Catalyst-free synthesized carbonitride ultrahigh temperature ceramic nanowires and preparation method thereof

Abstract

The application discloses a kind of catalyst-free synthesis of carbonitride ultrahigh temperature ceramic nanowires and preparation method thereof, first transition metal source, carbon source, nitrogen source is dissolved in solvent to form supersaturated solution under certain temperature, then adjust pH value to prepare sol;It is aged into gel-like material under certain temperature, and then it is naturally cooled to room temperature under normal pressure condition, and it is recrystallized to form one-dimensional nanowire structure precursor under specific temperature;Finally, through high-temperature heat treatment, the precursor is converted into carbonitride ultrahigh temperature ceramic nanowires due to morphology inheritance.The application controls ceramic morphology by regulating precursor morphology, and avoids catalyst pollution without using metal catalyst.The obtained carbonitride ultrahigh temperature ceramic nanowire powder is nano-flower-shaped, has excellent tip morphology, and the surface is uniformly coated with amorphous carbon layer, forming a core-shell structure, which has significant application advantages in aerospace, energy, special materials and other fields.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high temperature ceramic preparation technology, and relates to a catalyst-free synthesis of carbonitride ultra-high temperature ceramic nanowires and its preparation method. Background Technology

[0002] Carbide ultra-high temperature ceramics (such as HfC and ZrC) possess excellent thermal protection capabilities due to their extremely high melting points, good chemical stability, and thermal shock resistance. Recent studies have found that introducing nitrogen into the carbide lattice to form carbonitride solid solutions (MeCN, Me = Hf, Zr, Ta, Nb, Ti) can significantly improve the overall performance of the material. Nitrogen atoms can partially substitute for positions in the carbon sublattice, inducing strong hybridization between orbitals. This electronic structure not only enhances the chemical bonding strength but also introduces a configurational entropy increase effect due to compositional disorder, thus exhibiting superior high-temperature stability, oxidation resistance, corrosion resistance, and chemical stability, making it an ideal candidate material for next-generation high-speed aircraft thermal protection systems.

[0003] Furthermore, when carbonitride ultra-high temperature ceramics exist in the form of one-dimensional nanowire structures, their performance can achieve significant breakthroughs. Due to their high aspect ratio, anisotropic mechanical response, and quantum confinement effect, these nanowires not only inherit the inherent ultra-high melting point, high strength, and high hardness of carbonitride ceramics, but also exhibit excellent electrical conductivity, field emission performance, photoresponse characteristics, and catalytic activity, showing significant application potential in high-temperature electronic devices, field emission sources, electrochemical catalysis, and photoelectric conversion.

[0004] However, existing methods for synthesizing ultra-high temperature ceramic nanowires mainly focus on carbide systems, including chemical vapor deposition, polymer precursor pyrolysis, and template methods, and generally have the following limitations: (1) dependence on metal catalysts: For example, Liang Zhongtian et al. used nickel nitrate hexahydrate as a catalyst and prepared hafnium carbide nanowires based on the gas-liquid-solid growth mechanism using chemical vapor deposition. However, this method will form spherical nickel particles at the top of the nanowires, which not only reduces the purity of the product but also destroys the structural integrity of the nanowires; (2) limitation to specific substrates: Yan Ningning et al. used precursor impregnation pyrolysis method and carbon cloth as a substrate to prepare zirconium carbide whiskers through a solid-liquid-solid mechanism. However, this method depends on the morphology and pore structure of porous substrates such as carbon felt or carbon cloth and cannot achieve large-scale production.

[0005] The methods described above typically require high temperature, high vacuum, or specific atmospheric conditions, involving significant equipment investment, complex processes, and difficulty in controlling the chemical composition of the products. Most importantly, there are few reports on the controllable synthesis of carbonitride ultra-high temperature ceramic nanowires, and a preparation technique that requires no catalyst, is independent of templates or matrices, and has tunable composition is lacking. Therefore, there is an urgent need to develop a novel nanowire preparation technique to achieve the controllable synthesis of high-purity, highly crystalline carbonitride ultra-high temperature ceramic nanowires, which is crucial for promoting their application in thermal protection, vacuum microelectronics, and electrical fields. Summary of the Invention

