CN113620722B

CN113620722B - Rare earth niobate high-entropy powder, porous high-entropy ceramic, and preparation method and application thereof

Info

Publication number: CN113620722B
Application number: CN202111040102.2A
Authority: CN
Inventors: 许杰; 杨润伍; 朱嘉桐; 孟轩宇; 位明月; 高峰
Original assignee: Northwestern Polytechnical University
Current assignee: Xu Jie
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2022-07-01
Anticipated expiration: 2041-09-06
Also published as: CN113620722A

Abstract

The invention discloses rare earth niobate high-entropy powder, porous high-entropy ceramic, a preparation method and application, and belongs to the technical field of high-entropy materials. The raw materials of the rare earth niobate high-entropy powder comprise rare earth trioxide and niobium pentoxide; the rare earth trioxide is a mixture of 5-7 different trioxide of dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the trioxide with a large dosage to the trioxide with a small dosage in any two trioxide is 1-3. According to the invention, different rare earth metal cations are introduced through high entropy of niobate ceramic components, and due to different atom sizes in a high entropy phase, atom occupation of the niobate ceramic components shifts, so that lattice distortion is caused, and phonon scattering is increased; due to the introduction of the pore structure, the solid phase thermal conductivity of the material is reduced, and the rare earth niobate porous high-entropy ceramic has excellent heat insulation performance.

Description

Rare earth niobate high-entropy powder, porous high-entropy ceramic, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of high-entropy materials, and particularly relates to rare earth niobate high-entropy powder, porous high-entropy ceramic, a preparation method and application.

Background

In recent years, research has shown that rare earth niobate oxide systems (RE)₃NbO₇) Has lower intrinsic thermal conductivity, wherein RE and Nb atoms have the same occupation and can cause the crystal structure to change along with the change of doping element species. When RE is La to Gd, RE₃NbO₇Presenting an orthogonal structure; when RE is Dy-Lu and Y, RE₃NbO₇A disordered defective fluorite structure is present. Having a fluorite structure with disordered defects, resulting from the presence of disordered oxygen vacancies in the crystal lattice, due to oxygen vacanciesDisordered distribution and large chemical nonuniformity, and increases phonon scattering centers, so that the niobate ceramic has the advantages of excellent oxygen ion conductivity, lower lattice thermal conductivity, high melting point, high chemical stability, high radiation stability and the like, and is considered as a potential new-generation aviation thermal insulation material. However, the intrinsic mechanical properties are poor, and the lattice thermal conductivity needs to be further reduced by the component design. Therefore, the thermal conductivity can be further reduced by adopting high entropy and pore structure regulation, and the mechanical performance can be regulated and controlled.

High entropy, which generally refers to a multi-principal single-phase solid solution formed by 5 or more solid solution elements, has become one of the research hotspots in the ceramic field in recent years due to the huge lattice distortion brought by high entropy to bring many excellent thermophysical properties to the material. The intrinsic lattice thermal conductivity of the material can be obviously reduced by increasing phonon scattering centers after high entropy change. At present, people mainly research compact ceramics of rare earth niobate materials, realize the reduction of intrinsic thermal conductivity of the rare earth niobate materials through high-entropy component design, and further realize the preparation of low-thermal-conductivity rare earth niobate porous high-entropy ceramics by introducing air holes, thereby having important significance.

Disclosure of Invention

The invention aims to provide rare earth high-entropy powder, porous ceramic, a preparation method and application thereof aiming at the defects and shortcomings of the method.

The first purpose of the invention is to provide a rare earth niobate high-entropy powder, and the raw materials of the rare earth niobate high-entropy powder comprise rare earth trioxide and niobium pentoxide;

the rare earth trioxide is dysprosium oxide (Dy)₂O₃) Holmium oxide (Ho)₂O₃) Erbium oxide (Er)₂O₃) Thulium oxide (Tm)₂O₃) Ytterbium oxide (Yb)₂O₃) Lutetium oxide (Lu)₂O₃) Yttrium oxide (Y)₂O₃) The molar ratio of the more used trioxide to the less used trioxide in any two trioxide is 1-3.

Preferably, the molar ratio of the rare earth trioxide to the niobium pentoxide is 3: 1; the particle size of the niobium pentoxide is 20-50 nm; the particle size of the rare earth trioxide is 20-50 nm;

the rare earth niobate high-entropy powder is of a single-phase defect fluorite structure, and the particle size is 250-400 nm.

