High-entropy nitride ceramic fiber wave-absorbing material and preparation method thereof

Abstract

The invention belongs to the technical field of high-entropy nitride ceramic fibers, and particularly relates to a high-entropy nitride ceramic fiber wave-absorbing material and a preparation method thereof. The preparation method comprises the following steps: mixing a metal source, a spinning auxiliary agent and a spinning solvent to prepare a spinning precursor solution; wherein the metal sources are selected from any five or more than five of a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source, an iron source and a molybdenum source; preparing precursor fibers from the spinning precursor solution through electrostatic spinning; and carrying out high-temperature heat treatment on the precursor fiber, and carrying out reduction nitridation reaction in an ammonia gas atmosphere to obtain the high-entropy nitride ceramic fiber wave-absorbing material. According to the invention, the preparation method of the high-entropy nitride ceramic fiber wave-absorbing material is simple to operate, and the obtained ceramic fiber has excellent microwave absorption characteristic and electrochemical corrosion resistance, so that the application range of the high-entropy nitride ceramic fiber wave-absorbing material is wider.

Description

Technical Field

[0001] The invention belongs to the technical field of high entropy nitride ceramic fibers, and in particular relates to a high entropy nitride ceramic fiber absorbing material and a preparation method thereof. Background Art

[0002] With the development of modern electronic countermeasure technology, modern warfare has increasingly stringent requirements for the stealth technology of missiles, aircraft, ships and other weapons. As one of the important materials for stealth technology of weapons and equipment, electromagnetic wave absorbing materials can significantly reduce the radar cross section of weapons. In the increasingly complex and harsh environment during the application process, absorbing materials are required to have thin thickness, low density, wide frequency band, strong absorption, and multiple spectrum bands, as well as good corrosion resistance. Currently, common traditional absorbing materials, such as metals, ferrites, carbon and silicon carbide, are difficult to meet the requirements of absorbing materials in complex and harsh environments due to their high density, poor stability, narrow absorption band or large matching thickness, and low absorbing efficiency. Therefore, the development of a new type of absorbing material with excellent absorbing properties and corrosion resistance has important scientific significance and military application prospects for improving the stealth capability of modern weapons and equipment and ensuring the survivability and defense capabilities of weapons.

[0003] In recent years, the microwave absorption properties of high-entropy carbide ceramics, high-entropy boride ceramics, and high-entropy oxide ceramics have gradually been explored. For example, the research group of Researcher Zhou Yanchun of the Institute of Aerospace Materials and Technology has successfully designed and synthesized (Cr 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 / (Ce 0.2 Y 0.2 Sm 0.2 Er 0.2 Yb 0.2 )BO3(Journal of AdvancedCeramics,2021,10(1):62–77.)、(Y 0.2 Sm 0.2 Eu 0.2 Er 0.2 Yb 0.2 )B6 / (Y 0.2 Sm 0.2 Eu 0.2 Er 0.2 Yb 0.2 )B4 (Journal of Materials Science & Technology, 2021, 87: 155–166.) and (Ti 0.2 Zr 0.2 Hf0.2 Nb 0.2 Ta 0.2 )C (Journal of Materials Science & Technology, 2021, 74: 105–118.) and other high-entropy carbides, high-entropy borides and high-entropy oxide ceramics. Moreover, through the design of high-entropy components, the conductivity of the material and its transition metal d orbital crystal field splitting energy can be effectively balanced to achieve electrical / magnetic loss coupling, thereby adjusting its impedance matching and obtaining excellent wave absorption performance. In addition, the team of Researcher Song Lixin of the Shanghai Institute of Ceramics, Chinese Academy of Sciences, recently confirmed that spinel high-entropy oxides (Fe x CoNiCrMn) m O n The heterogeneous interface, lattice distortion and crystal defects give it good wave absorbing properties. It also has the characteristics of low thermal conductivity and strong antioxidant ability, and can be used as a high-temperature wave absorbing material (Journal of Materials Science & Technology, 2022, 116: 11-2.). S.M. Masoudpanah's research group at the Iran University of Technology has made high entropy oxide (MnNiCuZn) 1-x CoxFe2O4 and graphene are combined to obtain a composite material with high dielectric loss and wave absorption performance (Journal of materials research and technology, 2021, 14: 1099–1111.). In addition, Zhou Yanchun's research group successfully developed high-entropy spinel ferrite (Mg 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )Fe2O4、(Mg 0.2 Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2 )Fe2O4 and (Mg 0.2 Fe 0.2 Co 0.2 Ni 0.2 Zn 0.2) Fe2O4 (Journal of Advanced Ceramics, 2022, 11(5): 754–768.), the three high-entropy spinel ferrites prepared all showed good microwave absorption performance through the coupling effect of magnetic loss and dielectric loss. It can be seen that high-entropy carbides, high-entropy borides and high-entropy oxides have application prospects as microwave absorbing materials.

