Preparation method of hexagonal boron nitride

Abstract

The invention relates to a preparation method of hexagonal boron nitride, which comprises the following steps: weighing boric acid and melamine, and mixing to obtain a mixture; drying the mixture to obtain a blocky mixture; crushing the blocky mixture to obtain mixed particles; briquetting the mixed particles to obtain blocks; sintering the blocky body to obtain a sintered block; crushing the sintered block to obtain boron nitride particles; and washing the boron nitride particles with water to obtain the hexagonal boron nitride, the sintering temperature is high and reaches 1900 DEG C. And through a graded sintering mode, temperature rise and energy consumption utilization are effectively controlled, and the requirements for materials and tolerance of equipment in the sintering graded temperature rise process are met.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical engineering, and in particular to a method for preparing hexagonal boron nitride. Background Art

[0002] Hexagonal boron nitride, also known as white graphite, is the simplest boron-nitrogen polymer. Similar to the hexagonal carbon network in graphite, nitrogen and boron in hexagonal boron nitride also form hexagonal network layers, overlapping each other to form crystals. Crystals are similar to graphite, with diamagnetic properties and high anisotropy. Boron nitride is mainly used in refractory materials, semiconductor solid-phase doping sources, atomic pile structural materials, neutron radiation-proof packaging materials, rocket engine components, high-temperature lubricants and release agents.

[0003] There are many traditional methods for synthesizing and preparing hexagonal boron nitride, but the products have certain defects, which are mainly reflected in: the thermal conductivity and heat resistance of the materials obtained by traditional processes are not high. During the sintering process, the sintering temperature directly affects the physical properties of hexagonal boron nitride. Increasing the sintering temperature can promote the formation of ZrB2 phase, thereby improving the densification, flexural strength and fracture toughness of the composite ceramic. Studies have shown that when the sintering temperature is 1900℃, the relative density, flexural strength and fracture toughness of the material reach the highest values, which are 95.2%, 226.0MPa and 3.4MPa·m1 / 21 respectively. However, it is difficult to reach a sintering temperature of 1900℃ in the traditional preparation process. The main reason is that too high a sintering temperature will increase the energy consumption and cost of the equipment, because the high temperature environment has high requirements on the material and tolerance of the equipment. In addition, too high a temperature may cause uneven crystal growth, thereby affecting the performance of the material.

[0004] Therefore, a method for preparing hexagonal boron nitride is provided, which improves the sintering process, thereby solving the defects of low thermal conductivity and heat resistance in the prior art. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing hexagonal boron nitride with good thermal conductivity and heat resistance of the finished product, reasonable control of the overall sintering temperature curve, simple and easy operation of the overall process, low energy consumption and high yield, so as to overcome the defects in the prior art.

[0006] The technical solution of the present invention is achieved as follows: a method for preparing hexagonal boron nitride, the preparation method comprising the following steps:

[0007] S1, mixing boric acid and melamine to obtain a mixture;

[0008] S2, drying the mixed material to obtain a block mixture;

[0009] S3, crushing the block mixture to obtain mixed particles;

[0010] S4. Compress the mixed particles to obtain a block;

[0011] S5. Sinter the block to obtain a sintered block;

[0012] S6. Crush the sintered block to obtain boron nitride particles;

[0013] S7. Wash the boron nitride particles with water to obtain the hexagonal boron nitride.

[0014] Furthermore, in S1, the molar ratio of boric acid to melamine is 1:1 - 12.

[0015] Furthermore, in S2, the drying temperature is 200°C - 300°C, and the drying time is 6 - 9 hours.

[0016] Furthermore, in S3, the crushing particle size is 1 - 5 mm.

[0017] Furthermore, in S5, the sintering is carried out step by step. When the temperature rises to 600°C, sinter for 1.5 hours; when the temperature is 800°C, sinter for 1.5 hours; when the temperature is 1200°C, sinter for 1.5 hours; when the temperature is 1900°C, sinter for 3.5 hours.

[0018] Furthermore, in S6, the crushing is to first crush the sintered block with a rubber hammer and then put it into a hammer crusher for further crushing, and finally crush it into particles with a size of 3 - 5 mm.

[0019] Furthermore, in S7, the water washing is to place the boron nitride particles in a water washing tank, add pure water, heat it to 100°C, stir for 1 - 2 hours, and then filter and dry.

