CN114751728A - Preparation method of alumina ceramic granulation powder - Google Patents

Preparation method of alumina ceramic granulation powder Download PDF

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CN114751728A
CN114751728A CN202210577743.XA CN202210577743A CN114751728A CN 114751728 A CN114751728 A CN 114751728A CN 202210577743 A CN202210577743 A CN 202210577743A CN 114751728 A CN114751728 A CN 114751728A
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powder
alumina
ball
alpha
granulation
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陈东升
武鼎铭
王松
王蕾
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Henan Hongcheng New Material Technology Co ltd
Henan Mechanical and Electrical Vocational College
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Henan Hongcheng New Material Technology Co ltd
Henan Mechanical and Electrical Vocational College
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Abstract

The invention relates to the technical field of ceramic materials, and provides a preparation method of alumina ceramic granulated powder. Mixing alpha-alumina raw powder, a dispersing agent, a grinding aid and water, and carrying out first ball milling to obtain first ball milling slurry; mixing the first ball-milling slurry and a granulation binder aqueous solution, and carrying out second ball milling to obtain a second ball-milling slurry; and mixing the second ball-milling slurry, a lubricating agent and a defoaming agent, and then carrying out spray granulation to obtain the alumina ceramic granulated powder. The invention selects high-purity alpha-alumina powder as raw material, the granularity of the alpha-alumina powder primary crystal is small and the distribution is narrow after ball milling and dispersion, and the sintering activity can be improved. The alumina ceramic granulated powder prepared by the invention has good sintering performance and high ceramic density, and can meet the requirements of advanced ceramics, particularly functional ceramics and structural ceramics.

Description

Preparation method of alumina ceramic granulation powder
Technical Field
The invention relates to the technical field of ceramic materials, in particular to a preparation method of alumina ceramic granulated powder.
Background
Advanced ceramic materials, also known as precision ceramic materials, are products with excellent performance which are manufactured by adopting refined high-purity and superfine inorganic compounds as raw materials and advanced preparation technology. The alumina ceramic is prepared from alumina (Al)2O3) The advanced ceramic material as the main body has a series of excellent characteristics such as high mechanical strength, high volume resistivity, good electrical insulation, high strength, wear resistance, oxidation resistance and the like, and is mainly applied to the high-end ceramic fields such as functional ceramics, structural ceramics and the like.
The alumina ceramic material is mainly prepared by sintering alpha-alumina powder serving as a raw material. The alpha-alumina powder is generally prepared by stirring granulation, pressure granulation, spray granulation or freeze drying, wherein the spray drying method has the advantages of high drying speed and good powder dispersibility, and is most widely applied at present. However, the alpha-alumina powder prepared by the spray drying method at present has low purity (below 99 percent) and wide particle size distribution (D)90/D10More than 10), resulting in poor sintering performance of the powder, high sintering temperature (above 1550 ℃), poor compactness of the ceramic part (density of 3.5-3.9 g/cm)3) And large shrinkage (> 16%).
Disclosure of Invention
In view of this, the present invention provides a method for preparing alumina ceramic granulated powder. The alumina ceramic granulated powder prepared by the invention has small granularity, narrow granularity distribution, good sintering performance, good compactness of a ceramic part and small shrinkage rate.
In order to achieve the above object, the present invention provides the following technical solutions:
a preparation method of alumina ceramic granulated powder comprises the following steps:
mixing alpha-alumina raw powder, a dispersing agent, a grinding aid and water, and carrying out first ball milling to obtain first ball milling slurry; the purity of the alpha-alumina raw powder is more than or equal to 99.95 percent;
mixing the first ball-milling slurry and a granulation binder aqueous solution, and carrying out second ball milling to obtain a second ball-milling slurry;
and mixing the second ball-milling slurry, a lubricant and a defoaming agent, and then carrying out spray granulation to obtain alumina ceramic granulation powder.
Preferably, the mass fraction of the alpha-alumina raw powder is 10-50% based on 100% of the total mass of the alpha-alumina raw powder and water.
Preferably, the dispersing agent comprises one or more of polyacrylamide, polyethylene glycol, sodium hexametaphosphate, modified polyacrylamide and hexadecyl trimethyl ammonium bromide; the mass of the dispersing agent is 0.5-3% of that of the alpha-alumina raw powder;
The grinding aid comprises micromolecular alcohol, and the number of carbon atoms of the micromolecular alcohol is 2-5; the mass of the grinding aid is 1.8-3% of that of the alpha-alumina raw powder.
