Hexagonal boron nitride and preparation method thereof
By controlling the mixing of nitrogen and boron sources and heat treatment, high-purity hexagonal boron nitride was prepared, solving the problems of residual impurities and high cost in existing technologies, and realizing the performance requirements of high-end applications and large-scale production.
Patent Information
- Application Number
- CN202511894734.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-02-06
AI Technical Summary
Existing hexagonal boron nitride synthesis technologies cannot simultaneously meet the requirements of high purity, anisotropic thermal conductivity, excellent insulation performance, and low cost. Traditional methods suffer from problems such as residual impurities, poor crystal quality, high production costs, and difficulty in scaling up production.
A preparation method is adopted, which includes mixing solid raw materials of nitrogen source and boron source, pressing to form a densified green body, heat treatment and acid washing treatment. By controlling the reaction conditions and subsequent treatment, high-purity hexagonal boron nitride is obtained.
It achieves precise control over carbon and metallic impurities, and produces hexagonal boron nitride with high purity, significant thermal conductivity and wide-temperature-range insulation properties, making it suitable for high-end electronic packaging and high-temperature devices. Moreover, the process is simple and easy to scale up.
Smart Images
Figure CN121470441A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of hexagonal boron nitride, and particularly relates to a kind of hexagonal boron nitride and its preparation method. BACKGROUND
[0002] Hexagonal boron nitride occupies a core position in the fields of high-end electronic packaging, high-temperature devices and semiconductor heat dissipation due to its excellent comprehensive performance. These application scenarios have strict requirements for its performance indicators. Specifically, high-purity h-BN needs to achieve strict impurity control, and there are clear low-content standards for common impurities such as carbon and metal. High-end applications require higher precision in impurity control. At the same time, it needs to have anisotropic thermal conductivity characteristics, with significant differences in in-plane and out-of-plane thermal conductivity performance, and needs to have excellent insulation performance, maintaining stable insulation level in a wide temperature range.
[0003] The inherent limitations of current mainstream hexagonal boron nitride synthesis technology are the core reasons for the substandard product performance and cost imbalance. Although the traditional carbon thermal reduction method has lower raw material cost, the product purity problem is prominent. It is difficult to achieve the index requirements of high-purity products, and the crystalline quality is poor.
[0004] Although the high-temperature solid-phase reaction method can reduce the impurity content to some extent, the process is complicated and the environmental pressure is high, increasing the processing cost. The product prepared by this method still has defects in morphology and performance. Although the chemical vapor deposition method can prepare high-quality thin films, it relies on special metal substrates and expensive precursors, and the growth conditions are harsh, resulting in high production cost. It is impossible to mass-produce products that meet the performance indicators. In addition, the subsequent stripping of the metal substrate can damage the structure of the thin film and destroy its in-plane efficient thermal conductivity advantage.
[0005] Although there have been some progress in the exploration of solvothermal method and template method in morphology control, it is difficult to meet the performance and industrialization needs. The reaction conditions of the two methods are sensitive, the product yield is low and the stability is poor, and the particle size is difficult to control within the conventional range of high-quality products. The high cost of soft template and the complicated processing flow of hard template further increase the production cost. More importantly, the products prepared by these methods often have crystalline defects, and the insulation performance is difficult to meet the requirements of high-end applications, which cannot meet the standard of wide-temperature-range insulation performance for electronic packaging.
