阅读说明：本技术 一种稀土系复合材料及其制备方法和应用 (Rare earth series composite material and preparation method and application thereof ) 是由 王一光 于 2019-01-10 设计创作，主要内容包括：本发明提供一种稀土系复合材料及其制备方法和应用,所述稀土系复合材料的组成为(RE)<Sub>2</Sub>Si<Sub>x</Sub>O<Sub>y</Sub>；其中,RE为稀土元素中的至少三种,6+4x＝2y,1≤x≤3,5≤y≤7。该稀土系复合材料长期在水氧燃气环境中仍不易发生挥发,具有极其稳定的特性,有助于延长环境屏障涂层的服役寿命。(The invention provides a rare earth composite material and a preparation method and application thereof, wherein the rare earth composite material comprises (RE) 2 Si x O y (ii) a Wherein RE is at least three of rare earth elements, 6+4x is 2y, x is more than or equal to 1 and less than or equal to 3, and y is more than or equal to 5 and less than or equal to 7. The rare earth composite material is not easy to volatilize in a water oxygen gas environment for a long time, has extremely stable characteristic, and is beneficial to prolonging the service life of an environmental barrier coating.)

1. A rare earth composite material, characterized in that the rare earth composite material comprises (RE)₂Si_xO_y；

Wherein RE is at least three of rare earth elements, 6+4x is 2y, x is more than or equal to 1 and less than or equal to 3, and y is more than or equal to 5 and less than or equal to 9.

2. The rare earth-based composite material according to claim 1, wherein the molar content of each rare earth element in the total rare earth elements is 5 to 50%.

3. The rare earth-based composite material of claim 2, wherein the rare earth element comprises Sc, Y, L a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L u.

4. The rare-earth-based composite material as claimed in claim 3, wherein the rare-earth-based composite material has the composition (RE)₂Si₂O₇。

5. The rare-earth-based composite material as claimed in claim 3, wherein the rare-earth-based composite material has the composition (RE)₂SiO₅。

6. The method for producing a rare-earth-based composite material as claimed in any one of claims 1 to 5, comprising the steps of:

1) mixing a silicon source and salt solutions of at least three rare earth elements, and stirring to obtain a mixed solution;

2) stirring the mixed solution to obtain mixed gel;

3) sequentially drying and sintering the mixed gel to obtain a product precursor;

4) carrying out heat treatment on the product precursor to obtain the rare earth composite material;

wherein the silicon source comprises tetraethoxysilane, ethanol and water;

the temperature of the heat treatment is (800-.

7. The method according to claim 6, wherein the molar ratio of the tetraethoxysilane to the ethanol to the water in the silicon source is 1:4: 1.

8. the method as claimed in claim 6, wherein the sintering temperature is 400-600 ℃.

9. The method according to claim 8, wherein the sintering treatment is carried out for 2 to 5 hours.

10. Use of the rare earth-based composite material according to any one of claims 1 to 5 in environmental barrier coatings.

Technical Field

The invention relates to a material, in particular to a rare earth composite material, a preparation method and application thereof, and belongs to the technical field of coating design.

Background

Because the continuous fiber toughened silicon carbide ceramic matrix composite (CMC-SiC) has the characteristics of high specific strength, high specific modulus, oxidation resistance, low density and the like, the CMC-SiC part is gradually applied to the hot end part of the aeroengine in aeronautical countries such as Europe, America and the like. When the CMC-SiC is in service in air or dry oxygen environment, compact SiO can be formed on the surface of the CMC-SiC₂Protective film due to SiO₂The CMC-SiC has a low oxygen diffusion coefficient at high temperature, so that the CMC-SiC has very good oxidation resistance in air or dry oxygen environment.

However, in the engine combustion chamber environment, the SiO formed on the surface of CMC-SiC₂The protective film can be eroded by water vapor and molten salt impurities in the gas environment and lose the inner partThe protective effect of the composite material, and thus the service performance of the CMC-SiC component is sharply reduced. Aiming at the problem, a coating is usually prepared on the surface of CMC-SiC at present to overcome the early failure of CMC-SiC caused by oxidation and corrosion in the environment of an engine combustion chamber, thereby ensuring the environmental durability of CMC-SiC parts in the environment of the engine combustion chamber and meeting the requirements of safety and long service life of aeroengine parts.

At present, the coating material mainly comprises mullite (mullite) and barium-strontium-aluminum-silicon-oxygen system (Ba)_xSr_1-xAl₂Si₂O₇BSAS). Mullite with high SiO content₂Activity (0.3-0.4) which causes SiO to exist in water oxygen gas environment₂And the mullite is volatilized selectively, so that the phase stability of the mullite in the water-oxygen gas environment is poor, and the service life is short. While BSAS material is SiO₂The activity is low, the catalyst can have good phase stability in a water oxygen gas environment in a short period of time, but once the catalyst is in service for too long time, the catalyst still has high volatilization rate in the water oxygen gas environment to cause weight loss, so that the service life of the catalyst is limited.