Preferably, the rare earth trioxide is a mixture of dysprosium oxide, holmium oxide, thulium oxide, erbium oxide and ytterbium oxide, and the molar ratio of the rare earth trioxide to the ytterbium oxide is 1:1:1: 1;

or the rare earth trioxide is a mixture of dysprosium oxide, thulium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the dysprosium oxide, the thulium oxide, the ytterbium oxide, the lutetium oxide and the yttrium oxide is 1:1:1: 1;

or the rare earth trioxide is a mixture of dysprosium oxide, holmium oxide, thulium oxide, ytterbium oxide and lutetium oxide, and the molar ratio of the rare earth trioxide to the lutetium oxide is 2:1:1:3: 3;

or the rare earth trioxide is a mixture of dysprosium oxide, erbium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the rare earth trioxide to the yttrium oxide is 2:2:2.5:2.5: 1;

or the rare earth trioxide is a mixture of holmium oxide, thulium oxide, erbium oxide, ytterbium oxide and yttrium oxide, and the molar ratio of the holmium oxide to the erbium oxide to the ytterbium oxide to the yttrium oxide is 1:1:1: 1;

or the rare earth trioxide is a mixture of dysprosium oxide, holmium oxide, erbium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the rare earth trioxide to the yttrium oxide is 1:1:1:1: 1;

or the rare earth trioxide is a mixture of dysprosium oxide, holmium oxide, thulium oxide, erbium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the rare earth trioxide to the yttrium oxide is 1:1:1:1:1: 1.

The second purpose of the invention is to provide a preparation method of the rare earth niobate high-entropy powder, which comprises the following steps:

mixing and ball-milling rare earth trioxide, niobium pentoxide and absolute ethyl alcohol to obtain mixed slurry;

drying the obtained mixed slurry to obtain a mixed material;

and calcining the obtained mixed material to obtain the rare earth niobate high-entropy powder.

Preferably, the ball milling rotating speed is 250-350 r/min, and the ball milling time is 24-48 h;

the drying temperature is 60 ℃, and the drying time is 24 hours;

in the calcining process, the heating rate is 5 ℃/min, the temperature is 1300-1500 ℃, and the heat preservation time is 3-6 h.

The third purpose of the invention is to provide a rare earth niobate porous high-entropy ceramic, the raw materials of which comprise the rare earth niobate high-entropy powder; the chemical formula of the porous high-entropy ceramic is RE₃NbO₇Wherein RE is 5-7 different elements in Dy, Ho, Er, Tm, Yb, Lu and Y; the porosity of the porous high-entropy ceramic is 62-88%, the pore size is 0.5-5 mu m, the compressive strength is 5-62 MPa, and the thermal conductivity at room temperature is 0.030-0.075W/(m.K).

The fourth purpose of the invention is to provide a preparation method of the rare earth niobate porous high-entropy ceramic, which comprises the following steps:

mixing and ball-milling the rare earth niobate high-entropy powder, tert-butyl alcohol, a dispersing agent and ethylene glycol diglycidyl ether to obtain a rare earth niobate high-entropy ceramic suspension;

adding 3,3' -diaminodipropylamine into the obtained rare earth niobate high-entropy ceramic suspension, curing and drying to obtain a ceramic blank, then carrying out binder removal on the ceramic blank, and sintering the binder-removed ceramic blank at high temperature to obtain the rare earth niobate porous high-entropy ceramic.

Preferably, the dispersant is one of ammonium citrate, ammonium polyacrylate and polyethyleneimine;

the mass ratio of the rare earth niobate high-entropy powder to the tertiary butanol to the dispersing agent to the ethylene glycol diglycidyl ether is 10-50: 100: 0.05-0.2: 10-30;

the mass of the 3,3' -diamino dipropylamine is 20-50% of that of the ethylene glycol diglycidyl ether.

Preferably, the ball milling speed is 300r/min, and the ball milling time is 24-48 h;

the curing process comprises the following steps: curing for 12-24 h at 40-60 ℃;

the drying process comprises the following steps: drying for 24h at 100 ℃;

the glue discharging temperature is 600 ℃, and the heat preservation is carried out for 2 hours;

the heating rate is 5 ℃/min in the sintering process;

the sintering temperature is 1500-1700 ℃, and the heat preservation time is 3-6 h.

The fifth purpose of the invention is to provide the application of the rare earth niobate porous high-entropy ceramic in the preparation of high-temperature heat-insulating materials.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, different metalloid cations are introduced through high entropy of niobate ceramic components, and due to different sizes of cation atoms in a high entropy phase, atom occupation generates displacement, so that lattice distortion is further generated, phonon scattering is increased, and meanwhile, due to existence of inherent oxygen atom vacancies of a fluorite phase, the rare earth niobate high entropy ceramic has very low lattice thermal conductivity.