[0006] Therefore, the present application designs a kind of hexagonal boron nitride and its preparation method to solve the above problems. SUMMARY
[0007] In view of the above-mentioned shortcomings of the prior art, the present application provides a preparation method of hexagonal boron nitride, comprising the following steps: S1: Dry the solid raw materials in the nitrogen source and the boron source with a molar ratio of 1:1.05-1.10, mix them under inert atmosphere to obtain a mixed powder; S2: Transfer the mixed powder into a mold and press it to obtain a densified green body; S3: Under an inert atmosphere, the densified preform is transferred into a box-type resistance furnace, first heated to 180-220℃ and held, then heated to 400-700℃ and held, and then naturally cooled to room temperature to obtain a dense precursor. The dense precursor is then transferred to a graphite resistance furnace. Before being transferred to the graphite resistance furnace, the dense precursor is degassed, and under a positive pressure of 0.1-0.3MPa, heated to 1200-1400℃ and held, then heated to 1600-2000℃ and held to obtain boron nitride sintered blocks. S4: Cool the boron nitride sintered block, transfer it to a pulverizer, crush and sieve it, wash it with dilute nitric acid, then wash it with deionized water until the pH reaches 6.5-7.0, and dry it to obtain hexagonal boron nitride.
[0008] Furthermore, S1 specifically involves drying the solid raw materials in the nitrogen source and boron source at a molar ratio of 1:1.05-1.10 at 100-120℃ for 2-3 hours, then transferring them to a 3V type mixer and mixing them at 300-500 r / min for 2-4 hours under an inert atmosphere to obtain a mixed powder.
[0009] Furthermore, the nitrogen source is one of melamine, dicyandiamide, ammonium chloride, ammonia, or urea.
[0010] Furthermore, the boron source is one of boric acid, boron trioxide, borax, amorphous boron powder, boron trifluoride, or boron trichloride.
[0011] Furthermore, S2 specifically involves transferring the mixed powder into a mold, pressing it with a four-column hydraulic press at 10-20 MPa for 30-60 seconds to obtain a densed blank.
[0012] Furthermore, S3 specifically involves: under an inert atmosphere, transferring the densified preform into a box-type resistance furnace, first raising it to 180-220℃ at 5-8℃ / min and holding it for 1-2 hours, then raising it to 400-700℃ at 5-10℃ / min and holding it for 2-4 hours, and then allowing it to cool naturally to room temperature to obtain a dense precursor. The dense precursor is then transferred to a graphite resistance furnace. Before being transferred to the graphite resistance furnace, the dense precursor is first degassed at 1800-2000℃ for 1 hour under a positive pressure of 0.1-0.3MPa, raised to 1200-1400℃ at 10-15℃ / min and held for 1-2 hours, then raised to 1600-2000℃ at 5-8℃ / min and held for 3-6 hours to obtain boron nitride sintered blocks.
[0013] Furthermore, S4 specifically involves: reducing the temperature of the boron nitride sintered block to below 100°C at a rate of 5°C / min, transferring it to a pulverizer, and crushing it to D at a pressure of 0.6-0.8 MPa and a speed of 2000-4000 r / min. 50=1-5μm, sieved through a 400-1000 mesh vibrating screen, and acid-washed with 0.1-0.5mol / L dilute nitric acid at 60-80℃ for 1-2h at a solid-liquid ratio of 1:10-20, then washed with deionized water until pH 6.5-7.0, and dried at 600-700℃ for 2-4h to obtain hexagonal boron nitride.
[0014] A hexagonal boron nitride prepared according to the preparation method described above.
[0015] Compared with the prior art, the beneficial effects of this invention are as follows: 1. This invention effectively solves the problem of residual impurities in the products of traditional carbothermal reduction method, and achieves precise control over key impurities such as carbon and metals. The purity of the obtained hexagonal boron nitride meets the stringent requirements for ultrapure materials in high-end electronic packaging, semiconductor heat dissipation and other fields.
[0016] 2. The hexagonal boron nitride obtained by this invention has excellent crystal quality and significant anisotropic thermal conductivity. At the same time, it also has high dielectric strength and stable insulation performance over a wide temperature range. Even in high-temperature environments, it can maintain excellent insulation levels and can fully meet the performance requirements of high-end electronic packaging, high-temperature devices and other scenarios. Its low hardness and self-lubricating properties also expand its application potential in high-temperature bearings, mold release agents and other fields.
[0017] 3. The process of this invention is simple, easy to implement on a large scale, and the product morphology and performance are stable with controllable particle size. It not only meets the performance requirements of high-end applications, but also has the potential for large-scale production, and can stably supply hexagonal boron nitride products that meet the performance indicators. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.