[0004] Literature research shows that transition metal nitride high-entropy ceramics have higher stability and bulk modulus than carbide high-entropy ceramics of the same system, and due to the activity of nitrogen, high-entropy nitride ceramics have better crystal structure stability and are easier to form a single-phase solid solution (Journal of Applied Physics, 2020, 127: 145301.). At the same time, compared with high-entropy ceramic absorbers of other systems, the improvement of the crystal structure stability of high-entropy nitride ceramics has better application prospects in harsh environments such as high temperature and corrosion. However, as an important member of the high-entropy ceramic system, high-entropy nitride ceramics with excellent properties such as high hardness, high temperature resistance, and corrosion resistance have not yet been explored for their absorbing properties.

[0005] In a complex service environment, the absorbing material will age due to corrosion factors such as oxygen, salt, and acid rain, thereby reducing or even losing its absorbing performance. Therefore, in addition to the absorbing performance of the material, its excellent corrosion resistance plays a vital role in the survival ability of the absorbing material. In recent years, the excellent corrosion resistance of high-entropy nitride ceramics has increasingly attracted the attention of scientific researchers. For example, Zhang Shangzhou's research group at Yantai University prepared a (TiAlCrSiV)xNy high-entropy nitride ceramic coating with a self-corrosion current as low as 1.68×10 -8 A / cm 2 , showing excellent corrosion resistance (Ceramics International, 2022, 48: 9342-9352.). In addition, Liao Bin and others from Beijing Normal University developed (AlTiVCrMo)N for the surface of proton exchange membrane fuel cells. x High entropy ceramic coatings exhibit impressive corrosion resistance with corrosion current (Icorr) as low as 1.45×10 -7 A / cm 2 , the corrosion potential (Ecorr) is 0.375 V (Journal of Power Sources, 2022, 527: 231217.). It can be seen that high entropy nitrides have the potential to be used as absorbing materials with both high efficiency and excellent corrosion resistance.

[0006] At present, the morphology of high entropy ceramic absorbing materials is mainly powder. However, in actual use, powder absorbing materials have the problems of high quality and large dosage, and it is difficult to meet the requirements of complex environments for absorbing materials. However, fibrous high entropy nitride ceramic fiber absorbing materials have rarely been studied due to the high technical barriers in the preparation process. Summary of the invention

[0007] Based on this, the purpose of the present invention is to provide a high entropy nitride ceramic fiber absorbing material and a preparation method thereof, which has solved the problems in the prior art.

[0008] To achieve the above object, the present invention adopts the following technical solution.

[0009] The present invention provides a high entropy nitride ceramic fiber absorbing material and a preparation method thereof, comprising the following steps:

[0010] A metal source, a spinning aid and a spinning solvent are mixed to prepare a spinning precursor solution; wherein the metal source is selected from any five or more of a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source, an iron source and a molybdenum source;

[0011] Prepare precursor fibers by electrospinning the spinning solution;

[0012] The precursor fiber is subjected to high-temperature heat treatment, and then undergoes a reduction nitridation reaction in an ammonia atmosphere to obtain a high-entropy nitride ceramic fiber absorbing material.

