Boron nitride all-ceramic particles, method for their production and use

Abstract

The application provides a boron nitride all-ceramic particle, a preparation method and application thereof, and comprises the following steps: providing a two-dimensional boron nitride dispersion liquid, wherein the two-dimensional boron nitride dispersion liquid comprises two-dimensional boron nitride nanosheets and an organic solvent; adding an organic binder to the two-dimensional boron nitride dispersion liquid to obtain a mixed solution; performing spray drying on the mixed solution to obtain a precursor; performing pre-sintering on the precursor in an oxygen-containing atmosphere to remove the organic binder in the precursor and obtain an intermediate; and performing Joule heat sintering on the intermediate in an inert gas to obtain the boron nitride all-ceramic particle. In the boron nitride all-ceramic particle provided by the application, the two-dimensional boron nitride nanosheets are assembled into compact spherical bodies through layer-by-layer wrapping, and the two-dimensional boron nitride nanosheets in the spherical particles are sintered and bonded to each other, so that the boron nitride all-ceramic particle has excellent mechanical structural stability and thermal conductivity.

Description

Technical Field

[0001] This application relates to the field of thermal conductivity, and more particularly to a boron nitride all-ceramic particle, its preparation method, and its application. Background Technology

[0002] Two-dimensional boron nitride (BNNS) is a two-dimensional material composed of nitrogen and boron, also known as "white graphite," with the chemical formula BN. Like graphite, BNNS consists of stacked monolayers bound together by van der Waals forces. Within each layer, nitrogen and boron atoms are arranged in sp... 2 The hybridized form constitutes a hexagonal honeycomb structure. Two-dimensional boron nitride possesses high thermal conductivity, high insulation, and low dielectric constant, while also exhibiting flexibility, chemical stability, thermal stability, and biocompatibility. Therefore, it shows great application potential in many fields, such as electronic devices, optical equipment, thermal management, composite materials, and biomedicine.

[0003] Currently, the main method involves assembling two-dimensional boron nitride (2D boron nitride) into composite materials by mixing it with organic polymers (such as resins), with the 2D boron nitride crosslinking within the organic polymer. However, due to the high aspect ratio of 2D boron nitride, its dispersion in composite materials is poor, and it is prone to agglomeration, which limits the amount of 2D boron nitride that can be added to composite materials. Summary of the Invention

[0004] In view of this, this application provides boron nitride all-ceramic particles, their preparation method and application.

[0005] To achieve the above objectives, this application provides a method for preparing boron nitride all-ceramic particles, comprising: providing a two-dimensional boron nitride dispersion, wherein the two-dimensional boron nitride dispersion comprises two-dimensional boron nitride nanosheets and an organic solvent; adding an organic binder to the two-dimensional boron nitride dispersion to obtain a mixture; granulating the mixture by spray drying to obtain a precursor; pre-sintering the precursor in an oxygen-containing atmosphere to remove the organic binder from the precursor to obtain an intermediate; and sintering the intermediate by Joule heating in an inert atmosphere to obtain boron nitride all-ceramic particles.

[0006] In some embodiments, the sintering temperature of the Joule heating sintering is 1500-2500℃, and the sintering time is 10-1000s.

[0007] In some embodiments, the heating rate of the Joule heating sintering is 100-10000℃ / min.

[0008] In some embodiments, the pre-sintering temperature is 400–700°C.

[0009] In some embodiments, the organic binder includes at least one of polyurethane, epoxy resin, polyvinyl alcohol, polyvinyl butyrate, polyvinylpyrrolidone, polymethyl methacrylate, polydimethylsiloxane, polyvinylidene fluoride, or polytetrafluoroethylene.

[0010] In some embodiments, the mass of the organic binder is 0.1-5% of the mass of the two-dimensional boron nitride nanosheets.

[0011] This application also provides boron nitride all-ceramic particles, wherein the boron nitride all-ceramic particles comprise a plurality of interconnected two-dimensional boron nitride nanosheets.

[0012] In some embodiments, the median particle size of the boron nitride all-ceramic particles is 5–500 μm.