Preferably, the rotating speed of the first ball milling and the rotating speed of the second ball milling are independently 20-100 r/min, the time of the first ball milling is 8-18 h, and the time of the second ball milling is 0.5-1.5 h;
the grinding balls used in the first ball mill and the second ball mill are high-purity alumina grinding balls, and the purity of the high-purity alumina grinding balls is more than or equal to 99.99%;
and in the first ball milling process and the second ball milling process, cooling water is adopted for cooling circularly to keep the temperature of the slurry below 50 ℃.
Preferably, the mass fraction of the granulation binder in the granulation binder aqueous solution is 5 to 10%, and the mass of the granulation binder aqueous solution is 0.6 to 1.6% of the mass of the alpha-alumina raw powder.
Preferably, the lubricant comprises one or more of water-based paraffin, glycerol and n-butanol; the mass of the lubricant is 1.2-3% of that of the alpha-alumina raw powder;
the defoaming agent is a polyol ester defoaming agent, and the mass of the defoaming agent is 0.5-0.8% of the mass of the alpha-alumina raw powder.
Preferably, the second ball-milling slurry, the lubricant and the defoaming agent are mixed under the conditions of ultrasound and stirring, and the power of the ultrasound is 3-5 kw.
Preferably, the spray granulation is performed by using a centrifugal spray granulation tower, and the conditions of the spray granulation include: the outlet temperature is 105-115 ℃, the negative pressure of air in the tower is 250-350 Pa, and the temperature in the tower is 280-300 ℃.
Preferably, after the spray granulation, the method further comprises the step of screening the obtained powder lot in a grading manner; the grading screening comprises the following steps: and screening the powder obtained by spray granulation by using a double-layer sieve, wherein the material between sieves is the alumina ceramic granulated powder, the mesh number of an upper-layer sieve of the double-layer sieve is 160-180 meshes, and the mesh number of a lower-layer sieve is 440-460 meshes.
The invention provides a preparation method of alumina ceramic granulated powder, which comprises the following steps: mixing alpha-alumina raw powder, a dispersing agent, a grinding aid and water, and carrying out first ball milling to obtain first ball milling slurry; the purity of the alpha-alumina raw powder is more than or equal to 99.95 percent; mixing the first ball-milling slurry and a granulation binder aqueous solution, and carrying out second ball milling to obtain a second ball-milling slurry; and mixing the second ball-milling slurry, a lubricant and a defoaming agent, and then carrying out spray granulation to obtain alumina ceramic granulation powder. The alpha-alumina raw powder with the purity of more than or equal to 99.95 percent is used as a raw material, a dispersing agent and a grinding aid are added in the ball milling process, and the alpha-alumina raw powder obtained after ball milling dispersion has small grain size and narrow grain size distribution, so that the grain size of the finally obtained granulated powder is reduced, the grain uniformity of the powder is improved, and the sintering performance of the granulated powder is improved; in addition, before spray granulation, a lubricant and a defoaming agent are added into the second ball-milling slurry, wherein the lubricant can generate a foamless lubricating layer in the dry pressing and forming process of the granulated powder, so that the flow of granules under pressure is promoted, the pressure distribution is uniform, the internal structural stress of the blank can be reduced, and the blank is prevented from being damaged by cracking, spalling and the like in the subsequent working procedures; the addition of the defoaming agent can reduce bubbles in the slurry, is favorable for obtaining homogeneous and solid spherical granulation powder and improves the sintering density of the granulation powder.
Furthermore, the powder obtained after spray granulation is classified and screened by adopting the double-layer sieve, so that the uniformity of the granulated powder can be further improved, and further, the stacking density of the granulated powder, the density of the biscuit obtained by pressing and the strength of the porcelain are improved.
The results of the examples show that the alumina ceramic granulated powder prepared by the invention has the alumina content of more than or equal to 99.04 percent and the median particle diameter D 5040 to 80 μm, D90/D10Not more than 3, good fluidity, a repose angle not more than 30 degrees, and a loose packed density of the granulated powder of 0.9 to 1.1g/cm3The density of the formed biscuit is more than or equal to 2.3g/cm3Sintering the prepared alumina ceramic granulation powder at the sintering temperature of 1400-1450 ℃ for 1-2 h, wherein the sintering density is more than or equal to 3.935g/cm3The finished porcelain has smooth surface, compact inside, low porosity and small shrinkage rate (less than 16%). The bulk density of the conventional alumina ceramic granulated powder in the field is generally 0.6-0.9 g/cm3The density of the formed biscuit is 1.9-2.2 g/cm3The sintering temperature is 1500-1600 ℃, the sintering time is more than 2h, and the sintering density is 3.5-3.9 g/cm3The shrinkage rate of the ceramic is 16-20%. Therefore, compared with the prior art, the alumina ceramic granulated powder prepared by the invention has small granularity, narrow granularity distribution, good sphericity and fluidity, good sintering performance and high ceramic density, and can meet the requirements of advanced ceramics, particularly functional ceramics and structural ceramics, on high insulativity, high thermal shock resistance and high mechanical strength.