Disclosure of Invention

The invention provides a rare earth composite material, a preparation method and application thereof, wherein the rare earth composite material is not easy to volatilize in a water oxygen gas environment for a long time, has extremely stable characteristics, and is beneficial to prolonging the service life of an environmental barrier coating.

The invention provides a rare earth composite material, which comprises (RE)₂Si_xO_y；

Wherein RE is at least three of rare earth elements, 6+4x is 2y, x is more than or equal to 1 and less than or equal to 3, and y is more than or equal to 5 and less than or equal to 9.

The rare earth-based composite material as described above, wherein the molar content of each rare earth element in the total rare earth elements is 5 to 50%.

The rare earth-based composite material as described above, wherein the rare earth element includes Sc, Y, L a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L u.

The rare earth system as described aboveA composite material, wherein the rare earth-based composite material has the composition (RE)₂Si₂O₇。

The rare-earth composite material as described above, wherein the rare-earth composite material has the composition (RE)₂SiO₅。

The invention also provides a preparation method of any one of the rare earth composite materials, which comprises the following steps:

1) mixing a silicon source and salt solutions of at least three rare earth elements, and stirring to obtain a mixed solution;

2) stirring the mixed solution to obtain mixed gel;

3) sequentially drying and sintering the mixed gel to obtain a product precursor;

4) carrying out heat treatment on the product precursor to obtain the rare earth composite material;

wherein the silicon source comprises tetraethoxysilane, ethanol and water;

the temperature of the heat treatment is (800-.

The preparation method as described above, wherein, in the silicon source, the molar ratio of the ethyl orthosilicate, the ethanol and the water is 1:4: 1.

the preparation method comprises the following steps, wherein the sintering treatment temperature is 400-600 ℃.

The preparation method as described above, wherein the sintering time is 2-5 h.

The invention also provides an application of any one of the rare earth composite materials in an environmental barrier coating.

The implementation of the invention at least comprises the following advantages:

1. the rare earth composite material has good phase stability in the water oxygen gas environment, is not easy to be corroded by water oxygen and has extremely low volatilization rate;

2. the preparation method of the rare earth composite material is simple to operate, easy to control, free of assistance of large instruments and beneficial to forming the rare earth composite material with a single crystal structure;

3. the preparation method of the rare earth composite material can use a sol-gel method and can also obtain the rare earth composite material by a solid phase synthesis method;

4. the rare earth composite material can be used as an environmental barrier coating, is not easy to volatilize or corrode and lose weight even if being in a water oxygen gas environment for a long time, and can effectively protect the inner layer material, so that the rare earth composite material is suitable for prevention and popularization in the application field of the environmental barrier coating.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of a method for preparing a rare earth composite material according to the present invention;

FIG. 2 is an XRD pattern of a rare earth based composite material according to example 1 of the present invention;

FIG. 3 shows a rare-earth composite material and Yb in example 1 of the present invention₂Si₂O₇、Lu₂Si₂O₇、Sc₂Si₂O₇、Y₂Si₂O₇、Gd₂Si₂O₇XRD contrast pattern of (a);

FIG. 4 is a transmission electron micrograph of the rare earth based composite material of example 1 of the present invention magnified 14000 times;

FIG. 5 is an electron diffraction pattern of the rare earth composite material according to example 1 of the present invention;

FIG. 6 is an EDS profile of a rare earth based composite material of example 1 of the present invention;

FIG. 7 is a comparative XRD pattern of the rare earth based composite material of example 1 of the present invention before and after the test.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The present invention provides a rare earth composite material, which is composed of (RE)₂Si_xO_y；

Wherein RE is at least three of rare earth elements, 6+4x is 2y, x is more than or equal to 1 and less than or equal to 3, and y is more than or equal to 5 and less than or equal to 9.

In the rare earth-based composite material of the present invention, RE may be selected from at least three of rare earth elements.

Further, the molar content of each rare earth element in the total rare earth elements is 5-50%.

The inventors of the present application have found that a silicate comprising at least three rare earth elements has a remarkable corrosion resistance property against a water oxygen environment, and that the material can achieve an optimization of the corrosion resistance against the water oxygen environment when the ratio of the amount of each rare earth element substance to the sum of the amounts of all the rare earth element substances is 5 to 50%.

In the present invention, the ratio of the amount of each rare earth element substance to the amount of all rare earth element substances may be all the same, or may be partially the same or different from each other, and the present invention is not limited to them.

Further, the rare earth elements in the present invention include Sc, Y, L a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L u.