The invention can effectively introduce micropores in the ceramic by a non-water-based gel injection molding method. And forming a three-dimensional porous skeleton structure in the powder through the crosslinking and curing action between the epoxy resin and the curing agent, and removing the epoxy resin and the curing agent through high-temperature calcination, thereby forming a three-dimensional network pore structure in situ in the ceramic blank. The porosity of the ceramic material is improved, so that the solid phase thermal conductivity is reduced, and meanwhile, infrared radiation can be effectively scattered and reflected at high temperature, so that the thermal conductivity of the material is reduced.

According to the rare earth niobate high-entropy powder provided by the invention, the raw material powder is fully and uniformly mixed, and the beneficial effects are that the elements of the calcined rare earth niobate high-entropy powder are uniformly distributed, and element enrichment does not exist; and grinding the mixed powder to ensure that the particle size distribution of the high-entropy rare earth niobate powder obtained by calcination in the step is uniform.

The preparation method of the rare earth niobate porous high-entropy ceramic has the beneficial effects that the saturated vapor pressure of tertiary butanol is high, the surface tension is small, the tertiary butanol is volatile, and shrinkage cracking in the drying process of a green body can be effectively relieved. By adding a curing agent, the curing agent and ethylene glycol diglycidyl ether are subjected to a crosslinking action to form a high molecular chain segment, the rare earth niobate high-entropy ceramic slurry suspension is cured, and the high molecular chain segment forms a three-dimensional network skeleton. And removing the dispersing agent, the ethylene glycol diglycidyl ether and the 3,3' -diaminodipropylamine by degumming to form a three-dimensional network pore structure in the blank.

The rare earth niobate high-entropy powder obtained by the method is of a single-phase defect fluorite structure, the particle size distribution is uniform, and the average particle size is 250-400 nm; the rare earth niobate porous high-entropy ceramic prepared by the invention is white, faint yellow or pink, the porosity is 62-88%, the pore size is 0.5-5 mu m, the compressive strength is 5-62 MPa, and the compressive property is excellent due to uniform pore size distribution. The high porosity hinders heat transfer, and the iDPC picture shows that a large amount of lattice distortion is caused by high entropy of components, phonon scattering is increased, lattice thermal conductivity is further reduced, so that the rare earth niobate porous high-entropy ceramic has excellent heat insulation performance, and the thermal conductivity is 0.030-0.075W/(m.K) at room temperature.

Drawings

FIG. 1 shows (Dy) produced in example 1_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇XRD spectrum of rare earth niobate high-entropy powder;

FIG. 2 shows (Dy) produced in example 2_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇SEM picture of high entropy powder of rare earth niobate;

FIG. 3 shows (Dy) produced in example 2_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇SEM-EDS picture of rare earth niobate porous high-entropy ceramic；

FIG. 4 shows (Dy) produced in example 4_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇HAADF and iDPC pictures of the rare earth niobate porous high-entropy ceramic.

Detailed Description

In order to make the technical solutions of the present invention better understood and implemented by those skilled in the art, the present invention is further described below with reference to the following specific embodiments and the accompanying drawings, but the embodiments are not meant to limit the present invention.

It is to be noted that the particle size of the nano rare earth trioxide used in the following examples is 20-50 nm, and the purity is more than 99.9%; the particle size of the nano niobium pentoxide is 20-50 nm, and the purity is more than 99.9%; other reagents and materials, if not specifically stated, are commercially available; the experimental methods are all conventional methods unless otherwise specified.

The invention is further explained in detail by combining the attached drawings and examples, and the embodiment of the preparation examples of the rare earth niobate high-entropy powder and the porous ceramic is as follows:

step (1): weighing nano dysprosium oxide or nano erbium oxide or nano holmium oxide or nano thulium oxide or nano erbium oxide or nano ytterbium oxide or nano lutetium oxide or nano yttrium oxide and nano niobium pentoxide according to a proportion, wherein the molar ratio of the nano rare earth trioxide is 1-3, the total molar mass of the nano rare earth trioxide is 3:1, the total mass of the nano rare earth trioxide and the nano niobium pentoxide is 1:2, the mass ratio of the total mass of the nano rare earth trioxide and the nano niobium pentoxide to absolute ethyl alcohol is 1:1, and the nano rare earth trioxide and the nano ytterbium oxide are placed in a planetary ball mill to be ball-milled and mixed to obtain mixed slurry; the ball milling speed is 250-350 r/min, and the ball milling time is 24-48 h; the average particle size varies depending on the rotational speed and time of the ball mill.

