CN116693299A - Preparation and strength characterization method of spherical boron nitride with controllable high density granularity - Google Patents
Preparation and strength characterization method of spherical boron nitride with controllable high density granularity Download PDFInfo
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- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 title claims abstract description 116
- 229910052582 BN Inorganic materials 0.000 title claims abstract description 109
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000012512 characterization method Methods 0.000 title claims abstract description 10
- 239000000843 powder Substances 0.000 claims abstract description 89
- 238000000034 method Methods 0.000 claims abstract description 49
- 238000005469 granulation Methods 0.000 claims abstract description 32
- 230000003179 granulation Effects 0.000 claims abstract description 32
- 238000005245 sintering Methods 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000011230 binding agent Substances 0.000 claims abstract description 16
- 239000002270 dispersing agent Substances 0.000 claims abstract description 16
- 239000008367 deionised water Substances 0.000 claims abstract description 13
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 13
- 239000002518 antifoaming agent Substances 0.000 claims abstract description 11
- 238000001694 spray drying Methods 0.000 claims abstract description 10
- 239000002002 slurry Substances 0.000 claims description 23
- 239000007921 spray Substances 0.000 claims description 19
- 238000003756 stirring Methods 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 17
- 238000000498 ball milling Methods 0.000 claims description 16
- 238000002156 mixing Methods 0.000 claims description 16
- 239000012298 atmosphere Substances 0.000 claims description 11
- 238000007599 discharging Methods 0.000 claims description 11
- 239000003292 glue Substances 0.000 claims description 11
- 239000006185 dispersion Substances 0.000 claims description 10
- 239000011261 inert gas Substances 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 9
- -1 polysiloxane Polymers 0.000 claims description 9
- 238000009775 high-speed stirring Methods 0.000 claims description 8
- 238000011068 loading method Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 7
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 6
- 238000012360 testing method Methods 0.000 claims description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 5
- 239000013530 defoamer Substances 0.000 claims description 4
- 238000006073 displacement reaction Methods 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 239000004743 Polypropylene Substances 0.000 claims description 3
- 239000006087 Silane Coupling Agent Substances 0.000 claims description 3
- 150000001298 alcohols Chemical class 0.000 claims description 3
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 150000001408 amides Chemical class 0.000 claims description 3
- 239000001913 cellulose Substances 0.000 claims description 3
- 229920002678 cellulose Polymers 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 230000006835 compression Effects 0.000 claims description 3
- 235000014113 dietary fatty acids Nutrition 0.000 claims description 3
- 239000000194 fatty acid Substances 0.000 claims description 3
- 229930195729 fatty acid Natural products 0.000 claims description 3
- 125000005313 fatty acid group Chemical group 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 229920000642 polymer Polymers 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- 229920001296 polysiloxane Polymers 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 150000005846 sugar alcohols Polymers 0.000 claims description 3
- 239000002245 particle Substances 0.000 abstract description 9
- 239000007787 solid Substances 0.000 abstract description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000007613 environmental effect Effects 0.000 abstract 1
- 238000009826 distribution Methods 0.000 description 4
- 239000012798 spherical particle Substances 0.000 description 4
- 238000005303 weighing Methods 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241001391944 Commicarpus scandens Species 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000001010 compromised effect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000012113 quantitative test Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/583—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride
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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
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Abstract
The preparation method of the spherical boron nitride with controllable high density granularity selects small-particle-size boron nitride powder, and adopts a spray drying method to obtain the spherical boron nitride granulation powder with low porosity and high density by matching a sintering aid, a dispersing agent, a defoaming agent, deionized water and a binder, and the particle size of the granulation powder is controlled by different solid contents, so that the problems of more voids, poor compactness and uncontrollable particle size in the granulation process of the spherical boron nitride powder obtained by large-particle-size boron nitride powder are solved. The spherical hexagonal boron nitride prepared by the application has high compactness, controllable process granularity, excellent heat conduction isotropy, simple production process and environmental friendliness, and the application also provides a characterization method of the strength of the sintering granulation powder.
