High-purity superfine high-entropy nitride (Hf, Zr, Ta, Nb and Ti) N powder and low-temperature synthesis method and application thereof

Abstract

The invention discloses high-purity superfine high-entropy nitride (Hf, Zr, Ta, Nb and Ti) N powder as well as a low-temperature synthesis method and application of the high-purity superfine high-entropy nitride (Hf, Zr, Ta, Nb and Ti) N powder. The method comprises the following steps: by taking mixed powder of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide and titanium oxide as a raw material, adding magnesium as a catalyst, adding sodium chloride and potassium chloride as ion diffusants and adding carbon powder as an oxygen trapping agent, mixing, heating to 900-1100 DEG C in a nitrogen atmosphere at a gas flow rate of 100-300ml / min, carrying out heat treatment for 4-8 hours, and cooling along with a furnace temperature, thereby obtaining the hafnium oxide / zirconium oxide / tantalum oxide composite material. The powder obtained after heat treatment is soaked in a hydrochloric acid solution with the concentration being 0.5 mol / L for 0.5-2 h in the stirring state, then filtering and drying are conducted for 12 h, and the high-entropy nitride powder is prepared and has the molecular formula of (Hf < 0.2 > Zr < 0.2 > Ta < 0.2 > Nb < 0.2 > Ti < 0.2 >) Nx. The synthesis method is simple in process, the prepared high-entropy nitride powder has a single high-entropy nitride (Hf0. 2Zr0. 2Ta0. 2Nb0. 2Ti0. 2) Nx phase and has the characteristics of small particle size, low oxygen content and high purity, the particle size of the powder is 0.09-0.14 mu m, and the oxygen content is 0.07-0.18 wt%.

Description

Technical Field

[0001] The present invention relates to the technical field of non-oxide ceramic powders, and specifically, to a method for low-temperature synthesis of high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powders. Background Art

[0002] Compared with single-element or binary transition metal nitride ceramics, high-entropy nitride ceramics exhibit higher hardness, strength, and more excellent oxidation resistance and wear resistance. They are considered as alternative materials for traditional single-element or binary metal nitride ceramics and are expected to be applied in fields such as high-speed cutting tools and aerospace. High-entropy nitride ceramics are usually prepared by sintering high-entropy nitride powders. Up to now, various synthesis methods of high-entropy nitride powders have been developed, including carbothermal reduction nitridation method, silicon thermal reduction method, etc.

[0003] However, these methods have problems such as high synthesis temperature, high carbon and oxygen content, and low powder purity, which are not conducive to the application and development of high-entropy nitride materials. In the traditional preparation of single-element transition metal nitride powders (such as TiN, ZrN, etc.) by the molten salt method, there is a narrow liquid phase region (for example, NaCl melts only at >800 °C), resulting in limited diffusion kinetics in the low-temperature section and being not conducive to the low-temperature synthesis of powders. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for low-temperature synthesis of high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powders. Through a simple and easy-to-operate process, by the synergistic effect of a specific heating rate gradient and pulsed gas flow, the activation energy for the growth of powder particles is reduced, and high-entropy nitride powders with small particle size, low oxygen content, and high purity are prepared.

[0005] The present invention provides a method for low-temperature synthesis of high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powders, including the following steps:

[0006] Step S1. Weigh and mix hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide, and titanium oxide powders to obtain a mixed powder, add absolute ethanol and silicon nitride grinding balls, place them in a roller ball mill and mix for 24 h, then dry at 45 - 55 °C at a rate of 40 - 60 rpm through a rotary evaporator, and pass the dried powder through a 100-mesh sieve to obtain a uniformly mixed transition metal oxide mixed powder. Then add magnesium, sodium chloride, and potassium chloride powders, and add an appropriate amount of carbon powder, and mechanically mix in an agate mortar at a rate of 50 - 200 rpm for 0.5 h to obtain a high-entropy nitride precursor;

[0007] Step S2. Dry-press the prepared high-entropy nitride precursor into a green body. Under a nitrogen atmosphere, pulse-oscillate the gas flow rate in the range of 100 - 300 ml / min at a frequency of 10 - 15 Hz, heat it to 900 - 1100 °C at a certain heating program and hold for heat treatment for 4 - 8 h, then cool it with the furnace temperature. Place the heat-treated powder in a hydrochloric acid solution with a concentration of 0.5 mol / L, soak it for 0.5 - 2 h under stirring, then filter and dry for 12 h to obtain a high-entropy nitride powder, whose molecular formula is (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )N x .

[0008] Preferably, in the step S1, the purity of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide, and titanium oxide is greater than 99%, and the powder particle size is less than 1 μm.