Examples 1-7 embodiments of step (1) are given in table 1 below:

table 1 shows embodiments of step (1) of examples 1 to 7

Step (2): drying the slurry obtained in the step (1) in a drying oven to obtain dry powder, and grinding to obtain mixed powder; the drying temperature is 60 ℃, and the drying time is 24 hours;

and (3): placing the mixed powder obtained in the step (2) in a box-type resistance furnace, and carrying out heat preservation and calcination to prepare the rare earth niobate high-entropy powder; the calcination temperature is 1300-1500 ℃, the calcination time is 4-6 h, and the heating rate is 5 ℃/min; examples 1 to 7 each gave (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇High entropy powder, (Dy)_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇High entropy powder, (Dy)_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇High entropy powder, (Dy)_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇High entropy powder, (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇High entropy powder, (Dy)_0.167Ho_0.167Er_0.167Yb_0.167Lu_0.167Y_0.167)₃NbO₇High entropy powder of and (Dy)_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.143Lu_0.143Y_0.143)₃NbO₇High entropy powder; examples 1-7 embodiments of step (1) are given in table 2 below:

table 2 shows embodiments of step (3) of examples 1 to 7

And (4): adding a dispersing agent and ethylene glycol diglycidyl ether into the rare earth niobate high-entropy powder obtained in the step (3), ball-milling in a planetary ball mill by adopting tert-butyl alcohol as a solvent, and ball-milling for 24 hours at a rotating speed of 300r/min to obtain rare earth niobate high-entropy ceramic slurry; the mass ratio of the rare earth niobate high-entropy powder to the tertiary butanol to the dispersant to the ethylene glycol diglycidyl ether is 10-50: 100: 0.05-0.2: 10-30; the dispersant is one of ammonium citrate, polyethyleneimine and ammonium polyacrylate; examples 1-7 embodiments of step (4) are given in table 3 below:

table 3 shows embodiments of step (4) of examples 1 to 7

And (5): adding 3,3' -diamino dipropylamine as a curing agent into the rare earth niobate ceramic slurry obtained in the step (4), mechanically stirring to uniformly mix the rare earth niobate ceramic slurry, injecting the slurry into a mold, standing for curing, and drying to obtain a ceramic blank; the drying temperature is 100 ℃, and the drying time is 24 h; examples 1-7 embodiments of step (5) are given in table 4 below:

table 4 shows embodiments of step (5) of examples 1 to 7

And (6): placing the ceramic blank obtained in the step (5) in a box-type resistance furnace for heat preservation and glue discharge; the glue discharging temperature is 600 ℃, and the heat preservation time is 2 hours;

and (7): placing the ceramic blank obtained in the step (6) after the glue is removed into a box-type resistance furnace, and sintering to obtain the rare earth niobate porous high-entropy ceramic; the sintering temperature is 1500-1700 ℃, and the heat preservation time is 3-6 h; examples 1-7 embodiments of step (7) are given in table 5 below:

table 5 shows an embodiment of step (7) in examples 1 to 7

The following is a detailed description of examples 1 to 7:

example 1

Step 1, mixing 223.80g of nano dysprosium oxide, 226.72g of nano holmium oxide, 231.52g of nano thulium oxide, 229.51g of nano erbium oxide, 236.45g of nano ytterbium oxide, 265.81g of nano niobium pentoxide and 3576.11g of absolute ethyl alcohol, and carrying out ball milling for 48 hours at the ball milling rotation speed of 250 r/min;

step 2, drying for 24 hours at the temperature of 60 ℃ to obtain a mixed material;

step 3, calcining the mixed material at 1450 ℃ for 4h to obtain (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇High entropy powder;

step 4, mixing 100g of (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇High entropy powder, 1000g of tert-butyl alcohol, 0.5g of ammonium citrate and 300g of ethylene glycol diglycidyl ether are mixed and ball milled to prepare (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇The high-entropy ceramic suspension liquid is subjected to ball milling at the rotating speed of 300r/min for 24 hours;

step 5, adding 150g of 3,3' -diamino dipropylamine into the high-entropy ceramic suspension, curing at 40 ℃ for 24h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 6, keeping the temperature of the ceramic blank at 600 ℃ for 2h for removing glue, wherein the heating rate is 0.5 ℃/min;

step 7, finally, preserving heat at 1500 ℃ for 6h for sintering, wherein the heating rate is 5 ℃/min, and obtaining (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇Porous high entropy ceramics.

(Dy) prepared in this example_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average particle size is 300 nm; (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇The porosity of the porous high-entropy ceramic is 88%, the pore size is 5 mu m, the compressive strength is 5MPa, and the thermal conductivity is 0.030W/(m.K).

