High-purity high-entropy nitride ceramic powder as well as preparation method and application thereof

Abstract

The invention discloses high-purity high-entropy nitride ceramic powder as well as a preparation method and application thereof, and belongs to the technical field of high-entropy nitride materials. Adopting flocculent precipitation-carbothermal reduction ammonia gas nitridation, selecting chlorine salt of transition metal as a metal source, sorbitol as a carbon source and acetic acid as a solvent, mixing to form a precursor precipitation mixed solution, drying, grinding to obtain precursor powder, selecting ammonia gas as a nitrogen source, calcining in a tubular furnace, and controlling the calcining temperature and the like, so as to obtain the composite material. And the high-purity high-entropy nitride ceramic powder with high purity and uniform element distribution is prepared. The method for preparing the high-entropy nitride ceramic powder is simple in process, the reaction is easy to control, the production period is short, the production cost is low, the high-purity high-entropy ceramic powder can be prepared at the low temperature, and the prepared powder is high in purity and uniform in element distribution.

Description

Technical Field

[0001] This application belongs to the technical field of high-entropy nitride materials, and particularly relates to a high-purity high-entropy nitride ceramic powder, a preparation method thereof, and an application thereof. Background Art

[0002] High-entropy ceramics are a new type of material with no less than four different cations. In recent years, due to their unique composition, microstructure, adjustable properties, and diverse potential applications, they have been widely used in aerospace, military, nuclear industry, and functional devices. Compared with traditional materials, high-entropy materials exhibit unique advantages in composition design and performance, mainly due to their four special core effects: high-entropy effect, lattice distortion effect, slow diffusion effect, and "cocktail" effect, which not only ensure good structural stability but also endow the materials with unique physical and chemical properties, such as excellent thermal stability and oxidation ablation resistance, good mechanical properties, high corrosion resistance, versatility, and chemical stability. In addition, the high-entropy effect has been widely studied in high-entropy alloys and high-entropy ceramics. Especially when developing materials with different functions and properties, the high-entropy effect provides an innovative method.

[0003] Theoretically, high-entropy nitride ceramics are single-phase solid solutions formed by multiple metal elements and nitrogen, with strong metal-nitrogen covalent bonds, high melting points, and excellent mechanical properties, and are widely used in fields such as high temperature, corrosion, wear, electronics, and optics. However, their research and development are still in the initial stage. The main problem restricting their in-depth research is how to synthesize high-purity high-entropy nitride powder raw materials. At present, researchers have prepared high-entropy nitride powders by mechanical alloying-assisted combustion synthesis, but it is easy to introduce some oxide impurities and cannot meet the requirements of high-performance ceramics. In addition, some researchers have also selected transition metal nitride powders to directly carry out high-energy ball milling mixing and spark plasma sintering to obtain dense high-entropy nitride ceramics. Although the operation is simple, due to long-term ball milling, the powder will be contaminated, impurities are easily incorporated, and the element distribution is uneven, thus affecting the purity of the powder and the mechanical properties of the ceramic block.

[0004] Therefore, there is an urgent need to develop a method for preparing high-purity and ultrafine high-entropy nitride ceramic powders to obtain single-phase high-entropy nitride ceramic powders with high purity and uniform element distribution, so as to obtain ceramic materials with high density and excellent mechanical properties. Summary of the Invention

[0005] 1. Object of the Invention

[0006] The object of this application is to provide a high-purity high-entropy nitride ceramic powder, a preparation method thereof, and an application thereof. By using flocculation precipitation-carbothermal reduction ammonia nitridation and controlling the calcination temperature, etc., high-purity high-entropy nitride ceramic powders with high purity and uniform element distribution are prepared.

