Ultra-long aluminum nitride fiber and high-throughput preparation method thereof by self-generated combustion reactor

Abstract

The application belongs to the technical field of ceramic material preparation, and discloses a kind of super-long aluminium nitride fiber and its self-generating combustion reactor high-throughput preparation method.The technical scheme adopted is: with aluminum powder, polytetrafluoroethylene powder and ammonium chloride as raw materials, mixing, grinding uniformly, to obtain mixed powder;Mixed powder is placed in N porous graphite crucible respectively, N porous graphite crucible is arranged in array in combustion chamber, combustion reaction is carried out under nitrogen pressure, N≥2;After reaction, it is cooled to room temperature, and the self-generating combustion reactor with hollow structure is formed, and the super-long aluminium nitride fiber is grown in the core of the self-generating combustion reactor.The application has the advantages of simple process, short cycle, low energy consumption and batch preparation of super-long aluminium nitride fiber, and the high-throughput self-generating combustion reactor synthesis method can quickly realize the screening of different component raw material powder conditions, and also can quickly realize the batch preparation of the same super-long aluminium nitride fiber.

Description

Technical Field

[0001] This invention belongs to the field of ceramic material preparation technology, specifically relating to a high-throughput preparation method of ultra-long aluminum nitride fibers and their self-generating combustion reactor. Background Technology

[0002] Aluminum nitride (ANT) possesses a range of advantages, including high thermal conductivity (theoretical thermal conductivity up to 320 W / m / K), low coefficient of thermal expansion, low dielectric loss, excellent chemical stability, semiconductor properties, and good mechanical strength, making it widely used in thermally conductive substrates, packaging materials, and optoelectronic devices. ANT fibers combine the advantages of both aluminum nitride and fiber materials. For example, as a reinforcing material for aluminum nitride matrices, ANT fibers can improve the mechanical properties, especially the toughness, of ceramic matrices; as a thermally conductive filler, they can effectively form continuous heat flow channels in polymer matrices, thereby improving the thermal conductivity of composite materials, showing broad application prospects in numerous fields. However, existing methods for synthesizing ANT fibers suffer from complex processes, long cycles, low yields, and high costs. In particular, it is difficult to efficiently prepare ultra-long ANT fibers (length > 1 mm) with uniform morphology, thus severely restricting their large-scale application.

[0003] Currently, commonly used methods for preparing aluminum nitride fibers include carbothermal reduction, spinning, and combustion synthesis. For example, the invention patent CN104213252A, "A Method for Preparing Aluminum Nitride Fibers Using Carbon Fiber as a Template," combines carbothermal reduction and sol-gel methods to obtain aluminum nitride fibers. However, the preparation steps are cumbersome, the reaction temperature is high (1400-1600℃), the reaction time is long (about 12 hours), and the resulting aluminum nitride fibers are short, only 1-3 μm in length, limiting the application of aluminum nitride fibers. Another example is the invention patent CN111153685A, which discloses "A Continuous Aluminum Nitride Fiber and Its Preparation Method," using organic aluminum alkoxides as a precursor, and obtaining continuous aluminum nitride fibers through hydrolysis and aging, aluminum powder addition, polymer-assisted spinning, and high-temperature nitriding. This method is extremely complex, requires sophisticated equipment and control, consumes a lot of energy, and has a long cycle time.

[0004] Furthermore, the morphology of aluminum nitride fibers prepared by combustion synthesis is usually non-uniform. Wang et al. (H. Wang, DO Northwood, J. Han, S. Du, Combustion synthesis of AlN whiskers, Journal of Materials Science, 2006, 41(6): 1697-1703) prepared aluminum nitride fibers by adding ammonium chloride or ammonium fluoride using combustion synthesis, and the volume percentage of the combustion products exceeded 80%. However, the products contained a large number of helical and dendritic whiskers, making it still difficult to prepare ultra-long aluminum nitride fibers with uniform morphology using combustion synthesis.