[0019] Figure 1 The infrared spectrum of hexagonal boron nitride obtained in Example 1 of the present invention; Figure 2 The XRD pattern of hexagonal boron nitride obtained in Example 2 of the present invention; Figure 3 This is an electron microscope image of hexagonal boron nitride obtained in Example 1 of the present invention; Figure 4 This is an electron microscope image of hexagonal boron nitride obtained in Example 2 of the present invention; Figure 5 This is an electron microscope image of hexagonal boron nitride obtained in Example 3 of the present invention; Figure 6 This is an electron microscope image of the hexagonal boron nitride obtained in Example 4 of the present invention. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0021] Example 1: This example discloses a method for preparing hexagonal boron nitride, including the following steps: S1: The solid raw materials in the nitrogen source and boron source with a molar ratio of 1:1.10 are dried at 120°C for 3 hours, then transferred to a 3V type mixer and mixed at 500 r / min for 4 hours under an inert atmosphere to obtain a mixed powder. The nitrogen source is melamine; The boron source is boric acid; S2: The mixed powder is transferred to a mold (a blank disc mold with a diameter of 100 mm and a depth of 10 mm), and then pressed to obtain a dense blank by a four-column hydraulic press at 20 MPa for 60 seconds. S3: Under an inert atmosphere, the densified preform is transferred into a box-type resistance furnace. It is first heated to 220°C at 8°C / min and held for 2 hours, then heated to 700°C at 10°C / min and held for 4 hours. It is then allowed to cool naturally to room temperature to obtain a dense precursor. The dense precursor is then transferred to a graphite resistance furnace. Before being transferred to the graphite resistance furnace, the dense precursor is first degassed at 2000°C for 1 hour under a positive pressure of 0.3 MPa, heated to 1400°C at 15°C / min and held for 2 hours, then heated to 2000°C at 8°C / min and held for 6 hours to obtain boron nitride sintered blocks. S4: The boron nitride sintered block is cooled to below 100℃ at a rate of 5℃ / min, then transferred to a pulverizer and crushed to D at 0.8MPa and 4000r / min. 50 =1-5μm, sieved through a 400-1000 mesh vibrating screen, and acid-washed at 80℃ for 2h with 0.5mol / L dilute nitric acid at a solid-liquid ratio of 1:20. Then, it is washed with deionized water until the pH reaches 6.5-7.0, and dried at 700℃ for 4h to obtain hexagonal boron nitride.
[0022] Example 2: This example discloses a method for preparing hexagonal boron nitride, including the following steps: S1: The solid raw materials in the nitrogen source and boron source with a molar ratio of 1:1.05 are dried at 100°C for 2 hours, then transferred to a 3V type mixer and mixed at 300 r / min for 2 hours under an inert atmosphere to obtain a mixed powder. The nitrogen source is urea; The boron source is boron trichloride; S2: The mixed powder is transferred to a mold (a blank disc mold with a diameter of 100 mm and a depth of 10 mm), and then pressed to obtain a dense blank by a four-column hydraulic press at 10 MPa for 30 seconds. S3: Under an inert atmosphere, the densified preform is transferred into a box-type resistance furnace. The temperature is first raised to 180°C at 5°C / min and held for 1 hour. Then, the temperature is raised to 400°C at 5°C / min and held for 2 hours. The preform is then allowed to cool naturally to room temperature to obtain a dense precursor. The dense precursor is then transferred to a graphite resistance furnace. Before being transferred to the graphite resistance furnace, the preform is degassed at 1800°C for 1 hour under a positive pressure of 0.1 MPa. The temperature is then raised to 1200°C at 10°C / min and held for 1 hour. Then, the temperature is raised to 1600°C at 5°C / min and held for 3 hours to obtain boron nitride sintered blocks. S4: The boron nitride sintered block is cooled to below 100℃ at a rate of 5℃ / min, then transferred to a pulverizer and crushed to D at 0.6MPa and 2000r / min. 50 =1-5μm, sieved through a 400-1000 mesh vibrating sieve, and acid-washed at 60℃ for 1h with 0.1mol / L dilute nitric acid at a solid-liquid ratio of 1:10, then washed with deionized water until pH 6.5-7.0, and dried at 600℃ for 2h to obtain hexagonal boron nitride.