[0013] In some embodiments, the bulk density of the boron nitride all-ceramic particles is 0.3–0.7 g / cm³. 3 .

[0014] This application also provides an application of boron nitride all-ceramic particles in electronic devices.

[0015] In this application, an organic binder is added to a two-dimensional boron nitride dispersion to obtain a mixture. This mixture is then spray-dried and granulated to obtain a self-assembled spherical precursor. After pre-sintering to remove the organic solvent and organic binder from the precursor, Joule heating sintering is performed, causing the two-dimensional boron nitride nanosheets to fuse and form spherical boron nitride particles, thus obtaining boron nitride all-ceramic particles with high strength and high thermal conductivity. Scanning electron microscopy of the boron nitride all-ceramic particles (see...) Figure 1 As can be seen from the diagram, two-dimensional boron nitride nanosheets in boron nitride all-ceramic particles are assembled into dense spheres through layer-by-layer encapsulation. After sintering, the two-dimensional boron nitride nanosheets fuse together to form a high-strength whole. The two-dimensional boron nitride nanosheets within each spherical particle are sintered and bonded to each other, giving the boron nitride all-ceramic particles excellent mechanical structural stability and thermal conductivity. The two-dimensional boron nitride nanosheets have high thermal conductivity, and the dense spheres obtained after sintering have a high thermal conductivity coefficient.

[0016] The boron nitride all-ceramic particles provided in this application are spherical. Compared with existing two-dimensional boron nitride materials, spherical particles are also isotropic. In composite materials, spherical particles can form continuous network-like thermal conductive channels, thereby improving the overall thermal conductivity of the composite material and increasing the amount of boron nitride all-ceramic particles added. Two-dimensional nitride nanosheets assembled into spherical particles have good dispersibility and flowability. When added to composite materials, spherical particles can move freely, thereby improving the uniformity of boron nitride all-ceramic particles added to composite materials and improving the thermal conductivity of composite materials. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the boron nitride all-ceramic particles prepared in Example 1 of this application.

[0018] Figure 2 Scanning electron microscope image of boron nitride all-ceramic particles prepared for Comparative Example 2.

[0019] Figure 3 The particle size distribution of boron nitride all-ceramic particles prepared in Example 1 and Comparative Example 2 are shown.

[0020] Figure 4 To test the thermal conductivity distribution of boron nitride all-ceramic particles prepared in Example 1 and Comparative Example 2 under different filling ratios. Detailed Implementation

[0021] The embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] This application provides a method for preparing boron nitride all-ceramic particles, including:

[0024] S1. Provide a two-dimensional boron nitride dispersion, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and an organic solvent.

[0025] At least one of ball milling, ultrasonication, and high-speed shearing methods can be used to exfoliate boron nitride powder to obtain two-dimensional boron nitride nanosheets. In this embodiment, boron nitride and an organic solvent are mixed and ball-milled using a wet ball milling method, and the boron nitride is exfoliated to form two-dimensional boron nitride nanosheets, resulting in a two-dimensional boron nitride dispersion. The average particle size of the boron nitride powder before exfoliation is 1–50 μm, preferably 30–50 μm.

[0026] In some embodiments, the mass percentage of two-dimensional boron nitride nanosheets in the two-dimensional boron nitride dispersion is 1% to 50%, and in some embodiments, it is 20% to 40%, in order to obtain the two-dimensional boron nitride dispersion with high efficiency.

[0027] In some embodiments, the organic solvent includes at least one of ethanol, isopropanol, ethyl acetate, isoamyl acetate, toluene, xylene, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, or N-methylpyrrolidone.

[0028] S2. An organic binder is added to the two-dimensional boron nitride dispersion to obtain a mixture.

[0029] Organic binders can improve the rheological properties of two-dimensional boron nitride dispersions, which is beneficial for subsequent spray drying.

[0030] In some embodiments, the organic binder includes at least one of polyurethane, epoxy resin, polyvinyl alcohol, polyvinyl butyrate, polyvinylpyrrolidone, polymethyl methacrylate, polydimethylsiloxane, polyvinylidene fluoride, or polytetrafluoroethylene.

