Porous high-entropy carbide powder, preparation method and application thereof

Abstract

The application belongs to the field of non-oxide ceramic powder, and discloses a porous high-entropy carbide powder, a preparation method and application thereof. The porous high-entropy carbide powder is prepared by the following steps: adding mixed powder of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate, ammonium molybdate, ammonium metatungstate and ammonium citrate into deionized water, heating in a water bath at 70-80 DEG C until the powder is completely dissolved, drying the obtained ammonium salt aqueous solution at 45-75 DEG C to obtain a high-entropy carbide ammonium salt precursor; then drying and pressing the high-entropy carbide ammonium salt precursor into a blank body, performing heat treatment in a nitrogen atmosphere, heating to 1500-1600 DEG C and keeping the temperature, and cooling after the temperature is finished. The high-entropy carbide powder has a single high-entropy carbide phase, and the surface has a porous structure; the powder particle size is 0.47-0.79 mu m; and the powder is applied in aerospace parts or chemical catalysis.

Description

Technical Field

[0001] This invention belongs to the field of non-oxide ceramic powder technology, and more specifically, relates to a porous high-entropy carbide powder, its preparation method and application. Background Technology

[0002] High-entropy carbide ceramics possess excellent properties such as high melting point, high hardness, high modulus, and high wear resistance, making them suitable for applications in aerospace, machining, and nuclear energy. High-entropy carbide ceramics are typically prepared by sintering high-entropy carbide powders. To date, various methods for preparing high-entropy carbide ceramics have been developed, including carbothermal reduction, mechanical alloying, and precursor methods. However, these methods require sophisticated equipment and are costly, hindering the application and development of high-entropy carbide ceramic materials. Meanwhile, due to the excellent chemical stability of high-entropy carbide powders, they hold great promise as supporting materials in the field of chemical catalysis. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a porous high-entropy carbide powder; the high-entropy carbide powder has high purity, fine particle size, and the powder particles have a porous surface morphology.

[0004] Another objective of this invention is to provide a method for preparing the above-mentioned porous high-entropy carbide powder; the method uses an ammonium salt aqueous solution to prepare a high-entropy carbide precursor to obtain porous high-entropy carbide powder.

[0005] Another object of the present invention is to provide applications of the above-mentioned porous high-entropy carbide powder.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A porous high-entropy carbide powder is prepared by adding a mixture of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate powder to deionized water and heating in a water bath at 70–80°C until dissolved. The resulting ammonium salt aqueous solution is dried in a rotary evaporator at 45–75°C to obtain a high-entropy carbide ammonium salt precursor. The high-entropy carbide ammonium salt precursor is then dry-pressed into a green body and heat-treated in a nitrogen atmosphere with a gas flow rate controlled at 200–400 mL / min, heated to 1500–1600°C and held at that temperature, and then cooled with the furnace temperature after the treatment.

[0008] Preferably, based on the amount of the mixed powder being 100%, the molar ratio of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate is (1-2):(1-2)(1-2):(1-2):(0.084-0.167):(2.917-5.833); and the mass ratio of deionized water to the mixed powder is (6-8):1.

[0009] Preferably, the particle size of the porous high-entropy carbide powder is 0.47–1.79 μm.

[0010] Preferably, the purity of the ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, and ammonium metatungstate is greater than 99.5%, and the purity of the ammonium citrate is greater than 98.5%.

[0011] Preferably, the drying rate is 30-50 mm / min, and the heat preservation time is 1-3 h.

[0012] A method for preparing porous high-entropy carbide powder includes the following steps:

[0013] S1. A mixture of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate and ammonium citrate powders is added to deionized water and heated in a water bath at 70-80°C until the powders are completely dissolved. The resulting ammonium salt aqueous solution is dried in a rotary evaporator at 45-75°C at a rate of 30-50 rpm to obtain a high-entropy carbide ammonium salt precursor.

[0014] S2. The high-entropy carbide ammonium salt precursor is dry-pressed into a green body, and then heat-treated in a nitrogen atmosphere with a gas flow rate controlled at 200-400 mL / min. The temperature is raised to 1500-1600℃ and held for 1-3 hours. After the treatment, the powder is cooled with the furnace temperature to obtain porous high-entropy carbide powder.

[0015] Preferably, the specific procedure for the heat treatment in step S2 is as follows: the heating rate is 5℃ / min at room temperature to 500℃, the heating rate is 10℃ / min at 500℃ to 800℃, the heating rate is 5℃ / min at 800℃ to 1000℃, and the temperature is increased to 1400℃ to 1600℃ at a rate of 3℃ / min.

[0016] The application of the porous high-entropy carbide powder in aerospace components or chemical catalysis.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The high-entropy carbide powder prepared by this invention has a porous surface structure, and the particle size of the powder can be controlled by adjusting the heat treatment temperature.

