CN115196970A - Preparation method of high-fluidity AlON spherical powder - Google Patents
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Abstract
The invention provides a preparation method of high-fluidity AlON spherical powder, which comprises the following steps: (1) Dissolving a dispersing agent into an ethanol-water solution, wherein the ethanol content in the ethanol-water solution is 3-5% by volume, adding a carbon source, performing ball milling, adding an aluminum source, and performing ball milling to obtain a uniformly mixed raw material powder solution; (2) Adding a binder, performing ball milling to obtain slurry, and adjusting the solid content of the slurry to be 35-50%; (3) carrying out spray granulation on the slurry; (4) Collecting the small balls after physical and chemical treatment, preserving heat for 1h at 750-800 ℃, then obtaining pure-phase AlON spherical powder by a one-step sintering method, taking out the pure-phase AlON spherical powder after cooling, and then heating to 700 ℃ in the air and roasting for a period of time to obtain the high-fluidity AlON spherical powder. The AlON spherical powder prepared by the method has the advantages of good fluidity, narrow particle size distribution, high balling rate, small spherical particle size and difficult agglomeration in the sintering process.
Description
Technical Field
The invention belongs to the technical field of preparation of raw material powder of transparent ceramic, and particularly relates to a preparation method of high-fluidity AlON spherical powder.
Background
Aluminum oxynitride (γ -AlON) can obtain a transmittance of 80% or more in a wide band of 0.2 to 5 μm due to its isotropic crystal structure, shows excellent optical properties, and is an important transparent ceramic material. Meanwhile, the introduction of nitrogen atoms also enables the aluminum oxynitride material to show excellent physical and chemical properties, the high temperature resistance, the thermal vibration stability, the erosion resistance and the processability of the aluminum oxynitride material are all excellent, and the aluminum oxynitride material can replace sapphire to become an important material of a protective window due to light weight, and is widely applied to various fields such as civil use, military industry and the like.
In order to prepare the AlON transparent ceramic with good compactness and high transparency, a great deal of research is carried out on the preparation method by domestic and foreign researchers, and the current research results show that: firstly, the preparation of the AlON powder with excellent performance is a prerequisite condition for preparing the AlON transparent ceramic with high optical performance.
The most common methods for preparing AlON powder are solid phase reaction and carbothermic reduction of alumina. However, the existing AlON powder preparation method still has the following defects: firstly, the solid-phase reaction method requires that the used aluminum nitride powder raw material must have the characteristics of superfine property, high purity and easy dispersion, which causes the production cost of AlON powder to be higher and the raw material to be difficult to obtain; secondly, although the carbothermic reduction method does not need high-purity AlN powder, the carbothermic reduction method has the defects of long reaction time, large influence by the mixture ratio of raw materials and difficult synthesis of pure-phase gamma-AlON powder, so that the production efficiency of the AlON powder is low and the difference of different batches of raw material powder is large.
Therefore, the existing preparation method of AlON powder generally has the problems of higher reaction temperature, long heat preservation time, larger powder particle size, easy occurrence of nonuniform sintering, difficult crushing or long crushing time and the like.
Researches show that the application performance of the aluminum oxynitride product in many fields has a close relation with the shape and the size of raw material powder particles. Among powder particles with different shapes, the spherical particles have regular shapes, smaller specific surface areas, larger stacking densities and better flowing performance, so that the application performance of the transparent ceramic product can be greatly improved. Therefore, research on the preparation of the ceramic spherical raw material powder is further developed at home and abroad, and certain achievements are obtained.
The existing spherical powder preparation technology mainly comprises an atomization method and a spheroidizing method, wherein the atomization method is most widely applied and comprises a gas atomization method, a centrifugal atomization method and an ultrasonic atomization method. However, research shows that various operating factors (such as the rotating speed of the spray head, the inlet temperature of the drying air, the outlet temperature of the waste gas and the like, and the properties of the slurry, such as the solid content and viscosity of the slurry and the like) have great influence on the morphology and the particle size distribution of the powder in the process of granulation by centrifugal spray drying.