Description
Technical Field
The application relates to the technical field of new material manufacturing, in particular to a preparation method of spherical boron nitride with controllable high-density granularity, and also relates to a characterization method of spherical boron nitride prepared from the spherical boron nitride with controllable high-density granularity.
Background
Today, the new generation of 5G communication technology is rapidly developed, and higher requirements are put on miniaturization, high integration and high power density of related electronic components. Because the energy conversion efficiency of the device is limited under the conditions of miniaturization, high integration and high power density, most of energy which cannot be converted and utilized can be emitted in a heat energy mode, if the heat cannot be rapidly and effectively emitted, the service life of the device can be influenced, serious safety problems can be generated, and therefore, good heat-dissipation performance is a key for promoting rapid development of new-generation electronic components.
Hexagonal boron nitride is a lamellar structure similar to graphite, and has anisotropic heat conduction due to special structural characteristics, so that the exertion of the heat conduction property is limited, the fluidity is limited due to an irregular morphology structure, the defects are often compromised in practical application, the defect of anisotropic heat conduction of hexagonal boron nitride can be overcome by spheroidizing the boron nitride, the fluidity of the material can be further improved, and the filling property of the material is enhanced.
The spherical boron nitride has a lot of production processes, the spherical boron nitride obtained by spray granulation has better sphericity, but no study on the granularity controllability of spray granulation powder exists at present, and Chinese patent CN 108101546B discloses spherical hexagonal boron nitride granulation powder obtained by taking hexagonal boron nitride as a raw material through a spray drying method, but the hexagonal boron nitride powder used by the method has larger particle diameter, higher surface porosity, lower compactness and uncontrollable granularity; chinese patent CN 110041080a discloses a spherical hexagonal boron nitride granulated powder obtained by using boron nitride as a raw material and by a centrifugal granulation method, the hexagonal boron nitride powder used in the method has larger particle diameter, higher surface porosity, lower density, poorer sphericity and uncontrollable granularity.
In addition, the structural strength of the spherical boron nitride sintered sphere is also an important performance index of the granulated and sintered powder, the structural strength of the spherical boron nitride powder can directly influence the heat conduction performance at an application end, the structural strength is low, the spherical powder is easy to crush, the fluidity of the spherical powder in a resin and silicone oil matrix can be reduced, and the heat conduction isotropy of the crushed powder is lower than that of the spherical powder; by means of the characterization method of the strength, semi-quantitative test is conducted on the structural strength of the spherical granulating powder, control is conducted before the spherical granulating powder enters the application end, potential hazards possibly occurring at the application end are solved, and cost can be greatly reduced.
Disclosure of Invention
Aiming at the defects of the prior art, the application provides the preparation method of the spherical boron nitride with controllable high density granularity, small-particle-size boron nitride powder is selected, the spherical boron nitride granulation powder with low porosity and high density is obtained by a spray drying method, the granularity of the granulation powder is controlled by different solid contents, the problems of more voids of the spherical powder obtained by the large-particle-size boron nitride powder, poor compactness and uncontrollable granularity in the granulation process are solved.
The application aims to provide the strength characterization method of the spherical boron nitride with controllable high density granularity.
