Two-dimensional boron nitride all-ceramic membranes, methods of making and applications thereof

Abstract

This application provides a two-dimensional boron nitride all-ceramic membrane, its preparation method, and its application. The preparation method includes: providing a two-dimensional boron nitride dispersion, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and a solvent; processing the two-dimensional boron nitride dispersion using a wet forming technique to obtain a first membrane; applying pressure to the first membrane to obtain a second membrane; and subjecting the second membrane to Joule heating sintering at a temperature of 1500℃~2500℃ for a sintering time of 10~3000s to obtain the two-dimensional boron nitride all-ceramic membrane. The two-dimensional boron nitride all-ceramic membrane provided in this application comprises a plurality of stacked two-dimensional boron nitride nanosheets, adjacent two-dimensional boron nitride nanosheets being directly connected and bonded together by sintering. The membrane provided in this application eliminates the need for polymer materials introduced in the prior art, resulting in the two-dimensional boron nitride all-ceramic membrane in this application having excellent thermal conductivity.

Description

Technical Field

[0001] This application relates to the technical field of thermally conductive materials, and in particular to a two-dimensional boron nitride all-ceramic film, its preparation method and application. Background Technology

[0002] Currently, 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, two-dimensional boron nitride is composed 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, composite materials are mainly produced by mixing two-dimensional boron nitride with organic polymers (such as resins), with the two-dimensional boron nitride crosslinked within the organic polymer. However, the addition of organic polymers limits the performance of the composite materials, resulting in lower thermal conductivity and lower durability. Summary of the Invention

[0004] In view of this, this application provides a two-dimensional boron nitride all-ceramic membrane, its preparation method and application.

[0005] To achieve the above objectives, this application provides a method for preparing a two-dimensional boron nitride all-ceramic membrane. The method includes: providing a two-dimensional boron nitride dispersion, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and a solvent; processing the two-dimensional boron nitride dispersion using a wet forming technique to obtain a first membrane; applying pressure to the first membrane to obtain a second membrane; and subjecting the second membrane to Joule heating sintering at a sintering temperature of 1500℃~2500℃ and a sintering time of 10~3000s to obtain the two-dimensional boron nitride all-ceramic membrane.

[0006] In some embodiments, the heating rate of the Joule heating sintering is 100–10000 °C / min.

[0007] In some embodiments, the cooling rate of the Joule heating sintering is 100–10000 °C / min.

[0008] In some embodiments, the concentration of the two-dimensional boron nitride nanosheets in the two-dimensional boron nitride dispersion is 0.1–20 mg / ml.

[0009] In some embodiments, the solvent includes at least one selected from water, ethanol, isopropanol, ethyl acetate, isoamyl acetate, toluene, xylene, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0010] In some embodiments, the pressure applied to the first membrane is 10 to 500 MPa, and the pressure holding time is 0.5 to 30 min.

[0011] This application also provides a two-dimensional boron nitride all-ceramic membrane.

[0012] In some embodiments, the density of the two-dimensional boron nitride all-ceramic film is 1.8–2.25 g / cm³. 3 .

[0013] In some embodiments, the thickness of the two-dimensional boron nitride all-ceramic film is 0.015–2 mm.

[0014] This application also provides an application of a two-dimensional boron nitride all-ceramic membrane in sensors or energy storage devices.

[0015] The two-dimensional boron nitride all-ceramic membrane provided in this application includes several stacked two-dimensional boron nitride nanosheets. Adjacent two-dimensional boron nitride nanosheets are bonded by sintering, thereby eliminating the need for polymer materials introduced in the prior art. This results in the two-dimensional boron nitride all-ceramic membrane in this application having excellent thermal conductivity and durability. Attached Figure Description

[0016] Figure 1 A scanning electron microscope image of a two-dimensional boron nitride all-ceramic film provided in Embodiment 1 of this application.

[0017] Figure 2 This is a scanning electron micrograph of the cross-section of the two-dimensional boron nitride all-ceramic film prepared in Example 1 of this application.

[0018] Figure 3 This is a scanning electron micrograph of the membrane prepared from unpeeled boron nitride in Comparative Example 1 of this application.

[0019] Figure 4 This is a scanning electron micrograph of the two-dimensional boron nitride all-ceramic film prepared in Comparative Example 2 of this application.