[0020] The present invention has the following positive effects: By mixing boric acid and melamine in a specific ratio and improving the sintering process method, the present invention solves the problems of low composite insulation thermal conductivity and heat resistance in the prior art. The overall process is simple, the product yield is high, the material has high thermal conductivity and heat resistance, and the sintering temperature is high, reaching 1900°C. Through the step-by-step sintering method, the temperature rise and energy consumption utilization are effectively controlled, meeting the requirements of the equipment material and tolerance during the step-by-step temperature rise of sintering. The crystal growth uniformity is effectively controlled, and the product performance is improved as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of the preparation method of hexagonal boron nitride of the present invention.

[0022] Figures 2 to 10 It is a scanning electron microscope image of the hexagonal boron nitride prepared by the present invention;

[0023] Figure 11 It is an XRD spectrum of the hexagonal boron nitride prepared by the present invention;

[0024] Figure 12 Partial parameter diagram of hexagonal boron nitride prepared by the present invention;

[0025] Figure 13 It is a temperature control curve diagram of the sintering process in the preparation method of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the following description of the invention, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating directions or positional relationships, are based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. The term "connection" only indicates the connection between devices and has no special meaning.

[0028] like Figure 1 , 13 As shown, a method for preparing hexagonal boron nitride comprises the following steps:

[0029] S1, mixing boric acid and melamine to obtain a mixture;

[0030] S2, drying the mixed material to obtain a block mixture;

[0031] S3, crushing the block mixture to obtain mixed particles;

[0032] S4, briquetting the mixed particles to obtain a block;

[0033] S5, sintering the block to obtain a sintered block;

[0034] S6, crushing the sintered block to obtain boron nitride particles;

[0035] S7. Wash the boron nitride particles with water to obtain the hexagonal boron nitride.

[0036] The molar ratio of boric acid to melamine in the S1 is 1:1-12. The drying temperature in the S2 is 200℃-300℃, and the drying time is 6-9 hours. The crushing particle size in the S3 is 1-5㎜. The sintering in the S5 is carried out in stages, and the temperature is raised to 600℃ for sintering for 1.5 hours, 800℃ for sintering for 1.5 hours, 1200℃ for sintering for 1.5 hours, and 1900℃ for sintering for 3.5 hours. The crushing in the S6 is to crush the sintered block with a rubber hammer and then put it into a hammer crusher for further crushing, and finally crush it into 3-5㎜ particles. The water washing in the S7 is to put the boron nitride particles in a water washing tank, add pure water and heat it to 100℃, stir for 1-2 hours, and then filter and dry.

[0037] The above-mentioned hexagonal boron nitride preparation method adopts a specific ratio of boric acid and melamine to mix, thereby solving the common problems of low thermal conductivity and heat resistance of composite insulation in the prior art, with high yield, high thermal conductivity and heat resistance of the material, and high sintering temperature, reaching 1900°C.

[0038] In the above-mentioned hexagonal boron nitride preparation method, the temperature increase and energy consumption are effectively controlled by graded sintering, which meets the material and tolerance requirements of the equipment during the graded sintering temperature increase process, effectively controls the uniformity of crystal growth, and improves the overall product performance.

[0039] The invention is further described below through specific examples.

[0040] Example 1: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0041] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 200°C and the drying time is 6 hours. The crushing particle size is 1 mm.

[0042] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0043] like Figures 2 - 5 This is a scanning electron microscope image of the hexagonal boron nitride prepared in the present invention. Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0044] Example 2: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0045] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 300°C, the drying time is 9 hours, and the crushing particle size is 5 mm.

[0046] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0047] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0048] Example 3: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0049] The molar ratio of boric acid to melamine is 1:6. The drying temperature is 250°C and the drying time is 8 hours. The crushing particle size is 3 mm.

[0050] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 4mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1.5 hours, and then filter and dry.

[0051] like Figures 6 - 10 This is a scanning electron microscope image of the hexagonal boron nitride prepared in the present invention. Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0052] Example 4: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0053] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 300°C, the drying time is 9 hours, and the crushing particle size is 5 mm.

[0054] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0055] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0056] Example 5: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0057] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 200°C, the drying time is 9 hours, and the crushing particle size is 5 mm.

[0058] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0059] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0060] Example 6: Figure 1 ,13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0061] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 300°C, the drying time is 6 hours, and the crushing particle size is 5 mm.

[0062] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0063] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0064] Example 7: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0065] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 300°C and the drying time is 9 hours. The crushing particle size is 1 mm.

[0066] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0067] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0068] Example 8: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0069] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 300°C, the drying time is 9 hours, and the crushing particle size is 5 mm.