[0009] Preferably, in the step S1, the purity of magnesium, sodium chloride, and potassium chloride is greater than 98%, and the powder particle size is less than 5 μm; sodium chloride and potassium chloride are compounded as a molten salt medium in a mass ratio of (1 - 1.5):(0.5 - 3); the purity of carbon powder is greater than 99.99%, and the powder particle size is less than 100 nm.

[0010] Preferably, in the step S1, the molar ratio of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide, and titanium oxide is 2:2:1:1:2; the mass ratio of absolute ethanol to the mixed powder is (3 - 6):1; the mass ratio of silicon nitride grinding balls to the mixed powder is (5 - 15):1; the mass ratio of the mixed powder of transition metal oxides, magnesium, sodium chloride, potassium chloride, and carbon powder is 1:(2 - 3):(1 - 1.5):(0.5 - 3):(0.005 - 0.02).

[0011] Preferably, the heating program in the step S2 is: first heat it to 500 - 550 °C at a rate of 15 - 25 °C / min and hold for 0.5 - 1 h to form a pre-nitriding layer; then continue to heat it to 800 - 850 °C at a rate of 5 - 8 °C / min for lattice reconstruction, and finally heat it to 900 - 1100 °C at a rate of 2 - 3 °C / min to complete nitridation.

[0012] The present invention also provides a high-purity and ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder. The powder particle size of the high-purity and ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder is 0.09 - 0.14 μm, and the oxygen content is 0.07 - 0.18 wt%.

[0013] The present invention also provides an application of high-purity ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder, and the high-purity ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder is used in wear-resistant parts or the field of chemical catalysis.

[0014] Working principle of the present invention: The low-temperature synthesis method of the high-purity ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder of the present invention adopts a molten-salt-mediated magnesium thermal reduction low-temperature synthesis process. By adding magnesium, sodium chloride, and potassium chloride to the mixed powder of transition metal oxides, magnesium is used as a catalyst to promote the reaction and reduce the synthesis temperature, sodium chloride and potassium chloride are used as ionic diffusion agents, and carbon powder is used as an oxygen scavenger. Therefore, heat treatment is carried out at a lower temperature in a nitrogen atmosphere to form a eutectic salt, and then the formation of high-entropy nitride is promoted through the "dissolution-precipitation" mechanism. Among them, sodium chloride and potassium chloride are compounded as a molten-salt medium in a certain molar ratio, and the compounded molten salt can reduce the eutectic point temperature to 650°C and synergistically increase the ionic diffusion rate.

[0015] Beneficial effects of the present invention: The low-temperature synthesis method of the high-purity ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder of the present invention adopts a molten-salt-mediated magnesium thermal reduction low-temperature synthesis process. By adding magnesium, sodium chloride, and potassium chloride to the mixed powder of transition metal oxides, the reaction temperature is reduced. Adding carbon powder captures the remaining oxygen impurities through the carbothermal-assisted reduction mechanism (C + MO x → CO↑ + M) to further reduce the oxygen content, and avoids the introduction of carbon and silicon impurities in the traditional carbothermal reduction nitridation and silothermal reduction processes. Moreover, magnesium, sodium chloride, and potassium chloride involved in the process can be simply removed by the hydrochloric acid leaching process, improving the purity of the synthesized powder. This method has a simple process, and the obtained high-entropy nitride powder has the characteristics of small particle size, low oxygen content, and high purity. Specific embodiments

[0016] In order to make the technical solution of the present invention easier to understand, the technical solution of the present invention will be clearly and completely described by using specific embodiments.

[0017] Example 1:

[0018] The low-temperature synthesis method of the high-purity ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder in this example includes the following steps:

[0019] Step S1. Using hafnium oxide (HfO2), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), and titanium oxide (TiO2) as raw materials. Among them, based on the total amount of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide, and titanium oxide being 100%, weighing a total mass of 100 g according to the molar ratio of 2:2:1:1:2 to obtain a mixed powder of transition metal oxides; placing the mixed powder in a roller ball mill, using 300 g of anhydrous ethanol as a dispersant and 500 g of Si3N4 balls as the ball milling medium, mixing the materials at a speed of 200 r / min for 24 h, then drying through a rotary evaporator at 45 °C at a rate of 60 rpm, and passing the dried powder through a 100-mesh sieve to obtain a uniformly mixed powder of transition metal oxides. Subsequently, add 200 g of magnesium, 100 g of sodium chloride, 50 g of potassium chloride, and 0.5 g of carbon powder to the mixed powder of transition metal oxides, and mechanically mix in an agate mortar at a rate of 50 rpm for 0.5 h to prepare a high-entropy nitride precursor;

[0020] Step S2. Dry-press the prepared high-entropy nitride precursor into a green body and perform heat treatment in a nitrogen atmosphere with a gas flow rate of 100 - 200 ml / min. The specific heat treatment process is as follows: first, heat up to 500 °C at a rate of 15 °C / min and hold for 0.5 h, continuously introduce nitrogen, control the gas flow rate in the range of 100 - 200 ml / min and perform pulse oscillation at a frequency of 10 Hz, continue to heat the temperature to 800 °C at a rate of 5 °C / min, and finally heat to 900 °C at a rate of 3 °C / min. After the heating program is completed, hold for 8 h, then cool down with the furnace. Immerse the heat-treated powder in a hydrochloric acid solution with a concentration of 0.5 mol / L and stir for 2 h, then filter and dry for 12 h to obtain high-entropy nitride powder.

