Preparation method of spongy superfine aluminum nitride nanowhiskers

Abstract

The invention discloses a preparation method of spongy superfine aluminum nitride nanowhiskers. The preparation method comprises the following steps: mixing an aluminum-series material, a carbon-series material and a nitrogen-series material into a powder raw material according to a mass ratio; putting the powder raw material into an aluminum oxide ball milling tank, adding a dispersing agent, carrying out ball milling by taking a corundum ball as a ball milling medium, and then carrying out drying treatment to obtain a mixture; placing the mixture in a heating area, heating under a closed condition and in a nitrogen atmosphere, and carrying out heat preservation to obtain an intermediate product; the intermediate product is placed in a muffle furnace and sintered in the air atmosphere, a layer of spongy aluminum nitride nanowhiskers is finally formed at the bottom of the muffle furnace, the macroscopic morphology and position of the product are stable, the product is of a spongy structure macroscopically, the whiskers are bent microscopically, the diameter is 10-500 nm, and the length-diameter ratio of the diameter is about (100-5): 1. The method is simple in process, high in efficiency, low in energy consumption, very convenient in product collection, low in requirements on instruments and equipment and suitable for batch production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aluminum nitride whisker material preparation, and particularly relates to a preparation method of sponge-like superfine aluminum nitride nanometer whisker. BACKGROUND

[0002] Aluminum nitride whisker is a one-dimensional aluminum nitride material with high purity, and its physical properties are close to the theoretical properties of aluminum nitride. It is commonly used to reinforce various inorganic materials such as aluminum nitride ceramics, related organic materials, and composite phase change materials, to achieve the common improvement of the thermal conductivity and mechanical properties of the matrix. Due to its unique fluorescent properties, aluminum nitride nanometer whisker is also used as an important optical material and has a wide range of applications in optical devices such as diodes and medical devices. Meanwhile, it can also be used as an excellent flexible heat dissipation device and a catalyst carrier material, and is a one-dimensional material with a wide range of applications.

[0003] At present, common preparation methods of aluminum nitride whisker include direct nitriding method, evaporation condensation method, carbothermal reduction nitriding method, physical vapor transport method, combustion synthesis method, sublimation method, and chemical vapor deposition method. Among them, the evaporation condensation method, the physical vapor transport method, the sublimation method, and the chemical vapor deposition method have complex processes, high requirements for equipment, and low yield, which limits the development of these preparation methods. The direct nitriding method, the carbothermal reduction nitriding method, and the combustion synthesis method have the advantages of simple process and easy large-scale production, and are currently used more frequently. However, the raw material of the direct nitriding method and the combustion synthesis method is aluminum powder, resulting in high cost of the produced aluminum nitride whisker, while the carbothermal reduction nitriding method uses alumina as the raw material, which has a lower cost and is a very suitable method for industrial production.

[0004] The basic principle of carbothermal reduction nitriding is to flow nitrogen gas at a temperature above 1600℃ to treat alpha-Al2O3 and carbon black, and to grow aluminum nitride whisker material through gas-liquid-solid or gas-solid mechanism. Generally, the aluminum-based raw material and the carbon-containing raw material are in a solid state, while the flowing nitrogen gas and ammonia are in a gaseous state. The synthesized aluminum nitride whisker is generally in micrometer level, and most of the morphologies are straight rod single crystal fibers. Since it is a gas phase reaction, the product is generally scattered at the top, side, and other parts of the reaction container, which is not concentrated and is not conducive to collection. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a preparation method of sponge-like superfine aluminum nitride nanometer whisker, which has the advantages of simple process, high efficiency, low energy consumption, easy collection of products, and low requirements for instruments and equipment, and is suitable for batch production.