[0031] In some embodiments, the organic binder comprises 0.1-5% of the mass of the two-dimensional boron nitride nanosheets to ensure that the organic binder can be sufficiently mixed with the two-dimensional boron nitride nanosheets and that the two-dimensional boron nitride nanosheets can adhere to each other, resulting in a mixture that maintains a certain viscosity. In some embodiments, the organic binder comprises 0.5-1% of the mass of the two-dimensional boron nitride nanosheets, such as 0.5%, 0.7%, or 1%.

[0032] In step S2, the two-dimensional boron nitride dispersion and the organic binder can be mixed by one of ball milling, mechanical stirring or ultrasonic dispersion to obtain a homogeneous mixture.

[0033] S3. The mixture is granulated by spray drying to obtain the precursor.

[0034] Spray drying was used to granulate the mixture, and spherical precursors were obtained through self-assembly.

[0035] In some embodiments, the average particle size of the precursor is 5–500 μm.

[0036] S4. The precursor is pre-sintered in an oxygen-containing atmosphere to remove the organic binder in the precursor and obtain the intermediate.

[0037] In some embodiments, the pre-sintering temperature is 400–700°C to ensure the removal of organic matter from the precursor. For example, the pre-sintering temperature may be 400°C, 500°C, 600°C, or 700°C. The pre-sintering time is 0.5–1 hour.

[0038] In some embodiments, the pre-sintering heating rate is 1-10°C / min, such as 1°C / min, 2°C / min, 5°C / min or 10°C / min.

[0039] An oxygen-containing atmosphere includes oxygen or air.

[0040] S5. The intermediate is sintered by Joule heating in an inert atmosphere to obtain spherical boron nitride all-ceramic particles.

[0041] The boron nitride all-ceramic particles are composed of single two-dimensional boron nitride nanosheets, which are layered to form dense spheres. Within these spheres, the two-dimensional boron nitride nanosheets are sintered and bonded together, both between layers and within the same layer. In these spherical particles, the two-dimensional boron nitride nanosheets are oriented along the spherical surface, resulting in high fluidity and an angle of repose of 20–28°. Furthermore, the boron nitride all-ceramic particles prepared in this application are all-ceramic materials, exhibiting high density and structural stability.

[0042] The spherical orientation of the two-dimensional boron nitride nanosheets refers to a small deviation between the face direction of the two-dimensional boron nitride sheet layer and the spherical orientation at its location. In the boron nitride all-ceramic particles provided in this application, cases where the face of the two-dimensional boron nitride nanosheets deviates significantly from the spherical surface, forming protruding spherical sheets, are rare.

[0043] Joule heating sintering refers to placing powder in a graphite heater, energizing the heater, and using the inherent resistance of graphite to generate Joule heat, thereby rapidly sintering the powder in the graphite heater at ultra-high temperatures. In some embodiments, the graphite heater includes a trough shape, a plate shape, or a funnel shape.

[0044] In some embodiments, the resistance of the graphite heater is 0.1-10Ω, preferably 0.5-5Ω. The specific heat capacity of the graphite heater is 500-2000J / (kg·K), preferably 700-1000J / (kg·K).

[0045] An inert atmosphere includes at least one of argon, nitrogen, helium, or neon.

[0046] In some embodiments, the Joule heating sintering temperature is 1500-2500℃ and the sintering time is 10-1000s, so that the intermediate can be fully sintered, and the layers in the two-dimensional boron nitride nanosheets are fused and bonded by sintering to form spherical boron nitride particles, thereby obtaining boron nitride all-ceramic particles with high structural strength, high stability and high thermal conductivity.

[0047] In some embodiments, the heating rate of Joule heating sintering is 100-10000℃ / min, which helps to prevent the material from undergoing low-temperature curing during the sintering process and prevents small particles from being redeposited in large particles during curing, thus preventing an increase in porosity. At the above heating rate, the compactness and structural strength of the structure can be guaranteed.

[0048] The cooling rate of Joule heating sintering is 100-10000℃ / min. The heating and cooling rates of Joule heating sintering are related to the degree and time of low-temperature ripening during the sintering process, and also affect the possibility of damage to the sintered material when subjected to thermal shock.

