A method for preparing a boron nitride-coated spherical aluminum nitride composite material

Abstract

The application discloses a preparation method of a boron nitride-coated spherical aluminum nitride composite material, and belongs to the field of boron nitride-spherical aluminum nitride composite material preparation, characterized in that a dense hexagonal boron nitride layer is sintered on the surface of the spherical aluminum nitride, and the dense hexagonal boron nitride layer is obtained by using the oxidation reaction of the hexagonal boron nitride, so that the problem that the spherical aluminum nitride powder is seriously hydrated in the prior art, the heat conduction of the spherical aluminum nitride is deteriorated, the sphericity of the spherical core is reduced, the thermal conductivity of the core-shell structure composite particle is reduced, and the composite material containing an organic coating layer can only be used in a specific filling system is solved, and the application is mainly used in the production of boron nitride-spherical aluminum nitride composite materials.

Description

Technical Field

[0001] This invention relates to the field of boron nitride-spherical aluminum nitride composite material preparation, and more specifically to a method for preparing a composite material with boron nitride coated spherical aluminum nitride. Background Technology

[0002] Aluminum nitride, as a ceramic material, possesses excellent properties such as high thermal conductivity, low dielectric constant, and good insulation, making it widely used in many fields such as electronic packaging and heat dissipation. However, aluminum nitride also suffers from significant brittleness, which to some extent limits its further application and development in certain areas.

[0003] Application number CN202210065817.1 discloses a core-shell structured high thermal conductivity powder filler and its preparation method. The working principle is as follows: after ultrasonically cleaning spherical powder (including spherical aluminum nitride) with organic solvent to remove surface impurities, the spherical powder is added to a high-temperature aqueous solution of boric acid and melamine. The solution is heated and stirred until it is completely evaporated to obtain spherical powder coated with precursor. Then, the spherical powder is calcined under a high-temperature nitrogen atmosphere to form a dense boron nitride shell layer on the spherical surface. The calcined powder is then crushed and washed to obtain the core-shell structured spherical powder.

[0004] The aforementioned patent uses a precursor aqueous solution to treat spherical powder (including spherical aluminum nitride) at high temperature. During the treatment process, the spherical aluminum nitride powder will be severely hydrated, resulting in poor thermal conductivity of the spherical aluminum nitride and a decrease in the sphericality of the spherical core, ultimately leading to a decrease in the thermal conductivity of the core-shell structure particles.

[0005] Application number CN116836485A discloses a high thermal conductivity EV cable material containing a core-shell spherical thermally conductive filler and its preparation method. The working principle is that the sheet-like boron nitride filler and the spherical aluminum nitride filler are bonded together by liquid ethylene propylene rubber and then cross-linked and cured to achieve a structure in which the sheet-like boron nitride is coated on the surface of the spherical aluminum nitride.

[0006] The aforementioned patent uses liquid ethylene propylene rubber as a binder, which is still present in the final product. Such products can generally only be used as fillers in rubber systems. Using them in other filler systems would significantly reduce the thermal conductivity of the system.

[0007] Therefore, our company proposes a research method for preparing a composite material of boron nitride coated spherical aluminum nitride. Summary of the Invention

[0008] Purpose of the invention: The present invention solves the problem that the existing technology causes severe hydration of spherical aluminum nitride powder, which leads to poor thermal conductivity of spherical aluminum nitride and a decrease in the sphericality of the spherical core, ultimately resulting in a decrease in the thermal conductivity of core-shell structure particles and the fact that composite materials containing organic coatings can only be used in specific filling systems.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: by sintering a dense hexagonal boron nitride layer on the surface of spherical aluminum nitride, and utilizing the oxidation reaction of hexagonal boron nitride, composite particles with a dense boron nitride layer are obtained.

[0010] The specific technical solution of this invention is as follows:

[0011] A boron nitride-coated spherical aluminum nitride composite material, characterized in that a dense hexagonal boron nitride layer is sintered on the surface of the spherical aluminum nitride, utilizing the oxidation reaction of hexagonal boron nitride;

[0012] 4 BN + 7 O2 = 2 B2O3 + 4 NO 2，

[0013] Composite particles with dense boron nitride layers were obtained.

