O/W/O多重乳液法制备毫米级氧化铝空心球（英文）

Preparation of Millimeter-scale Alumina Hollow Spheres by Oil_1-in-water-in-oil_2 Emulsions

采用O/W/O多重乳液法,以液体石蜡为内核,氧化铝溶胶为外壳层组成的复合液滴作为前驱体,制备毫米级氧化铝空心球,研究了装置几何结构对前驱体的形成和固化过程对空心球结构的影响。结果表明,内部油相通过直流通道直接注射到水相液滴内部时,形成的复合液滴具有均一核壳结构,壁厚和直径在30~80mm和800~2200mm可控。液滴置于水平方向旋转固化,保持转速在20~60 r/min,所得凝胶球可以保持完整的球形度和核壳结构。1200℃高温煅烧制备出的氧化铝空心微球维持高的球形度和空心结构,表面粗糙度大约22 nm,壁厚达到几十微米,直径达到毫米级,主要晶型为稳定的a-Al2O3。

To prepare millimeter-scale alumina hollow spheres by oil1-in-water-in-oil2 emulsions, the influence factors of formation of precursor and curing process were studied. Composite droplets with paraffin liquid as inner core and alumina sol as outer shell were used as precursor. Results showed that the com-droplets had homogeneous and complete core-shell structure when emulsion generator was designed that inner oil could be injected into water phase with the size of millimeters scale. Thickness and diameter of droplets were adjusted by both controlling the injection speed of oil and water phase in the range of 30–80 μm and 800–2200 μm. In the curing process, the semisolid spheres kept hollow structure and spherical when the speed of rotation between 20 r/min to 60 r/min and the flask being put in horizontal. Finally, the prepared hollow ceramic spheres with wall thickness in micrometer-scale and diameter in millimeter-scale formed complete hollow structure and high sphericity after calcining at 1200 ℃ for 4 h. The surface of sphere was relatively smooth with roughness of about 22 nm. The main crystal of the prepared ceramic hollow spheres was alpha alumina.