[0007] 2. Technical Solution

[0008] To solve the above problems, the technical solution adopted in this application is as follows:

[0009] This application provides a method for preparing high-purity high-entropy nitride ceramic powder, and the method includes the following steps:

[0010] S1. Prepare solution A and solution B. Solution A is an acetic acid solution containing four or more transition metal elements with an equal molar ratio; solution B is an acetic acid solution containing sorbitol, and the molar ratio of carbon element in sorbitol to the total molar amount of transition metal elements is 1:1;

[0011] S2. Slowly and evenly drip solution A into solution B, and continuously stir to obtain a precipitate and precursor mixture;

[0012] S3. Let the precipitate and precursor mixture obtained in S2 stand and age at a low temperature of 80-90 °C for 6-8 h, and dry at a high temperature of 120-150 °C for 8-12 h to obtain a dry precipitate;

[0013] S4. Grind the precursor precipitate obtained in step S3 into powder (precursor powder), and perform calcination. The calcination process is as follows: First, introduce argon as a protective gas and heat from room temperature to 1000-1100 °C at a heating rate of 5-10 °C / min and hold for 30 min. After the holding ends, disconnect the argon and evacuate; then introduce ammonia (NH3) to react with the precursor powder, that is, heat to 1550-1650 °C at a rate of 2-5 °C / min and hold for 2 h; then cool to 1000 °C at a rate of 2-5 °C / min, and then cool to 300 °C at a rate of 5-10 °C / min, and finally naturally cool to room temperature to obtain high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

[0014] Furthermore, in the above step S1, the four or more transition metals are selected from any four or more of scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg).

[0015] Further, in the above step S1, the four or more transition metals are selected from four or more of titanium (Ti), vanadium (V), chromium (Cr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W).

[0016] Further, the four or more transition metals are selected from titanium (Ti), tantalum (Ta), niobium (Nb), and molybdenum (Mo), and the prepared high-purity high-entropy nitride is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N.

[0017] Further, in the above solution A, the metal source of the metal element is a salt of the metal element. Further still, in the above solution A, the metal source of the metal element is a chloride salt of the metal element.

[0018] Further, the preparation of solution A includes: mixing TiCl4, TaCl5, NbCl5, and MoCl5 in an equimolar ratio and then adding them to acetic acid, and stirring well to dissolve to obtain a dark green clear solution A.

[0019] Further, the above stirring speed is 300 - 400 rpm. Further still, the above stirring speed is 350 rpm.

[0020] Further, the preparation of solution B includes: under an oil bath condition of 60 - 90 °C, stirring sorbitol in acetic acid until completely dissolved, and then cooling to room temperature to obtain a colorless, clear, and transparent solution B.

[0021] Further, the above stirring speed is 300 - 400 rpm. Further still, the above stirring speed is 350 rpm.

[0022] Further, the above oil bath temperature is 60 °C.

[0023] Further, in the above step S2, solution A is uniformly and slowly dropped into solution B at a rate of 1 - 5 mL / min. Further still, solution A is uniformly and slowly dropped into solution B at a rate of 5 mL / min.

[0024] Further, in the above step S3, the precursor mixture is left standing and aged at 80 °C for 8 h, and then dried at 120 °C for 12 h to obtain a precursor precipitate.

[0025] Further, in the above step S4, the precursor precipitate obtained in step S3 is ground into powder and calcined. The calcination process is as follows: First, argon is introduced as a protective gas and heated from room temperature to 1050 °C at a heating rate of 5 °C / min, and held at 1050 °C for 30 min. After the holding is completed, the argon is disconnected and the vacuum is pumped; then ammonia gas (NH3) is introduced to react with the precursor powder, that is, heated to 1600 °C at a rate of 2 °C / min and held at 1600 °C for 2 h; then cooled to 1000 °C at a rate of 2 °C / min, and then cooled to 300 °C at a rate of 5 °C / min, and finally naturally cooled to room temperature to obtain high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

[0026] Further, in the above step S4, relative to 1 g of the precursor powder (the powder obtained by grinding the precursor precipitate), the gas flow rate of ammonia gas is 120 - 150 mL / min. Further still, relative to 1 g of the precursor powder, the gas flow rate of ammonia gas is 125 mL / min.

[0027] The present application also provides a high-purity high-entropy nitride ceramic powder prepared by the above method for preparing a high-purity high-entropy nitride ceramic powder.

[0028] Further, the above high-purity high-entropy nitride ceramic powder is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

[0029] Further, the above (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder has a particle size of about 500 nm.

[0030] Further, the above (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder has an interplanar spacing of 0.244 nm, corresponding to the (1 1 1) plane of the face-centered cubic structure, and an interplanar spacing of 0.217 nm, corresponding to the (2 0 0) plane of the face-centered cubic structure.

[0031] The present application also provides an application of the above high-purity high-entropy nitride ceramic powder in the preparation of ceramic products.