[0006] To avoid the shortcomings of the prior art, the purpose of this invention is to provide a catalyst-free synthesis of carbonitride ultra-high temperature ceramic nanowires and its preparation method. This invention can achieve the controllable synthesis of high-purity, highly crystalline carbonitride ultra-high temperature ceramic nanowires without the need for catalyst assistance or specific matrix-assisted growth.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing carbonitride ultra-high temperature ceramic nanowires without a catalyst, wherein the carbonitride ultra-high temperature ceramic nanowires contain metal elements, carbon elements, and nitrogen elements, and the raw materials used to prepare the carbonitride ultra-high temperature ceramic nanowires include a metal source, a carbon source, and a nitrogen source. The preparation includes the following steps: The metal source, carbon source, and nitrogen source are dissolved in a solvent to form a supersaturated solution; Adjust the pH of the supersaturated solution to 3-6 and continue stirring until the supersaturated solution is transformed into a precursor sol. The precursor sol is aged to form a gel precursor after aging. Then it is cooled to below 25°C and allowed to recrystallize to transform the gel precursor into precursor nanowires. Then it is dried to obtain nanowire precursor powder. Based on the morphological inheritance effect, the nanowire precursor powder is heat-treated in a protective atmosphere, and the nanowire precursor powder is transformed into the carbonitride ultra-high temperature ceramic nanowire.

[0008] Preferably, the metal source is at least one selected from hafnium acetylacetonate, zirconium acetylacetonate, hafnium oxychloride, zirconium oxychloride, butyl zirconate, butyl titanate, zirconium n-propoxide, titanium n-propoxide, hafnium ethoxide, tantalum ethoxide, and niobium ethoxide.

[0009] Preferably, the carbon source is at least one selected from glucose, sorbitol, furfuryl alcohol, and guar gum.

[0010] Preferably, the nitrogen source is at least one selected from urea, melamine, dicyandiamide, and monocyandiamide.

[0011] Preferably, the solvent is deionized water.

[0012] Preferably, when the metal source, carbon source and nitrogen source are dissolved in a solvent to form a supersaturated solution, the molar ratio of the metal source, carbon source and nitrogen source is 1:(1~2):(2~3), the mass percentage of solute is controlled at 15%~20%, and the dissolution temperature is controlled at 50~80℃.

[0013] Preferably, when adjusting the pH value of the supersaturated solution, the pH value is adjusted by adding ammonia water dropwise, and the mass concentration of the ammonia water is 1%.

[0014] Preferably, when aging the precursor sol, the aging temperature is 50~80℃ and the aging time is 12~16h.

[0015] Preferably, when the nanowire precursor powder is heat-treated in a protective atmosphere, the heating rate is 2~8℃ / min, the heat treatment temperature is 1500~1800℃, the time is 2-2.5h, and the protective atmosphere is argon, nitrogen, or a mixture of argon and nitrogen in any proportion.

[0016] The present invention also provides a catalyst-free synthesized carbonitride ultra-high temperature ceramic nanowire prepared by the above-described preparation method of the present invention.

[0017] The present invention has the following beneficial effects: This invention involves dissolving a metal source, carbon source, and nitrogen source to form a supersaturated solution, adjusting the pH to 3-6, and stirring to obtain a precursor sol. After aging, cooling, and recrystallization, precursor nanowires are obtained. These nanowires are then dried and heat-treated under a protective atmosphere. Utilizing morphology inheritance effects, carbonitride ultra-high temperature ceramic nanowires are directly prepared. The entire preparation process requires no catalyst, fundamentally avoiding impurities and structural defects caused by catalyst residues, effectively ensuring the purity and structural integrity of the nanowires. Furthermore, this method relies on the precursor sol... The gelation and recrystallization process enables precursor morphology control, eliminating the need for specific matrices or templates such as carbon cloth or carbon felt, and directly yielding nanowire products. This overcomes the substrate limitations of existing technologies and facilitates large-scale production. Furthermore, this invention employs a solution method combined with conventional heat treatment, eliminating the need for complex equipment requiring high temperatures and high vacuum. The process is simple, the conditions are mild, and the preparation process offers greater controllability and repeatability. In addition, this method directly synthesizes ultra-high temperature ceramic nanowires containing metal, carbon, and nitrogen using metal, carbon, and nitrogen sources as raw materials. This achieves catalyst-free and template-free controllable synthesis of one-dimensional nanostructures of this type of material, providing a new technical pathway for the preparation of ultra-high temperature ceramic nanowires. Attached Figure Description