[0021] The specific molecular formula of the high-purity and ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder prepared in this example is (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )N 0.89 , the particle size of the powder is 0.09 μm, and the oxygen content is 0.18 wt%.

[0022] Example 2:

[0023] The low-temperature synthesis method of the high-purity and ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder in this example includes the following steps:

[0024] Step S1. Using hafnium oxide (HfO2), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), and titanium oxide (TiO2) as raw materials. Among them, taking the total amount of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide, and titanium oxide as 100% in terms of the amount of substance, weighing a total mass of 100 g according to the molar ratio of 2:2:1:1:2, and mixing to obtain a mixed powder of transition metal oxides. Place the mixed powder in a roller ball mill, use 400 g of anhydrous ethanol as a dispersant, 1000 g of Si3N4 balls as the ball milling medium, mix the materials at a speed of 200 r / min for 24 h, then dry through a rotary evaporator at 45 °C at a rate of 60 ram / min, and pass the dried powder through a 100-mesh sieve to obtain a uniformly mixed powder of transition metal oxides. Subsequently, add 275 g of magnesium, 125 g of sodium chloride, 125 g of potassium chloride, and 2 g of carbon powder to the mixed powder of transition metal oxides, and mechanically mix in an agate mortar at a rate of 100 ram / min for 0.5 h to prepare a high-entropy nitride precursor.

[0025] Step S2. Dry-press the prepared high-entropy nitride precursor into a green body and perform heat treatment in a nitrogen atmosphere with a gas flow rate of 150 - 250 ml / min. The specific heat treatment process is as follows: First, heat up to 550 °C at a rate of 20 °C / min and hold for 0.5 h, continuously introduce nitrogen, control the gas flow rate in the range of 150 - 250 ml / min, and perform pulse oscillation at a frequency of 15 Hz. Then continue to heat up to 800 °C at a rate of 8 °C / min, and finally heat up to 1000 °C at a rate of 2 °C / min. After the heating program is completed, hold for 6 h, and then cool down with the furnace. Immerse the heat-treated powder in a hydrochloric acid solution with a concentration of 0.5 mol / L and stir for 1 h, then filter and dry for 12 h to prepare high-entropy nitride powder.

[0026] The specific molecular formula of the high-purity and ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder prepared in this example is (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )N 0.97 , the particle size of the powder is 0.12 μm, and the oxygen content is 0.10 wt%.

[0027] Example 3:

[0028] The low-temperature synthesis method of the high-purity and ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder in this example includes the following steps:

[0029] Step S1. Using hafnium oxide (HfO2), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), and titanium oxide (TiO2) as raw materials. Among them, based on the total amount of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide, and titanium oxide being 100% in terms of the amount of substance, weighing a total mass of 100 g according to the molar ratio of 2:2:1:1:2, and mixing to obtain a mixed powder of transition metal oxides; placing the mixed powder in a roller ball mill, using 600 g of anhydrous ethanol as a dispersant and 1500 g of Si3N4 balls as ball milling media, mixing the materials at a rotation speed of 200 r / min for 24 h, then drying through a rotary evaporator at 55 °C at a rate of 50 ram / min, and passing the dried powder through a 100-mesh sieve to obtain a uniformly mixed powder of transition metal oxides. Subsequently, add 300 g of magnesium, 150 g of sodium chloride, 300 g of potassium chloride, and 0.5 g of carbon powder to the mixed powder of transition metal oxides, and mechanically mix in an agate mortar at a rate of 100 ram / min for 0.5 h to prepare a high-entropy nitride precursor;

[0030] Step S2. Dry-press the prepared high-entropy nitride precursor into a green body and perform heat treatment in a nitrogen atmosphere with a gas flow rate of 200 - 300 ml / min. The specific heat treatment process is as follows: First, heat up to 550 °C at a rate of 25 °C / min and hold for 0.5 h, continuously introduce nitrogen, control the gas flow rate in the range of 200 - 300 ml / min, and perform pulse oscillation at a frequency of 15 Hz. Then continue to heat up to 850 °C at a rate of 8 °C / min, and finally heat up to 1100 °C at a rate of 3 °C / min. After the heating program is completed, hold for 4 h, and then cool down with the furnace. Immerse the heat-treated powder in a hydrochloric acid solution with a concentration of 0.5 mol / L and stir for 2 h, then filter and dry for 12 h to prepare high-entropy nitride powder.