[0020] Figure 5 This is a scanning electron micrograph of the two-dimensional boron nitride all-ceramic film prepared in Example 3 of this application. Detailed Implementation

[0021] 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 two-dimensional boron nitride all-ceramic film comprising a plurality of stacked two-dimensional boron nitride nanosheets (see...). Figure 1 and Figure 2 Adjacent two-dimensional boron nitride nanosheets are connected by sintering bonding, meaning that the grain boundaries between adjacent two-dimensional boron nitride nanosheets fuse, and some adjacent two-dimensional boron nitride nanosheets are bonded together through fusion, improving the density of the contact between adjacent two-dimensional boron nitride nanosheets. Meanwhile, the two-dimensional boron nitride all-ceramic film provided in this application eliminates the need for polymer materials introduced in the prior art, resulting in a two-dimensional boron nitride all-ceramic film with excellent thermal conductivity and durability.

[0024] Two-dimensional materials refer to materials with strong interatomic interactions within a single layer and weak interatomic interactions between different layers, resulting in 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.

[0025] In some embodiments, the density of the two-dimensional boron nitride all-ceramic film is 1.8–2.25 g / cm³. 3 In some embodiments, the density of the two-dimensional boron nitride all-ceramic film is 2.15–2.25 g / cm³. 3 For example, 2.15g / cm 3 The two-dimensional boron nitride all-ceramic film prepared in this application has a high density, reaching the theoretical density of boron nitride (2.17 g / cm³). 3 95% of ).

[0026] In some embodiments, the thickness of the two-dimensional boron nitride all-ceramic film is 0.015–2 mm, such as 0.015 mm, 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, or 2 mm. The thickness of the two-dimensional boron nitride all-ceramic film provided in this application can reach the millimeter level.

[0027] The two-dimensional boron nitride nanosheets have an in-plane diameter of 10–500 nm and a thickness of 3–50 nm. Preferably, the in-plane diameter is 200–500 nm and the thickness is 3–20 nm. The in-plane diameter refers to the lateral dimension of the nanosheet.

[0028] Two-dimensional boron nitride all-ceramic films have excellent thermal conductivity [e.g., 40–200 W / (m·K)].

[0029] This application also provides a method for preparing a two-dimensional boron nitride all-ceramic membrane, the method comprising:

[0030] S1. Provides a two-dimensional boron nitride dispersion, which includes two-dimensional boron nitride nanosheets and a solvent.

[0031] Two-dimensional boron nitride nanosheets can be obtained from boron nitride via mechanochemical methods. Mechanochemical methods include ball milling, ultrasonication, or high-speed shearing.

[0032] In some embodiments, the solvent includes at least one selected from water, ethanol, isopropanol, ethyl acetate, isoamyl acetate, toluene, xylene, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0033] In some embodiments, the concentration of two-dimensional boron nitride nanosheets in the two-dimensional boron nitride dispersion is 0.1–20 mg / ml. In some embodiments, the concentration of two-dimensional boron nitride nanosheets is 0.1–1 mg / ml to facilitate subsequent wet molding technology.

[0034] In some embodiments, the solvent includes at least one selected from water, ethanol, isopropanol, ethyl acetate, isoamyl acetate, toluene, xylene, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0035] S2. A two-dimensional boron nitride dispersion is processed using a wet molding technique to obtain a first film.

[0036] In some embodiments, wet forming techniques include at least one of vacuum filtration, blade coating, calendering, spraying, stretching, injection molding, or printing. In some embodiments, the first membrane is formed using vacuum filtration or spraying.

[0037] A two-dimensional boron nitride dispersion was prepared into a first film so that the two-dimensional boron nitride nanosheets in the first film have a certain degree of orientation.

[0038] S3. Apply pressure to the first membrane to obtain the second membrane.

[0039] Pressure is applied to the first membrane using pressure processing technology, which includes at least one of uniaxial cold isostatic pressing, cold isostatic pressing, or hot isostatic pressing.

[0040] In some embodiments, the pressure applied to the first membrane is 10–500 MPa, and the holding time is 0.5–30 min. By applying a vertical force to the first membrane, the density of the first membrane is increased, and the two-dimensional boron nitride nanosheets in the first membrane have a higher degree of horizontal orientation, that is, the two-dimensional boron nitride nanosheets extend along the direction of the surface of the first membrane.