[0032] The present application also provides a ceramic product, which includes any one of the above high-purity high-entropy nitride ceramic powders.

[0033] 3. Beneficial effects

[0034] Compared with the prior art, the beneficial effects of this application are as follows:

[0035] (1) A high-purity high-entropy nitride ceramic powder provided by this application, especially (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N. This high-purity high-entropy nitride ceramic powder is a single-phase solid solution pure phase. XRD detection shows that it does not contain MoTaN and oxide peaks, and has the characteristic of high purity; its particle size is about 500 nm, with a relatively small particle size, and the EDS element distribution map of the scanning electron microscope shows that the elements are evenly distributed.

[0036] (2) A preparation method of a high-purity high-entropy nitride ceramic powder provided by this application, especially the preparation method of (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N. The method of flocculation precipitation - carbothermal reduction ammonia nitridation is adopted. The chloride salts of transition metals are selected as metal sources, sorbitol is used as a carbon source, and acetic acid is used as a solvent. They are mixed to form a precursor precipitation mixed solution. After drying, it is ground to obtain a precursor powder. Ammonia is selected as a nitrogen source and calcined in a tube furnace to obtain a high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder. Among them, NH3 can be used as both a reducing agent and a nitrogen source, which can effectively reduce the carbon content and improve the powder purity; at the same time, according to the physical and chemical property changes during the temperature change process, the precursor powder is kept at about 1050 °C for about 30 min, which is beneficial to the progress of the carbothermal reduction reaction; then evacuate the air, which can evacuate other gases such as carbon monoxide in the system, is beneficial to the further nitridation and reduction of ammonia, and improves the nitridation efficiency.

[0037] (3) A preparation method of a high-purity high-entropy nitride ceramic powder provided by this application. This method has a simple process, easy reaction control, a short production cycle, and low production cost. High-purity high-entropy ceramic powder can be prepared at a relatively low temperature, and the prepared powder has a high purity and uniform element distribution. Brief description of the drawings

[0038] Figure 1 It is a schematic flow chart of the preparation of a high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder provided by this application.

[0039] Figure 2 For the XRD patterns of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powders prepared in the examples and comparative examples of this application, where: (a) is the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1, and (b)-(d) are the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powders prepared in Comparative Examples 1-3.

[0040] Figure 3 SEM images of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 of this application at different magnification ratios.

[0041] Figure 4 For the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 of this application, where: (a) is the TEM image; (b) is the HRTEM image and diffraction pattern; (c) is the EDS elemental distribution map.

[0042] Figure 5 TG-DTA-DSC curves of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N precursor powder prepared in Example 1 of this application in flowing argon. Detailed embodiments

[0043] The present application will be further described below in conjunction with specific examples.

[0044] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope of implementation of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0047] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. One of ordinary skill in the art can readily determine the degree of flexibility for a specific variable.

[0048] As used herein, the term "at least one of..." is intended to be synonymous with "one or more of...". For example, "at least one of A, B, and C" clearly includes only A, only B, only C, and their respective combinations.

[0049] Concentrations, amounts, and other numerical data may be presented herein in a range format. It should be understood that such range formats are used merely for convenience and brevity and should be interpreted flexibly as including not only the numerical values explicitly recited as the limits of the range, but also all individual numerical values or sub-ranges subsumed within the stated range as if each numerical value and sub-range were explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted as including not only the explicitly recited limit values of 1 to about 4.5, but also the individual numbers (such as 2, 3, 4) and sub-ranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that recite only one numerical value, such as "less than about 4.5", which should be interpreted as including all of the above values and ranges. In addition, this interpretation should apply regardless of the breadth of the range or feature described.

[0050] Example 1

[0051] This example provides a high-purity high-entropy nitride ceramic powder and a preparation method thereof.

[0052] In this example, the high-entropy nitride is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N.

[0053] The preparation method of the high-purity high-entropy nitride ceramic powder is as Figure 1 shown and includes the following steps:

[0054] S1. Weigh 1375 μL of TiCl4, 4.478 g of TaCl5, 3.377 g of NbCl5, and 3.415 g of MoCl5 into a beaker and mix them. Use a pipette to add 20 mL of acetic acid (analytical grade), and stir with a magnetic stirrer (350 rpm) until completely dissolved to obtain a dark green clear solution A. Weigh 1.528 g of sorbitol, use a pipette to add 20 mL of acetic acid (analytical grade), and stir with an oil bath magnetic stirrer at 60 °C under constant temperature (350 rpm) until completely dissolved. Cool to room temperature to obtain a colorless clear and transparent solution B.

