CN113105237A

CN113105237A - AB2O6 type tantalate ceramic and preparation method thereof

Info

Publication number: CN113105237A
Application number: CN202110479426.XA
Authority: CN
Inventors: 李柏辉; 冯晶; 陈琳; 罗可人; 张鹤瀛
Original assignee: Kunming University of Science and Technology
Current assignee: Kunming University of Science and Technology
Priority date: 2021-04-30
Filing date: 2021-04-30
Publication date: 2021-07-13
Anticipated expiration: 2041-04-30
Also published as: CN113105237B

Abstract

The invention belongs to the technical field of thermal barrier/environmental barrier coating materials, and discloses an AB2O6 type tantalate ceramic and a preparation method thereof, wherein the structural formula of the ceramic is AB₂O₆Wherein A is one of Ni, Co, Mg, Ca, Sr, Ba and Zn, and B is Ta; the ceramic crystal structure is a single phase structure. The preparation method comprises firstly carrying out treatment on A (OH) under the condition of water bath₂The solution was stirred and TaCl was added dropwise₅Carrying out ultrasonic treatment on the solution, and gradually dropwise adding concentrated ammonia water to enable the pH value of the solution to be larger than 10; stirring to obtain precipitate colloid, washing and precipitating with anhydrous ethanol and deionized water until pH reaches 7; and drying, sieving, calcining, sieving again and sintering by discharge plasma to obtain the blocky AB2O6 type tantalate ceramic. The AB2O6 type tantalate ceramic provided by the invention does not use rare earth elements,the cost of raw materials is low, so that the manufacturing cost of the ceramic material is low.

Description

AB2O6 type tantalate ceramic and preparation method thereof

Technical Field

The invention belongs to the technical field of thermal barrier/environmental barrier coating materials, and particularly relates to AB2O6 type tantalate ceramic and a preparation method thereof.

Background

In recent years, aviation and aerospace technologies have been developed, and the operating temperatures and pressures to which hot-end components of aircraft (e.g., engines, ground turbines, etc.) are subjected have been increasing. In order to meet the requirements, hot end parts of the aircraft are made of high-temperature materials, and in order to adapt to higher working temperature, a thermal barrier/environmental barrier coating is sprayed on the high-temperature materials to reduce the temperature of a base material (high-temperature material) and improve the impact-resistant and corrosion-resistant effects; the hot end part of the aircraft is coated with the high-temperature material of the thermal barrier/environmental barrier coating as a preparation raw material, so that the service life of the hot end part of the aircraft can be prolonged.

At present, the thermal barrier/environmental barrier coating material widely applied is Yttria Stabilized Zirconia (YSZ), but the use temperature of the Yttria Stabilized Zirconia (YSZ) is lower than 1200 ℃, and the Yttria Stabilized Zirconia (YSZ) has the defects of high thermal conductivity, poor thermal insulation performance and unmatched thermal expansion coefficient, so that the Yttria Stabilized Zirconia (YSZ) cannot meet the development requirements of the current aviation and aerospace technologies.

In recent years, rare earth tantalite is used as a new-generation thermal barrier/environmental barrier coating material, and has extremely low thermal conductivity (1.0W/m.K, 900 ℃) and controllable thermal expansion coefficient (4-12 multiplied by 10)^-6K^-1) And excellent comprehensive mechanical properties, gradually enter the visual field of people, and are widely applied and researched.

However, the main raw material of the rare earth tantalate is rare earth elements, and the rare earth elements are protected as strategic resources in China, and the exploitation amount is small, so the price is very high, and the manufacturing cost of the rare earth tantalate is high.

Disclosure of Invention

The invention aims to provide an AB2O6 type tantalate ceramic and a preparation method thereof, and solves the problem that the existing rare earth tantalate ceramic material is high in manufacturing cost due to the fact that the main raw material is rare earth element and the rare earth element is very high in price.

In order to achieve the purpose, the invention provides the following technical scheme that the AB2O6 type tantalate ceramic has a structural formula of AB₂O₆Wherein A is one of Ni, Co, Mg, Ca, Sr, Ba and Zn, and B is Ta; the ceramic crystal structure is a single phase structure.