The technical problems to be solved by the application are realized by the following technical proposal. The application relates to a preparation method of spherical boron nitride with controllable high density granularity, which comprises the following steps:
(1) Uniformly mixing a sintering aid and boron nitride powder according to the weight percentage of the sintering aid accounting for 0.1-10% of the boron nitride powder with the boron nitride powder to obtain a boron nitride powder mixture;
(2) Preparing boron nitride slurry by taking a boron nitride powder mixture, a dispersing agent, a defoaming agent, deionized water and a binder, wherein the mass percent of the boron nitride powder mixture is 10% -50%, the mass percent of the dispersing agent is 0.01% -5%, the mass percent of the defoaming agent is 0.0001% -0.005%, the mass percent of the deionized water is 25% -85%, and the mass percent of the binder is 0.01% -5%;
(3) Uniformly dispersing a dispersing agent and a defoaming agent in deionized water to obtain a uniform dispersion liquid, and then mixing a binder, a boron nitride powder mixture and the uniform dispersion liquid to obtain boron nitride slurry;
(4) Carrying out spray granulation on the boron nitride slurry in the step (3) by a spray drying method, and keeping continuous stirring on the boron nitride slurry in the spray drying process;
(5) Loading the powder obtained by spray granulation into a crucible, and discharging glue under the air atmosphere;
(6) Sintering the powder after the glue discharge under inert atmosphere.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with the controllable high density granularity, the sintering aid in the step (1) is a mixture of one or more of aluminum oxide, hydroxide, complex and aluminum salt in proportion.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with the controllable high density granularity, the boron nitride powder in the step (1) is the raw powder for granulation, and the raw powder for granulation is one or more of submicron-level and micron-level hexagonal boron nitride powder, spherical boron nitride powder and spherical boron nitride powder, which are obtained by grading and mixing.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with controllable high density granularity, the dispersing agent in the step (2) is polyalcohol, silane coupling agent, ammonium acid or ammonium acid polymer and derivatives thereof;
the defoamer is fatty acid, amide, lower alcohols, organic silicon or polysiloxane.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with the controllable high density granularity, the binder in the step (2) is cellulose and derivatives thereof, polypropylene and derivatives thereof or polyethylene and derivatives thereof.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with the controllable high density granularity, in the step (3), the dispersing agent and the defoaming agent are uniformly dispersed in deionized water in a stirring and ultrasonic mode to obtain uniform dispersion liquid.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with controllable high density granularity, in the step (3), the method for mixing the binder, the boron nitride powder mixture and the uniform dispersion liquid is selected from any one of the following methods:
a. ball milling method
During ball milling, the balls are alumina or zirconia balls, the diameter is one diameter or a mixture of a plurality of diameters between 1cm and 20cm, the mass ratio of the balls to the fed materials is 1-10:1, the ball milling rotating speed is 50-1000 revolutions per minute, and the ball milling time is 30 min-5 h;
b. high speed stirring method
And during high-speed stirring, the stirring rotating speed is 50-5000 revolutions per minute, and the stirring time is 10 min-5 h, so that stable water-based slurry is obtained.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with controllable high density granularity, in the step (5), the glue discharging temperature and time are between 200 ℃ and 2400 ℃.
The technical problem to be solved by the application can be further solved by the following technical scheme, and for the preparation method of the spherical boron nitride with controllable high density granularity, in the step (6), the inert atmosphere is a mixed gas of one or more inert gases according to different proportions, or a mixed gas of one or more inert gases according to different proportions and hydrogen; the sintering temperature and time are 3600 ℃ h to 22000 ℃ h.
The technical problem to be solved by the application can be further solved by the following technical scheme, for the preparation method of the spherical boron nitride with the controllable high density granularity, the strength characterization method of the spherical boron nitride with the controllable high density granularity, which is prepared by using the preparation method of the spherical boron nitride with the controllable high density granularity, the method comprises the steps of adopting a mechanical testing machine to obtain compression and displacement curves and strength data by using a standard sample with the mass of 0.05-1 g per sample and the loading speed of 0.05-5 mm/min.