Drawings
FIG. 1 is a particle size distribution diagram of a slurry prepared in step (1) of example 1;
FIG. 2 is a graph showing a particle size distribution of granulated alumina ceramic powder prepared in example 1;
FIG. 3 is an electron microscope photograph of the granulated alumina ceramic powder prepared in example 1.
Detailed Description
The invention provides a preparation method of alumina ceramic granulated powder, which comprises the following steps:
mixing alpha-alumina raw powder, a dispersing agent, a grinding aid and water, and carrying out first ball milling to obtain first ball milling slurry; the purity of the alpha-alumina raw powder is more than or equal to 99.95 percent, and the alpha-alumina phase inversion rate is 92-96 percent;
mixing the first ball-milling slurry and a granulation binder aqueous solution, and carrying out second ball milling to obtain a second ball-milling slurry;
and mixing the second ball-milling slurry, a lubricant and a defoaming agent, and then carrying out spray granulation to obtain alumina ceramic granulation powder.
The method comprises the steps of mixing alpha-alumina raw powder, a dispersing agent, a grinding aid and water, and carrying out first ball milling to obtain first ball milling slurry. In the invention, the purity of the alpha-alumina raw powder is more than or equal to 99.95%, preferably more than or equal to 99.99%, and in the invention, the alpha phase transformation rate of the alpha-alumina raw powder is preferably 92-96%, more preferably 95-96%; the source of the alpha-alumina raw powder is not particularly required by the invention, and the alpha-alumina raw powder sold in the market can be adopted, and in the specific embodiment of the invention, the grain diameter of the alpha-alumina raw powder is preferably less than 30 μm. High-purity alpha-alumina powder is selected as a raw material, and the primary crystals of the alpha-alumina powder after ball milling and dispersion have small particle size and narrow distribution, so that the sintering activity is improved, and the sintering temperature is reduced.
In the invention, the mass fraction of the alpha-alumina raw powder is 10-50%, preferably 20-40%, based on 100% of the total mass of the alpha-alumina raw powder and water; in the present invention, the mass fraction of the alpha-alumina raw powder is preferably controlled within the above range, which is advantageous for obtaining an alumina powder having a smaller particle size.
In the invention, the dispersant preferably comprises one or more of polyacrylamide, polyethylene glycol, sodium hexametaphosphate, modified polyacrylamide and hexadecyl trimethyl ammonium bromide, wherein the modified polyacrylamide is a commercially available product with the model of AD8098 or SN5027, wherein the AD8098 is a commercially available product produced by Oda environmental protection new material Co.Ltd in Dongguan, and the SN5027 is a commercially available product produced by Guangzhou Hengyu chemical industry Co.Ltd; the mass of the dispersant is preferably 0.5 to 3% of the mass of the alpha-alumina raw powder, and more preferably 1.5 to 2.5%.
In the invention, the grinding aid preferably comprises micromolecular alcohol, the number of carbon atoms of the micromolecular alcohol is preferably 2-5, and specifically, the micromolecular alcohol preferably comprises one or more of ethanol, ethylene glycol, propylene glycol and glycerol; the mass of the grinding aid is preferably 1.8-3% of the mass of the alpha-alumina raw powder, and more preferably 2-2.8%. In the ball milling process, the dispersing agent and the grinding aid are added, so that the alumina powder with fine particle size and narrow particle size distribution is obtained, and the dispersion stability of the powder in slurry is kept.
In the invention, the rotation speed of the first ball milling is preferably 20-100 r/min, more preferably 30-80 r/min, and the time of the first ball milling is preferably 8-18 h, preferably 10-15 h; the first ball milling grinding balls are preferably alumina grinding balls, the purity of the alumina grinding balls is preferably more than or equal to 99.99%, the diameter of the alumina grinding balls is preferably 2-8 mm, and more preferably 3-6 mm, in a specific embodiment of the invention, grinding balls with a single particle size can be adopted, or grinding balls with different particle sizes can be mixed for use, and the invention is not particularly limited; the mass ratio of the alpha-alumina raw powder to the alumina grinding balls is preferably 1 (2-8), and more preferably 1 (3-6). In the first ball milling process, the invention preferably adopts cooling water to circularly reduce the temperature, and the temperature of the slurry is kept below 50 ℃.