Example 2

Step 1, mixing 205.60g of nano dysprosium oxide, 212.69g of nano thulium oxide, 217.22g of nano ytterbium oxide, 219.34g of nano lutetium oxide, 124.47g of nano yttrium oxide, 244.19g of nano niobium pentoxide and 3285.29g of absolute ethyl alcohol, and carrying out ball milling for 36 hours at the ball milling rotating speed of 300 r/min;

step 3, calcining the mixed material at 1500 ℃ for 4h to obtain (Dy)_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇High entropy powder;

step 4, mixing 500g of (Dy)_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇High entropy powder, 1000g of tertiary butanol, 2g of polyethyleneimine and 100g of ethylene glycol diglycidyl ether are mixed and ball milled to prepare (Dy)_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇High entropy ceramic suspension;

step 5, adding 20g of 3,3' -diamino dipropylamine into the high-entropy ceramic suspension, curing at 60 ℃ for 12h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 7, finally, preserving heat at 1700 ℃ for 3h for sintering, wherein the heating rate is 5 ℃/min, and obtaining (Dy)_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇Porous high entropy ceramics.

(Dy) prepared in this example_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average particle size is 270 nm; (Dy)_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇Of porous high-entropy ceramicsThe porosity is 62%, the pore size is 0.5 μm, the compressive strength is 62MPa, and the thermal conductivity is 0.075W/(m.K).

Example 3

Step 1, mixing 230.50g of nano dysprosium oxide, 116.75g of nano holmium oxide, 119.23g of nano thulium oxide, 365.30g of nano ytterbium oxide, 368.87g of nano lutetium oxide, 273.77g of nano niobium pentoxide and 2948.84g of absolute ethyl alcohol, and carrying out ball milling for 36 hours at the ball milling rotation speed of 300 r/min;

step 3, calcining the mixed material at 1400 ℃ for 5 hours to obtain (Dy)_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇High entropy powder;

step 4, mixing 350g of (Dy)_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇High-entropy powder, 1000g of tert-butyl alcohol, 1.2g of ammonium citrate and 180g of ethylene glycol diglycidyl ether are mixed and ball-milled to prepare (Dy)_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇High entropy ceramic suspension;

step 5, adding 45g of 3,3' -diamino dipropylamine into the high-entropy ceramic suspension, curing at 50 ℃ for 15h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 7, finally, the mixture is sintered by keeping the temperature at 1600 ℃ for 5 hours, and the heating rate is 5 ℃/min to obtain (Dy)_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇Porous high entropy ceramics.

(Dy) prepared in this example_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average particle size is 250 nm; (Dy)_0.2Ho_0.1Tm_0.1Yb_0.3Lu_0.3)₃NbO₇The porosity of the porous high-entropy ceramic is 70 percent, and the pore diameterThe size is 2 μm, the compressive strength is 54MPa, and the thermal conductivity is 0.062W/(m.K).

Example 4

Step 1, mixing 215.50g of nano dysprosium oxide, 221.00g of nano erbium oxide, 284.60g of nano ytterbium oxide, 287.39g of nano lutetium oxide, 65.23g of nano yttrium oxide, 255.95g of nano niobium pentoxide and 2174.44g of absolute ethyl alcohol, and carrying out ball milling for 36 hours at the ball milling speed of 300 r/min;

step 3, calcining the mixed material at 1350 ℃ for 5 hours to obtain (Dy)_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇High entropy powder;

step 4, mixing 200g of (Dy)_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇High-entropy powder, 1000g of tert-butyl alcohol, 0.8g of ammonium polyacrylate and 230g of ethylene glycol diglycidyl ether are mixed and ball-milled to prepare (Dy)_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇High entropy ceramic suspension;

step 5, adding 71g of 3,3' -diaminodipropylamine into the high-entropy ceramic slurry suspension, curing at 45 ℃ for 20h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 7, finally, the mixture is sintered at 1650 ℃ for 4 hours with the heating rate of 5 ℃/min to obtain (Dy)_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇Porous high entropy ceramics.

(Dy) prepared in this example_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average grain size is 370 nm; (Dy)_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇The porosity of the porous high-entropy ceramic is 76%, the pore size is 4 μm,the compressive strength is 38MPa, and the thermal conductivity is 0.046W/(m.K).

Example 5

Step 1, mixing 217.80g of nano holmium oxide, 222.42g of nano thulium oxide, 220.49g of nano erbium oxide, 227.15g of nano ytterbium oxide, 130.16g of nano yttrium oxide, 255.36g of nano niobium pentoxide and 3435.49g of absolute ethyl alcohol, and carrying out ball milling for 36 hours at the ball milling rotating speed of 300 r/min;

step 3, calcining the mixed material at 1500 ℃ for 4h to obtain (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇High entropy powder;

step 4, mixing the 400g (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇High entropy powder, 1000g of tertiary butanol, 1.5g of ammonium polyacrylate and 135g of ethylene glycol diglycidyl ether by mixing and ball milling (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇High entropy ceramic suspension;

step 5, adding 29g of 3,3' -diamino dipropylamine into the high-entropy ceramic slurry suspension, curing at 60 ℃ for 15h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 7, finally, the mixture is sintered by heat preservation at 1650 ℃ for 5 hours with the heating rate of 5 ℃/min to obtain (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇Porous high entropy ceramics.