[0023] Example 3: The difference between this example and Example 2 is that the nitrogen source is dicyandiamide; The boron source is boron trioxide.
[0024] Example 4: The difference between this example and Example 2 is that the nitrogen source is ammonium chloride; The boron source is borax.
[0025] Example 5: The difference between this example and Example 2 is that the nitrogen source is ammonia; The boron source is amorphous boron powder.
[0026] Example 6: The difference between this example and Example 2 is that the nitrogen source is melamine; The boron source is boron trifluoride.
[0027] Characterization example: (1) The hexagonal boron nitride prepared in Example 1 was characterized by infrared spectroscopy, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that at 1359cm -1 and 808cm-1 There are two distinct characteristic absorption peaks at 1359 cm⁻¹. -1 The strong absorption peak at 808 cm⁻¹ is attributed to the in-plane stretching vibration of the BN bond in boron nitride, while the peak at 808 cm⁻¹ is attributed to the in-plane stretching vibration of the BN bond. -1 The absorption peak at that point corresponds to the out-of-plane bending vibration of the BNB bond. These two characteristic peaks are typical infrared signals of hexagonal boron nitride (h-BN), confirming the presence of a hexagonal crystal phase structure in the sample.
[0028] (2) The hexagonal boron nitride prepared in Example 2 was characterized by XRD, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that obvious diffraction peaks appeared at positions such as 2θ≈26.7°, 2θ≈41.6°, and 2θ≈55.1°. These peaks correspond to the (002), (100), and (004) crystal planes of hexagonal boron nitride (h-BN), respectively. Among them, the (002) crystal plane diffraction peak has high intensity and sharpness, indicating that the sample has a highly ordered layered crystal structure and good crystallinity.
[0029] (3) The hexagonal boron nitride samples from Examples 1-4 were characterized by microscopic features, and the electron microscope images are shown below. Figures 3-6 As shown in the figure, the particles are hexagonal-like plates with a lateral dimension of approximately 0.5–1.0 μm. The plates are predominantly randomly stacked with some agglomeration, and locally, curled / wrinkled edges are visible. The regularity of the hexagonal outlines suggests good crystallinity, and the absence of obvious impurity particles indicates high purity. The measured specific surface area is approximately 10–30 m². 2 / g, which conforms to the characteristics of high crystallinity h-BN.
[0030] Experimental example: The in-plane and out-of-plane thermal conductivity was tested according to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method". The dielectric strength was tested according to GB / T 29306.2-2012 "Methods for testing the dielectric properties of insulating materials at frequencies above 300 MHz - Part 2: Resonance method"; Volume resistivity was tested at room temperature and 1000℃ according to GB / T 31838 "Dielectric and resistive properties of solid insulating materials"; Mohs hardness is tested using a Mohs hardness tester. Carbon and iron content were determined according to GB / T 14849.4-2014 "Industrial Silicon Chemical Analysis Methods Part 4: Determination of Impurity Element Content"; The results are shown in the table below:
[0031] As shown in the table above, the hexagonal boron nitride prepared by this invention has high purity, meeting the demand for ultrapure materials in the electronics and semiconductor fields. Due to its layered crystal structure, it exhibits significant anisotropic thermal conductivity. The efficient conduction of phonons (heat carriers) by the covalent bonds within the layers results in a thermal conductivity of 300-400 W / (m·K). It has high dielectric strength, making it suitable for high-voltage applications. Even in a high-temperature environment of 1000℃, it can still maintain excellent insulation performance, meeting the insulation requirements of electronic packaging and high-temperature devices. With a Mohs hardness of only 1-2, the weak interlayer interactions allow the crystal layers to slide, giving it natural self-lubricating properties, supporting its application in high-temperature bearings, mold release agents, and other applications.
