Si2O7X-ray diffraction pattern of the powder of (4).
FIG. 2 shows the (Er) synthesized in example 2 of the present invention0.25Sc0.25Tm0.25Yb0.25)2Si2O7The Scanning Electron Microscope (SEM) morphology of the spark plasma sintered bulk sample.
FIG. 3 shows (Er) synthesized in example 3 of the present invention0.25Sc0.25Lu0.25Yb0.25)2Si2O7The thermal conductivity of the spark plasma sintered block sample is plotted as a function of temperature.
FIG. 4 shows the use of holmium oxide (Ho) in comparative example 1 according to the present invention2O3) Erbium oxide (Er)2O3) Scandium oxide (Sc)2O3) Ytterbium oxide (Yb)2O3) Lutetium oxide (Lu)2O3) Silicon dioxide (SiO)2) And (5) SEM topography of the fired ceramic block.
Fig. 5 is an elemental distribution diagram of the area photographed in comparative example 1 and corresponding to fig. 4 according to the present invention, measured by an energy spectrometer (EDS) of SEM.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
The embodiment provides a preparation method of high-entropy silicate ceramic with extremely low thermal conductivity and high thermal stability. In this example, erbium oxide (Er) was used as the raw material2O3) Scandium oxide (Sc)2O3) Ytterbium oxide (Yb)2O3) Lutetium oxide (Lu)2O3) Silicon dioxide (SiO)2) The powders were all 99.99 wt.% pure, with the following particle size ranges: er2 O 3 3～5μm，Sc2O3 3～8μm，Yb2O3 3～5μm，Lu2Ｏ3 3～8μm，SiＯ 2 1～5μm。
The preparation method provided by the embodiment comprises the following steps:
taking Er2Ｏ338.2 g, Sc2Ｏ313.8 g, Yb2Ｏ339.4 g, Lu2Ｏ339.8 g, SiO248 g, and mixing.
Acetone is used as a wet mixing medium, the powder and the acetone are added into a polytetrafluoroethylene ball milling tank, 530 g of grinding balls with different diameters are placed into the polytetrafluoroethylene ball milling tank for ball milling for 24 hours, and the rotating speed of the ball mill is 500 r/min.
And (3) putting the mixed powder into a drying box, drying at 180 ℃, taking out the dried powder, grinding and crushing the dried powder, sieving the powder on a 500-mesh vibrating screen, taking the sieved powder, and continuously grinding and crushing the sieved powder until the particle size requirement is met. Then putting the dried powder into a high-temperature furnace, carrying out pressureless calcination in an air environment, heating at the speed of 10 ℃/min, keeping the calcination temperature at 1550 ℃, cooling to 1200 ℃ along with the furnace after keeping the temperature for 4 hours, then taking out the powder together with a crucible, and forcibly cooling the Er (Er) which is fired into a ceramic block by using compressed air0.25Sc0.25Lu0.25Yb0.25)2Si2O7High entropy ceramics.
(Er) obtained in example0.25Sc0.25Lu0.25Yb0.25)2Si2O7The powder was subjected to X-ray diffraction, a schematic diagram of which is shown in FIG. 1.
Example 2
The embodiment provides a preparation method of high-entropy silicate ceramic with extremely low thermal conductivity and high thermal stability. In this example, erbium oxide (Er) was used as the raw material2O3) Scandium oxide (Sc)2O3) Ytterbium oxide (Yb)2O3) Thulium oxide (Tm)2O3) Silicon dioxide (SiO)2) The powders were all 99.99 wt.% pure, with the following particle size ranges: er2 O 33～5μm，Sc2O3 3～8μm，Yb2O33～5μm，Lu2O3 3～8μm，SiO 2 1～5μm。
The preparation method provided by the embodiment comprises the following steps:
taking Er2O338.2 g, Sc2O313.8 g, Yb2O339.4 g, Tm2O338.6 g, SiO248 g, and mixing. The method comprises the steps of adopting absolute ethyl alcohol as a wet mixing medium, putting powder and the absolute ethyl alcohol into a polytetrafluoroethylene ball milling tank, and putting about 530 g of grinding balls with different diameters for ball milling, wherein the rotating speed of the ball mill is 400 r/min, and the ball milling time is 48 hours.