Prepared in this example (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average particle size is 390 nm; (Ho)_0.2Tm_0.2Er_0.2Yb_0.2Y_0.2)₃NbO₇The porosity of the porous high-entropy ceramic is 65%, the pore size is 2 mu m, the compressive strength is 59MPa, and the heat is appliedThe conductivity was 0.068W/(mK).

Example 6

Step 1, mixing 150.50g of nano dysprosium oxide, 152.46g of nano holmium oxide, 154.34g of nano erbium oxide, 159.01g of nano ytterbium oxide, 160.56g of nano lutetium oxide, 91.11g of nano yttrium oxide, 214.50g of nano niobium pentoxide and 2164.96g of absolute ethyl alcohol, and carrying out ball milling for 24 hours at the ball milling speed of 350 r/min;

step 2, drying for 24 hours at 60 ℃ to obtain a mixed material;

step 3, calcining the mixed material at 1300 ℃ for 6h to obtain (Dy)_0.167Ho_0.167Er_0.167Yb_0.167Lu_0.16 ₇Y_0.167)₃NbO₇High entropy powder;

step 4, mixing 150g of (Dy)_0.167Ho_0.167Er_0.167Yb_0.167Lu_0.167Y_0.167)₃NbO₇High entropy powder, 1000g of tert-butyl alcohol, 0.6g of polyethyleneimine and 270g of ethylene glycol diglycidyl ether are mixed and ball milled to prepare (Dy)_0.167Ho_0.167Er_0.167Yb_0.16 ₇Lu_0.167Y_0.167)₃NbO₇High entropy ceramic suspension;

step 5, adding 95g of 3,3' -diaminodipropylamine into the high-entropy ceramic suspension, curing at 55 ℃ for 14h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 7, finally, preserving heat at 1700 ℃ for 4h for sintering, wherein the heating rate is 5 ℃/min, and obtaining (Dy)_0.167Ho_0.167Er_0.167Yb_0.167Lu_0.167Y_0.167)₃NbO₇Porous high entropy ceramics.

(Dy) prepared in this example_0.167Ho_0.167Er_0.167Yb_0.167Lu_0.167Y_0.167)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average particle size is 350 nm; (Dy)_0.167Ho_0.167Er_0.167Yb_0.167Lu_0.167Y_0.167)₃NbO₇The porosity of the porous high-entropy ceramic is 82%, the pore size is 3 mu m, the compressive strength is 42MPa, and the thermal conductivity is 0.039W/(m.K).

Example 7

Step 1, mixing 150.50g of nano dysprosium oxide, 152.46g of nano holmium oxide, 155.69g of nano thulium oxide, 154.34g of nano erbium oxide, 159.01g of nano ytterbium oxide, 160.56g of nano lutetium oxide, 91.11g of nano yttrium oxide, 250.25 g of nano niobium pentoxide and 2236.46 of absolute ethyl alcohol, and carrying out ball milling for 24 hours at the ball milling speed of 350 r/min;

step 3, calcining the mixed material at 1300 ℃ for 6h to obtain (Dy)_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.14 ₃Lu_0.143Y_0.143)₃NbO₇High entropy powder;

step 4, mixing 300g of (Dy)_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.143Lu_0.143Y_0.143)₃NbO₇High-entropy powder, 1000g of tert-butyl alcohol, 1.0g of polyacrylamide and 200g of ethylene glycol diglycidyl ether are mixed and ball-milled to prepare (Dy)_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.143Lu_0.143Y_0.143)₃NbO₇High entropy ceramic suspension;

step 5, adding 63g of 3,3' -diaminodipropylamine into the high-entropy ceramic suspension, curing at 50 ℃ for 20h, and drying at 100 ℃ for 24h to obtain a ceramic blank;

step 7, finally, preserving heat at 1700 ℃ for 4h for sintering, wherein the heating rate is 5 ℃/min, and obtaining (Dy)_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.143Lu_0.143Y_0.143)₃NbO₇Porous high entropy ceramics.

(Dy) prepared in this example_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.143Lu_0.143Y_0.143)₃NbO₇The high-entropy powder is of a single-phase defect fluorite structure, and the average particle size is 400 nm; (Dy)_0.143Ho_0.143Tm_0.143Er_0.143Yb_0.143Lu_0.143Y_0.143)₃NbO₇The porosity of the porous high-entropy ceramic is 71%, the pore size is 3 mu m, the compressive strength is 15MPa, and the thermal conductivity is 0.053W/(m.K).

