CN113024232B - A kind of light and heavy rare earth mixed high entropy rare earth silicate dense block and preparation method thereof - Google Patents

Abstract

The invention provides a light and heavy rare earth mixed high-entropy rare earth silicate dense block, the chemical formula is: (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ , the block is composed of Ho ₂ O ₃ , Lu ₂ O ₃ , Yb ₂ O ₃ , Eu ₂ O ₃ and SiO ₂ are used as raw materials, and are prepared through wet mixing, high temperature reaction, wet ball milling, cold pressing, cold isostatic pressing and high temperature sintering. The light and heavy rare earth mixed high-entropy rare earth silicate dense block of the invention has high solid solubility, good high temperature stability, high density, simple preparation method, high production efficiency, high safety and energy saving.

Description

A kind of light and heavy rare earth mixed high entropy rare earth silicate dense block and preparation method thereof

technical field

The invention belongs to the technical field of ceramic materials for aero-engine environmental barrier coatings, and in particular relates to a light and heavy rare earth mixed high-entropy rare earth silicate dense block and a preparation method thereof.

Background technique

Improving the thrust-to-weight ratio of aero-engines is the future development direction of the aviation industry. In order to achieve a high thrust-to-weight ratio, it is necessary to increase the temperature of the front inlet of the turbine. Therefore, the working temperature of hot-end components such as the combustion chamber and turbine blades will continue to rise. At present, the blade materials of aero-engines are superalloy materials, and the temperature of the front inlet of the turbine will further increase to reach the temperature limit of nickel-based superalloys, which makes it difficult for nickel-based superalloys to meet the working requirements of the engine. Silicon-based non-oxide ceramics and their composite materials (such as silicon-based ceramic materials) have excellent high-temperature thermal and mechanical properties, and are expected to replace traditional superalloys as thermal end-part materials for a new generation of aero-engines.

In a dry combustion environment, a layer of SiO ₂ film will form on the surface of the silicon-based ceramic material, which plays a good protective role and can prevent the silicon-based material from being further oxidized. However, in a combustion environment containing water vapor, silicon-based ceramics will react with water vapor to generate volatile Si(OH) ₄ , thereby causing the deterioration of material properties. Environmental barrier coatings (EBC) have good resistance to molten salt corrosion and water-oxygen corrosion. Coating them on the surface of engine hot-end components is expected to solve this problem.

Rare earth silicate ceramic materials have excellent water vapor corrosion resistance, CMAS (CaO-MgO-Al ₂ O ₃ -SiO ₂ ) corrosion resistance and low thermal expansion coefficient, and are popular candidates for a new generation of environmental barrier coatings . Some rare earth monosilicates and rare earth disilicates meet the basic requirements as silicon-based non-oxide ceramic environmental barrier coatings. However, the properties of single-phase rare earth silicates are not balanced in all aspects, and candidate materials that fully meet the performance requirements of environmental barrier coatings have not yet been found, so the material needs to be optimized.

High-entropy ceramics are ceramics that apply the design idea of high-entropy alloys to ceramics, replacing a single cation in traditional ceramics with several equimolar or nearly equimolar cations to form a multi-component solid solution. The inherent characteristics of various elements and the interaction between them can combine the excellent properties of each element, so that the high-entropy ceramics have the excellent properties of each component. Common high-entropy ceramics are mainly high-entropy rare earth silicate bulk, such as high-entropy rare earth monosilicate of heavy rare earth elements (Yb _0.25 Y _0.25 Lu _0.25 Er _0.25 ) ₂ SiO ₅ bulk, rare earth disilicate ( Yb _0.2 Y _0.2 Lu _0.2 Sc _0.2 Gd _0.2 ) ₂ Si ₂ O ₇ bulk, rare earth monosilicate (Y _0.25 Ho _0.25 Er _0.25 Yb _0.25 ) ₂ SiO ₅ bulk and the like. However, the current preparation methods of high-entropy rare earth silicate blocks have problems such as cumbersome process, low efficiency, insufficient block density, and single type of rare earth elements (all heavy rare earths).