A large number of documents show that the preparation of spherical powder with narrow particle size distribution range, high balling rate, small spherical particle size and good particle fluidity is a great problem.
Patent document CN 102060519A discloses a method for preparing rare earth doped yttrium aluminum garnet transparent ceramic by spray granulation modified powder, which is to firstly prepare rare earth doped Re: YAG powder by a coprecipitation method, and then modify the powder by a spray granulation process, but the method has poor formability on spherical powder and uneven particle size distribution, and the transmittance of the transparent ceramic obtained by final sintering is low and mostly only reaches between 69 and 75 percent.
Patent document CN 103785843B discloses a method for producing an ultrafine titanium carbonitride based cermet agglomerated spherical powder, which comprises subjecting an ultrafine titanium carbonitride based cermet powder slurry to spray granulation by a high-speed centrifugal spray granulation dryer, but the ceramic powder slurry has poor flowability and is excellent in sphericity, but the powder has poor uniformity and the spherical powder has a wide particle size distribution of 20 to 200 μm.
Patent document CN 104355609A discloses a spray granulation preparation method of YAG-based transparent ceramic powder, which comprises adding sintering aid, dispersant and solvent into raw material powder to prepare slurry, ball-milling and mixing on a planetary ball mill, adding binder, and further ball-milling and mixing to obtain slurry for spray granulation; and then, selecting a centrifugal spray dryer to spray and granulate the slurry, and sieving the collected granulated powder to obtain YAG-based transparent ceramic powder, wherein the spherical powder with good sphericity and fluidity can be prepared by the method, but the particle size distribution of the spherical powder is wider and is between 10 and 90 mu m.
Patent document CN 104591240A discloses a preparation technology of spherical alumina powder, which is to use aluminum nitrate and ammonia water as raw materials, control the reactant concentration, drop-add an aluminum nitrate solution with the ammonia water at a certain temperature, stop dropping the ammonia water when the pH value of a reaction system reaches a specified value, then spray-dry the reaction solution by using nozzles of different sizes to obtain a spherical alumina precursor, and calcine the precursor at 450-600 ℃ for 1-3 hours to obtain gamma-type spherical alumina powder with different average particle sizes. Although the spherical particles obtained by the method have small size and narrow particle size distribution, the concentration and the pH value of reactants need to be strictly controlled when the reaction solution is prepared, the operation is more complicated, the obtained spherical particles are easy to agglomerate, and the spherical powder has a more serious bonding phenomenon due to the small particle size.
Patent document CN 108002354A discloses a method for preparing a particle size controllable spheroidal aluminum nitride powder, which is to wet-grind alumina, carbon powder, calcium fluoride additive and aluminum nitride seed crystal in a ball mill according to a certain proportion, dry and put into a sintering furnace, react for 1 to 4 hours at 1550 to 1800 ℃ under the protection of nitrogen atmosphere, and remove carbon in a muffle furnace to obtain the spheroidal aluminum nitride powder. Although the method can make the particle size of the spheroidal particles smaller and the particle size distribution narrower, and can be controlled between 4 and 30 mu m, the method can not obtain powder particles with better sphericity.
The above patents show that in the method of preparing ceramic spherical powder by atomization method, it is still difficult to obtain spheres with narrow particle size distribution, high balling rate, small spherical particle size and good particle fluidityForming powder. In the preparation process of the AlON powder, the AlON transparent ceramic has higher requirements on the particle size and the distribution uniformity of the raw materials, and Al is sintered at high temperature 2 O 3 The method is easy to agglomerate, and the AlON spherical powder with high performance is difficult to obtain.