[0013] In the present invention, the metal source is selected from any five or more of a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source, an iron source, and a molybdenum source. For example, when the metal source contains five metals, the metal source is a niobium source, a vanadium source, a tantalum source, a hafnium source, and a molybdenum source; or the metal source is a niobium source, a vanadium source, a hafnium source, a titanium source, and an iron source; or the metal source is a niobium source, a vanadium source, a hafnium source, a titanium source, and a molybdenum source; or the metal source is a hafnium source, a tantalum source, a titanium source, an iron source, and a molybdenum source; or the metal source is a niobium source, a vanadium source, an iron source, a molybdenum source, and a titanium source.

[0014] In some embodiments, the molar ratio of any five of the metal sources is 1-2:1-2:1-2:1-2:1-2:1-2.

[0015] When the metal source contains six metals, the metal source is a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source and a molybdenum source; or the metal source is a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source and an iron source; or the metal source is a niobium source, a titanium source, a tantalum source, a hafnium source, an iron source and a molybdenum source; or the metal source is a niobium source, a vanadium source, a tantalum source, a hafnium source, an iron source and a molybdenum source; or the metal source is a niobium source, a vanadium source, a titanium ... tantalum source, an iron source and a molybdenum source.

[0016] In some embodiments, the molar ratio of any six of the metal sources is 1-2:1-2:1-2:1-2:1-2:1-2:1-2.

[0017] When the metal sources include seven metals, the metal sources are a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source, an iron source and a molybdenum source.

[0018] In some embodiments, the molar ratio of the seven metal sources is 1-2:1-2:1-2:1-2:1-2:1-2:1-2:1-2.

[0019] In some embodiments, the niobium source includes niobium pentachloride, the vanadium source includes vanadium acetylacetonate, the titanium source includes tetrabutyl titanate, the tantalum source includes tantalum chloride, the hafnium source includes hafnium chloride, the iron source includes iron acetylacetonate, and the molybdenum source includes ammonium molybdate tetrahydrate.

[0020] In some embodiments, the electrospinning process conditions are as follows: the electrospinning voltage is 20-28 kV, and the solution supply rate is 0.8-3 mL / h.

[0021] The precursor fiber prepared by electrospinning is a precursor fiber formed by various metal cations and polymer additives. After high-temperature heat treatment, it can play a curing role, and the polymer calcination can remove part of the organic solvent. However, too high a temperature or too long a time may cause the precursor fiber morphology to deteriorate, such as shrinking more severely. Therefore, in some embodiments, the conditions of the high-temperature heat treatment are: temperature 500°C to 700°C, treatment time 30min to 120min.

[0022] In some embodiments, in the reduction nitridation reaction, the temperature of the reduction nitridation reaction is 800°C to 1100°C; the NH3 flow rate is 200mL / min-1500mL / min, and the reduction nitridation time is 2 hours to 4 hours. When the reduction nitridation reaction temperature is too high or the reaction time is too long, the fiber morphology will be destroyed.

[0023] In some embodiments, the heating rate of the reduction nitridation reaction is 1° C. / min to 5° C. / min.

[0024] In some embodiments, the spinning aid is acetic acid and polyvinyl pyrrolidone; and the spinning solvent is a mixture of anhydrous ethanol and NN dimethylformamide.

[0025] In some embodiments, the volume ratio of anhydrous ethanol to N-N-dimethylformamide is 3 to 1:1.

[0026] In some embodiments, the volume ratio of the acetic acid, polyvinyl pyrrolidone and the spinning solvent is 0.8 mL to 1.3 mL: 1.8 g to 2.2 g: 3.8 mL to 4.2 mL.

[0027] The present invention also provides a high entropy nitride ceramic fiber wave absorbing material prepared by the above method.

[0028] In some embodiments, the cationic components in the high entropy nitride ceramic fiber absorbing material contain any five elements or more of niobium, vanadium, titanium, tantalum, hafnium, iron and molybdenum; the high entropy nitride ceramic fiber absorbing material has a porous structure with an average diameter of about 100nm to 300nm and a pore size range of 5nm to 50nm.