[0006] To solve the above technical problems and achieve the above technical effects, the present application realizes the following technical solutions: This invention proposes a method for preparing sponge-like ultrafine aluminum nitride nanocrystals. This method mainly uses solid or liquid aluminum-based materials, carbon-based materials, nitrogen-based materials, etc., as the main raw materials, and achieves the preparation of sponge-like ultrafine aluminum nitride nanocrystals through high-temperature reaction. The specific preparation steps are as follows: Step 1) Mix aluminum-based materials, carbon-based materials, and nitrogen-based materials in a certain mass ratio to obtain powder raw materials; Step 2) Place the powder raw material in an alumina ball mill jar, add a dispersant, and use corundum balls as the ball milling medium for ball milling. After ensuring that all components are evenly mixed during ball milling, perform drying treatment to obtain a mixture. Step 3) Place the mixture in a heating zone, heat it to a first specified temperature under sealed conditions and in a nitrogen atmosphere, and hold it thereafter to obtain an intermediate product; Step 4) The intermediate product is placed in a muffle furnace heated to a second specified temperature and sintered in an air atmosphere to remove excess carbon. Finally, a layer of aluminum nitride nanocrystals with a macroscopic sponge-like structure is formed at the bottom of the muffle furnace. The aluminum nitride nanocrystals are curved, with a diameter of 10~500nm and an aspect ratio of (100~5):1.

[0007] Furthermore, in step 1, the mass ratio of the aluminum-based material, the carbon-based material, and the nitrogen-based material is (10~40):(6~30):(30~84).

[0008] Furthermore, in step 1, the aluminum-based material can be one or a mixture of two or more of α-Al2O3, boehmite, gibbsite, and various transitional alumina.

[0009] Furthermore, in step 1, the carbon-based material refers to a raw material whose main component is carbon, which can be one or more of carbon-containing raw materials such as graphite, coke, carbon black, and glucose.

[0010] Furthermore, in step 1, the nitrogen-based material refers to a raw material whose main component contains nitrogen, which can be one or more of nitrogen-containing raw materials such as nitrogen carbide (C3N4), methylamine (CH3NH2), aniline (C6H5NH2), acetonitrile (CH3CN), benzonitrile (C6H5CN), and urea ((NH2)2CO).

[0011] Furthermore, in step 2, the dispersant can be one or more of methanol, ethanol, acetone, gasoline, hexane, and heptane.

[0012] Furthermore, in step 2, the particle size of the mixture is 0.01~10μm.

[0013] Furthermore, in step 3, the first specified temperature is 1300~2000℃, the heating rate is 3~20℃ / min, and the holding time is 1~10 hours.

[0014] Furthermore, in step 4, the second specified temperature is 600-1000℃, and the sintering time is 1-8 hours.

[0015] The present invention also proposes a sponge-like ultrafine aluminum nitride nanowhiskers prepared by the above preparation method. The sponge-like ultrafine aluminum nitride nanowhiskers exhibit a sponge-like structure on a macroscopic scale, and the aluminum nitride whiskers are curved with a diameter of 10~500nm and an aspect ratio of (100~5):1.

[0016] This invention uses solid or liquid aluminum-based materials, carbon-based materials, nitrogen-based materials, etc. as reaction raw materials. After mixing, they are calcined at high temperature under sealed conditions. Due to the high activity of the raw materials and the large contact area, the reaction is easier to proceed. A layer of sponge-like aluminum nitride nanofibers can be formed at the bottom of the reaction vessel. Not only are the prepared aluminum nitride whiskers curved and all of them nanofibers, but the macroscopic morphology and position of the product are also relatively stable, making it easy to collect.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention is the first to use solid and liquid aluminum-based, carbon-based, and nitrogen-based raw materials as reactants for the preparation of aluminum nitride whiskers. This not only enhances the reactivity but also controls the reaction zone primarily near the reactant region, forming a sponge-like layer of aluminum nitride nanofibers at the bottom of the reaction vessel. The macroscopic morphology and position of the product are relatively stable, facilitating product collection. Unlike existing carbothermal reduction nitridation methods for preparing aluminum nitride whiskers, the aluminum nitride whiskers synthesized in this invention exhibit a sponge-like structure macroscopically and are curved microscopically, consisting entirely of nanofibers with diameters ranging from 10 to 500 nm and an aspect ratio of approximately (100 to 5):1. The preparation method of this invention is simple, efficient, and energy-efficient, with convenient product collection and low requirements for equipment, making it suitable for mass production.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic flowchart of the preparation method of the sponge-like ultrafine aluminum nitride nanocrystals of the present invention. Figure 2 This is an electron microscope image of the aluminum nitride whiskers prepared in this invention. Detailed Implementation