Therefore, how to prepare the AlON spherical powder with narrow particle size distribution, high balling rate, small spherical particle size, good particle fluidity and difficult agglomeration by using an atomization method becomes a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to solve the technical problems and provide a preparation method of high-fluidity AlON spherical powder. The technical purpose of the invention is as follows: firstly, the method solves the problem that the existing preparation method of spherical powder does not relate to the preparation of AlON spherical powder, and provides a method for well preparing AlON spherical powder; secondly, the problems of wide particle size distribution, low balling rate, large spherical particle size, poor particle fluidity and easy agglomeration existing in the existing preparation process of the spherical powder are solved.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
a preparation method of high-fluidity AlON spherical powder comprises the following steps:
(1) Dissolving a dispersing agent into an ethanol-water solution, wherein the ethanol content in the ethanol-water solution is 3-5% by volume, uniformly mixing, adding a carbon source, performing ball milling for 1-1.5 h, adding an aluminum source, and performing ball milling for 2-4 h to obtain a uniformly mixed raw material powder solution;
(2) Adding a binder into the raw material powder solution, and performing ball milling for 3.5-4 h to ensure that the binder and the surface of the raw material powder fully act to obtain slurry, wherein the solid content of the slurry is adjusted to 35-50%;
(3) And (3) performing spray granulation on the slurry obtained in the step (2) by using a centrifugal spray dryer, wherein the parameters of the centrifugal spray dryer are controlled as follows: after the air outlet temperature reaches 107 ℃, starting a peristaltic pump, supplying water, adjusting the physicochemical frequency and the physicochemical temperature to be within the range of 105-109 ℃, and then conveying slurry for spray granulation;
(4) Collecting the small balls after the materialization in the step (3), and putting the small balls in N 2 Keeping the temperature at 750-800 ℃ for 1h under the atmosphere to completely carbonize the organic additive, then obtaining pure-phase AlON spherical powder by a one-step sintering method, cooling to normal temperature, heating to 700 ℃ in the air, roasting for a period of time, and removing residual impurities to obtain the high-fluidity AlON spherical powder.
The preparation method provided by the invention is a method for obtaining high-fluidity AlON spherical powder by using a centrifugal spraying method, wherein a carbon source and an aluminum source are used as raw materials, and a carbothermic reduction method is combined with a spraying granulation technology to ensure the high stability of slurry. The method has the characteristics of easily obtained raw materials, simple structure, low cost, high acquisition efficiency and the like, and the obtained spherical powder can be used for forming ceramic blanks and preparing approximate spheres with micron-sized particle sizes.
The inventor of the invention has made a lot of investigations on the preparation process of the AlON spherical powder, and initially found that the obtained spherical powder has poor effect, uneven particle size distribution and poor balling rate, the reason for the analysis is that the obtained slurry has poor stability, and the addition of the dispersing agent can easily generate bubbles in the ball milling process, which seriously affects the balling performance and the uniformity of particle size of the powder in the spray granulation process. On the other hand, parameters in the spray drying granulation process have a large influence on the sphericity, and the effect of the spherical powder obtained by the preparation is very easily influenced.
Finally, the inventors unexpectedly found that the problem that the powder solution is easy to generate bubbles can be well solved by adding the dispersing agent into an aqueous solution containing 3-5% of ethanol, then adding the carbon source and the aluminum source, and performing ball milling respectively; meanwhile, after the raw material powder solution is prepared, the binder is added into the raw material powder solution for ball milling, so that the stability of the slurry can be well ensured, the solid content of the slurry can be kept at a higher level, and the slurry has excellent protective colloid capacity, thereby improving the balling rate and the uniformity of particle size distribution of the spherical powder.
In addition, the inventor finds that each parameter of the centrifugal atomizer also needs to be accurately controlled, and when each parameter is poor in control effect, the obtained powder is low in balling rate. Finally, the inventor obtains a method for well preparing high-fluidity spherical powder by accurately controlling various parameters of a centrifugal atomizer, and the method can obtain pure-phase AlON spherical powder by sintering the small balls obtained by spraying and granulating in one step, and the spherical powder has the advantages of excellent fluidity, narrow particle size distribution, high granulation rate, small spherical particle size and difficult agglomeration in the sintering process.
The high-fluidity AlON spherical powder prepared by the method has good compression molding and sintering characteristics, can be used for preparing high-quality AlON ceramic products, and has the transmittance of 84 percent. On the other hand, the spherical powder can regulate and control the size distribution of particles by adjusting the size fraction configuration, so that the aluminum oxynitride can be applied to the fields of special ceramics such as catalyst carriers, packaging materials, 3D printing and the like and high and new technology, and has wide application prospects.
