O/W/O多重乳液法制备毫米级氧化铝空心球

doi:10.15541/jim20150462

摘要/Abstract

摘要：

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30~80 μm和800~2200 μm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α-Al₂O₃。

关键词: 氧化铝空心球, O/W/O多重乳液, 复合液滴, 直流通道

Abstract:

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.

Key words: alumina hollow spheres, oil₁-in-water-in-oil₂ emulsion, composite droplets, flow focusing micro-channel

中图分类号:

TQ174

李昊亭, 廖其龙, 王辅. O/W/O多重乳液法制备毫米级氧化铝空心球[J]. 无机材料学报, 2016, 31(3): 329-336.

LI Hao-Ting, LIAO Qi-Long, WANG Fu. Preparation of Millimeter-scale Alumina Hollow Spheres by Oil₁-in-water-in-oil₂ Emulsions[J]. Journal of Inorganic Materials, 2016, 31(3): 329-336.

图/表 9

Fig. 1 Schematic diagram of co-flow micro-emulsion generator

Table 1 Parameters of materials (T=25℃)

Parameters	Alumina sol aged for differeut time/d					Paraffin	Silicone oil
Parameters	1	5	10	15	20	Paraffin	Silicone oil
Density, ρ / (g﹒mL^-1)	1.012	1.024	1.027	1.052	1.073	0.835	0.963
Viscosity, η  (mPa﹒s)	26.56	37.90	48.23	58.44	98.36	35.98	400.00

Fig. 2 Three kinds of composite droplets (model A, model B, model C)

Fig. 3 Diameter and wall thickness of com-droplets at different velocities of water phase (Voil=1 mL·h-1)

Fig. 4 Diameter and wall thickness of com-droplets at different velocities of oil phase (Vwater=6 mL·h-1)

Fig. 5 Schematic of three different rotate types

Fig. 6 Number of intact droplets at different speed after curing (n=10)

Fig. 7 Photographs of com-droplets, semisolid spheres and SEM images of ceramic spheres by model A, B and C

Fig. 8 Characterization of the ceramic sphere(A, B, C): SEM of spheres; (D, E, F): optical images of spheres; (G, H): surface roughness analysis; (I): XRD patterns

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