氧化铝浆料性能对喷雾干燥微珠形貌的影响

Influence of Alumina Slurry on Morphology of Microspheres by Spray Drying

以氧化铝粉体为原料,通过改变固含量、分散剂加入量调节浆料流变性能,采用离心式喷雾干燥工艺制备出氧化铝微珠坯体。研究了固含量、分散剂加入量对氧化铝浆料流变性以及微珠坯体形貌的影响,分析了"苹果型"缺陷坯体的形成过程。结果表明:随着浆料固含量的增加,规则球形坯体数量呈现迅速增多然后缓慢减少的趋势,随着分散剂加入量的增加,规则球形坯体的数量先增多然后逐渐减少,当浆料固含量为40%(体积分数)、分散剂加入量为0.5(质量分数)%时,球形坯体数量的比例最高为92.9%;"苹果型"缺陷坯体的形成受浆料固含量的影响显著,固含量为20%时,颗粒间距为0.549μm,坯体中规则球形坯体仅有14.6%,大部分是"苹果球"坯体,固含量为40%时,颗粒间距为0.157μm,球形坯体比例为92.9%,仅形成少量的"苹果球"坯体,因此,固含量越低,颗粒间距越大,坯体形成过程中空洞出现的越多,导致最后形成大量的"苹果球"坯体。采用二次烧结的方法对Al_2O_3坯体进行烧成,经1 700℃烧成的Al_2O_3微珠抗压强度达到了105.6 MPa。

Alumina microspheres were prepared by centrifugal spray drying using alumina powder as a starting material. The influences of solid loading and dispersant addition amount in alumina slurry on the performance of the green body were investigated. The formation mechanism of apple-shaped green body was also discussed. The number of sphere-shaped green body first increases, and then decreases with the increase of solid loading. When the dispersant addition amount increases, the number of sphere-shaped green body first increases and then decreases. An aqueous slurry with 40% （in volume fraction） of alumina and 0.5% （in mass fraction） of dispersant addition amount can be transformed into a green body with microspheres, obtaining a high pellet yield of 92.9%. The solid loading of alumina slurry has a dominant effect on the apple-shaped green body. When solid loading is 20%, the distance between particles is 0.549 μm, the proportion of spherical green body is 14.6%, including most apple-shaped green bodies. When solid loading is 40%, the distance between particles is 0.157 μm, and the proportion of spherical green body is 92.9%. A lower solid loading results in a greater space, causing the more holes in the green bodies. As a result, massive apple-shaped green bodies appear. The two-step sintering process is adopted to prepare alumina microspheres, and the compressive strength of microspheres sintered at 1 700 ℃ can reach 105.6 MPa.