[0055] S2. Continuously stir solution B with a magnetic stirrer (350 rpm), and slowly drip solution A into solution B at a rate of 5 mL / min to obtain a mixture of white flocculent precipitate and light green precursor.

[0056] S3. Let the mixture of white flocculent precipitate and light green precursor obtained in step S2 stand and age at 80 °C for 8 h, and then dry it at 120 °C for 12 h to obtain a (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N precursor precipitate.

[0057] S4. Grind the precursor precipitate obtained in step S3 into powder (precursor powder) using an agate mortar. Place 2 g in a corundum boat and put it into a high-temperature tube furnace for calcination. The calcination process is as follows: First, introduce argon (50 mL / min) as a protective gas and heat from room temperature to 1050 °C at a heating rate of 5 °C / min, hold at 1050 °C for 30 min. After the holding is completed, disconnect the argon and evacuate. Then introduce ammonia (NH3) (250 mL / min) to react with the precursor powder, heat to 1600 °C at a rate of 2 °C / min, hold at 1600 °C for 2 h. Then cool to 1000 °C at a rate of 2 °C / min, and then cool to 300 °C at a rate of 5 °C / min, and finally cool to room temperature naturally to obtain high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

[0058] Comparative Example 1

[0059] This comparative example provides a high-entropy nitride ceramic powder and its preparation method.

[0060] In this comparative example, the high-entropy nitride is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N.

[0061] In this comparative example, the preparation method of (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder is basically the same as that in Example 1, except that the temperature maintained during the reaction of NH3 with the precursor powder is different. The specific steps are as follows:

[0062] S1. Weigh 1375 μL of TiCl4, 4.478 g of TaCl5, 3.377 g of NbCl5, and 3.415 g of MoCl5 into a beaker and mix them. Use a pipette to add 20 mL of acetic acid (analytical pure), and stir with a magnetic stirrer (350 rpm) until completely dissolved to obtain a dark green clear solution A; Weigh 1.528 g of sorbitol, use a pipette to add 20 mL of acetic acid (analytical pure), and stir with an oil bath magnetic stirrer at a constant temperature of 60 °C (350 rpm) until completely dissolved, and cool to room temperature to obtain a colorless clear and transparent solution B;

[0063] S2. Continuously stir solution B with a magnetic stirrer (350 rpm), and slowly drip solution A into solution B at a rate of 5 mL / min to obtain a mixture of white flocculent precipitate and light green precursor;

[0064] S3. Let the mixture of white flocculent precipitate and light green precursor obtained in step S2 stand and age at 80 °C for 8 h, and then dry it at 120 °C for 12 h to obtain a (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N precursor precipitate;

[0065] S4. Grind the precursor precipitate obtained in step S3 into powder using an agate mortar, place 2 g in a corundum boat, and put it into a high-temperature tube furnace for calcination. The calcination process is as follows: First, introduce argon (50 mL / min) as a protective gas and heat from room temperature to 1050 °C at a heating rate of 5 °C / min, hold at 1050 °C for 30 min. After the holding is completed, disconnect the argon and evacuate; Then introduce ammonia (NH3) (250 mL / min) to react with the precursor powder, heat to 1500 °C at a rate of 2 °C / min, hold at 1500 °C for 2 h; Then cool to 1000 °C at a rate of 2 °C / min, and then cool to 300 °C at a rate of 5 °C / min, and finally cool to room temperature naturally to obtain a high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

[0066] Comparative Example 2

[0067] This comparative example provides a high-entropy nitride ceramic powder and a preparation method thereof.

[0068] In this comparative example, the high-entropy nitride is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N.

