CN111777047A - Preparation method of nano-submicron sphere-like boron nitride - Google Patents
Preparation method of nano-submicron sphere-like boron nitride Download PDFInfo
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Abstract
The invention discloses a preparation method of nano-submicron sphere-like boron nitride, which uses a reaction system for generating boron nitride by using a solid boron source and a nitrogen source, uses alkali metal halide or alkaline earth metal halide as a reaction auxiliary agent, adopts a process route of primary sintering under normal pressure, and obtains boron nitride spherical particles with the particle size of hundreds of nanometers in large batch after further treatment. The method is suitable for mass production, greatly reduces ammonia pollution, and can obtain spherical boron nitride primary particles at normal pressure and low temperature.
Description
Technical Field
The invention belongs to the field of material preparation, and relates to a preparation method of nano-submicron sphere-like boron nitride.
Background
Boron nitride materials have been developed for decades and widely used in the fields of special ceramics, composite functional ceramics, heat-conducting fillers, casting and demoulding, antiwear lubricants and the like.
Boron nitride is used as an anti-wear additive to be added into lubricating oil, and has outstanding friction reduction performance and oxidation resistance at high temperature due to self-lubricating property. Meanwhile, boron nitride is subjected to nanocrystallization to be made into particles of one hundred to several hundred nanometers, micropores, defects and mechanical damage of the friction surface can be filled, and the particles can be attached to the surface to form a layer of protective film, so that the effect of lubricating oil is improved, and the loss of the friction surface is reduced. The boron nitride nano particles are made into a spherical shape, and can also play a role of micro balls and further play a role of reducing friction. Moreover, the spherical boron nitride nano particles are difficult to form bridges and have higher stacking density, and in the field of preparing composite ceramics by hot-pressing sintering of boron nitride, the porosity can be reduced, so that the ceramics are easier to densify; the filling amount can be larger in the field of boron nitride heat-conducting fillers, the heat-conducting speed is faster, and the strength of the filled material is not reduced.
At present, many achievements have been made on boron nitride nanocrystallization, for example, in patent 201610525087.3, boron oxide is used as a boron source, and reacts with ammonia gas at 700-1100 ℃ in a sodium chloride/potassium chloride molten salt environment to obtain a hexagonal boron nitride nanosheet which is densely arranged and has a size of 90-120 nm. In the patent 201711347319.1, boric acid and urea with a molar ratio of 1 (8-15) are used, and the temperature is maintained at 550 ℃ for 2-5h at 450-. The patent 201310541685.6 discloses ball-milling and mixing ammonium fluoroborate and sodium borohydride uniformly according to a certain ratio to obtain a precursor, placing the precursor in an alumina tube furnace, and treating at 1100-. Patent 201510022305.7 discloses adding a small amount of copper nitrate into boric acid and urea at a mass ratio of 1:6, reacting at 1250 ℃ in an ammonia atmosphere, and post-treating the product to obtain 2-4 layers of disk-shaped boron nitride with a thickness of 1.0nm and a diameter of 50-70 nm. And also due to the limitation of self-compatibility, particles with other shapes are mainly micron-sized secondary particles formed by aggregating flaky boron nitride primary particles.
If suitable raw materials and process are adopted to break through the autonomy, patent 200410068824.9 reports a preparation method of boron nitride nanotubes: selecting non-toxic boron compounds as raw materials, ball-milling and refining the boron compounds and a morphology control agent, heating the boron compounds and the morphology control agent to be more than 800 ℃ under flowing ammonia gas, and preserving heat for more than 0.5 h. The boron nitride nanotube is obtained after post-treatment, and the yield is over 80 percent. Patents CN201210400174.8 and 201610619062.X both report a method for preparing boron nitride nanotubes, in which a boron source and a morphology control agent are fully mixed, and reacted with ammonia gas at 1100-1400 ℃, and the obtained white product is post-treated to remove by-products, so as to obtain boron nitride nanotubes with a tube diameter of 10-300 nm and a length of more than 100 microns.
In summary, due to the self-plasticity of boron nitride crystals, that is, boron nitride crystals spontaneously tend to form primary particles with hexagonal platelet morphology, the research on nano boron nitride in the prior art is mainly focused on the synthesis of boron nitride nanosheets, and even though proper raw materials and processes can break through the self-plasticity to obtain boron nitride nanoparticles with other morphologies, the research on the prior art is also mainly focused on boron nitride nanotubes.