[0020] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to provide a clearer understanding of the invention's purpose, features, and advantages. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the invention, but are merely illustrative of the essential spirit of the invention's technical solution.

[0021] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0022] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0023] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0024] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] See Figure 1 As shown, a method for preparing sponge-like ultrafine aluminum nitride nanocrystals is described. This method mainly uses solid or liquid aluminum-based materials, carbon-based materials, nitrogen-based materials, etc., as the main raw materials, and achieves the preparation of sponge-like ultrafine aluminum nitride nanocrystals through high-temperature reaction. The specific preparation steps are as follows: Step 1) Mix aluminum-based materials, carbon-based materials, and nitrogen-based materials in a mass ratio of (10~40):(6~30):(30~84) to obtain powder raw materials.

[0027] The aluminum-based material can be one or a mixture of two or more of α-Al2O3, boehmite, gibbsite, and various transition alumina.

[0028] The carbon-based materials refer to raw materials whose main component is carbon, which can be one or more of the following carbon-containing raw materials: graphite, coke, carbon black, glucose, etc.

[0029] The nitrogen-based materials refer to raw materials whose main component is nitrogen, and can be one or more of nitrogen-containing raw materials such as nitrogen carbide (C3N4), methylamine (CH3NH2), aniline (C6H5NH2), acetonitrile (CH3CN), benzonitrile (C6H5CN), and urea ((NH2)2CO).

[0030] Step 2) Place the powder raw material in an alumina ball mill jar, add a dispersant, and ball mill with corundum balls as the ball milling medium for about 2 to 20 hours. After ensuring that all components are evenly mixed during ball milling, perform drying treatment to obtain a mixture with a particle size of 0.01 to 10 μm.

[0031] The dispersant can be one or more of methanol, ethanol, acetone, gasoline, hexane, and heptane.

[0032] Step 3) Place the mixture in a heating zone and heat it to 1300~2000℃ under sealed conditions and in a nitrogen atmosphere at a heating rate of 3~20℃ / min, and then hold it at that temperature for 1~10 hours to obtain the intermediate product.

[0033] Step 4) The intermediate product is placed in a muffle furnace heated to 600-1000°C and sintered in air atmosphere for 1-8 hours to remove excess carbon. Finally, a layer of aluminum nitride nanocrystals with a macroscopic sponge-like structure is formed at the bottom of the muffle furnace. The aluminum nitride nanocrystals are curved, with a diameter of 10-500 nm and an aspect ratio of (100-5):1.

[0034] This invention also proposes a sponge-like ultrafine aluminum nitride nanowhiskers prepared by the above-described method. These sponge-like ultrafine aluminum nitride nanowhiskers exhibit a macroscopic sponge-like structure, and the aluminum nitride whiskers are curved, with a diameter of 10-500 nm and an aspect ratio of (100-5):1. This invention uses solid or liquid aluminum-based materials, carbon-based materials, nitrogen-based materials, etc. as reaction raw materials. After mixing, they are calcined at high temperature under sealed conditions. Due to the high activity of the raw materials and the large contact area, the reaction is easier to proceed. A layer of sponge-like aluminum nitride nanofibers can be formed at the bottom of the reaction vessel. Not only are the prepared aluminum nitride whiskers curved and all of them nanofibers, but the macroscopic morphology and position of the product are also relatively stable, making it easy to collect.