[0018] Figure 1This is a SEM image of the hafnium carbonitride precursor prepared in Example 1 of the present invention; Figure 2 The XRD pattern of hafnium carbonitride nanowires prepared in Example 1 of this invention; Figure 3 This is a SEM image of the hafnium carbonitride nanowires prepared in Example 1 of the present invention; Figure 4 This is a SEM image of the hafnium carbonitride nanowires prepared in Example 2 of this invention; Figure 5 This is a SEM image of the zirconium carbonitride nanowires prepared in Example 3 of the present invention; Figure 6 This is a TEM image of the hafnium carbonitride nanowires prepared in Example 4 of the present invention; Figure 7 This is a SEM image of hafnium carbonitride prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, descriptions of well-known technologies are omitted in the following description to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0020] This invention proposes a catalyst-free synthesis method for ultra-high temperature carbonitride ceramic nanowires and its preparation method. The provided technical solution can prepare nanowires without catalysts or matrix, and has low raw material cost, simple preparation process, high yield and strong reproducibility.

[0021] Specifically, the technical solution and principle of this invention are as follows: Based on the principle of supersaturated recrystallization, this invention adjusts the supersaturation of the solution by regulating the ratio of raw materials in the precursor solution, and by controlling the solvent evaporation temperature, effectively suppresses the nucleation rate of the precursor, thereby promoting its anisotropic growth along the dominant crystal orientation, ultimately achieving the self-assembly of the precursor to form a nanowire-like precursor. Subsequent heat treatment, utilizing the morphology inheritance effect, successfully prepares carbonitride ultra-high temperature ceramic nanowires, completely avoiding the dependence on metal catalysts such as Ni in traditional gas-liquid-solid or solid-liquid-solid mechanisms, fundamentally eliminating the impurity contamination problem caused by catalyst residue, and significantly improving the chemical purity and structural integrity of the nanowires. It can be seen that this method is simple, requiring only the regulation of the precursor morphology without the introduction of a catalyst, effectively avoiding catalyst contamination; simultaneously, it can directly prepare nanowires under matrix-free conditions, providing a new technology and method for the preparation of ultra-high temperature ceramic nanowires.

[0022] Based on the above principles, the present invention provides a method for preparing catalyst-free carbonitride ultra-high temperature ceramic nanowires, comprising the following steps: Step 1: Dissolve the metal source, carbon source, and nitrogen source in a solvent at a molar ratio of 1:(1~2):(2~3) at 50~90℃, with the mass percentage of solute controlled at 15%~20%, to form a homogeneous and transparent supersaturated solution. The metal source is selected from at least one of hafnium acetylacetonate, zirconium acetylacetonate, hafnium oxychloride, zirconium oxychloride, butyl zirconate, butyl titanate, zirconium n-propoxide, titanium n-propoxide, hafnium ethoxide, tantalum ethoxide, and niobium ethoxide; the carbon source is selected from at least one of glucose, sorbitol, furfuryl alcohol, and guar gum; the nitrogen source is selected from at least one of urea, melamine, dicyandiamide, and cyanamide; the solvent can be water or an organic solvent, with deionized water being preferred.

[0023] Step 2: Under continuous stirring, ammonia water is added dropwise to the supersaturated solution obtained in Step 1 to adjust the pH of the system to 3-6 to promote the complexation and preliminary condensation reaction between the metal source and the organic components; wherein, the mass concentration of ammonia water is 1%. After the addition is complete, stirring is continued for 1-2 hours until the supersaturated solution is transformed into a homogeneous and stable precursor sol.

