Self-assembled spherical boron nitride and preparation method thereof

Abstract

The invention discloses a kind of self-assembled spherical boron nitride and preparation method thereof, the method comprises: silicon dioxide and boron powder are fully ground and mixed, obtain boron-containing precursor;The boron-containing precursor obtained is placed under growth substrate, after being warmed up to 1400 ℃~1500 ℃ in inert gas flow, inert gas flow is switched to ammonia, after carrying out ammoniation treatment at 1400 ℃~1500 ℃, ammonia is switched to inert gas flow and is cooled to room temperature, and white self-assembled spherical boron nitride is loaded on the growth substrate surface. The present invention solves the problem that prior art needs to carry out carbon removal treatment to product, and process is cumbersome, and high temperature operation has higher requirements for equipment. The spherical boron nitride of the present invention is self-assembled into spherical by sheet-like structure boron nitride, forms 0-dimensional 2-dimensional hierarchical structure, can give full play to the respective advantages of sheet-like and spherical structure and multidimensional synergy. The present invention has simple process, and high-purity spherical boron nitride can be obtained without impurity removal.

Description

Technical Field

[0001] The invention relates to a preparation method of boron nitride, in particular to self-assembled spherical boron nitride and a preparation method thereof. Background Art

[0002] Hexagonal boron nitride (h-BN) has low density, large specific surface area, high mechanical strength, and excellent thermal properties. In particular, compared to metal fillers and carbon-based nanomaterials, boron nitride has excellent electrical insulation properties. Because it can significantly improve the mechanical and thermal properties of polymers without changing their electrical properties, it has been widely used in electronics / optoelectronics, catalysis, energy storage and conversion, sensor and electronic product development, nanocomposites, and other fields.

[0003] Boron nitride has a range of structures, such as zero-dimensional spheres, one-dimensional tubes, rods, and two-dimensional sheets. Among the different structures, spherical BN has received special attention due to its isotropy. h-BN is a typical layered material, and crystal growth tends to grow laterally along the (002) plane rather than along the thickness direction. Therefore, it is difficult for h-BN to grow in an arched shape and form isotropic spherical particles. Compared with the preparation of rods, tubes, and sheets, there are fewer reports on the synthesis of spherical boron nitride. Most studies use toxic reactants, expensive equipment, or complex synthesis conditions.

[0004] The existing technology for preparing spherical boron nitride usually requires the introduction of carbon-containing materials for carbon thermal reduction at high temperature, and in order to obtain a high-purity product, the product must ultimately be decarbonized. The process is cumbersome and requires high equipment requirements to operate at high temperature. Summary of the Invention

[0005] The purpose of the present invention is to provide a self-assembled spherical boron nitride and a preparation method thereof, which solves the problems of the prior art that the product needs to be decarbonized, the process is cumbersome, and the high-temperature operation requires high equipment requirements. The three-dimensional spherical boron nitride formed by the self-assembly of flake boron nitride has a 0-dimensional to 2-dimensional hierarchical structure, which can give full play to the respective advantages of the flake and spherical structures and the multi-dimensional synergistic effect.

[0006] In order to achieve the above object, the present invention provides a method for preparing self-assembled spherical boron nitride, which comprises:

[0007] (1) grinding and mixing silicon dioxide and boron powder to obtain a boron-containing precursor;

[0008] (2) The obtained boron-containing precursor is placed under a growth substrate, and after heating to 1400°C to 1500°C in an inert gas flow, the inert gas flow is switched to ammonia gas, and an ammoniation treatment is performed at 1400°C to 1500°C. After the reaction is completed, the ammonia gas is switched to an inert gas flow and cooled to room temperature, and white self-assembled spherical boron nitride is loaded on the surface of the growth substrate, and the molar ratio of the silicon dioxide to the boron powder is 1: (5 to 20).

[0009] The main factors influencing this method include the ammoniating temperature and the ratio of silica to boron powder. Different ammoniating temperatures affect the degree of boron source reaction. Temperatures between 1400°C and 1500°C are beneficial for boron source reaction, promoting a higher degree of reaction and improving product purity. However, temperatures too high cannot withstand the high temperatures on the growth substrate, preventing the product from depositing on the substrate to form the desired product. The molar ratio of silica to boron powder is 1:(5-20). Boron powder provides more active material at the ammoniating temperature, allowing larger flake boron nitride to be loaded onto the self-assembled spherical boron nitride. When the boron powder ratio is too high, silica and boron powder cannot generate sufficient active boron source to react with ammonia at high temperatures. Similarly, when silica is excessive, it also fails to generate sufficient active boron source to react with ammonia, preventing the formation of self-assembled spherical boron nitride with a 0- to 2-dimensional hierarchical structure.