And (3) putting the mixed powder into a drying box, drying at 160 ℃, taking out the dried powder, grinding and crushing the dried powder, sieving the powder on a 500-mesh vibrating screen, taking the sieved powder, and continuously grinding and crushing the sieved powder until the particle size requirement is met. And then putting the dried powder into a high-temperature furnace, carrying out pressureless calcination in an air environment, heating at the speed of 10 ℃/min, keeping the temperature at 1500 ℃, cooling to 1100 ℃ along with the furnace after keeping the temperature for 6 hours, then taking out the powder, and forcibly cooling the high-entropy ceramic by using compressed air.
Crushing the prepared high-entropy ceramic block, grinding and sieving the high-entropy ceramic block into powder with the particle size of less than 100 mu m, putting the powder into a graphite mold, sintering the powder in a discharge plasma sintering furnace, wherein the sintering temperature is 1300 ℃, the average temperature rise speed is 100 ℃/min, the vacuum degree is 5Pa, the pressure is 50MPa, the heat preservation time is 6 minutes, and cooling the sintered powder to the room temperature along with the furnace after the sintering is finished to obtain a block body (Er) with the density of 98.56 percent0.25Sc0.25Tm0.25Yb0.25)2Si2O7The microstructure of the high-entropy ceramic is shown in figure 2.
Example 3
The embodiment provides a preparation method of high-entropy silicate ceramic with extremely low thermal conductivity and high thermal stability. In this example, erbium oxide (Er) was used as the raw material2O3) Scandium oxide (Sc)2O3) Ytterbium oxide (Yb)2O3) Lutetium oxide (Lu)2O3) Silicon dioxide (SiO)2) The powders were all 99.99 wt.% pure, with the following particle size ranges: er2 O 33～5μm，Sc2O3 3～8μm，Yb2O3 3～5μm，Lu2O3 3～8μm，SiO 2 1～5μm。
The preparation method provided by the embodiment comprises the following steps:
taking Er2O329.85 g, Sc2O310.35 g Yb2O328.65 g, Lu2O329.55 g, SiO236 g were mixed. The method comprises the steps of adopting absolute ethyl alcohol as a wet mixing medium, putting powder and the absolute ethyl alcohol into a polytetrafluoroethylene ball milling tank, putting about 400 g of grinding balls with different diameters, and carrying out ball milling for 24 hours, wherein the rotating speed of the ball mill is 500 r/min. And then putting the mixed powder into a drying box for drying at the drying temperature of 180 ℃ for 8 hours, taking out the dried powder, grinding and crushing the powder, sieving the powder on a 500-mesh vibrating screen, taking the sieved powder, and continuously grinding and crushing the sieved powder until the powder meets the requirement of granularity. And putting the dried powder into a high-temperature furnace, carrying out pressureless calcination in an air environment, heating at the speed of 10 ℃/min, keeping the calcination temperature at 1600 ℃, cooling to 1100 ℃ along with the furnace after keeping the temperature for 6 hours, then taking out the powder, and forcibly cooling the high-entropy ceramic which is fired into the ceramic block by using compressed air.
Crushing and grinding the pressureless calcined high-entropy ceramic, screening powder with the particle size of less than 100 mu m, putting the powder into a graphite die, sintering in a discharge plasma sintering furnace, wherein the sintering temperature is 1250 ℃, the average temperature rise speed is 100 ℃/min, the vacuum degree is 5Pa, the pressure is 50MPa, the heat preservation time is 6 minutes, and furnace cooling is carried out after sintering to the room temperature, so that compact (Er) can be obtained0.25Sc0.25Lu0.25Yb0.25)2Si2O7High entropy ceramic blocks.