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned deficiencies of the prior art, the present invention proposes a light and heavy rare earth mixed high-entropy rare earth silicate dense block, which has high solid solubility, good high temperature stability, high density, and a simple preparation method. , high production efficiency, and high safety, energy saving.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The invention provides a light and heavy rare earth mixed high-entropy rare earth silicate dense block, and the chemical formula of the light and heavy rare earth mixed high-entropy rare earth silicate dense block is: (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ , in which Ho (holmium), Lu (lutetium), and Yb (ytterbium) are heavy rare earth elements, and Eu (europium) is light rare earth elements.

The present invention also provides the above-mentioned preparation method of the light and heavy rare earth mixed high-entropy rare earth silicate dense block, comprising the following steps:

S1, weigh each raw material according to the molar ratio of Ho ₂ O ₃ :Lu ₂ O ₃ :Yb ₂ O ₃ :Eu ₂ O ₃ :SiO ₂ =1:1:1:1:4;

S2, adopt the method of wet mixing to mix the raw materials of step S1 evenly, and dry and sieve to obtain mixed raw materials;

S3, the mixed raw materials of step S2 are reacted at high temperature to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles;

S4, performing wet ball milling on the heavy rare earth mixed high-entropy rare earth silicate ceramic particles in step S3, drying and sieving to obtain a light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder;

S5, performing cold pressing and cold isostatic pressing on the light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder in step S4 to obtain a light and heavy rare earth mixed high-entropy rare earth silicate bulk body;

S6, performing high temperature sintering on the light and heavy rare earth mixed high-entropy rare earth silicate bulk green body in step S5 to obtain a heavy rare earth mixed high-entropy rare earth silicate dense block.

Preferably, the wet mixing in step S2 uses ethanol as a medium, the rotation speed is 100-300r/min, and the time is 4-12h.

Preferably, the high temperature reaction in step S3 is a reaction at 1500°C-1700°C for 2-8 hours in an air atmosphere.

Preferably, the wet ball milling in step S4 uses ethanol as a medium, the rotation speed is 100-300r/min, and the time is 4-12h.

Preferably, the pressure of the cold-press forming in step S5 is 10-30 MPa, and the pressure-holding time is 1-5 minutes; the pressure of cold isostatic pressing is 100-250 MPa, and the pressure-holding time is 10-30 minutes.

Preferably, the high temperature sintering temperature in step S5 is 1400-1750° C., and the holding time is 2-12 h.

Preferably, the purity of Ho ₂ O ₃ , Lu ₂ O ₃ , Yb ₂ O ₃ , Eu ₂ O ₃ and SiO ₂ described in step S1 is 99.9%-99.99%.

Preferably, the sieving described in steps S2 and S4 is 40-120 mesh sieve.

Preferably, the ball milling jar and the grinding balls of the wet mixing in step S2 and the wet ball milling in step S4 are made of zirconia or agate.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a light and heavy rare earth mixed high-entropy rare earth silicate dense block, the chemical formula is: (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ , the block is composed of Ho ₂ O ₃ , Lu ₂ O ₃ , Yb ₂ O ₃ , Eu ₂ O ₃ and SiO ₂ are used as raw materials, and are prepared through wet mixing, high temperature reaction, wet ball milling, cold pressing, cold isostatic pressing and high temperature sintering. The present invention has the following advantages:

(1) The preparation process has the advantages of simple process, high safety and energy saving.

(2) The present invention adopts the method of cold isostatic pressing + pressureless sintering in the preparation process of the light and heavy rare earth mixed high-entropy rare earth silicate dense block, and the production efficiency is high, and multiple samples can be prepared at the same time: the usual hot pressing For sintering, only one sample can be prepared at a time; while the cold isostatic pressing + pressureless sintering method of the present invention can sinter multiple samples in one furnace.

(3) The light and heavy rare earth mixed high-entropy rare earth silicate dense block of the present invention has high solid solubility, good high temperature stability and high density, which can reach more than 96%.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ ;

Fig. 2 is the surface scanning electron microscope image of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ ;

FIG. 3 is a SEM image of the fracture surface of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ .

Detailed ways

The specific embodiments of the present invention will be further described below. It should be noted here that the description of these embodiments is used to help the understanding of the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples can be purchased through conventional commercial channels unless otherwise specified.

Example 1 A kind of light and heavy rare earth mixed high entropy rare earth silicate dense block

The chemical formula of the light and heavy rare earth mixed high-entropy rare earth silicate dense block is: (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ , wherein Ho (holmium), Lu (lutetium) and Yb (ytterbium) are heavy rare earths element, Eu (europium) is a light rare earth element.

The preparation method of the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate dense block comprises the following steps:

(1) Weigh each raw material according to the molar ratio of Ho ₂ O ₃ :Lu ₂ O ₃ :Yb ₂ O ₃ :Eu ₂ O ₃ :SiO ₂ =1:1:1:1:4, Ho ₂ O ₃ , Lu The purity of ₂ O ₃ , Yb ₂ O ₃ , Eu ₂ O ₃ and SiO ₂ raw materials is 99.9%-99.99%;

(2) Use a ball mill to wet-mix the above-mentioned raw materials, use anhydrous ethanol as the medium, the ball mill tank and the grinding balls are made of zirconia or agate material, the rotating speed is 200r/min, the time is 8h, and after mixing, dry and pass through 80 mesh Sieve to obtain mixed raw materials;

(3) placing the mixed raw materials in a high-temperature reaction furnace, and reacting at 1600 °C for 5 hours in an air atmosphere to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles;

(4) Perform wet ball milling on the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles. The ball milling uses anhydrous ethanol as the medium, the ball mill tank and the grinding balls are made of zirconia or agate material, the rotating speed is 200r/min, and the time is 8h, ball-milled, dried and passed through an 80-mesh sieve to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder;

(5) cold pressing the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder, the pressure of cold pressing is 20MPa, and the holding time is 3min; then cold isostatic pressing is carried out, and the pressure of cold isostatic pressing is is 150MPa, and the pressure holding time is 20min, to obtain the light and heavy rare earth mixed high-entropy rare earth silicate bulk green body;

(6) placing the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic bulk body in a high-temperature reaction furnace, and sintering in an air atmosphere, the sintering temperature is 1650 ° C, and the holding time is 8 h, to obtain a heavy rare earth mixed High-entropy rare earth silicate dense bulk (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ .

工作电压为40kV，工作电流为45mA，扫描速度为10°/min。其中PDF#40-0383为单相稀土硅酸盐Ho₂SiO₅的标准PDF卡片，混合粉体为Ho₂SiO₅、Lu₂SiO₅、Yb₂SiO₅、Eu₂SiO₅四种稀土硅酸盐按照等摩尔比的机械混合粉体。The (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ prepared above was analyzed by X-ray diffraction (taking the mixed powder as a control), using an X-ray diffractometer (PANalytical Empyrean), the incident light was monochromatic The Kα1 ray of Cu filtered by the filter has a wavelength of

The working voltage is 40kV, the working current is 45mA, and the scanning speed is 10°/min. Among them, PDF#40-0383 is the standard PDF card of single-phase rare earth silicate Ho ₂ SiO ₅ , and the mixed powder is four rare earth silicates, namely Ho ₂ SiO ₅ , Lu ₂ SiO ₅ , Yb ₂ SiO ₅ and Eu ₂ SiO ₅ . The salt is mechanically mixed with the powder in an equimolar ratio.

From the diffraction pattern in Figure 1, it can be found that the peak of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ is consistent with the standard PDF card, but the peak position is shifted due to the lattice distortion of the high-entropy ceramic; the mixed powder The peaks are roughly consistent with the PDF card, but if you zoom in on a certain angle range, you will find that the mixed powder has obvious peaks, such as 21°~24° and 27°~29°, indicating that there are many kinds of mixed powders. Mutually. However, (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ prepared in this example is a pure-phase light and heavy rare earth mixed high-entropy rare earth silicate, which contains no impurities and has high solid solubility, rather than several rare earths. Mechanical mixture of silicates. In addition, although the preparation temperature of the sample was high and the time was long, other reactions did not occur to generate impurities, indicating that the sample has good high temperature stability.