Disclosure of Invention
Aiming at the technical problems, the preparation method of the nano-submicron sphere-like boron nitride provided by the invention limits the self-plasticity of the boron nitride, and spherical boron nitride primary particles are obtained at normal pressure and low temperature.
The technical scheme provided by the invention is specifically a preparation method of nano-submicron sphere-like boron nitride, which comprises the following steps:
1) mixing a solid boron source, a nitrogen source and a reaction auxiliary agent to obtain a mixed material;
2) pre-dehydrating the mixed material in the step 1);
3) filling the pre-dehydrated mixed material into a sintering furnace, and heating and reacting to obtain a sintered product;
4) and sequentially carrying out crushing and washing, acid washing, surfactant treatment, filtering and drying on the sintered product to obtain the nano-submicron sphere-like boron nitride.
Further, the boron source is boric acid, metaboric acid, pyroboric acid, ammonium borate.
Further, the nitrogen source is a carbon nitride compound.
Further, the reaction auxiliary agent is an alkali metal halide or an alkaline earth metal halide.
Further, the boron source, the nitrogen source and the reaction auxiliary agent are mixed according to the mass ratio of (1.5-5): 1: (0-0.4) mixing.
Further, the pre-dehydration temperature is greater than 125 ℃.
Further, the heating rate of the sintering furnace is 200-; the constant temperature is adopted during sintering, and the temperature is 750-1400 ℃.
Further, the step 4) is specifically as follows:
a. crushing the sintered product into small frits with the diameter of several millimeters to several centimeters by adopting crushing equipment;
b. putting the frit into hot water at 80-90 ℃ for water washing; the hot water amount is 10-40 times of the frit mass;
c. filtering the product after washing to obtain a wet filter cake;
d. acid washing the wet filter cake with sulfuric acid solution with the temperature of 80-90 ℃ and the concentration of 0.5-1.0%, wherein the amount of the acid solution is 10-20 times of the mass of the wet filter cake; filtering and washing the wet filter cake after the acid washing to obtain a neutral crude product filter cake;
e. repulping and dispersing the crude product filter cake by adopting a surfactant solution; the mass percentage concentration of the surfactant is 0.1-1.0%, the dosage of the surfactant is 10-15 times of the mass of the crude product filter cake, and the dispersion time is 30-60 minutes;
f. filtering the dispersed product to obtain a filter cake, and drying the filter cake at the temperature of 100-200 ℃.
The invention has the beneficial effects that:
according to the preparation method of the nano-submicron sphere-like boron nitride, provided by the invention, the solid boron source-nitrogen source is taken as a reaction system, so that the use of expensive substances such as borazine and the like is avoided, and the mass production is facilitated; in addition, ammonia gas atmosphere is not needed in the reaction, and gas protection can be provided by gas production of the reaction system, so that ammonia gas pollution is greatly reduced; alkali metal/alkaline earth metal halide is used as a reaction auxiliary agent, a halide molten salt system with a low melting point limits the autonomy of boron nitride, spherical boron nitride primary particles can be obtained at normal pressure and low temperature, and meanwhile, the melt obtained after sintering is insulated from oxygen in the processes of heat preservation and cooling, so that the oxidation of products at high temperature is prevented; by using the process route of washing and then pickling, the reaction auxiliary agent can be recovered to the maximum extent, and the impurity content in the boron nitride product is reduced.
Drawings
In order to facilitate understanding for those skilled in the art, the present invention will be further described with reference to the accompanying drawings.
FIG. 1 is a process flow diagram of the present invention for preparing nano-submicron boron nitride spherical particles;
FIG. 2 is an X-ray powder diffraction pattern of the spherical particles of boron nitride nanoparticles synthesized in example 1 of the present invention;
FIG. 3 is a scanning electron microscope photomicrograph of the nano boron nitride spherical particles synthesized in example 1 of the present invention at 24000 times magnification;
FIG. 4 is a scanning electron microscope photomicrograph of the spherical particles of boron nitride nanoparticles synthesized in example 1 of the present invention at 80000 times magnification;
Detailed Description
The invention is explained in detail by the following examples in conjunction with fig. 1, 2 and 3:
the technical scheme provides a process route of primary sintering under normal pressure by using alkali metal halide or alkaline earth metal halide as a reaction auxiliary agent in a reaction system for generating boron nitride by using a solid boron source and a nitrogen source, and boron nitride spherical particles with the particle size of hundreds of nanometers are obtained in large batch after further treatment.