[0035] See Figure 2 As shown, Figure 2 Electron micrographs of sponge-like ultrafine aluminum nitride nanowhiskers synthesized using the above-described preparation method are shown. The images reveal that the synthesized sponge-like ultrafine aluminum nitride nanowhiskers exhibit a macroscopic sponge-like structure, with the aluminum nitride whiskers being curved, having a diameter of 10–500 nm, and an aspect ratio of (100–5):1.

[0036] The following specific embodiments illustrate in detail the technical solution for preparing sponge-like ultrafine aluminum nitride nanocrystals according to the present invention.

[0037] Example 1: 10g boehmite, 6g carbon black, and 84g urea were weighed and mixed. The powder was placed in an alumina ball mill jar, and 100g ethanol was added as a dispersant. Corundum balls were used as the milling medium, with a ball-to-powder ratio of 20:1, and the milling time was 20 hours. The mixture was then dried in a constant-temperature forced-air drying oven at 80℃ for 4 hours to obtain a mixture with a particle size distribution D90 of 2μm. The resulting mixture was placed in a heating zone and heated to 1500℃ under a nitrogen atmosphere in a sealed environment at a heating rate of 10℃ / min for 5 hours to obtain an intermediate product. The obtained intermediate product was sintered in an air atmosphere at 600°C for 8 hours in a muffle furnace to remove excess carbon, and finally a layer of sponge-like aluminum nitride nanofibers was formed at the bottom of the muffle furnace. The macroscopic morphology and position of the sponge-like aluminum nitride nanofibers were relatively stable. The aluminum nitride whiskers were curved and all were nanofibers with a diameter of 10~100nm and a diameter-to-diameter ratio of approximately (100~5):1.

[0038] Example 2: 10g of γ-phase alumina, 6g of coke powder, and 84g of urea were weighed and mixed. The powders were placed in an alumina ball mill jar, and 100g of acetone was added as a dispersant. Corundum balls were used as the milling medium, with a ball-to-powder ratio of 20:1, and the milling time was 15 hours. The mixture was then dried in a constant-temperature forced-air drying oven at 80℃ for 8 hours to obtain a mixture with a particle size distribution D90 of 3μm. The resulting mixture was placed in a heating zone and heated to 1600℃ under a nitrogen atmosphere in a sealed environment at a heating rate of 10℃ / min for 5 hours to obtain an intermediate product. The obtained intermediate product was sintered in an air atmosphere at 600°C for 8 hours in a muffle furnace to remove excess carbon, and finally a layer of sponge-like aluminum nitride nanofibers was formed at the bottom of the muffle furnace. The macroscopic morphology and position of the sponge-like aluminum nitride nanofibers were relatively stable. The aluminum nitride whiskers were curved and all were nanofibers with a diameter of 20~200nm and a diameter-to-diameter ratio of approximately (100~5):1.

[0039] Example 3: 8g of γ-phase alumina, 6g of carbon black, and 90g of nitrogen carbide were weighed and mixed. The powder was placed in an alumina ball mill jar, and 100g of methanol was added as a dispersant. Corundum balls were used as the milling medium for ball milling at a ball-to-powder ratio of 20:1 for 20 hours. The mixture was then dried in a constant-temperature forced-air drying oven at 80℃ for 4 hours to obtain a mixture with a particle size distribution D90 of 5μm. The resulting mixture was placed in a heating zone and heated to 1600℃ under a nitrogen atmosphere in a sealed environment at a heating rate of 10℃ / min for 6 hours to obtain an intermediate product. The obtained intermediate product was sintered in an air atmosphere at 600°C for 8 hours in a muffle furnace to remove excess carbon, and finally a layer of sponge-like aluminum nitride nanofibers was formed at the bottom of the muffle furnace. The macroscopic morphology and position of the sponge-like aluminum nitride nanofibers were relatively stable. The aluminum nitride whiskers were curved and all were nanofibers with a diameter of 20~300nm and a diameter-to-diameter ratio of approximately (100~5):1.