[0049] In some embodiments, during Joule heating sintering, the heating and cooling rates are all between 100 and 3000 °C / min, such as 100 °C / min, 200 °C / min, 500 °C / min, 700 °C / min, 1000 °C / min, 1500 °C / min, 2000 °C / min, or 3000 °C / min. The heating and cooling rates can be the same or different.

[0050] This application also provides boron nitride all-ceramic particles prepared by the above method, wherein the boron nitride all-ceramic particles are spherical, and each boron nitride all-ceramic particle comprises a plurality of two-dimensional boron nitride nanosheets bonded to each other.

[0051] In this application, two-dimensional materials refer to materials with strong interatomic interactions within a single layer and weak interatomic interactions between different layers, thus forming a few-layered structure with a thickness at the nanoscale or larger. Two-dimensional boron nitride refers to boron nitride materials consisting of only a single layer or a few atomic layers.

[0052] Scanning electron microscopy (see) Figure 1 Observation revealed that two-dimensional boron nitride nanosheets in boron nitride all-ceramic particles are assembled layer by layer to form dense spheres, resulting in spherical boron nitride particles. After sintering, the two-dimensional boron nitride nanosheets fuse together to form a high-strength whole. The sintering bonding between layers and within the same layer of the two-dimensional boron nitride nanosheets within each spherical particle gives the boron nitride all-ceramic particles excellent mechanical structural stability and thermal conductivity. The two-dimensional boron nitride nanosheets have high thermal conductivity, and the dense spheres obtained after sintering exhibit a high thermal conductivity coefficient.

[0053] Compared to existing two-dimensional boron nitride materials, the spherical boron nitride all-ceramic particles provided in this application are isotropic. These spherical particles can also form a continuous network of thermally conductive channels in the composite material, thereby improving the overall thermal conductivity of the composite material and increasing the amount of boron nitride all-ceramic particles that can be added. The two-dimensional boron nitride nanosheets assembled into spherical particles exhibit good dispersibility and flowability. These spherical particles can move freely when added to the composite material, thus improving the uniformity of the boron nitride all-ceramic particles added to the composite material and enhancing its thermal conductivity.

[0054] The spherical particles in boron nitride all-ceramic particles have high strength and can withstand intense stirring. They can also be added to the polymer matrix to form composite materials, thereby improving the thermal conductivity of the composite materials.

[0055] In some embodiments, the median particle size of the boron nitride all-ceramic particles is 5–500 μm.

[0056] In some embodiments, the bulk density of the boron nitride all-ceramic particles is 0.3–0.7 g / cm³. 3 For example, 0.5–0.6 g / cm³ 3 .

[0057] The application of boron nitride all-ceramic particles as thermally conductive materials in electronic devices. Boron nitride all-ceramic particles can be added as thermally conductive fillers during the fabrication of electronic devices to dissipate heat generated by heat-generating components. Furthermore, the boron nitride all-ceramic particles exist as spherical two-dimensional boron nitride particles, eliminating the need to consider manufacturing orientation issues to improve high thermal conductivity. The boron nitride all-ceramic particles provided in this application have significant application value as thermal interface materials for electronic devices, helping to improve the heat dissipation efficiency and performance stability of equipment. Applications include thermally conductive substrates in energy storage devices, electronic packaging, and high-power integrated circuits, as well as applications in heat sinks and electrical insulation materials.

[0058] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the invention. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically described are all conventional commercially available products or open-source materials.

[0059] Example 1

[0060] Take 5g of boron nitride powder with an average particle size of 50 micrometers and 10g of isopropanol and put them into a 250ml zirconia ball mill jar. Add 100g of 99% zirconia balls with a diameter of 10mm and 25g of 99% zirconia balls with a diameter of 1mm. Place the jar on a planetary ball mill and ball mill at a speed of 600rpm for 12 hours. Collect the jar to obtain a two-dimensional boron nitride dispersion. The boron nitride is then exfoliated to form two-dimensional boron nitride nanosheets.