Comparative example 1

Same as example 1 except that (Dy) was prepared_0.5Ho_0.5)₃NbO₇A porous ceramic; wherein (Dy)_0.5Ho_0.5)₃NbO₇The porosity of the porous ceramic is 85%, the pore size is 5 μm, the compressive strength is 1MPa, and the thermal conductivity is 0.125W/(m.K).

Comparative example 2

Same as example 1 except that (Dy) was prepared_0.33Ho_0.33Tm_0.33)₃NbO₇A porous ceramic; wherein (Dy)_0.33Ho_0.33Tm_0.33)₃NbO₇The porosity of the porous ceramic is 83 percent, the pore size is 5 mu m, the compressive strength is 1.5MPa, and the thermal conductivity is 0.107W/(m.K).

Comparative example 3

Same as example 1 except that (Dy) was prepared_0.25Ho_0.25Tm_0.25Er_0.25)₃NbO₇A porous ceramic; wherein (Dy)_0.25Ho_0.25Tm_0.25Er_0.25)₃NbO₇The porosity of the porous ceramic is 83 percent, the pore size is 5 mu m, the compressive strength is 3.1MPa, and the thermal conductivity is 0.096W/(m.K).

It should be noted that the preparation methods adopted in comparative examples 1 to 3 are the same as those in example 1, except that the raw materials selected in the preparation process are different, and the raw materials are mainly selected according to the target product to be prepared, and the manner of using the raw materials is the same as that in example 1.

In order to illustrate the mechanical properties and thermal conductivity of the porous high-entropy ceramic provided by the invention, the analysis is as follows:

(Dy) obtained in comparative example 1_0.5Ho_0.5)₃NbO₇The porosity of the porous ceramic is 85 percent, the pore size is 5 mu m, the compressive strength is 1MPa, and the thermal conductivity is 0.125W/(m.K); (Dy) obtained in comparative example 2_0.33Ho_0.33Tm_0.33)₃NbO₇The porosity of the porous ceramic is 83 percent, the pore size is 5 mu m, the compressive strength is 1.5MPa, and the thermal conductivity is 0.107W/(m.K); (Dy) obtained in comparative example 3_0.25Ho_0.25Tm_0.25Er_0.25)₃NbO₇The porosity of the porous ceramic is 83 percent, the pore size is 5 mu m, the compressive strength is 3.1MPa, and the thermal conductivity is 0.096W/(m.K). (Dy) obtained in example 1_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇The porosity of the porous ceramic is 88%, the compressive strength is 5MPa, and the thermal conductivity is 0.030W/(m.K), so that the high entropy is beneficial to improving the mechanical property of the porous ceramic and reducing the thermal conductivity.

In order to further illustrate the influence of the high entropy of the components on the performance of the prepared rare earth niobate porous high-entropy ceramic, three groups of rare earth niobate porous ceramics obtained by comparison are listed, and then a comparison test is carried out.

In order to further illustrate the relevant properties of the rare earth niobate high-entropy powder and the rare earth porous high-entropy ceramic provided by the invention, relevant tests are carried out on the rare earth niobate high-entropy powder and the rare earth porous high-entropy ceramic provided by the embodiment, which are shown in fig. 1-4.

FIG. 1 shows (Dy) produced in example 1_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇XRD spectrum of rare earth niobate high-entropy powder; as can be seen in FIG. 1, the XRD pattern shows that the doping of five different elements Dy, Ho, Tm, Er and Yb forms single-phase niobate, and has the same diffraction peak as the single-phase defect fluorite structure.

FIG. 2 is a schematic view of an embodiment1 prepared (Dy)_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇SEM picture of high entropy powder of rare earth niobate; FIG. 2 shows that (Dy) was produced_0.2Ho_0.2Tm_0.2Er_0.2Yb_0.2)₃NbO₇The rare earth niobate high-entropy powder is uniformly dispersed, has no abnormal aggregation, has an average particle size of 270nm, and has good activity in the preparation process of porous ceramics.

FIG. 3 shows (Dy) produced in example 2_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇SEM-EDS picture of porous high-entropy pottery of rare earth niobate; FIG. 3 shows SEM picture of porous high-entropy ceramic provided in example 2 at the upper left corner of FIG. 3, and EDS pictures of Dy, Tm, Yb, Lu, Y, Nb and O, respectively, and (Dy) prepared from FIG. 3_0.2Tm_0.2Yb_0.2Lu_0.2Y_0.2)₃NbO₇The porous high-entropy ceramic pore structure of the rare earth niobate is uniformly distributed, and an energy spectrum picture shows that five doping elements of Dy, Tm, Yb, Lu and Y are uniformly dispersed without enrichment, so that high entropy of the components is formed.