Compared with the prior art, the application has the beneficial effects that:
1. the application provides a method for obtaining spherical granulated powder by spray granulating hexagonal boron nitride powder with small particle size;
2. the boron nitride powder selected by the application comprises, but is not limited to, submicron-level and micron-level hexagonal boron nitride powder, spherical boron nitride powder and spheroidal boron nitride powder, wherein the raw powder for granulation is one or more of the boron nitride powder obtained by grading, mixing and the like, and the spherical granulated powder obtained by granulating the boron nitride powder has less surface pores and high density;
3. the method for controlling the granularity, which is explored by the application, can controllably control the granularity of the granulated powder by adjusting the solid content of the boron nitride in the slurry and the frequency of the atomizer, thus realizing the production process method with controllable granularity, and has simple process steps, low cost and less energy consumption;
4. the method for controlling the granularity can semi-qualitatively characterize the structural strength of the granulated powder, solves the problem that the sphere at the application end is easy to break, and solves the hidden danger of influencing the performance of the spherical powder before entering the application end.
Drawings
FIG. 1 is an SEM image of a typical spherical granulation powder obtained under the prior art spray granulation technique;
FIG. 2 is an SEM image of spherical granulated powder obtained by spray granulation according to the application;
FIG. 3 is a graph showing the particle size distribution of spherical boron nitride according to a first embodiment of the present application;
FIG. 4 is a graph showing the particle size distribution of spherical boron nitride according to a second embodiment of the present application;
FIG. 5 is a graph showing the particle size distribution of spherical boron nitride according to a third embodiment of the present application;
FIG. 6 is a graph showing the particle size distribution of spherical boron nitride according to a fourth embodiment of the present application;
FIG. 7 is a graph depicting the strength test of the spherical powder of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Referring to fig. 1 to 7, a method for preparing spherical boron nitride with controllable high density granularity comprises the following steps:
1. taking one or more of aluminum oxide, hydroxide, complex and aluminum salt as a sintering aid, and uniformly mixing with boron nitride powder according to the mass percentage of 0.1-10% of the boron nitride powder;
preferably, the boron nitride powder is raw powder for granulation, and the selected boron nitride powder comprises, but is not limited to, submicron-level and micron-level hexagonal boron nitride powder, spherical boron nitride powder and spherical boron nitride powder, and the raw powder for granulation is one or more of the boron nitride powder obtained by grading, mixing and the like;
2. taking a dispersing agent, a binder, a defoaming agent, deionized water and the boron nitride powder obtained in the step one, wherein the mass percentage of the boron nitride powder is 10% -50%;
preferably, the dispersing agent is polyalcohol, silane coupling agent, ammonium acid polymer and derivatives thereof, and the mass percentage is 0.01% -5%;
preferably, the binder is cellulose and derivatives thereof, polypropylene and derivatives thereof, polyethylene and derivatives thereof, and the mass percentage is 0.01% -5%;
preferably, the defoamer is fatty acid (ester), amide, lower alcohols, organic silicon and polysiloxane, and accounts for 0.0001-0.005% of the mass of the slurry;
85-25% of deionized water;
3. dispersing the dispersant and the defoamer in deionized water evenly by stirring, ultrasonic and other modes to obtain uniform dispersion liquid.
4. Mixing the weighed binder, the uniform dispersion liquid obtained in the third step and the boron nitride powder obtained in the first step by a ball milling method or a high-speed stirring method;
during ball milling, the balls are alumina or zirconia balls, the diameter is one diameter or a mixture of a plurality of diameters between 1cm and 20cm, the mass ratio of the balls to the materials is (1-10): 1, the ball milling rotating speed is 50-1000 revolutions per minute, and the ball milling time is 30 min-5 h;
when stirring at a high speed, the stirring speed is 50-5000 revolutions per minute, and the stirring time is 10 min-5 h, so as to obtain stable water-based slurry;
5. carrying out spray granulation on the slurry in the third step by a spray drying method, and keeping continuous stirring on the slurry in the spray drying process;
6. placing the powder obtained by spraying the granulated powder into a crucible, and discharging the gel in an air atmosphere, wherein the gel discharging temperature and time are between 200 ℃ and 2400 ℃ and h; the glue discharging temperature and time control mode comprises continuous glue discharging at a certain temperature or different time gradients and different time for glue discharging treatment;
7. sintering the powder after the glue discharge under an inert atmosphere, wherein the inert atmosphere can be one inert gas or a mixture of a plurality of inert gases according to different proportions; or sintering under the mixed gas of inert gas and hydrogen, wherein the inert atmosphere can be mixed with hydrogen by one inert gas or a mixture of a plurality of inert gases according to different proportions; the sintering temperature and time are 3600-22000 ℃ and include, but are not limited to, continuous sintering at a certain temperature, different step heating or sintering at the same time;
a high-density granularity-controllable strength characterization method of spherical boron nitride utilizes a mechanical testing machine (the mechanical testing machine is not limited to brands), and the standard sample mass is 0.05-1 g per sample, the loading speed is 0.05-5 mm/min, so as to obtain compression and displacement curves and obtain strength data.