[0069] In this comparative example, the preparation method of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder is basically the same as that of Example 1, except that ammonia gas (NH3) is continuously introduced during the calcination process, that is, no protective gas is introduced. The specific steps are as follows:

[0070] S1, Weigh 1375 μL of TiCl4, 4.478 g of TaCl5, 3.377 g of NbCl5, and 3.415 g of MoCl5 respectively into a beaker and mix them. Use a pipette to add 20 mL of acetic acid (analytical pure), and stir with a magnetic stirrer (350 rpm) until completely dissolved to obtain a dark green clear solution A; Weigh 1.528 g of sorbitol, use a pipette to add 20 mL of acetic acid (analytical pure), and stir with an oil bath magnetic stirrer at 60 °C under constant temperature (350 rpm) until completely dissolved, and cool to room temperature to obtain a colorless clear and transparent solution B;

[0071] S2, Continuously stir solution B with a magnetic stirrer (350 rpm), and slowly drip solution A into solution B at a rate of 5 mL / min to obtain a mixture of white flocculent precipitate and light green precursor;

[0072] S3, Let the mixture of white flocculent precipitate and light green precursor obtained in step S2 stand and age at 80 °C for 8 h, and then dry it at 120 °C for 12 h to obtain the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N precursor precipitate;

[0073] S4, Grind the precursor precipitate obtained in step S3 into powder with an agate mortar, place 2 g in a corundum boat, and put it into a high-temperature tube furnace for calcination. The calcination process is as follows: Always introduce ammonia gas (250 mL / min) as the reaction gas source. First, heat from room temperature to 1050 °C at a heating rate of 5 °C / min; then heat to 1600 °C at a rate of 2 °C / min and hold at 1600 °C for 2 h; then cool to 1000 °C at a rate of 2 °C / min, and then cool to 300 °C at a rate of 5 °C / min, and finally cool to room temperature naturally to obtain the high-entropy nitride (Ti 0.25 Ta 0.25Nb 0.25 Mo 0.25 )N ceramic powder

[0074] Comparative Example 3

[0075] This comparative example provides a high-entropy nitride ceramic powder and a preparation method thereof.

[0076] In this comparative example, the high-entropy nitride is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N.

[0077] In this comparative example, the preparation method of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder is basically the same as that of Comparative Example 1, and the difference lies in the temperature maintained during the reaction of NH3 with the precursor powder during the calcination process. The specific steps are as follows:

[0078] S1. Weigh 1375 μL of TiCl4, 4.478 g of TaCl5, 3.377 g of NbCl5, and 3.415 g of MoCl5 into a beaker and mix them. Use a pipette to add 20 mL of acetic acid (analytical pure), and stir with a magnetic stirrer (350 rpm) until completely dissolved to obtain a dark green clear solution A; weigh 1.528 g of sorbitol, use a pipette to add 20 mL of acetic acid (analytical pure), and stir with an oil bath magnetic stirrer at 60 °C with constant temperature stirring (350 rpm) until completely dissolved, and cool to room temperature to obtain a colorless clear and transparent solution B;

[0079] S2. Continuously stir solution B with a magnetic stirrer (350 rpm), and slowly drip solution A into solution B at a rate of 5 mL / min to obtain a mixture of white flocculent precipitate and light green precursor;

[0080] S3. Let the mixture of white flocculent precipitate and light green precursor obtained in step S2 stand for aging at 80 °C for 8 h, and then dry it at 120 °C for 12 h to obtain the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N precursor precipitate;

[0081] S4. Use an agate mortar to grind the precursor precipitate obtained in step S3 into a powder. Weigh 2 g of the powder and place it in a corundum boat, then put it into a high-temperature tube furnace for calcination. The calcination process is as follows: Continuously introduce ammonia gas (250 mL / min) as the reaction gas source. First, heat from room temperature to 1050 °C at a heating rate of 5 °C / min; then heat to 1500 °C at a rate of 2 °C / min and hold at 1500 °C for 2 h; then cool to 1000 °C at a rate of 2 °C / min, and then cool to 300 °C at a rate of 5 °C / min, and finally cool naturally to room temperature to obtain high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

[0082] Example 2

[0083] This example provides the purity detection of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 and Comparative Examples 1-3.