[0029] In some embodiments, the high entropy nitride fiber is a single crystal phase, and each element is evenly distributed.

[0030] Based on the technical solution of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention combines electrostatic spinning and ammonia reduction nitridation to prepare a high entropy nitride ceramic fiber absorbent material, which is simple to operate and is an effective method for preparing nitride nanofibers, and is a method for preparing high entropy nitride ceramic fibers that are resistant to electrochemical corrosion. The high entropy nitride ceramic fiber absorbent material provided by the present invention has microwave absorption characteristics and electrochemical corrosion resistance characteristics, so that it meets the new requirements of modern military equipment in the field of absorbing materials, and has important practical significance and theoretical value.

[0032] The present invention provides a set of electrospinning process parameters that match the spinning precursor solution, which can synthesize precursor fibers that meet the requirements of later production of high entropy nitride ceramic fiber absorbent materials. The present invention also explores the raw material ratio in the preparation process of the spinning precursor solution so that it can be evenly dissolved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The high entropy nitride ceramic fiber absorbent material (Ti 0.2 Nb 0.2 V 0.2 Ta 0.2 Hf 0.2 )N scanning electron microscope (SEM) photograph; wherein, Figure 1 a in the figure indicates the photograph with a scale of 10 μm; Figure 1 b in the figure indicates the photograph with a scale of 5 μm; Figure 1 c in the figure indicates the photograph with a scale of 1 μm; Figure 1 The d in the figure indicates a photograph with a scale bar of 500 μm.

[0034] Figure 2 The high entropy nitride ceramic fiber absorbent material (Ti 0.2 Nb 0.2 V 0.2 Ta 0.2 Hf 0.2 (a) N2 adsorption-desorption isotherms of N.

[0035] Figure 3 The high entropy nitride ceramic fiber absorber (Ti 0.2 Nb 0.2 V 0.2 Fe 0.2 Mo 0.2 )N SEM photo; wherein, Figure 3 a in the figure indicates the photograph with a scale of 10 μm; Figure 3 b in the figure indicates the photograph with a scale of 5 μm; Figure 3 c in the figure indicates the photograph with a scale of 1 μm; Figure 3 The d in the figure indicates a photograph with a scale bar of 500 μm. DETAILED DESCRIPTION

[0036] The experimental methods in the following examples of the present invention without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0037] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0039] In the present invention, the term "multiple" refers to two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0040] The following describes the invention in conjunction with specific embodiments.

[0041] Example 1

[0042] A method for preparing a high entropy nitride ceramic fiber absorbing material comprises the following steps:

[0043] 1. Preparation of spinning precursor solution: Add 15 ml of anhydrous ethanol to a beaker. Then, add niobium pentachloride, vanadium acetylacetonate, hafnium chloride, tantalum chloride, tetrabutyl titanate, acetic acid, PVP (polyvinyl pyrrolidone) and DMF (N,N-dimethylformamide) to the beaker in sequence. After that, stir vigorously at room temperature for 2 hours until completely dissolved to obtain a spinning solution.

[0044] 2. Electrospinning: The solution was transferred to a plastic syringe (capacity: 20 mL) for electrospinning to obtain precursor fibers. The electrospinning voltage was 20 kV, and the solution supply rate was set to 0.8 mL / h.

[0045] 3. Pre-burning: The precursor fiber is burned in air at 500°C for 30 minutes (5°C / min) for pre-burning.

[0046] 4. Ammonia reduction nitridation: After the pre-sintered fiber is cooled to room temperature, it is reduced and nitrided in an NH3 atmosphere at 1000°C for 2 hours (5°C / min). Specifically, during the heating process of ammonia reduction nitridation, when the heating temperature is lower than 300°C, a N2 atmosphere is used. When the heating temperature is between 300°C and 500°C, NH3 with a flow rate of 400mL / min replaces N2. When the reduction nitridation temperature exceeds 500°C, the flow rate of NH3 is maintained at 800mL / min until the temperature rises to 1000°C and is kept for 2 hours, and then cooled to 300°C. Then the temperature is allowed to cool to room temperature in an N2 atmosphere, and finally a high entropy nitride ceramic fiber absorber is formed.