In one embodiment, the rare earth-based composite material of the present invention may have a composition of RE₂Si₂O₇。

In another embodiment, the rare earth composite material of the present invention may further have a composition of RE₂SiO₅。

Fig. 1 is a flow chart of a method for preparing a rare earth composite material of the present invention, and as shown in fig. 1, the method for preparing the rare earth composite material of the present invention comprises the following steps:

s101: and mixing a silicon source and salt solutions of at least three rare earth elements, and stirring to obtain a mixed solution.

In S101, a silicon source can be obtained by uniformly mixing tetraethoxysilane, ethanol, and water. Wherein, the ethanol is used for enhancing the intersolubility of the ethyl orthosilicate and the water, thereby being beneficial to promoting the uniformity of a silicon source.

In addition, before the mixed solution is prepared, salt solutions of at least three rare earth elements are also required to be prepared. The rare earth element salt solution is obtained by mixing rare earth element salt with water and stirring until the rare earth element salt is completely dissolved.

In the present invention, the anion in the salt of the rare earth element should be selected from volatile anions, such as nitrate of the rare earth element, acetate of the rare earth element, carbonate of the rare earth element, and the like.

Also, the anion of each rare earth element salt may be the same or different. For example, the salt solution of at least three rare earth elements may be a yttrium nitrate solution, a lanthanum acetate solution, and a cerium acetate solution, and may also be a yttrium nitrate solution, a lanthanum nitrate solution, and a cerium nitrate solution.

When the preparation of the salt solution of at least three rare earth elements is finished, the salt solution of at least three rare earth elements can be mixed with the silicon source after being mixed; the salt solutions of at least three rare earth elements may also be separately mixed with the silicon source.

It is to be noted here that if the molar content of each rare earth element in the total rare earth elements in the rare earth-based composite material to be prepared is 5 to 50%, the amount of the substance of each rare earth element salt should be 5 to 50% of the total substance of all rare earth element salts.

S102: the mixed solution was stirred to obtain a mixed gel.

In S102, the mixed solution is continuously stirred to form a stable sol system, and the sol-gel particles are polymerized to form a mixed gel with a three-dimensional network structure, wherein the mixed gel network is filled with a solvent losing fluidity.

S103: and sequentially carrying out drying treatment and sintering treatment on the mixed gel to obtain a product precursor.

Wherein, the drying treatment is used for removing the water in the mixed gel, and the roasting treatment is used for removing the anions introduced by the salt of the rare earth element in the mixed gel.

S104: and carrying out heat treatment on the product precursor to obtain the rare earth composite material.

In the product precursor, atoms of the rare earth element are randomly distributed therein, so that the product precursor can be subjected to further heat treatment which not only contributes to the decomposition of residual impurities, but also enables the atoms of the rare earth element to be arranged, thereby producing the rare earth-based composite material having a single crystal structure of the present invention.

Specifically in S104, the product precursor may be placed in a muffle furnace and heat treated at (800-1700) deg.C for 2-10h, preferably 1600 deg.C for 5 h.

Further, in the silicon source, the molar ratio of the ethyl orthosilicate to the ethanol to the water is 1:4: 1.

When the tetraethoxysilane and the water in the silicon source meet the requirements, the hydrolysis and the dissolution of the tetraethoxysilane can be ensured, and if the water content is too much, the subsequent drying cost is increased.

Further, the temperature of the sintering treatment in S103 is 400-600 ℃, and the time of the sintering treatment is 2-5 h.

Wherein the sintering process may be performed in a muffle furnace.

In addition, the drying process in S103 may adopt a step processing method, and specifically may include:

a first drying treatment: drying the mixed gel in an oven at 60-80 ℃, wherein the time length of the first drying treatment is not less than 12h, thereby being beneficial to obtaining the gel;

and (3) second drying treatment: and drying the mixed gel after the first drying treatment at the temperature of 110-130 ℃, wherein the time length of the second drying treatment is not less than 24h, so that the moisture in the gel is favorably removed, and the cost of subsequent heat treatment is reduced.

In addition, in the preparation of the rare earth composite material of the present invention, the molar ratio of ethyl orthosilicate to the salt of the rare earth element is x: 2.

for example, if the rare earth composite material to be prepared has a composition of RE₂Si₂O₇The molar ratio of the ethyl orthosilicate to the salt of the rare earth element is 1: 1;

if the composition of the rare earth composite material to be prepared is RE₂SiO₅The molar ratio of the ethyl orthosilicate to the salt of the rare earth element is 1: 2.

in addition to the above-mentioned preparation methods, the present invention can also adopt a solid-phase synthesis method to prepare a rare earth-based composite material.

Hereinafter, the rare earth composite material and the method for preparing the same according to the present invention will be described in more detail with reference to specific examples.