[0040] Example 4: 10g of p-phase alumina, 6g of carbon black, and 84g of methylamine were weighed and mixed. The powder was placed in an alumina ball mill jar, and 100g of methanol was added as a dispersant. Corundum balls were used as the milling medium for ball milling at a ball-to-powder ratio of 20:1 for 20 hours. The mixture was then dried in a constant-temperature forced-air drying oven at 80℃ for 4 hours to obtain a mixture with a particle size distribution D90 of 2μm. The resulting mixture was placed in a heating zone and heated to 1600℃ under a nitrogen atmosphere in a sealed environment at a heating rate of 10℃ / min for 10 hours to obtain an intermediate product. The obtained intermediate product was sintered in an air atmosphere at 700°C for 8 hours in a muffle furnace to remove excess carbon, and finally a layer of sponge-like aluminum nitride nanofibers was formed at the bottom of the muffle furnace. The macroscopic morphology and position of the sponge-like aluminum nitride nanofibers were relatively stable. The aluminum nitride whiskers were curved and all were nanofibers with a diameter of 20~300nm and a diameter-to-diameter ratio of approximately (100~5):1.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing sponge-like ultrafine aluminum nitride nanocrystals, characterized in that, Using raw materials including solid or liquid aluminum-based materials, carbon-based materials, and nitrogen-based materials, and through high-temperature reaction, sponge-like ultrafine aluminum nitride nanocrystals are prepared. The specific preparation steps are as follows: Step 1) Mix aluminum-based materials, carbon-based materials, and nitrogen-based materials in a certain mass ratio to obtain powder raw materials; Step 2) Place the powder raw material in an alumina ball mill jar, add a dispersant, and use corundum balls as the ball milling medium for ball milling. After ensuring that all components are evenly mixed during ball milling, perform drying treatment to obtain a mixture. Step 3) The mixture is placed in a heating zone and heated to a first specified temperature under sealed conditions and in a nitrogen atmosphere and held at that temperature to obtain an intermediate product; Step 4) The intermediate product is placed in a muffle furnace heated to a second specified temperature and sintered in an air atmosphere to remove excess carbon, and finally a layer of aluminum nitride nanocrystals with a macroscopic sponge-like structure is formed at the bottom of the muffle furnace.

2. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 1, the mass ratio of the aluminum-based material, the carbon-based material, and the nitrogen-based material is (10~40):(6~30):(30~84).

3. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 1, the aluminum-based material is one or a mixture of two or more of α-Al2O3, boehmite, gibbsite, and transition alumina.

4. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 1, the carbon-based material is one or more of graphite, coke, carbon black, and glucose.

5. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 1, the nitrogen-based material is one or more of nitrogen carbide, methylamine, aniline, acetonitrile, benzonitrile, and urea.

6. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 2, the dispersant is one or more of methanol, ethanol, acetone, gasoline, hexane, and heptane.

7. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 2, the particle size of the mixture is 0.01~10μm.

8. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 3, the first specified temperature is 1300~2000℃, the heating rate is 3~20℃ / min, and the holding time is 1~10 hours.

9. The method for preparing sponge-like ultrafine aluminum nitride nanocrystals according to claim 1, characterized in that, In step 4, the second specified temperature is 600-1000℃, and the sintering time is 1-8 hours.

10. A sponge-like ultrafine aluminum nitride nanocrystals prepared by the preparation method according to any one of claims 1-9, characterized in that, The sponge-like ultrafine aluminum nitride nanocrystals exhibit a sponge-like structure on a macroscopic scale. The aluminum nitride whiskers are curved, with a diameter of 10~500nm and an aspect ratio of (100~5):1.

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