As shown in fig. 1, a method for preparing nano-submicron boron nitride spherical particles comprises the following steps:
1) mixing materials: mixing a solid boron source, a nitrogen source and a reaction auxiliary agent (all pass through a 40-mesh sieve);
2) pre-dewatering: sending the mixed raw materials into an oven, and removing water contained in the raw materials and bound water which can be removed at low temperature to obtain pre-dehydrated raw materials;
3) high-temperature reaction: filling the dried raw materials into a sintering furnace, and heating and reacting to obtain a sintered product;
4) and (3) post-treatment: and sequentially carrying out crushing and washing, acid washing, surfactant treatment, filtering and drying on the sintered product to obtain the boron nitride nano-submicron product.
The principle of the technical scheme provided by the invention is based on the complex heterogeneous reaction of a solid boron source-nitrogen source after heating, and the following physical and chemical changes occur in sequence along with the rise of temperature: the method comprises the steps of generating an amorphous boron-oxygen compound by a boron source, carrying out deamination polycondensation on a nitrogen source, reacting newly generated ammonia gas with the boron-oxygen compound, reacting the boron-oxygen compound with a polycondensation product, carrying out ring-opening pyrolysis on the polycondensation product, forming an amorphous boron-carbon-nitrogen-oxygen compound, melting the boron-oxygen compound and a reaction auxiliary agent, and decarburizing and deoxidizing the boron-carbon-nitrogen-oxygen compound in a melt to form spherical boron nitride.
Based on the above principles and procedures, the boron source used in the present invention is a solid substance capable of generating boron-oxygen compounds under heat, including but not limited to boric acid, metaboric acid, pyroboric acid, ammonium borate, and the like;
the nitrogen source used in the present invention is a carbon nitrogen compound, preferably an amino group-containing small molecule solid carbon nitrogen compound, including but not limited to cyanuric acid, urea, biuret, melamine, etc.
The reaction assistant used in the present invention is an alkali metal halide or an alkaline earth metal halide, preferably an alkali metal halide or an alkaline earth metal halide which does not contain crystal water and has a solubility in water of more than 0.1g/100g, including but not limited to sodium chloride, potassium fluoride, calcium chloride, magnesium fluoride, etc.
The mass ratio range of the boron source, the nitrogen source and the reaction auxiliary agent is limited to (1.5-5): 1: (0-0.4), depending on the kind of boron source, nitrogen source and reaction assistant.
The invention has no special limitation on the mixing equipment applied in mixing.
The pre-dehydration temperature in the present invention is preferably in the range of 125 ℃ or higher and the decomposition temperature of the nitrogen source or lower. For a more stable nitrogen source, the upper limit of the interval is 300 ℃. For example, it is preferably 125 to 150 ℃ when urea is used and 125 to 300 ℃ when melamine is used.
Due to the process principle of the invention, the invention has no sealing requirement and ventilation protection requirement on the hearth part of the sintering equipment, but needs to consider the corrosion of trace ammonia gas and the deposition of high-temperature volatile matters.
The heating rate of the sintering furnace in the invention is preferably 200-. The constant temperature during sintering is preferably 750-1400 ℃, more preferably 850-1250 ℃, and most preferably 950-1150 ℃, and the constant temperature time is preferably 4-18h, more preferably 6-15h, and most preferably 8-12 h.
The invention has no requirement on the cooling speed and the protective atmosphere of the reaction system after sintering. After cooling, a mixed product, a small amount of by-products, an amorphous reaction aid and a melt of the amorphous boron-oxygen compound are obtained.
The melt is first crushed in the post-treatment step into small frits of several millimeters to several centimeters in diameter, and the crushing apparatus is not particularly limited herein.