The first embodiment is as follows: the preparation method of the spherical hexagonal boron nitride in the embodiment comprises the following steps:
1. weighing boron nitride powder, weighing sintering aid according to the weight percentage of 0.1-10% of the boron nitride powder, and pre-dispersing by adopting modes of stirring, ultrasonic treatment and the like;
2. weighing 0.2-1% of dispersing agent according to the mass percentage of the slurry; adding a dispersing agent and a defoaming agent accounting for 0.0002-0.002% of the mass percent of the slurry into deionized water accounting for the mass percent of the slurry, and uniformly mixing, wherein the mixing method adopts stirring or ultrasonic treatment to obtain uniform mixed solution;
3. weighing 20% of boron nitride powder in the first step, the mixed solution obtained in the second step and the binder accounting for 0.02% of the mass percentage of the slurry according to the mass percentage of the slurry, sequentially adding the boron nitride powder and the binder into a ball milling tank for ball milling and mixing or stirring by a high-speed stirring method, and then adding a pre-dispersed sintering auxiliary agent for continuing ball milling for 1-5 hours or stirring by the high-speed stirring method for 10 min-4 hours; ball mill ball milling mixing ball material ratio (1-10): 1, or stirring by a high-speed stirring method to obtain stable water-based slurry;
4. carrying out spray granulation on the slurry in the third step by a spray drying method, wherein the frequency of an atomizer of a spray dryer is 340-360 Hz, and stirring the slurry in the granulation process;
5. loading the powder obtained by spraying the granulated powder into a crucible, and discharging the gel at 1600-2400 ℃ in the temperature rising rate of 1-10 ℃ per minute under the air atmosphere;
6. sintering the powder after glue discharging in nitrogen atmosphere, wherein the sintering temperature and time are 1850 ℃ to 12000 ℃ at the heating rate of 1 to 10 ℃ per minute;
7. carrying out structural strength characterization on the sintered powder, and carrying out loading rate on a mechanical testing machine (load of 1-10 kN) with the sample mass of 0.1-1 g/sample: 0.1-1 mm/min, and obtaining compression-displacement curve and strength data;
the average diameter of spherical particles obtained by spray granulation in this embodiment is controlled to 15 to 25 μm.
The second embodiment is as follows: the first difference between this embodiment and the specific example is that: the solid content of the boron nitride in the third step is 30%, and the frequency of an atomizer of a spray dryer is 280-300 Hz; the other is the same as the first embodiment;
the average diameter of spherical particles obtained by spray granulation in this embodiment is controlled to 25 to 35 μm.
And a third specific embodiment: this embodiment differs from the first or second embodiment in that: the solid content of the boron nitride in the third step is 40%, and the frequency of an atomizer of a spray dryer is 240-280 Hz; the other is the same as the first embodiment;
the average diameter of spherical particles obtained by spray granulation in this embodiment is controlled to 50 to 70 μm.
The specific embodiment IV is as follows: this embodiment differs from one of the first to third embodiments in that: the solid content of the boron nitride in the third step is 50%, and the frequency of an atomizer of a spray dryer is 200-240 Hz; the other is the same as the first embodiment;
the average diameter of spherical particles obtained by spray granulation in this embodiment is controlled to 80 to 100. Mu.m.