[0019] 2. The high-entropy carbide precursor prepared by this invention has a uniform chemical element distribution, which improves the purity of the synthesized powder; the powder synthesis temperature is low, saving energy; the process is simple; and only water is needed as a solvent in the synthesis process, which improves operational safety.

[0020] Explanation of the attached diagram

[0021] Figure 1 These are the XRD patterns of the high-entropy carbide powders obtained in Examples 1-3.

[0022] Figure 2 These are photographs of the surface morphology of the high-entropy carbide powder obtained in Example 3. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0024] Example 1

[0025] 1. Ammonium metavanadate (NH4VO3), ammonium chromate (H8CrN2O4), ammonium niobate oxalate hydrate (C4H4NNbO9·nH2O), ammonium molybdate ((NH4)2MoO4), and ammonium metatungstate ((NH4)6H2W 12 O 40 ·XH2O) and ammonium citrate (C6H 17 Using N3O7 as the ammonium salt raw material, a mixed powder of ammonium salts of V, Cr, Nb, Mo, and W and ammonium citrate was obtained; wherein, based on the total amount of ammonium salts of V, Cr, Nb, Mo, and W and ammonium citrate as 100%, the molar ratio of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate was 1:1:1:3.5:0.292:5.833;

[0026] 2. Add the mixed powder to deionized water, the mass of which is 6 times the total mass of the mixed powder, and heat in a water bath at 75°C until the powder is completely dissolved; use a rotary evaporator to dry the resulting ammonium salt aqueous solution in a water bath at 75°C at a rotation speed of 40 rpm to obtain the high-entropy carbide ammonium salt precursor.

[0027] 3. The high-entropy carbide ammonium salt precursor was loaded into a steel mold and dry-pressed into a billet, which was then placed in a tube furnace for heat treatment. The heat treatment process in the tube furnace was as follows: a nitrogen atmosphere was used, and the gas flow rate was controlled at 200 ml / min; the heating rate varied depending on the temperature range. From room temperature to 500℃, the heating rate was set to 5℃ / min; from 500℃ to 800℃, the heating rate was set to 10℃ / min; from 800℃ to 1000℃, the heating rate was set to 5℃ / min; then, the temperature was increased to 1400℃ at a rate of 3℃ / min and held for 1 hour. After heat treatment, the temperature was cooled with the furnace temperature to obtain porous high-entropy carbide powder with the molecular formula (Cr...). 0.1 Nb 0.1 W 0.1 Mo 0.35 V 0.35 C.

[0028] The porous high-entropy carbide powder prepared in this embodiment has a single high-entropy carbide powder with a particle size of 0.47 μm.

[0029] Example 2

[0030] 1. Ammonium metavanadate (NH4VO3), ammonium chromate (H8CrN2O4), ammonium niobate oxalate hydrate (C4H4NNbO9·nH2O), ammonium molybdate ((NH4)2MoO4), and ammonium metatungstate ((NH4)6H2W 12 O 40 ·XH2O) and ammonium citrate (C6H 17 Using N3O7 as the ammonium salt raw material, a mixed powder of ammonium salts of V, Cr, Nb, Mo, and W and ammonium citrate was obtained; wherein, based on the total amount of ammonium salts of V, Cr, Nb, Mo, and W and ammonium citrate as 100%, the molar ratio of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate was 2:2:2:2:0.167:5.833;

[0031] 2. Add the mixed powder to deionized water, the mass of which is 6 times the total mass of the mixed powder, and heat in a water bath at 75°C until the powder is completely dissolved; use a rotary evaporator to dry the resulting ammonium salt aqueous solution in a water bath at 75°C at a rotation speed of 40 rpm to obtain the high-entropy carbide ammonium salt precursor.

[0032] 3. The high-entropy carbide ammonium salt precursor was loaded into a steel mold and dry-pressed into a billet, which was then placed in a tube furnace for heat treatment. The heat treatment process in the tube furnace was as follows: a nitrogen atmosphere was used, and the gas flow rate was controlled at 400 ml / min; the heating rate varied depending on the temperature range. From room temperature to 500℃, the heating rate was set to 5℃ / min; from 500℃ to 800℃, the heating rate was set to 10℃ / min; from 800℃ to 1000℃, the heating rate was set to 5℃ / min; then, the temperature was increased to 1500℃ at a rate of 3℃ / min and held for 3 hours. After heat treatment, the temperature was cooled with the furnace temperature to obtain porous high-entropy carbide powder with the molecular formula (Cr...). 0.2 Nb 0.2 W 0.2 Mo 0.2 V 0.2 C.

[0033] The porous high-entropy carbide powder prepared in this embodiment has a single high-entropy carbide powder with a particle size of 0.47 μm.