In the invention, the median particle diameter D of the alpha-alumina primary crystal in the first ball-milling slurry50Preferably less than or equal to 0.25 μm, more preferably 0.21 to 0.25 μm, D90/D10Preferably ≦ 3. The invention preferably detects the granularity of the alumina powder in the first ball-milling slurry, and when the granularity of the powder meets the requirement, the powder is qualified.
After the first ball milling slurry is obtained, the first ball milling slurry and the granulation binder aqueous solution are mixed for second ball milling, and second ball milling slurry is obtained. In the invention, after the first ball milling is finished, the grinding balls and the slurry do not need to be separated, and the granulation binder aqueous solution is directly added into a ball milling tank for second ball milling, wherein the rotation speed of the second ball milling is preferably 20-100 r/min, more preferably 30-80 r/min, and in the specific embodiment of the invention, the rotation speed of the second ball milling is preferably consistent with that of the first ball milling; in the invention, the time of the second ball milling is preferably 0.5-1.5 h, and more preferably 1 h; in the second ball milling process, cooling water is preferably adopted for cooling circularly, and the temperature of the slurry is controlled to be below 50 ℃. In industrial production, the ball mill has a large diameter, so that kinetic energy is large in the ball milling process, a system is easy to heat, most of slurry is low-boiling-point substances such as water and organic additives, gas pressure is formed after evaporation, potential safety hazards exist, and the stability of the additives can be influenced due to overhigh temperature.
In the invention, the mass fraction of the granulation binder in the granulation binder aqueous solution is preferably 5-10%, and the mass of the granulation binder aqueous solution is preferably 0.6-1.6%, more preferably 1-1.2% of the mass of the alpha-alumina raw powder; the granulation binder is preferably polyvinyl alcohol (PVA).
After the second ball milling is finished, the invention preferably separates the grinding balls from the slurry to obtain a second grinding slurry.
After the second grinding slurry is obtained, the second grinding slurry, the lubricant and the defoaming agent are preferably mixed and then spray-granulated to obtain the alumina ceramic granulated powder. In the present invention, the lubricant preferably includes one or more of aqueous paraffin, glycerol and n-butanol; the mass of the lubricant is preferably 1.2-3% of that of the alpha-alumina raw powder, and more preferably 1.5-2.5%; in the invention, the lubricant can generate a bubble-free lubricating layer in the process of granulating powder dry pressing and forming the blank, so that the flow of granules under pressure is promoted, the pressure is uniformly distributed, the internal structural stress of the blank can be reduced, the blank is prevented from being cracked, scattered and cracked in subsequent processes and other damages, and in addition, the lubricating layer formed between the blank and the die wall can also reduce the friction force and reduce the abrasion and wear to the die.
In the invention, the defoaming agent is preferably a polyol ester defoaming agent, the concrete type of the polyether defoaming agent is not specially required, and the polyether defoaming agent can be commercially available products well known to those skilled in the art, such as DS-3030E, MQ-232, polyoxyethylene glycerol ether and the like; the mass of the defoaming agent is preferably 0.5 to 0.8% of the mass of the alpha-alumina raw powder, and more preferably 0.6 to 0.7%.
In the invention, the mixing of the second ball-milling slurry, the lubricant and the defoaming agent is preferably carried out under the conditions of ultrasound and stirring, and the power of ultrasound is preferably 3-5 kw; the rotating speed of the stirring is preferably 30-80 rpm, and the mixing time is preferably 0.5-1 h; in a specific embodiment of the invention, the second ball-milling slurry is preferably placed in a stirring barrel with an ultrasonic function on the barrel wall, then ultrasonic and stirring are started, then the lubricant and the defoaming agent are added, stirring is carried out for 0.5-1 h, the mixture is fully and uniformly mixed, and then spray granulation is carried out on the obtained mixture.
In the present invention, the spray granulation is preferably performed using a centrifugal spray granulation tower, and the conditions of the spray granulation preferably include: the outlet temperature is 105-115 ℃, the preferred temperature is 110 ℃, the negative pressure of air in the tower is 250-350 Pa, the preferred pressure is 280-320 Pa, the temperature in the tower is 280-300 ℃, and the preferred temperature is 285-295 ℃. And (3) after spray granulation, obtaining homogeneous and solid spherical granulated powder, wherein the water content of the obtained granulated powder is preferably 0.2-0.5%.