FIG. 4 shows (Dy) produced in example 4_0.2Er_0.2Yb_0.25Lu_0.25Y_0.1)₃NbO₇HAADF-iDPC picture of rare earth niobate porous high-entropy ceramic. As can be seen from fig. 4, the HAADF picture shows that the prepared rare earth niobate porous ceramic has a cubic phase structure, and the iDPC picture shows that rare earth ions are shifted from the equilibrium position due to poor radius and mass, so that a large amount of lattice distortion is generated, phonon scattering is enhanced, and the reduction of thermal conductivity is facilitated.

The foregoing is illustrative of the preferred embodiments of the present invention and it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and should be considered as within the scope of the invention.

Claims

1. A rare earth niobate porous high-entropy ceramic is characterized in that the raw material comprises rare earth niobate high-entropy powder; the chemical formula of the porous high-entropy ceramic is RE₃NbO₇Wherein RE is 5-7 different elements in Dy, Ho, Er, Tm, Yb, Lu and Y; the porosity of the porous high-entropy ceramic is 62-88%, the pore size is 0.5-5 mu m, the compressive strength is 5-62 MPa, and the thermal conductivity at room temperature is 0.030-0.075W/(m.K);

the raw materials of the rare earth niobate high-entropy powder comprise rare earth trioxide and niobium pentoxide;

the rare earth trioxide is a mixture of 5-7 different trioxide of dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the trioxide with a large dosage to the trioxide with a small dosage in any two trioxide is 1-3.

2. The rare earth niobate porous high-entropy ceramic of claim 1, wherein a molar ratio of the rare earth trioxide to the niobium pentoxide is 3: 1; the particle size of the niobium pentoxide is 20-50 nm; the particle size of the rare earth trioxide is 20-50 nm;

3. The rare earth niobate porous high-entropy ceramic of claim 1,

the rare earth trioxide is a mixture of dysprosium oxide, holmium oxide, thulium oxide, erbium oxide and ytterbium oxide, and the molar ratio of the rare earth trioxide to the erbium oxide to the ytterbium oxide is 1:1:1: 1;

or the rare earth trioxide is a mixture of holmium oxide, thulium oxide, erbium oxide, ytterbium oxide and yttrium oxide, and the molar ratio of the holmium oxide to the thulium oxide to the erbium oxide to the ytterbium oxide to the yttrium oxide is 1:1:1: 1;

or the rare earth trioxide is a mixture of dysprosium oxide, holmium oxide, erbium oxide, ytterbium oxide, lutetium oxide and yttrium oxide, and the molar ratio of the components is 1:1:1:1: 1;

4. The rare earth niobate porous high-entropy ceramic of claim 1, wherein the preparation method of the rare earth niobate high-entropy powder comprises the following steps:

drying the obtained mixed slurry to obtain a mixed material;

5. The rare earth niobate porous high-entropy ceramic of claim 4,

the ball milling rotating speed is 250-350 r/min, and the ball milling time is 24-48 h;

the drying temperature is 60 ℃, and the drying time is 24 hours;

in the calcining process, the heating rate is 5 ℃/min, the temperature is 1300-1500 ℃, and the heat preservation time is 4-6 h.

6. The preparation method of the rare earth niobate porous high-entropy ceramic according to any one of claims 1 to 5, characterized by comprising the steps of:

adding 3,3' -diaminodipropylamine into the obtained high-entropy ceramic suspension, curing and drying to obtain a ceramic blank, then carrying out binder removal on the ceramic blank, and sintering the ceramic blank subjected to binder removal at high temperature to obtain the rare earth niobate porous high-entropy ceramic.

7. The method for preparing a rare earth niobate porous high-entropy ceramic according to claim 6, characterized in that,

the dispersant is one of ammonium citrate, ammonium polyacrylate and polyethyleneimine;

the mass ratio of the rare earth niobate high-entropy powder to the tertiary butanol to the dispersant to the ethylene glycol diglycidyl ether is 10-50: 100: 0.05-0.2: 10-30;

8. The method for preparing a rare earth niobate porous high-entropy ceramic according to claim 6, characterized in that,

the ball milling speed is 300r/min, and the ball milling time is 24 h;

the drying process comprises the following steps: drying for 24h at 100 ℃;

the heating rate is 5 ℃/min in the sintering process;

9. The use of the rare earth niobate porous high-entropy ceramic of claim 1 in the preparation of high-temperature thermal insulation materials.