[0010] Preferably, the molar ratio of silicon dioxide to boron powder is 1:(10-20). Preferably, the growth substrate is a high-purity aluminum oxide sheet or a SiO2 / Si sheet.

[0011] Preferably, the inert gas flow is nitrogen, argon, helium, neon or radon, and its flow rate is 100 sccm.

[0012] Preferably, the heating rate is 1-15°C / min.

[0013] Preferably, the flow rate of the ammonia gas is 100 sccm.

[0014] Preferably, the ammoniation treatment lasts for 1 to 10 hours.

[0015] The present invention provides a self-assembled spherical boron nitride prepared by the preparation method.

[0016] Preferably, the particle size of the self-assembled spherical boron nitride is 2 μm.

[0017] Preferably, the surface of the self-assembled spherical boron nitride is uniformly loaded with boron nitride having a flake structure.

[0018] The self-assembled spherical boron nitride and its preparation method of the present invention solve the problems of the prior art in that the product needs to be subjected to carbon removal treatment, the process is cumbersome, and the high-temperature operation requires high equipment requirements. It has the following advantages:

[0019] 1. The spherical boron nitride of the present invention is self-assembled into spheres by boron nitride with a flake structure, forming a 0-dimensional to 2-dimensional hierarchical structure, which can give full play to the respective advantages of the flake and spherical structures and the multi-dimensional synergy.

[0020] 2. The present invention has a simple process and can obtain high-purity spherical boron nitride without impurity removal. It provides a simple and efficient method for synthesizing spherical boron nitride without the use of toxic reactants, improves the performance of the material and broadens the application of boron nitride materials in the field of functional composite materials. It has important application prospects in the field of functional composite materials and provides a basis for the large-scale preparation of high-quality, high-purity spherical boron nitride. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a 3.00kx SEM image of the sample prepared in Example 1 of the present invention.

[0022] Figure 2 This is a 20.0kx SEM image of the sample prepared in Example 1 of the present invention.

[0023] Figure 3 This is the X-ray diffraction (XRD) pattern of the sample prepared in Example 1 of the present invention.

[0024] Figure 4 This is the Fourier transform infrared (FTIR) spectrum of the sample prepared in Example 1 of the present invention.

[0025] Figure 5 This is a 10.0kx SEM image of a sample prepared in Example 2 of the present invention.

[0026] Figure 6 This is a 5.00kx SEM image of a sample prepared in Example 3 of the present invention.

[0027] Figure 7 5.00kx SEM image of the sample prepared for Comparative Example 1 of the present invention.

[0028] Figure 8 This is a 3.00kx SEM image of a sample prepared for Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing self-assembled spherical boron nitride, the method comprising:

[0032] (1) Preparing a boron-containing precursor: grinding and mixing silicon dioxide and boron powder in a molar ratio of 1:10 to obtain a boron-containing precursor;

[0033] (2) Ammoniated treatment: The obtained boron-containing precursor is placed in an alumina crucible, and a high-purity alumina sheet is placed in the alumina crucible. After continuously heating to 1400°C at a heating rate of 2°C / min in a nitrogen atmosphere with a flow rate of 100 sccm, the nitrogen is switched to 100 sccm ammonia and the ammoniated treatment is carried out at 1400°C for 1 hour. After the reaction is completed, the ammonia is switched to 100 sccm nitrogen and cooled to room temperature. The high-purity alumina sheet is taken out, and the surface of the high-purity alumina sheet is covered with a white substance, which is self-assembled spherical boron nitride.

[0034] Example 2

[0035] A preparation method of self-assembled spherical boron nitride is basically the same as that in Example 1, except that:

[0036] In step (1), the molar ratio of silicon dioxide to boron powder is adjusted from 1:10 to 1:5.

[0037] Example 3

[0038] A preparation method of self-assembled spherical boron nitride is basically the same as that in Example 1, except that:

[0039] In step (1), the molar ratio of silicon dioxide to boron powder is adjusted from 1:10 to 1:20; in step (2), the amination time is adjusted from 1400°C to 1500°C.

[0040] Comparative Example 1

[0041] A preparation method of self-assembled spherical boron nitride is basically the same as that in Example 1, except that:

[0042] In step (2), the amination temperature is changed to 1300° C., and the other steps are the same as those in Example 1, thereby obtaining a self-assembled spherical boron nitride-supported flake boron nitride structure.

[0043] Comparative Example 2

[0044] A preparation method of self-assembled spherical boron nitride is basically the same as that in Example 2, except that:

[0045] In step (2), the amination temperature is changed to 1300° C., and the other steps are the same as those in Example 2, thereby obtaining a self-assembled spherical boron nitride-supported flake boron nitride structure.

[0046] Example 1 Characterization of Self-Assembled Spherical Boron Nitride

[0047] The self-assembled spherical boron nitride prepared in Examples 1 and 2 and the products prepared in Comparative Examples 1 and 2 were observed using a scanning electron microscope, and subjected to X-ray diffraction and Fourier transform infrared analysis.