Further, the dispersant in the step (1) is ammonium polyacrylate, and the addition amount of the dispersant is 3-5% of the total weight of the ethanol-water solution.
Further, the carbon source in the step (1) includes sucrose (C) 12 H 22 O 11 ) Or glucose (C) 12 H 22 O 11 ) Any one of the above-mentioned (b), the addition amount of which is 3% of the total weight of the raw material powder solution; the aluminum source is gamma-Al 2 O 3 The addition amount of the additive accounts for 47 percent of the total weight of the raw material powder solution.
Further, the revolution number of the two ball mills in the step (1) is 120rpm.
Further, in the step (2), the binder is hydroxyethyl cellulose (HEC), and the addition amount of the binder accounts for 1% of the total weight of the raw material powder solution.
Further, the operation of the one-step sintering method in the step (4) is as follows: placing the pellets in a boron nitride crucible, heating to 1750 ℃, and then preserving heat for 1h at the heating rate of 10 ℃/min.
Further, in the step (4), the cooling rate of the temperature to the normal temperature is 10 ℃/min, and then the temperature is raised to 700 ℃ in the air and then the mixture is roasted for 1h.
The invention has the following beneficial effects:
(1) The invention provides a method for preparing AlON spherical powder in batches, which has the characteristics of easily available raw materials, simple structure, low cost, high acquisition efficiency and the like;
(2) The preparation method of the AlON spherical powder provided by the invention has the characteristics of narrow particle size distribution, high balling rate, small spherical particle size, good particle fluidity and difficult agglomeration;
(3) According to the preparation method of the AlON spherical powder, the median particle size of AlON spheres can be reduced to 10 mu m, the specific surface area of the powder is improved while the high fluidity of the spherical powder is ensured, the activity of the powder is enhanced, and the transmittance of the prepared AlON transparent ceramic reaches 84%;
(4) The AlON pellets prepared by the method have good sphericity, the surfaces of the pellets have certain pore structures, and N is favorably promoted 2 The full contact of the components has certain promotion effect on improving the sintering efficiency.
Drawings
FIG. 1 is a surface topography diagram of AlON pellet powder obtained in example 1 of the present invention;
FIG. 2 is an enlarged view of the surface topography of AlON pellet powder obtained in example 1 of the present invention;
FIG. 3 is a distribution diagram of the particle size of AlON pellet obtained in example 1 of the present invention;
FIG. 4 is a surface topography of AlON pellet powder obtained in comparative example 3;
FIG. 5 is a surface topography of AlON pellet powder obtained in comparative example 4;
FIG. 6 is a surface topography of AlON pellet powder obtained in comparative example 5;
FIG. 7 is a surface topography of AlON pellet powder obtained in comparative example 6;
fig. 8 is a viscosity change curve of AlON slurry obtained in comparative example 6.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail with reference to the following embodiments, it should be noted that the following embodiments are only for explaining and illustrating the present invention and are not intended to limit the present invention. The invention is not limited to the embodiments described above, but rather, may be modified within the scope of the invention.