[0034] Example 3

[0035] 1. Ammonium metavanadate (NH4VO3), ammonium chromate (H8CrN2O4), ammonium niobate oxalate hydrate (C4H4NNbO9·nH2O), ammonium molybdate ((NH4)2MoO4), and ammonium metatungstate ((NH4)6H2W 12 O 40 ·XH2O) and ammonium citrate (C6H 17 Using N3O7 as the ammonium salt raw material, a mixed powder of ammonium salts of V, Cr, Nb, Mo, and W and ammonium citrate is prepared; based on the total amount of ammonium salts of V, Cr, Nb, Mo, and W and ammonium citrate as 100%, the molar ratio of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate is 2:2:2:2:0.167:5.833;

[0036] 2. Add the above mixed powder to deionized water, the mass of which is 6 times the total mass of the mixed powder. Heat in a water bath at 75°C until the powder is completely dissolved. Dry the resulting ammonium salt aqueous solution using a rotary evaporator in a water bath at 75°C at a rotation speed of 40 rpm to obtain the high-entropy carbide ammonium salt precursor.

[0037] 3. The obtained high-entropy carbide ammonium salt precursor was loaded into a steel mold, dry-pressed into a billet, and then placed in a tube furnace for heat treatment. The heat treatment process in the tube furnace was as follows: a nitrogen atmosphere was used, and the gas flow rate was controlled at 400 ml / min; the heating rate varied depending on the temperature range. From room temperature to 500℃, the heating rate was set to 5℃ / min; from 500℃ to 800℃, the heating rate was set to 10℃ / min; from 800℃ to 1000℃, the heating rate was set to 5℃ / min; then, the temperature was increased to 1600℃ at a rate of 3℃ / min and held for 3 hours. After heat treatment, the temperature was cooled with the furnace temperature to obtain porous high-entropy carbide powder with the molecular formula (Cr...). 0.2 Nb 0.2 W 0.2 Mo 0.2 V 0.2 C.

[0038] The porous high-entropy carbide powder prepared in this embodiment has a phase composition of a single high-entropy carbide (Cr). 0.2 Nb 0.2 W 0.2 Mo 0.2 V 0.2 C powder with a particle size of 0.79μm.

[0039] Figure 1 These are the XRD patterns of the high-entropy carbide powders obtained in Examples 1-3. Figure 1 As can be seen, the ammonium salt precursor powder prepared by this method, after heat treatment at 1400℃ for 3 hours, did not yield a single-phase high-entropy carbide, but instead consisted of a high-entropy carbide phase (HEC) and a cubic metal carbide phase (FCC). Further increasing the heat treatment temperature (1500-1600℃ / 3 hours), the phase composition of the powder after heat treatment became a single high-entropy carbide phase (HEC). This indicates that the precursor powder prepared from this ammonium salt aqueous solution can yield high-purity high-entropy carbide (Cr-Nb-W-Mo-V)C powder after heat treatment at 1500-1600℃ for 3 hours. Figure 2 These are photographs of the surface morphology of the high-entropy carbide powder obtained in Example 3. Figure 2 As can be seen, the powder has a fine particle size of 0.79 μm and a porous structure.

[0040] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing porous high-entropy carbide powder, characterized in that, Includes the following steps: S1. A mixed powder of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate is added to deionized water and heated in a water bath at 70-80°C until the powder is completely dissolved. The resulting ammonium salt aqueous solution is dried in a rotary evaporator at 45-75°C to obtain a high-entropy carbide ammonium salt precursor. Based on the amount of the mixed powder being 100%, the molar ratio of ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, ammonium metatungstate, and ammonium citrate is (…). 1~2):(1~2)(1~2):(1~2):(0.084~0.167):(2.917~5.833); the mass ratio of the deionized water to the mixed powder is (6~8):1; the purity of the ammonium metavanadate, ammonium chromate, ammonium niobate oxalate hydrate, ammonium molybdate, and ammonium metatungstate is greater than 99.5%, and the purity of the ammonium citrate is greater than 98.5%; the drying rate is 30~50 rad / min, and the holding time is 1~3 h; S2. The high-entropy carbide ammonium salt precursor was dry-pressed into a green body and heat-treated in a nitrogen atmosphere at a gas flow rate controlled at 200~400 mL / min. The specific procedure was as follows: the heating rate was 5℃ / min from room temperature to 500℃, 10℃ / min from 500 to 800℃, and 5℃ / min from 800 to 1000℃. The temperature was then increased to 1500~1600℃ at a rate of 3℃ / min and held for 3 hours. After the heating was completed, the powder was cooled with the furnace temperature to obtain porous high-entropy carbide powder. Its molecular formula is (Cr... 0.1 Nb 0.1 W 0.1 Mo 0.35 V 0.35 C or (Cr) 0.2 Nb 0.2 W 0.2 Mo 0.2 V 0.2 The porous high-entropy carbide powder has a particle size of 0.47~1.79μm.

2. A porous high-entropy carbide powder, characterized in that, The porous high-entropy carbide powder is prepared by the method described in claim 1.

3. The application of the porous high-entropy carbide powder according to claim 2 in aerospace components or chemical catalysis.

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