[0005] Therefore, developing a preparation method that can simultaneously achieve fiber length (>1 mm), morphological uniformity, and high-throughput production is of great significance for overcoming the application bottleneck of aluminum nitride fibers. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-throughput preparation method for ultra-long aluminum nitride fibers and their self-generating combustion reactor, so as to solve the technical problem that the existing aluminum nitride fiber preparation methods cannot efficiently prepare ultra-long (>1 mm) aluminum nitride fibers with uniform diameter due to long cycle, high reaction temperature, complex process and unstable reaction.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention discloses a high-throughput preparation method for a self-generating combustion reactor of ultra-long aluminum nitride fibers, characterized by comprising:

[0009] Aluminum powder, polytetrafluoroethylene powder and ammonium chloride are mixed and ground evenly in a certain proportion to obtain a mixed powder.

[0010] The mixed powder is placed into N porous graphite crucibles according to a certain loose density. The N porous graphite crucibles are arranged in an array in the combustion chamber and the combustion reaction is carried out under nitrogen pressure, where N≥2.

[0011] After the reaction is completed, the mixture is cooled to room temperature to form a hollow self-generating combustion reactor, and ultra-long aluminum nitride fibers are grown in the core of the self-generating combustion reactor.

[0012] Preferably, the particle size range of aluminum powder is 1-25 μm; the particle size range of polytetrafluoroethylene powder is 2-20 μm; the molar ratio of aluminum powder to polytetrafluoroethylene powder is 1:0.01-0.05; and the amount of ammonium chloride added is 3%-20% of the total mass of the mixed powder.

[0013] Preferably, the preparation of the mixed powder includes: using anhydrous ethanol as a solvent, ball milling and mixing aluminum powder and polytetrafluoroethylene powder and drying them, then adding ammonium chloride and grinding them evenly to obtain the mixed powder; the composition of the mixed powder in different porous graphite crucibles can be the same or different.

[0014] Preferably, the spacing between adjacent porous graphite crucibles is greater than one-third of the bottom diameter of a single porous graphite crucible.

[0015] Preferably, carbon felt is evenly distributed on the inner bottom surface and inner wall of the porous graphite crucible.

[0016] Preferably, an aerogel insulation layer is provided in the gap between adjacent porous graphite crucibles to avoid mutual interference between the porous graphite crucibles. The aerogel material used in the aerogel insulation layer can be silicon carbide aerogel, silicon nitride aerogel, or silicon carbide / silicon nitride composite aerogel, etc., and the thickness of the aerogel insulation layer is 5-40 mm.

[0017] Preferably, the loose density of the mixed powder is in the range of 0.4-0.8 g / cm³. 3 .

[0018] Preferably, the combustion reaction is initiated by igniting the mixed powder by electrifying the graphite paper strip at the bottom of the porous graphite crucible. The specific conditions are: nitrogen pressure of 1.5-2.5 MPa, electrification of the graphite paper strip at a voltage of 20 V and a current of 60 A for 10-60 s.

[0019] The present invention also discloses ultra-long aluminum nitride fibers prepared by the above-mentioned high-throughput preparation method of self-generating combustion reactor. The ultra-long aluminum nitride fibers have a length of 1-2 mm, uniform size distribution, and a diameter of 0.5-2 μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The advantages of the ultra-long aluminum nitride fibers and the high-throughput preparation method of the self-generating combustion reactor disclosed in this invention are as follows:

[0022] 1. Based on the synthesis method of aluminum nitride fiber by self-generating combustion reactor, a high-throughput method is introduced. When the raw material powder composition is different, the conditions of raw material powder with different components can be screened quickly, which accelerates the exploration of the optimal synthesis process parameters. When the raw material powder composition is the same, the batch preparation of the same / different aluminum nitride fibers can be achieved quickly, and the reactions of each porous graphite crucible will not affect each other.

[0023] 2. The method provided by this invention is a method that combines the dual functions of "research and development screening" and "mass production." It can quickly find the optimal formula and process for preparing fibers during the research and development stage (when the composition is different), and can be directly used for large-scale manufacturing of these high-quality fibers after the parameters are determined (when the composition is the same). Combining the high efficiency of the high-throughput method with the self-sustaining nature of the combustion reaction to prepare ultra-long aluminum nitride fibers has the advantages of simple process, short reaction time (not exceeding 150s), low reaction temperature, low cost and energy consumption, and the ability to mass-produce ultra-long aluminum nitride fibers.