Example 1
A preparation method of AlON spherical powder comprises the following steps:
(one) preparing the slurry for spraying
Deionized water is measured according to the required powder with 40 percent (wt) of solid content, 3 percent (vol) of ethanol is added, after ball milling is carried out for 10min, 3 percent (wt) of ammonium polyacrylate (C3H 7NO 2) is weighed and added into the solution, ball milling is carried out for 10min, and then 3 percent (wt) of glucose (C) is added 6 H 12 O 6 ) Ball milling for 1h as carbon source, mixing uniformly, adding 47% (wt) of gamma-Al 2 O 3 Ball milling for 2h to obtain a raw material powder solution; adding 1% (wt) of hydroxyethyl cellulose (HEC) into the raw material powder solution, and performing ball milling for 1h to ensure that a binder and the surface of the raw material powder fully act to obtain slurry, wherein the solid content of the slurry is 40% (wt);
(II) granulating by using a sprayer
Turning on an induced draft fan, ensuring that cooling water can normally circulate, turning on the induced draft fan, a stirring motor, pulse dust removal, electric heating (preset temperature is determined according to the needed materialization temperature) and an atomizer in sequence, turning on a peristaltic pump after the air outlet temperature (materialization temperature of a materialization plate, which can be considered as the same as the materialization temperature) reaches 107 ℃ which can be used for materialization, supplying water firstly, adjusting the materialization frequency and the materialization temperature in a sequence from low frequency (50 HZ) to high frequency (300 HZ), after the materialization frequency and the materialization temperature are stabilized (105-107 ℃), conveying the slurry (rotating speed of the peristaltic pump: 25 rpm), after the slurry is conveyed, conveying water for a while (2 min), turning off heating, after the temperature of a materialization chamber is reduced to room temperature, turning off the atomizer, collecting materialized raw material pellets, and screening the pellets by using a 300-mesh screen;
(III) sintering of the powder
Placing the materialized pellets in a boron nitride crucible in flowing N 2 Keeping the temperature for 1h at a certain temperature (780 ℃) in the atmosphere to add organic substancesCompletely carbonizing the agent, directly heating to 1750 ℃ at the heating rate of 10 ℃/min, and preserving the heat for 1h to obtain AlON phase spherical powder; and finally, cooling to normal temperature, taking out the spherical powder, then heating to 700 ℃ in air, roasting for 1h, and removing residual impurities to obtain the pure-phase spherical AlON powder.
Example 2
A preparation method of AlON spherical powder comprises the following steps:
(I) preparing the slurry for spraying
Weighing deionized water according to the required powder with 35 percent (wt) of solid content, adding 4 percent (vol) of ethanol, weighing 4 percent (wt) of ammonium polyacrylate after ball milling for 12min, adding into the solution, ball milling for 8min, and then adding 3 percent (wt) of glucose (C) 6 H 12 O 6 ) Ball milling for 1h as carbon source, mixing uniformly, adding 47% (wt) of gamma-Al 2 O 3 Ball milling for 3h to obtain a raw material powder solution; adding 1 percent (wt) of hydroxyethyl cellulose (HEC) into the raw material powder solution, and performing ball milling for 1h to ensure that the binder and the surface of the raw material powder fully act to obtain slurry, wherein the solid content of the slurry is 35 percent (wt);
(II) granulating by using a sprayer
Opening an induced draft fan, ensuring that cooling water can normally circulate, sequentially opening the induced draft fan, a stirring motor, pulse dust removal, electric heating (the preset temperature is determined according to the needed physicochemical temperature) and an atomizer, starting a peristaltic pump after the air outlet temperature (the temperature of a physicochemical plate) reaches the temperature (107 ℃) capable of being used for physicochemical treatment, supplying water, adjusting the physicochemical frequency and the physicochemical temperature according to the sequence from low frequency to high frequency, conveying the slurry after the physicochemical frequency and the physicochemical temperature are stabilized (stabilized between 107 ℃ and 109 ℃), conveying the slurry, conveying water for a while after the slurry is conveyed, then closing the heating, closing the atomizer after the temperature of a physicochemical bin is reduced to room temperature, collecting small material balls after physicochemical treatment, and sieving the small balls by using a 300-mesh sieve;
(III) sintering of the powder
Placing the materialized pellets in a boron nitride crucible in flowing N 2 Keeping the atmosphere at a certain temperature (780 ℃) for 1h to completely carbonize the organic additive, and then directly carrying outHeating to 1750 ℃ at a heating rate of 10 ℃/min, and preserving heat for 1h to obtain AlON phase spherical powder; and finally, cooling to normal temperature, taking out the spherical powder, then heating to 700 ℃ in the air, roasting for 1h, and removing residual impurities to obtain the pure-phase spherical AlON powder.