The invention also provides another technical scheme, and the preparation method of the AB2O6 type tantalate ceramic comprises the following steps:

in the first step of the method,

for A (OH) under the condition of water bath₂The solution was stirred gradually towards A (OH)₂TaCl is dripped into the solution₅Stirring and mixing the solution for half an hour, carrying out ultrasonic treatment, and gradually dropwise adding concentrated ammonia water to ensure that the pH value of the solution is more than 10; gradually stirring to obtain precipitate colloid, and washing and precipitating with anhydrous ethanol and deionized water until pH reaches 7;

in the second step, the first step is that,

and (4) taking out the filter residue obtained in the first step, and performing drying, sieving, calcining, sieving again and spark plasma sintering to obtain the blocky AB2O6 type tantalate ceramic.

The beneficial effects of the technical scheme are as follows:

1. the density of the AB2O6 type tantalate ceramic provided by the technical scheme is more than 95%, and the defects (cracks and air holes) in the ceramic are very few, so that the ceramic has low thermal conductivity at high temperature and good heat insulation protection effect; meanwhile, the higher density can effectively increase the Vickers hardness, reduce the generation of cracks in the material, reduce the damage caused by residual thermal stress and prolong the service life; therefore, the material can be used as a thermal barrier/environmental barrier coating material;

2. in the technical scheme, the crystal structure of the AB2O6 type tantalate ceramic is a single-phase structure, no second phase exists, the crystal grain size is small, the distribution is uniform, the boundary of a crystal grain is clear, and phonon scattering at the boundary of the crystal grain is enhanced, so that the heat transfer of the ceramic material is small, and the heat conductivity is reduced;

3. the technical scheme reduces the agglomeration phenomenon among powder raw materials through the ultrasonic action, so that the raw materials are uniformly distributed in the solution and fully react; and the precipitate is washed, so that the purity of the powder can be improved, and the purity of the prepared AB2O6 type tantalate ceramic block is improved;

4. the technical scheme combines a chemical coprecipitation method and a discharge plasma sintering method to prepare the AB2O6 type tantalate ceramic, so that the prepared ceramic block has high density, uniform components and low preparation cost; and the coating has low thermal conductivity at high temperature, good heat insulation performance and high thermal expansion coefficient at high temperature, and has excellent performance as a thermal barrier/environmental barrier coating material.

In conclusion, the AB2O6 type tantalate ceramic provided by the technical scheme does not need to use rare earth elements during preparation, and is low in raw material cost and low in overall manufacturing cost. The ceramic has low thermal conductivity, and can be used as a thermal barrier/environmental barrier coating material.

Further, in the first step, the water bath condition is 70-100 ℃.

Has the advantages that: by setting the water bath conditions, the raw materials can be fully reacted.

Further, in step one, TaCl₅The dropping speed of the solution is 200-400 mL/min, and the dropping speed of the concentrated ammonia water is 1-2 mL/min.

Has the advantages that: the parameter setting can meet the requirement of preparing ceramic powder by a chemical coprecipitation method.

Further, in the second step, the drying temperature is 70-90 ℃, and the drying time is 18-24 hours.

Has the advantages that: drying temperature and time in this scheme of adoption can make the solvent in the powder fully volatilize.

Further, in the second step, the sieving mesh is 400-600 meshes; the calcining temperature is 600-800 ℃, and the time is 360-480 min; and the secondary screening mesh is 600-800 meshes.

Has the advantages that: the purpose of removing impurities can be achieved by calcining; the powder is sieved twice, so that powder with larger particles can be avoided, and the density of the finally sintered block is ensured.

Further, in the second step, before spark plasma sintering, the powder needs to be compacted in a die; the temperature during sintering is 1300-1500 ℃, the sintering time is 1h, the heat preservation pressure is 60-70MPa, and the heat preservation time is 10 min.