[0032] 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 foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing hexagonal boron nitride, characterized in that, Includes the following steps: S1: Dry the solid raw materials in the nitrogen source and boron source with a molar ratio of 1:1.05-1.10, mix them under an inert atmosphere to obtain a mixed powder; S2: Transfer the mixed powder into a mold and press it to obtain a densified green body; S3: Under an inert atmosphere, the densified preform is transferred into a box-type resistance furnace, first heated to 180-220℃ and held, then heated to 400-700℃ and held, and then naturally cooled to room temperature to obtain a dense precursor. The dense precursor is then transferred to a graphite resistance furnace. Before being transferred to the graphite resistance furnace, the dense precursor is degassed, and under a positive pressure of 0.1-0.3MPa, heated to 1200-1400℃ and held, then heated to 1600-2000℃ and held to obtain boron nitride sintered blocks. S4: Cool the boron nitride sintered block, transfer it to a pulverizer, crush and sieve it, wash it with dilute nitric acid, then wash it with deionized water until the pH reaches 6.5-7.0, and dry it to obtain hexagonal boron nitride.
2. The hexagonal boron nitride and its preparation method according to claim 1, characterized in that, S1 specifically involves drying the solid raw materials in the nitrogen source and boron source at a molar ratio of 1:1.05-1.10 at 100-120℃ for 2-3 hours, then transferring them to a 3V type mixer and mixing them at 300-500 r / min for 2-4 hours under an inert atmosphere to obtain a mixed powder.
3. The hexagonal boron nitride and its preparation method according to claim 1, characterized in that, The nitrogen source is one of melamine, dicyandiamide, ammonium chloride, ammonia, or urea.
4. The hexagonal boron nitride and its preparation method according to claim 1, characterized in that, The boron source is one of boric acid, boron trioxide, borax, amorphous boron powder, boron trifluoride, or boron trichloride.
5. The hexagonal boron nitride and its preparation method according to claim 1, characterized in that, S2 specifically involves transferring the mixed powder into a mold, pressing it with a four-column hydraulic press at 10-20 MPa for 30-60 seconds to obtain a densed blank.
6. The hexagonal boron nitride and its preparation method according to claim 1, characterized in that, S3 specifically involves: under an inert atmosphere, transferring the densified preform into a box-type resistance furnace, first raising it to 180-220℃ at 5-8℃ / min and holding it for 1-2 hours, then raising it to 400-700℃ at 5-10℃ / min and holding it for 2-4 hours, and then allowing it to cool naturally to room temperature to obtain a dense precursor. The dense precursor is then transferred to a graphite resistance furnace. Before being transferred to the graphite resistance furnace, the dense precursor is first degassed at 1800-2000℃ for 1 hour under a positive pressure of 0.1-0.3MPa, then raised to 1200-1400℃ at 10-15℃ / min and held for 1-2 hours, then raised it to 1600-2000℃ at 5-8℃ / min and held for 3-6 hours to obtain boron nitride sintered blocks.
7. The hexagonal boron nitride and its preparation method according to claim 1, characterized in that, S4 specifically involves: cooling the boron nitride sintered block to below 100°C at a rate of 5°C / min, transferring it to a pulverizer, and crushing it to D at 0.6-0.8 MPa and 2000-4000 r / min. 50 =1-5μm, sieved through a 400-1000 mesh vibrating screen, and acid-washed with 0.1-0.5mol / L dilute nitric acid at 60-80℃ for 1-2h at a solid-liquid ratio of 1:10-20, then washed with deionized water until pH 6.5-7.0, and dried at 600-700℃ for 2-4h to obtain hexagonal boron nitride.
8. A hexagonal boron nitride prepared by the preparation method according to any one of claims 1-7.