[0014] A method for preparing a boron nitride-coated spherical aluminum nitride composite material, characterized in that:

[0015] Step 1: Raw material pretreatment: The coating material is selected as submicron or micron-sized hexagonal boron nitride, with a median particle size D50 between 0.1μm and 6μm;

[0016] Boron nitride was then pre-oxidized at 600-900℃ for 0.5-3 hours, increasing the total oxygen content of hexagonal boron nitride by 0.1-1.5%.

[0017] Step 2: Coating the surface of spherical aluminum nitride with boron nitride: Using centrifugal granulation or drum mixing process, mix spherical aluminum nitride, binder and pre-oxidized hexagonal boron nitride, and uniformly coat the surface of spherical aluminum nitride with hexagonal boron nitride.

[0018] Step 3: Densification: The mixed powder is debinded and sintered to obtain spherical aluminum nitride powder with dense sintered boron nitride on the surface.

[0019] Step 4: Separation of free boron nitride: Cleaning and separation using organic solvents. Immerse the densified spherical aluminum nitride powder in the organic solvent, stir thoroughly, and let it stand. Utilize the density difference between free boron nitride and spherical aluminum nitride powder to separate and remove the free boron nitride not coated on the surface of the spherical aluminum nitride, thus obtaining the final product.

[0020] Preferably, the adhesive is one of polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, and polyvinyl acetal.

[0021] Preferably, the organic solvent is one of ethanol, acetone, ethyl acetate, and isopropanol.

[0022] The present invention has the following beneficial effects:

[0023] 1. Submicron or micron-sized hexagonal boron nitride (D50=0.1-6μm) is selected as raw material. Compared with large-particle boron nitride, this raw material has a small particle size, which makes it easier to form a dense coating layer. It is not easy to peel off during production and processing, which is beneficial to improving the filling performance of composite particles in the system.

[0024] 2. Pre-oxidize hexagonal boron nitride to induce oxidation and generate a sufficient boron oxide layer on the surface (increasing the total oxygen content by 0.1-1.5%). By utilizing the reactivity between boron oxide and spherical aluminum nitride, and between boron oxides themselves, the sintering strength between the surfaces of hexagonal boron nitride and spherical aluminum nitride, and between hexagonal boron nitrides, is improved, giving the surface of spherical aluminum nitride sufficient coating strength.

[0025] 3. Boron oxide produced during the oxidation reaction of hexagonal boron nitride can be used as a sintering aid, resulting in better sintering uniformity compared to adding additional sintering aids such as boron oxide.

[0026] 4. The product preparation process includes a debinding step, and the final product does not contain organic matter, so there are no restrictions on the product's application system.

[0027] 5. After sintering, the composite particles are cleaned with organic solvents such as ethanol to separate and remove the free boron nitride that is not coated on the surface of the spherical aluminum nitride, thereby improving the filling performance of the composite particles in the system.

[0028] 6. No water is used in the entire production process, which prevents the performance of spherical aluminum nitride core particles from deteriorating during processing.

[0029] The production process of this invention is environmentally friendly, and it avoids the problems caused by existing technologies, such as poor thermal conductivity of spherical aluminum nitride and reduced sphericality of the spherical core, which limit the final product to specific filling systems. This invention has good economic benefits. Attached Figure Description

[0030] Figure 1 This is the final SEM image obtained in Example 4. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] A boron nitride-coated spherical aluminum nitride composite material, characterized in that a dense hexagonal boron nitride layer is sintered on the surface of the spherical aluminum nitride, utilizing the oxidation reaction of hexagonal boron nitride;

[0033] 4 BN + 7 O2 = 2 B2O3 + 4 NO 2，

[0034] Composite particles with dense boron nitride layers were obtained.

[0035] A method for preparing a boron nitride-coated spherical aluminum nitride composite material, characterized in that:

[0036] Step 1: Raw material pretreatment: The coating material is selected as submicron or micron-sized hexagonal boron nitride, with a median particle size D50 between 0.1μm and 6μm;

[0037] Boron nitride was then pre-oxidized at 600-900℃ for 0.5-3 hours, increasing the total oxygen content of hexagonal boron nitride by 0.1-1.5%.