[0031] The specific molecular formula of the high-purity and ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder prepared in this example is (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )N 1.03 , the particle size of the powder is 0.14 μm, and the oxygen content is 0.07 wt%.

[0032] It should be noted that the embodiments described herein are only partial embodiments of the present invention, rather than all implementation manners of the present invention. The embodiments are only exemplary, and their function is only to provide a more intuitive and clear way to understand the content of the present invention, rather than a limitation on the technical solutions described in the present invention. Without departing from the concept of the present invention, all other implementation manners that can be thought of by those of ordinary skill in the art without creative efforts, as well as other simple substitutions and various changes to the technical solutions of the present invention, all fall within the protection scope of the present invention.

Claims

1. A low-temperature synthesis method of high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder, characterized in that, It includes the following steps: Step S1. Weigh and mix hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide and titanium oxide powders to obtain a mixed powder. Then add anhydrous ethanol and silicon nitride grinding balls, place them in a roller ball mill and mix for 24 h. After that, use a rotary evaporator to dry at 45 - 55 °C at a rate of 40 - 60 rpm, and pass the dried powder through a 100-mesh sieve to obtain a uniformly mixed transition metal oxide mixed powder. Then add magnesium, sodium chloride and potassium chloride powders, and add an appropriate amount of carbon powder, and mechanically mix in an agate mortar at a rate of 50 - 200 rpm for 0.5 h to prepare a high-entropy nitride precursor; Step S2. The prepared high-entropy nitride precursor is dry-pressed into a green body. Under a nitrogen atmosphere, the gas flow rate is pulsed and oscillated in the range of 100-300 ml / min at a frequency of 10-15 Hz, and heated to 900-1100 °C at a certain heating program and heat-treated for 4-8 h, and then cooled with the furnace temperature. The heat-treated powder is placed in a hydrochloric acid solution with a concentration of 0.5 mol / L, soaked for 0.5-2 h under stirring, then filtered and dried for 12 h to obtain a high-entropy nitride powder with the molecular formula (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )N x .

2. The low-temperature synthesis method of high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder as claimed in claim 1, characterized in that, In step S1, the purities of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide and titanium oxide are all greater than 99%, and the powder particle size is less than 1 μm.

3. The low-temperature synthesis method of the high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder as described in claim 1, characterized in that, In step S1, the purities of magnesium, sodium chloride and potassium chloride are all greater than 98%, and the powder particle size is less than 5 μm; sodium chloride and potassium chloride are compounded as a molten salt medium at a mass ratio of (1 - 1.5):(0.5 - 3); the purity of the carbon powder is greater than 99.99%, and the powder particle size is less than 100 nm.

4. The low-temperature synthesis method of high-purity, ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder as claimed in claim 1, characterized in that, In step S1, the molar ratio of hafnium oxide, zirconium oxide, tantalum oxide, niobium oxide and titanium oxide is 2:2:1:1:2; The mass ratio of anhydrous ethanol to the mixed powder is (3 - 6):1; the mass ratio of silicon nitride grinding balls to the mixed powder is (5 - 15):1; the mass ratio of the transition metal oxide mixed powder, magnesium, sodium chloride, potassium chloride and carbon powder is 1:(2 - 3):(1 - 1.5):(0.5 - 3):(0.005 - 0.02).

5. The low-temperature synthesis method of high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder as claimed in claim 1, characterized in that, The heating program in step S2 is as follows: first heat up to 500 - 550 °C at a rate of 15 - 25 °C / min and keep it warm for 0.5 - 1 h to form a pre-nitriding layer; then continue to heat up to 800 - 850 °C at a rate of 5 - 8 °C / min for lattice reconstruction, and finally heat up to 900 - 1100 °C at a rate of 2 - 3 °C / min to complete nitridation.

6. A high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder, characterized in that, The high-purity ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder is prepared by the method described in any one of claims 1 - 5.

7. The high-purity ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder according to claim 6, characterized in that, The powder particle size of the high-purity ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder is 0.09 - 0.14 μm, and the oxygen content is 0.07 - 0.18 wt%.

8. Application of a high-purity, ultrafine high-entropy nitride (Hf, Zr, Ta, Nb, Ti)N powder, characterized in that, The high-purity ultrafine high-entropy nitride (Hf,Zr,Ta,Nb,Ti)N powder is used in wear-resistant parts or the field of chemical catalysis.