[0047] In this embodiment, the ratio of raw materials in the precursor solution in the above preparation method is explored, and the specific raw material usage is shown in Table 1 and Table 2.

[0048] Table 1 The usage of spinning aids and spinning solvents

[0049]

[0050]

[0051] Table 2 Metal sources

[0052]

[0053] The high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment was observed by scanning electron microscopy. The results showed that all test groups 1 to 5 could be prepared. The high entropy nitride ceramic fiber absorbent material with good performance required by the present invention had good crystallinity, fiber morphology, large aspect ratio, and a diameter of about 120 nm. Therefore, taking test group 1 as an example, the performance of the high entropy nitride ceramic fiber absorbent material was observed by scanning electron microscopy. Figure 1As shown, the high entropy nitride ceramic fiber absorbent material prepared by the scheme provided for test group 1 has good crystallinity, fiber morphology, large aspect ratio, and a diameter of about 120 nm. The nitrogen adsorption-desorption curve of the high entropy nitride ceramic fiber absorbent material prepared by test group 1 was tested, indicating that the high entropy nitride ceramic fiber has a porous structure.

[0054] The reflection loss of the high entropy nitride ceramic fiber absorber prepared in Experiments 1 to 5 at a filler content of 25 wt% was calculated using transmission line theory. The results are shown in Table 3.

[0055] Table 3 Reflection loss

[0056] Experimental Group Absorption layer thickness / mm Optimum reflection loss Test 1 1.53 -49.10dB Test 2 1.31 -47.47dB Test 3 1.70 -43.11dB Test 4 2.30 -40.70dB Test 5 3.90 -45.69dB

[0057] The electrochemical corrosion resistance of the high entropy nitride ceramic fiber absorbent materials prepared in test groups 1 to 5 was tested, and the results are shown in Table 4.

[0058] Table 4 Electrochemical corrosion resistance

[0059]

[0060]

[0061] As shown in Tables 3 and 4, it is shown that the high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment has high resistance to electrochemical corrosion, and the best resistance to electrochemical corrosion is in Experimental Group 1. In Table 2, in Experimental Group 1, the molar ratio of niobium, vanadium, hafnium, tantalum and titanium in the metal source is 1:1:1:1:1.

[0062] Example 2

[0063] A method for preparing a high entropy nitride ceramic fiber absorbing material. Compared with Example 1, the reaction conditions of ammonia reduction nitridation are different, and the other methods are the same. The specific method of ammonia reduction nitridation is: after the pre-sintered fiber is cooled to room temperature, the fiber is reduced and nitrided in an NH3 atmosphere at 1100°C for 3 hours (5°C / min). Specifically, during the heating process of ammonia reduction nitridation, when the heating temperature is lower than 300°C, an N2 atmosphere is used. When the heating temperature is between 300°C and 500°C, NH3 with a flow rate of 400mL / min replaces N2. When the reduction nitridation temperature exceeds 500°C, the flow rate of NH3 is maintained at 800mL / min until the temperature rises to 1100°C, kept warm for 3 hours, and then reduced to 300°C. Then the temperature is allowed to cool to room temperature in an N2 atmosphere, and a high entropy nitride ceramic fiber absorbing material is finally obtained.

[0064] The transmission line theory was used to calculate the reflection loss of high entropy nitride ceramic fiber absorber with 25wt% filler. When the thickness of the absorbing layer was only 1.30mm, the optimal reflection loss reached -32.16dB. 0.2 Nb 0.2 V 0.2 Fe 0.2 Mo 0.2 )N was tested for its electrochemical corrosion resistance. The results showed that the corrosion current (Icorr) was as low as 3.18×10 -7 A / cm 2 The corrosion potential (Ecorr) is 0.042 V, indicating that the high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment has high resistance to electrochemical corrosion.

