CN111453706A - Synthesis method of hexagonal boron nitride - Google Patents
Synthesis method of hexagonal boron nitride Download PDFInfo
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- CN111453706A CN111453706A CN202010344805.3A CN202010344805A CN111453706A CN 111453706 A CN111453706 A CN 111453706A CN 202010344805 A CN202010344805 A CN 202010344805A CN 111453706 A CN111453706 A CN 111453706A
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
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- C—CHEMISTRY; METALLURGY
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
- C01B21/0646—Preparation by pyrolysis of boron and nitrogen containing compounds
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
Abstract
The invention discloses a synthesis method of hexagonal boron nitride, which comprises the steps of solution preparation, precursor preparation, calcination, acid washing and the like; mixing melamine, boric acid and deionized water, stirring, heating and dissolving; and cooling to separate out crystals, and acid-washing a solid obtained after the crystals are calcined to obtain a finished product. The invention has simple process, convenient manufacture, energy saving and environmental protection; the method adopts the synthesis of the precursor in the solution, and the synthesis mode is simple and easy to operate and convenient to control; the precursor is calcined to obtain a finished product, the calcining condition is mild, and the two-stage calcining greatly reduces the use of protective atmosphere and saves energy.
Description
Technical Field
The invention relates to the technical field of boron nitride preparation, in particular to a synthesis method of hexagonal boron nitride.
Background
Hexagonal boron nitride (also called graphitic boron nitride, white graphite, like graphite). The nitrogen and the boron in the hexagonal boron nitride also form a hexagonal net layer surface which are overlapped with each other to form crystals. The crystal is similar to graphite, has diamagnetism and high anisotropy, and has similar crystal parameters. The relative density was 2.25. The mohs hardness is about 2. As a white powder, melted at about 3000 c under high pressure. Has good electrical insulation, thermal conductivity, corrosion resistance and good lubricity. Good chemical stability and no reaction with water, acid and alkali at normal temperature.
Hexagonal boron nitride can be used for manufacturing TiB2the/BN composite ceramic can also be used for high-grade refractory materials and superhard materials, separating rings of horizontal continuous rolling steel, high-temperature resistant lubricants andthe high-temperature coating is also a raw material for synthesizing cubic boron nitride. The boron nitride product can be used as high-temperature, high-pressure, insulating and heat-radiating components. Is widely applied to the electrical industry and the electronic industry. The synthesis method of hexagonal boron nitride mainly comprises a traditional high-temperature method, a hydrothermal method, a chemical vapor deposition method, a self-propagating method, a precursor method and the like. In industrial production, high temperature methods are mostly used for production, but the hexagonal boron nitride synthesized by the traditional high temperature method is limited by the synthesis method, so that the process is unstable, and the finished product synthesized by the method is unstable in purity, granularity, shape and crystallinity and has large fluctuation. Therefore, a process and product controllable synthesis method is needed for the production of hexagonal boron nitride.
Disclosure of Invention
The invention aims to overcome the defects and provide a method for synthesizing hexagonal boron nitride. In order to achieve the purpose, the invention is implemented according to the following technical scheme:
a synthesis method of hexagonal boron nitride comprises the following steps,
s1, preparation of solution
Mixing melamine, boric acid and deionized water, heating to 80-95 ℃, and stirring until the melamine, the boric acid and the deionized water are completely dissolved to obtain a mixed aqueous solution; the mol ratio of the melamine to the boric acid is 1: 2-4; in the mixed aqueous solution, the mass sum of the melamine and the boric acid accounts for 3-5.5 wt% of the total mass of the mixed aqueous solution;
s2, preparation of precursor
Cooling the mixed aqueous solution to 15-25 ℃ to obtain crystals; carrying out vacuum filtration on the crystals, and then sending the crystals into a drying oven for drying to obtain a precursor;
s3, calcination
The precursor is sent into an atmosphere sintering furnace for two-section type calcination; two-stage calcining, wherein the calcining temperature of the first stage is 900-950 ℃; the second stage calcining temperature is 1000-1400 ℃; naturally cooling to room temperature after calcination to obtain a calcined product;
s4, acid washing
And (4) after acid washing the calcined product, filtering and drying to obtain a hexagonal boron nitride finished product.
Preferably, in the step S1, the stirring speed is 200r/min to 300r/min, the stirring time is 30min to 40min, and the temperature is maintained at 80 ℃ to 95 ℃ during the stirring process.