At the same time, the surface of the prepared (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ was scanned by a scanning electron microscope (SU8010), as shown in Figure 2. It can be seen that the surface of the sample is very dense and has almost no holes.

Scanning electron microscope (SU8010) was used to scan the fracture surface of the prepared (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ . As shown in Figure 3, it can be seen that the sample has very few fracture holes, and the apertures are all 10 μm. Hereinafter, it is explained that the density of the sample is high.

In addition, the density calculation was performed on the prepared (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ : the unit cell of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ was established using Materials Studio, and its theoretical density was obtained as ρ ₀ =6.69934g/cm ³ ; the density of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ in this example was measured by the Archimedes drainage method, and the density was ρ=6.527g/cm ₃ , and the density was η= ρ/ρ ₀

According to the calculation, the density (ratio of the actual measured density to the theoretical density) of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ prepared in this example is 97.43%.

Example 2 A kind of light and heavy rare earth mixed high entropy rare earth silicate dense block

The chemical formula of the light and heavy rare earth mixed high-entropy rare earth silicate dense block is: (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ , wherein Ho (holmium), Lu (lutetium) and Yb (ytterbium) are heavy rare earths element, Eu (europium) is a light rare earth element.

The preparation method of the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate dense block comprises the following steps:

(1) Weigh each raw material according to the molar ratio of Ho ₂ O ₃ :Lu ₂ O ₃ :Yb ₂ O ₃ :Eu ₂ O ₃ :SiO ₂ =1:1:1:1:4, Ho ₂ O ₃ , Lu The purity of ₂ O ₃ , Yb ₂ O ₃ , Eu ₂ O ₃ and SiO ₂ raw materials is 99.9%-99.99%;

(2) Use a ball mill to wet-mix the above raw materials, use anhydrous ethanol as the medium, the ball mill jar and the grinding balls are made of zirconia or agate material, the rotating speed is 100r/min, the time is 4h, and after mixing, dry and pass through 40 mesh Sieve to obtain mixed raw materials;

(3) placing the mixed raw materials in a high-temperature reaction furnace, and reacting at 1500 °C for 8 hours in an air atmosphere to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles;

(4) Perform wet ball milling on the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles. The ball milling is carried out with anhydrous ethanol as the medium. The ball milling pot and the grinding balls are made of zirconia or agate material. 12h, ball-milled, dried and passed through a 40-mesh sieve to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder;

(5) cold-press molding the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder, the pressure of cold-pressing is 10MPa, and the pressure holding time is 5min; then cold isostatic pressing is performed, and the pressure of cold isostatic pressing is 100MPa, and the pressure holding time is 30min, to obtain light and heavy rare earth mixed high-entropy rare earth silicate bulk green body;

(6) placing the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate bulk body in a high-temperature reaction furnace, and sintering in an air atmosphere. High-entropy rare earth silicate dense bulk (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ .

The X-ray diffraction results, surface and fracture scanning electron microscope results of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ prepared in this example are consistent with those of Example 1, and the density is greater than 96%.

Example 3 A kind of light and heavy rare earth mixed high entropy rare earth silicate dense block

The chemical formula of the light and heavy rare earth mixed high-entropy rare earth silicate dense block is: (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ , wherein Ho (holmium), Lu (lutetium) and Yb (ytterbium) are heavy rare earths element, Eu (europium) is a light rare earth element.

The preparation method of the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate dense block comprises the following steps:

(1) Weigh each raw material according to the molar ratio of Ho ₂ O ₃ :Lu ₂ O ₃ :Yb ₂ O ₃ :Eu ₂ O ₃ :SiO ₂ =1:1:1:1:4, Ho ₂ O ₃ , Lu The purity of ₂ O ₃ , Yb ₂ O ₃ , Eu ₂ O ₃ and SiO ₂ raw materials is 99.9%-99.99%;

(2) Use a ball mill to wet-mix the above raw materials, use anhydrous ethanol as the medium, the ball-milling jar and the grinding balls are made of zirconia or agate material, the rotating speed is 300r/min, the time is 4h, and after mixing, dry and pass through 120 mesh Sieve to obtain mixed raw materials;