[0038] Step 2: Coating the surface of spherical aluminum nitride with boron nitride: Using centrifugal granulation or drum mixing process, mix spherical aluminum nitride, binder and pre-oxidized hexagonal boron nitride, and uniformly coat the surface of spherical aluminum nitride with hexagonal boron nitride.

[0039] Step 3: Densification: The mixed powder is debinded and sintered to obtain spherical aluminum nitride powder with dense sintered boron nitride on the surface.

[0040] Step 4: Separate free boron nitride: Use organic solvents such as ethanol to clean and remove the free boron nitride that is not coated on the surface of the spherical aluminum nitride, to obtain the final product.

[0041] Preferably, the adhesive is one of polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, and polyvinyl acetal.

[0042] Preferably, the organic solvent is one of ethanol, acetone, ethyl acetate, and isopropanol.

[0043] Example 1

[0044] Submicron hexagonal boron nitride with a D50 of 0.1 μm was pre-oxidized at 600 °C for 1 h, which increased the total oxygen content of the hexagonal boron nitride by 0.74%. 1000 g of spherical aluminum nitride with a D50 of 80 μm, polyvinyl butyral solution, and 200 g of the pre-oxidized hexagonal boron nitride were mixed in a can mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0045] The final detection performance in the organosilicon system is as follows:

[0046]

[0047] Example 2

[0048] Submicron hexagonal boron nitride with a D50 of 0.1 μm was pre-oxidized at 900 °C for 1 h, which increased the total oxygen content of the hexagonal boron nitride by 1.48%. 1000 g of spherical aluminum nitride with a D50 of 80 μm, polyvinyl butyral solution, and 200 g of the pre-oxidized hexagonal boron nitride were mixed in a pot mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0049] The final detection performance in the organosilicon system is as follows:

[0050]

[0051] Example 3

[0052] Micron-sized hexagonal boron nitride with a D50 of 0.1 μm was pre-oxidized at 800 °C for 2 h, which increased the total oxygen content of the hexagonal boron nitride by 1.24%. Spherical aluminum nitride, polyvinyl butyral solution, and hexagonal boron nitride were mixed in a can mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0053] The final detection performance in the organosilicon system is as follows:

[0054]

[0055] Example 4

[0056] Submicron hexagonal boron nitride with a D50 of 6 μm was pre-oxidized at 600 °C for 1 h, which increased the total oxygen content of the hexagonal boron nitride by 0.46%. 1000 g of spherical aluminum nitride with a D50 of 80 μm, polyvinyl butyral solution, and 200 g of the pre-oxidized hexagonal boron nitride were mixed in a pot mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0057] The final detection performance in the organosilicon system is as follows:

[0058]

[0059] Example 5

[0060] Submicron hexagonal boron nitride with a D50 of 6 μm was pre-oxidized at 900 °C for 1 h, which increased the total oxygen content of the hexagonal boron nitride by 1.21%. 1000 g of spherical aluminum nitride with a D50 of 80 μm, polyvinyl butyral solution, and 200 g of the pre-oxidized hexagonal boron nitride were mixed in a pot mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0061] The final detection performance in the organosilicon system is as follows:

[0062]

[0063] Example 6

[0064] Submicron hexagonal boron nitride with a D50 of 6 μm was pre-oxidized at 800 °C for 2 h, which increased the total oxygen content of the hexagonal boron nitride by 1.02%. 1000 g of spherical aluminum nitride with a D50 of 80 μm, polyvinyl butyral solution, and 200 g of the pre-oxidized hexagonal boron nitride were mixed in a pot mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0065] The final detection performance in the organosilicon system is as follows:

[0066]

[0067] Comparative Example 1

[0068] The detection performance of hexagonal boron nitride and spherical aluminum nitride mixed and compounded with the same proportions and particle sizes as in Example 1 in the organosilicon system is as follows:

[0069]