[0048] like Figure 1 As shown in FIG. 3.00kx SEM image of the sample prepared in Example 1 of the present invention. Figure 1 It can be seen that in Example 1, a large amount of spherical boron nitride is generated.

[0049] like Figure 2 As shown in FIG. 20.0kx SEM image of the sample prepared in Example 1 of the present invention. Figure 2 It can be seen that the surface of the spherical boron nitride in Example 1 also carries boron nitride with a flake structure.

[0050] like Figure 3 As shown, the X-ray diffraction (XRD) pattern of the sample prepared in Example 1 of the present invention, wherein the horizontal axis is 2θ and the vertical axis is intensity. Figure 3 It can be seen that the peaks at 26.6°, 41.8°, 54.1°, and 76.1° belong to the diffraction of hexagonal BN (JCPDS card number 34-0421), (002), (100), (004), and (110) planes, respectively. The appearance of the sharp main peaks (002) and (110) plane order-related peaks indicates that the synthesized spherical BN crystals are relatively well crystalline.

[0051] like Figure 4 As shown in FIG. , the Fourier transform infrared (FTIR) spectrum of the sample prepared in Example 1 of the present invention, wherein the horizontal axis is the wave number and the vertical axis is the transmittance. Figure 4 It can be seen that the FTIR spectrum of spherical BN has two locations at 798 cm -1 and 1375cm -1 The sharp peaks of are due to the out-of-plane bending vibration of BNB bond and the in-plane stretching vibration mode of BN bond. -1 The peak appearing nearby can be attributed to the OH bond, proving the existence of -OH groups.

[0052] like Figure 5 As shown in FIG. 1 , the 10.0kx SEM image of the sample prepared in Example 2 of the present invention. Figure 5 It can be seen that a large amount of spherical boron nitride is generated in Example 2. Compared with Example 1, the difference of Example 2 is mainly that a smaller proportion of boron source is added, and the size of the flake boron nitride supported on the self-assembled spherical boron nitride is smaller.

[0053] like Figure 6 As shown in FIG. 5.00kx SEM image of the sample prepared in Example 3 of the present invention. Figure 6It can be seen that a large amount of spherical boron nitride is generated in Example 3. Compared with Example 1, the difference of Example 3 mainly lies in the addition of a larger proportion of boron source and a higher amination temperature, which further increases the size of the flake boron nitride supported on the self-assembled spherical boron nitride.

[0054] like Figure 7 As shown in FIG. 5, the 5.00kx SEM image of the sample prepared in Comparative Example 1 of the present invention. Figure 6 It can be seen that in Comparative Example 1, spherical boron nitride is generated, but impurities are also generated.

[0055] like Figure 8 As shown in FIG. 3.00kx SEM image of the sample prepared in Comparative Example 2 of the present invention. Figure 7 It can be seen that in Comparative Example 2, spherical boron nitride is generated, but a large amount of impurities are generated.

[0056] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing self-assembled spherical boron nitride, characterized in that: The method includes: (1) grinding and mixing silicon dioxide and boron powder to obtain a boron-containing precursor; (2) placing the obtained boron-containing precursor under a growth substrate, heating it to 1400°C to 1500°C in an inert gas flow, switching the inert gas flow to ammonia gas, and performing an ammonia treatment at 1400°C to 1500°C. After the reaction is completed, switching the ammonia gas to an inert gas flow and cooling it to room temperature, white self-assembled spherical boron nitride is loaded on the surface of the growth substrate; The molar ratio of the silicon dioxide to the boron powder is 1:(5-20).

2. The preparation method according to claim 1, characterized in that The molar ratio of the silicon dioxide to the boron powder is 1:(10-20).

3. The preparation method according to claim 1, characterized in that The growth substrate is a high-purity aluminum oxide sheet or a SiO2 / Si sheet.

4. The preparation method according to claim 1, characterized in that The inert gas flow is nitrogen, argon, helium, neon or radon, and its flow rate is 100 sccm.

5. The preparation method according to claim 1, characterized in that The heating rate is 1-15°C / min.

6. The preparation method according to claim 1, characterized in that The flow rate of the ammonia gas is 100 sccm.

7. The preparation method according to claim 1, characterized in that The time of the ammoniation treatment is 1 to 10 hours.

8. A self-assembled spherical boron nitride prepared by the preparation method according to any one of claims 1 to 7.

9. The self-assembled spherical boron nitride according to claim 8, characterized in that: The particle size of the self-assembled spherical boron nitride is 2 μm.

10. The self-assembled spherical boron nitride according to claim 8, characterized in that: The surface of the self-assembled spherical boron nitride is uniformly loaded with boron nitride with a flake structure.

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