(3) placing the mixed raw materials in a high-temperature reaction furnace and reacting at 1700 °C for 2 hours in an air atmosphere to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles;

(4) Perform wet ball milling on the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles. The ball milling uses anhydrous ethanol as the medium, and the ball mill tank and the grinding balls are made of zirconia or agate material. 4h, ball-milled, dried and passed through a 120-mesh sieve to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder;

(5) cold-press molding the above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder, the pressure of cold-pressing is 30MPa, and the pressure holding time is 1min; then cold isostatic pressing is performed, and the pressure of cold isostatic pressing is 250MPa, and the pressure holding time is 10min, to obtain the light and heavy rare earth mixed high-entropy rare earth silicate bulk green body;

(6) The above-mentioned light and heavy rare earth mixed high-entropy rare earth silicate ceramic bulk body is placed in a high-temperature reaction furnace, and sintered in an air atmosphere. High-entropy rare earth silicate dense bulk (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ .

The X-ray diffraction results, surface and fracture scanning electron microscope results of (Ho _0.25 Lu _0.25 Yb _0.25 Eu _0.25 ) ₂ SiO ₅ prepared in this example are consistent with those of Example 1, and the density is greater than 96%.

The embodiments of the present invention have been described above in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions and alterations to these embodiments still fall within the protection scope of the present invention.

Claims (4)

1. The light and heavy rare earth mixed high-entropy rare earth silicate compact block is characterized in that the chemical formula of the light and heavy rare earth mixed high-entropy rare earth silicate compact block is as follows: (Ho)_0.25Lu_0.25Yb_0.25Eu_0.25)₂SiO₅The preparation method of the light and heavy rare earth mixed high-entropy rare earth silicate compact block comprises the following steps:

s1, according to Ho₂O₃:Lu₂O₃:Yb₂O₃:Eu₂O₃:SiO₂Weighing the raw materials according to the molar ratio of 1:1:1:1: 4;

s2, uniformly mixing the raw materials in the step S1 by adopting a wet mixing method, drying and sieving to obtain mixed raw materials;

s3, carrying out high-temperature reaction on the mixed raw materials in the step S2 to obtain light and heavy rare earth mixed high-entropy rare earth silicate ceramic particles, wherein the high-temperature reaction is carried out at 1500-1700 ℃ for 2-8h in an air atmosphere;

s4, carrying out wet ball milling on the heavy rare earth mixed high-entropy rare earth silicate ceramic particles obtained in the step S3, drying and sieving to obtain light rare earth mixed high-entropy rare earth silicate ceramic powder;

s5, carrying out cold press molding and cold isostatic pressing on the light and heavy rare earth mixed high-entropy rare earth silicate ceramic powder obtained in the step S4 to obtain a light and heavy rare earth mixed high-entropy rare earth silicate block blank, wherein the pressure of the cold press molding is 10-30MPa, and the pressure maintaining time is 1-5 min; the pressure of the cold isostatic pressing is 100-250MPa, and the pressure maintaining time is 10-30 min;

s6, performing high-temperature sintering on the light and heavy rare earth mixed high-entropy rare earth silicate block blank obtained in the step S5 in an air atmosphere to obtain a light and heavy rare earth mixed high-entropy rare earth silicate compact block, wherein the high-temperature sintering temperature is 1400-1750 ℃, and the heat preservation time is 2-12 h.

2. The dense block of light-heavy rare earth-mixed high-entropy rare earth silicate as claimed in claim 1, wherein in step S2, ethanol is used as a medium in the wet mixing, the rotation speed is 100-300r/min, and the time is 4-12 h.

3. The dense block of light and heavy rare earth mixed high-entropy rare earth silicate as claimed in claim 1, wherein the wet ball milling in step S4 uses ethanol as a medium, and the rotation speed is 100-300r/min and the time is 4-12 h.

4. The dense block of light-heavy rare earth-mixed high-entropy rare earth silicate in accordance with claim 1, wherein Ho is defined in step S1₂O₃、Lu₂O₃、Yb₂O₃、Eu₂O₃、SiO₂The purity of (A) is 99.9% -99.99%.

Images