Claims (10)
1. A preparation method of spherical boron nitride with controllable high density granularity is characterized by comprising the following steps: the method comprises the following steps:
(1) Uniformly mixing a sintering aid and boron nitride powder according to the weight percentage of the sintering aid accounting for 0.1-10% of the boron nitride powder with the boron nitride powder to obtain a boron nitride powder mixture;
(2) Preparing boron nitride slurry by taking a boron nitride powder mixture, a dispersing agent, a defoaming agent, deionized water and a binder, wherein the mass percent of the boron nitride powder mixture is 10% -50%, the mass percent of the dispersing agent is 0.01% -5%, the mass percent of the defoaming agent is 0.0001% -0.005%, the mass percent of the deionized water is 25% -85%, and the mass percent of the binder is 0.01% -5%;
(3) Uniformly dispersing a dispersing agent and a defoaming agent in deionized water to obtain a uniform dispersion liquid, and then mixing a binder, a boron nitride powder mixture and the uniform dispersion liquid to obtain boron nitride slurry;
(4) Carrying out spray granulation on the boron nitride slurry in the step (3) by a spray drying method, and keeping continuous stirring on the boron nitride slurry in the spray drying process;
(5) Loading the powder obtained by spray granulation into a crucible, and discharging glue under the air atmosphere;
(6) Sintering the powder after the glue discharge under inert atmosphere.
2. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: the sintering aid in the step (1) is a mixture of one or more of aluminum oxide, hydroxide, complex and aluminum salt in proportion.
3. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: the boron nitride powder in the step (1) is raw powder for granulation, and the raw powder for granulation is one or more of submicron-level and micron-level hexagonal boron nitride powder, spherical boron nitride powder and spherical boron nitride powder, which are obtained by grading and mixing.
4. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: the dispersant in the step (2) is polyalcohol, silane coupling agent, ammonium acid or ammonium acid polymer and derivatives thereof;
the defoamer is fatty acid, amide, lower alcohols, organic silicon or polysiloxane.
5. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: the binder in the step (2) is cellulose and derivatives thereof, polypropylene and derivatives thereof or polyethylene and derivatives thereof.
6. The method for preparing high-density spherical boron nitride with controllable granularity according to claim 1 or 4, which is characterized in that: in the step (3), dispersing agent and defoaming agent are uniformly dispersed in deionized water by stirring and ultrasonic modes to obtain uniform dispersion liquid.
7. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: in the step (3), the method of mixing the binder, the boron nitride powder mixture and the uniform dispersion is selected from any one of the following methods:
a. ball milling method
During ball milling, the balls are alumina or zirconia balls, the diameter is one diameter or a mixture of a plurality of diameters between 1cm and 20cm, the mass ratio of the balls to the fed materials is 1-10:1, the ball milling rotating speed is 50-1000 revolutions per minute, and the ball milling time is 30 min-5 h;
b. high speed stirring method
And during high-speed stirring, the stirring rotating speed is 50-5000 revolutions per minute, and the stirring time is 10 min-5 h, so that stable water-based slurry is obtained.
8. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: in the step (5), the glue discharging temperature and time are between 200 ℃ and 2400 ℃.
9. The method for preparing spherical boron nitride with controllable high density granularity according to claim 1, which is characterized in that: in the step (6), the inert atmosphere is a mixed gas of one or more inert gases mixed according to different proportions, or a mixed gas of one or more inert gases mixed with hydrogen according to different proportions; the sintering temperature and time are 3600 ℃ h to 22000 ℃ h.
10. A strength characterization method of spherical boron nitride with controllable high density granularity is characterized by comprising the following steps: the method is characterized in that a mechanical testing machine is adopted to obtain compression and displacement curves and strength data, wherein the mass of a standard sample is 0.05-1 g per sample, and the loading speed is 0.05-5 mm/min.
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