화학공학소재연구정보센터
Journal of Chemical Physics, Vol.105, No.16, 7200-7209, 1996
Dynamic Properties of Aqueous Dispersions of Nanometric Particles Near the Fluid-Solid Transition
Here we investigate a colloidal suspension of practical interest, silica particles, which provides a mesoscopic system for the study of a dynamic near fluid-solid transition, Dynamic properties of concentrated solutions of nearly monodisperse charged colloids (standard deviation/mean radius approximate to 0.11) at low ionic strength (approximate to 6 x 10(-4) M) have been studied by quasielastic light scattering Below a volume fraction of the order of 15%, the solutions are viscous fluids and the refractive index fluctuations relax in two steps. Above a volume fraction of 20%, and over a macroscopic time window extending up to few seconds or more, the solutions are elastic and fluctuations in the refractive index become frozen. This is typical of systems which pass from a fluid to a solid state. The results are critically analyzed within the same framework used for similar macroparticle systems.