[0024] 3. By forming a unique self-generating combustion reactor structure, not only is the reactor core kept at a low supersaturation, but the uniformity of the fiber growth environment is also guaranteed, providing a suitable environment for the nucleation and growth of aluminum nitride fibers via a gas-solid mechanism, ultimately producing ultra-long aluminum nitride fibers with uniform and controllable diameter and a length of 1-2 mm.

[0025] The aluminum nitride fibers prepared by the method of this invention have advantages such as uniform size, controllable diameter, extremely high aspect ratio, high morphological repeatability, high purity, and high thermal conductivity. They have broad application prospects in the fields of ceramic fiber toughening, polymer reinforcement phases, thermally conductive substrates, and optoelectronic devices. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the high-throughput self-generating combustion reactor synthesis device and a top view of the rectangularly arranged porous graphite crucibles of the present invention; wherein, (a) is a schematic diagram of the structure of the high-throughput self-generating combustion reactor synthesis device; and (b) is a top view of the rectangularly arranged porous graphite crucibles.

[0027] In the diagram, 1 is a pressure gauge; 2 is a combustion reaction chamber; 3 is a porous graphite crucible; 4 is raw material powder; 5 is graphite paper tape; 6 is an observation window; 7 is carbon felt; 8 is thermal insulation aerogel; 9 is the core of the self-generating combustion reactor; 10 is an inlet valve; 11 is an exhaust valve; 12 is a vacuum valve; L represents the distance between adjacent porous graphite crucibles; D represents the bottom diameter of the porous graphite crucible.

[0028] Figure 2 These are macroscopic photographs of the self-generating combustion reactor and ultra-long aluminum nitride fibers of Embodiment 1 of the present invention; wherein, (a) is a macroscopic photograph of the cross-section of the self-generating combustion reactor; (b) is a macroscopic photograph of the longitudinal section of the self-generating combustion reactor; and (c) is a macroscopic photograph of the ultra-long aluminum nitride fibers grown in the self-generating combustion reactor.

[0029] Figure 3 This is the XRD pattern of the aluminum nitride fiber obtained in Example 1 of the present invention;

[0030] Figure 4 This is a SEM image of the aluminum nitride fibers obtained in Example 1 of the present invention;

[0031] Figure 5 This is a TEM image of the aluminum nitride fiber prepared in Example 1 of the present invention;

[0032] Figure 6 These are SEM images of four different aluminum nitride fibers obtained in Example 2 of this invention; the SEM images of the four different products are shown in Figures (a), (b), (c) and (d), respectively. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0035] The present invention will now be described in further detail with reference to the accompanying drawings:

[0036] See Figure 1 This is a schematic diagram of the high-throughput self-generating combustion reactor synthesis apparatus used in the method of the present invention. The synthesis apparatus includes: a combustion reaction chamber 2, a pressure gauge 1 for testing nitrogen pressure, and an observation window 6 for observing the combustion reaction. The combustion reaction chamber 2 is equipped with a vacuum valve 12 for evacuation, a nitrogen inlet valve 10 for introducing nitrogen, and an exhaust valve 11 for discharging gas after the reaction. The combustion reaction chamber 2 contains N porous graphite crucibles 3 arranged in a rectangular array for filling raw material powder 4. The spacing L between adjacent porous graphite crucibles 3 is not less than one-third of the bottom diameter D of the porous graphite crucible. A layer of carbon felt 7 is evenly distributed on the bottom and inner wall of each porous graphite crucible 3. By energizing both ends of the graphite paper strip 5 at the bottom of the porous graphite crucible 3, the raw material powder 4 is ignited and a combustion reaction occurs.