[0024] Step 3: Transfer the precursor sol obtained in Step 2 into a silicone mold and place it in a constant temperature oven at 50~80℃ for 12~16 hours to allow the precursor sol to further crosslink and transform into a gel precursor with a three-dimensional network structure. Then, naturally cool the gel precursor to room temperature (e.g., 25-30℃, generally referring to 25℃) under normal pressure and recrystallize it at 0~25℃ for 3~5 hours to transform the gel precursor into precursor nanowires, generating a one-dimensional nanowire structure. Subsequently, dry it at room temperature (e.g., 25-30℃, generally referring to 25℃) for 48 hours to obtain nanowire precursor powder.

[0025] Step 4: Place the nanowire precursor powder obtained in Step 3 in a heat treatment furnace and heat it to 1500~1800℃ at a heating rate of 2~8℃ / min under a protective atmosphere (such as nitrogen atmosphere, argon atmosphere or a mixture of argon and nitrogen atmosphere), and hold it for 2~2.5 hours to finally transform it into carbonitride ultra-high temperature ceramic nanowires with good crystallinity.

[0026] The carbonitride ultra-high temperature ceramic nanowires prepared by the above-described preparation method of this invention have a length of over 80 μm, a diameter of 300 nm, an aspect ratio exceeding 200, a smooth surface, a straight morphology, and no obvious bending. Furthermore, the nanowires exhibit uniform morphology, excellent tip morphology, and a uniformly coated amorphous carbon layer on their surface, forming a core-shell structure.

[0027] As can be seen from the specific schemes described above, the preparation method of this invention is based on a solution method, using readily available and environmentally friendly raw materials. It requires no chemical vapor deposition equipment, high-temperature vacuum systems, or special substrates such as carbon cloth or bamboo strips. In-situ, controllable, and batch preparation of nanowires can be achieved through conventional steps such as sol-gel, recrystallization, and heat treatment. The entire process is short, energy-efficient, and highly reproducible, effectively overcoming the bottlenecks of existing methods, such as expensive equipment, demanding conditions, and difficulty in scaling up.

[0028] This invention directly obtains high-purity, high aspect ratio carbonitride ultra-high temperature ceramic nanowires through precursor design and heat treatment process; wherein, the chemical composition of the carbonitride nanowires can be adjusted by controlling the composition of the precursor raw materials, and the resulting product has a one-dimensional linear morphology with advantages such as uniform structure, good dispersibility and scalability.

[0029] Example 1 The method for preparing catalyst-free carbonitride ultra-high temperature ceramic nanowires in this embodiment includes the following steps: Step 1: Dissolve hafnium chloride octahydrate, glucose, and dicyandiamide in deionized water at a molar ratio of 1:1:2, so that the mass percentage of solute in the solution is 16%, and stir at 50°C for 1 hour to form a uniform and transparent supersaturated solution.

[0030] Step 2: Under continuous stirring, add 1% ammonia solution dropwise to the supersaturated solution obtained in Step 1 to adjust the pH of the supersaturated solution to 3. After the addition is complete, continue stirring for 1 hour until the solution is transformed into a homogeneous and stable precursor sol.

[0031] Step 3: Transfer the precursor sol obtained in Step 2 into a silicone mold and place it in a constant temperature oven at 50°C for 12 hours to allow the precursor sol to further crosslink and transform into a gel precursor with a three-dimensional network structure. Cool the gel precursor naturally to room temperature (25°C) under normal pressure and recrystallize it at 0°C for 3 hours to generate a one-dimensional nanowire structure. Then dry it at room temperature (25°C) for 48 hours to obtain the nanowire precursor powder.

[0032] Step 4: Place the precursor powder obtained in Step 3 in a heat treatment furnace, heat it to 1500℃ at a heating rate of 8℃ / min under a nitrogen atmosphere, hold it at that temperature for 2 hours, and finally transform it into hafnium carbonitride ultra-high temperature ceramic nanowires with good crystallinity.

[0033] Example 2 The method for preparing catalyst-free carbonitride ultra-high temperature ceramic nanowires in this embodiment includes the following steps: Step 1: Dissolve hafnium acetylacetonate, glucose and dicyandiamide in deionized water at a molar ratio of 1:1:3, so that the mass percentage of solute in the solution is 17%, and stir at 60°C for 1.5 hours to form a uniform and transparent supersaturated solution.