[0084] In this example, an X-ray diffractometer was used to detect the purity of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 and Comparative Examples 1-3. The results are as Figure 2 shown, where (a)-(d) are the XRD patterns of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. XRD analysis shows that when the reaction temperature of ammonia gas (NH3) with the precursor powder is increased to 1600 °C, the prepared (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N powder is a single-phase solid solution, forming a high-purity high-entropy nitride ceramic powder. However, when the reaction temperature is lowered to 1500 °C, there are impurity peaks of MoTaN and oxide peaks in the obtained high-entropy nitride powder. In Comparative Examples 2 and 3, nitrogen gas was continuously introduced, and a high-purity single-phase solid solution was not obtained. There are always impurity peaks of MoTaN and oxide peaks in their XRD patterns. This shows that evacuating other gases such as carbon monoxide in the system after the carbonization of sorbitol can empty the system, which is beneficial to the further nitridation and reduction of ammonia gas, avoiding the occurrence of other complex reactions and improving the nitridation efficiency.

[0085] Example 3

[0086] This example provides the high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb0.25 Mo 0.25 Material characterization of (Ti

[0087] (1) The morphology of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 was detected by scanning electron microscopy, and scanning photos were obtained at different magnification ratios. The results are as Figure 3 shown. Figure 3 In (a), it is the SEM photo at a magnification of 20k. Figure 3 In (b), it is the SEM photo at a magnification of 50k. It can be seen from Figure 3 that the powder prepared at a calcination temperature of 1600°C in Example 1 has obvious granularity, and the nano-scale particles gradually bond to form larger micron-scale particles.

[0088] (2) The transmission characterization, high-resolution imaging and selected area electron diffraction of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 were carried out by transmission electron microscopy. The results are as Figure 4 shown. As can be seen from Figure 4 (a), the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared at 1600°C is nearly spherical, with a particle size of about 500nm. The smaller particle size is beneficial to improving the sinterability. As can be seen from Figure 4 (b), the interplanar spacing is 0.244nm, corresponding to the (1 1 1) crystal plane of the face-centered cubic structure, and the interplanar spacing is 0.217nm, corresponding to the (2 0 0) crystal plane of the face-centered cubic structure. It can be seen that the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 is a single-phase solid solution of nitride.

[0089] (3) The EDS energy spectrum analysis of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 was carried out by scanning electron microscopy. The results are as Figure 4 shown in (c), which is the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25)EDS elemental distribution map of N ceramic powder. It can be seen that the four transition metal elements (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder prepared in Example 1 are evenly distributed and there is no element aggregation.

[0090] Example 4

[0091] This example provides an analysis of the physical and chemical property changes of the precursor powder prepared in Example 1 during the temperature change process.

[0092] In this example, thermogravimetric analysis (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) are used in combination to analyze the physical and chemical property changes of the precursor powder prepared in Example 1 during the temperature change process.

[0093] The TG-DTA-DSC curves of the precursor powder prepared in Example 1 in flowing argon gas are as Figure 5 shown. It can be seen from Figure 5 that the thermogravimetric curve shows three main mass loss stages: (I) below 500 °C, due to the decomposition of organic matter and the rapid evaporation of volatiles, the weight of the precursor decreases significantly by about 30%; (II) from 500 °C to 1050 °C, the weight loss is about 10%, and an endothermic peak appears at about 1000 °C, indicating that sorbitol is undergoing carbonization and oxides are gradually forming, that is, the decomposition of the precursor; (III) above 1050 °C, the third weight loss is due to the progress of the carbothermal reduction reaction of the four transition metal oxides. Therefore, in this application, it is selected to hold at 1050 °C for 30 min, which is beneficial to the progress of the carbothermal reduction reaction.

[0094] In summary, in this application, single-phase high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder can be successfully synthesized by the flocculation precipitation-carbothermal reduction ammonia nitridation method. Sorbitol is selected as the carbon source, and NH3 can be used as both a reducing agent and a nitrogen source, which can effectively reduce the carbon content and improve the powder purity. At the same time, after sorbitol is carbonized, vacuum pumping can evacuate other gases such as carbon monoxide in the system, which is beneficial to the further nitridation and reduction of ammonia and improves the nitridation efficiency. This application not only has a simple preparation process, does not involve complex reaction processes, can be prepared in a short cycle, but also the prepared (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25)The N powder has a high purity, good micro-morphology, and relatively uniform distribution of each element, which can provide a technical basis and commercial potential for the large-scale synthesis of high-entropy nitride ceramic materials.