Preferably, the stirring process is performed in an ultrasonic environment; the ultrasonic frequency is 20 kHz-35 kHz.
Preferably, in the step S2, the drying time of the oven is 60min to 120min, and the drying temperature is 60 ℃ to 75 ℃.
Preferably, in the step S3, the heat preservation time of the first stage of calcination is 2 to 4 hours; the heating rate is 60 ℃/h; the calcination atmosphere was air.
Preferably, in the step S3, the heat preservation time of the second stage of calcination is 4-8 h; the temperature rise rate was 60 ℃/h.
Preferably, in the second stage of calcination, a mixed gas of nitrogen and ammonia is used as the calcination atmosphere; the volume ratio of the nitrogen to the ammonia is 2: 1-2.
Preferably, in the step S4, dilute hydrochloric acid or dilute sulfuric acid is adopted for acid washing, the acid washing temperature is 60-80 ℃, the acid washing time is 1-2 h, and the concentration of the dilute hydrochloric acid or dilute sulfuric acid is 1 mol/L.
The invention has the following function principle:
the invention reacts melamine and boric acid in water solution to obtain a precursor, and the reaction equation is as follows: c3N6H6+2H3BO3＝C3N6H6·2H3BO3(ii) a Precursor C formed by melamine and boric acid in aqueous solution3N6H6·2H3BO3Formed by intermolecular hydrogen bonding.
Precursor C3N6H6·2H3BO3During calcination, boron nitride is formed by reaction according to the following reaction equation: c3N6H6·2H3BO3＝2BN+4NH3+3CO2。
The preparation process of the precursor is simple and easy to operate, and the precursor can be accurately prepared only by controlling the use amount of melamine and boric acid and the mass fraction of solute in the mixed aqueous solution. And the preparation process of the precursor is obtained by stirring in a heated aqueous solution, so that the operation is easier and the energy consumption is low.
The quality of the calcined product is ensured by controlling the calcining temperature and the calcining time in the process of calcining the precursor. In the first stage of calcination, only air atmosphere is adopted, the calcination condition is mild, and a large amount of protective atmosphere is not required to be consumed. Before the second-stage calcining process is started, the mixed atmosphere of nitrogen and ammonia is started to prevent the hexagonal boron nitride from being decomposed under the action of air and high temperature, and the purity of the hexagonal boron nitride is further improved due to the higher calcining temperature.
Compared with the prior art, the invention has the beneficial effects that:
the invention has simple process, convenient manufacture, energy saving and environmental protection; the method adopts the synthesis of the precursor in the solution, and the synthesis mode is simple and easy to operate and convenient to control; the precursor is calcined to obtain a finished product, the calcining condition is mild, and the two-stage calcining greatly reduces the use of protective atmosphere and saves energy.
Detailed Description
The present invention will be further described with reference to specific examples, which are illustrative of the invention and are not to be construed as limiting the invention.
Example 1
A synthesis method of hexagonal boron nitride comprises the following steps,
s1, preparation of solution
Mixing melamine, boric acid and deionized water, heating to 80 ℃, and stirring until the melamine, the boric acid and the deionized water are completely dissolved to obtain a mixed aqueous solution; the molar ratio of melamine to boric acid is 1: 2; in the mixed aqueous solution, the mass sum of melamine and boric acid accounts for 3wt% of the total mass of the mixed aqueous solution; the stirring process is carried out in an ultrasonic environment, the ultrasonic frequency is 20kHz, the stirring speed is 200r/min, the stirring time is 30min, and the temperature is kept at 80 ℃ in the stirring process.
S2, preparation of precursor
Cooling the mixed aqueous solution to 15 ℃ to obtain crystals; carrying out vacuum filtration on the crystals, and then sending the crystals into a drying oven for drying to obtain a precursor; the drying time of the oven is 60min, and the drying temperature is 75 ℃.