[0041] Because two-dimensional boron nitride nanosheets have fewer atomic layers and possess high intrinsic flexibility and processability, the second film obtained through pressure processing technology has a high degree of orientation. This is beneficial for increasing the contact density between the two-dimensional boron nitride nanosheets and giving them a higher relative density. This facilitates the reduction of the atomic migration barrier in boron nitride during subsequent high-temperature Joule thermal sintering, thereby increasing the atomic mobility and promoting Joule thermal sintering, which in turn improves the density of the sintered product.

[0042] S4. The second membrane is subjected to Joule heating sintering at a temperature of 1500℃~2500℃ for a time of 10~3000s to obtain a two-dimensional boron nitride all-ceramic membrane.

[0043] The two-dimensional boron nitride all-ceramic film comprises several stacked two-dimensional boron nitride nanosheets, with adjacent two-dimensional boron nitride nanosheets directly connected and bonded together by sintering.

[0044] The second membrane was sandwiched between two graphite felt sheets. The power was turned on, and the sintering temperature reached 1500℃~2500℃, with a holding time of 10~3000s. This allowed for rapid high-temperature sintering of the second membrane, ensuring the sintered product possessed a certain degree of density and structural integrity. Under this high-temperature sintering, a rearrangement and densification process of the two-dimensional boron nitride nanosheets was initiated. The crystallinity of the second membrane increased, and fusion occurred between the two-dimensional boron nitride nanosheets, improving the grain boundary contact between the sheets. The sheets were bonded together through sintering bonds, thus significantly reducing phonon heat dissipation and thereby improving the thermal conductivity of the two-dimensional boron nitride all-ceramic membrane.

[0045] Meanwhile, during the sintering process described above, the solvent in step S2 is completely removed by sintering, resulting in a two-dimensional boron nitride all-ceramic film containing only two-dimensional boron nitride. This avoids the introduction of polymer components and mitigates the low thermal stability of polymers. Furthermore, as a single-component material, the two-dimensional boron nitride all-ceramic film does not suffer from the problem of mismatched coefficients of thermal expansion caused by bonding with other materials. The two-dimensional boron nitride all-ceramic film provided in this application maintains good functionality and durability even under repeated high and low temperature shock environments. Due to the intrinsic thermal stability of boron nitride (around 800°C in air), and the fact that the operating temperature of the two-dimensional boron nitride all-ceramic film provided in this application exceeds 800°C, the film's durability is improved. It is also suitable for long-term use in high-humidity, strong acid and alkali environments.

[0046] In some embodiments, the two-dimensional boron nitride all-ceramic membrane provided in this application has good flexibility, with a bending radius of curvature between 1 and 10 mm; in some embodiments, the bending radius of curvature is between 1 and 4 mm. Compared with traditional ceramic sheets, the high flexibility of the two-dimensional boron nitride all-ceramic membrane gives it good mechanical shock resistance.

[0047] The resistivity of the graphite felt is 0.1-10Ω, preferably 0.5-5Ω; the specific heat capacity of the graphite felt is 500-2000J / (kg·K), preferably 700-1000J / (kg·K).

[0048] In some embodiments, the heating rate of Joule heating sintering is 100–10000 °C / min. At this high heating rate, low-temperature ripening of the second film during sintering can be prevented, as well as excessive growth of boron nitride grains and redeposition of small particles within larger particles leading to increased porosity. This ensures the compactness and structural integrity of the second film after sintering. In some embodiments, the heating rate is 100–3000 °C / min.

[0049] In some embodiments, the cooling rate of Joule heating sintering is 100–10000 °C / min. A higher cooling rate can prevent excessive boron nitride growth in the second film and prevent an increase in porosity during sintering, thus ensuring the compactness of the second film after sintering.

[0050] This application also provides an application of a two-dimensional boron nitride all-ceramic film in sensors or energy storage devices. The two-dimensional boron nitride all-ceramic film provided in this application has good flexibility, high thermal conductivity, and durability. It can be applied to devices with thermal conductivity requirements, such as 5G communication equipment, radio frequency devices, and high-speed communication devices. It also has potential application value in circuit boards and electronic packaging structures within sensors.

[0051] 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.

[0052] Example 1

[0053] 1g of boron nitride, 10g of xylene, 100g of 95% zirconia balls with a diameter of 10mm and 25g of 95% zirconia balls with a diameter of 1mm were placed together in a 250ml zirconia ball milling jar, sealed, and ball milled at 500rpm for 10 hours on a planetary ball mill to obtain a two-dimensional boron nitride dispersion.

[0054] The two-dimensional boron nitride dispersion was filtered by vacuum filtration at a pressure of -0.1 MPa, and then dried to obtain the first membrane.