[0061] The solid content of the two-dimensional boron nitride dispersion was determined. The two-dimensional boron nitride nanosheets were prepared to account for 40% of the mass of the two-dimensional boron nitride dispersion. An organic binder, polyvinylpyrrolidone (PVPK90), was added to the prepared two-dimensional boron nitride dispersion at 1% of the mass of boron nitride. The mixture was then mixed at 10,000 rpm for 5 minutes using a high-speed shear machine to obtain the mixture.

[0062] The mixture was spray-dried and granulated using spray drying technology to obtain spherical boron nitride assemblies with a median particle size of 50 micrometers, which is the precursor.

[0063] The precursor was pre-sintered by placing it in a crucible and then in a muffle furnace under an air atmosphere. The temperature was increased from 25°C to 700°C at a rate of 1°C / min and held for 1 hour to pre-sinter and burn off the organic binder, thus obtaining the intermediate.

[0064] The intermediate powder was placed in a trough-shaped graphite heater and sintered in argon gas at a heating rate of 10,000℃ / min until the temperature reached 2,000℃ and was held for 3 minutes. Then, it was cooled to room temperature at a cooling rate of 10,000℃ / min and removed to obtain boron nitride all-ceramic particles.

[0065] Example 2

[0066] The difference between Example 2 and Example 1 is that the intermediate sintering temperature is 1800°C, while the other conditions are the same as in Example 1.

[0067] Example 3

[0068] The difference between Example 3 and Example 1 is that the intermediate sintering time is 1 minute, while the other conditions are the same as in Example 1.

[0069] Comparative Example 1

[0070] The difference between Comparative Example 1 and Example 1 is that the 50-micron boron nitride particles were replaced with 1-micron boron nitride particles, and the ball milling time was changed to 0.5 hours. Under these conditions, the boron nitride in the dispersion did not peel off to form nanosheets. The change in boron nitride particle size was to match the particle size in the dispersion of Example 1. All other conditions were the same as in Example 1.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 1 is that during the sintering of the intermediate, the heating rate was 10°C / min and the cooling rate was 10°C / min, while the other conditions were the same as in Example 1.

[0073] This application presents scanning electron microscopy tests on the boron nitride all-ceramic particles prepared in Example 1 and Comparative Example 2, respectively. (See also...) Figure 1 In the boron nitride all-ceramic particles, two-dimensional boron nitride nanosheets fuse to form a dense sphere with a smooth and flat surface. The particle size distribution of the boron nitride all-ceramic particles prepared in Example 1 was tested using laser particle size distribution analysis, yielding a median particle size of 45 micrometers. The apparent density of the powder was measured using a powder bulk density meter, resulting in an apparent density of 0.39 g / cm³. 3 The tap density is 0.457 g / cm³. 3 The angle of repose is 27.6°, which indicates that the boron nitride all-ceramic particles have been well sintered, with high density and good flowability.

[0074] Table 1. Preparation conditions and test results of boron nitride all-ceramic particles in Examples 1-3 and Comparative Examples 1-2.

[0075]

[0076] As shown in Table 1, in Example 1 and Comparative Example 1, the material prepared from the unexfoliated boron nitride in Comparative Example 1 exhibits a bimodal particle size distribution, with a small peak at 3 μm and a large peak at 55 μm. This is because the smaller boron nitride powder particles disintegrate, releasing smaller particles and resulting in the small peak. Since the boron nitride was not exfoliated, the spray granulation process could not produce dense spheres, preventing the thicker boron nitride particles from making good contact and hindering further densification during sintering. Therefore, the resulting spheres have a larger median particle size and exhibit a small peak. Furthermore, combined with the scanning electron microscope image of the boron nitride powder prepared in Comparative Example 1, the surface of the spheres in the boron nitride powder is rough and contains numerous pores.