[0065] Example 3

[0066] A method for preparing a high entropy nitride ceramic fiber absorbing material. Compared with Example 1, the pre-firing conditions are different, and the remaining steps are the same. Specifically, in this embodiment, the specific method of pre-firing is: burning the precursor fiber in air at 700°C for 2 hours (5°C / min) to finally obtain a high entropy nitride ceramic fiber absorbing material.

[0067] The transmission line theory was used to calculate the reflection loss of high entropy nitride ceramic fiber absorber with 20wt% filler. When the thickness of the absorbing layer was only 1.30mm, the optimal reflection loss reached -19.8dB. 0.2 Nb 0.2 V 0.2 Fe 0.2 Mo 0.2 )N was tested for its anti-electrochemical corrosion performance. The results showed that the corrosion current (Icorr) was as low as 6.97×10 -7 A / cm 2 The corrosion potential (Ecorr) is 0.038 V, indicating that the high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment has high resistance to electrochemical corrosion.

[0068] Example 4

[0069] A method for preparing a high entropy nitride ceramic fiber absorbing material, compared with Example 1, the electrospinning parameters are different, and the other steps are the same. Specifically, in this embodiment, the electrospinning step is: transferring the solution to a plastic syringe (capacity: 20mL) for electrospinning to obtain a precursor fiber. The electrospinning voltage is 28kV, and the solution supply rate is set to 1mL / h.

[0070] The transmission line theory was used to calculate the reflection loss of high entropy nitride ceramic fiber absorber with a filler content of 30wt%. When the thickness of the absorbing layer was only 1.5mm, the optimal reflection loss reached -48.32dB. 0.2 Nb 0.2 V 0.2 Fe 0.2 Mo 0.2 )N was tested for its electrochemical corrosion resistance. The results showed that the corrosion current (Icorr) was as low as 4.68×10 -7 A / cm 2 The corrosion potential (Ecorr) is 0.086 V, indicating that the high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment has high resistance to electrochemical corrosion.

[0071] Example 5

[0072] A method for preparing a high entropy nitride ceramic fiber absorbing material. Compared with Example 1, the type of metal source is different, and the temperature of ammonia reduction nitridation is different. Specifically, this embodiment includes the following steps:

[0073] 1. Preparation of spinning precursor solution: Add 15 ml of anhydrous ethanol to a beaker. Then, add 0.45 g of niobium pentachloride, 0.45 g of vanadium acetylacetonate, 0.45 g of iron acetylacetonate, 0.29 g of ammonium molybdate tetrahydrate, 0.57 ml of tetrabutyl titanate, 1 ml of acetic acid, 2 g of PVP and 9 ml of DMF to the beaker in sequence. After that, stir vigorously at room temperature for 2 hours until completely dissolved. The molar ratio of niobium, vanadium, iron, molybdenum and titanium is 1:1:1:1:1.

[0074] 2. Electrospinning: The solution was transferred to a plastic syringe (capacity: 20 mL) for electrospinning. The electrospinning voltage was adjusted to 20 kV, and the solution supply rate was set to 0.8 mL / h.

[0075] 3. Pre-burning: burn the fiber in air at 500°C for 30 minutes (5°C / min) for pre-burning.

[0076] 4. Ammonia reduction nitridation: After the pre-sintered fiber is cooled to room temperature, the fiber is reduced and nitrided in an NH3 atmosphere at 800°C for 4 hours (5°C / min).

[0077] Specifically, during the temperature rise process of ammonia reduction nitridation, when the heating temperature is below 300°C, a N2 atmosphere is used. When the heating temperature is between 300°C and 500°C, NH3 with a flow rate of 400mL / min replaces N2. When the reduction nitridation temperature exceeds 500°C, the flow rate of NH3 is maintained at 800mL / min until the temperature is raised to 800°C and kept for 4 hours, and then reduced to 300°C. The temperature is then allowed to cool to room temperature under a N2 atmosphere.