[0055] The first membrane was compacted using cold uniaxial pressure at a pressure of 300 MPa for 10 minutes to obtain the second membrane.

[0056] The second film was sintered using the Joule heating method at a heating rate of 10,000 °C / min, with a sintering temperature of 1800 °C and a heat holding time of 30 s. Then, the film was cooled at a cooling rate of 10,000 °C / min and the sintering was terminated to obtain a two-dimensional boron nitride all-ceramic film.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 is that the Joule heating sintering method is used, and the heating rate and cooling rate are both 100℃ / min. The remaining steps are the same as in Example 1.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 is that Joule heating sintering is used, and the sintering holding time is 10 seconds. The remaining steps are the same as in Example 1.

[0061] Example 4

[0062] The difference between Example 4 and Example 1 is that Joule heating sintering is used, and the sintering holding time is 150 seconds. The remaining steps are the same as in Example 1.

[0063] Example 5

[0064] The difference between Example 5 and Example 1 is that Joule heating sintering is used, and the sintering temperature is 1600℃. The remaining steps are the same as in Example 1.

[0065] Example 6

[0066] The difference between Example 6 and Example 1 is that Joule heating sintering is used, and the sintering temperature is 2000℃. The remaining steps are the same as in Example 1.

[0067] Comparative Example 1

[0068] The difference between Comparative Example 1 and Example 1 is that the boron nitride in the boron nitride dispersion was not stripped.

[0069] 1g of boron nitride, 10g of xylene, 100g of 95% zirconia balls with a diameter of 10mm and 25g of 95% zirconia balls with a diameter of 1mm were placed together in a 250ml zirconia ball milling jar. After sealing, the mixture was ball milled at 500rpm for 0.5 hours in a planetary ball mill to obtain a boron nitride dispersion. In this step, ball milling for 0.5 hours did not cause the boron nitride to exfoliate and form two-dimensional boron nitride nanosheets.

[0070] Comparative Example 2

[0071] The difference between Comparative Example 2 and Example 1 is that Joule heating sintering was used, with both the heating rate and cooling rate being 1°C / min, while the remaining steps were the same as in Example 1.

[0072] See Figure 1 and Figure 2 This application describes scanning electron microscopy tests on the two-dimensional boron nitride all-ceramic film and its cross-section prepared in Example 1. From... Figure 1 As can be seen from this, the thin film exhibits a layered structure, with adjacent layers stacked together, showing high orientation and high density. From... Figure 2 As can be seen, the two-dimensional boron nitride nanosheets fuse to form a flat surface. At the same time, the film has a certain strength and flexibility, can achieve self-support, and exhibits a distinct ceramic texture.

[0073] Table 1. Test results of two-dimensional boron nitride all-ceramic films obtained at different heating and cooling rates.

[0074]

[0075] As shown in Table 1, in Example 1, the density of the second membrane prepared was 2.15 g / cm³, as measured by a density meter. 3 The theoretical density of boron nitride is 2.27 g / cm³. 3 This indicates that the second film has reached 95% of the theoretical density, demonstrating its high density. Furthermore, after sintering, the resulting two-dimensional boron nitride all-ceramic film also has a density of 2.15 g / cm³. 3 This indicates that the porosity did not increase significantly during the sintering process, and its structure has fewer defects; its thermal conductivity can reach 140 W / mK, indicating that it has a high thermal conductivity. During this sintering process, the two-dimensional boron nitride nanosheets undergo grain rearrangement, which improves the crystallinity and fuses the grain boundaries, reducing phonon scattering at the interface.

[0076] Under the same conditions as in Example 1, the second film obtained from the boron nitride dispersion prepared from unpeeled boron nitride in Comparative Example 1 had a lower density than the second film obtained in Example 1. This indicates that unpeeled boron nitride cannot produce a densed preform. See also... Figure 3In Comparative Example 1, the sintered film surface exhibits a porous structure, indicating poor sintering and numerous obvious structural defects. The low thermal conductivity of the sintered film in Comparative Example 1 suggests that boron nitride growth was limited during sintering, resulting in ineffective densification, poor structural strength, and an incomplete thermal network, thus contributing to the low thermal conductivity.