And then putting the crushed clinker into hot water preheated to 80-90 ℃ for water washing, wherein the washing water amount takes efficiency and energy consumption into consideration, and is preferably 10-40 times of the mass of the added clinker, depending on the solubility of the reaction auxiliary agent. In the process, the reaction auxiliary agent, the excessive boric oxide compound and a small amount of by-products are dissolved in the washing water, and the washing water can be recycled after cooling and crystallization.
Filtering the product after water washing, putting the filtered wet filter cake into a 0.5-1.0% sulfuric acid solution which is 10-20 times of the mass of the wet filter cake and is preheated to 80-90 ℃ in advance for acid washing, and removing most of by-products, residual boron oxide and residual reaction auxiliary agent in the process to obtain a crude product. And filtering the crude product, and washing the crude product with water in the filtering process to obtain a neutral crude product filter cake.
In order to prevent the crude product filter cake from agglomerating in the final drying process, a surfactant solution with the concentration of 0.1-1.0% and the mass of the crude product filter cake is 10-15 times that of the crude product filter cake for repulping and dispersing, the surfactant is selected from common types, such as sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, cetyl trimethyl ammonium bromide and the like, and the dispersing time is 30-60 minutes.
Filtering the dispersed product, and drying the filter cake at 100-200 ℃ to finally obtain the well-dispersed boron nitride nano spherical product.
The present invention is further illustrated by the following specific examples, which are not intended to limit the scope of the invention.
Example 1
87.5kg of boric acid, 25kg of melamine and 5kg of sodium fluoride, which had been previously agglomerated by a 40-mesh sieve, were mixed in a double cone mixer for 1 hour. The mixed raw materials are sent into an oven and dried for 12 hours at 220 ℃ for pre-dehydration to obtain a hardened material. Crushing the materials into blocks of tens of centimeters, loading the blocks into a cast iron trough, sending the blocks into a sintering furnace, heating to 1150 ℃ at the speed of 400 ℃/h, and preserving heat for 8 h. Naturally cooling to obtain the fusion cake.
The frit was sent to a crusher, crushed into small pieces of several centimeters in diameter, put into a water washing kettle previously charged with 600 liters of 90 ℃ hot water, and stirred for 1 hour. The wet filter cake is obtained by plate-frame filtration and is put into an acid washing kettle which is added with 300 liters of sulfuric acid with the concentration of 0.5 percent at 90 ℃ in advance, and the mixture is stirred for 1 hour. Plate-frame filtration to obtain a wet filter cake, and the wet filter cake is put into 200 liters of 0.5 percent sodium dodecyl sulfate solution and stirred for half an hour. And (3) performing solid-liquid separation by using a centrifugal machine, and drying the solid in an oven at 120 ℃ to obtain the boron nitride nano spherical particles with good dispersibility. The particle diameter is about 200 nanometers, and the specific surface area is 30m2/g。
As shown in FIG. 2, all peaks in the spectrum are matched with the boron nitride standard spectrum with the spectrum number "PDF # 73-2095", which indicates that the product is boron nitride.
As is clear from fig. 3, the product is a well-dispersed spherical particle of boron nitride, excluding that the product is a nano-scale boron nitride fragment which occurs by chance in a particle of several micrometers; the product is also excluded from being the surface of a certain huge particle, and the surface is determined to be formed by the nano spherical structure.
As can be seen from the high magnification of fig. 4, the product particles are approximately 200 nm in length, demonstrating that the product is indeed nano-boron nitride, not a micron particle.
Example 2
125kg of anhydrous borax, 25kg of melamine and 2.5kg of potassium chloride which are previously sieved out of lumps by using a 40-mesh sieve are mixed in a double-cone mixer for 1 hour. The mixed raw materials are sent into an oven and dried for 12 hours at 280 ℃ for pre-dehydration to obtain a hardened material. Crushing the materials into blocks of more than ten centimeters, filling the blocks into a cast iron trough, sending the blocks into a sintering furnace, heating the blocks to 1050 ℃ at the speed of 500 ℃/h, and preserving the heat for 12 h. Naturally cooling to obtain the fusion cake.