[0078] like Figure 3 As shown, the prepared high entropy nitride ceramic fiber absorber (Ti 0.2 Nb 0.2 V 0.2 Fe 0.2 Mo 0.2 )N was observed by scanning electron microscope. The results showed that the high entropy nitride ceramic fiber absorber had good crystallinity, fiber morphology, large aspect ratio and a diameter of about 90nm.

[0079] The transmission line theory was used to calculate the reflection loss of the high entropy nitride ceramic fiber absorber with a filler content of 30wt%. When the thickness of the absorbing layer was only 2.32mm, the optimal reflection loss reached -49.70dB. 0.2 Nb 0.2 V 0.2 Fe 0.2 Mo 0.2 )N was tested for its electrochemical corrosion resistance. The results showed that the corrosion current (Icorr) was as low as 1.21×10 -7 A / cm 2 The corrosion potential (Ecorr) is -0.077 V, indicating that the high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment has high resistance to electrochemical corrosion.

[0080] Example 6

[0081] A method for preparing a high entropy nitride ceramic fiber absorbing material. Compared with Example 5, the pre-firing conditions are different, and the remaining steps are the same. Specifically, in this embodiment, the specific method of pre-firing is: burning the precursor fiber in air at 600°C for 80 minutes (5°C / min) to finally obtain a high entropy nitride ceramic fiber absorbing material.

[0082] The transmission line theory was used to calculate the reflection loss of high entropy nitride ceramic fiber absorber with 25wt% filler. When the thickness of the absorbing layer was only 2.50mm, the optimal reflection loss reached -51.17dB. 0.2 Nb 0.2 V 0.2Fe 0.2 Mo 0.2) N was tested for its electrochemical corrosion resistance, and the results showed that the corrosion current (Icorr) was as low as 3.70×10 -6 A / cm 2 The corrosion potential (Ecorr) is 0.042 V, indicating that the high entropy nitride ceramic fiber absorbent material prepared by the method provided in this embodiment has high resistance to electrochemical corrosion.

[0083] Comparative Example 1

[0084] Compared with Example 1, the difference in the preparation method of Comparative Example 1 is that the steps of preparing the spinning precursor solution are different, and the other steps are the same. In this comparative example, the preparation method of the spinning precursor solution is: add 15 ml of anhydrous ethanol to a beaker. Then

[0085] 1g niobium pentachloride, 1g vanadium acetylacetonate, 1g hafnium chloride, 1g tantalum chloride, 1mL tetrabutyl titanate, 2mL acetic acid, 5g PVP and 5mL DMF were added to the beaker in sequence. After that, it was vigorously stirred at room temperature for 2 hours, and it was found that the above raw materials could not be completely dissolved in anhydrous ethanol. There are a small amount of undissolved particles deposited at the bottom of the beaker. It can be seen that too much cation or PVP and too little solvent will affect the solubility. When it is electrospun, the amount of precursor fiber collected is small, it has a large viscosity, and it cannot be filamented.

[0086] Comparative Example 2

[0087] Compared with Example 1, the difference in the preparation method of Comparative Example 2 is that the parameters of electrospinning are: electrospinning voltage: 18 kV, solution supply rate: 0.6 mL / h. The remaining steps are the same as those in Example 1 to prepare high entropy nitride ceramic fiber absorbent material. The prepared high entropy nitride ceramic (Ti 0.2 Nb 0.2 V 0.2 Ta 0.2 Hf 0.2 )N fiber morphology is poor, and the fiber bending and breakage are serious.

[0088] Comparative Example 3

[0089] Comparative Example 3 Compared with Example 1, the difference in the preparation method is that the precursor fiber is burned in air at 800°C for 150 minutes (5°C / min) during pre-sintering. The remaining steps are the same as those in Example 1 to prepare the high entropy nitride ceramic fiber absorbent material. The prepared high entropy nitride ceramic (Ti 0.2 Nb 0.2 V 0.2 Ta 0.2 Hf 0.2)N fiber morphology is poor, and the fiber bending and breakage are serious.