Example 3
A preparation method of AlON spherical powder comprises the following steps:
(one) preparing the slurry for spraying
Weighing deionized water according to the required powder with 50 percent (wt) of solid content, adding 5 percent (vol) of ethanol, after ball milling for 15min, weighing 5 percent (wt) of ammonium polyacrylate, adding the ammonium polyacrylate into the solution, ball milling for 15min, then adding 3 percent (wt) of carbon black as a carbon source, ball milling for 1.5h, after uniformly mixing, adding 47 percent (wt) of gamma-Al 2 O 3 Carrying out ball milling on aluminum oxide for 4 hours to obtain a raw material powder solution; adding 1 percent (wt) of hydroxyethyl cellulose (HEC) into the raw material powder solution, and performing ball milling for 1h to ensure that the binder and the surface of the raw material powder fully act to obtain slurry, wherein the solid content of the slurry is 50 percent (wt);
(II) granulating by using a sprayer
Opening an induced draft fan, ensuring that cooling water can normally circulate, sequentially opening the induced draft fan, a stirring motor, pulse dust removal, electric heating (preset temperature is determined according to the needed physicochemical temperature) and an atomizer, starting a peristaltic pump after the air outlet temperature (physicochemical plate temperature) reaches the temperature (107 ℃) capable of being used for physicochemical treatment, supplying water, adjusting the physicochemical frequency and the physicochemical temperature according to the sequence from low frequency to high frequency, conveying the slurry after the physicochemical frequency and the physicochemical temperature are stabilized (stabilized between 106 ℃ and 108 ℃), conveying the slurry, conveying water for a while after the slurry is conveyed, then closing the heating, closing the atomizer after the physicochemical cabin temperature is reduced to room temperature, collecting small materialized raw material balls, and sieving the small balls by using a 300-mesh sieve;
(III) sintering of the powder
Placing the materialized pellets in a boron nitride crucible in flowing N 2 Keeping the temperature of the atmosphere at a certain temperature (800 ℃) for 1h to completely carbonize the organic additive, then directly heating to 1750 ℃ at a heating rate of 10 ℃/min, and keeping the temperature for 1h to obtain the AlON ballForming powder; and finally, cooling to normal temperature, taking out the spherical powder, then heating to 700 ℃ in the air, roasting for 1h, and removing residual impurities to obtain the pure-phase AlON spherical powder.
Characterization example 1
By representing the pure phase spherical AlON powder obtained in the above examples 1-3, taking example 1 as an example (results of other examples are not very different), the SEM appearance is shown in figures 1-2, and the particle size distribution is shown in figure 3, it can be seen that the AlON spherical powder prepared by the invention has high sphericity, narrow particle size distribution, small size (10 μm) of spherical particles, pores on the surface, and no agglomeration phenomenon of the small particles.
Comparative example 1
The preparation method of example 1 was followed, except that the dispersant was directly added to water without adding ethanol in the step (one), to prepare an AlON spherical powder. In the experimental process, the dispersing agent is easy to generate bubbles when being ball-milled in water due to no addition of ethanol, a large amount of bubbles are generated in the raw material powder solution, and finally, the small balls obtained by spray granulation have poor balling performance, low balling rate and uneven particle size distribution.
Comparative example 2
The preparation process of example 1 was followed, except that the parameters for the atomizer granulation in step (ii) were adjusted as follows: the materialization temperature is changed from 107 ℃ to 120 ℃, or the rotating speed of a peristaltic machine is changed from 25rpm to 50rpm, and the result shows that the prepared small balls have poor forming effect, low balling rate and wider particle size distribution.
Comparative example 3
The preparation method of example 1 was followed, except that the binder HEC in the step (one) was replaced with PVA (polyvinyl alcohol) and the solid content of the slurry was increased to 50wt%, and the result of preparing the AlON spherical powder was as shown in fig. 4.
Since PVA has poor water solubility at room temperature and requires a long time of stirring, the binding ability is lowered, and thus the preparation is carried out by adjusting the solid content to 50%. However, even with high solids content, the product obtained by spray granulation still exhibits surface voids and irregular morphology of the lumps (see fig. 4), rather than regular spheroids, which have a low spheronization rate.
Comparative example 4
The preparation method of example 1 was followed except that the solid content of the slurry was adjusted to 30wt% in the step (one), pellets were prepared and then high-temperature sintering was performed, and the result is shown in fig. 5.