The frit was sent to a crusher and crushed into small pieces of several centimeters in diameter, and put into a water washing kettle previously charged with 800 liters of 90 ℃ hot water and stirred for 1 hour. The wet filter cake is obtained by plate-frame filtration and is put into an acid washing kettle which is added with 350 liters of sulfuric acid with the concentration of 1 percent at 90 ℃ in advance, and the mixture is stirred for 1 hour. Plate-frame filtration to obtain a wet filter cake, and the wet filter cake is put into 200 liters of 0.5 percent sodium dodecyl sulfate solution and stirred for half an hour. And (3) performing solid-liquid separation by using a centrifugal machine, and drying the solid in an oven at 150 ℃ to obtain the boron nitride nano spherical particles with good dispersibility. The particle diameter is about 350 nanometers, and the specific surface area is 27m2/g。
Example 3
40kg of boric acid, 25kg of urea and 10kg of calcium chloride which are previously subjected to lump removal by using a 40-mesh sieve are mixed in a double cone mixer for 1 hour. The mixed raw materials are sent into an oven and dried for 12 hours at the temperature of 130 ℃ for pre-dehydration, and hardened materials are obtained. The material is crushed into blocks of more than ten centimeters, the blocks are loaded into a cast iron trough and sent into a sintering furnace, the temperature is raised to 1100 ℃ at the speed of 400 ℃/h, and the temperature is preserved for 10 h. Naturally cooling to obtain the fusion cake.
The frit was sent to a crusher, crushed into small pieces of several centimeters in diameter, put into a water washing kettle previously charged with 300 liters of 90 ℃ hot water, and stirred for 1 hour. The wet filter cake is obtained by plate-frame filtration and is put into an acid washing kettle which is added with 150 liters of sulfuric acid with the concentration of 1 percent at 90 ℃ in advance, and the mixture is stirred for 1 hour. The wet cake was obtained by plate-and-frame filtration, and the wet cake was put into 100 liters of a 1% strength sodium lauryl sulfate solution and stirred for 1 hour. And (3) performing solid-liquid separation by using a centrifugal machine, and drying the solid in an oven at 150 ℃ to obtain the boron nitride nano spherical particles with good dispersibility. The particle diameter is about 230 nanometers, and the specific surface area is about 33m2/g。
Example 4
100kg of anhydrous sodium metaborate, 25kg of melamine and 1kg of sodium chloride which are previously subjected to lump removal by using a 40-mesh sieve are mixed in a double-cone mixer for 1 hour. The mixed raw materials are sent into an oven and dried for 12 hours at the temperature of 250 ℃ for pre-dehydration, and a hardened material is obtained. Crushing the materials into blocks of more than ten centimeters, filling the blocks into a cast iron trough, sending the blocks into a sintering furnace, heating to 900 ℃ at the speed of 450 ℃/h, and preserving heat for 8 h. Naturally cooling to obtain the fusion cake.
The frit was sent to a crusher, crushed into small pieces of several centimeters in diameter, put into a water washing kettle to which 750 liters of 90 ℃ hot water was added in advance, and stirred for 1 hour. The wet filter cake is obtained by plate-frame filtration and is put into an acid washing kettle which is added with 300 liters of sulfuric acid with the concentration of 1 percent at 90 ℃ in advance, and the mixture is stirred for 1 hour. The wet cake was obtained by plate-frame filtration, and the wet cake was put into 300 liters of a 1% strength sodium lauryl sulfate solution and stirred for 1 hour. And (3) performing solid-liquid separation by using a centrifugal machine, and drying the solid in an oven at 180 ℃ to obtain the boron nitride nano spherical particles with good dispersibility. The particle diameter is about 150 nanometers, and the specific surface area is about 35m2/g。
Comparative example 1
A preparation method of boron nitride nanoparticles adopts a vapor deposition method, takes boric acid ester and ammonia gas as raw materials, and obtains the boron nitride nanoparticles with the diameter of about 90 nanometers and the specific surface area of about 30m2Boron nitride nanospheres per gram.
Compared with the method, the reaction speed and yield of the method adopting the vapor deposition method are limited, and the method is difficult to produce in large scale.