[0077] Comparing Examples 1-2 and Comparative Example 2, under the same conditions, different heating and cooling rates during the sintering process resulted in films with different thermal conductivity. (See also...) Figure 4 The two-dimensional boron nitride all-ceramic film prepared in Comparative Example 2 also exhibits a porous surface with large pores between layers, poor sintering, and obvious structural defects. In Comparative Example 2, the prepared two-dimensional boron nitride all-ceramic film has a lower density. This is due to the longer low-temperature sintering time for the second film grains at a lower heating / cooling rate. During the low-temperature process, boron nitride undergoes grain ripening, and small particles are redeposited within larger particles, leading to increased porosity. As shown in Table 1 above, at higher heating / cooling rates, the second film mainly undergoes grain fusion and rearrangement, reducing phonon scattering and thus improving thermal conductivity.

[0078] Table 2. Test results of two-dimensional boron nitride all-ceramic films obtained at different sintering times and temperatures.

[0079]

[0080]

[0081] Table 2 shows that, based on Examples 1 and 3-4, the density and thermal conductivity of the two-dimensional boron nitride all-ceramic film are relatively high under different sintering times. It also indicates that different sintering times affect the density and thermal conductivity of the two-dimensional boron nitride all-ceramic film. (See also...) Figure 5 The two-dimensional boron nitride all-ceramic film prepared in Example 3 has a smooth surface, and the two-dimensional boron nitride nanosheets are fused together, exhibiting good compactness.

[0082] Table 2 shows that, according to Examples 1 and 5-6, the density and thermal conductivity of the two-dimensional boron nitride all-ceramic film are similar at sintering temperatures of 1800℃ and 2000℃. Both temperatures exhibit good density, and higher temperatures have a smaller impact on increasing the density of the two-dimensional boron nitride all-ceramic film. Compared to the sintering temperature of 1800℃ in Example 1, the density and thermal conductivity of the two-dimensional boron nitride all-ceramic film slightly decrease at the sintering temperature of 1600℃ in Example 5. This indicates that the sintering temperature affects the density and thermal conductivity of the two-dimensional boron nitride all-ceramic film. Compared to Example 1, this application also uses Joule heating sintering at temperatures below 1500℃, and it was found that two-dimensional boron nitride does not sinter, making it difficult to obtain a two-dimensional boron nitride all-ceramic film.

[0083] 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 a two-dimensional boron nitride all-ceramic film, characterized in that, The preparation method includes: A two-dimensional boron nitride dispersion is provided, the two-dimensional boron nitride dispersion comprising two-dimensional boron nitride nanosheets and a solvent; The two-dimensional boron nitride dispersion was processed using a wet molding technique to obtain a first film. Pressure is applied to the first membrane to obtain the second membrane; The second membrane is subjected to Joule heating sintering at a heating rate of 100~10000℃ / min, a sintering temperature of 1500℃~2500℃, a sintering time of 10~150s, and then cooled at a cooling rate of 100~10000℃ / min to obtain the two-dimensional boron nitride all-ceramic membrane.

2. The method for preparing a two-dimensional boron nitride all-ceramic film as described in claim 1, characterized in that, In the two-dimensional boron nitride dispersion, the concentration of the two-dimensional boron nitride nanosheets is 0.1~20 mg / ml.

3. The method for preparing a two-dimensional boron nitride all-ceramic film as described in claim 1, characterized in that, The solvent includes at least one of water, ethanol, isopropanol, ethyl acetate, isoamyl acetate, toluene, xylene, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

4. The method for preparing a two-dimensional boron nitride all-ceramic film as described in claim 1, characterized in that, The pressure applied to the first membrane is 10~500 MPa, and the pressure holding time is 0.5~30 min.

5. A two-dimensional boron nitride all-ceramic membrane, characterized in that, The two-dimensional boron nitride all-ceramic film is obtained by the preparation method of the two-dimensional boron nitride all-ceramic film as described in any one of claims 1 to 4. The two-dimensional boron nitride all-ceramic film comprises a plurality of stacked two-dimensional boron nitride nanosheets, and adjacent two-dimensional boron nitride nanosheets are bonded together.

6. The two-dimensional boron nitride all-ceramic membrane as described in claim 5, characterized in that, The density of the two-dimensional boron nitride all-ceramic film is 1.8~2.25 g / cm³. 3 .

7. The two-dimensional boron nitride all-ceramic membrane as described in claim 5, characterized in that, The thickness of the two-dimensional boron nitride all-ceramic film is 0.015~2mm.

8. The application of a two-dimensional boron nitride all-ceramic membrane as described in any one of claims 5 to 7 in a sensor or energy storage device.

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