[0037] Example 1

[0038] Weigh out six batches of aluminum powder and polytetrafluoroethylene powder in a molar ratio of 1 / 0.01, with the aluminum powder having a particle size of 3 μm and the polytetrafluoroethylene powder having a particle size of 2 μm. Mix each batch with an appropriate amount of anhydrous ethanol at a ball-to-particle ratio of 3:1. Ball mill at 200 rpm for 6 hours. After drying, grind each batch uniformly with 3% ammonium chloride. Then, mix the resulting powders at a concentration of 0.5 g / cm³. 3 The loosely packed powder was placed in a rectangular array of six porous graphite crucibles in a combustion reaction chamber. A layer of carbon felt was placed on the bottom and inner wall of each crucible, and the distance between adjacent crucibles was no less than one-third of their bottom diameter. A 10 mm thick layer of silicon carbide aerogel was placed between adjacent crucibles. After evacuating to a pressure less than 10 Pa, 2 MPa of 99.999% pure nitrogen gas was introduced. The mixed powder was ignited by electrifying the graphite paper strip at the bottom of the crucibles with a voltage of 20 V, a current of 60 A, and an energizing time of 30 s, initiating a combustion reaction. After the combustion reaction was complete, the mixture was cooled to room temperature, and the pressure in the combustion reaction chamber was released. The same product was obtained in all six porous graphite crucibles. The white flocculent material growing directionally inward from the core of the combustion reactor was aluminum nitride fiber, indicating that this method can achieve mass production of aluminum nitride fiber.

[0039] The obtained aluminum nitride fibers were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Figure 2 This is a macroscopic photograph of the self-generating combustion reactor and the ultra-long aluminum nitride fiber in this embodiment. Figure 3 The image shows the XRD pattern of aluminum nitride fibers. The product is a pure hexagonal aluminum nitride phase with a distinct preferred orientation. Figure 4 The image shows an SEM image of aluminum nitride fibers. It can be seen that the aluminum nitride fibers are evenly distributed, with a diameter of about 0.65 μm and an extremely long length of more than 1 mm. Figure 5 The image shows a TEM image of aluminum nitride fibers. The corresponding selected area diffraction pattern (inset) confirms that the AlN whiskers are single crystals with a hexagonal structure.

[0040] Example 2

[0041] Four batches of aluminum powder and polytetrafluoroethylene (PTFE) powder with a molar ratio of 1 / 0.015 were weighed, with the aluminum powder having a particle size of 1 μm and the PTFE powder having a particle size of 5 μm. Each batch was mixed with an appropriate amount of anhydrous ethanol at a ball-to-particle ratio of 3:1 and ball-milled at 250 rpm for 8 hours. After drying, ammonium chloride at mass fractions of 5%, 10%, 15%, and 20% was weighed and added to each batch, and the mixtures were ground uniformly. The mixed powders were then processed at a concentration of 0.4 g / cm³. 3The loosely packed powders were placed in four porous graphite crucibles arranged in a rectangular array within a combustion chamber. A layer of carbon felt was placed on the bottom and inner wall of each crucible, with the distance between adjacent crucibles being no less than one-third of their bottom diameter. A 20 mm thick layer of silicon carbide aerogel was placed between adjacent crucibles. After evacuating to a pressure less than 10 Pa, 2.5 MPa of 99.999% pure nitrogen gas was introduced. The mixed powder was ignited by passing an electric current through a graphite paper strip at the bottom of the porous graphite crucibles at 20 V and 60 A for 10 s, initiating a combustion reaction. After the combustion reaction was complete, the mixture was cooled to room temperature, and the pressure in the combustion chamber was released, yielding four different products, denoted as a, b, c, and d. The white flocculent material that grows directionally from the core of the combustion reactor is aluminum nitride fiber.