[0034] Step 2: Under continuous stirring, add 1% ammonia solution dropwise to the supersaturated solution obtained in Step 1 to adjust the pH of the supersaturated solution to 4. After the addition is complete, continue stirring for 2 hours until the solution transforms into a homogeneous and stable precursor sol.

[0035] Step 3: Transfer the precursor sol obtained in Step 2 into a silicone mold and place it in a constant temperature oven at 60°C for 14 hours to allow the precursor sol to further crosslink and transform into a gel precursor with a three-dimensional network structure. Cool the gel precursor naturally to room temperature (25°C) under normal pressure and recrystallize it at 5°C for 4 hours to generate a one-dimensional nanowire structure. Then dry it at room temperature (25°C) for 48 hours to obtain nanowire precursor powder.

[0036] Step 4: Place the precursor powder obtained in Step 3 in a heat treatment furnace, heat it to 1600℃ at a heating rate of 6℃ / min under an argon atmosphere, and hold it at that temperature for 2 hours and 10 minutes to finally transform it into hafnium carbonitride ultra-high temperature ceramic nanowires with good crystallinity.

[0037] Example 3 The method for preparing catalyst-free carbonitride ultra-high temperature ceramic nanowires in this embodiment includes the following steps: Step 1: Dissolve zirconium acetylacetonate, sorbitol and melamine in deionized water at a molar ratio of 1:2:2, so that the mass percentage of solute in the solution is 18%, and stir at 70°C for 2 hours to form a uniform and transparent supersaturated solution.

[0038] Step 2: Under continuous stirring, add 1% ammonia solution dropwise to the supersaturated solution obtained in Step 1 to adjust the pH of the supersaturated solution to 5. After the addition is complete, continue stirring for 1 hour until the solution transforms into a homogeneous and stable precursor sol.

[0039] Step 3: Transfer the precursor sol obtained in Step 2 into a silicone mold and place it in a constant temperature oven at 70°C for 16 hours to allow the precursor sol to further crosslink and transform into a gel precursor with a three-dimensional network structure. Cool the gel precursor naturally to room temperature (25°C) under normal pressure and recrystallize it at 10°C for 3 hours to generate a one-dimensional nanowire structure. Then dry it at room temperature (25°C) for 48 hours to obtain nanowire precursor powder.

[0040] Step 4: Place the precursor powder obtained in Step 3 in a heat treatment furnace, heat it to 1800℃ at a heating rate of 4℃ / min under a nitrogen atmosphere, and hold it at that temperature for 2 hours and 20 minutes to finally transform it into zirconium carbonitride ultra-high temperature ceramic nanowires with good crystallinity.

[0041] Example 4 The method for preparing catalyst-free carbonitride ultra-high temperature ceramic nanowires in this embodiment includes the following steps: Step 1: Dissolve hafnium chloride octahydrate, guar gum, and dicyandiamide in 50 ml of deionized water at a molar ratio of 1:2:3. The mass percentage of solute in the solution is 16%. Stir at 80 °C for 2 hours to form a uniform and transparent supersaturated solution.

[0042] Step 2: Under continuous stirring, add 1% ammonia solution dropwise to the supersaturated solution obtained in Step 1 to adjust the pH of the supersaturated solution to 6. After the addition is complete, continue stirring for 1.5 hours until the solution transforms into a homogeneous and stable precursor sol.

[0043] Step 3: Transfer the precursor sol obtained in Step 2 into a silicone mold and place it in a constant temperature oven at 80°C for 12 hours to allow the precursor sol to further crosslink and transform into a gel precursor with a three-dimensional network structure. Cool the gel precursor naturally to room temperature (25°C) under normal pressure and recrystallize it at 20°C for 5 hours to generate a one-dimensional nanowire structure. Then dry it at room temperature (25°C) for 48 hours to obtain nanowire precursor powder.

[0044] Step 4: Place the precursor powder obtained in Step 3 in a heat treatment furnace, heat it to 1700℃ at a heating rate of 2℃ / min under an argon atmosphere, and hold it at that temperature for 2 hours and 30 minutes to finally transform it into hafnium carbonitride ultra-high temperature ceramic nanowires with good crystallinity.