In the invention, after the spray granulation is finished, the method also preferably comprises the step of screening the obtained powder lot in a grading way; the grading screening comprises the following steps: screening the obtained powder material by using a double-layer screen, wherein the material among screens is the alumina ceramic granulation powder, the mesh number of the upper layer of the double-layer screen is preferably 160-180 meshes, more preferably 170 meshes, and the mesh number of the lower layer of the double-layer screen is preferably 440-460 meshes, more preferably 450 meshes; the invention preferably controls the particle size of the alumina ceramic granulated powder by classified screening, and further reduces the particle size distribution of the alumina ceramic granulated powder.
The invention adopts the optimized granulation formula and process, so that the granulation powder has the advantages of solid particles, good sphericity and good fluidity, and the particle size distribution is uniform after classification and screening, thereby the bulk density, the biscuit density and the strength can be improved, and the granulation powder has the advantages of good sintering performance, low sintering temperature, short sintering time and high ceramic density.
In the present invention, the alumina ceramic granulated powder contains components in mass fractionThe number is preferably: al (Al)2O3≥99.04％，SiO2≤0.002％，Fe2O3≤0.001％，Na2O is less than or equal to 0.01 percent, ignition loss is less than or equal to 0.94 percent, the ignition loss is specifically the mass reduction of the alumina ceramic granulated powder after being ignited for 2 hours at 1100 +/-20 ℃, and the reduced mass is mainly the mass of additives and moisture in the granulated powder. In the invention, the alumina ceramic granulated powder has small granularity and uniform granularity distribution, and particularly, the median grain diameter D of the alumina ceramic granulated powder 50Preferably 40 to 80 μm, more preferably 60 μm, D90/D10Less than or equal to 3. In addition, the alumina ceramic granulated powder has good fluidity, the repose angle is less than or equal to 30 degrees, and the dry pressing molding and the preparation of biscuit with high density are convenient.
In the invention, the loose packed density of the alumina ceramic granulated powder is preferably 0.94-1.1 g/cm3The density of the formed biscuit is more than or equal to 2.3g/cm3The sintering temperature of the ceramic is preferably 1400-1450 ℃, the sintering time is preferably 1-2 h, and the density of the sintered alumina ceramic is more than or equal to 3.935g/cm3The shrinkage is less than 16 percent.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) 50kg of high-purity alpha-alumina raw powder (the purity is more than or equal to 99.95 percent, and the alpha phase conversion rate is 92-96 percent), 75kg of deionized water (namely the solid content of slurry is 40 percent), 0.9kg of dispersing agent (1.8 percent of the mass of the high-purity alpha-alumina raw powder), 1.25kg of grinding aid (2.5 percent of the mass of the high-purity alpha-alumina raw powder), and 220kg of high-purity alumina grinding balls (the purity is more than or equal to 99.99 percent) are added into a ball milling tank, wherein the dispersing agent is polyacrylamide, and the grinding aid is ethylene glycol. Mixing and ball milling for 16h at the rotating speed of 65r/min, and starting cooling water circulation cooling barrel walls while ball milling to ensure that the temperature of a slurry system is lower than 50 ℃.
After the ball milling was completed, the particle size distribution of the powder in the slurry was measured, and the result is shown in fig. 1, in which fig. 1 shows the particle size D of the primary crystal of the α -alumina powder in the obtained slurry500.233 μm and a narrow particle size distribution, D90/D10＝2.91。
(2) And adding 500g of PVA aqueous solution with the mass fraction of 10% into the ball milling tank, and continuing ball milling for 0.5h after the addition to ensure that the system is uniformly distributed.
(3) After the ball milling is finished, separating the grinding balls from the slurry by using a 80-mesh screen, and transferring the slurry into a stirring barrel, wherein the wall of the stirring barrel has a 3kw ultrasonic wave function. Starting ultrasonic waves, starting stirring, adding 0.95kg of lubricant (1.9 percent of the mass of the high-purity alpha-alumina raw powder), adding 0.25kg of polyol ester defoamer (0.5 percent of the mass of the high-purity alpha-alumina raw powder), wherein the lubricant is water-based paraffin, and the polyester defoamer is DS-3030E, stirring for 1.0h, and fully and uniformly mixing to obtain mixed slurry.
(4) Feeding the mixed slurry into a centrifugal spray granulation tower with the water evaporation capacity of 25kg/h for granulation, and controlling the conditions as follows: the temperature in the tower is 285 ℃, the outlet temperature is controlled to be 108 ℃, the negative pressure of air in the tower is 300Pa, centrifugal atomization is carried out by a centrifugal disc, and homogeneous solid spherical granulation powder with the water content of 0.4 percent is formed by high-temperature drying.
(5) The granulated powder obtained by spray granulation is screened by a vibrating screen with 170 meshes and 450 meshes in a double-layer way, and a qualified product is obtained between the granulated powder and the vibrating screen, namely the alumina ceramic granulated powder obtained in the embodiment.