Test the above (Er)0.25Sc0.25Lu0.25Yb0.25)2Si2O7The thermal conductivity of the high-entropy ceramic block material obtains a curve of the thermal conductivity along with the temperature change as shown in figure 3.
The results of the above examples show that the present invention utilizes Sc, Lu, Yb, Tm and SiO2Can form a single stable beta phase, fully utilizes the design configuration strategy of the high-entropy material, and selects four elements of Sc, Lu, Yb, Tm or Er to form
Figure BDA0003495357960000091
High entropy ceramic powder material. The preparation process of the material is simple, the phase components of the synthesized product are easy to control, and the prepared block material has very low thermal conductivity, so that a new method is provided for designing and preparing high-performance thermal protection coatings and structural materials.
Comparative example 1
This comparative example is intended to attempt to prepare a five-membered high-entropy rare earth silicate (Ho) using five different rare earth oxides0.02Er0.2Sc0.2Lu0.2Yb0.2)2Si2O7However, after similar preparation processes, the prepared ceramic material is relatively seriously biased, and a uniform high-entropy ceramic material is difficult to prepare, as shown in fig. 4, as can be seen from comparison with fig. 2, the structure of fig. 4 is very uneven, and the synthesis of the high-entropy ceramic material is difficult to ensure.
In this example, the raw material used was holmium oxide (Ho)2O3) Erbium oxide (Er)2O3) Scandium oxide (Sc)2O3) Ytterbium oxide (Yb)2O3) Lutetium oxide (Lu)2O3) Silicon dioxide (SiO)2) The powders were all 99.99 wt.% pure, with the following particle size ranges: ho2O3 3～5μm， Er2O3 3～5μm，Sc2O3 3～8μm，Yb2O3 3～5μm，Lu2O3 3～8μm，SiO 21 to 5 μm. The five rare earth oxides and the silicon dioxide are mixed according to the molar ratio of 1: 10.
The preparation method provided by the embodiment comprises the following steps:
ho taking2O337.8 g, Er2O338.2 g, Sc2O313.8 g, Yb2O339.4 g, Lu2O339.8 g, SiO260 g, and mixing. Acetone is used as a wet mixing medium, the powder and the acetone are added into a polytetrafluoroethylene ball milling tank, about 680 g of grinding balls with different diameters are placed into the polytetrafluoroethylene ball milling tank for ball milling for 24 hours, and the rotating speed of the ball mill is 500 r/min. And (3) putting the mixed powder into a drying box, drying at 180 ℃, taking out the dried powder, grinding and crushing the dried powder, sieving the powder on a 500-mesh vibrating screen, taking the sieved powder, and continuously grinding and crushing the sieved powder until the particle size requirement is met. And then putting the dried powder into a high-temperature furnace, carrying out pressureless calcination in an air environment, heating at the speed of 10 ℃/min, keeping the temperature at 1600 ℃, cooling to 1100 ℃ along with the furnace after keeping the temperature for 4 hours, then taking out the powder together with the crucible, and carrying out forced cooling by using compressed air.
And crushing the prepared ceramic block, grinding and screening the ceramic block into powder with the particle size of less than 100 mu m, putting the powder into a graphite mold, putting the powder into a discharge plasma sintering furnace for sintering, wherein the sintering temperature is 1300 ℃, the average temperature rise speed is 100 ℃/min, the vacuum degree is 5Pa, the pressure is 50MPa, the heat preservation time is 6 minutes, and cooling the ceramic block to the room temperature along with the furnace after the sintering is finished to obtain the block ceramic prepared by the method. The microstructure of the scanning electron microscope is shown in fig. 4, and the element distribution corresponding to fig. 4 is shown in fig. 5.