[0077] See Figure 2 and Figure 3 , Figure 2 This is a scanning electron microscope image of the boron nitride all-ceramic particles prepared in Comparative Example 2. Figure 3 This shows the particle size distribution of the boron nitride all-ceramic particles prepared in Example 1 and Comparative Example 2, respectively. From... Figure 2 As can be seen from the above, in the boron nitride all-ceramic particles prepared in Comparative Example 2, the surface of the spherical particles is rough and has large pores. This is because at a low heating and cooling rate, the particle grains are at a low temperature for a long time. During this process, the grains mature, and small particles are redeposited inside the large particles, leaving the original positions of the small particles vacant, thus forming voids.

[0078] At the same time, and combined with Figure 3 As can be seen from the data, the boron nitride material prepared in Comparative Example 2 exhibits a bimodal particle size distribution, with the smaller peak at 3.3 micrometers and the larger peak at a median particle size of 43.6 micrometers. This indicates that the particles broke apart, and some of the smaller boron nitride particles were released.

[0079] Thermal conductivity tests were performed on the boron nitride all-ceramic particles prepared in Example 1 and Comparative Example 2, respectively. Specifically, an appropriate amount of boron nitride all-ceramic particles were mixed with polydimethylsiloxane (PDMS), cured to obtain the test body, and its thermal conductivity was measured. The thermal conductivity of the boron nitride all-ceramic particles was also tested at different filling ratios. The test results are shown below. Figure 4 The filling rate refers to the percentage of the mass of boron nitride ceramic particles relative to the mass of the test sample.

[0080] from Figure 4As can be seen, under the same conditions, with the increase of the filling rate, when the filling rate is greater than 50%, the thermal conductivity of the boron nitride all-ceramic particles prepared in Example 1 gradually increases, and the thermal conductivity is correlated with the filling rate. When the filling rate is 70%, its thermal conductivity can reach 10.7 W / m·K. However, the boron nitride material prepared in Comparative Example 2 shows a negative growth phenomenon when the filling rate is greater than 50%. This is because the pores in the boron nitride material particles in Comparative Example 2 are larger. With the increase of the filling rate, the organic matter cannot be effectively filled, resulting in voids and a decrease in thermal conductivity.

[0081] This application observed the boron nitride all-ceramic particles prepared in Examples 2 and 3 using a scanning electron microscope. A small number of pores appeared locally on the surface of the spheres, but the overall density was high.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended 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 to the technical solutions of the present invention should not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing boron nitride all-ceramic particles, characterized in that, include: A two-dimensional boron nitride dispersion is provided, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and an organic solvent; An organic binder was added to the two-dimensional boron nitride dispersion to obtain a mixture; The mixture was granulated by spray drying to obtain the precursor; The precursor is pre-sintered in an oxygen-containing atmosphere to remove the organic binder from the precursor, thereby obtaining an intermediate. In an inert atmosphere, the intermediate is sintered by Joule heating to obtain boron nitride all-ceramic particles. The sintering temperature of the Joule heating is 1500-2500℃, the heating rate of the Joule heating is 500-10000℃ / min, and the sintering time is 10-1000s.

2. The method for preparing boron nitride all-ceramic particles as described in claim 1, characterized in that, The pre-sintering temperature is 400~700℃.

3. The method for preparing boron nitride all-ceramic particles as described in claim 1, characterized in that, The organic binder includes at least one of polyurethane, epoxy resin, polyvinyl alcohol, polyvinyl butyrate, polyvinylpyrrolidone, polymethyl methacrylate, polydimethylsiloxane, polyvinylidene fluoride, or polytetrafluoroethylene.

4. The method for preparing boron nitride all-ceramic particles as described in claim 1, characterized in that, The mass of the organic binder is 0.1-5% of the mass of the two-dimensional boron nitride nanosheets.

5. A boron nitride all-ceramic particle, characterized in that, The boron nitride all-ceramic particles comprise multiple interconnected two-dimensional boron nitride nanosheets.

6. The boron nitride all-ceramic particles as described in claim 5, characterized in that, The median particle size of the boron nitride all-ceramic particles is 5~500μm.

7. The boron nitride all-ceramic particles as described in claim 5, characterized in that, The bulk density of the boron nitride all-ceramic particles is 0.3~0.7 g / cm³. 3 .

8. The application of boron nitride all-ceramic particles as described in any one of claims 5 to 7 in electronic devices.

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