화학공학소재연구정보센터
홈 로그인 로그아웃 연락처 사이트맵
Korean Journal of Chemical Engineering, Vol.21, No.5, 921-928, September, 2004
DOI10.1007/BF02705572  Export Citation
Microstructure and Phase Behavior of Concentrated Silica Particle Suspensions
Jae-Hyun So, Won-Kyoung Oh, and Seung-Man Yang†
  • Department of Chemical and Biomolecular Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea
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Dispersion stability and microstructural transition of colloidal silica suspensions were examined by rheological measurements under either steady simple shear or oscillatory flow. Monodisperse silica particles were prepared by the so-called modified Stober method and were stabilized by either steric or electrostatic repulsive force. Depending upon the methods of stabilization, the suspension showed hard-sphere or soft-sphere response. In particular, silica suspensions exhibited hardsphere response when the silica spheres coated with 3-(trimethoxysilyl)propyl methacrylate (MPTS;CH3O)3Si(CH2)3OCOC(CH3)=CH2) were dispersed in a refractive-index matching solvent, tetrahydrofurfuryl alcohol. On the other hand, silica particles in aqueous media behaved like soft spheres with long-range elec-trostatic repulsive interactions when they were coated with steric layer of aminosilane coupling agent, N-[3-(trimethoxysilyl)propyl]ethylenediamine((CH3O)3Si(CH2)3NHCH2CH2NH2). In this case, the electrostatic repulsion or equivalently the softness of the silica spheres was contorlled by the ionic strength using a symmetric salt KCI. Both the hardsphere and soft-sphere suspensions showed stable shear-thinning behavior without experiencing shear-induced flocculation. Moreover, the oscillatory shear rheology. showed that the electrostatically stabilized soft-sphere suspensions underwent a microstuctural transition from liquid-like to solid-like structure when either the particle loading increased or the ionic strength was recuced.
Keywords:Dispersion Stability;Silica Suspension;Silane Coupling Agent;Microstructure;Phase Transition;Hard Spheres;Soft Spheres;Rheological Behavior
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