[0070] Comparative Example 2

[0071] The detection performance of spherical boron nitride with the same particle size as in Example 1 in an organosilicon system with the same filling amount is as follows:

[0072]

[0073] Comparative Example 3

[0074] Micron-sized hexagonal boron nitride with a D50 of 10 μm was pre-oxidized at 900 °C for 1 h, which increased the total oxygen content of the hexagonal boron nitride by 0.98%. Spherical aluminum nitride, polyvinyl butyral solution, and hexagonal boron nitride were mixed in a can mill for 2 h. The mixed powder was debinded, sintered, and then washed with ethanol to remove free boron nitride, thus obtaining the final product.

[0075] The final detection performance in the organosilicon system is as follows:

[0076]

[0077] Reaction control table

[0078]

[0079] Summarize:

[0080] 1. Compared with the simple mixing of Comparative Example 1, the composite particles in Example 1 can significantly increase the extrusion rate (improving the filling performance of the product) while maintaining comparable thermal conductivity.

[0081] 2. Compared with Comparative Example 2, which uses a single spherical boron nitride (which is more fragile), Example 1 uses composite particles with a surface boron nitride that is not easy to fall off and has higher overall particle strength, which can improve extrusion performance (improve the filling performance of the product); the composite particles in the example contain spherical aluminum nitride, which has higher thermal conductivity than spherical boron nitride, and can improve overall thermal conductivity.

[0082] 3. Compared with Comparative Example 3, which used 10μm boron nitride, Example 1 used 0.1μm boron nitride as a surface coating material, which is less likely to fall off during processing and can improve extrusion performance (improve the filling performance of the product).

[0083] 4. As can be seen from Examples 1-6, the higher the oxidation amount of boron nitride, the higher the boron nitride bonding strength on the surface of the composite material, the less likely it is to fall off in the system, and the higher the product extrusion rate. However, relatively speaking, the higher the oxidation amount, the higher the boron oxide content in the boron nitride, and the lower the thermal conductivity of the composite material. Therefore, the oxidation amount of boron nitride is preferably controlled in the range of 0.1-1.5%.

[0084] 5. In Examples 1, 2, and 3, small-particle-size boron nitride was used. Under appropriate oxidation levels, the thermal conductivity and extrusion rate were higher. Compared with the larger-particle-size boron nitride used in Examples 4, 5, and 6, the effect was better and significantly better than Comparative Example 3. Therefore, the particle size of boron nitride in the composite material is preferably controlled in the range of 0.1-6 μm.

[0085] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a boron nitride-coated spherical aluminum nitride composite material, characterized in that: Step 1: Raw material pretreatment: The coating material is selected as submicron or micron-sized hexagonal boron nitride, with a median particle size D50 between 0.1μm and 6μm; Boron nitride was then pre-oxidized at 600-900℃ for 0.5-3 hours, increasing the total oxygen content of hexagonal boron nitride by 0.1-1.5%. Step 2: Coating the surface of spherical aluminum nitride with boron nitride: Using centrifugal granulation or drum mixing process, mix spherical aluminum nitride, binder and pre-oxidized hexagonal boron nitride, and uniformly coat the surface of spherical aluminum nitride with hexagonal boron nitride. Step 3: Densification: The mixed powder is debinded and sintered to obtain spherical aluminum nitride powder with dense sintered boron nitride on the surface; Step 4: Separation of free boron nitride: Cleaning and separation using organic solvents. Immerse the densified spherical aluminum nitride powder in the organic solvent, stir thoroughly, and let it stand. Utilize the density difference between free boron nitride and spherical aluminum nitride powder to separate and remove the free boron nitride not coated on the surface of the spherical aluminum nitride, thus obtaining the final product.

2. The method for preparing a boron nitride-coated spherical aluminum nitride composite material according to claim 1, characterized in that: The adhesive is one of polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, and polyvinyl acetal.

3. The method for preparing a boron nitride-coated spherical aluminum nitride composite material according to claim 1, characterized in that: The organic solvent is one of ethanol, acetone, ethyl acetate, or isopropanol.

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