S3, calcination
The precursor is sent into an atmosphere sintering furnace for two-section type calcination; two-stage calcining, wherein in the first stage calcining, the calcining atmosphere is air, the temperature is increased to 900 ℃ at the temperature increase rate of 60 ℃/h, and the temperature is kept at 900 ℃ for 2 h; the second stage of calcination, namely introducing mixed gas of nitrogen and ammonia into an atmosphere sintering furnace, wherein the volume ratio of the nitrogen to the ammonia is 2: 1; heating to 1200 ℃ at a heating rate of 60 ℃/h, and keeping the temperature at 1200 ℃ for 5 h; naturally cooling to room temperature after calcination to obtain a calcined product;
s4, acid washing
And (3) acid-washing the calcined product by using 1 mol/L dilute sulfuric acid, wherein the acid-washing temperature is 60 ℃, the acid-washing time is 2 hours, and then filtering and drying are carried out to obtain the finished product of the hexagonal boron nitride.
The hexagonal boron nitride finished product obtained in this example was measured for particle size distribution using a laser particle sizer, and the particle size was measured to be 13.6 μm.
Example 2
A synthesis method of hexagonal boron nitride comprises the following steps,
s1, preparation of solution
Mixing melamine, boric acid and deionized water, heating to 90 ℃, and stirring until the melamine, the boric acid and the deionized water are completely dissolved to obtain a mixed aqueous solution; the molar ratio of melamine to boric acid is 1: 3; in the mixed aqueous solution, the mass sum of the melamine and the boric acid accounts for 4.5 wt% of the total mass of the mixed aqueous solution; the stirring process is carried out in an ultrasonic environment, the ultrasonic frequency is 30kHz, the stirring speed is 270r/min, the stirring time is 37min, and the temperature is kept at 90 ℃ in the stirring process.
S2, preparation of precursor
Cooling the mixed aqueous solution to 20 ℃ to obtain crystals; carrying out vacuum filtration on the crystals, and then sending the crystals into a drying oven for drying to obtain a precursor; the drying time of the oven is 90min, and the drying temperature is 70 ℃.
S3, calcination
The precursor is sent into an atmosphere sintering furnace for two-section type calcination; two-stage calcining, wherein in the first stage of calcining, the calcining atmosphere is air, the temperature is increased to 950 ℃ at the temperature increase rate of 60 ℃/h, and the temperature is kept at 950 ℃ for 4 h; the second stage of calcination, namely introducing mixed gas of nitrogen and ammonia into an atmosphere sintering furnace, wherein the volume ratio of the nitrogen to the ammonia is 2: 2; heating to 1300 ℃ at the heating rate of 60 ℃/h, and preserving the heat at 1300 ℃ for 6 h; naturally cooling to room temperature after calcination to obtain a calcined product;
s4, acid washing
And (3) acid-washing the calcined product by using 1 mol/L diluted hydrochloric acid, wherein the acid-washing temperature is 80 ℃, the acid-washing time is 1h, and then filtering and drying are carried out to obtain the finished product of the hexagonal boron nitride.
The hexagonal boron nitride finished product obtained in this example was measured for particle size distribution using a laser particle sizer, and the particle size was found to be 16.2 μm.
Example 3
A synthesis method of hexagonal boron nitride comprises the following steps,
s1, preparation of solution
Mixing melamine, boric acid and deionized water, heating to 95 ℃, and stirring until the melamine, the boric acid and the deionized water are completely dissolved to obtain a mixed aqueous solution; the molar ratio of melamine to boric acid is 1: 4; in the mixed aqueous solution, the mass sum of the melamine and the boric acid accounts for 5.5 wt% of the total mass of the mixed aqueous solution; the stirring process is carried out in an ultrasonic environment, the ultrasonic frequency is 35 kHz, the stirring speed is 300r/min, the stirring time is 40min, and the temperature is kept at 95 ℃ in the stirring process.
S2, preparation of precursor
Cooling the mixed aqueous solution to 25 ℃ to obtain crystals; carrying out vacuum filtration on the crystals, and then sending the crystals into a drying oven for drying to obtain a precursor; the drying time of the oven is 120min, and the drying temperature is 60 ℃.
S3, calcination
The precursor is sent into an atmosphere sintering furnace for two-section type calcination; two-stage calcining, wherein in the first stage calcining, the calcining atmosphere is air, the temperature is increased to 930 ℃ at the temperature increase rate of 60 ℃/h, and the temperature is maintained at 930 ℃ for 3 h; the second stage of calcination, namely introducing mixed gas of nitrogen and ammonia into an atmosphere sintering furnace, wherein the volume ratio of the nitrogen to the ammonia is 2: 1; heating to 1400 ℃ at a heating rate of 60 ℃/h, and preserving heat for 7h at 1400 ℃; naturally cooling to room temperature after calcination to obtain a calcined product;
s4, acid washing
And (3) acid-washing the calcined product by using 1 mol/L diluted hydrochloric acid, wherein the acid-washing temperature is 70 ℃, the acid-washing time is 1h, and then filtering and drying are carried out to obtain the finished product of the hexagonal boron nitride.