[0070] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0071] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0072] Example 9: Figure 1 ,13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0073] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 300°C, the drying time is 9 hours, and the crushing particle size is 5 mm.

[0074] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0075] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0076] Example 10: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0077] The molar ratio of boric acid to melamine is 1:12. The drying temperature is 200°C, the drying time is 6 hours, and the crushing particle size is 1 mm.

[0078] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0079] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0080] Example 11: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0081] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 300°C and the drying time is 6 hours. The crushing particle size is 1 mm.

[0082] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0083] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0084] Example 12: Figure 1 ,13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0085] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 200°C, the drying time is 9 hours, and the crushing particle size is 1 mm.

[0086] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0087] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0088] Example 13: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0089] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 200°C, the drying time is 6 hours, and the crushing particle size is 5 mm.

[0090] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0091] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0092] Example 14: Figure 1 , 13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0093] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 200°C and the drying time is 6 hours. The crushing particle size is 1 mm.

[0094] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 5mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 1 hour, and then filter and dry.

[0095] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0096] Example 15: Figure 1 ,13 As shown, when preparing hexagonal boron nitride, firstly, the ingredients are mixed, and boric acid and melamine are weighed and mixed with an electronic balance to obtain a mixture; the mixture is dried to obtain a block mixture; the block mixture is crushed to obtain mixed particles; the mixed particles are pressed into blocks to obtain blocks; the blocks are sintered to obtain sintered blocks; the sintered blocks are crushed to obtain boron nitride particles; the boron nitride particles are washed with water to obtain the hexagonal boron nitride.

[0097] The molar ratio of boric acid to melamine is 1:1. The drying temperature is 200°C and the drying time is 6 hours. The crushing particle size is 1 mm.

[0098] Sintering is carried out in stages. It takes 0.5 hours for the temperature to rise from 0°C to 600°C, and then keep 600°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 800°C after 0.5 hours, and then kept at 800°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1200°C after 0.5 hours, and kept at 1200°C for 1.5 hours. Then, the sintering temperature is controlled to rise to 1900°C after 0.5 hours, and kept at 1900°C for 3.5 hours. Crushing is to crush the sintered block with a rubber hammer and put it into a hammer crusher for further crushing, and finally crush it into 3mm particles. Washing is to put the boron nitride particles in a washing tank, add pure water and heat to 100°C, stir for 2 hours, and then filter and dry.

[0099] Figure 11 The XRD spectrum of hexagonal boron nitride prepared by the present invention; Figure 12 This is a partial parameter diagram of hexagonal boron nitride prepared by the present invention.

[0100] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing hexagonal boron nitride, characterized in that: The preparation method thereof comprises the following steps: S1, mixing boric acid and melamine to obtain a mixture; S2, drying the mixed material to obtain a block mixture; S3, crushing the block mixture to obtain mixed particles; S4, briquetting the mixed particles to obtain a block; S5, sintering the block to obtain a sintered block; S6, crushing the sintered block to obtain boron nitride particles; S7. Wash the boron nitride particles with water to obtain the hexagonal boron nitride.

2. The method for preparing hexagonal boron nitride according to claim 1, characterized in that: The molar ratio of boric acid to melamine in the S1 is 1:1-12.

3. The method for preparing hexagonal boron nitride according to claim 1, characterized in that: The drying temperature in S2 is 200° C.-300° C., and the drying time is 6-9 hours.

4. The method for preparing hexagonal boron nitride according to claim 1, characterized in that: The crushing particle size in the S3 is 1-5 mm.

5. The method for preparing hexagonal boron nitride according to claim 1, characterized in that: The sintering in S5 is carried out in stages. When the temperature rises to 600°C, the sintering is carried out for 1.5 hours. When the temperature rises to 800°C, the sintering is carried out for 1.5 hours. When the temperature rises to 1200°C, the sintering is carried out for 1.5 hours. When the temperature rises to 1900°C, the sintering is carried out for 3.5 hours.

6. The method for preparing hexagonal boron nitride according to claim 1, characterized in that: The pulverization in S6 is to pulverize the sintered block with a rubber hammer and then put it into a hammer crusher for further pulverization, and finally pulverize it into 3-5mm particles.

7. The method for preparing hexagonal boron nitride according to claim 1, characterized in that: The water washing in S7 is to place the boron nitride particles in a water washing tank, add pure water, heat to 100° C., stir for 1-2 hours, and then filter and dry.

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