Has the advantages that: the spark plasma sintering has the advantages of high temperature rise speed, short sintering time, clean sintering process and capability of quickly preparing materials; gas in the powder can be discharged under the action of pressure by maintaining the pressure in the sintering process, so that block pores after sintering are reduced, and defects in the sintered ceramic are reduced; the AB2O6 type tantalate ceramic obtained by adopting the sintering parameters has good high-temperature thermal stability, high compactness and lower thermal conductivity at high temperature, has mechanical properties and thermal properties similar to those of rare earth tantalate, and can be used as a novel high-temperature ceramic material.

Drawings

FIG. 1 is CoTa prepared in example 2 of the present invention₂XRD pattern of O6 ceramic block;

FIG. 2 is CoTa prepared in example 2 of the present invention₂O₆SEM image of the ceramic block;

FIG. 3 shows CaTa according to embodiment 4 of the present invention₂O₆A plot of thermal conductivity of the ceramic mass as a function of temperature;

FIG. 4 is MgTa provided in example 3 of the present invention₂O₆Graph of the coefficient of thermal expansion of a ceramic block as a function of temperature.

Detailed Description

The following is further detailed by way of specific embodiments:

an AB2O6 type tantalate ceramic with a structural formula of AB₂O₆Wherein A is one of Ni, Co, Mg, Ca, Sr, Ba and Zn, and B is Ta; the ceramic crystal structure is a single phase structure.

An AB2O6 type tantalate ceramic is prepared by the following steps:

in the first step of the method,

according to ATa₂O₆The structural formula (1) is A (OH) with the measured concentration of 10-50%₂And A (OH)₂Placing the solution in a water bath at 70-100 ℃, and then adding the solution into A (OH) at a dropping speed of 200-400 m L/min₂TaCl with the concentration of 10-50% is dripped into the solution₅The solution was stirred at a rotation speed of 50rpm/min while being dropped.

After mixing and stirring for 0.5h, putting the mixed solution into an ultrasonic generator for ultrasonic treatment; meanwhile, dropwise adding 20-30% concentrated ammonia water at the dropping speed of 1-2 mL/min, continuously stirring the solution, and stopping adding the concentrated ammonia water until the pH value of the solution is more than 10.

And washing the precipitate with anhydrous ethanol and deionized water until the pH value is 7, and filtering to obtain a filter cake for later use.

In the second step, the first step is that,

placing the filter cake in the step one in an oven, drying at the temperature of 70-90 ℃ for 18-24h, then sieving with a sieve of 400-600 meshes, and calcining the filtered powder meeting the particle size requirement at the temperature of 600-800 ℃ for 480 min; then the calcined powder is sieved by a sieve with 600 meshes and 800 meshes to obtain the powder with the particle size.

Putting the powder with the particle size into a graphite mold, compacting, and then performing spark plasma sintering at the temperature of 1300-1500 ℃, wherein the sintering time is 1h, the heat preservation pressure is 60-70Mpa, and the heat preservation time is 10min, so as to obtain compact ATa₂O₆A ceramic block.

Example 1 is NiTa₂O₆Example 2 is CoTa₂O₆Example 3 is MgTa₂O₆Example 4 is CatA₂O₆Example 5 is SrTa₂O₆Example 6 is BaTa₂O₆Example 7 is ZnTa₂O₆。

Examples 1-7 differ only in the various parameters during preparation, the specific parameters being shown in table 1:

TABLE 1

Experiment:

the ceramic blocks prepared in examples 1 to 7 were examined as follows:

characterization by XRD

The ceramic blocks obtained in examples 1 to 7 were examined by an X-ray diffractometer, wherein CoTa provided in example 2 was used₂O₆The XRD pattern of the ceramic block is shown in FIG. 1. According to fig. 1, the diffraction peaks obtained by the test correspond to the standard PDF cards one-to-one, and the second diffraction peak exists. Known as PDF cards, CoTa₂O₆The crystal structure of the ceramic block is tetragonal phase, wherein alpha-beta-gamma-90 DEG, and the theoretical density is 8.337g/cm³。

SEM characterization

The ceramic blocks obtained in examples 1 to 7 were examined by scanning electron microscopy, wherein CoTa provided in example 2₂O₆The SEM spectra of the ceramic monolith is shown in figure 2. As can be seen from FIG. 2, CoTa₂O₆The ceramic block has uniform crystal grain size, the grain size is between 10 and 15 micrometers, the grain boundary is clear, and no second phase exists in or among the crystal grains, which is consistent with the XRD result; and no obvious air holes and cracks exist on the surface of the ceramic block body, and the density is as high as 97.3%.

