실리카 입자 분산계의 광유변학적 거동과 미세구조의 변화

Abstract

Rheo-optical behaviors of dispersions of monodispersed silica particles were investigated. Monodispersed silica was prepared by the sol-gel method proposed by Stober et al. and the final particle size was obtained through the control of ammonium hydroxide concentration. Also, the transparent dispersion was prepared by dispersing the silica particles in the index-matching solvent which was composed of 50 : 50 mixture of ethylene glycol and glycerin. All silica dispersions of 30 % and 50 % by weight exhibited the non-Newtonian behaviors such as shear thinning although they were dispersed in Newtonian medium. Furthermore, the deviation from Newtonian behavior was pronounced when the particle concentration was increased. With two different optical alignments designed in the present study, the flow-induced dichroism was measured. And the simultaneous detection of the dichroism and birefringence was shown to be possible for the sample which possesses both of the rheo-optical properties. The measured dichroisms for 30 % dispersions showed that the microstructure evolution was enhanced especially at high shear rates. For 50 % dispersion, the microstructural transition becomes more complicated and the sign of dichmism was changed with long relaxation behaviors. This is owing to the formation of micro-domain as cluster in microscale. The result was also checked by dichroism and multiple scattering after flow cessation.