And (4) performance testing:
1. particle size distribution and morphology testing
The particle size distribution of the obtained alumina ceramic granulated powder is shown in FIG. 2. FIG. 2 shows the alumina ceramic granulated powder D prepared in this example50＝63.68μm，D10＝33.53μm，D90＝98.31μm，D90/D10＝2.93。
An electron microscopic photograph of the obtained alumina ceramic granulated powder is shown in FIG. 3. As can be seen from FIG. 3, the obtained granulated powder has uniform particle size distribution and good sphericity, and the test shows that the repose angle of the obtained alumina ceramic granulated powder is 27 degrees, which indicates that the alumina ceramic granulated powder has good fluidity.
2. Purity test
The purity of the obtained alumina ceramic granulated powder was measured, and the results were as follows:
alumina content 99.04%, SiO20.002% of Fe2O3The content of Na is 0.001%2The O content is less than or equal to 0.01 percent, the ignition loss is 0.94 percent, and the test conditions of the ignition loss are as follows: 1100 +/-20 ℃ for 2 h.
3. Test of sintering Property
And (3) dry-pressing and molding the obtained alumina ceramic granulation powder under the pressure of 100MPa, sintering the powder in a high-temperature furnace at the low temperature of 1450 ℃ for 1 hour, and naturally cooling to room temperature to obtain the alumina ceramic.
The loose packed density of the granulated powder was 1.05g/cm3The density of the obtained molding biscuit is 2.32g/cm under the molding pressure of 100MPa3The density of the alumina ceramic obtained by sintering is 3.945g/cm 3The shrinkage was 15.7%.
Example 2
(1) 80kg of high-purity alpha-alumina raw powder (the purity is equal to or greater than 99.95 percent, and the alpha phase transition rate is 92-96 percent), 320kg of deionized water (namely the solid content of the slurry is 20 percent), 0.8kg of dispersing agent (1 percent of the mass of the high-purity alpha-alumina raw powder), 1.6kg of grinding aid (2 percent of the mass of the high-purity alpha-alumina raw powder), and 320kg of high-purity alumina grinding balls (the purity is equal to or greater than 99.99 percent) are added into a ball milling tank, wherein the dispersing agent is sodium hexametaphosphate, and the grinding aid is glycerol. Mixing and ball milling for 15h at the rotating speed of 50r/min, and starting cooling water circulation cooling barrel wall while ball milling to ensure that the temperature of a slurry system is lower than 50 ℃.
After the ball milling is finished, the powder particle size distribution in the slurry is detected, and the result shows that the particle size D of the alpha-alumina powder primary crystal in the obtained slurry500.241 μm and a narrow particle size distribution, D90/D10＝2.95。
(2) Adding 800g of PVA aqueous solution with the mass fraction of 10% into the ball milling tank, and continuing ball milling for 0.5h after the addition to ensure that the system is uniformly distributed.
(3) After the ball milling is finished, separating the grinding balls from the slurry by using a 80-mesh screen, and transferring the slurry into a stirring barrel, wherein the wall of the stirring barrel has a 3kw ultrasonic wave function. Starting ultrasonic waves, starting stirring, adding 1.2kg of lubricant (1.5 percent of the mass of the high-purity alpha-alumina raw powder), adding 0.48kg of polyol ester defoaming agent (0.6 percent of the mass of the high-purity alpha-alumina raw powder), wherein the lubricant is n-butyl alcohol, and the polyester defoaming agent is MQ-232, stirring for 1.0h, and fully and uniformly mixing to obtain mixed slurry.
(4) Feeding the mixed slurry into a centrifugal spray granulation tower with the water evaporation capacity of 25kg/h for granulation, and controlling the conditions as follows: the temperature in the tower is 290 ℃, the outlet temperature is controlled to be 110 ℃, the air negative pressure in the tower is 250Pa, centrifugal atomization is carried out by a centrifugal disc, and homogeneous solid spherical granulation powder with the water content of 0.35 percent is formed by high-temperature drying.
(5) The granulated powder obtained by spray granulation is screened by a vibrating screen with 170 meshes and 450 meshes in a double-layer way, and a qualified product is obtained between the granulated powder and the vibrating screen, namely the alumina ceramic granulated powder obtained in the embodiment.
Performance test
1. Particle size distribution and morphology testing
The particle size distribution of the obtained alumina ceramic granulated powder was measured, and the result showed that the alumina ceramic granulated powder D prepared in this example50＝66.54μm，D10＝35.77μm，D90＝99.55μm。
The electron microscope observation of the obtained alumina ceramic granulated powder shows that the obtained granulated powder has uniform particle size distribution and good sphericity, and the test shows that the repose angle of the obtained alumina ceramic granulated powder is 28 degrees, which indicates that the alumina ceramic granulated powder has good fluidity.