Comparative example 2
A preparation method of boron nitride micron solid spheres comprises the following steps: taking trichloroborazine as a basic raw material, heating the trichloroborazine to 140 ℃ in a toluene solution with the mass percent of 65-80%, and reacting for 3-15 h to obtain the polymeric trichloroborazine precursor. Cracking the polymeric boron trichloride azine at 1400 ℃ under the nitrogen atmosphere of 0.3-3 MPa to obtain boron nitride micron solid spheres with the purity of 99%;
the method uses borazine in the reaction system, the cost of the substance is high, and at least one step in the reaction process needs a pressure container, so that the cost and the danger of mass production equipment are increased.
Comparative example 3
Boric acid and ammonium chloride are used as raw materials, copper oxide is used as a morphology control agent, and the raw materials are directly heated to react to obtain the copper-based catalyst with the particle size of 30-100 nanometers and the specific surface area of 75m2Boron nitride nanospheres per gram.
The use of ammonium chloride in the system can generate a byproduct of hydrogen chloride, and the problems of corrosivity of the hydrogen chloride and discharge of chloride ions are solved, so that the system is not suitable for industrial mass production nowadays with higher and higher environmental requirements.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (8)
1. A preparation method of nano-submicron sphere-like boron nitride is characterized by comprising the following steps:
1) mixing a solid boron source, a nitrogen source and a reaction auxiliary agent to obtain a mixed material;
2) pre-dehydrating the mixed material in the step 1);
3) filling the pre-dehydrated mixed material into a sintering furnace, and heating and reacting to obtain a sintered product;
4) and sequentially carrying out crushing and washing, acid washing, surfactant treatment, filtering and drying on the sintered product to obtain the nano-submicron sphere-like boron nitride.
2. The method of claim 1, wherein the boron source is selected from the group consisting of boric acid, metaboric acid, pyroboric acid, and ammonium borate.
3. The method of claim 1, wherein the nitrogen source is a carbon nitride compound.
4. The method of claim 1, wherein the reaction promoter is an alkali metal halide or an alkaline earth metal halide.
5. The method for preparing nano-submicron sphere-like boron nitride according to claim 1, wherein the boron source, the nitrogen source and the reaction auxiliary agent are (1.5-5) in mass ratio: 1: (0-0.4) mixing.
6. The method of claim 1, wherein the pre-dehydration temperature is greater than 125 ℃.
7. The method as claimed in claim 1, wherein the sintering furnace has a temperature rise rate of 200-; the constant temperature is adopted during sintering, and the temperature is 750-1400 ℃.
8. The method for preparing nano-submicron spheroidal boron nitride according to claim 1, wherein the step 4) is specifically:
a. crushing the sintered product into small frits with the diameter of several millimeters to several centimeters by adopting crushing equipment;
b. putting the frit into hot water at 80-90 ℃ for water washing; the hot water amount is 10-40 times of the frit mass;
c. filtering the product after washing to obtain a wet filter cake;
d. acid washing the wet filter cake with sulfuric acid solution with the temperature of 80-90 ℃ and the concentration of 0.5-1.0%, wherein the amount of the acid solution is 10-20 times of the mass of the wet filter cake; filtering and washing the wet filter cake after the acid washing to obtain a neutral crude product filter cake;
e. repulping and dispersing the crude product filter cake by adopting a surfactant solution; the mass percentage concentration of the surfactant is 0.1-1.0%, the dosage of the surfactant is 10-15 times of the mass of the crude product filter cake, and the dispersion time is 30-60 minutes;
f. filtering the dispersed product to obtain a filter cake, and drying the filter cake at the temperature of 100-200 ℃.
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| 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 |
| CN113174147A (en) * | 2021-04-12 | 2021-07-27 | 华南理工大学 | Submicron spherical zinc oxide particle and preparation method thereof |
| CN113336203A (en) * | 2021-07-09 | 2021-09-03 | 丹东市化工研究所有限责任公司 | Small-particle-size boron nitride aggregate particles and preparation method thereof |
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| CN112919431B (en) * | 2021-02-07 | 2023-07-18 | 辽东学院 | Hexagonal boron nitride nano-sheet with high yield and high crystallinity and preparation method thereof |
| CN113174147A (en) * | 2021-04-12 | 2021-07-27 | 华南理工大学 | Submicron spherical zinc oxide particle and preparation method thereof |
| CN113336203A (en) * | 2021-07-09 | 2021-09-03 | 丹东市化工研究所有限责任公司 | Small-particle-size boron nitride aggregate particles and preparation method thereof |
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