The hexagonal boron nitride finished product obtained in this example was measured for particle size distribution using a laser particle sizer, and found to have a particle size of 14.3 microns.
The technical solution of the present invention is not limited to the limitations of the above specific embodiments, and all technical modifications made according to the technical solution of the present invention fall within the protection scope of the present invention.
Claims (8)
1. A synthesis method of hexagonal boron nitride is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
s1, preparation of solution
Mixing melamine, boric acid and deionized water, heating to 80-95 ℃, and stirring until the melamine, the boric acid and the deionized water are completely dissolved to obtain a mixed aqueous solution; the mol ratio of the melamine to the boric acid is 1: 2-4; in the mixed aqueous solution, the mass sum of the melamine and the boric acid accounts for 3-5.5 wt% of the total mass of the mixed aqueous solution;
s2, preparation of precursor
Cooling the mixed aqueous solution to 15-25 ℃ to obtain crystals; carrying out vacuum filtration on the crystals, and then sending the crystals into a drying oven for drying to obtain a precursor;
s3, calcination
The precursor is sent into an atmosphere sintering furnace for two-section type calcination; two-stage calcining, wherein the calcining temperature of the first stage is 900-950 ℃; the second stage calcining temperature is 1000-1400 ℃; naturally cooling to room temperature after calcination to obtain a calcined product;
s4, acid washing
And (4) after acid washing the calcined product, filtering and drying to obtain a hexagonal boron nitride finished product.
2. The method for synthesizing hexagonal boron nitride according to claim 1, wherein: in the step S1, the stirring speed is 200 r/min-300 r/min, the stirring time is 30 min-40 min, and the temperature is kept at 80-95 ℃ during the stirring process.
3. The method for synthesizing hexagonal boron nitride according to claim 2, wherein: the stirring process is carried out in an ultrasonic environment; the ultrasonic frequency is 20 kHz-35 kHz.
4. The method for synthesizing hexagonal boron nitride according to claim 1, wherein: in the step S2, the drying time of the oven is 60min to 120min, and the drying temperature is 60 ℃ to 75 ℃.
5. The method for synthesizing hexagonal boron nitride according to claim 1, wherein: in the step S3, the heat preservation time of the first stage of calcination is 2-4 h; the heating rate is 60 ℃/h; the calcination atmosphere was air.
6. The method for synthesizing hexagonal boron nitride according to claim 5, wherein: step S3, keeping the temperature for the second stage of calcination for 4-8 h; the temperature rise rate was 60 ℃/h.
7. The method for synthesizing hexagonal boron nitride according to claim 6, wherein: in the second stage of calcination, the mixed gas of nitrogen and ammonia is used as the calcination atmosphere; the volume ratio of the nitrogen to the ammonia is 2: 1-2.
8. The synthesis method of hexagonal boron nitride according to claim 1, wherein in step S4, dilute hydrochloric acid or dilute sulfuric acid is used for pickling, the pickling temperature is 60-80 ℃, the pickling time is 1-2 h, and the concentration of dilute hydrochloric acid or dilute sulfuric acid is 1 mol/L.
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| CN112143291A (en) * | 2020-09-21 | 2020-12-29 | 天元军融(辽宁)化工研究所新材料孵化器股份有限公司 | High-performance environment-friendly coating and preparation method thereof |
| CN112919431A (en) * | 2021-02-07 | 2021-06-08 | 辽东学院 | High-yield and high-crystallinity hexagonal boron nitride nanosheet and preparation method thereof |
| CN113753866A (en) * | 2021-08-03 | 2021-12-07 | 湖南大学 | Hexagonal boron nitride nanocrystal and solid phase preparation method thereof |
| CN114804041A (en) * | 2022-05-12 | 2022-07-29 | 安徽壹石通材料科技股份有限公司 | Hexagonal boron nitride, preparation method thereof and heat-conducting rubber |
| CN115925428A (en) * | 2023-01-06 | 2023-04-07 | 灵石鸿润和新材料有限公司 | Hexagonal boron nitride powder and preparation method and application thereof |
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