[0090] Comparative Example 4

[0091] Comparative Example 4 is different from Example 1 in that the pre-sintered fiber is subjected to reduction nitridation in an NH3 atmosphere at 1200°C for 3 hours (5°C / min). The remaining steps are the same as those in Example 1 to prepare a high entropy nitride ceramic fiber absorbent material.

[0092] The high entropy nitride ceramic fiber (Ti 0.2 Nb 0.2 V 0.2 Ta 0.2 Hf 0.2 )N has good crystallinity, large aspect ratio, and diameter of about 250nm. The transmission line theory is used to calculate the reflection loss of high entropy nitride fiber / paraffin composite material with 20wt% filler. When the thickness of the absorbing layer is only 1.30mm, the optimal reflection loss reaches -19.8dB. The electrochemical workstation is used to measure the high entropy nitride ceramic fiber (Ti 0.2 Nb 0.2 V 0.2 Ta 0.2 Hf 0.2 )N was tested for its electrochemical corrosion resistance. The results showed that the corrosion current (Icorr) was 1.97×10 -7 A / cm 2 , the corrosion potential (Ecorr) is 0.295 V. It can be seen that if the reduction nitridation temperature is too high and the holding time is prolonged, the grains will grow, the fiber diameter will become thicker, and the absorption performance will decrease.

[0093] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a high entropy nitride ceramic fiber absorbing material, characterized in that: The following steps are involved: A metal source, a spinning aid and a spinning solvent are mixed to prepare a spinning precursor solution; wherein the metal source is selected from any five or more of a niobium source, a vanadium source, a titanium source, a tantalum source, a hafnium source, an iron source and a molybdenum source; Prepare precursor fibers by electrospinning the spinning precursor solution; The precursor fiber is subjected to high-temperature heat treatment, and then undergoes a reduction nitridation reaction in an ammonia atmosphere to obtain a high-entropy nitride ceramic fiber absorbing material.

2. The preparation method according to claim 1, characterized in that The molar ratio of the niobium source, the vanadium source, the titanium source, the tantalum source, the hafnium source, the iron source and the molybdenum source is 1-2:1-2:1-2:1-2:1-2:1-2:1-2:1-2.

3. The preparation method according to claim 2, characterized in that: The niobium source includes niobium pentachloride, the vanadium source includes vanadium acetylacetonate, the titanium source includes tetrabutyl titanate, the tantalum source includes tantalum chloride, the hafnium source includes hafnium chloride, the iron source includes iron acetylacetonate, and the molybdenum source includes ammonium molybdate tetrahydrate.

4. The preparation method according to claim 1, characterized in that: The process conditions of the electrospinning are as follows: the voltage of the electrospinning is 20 kV to 28 kV, and the supply rate of the solution is 0.8 mL / h to 3 mL / h.

5. The preparation method according to claim 1, characterized in that: The conditions of the high temperature heat treatment are: temperature 500° C. to 700° C., and treatment time 30 min to 120 min.

6. The preparation method according to claim 1, characterized in that: In the reduction nitridation reaction, the temperature of the reduction nitridation reaction is 800° C. to 1100° C.; the NH 3 flow rate is 200 mL / min-1500 mL / min; and the reduction nitridation time is 2 hours to 4 hours.

7. The preparation method according to claim 1, characterized in that: The spinning aids are acetic acid and polyvinyl pyrrolidone; the spinning solvent is a mixture of anhydrous ethanol and NN dimethylformamide.

8. The preparation method according to claim 7, characterized in that: The volume ratio of the anhydrous ethanol to NN dimethylformamide is 3 to 1:

1.

9. The high entropy nitride ceramic fiber absorbing material prepared by the method according to any one of claims 1 to 8.

10. The high entropy nitride ceramic fiber absorbing material according to claim 9, characterized in that: The cationic components in the high entropy nitride ceramic fiber absorbing material contain any five elements or more than five elements of niobium, vanadium, titanium, tantalum, hafnium, iron and molybdenum; the high entropy nitride ceramic fiber absorbing material has a porous structure with an average diameter of about 100 to 300 nm and a pore size range of 5 nm to 50 nm.

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