[0042] The four types of aluminum nitride fibers obtained were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). Figure 6 Images (a), (b), (c), and (d) in the figure correspond to SEM images of the four types of aluminum nitride fibers labeled a, b, c, and d, respectively. It can be observed that the aluminum nitride fibers are uniformly distributed, and their diameters increase with increasing ammonium chloride content, reaching approximately 0.88 μm, 1.15 μm, 1.42 μm, and 1.67 μm, respectively. This indicates that ammonium chloride plays a crucial role in the combustion synthesis reaction. After decomposing at high temperature (approximately 338°C), ammonium chloride generates NH3 and HCl gases, which further react with aluminum to form aluminum halide gases. Gas supersaturation is a key factor determining the nucleation and growth of AlN whiskers in the chlorination-nitridation reaction. With increasing ammonium chloride content, the gaseous supersaturation gradually increases, allowing for sufficient nucleation and growth of AlN whiskers; therefore, the diameter of the aluminum nitride fibers increases with increasing ammonium chloride content. Other results are the same as in Example 1.

[0043] Example 3

[0044] Four sets of aluminum powder and polytetrafluoroethylene powder with molar ratios of 1 / 0.02, 1 / 0.03, 1 / 0.04, and 1 / 0.05 were weighed, with the aluminum powder having a particle size of 25 μm and the polytetrafluoroethylene powder having a particle size of 20 μm. Each was mixed with an appropriate amount of anhydrous ethanol at a ball-to-particle ratio of 3:1 and ball-milled at 300 rpm for 5 hours. After drying, 5% ammonium chloride was weighed and ground uniformly. The mixed powder was then processed at a concentration of 0.8 g / cm³. 3The loosely packed powders were placed in four porous graphite crucibles arranged in a rectangular array within a combustion chamber. A layer of carbon felt was placed on the bottom and inner wall of each crucible, and the distance between adjacent crucibles was no less than one-third of their bottom diameter. A 5 mm thick layer of silicon nitride aerogel was placed between adjacent crucibles. After evacuating to a pressure less than 10 Pa, 1.5 MPa of 99.999% pure nitrogen gas was introduced. The mixed powder was ignited by passing an electric current through a graphite paper strip at the bottom of the crucibles at 20 V and 60 A for 60 s, initiating a combustion reaction. After the combustion reaction was complete, the mixture was cooled to room temperature, and the pressure in the combustion chamber was released, yielding four different products. The white flocculent material that grows directionally from the core of the combustion reactor is aluminum nitride fiber.

[0045] The four types of aluminum nitride fibers obtained were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). It was found that the aluminum nitride fibers were uniformly distributed, and their diameters decreased with increasing molar ratio of aluminum powder to polytetrafluoroethylene (PTFE) powder, reaching approximately 1.45 μm, 1.12 μm, 0.91 μm, and 0.52 μm, respectively. This is because PTFE powder decomposes at high temperatures (approximately 600°C) and releases gases (C₂F₄, C₂F₃, and CF₂, etc.). As the molar ratio of aluminum powder to PTFE powder increases, the PTFE powder content increases, releasing more gases during decomposition. This reduces the saturation of AlCl₃ and NH₃ gases, gradually decreasing the diameter of the aluminum nitride fibers controlled by the chlorination-nitridation mechanism. Therefore, the diameter of the aluminum nitride fibers decreases with increasing molar ratio of aluminum powder to PTFE powder. Other results are the same as in Example 1.

[0046] Example 4

[0047] Four batches of aluminum powder and polytetrafluoroethylene (PTFE) powder with a molar ratio of 1 / 0.02 were weighed, with the aluminum powder having a particle size of 3 μm and the PTFE powder having a particle size of 10 μm. Each batch was mixed with an appropriate amount of anhydrous ethanol at a ball-to-powder ratio of 3:1. The mixtures were ball-milled at 300 rpm for 4, 6, 8, and 12 hours respectively. After drying, 15% ammonium chloride was weighed and ground uniformly. The mixed powders were then processed at a concentration of 0.6 g / cm³. 3The loosely packed powders were placed in four porous graphite crucibles arranged in a rectangular array within a combustion chamber. A layer of carbon felt was placed on the bottom and inner wall of each crucible, with the spacing between adjacent crucibles being no less than one-third of their bottom diameter. A 30 mm thick layer of silicon carbide / silicon nitride aerogel was placed between adjacent crucibles. After evacuating to a pressure less than 10 Pa, 2.5 MPa of 99.999% pure nitrogen gas was introduced. The mixed powder was ignited by passing an electric current through a graphite paper strip at the bottom of the porous graphite crucibles at 20 V and 60 A for 35 s, initiating a combustion reaction. After the combustion reaction was complete, the mixture was cooled to room temperature, and the pressure in the combustion chamber was released, yielding four different products. The white flocculent material that grows directionally from the core of the combustion reactor is aluminum nitride fiber.