The comparison example shows that the rare earth oxide with 5-element or more than 5-element is easy to cause element segregation and is not beneficial to the synthesis of the high-entropy ceramic material. Therefore, the method for preparing the ceramic by adopting the 4 kinds of rare earth oxides and the silicon dioxide is more beneficial to synthesizing target high-entropy ceramic.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (9)

1. The multielement high-entropy ceramic is characterized in that the chemical formula of the multielement high-entropy ceramic is
Figure FDA0003495357950000011
RE may be any four rare earth elements of Er, Sc, Lu, Yb or Tm, where w + x + y + z is 1.
2. The multi-element high-entropy ceramic of claim 1, wherein the rare earth element is a rare earth oxide Sc2O3、Yb2O3、Lu2O3、Tm2O3Or Er2O3In any four combinations, the four rare earth oxides each comprise the rare earth oxide RE in molar ratio2O320 to 30 percent of the total amount.
3. A preparation method of low-thermal-conductivity high-entropy rare earth silicate ceramic is characterized by comprising the following steps:
(1) with RE2O3Powder and SiO2The powder is taken as a raw material, RE is any four elements of Er, Sc, Lu, Yb or Tm, in terms of molar ratio,
Figure FDA0003495357950000012
SiO2＝(0.8～1.2)：(0.8～1.2)：(0.8～1.2)：(0.8～1.2)：(6.4～9.6)；
(2) fully mixing and crushing the ceramic powder by using acetone or absolute ethyl alcohol as a mixing medium by using a high-energy ball mill for 24-48 hours;
(3) drying, grinding and screening the fully mixed powder, and selecting fine powder with the granularity of below 500-800 meshesCalcining at 1500-1600 ℃ under no pressure, cooling, crushing and grinding the calcined ceramic to obtain the ceramic
Figure FDA0003495357950000013
The high-entropy ceramic powder material comprises a high-entropy ceramic powder material, wherein w + x + y + z is 1;
(4)
Figure FDA0003495357950000014
the block material of the high-entropy ceramic is prepared by adopting a spark plasma sintering method, wherein the sintering temperature is 1250-1400 ℃, the heating rate is 100 ℃/min, the vacuum degree is 5-10 Pa, the pressure is 50-100 MPa, and the heat preservation time is 5-10 minutes, so that the compact block high-entropy ceramic can be obtained.
4. The method for preparing the low-thermal-conductivity high-entropy rare earth silicate ceramic according to claim 3, wherein SiO is2And rare earth oxide RE2O3The purity of the powder is more than or equal to 99.99 wt.%, and the granularity of the original powder is less than 10 μm.
5. The preparation method of the low-thermal-conductivity high-entropy rare earth silicate ceramic according to claim 4, wherein in the step (3), after the high-temperature pressureless calcination and the furnace cooling to 1100-1300 ℃, the crucible and the high-temperature pressureless calcination are taken out and placed in an air environment for air cooling, or the crucible and the high-temperature pressureless calcination are forcibly air-cooled by using compressed air.
6. The preparation method of the low-thermal-conductivity high-entropy rare earth silicate ceramic is characterized in that the pressureless calcination process is carried out in an atmospheric air atmosphere, and the spark plasma sintering is carried out in an air environment with low pressure of 5-10 Pa.
7. The method for preparing a low-thermal-conductivity high-entropy rare-earth silicate ceramic according to claim 6, wherein the compactness of the prepared bulk ceramic material is greater than 98%.
8. The method for preparing a low-thermal-conductivity high-entropy rare-earth silicate ceramic according to claim 7, wherein the thermal conductivity of the prepared high-entropy bulk material is lower than 1.1W/m/K in the range from room temperature to 1000 ℃.
9. Use of the multi-element high-entropy ceramic of any one of claims 1 to 2 in the preparation of thermal insulation materials or high-density ceramic blocks.
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CN116217230B (en) * 2023-03-15 2024-05-07 沈阳大学 Preparation method of low-thermal-conductivity wide-mid-infrared band-pass high-entropy nano composite ceramic
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