2. Purity test
The purity of the obtained alumina ceramic granulated powder was measured, and the results were as follows:
alumina content 99.08%, SiO20.002% of Fe2O3The content of Na is 0.001%2The O content is less than or equal to 0.01 percent, the ignition loss is 0.90 percent, wherein the test conditions of the ignition loss are as follows: 1100 +/-20 ℃ for 0.5 h.
3. Test of sintering Property
And (3) dry-pressing and molding the obtained alumina ceramic granulation powder under the pressure of 100MPa, sintering the powder in a high-temperature furnace at the low temperature of 1400 ℃ for 1 hour, and naturally cooling to room temperature to obtain the alumina ceramic.
The loose packed density of the granulated powder was measured to be 1.01g/cm3The density of the obtained molding biscuit is 2.31g/cm under the molding pressure of 100MPa3The density of the alumina ceramic obtained by sintering is 3.943g/cm3The shrinkage was 15.8%.
Example 3
(1) 100kg of high-purity alpha-alumina raw powder (the purity is equal to or greater than 99.95 percent, and the alpha phase conversion rate is 92-96 percent), 300kg of deionized water (namely the solid content of slurry is 25 percent), 2kg of dispersing agent (2 percent of the mass of the high-purity alpha-alumina raw powder), 2.5kg of grinding aid (2.5 percent of the mass of the high-purity alpha-alumina raw powder), and 400kg of high-purity alumina grinding balls (the purity is equal to or greater than 99.99 percent) are added into a ball milling tank, wherein the dispersing agent is hexadecyl trimethyl ammonium bromide, and the grinding aid is propylene glycol. Mixing and ball milling for 18h at the rotating speed of 70r/min, and starting cooling water circulation cooling barrel walls while ball milling to ensure that the temperature of a slurry system is lower than 50 ℃.
After the ball milling is finished, the powder particle size distribution in the slurry is detected, and the result shows that the particle size D of the alpha-alumina powder primary crystal in the obtained slurry500.238 μm and a narrow particle size distribution, D 90/D10＝2.93。
(2) And adding 1000g of PVA aqueous solution with the mass fraction of 10% into the ball milling tank, and continuing ball milling for 0.5h after the addition to ensure that the system is uniformly distributed.
(3) After the ball milling is finished, separating the grinding balls from the slurry by using a 80-mesh screen, and transferring the slurry into a stirring barrel, wherein the wall of the stirring barrel has a 3kw ultrasonic wave function. Starting ultrasonic waves, starting stirring, adding 2kg of a lubricant (2% of the mass of the high-purity alpha-alumina raw powder), adding 0.5kg of a polyol ester defoamer (0.5% of the mass of the high-purity alpha-alumina raw powder), wherein the lubricant is glycerol, and the polyester defoamer is polyoxyethylene glyceryl ether, stirring for 1.0h, and fully and uniformly mixing to obtain mixed slurry.
(4) Feeding the mixed slurry into a centrifugal spray granulation tower with the water evaporation capacity of 25kg/h for granulation, and controlling the conditions as follows: the temperature in the tower is 300 ℃, the outlet temperature is controlled to be 115 ℃, the negative pressure of air in the tower is 300Pa, centrifugal atomization is carried out by a centrifugal disc, and homogeneous solid spherical granulation powder with the water content of 0.38 percent is formed by high-temperature drying.
(5) The granulated powder obtained by spray granulation is screened by a vibrating screen with 170 meshes and 450 meshes in a double-layer way, and a qualified product is obtained between the granulated powder and the vibrating screen, namely the alumina ceramic granulated powder obtained in the embodiment.
Performance test
1. Particle size distribution and morphology testing
The particle size distribution of the obtained alumina ceramic granulated powder was measured, and the result showed that the alumina ceramic granulated powder D prepared in this example50＝58.42μm，D10＝32.88μm，D90＝93.56μm。
The electron microscope observation of the obtained alumina ceramic granulated powder shows that the obtained granulated powder has uniform particle size distribution and good sphericity, and the test shows that the obtained alumina ceramic granulated powder has a repose angle of 27 degrees, which indicates that the alumina ceramic granulated powder has good fluidity.
2. Purity test
The purity of the obtained alumina ceramic granulated powder was measured, and the results were as follows:
alumina content of 99.06%, SiO20.002% of Fe2O3Content of Na is 0.001%2The O content is less than or equal to 0.01 percent, the ignition loss is 0.92 percent, wherein the test conditions of the ignition loss are as follows: 1100 +/-20 ℃ for 1.5 h.