3. Density detection

The ceramic blocks obtained in examples 1 to 7 were examined by archimedes' drainage method, and the results are shown in table 2, and it is understood from table 2 that the ceramic blocks obtained in examples 1 to 7 all had a degree of densification of more than 95%.

By combining the SEM characterization and the density measurement results, ATa prepared in examples 1-7 was used₂O₆The ceramic block has less microcrack and extremely low pore content, so that the density of the ceramic block is high.

4. Thermal conductivity and coefficient of thermal expansion measurements

The ceramic blocks obtained in examples 1 to 7 were each ground into pieces

The thermal conductivity of the round sheet was measured by a laser thermal conductivity meter, and example 1-conducted at 800 deg.CThe thermal conductivity of the ceramic block obtained in example 7 is shown in table 2. Wherein example 4 provides a CatA₂O₆The graph of the thermal conductivity of the ceramic block along with the temperature change is shown in fig. 3, and it can be known from fig. 3 that the thermal conductivity of the ceramic block is rapidly reduced along with the continuous increase of the temperature, and the thermal conductivity is slowly increased between 600 ℃ and 700 ℃; at a temperature of 800 ℃ of CaTa₂O₆The thermal conductivity of the ceramic block is reduced to 1.248W.m^-1.K^-1And has excellent heat insulation capability in high-temperature environment.

Example 3 MgTa₂O₆The graph of the thermal expansion coefficient of the ceramic block body changing with the temperature is shown in fig. 4, and it can be known from fig. 4 that the thermal expansion coefficient of the ceramic block body rapidly rises with the continuous increase of the temperature and gradually becomes stable at 800 ℃; when the temperature reaches 1200 ℃, the thermal expansion coefficient of the ceramic block reaches 7.3W.m^-1.K^-1And meets the characteristics of the thermal insulation coating material.

TABLE 2

In conclusion, the AB2O6 type tantalate ceramics prepared in the embodiments 1-7 of the present invention have high compactness of more than 95%, good high temperature thermal stability, and low thermal conductivity at high temperature, and can be used as high temperature ceramic materials. Compared with the rare earth tantalate ceramic material which takes the rare earth elements as the main raw material, the rare earth tantalate ceramic material has similar thermo-mechanical properties and low cost, and is more suitable for being used in various fields at present.

It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention, and these changes and modifications should not be construed as affecting the performance of the invention and its practical application.

Claims

1. An AB2O6 type tantalate ceramic, wherein: the structural formula of the ceramic is AB₂O₆Wherein A is Ni. One of Co, Mg, Ca, Sr, Ba and Zn, and B is Ta; the ceramic crystal structure is a single phase structure.

2. The method of claim 1, comprising the steps of:

in the first step of the method,

in the second step, the first step is that,

3. The method of claim 2, wherein the method comprises the steps of: in the first step, the water bath condition is 70-100 ℃.

4. The method of claim 3, wherein the method comprises the steps of: in step one, TaCl₅The dropping speed of the solution is 200-400 mL/min, and the dropping speed of the concentrated ammonia water is 1-2 mL/min.

5. The method of claim 4, wherein the method comprises the steps of: in the second step, the drying temperature is 70-90 ℃, and the drying time is 18-24 h.

6. The method of claim 5, wherein the method comprises the steps of: in the second step, the sieving mesh is 400-600 meshes; the calcining temperature is 600-800 ℃, and the time is 360-480 min; and the secondary screening mesh is 600-800 meshes.

7. The method of claim 6, wherein the method comprises the steps of: in the second step, before spark plasma sintering, the powder needs to be compacted in a die; the temperature during sintering is 1300-1500 ℃, the sintering time is 1h, the heat preservation pressure is 60-70MPa, and the heat preservation time is 10 min.