CN110950649A - Preparation method of submillimeter-level solid alumina ceramic microspheres - Google Patents

Preparation method of submillimeter-level solid alumina ceramic microspheres Download PDF

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CN110950649A
CN110950649A CN201911290978.5A CN201911290978A CN110950649A CN 110950649 A CN110950649 A CN 110950649A CN 201911290978 A CN201911290978 A CN 201911290978A CN 110950649 A CN110950649 A CN 110950649A
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powder
alumina
submillimeter
alumina ceramic
ceramic microspheres
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李蔚
孙小曼
宋雁翎
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East China University of Science and Technology
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East China University of Science and Technology
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    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
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Abstract

The invention relates to a preparation method of submillimeter-level solid alumina ceramic microspheres. The preparation method of the alumina ceramic microspheres comprises the following steps: firstly, screening and grading the alumina granulated powder obtained by spray granulation by using a screening process to obtain uniform granulated powder in different particle size ranges. Then evenly mixing the granulation powder in a certain particle size range with a proper amount of graphite powder. And placing the mixed powder in a covered crucible and calcining at high temperature to densify the alumina micro-beads. The crucible cover is then removed and the excess graphite powder is removed by calcining at low temperature. And sieving the calcined product to obtain the compact and well-dispersed alumina ceramic microbeads with the required particle size range.

Description

Preparation method of submillimeter-level solid alumina ceramic microspheres
Technical Field
The invention relates to the field of ceramic production, in particular to a method for manufacturing alumina ceramic microspheres.
Background
The alumina ceramic microspheres refer to ceramic spheres or approximate spheres with the diameter of micron to millimeter level, which are prepared by using alumina as a main raw material through various molding processes. The alumina ceramic microspheres not only have the excellent properties of alumina ceramic materials, such as high strength, good thermal stability, good flame retardance and insulation, low water absorption, stable chemical properties and the like, but also have the characteristics of microsphere particles, such as isotropy, point contact and the like. Due to the unique shape and excellent performance, the alumina ceramic microspheres are widely applied to industries such as aviation, aerospace, national defense and military industry, medicine, chemical industry, building materials, environmental protection, nuclear technology and the like. Along with the more and more intensive research on the alumina ceramic microspheres, the application field of the alumina ceramic microspheres is wider and wider, and the preparation method is more and more abundant. However, most methods such as sol-gel method are very expensive and can only be used in laboratory research, and only a few methods such as flame melting method and spray granulation method are suitable for large-scale production.
The flame fusion method is that the raw material micro powder is conveyed into burning flame, the raw material forms dispersed small drops after flame fusion, and the small drops enter a cooling zone to be condensed into spherical particles, thus obtaining the spherical particles. This process requires very high temperatures. If the melting temperature required for producing the spherical iron oxide reaches over 2400 ℃, and the melting temperature required for producing the spherical silicon dioxide reaches about 2000 ℃. The melting temperature for preparing the spherical alumina is controlled to be about 2050 ℃. Therefore, the method has the defects of high equipment requirement, high production cost, high energy consumption and the like.
Spray granulation is to spray and solidify the solution or suspension and other raw materials to prepare fine particles with certain shape and strength, and can also be used for preparing alumina ceramic microbeads. However, the density and strength of the alumina ceramic microspheres prepared by the method are low, and the alumina ceramic microspheres cannot be directly used in many occasions (such as being used as grinding media), and must be densified through further calcination to obtain the final product. However, the sintering process easily causes the adhesion between the small particles due to sintering, which results in greatly reduced dispersibility and flowability of the alumina ceramic microspheres. In order to avoid such adhesion, a gradient calcination process has been developed, in which ceramic beads obtained by spray granulation are sequentially calcined at different temperatures from low to high at certain temperature intervals, and after each calcination, the powder is taken out and ground to destroy the adhesion that may be formed, until finally dense ceramic beads are obtained. However, this process is too cumbersome to be applied on a large scale.
Disclosure of Invention
The invention aims to provide a novel method for preparing alumina ceramic solid microspheres by a two-step calcination method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: firstly, preparing spherical alumina powder by using spray granulation equipment, then classifying the obtained granulated powder by a screening process, mixing the classified granulated powder with a certain amount of graphite powder, then putting the mixed powder in a covered crucible to isolate air, and calcining at a preset temperature to densify the spherical alumina powder. And removing the crucible cover after cooling, burning the graphite powder at a certain temperature, taking out the powder, and sieving to obtain the sub-millimeter-grade alumina ceramic microspheres with uniform particle sizes.
In the above technical scheme: the addition amount of the graphite powder is 5-50wt%, and the mixing time of the granulation powder and the graphite powder is 6-24 h; the calcination temperature for removing the graphite powder is 900-1100 ℃, and the heat preservation time is 2-10 hours;
compared with the prior art, the invention has the following greatest characteristics: the compact ceramic microbeads are obtained by directly calcining at high temperature, and the graphite powder is burnt at low temperature after the adhesion among the alumina particles is prevented by the mixed graphite powder. The whole process is simple and reliable, and is suitable for large-scale production.
Drawings
FIG. 1 shows the dense alumina ceramic microbeads obtained by the present invention.
FIG. 1 is provided to provide a further understanding of the present invention and forms a part of the specification, and together with the embodiments of the invention serve to explain the invention and not to limit the invention.
Detailed Description
Example one
10kg of 99 alumina granulation powder obtained by spray granulation is taken and put in a vibration sieving machine for sieving to obtain 99 alumina granulation raw powder with different particle size ranges. 1kg of sieved 99 alumina powder is taken, 200g of graphite powder is added, and the mixture is put into a ball milling tank and mixed for 12 hours on a common ball mill. And placing the mixed powder into a corundum crucible, adding a cover, placing the corundum crucible into a muffle furnace, and calcining for 2 hours at 1650 ℃ to densify the ceramic microspheres. After cooling, the cover of the corundum crucible is taken away, and then the temperature is raised to 1000 ℃ to calcine for 4 hours, and the graphite powder is burnt off. After cooling, the obtained alumina ceramic microbeads were sieved again to obtain dense, well-dispersed alumina ceramic microbeads with the desired particle size range (as shown in fig. 1).

