REACTION-KINETICS AND SIZE CONTROL IN THE FORMATION OF MONOSIZED SILICA SPHERES BY CONTROLLED HYDROLYSIS OF TETRAETHYL ORTHOSILICATE IN ETHANOL

被引:13
作者
SADA, E
KUMAZAWA, H
KORESAWA, E
机构
[1] Department of Chemical Engineering, Kyoto University, Sakyo-Ku, Kyoto
来源
CHEMICAL ENGINEERING JOURNAL AND THE BIOCHEMICAL ENGINEERING JOURNAL | 1990年 / 44卷 / 03期
关键词
D O I
10.1016/0300-9467(90)80070-S
中图分类号
TQ [化学工业];
学科分类号
0817 ;
摘要
An investigation was made into the reaction kinetics and methods of particle size control in the hydrolytic polycondensation of tetraethyl orthosilicate (TEOS) to form spherical silica particles in ethanol with ammonia as catalyst. The reaction leading to the formation of the silica particles consists in hydrolysis followed by polycondensation. Polycondensation in ethanol was found to be first order in TEOS, water and ammonia. In the early stage of the reaction, uniform nuclei are generated and then particle growth alone takes place through polycondensation on the surface of the particles. This hypothesis is supported by the experimental evidence in that the volume mean diameter of the silica spheres was found to be proportional to the conversion of silicate monomer raised to the power of 1/3. Moreover, in the nucleation and aggregation model proposed by Bogush and Zukoski, nucleation is assumed to proceed for a substantial fraction of the reaction period and the nuclei are then assumed to aggregate quickly forming large particles. Particles of any desired mean size ranging from 0.03 to 0.3 μm, with a very narrow size distribution, can readily be prepared by changing the concentration of the ammonia catalyst. Larger particles of other sizes can be prepared as desired via a build-up process. © 1990.
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页码:133 / 139
页数:7
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