[0048] The four types of aluminum nitride fibers obtained were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). It was found that the aluminum nitride fibers were uniformly distributed, and their diameters decreased with increasing ball milling time, reaching approximately 1.17 μm, 0.87 μm, 0.71 μm, and 0.52 μm, respectively. This is because extending the ball milling time increases the reactivity of the aluminum powder and polytetrafluoroethylene powder, accelerates the combustion wave propagation rate, and shortens the fiber growth time window, thus reducing the aluminum nitride fiber diameter with increasing ball milling time. Other results were the same as in Example 1.

[0049] Example 5

[0050] Four batches of aluminum powder and polytetrafluoroethylene (PTFE) powder with a molar ratio of 1 / 0.03 were weighed, with the aluminum powder having a particle size of 10 μm and the PTFE powder having a particle size of 5 μm. Each batch was mixed with an appropriate amount of anhydrous ethanol at a ball-to-particle ratio of 3:1. The mixtures were ball-milled for 5 hours at speeds of 200 rpm, 250 rpm, 300 rpm, and 400 rpm, respectively. After drying, 8% ammonium chloride was weighed and ground uniformly. The mixed powders were then ball-milled at 0.8 g / cm³. 3 The loosely packed powders were placed in four porous graphite crucibles arranged in a rectangular array within a combustion chamber. A layer of carbon felt was placed on the bottom and inner wall of each crucible, with the distance between adjacent crucibles being no less than one-third of their bottom diameter. A 40 mm thick layer of silicon carbide aerogel was placed between adjacent crucibles. After evacuating to a pressure less than 10 Pa, 2 MPa of 99.999% pure nitrogen gas was introduced. The mixed powder was ignited by passing an electric current through a graphite paper strip at the bottom of the porous graphite crucibles at 20 V and 60 A for 45 s, initiating a combustion reaction. After the combustion reaction was complete, the mixture was cooled to room temperature, and the pressure in the combustion chamber was released, yielding four different products. The white flocculent material that grows directionally from the core of the combustion reactor is aluminum nitride fiber.

[0051] The four types of aluminum nitride fibers obtained were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). It was found that the aluminum nitride fibers were uniformly distributed, and their diameters decreased with increasing ball milling speed, reaching approximately 1.12 μm, 0.89 μm, 0.68 μm, and 0.56 μm, respectively. This is because increasing the ball milling speed helps to improve powder refinement and specific surface area, and accelerates the combustion wave velocity to limit the radial growth of fibers; therefore, the diameter of the aluminum nitride fibers decreases with increasing ball milling speed. Other results are the same as in Example 1.

[0052] Example 6

[0053] The process in this embodiment is the same as in embodiment 2, except that some process parameters have been changed: the nitrogen pressure is 1.5 MPa.

[0054] The four types of aluminum nitride fibers obtained were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). It was found that the aluminum nitride fibers were uniformly distributed, and the fiber diameters increased with increasing ammonium chloride content, reaching approximately 0.97 μm, 1.22 μm, 1.51 μm, and 1.73 μm, respectively. Compared to Example 2, under the same ammonium chloride conditions, the fiber diameters increased. This is because the reduced nitrogen pressure weakened the diffusion and penetration of nitrogen into the molten aluminum, and the lower reaction temperature led to the coalescence and coarsening of the molten aluminum droplets, ultimately forming thicker fibers. Therefore, the aluminum nitride fiber diameters in this example were all increased. Other results were the same as in Example 1.