[0095] Those skilled in the art should understand that the above are only several specific embodiments of the present invention, rather than all embodiments. It should be pointed out that many modifications and improvements can be made by those of ordinary skill in the art, and all modifications or improvements that do not exceed the scope of the claims should be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a high-purity high-entropy nitride ceramic powder, characterized in that, The method includes the following steps: S1. Prepare solution A and solution B. Solution A is an acetic acid solution containing four or more transition metal elements with an equimolar ratio; solution B is an acetic acid solution containing sorbitol, and the molar ratio of carbon element in sorbitol to the total molar amount of transition metal elements is 1:

1. S2. Slowly and evenly drip solution A into solution B, and continuously stir to obtain a precipitate and precursor mixture. S3. Let the precursor mixture obtained in S2 stand and age at a low temperature of 80 - 90 °C for 6 - 8 h, and dry at a high temperature of 120 - 150 °C for 8 - 12 h to obtain a dry powder. S4. Grind the precursor precipitate obtained in step S3 into powder and calcine it. The calcination process is as follows: First, introduce argon as a protective gas and heat from room temperature to 1000 - 1100 °C at a heating rate of 5 - 10 °C / min and hold for 30 min. After the holding ends, disconnect the argon and evacuate to vacuum. Then, introduce ammonia to react with the precursor powder, heat to 1550 - 1650 °C at a rate of 2 - 5 °C / min and hold for 2 h, and cool to room temperature to obtain high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

2. The preparation method of the high-purity high-entropy nitride ceramic powder according to claim 1, wherein, The four or more transition metals are selected from any four or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg.

3. The preparation method of the high-purity high-entropy nitride ceramic powder according to claim 2, wherein, The four or more transition metals are four transition metals, namely Ti, Ta, Nb, and Mo.

4. The preparation method of the high-purity high-entropy nitride ceramic powder according to claim 3, characterized in that, The preparation of solution A includes: mixing TiCl4, TaCl5, NbCl5, and MoCl5 with an equimolar ratio and adding them into acetic acid, and fully stirring and dissolving to obtain solution A; and / or the preparation of solution B includes: under the condition of an oil bath at 60 - 90 °C, stirring sorbitol in acetic acid until it is completely dissolved, and cooling to room temperature to obtain solution B.

5. A method for preparing a high-purity high-entropy nitride ceramic powder according to any one of claims 1 - 4, characterized in that In step S2, solution A is slowly and evenly dripped into solution B at a rate of 1 - 5 mL / min; and / or In step S3, the precursor mixture stands and ages at a temperature of 80 °C for 8 h, and then dries at a temperature of 120 °C for 12 h to obtain a precursor precipitate; and / or In step S4, the precursor precipitate obtained in step S3 is ground into powder and calcined. The calcination process is as follows: First, argon is introduced as a protective gas and heated from room temperature to 1050 °C at a heating rate of 5 °C / min, and kept at 1050 °C for 30 min. After the heat preservation ends, the argon is disconnected and the vacuum is pumped; then ammonia is introduced to react with the precursor powder, and then heated to 1600 °C at a rate of 2 °C / min and kept at 1600 °C for 2 h; after that, it is cooled to 1000 °C at a rate of 2 °C / min, and then cooled to 300 °C at a rate of 5 °C / min, and finally naturally cooled to room temperature to obtain high-purity high-entropy nitride (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

6. A high-purity high-entropy nitride ceramic powder prepared by the method for preparing a high-purity high-entropy nitride ceramic powder according to any one of claims 1 - 5.

7. The high-purity high-entropy nitride ceramic powder according to claim 6, characterized in that, The high-purity high-entropy nitride ceramic powder is (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder.

8. The high-purity high-entropy nitride ceramic powder according to claim 7, wherein The crystal plane spacing of the (Ti 0.25 Ta 0.25 Nb 0.25 Mo 0.25 )N ceramic powder is 0.244 nm, corresponding to the (1 1 1) crystal plane of the face-centered cubic structure; the crystal plane spacing is 0.217 nm, corresponding to the (2 0 0) crystal plane of the face-centered cubic structure.

9. Application of the high-purity high-entropy nitride ceramic powder according to any one of claims 6 - 8 in the preparation of ceramic products.

10. A ceramic product, characterized in that, The ceramic product includes the high-purity high-entropy nitride ceramic powder according to any one of claims 6 - 8.

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