[0045] Comparative Example 1 The preparation method of this comparative example includes the following steps: Step 1: Dissolve hafnium chloride octahydrate, glucose, and dicyandiamide in deionized water at a molar ratio of 1:1:2, so that the mass percentage of solute in the solution is 16%, and stir at 50°C for 1 hour to form a uniform and transparent supersaturated solution.

[0046] Step 2: Under continuous stirring, add 1% ammonia solution dropwise to the supersaturated solution obtained in Step 1 to adjust the pH of the supersaturated solution to 3. After the addition is complete, continue stirring for 1 hour until the solution is transformed into a homogeneous and stable precursor sol.

[0047] Step 3: Transfer the precursor sol obtained in Step 2 into a silicone mold, place it in a constant temperature oven and age it at 50°C for 12 hours to allow the precursor sol to further crosslink and transform into a gel precursor with a three-dimensional network structure. Dry the gel precursor at 50°C for 48 hours to finally obtain the precursor powder.

[0048] Step 4: Place the precursor powder obtained in Step 3 in a heat treatment furnace, raise the temperature to 1500℃ at a heating rate of 8℃ / min under a nitrogen atmosphere, and hold for 2 hours to finally transform the precursor powder into hafnium carbonitride ultra-high temperature ceramic particles.

[0049] Figure 1 The image shows a SEM image of the hafnium carbonitride precursor prepared in Example 1 of this invention. It can be seen that the prepared precursor has a dispersed nanoflower-like morphology, indicating that the nanowire-like precursor was successfully induced by the supersaturated recrystallization phenomenon.

[0050] Figure 2The image shows the XRD pattern of hafnium carbonitride nanowires prepared in Example 1 of this invention. The curve with the same font color as HFC: PDF#73-0475 represents the XRD pattern of HfC from the standard PDF card for HfC, and the curve with the same font color as HfN: PDF#33-0592 represents the XRD pattern of HfN from the standard PDF card for HfN. The other curve represents the XRD pattern of the hafnium carbonitride nanowires prepared in Example 1 of this invention. Figure 1 As can be seen from the data, the prepared hafnium carbonitride ceramic has a face-centered cubic crystal structure, and its XRD diffraction peak is located between HfC and HfN. The diffraction peak is sharp, indicating that the prepared hafnium carbonitride ceramic has good crystallinity.

[0051] Figure 3 This is a SEM image of the hafnium carbonitride nanowires prepared in Example 1 of this invention. Figure 3 As can be seen, the prepared hafnium carbonitride nanowires exhibit a nanoflower-like structure and are directly generated in the form of free powder, without relying on any matrix. This indicates that the preparation process has good feasibility and the potential to achieve high-yield synthesis of ultra-high temperature ceramic nanowires.

[0052] Figure 4 The image shows a SEM image of the hafnium carbonitride nanowires prepared in Example 2 of this invention. The hafnium carbonitride nanowires have a diameter of approximately 0.3 μm and a length exceeding 80 μm, exhibiting a high aspect ratio. The nanowires have smooth surfaces, straight morphology, and no obvious bending. The tips of the nanowires do not show the spherical catalyst characteristics associated with a gas-liquid-solid growth mechanism.

[0053] Figure 5 The image shows a SEM image of the zirconium carbonitride nanowires prepared in Example 3 of this invention. It can be seen that the zirconium carbonitride nanowires have distinct outlines, smooth surfaces, and no obvious agglomeration or breakage, indicating that the nanowire samples prepared by this process are of high quality.

[0054] Figure 6 This is a TEM image of the hafnium carbonitride nanowires prepared in Example 4 of this invention. Figure 6 As shown in Figures (a) and (b), the nanowires have excellent tip morphology and are uniformly coated with an amorphous carbon layer, forming a core-shell structure. They are expected to be widely used in energy storage, field emission, toughening materials, and nanocomposite materials.

[0055] Figure 7 The image shows a SEM image of the hafnium carbonitride ultra-high temperature ceramic prepared in Comparative Example 1. It can be seen that due to the excessively high drying temperature, the solvent in the gel evaporates too quickly, causing the structure to solidify rapidly. The recrystallization process lacks sufficient time, thus preventing the precipitation of nanowires, and the resulting hafnium carbonitride ceramic exhibits a granular morphology.