[0055] In summary, this invention employs a high-throughput preparation method for a self-generating combustion reactor. Using a mixture of aluminum powder, polytetrafluoroethylene powder, and ammonium chloride as raw materials, the mixture is combusted and synthesized under different nitrogen pressures to ultimately obtain a self-generating combustion reactor with a unique hollow structure. The core contains ultra-long aluminum nitride fibers with a length of 1-2 mm and a uniform diameter. The diameter of these fibers can be controlled by adjusting the polytetrafluoroethylene powder content, ammonium chloride content, nitrogen pressure, and the loose packing density of the raw material powder.

[0056] The method of this invention has advantages such as simple process, short cycle, low cost, low energy consumption, and the ability to mass-produce ultra-long aluminum nitride fibers. The high-throughput self-generating combustion reactor synthesis method can quickly screen raw material powders with different components, and also rapidly achieve mass production of the same type of ultra-long aluminum nitride fibers. The unique eggshell structure of the self-generating combustion reactor provides a suitable environment for the nucleation and growth of ultra-long aluminum nitride fibers via a gas-solid mechanism. The prepared ultra-long aluminum nitride fibers have broad application prospects in fields such as ceramic fiber toughening, polymer reinforcement phases, thermally conductive substrates, and optoelectronic devices.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for high-throughput production of ultra-long aluminum nitride fibers by self-propagating combustion synthesis, characterized in that, The application relates to a self-generating combustion reactor and a method for preparing the same. The aluminum powder has a particle size range of 1-25 mu m; the polytetrafluoroethylene powder has a particle size range of 2-20 mu m; the molar ratio of the aluminum powder to the polytetrafluoroethylene powder is 1:0.01-0.05; and the addition amount of the ammonium chloride is 3%-20% of the total mass of the mixed powder; The mixed powder is respectively arranged in N porous graphite crucibles, the N porous graphite crucibles are arranged in an array in a combustion chamber, and combustion reaction is carried out under nitrogen pressure, and N is greater than or equal to 2; an aerogel heat insulation layer is arranged in the gap between adjacent porous graphite crucibles, and the thickness of the aerogel heat insulation layer is 5-40 mm; After the reaction is completed and cooled to room temperature, a self-generating combustion reactor with a hollow structure is formed, and an ultralong aluminum nitride fiber is grown in the core of the self-generating combustion reactor.

2. The method for high-throughput production of ultra-long aluminum nitride fibers by self-generating combustion reaction according to claim 1, characterized in that, The preparation of the mixed powder comprises the following steps: ball-milling and uniformly mixing aluminum powder and polytetrafluoroethylene powder with anhydrous ethanol as a solvent, drying, then adding ammonium chloride, and uniformly grinding to obtain the mixed powder.

3. The method for high-throughput production of ultra-long aluminum nitride fibers by self-generating combustion reaction according to claim 1, characterized in that, The distance between adjacent porous graphite crucibles is greater than one-third of the diameter of the bottom surface of a single porous graphite crucible.

4. The method for high-throughput production of ultra-long aluminum nitride fibers by self-generating combustion reaction according to claim 1, characterized in that, The inner bottom surface and the inner wall of the porous graphite crucible are uniformly provided with carbon felt.

5. The method for high-throughput fabrication of ultra-long aluminum nitride fibers by self-generating combustion reaction according to claim 1, characterized in that, The material of the aerogel heat insulation layer is selected from silicon carbide aerogel, silicon nitride aerogel or silicon carbide / silicon nitride composite aerogel.

6. The method for high-throughput fabrication of ultra-long aluminum nitride fibers by self-generating combustion reaction according to claim 1, characterized in that, When the mixed powder is placed in N porous graphite crucibles, the bulk density of the mixed powder is in the range of 0.4-0.8 g / cm 3 .

7. The method for high-throughput fabrication of ultra-long aluminum nitride fibers by self-generated combustion reaction according to claim 1, characterized in that, The bottom of the porous graphite crucible is provided with a graphite paper strip, and the mixed powder is ignited by electrifying the graphite paper strip, and the specific conditions are as follows: the graphite paper strip is electrified under the conditions that the nitrogen pressure is 1.5-2.5 MPa, the voltage is 20 V, the current is 60 A, and the electrification time is 10-60 s.

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