In a high-temperature environment, the solution is centrifuged, and the formed spherical particles gradually evaporate water molecules from the inside to the outside in the drying process. Due to the reduced solids content, a thin shell is formed by the large amount of water during the drying process, resulting in the voiding of the spheres, which leads to the cracking of the spheres during high temperature sintering (see fig. 5).
Comparative example 5
The preparation method of example 1 was followed except that no dispersant was added in step (one) to cause the pellets to crack, the addition of the dispersant can significantly reduce the viscosity and surface tension of the suspension, and the slurry viscosity and quality significantly affect the changes in the size of the particles and the centrifugal shear force. Since the raw materials are not uniformly dispersed, the carbon source is easily coated with alumina, resulting in non-uniformity in the drying process (see fig. 6).
Comparative example 6
The preparation method of example 1 was followed, except that the carbon source in the step (one) was replaced with carbon black, and the results are shown in FIGS. 7 and 8. It can be seen that although the carbon black had a good spherical shape, the whole pellets had an uneven particle size distribution and a large particle size (80 μm or more). This is because carbon black has poor water solubility, and the addition of water significantly increases the viscosity of the slurry, resulting in a decrease in shear force, and thus is difficult to centrifuge into spheres having smaller crystal grains.
Claims (7)
1. A preparation method of high-fluidity AlON spherical powder is characterized by comprising the following steps:
(1) Dissolving a dispersing agent into an ethanol-water solution, wherein the ethanol content in the ethanol-water solution is 3-5% by volume, uniformly mixing, adding a carbon source, performing ball milling for 1-1.5 h, adding an aluminum source, and performing ball milling for 2-4 h to obtain a uniformly mixed raw material powder solution;
(2) Adding a binder into the raw material powder solution, performing ball milling for 1-4 h to ensure that the binder and the surface of the raw material powder fully act to obtain slurry, and adjusting the solid content of the slurry to 35-50%;
(3) And (3) performing spray granulation on the slurry obtained in the step (2) by using a spray dryer, wherein the parameters of the centrifugal spray dryer are controlled as follows: after the air outlet temperature reaches 107 ℃, starting a peristaltic pump, supplying water, adjusting the physicochemical frequency to stabilize the physicochemical temperature within the range of 105-109 ℃, and then conveying the slurry for spray granulation;
(4) Collecting the small balls after the materialization in the step (3), and putting the small balls in N 2 And (3) preserving the temperature for 1h at 750-800 ℃ in the atmosphere to completely carbonize the organic additive, then obtaining pure-phase AlON spherical powder by a one-step sintering method, cooling, taking out the pure-phase AlON spherical powder, heating the AlON spherical powder to 700 ℃ in the air, roasting the AlON spherical powder for a period of time, and removing residual impurities to obtain the high-fluidity AlON spherical powder.
2. The method according to claim 1, wherein the dispersant in the step (1) is ammonium polyacrylate, and the dispersant is added in an amount of 3 to 5% by weight based on the total weight of the ethanol-water solution.
3. The preparation method according to claim 1 or 2, wherein the carbon source in step (1) comprises any one of sucrose or glucose, and the amount of the carbon source is 3% of the total weight of the raw material powder solution; the aluminum source is gamma-Al 2 O 3 The addition amount of the composite powder is 47 percent of the total weight of the raw material powder solution.
4. The method according to claim 1 or 2, wherein the two ball mills in step (1) are rotated at 120r/min.
5. The preparation method according to claim 1 or 2, wherein the binder in the step (2) is hydroxyethyl cellulose, and the addition amount of the binder is 1% of the total weight of the raw material powder solution.
6. The method according to claim 1 or 2, wherein the one-step sintering process in step (4) is performed by: placing the pellets in a boron nitride crucible, heating to 1750 ℃, and then preserving heat for 1h at the heating rate of 10 ℃/min.
7. The preparation method according to claim 1 or 2, wherein the temperature reduction rate of the temperature reduction in the step (4) is reduced to normal temperature at 10 ℃/min, and then the mixture is baked in air at 700 ℃ for 1h.
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