4. Test of sintering Property
And (3) dry-pressing and molding the obtained alumina ceramic granulation powder under the pressure of 100MPa, sintering the powder in a high-temperature furnace at the low temperature of 1400 ℃ for 1 hour, and naturally cooling to room temperature to obtain the alumina ceramic.
The loose packed density of the granulated powder was tested to be 1.04g/cm3The density of the obtained molding biscuit is 2.32g/cm under the molding pressure of 100MPa3The density of the alumina ceramic obtained by sintering is 3.944g/cm3The shrinkage was 15.8%.
Comparative example 1
Other conditions were the same as in example 1, except that only step (3) was omitted, namely, the addition of the lubricant and the defoaming agent was omitted, and the slurry obtained in step (2) was directly subjected to spray drying and sieving to obtain alumina ceramic granulated powder. According to The alumina ceramic granulated powder obtained in example 1 was subjected to a sintering property test, and the result showed that the granulated powder had a bulk density of 0.89g/cm3The density of the obtained molding biscuit is 2.105g/cm under the molding pressure of 100MPa3The density of the alumina ceramic obtained by sintering is 3.917g/cm3The shrinkage was 18.1%.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (9)

1. The preparation method of the alumina ceramic granulated powder is characterized by comprising the following steps:
mixing alpha-alumina raw powder, a dispersing agent, a grinding aid and water, and carrying out first ball milling to obtain first ball milling slurry; the purity of the alpha-alumina raw powder is more than or equal to 99.95 percent;
mixing the first ball-milling slurry and a granulation binder aqueous solution, and carrying out second ball milling to obtain a second ball-milling slurry;
and mixing the second ball-milling slurry, a lubricant and a defoaming agent, and then carrying out spray granulation to obtain alumina ceramic granulation powder.
2. The method according to claim 1, wherein the mass fraction of the raw α -alumina powder is 10 to 50% based on 100% by mass of the total of the raw α -alumina powder and water.
3. The preparation method according to claim 1 or 2, wherein the dispersant comprises one or more of polyacrylamide, polyethylene glycol, sodium hexametaphosphate, modified polyacrylamide and hexadecyl trimethyl ammonium bromide; the mass of the dispersing agent is 0.5-3% of that of the alpha-alumina raw powder;
the grinding aid comprises micromolecular alcohol, and the number of carbon atoms of the micromolecular alcohol is 2-5; the mass of the grinding aid is 1.8-3% of that of the alpha-alumina raw powder.
4. The preparation method according to claim 1 or 2, characterized in that the rotation speed of the first ball mill and the second ball mill is independently 20-100 r/min, the time of the first ball mill is 8-18 h, and the time of the second ball mill is 0.5-1.5 h;
the grinding balls used in the first ball mill and the second ball mill are high-purity alumina grinding balls, and the purity of the high-purity alumina grinding balls is more than or equal to 99.99%;
in the first ball milling process and the second ball milling process, cooling water is adopted for circulating cooling to keep the temperature of the slurry below 50 ℃.
5. The method according to claim 1, wherein the granulation binder in the aqueous granulation binder solution is 5 to 10% by mass, and the aqueous granulation binder solution is 0.6 to 1.6% by mass of the α -alumina raw powder.
6. The preparation method according to claim 1, wherein the lubricant comprises one or more of aqueous paraffin, glycerol and n-butanol; the mass of the lubricant is 1.2-3% of that of the alpha-alumina raw powder;
the defoaming agent is a polyol ester defoaming agent, and the mass of the defoaming agent is 0.5-0.8% of the mass of the alpha-alumina raw powder.
7. The preparation method according to claim 1 or 6, characterized in that the mixing of the second ball-milling slurry, the lubricant and the defoaming agent is carried out under the conditions of ultrasound and stirring, and the power of the ultrasound is 3-5 kw.
8. The method according to claim 1, wherein the spray granulation is performed using a centrifugal spray granulation tower, and the conditions of the spray granulation include: the outlet temperature is 105-115 ℃, the negative pressure of air in the tower is 250-350 Pa, and the temperature in the tower is 280-300 ℃.
9. The method according to claim 1, further comprising, after the spray granulation, classifying the obtained powder; the grading screening comprises the following steps: and screening the powder obtained by spray granulation by using a double-layer sieve, wherein the material among the sieves is the alumina ceramic granulation powder, the mesh number of an upper-layer sieve of the double-layer sieve is 160-180 meshes, and the mesh number of a lower-layer sieve is 440-460 meshes.
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