Claims (4)

1. A method for preparing submillimeter solid alumina ceramic microspheres comprises the following basic processes: screening and grading the alumina granulation powder obtained by spray granulation by using a screening process, mixing the graded granulation powder with a certain amount of graphite powder, putting the mixed powder into a covered crucible, and calcining at a preset temperature to densify the spherical alumina powder; removing the crucible cover after cooling, and burning the graphite powder at a certain temperature; and taking out and sieving the obtained alumina micro-beads to obtain the submillimeter-level ceramic micro-beads with uniform particle size.
2. The method for preparing submillimeter-sized solid alumina ceramic microspheres according to claim 1, wherein the method comprises the following steps: the raw material for preparing the alumina microspheres is spray granulation alumina powder.
3. The method for preparing submillimeter-sized solid alumina ceramic microspheres according to claim 1, wherein the method comprises the following steps: firstly, pre-screening spray granulation alumina powder into spherical powder with uniform particle size in different particle size ranges; and mixing the screened alumina microspheres with a certain amount of graphite dispersing agent, wherein the addition amount of graphite powder is 5-50wt%, and the mixing time of the granulated powder and the graphite powder is 6-24 h.
4. The method for preparing submillimeter-sized solid alumina ceramic microspheres according to claim 1, wherein the method comprises the following steps: the granulation powder is firstly calcined at high temperature under the condition of air isolation to complete densification, and then calcined at low temperature in the air to remove graphite powder.
CN201911290978.5A 2019-12-16 2019-12-16 Preparation method of submillimeter-level solid alumina ceramic microspheres Pending CN110950649A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113060746A (en) * 2021-04-14 2021-07-02 雅安百图高新材料股份有限公司 Preparation method of large-particle-size alumina raw material and spherical alumina product thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113060746A (en) * 2021-04-14 2021-07-02 雅安百图高新材料股份有限公司 Preparation method of large-particle-size alumina raw material and spherical alumina product thereof

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