[0056] The experimental results above show that the preparation method of the present invention is based on the sol-gel mechanism. By adjusting the types and ratios of metal, carbon source and nitrogen source, the chemical composition of the obtained nanowires (such as Hf(C,N), (Hf,Zr)(C,N)) can be controlled at the atomic scale, thereby achieving continuous component control of carbonitrides and demonstrating excellent material designability.

[0057] The carbonitride ultra-high temperature ceramic nanowires prepared by this invention possess characteristics such as smooth surface, uniform morphology, high aspect ratio, and uniform structure, significantly outperforming existing technologies in terms of yield, purity, and microstructure consistency. These advantages make them promising for applications in high-performance energy storage devices, field emission cathodes, toughening of ceramic matrix composites, and multifunctional nanocomposite materials.

[0058] In summary, the technical solution provided by this invention has advantages such as low raw material cost, simple preparation process, strong process controllability, and high repeatability. The prepared carbonitride ultra-high temperature ceramic nanowires have significant advantages such as high aspect ratio, uniform structure, and high purity. This not only overcomes the limitation of traditional methods that require substrate growth for nanowires, but also eliminates the need for catalysts throughout the growth process, fundamentally avoiding the pollution problems caused by catalyst residues. This invention provides a new technology and method for preparing carbonitride ultra-high temperature ceramic nanowires, showing broad application prospects in advanced ceramics, nanocomposite materials, field emission devices, and high-temperature structural materials.

[0059] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis, characterized in that, The carbonitride ultra-high temperature ceramic nanowires contain metal, carbon, and nitrogen elements. The raw materials used to prepare the carbonitride ultra-high temperature ceramic nanowires include a metal source, a carbon source, and a nitrogen source. The preparation includes the following steps: The metal source, carbon source, and nitrogen source are dissolved in a solvent to form a supersaturated solution; Adjust the pH of the supersaturated solution to 3-6 and continue stirring until the supersaturated solution is transformed into a precursor sol. The precursor sol is aged to form a gel precursor after aging. Then it is cooled to below 25°C and allowed to recrystallize to transform the gel precursor into precursor nanowires. Then it is dried to obtain nanowire precursor powder. Based on the morphological inheritance effect, the nanowire precursor powder is heat-treated in a protective atmosphere, and the nanowire precursor powder is transformed into the carbonitride ultra-high temperature ceramic nanowire.

2. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, The metal source is at least one selected from hafnium acetylacetonate, zirconium acetylacetonate, hafnium oxychloride, zirconium oxychloride, butyl zirconate, butyl titanate, zirconium n-propoxide, titanium n-propoxide, hafnium ethanol, tantalum ethanol, and niobium ethanol.

3. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, The carbon source is at least one of glucose, sorbitol, furfuryl alcohol, and guar gum.

4. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, The nitrogen source is at least one of urea, melamine, dicyandiamide, and monocyandiamide.

5. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, The solvent used is deionized water.

6. A method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to any one of claims 1-5, characterized in that, When the metal source, carbon source and nitrogen source are dissolved in a solvent to form a supersaturated solution, the molar ratio of the metal source, carbon source and nitrogen source is 1:(1~2):(2~3), the mass percentage of solute is controlled at 15%~20%, and the dissolution temperature is controlled at 50~80℃.

7. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, When adjusting the pH value of the supersaturated solution, the pH value is adjusted by adding ammonia water dropwise, wherein the mass concentration of the ammonia water is 0.9%~1.1%.

8. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, When aging the precursor sol, the aging temperature is 50~80℃ and the aging time is 12~16h.

9. The method for preparing carbonitride ultra-high temperature ceramic nanowires without catalyst synthesis according to claim 1, characterized in that, When the nanowire precursor powder is heat-treated in a protective atmosphere, the heating rate is 2~8℃ / min, the heat treatment temperature is 1500~1800℃, the time is 2-2.5h, and the protective atmosphere is argon, nitrogen, or a mixture of argon and nitrogen in any proportion.

10. A catalyst-free synthesized carbonitride ultra-high temperature ceramic nanowire prepared by any one of the preparation methods of claims 1-9.

Images